Scalable fabrication of printed Zn//MnO planar micro-batteries with high volumetric energy density and exceptional safety.

The rapid development of printed and microscale electronics imminently requires compatible micro-batteries (MBs) with high performance, applicable scalability, and exceptional safety, but faces great challenges from the ever-reported stacked geometry. Herein the first printed planar prototype of aqueous-based, high-safety Zn//MnO MBs, with outstanding performance, aesthetic diversity, flexibility and modularization, is demonstrated, based on interdigital patterns of Zn ink as anode and MnO ink as cathode, with high-conducting graphene ink as a metal-free current collector, fabricated by an industrially scalable screen-printing technique. The planar separator-free Zn//MnO MBs, tested in neutral aqueous electrolyte, deliver a high volumetric capacity of 19.3 mAh/cm (corresponding to 393 mAh/g) at 7.5 mA/cm, and notable volumetric energy density of 17.3 mWh/cm, outperforming lithium thin-film batteries (≤10 mWh/cm). Furthermore, our Zn//MnO MBs present long-term cyclability having a high capacity retention of 83.9% after 1300 cycles at 5 C, which is superior to stacked Zn//MnO batteries previously reported. Also, Zn//MnO planar MBs exhibit exceptional flexibility without observable capacity decay under serious deformation, and remarkably serial and parallel integration of constructing bipolar cells with high voltage and capacity output. Therefore, low-cost, environmentally benign Zn//MnO MBs with in-plane geometry possess huge potential as high-energy, safe, scalable and flexible microscale power sources for direction integration with printed electronics.