Preparation method and application of pole piece

Abstract

The invention provides a preparation method and application of a pole piece, and the preparation method comprises the following steps: dispersing an active material, a first binder and a conductive agent in a first solvent according to a mass ratio to obtain active slurry; dispersing ceramic particles, a second binder and a color developing agent in a second solvent according to a mass ratio to obtain reinforcing layer slurry; coating the active slurry and the reinforcing layer slurry on a current collector at a preset coating speed and a preset interval; and the coated current collector is sequentially subjected to segmented drying at the preset temperature and the preset wind frequency, and the active material layer and the reinforcing layer are obtained. According to the preparation method and the application of the pole piece, the condition that the stress of the current collector is not uniform in the drying process is reduced, the reinforcing layer plays a supporting role, and the conditions that the uncoated area of the active substance layer is wrinkled, folded and the like are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and in particular to a method for preparing a pole piece and its application. Background Art

[0002] Lithium-ion batteries are widely used in new energy vehicles, consumer electronics, energy storage systems, and other fields due to their high energy density, rechargeability, safety, and environmental friendliness. However, during the electrode preparation process, during the active slurry coating and drying process, uneven stress on the current collector can occur, leading to wrinkles and folds. This can affect the consistency of the stacking and winding processes, and even the charge-discharge performance and safety of the finished battery cell. Summary of the Invention

[0003] The present invention proposes a preparation method and application of a pole piece, which reduces the uneven stress of the current collector during the drying process. The reinforcement layer plays a supporting role and reduces the occurrence of wrinkles and folds in the uncoated area of the active material layer.

[0004] To solve the above technical problems, the present invention is achieved through the following technical solutions.

[0005] The present invention provides a method for preparing a pole piece, comprising:

[0006] dispersing the active material, the first binder and the conductive agent in a first solvent according to a mass ratio to obtain an active slurry;

[0007] Dispersing ceramic particles, a second binder, and a color developer in a second solvent according to a mass ratio to obtain a reinforcement layer slurry;

[0008] coating the active slurry and the reinforcement layer slurry on the current collector at a preset coating rate and a preset interval; and

[0009] The coated current collector is sequentially dried in stages at a preset temperature and a preset wind frequency to obtain an active material layer and a reinforcement layer.

[0010] In one embodiment of the present invention, the preset coating rate is 6 m / min-10 m / min.

[0011] In one embodiment of the present invention, the segmented drying includes a first segment, a second segment, a third segment, a fourth segment and a fifth segment. In the first segment, the preset temperature is 75°C-80°C, and the preset wind frequency is 35Hz-38Hz; in the second segment, the preset temperature is 80°C-85°C, and the preset wind frequency is 35Hz-40Hz; in the third segment, the preset temperature is 80°C-85°C, and the preset wind frequency is 40Hz-45Hz; in the fourth segment, the preset temperature is 75°C-80°C, and the preset wind frequency is 40Hz-45Hz; the preset temperature of the oven is 75°C-80°C, and the preset wind frequency is 38Hz-43Hz.

[0012] In one embodiment of the present invention, the active slurry and the reinforcement layer slurry are coated on the current collector simultaneously.

[0013] In one embodiment of the present invention, the weight loss rate of the reinforcement layer is less than 3%, and the weight loss rate of the active material layer is less than 0.5%.

[0014] In one embodiment of the present invention, the width of the uncoated area of the active material layer on the current collector is W1 mm, and the width of the reinforcement layer is W2 mm, satisfying 2.5≤W1 / W2≤7.5.

[0015] In one embodiment of the present invention, the preset distance between the active slurry and the reinforcement layer slurry is G mm, satisfying 22≤W1 / G≤400;

[0016] The preset spacing is 0.1 mm-1.1 mm.

[0017] In one embodiment of the present invention, the mass ratio of the ceramic particles, the second binder, and the color developer is 10-20:75-90:0.5-5, and the second binder is a water-based binder;

[0018] The second binder comprises at least one of polyacrylic acid, styrene-butadiene rubber, polyvinyl alcohol, polyacrylamide, methyl cellulose and its salts, chitosan and its salts, and alginic acid and its salts;

[0019] The developer includes at least one of carbon black, chromium oxide green, cobalt green, cobalt blue, iron blue, cadmium red, carbon black or iron oxide red.

[0020] In one embodiment of the present invention, the grayscale value of the reinforcement layer is 0-110, and the electrode is a negative electrode.

[0021] The present invention also provides a battery, comprising:

[0022] A shell having an upper opening;

[0023] An electrode assembly and a cover assembly sealing the upper end opening are arranged in the housing; the electrode assembly is formed by stacking a positive electrode sheet, a separator, and a negative electrode sheet and then winding or laminating them, and the negative electrode sheet is obtained by the above-mentioned preparation method; along a first direction, the electrode assembly includes a main body and an uncoated area of the active material layer, the uncoated area of the active material layer includes a bent portion and a connecting portion, the connecting portion is fixedly connected to the cover assembly, and the bent portion is connected between the main body and the connecting portion; the reinforcing layer covers at least a portion of the bent portion;

[0024] The electrode assembly is covered with a first tape, which is arranged on the side of the active material layer uncoated area facing away from the cover assembly. The first tape includes a first adhesive area, a second adhesive area, and a non-adhesive area between the first adhesive area and the second adhesive area. The first adhesive area covers the main body, and the second adhesive area covers the connecting part. In the thickness direction of the electrode assembly, the orthographic projection of the reinforcement layer is completely located within the non-adhesive area.

[0025] The present invention also provides an electronic device comprising the battery described above.

[0026] In summary, the present invention provides a method for preparing and applying a pole piece, which can prevent the solvent from volatilizing too quickly during the drying process of the slurry, reduce the uneven stress of the current collector during the drying process, and reduce the wrinkles and folds in the uncoated area of the active material layer by providing a reinforcement layer. At the same time, when the pole piece is assembled into a battery, because the uncoated area of the active material layer will be bent, the problem of intercalation of the uncoated area of the active material layer can be avoided, thereby avoiding short circuits and other related failures caused by intercalation. The uniformity of the obtained pole piece can be improved, thereby improving the cycle life and safety of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 Schematic diagram of a pole piece in one embodiment.

[0029] Figure 2 For the Figure 1 Cross-sectional view of the pole piece in the AA direction.

[0030] Figure 3 Schematic diagram of the tab on the electrode sheet in one embodiment.

[0031] Figure 4Schematic diagram of the pole tabs and reinforcing ribs on a pole piece in one embodiment.

[0032] Figure 5 Schematic diagram of the tab on the electrode sheet in another embodiment.

[0033] Figure 6 Schematic diagram of the pole tabs and reinforcing ribs on a pole piece in another embodiment.

[0034] Figure 7 Schematic diagram of a positive electrode plate in one embodiment.

[0035] Figure 8 Schematic diagram of a positive electrode tab on a positive electrode sheet in one embodiment.

[0036] Figure 9 Schematic diagram of the positive electrode tab on the positive electrode sheet in another embodiment.

[0037] Figure 10 Schematic diagram of an electrode assembly in one embodiment.

[0038] Figure 11 Schematic diagram of an electrode assembly in another embodiment.

[0039] Figure 12 Schematic diagram of a portion of an electrode assembly in one embodiment.

[0040] Figure 13 Schematic diagram of a battery in one embodiment.

[0041] Description of labels:

[0042] 10. Housing; 11. Cover assembly; 12. First pole; 13. Second pole; 14. Explosion-proof valve; 15. Liquid injection hole; 20. Electrode assembly; 100. Pole piece; 101. Active material layer coating area; 102. Active material layer uncoated area; 110. Current collector; 120. Active material layer; 130. Reinforcement layer; 140. Tab; 150. Reinforcement rib; 160. Transition zone; 2 00. Positive electrode sheet; 210. Positive electrode current collector; 220. Positive electrode active material layer; 230. Positive electrode tab area; 240. Positive electrode tab; 241. Connection area; 1. Main body; 111. Connection part; 112. Bending part; 1112. Adapter; 30. First adhesive tape; 31. First adhesive area; 32. Non-adhesive area; 33. Second adhesive area; 300. Diaphragm; 40. Second adhesive tape. DETAILED DESCRIPTION

[0043] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0044] It should be understood that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so that people familiar with this technology can understand and read them. They are not used to limit the conditions for the implementation of this solution, so they have no technical significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed in this solution without affecting the efficacy and purpose of this solution. At the same time, the terms such as "upper", "lower", "left", "right", "middle", "under", "below", "first", "second" and "one" quoted in this specification are only for the convenience of description and are not used to limit the scope of the implementation of this solution. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of this solution without substantially changing the technical content.

[0045] The technical solutions of the present invention are further described in detail below with reference to the embodiments and accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0046] The present application provides an electronic device, which includes at least one battery, and the battery is used to provide electrical energy. The electronic device may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, and an electric tool, etc. In one embodiment of the present invention, the vehicle is, for example, a new energy vehicle, which may be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc.

[0047] The present application also provides a battery capable of being used in the aforementioned electronic device, the battery comprising a pole piece. In some embodiments, the pole piece comprises a current collector, and at least one side of the current collector comprises an active material layer-coated region and an active material layer-uncoated region adjacent to each other along a first direction, wherein an active material layer is coated on the active material layer-coated region. A reinforcing layer is coated on at least a portion of the active material layer-uncoated region along a second direction, the second direction being perpendicular to the first direction. The pole piece is, for example, a negative electrode pole piece.

[0048] See also Figure 4 and Figure 6 As shown, in one embodiment of the present invention, a pole piece 100 includes a current collector 110, and at least one side of the current collector 110 includes an active material layer coated area 101 and an active material layer uncoated area 102 adjacent to each other along a first direction Y. An active material layer 120 is coated on the active material layer coated area 101, and a reinforcing layer 130 is coated on at least a portion of the active material layer uncoated area 102 along a second direction X, wherein the second direction X is perpendicular to the first direction Y. By providing the reinforcing layer, it is possible to improve the energy density of the battery while avoiding wrinkles, folds, and the like in the uncoated area of the active material layer. At the same time, when the pole piece is assembled into a battery, since the uncoated area of the active material layer will be bent, the problem of intercalation of the uncoated area of the active material layer can be avoided, thereby avoiding short circuits and other related failures caused by intercalation.

[0049] See also Figure 4 and Figure 6 As shown, in one embodiment of the present invention, the current collector 110 is, for example, a negative electrode current collector, and the current collector 110 is, for example, copper foil, and the active material layer 120 is, for example, a negative electrode active material layer. Among them, the active material layer 120 also includes, for example, an active material and a conductive agent, and the active material is, for example, selected from any one or a combination of at least two of soft carbon, hard carbon, artificial graphite, silicon, silicon oxide, silicon carbon compound or lithium titanate. The first binder is, for example, selected from any one or more of polypropylene, polyacrylic acid and its derivatives or styrene-butadiene rubber. The conductive agent is, for example, selected from any one or more of conductive carbon black (Super-P, SP), acetylene black, carbon nanotubes and graphene, and the active material layer 120 also includes a thickener, and the thickener is, for example, selected from sodium carboxymethyl cellulose. The thickness of the active material layer 120 is consistent on the current collector 110, which can improve the charge and discharge consistency of the battery. This application does not limit the mass ratio of the active material, the first binder, the thickener and the conductive agent, and they are selected according to the preparation requirements.

[0050] See also Figure 4 and Figure 6As shown, in one embodiment of the present invention, the reinforcing layer 130 includes, for example, ceramic particles, a second binder and a color developer, wherein the ceramic particles include, for example, at least one of boehmite, aluminum oxide, titanium dioxide, zirconium dioxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride or magnesium nitride, and the second binder is, for example, a water-based binder, and for example includes at least one of polyacrylic acid (PAA), styrene butadiene rubber (SBR), polyvinyl alcohol (PVA), polyacrylamide (PAM), methyl cellulose and its salts, chitosan and its salts, alginic acid and its salts, and the color developer includes, for example, at least one of carbon black, chromium oxide green, cobalt green, cobalt blue, iron blue, cadmium red, carbon black or iron oxide red.

[0051] See also Figure 4 and Figure 6 As shown, in one embodiment of the present invention, the electrode 100 further includes a tab 140, wherein a portion of the active material layer 120 covers at least a portion of the surface of the tab 140 along the first direction Y, or a transition region 160 is provided between the tab 140 and the active material layer coating region 101, and the reinforcement layer 130 is located on a portion of the transition region 160 and a portion of the surface of the tab 140. A plurality of reinforcement ribs 150 are further provided on the tab, and along the first direction and / or the second direction, each two adjacent reinforcement ribs 150 are spaced apart from each other.

[0052] The present invention also provides a method for preparing a pole piece, comprising the following steps:

[0053] dispersing the active material, the first binder and the conductive agent in a first solvent according to a mass ratio to obtain an active slurry;

[0054] Dispersing ceramic particles, a second binder, and a color developer in a second solvent according to a mass ratio to obtain a reinforcement layer slurry;

[0055] Applying the active slurry and the reinforcement layer slurry on the current collector at a preset coating rate and a preset spacing;

[0056] The coated current collector is sequentially dried in stages at a preset temperature and a preset wind frequency to obtain an active material layer and a reinforcement layer.

[0057] See also Figure 1As shown, in one embodiment of the present invention, the active slurry also includes a thickener, and the mass ratio of the active material, first binder, thickener, and conductive agent is, for example, 92-98:0.1-4:1-2:0.9-2. The mass ratio of the ceramic particles, second binder, and color developer in the reinforcement layer 130 is, for example, 10-20:75-90:0.5-5. The high content of the second binder improves the adhesion between the reinforcement layer 130 and the current collector 110, preventing peeling of the reinforcement layer 130 during the subsequent tab bending process. In one embodiment of the present invention, during the tab bending process, the peel force between the reinforcement layer 130 and the current collector 110 is greater than 300 N / m. The ceramic particles can provide support for the reinforcement layer 130, thereby improving the design of the width of the uncoated area 102 of the active material layer, thereby achieving a larger width of the uncoated area 102 of the active material layer. At the same time, the insulation of the reinforcement layer 130 is improved to prevent leakage.

[0058] See also Figure 1 As shown, in one embodiment of the present invention, the active material, the first binder, the thickener, and the conductive agent are uniformly mixed according to a mass ratio, and a first solvent is added. The mixture is uniformly mixed in a vacuum mixer to obtain an active slurry. The viscosity of the active slurry is 4000 Pa·s-10000 mPa·s. The ceramic particles, the second binder, and the color developer are uniformly mixed according to a mass ratio, and a second solvent is added to obtain a reinforcing layer slurry. The viscosity of the reinforcing layer slurry is 1500 Pa·s-2500 mPa·s. The first solvent and the second solvent can be aqueous solvents such as deionized water and ultrapure water, for example. After obtaining the active slurry and the reinforcing layer slurry, the active slurry and the reinforcing layer slurry are simultaneously coated on at least one side of the current collector 110 along the second direction X at a preset coating rate and a preset spacing, and the coating lengths of the active slurry and the reinforcing layer slurry are equal. In this application, simultaneous coating means that the active slurry and the reinforcing layer slurry are simultaneously coated on one side of the current collector, that is, the active material layer 120 and the reinforcing layer 130 on one side of the current collector are completed from coating to drying at the same time. Among them, the active slurry is coated on the active material layer coating area 101, and the reinforcing layer slurry is coated on part of the active material layer uncoated area 102 to form the active material layer 120 and the reinforcing layer 130, and when coating, the preset coating spacing G between the active slurry and the reinforcing layer slurry is set to, for example, 0.1mm-1.1mm. The preset coating rate is, for example, 6m / min-10m / min to control the uniformity and thickness of the coating to improve the uniformity of the obtained electrode sheet, thereby improving the cycle life and safety of the battery.

[0059] See also Figure 1As shown, in one embodiment of the present invention, after applying the active slurry and the reinforcement layer slurry, the coated current collector is sequentially dried in stages at different preset temperatures and preset wind frequencies to obtain the active material layer 120 and the reinforcement layer 130. In the present application, the active slurry and the reinforcement layer slurry are applied in a coater, for example, and a plurality of ovens are arranged in sequence along the conveying direction of the coater to divide the drying stage into multiple stages. In this embodiment, the drying stage is divided into, for example, the first stage, the second stage, the third stage, the fourth stage, and the fifth stage, and the preset temperature and preset wind frequency are different for each stage.

[0060] See also Figure 1 As shown, in one embodiment of the present invention, in the first stage, the preset temperature of the oven is, for example, 75°C-80°C, and the preset wind frequency is, for example, 35Hz-38Hz. In the second stage, the preset temperature of the oven is, for example, 80°C-85°C, and the preset wind frequency is, for example, 35Hz-40Hz. In the third stage, the preset temperature of the oven is, for example, 80°C-85°C, and the preset wind frequency is, for example, 40Hz-45Hz. In the fourth stage, the preset temperature of the oven is, for example, 75°C-80°C, and the preset wind frequency is, for example, 40Hz-45Hz. In the fifth stage, the preset temperature of the oven is, for example, 75°C-80°C, and the preset wind frequency is, for example, 38Hz-43Hz. Using a "low-high-low" temperature and a "low-high-low" wind frequency to set the oven temperature and wind frequency can prevent excessive solvent evaporation during the slurry drying process, reduce uneven stress on the current collector during the drying process, and thus reduce wrinkles and folds in the uncoated area 102 of the active material layer. Furthermore, by selecting an aqueous binder as the second binder, when preparing the active material layer 120 and the reinforcement layer 130 , the negative electrode sheet production line may not require organic gas recovery equipment.

[0061] See also Figure 1 and Figure 2 As shown, in one embodiment of the present invention, an active material layer 120 and a reinforcement layer 130 are provided on at least one side of the current collector 110. In another embodiment of the present invention, active material layers 120 are provided on both sides of the current collector 110, and reinforcement layers 130 are provided on both sides of the current collector 110 along the first direction Y, spaced apart from the active material layers 120. For example, the process is prepared using a double-sided coater. That is, the current collector 110 has two surfaces opposite to each other in its own thickness direction, and the active material layer 120 and the reinforcement layer 130 are simultaneously spaced apart on one surface of the current collector 110; or the active material layer 120 is simultaneously provided on both surfaces of the current collector 110, and the reinforcement layer 130 is provided on one surface of the current collector 110; or the active material layer 120 and the reinforcement layer 130 are simultaneously spaced apart on both surfaces of the current collector 110.

[0062] See also Figure 1 and Figure 2As shown, in one embodiment of the present invention, the thickness of the active material layer 120 on one side of the current collector is H1μm, and the thickness of the current collector is hμm, satisfying 3≤H1 / h≤35. When the thickness of the active material layer 120 is too large or the thickness of the current collector is too small, wrinkles and folds are likely to occur in the uncoated area of the active material layer during die-cutting and winding. On the basis of providing a reinforcement layer, by controlling the ratio of the thickness of the active material layer to the thickness of the current collector within a set range, problems such as wrinkles and folds in the uncoated area of the active material layer can be improved, thereby improving battery safety. The thickness of the reinforcement layer 130 on one side of the current collector is H2μm, satisfying 1≤H2 / h≤6, and the thickness of the current collector is 4μm-5.5μm. The thinner the current collector, the more likely it is to wrinkle during die-cutting and winding. For thin materials ≤5.5μm, setting appropriate active material layer and current collector thicknesses, along with matching reinforcement layer design, can prevent current collector wrinkling and maintain the strength of the uncoated area of the active material layer, avoiding wavy edges caused by laser cutting at the interface between the active material layer and the uncoated area. Furthermore, improving the bottom support of the uncoated area of the active material layer prevents insets during bending.

[0063] See also Figure 1 As shown, in one embodiment of the present invention, along the first direction Y, the width of the uncoated active material layer area 102 is W1 mm, and the width of the reinforcing layer 130 is W2 mm, satisfying 2.5 ≤ W1 / W2 ≤ 7.5. In a specific embodiment of the present invention, the width W2 of the reinforcing layer 130 is, for example, 3 mm to 12 mm. When the width of the uncoated active material layer area 102 is large, there is a high risk of the uncoated active material layer area 102 folding or wrinkling during the drying process and subsequent die-cutting and winding. By controlling the ratio of the width of the uncoated active material layer area 102 to the width of the reinforcing layer 130, when the width of the uncoated active material layer area 102 is large, it can provide support and prevent folding and wrinkling. When the width of the uncoated active material layer area 102 is small, it can also prevent the width of the reinforcing layer 130 from occupying the welding area of the uncoated active material layer area 102 used for connection to the external electrode, thereby affecting the welding of the uncoated active material layer area 102.

[0064] See also Figure 1As shown, in one embodiment of the present invention, along the first direction Y, the preset spacing between the active material layer 120 and the reinforcement layer 130 is denoted as G mm, satisfying 22≤W1 / G≤400. By controlling the ratio W1 / G, within a suitable range of the width of the uncoated area 102 of the active material layer and the preset spacing, the preset spacing is prevented from being too large, which would weaken the reinforcement layer and potentially result in insufficient welding area in the uncoated area 102 of the active material layer for connection to the external terminal. By taking into account the width of the uncoated area 102 of the active material layer and the preset spacing, the preset spacing is prevented from being too small, which would cause the reinforcement layer 130 and the active material layer 120 to blend together and cause bulging edges, thereby making the boundary between the reinforcement layer 130 and the active material layer 120 clear, thereby improving battery performance and reducing safety hazards.

[0065] See also Figure 1 As shown, in one embodiment of the present invention, along the first direction Y, the width of the active material layer 120 is W3mm, satisfying 3≤W3 / W1≤11. In a specific embodiment of the present invention, the width W1 of the uncoated area 102 of the active material layer is, for example, 30mm-40mm. By controlling the ratio of the width of the active material layer 120 to the width of the uncoated area 102 of the active material layer, on the basis of providing a reinforcement layer, the widths of the active material layer 120 and the uncoated area 102 of the active material layer can be taken into account, thereby facilitating the bending of the uncoated area to electrically connect with the pole, and avoiding folding and wrinkling, while taking into account the balance of the mass energy density of the battery.

[0066] See also Figure 1As shown, in one embodiment of the present invention, the obtained electrode sheet is rolled and slit before being wound up to reduce the contact resistance between the materials, increase the battery capacity, and enhance the bonding strength between the active material layer 120 and the reinforcing layer 130 and the current collector 110 to prevent peeling during use and ensure that the electrode sheet meets specific size and shape requirements. A portion of the electrode sheet is selected and cut from the preset gap between the active material layer 120 and the reinforcing layer 130. The weight of the side with the active material layer 120 is A1, and the weight of the side with the reinforcing layer 130 is A2. The electrode sheet is then dried at 140°C for 5 minutes and cooled to room temperature. The weight of the side with the active material layer 120 is B1, and the weight of the side with the reinforcing layer 130 is B2. Here, 1-B1 / A1 is defined as the weight loss rate of the active material layer 120, and 1-B2 / A2 is defined as the weight loss rate of the reinforcing layer 130. In this embodiment, the weight loss rate of the active material layer 120 is less than 0.5%, and the weight loss rate of the reinforcement layer 130 is less than 3%. This is because the binder is evenly dispersed during the drying process, reducing the risk of structural stress concentration and interfacial delamination caused by high temperatures. The bonding strength between other materials and the binder is enhanced, suppressing the propagation of microcracks caused by high-temperature expansion. By minimizing the weight loss rate of the active material layer 120 and the reinforcement layer 130, the stability of the electrode structure is improved, and the subsequent die-cutting power can be reduced. There is no breakage of the strips, and there is no folding of the active material layer coating area 101.

[0067] See also Figure 3 and Figure 5 As shown, in one embodiment of the present invention, before use, the electrode piece is obtained by die-cutting a portion of the uncoated area 102 of the active material layer or die-cutting the uncoated area 102 of the active material layer and a portion of the coated area 101 of the active material layer to obtain the electrode tab 140, wherein the die-cutting stop position is recorded as the shoulder B of the electrode tab 140, and the electrode tab 140 extends from the shoulder B to the side of the uncoated area 102 of the active material layer away from the active material layer 120. By setting a color developer in the reinforcing layer 130, the grayscale value of the reinforcing layer 130 is, for example, 0-110, that is, the color difference between the reinforcing layer 130 and the current collector 110 is increased, and the grayscale value of the reinforcing layer is smaller than the grayscale value of the current collector. In the die-cutting process of forming the tab, it is convenient for the charge-coupled device detection (CCD) to identify the size and position of the reinforcing layer 130, and the reinforcing layer 130 can absorb laser energy, reduce the reflection and scattering of the laser, etc., so that the laser energy is more concentrated, thereby reducing the die-cutting power, reducing energy consumption, and making the cutting edge less likely to produce burrs, thereby reducing the problem of short circuit caused by burrs.

[0068] See also Figure 3As shown, in one embodiment of the present invention, the die-cutting stop position is within the active material layer 120, that is, part of the active material layer 120 covers at least a portion of the surface of the tab 140 along the first direction Y. In this case, the height of the tab 140 includes the size of the active material layer that may extend to both the front and back sides of the tab 140.

[0069] See also Figure 5 As shown, in another embodiment of the present invention, the die-cutting stop position is within the reinforcement layer 130, and a transition zone 160 is provided between the tab 140 and the active material layer coating area 101. The reinforcement layer 130 is located on a portion of the transition zone 160 and a portion of the tab 140 surface. In this case, the height of the tab includes the size of the reinforcement layer located on the portion of the tab 140. By providing the transition zone 160, the laser energy for die-cutting can be reduced, thereby reducing energy consumption. In other words, compared to die-cutting to a portion of the area where the active material layer is located, the laser energy is lower, the laser power is reduced, the foil leakage phenomenon is reduced, the energy density and cycle performance of the battery are improved, and the safety performance is improved.

[0070] See also Figures 3 to 6 As shown, in one embodiment of the present invention, after obtaining the tab 140, the tab 140 is stamped and formed to form a plurality of reinforcing ribs 150 on the tab 140. The reinforcing ribs 150 are arranged on the tab 140 in at least one shape such as a dot, strip, wave, or broken line. In addition, along the first direction and / or the second direction, each two adjacent reinforcing ribs 150 are spaced apart from each other. When the reinforcing ribs 150 are distributed in a strip shape, the reinforcing ribs 150 are similar to a plurality of parallel long strips. The ratio of the width of the maximum overlapping position of the reinforcing ribs 150 and the reinforcing layer 130 (W4 mm) to the width of the reinforcing layer 130 (W2 mm) is 0.1-1, wherein the maximum distance from the reinforcing ribs 150 located on the reinforcing layer 130 away from the active material layer 120 and away from the first direction is defined as W4. When W4 / W2 is 1, it means that the reinforcing rib 150 at least overlaps with the side of the reinforcing layer 130 close to the active material layer 120, or part of the reinforcing rib 150 is located within the preset distance between the reinforcing layer 130 and the active material layer 120. In other embodiments, the reinforcing rib 150 can also be made in other ways. For example, the reinforcing rib 150 is formed separately and then fixed on the current collector 110. By controlling the ratio of W4 / W2 within an appropriate range, the strength of the reinforcing layer can be improved, the wrinkles of the tabs can be reduced, and the width of the uncoated area 102 of the active material layer can be further increased, thereby adapting to more layers of tabs and reducing the direct current resistance (DCR) of the battery.

[0071] See also Figure 7As shown, in one embodiment of the present invention, the battery further includes a positive electrode sheet 200, which includes a positive electrode collector 210 and a positive electrode active material layer 220 coated on at least one surface of the positive electrode collector 210. That is, the positive electrode collector 210 has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer 220 can be provided on either or both of the two surfaces of the positive electrode collector 210. The positive electrode collector 210 can be an aluminum foil collector, and the thickness of the aluminum foil collector is, for example, 5μm-20μm. Further, the thickness of the aluminum foil collector is, for example, 10μm-15μm. The positive electrode collector 210 can also be a composite current collector, which includes a polymer matrix and aluminum layers located on the upper and lower surfaces of the polymer matrix. The polymer matrix can be polyethylene terephthalate, polypropylene, polyimide, polystyrene or polyamide, etc.

[0072] See also Figure 7 As shown, in one embodiment of the present invention, on the positive electrode current collector 210, the area coated with the positive electrode active material layer 220 is defined as the electrode sheet area, and the area of the positive electrode current collector 210 not coated with the positive electrode active material layer 220 is defined as the positive electrode tab area 230, which is used to form the positive electrode tab. The electrode sheet area and the positive electrode tab area 230 are arranged adjacent to each other. The positive electrode active material layer 220 includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. The positive electrode active material can be selected from one or more combinations of lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium titanate, lithium nickel cobalt manganese aluminum oxide, lithium iron phosphate, and lithium manganese iron phosphate. The positive electrode conductive agent can be selected from one or more of conductive carbon black, acetylene black, nanometal powder, graphene, carbon nanotubes, or carbon nanofibers, or a combination of two or more of these in any proportion. The positive electrode binder can be selected from one or more mixtures of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene, or polytetrafluoroethylene. The present invention does not limit the thickness of the positive electrode active material layer 220 , and the thickness is selected based on the battery design requirements.

[0073] See also Figure 8 and Figure 9 As shown, in one embodiment of the present invention, the positive electrode plate 200 includes a plurality of positive electrode tabs 240, and part of the positive electrode active material layer 220 covers at least part of the surface of the positive electrode tab 240; or a connection area 241 is set between the positive electrode tab 240 and the positive electrode active material layer 220, and the connection area 241 is located in the positive electrode tab area 230, that is, the positive electrode active material layer 220 is not set on the connection area 241, and the positive electrode active material layer 220 does not cover the positive electrode tab 240.

[0074] See also Figure 10 and Figure 11As shown, in one embodiment of the present invention, the battery further includes a separator 300, which is disposed between the positive electrode sheet 200 and the negative electrode sheet to prevent the positive electrode sheet 200 and the negative electrode sheet from contacting each other and causing safety problems. The separator 300 is, for example, a polyethylene film (PE), a polypropylene film (PP), a glass fiber film, a polyethylene film, or a composite film. In this application, the thickness of the separator 300 is not limited, and it can meet the requirements of use.

[0075] See also Figures 10 to 12 As shown, in one embodiment of the present invention, the negative electrode plate is selected from the above-mentioned plate 100, and the plate 100 and the positive electrode plate 200 are made into an electrode assembly 20, for example, by winding or lamination, and the lamination is, for example, a layered lamination or a Z-shaped lamination, etc., and this application does not impose specific restrictions.

[0076] See also Figure 13 As shown, in one embodiment of the present invention, the battery further includes a housing 10 having an upper opening, an electrode assembly disposed within the housing 10, and a cover assembly 11 that closes the upper opening. The present invention does not limit the type and shape of the battery. The battery may be, for example, a primary battery or a secondary battery. The secondary battery may be, for example, a pouch cell, a cylindrical cell, or a prismatic cell, or a sodium ion secondary battery or a lithium ion secondary battery. In this embodiment, a lithium ion secondary battery is used as an example for illustration.

[0077] See also Figures 10 to 13 As shown, in one embodiment of the present invention, when the secondary battery is, for example, a prismatic battery, the prismatic battery includes, for example, a housing 10, a cover assembly 11, and an electrode assembly 20 disposed within the housing 10, wherein the tabs of the electrode assembly 20 are electrically connected to the posts on the housing 10. The shape of the housing 10 matches that of the electrode assembly 20, and the material of the housing 10 is, for example, an aluminum housing, a steel housing, or a flexible housing. The housing 10 is a receiving cavity with an upper opening for accommodating the electrode assembly 20. Specifically, after the electrode assembly 20 is placed in the housing 10 through the upper opening, the housing 10 is sealed using the cover assembly 11.

[0078] See also Figures 10 to 13As shown, in one embodiment of the present invention, the electrode assembly 20 includes a main body 1 and an active material layer uncoated area 102 and a positive electrode tab 240 located at one end of the main body 1. The active material layer uncoated area 102 is used to form a tab 140 to serve as a negative electrode tab. Among them, the main body 1 is a portion formed by a stack of shoulders B of the tab. Two electrode assemblies 20 are arranged oppositely in the shell 10. Each set of electrode assemblies 20 is provided with an active material layer uncoated area 102 and a positive electrode tab 240 at one end facing the cover assembly 11. The active material layer uncoated area 102 and the positive electrode tab 240 can be connected to the cover assembly 11 through corresponding adapter sheets 1112. The positive electrode tabs 240 of the two electrode assemblies 20 are welded to each other, and the active material layer uncoated areas 102 of the two electrode assemblies 20 are welded to each other. The positive electrode tabs 240 and the active material layer uncoated areas 102 of the two electrode assemblies 20 are welded correspondingly and welded to the adapter sheet 1112. Then, the two sets of electrode assemblies 20 are bent relative to each other and then installed in the housing 10. The active material layer uncoated area 102 includes a connecting portion 111 and a bending portion 112. The connecting portion 111 is fixedly connected to the adapter sheet 1112. The bending portion 112 is connected between the main body 1 and the connecting portion 111. The reinforcing layer 130 covers at least a portion of the bending portion 112. The uncoated area 102 of the active material layer is covered with a first tape 30. The first tape 30 is located on the side of the uncoated area 102 facing away from the cover plate assembly 11 to protect the uncoated area 102 of the active material layer. The first tape 30 includes a first adhesive area 31, a second adhesive area 33, and a non-adhesive area 32 located between the first and second adhesive areas 31, 33. The first adhesive area 31 covers the main body 1, and the second adhesive area 33 covers the connection portion 111. In the thickness direction of the electrode assembly, the orthographic projection of the reinforcement layer 130 is completely located within the non-adhesive area 32, thereby preventing the reinforcement layer from falling off when the tab is static or when the tab is assembled. The positive electrode tab 240 is covered with a second tape 40. The second tape 40 is located on the side of the positive electrode tab 240 facing away from the cover plate assembly 11 to protect the positive electrode tab 240. The tape improves the safety of the leaking foil, and the non-sticky area covers the reinforcement layer to prevent the reinforcement layer from falling off. The tape provides support to prevent the negative electrode tab from being inserted and torn.

[0079] See also Figures 10 to 13As shown, in one embodiment of the present invention, a first pole 12, a second pole 13, an explosion-proof valve 14 and an injection hole 15 are provided on the cover plate assembly 11, and the electrolyte is injected through the injection hole 15, and then the injection hole 15 is sealed. Among them, the polarity of the first pole 12 and the second pole 13 are opposite, and the first pole 12 and the second pole 13 are respectively positive or negative poles, and the present invention does not limit the specific polarity categories corresponding to the first pole 12 and the second pole 13. The first pole 12 is electrically connected to the pole tab with the same polarity on the electrode assembly 20, and the second pole 13 is electrically connected to the pole tab with the same polarity on the electrode assembly 20. In this embodiment, the positions of the first pole 12 and the second pole 13 are not limited, and can be located at the same end of the shell or at both ends of the shell, and are specifically set according to the position of the pole tab on the electrode assembly 20 or design requirements.

[0080] See also Figure 13 As shown, in one embodiment of the present invention, when the first and second poles 12 and 13 are disposed at one end of the housing, the explosion-proof valve 14 and the injection hole 15 are disposed between the first and second poles 12 and 13. For example, the explosion-proof valve 14 is disposed midway between the first and second poles 12 and 13, with a predetermined distance therebetween. The injection hole 15 is disposed between the explosion-proof valve 14 and the first pole 12, or between the explosion-proof valve 14 and the second pole 13. That is, the explosion-proof valve 14, the injection hole 15, the first and second poles 12 and 13 are spaced apart from each other. The explosion-proof valve 14 can activate its ventilation function when the battery cell is operating normally, allowing air to flow inside and outside the battery cell while preventing particulate matter from flowing. In the event of thermal runaway of the battery cell, when the pressure difference between the inside and outside of the battery cell reaches a predetermined explosion-proof value, the explosion-proof valve opens, allowing both gas and solids to be discharged from the inside of the battery cell to the outside of the battery cell through the explosion-proof valve, thereby improving the safety performance of the battery cell.

[0081] See also Figures 10 to 13 As shown, in one embodiment of the present invention, an electrolyte (not shown) is filled between the electrode sheet 100, the positive electrode sheet 200, and the separator 300, as well as between the electrode assembly 20 and the housing 10, to conduct ions between the positive and negative electrode sheets. The electrolyte can be any suitable lithium-ion battery electrolyte. The stacking method of the positive and negative electrode sheets is not specifically limited in this application and is selected based on manufacturing requirements.

[0082] In one embodiment of the present invention, the electrolyte includes, for example, an organic solvent and a lithium salt. The organic solvent is selected from any one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl acetate (EA), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or diethyl carbonate (DEC). The lithium salt is selected from any one or more of lithium bis(fluorosulfonyl)imide (LiFSi), lithium difluorophosphate (LiPO2F2), lithium hexafluorophosphate (LiPF6), or lithium tetrafluoroborate (LiBF4). In one embodiment of the present invention, the lithium salt is selected from lithium hexafluorophosphate, for example, and the organic solvent is selected from a mixture of ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, and propylene carbonate. Ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate are mixed, for example, in a volume ratio of 1:1:1:1, and fully dried LiPF6 is dissolved in a mixed organic solvent in an argon atmosphere glove box with a water content of less than 10 ppm. After mixing evenly, an electrolyte is obtained, wherein the concentration of LiPF6 is, for example, 1 mol / L.

[0083] Hereinafter, the present invention will be explained in more detail by citing examples, which should not be construed as limiting. Appropriate modifications may be made within the scope consistent with the gist of the present invention, all of which fall within the technical scope of the present invention.

[0084] Example 1

[0085] Preparation of the negative electrode: Boehmite, polyacrylic acid, and carbon black were mixed in a mass ratio of 20:75:5, deionized water was added, and the mixture was mixed thoroughly in a vacuum mixer to obtain a reinforcement layer slurry. Artificial graphite, conductive carbon black, sodium carboxymethyl cellulose, and polyacrylic acid were mixed in a mass ratio of 96:1:1:2, deionized water was added, and the mixture was mixed thoroughly in a vacuum mixer to obtain an active slurry. The active slurry and reinforcement layer slurry were simultaneously coated onto 6μm-thick copper foil at a speed of 8m / min with a preset spacing of 0.6mm. The mixture was then transferred to an oven for drying at 79°C and 36Hz, 83°C and 37Hz, 83°C and 41Hz, 77°C and 42Hz, and finally 76°C and 40Hz. After rolling, slitting, die-cutting, and cutting, the negative electrode was obtained. When forming the tab, the tab extends from the side of the uncoated area of the active material layer away from the active material layer to the inside of the reinforcement layer, i.e., a transition zone is provided. The width of the active material layer coated area is 210 mm, the width of the uncoated area of the active material layer is 30 mm, the width of the reinforcement layer is 12 mm, the thickness of the reinforcement layer is 18 μm, and the preset spacing between the reinforcement layer and the active material layer is 0.6 mm. In other words, the ratio of the width of the uncoated area of the active material layer to the width of the reinforcement layer is 2.5, the ratio of the width of the uncoated area of the active material layer to the preset spacing is 50, the ratio of the thickness of the reinforcement layer to the thickness of the current collector is 3, the ratio of the width of the active material layer to the uncoated area of the active material layer is 7, and the ratio of the width of the maximum overlapping position of the reinforcement rib and the reinforcement layer to the width of the reinforcement layer is 0.5.

[0086] Preparation of positive electrode: LiNi 08 Co 0.1 Mn 0.1 After mixing O2, acetylene black, and polyvinylidene fluoride in a mass ratio of 97:1:2, N-methylpyrrolidone was added and stirred in a vacuum mixer until the system was uniform to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on aluminum foil, then dried at room temperature and transferred to an oven for drying. After cold pressing, trimming, cutting, and slitting, the positive electrode sheet was obtained.

[0087] Preparation of electrolyte: Ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate are mixed, for example, in a volume ratio of 1:1:1:1, and in an argon atmosphere glove box with a water content of less than 10 ppm, fully dried LiPF6 is dissolved in a mixed organic solvent, and the mixture is mixed evenly to obtain an electrolyte, wherein the concentration of LiPF6 is, for example, 1 mol / L.

[0088] Selection of diaphragm: Polyethylene with a thickness of 9 μm is used as the diaphragm.

[0089] Battery Preparation: The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence and wound, with the separator positioned between the positive and negative electrodes to provide isolation. Except for the innermost and outermost circles, each circle of the negative electrode sheet has a tab, resulting in a wound bare cell. The bare cell is then placed in an aluminum casing, fitted with a top cover assembly, and then electrolyte is injected and sealed to create a lithium-ion battery.

[0090] Example 2

[0091] The active slurry and the reinforcement layer slurry were fed at a speed of 6 m / min, and the rest of the operations were the same as in Example 1.

[0092] Example 3

[0093] The active slurry and the reinforcement layer slurry were made at a speed of 10 m / min and a h / A of 1.5. The other operations were the same as in Example 1.

[0094] Example 4

[0095] After applying the active slurry and the reinforcing layer slurry, drying was carried out in an oven at 77°C and 37HZ, 80°C and 37HZ, 82°C and 42HZ, 75°C and 42HZ, and 75°C and 41HZ, respectively. The remaining operations were the same as in Example 1.

[0096] Example 5

[0097] After applying the active slurry and the reinforcing layer slurry, drying was carried out in an oven at 80°C and 38HZ, 84°C and 40HZ, 85°C and 42HZ, 75°C and 44HZ, and 75°C and 38HZ, respectively. The remaining operations were the same as in Example 1.

[0098] Example 6

[0099] The thickness of the reinforcement layer is 6 μm, the ratio of the thickness of the reinforcement layer to the thickness of the current collector is 1, and the remaining operations are the same as those in Example 1.

[0100] Example 7

[0101] The thickness of the reinforcement layer is 36 μm, the ratio of the thickness of the reinforcement layer to the thickness of the current collector is 6, and the remaining operations are consistent with those in Example 1.

[0102] Example 8

[0103] The thickness of the current collector is 5 μm, the thickness of the reinforcement layer is 15 μm, the ratio of the thickness of the reinforcement layer to the thickness of the current collector is 3, and the remaining operations are the same as in Example 1.

[0104] Example 9

[0105] The thickness of the current collector is 4.5 μm, the thickness of the reinforcement layer is 13.5 μm, the ratio of the thickness of the reinforcement layer to the thickness of the current collector is 3, and the remaining operations are the same as in Example 1.

[0106] Example 10

[0107] The thickness of the current collector is 4 μm, the thickness of the reinforcement layer is 12 μm, the ratio of the thickness of the reinforcement layer to the thickness of the current collector is 3, and the remaining operations are the same as those in Example 1.

[0108] Example 11

[0109] The width of the reinforcement layer is 6 mm, that is, the ratio of the width of the uncoated area of the active material layer to the width of the reinforcement layer is 5. The remaining operations are the same as those in Example 1.

[0110] Example 12

[0111] The width of the reinforcement layer is 4 mm, that is, the ratio of the width of the uncoated area of the active material layer to the width of the reinforcement layer is 7.5. The remaining operations are the same as those in Example 1.

[0112] Example 13

[0113] The width of the uncoated area of the active material layer is 40 mm, and the width of the reinforcing layer is 8 mm, that is, the ratio of the width of the uncoated area of the active material layer to the width of the reinforcing layer is 5. The remaining operations are the same as in Example 1.

[0114] Example 14

[0115] The width of the uncoated area of the active material layer is 40 mm, the preset spacing between the reinforcing layer and the active material layer is 0.1 mm, the ratio of the width of the uncoated area of the active material layer to the preset spacing is 400, and the remaining operations are the same as in Example 1.

[0116] Example 15

[0117] The preset distance between the reinforcing layer and the active material layer is 1.1 mm, the ratio of the width of the uncoated area of the active material layer to the preset distance is 27.3, and the remaining operations are the same as those in Example 1.

[0118] Comparative Example 1

[0119] The active slurry and the reinforcement layer slurry were fed at a speed of 5 m / min, and the rest of the operations were the same as in Example 1.

[0120] Comparative Example 2

[0121] The active slurry and the reinforcement layer slurry were fed at a speed of 11 m / min, and the rest of the operations were the same as in Example 1.

[0122] Comparative Example 3

[0123] After the active slurry and the reinforcing layer slurry were applied, the whole process was dried in an oven at 83° C. and 50 Hz. The remaining operations were the same as those in Example 1.

[0124] Comparative Example 4

[0125] After the active slurry and the reinforcing layer slurry were applied, the whole process was dried in an oven at 73° C. and 50 Hz. The remaining operations were the same as those in Example 1.

[0126] Comparative Example 5

[0127] After applying the active slurry and the reinforcing layer slurry, drying was carried out in an oven at 81°C and 40HZ, 86°C and 41HZ, 86°C and 39HZ, 74°C and 39HZ, and 74°C and 35HZ, respectively. The remaining operations were the same as in Example 1.

[0128] Comparative Example 6

[0129] The thickness of the reinforcing layer is 3 mm, that is, the ratio of the thickness of the strong layer to the thickness of the reinforcing layer is 0.5. The remaining operations are the same as those in Example 1.

[0130] Comparative Example 7

[0131] The width of the reinforcement layer is 15 mm, that is, the ratio of the width of the uncoated area of the active material layer to the width of the reinforcement layer is 2. The remaining operations are the same as those in Example 1.

[0132] Comparative Example 8

[0133] The width of the reinforcement layer is 3.5 mm, that is, the ratio of the width of the uncoated area of the active material layer to the width of the reinforcement layer is 8.6. The remaining operations are the same as those in Example 1.

[0134] Comparative Example 9

[0135] The preset distance between the reinforcing layer and the active material layer is 1.4 mm, the ratio of the width of the uncoated area of the active material layer to the preset distance is 21.4, and the remaining operations are the same as those in Example 1.

[0136] Comparative Example 10

[0137] The preset distance between the reinforcing layer and the active material layer is 0.05 mm, the ratio of the width of the uncoated area of the active material layer to the preset distance is 600, and the remaining operations are the same as those in Example 1.

[0138] In one embodiment of the present invention, in order to obtain the tab wrinkle performance, after obtaining the bare battery cell, the distance from the side of each tab away from the active material layer to the active material layer is tested by a camera, and the difference from the design value of the width of the uncoated area of the active material layer is calculated (if it is the design value after the battery is disassembled, for tabs of equal height, the maximum value of the uncoated area width is taken), and the average value of the difference is obtained, and the average value is defined as the tab deviation value (if the deviation value of the uncoated area of the active material layer is obtained, the distance from the side of the uncoated area of each active material layer away from the active material layer to the active material layer is obtained by a camera). The tab deviation value is used to characterize the tab wrinkle performance. The smaller the tab deviation value, the less wrinkles the tab has.

[0139] In one embodiment of the present invention, in order to obtain the folding condition of the tab, after obtaining the bare battery cell, the orthographic projection area of each tab on the plane where the current collector is located is obtained by a CCD camera, which is recorded as S1, and the orthographic projection area of each tab on the plane where the current collector is located after being flattened is recorded as S2 (if the folding condition of the uncoated area of the active material layer is obtained, the orthographic projection area of the uncoated area of each layer of the active material layer on the plane where the current collector is located, and the orthographic projection area of the uncoated area of each layer of the active material layer on the plane where the current collector is located after being flattened) is obtained by a CCD camera, and the calculation error = (S2-S1) / S2×100%, and the tab with an error greater than 5% is defined as a tab with folding, and the ratio of the number of tab layers with folding to the total number of tab layers is calculated.

[0140] In one embodiment of the present invention, after obtaining the negative electrode sheet, it is observed whether the reinforcing layer and the negative electrode active material layer are fused. The fused state is that the material of the active material layer is fused in the reinforcing layer area, and the unfused appearance state is that the reinforcing layer and the active material layer are completely separated, and the corresponding spacing is relatively uniform.

[0141] In one embodiment of the present invention, after disassembling the battery cells of Examples 1-15 and Comparative Examples 1-10, the actual number of tab welding layers is observed, and the ratio of the actual number of tab welding layers to the designed number of tabs is calculated (if the number of welding layers in the uncoated area of the active material layer is obtained, the actual number of welding layers and the designed number of layers in the uncoated area of the active material layer are obtained).

[0142] In one embodiment of the present invention, during the coating process, after every 3000m of electrode sheet, a comprehensive inspection is conducted on the electrode sheet to count the number of coating cracks and wrinkles in the electrode sheet. A wrinkle frequency of ≤ 1 / 1000 is considered acceptable, and a crack count of ≤ 1 / 1000 is considered acceptable. A count greater than 1 / 1000 may cause safety issues in the subsequent battery cells.

[0143] Table 1. Some characteristics and properties of the negative electrode sheets in Examples 1-3 and Comparative Examples 1-2

[0144]

[0145] Please refer to Table 1. Comparing Examples 1-3 and Comparative Example 1-2, it can be seen that when the thickness of the current collector is consistent, the frequency of wrinkling of the coated electrode gradually increases with the increase in coating speed. When the coating speed is too fast, the electrode will not be dried. This is because the coating speed does not match the oven parameters. High-speed coating needs to match high oven temperature and wind frequency parameters to ensure that the electrode can be dried and produce effective electrodes. Especially in Comparative Example 2, the oven parameters do not match the coating speed, the electrode is unevenly baked, and the force is uneven, which further leads to an increase in the frequency of wrinkling of the coating. Comparing Examples 1-3 and Comparative Example 1, when the wrinkling frequency is qualified, the greater the coating speed, the greater the improvement. However, when the coating speed is slow, the production capacity, electrode operation and factory energy consumption are greatly affected. In order to match the production capacity, the coating speed is controlled to be 6m / min-10m / min.

[0146] Table 2. Some characteristics and properties of the negative electrode sheets in Examples 1, 4-5 and Comparative Examples 3-5

[0147]

[0148] Please refer to Table 2. By comparing Examples 1, 4-5 and Comparative Examples 3-5, it can be seen that when the drying temperature and wind frequency are set according to the "low-high-low" mode, the cracking of the electrode output during coating is not serious. However, there are slight differences between the different settings. When the temperature is high, the electrode is prone to cracking. This is because the electrode evaporates quickly and upward stress is more likely to be generated. When the drying temperature and wind frequency remain unchanged, the electrode output during coating cracks seriously. Therefore, the drying temperature and wind frequency need to be set to the "low-high-low" mode during coating, and the temperature and wind frequency settings need to be matched according to the actual situation.

[0149] Table 3. Some characteristics and properties of the negative electrode sheets in Examples 1, 6-10 and Comparative Example 6

[0150]

[0151] As shown in Table 3, by comparing Examples 1, 6-10 and Comparative Example 6, when the current collector thickness is consistent, as the ratio of the reinforcement layer thickness to the current collector thickness increases, the tab deviation value and the tab folding ratio decrease. This shows that increasing the thickness of the reinforcement layer can reduce tab wrinkling and folding, and as the ratio increases, the tab deviation value and the tab folding ratio tend to be stable. To control costs, the ratio of the reinforcement layer thickness to the current collector thickness is controlled between 1 and 6. Comparing Examples 1, 9-11, it can be seen that when the ratio of the reinforcement layer thickness to the current collector thickness is consistent, as the current collector thickness decreases, the tab deviation value and the tab folding ratio increase, but overall remain within a small range. This shows that as the current collector thickness decreases, the number of tab wrinkles and folds increases, and the provision of a reinforcement layer can improve the tab wrinkling and folding. Therefore, as the current collector thickness decreases, the ratio of the reinforcement layer thickness to the current collector thickness can be increased to improve the tab wrinkling and folding.

[0152] Table 4. Some characteristics and properties of the negative electrode sheets in Examples 1, 11-13 and Comparative Examples 7-8

[0153]

[0154] As shown in Table 4, a comparison of Examples 1, 11-13, and Comparative Examples 7-8 shows that when the width of the reinforcement layer is small (i.e., when W1 / W2 is large), the deviation value of the uncoated area of the active material layer is large, and the proportion of folds in the uncoated area of the active material layer is large, indicating that the uncoated area of the active material layer has more wrinkles and folds. As the width of the reinforcement layer gradually increases, the deviation value of the uncoated area of the active material layer gradually decreases, and the proportion of folds in the uncoated area of the active material layer is less than 0.5%, indicating that increasing the width of the reinforcement layer can reduce wrinkles and folds in the uncoated area of the active material layer. When the width of the reinforcement layer is too large, that is, when W1 / W2 is less than 2.5, the area used for welding in the uncoated area of the active material layer and the adapter will cause a cavity explosion when welding. As a result, the number of welding layers in the actual uncoated area of the active material layer is different from the number of layers designed for the uncoated area of the active material layer, which may increase the interface contact resistance and reduce the bonding strength between the uncoated area of the active material layer and the electrode. This may further cause the uncoated area of the active material layer to fall off or become a poor connection, or a significant local temperature rise in the battery, which may trigger a thermal runaway chain reaction. Therefore, controlling W1 / W2 within the range of 2.5-7.5 can improve the safety performance of the battery while reducing wrinkles and folds in the uncoated area of the active material layer.

[0155] Table 5. Some characteristics and properties of the negative electrode sheets in Examples 1, 14-15 and Comparative Examples 9-10

[0156]

[0157] Please refer to Table 5. It can be seen from Comparative Examples 1, 14-15 and Comparative Examples 9-10 that when the ratio of the width of the uncoated area of the active material layer to the preset spacing between the reinforcing layer and the active material layer is greater than 400, that is, when the preset spacing is small, the reinforcing layer and the negative electrode active material layer fuse, which may lead to problems such as abnormal interface contact and stress concentration, and also cause a decrease in the utilization rate of the active material. As the preset spacing increases, that is, the W1 / G ratio decreases, the fusion of the reinforcing layer and the negative electrode active material layer can be avoided, and as the W1 / G ratio decreases, the tab deviation value is relatively stable, but when the W1 / G ratio is less than 22, the tab deviation value is large. This is because the spacing between the reinforcing layer and the active material layer is too large, and the role of the reinforcing layer cannot be played, resulting in an increase in wrinkles. Therefore, controlling the W1 / G ratio reduces the mutual dissolution and reduces the wrinkles and folding of the tabs, thereby improving the safety performance of the battery.

[0158] In summary, the present invention provides a method and application for preparing a pole piece, which can avoid the solvent from volatilizing too quickly during the drying process of the slurry, reduce the uneven stress of the current collector during the drying process, and reduce the occurrence of wrinkles, folds, etc. in the uncoated area of the active material layer by setting a reinforcement layer. At the same time, when the pole piece is assembled into a battery, because the uncoated area of the active material layer will be bent, the problem of interpolation of the uncoated area of the active material layer can also be avoided, thereby avoiding related failures such as short circuits caused by interpolation. The uniformity of the obtained pole piece can be improved, thereby improving the cycle life and safety of the battery. By controlling the width ratio of the uncoated area of the active material layer and the reinforcement layer, when the width of the uncoated area of the active material layer is large, the reinforcement layer can play a better supporting effect, avoiding the occurrence of wrinkles, folds and interpolation of the tab, and also avoiding the width of the reinforcement layer being too large and occupying the tab welding area, which can ensure the size of the tab welding area and improve the safety performance of the battery. By controlling the preset spacing, it is possible to avoid bulging caused by the intermingling of the reinforcement layer and the active material layer, while ensuring the welding area of the tabs and reducing the wrinkles and folding of the tabs, thereby improving battery performance and reducing safety hazards. It can be applied to thinner current collectors, and in the case of thinner current collectors or multi-layer tabs, it can reduce the wrinkling of the current collector. By controlling the composition of the reinforcement layer, the negative electrode production line does not require organic gas recovery equipment, simplifying the preparation process. By controlling the grayscale value of the reinforcement layer, the reflection of the laser can be reduced during laser cutting. For the same cut thickness, the laser power can be lower, which can reduce the laser energy for die cutting, reduce energy consumption, reduce foil leakage, improve the energy density and cycle performance of the battery, and improve the adhesion between the reinforcement layer and the current collector, reducing the peeling of the reinforcement layer.

[0159] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept, such as the technical solutions formed by the mutual replacement of the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

[0160] Except for the technical features described in the specification, the remaining technical features are known technologies to those skilled in the art. In order to highlight the innovative features of the present invention, the remaining technical features will not be described here in detail.

Claims

1. A method for preparing a pole piece, characterized in that: include: dispersing the active material, the first binder and the conductive agent in a first solvent according to a mass ratio to obtain an active slurry; Dispersing ceramic particles, a second binder, and a color developer in a second solvent according to a mass ratio to obtain a reinforcement layer slurry; Applying the active slurry and the reinforcement layer slurry on the current collector at a preset coating rate and a preset distance; as well as The coated current collector is sequentially dried in stages at a preset temperature and a preset wind frequency to obtain an active material layer and a reinforcement layer.

2. The method for preparing a pole piece according to claim 1, characterized in that: The preset coating rate is 6 m / min-10 m / min.

3. The method for preparing a pole piece according to claim 1, characterized in that: The segmented drying includes a first section, a second section, a third section, a fourth section and a fifth section. In the first section, the preset temperature is 75°C-80°C, and the preset wind frequency is 35Hz-38Hz; in the second section, the preset temperature is 80°C-85°C, and the preset wind frequency is 35Hz-40Hz; in the third section, the preset temperature is 80°C-85°C, and the preset wind frequency is 40Hz-45Hz; in the fourth section, the preset temperature is 75°C-80°C, and the preset wind frequency is 40Hz-45Hz; the preset temperature of the oven is 75°C-80°C, and the preset wind frequency is 38Hz-43Hz.

4. The method for preparing a pole piece according to claim 1, characterized in that: The active slurry and the reinforcement layer slurry are simultaneously coated on the current collector.

5. The method for preparing a pole piece according to claim 1, characterized in that: The weight loss rate of the reinforcement layer is less than 3%, and the weight loss rate of the active material layer is less than 0.5%.

6. The method for preparing a pole piece according to claim 1, characterized in that: The width of the uncoated area of the active material layer on the current collector is W1 mm, and the width of the reinforcement layer is W2 mm, satisfying 2.5≤W1 / W2≤7.

5.

7. The method for preparing a pole piece according to claim 6, characterized in that: The preset distance between the active slurry and the reinforcement layer slurry is G mm, satisfying 22≤W1 / G≤400; The preset spacing is 0.1 mm-1.1 mm.

8. The method for preparing a pole piece according to claim 1, characterized in that: The mass ratio of the ceramic particles, the second binder and the developer is 10-20:75-90:0.5-5, and the second binder is a water-based binder; The second binder comprises at least one of polyacrylic acid, styrene-butadiene rubber, polyvinyl alcohol, polyacrylamide, methyl cellulose and its salts, chitosan and its salts, and alginic acid and its salts; The developer includes at least one of carbon black, chromium oxide green, cobalt green, cobalt blue, iron blue, cadmium red, carbon black or iron oxide red.

9. The method for preparing a pole piece according to claim 8, characterized in that: The grayscale value of the reinforcement layer is 0-110, and the electrode is a negative electrode.

10. A battery, characterized in that: include: A shell having an upper opening; An electrode assembly and a cover assembly sealing the upper end opening are arranged in the shell; the electrode assembly is formed by stacking a positive electrode sheet, a separator and a negative electrode sheet and then winding or laminating them, and the negative electrode sheet is obtained by the preparation method according to any one of claims 1 to 9; along a first direction, the electrode assembly includes a main body and an uncoated area of the active material layer, the uncoated area of the active material layer includes a bent portion and a connecting portion, the connecting portion is fixedly connected to the cover assembly, and the bent portion is connected between the main body and the connecting portion; the reinforcement layer covers at least a portion of the bent portion; The electrode assembly is covered with a first tape, which is arranged on the side of the active material layer uncoated area facing away from the cover assembly. The first tape includes a first adhesive area, a second adhesive area, and a non-adhesive area between the first adhesive area and the second adhesive area. The first adhesive area covers the main body, and the second adhesive area covers the connecting part. In the thickness direction of the electrode assembly, the orthographic projection of the reinforcement layer is completely located within the non-adhesive area.

11. An electronic device, characterized in that: A battery comprising the battery of claim 10.

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