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

LiCoO2 and LiCo0.5Al0.5O2 thin films have been grown by pulsed laser ablation on SnO2-coated glass substrates. For both stoichiometries, the resultant films are dense and uniaxially textured films with the Li and Co layers parallel to the substrate. In general, to grow LiCo0.5Al0.5O2 films, a laser flux roughly 80 mJ pulse−1 higher than that used for LiCoO2 films is required to achieve a similar deposition rate. LiCoO2 films grown at Ts=600°C and p[O2]=2000 mTorr have a typical grain size of not, vert, similar100 nm. For constant current cycling between 3.8 and 4.2 V at 5 μA, the LiCoO2 films have an initial discharge capacity of not, vert, similar0.33 Li per LiCoO2 (89 (mA h) g−1) decreasing to not, vert, similar0.18 Li/LiCoO2 (49 (mA h) g−1) after 100 cycles and have a continued capacity loss of not, vert, similar0.25% per cycle. The LiCo0.5Al0.5O2 films grown to date have roughly 3 times less capacity than the LiCoO2 films and apparently a large asymmetry between Li extraction and reintercalation.