Discharge rate capability of the LiCoO2 electrode

LiCoO2 is shown to be a very high rate cathode. Power densities as high as 5500 W/kg have been demonstrated for Li/LiCoO2 cells. Such high power was obtained with approximately 75-mu m-thick electrodes fabricated with 5 mu m or smaller diameter LiCoO2 particles and having about 65% porosity. A 2 M solution LiAsF6 in a mixed solvent consisting of 25 vol% propylene carbonate and 75 vol% methyl acetate was the electrolyte. The high Li+ concentration of this electrolyte, together with its room temperature conductivity of 2 x 10(-2) Omega(-1) cm(-1), allowed the discharge of Li/LiCoO2 cells at currents as high as 100 mA/cm(2). The LiCoO2 utilization at 50 mA/cm(2) and higher current densities showed a strong dependence on separator porosity. Cells with a 25-mu m-thick separator having about 55% porosity showed significantly better power output than ones containing a separator of the same thickness having 32% porosity.