3D Printed Stretchable Liquid Gallium Battery

Abstract Despite the rapid progress on soft and stretchable batteries, current fabrication techniques involve manual disposition and stencil/screen printing. Here, for the first time, a 3D‐printed Ag–Ga battery is introduced through subsequent printing of four sinter‐free composites: a stretchable Liquid Metal (LM) EGaIn‐Ag‐Styrene‐isoprene block copolymers (SIS), and Carbon‐SIS current collectors; Ag₂O‐SIS cathode; and a novel Ga‐C‐SIS anode. Being sinter‐free results in faster printing, and compatibility with heat‐sensitive substrates. Although the Ga‐C‐SIS is solid‐like and nonsmearing after printing, it creates a liquid interface after contacting with the electrolyte. This results in a self‐feeding and self‐aggregation mechanism that brings more gallium to the surface and delays the formation of the dead surface. The record‐breaking areal capacity of ≈19.4 mAh cm⁻², along with excellent stretchability (>130% Max. strain), makes the Ag–Ga battery an excellent alternative to Ag–Zn batteries. Surprisingly, digital printing results in 3x higher areal capacity compared to stencil printing, due to greater gallium exposure at the surface. The desired voltage and current output can be customized by printing several battery cells and interconnect them in series/parallel. Also, printing of sensors, electrodes, batteries, and interconnects on a biomonitoring e‐textile for simultaneous monitoring of electrocardiography, body temperature, and respiration is demonstrated.