A battery for oilfield applications which may include: a housing and an electrolytic cell disposed in the housing. The electrolytic cell may include: a cathode, an anode, and a polymeric separator disposed between the cathode and anode. The cathode may include a cathode composite material coated on a substrate. The cathode composite material may include: a polymeric continuous phase; an active material; a carbon source; and; a first lithium salt. The anode may comprise lithium. The polymeric separator may include: a first polymer crosslinked by a photoinitiator; and a second lithium salt.