基于硫系固态电解质的新体系探索及其界面演变机制研究

Abstract: One of the key parts for the all-solid-state lithium batteries is the research and development of the solid state electrolyte materials with the excellent comprehensive performance such as the high ionic conductivity, wide electrochemical window, and formation of a favorable solid–solid interface between electrode and solid electrolyte. Furthermore, it is necessary to understand the kinetics of the ionic transport in solid electrolyte and solid electrode/electrolyte interface. Due to their high ionic conductivity, Li2S–P2S5 system lithium ion conductors are extensively studied, however, the chemical stability of the Li2S–P2S5 system is low, the system is prone to react with moisture and the charge transfer resistance at the interface between the electrode and the solid electrolyte is large which results in low power&energy density and poor cycle life.Electrochemical impedance spectroscopy, or EIS, is a powerful tool to analyze electrochemical processes occurring at electrode/electrolyte interfaces. In the present project, it is planned to investigate the design and optimization methods of sulfide solid electrolytes with high lithium-ion conductivity at room temperature and interfacial modification methods to reduce the interface resistance , moreover, the properties of electrode/electrolytes interfaces is investigated by EIS. Based on elucidation of the key condition parameter and controlling steps of preparation of sulfide solid electrolytes and interfacial modification, we will reveal the ionic transport and electrode reaction mechanisms at the electrolyte/electrode interface and its relationship with material composition and microstructure as well as the evolution law of the electrode/solid electrolyte interface in the whole life of all-solid-state lithium batteries, thus offering that high-performance all-solid-state cells will be eventually constructed.

摘要：寻找综合性能优异的锂离子固态电解质材料并理解锂离子在其中及相关界面中的输运机理一直是全固态锂电池的研究重点和难点。Li2S-P2S5体系硫化物是目前最具应用前景的电解质材料之一，然而其应用于全固态锂电池中还存在化学稳定性差、构效关系认识不深以及电极/固态电解质界面阻抗过高等问题。电化学阻抗谱技术对获取反应过程中电极/电解质界面的特征及动态变化具有独特的优势。本项目围绕上述问题开展硫化物固态电解质的组分设计和性能优化、界面修饰及电极界面反应机制的电化学阻抗谱研究。通过阐明固态电解质制备与电极界面修饰改性的关键控制步骤和条件参数，揭示全固态锂电池中电极界面反应机制及其与材料组成和微观结构演变规律之间的关系以及固固界面在电池全寿命阶段的演化规律，为提升全固态锂电池电化学性能提供思路。

电极/固态电解质界面问题是制约全固态锂电池的能量密度、功率密度及其长期循环稳定性的关键因素之一，解决固态锂电池中的界面问题是取得电池性能根本性突破的关键因素，是目前全固态锂电池实现商业化应用中最难解决的问题。本项目聚焦具有高离子电导、宽电化学窗、机械性能(应力/热膨胀系数等）匹配等综合性能优异的Li2S-P2S5体系硫化物固态电解质材料中性能最为优异的Li10GeP2S12固态电解质、Li7P3S11固态电解质、Li10SiP2S12和Li9.54Si1.74P1.44S11.7Cl0.3固态电解质。利用电化学阻抗谱(EIS)技术对获取电化学反应过程中电极/固态电解质界面的特征及动态变化具有特的独优势并结合显微学、光谱学研究以及充放电测试技术和循环伏安法，深入研究了在层状过渡金属氧化物正极材料LiCoO2、LiNi1/3Co1/3Mn1/3O2、LiNi0.5Co0.2Mn0.3O2、LiNi0.8Co0.15Al0.05O2 以及尖晶石Li4Ti5O12等表面构筑纳米粒子过渡层（炭、LiNbO3和Li4Ti5O12）的方法及相关界面微结构与锂离子传导的构效关系，系统解析了层状过渡金属氧化物正极材料与硫化物固态电解质组成的全固态锂电池的电化学阻抗谱特征，归属了各时间常数，分析了全固态锂电池中各不同物理和化学过程的相关动力学参数对电极电位、温度、压力、电极组成和循环周数等的依赖关系。获得了在正极材料表面构筑纳米过渡层改善电极/电解质界面稳定性、降低界面电阻的方法，阐明了描述固态电解质离子输运机制各物理模型的优缺点，建立了界面电阻、势垒电容和电荷传递电阻、双电层电容与材料组成和微观结构演变规律之间的关系。发表Journal of Power Sources、Chemistry - A European Journal、化学学报等SCI论文13篇；申请中国发明专利11项，已获得授权3项；国内外学术会议邀请口头报告3次；培养博士生毕业生1名/硕士毕业生2名、在读硕士生4名; 访问中国工程物理研究院电子工程研究所506室4次并做学术报告3次。