Structural and electrochemical studies on thin film LiNi_0.8Co_0.2O₂ by PLD for micro battery

Thin film of LiNi_0.8Co_0.2O₂ (LNCO) has been prepared by Pulsed Laser Deposition (PLD) technique at various post annealing temperatures. XRD results of LNCO thin film deposited on both Pt and Si substrates reveal relatively good crystalline nature at 500 °C which is in good agreement with the electrochemical results. ICP-AES composition analysis indicates 10 to 5% Li loss in the post annealed (400-700 °C) LNCO/Pt thin films; however the as prepared LNCO/Pt films show 17% excess of Li which are comparable with the LNCO target results. SEM analysis indicates phase separation at 600 °C and porous nature at 700-800 °C for LNCO/Pt films. Cyclic voltammetry (CV) scans of LiNi_0.8Co_0.2O₂ film post annealed at 500 °C show a pair of main cathodic and anodic peaks at 3.64 and 3.4 V, respectively with a narrow peak separation reveals good stability upon cycling. Whereas the LNCO films annealed at 600 °C and 700 °C indicate an additional anodic peak at lower potential besides a pair of major peaks which may be due to the phase separated morphology as evidenced from SEM analysis. Based on the structural and electrochemical results, a lithium-ion micro cell has been constructed with LNCO/Li_3.4V_0.6Si_0.4O₄(LVSO)/SnO configuration with the thickness of 1.535 μm and its electrochemical properties have been studied.