Optimization of Recycled a-FePO4/rGO Composites via Thermal Reduction for Enhanced-Performance Lithium-Ion Batteries

TL;DR

This study shows how to recycle old lithium-ion battery materials into high-performance cathodes using a thermal reduction method with graphene oxide.

Contribution

The novel approach is using moderate-temperature thermal reduction to optimize a-FePO4/rGO composites for improved battery performance.

Findings

a-FePO4-rGO-1 (reduced at 250°C) delivered 117 mAh·g−1 after 100 cycles at 1 C.

The composite showed excellent rate capability of 98 mAh·g−1 at 10 C.

Moderate thermal reduction improved Li+ diffusion and reduced charge transfer resistance.

Abstract

In this study, spent LiFePO4 (LFP) cathode materials were recycled and transformed into amorphous FePO4 (a-FePO4) via a leaching–precipitation method for further use as a high-performance cathode material in lithium-ion batteries. To enhance its electrochemical performance, a-FePO4 was composited with graphene oxide (GO) and subsequently reduced at different temperatures (250–450 °C) under N2 atmosphere to obtain a series of a-FePO4/rGO composites. Among them, the a-FePO4-rGO-1 (reduced at 250 °C) exhibited the most superior performance, delivering a specific high discharge capacity of 117 mAh·g−1 after 100 cycles at 1 C and an excellent rate capability of 98 mAh·g−1 even at 10 C. Electrochemical impedance spectroscopy revealed that this composite possessed the lowest charge transfer resistance and most efficient Li+ diffusion kinetics. This study demonstrates that moderate-temperature thermal reduction is a critical strategy for optimizing the conductive network of a-FePO4-rGO composites, thereby significantly improving the electrochemical properties of recycled FePO4-based cathode materials.

Figures