A battery includes an electrolyte disposed on a substantially planar substrate. The electrolyte has a first surface extending from the substrate and in contact with a cathode. The electrolyte has a second surface extending from the substrate and in contact with an anode. The second surface is opposite the first surface. The anode and the cathode are non-overlapping. The battery additionally includes a biocompatible protective layer that covers the electrolyte and at least portions of the anode and cathode. The battery can be disposed in an eye-mountable device or other device to power electronics in the device. The battery can be configured to be rechargeable.