Enhancement of LiFePO4 cathodic material through incorporation of reduced graphene oxide via a simple two-step procedure

Abstract

The aim of the present work is the improvement of LiFePO₄ (LFP) as cathodic material for Lithium Batteries (LIBs) by controlled incorporation of graphene oxide (GO) and its subsequent reduction during LFP synthesis. The electrochemical performance of the samples is analysed after reduction treatment of GO in different steps of the synthesis. The purpose of the reduction is to provide LFP particles with higher conductivity through a uniform conductive carbon coating that facilitates the migration of Li⁺ ions in the cathode for charge-discharge process. These electrochemical measurements revealed an initial discharge capacity of 70.19 mAh g⁻¹ for LFP without GO, 141.3 mAh g⁻¹ and 154.3 mAh g⁻¹ with GO added in heat-treatment and solvothermal step, at 0.5C rate, respectively. Additionally, the cycling stability of the samples with GO improves the corresponding one obtained for pristine LFP. At 0.5C rate cycle-life, the LFP with GO combined with raw materials during solvothermal synthesis, attained capacity retention of 99 % after 100 cycles, decreasing to values of 88 % and 87 % for LFP with GO incorporated just before thermal treatment and LFP without GO. These results indicate that the LFP with GO incorporated initially in the synthesis improves rate capability of the material, reaching reversible capacity of 158.5 mAh g⁻¹ at 0.1C, 154.4 mAh g⁻¹ at 0.2C, 151.3 mAh g⁻¹ at 0.5C, 122.7 mAh g⁻¹ at 1C and 112.6 mAh g⁻¹ at 2C. The improvement in electrochemical behaviour can be attributed to the optimization of the synthesis process that provides a well-crosslinked interior of the composite and, therefore, a stable conductive network which has an associated higher diffusion coefficient.