The Fundamental Study On The Polymer Electrolyte For Lithium Ion Battery

A novel polymer material of Poly(methyl methacrylate-co-acrylonitrile-co-lithium methacrylate)(hereinafter abbreviated to PMAML) was synthesized, andpolymer electrolytes based on PVDF-HFP, PMMA, PVDF-HFP and PMAML blendwere prepared respectively. A new method for preparing polymer electrolyte membraneand a new method for fabricating lithium ion battery with polymer electrolyte wasintroduced respectively. The ion conductive mechanism and characterization methods ofpolymer electrolyte were discussed. The interfacial properties, fast test method andstatus forecast related to lithium ion battery were studied. The main contents of thisthesis as follow: Polymer membranes of PVDF-HFP were prepared by extraction and phaseinversion method respectively, and the affects of organic plasticizer on the performanceof polymer electrolyte and the electrochemical performance of electrode active materialwere investigated, then fabrication art of lithium ion battery with polymer electrolytewere optimized. Content of plasticizer and Inorganic nano powder (in extractionmethod), the content of polymer and non-solvent in the casting liquid (in phaseinversion method) affect pore structure of polymer membrane. The uptake of liquidelectrolyte is critical to conductivity of polymer electrolyte, and the conductivity ofpolymer electrolyte with good mechanical stability can reach 3.53mS?cm-1 at ambienttemperature. The performance of negative material was affected strongly by plasticizers. The mechanical property of polymer electrolyte based on PMMA can be improvedafter PMMA was crosslinked by EGD. The experimental results display that theoptimized component of the polymer electrolyte was 25%MMA,2%EGD,73% liquidelectrolyte. The conductivity and the electrochemical window of the resulted polymerelectrolyte was about 2mS?cm-1 and 4.8V respectively. In this thesis, polymer electrolyte based on the blend of PMAML and PVDF-HFPwas prepared originally, and a novel method for preparing polymer membrane wasintroduced. The pore structure of the polymer membrane can be controlled by changingthe ratio of PMAML to PVDF-HFP, evaporation velocity of solvent, environmentalhumidity and the content of polymer materials in the casting liquid. The conductivity of II the resulted polymer electrolyte was 3.7mS?cm-1. The ratio of PMAML to PVDF-HFPand the composition of PMAML affect ionic conductivity, liquid electrolyte uptake andinterfacial property. A novel method (abbreviated to DC) for assembling lithium ion battery withpolymer electrolyte was introduced originally. In DC method, the polymer material wascoated onto the electrode substrate directly, and lithium ion battery with polymerelectrolyte can be obtained by injecting liquid electrolyte. This process is simple andpractical because the ultra dry environment is unnecessary except the step of liquidelectrolyte injection. Lithium ion batteries with polymer electrolyte based on PMAMLand PVDF-HFP blend display good electrochemical performance and high ratedischarge capability. Ion transport mechanism in polymer electrolyte was analyzed by theoretical model,FT-IR and XRD respectively, and the transport properties were investigated withtransference number and diffusion coefficient. The charge status of lithium ion batterywith polymer electrolyte were forecasted by Peukert equation and AC impedancetechnology. The discharge capability of lithium ion battery with polymer electrolyte atdifferent rate can be tested rapidly by decreasing discharge current consistently. Several kinds of interface were designed, and then interfacial properties betweenpolymer electrolyte and electrode were investigated by AC impedance technologyoriginally. The test results display that interfacial impedance of GPE/Li comprise of twoparts which are interfacial passive layer impedance and charge transfer impedance.Interfacial impedance value...