S-O bond chemically constrained NiS2/rGO nanocomposite with enhanced Na-ion storage capacity

NiS2 has become a research hotspot of anode materials for Na-ion batteries due to its high theoretical specific capacity.However,the volume effect,the dissolution of polysulfide intermediates and the low conductivity during the charge/discharge process lead to the low specific capacity and poor cycling stability.NiS2/rGO nanocomposite was prepared by a facile two-step process:GO was prepared by modified Hummers method,and then NiS2/rGO nanocomposite was synthesized by L-cys assisted hydrothermal method.NiS2/rGO nanocomposite shows excellent cycle performance and rate performance,which could be attributed to the mesoporous structure on the graphene skeleton with high conductivity.Besides,the chemical constraint of a unique S—O bond on NiS2 could inhibit the dissolution of intermediates and the loss of irreversible capacity.

In-situ conversion of Ni2P/rGO from heterogeneous self-assembled NiO/rGO precursor with boosted pseudocapacitive performance

Two-dimensional(2 D)heterostructural Ni2 P/rGO is successfully fabricated by in-situ phosphating selfassembled NiO/rGO composites and shows the enhanced electrochemical performances.In this design,the rGO sheets effectively reduce the lattice strain created during the phase transformation from NiO to Ni2 P,thereby maintaining ultrathin nanostructures of Ni2 P.The resulting Ni2 P/rGO layered heterostructure gives the composite plenty of pores or channels,good electrical conductivity and well-exposed active sites.Density functional theory(DFT)calculation further demonstrates that the Fermi energy level and electron localize of near Ni atoms in Ni2 P is higher than that of NiO,which endow Ni2 P with faster and more reversible redox reactivity in dynamic.Benefiting from their structural and compositional merits,the as-synthesized Ni2 P/rGO exhibits high specific discharge capacity and excellent rate performance.Furthermore,a hybrid supercapacitor built with Ni2 P/rGO and activated carbon shows a high specific energy of 38.6 Wh/kg at specific power of 375 W/kg.