Traditional lithium ion batteries are produced in fixed shapes, which limits their applications and often forces designers to build devices around a battery. However, a 3D printed battery could not only fit in any form factor, but be used as a more prominent structural element in devices. Researchers have developed such a battery, infusing plastic with a mix of ethyl methyl carbonate, propylene carbonate, and LiClO4 to achieve the conductivity needed for a battery. Theoretically, the conductive polymer could also be used to print other devices, such as circuit boards. Unfortunately, the capacity of the test batteries were "about 2 orders of magnitude" lower than commercial lithium ion batteries, but the researchers think that some alternative materials could bring the capacity up to practical levels. Different electrically conductive (Super P, graphene, multiwall carbon nanotubes) and active (lithium titanate, lithium manganese oxide) materials were blended into PLA to determine the relationships among filler loading, conductivity, charge storage capacity, and printability. Up to 30 vol % of solids could be mixed into PLA without degrading its printability, and an 80:20 ratio of conductive to active material maximized the charge storage capacity. The highest capacity was obtained with lithium titanate and graphene nanoplatelets in the anode, and lithium manganese oxide and multiwall carbon nanotubes in the cathode. We demonstrate the use of these novel materials in a fully 3D printed coin cell, as well as 3D printed wearable electronic devices with integrated batteries.