Upcycling of spent LiMn2O4 cathode towards sodium-ion battery cathode through molten salt electrolysis approach

Abstract

Recycling and valorizing spent lithium-ion batteries (LIBs) are requisite to achieve resource sustainability and environment safety. Herein, we reported a molten salt electrolysis method to recycle degraded LiMn2O4, synergistically achieving the selective leaching of lithium (Li) and high-valued reutilization of manganese (Mn). In molten Na2CO3-K2CO3, 94.3 % of Li from LiMn2O4 was released into molten salt by the electrolysis at 1.2 V for 7 h, while in-situ forming Na0.55Mn2O4⋅1.5H2O. During the electrolysis, LiMn2O4 at the cathode was electrochemically decomposed to Li2O and manganese oxide, accompanied by the reaction of resultant Mn oxide with Na2CO3 salt to generate Na0.55Mn2O4⋅1.5H2O. Finally, Li2CO3 in molten salt can be selectively extracted by water leaching. The obtained Na0.55Mn2O4⋅1.5H2O material as a sodium-ion battery (SIB) cathode delivers a discharge specific capacity of 58.9 mAh g−1 at 100 mA g−1, showing good cycle performance with a capacity retention of 93.9 % after 100 cycles. Hence, molten salt electrolysis achieves both extraction of Li and high-value reutilization of Mn, offering an electricity-driven materials separation, recovery, and reutilization with reduced environmental impact.