Research On Preparation,modification And Electrochemical Properties Of FeS₂ And MgS As Anode Materials For Lithium-ion Batteries

Energy conservation and emission reduction,developing green and renewable energy is the inevitable trend of the development of current era.In addition to the rapid development of various small portable electronic products and new energy automotive industry,people's requirements for energy storage devices are increasing.Lithium-ion battery has attracted more and more attention due to its advantages in high working voltage,high energy density,long cycle life,wide range of operating temperature and environmental friendliness.However,graphite carbon anode material is widely used as the anode material of commercial lithium-ion battery at present.The specific capacity is only 372 mAh g^-11 and its low capacity and power density can not meet the needs of electric vehicles and some other large electric equipment.Therefore,for the anode material of lithium-ion battery,the key research work now is to develop new electrode materials with higher specific capacity,longer cycle life,more safety and low cost.Sulfide is regarded as a feasible anode material for the next generation of lithium ion batteries due to its excellent electrical properties,abundant reserves and non-toxic and harmless advantages.In this paper,the transition metal sulphide?FeS₂?and non-transition metal sulphide?MgS?were studied and their electrochemical properties as anode materials of lithium-ion batteries were improved through structural regulation by coating and doping respectively.?1?The transition metal sulphide FeS₂ was synthesized by ball milling assisted solid state sintering method and further coated by sucrose?C?and conducting polymer?PANI?respectively to obtain FeS₂/C and FeS₂/PANI composites.The composition,structure and microstructure of FeS₂,FeS₂/C and FeS₂/PANI were characterized and analyzed by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,infrared spectroscopy?IR?and thermogravimetric Analysis?TGA?.The results show that three kinds of target products FeS₂,FeS₂/C and FeS₂/PANI have been successfully prepared.The pure FeS₂ presents rod secondary particles with the width ranging from 160 nm to 320 nm,and the length ranging from 0.8-1.2?m.In addition to improving the conductivity,side reactions caused by direct contact with electrolyte are effectively avoided and the volume change of material during the charge-discharge rocess is inhibited to some extent.The electrochemical test results show that the composite material FeS₂/C and FeS₂/PANI,as the anode material of lithium ion battery,show higher comprehensive performance than pure FeS₂,especially in the performance of cycle life and charging and discharging with high current density.FeS₂/C,as the anode material of lithium ion battery,has better multiplier performance and cycling stability.?2?The non-transition metal sulfide MgS was also synthesized by ball milling assisted solid state sintering.MgS/SnS materials were obtained by doping Sn elements.The anode materials were characterized by XRD and SEM.Through battery performance test and analysis,MgS,as the anode material of lithium ion battery,performs general electrochemical properties,poor electrical conductivity and low discharge specific capacity but good cycling stability.Sn doping greatly improved the discharge capacity of the material but the cycle life was poor.However,from the data,the comprehensive performance of the material has been improved.