Battery cell, battery pack and electrical device

Abstract

The present application relates to a battery cell, which comprises an electrode assembly, a connecting piece and a back protective film; the electrode assembly comprises a body and a tab connected to the body, the tab being connected to the connecting piece; the back protective film comprises a first protective film, a second protective film and a third protective film which are connected in sequence, the first protective film being connected to the body, the third protective film being connected to the connecting piece, and the second protective film being arranged on one side of the tab. The service life of the battery cell of the present application can be prolonged.

Description

Battery monomer, battery pack, and electrical equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese Patent Application No. 202311237042.2 filed on September 22, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a battery cell, a battery pack and an electrical device. Background Art

[0004] A battery cell includes a housing with a cavity within which an electrode assembly is positioned. The electrode assembly comprises a body and tabs connected to the body. The tabs are connected to connecting tabs, which are electrically connected to the top cover assembly. During the manufacture and assembly of a battery cell, the tabs and tabs are first welded together outside the cell's cavity. Tape is then applied to the tab welds before the cells are assembled. Currently, the tab tape commonly used during cell assembly can cause displacement due to insufficient redundancy, which can pull on the outer tabs, causing them to crack and impacting the battery cell's lifespan and safety.

[0005] In the development of battery technology, improving the service life and safety of battery cells is a technical problem that needs to be solved urgently.

[0006] Application Contents

[0007] The purpose of this application is to provide a battery cell, a battery pack, and an electrical device that can improve the service life of the battery cell and the safety performance of the battery.

[0008] In order to achieve the above objectives, this application is implemented through the following technical means:

[0009] In a first aspect, the present application provides a battery cell, comprising an electrode assembly, a connecting sheet, and a back protective film;

[0010] The electrode assembly includes a body and a tab connected to the body;

[0011] The tab is connected to the connecting piece;

[0012] The back protective film includes a first protective film, a second protective film and a third protective film;

[0013] The second protective film is disposed between the first protective film and the third protective film, and the second protective film is connected to the first protective film and the third protective film;

[0014] The first protective film has a first bonding surface, which is connected to the main body; the third protective film has a third bonding surface, which is connected to the connecting piece; the second protective film has a second non-bonding surface, which is arranged on one side of the tab.

[0015] Optionally, an adhesive layer is provided on the first adhesive surface and the third adhesive surface, and no adhesive layer is provided on the second non-adhesive surface.

[0016] Optionally, the first protective film and the third protective film are connected to both ends of the second protective film in the length direction, and the first protective film, the second protective film, and the third protective film are integrally formed.

[0017] Optionally, the surface area of ​​the back protective film close to the tab side is S, the area of ​​the second non-bonding surface is S2, the elongation of the second protective film is δ, the area of ​​the first bonding surface is S1, the area of ​​the third bonding surface is S3, the strength of the first protective film connected through the adhesive layer connecting piece is σ1, the strength of the third protective film connected to the body through the adhesive layer is σ3, and the battery cell satisfies: 0.033≤(S2 / S)*δ / {(S1 / S)*[σ1 / (σ1+σ3)]+(S3 / S)*[σ3 / (σ1+σ3)]}≤24.

[0018] Optionally, the battery cell satisfies: 0.1≤(S2 / S)*δ / {(S1 / S)*[σ1 / (σ1+σ3)]+(S3 / S)*[σ3 / (σ1+σ3)]}≤4.5.

[0019] Optionally, along the length direction of the back protective film, the size of the first protective film is L1, the size of the second protective film is L2, and the size of the third protective film is L3. The battery cell meets any one or more of the following conditions:

[0020] (a) 10mm≤L1≤60mm;

[0021] (b) 20 mm ≤ L2 ≤ 100 mm;

[0022] (c)10mm≤L3≤60mm.

[0023] Optionally, along the length direction of the back protective film, the size of the first protective film is L1, the size of the second protective film is L2, and the size of the third protective film is L3. The battery cell meets any one or more of the following conditions:

[0024] (d) 20 mm ≤ L1 ≤ 50 mm;

[0025] (e) 40 mm ≤ L2 ≤ 60 mm;

[0026] (f)20mm≤L3≤50mm.

[0027] Optionally, the battery cell satisfies any one or more of the following conditions:

[0028] (g)200mm 2 ≤S1≤3600mm 2 ;

[0029] (h)400mm 2 ≤S2≤6000mm 2 ;

[0030] (i) 200mm 2 ≤S3≤3600mm 2 ;

[0031] (j)800mm 2 ≤S≤13200mm 2 .

[0032] Optionally, the battery cell satisfies any one or more of the following conditions:

[0033] (k)400mm 2 ≤S1≤3000mm 2 ;

[0034] (l) 600mm 2 ≤S2≤3600mm 2 ;

[0035] (m)400mm 2 ≤S3≤3000mm 2 ;

[0036] (n)1400mm 2 ≤S≤9600mm 2 .

[0037] Optionally, along the width direction of the back protective film, the size W of the second protective film and the size w of the tab meet any one or more of the following conditions:

[0038] (o) 20mm≤W≤100mm;

[0039] (p)10mm≤w≤80mm.

[0040] Optionally, along the width direction of the back protective film, the size W of the second protective film and the size w of the tab meet any one or more of the following conditions:

[0041] (q) 30mm≤W≤70mm;

[0042] (r)20mm≤w≤50mm.

[0043] Optionally, the body has a second direction; in the second direction, the tab is bent and connected to a side of the connecting piece facing the body, and the bending position of the tab is located between the connecting piece and the body;

[0044] The third bonding surface is connected to a side of the connecting sheet facing away from the tab;

[0045] The second non-adhesive surface is arranged corresponding to the bending position of the tab.

[0046] Optionally, the first protective film and the third protective film have the same thickness of D1 μm, and the second protective film has a thickness of D2 μm, satisfying: 1.1≤D1 / D2≤2.

[0047] Optionally, two fourth protective films are further included, and the fourth protective films are respectively connected to the same side of the first protective film and the second protective film in the thickness direction.

[0048] Optionally, the thicknesses of the first protective film, the second protective film and the third protective film are the same, namely D, and satisfy: 10 μm ≤ D ≤ 150 μm, and / or 30 μm ≤ D ≤ 70 μm.

[0049] In a second aspect, the present application provides a battery pack comprising the battery cells in the above-mentioned embodiment.

[0050] In a third aspect, the present application provides an electrical device, which includes the battery cell in the above embodiment, and the battery cell is used to provide electrical energy.

[0051] Compared with the prior art, the battery cell in the embodiment of the present application has the following advantages: it includes an electrode assembly, a connecting sheet, and a back protective film; the electrode assembly includes a body and a tab connected to the body; the tab is connected to the connecting sheet; the back protective film includes a first protective film, a second protective film, and a third protective film; the second protective film is disposed between the first and third protective films, and the second protective film is connected to the first and third protective films; the first protective film has a first adhesive surface, which is connected to the body; the third protective film has a third adhesive surface, which is connected to the connecting sheet; the second protective film has a second non-adhesive surface, which is disposed on one side of the tab. The battery cell of the present application avoids cracking of the tab due to pulling between the tab and the back protective film during core assembly, thereby improving the service life and safety performance of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] FIG1 is a schematic diagram of the overall structure of a battery cell according to an embodiment of the present application.

[0053] FIG2 is a top view of the back protective film of an embodiment of the present application before bonding.

[0054] FIG3 is a side view of a single-layer back protective film according to an embodiment of the present application.

[0055] FIG4 is a side view of a single-layer back protective film according to another embodiment of the present application.

[0056] FIG5 is a top view of a battery cell after core assembly according to an embodiment of the present application.

[0057] FIG6 is a side view of a battery cell before core assembly according to an embodiment of the present application.

[0058] FIG. 7 is a top view of a battery cell before core assembly according to an embodiment of the present application.

[0059] In the figure: 1. Electrode assembly; 2. Main body; 20. Connection end surface; 21. First adhesive surface; 22. Second adhesive surface; 3. Tab; 4. Connecting piece; 41. First side surface; 42. Second side surface; 5. Back protective film; 511. Second protective film; 521. Third protective film; 522. First protective film; 523. Bending space; 524. Fourth protective film; 6. Front protective film; X, first direction; Z, second direction; Y, third direction. DETAILED DESCRIPTION

[0060] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0061] In the description of this application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like used in this application to indicate orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply 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 understood as a limitation on this application.

[0062] In the description of this application, it should be understood that the terms "connected," "connected," "fixed," etc. used in this application should be understood in a broad sense. For example, it can mean fixed connection, detachable connection, or integration; it can mean mechanical connection or welding connection; it can mean direct connection or indirect connection through an intermediate medium; it can mean internal communication between two elements or interaction between two elements, unless otherwise clearly defined. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0063] During the battery production process, in order to prevent the battery from short-circuiting, protective film (such as tape) needs to be attached to the front and back of the tabs after the tabs are welded to the connecting pieces. During the manufacturing process of the battery cells, the protective film will exert tension on the tabs. Especially during the core assembly process, the protective film on the back exerts a large tension on the tabs, which can easily cause the tabs to crack. The cracking of the tabs will reduce the current carrying capacity of the tabs, causing the temperature of the battery cells to rise. The cracked tabs can easily scratch the protective film, causing a short circuit and affecting the service life of the battery cells.

[0064] In view of this, in order to solve the problem of easy cracking of the tab, the inventors have designed a battery cell after in-depth research. As shown in Figures 1 to 7, in one embodiment of the present invention, a battery cell includes an electrode assembly 1, a connecting piece 4 and a back protective film 5; the electrode assembly 1 includes a body 2 and a tab 3 connected to the body 2; the tab 3 is connected to the connecting piece 4; the back protective film 5 includes a first protective film 522, a second protective film 511 and a third protective film 521; the second protective film 511 is arranged between the first protective film 522 and the third protective film 521, and the second protective film 511 is connected to the first protective film 522 and the third protective film 521;

[0065] The first protective film 522 has a first bonding surface, which is connected to the body 2 ; the third protective film 521 has a third bonding surface, which is connected to the connecting piece 4 ; the second protective film 511 has a second non-bonding surface, which is provided on one side of the tab 3 .

[0066] In the battery cell of the present application, the back protective film 5 is located on the side of the tab 3 away from the body 2 , so that the back protective film 5 has the effect of insulating protection to avoid short circuit and prevent foreign matter from falling into the electrode assembly 1 .

[0067] Furthermore, the first adhesive surface and the third adhesive surface are provided with adhesive layers, and the second non-adhesive surface is not provided with an adhesive layer.

[0068] In the battery cell of the present application, the back protective film 5 includes a first protective film 522, a second protective film 511 and a third protective film 521. The opposite ends of the second protective film 511 are respectively connected to the first protective film 522 and the third protective film 521. The main body 2 includes a first adhesive surface 21. The first adhesive surface 21 provides a connection position for the back protective film 5. The first protective film 522 is connected to the first adhesive surface 21 to realize the connection between the back protective film 5 and the main body 2. The third protective film 521 is connected to the connecting piece 4 to realize the connection between the back protective film 5 and the connecting piece 4. The back protective film 5 is fixed by the first protective film 522 and the third protective film 521. Among them, Figures 6-7 show the state of the electrode assembly 1 before the core is closed, and Figure 5 shows the state of the electrode assembly 1 after the core is closed. When the electrode assembly 1 is in the core closing stage, that is, when it changes from Figures 6-7 to the state of Figure 5, the pole ear 3 needs to be bent. When the pole ear 3 is bent, since the second protective film 511 is not provided with a glue layer, a certain relative movement can occur between the pole ear 3 and the second protective film 511. The pole ear 3 is movably arranged relative to the second protective film 511, providing a relative movement amount between the pole ear 3 and the second protective film 511 to avoid mutual pulling and tearing of the pole ear 3 and the back protective film 5 after bonding, which helps to improve the yield of the pole ear 3 in the core closing stage, reduce production costs, and improve the service life and safety of the battery cell.

[0069] In one embodiment, the shapes and sizes of the first protective film 522 , the second protective film 511 , and the third protective film 521 are not limited.

[0070] In one embodiment, the side of the second protective film 511 facing the tab 3 is a second non-adhesive surface, which ensures that the second protective film 511 and the tab 3 do not adhere to each other and can maintain relative movement, thereby preventing the tab 3 from being pulled and torn during core closing.

[0071] In one embodiment, the first and third protective films 522 and 521 are connected to the longitudinal ends of the second protective film 511. The first, second, and third protective films 522 and 511 are integrally formed. This integrated formation can reduce the production cost of the back protective film 5, improve production efficiency, and facilitate bonding and fixation, thereby improving bonding efficiency.

[0072] In one embodiment, the surface area of ​​the back protective film 5 close to the tab 3 is S, that is, the area of ​​the back protective film 5 is S, the area of ​​the second non-bonding surface is S2, the elongation δ of the second protective film 511, the area of ​​the first bonding surface is S1, the area of ​​the third bonding surface is S3, the strength of the connection between the first protective film 522 and the connecting piece 4 through the glue layer is σ1, the strength of the connection between the third protective film 521 and the body 2 through the glue layer is σ3, and the battery cell satisfies: 0.033≤(S2 / S)*δ / {(S1 / S)*[σ1 / (σ1+σ3)]+(S3 / S)*[σ3 / (σ1+σ3)]}≤24.

[0073] When the back protective film 5 of the battery cell is set to meet the above conditions, the tab 3 is not easily torn while the bonding strength of the back protective film 5 can be ensured.

[0074] Furthermore, the battery cell also satisfies the following: 0.1≤(S2 / S)*δ / {(S1 / S)*[σ1 / (σ1+σ3)]+(S3 / S)*[σ3 / (σ1+σ3)]}≤4.5. When the backside protective film 5 of the battery cell meets the above conditions, the tab 3 is not easily torn and the adhesive strength of the backside protective film 5 is ensured to be good.

[0075] Further embodiments are provided: wherein, the size S1 can be obtained by disassembling the battery cell, unfolding the back protective film 5, and measuring the area of ​​the first adhesive surface of the first protective film 522 corresponding to the adhesive layer attached to the body 2 using a projection measuring instrument; the size S2 can be obtained by disassembling the battery cell, unfolding the back protective film 5, and measuring the area of ​​the second non-adhesive surface of the second protective film 511 not provided with an adhesive layer using a projection measuring instrument; the size S3 can be obtained by disassembling the battery cell, unfolding the back protective film 5, and measuring the area of ​​the third adhesive surface of the third protective film 521 corresponding to the adhesive layer attached to the connecting piece 4 using a projection measuring instrument; the size S is the sum of the areas of S1, S2, and S3;

[0076] The elongation is measured as follows: the percentage of the total deformation ΔL of the gauge section after the second protective film 511 is stretched and broken to the original gauge section length L: δ = ΔL / L × 100%.

[0077] The mechanical impact test method is used to measure the strength σ1 of the connection between the first protective film 522 and the connecting piece 4 through the adhesive layer and the strength σ3 of the connection between the third protective film 521 and the body 2 through the adhesive layer.

[0078] Method for measuring the peeling force of the back protective film 5: Use a special clamp to clamp the second protective film 511 of the battery cell and tear off the back protective film 5. Record the maximum tensile force when the back protective film 5 is completely torn off as the peeling force of the back protective film 5.

[0079] Method for measuring the number of torn layers in the tab 3: The number of torn layers in the tab 3 can be determined by disassembling the battery cell and observing the number of torn layers in the tab 3. The results are shown in Table 1.

[0080] Table 1 Results of the number of tab tearing layers in Examples 1-31

[0081] According to Table 1 above, when the battery cell satisfies: 0.033≤(S2 / S)*δ / {(S1 / S)*[σ1 / (σ1+σ3)]+(S3 / S)*[σ3 / (σ1+σ3)]}≤24, the peeling force required to tear off the back protective film 5 is greater, the back protective film 5 is not easy to fall off, and can provide good protection for the tab 3 to avoid short circuit. At the same time, it can better ensure that the tab 3 is not easily torn, thereby improving the service life of the battery cell.

[0082] In one embodiment, along the length direction of the back protective film 5, the size of the first protective film 522 is L1, where 10mm≤L1≤60mm. Setting L1 within this range can ensure the connection strength between the first protective film 522 and the body 2.

[0083] Furthermore, 20 mm ≤ L1 ≤ 50 mm, and setting L1 within this range can better ensure the connection strength between the first protective film 522 and the body 2 .

[0084] In one embodiment, along the length direction of the back protective film 5, the size of the second protective film 511 is L2, where 20mm≤L2≤100mm. Setting L2 within this range can ensure a certain redundancy between the second protective film 511 and the tab 3, thereby reducing the tearing of the tab 3.

[0085] Furthermore, 40 mm ≤ L2 ≤ 60 mm. Setting L2 within this range can better ensure a certain redundancy between the second protective film 511 and the tab 3 , thereby reducing the tearing of the tab 3 .

[0086] In one embodiment, the length of the third protective film 521 is L3, where 10 mm ≤ L3 ≤ 60 mm. Setting the length of the third protective film 521 within this range ensures the bonding strength between the third protective film 521 and the connecting sheet 4.

[0087] Furthermore, 20 mm ≤ L3 ≤ 50 mm, and setting the length of the third protective film 521 within this range can better ensure the bonding strength between the third protective film 521 and the connecting piece 4 .

[0088] In one embodiment, the surface area of ​​the back protective film 5 close to the tab 3 is S, that is, the area of ​​the back protective film 5 is S, where 800 mm 2 ≤S≤13200mm 2 Setting the area of ​​the back protective film 5 within this range can not only be applicable to battery cells of different sizes, but also reduce the waste of the back protective film 5.

[0089] Furthermore, 1400mm 2 ≤S≤9600mm 2 Setting the area of ​​the back protective film 5 within this range can not only better adapt to battery cells of different sizes, but also reduce the waste of the back protective film 5.

[0090] In one embodiment, the area of ​​the first bonding surface is S1, wherein 200 mm 2 ≤S1≤3600mm 2 Setting the area of ​​the first bonding surface within this range can better ensure the bonding strength between the first protective film 522 and the body 2.

[0091] Furthermore, 400mm 2 ≤S1≤3000mm 2 Setting the area of ​​the first bonding surface within this range can better ensure the bonding strength between the first protective film 522 and the body 2.

[0092] In one embodiment, the area of ​​the second non-adhesive surface is S2, wherein 400 mm 2 ≤S2≤6000mm 2 Setting the area of ​​the second non-adhesive surface within this range can better ensure that there is sufficient movable space between the tab 3 and the second protective film 511, thereby reducing the tearing of the tab 3.

[0093] Furthermore, 600mm 2 ≤S2≤3600mm 2 Setting the area of ​​the second non-adhesive surface within this range can better ensure that there is sufficient movable space between the tab 3 and the second protective film 511, thereby reducing the tearing of the tab 3.

[0094] In one embodiment, the area of ​​the third bonding surface is S3, wherein 200 mm 2 ≤S3≤3600mm 2 The area S3 of the third bonding surface is set within this range to better ensure the connection strength between the third protective film 521 and the connecting sheet 4 .

[0095] Furthermore, 400mm 2 ≤S3≤3000mm2 The area S3 of the third bonding surface is set within this range to better ensure the connection strength between the third protective film 521 and the connecting piece 4.

[0096] In one embodiment, the elongation of the second protective film 511 is δ, wherein 0.3≤δ≤0.8. Setting the elongation of the second protective film 511 within this range can reduce the probability of tearing of the tab 3 during the core assembly process.

[0097] Furthermore, 0.5≤δ≤0.6, and setting the elongation of the second protective film 511 within this range can reduce the probability of the tab 3 being torn during the core closing process.

[0098] In one embodiment, along the width direction of the back protective film 5 , the size W of the second protective film 511 is 20 mm ≤ W ≤ 100 mm. When the second protective film 511 is set within this range, it can provide better insulation protection for the tab 3 .

[0099] Furthermore, 30 mm ≤ W ≤ 70 mm, when the second protective film 511 is set within this range, it can provide better insulation protection for the tab 3 .

[0100] In one embodiment, along the width direction of the back protective film 5 , the dimension w of the tab 3 is 10 mm ≤ w ≤ 80 mm. Setting the tab 3 within this range can better ensure the overcurrent of the battery cell.

[0101] Furthermore, 20 mm ≤ w ≤ 50 mm, and the tab 3 is set within this range, which can better ensure the overcurrent of the battery cell and improve the energy density of the battery cell.

[0102] In one embodiment, the main body 2 has a second direction Z; in this embodiment, the second direction Z is the height direction of the main body 2. In the second direction Z, the tab 3 is bent and connected to the side of the connecting piece facing the main body 2, and the bending position of the tab 3 is located between the connecting piece 4 and the main body 2; the third bonding surface is connected to the side of the connecting piece 4 facing away from the tab 3; the second non-bonding surface is arranged corresponding to the bending position of the tab 3.

[0103] In one embodiment, the first and third protective films 522 and 521 have the same thickness, D1 μm, and the second protective film 511 has a thickness of D2 μm, satisfying the following: 1.1 ≤ D1 / D2 ≤ 2. The thickness of the first protective film 522 is the same as that of the third protective film 521 and is greater than that of the second protective film 511. This allows for a bending space 523 for the tab 3 to be formed at the location of the second protective film 511 corresponding to the tab 3, thereby better preventing the tab 3 from tearing.

[0104] Furthermore, by setting 1.1≤D1 / D2≤2, a certain bending space can be ensured to avoid the tab 3 from being torn, and at the same time the bending space 523 will not be too large, resulting in excessive space occupied by the back protective film 5.

[0105] In one embodiment, two fourth protective films 524 are further included, and the fourth protective films 524 are respectively connected to the same side of the thickness direction of the first protective film 522 and the second protective film 511. Preferably, one fourth protective film 524 is connected to the side of the first protective film 522 close to the body 2, and the other fourth protective film 524 is connected to the side of the third protective film 521 close to the connecting piece 4. More preferably, both sides of the fourth protective film 524 are provided with an adhesive layer. By providing the fourth protective film 524, a bending space 523 can be formed at the bending position of the corresponding tab 3, which can better prevent the tab 3 from being torn.

[0106] In one embodiment, the thicknesses of the first protective film 522, the second protective film 511 and the third protective film 521 are the same, all D, where 10μm≤D≤150μm. The first protective film 522, the second protective film 511 and the third protective film 521 are set to have the same thickness to facilitate the integrated processing and manufacturing of the back protective film 5. In addition, setting the thickness within this range can ensure that the back protective film 5 is wear-resistant and can save material costs.

[0107] Furthermore, D can be set to: 30 μm≤D≤70 μm, which can save more material costs while ensuring the wear resistance of the back protection film 5.

[0108] Furthermore, the battery cell also includes a front protective film 6 disposed opposite the back protective film 5. The body 2 includes a second adhesive surface 22 and a connection end surface 20 facing the connection piece 4. The body 2 also has a third direction Y. In this embodiment, the third direction Y is the width of the body 2. The second adhesive surface 22 and the first adhesive surface 21 are respectively connected to opposite sides of the connection end surface 20 in the third direction Y. The front protective film 6 is respectively bonded to the second adhesive surface 22, the tab 3, and the connection piece 4. The front adhesive film 6 further secures and insulates the tab 3 to the connection piece 4. The first direction X, the second direction Z, and the third direction Y are mutually perpendicular.

[0109] In one embodiment, in the width direction of the front protective film 6, the size of the front protective film 6 is larger than the size of the tab 3, thereby providing better insulation protection for the tab 3 and preventing foreign matter from falling into the body 2, thereby improving safety in use.

[0110] Furthermore, after the tab 3 is bent, the connecting piece 4 includes a first side surface 41 facing the connecting end surface 20 in the second direction Z and a second side surface 42 disposed opposite the first side surface 41. The front protective film 6 and the tab 3 are connected to the first side surface 41, and the back protective film 5 is connected to the second side surface 42. The two opposite sides of the connecting piece 4 in the second direction Z are connected to the body 2 via the front protective film 6 and the back protective film 5, respectively, thereby improving the connection strength between the connecting piece 4 and the body 2. At the same time, the opposite sides of the tab 3 are insulated and protected by the front protective film 6 and the back protective film 5, respectively, to prevent foreign matter from falling into the body 2 and causing a short circuit, thereby improving safety in use.

[0111] In one embodiment, the main body 2 has a first direction X. In this embodiment, the first direction X is the length direction of the main body 2. The main body 2 is connected to at least two spaced-apart tabs 3 in the first direction X. A back protective film 5 simultaneously achieves synchronous covering of the spaced-apart tabs 3 in the first direction X, thereby improving the efficiency of the bonding operation.

[0112] The present application provides a battery pack, which includes a box body, in which the battery cells of the above embodiment are arranged.

[0113] The present application also provides an electrical device, in which the battery pack in the above embodiment serves as an energy source for the electrical device.

[0114] The present application also provides a method for manufacturing a battery cell, which is applicable to the above-mentioned battery cell and includes the following steps: the back protective film 5 includes a first protective film 522, a second protective film 511, and a third protective film 521; the second protective film 511 has opposite ends connected to the first protective film 522 and the third protective film 521, respectively; during the battery cell gluing step, the first protective film 522 has a first bonding surface, which has an adhesive layer and is connected to the first bonding surface 21 of the body 2 to achieve the connection between the back protective film 5 and the body 2; the third protective film 521 has a third bonding surface, which has an adhesive layer and is connected to the connecting piece 4; the tab 3 and the connecting piece 4 are welded, and the third bonding surface covers the welding position to achieve the connection between the back protective film 5 and the connecting piece 4. The side of the tab 3 facing the back protective film 5 is installed corresponding to the position of the second non-bonding surface of the second protective film 511 in the first direction X; the second non-bonding surface is not provided with an adhesive layer, so that the tab 3 and the second protective film 511 can move relative to each other. During the core assembling step, the battery cell changes from the state of Figures 6-7 to the state of Figure 5, wherein the back protective film 5 is located on the outer side of the pole tab 3. When the pole tab 3 is bent, the pole tab 3 and the second protective film 511 are correspondingly arranged in the first direction X. The second protective film 511 and the pole tab 3 can move relative to each other to avoid tearing force between the pole tab 3 and the second protective film 511, thereby ensuring the integrity of the pole tab 3 and improving the yield rate of the core assembling step.

[0115] Furthermore, as shown in the figure, in the battery cell gluing step, the connecting piece 4 includes a first side surface 41 and a second side surface 42 arranged relatively to each other along the second direction Z, wherein the first side surface 41 faces the connecting end surface 20 of the main body 2, and the second side surface 42 faces away from the connecting end surface 20 of the main body 2. The pole tab 3 is connected to the first side surface 41, and the third protective film 521 is adhered to the second side surface 42. The pole tab 3 and the third protective film 521 are respectively connected to two opposite surfaces of the connecting piece 4, thereby avoiding contact between the pole tab 3 and the third protective portion 521, further avoiding tearing and tearing between the back protective film 5 and the pole tab 3, and further improving the yield rate of the core assembly step.

[0116] As one embodiment, as shown in Figure 7, before the core assembly step, the battery cell includes two electrode assemblies 1, two connecting sheets 4 and four back protective films 5. The main bodies 2 in the two battery cell assemblies 1 are respectively located on opposite sides of the connecting sheets 4, and the connecting end faces 20 of the main bodies 2 face the peripheral side surfaces of the connecting sheets 4. The opposite sides of the connecting sheets 4 are respectively connected to the main body 2 through the back film 5, and the second protective film 511 is arranged corresponding to the position of the tab 3.

[0117] During the cell assembly step, as shown in FIG1 , the first side surface 41 is rotated toward the connection end surface 20 , the connection end surface 20 and the first side surface 41 are disposed opposite each other, and the tab 3 is bent away from the first adhesive surface 21 , with the tab 3 located between the connection end surface 20 and the first side surface 41 . The bent tab 3 is more easily connected to the connecting piece 4 .

[0118] Furthermore, the battery cell also includes a front protective film 6 arranged opposite to the back protective film 5, and the battery cell includes a second adhesive surface 22, and the second adhesive surface 22 and the first adhesive surface 21 are respectively connected to the opposite sides of the connecting end surface 20 in the third direction Y. Before the battery cell gluing step, the connecting piece 4 is welded and fixed to the pole ear 3, that is, the pole ear 3 is welded on the first side 41 to form a weld. In the battery cell gluing step, the front protective film 6 is respectively bonded to the second adhesive surface 22 and the first side 41, and one end of the front protective film 6 is connected to the second adhesive surface 22 to achieve fixation of the front protective film 6 to the main body 2, and the other end of the front protective film 6 is connected to the first side 41 to achieve fixation of the front film 6 to the connecting piece 4, wherein one end of the pole ear 3 is located between the front protective film 6 and the first side 41, and the front protective film 6 covers the weld, thereby preventing welding slag from falling into the main body 2, thereby improving battery safety.

[0119] In summary, the present embodiment provides a battery cell. The electrode assembly 1 includes a body 2 and a tab 3. The tab 3 is connected to the body 2, and the tab 3 is connected to the connecting piece 4, so that the body 2 is electrically connected to the connecting piece 4 through the tab 3. A back protective film 5 is bonded to a corresponding position of the tab 3. The back protective film 5 is used to insulate the tab 3 and prevent particulate matter from falling into the body 2. Among them, the back protective film 5 includes a first protective film 522, a second protective film 511 and a third protective film 521. The opposite ends of the second protective film 511 are respectively connected to the first protective film 522 and the third protective film 521. The body 2 includes a first adhesive surface 21. The first adhesive surface 21 provides a connection position for the back protective film 5. The first protective film 522 is connected to the first adhesive surface 21 to achieve the connection between the back protective film 5 and the body 2. The third protective film 521 is connected to the connecting piece 4 to achieve the connection between the back protective film 5 and the connecting piece 4. The first protective film 522 has a first adhesive surface, and an adhesive layer is provided on the first adhesive surface. The third protective film 521 has a third adhesive surface, and an adhesive layer is provided on the third adhesive surface. The backside protective film 5 is secured by the first and third protective films 522 and 521. The side of the second protective film 511 facing the tab 3 corresponds to the tab 3. The side of the second protective film 511 facing the tab 3 is a second non-bonding surface, and no adhesive layer is provided on the second non-welding surface. When the tab 3 is bent, a certain amount of relative movement occurs between the tab 3 and the second protective film 511. The tab 3 is movable relative to the second protective film 511, providing a relative movement between the tab 3 and the second protective film 511 to prevent the tab 3 and the backside protective film 5 from pulling and tearing after bonding. This helps improve the tab 3 yield rate during the core assembly stage, reduce production costs, and extend the service life and safety of the battery cells. Furthermore, the backside protective film 5 is located on the side of the tab 3 facing away from the body 2, providing insulation protection and preventing foreign matter from falling into the interior of the electrode assembly 1, thereby reducing the defective rate of the battery cells and reducing production costs.

[0120] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and replacements can be made without departing from the technical principles of the present application. These improvements and replacements should also be regarded as the scope of protection of the present application.

Claims

1. A battery cell, comprising an electrode assembly (1), a connecting sheet (4) and a back protective film (5); The electrode assembly (1) comprises a body (2) and an electrode tab (3) connected to the body (2); The pole lug (3) is connected to the connecting piece (4); The back protective film (5) comprises a first protective film (522), a second protective film (511) and a third protective film (521); The second protective film (511) is disposed between the first protective film (522) and the third protective film (521), and the second protective film (511) is connected to the first protective film (522) and the third protective film (521); The first protective film (522) has a first adhesive surface, which is connected to the main body (2); the third protective film (521) has a third adhesive surface, which is connected to the connecting piece (4); the second protective film (511) has a second non-adhesive surface, which is arranged on one side of the tab (3).

2. The battery cell according to claim 1, wherein: The first bonding surface and the third bonding surface are provided with adhesive layers.

3. The battery cell according to claim 2, wherein: The first protective film (522) and the third protective film (521) are connected to the two ends of the second protective film (511) in the length direction, and the first protective film (522), the second protective film (511) and the third protective film (521) are integrally formed.

4. The battery cell according to claim 3, wherein: The surface area of ​​the back protective film (5) on the side close to the pole ear (3) is S, the area of ​​the second non-bonding surface is S2, the elongation of the second protective film (511) is δ, the area of ​​the first bonding surface is S1, the area of ​​the third bonding surface is S3, the strength of the connection between the first protective film (522) and the connecting sheet (4) is σ1, the strength of the connection between the third protective film (521) and the body (2) is σ3, and the single battery satisfies: 0.033≤(S2 / S)*δ / {(S1 / S)*[σ1 / (σ1+σ3)]+(S3 / S)*[σ3 / (σ1+σ3)]}≤24.

5. The battery cell according to claim 4, wherein: The battery cell satisfies: 0.1≤(S2 / S)*δ / {(S1 / S)*[σ1 / (σ1+σ3)]+(S3 / S)*[σ3 / (σ1+σ3)]}≤4.

5.

6. The battery cell according to claim 1, wherein: Along the extension direction of the back protective film (5), the size of the first protective film (522) is L1, the size of the second protective film (511) is L2, the size of the third protective film (521) is L3, and the battery cell satisfies any one or more of the following conditions at the same time: (a) 10mm≤L1≤60mm; (b) 20 mm ≤ L2 ≤ 100 mm; (c)10mm≤L3≤60mm.

7. The battery cell according to claim 6, wherein: The battery cell satisfies any one or more of the following conditions: (d) 20 mm ≤ L1 ≤ 50 mm; (e) 40 mm ≤ L2 ≤ 60 mm; (f)20mm≤L3≤50mm.

8. The battery cell according to claim 4, wherein: The battery cell satisfies any one or more of the following conditions: (g)200mm 2 ≤S1≤3600mm 2 ; (h)400mm 2 ≤S2≤6000mm 2 ; (i)200mm 2 ≤S3≤3600mm 2 ; (j)800mm 2 ≤S≤13200mm 2 。 9. The battery cell according to claim 8, wherein: The battery cell satisfies any one or more of the following conditions: (k)400mm 2 ≤S1≤3000mm 2 ; (l)600mm 2 ≤S2≤3600mm 2 ; (m)400mm 2 ≤S3≤3000mm 2 ; (n)1400mm 2 ≤S≤9600mm 2 。 10. The battery cell according to claim 1, wherein: Along the width direction of the back protective film (5), the size W of the second protective film (511) and the size w of the tab (3) satisfy any one or more of the following conditions: (o) 20 mm ≤ W ≤ 100 mm; (p)10mm≤w≤80mm.

11. The battery cell according to claim 10, wherein: The battery cell meets any one of the following conditions: (q) 30 mm ≤ W ≤ 70 mm; (r)20mm≤w≤50mm.

12. The battery cell according to claim 1, wherein: The body (2) has a second direction (Z); In the second direction (Z), the pole lug (3) is connected to a side of the connecting sheet (4) facing the body (2) after being bent, and the bending position of the pole lug (3) is located between the connecting sheet (4) and the body (2); The third bonding surface is connected to a side of the connecting sheet (4) facing away from the tab (3); The second non-adhesive surface is arranged corresponding to the bending position of the tab (3).

13. The battery cell according to claim 2, wherein: The thickness of the first protective film (522) and the third protective film (521) are the same, both being D1 μm, and the thickness of the second protective film (511) is D2 μm, satisfying: 1.1≤D1 / D2≤2.

14. The battery cell according to claim 3, wherein: It also includes two fourth protective films (524), and the fourth protective films (524) are respectively connected to the same side of the first protective film (522) and the second protective film (511) in the thickness direction.

15. The battery cell according to claim 3, wherein: The thicknesses of the first protective film (522), the second protective film (511) and the third protective film (521) are the same, namely D, satisfying the following: 10 μm≤D≤150 μm.

16. The battery cell according to claim 5, wherein: The battery cell satisfies any one or more of the following conditions: (g)200mm 2 ≤S1≤3600mm 2 ; (h)400mm 2 ≤S2≤6000mm 2 ; (i)200mm 2 ≤S3≤3600mm 2 ; (j)800mm 2 ≤S≤13200mm 2 。 17. The battery cell according to claim 6, wherein: The surface area of ​​the back protective film (5) on the side close to the pole ear (3) is S, the area of ​​the second non-bonding surface is S2, the area of ​​the first bonding surface is S1, the area of ​​the third bonding surface is S3, and the battery cell satisfies any one or more of the following conditions at the same time: (g)200mm 2 ≤S1≤3600mm 2 ; (h)400mm 2 ≤S2≤6000mm 2 ; (i)200mm 2 ≤S3≤3600mm 2 ; (j)800mm 2 ≤S≤13200mm 2 。 18. The battery cell according to claim 7, wherein: The surface area of ​​the back protective film (5) on the side close to the pole ear (3) is S, the area of ​​the second non-bonding surface is S2, the area of ​​the first bonding surface is S1, the area of ​​the third bonding surface is S3, and the battery cell satisfies any one or more of the following conditions at the same time: (g)200mm 2 ≤S1≤3600mm 2 ; (h)400mm 2 ≤S2≤6000mm 2 ; (i)200mm 2 ≤S3≤3600mm 2 ; (j)800mm 2 ≤S≤13200mm 2 。 19. A battery pack comprising the battery cell according to any one of claims 1 to 18.

20. An electrical device comprising the battery cell according to any one of claims 1 to 18, wherein the battery cell is used to provide electrical energy.

Images