Sustainable metal recovery from spent lithium-ion battery using electrochemical technique: A comprehensive method review

Review Highlights

• •Recycling of Spent Lithium-ion Batteries using electrochemical techniques
• •Methods and patents on electrochemical methods for the recovery of precious metals
• •Novelty and limitations of prominent electrochemical recycling techniques

Abstract

The pervasive presence of Spent Lithium-Ion Batteries (S-LIB) poses a significant environmental threat due to their hazardous components and the resource-intensive mining of scarce metals like lithium, cobalt, and nickel. Efficient recycling offers a solution by fostering a circular economy and mitigating the environmental impact of disposal and primary resource extraction. Electrochemical recycling (ECR) has emerged as a promising sustainable technology for recovering scarce metals and promoting the circular economy.

The paper discusses methods for ECR of S-LIBs, emphasizing the latest developments targeting the increasing demand for critical metals. The U.S. patent data available through January 2025 is accessed from the Lens database using different keywords. Focusing on the latest and highly cited patents, the paper establishes benefits, drawbacks, research gaps, and future scopes in the domain of ECR.

Higher selectivity, reduced energy usage, less environmental footprint, increased recovery rates, and possibilities of electrolyte regeneration appeared as some strengths of electrochemical techniques. However, challenges like process complexity due to multi-element systems, employment of strongly corrosive solvents, membrane fouling, and scalability are also witnessed. Future work must aim to improvise the electrochemical recovery system using high-performance anodes, decrease corrosiveness to enhance the electrode durability, and improve membrane performance to make scalable, cost-efficient, and environmentally friendly electrochemical recovery of high-purity metals from S-LIBs.

Graphical abstract

Specifications table

Subject area	Engineering
More specific subject area	Recycling of spent lithium-ion batteries
Name of the reviewed methodology	Electrochemical method
Keywords	Lithium-ion battery, electrochemical recycling, metal recovery, critical metals, patent analysis
Resource availability	https://www.lens.org
Review question	1) How to address the ever-increasing demand for critical metals required for battery production and their associated depletion?
	2) Can the electrochemical process effectively recycle spent LIBs?
	3) What is the trend of patent publication on the electrochemical recycling of spent lithium-ion batteries?
	4) What are the advantages and drawbacks of using the electrochemical process for recycling used LIBs
	5) What are the novelties and limitations in prominent patent papers on the electrochemical recycling of lithium-ion batteries

Background

The dearth of fossil fuels and the environmental breakdown caused by their injudicious use have restricted their usage [1]. This gave a boost to rechargeable batteries, like lithium-ion batteries (LIBs) that can decarbonize the transportation sector [2]. LIBs are used in electric vehicles (EVs) [3] as well as in portable electronic devices, such as mobile phones, laptops, tablets, camcorders, digital cameras, watches, and calculators [4]. Their high energy density, ability to operate over a wide temperature range, charge retention, outstanding cyclic performance, and low discharge rate make them better than other rechargeable power sources [[5], [6], [7], [8], [9], [10], [11]]. By the year 2030, the world EV market is expected to rise to nearly 130 million vehicles, generating approximately 11 million tons of LIB trash [12]. The rapid increase in battery material available worldwide for recycling is estimated in Fig. 1 [13]. This rate projects an increase in the demand for critical metals. For instance, lithium demand alone is estimated to increase from 0.5 million tons in 2020 to 3.2 million tons in 2040 [12,14].

Fig. 1.

Battery material available for recycling worldwide from 2020–2040.

The fact that LIBs retire after around 3 years in the case of small instruments, such as cell phones, and 5 to 10 years for larger devices, like EVs, is one of the pitfalls in the usage of these batteries [15]. The components present in these end-of-life (EOL) batteries can be injurious to the environment and harmful to human health [16]. Table 1 shows the general composition of LIBs used during the 2020s [16,17].

Table 1.

Composition of different types of LIBs used in the 2020s.

Sr. No.	Components	Form	Chemical composition	% by weight
1	Casing	Prismatic cylindrical pouch	Fe-Ni alloy	20–26
			Aluminium	10
2	Separator	Polymer	Polypropylene (PP), Polyethylene (PE)	4–10
3	Electrolyte	Liquid	Lithium salts (LiPF6, LiAsF6, LiClO4, LiBF4)	10–15
			Organic salts [Dimethyl Carbonate and Ethylene Carbonate (DMC-EC), Propylene Carbonate and Dimethoxyethane (PC-DME), and n‑butyl levulinate Tetrahydrofuran (BL-THF)]
4	Cathode	Current collector foil	Al	5–10
		Binder (polymer)	Polyvinylidene Fluoride	1–2
		Metal oxide	Li	1.5–7
			Co	5–20
			Ni	5–10
			Mn	5
5	Anode	Current collector foil	Cu	8–10
		Binder (polymer)	Polyvinylidene Fluoride	1–2
		Graphite	–	15–17

Note: LiPF₆ – Lithium hexafluorophosphate, LiAsF₆ - Lithium hexafluoroarsenate, LiClO₄ – Lithium perchlorate, LiBF₄ – Lithium tetrafluoroborate.

LIBs contain precious resources like nickel, cobalt, lithium, and manganese, 70–82 % of which are limited to countries like China, the Democratic Republic of Congo, and Chile [[18], [19], [20], [21], [22]]. Also, mining these mineral resources is expensive and hazardous to the environment [18]. Maintaining the supply chain of these raw materials requires developing economically and environmentally sustainable systems, aiming for a circular economy [23,24]. The critical metals used in LIB manufacturing remain intact in spent LIBs, making them excellent secondary sources of such metals, especially critical ones like lithium and cobalt [25,26]. Many innovative energy storage systems that can act as improved alternatives to Li-ion batteries have also been developed. For example, advanced hybrid capacitors derived from ultrafine nickel-phosphorus nanowires and Ni₃Se₂ nanowires [27,28], or oxide cathode materials using Na_0.91MnO₂ [29]. But they also need critical metals like nickel and manganese for manufacturing, and just like any other power storage device, they also retire after serving for a while, necessitating their recycling.

Literature reviews discussing the research publications on the electrochemical recycling are available, but fewer discussions are found on the latest innovations in the area of electrochemical recycling of the S-LIB through patent analysis. The present paper explores the latest and promising innovative methods for recycling the S-LIB through systematic patent analysis. The patent analysis is carried out using multiple keyword searches, analysis of trends, citation analysis, and recent published patents.

Method details

Electrochemical recycling implements the use of electrical power to convert waste into precious resources. It precisely regulates redox reactions to dissolve and dissociate target materials from complex waste streams, making the recovery of highly pure elements with less consumption of chemicals. This method offers sustainable and universal reclamation of metals from LIBs and other electronic items, including various other types of waste. Electrochemical recycling systems are usually composed of an electrochemical cell with a power supply and a control unit. The electrochemical cell, where actual recycling reactions take place, usually employs a two or three-electrode configuration for control precision dipped in electrolyte. They are the working electrode (either anode or cathode), where the target recycling reaction takes place, the counter electrode that serves to close the circuit by conducting the balancing current, and the reference electrode that supplies a stable potential to have accurate monitoring and control over the potential of the working electrode to make efficient and selective recovery of the material or treatment of waste. These electrodes are either reactive, taking an active role in the chemical conversion of the waste product, or inert, offering a site for electron transfer without themselves being consumed. The power supply powers such reactions by supplying the requisite electrical energy, while the control unit controls and regulates parameters such as current, voltage, and temperature to achieve the optimal recycling. Fig. 2 is a general depiction of a typical electrochemical cell that explains the concept of electrochemical recycling.

Fig. 2.

Concept of electrochemical recycling.

Based on the understanding from the literature available on electrochemical recycling of LIBs, a framework for the entire electrochemical recycling process is shown in Fig. 3. Spent Lithium-ion Batteries (LIBs) are first pretreated through segregation and direct removal of components, after which they are crushed to obtain "black mass". The black mass is further treated with solvents to obtain a leachate, which is then fed into an electrochemical cell for recycling. In the electrochemical cell, the LIB leachate is subjected to electrochemical degradation under the influence of electric current. Metal recovery is finally obtained through processes like electrochemical precipitation, electrodeposition, electrodialysis, or electro-sorption on high-surface-area electrodes.

Fig. 3.

Framework for electrochemical recycling of spent LIBs.

For understanding the latest research, innovations, and advancements in electrochemical recycling, a detailed analysis of patents is performed. The section below contains a systematic and detailed analysis of the same.

Patent data source

The Lens database is used for this study. This free, open-access repository system has been in existence since 2000, and it enables users to explore, scrutinize, and manage patent works done worldwide. The lens allows its users to select data based on dates, which helps in obtaining recent data and makes it possible to study documents during a particular period. Using Lens, data can be filtered to obtain patents as per jurisdictions, i.e., patents of the USA, WO-WIPO, Europe, China, and France. It also provides forward and backward citations of all the documents. The Lens furnishes a detailed analysis of publications over time, top applicants, top owners, top inventors, top cited patents, the legal status of documents, jurisdictions, and document types. The patents reviewed here include patents on electrochemical methods for recycling spent lithium-ion batteries.

Search strategy

A search for patents is run based on a keyword search strategy. The study utilizes the most significant patents on electrochemical recycling of lithium-ion batteries till January 2025 concerning the title, abstract, and claims of the patent. The master set of keywords ‘Lithium AND Ion AND Batteries’ gives 511,215 patent papers as a result. The data is further refined based on ‘jurisdiction’, as it is seen that the United States jurisdiction has the maximum number of patents, i.e., 262,008, on the concerned topic, and all further patent analysis deals with the United States jurisdiction only. The sets of keywords used are shown in Table 2.

Table 2.

Sets of keywords used for publication and patent search on recycling of lithium-ion batteries by electrochemical method.

Sr. No.	Process	Keywords
1	Electrostatic separation	Electrostatic AND Separation AND of AND Lithium AND Ion AND Batteries
2	Electrodeposition	Recycling AND of AND Lithium AND Ion AND Batteries AND by AND Electrodeposition
3	Electrocoagulation	Recycling AND of AND Lithium AND Ion AND Batteries AND by AND Electrocoagulation
4	Electrochemical leaching	Electrochemical AND Leaching AND of AND Lithium AND Ion AND Batteries

The Patent Lens database provided 764 patent works for keywords ‘Electrostatic AND Separation AND of AND Lithium AND Ion AND Batteries’ and 297 results for ‘Electrochemical AND Leaching AND of AND Lithium AND Ion AND Batteries’, whereas for keywords ‘Recycling AND of AND Lithium AND Ion AND Batteries AND by AND Electrodeposition’ and ‘Recycling AND of AND Lithium AND Ion AND Batteries AND by AND Electrocoagulation’ fetched zero patents. From these observations, it can be concluded that patenting activities are the most common in the electrostatic separation of LIBs.

The paper focuses on US patent documents, as most of the patent work is from this category. The US kind codes and their descriptions are given in Table 3: [30]

Table 3.

United States Patent and Trademark Office (USPTO) kind codes.

Sr. No.	Kind code	Description
1	A	Utility Patent Grant used before January 2, 2001
2	A1	Utility Patent Application published since January 2, 2001
3	A2	Second or succeeding publication of a Utility Patent Application
4	A9	Utility Patent Application corrected and published
5	B1	Utility Patent Grant (no pre-grant publication) issued since January 2, 2001
6	B2	Utility Patent Grant (with pre-grant publication) issued since January 2, 2001
7	Cn (n = 1 to 9 publication level)	Re-examination Certificate issued on or after January 2, 2001
8	Fn (n = 1 to 9 publication sequence)	Supplemental Examination Certificate published after September 16, 2012
9	Jn (n = 1 to 9 publication sequence)	Post-Grant Review Certificate published after September 16, 2012
10	Kn (n = 1 to 9 publication sequence)	Inter Partes Review Certificate published after September 16, 2012
11	On (n = 1 to 9 publication sequence)	Derivation Certificate published after March 16, 2013
12	E	Reissue Patent
13	S	Design Patent

The patent analysis

Battery waste has become a threat to the environment and health, which can jeopardize society’s sustainable development. LIBs as a valuable source of critical metals to be used in future batteries have attracted researchers towards developing new technologies to cope with the intricacies of battery designs and their chemistries [31]. Patent analysis concentrates on delineating and interpreting a particular set of patents in a chosen area in an elaborate way. Such an analysis may bring about the evolution of new theories and concepts. The process of patent analysis considers the advantages, limitations, efficiency, and future scope for the application of a particular method, keeping in mind the upcoming technologies [32]. The study of patents is very useful in identifying the key mechanisms, analyzing the research gaps, recognizing the prominent researchers, understanding the global trends of patenting research, and knowing how the technology in a field progresses [33].

Patent publication trend

The patent publication trend for the electrochemical recycling of spent lithium-ion batteries is demonstrated in Fig. 4. There is a visible fluctuation in the patenting numbers over the period 2001 to 2017, but there has been a constant rise in the patenting trend in the electrochemical recycling of LIB trash after 2018 till date (Source: www.lens.org, data accessed on January 8th, 2025). This sharp increase in the number of patents after 2018 demonstrates the increased focus of researchers on developing novel techniques to explore LIBs as a secondary source of critical metals based on the principles of electrochemical metal recovery. Also, due to the sudden emergence of lithium-ion batteries as an efficient replacement for traditional fossil fuels, the tremendous amount of the resulting waste generation, and the ardent need to maintain the supply chain of scarce raw materials required for manufacturing these batteries, innovative green technologies, like the electrochemical process, must have received ample finances necessary for patent filling.

Fig. 4.

Patent publication trend on the electrochemical metal recovery.

Citation analysis

‘Citation count’ is a number that indicates how often a particular research document has been cited by others. It determines how much influence the work has made: the higher the citation count, the greater its impact in the area. It shows how crucial that work has been to other researchers.

Citation counts also measure the productivity of researchers and institutions. Citation analysis has been conducted using www.lens.org (data assessed on January 8th, 2025). The top 15 patents on the electrochemical recycling of spent lithium-ion batteries with maximum citation counts are discussed in Table 4.

Table 4.

Summary of top-cited patents on electrochemical recycling of S-LIBs.

Sr. No.	Title of the patent paper and citation	Description	Novelty/Advantage	Limitations	Reference
1	Method of making high-purity lithium hydroxide and hydrochloric acid (Citations −108)	Brine enriched with lithium was concentrated at pH 10.5 to 11 and refined to minimize the concentration of ions other than lithium to generate highly pure lithium hydroxide monohydrate. The brine was electrolyzed to lower the concentration of calcium and magnesium to <150 ppb, which produced chlorine and hydrogen as byproducts. The combustion of this chlorine gas in the presence of surplus hydrogen led to the production of hydrochloric acid, and the succeeding scouring of the concomitant gas with clean water crystallized the lithium hydroxide solution to give lithium hydroxide monohydrate crystals.	Obtaining a highly pure lithium hydroxide, especially for calcium and magnesium content, made this patent work novel. Obtaining lithium brines with a combined concentration of calcium and magnesium below 150 ppb appeared as a challenge in earlier methods.	i) The inclusion of multiple steps for removing contaminants such as boron, calcium, magnesium, and similar ions increased the complexity, cost, and time involved in the process. ii) The ‘pseudo zero gap’ configuration of the cell, specifically coated titanium and nickel electrodes, and the use of cation exchange membranes reduced the flexibility of the process and added to the initial cost. iii) The sensitivity of the membrane to impurities like Ca, Mg, and Fe cations, which may precipitate on it and reduce its competence and curtail the life of the electrolysis cell, may demand supplementary purification steps to control the composition of the brine. iv) For optimum results, the concentration of lithium in the brine should be 2–7 % by weight. Lower values would make the system uneconomical, whereas higher amounts may cause chloride to migrate across the membrane. v) The final product may contain some amount of undesirable chloride.	[34]
2	Active metal electrolyzer (Citations −29)	An electrolytic cell capable of electro-winning the ions of active material, such as lithium, from diverse materials, like reprocessed lithium and lithium-ion batteries and other industrial wastes, was designed. The preventive diaphragm of the electrolytic cell was steady against harsh solvents, inclusive of water, aqueous electrolytes, acid, base, and a gamut of protic and aprotic solvents. The membrane allowed the free transport of ions in and out of the cell, allowing the recovery of lithium from waste LIBs.	The method used a highly ionically conductive protective membrane next to an active metal cathode for electro-winning active metals from industrial waste and recycled batteries. This membrane kept the electrode isolated from hostile solvents and electrolytes even when the transport of ions occurred.	i) The use of a specialized, highly ionically conductive protective membrane may hinder the extensive use of this method. ii) Since this method was completely dependent on the protective membrane, any misfiring in its function might fully compromise the system. iii) Even though the patent mentioned that this process could work well at varying temperatures in aqueous as well as molten salt solutions, applications and material-oriented optimal temperature conditions should be determined.	[35]
3	Metal recovery method and dialysis device (Citations −24)	An easy recovery method for reclaiming metals in batteries was invented using a dialysis step during treatment. This step would require dialysis of the anode having lithium and a transition metal in a bath in the presence of an anion exchange film to selectively permeate lithium and an acid solution.	The method used an anion exchange membrane for recovering lithium ions from lithium-ion batteries as a solution to the conventional methods employing acid leaching, precipitation, solubility differences, and solvent extraction.	The efficiency of the process highly depended on the performance and stability of the anion exchange membrane used for metal recovery. Employing numerous steps such as dismantling batteries, identifying materials, leaching with acid, dialysis separation, and other proceeding steps to recover acids and metals complicated the process and made it costly. The acids used for leaching are usually corrosive mineral acids and need to be handled with care. Auxiliary steps may be required for separating lithium ions from other metal ions like cobalt. The efficiency of this method may vary with the composition of the battery. Hence, optimization would be needed for different types of batteries.	[36]
4	Processes and systems for preparing lithium carbonate (Citations −22)	A technique was developed to prepare lithium carbonate from lithium sulfate or bisulfate. A solution containing lithium sulfate and/or bisulfate was electrolyzed to transform at least some part of the ‘sulfate’ present in it into lithium hydroxide, which further formed lithium carbonate. For the reaction to occur, the pH was maintained at 1 to 4 throughout the electrodialysis.	i) Highly pure lithium hydroxide monohydrate was obtained from lithium-containing brine through purification of brine, pH adjustment, exchange of ions, and electrolysis. ii) Hydrochloric acid was also obtained as a byproduct. iii) A cathode protected from belligerent solvents was used for the electro-winning of metals like lithium from industrial wastes and used batteries. iv) An anion exchange membrane was used to specifically recover lithium ions.	i) The method involved complex purification steps, specifically a developed electrolytic cell having a protected electrode and a particular type of membrane. These factors limited its application. ii) The system was sensitive to impurities, showed potential chances of membrane fouling, and generated end products with some amounts of chloride in them, and also used hostile acids. iii) The efficiency of this process depended thoroughly on the stability of the membrane and its ability to retrieve metals from various sources. iv) The method may have different efficiencies and costs for different sources of metals.	[37]
5	Device and method for recovery or extraction of lithium (Citations −16)	This invention involved extracting lithium from a feed solution encompassing both lithium and non-lithium salts by concentrating lithium compounds and intermediary products employing a wide range of procedures. This approach explained how to use an inorganic Li-selective membrane or electrodialysis to escalate the concentration of lithium.	i) This method used an innovative inorganic membrane for electrodialysis that could selectively allow lithium-ion passage through it, thus solving the issue of non-lithium ions by restricting them. ii) A combination of different techniques was used to obtain highly concentrated lithium and eliminate impurities in multiple stages.	i) The use of lithium-ion selective inorganic membrane questioned the flexibility of this method. ii) Sodium and potassium ions present in the feed could reduce the efficiency of the membrane by blocking its pores. iii) Divalent and trivalent cations precipitate in alkaline solutions and may cause scaling and fouling of the membrane. iv) To safeguard the membrane from fouling, pre-treatments would be required to remove sodium, potassium, and divalent or trivalent cations, thus increasing the cost.	[38]
6	Process for the recycling of electrical batteries, assembled printed circuit boards, and electric components (Citations −15)	Batteries were pyrolyzed in a closed incinerator at 450 °C to 650 °C. The slag obtained after pyrolysis was filtered after being treated with water or diluted borofluoric acid. The filter cake so formed was diffused in a borofluoric acid solution, which served as an electrolyte for the electrolysis of the liquidized slag at low temperatures. The anode sludge and cathode sludge collected under both electrodes were used for metal regeneration.	Pyrolysis at a temperature between 450 °C and 650 °C, followed by the separation of products in the pyrolyzed slag through its electrolysis process, eliminated the requirement of initial sorting of the materials, which was an inevitable and expensive step in conventional recycling techniques.	i) Borofluoric acid is abrasive and perilous. ii) Temperature and pressure regulation is not only tricky but also energy-intensive. iii) The gaseous products emitted during this process need to be refined, thus making the process costly. iv) The electrochemical process does recover metals efficiently. But it may simultaneously lead to the generation of by-products needing extra treatment steps.	[39]
7	Selective reductive electrowinning apparatus and method (Citations −15)	An ion-conducting separator placed between the anode and cathode divided an electrowinning apparatus into anodic and cathodic chambers. An alkaline anolyte having a sacrificial reductant, an acidic catholyte with metal ions dissolved in it, and an electric current resulted in selective reductive electrowinning of metals present in the solution. The sacrificial reductant was oxidized at the anode.	i) A sacrificial reductant was used. ii) The high over-potential of water oxidation requires high cell voltages, making the conventional electrowinning processes for metal recovery expensive. The use of sacrificial reductant in a basic anolyte reduces the energy consumption. iii) Sacrificial reductant also reduces hydrogen production in the cathode chamber, which otherwise tampers with the quality and quantity of the recovered metal.	i) The method depends entirely on the availability and price of sacrificial reductants. ii) This technique works only for specific conditions of the electrolytic cell, temperature, and pressure.	[40]
8	A lithium-ion battery materials recycling method (Citations −9)	This process intended to reclaim lithium from used LIBs included a redox-targeting reaction of a waste LiFePO4 battery active material using [Fe(CN)6​]3− as a redox mediator in a large container to obtain lithium ions, disseminating the reacted redox solution into a cell to reprocess the redox mediator and allow the lithium ions to pass through a membrane towards a cathode. This cathode arrests the lithium ions in the form of LiOH via an electrochemical reaction	i) This method integrated leaching and separation into a single step, which developed more compact equipment and lowered the cost for reclaiming lithium or sodium from waste LIBs. ii) Less secondary waste generation was observed compared to the conventional methods of extraction, which involved multiple stages, required too many chemicals, and were less efficient at LiFePO4 extraction.	i) The use of membranes limits the use of this method. ii) Arrest of lithium ions on the cathode will reduce the life of the cathode, requiring it to be changed or regenerated after some time.	[41]
9	Electrolyte regeneration (Citations −9)	Spent electrolyte solutions containing metal ions were electrolyzed for metal recovery. The electrolysis cell incorporated an anode, a cathode that would absorb oxygen, and a cation exchange membrane positioned between the anode and the cathode to separate the anode and the cathode compartments. The electrolyte from spent LIB materials was poured into the anode section, thus forming an anolyte solution. An alkaline solution acted as a catholyte solution. An electric current flown through the cell lowered the concentration of the alkali hydroxide in the anolyte solution and improved its concentration in the catholyte solution.	i) This method used electrolysis for regenerating electrolyte solutions present in spent LIBs and successfully reclaimed precious electrolytic substances. ii) Particularly designed for regenerating electrolyte solutions of metal-air batteries. iii) Electrolysis in two stages boosted up the electrolyte regeneration.	Aluminium in spent electrolytes is usually present in the form of aluminates, isolating which from the electrolyte is challenging.	[42]
10	Electrochemically recycling a lithium-ion battery (Citations −4)	It suggested a technique for recovering the anode of a LIB electrochemically. Li-ions, an anode, and an oxidizing agent were integrated to produce a reaction mixture. The oxidizing agent maintained the n+ oxidation state of the metal (m) in the anode and electrochemically reduced the lithium ions to recharge the anode material.	i) A novel reactor was designed that included a specifically configured continuous-flow reactor. ii) The oxidation state of the metal was preserved. iii) The process specifically considered challenges associated with recycling some particular electrode materials, like NMC, LCO, and LFP, whose metal ion reduction may cause structural problems and reduce the process efficiency.	i) The method focused on electrochemically replenishing anodes only. ii) The efficiency of the process for metal recovery varied with the type of electrode material being recycled.	[43]
11	Method for coating metallic interconnect of solid fuel cell (Citations −4)	The patent considered a procedure for laminating a metallic interlink of a solid oxide fuel cell. A solution of cobalt compounds made from spent lithium-ion batteries was used to develop a preventive coating on the metal link. The application of this methodology increased the life and effectiveness of solid oxide fuel cells.	i) LiCoO2 from LIB anodes was used to produce a cobalt compound solution, later used for coating. ii) The method solves the issue of chromium volatization at high temperatures, which affects the productivity of the cell. iii) The method also prevents the oxidation of the metal interconnect at high temperatures. iv) Economic materials, like stainless steel, are used as the interconnect.	i) How effectively the cobalt coated on the metallic interconnect adhered to it depended on its structure and surface characteristics. ii) There may exist a friction between the coated layers and the metallic interconnect. This may influence the cell performance. iii) Cost-effectiveness for coating on a large scale is not described in detail. iv) Parameters such as the composition of the solution, current density, etc., greatly influence electroplating. The paper lacks optimization of these parameters.	[44]
12	Producing lithium (Citations −4)	This patent explains a method of regenerating lithium metal from lithium carbonate or other lithium salts. A lithium solution was prepared in sulfuric acid as a source of lithium ions for electrolysis. An anode was placed in contact with the lithium solution. A composite layer made of glass-ceramic substance and lithium-conducting electrolyte, capable of conducting lithium ions, was placed between the cathode and the lithium solution. An electric current would ionize lithium ions at the cathode, which would be removed from the solution with the help of the composite layer.	The method enabled continuous production of lithium using an aqueous acid electrolyte and a specifically designed cell structure, including a composite layer prepared with lithium-ion conductive glass (LI-GC) and a lithium-ion conductive barrier film (LI-BF) for separating the cathode and liquid electrolyte.	i) The paper talked about the materials required for producing the composite layer and its purpose. But it said nothing about the difficulties faced during its preparation. ii) Nothing was mentioned about the longevity of the composite layer. iii) The effectiveness of LI-GC and LI-BF in controlling the unnecessary reactions with the electrolyte must be discussed. iv) The energy efficiency of the process and the related functional costs need to be discussed. v) The rate at which lithium is produced and the scalability of the method also need to be specified. vi) The purity of the lithium obtained and the contaminants analysis are required.	[45]
13	Battery recycling with electrolysis of the leach to remove copper impurities (Citations −3)	This patent describes a procedure for recuperating transition metals from battery trash by using a leaching agent to form a leachate carrying disintegrated copper and unloading these copper adulterations as elemental copper on a cathode as a result of electrolysis of an electrolyte containing the leach.	The process involved employing a particulate deposition cathode for the elimination of copper impurities from a leached solution of batteries for reclaiming transition metals.	i) Absolute abolition of copper and other targeted noble metals may not be possible every time. ii) Additional purification steps might be needed, increasing the cost and complexity of the process. iii) Selective recovery of copper might be hindered by the co-deposition of other metals. iv) The speed of the process may vary with the configuration of the leach solution, cell structure, and operating conditions.	[46]
14	Preparation of lithium carbonate from lithium chloride containing brines (Citations −3)	Lithium carbonate was processed from brines rich in lithium chloride. Employing silica removal and recovery of lithium chloride was achieved. This lithium chloride produced lithium hydroxide in an electrochemical cell. Contact of lithium hydroxide with carbon dioxide generated lithium carbonate.	i) A pre-treatment step for silica removal from brine was employed. ii) Lithium chloride obtained from brine was supplied to an electrochemical cell for producing lithium hydroxide, which further gave lithium carbonate on contact with carbon dioxide.	i) Pre-treatment would add up to the cost of the process and also complicate it. ii) The quantity of lithium chloride captured would depend on the chemical make-up of brine, which will impact the quantity and quality of the ultimate yield. iii) The efficiency of the process would depend highly on the working of the electrochemical cell producing lithium hydroxide. This cell may pose obstacles like electrode fouling, membrane selectivity, and scalability. iv) Producing lithium carbonate particles of particular size and structure would require absolute control over the reactions. v) Wastes produced would need treatment before disposal.	[47]
15	Methods and compositions for isolation of copper group metals (Citations −2)	A novel technique for the reclamation of copper, nickel, cobalt, and other metals found in mine tailings, along with post-consumer wastes, was developed. On establishing contact between the source material and an extractant having amine, a solution containing a metal is produced, from which the metal is recovered.	The process used an amine-containing lixiviant for metal extraction from insoluble salts of mine tailings and ores through electrowinning, crystallizations, reduction, and extraction into an immiscible organic solvent.	i) Though copper is dissolved better than other metals present in the mine tailings, pre-treatment may lower the alkaline and alkaline earth metal content to obtain high-purity products. ii) The optimal quantity of lixiviant used may vary with applications, which might prove difficult to determine. iii) The paper did not analyze the challenges of scaling up the system and provided no discussion on the associated economics. iv) The aspects of energy consumption, lixiviant regeneration efficiency, waste management, and their impacts on project cost are not mentioned. v) The long-term impacts of using amine-containing lixiviants on soil and water need to be studied in detail.	[48]

This analysis of 15 top-cited patents using lens.org throws light on the variety of ways in which electrochemical techniques have been used for LIB recycling. Though each application differs from the other in one way or the other, they also struggle with common issues like complexity in the process, membrane fouling, and handling deleterious chemical wastes. For achieving sustainability and developing economically viable recycling methods, emphasis must be given to obtaining high-purity products, waste minimization, and improving energy efficiency. It is necessary to work on overcoming the limitations observed in the current techniques to have a successful large-scale application of these technologies and promote a circular economy for lithium-ion batteries.

Review of recent patents

A study of recent patent papers gives a clear idea of the latest technologies developed in a particular domain. It brings forth the novelties adopted by different researchers, which can form the base of future research. The study of recent patents is very useful for understanding the existing intellectual property scenario, which is indispensable for circumventing violations of research ethics and recognizing prospective licensing opportunities. Table 5 summarizes the most recent patent papers on the electrochemical recycling of spent LIBs.

Table 5.

Summary of most recent patents on electrochemical recycling of S-LIBs.

Sr. No.	Title of the patent paper and year of publication	Description	Novelty/Advantage	Limitations	References
1	System and Method of Selective Electrodeposition for Metal Recycling (2024)	A working liquid with two metal species was introduced in an electrochemical cell having working and counter electrodes coated with polyelectrolyte and a concentrated salt that would enable the formation of complexes of opposite charges. A cathodic potential would encourage the selective electrodeposition of a targeted metal species. This method produces an electrodeposit of the target metal with a higher molar ratio as compared to the original fluid.	This process used a working electrode laminated with a positive polyelectrolyte and a highly concentrated (>1 M) salt for selective metal electrodeposition. The method formed complexes of metal ions with opposite charges, allowing the isolation of metals having identical electrochemical characteristics.	i) A highly concentrated electrolyte salt used to attain selectivity could take up more energy and lead to corrosion inside the cell. The paper didn't address this. ii) The positive polyelectrolyte coating on the working electrode provides stability and durability under electrochemical reactions and high concentrations of salt. The paper does not delve into the time of degradation or replacement. iii) Optimization of factors like applied potential, salt type, concentration of the salt, etc., for varying types of metals would be essential in future applications. iv) The experiments done were on a small scale. Industrial-scale application would require improved electrode structure, electrolytes, and a complete study of system efficiency.	[49]
2	Monovalent Anion Selective Membrane Enabled by High Concentration Brine (2024)	The paper addresses paths of refining the monovalent selectivity of anion exchange membranes in highly saline brines for lithium recovery. High salinity solutions enhance the selectivity of monovalent negative ions, which is important in direct lithium extraction (DLE), chlor-alkali production, and sea salt harvesting	The high salinity of the solution boosts the monovalent anion selectivity of a regular anion exchange membrane over multivalent anions with no further modifications of the membrane. This system finds application in solutions with high total dissolved solids (TDS) where the solids can be hurdles for other separation techniques, for instance, for the removal of lithium from brines.	i) Used highly concentrated brines only (TDS>5 %) to get the expected selectivity of monovalent anions, thus reducing their applicability. ii) The paper discusses little about how the membrane could be stable and durable in such high salinity. iii) Optimizing the selectivity would need tuning several parameters like the material of the membrane, operating conditions, and chemical composition of the solution. iv) Naturally obtained brines have extremely divergent configurations. Based on their chemical makeup, the method may work differently.	[50]
3	Energy Reclamation and Carbon-Neutral System for Critical Mineral Extraction (2024)	This green battery recycling system reclaimed and refined critical alkali metals, especially lithium, from a feed solution, employing a solid electrolyte membrane and electrodes positioned in redox configuration. The energy spent initially for the extraction was electrochemically stored and recuperated in succeeding stages. These reduced energy losses made powering the system by renewable energy possible. At least 99 % pure lithium carbonate/lithium hydroxide/refined lithium was obtained.	i) The method integrated a solid electrolyte membrane with electrodes in a redox disposition to reclaim lithium and also the energy spent during initial recovery. ii) The system used locally produced renewable energy.	The success of the method depended primarily on the efficiency of solid electrolyte membranes and electrodes.	[51]
4	Process for the Production of Lithium Metal or an Alloy Thereof or for the Pre-lithiation of an Electrode Material (2024)	This work represented a technique of producing lithium or its alloys and for the pre-lithiation of electrode substances using an electrolysis cell. An electrolysis cell having relithiated intercalation material in the form of an anode was employed in this procedure. A lithium salt acted as the electrolyte.	The utilization of a relithiated Li intercalation material as an anode for electrolysis to obtain lithium or its alloys, and similarly for pre-lithiation of electrode materials, was the innovation of this process.	i) The discharge capacity of the Li electrodes fabricated by this system diminished on cycling, questioning their longevity. ii) Instability was detected at the interface between the electrodes and the electrolyte. iii) A particular current density was used, which may limit the efficacy of the process. iv) For different collectors, like nickel, brass, and silver-plated copper, results varied, suggesting that for different materials, the system may respond differently.	[52]
5	A Recycling Method for Recovery of Lithium from Materials Comprising Lithium and one or more Transition Metals. (2024)	This patent was about reclaiming lithium from media having lithium and transition metals. The sample was leached with an organic acid, like formic acid, to form organic lithium salt (lithium formate), which was electrolytically transformed into inorganic lithium hydroxide or lithium carbonate.	i) Use of organic acid (formic acid) for leaching lithium-containing medium ii) Electrolytic conversion of organic lithium salt (lithium formate) into inorganic lithium salt (lithium hydroxide or lithium formate)	i) Leaching conditions have a considerable effect on the leaching efficiency and selectivity of Li over other metals, demanding further processing steps. ii) Electrolysis for converting organic lithium salts into their inorganic forms requires cautious control and optimization to minimize acid and energy consumption. It also involves electrode degeneration and the requirement of ion-selective membranes. iii) Multiple steps of leaching, purification, solvent recovery, electrolysis, etc., increase the complexity of the process and, consequently, the associated capital and operational costs. iv) The liquid waste generated needs processing before disposal.	[53]
6	Processes for Preparing Hydroxides and Oxides of Various Metals and Derivatives Thereof (2024)	A reaction between a metal sulfate and lithium hydroxide formed a metal hydroxide and a solution of lithium sulfate. An electromembrane treatment reclaimed lithium hydroxide from the solution of lithium sulfate, while the metal hydroxide was further treated with lithium hydroxide before being heated to give the desired metal oxide having Ni, Co, Mn, Li, and Al.	i) The electromembrane process was used for the regeneration of lithium hydroxide from lithium sulfate and its further reuse in producing metal oxide. ii) Reuse of LiOH eliminated the requirement of additional steps for waste minimization. iii) The metal oxides produced had the key metals for battery manufacturing (Ni, Co, Mn, Li, & Al). iv) Using an electrochemical process makes the system more economical and environmentally friendly.	i) Too many steps increased the complexity of the method, challenging large-scale applications. ii) The energy-intensive electromembrane process impacted the economy of the method. iii) Membranes usually lead to membrane fouling and increase maintenance costs. iv) The recovery of expensive chelating agents, which may increase the cost and environmental impact, should also be considered. v) Additional efforts would be needed to control reaction conditions vi) The method focused on recycling lithium only, ignoring other stuff in the waste stream.	[54]
7	Lithium-ion Battery Materials Recycling Method (2024)	The technique used a redox-targeting reaction to reclaim Na and Li ions from the active components of Na and Li batteries. Na and Li ions were produced by dissolving the active battery material into a redox solution, which was subsequently shifted to a redox flow cell to make the lithium ions diffuse through the membrane, and the redox mediator was revived. These ions were arrested to give LiOH.	i) Reduced use of concentrated acids and harsh chemicals, ideally employed in hydrometallurgical processes, minimized the generation of secondary waste. ii) The issues faced by conventional methods for recovering lithium from salts (like LiPO4) insoluble in acids were overcome. iii) Simplified the processes by merging leaching and separation.	i) Multiple tanks, a redox flow cell split into anode and cathode sections by ion exchange membranes (IEMs), pumps, and pipes, made the system complicated, questioning its scalability and economy. ii) The dependency on distinct redox mediators for leaching and conveyance of Li ions raised concerns about their availability, price, and firmness. iii) The efficiency and stability of IEMs would also matter. iv) The kinetics of reactions and the energy absorbed may influence the effectiveness and price of the process.	[55]
8	Electrochemical Membrane Apparatus Including an Electrochemical Membrane Reactor and Related Methods (2024)	Salts containing Li, Cu, Al, Ni, Mn, Fe, and Co are leached into a solution before applying an electric current through it in an electrochemical membrane reactor. The applied current regulates the pH of the solution and coats copper on the cathode, enabling the filtering of Al and Fe from the leaching solution. Co, Mn, and Ni are further reclaimed from the liquid.	i) The electrochemical membrane reactor enhanced the recovery of Ni and Co against the conventional precipitation techniques. ii) The elimination of Al and Fe and the recovery of Co, Mn, and Ni were integrated into one step. iii) The electrochemical adjustment of the pH reduced the use of bases. iv) Applicable for solutions of divergent precious metal sources, like spent LIBs and mine tailings	i) The setup of the electrochemical membrane reactor was complicated, posing difficulty in large-scale application. ii) The partition of electrodes and the method's effectiveness depended on the membrane's function and stability. iii) Factors like energy consumption and electrode efficiency were some constraints.	[56]
9	Method for Producing High-Purity Lithium Hydroxide Monohydrate (2024)	Highly pure lithium hydroxide monohydrate (LiOH.H2O) was produced from solutions containing Li2SO4, LiCl, Li2CO3 individually or in combination using membrane electrolysis with a cation exchange membrane and nickel-coated stainless-steel electrodes. The catholyte was pulled out to give LiOH.H2O crystals on evaporation, where some spent washing solution is fed. The return flow of the anolyte is replaced with a concentrated solution of lithium salt made from the original lithium salt.	i) The method introduced 3 unconventional salts: Li2SO4, LiCl, and Li2CO3, and their mixtures as sources for metal recovery. ii) Ni-coated stainless-steel cathodes avert corrosion through hydrogen absorption, improving the electrolysis. iii) Recycling of spent catholyte, rich in NaOH and KOH, generates solid Li2CO3 and LiHCO3, reducing waste and reclaiming valuable by-products. iv) Reusing spent wash from washing LiOH.H2O crystals as a basic reagent to pre-treat lithium salts minimized waste and additional reagents. v) The method suggested solutions to use the co-products obtained in the cathodic and anodic sections.	i) Multiple steps (membrane electrolysis, chemical separation, ion exchange, evaporation, crystallization, recycling spent liquids) complicated the process and questioned its large-scale applicability. Controlling, optimizing the process, and maintaining purity could be a challenge. ii) Electrolysis is fundamentally an energy-intensive process. iii) Membranes, prone to fouling, require cyclic replacements, escalating operational costs. iv) The availability, cost, and safe handling of the chemicals used played a significant role in the effective operation of the process.	[57]
10	Process for Recovering Metals from Recycled Rechargeable Batteries (2024)	Hydrobromic acid (HBr) was used to leach spent lithium-ion batteries for hydrometallurgical recovery of metals. Elemental bromide, a byproduct of leaching, was chemically removed from the soluble metal bromide salts formed from leaching. The insoluble substances in the leachate were eliminated to give a solution rich in metal, from which metal/s were separated.	i) HBr showed better metal leaching than the conventionally used HCl, especially for Mn-containing cathodes. ii) The byproduct bromine was arrested in an alkaline solution to give bromate, later used as a means of oxidation for precipitating divalent metals such as Mn. iii) Multiple techniques, like precipitation and electrodeposition, offer flexibility by enabling the removal of multiple valuable metals such as Li, Co, Ni, and Mn.	i) HBr is highly corrosive and hazardous. ii) The elemental bromine generated is noxious and volatile. iii) Too many steps (leaching, separation, precipitation, electrodeposition) make the process complex. iv) The method requires maintaining a particular range of temperature for leaching. This, along with electrodeposition, makes the process energy-intensive and expensive. v) Chemicals used like NaOH, dimethylglyoxime, etc., are expensive and add up to waste generation.	[58]
11	Electrochemical Lithium Recovery System (2024)	In this electrochemical system of lithium recovery, a first flow electrode module selectively separated Li ions from the spent battery solution, and a second flow electrode module then recovered them. The process was independent of high temperatures and huge quantities of chemicals and offered high recovery efficiency.	i) The first flow electrode module used electrical attraction for the selective extraction of Li ions, while the second flow electrode module reclaimed Li ions through electric repulsion. ii) The design of the system enabled Li recovery without heat and excessive use of chemicals. iii) Application of MnO as a flow electrode enhanced the selective absorption of Li ions. iv) Two-electrode flow modules facilitate continuous Li extraction and recovery. v) The sulfuric acid used for leaching was also recovered.	i) Other ions may interfere with the selective recovery of Li ions. ii) Membrane fouling associated with ion exchange membranes may reduce their efficiency and lifespan. iii) The flow electrodes would degrade periodically, deteriorating their performance. iv) The need to regulate flow rates, pH, and concentrations of the solutions could be tricky. v) Investment and operational costs were not discussed.	[59]
12	Methods and Devices for Electrochemical Relithiation of Lithium-ion Batteries (2024)	The battery electrode was treated with one of the solvents (acetone, diethyl carbonate, isopropyl alcohol, and propylene carbonate) before relithiation. Sometimes, a device like a film roller was employed. The electrode was connected to the rollers, uncoiled, and immersed in a liquid having electrolytes. Then, the electrode was electrically relithiated.	The treatment of electrodes with solvent before the electrochemical relithiation was the novelty of this process.	i) Multiple steps add complexity to the process. ii) Dependency on solvents may pose environmental and safety apprehensions regarding manoeuvering, disposal, and possible residual contamination. iii) Large-scale and industrial application of this roll-to-roll relithiation may be challenging. iv) The process may be distinctly efficient for different electrode materials, making optimization necessary for different battery chemistries. v) Electrochemical relithiation consumes a large amount of energy.	[60]
13	Process for Production of Refined Lithium Metal (2023)	Refined lithium was obtained by electrowinning a lithium feedstock, which initially gave crude lithium. An alloy rich in lithium was prepared by mixing this crude lithium with another carrier metal. An electrorefining system produced pure lithium and a lithium-free alloy by separating the carrier metal from it. This alloy was further recycled to use at least one part of it as a carrier metal in next stages.	Electrowinning to obtain crude lithium metal from lithium feedstock, adding a carrier metal to it to form an alloy rich in lithium, and electrorefining the alloy to extract pure lithium out of it and an alloy free from lithium to be used in further steps as a carrier metal.	i) Electrowinning, alloy making, electrochemically refining Li, & recycling the alloy may complicate the process regulation & optimization. ii) Electrowinning & electrorefining need excessive energy, rendering this method uneconomic & environmentally unsustainable. iii) The highly reactive Li, crude or alloy, necessitates safety protocols & specific tools. iv) The electrorefining's effectiveness depends on the electrolyte's stability & minimizing side reactions, which could be challenging. v) Choosing the right carrier metal is crucial; failure may lead to losses & increased cost. vi) Design of electrode, current density, and mass shifting might challenge the scalability.	[61]
14	Novel Systems and Methods of Reductive-Acid Leaching of Spent Battery Electrodes to Recover Valuable Materials (2023)	The hydrometallurgical method used SO2 and H2SO4 for reductive-acid leaching to extract precious metals from waste lithium-ion battery electrodes. From the leachate formed, Li, Co, and Ni could be separated employing precipitations, oxidation, and electrowinning. Apart from the leachate, the reductive-acid leaching also produced a bulk solid graphite.	i) Employed reductive-acid leaching to recover precious elements (Li, Co, Ni, Mn, & graphite) from electrodes of used LIBs. ii) Li separation in an initial step, succeeded by recovery of other precious metals, enhanced the productivity. iii) High concentrations of Mn, which may impede the electrowinning process, were addressed through reductive-acid leaching iv) Aimed to achieve zero discharge by recycling acid solutions and other by-products formed during the process.	i) The varying composition of the black mass needed a highly adaptive process to achieve constant efficiency and recovery rates. ii) Effective Mn removal was necessary to avoid fouling of the anode during electrowinning. iii) Corrosive chemicals used, like H2SO4 and SO2, needed skilled handling and were responsible for the formation of concentrated waste streams needing proper treatment before disposal. iv) Electrowinning was energy-intensive, and acid leaching affected the environment. v) Inclusion of multiple steps (leaching, precipitation, electrowinning, etc.) and the need to maintain crucial parameters (temperature, pH, etc.) made the process complex.	[62]
15	Process to Produce Lithium Compounds (2023)	Lithium phosphate was obtained from a lithium source by concentrating the source with an ion exchange sorbent. This concentrate was reacted with phosphate anions to produce lithium phosphate, which was later transformed into lithium hydroxide or lithium 5 carbonate by reacting with calcium hydroxide or by electrolysis.	i) Using ion exchange sorbent improved the selective recovery of Li as compared to conventional methods. ii) Specific pH levels and molar ratios of acid to Li were maintained at the time of desorption to avoid damaging the sorbent. iii) Precipitation of lithium phosphate facilitated the isolation of Li from other metals (ions). iv) Electrolysis was used to transform lithium phosphate into lithium hydroxide. v) The phosphoric acid used could be recycled during electrolysis.	i) Concentrated acids lead to the degradation of the sorbent during desorption. ii) Protecting the sorbent required dilute acids, while efficient Li recovery needed concentrated acids. Balancing this was a challenge. iii) An additional step was required to eliminate multivalent ions, adding to the cost and complicating the process. iv) For the method to be effective, Li concentration had to be 2000 to 3000 ppm. v) Precipitation of lithium phosphate occurred only under proper temperature and pH control. vi) Waste streams produced required additional treatment, making the system expensive.	[63]

This analysis of the 15 most recent patent documents on electrochemical techniques for LIB recycling gives knowledge of the latest developments in the field of electrochemical metal recovery from spent LIBs. It has been observed that despite coming up with some advantages over earlier methods, each of these systems faces some common hurdles while achieving a completely effective and sustainable metal reclamation. Concentrated acids used for leaching do show better results, but also lead to the generation of highly corrosive waste streams. Inclusion of too many steps increases metal recovery, as well as the cost complexity of the process. Using membranes for the ionic separation renders the process completely dependent on the effectiveness, durability, and ability of the membrane to work under extremely saline conditions, as usually found in natural brines. Membrane fouling is another critical issue to be dealt with. Also, the electrochemical process is an energy-intensive method and requires a detailed study of kinetics to understand the rate and flow of reactions. Implementing the electrochemical process for metal recovery requires careful consideration along multiple dimensions, including large-scale feasibility, large amounts of electrolytes consumed, membrane design to reduce fouling, the design of membrane configuration to give optimum removal of desired metals, and recognizing the techno-economic assessments [64]. Adopting subtractive transformation of cathode materials prior to the selective extraction of target metals from depleted battery materials—potentially via electrochemical means—there is a potential benefit of foregoing the introduction of additional raw materials, as would normally be the case with direct recycling methods [65]. Modification in the design of the electrochemical reactor can also result in improved metal recovery [66]. Development of closed-loop systems also needs to be considered, where solid waste and/or wastewater can be recycled and reused [67]. Compared to traditional lithium-ion batteries, all-solid-state lithium-metal batteries (ASSLMBs) provide many benefits, especially in terms of safety and energy density. But the market advocacy of ASSLMBs depends on investigating and developing sustainable recycling pathways and acknowledging avenues for the recovery of critical materials [68]. These points can form the base of future research in the concerned area.

Techno-economic aspect of electrochemical recycling

In the year 2023, the average price of a lithium-ion battery hit USD150 per kWh, and manufacturing costs increased by 5 %, mainly as a result of higher materials and electricity expenses [69]. Rising import prices for essential elements like lithium, nickel, and cobalt have a pronounced effect on the cost to produce EV batteries. The continued increase in battery costs has also resulted in an increased demand for battery recycling practices. Good recycling practices can help reduce the estimated need for costly imported raw materials [70]. Recycling can prevent potential shortages of valuable minerals from an economic viewpoint and mitigate the reliance on mining in specific areas [71]. Rapidly expanding electric vehicle adoption has created enormous opportunities in battery recycling, as well as employment opportunities [70].

The battery recycling industry offers significant potential for direct economic benefits; however, it faces a number of significant challenges. Recycling requires substantial capital investment in establishing recycling facilities, but the technological and regulatory investment costs are too high, and this deters SMEs from engaging with the industry [72]. The lack of sufficient infrastructure for lithium-ion battery (LIB) recycling, combined with the large costs to create facilities capable of safely recovering valuable materials, continues to create significant barriers for the growth of the recycling sector [73]. It is imperative that battery reprocessing firms act decisively and commit resources to advanced technologies, and collaborate with manufacturers to create smooth, end-to-end battery lifecycles [74]. The economic feasibility studies of large-scale recycling techniques suggest that the hydrometallurgical method, which electrochemical recycling happens to fall under, can be one such economically and environmentally sound process. Fig. 5 establishes a percentage-wise comparison between the cost and the possible environmental impact occurring as a result of using hydrometallurgically recycled materials over virgin materials. Based on the data from the report “Decoding the Economic Viability of Lithium-Ion Battery Recycling”, of the year 2023, Figs. 5, 6, and 7 depicts the comparative cost and environmental impact of virgin materials and recycled materials, capital cost breakdown, and operational cost breakdown at recycling plants, respectively [71].

Fig. 5.

Comparative cost and environmental impact of virgin material vs using recycled battery material from hydrometallurgical recycling for NMC111 battery.

Note: SO_x – Sulphur Oxide NMC111 – Nickel-Manganese-Cobalt oxide

Fig. 6.

Capital Cost Breakdown.

Fig. 7.

Operational Cost Breakdown.

The total recycling cost of lithium-ion batteries involves adding together eight crucial parameters: depreciation, the cost of new battery materials, environmental treatment of waste, auxiliary machinery, electricity, manpower, maintenance, and tax [75]. Presently, the cost of recycling LIBs is about US$26 per kilowatt-hour (kWh) [76]. The cost at recycling plants can be broken down into capital cost and operational cost. Fig. 6 shows a further breakdown of the capital cost of recycling. Whereas Fig. 7 elaborates on the percentage breakdown of indirect costs.

Apart from techno-economic advantages, electrochemical recycling of LIBs also has some intangible benefits such as increased resource security through a reduction in dependence on foreign mining, and environmental sustainability through increased commitment to it by means of reduced pollution and a circular economy.

Conclusion

The patent analysis indicates that the electrochemical process offers a promising solution to tackle the issues of environmental degradation and resource management arising from improperly discarded spent lithium-ion batteries (S-LIBs). The escalation in patent publications, specifically after 2018, reflects the acceptance of electrochemical methods for the recovery of critical metals from S-LIBs, serving as a milestone toward achieving a circular economy. This can minimize our reliance on primary resources and attenuate the environmental scarring linked with inappropriate battery waste disposal.

The study of highly cited and most recent patents exhibits the principal constraints to be overcome to ensure the pragmatic and sustainable application of electrochemical recovery methods. Complexity of multiple elements, membrane fouling, highly concentrated waste streams, and the need for better energy efficiency being some of these common constraints. Establishment of an economically competent and environmentally benign recycling process needs to resolve these limitations. The research and development in the coming days need to emphasize designing simpler mechanisms, obtaining high-purity substances from recycling activities, and minimizing waste production.

To deal with membrane fouling, constant revolution in materials science and engineering is required to come up with strong and selective membranes. Optimization studies can find out the most efficient designs for electrochemical cells. Collaborative efforts by researchers, industry partners, and policymakers are required to transform the potency of electrochemical recycling techniques into practical solutions for resource recovery. Ultimately, conquering the above limitations will open the doors for the wide-scale implementation of electrochemical recycling of S-LIBs, thus promoting circular economy and sustainability.

Ethics statements

The present work does not involve any data collected from social media platforms.

Supplementary material and/or additional information [OPTIONAL]

None.

CRediT authorship contribution statement

Sayali Apte: Conceptualization, Supervision, Writing – review & editing. Aparna Mukherjee: Writing – original draft, Data curation. Preeti Mishra: Writing – review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.