Co/Li-dual-site doping towards LiCoO2 as a high-voltage, fast-charging, and long-cycling cathode material

Abstract

The design of fast-charging, long-cycling, and high-voltage cathode materials remains challenging. Herein, through different strategies, Al and Nb/W are doped into the Co- and Li-sites in LiCoO₂ (LCO), respectively; according to density functional theory calculations, compared with the Co-site, doping at Li-site is thermodynamically unfavourable, which is primarily driven by the kinetic motif. We demonstrate that the Al-dopant at the Co-site inhibits the adverse phase transformation of LiCoO₂ under high voltage, while the Nb/W dopants intercalated within the Li-slab can serve as pillars that not only increase the interlayer spacing but also decrease the electronic coupling around Li⁺, thus increasing the population of highly active Li⁺ and enabling fast Li⁺ diffusion kinetics. Owing to the synergy effect from dual-site doping at both Co- and Li-sites, together with a discrete coating layer of niobium tungsten oxide (NWO) nanoparticles, the thus modified LiCoO₂ (denoted as ANW-LCO) cathode delivers highly stable and superior rate performance even under high voltage. Specifically, with a cut-off potential of 4.5 V, it displays a specific capacity of as high as 142.1 mA h g⁻¹ at 15C and can maintain a reversible capacity of 85.3 mA h g⁻¹ after 1000 cycles at 10C under 4.5 V, translating into a capacity retention of 60.4%. When evaluated at 4.6 V, it shows a capacity retention of as high as 77.5% after 100 cycles. When tested in all-solid-state lithium-ion batteries, it delivers a primal discharge specific capacity of 139 mA h g⁻¹ and retains 71% of its capacity after 200 cycles. The full-cell also demonstrates outstanding cycling stability, with a capacity retention of 71% after 500 cycles at 2C.