Yunhui Wang

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.

Prussian Blue: A Potential Material to Improve the Electrochemical Performance of Lithium–Sulfur Batteries

The Prussian blue, as a potential adsorbent of polysulfides to suppress the dissolution and shuttle of polysulfides for lithium-sulfur batteries, has been studied in this work. Our results show that Prussian blue improves the electrochemical reaction kinetics during discharge/charge processes. More importantly, the cathode with Prussian blue exhibits better cycling stability and higher discharge capacity retention (722 mAh g-1 at 0.2 A g-1 after 100 cycles) than the one without Prussian blue (151 mAh g-1). These improvements of electrochemical performances are ascribed to the fact that Prussian blue is very effective in suppressing the dissolution of polysulfides into liquid electrolyte by chemical adsorption.

Investigation of the Reversible Intercalation/Deintercalation of Al into the Novel Li3VO4@C Microsphere Composite Cathode Material for Aluminum-Ion Batteries

The Li3VO4@C microsphere composite was first reported as a novel cathode material for rechargeable aluminum-ion batteries (AIBs), which manifests the initial discharge capacity of 137 mAh g-1 and and remains at 48 mAh g-1 after 100 cycles with almost 100% Coulombic efficiency. The detailed intercalation mechanism of Al into the orthorhombic Li3VO4 is investigated by ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) of Li3VO4@C electrodes and the nuclear magnetic resonance aluminum spectroscopy (27Al NMR) of ionic liquid electrolytes in different discharge/charge states. First-principle calculations are also carried out to investigate the structural change as Al inserts into the framework of Li3VO4. It is revealed that the Al/Li3VO4@C battery goes through electrochemical dissolution and deposition of metallic aluminum in the anode, as well as the insertion and deinsertion of Al3+ cations in the cathode in the meantime. The rechargeable AIBs fabricated in this work are of low cost and high safety, which may make a step forward in the development of novel cathode materials based on the acidic ionic liquid electrolyte system.

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.

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.