Battery cell

Abstract

The invention relates to the technical field of power batteries, and particularly discloses a battery cell, the battery cell can be calculated and reversely deduced through the sizes of a shell, a first cover plate assembly and a second cover plate assembly to obtain the related size of a pole group, and then the related size of the pole group is substituted into a calculation formula to obtain the capacity C of the battery cell. By adopting the calculation formula in the invention, the value interval of the capacity C of the battery cell can be quickly judged, the used parameters are fewer, the calculation process is simpler and more convenient, and the capacity requirement of the battery cell is met.

Description

Technical Field

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

[0002] With the increasing maturity of lithium-ion battery technology, lithium-ion batteries are widely used as power batteries in the field of electric vehicles. A lithium-ion battery includes a plurality of battery cells. The design of the related structural components of the existing battery cells, including the area / initiation value of the explosion-proof valve, the current-carrying area of the terminal post, etc., is closely related to the capacity of the battery cell. However, due to the diverse material systems and design parameters of the battery cell, it is difficult to calculate the capacity of the battery cell by a simple method. Generally speaking, the capacity of the battery cell is calculated through a series of complex parameters such as its positive and negative material systems, compaction density, specific capacity, etc. The calculation process is relatively complex and cumbersome, which is not conducive to the design of the related structural components of the battery cell, including the terminal post with what current-carrying area should be configured for the battery cell, the explosion-proof valve with what area should be configured, and determining the initiation value of the explosion-proof valve. Summary of the Invention

[0003] The purpose of the present invention is to provide a battery cell, based on the relevant dimensions of its housing, the first cover assembly, and the second cover assembly, the capacity of the battery cell can be obtained through a formula, and the calculation process is relatively simple and convenient, providing guidance for the rapid design of other structural components of the battery cell, meeting the over-current requirement and safety requirement of the battery cell.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides a battery cell, including:

[0006] A housing, on opposite sides of the housing along a first direction, a first opening and a second opening are respectively provided. The housing includes a first side wall, a second side wall, a third side wall, and a fourth side wall. The first side wall and the fourth side wall are opposite along a second direction, the second side wall and the third side wall are opposite along a third direction, and the first side wall, the second side wall, the third side wall, and the fourth side wall are connected and enclose a cylindrical structure, and the first direction, the second direction, and the third direction are perpendicular to each other in pairs;

[0007] A first cover assembly, the first cover assembly includes a first cover body, a first plastic part, and a first overlapping part. The first overlapping part is provided on the circumference of the first cover body, and the first overlapping part abuts against the edge of the housing on the side where the first opening is provided;

[0008] The second cover plate assembly, the second cover plate assembly includes a second cover plate body, a second plastic part and a second overlapping part, the second overlapping part is arranged on the circumference of the second cover plate body, the second overlapping part abuts against the edge of the side of the housing where the second opening is provided, and the housing, the first cover plate assembly and the second cover plate assembly enclose a containing cavity;

[0009] The electrode group is arranged in the containing cavity, the electrode group includes positive electrode plates and negative electrode plates that are stacked and arranged alternately along the third direction, a separator is clamped between the positive electrode plates and the negative electrode plates, and the positive electrode plates are electrically connected to the electrode posts integrated on the first cover plate assembly or the second cover plate assembly;

[0010] The capacity of the battery cell is C, and the unit is Ah;

[0011] The calculation formula of C is:

[0012] C = (L + b1 + b2 - a1 - a2 - x)(H - t1 - t4 - y)(T - t2 - t3)×δ;

[0013] Wherein, L is the dimension of the housing along the first direction, and the unit is mm;

[0014] H is the dimension of the housing along the second direction, and the unit is mm;

[0015] T is the dimension of the housing along the third direction, and the unit is mm;

[0016] a1 is the distance between the end face of the first cover plate body facing away from the electrode group side along the first direction and the end face of the first plastic part close to the electrode group side, and the unit is mm;

[0017] b1 is the dimension of the first overlapping part along the first direction, and the unit is mm;

[0018] a2 is the distance between the end face of the second cover plate body facing away from the electrode group side along the first direction and the end face of the second plastic part close to the electrode group side, and the unit is mm;

[0019] b2 is the dimension of the second overlapping part along the first direction, and the unit is mm;

[0020] t1 is the thickness of the first side wall along the second direction, and the unit is mm;

[0021] t2 is the thickness of the second side wall along the third direction, and the unit is mm;

[0022] t3 is the thickness of the third side wall along the third direction, and the unit is mm;

[0023] t4 is the thickness of the fourth side wall along the second direction, and the unit is mm;

[0024] x is the dimension of the space reserved for the electrode group in the accommodation cavity along the first direction, with the unit of mm;

[0025] y is the dimension of the space reserved for the electrode group in the accommodation cavity along the second direction, with the unit of mm;

[0026] δ is the volume capacity, with the unit of Ah / mm 3 ;

[0027] The value range of δ is 1.12×10 -4 Ah / mm 3 ≤δ≤3.34×10 -4 Ah / mm 3 .

[0028] Optionally, the calculation formula of δ is:

[0029]

[0030] 2 -0.00025g / mm 2 , the value range of the positive electrode surface density is 0.00020g / mm

[0031] w1 is the thickness of the positive electrode sheet, and the value range of w1 is 0.155mm ≤ w1 ≤ 0.215mm;

[0032] w2 is the thickness of the negative electrode sheet, and the value range of w2 is 0.105mm ≤ w2 ≤ 0.167mm;

[0033] w3 is the thickness of the separator, and the value range of w3 is 0.010mm ≤ w3 ≤ 0.012mm.

[0034] Optionally, the calculation formula of w1 is:

[0035]

[0036] 3 -0.0028g / mm 3 ;

[0037] w11 is the thickness of the aluminum foil, and the value range of w11 is 0.012mm ≤ w11 ≤ 0.015mm.

[0038] Optionally, the calculation formula of w2 is:

[0039]

[0040] Among them, the value range of the negative electrode surface density is 0.00009 g / mm 2 -0.00012 g / mm 2 ;

[0041] The value range of the negative electrode compaction density is 0.0015 g / mm 3 -0.0018 g / mm 3 ;

[0042] w12 is the thickness of the copper foil, and the value range of w12 is 0.005 mm ≤ w12 ≤ 0.007 mm.

[0043] Optionally, when the battery cell is a ternary lithium battery system, the value range of the positive electrode specific capacity is 0.180 Ah / g - 0.210 Ah / g; when the battery cell is a lithium iron phosphate battery system, the value range of the positive electrode specific capacity is 0.135 Ah / g - 0.155 Ah / g.

[0044] Optionally, the calculation formula of x is:

[0045] x = x1 + x2;

[0046] Among them, x1 is the dimension difference between the separator and the negative electrode sheet along the first direction; x2 is the dimension difference between the negative electrode sheet and the positive electrode sheet along the first direction;

[0047] The value range of x is 8 mm ≤ x ≤ 12 mm.

[0048] Optionally, the calculation formula of y is:

[0049] y = y1 + y2 + y3;

[0050] y1 = y11 + y12;

[0051] Among them, y1 is the gap between the electrode group and the inner surface of the shell along the second direction, y11 is the distance between the electrode group and the inner surface of the first side wall along the second direction; y12 is the distance between the electrode group and the inner surface of the fourth side wall along the second direction; y2 is the dimension difference between the separator and the negative electrode sheet along the second direction; y3 is the dimension difference between the negative electrode sheet and the positive electrode sheet along the second direction;

[0052] The value range of y is 6 mm ≤ y ≤ 9 mm.

[0053] Optionally, when the battery cell is a ternary lithium battery system;

[0054] The value range of δ is 1.50 × 10 -4 Ah / mm3 ≤δ≤3.34×10 -4 Ah / mm 3 ;

[0055] The value range of the capacity C of the battery cell is: 82.0 Ah ≤ C ≤ 189.5 Ah.

[0056] Optionally, when the battery cell is a lithium iron phosphate battery system;

[0057] The value range of δ is 1.12×10 -4 Ah / mm 3 ≤δ≤2.47×10 -4 Ah / mm 3 ;

[0058] The value range of the capacity C of the battery cell is: 61.2 Ah ≤ C ≤ 140.1 Ah.

[0059] Optionally, the value range of the dimension b1 of the first overlapping part along the first direction is 0.5 mm ≤ b1 ≤ 3 mm;

[0060] The value range of the dimension b2 of the second overlapping part along the first direction is 0.5 mm ≤ b2 ≤ 3 mm.

[0061] The beneficial effects of the present invention are as follows:

[0062] The present invention provides a battery cell. The relevant dimensions of the electrode group can be calculated and deduced from the dimensions of the housing, the first cover assembly, and the second cover assembly of the battery cell. Then, the relevant dimensions of the electrode group are brought into the calculation formula to obtain the capacity C of the battery cell. By using the calculation formula in the present invention, the value range of the capacity C of the battery cell can be quickly judged, with fewer parameters used and the calculation process being relatively simple and convenient. Furthermore, based on the value range of the capacity C of the battery cell, it provides guidance for the rapid design of other structural components of the battery cell, meeting the over-current requirement and safety requirement of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the content of the embodiments of the present invention and these drawings.

[0064] Figure 1 It is an exploded view of the battery cell provided in the embodiment of the present invention;

[0065] Figure 2 It is a cross-sectional view of the battery cell provided in the embodiment of the present invention;

[0066] Figure 3 is Figure 2 the partial enlarged view of A in

[0067] Figure 4 is Figure 2 the partial enlarged view of B in

[0068] Figure 5 the side view of the housing provided in the embodiment of the present invention.

[0069] In the figure:

[0070] 100, housing; 101, first opening; 102, second opening; 110, first side wall; 120, second side wall; 130, third side wall; 140, fourth side wall;

[0071] 200, first cover assembly; 210, first cover body; 211, first overlapping portion; 220, first plastic part; 300, second cover assembly; 310, second cover body; 311, second overlapping portion; 320, second plastic part; 400, electrode group; 500, electrode post. Detailed implementation manners

[0072] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0073] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention 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 of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions, and moreover, the first feature being "above", "over" and "on" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0074] In the description of the present invention, it should be noted that, unless otherwise clearly defined and limited, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; 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 communication inside two components. 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 circumstances.

[0075] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, in which the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0076] As Figures 1-4 shown, this embodiment provides a battery cell, and the battery cell is a blade battery cell. The battery cell includes a housing 100, a first cover assembly 200, a second cover assembly 300, and an electrode assembly 400.

[0077] Among them, the housing 100 includes a first side wall 110, a second side wall 120, a third side wall 130, and a fourth side wall 140. The first side wall 110, the second side wall 120, the third side wall 130, and the fourth side wall 140 all extend along a first direction, that is, the length direction of the housing 100 is the first direction ( Figure 1 the X-axis direction shown in Figure 1 ), the first side wall 110 and the fourth side wall 140 are opposite to each other along a second direction (the second direction is Figure 1 the Y-axis direction shown in

[0078] The first cover plate assembly 200 includes a first cover plate body 210, a first plastic part 220, and a first overlapping portion 211. The first overlapping portion 211 is provided on the circumference of the first cover plate body 210. The first overlapping portion 211 abuts against the edge of the housing 100 on the side where the first opening 101 is provided. Then, the joint between the first overlapping portion 211 and the housing 100 is peripherally welded, and a first weld seam is formed at the joint. The second cover plate assembly 300 includes a second cover plate body 310, a second plastic part 320, and a second overlapping portion 311. The second overlapping portion 311 is provided on the circumference of the second cover plate body 310. The second overlapping portion 311 abuts against the edge of the housing 100 on the side where the second opening 102 is provided. Then, the joint between the second overlapping portion 311 and the housing 100 is peripherally welded, and a second weld seam is formed at the joint. Thus, a closed accommodation cavity is formed by the housing 100, the first cover plate assembly 200, and the second cover plate assembly 300.

[0079] The electrode group 400 is arranged in the accommodation cavity. The electrode group 400 includes a positive electrode plate, a negative electrode plate, and a separator stacked in the third direction. There are multiple positive electrode plates, negative electrode plates, and separators. The positive electrode plates and the negative electrode plates are alternately arranged in the third direction, and a separator is interposed between each positive electrode plate and the negative electrode plate. Thus, multiple positive electrode plates, multiple negative electrode plates, and multiple separators constitute the electrode group 400. Among them, the positive electrode plate is electrically connected to the electrode post 500 integrated on the first cover plate assembly 200 or the second cover plate assembly 300. In this embodiment, taking the positive electrode plate being electrically connected to the electrode post 500 on the first cover plate assembly 200 as an example for illustration, the electrode post 500 on the first cover plate assembly 200 electrically connected to the positive electrode plate is the positive electrode post. The negative electrode plate is electrically connected to the electrode post 500 on the second cover plate assembly 300, and the electrode post 500 on the second cover plate assembly 300 electrically connected to the negative electrode plate is the negative electrode post.

[0080] See Figure 2 and Figure 5, in this embodiment, the dimension of the housing 100 in the first direction is L, with the unit of mm; the dimension of the housing 100 in the second direction is H, with the unit of mm; the dimension of the housing 100 in the third direction is T, with the unit of mm; L > H > T. The thickness of the first side wall 110 in the second direction is t1, with the unit of mm; the thickness of the second side wall 120 in the third direction is t2, with the unit of mm; the thickness of the third side wall 130 in the third direction is t3, with the unit of mm; the thickness of the fourth side wall 140 in the second direction is t4, with the unit of mm. Among them, the first side wall 110, the second side wall 120, the third side wall 130, and the fourth side wall 140 can be set to have the same wall thickness. At this time, the housing 100 is processed by bending an aluminum plate and welding the bent aluminum plate into a cylindrical structure. Of course, in other embodiments, the first side wall 110, the second side wall 120, the third side wall 130, and the fourth side wall 140 can also be set to have non-uniform wall thickness. At this time, the housing 100 can be manufactured by an extrusion process. In this embodiment, an example is given with the first side wall 110, the second side wall 120, the third side wall 130, and the fourth side wall 140 set to have the same wall thickness, and t1 = t2 = t3 = t4.

[0081] Further, referring to Figure 3 and Figure 4 , the first overlapping portion 211 of the first cover assembly 200 cooperates with the edge at the first opening 101 of the housing 100 to achieve the encapsulation of the first opening 101 on the housing 100. Among them, the distance between the end face of the first cover body 210 facing away from the electrode group 400 in the first direction and the end face of the first plastic part 220 close to the electrode group 400 in the first direction is a1, with the unit of mm; the dimension of the first overlapping portion 211 in the first direction is b1, with the unit of mm. In order to ensure that there is enough solder between the housing 100 and the first overlapping portion 211, it should be ensured that the value range of b1 is 0.5 mm ≤ b1 ≤ 3 mm. For example, the value of b1 can be 0.5 mm, 0.8 mm, 1.0 mm, 2.0 mm, 3.0 mm, etc. By controlling the value of b1 to be greater than or equal to 0.5 mm, it can be ensured that the welding strength of the first weld between the housing 100 and the first overlapping portion 211 is relatively high and the welding quality is good. Otherwise, when the value of b1 is small (<0.5 mm), the dimension of the first overlapping portion 211 in the first direction is small, the solder during welding is insufficient, and it is easy to have problems with poor welding. The welding quality of the first weld cannot be guaranteed, and the seal between the housing 100 and the first cover assembly 200 is unreliable.

[0082] The second overlap portion 311 of the second cover plate assembly 300 cooperates with the edge of the second opening 102 of the shell 100 to achieve the encapsulation of the second opening 102 on the shell 100. Among them, the distance between the end face of the second cover plate body 310 away from the pole group 400 and the end face of the second plastic part 320 close to the pole group 400 along the first direction is a2, in mm; the size of the second overlap portion 311 along the first direction is b2, in mm. In order to ensure that there is enough solder between the shell 100 and the second overlap portion 311, the value range of b2 should be 0.5mm≤b2≤3mm. For example, the value of b2 can be 0.5mm, 0.8mm, 1.0mm, 2.0mm or 3.0mm, etc. By controlling the value of b2 to be greater than or equal to 0.5mm, it can be ensured that the welding strength of the second weld between the shell 100 and the second overlap portion 311 is high and the welding quality is good. Otherwise, when the value of b2 is small (<0.5mm), the size of the second overlap portion 311 along the first direction is small, the solder is insufficient during welding, and poor welding is likely to occur. The welding quality of the second weld cannot be guaranteed, and the seal between the shell 100 and the second cover plate assembly 300 is unreliable.

[0083] In summary, in this embodiment, the size of the accommodating cavity enclosed by the housing 100 and the first cover assembly 200 and the second cover assembly 300 along the first direction is L+b1+b2-a1-a2; the size of the accommodating cavity along the second direction is H-t1-t4; the size of the accommodating cavity along the third direction is T-t2-t3. In order to ensure smooth assembly of the electrode group 400 with the housing 100, the first cover assembly 200, and the second cover assembly 300, it is necessary to ensure that space is reserved for the electrode group 400 in the accommodating cavity along the first direction, space is reserved for the electrode group 400 in the accommodating cavity along the second direction, and space is reserved for the electrode group 400 in the accommodating cavity along the third direction.

[0084] Generally speaking, when designing the electrode group 400 of the battery cell, it is necessary to calculate the capacity C1 of the battery cell based on conventional parameters such as the gram capacity of the positive and negative electrode sheets of the electrode group 400, the surface density, the number of electrode sheet layers, and the content of positive electrode active materials, which is a forward logic calculation.

[0085] In this embodiment, the relevant dimensions of the electrode group 400 can be calculated and deduced by the dimensions of the housing 100, the first cover assembly 200, and the second cover assembly 300. Then, the relevant dimensions of the electrode group 400 are substituted into the calculation formula to obtain the capacity C of the battery cell. It should be noted that the capacity C of the battery cell obtained by using this calculation formula is a range value, and the capacity C1 of the battery cell obtained through the forward logic is included in the range value of the capacity C of the battery cell deduced by the dimensions of the housing 100, the first cover assembly 200, and the second cover assembly 300 in the present invention. By using the calculation formula in this embodiment, the value range of the capacity C of the battery cell can be quickly obtained, with fewer parameters used and relatively simple calculation. Then, the design dimensions of other relevant structural components of the battery cell can be quickly obtained according to the capacity C of the battery cell. For example, the minimum current-carrying area that the pole column 500 should satisfy can be obtained according to the capacity C of the battery cell, providing a basis for the design of the pole column 500. And the minimum effective area that the explosion-proof valve (not shown in the figure) should satisfy can be obtained according to the capacity C of the battery cell, as well as the safety range that the detonation value of the explosion-proof valve should satisfy, providing a basis for the design of the explosion-proof valve.

[0086] Specifically, the capacity of the battery cell provided in this embodiment is C, with the unit of Ah;

[0087] The calculation formula of C is as follows:

[0088] C = (L + b1 + b2 - a1 - a2 - x)(H - t1 - t4 - y)(T - t2 - t3)×δ;

[0089] Among them, x is the dimension of the space reserved for the electrode group 400 in the accommodation cavity along the first direction, with the unit of mm; y is the dimension of the space reserved for the electrode group 400 in the accommodation cavity along the second direction, with the unit of mm; δ is the volume capacity, with the unit of Ah / mm 3 .

[0090] The value range of δ is 1.12×10 -4 Ah / mm 3 ≤δ≤3.34×10 -4 Ah / mm 3 . For example, the value of δ can be 1.12×10 -4 Ah / mm 3 、1.32×10 -4 Ah / mm 3 、1.50×10 -4 Ah / mm 3 、2.12×10 -4 Ah / mm 3 、2.47×10 -4 Ah / mm 3 、2.87×10 -4 Ah / mm3 、 3.34×10 -4 Ah / mm 3 etc. The specific value of δ can be determined according to the type of the battery cell, and will not be listed one by one here.

[0091] The origin of the calculation formula for the capacity C of the above battery cell will be described below.

[0092] When generally determining the capacity C1 of the battery cell using the positive logic, the following formula can be used:

[0093] C1 = length of the positive electrode sheet material area × width of the positive electrode sheet material area × positive electrode surface density × positive electrode active material content × 2 × positive electrode gram capacity × number of positive electrode sheet layers;

[0094] Among them, the positive electrode sheet includes aluminum foil and the positive electrode active material layer coated on the aluminum foil. Since the positive electrode active material layers are provided on both end faces of the aluminum foil along its thickness direction (the third direction), "×2" is required in the above formula.

[0095] The length of the positive electrode sheet material area is the dimension of the positive electrode sheet along the first direction, that is, L + b1 + b2 - a1 - a2 - x.

[0096] The calculation formula for x is:

[0097] x = x1 + x2.

[0098] Among them, x1 is the dimension difference between the separator and the negative electrode sheet along the first direction. Since the center points are on the same axis when the negative electrode sheet, separator, positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, x1 is twice the dimension of the end of the separator along one side of the first direction exceeding the adjacent end of the negative electrode sheet along the first direction (the dimensions of the two ends of the separator along the first direction exceeding the adjacent ends of the negative electrode sheet along the first direction are the same).

[0099] x2 is the dimension difference between the negative electrode sheet and the positive electrode sheet along the first direction. Since the center points are on the same axis when the negative electrode sheet, separator, positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, x2 is twice the dimension of the end of the negative electrode sheet along one side of the first direction exceeding the adjacent end of the positive electrode sheet along the first direction (the dimensions of the two ends of the negative electrode sheet along the first direction exceeding the adjacent ends of the positive electrode sheet along the first direction are the same).

[0100] That is, the dimension of the positive electrode sheet along the first direction is smaller than that of the negative electrode sheet along the first direction, and the dimension of the negative electrode sheet along the first direction is smaller than that of the separator along the first direction.

[0101] Generally speaking, in the design of the pole group 400, the design values of x1 and x2 are within a certain range. Here, the value range of the sum of x1 and x2 is limited to 8mm≤x≤12mm. For example, the value of x can be 8mm, 9mm, 10mm, 11mm or 12mm, etc. By controlling the value of x within the above range, the pole group 400 can be well assembled with the shell 100, the first cover plate assembly 200, and the second cover plate assembly 300. Otherwise, when the value of x is too small, the pole ear of the pole group 400 has no bending space, and the pole group 400 is easily crushed; when the value of x is too large, the fixing effect of the pole group 400 in the shell 100 is not good, it is easy to move, pull the pole ear, and the battery cell is poorly assembled.

[0102] The above conclusions are illustrated below with some specific battery cell implementation cases, see Table 1.

[0103] Table 1

[0104]

[0105] It can be seen from the above results that in comparative example 1, the value of x is less than the minimum value of 8 mm ≤ x ≤ 12 mm. At this time, the pole ear of the pole group 400 has no bending space, the pole group 400 is easily crushed, the reliability of the battery cell is reduced, and the product is defective.

[0106] In comparative example 2, the value of x is greater than the maximum value of 8mm≤x≤12mm, the electrode group 400 is not well fixed in the housing 100, and is prone to movement or even pulling of the electrode tabs, resulting in the risk of failure of the battery cell, poor assembly of the battery cell, and a defective product.

[0107] In Example 1, Example 2 and Example 3, the value of x is in the range of 8mm≤x≤12mm. At this time, the electrode group 400 can be well fixed in the shell 100 and is not easy to move. The electrode ear has sufficient bending space, the electrode group 400 is not easily crushed, the reliability of the battery cell is high, and the product is good.

[0108] The width of the positive electrode sheet area is the dimension of the positive electrode sheet along the second direction, that is, H-t1-t4-y.

[0109] The calculation formula for y is:

[0110] y=y1+y2+y3;

[0111] y1=y11+y12.

[0112] Among them, y1 is the shell entry gap of the pole group 400 along the second direction, y11 is the distance between the pole group 400 and the inner surface of the first side wall 110 along the second direction; y12 is the distance between the pole group 400 and the inner surface of the fourth side wall 140 along the second direction.

[0113] y2 is the dimension difference between the separator and the negative electrode along the second direction. Since the central points are on the same axis when the negative electrode, separator, positive electrode, separator, and negative electrode are stacked in sequence, y2 is twice the dimension that the end of the separator on one side along the second direction exceeds the adjacent end of the negative electrode along the second direction (the dimensions that the two ends of the separator along the second direction exceed the adjacent ends of the negative electrode along the second direction are the same).

[0114] y3 is the dimension difference between the negative electrode and the positive electrode along the second direction. Since the central points are on the same axis when the negative electrode, separator, positive electrode, separator, and negative electrode are stacked in sequence, y3 is twice the dimension that the end of the negative electrode on one side along the second direction exceeds the adjacent end of the positive electrode along the second direction (the dimensions that the two ends of the negative electrode along the second direction exceed the adjacent ends of the positive electrode along the second direction are the same).

[0115] That is, the dimension of the positive electrode along the second direction is smaller than that of the negative electrode along the second direction, and the dimension of the negative electrode along the second direction is smaller than that of the separator along the second direction.

[0116] Generally, in the design of the electrode assembly 400, the design values of y1, y2, and y3 are all within a certain range. Here, the value range of the sum y of y1, y2, and y3 is restricted to 6 mm ≤ y ≤ 9 mm. For example, the value of y can be 6 mm, 7 mm, 8 mm, 9 mm, etc. By controlling the value of y within the above range, the electrode assembly 400 can be well assembled with the housing 100, the first cover assembly 200, and the second cover assembly 300. Otherwise, when the value of y is too small, it is difficult to insert the electrode assembly 400 into the housing, and the inner surfaces of the first side wall 110 and the fourth side wall 140 of the housing 100 may scratch the electrode assembly 400; when the value of y is too large, the fixing effect of the electrode assembly 400 in the housing 100 is poor, and it is easy to move around, even pulling the tab, reducing the reliability of the battery cell.

[0117] The following uses some specific battery cell implementation cases to illustrate the above conclusions. See Table 2.

[0118] Table 2

[0119]

[0120] As can be seen from the above results, in Comparative Example 1, the value of y is less than the minimum value of 6 mm ≤ y ≤ 9 mm. At this time, it is difficult to insert the electrode assembly 400 into the housing, and the inner surfaces of the first side wall 110 and the fourth side wall 140 of the housing 100 may scratch the electrode assembly 400, resulting in defective battery cell products.

[0121] In Comparative Example 2, the value of y is greater than the maximum value of 6 mm ≤ y ≤ 9 mm. The fixing effect of the electrode assembly 400 in the housing 100 is poor, and it is easy to move around, even pulling the tab, reducing the reliability of the battery cell and resulting in defective battery cell products.

[0122] In Embodiment 1, Embodiment 2 and Embodiment 3, the value of y is in the range of 6 mm ≤ y ≤ 9 mm. At this time, the electrode group 400 can be well fixed in the housing 100, is not prone to crosstalk, and the tabs are not easily pulled. The electrode group 400 remains intact, the reliability of the battery cell is high, and the battery cell product is good.

[0123] Furthermore, the outermost layers of the electrode group 400 are all negative electrode sheets, and the positive electrode sheets and negative electrode sheets are alternately arranged in the third direction. Therefore, when the number of positive electrode sheets is m, the number of negative electrode sheets is m + 1, and a separator is provided between each positive electrode sheet and negative electrode sheet. So the number of separator layers is 2m + 2.

[0124] Considering the ease of inserting the electrode group 400 into the housing and the expansion of the electrode group 400 during charging and discharging, it is necessary to reserve an assembly space and an expansion space for the electrode group 400 in the accommodation cavity in the third direction. Here, the ratio of the dimension of the electrode group 400 in the third direction to the dimension of the accommodation cavity in the third direction is defined as the assembly ratio, and the assembly ratio is denoted as η.

[0125] That is, the dimension of the electrode group 400 in the third direction calculated from the dimension of the accommodation cavity should be:

[0126] η × (T - t2 - t3).

[0127] The dimension of the electrode group 400 in the third direction calculated using forward logic is:

[0128] w1 × m + w2 × (m + 1) + w3 × (2m + 2);

[0129] where w1 is the thickness of the positive electrode sheet, w2 is the thickness of the negative electrode sheet, and w3 is the thickness of the separator.

[0130] The dimensions of the electrode group 400 in the third direction calculated by the two methods should be equal. Therefore:

[0131] w1 × m + w2 × (m + 1) + w3 × (2m + 2)

[0132] = η × (T - t2 - t3).

[0133] From the above formula, it is deduced that:

[0134]

[0135] Continuing to substitute the above-mentioned length of the positive electrode sheet material area, width of the positive electrode sheet material area, and the value of m into the calculation formula of C1, we get:

[0136]

[0137] Among them, the thicknesses w2 of the negative electrode sheet and w3 of the separator are both in the order of micrometers. Ignoring w2 and w3 in the numerator part of the above formula and simplifying the above formula, we get:

[0138]

[0139] Denote as δ, then the calculation formula for C1 is obtained:

[0140] C1 = (L + b1 + b2 - a1 - z2 - x)(H - t1 - t4 - y)(T - t2 - t3)×δ.

[0141] That is, the formula for calculating the capacity C of the battery cell provided in the present invention:

[0142] C = (L + b1 + b2 - a1 - a2 - x)(H - t1 - t4 - y)(T - t2 - t3)×δ.

[0143] Among them, the calculation formula for δ is:

[0144]

[0145] When calculating δ, the following several parameters are required: η, the positive electrode surface density, the positive electrode active material content, the positive electrode specific capacity, the thickness w1 of the positive electrode sheet, the thickness w2 of the negative electrode sheet, and the thickness w3 of the separator.

[0146] Generally speaking, the value range of the assembly ratio η when the electrode group 400 is put into the shell is 89% - 91%. For example, the value of η can be 89%, 90%, or 91%, etc.

[0147] The value range of the positive electrode surface density is 0.00020 g / mm 2 - 0.00025 g / mm 2 . For example, the value of the positive electrode surface density can be 0.00020 g / mm 2 , 0.00022 g / mm 2 , 0.00024 g / mm 2 or 0.00025 g / mm 2 , etc.

[0148] The value range of the positive electrode active material content is 95% - 98%. For example, the value of the positive electrode active material content can be 95%, 96%, 97%, or 98%, etc.

[0149] The value range of the positive electrode specific capacity is 0.135 Ah / g - 0.210 Ah / g. For example, the value of the positive electrode specific capacity can be 0.135 Ah / g, 0.155 Ah / g, 0.180 Ah / g, 0.195 Ah / g, or 0.210 Ah / g, etc.

[0150] The calculation formula for the thickness w1 of the positive electrode sheet is as follows:

[0151]

[0152] Among them, w11 is the thickness of the aluminum foil, and the value range of w11 is 0.012 mm ≤ w11 ≤ 0.015 mm. For example, the value of w11 can be 0.012 mm, 0.013 mm, 0.014 mm or 0.015 mm. Since the positive electrode sheet includes the aluminum foil and the positive electrode active material layers coated on both end faces of the aluminum foil along its thickness direction, "×2" is required in the above calculation formula for the thickness w1 of the positive electrode sheet.

[0153] Furthermore, the value range of the positive electrode compaction density is 0.0025 g / mm 3 -0.0028 g / mm 3 . For example, the value of the positive electrode compaction density can be 0.0025 g / mm 3 , 0.0026 g / mm 3 , 0.0027 g / mm 3 or 0.0028 g / mm 3 etc.

[0154] Substitute the positive electrode areal density, the positive electrode compaction density, and the thickness w11 of the aluminum foil into the above calculation formula for the thickness w1 of the positive electrode sheet. It is deduced that the value range of the thickness w1 of the positive electrode sheet is 0.155 mm ≤ w1 ≤ 0.215 mm.

[0155] The calculation formula for the thickness w2 of the negative electrode sheet is as follows:

[0156]

[0157] Among them, the value range of the negative electrode areal density is 0.00009 g / mm 2 -0.00012 g / mm 2 . For example, the value of the negative electrode areal density can be 0.00009 g / mm 2 , 0.00011 g / mm 2 or 0.00012 g / mm 2 etc.

[0158] The value range of the negative electrode compaction density is 0.0015 g / mm 3 -0.0018 g / mm 3 . For example, the value of the negative electrode compaction density can be 0.0015 g / mm 3 , 0.0016 g / mm 3 , 0.0017 g / mm 3 or 0.0018 g / mm 3 etc.

[0159] w12 is the thickness of the copper foil, and the value range of w12 is 0.005 mm ≤ w12 ≤ 0.007 mm. For example, the value of w12 can be 0.005 mm, 0.006 mm, or 0.007 mm. Since the negative electrode sheet includes a copper foil and negative electrode active material layers coated on both end faces of the copper foil along its thickness direction, "×2" is required in the calculation formula for the thickness w12 of the above negative electrode sheet.

[0160] Substitute the negative electrode surface density, negative electrode compaction density, and the thickness w12 of the copper foil into the calculation formula for the thickness w2 of the negative electrode sheet. It is estimated that the value range of the thickness w2 of the negative electrode sheet is 0.105 mm ≤ w2 ≤ 0.167 mm.

[0161] Optionally, the value range of the thickness w3 of the separator is generally 0.010 mm ≤ w3 ≤ 0.012 mm.

[0162] Then, substitute η, the positive electrode surface density, the positive electrode active material content, the positive electrode specific capacity, the thickness w1 of the positive electrode sheet, the thickness w2 of the negative electrode sheet, and the thickness w3 of the separator into the calculation formula for δ to obtain the value range of δ.

[0163] The positive electrode specific capacity is related to the system of the battery cell, and the value ranges of the remaining parameters η, the positive electrode surface density, the positive electrode active material content, the thickness w1 of the positive electrode sheet, the thickness w2 of the negative electrode sheet, and the thickness w3 of the separator are the same.

[0164] When the battery cell is a ternary lithium battery system, the value range of the positive electrode specific capacity is 0.180 Ah / g - 0.210 Ah / g. Substitute the above parameters into the calculation formula for δ, and the calculated value range of δ in the battery cell of the ternary lithium battery system is 1.50×10 - 4 Ah / mm 3 ≤ δ ≤ 3.34×10 -4 Ah / mm 3 .

[0165] When the battery cell is a lithium iron phosphate battery system, the value range of the positive electrode specific capacity is 0.135 Ah / g - 0.155 Ah / g. The value ranges of the remaining parameters η, the positive electrode surface density, the positive electrode active material content, w1, w2, and w3 are the same as those of the ternary lithium battery system.

[0166] Substitute the above parameters into the calculation formula for δ, and the calculated value range of δ in the battery cell of the lithium iron phosphate battery system is 1.12×10 -4 Ah / mm 3 ≤ δ ≤ 2.47×10 -4 Ah / mm 3 .

[0167] The capacity C of the above-mentioned battery cell is calculated and verified with specific implementation cases below. The relevant parameters of the battery cell housing 100, the first cover assembly 200, and the second cover assembly 300 are shown in Table 3 below.

[0168] Table 3

[0169]

[0170] When the battery cell is a ternary lithium battery system, the value range of δ is 1.50×10 -4 Ah / mm 3 ≤δ≤3.34×10 - 4 Ah / mm 3 。The minimum value of δ is 1.50×10 -4 Ah / mm 3 ,and the maximum value of δ is 3.34×10 -4 Ah / mm 3 。

[0171] Substitute the maximum values of the above parameters L + b1 + b2 - a1 - a2 - x, H - t1 - t4 - y, T - t2 - t3, and δ into the following calculation formula for the capacity C of the battery cell:

[0172] C = (L + b1 + b2 - a1 - a2 - x)(H - t1 - t4 - y)(T - t2 - t3)×δ;

[0173] The maximum value of the capacity C of the battery cell in the ternary lithium battery system is obtained as 189.5 Ah.

[0174] Substitute the minimum values of the above parameters L + b1 + b2 - a1 - a2 - x, H - t1 - t4 - y, T - t2 - t3, and δ into the above calculation formula for the capacity C of the battery cell, and the minimum value of the capacity C of the battery cell in the ternary lithium battery system is obtained as 82.0 Ah.

[0175] That is, the range of the capacity C of the battery cell in the ternary lithium battery system obtained by using the calculation formula for the capacity C of the battery cell in the present invention is 82.0 Ah ≤ C ≤ 189.5 Ah. The capacity C1 of the battery cell actually designed according to the forward logic is within the above range of C.

[0176] This proves that the calculation formula for the capacity C of the battery cell given in the present invention has guiding significance for the design of the electrode group 400. The value of the capacity C of the battery cell can be deduced from the relevant dimensions of the housing 100, the first cover assembly 200, and the second cover assembly 300 according to the calculation formula for the capacity C of the battery cell.

[0177] Similarly, when the battery cell is a lithium iron phosphate battery system, the value range of δ is 1.12×10 -4 Ah / mm3 ≤δ≤2.47×10 -4 Ah / mm 3 。The minimum value of δ is 1.12×10 -4 Ah / mm 3 ,and the maximum value of δ is 2.47×10 -4 Ah / mm 3 。

[0178] Substitute the maximum values of the above parameters L + b1 + b2 - a1 - a2 - x, H - t1 - t4 - y, T - t2 - t3, and δ into the calculation formula for the capacity C of the battery cell, and the maximum value of the capacity C of the battery cell in the lithium iron phosphate battery system is obtained as 140.1 Ah.

[0179] Substitute the minimum values of the above parameters L + b1 + b2 - a1 - a2 - x, H - t1 - t4 - y, T - t2 - t3, and δ into the calculation formula for the capacity C of the battery cell, and the minimum value of the capacity C of the battery cell in the lithium iron phosphate battery system is obtained as 61.2 Ah.

[0180] That is, the range of the capacity C of the battery cell in the lithium iron phosphate battery system obtained by using the calculation formula for the capacity C of the battery cell in the present invention is 61.2 Ah ≤ C ≤ 140.1 Ah. The capacity C1 of the battery cell actually designed according to the forward logic is within the above range of C.

[0181] This proves that the calculation formula for the capacity C of the battery cell given in the present invention has guiding significance for the design of the electrode group 400. The value of the capacity C of the battery cell can be calculated from the relevant dimensions of the housing 100, the first cover assembly 200, and the second cover assembly 300 according to the calculation formula for the capacity C of the battery cell.

[0182] Obviously, the above embodiments of the present invention are merely examples for clearly explaining the present invention, and are not intended to limit the embodiments of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A battery cell, characterized in that, include: A shell, wherein the shell is provided with a first opening and a second opening on opposite sides along a first direction, respectively, and the shell comprises a first side wall, a second side wall, a third side wall and a fourth side wall, the first side wall and the fourth side wall are opposite to each other along the second direction, the second side wall and the third side wall are opposite to each other along the third direction, the first side wall, the second side wall, the third side wall and the fourth side wall are connected and enclosed to form a cylindrical structure, and the first direction, the second direction and the third direction are perpendicular to each other; A first cover plate assembly, the first cover plate assembly comprising a first cover plate body, a first plastic part and a first overlap portion, the first overlap portion being arranged in the circumference of the first cover plate body, and the first overlap portion abutting against an edge of the housing on a side where the first opening is arranged; A second cover assembly, the second cover assembly comprising a second cover body, a second plastic part and a second overlap portion, the second overlap portion being arranged in the circumference of the second cover body, the second overlap portion being in contact with an edge of the shell on which the second opening is arranged, and the shell, the first cover assembly and the second cover assembly enclose a containing cavity; An electrode group is arranged in the accommodating cavity, the electrode group includes positive electrode sheets and negative electrode sheets stacked and alternately arranged along a third direction, a separator is sandwiched between the positive electrode sheets and the negative electrode sheets, and the positive electrode sheets are electrically connected to the electrode column integrated on the first cover plate assembly or the second cover plate assembly; The capacity of the battery cell is C, in Ah; The calculation formula of C is: C=(L+b1+b2-a1-a2-x)(H-t1-t4-y)(T-t2-t3)×δ; Wherein, L is the dimension of the housing along the first direction, in mm; H is the dimension of the housing along the second direction, in mm; T is the dimension of the shell along the third direction, in mm; a1 is the distance between the end surface of the first cover body facing away from the electrode group and the end surface of the first plastic part close to the electrode group along the first direction, in mm; b1 is the size of the first overlapping portion along the first direction, in mm; a2 is the distance between the end surface of the second cover body facing away from the electrode group and the end surface of the second plastic part close to the electrode group along the first direction, in mm; b2 is the size of the second overlapping portion along the first direction, in mm; t1 is the thickness of the first side wall along the second direction, in mm; t2 is the thickness of the second side wall along the third direction, in mm; t3 is the thickness of the third side wall along the third direction, in mm; t4 is the thickness of the fourth side wall along the second direction, in mm; x is the size of the space reserved for the electrode group in the accommodating cavity along the first direction, in mm; y is the size of the space reserved for the electrode group in the accommodating cavity along the second direction, in mm; δ is the volume capacity, with the unit of Ah / mm 3 ; The value range of δ is 1.12×10 -4 Ah / mm 3 ≤δ≤3.34×10 -4 Ah / mm 3 .

2. The battery cell according to claim 1, characterized in that, The calculation formula of δ is: Among them, η is the assembly ratio when the electrode group is put into the shell, and the value range of η is 89%-91%; the value range of the positive electrode surface density is 0.00020 g / mm 2 -0.00025 g / mm 2 , the value range of the positive electrode active material content is 95%-98%, and the value range of the positive electrode specific capacity is 0.135 Ah / g-0.210 Ah / g; w1 is the thickness of the positive electrode sheet, and the value range of w1 is 0.155mm≤w1≤0.215mm; w2 is the thickness of the negative electrode sheet, and the value range of w2 is 0.105mm≤w2≤0.167mm; w3 is the thickness of the separator, and the value range of w3 is 0.010 mm ≤ w3 ≤ 0.012 mm.

3. The battery cell according to claim 2, wherein, The calculation formula of w1 is: Among them, the value range of the positive electrode compaction density is 0.0025 g / mm 3 - 0.0028 g / mm 3 ; w11 is the thickness of the aluminum foil, and the value range of w11 is 0.012 mm ≤ w11 ≤ 0.015 mm.

4. The cell according to claim 2, wherein The calculation formula of w2 is: Among them, the value range of the negative electrode surface density is 0.00009 g / mm 2 -0.00012 g / mm 2 ; The value range of the compaction density of the negative electrode is 0.0015 g / mm 3 - 0.0018 g / mm 3 ; w12 is the thickness of the copper foil, and the value range of w12 is 0.005 mm ≤ w12 ≤ 0.007 mm.

5. The cell according to claim 2, wherein, When the battery cell is a ternary lithium battery system, the value range of the positive electrode specific capacity is 0.180 Ah / g - 0.210 Ah / g; when the battery cell is a lithium iron phosphate battery system, the value range of the positive electrode specific capacity is 0.135 Ah / g - 0.155 Ah / g.

6. The battery cell according to claim 1, characterized in that The calculation formula of x is: x = x1 + x2; Wherein, x1 is the dimension difference between the separator and the negative electrode sheet along the first direction; x2 is the dimension difference between the negative electrode sheet and the positive electrode sheet along the first direction; The value range of x is 8 mm ≤ x ≤ 12 mm.

7. The battery cell according to claim 1, wherein, The calculation formula of y is: y = y1 + y2 + y3; y1 = y11 + y12; Wherein, y1 is the gap between the electrode assembly and the inner surface of the shell along the second direction, y11 is the distance between the electrode assembly and the inner surface of the first side wall along the second direction; y12 is the distance between the electrode assembly and the inner surface of the fourth side wall along the second direction; y2 is the dimension difference between the separator and the negative electrode sheet along the second direction; y3 is the dimension difference between the negative electrode sheet and the positive electrode sheet along the second direction; The value range of y is 6 mm ≤ y ≤ 9 mm.

8. The battery cell according to claim 1, characterized in that, When the battery cell is a ternary lithium battery system, the value range of δ is 1.50×10 -4 Ah / mm 3 ≤δ≤3.34×10 -4 Ah / mm 3 ; The value range of the capacity C of the battery cell is: 82.0 Ah ≤ C ≤ 189.5 Ah.

9. The battery cell according to claim 1, wherein When the battery cell is of a lithium iron phosphate battery system, the value range of δ is 1.12×10 -4 Ah / mm 3 ≤δ≤2.47×10 -4 Ah / mm 3 ; The value range of the capacity C of the battery cell is: 61.2 Ah ≤ C ≤ 140.1 Ah.

10. The battery cell according to claim 1, characterized in that, The value range of the dimension b1 of the first overlapping part along the first direction is 0.5 mm ≤ b1 ≤ 3 mm; The value range of the dimension b2 of the second overlapping part along the first direction is 0.5 mm ≤ b2 ≤ 3 mm.

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