Xiaoyan Li

Hollow-tunneled graphitic carbon nanofibers through Ni-diffusion-induced graphitization as high-performance anode materials

N-doped nanoporous graphitic carbon has attracted great interest because of its distinctive structure and physical properties. In this paper, we have proposed a novel method to control Ni-induced graphitization by diffusing Ni nanoparticles from graphitic carbon spheres into N-doped amorphous carbon nanofibers, which turns amorphous carbon into graphitic carbon and produces a hollow-tunnel structure in electrospun carbon/Ni nanofibers. The resultant materials were further treated by chemical activation and acid treatment to develop activated N-doped hollow-tunneled graphitic carbon nanofibers (ANHTGCNs). In a typical application, we demonstrate that ANHTGCNs are excellent anode materials for lithium ion batteries (LIBs), displaying a superhigh reversible specific capacity of ∼1560 mA h g−1 and a remarkable volumetric capacity of ∼1.8 A h cm−3 at a current density of 0.1 A g−1 with outstanding rate capability and good cycling stability.

Exceptional electrochemical performance of porous TiO2-carbon nanofibers for lithium ion battery anodes

We have developed one-dimensional (1D) porous TiO2–carbon nanofibers (ODPTCNs) by a simple coaxial electrospinning technique combined with subsequent calcination treatment as anode materials for Li-ion batteries. The prepared ODPTCNs contain plentiful surface pores through which lithium ions can transport from outer space into inner space as storage regions, thus activating all the materials. In addition, the high conductivity of the overall electrode and the porous structure aid Li+ access and the rapid transportation of lithium ions, thus reducing the diffusion paths for Li+ and yielding a better rate capability. The novel ODPTCNs show a remarkable specific reversible capacity of ∼806 mA h g−1 and a high volumetric capacity of ∼1.2 A h cm−3, maintain a capacity of ∼680 mA h g−1 after 250 cycles at a current density of 100 mA g−1 and exhibit an exceptional discharge rate capability of 5 A g−1 while retaining a capacity of ∼260 mA h g−1 after 1600 cycles. The ODPTCNs will serve as excellent anode materials for next-generation, high-power, and environmentally benign Li-ion batteries.

Hollow Nanotubes of N-Doped Carbon on CoS.

Low-cost, single-step synthesis of hollow nanotubes of N-doped carbon deposited on CoS is enabled by the simultaneous use of three functionalities of polyacrylonitrite (PAN) nanofibers: 1)u2005a substrate for loading active materials, 2)u2005a sacrificial template for creating hollow tubular structures, and 3)u2005a precursor for inu2005situ nitrogen doping. The N-doped carbon in hollow tubes of CoS provides a high-capacity anode of long cycle life for a rechargeable Li-ion or Na-ion battery cell that undergoes the conversion reaction 2u2009A+ +2u2009e- +CoSu2009→Co+A2 S with A=Li or Na.

Core/shell TiO2–MnO2/MnO2 heterostructure anodes for high-performance lithium-ion batteries

Core/shell TiO2–MnO2/MnO2 heterostructures were synthesized by combining an electrospinning technique with a hydrothermal reaction. To create the starting materials, porous TiO2–carbon nanofibers were first prepared using a simple electrospinning technique followed by calcination. The porous structure in TiO2–carbon nanofibers caused by the partial decomposition of polystyrene is beneficial to the diffusion of KMnO4 from the outer surface into inner fibers to completely react with carbon and produce MnO2 nanosheets. Some MnO2 nanosheets in the TiO2 core connect with other MnO2 nanosheets surrounding the TiO2 core to form core/shell TiO2–MnO2/MnO2, which can enhance the stability of the structure. The large surface area of the resulting materials offers a sufficient electrode–electrolyte interface to promote the charge-transfer reactions, which yields a better rate capability. The porous structure of TiO2–MnO2/MnO2 nanofibers not only facilitates Li-ion access, but also accommodates large volumetric expansion during the charging–discharging processes, resulting in an excellent cycle performance. As an anode, this material delivered a high reversible capacity of 891 mA h g−1 at the first cycle and maintained the capacity of 888 mA h g−1 after 50 cycles at the current density of 0.1 A g−1; it also showed a remarkable rate capability of 2 A g−1 while retaining a capacity of 185 mA h g−1 after 500 cycles. Given their enhanced electrochemical performance, core/shell TiO2–MnO2/MnO2 heterostructure nanofibers are promising anode candidates for lithium-ion batteries.

High-performance electrospun nanostructured composite fiber anodes for lithium–ion batteries

Rechargeable lithium–ion batteries (LIBs) have attracted considerable attention owing to their high specific energy and cost effectiveness, making them suitable for many applications including portable electronics, electric vehicles, and hybrid vehicles. Unfortunately, they suffer from some critical drawbacks like slow power capability and unsafety. One-dimensional (1D) nanostructured multifunctional composite fiber anodes fabricated using electrospun polymer nanofibers through thermal and chemical treatments have recently been developed to address these challenges, since they provide faster reaction kinetics, shorter Li ion diffusion pathways, mechanical integrity, and continuous fibrous networks. In this chapter, we review recent developments on 1D nanostructured composite fiber anodes for LIBs with special emphases on their syntheses, electrochemical performance, and electrode reaction mechanisms.