基于复合电解质的全固态锂硫电池构建及其电极/电解质界面优化研究

Because of the advantages including high theoretical energy density and abundant resource, lithium–sulfur (Li–S) batteries show promising potentials in various applications, such as electric vehicle and more/all electric aircraft systems. However, Li–S batteries using liquid electrolyte still suffer from the serious problems of poor cycling life and low safety. This project proposes to prepare composite polymer electrolyte (CPE) based on poly(ethylene oxide) (PEO)-based polymer electrolyte and garnet-type Li7La3Zr2O12 (LLZO) inorganic electrolyte. The surface of the CPE will be modified by in-situ atomic/molecular layer deposition (ALD/MLD). The effects of the component and structure of the CPE and deposited layer on the lithium conducting performance of the CPE, stability of the solid electrolyte interface (SEI) on metal lithium anode and electrode/electrolyte solid/solid interfacial impedance will be investigated through electrochemical methods and characterization technologies including Focused Ion Beam (FIB) and Time of Flight-Secondary Ion Mass Spectrometry (ToF-SIMS). The three-dimensional reconstruction of electrode/electrolyte solid/solid interface depending on the depth of charge/discharge will be realized. All solid-state (ASS) Li–S batteries will be further constructed by using rationally designed sulfur cathode with high gravimetric/areal capacity and modified CPE. The critical factors on the electrochemical performances and energy-storage mechanism of the ASS Li–S batteries will be deeply investigated. This project aims to provide important theoretical basis and experiment instruction for developing ASS Li–S batteries with high-energy density and long-cycle life.

锂硫电池具有理论能量密度高、资源丰富等优点，在电动汽车及多电/全电飞机等领域均具有广阔的应用前景。然而，采用液态电解液的锂硫电池依然面临着循环稳定性差、安全可靠性低等问题。本项目拟制备基于聚氧化乙烯基聚合物电解质与石榴石型Li7La3Zr2O12电解质的复合电解质，并通过原子层沉积/分子层沉积技术对复合电解质表面原位改性，结合电化学测试技术与聚焦离子束、飞行时间-二次离子质谱联用等表征技术，阐明复合电解质及改性层的组成、结构与复合电解质的离子传导性能、锂负极固态电解质界面膜(SEI膜)的稳定性、电极/电解质固/固界面阻抗之间的内在关联，实现电极/电解质界面随充放电深度的三维重构。通过结构设计构建具有高质量/面积比容量硫电极，进而构建全固态锂硫电池，揭示影响电池性能的关键因素及其储荷机理。本项目研究将会为构建高比能量、长循环寿命的全固态锂硫电池提供理论依据和实验指导。

本项目围绕全固态锂硫电池目前面临的关键问题，主要开展了硫电极的结构多层级设计、电极/电解质界面改性以及基于有机-无机复合电解质的全固态锂硫电池构建与结构优化研究等研究工作，解决了硫正极电子/离子电导率低、充放电中间产物在复合电解质中的“穿梭效应”以及金属锂枝晶生长等问题，实现全固态锂硫电池电化学性能的改善。(1) 通过电化学反应动力学研究方法以及理论计算探究了硫电极电化学反应动力学过程，提高了硫活性材料的电子/离子电导率，减缓了充放电中间产物的“穿梭效应”，显著优化了硫正极的电化学性能。(2) 探究了复合电解质的组成、填料等对复合电解质离子传导性能、抑制金属锂枝晶能力及电极/电解质界面离子传导的影响，明确了电极/电解质界面的演变过程以及界面失效机制。(3) 发展了基于复合电解质添加剂、界面改性层等电极/电解质界面优化方法以及电池结构优化方法，解决了基于复合电解质的全固态锂硫电池面临的电池循环寿命差、自放电严重等问题。全固态锂硫电池在100%充电状态下静置7天，电池比容量保持率可达80%，后续循环过程中电极/电解质界面可自修复、电池容量可回复至100%。在本项目支持下，在Materials Today、Advanced Energy Materials、Small、ACS Applied Materials & Interfaces等期刊发表SCI论文12篇，申请发明专利5项，其中已授权2项。