The Design And Synthesis Of Nitrides With Micro-nano Structure For Li-S Battery System

Due to the high high theoretical capacity and environmental friendliness,Lithium-sulfur(Li-S)battery has been regarded as the most promising Secondary battery system.However,due to the poor conductivity of sulfur,volume expansion,the conplexity of reaction kinetics and the "shuttle effec" during the discharge/charge process which restrict the practical application of lithium-sulfur batteries.Moreover,different from other traditional secondary battery system,"catalyst" is an indispensable component for the reaction process of sulfur electrode.Most of the current researches for sulfur composites are focused on the carbon matrix.The carbon matrix has many advantages but lack of the "functional" role.This paper carried out based on the research of non-carbon matrix materials,design synthesis the nitrides multi-functional materials with micro-nano structure and applied in the host:materials or interlayer for Li-S batteries.The main content are listed as follows:1.The sulfur composites based on titanium nitride:A hollow mesoporous TiN tubes has been synthesized.These TiN tubes exhibited a high bulk metallic conductivity,and the hollow structure can alleviate the volume expansion during the charge and discharge process of Li-S battery.TiN have a high affinity for LiPSs and also play a good role in promoting the oxidation and reduction process in Li-S batteries.When use the TiN tubes as host materials for the cathode of Li-S battery,the cell shows a high utilization of sulfur and outstanding cycling life.2.The sulfur composites based on cobalt nitride:A Co4N mesoporous sphere composed of nanosheets with high conductivity has been synthesized.This Co4N mesoporous sphere exhibited not only higher affinity for polysulfide but also stronger capability for polysulfide adsorption.Fast adsorption for polysulphide could make the cell has the good cycle stability at large rate and the high adsorption capacity could increase the sulphur content in the electrode.The cell shows an excellent electrochemical performance at 5 C and a outstanding cycling stability when the weight ratio of elemental S was as high as 95%.3.The sulfur composites based on BN/graphene:A graphene supported BN nanosheets(BN/graphene)has been synthesized.Due to the BN/graphene composite has excellent electrical conductivity,mechanical properties,strong adsorption effect for LiPSs and the effective catalysis for both the discharge and charge process of Li-S battery.When used it as a host materials of anode,it can make the Li-S bettery shows an excellent battery performance in a wider range of temperatures.4.The macro-chamber for S conversion reactions based on functional interlayer:A uniform rGO-supported TiN nanoparticles(TiN/rGO)was carried out via an in situ method and then the TiN/rGO was used as a multifunctional cover layer for Li-S batteries.The synergy between rGO and the TiN nanoparticles drastically reduced the size of the channel for LiPSs,and quite effectively block the shuttle effect.rGO in the cover layer acts as an extended collector to form an overall conductive network,which can improve the electron conductivities of the positive area,whereas the TiN nanoparticles support the catalytic activity of S in the chamber.In fact,the multiple ffects built a macro-chamber for sulfur conversion reaction,the cell shows an excellent performance even at the high areal S loading without host materials.5.The g-C3N4@ BN/graphene double interlayer:Use the 2D graphen-like g-C3N4 with BN/graphene at the same time to built a double interlayer in Li-S batteries.g-C3N4 in the double interlayer can from the molecular structure and morphology structure to reduce the shuttle effect,and the BN/graphene has a a very effective catalysis for the reaction of Li-S battery.The cell used this double interlayer shows an excellent performance even at the a high areal S loading without host materials at a large current density.When the areal S loading was 6 mg cm-2 without host materials,the cell shows a reversible capacity above 400 mAh g-1 at 2 C.At a rate of 1C,after 500 cycles,the the discharge capacity finally stabilized at 600 mAh g-1 with a capacity decay of 0.01%per cycle.