One-Pot Synthesized Amorphous Cobalt Sulfide With Enhanced Electrochemical Performance as Anodes for Lithium-Ion Batteries

In order to solve the poor cycle stability and the pulverization of cobalt sulfides electrodes, a series of amorphous and crystalline cobalt sulfides were prepared by one-pot solvothermal synthesis through controlling the reaction temperatures. Compared to the crystalline cobalt sulfide electrodes, the amorphous cobalt sulfide electrodes exhibited superior electrochemical performance. The high initial discharge and charge capacities of 2,132 mAh/g and 1,443 mAh/g at 200 mA/g were obtained. The reversible capacity was 1,245 mAh/g after 200 cycles, which is much higher than the theoretical capacity. The specific capability was 815 mAh/g at 800 mA/g and increased to 1,047 mAh/g when back to 100 mA/g, indicating the excellent rate capability. The outstanding electrochemical performance of the amorphous cobalt sulfide electrodes could result from the unique characteristics of more defects, isotropic nature, and the absence of grain boundaries for amorphous nanostructures, indicating the potential application of amorphous cobalt sulfide as anodes for lithium-ion batteries.

Effect of Stoichiometry on Shape Memory Properties of Ti-Ni-Hf-Cu-Nb Shape Memory Alloys Manufactured by Suspended Droplet Alloying

A novel Ti-Ni-Hf-Cu-Nb shape memory alloy has been developed by a new combinatorial alloy synthesis method, the Suspended Droplet Alloying. The influence of alloying elements on the transformation temperature, the microstructure and the shape memory effect of this alloy have also been studied. It was found that Cu has a greater negative influence on the transformation temperature of Ti-Ni-Hf-CuX alloys (about −5 K/at.%) than on the Ti-Ni-CuX alloys (−0.67 K/at.%). In addition, the negative effect intensifies with increasing Hf content. The transformation temperature rapidly decreases with increasing Nb composition in the Ti-Ni-Cu-Nb and Ti-Ni-Hf-Cu-Nb alloys, with the solid solution of Nb in the matrix being 1 at.%. A Ti-Ni-Cu-Hf-Nb alloy with high thermal cycle stability has been developed, where the alloying elements affect the transformation behaviour via altering the slipping energy and forming different types of precipitations.

Robust Redox-Active Hydrogen-Bonded Organic Framework for Rechargeable Batteries

The problems such as low cycle stability, poor ion mobility and weak conductivity hinder the development of organic electrode materials. Herein, one of robust porous hydrogen-bonded organic framework (HOF), CPHATN-1a,...

Embedding Co2P nanoparticles in Cu doping carbon fibers for Zn-Air batteries and supercapacitors

Developing highly efficient and non-precious materials for Zn-air batteries (ZABs) and supercapacitors (SCs) are still crucial and challenging. Herein, electronic reconfiguration and introducing conductive carbon-based materials are simultaneously conducted to enhance the ZABs and SCs performance of Co2P. We develop a simple and efficient electrospinning technology followed by carbonization process to synthesize embedding Co2P nanoparticles in Cu doping carbon nanofibers (Cu-Co2P/CNFs). As a result, the 7% Cu-Co2P/CNFs presents high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity. (half-wave potential of 0.792 V for ORR, overpotential of 360 mV at 10 mA cm-2 for OER). ZABs that employed 7% Cu-Co2P/CNFs and acetylene black at a mass ratio of 1:2 as the cathode electrocatalyst exhibit a power density of 230 mW cm-2 and excellent discharge-charge reversibility of 80 h. In addition, the 7% Cu-Co2P/CNFs show the specific capacitance of 558 F g-1 at 1 A g-1. Moreover, the asymmetric supercapacitor (ASC) is assembled applying 7% Cu-Co2P/CNFs electrode and pure CNFs, which exhibits a high energy density (25.9 Wh kg-1), exceptional power density (217.5 kW kg-1) and excellent cycle stability (96.6% retention after 10,000 cycles). This work may provide an effective way to prepared Co2P based materials for ZABs and SCs applications.

Pyrite as a Low-Cost Additive in Sulfur Cathode Material for Stable Cycle Performance

Various materials have been reported as an efficient host for sulfur to suppress large volume variation and polysulfide shuttle in lithium-sulfur batteries. Carbon materials are widely used as a matrix for sulfur to improve cycle performance and confine sulfur. Addition of transition metal sulfides into cathode material can improve cycle stability due to high efficiency of chemisorption and suppressing the polysulfide diffusion. In this work, various additions of pyrite to carbon and sulfur in the cathode material were investigated. The results show that the amount of pyrite has an affect on capacity and cycle stability of the electrode. Consequently, the lithium-sulfur batteries with the composite cathodes, containing 10 % of pyrite, exhibits stable discharge capacity of 788 mAh g-1 after 60 cycles at 0.2 C. Pyrite is a promising electrocatalyst in advanced lithium-sulfur batteries in the merits of low-cost, eco-friendliness and high activity towards polysulfides conversion reaction.