Flexible Li–CO₂ Batteries with Boosted Reaction Kinetics and Cyclelife Enabled by Heterostructured Mo₃N₂@TiN Cathode and Interface-protected Li Anode

With theoretically endowing with high energy densities and environmentally friendly carbon neutralization ability, flexible fiber-shaped Li–CO₂ battery emerges as a multipurpose platform for next-generation wearable electronics. Nevertheless, the ineluctable issues faced by cathode catalysts and Li anodes have brought enormous obstacles to the development of flexible fiber-shaped Li–CO₂ batteries. Herein, a flexible fiber-shaped Li–CO₂ battery based on Mo₃N₂ cathode coating with atomic layer deposited TiN and Li₃N protected Li anode is constructed. Owing to the regulation surface electrons of Mo₃N₂ by TiN, heterostructured cathode has more delocalized electrons which enable cathodes to stabilize 2-electron intermediate products Li₂C₂O₄ by electron bridge bonds and avoid disproportionation into Li₂CO₃. Li₃N layers not only accelerate Li⁺ transportation but also avoid contact between Li and CO₂ to form Li₂CO₃. Thus, the constructed Li–CO₂ battery demonstrates a low charge potential of 3.22 V, low overpotential of 0.56 V, outstanding rate capabilities up to 1 A g⁻¹, and excellent long-term cycling (≈2000 h) with an energy efficiency of ≈80%. The fabricated flexible fiber-shaped Li–CO₂ battery shows an ultrahigh energy density of 14 772.5 Wh kg⁻¹ based on cathodes (340.8 Wh kg⁻¹ based on device mass), and outstanding deformations adaptability, giving it great potential for wearable electronics.