First-principles Study Of Heterostructures Constructed By Blue Phosphorene As Anode For Li/Na-ion Batteries

Lithium/Sodium ion batteries have been used as a key component in portable electronic devices,and more importantly,they may offer a possible near-term solution for environment-friendly transportation and energy storage for renewable energies sources,such as solar and wind.To design and develop new anode materials for lithium/Sodium ion batteries,experimentalists have focused on mapping the synthesis–structure–property relations in different materials' families.However,this approach is time and labor consuming and not very efficient.First principles can predicte accurately the structure–property relations,and will have a significant impact on and change the traditional trial-and-true way of anode materials design.Using first-principles,three kinds of two-dimensional materials utilized as Li/Na-ion batteries anode were studied in the thesis on geometric structure,electronic structure and iondiffusion and theoretical capacity,etc.,the details are as follows:1.Combining blue phosphorene(BP)and hexagonal boron nitride(BN)together to construct BN/BP heterostructure can break the limitation of the restricted properties of BP.By means of first-principles computations,we explored the potential of using BN/BP as anode material for LIBs/NIBs.Our computations show that the adsorption energies of Li/Na in BN/BP are stronger than those in BP.Interestingly,although Li has similar chemical properties to Na,their the most energetically favorable sites on BN/BP are different.Li prefers to insert into the interlayer of BN/BP while Na prefers to absorb on the BP surface of BN/BP.Furthermore,BN/BP can achieve high theoretical specific capacities801 and 541 m Ah/g and low diffusion barriers 0.08 and 0.07 e V for LIBs and NIBs,respectively.All these characteristics suggest that the BN/BP could be an ideal candidate used as promising anode material for high-performance LIBs/NIBs.2.We construct the C3N/BP heterostructure consisting of C3 N monolayer and blue-P monolayer to overcome the inherent defects in BP.The geometric,mechanical,electronic and electrochemical properties of C3N/BP as anode material in LIBs/NIBs have been systematically studied by the first-principle computations.Our computations show that compared with BP monolayer,the C3N/BP has better mechanical properties,lower band gap and stronger adsorption energy for Li/Na.Furthermore,it is predicted that the C3N/Phas low diff usion barriers of 0.17 and 0.10 e V,low open circuit voltage of 0.54 and0.35 V and high theoretical specific capacities 333 and 658 m Ah/g for Li and Na,respectively.All of these characteristics ensure that the C3N/BP could serve as an ideal anode material for LIBs/NIBs,especially for NIBs.3.A new type of heterojunction with layer spacing smaller than those of the previous two heterojunctions was obtained by stacking hydrogenated boronene and blue phosphorene.The heterojunction has metal conductivity,the maximum adsorption energiesfor lithium and sodium are 2.61 and 2.17 ev,respectively,and the minimum diffusion barriers for lithium and sodium are 0.11 and 0.10 ev,respectively.It can stably hold up to128 lithium and 96 sodium atoms,and the theoretical specific capacity for lithium and sodium are up to 1520 m Ah/g and 719 m Ah/g,respectively.In particular,the layer spacing of the heterojunction will buffer the anode volume change during the charging and discharging processes,which can improve the cycle efficiency and service life of the battery.