Zhaolin Na

Coated/Sandwiched rGO/CoSx Composites Derived from Metal-Organic Frameworks/GO as Advanced Anode Materials for Lithium-Ion Batteries.

Rational composite materials made from transition metal sulfides and reduced graphene oxide (rGO) are highly desirable for designing high-performance lithium-ion batteries (LIBs). Here, rGO-coated or sandwiched CoSx composites are fabricated through facile thermal sulfurization of metal-organic framework/GO precursors. By scrupulously changing the proportion of Co(2+) and organic ligands and the solvent of the reaction system, we can tune the forms of GO as either a coating or a supporting layer. Upon testing as anode materials for LIBs, the as-prepared CoSx -rGO-CoSx and rGO@CoSx composites demonstrate brilliant electrochemical performances such as high initial specific capacities of 1248 and 1320 mA h g(-1) , respectively, at a current density of 100 mA g(-1) , and stable cycling abilities of 670 and 613 mA h g(-1) , respectively, after 100 charge/discharge cycles, as well as superior rate capabilities. The excellent electrical conductivity and porous structure of the CoSx /rGO composites can promote Li(+) transfer and mitigate internal stress during the charge/discharge process, thus significantly improving the electrochemical performance of electrode materials.

A Core–Shell Fe/Fe2O3 Nanowire as a High‐Performance Anode Material for Lithium‐Ion Batteries

The preparation of novel one-dimensional core-shell Fe/Fe2 O3 nanowires as anodes for high-performance lithium-ion batteries (LIBs) is reported. The nanowires are prepared in a facile synthetic process in aqueous solution under ambient conditions with subsequent annealing treatment that could tune the capacity for lithium storage. When this hybrid is used as an anode material for LIBs, the outer Fe2 O3 shell can act as an electrochemically active material to store and release lithium ions, whereas the highly conductive and inactive Fe core functions as nothing more than an efficient electrical conducting pathway and a remarkable buffer to tolerate volume changes of the electrode materials during the insertion and extraction of lithium ions. The core-shell Fe/Fe2 O3 nanowire maintains an excellent reversible capacity of over 767 mA h g(-1) at 500 mA g(-1) after 200 cycles with a high average Coulombic efficiency of 98.6 %. Even at 2000 mA g(-1) , a stable capacity as high as 538 mA h g(-1) could be obtained. The unique composition and nanostructure of this electrode material contribute to this enhanced electrochemical performance. Due to the ease of large-scale fabrication and superior electrochemical performance, these hybrid nanowires are promising anode materials for the next generation of high-performance LIBs.

Tin dioxide as a high-performance catalyst towards Ce(VI)/Ce(III) redox reactions for redox flow battery applications

A novel SnO2-modified graphite felt electrode with a high-performance and non-precious electrocatalyst of SnO2 deposited onto the graphite felt surface is prepared for cerium-based redox flow batteries (RFBs). Through a facile and one-pot solvothermal route, a thin and uniform SnO2 coating layer could be successfully introduced onto the surfaces of graphite felt fibers for the first time. The electrochemical reactivity of the SnO2 decorated graphite felt toward the redox reactions of Ce(IV)/Ce(III) could be substantially enhanced, which is ascribed to the superior electrocatalytic activity of this SnO2 catalyst. What is more, the undesirable side reaction of oxygen evolution can be suppressed by introducing the SnO2 coating layer that possesses a high oxygen evolution overpotential. The charge/discharge test with the catalyzed electrode exhibits a 41.2% and 25.1% increase in energy efficiency as compared with the pristine graphite felt and acid treated graphite felt at a high current density of 30 mA cm−2. Also, the long-term cycling performance confirms the outstanding stability of the as-prepared SnO2 catalyst enhanced electrode. These results suggest that the graphite felt modified by the low-cost and uniform SnO2 coating layer could serve as a highly promising electrode towards the Ce(IV)/Ce(III) redox couple for cerium-based RFB applications.

Evaluation of the catalytic effect of non-noble bismuth on the lead half-cell reaction for lead-based redox flow batteries

Bi3+ ions are introduced into the lead electrolyte of lead-based redox flow batteries (RFBs), and their influence on the electrochemical performance of the redox cell is thoroughly investigated. The metallic Bi particles, which are simultaneously electrodeposited onto the electrode surface during the charge process of the RFBs, significantly improve the electrochemical performance of lead-based RFBs by enhancing the activity and reversibility of the sluggish Pb(II)/Pb(0) redox reaction and suppressing hydrogen evolution. The cell using a negative electrolyte with Bi3+ ions exhibits considerable enhancement both in the columbic efficiency (CE) and voltage efficiency (VE), and therefore in the energy efficiency (EE). Moreover, a mechanism accounting for the role that Bi particles play in the redox reactions in this lead half-cell is proposed. Bi particles favor the formation of a BiHx compound, an intermediate that reduces Pb(II) to Pb(0), and thereby curbs the competitive side reaction of hydrogen evolution responsible for the major loss for the CE. Additionally, the morphology of lead electrodeposition is also presented and the deposits become more uniform and smooth without any dendrites upon the addition of Bi3+. The results suggest that the utilization of non-noble Bi as a high-performance additive promises to be applicable to lead-based RFBs.

Unique Co3O4/nitrogen-doped carbon nanospheres derived from metal–organic framework: insight into their superior lithium storage capabilities and electrochemical features in high-voltage batteries

The development of versatile strategies to create new structured materials via heteroatom doping has become a fascinating research topic owing to their fantastic properties, while the popular metal–organic framework opens promising avenues for the design of diverse architectures. Herein, an intriguing type of spherical N-doped porous carbon (i.e., N–C) particles containing numerous Co3O4 nanocrystals (i.e., Co3O4/N–C) is introduced, in which the Zn–Co based Prussian blue analogue acts as a sacrificial template and carbon source, while the volatilization of zinc and oxidation of Co produce rich pores and form highly active Co3O4 nanocrystals. The resultant Co3O4/N–C particles have an extremely high lithium storage capacity of 1255 mA h g−1 and excellent rate capability even at a current of 2000 mA g−1. Their long cycle life of over 500 cycles at 1000 mA g−1 with a high capacity of 798 mA h g−1 further demonstrates their prominent properties. Our kinetic analysis reveals that the high performances of Co3O4/N–C beyond the theoretical values mainly stem from the active Co3O4 nanocrystals, fast diffusion of lithium ions within its structure and its pseudocapacitive behaviors. Furthermore, the Co3O4/N–C particles also demonstrate impressive stability and rate capabilities in a lithium-ion battery versus a cathode of lithium layered oxide even at high voltage conditions.