三维碳网络限域锑基合金纳米复合结构的原位构筑、表界面调控及储钾机理研究

Antimony-based materials can react with potassium by multi-electron alloying and deliver a high capacity, showing great potential in the new low-cost potassium ion batteries. However, its application is limited by the poor cycle stability and the low first efficiency caused by the huge volume change during the alloying-dealloying process. In this work, a three-dimensional carbon network confined Sb-based alloy nanocomposite will be in-situ prepared by catalytic pyrolysis with salt-template assisted, and controlling preparation in large-scale will also be achieved. The effect of the composition, content, size, shape, structure of antimony-based alloy and matrix on the storage performance of potassium will be investigated; and the effects of surface doping on electron transmission, potassium ion diffusion and surface storage of potassium will be studied combined with the first-principles calculation, the influence mechanism of in situ catalytic, confinement effect of carbon shells, and the interface storage of K+ will be revealed. Moreover, The effect of the multiphase composite structure on the potassiation/depotassiation potential, K+ transfer kinetics, electron transmission of antimony-based materials will be investigated, and the storage mechanism of potassium will be clarify via proposing a theoretical model. The initial irreversible capacity will be reduced by pre-potassium and optimizing the electrolyte. The structure evolution, the formation and evolution mechanism of SEI film will also be studied via in-situ characterization technology. Meanwhile, the mechanism of its improvement will also be explored. The research results will lay a sound theoretical and experimental foundation for the design of high-capacity and high-stability composite negative material and its practical application in the potassium ion battery.

锑基材料可与钾发生多电子合金化反应而释放出高容量，在新型低成本钾离子电池中表现出巨大应用潜力。但其合金化过程中巨大体积效应导致的循环稳定性差和首次效率低限制了其应用。本课题拟采用溶盐模板辅助的催化热解法原位构筑三维碳网络限域锑基合金纳米复合结构，实现其宏量可控制备。研究合金及基体相的成分、含量、尺度、形态、结构对储钾性能的影响；结合理论计算，探究表面掺杂对电子传输、钾离子扩散以及表面储钾的影响，揭示纳米锑基合金的原位催化机理、有序碳层限域效应及对界面储钾影响机制；探明多相复合结构对锑基材料的嵌钾/脱钾电位、钾离子迁移动力学、电子传输等的影响，构建模型阐明其储钾机理。通过预钾化及电解液优化降低其首次不可逆容量，结合原位表征技术研究复合结构的结构演变、SEI膜形成及演化机制，探明其改善机理。研究结果将为高容量和高稳定性复合负极材料设计及其在钾离子电池中的应用奠定坚实的理论和实验基础。

锑基材料由于其拥有较低的合金化电位以及较高的理论容量，在钾离子电池负极材料中备受瞩目，但是由于其合金化过程中的体积效应会导致较差的循环稳定性，从而限制其实际应用。针对上述问题，本项目利用溶盐模板法原位构筑三维碳网络限域锑基合金纳米复合结构，系统研究了合金及基体相的成分、含量、尺度、形态、结构对储钾性能的影响；结合理论计算，分析了材料在储钾过程中的失效机制，探究了表面掺杂、电解液优化，微观机制对电子传输、钾离子扩散以及表面储钾的影响。具体如下：首先结合第一性原理计算探究吡啶氮和吡咯氮掺杂对于多孔碳材料电化学储钾性能的影响，并对掺杂后的电子结构和对钾原子的吸附能进行计算，阐明了掺杂改善机制；之后利用第一性原理计算明确Sb在脱嵌钾过程中失效机制，结合实验验证Sb/C复合材料能有效改善循环稳定性，随后合成了氮掺杂多孔碳限域的纳米SnSb@NC，阐明了电解液体系对SEI膜形成、电荷转移电阻及电化学性能所产生的影响规律。在此基础上，合成了多孔碳限域的FeSb合金复合结构，明确了微观结构对电导率和循环稳定性所产生的影响。通过在纳米尺度的合金化处理揭示了复合结构尺度对脱嵌钾体积变化产生的影响规律，最终合成具有更多活性位点的SnO2@C复合材料，其作为钾离子电池负极表现出较高的可逆比容量以及良好的循环稳定性。此外，还精确可控地制备了不同比例组分、不同结晶程度的Sb/Sb2O3复合材料并深入探究了其储钾行为。最终制备得到具有非晶层的Sb2O3@Sb@C复合材料具有优异电化学性能（2 A g-1下循环2000圈比容量仍保持241.67 mAh g-1，保持率为88.5%；在5 A g-1下，可逆比容量为231 mAh g-1），优于现有报道的大多数负极材料。研究结果为新型复合结构设计及钾离子电池负极的开发提供了新思路及实验指导。