Enhancing the reaction kinetics and structural stability of high-voltage LiCoO2via 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.