Battery cell preparation method, battery cell preparation device and battery cell

Abstract

The invention provides a battery cell preparation method, a battery cell preparation device and a battery cell, the battery cell preparation method comprises the following steps: providing a feeding assembly and a rolling assembly, the rolling assembly is located at the downstream of the feeding assembly, and the feeding assembly is used for conveying a pole piece unit; the pole piece unit is rolled through a rolling assembly, so that a rolling groove is formed in the surface of at least one side of the pole piece unit; and laminating and winding the rolled pole piece units to form the battery cell. By applying the technical scheme provided by the invention, the technical problem of poor liquid retention capability of the battery cell can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery cells, and in particular to a battery cell preparation method, a battery cell preparation device and a battery cell. Background Art

[0002] In the relevant technology, the battery industry mainly uses the winding process. The positive electrode, the separator and the negative electrode are tightly attached together by hot pressing after winding. The conventional assembly process of the battery is as follows: electrode die cutting → winding → hot pressing. The environmental conditions of hot pressing are usually: temperature 95℃±5℃, time 120s±1s, pressure: 2.0Mpa±0.1Mpa. However, after the battery is assembled through the above process, after the liquid injection process, it is found through testing that the battery cell has poor liquid retention capacity, which will cause the battery cycle performance to deteriorate, and thus cannot meet the user's usage needs. Summary of the invention

[0003] The embodiments of the present invention provide a method for preparing a battery cell, a device for preparing a battery cell, and a battery cell, which can improve the technical problem of poor liquid retention ability of the battery cell.

[0004] In the first aspect, an embodiment of the present invention provides a method for preparing a battery cell, which includes: providing a feeding assembly and a rolling assembly, wherein the rolling assembly is located downstream of the feeding assembly, and the feeding assembly is used to convey a pole piece unit; rolling the pole piece unit by the rolling assembly to form a rolling groove on the surface of at least one side of the pole piece unit; and stacking and winding the rolled pole piece unit to form a battery cell.

[0005] In one embodiment, the groove depth of the rolled groove is 30 μm.

[0006] In one embodiment, rolling the pole piece unit by the rolling assembly specifically includes:

[0007] The pole piece unit was rolled at a temperature of 85±5°C and a roller speed of 30 M / min.

[0008] In one embodiment, the thickness of the pole piece unit is L1, the rolling assembly includes an upper rolling piece and a lower rolling piece, the gap between the upper rolling piece and the lower rolling piece is L2, and the pole piece unit is rolled by the rolling assembly, which also includes: rolling the pole piece unit under the condition of L2=L1-a, wherein 7μm≤a≤13μm.

[0009] In one embodiment, after the step of winding the rolled pole piece unit, the method further includes: hot pressing the wound pole piece unit.

[0010] In one embodiment, hot pressing the wound pole piece unit specifically includes: hot pressing the wound pole piece unit under the conditions of a temperature of 95° C.±5° C., a hot pressing time of 30s±1s, and a pressure of 1.0Mpa±0.1Mpa.

[0011] In one embodiment, after the step of hot pressing the wound pole piece unit, the method further includes: performing insulation resistance detection on the pole piece unit and / or performing winding diameter detection on the pole piece unit.

[0012] In the second aspect, an embodiment of the present invention provides a battery cell preparation device, which includes: a feeding assembly, which is used to convey a pole piece unit; a rolling assembly, which is arranged downstream of the feeding assembly, and is used to roll the pole piece unit to form a rolling groove on the surface of at least one side of the pole piece unit.

[0013] In one embodiment, the rolling assembly includes an upper rolling member and a lower rolling member, there is a gap between the upper rolling member and the lower rolling member, and the pole piece unit is inserted in the gap.

[0014] In one embodiment, a protrusion is provided on the surface of the upper rolling member or the lower rolling member, and the protrusion can contact the surface of the pole piece unit to form a rolling groove on the surface of the pole piece unit.

[0015] In one embodiment, the cross section of the protrusion is square or trapezoidal.

[0016] In one embodiment, a heating element is disposed in the upper rolling member and / or the lower rolling member, and the upper rolling member and / or the lower rolling member heats the pole piece unit through the heating element.

[0017] In one embodiment, the feeding assembly includes: a positive electrode unwinding member, which is used to convey the positive electrode unit; a first diaphragm unwinding member, which is used to convey the first diaphragm; a second diaphragm unwinding member, which is used to convey the second diaphragm; a negative electrode unwinding member, which is used to convey the negative electrode unit; wherein the positive electrode unit and the negative electrode unit are respectively arranged on both sides of the first diaphragm, the second diaphragm is located on the side of the positive electrode unit away from the first diaphragm, the upper roller is used to contact with the side of the second diaphragm away from the positive electrode unit, and the lower roller is used to contact with the side of the negative electrode unit away from the first diaphragm, and the first diaphragm, the second diaphragm, the positive electrode unit and the negative electrode unit together form a pole piece unit.

[0018] In a third aspect, an embodiment of the present invention provides a battery cell, the battery cell comprising a plurality of pole piece units, at least one side of at least one pole piece unit having a rolled groove on its surface.

[0019] By applying the technical solution of the present invention, a rolling assembly is arranged downstream of the feeding assembly, so that the pole piece unit is rolled by the rolling assembly before the pole piece unit is wound, so that a rolling groove is formed on the surface of at least one side of the pole piece unit. This can improve the wettability of the electrolyte and the pole piece unit, thereby improving the liquid retention capacity of the pole piece unit, and further improving the cycle performance of the battery cell to meet the user's usage requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 is a schematic flow chart of a method for preparing a battery cell provided by an embodiment of the present invention;

[0022] Figure 2 is a schematic structural diagram of a battery cell preparation device provided in an embodiment of the present invention;

[0023] Figure 3 is a schematic structural diagram of a square battery cell provided by an embodiment of the present invention;

[0024] Figure 4 is a schematic structural diagram of a cylindrical battery cell provided by an embodiment of the present invention;

[0025] Figure 5 Schematic diagram of the structure of the protrusion provided by different embodiments of the present invention.

[0026] The above drawings include the following reference numerals:

[0027] 10. Feeding assembly; 11. Positive electrode unwinding member; 111. Positive electrode unit; 12. First diaphragm unwinding member; 121. First diaphragm; 13. Second diaphragm unwinding member; 131. Second diaphragm; 14. Negative electrode unwinding member; 141. Negative electrode unit; 15. Rolling trough;

[0028] 20. Rolling assembly; 21. Upper rolling piece; 22. Lower rolling piece; 23. Protrusion. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0030] like Figures 1 to 5 As shown, in the first aspect, an embodiment of the present invention provides a method for preparing a battery cell, the method for preparing a battery cell comprising:

[0031] S1: providing a feeding assembly 10 and a rolling assembly 20, wherein the rolling assembly 20 is located downstream of the feeding assembly 10, and the feeding assembly 10 is used to transport the electrode unit;

[0032] S2: rolling the pole piece unit by a rolling assembly 20, so that a rolling groove 15 is formed on the surface of at least one side of the pole piece unit;

[0033] S3: Winding the rolled pole piece unit.

[0034] By applying the technical solution of the present invention, a rolling assembly 20 is arranged downstream of the feeding assembly 10, so that the pole piece unit is rolled by the rolling assembly 20 before the pole piece unit is wound, so that a rolling groove 15 is formed on the surface of at least one side of the pole piece unit. This can improve the wettability of the electrolyte and the pole piece unit, thereby improving the liquid retention capacity of the pole piece unit, and further improving the cycle performance of the battery cell to meet the user's usage requirements.

[0035] In one embodiment, the groove depth of the rolling groove 15 is 30 μm. This arrangement can increase the contact area between the electrolyte and the electrode unit, thereby improving the wettability of the electrolyte and the electrode unit, which is beneficial to improving the liquid retention capacity of the electrode unit.

[0036] In one embodiment, rolling the pole piece unit by the rolling assembly 20 specifically includes:

[0037] The pole piece unit was rolled at a temperature of 85±5°C and a roller speed of 30 M / min.

[0038] In one embodiment, the thickness of the pole piece unit is L1, the rolling assembly 20 includes an upper rolling member 21 and a lower rolling member 22, the gap between the upper rolling member 21 and the lower rolling member 22 is L2, and the pole piece unit is rolled by the rolling assembly 20, which also includes: rolling the pole piece unit under the condition of L2=L1-a, wherein 7μm≤a≤13μm.

[0039] In one embodiment, after the step of winding the rolled pole piece unit, the method further includes: hot pressing the wound pole piece unit.

[0040] In one embodiment, hot pressing the wound pole piece unit specifically includes: hot pressing the wound pole piece unit under the conditions of a temperature of 95° C.±5° C., a hot pressing time of 30s±1s, and a pressure of 1.0Mpa±0.1Mpa.

[0041] In one embodiment, after the step of hot pressing the wound pole piece unit, the method further includes: performing insulation resistance detection on the pole piece unit.

[0042]

[0043]

[0044] Table 1

[0045] Table 1 shows the test results of the pole piece unit after roller pressing and hot pressing when the battery cell is wound into a square shape.

[0046] In Scheme 1, the hot pressing conditions are 95±5℃, 120±1s, 2.0±0.1Mpa, and the rolling conditions of the pole piece unit are 85±5℃, 30M / min, L2=L1-5μm. The fully charged and disassembled battery cell confirms that the state of the battery cell is powder loss and insufficient wetting. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 90.5%.

[0047] In Scheme 2, the hot pressing conditions are 95±5℃, 90±1s, 2.0±0.1Mpa, and the rolling conditions of the electrode unit are 85±5℃, 30M / min, L2=L1-5μm. The fully charged and disassembled battery cell confirms that the state of the battery cell is powder loss and insufficient wetting. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 91.0%.

[0048] In Scheme 3, the hot pressing conditions are 95±5℃, 60±1s, 2.0±0.1Mpa, and the rolling conditions of the pole piece unit are 85±5℃, 30M / min, L2=L1-10μm. The fully charged and disassembled battery cell confirms that the battery cell is slightly powdered and insufficiently wetted. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 90.8%.

[0049] In Scheme 4, the hot pressing conditions are 95±5℃, 30±1s, 2.0±0.1Mpa, and the rolling conditions of the pole piece unit are 85±5℃, 30M / min, L2=L1-10μm. The fully charged disassembly confirms that the state of the battery cell is slight powder loss and insufficient wetting. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 91.2%.

[0050] In Scheme 5, the hot pressing conditions are 95±5℃, 120±1s, 1.5±0.1Mpa, and the rolling conditions of the pole piece unit are 85±5℃, 30M / min, L2=L1-5μm. The fully charged and disassembled battery confirms that the battery cell is slightly powdered and fully wetted. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 91.6%.

[0051] In Scheme 6, the hot pressing conditions are 95±5℃, 90±1s, 1.5±0.1Mpa, the rolling conditions of the pole piece unit are 85±5℃, 30M / min, L2=L1-5μm, and the fully charged disassembly confirms that the state of the battery cell is slight powder loss and sufficient wetting. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 91.5%.

[0052] In Scheme 7, the hot pressing conditions are 95±5℃, 60±1s, 1.5±0.1Mpa, the rolling conditions of the pole piece unit are 85±5℃, 30M / min, L2=L1-10μm, and the fully charged and disassembled state confirms that the battery cell is fully wetted. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 92.2%.

[0053] In Scheme 8, the hot pressing conditions are 95±5℃, 30±1s, 1.5±0.1Mpa, the rolling conditions of the electrode unit are 85±5℃, 30M / min, L2=L1-10μm, and the fully charged and disassembled state confirms that the battery cell is fully wetted. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 93.1%.

[0054] In Scheme 9, the hot pressing conditions are 95±5℃, 120±1s, 1.0±0.1Mpa, the rolling conditions of the electrode unit are 85±5℃, 30M / min, L2=L1-5μm, and the fully charged and disassembled state confirms that the battery cell is fully wetted. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 93.2%.

[0055] In Scheme 10, the hot pressing conditions are 95±5℃, 90±1s, 1.0±0.1Mpa, the rolling conditions of the electrode unit are 85±5℃, 30M / min, L2=L1-5μm, and the fully charged and disassembled state confirms that the battery cell is fully wetted. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 93.0%.

[0056] In Scheme 11, the hot pressing conditions are 95±5℃, 60±1s, 1.0±0.1Mpa, the rolling conditions of the electrode unit are 85±5℃, 30M / min, L2=L1-10μm, and the fully charged and disassembled state confirms that the battery cell is fully wetted. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 93.2%.

[0057] In Scheme 12, the hot pressing conditions are 95±5℃, 30±1s, 1.0±0.1Mpa, the rolling conditions of the electrode unit are 85±5℃, 30M / min, L2=L1-10μm, and the fully charged and disassembled state confirms that the battery cell is fully wetted. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 93.2%.

[0058] Therefore, based on the above, Scheme 12 is the best solution.

[0059]

[0060]

[0061] Table 2

[0062] Table 2 shows the test results of the pole piece unit after rolling when the battery cell is wound into a cylindrical shape.

[0063] In Scheme 1, the rolling conditions of the pole piece unit are 85±5℃, 30M / min, L2=L1-0μm, and the fully charged and disassembled state confirms that the battery cell is fully wetted. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 87.5%.

[0064] In Scheme 2, the rolling conditions of the pole piece unit are 85±5℃, 30M / min, L2=L1-5μm, and the fully charged and disassembled state confirms that the battery cell is fully wetted. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 87.2%.

[0065] In Scheme 3, the rolling conditions of the pole piece unit are 85±5℃, 30M / min, L2=L1-10μm, and the fully charged and disassembled state of the battery cell confirms that it is fully wetted. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 90.2%.

[0066] In Scheme 4, the rolling conditions of the pole piece unit are 85±5℃, 30M / min, L2=L1-15μm, and the fully charged disassembly confirms that the state of the battery cell is slight powder loss and sufficient wetting. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 88.8%.

[0067] In Scheme 5, the rolling conditions of the pole piece unit are 85±5℃, 30M / min, L2=L1-20μm, and the fully charged disassembly confirms that the state of the battery cell is slight powder loss and sufficient wetting. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 89.6%.

[0068] In Scheme 6, the rolling conditions of the pole piece unit are 85±5℃, 30M / min, L2=L1-25μm, and the fully charged disassembly confirms that the state of the battery cell is slight powder loss and sufficient wetting. At the same time, at 45℃, the average capacity retention rate at the 500th cycle is 89.7%.

[0069] Therefore, based on the above, Solution 3 is the best solution.

[0070] In one embodiment, after the step of winding the rolled pole piece unit, the method further includes: detecting the winding diameter of the wound pole piece unit. Through this step, it can be ensured that the wound pole piece unit meets the use requirements of the device, so as to improve the product yield.

[0071] In the second aspect, an embodiment of the present invention provides a battery cell preparation device, which includes: a feeding assembly 10, which is used to convey a pole piece unit; a rolling assembly 20, which is arranged downstream of the feeding assembly 10, and is used to roll the pole piece unit to form a rolling groove 15 on the surface of at least one side of the pole piece unit.

[0072] In one embodiment, the rolling assembly 20 includes an upper rolling member 21 and a lower rolling member 22, and there is a gap between the upper rolling member 21 and the lower rolling member 22, and the pole piece unit is arranged in the gap. This arrangement can improve the rolling efficiency of the pole piece unit by the upper rolling member 21 and the lower rolling member 22, thereby improving the production efficiency of the pole piece unit.

[0073] In one embodiment, the surface of the upper rolling member 21 or the lower rolling member 22 is provided with a protrusion 23, and the protrusion 23 can contact the surface of the pole piece unit to form a rolling groove 15 on the surface of the pole piece unit. In the present application, only the protrusion 23 is provided on the surface of the upper rolling member 21, so that the stability when the rolling groove 15 is formed on the surface of the pole piece unit can be ensured.

[0074] In one embodiment, the cross-section of the protrusion 23 is square or trapezoidal. The cross-section of the protrusion 23 may also include at least one of a circle, a triangle or a bar. It should be noted that the cross-sectional shape of the protrusion 23 in the present application can be a plurality of circles, triangles and bars arranged in an array, for example, the cross-sectional shape of the protrusion 23 includes a plurality of circles arranged in an array, or a plurality of triangles arranged in an array, or a plurality of bars arranged in an array; in addition, the cross-sectional shape of the protrusion 23 includes at least two of a circle, a triangle and a bar, and each shape is still arranged in an array.

[0075] exist Figure 5 In the first figure from the left, the protrusions 23 are arranged in an array, the protrusions 23 in the second figure from the left are arranged in a pattern spaced apart, the protrusions 23 in the third figure from the left are arranged in a pattern spaced apart, and the protrusions 23 in the fourth figure from the left are arranged in a pattern spaced apart.

[0076] In some embodiments, the battery cell preparation device further includes at least one transmission roller, which is disposed in the positive electrode unwinding member 11, the negative electrode unwinding member 14, the first separator 121 unwinding member 12, and the second separator 131 unwinding member 13, and the transmission roller is used to assist in conveying the positive electrode unit 111, the negative electrode unit 141, the first separator 121, and the second separator 131, respectively. It should be noted that the positive electrode unit 111, the negative electrode unit 141, the first separator 121, and the second separator 131 are assisted in transmission by the transmission roller, for example, the transmission roller is disposed between each device component, so that during the transmission process, the transmission roller can provide tension or transportation force; further, a plurality of the transmission rollers are alternately disposed, so that the positive electrode unit 111, the negative electrode unit 141, the first separator 121, and the second separator 131 shuttle back and forth on the transmission roller, thereby increasing the transmission path of the electrode sheet or separator, thereby reducing the volume of the device.

[0077] In one embodiment, a heating element is provided in the upper roller pressing member 21 and / or the lower roller pressing member 22, and the upper roller pressing member 21 and / or the lower roller pressing member 22 heats the pole piece unit through the heating element. In the present application, the upper roller pressing member 21 and / or the lower roller pressing member 22 are hot pressing rollers. It should be noted that the hot pressing roller in the present application refers to a pressing roller with a heating function, and the heating method can be electric heating or heat-conducting medium heating. Those skilled in the art can reasonably choose according to actual needs. Furthermore, the hot pressing roller that can be selected in the present invention refers to a hot pressing roller including a fixed roller and a movable roller, and the movable roller is provided with a mover, and the mover is used to move the movable roller, so as to adjust the distance between the fixed roller and the movable roller, and then adjust the pressing pressure, wherein the mover can be selected as a telescopic cylinder, and the telescopic cylinders are respectively arranged at both ends of the movable roller.

[0078] In some embodiments, a temperature sensor (not shown in the figure) is also provided in the upper roller pressing member 21 and / or the lower roller pressing member 22, and the temperature sensor is used to detect the temperature in the upper roller pressing member 21 and / or the lower roller pressing member 22. The present application detects the temperature in the upper roller pressing member 21 and / or the lower roller pressing member 22, thereby reasonably adjusting the heating temperature in the upper roller pressing member 21 and / or the lower roller pressing member 22 according to different heating needs, thereby ensuring the heating effect. Furthermore, the battery cell preparation device is also provided with a controller, and the controller is electrically connected to the temperature sensor and the upper roller pressing member 21 and / or the lower roller pressing member 22, respectively. The controller receives the detection signal of the temperature sensor and adjusts and controls the heating temperature of the upper roller pressing member 21 and / or the lower roller pressing member 22 according to the preset temperature feedback. It should be noted that the controller in the present invention is a conventional controller, which is not the innovation point of the present application. For example, the controller is a PLC controller.

[0079] In one embodiment, the feeding assembly 10 includes: a positive electrode unwinding member 11, the positive electrode unwinding member 11 is used to convey the positive electrode unit 111; a first diaphragm 121 unwinding member 12, the first diaphragm 121 unwinding member 12 is used to convey the first diaphragm 121; a second diaphragm 131 unwinding member 13, the second diaphragm 131 unwinding member 13 is used to convey the second diaphragm 131; a negative electrode unwinding member 14, the negative electrode unwinding member 14 is used to convey the negative electrode unit 141; wherein the first diaphragm 121 has two The positive electrode unit 111 and the negative electrode unit 141 are respectively arranged on the sides, the second diaphragm 131 is located on the side of the positive electrode unit 111 away from the first diaphragm 121, the upper roller 21 is used to contact the side of the second diaphragm 131 away from the positive electrode unit 111, and the lower roller 22 is used to contact the side of the negative electrode unit 141 away from the first diaphragm 121. The first diaphragm 121, the second diaphragm 131, the positive electrode unit 111 and the negative electrode unit 141 together form a pole piece unit. In the present application, the thickness of the pole piece unit is the common thickness of the first diaphragm 121, the second diaphragm 131, the positive electrode unit 111 and the negative electrode unit 141.

[0080] It should be noted that in the present application, there are no specific requirements or special limitations on the structure and material of the positive electrode unit 111, the negative electrode unit 141, the first diaphragm 121, and the second diaphragm 131. Those skilled in the art can reasonably select the structure and material of the positive electrode unit 111, the negative electrode unit 141, the first diaphragm 121, and the second diaphragm 131 according to the battery type and battery requirements. For example, the positive electrode unit 111 and the negative electrode unit 141 can be coated on one side or on both sides, and the first diaphragm 121 and the second diaphragm 131 can be a single-layer structure or a multi-layer structure; further, the battery can be a lithium-ion battery, so the materials of the positive electrode unit 111, the negative electrode unit 141, the first diaphragm 121, and the second diaphragm 131 can be selected according to the lithium-ion battery.

[0081] In some embodiments, the positive electrode unit 111 includes a positive electrode current collector and a positive electrode active layer disposed on at least one side of the surface of the positive electrode current collector. Optionally, the positive electrode current collector includes aluminum foil. Optionally, the positive electrode material in the positive electrode material layer includes lithium iron phosphate material or nickel-cobalt-manganese ternary material. In some embodiments, the negative electrode unit 141 includes a negative electrode current collector and a negative electrode material layer disposed on at least one side of the surface of the negative electrode current collector. Optionally, the negative electrode current collector includes copper foil. Optionally, the negative electrode material in the negative electrode material layer includes graphite material or silicon negative electrode material. In some embodiments, the materials of the first diaphragm 121 and the second diaphragm 131 include polyethylene diaphragm, polypropylene diaphragm or polyimide diaphragm. The raw materials in the following embodiments and comparative examples, if not otherwise specified, are all commercially available products; the preparation parameters, if not otherwise specified, can be achieved by conventional operating means.

[0082] In a third aspect, an embodiment of the present invention provides a battery cell, the battery cell comprising a plurality of pole piece units, at least one side of at least one pole piece unit having a rolling groove 15 on its surface.

[0083] By applying the technical solution of the present invention, a rolling assembly 20 is arranged downstream of the feeding assembly 10, so that the pole piece unit is rolled by the rolling assembly 20 before the pole piece unit is wound, so that a rolling groove 15 is formed on the surface of at least one side of the pole piece unit. This can improve the wettability of the electrolyte and the pole piece unit, thereby improving the liquid retention capacity of the pole piece unit, and further improving the cycle performance of the battery cell to meet the user's usage requirements.

[0084] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0085] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0086] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0087] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0088] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a battery cell, characterized in that: The battery core preparation method comprises: Providing a feeding assembly and a rolling assembly, wherein the rolling assembly is located downstream of the feeding assembly, and the feeding assembly is used to transport the pole piece unit; Rolling the pole piece unit by the rolling assembly so that a rolling groove is formed on the surface of at least one side of the pole piece unit; The rolled pole piece unit and the separator are stacked and wound to form a battery cell.

2. The method for preparing a battery cell according to claim 1, characterized in that: The groove depth of the roll-embossed groove is 30 μm.

3. The method for preparing a battery cell according to claim 1, characterized in that: The step of rolling the pole piece unit by the rolling assembly specifically includes: The pole piece unit is rolled at a temperature of 85±5° C. and a roller speed of 30 M / min.

4. The method for preparing a battery cell according to claim 1, characterized in that: The thickness of the pole piece unit is L1, the rolling assembly includes an upper rolling piece and a lower rolling piece, the gap between the upper rolling piece and the lower rolling piece is L2, and the pole piece unit is rolled by the rolling assembly, and further includes: The pole piece unit is rolled under the condition of L2=L1-a, wherein 7μm≤a≤13μm.

5. The method for preparing a battery cell according to any one of claims 1 to 4, characterized in that: After the step of winding the rolled pole piece unit, the method further comprises: The wound pole piece unit is hot pressed.

6. The method for preparing a battery cell according to claim 5, characterized in that: The hot pressing of the wound pole piece unit comprises: The wound pole piece unit is hot pressed at a temperature of 95°C±5°C, a hot pressing time of 30s±1s, and a pressure of 1.0Mpa±0.1Mpa.

7. The method for preparing a battery cell according to claim 5, characterized in that: After the step of hot pressing the wound pole piece unit, the method further comprises: Conduct insulation resistance test on the pole piece unit and / or The coil diameter of the pole piece unit is detected.

8. A battery cell preparation device, characterized in that: The battery cell preparation device comprises: A feeding assembly, the feeding assembly is used to convey the pole piece unit; A rolling assembly is arranged downstream of the feeding assembly, and the rolling assembly is used to roll the pole piece unit so that a rolling groove is formed on the surface of at least one side of the pole piece unit.

9. The battery cell preparation device according to claim 8, characterized in that: The rolling assembly comprises an upper rolling member and a lower rolling member, a gap is provided between the upper rolling member and the lower rolling member, and the pole piece unit is arranged in the gap.

10. The battery cell preparation device according to claim 9, characterized in that: The surface of the upper rolling piece or the lower rolling piece is provided with a protrusion, and the protrusion can contact with the surface of the pole piece unit so that the rolling groove is formed on the surface of the pole piece unit.

11. The battery cell preparation device according to claim 10, characterized in that: The cross section of the protrusion is square or trapezoidal.

12. The battery cell preparation device according to claim 9, characterized in that: A heating element is arranged inside the upper rolling member and / or the lower rolling member, and the upper rolling member and / or the lower rolling member heats the pole piece unit through the heating element.

13. The battery cell preparation device according to any one of claims 9 to 12, characterized in that: The feeding assembly comprises: A positive electrode unwinding member, the positive electrode unwinding member is used to transport the positive electrode unit; a first diaphragm unwinding member, the first diaphragm unwinding member being used for conveying the first diaphragm; a second diaphragm unwinding member, the second diaphragm unwinding member being used for conveying a second diaphragm; A negative electrode unwinding member, the negative electrode unwinding member is used to transport the negative electrode unit; The positive electrode unit and the negative electrode unit are respectively arranged on both sides of the first diaphragm, the second diaphragm is located on the side of the positive electrode unit away from the first diaphragm, the upper roller is used to contact with the side of the second diaphragm away from the positive electrode unit, and the lower roller is used to contact with the side of the negative electrode unit away from the first diaphragm, and the first diaphragm, the second diaphragm, the positive electrode unit and the negative electrode unit together form the pole piece unit.

14. A battery cell, characterized in that: The battery core comprises a plurality of pole piece units, and at least one side of the surface of at least one of the pole piece units is provided with a rolling groove.

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