目前可充电电池已广泛应用于人们的生产生活，但随着社会生产水平的提高和科学技术的进步，商业化锂离子电池现有的能量密度已无法满足人们日益增长的需求，开发具有更高能量密度的可充电电池迫在眉睫。锂金属因其高的理论比容量和低的电极电势被认为是下一代可充电电池理想的电极材料之一。然而，不可控的锂枝晶生长和锂金属粉化限制了锂金属电池大规模应用。凝胶聚合物电解质能够改善锂枝晶生长、提高电池安全性能，因此开发新型凝胶聚合物电解质成为当前锂金属电池研究的重要方向之一。本论文围绕凝胶聚合物电解质中锂离子的扩散行为及其在锂金属电池中的应用进行研究，主要开展了以下四个工作：

1.      通过脉冲梯度核磁共振和拉曼光谱测试相结合的方法，建立了锂离子扩散与温度、电解质中盐浓度的相关性。以1,3-二氧戊环（DOL）的液态电解质与其相应的凝胶聚合物电解质为模型体系，研究了液态和凝胶聚合物电解质中锂离子的化学环境，结合锂离子扩散系数和离子电导率测试，探讨了影响锂离子扩散的因素。研究表明，液态电解质与凝胶聚合物电解质中锂离子的扩散行为基本一致，温度升高可促进锂离子扩散，盐浓度增加使锂离子扩散受限。不过，受聚合物体系的粘度和聚合物的链段结构等因素的影响，凝胶聚合物电解质中锂离子的扩散受锂周围化学环境的影响更大，而锂周围化学环境与锂盐浓度有密切关系，该研究工作为设计和制备新型凝胶聚合物电解质提供了科学的指导。

2.      设计并合成了交联型凝胶聚合物电解质，有效地保护锂金属负极，改善电池的循环寿命和安全性。利用电池内部原位阳离子开环聚合的方法，以DOL为聚合单体，通过交联剂3,4-环氧环己基甲基-3,4-环氧环已基甲酸酯（EHC）的交联作用得到呈网状结构的聚合物电解质，在电极材料内构建良好的离子导通网络，并有效地降低电解质与电极间的界面电阻。研究表明，引入交联剂可降低聚合物的结晶度，提高聚合物链段对锂离子的传输能力，提高电解质的离子电导率。交联型凝胶聚合物电解质具有较好的热稳定性和较宽的电化学稳定窗口，表现出了优异的电化学性能，能有效地保护锂金属负极，改善电池的循环寿命和安全性。该电解质的制备工艺简单，适用于大规模生产，有望成为未来锂金属电池中的电解质体系之一。

3.      基于原位聚合策略，设计并合成了三元共聚型凝胶聚合物电解质，并研究了其电解质性能和电池性能。以EHC为交联剂，DOL和三聚甲醛（TOM）为聚合单体，开环聚合得到了三元共聚型凝胶聚合物电解质。研究表明，TOM的加入进一步降低了聚合物的结晶度，使聚合物熔点趋近于室温，促进了聚合物分子链段运动，使其具有可与液态电解质相媲美的室温离子电导率，高达8.1×10^-4 S cm^-1。Li/Li对称电池循环测试表明该共聚型凝胶聚合物电解质与锂金属具有很好的界面相容性。将其应用于Li/LFP电池中表现出优异的长循环稳定性，表明该共聚型凝胶聚合物电解质具有很好的应用前景，有望成为下一代高安全性锂金属电池的电解质体系之一。

4.      合成了聚丙烯酸衍生物，并研究了聚丙烯酸衍生物作为人工固态电解质界面膜（SEI）对锂金属负极界面稳定性的影响。研究表明，以聚丙烯酸衍生物为骨架的人工SEI膜在锂金属电池充放电循环过程中可提高锂沉积/析出的稳定性，保护锂金属负极。研究表明人工SEI膜具有极好的应变能力，可充分容纳电池充放电过程中由于锂沉积/析出引起的体积应变，同时具有较好的弹性模量，降低了SEI膜破裂导致裸露的锂金属与电解质反应的概率，有效地抑制了锂枝晶生长，显著提高了电池的安全性，符合未来可充电电池的发展需求。

At present, rechargeable batteries have been widely used in people's daily life. However, commercial lithium-ion batteries (LIBs) can't meet the growing demand due to the low energy density. Rechargeable batteries with higher energy density are in urgent need of development. Lithium metal is considered to be one of the ideal electrode materials for the next generation of rechargeable batteries due to its high theoretical specific capacity and low electrode potential. However, the traditional liquid electrolytes (LEs) easily react with lithium metal, accompanied by heat release, which can cause serious safety hazards. Therefore, the development of new electrolyte systems has become the general trend. This thesis focuses on the diffusion behavior of lithium ions in gel polymer electrolytes (GPEs) and the application of GPEs in lithium metal batteries (LMBs). Following works have been carried out and the results are as follows:

1.      The correlation between lithium ion diffusion coefficient, temperature and lithium salt concentration of the LE have been constructed by combining of the results from pulsed gradient NMR and Raman spectroscopy testing methods. LEs and the corresponding gel electrolytes with 1,3-dioxolane are used as model system to study the chemical environment of Li ions by determining the diffusion coefficient and ionic conductivity, and the factors that affects the diffusion coefficient had also been discussed. Studies have shown that the diffusion behavior of lithium ions in LEs and GPEs is basically the same. The rules are followed that the diffusion of lithium ions is promoted with rising temperature and the diffusion of lithium ions is refrained with the increasing salt concentrations. However, the diffusion of lithium ions in GPEs is more affected by the chemical environment around lithium related to lithium salt concentrations. That may be attributed to the polymer system high viscosity and polymer chain structure. This work provides scientific guidance for the design and preparation of new GPEs.

2.      A cross-linked GPE is designed and synthesized to effectively protect the lithium metal anode and improve the cycle life and safety of LMBs. Using the in-situ cationic ring-opening polymerization method, the cross-linked GPE can be obtained with DOL as the polymerization monomer and 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (EHC) as cross-linking agent. The in situ formed GPE builds a good ion conduction network in the electrode materials, effectively reducing the interface resistance between the electrolyte and the electrode. Studies have shown that the introduction of EHC can reduce the crystallinity of the polymer, improve the ability of the polymer segment to transport lithium ions, and enhance the ionic conductivity of the cross-linked GPE. Furthermore, the cross-linked GPE has good thermal stability and a wide electrochemical stability window. The GPE displays excellent electrochemical performance, including the impressive suppression capacity of lithium dendrite growth, and improvement of the cycle life and safety for the battery. The preparation process of the GPE is suitable for large-scale production, and is expected to become one of the electrolyte systems in LMBs in the future.

3.      A ternary copolymerized GPE is designed and synthesized based on the in-situ polymerization strategy, and its electrolyte characterizations and battery performances are studied. The ternary copolymer GPE is obtained by ring-opening polymerization, with EHC as a cross-linking agent, DOL and TOM as the polymerized monomers. Studies have shown that the addition of TOM further reduces the crystallinity of the polymer, makes the melting point of the polymer approach room temperature, and promotes the movement of polymer molecular segments, which makes the room temperature ionic conductivity (8.1×10^-4 S cm^-1) of the ternary GPE to be comparable to that of LEs. The cycle test of Li/Li symmetric battery shows that the ternary copolymerized GPE has good interfacial compatibility with lithium metal anodes. And the GPE endows the Li/LFP battery with excellent long-cycle stability, indicating that the copolymerized GPE has good application prospects and is expected to become one of the electrolyte systems of next-generation high-security LMBs.

4.      The effect of polyacrylic acid derivatives (PAA) as artificial solid electrolyte interface layer (SEI) on the interface stability of lithium metal anodes is studied. The investigation shows that the artificial SEI film with PAA as the framework can improve the stability of lithium deposition/precipitation during the charging and discharging cycle of LMBs and protect the lithium metal anodes. And the artificial SEI possesses excellent strain capacity, which can fully accommodate the volumetric strain caused by lithium deposition/precipitation during charging.and discharging processes. In addition, the artificial SEI has a good elastic modulus, which reduces the reaction probability between LE and exposed lithium metal caused by broken SEI. That effectively suppression capacity of the growth of lithium dendrites significantly improves the safety of the battery, meeting the future developed requirement of rechargeable batteries.