Battery external short circuit simulation method and system

Abstract

The invention discloses a battery external short circuit simulation method and system, and relates to the technical field of battery management. The battery external short circuit simulation method comprises the following steps: establishing an electrochemical model of a to-be-tested battery; determining the external short-circuit voltage of the to-be-tested battery according to the electrochemical model of the to-be-tested battery; and acquiring the external short-circuit resistance of the to-be-tested battery, and determining the external short-circuit current of the to-be-tested battery according to the external short-circuit voltage and the external short-circuit resistance of the to-be-tested battery. According to the application, the external short-circuit voltage and current when the external short circuit occurs to the battery can be calculated, so that dynamic characteristic analysis can be performed when the external short circuit occurs to the battery, and the safety evaluation of the battery is realized. And the voltage and the current of the battery under the external short circuit are calculated according to the established electrochemical model of the battery, and the safety evaluation of the external short circuit working condition of the battery can be realized without a large number of experimental tests and the like, so that the number of experiments can be reduced, the test period can be shortened, and the cost can be reduced.

Description

Technical Field

[0001] The present application relates to the field of battery management technology, and in particular to a battery external short circuit simulation method and system. Background Art

[0002] Battery safety has always been one of the focuses of people's attention. Among them, external short circuit of battery is one of the most common safety threats, which may cause the battery temperature to rise rapidly and trigger thermal runaway.

[0003] At present, the safety assessment of battery external short circuit mainly relies on traditional experimental methods and empirical safety standards. Although these methods are effective, they have the following shortcomings: the cost of experimental materials, equipment use costs and labor costs are relatively high, and the number of experiments is large, the test cycle is long, and the efficiency is low. Summary of the invention

[0004] The embodiments of the present application provide a battery external short circuit simulation method and system to achieve safety assessment of the battery when an external short circuit occurs, reduce experimental tests, shorten the test cycle, and reduce costs.

[0005] In order to solve the above technical problems, the embodiments of the present application disclose the following technical solutions:

[0006] In a first aspect, a battery external short circuit simulation method is provided, comprising: establishing an electrochemical model of a battery to be tested;

[0007] Determining the external short-circuit voltage of the battery to be tested according to the electrochemical model of the battery to be tested;

[0008] The external short-circuit resistance of the battery to be tested is obtained, and the external short-circuit current of the battery to be tested is determined according to the external short-circuit voltage and the external short-circuit resistance of the battery to be tested.

[0009] In combination with the first aspect, the electrochemical model of the battery to be tested includes five material domains, namely: a negative electrode current collector, a negative electrode porous electrode, a separator, a positive electrode porous electrode and a positive electrode current collector.

[0010] In combination with the first aspect, the battery external short circuit simulation method further includes:

[0011] Decomposing the voltage of the battery to be tested to obtain a plurality of decomposed voltages;

[0012] Establish the solution model of each decomposed voltage;

[0013] Determine the external short-circuit full voltage of the battery to be tested according to the solution models of each decomposition voltage and the electrochemical model of the battery to be tested;

[0014] The external short-circuit current of the battery to be tested is determined according to the external short-circuit full voltage of the battery to be tested and the external short-circuit resistance.

[0015] In combination with the first aspect, the method of determining the external short-circuit full voltage of the battery to be tested according to the solution model of each decomposition voltage and the electrochemical model of the battery to be tested includes:

[0016] Obtaining each decomposition voltage of the battery to be tested under external short circuit according to the solution model of each decomposition voltage and the electrochemical model of the battery to be tested;

[0017] The external short-circuit full voltage of the battery to be tested is determined according to each decomposition voltage of the battery to be tested under external short circuit.

[0018] In combination with the first aspect, the method of obtaining the decomposition voltages of the battery to be tested under an external short circuit according to the solution model of the decomposition voltages and the electrochemical model of the battery to be tested includes:

[0019] Determining internal battery parameter information of the battery under external short circuit according to the electrochemical model of the battery under test;

[0020] The various decomposition voltages of the battery under the external short circuit are obtained according to the internal parameter information of the battery under the external short circuit and the solution model of each decomposition voltage.

[0021] In combination with the first aspect, determining the external short-circuit full voltage of the battery to be tested according to each decomposition voltage of the battery to be tested under external short circuit includes:

[0022] The external short-circuit full voltage of the battery to be tested is obtained according to the sum of the various decomposition voltages of the battery to be tested under external short circuit.

[0023] In combination with the first aspect, the multiple decomposition voltages include at least: liquid phase ohmic polarization voltage, solid phase ohmic polarization voltage, electrochemical reaction activation polarization voltage, liquid phase diffusion polarization voltage and solid phase diffusion polarization voltage.

[0024] In combination with the first aspect, after determining the external short-circuit current of the battery to be tested, the method further includes:

[0025] Establish an electro-thermal model of the battery under test;

[0026] The temperature rise distribution of the battery under external short circuit is determined according to the external short circuit current of the battery under test and the electric-thermal model of the battery under test.

[0027] In combination with the first aspect, the electro-thermal model of the battery to be tested includes: a negative electrode palladium sheet, a negative electrode cover, a negative electrode column, a negative electrode adapter, a negative electrode tab, an electrode group, a shell, a positive electrode cover, a positive electrode column, a positive electrode adapter, a positive electrode tab and a positive electrode palladium sheet.

[0028] In a second aspect, a battery external short circuit simulation system is provided, comprising: an electrochemical model building module, for building an electrochemical model of a battery to be tested;

[0029] An external short-circuit voltage determination module, used to determine the external short-circuit voltage of the battery to be tested according to the electrochemical model of the battery to be tested;

[0030] An acquisition module, used to obtain the external short-circuit resistance of the battery to be tested;

[0031] The external short-circuit current determination module is used to determine the external short-circuit current of the battery to be tested according to the external short-circuit voltage and the external short-circuit resistance of the battery to be tested.

[0032] One of the above technical solutions has the following advantages or beneficial effects:

[0033] Compared with the prior art, the present application provides a method for simulating an external short circuit of a battery, including: establishing an electrochemical model of the battery to be tested; determining the external short circuit voltage of the battery to be tested according to the electrochemical model of the battery to be tested; obtaining the external short circuit resistance of the battery to be tested, and determining the external short circuit current of the battery to be tested according to the external short circuit voltage and the external short circuit resistance of the battery to be tested. The method for simulating an external short circuit of a battery provided by the present application can calculate the external short circuit voltage and current of the battery when an external short circuit occurs, so as to realize dynamic characteristic analysis when an external short circuit occurs in the battery, and realize safety assessment of the battery. In addition, the present application can realize safety assessment of the external short circuit condition of the battery by establishing and calculating the voltage and current of the battery under an external short circuit according to the electrochemical model of the battery, without the need for a large number of experimental tests, etc., thereby reducing the number of experiments, shortening the test cycle, and reducing costs.

[0034] The battery external short circuit simulation system of the present application can calculate the external short circuit voltage and current of the battery when an external short circuit occurs, so as to realize dynamic characteristic analysis when the battery has an external short circuit, and realize the safety assessment of the battery. In addition, the present application calculates the voltage and current of the battery under an external short circuit based on the electrochemical model of the battery, and can realize the safety assessment of the battery external short circuit condition without a large number of experimental tests, thereby reducing the number of experiments, shortening the test cycle, and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1is a flow chart of a battery external short circuit simulation method provided in an embodiment of the present application;

[0037] Figure 2 is a schematic structural diagram of a one-dimensional electrochemical model provided in an embodiment of the present application;

[0038] Figure 3 is a flow chart of another battery external short circuit simulation method provided in an embodiment of the present application;

[0039] Figure 4 is a flow chart of another battery external short circuit simulation method provided in an embodiment of the present application;

[0040] Figure 5 is a schematic structural diagram of a negative electrode structure provided in an embodiment of the present application;

[0041] Figure 6 is a schematic structural diagram of a positive electrode structural member provided in an embodiment of the present application;

[0042] Figure 7 It is a schematic diagram of the structure of the pole group and the digital model provided in the embodiment of the present application;

[0043] Figure 8 It is a quality schematic diagram of a complete 3D geometric mesh division unit provided in an embodiment of the present application;

[0044] Fig. 9 It is a schematic diagram of the technical route provided in the embodiments of the present application;

[0045] Fig.10 It is a schematic diagram of the overall process provided in the embodiments of the present application;

[0046] Fig.11 A schematic diagram of a measured curve of external short-circuit resistance provided in an embodiment of the present application;

[0047] Fig.12 A schematic diagram of the positive electrode palladium sheet fusing due to an external short circuit provided in an embodiment of the present application;

[0048] Fig.13 It is a schematic diagram of the comparison structure of the measured value and the simulated value of the voltage under the external short circuit of the battery provided in the embodiment of the present application;

[0049] Fig.14 It is a schematic diagram of the structure of comparison between the measured value and the simulated value of the current under the external short circuit of the battery provided in the embodiment of the present application;

[0050] Fig.15 Schematic diagram of temperature distribution of positive electrode structural parts when external short circuit is performed for 180s provided in an embodiment of the present application;

[0051] Fig.16Schematic diagram of temperature distribution of negative electrode structural parts when external short circuit is performed for 180s provided in an embodiment of the present application;

[0052] Fig.17 It is a schematic diagram of the temperature distribution of the battery cell when the external short circuit is 180s provided in the embodiment of the present application;

[0053] Fig.18 is a schematic diagram of current changes of batteries with different external short-circuit resistance values ​​provided in the embodiments of the present application;

[0054] Fig.19 It is a principle structural block diagram of a battery external short circuit simulation system provided in an embodiment of the present application.

[0055] Reference numerals:

[0056] 10-electrochemical model building module; 20-external short-circuit voltage determination module; 30-acquisition module; 40-external short-circuit current determination module; 100-battery external short-circuit simulation system. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0058] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, "multiple" means two or more, and at least one means one, two or more, unless otherwise clearly and specifically defined.

[0059] Figure 1This is a flow chart of a battery external short circuit simulation method provided in an embodiment of the present application. This method can be applied to analyze the operating conditions of the battery in a battery management system, for example, to test the battery external short circuit according to national standards, or to simulate the battery external short circuit condition in a simulation test when the battery has an external short circuit during use to evaluate the battery safety performance. This method can be executed by a battery external short circuit simulation system, which can be implemented by software and / or hardware, and which can be configured in the processor of the battery management platform. Please refer to Figure 1 , the method comprises the following steps:

[0060] Step 110: Establish an electrochemical model of the battery to be tested.

[0061] The electrochemical model of the battery to be tested may be a one-dimensional electrochemical model, for example, a one-dimensional finite element electrochemical geometric model.

[0062] Figure 2 is a schematic diagram of the structure of a one-dimensional electrochemical model provided in the embodiment of the present application. For example, the embodiment of the present application establishes a one-dimensional finite element electrochemical geometric model with a five-layer structure. Figure 2 , the one-dimensional electrochemical model of the battery to be tested includes: one-dimensional five-layer material domains arranged in sequence, namely: negative electrode current collector, negative electrode porous electrode, separator, positive electrode porous electrode and positive electrode current collector. Specifically, the process of constructing the electrochemical model is: define the basic material parameters of each material domain of the electrochemical model. Exemplarily, the electrical grounding position is set to the left end point of the negative electrode current collector, and the electrode current density acquisition position is set to the right end point of the positive electrode current collector. Among them, the variables in the electrochemical model include but are not limited to the voltage of the battery to be tested, the state of charge of the negative electrode material, the state of charge of the positive electrode material, and the heat generation power of the battery cell. In particular, the solid phase diffusion coefficient and reaction rate constant of the electrode material are related to temperature, and the specific relationship is as follows:

[0063]

[0064] Among them, D s and k represent the reference temperature T ref The solid phase lithium ion effective diffusion coefficient and electrochemical effective reaction rate constant under a，D and E a，k Corresponding to D s and activation energy of k parameters, and R is the ideal gas constant.

[0065] The material basic parameters of each material domain of the electrochemical model refer to the following equations:

[0066] First, the solid phase charge conservation equation:

[0067]

[0068] Among them, σ s eff is the effective electronic conductivity of the solid phase material ( where σ s is the electronic conductivity of the solid phase material, ε s is the solid phase volume fraction, γ is the correction coefficient), φ s is the solid phase potential, S a is the specific surface area of ​​the solid phase material, r s is the particle radius of the solid material, i loc is the local current density.

[0069] Second, the liquid phase charge conservation equation:

[0070]

[0071] Among them, σ e eff is the effective conductivity of the liquid phase material, φ e is the liquid phase potential, R is the ideal gas constant, T is the temperature, F is the Faraday constant, f is the activity coefficient, c e is the liquid phase lithium ion concentration, t + is the liquid phase ion transfer number, S a is the specific surface area of ​​the solid phase material, i loc is the local current density.

[0072] Third, the solid phase mass conservation equation:

[0073]

[0074] Among them, c s is the solid phase lithium concentration, t is the time, r is the radius of the spherical coordinate system established with the center of the spherical particle as the origin, D s eff is the effective diffusion coefficient of solid-phase lithium ions.

[0075] Fourth, the liquid mass conservation equation:

[0076]

[0077] Among them, ε e is the liquid volume fraction, c e is the liquid phase lithium ion concentration, t is the time, D e eff is the effective diffusion coefficient of lithium ions in liquid phase, S a is the specific surface area of ​​the solid phase material, i loc is the local current density, F is the Faraday constant, t + is the liquid phase ion transfer number.

[0078] Fifth, the electrode reaction kinetic equation:

[0079]

[0080] Among them, i loc is the local current density, i0 is the exchange current density, α is the charge transfer coefficient, η is the electrode overpotential, F is the Faraday constant, R is the ideal gas constant, T is the temperature, k eff is the electrochemical effective reaction rate constant, c s，max is the maximum lithium ion concentration in the solid phase, c s，surf is the lithium ion concentration on the particle surface, c e is the liquid phase lithium ion concentration, c e，ref =1.2 mol m -3 is the reference concentration of electrolyte, φ s is the solid phase potential, φ l is the liquid phase potential, E eq is the open circuit voltage.

[0081] Sixth, the energy conservation equation of the battery cell:

[0082]

[0083] Q dis =h(T amb -T)+ελ(T amb 4 -T 4 );

[0084] Where ρ is the density, C P is the specific heat capacity, K T is thermal conductivity, T is temperature, t is time, Q act is the electrochemical polarization heat, Q rea is the reversible entropy heat, Q ohm is Ohmic heat, Q short The internal short circuit generates heat, Q j The heat generated by the thermal runaway side reaction, Q dis is the heat dissipation term, H is the convection heat transfer coefficient between the battery and the environment, T amb is the ambient temperature, ε is the surface emissivity, and λ is the Stefan-Boltzmann constant.

[0085] Seventh, Ohm's law equation for structural parts:

[0086] J=σE+J e ;

[0087] Where σ is the conductivity, E is the electric field strength, J e is the current density generated externally, and J is the current density.

[0088] Eighth, Ohm heat equation of structural parts:

[0089] Q e = J.E;

[0090] Where J is the current density, E is the electric field strength, and Q e It is Ohm heat.

[0091] Step 120: Determine the external short-circuit voltage of the battery to be tested according to the electrochemical model of the battery to be tested.

[0092] Among them, various battery parameter information of the battery when an external short circuit occurs can be obtained according to the battery electrochemical model, and then the external short circuit voltage of the battery can be calculated according to the battery parameter information when the battery is externally short-circuited. Among them, various battery parameter information of the battery when an external short circuit occurs includes the diffusion coefficient of the electrode material, the reaction rate of the electrode material, the lithium ion concentration, the effective electronic conductivity, the liquid phase current density, the solid phase current density, etc.

[0093] Step 130 : obtaining the external short-circuit resistance of the battery to be tested, and determining the external short-circuit current of the battery to be tested according to the external short-circuit voltage and the external short-circuit resistance of the battery to be tested.

[0094] Among them, the external short-circuit resistance of the battery to be tested can be determined according to the actual application scenario. For example, when the battery external short circuit is tested according to the national standard, the external short-circuit resistance of the battery to be tested is the test resistance specified by the national standard, such as 1 milliohm. When the battery has an external short circuit condition, the external short-circuit resistance of the battery to be tested is the resistance actually measured when the battery has an external short circuit.

[0095] After the external short-circuit voltage and the external short-circuit resistance of the battery to be tested are calculated, the external short-circuit current of the battery can be obtained according to Ohm's law.

[0096] In the technical solution of this embodiment, the working principle of the battery external short circuit simulation method is as follows: Figure 1 First, an electrochemical model of the battery to be tested is established. Then, the external short-circuit voltage of the battery to be tested is determined according to the electrochemical model of the battery to be tested. Finally, the external short-circuit resistance of the battery to be tested is obtained, and the external short-circuit current of the battery to be tested is determined according to the external short-circuit voltage and the external short-circuit resistance of the battery to be tested. This method can be achieved by: by establishing an electrochemical model of the battery, when the battery has an external short circuit or an external short-circuit test is performed according to the national standard, the external short-circuit voltage and the external short-circuit current of the battery when an external short circuit occurs can be calculated according to the electrochemical model of the battery, so that dynamic characteristic analysis can be performed when the battery has an external short circuit, and the safety assessment of the battery can be achieved, thereby improving the safety and reliability of the battery. And compared with traditional experimental means and methods, the present application does not need to conduct a large number of experimental tests, etc., to achieve a safety assessment of the battery external short-circuit condition, thereby reducing the number of experiments, shortening the test cycle, and reducing costs.

[0097] Figure 3 is a flow chart of another battery external short circuit simulation method provided in the embodiment of the present application. Figure 3 , the method comprises the following steps:

[0098] Step 210: Decompose the voltage of the battery to be tested to obtain a plurality of decomposed voltages.

[0099] Among them, the multiple decomposition voltages obtained by decomposing the voltage of the battery to be tested include at least: liquid phase ohmic polarization voltage, solid phase ohmic polarization voltage, electrochemical reaction activation polarization voltage, liquid phase diffusion polarization voltage and solid phase diffusion polarization voltage.

[0100] Step 220: Establish a solution model for each decomposition voltage and an electrochemical model of the battery to be tested.

[0101] Among them, the solution models of each decomposition voltage are: liquid phase ohmic polarization voltage solution equation, solid phase ohmic polarization voltage solution equation, electrochemical reaction activation polarization voltage solution equation, liquid phase diffusion polarization voltage solution equation and solid phase diffusion polarization voltage solution equation.

[0102] Among them, the solution equation for the liquid phase ohmic polarization voltage is:

[0103]

[0104] Among them, E e_ohm is the liquid phase ohmic polarization voltage, j tot Total current density (A / m 2 ), j L Liquid phase current density (A / m 2 ), κ eff Liquid phase effective ionic conductivity (S / m), L length / thickness of battery component (m).

[0105] Among them, the equation for solving the solid phase ohmic polarization voltage is:

[0106]

[0107] Among them, E s_ohm is the solid phase ohmic polarization voltage, j tot Total current density (A / m 2 ), j s Solid phase current density (A / m 2 ), L length / thickness of battery assembly (m), σ eff Effective electronic conductivity (S / m).

[0108] Among them, the equation for solving the activation polarization voltage of the electrochemical reaction is:

[0109]

[0110] Among them, E act is the activation polarization voltage of the electrochemical reaction, j tot Total current density (A / m 2 ), j loc Local current density (A / m 2 ), L is the length / thickness of the battery assembly (m), a is the specific surface area (1 / m), is the solid phase potential, is the liquid phase potential, E surf is the surface potential of the active material (V).

[0111] Among them, the solution equation for liquid phase diffusion polarization voltage is:

[0112]

[0113] Among them, E e_diff is the liquid phase diffusion polarization voltage, j tot Total current density (A / m 2 ), j L Liquid phase current density (A / m 2 ), L battery assembly length / thickness (m), k c Concentration correlation coefficient, R is the gas constant (8.3143 J / mol / K), T is the temperature (K), F is the Faraday constant (96487 1 / mol), c L is the liquid phase lithium ion concentration.

[0114] Among them, the equation for solving the solid phase diffusion polarization voltage is:

[0115]

[0116] Among them, E s_diff is the solid phase diffusion polarization voltage, j tot Total current density (A / m 2 ), j loc Local current density (A / m 2 ), L is the length / thickness of the battery assembly (m), a is the specific surface area (1 / m), E is the surf is the surface potential of the active material (V), E ave is the average potential of the active material (V).

[0117] Step 230: determine the external short-circuit full voltage of the battery to be tested according to the solution models of the decomposition voltages and the electrochemical model of the battery to be tested.

[0118] Among them, the implementation method of determining the external short-circuit full voltage of the battery to be tested according to the solution model of each decomposition voltage and the electrochemical model of the battery to be tested is: obtaining each decomposition voltage of the battery to be tested under an external short circuit according to the solution model of each decomposition voltage and the electrochemical model of the battery to be tested; and determining the external short-circuit full voltage of the battery to be tested according to each decomposition voltage of the battery to be tested under an external short circuit.

[0119] Optionally, the method for obtaining each decomposition voltage of the battery to be tested under external short circuit according to the solution model of each decomposition voltage and the electrochemical model of the battery to be tested is: determining the battery internal parameter information of the battery to be tested under external short circuit according to the electrochemical model of the battery to be tested; and obtaining each decomposition voltage of the battery to be tested under external short circuit according to the battery internal parameter information of the battery to be tested under external short circuit and the solution model of each decomposition voltage.

[0120] Specifically, the battery parameter information required for the solution model of each decomposition voltage under external short circuit can be obtained according to the electrochemical model of the battery to be tested. Then, according to the battery parameter information required for the solution model of each decomposition voltage and the corresponding solution model of the decomposition voltage, the decomposition voltage of the battery to be tested under external short circuit can be calculated. For example, first, according to the electrochemical model, the battery parameter information required for the solution equation of the liquid phase ohmic polarization voltage can be obtained, such as the total current density j tot , liquid phase current density j L , liquid phase effective ionic conductivity κ eff , the length / thickness of the battery assembly L. Then, the various battery parameter information required in the liquid phase ohmic polarization voltage solution equation is substituted into the liquid phase ohmic polarization voltage solution equation to obtain the liquid phase ohmic polarization voltage.

[0121] For example, first, the various battery parameter information required to solve the solid phase ohmic polarization voltage equation can be obtained based on the electrochemical model, such as the total current density j tot , solid phase current density j s , length / thickness L of the battery component, effective electronic conductivity σ eff Then, the solid-phase ohmic polarization voltage can be obtained by substituting the various battery parameter information required in the solid-phase ohmic polarization voltage solution equation into the solid-phase ohmic polarization voltage solution equation.

[0122] For example, firstly, the electrochemical model can be used to obtain the various battery parameter information required to solve the electrochemical reaction activation polarization voltage equation, such as the total current density j tot , local current density j loc , length / thickness L of battery components, specific surface area a, solid phase potential Liquid potential Active material surface potential E surfThen, the electrochemical reaction activation polarization voltage can be obtained by substituting the various battery parameter information required in the electrochemical reaction activation polarization voltage solution equation into the electrochemical reaction activation polarization voltage solution equation.

[0123] For example, first, the various battery parameter information required to solve the liquid phase diffusion polarization voltage equation can be obtained based on the electrochemical model, such as the total current density j tot , liquid phase current density j L , length / thickness L of battery component, concentration correlation coefficient k c , gas constant R, temperature T, Faraday constant F, liquid phase lithium ion concentration c L Then, the liquid phase diffusion polarization voltage can be obtained by substituting the various battery parameter information required in the liquid phase diffusion polarization voltage solution equation into the liquid phase diffusion polarization voltage solution equation.

[0124] For example, first, the various battery parameter information required to solve the solid-phase diffusion polarization voltage equation can be obtained based on the electrochemical model, such as the total current density j tot , local current density j loc , length / thickness L of battery components, specific surface area a, surface potential E of active materials surf , the average potential of the active material E ave Then, the various battery parameter information required in the solid-phase diffusion polarization voltage solution equation is substituted into the solid-phase diffusion polarization voltage solution equation to obtain the solid-phase diffusion polarization voltage.

[0125] Optionally, determining the external short-circuit full voltage of the battery under test according to each decomposition voltage of the battery under test under external short circuit includes: obtaining the external short-circuit full voltage of the battery under test according to the sum of each decomposition voltage of the battery under test under external short circuit.

[0126] Among them, the calculation formula of the external short-circuit full voltage of the battery to be tested is as follows:

[0127] E cell =E e_ohm +E s_ohm +E act +E e_diff +E s_diff

[0128] Among them, E cell It is the external short-circuit full voltage of the battery under test.

[0129] Step 240: Determine the external short-circuit current of the battery to be tested according to the external short-circuit full voltage and the external short-circuit resistance of the battery to be tested.

[0130] Among them, the calculation formula of the external short-circuit current of the battery to be tested is as follows:

[0131] Icell =E cell / R short

[0132] Among them, I cell is the external short-circuit current of the battery to be tested, R short is the external short-circuit resistance of the battery under test.

[0133] In the technical solution of this embodiment, the working principle of the battery external short circuit simulation method is as follows: Figure 3 First, the voltage of the battery to be tested is decomposed to obtain multiple decomposition voltages. Then, a solution model for each decomposition voltage and an electrochemical model of the battery to be tested are established. Secondly, the external short-circuit full voltage of the battery to be tested is determined according to the solution model of each decomposition voltage and the electrochemical model of the battery to be tested. Finally, the external short-circuit current of the battery to be tested is determined according to the external short-circuit full voltage and the external short-circuit resistance of the battery to be tested. It can be seen that this method can be achieved by: decomposing the voltage of the battery, establishing the solution model of each decomposition voltage and the electrochemical model of the battery, and solving each decomposition voltage under the external short circuit according to the solution model of each decomposition voltage and the electrochemical model of the battery, and then obtaining the battery external short-circuit full voltage and external short-circuit current, so as to realize the dynamic characteristic analysis of the battery when an external short circuit occurs, realize the safety assessment of the battery, and then improve the safety and reliability of the battery. And compared with the traditional experimental means and methods, the present application does not need to carry out a large number of experimental tests, etc., to realize the safety assessment of the battery external short-circuit working condition, thereby reducing the number of experiments, shortening the test cycle, and reducing costs.

[0134] Figure 4 is a flow chart of another battery external short circuit simulation method provided in the embodiment of the present application. Based on the above embodiment, optionally, refer to Figure 4 , the method comprises the following steps:

[0135] Step 310: Decompose the voltage of the battery to be tested to obtain a plurality of decomposed voltages.

[0136] Step 320: Establish a solution model for each decomposition voltage and an electrochemical model of the battery to be tested.

[0137] Step 330: determine the external short-circuit full voltage of the battery to be tested according to the solution models of the decomposition voltages and the electrochemical model of the battery to be tested.

[0138] Step 340: Determine the external short-circuit current of the battery to be tested according to the external short-circuit full voltage and the external short-circuit resistance of the battery to be tested.

[0139] Step 350: Establish an electro-thermal model of the battery to be tested.

[0140] The electric-thermal model of the battery to be tested is a 3D electric-thermal model. Exemplarily, a 3D finite element "electric-thermal" geometric model is established at a ratio of 1:1 according to the actual module of the battery cell.

[0141] Among them, the "electric-thermal" field includes a three-dimensional geometric structure: a negative electrode palladium sheet, a negative electrode cover, a negative electrode column, a negative electrode adapter, a negative electrode lug, an electrode group, a shell, a positive electrode cover, a positive electrode column, a positive electrode adapter, a positive electrode lug and a positive electrode palladium sheet.

[0142] Figure 5 Schematic diagram of the structure of the negative electrode structure provided in the embodiment of the present application. Figure 5 The negative electrode palladium sheet, negative electrode cover plate, negative electrode column, negative electrode adapter plate and negative electrode ear constitute the negative electrode structural parts of the battery.

[0143] Figure 6 Schematic diagram of the structure of the positive electrode structure provided in the embodiment of the present application. Figure 6 The positive electrode structural parts of the battery are composed of the shell, positive electrode cover, positive electrode column, positive electrode adapter, positive electrode ear and positive electrode palladium sheet.

[0144] Figure 7 Schematic diagram of the structure of the electrode group and digital model provided in the embodiment of the present application. Figure 7 shown.

[0145] The boundary conditions of the 3D electro-thermal model are: the negative palladium sheet and the positive palladium sheet are set as terminals, and the input current is the external short-circuit current of the battery calculated above. The negative and positive tabs are set to be grounded, and the potential is 0V. The contact impedances of the negative and positive palladium sheets are set to be 2.34e -8 Ω*m 2 and 3.1e -8 Ω*m 2 The convection heat transfer coefficient between the battery cell and the environment is 20W / (m 2 *K), the surface emissivity is 0.6. The heat sources of the positive and negative electrode structures come from Joule heat, and the heat source of the electrode group comes from the one-dimensional electrochemical model.

[0146] Figure 8 is a quality diagram of a complete 3D geometric mesh division unit provided in an embodiment of the present application. Figure 8 The meshing of the 3D electro-thermal model is as follows: the 3D geometry is divided by free tetrahedrons, the positive and negative electrode structures are divided by ultra-fine free tetrahedrons, and the shell and electrode group are divided by conventional free tetrahedrons. Figure 8 The closer the value is to 1, the higher the quality of the meshing is, and the closer the value is to 0, the lower the quality of the meshing is.

[0147] Step 360: Determine the temperature rise distribution of the battery under external short circuit according to the external short circuit current of the battery and the electro-thermal model of the battery.

[0148] Specifically, the voltage of the battery is decomposed, and the solution model of each decomposition voltage and the electrochemical model of the battery are established. According to the solution model of each decomposition voltage and the electrochemical model of the battery, each decomposition voltage under external short circuit is obtained, and then the battery external short circuit full voltage and external short circuit current are obtained, thereby analyzing the dynamic characteristics of the battery such as current and voltage when an external short circuit occurs, and inputting the external short circuit current of the battery to be tested into the electric-thermal model of the battery to be tested, the temperature rise distribution of the entire battery unit of the battery to be tested under external short circuit can be obtained, such as the temperature rise distribution of the pole group, the temperature rise distribution of the positive electrode structural parts, and the temperature rise distribution of the negative electrode structural parts. In this way, the current, voltage and temperature rise distribution of the external short circuit of the battery are simulated and predicted, which is conducive to further evaluating and analyzing the safety and reliability of the battery, for example, judging whether the battery will have a fuse of a structural part or a pole ear under an external short circuit, and whether thermal runaway of the battery cell will occur.

[0149] In the technical solution of this embodiment, the working process of the battery external short circuit simulation method is as follows: Figure 4 First, the voltage of the battery to be tested is decomposed to obtain multiple decomposition voltages. Then, the solution model of each decomposition voltage and the electrochemical model of the battery to be tested are established. Secondly, the external short-circuit full voltage of the battery to be tested is determined according to the solution model of each decomposition voltage and the electrochemical model of the battery to be tested. The external short-circuit current of the battery to be tested is determined according to the external short-circuit full voltage and the external short-circuit resistance of the battery to be tested. Finally, the electro-thermal model of the battery to be tested is established, and the temperature rise distribution of the battery to be tested under external short circuit is determined according to the external short-circuit current of the battery to be tested and the electro-thermal model of the battery to be tested. It can be seen that this method can be implemented by: decomposing the voltage of the battery, establishing the solution model of each decomposition voltage and the electrochemical model of the battery, and solving the various decomposition voltages under the external short circuit according to the solution model of each decomposition voltage and the electrochemical model of the battery, and then obtaining the battery external short circuit full voltage and external short circuit current, and inputting the external short circuit current into the electric-thermal model to obtain the temperature rise distribution of the battery, so as to realize the analysis of the dynamic characteristics of the battery external short circuit voltage, current, resistance, etc., and analyze the temperature rise distribution of the battery structure, such as the temperature rise of the positive electrode structure, the temperature rise of the negative electrode structure, and the temperature rise of the pole group, so as to realize the simulation and risk prediction of the battery external short circuit working condition, realize the safety assessment of the battery, and then improve the safety and reliability of the battery. And compared with the traditional experimental means and methods, the present application does not need to carry out a large number of experimental tests, etc., to realize the safety assessment of the battery external short circuit working condition, thereby reducing the number of experiments, shortening the test cycle, and reducing costs.

[0150] Fig. 9 It is a schematic diagram of the technical route provided in the embodiments of this application. Fig. 9 , the present application determines the external short-circuit full voltage of the battery by voltage decomposition. Then, the external short-circuit current of the battery and the heat generation power of the pole group are obtained through the lithium ion electrochemical model (i.e., electrochemical field). Subsequently, the heat generation power of the pole group is input into the solid heat transfer model (i.e., solid heat transfer field), and the external short-circuit current data is applied to the current field analysis to calculate the Joule heat in the battery structure. Finally, the Joule heat information obtained from the current field is fed back to the solid heat transfer model, thereby realizing the accurate calculation of the temperature distribution of the entire battery cell. Thus, through the coupling of the three physical fields of electrochemical field, current field, and solid heat transfer field, the external short-circuit current of the lithium-ion battery, the temperature distribution of the pole group, and the temperature distribution of the structural parts can be accurately predicted, so as to facilitate the judgment of whether the structural parts or the pole ears of the battery will be blown under the external short-circuit condition, and whether the thermal runaway phenomenon of the battery cell will occur.

[0151] Fig.10 It is a schematic diagram of the overall process provided in the embodiments of this application. Fig.10 , Step S1: First, establish a set of electrochemical, electrical and thermal equations to describe the behavior of the battery under different states in mathematical form. Step S2: Build a geometric model, such as a one-dimensional electrochemical model and a three-dimensional "electric-thermal" model, set boundary conditions and mesh division. Step S3: Use numerical methods (such as finite element analysis) to solve the set of equations in the above physical model. Step S4: Experimental testing collects data on the battery under different short-circuit conditions to calibrate and verify the effectiveness of the model. Step S5: Predict other short-circuit conditions.

[0152] The specific process of calibration and calculation of the above model is as follows:

[0153] Fig.11 This is a schematic diagram of the measured curve of the external short-circuit resistance provided in the embodiment of the present application, Fig.12 Schematic diagram of the external short circuit causing the positive electrode palladium sheet to fuse provided in the embodiment of the present application. For example, taking the external short circuit test of a large-capacity battery cell 362Ah fully charged as an example, the external short circuit resistance obtained is as follows: Fig.11 As shown. Combined Fig.11 and Fig.12 At 125 seconds, the positive electrode palladium sheet of the battery melted, and the battery cell did not catch fire or explode.

[0154] Fig.13 : is a schematic diagram of the comparison structure of the measured value and the simulated value of the voltage under the external short circuit of the battery provided in the embodiment of the present application, Fig.14 : is a schematic diagram of the comparison of the measured value and the simulated value of the current under the external short circuit of the battery provided in the embodiment of the present application. Fig.11The external short-circuit resistance is used as the simulation input to simulate the battery's external short-circuit current change, external short-circuit voltage change, temperature rise distribution, and microscopic physical changes inside the battery.

[0155] according to Fig.13 Comparison of the measured and simulated voltage values ​​of the battery under external short circuit. It can be seen from the figure that the measured voltage value and the simulated voltage value match relatively well, which confirms that the above model is highly consistent with the actual external short circuit process of the battery. Fig.14 Comparison of the measured current value and the simulated current value of the battery under external short circuit. It can be seen from the figure that the measured current value and the simulated current value are also relatively well matched, which once again confirms that the above model is highly consistent with the actual external short circuit process of the battery. Since the fully charged voltage of the battery cell is about 3.6V, but the voltage drops directly to 2.4V at the beginning of the external short circuit test, this is because the applied external short circuit resistance is very small, and the capacity of the battery cell is relatively large at 362Ah, so the external short circuit current can reach more than 3000A. At this time, the positive and negative polarization of the battery is too large, deviating from the equilibrium potential, that is, the overpotential is large.

[0156] Fig.15 : is a schematic diagram of the temperature distribution of the positive electrode structure when the external short circuit is 180s provided in the embodiment of the present application, Fig.16 : is a schematic diagram of the temperature distribution of the negative electrode structure when the external short circuit is 180s provided in the embodiment of the present application, Fig.17 1 is a schematic diagram of the temperature distribution of the battery cell when the external short circuit is 180s provided in the embodiment of the present application. Further, the temperature distribution of the positive electrode structure, the negative electrode structure and the electrode group of the battery is simulated. Figure 15-17 , when the external short circuit lasts for 180s, the maximum temperature of the positive electrode structural parts reaches 252°C, and the maximum temperature of the negative electrode structural parts reaches 278°C. The overall temperature difference of the battery cell is large, and the temperature on the electrode group is kept below 100°C. However, the temperatures of the structural parts and the pole ears exceed 200°C. That is, in the event of an external short circuit, the positive and negative electrode structural parts and the pole ears of the battery are prone to melting. Due to the excessive temperature at the pole ears, the diaphragm near the pole ears may be melted, further causing the battery to catch fire and explode, resulting in thermal runaway. Therefore, the simulation method of battery external short circuit provided by the present application is conducive to the simulation and testing of external short circuits of batteries by relevant personnel, so as to facilitate a clear understanding of the current state of the battery and determine whether the battery has safety risks.

[0157] Fig.18 Schematic diagram of current change of batteries with different external short-circuit resistance values ​​provided in the embodiments of the present application. In addition, the present application also analyzes the temperature distribution of battery structural parts and pole groups under other external short-circuit resistance values. Fig.18, when the external short-circuit resistance is 2mΩ and 5mΩ respectively, and the external short-circuit time is 600s, the maximum current of the battery is about 1500A and 656A respectively. Among them, the maximum temperature rise of each component is shown in Table 1.

[0158] Table 1 Maximum temperature rise of each component with different external short-circuit resistance values

[0159]

[0160] Fig.19 is a principle structure block diagram of a battery external short circuit simulation system provided in the embodiment of the present application. Correspondingly, the embodiment of the present application also provides a battery external short circuit simulation system, see Fig.19 The system 100 includes: an electrochemical model building module 10, used to build an electrochemical model of the battery to be tested; an external short-circuit voltage determination module 20, used to determine the external short-circuit voltage of the battery to be tested according to the electrochemical model of the battery to be tested; an acquisition module 30, used to obtain the external short-circuit resistance of the battery to be tested; an external short-circuit current determination module 40, used to determine the external short-circuit current of the battery to be tested according to the external short-circuit voltage and the external short-circuit resistance of the battery to be tested.

[0161] The technical solution of the embodiment of the present application provides a battery external short circuit simulation system, which includes an electrochemical model establishment module for establishing an electrochemical model of the battery to be tested; an external short circuit voltage determination module for determining the external short circuit voltage of the battery to be tested according to the electrochemical model of the battery to be tested; an acquisition module for obtaining the external short circuit resistance of the battery to be tested; an external short circuit current determination module for determining the external short circuit current of the battery to be tested according to the external short circuit voltage and external short circuit resistance of the battery to be tested. Through this system, the external short circuit voltage and current of the battery when an external short circuit occurs can be calculated, so that dynamic characteristic analysis can be performed when an external short circuit occurs in the battery, and the safety assessment of the battery has been achieved. And the present application calculates the voltage and current of the battery under external short circuit by establishing and calculating the voltage and current of the battery under external short circuit according to the electrochemical model of the battery, without a large number of experimental tests, etc., so that the number of experiments can be reduced, the test cycle can be shortened, and the cost can be reduced.

[0162] In some embodiments, the electrochemical model of the battery to be tested includes five material domains, namely: a negative electrode current collector, a negative electrode porous electrode, a separator, a positive electrode porous electrode and a positive electrode current collector.

[0163] In some embodiments, the battery external short circuit simulation system further includes: a decomposition module, used to decompose the voltage of the battery to be tested to obtain multiple decomposition voltages. A solution model establishment module, used to establish a solution model for each decomposition voltage. An external short circuit full voltage determination module, used to determine the external short circuit full voltage of the battery to be tested based on the solution model of each decomposition voltage and the electrochemical model of the battery to be tested. An external short circuit current determination module, used to determine the external short circuit current of the battery to be tested based on the external short circuit full voltage and external short circuit resistance of the battery to be tested.

[0164] In some embodiments, the external short-circuit full voltage determination module further includes: a decomposition voltage determination unit, which is used to obtain each decomposition voltage of the battery under external short circuit according to the solution model of each decomposition voltage and the electrochemical model of the battery under test. The external short-circuit full voltage determination unit is used to determine the external short-circuit full voltage of the battery under test according to each decomposition voltage of the battery under external short circuit.

[0165] In some embodiments, the decomposition voltage determination unit is used to determine the internal battery parameter information of the battery to be tested under external short circuit according to the electrochemical model of the battery to be tested; and obtain each decomposition voltage of the battery to be tested under external short circuit according to the internal battery parameter information of the battery to be tested under external short circuit and the solution model of each decomposition voltage.

[0166] In some embodiments, the external short-circuit full voltage determination unit is used to obtain the external short-circuit full voltage of the battery to be tested according to the sum of various decomposition voltages of the battery to be tested under external short circuit.

[0167] In some embodiments, the plurality of decomposition voltages include at least: a liquid phase ohmic polarization voltage, a solid phase ohmic polarization voltage, an electrochemical reaction activation polarization voltage, a liquid phase diffusion polarization voltage, and a solid phase diffusion polarization voltage.

[0168] In some embodiments, the battery external short circuit simulation system further includes: an electro-thermal model establishment module, used to establish an electro-thermal model of the battery to be tested; and a temperature rise distribution determination module, used to determine the temperature rise distribution of the battery to be tested under external short circuit according to the external short circuit current of the battery to be tested and the electro-thermal model of the battery to be tested.

[0169] In some embodiments, the electro-thermal model of the battery to be tested includes: a negative electrode palladium sheet, a negative electrode cover, a negative electrode column, a negative electrode adapter, a negative electrode tab, an electrode group, a shell, a positive electrode cover, a positive electrode column, a positive electrode adapter, a positive electrode tab and a positive electrode palladium sheet.

[0170] The above is a detailed introduction to a battery attenuation data processing method and device provided in an embodiment of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solution and core idea of ​​the present application. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery external short circuit simulation method, characterized in that: include: Establish an electrochemical model of the battery to be tested; Determining the external short-circuit voltage of the battery to be tested according to the electrochemical model of the battery to be tested; The external short-circuit resistance of the battery to be tested is obtained, and the external short-circuit current of the battery to be tested is determined according to the external short-circuit voltage and the external short-circuit resistance of the battery to be tested.

2. The battery external short circuit simulation method according to claim 1, characterized in that: The electrochemical model of the battery to be tested includes five material domains, namely, a negative electrode current collector, a negative electrode porous electrode, a separator, a positive electrode porous electrode and a positive electrode current collector.

3. The battery external short circuit simulation method according to claim 1, characterized in that: Also includes: Decomposing the voltage of the battery to be tested to obtain a plurality of decomposed voltages; Establish the solution model of each decomposed voltage; Determine the external short-circuit full voltage of the battery to be tested according to the solution models of each decomposition voltage and the electrochemical model of the battery to be tested; The external short-circuit current of the battery to be tested is determined according to the external short-circuit full voltage of the battery to be tested and the external short-circuit resistance.

4. The battery external short circuit simulation method according to claim 3, characterized in that: The method of determining the external short-circuit full voltage of the battery to be tested according to the solution model of each decomposition voltage and the electrochemical model of the battery to be tested comprises: Obtaining each decomposition voltage of the battery to be tested under external short circuit according to the solution model of each decomposition voltage and the electrochemical model of the battery to be tested; The external short-circuit full voltage of the battery to be tested is determined according to each decomposition voltage of the battery to be tested under external short circuit.

5. The battery external short circuit simulation method according to claim 4, characterized in that: The method of obtaining the decomposition voltages of the battery to be tested under external short circuit according to the solution model of the decomposition voltages and the electrochemical model of the battery to be tested comprises: Determining internal battery parameter information of the battery under external short circuit according to the electrochemical model of the battery under test; The various decomposition voltages of the battery under the external short circuit are obtained according to the internal parameter information of the battery under the external short circuit and the solution model of each decomposition voltage.

6. The battery external short circuit simulation method according to claim 4, characterized in that: The step of determining the external short-circuit full voltage of the battery under test according to each decomposition voltage of the battery under test under external short-circuit comprises: The external short-circuit full voltage of the battery to be tested is obtained according to the sum of the various decomposition voltages of the battery to be tested under external short circuit.

7. The battery external short circuit simulation method according to claim 3, characterized in that: The multiple decomposition voltages include at least: liquid phase ohmic polarization voltage, solid phase ohmic polarization voltage, electrochemical reaction activation polarization voltage, liquid phase diffusion polarization voltage and solid phase diffusion polarization voltage.

8. The battery external short circuit simulation method according to claim 3, characterized in that: After determining the external short-circuit current of the battery to be tested, it also includes: Establish an electro-thermal model of the battery under test; The temperature rise distribution of the battery under external short circuit is determined according to the external short circuit current of the battery under test and the electric-thermal model of the battery under test.

9. The battery external short circuit simulation method according to claim 8, characterized in that: The electric-thermal model of the battery to be tested includes: a negative electrode palladium sheet, a negative electrode cover plate, a negative electrode column, a negative electrode adapter sheet, a negative electrode tab, an electrode group, a shell, a positive electrode cover plate, a positive electrode column, a positive electrode adapter sheet, a positive electrode tab and a positive electrode palladium sheet.

10. A battery external short circuit simulation system, characterized in that: include: Electrochemical model building module, used to build the electrochemical model of the battery to be tested; An external short-circuit voltage determination module, used to determine the external short-circuit voltage of the battery to be tested according to the electrochemical model of the battery to be tested; An acquisition module, used to obtain the external short-circuit resistance of the battery to be tested; The external short-circuit current determination module is used to determine the external short-circuit current of the battery to be tested according to the external short-circuit voltage and the external short-circuit resistance of the battery to be tested.

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