Si/C Composites as Negative Electrode for High Energy Lithium Ion Batteries

Silicon is very promising negative electrode materials for improving the energy density of lithium-ion batteries （LIBs） because of its high specific capacity, moderate potential, environmental friendliness, and low cost. However, the volume variation of Si negative electrodes is huge during lithiation/delithiation processes which results in pulverization, low cycling efficiency, and permanent capacity loss. In order to overcome this problem, tremendous efforts have been attempted. Among them the most successful strategy is to incorporate other components into silicon to form composite, especially the carbon medium. In this mini review, the recent progress on Si/C materials used as negative electrode of LIBs is summarized such as Si/amorphous carbon composite, Si/graphene composites, Si/carbon nanotubes or fibers composites. The fabrication, structure, electrochemical performances of different Si/C composites are discussed. In addition, some future directions are pointed out.

Latest Advances in High-Voltage and High-Energy-Density Aqueous Rechargeable Batteries

Aqueous rechargeable batteries(ARBs)have become a lively research theme due to their advantages of low cost,safety,environmental friendliness,and easy manufacturing.However,since its inception,the aqueous solution energy storage sys-tem has always faced some problems,which hinders its development,such as the narrow electrochemical stability window of water,poor percolation of electrode materials,and low energy density.In recent years,to overcome the shortcomings of the aqueous solution-based energy storage system,some very pioneering work has been done,which also provides a great inspiration for further research and development of future high-performance aqueous energy storage systems.In this paper,the latest advances in various ARBs with high voltage and high energy density are reviewed.These include aqueous rechargeable lithium,sodium,potassium,ammonium,zinc,magnesium,calcium,and aluminum batteries.Further chal-lenges are pointed out.

Efficient oxygen electrocatalysts with highly-exposed Co-N4 active sites on N-doped graphene-like hierarchically porous carbon nanosheets enhancing the performance of rechargeable Zn-air batteries

Designing bifunctional oxygen electrocatalysts with high activity,lasting stability,and low-cost for rechargeable zinc-air batteries(RZABs)is a tough challenge.Herein,an advanced electrocatalyst is prepared by anchoring atomically dispersed Co atoms on Ndoped graphene-like hierarchically porous carbon nanosheets(SA-Co-N4-GCs)and thereby forming Co-N4-C architecture.Its unique structure with excellent conductivity,large surface area,and three dimensional(3D)interconnected hierarchically porous architecture exposes not only more Co-N4 active sites to accelerate the kinetics of both oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),but also provides an efficient charge/mass transport environment to reduce diffusion barrier.Consequently,SA-Co-N4-GCs exhibits excellent ORR/OER bifunctional activities and durability,surpassing noble-metal catalysts.Liquid RZABs using SA-Co-N4-GCs cathodes display a high open-circuit voltage of 1.51 V,a remarkable power density of 149.3 mW·cm−2,as well as excellent stability and rechargeability with faint increase in polarization even at a large depth of charge–discharge cycle with 16 h per cycle over an entire 600 h long-term test.Moreover,flexible quasi-solid-state RZABs with SA-Co-N4-GCs cathodes also deliver a considerable power density of 124.5 mW·cm−2,which is even higher than that of liquid batteries using noble-metal catalysts.This work has thrown new insight into development of high-performance and low-cost electrocatalysts for energy conversion and storage.