Pole piece assembly and battery cell

Abstract

The utility model provides a pole piece assembly and a battery cell, the pole piece assembly comprises a current collector-free pole piece and a pole lug, the pole lug comprises an exposed part and a connecting part which are connected with each other, the exposed part is exposed outside the current collector-free pole piece, and the connecting part is embedded in the current collector-free pole piece so as to be fixed with the current collector-free pole piece. And the thickness of the current collector-free pole piece is small, so that the energy density of the battery cell can be improved. Because the connecting part is embedded in the current collector-free pole piece, the binding force between the active material slurry of the current collector-free pole piece and the connecting part enables the tab and the current collector-free pole piece to be firmly connected together. Moreover, under the condition that the positive plate adopts a current collector-free pole plate, the short circuit condition caused by mutual contact of the aluminum foil and the negative active material of the battery cell is avoided, the passing rate of the battery cell in a needling test and a collision test is relatively high, and the safety of the battery cell is relatively high.

Description

TECHNICAL FIELD

[0001] The utility model relates to battery technology field especially relates to a pole piece subassembly and electric core. BACKGROUND

[0002] There is no current collector pole piece in the prior art. For example, patent document CN116722096A discloses a current collector-free pole piece, which includes an active material layer, and the material of the active material layer includes electrode active material, conductive agent, binder and solvent, but the pole piece does not need to be provided with a current collector.

[0003] For a traditional pole piece containing a current collector, the connection mode of the pole piece and the current collector is that the active material layer and the current collector jointly define a tab slot, and a part of the current collector is exposed from the tab slot and welded with the tab. However, for a current collector-free pole piece, the active material layer of the current collector-free pole piece cannot be welded with the tab, otherwise the active material layer will be damaged in the high-temperature environment generated by welding. How to firmly connect the current collector-free pole piece with the tab without welding is a problem to be solved in the current battery industry. SUMMARY

[0004] The utility model aims at least to solve one of the technical problems existing in the prior art. To this end, the utility model provides a pole piece subassembly, a part of the tab of which is embedded in the current collector-free pole piece, solving the problem that the tab and the current collector-free pole piece cannot be firmly connected without welding in the prior art.

[0005] The utility model also provides an electric core comprising the above pole piece subassembly.

[0006] According to the pole piece subassembly of the first aspect embodiment of the utility model, the tab includes an exposed part and a connecting part connected with each other, the exposed part is exposed outside the current collector-free pole piece, and the connecting part is embedded in the current collector-free pole piece to be fixed with the current collector-free pole piece.

[0007] According to the pole piece subassembly of the first aspect embodiment of the utility model, at least has the following beneficial effects: since the connecting part is embedded in the current collector-free pole piece, the binding force between the active material paste of the current collector-free pole piece and the connecting part makes the tab and the current collector-free pole piece firmly connected together.

[0008] According to some embodiments of the utility model, the pole piece subassembly further comprises an adhesive layer connected to the surface of the connecting part, at least a part of the adhesive layer is embedded in the current collector-free pole piece, and the current collector-free pole piece and the connecting part are further bonded through the adhesive layer.

[0009] According to some embodiments of the present application, the connecting portion comprises a plurality of sawteeth, and the sawteeth are embedded in the current collector-free pole piece.

[0010] According to some embodiments of the present application, the exposed portion comprises a reference surface, the sawteeth are connected to the reference surface and protrude relative to the reference surface, and the pole piece assembly further comprises an adhesive layer, a portion of the adhesive layer covers the surface of the sawteeth, and another portion of the adhesive layer covers the reference surface.

[0011] According to some embodiments of the present application, the current collector-free pole piece comprises a first surface and a second surface opposite to each other, the first surface and the second surface are located at two ends of the current collector-free pole piece in the thickness direction of the current collector-free pole piece, one of the first surface and the second surface is formed with a tab slot, a portion of the exposed portion is arranged in the tab slot, and the connecting portion is embedded in the current collector-free pole piece from the slot wall of the tab slot.

[0012] According to some embodiments of the present application, the exposed portion and the connecting portion are distributed along the thickness direction of the current collector-free pole piece, the slot wall of the tab slot comprises a bottom wall, the bottom wall is arranged opposite to the opening of the tab slot, and the connecting portion is embedded in the current collector-free pole piece from the bottom wall.

[0013] According to some embodiments of the present application, the thickness of the current collector-free pole piece is H1, the depth of the tab slot is H2, and H2≤0.5H1.

[0014] According to some embodiments of the present application, the thickness of the exposed portion is H3, H3≤1.2H2, and / or the thickness of the connecting portion is H4, 0.2H2≤H4≤0.9H2.

[0015] The battery cell according to the second aspect of the present application comprises the pole piece assembly according to the first aspect of the present application.

[0016] According to some embodiments of the present application, a positive pole piece assembly comprises a positive pole piece and a positive tab, the positive pole piece is a current collector-free pole piece, the positive tab comprises an exposed portion and a connecting portion connected to each other, the exposed portion is exposed outside the current collector-free pole piece, and the connecting portion is embedded in the current collector-free pole piece to be fixed with the current collector-free pole piece; a negative pole piece assembly comprises a negative pole piece and a negative tab, the negative pole piece comprises a negative current collector and a negative active material layer arranged on the surface of the negative current collector, and the negative tab is welded with the negative current collector; and an insulating separator separates the positive pole piece assembly and the negative pole piece assembly.

[0017] Additional aspects and advantages of the present application will be set forth in part in the following description, and in part will become apparent to those skilled in the art upon examination of the following description, or can be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0018] The present application will be further described below in conjunction with the drawings and embodiments, wherein:

[0019] Figure 1 is a sectional view of the pole piece assembly of one embodiment of the present application;

[0020] Figure 2 is Figure 1 is a sectional view of the pole piece assembly shown in another cross-section;

[0021] Figure 3 is a sectional view of the tab of another embodiment of the present application;

[0022] Figure 4 is a schematic view of the wound-type battery cell of one embodiment of the present application;

[0023] Figure 5 is a schematic view of the wound-type battery cell (in a cylindrical shape) of another embodiment of the present application;

[0024] Figure 6 is a schematic view of the stacked-type battery cell of one embodiment of the present application.

[0025] Reference numerals: 101 - pole piece assembly, 102 - pole piece without current collector, 103 - first surface, 104 - tab groove, 105 - exposed portion, 106 - tab, 107 - bottom wall, 108 - second surface, 109 - sawtooth, 110 - connecting portion, 111 - reference surface, 112 - battery cell, 113 - negative pole piece, 114 - positive pole piece, 115 - insulating separator, 116 - negative tab, 117 - positive tab, 118 - adhesive layer. DETAILED DESCRIPTION

[0026] Embodiments of the present application will be described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary and are only used to explain the present application and cannot be understood as a limitation of the present application.

[0027] In the description of the utility model, it is understood that, if the direction description is related, for example, the direction or position relation of the indication such as upper, lower, front, back, left, right is based on the direction or position relation shown in the drawing, only for the convenience of describing the utility model and simplifying the description, and it is not indicated or implied that the indicated device or element must have a specific direction, a specific direction structure and operation, therefore it cannot be understood as the limitation of the utility model.

[0028] 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 and the like are understood as not including the number, above, below, within and the like are understood as including the number.If it is described to the first, second, it is only used for distinguishing the purpose of technical features, 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.

[0029] In the description of the utility model, unless otherwise explicitly limited, the words such as setting, installation, connection should be understood in a broad sense, and the person skilled in the art can reasonably determine the specific meaning of the above words in the utility model according to the specific content of the technical scheme.

[0030] Figure 1 The pole piece assembly 101 of one embodiment of the utility model is shown, the pole piece assembly 101 includes the pole piece 102 without current collector and the tab 106, the tab 106 includes the exposed part 105 and the connecting part 110 connected with each other, the exposed part 105 is exposed outside the pole piece 102 without current collector, the connecting part 110 is embedded in the pole piece 102 without current collector, and the connecting part 110 is fixed with each other with the pole piece 102 without current collector.

[0031] The current collector-free electrode tab 102 can be a positive electrode tab, and the tab 106 is a positive tab accordingly. In other embodiments, the current collector-free electrode tab 102 can also be a negative electrode tab, and the tab 106 is a negative tab accordingly. The current collector-free electrode tab 102 is formed by solidification of an active material slurry, which includes active material, binder and conductive agent in the case of a dry process, and the active material slurry can not contain solvent. In the case of a wet process, the active material slurry includes active material, binder, conductive agent and solvent. If the current collector-free electrode tab 102 is a positive electrode tab, the positive active material can include one or more of lithium cobaltate, nickel cobalt manganese ternary positive electrode, nickel cobalt aluminum ternary positive electrode, lithium iron phosphate, lithium manganese iron phosphate, spinel lithium manganate, nickel manganate, lithium-rich manganese-based positive electrode. The binder can include one or more of PTFE (polytetrafluoroethylene), PVDF (polyvinylidene difluoride), PAA (polyacrylic acid). The conductive agent includes one or more of SP (conductive carbon black), CNT (carbon nanotube), SWCNT (single-walled carbon nanotube), VGCF (vapor grown carbon fiber), graphene. The tab 106 can be a metal foil. In other embodiments not shown, the current collector-free electrode tab 102 can also be a negative electrode tab, and the negative active material used by the negative electrode tab can refer to the negative materials commonly used in the art, which will not be described here.

[0032] In some embodiments, a portion of the tab 106 can be pressed on the active material slurry before the active material slurry is completely solidified, so that a portion of the tab 106 is embedded in the active material slurry. After the active material slurry is solidified, the current collector-free electrode tab 102 is formed, and the portion of the tab 106 embedded in the current collector-free electrode tab 102 is the connection portion 110, and the portion of the tab 106 exposed is the exposed portion 105.

[0033] In other embodiments, the current collectorless electrode 102 can be formed first (the active material slurry solidifies), then the current collectorless electrode 102 is locally heated, and a portion of the tab 106 is pressed into the heated portion of the current collectorless electrode 102. For example, the tab 106 can be pressed onto the current collectorless electrode 102 by a high-temperature pressure head (not shown). The portion of the current collectorless electrode 102 corresponding to the pressure head melts due to the high temperature, and the tab 106 can be embedded in the current collectorless electrode 102. After the pressure head is removed from the current collectorless electrode 102, the previously melted area cools down and solidifies, and a portion of the tab 106 is embedded in the current collectorless electrode 102, thus fixing the tab 106 to the current collectorless electrode 102.

[0034] Since the connecting part 110 is embedded in the current-free electrode 102, the bonding force between the active material slurry of the current-free electrode 102 and the connecting part 110 makes the tab 106 firmly connected to the current-free electrode 102.

[0035] like Figure 1 As shown, in one embodiment, the connecting portion 110 includes a plurality of serrations 109 embedded in the current collector-less electrode 102. More specifically, please refer to... Figure 1 and Figure 2 The multiple serrations 109 can be arranged in a rectangular array, with multiple rows of serrations 109 in the left-right direction and multiple columns of serrations 109 in the front-back direction. Since the connecting part 110 is composed of multiple serrations 109, the surface area of ​​the connecting part 110 is large, and the connection area between the connecting part 110 and the current-free electrode 102 is large, which is beneficial to improving the connection strength between the current-free electrode 102 and the electrode tab 106.

[0036] In some other embodiments not shown, in order to reduce the processing difficulty of the tab 106, the tab 106 may not have serrations 109, and the exposed portion 105 and the connecting portion 110 of the tab 106 may both be cuboid in shape.

[0037] like Figure 3 As shown, in some embodiments, the electrode assembly 101 further includes an adhesive layer 118, which is attached to the surface of the connecting portion 110. At least a portion of the adhesive layer 118 is embedded in the current-free electrode 102, and the current-free electrode 102 and the connecting portion 110 are also bonded by the adhesive layer 118. The adhesive layer 118 is provided to improve the connection strength between the tab 106 and the current-free electrode 102.

[0038] When the connecting portion 110 is composed of a plurality of serrations 109, the exposed portion 105 includes a reference surface 111, the serrations 109 are connected to the reference surface 111 and protrude relative to the reference surface 111, a portion of the adhesive layer 118 covers the surface of the serrations 109, and another portion of the adhesive layer 118 covers the reference surface 111. Figure 3 In the middle, the reference surface 111 is the bottom surface of the exposed part 105, and the serration 109 protrudes downward relative to the reference surface 111. In addition to improving the connection between the current collector and the tab 106, the adhesive layer 118 covering the surface of the serration 109 can also reduce the risk of the serration 109 piercing the current collector electrode 102.

[0039] like Figure 1 As shown, in some embodiments, the exposed portion 105 and the connecting portion 110 are distributed along the thickness direction of the current collectorless electrode 102. Figure 1 For example, the thickness direction of the current collectorless electrode 102 is upward-downward, and the thickness direction of the current collectorless electrode 102 is the same as that of the tab 106. Both the current collectorless electrode 102 and the tab 106 are relatively thin, and they belong to sheet-like materials (or film-like materials). Therefore, the end face area of ​​the current collectorless electrode 102 in its own thickness direction is larger, and the end face area of ​​the tab 106 in its own thickness direction is also larger. Since the exposed portion 105 and the connecting portion 110 are distributed along the thickness direction of the current collectorless electrode 102, when the pressure head presses the tab 106 into the current collectorless electrode 102, the pressure head can contact one end face of the tab 106 in the thickness direction (e.g., the top surface of the exposed portion 105). The contact area between the pressure head and the tab 106 is large, which facilitates the pressure head pressing the tab 106 into the current collectorless electrode 102. Furthermore, during the pressing of the tab 106, the current-free electrode 102 is also pressed through its end face in the thickness direction, which also facilitates the pressing head to press the tab 106 into the current-free electrode 102.

[0040] like Figure 1 As shown, the current collectorless electrode 102 includes a first surface 103 and a second surface 108 facing each other, located at opposite ends of the current collectorless electrode 102 in its thickness direction. One of the first surface 103 and the second surface 108 forms a tab groove 104, with an exposed portion 105 disposed within the tab groove 104, and a connecting portion 110 embedded in the current collectorless electrode 102 from the groove wall of the tab groove 104. Figure 1As shown, the first surface 103 is the upper surface of the current-free electrode 102, and the second surface 108 is the lower surface of the current-free electrode 102. The middle region of the first surface 103 is recessed to form a tab groove 104. The tab groove 104 facilitates the positioning of the tab 106 before it is pressed into the current-free electrode 102. Furthermore, since the tab 106 is located within the tab groove 104, the portion of the tab 106 protruding outside the tab groove 104 is small, resulting in a smaller maximum thickness of the electrode assembly 101. This helps prevent excessive local thickness of the cell 112 at the tab 106. It should be noted that... Figure 1 The electrode assembly 101 shown adopts a design with the tab 106 in the middle and the tab groove 104 located in the middle of the current collector-less electrode 102; in some other embodiments not shown, the tab groove 104 may also be located at one end of the current collector-less electrode 102 in its own length direction.

[0041] like Figure 1 As shown, when the exposed portion 105 and the connecting portion 110 are distributed along the thickness direction of the current-free electrode 102, and the current-free electrode is provided with an electrode tab groove 104, the groove wall of the electrode tab groove 104 includes a bottom wall 107, the bottom wall 107 is arranged facing the opening of the electrode tab groove 104, and the connecting portion 110 is embedded in the current-free electrode 102 from the bottom wall 107, thereby realizing the connection between the electrode tab 106 and the current-free electrode 102.

[0042] It should be noted that a portion of the exposed portion 105 is located within the tab groove 104, while the other portion of the exposed portion 105 may be located outside the tab groove 104. For example, as... Figure 1 As shown, the upper part of the exposed portion 105 can extend from the opening of the tab groove 104 to the outside of the tab groove 104. For example, as... Figure 2 As shown, the front end of the exposed portion 105 can extend out of the tab groove 104 and protrude forward relative to the front edge of the current-free electrode 102. The forward-protruding part of the exposed portion 105 can be used to weld to the current collector, electrode post or other tabs 106.

[0043] In some embodiments, the current collectorless electrode 102 can be formed by pressing two active material slurry layers together. That is, two relatively thin active material slurry layers can be processed first, and then these two active material slurry layers can be hot-pressed together to form a thicker current collectorless electrode 102. Figure 1 As shown, the thickness of the current collectorless electrode 102 is H1, which can satisfy: 40um ≤ H1 ≤ 2000um. Correspondingly, the thickness of a single active material slurry layer mentioned above can be half of H1. Of course, the current collectorless electrode 102 can also be formed by pressing two active material slurry layers of different thicknesses together.

[0044] To form the tab groove 104, a notch (not shown) can be made in one of the active material slurry layers first, and then the active material slurry layer with the notch can be pressed together with another active material slurry layer without a notch; after pressing, the position of the tab groove 104 is the original position of the notch. Alternatively, two active material layers without notches can be pressed together first, and then the tab groove 104 can be formed on the pressed current-free electrode 102.

[0045] like Figure 1 As shown, if the thickness of the current-collectorless electrode 102 is H1 and the depth of the tab groove 104 is H2, then H2 ≤ 0.5H1 to prevent the depth of the tab groove 104 from being too large, thereby preventing the current-collectorless electrode 102 from having too low strength at the tab groove 104. The thickness of the exposed portion 105 is H3, and H3 ≤ 1.2H2 to prevent the exposed portion 105 from extending too far from the opening of the tab groove 104, thereby preventing the local thickness of the electrode assembly 101 from being too large. The thickness of the connecting portion 110 is H4, and 0.2H2 ≤ H4 ≤ 0.9H2. The strength of the connection between the tab 106 and the current-collectorless electrode 102 is related to the thickness of the connecting portion 110; the thicker the connecting portion 110, the stronger the connection between the connecting portion 110 and the current-collectorless electrode 102. 0.2H2≤H4 can prevent the thickness of the connecting part 110 from being too small, thereby preventing the tab 106 and the current-free electrode 102 from being loosely connected. H4≤0.9H2 can prevent the thickness of the connecting part 110 from being too large, thereby preventing the connecting part 110 from piercing the current-free electrode 102, especially when the connecting part 110 is composed of multiple serrations 109.

[0046] This utility model also provides a battery cell 112, which includes the electrode assembly 101 in any of the above embodiments. For example, the battery cell 112 includes a positive electrode assembly, a negative electrode assembly, and an insulating separator 115, the insulating separator 115 separating the positive electrode assembly and the negative electrode assembly. Figure 4 As shown, the positive electrode assembly includes a positive electrode 114 and a positive electrode tab 117. The positive electrode 114 is a current-free electrode 102. The positive electrode tab 117 includes an exposed portion 105 and a connecting portion 110 connected to each other. The exposed portion 105 is exposed outside the current-free electrode 102, and the connecting portion 110 is embedded in the current-free electrode 102 to fix it to the current-free electrode 102. The negative electrode assembly includes a negative electrode 113 and a negative electrode tab 116. The negative electrode 113 includes a negative current collector and a negative active material layer disposed on the surface of the negative current collector. The negative electrode tab 116 is welded to the negative electrode 113.

[0047] Figure 4 The shown cell 112 is a wound cell with a racetrack-shaped outer profile in its cross-section. This cell 112 is suitable for prismatic batteries, pouch batteries, etc. Figures 4 to 6In the diagram, the insulating diaphragm 115 is drawn with a dashed line. Figure 5 The cell 112 shown is also a wound cell. The cross-section of the cell 112 is cylindrical. The cell 112 can be used in cylindrical batteries. Figure 6 The shown cell 112 is a laminated cell, which can be used in prismatic batteries, pouch batteries, etc. It should be noted that the negative electrode tab 116 included in the laminated cell 112 is not... Figure 6 As shown, the connection between the multiple negative tabs 116 is similar to the connection between the multiple positive tabs 117.

[0048] It should be noted that in some other embodiments not shown, in order to further reduce the thickness of the cell 112, the positive electrode 114 and the negative electrode 113 of the cell 112 can both be set as current collector-free electrode 102. Accordingly, a part of the positive electrode tab 117 is embedded in the positive electrode 114, and a part of the negative electrode tab 116 is embedded in the negative electrode 113.

[0049] With the thickness of the active material layer remaining constant, the thickness of the current collector-less electrode 102 is smaller compared to the electrode with a current collector. The use of the current collector-less electrode 102 in the battery cell 112 reduces the overall thickness and volume of the battery cell 112 and improves the energy density of the battery cell 112.

[0050] The current collector for the positive electrode is typically made of aluminum foil, while the current collector for the negative electrode is typically made of copper foil. In several scenarios where an internal short circuit occurs in the battery cell, the risk of a short circuit is higher when the positive electrode current collector (aluminum foil) comes into direct contact with the negative electrode active material layer. This is especially true when the positive electrode 114 is configured as a current collector-less electrode 102 (e.g., ...). Figures 4 to 6 As shown, since the positive electrode 114 eliminates the current collector (aluminum foil), during nail penetration and impact tests of the cell 112, there will be no direct contact between the aluminum foil and the negative electrode active material, which could lead to a short circuit within the cell 112. Therefore, the cell 112 has a high pass rate in nail penetration and impact tests, and the cell 112 has high safety. In addition, the current collector-less electrode 102 can be manufactured using a dry process, and it can be made thicker (up to 2000um), overcoming the limitation of traditional electrodes where the active material layer cannot be made thicker.

[0051] In the description of this utility model, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A pole piece assembly characterized by, The tab includes a connection portion embedded in the current collector-free tab and a protruding portion exposed outside the current collector-free tab.

2. The pole piece assembly of claim 1, wherein, The tab assembly further includes an adhesive layer connected to a surface of the connection portion, at least a portion of the adhesive layer being embedded in the current collector-free tab, the current collector-free tab being further bonded to the connection portion via the adhesive layer.

3. The pole piece assembly of claim 1, wherein, The connection portion includes a plurality of serrations embedded in the current collector-free tab.

4. The pole piece assembly of claim 3, wherein, The protruding portion includes a reference surface to which the serrations are connected and protrude relative to, and the tab assembly further includes an adhesive layer, a portion of the adhesive layer covering a surface of the serrations and another portion of the adhesive layer covering the reference surface.

5. The pole piece assembly of claim 1, wherein, The current collector-free tab includes first and second surfaces opposite to each other, the first and second surfaces being located at two ends of the current collector-free tab in a thickness direction of the current collector-free tab, one of the first and second surfaces being formed with a tab slot, a portion of the protruding portion being disposed in the tab slot, and the connection portion being embedded in the current collector-free tab from a slot wall of the tab slot.

6. The pole piece assembly of claim 5, wherein, The protruding portion and the connection portion are distributed along the thickness direction of the current collector-free tab, the slot wall of the tab slot includes a bottom wall disposed opposite to an opening of the tab slot, and the connection portion is embedded in the current collector-free tab from the bottom wall.

7. The pole piece assembly of claim 6, wherein, The current collector-free tab has a thickness H1, the tab slot has a depth H2, and H2≤0.5H1.

8. The pole piece assembly of claim 7, wherein, The protruding portion has a thickness H3, and H3≤1.2H2. The connection portion has a thickness H4, and 0.2H2≤H4≤0.9H2. The tab assembly includes the tab assembly according to any one of claims 1 to 8.

9. An electric cell, characterized by The tab assembly includes:

10. An electric cell, characterized by The positive tab assembly includes a positive tab and a positive tab, the positive tab being a current collector-free tab, the positive tab including a protruding portion exposed outside the current collector-free tab and a connection portion embedded in the current collector-free tab to be fixed to the current collector-free tab. The negative tab assembly includes a negative tab and a negative tab, the negative tab including a negative current collector and a negative active material layer disposed on a surface of the negative current collector, and the negative tab being welded to the negative current collector. The insulating separator separates the positive tab assembly and the negative tab assembly. ​

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