THE IMPORTANCE OF THE LITHIUM ION TRANSFERENCE NUMBER IN LITHIUM POLYMER CELLS

Simulation results are presented for a lithium negative electrode, sol id polymer separator, manganese dioxide composite positive electrode c ell. In particular, we assess the effect of conductivity and transfere nce number on cell performance, establishing criteria for situations w hen a trade-off between these two properties is expected. We show that polymer-electrolyte systems with a unity transference number have imp roved performance over systems with t+0 = 0.2, even when the conductiv ity is decreased by an order of magnitude. The improvements are primar ily at higher rates of discharge, where the latter cell would be deple ted of electrolyte due to large concentration gradients that develop. Cells with a unity transference number have larger energy densities an d can attain higher peak-power densities.