Flexible, Stretchable, Water‐/Fire‐Proof Fiber‐Shaped Li‐CO2 Batteries with High Energy Density

Abstract Flexible fiber‐shaped Li‐CO 2 batteries are regarded to be a potential candidate to power accessories for wearable electronics due to their high theoretical energy density and carbon‐neutral capability. However, the difficulties of electrode preparation and architecture design make it challenging for current Li‐CO 2 batteries to keep a suitable balance between electrochemical performance and multifunctionality, one‐dimensional configuration and so forth. Herein, a flexible, stretchable, water‐/fire‐proof fiber‐shaped Li‐CO 2 battery is constructed through an integrated electrode design strategy and a mechanical engineering‐inspired “spring”‐like device architecture. Impressively, the as‐prepared highly‐active Mo 2 N anchored N‐doped carbon nanotubes/carbon fiber hybrid bundle (CFB@NCNT‐Mo 2 N) cathode delivers a large full capacity of 5586.0 µAh cm −1 , corresponding to a high energy density of 14 250 . Meanwhile, it also demonstrates a low charge potential of ≈3.7 V, excellent rate capabilities, and outstanding long‐term cycling stability of 525 cycles. Furthermore, the constructed “spring”‐like fiber‐shaped Li‐CO 2 battery device using CFB@NCNT‐Mo 2 N and a newly‐proposed gracile fibrous Li metal anode exhibits excellent adaptability to deformations including bending and stretching, as well as other favorable features like water‐/fire‐resistance. The successful demonstration of the proposed high‐performance and multifunctional Li‐CO 2 batteries provide an effective model for designing future flexible energy storage devices beyond metal‐gas batteries for wearables in specific application scenarios.