(597f) Study on the Gel Polymer Electrolyte Based on the Synthesized Copolymer of Pmma-Mah

In liquid-filled batteries, the liquid electrolytes may escape or present a fire hazard and an inert spacer is needed to separate the electrodes. Polymer electrolytes are of technological interest. Solid polymer electrolyte systems typically possess the required mechanical properties, but have inherently lower conductivity due to the more restricted motion of polymer molecules. A gel system is an attempt to strike a balance between the high conductivity of organic liquid electrolytes and the dimensional stability of a solid polymer. Gel polymer electrolytes (GPEs) are reported to be suitable for electrochemical devices since their transport properties are quite exceptional and they have an ionic conductivity of the order of 10^-3S/cm, an electrochemical stability window exceeding 4.5V and lithium-ion transference numbers averaging 0.9. So gel electrolytes are alternatives to both solid polymer electrolytes and liquid electrolytes for lithium battery application. But in GPEs, the addition of plasticizer into the polymer electrolyte decreases the dimensional mechanical stability of the electrolyte, so recently, to overcome the shortcoming, the GPE based on the synthesized copolymer with appropriate design component and structure.

In the research, poly(methyl metacrylate-maleic anhydride) (P(MMA-MAh)) has been synthesized in toluene from methyl metacrylate (MMA) and maleic anhydride (MAh) monomers according to free radical polymerization in the presence of 2,2'-Azo-bis-isobutyromitril (AIBN) as initiator at 80°C for 8h. The molar ratio of monomers was found to be 1MAh:8MMA by method of hydrolysis and titration. The molecule weight of copolymer was determined in the order 10⁴(g/mol) by gel permeation chromatography (GPC). The characterization of copolymer has been done with characteristic peak observed in Fourier transform infrared (FTIR) and NMR spectroscopy. Thermogravimetric analysis (TGA) indicated the initial decomposition temperature (IDT) was about 322°C. The glass transition temperature could be determined as around 120°C by differential scanning calorimeter (DSC).

Rectorite modified with dodecyl benzyl dimethyl ammonium chloride was used as a filler additive to modify gel polymer electrolytes (GPEs) which consisted of P(MMA-MAh) used as polymer matrix, propylene carbonate (PC) as a plasticizer and LiClO4 as lithium ion producer. XRD analysis indicates that OREC can disperse well in GPEs when clay adding amount is appropriate. The temperature dependence of ionic conductivity of GPEs is well fitted by the VTF (Vogel-Tamman-Fulcher) relation. OREC doses of 5 phr gave the highest ionic conductivity. This amount also greatly increased plasticizer maintenance levels. Due to the occupancy of free volume space in the polymer matrix of GPEs by OREC, the bulk resistance of the GPEs was lowered and the glass transition temperature (Tg) increased