Hierarchical porous carbon sheets with compressed framework and optimized pore configuration for high-rate and long-term sodium and lithium ions storage

Porous or soft carbon materials have attracted widespread attention as anodes for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs). Herein, we report a new type of porous carbon sheets (PCS) which are able to accommodate high-rate and long-term storage of sodium and lithium ions. A facile phase transformation process from MgCO₃·3H₂O rods to Mg(OH)₂ lamellas is employed to fabricate the templated PCS, which simultaneously features a compressed carbon framework, an optimized hierarchical pore structure with greatly reduced surplus meso-/macropores as well as an enlarged interlayer distance. These structural merits have a synergistic effect and confer upon the fabricated PCS electrode the combined diffusion-controlled and capacitive charge storage for both SIBs and LIBs. At a low current density of 0.1 A g⁻¹, PCS can deliver high storage capacities of 317 and 1328 mAh g⁻¹ for Na⁺ and Li⁺, respectively. At an increased current density of 1 A g⁻¹, PCS still offers superior rate and cycling capabilities of 113 mAh g⁻¹ and 710 mAh g⁻¹ for Na⁺ and Li⁺, respectively, even after 2000 cycles. Furthermore, the compressed carbon framework enables an electrode fabricated from PCS to endure a high active material loading (4–5 mg cm⁻²).