A high-capacity sodium-ion battery negative electrode material prediction method based on first-principle calculation

Abstract

The application discloses a high-capacity sodium ion battery negative electrode material prediction method based on first-principle calculation and belongs to the field of electrochemical energy storage material calculation. The method firstly constructs two-dimensional Be3N2 and BP monolayer models and performs structural optimization based on the first principle; then, a heterostructure is constructed by stacking layers, and the negative formation energy is obtained by static self-consistent calculation to verify the structural feasibility; then, ab initio molecular dynamics is used to verify the thermal stability; finally, the best sodium storage site is selected by comparing the adsorption energies of different sites, and the theoretical capacity and ion migration performance are accurately predicted by comprehensively considering the structural deformation and average open circuit voltage (OCV) limitation. The application proves that the Be3N2 / BP heterostructure has excellent structural stability and high sodium storage potential, and provides theoretical guidance for the design of a novel two-dimensional sodium ion battery negative electrode material.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of electrochemical energy storage technology and computational materials science, specifically to a method for predicting high-capacity sodium-ion battery anode materials based on first-principles calculations. Background Technology

[0002] With the rapid development of large-scale electrochemical energy storage technology, sodium-ion batteries are considered one of the most commercially promising new energy storage devices due to the abundant and widely distributed sodium resources and low cost. In sodium-ion battery systems, the anode material is the core component that determines the overall energy density, charge / discharge rate, and cycle life of the battery. However, compared to lithium ions, sodium ions have a larger ionic radius (approximately 1.02 Å) and a heavier mass. This results in extremely high diffusion barriers when sodium ions are inserted into and extracted from traditional bulk anode materials (such as hard carbon and transition metal oxides), leading to extremely slow ion diffusion kinetics and severe lattice distortion and huge volume expansion. These repeated drastic volume changes cause internal stress accumulation, particle pulverization and spalling in the electrode material, and continuous rupture and reconstruction of the solid electrolyte interphase (SEI) film, resulting in irreversible rapid capacity decay and extremely poor rate performance. Therefore, exploring new sodium-ion battery anode materials with high sodium storage capacity, excellent rate performance, and long cycle life has become a critical technical challenge that urgently needs to be addressed in the field of electrochemical energy storage.

[0003] Two-dimensional nanomaterials, due to their extremely high specific surface area, abundant surface and edge active sites, and unique single-atom-layer or few-layer structures, can effectively buffer volume expansion stress and provide extremely short two-dimensional diffusion paths for alkali metal ions, showing great potential in the field of anode materials. Among them, beryllium (Be)-based two-dimensional materials (such as two-dimensional beryllium nitride Be3N2) composed of lightweight elements have attracted widespread attention in recent years. Due to the extremely small relative atomic masses of Be and N elements, such two-dimensional materials can break through the capacity bottleneck of traditional intercalation materials when used as battery anodes, exhibiting ultra-high theoretical specific capacity and extremely low ion diffusion barrier. However, single-layer Be3N2 materials have obvious inherent defects in practical applications: during repeated high-concentration sodium ion intercalation and deintercalation processes, its atomic-level two-dimensional honeycomb framework is prone to irreversible structural deformation and out-of-plane distortion. This structural instability caused by sodium storage leads to deactivation of active materials, a decrease in overall conductivity, and a sharp reduction in cycle life, which greatly restricts its further development as a high-performance anode material.

[0004] To overcome the structural defects of monolayer two-dimensional materials, constructing van der Waals heterostructures by stacking different two-dimensional materials has become an effective strategy for regulating and optimizing electrochemical performance. Based on this, this invention proposes the construction of a Be3N2 / BP (boron phosphide) two-dimensional heterostructure as a novel anode material for sodium-ion batteries. Introducing a two-dimensional BP monolayer with high Young's modulus and good electron transport properties can effectively limit the volume deformation of Be3N2 during sodium storage through the synergistic effect of interlayer van der Waals forces, compensating for its poor cycle stability. This invention aims to comprehensively evaluate the thermodynamic feasibility and energy storage characteristics of this heterostructure through first-principles calculations, providing a reliable theoretical basis and design ideas for developing structurally stable, high-capacity sodium-ion battery anode materials with excellent kinetic performance. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of poor cycle stability, deactivation of active materials, and decreased conductivity of monolayer two-dimensional Be3N2 materials during high-concentration sodium ion intercalation and deintercalation caused by structural deformation and out-of-plane distortion.

[0006] To achieve the above objectives, the present invention employs the following technical means:

[0007] This invention provides a method for predicting high-capacity sodium-ion battery anode materials based on first-principles calculations, comprising the following steps:

[0008] Step 1: Import the bulk Be3N2 and BP structure files into the materials simulation and molecular modeling software, and establish two-dimensional Be3N2 monolayer and BP monolayer structure models respectively. Use first-principles calculation software to perform full geometric relaxation optimization on the monolayer structure, and select the PBE method of GGA for exchange-correlation functional selection.

[0009] Step 2: Construct a Be3N2 / BP heterojunction model using the optimized Be3N2 monolayer and BP monolayer according to the requirement of crystal mismatch less than 5%, and then optimize the structure.

[0010] Step 3: Perform static self-consistent calculations on the Be3N2 / BP heterojunction and the two monolayer two-dimensional materials to obtain the formation energy and determine whether the formation energy is negative.

[0011] Step 4: The thermal stability of the optimized Be3N2 / BP heterostructure is evaluated using ab initio molecular dynamics.

[0012] Step 5: Set multiple candidate adsorption sites on the surface of the heterojunction, calculate the adsorption energy corresponding to each candidate site, and screen out the best sodium ion adsorption site by comparing and analyzing the adsorption energy values.

[0013] Step 6: Based on the optimal adsorption sites, calculate the diffusion path and migration barrier of sodium ions in the heterojunction;

[0014] Step 7: Based on the optimal sodium ion adsorption sites calculated in Step 5, gradually increase the sodium ion concentration. Taking into account the degree of structural deformation and the influence of open circuit voltage during the adsorption process, calculate the theoretical capacity of the heterojunction material.

[0015] Degree of structural deformation: Based on the optimal sodium ion adsorption sites calculated in step 5, the charge and discharge process was simulated by gradually increasing the sodium ion loading concentration; the structural stability criterion was that the two-dimensional lattice expansion rate was less than 3% and the main chemical bonds did not undergo irreversible breakage; at the same time, the thermodynamic cutoff standard was that the open circuit voltage (OCV) was between 0V and 1.0V and no potential turned negative. When the above dual constraints were met, the maximum theoretical sodium storage capacity of the heterojunction material under the safe electrochemical window was calculated.

[0016] In the above scheme, the formation energy in step 3 The calculation formula is:

[0017]

[0018] in, The total energy of the heterostructure. This represents the total energy of a relaxed Be3N2 monolayer. The total energy of a relaxed BP monolayer; formation energy The results demonstrate that the composite process of the system is exothermic and that the structure is stable and feasible.

[0019] In the above scheme, the adsorption energy in step 5 The calculation formula is:

[0020]

[0021] in, This represents the total energy of the system after the adsorption of a single sodium ion. This represents the total energy of the heterostructure before sodium ions were adsorbed. This represents the average energy of a single sodium atom in bulk metallic sodium; the more negative the adsorption energy, the stronger the ability of that site to capture sodium ions, and the more stable the structure.

[0022] In the above scheme, step 4 uses ab initio molecular dynamics to evaluate the structural stability of the material: molecular dynamics simulation is used, the NVT ensemble is used, the temperature is set to 300K, the time step is 1fs and the total duration is 5ps.

[0023] In the above scheme, the steps for determining the adsorption sites in step 5 are as follows: The adsorption energies of all possible adsorption sites are calculated on the upper and lower surfaces of the substrate material to determine the optimal adsorption site, as detailed below:

[0024] Based on the lattice geometric symmetry characteristics of the heterostructure surface and interlayer, typical high symmetry sites are selected as initial candidate adsorption sites. These high symmetry sites include top sites directly above atoms, bridge sites formed by bonding between adjacent atoms, and center sites formed by geometric polygons composed of atoms. Subsequently, the adsorption energies of the selected initial candidate adsorption sites are calculated on the upper and lower surfaces of the substrate material. The site with the lowest adsorption energy is selected as the optimal adsorption site by comparison.

[0025] In the above scheme, the diffusion path and migration barrier of Na ions in step 6 include the following steps: taking the optimal adsorption site as the initial site and the termination site, interpolating between the initial and termination sites, using the climbing micro-motion elastic band method to search for the transition state and calculate the migration barrier, and drawing the barrier diagram of the diffusion path.

[0026] In the above scheme, the formulas for calculating the open-circuit voltage and theoretical capacity in step 7 are as follows:

[0027] The formula for calculating open-circuit voltage (OCV) is:

[0028]

[0029] in Open-circuit voltage, in volts (V).

[0030] and : These represent the number of Na atoms adsorbed by two adjacent stable intermediate phases during the sodium intercalation process, where ;

[0031] Adsorption The total energy of the heterojunction system after adding one Na atom;

[0032] Adsorption The total energy of the heterojunction system after adding one Na atom;

[0033] : The average energy of a single Na atom in bulk metallic sodium;

[0034] Elementary charge.

[0035] In the above scheme, the theoretical capacity calculation formula in step seven is: The theoretical capacity calculation formula is:

[0036] .

[0037] in, The maximum theoretical specific capacity of the system, expressed in mAh / g;

[0038] The number of valence electrons in the ions that participate in the electrochemical reaction;

[0039] The maximum number of Na atoms that the Be3N2 / BP heterojunction system can adsorb;

[0040] .: Faraday constant;

[0041] Molar mass of a unit cell in the Be3N2 / BP heterojunction, in g / mol.

[0042] .: A conversion factor used to convert the unit of electrical energy, coulomb, to milliampere-hour.

[0043] The present invention also provides a sodium-ion battery anode material, wherein the anode material is a Be3N2 / BP heterostructure, and its performance is predicted by the method described herein.

[0044] In the above scheme, the formation energy of the Be3N2 / BP heterostructure is negative.

[0045] Because the present invention employs the above-mentioned technical means, it has the following beneficial effects:

[0046] 1. This invention constructs models of the Be3N2 / BP heterostructure and its respective monolayer structure using first-principles calculation software, and performs structural relaxation optimization to obtain a stable structure. The optimal adsorption sites for sodium ions on the junction surface are calculated, and the charging process is simulated by sequentially placing sodium ions into the most stable energy storage sites. The calculated theoretical capacity and open-circuit voltage characterize the energy storage capacity of this heterostructure at the maximum sodium ion doping concentration. In summary, this invention not only proposes a novel and superior sodium-ion battery anode material but also provides a specific method for predicting its performance, promoting the development of sub-cell anode materials and providing positive implications for future experimental research. Attached Figure Description

[0047] Figure 1 The geometric configuration diagram of the Be3N2 / BP heterostructure constructed in the embodiments of the present invention after complete geometric relaxation optimization;

[0048] Figure 2 Figure 1 shows the results of an ab initio molecular dynamics (AIMD) simulation of the Be3N2 / BP heterostructure at 300K.

[0049] Figure 3The evolution of the open-circuit voltage (OCV) plateau and the theoretical capacity prediction of the Be3N2 / BP heterostructure during the gradual sodium intercalation process are shown in the figure. Detailed Implementation

[0050] The embodiments of the present invention will be described in detail below. Although the present invention will be described and illustrated in conjunction with some specific embodiments, it should be noted that the present invention is not limited to these embodiments. On the contrary, any modifications or equivalent substitutions made to the present invention should be covered within the scope of the claims of the present invention.

[0051] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art will understand that the present invention can be practiced without these specific details.

[0052] This invention aims to provide a first-principles-based method for predicting high-capacity sodium-ion battery anode materials. By constructing highly stable heterostructures and combining rigorous thermodynamic stability, open-circuit voltage, and structural deformation assessments, it provides reliable theoretical design guidance and screening schemes for developing novel sodium-ion battery anode materials with high capacity, high rate capability, and excellent cycle life.

[0053] Referring to Figure 1, this is a geometric configuration diagram of the Be3N2 / BP heterostructure constructed according to an embodiment of the present invention after complete geometric relaxation optimization. The figure includes a top view and a side view of the system, which intuitively shows the stable stacking configuration formed by the Be3N2 monolayer and the BP monolayer through interlayer van der Waals forces. This indicates that the two monolayers can achieve matching with a small lattice mismatch (3%), providing a reliable thermodynamic steady-state structural basis for subsequent energy storage performance prediction.

[0054] Figure 2 shows the ab initio molecular dynamics (AIMD) simulation results of the Be3N2 / BP heterostructure at 300 K. The black curve in the figure reflects the fluctuation of the total energy of the system over time during the simulation duration of 5000 fs (5 ps); the two insets in the figure correspond to the initial state of the simulation and the supercell snapshot after the simulation, respectively. This figure demonstrates that the system energy oscillates slightly around the equilibrium value, and that no chemical bonds in the atomic framework have broken or been severely distorted, fully verifying that this heterojunction, as a negative electrode material, possesses excellent thermal stability and structural retention capabilities at room temperature.

[0055] Figure 3 illustrates the evolution of the open-circuit voltage (OCV) plateau and theoretical capacity prediction of the Be3N2 / BP heterostructure during the stepwise sodium intercalation process. The black step line in the figure reflects the trend of the open-circuit voltage as the sodium atom loading concentration increases (from 0 to 30 Na atoms). The insets in the figure show the stable multilayer adsorption configurations corresponding to different sodium concentration stages. This figure visually demonstrates that the OCV remains strictly within a safe electrochemical window greater than 0 V throughout the entire sodium intercalation process (effectively avoiding the risk of sodium precipitation), and that the material does not pulverize or undergo interlayer delamination even when reaching the maximum sodium storage limit. This strongly supports the conclusion of this invention that the material possesses an ultra-high theoretical sodium storage capacity and excellent resistance to volume expansion.

[0056] The following are two specific embodiments used to further illustrate the technical solutions provided by the present invention:

[0057] Example 1: Construction and structural stability verification of a two-dimensional Be3N2 / BP heterojunction model

[0058] 1) Construct a single layer of Be3N2:

[0059] a) Using materials simulation and molecular modeling software, import the bulk Be3N2.cif file and cut the bulk Be3N2 using the CleaveSurface function in the Surfaces section of Build.

[0060] b) By using the BuildVacuumSlab function in the Crystals section of Build, a 23A vacuum layer is added to the z-axis of the cut monolayer Be3N2 two-dimensional material to eliminate the spurious interaction caused by the periodic boundary conditions between adjacent layers.

[0061] c) Optimize the structure of the single-layer Be3N2 two-dimensional material configuration and perform static self-consistent calculations.

[0062] 2) Construct a single-layer BP layer:

[0063] a) Using materials simulation and molecular modeling software, import the bulk phase BP.msi file in File → Import → Structures → Semiconductors, and then cut the bulk phase BP using the CleaveSurface function in Build.

[0064] b) By using the BuildVacuumSlab function in Crystals of Build, a 23A vacuum layer is added to the z-axis of the cut single-layer BP two-dimensional material to eliminate the spurious interaction caused by the periodic boundary conditions between adjacent layers.

[0065] c) Optimize the structure of the single-layer BP two-dimensional material configuration and perform static self-consistent calculations.

[0066] 3) Constructing a Be3N2 / BP heterojunction:

[0067] a) After the optimization of the two monolayer material structures mentioned above converged, a Be3N2 / BP heterojunction (lattice mismatch rate of 2.39%) was built using material simulation and molecular modeling software, File Build→BuildLayer.

[0068] b) Construct a Be3N2 / BP heterojunction with a vacuum layer of 23Å using methods a) and b) in 2).

[0069] c) Export the Be3N2 / BP .cif file and import it into VESTA. Then export it as a VASPfile file, select Cartesian coordinates, and rename it to POSCAR.

[0070] d) Perform structural optimization on the Be3N2 / BP heterostructure and conduct static self-consistent calculations.

[0071] 4) Calculation of Be3N2 / BP heterojunction formation energy: The energies obtained from the static self-consistent calculations in steps 1), 2), and 3) are calculated using the formula...

[0072]

[0073] in, The total energy of the heterostructure. This represents the total energy of a relaxed Be3N2 monolayer. The total energy of the relaxed BP monolayer is given, and the formation energy of the Be3N2 / BP heterojunction is -0.6186 eV. The negative formation energy initially indicates that the formation process of this heterostructure is exothermic and thermodynamically stable.

[0074] 5) Evaluate the thermodynamic stability of the Be3N2 / BP heterojunction:

[0075] a) Import the optimized CONTCAR of the Be3N2 / BP structure from 3) into VESTA, use Edit→Unitcell→Transform to expand the cell of the structure into a 3×3×1 supercell, and export it as the POSCAR for ab initio molecular dynamics (AIMD) simulation;

[0076] b) Under the NVT canonical ensemble, the temperature is set to 300K (room temperature), the time step is set to 1fs, and the total simulation time is 5ps;

[0077] c) After the simulation, it was found that the energy of the Be3N2 / BP heterojunction fluctuated in the range of -610±2eV. No obvious bond breakage or structural deformation occurred in the heterojunction framework, indicating that the Be3N2 / BP heterostructure has excellent thermodynamic stability.

[0078] Example 2: Energy storage performance prediction of two-dimensional Be3N2 / BP heterojunction as a sodium-ion battery anode

[0079] 1) Screening for optimal adsorption sites

[0080] a) Based on the stable Be3N2 / BP heterojunction obtained by structural optimization in Implementation Case 1, Na ions are adsorbed at different sites on the upper surface of BP and the lower surface of Be3N2. There are 4 possible adsorption sites on the upper surface of BP, namely center / B-top / P-top / bridge, and there are 4 possible adsorption sites on the lower surface of Be3N2, namely center / Be-top / N-top / bridge.

[0081] b) For the eight adsorption sites constructed in a), structural optimization and static self-consistent calculations were performed respectively.

[0082] c) Based on the static self-consistency results, the adsorption energies of the eight adsorption sites were calculated as shown in the table below.

[0083] BP <![CDATA[E ads ]]> <![CDATA[Be3N2]]> <![CDATA[E ads ]]> site / site / center -0.4370 Be-top -0.6373 B-top -0.3121 N-top -0.4154 P-top -0.3853 bridge -0.6374 bridge -0.3854 center -0.2357

[0084] The smaller the adsorption energy, the higher the adsorption strength with the substrate and the better the adsorption performance.

[0085] d) Based on the comparison of adsorption energy data in the table, it can be concluded that the optimal adsorption site on the upper surface of BP is the center site, and the optimal adsorption site on the lower surface of Be3N2 is the Be-top site (Na at the bridge site will migrate to the Be-top).

[0086] 2) Determine diffusion paths and migration barriers

[0087] a) Based on the optimal adsorption sites of the Be3N2 / BP heterojunction selected in 1) above, the different positions of the optimal adsorption sites are used as the initial and termination sites.

[0088] b) Insert points at the initial and final sites, use the climbing micro-motion elastic band (CI-NEB) method to search for the transition state and calculate the migration barrier, and draw the barrier diagram of the diffusion path.

[0089] c) After CI-NEB calculations, it was found that the highest migration barrier of sodium ions on the BP surface was only 0.3069 eV, and the highest migration barrier on the Be3N2 surface was 0.4669 eV. This confirms that the heterostructure material has ultrafast sodium ion diffusion kinetics and can meet the requirements of high-rate sodium ion batteries (fast charging).

[0090] 3) Calculate the theoretical capacity and open-circuit voltage.

[0091] a) Based on the optimal adsorption sites, the sodium ion concentration on the surface of the heterostructure is gradually increased to simulate the sodium intercalation process during battery charging. A differential formula is used, namely:

[0092]

[0093] in, .and . : Represents the number of Na atoms adsorbed by two adjacent stable intermediate phases during the sodium intercalation process (where... ). .: Adsorption The total energy of the heterojunction system after adding one Na atom. Adsorption The total energy of the heterojunction system after adding one Na atom. : The average energy of a single Na atom in bulk metallic sodium. The open-circuit voltage (OCV) at the corresponding concentration is calculated using the elementary charge (since sodium has a valence of +1, the denominator is directly taken as the elementary charge, i.e., the number of electrons transferred is equal to the number of adsorbed sodium atoms). The calculation shows that the highest plateau of the open-circuit voltage during sodium intercalation is 0.59241V, and the average OCV is stable at 0.5655V.

[0094] b) Under the premise of comprehensively considering OCV limitations and ensuring that the structure does not undergo severe cracking or deformation, this heterogeneous crystal cell can stably accommodate a maximum of 30 sodium atoms. (Based on the theoretical capacity calculation formula...) , : The number of valence electrons of the ions participating in the electrochemical reaction (for sodium ions Na ions) + , here ; The maximum number of Na atoms that the Be3N2 / BP heterojunction system can adsorb; Faraday constant (usually taken as 96485 C / mol); Molar mass of a single cell in the Be3N2 / BP heterojunction, in g / mol. The calculated theoretical capacity of the Be3N2 / BP heterostructure is as high as 4456.87 mAh / g.

[0095] The applicant declares that the detailed methods of the present invention are illustrated through the above embodiments, but the present invention is not limited to the above detailed methods, that is, it does not mean that the present invention must rely on the above detailed methods to be implemented. The above descriptions are merely embodiments of the present invention and do not limit the scope of this patent. All equivalent structures and methods made using the content of this invention and its drawings are similarly included within the patent protection scope of this invention.

Claims

1. A method for predicting high-capacity sodium-ion battery anode materials based on first-principles calculations, characterized in that, Includes the following steps: Step 1: Import the bulk Be3N2 and BP structure files into the materials simulation and molecular modeling software, and establish two-dimensional Be3N2 monolayer and BP monolayer structure models respectively. Use first-principles calculation software to perform full geometric relaxation optimization on the monolayer structure, and select the PBE method of GGA for exchange-correlation functional selection. Step 2: Construct a Be3N2 / BP heterojunction model using the optimized Be3N2 monolayer and BP monolayer according to the requirement of crystal mismatch less than 5%, and then optimize the structure. Step 3: Perform static self-consistent calculations on the Be3N2 / BP heterojunction and the two monolayer two-dimensional materials to obtain the formation energy and determine whether the formation energy is negative. Step 4: The thermal stability of the optimized Be3N2 / BP heterostructure is evaluated using ab initio molecular dynamics. Step 5: Set multiple candidate adsorption sites on the surface of the heterojunction, calculate the adsorption energy corresponding to each candidate site, and screen out the best sodium ion adsorption site by comparing and analyzing the adsorption energy values. Step 6: Based on the optimal adsorption sites, calculate the diffusion path and migration barrier of sodium ions in the heterojunction; Step 7: Based on the optimal sodium ion adsorption sites calculated in Step 5, gradually increase the sodium ion concentration. Taking into account the degree of structural deformation and the influence of open circuit voltage during the adsorption process, calculate the theoretical capacity of the heterojunction material.

2. The method according to claim 1, characterized in that, The formation energy in step 3 The calculation formula is: in, The total energy of the heterostructure. This represents the total energy of a relaxed Be3N2 monolayer. The total energy of a relaxed BP monolayer; formation energy The results demonstrate that the composite process of the system is exothermic and that the structure is stable and feasible.

3. The method according to claim 1, characterized in that, The adsorption energy in step 5 The calculation formula is: in, This represents the total energy of the system after the adsorption of a single sodium ion. This represents the total energy of the heterostructure before sodium ions were adsorbed. This represents the average energy of a single sodium atom in bulk metallic sodium; the more negative the adsorption energy, the stronger the ability of that site to capture sodium ions, and the more stable the structure.

4. The method according to claim 1, characterized in that, In step 4, the structural stability of the material is evaluated using ab initio molecular dynamics: molecular dynamics simulation is used with an NVT ensemble, the temperature is set to 300K, the time step is 1fs and the total duration is 5ps.

5. The method according to claim 1, characterized in that, The steps for determining the adsorption sites in step 5 are as follows: on the upper and lower surfaces of the substrate material, the adsorption energy of all possible adsorption sites is calculated to determine the optimal adsorption site.

6. The method according to claim 1, characterized in that, Step 6 involves determining the diffusion path and migration barrier of Na ions, including the following steps: using the optimal adsorption site as the initial and final sites, interpolating between the initial and final sites, employing the climbing micro-motion elastic band method to search for the transition state and calculate the migration barrier, and plotting the barrier diagram of the diffusion path.

7. The method according to claim 1, characterized in that, The formulas for calculating the open-circuit voltage and theoretical capacity in step 7 are as follows: The formula for calculating open-circuit voltage is: in Open-circuit voltage, in volts (V). and : These represent the number of Na atoms adsorbed by two adjacent stable intermediate phases during the sodium intercalation process, where ; Adsorption The total energy of the heterojunction system after adding one Na atom; Adsorption The total energy of the heterojunction system after adding one Na atom; : The average energy of a single Na atom in bulk metallic sodium; Elementary charge.

8. The method according to claim 1, characterized in that, The theoretical capacity calculation formula in step 7 is: The theoretical capacity calculation formula is: in, The maximum theoretical specific capacity of the system, expressed in mAh / g; The number of valence electrons in the ions that participate in the electrochemical reaction; The maximum number of Na atoms that the Be3N2 / BP heterojunction system can adsorb; Faraday constant; Molar mass of a Be3N2 / BP heterojunction unit cell, in g / mol; : A conversion factor used to convert the unit of electrical energy, coulomb, to milliampere-hour.

9. A sodium-ion battery anode material, characterized in that, The negative electrode material is a Be3N2 / BP heterostructure, and its performance is predicted by the method described in any one of claims 1-8.

10. The sodium-ion battery anode material according to claim 9, characterized in that, The formation energy of the Be3N2 / BP heterostructure is negative.

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