Battery interface current calculation method and system and storage medium

Abstract

The invention discloses an interface current calculation method and device of an all-solid-state battery and a storage medium. The battery comprises a plurality of components which are stacked in sequence: a positive electrode current collector, a positive electrode, an insulating component, a solid electrolyte layer, a negative electrode and a negative electrode current collector, the insulating member is arranged in a ring shape and covers a part of the periphery of the positive electrode; the positive electrode comprises a first part which is not covered by the insulating member and a second part which is covered by the insulating member; the solid electrolyte layer comprises a third part corresponding to the second part and a fourth part located outside the third part; the method comprises the following steps: calculating the ion flux of each part: respectively calculating the stress distribution of a first part and a second part of a positive electrode, and calculating the ion flux of the positive electrode based on the stress distribution; respectively calculating stress distribution of the third part and the fourth part of the solid electrolyte layer, and calculating the ion flux of the solid electrolyte layer based on the stress distribution; and calculating the current at the negative electrode interface based on the ion flux.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a method, device and storage medium for calculating the interface current of a battery. Background Art

[0002] With the rapid development of energy technology, solid-state batteries have become a new type of battery with great application prospects. The main difference between solid-state batteries and traditional lithium-ion batteries lies in the state of the electrolyte: solid-state batteries use solid electrolytes, while traditional ones are liquid electrolytes. The use of solid electrolytes may affect the ion transport, electron blocking, and interface contact inside the battery. This will lead to current distribution inside the battery and at the interface between different components, that is, the magnitude of the interface current. High interface current means high charge transfer efficiency and fast redox reaction rate, so that the output power of the battery will be better, and high interface current means faster charging and discharging speed. At high current density, the concentration polarization and electrochemical polarization at the interface between the components of the battery will be weakened, making the output voltage of the battery closer to the theoretical value and improving the energy conversion efficiency. Moreover, in the lithium metal negative electrode system, high interface current helps to inhibit the growth of lithium dendrites. Therefore, high interface current is the core of improving the power density and energy efficiency of solid-state batteries, especially in fast charging and high performance scenarios. As a result, the parameter of interface current has become an important reference object for the design and manufacture of solid-state batteries.

[0003] In solid-state batteries, solid electrolytes replace traditional diaphragms to become barriers between the positive and negative electrodes. Since the solid electrolyte membrane itself has poor mechanical properties and cannot form a complete wrapping structure for the positive electrode, the burr problem on the edge of the positive electrode is relatively serious. In the prior art, there is a solution to set an insulating structure on the edge of the positive electrode to reduce the risk of short circuits caused by burrs. However, there is no report on the method of setting an insulating component at the contact interface between the solid electrolyte layer and the positive electrode layer. The applicant has confirmed in previous studies that the insulating frame part is set between the positive electrode and the solid electrolyte layer to help improve the performance of the battery. However, since the insulating structure part intervenes between the positive electrode and the solid electrolyte, it affects the ion path between the positive and negative electrodes. Whether this structure will cause electrochemical performance is still unknown. For this reason, it is very necessary to simulate the electrochemical performance of the battery structure by simulation means. Summary of the invention

[0004] In order to achieve the above purpose, the present application discloses an interface current calculation method, system and storage medium. The interface current calculation method can accurately calculate the interface current of a battery, especially a new solid-state battery with an insulating component, and provide an important basis for battery design and production.

[0005] The first aspect of the present application provides a method for calculating the interface current of an all-solid-state battery. The battery includes the following multiple components stacked in sequence: a positive electrode current collector, a positive electrode, an insulating member, a solid electrolyte layer, a negative electrode, and a negative electrode current collector; the insulating member is arranged in a ring shape and covers a portion of the outer periphery of the positive electrode; the insulating member is arranged in a ring shape and covers a portion of the outer periphery of the positive electrode; the positive electrode includes a first part not covered by the insulating member and a second part covered by the insulating member; the solid electrolyte layer includes a third part corresponding to the first part and a fourth part located outside the third part; the interface current calculation method may include: S1. Calculate the ion flux of each part; S1-1. Calculate the stress distribution of the first part and the second part of the positive electrode respectively, and calculate the positive electrode ion flux based on the stress distribution; S1-2. Calculate the stress distribution of the third part and the fourth part of the solid electrolyte layer respectively, and calculate the solid electrolyte layer ion flux based on the stress distribution; S2. Based on the ion flux calculated in step 1, calculate the interface current of the negative electrode facing the positive electrode center area and the positive electrode edge area.

[0006] According to some embodiments of the present application, the second portion of the positive electrode accounts for 1%-10% of the positive electrode.

[0007] According to some embodiments of the present application, the step S1 further includes S1-3. calculating the negative electrode ion flux, and the negative electrode is metallic lithium.

[0008] According to some embodiments of the present application, the stress distribution of the first portion of the positive electrode satisfies: ;in, is the area of ​​the second part, is the area of ​​the insulating member, is the positive electrode Young's modulus, is the Young's modulus of the insulating component, is the external load.

[0009] According to some embodiments of the present application, the step S2 further includes determining a current density distribution using the ion flux; and determining the interface current based on the current density distribution.

[0010] According to some embodiments of the present application, the Young's modulus of the insulating member is different from the Young's modulus of the positive electrode.

[0011] The second aspect of the present application provides an interface current calculation device for a battery. The battery includes the following multiple components stacked in sequence: a positive electrode current collector, a positive electrode, a solid electrolyte layer, a negative electrode, and a negative electrode current collector; an insulating member having the same cross-sectional area as the positive electrode covers the portion of the positive electrode close to the solid electrolyte in a contact pressurized manner. The interface current calculation device may include a first determination module, a second determination module, and a third determination module that perform operations on the positive electrode, the solid electrolyte, and the negative electrode, respectively. The first determination module is configured to determine the hydrostatic stress distribution and ion concentration of each component; the second determination module is configured to determine the ion flux using the hydrostatic stress distribution and the ion concentration; the third determination module is configured to determine the interface current based on the ion flux; wherein the ion concentration is determined based on Fick's diffusion law, the hydrostatic stress distribution is determined based on the ion concentration and the Poisson's ratio, Young's modulus and partial molar volume of one or more of the components related to the positive electrode, the solid electrolyte or the negative electrode; the ion flux is determined based on the ion diffusion coefficient, the hydrostatic stress distribution, the ion concentration and the partial molar volume; and the interface current is also related to the Faraday constant.

[0012] The third aspect of the present application provides a computing system, which may include: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, may implement the steps of the interface current calculation method as described above.

[0013] A fourth aspect of the present application provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the interface current calculation method described above can be implemented.

[0014] A fifth aspect of the present application provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the steps of the interface current calculation method described above can be implemented.

[0015] A sixth aspect of the present application provides a battery interface current calculation device, and the interface current calculation may include the interface current calculation method device or calculation system as described above.

[0016] The interface current calculation method disclosed in the present application can accurately calculate the interface current of batteries, especially new solid-state batteries with insulating components, and provide an important basis for battery design and production.

[0017] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present application will be further described in the form of exemplary embodiments, which will be described in detail by way of the accompanying drawings. These embodiments are not restrictive, and in these embodiments, the same number represents the same structure, wherein: Figure 1 is an exemplary structural schematic diagram and cross-sectional diagram of a solid-state battery according to the present application; Figure 2 is an exemplary flow chart of a method for determining an interface current according to some embodiments of the present application; Figure 3 It is an exemplary illustration of a current density distribution diagram and a local enlarged diagram according to some embodiments of the present application; Figure 4 is an exemplary illustration of another current density distribution diagram and a local enlarged diagram according to some embodiments of the present application; Figure 5 is an exemplary illustration of another current density distribution diagram and a local enlarged diagram according to some embodiments of the present application; Figure 6 is an exemplary module diagram of a device for calculating the interface current of a battery according to some embodiments of the present application; and Figure 7 is an exemplary block diagram of a computing device according to some embodiments of the present application. DETAILED DESCRIPTION

[0019] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0020] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by technicians in the technical field of this application. The terms used in this application and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The words "including" or "comprising" and the like used in this application mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. The terms "and / or" or "and / or" used in this application include any and all combinations of one or more related listed items.

[0021] The terms "including", "having" and their cognates used in this application are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0022] It should be noted that the terms "first", "second", "third", etc. used in this application are only used to distinguish descriptions and should not be understood as indicating or implying relative importance. When a component is referred to as being "fixed to", "mounted on" or "disposed on" another component, it can be directly on the other component or there can also be other components centered. When a component is considered to be "connected to" another component, it can be directly connected to the other component or there can be other components centered at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0023] Some preferred embodiments of the present application are described below. It should be noted that the following description is for the purpose of illustration and is not intended to limit the scope of protection of the present application. The steps involved in the present application can be performed accurately in sequence, or various steps can be processed in reverse order or simultaneously. At the same time, other operations can also be added to these processes, or one or more operations can be removed from these processes.

[0024] The present application provides a method for determining the interface current of an all-solid-state battery, wherein the all-solid-state battery may include: Figure 1 The solid-state battery 100 shown in FIG. 1 may include a plurality of components stacked in sequence: a positive electrode collector 110 , a positive electrode 120 , an insulating member 130 , a solid electrolyte layer 140 , a negative electrode 150 , and a negative electrode collector 160 .

[0025] The positive electrode current collector 110 and the negative electrode current collector 160 can be formed of conductive materials, such as stainless steel, nickel (Ni), aluminum (Al), iron (Fe), titanium (Ti), copper (Cu), palladium (Pd), gold (Au) or platinum (Pt) or alloys of two or more of the above materials, such as foil, plate or mesh. Exemplarily, the positive electrode current collector 110 and the negative electrode current collector 160 can be a cladding material formed by decoupling copper foil or stacking heterogeneous metal foils.

[0026] The positive electrode may contain a material capable of inserting or extracting metal ions such as lithium ions, such as a positive electrode active material, which may be, for example, a lithium-containing transition metal oxide, a transition metal fluoride, a polyanion material, a fluorinated polyanion material, a transition metal sulfide, a transition metal fluoride oxide, a transition metal oxysulfide, or a transition metal oxynitride. Among them, an example of a lithium-containing transition metal oxide may be Li(NiCoAl)O2 or LiCoO2.

[0027] The negative electrode may also be a material containing metal ions capable of embedding or de-embedding lithium ions, such as a negative electrode active material, exemplified by metal materials, carbon materials, oxides, nitrides, tin compounds, silicon compounds, etc. The metal material may be a metal element or alloy such as lithium metal or lithium alloy. The carbon material may be natural graphite, coke, graphitizable carbon, carbon fiber, spherical carbon, artificial graphite or amorphous carbon, etc. Alternatively or preferably, the negative electrode may be a lithium metal negative electrode.

[0028] At least one of the positive electrode or the negative electrode may also contain a conductive additive, for example, a carbon-based material such as graphite (natural graphite or artificial graphite, etc.), carbon black (acetylene black or Ketjen black, etc.), carbon nanotubes, graphene, etc., a metal-based material such as metal powder (aluminum powder, nickel powder, etc.), a metal oxide (titanium oxide, etc.), a metal whisker (aluminum oxide, oxidizing, etc.), etc., a conductive polymer such as polyaniline, polypyrrole, polythiophene, etc., a conductive fiber such as carbon fiber, metal fiber, metal compound fiber, polymer fiber, etc. The conductive additive may also be a mixture of one or more of the above.

[0029] The solid electrolyte layer 140 may be in the form of a layer or a film, and may include an oxide solid electrolyte, a halide solid electrolyte, or a sulfide solid electrolyte. For example, the oxide solid electrolyte may include a NASICON type solid electrolyte such as LiTi2(PO4)3 or its element substitution body, a perovskite type solid electrolyte such as (LaLi)TiO3, a Li 14 ZnGe4O 16 , LISICON type solid electrolytes such as Li4SiO4, LiGeO4 or their element substitution bodies, Li7La3Zr2O 12 Or a garnet-type solid electrolyte such as an element substitution body thereof, or Li3PO4 or its N substitution body, etc. For example, the oxide solid electrolyte may include one or more of LLZO, LLTO, LAGP, LATP, LBSPO, LPO, Li3PO4, Li4SiO4, Li2ZnTi3O8, and / or one or more of their derivatives. The halide solid electrolyte may include a lithium halide solid electrolyte, which may be a solid electrolyte having a chemical formula of Li a MX bIndicates that M represents a metal element or a metalloid element, and X represents a halogen element. Wherein, "metalloid element" can represent an element with similar metal properties, and can include B, Si, Ge, As, Sb, Te, etc. Optionally or preferably, M can include but is not limited to Al, Zn, Mg, Ca, Ba, Mn, Cd, Co, Yb, Y, Cr, In, Ga, Sr, Hf, Ti, Ta, Sn, Nb, Er, Sc, etc. or any combination thereof. For example, the halide solid electrolyte can include Li2ZrCl6 or its derivatives. The sulfide solid electrolyte can include lithium sulfides such as Li2S-P2S5 system, Li2S-SiS2 system, Li2S-B2S3 system, Li2S-GeS2 system, Li2S-SiS2-LiI system, Li2S-SiS2-Li3PO4 system, Li2S-Ge2S2 system, Li2S-GeS2.P2S5 system or Li2S-GeS2-ZnS system. For example, sulfide solid electrolytes may include LGPS, , The solid electrolyte layer 140 may include one or more of the above materials. In some implementations, the solid electrolyte layer 140 may include a solid electrolyte having lithium ion conductivity.

[0030] The solid-state battery 100 may further include an insulating member 130. The insulating member 130 may cover the outer side of the portion of the positive electrode 120 close to the solid electrolyte layer 140 and contact and pressurize the portion. For example, the insulating member 130 may be provided in a ring shape and cover a portion of the outer periphery of the positive electrode 120. Figure 1 As shown, it can be considered that the outer side of the lower part of the positive electrode 120 is covered by the insulating member 130. The insulating member 130 can block foreign matter (e.g., air, moisture, tiny dust, etc.), and improve the cycle performance and safety of the solid-state battery 100. In one implementation, the insulating member 130 can have the same cross-sectional area as the positive electrode 120, so that the design of the solid-state battery can be kept uniform. For example, assuming that the size (length) of the positive electrode 120 Width Thickness) is , then the outer dimensions of the insulating member (length Width Thickness) can be In this way, after adding the insulating member 130, the cross-sectional area of ​​the portion of the positive electrode 120 that contacts the solid electrolyte layer 140 (that is, the compressed portion) will be reduced. The length and width dimensions of the insulating member 130 can be adjusted according to actual conditions so as not to affect the energy density of the solid-state battery 100.

[0031] The method for determining the interfacial current of the battery provided in this application can refer to Figure 2, wherein the process 200 shown can be implemented in a computing device, such as an industrial computer, a server, a computer, a tablet, a smart mobile device, etc. In some embodiments, the process 200 can be stored in a storage device (such as a storage unit or an external storage device of the above-mentioned computing device) in the form of a program or instruction, and the program or instruction can implement the process 200 when executed. In some embodiments, the process 200 can be executed separately for the relevant components (including the positive electrode, the solid electrolyte, and the negative electrode) of the battery (for example, the solid-state battery 100). In the present application, a coordinate system can be first established based on the battery (that is, the solid-state battery 100) to facilitate subsequent various mathematical calculations. Return to reference Figure 1 ,by Figure 1 The direction of the arrow shown in the x Axis, that is, along the thickness direction of the solid-state battery 100. Then perpendicular to x Axis creation yoz plane, that is, along the length direction and width direction of the solid-state battery 100, respectively y Axis and z In this way, the position of a certain particle belonging to the solid-state battery 100 can be expressed as a point in the above coordinate system ( x , y , z ) indicates. At the same time, you can use x The coordinates are used to indicate which component or interface of the solid-state battery 100 the particle is located at. x 1 is the outer surface position of the positive electrode 120, that is, at the interface between the positive electrode current collector 110 and the positive electrode 120. x 2 is the interface position between the positive electrode 120 and the insulating member 130, x 3 is the interface position between the positive electrode 120 and the solid electrolyte layer 140, x 4 is the interface position between the solid electrolyte layer 140 and the negative electrode 150, x 5 is the outer surface position of the negative electrode 150, that is, the interface between the negative electrode 150 and the negative electrode current collector 160. The above can be recorded as x k Thus, the region where charge transfer occurs in the solid-state battery 100 can be represented by the x-coordinate, including the positive electrode 120: x 1< x < x 3. Solid electrolyte layer 140: x 3< x < x 4. And the negative electrode: x 4< x < x5. By calculating the current density distribution in each area, the current distribution of the entire battery can be obtained, and then the magnitude of the interface current can be obtained.

[0032] In addition, since the insulating member 130 covers a portion of the outer periphery of the positive electrode 120, the positive electrode 120 can also be divided into multiple parts. Exemplarily, the positive electrode 120 can be divided into a first part P1 not covered by the insulating member 130 and a second part P2 covered by the insulating member 130. Due to the contact pressure of the insulating member 130, the physical parameters related to the first part P1 and the second part P2 will change, thereby affecting the corresponding calculation process. Combined with the above-mentioned position division, the first part P1 can be expressed as: x 1< x < x 2. The second part P2 can be expressed as: x 2< x < x 3. In one implementation, the second portion P2 accounts for 1%-10% of the positive electrode.

[0033] At the same time, the solid electrolyte layer 140 is in contact with the positive electrode 120 and the insulating member 130, and will also be affected. Similarly or similarly, the solid electrolyte layer 140 can also be divided. For example, the solid electrolyte layer 140 can be divided into a third part P3 corresponding to the second part P2 (e.g. Figure 1 The second portion P2 of the positive electrode 120 in contact with the pressure will affect the relevant physical parameters of a part of the solid electrolyte layer 140, that is, the third portion P3. Similarly, the calculation process related to different regions will be different.

[0034] Return to reference Figure 2 , process 200 may include the following operations.

[0035] S1: Calculate the ion flux of each part.

[0036] The above step S1 may include the following operations.

[0037] S1-1: Calculate the stress distribution of the first part and the second part of the positive electrode respectively, and calculate the positive electrode ion flux based on the stress distribution.

[0038] For positive electrode 120 ( x 1< x < x 3), the corresponding ion concentration satisfies Fick's diffusion law. Exemplarily, the ion concentration satisfies the following formula (1): (1) Among them, the subscript Indicates the positive electrode, represents the ion concentration, is the ion diffusion coefficient, Indicates location, Indicates time, Represents the boundary conditions. The boundary conditions for the above equation (1) can be expressed as the following equation (2), and the initial conditions can be expressed as the following equation (3): (2) (3) in, represents the positive electrode reaction rate, Represents the external input current, which is a known value. Indicates the number of electrons participating in the reaction at the positive electrode, is the Faraday constant, Represents the initial known concentration. Based on the above conditions, the ion concentration of the positive electrode 120 can be obtained by solving equation (1): expression.

[0039] The hydrostatic stress distribution corresponding to the positive electrode 120 can be determined based on the above ion concentration and the Poisson's ratio, Young's modulus and partial molar volume of the positive electrode 120. For example, the hydrostatic stress distribution can be expressed as the following formula (4): (4) in, represents the hydrostatic stress distribution, represents Poisson's ratio, represents Young's modulus, represents the partial molar volume, In combination with the above description, the positive electrode 120 will change its internal initial stress due to the pressure contact of the insulating member 130. That is, for the first part P1: x 1< x < x 2 and the second part P2: x 2< x < x 3 The initial stresses of the two regions are different. For example, the first part P1 and the second part P2 have different initial stress distributions, and their corresponding first initial stress distributions are And the second initial stress distribution For the determination of the above initial stress distribution, the initial stresses in different regions can be obtained based on the stress equilibrium equation and the principle of equal forces at the continuous interface, and then brought into the above formula (4) to calculate the hydrostatic stress distribution, thus obtaining different first hydrostatic stress distributions: And the second hydrostatic stress distribution .

[0040] For example, the second portion P2 ( x 2< x < x 3) Stress distribution (that is, initial stress distribution ) can be determined based on the following formula (5): (5) in, represents the area of ​​the second part P2, which may be the outer area of ​​the second part P2 covered. represents the area of ​​the insulating member 130, which may be the outer area of ​​the insulating member 130, represents the positive electrode Young's modulus, represents the Young's modulus of the insulating member 130, In some implementations, the positive electrode and the insulating member have different Young's moduli.

[0041] The ion flux corresponding to the positive electrode 120 can be determined based on the ion concentration, the hydrostatic stress distribution, the ion diffusion coefficient and the partial molar volume. For example, the ion flux can be expressed as follows (6): (6) in, represents the ion flux, represents the ion concentration, Indicates the maximum storage ion concentration of the positive electrode, which is used to indicate the degree of lithium. represents the ideal gas constant, and its value is 8.314 J / (mol·K). represents the temperature. The initial condition and boundary condition for the above equation (6) can be expressed as the following equations (7) and (8): (7) (8) Among them, when located x = x 1, that is, at the interface between the positive electrode 120 and the positive electrode current collector 110, the ion flux is 0. x = xAt 3, which is the interface between the positive electrode 120 and the solid electrolyte layer 140, the ion flux can be the quotient between the current density and the Faraday constant. Based on the above conditions and the aforementioned ion concentration and hydrostatic stress distribution, equation (6) is solved to obtain the current density distribution related to the positive electrode 120. For example, the current density distribution related to the positive electrode 120 It can be expressed as the following formula (9): (9) in, can be expressed as the solved ion flux, represents the Faraday constant. Based on the above formula (9), the value x = x 2 or x = x 3, the interface current at the interface between the positive electrode 120 and the insulating member 130, or the interface current at the interface between the positive electrode 120 and the solid electrolyte layer 140 can be obtained. and By using different combinations of , we can get the current magnitude at different positions on the above interface.

[0042] The above-mentioned hydrostatic stress distribution includes different first hydrostatic stress distributions. And the second hydrostatic stress distribution , then combined with formula (6), the ion flux associated with the positive electrode 120 may include different first ion fluxes and the second ion flux , so that the current density distribution of the positive electrode 120 is based on x There are two different expressions due to the difference in . That is, formula (9) can also be expressed as:

[0043] S1-2: Calculate the stress distribution of the third part and the fourth part of the solid electrolyte layer respectively, and calculate the ion flux of the solid electrolyte layer based on the stress distribution.

[0044] For the solid electrolyte layer 140 ( x 3< x < x 4), its ion concentration and hydrostatic stress distribution may be the same or similar to the related calculations of the positive electrode 120. Exemplarily, the ion concentration satisfies the following formula (10): (10) Among them, the subscript represents a solid electrolyte, represents the ion concentration, represents the ion diffusion coefficient, which can be calculated based on the following formula (11): (11) represents the diffusion coefficient of lithium ions, represents the diffusion coefficient of negative ions. For the solution of equation (10), the boundary condition can be x = x 3 interface, the ion flux of the positive electrode 120 and the solid electrolyte layer 140 is the same, and the initial condition can be that the ion concentration at the initial moment is the initial known concentration Based on the above conditions, the ion concentration of the solid electrolyte layer 140 can be obtained by solving the above equation (10): expression.

[0045] The hydrostatic stress distribution corresponding to the solid electrolyte layer 140 can be determined based on the above ion concentration and the Poisson's ratio, Young's modulus and partial molar volume of the solid electrolyte layer 140. For example, the hydrostatic stress distribution can be expressed as the following formula (12): (12) in, represents the hydrostatic stress distribution, represents Poisson's ratio, represents Young's modulus, represents the partial molar volume, Represents the initial stress of the solid electrolyte. For the initial stress, the solid electrolyte layer 140 in contact with the positive electrode 120 is affected due to the contact pressure of the insulating member 130 on the positive electrode 120. For example, the relevant physical parameters of the solid electrolyte layer 140 corresponding to the portion of the positive electrode 120 covered by the insulating member 130 and the portion corresponding to the insulating member 130 and the portion outside the insulating member 130 will change. In the present application, the solid electrolyte layer 140 can be divided into a third portion P3 corresponding to the second portion P2 and a fourth portion P4 located outside the third portion P3. The initial stress distributions of the two portions are different, including the corresponding initial stress distributions And the initial hydrostatic stress distribution The calculation of the initial stress distribution of the third part P3 and the fourth part P4 may be the same or similar to the calculation process of the first part P1 and the second part P2 related to the positive electrode, and the corresponding description may be referred to.

[0046] For partial molar volume , which can be calculated based on the following formula (13): (13) represents the partial molar volume of lithium ions, represents the partial molar volume of negative ions. Substituting the relevant parameters and equations into equation (12) can calculate the hydrostatic stress distribution and obtain the third hydrostatic stress distribution And the fourth hydrostatic stress distribution .

[0047] The ion flux corresponding to the solid electrolyte layer 140 can be determined based on the ion concentration, the hydrostatic stress distribution, the ion diffusion coefficient and the partial molar volume. For example, the ion flux can be expressed as the following formula (14): (14) in, represents the ion flux, represents the partial molar volume of the electrolyte, represents the ion concentration, represents the ideal gas constant, and its value is 8.314 J / (mol·K). Indicates temperature. At the same time, the calculation formula of the current exchange density related to the solid electrolyte layer 140 is as follows (15): (15) in, represents the electric potential. The initial conditions and boundary conditions for the above equations can be shown as follows (16) to (19): (16) (17) (18) (19) Based on the above conditions and the aforementioned ion concentration and hydrostatic stress distribution, the current density distribution related to the solid electrolyte layer 140 can be obtained. For example, the current density distribution related to the solid electrolyte layer 140 is It can be expressed as the following formula (20): (20) Based on the above formula (9), the value x = x 3 or x = x 4, the interface current at the interface between the solid electrolyte layer 140 and the positive electrode 120, or the interface current at the interface between the solid electrolyte layer 140 and the negative electrode 150 can be obtained. and By using different combinations of , we can get the current magnitude at different positions on the above interface.

[0048] The aforementioned hydrostatic stress distribution includes different third hydrostatic stress distributions. And the fourth hydrostatic stress distribution , then combined with formula (14), the ion flux associated with the solid electrolyte layer 140 may include different third ion fluxes and the fourth ion flux , so that the current density distribution of the solid electrolyte layer 140 is based on y and z There are two different expressions due to the difference in . That is, formula (20) can also be expressed as:

[0049] S1-3: Calculate the negative electrode ion flux.

[0050] For the negative electrode 150 ( x 4< x < x 5), its ion concentration satisfies Fick's diffusion law. Exemplarily, the ion concentration satisfies the following formula (21): (twenty one) Among them, the subscript Indicates the negative pole, represents the ion concentration, is the ion diffusion coefficient, Represents the boundary conditions. The boundary conditions for the above equation (21) can be expressed as the following equation (22), and the initial conditions can be expressed as the following equation (23): (twenty two) (twenty three) in, represents the negative electrode reaction rate, represents the external known current, Indicates the number of electrons participating in the reaction at the negative electrode, is the Faraday constant, represents the initial known concentration. Based on the above conditions, the ion concentration of the negative electrode 150 can be obtained by solving equation (21): expression.

[0051] The hydrostatic stress distribution corresponding to the negative electrode 150 can be determined based on the above ion concentration and the Poisson's ratio, Young's modulus and partial molar volume of the negative electrode 150. For example, the hydrostatic stress distribution can be expressed as the following formula (24): (twenty four) in, represents the hydrostatic stress distribution, represents Poisson's ratio, represents Young's modulus, represents the partial molar volume, Represents the initial stress of the negative electrode. After the relevant parameters are brought in, the hydrostatic stress distribution can be calculated.

[0052] The ion flux corresponding to the negative electrode 150 can be determined based on the ion concentration, the hydrostatic stress distribution, the ion diffusion coefficient, and the partial molar volume. For example, the ion flux can be expressed as follows (25): (25) in, Represents the ion flux represents the ion concentration, Indicates the maximum storage ion concentration of the negative electrode, represents the ideal gas constant, and its value is 8.314 J / (mol·K). represents the temperature, and its value is 298.15 K. The initial conditions and boundary conditions for the above equation (25) can be expressed as follows: (26) (27) Among them, when located x = x 4, that is, at the interface between the solid electrolyte layer 140 and the negative electrode 150, the ion flux can be the quotient between the current density and the Faraday constant. x = x At 5, which is the interface between the negative electrode 150 and the negative electrode current collector 160, the ion flux is zero. Based on the above conditions and the aforementioned ion concentration and hydrostatic stress distribution, equation (25) is solved to obtain the current density distribution related to the negative electrode 150. For example, the current density distribution related to the negative electrode 150 It can be expressed as the following formula (28): (28) in, can be expressed as the solved ion flux, represents the Faraday constant. Based on the above formula (28), when the value x = x 4 can be used to obtain the interface current at the interface between the negative electrode 150 and the negative electrode current collector 160. At the same time, the value and By using different combinations of , we can get the current magnitude at different positions on the above interface.

[0053] In some implementations, the negative electrode 150 can be a lithium metal negative electrode. Since the negative electrode is lithium metal, the electrochemical reaction only occurs on the surface in contact with the solid electrolyte layer, and the remaining lithium metal will act as a current conductor. Therefore, the current will be transmitted in the form of a conductor inside the lithium metal negative electrode. The ion flux expression of the reaction on the surface of the lithium metal negative electrode is the same as the ion concentration flux expression of the solid electrolyte membrane at this interface. In other words, the ion flux expression of the negative electrode 150 can be expressed by the solid electrolyte layer 140 at x = x 4, the current density of the negative electrode 150 can be expressed as follows:

[0054] Combining the expressions of the current density distribution of the above three components, the overall current density distribution of the solid-state battery 100 can be obtained, which can be expressed as the following formula (29): (29) For the above calculation formulas, there are two boundaries for the electrochemical reaction in the positive electrode 120. One is the interface between the positive electrode 120 and the positive electrode current collector 110, and the other is the interface between the positive electrode 120 and the solid electrolyte layer 140. At the same time, on the side close to the solid electrolyte layer 140, the cross-sectional area of ​​the positive electrode 120 is reduced due to the insulating member 130. Therefore, for the positive electrode 120 ( x 1< x < x 3) will calculate the ion reaction current at the interface and the internal ion diffusion based on the reaction chemical formula and stress distribution. For the solid electrolyte layer 140, ion diffusion occurs inside it, and there are two boundaries. One is the interface between the solid electrolyte layer 140 and the positive electrode 120, and the other is the interface between the solid electrolyte layer 140 and the negative electrode 150. The electrolyte conductivity is affected by pressure. Therefore, for the solid electrolyte layer 140 ( x 3< x < x 4), the stress-related ionic conductivity is calculated to obtain the internal ion diffusion. For the negative electrode 150, especially the lithium metal negative electrode, the electrochemical reaction occurs on its surface, and there is no intercalation reaction. The reaction only occurs on the negative electrode surface in contact with the solid electrolyte layer 140, and the rest can be regarded as a metal conductor. Therefore, for the negative electrode 150 ( x 4< x < x 5) Calculate the interfacial ion reaction current and the impedance change caused by the stress-related solid-solid interface contact area based on the reaction chemical formula and stress distribution.

[0055] S2: Based on the calculated ion fluxes of each part, calculate the interface currents at two locations, where the negative electrode faces the central area of ​​the positive electrode and the edge area of ​​the positive electrode.

[0056] According to the current density distribution of each part obtained above, by determining x, y, z By selecting the value of , the interface current at each position inside the solid-state battery 100 can be obtained. x = x 4, and select y and z By taking the value of , we can obtain the interface currents at two locations where the negative electrode is facing the central area of ​​the positive electrode and the edge area of ​​the positive electrode.

[0057] For battery 100, the currents at the boundary connections between the components are equal, and the sum of the voltages of the components is equal to the overall voltage of the battery. It can be expressed as the following formula (30): (30) in, represents the potential, as well as 1 and 2 represent the interface potentials, which are the interface potential between the positive electrode 120 and the solid electrolyte layer 140 and the interface potential between the solid electrolyte layer 140 and the negative electrode 150 . represents the SEI membrane polarization voltage. According to the relationship between overpotential and current density, the above overpotentials can be solved based on the current density based on the Butler-Volmer equation. For example, the interfacial point position can be based on the following formula (31): , (31) in, represents the current density, represents the current exchange density, represents the solid-solid interface contact factor, represents the transfer coefficient.

[0058] In order to evaluate the battery performance, the average overpotential can be used to replace the overpotential. For example, it can be based on the following formula (32): (32) The above process is exemplified below with a specific implementation process. It should be noted that the following content is only for illustration and not for limiting the present application.

[0059] Adopt all-solid-state single-chip battery, the battery parameters are as follows: Positive electrode size: , Outer ring size of insulating component: , Insulating component inner ring size: , solid electrolyte membrane size: , negative electrode size: . Chemical system: NMC / Li. Young's modulus of positive electrode: 400MPa, Young's modulus of solid electrolyte membrane: 900MPa, Young's modulus of lithium metal: 2GPa, Young's modulus of insulating component: 900MPa. The Poisson's ratio of the positive electrode is 0.25, the Poisson's ratio of the solid electrolyte membrane is 0.33, and the Poisson's ratio of the negative electrode is 0.34. The diffusion coefficient of the positive electrode is: The positive electrode ion conductivity is 3.8S / m, the electrolyte ion conductivity is a function related to the stress distribution, the positive electrode partial molar volume strain is a function related to the degree of particle lithiation, and the ideal gas constant R is 8.31J / (K mol), Faraday constant F is 96485C / mol, temperature T is 298.15K, external pressure: 5MPa.

[0060] Indicates the positive electrode reaction rate, in this embodiment, 5e -10 m / s, Indicates the number of electrons participating in the reaction at the positive electrode, which is 1 in this embodiment. Indicates the maximum storage ion concentration of the positive electrode. In this embodiment, it is 22860 mol / m 3 ; represents the transfer coefficient, which is 0.5 in this embodiment.

[0061] The overall stress distribution of the battery satisfies: ; Since it is in static equilibrium, it can be simplified as: ; At the continuous interface , into the model, in ( x 2 <x<x 3) When satisfied: ; Ignoring the size edge effect, the upper side of the insulating component can be calculated by external pressure, interface size, Young's modulus, and Poisson's ratio ( x 1 <x<x 2) The initial stress of the positive electrode is , parallel to the insulating member ( x 2 <x<x 3) The initial stress of the positive electrode is The initial stress of the solid electrolyte membrane is in the area opposite to the insulating component and the area outside it. The initial stress of the solid electrolyte membrane is , the internal initial stress of the negative electrode is , the external initial stress of the negative electrode is .

[0062] 1. For the positive electrode, Fick's diffusion law is satisfied, that is: ; The boundary conditions are: ; The initial conditions are: ; The expression for concentration is: ; The coefficient and wave number It can be determined based on boundary conditions and initial conditions.

[0063] The hydrostatic stress distribution is: when( x 1 <x<x 2) When: ; when( x 2 <x<x 3) When: ; Substitute the hydrostatic stress distribution and concentration distribution into the flux formula: ; Right now: ; Then the current density distribution of the positive electrode is: ; 2. For the solid electrolyte membrane, similar to the positive electrode, the ion flux expression can be calculated based on the hydrostatic stress distribution and concentration distribution.

[0064] Concentration distribution: ; The coefficient and wave number It can be determined based on boundary conditions and initial conditions. The boundary condition is that at the x=x3 interface, the ion flux of the positive electrode and the solid electrolyte membrane is the same, and the initial condition is that the ion concentration distribution at the initial moment is the initial known concentration .

[0065] Hydrostatic stress distribution: In the area of the solid electrolyte separator facing the positive electrode: ; In the area of the solid electrolyte separator other than the area facing the positive electrode: ; The ion flux expression is: ; The current density distribution of the solid electrolyte separator is: ; 3. For the ion flux expression of the negative electrode, since the negative electrode is lithium metal, the electrochemical reaction only occurs on the surface in contact with the solid electrolyte separator, and the remaining lithium metal will act as a current conductor. Therefore, the current will be conducted in the form of a conductor inside the lithium metal negative electrode. The ion flux expression for the reaction on the surface of the lithium metal negative electrode is the same as the ion concentration flux expression of the solid electrolyte separator at this interface, that is: Concentration distribution: ; In summary, for the entire lithium metal NMC solid-state battery, in the regions where electrochemical reactions and ion diffusion occur, that is, in x1 < x < x4, the current distribution satisfies: ; The input current is 0.06 A. Substituting it back into the formula, the current density at the negative electrode interface can be obtained. The current density in the central region facing the positive electrode is 150.9 A / m 2 , and the current density in the edge region facing the positive electrode is 344.1 A / m 2 .

[0066] Battery acupuncture test: The storage battery is subjected to a cycle performance test for 50 cycles according to the charge and discharge conditions of GB / T31484: 1. Constant current charge at a current of 1C until the specified charge termination voltage, then switch to constant voltage charge until the charge current drops to 0.05C, and stop charging. After charging, let it stand for 1h; 2. In an environment of 22°C ± 5°C, a high-temperature resistant steel needle with a diameter of 5 mm and a conical angle of 30° at the tip is penetrated through the battery in a direction perpendicular to the battery plate at a speed of (25 ± 5) mm / s, and the steel needle is left in the battery; 3. Observe for 2h at the test environment temperature.

[0067] If there is no fire or explosion, it means passing; if there is a fire or explosion, it means failing.

[0068] The calculation results obtained by changing the Young's modulus of the insulating member can be referred to in the following Table 1: Table 1 Current density calculation results

[0069] When the Young's modulus of the insulating component is 100 MPa, the current density distribution diagram and local enlarged diagram of the negative electrode interface can be referred to Figure 3 When the Young's modulus of the insulating component is 400MPa, the current density distribution diagram and local enlarged diagram of the negative electrode interface can be referred to Figure 4 When the Young's modulus of the insulating component is 900MPa, the current density distribution diagram and local enlarged diagram of the negative electrode interface can be referred to Figure 5 .

[0070] It can be seen that the use of insulating parts with a smaller Young's modulus can effectively reduce the negative electrode interface current and improve the safety performance of the battery. This is the same as the battery performance trend in the actual battery evaluation process. The use of insulating parts with a lower Young's modulus can significantly improve the safety performance of the battery and avoid the formation of dendrites.

[0071] The above conclusions are consistent with the actual safety test conclusions of the battery.

[0072] The interface current calculation method disclosed in the present application can accurately calculate the interface current of a battery (especially a new solid-state battery with an insulating component), providing an important basis for battery design and generation.

[0073] It should be noted that the above Figure 1 The description of each step in the embodiment is only for example and explanation, and does not limit the scope of application of this specification. For those skilled in the art, under the guidance of this specification, Figure 1 Various modifications and changes may be made to the various steps in the present invention. However, these modifications and changes are still within the scope of this specification.

[0074] The present application also discloses a battery interface current calculation device. The interface current calculation device can be used to perform the following Figure 2 For details of the steps shown in FIG. 1 , please refer to the corresponding drawings. Figure 6 is an exemplary module diagram of an interface current calculation device according to some embodiments of the present application, such as Figure 6 As shown, the interface current calculation device 600 may include a first determination module 610 , a second determination module 620 and a third determination module 630 .

[0075] The first determination module 610 can be configured to determine the ion concentration and the hydrostatic stress distribution. The first determination module 610 can determine the equation satisfied by the ion concentration based on Fick's diffusion law, and combine the relevant initial conditions and boundary conditions to determine the specific expression of the ion concentration. The first determination module 610 can also determine the corresponding hydrostatic stress distribution based on the Poisson's ratio, Young's modulus and partial molar volume of the component.

[0076] The second determination module 620 may be configured to determine the ion flux using the hydrostatic stress distribution and the ion concentration. The second determination module 620 may determine the ion flux based on the ion concentration, the hydrostatic stress distribution, the ion diffusion coefficient, and the partial molar volume.

[0077] The third determination module 630 may determine the interface current based on the ion flux. The third determination module 630 may determine the current density distribution using the ion flux, for example, by taking the product of the ion flux and the Faraday constant as the current density distribution.

[0078] For other descriptions of the above components, please refer to this application Figure 1-Figure 5 part.

[0079] It should be understood that Figure 6 The system and its modules shown can be implemented in various ways. For example, in some embodiments, the system and its modules can be implemented by hardware, software, or a combination of software and hardware. Among them, the hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or a dedicated design hardware. Those skilled in the art will understand that the above methods and systems can be implemented using computer executable instructions and / or included in processor control codes, such as carrier media such as disks, CDs or DVD-ROMs, programmable memories such as read-only memories (firmware), or data carriers such as optical or electronic signal carriers. Such codes are provided on. The system and its modules of the present application can be implemented not only by hardware circuits such as ultra-large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., but can also be implemented by software executed by various types of processors, and can also be implemented by a combination of the above hardware circuits and software (e.g., firmware).

[0080] It should be noted that the above description of the modules is only for convenience of description and does not limit the present application to the scope of the embodiments. It is understandable that for those skilled in the art, after understanding the principle of the system, it is possible to arbitrarily combine the modules or form a subsystem connected with other modules without deviating from this principle. For example, the first determination module 610, the second determination module 620 and the third determination module 630 are the same determination module. For another example, the modules can share a storage module, or the modules can have their own storage modules. Such variations are within the scope of protection of the present application.

[0081] The present application also provides a computing device. Figure 7 The computing device 700 may include a computer program product for implementing the process described in the embodiments of the present application (for example, Figure 1-Figure 5 ) or systems (e.g. Figure 6 ) as shown in the figure. For example, the computing device 700 can be implemented by hardware, software program, firmware or a combination thereof. For convenience, Figure 7 Only one computing device is drawn in the figure, but the computing functions related to the process and / or system / apparatus described in the embodiments of the present application can be implemented in a distributed manner by a group of similar platforms to disperse the processing load of the system.

[0082] In some embodiments, the computing device 700 may include a processor 710, a memory 720, an input / output component 730, and a communication port 740. In some embodiments, the processor (e.g., CPU) 710 may execute program instructions in the form of one or more processors. In some embodiments, the memory 720 includes different forms of program memory and data memory, such as a hard disk, a read-only memory (ROM), a random access memory (RAM), etc., for storing various data files processed and / or transmitted by the computer. In some embodiments, the input / output component 730 may be used to support input / output between the computing device 700 and other components. In some embodiments, the communication port 740 may be connected to a network for data communication. An exemplary computing device may include program instructions executed by the processor 710 stored in a read-only memory (ROM), a random access memory (RAM), and / or other types of non-temporary storage media. The method and / or process of the embodiment of the present application may be implemented in the form of program instructions. The computing device 700 may also receive the programs and data disclosed in the present application through network communication.

[0083] For ease of understanding, Figure 7Only one processor is drawn as an example. However, it should be noted that the computing device 700 in the embodiment of the present application may include multiple processors, so the operations and / or methods implemented by one processor described in the embodiment of the present application may also be implemented jointly or independently by multiple processors. For example, if in the present application, the processor of the computing device 700 performs operations A and B, it should be understood that operations A and B may also be performed jointly or independently by two different processors of the computing device 700 (for example, the first processor performs operation A, the second processor performs operation B, or the first and second processors perform operations A and B jointly).

[0084] The present application has described the basic concepts. Obviously, for those skilled in the art, the above detailed disclosure is only for example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0085] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or multiple times in different positions in the present application does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0086] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more embodiments of the invention, in the above description of the embodiments of this application, multiple features are sometimes combined into one embodiment or its description. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0087] Finally, it should be understood that the embodiments described in this application are only used to illustrate the principles of the embodiments of the present application. Other variations may also fall within the scope of the present application. Therefore, as an example and not a limitation, the alternative configurations of the embodiments of the present application may be considered to be consistent with the teachings of the present application. Accordingly, the embodiments of the present application are not limited to the embodiments explicitly introduced and described in the present application.

Claims

1. A method for calculating the interface current of an all-solid-state battery, wherein the battery comprises the following multiple components stacked in sequence: a positive electrode current collector, a positive electrode, a solid electrolyte layer, a negative electrode, an insulating member, and a negative electrode current collector; the insulating member is arranged in a ring shape and covers a portion of the outer periphery of the positive electrode; the positive electrode comprises a first portion not covered by the insulating member and a second portion covered by the insulating member; the solid electrolyte layer comprises a third portion corresponding to the first portion and a fourth portion located outside the third portion; It is characterized in that The interface current calculation method comprises: S1. Calculate the ion flux of each part; S1-1. Calculating the stress distribution of the first and second parts of the positive electrode, respectively, and calculating the positive electrode ion flux based on the stress distribution; S1-2 respectively calculates the stress distribution of the third and fourth parts of the solid electrolyte layer, and calculates the ion flux of the solid electrolyte layer based on the stress distribution; S2. Based on the ion flux calculated in step 1, calculate the interface currents at two locations where the negative electrode faces the central area of ​​the positive electrode and the edge area of ​​the positive electrode.

2. The method for calculating the interface current according to claim 1, characterized in that: The second portion of the positive electrode accounts for 1%-10% of the positive electrode.

3. The method for calculating interface current according to claim 1, characterized in that: The step S1 further includes S1-3 calculating the negative electrode ion flux, where the negative electrode is metallic lithium.

4. The method for calculating the interface current according to claim 1, characterized in that: The stress distribution of the second part of the positive electrode satisfies: ;in, is the area of ​​the second part, is the area of ​​the insulating member, is the positive electrode Young's modulus, is the Young's modulus of the insulating component, is the external load.

5. The method for calculating interface current according to claim 1, characterized in that: The step S2 further comprises: determining a current density distribution using the ion flux; The interface current is determined based on the current density distribution.

6. The method for calculating interface current according to claim 1, characterized in that: The Young's modulus of the insulating member is different from that of the positive electrode.

7. A battery interface current calculation system, the calculation system comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, can implement the steps of the method for calculating the interface current of a battery as described in any one of claims 1 to 6.

8. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method for calculating the interface current of a battery as described in any one of claims 1 to 6 are implemented.

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