Abstract Transition-metal selenides have attracted extensive concern as one of the alternatives for sodium-ion batteries (SIBs) anodes due to their high theoretical capacities, good cycling stability and environmental benignity. However, the application of metal selenides is restricted by severe volume variation and sluggish kinetics during cyclings, which cause capacity fading induced by the pulverization and aggregation of the electrode materials. Herein, the FeSe2@C microspheres assembled with FeSe2 nanoparticles cotaed by carbon layers are fabricated using a hydrothermal method and the subsequent annealing treatment. When served as anodes for SIBs, the FeSe2@C electrodes exhibit excellent electrochemical performances. A high reversible capacity of 461 mA h g−1 is retained after 100 cycles at 50 mA g−1. Even at high rate of 1000 mA g−1, a long-term cycling capacity of 428 mA h g−1 is achieved after 1000 cycles. The kinetic analyses confirm that the superior sodium storage performances of FeSe2@C composites are mainly attributed to the pseudocapacitive contribution facilitated by the unique nano-micro hierarchical structure.

中文翻译：

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碳层包覆的FeSe2微球作为钠离子电池的负极材料

摘要 过渡金属硒化物作为钠离子电池（SIBs）负极的替代品之一，因其高理论容量、良好的循环稳定性和环境友好性而受到广泛关注。然而，金属硒化物的应用受到循环过程中严重的体积变化和缓慢的动力学的限制，这会导致电极材料粉化和聚集引起的容量衰减。在本文中，使用水热法和随后的退火处理制造了由碳层包覆的 FeSe2 纳米粒子组装而成的 FeSe2@C 微球。当用作 SIB 的阳极时，FeSe2@C 电极表现出优异的电化学性能。在 50 mA g-1 下循环 100 次后仍保持 461 mA hg-1 的高可逆容量。即使在 1000 mA g−1 的高倍率下，1000 次循环后可实现 428 mA hg-1 的长期循环容量。动力学分析证实，FeSe2@C 复合材料优异的储钠性能主要归因于独特的纳米级分层结构促进的赝电容贡献。