Yiyong Zhang

Synthesis of One‐Dimensional Copper Sulfide Nanorods as High‐Performance Anode in Lithium Ion Batteries

Nanorod-like CuS and Cu2 S have been fabricated by a hydrothermal approach without using any surfactant and template. The electrochemical behavior of CuS and Cu2 S nanorod anodes for lithium-ion batteries reveal that they exhibit stable lithium-ion insertion/extraction reversibility and outstanding rate capability. Both of the electrodes exhibit excellent capacity retentions irrespective of the rate used, even at a high current density of 3200 mA g(-1) . More than 370 mAh g(-1) can be retained for the CuS electrode and 260 mAh g(-1) for the Cu2 S electrode at the high current rate. After 100 cycles at 100 mA g(-1) , the obtained CuS and Cu2 S electrodes show discharge capacities of 472 and 313 mAh g(-1) with retentions of 92% and 96%, respectively. Together with the simplicity of fabrication and good electrochemical properties, CuS and Cu2 S nanorods are promising anode materials for practical use the next-generation lithium-ion batteries.

High sulfur loading lithium–sulfur batteries based on a upper current collector electrode with lithium-ion conductive polymers

We report an effective double current collector electrode. In this study, we achieve a high areal loading double current collector electrode with high areal capacity density and long cycle life. We also adjust the charging condition (constant capacity charging) which leads to long cycle life with almost no capacity fading.

Fabrication of polymer matrix composites reinforced with controllably oriented whiskers

Polyvinyl chloride (PVC) reinforced with controllably oriented potassium titanate whisker (PTW) has been prepared. The preparation includes wet-spinning a polymer solution that contains the whiskers, placing the resultant precursor fiber in a die and hot-pressing to form composite. The whiskers are highly aligned along the axis of the fiber as the result of extrusion and drawing in spinning. Therefore, the whisker orientation in the composite can be closely controlled through controlling the directions of the precursor. The degree of whisker alignment is found to depend strongly on drawing ratio, and a simplified mathematical relation is presented. The mechanical properties of the PTW reinforced PVC are reported. The applications of the composite processing technique described above in functional composites are also discussed.

Facile Synthesis of Rod-like Cu2−xSe and Insight into its Improved Lithium-Storage Property

A rod-like Cu2-x Se is synthesized by a facile water evaporation process. The electrochemical reaction mechanism is investigated by ex situ X-ray diffraction (XRD). By adopting an ether-based electrolyte instead of a carbonate-based electrolyte, the electrochemical performance of Cu2-x Se electrodes improved significantly. The Cu2-x Se electrodes exhibit outstanding cycle performance: after 1000 cycles, 160 mA h g-1 can be maintained with a retention of 80.3 %. At current densities of 100, 200, 500, and 1000 mA g-1 , the capacity of a Cu2-x Se/Li battery was 208, 202, 200, and 198 mA h g-1 , respectively, showing excellent rate capability. The 4-probe conductivity measurements along with electrochemical impendence spectroscopy (EIS) and cyclic voltammetry (CV) tests illustrate that the Cu2-x Se electrodes display high specific conductivity and impressive lithium-ion diffusion rate, which makes the Cu2-x Se a promising anode material for lithium-ion batteries.

A Promising High-Voltage Cathode Material Based on Mesoporous Na3V2(PO4)3/C for Rechargeable Magnesium Batteries

The lack of suitable high-voltage cathode materials has hindered the development of rechargeable magnesium batteries (RMBs). Here, mesoporous Na3 V2 (PO4 )3 /C (NVP/C) spheres have been synthesized through a facile spray-drying-annealing method, and their electrochemically desodiated phase NaV2 (PO4 )3 /C (ED-NVP/C) has been investigated as an intercalation host for Mg2+ ions. The obtained ED-NVP/C exhibits an average discharge voltage of around 2.5 V (vs. Mg2+ /Mg), higher than those of most previously reported cathode materials. In addition, it can deliver an initial discharge capacity of 88.8 mA h g-1 at 20 mA g-1 , with good cycling stability. Ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results demonstrate that the electrochemical reaction is based on an intercalation mechanism and shows good reversibility. Galvanostatic intermittent titration technique (GITT) data have revealed that the intercalation process involves a two-phase transition. The reported ED-NVP/C cathode material with high working voltage offers promising potential for application in RMBs.

High sulfur-containing carbon polysulfide polymer as a novel cathode material for lithium-sulfur battery

The lithium-sulfur battery, which offers a high energy density and is environmental friendly, is a promising next generation of rechargeable energy storage system. However, despite these attractive attributes, the commercialization of lithium-sulfur battery is primarily hindered by the parasitic reactions between the Li metal anode and dissolved polysulfide species from the cathode during the cycling process. Herein, we synthesize the sulfur-rich carbon polysulfide polymer and demonstrate that it is a promising cathode material for high performance lithium-sulfur battery. The electrochemical studies reveal that the carbon polysulfide polymer exhibits superb reversibility and cycle stability. This is due to that the well-designed structure of the carbon polysulfide polymer has several advantages, especially, the strong chemical interaction between sulfur and the carbon framework (C-S bonds) inhibits the shuttle effect and the π electrons of the carbon polysulfide compound enhance the transfer of electrons and Li+. Furthermore, as-prepared carbon polysulfide polymer-graphene hybrid cathode achieves outstanding cycle stability and relatively high capacity. This work highlights the potential promise of the carbon polysulfide polymer as the cathode material for high performance lithium-sulfur battery.

Self-templating thermolysis synthesis of Cu 2– x S@M (M = C, TiO 2 , MoS 2 ) hollow spheres and their application in rechargeable lithium batteries

Owing to their unique structural stability and impressive long-term cycling performance, coated hollow structures are highly attractive for energy storage systems, especially batteries. Many efforts have been devoted and various strategies have been proposed to prepare such materials. In the present work, we propose a self-templating thermolysis strategy, different from traditional wet processing methods, to fabricate cuprous sulfide hollow spheres coated with different shells, by exploiting the thermal decomposition properties of the core (CuS) and the protection provided by the shell. To demonstrate the generality of this synthetic approach, three different coating materials (carbon, TiO2, MoS2) have been chosen to prepare Cu2–xS@C, Cu2–xS@TiO2 and Cu2–xS@MoS2 hollow spheres. All synthesized composite materials were then assembled as electrodes and tested in lithium batteries, showing excellent cycling stability. In particular, the electrochemical properties of Cu2–xS@C were thoroughly investigated. The results of this work provide an alternative route to prepare coated metal sulfide hollow spheres for energy storage applications.

Directly Coating a Multifunctional Interlayer on the Cathode via Electrospinning for Advanced Lithium–Sulfur Batteries

The lithium-sulfur battery is considered as a prospective candidate for a high-energy-storage system because of its high theoretical specific capacity and energy. However, the dissolution and shutter of polysulfides lead to low active material utilization and fast capacity fading. Electrospinning technology is employed to directly coat an interlayer composed of polyacrylonitrile (PAN) and nitrogen-doped carbon black (NC) fibers on the cathode. Benefiting from electrospinning technology, the PAN-NC fibers possess good electrolyte infiltration for fast lithium-ion transport and great flexibility for adhering on the cathode. The NC particles provide good affinity for polysufides and great conductivity. Thus, the polysulfides can be trapped on the cathode and reutilized well. As a result, the PAN-NC-coated sulfur cathode (PAN-NC@cathode) exhibits the initial discharge capacity of 1279 mAh g-1 and maintains the reversible capacity of 1030 mAh g-1 with capacity fading of 0.05% per cycle at 200 mA g-1 after 100 cycles. Adopting electrospinning to directly form fibers on the cathode shows a promising application.

Investigation of the Na Storage Property of One-Dimensional Cu2–xSe Nanorods

In this study, one-dimensional Cu2- xSe nanorods synthesized by a simple water evaporation-induced self-assembly approach are served as the anode material for Na-ion batteries for the first time. Cu2- xSe electrodes express outstanding electrochemical properties. The initial discharge capacity is 149.3 mA h g-1 at a current density of 100 mA g-1, and the discharge capacity can remain at 106.2 mA h g-1 after 400 cycles. Even at a high current density of 2000 mA g-1, the discharge capacity of the Cu2- xSe electrode still remains at 62.8 mA h g-1, showing excellent rate performance. Owing to the excellent electronic conductivity and one-dimensional structure of Cu2- xSe, the Cu2- xSe electrodes manifest fast Na+ ion diffusion rate. Moreover, detailed Na+ insertion/extraction mechanism is further investigated by ex situ measurements and theoretical calculations.

Structure and Magnetic Properties of the Co-Ni Alloy Nanowires Prepared by AC Electrodeposition

Ordered Co-Ni nanowires have been fabricated by alternating current (AC) electrodeposition method using anodic porous alumina as a template. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) test results reveal that the samples are polycrystalline with uniform diameters around 50 nm and lengths up to several micrometers. X-ray diffraction (XRD) pattern indicate the crystalline structure change from fcc to hcp as the Co composition increasing. Magnetic measurements show that the nanowires have high magnetic anisotropy with their easy axis parallel to the nanowire arrays. The coercivity (Hc) and squareness (Mr/Ms) are found to increase with the increase of ferromagnetic Co component.