【作者】 周晓燕；

【导师】 郭新；

【作者基本信息】 华中科技大学 ， 材料物理与化学， 2022， 博士

【摘要】 开发高能量密度、长循环寿命和低成本的电化学能量存储系统是实现“碳达峰”和“碳中和”目标不可或缺的一部分。碱（锂、钠）金属电池具有高能量密度,是最有前景的电化学能量存储系统之一。然而,现有的商用有机电解液与碱金属负极副反应严重导致枝晶不可控生长,同时电解液易燃、易挥发、易泄露等缺点给电池造成严重的安全隐患。准固体聚合物电解质有更高的安全性,但是仍存在室温离子电导率低、阳离子迁移数低及电解质/碱金属负极界面相容性差等问题,严重限制其在碱金属电池中的应用。基于上述问题,本论文以准固体聚合物电解质为研究对象,从提升阳离子迁移数和改善准固体电解质/碱金属负极界面相容性的角度出发,开展准固体聚合物电解质的组成设计及电解质/碱金属负极界面优化等方面的研究工作。具体内容如下:（1）从准固体聚合物电解质的设计角度出发,通过开发具有强阴离子吸附能力的填料,以抑制聚合物电解质中阴离子的移动,实现具有高阳离子迁移数的聚合物电解质。通过溶剂热法和煅烧过程合成具有强阴离子吸附能力的α-Li Al O₂/γ-Al₂O₃（LAO）复合纳米片,并将LAO作为填料与聚偏氟乙烯-六氟丙烯共聚物复合制备准固体聚合物电解质。所制备的电解质具有超高的锂离子迁移数（0.92）,高离子电导率(0.85 m S cm^-1@25℃)。在0.5 m A cm^-2的电流密度下,使用该电解质的Li||Li电池能够稳定循环超过1000 h;Li Fe PO₄||Li及高压Li Ni_0.85Co_0.05Al_0.1O₂|Li电池表现出优异的倍率性能和长期循环稳定性。（2）从准固体聚合物电解质/碱金属负极界面设计的角度出发,通过原位热引发聚合制备聚丙烯酸酯衍生的准固体聚合物电解质,实现对电解质/电极界面相容性的改善。通过在电池内部原位热引发聚乙二醇二丙烯酸酯和三乙二醇二丙烯酸酯的交联聚合制备准固体电解质,所制备的电解质具有优异的电化学性能,离子电导率高达1.4 m S cm^-1@25℃,钠离子迁移数为0.52。由于聚丙烯酸酯衍生的聚合物网络不仅能够阻止溶剂在钠金属负极表面的副反应,且其中的羰基（C=O）参与Na⁺的配位,减小了Na⁺的去溶剂化能,从而促进Na⁺在负极表面的均匀沉积,抑制枝晶生长。室温下,使用该电解质的Na||Na电池能够在0.1 m A cm^-2的电流密度下稳定循环超过2000 h;同时,Na₃V₂（PO₄）₃|Na电池表现出良好的倍率和循环性能。（3）结合（1）和（2）,设计同时具有高阳离子迁移数和良好的电解质/电极界面相容性的准固体聚合物电解质,进一步抑制枝晶生长,实现高性能的碱金属电池。通过设计多孔的聚偏氟乙烯-六氟丙烯共聚物/聚氧化乙烯/LAO机械支撑网络并在其中填充原位固化的聚乙二醇二丙烯酸酯和三乙二醇二丙烯酸酯的交联网络,得到同时具有高钠离子迁移数和良好界面相容性的复合结构准固体聚合物电解质。结果表明,所制备的电解质显示出高离子电导率(3.4×10^-4 S cm^-1@30℃)和高Na⁺迁移数（～0.62）。复合结构中LAO和聚丙烯酸酯衍生的交联网络共同作用能同时促进Na⁺的均匀沉积并和提高Na⁺扩散动力学速率。因此,使用该电解质的Na||Na电池能够稳定循环超过900 h,且高正极载量(9.7 mg cm^-2)的Na₃V₂（PO₄）₃||Na电池显示出优异的放电容量和循环稳定性。更多还原

【Abstract】 The development of electrochemical energy storage systems with high energy density,long cycle lifetime and low cost plays an integral role to fulfil the goal of“peaking carbon dioxide emissions”and“carbon neutrality”.Alkali metal batteries are one of the most promising electrochemical energy storage systems due to their high energy density.However,current commercial organic liquid electrolytes have serious side reactions with alkali metal anodes,leading to uncontrolled dendrite growth.In addition,the electrolytes are flammable,volatile and prone to leakage,posing a serious safety hazard to the development of alkali metal batteries.Quasi-solid polymer electrolytes have higher safety,but the low room-temperature ionic conductivity,low cationic transference number and poor electrolyte/alkali metal anode interfacial compatibility,seriously hinder them from applications in alkali metal batteries.To solve the above problems,this thesis aims to improve the cationic transference number and enhance the quasi-solid electrolyte/alkali metal anode interface compatibility via composition design of quasi-solid polymer electrolytes and optimization of electrolyte/alkali metal anode interface.The main research contents are as follows:（1）From the perspective of quasi-solid polymer electrolyte design,fillers with strong anion adsorption capacity were designed and developed to endow quasi-solid polymer electrolyte with high cationic transference number.α-Li Al O₂/γ-Al₂O₃（LAO）composite nanosheets with strong anion adsorption ability were synthesized by the solvothermal method and calcination process,and LAO nanosheets were used as fillers to composite with polyvinylidene fluoride-hexafluoropropylene copolymer to prepare polymer electrolytes.The prepared electrolyte has a high lithium ion transference number（0.92）,high ionic conductivity(0.85 m S cm^-1@25℃).Using the electrolyte,the Li||Li cell can be cycled stably for more than 1000 h at a current density of 0.5 m A cm^-2,and Li Fe PO₄||Li and high voltage Li Ni_0.85Co_0.05Al_0.1O₂||Li batteries show excellent rate performance and long-term cycle stability.（2）From the perspective of electrolyte/anode interfacial design,polyacrylate-derived quasi-solid polymer electrolytes were prepared by in-situ thermo-polymerization to improve the quasi-solid electrolyte/alkali metal anode interfacial compatibility.A quasi-solid electrolyte with excellent electrochemical properties was successfully prepared by in-situ thermo-initiated polymerization of polyethylene glycol diacrylate and triethylene glycol diacrylate in the battery.The prepared electrolyte presents a high ionic conductivity of 1.4m S cm^-1@25℃and a wide electrochemical window（>4.8 V）.The polyacrylate derived crosslinking network can prevent side reactions of the solvent on the surface of the sodium metal anode,and carbonyl groups（C=O）in the network participate in the coordination of Na⁺in the electrolyte,reducing the desolvation energy,promoting the uniform Na deposition and inhibiting the dendrite growth.Using the quasi-solid polymer electrolyte,the Na||Na battery can be stably cycled for more than 2000 h at room temperature and at a current density of 0.1 m A cm^-2.Moreover,Na₃V₂（PO₄）₃@C||Na batteries with the electrolyte show good electrochemical performances.（3）Combining points（1）and（2）,a quasi-solid polymer electrolyte with both high cationic transference number and good electrolyte/electrode interface compatibility was designed to further suppress the dendrite growth and realize high-performance alkali metal batteries.By designing a porous polyvinylidene fluoride-hexafluoropropylene copolymer/polyethylene oxide/LAO network as the mechanical support for the polyacrylate derived polymer electrolyte network,a double network quasi-solid polymer electrolyte with high cationic transference number and good interfacial compatibility was acquired.The obtained electrolyte exhibits high ionic conductivity(3.4×10^-4 S cm^-1@30°C)and high sodium ion transference number（～0.62）.The LAO and polyacrylate-derived cross-linked networks in the electrolyte enhance the diffusion kinetics and promote the uniform deposition of Na⁺,therefore,the Na||Na battery with the electrolyte can be cycled stably for more than 900 h,and Na₃V₂（PO₄）₃@C||Na battery with a high cathode loading(9.7 mg cm^-2)shows excellent discharge capacity and cycling stability.更多还原