The Research On Anode Materials Application For High Performance Potassium Ion Power Battery

At present,the power source of mechanical equipment represented by new energy vehicles is changing from the traditional high-emission and high-polluting internal combustion engine to environmentally friendly and efficient new energy batteries.At the same time,in order to meet the power and endurance of power batteries,developing new energy batteries with large-capacity,long cycle life,and good rate performance has become the research focus of industry development.Lithium-ion batteries are widely used in electric vehicles due to their advantages such as environmental friendness,high energy density and long cycle life.However,the scarcity and uneven distribution of lithium resources limit its further application.At the same time,potassium ion batteries have become the most promising alternatives for energy storage devices,benefiting from its merits of the low cost,abundant of potassium resources as well as low standard electrode potential（-2.93 V vs.E⁰）.However,due to the large radius of potassium ions,it is easy to cause the collapse or pulverization of the anode material structure,resulting in the low capacity and poor cycle stability,which makes it face severe challenges on the road of large-scale commercial application.Therefore,a key point in potassium ion batteries technology development is exploring electrode materials with high capacity and long cycle life.It will definitely provide sufficient power support for advanced new energy machinery manufacturing in the industry 4.0 era.In order to improve the performance of potassium ion battery anode,the potassium ion battery with high capacity,long-cycle life and good rate performance is developed to promote its application in the field of electric vehicle power battery.In this paper,based on the advantages of high theoretical capacity of alloy material,controllable structure,high electronic conductivity and adjustable composition of carbon material.Using graphite,antimony,bismuth and other materials,four kinds of anode materials with different structures,including graphite（artificial SEI）、antimony@graphene@carbon Sb@G@C、antimony@nano-graphite(Sb_x@G_1-x)、“soft-carbon”-like structure Bi quantum dots with high capacity and long cycle stability have been developed.The morphology,electrochemical properties and potassium storage mechanism of the four kinds of composites were studied in depth,which provides theoretical guidance for the research and development of high-performance potassium ion batteries.The main contents are as follows:（1）In order to improve the cycle stability and capacity of potassium ion battery,an ultra-thin,uniform,dense and stable artificial inorganic SEI film proposed by a simple and commercially available method for graphite anode.As a result,the commercial graphite anodes with the artificial SEI could deliver a reversible capacity of 260 m Ah g^-1 for more than 1000 cycles with a capacity retention as high as 100%at100 m A g^-1,which is the longest cycle stability of graphite anode for potassium ion batteries within the traditional carbonate electrolyte systems up to now.（2）Design and construct confined Sb nanoparticles with double carbon,denoted as Sb@G@C.Sb nanoparticles are embedded or deposited on the graphene framework,while the carbon layer is coated on the Sb particles,leading to a confined Sb with carbon structure by transmission electron microscopy.The nano-dispersion of Sb in Sb@G@C can shorten the diffusion and transferring distance of potassium ions forming stable SEI film,which is conductive to obtain high capacity.As a result,the Sb@G@C electrodes exhibit a reversible capacity of 474 m Ah g^-1 at 100 m A g^-1（second charge）,an outstanding long cycle stability over 800 cycles with a capacity retention as high as72.3%.（3）In order to realize the high capacity and long-cycle stability as well as improve the rate performance of potassium ion batteries,using the high theoretical capacity of antimony and the cycle stability of graphite to prepare antimony@graphite composites(Sb_x@G_1-x).Sb_x@G_1-x structure can increase the interface contact between Sb and graphite layer,forming a stable,ultra-thin SEI film,this ultra-thin SEI film in the process of circulation can also be very good protection of its structure from damage.As a result,the Sb_x@G_1-x electrodes deliver a high reversible capacity(524 m A h g^-1at 50 m A g^-1),a superior capacity retention（96.8%after 100 cycles）,and an excellent rate performance(340 m Ah g^-1 at 1000 m A g^-1).（4）In order to solve the problem of large-volume-change and poor cycle of Bi-anode materials,“soft-carbon”-like structure Bi quantum dots were designed by simple annealing method for potassium ion batteries.The“soft-carbon”-like structure Bi quantum dots anode by providing an inner void space insert K⁺to accommodate volume changes instead of just changing the volume during cycling.As the anode electrode of potassium ion battery,“soft-carbon”-like structure Bi quantum dots deliver high-capacity(450 m Ah g^-1 at 100 m A g^-1),an outstanding long-term stability(over 300cycles with a superior capacity retention as high as 94.9%at 500 m A g^-1).