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

Flexible fiber-shaped Li-CO₂ 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-CO₂ 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-CO₂ battery is constructed through an integrated electrode design strategy and a mechanical engineering-inspired “spring”-like device architecture. Impressively, the as-prepared highly-active Mo₂N anchored N-doped carbon nanotubes/carbon fiber hybrid bundle (CFB@NCNT-Mo₂N) cathode delivers a large full capacity of 5586.0 µAh cm⁻¹, corresponding to a high energy density of 14 250 Wh kg^-1_cathode. 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-CO₂ battery device using CFB@NCNT-Mo₂N 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-CO₂ batteries provide an effective model for designing future flexible energy storage devices beyond metal-gas batteries for wearables in specific application scenarios.