3D Printed Compressible Quasi-Solid-State Nickel-Iron Battery.

The design of a compressible battery with stable electrochemical performance is extremely important in compression-tolerant and flexible electronics. While this remains challenging with the current battery manufacturing method, the field of 3D printing offers unique possibility to produce free-standing 3D printed electrodes with various structural configurations. Through the simple and scalable strategy, various structural configurations can be produced. Herein, we demonstrate, for the first time, a 3D printed quasi-solid-state Ni-Fe battery (QSS-NFB) that shows excellent compressibility, ultra-high energy density and superior long-term cycling durability. Through a rational design and adjustment of chemical components, two electrodes consisting of ultrathin Ni(OH)2 nanosheet array cathode and holey α-Fe2O3 nanorod array anode are achieved with a ultrahigh active material loading over 130 mg cm-3 and excellent compressibility up to 60%. Remarkably, the compressible QSS-NFB demonstrated an extremely high cycling stability (~91.3% capacity retentions after 10000 cycles) and ultra-high energy densities (28.1 mWh cm-3 at a power of 10.6 mW cm-3). Our work opens a new method for producing compression-tolerant energy-storage devices, which are expected to have promising applications in new generation stretchable/wearable electronics.