Polymer battery

A battery device has an anode 101 having an n-type polymer, a cathode 105 having a p-type polymer, and a separator 103 comprising a polymer mesh with a crosslinked ion-conducting polymer gel in the pores. The n-type polymer comprises a repeat unit of formula (I) and the p-type polymer comprises a repeat unit of formula (II): wherein R1 and R2 are H or a substituent; Ar1 and Ar2 are optionally substituted C6-20 arylene or heteroarylene; and Ar3, Ar4 and Ar5 are optionally substituted C6-20 arylene or heteroarylene, with at least one aromatic ring atom of Ar3 being bound directly to an adjacent repeat unit or end group of the polymer, and at least one aromatic ring atom of Ar4 being bound directly to an adjacent repeat unit or end group of the polymer. Preferably, Ar1 is phenylene and Ar2 is napthylene. Preferably, Ar3, Ar4 and Ar5 are each optionally substituted phenyl, and Ar5 may also be bound directly to an adjacent repeat unit. An electrolyte is also provided between the anode and the cathode, and is preferably an ionic liquid such as BMP-TFSI. The ion-conducting polymer in the gel separator is preferably polyethylene oxide.