Thermal Simulation Method and Device Based on the Coupling of Lithium Battery Internal Resistance MAP and Temperature

Abstract

The present invention discloses a thermal simulation method and device based on the coupling of lithium battery internal resistance MAP and temperature. The method includes: obtaining battery design parameters, building a one-dimensional electrochemical model of a battery cell, calculating the internal resistance of a lithium battery under different conditions based on the electrochemical model, and drawing a lithium battery internal resistance MAP; based on the lithium battery internal resistance MAP, calculating the heat generation power of the battery cell under different conditions in the operating condition, and drawing a heat generation power MAP; fitting the heat generation power MAP of the battery cell into a binary function affected by the real-time temperature and different SOC states as the heat source input for the battery module thermal simulation; inputting the binary function as the heat source into the battery module thermal simulation model for thermal simulation calculation. The advantages of the present invention are: relatively low calculation cost, shortened project design cycle, and compliance with the actual situation that the heat source of the battery cell changes with temperature when the battery module is working.

Description

Technical Field

[0001] The present invention relates to the technical field of battery thermal simulation, and more particularly to a thermal simulation method and device based on the coupling of lithium battery internal resistance MAP and temperature. Background Art

[0002] Safety has always been one of the problems that the public is worried about. Therefore, it is urgent to improve the technology of lithium battery thermal safety.

[0003] At present, the main thermal simulation methods for lithium battery modules in the industry are the equivalent circuit method and the fixed heat source method. The equivalent circuit method has a large calculation cost, high simulation accuracy, and requires strict HPPC data test support, which will inevitably cause the extension of the project design cycle and cannot provide timely synchronous feedback during product iteration. The fixed heat source method cannot couple the influence of different conditions such as different rates, different temperatures, different SOC states, and different pulse times on the heat generation power of the battery. For example, the thermal simulation method of a lithium ion battery system disclosed in Chinese Patent Publication No. CN106650134A and the thermal simulation method of a lithium ion battery disclosed in Chinese Patent Publication No. CN107977500A both belong to the fixed heat source method. They only consider the thermal simulation of the battery under specific conditions, cannot couple the influence of different conditions such as different rates, different temperatures, different SOC states, and different pulse times on the heat generation power of the battery, and cannot simulate the thermal distribution of the battery pack under complex driving or application conditions, which does not conform to the actual situation of the heat source of the battery unit changing with temperature during the operation of the battery module. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the existing lithium battery thermal simulation method has problems such as large calculation cost, extended project design cycle, and does not conform to the actual situation of the heat source of the battery unit changing with temperature during the operation of the battery module.

[0005] The present invention solves the above technical problems through the following technical means: a thermal simulation method based on the coupling of lithium battery internal resistance MAP and temperature, the method comprising:

[0006] Step 1: Obtain battery design parameters, build a one-dimensional electrochemical model of the battery unit, calculate the internal resistance of the lithium battery under different conditions based on the electrochemical model, and draw the lithium battery internal resistance MAP;

[0007] Step 2: Based on the lithium battery internal resistance MAP, calculate the heat generation power of the battery unit under different conditions in the usage condition, and draw it into a heat generation power MAP diagram;

[0008] Step 3: Fit the heat generation power MAP diagram of the battery unit into a binary function affected by real-time temperature and different SOC states as the heat source input for battery module thermal simulation;

[0009] Step 4: Input the binary function as a heat source into the battery module thermal simulation model for thermal simulation calculation.

[0010] During the calculation process of the thermal simulation model of the present invention, due to differences in structure, position, operating conditions, etc. of each unit in the battery module, there are differences in the temperature field and SOC state. This simulation method can accurately feedback the SOC state and real-time temperature of different battery cells to the battery heat source input, realizing accurate simulation of uneven distribution of temperature field and SOC state of the battery heat source under different usage conditions, which conforms to the actual situation of the battery cell heat source changing with temperature during the operation of the battery module. Only by obtaining battery design parameters at the front end of battery design can the design simulation requirements of modules such as modules and battery packs be solved, without the support of strict HPPC data testing, with low calculation cost and greatly shortened design cycle.

[0011] Further, the battery design parameters include the ratio of positive and negative electrode materials, the ratio of electrolyte materials, concentration, conductivity, winding core component materials, size, and surface density.

[0012] Further, the one-dimensional electrochemical model of the battery cell is built based on the Newman model using battery design parameters.

[0013] Further, the different conditions include different rates, different temperatures, different SOC states, and different pulse times.

[0014] Even further, Step 2 includes: Based on the lithium battery internal resistance MAP, calculate the heat generation power of the battery cell under the operating conditions under different conditions according to P = I 2 R, and draw a heat generation power MAP diagram.

[0015] Even further, Step 3 includes: When the operating conditions are determined, the usage rate and pulse time of the battery cell are both determined. Therefore, the heat generation power MAP diagram of the battery cell can be directly fitted into a binary function affected by real-time temperature and different SOC states with the help of MATLAB.

[0016] Even further, Step 4 includes: In the Fluent software, input the binary function as a heat source into the battery module thermal simulation model, and monitor the SOC state and real-time temperature of each unit in the battery module in real time, and feedback them to the binary function to achieve bidirectional coupling. After setting the correct boundary conditions and assigning initial values according to the battery module, thermal simulation calculation is carried out.

[0017] The present invention also provides a thermal simulation device based on the coupling of lithium battery internal resistance MAP and temperature. The device includes:

[0018] The battery internal resistance MAP drawing module is used to obtain battery design parameters, build a one-dimensional electrochemical model of the battery cell, calculate the internal resistance of the lithium battery under different conditions based on the electrochemical model, and draw the lithium battery internal resistance MAP;

[0019] The heat generation power MAP drawing module is used to calculate the heat generation power of the battery cell under different conditions in the operating condition based on the lithium battery internal resistance MAP, and draw it into a heat generation power MAP diagram;

[0020] The simulation heat source determination module is used to fit the heat generation power MAP diagram of the battery cell into a binary function affected by the real-time temperature and different SOC states, and use it as the input of the heat simulation heat source of the battery module;

[0021] The heat simulation calculation module is used to input the binary function as the heat source into the heat simulation model of the battery module to perform heat simulation calculations.

[0022] Furthermore, the battery design parameters include the positive and negative electrode material ratios, electrolyte material ratios, concentration, conductivity, winding core component materials, dimensions, and areal density.

[0023] Furthermore, the one-dimensional electrochemical model of the battery cell is built based on the Newman model using the battery design parameters.

[0024] Furthermore, the different conditions include different rates, different temperatures, different SOC states, and different pulse times.

[0025] Even further, the heat generation power MAP drawing module is also used for: based on the lithium battery internal resistance MAP, according to P = I 2 R to calculate the heat generation power of the battery cell under different conditions in the operating condition, and draw it into a heat generation power MAP diagram.

[0026] Even further, the simulation heat source determination module is also used for: when the conditions determined by the operating condition are such that the rate and pulse time of the battery cell are both determined, the heat generation power MAP diagram of the battery cell can be directly fitted into a binary function affected by the real-time temperature and different SOC states with the help of MATLAB.

[0027] Even further, the heat simulation calculation module is also used for: in the Fluent software, input the binary function as the heat source into the heat simulation model of the battery module, and monitor the SOC state and real-time temperature of each unit in the battery module in real time, and feedback them to the binary function to achieve bidirectional coupling. After setting the correct boundary conditions and assigning initial values to the battery module, heat simulation calculations are performed.

[0028] The advantages of the present invention are:

[0029] (1) During the calculation process of the thermal simulation model of the present invention, due to differences in structure, position, operating conditions, etc. among the units in the battery module, there are differences in the temperature field and SOC state. This simulation method can accurately feedback the SOC state and real-time temperature of different battery units to the battery heat source input, realizing the accurate simulation of uneven temperature field and SOC state distribution of the battery heat source under different usage conditions, which conforms to the actual situation of the battery unit heat source changing with temperature during the operation of the battery module. Only by obtaining the battery design parameters at the front end of the battery design can the design simulation requirements of modules such as modules and battery packs be solved, without the support of strict HPPC data testing, with low calculation cost and greatly shortened design cycle.

[0030] (2) The simulation method of the present invention can comprehensively consider the influence of different parameters in the actual working conditions on the heat generation power of the battery unit, and better improve the simulation accuracy.

[0031] (3) The present invention can carry out simulation work through battery design parameters, greatly shortening the R & D and production cycle of lithium-ion batteries and reducing the R & D production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the flowchart of the thermal simulation method based on the coupling of lithium battery internal resistance MAP and temperature provided in Embodiment 1 of the present invention;

[0033] Figure 2 is the schematic diagram of the battery module in the thermal simulation method based on the coupling of lithium battery internal resistance MAP and temperature provided in Embodiment 1 of the present invention;

[0034] Figure 3 is the comparison diagram of the simulation effects of the thermal simulation method based on the coupling of lithium battery internal resistance MAP and temperature provided in Embodiment 1 of the present invention and the existing equivalent circuit method. Among them, Figure 3 (a) is the comparison of the highest temperature and lowest temperature curves, Figure 3 (b) is the comparison of the heat generation power curves. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] Embodiment 1

[0037] As Figure 1 shown, a thermal simulation method based on the coupling of lithium battery internal resistance MAP and temperature, the method includes:

[0038] S1: Obtain battery design parameters from the front end of battery design. The battery design parameters include, but are not limited to, the positive and negative electrode material ratios, electrolyte material ratios, concentration, conductivity, winding core component materials, dimensions, and areal density. Based on the battery design parameters, use the Newman model to build a one-dimensional electrochemical model of the battery cell. Based on the electrochemical model, calculate the internal resistance of the lithium battery under different conditions such as different rates, different temperatures, different SOC states, and different pulse times, and draw the internal resistance MAP of the lithium battery.

[0039] S2: Since the batteries are in series and the working conditions are determined, the current in the circuit where the battery is located is determined. The resistance can be obtained according to the internal resistance MAP of the lithium battery. Therefore, based on the internal resistance MAP of the lithium battery, the heat generation power of the battery cell under different conditions in the working condition can be directly calculated according to P = I 2 R, and draw a heat generation power MAP diagram.

[0040] S3: When the working conditions are determined, the use rate and pulse time of the battery cell are both determined. Therefore, the heat generation power MAP diagram of the battery cell can be directly fitted into a binary function affected by the real-time temperature and different SOC states with the help of MATLAB and used as the heat source input for the battery module thermal simulation.

[0041] S4: In the Fluent software, input the binary function as the heat source into the battery module thermal simulation model, and monitor the SOC state and real-time temperature of each unit in the battery module in real time, and feedback them to the binary function to achieve bidirectional coupling. After setting the correct boundary conditions and assigning initial values according to the battery module, perform the thermal simulation calculation. During the calculation process of the thermal simulation model, due to differences in structure, position, working conditions, etc. of each unit in the battery module, there are differences in the temperature field and SOC state. This simulation method can accurately feedback the SOC state and real-time temperature of different battery units to the battery heat source input, and achieve accurate simulation of the uneven distribution of the temperature field and SOC state of the battery heat source under different use conditions. It should be noted that the boundary condition setting includes the initial temperature of the battery during operation and the convective heat transfer coefficient of natural cooling. In the embodiment of the present invention, the initial temperature of the battery during operation is 25 °C, and the convective heat transfer coefficient is 7 W / (m 2 *K).

[0042] The following is the verification of the simulation effect:

[0043] As Figure 2 shown, taking a certain type of ternary square battery module (module) as an example, to verify the authenticity and reliability of the method provided by the present invention, an equivalent circuit with a high recognition in the industry is selected for comparison, and the temperature distribution of the battery module during charging from 10% SOC to 80% SOC at 1C in a natural environment is calculated using two methods respectively. Figure 2Among them, 1 is the battery cell in the battery module.

[0044] First, based on the equivalent circuit method of the prior art, after selecting battery samples, the HPPC data of the single cell at 1C and 30S pulses obtained from experimental tests are processed and input into the equivalent circuit model. After setting the correct boundary conditions, thermal simulation calculations are carried out, and the heat generation power curve of the battery cell and the highest and lowest temperature curves of the battery in the model are obtained.

[0045] Then, based on the simulation method of the present invention, according to the design parameters of the battery cell, the internal resistance MAP diagram of the battery at 1C and 30S pulses under 10% SOC - 80% SOC in the natural environment is calculated using the electrochemical model. According to P = I 2 R, the heat generation power density MAP diagram of the battery cell under different conditions is calculated. The data table of the heat generation power density MAP diagram is shown in Table 1, and it is fitted into a binary function affected by temperature and different SOC states using MATLAB. After dividing by the volume of the battery cell, the heat generation power density is used as the heat source term input of the battery module. The real-time temperature and SOC state of each cell in the battery module are monitored and fed back to the heat source term input. After coupling, the correct boundary conditions are set for thermal simulation calculations, and the heat generation power curve of the battery cell and the highest and lowest temperature curves of the battery in the model are obtained.

[0046] Table 1 Data table of the heat generation power density MAP diagram

[0047]

[0048] As Figure 3 shown, by comparing the two simulation methods, the trends of the heat generation power calculated by the equivalent circuit model and the present invention and the defined heat generation power are completely consistent, and the maximum error is 6.8%. The maximum temperature difference of the battery module is 0.87°C, which proves that the method of the present invention is effective and reliable. The method of the present invention not only solves the disadvantages of the equivalent circuit model requiring actual measurement data support, high simulation cost, and long cycle, but also can ensure extremely high simulation accuracy, greatly shorten the design cycle, reduce the R & D cost, accelerate the iteration of the product to a better item, and efficiently improve the product competitiveness.

[0049] Through the above technical solutions, in the process of calculating the thermal simulation model of the present invention, due to differences in the structure, position, usage conditions, etc. of each cell in the battery module, there are differences in the temperature field and SOC state. This simulation method can accurately feed back the SOC state and real-time temperature of different battery cells to the battery heat source input, realizing the accurate simulation of the uneven distribution of the temperature field and SOC state of the battery heat source under different usage conditions, which conforms to the actual situation of the battery cell heat source changing with temperature during the operation of the battery module. Only by obtaining the battery design parameters at the front end of the battery design can the design simulation requirements of modules such as modules and battery packs be solved, without the need for strict HPPC data test support, with low calculation cost, and greatly shortening the design cycle.

[0050] Example 2

[0051] Based on Example 1, Embodiment 2 of the present invention further provides a thermal simulation device based on the coupling of the lithium battery internal resistance MAP and temperature. The device includes:

[0052] A battery internal resistance MAP drawing module, configured to obtain battery design parameters, build a one-dimensional electrochemical model of a battery cell, calculate the internal resistance of a lithium battery under different conditions based on the electrochemical model, and draw a lithium battery internal resistance MAP;

[0053] A heat generation power MAP drawing module, configured to calculate the heat generation power of a battery cell under different conditions in the operating condition based on the lithium battery internal resistance MAP, and draw it into a heat generation power MAP diagram;

[0054] A simulation heat source determination module, configured to fit the heat generation power MAP diagram of the battery cell into a binary function affected by real-time temperature and different SOC states as the input of the heat simulation heat source of the battery module;

[0055] A thermal simulation calculation module, configured to use the binary function as a heat source to input into the thermal simulation model of the battery module for thermal simulation calculation.

[0056] Specifically, the battery design parameters include the positive and negative electrode material ratios, electrolyte material ratios, concentration, conductivity, winding core component materials, dimensions, and areal density.

[0057] Specifically, the one-dimensional electrochemical model of the battery cell is built based on the Newman model using the battery design parameters.

[0058] Specifically, the different conditions include different rates, different temperatures, different SOC states, and different pulse times.

[0059] More specifically, the heat generation power MAP drawing module is further configured to: based on the lithium battery internal resistance MAP, calculate the heat generation power of the battery cell under different conditions in the operating condition according to P = I 2 R and draw it into a heat generation power MAP diagram.

[0060] More specifically, the simulation heat source determination module is further configured to: when the conditions determined by the operating condition are such that the rate and pulse time of the battery cell are both determined, the heat generation power MAP diagram of the battery cell can be directly fitted into a binary function affected by real-time temperature and different SOC states with the help of MATLAB.

[0061] More specifically, the thermal simulation calculation module is further configured to: input the binary function as a heat source into the battery module thermal simulation model in Fluent software, and real-time monitor the SOC status and real-time temperature of each unit in the battery module, and feedback them to the binary function to achieve bidirectional coupling. After setting the correct boundary conditions and assigning initial values according to the battery module, thermal simulation calculation is carried out.

[0062] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A thermal simulation method based on the coupling of lithium battery internal resistance MAP and temperature, characterized in that, The method includes: Step 1: Obtain battery design parameters, build a one-dimensional electrochemical model of the battery cell, calculate the internal resistance of the lithium battery under different conditions based on the electrochemical model, and draw a lithium battery internal resistance MAP; Step 2: Based on the lithium battery internal resistance MAP, calculate the heat generation power of the battery cell under the operating conditions under different conditions, and draw a heat generation power MAP; Step 3: Fit the heat generation power MAP of the battery cell into a binary function affected by the real-time temperature and different SOC states, and use it as the heat source input for the battery module thermal simulation; Step 4: Use the binary function as the heat source input into the battery module thermal simulation model for thermal simulation calculation; in the Fluent software, use the binary function as the heat source input into the battery module thermal simulation model, and monitor the SOC state and real-time temperature of each unit in the battery module in real time, and feedback to the binary function to achieve bidirectional coupling. After setting the correct boundary conditions and initial values according to the battery module, thermal simulation calculation is carried out.

2. The thermal simulation method based on the coupling of lithium battery internal resistance MAP and temperature according to claim 1, wherein The battery design parameters include the positive and negative electrode material ratios, electrolyte material ratios, concentration, conductivity, winding core component materials, dimensions, and areal density.

3. The thermal simulation method based on the coupling of lithium battery internal resistance MAP and temperature according to claim 1, wherein The one-dimensional electrochemical model of the battery cell is built using the Newman model based on the battery design parameters.

4. The thermal simulation method based on the coupling of lithium battery internal resistance MAP and temperature according to claim 1, wherein The different conditions include different rates, different temperatures, different SOC states, and different pulse times.

5. The thermal simulation method based on the coupling of lithium battery internal resistance MAP and temperature according to claim 4, characterized in that, The second step includes: based on the lithium battery internal resistance MAP, calculating the heat generation power of the battery cell under different conditions in the operating condition according to P = I 2 R, and plotting a heat generation power MAP graph.

6. The thermal simulation method based on the coupling of lithium battery internal resistance MAP and temperature according to claim 5, wherein Step 3 includes: When the conditions of the operating conditions are determined, the use rate and pulse time of the battery cell are both determined. Therefore, the heat generation power MAP of the battery cell can be directly fitted into a binary function affected by the real-time temperature and different SOC states with the help of MATLAB.

7. A thermal simulation device based on the coupling of lithium battery internal resistance MAP and temperature, characterized in that The device includes: A battery internal resistance MAP drawing module, which is used to obtain battery design parameters, build a one-dimensional electrochemical model of the battery cell, calculate the internal resistance of the lithium battery under different conditions based on the electrochemical model, and draw a lithium battery internal resistance MAP; A heat generation power MAP drawing module, which is used to calculate the heat generation power of the battery cell under the operating conditions under different conditions based on the lithium battery internal resistance MAP, and draw a heat generation power MAP; A simulation heat source determination module, which is used to fit the heat generation power MAP of the battery cell into a binary function affected by the real-time temperature and different SOC states, and use it as the heat source input for the battery module thermal simulation; A thermal simulation calculation module, which is used to use the binary function as the heat source input into the battery module thermal simulation model for thermal simulation calculation; in the Fluent software, use the binary function as the heat source input into the battery module thermal simulation model, and monitor the SOC state and real-time temperature of each unit in the battery module in real time, and feedback to the binary function to achieve bidirectional coupling. After setting the correct boundary conditions and initial values according to the battery module, thermal simulation calculation is carried out.

8. The thermal simulation device based on the coupling of lithium battery internal resistance MAP and temperature according to claim 7, characterized in that, The battery design parameters include the positive and negative electrode material ratios, electrolyte material ratios, concentration, conductivity, winding core component materials, dimensions, and areal density.

9. The thermal simulation device based on the coupling of lithium battery internal resistance MAP and temperature according to claim 7, wherein, The one-dimensional electrochemical model of the battery cell is built using the Newman model based on the battery design parameters.

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