Flexible and Tailorable Na−CO 2 Batteries Based on an All‐Solid‐State Polymer Electrolyte

Rechargeable Na< C‐>CO 2 batteries coupling Na anodes with the greenhouse gas CO 2 cathode are promising energy‐storage devices due to the high energy density, environmental friendliness and cost‐effectiveness. However, major challenges impeding the application of Na−CO 2 batteries are safety concern regarding the leakage of flammable liquid electrolytes and the instability of the Na anodes. Herein, we construct all‐solid‐state flexible Na−CO 2 batteries by designing an integrated structure built of a Na anode, poly(ethylene oxide)/NaClO 4 /SiO 2 electrolyte and multiwall carbon nanotubes cathode. The batteries exhibit much improved safety and good cyclability (240 cycles with an overpotential increase of ∼0.4 V). Remarkably, we fabricated lab scale‐up integrated batteries (8×16 cm 2 ), which display large capacity (450 mAh) and high energy density (173 Wh kg −1 ). Moreover, the integrated batteries show excellent bendability (≥1,000 times), foldability in individual shapes, as well as stable operation time (80 h) at bending states of 0° to 360°. Our work demonstrates a way to exploit flexible and safe solid‐state Na−CO 2 batteries.