LiCoO2 is shown to be a very high rate cathode. Power densities as hig
h as 5500 W/kg have been demonstrated for Li/LiCoO2 cells. Such high p
ower was obtained with approximately 75-mu m-thick electrodes fabricat
ed with 5 mu m or smaller diameter LiCoO2 particles and having about 6
5% porosity. A 2 M solution LiAsF6 in a mixed solvent consisting of 25
vol% propylene carbonate and 75 vol% methyl acetate was the electroly
te. 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 sho
wed a strong dependence on separator porosity. Cells with a 25-mu m-th
ick separator having about 55% porosity showed significantly better po
wer output than ones containing a separator of the same thickness havi
ng 32% porosity.