ELECTROCHEMICAL IMPEDANCE SPECTRA OF FULL CELLS - RELATION TO CAPACITY AND CAPACITY-RATE OF RECHARGEABLE LI CELLS USING LICOO2, LIMN2O4, AND LINIO2 CATHODES
J. Fan et Ps. Fedkiw, ELECTROCHEMICAL IMPEDANCE SPECTRA OF FULL CELLS - RELATION TO CAPACITY AND CAPACITY-RATE OF RECHARGEABLE LI CELLS USING LICOO2, LIMN2O4, AND LINIO2 CATHODES, Journal of power sources, 72(2), 1998, pp. 165-173
Electrochemical impedance spectra (EIS) are reported for rechargeable
lithium cells using cathodes LiMyOx (M = Co, Ni, and Mn) prepared from
casting and high-pressure compacting. The composite cathodes were cas
t from a slurry mixture consisting of 30% NMP solvent and 70% solid (9
1% LiMyOx, 3% PVDF and 6% KS44 graphite) onto a 25-mu m thick Al curre
nt collector. The compacted cathodes were made from the cast cathode u
sing a laboratory press. The most compacted cathodes have the smallest
impedance and the highest specific capacity and capacity-rate. Three
equivalent circuits are proposed according to the effect of compaction
pressure on our EIS results and work reported in the literature. The
EIS results and relationship to the capacity and capacity-rate are dis
cussed using these circuits. It appears that the ohmic resistance of t
he composite cathode is an important factor in the overall resistance
of the cell and unfavorably affects the performance (capacity and capa
city-rate) of the cathode. (C) 1998 Elsevier Science S.A.