三维多孔SnS@C/graphene复合材料可控制备与储钠性能研究

Layered SnS has attracted significant attentions due to its high reversible capacity and long cycle life as anode for sodium ion battery. However, the Na-Sn-S system is quite new, and does not have the same level of understanding of the Li-Sn-S system, which results in the unclear mechanism of sodium storage for SnS. Moreover, the huge volume change during sodiation/desodiation process leads to a poor cycle life and still cannot meet the demands of the industry. Due to these problems encountered in sodium ion batteries, in-operando Raman spectroscopy will be used in this proposal to evaluate the mechanism of sodium storage for SnS thin film electrode based on the evolution of species at different stages of charge/discharge. The thin film electrode is fabricated via electrodeposition process. According to the degree of reversible reaction between the species at different stages, the electrochemical performance can be optimized by tuning the cut-off voltage. To further boost the electrochemical performances of SnS, a novel and simple synthesis method will be designed to prepare three dimensional and porous SnS@C/graphene composite. It involves self-assembly of SnS2, organic carbon source and graphene oxide in (NH4)2S solution at room temperature based on the discovery of the high solubility of SnS2 in (NH4)2S solution, and then followed by freezing in liquid nitrogen and annealing in N2. The mechanism of this new method will figure out via studying the effects of parameters involved in this process. Finally, a new type of anode material for sodium ion battery with high capacity and excellent cycling performance will be obtained. The accomplishment of the project will be of great importance in the field of energy material research, including fundamental research and application.

层状SnS材料因可逆容量高、循环性能优良，成为钠离子电池负极材料研究热点。然而，对Na-Sn-S体系的研究处于起步阶段，SnS储钠机理尚未明确，充放电中巨大体积变化使SnS循环寿命无法达到使用要求。针对这些问题，本项目借助原位拉曼研究无粘结SnS薄膜电极充放电中物相变化规律，揭示SnS储钠机理。同时，根据中间产物转换可逆程度计算调节充放电电压范围，优化材料性能。为进一步改善材料循环寿命，本项目采用一种新颖、高效方法设计三维多孔SnS@C/graphene纳米材料。该方法基于SnS2在硫化铵中形成稳定溶液，在该溶液中与有机碳源、氧化石墨烯完成组装，结合液氮冷冻和烧结工艺制备复合材料，并根据工艺参数对材料结构和电化学性能的影响阐述合成机理。通过本研究，建立一种新的原位研究储钠机理和电化学性能优化方法，获得一种高容量、长寿命的新型负极材料，同时也为钠离子电池材料的基础研究和开发应用提供新思路。

层状SnS材料因可逆容量高、循环性能优良，成为钠离子电池负极材料研究热点。然而，对Na-Sn-S体系的研究处于起步阶段，SnS储钠机理尚未明确，充放电中巨大体积变化使SnS循环寿命无法达到使用要求。针对这些问题，项目借助原位表征技术揭示了SnS材料的储钠机理。在此基础上，提出了一种一种新颖、高效方法设计三维多孔SnS/graphene纳米材料。该方法基于SnS2在硫化铵中形成稳定溶液，在该溶液中与有机碳源、氧化石墨烯完成组装，结合液氮冷冻和烧结工艺制备复合材料。系统研究了界面结构与合金负极/碳复合材料电化学性能之间的关系，揭示了稳定的界面结构通过增加原子迁移路径和迁移难度来改善复合材料的循环寿命。最后，本项目的实施获得了一种长期稳定的钠离子电池负极，在电流密度为2A g-1循环1000次容量保持率为87.1%，容量仍高达509.9 mAh g-1，为文章报道时的最优典型。