Structural evolution and conductivity of PEO : LiBF4-MgO composite electrolytes

This paper explores and proposes a structure-conductivity correlation in th e PEO:LiBF4-MgO composite electrolyte system. The proposed correlation is d erived from interpretations of DSC and conductivity measurements. Thermal c ycling in the 0-100 degreesC range yields an amorphous polymer structure be lieved to be beneficial for enhanced conductivity. The proposed roles of Mg O are to depress the PEO melting temperature and retard the kinetics of its crystallization. A resistivity relaxation or conductivity enhancement belo w the melting temperature of PEO (68 degreesC) occurs, which appears to be a characteristic of these electrolytes and related to an interaction of dip oles associated with polymer chains and MgO. A higher concentration (simila r or equal to 30%) of MgO leads to its segregation and reduction in conduct ivity resulting from crystallization of PEG. (C) 2001 Elsevier Science Ltd. All rights reserved.