Upcycling end of lithium cobalt oxide batteries to electrocatalyst for oxygen reduction reaction in direct methanol fuel cell via sustainable approach

Abstract

Recycling spent lithium-ion batteries (SLIBs) has become essential to preserve the environment and reclaim vital resources for sustainable development. The typical SLIBs recycling concentrated on separating valuable components had limitations, including high energy consumption and complicated separation processes. This work suggests a safe hydrometallurgical process to recover usable metallic cobalt from depleted LiCoO2 batteries by utilizing citric acid as leachant and hydrogen peroxide as an oxidizing agent, with ethanol as a selective precipitating agent. The anode graphite was also recovered and converted to graphene oxide (GO). The above components were directly resynthesized to cobalt-integrated nitrogen-doped graphene (Co@NG).The Co@NG showed a decent activity towards oxygen reduction reaction (ORR) with a half-wave potential of 0.880 V vs. RHE, almost similar to Pt/C (0.888 V vs. RHE) and with an onset potential of 0.92 V vs. RHE. The metal-nitrogen-carbon (Co-N-C) having the highest nitrogen content has decreased the barrier for ORR since the reaction was enhanced for Co@NG-800, as confirmed by density functional theory (DFT) simulations. The Co@NG cathode catalyst coupled with commercial Pt-Ru/C as anode catalyst exhibits excellent performance for direct methanol fuel cell (DMFC) with a peak power density of 34.7 mW cm−2 at a discharge current density of 120 mA cm−2 and decent stability, indicating the promising utilization of spent battery materials in DMFC applications. Besides, lithium was recovered from supernatant as lithium carbonate by coprecipitation process. This work avoids sophisticated elemental separation by utilizing SLIBs for other renewable energy applications, lowering the environmental concerns associated with recycling.