Determination method of sodium ion battery positive electrode material, positive electrode plate and sodium ion battery

Abstract

The invention is suitable for the technical field of battery preparation, and provides a determination method of a sodium-ion battery positive electrode material, a positive electrode plate and a sodium-ion battery. The method comprises the following steps: inputting positive plate parameters corresponding to different positive electrode materials into a preset evaluation model to obtain evaluation factors output by the evaluation model; the evaluation model inputs positive plate parameters and outputs evaluation factors used for evaluating the energy density and the rapid charging capability of the sodium ion battery; the parameters of the positive plate comprise the coating amount, the resistance and the particle size of the positive plate; and determining an optimal positive electrode material according to each evaluation factor, and preparing the sodium ion battery according to the optimal positive electrode material. According to the method, the energy density and the rapid charging capacity of the sodium-ion battery can be predicted in the initial design stage of the sodium-ion battery, so that the optimal positive electrode material is determined to prepare the sodium-ion battery, repeated optimization verification is avoided while the energy density and the rapid charging capacity of the sodium-ion battery are ensured, and the reliability of the sodium-ion battery is improved. And the whole development period of the sodium ion battery is shortened.

Description

Technical Field

[0001] The present application relates to the technical field of battery preparation, and in particular to a method for determining a positive electrode material for a sodium ion battery, a positive electrode sheet, and a sodium ion battery. Background Art

[0002] Sodium is an abundant resource with a stable and low price. Therefore, sodium-ion batteries have obvious cost advantages over lithium-ion batteries. In addition, sodium-ion batteries have higher safety performance and are the most likely next-generation products to replace lithium-ion batteries. However, the energy density of sodium-ion batteries is significantly lower than that of lithium-ion batteries. How to improve the energy density of sodium-ion batteries is the key development direction of sodium-ion battery products.

[0003] At present, the methods to improve the energy density of batteries include: using positive and negative active materials with higher specific capacity, increasing the coating amount of active materials, and reducing the mass of inactive substances in the battery. However, some of the above methods have higher performance requirements for active materials, and some will reduce the fast charging ability of the battery, affecting the use of the product. Therefore, the relevant technology usually selects relatively mature positive and negative active materials, and makes multiple sodium-ion batteries based on different active materials according to different design schemes. After that, the energy density and fast charging capability of sodium-ion batteries with different design schemes are compared to screen out the design schemes that meet the requirements. However, the production cycle of sodium-ion batteries itself is relatively long, and the repeated optimization and verification in related technologies leads to a long entire development cycle of sodium-ion batteries. Summary of the invention

[0004] In view of this, the embodiments of the present application provide a method for determining a positive electrode material for a sodium ion battery, a positive electrode sheet, and a sodium ion battery to solve the technical problem that the entire development cycle of a sodium ion battery is relatively long.

[0005] In a first aspect, an embodiment of the present application provides a method for determining a positive electrode material for a sodium ion battery, the method comprising:

[0006] Inputting the positive electrode sheet parameters corresponding to different positive electrode materials into a preset evaluation model to obtain various evaluation factors output by the evaluation model; wherein the evaluation model inputs the positive electrode sheet parameters and outputs evaluation factors for evaluating the energy density and fast charging capability of the sodium ion battery; the positive electrode sheet parameters include the coating amount of the positive electrode sheet, the electrode sheet resistance of the positive electrode sheet and the particle size of the positive electrode material;

[0007] According to the evaluation factors, the optimal positive electrode material is determined, so as to prepare the sodium ion battery according to the optimal positive electrode material.

[0008] In a possible implementation, determining the optimal positive electrode material according to the evaluation factors includes:

[0009] According to the evaluation factors, determining the optimal positive electrode sheet parameters from the positive electrode sheet parameters corresponding to different positive electrode materials;

[0010] Based on the optimal positive electrode sheet parameters, the optimal positive electrode material is determined.

[0011] In a possible implementation, determining the optimal positive electrode sheet parameters from the positive electrode sheet parameters corresponding to different positive electrode materials according to the evaluation factors includes:

[0012] Determine whether each evaluation factor is within a preset factor range;

[0013] For each evaluation factor within the preset factor range, the positive electrode sheet parameter corresponding to the evaluation factor is used as the optimal positive electrode sheet parameter; wherein the preset factor range is greater than or equal to 4 and less than or equal to 8.

[0014] In a possible implementation, the particle size of the positive electrode sheet includes a particle size value corresponding to when the cumulative distribution of the particle size of the positive electrode sheet material reaches 10%, a particle size value corresponding to when the cumulative distribution of the particle size of the positive electrode sheet material reaches 50%, and a particle size value corresponding to when the cumulative distribution of the particle size of the positive electrode sheet material reaches 90%;

[0015] The expression of the evaluation model is:

[0016]

[0017] In the formula, x is the evaluation factor, C is the coating amount of the positive electrode, R is the electrode resistance of the positive electrode, and D 10 D is the particle size value corresponding to the cumulative distribution of the particle size of the positive electrode material reaching 10%, 50 D is the particle size value corresponding to the cumulative distribution of the particle size of the positive electrode material reaching 50%. 90 It is the particle size value corresponding to when the cumulative distribution of the particle size of the positive electrode material reaches 90%.

[0018] In a second aspect, an embodiment of the present application provides a device for determining a positive electrode material of a sodium ion battery, comprising:

[0019] An evaluation module is used to input the positive electrode sheet parameters corresponding to different positive electrode materials into a preset evaluation model to obtain various evaluation factors output by the evaluation model; wherein the evaluation model inputs the positive electrode sheet parameters and outputs the evaluation factors used to evaluate the energy density and fast charging capability of the sodium ion battery; the positive electrode sheet parameters include the coating amount of the positive electrode sheet, the electrode sheet resistance of the positive electrode sheet and the particle size of the positive electrode material.

[0020] A determination module is used to determine the optimal positive electrode material according to the evaluation factors, so as to prepare the sodium ion battery according to the optimal positive electrode material.

[0021] In a third aspect, an embodiment of the present application provides a positive electrode material for a sodium ion battery, wherein the positive electrode material is determined using the method for determining the positive electrode material for a sodium ion battery as described in any one of the first aspects.

[0022] In a possible implementation, the positive electrode material includes a positive electrode active material, a positive electrode conductor and a positive electrode binder;

[0023] The positive electrode active material includes at least one polyanionic compound;

[0024] The polyanionic compounds include NaFePO4, Na4Fe3(PO4)2P2O7, Na3V2(PO4)3, NaM'PO4F and Na3(VO y )2(PO4)2F 3-2y ;

[0025] Wherein, M' includes at least one of V, Fe, Mn and Ni; and y is greater than or equal to 0 and less than or equal to 1.

[0026] In a fourth aspect, an embodiment of the present application provides a positive electrode sheet for a sodium ion battery, the positive electrode sheet comprising a positive electrode current collector and a positive electrode material as described in any one of the third aspects.

[0027] In a fifth aspect, an embodiment of the present application provides a sodium ion battery, comprising a negative electrode sheet, a separator, an electrolyte, and a sodium ion battery positive electrode sheet as described in the fourth aspect.

[0028] In a possible implementation, the negative electrode sheet includes a negative electrode material and a negative electrode current collector; the negative electrode material includes a negative electrode active material, a negative electrode conductive agent and a negative electrode binder; the negative electrode active material includes hard carbon;

[0029] The diaphragm is disposed between the positive electrode sheet and the negative electrode sheet, and is used to separate the positive electrode sheet from the negative electrode sheet;

[0030] The electrolyte impregnates the positive electrode sheet and the negative electrode sheet.

[0031] It can be understood that the beneficial effects of the second to fifth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0032] The method for determining the positive electrode material of a sodium ion battery, the positive electrode sheet and the sodium ion battery provided in the embodiments of the present application are provided with an evaluation model, the evaluation model inputs the positive electrode sheet parameters including the coating amount of the positive electrode sheet, the electrode sheet resistance of the positive electrode sheet and the particle size of the positive electrode material, and outputs the evaluation factors for evaluating the energy density and fast charging capability of the sodium ion battery. Thus, the positive electrode sheet parameters corresponding to different positive electrode materials are input into the evaluation model to obtain the evaluation factors output by the evaluation model. Thereafter, the optimal positive electrode material is determined according to the evaluation factors to prepare the sodium ion battery according to the optimal positive electrode material. The present application can predict the energy density and fast charging capability of the sodium ion battery in the early stage of the design of the sodium ion battery through the evaluation model, so as to carry out targeted material selection and determine the optimal positive electrode material to prepare the sodium ion battery. While ensuring the energy density and fast charging capability of the sodium ion battery, repeated optimization verification is avoided, and the entire development cycle of the sodium ion battery is shortened.

[0033] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0035] Figure 1 It is a schematic diagram of an application scenario provided by an embodiment of the present application;

[0036] Figure 2 It is a schematic flow chart of a method for determining a positive electrode material for a sodium ion battery provided in one embodiment of the present application;

[0037] Figure 3 It is a structural schematic diagram of a device for determining a positive electrode material for a sodium ion battery provided in one embodiment of the present application. DETAILED DESCRIPTION

[0038] The present application is described more clearly below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the effects of the present application, but are not intended to limit the present application in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present application. These all fall within the scope of protection of the present application.

[0039] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0040] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0041] In the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0042] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0043] In addition, the “plurality” mentioned in the embodiments of the present application should be interpreted as two or more.

[0044] Commonly used electrode materials for sodium-ion batteries include layered transition metal oxides, polyanionic compounds, and Prussian blue compounds. Among them, polyanionic compounds are an important direction for the development of sodium-ion batteries in the future due to their advantages such as good cycle performance, good thermal stability, and low cost. However, due to the low capacity and poor conductivity of the positive electrode materials of batteries made of polyanionic compounds, the final sodium-ion battery has low energy density and poor fast charging capability. Therefore, when polyanionic compounds are used as positive electrode materials for sodium-ion batteries, the design of the positive electrode sheet is the bottleneck of the entire battery design.

[0045] In order to shorten the development cycle of sodium-ion batteries while ensuring the energy density and fast charging capability of sodium-ion batteries, the inventors found that a high coating amount of the positive electrode sheet would cause the positive electrode sheet to have poor conductivity. To solve this problem, increasing the content of the conductive agent in the positive electrode material or using a highly conductive conductive agent would increase the mass of the inactive material in the positive electrode sheet and reduce the energy density of the sodium-ion battery. In addition, the smaller the particle size of the positive electrode material, the shorter the transmission distance of the sodium ions inside the material, the lower the coating amount of the positive electrode sheet, the shorter the transmission distance of the sodium ions outside the material, and the relatively increased fast charging capability. However, as mentioned above, the low coating amount would reduce the energy density of the sodium-ion battery due to the increased mass of the inactive materials (aluminum foil, diaphragm, etc.) in the positive electrode sheet.

[0046] That is, the coating amount of the positive electrode sheet, the electrode sheet resistance and the particle size of the positive electrode material affect the energy density and fast charging capability of the battery. Therefore, we can consider the above three aspects to construct an evaluation model, which inputs the coating amount of the positive electrode sheet, the electrode sheet resistance and the particle size of the positive electrode material (positive electrode sheet parameters), and outputs an evaluation factor for evaluating the energy density and fast charging capability of the sodium ion battery. Then, the positive electrode sheet parameters corresponding to different positive electrode materials are input into the evaluation model, and each evaluation factor can be obtained. According to each evaluation factor, the optimal positive electrode material is determined to prepare a sodium ion battery according to the optimal positive electrode material. In this way, the energy density and fast charging capability of the sodium ion battery can be predicted in the early stage of the design of the sodium ion battery, so as to carry out targeted material selection, determine the optimal positive electrode material to prepare the sodium ion battery, avoid repeated optimization and verification, and shorten the development cycle.

[0047] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0048] Figure 1 Schematic diagram of an application scenario provided by an embodiment of the present application. Figure 1 As shown, the application scenario includes an electronic device, and the evaluation model is built in the electronic device.

[0049] The electronic device inputs the positive electrode sheet parameters corresponding to different positive electrode materials into a preset evaluation model, obtains the evaluation factors output by the evaluation model, and determines the optimal positive electrode material based on the evaluation factors to prepare a sodium ion battery based on the optimal positive electrode material.

[0050] Optionally, the electronic device may be a hardware device with data storage, processing and analysis functions, such as a computer.

[0051] Figure 2 FIG. 1 is a flow chart of a method for determining a positive electrode material for a sodium ion battery provided in an embodiment of the present application. Figure 2As shown, the method in the embodiment of the present application may include:

[0052] Step 201: inputting the positive electrode sheet parameters corresponding to different positive electrode materials into a preset evaluation model to obtain various evaluation factors output by the evaluation model.

[0053] The evaluation model inputs the positive electrode sheet parameters and outputs the evaluation factors for evaluating the energy density and fast charging capability of the sodium ion battery. The positive electrode sheet parameters include the coating amount of the positive electrode sheet, the electrode sheet resistance of the positive electrode sheet and the particle size of the positive electrode material.

[0054] In this embodiment, at least one of the parameters of the positive electrode sheets of different positive electrode materials is different, that is, at least one of the coating amount of the positive electrode sheets of different positive electrode materials, the electrode sheet resistance of the positive electrode sheets and the particle size of the positive electrode materials is different. The coating amount of the positive electrode sheet, that is, the coating amount of the positive electrode material, refers to the unit area amount of the positive electrode material coated on the surface of the positive electrode collector, usually the unit area mass. The electrode sheet resistance of the positive electrode sheet is used to measure the resistance of electron transmission in the positive electrode sheet, which is related to the positive electrode material, etc. The particle size of the positive electrode material includes the particle size value corresponding to the cumulative distribution of the particle size of the positive electrode sheet material when it reaches 10%, the particle size value corresponding to the cumulative distribution of the particle size of the positive electrode sheet material when it reaches 50%, and the particle size value corresponding to the cumulative distribution of the particle size of the positive electrode sheet material when it reaches 90%. Among them, the particle size value corresponding to the cumulative distribution of the particle size of the positive electrode sheet material when it reaches 10% indicates that the particles in the positive electrode material with a particle size smaller than the particle size value account for 10% of all the particles in the positive electrode material. The other two particle size values ​​included in the particle size of the positive electrode material are similar and will not be repeated this time.

[0055] Optionally, the expression for the evaluation model is:

[0056]

[0057] In the formula, x is the evaluation factor, C is the coating amount of the positive electrode, R is the electrode resistance of the positive electrode, and D 10 D is the particle size value corresponding to the cumulative distribution of the particle size of the positive electrode material reaching 10%, 50 D is the particle size value corresponding to the cumulative distribution of the particle size of the positive electrode material reaching 50%. 90 It is the particle size value corresponding to when the cumulative distribution of the particle size of the positive electrode material reaches 90%.

[0058] The above evaluation model expresses the relationship between the energy density, fast charging capability and positive electrode parameters of sodium-ion batteries. Through the evaluation model, the energy density and fast charging capability of sodium-ion batteries can be predicted in the early design stage of sodium-ion batteries, so as to carry out targeted material selection. While ensuring the energy density and fast charging capability of sodium-ion batteries, the entire development cycle of sodium-ion batteries is shortened.

[0059] Here, the coating amount, electrode sheet resistance and particle size of the positive electrode sheet of different positive electrode materials are measured, that is, the positive electrode sheet parameters of different positive electrode materials are measured, and the above-mentioned positive electrode sheet parameters are input into the evaluation model to obtain the evaluation factors output by the evaluation model. The evaluation factor is used to evaluate the energy density and fast charging capability of the sodium ion battery. In this embodiment, the larger the value of the evaluation factor, the greater the energy density of the sodium ion battery finally obtained based on the corresponding positive electrode material, and the stronger the fast charging capability.

[0060] Step 202: Determine the optimal positive electrode material according to each evaluation factor, so as to prepare a sodium ion battery according to the optimal positive electrode material.

[0061] In this embodiment, the positive electrode material includes a positive electrode active material, a positive electrode conductive agent and a positive electrode binder, and the positive electrode active material includes at least one polyanionic compound. Here, the polyanionic compound may include NaFePO4, Na4Fe3(PO4)2P2O7, Na3V2(PO4)3, NaM'PO4F and Na3(VO y )2(PO4)2F 3-2y , wherein M' includes at least one of V, Fe, Mn and Ni, and y is greater than or equal to 0 and less than or equal to 1. The positive electrode conductor may include carbon black and carbon nanotubes, and the positive electrode binder may be polyvinylidene fluoride.

[0062] In a possible implementation, when determining the optimal positive electrode material, this embodiment can determine the optimal positive electrode sheet parameters from the positive electrode sheet parameters corresponding to different positive electrode materials according to various evaluation factors, and determine the optimal positive electrode material based on the optimal positive electrode sheet parameters.

[0063] In this embodiment, the optimal positive electrode sheet parameters can be determined from different positive electrode sheet parameters according to the numerical values ​​of each evaluation factor, so that the positive electrode material corresponding to the optimal positive electrode sheet parameters is used as the optimal positive electrode material. In this way, the sodium ion battery prepared according to the optimal positive electrode material has high energy density and strong fast charging capability. At the same time, the optimal positive electrode material is determined according to the evaluation factors corresponding to different positive electrode materials, which avoids repeated optimization and verification and shortens the entire development cycle of the sodium ion battery.

[0064] In some embodiments, when determining the optimal positive electrode sheet parameters, it can be determined whether each evaluation factor is within a preset factor range, and for each evaluation factor within the preset factor range, the positive electrode sheet parameter corresponding to the evaluation factor is used as the optimal positive electrode sheet parameter. The preset factor range is greater than or equal to 4 and less than or equal to 8.

[0065] In this embodiment, the preset factor range can be obtained based on a large number of experiments. For example, the preset factor range is preferably greater than or equal to 4 and less than or equal to 8, that is, the preset factor range is [4,8]. The sodium ion battery prepared using the positive electrode material with the evaluation factor within the preset factor range has a positive electrode material that matches the electrochemical design, so the sodium ion battery has a high energy density and a strong fast charging capability.

[0066] Exemplarily, this embodiment constructs an evaluation model based on a large number of experiments. Specifically, first, different schemes are formulated, and different schemes include different positive and negative electrodes.

[0067] Different positive electrode active materials are mixed with conductive agents and binders according to a preset mass ratio, such as mixing different positive electrode active materials with conductive carbon black, conductive carbon nanotubes and binder polyvinylidene fluoride according to a mass ratio of (93-95):(1.5-3):(0-2):3. Afterwards, the obtained different positive electrode mixtures are respectively put into a mixer such as a planetary mixer with N-methylpyrrolidone (NMP) solvent to obtain different positive electrode slurries, that is, positive electrode materials. For each positive electrode material, the positive electrode material is uniformly coated on the two surfaces of the positive current collector (such as aluminum foil), and dried, rolled and cut to obtain the corresponding positive electrode sheet. Among them, positive electrode sheets with different sheet resistances are prepared by adjusting the type and content of the conductive agent.

[0068] The negative electrode active material, conductive agent, thickener and binder are mixed in a certain mass ratio, such as mixing the negative electrode active material hard carbon, conductive agent carbon black, thickener sodium carboxymethyl cellulose and binder styrene butadiene rubber (SBR) in a mass ratio of 94:2:2:2. Then, the obtained negative electrode mixture and deionized water solvent are placed in a mixer such as a planetary mixer and stirred to obtain a negative electrode slurry, that is, to obtain a negative electrode material. For the negative electrode materials in different schemes, the coating amount of the negative electrode material is determined according to the specific capacity of the negative electrode material and the negative electrode active material, as well as the specific capacity of the positive electrode material and the positive electrode active material in the scheme and the coating amount of the positive electrode material. The N / P (Negative / Positive) in different schemes is 1.1, wherein N / P refers to the ratio of the reversible capacity of the negative electrode to the reversible capacity of the positive electrode. Then, for the negative electrode material corresponding to each scheme, the negative electrode material is evenly coated on the two surfaces of the negative current collector (such as aluminum foil), and dried, rolled and cut to obtain the corresponding negative electrode sheet.

[0069] After obtaining the positive and negative electrodes of each scheme, for each scheme, the positive and negative electrodes corresponding to the scheme are vacuum dried, and then the positive electrode sheets, separators and negative electrodes are stacked in order to obtain a core package, and the core package is placed in an aluminum-plastic packaging shell for packaging and vacuum drying. Among them, the separator can be a polyethylene separator. The core package after vacuum drying is injected with electrolyte, and the electrolyte may include NaPF6, ethylene carbonate (EC), ethane methyl carbonate (EMC) and diethyl carbonate (DEC), wherein EC:EMC:DEC=1:1:1, NaPF6=1mol / L. Afterwards, the core package injected with the electrolyte is subjected to vacuum evacuation, secondary packaging, standing, pre-charging, degassing, formation and aging processes to prepare a sodium ion battery.

[0070] During preparation, the sodium-ion batteries corresponding to each scheme are designed to have the same external dimensions (including length, width and thickness) to compare the energy density and fast charging capability of sodium-ion batteries of different schemes.

[0071] First, the capacity of the prepared different sodium ion batteries was tested. For each sodium ion battery, at 25°C, it was first charged to 3.8V at a 1 / 3C constant current (1 / 3C current means that the charging current is 1 / 3 of the rated capacity of the battery), and then the constant voltage charging cutoff current was 0.05C. After standing for 10 minutes, it was discharged to 1.5V at a 1 / 3C constant current, and the discharge energy of the sodium ion battery was recorded and stood for 10 minutes. The above charge and discharge steps were cycled 3 times, and the average value of the 3 discharge energies was taken as the ratio of the battery mass of the sodium ion battery as the energy density of the sodium ion battery. In this way, the energy density of all sodium ion batteries was obtained.

[0072] Afterwards, the different prepared sodium ion batteries were charged and tested. For each sodium ion battery, at 25°C, the current was first increased by 0.5C at a charging current rate, and then charged to 3.8V, and then switched to constant voltage charging, with a constant voltage charging cutoff current of 0.05C. After that, each discharge was performed at a constant current of 1C to 1.5V, with an interval of 10 minutes between charging and discharging, and the charge and discharge cycle was fully charged after 10 cycles. The sodium ion battery after the cycle was disassembled, and the maximum charging current rate at which no sodium was precipitated at the interface of the negative electrode sheet was used to characterize the fast charging capability of the sodium ion battery. In this way, the fast charging capability of all sodium ion batteries was obtained.

[0073] The positive electrode sheet parameters corresponding to the positive electrode material in the above-mentioned sodium ion battery are measured, and an evaluation model is obtained based on the positive electrode sheet parameters, energy density and fast charging capability corresponding to all sodium ion batteries, that is, an evaluation factor for evaluating the energy density and fast charging capability of the sodium ion battery, and a relationship between the evaluation factor and the positive electrode sheet parameters are obtained, and a preset factor range is determined based on the positive electrode sheet parameters, energy density and fast charging capability corresponding to all sodium ion batteries.

[0074] The method for determining the positive electrode material of a sodium ion battery provided in an embodiment of the present application sets an evaluation model, wherein the evaluation model inputs positive electrode sheet parameters including the coating amount of the positive electrode sheet, the electrode sheet resistance of the positive electrode sheet, and the particle size of the positive electrode material, and outputs an evaluation factor for evaluating the energy density and fast charging capability of the sodium ion battery. Thus, the positive electrode sheet parameters corresponding to different positive electrode materials are input into the evaluation model to obtain each evaluation factor output by the evaluation model. Thereafter, the optimal positive electrode material is determined according to each evaluation factor, so as to prepare a sodium ion battery according to the optimal positive electrode material. The present application can predict the energy density and fast charging capability of the sodium ion battery in the early stage of the design of the sodium ion battery through the evaluation model, so as to carry out targeted material selection and determine the optimal positive electrode material to prepare the sodium ion battery. While ensuring the energy density and fast charging capability of the sodium ion battery, repeated optimization verification is avoided, thereby shortening the entire development cycle of the sodium ion battery.

[0075] As an example, Table 1 shows the positive electrode sheet parameters of the positive electrode material in the sodium ion battery corresponding to different schemes, as well as the evaluation factors obtained by inputting the positive electrode sheet parameters into the evaluation model, and the comparison of the energy density and fast charging capability of the sodium ion batteries corresponding to different schemes. As mentioned above, the maximum charging current rate at which no sodium is precipitated at the interface of the negative electrode sheet is used to characterize the fast charging capability. Generally speaking, a charging current rate of 4C to 6C is the conventional fast charging capability of a sodium ion battery. Above 6C indicates that the sodium ion battery has a higher fast charging capability, and below 4C indicates that the sodium ion battery has a poor fast charging capability. An energy density less than or equal to 113Wh / kg indicates that the energy density is relatively low, and an energy density greater than 113Wh / kg indicates that the energy density is relatively high.

[0076] Table 1

[0077]

[0078]

[0079] From the comparison of the evaluation factors corresponding to different sodium-ion batteries in Table 1, and the energy density and fast charging capability, it can be found that the sodium-ion batteries with the corresponding evaluation factors in the numerical range of 4 to 8 have higher energy density and stronger fast charging capability, that is, when the evaluation factors are in the numerical range of 4 to 8, the energy density and fast charging capability of the sodium-ion battery can be at a higher level. Therefore, in the aforementioned embodiment, the preset factor range is set to [4,8]. Here, only a part of the data is given in Table 1, and a large number of experiments have been carried out in practice.

[0080] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0081] Figure 3 Schematic diagram of the structure of a device for determining a positive electrode material of a sodium ion battery provided in one embodiment of the present application. Figure 3 As shown, the device for determining the positive electrode material of a sodium ion battery provided in this embodiment may include: an evaluation module 301 and a determination module 302.

[0082] Among them, the evaluation module 301 is used to input the positive electrode sheet parameters corresponding to different positive electrode materials into a preset evaluation model to obtain various evaluation factors output by the evaluation model; wherein the evaluation model inputs the positive electrode sheet parameters and outputs the evaluation factors used to evaluate the energy density and fast charging capability of the sodium ion battery; the positive electrode sheet parameters include the coating amount of the positive electrode sheet, the electrode sheet resistance of the positive electrode sheet and the particle size of the positive electrode material.

[0083] The determination module 302 is used to determine the optimal positive electrode material according to the evaluation factors, so as to prepare the sodium ion battery according to the optimal positive electrode material.

[0084] Optionally, the determination module 302 is further configured to:

[0085] According to the evaluation factors, determining the optimal positive electrode sheet parameters from the positive electrode sheet parameters corresponding to different positive electrode materials;

[0086] Based on the optimal positive electrode sheet parameters, the optimal positive electrode material is determined.

[0087] Optionally, the determination module 302 is further configured to:

[0088] Determine whether each evaluation factor is within a preset factor range;

[0089] For each evaluation factor within the preset factor range, the positive electrode sheet parameter corresponding to the evaluation factor is used as the optimal positive electrode sheet parameter; wherein the preset factor range is greater than or equal to 4 and less than or equal to 8.

[0090] It should be noted that the information interaction, execution process, etc. between the above-mentioned devices / units are based on the same concept as the method embodiment of the present application. Their specific functions and technical effects can be found in the method embodiment part and will not be repeated here.

[0091] An embodiment of the present application further provides a positive electrode material for a sodium ion battery, and the positive electrode material is determined using a method for determining a positive electrode material for a sodium ion battery.

[0092] Among them, the above-mentioned method for determining the positive electrode material of a sodium ion battery can be the method for determining the positive electrode material of a sodium ion battery provided in any embodiment of the present application.

[0093] As mentioned above, the positive electrode material includes a positive electrode active material, a positive electrode conductive agent and a positive electrode binder, and the positive electrode active material includes at least one polyanionic compound, and the polyanionic compound may include NaFePO4, Na4Fe3(PO4)2P2O7, Na3V2(PO4)3, NaM'PO4F and Na3(VO y )2(PO4)2F 3-2y , wherein M' includes at least one of V, Fe, Mn and Ni, and y is greater than or equal to 0 and less than or equal to 1.

[0094] Optionally, the positive electrode conductive agent may include carbon black and carbon nanotubes, and the positive electrode binder may be polyvinylidene fluoride.

[0095] An embodiment of the present application also provides a positive electrode sheet for a sodium ion battery, which includes a positive electrode collector and a positive electrode material.

[0096] For example, the positive electrode material may be the positive electrode material provided in any embodiment of the present application. The positive electrode current collector may be aluminum foil.

[0097] An embodiment of the present application further provides a sodium ion battery, which includes a negative electrode sheet, a separator, an electrolyte and a sodium ion battery positive electrode sheet.

[0098] Optionally, the above-mentioned positive electrode sheet can be the positive electrode sheet provided in any embodiment of the present application. The negative electrode sheet includes a negative electrode material and a negative electrode current collector, and the negative electrode material includes a negative electrode active material, a negative electrode conductor and a negative electrode binder, wherein the negative electrode active material includes hard carbon, the negative electrode conductor can be carbon black, and the negative electrode binder can be styrene-butadiene rubber. The negative electrode material may also include a thickener such as sodium carboxymethyl cellulose. The diaphragm is arranged between the positive electrode sheet and the negative electrode sheet to separate the positive electrode sheet and the negative electrode sheet. In practical applications, the positive electrode sheet, the diaphragm and the negative electrode sheet are stacked in sequence to obtain a core package, and the core package is placed in an aluminum-plastic packaging shell for packaging. The electrolyte impregnates the positive electrode sheet and the negative electrode sheet. In practical applications, the electrolyte is injected into the core package, where the electrolyte may include NaPF6, EC, EMC and DEC, wherein EC:EMC:DEC=1:1:1, NaPF6=1mol / L.

[0099] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0100] Those of ordinary skill in the art will appreciate that the templates, units, and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0101] If the module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal and software distribution medium.

[0102] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A method for determining a positive electrode material for a sodium ion battery, characterized in that: The method comprises: Inputting the positive electrode sheet parameters corresponding to different positive electrode materials into a preset evaluation model to obtain various evaluation factors output by the evaluation model; wherein the evaluation model inputs the positive electrode sheet parameters and outputs evaluation factors for evaluating the energy density and fast charging capability of the sodium ion battery; the positive electrode sheet parameters include the coating amount of the positive electrode sheet, the electrode sheet resistance of the positive electrode sheet and the particle size of the positive electrode material; According to the evaluation factors, the optimal positive electrode material is determined, so as to prepare the sodium ion battery according to the optimal positive electrode material.

2. The method for determining the positive electrode material of a sodium ion battery according to claim 1, characterized in that: Determining the optimal positive electrode material according to the evaluation factors includes: According to the evaluation factors, determining the optimal positive electrode sheet parameters from the positive electrode sheet parameters corresponding to different positive electrode materials; Based on the optimal positive electrode sheet parameters, the optimal positive electrode material is determined.

3. The method for determining the positive electrode material of a sodium ion battery according to claim 2, characterized in that: Determining the optimal positive electrode sheet parameters from the positive electrode sheet parameters corresponding to different positive electrode materials according to the evaluation factors includes: Determine whether each evaluation factor is within a preset factor range; For each evaluation factor within the preset factor range, the positive electrode sheet parameter corresponding to the evaluation factor is used as the optimal positive electrode sheet parameter; wherein the preset factor range is greater than or equal to 4 and less than or equal to 8.

4. The method for determining the positive electrode material of a sodium ion battery according to any one of claims 1 to 3, characterized in that: The particle size of the positive electrode sheet includes the particle size value corresponding to when the cumulative distribution of the particle size of the positive electrode sheet material reaches 10%, the particle size value corresponding to when the cumulative distribution of the particle size of the positive electrode sheet material reaches 50%, and the particle size value corresponding to when the cumulative distribution of the particle size of the positive electrode sheet material reaches 90%; The expression of the evaluation model is: In the formula, x is the evaluation factor, C is the coating amount of the positive electrode, R is the electrode resistance of the positive electrode, and D 10 D is the particle size value corresponding to the cumulative distribution of the particle size of the positive electrode material reaching 10%, 50 D is the particle size value corresponding to the cumulative distribution of the particle size of the positive electrode material reaching 50%. 90 It is the particle size value corresponding to when the cumulative distribution of the particle size of the positive electrode material reaches 90%.

5. A device for determining positive electrode materials of sodium ion batteries, characterized in that: include: An evaluation module, used for inputting the positive electrode sheet parameters corresponding to different positive electrode materials into a preset evaluation model to obtain various evaluation factors output by the evaluation model; wherein the evaluation model inputs the positive electrode sheet parameters and outputs the evaluation factors for evaluating the energy density and fast charging capability of the sodium ion battery; the positive electrode sheet parameters include the coating amount of the positive electrode sheet, the electrode sheet resistance of the positive electrode sheet and the particle size of the positive electrode material; A determination module is used to determine the optimal positive electrode material according to the evaluation factors, so as to prepare the sodium ion battery according to the optimal positive electrode material.

6. A sodium ion battery positive electrode material, characterized in that: The positive electrode material is determined by the method for determining the positive electrode material for a sodium ion battery as described in any one of claims 1 to 4.

7. The sodium ion battery positive electrode material according to claim 6, characterized in that The positive electrode material comprises a positive electrode active material, a positive electrode conductor and a positive electrode binder; The positive electrode active material includes at least one polyanionic compound; The polyanionic compounds include NaFePO4, Na4Fe3(PO4)2P2O7, Na3V2(PO4)3, NaM'PO4F and Na3(VO y )2(PO4)2F 3-2y ; Wherein, M' includes at least one of V, Fe, Mn and Ni; and y is greater than or equal to 0 and less than or equal to 1.

8. A sodium ion battery positive electrode sheet, characterized in that: The positive electrode sheet comprises a positive electrode current collector and the positive electrode material as claimed in claim 6 or 7.

9. A sodium ion battery, characterized in that: It comprises a negative electrode sheet, a separator, an electrolyte and a positive electrode sheet for a sodium ion battery as claimed in claim 8.

10. The sodium ion battery according to claim 9, characterized in that: The negative electrode sheet comprises a negative electrode material and a negative electrode current collector; the negative electrode material comprises a negative electrode active material, a negative electrode conductive agent and a negative electrode binder; the negative electrode active material comprises hard carbon; The diaphragm is disposed between the positive electrode sheet and the negative electrode sheet, and is used to separate the positive electrode sheet from the negative electrode sheet; The electrolyte impregnates the positive electrode sheet and the negative electrode sheet.

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