Battery module and battery pack

Abstract

The invention belongs to the technical field of batteries, and discloses a battery module and a battery pack, the battery module comprises a sheet and a plurality of single batteries, each single battery comprises a pole group, a cover plate module and a shell body with a single-side opening, the cover plate module is arranged at the opening of the shell body and is used for forming an accommodating cavity for accommodating the pole group, and the sheet is arranged in the accommodating cavity. The cover plate module is provided with a pole terminal welded with the sheet, and the effective area of the sheet welded with the pole terminal is determined according to the following formula: # imgabs0 #, so that when the lower limit value of the effective area of the sheet welded with the pole terminal is obtained, only the space size of the accommodating cavity is needed; according to the method, the charge-discharge rate A of the single battery and the capacity coefficient delta of the single battery are combined, and the capacity of the single battery does not need to be calculated, so that parameters needing to be calculated are reduced, the calculation difficulty is reduced, the calculation speed is improved, and the calculation period is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a battery module and a battery pack. Background Art

[0002] Lithium-ion power batteries are a new type of high-energy battery, based on the movement of lithium ions between the positive and negative electrodes. During charging, lithium ions are deintercalated from the positive electrode and embedded in the negative electrode through the electrolyte; during discharging, on the contrary, lithium ions are deintercalated from the negative electrode and return to the positive electrode to form a current for device use. Due to the advantages of high energy, high battery voltage, wide operating temperature range, long storage life, etc. of lithium-ion power batteries, they are widely used in various fields, including electric vehicles, energy storage systems, military equipment, etc. With continuous development, various different types of lithium-ion power batteries have emerged, such as blade batteries, square shell batteries, or large cylindrical batteries, etc.

[0003] Among them, the bus bar is welded to the pole terminal on multiple single cells to form a battery module with a higher capacity. The effective welding area of the bus bar welded to the pole terminal needs to meet the overcurrent requirement of the single cell. Otherwise, overheating will occur at the weld mark, affecting the cycle performance of the battery and requiring a higher cooling level in the module, which is not conducive to cost reduction.

[0004] When calculating the effective area during the welding of the bus bar and the pole terminal in the battery module, it is necessary to rely on the capacity of the single cell for calculation. However, the capacity calculation of the existing single cells is very cumbersome and requires calculating multiple parameters, such as the gram capacity of the material, the compaction density, the areal density, the proportion of active material, the coating area of the electrode sheet, etc., resulting in a large calculation difficulty and a long calculation period for the effective area during the welding of the bus bar and the pole terminal in the battery module. Summary of the Invention

[0005] The purpose of the present invention is to provide a battery module and a battery pack with small calculation difficulty and short calculation period.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] On the one hand, a battery module is provided. The battery module includes a bus bar and multiple single cells. The single cell includes a pole group, a cover plate module, and a housing body with a single-sided opening. The cover plate module is arranged at the opening of the housing body to form a receiving cavity for accommodating the pole group. The cover plate module is provided with a pole terminal welded to the bus bar. The effective area during the welding of the bus bar and the pole terminal is determined according to the following formula:

[0008] In the formula:

[0009] S is the effective area when the bus bar is welded to the terminal post, with the unit of mm 2 ;

[0010] U is the spatial dimension of the accommodation cavity along the first direction, with the unit of mm;

[0011] V is the spatial dimension of the accommodation cavity along the second direction, with the unit of mm;

[0012] W is the spatial dimension of the accommodation cavity along the third direction, with the unit of mm;

[0013] x is the gap coefficient of the electrode group along the second direction, with the unit of mm;

[0014] y is the gap coefficient of the electrode group along the first direction, with the unit of mm;

[0015] δ is the capacity coefficient of the single cell, with the unit of Ah / mm 3 ;

[0016] A is the charge and discharge rate of the single cell;

[0017] 7 is the overcurrent coefficient for the welding of the bus bar to the terminal post, with the unit of Ah / mm 2 。

[0018] Optionally, the cover module includes a first surface facing away from the electrode group and a second surface in contact with the electrode group. The housing body includes a first wall surface opposite to the open end. The spatial dimension U of the accommodation cavity along the first direction is determined according to the following formula: U = H - J - a;

[0019] In the formula:

[0020] H is the dimension of the housing body along the first direction, with the unit of mm;

[0021] a is the spacing dimension between the first surface and the second surface along the first direction, with the unit of mm;

[0022] J is the thickness dimension of the first wall surface, with the unit of mm.

[0023] Optionally, the housing body includes two second wall surfaces oppositely arranged along the second direction. The spatial dimension V of the accommodation cavity along the second direction is determined according to the following formula: V = L - I1 - I2;

[0024] In the formula:

[0025] L is the dimension of the housing body along the second direction, with the unit of mm;

[0026] I1 is the thickness dimension of one of the two second wall surfaces, with the unit of mm;

[0027] I2 is the thickness dimension of the other one of the two second wall surfaces, with the unit of mm.

[0028] Optionally, the housing body includes two third wall surfaces oppositely arranged along the third direction, and the spatial dimension W of the accommodation cavity along the third direction is determined according to the following formula: W = T - M1 - M2;

[0029] In the formula:

[0030] T is the dimension of the housing body along the third direction, with the unit of mm;

[0031] M1 is the thickness dimension of one of the two third wall surfaces, with the unit of mm;

[0032] M2 is the thickness dimension of the other one of the two third wall surfaces, with the unit of mm.

[0033] Optionally, the gap coefficient x of the electrode group along the second direction satisfies 5mm ≤ x ≤ 8mm.

[0034] Optionally, the gap coefficient y of the electrode group along the first direction satisfies 5mm ≤ y ≤ 10mm.

[0035] Optionally, in the lithium iron phosphate system, the capacity coefficient δ of the single battery satisfies 1.12×10 -4 Ah / mm 3 ≤ δ ≤ 2.47×10 -4 Ah / mm 3 .

[0036] Optionally, in the ternary system, the capacity coefficient δ of the single battery satisfies 1.50×10 -4 Ah / mm3 ≤ δ ≤ 3.35×10 -4 Ah / mm 3 .

[0037] Optionally, a placement groove for accommodating the cover plate module is provided on the side of the second wall surface where the housing body is open.

[0038] On the other hand, a battery pack is also provided. The battery pack includes an electrical connection structure and a plurality of battery modules as described in any one of the above. The plurality of battery modules are arranged in sequence and connected, and the electrical connection structure is electrically connected to the plurality of battery modules.

[0039] Advantages of the present invention:

[0040] The present invention provides a battery module. Through the formula When calculating the lower limit value of the effective area during the welding of the tab and the terminal of the battery module, only the spatial dimensions of the accommodating cavity are required, that is, the spatial dimension U of the accommodating cavity along the first direction, the spatial dimension V of the accommodating cavity along the second direction, and the spatial dimension W of the accommodating cavity along the third direction. Combining with the charge-discharge rate A of the single battery and the capacity coefficient δ of the single battery is sufficient, without the need for separate calculation of the capacity of the single battery. Thus, the parameters to be calculated are reduced, the calculation difficulty is lowered, the calculation speed is increased, and the calculation cycle is shortened.

[0041] The present invention also provides a battery pack. By applying the above-mentioned battery module, with the improvement of the calculation speed, the waiting time can be reduced during the production process of the battery pack, thereby improving the overall production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a schematic structural diagram of the tab welded to the single battery provided by the present invention;

[0043] Figure 2 is an exploded view of the structure of the single battery provided by the present invention;

[0044] Figure 3 is a cross-sectional view of the structure of the single battery provided by the present invention;

[0045] Figure 4 is Figure 3 an enlarged view of the structure of part I in ;

[0046] Figure 5 is an isometric view of the outer shell body of the single battery provided by the present invention;

[0047] Figure 6 is Figure 5 an enlarged view of the structure of part II in ;

[0048] Figure 7 is a front cross-sectional view of the outer shell body of the single battery provided by the present invention;

[0049] Figure 8 is a side cross-sectional view of the outer shell body of the single battery provided by the present invention.

[0050] In the figure:

[0051] 100, strip-shaped weld mark; 200, circular weld mark; 300, square weld mark;

[0052] 1, tab;

[0053] 2. Single cell; 21. Electrode group; 22. Cover plate module; 221. First surface; 222. Second surface; 223. Cover plate body; 224. Inner insulating part; 23. Outer shell body; 231. First wall surface; 232. Second wall surface; 233. Placing groove; 234. Third wall surface; 24. Accommodating cavity. Detailed implementation manners

[0054] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. In addition, it should be noted that for the sake of description, only the parts related to the present invention are shown in the drawings, rather than all the structures.

[0055] In the description of the present invention, unless otherwise clearly defined and limited, the terms "connected", "connected to", and "fixed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0056] In the present invention, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "above the top of", and "on the top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "below the bottom of", and "under the bottom of" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the horizontal height of the first feature is lower than that of the second feature.

[0057] In the description of this embodiment, the orientation or positional relationships such as "above", "below", "right", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of description and simplifying the operation, 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 thus should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for distinction in description and have no special meanings.

[0058] When calculating the effective area during the welding of the tab and the pole terminal in the battery module, it is necessary to rely on the capacity of the single battery for calculation. However, the existing calculation of the capacity of the single battery is very cumbersome and requires calculating multiple parameters, such as the gram capacity of the material, the compaction density, the areal density, the proportion of the active material, the coating area of the electrode sheet, etc., resulting in a relatively large difficulty in calculating the effective area during the welding of the tab and the pole terminal in the battery module and a long calculation cycle.

[0059] In order to reduce the calculation difficulty and improve the calculation speed, this embodiment provides a battery module.

[0060] As Figures 1 to 8 shown, the battery module includes a tab 1 and a plurality of single batteries 2. The single battery 2 includes a pole group 21, a cover plate module 22, and a housing body 23 with a single-sided opening. The cover plate module 22 is arranged at the opening of the housing body 23 to form a receiving cavity 24 for accommodating the pole group 21. A pole terminal welded to the tab 1 is provided on the cover plate module 22. The effective area during the welding of the tab 1 and the pole terminal is determined according to the following formula:

[0061] In the formula:

[0062] S is the effective area during the welding of the tab 1 and the pole terminal, with the unit of mm 2 ;

[0063] U is the spatial dimension of the receiving cavity 24 along the first direction, with the unit of mm;

[0064] V is the spatial dimension of the receiving cavity 24 along the second direction, with the unit of mm;

[0065] W is the spatial dimension of the receiving cavity 24 along the third direction, with the unit of mm;

[0066] x is the gap coefficient of the pole group 21 along the second direction, with the unit of mm;

[0067] y is the gap coefficient of the pole group 21 along the first direction, with the unit of mm;

[0068] δ is the capacity coefficient of the single battery 2, with the unit of Ah / mm 3 ;

[0069] A is the charge and discharge rate of the single battery 2;

[0070] 7 is the overcurrent coefficient of the welding of the tab 1 and the pole terminal, with the unit of Ah / mm 2 .

[0071] Through the formula When calculating the lower limit value of the effective area during the welding of the tab and the terminal of the battery module, only the spatial dimensions of the accommodation cavity are required, namely the spatial dimension U of the accommodation cavity in the first direction, the spatial dimension V of the accommodation cavity in the second direction, and the spatial dimension W of the accommodation cavity in the third direction. Combining the charge-discharge rate A of the single battery and the capacity coefficient δ of the single battery is sufficient, without the need for separate calculation of the capacity of the single battery. This reduces the parameters to be calculated, lowers the calculation difficulty, improves the calculation speed, and shortens the calculation cycle.

[0072] In this embodiment, since the charge-discharge rates A of batteries with different specifications and sizes are different, when calculating the charge-discharge rate A of the single battery 2, first determine the time Z required for the current single battery 2 to be fully charged, with the unit of min; secondly, calculate according to the formula A = 60min / Z to obtain the charge-discharge rate A of the current single battery 2.

[0073] Among them, since the material of the tab 1 is aluminum and the tab 1 and the terminal are welded outside the single battery 2, according to the national standard, the overcurrent coefficient in this calculation formula is determined to be 7. In addition, as Figure 1 shown, the welding trajectory of the tab 1 and the terminal can be set to form a strip-shaped weld mark 100, a circular weld mark 200, a square weld mark 300, etc., as long as the effective area after welding meets the calculation requirements.

[0074] Optionally, as Figure 4 and Figure 7 shown, the cover module 22 includes a first surface 221 facing away from the electrode group 21 and a second surface 222 in contact with the electrode group 21. The housing body 23 includes a first wall surface 231 opposite to the opening. The spatial dimension U of the accommodation cavity 24 in the first direction is determined according to the following formula: U = H - J - a;

[0075] In the formula:

[0076] H is the dimension of the housing body 23 in the first direction, with the unit of mm;

[0077] a is the spacing dimension of the first surface 221 and the second surface 222 of the cover module 22 in the first direction, with the unit of mm;

[0078] J is the thickness dimension of the first wall surface 231, with the unit of mm.

[0079] By determining the dimension H of the housing body 23 in the first direction, the spacing dimension a of the first surface 221 and the second surface 222 of the cover module 22 in the first direction, and the thickness dimension J of the first wall surface 231, the spatial dimension U of the accommodation cavity 24 in the first direction can be more intuitively calculated through the above structural parameters, reducing the difficulty of obtaining the spatial dimension U of the accommodation cavity 24 in the first direction.

[0080] In this embodiment, the cover module 22 includes a cover body 223 and an inner insulating member 224. The inner insulating member 224 is connected to the side of the cover body 223 facing the open end of the housing body 23 and abuts against the electrode group 21. The surface of the cover body 223 facing away from the electrode group 21 is the first surface 221, and the surface of the inner insulating member 224 abutting against the electrode group 21 is the second surface 222.

[0081] Optionally, as Figure 7 shown, the housing body 23 includes two second wall surfaces 232 oppositely arranged along the second direction. The spatial dimension V of the accommodating cavity 24 along the second direction is determined according to the following formula: V = L - I1 - I2;

[0082] In the formula:

[0083] L is the dimension of the housing body 23 along the second direction, in mm;

[0084] I1 is the thickness dimension of one of the two second wall surfaces 232, in mm;

[0085] I2 is the thickness dimension of the other of the two second wall surfaces 232, in mm.

[0086] By determining the dimension L of the housing body 23 along the second direction, and the thickness dimensions I1 and I2 of the two second wall surfaces 232 oppositely arranged along the second direction of the housing body 23, the dimension V of the accommodating cavity 24 along the second direction can be more intuitively calculated through the above structural parameters, reducing the difficulty of obtaining the spatial dimension V of the accommodating cavity 24 along the second direction.

[0087] Among them, the thickness dimensions I1 and I2 of the two second wall surfaces 232 oppositely arranged along the second direction of the housing body 23 can be the same or different. In this embodiment, I1 = I2.

[0088] Furthermore, as Figure 5 、 Figure 6 shown, a placement groove 233 for accommodating the cover module 22 is provided on the second wall surface 232 located at the open end of the housing body 23. By providing the placement groove 233 on the two second wall surfaces 232 arranged along the second direction of the housing body 23, after the cover module 22 and the housing body 23 are assembled, the cover module 22 can be smoothly inserted into the housing body 23. In this embodiment, the depth dimension of the placement groove 233 along the second direction is 0.05 mm. Therefore, when the length dimension of the cover module 22 along the second direction is set as P, it satisfies P = L - I1 - I2 + 0.1.

[0089] Optionally, as Figure 8As shown, the housing body 23 includes two third wall surfaces 234 oppositely arranged in the third direction. The spatial dimension W of the accommodating cavity 24 in the third direction is determined according to the following formula: W = T - M1 - M2;

[0090] In the formula:

[0091] T is the dimension of the housing body 23 in the third direction, with the unit of mm;

[0092] M1 is the thickness dimension of one of the two third wall surfaces 234, with the unit of mm;

[0093] M2 is the thickness dimension of the other of the two third wall surfaces 234, with the unit of mm.

[0094] By determining the dimension T of the housing body 23 in the third direction, and the thickness dimensions M1 and M2 of the two third wall surfaces 234 oppositely arranged in the third direction of the housing body 23, the dimension W of the accommodating cavity 24 in the third direction can be more intuitively calculated through the above structural parameters, reducing the difficulty of obtaining the spatial dimension W of the accommodating cavity 24 in the third direction.

[0095] Among them, the thickness dimensions M1 and M2 of the two third wall surfaces 234 oppositely arranged in the third direction of the housing body 23 can be the same or different. In this embodiment, M1 = M2.

[0096] For the housing body 23, the first wall surface 231 opposite to the opening needs to carry the electrode group 21, and a placement groove 233 for accommodating the cover plate module 22 needs to be opened on the second wall surface 232. Therefore, the thickness relationship between the wall surfaces of the housing body 23 satisfies J > I1 = I2 > M1 = M2.

[0097] Since the spatial dimension U of the accommodating cavity 24 in the first direction, the spatial dimension V of the accommodating cavity 24 in the second direction, and the spatial dimension W of the accommodating cavity 24 in the third direction can be calculated through the structural dimensions of the components in the housing body 23 and the cover plate module 22, the formula for calculating the effective area S when the tab 1 is welded to the pole terminal can be deformed into Compared with calculating using the spatial dimensions of each direction of the accommodating cavity 24, the calculation difficulty is lower and the calculation speed is faster.

[0098] Optionally, the gap coefficient x of the electrode group 21 in the second direction satisfies 5mm ≤ x ≤ 8mm. By limiting the gap coefficient x of the electrode group 21 in the second direction to satisfy 5mm ≤ x ≤ 8mm, on the one hand, it avoids being too small, which makes it difficult for the electrode group 21 to enter the shell and causes the electrode group 21 to be scratched. On the other hand, it avoids being too large, which causes a gap between the electrode group 21 and the inner wall of the housing body 23 even after charging and expansion, resulting in the electrode group 21 moving and pulling the electrode tab.

[0099] The clearance coefficient x of the electrode group 21 in the second direction is the sum of the clearance of the electrode group 21 when entering the housing, the length of the diaphragm overhanging the negative electrode plate, and the length of the negative electrode plate overhanging the positive electrode plate. The clearance of the electrode group 21 when entering the housing is the distance between the two side edges of the electrode group 21 and the inner surface of the adjacent second wall surface 232 in the second direction. The length of the diaphragm overhanging the negative electrode plate refers to the distance of the part where the two sides of the diaphragm exceed the two sides of the negative electrode plate in the second direction. The length of the negative electrode plate overhanging the positive electrode plate refers to the distance of the part where the two sides of the negative electrode plate exceed the two sides of the positive electrode plate in the second direction.

[0100] To verify the influence of the clearance coefficient x of the electrode group 21 in the second direction on the entry of the electrode group 21 into the housing, as shown in Table 1, three sets of examples and two sets of comparative examples are provided for verification.

[0101] Table 1

[0102]

[0103] As can be seen from the above table, when the clearance coefficient x of the electrode group 21 in the second direction meets the range requirement of 5 mm ≤ x ≤ 8 mm, the entry into the housing is smooth. When the clearance coefficient x of the electrode group 21 in the second direction is less than the minimum value of the range of 5 mm ≤ x ≤ 8 mm, the clearance when the electrode group 21 enters the housing is too small, making it difficult to enter the housing, resulting in scratches on the electrode group 21. When the clearance coefficient x of the electrode group 21 in the second direction is greater than the maximum value of the range of 5 mm ≤ x ≤ 8 mm, the electrode group 21 moves around, resulting in damage to the electrode tab.

[0104] Optionally, the clearance coefficient y of the electrode group 21 in the first direction satisfies 5 mm ≤ y ≤ 10 mm. By limiting the clearance coefficient y of the electrode group 21 in the first direction to satisfy 5 mm ≤ y ≤ 10 mm, on the one hand, it avoids being too small, which may not provide enough space for the bending of the electrode tab and cause damage to the electrode tab. On the other hand, it avoids being too large, which may result in a gap between the electrode group 21 and the inner wall of the housing body 23 even after charging and expansion, causing the electrode group 21 to move around and damage the electrode tab.

[0105] In this embodiment, the clearance coefficient y of the electrode group 21 in the first direction is the sum of the length of the diaphragm overhanging the negative electrode plate and the length of the negative electrode plate overhanging the positive electrode plate. The length of the diaphragm overhanging the negative electrode plate refers to the distance of the part where the two sides of the diaphragm exceed the two sides of the negative electrode plate in the first direction. The length of the negative electrode plate overhanging the positive electrode plate refers to the distance of the part where the two sides of the negative electrode plate exceed the two sides of the positive electrode plate in the first direction.

[0106] To verify the influence of the clearance coefficient y of the electrode group 21 in the first direction on the entry of the electrode group 21 into the housing, as shown in Table 2, three sets of examples and two sets of comparative examples are provided for verification.

[0107] Table 2

[0108]

[0109] As can be seen from the above table, when the gap coefficient y of the electrode group 21 in the first direction satisfies the range requirement of 5 mm ≤ y ≤ 10 mm, the insertion into the shell is smooth. When the gap coefficient y of the electrode group 21 in the first direction is less than the minimum value of the range of 5 mm ≤ y ≤ 10 mm, there is not enough space for the bending of the tab, resulting in the tab being crushed. When the gap coefficient y of the electrode group 21 in the first direction is greater than the maximum value of the range of 5 mm ≤ y ≤ 10 mm, the electrode group 21 moves around, resulting in the tab being strained.

[0110] Optionally, in the lithium iron phosphate system, the capacity coefficient δ of the single cell 2 satisfies 1.12×10 -4 Ah / mm 3 ≤ δ ≤ 2.47×10 -4 Ah / mm 3 . By limiting the capacity coefficient δ of the single cell 2 in the lithium iron phosphate system to satisfy 1.12×10 - 4 Ah / mm 3 ≤ δ ≤ 2.47×10 -4 Ah / mm 3 , the effective area S obtained by calculation for the welding of the tab 1 and the terminal of the pole column is ensured to be highly targeted and accurate.

[0111] Optionally, in the ternary system, the capacity coefficient δ of the single cell 2 satisfies 1.50×10 -4 Ah / mm 3 ≤ δ ≤ 3.35×10 -4 Ah / mm 3 . By limiting the capacity coefficient δ of the single cell 2 in the ternary system to satisfy 1.50×10 - 4 Ah / mm 3 ≤ δ ≤ 3.35×10 -4 Ah / mm 3 , the effective area S obtained by calculation for the welding of the tab 1 and the terminal of the pole column is ensured to be highly targeted and accurate.

[0112] In this embodiment, the capacity coefficient of the single cell 2 is derived from the capacity calculation of the single cell 2. The capacity of the single cell 2 is defined as C, and the capacity C of the single cell 2 = the length of the positive electrode sheet material area × the height of the positive electrode sheet material area × the surface density of the positive electrode × the active material content × 2 × the positive electrode gram capacity × the number of positive electrode sheets. Among them, the units of the length and height of the positive electrode sheet material area are mm, and the unit of the surface density is mg / cm 2, the unit of gram capacity is mAh / g, and the active material content is %, further, the length of the positive electrode sheet material area = L - I1 - I2 - x, and the height of the positive electrode sheet material area = H - J - a - y, where the assembly ratio is 89% - 91%, so we can get In the formula is denoted as δ, thus obtaining the capacity coefficient δ of the single cell 2, where the units of each parameter in the formula are converted, that is, mm 2 is converted to cm 2 , mg is converted to g, mAh is converted to Ah, and the parameter "2" represents coating on both sides of the foil.

[0113] Among them, in this formula, the positive electrode surface density = 20mg / cm 2 ~25mg / cm 2 , the active material content = 95% - 98%, the positive electrode gram capacity in the lithium iron phosphate system = 135mAh / g - 155mAh / g, the positive electrode gram capacity in the ternary system = 180mAh / g - 210mAh / g, the positive electrode sheet thickness = 155um - 215um, the negative electrode sheet thickness 105um - 167um, the separator thickness = 10um - 12um. Substituting the above data, the capacity coefficient δ of the single cell 2 under the lithium iron phosphate system is obtained, that is, 1.12×10 -4 Ah / mm 3 ≤δ≤2.47×10 -4 Ah / mm 3 , the capacity coefficient δ of the single cell 2 under the ternary system is obtained, that is, 1.50×10 -4 Ah / mm 3 ≤δ≤3.35×10 -4 Ah / mm 3 .

[0114] Table 3

[0115]

[0116] Limiting the above parameters according to the values in Table 3, the lower limit value of the effective area S when the pole terminal of the single cell 2 is welded to the tab 1 in different systems under the current size specification is obtained. That is, in the ternary system, the effective area S when the tab 1 is welded to the pole terminal satisfies S≮23.97mm 2 , in the lithium iron phosphate system, the effective area S when the tab 1 is welded to the pole terminal satisfies S≮17.91mm 2 .

[0117] In order to verify the rationality of the effective area S of the tab 1 and the pole terminal during welding calculated through the above various parameters, as shown in Table 4, three groups of examples and three groups of comparative examples are selected to verify the calculation results in the ternary system, and observe the temperature conditions of the welding area between the pole terminal and the tab 1 under different lower weld mark areas.

[0118] Table 4

[0119]

[0120] As can be seen from Table 4, in the ternary system, when the effective area S of the tab 1 and the pole terminal during welding is greater than the lower limit value of the effective area S of the tab 1 and the pole terminal during welding calculated through the above various parameters, the temperature of its weld mark area is less than 65°C, and the performance is good. When the effective area S of the tab 1 and the pole terminal during welding is less than the lower limit value of the effective area S of the tab 1 and the pole terminal during welding calculated through the above various parameters, the temperature of its weld mark area exceeds 65°C, the cycle performance of the battery cell decreases, and a cooling device needs to be added externally, resulting in high costs.

[0121] In this embodiment, a battery pack is also provided. The battery pack includes an electrical connection structure and a plurality of the above battery modules. The plurality of battery modules are arranged in sequence and connected, and the electrical connection structure is electrically connected to the plurality of battery modules. By applying the above battery module, with the improvement of the calculation speed, the waiting time can be reduced during the production process of the battery pack, thereby improving the overall production efficiency.

[0122] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation manners of the present invention. For those of ordinary skill in the art, various obvious changes, re-adjustments, and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A battery module, characterized in that: The battery module includes a tab and a plurality of single cells, wherein the single cells include a pole group, a cover plate module and a shell body with a single-side opening, wherein the cover plate module is arranged at the opening of the shell body to form a receiving cavity for accommodating the pole group, and the cover plate module is provided with a pole terminal welded to the tab. The effective area of ​​the tab when welded to the pole terminal is determined according to the following formula: Where: S is the effective area when the bar and the pole terminal are welded, in mm 2 ; U is the spatial dimension of the accommodating cavity along the first direction, in mm; V is the spatial dimension of the accommodating cavity along the second direction, in mm; W is the spatial dimension of the accommodating cavity along the third direction, in mm; x is the gap coefficient of the pole group along the second direction, in mm; y is the gap coefficient of the pole group along the first direction, in mm; δ is the capacity coefficient of the single cell, in Ah / mm 3 ; A is the charge and discharge rate of the single cell; 7 is the overcurrent coefficient of the welding between the bar and the pole terminal, in Ah / mm 2 .

2. The battery module according to claim 1, characterized in that: The cover plate module includes a first surface facing away from the pole group and a second surface abutting against the pole group, the shell body includes a first wall surface opposite to the opening, and the spatial dimension U of the accommodating cavity along the first direction is determined according to the following formula: U=HJa; Where: H is the dimension of the housing body along the first direction, in mm; a is the distance between the first surface and the second surface along the first direction, in mm; J is the thickness of the first wall, in mm.

3. The battery module according to claim 1, characterized in that: The shell body includes two second walls arranged opposite to each other along the second direction, and the spatial dimension V of the accommodating cavity along the second direction is determined according to the following formula: V=L-I1-I2; Where: L is the size of the housing body along the second direction, in mm; I1 is the thickness of one of the two second walls, in mm; I2 is the thickness dimension of the other one of the two second walls, in mm.

4. The battery module according to claim 1, characterized in that: The shell body includes two third walls arranged opposite to each other along the third direction, and the spatial dimension W of the accommodating cavity along the third direction is determined according to the following formula: W=T-M1-M2; Where: T is the dimension of the housing body along the third direction, in mm; M1 is the thickness of one of the two third walls, in mm; M2 is the thickness dimension of the other one of the two third walls, in mm.

5. The battery module according to claim 1, characterized in that: The gap coefficient x of the pole group along the second direction satisfies 5mm≤x≤8mm.

6. The battery module according to claim 1, characterized in that: The gap coefficient y of the pole group along the first direction satisfies 5mm≤y≤10mm.

7. The battery module according to claim 1, characterized in that: In the iron-lithium system, the capacity coefficient δ of the single cell satisfies 1.12×10 -4 Ah / mm 3 ≤δ≤2.47×10 -4 Ah / mm 3 .

8. The battery module according to claim 1, characterized in that: In the ternary system, the capacity coefficient δ of the single cell satisfies 1.50×10 -4 Ah / mm 3 ≤δ≤3.35×10 -4 Ah / mm 3 .

9. The battery module according to claim 3, characterized in that: The second wall surface is located on one side of the opening of the shell body and is provided with a placement groove for accommodating the cover module.

10. A battery pack, characterized in that: The battery pack comprises an electrical connection structure and a plurality of battery modules as described in any one of claims 1 to 9, wherein the plurality of battery modules are arranged in sequence and connected to each other, and the electrical connection structure is electrically connected to the plurality of battery modules.

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