Humidity and Pressure Dual-Responsive Metal–Water Batteries Enabled by Three-In-One All-Polymer Cathodes for Smart Self-Powered Systems

A conceptually new class of humidity and pressure dual-responsive smart metal–water batteries (SMWBs) is presented, which displays self-tunable energy release and intriguing perceptibility of human respiration and environmental pressure. This battery is enabled by the direct contact of a metal (e.g., Mg or Zn) anode and a well-designed all-polymer dual-sensitive moisture electrode (DSME) made from semiconductive polymer (e.g., polypyrrole)-wrapped 3D macroporous polyurethane sponge, without additional electrolytes and separator. A DSME is cost-effective, easily scalable, compressible, and able to act as a moisture carrier, a hydrogen evolution catalyst, and a pressure and humidity dual-sensitive unit simultaneously. Unique three-in-one integration in the DSME enables favorable modulation of electron/mass transport or redox reactions in the SMWB upon different stimulations. Thus, the assembled SMWB not only delivers good discharge performance with smart energy management but also serves as a reliable self-powered bifunctional responsor for the real-time monitoring of respiration and the perceptibility of pressure. Based on various active metal–polymer pairs (Mg/Zn vs polypyrrole/polyaniline), we also developed a series of dual-responsive batteries, demonstrating a general design idea.