Thermomechanical Coupling Fabrication of Freestanding Porous Carbon for Sodium‐Ion Batteries

Abstract Porous carbons have demonstrated excellent capacity and rate performance advantages as a widely used anode material for sodium‐ion batteries. However, the conventional high‐temperature and high‐pressure preparation methods limit the practical applications of porous carbons, complicating battery manufacturing processes and hindering flexible electrode development. This work used polyimide as a carbon source to prepare freestanding porous carbon films on nickel foam substrates via a thermomechanical coupling process under micropressure. The micropressure‐derived porous carbon exhibits enhanced crystallinity and a more ordered carbon layer arrangement than directly carbonized products. Additionally, its rich pore structure facilitates the electrolyte diffusion and ion migration. As a result, the as‐prepared porous carbon material delivers a reversible capacity of 298 mAh g⁻ 1 at 0.05 A g⁻ 1 , with an initial Coulombic efficiency of 81.6%. Remarkably, it maintains over 85% capacity retention after 600 cycles, demonstrating superior cycling stability.