Investigating The Lithium Storage Properties Of MBene From First-Principles

To meet the increasing market demand for energy storage equipment and break the bottleneck of lithium-ion battery capacity,it’s necessary to find anode materials with high performance.The twodimensional material MBene has attracted widespread attention due to its superiorities of large specific surface area and high conductivity,which make it best candidate as electrode materials for energy storage devices.However,researches on MBene is still in its infancy,with only a few investigations on employing MBene as an electrode material.In this thesis,by means of density functional theory simulations,the lithium storage properties of MBene with different chemical compositions and MBene intercalated with different organic molecules are systematically studied.The factors which influence the overall lithium storage performance of MBene based devices have also been analyzed in-depth from atomic scale.By constructing MBene structures with different transition metal elements(Sc,Ti,Hf,Zr)and different terminal groups(-F,-O,-OH),we firstly explore their geometric and electronic structures,lithium storage properties,and Li-ions migration behaviors and explore the effects of each building blocks on the lithium storage performance of MBene.We have found that the investigated MBene materials are all metal,whose structures are thermodynamically stable at room temperature.Among the MBenes we calculated,ScBO and TiBO have better lithium storage performance with high theoretical capacity(1120.29 mAh/g,1076.64 mAh/g),low open circuit voltage and suitable diffusion barrier.Moreover,we have further studied the lithium storage performance of ScBO-MBene after intercalation of organic molecules.Three organic molecules of benzoic acid(C9H6O6),benzamine(C6H6N3)and benzyl alcohol(C6H9O3)have been inserted into the interlayer of two ScBO MBene,whose interlayer space has been effectively expanded after intercalation.The insertion of benzoic acid leads to and the largest interlayer space of 10.9 A.The enlarged interlayer space allows ScBO to accommodate more lithium atoms between adjacent atomic layers,thus leading to increased theoretical capacity.The enlarged interlayer spacing also weakens the quantum interactions between the upper ScBO and lithium ions,resulting in reduced the energy barrier for lithium ions to migrate on the surface of ScBO.Our study suggests that ScBO and TiBO are potential anode materials for lithium-ion batteries compared with other MBenes materials.In addition,adjusting the interlayer spacing of MBene by atomic insertion is found to be another efficient approach to further improve the theoretical specific capacity of MBene based lithium ions batteries and reduce the migration barrier for lithium ions.Our study provides valuable guidance for further deign of high-performance anode materials for lithium-ion batteries.