Enhancing the reaction kinetics and structural stability of high-voltage LiCoO₂ via polyanionic species anchoring

Increasing the charging voltage to 4.6 V directly enhances battery capacity and energy density of LiCoO₂ cathodes for lithium-ion batteries. However, issues of the activated harmful phase evolution and surface instability in high-voltage LiCoO₂ lead to dramatic battery capacity decay. Herein, polyanionic PO₄³⁻ species have been successfully anchored at the surface of LiCoO₂ materials, achieving superior battery performance. The polyanionic species acting as micro funnels at the material surface, could expand LiCoO₂ surface lattice spacing by 10%, contributing to enhanced Li diffusion kinetics and consequent excellent rate performance of 164 mA h g⁻¹ at 20C (1C = 274 mA g⁻¹). Crucially, polyanionic species with high electronegativity could stabilize surface oxygen at high voltage by reducing O 2p and Co 3d orbital hybridization, thus suppressing surface Co migration and harmful H1-3 phase formation and leading to superior cycling stability with 84% capacity retention at 1C after 300 cycles. Furthermore, pouch cells containing modified LiCoO₂ and Li metal electrodes deliver an ultra-high energy density of 513 W h kg⁻¹ under high loadings of 32 mg cm⁻². This work provides insightful directions for modifying the material surface structure to obtain high-energy-density cathodes with high-rate performance and long service life. © 2024 The Royal Society of Chemistry.