Youguo Huang

Preparation of a Sn@SnO2@C@MoS2 composite as a high-performance anode material for lithium-ion batteries

A new type of Sn@SnO2@C@MoS2 composite, composed of Sn@SnO2@C nanosheets and decorated with MoS2, exhibits significantly improved electrochemical performance. This composite has excellent long-term cycling stability (841 mA h g−1 at 1.0 A g−1 after 400 cycles) and superior high-rate capability (458.3 mA h g−1 at 10.0 A g−1) due to the strong synergistic effect between the MoS2 and Sn@C nanosheets.

Direct growth of flower-like 3D MnO2 ultrathin nanosheets on carbon paper as efficient cathode catalyst for rechargeable Li–O2 batteries

Flower-like 3D MnO2 ultrathin nanosheets were synthesized by direct growth of MnO2 on carbon paper (CP) through a facile electro-deposition method. When applied as a self-supporting, binder-free cathode material for rechargeable non-aqueous lithium-oxygen batteries, the as-prepared MnO2/CP electrode exhibited comparable catalytic performance (discharge capacity of 5132 mA h g−1 at a current density of 500 mA g−1) and long cycle stability (up to 125 cycles with controlling capacity of 500 mA h g−1). The superior performance is proposed to be associated with the 3D nanoporous structures and abundant oxygen defects as well as the absence of side reactions related to carbon based conductive additives and binders.

Synthesis of Sn/MoS2/C composites as high-performance anodes for lithium-ion batteries

Tin (Sn) has been considered as one of the most promising anode materials for high-performance lithium ion batteries (LIBs) due to its high theoretical capacity, abundance and low toxicity. However, fast capacity fading and poor rate capability hinder its application in LIBs. Herein, we report a novel composite consisting of few-layer MoS2 and Sn nanoparticles synthesized as an anode for LIBs. In such a composite anode, MoS2 nanosheets provide flexible substrates for the nanoparticle decoration, accommodating the volume changes of Sn during the cycling process, while Sn nanoparticles also can act as spacers to stabilize the composite structure and make the active surfaces of MoS2 nanosheets accessible for electrolyte penetration during the charge/discharge process. Electrochemical measurements demonstrated that the Sn/MoS2/C composite exhibits extremely long cycling stability even at high rate (a reversible capacity of 624.5 mA h g−1 at a current density of 1 A g−1 after 500 cycles) and superior rate capability (1050 mA h g−1 at 100 mA g−1, 895 mA h g−1 at 200 mA g−1, 800 mA h g−1 at 500 mA g−1, 732 mA h g−1 at 1 A g−1 and 630 mA h g−1 at 2 A g−1).

Three-Dimension Hierarchical Al2O3 Nanosheets Wrapped LiMn2O4 with Enhanced Cycling Stability as Cathode Material for Lithium Ion Batteries

A three dimensional (3D) Al2O3 coating layer was synthesized by a facile approach including stripping and in situ self-assembly of γ-AlOOH. The uniform flower-like Al2O3 nanosheets with high specific area largely sequesters acidic species produced by side reaction between electrode and electrolyte. The inner coating layer wrapping spinel LiMn2O4 effectively inhibits the dissolution of Mn by suppressing directive contact with electrolyte to enhance cycling stability. The rate performance is improved because of the better electrolyte storage of the assembled hierarchical architecture of the 3D coating layer affording unimpeded Li(+) diffusion from electrode to electrolyte. The electrochemical results reveal the as-prepared coated LiMn2O4 sample with the amount of Al2O3 at 1 wt % exhibits superior cycle stability under room temperature even at elevated temperature. The initial specific discharge capacity is 128.5 mAh g(-1) at 0.1 C and retains 89.8% of the initial capacity after 800 cycles at 1 C rate. When cycling at 55 °C, the composite shows 93.6% capacity retention after 500 cycles. This facile surface modification and effective structure of coating layer can be adopted to enhance the cycling performance and thermal stability of other electrode materials for which Al2O3 plays its role.

Surfactants assisted synthesis of nano-LiFePO4/C composite as cathode materials for lithium-ion batteries

The goal of this research was to study the effect of molecular structure surfactant on the performance of LiFePO4/C composite. The solid state reaction method was applied to prepare a series of LiFePO4/C materials by adding various surfactants. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Infrared spectrum analysis (FTIR), Raman spectral analysis and electrochemical methods. The results confirm the existence of interactions between the surfactant molecules and the precursor that contribute to the formation of nanoparticles and a homogeneous carbon coating layer on the surface. The structure of the surfactants played an important role in improving the performance of LiFePO4/C composites. The structures of surfactants affect the particle size and the amount of graphite-like carbons of LiFePO4/C composites. The surfactant with longer alkyl C–C chain length could effectively prevent particle growth, while the surfactant with shorter alkyl C–C chain length form more graphene-like carbon during pyrolysis. The as-prepared LiFePO4/C particles using various surfactants show different electrochemical performances. According to Raman spectroscopy and EIS analysis, these composites have different ID/IG peak ratios and charge transfer resistance. Especially, LiFePO4/C synthesis with composite surfactant (weight ratio of Tween80 to Tween20 equal to 1.5) showed an excellent electrochemical performance with a discharge capacity of 167.3 mA h g−1 at 0.1 C rate and 129.4 mA h g−1 at 5 C rate.

Ultrasmall MoS2 embedded in carbon nanosheets-coated Sn/SnOx as anode material for high-rate and long life Li-ion batteries

A Sn/SnOx/MoS2/C composite material with superior performance was developed as an anode for lithium-ion batteries via a facile and scalable ball-milling method using a three-dimensional (3D) self-assembly of NaCl particles as a template. In the constructed architecture, carbon nanosheets avoided the direct exposure of encapsulated Sn/SnOx nanoparticles to the electrolyte and preserved the structural and interfacial stability of the nanoparticles, protecting them from volume expansion during the charge/discharge process. The MoS2 particles, uniformly dispersed on the carbon nanosheets, facilitate an efficient ion transport and ensure structural durability as a particle reinforcing agent. When used as an anode material in lithium-ion batteries, the as-prepared Sn/SnOx/MoS2/C composite exhibit a high rate performance and long cyclic stability, even at a high current density of 3 A g−1 (specific capacity of 725.3 mA h g−1 after 800 cycles). This simple fabrication method and the excellent electrochemical performance demonstrates the potential use of the Sn/SnOx/MoS2/C composite as an anode material for high-performance lithium-ion batteries.

Controlled synthesis of three-dimensional interconnected graphene-like nanosheets from graphite microspheres as high-performance anodes for lithium-ion batteries

Three-dimensional (3D) graphene-based materials have received increasing attention due to their application potential in electrochemical energy storage and conversion. Herein, we demonstrate a facile and efficient strategy to synthesize 3D interconnected graphene-like nanosheets (3DGNs) directly developed from graphite microspheres. The graphene-like nanosheets are interwoven into a unique 3D macroporous network architecture, which can prevent the graphene nanosheets from aggregating effectively. When used as an anode in lithium ion batteries, the 3DGN architecture is capable of reaching an extremely high reversible discharge capacity of 2795.6 mA h g−1, while maintaining a good electrochemical stability with a very high capacity of 1708.5 mA h g−1 after 120 cycles. The superior electrochemical performances of the 3DGN architecture may be attributed to its unique structural features, such as efficient ion/electron conductive channels of 3D interconnected nanosheets, enhanced specific surface area as well as its favorable surface structural features.

Enhanced electrochemical performance of LiMn2O4 cathode with a Li0.34La0.51TiO3-coated layer

Spinel cathode materials consisting of LiMn2O4@Li0.34La0.51TiO3 (LMO@LLTO) have been synthesized by a new and facile solid-phase route in air. When used as cathode for lithium ion batteries, the LLT01 (LiMn2O4 with 20 nm Li0.34La0.51TiO3 coating) sample tested at 1 C rate exhibits 9.2% capacity loss and 90.4% capacity retention after 200 cycles at 25 °C and 55 °C. The improved cycling performance of composites is attributed to the LLT01 coating on the surface of spinel particles. The polycrystalline LLTO-coated layer could provide superior ionic conductivity and prevent Mn dissolution in electrolyte during electrochemical cycling.

Facile synthesis of Sn/MoS2/C composite as an anode material for lithium-ion batteries with outstanding performance

A facile strategy for preparing a novel Sn/MoS2/C composite has been developed via a simple hydrothermal route and then annealing in an Ar atmosphere. The synthesis of layer-structured MoS2 and amorphous carbon can effectively restrict the volume change of Sn during the charge and discharge process. The Sn/MoS2/C composite was evaluated as an anode material for lithium-ion batteries, and exhibits a stable and high reversible capacity of 707 mA h g−1 at 500 mA g−1 after 100 cycles. The significantly improved Li ion storage and stable capability are attributed to the layer-structured MoS2 nanosheets and the amorphous carbon coated layer, which alleviate the large volume changes of Sn and enhance the electron and Li ion diffusion transport in the composite.

In situ growth of NiO nanoparticles on carbon paper as a cathode for rechargeable Li–O2 batteries

Novel NiO nanoparticles have been successfully designed and directly grown on carbon paper (CP) as a cathode for rechargeable Li–O2 batteries via a facile two-step in situ synthesis strategy, including a simple electro-deposition technique, following by high temperature oxidation. Using in situ synthesis methods means that the porous structure of CP is effectively inherited and the use of a binder avoided, which eliminates possible side reactions and over-potential from the binder and enhances the electrochemical performance. SEM and TEM show that the NiO nanoparticles homogenously cover the exposed surface of CPs and the size of the NiO particles is around 10 nm. Benefiting from these structural advantages, the binder-free cathode of NiO/CP exhibits a high discharge capacity of 8934 mA h g−1 under the current density of 100 mA g−1 and could cycle more than 112 times within a capacity limitation of 500 mA h g−1.