Hydrothermal synthesis of Ni@C core–shell composites with high capacitance

• Published in: Journal of alloys and compounds Vol. 575; pp. 152 - 157
• Main Authors: Niu, Lengyuan, Li, Zhangpeng, Sun, Jinfeng, Fan, Zengjie, Xu, Ye, Gong, Peiwei, Yang, Shengrong, Wang, Jinqing
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 25.10.2013; Elsevier
• Subjects: Carbon coating; Chemistry; Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Composite; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electrochemistry; Electrodes: preparations and properties; Exact sciences and technology; General and physical chemistry; Materials science; Nanopowders; Nanoscale materials and structures: fabrication and characterization; Nickel nanoparticles; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Supercapacitor; Treatment of materials and its effects on microstructure and properties; Supercapacitor; Composite; Carbon coating; Nickel nanoparticles; Cubic lattices; Annealing temperature; Controlled atmospheres; Electrode material; Coatings; Acetates; Nanoparticles; Chemical reduction; HCP lattices; Thermal annealing; Current density; X-ray diffraction analysis; Crystal structure; Temperature dependence; Ethylene glycol; Core shell structure; Citrates; Carbon; Hexagonal lattices; Electrochemical properties; Composite materials; Hydrothermal synthesis; Sodium; Capacitance; Nickel; Nanostructured materials
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.04.010

•Ni@C core–shell composites were prepared by a simple hydrothermal method.•Ni@C composites exhibit good electrochemical performance for supercapacitors.•The composite displays the highest specific capacitance of 530Fg−1 at 1Ag−1.•An uniform carbon layer is very important for achieving a high electrochemical performance. Ni@C core–shell composites with different crystal structures were synthesized by chemical reduction of nickel (II) acetate tetrahydrate using ethylene glycol as reducing agent and sodium citrate as a carbon source, followed by annealing at different temperatures in the nitrogen atmosphere. X-ray diffraction analysis indicates that the crystal structure of Ni is dependent on the annealing temperatures. At 250°C, both face-centered cubic and hexagonal closed-packed (hcp) phases of Ni coexist in the Ni@C composites, whereas there is only hcp phase Ni observed as being annealed at 300°C. The synthesized Ni@C composites were applied as electrode materials for supercapacitors and exhibited superior electrochemical performances. Especially, the electrode annealed at 250°C displays the highest specific capacitance of 530Fg−1 in 2MKOH solution at a current density of 1Ag−1. In addition, the synthesized Ni@C composite electrodes also show excellent rate capability and cycle stability, presenting the promising potential as electrode material for supercapacitors.