T#2-Li0.69CoO2: A Durable, High-Capacity, High-Rate Cathode Material for Lithium-Ion Batteries

Abstract

Efficient utilization of resources is crucial for the sustainable development of the lithium-ion battery industry. Although the traditional R$\overline{3}$m space group LiCoO₂ can provide a current advanced discharge capacity of 215–220 mAh g⁻¹ at an upper cut-off voltage of 4.6 V (relative to Li⁺/Li), it still falls far short of its theoretical specific capacity of 273 mAh g⁻¹, and exhibits structural instability and labile oxygen loss, leading to rapid capacity degradation. T^#2-Li_0.69CoO₂ is synthesized with Cmca space group and Li─O tetrahedral coordination. Owing to the unique Li─O tetrahedral coordination structure and the dominant cobalt oxidation under high voltage, T^#2-Li_0.69CoO₂ delivers an ultra-high specific capacity of 258 mAh g⁻¹, close to the theoretical capacity, in liquid electrolyte batteries and 253 mAh g⁻¹ in solid state batteries, overcoming the structural instability of layered oxide cathodes during charging and discharging processes. This study broadens the possibilities of creating high energy-density cathodes for next-generation Li-ion batteries.