Qiang Pang

Improved Lithium-Ion and Sodium-Ion Storage Properties from Few-Layered WS2 Nanosheets Embedded in a Mesoporous CMK-3 Matrix

An integrated WS2 @CMK-3 nanocomposite has been prepared by a one-step hydrothermal method and then used as the anode material for lithium-ion and sodium-ion batteries. Ultrathin WS2 nanosheets have been successfully embedded into the ordered mesoporous carbon (CMK-3) framework. Owing to the few-layered nanostructure of WS2 , as well as the high electronic conductivity and the volume confinement effect of CMK-3, the material shows larger discharge capacity, better rate capability, and improved cycle stability than pristine WS2 . When tested in lithium-ion batteries, the material delivers a reversible capacity of 720 mA h g-1 after 100 cycles at a current density of 100 mA g-1 . A large discharge capacity of 307 mA h g-1 is obtained at a current density of 2 A g-1 . When used in sodium-ion batteries, the material exhibits a capacity of 333 mA h g-1 at 100 mA g-1 without capacity fading after 70 cycles. A discharge capacity of 230 mA h g-1 is obtained at 2 A g-1 . This excellent performance demonstrates that the WS2 @CMK-3 nanocomposite has great potential as a high-performance anode material for next-generation rechargeable batteries.

Multi-Functional Surface Engineering for Li-Excess Layered Cathode Material Targeting Excellent Electrochemical and Thermal Safety Properties.

The Li(Li(0.18)Ni(0.15)Co(0.15)Mn(0.52))O2 cathode material is modified by a Li4M5O12-like heterostructure and a BiOF surface layer. The interfacial heterostructure triggers the layered-to-Li4M5O12 transformation of the material which is different from the layered-to-LiMn2O4 transformation of the pristine Li(Li(0.18)Ni(0.15)Co(0.15)Mn(0.52))O2. This Li4M5O12-like transformation helps the material to keep high working voltage, long cycle life and excellent rate capability. Mass spectrometry, in situ X-ray diffraction and transmission electron microscope show that the Li4M5O12-like phase prohibits oxygen release from the material bulk at elevated temperatures. In addition, the BiOF coating layer protects the material from harmful side reactions with the electrolyte. These advantages significantly improve the electrochemical performance of Li(Li(0.18)Ni(0.15)Co(0.15)Mn(0.52))O2. The material shows a discharge capacity of 292 mAh g(-1) at 0.2 C with capacity retention of 92% after 100 cycles. Moreover, a high discharge capacity of 78 mAh g(-1) could be obtained at 25 C. The exothermic temperature of the fully charged electrode is elevated from 203 to 261 °C with 50% reduction of the total thermal release, highlighting excellent thermal safety of the material.

NASICON-Type Mg0.5Ti2(PO4)3 Negative Electrode Material Exhibits Different Electrochemical Energy Storage Mechanisms in Na-Ion and Li-Ion Batteries

A carbon-coated Mg0.5Ti2(PO4)3 polyanion material was prepared by the sol-gel method and then studied as the negative electrode materials for lithium-ion and sodium-ion batteries. The material showed a specific capacity of 268.6 mAh g-1 in the voltage window of 0.01-3.0 V vs Na+/Na0. Due to the fast diffusion of Na+ in the NASICON framework, the material exhibited superior rate capability with a specific capacity of 94.4 mAh g-1 at a current density of 5A g-1. Additionally, 99.1% capacity retention was achieved after 300 cycles, demonstrating excellent cycle stability. By comparison, Mg0.5Ti2(PO4)3 delivered 629.2 mAh g-1 in 0.01-3.0 V vs Li+/Li0, much higher than that of the sodium-ion cells. During the first discharge, the material decomposed to Ti/Mg nanoparticles, which were encapsulated in an amorphous SEI and Li3PO4 matrix. Li+ ions were stored in the Li3PO4 matrix and the SEI film formed/decomposed in subsequent cycles, contributing to the large Li+ capacity of Mg0.5Ti2(PO4)3. However, the lithium-ion cells exhibited inferior rate capability and cycle stability compared to the sodium-ion cells due to the sluggish electrochemical kinetics of the electrode.

Self-assembled CoS nanoflowers wrapped in reduced graphene oxides as the high-performance anode materials for sodium-ion batteries

It remains a big challenge to identify high-performance anode materials to promote practical applications of sodium-ion batteries. Herein, the facile synthesis of CoS nanoflowers wrapped in reduced graphene oxides (RGO) is reported, and their sodium storage properties are systematically studied in comparison with bare CoS. The CoS@RGO nanoflowers deliver a high reversible capacity of 620 mAh g-1 at a current density of 100 mA g-1 and superior rate capability with discharge capacity of 329 mAh g-1 at 4 A g-1 , much higher than those of the bare CoS. Evidenced by electrochemical impedance spectra and ex-situ SEM images, the improvement in the sodium storage performance is found to be due to the introduction of RGO which serves as a conducting matrix, to not only increase the kinetic properties of CoS, but also buffer the volume change and maintain the integrity of working electrodes during (de)sodiation processes. More importantly, the pseudocapacitive contribution of more than 89 % is only observed in the CoS@RGO nanocomposites, owing to the enhanced specific area and surface redox behavior.

Li+/Mg2+ Hybrid-Ion Batteries with Long Cycle Life and High Rate Capability Employing MoS2 Nano Flowers as the Cathode Material.

The demand for large-scale and safe energy storage is increasing rapidly due to the strong push for smartphones and electric vehicles. As a result, Li+ /Mg2+ hybrid-ion batteries (LMIBs) combining a dendrite-free deposition of Mg anode and Li+ intercalation cathode have attracted considerable attention. Here, a LMIB with hydrothermal-prepared MoS2 nano flowers as cathode material was prepared. The battery showed remarkable electrochemical properties with a large discharge capacity (243 mAh g-1 at the 0.1 C rate), excellent rate capability (108 mAh g-1 at the 5 C rate), and long cycle life (87.2 % capacity retention after 2300 cycles). Electrochemical analysis showed that the reactions occurring in the battery cell involved Mg stripping/plating at the anode side and Li+ intercalation at the cathode side with a small contribution from Mg2+ adsorption. The excellent electrochemical performance and extremely safe cell system show promise for its use in practical applications.

Co9S8/Co as a High Performance Anode for Sodium Ion Batteries with a Preferred Ether-based Electrolyte

Co9 S8 has been regarded as a desirable anode material for sodium-ion batteries because of its high theoretical capacity. In this study, a Co9 S8 anode material containing 5.5 wt % Co (Co9 S8 /Co) was prepared by a solid-state reaction. The electrochemical properties of the material were studied in carbonate and ether-based electrolytes (EBE). The results showed that the material had a longer cycle life and better rate capability in EBE. This excellent electrochemical performance was attributed to a low apparent activation energy and a low overpotential for Na deposition in EBE, which improved the electrode kinetic properties. Furthermore, EBE suppressed side reactions of the electrode and electrolyte, which avoided the formation of a solid electrolyte interphase film.

Dual Roles of Li3N as an Electrode Additive for Li-Excess Layered Cathode Materials: A Li-Ion Sacrificial Salt and Electrode-Stabilizing Agent

Li2 CO3 -passivated Li3 N with high stability is prepared by aging Li3 N powder in dry air, and is then used as an electrode additive for a Li(Li0.18 Ni0.15 Co0.15 Mn0.52 )O2 (LLMO) cathode material. The material shows a large irreversible capacity of 800 mA h g-1 during the first charge, with the formation of a Li2 N intermediate product. Acting as a Li+ sacrificial salt for a LLMO(+)/graphite(-) Li-ion battery, 2 wt % Li3 N results in a 10 % increase in discharge capacity. The Li2 N intermediate product reacts with the electrolyte, forming a uniform and regular surface film on the cathode. Moreover, chemical bonding between LLMO and N improves the electrode stability, resulting in excellent electrochemical performance.