Disclosed herein is a battery with a pouch-type enclosure for use with an implantable electronic device. The battery may have greater than 20 megaohms of isolation between the anode and the external surface of the pouch-type battery enclosure and the cathode and the external surface of the pouch-type battery enclosure. The battery may have a pouch-type enclosure with a contoured shape, including a cathode, anode, and electrolyte disposed within the pouch-type enclosure. The cathode and/or anode may have variable thicknesses. The variable thickness anode and/or cathode may be contoured in shape to at least partially provide the contoured shape of the pouch-type enclosure.