Approaching theoretical capacity of LiFePO4 at room temperature at high rates

Nanocomposites of LiFePO4 and conductive carbon were prepared by two different methods which lead to enhanced electrochemical accessibility of the Fe redox centers in this insulating material. Method A employs a composite of the phosphate with a carbon xerogel formed from a resorcinol-formaldehyde precursor; method B uses surface-oxidized carbon particles to act as a nucleating agent for phosphate growth. Both particle size minimization and intimate carbon contact are necessary to optimize electrochemical performance. Although both methods succeed for the first criteria, the latter is best achieved with method A, affording excellent characteristics in room temperature, liquid electrolyte cells. The resultant LiFePO4 /C composite achieves 90% theoretical capacity at C/2, with very good rate capability and excellent stability. (C) 2001 The Electrochemical Society.