Construction of 3D porous Cu_1.81S/nitrogen-doped carbon frameworks for ultrafast and long-cycle life sodium-ion storage

Transition metal sulfides have great potential as anode materials for sodium-ion batteries (SIBs) due to their high theoretical specific capacities. However, the inferior intrinsic conductivity and large volume variation during sodiation–desodiation processes seriously affect its high-rate and long-cycle performance, unbeneficial for the application as fast-charging and long-cycling SIBs anode. Herein, the three-dimensional porous Cu_1.81S/nitrogen-doped carbon frameworks (Cu_1.81S/NC) are synthesized by the simple and facile sol–gel and annealing processes, which can accommodate the volumetric expansion of Cu_1.81S nanoparticles and accelerate the transmission of ions and electrons during Na⁺ insertion/extraction processes, exhibiting the excellent rate capability (250.6 mAh·g⁻¹ at 20.0 A·g⁻¹) and outstanding cycling stability (70% capacity retention for 6000 cycles at 10.0 A·g⁻¹) for SIBs. Moreover, the Na-ion full cells coupled with Na₃V₂(PO₄)₃/C cathode also demonstrate the satisfactory reversible specific capacity of 330.5 mAh·g⁻¹ at 5.0 A·g⁻¹ and long-cycle performance with the 86.9% capacity retention at 2.0 A·g⁻¹ after 750 cycles. This work proposes a promising way for the conversion-based metal sulfides for the applications as fast-charging sodium-ion battery anode.