Experimental Research On Synthesis And Properties Of New Borate Electrolyte For Lithium-ion Batteries

With the growing population and the limited earth's resources, we are urged to improve resource utilization. Using rechargeable batteries is one of effective ways to promote the lithium battery research and development. Meanwhile, with growing awareness of environmental protection, the use of toxic metals such as lead and nickel is increasingly restricted. Therefore, people need to find new alternative rechargeable batteries to substitute traditional lead-acid batteries and nickel-cadmium batteries, lithium batteries naturally become one of the most powerful candidate.Electrolyte and organic solvent constitute lithium-ion battery electrolytes, which determines the transmission speed and efficiency during the charge and discharge process. As we can see, the research on electrolyte is critical. As croconic acid o-hydroxyl and oxalic acid both can formπchelate anion with B, and by combining with the lithium-ion, a lithium borate electrolyte with stable structure and good electrochemical properties is formed.The thesis is divided into four chapters.In the first chapter, through extensive literature research, the author summarizes various components of lithium-ion battery research progress.In the second chapter, design and synthesis of the four kinds of lithium borate: lithium difluoro[croconato]borate (LDFCB), lithium (3,4,5,6-Tetrafluorocatechol oxalicdiolato)borate (PFLBDOB), lithium bis[croconato]borate (LBCB), lithium [croconato oxalicdiolato](LOCB). LDFCB and PFLBDOB were characterized by NMR,TG analysis. Four lithium salts were tested on thermal stability, solubility, conductivity and oxidation potential. Then its chemical properties were studied.In the third chapter, Using DFT methods, we did a theoretical study of LDFCB and its derivatives, and analyzed the molecular structure and electronic structure of such lithium salt. Theoretically explained the essence of the relationship between thermal stability, solubility, conductivity, electrochemical stability of such lithium salts and molecular structure.In the fourth chapter, achievements and shortcomings in this thesis are bri efly described, and future research directions are suggested.In summary, two kinds of lithium borate (LDFCB and PFLBDOB) were successfully synthesised, its structure and electrochemical properties were tested. The results show that the lithium salts have good solubility, high electrical conductivity and oxidation potential, and battery standard lithium borate.