Chunlei Jiang

Uniform Incorporation of Flocculent Molybdenum Disulfide Nanostructure into Three-Dimensional Porous Graphene as an Anode for High-Performance Lithium Ion Batteries and Hybrid Supercapacitors

Hybrid supercapacitors (HSCs) with lithium-ion battery-type anodes and electric double layer capacitor-type cathodes are attracting extensive attention and under wide investigation because of their combined merits of both high power and energy density. However, the performance of most HSCs is limited by low kinetics of the battery-type anode which cannot match the fast kinetics of the capacitor-type cathode. In this study, we have synthesized a three-dimensional (3D) porous composite with uniformly incorporated MoS2 flocculent nanostructure onto 3D graphene via a facile solution-processed method as an anode for high-performance HSCs. This composite shows significantly enhanced electrochemical performance due to the synergistic effects of the conductive graphene sheets and the interconnected porous structure, which exhibits a high rate capability of 688 mAh/g even at a high current density of 8 A/g and a stable cycling performance (997 mAh/g after 700 cycles at 2 A/g). Furthermore, by using this composite as the anode for HSCs, the HSC shows a high energy density of 156 Wh/kg at 197 W/kg, which also remains at 97 Wh/kg even at a high power density of 8314 W/kg with a stable cycling life, among the best results of the reported HSCs thus far.

Reversible calcium alloying enables a practical room-temperature rechargeable calcium-ion battery with a high discharge voltage

AbstractCalcium-ion batteries (CIBs) are attractive candidates for energy storage because Ca2+ has low polarization and a reduction potential (−2.87 V versus standard hydrogen electrode, SHE) close to that of Li+ (−3.04 V versus SHE), promising a wide voltage window for a full battery. However, their development is limited by difficulties such as the lack of proper cathode/anode materials for reversible Ca2+ intercalation/de-intercalation, low working voltages (<2 V), low cycling stability, and especially poor room-temperature performance. Here, we report a CIB that can work stably at room temperature in a new cell configuration using graphite as the cathode and tin foils as the anode as well as the current collector. This CIB operates on a highly reversible electrochemical reaction that combines hexafluorophosphate intercalation/de-intercalation at the cathode and a Ca-involved alloying/de-alloying reaction at the anode. An optimized CIB exhibits a working voltage of up to 4.45 V with capacity retention of 95% after 350 cycles.Calcium-ion batteries are potentially attractive alternatives to lithium-ion batteries, but remain largely unexplored because of low performance. A reversible calcium alloying/de-alloying reaction with the tin anode has now been coupled with the intercalation/de-intercalation of hexafluorophosphate in the graphite cathode to enable a calcium-ion battery that operates stably at room temperature.

Deposition of Diamond Films on Complex Cutting Tools by Hot-Filament Chemical Vapor Deposition

Diamond films were deposited on cemented carbide cutting inserts and end mills by hot-filament chemical vapor deposition. The morphology of the diamond film surface was controlled by adjusting the substrate temperature and the gas concentration. The film adhesion strength was enhanced by applying lower substrate temperatures. With increase of methane gas concentration from 2% to 5%, the diamond grain size decreased from 1 μm to 200 nm, and the diamond film adhesion was improved. Furthermore, diamond films were homogenously and densely deposited on end mills by carefully manipulating the position of filaments and substrates. These results suggest that this technique is helpful for coating tools with complex shape in the industrial applications.

Deposition of Diamond/β-SiC Composite Interlayers for Improved Machining Performance of Diamond Coated Cemented Carbide Cutting Tools

Diamond/β-SiC composite films and diamond film with composite interlayers were synthesized on cemented carbide substrates and hard metal cutting tools. Diamond top layers and the interlayers were deposited in one single process by hot filament chemical vapor deposition (HFCVD) technique using a gas mixture of hydrogen, methane and tetramethylsilane (TMS). Two different kinds of interlayers have been employed, namely, gradient interlayer and interlayer with constant composition. The gradient composite film, featuring a cross-sectional gradient with increasing diamond/β-SiC content from film-substrate interface to the top of the film, showed the best film adhesion. Turning test was carried out using diamond coated and uncoated cutting tools to machine aluminum alloy. It was confirmed that the diamond films with gradient interlayer showed best adhesion to the hard metal cutting tools. Diamond coated cutting tool with gradient composite interlayer showed also higher wear resistance than uncoated cutting tool. The tool lifetime of such diamond coated cutting tool was 10 times higher than that of uncoated cutting tool. Moreover, diamond coated cutting tools performed non-sticking machining, which leaded to much higher surface quality of machined surface than uncoated insert.