Preparation Of Anode Materials And Electrochemical Properties Of Phosphorus/carbon Lithium Ion Batteries By High Energy Ball Milling

Red phosphorus(P)has been promising new type of high energy anode materials due to its high theoretical specific capacity 2596 mAh g-1,abundant reserves and good security.However,red phosphorus is easy to suffer tremendous volume increase during repeated charge and discharge processes and its conductivity is poor,which lead to poor electrochemical performance.Many studies have made people realize that it is an effective way to solve the above problems by using carbon material as carrier to prepare red phosphorus/carbon composites.Moreover,the structure and type of carbon carrier materials have a significant effect on the properties of phosphorus/carbon composites.But the optimal carrier structure which can achieve the best performance of P/C composites is still to be studied.In this paper,the influence of the structure changes of carbon carrier on the structure and properties of P/C composites is explored.Combined with the current research situation,the preparation method and the structure of carbon carrier are designed and improved.The main research contents are as follows:(1)Locking the P/C ratio,two kinds of carbon materials(MWCNTs)and CB(conductive carbon black)were used to construct the carbon composite support materials of P/C composites.The ratios of MWCNTs to CB were designed as 0:5,1:4,2:3,1:1,3:2,4:1,5:0.And the preparation process were improved.Phosphorus/carbon composite electrode paste was prepared by a simple and efficient anaerobic wet-high-energy-ball-milling method.The structure and electrochemical properties of the composites were compared and analyzed under different ratios.The experimental results show that the size of the red phosphorus particles is reduced and the edge of the red phosphorus particles is smoother.It is helpful to form stable SEI membrane.MWCNTs easily overlapped with each other to form a solid three-dimensional conductive network,which enhanced the stability of the whole structure.The synergistic effect of CB and MWCNTs greatly alleviated the volume expansion of the red phosphorus material.It can effectively enhance the conductivity of the composite material and greatly improve the utilization ratio of the active materials.The mixed use of the two materials is better than using any of the carbon materials alone.Moreover,when the ratio of MWCNTs to CB is 3:2,phosphorus/carbon composites have the best capacity retention and cyclic stability.(2)In the process of high-energy-ball-milling,the high-speed collision will inevitably destroy the structure of MWCNTs and form massive defects,which will damage the mechanical properties,conductivity and structural integrity of MWCNTs.In this paper,we proposed gamma irradiation to restore the defects.The results showed that the graphitization degree of carbon nanotubes in P/C composites after gamma irradiation was enhanced.And the cyclic voltammetry and the first coulomb efficiency of the electrode materials were improved.