RESUMEN
Se-based cathodes have caught tremendous attention owing to their comparable volumetric capacity and better electronic conductivity to S cathodes. However, its low utilization ratio and sluggish redox kinetics due to the high reaction barrier of solid-phase transformation from Se to Li2Se limit its practical application. Herein, an in-situ texturing hollow carbon host by gas-solid interface reaction anchored with Fe single-atomic catalyst is designed and prepared for advanced Li-Se batteries. This Se host presents high pore volume of 1.49 cm3 g-1, Fe single atom content of 1.53 wt%, and its specific structure protects single-atomic catalyst from the destructive reaction environment, thus balancing catalytic activity and durability. After Se loading by reduction of H2SeO3, this homogenous Se-based cathode delivers a superior rate capacity of 431.3 mA h g-1 at 4C, and great discharge capacity of 301.8 mA h g-1 after 1000 cycles at 10C, with high Li-ion diffusion coefficient and capacitance-contributed ratio. The distribution of relaxation times analysis verifies solid-phase transformation mechanism of this cathode and density functional theory calculations confirm the adsorption and bidirectionally catalysis effect of Fe single-atomic catalyst. This work provides a new strategy to prepare high-efficient Se cathode associated with non-noble metal single atoms for high-performance Li-Se batteries.
RESUMEN
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 Lix Co2 O4 shells on and the gradient doping of SO4 2- polyanions into LCO are in situ realized simultaneously in terms of gas-solid interface reactions between metal oxides and generated SO2 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.