Preparation Of New Lithium Ion Battery Materials And Properties Research

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.