Synthesis Of Novel Lithium Borate Salt Electrolytes For High Performance Lithium Batteries

Lithium ion batteries with high operating voltage,high energy density,long cycle,no memory effect,rapid charge and discharge,and low environmental pollution properties have been used in ideal power supply for electronic devices and electric vehicles.Electrolyte is an important part of lithium-ion batteries and plays an important role in improving the performance of lithium-ion batteries.Two kinds of electrolytes based on lithium borate salts were designed and prepared to use in lithium batteries.The main work is as follows:1.The effects of different anion structures on the oxidation stability and dissociation energy of lithium salts were calculated by using density functional theory.The lithium salt,LiTFPFB,were screened and synthesized.Then 1.0 M LiTFPFB/PC electrolyte was prepared,and electrochemical properties such as ionic conductivity,lithium ion transference number,oxidation stability,and corrosiveness to current collector Al were measured.And then LiFePO₄/Li and LiCoO₂ batteries based on the electrolyte were assembled,and the cycle and rate performance of the battery were tested at room temperature and high temperature.The capacity retention of LiCoO₂/Li battery based on 1.0 M LiTFPFB/PC electrolyte can still reach 99.1%with the coulombic efficiency of 99.5%after 500 cycles.Finally,the chemical and electrochemical principles behind the excellent performance of the battery were explained by means of AC impedance method,scanning electron microscope?SEM?and X-ray photoelectron spectroscopy?XPS?.2.A novel single-ion-conductor lithium salt PLDPB was synthesized by one-step method,and a novel PLDPB@PEO polymer electrolyte was prepared by combining this single-ion conductor lithium salt with polymer matrix PEO.The PLDPB@PEO polymer electrolyte has a relatively high ionic conductivity(2.88×10^-6 S cm^-1)and a high lithium ion transference number?0.84?,and exhibits excellent oxidation stability?5 V?.In addition,the capacity retention of LiFePO₄/Li battery based on the gel polymer electrolyte can still reach 92.82%with the coulombic efficiency of 98.88% after 500 cycles at 55 oC.