【作者】 刘东；

【导师】 韦伟峰；

【作者基本信息】 中南大学 ， 材料与化工（专业学位）， 2023， 硕士

【摘要】 化石能源枯竭和环境污染等问题使得人们对新型可再生清洁能源的需求不断提升,而传统的锂离子电池难以满足高能量密度和高安全性储能设备的需求。高压锂金属固态电池能进一步提升储能设备的能量密度和安全性,但离子电导率低、电化学稳定窗口窄、界面接触差等问题限制了其应用。原位聚合方法能极大改善固态电池界面接触的问题。为此,本论文从聚合物的链段设计以及固态电池的界面调控角度出发,对聚碳酸亚乙烯酯基聚合物（PVC）固态电解质进行改进,实现了高压锂金属固态电池室温下的稳定循环。本文详细工作如下:（1）借助原位聚合方法在PVC链段中同时引入含有环状硼酸酯基团的聚乙二醇甲基丙烯酸酯和耐高压的氰基,制备了一种氰基-有机硼共增强的固态电解质（PVNB）,通过调控PVNB电解质中氰基的含量,获得了兼具高离子电导率(σ=9.24×10^-4 S cm^-1)、高锂离子迁移数(t_Li⁺=0.86)、宽电化学稳定窗口（>5 V）且具有自熄灭特性的聚合物固态电解质。PVNB优秀的机械性能和高的锂离子迁移数有效抑制了锂枝晶的生长,Li|PVNB|Li电池在30℃、0.3 mA cm^-2且沉积容量为0.3 mAh cm^-2条件下稳定循环超1000 h。Li|PVNB|LiFePO₄电池在1C倍率下循环1000圈后放电比容量为131 mAh g^-1,容量保持率高达90.1%,在5C倍率下,Li|PVNB|LiFePO₄电池循环1000次后容量保持率仍为80%。借助EIS、XPS、TEM等手段分析了Li|LiNi_0.8Co_0.1Mn_0.1O₂固态电池的失效机理,研究发现氰基的引入能抑制界面副反应的持续进行,进而提升高压锂金属固态电池的循环稳定性。（2）在前面工作的基础上引入耐高压的砜类塑化剂,制备了新型聚合物固态电解质PVNB-SL,通过调节锂盐成分和浓度将电解质的电化学稳定窗口拓宽至5.81 V。研究发现,随着锂盐浓度的升高,电解质前驱体溶液的锂金属稳定性得到改善,当锂盐浓度为3M时,聚合物固态电解质的锂金属相容性最佳,锂对称电池在30℃、0.5 mA cm^-2、沉积容量为0.5 mAh cm^-2条件下稳定循环超550 h。此外,高浓度固态电解质在循环过程中构筑了更优质的界面层,界面层中无机成分含量的提升抑制了界面副反应的持续进行,加速了界面处的电荷转移,进而提升了高压锂金属电池的循环稳定性,Li|LiNi_0.8Co_0.1Mn_0.1O₂电池在30℃,4.3 V下循环250次后放电比容量为142.2 mAh g^-1容量保持率高达73%。图55幅,表13个,公式3个,参考文献111篇更多还原

【Abstract】 Problems such as fossil energy depletion and environmental pollution have led to a rising demand for new renewable and clean energy sources,while traditional Li-ion batteries are unable to meet the demand for high energy density and high safety energy storage devices.High voltage lithium metal solid-state batteries can improve the energy density and safety of energy storage devices,but the low ionic conductivity,narrow electrochemical stability window and poor interfacial contact of solid-state electrolytes limit their application.In-situ polymerization can greatly enhance interfacial contact properties.In this work,a poly（vinylene carbonate）-based solid-state polymer electrolyte was prepared by in situ polymerization from the perspective of designing polymer chain segments and regulating interfacial composition,achieved stable operation of high-voltage lithium metal solid-state batteries at room temperature.The work is detailed as follows:（1）A cyano and organoboron co-enhanced solid-state polymer electrolyte（PVNB）was prepared by introducing poly（ethylene glycol）methacrylate containing cyclic borate groups and high-voltage stabilized cyano into the chain segment of poly（vinylene carbonate）by in situ polymerization method.By adjusting the content of cyano group,PVNB possesses high ionic conductivity(σ=9.24×10^-4 S cm^-1),high Li-ion transference number(t_Li⁺=0.86),wide electrochemical stability window（>5 V）,and self-extinguishing characteristics.The excellent mechanical properties and high Li-ion transference number of PVNB greatly inhibit the growth of lithium dendrites,and the Li|PVNB|Li cell display excellent cycling stability for over 1000 h at 30℃,0.3 mA cm^-2 and an areal capacity of 0.3 mAh cm^-2.The Li|PVNB|LiFePO₄ cells display a discharge specific capacity of 131 mAh g^-1 after 1000 cycles at 1C,corresponding a capacity retention of 90.1%,and the Li|PVNB|Li cells still show a capacity retention of 80%after 1000 cycles at 5C.The failure mechanism of Li|LiNi_0.8Co_0.1Mn_0.1O₂ solid-state cells was studied via EIS,XPS,and TEM etc.and it was found that the introduction of cyano can inhibit side reactions on the interface from continuing,thus enhancing the cycling stability of high-voltage lithium metal solid-state batteries.（2）Based on the previous work,a new solid-state polymer electrolyte PVNB-SL was prepared by introducing a high voltage resistant sulfone plasticizer,and the electrochemical stability window of the electrolyte was broadened to 5.81 V by adjusting the lithium salt composition and concentration.We found that the lithium metal stability of the electrolyte precursor solution was improved with increasing lithium salt concentration,and the best lithium metal compatibility of solid-state polymer electrolyte was achieved when the lithium salt concentration was 3M.The Li-symmetric cells showed a stable cycle of over 550 h at 30℃,0.5 mA cm^-2,and an areal capacity of 0.5 mAh cm^-2.In addition,the high concentration of electrolytes constructs a high-quality interfacial layer during operation.The side reactions on the interface were suppressed due to the increase of inorganic content in the interfacial layer and the acceleration of charge transfer at the interface,which improved the cycling stability of the high-voltage lithium metal battery and achieved a discharge specific capacity of 142.2 mAh g^-1（corresponding retention of 73%）after 250 cycles of the Li|LiNi_0.8Co_0.1Mn_0.1O₂ cells at 30℃and 4.3 V cutoff voltage.55 figures;13 tables;3 equations and 111 pieces of references更多还原