Fabrication of highly effective electrodes for iron chromium redox flow battery

Iron-chromium redox flow batteries(ICRFBs)have emerged as promising energy storage devices due to their safety,environmental protection,and reliable performance.The carbon cloth(CC),often used in ICRFBs as the electrode,provides a suitable platform for electrochemical processes owing to its high surface area and interconnected porous structure.However,the CC electrodes have issues,such as,insufficient electron transfer performance,which limits their industrial application.Here,we employed silicic acid etching to carve dense nano-porous structures on the surface of CC electrodes based on the favorable design of ICRFBs and the fundamental principles of electrode polarization losses.As a result,we developed a multifunctional carbon cloth electrode with abundant vacancies,notably enhancing the performance of the battery.The fabricated electrode showcased a wealth of defect sites and superior electronic transport properties,offering an extensive and effective reaction area for rapidly flowing electrolytes.With an electrode compression ratio of 40%and the highest current density in ICRFBs so far(140 mA·cm^(-2)),the battery achieved the average energy efficiency of 81.3%,11.24%enhancement over the previously published work.Furthermore,throughout 100 charge-discharge cycles,the average energy efficiency degradation was negligible(~0.04%),which has the potential to become the most promising candidate for large-scale and long-term electrochemical energy storage applications.

Synergistic effect of electrode defect regulation and Bi catalyst deposition on the performance of iron–chromium redox flow battery

Iron-chromium redox flow batteries (ICRFBs) possess advantages of high safety,long cycle time,and lowcost.Increasing Cr^(3+)/Cr^(2+)reaction activity is suggested as one of the most promising strategies to improve the performance and prolong the lifetime of ICRFBs.To improve the slow reaction kinetics of the negative electrode,a type of defected carbon cloth with Bismuth (Bi) catalyst introduction is prepared by defect engineering method and electrochemical deposition,which provided defect sites and active sites to catalyze the redox couple’s reaction of ICRFBs.Furthermore,this modified carbon cloth adsorbs Cr(Ⅲ)hydrate more easily,which has a more stable structure and can significantly improve the performance of ICRFBs.Both experimental analysis and theoretical calculation indicated that the modified electrode has excellent electrocatalytic ability,which can enhance the reaction rate of Cr^(3+)/Cr^(2+),improve capacity retention and stabilize cycling performance.The capacity degradation rate of an ICRFB single cell with the modified electrodes is just 0.23%per cycle at a current density of 140 m A/cm^(2).Additionally,the energy efficiency (EE) remains around 83%,which is 8.45%higher than that of the pristine electrode assembled battery under 60 cycles.This work supplies a simple method to obtain a high-performance electrode material for ICRFBs and makes it a practical solution to promote ICFRBs large-scale commercialization process.

Co3O4 nanocage derived from metal-organic frameworks: An excellent cathode catalyst for rechargeable Li-O2 battery

Rechargeable non-aqueous Li-O2 battery is regarded as one of the most promising energy-storage technologies on account of its high energy density.It is believed that the rational design of three-dimensional (3D) architecture for catalyst is a key factor for the remarkable performance.Metal-organic frameworks (MOFs) derived materials possess excellent architecture,which is beneficial for Li-O2 batteries.In this work,ZIF-67 is used as precursor template and calcinated under different temperature to produce Co3O4 crystals.When the anneal treatment is under 350℃,the derived Co3O4 nanocage holds the most complete skeleton,which provides better charge transfer ability as well as O2 and Li^+ diffusion.Meanwhile,the Co3O4 nanocage owns more oxygen vacancies,offering more active sites.With the synergistic effect of nanocage structure and active sites,the Co3O4 nanocage stably delivers a large specific capacity of 15,500 mAh·g^-1 as well as a long cycle-life of 132 cycles at limited discharge capacity of 1,000 mAh·g^-1 under discharge/charge current density of 0.5 A·g^-1.