LiMn2O4 Films Grown by Pulsed-Laser Deposition

LiMn2O4 films have been deposited onto silicon wafer by pulsed-laser deposition (PLD) technique in order to test their reliability as cathode materials in rechargeable lithium microbatteries. The film formation has been studied as a function of the preparation conditions, i.e., composition of the target, substrate temperature, and oxygen partial pressure in the deposition chamber. Depending on the conditions of deposition, Mn2O3 was present as an impurity phase. When deposited onto silicon substrate maintained at 300 degrees C in an oxygen pressure of 100 mTorr from the target LiMn2O4+15 % Li2O, the PLD films are well-textured with crystallite size of 300 nm. It is found that such a film crystallizes in the spinel structure (Fd3m symmetry) as evidenced by x-ray diffraction and Raman scattering measurements. Surface morphologies of layers were investigated by SEM. The cells Li//LiMn2O4 have been tested by cyclic voltammetry and galvanostatic charge-discharge techniques in the range 3.0-4.2 V. The voltage profiles show the two expected steps for LixMn2O4 with a specific capacity as high as 120 mC/cm(2) mu m. The chemical diffusion coefficients for the LixMn2O4 thin films appear to be in the range of 10(-11)-10(-12) cm(2)/s.