TiOx Surface modified LiNixMnyCozO2 as high rate cathode for Lithium ion batteries

Abstract

Ni-rich lithium nickel manganese cobalt oxide materials (LiNixMnyCozO2, NMC) are an attractive alternative to LiCoO2 as cathode for lithium-ion batteries because of their high capacity and cost-effectiveness. However, their poor cycling stability and poor rate capability at high cutoff potentials limits their electrochemical performances to achieve practical applicability.1 At high potentials, Ni-rich NMC suffers from parasitic reactions. This leads to structural degradation, inter-particle disintegration and capacity loss. Surface modification and doping have been previously used as strategies to overcome these issues. Amine et al.2 recently showed that ALD surface modified NMC particles exhibit an improved capacity retention at high cut-off potentials. The ALD technique, however, suffers from limited upscaling potential. Wet chemical routes are an alternative cost-effective deposition route which can be readily up scalable. Here, we demonstrate the influence of the wet chemical deposition of a thin TiOx shell on LiNi0.6Mn0.2Co0.2O2 (NMC622) particles.3 The crystallinity and morphology of the NMC622 particles was unaffected by the deposition reaction (as determined by powder X-ray diffraction and scanning electron microscopy, respectively). The electrochemical performances of the bare and TiOx-coated NMC622 were compared by incorporating them in half-cell coin cells and performing galvanostatic cycling. The TiOx-coated material had an improved rate performance compared to the bare material. As determined by cyclic voltammetry, the former also had an improved reversibility. Electrochemical impedance spectroscopy measurements showed that the coated material experiences a lower charge transfer resistance.