Single battery and battery pack

Abstract

The utility model discloses a single battery and a battery pack. Each single battery comprises a battery cell, a cover body assembly and a reinforcing plate; each battery cell comprises a main body and a tab bundle connected with the main body; the cover body assembly comprises a top cover and a pole arranged on the top cover, and the pole is provided with a connecting surface facing the tab bundle; the tab bundle and the connecting surface are welded through ultrasonic waves, and a first welding mark is formed on the surface, back to the connecting surface, of the tab bundle; the reinforcing plate is provided with a hollow part; the reinforcing plate, the tab bundle and the connecting surface are welded through laser, a second welding mark is formed on the surface, back to the tab bundle, of the reinforcing plate, and the orthographic projection of the second welding mark on the connecting surface falls in an area limited by the outer edge of the orthographic projection of the hollow part on the connecting surface. According to the battery, the tab bundle is respectively connected with the pole through the first welding mark and the second welding mark, and through the connecting structure of the reinforcing plate, the overcurrent effect and the structural connection stability of the single battery are effectively ensured.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a single cell and a battery pack. Background Art

[0002] With the rapid development of new energy technology, batteries, as the core structure in this field, have also developed rapidly in recent years. Single cells generally include a shell, a battery cell, a top cover assembly, etc. Among them, the tabs on the battery cell need to be electrically connected to the poles on the top cover assembly.

[0003] In the current battery manufacturing process, the common structures for the electrical connection between the pole ear and the pole column are mainly the following. 1. The pole ear and the pole column are electrically connected through a connecting piece. Generally, the pole ear and the connecting piece are first welded together by ultrasound, and then the connecting piece is welded to the pole column by laser welding to indirectly achieve electrical connection between the pole ear and the pole column. This manufacturing process involves many steps, the battery cell structure is complex and the space utilization rate is low, so it is at a disadvantage in terms of energy density and manufacturing cost; 2. The pole ear is directly ultrasonically welded to the pole column, but the structural strength of ultrasonic welding is difficult to take into account. If you want to ensure the structural strength, you need to increase the power of the ultrasonic wave, which will increase the vibration intensity at the welding position, which may cause problems with the sealing of the battery; 3. First, the pole ear itself is ultrasonically welded into one, and then laser welded to the pole to ensure strength. However, due to the high energy density of laser welding, cracks, pores and other undesirable conditions may occur inside the laser weld mark, resulting in a poor current flow effect.

[0004] Therefore, it is necessary to seek a more stable electrical connection structure between the tab and the pole to make the structure of the single cell stable and reliable. Utility Model Content

[0005] The present application provides a single cell and a battery pack to solve the current technical problem that the electrical connection structure between the tab and the pole is not stable and reliable enough.

[0006] In a first aspect, the present application provides a single cell, comprising:

[0007] A battery cell, the battery cell comprising a main body and a tab bundle connected to the main body;

[0008] A cover assembly, the cover assembly comprising a top cover and a pole arranged on the top cover, the pole having a connection surface facing the pole lug bundle;

[0009] The tab bundle and the connection surface are ultrasonically welded, and a first weld mark is formed on the surface of the tab bundle facing away from the connection surface;

[0010] Also included is a reinforcing plate, the reinforcing plate having a hollow portion;

[0011] The reinforcing plate, the tab bundle and the connecting surface are laser welded, and a second weld mark is formed on the surface of the reinforcing plate facing away from the tab bundle. The orthographic projection of the second weld mark on the connecting surface falls within the area defined by the outer edge of the orthographic projection of the hollow portion on the connecting surface.

[0012] To implement the above technical solution, ultrasonic welding is performed between the tab bundle and the connection surface in the single cell, and ultrasonic welding can provide a relatively stable flow effect, while laser welding is performed between the reinforcement plate, the tab bundle and the connection surface to provide a relatively reliable fixing effect. The combination of the two can ensure that the tab bundle is reliably connected to the pole while ensuring the flow effect. In addition, during laser welding, the reinforcement plate can be partially melted and filled into the laser welding molten pool, thereby avoiding the shrinkage of the molten pool during cooling, which causes a gap between the edge of the molten pool and the boundary of the connection between the tab, thereby reducing the adverse conditions of cracks and pores, further ensuring the flow effect and stable connection, effectively improving the reliability and strength of the connection between the tab and the pole, and ultimately effectively improving the connection reliability of each component in the single cell.

[0013] As one of the optional embodiments of the present solution, the orthographic projection of the hollow portion on the connecting surface is located within an area defined by an outer edge of the orthographic projection of the reinforcing plate on the connecting surface.

[0014] As one of the optional embodiments of the present scheme, the orthographic projection of the reinforcement plate on the connecting surface and the orthographic projection of the first weld on the connecting surface overlap in at least part of the area to form an overlapping area, and the orthographic projection of the hollow portion on the connecting surface is located within the area defined by the outer edge of the overlapping area.

[0015] To implement the above technical solution, the hollow portion is limited to the area of ​​the first weld mark, that is, the area through which the ultrasonic welding passes during laser welding. The laser welding simultaneously fixes the pole ear and the reinforcement plate to the pole, making the connection more reliable.

[0016] As one of the optional embodiments of the present solution, the reinforcement plate has a first surface facing the connecting surface and a second surface facing away from the connecting surface; the distance from the second weld mark to the connecting surface is greater than the distance from the first surface to the connecting surface and less than the distance from the second surface to the connecting surface.

[0017] As one of the optional embodiments of the present solution, the area enclosed by the orthographic projection of the first weld mark on the connection surface falls within the area formed by the orthographic projection of the reinforcement plate on the connection surface.

[0018] As one of the optional embodiments of this solution, the single battery has a first direction and a second direction, the first direction intersects with the second direction, and the first direction and the second direction are both parallel to the connection surface;

[0019] The second weld mark includes a first portion and a second portion connected to each other, the first portion extends along the first direction, and the second portion extends along the second direction.

[0020] To implement the above technical solution, the second weld mark at least has a turning shape, that is, the direction of the second weld mark changes during its extension. Under the setting of the same width, the second weld mark and the pole are fixed with parts in different directions, and the connection is more stable and reliable.

[0021] As one of the optional embodiments of the present solution, the number of the first parts is at least two, the first parts are spaced apart along the second direction, and the two ends of the first parts in the first direction are respectively connected by the second parts to form a closed structure.

[0022] To implement the above technical solution, it is pointed out that the second weld mark is a closed shape with a hole inside to improve the connection reliability.

[0023] As one of the optional embodiments of the present solution, a weight-reducing hole is provided through the reinforcing plate; the area defined by the outer edge of the orthographic projection of the second weld on the connecting surface covers the orthographic projection of the weight-reducing hole on the connecting surface.

[0024] As one of the optional embodiments of the present solution, the distance between the outer boundary of the second weld mark and the boundary of the overlap area is L, 1mm≤L.

[0025] As one of the optional embodiments of this solution, the single battery further includes at least one of the following technical features:

[0026] a. The width of the second weld mark at any position is D, D ≥ 1 mm;

[0027] b. The thickness of the reinforcing plate is S, 0.1mm≤S≤1.5mm;

[0028] c. The penetration depth of the second weld mark on the pole along the direction perpendicular to the connection surface is H, 0.1mm≤H≤1.5mm.

[0029] On the other hand, the present application also provides a battery pack, comprising:

[0030] a housing; and,

[0031] The above-mentioned single cell.

[0032] One of the above technical solutions has the following advantages or beneficial effects:

[0033] In a single cell, ultrasonic welding is used between the tab bundle and the connection surface. Ultrasonic welding can provide a relatively stable flow effect, while laser welding between the reinforcement plate, the tab bundle and the connection surface can provide a relatively reliable fixing effect. The combination of the two can ensure that the tab bundle is reliably connected to the pole while ensuring the flow effect. In addition, during laser welding, the reinforcement plate can be partially melted and filled into the laser welding molten pool, thereby avoiding the shrinkage of the molten pool during cooling, which causes a gap between the edge of the molten pool and the boundary of the tab connection, thereby reducing the adverse conditions of cracks and pores, further ensuring the flow effect and stable connection, effectively improving the reliability and strength of the connection between the tab and the pole, and ultimately effectively improving the connection reliability of each component in the single cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The technical solution and other beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.

[0035] Figure 1 is an overall view of a single cell provided in Example 1 of the present application;

[0036] Figure 2 This is an exploded structure diagram provided in Example 1 of the present application for showing the tab before welding;

[0037] Figure 3 This is a structural diagram provided in Example 1 of the present application for showing the reinforcement plate before welding;

[0038] Figure 4 This is a cross-sectional structure diagram provided in Example 1 of the present application for showing the ultrasonic welding and laser welding of the pole lug and the pole;

[0039] Figure 5 This is provided in Example 1 of the present application Figure 4 A partial enlarged view of part A;

[0040] Figure 6 This is a bottom view provided in Example 1 of the present application for showing the ultrasonic welding and laser welding of the pole lug and the pole;

[0041] Figure 7 It is a schematic diagram provided in Example 1 of the present application mainly for demonstrating the laser welding structure;

[0042] Figure 8 is a schematic diagram of another structure of laser welding in Example 2 of the present application;

[0043] Fig. 9 is a schematic diagram of another structure of laser welding in Example 3 of the present application;

[0044] Fig.10It is used in Example 4 of the present application to indicate the area where the reinforcing plate overlaps with the first weld print portion;

[0045] Fig.11 This is a schematic diagram of Example 5 of the present application used to indicate that the reinforcement plate is entirely located within the first weld print area.

[0046] Reference numerals: 1, battery cell; 11, main body; 12, tab bundle;

[0047] 2. Cover assembly; 21. Top cover; 22. Pole; 221. Connection surface;

[0048] 3. First welding part; 31. First welding mark;

[0049] 4, reinforcing plate; 41, hollow portion; 42, weight-reducing hole; X1, first side; X2, second side;

[0050] 5, second welding part; 51, second welding mark; 511, first part; 512, second part; Y1, second welding mark;

[0051] 6. Overlapping area;

[0052] 7. Shell. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0054] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the term "and / or" in this article is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article, unless otherwise specified, generally indicates that the associated objects before and after are in an "or" relationship.

[0055] The following is combined with Figure 1-11 The present application is further described.

[0056] Reference Figure 1 and Figure 2The present application provides a single cell battery, which includes a shell 7, a battery cell 1 and a cover assembly 2. One end of the shell 7 has an opening, and the battery cell 1 is loaded into the shell 7 through the opening. The cover assembly 2 covers the opening to close the opening. The battery cell 1 includes a main body 11 and a tab bundle 12 connected to the main body 11. The tab bundle 12 refers to a collection formed by stacking multiple individual tabs together, and each tab is connected to the main body 11. The cover assembly 2 includes a top cover 21 and a pole 22 arranged on the top cover 21. The bottom of the pole 22 vertically passes through the top cover 21 and protrudes downward. The pole 22 has a connection surface 221 facing the tab bundle 12.

[0057] Reference Figure 2 , Figure 3 and Figure 4 , the tab bundle 12 and the connection surface 221 are fixedly connected and electrically conductive. The tab bundle 12 and the connection surface 221 are fixedly connected by ultrasonic welding, and a three-dimensional first welding portion 3 is formed between the tab bundle 12 and the connection surface 221 after welding. The formation process of the first welding portion 3 is: the tab bundle 12 is attached to the connection surface 221 and then ultrasonic welding is directly performed using ultrasonic welding equipment. This method will form a preliminary fixed connection between two adjacent tabs in the tab bundle 12, and a preliminary fixed connection relationship is first formed between the tab bundle 12 and the pole 22, thereby enhancing the connection strength between the tab and the pole 22, which is conducive to improving the reliability of subsequent further welding. The ultrasonic weld mark formed has certain advantages in the overcurrent conduction of the current, and at the same time, the welding process between the tabs is omitted.

[0058] It should be noted that the tab bundle 12 includes a positive tab bundle and a negative tab bundle, wherein the positive tab bundle is connected to the positive portion of the main body 11, and the negative tab bundle is connected to the negative portion of the main body 11, and the positive tab bundle and the negative tab bundle are spaced apart from each other. When ultrasonic welding is performed, adjacent single-layer tabs in the same tab bundle 12 and between the tab bundle 12 and the connecting surface 221 will form a fixed connection relationship due to the high-speed vibration of ultrasonic welding. Therefore, the first welding portion 3 here refers to the three-dimensional structure formed during the ultrasonic welding process, that is, the fixed connection structure formed between multiple layers of tabs and between the tab bundle and the connecting surface.

[0059] After the first welding portion 3 is formed, a first welding mark 31 is formed on the side of the tab bundle 12 facing away from the connecting surface 221 . The first welding mark 31 referred to here refers to the area defined by the edge of the first welding portion 3 when observing the first welding portion 3 from a direction perpendicular to the connecting surface 221 .

[0060] Reference Figure 4, the reinforcing plate 4 is attached to the side of the first welding part 3 away from the connecting surface 221, and the reinforcing plate 4 is parallel to the connecting surface 221; the reinforcing plate 4, the pole lug bundle 12 and the connecting surface 221 are also fixedly connected by laser welding. After laser welding, the reinforcing plate 4, the pole lug bundle 12 and the connecting surface 221 form a three-dimensional second welding part 5. The formation process of the second welding part 5 is: using a laser welding device to emit a laser to melt through the reinforcing plate 4, the first welding part 3 and finally melt part of the pole 22, and finally solidify to form. Among them, a molten pool will be formed during the laser welding process, and the reinforcing plate 4 will be partially melted and added to the molten pool, so that there is enough liquid when the molten pool solidifies, avoiding the edge of the molten pool and the boundary of the pole lug 12 or the first welding part 3 due to the principle of cold shrinkage when the molten pool cools, causing a pull and a gap, reducing the situation of cold welding and pores, ensuring the flow effect and stable connection, so as to improve the welding quality. Furthermore, during laser welding, the positioning structure of the welding equipment abuts against the edge of the reinforcing plate 4, applying pressure to the reinforcing plate 4 toward the connection surface 221, so that the reinforcing plate 4 squeezes the tab bundle 12, which can prevent the displacement of the tab bundle 12 during welding, and ensure that the tab bundle 12 is flatly squeezed on the connection surface 221, which is beneficial to improve the structural strength of the welding. After the second welding portion 5 is finally formed, the second welding portion 5 is observed from the direction perpendicular to the connection surface 221, and the area formed by the edge of the second welding portion 5 is the second weld mark 51. When forming the second welding portion 5, the laser melts through the reinforcing plate 4 and forms a hollow portion 41 on the reinforcing plate 4.

[0061] It should be noted that the hollow portion 41 referred to here is the hollow portion 41 formed when the reinforcement plate 4 is melted by the laser during the laser welding process, so that part of the material of the reinforcement plate 4 is dissolved into the molten pool, thereby causing the reinforcement plate 4 to be missing. It can be understood that the reinforcement plate 4 does not have the hollow portion 41 before welding. A weight-reducing hole 42 is also provided in the middle of the reinforcement plate 4. In this embodiment, the hollow portion 41 is formed just around the inner edge of the weight-reducing hole 42. The hollow portion 41 is Figure 3 The diagram in the figure is the area formed by the dotted line part and the inner edge of the weight-reducing hole 42. In this embodiment, the hollow portion 41 is connected to the inner edge of the weight-reducing hole 42, but it is not excluded that the hollow portion 41 is not connected to the weight-reducing hole 42 in other embodiments, for example, there is a gap between the inner edge of the hollow portion 41 and the outer edge of the weight-reducing hole 42.

[0062] Reference Figure 4 and Figure 5, the reinforcing plate 4 has a first surface X1 facing the connecting surface 221 and a second surface X2 facing away from the connecting surface 221 in the vertical direction shown in the figure, and the distance between the second weld mark 51 and the connecting surface 221 is greater than the distance between the first surface X1 and the connecting surface 221 and is less than the distance between the second surface X2 and the connecting surface 221. This means that during the laser welding process, part of the molten pool will flow into between the first surface X1 and the second surface X2 and solidify with the inner edge of the hollow portion 41 and then be fixedly connected to the reinforcing plate 4 to ensure the connection stability.

[0063] Reference Figure 4 and Figure 6 , the area enclosed by the orthographic projection of the first welding portion 3 on the connection surface 221 falls within the area formed by the orthographic projection of the reinforcing plate 4 on the connection surface 221. The orthographic projection of the hollow portion 41 on the connection surface 221 is located in the area defined by the outer edge of the orthographic projection of the reinforcing plate 4 on the connection surface 221, and the orthographic projection of the reinforcing plate 4 on the connection surface 221 overlaps with the orthographic projection of the first welding portion 3 on the connection surface 221 at least in part and forms an overlap area 6, and the orthographic projection of the hollow portion 41 on the connection surface 221 is located in the area defined by the outer edge of the overlap area 6. That is, in this embodiment, the second welding portion 5 refers to the laser melting through the reinforcing plate 4, the first welding portion 3, and the melting of part of the pole 22 and finally solidification. In this embodiment, the outer edge of the reinforcing plate 4 completely covers the area of ​​the first welding portion 3, so the overlap area 6 is the area of ​​the first welding portion 3.

[0064] However, it should be noted that it is not excluded that the laser only melts through the reinforcing plate 4 and the tab bundle 12 located outside the first welding portion 3. That is, the orthographic projection of the second welding portion 5 on the connection surface 221 falls outside the area defined by the outer edge of the orthographic projection of the first welding portion 3 on the connection surface 221. At this time, the reinforcing plate 4 still has the function of supplementing the molten pool and improving the quality of laser welding.

[0065] Reference Figure 7 As one of the optional embodiments of the present solution, the single battery has a first direction and a second direction, the first direction intersects with the second direction, and the first direction and the second direction are parallel to the connection surface 221. The second weld mark 51 includes a first portion 511 and a second portion 512 connected to each other, the first portion 511 extends along the first direction, and the second portion 512 extends along the second direction. This part is set so that the second welding portion 5 and the second weld mark 51 at least have a turning shape, that is, during the process of laser welding to form the second welding portion 5, the moving trajectory of the laser changes direction. This setting enables, under the condition of the same width, the parts of the second welding portion 5 with different directions to form a fixed connection with the pole 22, and the connection is more stable and reliable. For example Figure 7A first portion 511 and a second portion 512 form an L-shape, which forms a fixed connection with the pole 22 in both the first direction and the second direction compared to the straight shape, and is more stable when the second welding portion 5 is subjected to pulling forces in different directions.

[0066] Reference Figure 7 In order to further improve the reliability of the fixed connection between the second welding portion 5 and the pole 22, the number of the first portions 511 is at least two, and the first portions 511 are spaced apart along the second direction. The two ends of the first portions 511 in the first direction are respectively connected by the second portions 512 to form a closed structure.

[0067] Reference Figure 8 and Fig. 9 The first direction and the second direction may be perpendicular or intersecting. To some extent, it can be extended to mean that the first direction and the second direction may be arc-shaped or curved, so as to form closed figures of arc, irregular shape, triangle, circle or other shapes.

[0068] Reference Figure 4 and Figure 8 , the distance between the outer boundary of the second weld mark 51 and the boundary of the overlap area 6 is L, 1mm≤L. This setting maintains the coverage of the second weld portion 5 and the coverage of the overlap area 6 in a suitable ratio, thereby ensuring the reliability of the fixing of the overlap area 6. In some embodiments, the width of the second weld mark 51 at any position is D, D≥1mm, so as to ensure that the connection function of the second weld portion 5 is reliable and stable; in some embodiments, the thickness of the reinforcement plate 4 is S, 0.1mm≤S≤1.5mm, so as to ensure that the reinforcement plate 4 has a sufficient amount of material melted into the molten pool during laser welding to ensure the welding quality; in some optional embodiments, the depth of the second weld mark 51 on the pole 22 along the direction perpendicular to the connection surface 221 is H, 0.1mm≤H≤1.5mm, so as to ensure the reliability of the fixing of the second weld portion 5.

[0069] Reference Fig.10 and Fig.11 , respectively showing two situations in which the reinforcing plate 4 and the connecting surface 221 partially overlap and the projection of the reinforcing plate 4 on the connecting surface 221 falls within the area defined by the connecting surface 221.

[0070] The welding process in this embodiment is as follows:

[0071] The tab bundle 12 is attached to the connection surface 221 and then ultrasonically welded directly using ultrasonic welding equipment. Two adjacent tabs of the same tab are ultrasonically welded, and the same tab bundle 12 is ultrasonically welded to the pole 22 of the same polarity, so as to form a first welding portion 3 on the tab bundle 12 and the pole 22;

[0072] The reinforcing plate 4 is attached to the side of the pole lug bundle 12 facing away from the connecting surface 221, and the reinforcing plate 4 is pressed by external auxiliary equipment. The laser is emitted by the laser welding equipment. The laser moves along the inner track of the weight-reducing hole 42, and while the laser moves, the reinforcing plate 4 and the first welding part 3 are melted through, and part of the pole 22 is melted, and finally cooled to form the second welding part 5.

[0073] Embodiments 1 to 8 are provided respectively, and 1000 single cells are produced in each embodiment. In each embodiment, the outer boundary of the second weld mark 51 and the boundary of the overlap area 6 are spaced apart by L mm, the width of the second weld mark 51 at any position is D mm, the thickness of the reinforcing plate 4 is S mm, and the depth of the second weld portion 5 on the pole 22 along the direction perpendicular to the connecting surface 221 is H mm. For specific parameters, see Table 1.

[0074] Table 1

[0075]

[0076] Among them, the specific measurement method of L is: looking toward the second weld mark 51 along the direction perpendicular to the connecting surface 221, using a caliper or other measuring tool to measure the distance between the outer boundary of the second weld mark 51 and the outer boundary of the overlap area 6 to obtain L; the specific measurement method of D is: looking toward the second weld mark 51 along the direction perpendicular to the connecting surface 221, using a caliper or other measuring tool to measure the width of the second weld mark 51 to obtain the value of D; the specific measurement method of S is: before welding, using a caliper or other measuring tool to measure the thickness of the reinforcing plate 4 to obtain S; the specific measurement method of H is: using a caliper or other measuring tool to measure the thickness of the reinforcing plate 4 to obtain S; Figure 4 or Figure 6 Taking the cross-sectional view in as an example, the surface is polished and then treated with chemical solutions. Since the grain shapes of the molten metal and the unmelted metal are different, after the chemical solution treatment, it can be clearly seen that the second welding part 5 is different from the surrounding area that has not been melted and solidified. The size of the second welding part 5 along the direction perpendicular to the connecting surface 221 is measured with a measuring tool such as a caliper, and H is obtained.

[0077] The technical effect is characterized by the cracking ratio after the lug welding, the deformation and damage ratio of the protection plate, the peeling strength after welding, and the energy density of the battery cell. Among them, the cracking ratio is mainly affected by L, the deformation and damage ratio of the protection plate is mainly affected by S, the peeling strength after welding is mainly affected by D and H, and the energy density of the battery cell is mainly affected by S.

[0078] Among them, the test method of each technical effect parameter is as follows: taking the first group of embodiments 1-4 which are mainly used to characterize the cracking ratio as an example, four groups of single cells with the same number are taken corresponding to embodiments 1-4, and the number of cracks in the tab bundle in each group of single cells, the number of damage and deformation of the protection plate, the peel strength of the tab bundle in each single cell, and the energy density of each battery are tested respectively. The ratio of the number of cracks in each embodiment to the total number is the cracking ratio of the embodiment, and the same is true for the damage and deformation of the protection plate. The peel strength is the average of all the peel strengths in each embodiment, and the energy density is the average of all the energy densities in each embodiment.

[0079] Among them, the test method of peel strength is: pull the tab bundle 12 by a tensile testing machine until the tab bundle 12 is completely separated from the connection surface 221, and the maximum value of the tensile force obtained is the peel strength; the test method of cracking is: use the naked eye or a magnifying glass to observe whether there are cracks on the surface of the tab bundle welding; the test method of deformation and damage of the protection plate is: the operator can observe with the naked eye; the test method of energy density (refer to this standard IEC61960) is: multiple single cells are placed in the charger respectively, using a standardized charging mode, and stand for 2 hours after being fully charged, and then placed at room temperature to stop discharging at a fixed voltage, usually 3.0V. During the charging and discharging process, the battery capacity, battery operating voltage and battery weight are measured. Finally, the battery cell energy density is obtained using the formula battery capacity × battery operating voltage / battery weight.

[0080] On the other hand, the present application also provides a battery pack, which includes a box body; and the above-mentioned single cells, the single cells are placed in the box body, and a stable electrical connection is formed between the single cells.

[0081] The above description is only a partial implementation method of the embodiments of the present application and does not constitute any form of limitation on the application. The protection scope of the embodiments of the present application is not limited thereto. Any simple modifications, equivalent changes and modifications that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the embodiments of the present application should be covered within the protection scope of the embodiments of the present application.

Claims

1. A single cell battery, characterized in that: include: A battery cell (1), the battery cell (1) comprising a main body (11) and a tab bundle (12) connected to the main body (11); A cover assembly (2), the cover assembly (2) comprising a top cover (21) and a pole (22) arranged on the top cover (21), the pole (22) having a connection surface (221) facing the pole lug bundle (12); The tab bundle (12) and the connection surface (221) are welded by ultrasonic welding, and a first welding mark (31) is formed on the surface of the tab bundle (12) facing away from the connection surface (221); It also includes a reinforcing plate (4), wherein the reinforcing plate (4) has a hollow portion (41); The reinforcing plate (4), the tab bundle (12) and the connecting surface (221) are welded by laser, and a second weld mark (51) is formed on the surface of the reinforcing plate (4) facing away from the tab bundle (12), and the orthographic projection of the second weld mark (51) on the connecting surface (221) falls within an area defined by the outer edge of the orthographic projection of the hollow portion (41) on the connecting surface (221).

2. The single cell according to claim 1, characterized in that: The orthographic projection of the hollow portion (41) on the connecting surface (221) is located within a region defined by the outer edge of the orthographic projection of the reinforcing plate (4) on the connecting surface (221).

3. The single cell according to claim 2, characterized in that: The orthographic projection of the reinforcing plate (4) on the connecting surface (221) and the orthographic projection of the first weld mark (31) on the connecting surface (221) overlap in at least a partial area and form an overlapping area (6), and the orthographic projection of the hollow portion (41) on the connecting surface (221) is located within an area defined by an outer edge of the overlapping area (6).

4. The single cell according to claim 3, characterized in that: The reinforcing plate (4) has a first surface (X1) facing the connecting surface (221) and a second surface (X2) facing away from the connecting surface (221); The distance from the second weld mark (51) to the connecting surface (221) is greater than the distance from the first surface (X1) to the connecting surface (221) and is less than the distance from the second surface (X2) to the connecting surface (221).

5. The single cell according to claim 3, characterized in that: The area enclosed by the orthographic projection of the first weld mark (31) on the connection surface (221) falls within the area formed by the orthographic projection of the reinforcing plate (4) on the connection surface (221).

6. The single cell according to claim 1, characterized in that: The single battery has a first direction and a second direction, the first direction intersects with the second direction, and the first direction and the second direction are both parallel to the connection surface (221); The second weld mark (51) comprises a first portion (511) and a second portion (512) which are connected, wherein the first portion (511) extends along the first direction, and the second portion (512) extends along the second direction.

7. The single cell according to claim 6, characterized in that: The number of the first parts (511) is at least two, and the first parts (511) are spaced apart along the second direction, and the two ends of the first parts (511) in the first direction are respectively connected by the second parts (512) to form a closed structure.

8. The single cell according to claim 7, characterized in that: The reinforcing plate (4) is provided with a weight-reducing hole (42) extending therethrough; and an area defined by an outer edge of an orthographic projection of the second weld mark (51) on the connecting surface (221) covers an orthographic projection of the weight-reducing hole (42) on the connecting surface (221).

9. The single cell according to claim 3, characterized in that: The distance between the outer boundary of the second weld mark (51) and the boundary of the overlap area (6) is L, 1mm≤L.

10. The single cell according to claim 1, characterized in that: The single cell battery also includes at least one of the following technical features: a. The width of the second weld mark (51) at any position is D, D≥1mm; b. The thickness of the reinforcing plate (4) is S, 0.1 mm ≤ S ≤ 1.5 mm; c. The penetration depth of the second weld mark (51) on the pole (22) along a direction perpendicular to the connection surface (221) is H, and 0.1 mm ≤ H ≤ 1.5 mm.

11. A battery pack, characterized in that: include: a housing; and, A single cell as claimed in any one of claims 1 to 10.

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