| Abstract:Traditional lithium ion batteries may cause safety problem due to the use of volatile and flammable liquid electrolyte. Lithium ion batteries with solid electrolyte not only have safety performance improved but also are able to be fabricated into various shapes. This thesis mainly concentrates on two points:One is the synthesis of porous metal-organic framwork MOF-5as a filler for solid poly(ethylene oxide)(PEO) electrolyte; Another is the preparation of a cross-linked solid PEO-like electrolyte. All-solid-state lithium ion batteries based on the two electrolytes were assembled. The results are as follows:1. Results from X-ray diffraction and scanning electron microscope show that porous MOF-5particles with microscale sizes were synthesized respectively by the dripping solvothermal method and direct solvothermal method. The laser particle size analysis demonstrates that the size distribution of MOF-5synthesized by the dripping solvothermal method is narrower than that by the direct solvothermal method. The LiFePO4/Li battery based on PEO solid electrolyte with MOF-5filler can deliver the discharge capacities of110mAh g"1in the first cycle and98.5mAh g-1in the120th cycle at1C and80℃.2. Through the reaction between methoxy in y-(2,3-epoxypropoxy) propytrimethoxysilane and hydroxy in polyethylene glycol (Mn～600), a cross-linked solid polymer was formed. The polymer was mixed with LiN(SO2CF3)2, and a translucent solid electrolyte membrane was obtained by directly using the hot-pressing method. The electrolyte has an ionic conductivity of3.15×10-5S cm-1at25℃when the ethylene oxide unit (EO):Li=20:1, and it is thermally stable below300℃. The LiFePO4/Li batteries assembled with the electrolyte present reversible rate cycling in the temperature range of80-140℃. At120℃, the initial discharge capacity and discharge capacity after100cycles for the battery operating at1C rate are157mAh g-1and92.8mAh g-1, respectively. |
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