Sodium storage materials based on conversion and alloying reactions often suffer from low initial Coulombic efficiency (ICE). Most of literature shows that the SnO-based anode commonly reveals an ICE below 50 %, and the reasons could be attributed to the partial reversibility in conversion reaction by forming an intermediate phase. This work focuses on using an element doping strategy to suppress the formation of an inert intermediate phase and improves the ICE for SnO-based anodes in sodium storage applications. Mechanisms of performance enhancement are also carefully investigated. The 3 % Sb doped sample is demonstrated with enhanced electrochemical performance. Specifically, it delivers an initial discharge capacity of 847 mAh g at 50 mA g, combining an average enhanced ICE of 57.1 % (37.8 % for the undoped comparison), and it also presents a good rate performance of 206 mAh g at a high current density of 1600 mA g. It is found that the Sb dopant reduces the specific capacity of active materials, but it enhances reaction reversibility; improves the overall conductivity of active materials, but does not directly enhance the Na diffusion coefficient; helps to restrain the formation of inert phase (the SnO phase) in sodium storage reactions to improve reversibility and initial Coulombic efficiency. Therefore, reversible capacities and initial Coulombic efficiencies can be effectively enhanced after introducing the Sb dopant at an optimized percentage. This work could provide valuable inspiration for designing conversion and alloying-type anodes for sodium storage applications via ion doping methods.

中文翻译：

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揭示Sb掺杂剂对SnO2-石墨烯作为钠存储阳极的可逆容量和初始库仑效率的影响

基于转化和合金化反应的钠存储材料通常初始库仑效率（ICE）较低。大多数文献表明，SnO基阳极的ICE通常低于50%，其原因可能是由于形成中间相而导致转化反应的部分可逆性。这项工作的重点是使用元素掺杂策略来抑制惰性中间相的形成，并改善钠存储应用中 SnO 基阳极的 ICE。还仔细研究了性能增强的机制。 3% Sb 掺杂样品具有增强的电化学性能。具体来说，它在 50 mA g-1 下的初始放电容量为 847 mAh g-1，平均增强的 ICE 为 57.1%（未掺杂的比较为 37.8%），并且在高电流下还具有 206 mAh g-1 的良好倍率性能。密度为1600 mA g。研究发现，Sb掺杂降低了活性材料的比容量，但增强了反应的可逆性；提高了活性材料的整体电导率，但并不直接提高Na扩散系数；有助于抑制钠储存反应中惰性相（SnO相）的形成，以提高可逆性和初始库仑效率。因此，以优化百分比引入Sb掺杂剂后，可以有效提高可逆容量和初始库仑效率。这项工作可以为通过离子掺杂方法设计用于钠存储应用的转化型和合金化型阳极提供宝贵的灵感。