Fig. 3. Strategies to solve the issues in stage 1.
(A) Shear thickening electrolyte. Top: For normal electrolyte, mechanical impact can lead to battery internal shorting, causing fires and explosions. Bottom: The novel smart electrolyte with shear thickening effect under pressure or impact demonstrates excellent tolerance to crushing, which could significantly improve the mechanical safety of batteries. (B) Bifunctional separators for early detection of lithium dendrites. Dendrite formation in a traditional lithium battery, where complete penetration of the separator by a lithium dendrite is only detected when the battery fails because of an internal short circuit. In comparison, a lithium battery with a bifunctional separator (consisting of a conducting layer sandwiched between two conventional separators), where the overgrown lithium dendrite penetrates the separator and makes contact with the conducting copper layer, resulting in a drop in VCu−Li, which serves as a warning of impending failure due to an internal short circuit. However, the full battery remains safely operational with nonzero potential. (A) and (B) are adapted or reproduced with permission from Springer Nature. (C) Trilayer separator to consume hazardous Li dendrites and extend battery life. Left: Lithium anodes can easily form dendritic deposits, which can gradually grow bigger and penetrate the inert polymer separator. When the dendrites finally connect the cathode and anode, the battery is short-circuited and fails. Right: A layer of silica nanoparticles was sandwiched by two layers of commercial polymer separators. Therefore, when lithium dendrites grow and penetrate the separator, they will contact the silica nanoparticles in the sandwiched layer and be electrochemically consumed. (D) Scanning electron microscopy (SEM) image of the silica nanoparticle sandwiched separator. (E) Typical voltage versus time profile of a Li/Li battery with a conventional separator (red curve) and the silica nanoparticle sandwiched trilayer separator (black curve) tested under the same conditions. (C), (D), and (E) are reproduced with permission from John Wiley and Sons. (F) Schematic illustration of the mechanisms of the redox shuttle additives. On an overcharged cathode surface, the redox additive is oxidized to the form [O], which subsequently would be reduced back to its original state [R] on the surface of the anode by diffusion through the electrolyte. The electrochemical cycle of oxidation-diffusion-reduction-diffusion can be maintained indefinitely and hence locks the cathode potential from hazardous overcharging. (G) Typical chemical structures of the redox shuttle additives. (H) Mechanism of the shutdown overcharge additives that can electrochemically polymerize at high potentials. (I) Typical chemical structures of the shutdown overcharge additives. The working potentials of the additives are listed under each molecular structure in (G), (H), and (I).