Shun Tang

In-Situ Template Formation Strategy for the Preparation of Nitrogen Doped Carbon Nanocage with Graphitic Shell as Electrode Material for Supercapacitor

Nitrogen doped carbon nanocage with graphitic shell (NGCS) was fabricated through in-situ solid reaction between calcium acetate and dicyandiamide in an inert atmosphere followed by acid etching. The role played by the calcium acetate (Ca(Ac)2) and dicyandiamide (DCD) during the synthesis process is one-stone-two-birds. Calcium acetate plays multiple functions: template agent, graphitization catalyst, and carbon source. Dicyandiamide can be considered as the nitrogen sources and the chemical reaction agent that can be reacted with calcium acetate to form it into CaCN2. The NGCS obtained at 800 °C has a specific surface area of 420 m2/g and nitrogen content of 8.87 at%. The excellent electrochemical performance can be attributed to the combination effects of porous structure, nitrogen doping and graphitized nanocage shell of NGCS electrode. The hollow structure serves as the reservoir for fast electrolyte ion supplement. Nitrogen groups not only improve the wettability of interfaces between carbon surface and electrolyte, but also generate extra pseudocapacitance through redox reaction. The graphitic carbon nanocage shell can enhance the conductivity and facilitates the fast charge transfer. At a current density of 0.5 A/g, the specific capacitance of the NGCS-800 electrode is 215 F/g. Furthermore, the NGCS-800 electrode exhibits excellent rate capability (80% capacitance retention at 10 A/g) and outstanding cycling stability (96.89% capacitance retention after 5000 cycles). These intriguing results demonstrate that nitrogen doped carbon with graphitic shell will be highly promising as electrode materials for supercapacitors and other energy storage and conversation applications.

High Rate Performance of Ca-Doped Li4Ti5O12 Anode Nanomaterial for the Lithium-Ion Batteries

The spinel Li4Ti5O12 (LTO) has been doped by Ca2+ via a solid-state reaction route, generating highly crystalline Li3.9Ca0.1Ti5O12 powders in order to improve the electrochemical performance as an anode. The structure changes, morphologies, and electrochemical properties of the resultant powders have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and cyclic voltammetry (CV), respectively. Crystal structure and composition were analyzed, and results were obtained with various tests of LTO. Electrochemical measurements revealed that Li3.9Ca0.1Ti5O12 anodes exhibit better rate capability, better cycling stability, and a higher specific capacity than pure LTO anodes.