Sustainable and facile synthesis of high-performance nitrogen-doped carbon/graphene@LiFePO4 cathode materials from spent LiFePO4

Abstract

Despite the significant importance of regenerating spent LiFePO₄ (LFP) cathode materials to address resource shortages and environmental pollution, significant obstacles remain with ecologically friendly and cost-effective recycling processes. Herein, we propose a novel strategy to synthesize new high-performance nitrogen-doped carbon/graphene@LiFePO₄ (N-DC/G@LFP) cathode materials by utilizing the spent LFP cathode material as raw materials. The regeneration strategy was performed in an alkaline solution, after repeated freezing and thawing, spray-drying, and subsequent thermal annealing under an Ar atmosphere. Benefiting from the synergistic effects that resulted from the tight contact between LiFePO₄ and the high-conductivity nitrogen-doped carbon and graphene network, the refabricated N-DC/G@LFP cathodes delivered 124.8 mA h g⁻¹ of excellent reversible discharge capacities at 2C, 117.5 mA h g⁻¹ at 5C, and 149.7 mA h g⁻¹ at 0.2C current rate. Furthermore, a 94.2% high-capacity retention ratio was observed over 500 cycles at 0.2C. This regeneration approach offers novel insight into the transformation from spent LFP cathodes to new cathode materials with efficient reutilization, which takes full advantage of the valuable components within the spent cathodes. Thus, this method enables the win–win situation of environmental protection and sustainable development of the LIB industry.