Method for estimating thermal exchange capacity of an electric cell

Abstract

The application provides a method for estimating the heat exchange capacity of an electric core, comprising the following steps: obtaining the relationship between the radial cross-sectional area of an output part and the current flowing therethrough, wherein the output part comprises the tab, the adapter sheet and the pole of the electric core; correcting the relationship between the radial cross-sectional area of the output part and the current flowing therethrough by using k, wherein k is the heat exchange coefficient of the output part and the environment thereof; obtaining the radial design cross-sectional area of the output part, and obtaining the value range of the heat exchange coefficient k according to the radial design cross-sectional area of the output part; calculating the maximum theoretical temperature rise of the output part under a set discharge current condition according to the value range of k, and correcting the value range of the heat exchange coefficient k by measuring the maximum actual temperature rise under an actual condition through a test. Through the estimation and correction of the heat exchange coefficient, the continuous working capacity and stability of the electric core under specific output conditions can be evaluated.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy power batteries, and in particular to a method for estimating the heat exchange capacity of a battery cell. Background Art

[0002] The packaging structure of a conventional soft-pack lithium-ion battery cell includes a winding core, a transfer plate, a pole, etc. arranged in a shell. The output current of the winding core must be led out through its tabs, transfer plates, and poles in sequence. The material, size, and lead-out method of the tabs, transfer plates, or poles all affect the rate discharge performance and cycle performance of the lithium-ion battery. Generally speaking, the rate discharge capability of a lithium-ion battery is proportional to the cross-sectional area of ​​the tabs, transfer plates, and poles. The larger the cross-sectional area, the greater the current allowed to pass through. Selecting the appropriate size of the conductive component can fully utilize the internal space of the battery cell and meet the requirements of high-rate output. However, the greater the current of high-rate discharge, the higher the heat generated, which may have an adverse effect on the sealing of the lithium-ion battery cell's packaging structure and the reliability of the battery cell.

[0003] The Chinese patent application with publication number CN111929581A provides a method for predicting the internal and external temperature of a power lithium battery. By modeling a thermal-thermal coupling model of a lithium-ion battery at ambient temperature, the established model is verified at the simulation level in combination with operating condition tests to obtain the predicted value of the internal and external temperature of the lithium battery. When a lithium-ion battery is working, the tabs, adapters, and poles will all generate heat, and the shapes and cross-sectional areas of the three components are different. Heat will be transferred between the three. If conventional design methods are used, the process and time cost of obtaining the dimensions of the tabs, adapters, or poles through repeated mold opening and testing are extremely high. Therefore, it is necessary to provide a method for estimating the heat exchange capacity of the output components of the battery cell to reduce the cost and time overhead of the conductive component design process. Summary of the Invention

[0004] In view of this, the present invention proposes a method for estimating the heat exchange capacity of an output component based on equivalent structural parameters of the current output component.

[0005] The technical solution of the present invention is implemented as follows: The present invention provides a method for estimating the heat exchange capacity of a battery cell, comprising the following steps:

[0006] Obtaining a relationship between a current flowing through the battery and a radial cross-sectional area of ​​an output portion, wherein the output portion includes a tab (1), a switching plate (2), and a pole (3) of the battery cell;

[0007] Using k to correct the relationship between the radial cross-sectional area of ​​the output portion and the current flowing through it, wherein k is the heat exchange coefficient between the output portion and its environment;

[0008] Obtaining a radial design cross-sectional area of ​​the output portion, and determining a value range of a heat exchange coefficient k based on the radial design cross-sectional area of ​​the output portion;

[0009] The maximum theoretical temperature rise of the output part under the set discharge current working condition is calculated based on the value range of k, and the maximum actual temperature rise under the actual working condition is measured through experiments, and the value range of the heat exchange coefficient k is corrected.

[0010] On the basis of the above technical solution, preferably, the relationship between the current flowing through and the radial cross-sectional area of ​​the output portion is obtained by setting the radial cross-sectional area of ​​the output portion S0=I 2 ρL t0 / (CmΔT), where the length of the path through which the current I passes through the output part is L, the heat generated by the output part is Q, and the current output time is t0, then Q=I 2 Rt0, where R is the equivalent resistance of the output part, R = ρL / S0, ρ is the equivalent resistivity of the output part; there is a relationship Q = CmΔT, m is the mass of the output part, C is the specific heat capacity of the output part, and ΔT is the temperature rise of the output part during the period when the current Iout flows through it.

[0011] Preferably, the path length L of the current flowing through the output portion is the sum of the length of the tab (1) extending out of the winding core, and the projected lengths of the end face of the tab (1) away from the winding core, the adapter plate (2) and the pole (3) on the center plane of the winding core.

[0012] Preferably, when the materials of the tab (1), the adapter (2) and the pole (3) are exactly the same, the equivalent resistivity ρ of the output portion is equal to the resistivity of the tab (1); when the materials of the adapter (2) and / or the pole (3) are different from the material of the tab (1), the equivalent resistivity is ρ=ρ0+p*ρ0*(cross-sectional area of ​​the tab in the direction of current flow / cross-sectional area of ​​the adapter in the direction of current flow)+q*ρ0*(cross-sectional area of ​​the tab in the direction of current flow / cross-sectional area of ​​the pole in the direction of current flow), wherein ρ0 is the resistivity of the tab (1), so that the resistivity of the adapter (2) is p times the resistivity of the tab (1), and the resistivity of the pole (3) is q times the resistivity of the tab (1).

[0013] Preferably, the use of k to correct the relationship between the radial cross-sectional area of ​​the output portion and the current flowing through is to add the heat exchange coefficient k to the right side of the relationship between the current flowing through and the radial cross-sectional area of ​​the output portion, and obtain S0=kI 2 ρL t0 / (CmΔT), the limit value of the range of heat exchange coefficient k is (0, 1).

[0014] Preferably, the radial design cross-sectional area of ​​the output portion is obtained without considering the influence of the heat exchange coefficient k, and the maximum current I of the battery cell continuously discharged is obtained. m, discharge duration t1 and the maximum allowable temperature rise ΔT0 of the output part during discharge, as well as the path length L of the output part, the mass m of the output part, the equivalent resistance R of the output part, the equivalent resistivity ρ of the output part and the specific heat capacity C of the output part, ΔT1 is the maximum current I m Temperature rise during output, calculate the radial design cross-sectional area of ​​the output part S1 = I m 2 ρL t1 / (CmΔT1); ΔT1 does not exceed ΔT0;

[0015] If the discharge current and discharge duration are not unique during the discharge process, the radial design cross-sectional area S1 of the output portion under different discharge currents and corresponding discharge durations is calculated respectively, and the maximum value is selected as the radial design cross-sectional area of ​​the output portion.

[0016] Preferably, the range of values ​​of the heat exchange coefficient k is obtained based on the radial design cross-sectional area of ​​the output part, and a certain ambient temperature is selected. Under the condition that the maximum allowable temperature rise ΔT0 of the output part during discharge is not exceeded, the theoretical temperature rise ΔT2 and the actual temperature rise ΔT3 are calculated under different discharge current and discharge time conditions, and the range of values ​​of the heat exchange coefficient k is obtained based on the relationship between the actual temperature rise ΔT3 and the theoretical temperature rise ΔT2; both ΔT2 and ΔT3 do not exceed ΔT0.

[0017] Preferably, the maximum theoretical temperature rise of the output part under the set discharge current working condition is calculated based on the value of k, and the maximum actual temperature rise under the actual working condition is measured by experiment, and the value range of the heat exchange coefficient k is corrected. Under the set discharge current working condition, if the actual temperature rise of the output part measured several times under the same working condition does not exceed the actual temperature rise of the endpoint corresponding to the upper limit value of the value range of the heat exchange coefficient k, then the upper limit value of the current heat exchange coefficient k is retained; if at least one of the actual temperature rises of the output part measured several times under the same working condition exceeds the upper limit value of the value range of the heat exchange coefficient k, then the upper limit value of the current heat exchange coefficient k is retained. If the actual temperature rise of the endpoint corresponds to the upper limit of the value range of the heat exchange coefficient k, and the measured actual temperature rise does not exceed 5% of the actual temperature rise of the endpoint, the heat exchange coefficient corresponding to the measured actual temperature rise is used as the new upper limit of the value range of the heat exchange coefficient k; if at least one of the measured actual temperature rises of the output part of the same working conditions performed intermittently exceeds the theoretical temperature rise of the endpoint corresponding to the upper limit of the value range of the heat exchange coefficient k, and the actual temperature rise exceeds 5% of the theoretical temperature rise of the endpoint, it means that the value range of the heat exchange coefficient k is unreasonable, and it is necessary to adjust the radial design cross-sectional area and execute the last two steps in sequence.

[0018] Preferably, the dimension corresponding to the radial design cross-sectional area of ​​the output portion does not exceed 50% of the cross-sectional dimension of the winding core.

[0019] The present invention provides a method for estimating the heat exchange capacity of a battery cell, which has the following advantages over the prior art:

[0020] (1) This solution treats the tab, adapter, and pole as a whole and obtains the corresponding design cross-sectional area through its discharge parameters, which is conducive to simplifying the structure. The mutual heat exchange process between the tab and adapter, and between the adapter and pole can be ignored, reducing the difficulty of design and calculation.

[0021] (2) By introducing the heat exchange coefficient of the output part and obtaining the value range of the heat exchange coefficient corresponding to the radial design cross-sectional area, we can confirm whether the heat exchange coefficient can adapt to the local temperature rise limit of the battery cell under the corresponding output working conditions, and verify the reliability of the heat exchange coefficient and the radial design cross-sectional area, so as to adjust the values ​​of the heat exchange coefficient and the design cross-sectional area to achieve a balance between cost and reliability of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is a flow chart of a method for estimating the overheat exchange capacity of a battery cell according to the present invention;

[0024] Figure 2 A three-dimensional diagram of a cell packaging structure with the shell removed, in accordance with a method for estimating the heat exchange capacity of a cell according to the present invention;

[0025] Figure 3 for Figure 2 A top view of

[0026] Figure 4 for Figure 3 A-A section view.

[0027] Reference numerals: 1. terminal tab; 2. adapter plate; 3. terminal post. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] The technical solution of the present invention is achieved as follows: Figure 1 — Figure 4 As shown, the present invention provides a method for estimating the heat exchange capacity of a battery cell, comprising the following steps:

[0030] S1: Obtain the relationship between the flowing current and the radial cross-sectional area of ​​the output part. The output part is obtained by integrating the tab 1, the adapter 2, and the pole 3 into a whole.

[0031] Specifically, the tab 1, adapter 2 and pole 3 are equivalent to an output part, and the path length of the current flowing through the output part is L, and the path length L is the length of the tab 1 extending out of the winding core, and the sum of the projected lengths of the end face of the tab 1 away from the winding core, the adapter 2 and the pole 3 on the center plane of the winding core. That is, the path length L here includes two parts, one is the part where the current flows through the tab, and the sum of the distances drawn from the end of the tab 1 away from the winding core, the adapter 2 and the pole 3. The former is determined by the shape of the tab, and the latter is determined by the thickness of the tab cross section, the winding core and the electrical end cover lead-out direction and size. This is also the channel for the current to flow through the output. A simplified process is adopted here. The end face of the tab 1 needs to be bent and fitted with the adapter 2. Therefore, the tab 1 is divided into two parts, namely the extended part extending out of the winding core and the fitted part with the adapter 2, and they are considered separately when calculating the path length L. As Figure 4 As shown, let H be the sum of the projected lengths of the tab 1 cross section, the adapter 2, and the pole 3 on the center plane of the winding core, and let W be the length of the tab extending from the winding core, then L = W + H. The length W of the tab extending from the winding core and the path length L are not shown in the figure.

[0032] Here, let S0 be the radial cross-sectional area of ​​the output part, the heat generated by the output part be Q, the current flowing through the output part be I, and the current output time be t0, then Q = I 2 Rt0, where R is the equivalent resistance of the output part, R = ρL / S0, ρ is the equivalent resistivity of the output part; in addition, Q = CmΔT, m is the mass of the output part, C is the specific heat capacity of the output part, ΔT is the temperature rise of the output part during the output current I output, then S0 = I 2 ρLt0 / (CmΔT). When the output unit is equivalent, the mutual heat transfer between the components within the output unit is no longer considered. Instead, the output unit is considered as a whole, and the heat exchange capacity with the external environment or electrolyte is considered. The equivalent resistance R of the output unit is related to the size and resistivity of the tab 1, adapter 2, and pole 3. When the material is determined, the resistivity is easy to obtain. The specific heat capacity of the output unit is limited by the component with the smallest specific heat capacity. For example, the specific heat capacity C of the output unit is based on the smallest specific heat capacity of the tab 1, adapter 2, or pole 3.

[0033] To facilitate the calculation of equivalent resistance, the following restrictions apply: When the materials of tab 1, adapter plate 2, and post 3 are identical, the equivalent resistivity ρ of the output section equals the resistivity of tab 1. When the materials of adapter plate 2 and / or post 3 differ from those of tab 1, the volumes and resistances of each of tab 1, adapter plate 2, and post 3 are calculated, and the average resistivity, expressed as a multiple of the resistivity of tab 1, is used as the equivalent resistivity ρ of the output section. Using the tab resistivity as a benchmark to measure changes in the equivalent resistance of the output section helps reduce the amount of calculation and improve calculation speed. If the resistivity of adapter plate 2 is p times the resistivity of tab 1, the resistivity of adapter plate 2 is p*ρ0*(tab cross-sectional area / adapter cross-sectional area), where ρ0 is the resistivity of tab 1. Similarly, the resistivity of pole 3 is q times the resistivity of tab 1, so the resistivity of pole 3 is q*ρ0*(tab cross-sectional area / pole cross-sectional area), and the equivalent resistivity of the output part ρ=ρ0+p*ρ0*(tab cross-sectional area / adapter cross-sectional area)+q*ρ0*(tab cross-sectional area / pole cross-sectional area).

[0034] S2: Let the heat exchange coefficient between the output part and the surrounding environment be defined as k; use k to correct the relationship between the cross-sectional area of ​​the output part and the current flowing through it.

[0035] Specifically, the heat exchange coefficient k is added to the right side of the equation for the relationship between the radial design cross-sectional area of ​​the output portion and the current flowing through it, and S0=kI is obtained. 2 ρL t0 / (CmΔT), the limit value of the value range of the heat exchange coefficient k, that is, the theoretical value is (0, 1), and the actual value range needs to be calculated.

[0036] S3: Obtaining a radial design cross-sectional area of ​​the output portion, and calculating a value range of the heat exchange coefficient k based on the radial design cross-sectional area of ​​the output portion.

[0037] Specifically, without considering the influence of the heat exchange coefficient k, the maximum current I of the battery cell that can be continuously discharged is obtained. m , discharge duration t1 and the maximum allowable temperature rise ΔT0 of the output part during discharge, as well as the path length L of the output part, the mass m of the output part, the equivalent resistance R of the output part, the equivalent resistivity ρ of the output part and the specific heat capacity C of the output part, ΔT1 is the maximum current I m Temperature rise during output, calculate the radial design cross-sectional area of ​​the output part S1 = I m 2 ρL t1 / (CmΔT1); ΔT1 does not exceed ΔT0.

[0038] If there is only one discharge process and the discharge current remains unchanged during the discharge process, only one radial design cross-sectional area of ​​the output portion can be obtained.

[0039] If the discharge current and discharge duration are not unique during the discharge process, such as the discharge process is divided into two or more stages: continuous discharge and peak discharge, the cross-sectional area of ​​the output part under different discharge currents and corresponding discharge durations is calculated respectively, and the maximum radial design cross-sectional area of ​​the output part is selected for use. For example, taking two discharge stages as an example, S 11 =I m1 2 ρL t 11 / (CmΔT 11 ), S 12 =I m2 2 ρL t 12 / (CmΔT 12 );In the above formula I m1 and I m2 are the maximum current of continuous discharge at different discharge stages, and the discharge duration is t 11 With t 12 , ΔT 11 and ΔT 12 For output units with different maximum currents I m1 and I m2 The temperature rise during output is as follows: the radial design cross-sectional area of ​​the output part S1=max(S 11 , S 12 ), max is the maximum value operation.

[0040] The range of values ​​for the heat exchange coefficient k is determined by selecting a certain ambient temperature. Under different discharge current and discharge time conditions, the theoretical temperature rise ΔT2 and actual temperature rise ΔT3 are calculated, while not exceeding the maximum allowable temperature rise ΔT0 of the output unit during discharge. Based on the relationship between the actual temperature rise ΔT3 and the theoretical temperature rise ΔT2, the range of values ​​for the heat exchange coefficient k is determined, with neither ΔT2 nor ΔT3 exceeding ΔT0. Because the range of values ​​for the heat exchange coefficient varies at different starting ambient temperatures, a smaller value for the heat exchange coefficient k indicates faster heat exchange with the environment, allowing the battery cell to maintain reliable operation for a longer period of time. A larger value for the heat exchange coefficient k indicates slower heat exchange with the environment, and prolonged discharge may result in local overheating.

[0041] As a preferred embodiment of this solution, the radial cross-sectional area of ​​the output portion should not exceed 50% of the cross-sectional area of ​​the winding core. This design is to fully utilize the internal space of the battery cell while meeting the demand for reliable high current output.

[0042] S4: Calculating the theoretical temperature rise of the output portion under a set discharge current condition according to the value range of k; and measuring the actual temperature rise under actual conditions through experiments, and correcting the value range of the heat exchange coefficient k.

[0043] The process of correcting the value of the heat exchange coefficient k is as follows: under the set discharge current working condition, if the measured actual temperature rise of the output part under the same working condition for several times intermittent operation does not exceed the actual temperature rise of the endpoint corresponding to the upper limit of the value range of the heat exchange coefficient k, then the upper limit value of the current heat exchange coefficient k is retained; if at least one of the measured actual temperature rises of the output part under the same working condition for several times intermittent operation exceeds the actual temperature rise of the endpoint corresponding to the upper limit of the value range of the heat exchange coefficient k, and the measured actual temperature rise does not exceed 5% of the actual temperature rise of the endpoint, then the heat exchange coefficient corresponding to the measured actual temperature rise is used as the new upper limit value of the value range of the heat exchange coefficient k; if at least one of the measured actual temperature rises of the output part under the same working condition for several times intermittent operation exceeds the theoretical temperature rise of the endpoint corresponding to the upper limit of the value range of the heat exchange coefficient k, and the actual temperature rise exceeds 5% of the theoretical temperature rise of the endpoint, then it means that the value range of the heat exchange coefficient k is unreasonable, and it is necessary to repeat back to step S3, try to adjust the radial design cross-sectional area and execute steps S3 and S4 in sequence.

[0044] The following strategy can be used to adjust the radial design cross-sectional area: The radial design cross-sectional area is rectangular, with the design cross-sectional area including a first axial direction and a second axial direction that are orthogonal to each other. Each time the radial design cross-sectional area is adjusted, only one axial dimension is adjusted. For example, if the first axial dimension of the radial design cross-sectional area remains unchanged, the second axial dimension is increased. If the range of values ​​for the heat exchange coefficient k is found to be unreasonable after adjusting the radial design cross-sectional area, the second axial dimension is further increased; alternatively, the current second axial dimension is maintained unchanged, while the first axial dimension is increased. Each adjustment of the radial design cross-sectional area should ensure that the increase in the size of a single axial dimension does not exceed 3%-5% of the current axial dimension. To maintain the long-term reliable operation of the battery cell, the heat exchange coefficient k should be kept as low as possible at higher ambient temperatures. The first axial direction can be the length of the radial design cross-sectional area, and the second axial direction can be the width of the radial design cross-sectional area.

[0045] To facilitate understanding of the specific process of this solution, an example is given below:

[0046] After the cell is packaged, it has two discharge processes: 1) continuous discharge current of 200A and discharge time of 3600 seconds; 2) peak discharge current of 600A and discharge time of 300 seconds. The current path length L is 45mm. Assuming that the material of the output part, the material of the tab 1, the adapter 2 and the pole 3 are all aluminum, the equivalent resistivity ρ of the output part is 2.83×10 -8 Ω·m; the mass m of the output part is 129g; the specific heat capacity of the output part is 0.88×10 3J / (kg·℃); the maximum allowable temperature rise of the output part during discharge is 30℃; without considering the influence of the heat exchange coefficient k, calculate the radial design cross-sectional area of ​​the output part under the above two discharge conditions respectively. The radial design cross-sectional area of ​​the output part in the former discharge process is S 11 =53.85mm 2 The radial design cross-sectional area of ​​the output part of the latter discharge process is S 12 =64.62mm 2 The radial design cross-sectional area of ​​the output part in the latter case is 64.62mm 2 shall prevail.

[0047] After obtaining the radial design cross-sectional area of ​​the output part, considering the influence of the heat exchange coefficient k, according to the formula S0=I 2 ρLt0 / (CmΔT) is used to calculate the theoretical temperature rise under different environmental conditions. The obtained radial design cross-sectional area S1 is substituted for the left side of the formula, and the theoretical temperature rise ΔT2 is substituted for ΔT on the right side of the formula, and the above formula is changed to S1=I 2 ρL t0 / (CmΔT2). Since I, ρ, L, t0, C, and m are all known in the formula, the theoretical temperature rise ΔT2 can be calculated, and the actual temperature rise ΔT3 can be obtained through actual measurement; the results are shown in the following table.

[0048]

[0049]

[0050] According to the above table, the range of the heat exchange coefficient k derived from the average value of k is [0.61, 0.87]∈(0.1), which means that the radial design cross-sectional area of ​​the output part is 64.62mm 2 Make a reasonable choice.

[0051] When the ambient temperature is 45°C, the average value of the heat exchange coefficient k is 0.87, which reflects the heat exchange capacity between the output part and the environment. Further, under the ambient temperature of 45°C, the heat exchange coefficient k is set to 0.87, and the actual temperature rise of the output part under the same working conditions under different discharge states is calculated again to observe whether the actual temperature rise exceeds the theoretical temperature rise of the endpoint corresponding to the given heat exchange coefficient k, that is, in the above formula S1=I 2 The heat exchange coefficient k is introduced on the right side of the equal sign of ρL t0 / (CmΔT2), and the formula S1=kI 2The theoretical endpoint temperature rise, ΔT2', is calculated using ρL t0 / (CmΔT2'). The corresponding actual temperature rise is measured and shown in the table below. Each measurement of the actual temperature rise under the corresponding operating conditions is independent. This means that after the previous measurement, the battery cell must be fully charged and the overall cell temperature must reach the set starting temperature before current output can begin and the actual temperature rise measurement can be repeated.

[0052]

[0053] As can be seen from the table above, under a 200A discharge current, the measured actual temperature rises did not exceed the theoretical endpoint temperature rise ΔT2' = 21.75°C, based on a heat exchange coefficient k of 0.87. Therefore, the upper limit of the heat exchange coefficient k of 0.87 under this discharge condition remains unchanged. If this is the only output condition, the heat exchange coefficient k range remains unchanged within [0.61, 0.87]. This means that the battery cell can maintain long-term operation at a relatively low discharge current.

[0054] Under the discharge current of 600A, some of the measured actual temperature rises exceeded the endpoint theoretical temperature rise ΔT2'=26.10℃ under the heat exchange coefficient k of 0.87, and none of them exceeded 5% of the endpoint theoretical temperature rise of 26.10℃ under the heat exchange coefficient k of 0.87. The latest maximum actual temperature rise of 27.01℃ is taken as the endpoint theoretical temperature rise, and the upper limit of the heat exchange coefficient k under this temperature and discharge current is adjusted to ΔT3 / ΔT2=27.01 / 30=0.90. The value range of the corrected heat exchange coefficient k is [0.61, 0.90], indicating that under higher ambient temperature, when discharging with a large current, the heat exchange capacity of the output part is worse than that under the small current case. The battery cell is not suitable for intermittent or long-term continuous discharge with this current without appropriate cooling measures. It is necessary to adjust the radial design cross-sectional area of ​​the output part under the discharge current of 600A.

[0055] Through the above verification process, we can determine whether the battery cell can adapt to the reliability and heat exchange performance under high discharge current conditions, thereby reducing the workload and difficulty of the structural design of the battery cell and battery.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for estimating heat exchange capacity of a battery cell, characterized in that: The steps include: Obtaining a relationship between a current flowing through the battery and a radial cross-sectional area of ​​an output portion, wherein the output portion includes a tab (1), a switching plate (2), and a pole (3) of the battery cell; The relationship between the current flowing through and the radial cross-sectional area of ​​the output portion is obtained by setting the radial cross-sectional area of ​​the output portion S0 = I 2 ρLt0 / (CmΔT), where the path length of the current I passing through the output part is L, the heat generated by the output part is Q, and the current output time is t0, then Q=I 2 Rt0, where R is the equivalent resistance of the output part, R = ρL / S0, ρ is the equivalent resistivity of the output part; There is a relationship Q = CmΔT, where m is the mass of the output part, C is the specific heat capacity of the output part, and ΔT is the temperature rise of the output part during the period when the current Iout flows through it; Using k to correct the relationship between the radial cross-sectional area of ​​the output portion and the current flowing through it, wherein k is the heat exchange coefficient between the output portion and its environment; Add the heat exchange coefficient k to the right side of the relationship between the current flowing through and the radial cross-sectional area of ​​the output part to obtain S0 = kI 2 ρL t0 / (CmΔT); Obtaining a radial design cross-sectional area of ​​the output portion, and determining a value range of a heat exchange coefficient k based on the radial design cross-sectional area of ​​the output portion; The radial design cross-sectional area of ​​the output portion is obtained without considering the influence of the heat exchange coefficient k, and the maximum current I of the battery cell continuously discharged is obtained. m , discharge duration t1 and the maximum allowable temperature rise ΔT0 of the output part during discharge, as well as the path length L of the output part, the mass m of the output part, the equivalent resistance R of the output part, the equivalent resistivity ρ of the output part and the specific heat capacity C of the output part, ΔT1 is the maximum current I m Temperature rise during output, calculate the radial design cross-sectional area of ​​the output part S1 = I m 2 ρL t1 / (CmΔT1); ΔT1 does not exceed ΔT0; If the magnitude of the discharge current and the discharge duration are not unique during the discharge process, the radial design cross-sectional area S1 of the output portion under different discharge current magnitudes and corresponding discharge durations is calculated respectively, and the maximum value thereof is selected as the radial design cross-sectional area of ​​the output portion; The range of values ​​of the heat exchange coefficient k obtained based on the radial design cross-sectional area of ​​the output portion is determined by selecting a certain ambient temperature, calculating the theoretical temperature rise ΔT2 and the actual temperature rise ΔT3 under different discharge current and discharge time conditions, without exceeding the maximum allowable temperature rise ΔT0 of the output portion during discharge, and obtaining the range of values ​​of the heat exchange coefficient k based on the relationship between the actual temperature rise ΔT3 and the theoretical temperature rise ΔT2; neither ΔT2 nor ΔT3 exceeds ΔT0; Calculate the maximum theoretical temperature rise of the output portion under a set discharge current condition based on the value range of k, measure the maximum actual temperature rise under actual conditions through experiments, and correct the value range of the heat exchange coefficient k; The specific content includes: after obtaining the radial design cross-sectional area S1 of the output part, considering the influence of the heat exchange coefficient k, the obtained radial design cross-sectional area S1 is replaced by the formula S0=kI 2 The left side of ρL t0 / (CmΔT) is replaced by the theoretical temperature rise ΔT2 on the right side of the formula, and the formula becomes S1=kI 2 ρL t0 / (CmΔT2), through the proportional relationship between the actual temperature rise ΔT3 and the theoretical temperature rise ΔT2, correct the value range of the heat exchange coefficient k.

2. The method for estimating heat exchange capacity of a battery cell according to claim 1, characterized in that: The path length L of the current flowing through the output portion is the length of the tab (1) extending out of the winding core, and the sum of the projected lengths of the end face of the tab (1) away from the winding core, the adapter (2) and the pole (3) on the central plane of the winding core.

3. The method for estimating heat exchange capacity of a battery cell according to claim 1, characterized in that: When the materials of the tab (1), the adapter (2) and the pole (3) are exactly the same, the equivalent resistivity ρ of the output portion is equal to the resistivity of the tab (1); when the materials of the adapter (2) and / or the pole (3) are different from the material of the tab (1), the equivalent resistivity is ρ=ρ0+p*ρ0*(cross-sectional area of ​​the tab in the direction of current flow / cross-sectional area of ​​the adapter in the direction of current flow)+q*ρ0*(cross-sectional area of ​​the tab in the direction of current flow / cross-sectional area of ​​the pole in the direction of current flow), where ρ0 is the resistivity of the tab (1), so that the resistivity of the adapter (2) is p times the resistivity of the tab (1), and the resistivity of the pole (3) is q times the resistivity of the tab (1).

4. The method for estimating heat exchange capacity of a battery cell according to claim 1, characterized in that: The maximum value range of the heat exchange coefficient k is (0, 1).

5. The method for estimating heat exchange capacity of a battery cell according to claim 1, characterized in that: The maximum theoretical temperature rise of the output part under the set discharge current working condition is calculated according to the value of k, and the maximum actual temperature rise under the actual working condition is measured by experiment, and the value range of the heat exchange coefficient k is corrected. Under the set discharge current working condition, if the actual temperature rise of the output part under the same working condition is measured several times intermittently does not exceed the actual temperature rise of the endpoint corresponding to the upper limit of the value range of the heat exchange coefficient k, then the upper limit of the current heat exchange coefficient k is retained; if at least one of the actual temperature rises of the output part under the same working condition is measured several times intermittently, it exceeds the actual temperature rise of the endpoint corresponding to the upper limit of the value range of the heat exchange coefficient k, and the actual temperature rise is measured If the actual temperature rise does not exceed 5% of the actual temperature rise of the endpoint, the heat exchange coefficient corresponding to the measured actual temperature rise is used as the new upper limit of the value range of the heat exchange coefficient k; if at least one of the actual temperature rises of the output part under the same working conditions measured intermittently exceeds the theoretical temperature rise of the endpoint corresponding to the upper limit of the value range of the heat exchange coefficient k, and the actual temperature rise exceeds 5% of the theoretical temperature rise of the endpoint, it means that the value range of the heat exchange coefficient k is unreasonable, and the radial design cross-sectional area needs to be adjusted, and the steps of obtaining the value range of the heat exchange coefficient k according to the radial design cross-sectional area of ​​the output part and correcting the value range of the heat exchange coefficient k are sequentially performed.

6. The method for estimating heat exchange capacity of a battery cell according to claim 1, characterized in that: The radial design cross-sectional area of ​​the output portion does not exceed 50% of the cross-sectional area of ​​the winding core.

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