Research On The Properties Of Novel 2D Heterostructure Materials As The Anode For Li-ion Batteries

In order to meet the needs of a low-carbon economy and society,promoting the development of carbon-neutral industries and technologies has become a key link in the efficient use of renewable energy.As an important technology in energy storage and conversion applications,lithium-ion batteries still have a lot of room to improve their performance.The selection and design of anode materials have become the key to the development of a new generation of high-performance lithium-ion batteries.With the continuous emergence of novel two-dimensional materials,the novel heterostructures composed of different two-dimensional materials via van der Waals forces are expected to be the candidate material for anode materials of lithium-ion battery due to their unique electrochemical properties.In this thesis,the first-principles calculations based on density functional theory were carried out to study the geometric structure and electronic properties of Si C₂/C₃B and BP/AlN heterostuctures.Combined with the analysis of the storage and migration mechanism of lithium ions,the excellent performance of these two new two-dimensional heterostructures when used as the anode materials of lithium-ion battery is predicted.The calculated results show that the Si C₂/C₃B heterostructure constructed by van der Waals coupling effect has good kinetic and thermodynamic stability.After lithiation,the Si C₂/C₃B heterostructure changes from intrinsic semiconductor to metallic properties.The good electrical conductivity of the system and the low diffusion barrier of lithium ion in the Si C₂/C₃B heterostructure could guarantee the high-rate performance of lithium-ion batteries.Compared with the isolated Si C₂ and C₃B monolayers,an enhancement of the storage capacity of Li ions on the Si C₂/C₃B heterostructure is observed,which could reach up to 1489.72m Ah/g.To determine the theoretical specific capacity of the Si C₂/C₃B heterostructure,we give multiple criteria for saturated adsorption and discuss them in detail in this thesis.In addition,Si C₂/C₃B heterostructure shows excellent mechanical properties,which can effectively cope with the volume expansion effect caused by lithium ions intercalation and deintercalation,so as to ensure good cyclic stability of the anode.Similarly,the most stable BP/AlN was optimized by constructing heterostructures and comparing their binding energies of different stacking modes.The calculation results show that the BP/AlN heterostructure has good energetic and structural stability.Compared with the isolated BP and AlN monolayers,the combined heterostructure has further improved electrical conductivity.Lithium ion exhibits excellent rate performance when diffusing in the BP/AlN heterostructure,with energy barrier less than 0.40 e V.The maximum storage capacity of novel BP/AlN heterostructure is 971.42 m Ah/g by saturation adsorption.The molecular dynamics simulation results also show that the BP/AlN heterostructure can maintain good structural stability in saturated adsorption state at 350 K.After calculation and analysis,Si C₂/C₃B and BP/AlN,two novel heterostructure materials,have great potential to be used as the anode materials of lithium-ion batteries.The engineering modification strategy of heterostructures designed in our work provides a new idea for the design and selection of candidate anode materials for lithium-ion batteries,and also provides a theoretical basis for the subsequent experimental exploration of two-dimensional heterostructure materials applied to lithium-ion batteries.