High surface area templated LiFePO4 from 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.