In-situ and selectively laser reduced graphene oxide sheets as excellent conductive additive for high rate capability LiFePO4 lithium ion batteries

We report an ultrafast in-situ laser reduction process of graphene oxides (GO) in LiFePO4 electrodes, where the selective laser reduction of GO sheets is conducted after coating LiFePO4 on current collector. This novel process technique avoids the solvophobicity and agglomeration problems of graphene in 1-methyl-2-pyrrolidinone (NMP) or other solvents for the electrode material slurry preparation because of GO's solvophilicity in various solvents. Under the optimized laser reduction condition, a hierarchical structure of graphene conductive network is formed without wrapping the LiFePO4 surface, which can greatly improve the rate capability and cycle performance. The battery capacity remains 84.5% after 1000 cycles and 72.9% when the charge/discharge current density increases from 0.5C to 20C. The method developed in this work is also applicable for other material systems to selectively reduce GO for performance enhancement.