Advanced Lithium Battery Cathodes Using Dispersed Carbon Fibers as the Current Collector

To fabricate LiFePO 4 battery cathodes, highly conductive carbon fibers of 10–20 μ m in diameter have been used to replace a conventional aluminum (Al) foil current collector. This disperses the current collector throughout the cathode sheet and increases the contact area with the LiFePO 4 (LFP) particles. In addition, the usual organic binder plus carbon-black can be replaced by a high temperature binder of <5 wt % carbonized petroleum pitch (P-pitch). Together these replacements have potential to increase the specific energy density and energy per unit area of the electrode. In a side-by-side comparison with conventional cathodes sheets of LFP on Al foil, the carbon fiber composite cathodes have a much longer cycle life, higher thermal stability, and high capacity utilization at rates to 6C. Details of the coating procedure, characterization and approach for maximizing the energy density are discussed.