POLYPHOSPHAZENE-POLY(OLEFIN OXIDE) MIXED POLYMER ELECTROLYTES .2. CHARACTERIZATION OF MEEP/PPO-(LIX)N

The preparation, and conductivity, calorimetric, and electrochemical studies of MEEP/PPO-(LiX)n mixed polymer electrolytes, where MEEP = poly[bis-(methoxyethoxyethoxide)phosphazene], PPO = poly(propylene oxide) and LiX = LiBF4, LiClO4, LiCF3SO3, LiAsF6, and LiAlCl4, are described. The addition of PPO in various proportions to MEEP-(LiX)n electrolytes significantly improved the latter's dimensional stability but caused a slight decrease in its conductivity. The conductivities of these mixed polymer electrolytes are much higher than that of PPO-(LiX)n. The Li+ transport number in MEEP/PPO-(LiX)0.13 electrolytes, with LiX = LiBF4 and LiClO4, was determined to be between 0.3 and 0.5. Differential scanning calorimetric data established the predominantly amorphous nature of the mixed polymer complexes. Cyclic voltammetric studies of these electrolytes at a stainless steel electrode indicated a stability domain between 1 and 4.5V (vs. Li+/Li), and established the good Li plating and stripping efficiency in these electrolytes.