A method for designing and screening new sodium salts based on density functional theory

Abstract

This invention provides a method for designing and screening novel sodium salts based on density functional theory. The invention proposes a method for designing novel sodium salt structures using small molecule functional group substitution and density functional theory-based simulations, and utilizes quantum mechanical DFT calculations to analyze DFOP. ‑ DFOB ‑ and BOB ‑ The redox properties of functional groups are theoretically studied, and the geometric and electronic structures of sodium salts are analyzed in depth. New sodium salt structures with high redox stability and dissociation are developed, which greatly reduces the human and material resources required for sodium salt structure design and also reduces the corresponding time costs.

Description

Technical Field

[0001] This invention belongs to the field of sodium salt molecular structure design and screening technology for sodium-ion batteries. It relates to a method for designing and screening sodium salts based on density functional theory, and more particularly to a method for designing and screening novel sodium salts based on density functional theory and a novel sodium salt molecular structure with high redox stability and dissociation degree. Background Technology

[0002] Lithium and sodium both belong to Group IA alkali metals in the periodic table and have similarities in physics and chemistry. However, global reserves of lithium are limited, with only 0.0065% of the earth's crust, while sodium resources are much more abundant at 2.64%, which is 440 times that of lithium. As an alternative to lithium-ion rechargeable batteries, sodium-ion rechargeable batteries have many advantages such as abundant sodium resources and low development costs, making them one of the ideal choices for next-generation large-scale energy storage technologies.

[0003] Sodium salts, as a crucial component of sodium-ion batteries, provide freely transporting ions and play a vital role in ion transport within the battery. Their anions also significantly contribute to the formation of the SEI film, largely determining the battery's capacity, operating temperature, cycle performance, power density, energy density, and safety. Developing new sodium salts can further improve battery lifespan.

[0004] Currently, the structural design of novel sodium salts is mostly carried out through manual experimentation and trial and error, which requires a large investment of human and material resources, has a high time cost, and also involves a large number of potential structures.

[0005] Therefore, finding a more suitable method for designing novel sodium salt structures to overcome the aforementioned problems of existing manual experimental trial-and-error methods has become one of the urgent problems to be solved by many front-line researchers in the industry. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a method for designing and screening sodium salts based on density functional theory. The present invention proposes a method for designing novel sodium salt structures by substituting small molecule functional groups and by using frontier molecular orbital theory to analyze the highest occupied orbital and lowest unoccupied orbital (HOMO / LUMO) and dissociation energy of novel sodium salt molecular structures. This method greatly reduces the human and material resources required for sodium salt structure design and also reduces the corresponding time cost.

[0007] This invention provides a method for designing and screening sodium salts based on density functional theory, comprising the following steps:

[0008] 1) The initial molecular structure was established using the Gaussian view program, and anionic functional groups were constructed as shown in formulas (I) to (XI);

[0009]

[0010] 2) For the anionic groups constructed in the above steps, under the density functional theory level, based on the functional B3LYP and the basis set 6-311++G(d,p), the structure optimization and frequency calculation were performed in the gas phase using Gaussian 16 software.

[0011] 3) Review the structural optimization results obtained from the above steps to ensure that the structural optimization forces and displacements meet the convergence conditions;

[0012] Check the frequency calculation results obtained from the above steps to ensure that there are no negative frequencies.

[0013] 4) Use Gaussian View software to read the highest occupied / lowest unoccupied orbital, dipole moment, and enthalpy of the optimized structure;

[0014] Na was introduced into the optimized structure respectively. + The Na salt structure was established, and the optimized highest occupied orbital, lowest unoccupied orbital, dipole moment, and enthalpy were read using Gaussian View software.

[0015] 5) Organize the data obtained in the above steps to obtain the physicochemical properties of different anionic functional groups, and screen the Na salt molecular structures with high redox stability and dissociation.

[0016] Preferably, in the basis set 6-311++G(d,p), a dispersion function is introduced for the heavy atoms and hydrogen atoms in the anionic group.

[0017] Preferably, the convergence conditions include maximum force, root-mean-square force, maximum displacement, and root-mean-square displacement.

[0018] Preferably, the maximum force is <0.0004;

[0019] The root mean square force is <0.0002.

[0020] Preferably, the maximum displacement is <0.0009;

[0021] The root mean square displacement is <0.0006.

[0022] Preferably, the absence of negative frequencies specifically means: when the molecular configuration energy reaches a minimum point, the frequency calculation results are checked to determine that no negative frequencies exist.

[0023] Preferably, in step 3), when a negative frequency exists, the structure is adjusted and re-optimized.

[0024] Preferably, the Na salt molecules include Na salt molecules used in battery electrolytes;

[0025] The battery includes a sodium-ion battery.

[0026] Preferably, the screening process further includes a verification step.

[0027] Preferably, the verification step specifically includes:

[0028] The Na salt molecules obtained after screening in step 5) are combined with a solvent to form an electrolyte, which is then assembled into a battery for verification.

[0029] This invention provides a method for designing and screening sodium salts based on density functional theory, characterized by the following steps: First, an initial molecular structure is established using Gaussian View software, constructing anionic functional groups as shown in equations (I) to (XI); then, for the anionic groups constructed in the above steps, under the density functional theory level, based on the functional B3LYP and the basis set 6-311++G(d,p), structural optimization and frequency calculation are performed in the gas phase using Gaussian 16 software; subsequently, the structural optimization results obtained in the above steps are checked to ensure that the structural optimization forces and displacements meet the convergence conditions; the frequency calculation results obtained in the above steps are checked to ensure that no negative frequencies exist; then, Gaussian View software is used to read the highest occupied orbital / lowest unoccupied orbital, dipole moment, and enthalpy of the optimized structure; and Na is introduced into the optimized structure respectively. + The structure of Na salt was established, and Gaussian View software was used to read the optimized highest occupied orbital, lowest unoccupied orbital, dipole moment, and enthalpy. Finally, the data obtained from the above steps were processed to obtain the physicochemical properties of different anionic functional groups, and Na salt molecular structures with high redox stability and dissociation were screened. Compared with existing technologies, this invention suggests that using density functional theory (DFT) as a simple and inexpensive method for structure prediction is an important and effective approach. Furthermore, based on existing difluorodioxalic acid phosphate (DFOP)... - ), difluorooxalate boric acid (DFOB) - ) and boric acid dioxalate (BOB) - The structure was designed using anionic groups. Among them, DFOP... - and DFOB - Both have the effect of reducing impedance, but they are not resistant to high temperatures. Methylene methane disulfonate (MMDS), on the other hand, has better high-temperature performance. Therefore, when designing anionic functional groups, the -S(=O)2 group in MMDS is introduced to improve the high-temperature performance of the sodium salt.

[0030] Based on this, the present invention specifically designed a sodium salt molecular structure design and screening scheme for sodium-ion batteries. According to density functional theory, the highest occupied orbital and lowest unoccupied orbital (HOMO / LUMO) and dissociation energy of the novel sodium salt molecular structure were analyzed using frontier molecular orbital theory, and a novel sodium salt molecular structure with redox stability and high degree of dissociation was obtained.

[0031] This invention proposes a method for designing novel sodium salt structures based on small molecule functional group substitution and density functional theory, utilizing quantum mechanical DFT calculations to analyze DFOP. - DFOB - and BOB - The redox properties of functional groups are theoretically studied, and the geometric and electronic structures of sodium salts are analyzed in depth. New sodium salt structures with high redox stability and dissociation are developed, which greatly reduces the human and material resources required for sodium salt structure design and also reduces the corresponding time costs.

[0032] Experimental results show that this invention utilizes quantum mechanical DFT theory to calculate DFOP. - DFOB - and BOB - The redox properties of functional groups were theoretically studied, and the molecular configuration and electronic structure of sodium salt were analyzed theoretically, avoiding a large number of chemical experiments. A novel sodium salt structure, codenamed NaDFOP-2SO2, was screened out. Its theoretical redox stability and degree of dissociation were significantly improved. The electrolyte prepared with NaDFOP-2SO2 was verified to have better conductivity by constant potential polarization method and electrochemical impedance spectroscopy. Sodium salt codenamed NaDFOP-2SO2 can be used as a superior new sodium salt for production and preparation. Attached Figure Description

[0033] Figure 1 The structural formula of the novel anionic group screened by the method for screening sodium salts provided by this invention. Detailed Implementation

[0034] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention and not for limiting the claims of the present invention.

[0035] All terms and abbreviations used in this invention are conventional terms and abbreviations in the field. Each term and abbreviation is clear and distinct in its relevant application area, and those skilled in the art can understand it clearly, accurately, and uniquely based on the terms and abbreviations.

[0036] This invention provides a method for designing and screening sodium salts based on density functional theory, comprising the following steps:

[0037] 1) The initial molecular structure was established using the Gaussian view program, and anionic functional groups were constructed as shown in formulas (I) to (XI);

[0038]

[0039]

[0040] 2) For the anionic groups constructed in the above steps, under the density functional theory level, based on the functional B3LYP and the basis set 6-311++G(d,p), the structure optimization and frequency calculation were performed in the gas phase using Gaussian 16 software.

[0041] 3) Review the structural optimization results obtained from the above steps to ensure that the structural optimization forces and displacements meet the convergence conditions;

[0042] Check the frequency calculation results obtained from the above steps to ensure that there are no negative frequencies.

[0043] 4) Use Gaussian View software to read the highest occupied / lowest unoccupied orbital, dipole moment, and enthalpy of the optimized structure;

[0044] Na was introduced into the optimized structure respectively. + The Na salt structure was established, and the optimized highest occupied orbital, lowest unoccupied orbital, dipole moment, and enthalpy were read using Gaussian View software.

[0045] 5) Organize the data obtained in the above steps to obtain the physicochemical properties of different anionic functional groups, and screen the Na salt molecular structures with high redox stability and dissociation.

[0046] This invention first uses the Gaussian view program to establish the initial molecular structure and constructs anionic functional groups as shown in formulas (I) to (XI).

[0047]

[0048]

[0049] In this invention, the anionic groups constructed in the above steps are further optimized and their frequencies are calculated in the gas phase using Gaussian 16 software at the density functional theory level, based on the functional B3LYP and the basis set 6-311++G(d,p).

[0050] In this invention, in the basis set 6-311++G(d,p), dispersion functions are preferably introduced for the heavy atoms and hydrogen atoms in the anionic groups. Specifically, 6-311G is a basis set with good speed and accuracy, and the molecular structure in this invention consists of anionic groups and sodium salts involving weak interactions, with obvious local negative charges. To obtain energy changes more accurately, and to be more suitable for the analysis of the highest occupied orbital, lowest unoccupied orbital, dipole moment, dissociation energy, and enthalpy, polarization and dispersion functions are introduced on this basis set.

[0051] The present invention then examines the structural optimization results obtained from the above steps to ensure that the structural optimization forces and displacements meet the convergence conditions.

[0052] Check the frequency calculation results obtained from the above steps to ensure that there are no negative frequencies.

[0053] In this invention, the convergence conditions preferably include maximum force, root mean square force, maximum displacement, and root mean square displacement.

[0054] In this invention, the maximum force is preferably <0.0004, more preferably <0.0003, and even more preferably <0.0002.

[0055] In this invention, the root mean square force is preferably <0.0002, more preferably <0.00015, and even more preferably <0.0001.

[0056] In this invention, the maximum displacement is preferably <0.0009, more preferably <0.0008, and even more preferably <0.0007.

[0057] In this invention, the root mean square displacement is preferably <0.0006, more preferably <0.0005, and even more preferably <0.0004.

[0058] In this invention, the absence of negative frequencies is preferably determined by checking the frequency calculation results when the molecular configuration energy reaches a minimum point, thus confirming the absence of negative frequencies.

[0059] In this invention, in step 3), when a negative frequency exists, it is preferable to adjust the structure for re-optimization.

[0060] The present invention then used Gaussian View software to read the highest occupied orbital / lowest unoccupied orbital, dipole moment, and enthalpy of the optimized structure;

[0061] Na was introduced into the optimized structure respectively. + The Na salt structure was established, and the optimized highest occupied orbital, lowest unoccupied orbital, dipole moment, and enthalpy were read using Gaussian View software.

[0062] In this invention, the Na salt molecules preferably include Na salt molecules used in battery electrolytes.

[0063] In this invention, the battery preferably comprises a sodium-ion battery.

[0064] Finally, this invention organizes the data obtained from the above steps to obtain the physicochemical properties of different anionic functional groups, and screens Na salt molecular structures with high redox stability and dissociation.

[0065] In this invention, the screening process preferably includes a verification step.

[0066] In this invention, the verification step preferably includes:

[0067] The Na salt molecules obtained after screening in step 5) are combined with a solvent to form an electrolyte, which is then assembled into a battery for verification.

[0068] This invention aims to complete and refine the overall technical solution, improve the timeliness of the method for designing and screening sodium salts, further reduce time, manpower, and material costs, and improve the accuracy of screening results. The aforementioned method for designing and screening novel sodium salts based on density functional theory may specifically include the following steps:

[0069] This invention addresses the functional groups of existing lithium salt anions by proposing a small-molecule functional group substitution method and a simulation method for designing novel sodium salt structures based on density functional theory and frontier molecular orbital theory to analyze the highest occupied orbitals (HOMO) and lowest unoccupied orbitals (LUMO) and dissociation energies of the molecular structure.

[0070] 1. Use Gaussian View to establish the initial molecular structure and construct the following anionic functional groups;

[0071]

[0072] 2. For each anionic group, at the density functional theory (DFT) level, using functional B3LYP and basis set 6-311++G(d,p) (with dispersion functions added for both heavy atoms and hydrogen atoms), the structure was optimized and the frequency was calculated in the gas phase using Gaussian 16 software.

[0073] 3. Check the optimization results and ensure that the optimized force and displacement meet the four convergence conditions: maximum force < 0.0004, root mean square force < 0.0002, maximum displacement < 0.0009, root mean square displacement < 0.0006, molecular configuration energy reaches the minimum point, and check the frequency to ensure that there are no negative frequencies. If negative frequencies exist, the structure needs to be adjusted and optimized again.

[0074] 4. Use Gaussian View software to read the optimized highest occupied orbital, lowest unoccupied orbital (HOMO / LUMO), dipole moment, and enthalpy (for calculating the dissolution free energy);

[0075] 5. Introduce Na into the optimized structure respectively. + Ions, establish Na salt structure, repeat the above process, and read the optimized HOMO / LUMO, Dipole Moment and enthalpy;

[0076] 6. Organize the data and derive the physicochemical properties of different anionic functional groups;

[0077] 7. Screen and verify novel Na salt molecular structures with high redox stability and dissociation.

[0078] This invention utilizes quantum mechanical DFT theory to calculate DFOP. - DFOB - and BOB - The redox properties of functional groups were theoretically studied, and the geometric and electronic structures of sodium salts were analyzed in depth to develop novel sodium salt structures with high redox stability and dissociation.

[0079] The present invention provides a method for designing and screening novel sodium salts based on density functional theory, and novel sodium salt molecular structures with high redox stability and dissociation degree. Specifically, the present invention designs and screens sodium salt molecular structures for sodium-ion batteries. Based on density functional theory, it uses frontier molecular orbital theory to analyze the highest occupied orbital (HOMO) and lowest unoccupied orbital (LUMO) and dissociation energy of novel sodium salt molecular structures, resulting in novel sodium salt molecular structures with high redox stability and dissociation degree.

[0080] This invention proposes a method for designing novel sodium salt structures based on small molecule functional group substitution and density functional theory, utilizing quantum mechanical DFT calculations to analyze DFOP. - DFOB - and BOB - The redox properties of functional groups are theoretically studied, and the geometric and electronic structures of sodium salts are analyzed in depth. New sodium salt structures with high redox stability and dissociation are developed, which greatly reduces the human and material resources required for sodium salt structure design and also reduces the corresponding time costs.

[0081] Experimental results show that this invention utilizes quantum mechanical DFT theory to calculate DFOP. - DFOB - and BOB -The redox properties of functional groups were theoretically studied, and the molecular configuration and electronic structure of sodium salt were analyzed theoretically, avoiding a large number of chemical experiments. A novel sodium salt structure, codenamed NaDFOP-2SO2, was screened out. Its theoretical redox stability and degree of dissociation were significantly improved. The electrolyte prepared with NaDFOP-2SO2 was verified to have better conductivity by constant potential polarization method and electrochemical impedance spectroscopy. Sodium salt codenamed NaDFOP-2SO2 can be used as a superior new sodium salt for production and preparation.

[0082] To further illustrate the present invention, the following describes in detail a method for designing and screening sodium salts based on density functional theory, provided by the present invention, with reference to embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, only to further illustrate the features and advantages of the present invention, and not to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0083] Example 1

[0084] 1. Create a DFOB using Gaussian View - DFOB-2SO2 - and DFOB-Si(CH3)3 - ;DFOP, DFOP-2SO2, DFOP-SO2, DFOP-N and DFOP-S; BOB, BOB-SO2 - BOB-2SO2 - And the initial molecular structure model of DFOB-Si(CH3)3.

[0085] 2. After building the model, optimize the structure of the anionic groups and install a frequency meter. The settings are as follows:

[0086] #opt freq b3lyp / 6-311++g(d,p)

[0087] -1 1

[0088] 3. Submit the task on Gaussian 16w and perform the calculations.

[0089] 4. Read the optimized *.log file to check for the presence of virtual frequencies.

[0090] 5. If no imaginary frequency exists, select Results-Summary to read the Dipole Moment and EE+ThermalEnthalpy Correction values, and select Mo Editor to read the HOMO and LUMO values.

[0091] 6. Add Na to the above structure + Ions, structural optimization of sodium salts, and frequency meters.

[0092] The settings are as follows:

[0093] #opt freq b3lyp / 6-311++g(d,p) 0 1

[0095] 7. Repeat the above process to read the optimized HOMO / LUMO, Dipole Moment, and enthalpy, and organize the data.

[0096] See Table 1, which shows the HOMO and LUMO of three different sodium salts based on the DFOB-anionic group in Example 1 of this invention, as well as their dissociation energies.

[0097] Table 1

[0098]

[0099] When molecules or ions undergo oxidation, they lose electrons. The HOMO energy determines the oxidative stability of the molecule or ion. The higher the HOMO, the less bound the electrons are, and the easier it is for them to jump; the lower the HOMO, the more bound the electrons are, and the better the antioxidant capacity (high voltage). When molecules or ions undergo reduction, they gain electrons. The LUMO energy determines the reduction stability of the molecule or ion. The lower the LUMO, the easier it is to accept foreign electrons; the higher the LUMO, the less likely it is to gain electrons, and the better the reduction resistance. Dissociation energy is a physical quantity that evaluates the strength of chemical bonds. Generally speaking, the lower the dissociation energy of an electrolyte salt, the greater the degree of dissociation, the more ions that can conduct electricity, and the greater the ionic conductivity.

[0100] Table 1 shows the HOMO, LUMO, and dissociation energies of three different sodium salts based on the DFOB-anionic group. It can be seen that the trends of HOMO and LUMO in sodium salts differ from those of the anionic groups. The HOMO of NaDFOB-Si(CH3)3 is -6.91 eV, and the LUMO is -1.77 eV, both slightly higher than that of NaDFOB, indicating that the introduction of trimethylsilane Si(CH3)3 reduces the antioxidant capacity of the sodium salt while improving its anti-reduction capacity. NaDFOB-SO2 has the lowest HOMO energy at -9.22 eV and the highest LUMO energy at -1.63 eV, indicating the highest redox stability. However, the dissociation energies of NaDFOB-2SO2 and NaDFOB-Si(CH3)3 are 124.49 and 124.30 kcal / mol, respectively, both slightly higher than that of NaDFOB. This indicates a decrease in the degree of dissociation of the anionic groups in both novel structures, which is unfavorable for the transfer of Na ions.

[0101] Referring to Table 2, Table 2 shows the HOMO\LUMO and dissociation energy of five different sodium salts based on DFOP-anion groups in Example 1 of the present invention.

[0102] Table 2

[0103]

[0104] It can be seen from the HOMO\LUMO and dissociation energy of five different sodium salts based on DFOP-anion groups shown in Table 2 that the HOMO energy level presents a trend of NaDFOP-2SO2<NaDFOP-SO2<NaDFOP<NaDFOP-N<NaDFOP-S. The LUMO energy presents a trend of NaDFOP-SO2>NaDFOP-2SO2>NaDFOP>NaDFOP-S>NaDFOP-N. The dissociation energy presents a trend of NaDFOP-2SO2<NaDFOP-S<NaDFOP-SO2<NaDFOP<NaDFOP-N. After sulfo group substitution on the DFOP-anion group, the redox stability of the novel ionic structure is improved to a certain extent. The dissociation energy of NaDFOP-SO2 decreases slightly compared with that of NaDFOP, while the dissociation energy of NaDFOP-2SO2 is only 44% of that of NaDFOP, showing the maximum dissociation degree, and can be used as the optimal sodium salt structure for preparation research.

[0105] Referring to Table 3, Table 3 shows the HOMO\LUMO and dissociation energy of four different sodium salts based on BOB-anion groups in Example 1 of the present invention.

[0106] Table 3

[0107]

[0108] It can be seen from the HOMO\LUMO and dissociation energy of four different sodium salts based on BOB-anion groups shown in Table 3 that the HOMO energy level presents a trend of NaBOB-2SO2<NaBOB-SO2<NaBOB<NaBOB-Si(CH3)3. The LUMO energy presents a trend of NaBOB-SO2>NaBOB-2SO2>NaBOB>NaBOB-Si(CH3)3. The dissociation energy presents a trend of NaBOB<NaBOB-Si(CH3)3<NaBOB-2SO2<NaBOB-SO2. After sulfo group substitution on the BOB-anion group, the redox stability of the novel ionic structure is improved to a certain extent, but the dissociation degree of all novel structured sodium salts decreases significantly, leading to a reduction in ionic conductivity.

[0109] The redox properties of DFOP-, DFOB-, and BOB- functional groups were theoretically studied using quantum mechanical DFT calculations, and DFOP-2SO2 (whose molecular structure is shown in Figure 1) was selected as the redox group. Figure 1 The novel anionic group (shown) exhibits significantly improved redox stability and dissociation, making it an optimal candidate for preparation research of sodium salts.

[0110] See Figure 1 , Figure 1 The structural formula of the novel anionic group screened by the method for screening sodium salts provided by this invention.

[0111] 8. To verify the simulation results, two electrolytes were prepared in the following proportions: 30% ethylene carbonate (EC), 60% ethyl methyl carbonate (EMC), and 10% NaDFOP-2SO2; and 30% EC, 60% EMC, and 10% NaDFOP. These electrolytes were named Imp and Ori electrolytes, respectively.

[0112] Na / electrolyte / Na symmetric cells were constructed (named Imp and Ori symmetric cells, respectively). A constant potential difference of 10 mV was applied to the measured symmetric cells, and the transport number of Na+ ions was calculated using the potentiostatic polarization method. It was found that Na+ in the Imp symmetric cell... + The transport number is about 1.5 times that of the Ori symmetric cell, which is similar to the dissociation degree shown in the simulation. The novel sodium salt, codenamed NaDFOP-2SO2, exhibits better dissociation degree.

[0113] Note: All substances in the electrolyte formulation are expressed as mass percentages. The number of Na moles in the Imp electrolyte is slightly lower than that in the Ori electrolyte, resulting in a lower Na content calculated using the constant potential polarization method. + There is a certain difference between the transport number of ions and the simulated degree of dissociation.

[0114] Oral full cells of NaFePO4 / electrolyte / graphite were constructed (named Imp and Ori coin cells, respectively). Electrochemical impedance spectroscopy was used to derive the NaFePO4 / electrolyte / graphite coin cells for Imp and Ori coin cells. + The diffusion coefficients of the ions are 2.23 × 10⁻⁶. -12 and 1.56×10 -12 cm 2 / s, Imp electrolyte exhibits better conductivity.

[0115] In summary, this experiment utilizes quantum mechanical DFT theory to calculate DFOP. -The redox properties of the DFOB- and BOB- functional groups were theoretically studied, and the molecular configuration and electronic structure of sodium salt were analyzed theoretically, avoiding a large number of chemical experiments. A novel sodium salt structure, codenamed NaDFOP-2SO2, was screened out. Its theoretical redox stability and degree of dissociation were significantly improved. The electrolyte prepared with NaDFOP-2SO2 was verified to have better conductivity by constant potential polarization method and electrochemical impedance spectroscopy. Sodium salt codenamed NaDFOP-2SO2 can be used as a superior new sodium salt for production and preparation.

[0116] The foregoing has provided a detailed description of a method for designing and screening novel sodium salts based on density functional theory, and a novel sodium salt molecular structure with high redox stability and dissociation degree. Specific examples have been used to illustrate the principles and implementation methods of the invention. The above descriptions of the embodiments are merely to aid in understanding the method and core ideas of the invention, including the best mode, and to enable any person skilled in the art to practice the invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the wording of the claims, or if they include equivalent structural elements that are not substantially different from the wording of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. Application of a method for screening sodium salts based on density functional theory in screening sodium salts for sodium-ion battery electrolytes; The method for screening sodium salts based on density functional theory includes the following steps: 1) Use the Gaussian view program to establish the initial molecular structure and construct the anionic functional groups as shown in formulas (I) to (XI); (AND) (II) (III) (IV)) （V）； (VI) (VII) (VIII) (IX)) (X) (XI); 2) For the anionic groups constructed in the above steps, under the density functional theory level, based on the functional B3LYP and the basis set 6-311++G(d,p), the structure optimization and frequency calculation were performed in the gas phase using Gaussian 16 software. In the basis set 6-311++G(d,p), dispersion functions are introduced for heavy atoms and hydrogen atoms in the anionic groups; 3) Review the structural optimization results obtained from the above steps to ensure that the structural optimization forces and displacements meet the convergence conditions; The convergence conditions include maximum force, root-mean-square force, maximum displacement, and root-mean-square displacement; The maximum force is <0.0004; the root mean square force is <0.0002; the maximum displacement is <0.0009; the root mean square displacement is <0.0006; Check the frequency calculation results obtained from the above steps to ensure that there are no negative frequencies. 4) Use Gaussian View software to read the highest occupied / lowest unoccupied orbital, dipole moment, and enthalpy of the optimized structure; Na was introduced into the optimized structure respectively. + The Na salt structure was established, and the optimized highest occupied orbital, lowest unoccupied orbital, dipole moment, and enthalpy were read using Gaussian View software. 5) Organize the data obtained in the above steps, evaluate redox stability by the highest occupied orbital / lowest unoccupied orbital energy level, calculate the dissociation energy and evaluate the dissociation property by the enthalpy change between the anion and the sodium salt, and screen the Na salt molecular structure with high redox stability and dissociation property.

2. The application according to claim 1, characterized in that, The absence of negative frequencies is specifically defined as follows: when the molecular configuration energy reaches a minimum point, the frequency calculation results are checked to confirm the absence of negative frequencies.

3. The application according to claim 1, characterized in that, In step 3), if a negative frequency exists, the structure is adjusted and re-optimized.

4. The application according to claim 1, characterized in that, The screening process also includes a verification step.

5. The application according to claim 4, characterized in that, The verification steps specifically include: The Na salt molecules obtained after screening in step 5) are combined with a solvent to form an electrolyte, which is then assembled into a battery for verification.

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