Tandem Topotactic Reactions for Low-Temperature Synthesis of Ni-Rich Layered Oxide Cathodes without Anti-site Defect

> 0.6) have garnered significant attention in electric transportation due to the high energy density (>700 Wh/kg). Traditional synthesis of Ni-rich cathodes typically involves high-temperature (>700 °C) long-duration (∼10 h) sintering procedures, which not only increase energy consumption but also present challenges in precisely controlling the synthesis conditions. Here we designed a two-step tandem topotactic phase-transition route that allows low-temperature synthesis of Ni-rich cathodes. Temperature-resolved X-ray scattering techniques combined with ex situ spectroscopy experiments substantiated that the layered hydroxide precursor first transformed to a layered oxyhydroxide intermediate through a topotactic deprotonation reaction, which was then converted to Ni-rich layered oxide cathode by a rapid topotactic lithiation. Radically distinguished from the destruction-reconstruction process of layered structures in the conventional synthesis route, the layered framework was maintained throughout the whole topotactic route, lowering the energy barrier of synthetic kinetics and thus enabling the successful preparation of Ni-rich cathodes at low temperature (150 °C), which brings an unprecedented reduction of energy consumption (by 57%) and considerable cost-savings. Furthermore, Ni-rich cathodes synthesized through the topotactic route exhibited comparable electrochemical activity and even better cycling stability (∼80% after 500 cycles) than those synthesized through conventional routes. This work presents an enlightening methodology of Ni-rich layered cathode synthesis, laying a substantial foundation for cost-effective and eco-friendly production of high-performance cathode materials on an industrial scale.