LiCoO2 and LiCo1-xAlxO2 thin film cathodes grown by pulsed laser ablation

LiCoO2 and LiC0.5Al0.5O2 thin films have been grown by pulsed laser ablatio n on SnO2-coated glass substrates. For both stoichiometries, the resultant films are dense and uniaxially textured films with the Li and Co layers par allel to the substrate. In general, to grow LiCo0.5Al0.5O2 films, a laser f lux roughly 80 mi pulse(-1) higher than that used for LiCoO2 films is requi red to achieve a similar deposition rate. LiCoO2 films grown at T-s = 600 d egrees C and p[O-2] = 2000 mTorr have a typical grain size of similar to 10 0 nm. For constant current cycling between 3.8 and 4.2 V at 5 mu A, the LiC oO2 films have an initial discharge capacity of similar to 0.33 Li per LiCo O2 (89 (mA h) g(-1)) decreasing to similar to 0.18 Li/LiCoO2 (49 (mA h) g(- 1)) after 100 cycles and have a continued capacity loss of similar to 0.25% per cycle. The LiCo0.5Al0.5O2 films grown to date have roughly 3 times les s capacity than the LiCoO2 films and apparently a large asymmetry between L i extraction and reintercalation. (C) 1999 Elsevier Science S.A. All rights reserved.