| Two-dimensional（2D）nanomaterials,including blue phosphorene,graphdiyne and Mo S2,have attracted more attention for the application of lithium-ion batteries（LIBs）as anode materials,due to their unique structure and physicochemical properties.However,poor electrical conductivity,mechanical properties and chemical properties limit the application of blue phosphorene.While the 2H-Mo S2also exhibits poor electrical conductivity and structural stability during the charging and discharging process.Therefore,it is extremely important to explore new generation battery materials with higher performance.In this paper,we systematically investigated the blue phosphorene/graphdiyne（Blue P/GDY）heterostructure and1T′-Mo S2as anode materials for LIBs based on density functional theory（DFT）and focused on the adsorption performances,electronic structures and migration properties of lithium ions on the anode materials.Our results provide new insight for developing potential anode materials for LIBs with high electrochemical performance.We firstly investigated the Blue P/GDY heterostructure as anode materials for LIBs.The results show that the Blue P/GDY heterostructure exhibits good thermodynamic stability and mechanical properties.Compared with monolayer blue phosphorene（1.92 e V）and graphdiyne（2.36 e V）,the adsorption energies of a single lithium ion in the interlayer of the Blue P/GDY heterostructure（2.41～2.75 e V）are greatly enhanced,owing to the synergy effect between blue phosphorene and graphadiyne.Next,the theoretical specific capacity reaches 761.76 m Ah/g,which is more than twice that of graphite（372 m Ah/g）.The open-circuit voltage decreases gradually with the lithium ion concentration and the average open-circuit voltage is0.27 e V,indicated that the heterostructure owns a stable and low insertion-lithium potential.The analysis of electronic structures show that the transition of semiconducting to metallic induced by Li intercalation of the Blue P/GDY heterostructure was observed,indicating effectively improvement of the internal resistance,cyclicity and safety of materials.The calculated diffusion energy barrier of lithium ions on the outside of blue phosphorene surface of the heterostructure is 0.11e V.While the diffusion energy barriers of lithium ions inserting into the interlayer of heterostructure are around 0.12～0.23 e V,which are much lower than that of monolayer blue phosphorene（0.16 e V）and monolayer graphdiyne（0.52 e V）,indicating excellent rate capability after the Blue P combining with the GDY.We also investigated the 1T’-Mo S2（monolayer,bilayer and bulk phase）as anode materials for LIBs.The results show that the average adsorption energy for lithium ions on two sides of the monolayer 1T’-Mo S2surface is 2.39 e V,which is higher than the cohesive energy（1.68 e V）of the lithium metal bulk phase.It is indicated that the monolayer 1T’-Mo S2could effectively inhibit the formation of lithium dendrites and the cyclicity and safety of materials is improved.The average open-circuit voltage is0.72 V,suggested that the ideal open circuit voltage could be provided.Unlike the2H-Mo S2,the 1T’-Mo S2monolayer is metallic.And the electrical conductivity becomes better as the lithium ion concentration increased,reducing internal resistance of battery and improving ohmic heat conversion rate.The diffusion energy barrier of low-concentration lithium ion is 0.32 e V,which is lower than that of 1T-Mo S2（0.35e V）,graphdiyne（0.47 e V）and Sn S（0.45 e V）.In addition,the diffusion energy barrier of high-concentration lithium ion adsorption is about 0.40 e V,indicating faster lithium ions diffusion rate for different concentrations and excellent rate capability of the monolayer 1T’-Mo S2.We further studied the bilayer 1T’-Mo S2as anode materials for LIBs.The average adsorption energies for lithium ions on the interlayer and surface of the bilayer1T’-Mo S2are 3.80 e V and 2.39 e V,respectively,which are higher than the cohesive energy（1.68 e V）of the lithium metal bulk phase.Thus,the bilayer 1T’-Mo S2could effectively inhibit the formation of lithium dendrites.The diffusion energy barriers for low-concentration and high-concentration lithium ions on the surface of the bilayer1T’-Mo S2are lower,which are 0.24 e V and 0.54～0.63 e V,respectively.In addition,the diffusion energy barriers of low-concentration and high-concentration lithium ion in the bulk 1T’-Mo S2are 0.35 e V and 0.65～0.79 e V,respectively,which are higher than the diffusion energy barriers for lithium ions on the surface of monolayer and bilayer 1T’-Mo S2.Thus,compared with bulk 1T’-Mo S2,the diffusion rate of lithium ions on the surface of two-dimensional 1T’-Mo S2nanomaterials is faster than that of bulk 1T’-Mo S2,suggested that two-dimensional 1T’-Mo S2nanomaterials could provide better electrochemical performance as anode materials for LIBs. |
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