Low-energy and green in situ recycling of spent lithium-ion batteries to achieve graphite regeneration and pre-lithiation

Abstract

The cyclic regeneration of non-renewable graphite anode materials in lithium-ion batteries (LIBs) is crucial for battery recycling, aiming to reduce carbon footprints and minimize resource waste. Traditional methods often involve high energy use and significant environmental pollution. To tackle this, a green, closed-loop regeneration method using only oxalic acid was developed. This approach efficiently recovers precious metals from the anode and allows for in situ regeneration of the spent anode, as well as the synthesis of pre-lithiation reagents. The findings indicate that lithium oxalate on the surface of pre-lithiated regenerated graphite compensates for active Li⁺ loss and acts as a pre-lithiation sacrificial salt during battery operation. It also decomposes to release carbon dioxide, preventing the formation of soluble lithium alkoxides and electrolyte ester exchange reactions, significantly enhancing battery performance without leaving impurities. This method allows effective lithium utilization from spent anodes and in situ closed-loop regeneration. Under optimal conditions, the Li⁺ leaching rate reaches 97.64%. The electrochemical performance of the regenerated prelithiated graphite maintains a high specific capacity of 320.5 mAh g⁻¹ after 200 cycles, with a specific capacity retention rate of 90.4%. Environmental and economic assessment shows an outstanding economic profit of $3259.22 and a negligible environmental footprint for recycling each ton of retired graphite. This work advances material recycling, reduces the environmental impact of waste batteries, and supports a low-carbon transition.