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The ability to 3D print lithium ion batteries (LIBs) in an arbitrary geometry would not only allow the battery form factor to be customized to fit a given product design but also facilitate the use of the battery as a structural component. A major hurdle to achieving this goal is the low ionic conductivity of the polymers used for 3D printing. This article reports the development of anode, cathode, and separator materials that enable 3D printing of complete lithium ion batteries with low cost and widely available fused filament fabrication (FFF) 3D printers. Poly(lactic acid) (PLA) was infused with a mixture of ethyl methyl carbonate, propylene carbonate, and LiClO4 to obtain an ionic conductivity of 0.085 mS cm–1, a value comparable to that of polymer and hybrid electrolytes. 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.
Reyes et al. (Tue,) studied this question.