MATERIAL BALANCE OF PETROLEUM COKE LINIO2 LITHIUM-ION CELLS/

A method is described for the estimation of the volumetric specific ca pacity of balanced Li-ion cells. The effect of the material balance or the cathode/anode mass ratio, r, in Li-ion cells on the volumetric sp ecific capacity, q(v), of the electrode pair is studied in the example of a petroleum coke/LiNiO2 couple. The values of q(v) of several elec trode pairs used in Li-ion cells, calculated on the basis of present e xperimental and previously published data are juxtaposed. A good agree ment between calculated and experimentally determined q(v) values is f ound. The q(v) value of the natural graphite/LiNiO2 pair exceeds by ne arly 28% that of the commercialized PFA-C/LiCoO2 pair, considered so f ar as the best available. This advantage will however be reduced by 30 to 50% in a real cell, when the volumes of all cell components are ta ken into account. The influence of r on the cycling stability is also demonstrated experimentally. The possibility of using unbalanced cells with moderately overcharged anodes appears feasible, while cells with precharged anodes from an auxiliary Li source seem impractical.