Preparation And Property Research Of The Composite Cathode Materials For Lithium-sulfur/tellurium Battery

There are growing concerns over the environmental,climate,and health impacts caused by using non-renewable fossil fuels.The green energy,including solar and wind power,is believed to be one of the most promising alternatives to support more sustainable economic growth.In this respect,lithium-ion batteries(LIBs)play a critically important role.The inherent low energy density and poor cycle stability of lithium-ion batteries have also hindered their application in the rapidly-growing electronics industry and emerging mobile transportation devices,such as electric vehicles.Therefore,it is imperative of develop the non-polluting,low cost,high energy density,good cycle stability of the battery energy system.Elemental sulfur and tellurium are the same as the main group elements.Sulfur is abundant in nature,non-polluting and has high energy density.However,its conductivity is poor and it is easy to generate polysulfide that reacts with the electrolyte to form a shuttle effect.The cycling stability of the battery system is reduced.Tellurium and sulfur have similar chemical properties,good conductivity,due to Te have large density,make it has a considerable volumetric energy density with S and Se.In this paper,we prepared a series of sulfur/tellurium-carbon composite cathode materials with sulfur and tellurium as active materials by a simple method to solve a series of problems in the battery system,such as low energy density and poor circulation stability.The porous carbon structure for the positive active material and intermediate products have a fixed role.Can achieve better battery performance.Compared with lithium-ion battery,lithium-sulfur battery is attracted the attention of researchers now.The energy density of lithium-sulfur batteries is about five times that of commercial lithium cobalt oxide batteries,which has great potential for application.However,the poor conductivity of sulfur,low load rates and the"shuttle effect" of polysulfides have affected the commercial development of lithium-sulfur batteries.In this paper,we prepared the composite material PPy/S by loading sulfur anode active material in loose porous polypyrrole nanofibers,and then performing suction filtration according to the order of graphene oxide-polypyrrole/sulfur-graphene oxide to obtain(GO-PPy/S-GO)composite with a sandwich structure.Finally,the material is immersed in hydrofluoric acid to reduce the graphene oxide to graphene to obtain a graphene-polypyrrole/sulfur-graphene cathode material,the material showed excellent electrochemical performance in lithium-sulfur batteries,discharge at the rate of 0.1C,the first discharge of 1165 mAh g-1,at this rate still holds the reversible specific capacity of 680 mA h g-1 after 50 cycles.In the override cycle,the reversible specific capacities of 630 mA h g-1,370 mA h g-1 are held at high magnifications of 1C and 2C,respectively.In coulombic efficiency,the material's coulombic efficiency is stable at about 100%.The material loose porous PPy,effectively increase the sulfur load,and the graphene sandwich structure,can effectively improve the positive electrode conductivity,inhibition of polysulfide dissolution,ease the volume expansion of sulfur active substances,improve the electrochemical properties of the material.Lithium-tellurium battery and lithium-sulfur,lithium-selenium battery have the same volume energy density,has become the current research focus.In this paper,we have taken a novel ion exchange method to prepare a composite tellurium cathode.The carbon substrate uses dopamine,which contains nitrogen and contains more micropores,which allows for better immobilization of intermediates for superior electrochemical performance.In the lithium tellurium battery,the first cycle charging capacity is 323.2 mA h g-1 at 0.1C magnification.After 300 cycles,the specific charging capacity is 266.1 mA h g-1 the cycle retention is 82%,and the coulombic efficiency nearly 100%.Lithium tellurium battery has a short history of research with lithium-sulfur and lithium-selenium battery,which make the lithium telluride battery has become a hot spot.