Synthesis of CoS 2 Nanoparticles/Nitrogen‐Doped Graphitic Carbon/Carbon Nanotubes Composite as an Advanced Anode for Sodium‐Ion Batteries

Facile synthesis of in situ carbon-coated CoS2 micro/nano-spheres as high-performance anode materials for sodium-ion batteries

In situ carbon-coated CoS2 micro/nano-spheres were successfully prepared by sulfuric calcination using the solvothermal method with glycerol as the carbon source without introducing extraneous carbon. This method prevents carbon agglomeration and avoids the cumbersome steps of the current technology. The composite demonstrates excellent sodium storage capacity as an anode material for sodium-ion batteries. The initial charge and discharge capacities were 1027 and 1224 mA h g-1 at 50 mA g-1, respectively, with an initial coulombic efficiency of 83.9%. The capacity of CoS2@C at 350 °C was maintained at 937 mA h g-1 after 140 cycles at a current density of 2 A g-1. The outstanding electrochemical performance is mainly attributed to the nanostructure design and the presence of in situ carbon. As revealed by the kinetic analysis, the pseudo-capacitive behaviour also contributed to the excellent electrochemical performance.

Metal-Organic Framework-Based Materials for Advanced Sodium Storage: Development and Anticipation

As a pioneering battery technology, even though sodium-ion batteries (SIBs) are safe, non-flammable, and capable of exhibiting better temperature endurance performance than lithium-ion batteries (LIBs), because of lower energy density and larger ionic size, they are not amicable for large-scale applications. Generally, the electrochemical storage performance of a secondary battery can be improved by monitoring the composition and morphology of electrode materials. Because more is the intricacy of a nanostructured composite electrode material, more electrochemical storage applications would be expected. Despite the conventional methods suitable for practical production, the synthesis of metal-organic frameworks (MOFs) would offer enormous opportunities for next-generation battery applications by delicately systematizing the structure and composition at the molecular level to store sodium ions with larger sizes compared with lithium ions. Here, the review comprehensively discusses the progress of nanostructured MOFs and their derivatives applied as negative and positive electrode materials for effective sodium storage in SIBs. The commercialization goal has prompted the development of MOFs and their derivatives as electrode materials, before which the synthesis and mechanism for MOF-based SIB electrodes with improved sodium storage performance are systematically discussed. Finally, the existing challenges, possible perspectives, and future opportunities will be anticipated.

Multi-Dimensional Composite Frame as Bifunctional Catalytic Medium for Ultra-Fast Charging Lithium-Sulfur Battery

The shuttle effect of soluble lithium polysulfides (LiPSs) between electrodes and slow reaction kinetics lead to extreme inefficiency and poor high current cycling stability, which limits the commercial application of Li-S batteries. Herein, the multi-dimensional composite frame has been proposed as the modified separator (MCCoS/PP) of Li-S battery, which is composed of CoS₂ nanoparticles on alkali-treated MXene nanosheets and carbon nanotubes. Both experiments and theoretical calculations show that bifunctional catalytic activity can be achieved on the MCCoS/PP separator. It can not only promote the liquid-solid conversion in the reduction process, but also accelerate the decomposition of insoluble Li₂S in the oxidation process. In addition, LiPSs shuttle effect has been inhibited without a decrease in lithium-ion transference numbers. Simultaneously, the MCCoS/PP separator with good LiPSs adsorption capability arouses redistribution and fixing of active substances, which is also beneficial to the rate performance and cycling stability. The Li-S batteries with the MCCoS/PP separator have a specific capacity of 368.6 mAh g^-1 at 20C, and the capacity decay per cycle is only 0.033% in 1000 cycles at 7C. Also, high area capacity (6.34 mAh cm^-2) with a high sulfur loading (7.7 mg cm^-2) and a low electrolyte/sulfur ratio (7.5 μL mg^-1) is achieved.