【作者】 周志强；

【导师】 邱志明； 宏途；

【作者基本信息】 华南理工大学 ， 材料工程， 2015， 硕士

【摘要】 锂电行业发展迅速,其具有容量大、电压高、体积小、重量轻、比能量高等优点,但同时存在电解液溢流、挥发、爆炸以及聚烯烃隔膜热稳定性不佳等安全问题。本文尝试通过三方面来改善:合成新型的纳米二氧化硅类流体作为导电载体,改善电解液安全问题,制备三元电解液;为了进一步改善电解液的溢流、挥发问题,以及提高电解质的离子电导率,利用合成的可溶性聚醚酰亚胺与基于咪唑的纳米二氧化硅类流体制备凝胶电解质;另外,通过静电纺丝及热处理得到高孔隙率、良好浸润性及一定机械性能的聚酰亚胺纳米纤维毡锂离子电池用隔膜。1、通过在纳米二氧化硅表面改性,得到了含有PEG磺酸盐结构的基于咪唑纳米Si O2类流体(NSIF-Ims)和羟基纳米Si O2类流体(NSIF-Hs);分别与碳酸丙烯酯(PC)-双三氟甲基磺酰亚胺锂(Li TFSI)体系混合制备出三元电解液(NSi F-PC-Li TFSI),类流体含量为0wt.%-80wt.%,以期改善电解液的溢流、挥发、爆炸等问题。测试表明,NSIF-Ims和NSIF-Hs的T(d,5%)分别高达349.3℃和262.0℃,有较好的热稳定性。交流测抗测试表明,两种三元电解液,常温离子电导率较高,NSIF-Ims-60wt.%为9.201*10-4S/cm,尤其是NSIF-Hs-40wt.%可高达1.671*10-3S/cm,都随温度升高有提高。且电解液(PC-Li TFSI)的纽扣电池短期就出现了电压下降的不稳定现象,而类流体纽扣电池1月后还是很稳定,特别是NSIF-Ims的三元电解液充放电速率稳定且快速。2、合成可溶性的含氟聚醚酰亚胺(6FAPB-ODPA),NSIF-Ims作为导电载体与含氟聚酰亚胺混合制备杂化凝胶电解质,聚酰亚胺作为基体提供必要的机械强度。实验中合成了1,4-双(2-三氟甲基-4-氨基苯氧基)苯二胺单体(6FAPB),并和4,4’-联苯醚二酐(ODPA)通过高温一步法聚合为含氟聚醚酰亚胺。红外测试验证了单体及PI的结构,PI的T(d,5%)高达550.5℃,NSIF-Ims-50wt.%凝胶电解质分解温度也高达420.0℃。拉伸强度即使在NSIF-Ims-50wt.%也达到22.0MPa,且显示了良好的疏水性。未加锂盐的凝胶电解质离子电导率(25℃)处在10-5S/cm数量级,添加Li Cl和Li Cl O4两种锂盐提高到10-4 S/cm以上,相比传统的PEO基聚合物电解质的离子电导率有长足的提高,且比未加锂盐时的电解质10-5S/cm有了一个数量级的提高,尤其是添加Li Cl后,NSIF-Ims-80%杂化凝胶电解质离子电导率达到7.67*10-4 S/cm。3、可溶性的含氟聚醚酰亚胺(6FAPB-ODPA)通过静电纺丝及高温热处理制备了纳米纤维毡,比商用的聚烯烃隔膜具有更高的孔隙率、吸液率及更佳的热稳定性。PI-20%未热处理前拉伸强度37.72MPa,经过高温热处理最高可达60MPa。在300℃、320℃、340℃处理的PI-20%纤维毡孔隙率均分别高达82.49°、73.00°、67.50°,PI-20%(300℃)吸液率和保液率高达584.8%和294.0%,明显高于商用PE膜。接触角测试表明纤维毡疏水性强,且电解液浸润性良好,PI-20%(300℃)的电解液接触角约0°。SEM测试表明纤维毡的纤维及孔径分布均匀,直径为300-600nm。三种纤维毡组装的纽扣电池恒流充放电结果显示,PI(300℃)和PI(320℃)充放电速率快且循环稳定,显示了作为电池隔膜的潜力。更多还原

【Abstract】 Recent years, the lithium battery industry has developed rapidly, lithium ion batterieshave high working voltage and capacity、little volume and light、high specific energy. But itexists security issues of electrolytes overflow、volatilization、explosion and poor thermalstability of polyolefin membranes. In this article we try to improve through three aspects:New type of silica nanofluids were synthesized to prepare ternary electrolyte to improve thesafety; In order to further improve the electrolyte safety, soluble fluorinated polyimide wassynthesized and mixed with nanofluid to make hybrid gel electrolyte; At the same time, PIwas used to make nanometer fiber mat with high porosity 、 good invasive and necessarymechanical properties by electrospinning for Lithium-ion batteries.1、Si O2 nanofluid(NSIF-Ims) based on imidazole and Si O2 nanofluid(NSIF-Hs) containinghydroxy were synthesized through surface modification and grafting PEG sulfonate. Ternaryelectrolyte( NSi F-PC-Li TFSI) were got through by replacing part of solvent(PC) ofPC-Li TFSI electrolytes with 0wt.%-80 wt.% nanofluids, respectively. Nanofluids were goodthermal performance, their T(d,5%) were as high as 349.3 ℃ and 262.0 ℃. AC impedance testshow that the two hybrid electrolytes’ ionic conductivity s(25℃) were above 10-4S/cm,especially NSIF-Ims-60 wt.%(9.201*10-4 S/cm) and NSIF-Hs-40 wt.%(1.671*10-3S/cm),s rised as the temperature rised; Battery system test showed voltage of NSIF-PC-Li TFSIbatteries’ constant current charge and discharge were more stability than PC-Li TFSI batterywhich just last two days’ stable cycle.2、Conductive NSIF-Ims was mixed with polyimide(6FAPB-ODPA) to prepare hybrid gelelectrolyte, polyimide provide necessary mechanical strength as substrate.1,4-bis(4-amino-2- trifluoromethylphenoxy) benzene(6FAPB) was synthesised and used forone-step polycondensation with 4,4’-diphenyl ether dianhydride(ODPA) to get soluble PI.Infrared spectrum had confirmed the structure, PI-T(d,5%) was 550.5 ℃, initial decompositiontemperature of NSIF-Ims-50% hybrid electrolyte is up to 420.0℃, tensile strength ofNSIF-Ims-50% was more than 22.0MPa; The hybrid electrolytes were hydrophobic. Ionicconductivity(25℃) of these hybrid electrolytes without lithium salt were all above 10-5S/cm,after adding Li Cl and Li Cl O4 to the hybrid electrolytes, ionic conductivity(25℃) overall reachabove 10-4 S/cm, which were higher than normal PEO electrolytes; especially after addingLi Cl, ion conductivity of NSIF-Ims-80% gel electrolyte reached 7.67*10-4 S/cm.3 、 Nanofiber mats were made with soluble fluorinated polyimide( 6FAPB-ODPA) byelectrospinning and high temperature heat treatment, they have higher porosity 、 betterelectrolyte invasive、higher uptake and better thermal performance than Polyolefin Lithiumbattery membrane. No heat treatment PI-20% nanofiber mat’s tensile strength was 37.72 MPa,up to above 60 MPa after heat treatment. Porosity of PI-20%(300℃, 320℃, 340℃) fiber matswere as high as 82° and 73° and 67°, respectively. Uptake and liquid rate of PI-20%(300℃)were 584.8% and 294.0%, respectively; Contact angle test shows that fiber matwere hydrophobic, and, the EC/DMC(1:1) contact angle of PI-20%(300℃) was about 0°;SEM test showed that fiber mats had uniform pore size distribution, fiber diameter was about300-600nm; Assembled battery with PI-20%(300℃, 320℃, 340℃) fiber mats and 1 M Li PF6,charge and discharge test results were fast and stability, especially of PI(300℃) and PI(320℃) fiber mat.更多还原