【作者】 刘倩；

【导师】 杨应奎；

【作者基本信息】 中南民族大学 ， 高分子化学与物理， 2021， 硕士

【摘要】 电化学储能是消费电子、电动汽车和智能电网等领域的重要组成部分和关键支撑技术。2020年全球电化学储能市场的累计装机规模约2.8 GW,其中锂离子电池（LIBs）的装机规模高达1.4 GW,在能源领域的地位举足轻重。电极材料是决定LIBs的储能特性和器件成本的关键因素,并可分为无机材料（金属、非金属或其化合物）和有机材料（小分子化合物、有机聚合物）。然而,无机电极材料存在体积波动大、服役寿命短或材料成本高等问题,而有机电极材料会面临导电性差、倍率性能低等限制。因此,本学位论文基于无机纳米相选择、有机聚合物设计和合成方法调控,发展有机-无机复合型电极新材料,并通过循环伏安、恒流充放电和电化学阻抗等技术,研究材料结构与储锂性能之间的构效关系、储锂机制和调控规律,为解决单一无机或有机电极材料面临的挑战寻求新思路。其创新性工作包括以下三部分:（1）建立了简易的一步原位水热聚合新方法,可控制备Sn O₂纳米晶/聚酰亚胺（Sn O₂@PI）复合电极材料。通过三氨基三苯胺、联苯四羧酸二酐单体与Sn Cl₄·5H₂O同步水热反应,聚酰亚胺大分子链能够抑制Sn O₂纳米粒子的生长,并因空间限域效应阻止Sn O₂聚集,致使超细（<5 nm）Sn O₂纳米晶均匀地嵌入在聚酰亚胺基体相中。聚酰亚胺基体可以用作Sn O₂保护层,抑制其在电极充电/放电过程中的体积变化,改善电极的循环和倍率性能。同时,聚酰亚胺链中羰基具有氧化还原活性,能够提高电极的导离子能力,并赋予一定比容量。以Sn O₂@PI复合材料为负极,发现在电流密度为0.1 A g^-1时,可逆容量为897 m Ah g^-1,增加至2.0 A g^-1时保持在479 m Ah g^-1,其比容量的保持率（53%）高于纯Sn O₂负极（39%）,且在循环150次后,Sn O₂@PI复合负极在0.5 A g^-1时仍保留653m Ah g^-1的比容量,表现出较高的比容量、优异的倍率性能和循环稳定性。（2）设计发展了以碳纳米管（CNTs）为导电内核、环化丙烯腈（CPAN）为电活性外壳的新型CNT@CPAN异质结构负极材料。通过CNTs与丙烯腈进行原位溶液自由基聚合产生花瓣状聚丙烯腈包覆CNTs,并在惰性气体中进行热环化反应,得到CPAN层厚度为40～52 nm、均匀包覆的CNT@CPAN核-壳结构复合材料。同时,准一维CNT@CPAN相互搭接,构建起三维多孔网络结构,提供丰富的内部孔道结构,并充分暴露CPAN链中不饱和的多电子氧化还原活性位点（C=N,C=C）。以CNT@CPAN为负极,在电流密度0.1 A g^-1时的可逆容量高达1176 m Ah g^-1,增加至2 A g^-1时维持在439 m Ah g^-1,且在10 A g^-1时充放电5000次后的比容量仍高达330 m Ah g^-1,并发现CNT@CPAN的比容量、倍率和循环性能均优于纯CPAN负极。（3）通过原位沉淀聚合法预先合成纳米硅（～50 nm）/聚丙烯腈复合材料,继而热环化处理得到纳米硅/环化聚丙烯腈（Si@CPAN）复合材料。以Si@CPAN为负极,CPAN稳定的共轭链结构能够抑制纳米Si在充放电过程中的大体积变化,提高倍率能力和循环环稳定性,同时保持Si超高的比容量优势。结果发现,Si@CPAN负极在0.2 A g^-1时的可逆容量为1032 m Ah g^-1,在1.0 A g^-1时循环70圈后比容量稳定在546 m Ah g^-1,远高于纯纳米Si负极的比容量(162 m Ah g^-1)。更多还原

【Abstract】 Electrochemical energy storage is an important part and key supporting technology in the fields of consumer electronics,electric vehicles and smart grids.The cumulative installed capacity of the global electrochemical energy storage market in2020 is about 2.8 GW,among which the installed capacity of lithium-ion batteries（LIBs）is as high as 1.4 GW,which plays an important role in the energy sector.Electrode material is a key factor that determines the energy storage characteristics of LIBs and the cost of the device,and can be divided into inorganic materials（metals,non-metals or their compounds）and organic materials（small molecule compounds,organic polymers）.However,inorganic electrode materials have problems such as large volume fluctuations,short service life,or high material costs,while organic electrode materials face limitations such as poor conductivity and low rate performance.Therefore,this dissertation is based on inorganic nanophase selection,organic polymer design and synthesis method regulation,develops new organic-inorganic composite electrode materials,and studies the material structure through cyclic voltammetry,constant current charge and discharge,and electrochemical impedance technology.The structure-activity relationship with lithium storage performance,lithium storage mechanism and regulation laws,seek new ideas for solving the challenges faced by single inorganic or organic electrode materials.Its innovative work includes the following three parts:（1）A simple one-step in-situ hydrothermal polymerization method has been established to control the preparation of Sn O₂ nanocrystalline/polyimide（Sn O₂@PI）composite electrode materials.Through the simultaneous hydrothermal reaction of triaminotriphenylamine,biphenyltetracarboxylic dianhydride monomer and Sn Cl₄·5H₂O,the polyimide macromolecular chain can inhibit the growth of Sn O₂nanoparticles and prevent the aggregation of Sn O₂ due to the spatial confinement effect.Ultrafine（<5 nm）Sn O₂ nanocrystals are uniformly embedded in the polyimide matrix phase.The polyimide matrix can be used as a Sn O₂ protective layer to suppress the volume change during electrode charging/discharging and improve the cycle and rate performance of the electrode.At the same time,the carbonyl group in the polyimide chain has redox activity,which can improve the ion conductivity of the electrode and give a certain specific capacity.Using Sn O₂@PI composite material as the negative electrode,it is found that when the current density is 0.1 A g^-1,the reversible capacity is 897 m Ah g^-1,and when it increases to 2.0 A g^-1,it remains at 479 m Ah g^-1,which is lower than the specific capacity.The retention rate（53%）is higher than that of pure Sn O₂ anode（39%）,and after 150 cycles of cycles,the Sn O₂@PI composite anode still retains a specific capacity of 653 m Ah g^-1 at 0.5 A g^-1,showing a higher specific capacity,excellent rate performance and cycle stability.（2）Designed and developed a new type of CNT@CPAN heterostructure anode material with carbon nanotubes（CNTs）as the conductive core and cyclized acrylonitrile（CPAN）as the electroactive shell.In situ solution radical polymerization of CNTs and acrylonitrile to produce petaloid polyacrylonitrile coated CNTs,and thermal cyclization in an inert gas,the CPAN layer thickness of 40～52 nm,uniformly coated CNT@CPAN Core-shell structure composite material.At the same time,the quasi-one-dimensional CNT@CPAN overlap each other to build a three-dimensional porous network structure,provide a rich internal pore structure,and fully expose the unsaturated multi-electron redox active sites in the CPAN chain（C=N,C=C）.With CNT@CPAN as the negative electrode,the reversible capacity is as high as 1176 m Ah g^-1 when the current density is 0.1 A g^-1,and it is maintained at 439 m Ah g^-1 when the current density is increased to 2 A g^-1,and at 10 A g^-1 After 5000 times of charging and discharging,the specific capacity is still as high as 330 m Ah g^-1,and it is found that the specific capacity,rate and cycle performance of CNT@CPAN are better than pure CPAN anode.（3）The nano-silicon（～50 nm）/polyacrylonitrile composite material was pre-synthesized by in-situ precipitation polymerization,followed by thermal cyclization to obtain the nano-silicon/cyclized polyacrylonitrile（Si@CPAN）composite material.With Si@CPAN as the negative electrode,the stable conjugated chain structure of CPAN can inhibit the large volume change of nano-Si during charge and discharge,improve the rate capability and cycle stability,while maintaining the ultra-high specific capacity advantage of Si.The results show that the reversible capacity of Si@CPAN anode at 0.2 A g^-1 is 1032 m Ah g^-1,and the specific capacity is stable at 546 m Ah g^-1after 70 cycles at 1.0 A g^-1,which is much higher than that of the specific capacity of the pure nano Si anode(162 m Ah g^-1).更多还原