Enhancement of electrochemical properties of cathode in lithium ion batteries by using poly(triethylene glycol methyl ether methacrylate-co-methyl methacrylate)
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초록
내용
To improve the ionic conductivities of binders used for the cathode of the lithium ion batteries, copolymers having ethylene glycol (EG) were synthesized by free radical polymerization using ethylene glycol methyl ether methacrylate (EGMMA) and methyl methacrylate, and the numbers of EG groups were varied from 3 to 9. The ionic conductivities depending on the temperature were measured from -15 to 100 oC, and ionic conductivities of binders increased as the lengths of EG group increased. When the number of EG group was 9, it had the highest ion conductivity of 6.6X10-6 S cm-1, while PVDF had 3.7X10-9 S cm-1 at 25 oC. Binders prepared in this experiment were also electrochemically stable up to 5 V. At 45 oC, cycle performance and initial discharge capacity of binders having EG groups were significantly improved compared to those of PVDF. Binders exhibited much higher discharge capacity (83.6 ~ 113.3 mAh g-1) than that of PVDF (40.0 mAh g-1) at high rate (2 C).