Battery cell

Abstract

The present application relates to the technical field of battery cells. Provided in the present application is a battery cell. The battery cell comprises an electrode assembly and a housing; the electrode assembly is provided within the housing; an explosion-proof structure is provided on the housing; a valve opening area S of the explosion-proof structure, a valve opening pressure P of the explosion-proof structure, an electrolyte injection amount m of the battery cell, and a capacity C of the battery cell satisfy the following formula: 2.4≤S×P-C / (m×1000)≤5.4. In the present application, by means of reasonably configuring the valve opening area and the valve opening pressure of the explosion-proof structure, the electrolyte injection amount of the battery cell, and the capacity of the battery cell, the explosion-proof structure can be opened in a timely manner when the battery cell undergoes thermal runaway due to a fault; and different parameters can also be configured according to actual conditions, such as the capacity of the battery cell, thereby meeting explosion-proof requirements of large-capacity battery cells.

Description

battery cells

[0001] This application claims priority to Chinese Patent Application No. 202411876416.X, filed with the Chinese Patent Office on December 18, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery cell technology, and more particularly to a battery cell. Background Technology

[0003] In related technologies, power battery cells typically employ an aluminum shell structure with an explosion-proof feature on the shell. This explosion-proof feature activates in the event of thermal runaway, venting pressure and preventing the cell from exploding due to excessive internal pressure. Invention Overview

[0004] As the capacity of battery cells increases, the explosion-proof structures in related technologies are gradually becoming unable to meet the explosion-proof requirements. The explosion-proof structures may fail to open in time after thermal runaway, leading to the risk of battery cell explosion.

[0005] This application provides a battery cell, including an electrode assembly and a housing, wherein the electrode assembly is disposed within the housing, and the housing is provided with an explosion-proof structure;

[0006] The valve opening area S of the explosion-proof structure, the valve opening pressure P of the explosion-proof structure, the electrolyte injection volume m of the battery cell, and the capacity C of the battery cell satisfy the following formula:

[0007] 2.4≤S×P-C / (m×1000)≤5.4. . Beneficial effects

[0008] In this application, the cover plate, through reasonable settings of the valve opening area, valve opening pressure, electrolyte injection volume, and cell capacity of the explosion-proof structure, ensures that the explosion-proof structure can open promptly when the cell experiences thermal runaway due to a fault. Furthermore, it allows for parameter settings based on actual conditions, such as cell capacity, to meet the explosion-proof requirements of large-capacity cells. Specifically, the formula 2.4 ≤ S×P-C / (m×1000) ≤ 5.4 links the four parameters: valve opening area, valve opening pressure, electrolyte injection volume, and cell capacity. This formula allows technicians to adjust the parameters according to the actual situation of the cell to adapt to the explosion-proof requirements of cells with different capacities. The values ​​of the left and right boundaries of this formula constitute the safe range within which the explosion-proof structure can function effectively. Specifically, when the parameters of the explosion-proof structure satisfy S×P-C / (m×1000) ≥ 2.4, it ensures that the valve opening area and valve opening pressure of the explosion-proof structure can effectively cope with the rapid increase in internal pressure of the cell. When the parameters of the explosion-proof structure meet S×P-C / (m×1000)≤5.4, it can prevent the opening conditions of the explosion-proof structure from being too harsh, that is, avoid the situation where the explosion-proof structure cannot be opened in time during thermal runaway, and ensure that the battery cell will not explode due to excessive pressure when overheated. Attached Figure Description

[0009] Figure 1 is a schematic diagram of the structure of a battery cell provided in an embodiment of this application;

[0010] Figure 2 is a schematic diagram of the structure of a cover plate provided in an embodiment of this application.

[0011] Explanation of reference numerals in the attached figures:

[0012] 1-Battery cell; 11-Housing shell; 12-Cover plate; 121-Board body; 122-Explosion-proof structure; 1221-Scratches; 123-Terminal post. Embodiments of the present invention

[0013] Referring to Figure 1, an embodiment of this application provides a battery cell 1, including a housing 11, an electrode assembly (not shown in the figure), and a cover plate 12. The housing 11 has an opening on one side to facilitate the assembly of components within the battery cell 1, such as allowing the electrode assembly to be inserted into the housing 11. The electrode assembly is disposed within the housing 11 and connected to the cover plate 12, specifically electrically connected to the terminal post 123 of the cover plate 12, for conducting electrical energy of the electrode assembly. The cover plate 12 covers the opening of the housing 11 to seal the opening, ensuring a sealed connection between the cover plate 12 and the housing 11.

[0014] It should be noted that the active material inside cell 1 can be any one of the following: lithium iron phosphate system, medium nickel ternary system, high nickel ternary system, sodium battery system, or lithium manganese iron phosphate system.

[0015] Please refer to Figure 2. The cover plate 12 includes a plate body 121, an electrode post 123, and an explosion-proof structure 122. The electrode post 123 includes a positive electrode post and a negative electrode post, which are arranged opposite to each other along the length of the plate body 121. The explosion-proof structure 122 is located between the positive electrode post and the negative electrode post. The plate body 121 is disposed on the housing 11 and seals and covers the opening of the housing 11. An explosion-proof hole is also provided on the plate body 121. Correspondingly, the explosion-proof structure 122 is located at the explosion-proof hole and covers the explosion-proof hole. The positive electrode post and the negative electrode post are respectively connected to the positive and negative electrodes in the electrode assembly.

[0016] The valve opening area S of the explosion-proof structure 122, the valve opening pressure P of the explosion-proof structure 122, the electrolyte injection volume m of the battery cell 1, and the capacity C of the battery cell 1 satisfy the following formula:

[0017] 2.4≤S×P-C / (m×1000)≤5.4;

[0018] S represents the valve opening area of ​​the explosion-proof structure 122, P represents the valve opening pressure of the explosion-proof structure 122, m represents the electrolyte injection volume of cell 1, and C represents the capacity of cell 1. It should be noted that the valve opening area of ​​the explosion-proof structure 122 refers to the effective channel area of ​​the internal gas through the pressure relief channel of the explosion-proof structure 122 when it is in the open state. The valve opening pressure of the explosion-proof structure 122 refers to the pressure value inside the cell when the explosion-proof structure 122 starts and forms the pressure relief channel. The electrolyte injection volume of cell 1 refers to the total mass of electrolyte filling the cell. The capacity of cell 1 refers to the total amount of electricity that the cell can provide under specific charge and discharge conditions.

[0019] The technical solution provided in this application, by reasonably setting the valve opening area, valve opening pressure, electrolyte injection volume of cell 1, and capacity of cell 1, enables the explosion-proof structure 122 to open promptly when cell 1 experiences thermal runaway due to a fault. Furthermore, it allows for parameter settings based on actual conditions, such as the capacity of cell 1, to meet the explosion-proof requirements of large-capacity cells 1. Specifically, by using the formula 2.4≤S×P-C / (m×1000)≤5.4, the four parameters of the explosion-proof structure 122—valve opening area, valve opening pressure, electrolyte injection volume of cell 1, and capacity of cell 1—are linked. This allows technicians to adjust the parameters according to the actual conditions of cell 1 using this formula to adapt to the explosion-proof requirements of cells 1 with different capacities. The values ​​of the left and right boundaries of this formula constitute the safe range within which the explosion-proof structure 122 can provide explosion protection. Specifically, when the parameters of the explosion-proof structure 122 satisfy S×P-C / (m×1000)≥2.4, it ensures that the opening area and opening pressure of the explosion-proof structure 122 can effectively cope with the rapid increase in internal pressure of the battery cell 1. When the parameters of the explosion-proof structure 122 satisfy S×P-C / (m×1000)≤5.4, it prevents the opening conditions of the explosion-proof structure 122 from being too stringent, that is, it avoids the situation where the explosion-proof structure 122 cannot open in time during thermal runaway, ensuring that the battery cell 1 will not explode due to excessive pressure when overheated.

[0020] Specifically, in the aforementioned formula, S represents the valve opening area of ​​the explosion-proof structure 122, with the unit of S being cm², indicating the area through which gas can pass after the explosion-proof structure 122 is opened. A larger valve opening area results in faster pressure release. P represents the valve opening pressure of the explosion-proof structure 122 (unit: MPa), i.e., the pressure at which the explosion-proof structure 122 begins to open. A higher valve opening pressure indicates stronger pressure tolerance of the explosion-proof structure 122 to the internal pressure of the battery cell 1. m represents the electrolyte injection volume of the battery cell 1 (unit: kg), i.e., the total weight of the electrolyte filling the battery cell 1. The injection volume affects the rate of pressure accumulation within the battery cell 1; a larger injection volume results in faster internal pressure accumulation. C represents the capacity of the battery cell 1 (unit: Ah), i.e., the rated capacity of the battery cell 1, which affects its charge and discharge performance. A larger capacity allows the battery cell 1 to provide more energy, but it also makes it more prone to generating heat during charging and discharging.

[0021] In one embodiment, the parameters of cell 1 are assumed to be as follows:

[0022] The capacity of cell 1 is C=300Ah; the electrolyte injection volume is m=1kg; the valve opening area of ​​explosion-proof structure 122 is S=3cm²; the valve opening pressure is P=1MPa.

[0023] Substituting the specific values ​​above into the formula, we get:

[0024] S×P-C / (m×1000)=−0.33, indicating that the calculated value does not fall within the range of 2.4≤S×P-C / (m×1000)≤5.4. Those skilled in the art can then selectively adjust the four parameters—the valve opening area of ​​the explosion-proof structure 122, the valve opening pressure of the explosion-proof structure 122, the electrolyte injection volume of the battery cell 1, and the capacity of the battery cell 1—based on the calculated value. In the example embodiment described above, since the calculated result is below the lower limit of the formula (2.4), this indicates that the current combination of valve opening area and valve opening pressure may be insufficient to counteract pressure buildup inside the battery cell 1 in actual use. Therefore, operators may need to increase the valve opening area or increase the valve opening pressure to raise the calculated result above 2.4, thereby ensuring the safety of the explosion-proof structure 122. The ratio of the injection volume to the capacity in the formula plays a significant role in the pressure response of the explosion-proof structure 122. In this example, the large injection volume (1 kg) and relatively small capacity (300 Ah) resulted in a high ratio of injection volume to capacity, directly reducing the final calculation result. Therefore, if the injection volume is relatively large, a larger valve opening area or valve opening pressure is needed to offset this effect. By using this formula, operators can ensure the reliable opening of the explosion-proof structure 122 under different capacity and injection volume conditions by setting reasonable valve opening area and pressure ranges. In cases where conditions are not met, the formula provides guidance to operators, indicating which parameters need to be adjusted to meet safety requirements.

[0025] In some embodiments, the valve opening area S of the explosion-proof structure 122 ranges from 0.5 to 10 cm². 2 The opening pressure P of the explosion-proof structure 122 ranges from 0.5 to 1 MPa; the electrolyte injection volume m of cell 1 ranges from 0.25 to 3.2 kg; and the capacity C of cell 1 ranges from 100 to 800 Ah. All these parameter ranges were obtained experimentally. Operators can set the parameters of cell 1 according to these ranges. An example is as follows:

[0026] Assume the design parameters of a certain battery cell 1 are as follows: the capacity of battery cell 1 is C=400 Ah; the electrolyte injection volume is m=1.5kg; the valve opening area of ​​the explosion-proof structure 122 is S=6cm²; and the valve opening pressure is P=0.8 MPa.

[0027] Substitute these parameters into the formula:

[0028] 2.4 ≤ S×P-C / (m×1000) ≤ 5.4, therefore,

[0029] S×P-C / (m×1000)=1.05.

[0030] The calculation result does not satisfy the formula 2.4≤S×P-C / (m×1000)≤5.4, so the staff knew that cell 1 needed further adjustments to parameters such as valve opening area, valve opening pressure, liquid injection volume or capacity.

[0031] To satisfy the formula, the operator increased the valve opening pressure to 1 MPa, and the calculated value was 2.25. At this point, the calculation result was within the range of the formula and met the safety requirements. The operator could then select this parameter combination for specific applications of the explosion-proof structure 122.

[0032] Furthermore, the value range of the valve opening area S of the explosion-proof structure 122 can be further limited to 2.5-5.0 cm². 2 This range of valve opening area values ​​is suitable for specific medium-to-large capacity battery cells 1 (such as 300-600 Ah cells 1) to more precisely balance the requirements between pressure relief and the structural strength of the explosion-proof structure 122. By narrowing the range of valve opening area values, further control over the pressure relief effect can be achieved, allowing the explosion-proof structure 122 to operate more stably under specific capacity and pressure conditions.

[0033] In some embodiments, the portion of the explosion-proof structure 122 that aligns with the explosion-proof hole is provided with a notch 1221, and the depth of the notch 1221 and the valve opening area of ​​the explosion-proof structure 122 satisfy the following relationship:

[0034] 0.05≤d / S≤0.2;

[0035] The length of the notch 1221 and the valve opening area of ​​the explosion-proof structure 122 satisfy the following relationship:

[0036] L = β × 1 / P + γ;

[0037] The width of the notch 1221 is inversely proportional to the valve opening area of ​​the explosion-proof structure 122;

[0038] Where d is the depth of the notch 1221, S is the valve opening area of ​​the explosion-proof structure 122, L is the length of the notch 1221, P is the valve opening pressure of the explosion-proof structure 122, and β and γ are constants.

[0039] In detail, by controlling the depth, length, and width of the notch 1221, the explosion-proof structure 122 is preferentially torn along the notch 1221 when the set valve opening pressure is reached, ensuring timely pressure release within a safe range. The depth of the notch 1221 is proportional to the valve opening area, i.e., 0.05≤d / S≤0.2. This means that the depth of the notch 1221, while meeting the valve opening area requirement, ensures a preferential tearing point on the surface of the explosion-proof structure 122. Combined with the inverse relationship between the length of the notch 1221 and the valve opening pressure, L=β×1 / P+γ, the length of the notch 1221 increases at lower pressures, thereby increasing the tearing path and preventing unstable tearing when high pressure accumulates. Furthermore, by utilizing the inverse relationship between the width of the notch 1221 and the valve opening pressure, the width of the notch 1221 is larger at lower pressures, which is beneficial for achieving directional tearing at low pressures, further improving the pressure release effect. At lower valve opening pressures, the wider notch 1221 makes the area of ​​notch 1221 easier to tear, thus ensuring that the explosion-proof structure 122 will not open unnecessarily below the set pressure. At higher valve opening pressures, the width of notch 1221 narrows to ensure the structural strength of the valve body. With the depth, length, and width of notch 1221 limited, the opening tear path of the explosion-proof structure 122 will not become uncontrollable under specific pressure conditions, while the total area of ​​notch 1221 still satisfies the formula conditions, ensuring the structural stability of the explosion-proof structure 122.

[0040] Furthermore, the total area of ​​the notch 1221 and the valve opening area satisfy the following relationship:

[0041] S k =ζS;

[0042] Where Sk is the total area of ​​the notch 1221, ζ is a constant, and the value of ζ ranges from 0.1 to 0.3.

[0043] Through S k The formula =ζS ensures that the area of ​​the notch 1221 is not too large, thus weakening the structural strength of the explosion-proof structure 122, nor too small, thus affecting the tear resistance. It should be noted that S... k The total area of ​​the notches 1221 refers specifically to the sum of the surface areas of all notches 1221 on the explosion-proof structure 122. The total area of ​​the notches 1221 is used to control the tearing area of ​​the explosion-proof structure 122, preventing structural failure caused by large-area tearing. The proportionality coefficient ζ represents the ratio between the total area of ​​the notches 1221 and the valve opening area, controlling the size of the notch area. A larger proportionality coefficient results in a relatively larger total area of ​​the notches 1221; a smaller proportionality coefficient results in a relatively smaller area of ​​the notches 1221.

[0044] In some embodiments, the valve opening area of ​​the explosion-proof structure 122 satisfies the following relationship:

[0045] S = αm + δ1. This formula stipulates that the valve opening area S should be linearly proportional to the injection volume m, so as to ensure that the explosion-proof structure 122 can adaptively adjust the valve opening area according to the amount of injection volume m. Among them, α and δ1 are constants, and the value of α ranges from 1.2 to 1.8, and the value of δ1 ranges from 0.8 to 1.8.

[0046] Workers can determine the valve opening area of ​​the explosion-proof structure 122 by using the formula for the valve opening area. Then, by substituting the determined valve opening area into the formula 2.4≤S×P-C / (m×1000)≤5.4, they can verify whether the current valve opening area meets the requirements.

[0047] Furthermore, the adjustment coefficient α can be in the range of 1.4-1.6, and the constant offset δ1 can be in the range of 1.2-1.5.

[0048] In some embodiments, the electrolyte injection volume of cell 1 and the capacity of cell 1 satisfy the following relationship:

[0049] m = kC / 1000;

[0050] Where k is a constant, and the value of k ranges from 2.5 to 4. The value of k can be obtained through a large amount of experimental data.

[0051] To verify the correctness of 2.4 ≤ S×P-C / (m×1000) ≤ 5.4, multiple sets of examples and comparative examples are compared below:

[0052] In the following embodiments and comparative examples, lithium iron phosphate cell 1 is selected. The parameters of each embodiment and comparative example are shown in the table below:

[0053] Valve opening area (cm²) Valve opening pressure (MPa) Liquid injection volume (kg) Capacity (AhS×P-C / (m×1000)) Example 1 3.65 0.9 0.48 160 2.95 Example 2 7.09 0.65 2.01 630 4.30 Example 3 3.65 0.75 0.71 230 2.41 Example 4 7.09 0.8 2.01 630 5.36 Comparative Example 1 3.65 0.65 0.48 160 2.04 Comparative Example 2 7.09 12.01 630 6.78 Comparative Example 3 7.09 0.8 2.52 630 5.42 Comparative Example 4 1.58 0.8 0.52 160 0.96

[0054] As can be seen from the table above, the values ​​calculated by the formula S×P-C / (m×1000) for Examples 1 to 4 are all in the range of 2.4 to 5.4, while the values ​​calculated by the formula S×P-C / (m×1000) for Comparative Examples 1 to 4 are not in the range of 2.4 to 5.4.

[0055] Overcharge tests were conducted on battery cells 1 from Examples 1-4 and Comparative Examples 1-4 respectively. The specific test process is as follows:

[0056] At 25℃, cell 1 is charged with a constant current and constant voltage at 0.5C, with the cutoff voltage at 3.65V and the cutoff current at 0.05C. Cell 1 is then discharged with a constant current at 0.5C to 2.5V, repeated 3 times. The capacity of the last discharge cycle is used as the initial capacity and recorded as Q. Cell 1 is then charged with a constant current and constant voltage at 0.5Q, with the cutoff voltage at 3.65V and the cutoff current at 0.05Q. After full charge, it is continuously charged at 1Q until thermal runaway, and the open-valve SOC and thermal runaway SOC are recorded. The criteria for determining thermal runaway refer to the national standard GB38031-2020 for the safety of power cells 1 for electric vehicles. It should be noted that C refers to the nominal capacity of cell 1, in Ah. The aforementioned 0.5C current represents the current at a charge / discharge rate of half the nominal capacity. For a 100Ah cell 1, 0.5C current is 50A, which is the current rate at which cell 1 is fully charged or discharged in 2 hours. Q is the discharge capacity after multiple charge-discharge cycles, measured in Ah (ampere-hours), which is the remaining capacity when discharged to a specific voltage (e.g., 2.5V) under specified conditions. SOC (State of Charge) represents the current remaining percentage of charge in cell 1, describing its charging state. The SOC value typically ranges from 0% to 100%, with 0% indicating complete discharge and 100% indicating a full charge. For example, in charging tests, valve-opening SOC indicates the charge state when the explosion-proof structure 122 is open, while thermal runaway SOC indicates the charge state when cell 1 reaches thermal runaway.

[0057] The following are the experimental results obtained from Examples 1-4 and Comparative Examples 1-4:

[0058] Valve opening SOC / % Thermal runaway SOC / % Explosion Example 1 1 15 127 No Example 2 1 16 126 No Example 3 1 16 126 No Example 4 1 16 127 No Comparative Example 1 1 10 126 No Comparative Example 2 1 21 125 Comparative Example 3 1 14 118 No Comparative Example 4 1 13 121 Yes

[0059] As can be seen from the above Examples 1-4 and Comparative Examples 1-4: in Examples 1-4, the valves were opened before thermal runaway occurred, and no explosion occurred; in Comparative Example 1, the valve was opened after overcharging to 110% SOC, which was too low and could not meet market demand; in Comparative Example 2, the valve opening pressure was too high, and the valve was opened at 121% SOC, and thermal runaway and explosion occurred at 125% SOC; in Comparative Example 3, the injection volume was too high, and the valve opening pressure was too low, so the valve was opened after overcharging to 114% SOC, which could not meet market demand; in Comparative Example 4, the valve opening area was set too small, and thermal runaway occurred at 121% SOC, followed by an explosion.

[0060] In summary, by referring to the formula 2.4≤S×P-C / (m×1000)≤5.4, the staff set the valve opening area, valve opening pressure, electrolyte injection volume, and capacity of the explosion-proof structure 122 in the battery cell 1. This can accommodate various battery cells 1 with different capacities, such as small-capacity battery cells 1 and large-capacity battery cells 1, so that the explosion-proof structure 122 can open the valve in a timely manner while avoiding premature valve opening.

Claims

1. A battery cell, the battery cell comprising an electrode assembly and a housing, the electrode assembly being disposed within the housing, and the housing being provided with an explosion-proof structure; in, The valve opening area S of the explosion-proof structure, the valve opening pressure P of the explosion-proof structure, the electrolyte injection volume m of the battery cell, and the capacity C of the battery cell satisfy the following formula: 2.4≤S×P-C / (m×1000)≤5.

4.

2. The battery cell as described in claim 1, wherein, The explosion-proof structure is provided with grooves.

3. The battery cell as described in claim 2, wherein, The depth of the groove and the valve opening area of ​​the explosion-proof structure satisfy the following relationship: 0.05≤d / S≤0.2; Where d is the depth of the groove, and S is the valve opening area of ​​the explosion-proof structure.

4. The battery cell as described in claim 3, wherein, The length of the groove and the valve opening pressure of the explosion-proof structure satisfy the following relationship: L = β × 1 / P + γ; Where L is the length of the groove, P is the valve opening pressure of the explosion-proof structure, and β and γ are both constants.

5. The battery cell according to any one of claims 2 to 4, wherein, The total area of ​​the grooves and the valve opening area satisfy the following relationship: S k =ζS; Among them, S k Let ζ be the total area of ​​the indentation, and ζ be a constant.

6. The battery cell as described in claim 5, wherein, The value of ζ ranges from 0.1 to 0.

3.

7. The battery cell according to any one of claims 1 to 6, wherein, The valve opening area of ​​the explosion-proof structure satisfies the following relationship: S = αm + δ1; Where α and δ1 are constants.

8. The battery cell as described in claim 7, wherein, The value of α ranges from 1.2 to 1.8, and the value of δ1 ranges from 0.8 to 1.

8.

9. The battery cell as described in claim 8, wherein, The value of α ranges from 1.4 to 1.6, and the value of δ1 ranges from 1.2 to 1.

5.

10. The battery cell according to any one of claims 1 to 5, wherein, The electrolyte injection volume of the battery cell and the capacity of the battery cell satisfy the following relationship: m = kC / 1000; Where k is a constant.

11. The battery cell as claimed in claim 10, wherein, The value of k ranges from 2.5 to 4.

12. The battery cell according to any one of claims 1 to 5, wherein, The value of the valve opening area S of the explosion-proof structure ranges from 0.5 to 10 cm². 2 .

13. The battery cell as claimed in claim 12, wherein, The valve opening area S of the explosion-proof structure ranges from 2.5 to 5.0 cm². 2 .

14. The battery cell according to any one of claims 1 to 5, wherein, The valve opening pressure P of the explosion-proof structure ranges from 0.5 to 1 MPa.

15. The battery cell according to any one of claims 1 to 5, wherein, The electrolyte injection volume m of the battery cell ranges from 0.25 to 3.2 kg.

16. The battery cell according to any one of claims 1 to 5, wherein, The capacity C of the battery cell ranges from 100 to 800 Ah.

17. The battery cell according to any one of claims 1 to 5, wherein, The battery cell includes a cover plate, on which the explosion-proof structure is provided and an explosion-proof hole is opened, the explosion-proof hole being in communication with the housing; the explosion-proof structure is provided on the cover plate and covers the explosion-proof hole.

18. The battery cell according to any one of claims 1 to 5, wherein, The active material of the battery cell is any one of the following: lithium iron phosphate system, medium nickel ternary system, high nickel ternary system, sodium battery system, and lithium manganese iron phosphate system.

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