Kesong Xiao

Three-dimensional Li3V2(PO4)3/C nanowire and nanofiber hybrid membrane as a self-standing, binder-free cathode for lithium ion batteries

A three-dimensional (3D) mace-like Li3V2(PO4)3/C nanowire and nanofiber hybrid membrane was fabricated by using Ni nanoparticles as a catalyst and a modified electrospinning method followed by a hot-pressing heat treatment. The results indicate that the prepared membrane is composed of Li3V2(PO4)3 nanowires and Li3V2(PO4)3/C composite fibers. This hybrid membrane has a high specific surface area of 227.56 m2 g−1 with a combination of micropores and mesopores, which can be used as self-standing, binder-free cathodes for lithium ion batteries. This hybrid membrane electrode exhibits good rate performance and cyclic stability in the voltage range of 3.0–4.8 V with an initial discharge capacity of 115.3 mA h g−1 at 5C and 108.6 mA h g−1 at 10C and a capacity retention of 81.4% and 75.1% respectively after 500 cycles, 78.8% and 70.3% after 1000 cycles. The coulombic efficiencies both at 5C and 10C maintain about 100% during cycling. This excellent electrochemical performance may be attributed to the unique 3D long-range conductive networks and mace-like fiber structure, which favorably improve the reaction kinetics of Li3V2(PO4)3.

CeO2 nanodots decorated ketjen black for high performance lithium–sulfur batteries

A CeO2 nanodots decorated ketjen black composite was fabricated by a simple wet impregnation method and used as the host of sulfur for a lithium–sulfur battery. The microstructure and chemical components were evaluated by XRD, SEM, TEM, surface area analysis and thermogravimetric analysis. Electrochemical tests and microanalysis demonstrated that CeO2 nanodots served as the sulfur fixation spots as well as the catalytic agent compared with the reference sample without CeO2 nanodots. The CeO2/KB–S cathode material with the CeO2/KB mass ratio of approximately 15/85 shows a high initial discharge capacity of 905 mA h g−1 at the current rate of 1C and remains at 710 mA h g−1 after 300 cycles. Furthermore, the CeO2/KB–S cathode shows a promising rate performance with the discharge capacity of 800 mA h g−1 even at the current rate of 2C.

Electrospinning preparation of oxygen-deficient nano TiO 2-x /carbon fibre membrane as a self-standing high performance anode for Li-ion batteries

Improving the specific capacity and electronic conductivity of TiO2 can boost its practical application as a promising anode material for lithium ion batteries. In this work, a three-dimensional networking oxygen-deficient nano TiO2-x/carbon fibre membrane was achieved by combining the electrospinning process with a hot-press sintering method and directly used as a self-standing anode. With the synergistic effects of three-dimensional conductive networks, surface oxygen deficiency, high specific surface area and high porosity, binder-free and self-standing structure, etc., the nano TiO2-x/carbon fibre membrane electrode displays a high electrochemical reaction kinetics and a high specific capacity. The reversible capacity could be jointly generated from porous carbon, full-lithiation of TiO2 and interfacial lithium storage. At a current density of 100 mA g−1, the reversible discharge capacity can reach 464 mA h g−1. Even at 500 mA g−1, the discharge capacity still remains at 312 mA h g−1. Compared with pure carbon fibre and TiO2 powder, the TiO2-x/C fibre membrane electrode also exhibits an excellent cycle performance with a discharge capacity of 209 mA h g−1 after 700 cycles at the current density of 300 mA g−1, and the coulombic efficiency always remains at approximately 100%.

High loading LiFePO4 on activated carbon fiber cloth as a high capacity cathode for Li-ion battery

The LiFePO4/carbon fiber (LFP/CF) cathodes were prepared by using activated carbon fiber cloth as current collector in place of conventional Al foil. The electrochemical properties of LFP/CF electrodes were analyzed by the cyclic voltammetry and galvanostatic charge/discharge tests. The results indicate that the activated carbon fiber cloth with high specific surface area and high porosity makes the LFP/CF electrode that possesses higher mass loading of 18–21 mg cm–2 and stronger redox reaction ability compared with Al foil-based electrode. The LFP/CF electrode shows excellent rate performance and cycle stability. At 0.1C, the discharge capacity is up to 190.1 mAh g–1 that exceeds the theoretical capacity due to the combination effect of battery and capacitor. Furthermore, the LFP/CF electrode shows an initial capacity of 150.4 mAh g–1 at 1C with a capacity retention of 74.7% after 425 cycles, which is higher than 62.4% for LFP/Al foil electrode, and an initial discharge capacity of 130 mAh g–1 at 5C with a capacity retention of 61.5% after 370 cycles. But this composite electrode is not suitable for charging/discharging at higher rate as 10C due to too much mass loading.

Electrospun LiFePO4/C Composite Fiber Membrane as a Binder-Free, Self-Standing Cathode for Power Lithium-Ion Battery

A LiFePO4/C composite fiber membrane was fabricated by the electrospinning method and subsequent thermal treatment. The thermal decomposition process was analyzed by TG/DSC, the morphology, microstructure and composition were studied using SEM, TEM, XRD, Raman, respectively. The results indicated that the prepared LiFePO4/C composite fibers were composed of nanosized LiFePO4 crystals and amorphous carbon coatings, which formed a three dimensional (3D) long-range networks, greatly enhanced the electronic conductivity of LiFePO4 electrode up to 3.59× 10-2 S · cm-2. The 3D LiFePO4/C fiber membrane could be directly used as a binder-free, self-standing cathode for lithium-ion battery, and exhibited an improved capacity and rate performance. The LiFePO4/C composite electrode delivered a discharge capacity of 116 mAh·g-1, 109 mAh·g-1, 103 mAh·g-1, 91 mAh·g-1, 80 mAh·g-1 at 0.1 C, 0.5 C, 1 C, 3 C, 5 C, respectively. And a stable cycling performance was also achieved that the specific capacity could retain 75 mA·g-1 after 500 cycles at 5 C. Therefore, this LiFePO4/C composite fiber membrane was promising to be used as a cathode for power lithium ion battery.

Synthesis and characterization of electrospun molybdenum dioxide–carbon nanofibers as sulfur matrix additives for rechargeable lithium–sulfur battery applications

One-dimensional molybdenum dioxide–carbon nanofibers (MoO2–CNFs) were prepared using an electrospinning technique followed by calcination, using sol–gel precursors and polyacrylonitrile (PAN) as a processing aid. The resulting samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Brunauer–Emmet–Teller (BET) surface area measurements, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). MoO2–CNFs with an average diameter of 425–575 nm obtained after heat treatment were used as a matrix to prepare sulfur/MoO2–CNF cathodes for lithium–sulfur (Li–S) batteries. The polysulfide adsorption and electrochemical performance tests demonstrated that MoO2–CNFs did not only act as polysulfide reservoirs to alleviate the shuttle effect, but also improve the electrochemical reaction kinetics during the charge–discharge processes. The effect of MoO2–CNF heat treatment on the cycle performance of sulfur/MoO2–CNFs electrodes was examined, and the data showed that MoO2–CNFs calcined at 850 °C delivered optimal performance with an initial capacity of 1095 mAh g−1 and 860 mAh g−1 after 50 cycles. The results demonstrated that sulfur/MoO2–CNF composites display a remarkably high lithium–ion diffusion coefficient, low interfacial resistance and much better electrochemical performance than pristine sulfur cathodes.