A Calculation Method and System for the Theoretical Energy Density of a Sodium-Ion Battery

Abstract

The present invention provides a method and system for calculating the theoretical energy density of a sodium-ion battery, relating to the technical field of battery energy density calculation. The method includes experimentally obtaining the relationship curves between the state of charge and the potential of the positive and negative electrodes; normalizing the specific capacities of the positive and negative electrodes based on the curves to generate normalized state-of-charge curves; adjusting the abscissa scaling ratio of the corresponding normalized curve according to the excess setting of the positive or negative electrode; integrating the scaled curve in the 0-1 interval to obtain an integral value; combining the integral value, the specific capacities of the positive and negative electrodes, and the excess ratio to calculate the total energy of the battery and the total mass of the electrodes; and obtaining the theoretical energy density of the battery through the ratio of the total energy of the battery to the total mass of the electrodes. The present invention effectively solves the error problem caused by the irregularity of the platform and the capacity ratio in the traditional method, and provides a more scientific and reliable theoretical tool for the performance evaluation and optimization of sodium-ion battery materials.

Description

Technical Field

[0001] The present invention relates to the technical field of battery energy density calculation, and particularly to a method and system for calculating the theoretical energy density of a sodium-ion battery. Background Art

[0002] In the research and development and optimization of sodium-ion batteries, the accurate calculation of the theoretical energy density is a key basis for evaluating the performance and development potential of battery systems. The energy density calculation method of traditional lithium-ion batteries is usually based on the product of the voltage difference between the positive and negative electrode platforms and the equivalent specific capacity, and this method relies on the obvious charge and discharge platforms and large potential differences of the positive and negative electrode materials. However, the electrode materials of sodium-ion batteries often exhibit irregular charge and discharge platforms or long slope region characteristics, resulting in a significant deviation between the calculation results of traditional methods and the actual values.

[0003] In the prior art, researchers usually ignore the non-linear characteristics of the charge and discharge curves and directly use the average voltage or the platform voltage to replace the actually changing electric potential. This simplified treatment cannot accurately reflect the dynamic working state of sodium-ion batteries. In addition, in the scenario of the capacity ratio of the positive and negative electrodes (such as over-design), the traditional method does not consider the scaling effect of the capacity difference on the state of charge (SOC) curve, further exacerbating the calculation error. These problems make the existing methods insufficient in applicability for predicting the theoretical energy density of sodium-ion batteries and difficult to meet the high-precision research and development requirements.

[0004] Aiming at the above defects, there is an urgent need for a theoretical energy density calculation method that can accurately quantify the dynamic voltage response of sodium-ion batteries and is compatible with the over-design of the positive and negative electrodes. Summary of the Invention

[0005] Therefore, the embodiments of the present invention provide a method and system for calculating the theoretical energy density of a sodium-ion battery to solve the error problems caused by the irregularity of the platform and the capacity ratio in the traditional battery energy density calculation method in the prior art.

[0006] To solve the above problems, the embodiments of the present invention provide a method for calculating the theoretical energy density of a sodium-ion battery, and the method includes:

[0007] S1: Experimentally obtain the relationship curves between the state of charge and the electric potential of the positive electrode and the negative electrode respectively;

[0008] S2: Based on the relationship curves, perform normalization processing on the positive electrode specific capacity and the negative electrode specific capacity respectively to generate the positive electrode and negative electrode normalized state of charge curves;

[0009] S3: According to the set conditions of positive electrode excess or negative electrode excess, correspondingly adjust the abscissa scaling ratio of the positive electrode or negative electrode normalized state of charge curve;

[0010] S4: Integrate the normalized state of charge curve of the scaled positive electrode or negative electrode and the normalized state of charge curve of the negative electrode or positive electrode in the range of 0 - 1 to obtain an integral value;

[0011] S5: Calculate the total energy of the battery and the total mass of the electrodes based on the integral value, the specific capacities of the positive and negative electrodes, and the excess ratio;

[0012] S6: Obtain the theoretical energy density of the battery by taking the ratio of the total energy of the battery to the total mass of the electrodes.

[0013] Preferably, the set condition for the excess of the positive electrode is that the capacity of the positive electrode is times that of the negative electrode, where is the excess ratio; at this time, in step S3, the abscissa of the normalized state of charge curve of the positive electrode needs to be magnified by times, and the integral value A1 is obtained by integrating the scaled normalized state of charge curve of the positive electrode in the range of 0 - 1, and the integral value B1 is obtained by directly integrating the normalized state of charge curve of the negative electrode in the range of 0 - 1.

[0014] Preferably, the set condition for the excess of the negative electrode is that the capacity of the negative electrode is times that of the positive electrode, where is the excess ratio; at this time, in step S3, the abscissa of the normalized state of charge curve of the negative electrode needs to be magnified by times, and the integral value B2 is obtained by integrating the scaled normalized state of charge curve of the negative electrode in the range of 0 - 1, and the integral value A2 is obtained by directly integrating the normalized state of charge curve of the positive electrode in the range of 0 - 1.

[0015] Preferably, the calculation formula for the total energy of the battery is:

[0016] When the positive electrode is in excess,

[0017] ;

[0018] When the negative electrode is in excess,

[0019] ;

[0020] Among them, is the total energy of the battery, is the reference capacity.

[0021] Preferably, the calculation formula for the total mass of the electrodes is:

[0022] When the positive electrode is in excess,

[0023] ;

[0024] When the negative electrode is in excess,

[0025] ;

[0026] Wherein, is the total mass of the electrodes, and are the specific capacity of the positive electrode and the specific capacity of the negative electrode, respectively, is the excess ratio.

[0027] Preferably, the calculation formula of the theoretical energy density is:

[0028] When the positive electrode is in excess,

[0029] ;

[0030] When the negative electrode is in excess,

[0031] ;

[0032] Wherein, is the theoretical energy density.

[0033] Preferably, in the step S1, the relationship curve between the state of charge and the electric potential of the positive electrode and the negative electrode is obtained by the following method:

[0034] Using a sodium sheet as the counter electrode, assemble a Na-positive electrode to be measured button cell and a Na-negative electrode to be measured button cell respectively, and test the change of the electric potential during the charge and discharge process.

[0035] The embodiment of the present invention also provides a calculation system for the theoretical energy density of a sodium-ion battery, which is used to implement the above-mentioned calculation method for the theoretical energy density of a sodium-ion battery, and specifically includes:

[0036] A data acquisition module, which is used to respectively obtain the relationship curves between the state of charge and the electric potential of the positive electrode and the negative electrode through experiments;

[0037] A normalization processing module, which is used to respectively normalize the specific capacity of the positive electrode and the specific capacity of the negative electrode based on the relationship curve, and generate the normalized state of charge curves of the positive electrode and the negative electrode;

[0038] A scaling adjustment module, which is used to correspondingly adjust the horizontal coordinate scaling ratio of the normalized state of charge curve of the positive electrode or the negative electrode according to the set conditions of positive electrode excess or negative electrode excess;

[0039] An integral calculation module, which is used to integrate the scaled normalized state of charge curve of the positive electrode or the negative electrode, and the normalized state of charge curve of the negative electrode or the positive electrode in the 0-1 interval to obtain an integral value;

[0040] A battery total energy and electrode total mass calculation module, which is used to calculate the battery total energy and the electrode total mass based on the integral value, the specific capacity of the positive and negative electrodes, and the excess ratio;

[0041] An energy density calculation module, configured to obtain the theoretical energy density of the battery by the ratio of the total energy of the battery to the total mass of the electrodes.

[0042] An embodiment of the present invention further provides an electronic device, which includes a processor, a memory, and a bus system. The processor and the memory are connected through the bus system. The memory is used to store instructions, and the processor is used to execute the instructions stored in the memory to implement the above-mentioned method for calculating the theoretical energy density of a sodium-ion battery.

[0043] An embodiment of the present invention further provides a computer storage medium, which stores a computer software product. The computer software product includes several instructions for causing a computer device to execute the above-mentioned method for calculating the theoretical energy density of a sodium-ion battery.

[0044] As can be seen from the above technical solutions, the present invention application has the following beneficial effects:

[0045] (1) High calculation accuracy: In the traditional medium-pressure method, there are errors due to linear assumptions. The present invention quantifies the dynamic voltage response through integration, can more accurately handle problems in irregular charge and discharge platforms or ramp regions, avoid calculation errors caused by platform irregularities, and improve the accuracy of energy density calculation.

[0046] (2) Strong adaptability: Whether it is a design with an excessive positive electrode or an excessive negative electrode, this method can support it, and can be calculated according to different battery capacity ratio requirements, adapt to various battery design scenarios, and has good compatibility.

[0047] (3) Facilitate the improvement of R & D efficiency: It has scalability and can be integrated into battery design software, providing convenience for battery R & D personnel to quickly and accurately obtain the theoretical energy density of the battery in the design stage, accelerating the battery R & D process, and improving the overall R & D efficiency. Description of the Drawings

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly describe the drawings required in the embodiments. By referring to the drawings, the features and advantages of the present invention will be more clearly understood. The drawings are schematic and should not be construed as limiting the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Among them:

[0049] Figure 1 It is a flowchart of a method for calculating the theoretical energy density of a sodium-ion battery provided in the embodiment;

[0050] Figure 2The normalized SOC curve after scaling of the negative electrode NTP in the embodiment;

[0051] Figure 3 The normalized SOC curve of the positive electrode NFPP in the embodiment;

[0052] Figure 4 It is a block diagram of a sodium-ion battery theoretical energy density calculation system provided in the embodiment. Specific implementation mode

[0053] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Embodiment 1

[0054] To solve the error problem caused by the platform irregularity and capacity ratio in the traditional battery energy density calculation method in the prior art. As Figure 1 shown, the embodiment of the present invention proposes a sodium-ion battery theoretical energy density calculation method, and the method includes:

[0055] S1: Experimentally obtain the relationship curves between the state of charge and the potential of the positive electrode and the negative electrode respectively;

[0056] S2: Based on the relationship curves, normalize the specific capacity of the positive electrode and the negative electrode respectively to generate the normalized state of charge curves of the positive electrode and the negative electrode;

[0057] S3: According to the set conditions of positive electrode excess or negative electrode excess, correspondingly adjust the abscissa scaling ratio of the normalized state of charge curve of the positive electrode or the negative electrode;

[0058] S4: Integrate the scaled normalized state of charge curve of the positive electrode or the negative electrode and the normalized state of charge curve of the negative electrode or the positive electrode in the 0-1 interval to obtain an integral value;

[0059] S5: Based on the integral value, the specific capacities of the positive and negative electrodes and the excess ratio, calculate the total battery energy and the total electrode mass;

[0060] S6: Obtain the theoretical energy density of the battery by the ratio of the total battery energy to the total electrode mass.

[0061] As can be seen from the above technical solution, the present invention proposes a method for calculating the theoretical energy density of a sodium-ion battery. This method first obtains the relationship curves between the state of charge (SOC) and the potential of the positive and negative electrodes through experiments, which provides basic data support for subsequent accurate calculations. Then, the specific capacities of the positive and negative electrodes are normalized to generate corresponding curves, facilitating the unification of data standards and improving the accuracy and generality of calculations. Next, according to the overcharge settings of the positive and negative electrodes, the scaling ratio of the abscissa of the curve is adjusted, reflecting the compatibility of the method with different battery designs and adapting to different ratio requirements of positive / negative overcharge. Then, the integral value is obtained by integrating the scaled curve in the 0-1 interval. By integrating, the dynamic voltage response is quantified, avoiding the linear assumption error of the traditional mid-voltage method and achieving high-precision calculations. Finally, based on the integral value, the specific capacities of the positive and negative electrodes, and the overcharge ratio, the total energy of the battery and the total mass of the electrodes are calculated, and the theoretical energy density is obtained. Moreover, this method is scalable and can be integrated into battery design software to improve the R & D efficiency.

[0062] In step S1, the present invention assembles a sodium-ion button battery and obtains the relationship curves between the state of charge (SOC) and the potential of the positive and negative electrodes through experiments, specifically including:

[0063] Positive electrode test: Using a sodium sheet as the counter electrode, the positive electrode material to be tested is mixed with a conductive agent and a binder to form a pole piece, and a button battery is assembled. Charge-discharge tests are carried out under a constant current, and the change curve of the positive electrode potential with respect to SOC is recorded, denoted as , where SOC is a constant between 0 and 1, representing the depth of charge and discharge.

[0064] Negative electrode test: Similarly, using a sodium sheet as the counter electrode, the negative electrode material to be tested is mixed with a conductive agent and a binder to form a pole piece, a button battery is assembled, and the change curve of the negative electrode potential with respect to SOC is tested and recorded, denoted as .

[0065] In step S2, based on the SOC curves obtained above, the present invention normalizes the specific capacities of the positive and negative electrodes respectively to generate the normalized SOC curves of the positive and negative electrodes.

[0066] Specifically, first, the specific capacity of the positive electrode and the specific capacity of the negative electrode are normalized to the 0-1 interval, with the abscissa being the normalized capacity and the ordinate being the corresponding voltage value.

[0067] Then, the normalized SOC curves are plotted through software (such as Origin), with the abscissa range being 0-1 and the ordinate being the voltage value.

[0068] In step S3, according to the set conditions of positive overcharge or negative overcharge, the present invention correspondingly adjusts the scaling ratio of the abscissa of the normalized SOC curve of the positive or negative electrode, specifically including:

[0069] Case 1: Positive electrode excess (the capacity of the positive electrode is times that of the negative electrode, where is the excess ratio).

[0070] Magnify the abscissa of the normalized SOC curve of the positive electrode by times. For example, if the positive electrode is in excess by 20% (𝑥 = 0.2), the abscissa range is extended to 0 - 1.2 and remapped to the 0 - 1 interval (i.e., the actual SOC value is ).

[0071] The normalized SOC curve of the negative electrode remains unchanged, with the abscissa being 0 - 1.

[0072] Case 2: Negative electrode excess (the capacity of the negative electrode is times that of the positive electrode, where is the excess ratio).

[0073] Magnify the abscissa of the normalized SOC curve of the negative electrode by times, and the normalized SOC curve of the positive electrode remains unchanged.

[0074] In step S4, the present invention integrates the scaled normalized state - of - charge curve of the positive or negative electrode and the normalized state - of - charge curve of the negative or positive electrode in the 0 - 1 interval to obtain an integral value, specifically including:

[0075] When the positive electrode is in excess:

[0076] Integrate the scaled normalized SOC curve of the positive electrode in the 0 - 1 interval to obtain an integral value .

[0077] Integrate the normalized SOC curve of the negative electrode directly in the 0 - 1 interval to obtain an integral value .

[0078] When the negative electrode is in excess:

[0079] Integrate the scaled normalized SOC curve of the negative electrode in the 0 - 1 interval to obtain an integral value .

[0080] Integrate the normalized SOC curve of the positive electrode directly in the 0 - 1 interval to obtain an integral value .

[0081] In step S5, the present invention is based on the above integral values ( , , , ), the specific capacity ratio of the positive and negative electrodes ( , ) and the excess ratio ( ), calculate the total battery energy and the total electrode mass, specifically including:

[0082] When the positive electrode is in excess,

[0083] ;

[0084] ;

[0085] When the negative electrode is in excess,

[0086] ;

[0087] ;

[0088] Among them, is the total battery energy, is the total electrode mass, is the reference capacity (determined by the design capacity).

[0089] In step S6, the theoretical energy density of the battery is obtained by the ratio of the above total battery energy to the above total electrode mass. The calculation formula for the theoretical energy density is:

[0090] When the positive electrode is in excess,

[0091] ;

[0092] When the negative electrode is in excess,

[0093] ;

[0094] Among them, is the theoretical energy density.

[0095] Case 1: Taking the NTP negative electrode (specific capacity 126 mAh / g) and the NFPP positive electrode (specific capacity 70 mAh / g) as an example, the negative electrode is in excess by 20% ( ):

[0096] The integral value B2 of the normalized SOC curve of the scaled NTP negative electrode in the 0-1 interval is 2.09, as Figure 2 shown.

[0097] The integral value 𝐴2 of the normalized SOC curve of the NFPP positive electrode in the 0-1 interval is 3.04, as Figure 3 shown.

[0098] Substitute into the formula:

[0099] ;

[0100] If the energy density calculated based on the charge-discharge mid-voltage is:

[0101] ;

[0102] Compared with the traditional medium-pressure method (error 11.8%), the calculation result of the method of the present invention is closer to the measured value. Example Two

[0103] As Figure 4 shown, the present invention provides a calculation system for the theoretical energy density of a sodium-ion battery, which is used to implement the method for calculating the theoretical energy density of the sodium-ion battery in the above-mentioned Example One, and specifically includes:

[0104] A data acquisition module 100, configured to respectively obtain the relationship curves between the state of charge and the electric potential of the positive electrode and the negative electrode through experiments;

[0105] A normalization processing module 200, configured to respectively perform normalization processing on the positive electrode specific capacity and the negative electrode specific capacity based on the relationship curves, and generate the positive electrode and negative electrode normalized state of charge curves;

[0106] A scaling adjustment module 300, configured to correspondingly adjust the horizontal coordinate scaling ratio of the positive electrode or negative electrode normalized state of charge curve according to the set condition of positive electrode excess or negative electrode excess;

[0107] An integral calculation module 400, configured to integrate the scaled positive electrode or negative electrode normalized state of charge curve and the negative electrode or positive electrode normalized state of charge curve in the 0-1 interval to obtain an integral value;

[0108] A battery total energy and electrode total mass calculation module 500, configured to calculate the battery total energy and the electrode total mass based on the integral value, the positive and negative electrode specific capacities, and the excess ratio;

[0109] An energy density calculation module 600, configured to obtain the theoretical energy density of the battery by the ratio of the battery total energy to the electrode total mass.

[0110] A calculation system for the theoretical energy density of a sodium-ion battery in this embodiment is used to implement the foregoing method for calculating the theoretical energy density of a sodium-ion battery. Therefore, the specific implementation manners in the calculation system for the theoretical energy density of a sodium-ion battery can be seen in the embodiment part of the foregoing method for calculating the theoretical energy density of a sodium-ion battery. For example, the data acquisition module 100, the normalization processing module 200, the scaling adjustment module 300, the integral calculation module 400, the battery total energy and electrode total mass calculation module 500, and the energy density calculation module 600 are respectively used to implement steps S1, S2, S3, S4, S5, and S6 in the foregoing method for calculating the theoretical energy density of a sodium-ion battery. Therefore, the specific implementation manners thereof can refer to the descriptions of the corresponding various part embodiments. For the sake of avoiding redundancy, they will not be elaborated herein. Example Three

[0111] An embodiment of the present invention provides an electronic device, which includes a processor, a memory, and a bus system. The processor and the memory are connected through the bus system. The memory is used to store instructions, and the processor is used to execute the instructions stored in the memory to implement the above-mentioned method for calculating the theoretical energy density of a sodium-ion battery. Embodiment 4

[0112] An embodiment of the present invention provides a computer storage medium, which stores a computer software product. The computer software product includes several instructions for causing a computer device to execute the above-mentioned method for calculating the theoretical energy density of a sodium-ion battery.

[0113] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0114] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as the combination of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the specified functions in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0115] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device implements the specified functions in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks. These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide for implementing the specified functions in Figure 1 one process or multiple processes and / or blocks Figure 1Steps of functions specified in one or more boxes.

[0116] Obviously, the above embodiments are only examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for calculating the theoretical energy density of a sodium ion battery, characterized in that: Includes steps: S1: Obtain the relationship curves between the state of charge and potential of the positive electrode and the negative electrode respectively through experiments; S2: Based on the relationship curve, normalizing the positive electrode specific capacity and the negative electrode specific capacity respectively to generate normalized state of charge curves of the positive electrode and the negative electrode; S3: According to the set condition of positive electrode excess or negative electrode excess, the horizontal axis scaling ratio of the normalized state of charge curve of the positive electrode or the negative electrode is correspondingly adjusted; S4: integrating the scaled normalized state of charge curve of the positive electrode or the negative electrode and the normalized state of charge curve of the negative electrode or the positive electrode in the range of 0-1 to obtain an integral value; S5: Calculate the total energy of the battery and the total mass of the electrodes based on the integral value, the specific capacity of the positive and negative electrodes, and the excess ratio; S6: Obtain the theoretical energy density of the battery through the ratio of the total energy of the battery to the total mass of the electrodes.

2. The method for calculating the theoretical energy density of a sodium ion battery according to claim 1, wherein: The setting condition for the positive electrode excess is: the positive electrode capacity is (1+x) times the negative electrode capacity, where x is the excess ratio; at this time, in the step S3, the horizontal coordinate of the positive electrode normalized state of charge curve needs to be enlarged by (1+x) times, and the scaled positive electrode normalized state of charge curve is integrated in the range of 0-1 to obtain the integral value A1, and the negative electrode normalized state of charge curve is directly integrated in the range of 0-1 to obtain the integral value B1.

3. The method for calculating the theoretical energy density of a sodium ion battery according to claim 1, wherein: The setting condition for the excess of the negative electrode is: the capacity of the negative electrode is (1+x) times the capacity of the positive electrode, where x is the excess ratio; at this time, in the step S3, the horizontal coordinate of the normalized state of charge curve of the negative electrode needs to be enlarged by (1+x) times, and the scaled normalized state of charge curve of the negative electrode is integrated in the interval of 0-1 to obtain the integral value B2, and the normalized state of charge curve of the positive electrode is directly integrated in the interval of 0-1 to obtain the integral value A2.

4. The method for calculating the theoretical energy density of a sodium ion battery according to claim 2 or 3, characterized in that: The calculation formula of the total battery energy is: When the positive electrode is excessive, E = Q0·|A1-B1|; When the negative electrode is excessive, E = Q0·|A2-B2|; Among them, A1 is the integral value obtained by integrating the scaled normalized state of charge curve of the positive electrode in the interval of 0-1 when the positive electrode is in excess, B1 is the integral value obtained by directly integrating the normalized state of charge curve of the negative electrode in the interval of 0-1 when the positive electrode is in excess, A2 is the integral value obtained by directly integrating the normalized state of charge curve of the positive electrode in the interval of 0-1 when the negative electrode is in excess, B2 is the integral value obtained by integrating the scaled normalized state of charge curve of the negative electrode in the interval of 0-1 when the negative electrode is in excess, E is the total energy of the battery, and Q0 is the reference capacity.

5. The method for calculating the theoretical energy density of a sodium ion battery according to claim 4, characterized in that: The calculation formula of the total mass of the electrode is: When the positive electrode is excessive, When the negative electrode is excessive, Where m is the total mass of the electrode, C + and C - are the positive electrode specific capacity and the negative electrode specific capacity respectively, and x is the excess ratio.

6. The method for calculating the theoretical energy density of a sodium ion battery according to claim 5, characterized in that: The calculation formula of the theoretical energy density is: When the positive electrode is excessive, When the negative electrode is excessive, Here, ρ is the theoretical energy density.

7. The method for calculating the theoretical energy density of a sodium ion battery according to claim 1, wherein: In step S1, the relationship curves between the state of charge and the potential of the positive electrode and the negative electrode are obtained by: Using sodium sheets as counter electrodes, Na-tested positive electrode button cells and Na-tested negative electrode button cells were assembled to test their potential changes during charge and discharge.

8. A sodium ion battery theoretical energy density calculation system, characterized in that: The system is used to implement the sodium ion battery theoretical energy density calculation method according to any one of claims 1 to 7, specifically comprising: A data acquisition module, used to obtain the relationship curves between the charge state and the potential of the positive electrode and the negative electrode respectively through experiments; A normalization processing module, used to normalize the positive electrode specific capacity and the negative electrode specific capacity respectively based on the relationship curve to generate normalized state of charge curves of the positive electrode and the negative electrode; A scaling adjustment module, used to adjust the horizontal coordinate scaling ratio of the normalized state of charge curve of the positive electrode or the negative electrode according to the set conditions of positive electrode excess or negative electrode excess; An integral calculation module, used to integrate the scaled normalized state of charge curve of the positive electrode or the negative electrode, and the normalized state of charge curve of the negative electrode or the positive electrode in the range of 0-1 to obtain an integral value; A battery total energy and electrode total mass calculation module, used to calculate the battery total energy and electrode total mass based on the integral value, positive and negative electrode specific capacity and excess ratio; The energy density calculation module is used to obtain the theoretical energy density of the battery through the ratio of the total energy of the battery to the total mass of the electrodes.

9. An electronic device, characterized in that: The electronic device includes a processor, a memory and a bus system, the processor and the memory are connected through the bus system, the memory is used to store instructions, and the processor is used to execute the instructions stored in the memory to implement the sodium ion battery theoretical energy density calculation method according to any one of claims 1 to 7.

10. A computer storage medium, characterized in that: The computer storage medium stores a computer software product, which includes a number of instructions for enabling a computer device to execute the sodium ion battery theoretical energy density calculation method according to any one of claims 1 to 7.

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