Synthesis And Properties Of Modified Lithium-Ion Battery Separator And The Electrolyte Flame Retardant

As we all know, the lithium-ion batteries(LIB) has many obvious advantages of high energy density,high voltage, no memory and environmentally friendly etc., they have been widely used in our daily life. But in the past few years, the world has undergone a lot of battery safety accidents, the main cause of these accidents is an organic solvent leaks,combustion or even an explosion, In this case, the polymer composite electrolyte with its advantages of high safety performance has become the material of choice for Li-ion battery, In recent years it has been widespread public concern, Compared with our conventional liquid electrolyte, it has not prone to leakage, high flexibility, high physical and chemical stability,etc. compared to polymer electrolyte, its ionic conductivity and compatibility of electrolyte and electrode interface has been significantly improved, In addition, it added in organic electrolyte additive flame retardant, thus bringing the electrolyte into a flame-retardant or non-combustible liquid, which is a simple and practical method of technology, but also greatly enhance the Li-ion battery safety performance, thus, this paper has been studied in two ways and summarized as follows:(1) Composite electrolyte separator was prepared with celgard as supporting membrane which was coated with highly dispersed nano-Al2O3@Polymethylmethacrylate(PMMA) hybrid and PVDF-HFP(poly(vinylidenefluoride-co-hexafluoropropylene)). The structure and electrochemical performance of the obtained composite separator was studied by SEM, AC impedance and charge-discharge tests. Experiment results indicate that Al2O3@PMMA/PVDF- HFP coating can improve the ionic conductivity of the separator, increase the liquid absorption, reduce the interfacial impedance and improve the cell performance. The discharge capacity of the assembled NCM/Li coin cell with the composite separator could reach to 122 mAh/g at 8.0 C with the charged-discharged range of 2.8~4.3V.(2) The homemade fluorinated phosphazene flame retardant added to the 20% of the electrolyte can achieve the desired flame retardant effect, but after adding the fluorine-containing phosphazene flame retardants, the ionic conductivity of the electrolyte has reduced. The electrochemical tests found that flame retardants have not effect in NCMpositive and Graphite electrode, The discharge capacity of the assembled NCM/Li coin cell could reach to 149 mAh/g and the capacity retention rate reached to 96% after 100 cycles, The discharge capacity of the assembled Graphite/Li coin cell could reach to 355.5mAh/g and the capacity retention rate was 96.9% after 100 cycles.