First-principles Study On Sodium Storage Properties Of ?-graphyne-based Materials

With the rapid development of power vehicles and mobile communication equipment,lithium-ion batteries?LIBs?have been unable to meet the demand for large-capacity batteries,while sodium-ion batteries?SIBs?have similar charging and discharging mechanisms to LIBs,and some are suitable for electrodes of LIBs.Materials can also be applied to SIBs,and sodium is abundant in the earth.If SIBs are successfully replaced by LIBs,the material cost of the battery will be greatly reduced.One of the main factors limiting the commercialization of SIBs is that there is no suitable anode material,so the breakthrough of SIBs anodes will bring huge economic benefits to society.Graphene alkyne is a new layered two-dimensional material.It has a similar electronic structure to graphene and has a large specific surface area and good electrical conductivity.Unlike graphene,its layer spacing is large and has a large Hole gap,such a structure allows ions to pass through the pores more easily,that is,ions can migrate in three dimensions in the graphene,thereby increasing ion mobility and increasing storage capacity,so it is considered to be one A potential battery anode material.In this paper,the performance of sodium storage of the most stable?-graphene alkyne in the graphene family as the anode of SIBs is studied by density functional theory.It is characterized by the adsorption energy,the maximum sodium storage capacity and the range of open circuit voltage during sodium storage.The electrochemical performance is good and bad;then,in order to improve the sodium storage performance of?-graphene,the doping and interfacial modification methods are adopted,which are as follows:1)simultaneously doping Be and B atoms on the surface?study shows that Double doping in the system is easier to achieve than single doping,and the P-type doping atom is better than the N-type doping atom in the original system,so the Be and B atoms are double-doped.2?composite with anatase TiO₂?anatase TiO₂ is a potential sodium storage material,and it will produce tantalum capacitance at the interface after compounding with graphene.Therefore,the interface of anatase TiO₂ to graphene is used in this paper.modified?.Compared with the related properties of?-graphene,the analysis of the addition of doping atoms or the combination with anatase TiO₂ has a positive effect on the electrochemical performance of the pure system.The results show that the maximum sodium storage capacity of?-graphene in the ground state is 558 mAh/g,which is larger than the maximum capacity of lithium in graphite is 372 mAh/g,the average adsorption energy of saturated adsorption is-0.4eV,and the average adsorption energy at 400K becomes 0.012.eV,open circuit voltage range is 0.43-1.38V.After doping modification,the addition of double-doped atoms increases the surface of the pure system by adding more holes,so that the charge of Na atoms is more easily transferred to the surface.The sodium storage capacity of the double-doped system is 562 mAh/g,and the saturated average adsorption It can be-0.57eV,and it is-0.11eV at 400K,which is significantly improved compared with the original system.In the working temperature range,the doping system can adsorb a Na atom more stably than the original system of 2�2 supercell.The open circuit voltage range is 0.6²V.The Be and B doping have a positive effect on the electrochemical properties of the system.After interfacial modification,the composite system of?-graphene and TiO₂ is mainly bonded by covalent bond,the binding energy is-0.11eV/?²,and the surface of?-graphene has wrinkles,and peaks and troughs appear,which can be increased at the peak.More sodium storage sites produce a tantalum effect,which significantly increases the amount of sodium stored in the original system.