Cobalt-Free Layered Nickel Oxides with Antisite Defects for Long-Lived Lithium-Ion Batteries

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Toward the realization of sustainable society, the development of high-energy lithium-ion batteries is required. LiNiO2 is considered a promising positive electrode candidate owing to its high capacity. However, the gradual loss of electrode reversibility at high voltage region coupled with Ni migration to tetrahedral site on charging is observed on cycling.1 In this study, to improve electrode reversibility of LiNiO2, Li- deficient Li1–x Ni1+x O2 are synthesized and their electrochemical properties were examined. Stoichiometric LiNiO2 and Li-deficient Li1–x Ni1+x O2 were synthesized by mixing LiOH・H2O and Ni(OH)2 and calcined for 12 h at 650 oC under oxygen atmosphere. As shown Figure 1, Li deficiency significantly reduces particle size and crystallinity. In addition, the peak intensity ratio of 003 and 104 diffraction lines is decreased as Li content decreases, which indicates the increase of Ni ion occupation in Li layers. Compared with stoichiometric LiNiO2, Li deficient samples deliver a smaller discharge capacity, but higher electrode reversibility is achieved (Fig. 2). These facts suggest that Ni migration to adjacent tetrahedral sites is effectively suppressed by the presence of extra Ni ions in Li layers for the Li-deficient samples, leading to the high electrode reversibility.2 The impact of Li deficiency on electrochemical properties of LiNiO2 will be discussed in detail. N. Ikeda et al., and N. Yabuuchi, J. Mater. Chem. A, 9, 15963 (2021).I. Konuma et al., and N. Yabuuchi, Energy Stor. Mater. 66, 103200 (2024). Figure 1