Summary of the leaching systems for metals recovery from spent LCO batteries.

Spent materials	Leaching reagents	Reaction conditions			Leaching efficiency (%)	Ref.
		Temp. (°C)	S/L ratio (g L−1)	Time (min)
LCO	2 M H2SO4 + 5 vol% H2O2	75	100	30	Li = 94, Co = 93	23
	2 M H2SO4 + 8 vol% H2O2	70	20	60	Li = 99, Co = 99	24
	2 M H2SO4 + 5 vol% H2O2	80	50	60	Li = 99, Co = 99	25
	1 M H2SO4 +0.075 M NaHSO3	95	20	240	Li = 97, Co = 92	26
	0.23 M H2C2O4 + 3.6 vol% H2O2	100	15	180	Li = 91, Co = 97	27
	2 M citric acid + 0.6 g g−1 H2O2	90	15	30	Li = 100, Co = 91	28
	0.1 M citric acid + 0.02 M ascorbic acid	80	10	360	Li = 100, Co = 80	29
	57.8 vol% lemon juice + 8.07 vol% H2O2	60	9.8	45	Li = 100, Co = 96	30
	2 M l-tartaric acid + 4 vol% H2O2	70	17	30	Li = 99, Co = 96	31
	1.5 M succinic acid + 4 vol% H2O2	70	15	40	Li = 96, Co = 99.5	32