Harnessing the Full Potential of Zr Dopant for LiNiO₂ by Tailoring Spatial Distribution

High-nickel layered oxide materials are crucial for high-energy lithium-ion batteries; however, their stability remains a significant challenge. While doping has emerged as a promising strategy for stabilization, the inconsistent doping effects reported in the literature necessitate a more profound mechanistic understanding. To address this, a Zr-doped LiNiO₂ model system is employed to investigate the influence of dopant distribution. These findings reveal that the spatial distribution of the dopant, primarily dictated by the slow solid-state diffusion kinetics during sintering, critically influences its functional role. By utilizing different doping methodologies, varying Zr distributions are achieved within the LiNiO₂ matrix. Solid-state doping resulted in the formation of a monoclinic Li₂ZrO₃ surface layer, attributed to diffusion limitations, which led to an enhanced initial capacity. Conversely, co-precipitation facilitated a more uniform Zr distribution and induced surface cation mixing, thereby improving structural stability. Given these insights, a novel hybrid doping strategy that synergistically combines the benefits of both distribution profiles, ultimately achieving superior electrochemical performance, is proposed. This work highlights the critical importance of precisely controlling dopant spatial distribution, suggesting that this challenge, exemplified by Zr in this study, represents a general consideration for various dopants in the rational design of advanced materials for energy applications.