Synthesis And Application Of Novel Materials For Improving The Safety Of Li-ion Batteries

In this thesis, two effective ways to improve the safety performance of the lithium-ion batteries were studied. The results are as follows:1. Synthesis, characterization and application of hight-content organic phosphorus flame retardants:We prepared the intermediates by the reaction of DOPO with p-benzoquinone and formaldehyde, then the intermediates reacted with dialkyl phosphoryl chloride produced two series of high density phosphorus derivatives. The structures of target compounds were identified by1H NMR,13C NMR,31P NMR, FT-IR, HR-MS and ESI-MS. Take the TGA, DSC and cyclic voltammetry tests of the representative compounds al and a5, the results showed that they all have excellent thermal and electrochemical stabilities. Furthermore, we carried out the combustion experiments of compound a5, found that the lithium-ion electrolyte with compound a5displayed excellent flame retardant effect, namely have both small additive amount and high flame retardant properties.2. Synthesis and characterization of alkyl acrylates gel polymer electrolytes for Li-ion batteries:The polymers of alkyl acrylates have good compatibility with the electrodes, wide electrochemical window, good thermal stability and sufficient mechanical strength enabling its easy handling, etc. The lower glass transition temperature can increase the movement ability of the polymer chain, and enhance the ionic conductivity of the gel polymer electrolytes.The gel polymer electrolytes containing alkyl acrylates, other monomers, TEGDMA and liquid electrolyte were prepared by the in-situ radical polymerization. The ionic conductivity and mechanical properties of the gel polymer electrolytes were studied in detail. The results showed that the gel copolymer electrolytes have good mechanical properties and high ionic conductivity (exceed5mS/cm). The TGA and DSC results displayed the polymers and copolymers of alkyl acrylates have excellent thermal stability. The cyclic voltammetry tests showed that they have wide electrochemical window. The dimensional network structures of the host polymer matrix of the cross-linking gel polymer electrolytes were studied using the scanning electron microscopy, and the results showed that they have three-dimensional porous structures. In the synthesis process, the in-situ thermal polymerization method was explored and studied. In a word, the alkyl acrylates gel copolymer electrolytes have high ionic conductivity, excellent stability and good mechanical property, and have the ability to enhance the safety of Li-ion batteries.