Battery cell and battery

Abstract

The utility model relates to the technical field of batteries, in particular to a battery cell and a battery. The battery cell comprises a first pole piece; a second pole piece; the diaphragm is arranged between the first pole piece and the second pole piece, and the diaphragm, the first pole piece and the second pole piece are stacked and wound to form a winding body; and a connector. Wherein the winding body comprises a straight section and two arc-shaped sections located on the two sides of the straight section respectively, and the winding tail end of the first pole piece and / or the winding tail end of the second pole piece are / is located on the arc-shaped sections; and in the first pole piece and the second pole piece, at least one winding tail end positioned on the arc-shaped section is fixed on the diaphragm through a connecting piece. The at least one winding tail end located on the arc-shaped section is fully fixed through the connecting piece, the pole piece of the battery cell cannot be loosened at the winding tail end of the pole piece provided with the connecting piece, and OH failure and lithium precipitation caused by the fact that the pole piece of the battery cell is loosened at the winding tail end of the pole piece are relieved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell and a battery. Background Art

[0002] During the lithium battery production process, the assembly of positive and negative electrodes and separators usually adopts two methods: winding and stacking. Among them, the winding method has a higher production line PPM (Pieces Per Minutes) and yield rate, and is widely used in lithium battery production.

[0003] Currently, during the production of lithium battery cells, the positive electrode sheet, separator, and negative electrode sheet are stacked and then wound from the starting point to the end of the winding. The wound cell has a straight section and two curved sections on either side of the straight section. The wound cell is then hot-pressed. To prevent indentations on the cell surface at the end of the electrode sheet after hot-pressing, the end of the electrode sheet is typically positioned within the curved section of the cell.

[0004] However, at the end of the winding of the pole piece, there is no tension on the surface of the pole piece, and the tightening force is provided only by the tension of the diaphragm flipping. The pole piece is prone to loosening at the end of the winding of the pole piece. Utility Model Content

[0005] Based on this, the embodiments of the present application provide a battery cell, a battery, and an electrical device to improve the phenomenon that the pole piece is prone to loosening at the end position of the pole piece winding.

[0006] In the first aspect, the present application provides a battery cell comprising a first pole piece, a second pole piece, a diaphragm and a connector, wherein the diaphragm is arranged between the first pole piece and the second pole piece and is stacked with the first pole piece and the second pole piece and wound to form a winding body; wherein the winding body comprises a straight section and two arc-shaped sections respectively located on both sides of the straight section, and the winding end of the first pole piece and / or the winding end of the second pole piece is located in the arc-shaped section; in the first pole piece and the second pole piece, at least one winding end located in the arc-shaped section is fixed to the diaphragm by a connector.

[0007] In the technical solution of the embodiment of the present application, the winding end of the first pole piece and / or the winding end of the second pole piece are located in the arc section of the winding body. After the winding body is hot-pressed, the winding end of the pole piece located at the arc section will not cause indentations on the surface of the battery cell. In the first pole piece and the second pole piece, at least one winding end located in the arc section is fixed to the diaphragm by a connector. In this way, at least one winding end located in the arc section is fully fixed, and the battery cell will not have loose pole pieces at the winding end position of the pole piece with the connector, thereby alleviating OH (Overhang, the part of the negative pole piece that exceeds the positive pole piece in the length and width directions) failure and lithium plating caused by loose pole pieces at the winding end position of the pole piece.

[0008] In some embodiments, the winding end of the first pole piece and the winding end of the second pole piece are both provided with connectors; the winding end of the first pole piece and the winding end of the second pole piece are both fixed to the diaphragm through the connectors.

[0009] In some embodiments, the connecting piece is located on at least one side of the corresponding connected winding end in the thickness direction.

[0010] In some embodiments, the connecting pieces are located on both sides of the corresponding connected winding ends in the thickness direction.

[0011] In some embodiments, the connector extends beyond the end of the corresponding connected winding end along a preset direction; the preset direction is the length direction and / or width direction of the corresponding connected pole piece.

[0012] In some embodiments, portions of the connectors on both sides of the corresponding connected pole pieces that extend beyond the pole pieces are connected to each other.

[0013] In some embodiments, in the length direction of the pole piece to which the connector is connected, the ratio between the size of the connector provided on the corresponding winding end and the size of the connector is less than or equal to 0.5.

[0014] In some embodiments, the size of the connector in the length direction of the corresponding pole piece is 10 mm-20 mm.

[0015] In some embodiments, in the width direction of the electrode piece to which the connecting member is connected, the ratio between the size of the connecting member and the size of the corresponding electrode piece is X;

[0016] X satisfies: 1<X≤1.2.

[0017] In some embodiments, the winding end of the first pole piece is located at the straight section or at the connection position between the straight section and the arc section, and the winding end of the second pole piece exceeds the winding end of the first pole piece and is located on the arc section.

[0018] In some embodiments, the winding end of the first pole piece is located in the arc segment, and the winding end of the second pole piece exceeds the winding end of the first pole piece and is located in the straight segment or at the connection position between the straight segment and the arc segment.

[0019] In some embodiments, the winding end of the second pole piece exceeds the winding end of the first pole piece, and the winding end of the first pole piece and the winding end of the second pole piece are respectively located on arc segments.

[0020] In some embodiments, a connecting layer is further provided on the winding starting end of at least one of the first pole piece and the second pole piece, and in the first pole piece and the second pole piece, the winding starting end provided with the connecting layer is fixed to the diaphragm through the connecting layer.

[0021] In some embodiments, a winding starting end of at least one of the first pole piece and the second pole piece is located in an arc segment.

[0022] In some embodiments, the battery cell further includes a connector, at least a portion of which is connected to the winding end of the outermost separator of the wound body, and the winding end of the outermost separator of the wound body is fixed by the connector.

[0023] In a second aspect, an embodiment of the present application provides a battery, comprising a housing and the battery cell of the above embodiment, wherein the battery cell is installed inside the housing.

[0024] In some embodiments, the number of battery cells is two, and the two battery cells are arranged side by side and are centrally symmetrically distributed.

[0025] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0027] Figure 1 A schematic diagram of the structure of a battery provided in an embodiment of the present application;

[0028] Figure 2 A side view of the first battery cell provided in an embodiment of the present application;

[0029] Figure 3 for Figure 2 A front view of the battery cell shown;

[0030] Figure 4 A side view of the second battery cell provided in an embodiment of the present application;

[0031] Figure 5 A side view of a third battery cell provided in an embodiment of the present application;

[0032] Figure 6 A side view of a fourth battery cell provided in an embodiment of the present application;

[0033] Figure 7 A front view of the first pole piece and the second pole piece provided in an embodiment of the present application at the end of the winding after being stacked;

[0034] Figure 8 A side view of the first and second pole pieces at the end of the winding after being stacked according to an embodiment of the present application Figure 1 ;

[0035] Figure 9 A side view of the first and second pole pieces at the end of the winding after being stacked according to an embodiment of the present application Figure 2 ;

[0036] Figure 10 A side view of the first and second pole pieces at the end of the winding after being stacked according to an embodiment of the present application Figure 3 .

[0037] Description of reference numerals:

[0038] 10-battery cell;

[0039] 11-straight segment; 12-arc segment;

[0040] 100-first pole piece;

[0041] 200-second pole piece;

[0042] 300-diaphragm;

[0043] 400-connector;

[0044] 500-connector;

[0045] 600-connection layer;

[0046] 20-shell. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below in conjunction with the drawings in the preferred embodiments of the present application. In the drawings, the same or similar reference numerals throughout represent the same or similar parts or parts with the same or similar functions. The described embodiments are part of the embodiments of the present application, not all of the embodiments. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain the present application, and should not be understood as limitations on the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The embodiments of the present application are described in detail below in conjunction with the drawings.

[0048] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to a fixed connection, an indirect connection via an intermediate medium, internal communication between two components, or an interaction between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on specific circumstances.

[0049] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are orientations or positional relationships based on the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this application.

[0050] The terms "first", "second" and "third" (if any) in the description and claims of this application and the above drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0051] In addition, the terms "comprises" and "having" and any variations thereof are intended to cover a non-exclusive inclusion, for example, a process, method, system, product or display that includes a series of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, product or display.

[0052] Currently, battery applications are becoming increasingly widespread. They are used not only in energy storage systems such as hydropower, thermal, wind, and solar power plants, but also in electric vehicles like electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. As battery applications continue to expand, market demand is also increasing, placing higher demands on battery capacity retention and manufacturing costs.

[0053] The inventors of the present invention have noticed that in the related art, the wound battery cell has a straight section and two arc-shaped sections located on both sides of the straight section. The wound battery cell is hot-pressed. In order to prevent the battery cell from generating an indentation on the surface of the battery cell at the end of the electrode winding after hot pressing, and the stress concentration at the indentation may cause the inner ring electrode to break, resulting in abnormal battery cell performance, the winding end of the electrode is set at the arc-shaped section of the battery cell. However, at the winding end of the electrode, there is no tension on the surface of the electrode, and the tightening force is provided only by the tension of the diaphragm flipping. After the battery cell is transported on the assembly line and hot-pressed, the electrode is prone to loosening at the end of the electrode winding. In addition, during the charge and discharge cycle of the battery cell, its negative electrode will gradually expand. The arc-shaped section of the battery cell has less binding force on the electrode than the straight section of the battery cell, which aggravates the loosening at the end of the electrode winding.

[0054] When the pole piece becomes loose at the end of the winding, the gap between the outermost negative and positive pole pieces will increase, making it easy for black spots, purple spots, and lithium deposition to appear on the surface of the negative pole piece. Currently, double-sided adhesive diaphragms are mainly used to improve the restraint of the diaphragm on the pole piece after pressurization. Both sides of the double-sided adhesive diaphragm are provided with an adhesive layer. After the battery cell is pressurized, the pole piece and the diaphragm are fixed by the adhesive layer to prevent loosening at the end of the pole piece winding. However, the cost of double-sided adhesive diaphragms is relatively high. Compared with conventional ceramic coated diaphragms, the cost is 2-3 times higher, and compared with adhesive-free diaphragms, the cost is 3-4 times higher.

[0055] In order to improve the above problems, the applicant has found that a connector can be provided at the winding end of the electrode. After the electrode and the diaphragm are stacked and wound to form a wound body, the winding end of the electrode located at the arc section of the wound body can be fixed to the diaphragm through the connector. The electrode will not become loose at the end of the winding of the electrode, thereby alleviating OH failure and lithium plating caused by loose electrode at the winding end of the electrode. At the same time, the cost of the battery cell is lower than that of the battery cell using a double-sided adhesive-coated diaphragm.

[0056] The battery provided in the embodiments of the present application can be used as a power source for electrical devices, including but not limited to mobile phones, tablets, laptops, electric toys, electric tools, electric vehicles, electric cars, ships, spacecraft, etc.

[0057] Please refer to Figure 1 The battery provided in this application includes a shell 20 and a battery cell 10 of any of the following embodiments, and the battery cell 10 is installed inside the shell 20.

[0058] The housing 20 may be a box structure, including a bottom shell and a cover disposed on the bottom shell. Alternatively, the housing 20 may be formed by encapsulating an aluminum-plastic film. The number of battery cells 10 may be one or more, and this is not a specific limitation.

[0059] In this embodiment, the battery may be a lithium-ion secondary battery, a lithium-ion primary battery, a lithium-sulfur battery, a sodium-lithium-ion battery, a sodium-ion battery, or a magnesium-ion battery, etc., without limitation herein.

[0060] The battery provided in this embodiment is less likely to have loose pole pieces at the winding end of the pole piece due to the connector 400 at the winding end of the pole piece, and the battery cell 10 is less likely to have OH failure and lithium deposition, and the battery safety and capacity retention rate are high.

[0061] In a specific embodiment, Figure 1 As shown, there are two battery cells 10, which are arranged side by side and are centrally symmetrical. The centrally symmetrical distribution of the two battery cells 10 can make the winding ends of the pole pieces of the two battery cells 10 in opposite positions and the connectors 400 of the two battery cells 10 in opposite positions.

[0062] For example, the winding ends of the outermost separator 300 of the battery cell 10 are fixed by a connector 500 , and the connectors 500 of the two battery cells 10 can be arranged opposite to each other or back to back.

[0063] Through the above arrangement, the connectors 400 of the two battery cells 10 can face different side walls of the housing 20 , and the housing 20 is subjected to more uniform pressure from the battery cells 10 , which is beneficial to improving the service life of the battery.

[0064] like Figure 2-Figure 8 As shown, an embodiment of the present application provides a battery cell 10, comprising a first pole piece 100, a second pole piece 200, a diaphragm 300 and a connector 400. The diaphragm 300 is disposed between the first pole piece 100 and the second pole piece 200 and is stacked with the first pole piece 100 and the second pole piece 200 and wound to form a wound body. The wound body comprises a straight section 11 and two arcuate sections 12 located on both sides of the straight section 11, respectively. The winding end of the first pole piece 100 and / or the winding end of the second pole piece 200 is located in the arcuate section 12; in the first pole piece 100 and the second pole piece 200, at least one winding end located in the arcuate section 12 is fixed to the diaphragm 300 via the connector 400.

[0065] The first electrode 100 and the second electrode 200 have opposite polarities, that is, one of the first electrode 100 and the second electrode 200 is a positive electrode and the other is a negative electrode. This embodiment is described by taking the first electrode 100 as a positive electrode and the second electrode 200 as a negative electrode as an example, but this does not limit the scope of protection.

[0066] The diaphragm 300 isolates the first electrode piece 100 from the second electrode piece 200 , and the diaphragm 300 can prevent the first electrode piece 100 and the second electrode piece 200 from contacting each other and causing a short circuit.

[0067] It is worth mentioning that after the first pole piece 100, the diaphragm 300, and the second pole piece 200 are stacked and wound to form a jelly roll, the two arcuate segments 12 of the jelly roll are located at the two ends of the jelly roll. The winding ends of the first pole piece 100, the winding ends of the second pole piece 200, and the winding ends of the diaphragm 300 are located on the outside of the jelly roll, and the winding starting ends of the first pole piece 100, the winding starting ends of the second pole piece 200, and the winding starting ends of the diaphragm 300 are located on the inside of the jelly roll.

[0068] It can be understood that after the first pole piece 100, the diaphragm 300 and the second pole piece 200 are stacked and wound to form a wound body, only the winding end of the first pole piece 100 can be located in the arc segment 12, or only the winding end of the second pole piece 200 can be located in the arc segment 12, or the winding end of the first pole piece 100 and the winding end of the second pole piece 200 can be located in the arc segment 12 respectively. When only the winding end of the first pole piece 100 is located in the arc segment 12, the winding end of the first pole piece 100 is fixed to the diaphragm 300 through the connecting piece 400; when only the winding end of the second pole piece 200 is located in the arc segment 12, the winding end of the second pole piece 200 is fixed to the diaphragm 300 through the connecting piece 400; when the winding end of the first pole piece 100 and the winding end of the second pole piece 200 are both located in the arc segment 12, at least one of the winding end of the first pole piece 100 and the winding end of the second pole piece 200 is fixed to the diaphragm 300 through the connecting piece 400.

[0069] In one possible implementation, Figure 9 As shown, the connector 400 may be provided only on one side of the winding end of the corresponding electrode, and the winding end of the electrode is fixed to the diaphragm 300 on one side through the connector 400. In another possible implementation, as shown in FIG. Figure 8 and Figure 10 As shown, connectors 400 may be provided on both sides of the winding end of the corresponding pole piece, and the two sides of the winding end of the pole piece are fixed to the diaphragms 300 on both sides through the connectors 400 .

[0070] Among them, a hot melt adhesive film, pressure sensitive adhesive or double-sided adhesive can be set at the winding end of the corresponding electrode as a connector 400. The connector 400 is easy to obtain, which makes the manufacturing cost of the battery cell 10 low. Figure 8 and Figure 10 As shown, when pressure-sensitive adhesive or double-sided adhesive is used as the connector 400, the edge of the connector 400 may or may not exceed the edge of the corresponding electrode. Figure 9As shown, when a hot melt adhesive film is used as the connector 400, the edge of the connector 400 needs to extend beyond the edge of the corresponding electrode, that is, a part of the connector 400 is connected to the corresponding electrode, and the other part of the connector 400 is connected to the diaphragm 300 to fix the winding end of the corresponding electrode on the diaphragm 300.

[0071] Illustratively, the ratio between the width of the connector 400 and the width of the corresponding electrode piece may be in the range of 0.5-1.2, ensuring that the connector 400 can reliably fix the winding end of the electrode piece to the diaphragm 300 .

[0072] In the battery cell 10 provided in this embodiment, the winding end of the first pole piece 100 and / or the winding end of the second pole piece 200 are located at the arc segment 12 of the winding body. After the winding body is hot-pressed, the winding end of the pole piece located at the arc segment 12 will not cause indentations on the surface of the battery cell 10. In the first pole piece 100 and the second pole piece 200, at least one winding end located at the arc segment 12 is fixed to the diaphragm 300 by the connector 400. In this way, at least one winding end located at the arc segment 12 is fully fixed, and the pole piece of the battery cell 10 will not loosen at the winding end position of the pole piece where the connector 400 is provided, thereby alleviating OH failure and lithium deposition caused by loose pole piece at the winding end position of the pole piece of the battery cell 10.

[0073] like Figure 2 and Figure 4-Figure 6 As shown, the battery cell 10 further includes a connector 500, at least a portion of which is connected to the winding end of the outermost separator 300 of the wound body, and the winding end of the outermost separator 300 of the wound body is fixed by the connector 500. By fixing the winding end of the separator 300 by the connector 500, after the winding end of at least one of the first pole piece 100 and the second pole piece 200 located in the arc segment 12 is fixed to the separator 300 by the connector 400, OH failure and lithium deposition caused by loose pole pieces at the winding end of the pole pieces of the battery cell 10 can be further alleviated.

[0074] In a specific embodiment, Figure 2 、 Figure 7 and Figure 8 As shown, the winding ends of the first pole piece 100 and the winding ends of the second pole piece 200 are both provided with connectors 400. The winding ends of the first pole piece 100 and the winding ends of the second pole piece 200 are both fixed to the diaphragm 300 through the connectors 400.

[0075] Illustratively, the connector 400 on the first pole piece 100 covers at least a portion of the wound end of the first pole piece 100, and the connector 400 on the second pole piece 200 covers at least a portion of the wound end of the second pole piece 200. The wound end of the first pole piece 100 and the wound end of the second pole piece 200 are respectively bonded and fixed to the diaphragm 300 via the connector 400. Specifically, after the wound body is hot-pressed, the wound ends of the pole pieces, the connector 400, and the diaphragm 300 are fully bonded, so that the wound ends of the first pole piece 100 and the wound ends of the second pole piece 200 are fully fixed.

[0076] The winding ends of the first pole piece 100 and the winding ends of the second pole piece 200 are respectively fixed to the diaphragm 300 by the connecting piece 400, so that the winding ends of the first pole piece 100 and the winding ends of the second pole piece 200 are fully fixed, and the pole pieces of the battery cell 10 will not be loose at the winding ends of the first pole piece 100 and the winding ends of the second pole piece 200, thereby avoiding OH failure and lithium deposition caused by loose pole pieces at the winding ends of the pole pieces of the battery cell 10.

[0077] Those skilled in the art will appreciate that the first electrode sheet 100 and the second electrode sheet 200 both include a foil and an active material layer disposed on the foil. The first electrode sheet 100 and the second electrode sheet 200 are cut at the end of the winding, and burrs may appear on the foil (aluminum foil or copper foil) at the cut position. The connector 400 at least covers the portion of the winding end of the corresponding electrode sheet. The burrs at the position of the winding end of the corresponding electrode sheet covered by the connector 400 are unlikely to pierce the diaphragm 300 and cause a short circuit.

[0078] According to some embodiments of the present application, Figure 2 、 Figure 7 and Figure 8 As shown, the connector 400 extends beyond the end of the corresponding winding end in a preset direction. The preset direction is the length direction and / or width direction of the corresponding connected pole piece.

[0079] It should be noted that Figure 7 The X-axis indicates the length direction of the pole piece, and the Y-axis indicates the width direction of the pole piece.

[0080] That is to say, the connector 400 only extends beyond the corresponding electrode in the length direction of the corresponding electrode, or the connector 400 only extends beyond the corresponding electrode in the width direction of the corresponding electrode, or the connector 400 extends beyond the corresponding electrode in both the length and width directions of the corresponding electrode. When the connector 400 extends beyond the corresponding electrode in the width direction of the corresponding electrode, the connector 400 may extend beyond the electrode only on one side of the corresponding electrode, or the connector 400 may extend beyond the electrode on both sides of the corresponding electrode. For example, when double-sided tape is used as the connector 400 and connectors 400 are provided on both sides of the electrode, the portions of the connector 400 on both sides of the electrode that extend beyond the electrode can be fixed to each other.

[0081] In one possible implementation, the portion of the connector 400 covering the electrode is fixed to the electrode, and the portion of the connector 400 extending beyond the electrode is fixed to the diaphragm 300, thereby reliably fixing the wound end of the electrode to the diaphragm 300. When the connector 400 extends beyond the electrode on both sides in the width direction of the electrode, the connector 400 can reliably cover burrs on the electrode, making it less likely for the burrs on the electrode to pierce the diaphragm 300 and cause a short circuit.

[0082] In another possible implementation, Figure 10 As shown, when double-sided tape or pressure-sensitive adhesive is used as the connector 400, the edge of the connector 400 can be flush with the winding end of the corresponding electrode, the side of the connector 400 facing the electrode is fixed to the electrode, and the side of the connector 400 facing the diaphragm 300 is fixed to the diaphragm 300 to fix the winding end of the connector 400 on the diaphragm 300.

[0083] According to some embodiments of the present application, in the length direction of the pole piece to which the connector 400 is connected, the ratio between the size of the connector 400 at the corresponding winding end and the size of the connector 400 is less than or equal to 0.5.

[0084] For example, the ratio between the size of the connector 400 set on the corresponding winding end and the size of the connector 400 can be in the range of 0.3-0.5, such as 0.3, 0.4 or 0.5, etc., which is not limited here.

[0085] In a specific embodiment, when the connector 400 is set, it is symmetrically pasted on the pole piece with the cut part of the pole piece as the center line, that is, in the length direction of the pole piece, the size of the connector 400 set on the winding end is the same as the size of the connector 400 exceeding the winding end.

[0086] By limiting the ratio between the size of the connector 400 set on the corresponding winding end and the size of the connector 400, it is possible to avoid the connector 400 covering the winding end of the corresponding electrode being too large, thereby preventing the battery capacity from being reduced.

[0087] For example, the dimension L1 of the connector 400 in the length direction of the corresponding electrode piece can be 10mm-20mm, such as 10mm, 12mm, 16mm or 20mm, and can be set according to the specific situation. When the dimension of the connector 400 in the length direction of the corresponding electrode piece is less than 10mm, the adhesion and covering effects of the connector 400 will be deteriorated, affecting the reliability of the connection between the winding end of the electrode piece and the diaphragm 300; when the dimension of the connector 400 in the length direction of the corresponding electrode piece is greater than 20mm, the coverage area of ​​the electrode piece by the connector 400 will be too large, affecting the performance of the electrode piece capacity, and the end of the connector 400 that extends beyond the electrode piece may extend to the straight section 11 of the winding body, causing wrinkles on the surface of the battery cell 10 during hot pressing of the winding body, affecting the charge and discharge performance of the battery cell 10.

[0088] According to some embodiments of the present application, Figure 7 As shown, in the width direction of the electrode piece connected to the connecting member 400, the ratio between the size of the connecting member 400 and the size of the corresponding electrode piece is X, and X satisfies: 1<X≤1.2.

[0089] That is to say, the width of the connector 400 is greater than the width of the corresponding electrode but not more than 1.2 times the width of the corresponding electrode. For example, the ratio between the width of the connector 400 and the width of the corresponding electrode can be 1.05, 1.1 or 1.2. In which, both ends of the connector 400 in the width direction of the corresponding electrode extend beyond the corresponding electrode, and the dimensions of the connector 400 extending beyond the corresponding electrode can be equal. In a specific embodiment, Figure 7 As shown, in the width direction of the pole piece, the two sides of the connector 400 may respectively exceed the pole piece by a dimension L2 of 1 mm to 3 mm.

[0090] When the ratio between the width of the connector 400 and the width of the corresponding electrode is no more than 1, during the process of setting the connector 400 on the electrode, the connector 400 may fail to completely cover the winding end of the electrode in the width direction of the electrode due to assembly tolerance, and the burrs on the winding end of the electrode may pierce the diaphragm 300 and cause a short circuit; when the ratio between the width of the connector 400 and the width of the corresponding electrode is greater than 1.2, the connector 400 exceeds the size of the electrode in the width direction of the electrode too much, and the connector 400 occupies a large space in the width direction of the electrode, resulting in a decrease in the energy density of the battery.

[0091] By limiting the ratio between the size of the connector 400 in the width direction of the electrode and the width of the corresponding electrode, it can be ensured that the connector 400 completely covers the winding end of the electrode in the width direction of the electrode, so that the burrs at the winding end of the electrode are not easy to pierce the diaphragm 300 and cause a short circuit, and it can also avoid the connector 400 occupying a large space in the width direction of the electrode, which leads to a decrease in the energy density of the battery.

[0092] According to some embodiments of the present application, Figure 8 As shown, the thickness H of the connecting member 400 is 10 μm-200 μm.

[0093] For example, the thickness H of the connector 400 can be 10μm, 50μm, 100μm, 150μm or 200μm, etc. It is worth mentioning that the connector 400 is denser than the porous structure of the diaphragm 300, and thus the thickness of the connector 400 is not less than 10μm to eliminate the burrs on the diaphragm electrode, effectively preventing the burrs at the end of the electrode winding from piercing the connector 400 and the diaphragm 300 and causing a short circuit. When the thickness of the connector 400 is greater than 200μm, wrinkles are easily generated on the surface of the wound body after hot pressing. In other words, the thickness of the connector 400 is relatively thin, and the thickness of the connector 400 differs from the thickness of the electrode by roughly an order of magnitude. The connector 400 is not likely to cause wrinkles on the surface of the wound body after hot pressing.

[0094] By limiting the thickness of the connector 400 , it is ensured that the burrs at the end of the pole piece winding will not extend from the connector 400 to cause a short circuit, and at the same time, wrinkles are not easily generated on the surface of the winding body after hot pressing.

[0095] In one possible implementation, the winding end of the first pole piece 100 is located at the straight section 11 or at the connection position between the straight section 11 and the arc section 12 , and the winding end of the second pole piece 200 exceeds the winding end of the first pole piece 100 and is located on the arc section 12 .

[0096] The first electrode sheet 100 is a positive electrode sheet, and the second electrode sheet 200 is a negative electrode sheet. The winding end of the second electrode sheet 200 extends beyond the winding end of the first electrode sheet 100 to ensure OH of the battery cell 10 and prevent lithium deposition at the winding end of the negative electrode sheet. Those skilled in the art can set the specific length by which the winding end of the second electrode sheet 200 extends beyond the winding end of the first electrode sheet 100 as needed, and this is not a sole limitation here.

[0097] After hot pressing the wound body formed by stacking and winding the first electrode sheet 100, the separator 300, and the second electrode sheet 200, the battery cell 10 will not have an indentation at the winding end of the second electrode sheet 200. A connector 400 can be provided at the winding end of the second electrode sheet 200, which is fixed to the separator 300 via the connector 400. This prevents the battery cell 10 from experiencing loosening at the winding end of the second electrode sheet 200. Burrs at the location where the winding end of the second electrode sheet 200 is covered by the connector 400 are less likely to pierce the separator and cause a short circuit.

[0098] In another possible implementation, the winding end of the first pole piece 100 is located at the arc segment 12 , and the winding end of the second pole piece 200 exceeds the winding end of the first pole piece 100 and is located at the straight segment 11 or the connection position between the straight segment 11 and the arc segment 12 .

[0099] Schematically, the first electrode sheet 100 is the positive electrode sheet, and the second electrode sheet 200 is the negative electrode sheet. A connector 400 can be provided at the wound end of the first electrode sheet 100. The wound end of the first electrode sheet 100 is secured to the separator 300 via the connector 400, preventing the battery cell 10 from becoming loose at the wound end of the first electrode sheet 100. Burrs at the location where the wound end of the first electrode sheet 100 is covered by the connector 400 are less likely to pierce the separator and cause a short circuit.

[0100] According to some embodiments of the present application, Figure 2 and Figure 4-Figure 6 As shown, the winding end of the second pole piece 200 exceeds the winding end of the first pole piece 100 , and the winding end of the first pole piece 100 and the winding end of the second pole piece 200 are respectively located on the arc segment 12 .

[0101] The first electrode 100 is a positive electrode, the second electrode 200 is a negative electrode, and the winding end of the second electrode 200 exceeds the winding end of the first electrode 100 to ensure the OH of the battery cell 10. The winding end of the first electrode 100 and the winding end of the second electrode 200 can be located on the arc segment 12 on one side of the winding body, such as Figure 2 and Figure 4-Figure 6 As shown, the winding ends of the first pole piece 100 and the second pole piece 200 are respectively located at the arc segment 12 on the right side of the winding body. The winding end of the first pole piece 100 can be located in the middle of the arc segment 12. The winding ends of the first pole piece 100 and the second pole piece 200 can also be located on the arc segments 12 on both sides of the winding body.

[0102] Optionally, only the winding end of the first pole piece 100 may be fixed to the diaphragm 300 through the connector 400, or only the winding end of the second pole piece 200 may be fixed to the diaphragm 300 through the connector 400, or the winding end of the first pole piece 100 and the winding end of the second pole piece 200 may be fixed to the diaphragm 300 through the connector 400 respectively.

[0103] Through the above arrangement, after the winding body is hot pressed, no indentations will appear at the winding ends of the first electrode sheet 100 and the second electrode sheet 200 of the battery cell 10, and the electrode sheets of the battery cell 10 will not become loose at the winding end where the connector 400 is provided.

[0104] According to some embodiments of the present application, Figure 6 As shown, a connection layer 600 is further provided on the winding starting end of at least one of the first pole piece 100 and the second pole piece 200. In the first pole piece 100 and the second pole piece 200, the winding starting end provided with the connection layer 600 is fixed to the diaphragm 300 through the connection layer 600.

[0105] Among them, only the winding starting end of the first pole piece 100 can be fixed to the diaphragm 300 through the connecting layer 600, or only the winding starting end of the second pole piece 200 can be fixed to the diaphragm 300 through the connecting layer 600, or the winding starting end of the first pole piece 100 and the winding starting end of the second pole piece 200 are respectively fixed to the diaphragm 300 through the connecting layer 600.

[0106] Schematically, the connecting layer 600 covers the winding starting end of the corresponding electrode. It can be understood that the first electrode 100 and the second electrode 200 are cut off at the winding starting end, so that the winding starting end of the first electrode 100 and the winding starting end of the second electrode 200 are formed with burrs. The connecting layer 600 can be a hot melt adhesive film, a pressure-sensitive adhesive or a double-sided adhesive. When the connecting layer 600 is a hot melt adhesive film, the edge of the connecting layer 600 exceeds the winding starting end of the corresponding electrode. The portion of the connecting layer 600 covering the corresponding electrode is attached to the electrode, and the portion of the connecting layer 600 exceeding the electrode is attached to the diaphragm 300. When the connecting layer 600 is a pressure-sensitive adhesive or a double-sided adhesive, the edge of the connecting layer 600 can exceed the corresponding electrode or be flush with the corresponding electrode. One side of the connecting layer 600 is fixed to the electrode, and the other side of the connecting layer 600 is fixed to the diaphragm 300.

[0107] By providing a connecting layer 600 at the winding starting end of the corresponding electrode, the connecting layer 600 fixes the winding starting end of the corresponding electrode to the diaphragm 300, thereby improving the fixation of the winding starting end of the electrode and preventing the winding starting end of the electrode from moving relative to the diaphragm 300. In addition, the connecting layer 600 covers the winding starting end of the electrode and then covers the burrs on the winding starting end, making it less likely for the burrs on the winding starting end of the electrode to pierce the diaphragm 300 and cause a short circuit.

[0108] Hereinafter, the present application will be explained in more detail by citing examples, which should not be construed as limiting. Within the scope consistent with the gist of the present application, appropriate modifications may be made, which all fall within the technical scope of the present application.

[0109] Example 1

[0110] 1. Preparation of positive electrode

[0111] The positive electrode active material LFP (lithium iron phosphate), conductive agent, SP (conductive carbon black), and binder PVDF (polyvinylidene fluoride) are evenly dispersed in a solvent according to mass percentages of 97.0%, 0.1%, 0.7%, and 2.2%, respectively. The solvent is NMP with a solid content of 60%. The positive electrode sheet is formed after being coated on the positive electrode collector and dried, rolled, and cut.

[0112] Connectors 400 are provided on either side of the second end of the positive electrode sheet, covering the second end. Along the length of the positive electrode sheet, the extent of the connector 400 covering the second end of the positive electrode sheet is equal to the extent of the connector 400 extending beyond the second end of the positive electrode sheet. The connector 400 extends 20 mm along the length of the positive electrode sheet. Along the width of the positive electrode sheet, each end of the connector 400 extends 2 mm beyond the positive electrode sheet.

[0113] 2. Preparation of negative electrode sheet

[0114] The negative electrode active materials artificial graphite, SP, thickener CMC, and binder SBR are evenly dispersed in a solvent according to mass percentages of 96.6%, 0.4%, 2%, and 1.0%, respectively, wherein the solvent is water with a solid content of 55%. The negative electrode sheets are formed after being coated on the negative electrode collector, dried, rolled, and cut.

[0115] Connectors 400 are provided on either side of the second end of the negative electrode sheet, covering the second end. Along the length of the negative electrode sheet, the length of the connector 400 covering the second end of the negative electrode sheet is equal to the length of the connector 400 extending beyond the second end of the negative electrode sheet. The connector 400 extends 20 mm along the length of the negative electrode sheet. Along the width of the negative electrode sheet, each end of the connector 400 extends 2 mm beyond the negative electrode sheet.

[0116] 3. Preparation of diaphragm 300

[0117] A polyethylene (PE) porous polymer film is used as the separator 300 .

[0118] 4. Assembly

[0119] The separator 300 is placed between the first electrode sheet 100 and the second electrode sheet 200, and is stacked and wound together to form a jellyroll. The first end of the positive electrode sheet is the starting end of the jellyroll, and the second end of the positive electrode sheet is the ending end of the jellyroll. The first end of the negative electrode sheet is the starting end of the jellyroll, and the second end of the negative electrode sheet is the ending end of the jellyroll. The jellyroll is hot-pressed to form the battery cell 10. The second ends of the positive and negative electrodes are secured to the separator 300 via corresponding connectors 400.

[0120] The battery cell 10 is installed in the housing 20, and the electrolyte is injected. After aging and formation processes, the corresponding battery is obtained. The electrolyte includes an organic solvent and a lithium salt. The organic solvent is a mixture of propylene carbonate, ethylene carbonate, and dimethyl carbonate, with the volume ratio of the three solvents being 1:1:1. The lithium salt is LiPF6 with a concentration of 1M.

[0121] Example 2

[0122] Example 2 is carried out with reference to Example 1, except that no connector 400 is provided at the second end of the negative electrode sheet.

[0123] Example 3

[0124] Example 3 was carried out similarly to Example 1, with the following differences: connectors 400 were also provided on both sides of the first end of the positive electrode sheet, covering the first end of the positive electrode sheet. Along the length of the positive electrode sheet, the connector 400's coverage of the first end of the positive electrode sheet was equal to the extent that the connector 400 extended beyond the first end of the positive electrode sheet. The connector 400's length along the length of the positive electrode sheet was 20 mm. Along the width of the positive electrode sheet, each end of the connector 400 extended 2 mm beyond the positive electrode sheet.

[0125] Connectors 400 are also provided on either side of the first end of the negative electrode sheet, covering the first end. Along the length of the negative electrode sheet, the length of the connector 400 covering the first end of the negative electrode sheet is equal to the length of the connector 400 extending beyond the first end of the negative electrode sheet. The connector 400 measures 20 mm along the length of the negative electrode sheet. Along the width of the negative electrode sheet, each end of the connector 400 extends 2 mm beyond the negative electrode sheet.

[0126] After the positive electrode sheet, the separator 300 and the negative electrode sheet are formed into the battery cell 10, the first and second ends of the positive electrode sheet are fixed to the separator 300 through the connector 400, and the first and second ends of the negative electrode sheet are fixed to the separator 300 through the connector 400.

[0127] Comparative Example 1

[0128] Comparative Example 1 was carried out with reference to Example 1, except that no connector 400 was provided at the first and second ends of the positive electrode sheet and the first and second ends of the negative electrode sheet.

[0129] The relevant performances of the batteries in the above examples and comparative examples were tested, and the test results are recorded in Table 1. The test method is as follows:

[0130] 1. Capacity retention rate

[0131] At 25°C, the batteries in the above examples and comparative examples were charged at a constant current of 0.5C to 3.65V, then charged at a constant voltage of 3.65V to a current less than 0.05C. After standing for 10 minutes, they were discharged at a constant current of 0.5C to 2.5V, and then discharged at a constant current of 0.25C to 2.0V. The discharge capacity of the battery at this time was tested, which was the discharge capacity of the first cycle. The battery was cycled multiple times under the above conditions, and the capacity retention rate of the battery after 1000 cycles was calculated. The capacity retention rate after the cycle was calculated according to the following formula:

[0132] Capacity retention (%) = (discharge capacity corresponding to 1000 cycles / discharge capacity of the first cycle) × 100%.

[0133] 2. Short circuit rate test

[0134] 500 cells 10 (JR windings) from each of the above-described examples and comparative examples were tested using a Ruijie pulse-type lithium battery short-circuit tester. The number of cells 10 shorted was determined under the following conditions: a voltage of 100V, a test time of 200ms, a voltage drop of 10%, and free discharge mode. During the test, any cell 10 whose voltage drop exceeded 10% of 100V was considered a short circuit.

[0135] Cell short-circuit rate = number of short-circuited cells / total number of measured cells × 100%.

[0136] Table 1:

[0137]

[0138] According to Table 1, by fixing the end of the electrode to the diaphragm 300 through the connector 400, loosening of the electrode at the end of the electrode of the battery cell 10 can be avoided, thereby improving the capacity retention rate of the battery. At the same time, the connector 400 on the electrode can effectively reduce the short circuit rate of the battery.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery cell (10), comprising: a first pole piece (100); a second pole piece (200); a diaphragm (300), the diaphragm (300) being disposed between the first pole piece (100) and the second pole piece (200), and being stacked with the first pole piece (100) and the second pole piece (200) and wound to form a winding body; and Connector (400); The wound body comprises a straight section (11) and two arc-shaped sections (12) respectively located on both sides of the straight section (11); the winding end of the first pole piece (100) and / or the winding end of the second pole piece (200) are located in the arc-shaped sections (12); and in the first pole piece (100) and the second pole piece (200), at least one winding end located in the arc-shaped section (12) is fixed to the diaphragm (300) through the connecting member (400).

2. The battery cell (10) according to claim 1, characterized in that The connecting member (400) extends beyond the end of the corresponding connected winding end in a preset direction; The preset direction is the length direction and / or width direction of the corresponding connected electrode.

3. The battery cell (10) according to claim 2, characterized in that In the length direction of the pole piece to which the connector (400) is connected, the ratio between the size of the connector (400) disposed on the corresponding winding end and the size of the connector (400) is less than or equal to 0.

5.

4. The battery cell (10) according to claim 2, characterized in that In the width direction of the pole piece to which the connecting piece (400) is connected, the ratio between the size of the connecting piece (400) and the size of the corresponding pole piece is X; The X satisfies: 1<X≤1.

2.

5. The battery cell (10) according to any one of claims 1 to 4, characterized in that: The thickness of the connecting member (400) is 10 μm-200 μm.

6. The battery cell (10) according to any one of claims 1 to 4, characterized in that: The winding end of the first pole piece (100) is located at the straight section (11) or at the connection position between the straight section (11) and the arc section (12), and the winding end of the second pole piece (200) exceeds the winding end of the first pole piece (100) and is located on the arc section (12).

7. The battery cell (10) according to any one of claims 1 to 4, characterized in that: The winding end of the first pole piece (100) is located in the arc segment (12), and the winding end of the second pole piece (200) exceeds the winding end of the first pole piece (100) and is located in the straight segment (11) or at the connection position between the straight segment (11) and the arc segment (12).

8. The battery cell (10) according to any one of claims 1 to 4, characterized in that: The winding end of the second pole piece (200) exceeds the winding end of the first pole piece (100), and the winding end of the first pole piece (100) and the winding end of the second pole piece (200) are respectively located on the arc segment (12).

9. The battery cell (10) according to any one of claims 1 to 4, characterized in that: A connecting layer (600) is further provided on the winding starting end of at least one of the first pole piece (100) and the second pole piece (200); in the first pole piece (100) and the second pole piece (200), the winding starting end provided with the connecting layer (600) is fixed to the diaphragm (300) through the connecting layer (600).

10. A battery, characterized in that: The invention comprises a shell (20) and a battery core (10) according to any one of claims 1 to 9, wherein the battery core (10) is installed inside the shell (20).

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