Nickel nanoparticles activated highly porous carbon for excellent sodium storage

Highlights: • Construct highly porous activated loofah sponge carbon (ALSC)/Ni composite. • Porous ALSC/Ni composite shows high sodium ion storage capacity. • Hierarchical porous structure is favorable for fast ion/electron transfer. The development of sodium ion batteries (SIBs) is greatly restricted by the unsatisfactory anode materials with low capacity and poor cycling stability. Herein, we report a dual-activation hydrothermal process to prepare highly porous activated loofah sponge carbon (ALSC) and ALSC/Ni composite. ALSC is prepared by a facile KOH-based hydrothermal method and further embedded with Ni nanoparticles to form ALSC/Ni composite material by a simple NiCl₂-treated hydrothermal pyrolysis. The as-obtained ALSC/Ni composite material has a 3D connected porous structure and a large specific surface area of 689.6 m² g⁻¹ due to the etching reaction between NiCl₂ and carbon. Moreover, higher electrical conductivity and more active sites are achieved in the ALSC/Ni composite material. When applied as anode for sodium ion batteries, the ALSC/Ni electrode delivers a high reversible capacity of 325.4 mA h g⁻¹ and keeps a capacity retention of 72.5% after 100 cycles at 20 mA g⁻¹, much better than ALSC and other counterparts. Due to the unique porous structure and embedded nickel nanoparticles, the designed ALSC/Ni electrode also shows enhanced rate performance. Our work paves a new road for fabrication of high-performance carbon composite electrodes for SIBs.