Electrochemical Properties and Crystal Structure of Li <sup>+</sup> /H <sup>+</sup> Cation-Exchanged LiNiO <sub>2</sub>
Takahiro Toma, Ryo Maezono, Kenta Hongo
Abstract
High Resolution Image Download MS PowerPoint Slide LiNiO 2 has high energy density but readily reacts with moisture in the atmosphere and deteriorates. We performed qualitative and quantitative evaluations of the degraded phase of LiNiO 2 and the influence of the structural change on the electrochemical properties of the phase. The formation of the Li 1– x H x NiO 2 phase with cation exchange between Li + and H + was confirmed by thermogravimetric analysis and Karl Fischer titration measurement. As the H concentration in Li 1– x H x NiO 2 increased, the rate capability deteriorated, especially in the low-temperature range and under low state of charge. Experimental and density functional theory (DFT) calculation results suggested that this outcome was attributed to an increased activation energy of Li + diffusion because of cation exchange. Rietveld analysis of X-ray diffraction and DFT calculation confirmed that the c lattice parameter and Li–O layer decreased because of the Li + /H + cation exchange. These results indicate that LiNiO 2 reacting with moisture in the atmosphere has a narrowed Li–O layer, which is the Li diffusion path, and the rate characteristics are degraded.