Lithium-ion batteries have rapidly become the dominant power sources for portable electronic devices and electric vehicles, due to their high energy density and long cycle life.[1,2] However, safety issues have become a significant concern owing to the use of flammable liquid electrolytes.  In this respect, the development of non-flammable solid electrolytes may provide a fundamental solution to the safety issue of lithium batteries.  Solid polymer electrolytes based on poly(ethylene oxide) (PEO) present advantageous features such as flexibility in the shape of battery design, absence of leakage of organic solvents and better safety than liquid electrolytes.[3] However, they show poor ionic conductivity at ambient temperatures due to their tendency to crystallize. Moreover, their poor mechanical properties at high temperature due to the melting transition may cause short circuits between two electrodes in cases where unusually high heat is generated.  In order to overcome these problems, we prepared polymer electrolytes based on alternating copolymer composed of ethylene oxide and ethylene carbonate (poly(ethylene ether carbonate), PEEC) in the form of flexible thin film, and their electrochemical properties were investigated.  The polymer electrolytes showed higher ionic conductivity and superior electrochemical stability compared to those of PEO-based polymer electrolyte. The polymer electrolytes were applied to the all solid-state lithium batteries, and their electrochemical performance was evaluated.

 References

[1] J. M. Tarascon, and M. Armand, Nature, 414 (2001) 359.

[2] P. G. Bruce, B. Scrosati, and J. M. Tarascon, Angew. Chem. Int. Ed. 47 (2008) 2930.

[3] E. Quartarone, and P. Mustarelli, Chem. Soc. Rev. 40 (2011) 2525.