钠离子电池中空结构CoSe2/C负极材料的制备及储钠性能研究

过渡金属硒化物具有较高的理论比容量和良好的导电能力, 是钠离子电池潜在的负极材料, 但其在电化学过程中会发生较大体积变化, 循环寿命不佳, 发展受到了限制。为缓解上述问题, 本研究以金属有机框架材料ZIF-67为前驱体, 用单宁酸(Tannic acid, TA)将ZIF-67刻蚀为空心结构, 再通过碳化、硒化制备出以碳为骨架的纳米中空CoSe₂材料(H-CoSe₂/C), 相较于未经刻蚀处理的CoSe₂材料(CoSe₂/C), H-CoSe₂/C表现出更好的储钠性能, 特别是循环稳定性得到显著提高。50 mA·g^-1电流密度下, 经过350次循环, 可逆比容量保持在383.4 mAh·g^-1, 容量保持率为83.6%; 在500 mA·g^-1电流密度下, 经过350次循环后容量保持率仍能达到72.2%。本研究表明, 中空结构能够提供足够的空间以缓解材料在电化学过程中的体积变化, 进而提高电极材料的循环性能。

Hollow-structured CoSe2/C Anode Materials: Preparation and Sodium Storage Properties for Sodium-ion Batteries

Transition metal selenides (TMSs) with the merits of their versatile material species, ample abundance and high theoretical specific capacity have been regarded as attractive anode materials for sodium-ion batteries (SIBs). However, the large volume changes during the electrochemical reactions which result in limited cycle performance hinder their commercialization. Herein, the hollow structure composed of CoSe₂ and carbon skeleton (denoted as H-CoSe₂/C), derived from the metal organic framework material ZIF-67 using tannic acid as the etching agent, was used as the anode for SIBs. Owing to the unique hollow structure which can alleviate the volume change of the material, H-CoSe₂/C exhibited excellent sodium ions storage performances in terms of cycling stability. Compared with the solid counterpart, the reversible specific capacity of the H-CoSe₂/C electrode remains 383.4 mAh·g^-1 after 350 cycles at a current density of 50 mA·g^-1 with the capacity retention of 83.6%. Even at 500 mA·g^-1, the capacity retention can still reach 72.2% after 350 cycles. This work manifests that hollow structure can provide enough space to alleviate the problem of volume changes for TMSs during the sodiation/desodiation process, thus the cycle performances can be improved.