The Preparation And Lithium Storage Performance Of Pitch-Based Metal/Carbon Composites

With the development of the economy,the demand for energy is getting higher and higher,but the consumption of traditional fossil energy has an irreversible impact on the environment on which human beings live.The development of renewable energy such as solar energy,wind energy,and tidal energy has become a solution for all countries.However,these new energy sources are intermittent and fluctuating,so energy storage technologies with higher capacity,large scale and low cost are required.Lithiumion batteries（LIBs）are by far the fastest growing energy storage devices,which are characterized by good stability,high en-ergy density,durability,and environmental friendliness.But traditional graphite electrodes cannot meet the demands of higher-performance batteries.The alloy-type anode material SnO has the advantages of high theoretical capacity,high hole mobility and good cycle performance,and the conversion-type anode material FeS has the advantages of high theoretical re-versible specific capacity,abundant natural reserves,and low cost.These two types of materials are very active as anode materials for high-performance lithium-ion batteries.However,the volume expansion of such materials during charging and discharging can damage the structure of electrode materials and thus affect their lithium storage properties.Carbon materials have good electrical conductivity,stable structure,and are cheap and easy to obtain.Combining them with carbon materials can effectively alleviate the above problems and improve the electrochemical performance of batteries.There are many methods for preparing metal/carbon composites,and low-cost and rapid synthesis technology is undoubtedly a topic of concern to the industry.Coal tar pitch has a high carbon content,is cheap and easy to obtain,and is a high-quality precursor of carbon materials.Its application in the field of energy storage is one of the methods to realize the high value-added utilization of coal tar pitch.In this paper,coaltar pitch was used as carbon source,and tin/carbon and FeS/C composites were prepared by mechanical ball milling and microwave synthesis.The details are as follows.The tin/carbon composite material was prepared by using cheap and easy-to-obtain medium-temperature coal tar pitch as raw material,after carbonization,ball milling with tin powder,and oxidation.The effects of different ball milling speeds and different tin contents on the composition,structure,morphology and lithium storage properties of tin/carbon composites were investigated.The results showed that tin was uniformly dispersed in the carbon matrix.The size becomes smaller and the disorder degree increases;after oxidation treatment,Sn is oxidized and converted into SnO;when the ball milling speed is 600 r min^-1,all the tin in the composite exists in the form of SnO.The electrochemical performance results show that the introduction of carbon effectively alleviates the volume expansion problem of the tin-based anode material,and the structural stability of the material is significantly enhanced.The carbon content affects the lithium storage properties of the composites.When the carbontin ratio is 7:3 and the ball milling speed is 600 r min^-1,C/Sn-7/3-600-7-O has the best lithium storage performance.The discharge specific capacity is 1226.6 mAhg^-1,and the initial coulombic efficiency is 66.44%at the current density of 0.1 Ag^-1.At a large current density of 3Ag^-1,its specific capacity is 474.3 mAhg^-1.After 130 cycles at 0.1 Ag^-1,the discharge specific capacity is 664.6 mAhg^-1.Using sulfonated asphalt powder and ferric chloride as raw materials,the iron-exchanged composite was obtained by ion exchange,and then the microwave medium was added to generate FeS phase through microwave reaction,and the FeS/C composite material was rapidly prepared.FeS attaches to the surface of the carbon matrix,which effectively prevents the volume expansion of FeS anode material and exhibits good lithium storage performance.After250 cycles at a current density of 0.1 Ag^-1,the discharge specific capacity is 425.8 mAhg^-1.