(Invited) Structural Lithium-Ion Battery Based on LiFePO4/Reduced Graphene Oxide Composite Cathode and Graphene Anode Prepared via Electrophoretic Deposition on Carbon Cloth

Abstract

Structural lithium-ion batteries based on binder-free LiFePO4/reduced graphene oxide composite cathode electrode and graphene anode electrode are prepared respectively via electrophoretic co-deposition of LiFePO4, reduced graphene oxide, and carbon black on carbon cloth substrate for the cathode, and graphene oxide and carbon black on carbon cloth substrate for the anode. Following deposition, the electrode materials were dried. The graphene oxide of the anode was reduced to graphene via rapid thermal annealing. Possessing excellent stiffness, strength-to-weight ratio, and good electrical conductivity, the carbon cloth substrate serves multifunctional roles in the battery: as structural reinforcement and mechanical load bearing element and as current collector. Given its good electrical conductivity, high aspect ratio, and high surface area, reduced graphene oxide improves electrical conductivity within the cathode and provides sites for hosting LiFePO4; this enhances reversible Li ion extraction from the host during cycling. Graphene with its good electrical conductivity and high aspect ratio provides sites for insertion of Li ions in the anode; this enhances the aerial lithiation capacity of the battery system. Carbon black enhances conductivity within the two electrodes and reduces interfacial impedance. The electrochemical properties of the electrodes are strongly correlated to their microstructure and phase composition. Electrochemical characterization of the electrodes and their performance in half-cell and full cell configurations are evaluated. Additionally, Li-ion diffusivity within the materials is evaluated with three independent electroanalytical methods, including potentiostatic and galvanostatic and intermittent titration techniques, and electrochemical impedance spectroscopy.