Polymer Electrolytes for Lithium Batteries : A Review on Types, Characteristics and Challenges

Today, the economic growth of countries depends on the supply of energy resources. In most countries, these resources include coal, oil, natural gas, and nuclear energy. However, the use of these resources faces various challenges, including the depletion of fossil fuel resources, environmental pollution and an escalating price. In order to reduce global reliance on finite natural resources and environmentally destructive fuels, many efforts have been made to replace them with renewable resources, such as solar energy, water, wind, and etc. Batteries are one of the most potential technologies for this purpose. Lithium batteries have become increasingly important energy storage systems in our daily lives, which play a significant role in electronics and electric vehicles. However, their practical applications are plagued by the safety issues from liquid electrolytes, especially when the batteries are exposed to mechanical, thermal, or electrical abuse conditions. Polymer electrolytes are being proposed as an alternative liquid electrolyte for building safer lithium batteries. In this review article, polymer electrolytes are divided into two large categories of solid polymer electrolytes and gel polymer electrolytes. The characteristics and properties of solid polymer electrolytes and gel polymer electrolytes are presented at the first. Then, the recent progress of common polymers, namely, poly(ethylene oxide), poly(methyl methacrylate), polyacrylonitrile, poly(vinylidene difluoride) and poly(vinylidene fluoride-hexafluoropropylene) copolymer, biopolymers (cellulose, polyurethane, polycaprolactone), polycarbonate and polysiloxanes as polymer host of polymer electrolytes will be discussed. Finally, we will discuss remaining challenges and future perspectives of the polymer electrolytes for high-performance lithium batteries. We hope that this paper can provide useful information for the development of new polymer electrolytes with excellent properties for use in lithium batteries.