Strategy for Efficient Recovery of NCM Materials by the Reagent-Free Method: Green Recovery of Lithium and High-Value Byproducts through Capacitive Deionization Reverse Applications

The traditional lithium-ion battery (LIB) recycling method is inseparable from the application of chemical reagents such as acid and alkali, so efficient and green valuable metal recovery technology is invaluable. Moreover, the current development of environmentally friendly capacitive deionization (CDI) has been limited by the field of desalination. This work proposes a reagent-free method for the efficient recovery of spent LIB cathode materials, which realizes the green recovery of lithium by leaching lithium ions into the ultrapure water through CDI reverse application. Lithium ions in the leaching solution can be recovered by evaporation crystallization in the form of LiOH·H2O. Studies have shown that the CDI leaching process has a unidirectional selectivity for Li+. The leaching capacity of lithium in LiNixCoyMn1–x–yO2 (NCM) materials can reach 42.95 mg/g, but the leaching capacity of other metal elements (Ni, Co, and Mn) was 0 mg/g. The lithium content in the recycled cathode material after the CDI experiment was reduced by 90%, which can be used as a precursor for the preparation of fresh NCM materials. Meanwhile, under the action of current and voltage, the arrangement of bulk graphite crystals in the anode electrode after the experiment changes from disordered to orderly layered, which can be reused in the CDI system or as a high-value prelithium graphite for the production of fresh batteries. This work expands the new application field of CDI and realizes the green recycling of spent LIB cathode materials without using any acid or alkali reagents, which is conducive to the sustainable development of the environment.