High surface area templated LiFePO4from a single source precursor molecule

Abstract

The preparation of a stoichiometric dispersion of nanostructured LiFePO4 clusters with intimate contact to carbon is described. This material exhibits outstanding performance for hybrid energy storage applications. A synthetic process, involving a novel single molecular source precursor, was developed and used to infiltrate a structured mesoporous carbon template. Subsequent optimisation of the infiltration process, reductive pyrolysis and secondary dispersion of the active materials for electrode coatings gave highly effective LiFePO4/C composite electrodes suitable for high power applications. The materials were found to have surface areas in excess of 800 m2 g−1 and TEM revealed an intimate contact to the carbon matrix as a result of the single source precursor employed. Extensive electrochemical performance evaluation, at rates exceeding 20 C, confirmed a resilient stable material capable of delivering exceptional high rate performance which is attributed to the periodic, interconnected mesopores (5–6 nm) and also the intimate LiFePO4/C content delivered from the single source precursor. Galvanostatic charge–discharge cycling demonstrated the materials' excellent stability and high utilization, with a specific discharge capacity of 163 A h kg−1 (close to theoretical unity of 170 A h kg−1) at 0.2 C and 128 A h kg−1 at 23 C, an exceptional result relative to lower surface area analogues. Power delivery was almost three times that of commercial LiFePO4 at 10 C. These materials are well suited for application in high power energy storage devices including high power lithium batteries and hybrid devices.