Purifying spent carbon anode (SCA) from aluminum reduction industry by alkali fusion method to apply for Li-ion batteries anodes: From waste to resource

Abstract

To end the elimination the harm to the environment of spent carbon anode (SCA), which is a hazardous solid waste from the aluminum reduction cell, the SCA is treated by the alkali fusion method and the purified SCA (PSCA) is evaluated as the anode of Li ion batteries (LIBs) for the first time. In this work, the alkali fusion technologies are optimized using the single factor experiment and the orthogonal tests (L9 orthogonal array). And the best carbon content can reach 99.10% when the reaction temperature is 600 °C, reaction time is 6.5 h, and NaOH / SCA mass ratio is 5.5 ∶ 1. Evaluation of the importance of the effects of key parameters was performed using analysis of variance (ANOVA). The PSCA shows the abundant layered structure and pores. It is composed of amorphous carbon and graphitized carbon with an average carbon layer spacing of 0.3398 nm. The PSCA exhibits a considerable reversible capacity of 286.8 mAh/g at 1 C and a good capacity decay rate (a decay rate per cycle of 0.030% in 500 cycles) which are much higher than those of commercial soft carbon (213.7 mAh/g and 0.039%). It is demonstrated that SCA can be transformed into a potential anode of LIBs after purification, and this sustainable approach can easily be extended to the recovery and utilization of other carbonaceous solid waste.