Precursor derived LiMn2O4 thin films as ionic conductor

Thin films of spinel LiMn₂O₄ have been fabricated using a metallorganic precursor. Crystalline films have been deposited on Au substrates to exhibit as the cathode in rechargeable thin film lithium batteries. The nucleation and growth of spinel LiMn₂O₄ crystallites were investigated with heat treatment of the deposited thin films. Film capacity density as high as 22 µAh/cm² was measured for LiMn₂O₄. The film heat treated at 700 °C were cycled electrochemically up to 30 cycles against Li metal without any degradation of the capacity. There were neither open area nor amorphous layers which prevent the Li⁺ions transfer at the boundaries in the LiMn₂O₄ thin film. The microscopic study revealed that (111) planes in the two grains directly bonded at the grain boundary which could proceed the lithium ion intercalation or deintercalation smoothly.