Tailoring Defect‐Rich Porous Carbon Nanosheets Via Phase‐Transition Salt Templating for Ultrahigh Lithium‐Ion Storage and Robust Oxygen Electrocatalysis

Abstract Precise control over defects and porous structures in carbon materials is crucial for enhancing their performance in energy storage and conversion. In this study, an innovative salt template method is introduced to synthesize nitrogen‐doped, defect‐rich porous carbon nanosheets (ST/MS‐NC‐1000) using leafy zeolitic imidazolate frameworks and NaCl salt. Results reveal that crystalline NaCl acts as a structural template to guide the formation of nanosheet, while molten NaCl etches the carbon framework, significantly increasing defect density and specific surface area. The optimized ST/MS‐NC‐1000 delivers an excellent rate capability (512 mAh g ⁻¹ at 5 A g ⁻¹ ), and a remarkable cycling stability (358 mAh g ⁻¹ after 5000 cycles at 2 A g ⁻¹ ) as anode materials for lithium‐ion batteries. As a metal‐free bifunctional electrocatalyst, ST/MS‐NC‐1000 demonstrates a half‐wave potential of 0.85 V for oxygen reduction and an overpotential of 350 mV at 10 mA cm ⁻² for oxygen evolution. These superior properties stem from the synergistic effects of high defect density, large specific surface area, and nitrogen doping. This work not only provides a scalable strategy for synthesizing high‐performance carbon materials but also uncovers the underlying mechanisms of defect and heteroatom engineering during salt‐templated pyrolysis, offering new design principles for lithium‐ion batteries and oxygen electrocatalysis.