NiS2@聚多巴胺/聚丙烯酸三维交联电极的可控制备及储钠性能研究

In order to solve the rapid capacity fading and poor cycling stability of nickel sulfides when they served as anode materials in sodium ion batteries, choline chloride-ethylene glycol deep eutectic solvent is used as electrolyte, for the preparation of nano nickel disulfide (NiS2) through electrodeposition at low temperature. On this basis, from the whole anode electrode of view, a system-level strategy of fabrication of three-dimensional crosslinked NiS2@polydopamine/polyacrylic acid (NiS2@PD/PAA) electrode is developed via prepolymerizing dopamine on the NiS2 particle surface, in turn, conjugates to PAA binder. This innovative structure can effectively diminish the volume change of NiS2 and maintain the whole electrode with favorable structural stability and integrity during repeated charge/discharge process, so that the cycling stability can be enhanced. The fundamental purposes of this project is to clarify the electrochemical behavior of nickel ion and sulphate ion during the electrochemical deposition process and the corresponding charge transfer mechanisms, to provide a new controllable preparation route of nano NiS2 in deep eutectic solvent with advantages of lower equipment requirement and mild synthesis condition. Also, it will reveal the effects and mechanisms of dual-interface layer in three-dimensional cross-linked electrode on conversion reaction, dissolution of discharge products, and the transmitting capacity of electron/sodium ion. And then the project will provide novel ideas for the controllable synthesis and electrode structural design of other key materials for lithium (sodium) ion batteries.

为解决镍硫化合物用作钠离子电池负极材料时存在的容量衰减快、循环稳定性差等问题，本项目在以氯化胆碱-乙二醇（ChCl-EG）低共熔溶剂为新型电解质电沉积制备得到纳米二硫化镍（NiS2）的基础之上，立足于电极整体结构设计，采用氧化自聚合-负压原位缩合方法构建NiS2@聚多巴胺/聚丙烯酸（NiS2@PD/PAA）三维交联复合电极，该复合结构可有效缓冲NiS2储钠过程中产生的体积膨胀，同时可使电极系统保持良好的结构稳定性和整体性，从而改善循环性能。通过本项目的研究，明确电沉积过程中镍离子和硫离子的电化学行为及其电荷转移规律，创立一种合成条件温和、设备要求低的纳米NiS2可控制备新方法；揭示三维交联结构中双界面层对NiS2储钠转化反应、放电产物溶解、电子/Na+传输能力等的影响规律及作用机制，为其他锂（钠）电池关键材料的可控合成和电极结构设计提供新思路。

本项目在以氯化胆碱-乙二醇（ChCl-EG）为辅助溶剂制备得到纳米二硫化镍（NiS2）的基础之上，立足于电极整体结构设计，采用氧化自聚合-负压原位缩合方法构建NiS2@聚多巴胺/聚丙烯酸（NiS2@PD/PAA）三维交联复合储钠电极，交联电极的循环稳定性及结构稳定性显著提升。另外，项目拓展研究了镍基硫化物在锂电负极、锂硫电池固硫载体中的应用。.（1）开发了低温常压ChCl-EG辅助制备NiS2的方法，系统考察温度、时间等参数对产物晶体结构及形貌的作用规律。.（2）设计合成了储钠性能优异的三维交联复合电极NiS2@PD/PAA，与未交联电极（NiS2/PAA）比较，其在100 mA/g电流密度下的首次放电比容量以及循环稳定性显著提高。.（3）制备得到生物质碳负载NiS/C复合储锂负极，生物质碳具有多孔道结构，复合材料比表面积增大，反应活性位点增多，表层无定型碳在改善电导率同时有效缓解硫化物体积效应，初始比容量高达1042.3 mAh/g。.（4）制备得到柔性三维自支撑生物质衍生碳(SSC)/NiS/C复合锂硫电池集流体，具有大比表面的SSC/NiS/C复合集流体表现出良好的物理化学固硫作用，在5.3 mg/cm2的高硫负载量下，首次放电比容量为1295 mAh/g。