COMPOSITE POLYMER ELECTROLYTES BASED ON HYPERBRANCHED POLYMER AND APPLICATION TO LITHIUM POLYMER BATTERIES

摘要

Composite polymer electrolytes based on poly(ethylene oxide) (PEO), hyperbranched polymer (HBP), poly[bis(triethylene glycol)benzoate] capped with an acetyl group, a ceramic filler BaTiO_3, and a lithium salt such as LiN(CF_3SO_2)_2, LiN(CF_3CF_2SO_2)_2, or LiN(CF_3SO_2)_2/LiPF_5 were investigated as the electrolyte for all solid-state lithium polymer batteries. The ionic conductivities of the optimized [(PEO-20wt%HBP)_(12)(LiN(CF_3SO_2)_2)]-10wt% BaTiO_3, [(PEO-20wt%HBP)_(12)(LiN(CF_3CF_2SO_2)_2)]-10wt%BaTiO_3, and [(PEO-10wt%HBP)_(10)(LiN(CF_3SO_2)_2-10wt%LiPF_6)]-10wt%BaTiO_3 electrolytes were found to be 2.6 x 10~(-4) S/cm at 30°C and 5.2 x 10~(-3) S/cm at 80°C, 1.3 x 10~(-4) S/cm at 30°C and 1.6 x 10~(-3) S/cm at 80°C, and 1.6 x 10~(-4) S/cm at 25°C and 1.5 x 10~(-3) S/cm at 60°C, respectively. The lithium polymer batteries composed of the [(PEO-10wt%HBP)_(10)(LiN(CF_3SO_2)_2-10wt%LiPF_6)]-10wt%BaTiO_3 electrolyte and 4 V class cathode, LiNi_(0.8)Co_(0.2)O_2, showed excellent charge-discharge cycling performance. The initial cathode discharge capacity of 154 mAh/g declined only 0.1 %/cycle during first 30 cycles at 60°C.