Long-Term Highly Stable High-Voltage LiCoO 2 Synthesized via a Solid Sulfur-Assisted One-Pot Approach.

Commercialized lithium cobalt oxide (LCO) only shows a relatively low capacity of ≈175 mAh g -1 despite a high theoretical capacity of ≈274 mAh g -1 . As an effective and direct strategy, increasing its charge cutoff voltage can, in principle, escalate the capacity, which is however precluded by the irreversible phase transition, oxygen loss, and severe side reactions with electrolytes normally. Herein, an in situ sulfur-assisted solid-state approach is proposed for one-pot synthesis of long-term highly stable high-voltage LCO with a novel compound structure. The coating of coherent spinel Li x Co 2 O 4 shells on and the gradient doping of SO 4 2- polyanions into LCO are in situ realized simultaneously in terms of gas-solid interface reactions between metal oxides and generated SO 2 gas from sulfur during synthesis. At 4.6 V, this LCO shows the discharge capacities of 232.4 mAh g -1 at 0.1 C (1 C = 280 mA g- 1 ), 215 mAh g -1 at 1 C and 139 mAh g -1 even at 20 C and the capacity retentions of 97.4% (89.7%) after 100 (300) cycles at 1 C. This approach is facile, low-cost and up-scalable and may provide a route to improve the performance of LCO and other electrode materials greatly.