LiNi_0.8Co_0.15Ti_0.05O₂: synthesis by solid state reaction and investigation of structural and electrochemical properties with enhanced battery performance

Solid state synthesis is an essential technique for large-scale production of electrode active materials in battery industry. However, solid state synthesis of LiNi_0.8Co_0.15Al_0.05O₂ (NCA), which is a well-known commercial cathode material for Li-ion batteries, provides electrochemically inactive compound. Here, we report the solid state synthesis of Li_xNi_0.8Co_0.15Ti_0.05O₂ where x = 1.03, 1.06, and 1.09, which is a modified version of conventional NCA. Our thorough studies consist of characterization of compounds by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and magnetization measurements. The results point out the significant effects of Li content on structural and magnetic properties of the samples. Battery performance tests show that Li_1.06Ni_0.8Co_0.15Ti_0.05O₂ exhibits better cycling properties than conventional NCA. X-ray absorption spectroscopy (XAS) technique is utilized to determine structural modifications upon cycling of this compound via ex-situ analysis. We conclude that substitution of Ti ions in Li_1.06Ni_0.8Co_0.15Ti_0.05O₂ improves the cycling capability of the cells by reducing the formation of NiO insulating layer which hinders the redox reactions. The capacity value of x = 1.06 sample increases up to 150 mAh g⁻¹ at C/3 rate during cycling and the capacity fade is negative for the first 10 cycles. Possible mechanism for the negative capacity fade is also discussed.