Hongwei Yue

Germanium Anode with Excellent Lithium Storage Performance in a Germanium/Lithium–Cobalt Oxide Lithium-Ion Battery

Germanium is a highly promising anode material for lithium-ion batteries as a consequence of its large theoretical specific capacity, good electrical conductivity, and fast lithium ion diffusivity. In this work, Co3O4 nanowire array fabricated on nickel foam was designed as a nanostructured current collector for Ge anode. By limiting the voltage cutoff window in an appropriate range, the obtained Ge anode exhibits excellent lithium storage performance in half- and full-cells, which can be mainly attributed to the designed nanostructured current collector with good conductivity, enough buffering space for the volume change, and shortened ionic transport length. More importantly, the assembled Ge/LiCoO2 full-cell shows a high energy density of 475 Wh/kg and a high power density of 6587 W/kg. A high capacity of 1184 mA h g(-1) for Ge anode was maintained at a current density of 5000 mA g(-1) after 150 cycles.

Facile preparation of Mn3O4-coated carbon nanofibers on copper foam as a high-capacity and long-life anode for lithium-ion batteries

Carbon nanofibers (CNFs) were deposited on Cu foam by a floating catalyst method, and a Mn3O4 layer was then coated onto the deposited CNFs via a hydrothermal process based on the redox reaction of carbon and potassium permanganate. The obtained architecture of Mn3O4-coated CNFs (CNFs@Mn3O4) on Cu foam was directly used as an anode for lithium-ion batteries without using any binder or conducting additive. The anode showed high reversible capacity, good cycle stability and superior rate capability. A reversible capacity of up to 1210.4 mA h g(-1) was obtained after 50 cycles at a current density of 100 mA g(-1). When the current density increased to 5000 mA g(-1), it could deliver a capacity of more than 300 mA h g(-1). The excellent electrochemical performance could be attributed to the unique morphology of the CNFs@Mn3O4 nanocomposites, which can buffer the volume change, decrease the contact resistance, shorten the ionic diffusion path and make the electron transport more efficient.

Synthesis of core-shell architectures of silicon coated on controllable grown Ni-silicide nanostructures and their lithium-ion battery application

Crystalline Ni3Si2 nanostructures were grown on nickel foams via a simple and high-yield chemical vapor deposition (CVD). The morphologies were found to be dependent on the growth pressure. The obtained nanostructures have good crystallinity and uniform distribution. After coating amorphous silicon (a-Si) layers onto the obtained Ni3Si2 nanostructures by an inductively coupled plasma CVD, the architectures were assembled as anodes for lithium-ion batteries. High initial reversible specific capacity of 3733 mA h g−1 is obtained for the prepared a-Si coated Ni3Si2 nanowire electrode at a current density of 2.1 A g−1. After 50 cycles, the specific capacity still stays at above 2000 mA h g−1. When the current density is as high as 8.4 A g−1, the specific capacity maintains at about 1500 mA h g−1. For such core–shell configuration electrodes, the inactive and metallic Ni3Si2 core conducts electrons and provides a mechanically stable anchoring basis for the a-Si layers, resulting in improved electrochemical performance.

Vertical graphene nanosheets synthesized by thermal chemical vapor deposition and the field emission properties

In this paper, we explored synthesis of vertical graphene nanosheets (VGNs) by thermal chemical vapor deposition (CVD). Through optimizing the experimental condition, growth of well aligned VGNs with uniform morphologies on nickel-coated stainless steel (SS) was realized for the first time by thermal CVD. In the meantime, influence of growth parameters on the VGN morphology was understood based on the balancing between the concentration and kinetic energy of carbon-containing radicals. Structural characterizations demonstrate that the achieved VGNs are normally composed of several graphene layers and less corrugated compared to the ones synthesized by other approaches, e.g. plasma enhanced (PE) CVD. The field emission measurement indicates that the VGNs exhibit relatively stable field emission and a field enhancement factor of about 1470, which is comparable to the values of VGNs prepared by PECVD can be achieved.

A facile and inexpensive approach to improve the performance of silicon film as an anode for lithium-ion batteries

Silicon is considered as a promising candidate for next-generation lithium-ion battery anodes. However, severe capacity fading caused by volume change during Li-ion insertion and extraction hinders its practical application. In this work, gold granular film and polyvinylidene fluoride coating are sequentially prepared on the deposited Si film to solve the aforementioned problem.

Electrochemically deposited interconnected porous Co3O4 nanoflakes as anodes with excellent rate capability for lithium ion batteries

Interconnected porous Co3O4 nanoflakes were prepared on nickel foam by a simple electrochemical deposition combined with a subsequent heat treatment. The featured nanoflakes consisted of interconnected primary nanoparticles and nanopores resulting in a large specific surface area. As an anode material of lithium ion batteries, the as-prepared samples exhibited superior cyclic performance and excellent rate capacity. The discharge capacity remained at 1211 mA h g−1 after 100 cycles at a current density of 1 A g−1. Notably, after cycling at various current densities up to 5 A g−1, the capacity recovered to 1266 mA h g−1 at 0.1 A g−1.

In situ coating of NiO on Ni-silicide nanowires with roughened surfaces for improved electrochemical energy storage

NiO layers were coated in situ onto Ni-silicide nanowires by an oxidation in air. The surface of the nanowires had been previously roughened by etching in HF solution. It is found that the roughened surface is very helpful to enhance the in situ coating ability of NiO on the nanowires. When the resulting samples were used as anodes for lithium-ion batteries, a high reversible capacity of 1.28 mA h cm−2 was obtained for the surface-roughened nanowires with 30 min HF-treatment, which is 3 times higher than that of the nanowires without HF-treatment. The current density can reach up to 2.15 mA cm−2 for the 60 min HF-treated and then oxidized nanowires, while the capacity is maintained at as high as 0.52 mA h cm−2. The improved cyclic performance could be attributed to the roughened surface of the nanowires, which enhanced the coating ability of the NiO layers, and provided a porous structure that is of benefit to increase the area of the electrode/electrolyte interface for the adsorption of ions. In addition, the Ni-silicide nanowires can improve the electrode conductivity and act as a stable support for the NiO coating layers during cycling, making a positive contribution to the electrochemical performance.

Rational design of hierarchical Ni embedded NiO hybrid nanospheres for high-performance lithium-ion batteries

Novel hierarchical Ni/NiO hybrid nanospheres were fabricated by a simple solvothermal synthesis method followed by thermal oxidation. The hybrid nanospheres are uniform-sized and composed of tiny Ni embedded NiO nanoparticles. Galvanostatic battery tests show that the corresponding electrode can deliver a high reversible capacity of 712 mA h g−1 for the second discharge and a capacity of 825 mA h g−1 was obtained after 132 cycles at a rate of 0.2C. Good rate performance was achieved even when the rate is as high as 12C with a high capacity of 453 mA h g−1, and a capacity of 800 mA h g−1 was retained when it returned to 0.2C after 300 cycles. The excellent cycling stability and rate performance are derived from the special nanostructural characteristics of the prepared hybrid nanospheres, indicating that they are a promising anode material for high-performance lithium-ion batteries.