Prepatation And Study Of Nano-tiO₂ Composite Polymer Electrolytes With High Electrochemical Performance

As lithium-ion batteries(LIB) possesses the advantages of high energy density and environmentally friendly etc., they have been widely used in the field of electronic products. With the industrialization of electric vehicles, the leakage and poor thermal performance problems of traditional liquid lithium-ion batteries caused people to worry about battery safety issues. In contrast, polymer lithium-ion batteries(PLIB) many superiority, such as small, ultra-thin, no leakage, the shape of the design is more flexible. Therefore, the PLIB has become research hot spot of high-performance lithium-ion battery. However, the low ionic conductivity of polymer electrolyte and poor interface compatibility with electrode affect the battery performance. It is difficult to achieve practical application. In this paper, we prepared homogeneous casting solution by blending high dispersion of nano-Ti O2 polymer with poly(vinylidene fluoride-hexafluoropropylene)(PVDF-HFP). Then, we prepared different composite polymer electrolyte membranes by phase separation method, the electrochemical properties and battery performance were investigated.1) With the aims to overcome the high thermal shrinkage of conventional polyolefin separators and improve the electrochemical properties of lithium-ion batteries, a glass fiber nanocomposite polymer electrolyte membrane(NCPE) was prepared by introduction of high-dispersed nano-Ti O2 hybrid into a glass fiber nonwoven. The physical and electrochemical properties of the obtained composite NCPE membrane were characterized with SEM, TG, AC impedance and charge-discharge tests. The results show that, NCPE composite electrolyte membrane possesses higher porosity(58%), liquid uptake(330%), ionic conductivity(3.46 m S/cm), and excellent thermal dimensional stability temperature(500 ℃). The interface compatibility of composite electrolyte with metallic Li electrode was greatly enhanced. The discharge capacity of Li Co O2/Li cell assembled with NCPE retain 122 m Ah/g at 10 C rate, and the capacity retention ratio up to 75% after 1500 cycles among cycle test. The battery performance of NCPE is significantly improved compared with PE separator and pure PVDF-HFP gel polymer electrolyte GPE.2) In the LIB, the thickness of the polymer electrolyte will affect the battery capacity. To reduce the thickness of the separator, and prepare high performance polymer electrolyte, the PAN nanofibers membrane was prepared by electrospinning, the average fiber diameter was between 250-300 nm. And a new composite electrospun polymer electrolyte(CEPE) were prepared with PAN nanofibers as a support layer. The physical and electrochemical properties of twere characterized by SEM, TG, AC impedance and charge-discharge tests. The results show that, the CEPE membrane possessed higher porosity(50%), better wettability and higher thermal stability(150 ℃). Cells with the CEPE separator shown better C-rate property and cycle performance than PE and PE based composite polymer electrolyte CPE.