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

Abstract

To fabricate LiFePO4 battery cathodes, highly conductive carbon fibers of 10–20 μm 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 LiFePO4 (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.