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, and the calculation process is simpler and more convenient. And the minimum over-current area which should be met by the pole can be quickly obtained, a basis is provided for the design of the pole, and the over-current requirement and the safety requirement of the battery cell are met.

Description

Technical Field

[0001] The present invention relates to the technical field of power batteries, and particularly to an electric core. 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 electric cores, and the current of the electrode group inside the electric core is led out through the electrode posts. Generally speaking, the size design of the electrode posts is closely related to the capacity of the electric core, and the capacity of the electric core is generally calculated through a series of complex parameters such as its positive and negative material systems, compaction density, and specific capacity. The calculation process is relatively complex and cumbersome, and it is impossible to quickly obtain the over-current area of the electrode posts that the electric core should be configured with. Summary of the Invention

[0003] The purpose of the present invention is to provide an electric core, based on the relevant dimensions of its housing, first cover plate assembly, and second cover plate assembly, the over-current area of the corresponding electrode posts can be obtained through two formulas. The calculation process is relatively simple and convenient, which is conducive to realizing the rapid design of the electrode post structure and meeting the over-current requirements and safety requirements of the electric core.

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

[0005] The present invention provides an electric core, 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. The first direction, the second direction, and the third direction are perpendicular to each other in pairs;

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

[0008] A 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 provided on the circumference of the second cover plate body, and the second overlapping part abuts against the edge of the housing on the side where the second opening is provided. The housing, the first cover plate assembly, and the second cover plate assembly enclose an accommodation cavity;

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

[0010] The capacity of the battery cell is C, with the unit of 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 in the first direction, with the unit of mm;

[0014] H is the dimension of the housing in the second direction, with the unit of mm;

[0015] T is the dimension of the housing in the third direction, with the unit of mm;

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

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

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

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

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

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

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

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

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

[0025] y is the dimension of the space reserved for the electrode group in the second direction in the accommodating cavity, 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] The current-carrying area of the terminal post is S, with the unit of mm 2 ;

[0029] The calculation formula of S is:

[0030]

[0031] where A is the charging rate of the battery cell, with the unit of A / Ah; ξ is the current-carrying coefficient of the terminal post, with the unit of A / mm 2 .

[0032] Optionally, the calculation formula of δ is:

[0033]

[0034] where 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 0.00020g / mm 2 -0.00025g / mm 2 , the value range of the positive electrode active material content is 95%-98%, and the value range of the positive electrode gram capacity is 0.135Ah / g-0.210Ah / g;

[0035] w1 is the thickness of the positive electrode plate, and the value range of w1 is 0.155mm≤w1≤0.215mm;

[0036] w2 is the thickness of the negative electrode plate, and the value range of w2 is 0.105mm≤w2≤0.167mm;

[0037] w3 is the thickness of the separator, and the value range of w3 is 0.010mm≤w3≤0.012mm.

[0038] Optionally, the calculation formula of w1 is:

[0039]

[0040] where the value range of the positive electrode compaction density is 0.0025g / mm 3 -0.0028g / mm 3 ;

[0041] w11 is the thickness of the aluminum foil, and the value range of w11 is 0.012 mm ≤ w11 ≤ 0.015 mm.

[0042] Optionally, the calculation formula of w2 is:

[0043]

[0044] wherein, the value range of the negative electrode surface density is 0.00009 g / mm 2 -0.00012 g / mm 2 ;

[0045] the value range of the negative electrode compaction density is 0.0015 g / mm 3 -0.0018 g / mm 3 ;

[0046] w12 is the thickness of the copper foil, and the value range of w12 is 0.005 mm ≤ w12 ≤ 0.007 mm.

[0047] Optionally, the calculation formula of x is:

[0048] x = x1 + x2;

[0049] wherein, x1 is the dimension difference between the separator and the negative electrode along the first direction; x2 is the dimension difference between the negative electrode and the positive electrode along the first direction;

[0050] the value range of x is 8 mm ≤ x ≤ 12 mm.

[0051] Optionally, the calculation formula of y is:

[0052] y = y1 + y2 + y3;

[0053] y1 = y11 + y12;

[0054] wherein, y1 is the gap between the electrode group and the inner surface of the housing 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 along the second direction; y3 is the dimension difference between the negative electrode and the positive electrode along the second direction;

[0055] the value range of y is 6 mm ≤ y ≤ 9 mm.

[0056] 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;

[0057] the value range of δ is 1.50×10 -4 Ah / mm3 ≤ δ ≤ 3.34×10 -4 Ah / mm 3 ;

[0058] The value range of S is S ≥ 47.4 mm 2 ;

[0059] Optionally, when the battery cell is a lithium iron phosphate battery system, the value range of the positive electrode gram capacity is 0.135 Ah / g - 0.155 Ah / g;

[0060] The value range of δ is 1.12×10 -4 Ah / mm 3 ≤ δ ≤ 2.47×10 -4 Ah / mm 3 ;

[0061] The value range of S is S ≥ 35.0 mm 2 .

[0062] Optionally, the terminal post includes a first conductive terminal and a second conductive terminal. The current-carrying area of the first conductive terminal is S1, and the current-carrying area of the second conductive terminal is S2. The relationship among S, S1, and S2 satisfies: S = S1 + S2.

[0063] Optionally, the value range of the dimension b1 of the first overlapping portion in the first direction is 0.5 mm ≤ b1 ≤ 3 mm;

[0064] The value range of the dimension b2 of the second overlapping portion in the first direction is 0.5 mm ≤ b2 ≤ 3 mm.

[0065] The beneficial effects of the present invention are as follows:

[0066] The present invention provides a battery cell. The relevant dimensions of the electrode group can be calculated and deduced inversely through the dimensions of the housing, the first cover assembly, and the second cover assembly. Then, the relevant dimensions of the electrode group are substituted 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. The parameters used are fewer, and the calculation process is relatively simple and convenient. And the minimum current-carrying area that the terminal post should meet can be quickly obtained accordingly, providing a basis for the design of the terminal post and meeting the over-current requirement and safety requirement of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] 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 drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the content of the embodiments of the present invention and these drawings without creative efforts.

[0068] Figure 1 This is an exploded view of the battery cell provided in the first embodiment of the present invention;

[0069] Figure 2 This is a sectional view of the battery cell (the electrode group is not shown) provided in the first embodiment of the present invention;

[0070] Figure 3 is Figure 2 a partial enlarged view of part A in

[0071] Figure 4 is Figure 2 a partial enlarged view of part B in

[0072] Figure 5 This is a side view of the housing provided in the first embodiment of the present invention;

[0073] Figure 6 This is a sectional view of the first cover assembly provided in the first embodiment of the present invention;

[0074] Figure 7 This is a schematic structural view of the first cover assembly provided in the second embodiment of the present invention;

[0075] Figure 8 This is a sectional view of the first cover assembly provided in the second embodiment of the present invention.

[0076] In the figure:

[0077] 100, housing; 101, first opening; 102, second opening; 110, first side wall; 120, second side wall; 130, third side wall; 140, fourth side wall; 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, pole; 510, first conductive terminal; 520, second conductive terminal. Detailed implementation manners

[0078] 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 some, but not all, of the embodiments of the present invention. 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.

[0079] 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 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 should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions, and 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", "beneath" and "under" 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.

[0080] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, 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 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 circumstances.

[0081] 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 denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0082] Embodiment 1

[0083] 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.

[0084] 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 1in the Y-axis direction shown in the figure), the second side wall 120 and the third side wall 130 are opposite to each other in the third direction (the third direction is the Figure 1 Z-axis direction shown in the figure), the first side wall 110, the second side wall 120, the third side wall 130 and the fourth side wall 140 enclose a cylindrical structure, and the housing 100 has a first opening 101 and a second opening 102 on opposite sides in the first direction. The first direction, the second direction and the third direction are perpendicular to each other in pairs.

[0085] The first cover plate assembly 200 includes a first cover plate body 210, a first plastic part 220 and a first overlapping part 211. The first overlapping part 211 is arranged on the circumference of the first cover plate body 210. The first overlapping part 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 part 211 and the housing 100 is welded peripherally, 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 part 311. The second overlapping part 311 is arranged on the circumference of the second cover plate body 310. The second overlapping part 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 part 311 and the housing 100 is welded peripherally, and a second weld seam is formed at the joint. A closed accommodating cavity is formed by the housing 100, the first cover plate assembly 200 and the second cover plate assembly 300.

[0086] The electrode group 400 is arranged in the accommodating cavity. The electrode group 400 includes a positive electrode plate, a negative electrode plate and a separator laminated 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 clamped 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.

[0087] 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 sidewall 110 in the second direction is t1, with the unit of mm; the thickness of the second sidewall 120 in the third direction is t2, with the unit of mm; the thickness of the third sidewall 130 in the third direction is t3, with the unit of mm; the thickness of the fourth sidewall 140 in the second direction is t4, with the unit of mm. Among them, the first sidewall 110, the second sidewall 120, the third sidewall 130, and the fourth sidewall 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 sidewall 110, the second sidewall 120, the third sidewall 130, and the fourth sidewall 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 sidewall 110, the second sidewall 120, the third sidewall 130, and the fourth sidewall 140 set to have the same wall thickness, t1 = t2 = t3 = t4.

[0088] 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 0.5mm ≤ b1 ≤ 3mm. For example, the value of b1 can be 0.5mm, 0.8mm, 1.0mm, 2.0mm, 3.0mm, etc. By controlling the value of b1 to be greater than or equal to 0.5mm, it can be ensured that the welding strength of the first weld seam 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 (<0.5mm), the dimension of the first overlapping portion 211 in the first direction is small, the solder during welding is insufficient, it is easy to have problems with poor welding, the welding quality of the first weld seam cannot be guaranteed, and the seal between the housing 100 and the first cover assembly 200 is unreliable.

[0089] 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.

[0090] In summary, 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.

[0091] 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.

[0092] 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. Therefore, by using the calculation formula in this embodiment, the value range of the capacity C of the battery cell can be quickly judged, with fewer parameters used and relatively simple calculation. And based on this, the minimum over-current area that the terminal 500 should satisfy can be quickly obtained, providing a basis for the design of the terminal 500.

[0093] Specifically, the capacity of the battery cell provided in this embodiment is C, with the unit of Ah;

[0094] The calculation formula of C is as follows:

[0095] C = (L + b1 + b2 - a1 - a2 - x)(H - t1 - t4 - y)(T - t2 - t3) × δ;

[0096] Among them, x is the dimension of the space reserved for the electrode group 400 in the accommodating 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 accommodating cavity along the second direction, with the unit of mm; δ is the volume capacity, with the unit of Ah / mm 3 .

[0097] 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 / mm 3 、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.

[0098] The current-carrying area of the terminal post 500 is S, with the unit of mm 2 ;

[0099] The calculation formula for S is as follows:

[0100]

[0101] Among them, A is the charging rate of the battery cell, with the unit of A / Ah. The meaning of the charging rate is: the current value required for the battery cell to be charged to its rated capacity (C) within a specified time. Among them, the unit of the rated capacity (C) is Ah, the unit of the current value is A, and the unit of time is hours. For example, for a battery with a capacity of 100 Ah, if it is charged with a current of 100 A, then the charging rate is 1 (C) and it can be fully charged in 1 hour; if it is charged with a current of 200 A, then the charging rate is 2 (C) and it can be fully charged in 30 minutes. ξ is the current-carrying coefficient of the terminal post 500, with the unit of A / mm 2 .

[0102] Through the above two calculation formulas, the value range of the capacity C of the battery cell is deduced from the relevant dimensions of the housing 100, the first cover assembly 200, and the second cover assembly 300. Furthermore, the current-carrying area S required to meet the current-carrying of the terminal post 500 is calculated to ensure the current-carrying temperature rise and safety requirements of the battery cell. It should be noted that in this embodiment, only one terminal post 500 is provided on the first cover assembly 200, and this terminal post 500 is the positive terminal post, which plays a role in leading out the internal electrode group 400 to realize the conduction of the circuit. Although the specific structure of the terminal post 500 on the first cover assembly 200 is slightly different, the current-carrying area S is the cross-sectional area of the smallest cross-section in the terminal post 500. When the cross-sectional area of the smallest cross-section in the terminal post 500 meets the current-carrying requirement, it can ensure that the current-carrying area during the charge and discharge of the battery cell is sufficient, the temperature rise is not too large, and the safety is good.

[0103] In addition, the current-carrying coefficient ξ of the aluminum material specified by the national standard is 8 A / mm 2 , and the current-carrying coefficient ξ of the copper material is 12 A / mm 2 . To ensure that the current-carrying capacity of the terminal post 500 meets the requirements, the aluminum material with a smaller current-carrying coefficient ξ is used here to calculate the current-carrying area S of the terminal post 500 (at this time, the current-carrying coefficient ξ = 8 A / mm 2 ), so as to ensure that both the positive terminal post and the negative terminal post can meet the current-carrying requirements. Because the negative terminal post is made of copper material and its current-carrying capacity is better than that of the positive terminal post, if the current-carrying area S of the positive terminal post can ensure meeting the current-carrying requirement, then the negative terminal post can also definitely meet the current-carrying requirement when adopting the same current-carrying area.

[0104] The origin of the calculation formula for the capacity C of the above battery cell is described below:

[0105] When generally determining the capacity C1 of the battery cell using the forward logic, the following formula can be used:

[0106] C1 = the length of the positive electrode sheet material area × the width of the positive electrode sheet material area × the positive electrode surface density × the content of the positive electrode active material × 2 × the positive electrode gram capacity × the number of positive electrode sheets;

[0107] Among them, the positive electrode sheet includes an aluminum foil and a 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.

[0108] 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.

[0109] The calculation formula of x is:

[0110] x = x1 + x2;

[0111] 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 that one end of the separator extends beyond the adjacent end of the negative electrode sheet along the first direction (the dimensions that both ends of the separator extend beyond the adjacent ends of the negative electrode sheet along the first direction are the same).

[0112] 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 that one end of the negative electrode sheet extends beyond the adjacent end of the positive electrode sheet along the first direction (the dimensions that both ends of the negative electrode sheet extend beyond the adjacent ends of the positive electrode sheet along the first direction are the same).

[0113] 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.

[0114] Generally speaking, in the design of the electrode group 400, the design values of x1 and x2 are both within a certain range. Here, the value range of the sum x of x1 and x2 is limited to 8 mm ≤ x ≤ 12 mm. For example, the value of x can be 8 mm, 9 mm, 10 mm, 11 mm, or 12 mm, etc. By controlling the value of x within the above range, the electrode group 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 x is too small, there is no bending space for the tabs of the electrode group 400, and the electrode group 400 is easily crushed; when the value of x is too large, the fixing effect of the electrode group 400 in the housing 100 is poor, and it is easy to move around, resulting in poor assembly of the battery cell.

[0115] The above conclusions are illustrated below with some specific implementation cases of battery cells. Refer to Table 1.

[0116] Table 1

[0117]

[0118] As can be seen from the above results, in Comparative Example 1, the value of x is less than the minimum value of 8 mm ≤ x ≤ 12 mm. At this time, the tab of the electrode group 400 has no bending space, and the electrode group 400 is easily crushed, reducing the reliability of the battery cell and resulting in defective products.

[0119] In Comparative Example 2, the value of x is greater than the maximum value of 8 mm ≤ x ≤ 12 mm. The fixing effect of the electrode group 400 in the housing 100 is not good, and it is prone to displacement, even pulling the tab. The battery cell has a risk of failure, and the assembly of the battery cell is not good, resulting in defective products.

[0120] In Example 1, Example 2, and Example 3, the value of x is within the range of 8 mm ≤ x ≤ 12 mm. At this time, the electrode group 400 can be well fixed in the housing 100, is not prone to displacement, and the tab 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.

[0121] The width of the positive electrode sheet material area is the dimension of the positive electrode sheet along the second direction, that is, H - t1 - t4 - y.

[0122] The calculation formula for y is:

[0123] y = y1 + y2 + y3;

[0124] y1 = y11 + y12;

[0125] Among them, y1 is the gap between the electrode group 400 and the housing along the second direction, y11 is the distance between the electrode group 400 and the inner surface of the first side wall 110 along the second direction; y12 is the distance between the electrode group 400 and the inner surface of the fourth side wall 140 along the second direction.

[0126] y2 is the difference in the dimensions of the separator and the negative electrode sheet along the second direction. Since the center points of the negative electrode sheet, separator, positive electrode sheet, separator, and negative electrode sheet are located on the same axis when stacked in sequence, y2 is twice the dimension of the end of one side of the separator exceeding the adjacent end of the negative electrode sheet along the second direction (the dimensions of the two ends of the separator exceeding the adjacent ends of the negative electrode sheet along the second direction are the same).

[0127] y3 is the difference in size between the negative electrode sheet and the positive electrode sheet along the second direction. Since the central points are on the same axis when the negative electrode sheet, separator, positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, y3 is thus twice the size by which the end of the negative electrode sheet on one side along the second direction exceeds the adjacent end of the positive electrode sheet along the second direction (the sizes by which the two ends of the negative electrode sheet along the second direction exceed the adjacent ends of the positive electrode sheet along the second direction are the same).

[0128] That is to say, the size of the positive electrode sheet along the second direction is smaller than that of the negative electrode sheet along the second direction, and the size of the negative electrode sheet along the second direction is smaller than that of the separator along the second direction.

[0129] Generally, in the design of the electrode group 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 group 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 group 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 group 400; when the value of y is too large, the fixing effect of the electrode group 400 in the housing 100 is not good, it is easy to move around, and even pull the tab, reducing the reliability of the battery cell.

[0130] The following uses some specific battery cell implementation cases to illustrate the above conclusion. See Table 2.

[0131] Table 2

[0132]

[0133] 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 group 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 group 400, resulting in defective battery cell products.

[0134] 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 group 400 in the housing 100 is not good, it is easy to move around, and even pull the tab, reducing the reliability of the battery cell and resulting in defective battery cell products.

[0135] In Embodiment 1, Embodiment 2, and Embodiment 3, the value of y is within 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 easy to move around, and the tab is not easy to be pulled. The electrode group 400 remains intact, the reliability of the battery cell is high, and the battery cell products are good.

[0136] Further, the outermost layers of the electrode group 400 are all negative electrode sheets, and the positive electrode sheets and negative electrode sheets are arranged alternately 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.

[0137] Considering the ease of inserting the electrode group 400 into the housing and the expansion of the electrode group 400 during charging and discharging, an assembly space and an expansion space for the electrode group 400 need to be reserved in the accommodation cavity in the third direction. Here, the ratio of the size of the electrode group 400 in the third direction to the size of the accommodation cavity in the third direction is defined as the assembly ratio, and the assembly ratio is denoted as η.

[0138] That is, the size of the electrode group 400 in the third direction calculated from the size of the accommodation cavity should be:

[0139] η×(T - t2 - t3).

[0140] The size of the electrode group 400 in the third direction calculated using forward logic is:

[0141] w1×m + w2×(m + 1) + w3×(2m + 2);

[0142] 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.

[0143] The sizes of the electrode group 400 in the third direction calculated by the two methods should be equal. Therefore:

[0144] w1×m + w2×(m + 1) + w3×(2m + 2)

[0145] = η×(T - t2 - t3).

[0146] From the above formula, it can be derived that:

[0147]

[0148] Continuing to substitute the above lengths of the positive electrode sheet material area, widths of the positive electrode sheet material area, and the value of m into the calculation formula of C1, we get:

[0149]

[0150] where, 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:

[0151]

[0152] Denote as δ, then the calculation formula of C1 is obtained:

[0153] C1 = (L + b1 + b2 - a1 - a2 - x)(H - t1 - t4 - y)(T - t2 - t3)×δ。

[0154] That is, the formula for calculating the capacity C of the battery cell provided in the present invention is:

[0155] C = (L + b1 + b2 - a1 - a2 - x)(H - t1 - t4 - y)(T - t2 - t3)×δ。

[0156] Among them, the calculation formula for δ is:

[0157]

[0158] When calculating δ, the following several parameters are required: η, the positive electrode surface density, the content of the positive electrode active material, 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.

[0159] Generally speaking, the value range of the assembly ratio η when the electrode group 400 is inserted into the shell is 89% - 91%. For example, the value of η can be 89%, 90%, 91%, etc.

[0160] 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.

[0161] The value range of the content of the positive electrode active material is 95% - 98%. For example, the value of the content of the positive electrode active material can be 95%, 96%, 97%, 98%, etc.

[0162] 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, 0.210 Ah / g, etc.

[0163] The calculation formula for the thickness w1 of the positive electrode sheet is:

[0164]

[0165] 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 calculation formula of the thickness w1 of the above positive electrode sheet.

[0166] 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.

[0167] Substitute the positive electrode areal density, the positive electrode compaction density, and the thickness w11 of the aluminum foil into the above calculation formula of 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.

[0168] The calculation formula for the thickness w2 of the negative electrode sheet is:

[0169]

[0170] 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.

[0171] 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.

[0172] 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-mentioned negative electrode sheet.

[0173] 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 above-mentioned negative electrode sheet. It is deduced that the value range of the thickness w2 of the negative electrode sheet is 0.105 mm ≤ w2 ≤ 0.167 mm.

[0174] Optionally, the value range of the thickness w3 of the separator is generally 0.010 mm ≤ w3 ≤ 0.012 mm.

[0175] 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.

[0176] 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.

[0177] 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 .

[0178] 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 battery cell of the ternary lithium battery system.

[0179] 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 .

[0180] The capacity C of the above-mentioned battery cell and the current-carrying area S of the terminal 500 are calculated and verified by 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.

[0181] Table 3

[0182]

[0183] 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 。

[0184] 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 formula: C = (L + b1 + b2 - a1 - a2 - x)(H - t1 - t4 - y)(T - t2 - t3)×δ;

[0185] The maximum value of the capacity C of the battery cell in the ternary lithium battery system is obtained as 189.5 Ah.

[0186] 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 formula, and the minimum value of the capacity C of the battery cell in the ternary lithium battery system is obtained as 82.0 Ah.

[0187] That is, the range of the capacity C of the battery cell in the ternary lithium battery system obtained by using the calculation formula of 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 range of the above C. This proves that the calculation formula of the capacity C of the battery cell given in the present invention has guiding significance for the design of the electrode group 400.

[0188] Then, the value of the capacity C of the battery cell is calculated from the relevant dimensions of the housing 100, the first cover assembly 200, and the second cover assembly 300, and the design dimensions of the terminal 500 that meet the current-carrying requirements of the battery cell are further determined.

[0189] To ensure that the current-carrying area at the minimum cross-sectional area of the terminal post 500 meets the current-carrying requirements when the battery cell is charged and discharged at the rated rate, and the temperature rise during charging and discharging at the rated rate is small. Let the charging rate A of the battery cell be 2 (C), that is, a current of 2 times the battery cell capacity is used for charging, and the overcurrent coefficient ξ is taken as 8 A / mm 2 , substitute into the following formula:

[0190]

[0191] According to the two end values (minimum value 82.0 Ah and maximum value 189.5 Ah) of the capacity C of the above battery cell, the range interval of the minimum value of the current-carrying area S of the terminal post 500 is obtained (20.5 mm 2 -47.4 mm 2 ). To reduce the temperature rise during rate charging, only when the current-carrying area S of the terminal post 500 is greater than or equal to 47.4 mm 2 can it be fully ensured that the dimension design of the terminal post 500 meets the maximum current-carrying requirements of the battery cell at this dimension.

[0192] That is, when C takes the maximum value, the current-carrying area S of the terminal post 500 satisfies the following formula:

[0193]

[0194] Similarly, when the battery cell is of the 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 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 .

[0195] 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 of the capacity C of the battery cell, and the maximum value of the capacity C of the battery cell of the lithium iron phosphate battery system is obtained as 140.1 Ah.

[0196] 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 of the capacity C of the battery cell, and the minimum value of the capacity C of the battery cell of the lithium iron phosphate battery system is obtained as 61.2 Ah.

[0197] 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 of 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 range of the above C. This proves that the calculation formula of the capacity C of the battery cell given in the present invention has guiding significance for the design of the electrode group 400.

[0198] Then, the value of the capacity C of the battery cell is calculated from the relevant dimensions of the housing 100, the first cover assembly 200, and the second cover assembly 300, and the design dimensions of the terminal 500 that satisfy the overcurrent of the battery cell are continuously determined. Let the charging rate A of the battery cell be 2(C), that is, the current of 2 times the capacity of the battery cell is used for charging, and the overcurrent coefficient ξ is taken as 8 A / mm 2 , and substitute it into the following formula:

[0199]

[0200] According to the two endpoint values (the minimum value of 61.2 Ah and the maximum value of 140.1 Ah) of the capacity C of the above battery cell, the range interval of the minimum value of the overcurrent area S of the terminal 500 is obtained (15.3 mm 2 -35.0 mm 2 ). To reduce the temperature rise during charging at a high rate, only when the overcurrent area S of the terminal 500 is greater than or equal to 35.0 mm 2 can it fully ensure that the size design of the terminal 500 meets the maximum overcurrent requirement of the battery cell at this size.

[0201] That is, when C takes the maximum value, the overcurrent area S of the terminal 500 satisfies the following formula:

[0202]

[0203] See Figure 6 , the minimum cross-section of the terminal 500 is the position where the diameter of the terminal 500 marked as d in Figure 6 . Among them, the diameter d of the terminal 500 can be calculated by the following formula:

[0204]

[0205] Thus, a reference value of the diameter d at the minimum cross-section in the structural design of the terminal 500 can be obtained. When the designed diameter of the terminal 500 is greater than the above calculated reference value of d, it can fully ensure the maximum overcurrent requirement of the battery cell of this size.

[0206] Embodiment 2

[0207] This embodiment also provides a battery cell. See Figure 7 and Figure 8, which is different from the battery cell in the first embodiment in that: in the battery cell of this embodiment, the terminal 500 (positive terminal or negative terminal) of the battery cell includes a first conductive terminal 510 and a second conductive terminal 520. The current-carrying area of the first conductive terminal 510 is S1, and the current-carrying area of the second conductive terminal 520 is S2. The relationship among S, S1, and S2 satisfies: S = S1 + S2.

[0208] Among them, the position where the diameter of the terminal 500 marked in Figure 8 is d1 at the minimum cross-section of the first conductive terminal 510. The position where the diameter of the terminal 500 marked in Figure 8 is d2 at the minimum cross-section of the second conductive terminal 520. The diameter d1 of the first conductive terminal 510 and the diameter d2 of the second conductive terminal 520 can be calculated using the following formula:

[0209]

[0210]

[0211] S satisfies the following calculation formula:

[0212]

[0213] Among them, A is the charging rate of the battery cell, with the unit of A / Ah; ξ is the current-carrying coefficient of the terminal 500, with the unit of A / mm 2 . Generally, A can be taken as 2(C), and the current-carrying coefficient ξ of the terminal 500 can be taken as 8A / mm 2 .

[0214] The calculation formula for the capacity C of the battery cell is as follows:

[0215] C = (L + b1 + b2 - a1 - a2 - x)(H - t1 - t4 - y)(T - t2 - t3)×δ;

[0216] Wherein, L is the dimension of the housing 100 in the first direction, H is the dimension of the housing 100 in the second direction, T is the dimension of the housing 100 in the third direction, a1 is 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, b1 is the dimension of the first overlapping part 211 in the first direction, a2 is the distance between the end face of the second cover body 310 facing away from the electrode group 400 in the first direction and the end face of the second plastic part 320 close to the electrode group 400 in the first direction, b2 is the dimension of the second overlapping part 311 in the first direction, t1 is the thickness of the first side wall 110 in the second direction, t2 is the thickness of the second side wall 120 in the third direction, t3 is the thickness of the third side wall 130 in the third direction, t4 is the thickness of the fourth side wall 140 in the second direction; x is the dimension of the space reserved for the electrode group 400 in the first direction in the accommodation cavity; y is the dimension of the space reserved for the electrode group 400 in the second direction in the accommodation cavity. The units of the above parameters are all mm.

[0217] δ is the volume capacity, and the unit is Ah / mm 3 . The value range of δ is 1.12×10 -4 Ah / mm 3 ≤δ≤3.34×10 - 4 Ah / mm 3 , and the specific value of δ can be determined according to the type of the battery cell, which will not be listed one by one here.

[0218] The remaining structures of the battery cell in this embodiment are the same as those in Embodiment 1, and will not be elaborated here.

[0219] Obviously, the above are only the preferred embodiments of the present invention and the applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments here, and various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

[0220] Note that in the description of this specification, the descriptions referring to the reference terms "some embodiments", "other embodiments", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

Claims

1. A battery cell, characterized in that, Comprising: A housing, on opposite sides of which along a first direction there are respectively a first opening and a second opening. 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 to each other along a second direction, the second side wall and the third side wall are opposite to each other along a third direction. The first side wall, the second side wall, the third side wall and the fourth side wall are connected and enclose a cylindrical structure. The first direction, the second direction and the third direction are perpendicular to each other in pairs; A first cover assembly, which 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; A second cover assembly, which includes a second cover body, a second plastic part and a second overlapping part. The second overlapping part is provided on the circumference of the second cover body, and the second overlapping part abuts against the edge of the housing on the side where the second opening is provided. The housing, the first cover assembly and the second cover assembly enclose a receiving cavity; An electrode group, arranged in the receiving cavity. The electrode group includes a positive electrode plate and a negative electrode plate that are stacked and alternately arranged along the third direction, and a separator is clamped between the positive electrode plate and the negative electrode plate. The positive electrode plate is electrically connected to a pole column integrated on the first cover assembly or the second cover assembly; The capacity of the battery cell is C, with the unit of 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, with the unit of mm; H is the dimension of the housing along the second direction, with the unit of mm; T is the dimension of the housing along the third direction, with the unit of mm; a1 is the distance between the end face of the first cover body facing away from the electrode group along the first direction and the end face of the first plastic part close to the electrode group along the first direction, with the unit of mm; b1 is the dimension of the first overlapping part along the first direction, with the unit of mm; a2 is the distance between the end face of the second cover body facing away from the electrode group along the first direction and the end face of the second plastic part close to the electrode group along the first direction, with the unit of mm; b2 is the dimension of the second overlapping part along the first direction, with the unit of mm; t1 is the thickness of the first side wall along the second direction, with the unit of mm; t2 is the thickness of the second side wall along the third direction, with the unit of mm; t3 is the thickness of the third side wall along the third direction, with the unit of mm; t4 is the thickness of the fourth side wall along the second direction, with the unit of mm; x is the dimension of the space reserved for the electrode group along the first direction in the receiving cavity, with the unit of mm; y is the dimension of the space reserved for the electrode group along the second direction in the receiving cavity, with the unit of 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 ; The current-carrying area of the terminal post is S, with the unit of mm 2 ; The calculation formula of S is: Among them, A is the charging rate of the battery cell, with the unit of A / Ah; ξ is the over-current coefficient of the terminal post, with the unit of A / mm 2 .

2. The battery cell according to claim 1, wherein 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 plate, and the value range of w1 is 0.155mm ≤ w1 ≤ 0.215mm; w2 is the thickness of the negative electrode plate, 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 compaction density of the positive electrode 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 battery 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 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 in the first direction; x2 is the dimension difference between the negative electrode sheet and the positive electrode sheet in the first direction; The value range of x is 8 mm ≤ x ≤ 12 mm.

6. The 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 group and the inner surface of the housing in the second direction, y11 is the distance between the electrode group and the inner surface of the first side wall in the second direction; y12 is the distance between the electrode group and the inner surface of the fourth side wall in the second direction; y2 is the dimension difference between the separator and the negative electrode sheet in the second direction; y3 is the dimension difference between the negative electrode sheet and the positive electrode sheet in the second direction; The value range of y is 6 mm ≤ y ≤ 9 mm.

7. The battery cell according to claim 1, 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; 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 S is S≥47.4mm 2 .

8. The battery cell according to claim 1, wherein 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 range of δ is 1.12×10 -4 Ah / mm 3 ≤δ≤2.47×10 -4 Ah / mm 3 ; The value range of S is S≥35.0mm 2 。 9. The battery cell according to claim 1, wherein The pole column includes a first conductive terminal and a second conductive terminal. The current-carrying area of the first conductive terminal is S1, and the current-carrying area of the second conductive terminal is S2. S, S1, and S2 satisfy: S = S1 + S2.

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

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