Sodium Storage Mechanism And Performance Optimization Of FeS₂/MnS Anodes

Grid-scale energy storage systems with low-cost and high-performance electrodes are needed to meet the requirements of sustainable energy systems.Due to the abundance and low cost of sodium resources and similar electrochemistry to lithium-ion batteries,sodium-ion batteries?SIBs?are considered as ideal candidates for grid-scale energy storage systems.In the past decade,tremendous efforts have been made to promote the development of SIBs,and significant advances have been achieved,but some problems still remains in terms of energy/power density and commercialization.Study of the preparation and mechanism of novel electrodes should challenging and need to be continue.For the advantages of high specific capacity,low-cost and environmental friendly,the sodium storage mechanisms of many metal sulfides have been studied intensively,and kinds of optimazations were proposed.Besides,preconditions of low-cost,simple craft and scale production are also essential before the commercial application of SIBs.In this work,mesh-like Fe S2/carbon tube/FeS2 composites are prepared simply from green,low-cost and renewable natural herb.With the assistance of protogenetic interconnect carbon tube network?only 5.3%wt?,FeS2/carbon tube/FeS₂ composites show high capacity(542.2 mA h g^-1),good stability?<0.005%per cycle over 1000 cycles?,and excellent rate performance(426.2mA h g^-11 at 2 A g^-1).The outstanding electrochemical performance of FeS₂/carbon tube/FeS₂ composites may be attributed to the unique interconnected reticular structure,which FeS₂ nanoparticles are effectively immobilized by carbon tube network via physical encapsulation and chemical bonding.More importantly,this work may provide green and low cost preparation method for special structure metal sulfides/carbon composites,which promotes their commercial utilization in environmental friendly energy storage system.In this work,cream rolls-like MnS/N,S co-doped carbon tubes?MnS/NSCTs?composite is prepared via an ultra-simple and green method with natural biomass precursor.During the material preparation,significant capillary effect realized the effective encapsulation of MnS particles in carbon tubes,thus forming unique cream rolls-like MnS/C composites.This structure can improve the electrical conductivity and shorten the electron/ion transport distance of MnS.As anode for SIBs,cream rolls-like MnS/NSCTs composite delivers the best electrochemical performance until now(the highest capacity of 550.6 mA h g^-11 at100 mA g^-1,the highest capacity of 447.0 mA h g^-11 after 1400 cycles at 1000 mA g^-1,and the best rate performance of 319.8 mA h g^-11 at 10000 mA g^-1).Besides,according to several in-situ and ex-situ techniques,the sodium storage mechanism of MnS/NSCTs is mainly made of conversion reaction.A low-cost and universal preparation of special-structure metal sulfides can be verified by the above two works.In this work,MnS/carbon cloth?MnS/CFs?composite was in-situ constructed by a simple high temperature sulfuration method from waste non-woven fabrics,then the self-supported composites was directly used as flexible electrodes for SIBs.The interconnected carbon cloth can improve the conductivity and promote the infiltration of the electrolyte.Porous structure and uniform carbon shell can accommodate the volume change,then the cyclability and rate capability of MnS can be improved.MnS/CFs electrode delivers a high initial charge capacity of 348.7 m A h g-1,with a capacity of 227.9 mA h g^-11 after 100 cycles,corresponding to capacity retention of 65.36%.At a high current density of 5000 mA g^-1,MnS/CFs electrode shows a high specific capacity of 115.0 mA h g^-1.This work provides a new idea for the recycle of waste non-woven textiles and the preparation of flexible MnS/CFS electrode.What's more,a feasible scheme is proposed to optimize the sodium storage performance of MnS/carbon cloth composite.