Thermal and Conduction Properties of a PCL-biodegradable Gel Polymer Electrolyte with LiClO4, LiF3CSO3, and LiBF4 Salts

A biodegradable gel polymer electrolyte was prepared using Poly(e-caprolactone) as a polymer host and its electrochemical performance was evaluated. The biodegradable gel polymer electrolyte was produced by casting through dissolution of PCL in tetrahydrofuran (THF) with 5, 10, and 15% wt. of the propylene carbonate and several salt concentrations of LiClO4, LiF3CSO3, and LiBF4. The thermal behavior of the gel polymer electrolytes has shown that the addition of propylene carbonate as a plasticizer agent in the PCL promotes an increase in the disorder of the crystalline phase, decreasing the crystallinity degree. The glass transition temperature increased as the concentration of lithium salts was increased. The ionic conductivities of the PCL/10% PC to LiClO4, LiF3CSO3, and LiBF4 with 12% wt at room temperature were about 2.26 x 10-4, 4 x 10-5, and 1.5 x 10-7S cm-1, respectively. The conductivity enhancement with temperature can be understood in terms of a free-volume model. The biodegradable gel polymer electrolyte was stable electrochemically up to 5.0 V vs Li/Li+.