Evaluation of graphene-wrapped LiFePO4 as novel cathode materials for Li-ion batteries

Abstract

Graphene-wrapped LiFePO₄ (LiFePO₄/G) is introduced as a cathode material for Li-ion batteries with an excellent rate capability. A straightforward solid-state reaction between graphene oxide-wrapped FePO₄ and a lithium precursor resulted in highly conducting LiFePO₄/G composites, which feature ∼70 nm-sized LiFePO₄ crystallites with robust connection to the external graphene network. This unique morphology enables all LiFePO₄ particles to be readily accessed by electrons during battery operation, leading to a remarkably enhanced rate capability. The in situ electrochemical impedance spectra were studied in detail throughout charge and discharge processes, by which enhanced electronic conductance and thereby reduced charge transfer resistance was confirmed as the origin of the superior performance in the novel LiFePO₄/G.