Rechargeable batteries play a crucial role in the improved performance of portable electronic devices, as well as electric/hybrid electric vehicles. Ceramic electrolytes are a type of electrolyte in which the ionic conduction takes place by the movement of ionic point defects. The problems associated with liquid electrolytes and ceramic electrolytes can be solved by using solid polymer electrolytes, which possess high ionic conductivity with negligible electronic conductivity. The choices of polymer host and the metal salt play a key role in achieving a good complexed polymer-metal-salt system. The crystallinity of the polymer host for the preparation of polymer electrolytes, especially for solid polymer electrolytes, has a great influence on their room-temperature lithium-ion conductivity and ion transport number. Copolymerisation with another monomer can effectively improve the amorphous content of the resulting copolymer. Polymer electrolytes have been a promising alternative for electrolytes in lithium-ion batteries.