High-throughput calculation method of electrolyte electrochemical window considering zwitterion influence

Abstract

The invention discloses a high-throughput calculation method of an electrolyte electrochemical window considering the influence of anions and cations, and belongs to the technical field of quantum chemistry calculation and new energy materials. A molecular structure is optimized, electrostatic potential of the molecular structure is calculated, a maximum value (minimum value) point of the electrostatic potential is combined with negative (positive) ions to construct a structure file in which a solvent is combined with the negative (positive) ions, the constructed structure file is imported in batches, high-flux optimization calculation is repeated, and energy corresponding to each structure file is output. An optimized structure combined with anions is obtained, the number of electrons is reduced by 1, and the number of spinning electrons is correspondingly modified; and obtaining an optimized structure combined with cations, adding 1 to the number of electrons, correspondingly modifying the number of spinning electrons, importing all structure files in batches, repeating high-throughput optimization calculation, and outputting energy corresponding to each structure file. And substituting the energy of the ground state, the oxidation state and the reduction state into a Nernst equation to calculate the oxidation-reduction potential of the molecule. According to the invention, beneficial help is provided for electrolyte design.

Description

Technical Field

[0001] The present invention belongs to the technical fields of quantum chemical calculations and new energy materials, and particularly relates to a high-throughput calculation method for the electrochemical window of an electrolyte considering the influence of cations and anions. Background Art

[0002] Lithium-ion batteries (LIBs), as an important pillar of current energy storage technologies, are widely used in fields such as electronic devices, electric vehicles, and energy storage systems. With the continuous increase in application requirements, the requirements for their performance are also increasing day by day, especially in terms of energy density, cycle life, and safety. To further improve the energy density of LIBs, the most promising strategies are to increase the cut-off voltage of the mainstream cathode, explore new high-capacity and high-voltage cathode materials, and use silicon / silicon-carbon composite materials or lithium metal instead of graphite anodes. The working voltage of traditional LIBs is generally around 3.7V. To further improve the energy density, researchers are exploring battery systems with higher voltage ranges, such as 4.5V or even higher. However, in a high-voltage environment, traditional electrolytes are prone to decomposition, resulting in a decline in battery performance, reduced safety, and even problems such as thermal runaway. Therefore, developing a matching high-performance high-voltage electrolyte is the key to improving the performance of LIBs.

[0003] The research and development of traditional high-voltage electrolytes rely on the accumulation of a large amount of experimental data and repeated trials. The process is cumbersome and costly, and it is difficult to quickly respond to market demands. The development of quantum computing technology has brought new opportunities to materials science. Through high-throughput calculations, the redox potentials of hundreds or thousands of solvents can be obtained. Combining reasonable voltage thresholds, electrolytic solvent resistant to high voltage can be quickly screened out, thereby reducing the number of experimental trials and costs, and significantly shortening the R & D cycle.

[0004] Currently, common strategies for predicting the electrochemical window of electrolytes are usually based on the regulation of the standard hydrogen electrode potential. Among these strategies, the most extensive and simple method is to represent the electrochemical window of the electrolyte by the energy level difference between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). However, an increasing number of studies have pointed out that this method is not accurate in predicting the electrochemical window of electrolytes. This is not surprising because the traditional HOMO / LUMO originates from the reduced electronic structure theory, reflecting the electronic properties of isolated neutral molecules and unable to accurately predict the true electrochemical window when substances participate in redox reactions. Peljo et al. even pointed out in a recent study that the use of HOMO / LUMO should be avoided when discussing the electrochemical window of electrolytes (P. Peljo, H. H. Girault, Energ. Environ. Sci. 2018, 11, 2306). At the same time, the interactions between anions, cations and solvents in the electrolyte can also significantly affect their redox potentials. (Gao Y C, Yao N, Chen X, et al. Data-driven insight into the reductive stability of ion–solvent complexes in lithium battery electrolytes[J]. Journal of the American Chemical Society, 2023, 145(43):23764-23770; Wang Y, Xing L, Li W, et al. Why do sulfone-based electrolytes show stability at high voltages? Insight from density functional theory[J]. The Journal of Physical Chemistry Letters, 2013, 4(22):3992-3999.). Therefore, a key question is: how to develop a fast and accurate method to obtain the electrochemical window of electrolytes on the basis of considering the complex local environment? Summary of the Invention

[0005] Aiming at the problem that the electrochemical window of solvent components cannot be accurately calculated in theoretical calculations, the present invention discloses a high-throughput calculation method for the electrochemical window of electrolytes considering the influence of anions and cations. By considering the influence of anions and cations in the electrolyte on the redox potential of the solvent, the purpose of accurately calculating the open-circuit voltage of the electrolyte environment is achieved.

[0006] To achieve the above object, the technical route adopted by the present invention is as follows:

[0007] A high-throughput calculation method for the electrochemical window of an electrolyte considering the influence of anions and cations, the method steps are as follows:

[0008] Step 1: Download the SMILE of the molecule from the database PubChem and screen the appropriate SMILE;

[0009] Step 2: Convert the SMILE into a structure file recognizable by the quantum chemistry calculation software;

[0010] Step 3: Use the molecular simulation software to optimize the structure of the structure file, and determine whether the optimization result ends normally. If so, calculate the electrostatic potential of the molecule. Otherwise, continue to optimize the molecule until it ends normally;

[0011] The molecular simulation software includes but is not limited to Gaussian, and the content of the Gaussian structure file includes: the system charge number, the electron spin multiplicity, the element type, and the atomic coordinates.

[0012] Step 4: Obtain the coordinates of the maximum point A(x max , y max , z max ) and the minimum point B(x min , y min , z min ) in the optimized structure file and electrostatic potential in Step 3, and construct a structure file combined with anions (cations);

[0013] The coordinates of the maximum and minimum values of the electrostatic potential can be obtained through the wave function processing software Multiwfn.

[0014] The method for constructing the structure file combined with anions is: obtain the minimum point C(x aion_min , y aion_min , z aion_min ) of the electrostatic potential of the anion and the optimized atoms and coordinates, translate the minimum value C of the anion to the maximum point A, and make corresponding translation changes to other elements in the anion. Assume that the coordinates of one atom are (x1, y1, z1). Then the coordinates of the atom after translation are (x1-(x aion_min -x max ), y1-(y aion_min -y max ), z1-(z aion_min -z max ))).

[0015] The method for constructing the structure file combined with cations is: the coordinates of the minimum point B (x min , y min,z min ) is added to the last line of the structure file, and the chemical element symbol of the cation is added to the first column of the line, and the charge number and electron spin multiplicity of the system are modified according to the valence state of the cation.

[0016] Step 5: Use molecular simulation software to optimize the structure file obtained in step 4, and determine whether the optimization result is completed normally. If so, obtain the energy G of the structure. neu , otherwise, continue to optimize the molecule until it ends normally;

[0017] Step 6: Obtain the optimized structure in step 5, wherein the number of electrons in the structure combined with cations is increased by 1, and the corresponding number of spin electrons is changed; the number of electrons in the structure combined with anions and cations is decreased by 1, and the corresponding number of spin electrons is changed; all the obtained structure files are optimized by molecular simulation software, and it is determined whether the optimization result is completed normally. If so, the energy G of the oxidation state structure is obtained respectively. ox and the energy of the reduced structure G red , otherwise, continue to optimize the molecule until it ends normally;

[0018] Step 7: According to G neu , G ox , G red Calculate the oxidation potential E ox and reduction potential E red (The counter electrode is Li + / Li).

[0019] The oxidation potential E ox The calculation formula is:

[0020]

[0021] The reduction potential E red The calculation formula is

[0022]

[0023] Where F is the Faraday constant and n is the number of electrons involved in the redox reaction.

[0024] The advantages of the present invention are as follows:

[0025] (1) A high-throughput calculation method for the electrochemical window of electrolytes that takes into account the influence of anions and cations. The model file that combines anions and cations can be generated through molecular electrostatic potential, which shortens the calculation modeling time, improves the model accuracy, and provides conditions for high-throughput calculations.

[0026] (2) The present invention provides a high-throughput calculation method for the electrochemical window of an electrolyte considering the influence of cations and anions. By considering the influence of cations and anions on the redox potential of the electrolyte, the calculated result of the electrochemical window is more reliable, shortening the development time and cost of the electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Li(SL) constructed by the extreme points of the electrostatic potential in the example of the present invention; + (SL);

[0028] Figure 2 Li(SL) after structural optimization in the example of the present invention; + (SL);

[0029] Figure 3 SL(PF6) constructed by the extreme points of the electrostatic potential in the example of the present invention; - );

[0030] Figure 4 SL(PF6) after structural optimization in the example of the invention; - );

[0031] Figure 5 It is the drawing of the abstract.

[0032] SPECIFIC IMPLEMENTATION STEPS

[0033] The present invention will be further described in detail below by taking sulfolane (SL) as the solvent and lithium hexafluorophosphate (LiPF6) as the solute as an example.

[0034] First step, use the molecular calculation software Gaussian to optimize the structure of sulfolane, and calculate the electrostatic potential of sulfolane. The coordinates of the maximum and minimum points of the electrostatic potential are (-4.281805, 0.559817, -0.075828) (3.920587, 0.030542, -1.001829);

[0035] Second step, construct the structural file of Li combined with SL, add Li 3.427477, 0.049440, -1.243379 to the structural file of optimized sulfolane, and optimize the constructed Li(SL) to obtain the system energy of -712.072 a.u. + with SL, and add Li 3.427477, 0.049440, -1.243379 to the structural file of the optimized sulfolane. Optimize the constructed Li(SL) to obtain the system energy of -712.072 a.u. + (SL) to obtain a system energy of -712.072 a.u.

[0036] Third step, construct the structural file of PF6 combined with SL. The following are the structural coordinates of PF6. Calculate PF6 through the electrostatic potential. - combined with SL. The following are the structural coordinates of PF6. Calculate PF6 through the electrostatic potential. - The following are the structural coordinates of PF6, and PF6 is obtained through electrostatic potential calculation. -The minimum point is (1.732441, 1.732441, 1.732441).

[0037]

[0038]

[0039] After translation, PF6 - The coordinates are:

[0040]

[0041] The constructed SL(PF6 - ) is structurally optimized to obtain a system energy of -1645.690 a.u.

[0042] In the fourth step, the optimized ground-state structures in the second and third steps are obtained. Let Li + (SL) system gains one electron, and the SL(PF6 - ) system loses one electron. Continue the optimization. The energies of the reduced state and the oxidized state are -712.268 a.u. and -1645.410 a.u., respectively.

[0043] In the fifth step, according to the calculation formulas of the oxidation potential and the reduction potential, the oxidation potential and the reduction potential of SL in the electrolyte are calculated to be 6.40 V and 0.70 V, respectively.

[0044] Among them, the specific method used for structural optimization in all steps is the density functional theory, the basis set is 6-311+G(d,p), the functional is B3LYP, the solution environment is described by the solvation model, and the dielectric constant of the solvation model is set to 20.7; the obtained optimized structure is determined to be the ground-state structure through vibrational frequency analysis.

[0045] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited only to these descriptions. The present invention includes but is not limited to the above embodiments. Any equivalent replacement or partial improvement made under the spirit and principle of the present invention will be regarded as within the protection scope of the present invention.

Claims

1. A high-throughput calculation method for the electrochemical window of an electrolyte taking into account the influence of anions and cations, characterized in that: The specific steps are as follows: Use molecular simulation software to optimize the structure file, determine whether the optimization result ends normally, if yes, calculate the electrostatic potential of the molecule, and obtain the coordinates of the maximum and minimum values ​​in the electrostatic potential, otherwise, continue to optimize the molecule until it ends normally; Combine the maximum (minimum) point with the anion (cation) to construct the structural file of the solvent and the anion (cation), batch import all the structural files, repeat the high-throughput optimization calculation, and determine whether the optimization result ends normally. If so, obtain the energy G of the structure. neu , otherwise, continue to optimize the molecule until it ends normally; Obtain the optimized structure combined with the anion, reduce the number of electrons by 1, and modify the corresponding number of spin electrons; import all structure files in batches, repeat the high-throughput optimization calculation, and determine whether the optimization result ends normally. If so, obtain the energy G of the structure. ox ; Get the optimized structure after binding with cations, increase the number of electrons by 1, modify the corresponding number of spin electrons, batch import all structure files, repeat the high-throughput optimization calculation, and determine whether the optimization result ends normally. If so, obtain the energy G of the structure. red ; G neu , G ox , G red Substituting into the redox potential calculation formula, we can get the oxidation potential E ox and reduction potential E red .

2. A high-throughput calculation method for the electrochemical window of an electrolyte taking into account the influence of anions and cations as claimed in claim 1, characterized in that: The molecular simulation software includes but is not limited to Gaussian, wherein the Gaussian structure file content includes: system charge number, electron spin multiplicity, element type, and atomic coordinates.

3. The high-throughput calculation method of the electrochemical window of an electrolyte taking into account the influence of anions and cations as claimed in claim 1, characterized in that: The wave function processing software Multiwfn can be used to calculate the electrostatic potential of molecules and obtain the coordinates of the maximum and minimum values ​​of the electrostatic potential.

4. The high-throughput calculation method of the electrochemical window of an electrolyte taking into account the influence of anions and cations as claimed in claim 1, characterized in that: The method for constructing the structure file for binding with anions is to obtain the minimum point C(x aion_min ,y aion_min ,z aion_min ) and the optimized atoms and coordinates, translate the minimum value C of the anion to the maximum value point A, and make corresponding translation changes to other elements in the anion. Assume that the coordinates of one of the atoms are (x1, y1, z1). Then the coordinates of the atom after translation are (x1-(x aion_min -x max ),y1-(y aion_min -y max ),z1-(z aion_min -z max )).

5. The high-throughput calculation method of the electrochemical window of an electrolyte taking into account the influence of anions and cations as claimed in claim 1, characterized in that: The method for constructing the structure file for the cation binding is to convert the coordinates of the minimum point B (x min ,y min ,z min ) is added to the last line of the structure file, and the chemical element symbol of the cation is added to the first column of the line, and the charge number and electron spin multiplicity of the system are modified according to the valence state of the cation.

6. A high-throughput calculation method for the electrochemical window of an electrolyte taking into account the influence of anions and cations as claimed in claim 1, characterized in that: Oxidation potential E ox The calculation formula is: Where F is the Faraday constant and n is the number of electrons involved in the redox reaction.

7. The high-throughput calculation method of the electrochemical window of an electrolyte taking into account the influence of anions and cations as claimed in claim 1, characterized in that: Reduction potential E red The calculation formula is: Where F is the Faraday constant and n is the number of electrons involved in the redox reaction.

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