Guanglei Tian

Bimetallic nickel cobalt selenides: a new kind of electroactive material for high-power energy storage

For the first time, bimetallic Ni–Co selenides with different Ni and Co ratios have been synthesized and used as electrode materials for high-power energy storage. Owing to the synergistic effect between Ni and Co, bimetallic Ni–Co selenides, especially for Ni0.67Co0.33Se, show higher specific capacity and improved rate capability combined with excellent cycling stability than the monometallic Ni or Co selenide.

Hierarchical NiCo2S4 nanotube@NiCo2S4 nanosheet arrays on Ni foam for high‐performance supercapacitors

Hierarchical NiCo2 S4 nanotube@NiCo2 S4 nanosheet arrays on Ni foam have been successfully synthesized. Owing to the unique hierarchical structure, enhanced capacitive performance can be attained. A specific capacitance up to 4.38 F cm(-2) is attained at 5 mA cm(-2) , which is much higher than the specific capacitance values of NiCo2 O4 nanosheet arrays, NiCo2 S4 nanosheet arrays and NiCo2 S4 nanotube arrays on Ni foam. The hierarchical NiCo2 S4 nanostructure shows superior cycling stability; after 5000 cycles, the specific capacitance still maintains 3.5 F cm(-2) . In addition, through the morphology and crystal structure measurement after cycling stability test, it is found that the NiCo2 S4 electroactive materials are gradually corroded; however, the NiCo2 S4 phase can still be well-maintained. Our results show that hierarchical NiCo2 S4 nanostructures are suitable electroactive materials for high performance supercapacitors.

Enhanced cycling stability of spinel LiMn2O4 cathode by incorporating graphene sheets

LiMn2O4-graphene nanocomposites with different weight ratios of LiMn2O4/graphene were successfully prepared via a simple method by ball-milling of commercially available LiMn2O4 particles and graphene nanosheets. Experimental results revealed that the spinel LiMn2O4 particles within the as-prepared LiMn2O4-graphene nanocomposites were well distributed onto the flexible graphene sheets, and the nano-composites with a higher graphene content were favorable to form more uniform composite materials. Compared to the pristine spinel LiMn2O4 particles, the as-prepared LiMn2O4-graphene nanocomposites exhibited lower initial discharge capacities owing to the reduced amount of active materials (LiMn2O4 particles) in the nanocomposites. However, their electrochemical cycling performance was significantly enhanced, high-lighting the advantages of anchoring LiMn2O4 particles on graphene sheets. The enhanced cycling performance could be ascribed to the fact that the graphene nanosheets within the LiMn2O4-graphene nanocomposites could provide a 3D conducting scaffold, which could not only alleviate the aggregation of LiMn2O4 particles and accommodate the volume changes of LiMn2O4 particles, but also enhance the ionic conductivity and charge transfer during the lithiation/delifhiation process.

Polyaniline-coated selenium/carbon composites encapsulated in graphene as efficient cathodes for Li-Se batteries

In this work, we developed a polyaniline (PANI)-coated selenium/carbon nanocomposite encapsulated in graphene sheets (PANI@Se/C-G), with excellent performance in Li-Se batteries. The PANI@Se/C-G nanostructure presents attractive properties as cathode of Li-Se batteries, with a high specific capacity of 588.7 mAh·g–1 at a 0.2C (1C = 675 mA·g−1) rate after 200 cycles. Even at a high rate of 2C, a high capacity of 528.6 mAh·g–1 is obtained after 500 cycles. The excellent cycle stability and rate performance of the PANI@Se/C-G composite can be attributed to the synergistic combination of carbon black (as the conductive matrix for Se) and the double conductive layer comprising the uniform PANI shell and the graphene sheets, which effectively improves the utilization of selenium and significantly enhances the electronic conductivity of the whole electrode.

Hierarchical NiCo2S4Nanotube@NiCo2S4Nanosheet Arrays on Ni Foam for High-Performance Supercapacitors

Hierarchical NiCo2 S4 nanotube@NiCo2 S4 nanosheet arrays on Ni foam have been successfully synthesized. Owing to the unique hierarchical structure, enhanced capacitive performance can be attained. A specific capacitance up to 4.38 F cm(-2) is attained at 5 mA cm(-2) , which is much higher than the specific capacitance values of NiCo2 O4 nanosheet arrays, NiCo2 S4 nanosheet arrays and NiCo2 S4 nanotube arrays on Ni foam. The hierarchical NiCo2 S4 nanostructure shows superior cycling stability; after 5000 cycles, the specific capacitance still maintains 3.5 F cm(-2) . In addition, through the morphology and crystal structure measurement after cycling stability test, it is found that the NiCo2 S4 electroactive materials are gradually corroded; however, the NiCo2 S4 phase can still be well-maintained. Our results show that hierarchical NiCo2 S4 nanostructures are suitable electroactive materials for high performance supercapacitors.

Hierarchical NiCo2 S4 Nanotube@NiCo2 S4 Nanosheet Arrays on Ni Foam for High-Performance Supercapacitors.

Hierarchical NiCo2 S4 nanotube@NiCo2 S4 nanosheet arrays on Ni foam have been successfully synthesized. Owing to the unique hierarchical structure, enhanced capacitive performance can be attained. A specific capacitance up to 4.38 F cm(-2) is attained at 5 mA cm(-2) , which is much higher than the specific capacitance values of NiCo2 O4 nanosheet arrays, NiCo2 S4 nanosheet arrays and NiCo2 S4 nanotube arrays on Ni foam. The hierarchical NiCo2 S4 nanostructure shows superior cycling stability; after 5000 cycles, the specific capacitance still maintains 3.5 F cm(-2) . In addition, through the morphology and crystal structure measurement after cycling stability test, it is found that the NiCo2 S4 electroactive materials are gradually corroded; however, the NiCo2 S4 phase can still be well-maintained. Our results show that hierarchical NiCo2 S4 nanostructures are suitable electroactive materials for high performance supercapacitors.

Hydrolysis Precipitation-assisted Solid-state Reaction to Li 4 Ti 5 O 12 and its Electrochemical Properties

Spinel lithium titanate (Li4Ti5O12) materials were synthesized by a hydrolysis precipitation-assisted solid-state method in the temperature range from 600 to 900 for large-scale production. DSC/TGA, XRD and SEM were used to characterize the as-prepared samples. The optimum synthesis condition was examined in relation to the charge–discharge performance. It was found that when the dry hydrolysis precipitation precursor with 8% Li excess was calcined at 700–800 for 12 h in air, a pure Li4Ti5O12 phase was obtained. The as-obtained material has the best electrochemical performance due to its narrow size distribution and precise stoichiometry of the oxide.