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The Preparation And Its Performance Study Of Lithium Ion Battery Li3V2(PO43Cathode Material

Posted on:2015-02-05Degree:MasterType:Thesis
Country:ChinaCandidate:Q J LiuFull Text:PDF
GTID:2251330431953892Subject:Applied Chemistry
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With the development of economy and society, people committed to developing new, renewable and clean energy because of fossil fuels,energy and environmental crisis.The demand for lithium ion batteries is becoming more and more urgent in electric cars, intelligent storage grid and other high-power applications with its advantages of no pollution and good stability. The monoclinic Li3V2(PO4)3will be the future high power lithium ion battery cathode materials of high capacity of major candidate materials because of its good performance of deintercalation, low price, simple preparation, environment friendly and high theoretical capacity. However, its material conductivity is low due to the VO6eight surface in the structure of Li3V2(PO4)3being separated by PO4tetrahedra, which limed its large-scale application. In this paper, we improve the electrochemical performance of Li3V2(PO4)3by coating, doping and other modified research. The results show that:When the glucose concentration was10wt%, the electrochemical performance of Li3V2(PO4)3sintering at800℃,8h through sol-gel method was optimal, and the monoclinic structure remains unchanged after cycle. During the synthesis process, due to the addition of surface active agent diethylene glycol and osteoporosis agent NH4NO3, Li3V2(PO4)3showed spherical, and the adhesion degree of the Li3V2(PO4)3balls also significantly reduced. The particle size became smaller gradually with the addition of glucose. When the glucose concentration was10wt%, Li3V2(PO4)3ball about400nm~1μm uniformly dispersed in the remaining carbon layer, and exhibited the best electrochemical performance, the discharge capacity were131.8mAh g-1,126.5mAh g-1,102.4mAh g-1and82.8mAh g-1at0.1C,1C,10C and20C. The lithium ion diffusion coefficient DLi+is3.37×10-9cm2s-1through calculation, which is much higher than other materials.When we modified Li3V2(PO4)3through CeO2coating and found that Ce has not entered the Li3V2(PO4)3lattice, but existed on the surface of Li3V2(PO4)3particles in the form of CeO2. The electrochemical performance of Li3V2(PO4)3was significantly improved due to the reduction of the particle size and conductivity increase when CeO2was imported. Compared with the unmodified pure phase, CeO2coated samples of Li3V2(PO4)3has improved significantly in capacity, rate capability and cycle stability. Its capacity can release up to129.9mAh g-1at0.1C, the capacity retention rate was93.8%after200cycles at1C. Reason was that CeO2coating can effectively inhibit V dissolving in the electrolyte, improve Li3V2(PO4)3structural stability and reduce charge transfer resistance.The Li3V2(PO4)3was modified by Co doping, the results showed that: the composite capacity, cycle performance and rate performance of Co doped Li3V2(PO4)3composite has been improved significantly, this is because the particle size of material is decreased, the charge transfer resistance is decreased and the structure stability is improved as with the Co imported.
Keywords/Search Tags:lithium ion battery, lithium vanadium phosphate, coating, doping, electrochemical performance
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