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

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.