Potential regulation strategy of molar ratio and solid-state sintering temperature on regeneration of spent lithium nickel manganese cobalt oxides (NMC 111) cathode

Abstract

Lithium-ion batteries (LIBs) are extensively utilized for energy storage due to their high energy density, minimal memory effect, low self-discharge rates, and excellent cycling stability. Approximately 180.000 tonnes of LIBs have been utilized, with nickel batteries representing 40 % of the overall consumption. Addressing the issue of accumulated battery waste is crucial, particularly regarding the challenges presented by nickel manganese cobalt (NMC) cathode waste. Therefore, this study proposes the use of a solid-state sintering method to regenerate the decomposed cathode material of lithium nickel manganese cobalt oxide (LiNi_0.3Mn_0.3Co_0.3O₂) from LIBs. LIBs are regenerated through the addition of lithium doping, allowing the structure to revert to its original state with lithium carbonate serving as the lithium source. The regeneration process is conducted by incorporating lithium along with its transition metal ratio (Li/TM = 1.05:1; 1.10:1; 1.15:1; 1.20:1) and varying the sintering temperature (700 °C, 750 °C, 800 °C, and 850 °C). The findings demonstrate that configurations featuring a Li/TM ratio of 1.10 and a sintering temperature of 800 °C show optimal electrochemical performance, achieving a discharge capacity of 124.87 mAh/g at 0.1C and 111.59 mAh/g at 0.5C, along with a capacity retention of 94.7 % after 50 cycles. This outcome demonstrates reduced efficiency and emissions as a result of the process's brief duration and absence of ion extraction. The NMC recycling process serves as an important mechanism for quality control.