Boyang Ruan

A phosphorus/N-doped carbon nanofiber composite as an anode material for sodium-ion batteries

Sodium-ion batteries (SIBs) have been attracting intensive attention at present as the most promising alternative to lithium-ion batteries in large-scale electrical energy storage applications, due to the low-cost and natural abundance of sodium. Elemental phosphorus (P) is a very promising anode material for SIBs, with the highest theoretical capacity of 2596 mA h g−1. Recently, there have been many efforts devoted to phosphorus anode materials for SIBs. As pure red phosphorus cannot react with Na reversibly, many attempts to prepare composite materials containing phosphorus have been reported. Here, we report the facile preparation of a red phosphorus/N-doped carbon nanofiber composite (P/NCF) that can deliver a reversible capacity of 731 mA h g−1 in sodium-ion batteries (SIBs), with a capacity retention of 57.3% over 55 cycles. Our results suggest that it would be a promising anode candidate for SIBs with a high capacity and low cost.

Amorphous carbon layer contributing Li storage capacity to Nb2O5@C nanosheets

In this work, amorphous carbon very thin layers coated on a Nb2O5 nanosheet flexible composite have been successfully synthesized. The composite delivers a discharge capacity of 396 mA h g−1 after 100 cycles at a current density of 100 mA g−1, which is very much higher than for bare Nb2O5 nanosheets.

Carbon‐Coated Hierarchical SnO2 Hollow Spheres for Lithium Ion Batteries

Hierarchical SnO2 hollow spheres self-assembled from nanosheets were prepared with and without carbon coating. The combination of nanosized architecture, hollow structure, and a conductive carbon layer endows the SnO2 -based anode with improved specific capacity and cycling stability, making it more promising for use in lithium ion batteries.

Carbon-Encapsulated Sn@N-Doped Carbon Nanotubes as Anode Materials for Application in SIBs

Carbon-encapsulated Sn@N-doped carbon tubes with submicron diameters were obtained via the simple reduction of C@SnO2@N-doped carbon composites that were fabricated by a hydrothermal approach. Sn nanoparticles encapsulated in carbon layers were distributed uniformly on the surfaces of the N-doped carbon nanotubes. The electrochemical performances of the composites were systematically investigated as anode materials in sodium-ion batteries (SIBs). The composite electrode could attain a good reversible capacity of 398.4 mAh g-1 when discharging at 100 mA g-1, with capacity retention of 67.3% and very high Coulombic efficiency of 99.7% over 150 cycles. This good cycling performance, when compared to only 17.5 mAh g-1 delivered by bare Sn particles prepared via the same method without the presence of N-doped carbon, could be mainly ascribed to the uniform distribution of the precursor SnO2 on the substrate of N-doped carbon tubes with three-dimensional structure, which provides more reaction sites to reduce the diffusion distance of Na+, further facilitating Na+-ion diffusion and relieves the huge volume expansion during charging/discharging. These outcomes imply that such a Sn/C composite would provide more options as an anode candidate for SIBs.

Capillary-Induced Ge Uniformly Distributed in N-Doped Carbon Nanotubes with Enhanced Li-Storage Performance

Germanium (Ge) is a prospective anode material for lithium-ion batteries, as it possesses large theoretical capacity, outstanding lithium-ion diffusivity, and excellent electrical conductivity. Ge suffers from drastic capacity decay and poor rate performance, however, owing to its low electrical conductivity and huge volume expansion during cycling processes. Herein, a novel strategy has been developed to synthesize a Ge@N-doped carbon nanotubes (Ge@N-CNTs) composite with Ge nanoparticles uniformly distributed in the N-CNTs by using capillary action. This unique structure could effectively buffer large volume expansion. When evaluated as an anode material, the Ge@N-CNTs demonstrate enhanced cycling stability and excellent rate capabilities.

3-D structured SnO2–polypyrrole nanotubes applied in Na-ion batteries

SnO2-coated polypyrrole (PPy) with a three-dimensional (3-D) structured nanotube network has been prepared via a facile hydrothermal method and tested as an anode material for Na-ion batteries. The crystalline SnO2 nanoparticles (less than 25 nm in size) are distributed uniformly on the surfaces of the PPy tubes. When it is used as an anode material for sodium-ion batteries (SIBs), the composite electrode can deliver a good reversible capacity of nearly 288 mA h g−1 when discharging at 100 mA g−1, with more than 69.1% capacity retention and stable coulombic efficiency of 99.6% after 150 cycles. The good electrochemical performance compared to the 151 mA h g−1 achieved by bare SnO2, which was fabricated by the same method in the absence of PPy, could be mainly attributed to the good dispersion of SnO2 on the 3-D matrix of PPy tubes, which facilitates the diffusion of Na+ ions and buffers the large volumetric changes during charge/discharge. Our results suggest that such SnO2/carbonaceous composites would be good anode candidates for SIBs.