Pole piece, battery cell and lithium ion battery
By designing a pole sheet with a specific end structure, the problem of short circuit caused by puncture of the hollow foil of the lithium-ion battery cell is solved, and the effect of reducing the internal short circuit of the battery is achieved.
Patent Information
- Application Number
- CN202420324532.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-02-21
- Publication Date
- 2025-02-28
- Estimated Expiration
- 2034-02-21
AI Technical Summary
During the battery cell preparation process of lithium-ion batteries, the empty foil is prone to pierce the isolation film, resulting in a short circuit inside the battery.
An electrode sheet structure is designed in which the current collector is provided with a first end, an intermediate region and a second end along its length direction, and the active material layer is provided in the intermediate region, and the arc portions and straight portions of the first and second ends form a smooth transition end angle to reduce the pressure when in contact with the isolation film.
With this pole sheet structure, it is difficult for the end angle of the empty foil to poke the isolation film, reducing the possibility of short circuit inside the battery.
Smart Images
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Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of lithium ion batteries, in particular to a pole piece, a battery core and a lithium ion battery. Background Art
[0002] Lithium-ion batteries have the advantages of high specific energy, strong endurance, long cycle life, wide operating range, short charging time and large discharge current. Therefore, they are widely used in power fields such as electric vehicles and consumer fields such as mobile phones, watches, tablets and notebooks.
[0003] In the preparation of lithium-ion battery cells used in small lithium-ion batteries for consumer electronics, due to the problems of the existing pole piece preparation process itself, after the active material is coated on the current collector, the corner part of the current collector will inevitably be left, thus generating empty foil. In the process of winding the pole piece to form a battery cell, these empty foils will be located at the inner layer of the battery cell.
[0004] However, these empty foils, whether in the straight area or the corner area where the battery cell is rolled up, may pierce the separator during the formation and cyclic charge and discharge of the battery, causing an internal short circuit in the battery. Utility Model Content
[0005] The main purpose of the utility model is to provide a pole piece, aiming to solve the problem that the empty foil located at the rolling position of the inner layer of the battery core pierces the isolation film.
[0006] To achieve the above-mentioned purpose, one aspect of the utility model proposes a pole piece, which includes a current collector and an active material layer arranged on the surface of at least one side of the current collector, the current collector is provided with a first end, a middle area and a second end in sequence along its length direction, the active material layer is arranged in the middle area, and in the width direction of the current collector, the first end and the second end are respectively provided with a first arc portion, a straight portion and a second arc portion, one end of the first arc portion is connected with the middle area and the connection is smoothly transitioned, the other end of the first arc portion is connected with one end of the straight portion and the connection is smoothly transitioned, the other end of the straight portion is connected with one end of the second arc portion and the connection is smoothly transitioned, and the other end of the second arc portion is connected with the middle area and the connection is smoothly transitioned.
[0007] In some embodiments, surfaces of the first end portion and the second end portion are respectively coated with an insulating layer.
[0008] In some embodiments, the insulating layer is made of one of ceramic, epoxy resin, silicone ester, silicone ester, polyethylene, and fluororesin.
[0009] In some embodiments, the thickness of the insulating layer is less than or equal to the thickness of the active material layer.
[0010] In some embodiments, the first end portion, the middle region, and the second end portion of the current collector are an integrally connected structure.
[0011] In some embodiments, the active material layers are disposed on two opposite surfaces of the middle region.
[0012] In some embodiments, the pole piece further includes a pole ear connected to the middle region.
[0013] In some embodiments, the connection between the tab and the middle region is wrapped with tab glue.
[0014] Another aspect of the present invention provides a battery cell, which includes a stacked positive electrode sheet and a negative electrode sheet, and a separator sandwiched between the positive electrode sheet and the negative electrode sheet; wherein the positive electrode sheet and the negative electrode sheet are the electrode sheets described above.
[0015] Another aspect of the present invention provides a lithium-ion battery, which includes the battery cell as described above.
[0016] The beneficial effect of the utility model is that after the pole piece of the utility model is used to prepare a battery cell, the first end and the second end will form a hollow foil of the battery cell, and the first arc portion and the second arc portion form the end angle of the hollow foil. When the first arc portion and the second arc portion are in contact with the isolation membrane, the pressure between the two is small, so that the end angle of the hollow foil is difficult to puncture the isolation membrane, reducing the possibility of a short circuit inside the battery. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 A top view of a pole piece according to an embodiment of the utility model;
[0018] Figure 2 for Figure 1 A front view of the pole piece shown;
[0019] Figure 3 Based on Figure 2 A schematic diagram of an improved structure of the pole piece shown;
[0020] Figure 4 Based on Figure 2 Schematic diagram of another improved structure of the pole piece shown.
[0021] Description of Figure Numbers:
[0022] The current collector 100 , the first end 110 , the middle region 120 , the second end 130 , the first arc portion 140 , the straight portion 150 , the second arc portion 160 , the active material layer 200 , the insulating layer 300 , and the tab 400 .
[0023] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION
[0024] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the scheme in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0025] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, top, bottom, side...) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.
[0026] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.
[0027] In addition, the descriptions involving "first", "second", etc. in the present utility model are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features.
[0028] Before describing the technical solution of the present application, the concept of lithium-ion battery is briefly described below.
[0029] Lithium-ion battery is a secondary battery (rechargeable battery) that mainly relies on the movement of lithium ions between the positive electrode and the negative electrode to work. During the charge and discharge process, lithium ions are intercalated and deintercalated back and forth between the two electrodes: during charging, lithium ions are deintercalated from the positive electrode, embedded in the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; the opposite is true during discharge. The structure of a lithium-ion battery usually includes a battery cell and a shell that wraps the battery cell. The battery cell is wound by stacking the positive electrode sheet, the isolation film and the negative electrode sheet in sequence. However, as described in the background technology section of this application, due to the problems of the existing electrode sheet preparation process itself, after the active material is coated on the current collector, a part of the empty foil will inevitably remain. In the process of winding the electrode sheet to form a battery cell, these empty foils will be located at the inner layer of the battery cell. Whether these empty foils are in the straight area or the corner area of the battery cell rolling position, they may pierce the isolation film during the formation and cyclic charge and discharge of the battery, causing an internal short circuit in the battery.
[0030] In view of the above problems, this embodiment provides a pole piece structure that can improve the above problems. Figure 1 and Figure 2As shown, the pole piece of this embodiment includes a current collector 100 and an active material layer 200 disposed on one side of the current collector 100. The current collector 100 is Figure 1 and Figure 2 The first end 110, the middle area 120 and the second end 130 are sequentially provided in the direction A). The first end 110, the middle area 120 and the second end 130 are integrally connected.
[0031] The active material layer 200 is disposed in the middle region 120 and is disposed in the width direction ( Figure 1 In the direction B), the first end portion 110 and the second end portion 130 are respectively provided with a first arc portion 140, a straight portion 150 and a second arc portion 160. One end of the first arc portion 140 is connected to the middle area 120 with a smooth transition at the connection, the other end of the first arc portion 140 is connected to one end of the straight portion 150 with a smooth transition at the connection, the other end of the straight portion 150 is connected to one end of the second arc portion 160 with a smooth transition at the connection, and the other end of the second arc portion 160 is connected to the middle area 120 with a smooth transition at the connection.
[0032] After the electrode sheet of this embodiment is used to prepare a battery cell, the first end 110 or the second end 130 will form a hollow foil of the battery cell, and the end corner of the hollow foil is formed by the first arc portion 140 and the second arc portion 160. When the first arc portion 140 and the second arc portion 160 are in contact with the separator, the pressure between the two is small, so that the end corner of the hollow foil is difficult to puncture the separator, reducing the possibility of a short circuit inside the battery.
[0033] Furthermore, if Figure 3 As shown, in some embodiments, the surfaces of the first end 110 and the second end 130 are respectively coated with an insulating layer 300. The insulating layer 300 can block the electron exchange between the current collector 100 and other electrode structures, and can further prevent the internal short circuit of the battery. Optionally, the thickness of the insulating layer 300 is less than the thickness of the active material layer 200, but the maximum thickness of the insulating layer 300 should be equal to the thickness of the active material layer 200 to avoid the insulating layer 300 hindering the active material layer 200 from releasing lithium ions.
[0034] The insulating layer 300 is made of at least one of ceramic, epoxy resin, silicone ester, silicone ester, polyethylene, and fluororesin.
[0035] In an optional example, the insulating layer 300 is formed by coating enamel on opposite ends of the current collector 100 in the length direction. Enamel is an insulating coating that forms an alumina glass ceramic film on the surface of the coating object to play an insulating role.
[0036] In another optional example, the insulating layer 300 is completed by coating a mixed paint of epoxy resin and silicone ester on opposite ends in the length direction of the current collector 100. The mixture of epoxy resin paint and silicone ester has high mechanical strength and insulation performance, and is also resistant to chemical corrosion, so that it will not corrode even if it is immersed in the electrolyte for a long time.
[0037] In another optional example, the insulating layer 300 is completed by coating a mixed paint of silicone ester, polyethylene and fluororesin on opposite ends in the length direction of the current collector 100. The mixed paint of silicone ester, polyethylene and fluororesin has good chemical corrosion resistance and high temperature resistance, so it can withstand the heat generated during the charging and discharging process of the lithium battery.
[0038] Furthermore, the pole piece of this embodiment further includes a pole ear 400. The pole ear 400 is connected to the middle area 120 for powering an external electronic device. The connection between the pole ear 400 and the middle area 120 is wrapped with a pole ear 400 glue to improve the sealing between the pole ear 400 and the aluminum-plastic film when the aluminum-plastic film is subsequently wrapped to prevent the electrolyte from leaking outward.
[0039] Continue to refer to Figure 4 As shown, in the pole piece structure of some embodiments, the active material layer 200 is arranged on the opposite side surfaces of the middle area 120. Since the charging and discharging process of lithium-ion batteries is a process of transfer and deintercalation of lithium ions, the total amount of the active material layer 200 of the pole piece will determine the total energy of the lithium-ion battery. When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the generated lithium ions move to the negative electrode through the electrolyte. The carbon as the negative electrode has a layered structure and has many micropores. The lithium ions reaching the negative electrode are embedded in the micropores of the carbon layer. The more lithium ions are embedded, the higher the charging capacity. Similarly, when the battery is discharged (i.e. connected to a load), the lithium ions embedded in the negative electrode carbon layer are released and move back to the positive electrode. The more lithium ions return to the positive electrode, the higher the discharge capacity. Since the charging and discharging process of a lithium-ion battery is the process of embedding and de-embedding of lithium ions, the more active material layers 200 there are at the positive and negative electrodes, the more lithium ions and electrons are generated. Therefore, providing active material layers 200 on both opposite sides of the middle region 120 can increase the total energy of the lithium-ion battery.
[0040] It is understandable that the pole piece of the above embodiment can be applied to the positive pole piece. When the pole piece of this embodiment is used as the positive pole piece, the current collector 100 adopts aluminum foil. Accordingly, in order to make the positive pole piece generate lithium ions, when the pole piece is used as the positive pole piece, the active material layer 200 is made of one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium iron phosphate. Lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, or lithium iron phosphate generates lithium ions during the charging process of the lithium-ion battery. These lithium ions are transferred to the negative pole piece through the isolation membrane and embedded in the active material layer 200 of the negative pole piece. The electrons generated in the positive pole piece cannot pass through the isolation membrane, and are thus transferred to the negative electrode through the wire. The pole piece of this embodiment is also applicable to the negative pole piece. When the pole piece of this embodiment is used as the negative pole piece, the current collector 100 adopts copper foil. Accordingly, in order to embed lithium ions in the negative electrode plate, when the plate is used as a negative electrode plate, the active material layer 200 is made of graphite or soft or hard carbon to embed lithium ions generated by the positive electrode during the charging process of the battery. During the discharge process of the battery, the lithium ions embedded in the negative electrode active material layer 200 are separated and transferred to the positive electrode plate through the isolation membrane.
[0041] In some embodiments, a battery cell is also provided, which includes a stacked positive electrode sheet and a negative electrode sheet, and a separator sandwiched between the positive electrode sheet and the negative electrode sheet. Among them, the structure of the positive electrode sheet and the negative electrode sheet of this embodiment adopts the electrode sheet structure described in the aforementioned embodiment. When forming the battery cell of this embodiment, the stacked positive electrode sheet and the negative electrode sheet and the separator are wound along the length direction of the electrode sheet. After the battery cell is formed, the first end or the second end of the current collector forms an empty foil to be located at the rolling position of the battery cell. Since the first arc portion and the second arc portion form the end angle of the empty foil, when the first arc portion and the second arc portion contact the separator, the pressure between the two is small, so that the end angle of the empty foil is difficult to puncture the separator, reducing the possibility of a short circuit inside the battery.
[0042] In some embodiments, a battery is also provided. The battery of this embodiment includes the battery cell described in the above embodiment and a shell that wraps the battery cell. Among them, the shell contains an electrolyte, and the solute of the electrolyte is usually prepared by lithium salt, such as lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4). The solvent of the electrolyte is because the operating voltage of the battery is much higher than the decomposition voltage of water, so organic solvents are often used in lithium-ion batteries, such as ether, ethylene carbonate, propylene carbonate, diethyl carbonate, etc.
[0043] The above description is only a partial or preferred embodiment of the present invention. Neither the text nor the drawings can limit the scope of protection of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the overall concept of the present invention, or direct / indirect application in other related technical fields are included in the scope of protection of the present invention.
Claims
1. A pole piece, comprising a current collector and an active material layer disposed on at least one side of the current collector, characterized in that: The current collector is provided with a first end, a middle area and a second end in sequence along its length direction, the active material layer is provided in the middle area, and in the width direction of the current collector, the first end and the second end are provided with a first arc portion, a straight portion and a second arc portion respectively, one end of the first arc portion is connected with the middle area with a smooth transition at the connection, the other end of the first arc portion is connected with one end of the straight portion with a smooth transition at the connection, the other end of the straight portion is connected with one end of the second arc portion with a smooth transition at the connection, and the other end of the second arc portion is connected with the middle area with a smooth transition at the connection.
2. The pole piece according to claim 1, characterized in that: The surfaces of the first end portion and the second end portion are respectively coated with an insulating layer.
3. The pole piece according to claim 2, characterized in that: The insulating layer is made of one of ceramic, epoxy resin, silicone ester, silicone ester, polyethylene and fluororesin.
4. The pole piece according to claim 2, characterized in that: The thickness of the insulating layer is less than or equal to the thickness of the active material layer.
5. The pole piece according to claim 1, characterized in that: The first end, the middle area and the second end of the current collector are an integrally connected structure.
6. The pole piece according to claim 1, characterized in that: The active material layers are arranged on two opposite surfaces of the middle region.
7. The pole piece according to claim 1, characterized in that: The pole piece further includes a pole ear connected to the middle region.
8. The pole piece according to claim 7, characterized in that: The connection between the pole ear and the middle area is wrapped with pole ear glue.
9. A battery cell, characterized in that: It comprises a stacked positive electrode sheet and a negative electrode sheet, and a separator sandwiched between the positive electrode sheet and the negative electrode sheet; wherein the positive electrode sheet and the negative electrode sheet are the electrode sheets as claimed in any one of claims 1 to 8.
10. A lithium ion battery, characterized in that: Comprising the battery cell as claimed in claim 9.