Single battery and battery pack

Abstract

The invention discloses a single battery and a battery pack, and belongs to the technical field of batteries, and the single battery comprises a shell, an electrode assembly, a cover plate and an anti-explosion valve. According to the embodiment of the invention, the reasonable area S of the explosion-proof valve is obtained by measuring the maximum sizes L, T and H of the shell in three directions, the thicknesses I, M and J of the first wall, the second wall and the third wall of the shell and the maximum size a of the cover plate in the third direction, and the area S of the explosion-proof valve does not need to be calculated through complex parameters such as surface density, gram volume and active matter mass; errors caused by complex measurement and calculation are avoided, and the calculation method is simplified. The size of the anti-explosion valve is reasonably designed, so that the anti-explosion valve can be normally opened for exhausting when the single battery is in thermal runaway, and the safety and the reliability of the single battery are further improved.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and specifically relates to a single cell and a battery pack. Background Art

[0002] As lithium-ion battery technology becomes increasingly mature, lithium-ion batteries are widely used as power batteries in the field of electric vehicles. Among them, the area design of the explosion-proof valve is particularly important. If the size of the explosion-proof valve is not set properly, the battery may not open the valve in time or the valve may not be vented smoothly, causing the battery to spray or cause a fire or explosion. At present, the design of the explosion-proof valve size usually needs to be calculated based on the capacity, material system, rated voltage of the single battery and other parameters. The calculation process is too cumbersome, and different measurement and calculation links may introduce errors. Summary of the invention

[0003] Purpose of the invention: The embodiments of the present application provide a single cell and a battery pack, aiming to solve the technical problem that the calculation process of explosion-proof valve size design is cumbersome and easy to introduce errors.

[0004] Technical solution: The present application embodiment provides a single battery, including:

[0005] A housing having a receiving cavity;

[0006] An electrode assembly is disposed in the accommodating cavity;

[0007] A cover plate covers the accommodating cavity, and at least one of the shell and the cover plate has an explosion-proof hole;

[0008] Explosion-proof valve, cover and seal explosion-proof hole;

[0009] The maximum dimension of the shell in the first direction is L mm, the maximum dimension of the shell in the second direction is T mm, and the maximum dimension of the shell in the third direction is H mm. The shell comprises a first wall arranged opposite to each other in the first direction, a second wall arranged opposite to each other in the second direction, and a third wall arranged opposite to the cover plate in the third direction. The thickness of the first wall is I mm, the thickness of the second wall is M mm, and the thickness of the third wall is J mm. The maximum dimension of the cover plate in the third direction is a mm. The first direction, the second direction and the third direction intersect each other.

[0010] Single battery meets:

[0011] or

[0012]

[0013] Where S is the area of ​​the explosion-proof valve, V is the rated voltage, and ξ is the correction coefficient.

[0014] In some embodiments, the battery cell satisfies:

[0015] or

[0016]

[0017] Among them, C is the rated capacity of the single battery.

[0018] In some embodiments, the battery cell satisfies at least one of the following characteristics:

[0019] a) L>T;

[0020] b) H>T;

[0021] c) J>I;

[0022] d)I≥M.

[0023] In some embodiments, the explosion-proof valve includes a connecting portion and a weak portion, the connecting portion is connected to the weak portion in a surrounding manner, the connecting portion is connected to the cover plate, the weak portion is provided with a notch, the weak portion is configured to be destroyed along the notch when subjected to a preset pressure impact, the area enclosed by the notch is S', the number of explosion-proof valves is n, and satisfies: S = n × S'.

[0024] In some embodiments, the dimension of the connecting portion in the third direction is d mm, the maximum dimension of the weak portion in the third direction is e mm, the residual thickness at the notch on the weak portion is f mm, and the single cell satisfies at least one of the following characteristics:

[0025] e) 0.3≤d≤0.8;

[0026] f)0.1≤e <d;

[0027] g)0.04≤f <e。

[0028] In some embodiments, the single battery satisfies: 0.08≤f<0.2.

[0029] In some embodiments, the first wall includes a body and a step portion, the step portion is located on a side of the body facing the electrode assembly, and the cover plate abuts against the step portion in the third direction.

[0030] In some embodiments, the cover plate has a maximum dimension B mm in the first direction, satisfying: 0≤L-B≤0.3.

[0031] In some embodiments, the single cell is a lithium iron phosphate single cell or a ternary lithium single cell.

[0032] Accordingly, an embodiment of the present application provides a battery pack, comprising the above-mentioned single battery.

[0033] Beneficial effects: The single cell battery of the embodiment of the present application comprises a shell, an electrode assembly, a cover plate and an explosion-proof valve. The shell has a receiving cavity; the electrode assembly is arranged in the receiving cavity; the cover plate covers the receiving cavity, and at least one of the shell and the cover plate has an explosion-proof hole; the explosion-proof valve covers the explosion-proof hole; the maximum size of the shell in the first direction is L mm, the maximum size of the shell in the second direction is T mm, and the maximum size of the shell in the third direction is H mm. The shell comprises a first wall arranged oppositely in the first direction, a second wall arranged oppositely in the second direction, and a third wall arranged oppositely to the cover plate in the third direction, the thickness of the first wall is 1 mm, the thickness of the second wall is M mm, and the thickness of the third wall is J mm; the maximum size of the cover plate in the third direction is a mm; the first direction, the second direction and the third direction intersect each other; the single cell battery satisfies:

[0034] or

[0035] Wherein, S is the area of ​​the explosion-proof valve, V is the rated voltage, and ξ is the correction coefficient. The embodiment of the present application measures the maximum dimensions L, T and H of the shell in three directions, the thickness I, M and J of the first wall, the second wall and the third wall of the shell, and the maximum dimension a of the cover plate in the third direction to obtain a reasonable area S of the explosion-proof valve. There is no need to calculate the area S of the explosion-proof valve through complex parameters such as surface density, gram capacity, and active substance mass, thereby avoiding errors introduced due to complex measurements and calculations and simplifying the calculation method. By reasonably designing the size of the explosion-proof valve, it can be ensured that the explosion-proof valve can open normally to exhaust gas when the single cell thermal runaways, thereby improving the safety and reliability of the single cell.

[0036] The battery pack of the embodiment of the present application includes the above-mentioned single battery, so the battery pack can have all the technical features and beneficial effects of the above-mentioned single battery, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 is a schematic structural diagram of a single cell according to an embodiment of the present application;

[0039] Figure 2 is a schematic structural diagram of a single cell according to another embodiment of the present application;

[0040] Figure 3 is an exploded diagram of a single cell of an embodiment of the present application;

[0041] Figure 4 is a cross-sectional view of a single cell according to an embodiment of the present application;

[0042] Figure 5 is a front view of a single cell according to an embodiment of the present application;

[0043] Figure 6 yes Figure 5 A magnified view of part A;

[0044] Figure 7 yes Figure 5 A magnified view of part B;

[0045] Figure 8 yes Figure 5 Enlarged view of part C;

[0046] Fig. 9 yes Figure 5 A magnified view of the D portion;

[0047] Fig.10 is a side view of a single cell according to an embodiment of the present application;

[0048] Fig.11 yes Fig.10 A magnified view of part E;

[0049] Fig.12 yes Fig.10 Magnified view of part F;

[0050] Fig.13 is a cross-sectional view of a single cell according to another embodiment of the present application;

[0051] Fig.14 yes Fig.13 Enlarged view of the G section;

[0052] Fig.15 is a top view of a single cell according to an embodiment of the present application;

[0053] Fig.16 It is a structural schematic diagram of an explosion-proof valve according to an embodiment of the present application;

[0054] Fig.17 is a side view of a cover plate according to an embodiment of the present application;

[0055] Fig.18 yes Fig.17 Enlarged view of the H part.

[0056] Figure numerals: 1, shell; 2, electrode assembly; 3, cover plate; 4, explosion-proof valve; 5, explosion-proof hole; 10, accommodating chamber; 11, first wall; 12, second wall; 13, third wall; 40, connecting part; 41, weak part; 110, main body; 111, step part; 410, notch; X, first direction; Y, second direction; Z, third direction. DETAILED DESCRIPTION

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

[0058] In the description of the present application, it should be understood that the terms "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, "multiple" means two or more, and at least one means one, two or more, unless otherwise clearly and specifically defined. In the description of this application, "vertical" means completely vertical at 90° or almost completely vertical, for example, an angle within the range of 80° to 100° is considered vertical. Similarly, "parallel" means completely parallel or almost completely parallel, for example, an angle within 10° of completely parallel is considered parallel.

[0059] The applicant noted that with the increasing maturity of lithium-ion battery technology, lithium-ion batteries are widely used as power batteries in the field of electric vehicles. Among them, the area design of the explosion-proof valve is particularly important. If the size of the explosion-proof valve is improperly set, the battery will not be able to open the valve in time or the valve will not be vented smoothly, causing the battery to spray or cause fire and explosion. At present, the design of the explosion-proof valve size usually needs to be calculated based on parameters such as the capacity, material system, and rated voltage of the single battery. The calculation process is too cumbersome, and different measurement and calculation links may introduce errors.

[0060] In view of this, the single cell of the embodiment of the present application includes a shell, an electrode assembly, a cover plate and an explosion-proof valve. The shell has a accommodating cavity; the electrode assembly is arranged in the accommodating cavity; the cover plate seals the accommodating cavity, and at least one of the shell and the cover plate has an explosion-proof hole; the explosion-proof valve seals the explosion-proof hole; the maximum size of the shell in the first direction is L mm, the maximum size of the shell in the second direction is T mm, and the maximum size of the shell in the third direction is H mm. The shell includes a first wall arranged oppositely in the first direction, a second wall arranged oppositely in the second direction, and a third wall arranged oppositely to the cover plate in the third direction, the thickness of the first wall is 1 mm, the thickness of the second wall is M mm, and the thickness of the third wall is J mm; the maximum size of the cover plate in the third direction is a mm; the first direction, the second direction and the third direction intersect each other; the single cell satisfies:

[0061] or

[0062] Wherein, S is the area of ​​the explosion-proof valve, V is the rated voltage, and ξ is the correction coefficient. The embodiment of the present application measures the maximum dimensions L, T and H of the shell in three directions, the thickness I, M and J of the first wall, the second wall and the third wall of the shell, and the maximum dimension a of the cover plate in the third direction to obtain a reasonable area S of the explosion-proof valve. There is no need to calculate the area S of the explosion-proof valve through complex parameters such as surface density, gram capacity, and active substance mass, thereby avoiding errors introduced due to complex measurements and calculations and simplifying the calculation method. By reasonably designing the size of the explosion-proof valve, it can be ensured that the explosion-proof valve can open normally to exhaust gas when the single cell thermal runaways, thereby improving the safety and reliability of the single cell.

[0063] The single cell and battery pack of the present application are described in detail below in conjunction with the accompanying drawings. The features of the following embodiments and implementations can be combined with each other if there is no conflict.

[0064] 1. Shell; 2. Electrode assembly; 3. Cover plate; 4. Explosion-proof valve; 5. Explosion-proof hole; 10. Accommodating chamber; 11. First wall; 12. Second wall; 13. Third wall; 40. Connecting part; 41. Weak part; 110. Main body; 111. Step part; 410. Notch; X, first direction; Y, second direction; Z, third direction.

[0065] Figure 1 is a schematic structural diagram of a single cell according to an embodiment of the present application; Figure 2 is a schematic structural diagram of a single cell according to another embodiment of the present application; Figure 3 is an exploded diagram of a single cell of an embodiment of the present application; Figure 4 is a cross-sectional view of a single cell according to an embodiment of the present application; Figure 5 is a front view of a single cell according to an embodiment of the present application; Figure 6 yes Figure 5 A magnified view of part A; Figure 7 yes Figure 5 A magnified view of part B;

[0066] Figure 8 yes Figure 5 Enlarged view of part C; Fig. 9 yes Figure 5 A magnified view of the D portion; Fig.10 is a side view of a single cell according to an embodiment of the present application; Fig.11 yes Fig.10 A magnified view of part E; Fig.12 yes Fig.10 Magnified view of part F; Fig.13 is a cross-sectional view of a single cell according to another embodiment of the present application; Fig.14 yes Fig.13 Enlarged view of the G section; Fig.15 is a top view of a single cell according to an embodiment of the present application; Fig.16 This is a schematic diagram of the structure of an explosion-proof valve 4 according to an embodiment of the present application; Fig.17 is a side view of a cover plate 3 according to an embodiment of the present application; Fig.18 yes Fig.17 Enlarged view of the H section. Figures 1 to 18 The single cell of the embodiment of the present application comprises a housing 1, an electrode assembly 2, a cover plate 3 and an explosion-proof valve 4. The housing 1 has a receiving cavity 10; the electrode assembly 2 is arranged in the receiving cavity 10; the cover plate 3 covers the receiving cavity 10, at least one of the housing 1 and the cover plate 3 has an explosion-proof hole 5; the explosion-proof valve 4 covers the explosion-proof hole 5. For example, in Figure 1 In the embodiment shown, the cover plate 3 has an explosion-proof hole 5, and the explosion-proof valve 4 is connected to the cover plate 3 and covers the explosion-proof hole 5; Figure 2 In the illustrated embodiment, the shell 1 has an explosion-proof hole 5, and the explosion-proof valve 4 is connected to the shell 1 and covers the explosion-proof hole 5. The maximum dimension of the shell 1 in the first direction X is L mm, the maximum dimension of the shell 1 in the second direction Y is T mm, and the maximum dimension of the shell 1 in the third direction Z is H mm. The shell 1 includes a first wall 11 arranged opposite to each other in the first direction X, a second wall 12 arranged opposite to each other in the second direction Y, and a third wall 13 arranged opposite to the cover plate 3 in the third direction Z. The thickness of the first wall 11 is I mm, the thickness of the second wall 12 is M mm, and the thickness of the third wall 13 is J mm; the maximum dimension of the cover plate 3 in the third direction Z is a mm; the first direction X, the second direction Y and the third direction Z intersect each other. Specifically, in Figure 1 In the embodiment shown, the first direction X is the length direction of the housing 1, the second direction Y is the width direction of the housing 1, and the third direction Z is the height direction of the housing 1. The first direction X, the second direction Y and the third direction Z are perpendicular to each other. The single battery satisfies:

[0067] or

[0068] Wherein, S is the area of ​​the explosion-proof valve 4, V is the rated voltage, and ξ is the correction coefficient.

[0069] In the embodiment of the present application, the maximum dimensions L, T and H of the shell 1 in three directions, the thickness I, M and J of the first wall 11, the second wall 12 and the third wall 13 of the shell 1, and the maximum dimension a of the cover plate 3 in the third direction Z are measured to obtain a reasonable area S of the explosion-proof valve 4. There is no need to calculate the area S of the explosion-proof valve 4 through complex parameters such as surface density, gram capacity, and amount of active substances, thereby avoiding errors introduced due to complex measurements and calculations and simplifying the calculation method. By reasonably designing the size of the explosion-proof valve 4, it can be ensured that the explosion-proof valve 4 can open the valve normally to exhaust air when the single cell battery is thermally runaway, thereby improving the safety and reliability of the single cell battery. In addition, according to the above formula, a reference can be provided for the size setting of the shell 1 and the cover plate 3, so that the overall structure of the battery cell is more reasonable, thereby improving the production efficiency of the single cell battery.

[0070] In some embodiments, the single cell is a lithium iron phosphate single cell, and the area S of the explosion-proof valve 4 of the lithium iron phosphate single cell can be obtained by the following formula:

[0071]

[0072] S≥C MAX *V*ξ;

[0073] Wherein, S is the area of ​​the explosion-proof valve 4 of the lithium iron phosphate single battery, and its unit is mm 2 , V is the rated voltage of the lithium iron phosphate battery, its unit is V, ξ is the correction factor of the lithium iron phosphate battery, C is the rated capacity of the lithium iron phosphate battery, C maxThe rated capacity of the lithium iron phosphate single cell when δ takes the maximum value. Exemplarily, V can be 3.2V, and ξ can be 0.6. C = the size of the positive electrode sheet area in the first direction X * the size of the positive electrode sheet area in the third direction Z / 100 * compaction density * active material ratio / 100 * 2 (double-sided coating) / 1000 * gram capacity * number of positive electrode sheet layers / 1000; wherein, the number of negative electrode sheet layers = the number of positive electrode sheet layers + 1, the number of diaphragm layers = 2 * the number of positive electrode sheet layers + 1; the thickness of the diaphragm, the thickness of the positive electrode sheet aluminum foil, and the thickness of the negative electrode sheet copper foil are known parameters, generally the diaphragm is 10-12um, the aluminum foil is 10-15um, and the copper foil is 4-6um; The thickness of the positive and negative electrodes can be deduced from the compaction density; the number of positive electrode layers contained in the space of the shell 1 in the second direction Y can be inferred from the above; through the above derivation process, a formula for directly calculating the capacity of a single battery cell through the size of the structural parts is obtained. Due to slight fluctuations in the compaction density, surface density, gram capacity, copper and aluminum foil, and diaphragm thickness, a fluctuation range of 0.9 to 1.1 times can be calculated comprehensively, so a correction coefficient δ is introduced into the formula, and the range of δ is between 0.9 and 1.1.

[0074] In some embodiments, the maximum dimension H of the shell 1 in the third direction Z is 112 mm, the maximum dimension L of the shell 1 in the first direction X is 148 mm, the maximum dimension T of the shell 1 in the second direction Y is 52 mm, the thickness J of the third wall 13 is 1.2, the thickness I of the first wall 11 is 0.8 mm, the thickness M of the second wall 12 is 0.6 mm, and the maximum dimension a of the cover plate 3 in the third direction Z is 7.5 mm. Substituting into the formula, C=96.07-117.42AH; if calculated by the traditional calculation method , C=98.57-116.83AH; It can be seen that through the above-derived formula, a reasonable area S of the explosion-proof valve 4 can be obtained by measuring the maximum dimensions L, T and H of the shell 1 in three directions, the thicknesses I, M and J of the first wall 11, the second wall 12 and the third wall 13 of the shell 1, and the maximum dimension a of the cover plate 3 in the third direction Z. There is no need to calculate the area S of the explosion-proof valve 4 through complex parameters such as surface density, gram capacity, and active substance mass, thereby avoiding errors introduced due to complex measurements and calculations and simplifying the calculation method.

[0075] C max =117.42AH, substitute S≥C MAX *V*ξ, we get S≥225.45mm 2That is, the area S of the explosion-proof valve 4 should be designed according to the upper limit of the single cell capacity to fully ensure the normal valve opening of the single cell during thermal runaway. The following will also verify the rationality of the area design of the explosion-proof valve 4 by conducting thermal runaway tests on multiple samples. Specifically, each sample includes 5 single cells. The thermal runaway test refers to verifying the rationality of the area design of the explosion-proof valve 4 by heating with a heating plate. The test results are shown in Table 1.

[0076] Table 1:

[0077]

[0078]

[0079] With reference to Examples 1 to 3, when the area of ​​the explosion-proof valve 4 is between 225.5 and 300, the verification result is that the valves of the five single cells are opened normally. It can be understood that when the area of ​​the explosion-proof valve 4 reaches or approaches 225.45 calculated according to the upper limit of the single cell capacity, it can be ensured that the explosion-proof valve 4 can open the valve normally to exhaust gas when the single cell thermal runaway occurs, thereby improving the safety and reliability of the single cell. With reference to Comparative Examples 1 to 5, when the area of ​​the explosion-proof valve 4 is less than 225.45, the verification result is that some single cells have problems such as poor exhaust, fire or eruption. It can be understood that when the area of ​​the explosion-proof valve 4 is less than 225.45 calculated according to the upper limit of the single cell capacity, the exhaust area of ​​the explosion-proof valve 4 is insufficient, which will cause the single cell to have poor exhaust, fire or eruption, etc., seriously affecting the safety of the single cell.

[0080] In other embodiments, the single cell is a ternary lithium single cell, and the explosion valve area S of the ternary lithium single cell can be obtained by the following formula:

[0081]

[0082] S≥C max *V*ξ

[0083] Wherein, S is the area of ​​the explosion-proof valve 4 of the ternary lithium single battery, and its unit is mm 2 , V is the rated voltage of the ternary lithium battery, the unit is V, ξ is the correction factor of the ternary lithium battery, and C is the rated capacity of the ternary lithium battery. For example, V can be 3.6V. Since the materials of the ternary system are more active, the gas production and production rate are larger than those of iron lithium, and ξ can be 1.2.

[0084] C = size of positive electrode sheet area in first direction X * size of positive electrode sheet area in third direction Z / 100 * compaction density * active material ratio / 100 * 2 (double-sided coating) / 1000 * gram capacity * number of positive electrode sheet layers / 1000; wherein, number of negative electrode sheet layers = number of positive electrode sheet layers + 1, number of separator layers = 2 * number of positive electrode sheet layers + 1; the thickness of separator, thickness of positive electrode sheet aluminum foil, thickness of negative electrode sheet copper foil are known parameters, generally 10-12um for separator, 10-15um for aluminum foil, and 4-6um for copper foil; The thickness of the positive and negative electrodes can be deduced from the compaction density; the number of positive electrode layers contained in the space of the shell 1 in the second direction Y can be inferred from the above; through the above derivation process, a formula for directly calculating the capacity of a single battery cell through the size of the structural parts is obtained. Due to slight fluctuations in the compaction density, surface density, gram capacity, copper and aluminum foil, and diaphragm thickness, a fluctuation range of 0.9 to 1.1 times can be calculated comprehensively, so a correction coefficient δ is introduced into the formula, and the range of δ is between 0.9 and 1.1.

[0085] In some embodiments, the maximum dimension H of the shell 1 in the third direction Z is 112 mm, the maximum dimension L of the shell 1 in the first direction X is 148 mm, the maximum dimension T of the shell 1 in the second direction Y is 52 mm, the thickness J of the third wall 13 is 1.2, the thickness I of the first wall 11 is 0.8 mm, the thickness M of the second wall 12 is 0.6 mm, and the maximum dimension a of the cover plate 3 in the third direction Z is 7.5 mm. Substituting into the formula, C=115.21-140.81AH; if calculated by traditional calculation method Calculate, C=119.7-138.25AH; it can be seen that through the above-derived formula, a reasonable area S of the explosion-proof valve 4 can be obtained by measuring the maximum dimensions L, T and H of the shell 1 in three directions, the thicknesses I, M and J of the first wall 11, the second wall 12 and the third wall 13 of the shell 1, and the maximum dimension a of the cover plate 3 in the third direction Z. There is no need to calculate the area S of the explosion-proof valve 4 through complex parameters such as surface density, gram capacity, and active substance mass, thereby avoiding errors introduced due to complex measurements and calculations and simplifying the calculation method.

[0086] C max =140.81AH, substitute S≥C MAX *V*ξ, yes, S≥608.3mm 2 That is, the area of ​​explosion-proof valve 4 should be designed according to the upper limit of the single cell capacity, so as to fully guarantee the normal valve opening of the single cell in thermal runaway. The following will also verify the rationality of the design of the area of ​​explosion-proof valve 4 by conducting thermal runaway tests on multiple samples. Specifically, each sample includes 5 single cells. The thermal runaway test refers to verifying the rationality of the design of the area of ​​explosion-proof valve 4 by heating with a heating plate. The test results are shown in Table 2.

[0087] Table 2:

[0088] <![CDATA[Explosion-proof valve 4 area / mm 2 > result Example 4 700 All five cells open normally and are in good condition. Example 5 650 All five cells open normally and are in good condition. Example 6 610 All five cells open normally and are in good condition. Comparative Example 6 500 A single battery caught fire Comparative Example 7 400 One battery cell caught fire, and the rest of the batteries erupted violently. Comparative Example 8 300 Three batteries caught fire Comparative Example 9 200 All five batteries caught fire Comparative Example 10 100 All five cells caught fire, and one side of the shell was sprayed with

[0089] With reference to Examples 4 to 6, when the area of ​​explosion-proof valve 4 is between 610 and 700, the verification result is that the valves of the five single cells are opened normally. It can be understood that when the area of ​​explosion-proof valve 4 reaches or approaches 608.3 calculated according to the upper limit of the single cell capacity, it can be ensured that the explosion-proof valve 4 can open the valve normally to exhaust gas when the single cell thermal runaway occurs, thereby improving the safety and reliability of the single cell. With reference to Comparative Examples 5 to 10, when the area of ​​explosion-proof valve 4 is less than 608.3, the verification result is that some single cells have problems such as poor exhaust, fire or eruption. It can be understood that when the area of ​​explosion-proof valve 4 is less than 608.3 calculated according to the upper limit of the single cell capacity, the exhaust area of ​​explosion-proof valve 4 is insufficient, which will cause the single cell to have poor exhaust, fire or eruption, etc., seriously affecting the safety of the single cell.

[0090] exist Figure 5 and Fig.10 In the illustrated embodiment, the maximum dimension L of the housing 1 in the first direction X and the maximum dimension T of the housing 1 in the second direction Y satisfy: L>T. The first direction X is the length direction of the housing 1, and the second direction Y is the width direction of the housing 1. The maximum dimension L of the housing 1 in the first direction X is greater than the maximum dimension T of the housing 1 in the second direction Y, which helps to optimize the space utilization and layout inside the single battery and improve the space utilization rate.

[0091] exist Fig.10 In the illustrated embodiment, the maximum dimension H of the housing 1 in the third direction Z and the maximum dimension T of the housing 1 in the second direction Y satisfy: H>T. The second direction Y is the width direction of the housing 1, and the third direction Z is the height direction of the housing 1. The maximum dimension H of the housing 1 in the third direction Z is greater than the maximum dimension T of the housing 1 in the second direction Y, thereby providing more space for internal components such as the electrode assembly 2, which is beneficial to improving energy density.

[0092] In some embodiments, the housing 1 includes a first wall 11 arranged oppositely in a first direction X, a second wall 12 arranged oppositely in a second direction Y, and a third wall 13 of the cover plate 3 arranged oppositely in a third direction Z, the thickness of the first wall 11 is I mm, the thickness of the second wall 12 is M mm, and the thickness of the third wall 13 is J mm, satisfying: J>I. The third wall 13 is the opposite surface of the housing 1, and is used to carry the electrode assembly 2. Therefore, the thickness J of the third wall 13 is greater than the thickness I of the first wall 11, thereby providing a certain degree of support for the electrode assembly 2.

[0093] Specifically, in Figure 5 , Figure 7 and Figure 8 In the embodiment shown, the first walls 11 of the housing 1 opposite to each other in the first direction X have thicknesses I1 and I2 respectively, and usually, the third wall 13 has the same wall thickness, that is, I1=I2. Figures 10 to 12 In the illustrated embodiment, the thicknesses of the second walls 12 of the housing 1 opposite to each other in the second direction Y are respectively M1 and M2. Usually, the second walls 12 have the same wall thickness, ie, M1 = M2.

[0094] In some embodiments, the thickness I of the first wall 11 and the thickness M of the second wall 12 satisfy: I>M. The first wall 11 includes a body 110 and a step portion 111, the step portion 111 is located on the side of the body 110 facing the electrode assembly 2 and connected to the body 110, and the cover plate 3 abuts against the step portion 111 in the third direction Z. The step portion 111 is used to support the cover plate 3, therefore, the thickness I of the first wall 11 is greater than the thickness M of the second wall 12, so as to provide a certain degree of support for the cover plate 3.

[0095] In some embodiments, the cover plate 3 and the housing 1 may be connected by laser welding.

[0096] In some embodiments, the explosion-proof valve 4 includes a connecting portion 40 and a weak portion 41, the connecting portion 40 is connected to the weak portion 41 in a surrounding manner, the connecting portion 40 is connected to the cover plate 3, the weak portion 41 is configured to be destroyed when subjected to a preset pressure impact, the weak portion 41 is provided with a notch 410, the area enclosed by the notch 410 is S', the number of explosion-proof valves 4 is n, and the following is satisfied: S = n × S'. By providing the notch 410, the weak portion 41 can be more accurately ruptured at the notch 410 when subjected to a preset pressure, ensuring that the explosion-proof valve 4 can release the internal gas of the single cell in time when thermal runaway occurs, thereby effectively reducing the internal pressure and preventing the single cell from catching fire or exploding. This application does not limit the number of explosion-proof valves 4.

[0097] exist Fig.18 In the illustrated embodiment, the dimension of the connection portion 40 in the third direction Z is d mm, the maximum dimension of the weak portion 41 in the third direction Z is e mm, the residual thickness at the notch 410 on the weak portion 41 is f mm, and the single cell satisfies: 0.3≤d≤0.8. For example, the dimension d of the connection portion 40 in the third direction Z can be any value among 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or a range of values ​​between any two. It can be understood that the penetration depth when the connection portion 40 is welded to the cover plate 3 or the shell 1 is generally 0.3 mm. If the thickness of the connection portion 40 is too thin, it is not easy to weld and the connection strength is insufficient. If the connection portion 40 is too thick, there is no cost advantage and the design is redundant. By limiting the dimension d of the connection portion 40 in the third direction Z, the present application can ensure the connection strength between the connection portion 40 and the cover plate 3 or the shell 1 and ensure that the overall occupied size is small.

[0098] In Fig.18 the illustrated embodiment, the dimension of the connecting portion 40 in the third direction Z is d mm, and the maximum dimension of the weak portion 41 in the third direction Z is e mm. The single cell satisfies: 0.1 ≤ e < d. It can be understood that when the maximum dimension of the weak portion 41 in the third direction Z is less than the dimension of the connecting portion 40 in the third direction Z, it can be ensured that the weak portion 41 can rupture timely along the notch 410 when subjected to a preset pressure. On the other hand, when the maximum dimension e of the weak portion 41 in the third direction Z is greater than or equal to 0.1, it can avoid the deformation of the weak portion 41 caused by insufficient strength of the weak portion 41 during the welding of the connecting portion 40 to the cover plate 3 or the housing 1, or due to the internal and external pressure difference during the manufacturing process of the single cell, thereby ensuring that the explosion-proof valve 4 can work properly during thermal runaway.

[0099] In Fig.18 the illustrated embodiment, the maximum dimension of the weak portion 41 in the third direction Z is e mm, and the remaining thickness of the notch 410 on the weak portion 41 is f mm. The single cell satisfies: 0.04 ≤ f < e. It can be understood that when the remaining thickness of the notch 410 on the weak portion 41 is less than the maximum dimension of the weak portion 41 in the third direction Z, it can be ensured that the weak portion 41 can rupture more accurately along the notch 410 when subjected to a preset pressure, ensuring that the explosion-proof valve 4 can release the gas inside the single cell in time during thermal runaway, thereby effectively reducing the internal pressure and preventing the single cell from catching fire and exploding. On the other hand, when the remaining thickness f of the notch 410 on the weak portion 41 is greater than or equal to 0.04, it can avoid the problem that the explosion-proof valve 4 is prone to open in advance along the notch 410 during the welding of the connecting portion 40 to the cover plate 3 or the housing 1 or during the manufacturing process of the single cell due to insufficient strength at the notch 410.

[0100] Furthermore, in Fig.18 the illustrated embodiment, the remaining thickness of the notch 410 on the weak portion 41 is f mm, satisfying: 0.08 ≤ f < 0.2. Exemplarily, the remaining thickness f of the notch 410 on the weak portion 41 can be any value among 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2 or the range value between any two of them. It can be understood that by reasonably limiting the remaining thickness f of the notch 410 on the weak portion 41, it is ensured that the weak portion 41 can rupture more accurately along the notch 410 when the single cell is subjected to a preset pressure during thermal runaway. Because of the reasonable design of the size of the remaining thickness f, it will not be difficult to rupture due to being too thick, resulting in the inability to release the internal gas in time and causing dangerous situations such as too high internal pressure leading to fire and explosion; nor will it have the problem of opening in advance during non-thermal runaway normal situations, such as during the welding of the connecting portion 40 to the cover plate 3 or the housing 1 or during the manufacturing process of the single cell due to being too thin.

[0101] exist Fig.15 In the illustrated embodiment, the maximum dimension of the housing 1 in the first direction X is L mm, and the cover plate 3 has a maximum dimension B mm in the first direction X, satisfying: 0≤L-B≤0.3. It can be understood that the maximum dimension B of the cover plate 3 in the first direction X is smaller than the maximum dimension L of the housing 1 in the first direction X, and the difference between the two is less than 0.3. If the difference between the two is too large, the cover plate 3 may shake in the housing 1, affecting the stability of the assembly; if the difference is too small, the cover plate 3 cannot be smoothly installed into the housing 1. By reasonably limiting the maximum dimension B of the cover plate 3 in the first direction X and the maximum dimension L of the housing 1 in the first direction X, the difficulty of assembly can be reduced and the stability and sealing after assembly can be ensured.

[0102] Accordingly, an embodiment of the present application provides a battery pack, including the above-mentioned single cell battery, so the battery pack can have all the technical features and beneficial effects of the above-mentioned single cell battery, which will not be repeated here.

[0103] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0104] The above is a detailed introduction to a single cell and a battery pack provided in the embodiments of the present application, and the principles and implementation methods of the present application are explained by applying specific examples. The description of the above embodiments is only used to help understand the technical solution and its core idea of ​​the present application; ordinary technicians in this field should understand that: they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A single cell battery, characterized in that: include: A housing having a receiving cavity; An electrode assembly is disposed in the accommodating cavity; A cover plate, covering the accommodating cavity, wherein at least one of the shell and the cover plate has an explosion-proof hole; An explosion-proof valve, covering and sealing the explosion-proof hole; The maximum dimension of the shell in the first direction is L mm, the maximum dimension of the shell in the second direction is T mm, and the maximum dimension of the shell in the third direction is H mm. The shell includes a first wall arranged opposite to each other in the first direction, a second wall arranged opposite to each other in the second direction, and a third wall arranged opposite to the cover plate in the third direction. The thickness of the first wall is I mm, the thickness of the second wall is M mm, and the thickness of the third wall is J mm. The maximum dimension of the cover plate in the third direction is a mm. The first direction, the second direction and the third direction intersect each other. The single cell meets the following requirements: Wherein, S is the area of ​​the explosion-proof valve, V is the rated voltage, and ξ is the correction coefficient.

2. The single cell according to claim 1, characterized in that: The single cell meets the following requirements: Wherein, C is the rated capacity of the single cell.

3. The single cell according to claim 1, characterized in that: The single cell meets at least one of the following characteristics: a) L>T; b) H>T; c) J>I; d)I≥M.

4. The single cell according to claim 1, characterized in that: The explosion-proof valve includes a connecting portion and a weak portion, wherein the connecting portion is connected to the weak portion in a surrounding manner, the connecting portion is connected to one of the cover plate and the shell, the weak portion is provided with a notch, and the weak portion is configured to be destroyed along the notch when impacted by a preset pressure, the area enclosed by the notch is S', the number of the explosion-proof valves is n, and the following satisfies: S=n×S'.

5. The single cell according to claim 4, characterized in that: The dimension of the connecting portion in the third direction is d mm, the maximum dimension of the weak portion in the third direction is e mm, the residual thickness of the notch on the weak portion is f mm, and the single battery meets at least one of the following characteristics: e) 0.3≤d≤0.8; f)0.1≤e <d; g)0.04≤f <e。 6. The single cell according to claim 5, characterized in that: The single cell satisfies: 0.08≤f<0.

2.

7. The single cell according to claim 1, characterized in that: The first wall includes a body and a step portion, wherein the step portion is located on a side of the body facing the electrode assembly and connected to the body, and the cover plate abuts against the step portion in the third direction.

8. The single cell according to claim 7, characterized in that: The cover plate has a maximum dimension B mm in the first direction, satisfying: 0≤L-B≤0.

3.

9. The single cell according to claim 1, characterized in that: The single cell is a lithium iron phosphate single cell or a ternary lithium single cell.

10. A battery pack, characterized in that: The invention comprises a single cell as claimed in any one of claims 1 to 9.

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