Polymer electrolytes for rechargeable lithium metal batteries
High-energy-density lithium metal battery systems have been attracting significant attention, but their serious safety and stability issues due to the growth of lithium dendrites and strong chemical reactivity of Li metal hinder their practical application. Fortunately, polymer electrolytes may allow lithium metal batteries to flourish. Usually, polymer electrolytes can be divided into dry polymer electrolytes and gel polymer electrolytes. Firstly, we review dry polymer electrolytes based on different polymer materials. This type of electrolyte usually suffers from insufficient room-temperature ionic conductivity and poor interfacial compatibility with electrodes. Thus, many meaningful approaches have been proposed to overcome these issues. Secondly, we review the formulation and development of gel polymer electrolytes. Although some gel polymer electrolytes show excellent lithium ionic conductivity, their mechanical properties are insufficient. Thus, many efforts, including blending, copolymerization, crosslinking and addition of inorganic particles, have been made to address these issues to achieve strong mechanical strength and superior electrochemical performances. Thirdly, special functional polymer electrolytes can solve some pivotal problems to further improve the battery performance. We review some special functional polymer electrolytes such as non-flammable polymer electrolytes, polymer electrolytes for the shuttle inhibition of polysulfides and manganese (Mn2+), and self-healing polymer electrolytes. Finally, the developing trends and challenges of polymer electrolytes are analyzed to foresee the promising future of rechargeable lithium metal batteries based on polymer electrolytes.