Lithium (Li) metal is widely recognized as a highly promising negative electrode material for next-generation high-energy-density rechargeable batteries due to its exceptional specific capacity (3860 mAh g −1), low electrochemical potential (−3.04 V vs. standard hydrogen electrode), and low density (0.534 g cm −3).
In the presence of sufficient lithium, Li + can occupy the vacancies in the spent cathode material through the action of an electric current, bringing the Li content back to the original level. In the repair process, electrolyte concentration and current density affect the repair effect [161, 162].
Currently, the recycling of waste lithium battery electrode materials primarily includes pyrometallurgical techniques [ 11, 12 ], hydrometallurgical techniques [ 13, 14 ], biohydrometallurgical techniques [ 15 ], and mechanical metallurgical recovery techniques [ 16 ].
Cathode materials for power lithium batteries usually require pretreatment before direct repair, which includes discharge, disassembly and separation of the spent cathode materials (Fig. 1 a). Since direct repair is based on the structure of the original cathode material, the pretreatment process needs to avoid any damage to its crystal structure.
Lithium ions are embedded in the spent materials under the action of electric current. The capacity of spent materials after electrochemical repair is low (Table 3), which is likely to be due to the SEI film on the surface of the spent materials hindering the replenishment of Li, and lithium defects have not been completely repaired.
The waste lithium-ion battery electrode materials used in this study were procured from the electronic market. The obtained lithium-ion battery electrode powder underwent sieving with a 100-mesh sieve to eliminate impurities like battery plastic packaging.