Modification Of Polyacrylic Acid Lithium-based Solid Polymer Electrolyte

In order to obtain a kind of composite polymer electrolyte(CPE) with good properties, the base of CPE, PAALi was modifided and the proportion of lithium salts available was optimized.Firstly, the monomers of acrylonitrile(AN) with high dielectric constant and butyl acrylate(BA) with flexibility were introduced into the base of CPE and terpolymer of AALi, AN, BA was synthesized by solution copolymerization in methanol. Then self-sustained membranes with good mechanical properties can be obtained. It is also proved that the blends of AALi, AN and BA are compatible system.Two orthogonal experiments on lithium salts were done to optimize proportion of lithium salts and a new type of eutectic salt(LiX) was obtained ,which has high room temperature conductivity?3.1 10-4S.cm-1) and low molten point(138). The eutectic salt consists of lithium perchlorate (LiClO4), lithium nitrate(LiNO3) and lithium bromide(LiBr) and its composition is LiClO4/LiNO3/LiBr=2/3/l in mass ratio. The eutectic salt was mixed with copolymer P(AALi-AN) to form polymer in salt electrolyte(PISE), which exhibits a lower glass transition temperature(Tg)(75 ) compared to the pure polymer(105) by differential thermal analysis (DTA). X-ray diffraction(XRD) and Fourier transform Raman spectra(FTIR) indicat that a new complex was formed between polymer and salt by interacting Li+ with -CN and polymer matrix can suppress the salt crystallinity.In order to introduce inorganic compound into CPE, a series of hybrids comprising P(AALi-AN-BA) and silica(SiO2) were synthesized in situ by a sol-gel process and the hydrolyzation of the tetraethyl orthosilicate(TEOS) precursors and polymerization of monomers reacted spontaneously in methanol. A mechanical uniformly membrane idetifided by TEM was obtained, which exhibits good thermal stability characterized by DTA and thermogravimetry (TG). The hybrids was successfully used to enhance the conductivity of P(AALi-AN-BA)/LiXby mixing the hybrids with LiX to form P(AALi-AN-BA)/SiO2/LiX electrolytes. In the curves of conductivity versus composition for the CPEs, the room temperature conductivity shows a maximun value of 6.26 l0S.cm-1,corresponding to the sample with a 10 wt% of silica. The CPEs were examined by AC impedenc, DTA and FTIR. The results indicated that SiO2 can reduced the ion transfer activation energy(Ea) in the system. The interactions of components of the investigated system in the system and the possible conduction mechanism were also discussed. In addition, some interesting phenomena such as thermal hysteresis and stability of conductivity to time also were discussed.