Metal selenides have attracted increasing attention recently as anodes for sodium-ion batteries (SIBs) because of their large capacities, high electric conductivity, as well as environmental benignity. However, the application of metal selenides is hindered by the huge volume variation, which causes electrode structure devastation and the consequent degrading cycling stability and rate capability. To overcome the aforementioned obstacles, herein, SnSe₂/FeSe₂ nanocubes capsulated in nitrogen-doped carbon (SFS@NC) are fabricated via a facile co-precipitation method, followed by poly-dopamine wrapping and one-step selenization/carbonization procedure. The most remarkable feature of SFS@NC is the ultra-stability under high current density while delivering a large capacity. The synergistic effect of dual selenide components and core-shell architecture mitigates the volume effect, alleviates the agglomeration of nanoparticles, and further improves the electric conductivity. The as-prepared SFS@NC nanocubes present a high capacity of 408.1 mAh g⁻¹ after 1200 cycles at 6 A g⁻¹, corresponding to an 85.3% retention, and can achieve a capacity of 345.0 mAh g⁻¹ at an extremely high current density of 20 A g⁻¹. The outstanding performance of SFS@NC may provide a hint to future material structure design strategy, and promote further developments and applications of SIBs.

中文翻译：

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SnSe2/FeSe2 纳米立方体封装在掺氮碳中实现了稳定的超高速率钠离子存储

金属硒化物作为钠离子电池（SIBs）的负极，由于其大容量、高导电性以及环境友好性，最近引起了越来越多的关注。然而，巨大的体积变化阻碍了金属硒化物的应用，这会导致电极结构破坏，从而降低循环稳定性和倍率性能。为了克服上述障碍，在此，SnSe ₂ /FeSe ₂封装在掺氮碳（SFS@NC）中的纳米立方体是通过一种简便的共沉淀方法制造的，然后是聚多巴胺包裹和一步硒化/碳化程序。SFS@NC 最显着的特点是在高电流密度下具有超稳定性，同时提供大容量。双硒化物组分和核壳结构的协同作用减轻了体积效应，减轻了纳米颗粒的团聚，进一步提高了电导率。所制备的 SFS@NC 纳米立方体在 6 A g ^{-1 下}循环 1200 次后具有 408.1 mAh g ^-1的高容量，对应于 85.3% 的保留率，并且在极高的情况下可实现 345.0 mAh g ^-1的容量20 A g ^{-1 的}电流密度. SFS@NC的优异性能可能为未来的材料结构设计策略提供启示，促进SIBs的进一步发展和应用。