Washable and Stretchable Zn–MnO 2 Rechargeable Cell

A cell that can operate even when doubled in length, and that withstands washing is demonstrated. The cell employs rechargeable and safe zinc/manganese dioxide chemistry. It incorporates a biocompatible poly(styrene – isobutylene – styrene) (SIBS) polymer as encapsulation, and in all layers. The SIBS‐based separator, made using solvent evaporation‐induced phase separation, has an ionic conductivity of 0.05 S m −1 . Electrodes contain carbon black, combined with active particles and SIBS as the binder. Stretchable current collectors are carbon black/carbon nanofiber/SIBS composites and exhibit a sheet resistance of 27 Ω ⬜ −1 under 100% strain. These components are encapsulated by SIBS membranes into a full cell, thin‐film configuration, creating a single, polymer‐based intrinsically stretchable battery. The resulting cell has a reversible specific capacity of 160 mAh g −1 cathode active mass. Capacity retention is 75% following 500 charge and discharge cycles. Owing to the low permeability of SIBS and the excellent adhesion between its layers, the battery has a good shelf‐life (22% mass loss of electrolyte after 523 days) and can withstand 39 washing cycles. The high capacity relative to other stretchable cells, along with the low materials cost, safe chemistry, durability, and washability, make this SIBS cell attractive for wearables and other applications that benefit from stretchability.