Synthesis Of Sulphur-Iron Composite And Its Application In Lithium Ion Battery

Li-ion battery technology has become very important in recent years as these batteries show great promise as power sources that can lead us to the electric vehicle?EV?revolution.However,the low lithium storage capacity of current commercial electrode materials limits the application of lithium-ion batteries.As a branch of lithium-ion battery materials,iron sulphides have become a research hotspot recently because of its high theoretical capacity,low price,abundant resources and environmental protection.However,they are usually hindered by large volume changes,low conductivity,and other factors,which make its poor electrochemical reversibility,and is difficult to use for commercial rechargeable LIBs.Therefore,in order to solve these problems,we use different methods of synthesis to prepare iron sulphide composites.The specific research contents and conclusions of this paper are as follows:?1?Lithium-FeS₂ battery has the prospect of sustainable and low cost application.Nevertheless,the realization of high capacity and cyclic stability is still a huge challenge.To solve the problems of FeS₂ as a cathode material,such as the unstable structure and poor electronic conductivity,the eco-friendliness doughnut-structured FeS₂@C nanorings have been successfully synthesized in this work.When used as a cathode material for lithium-ion batteries?LIBs??1-3 V?,the doughnut-structured FeS₂@C nanorings can maintain the discharge capacity of 688.11 mAh g^-1 after 100cycles at the current density of 200 mA g^-1,showing excellent cyclic stability and capacity retention.More importantly,even under the high current density of 2 A g^-1,they still maintain average specific discharge capacity of 380.36 mAh g^-1 after 500cycles,showing a long cycle life.Furthermore,they have fairly excellent discharge energy density at the material level??1040.21Wh/kg-FeS₂?after 100 cycles at a current density of 0.2 A g^-1.All the results show that our prepared doughnut-structured FeS₂@C nanorings cathode materials have a great application potential in LIBs.?2?we successfully synthesised one-dimensional?1D?Fe₇S₈@C nanorods via hydrothermal and carbonisation methods and used them as anode materials for LIBs.When used as an anode material for LIBs,the Fe₇S₈@C nanorods maintained a discharge capacity of 825.45 mA h g^-1 after 100 cycles at a current density of 100 mA g^-1,showing excellent cyclic stability and capacity retention.More importantly,the Fe₇S₈@C nanorods exhibited a very high reversible capacity(433.31mA h g^-1)even after 1000 cycles at a high current density of 2000 mA g^-1.The 1D nanostructure of the Fe₇S₈@C nanorods has higher breaking strength than other structures,which leads to small volume changes in electrochemical reactions,yielding excellent structural integrity and cyclic stability.The large surface area of the nanorods promoted the rapid electrochemical reaction.The carbon layer structure profited from poly?dopamine??PDA?significantly improved the reversibility of the electrochemical reactions and promoted the transport of Li ions and electrons,resulting in a high Coulombic efficiency and long cycle life.