| As a new type of environmental protection and saving energy, the lithium-ion secondary batteries attract much attention since their appearance. People’s needs become more and more with the development of the society, and becaus e the various resources shortages and energy poverty, people have to seek rene w-able energies what can meet their development needs. Compare the lithiumi-on secondary batteries with other secondary batteries (such as nickel-hydrogen battery, nickel-chromium battery), they have favorable advantages of light quali-ty, low self-discharge rate, non memory effect, long cycle life and non-pollutio-n and so on, that make them have a good prospect in application. So rapidly and all-round development of the lithium-ion secondary batteries has already become the irreversible trend. The study on the lithium-ion battery by electroc-hemical researchers is emerging in an endless way. Synthesis of novel electrol-yte lithium salt has become a new direction of development for lithium-ion ba-tteries. Electrolyte is one of the essential parts of lithium-ion battery, carrying lithium-ion transfer between positive and negative terminals. Its performance directly affects their performances. So, development of the electrolyte lithium salt which has high electric conductivity, good electrochemical stability and int-ermal domain thermal stability, and non-toxic is one of the effective ways to develop new type lithium-ion battery.The main objective of this thesis is to synthesize three lithium borates lit-hium with croconic acid, and their properties were investigated, anions of these lithium borates salts which form large conjugated structure are B-centric large chelating anions, this structure is conducive to the stability of the anions, and we introduce strong electron-withdrawing group-NCN into the anions, that can more scatter the negative charge on the central ion, enhance the stability of the anions, and increase the solubility of lithium boron salt in organic solvents. When lithium-ion binds to this anion, it is more likely to exist in the state of ion in the electrolyte, thus the conductivity of the lithium boron salt can be improvedIn the present thesis, research work mainly includes four steps:First, synt-hetic three lithium borates salt with croconic acid-Lithium difluoro [1,2-di(cy-anoamino)-3-oxo-4-cyclopentene-4,5-diol croconato] borate (DFLNBC), Lithium[1,2-benzenediolato(2)-O,O’-1,2-di(cyanoamino)-3-oxo-4-cyclopentene-4,5-diol croco-nato] borate (BLNBC), Lithium [3,4,5,6-Tetrafluorocatechol-O,O’-1,2-di(cyanoa mino)-3-oxo-4-cyclopentene-4,5-diol croconato] borate (PFLNBC). The ligands and complexes were characterized by IR, elemental analysis, ICP, and the resu-Its were roughly identical to the target products. Second, the properties of the thermodynamic and electrochemical are tested and preliminary analysized, and the properties of the thermodynamic are explored thermostability, solubility in mixed organic solvent, the properties of the electrochemical are explored from electrical conductivity in organic solvent, and its oxidative potential. Three var-ied performances of the three kinds of lithium boron salts are compared on the basis of numeral results, and some conclusions are obtained, thus further realizes relationship between the properties and structure. At last, the deficien-cy of this subject and the future of the lithium-ion secondary batteries were described.Our test results show that three new lithium salts can be synthesized and have good thermal stability and electrochemical stability, good solubleness in some kinds of mixed organic solvents, and high conductivity, it makes sense to do further research on this series of lithium boron salts for their practical application. |
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