Method and device for analyzing solid electrolyte interfacial film of sodium ion capacitor

Abstract

The invention discloses an analysis method and device for a solid electrolyte interfacial film of a sodium ion capacitor, and relates to the technical field of sodium ion capacitors. The analysis method comprises the following steps: establishing a simulation model of the solid electrolyte interfacial film of the sodium ion capacitor; in a preset simulation environment, performing finite element solution on the simulation model according to the actual control parameters, and performing simulation to obtain electrodeposition distribution parameters of sodium ions; generating a current flow velocity distribution diagram in the internal space of the sodium ion capacitor based on a preset simulation environment and the electrodeposition distribution parameters of the sodium ions obtained through simulation; acquiring stress analysis data of the solid electrolyte interfacial film according to a preset stress analysis rule on the basis of the electrodeposition distribution parameters of the sodium ions and the current flow velocity distribution diagram; according to the technical scheme, the design and optimization process of the sodium ion capacitor is simplified.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion capacitors, and in particular to an analysis method and device for a solid electrolyte interface film of a sodium ion capacitor. Background Art

[0002] Sodium-ion capacitors (SICs) have the advantages of low cost, high safety, and recyclable materials, and therefore have good application prospects in the next generation of energy storage technologies. However, the poor low-temperature performance of SICs limits their practical application. Current research generally only improves the low-temperature performance of SICs through a combination of electrolyte optimization, interface engineering, advanced characterization, and other means. Similar to sodium-ion batteries (SIBs), the formation and stability of the solid electrolyte interface film (SEI) in SICs and its relationship with charge and discharge current are key factors affecting their performance (such as cycle life, rate performance, and safety). For example, the charge and discharge current density directly regulates the kinetic formation process, chemical composition, and mechanical stability of the SEI, thereby affecting sodium ion transport and electrode / electrolyte interface stability. When the current exceeds the critical current density (CCD), the SEI will rupture and sodium dendrites will grow. Therefore, the design of SICs often needs to focus on the mechanical properties and interface contact characteristics of the electrolyte interface film.

[0003] Under low-temperature conditions, the formation and properties of SEI in sodium-ion capacitors will change significantly compared to room temperature, and their performance is often affected by microscopic atomic-scale characteristics. However, the microstructure of SEI in sodium-ion capacitors under low-temperature conditions is complex, and experimental methods cannot directly observe dynamic changes at the atomic level. Currently, computational material simulation has been widely used in the research of solid battery materials, including the research of electrode and electrolyte materials, especially first-principles calculations and high-throughput machine learning, which are undoubtedly powerful tools for new material screening and device performance research. However, the current research on the surface structure and performance of SEI in sodium-ion capacitors still lacks an effective theoretical model, which restricts the development of related sodium-ion capacitor products. Summary of the Invention

[0004] The present invention provides a method and device for analyzing the solid electrolyte interface film of a sodium ion capacitor, aiming to efficiently explore the laws of the SEI structure and surface stability of the sodium ion capacitor through finite element simulation, so as to simplify the design and optimization process of the sodium ion capacitor.

[0005] The method for analyzing the solid electrolyte interface film of a sodium ion capacitor provided by the present invention comprises the following steps:

[0006] S1, establishing a simulation model of a solid electrolyte interface membrane of a sodium ion capacitor; the simulation model includes an electrode substrate and an internal space of a sodium ion capacitor provided thereon, wherein the surface of the electrode substrate has a serrated structure and is covered with a solid electrolyte interface membrane, and the internal space of the sodium ion capacitor is filled with a sodium ion electrolyte;

[0007] S2, in a preset simulation environment, performing finite element solution on the simulation model according to actual control parameters to simulate and obtain distribution parameters of sodium ion electrodeposition;

[0008] S3, generating a current flow velocity distribution diagram in the internal space of the sodium ion capacitor based on the preset simulation environment and the simulated sodium ion electrodeposition distribution parameters;

[0009] S4, based on the sodium ion electrodeposition distribution parameter and the current flow rate distribution diagram, obtaining stress analysis data of the solid electrolyte interface film according to a preset stress analysis rule.

[0010] Optionally, in step S4, the preset stress analysis rules include:

[0011] The contact between sodium ions and solid electrolyte interface membrane is equivalent to a ball / plate contact model;

[0012] In the ball / plate contact model, the functional relationship between the von Mises stress in the contact area and the x-coordinate satisfies the following equation:

[0013] ;in

[0014] Where P represents von Mises stress, represents the load per unit length, represents the combined elastic modulus, represents the combined radius;

[0015] Among them, the combined elastic modulus Calculated by the following formula:

[0016]

[0017] Where, and represent the Young's modulus of the interface film between sodium ions and solid electrolyte, and represent the Poisson's ratio of the sodium ion and solid electrolyte interface film respectively;

[0018] Combined radius Calculated by the following formula:

[0019]

[0020] Where, represents the radius of the sodium ion, represents the curvature radius of the solid electrolyte interface film.

[0021] Optionally, in step S4, the preset stress analysis rule further includes:

[0022] The displacement of the interface between the sodium ions and the solid electrolyte interface membrane is represented by the local curvature K, which is calculated by the following formula:

[0023]

[0024] Where, represents the local curvature, and Represents coordinate variables in two perpendicular directions.

[0025] Optionally, in step S2, the preset simulation environment includes a preset sodium ion transmission rule;

[0026] The sodium ion transport rule satisfies the following mass conservation equation:

[0027]

[0028] Where, represents the concentration gradient, represents the flux, Indicates flux The divergence of

[0029] Among them, the flux of sodium ions in the electrolyte and the solid electrolyte interface membrane satisfies the following formula:

[0030]

[0031] Where, 、 、 、 、 They represent the transfer vector, diffusion coefficient, concentration, ion mobility, and potential of sodium ions in the electrolyte respectively; 、 、 、 、 represent the transfer vector, diffusion coefficient, concentration, ion mobility, and potential of sodium ions in the solid electrolyte interface film, respectively; Represents the charge of the sodium ion.

[0032] Optionally, in step S2, the preset simulation environment further includes a preset sodium ion deposition rule;

[0033] The sodium ion deposition rule satisfies the modified Butler-Volmer equation:

[0034]

[0035] Where, represents the local current density, represents the exchange current density, α and β are the anodic and cathode transfer coefficients respectively, represents overpotential, R is the gas constant, T is the thermodynamic temperature, F is the Faraday constant, represents the change in electrochemical potential caused by local strain;

[0036] in, and represent the sodium ion concentrations in the electrolyte near the electrode substrate and in the solid electrolyte interface film, respectively, and satisfy the following formula:

[0037]

[0038] Where, represents the current density, t represents the reaction time, is the Boltzmann constant, Represents the ionic conductivity in the solid electrolyte interface membrane.

[0039] Optionally, the sodium ion deposition rule further includes obtaining an expression for the anode equilibrium potential according to the modified Butler-Volmer equation:

[0040]

[0041] Where, is the anode equilibrium potential, is the standard electrode potential, It represents the stoichiometric coefficient of sodium ions participating in the electrode chemical reaction;

[0042] The boundary conditions of the sodium ion deposition reaction are set to satisfy the following equation:

[0043]

[0044] Where, represents the sodium ion flux.

[0045] Optionally, the sodium ion deposition rule further includes:

[0046] The electrochemical potential change caused by local strain Corrected to deformation parameters ;

[0047] The deformation parameters Expressed as:

[0048]

[0049]

[0050] Where, and represent the partial molar volumes of sodium atoms and sodium salts, respectively. represents the migration number of sodium ions, and represent the surface energy and surface gradient respectively, is the normal vector of the interface between the sodium atom and the solid electrolyte interface film, and denote the deviatoric stress of sodium atoms and solid electrolyte interface film, respectively, and represent the hydrostatic stress of sodium atoms and solid electrolyte interface film, respectively;

[0051] If two-dimensional calculation is used, It is expressed as the local curvature K.

[0052] Optionally, the method for analyzing the solid electrolyte interface film of a sodium ion capacitor further comprises the steps of:

[0053] S5, dynamically cycling steps S2-S4; wherein, after each step S4 is performed, the stress and strain caused by the local deformation of the solid electrolyte interface membrane are applied to the next step S2;

[0054] Based on the dynamic simulation process, it is detected whether there is a current flow dead zone or an area where the current flow velocity is less than a preset flow velocity in the dynamically changing current flow velocity distribution diagram; if there is a current flow dead zone or an area where the current flow velocity is less than the preset flow velocity in the current flow velocity distribution diagram of at least one cross section, the stress analysis data of the solid electrolyte interface membrane is obtained.

[0055] The present invention also provides an analysis device for the solid electrolyte interface film of a sodium ion capacitor.

[0056] The device comprises:

[0057] A simulation model establishment module, configured to establish a simulation model of a solid electrolyte interface membrane of a sodium ion capacitor; the simulation model includes an electrode substrate and an internal space of a sodium ion capacitor disposed thereon, wherein the surface of the electrode substrate has a serrated structure and is covered with a solid electrolyte interface membrane, and the internal space of the sodium ion capacitor is filled with a sodium ion electrolyte;

[0058] Simulation environment setting module, used to set sodium ion transmission rules and sodium ion deposition rules;

[0059] A simulation calculation module is used to dynamically simulate the simulation model according to actual control parameters to obtain the sodium ion electrodeposition distribution parameters and the current flow velocity distribution diagram in the internal space of the sodium ion capacitor;

[0060] Cross-section generation module, used to intercept the current velocity distribution diagram during dynamic simulation;

[0061] The analysis and processing module is used to analyze and process the intercepted current velocity distribution diagram and its corresponding electrodeposition distribution parameters, and obtain stress analysis data of the solid electrolyte interface film according to preset stress analysis rules.

[0062] The present invention also provides a computer device.

[0063] The computer device includes a memory and a processor; the memory stores a computer program, and the processor implements the above-mentioned analysis method of the sodium ion capacitor solid electrolyte interface film when executing the computer program.

[0064] The present invention has the following beneficial effects:

[0065] The solid electrolyte interface membrane simulation model established by the present invention takes into account the structural fluctuations caused by defects in sodium ion capacitors during the cycle process, abstracts the growth of the solid electrolyte interface membrane into a sawtooth structure, and through the design of reasonable sodium ion transmission rules and sodium ion deposition rules, performs finite element simulation on the theoretical model according to actual control parameters to obtain the electrodeposition distribution parameters and current flow rate distribution diagram of sodium ions in the simulation model. The electrodeposition distribution parameters and current flow rate distribution diagram are analyzed and processed to obtain the stress and strain data of the target solid electrolyte interface membrane. The technical solution of the present invention provides an accurate automated simulation calculation method for the study of the growth mechanism, structure and performance of the solid electrolyte membrane of sodium ion capacitors under low temperature conditions, greatly simplifying the design and optimization process of sodium ion capacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0067] Figure 1 Schematic diagram of the process of some embodiments of the method for analyzing the solid electrolyte interface film of a sodium ion capacitor of the present invention;

[0068] Figure 2 Schematic diagram of the overall structure of some embodiments of the simulation model of the solid electrolyte interface membrane of the sodium ion capacitor of the present invention;

[0069] Figure 3 Graphs of electrodeposition distribution parameters for some embodiments of the method for analyzing the solid electrolyte interface film of a sodium ion capacitor according to the present invention;

[0070] Figure 4 A cross-sectional current velocity distribution diagram during a dynamic simulation of some embodiments of the method for analyzing the solid electrolyte interface film of a sodium ion capacitor of the present invention;

[0071] Figure 5 Graphs showing stress analysis data for some embodiments of the method for analyzing the solid electrolyte interface film of a sodium ion capacitor according to the present invention. DETAILED DESCRIPTION

[0072] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0073] In the present invention, the terms "comprise" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0074] Sodium ion capacitors are an emerging energy storage device that combines the advantages of high energy density of sodium ion batteries and high power density of supercapacitors. Their principle is based on two charge storage mechanisms: double-layer capacitance and faradaic pseudocapacitance. At the electrode / electrolyte interface, double-layer capacitance is formed by ion adsorption and desorption, and the electrode material undergoes redox reaction with sodium ions to produce faradaic pseudocapacitance.

[0075] The solid electrolyte interface film (abbreviated as SEI) is a film covering the electrode surface formed by the reaction of electrons on the electrode surface with sodium ions and decomposition products in the electrolyte. These compounds polymerize and deposit on the electrode surface to form a layer of film; SEI allows sodium ions to be transported quickly, providing a channel for the migration of sodium ions between the electrolyte and the electrode, while blocking the passage of electrons, preventing the electrolyte from being further electrolyzed, reducing the corrosion and erosion of the electrolyte on the electrode, inhibiting various unnecessary side reactions, and improving the performance and cycle life of sodium ion capacitors.

[0076] Under low-temperature conditions, the formation and properties of SEI in sodium-ion capacitors will change significantly compared to room temperature, which in turn has many effects on the electrochemical performance; the study of SEI at low temperatures stems from the application needs of sodium batteries in extreme environments, and the technical challenges are concentrated on the unclear film formation mechanism, poor interface dynamics, and insufficient mechanical stability; current research generally improves low-temperature performance through electrolyte optimization, interface engineering, advanced characterization and other means, but experimental methods are difficult to directly observe dynamic changes at the atomic level. It is still necessary to deeply understand the low-temperature formation rules of SEI in sodium-ion capacitors through theoretical models to promote the development of wide-temperature sodium-ion energy storage devices.

[0077] In response to the development needs of sodium ion capacitors, the present invention proposes an analysis method for the solid electrolyte interface film of sodium ion capacitors, aiming to use finite element analysis simulation to efficiently explore the laws of the SEI structure and surface stability of sodium ion capacitors, provide strong support for the screening and evaluation process of the SEI surface of sodium ion capacitors, and simplify the design and optimization process of sodium ion capacitors.

[0078] participate Figure 1 The method for analyzing the solid electrolyte interface film of a sodium ion capacitor provided by an embodiment of the present invention includes the following steps S1-S4:

[0079] S1, establish a simulation model of the solid electrolyte interface membrane of the sodium ion capacitor.

[0080] The simulation model can be generated by inputting relevant parameters into finite element simulation software. The relevant parameters include structural parameters such as the shape and size of the sodium ion capacitor, as well as material parameters such as electrode materials and electrolyte materials. These parameters are not limited in the embodiments of the present invention; it can be understood that the analysis method provided in the embodiments of the present invention is applicable to sodium ion capacitors of various shapes, sizes and materials.

[0081] The simulation model includes an electrode substrate and an internal space of a sodium ion capacitor provided thereon. The surface of the electrode substrate has a serrated structure and is covered with a solid electrolyte interface film. The internal space of the sodium ion capacitor is filled with a sodium ion electrolyte.

[0082] In an embodiment of the present invention, finite element solution refers to obtaining a suitable approximate solution for each interconnected sub-region in the solid electrolyte interface membrane simulation model after meshing under the constraints of the model boundary conditions, and then deriving the overall satisfaction conditions of the simulation model after meshing to obtain the solution of the target simulation calculation; the principle of finite element solution can refer to the relevant existing technology and will not be described in detail in the embodiment of the present invention.

[0083] In an embodiment of the present invention, in order to study the electrodeposition of Na under a coupled physical field near the electrode surface, a structured substrate must first be constructed. Usually, the surface of sodium metal should be flat after being covered with SEI, but in the repeated electroplating / stripping process, the actual surface will not be completely flat, and the defects generated during the cycle will inevitably lead to structural fluctuations. Therefore, the embodiment of the present invention abstracts this structural fluctuation as a serrated structure on the surface of the electrode substrate, so that the simulation results of the finite element analysis are closer to the actual situation. The serrated structure includes but is not limited to uniformly or unevenly arranged triangles, rectangles, trapezoids, sinusoidal waveforms, irregular polygons, etc.

[0084] For example, see Figure 2 In some feasible implementations, a two-dimensional simulation model is established, and the surface of the electrode substrate is abstracted as a serrated shape formed by continuously spaced rectangular columns (10×5μm) and covered with SEI (the thickness can be set to 1μm). The simulation area size of the entire model can be set to 41×50 , an ultrafine grid with a maximum grid size of 0.02 μm was used, and the simulated current density was set to .

[0085] It should be noted that in the following simulation process, the stress analysis data of the target SEI needs to meet certain accuracy requirements. The accuracy can be defined as the ratio of the current volume after meshing to the current volume before meshing. Usually, when establishing a simulation model, finite element analysis is used for meshing. The smaller the mesh size, the more accurate the simulation results obtained based on the simulation model, and the higher the accuracy of the corresponding stress analysis data.

[0086] S2, in a preset simulation environment, the simulation model is solved by finite element method according to the actual control parameters to simulate the electrodeposition distribution parameters of sodium ions.

[0087] Among them, the actual control parameters refer to the dynamic parameters when a single actual process is performed on the target sodium ion capacitor, including current speed, current pressure, temperature and other parameters.

[0088] The preset simulation environment includes preset sodium ion transport rules and sodium ion deposition rules.

[0089] Specifically, the embodiment of the present invention derives the mass transfer flux of sodium ions based on the Nernst–Planck equation, assuming that the electrolyte / SEI and SEI / matrix interfaces are ideal interfaces, and applies Fick's first law at these interfaces to calculate the sodium ion transport rate. The rate of ions passing through the interface depends only on the concentration gradient and the electrodeposition kinetics; the sodium ion transport rule satisfies the following mass conservation equation:

[0090]

[0091] Where, represents the concentration gradient, represents the flux, Indicates flux The divergence of .

[0092] In order to simulate the electrodeposition process of Na in the electrolyte, a 2D transient model is used. The flux of sodium ions is given by the Nernst-Planck equation, which satisfies the following equation:

[0093]

[0094] Where, 、 、 、 、 They represent the transfer vector, diffusion coefficient, concentration, ion mobility, and potential of sodium ions in the electrolyte respectively; 、 、 、 、 represent the transfer vector, diffusion coefficient, concentration, ion mobility, and potential of sodium ions in the solid electrolyte interface film, respectively; Represents the charge of the sodium ion.

[0095] In the embodiment of the present invention, the deposition process of sodium ions can be simplified as follows:

[0096]

[0097] The sodium ion deposition rule satisfies the modified Butler-Volmer equation:

[0098]

[0099] Where, represents the local current density, represents the exchange current density, α and β are the anodic and cathode transfer coefficients respectively, represents overpotential, R is the gas constant, T is the thermodynamic temperature, F is the Faraday constant, represents the change in electrochemical potential caused by local strain.

[0100] in, and represent the sodium ion concentrations in the electrolyte near the electrode substrate and in the solid electrolyte interface film, respectively, and satisfy the following formula:

[0101]

[0102] Where, represents the current density, t represents the reaction time, is the Boltzmann constant, Represents the ionic conductivity in the solid electrolyte interface membrane.

[0103] According to the modified Butler-Volmer equation, the expression of the anode equilibrium potential can be obtained:

[0104]

[0105] Where, is the anode equilibrium potential, is the standard electrode potential, It represents the stoichiometric coefficient of sodium ions participating in the electrode chemical reaction (the stoichiometric coefficient of sodium ions in the electrolyte and SEI is -1).

[0106] The anode equilibrium potential refers to the potential of the anode when there is no net current passing through the electrode, that is, when the electrode is in thermodynamic equilibrium. At this time, the rates of oxidation and reduction reactions on the anode are equal, and the charge transfer and material exchange at the electrode interface are in dynamic equilibrium.

[0107] Set the boundary conditions for the sodium ion deposition reaction, and the boundary conditions satisfy the following equation:

[0108]

[0109] Where, represents the sodium ion flux.

[0110] Based on the simulation model established in step S1, after determining the preset simulation environment according to the above-mentioned sodium ion transport rules and sodium ion deposition rules, the deposition process of sodium ions in the electrolyte on the surface of the electrode substrate and the growth process of the solid electrolyte interface film can be simulated in the simulation environment of the finite element analysis software, that is, the electrodeposition distribution parameters of the sodium ions are obtained; Figure 3 As shown, Figure 3 The four figures from top to bottom show the deposition process of sodium ions on the electrode substrate. Electrochemical reactions occur on the rectangular columns on the surface of the electrode substrate, continuously depositing sodium ions, resulting in obvious volume expansion and deformation.

[0111] S3, based on the preset simulation environment and the simulated sodium ion electrodeposition distribution parameters, generating a current flow velocity distribution diagram in the internal space of the sodium ion capacitor.

[0112] Specifically, according to the sodium ion transport rules and sodium ion deposition rules set above, the deposition process of sodium ions is dynamically simulated; in sodium ion capacitors, the current is mainly formed by the migration of sodium ions between the electrolyte and the electrode substrate, and the current flow rate reflects the rate of migration of sodium ions inside the capacitor. A higher current flow rate means that sodium ions can be transported quickly, thereby making the sodium ion capacitor have a better charge and discharge rate and rate capability; the appearance of a current flow dead zone means that there is an area or state where the current flow rate is almost zero or extremely small, which usually indicates that the electrode reaction is limited or the ion transport is blocked, and the capacitor performance is abnormal.

[0113] Since the deposition of sodium ions is a dynamic process, the current velocity distribution is also a dynamically changing process. The current velocity distribution at a specific reaction time node can be obtained by intercepting the current velocity distribution diagram in the visual simulation interface of the finite element analysis software.

[0114] For example Figure 4 As shown, Figure 4 Arrows are used to represent the current vector in the internal space of the sodium ion capacitor, and different colors are used to distinguish the different flow rates of the current (red area > yellow area > green > light blue > dark blue). Figure 4 The bd diagram shows that with the deposition of sodium ions, SEI continues to grow and the current flow rate in the space close to the electrode substrate continues to decrease, which can be intuitively reflected by the upward movement of the green area in the figure.

[0115] S4, based on the sodium ion electrodeposition distribution parameters and the current flow rate distribution diagram, obtain stress analysis data of the solid electrolyte interface film according to preset stress analysis rules.

[0116] In an embodiment of the present invention, the contact between sodium ions and the solid electrolyte interface membrane is equivalent to a sphere / plate contact model (two-dimensional circular / rectangular contact). In the established ultrafine mesh simulation model, thousands of contact units constitute the interface structure. Based on this setting, the distribution of von Mises stress and the resulting deformation can be studied.

[0117] Among them, von Mises stress is equivalent stress, which is established based on the yield criterion of the material. It comprehensively considers the complex stress state of the material and converts the three-dimensional stress state into an equivalent one-dimensional stress value.

[0118] In the ball / plate contact model, the von Mises stress in the contact area is expressed as a function of the x-coordinate as follows:

[0119] ;in

[0120] Where P represents von Mises stress, represents the load per unit length, represents the combined elastic modulus, represents the combined radius;

[0121] Among them, the combined elastic modulus Calculated by the following formula:

[0122]

[0123] Where, and represent the Young's modulus of the interface film between sodium ions and solid electrolyte, and represent the Poisson's ratio of the sodium ion and solid electrolyte interface film respectively;

[0124] Combined radius Calculated by the following formula:

[0125]

[0126] Where, represents the radius of the sodium ion, represents the curvature radius of the solid electrolyte interface film.

[0127] The chemical reaction at the interface of the sodium ion capacitor and the deformation of the solid electrolyte interface membrane will cause interface displacement between the sodium ion electrolyte and the solid electrolyte interface membrane, which will affect the performance of the capacitor. In the embodiment of the present invention, the displacement of the sodium ion and the Na-SEI interface (the interface between the solid electrolyte interface membrane) is represented by the local curvature K, and the local curvature K is calculated by the following formula:

[0128]

[0129] Where, represents the local curvature, and Represents coordinate variables in two perpendicular directions.

[0130] In actual situations, changes in the stress field will have a significant impact on the local current density. Therefore, in the dynamic simulation process of the embodiment of the present invention, the stress and strain caused by the local deformation will be applied in the subsequent simulation steps, and the parameters used for the local current density calculation will be updated for the next step of sodium ion electrodeposition.

[0131] Specifically, the analysis method of the solid electrolyte interface film of the sodium ion capacitor provided by the embodiment of the present invention further includes step S5: dynamically cycling the above steps S2-S4; wherein, after each step S4 is performed, the stress and strain caused by the local deformation of the solid electrolyte interface film is applied to the next step S2.

[0132] To this end, the electrochemical potential change caused by local strain in the modified Butler-Volmer equation needs to be included in the sodium ion deposition rule. Further modified to deformation parameters .

[0133] Deformation parameters It can be expressed as:

[0134]

[0135]

[0136] Where, and represent the partial molar volumes of sodium atoms and sodium salts, respectively. represents the migration number of sodium ions, and represent the surface energy and surface gradient respectively, is the normal vector of the interface between the Na atom and the solid electrolyte interface film, and denote the deviatoric stress of sodium atoms and solid electrolyte interface film, respectively, and represent the hydrostatic stress of sodium atoms and solid electrolyte interface film, respectively.

[0137] The stress and strain can be obtained by solving the following steady-state equations of motion:

[0138] , Represents stress

[0139] For two-dimensional simulation models, It can be defined as the local curvature K of the Na-SEI interface. Assuming that the strain of the interface is small, the stress-strain constitutive relationship can be given by Hooke's law, as shown below:

[0140]

[0141] Where E is Young's modulus, is Poisson's ratio, represents the displacement of the Na-SEI interface.

[0142] Therefore, in the deposition rule of sodium ions, the further modified Butler-Volmer equation is actually the local Faraday current density and SEI ionic conductivity , local stress , overpotential Function:

[0143]

[0144] The stress analysis data obtained by the embodiment of the method of the present invention can be found in Figure 5 , Figure 5 The stress cloud diagram and stress distribution point diagram of the relationship between the von Mises stress and the x-coordinate of the solid electrolyte interface membrane are illustrated. Among them, Figures ad show the change of local mechanical stress over time. It can be seen that the local mechanical stress of the solid electrolyte interface membrane decreases over time, which may be related to the viscoelastic relaxation effect of SEI and the self-repair and pore collapse of the local structure.

[0145] Since the current flow dead zone means an area or state where the current flow rate is almost zero or extremely small, it usually indicates that the electrode reaction is limited or the ion transmission is blocked, and the capacitor performance is abnormal; therefore, based on the dynamic simulation process of steps S1-S5 of the above embodiment, the analysis method of the solid electrolyte interface film of the sodium ion capacitor further includes the following steps:

[0146] Detect whether there is a current flow dead zone or an area where the current flow velocity is less than a preset flow velocity in the dynamically changing current flow velocity distribution diagram; if there is a current flow dead zone or an area where the current flow velocity is less than the preset flow velocity in the current flow velocity distribution diagram of at least one cross section (i.e., one frame), obtain stress analysis data of the solid electrolyte interface membrane.

[0147] For example, based on the changes in current flow velocity information, it is determined whether there is a current flow dead zone in the current flow velocity distribution diagram of each section. The area with zero current flow velocity can be used as the current flow dead zone; if there is no flow dead zone with zero current flow velocity, it can be replaced by a sub-area where the current flow velocity is less than the preset flow velocity. The preset flow velocity can be set according to actual research needs.

[0148] Furthermore, the analysis method of the solid electrolyte interface film of the sodium ion capacitor also includes the steps of calculating the sum of the flow dead zone areas of the current in the cross-sectional current velocity distribution diagram, judging the capacity loss and rate performance of the sodium ion capacitor by calculating the flow dead zone areas, and combining the stress analysis data to explore the relationship between SEI growth changes and the performance of the sodium ion capacitor.

[0149] The solid electrolyte interface membrane simulation model established in the embodiment of the method of the present invention takes into account the structural fluctuations caused by defects in the sodium ion capacitor during the cycle process, abstracts the growth of the solid electrolyte interface membrane into a serrated structure, and through the design of reasonable sodium ion transmission rules and sodium ion deposition rules, performs finite element simulation on the theoretical model according to actual control parameters to obtain the electrodeposition distribution parameters and current flow rate distribution diagram of the sodium ions in the simulation model. The electrodeposition distribution parameters and current flow rate distribution diagram are analyzed and processed to obtain the stress and strain data of the target solid electrolyte interface membrane.

[0150] The technical solution of the present invention provides an accurate automated simulation calculation method for studying the growth mechanism, structure and performance of the solid electrolyte membrane of sodium ion capacitors under low temperature conditions, greatly simplifying the design and optimization process of sodium ion capacitors.

[0151] For example, the analysis method of the solid electrolyte interface film of the sodium ion capacitor provided in the embodiment of the present invention is used to simulate sodium ion capacitors with different structures, material parameters and actual control parameters. The sodium ion capacitor design scheme that meets the requirements can be screened based on the current flow velocity distribution diagram and stress analysis data obtained by simulation.

[0152] In addition, taking into account the actual flow of current in the target solid electrolyte interface membrane, the analysis method provided by the embodiment of the present invention can set multiple cross-sectional current density distribution diagrams to correspond to the lamination process of the target sodium ion capacitor, making the analysis of sodium ion capacitors using the lamination process more convenient and accurate.

[0153] The present invention also provides an analysis device for the solid electrolyte interface film of a sodium ion capacitor.

[0154] In some embodiments, an analysis device for a sodium ion capacitor solid electrolyte interface film includes a simulation model establishment module, a simulation environment setting module, a simulation calculation module, a cross-section generation module, and an analysis and processing module.

[0155] Specifically, the simulation model establishment module is used to establish a simulation model of the solid electrolyte interface membrane of a sodium ion capacitor; the simulation model includes an electrode substrate and the internal space of the sodium ion capacitor provided thereon, the surface of the electrode substrate has a serrated structure and is covered with a solid electrolyte interface membrane, the internal space of the sodium ion capacitor is filled with a sodium ion electrolyte, and the virtual space in which the simulation model is located is ultrafinely meshed using the finite element analysis method.

[0156] The simulation environment setting module is used to set the sodium ion transmission rules and sodium ion deposition rules. The specific sodium ion transmission rules and sodium ion deposition rules are set with reference to the aforementioned method embodiment and will not be described in detail here.

[0157] The simulation calculation module is used to dynamically simulate the simulation model according to the actual control parameters to obtain the electrodeposition distribution parameters of sodium ions and the current flow rate distribution diagram in the internal space of the sodium ion capacitor; the actual control parameters refer to the kinetic parameters when a single actual process is performed on the target sodium ion capacitor, including current speed, current pressure, temperature and other parameters.

[0158] The cross-section generation module is used to intercept the current velocity distribution diagram during the dynamic simulation process.

[0159] The analysis and processing module is used to analyze and process the intercepted current velocity distribution diagram and its corresponding electrodeposition distribution parameters, and obtain stress analysis data of the solid electrolyte interface film according to the preset stress analysis rules; the specific stress analysis rules are set with reference to the aforementioned method embodiment and are not described here in detail.

[0160] The present invention also provides a computer device; the computer device includes a memory and a processor; the memory stores a computer program, and when the processor executes the computer program, the analysis method of the sodium ion capacitor solid electrolyte interface film proposed in the above embodiment is implemented.

[0161] Those skilled in the art will understand that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing related hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods; wherein, any reference to memory, storage, database or other media used in the embodiments provided by the present invention can include at least one of non-volatile and volatile memory.

[0162] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these 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 application.

Claims

1. A method for analyzing a solid electrolyte interface film of a sodium ion capacitor, characterized in that: The following steps are involved: S1, establishing a simulation model of a solid electrolyte interface membrane of a sodium ion capacitor; the simulation model includes an electrode substrate and an internal space of a sodium ion capacitor provided thereon, wherein the surface of the electrode substrate has a serrated structure and is covered with a solid electrolyte interface membrane, and the internal space of the sodium ion capacitor is filled with a sodium ion electrolyte; S2, in a preset simulation environment, performing finite element solution on the simulation model according to actual control parameters to simulate and obtain distribution parameters of sodium ion electrodeposition; S3, generating a current flow velocity distribution diagram in the internal space of the sodium ion capacitor based on the preset simulation environment and the simulated sodium ion electrodeposition distribution parameters; S4, based on the sodium ion electrodeposition distribution parameter and the current flow rate distribution diagram, obtaining stress analysis data of the solid electrolyte interface film according to a preset stress analysis rule.

2. The method for analyzing the solid electrolyte interface film of a sodium ion capacitor according to claim 1, wherein: In step S4, the preset stress analysis rules include: The contact between sodium ions and solid electrolyte interface membrane is equivalent to a ball / plate contact model; In the ball / plate contact model, the functional relationship between the von Mises stress in the contact area and the x-coordinate satisfies the following equation: ;in Where P represents von Mises stress, represents the load per unit length, represents the combined elastic modulus, represents the combined radius; Among them, the combined elastic modulus Calculated by the following formula: Where, and represent the Young's modulus of the interface film between sodium ions and solid electrolyte, and represent the Poisson's ratio of the sodium ion and solid electrolyte interface film respectively; Combined radius Calculated by the following formula: Where, represents the radius of the sodium ion, represents the curvature radius of the solid electrolyte interface film.

3. The method for analyzing the solid electrolyte interface film of a sodium ion capacitor according to claim 2, wherein: In step S4, the preset stress analysis rules further include: The displacement of the interface between the sodium ions and the solid electrolyte interface membrane is represented by the local curvature K, which is calculated by the following formula: Where, represents the local curvature, and Represents coordinate variables in two perpendicular directions.

4. The method for analyzing the solid electrolyte interface film of a sodium ion capacitor according to claim 1, wherein: In step S2, the preset simulation environment includes preset sodium ion transmission rules; The sodium ion transport rule satisfies the following mass conservation equation: Where, represents the concentration gradient, represents the flux, Indicates flux The divergence of Among them, the flux of sodium ions in the electrolyte and the solid electrolyte interface membrane satisfies the following formula: Where, 、 、 、 、 They represent the transfer vector, diffusion coefficient, concentration, ion mobility, and potential of sodium ions in the electrolyte respectively; 、 、 、 、 represent the transfer vector, diffusion coefficient, concentration, ion mobility, and potential of sodium ions in the solid electrolyte interface film, respectively; Represents the charge of the sodium ion.

5. The method for analyzing the solid electrolyte interface film of a sodium ion capacitor according to claim 3, characterized in that: In the step S2, the preset simulation environment further includes a preset sodium ion deposition rule; The sodium ion deposition rule satisfies the modified Butler-Volmer equation: Where, represents the local current density, represents the exchange current density, α and β are the anodic and cathode transfer coefficients respectively, represents overpotential, R is the gas constant, T is the thermodynamic temperature, F is the Faraday constant, represents the change in electrochemical potential caused by local strain; in, and represent the sodium ion concentrations in the electrolyte near the electrode substrate and in the solid electrolyte interface film, respectively, and satisfy the following formula: Where, represents the current density, t represents the reaction time, is the Boltzmann constant, Represents the ionic conductivity in the solid electrolyte interface membrane.

6. The method for analyzing the solid electrolyte interface film of a sodium ion capacitor according to claim 5, characterized in that: The sodium ion deposition rule also includes, according to the modified Butler-Volmer equation, obtaining an expression for the anode equilibrium potential: Where, is the anode equilibrium potential, is the standard electrode potential, It represents the stoichiometric coefficient of sodium ions participating in the electrode chemical reaction; The boundary conditions of the sodium ion deposition reaction are set to satisfy the following equation: Where, represents the sodium ion flux.

7. The method for analyzing the solid electrolyte interface film of a sodium ion capacitor according to claim 5, characterized in that: The sodium ion deposition rules also include: The electrochemical potential change caused by local strain Corrected to deformation parameters ; The deformation parameters Satisfy the following formula: Where, and represent the partial molar volumes of sodium atoms and sodium salts, respectively. represents the migration number of sodium ions, and represent the surface energy and surface gradient respectively, is the normal vector of the interface between the sodium atom and the solid electrolyte interface film, and denote the deviatoric stress of sodium atoms and solid electrolyte interface film, respectively, and represent the hydrostatic stress of sodium atoms and solid electrolyte interface film, respectively; If two-dimensional calculation is used, It is expressed as the local curvature K.

8. The method for analyzing the solid electrolyte interface film of a sodium ion capacitor according to any one of claims 1 to 7, characterized in that: Also includes the steps: S5, dynamically cycling steps S2-S4; wherein, after each step S4 is performed, the stress and strain caused by the local deformation of the solid electrolyte interface membrane are applied to the next step S2; Based on the dynamic simulation process, it is detected whether there is a current flow dead zone or an area where the current flow velocity is less than a preset flow velocity in the dynamically changing current flow velocity distribution diagram; if there is a current flow dead zone or an area where the current flow velocity is less than the preset flow velocity in the current flow velocity distribution diagram of at least one cross section, the stress analysis data of the solid electrolyte interface membrane is obtained.

9. An analysis device for a sodium ion capacitor solid electrolyte interface film, characterized in that: include: A simulation model establishment module, configured to establish a simulation model of a solid electrolyte interface membrane of a sodium ion capacitor; the simulation model includes an electrode substrate and an internal space of a sodium ion capacitor disposed thereon, wherein the surface of the electrode substrate has a serrated structure and is covered with a solid electrolyte interface membrane, and the internal space of the sodium ion capacitor is filled with a sodium ion electrolyte; Simulation environment setting module, used to set sodium ion transmission rules and sodium ion deposition rules; A simulation calculation module is used to dynamically simulate the simulation model according to actual control parameters to obtain the sodium ion electrodeposition distribution parameters and the current flow velocity distribution diagram in the internal space of the sodium ion capacitor; Cross-section generation module, used to intercept the current velocity distribution diagram during dynamic simulation; The analysis and processing module is used to analyze and process the intercepted current velocity distribution diagram and its corresponding electrodeposition distribution parameters, and obtain stress analysis data of the solid electrolyte interface film according to preset stress analysis rules.

10. A computer device, characterized in that: including memory and processor; The memory stores a computer program, and when the processor executes the computer program, the analysis method of the sodium ion capacitor solid electrolyte interface film according to any one of claims 1 to 8 is implemented.

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