Battery cell and battery

Abstract

The utility model discloses a battery cell and a battery. The battery cell provided by the utility model comprises a first pole piece, a second pole piece and an isolating membrane, one of the first pole piece and the second pole piece is a positive pole piece, and the other one is a negative pole piece. The first pole piece and the second pole piece are separated by the isolating membrane, the first pole piece, the isolating membrane and the second pole piece are mutually laminated, the isolating membrane comprises a plurality of straight sections and bent sections which are alternately connected, at least one bent section comprises a thinned part, and the thickness of the thinned part is smaller than that of the straight section. According to the battery cell disclosed by the embodiment of the utility model, the isolating membrane at the corner is thinned instead of thinning the pole piece, so that the thickness of the corner of the battery cell is reduced, a space is provided for bending the pole piece, stress concentration is avoided, the cracking phenomenon is reduced, and meanwhile, as the active substance layer is not thinned, dust and puncture phenomena are not easy to generate.

Description

TECHNICAL FIELD

[0001] The utility model relates to secondary battery technical field, concretely relates to a battery and electric core. BACKGROUND

[0002] The electric core is usually composed of a positive electrode sheet, a negative electrode sheet and a separator. In the mainstream electric core processing technology, a winding type electric core is included, that is, the positive electrode sheet, the separator and the negative electrode sheet are sequentially laminated and wound to form the electric core. However, in the long cycle use process of the electric core, the winding core will swell, and the stress of the electrode sheet at the corner will concentrate, and the electrode sheet at the corner is prone to cracking after being repeatedly extruded. SUMMARY

[0003] The utility model discloses at least one of the technical problems in the prior art. To this end, the utility model provides an electric core, which can reduce the cracking at the corner and avoid problems such as dust and puncture.

[0004] The utility model further provides a battery with the electric core.

[0005] According to the electric core of the first aspect embodiment of the utility model, one of the first electrode sheet and the second electrode sheet is a positive electrode sheet, and the other is a negative electrode sheet. The separator separates the first electrode sheet and the second electrode sheet, and the first electrode sheet, the separator and the second electrode sheet are laminated with each other. The separator includes a plurality of alternating straight sections and curved sections. At least one curved section includes a thinning portion, and the thickness of the thinning portion is less than the thickness of the straight section.

[0006] According to the electric core of the utility model embodiment, at least the following beneficial effects are obtained: in the prior art, the active material layer of the electrode sheet is thinned. During the charging and discharging process, the active material layer repeatedly participates in the charging and discharging process. Therefore, the active material layer at the edge of the thinned part will be subjected to a large stress and will fall off, thereby generating dust. The dust may puncture the separator in the later stage, affecting the quality of the electric core and causing safety problems. The electric core of the utility model embodiment is thinned at the corner of the separator instead of the electrode sheet, thereby reducing the thickness of the corner of the electric core, providing space for the bending of the electrode sheet and avoiding stress concentration, thereby reducing the cracking phenomenon. Since the active material layer is not thinned, dust and puncture are also less likely to occur.

[0007] According to some embodiments of the utility model, the thinning portion is formed with a groove, and the groove is located on any side of the curved section in the thickness direction.

[0008] According to some embodiments of the present application, the groove is towards the first pole piece, and the first pole piece is a negative pole piece.

[0009] According to some embodiments of the present application, the thinning portion is formed with a plurality of grooves, at least one of which is located on one side of the bending segment towards the center of the battery cell, and at least one of which is located on one side of the bending segment away from the center of the battery cell.

[0010] According to some embodiments of the present application, the thinning portion is provided with a plurality of grooves along the direction of stacking of the first pole piece, the separator and the second pole piece.

[0011] According to some embodiments of the present application, the length of the thinning portion gradually increases from the center of the battery cell to the periphery of the battery cell.

[0012] According to some embodiments of the present application, the length of the thinning portion is L1, and 0.5mm≤L1≤2mm.

[0013] According to some embodiments of the present application, the separator includes a diaphragm base layer and two diaphragm coating layers, the diaphragm base layer includes a coated area and a bare area, the two sides of the coated area are covered by the two diaphragm coating layers respectively, and at least one side of the bare area is exposed outside the diaphragm coating layer to form the thinning portion.

[0014] According to some embodiments of the present application, the thickness of a single diaphragm coating layer is D1, and 0.5μm≤D1≤4μm.

[0015] The battery according to the second aspect of the embodiments of the present application comprises a shell and the battery cell according to any one of the first aspect of the embodiments.

[0016] The battery according to the embodiments of the present application has at least the following beneficial effects: in the prior art, the active material layer of the thinned pole piece is repeatedly involved in the charging and discharging process, so the active material layer at the edge of the thinned portion will be subjected to a large stress and will fall off, thereby generating dust, which may pierce the separator in the later stage and affect the quality of the battery cell and cause safety problems. The battery cell according to the embodiments of the present application is thinned by the separator at the corner, rather than the pole piece, thereby reducing the thickness of the corner of the battery cell, providing space for the bending of the pole piece and avoiding stress concentration, thereby reducing the cracking phenomenon, and since the active material layer is not thinned, dust and piercing phenomenon are also less likely to occur, thereby improving the quality of the battery.

[0017] Additional aspects and advantages of the present application will be given in part in the following description, and will become apparent from the following description, or will be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0018] The utility model will be further explained in connection with the drawings and embodiments, wherein:

[0019] Figure 1 It is the structure schematic drawing of the electric core in an embodiment of the utility model;

[0020] Figure 2 It is the structure schematic drawing of the electric core in an embodiment of the utility model; Figure 1 It is the first embodiment enlarged view of A area in the utility model;

[0021] Figure 3 It is the second embodiment enlarged view of A area in the utility model; Figure 1 It is the second embodiment enlarged view of A area in the utility model;

[0022] Figure 4 It is the local schematic view of the isolation film of the electric core in an embodiment of the utility model.

[0023] Reference signs: electric core 100, first pole piece 101, isolation film 102, second pole piece 103, flat section 104, curved section 105, first pole lug 106, second pole lug 107, thinning part 201, recess 202, diaphragm base layer 401, diaphragm coating layer 402. DETAILED DESCRIPTION

[0024] The embodiments of the utility model are described in detail below, and the examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the utility model, and cannot be understood as limiting the utility model.

[0025] In the description of the utility model, it is understood that the orientation description, such as up, down, front, back, left, right, etc. The orientation or positional relationship shown in the drawing is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the utility model.

[0026] In the description of the utility model, the meaning of several is more than one, the meaning of multiple is more than two, greater than, less than, more than, etc. It is understood that the number is not included, and the above, below, etc. It is understood that the number is included. If it is described to the first, the second is only used for distinguishing the technical features for the purpose, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the sequence of indicated technical features.

[0027] In the description of the utility model, unless otherwise explicitly limited, the words such as setting, installing, connecting should be understood broadly, and the skilled in the art can determine the specific meaning of the above words in the utility model according to the specific content of the technical scheme.

[0028] In the description of the utility model, the description of the reference terms '' an embodiment '', '' some embodiments '', '' illustrative embodiment '', '' example '', '' specific example '' or '' some examples '' means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are contained in at least one embodiment or example of the utility model. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0029] Reference Figure 1 And Figure 2 According to the first aspect embodiment of the utility model, the electric core 100 includes the first pole piece 101, the second pole piece 103 and the isolation film 102. One of the first pole piece 101 and the second pole piece 103 is the positive pole piece, and the other is the negative pole piece. The isolation film 102 separates the first pole piece 101 and the second pole piece 103, and the first pole piece 101, the isolation film 102 and the second pole piece 103 are mutually laminated, the isolation film 102 includes a plurality of alternating connection straight sections 104 and curved sections 105, at least one curved section 105 includes a thinning portion 201, and the thickness of the thinning portion 201 is less than the thickness of the straight section 104. In the prior art, the active material layer of the thinned pole piece is selected, and in the charging and discharging process, the active material layer repeatedly participates in the charging and discharging process, so that the active material layer at the edge of the thinned portion will be subjected to a greater stress and will fall off, thereby generating dust, which may pierce the isolation film 102 in the later stage, affecting the quality of the electric core 100 and causing safety problems. The electric core 100 of the utility model embodiment is thinned at the corner of the isolation film 102, not the pole piece, which reduces the thickness of the corner of the electric core 100, provides space for the bending of the pole piece and avoids stress concentration, thereby reducing the cracking phenomenon, and since the active material layer is not thinned, dust and piercing phenomenon are also less likely to occur.

[0030] It should be noted that, reference Figure 1 And Figure 2 Specifically, the lamination mode of the electric core 100 is that two isolation films 102 are provided, the second pole piece 103, the isolation film 102, the first pole piece 101, the isolation film 102 are laminated in sequence and then wound to form the electric core 100, so that the isolation film 102 can isolate the first pole piece 101 and the second pole piece 103 after winding, and the safety performance of the electric core 100 is improved.

[0031] It should be noted that the aforementioned straight section 104 and curved section 105, in Figure 1 In the structure shown, the straight section 104 is the middle part of the waist-shaped cell 100, and the curved section 105 is the curved part on both sides of the cell 100. The cell 100 can also be square, round, or other shapes. When the cell 100 is round, there is no clear division between the curved section 105 and the straight section 104. Specifically, depending on the contact situation between the cell 100 and the housing after it is placed in the housing, a thinning section can be set on the separator 102 on the connecting line pointing to the center of the cell 100 at the contact position with the housing. When the cell 100 is square, if the cell 100 is squeezed against the housing from the side after it is placed in the housing, it can also be thinned in the straight area. This can also provide space for the expansion and compression of the electrode sheet and reduce cracking.

[0032] It should be noted that in some embodiments of this utility model, the thinning portion 201 can be the entire curved section 105, or it can be as follows: Figure 2 The shown section is only provided in the curved section 105, when as... Figure 2 In the structure shown, the thickness of the thinned portion 201 is less than the thickness of the unthinned portion of the bent section 105. Furthermore, the thickness of the unthinned portion of the bent section 105 is the same as the thickness of the straight section 104, which can reduce the processing difficulty and improve the processing efficiency.

[0033] It should be noted that the reference Figure 1 In some embodiments of this utility model, the battery cell 100 further includes a first tab 106 and a second tab 107. The first tab 106 is connected to the first electrode 101, and the second tab 107 is connected to the second electrode 103. The first tab 106 and the second tab 107 are contact points during charging and discharging of the battery cell 100, responsible for drawing current from the positive terminal, flowing through the inside of the battery cell 100, and finally reaching the negative terminal to form a complete circuit. This ensures the electrical connection between the inside and outside of the battery cell 100, enabling the battery cell 100 to operate normally. The first tab 106 and the second tab 107 also reduce the internal resistance of the battery cell 100, reducing energy loss during operation, thereby improving the energy utilization rate and efficiency of the battery cell 100.

[0034] refer to Figure 1 and Figure 2In some embodiments of the present application, the thinning portion 201 is formed with a groove 202, and the groove 202 is located on any one side of the bending section 105 in the thickness direction. In some embodiments of the present application, the groove 202 is formed in various ways. Specifically, the entire isolation film 102 can be formed first, then the position where the thinning portion 201 is needed is glued, and the part of the coating at this position is made to fall off by using the adhesive force, so as to form the thinning portion 201, or the thinning portion 201 is formed by thinning or other methods. When coating, interval coating can be performed to form the thinning portion 201 with smaller thickness, and the thinning portion 201 is formed on one side of the bending section 105, so only one side of the isolation film 102 needs to be processed, which can reduce the process steps and improve the processing efficiency.

[0035] In some embodiments of the present application, the groove 202 faces the first pole piece 101, and the first pole piece 101 is a negative pole piece. The negative pole piece contains a negative active material layer, which plays a key role in the charging and discharging process of the battery. During charging, lithium ions flow from the positive electrode to the negative electrode and are adsorbed and inserted by the negative active material, while electrons flow from the negative electrode to the positive electrode, generating an electric current. During discharging, lithium ions flow from the negative electrode to the positive electrode, and the negative active material releases lithium ions and electrons, generating an electric current. The groove 202 of the thinning portion 201 provided on the isolation film 102 on one side of the negative pole piece can increase the content of the negative active material layer, improve the energy density of the battery cell 100, optimize the electrochemical reaction, improve the electrochemical reaction efficiency of the battery cell 100, reduce the internal resistance of the battery cell 100, and thus improve the overall performance of the battery cell 100. Moreover, during the charging process of the lithium ion battery, intercalation lithium insertion (such as graphite negative electrode, hard carbon negative electrode) or alloying lithium insertion (such as silicon-based negative electrode, lithium metal negative electrode) occurs on the negative side. With the increase of the depth of lithium insertion, the negative electrode material will undergo obvious volume expansion, for example, the graphite negative electrode generally produces 10%~15% volume expansion, and the silicon-based negative electrode can produce up to 300% volume expansion. Unlike the negative electrode, the positive electrode undergoes a delithiation process during charging, and compared with the negative electrode material, the positive electrode material generally has better structural stability during charging and discharging. Therefore, preferentially thinning the isolation film 102 on the negative side can better provide space for expansion and deformation at the bending and extrusion position, reducing the occurrence of corner cracking.

[0036] Reference Figure 3 In some embodiments of the present application, the thinning portion 201 is formed with a plurality of grooves 202, at least one groove 202 is located on one side of the bending section 105 facing the center of the battery cell 100, and at least one groove 202 is located on one side of the bending section 105 away from the center of the battery cell 100. Reference Figure 4The isolation film 102 is usually also a structure composed of a base layer and a coating layer, and the thinned portion 201 formed by the groove 202 opened on one side has a limited minimum thickness, and the groove cannot remove the middle base layer, so the groove 202 is opened on both sides of the bending section 105 to form the thinned portion 201, which can further reduce the thickness of the thinned portion 201, improve the thinning effect, and better prevent cracking.

[0037] It should be noted that in some embodiments of the present application, the groove 202 of the thinned portion 201 can be opened at the same position on both sides of the isolation film 102 as shown in Figure 3 , or can be opened at different positions according to production needs and process means, Figure 3 The structure shown is not a necessary structure for opening the double-sided groove 202.

[0038] Referring to Figure 2 and Figure 3 , in some embodiments of the present application, the thinned portion 201 is provided along the stacking direction of the first pole piece 101, the isolation film 102 and the second pole piece 103. A plurality of thinned portions 201 are provided. The plurality of thinned portions 201 can further reduce the thickness of the bending portion of the battery cell 100, thereby reducing the degree of extrusion of the battery cell 100 by the shell after assembly, reducing the cracking of the pole piece at the corner, and improving the quality of the battery cell 100.

[0039] It should be noted that the position of the thinned portion 201 can be opened at the same position of each layer as shown in Figure 2 and Figure 3 , or can be staggered by being opened at different positions according to production needs and process means, as long as a plurality of thinned portions 201 are provided along the stacking direction, Figure 2 and Figure 3 The structure shown is not a necessary structure for opening the plurality of thinned portions 201, but is a preferred embodiment for maximizing stress relief. Further, when the battery cell 100 is a waist-shaped battery cell 100 as shown in Figure 1 , the thinned portion 201 is preferably provided at the middle position of the bending section 105, which has the maximum bending degree and the maximum extrusion force from the shell. Opening at this position can maximize the stress reduction to avoid the corner cracking of the battery cell 100.

[0040] Referring to Figure 2 and Figure 3 , in some embodiments of the present application, the length of the thinned portion 201 gradually increases from the center of the battery cell 100 to the outer periphery of the battery cell 100. The closer to the outer periphery, the greater the curvature of the corner of the battery cell 100, so as the curvature of the corner of the battery cell 100 increases, the length of the thinned portion 201 is increased, which can make the overall thinning effect of the corner more significant, thereby improving the effect of preventing the corner cracking of the battery cell 100. It should be noted that as shown in Figure 3 andFigure 4 As shown, the length L1 of the thinning portion 201 refers to the arc length after winding into an arc shape, and also refers to the length of the isolation film 102 after the thinning portion 201 is processed before winding, both of which are the same parameters, only the shapes of the isolation film 102 before and after winding are different.

[0041] It should be noted that in some embodiments of the present application, the lengths of the thinning portions 201 on the various layers of the isolation film 102 can also be set to be the same, which can reduce the difficulty of processing the thinning portions 201. Specifically, when the thinning portion 201 is processed by gluing the separator coating layer 402 on the separator base layer 401, the same length of the adhesive tape can be used for gluing, and the specific structure selection can be considered according to the production process requirements and processing difficulty, and the appropriate length of the thinning portion 201 can be selected.

[0042] Reference Figure 3 and Figure 4 In some embodiments of the present application, the length of the thinning portion 201 is L1, 0.5mm≤L1≤2mm. Specifically, L1 can be 0.5mm, 1mm, 2mm, etc. When L1 is less than 0.5mm, the length of the thinning portion 201 is too short, and the thinning effect is not obvious, so the improvement of the corner cracking phenomenon of the battery cell 100 is not significant. When L1 is greater than 2mm, the length of the thinning portion 201 is too large, and since the isolation film 102 itself isolates the positive and negative electrodes, it will also generate heat shrinkage and other phenomena during use. The thinning of the coating layer and other materials on the isolation film 102 is too much, which will affect the adhesion and heat shrinkage resistance of the isolation film 102, thereby reducing the service life of the isolation film 102 and the quality of the battery cell 100. Therefore, selecting an appropriate length of the thinning portion 201 can achieve the dual purpose of considering the performance of the isolation film 102 itself and preventing the corner cracking phenomenon of the battery cell 100.

[0043] Reference Figure 4In some embodiments of the utility model, the isolation film 102 includes diaphragm base layer 401 and two diaphragm coating layers 402, diaphragm base layer 401 includes coating area and bare area, both sides of coating area are covered by two diaphragm coating layers 402 respectively, at least one side of bare area is exposed outside diaphragm coating layer 402 to form thinning portion 201.Diaphragm base layer 401 is the basis of isolation film 102, mainly used to isolate positive and negative, and has porous structure, provides flow path for lithium ion, enables battery to normally charge and discharge, and diaphragm coating layer 402 has more diverse functions, mainly improves the thermal stability and mechanical strength of isolation film 102 as a whole, to further improve the safety performance and service life of battery, and the isolation film 102 is designed to the structure of diaphragm base layer 401 in the middle and two diaphragm coating layers 402 on the top and bottom, on the one hand, the isolation film 102 has the performance of isolating positive and negative and its thermal stability, on the other hand, it is also convenient to process thinning portion 201, and the thinning portion 201 of the formed isolation film 102 still has diaphragm base layer 401 to provide the function of isolating positive and negative.

[0044] In some embodiments of the utility model, the thickness of single diaphragm coating layer 402 is D1, 0.5 μm≤D1≤4 μm. Specifically, the thickness of diaphragm coating layer 402 can be 0.5 μm, 2 μm, 4 μm and the like, when the thickness of diaphragm coating layer 402 is less than 0.5 μm, the thickness is too small, and the thermal stability and mechanical strength provided by diaphragm coating layer 402 are limited, under high temperature or external force impact, the diaphragm may occur thermal runaway or rupture, and the safety performance is low, when the thickness of diaphragm coating layer 402 is greater than 4 μm, the thickness is too large, thereby leading to the increase of internal resistance of battery cell 100, affecting the energy loss in the process of charging and discharging, reducing the energy conversion efficiency, and at the same time, there are multiple shortcomings such as reducing the performance of battery cell 100 and increasing the cost, therefore, selecting appropriate thickness can take into account the safety performance of isolation film 102 and multiple advantages such as improving the energy conversion efficiency of battery cell 100.

[0045] The battery according to the second aspect of the present application comprises a shell and the battery cell 100 according to any one of the first aspect of the present application, and the battery cell 100 is packaged in the shell. In the prior art, the active material layer of the thinned tab is selected, and in the charging and discharging process, the active material layer repeatedly participates in the charging and discharging process, so that the active material layer at the edge of the thinned part will be subjected to a greater stress and fall off, thereby generating dust, which may pierce the separator 102 in the later stage, affecting the quality of the battery cell 100 and causing safety problems. The battery cell 100 of the embodiment of the present application is thinned by the separator 102 at the corner, rather than the tab, which reduces the thickness of the corner of the battery cell 100, provides space for the bending of the tab, avoids stress concentration, thereby reducing the cracking phenomenon, and at the same time, since the active material layer is not thinned, dust and piercing phenomenon are not easy to occur, thereby improving the quality of the battery.

[0046] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge range of those skilled in the art without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. An electric cell, characterized by, Comprising; A first electrode sheet; A second electrode sheet, one of the first electrode sheet and the second electrode sheet is a positive electrode sheet, and the other is a negative electrode sheet; A separator film separating the first electrode sheet and the second electrode sheet, the first electrode sheet, the separator film and the second electrode sheet being stacked with each other, the separator film comprising a plurality of alternating straight sections and curved sections, at least one of the curved sections comprising a thinned portion, the thinned portion having a thickness smaller than that of the straight sections.

2. The electric cell of claim 1, wherein, The thinned portion is formed with a groove on either side of the curved section in the thickness direction.

3. The electric cell of claim 2, wherein, The groove faces the first electrode sheet, which is a negative electrode sheet.

4. The electric cell of claim 2, wherein, The thinned portion is formed with a plurality of the grooves, at least one of the grooves being located on a side of the curved section facing the center of the battery cell, and at least one of the grooves being located on a side of the curved section facing away from the center of the battery cell.

5. The electric cell of claim 1, wherein, The thinned portion is provided with a plurality of the grooves in a direction in which the first electrode sheet, the separator film and the second electrode sheet are stacked.

6. The electric cell of claim 5, wherein, The length of the thinned portion gradually increases from the center of the battery cell toward the periphery of the battery cell.

7. The electric cell of claim 1, wherein, The length of the thinned portion is L1, 0.5mm≤L1≤2mm.

8. The electric cell of claim 1, wherein, The separator film comprises a separator base layer and two separator coating layers, the separator base layer comprising a coated region and a bare region, both sides of the coated region being covered by the two separator coating layers respectively, and at least one side of the bare region being exposed outside the separator coating layers to form the thinned portion.

9. The electric cell of claim 8, wherein, The thickness of a single separator coating layer is D1, 0.5μm≤D1≤4μm.

10. A battery characterized by Comprising; The battery cell of any one of claims 1-9; A housing, the battery cell being packaged in the housing.

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