Battery-on-Separator: A platform technology for arbitrary-shaped lithium ion batteries for high energy density storage

Abstract Arbitrary-shaped batteries with high energy densities are strongly desired for weight- and power-sensitive applications to meet various layout and function demands. Conventional battery electrode fabrication protocol requires a relatively thick metal foil (9–15 μm) to provide sufficient mechanical strength for slurry coating, leading to high occupancy of inactive components. Besides, conventional battery assembly methods result in limited battery layouts, which is difficult for well-fitting complex-shaped electronics. To overcome these limitations, developing novel battery fabrication technologies is critically urgent and important. Herein, we report a scalable method to fabricate arbitrary-shaped lithium-ion batteries with ultra-thin current collectors. Built on a commercial polypropylene separator, an all-in-one structured lithium ion battery is fabricated by integrating active material layers and ultra-thin metal film current collectors (optimally 2-μm-thick) through stencil printing and magnetron sputtering methods. By reducing the thickness of current collectors down to 2 μm, the energy density of a LiFePO4//Li4Ti5O12 full cell can be increased by 16%–64% based on the designed areal capacities between 1 mAh cm−2 to 3 mAh cm−2. Such battery fabrication method can effectively realize the shape diversity of electrodes, thereupon enabling the seamless integration of arbitrary-shaped batteries into versatile potable electronics to improve their space utilization.