Auxiliary assembly for pole piece coating, pole piece coating device and lithium ion battery

Abstract

The invention provides an auxiliary assembly for pole piece coating, a pole piece coating device and a lithium ion battery. The auxiliary assembly comprises a roller body with a plurality of thermal expansion adhesive tapes, and a plurality of compression rollers, the roller body is used for being driven to rotate to unwind the thermal expansion adhesive tape, the unwound thermal expansion adhesive tape is used for being bonded to a pole piece blank area, and the pressing roller is used for pressing the thermal expansion adhesive tape to the surface of the pole piece blank area; and a non-thermal expansion adhesive tape is laminated at the starting end of the unwound thermal expansion adhesive tape. Edge thinning treatment is not needed during coating of the pole piece, the thick edge formed by the active substance during coating is located in the adhesive tape area, the thickness of the pole piece main body part meets the requirement, it is guaranteed that the NP ratio of all the areas meets the design requirement, the lithium precipitation risk caused by insufficient NP ratio brought by the thinning technology is avoided, the safety performance of the lithium ion battery is improved, and the service life of the lithium ion battery is prolonged. The thermal expansion adhesive tape is heated to fall off after entering the drying oven, and is pulled to the tail of the coating machine by the non-thermal expansion adhesive tape at the front end to be wound, so that the thermal expansion adhesive tape is prevented from scattering in the drying oven.

Description

Technical Field

[0001] The present invention belongs to the technical field of pole piece processing, and relates to an auxiliary component for pole piece coating, a pole piece coating device and a lithium ion battery. Background Art

[0002] During the coating process of lithium-ion battery pole pieces, the slurry fluid is subjected to the shear stress of the die edge wall at the die outlet, and the shear stress decreases rapidly after the outlet, causing the slurry fluid to expand at the edge. When the pole piece is dry, the solvent at the coating edge evaporates faster than the solvent in the internal area. The coating slurry flows to the edge area with high surface tension and accumulates, resulting in an increase in the thickness of the edges on both sides of the coating, making it impossible to rewind it subsequently, affecting the performance of the battery cell.

[0003] The lithium battery industry typically uses a "thinning" coating process to address the problem of thick edges. Thinning the edges of the negative electrode reduces the amount of active material. If the NP ratio at the negative electrode corresponding to the positive electrode is lower than the designed value, during charging, due to insufficient negative electrode capacity, some lithium ions migrate to the negative electrode surface and precipitate. After circulation, they form lithium dendrites, which can cause safety issues.

[0004] The existing technical solution discloses a pole piece coating auxiliary component, a pole piece coating device and a pole piece processing system, which uses a heat-expanding tape to stick on the foil to prevent the appearance of thinning areas. The system uses blowing in an oven to recycle the heat-expanding tape. This method is suitable for recycling the tape on both sides of the foil. For the tape in the middle of the foil, this recycling method may cause scratches and damage to the surface of the active material during tape recycling.

[0005] Therefore, it is urgent to design an auxiliary component for electrode coating, an electrode coating device and a lithium-ion battery to overcome the defects of the existing technology and meet the needs of actual applications. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an auxiliary component for electrode coating, a electrode coating device and a lithium-ion battery. In the present invention, the electrode coating does not require edge thinning. The thick edge formed by the active material during coating is in the tape area, and the thickness of the main part of the electrode meets the requirements, ensuring that the NP ratio of all areas meets the design requirements, avoiding the risk of lithium plating caused by insufficient NP ratio caused by the thinning process, and improving the safety performance of lithium-ion batteries. The thermal expansion tape falls off due to heat after entering the oven, and is pulled to the tail of the coating machine by the non-thermal expansion tape at the front end for winding, avoiding the problem of thermal expansion tape scattering in the oven and the need to open the oven regularly to collect the tape.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides an auxiliary component for pole piece coating, the auxiliary component comprising a roller body having a plurality of heat-expandable adhesive tapes, and a plurality of pressure rollers;

[0009] The roller is driven to rotate and unwind the thermal expansion tape, the unwound thermal expansion tape is used to adhere to the blank area of ​​the electrode, and the pressing roller is used to press the thermal expansion tape against the surface of the blank area of ​​the electrode;

[0010] A non-thermal expansion tape is stacked on the starting end of the unwound thermal expansion tape;

[0011] The heat-expandable tape, the non-heat-expandable tape and the electrode coating area can be coated at the same time. The heat-expandable tape can be peeled off from the electrode blank area due to heating, and the non-heat-expandable tape is not peeled off from the electrode blank area due to heating, and the electrode is pulled for subsequent winding.

[0012] In the present invention, the electrode coating does not require edge thinning. The thick edge formed by the active material during coating is in the tape area, and the thickness of the main part of the electrode meets the requirements, ensuring that the NP ratio of all areas meets the design requirements, avoiding the risk of lithium plating caused by insufficient NP ratio caused by the thinning process, and improving the safety performance of lithium-ion batteries. The thermal expansion tape falls off due to heat after entering the oven and is pulled to the tail of the coating machine by the non-thermal expansion tape at the front end for winding, avoiding the problem of the thermal expansion tape scattering in the oven and the need to open the oven regularly to collect the tape.

[0013] It should be noted that the number represented by "several" in the present invention can be 1, 2, 3, 4, 5, etc., but is not limited to the listed values. Other unlisted values ​​are also applicable within this meaning.

[0014] As a preferred technical solution of the present invention, the width of the heat expansion tape is 10 mm to 20 mm, for example, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0015] The width of the thermal expansion tape in the present invention is 10 mm to 20 mm. When coating the negative electrode, if no thinning treatment is performed, the width of the thicker coating edge is about 3 mm to 8 mm. In order to ensure that all the thicker coating parts are on the tape and the tape width is not greater than the width of the blank space of the foil, while taking into account the economic efficiency of production, the width of the thermal expansion tape is selected to be 10 mm to 20 mm.

[0016] Preferably, the thickness of the thermal expansion tape is 10 μm to 190 μm, for example, 10 μm, 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 190 μm, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0017] The thickness of the thermal expansion tape in the present invention is 10μm to 190μm. The coating thickness of the negative electrode sheet of different types of battery cells is different. Generally speaking, the coating thickness of power-type battery cells is thinner, and the coating thickness of energy-type battery cells is thicker. When thin coating, the gap between the nozzle of the coating machine and the foil is small. In order to ensure that there is still a certain gap between the foil and the nozzle after the foil is superimposed with the tape, a relatively thin thermal expansion tape (10μm to 35μm) is generally selected; when thick coating, the gap between the nozzle of the coating machine and the foil is relatively large. While ensuring that there is still a certain gap between the foil and the nozzle after the foil is superimposed with the tape, taking into account the common tape specifications of suppliers, the tape thickness can be selected from 10μm to 190μm.

[0018] As a preferred technical solution of the present invention, the width of the thermal expansion tape does not exceed the width of the blank area of ​​the electrode.

[0019] Preferably, the width of the blank area of ​​the pole piece is 10mm to 40mm, for example, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] Preferably, the width of the electrode coating area is 20mm to 1500mm, for example, 20mm, 50mm, 100mm, 200mm, 300mm, 400mm, 500mm, 600mm, 700mm, 800mm, 900mm, 1000mm, 1100mm, 1200mm, 1300mm, 1400mm, 1500mm, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0021] As a preferred technical solution of the present invention, the width of the non-thermal expansion tape is 10 mm to 20 mm, for example, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0022] The width of the non-thermal expansion tape in the present invention is 10 mm to 20 mm. When the negative electrode is coated, if no thinning treatment is performed, the width of the thicker coating edge is about 3 mm to 8 mm. In order to ensure that all the thicker coating portions are on the tape and the tape width is not greater than the width of the blank portion of the foil, while taking into account the economic efficiency of production, the width of the non-thermal expansion tape is selected to be 10 mm to 20 mm.

[0023] Preferably, the thickness of the non-thermal expansion tape is 10μm to 190μm, for example, 10μm, 20μm, 40μm, 60μm, 80μm, 100μm, 120μm, 140μm, 160μm, 180μm, 190μm, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0024] The thickness of the non-thermal expansion tape in the present invention is 10μm to 190μm. The coating thickness of the negative electrode sheet of different types of battery cells is different. Generally speaking, the coating thickness of power-type batteries is thinner, and the coating thickness of energy-type batteries is thicker. When thin coating, the gap between the nozzle of the coating machine and the foil is small. To ensure that there is still a certain gap between the foil and the nozzle after the foil is superimposed with the tape, a relatively thin non-thermal expansion tape (10μm to 35μm) is generally selected; when thick coating, the gap between the nozzle of the coating machine and the foil is relatively large. While ensuring that there is still a certain gap between the foil and the nozzle after the foil is superimposed with the tape, taking into account the common tape specifications of suppliers, the tape thickness can be selected from 10μm to 190μm.

[0025] As a preferred technical solution of the present invention, the length of the non-thermal expansion tape is 100 mm to 200 mm, for example, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0026] The length of the non-thermal expansion tape in the present invention is 100 mm to 200 mm. To ensure that the non-thermal expansion tape does not fall off during the pulling process, the bonding length between the non-thermal expansion tape and the foil and the thermal expansion tape must be guaranteed. Test results show that when the length of the non-thermal expansion tape is less than 100 mm, it may fall off during coating. To avoid the above phenomenon and take into account the convenience of winding the tail roll of the non-thermal expansion tape, the length of the non-thermal expansion tape is selected to be 100 mm to 200 mm.

[0027] As a preferred technical solution of the present invention, the length of the laminated portion of the non-thermal expansion tape and the thermal expansion tape is 30 mm to 50 mm, for example, 30 mm, 32 mm, 34 mm, 36 mm, 38 mm, 40 mm, 42 mm, 44 mm, 46 mm, 48 mm, 50 mm, etc., but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0028] In the present invention, the length of the stacked portion of the non-thermal expansion tape and the thermal expansion tape is 30 mm to 50 mm. To ensure that the two tapes do not fall off during the coating process, the bonding stacking length between the non-thermal expansion tape and the thermal expansion tape must be ensured. Test results show that when the bonding stacking length of the two tapes is less than 30 mm, falling off may occur during coating. To avoid the above phenomenon and take into account economic efficiency, the stacking length is selected to be 30 mm to 50 mm.

[0029] As a preferred technical solution of the present invention, the material of the thermal expansion tape includes any one of a silica gel thermal expansion microsphere powder mixture, a polyurethane thermal expansion microsphere powder mixture, a polyacrylic acid thermal expansion microsphere powder mixture, a polyvinyl chloride thermal expansion microsphere powder mixture and an epoxy resin thermal expansion microsphere powder mixture.

[0030] Preferably, the material of the non-thermal expansion tape includes any one of silicone, polyurethane, polyacrylic acid, polyvinyl chloride and epoxy resin.

[0031] It should be noted that the thermally expandable microsphere powder of the present invention comprises a core coated with a low-boiling-point liquid hydrocarbon (such as isobutane or propane) and an outer shell of a thermoplastic polymer (such as acrylonitrile-methacrylate copolymer). These particles can be combined with adhesives such as silicone, polyurethane, polyacrylic acid, polyvinyl chloride, and epoxy resin to form a mixture of these substances, thereby forming the adhesive on the thermally expandable tape. The base material of the thermally expandable tape can be PET, TAC, PVC, PE, PP, etc., while the base material of the non-thermal expandable tape can be PI, PET, PP, PE, etc.

[0032] It should be noted that the method for using the auxiliary components for electrode coating in the present invention may include:

[0033] The graphite, conductive agent and adhesive glue are evenly mixed to form a slurry and transported to the coating and feeding system.

[0034] Paste the tape on the blank area of ​​the foil, first paste the heat expansion tape, and then laminate the non-heat expansion tape on the starting end of the heat expansion tape.

[0035] Specifically, first stick a section of heat-expandable tape on the blank area of ​​the foil, and then stick a non-heat-expandable tape on the heat-expandable tape and the blank area of ​​the front foil. The distance between the inner edges of the two adjacent tapes should not be less than the design requirements.

[0036] Apply the slurry to the foil and tape areas without skiving. Ensure the coating width in the non-tape area meets the design requirements. The bulk of the coating is located in the non-tape area of ​​the foil, with the thicker edge located in the tape area. The active material thickness in the tape area is greater than the bulk.

[0037] After the slurry coating is completed and enters the oven, the oven temperature can be 70℃~120℃. The non-thermal expansion tape continues to adhere to the foil, and the thermal expansion tape loses its stickiness due to heat and separates from the foil. The non-thermal expansion tape pulls the thermal expansion tape to continue flowing to the tail of the coating machine for reeling.

[0038] In a second aspect, the present invention provides a pole piece coating device, comprising an unwinding roller for unwinding the pole piece, a winding roller for winding the pole piece, a coating die head, and the auxiliary components described in the first aspect;

[0039] The roller is located upstream of the coating die, and the coating die can simultaneously coat the pole piece coating area and the thermal expansion tape.

[0040] It should be noted that the electrode coating device in the present invention, by setting the above-mentioned auxiliary components for electrode coating, is conducive to the coating die head to coat the electrode coating area and the thermal expansion tape at the same time, thereby helping to improve the coating consistency of the electrode coating area and can improve the safety of the electrode.

[0041] In a third aspect, the present invention provides a negative electrode sheet, which is formed by coating using the electrode sheet coating device described in the second aspect.

[0042] It should be noted that the method for preparing the positive electrode sheet of the present invention may include:

[0043] The positive electrode active material, conductive agent, and polyvinylidene fluoride are weighed in a ratio of 95:2:3, and N-methylpyrrolidone is used as a solvent. The mixture is stirred evenly into a slurry and then coated on the positive electrode current collector. The coating is dried, rolled, slit, and die-cut to obtain a positive electrode sheet.

[0044] It should be noted that the preparation method of the positive and negative electrode sheets in the present invention may include:

[0045] Graphite, conductive agent, styrene-butadiene rubber, and carboxymethyl cellulose were weighed in a mass ratio of 94:2:2:2, and an appropriate amount of deionized water was added and stirred into a uniform slurry, which was then coated on the negative electrode current collector. Before coating, a 10 mm wide thermal expansion tape was pasted on the foil, and a 100 mm long silicone tape of equal width was cut and pasted on the thermal expansion tape and the foil. The overlapping length of the two tapes was 30 mm. During coating, the unwinding speed of the thermal expansion tape was the same as the unwinding speed of the foil. After passing through the oven, the foil and tape were reeled up at the tail of the coater, and the dried electrode was rolled, slit, and die-cut to obtain the negative electrode.

[0046] In a fourth aspect, the present invention provides a lithium-ion battery, comprising a positive electrode sheet, a separator, and a negative electrode sheet stacked in sequence, wherein the negative electrode sheet is the negative electrode sheet described in the third aspect.

[0047] It should be noted that the assembly of the lithium-ion battery in the present invention may include:

[0048] The positive electrode sheet, separator and negative electrode sheet are stacked in sequence to form a battery cell, which is then ultrasonically welded to the tabs and packaged. The battery cell is vacuum-baked and then subjected to processes such as liquid injection, formation, and capacity separation to prepare a lithium-ion battery.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] In the present invention, the electrode coating does not require edge thinning. The thick edge formed by the active material during coating is in the tape area, and the thickness of the main part of the electrode meets the requirements, ensuring that the NP ratio of all areas meets the design requirements, avoiding the risk of lithium plating caused by insufficient NP ratio caused by the thinning process, and improving the safety performance of lithium-ion batteries. The thermal expansion tape falls off due to heat after entering the oven and is pulled to the tail of the coating machine by the non-thermal expansion tape at the front end for winding, avoiding the problem of the thermal expansion tape scattering in the oven and the need to open the oven regularly to collect the tape. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic structural diagram of an auxiliary component for electrode coating provided in one embodiment of the present invention;

[0052] Figure 2 A schematic diagram of the thickness distribution of the active material during electrode coating according to a specific embodiment of the present invention;

[0053] Figure 3 A schematic diagram of the thickness distribution of the active material after the electrode coating is completed according to a specific embodiment of the present invention;

[0054] Figure 4 A schematic structural diagram of a pole piece coating device provided in a specific embodiment of the present invention;

[0055] Figure 5 Graphs showing performance tests of lithium-ion batteries in Example 1 and Comparative Example 1 of the present invention;

[0056] Among them, 1-roller; 2-pressing roller; 3-non-thermal expansion tape; 4-thermal expansion tape; 5-stacked portion of the non-thermal expansion tape and the thermal expansion tape; a-width of the thermal expansion tape. DETAILED DESCRIPTION

[0057] It should be understood that, in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0058] It should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0059] Those skilled in the art should understand that the present invention must include necessary pipelines, conventional valves and general pump equipment for realizing a complete process, but the above content does not belong to the main invention point of the present invention. Those skilled in the art can add layouts on their own based on the process flow and equipment structure selection, and the present invention does not make special requirements and specific limitations on this.

[0060] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0061] In a specific embodiment, the present invention provides an auxiliary component for pole piece coating, such as Figure 1 As shown, the auxiliary assembly includes a roller body 1 having a plurality of heat-expandable adhesive tapes 4, and a plurality of pressure rollers 2;

[0062] The roller body 1 is driven to rotate and unwind the thermal expansion tape 4. The unwound thermal expansion tape 4 is used to adhere to the blank area of ​​the electrode. The pressing roller 2 is used to press the thermal expansion tape 4 against the surface of the blank area of ​​the electrode.

[0063] The non-thermal expansion tape 3 is stacked on the starting end of the unwound thermal expansion tape 4;

[0064] The thermal expansion tape 4, the non-thermal expansion tape 3 and the electrode coating area can be coated at the same time. The thermal expansion tape 4 can be peeled off from the electrode blank area due to heating, and the non-thermal expansion tape 3 will not be peeled off from the electrode blank area due to heating, and the electrode is pulled for subsequent winding.

[0065] It should be noted that the pole piece Figure 1 The electrode sheet travels between the unwinding roller and the winding roller (not shown). The electrode sheet has blank areas and coating areas arranged alternately along its width direction. There are three blank areas and two coating areas. The roller body 1 is arranged above the electrode sheet and is wound with three rolls of heat-expandable adhesive tape 4. The heat-expandable adhesive tape 4 in each roll is respectively arranged corresponding to each blank area to facilitate bonding to the blank area. It can be understood that the number of blank areas on the electrode sheet can be increased or decreased according to usage requirements. In this case, it is sufficient to ensure that the number of heat-expandable adhesive tapes 4 matches the number of blank areas.

[0066] It should be noted that the number represented by "several" in the present invention can be 1, 2, 3, 4, 5, etc., but is not limited to the listed values. Other unlisted values ​​are also applicable within this meaning.

[0067] In one embodiment, the width a of the heat expansion tape 4 is 10 mm to 20 mm, for example, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, etc., but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0068] In one embodiment, the thickness of the thermal expansion tape 4 is 10 μm to 190 μm, for example, 10 μm, 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 190 μm, etc., but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0069] In one embodiment, the width a of the thermal expansion tape 4 does not exceed the width of the blank area of ​​the electrode.

[0070] In one embodiment, the width of the blank area of ​​the pole piece is, for example, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, etc., but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable.

[0071] In one embodiment, the width of the electrode coating area is 20 mm to 1500 mm, for example, 20 mm, 50 mm, 100 mm, 200 mm, 300 mm, 400 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 1000 mm, 1100 mm, 1200 mm, 1300 mm, 1400 mm, 1500 mm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0072] In one embodiment, the width of the non-thermal expansion tape 3 is 10 mm to 20 mm, for example, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, etc., but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0073] In one embodiment, the thickness of the non-thermal expansion tape 3 is 10 μm to 190 μm, for example, 10 μm, 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 190 μm, etc., but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0074] In one embodiment, the length of the non-thermal expansion tape 3 is 100 mm to 200 mm, for example, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm, etc., but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0075] In one embodiment, the length of the laminated portion 5 of the non-thermally expandable tape 3 and the thermally expandable tape 4 is 30 mm to 50 mm, for example, 30 mm, 32 mm, 34 mm, 36 mm, 38 mm, 40 mm, 42 mm, 44 mm, 46 mm, 48 mm, 50 mm, etc., but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0076] In one embodiment, the material of the thermal expansion tape 4 includes any one of a silica gel thermal expansion microsphere powder mixture, a polyurethane thermal expansion microsphere powder mixture, a polyacrylic acid thermal expansion microsphere powder mixture, a polyvinyl chloride thermal expansion microsphere powder mixture, and an epoxy resin thermal expansion microsphere powder mixture.

[0077] In one embodiment, the material of the non-thermal expansion tape 3 includes any one of silicone, polyurethane, polyacrylic acid, polyvinyl chloride and epoxy resin.

[0078] It should be noted that the method for using the auxiliary components for electrode coating in the present invention may include:

[0079] The graphite, conductive agent and adhesive glue are evenly mixed to form a slurry and transported to the coating and feeding system.

[0080] Adhesive tapes are pasted on the blank area of ​​the foil. The heat-expandable adhesive tape 4 is pasted first, and then the non-heat-expandable adhesive tape 3 is laminated and pasted on the starting end of the heat-expandable adhesive tape 4 .

[0081] Specifically, first stick a section of heat-expandable tape 4 to the blank area of ​​the foil, and then stick the non-heat-expandable tape 3 to the heat-expandable tape 4 and the blank area of ​​the front foil. The distance between the inner edges of the two adjacent tapes should not be less than the design requirements.

[0082] like Figure 2 As shown, the slurry is applied to the foil and tape areas without skiving. The coating width in the non-tape area of ​​the foil meets the design requirements. The bulk of the coating is located in the non-tape area of ​​the foil, with the thick edge located in the tape area. The active material thickness in the tape area is greater than the bulk.

[0083] After the slurry coating is completed and enters the oven, the non-thermal expansion tape 3 continues to adhere to the foil, and the thermal expansion tape 4 loses its stickiness due to heat and separates from the foil. The non-thermal expansion tape 3 pulls the thermal expansion tape 4 to continue to flow to the tail of the coating machine for winding. The thickness distribution of the active material on the electrode is as follows: Figure 3 shown.

[0084] In another embodiment, the present invention provides a pole piece coating device, such as Figure 4 As shown, the electrode coating device includes an unwinding roller for unwinding the electrode, a winding roller for winding the electrode, a coating die and the above-mentioned auxiliary components; the roller body 1 is located upstream of the coating die, and the coating die can simultaneously coat the electrode coating area and the thermal expansion tape 4.

[0085] It should be noted that the electrode coating device in the present invention, by setting the above-mentioned auxiliary components for electrode coating, is conducive to the coating die head to coat the electrode coating area and the thermal expansion tape 4 at the same time, thereby helping to improve the coating consistency of the electrode coating area and can improve the safety of the electrode.

[0086] In another specific embodiment, the present invention provides a negative electrode sheet, which is coated and formed using the above-mentioned electrode sheet coating device.

[0087] It should be noted that the method for preparing the positive electrode sheet of the present invention may include:

[0088] The positive electrode active material, conductive agent, and polyvinylidene fluoride are weighed in a ratio of 95:2:3, and N-methylpyrrolidone is used as a solvent. The mixture is stirred evenly into a slurry and then coated on the positive electrode current collector. The coating is dried, rolled, slit, and die-cut to obtain a positive electrode sheet.

[0089] It should be noted that the preparation method of the positive and negative electrode sheets in the present invention may include:

[0090] Graphite, conductive agent, styrene-butadiene rubber, and carboxymethyl cellulose were weighed in a mass ratio of 94:2:2:2, and an appropriate amount of deionized water was added and stirred into a uniform slurry, which was then coated on the negative electrode current collector. Before coating, a thermal expansion tape 4 with a width a of 10 mm was pasted on the foil, and a 100 mm long silicone tape of equal width was cut and pasted on the thermal expansion tape 4 and the foil. The overlapping length of the two tapes was 30 mm. During coating, the unwinding speed of the thermal expansion tape 4 was the same as the unwinding speed of the foil. After passing through the oven, the foil and tape were reeled up at the tail of the coater, and the dried electrode was rolled, slit, and die-cut to obtain the negative electrode.

[0091] In another specific embodiment, the present invention provides a lithium-ion battery, comprising a positive electrode sheet, a separator, and a negative electrode sheet stacked in sequence, wherein the negative electrode sheet is the negative electrode sheet described above.

[0092] It should be noted that the assembly of the lithium-ion battery in the present invention may include:

[0093] The positive electrode sheet, separator and negative electrode sheet are stacked in sequence to form a battery cell, which is then ultrasonically welded to the tabs and packaged. The battery cell is vacuum-baked and then subjected to processes such as liquid injection, formation, and capacity separation to prepare a lithium-ion battery.

[0094] Example 1

[0095] This embodiment provides a method for preparing a lithium-ion battery, wherein:

[0096] The positive electrode sheet preparation method includes: weighing a positive electrode active material, a conductive agent, and polyvinylidene fluoride in a ratio of 95:2:3, using N-methylpyrrolidone as a solvent, stirring the mixture into a slurry, and then coating the mixture on a positive electrode current collector, and drying, rolling, slitting, and die-cutting to obtain a positive electrode sheet;

[0097] The negative electrode sheet preparation method includes: weighing graphite, conductive agent, styrene-butadiene rubber, and carboxymethyl cellulose according to a mass ratio of 94:2:2:2, adding an appropriate amount of deionized water, stirring into a uniform slurry, and coating the slurry on the negative electrode current collector. Before coating, a 10 mm wide thermal expansion tape is adhered to the foil, and a 100 mm long silicone tape of equal width is cut and adhered to the thermal expansion tape 4 and the foil. The length of the stacked portion 5 of the non-thermal expansion tape 3 and the thermal expansion tape 4 is 30 mm. During coating, the unwinding speed of the thermal expansion tape 4 is the same as the unwinding speed of the foil. After passing through the oven, the foil and the tape are respectively wound at the tail of the coating machine. The dried electrode sheet is rolled, slit, and die-cut to obtain the negative electrode sheet.

[0098] Assembly of lithium-ion batteries: The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence to form a battery cell. The battery cell is then ultrasonically welded to the tabs and packaged. After the battery cell is vacuum-baked, it is filled with liquid, formed, and divided into different capacities to prepare a lithium-ion battery.

[0099] Comparative Example 1

[0100] This comparative example provides a method for preparing a lithium ion battery, wherein:

[0101] The positive electrode sheet preparation method includes: weighing a positive electrode active material, a conductive agent, and polyvinylidene fluoride in a ratio of 95:2:3, using N-methylpyrrolidone as a solvent, stirring the mixture into a slurry, and then coating the mixture on a positive electrode current collector, and drying, rolling, slitting, and die-cutting to obtain a positive electrode sheet;

[0102] The negative electrode sheet preparation method includes: weighing graphite, conductive agent, styrene-butadiene rubber, and carboxymethyl cellulose in a mass ratio of 94:2:2:2, adding an appropriate amount of deionized water, stirring to form a uniform slurry, applying the slurry on the negative electrode current collector according to a conventional edge thinning coating process, and drying, rolling, slitting, and die-cutting to obtain the negative electrode sheet;

[0103] Assembly of lithium-ion batteries: The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence to form a battery cell. The battery cell is then ultrasonically welded to the tabs and packaged. After the battery cell is vacuum-baked, it is filled with liquid, formed, and divided into different capacities to prepare a lithium-ion battery.

[0104] The lithium ion batteries in Example 1 and Comparative Example 1 were subjected to a cell performance test. The specific test method included conducting a 55°C 1C / 1C accelerated cycle life test on the lithium ion batteries prepared in Example 1 and Comparative Example 1. The test results were as follows: Figure 5 shown.

[0105] The lithium-ion batteries prepared in Example 1 and Comparative Example 1 were subjected to a 55°C 1C / 1C accelerated cycle life test. After 1500 cycles, at 100% SOC, the battery cells were disassembled and the interface of the negative electrode sheet was observed. It was found that the lithium-ion battery using the negative electrode sheet without the thinning process in Example 1 was golden yellow as a whole, and no lithium deposition was visually observed; the main body of the lithium-ion battery using the negative electrode sheet with the thinning process was golden yellow, and obvious lithium deposition was observed in the thinned area of ​​the head. The lithium deposition resulted in a large amount of lithium ion loss, and the battery cell cycle capacity retention rate decayed faster.

[0106] Example 2

[0107] This embodiment provides a method for preparing a lithium-ion battery. The difference from Example 1 is that the length of the non-thermal expansion tape 3 is 90 mm. Other parameters and test conditions are the same as those in Example 1.

[0108] Example 3

[0109] This embodiment provides a method for preparing a lithium-ion battery. The difference from Example 1 is that the length of the non-thermal expansion tape 3 is 210 mm. Other parameters and test conditions are the same as those in Example 1.

[0110] Example 4

[0111] This embodiment provides a method for preparing a lithium-ion battery. The difference from Example 1 is that the length of the laminated portion of the non-thermal expansion tape 3 and the thermal expansion tape 4 is 25 mm. Other parameters and test conditions are the same as those in Example 1.

[0112] Example 5

[0113] This embodiment provides a method for preparing a lithium-ion battery. The difference from Example 1 is that the length of the laminated portion of the non-thermal expansion tape 3 and the thermal expansion tape 4 is 55 mm. Other parameters and test conditions are the same as those in Example 1.

[0114] Comparative Example 2

[0115] This comparative example provides a method for preparing a lithium-ion battery, which differs from Example 1 in that the non-thermal expansion tape 3 is not used, and other parameters and test conditions are the same as those of Example 1.

[0116] The lithium-ion batteries in Examples 2-5 and Comparative Example 2 were subjected to 55°C 1C / 1C accelerated cycle life testing. The test results indicate that if the non-thermally expandable tape is too short or the overlapping portion with the thermally expandable tape is too short, it may fall off during the pulling process. If the overlapping portion with the thermally expandable tape is too long, economic efficiency is reduced. If the non-thermally expandable tape is too long, manual removal of the tape during rewinding is relatively inconvenient. The length of the tape in Examples 2-5 does not significantly affect the performance of the battery cells.

[0117] The heat expansion tape in Comparative Example 2 will be blown off by the wind in the oven after being heated and de-viscosified in the oven. The heat expansion tape is not pulled in a direction and is randomly scattered on the surface of the coated foil, causing scratches and damage to the slurry on the surface of the foil, reducing the active material in that part, resulting in an excessively low NP ratio in the damaged part, and lithium plating occurs during the use of the battery cell, which ultimately causes safety problems.

[0118] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. An auxiliary component for electrode coating, characterized in that: The auxiliary assembly includes a roller body having a plurality of heat-expandable adhesive tapes, and a plurality of pressure rollers; The roller is driven to rotate and unwind the thermal expansion tape, the unwound thermal expansion tape is used to adhere to the blank area of ​​the electrode, and the pressing roller is used to press the thermal expansion tape against the surface of the blank area of ​​the electrode; A non-thermal expansion tape is stacked on the starting end of the unwound thermal expansion tape; The heat-expandable tape, the non-heat-expandable tape and the electrode coating area can be coated at the same time. The heat-expandable tape can be peeled off from the electrode blank area due to heating, and the non-heat-expandable tape is not peeled off from the electrode blank area due to heating, and the electrode is pulled for subsequent winding.

2. The auxiliary assembly according to claim 1, characterized in that The width of the thermal expansion tape is 10 mm to 20 mm; Preferably, the thickness of the thermal expansion tape is 10 μm to 190 μm.

3. The auxiliary assembly according to claim 1 or 2, characterized in that The width of the thermal expansion tape does not exceed the width of the blank area of ​​the electrode; Preferably, the width of the blank area of ​​the electrode is 10 mm to 40 mm; Preferably, the width of the electrode coating area is 20 mm to 1500 mm.

4. The auxiliary component according to any one of claims 1 to 3, characterized in that: The width of the non-thermal expansion tape is 10 mm to 20 mm; Preferably, the thickness of the non-thermal expansion tape is 10 μm to 190 μm.

5. The auxiliary component according to any one of claims 1 to 4, characterized in that: The length of the non-thermal expansion tape is 100 mm to 200 mm.

6. The auxiliary component according to any one of claims 1 to 5, characterized in that: The length of the laminated portion of the non-thermally expandable tape and the thermally expandable tape is 30 mm to 50 mm.

7. The auxiliary component according to any one of claims 1 to 6, characterized in that: The material of the thermal expansion tape includes any one of a silica gel thermal expansion microsphere powder mixture, a polyurethane thermal expansion microsphere powder mixture, a polyacrylic acid thermal expansion microsphere powder mixture, a polyvinyl chloride thermal expansion microsphere powder mixture and an epoxy resin thermal expansion microsphere powder mixture; Preferably, the material of the non-thermal expansion tape includes any one of silicone, polyurethane, polyacrylic acid, polyvinyl chloride and epoxy resin.

8. A pole piece coating device, characterized in that: The electrode coating device comprises an unwinding roller for unwinding the electrode, a winding roller for winding the electrode, a coating die head, and the auxiliary component according to any one of claims 1 to 7; The roller is located upstream of the coating die, and the coating die can simultaneously coat the pole piece coating area and the thermal expansion tape.

9. A negative electrode sheet, characterized in that: The negative electrode sheet is coated and formed using the electrode sheet coating device described in claim 8.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises a positive electrode sheet, a separator and a negative electrode sheet stacked in sequence, and the negative electrode sheet is the negative electrode sheet according to claim 9.

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