Preparation method of secondary battery and secondary battery

Abstract

The present invention provides a secondary battery preparation method and a secondary battery, the method comprising: providing a laminated structure, the laminated structure comprising a first electrode, a first diaphragm and a second electrode which are sequentially laminated, the first electrode comprising a first current collector and a plurality of first active material layers which are sequentially arranged at intervals, the second electrode comprising a second current collector and a plurality of second active material layers which are sequentially arranged at intervals; the first electrode comprises a first current collector and a plurality of first active material layers which are sequentially arranged at intervals, a first blank area is formed between every two adjacent first active material layers, the second electrode comprises a second current collector and a plurality of second active material layers which are sequentially arranged at intervals, and a second blank area is formed between every two adjacent second active material layers; the laminated structure is wound to form a wound battery cell, and the first blank area and the second blank area are located in two opposite corner areas of the wound battery cell; and cutting and removing two opposite corner areas of the wound battery cell to obtain the secondary battery. According to the invention, the problems of low yield, low production efficiency and the like in the production process of the laminated secondary battery are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery manufacturing, and particularly relates to a preparation method for a secondary battery and a secondary battery. Background Art

[0002] At present, the production processes of laminated secondary batteries include Z-type lamination and composite lamination. Among them, in Z-type lamination, the positive and negative electrode plates are stacked alternately on the separator to form an electrode core. During the preparation process of the Z-type lamination process, due to the high folding frequency, misalignment is likely to occur between the separator and the positive and negative electrode plates, resulting in a low yield of the prepared electrode core. For composite lamination, the positive and negative electrode plates and the separator need to be first compounded to obtain a plurality of single composite units, and then the plurality of single composite units are stacked to form an electrode core, resulting in a relatively complex process flow of the composite lamination process and a low production efficiency of the electrode core.

[0003] Therefore, there is an urgent need for a new preparation method for laminated secondary batteries, which can not only ensure the yield during the production process of laminated secondary batteries, but also improve the production efficiency of laminated secondary batteries. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a preparation method for a secondary battery and a secondary battery to solve the problems such as low yield and low production efficiency during the production of laminated secondary batteries.

[0005] To solve or improve the above technical problems to a certain extent, the present invention provides a preparation method for a secondary battery, which includes:

[0006] Providing a laminated structure, the laminated structure includes a first electrode, a first separator, and a second electrode which are sequentially laminated. The first electrode includes a first current collector and a plurality of first active material layers which are sequentially spaced along the length direction of the first current collector. A first blank area is between adjacent first active material layers. The second electrode includes a second current collector and a plurality of second active material layers which are sequentially spaced along the length direction of the second current collector. A second blank area is between adjacent second active material layers;

[0007] Winding the laminated structure along the length direction of the laminated structure to form a wound electrode core, and the first blank area and the second blank area are located in two opposite corner areas of the wound electrode core;

[0008] Cutting and removing two opposite corner areas of the wound electrode core to obtain the secondary battery.

[0009] In some embodiments, along the winding direction of the laminated structure, the distance between adjacent first active material layers gradually increases.

[0010] In some embodiments, along the winding direction of the laminated structure, the spacing between adjacent second active material layers gradually increases.

[0011] In some embodiments, along the winding direction of the laminated structure, the length of the first active material layer is the same as the length of the second active material layer.

[0012] In some embodiments, in the wound battery cell, the orthographic projection of the first active material layer on the innermost first separator is located within the orthographic projection area of the second active material layer on the innermost first separator.

[0013] In some embodiments, in the wound battery cell, the orthographic projection of the first active material on the innermost first separator coincides with the orthographic projection of the second active material layer on the innermost first separator.

[0014] In some embodiments, along the winding direction of the laminated structure, the length of the first active material layer is 12 mm to 800 mm.

[0015] In some embodiments, along the winding direction of the laminated structure, the length of the second active material layer is 12 mm to 800 mm.

[0016] In some embodiments, along the winding direction of the laminated structure, the length of the first blank area is 1.2 mm to 50.8 mm.

[0017] In some embodiments, along the winding direction of the laminated structure, the length of the second blank area is 1.2 mm to 50.8 mm.

[0018] In some embodiments, the thickness of the first active material layer is 80 μm to 300 μm.

[0019] In some embodiments, the thickness of the second active material layer is 80 μm to 300 μm.

[0020] In some embodiments, an insulating layer is provided on the first blank area, and the first electrode is formed by the following steps: the first active material layers are sequentially and spacedly coated on the first current collector, the first blank area is between adjacent first active material layers, and the insulating layer is sequentially coated on the first blank area; alternatively, the first active material layer and the insulating layer are alternately coated on the first current collector.

[0021] In some embodiments, an insulating layer is provided on the second blank area, and the second electrode is formed through the following steps: successively and spacedly coating on the second current collector to form the second active material layer, with the second blank area between adjacent second active material layers, and successively coating on the second blank area to form the insulating layer; alternatively, successively and alternately coating on the second current collector to form the second active material layer and the insulating layer.

[0022] In some embodiments, the insulating layer includes ceramic particles, a stabilizer, and a binder; wherein, the ceramic particles include at least one of alumina, boehmite, silica, and aluminum hydroxide, the stabilizer includes at least one of gelatin, methylcellulose, carboxymethylcellulose, sodium polyacrylate, polyethylene oxide, and polyvinyl alcohol, and the binder includes at least one of acrylic acid, styrene-butadiene rubber, polystyrene, and polyacrylate; based on the mass of the insulating layer, the weight percentage of the ceramic particles is 45% - 65%, the weight percentage of the stabilizer is 15% - 20%, and the weight percentage of the binder is 10% - 40%.

[0023] In some embodiments, the laminated structure further includes a second separator, and the second separator is disposed on a side of the first electrode away from the first separator, and / or, the second separator is disposed on a side of the second electrode away from the first separator.

[0024] In some embodiments, the first electrode includes a first single-sided area with the first active material layer disposed on one side and a first double-sided area with the first active material layer disposed on both sides, and the second electrode includes a second single-sided area with the second active material layer disposed on one side and a second double-sided area with the second active material layer disposed on both sides;

[0025] The step of winding the laminated structure along the length direction of the laminated structure to form a wound battery cell includes:

[0026] After the first single-sided area of the first electrode and the first separator are wound half a turn, the first double-sided area of the first electrode, the second double-sided area of the second electrode, and the first separator are wound, and the winding is ended through the second single-sided area of the second electrode and the first separator to form the wound battery cell.

[0027] In some embodiments, after the step of cutting two opposite corner regions of the wound battery cell, the following steps are further included:

[0028] Welding the electrode tabs of the first electrode and the electrode tabs of the second electrode respectively to obtain a stacked battery cell;

[0029] Performing post-treatment on the stacked battery cell to obtain the secondary battery.

[0030] In some embodiments, the first electrode is one of the positive electrode tab and the negative electrode tab, and the second electrode is the other of the positive electrode tab and the negative electrode tab.

[0031] The present invention also provides a secondary battery, which is prepared by the preparation method of the above secondary battery.

[0032] Compared with the prior art, the present invention has obvious advantages and beneficial effects. By means of the above technical solutions, the preparation method of the secondary battery and the secondary battery of the present invention can achieve considerable technological progress and practicality, and have wide industrial utilization value. It has at least the following advantages:

[0033] In the process of preparing the stacked sheet of the present invention, combining the advantages of preparing a wound battery, first a wound core is prepared by a winding process, and then the opposite corners of the wound core are cut. After removing the connection of the electrode tabs at the corners, a stacked sheet core is obtained. On the one hand, it can ensure the accuracy of the alignment of the separator and the positive and negative electrode tabs, and ensure the yield of the preparation of the stacked sheet type secondary battery. On the other hand, it can improve the preparation rate of the stacked sheet type secondary battery and improve the production efficiency of the stacked sheet type secondary battery.

[0034] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable, the following preferred embodiments are specifically given and described in detail in conjunction with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic flow chart of the preparation method of the secondary battery according to an embodiment of the present invention;

[0036] Figure 2 It is a schematic flow chart of the preparation method of the secondary battery according to another embodiment of the present invention;

[0037] Figure 3 It is a schematic structural diagram of the first electrode according to an embodiment of the present invention;

[0038] Figure 4 It is a schematic structural diagram of the second electrode according to an embodiment of the present invention;

[0039] Figure 5 It is a schematic structural diagram of the wound core according to an embodiment of the present invention;

[0040] Figure 6 It is a schematic structural diagram of the stacked sheet core according to an embodiment of the present invention.

[0041] Description of the reference numerals:

[0042] 10: First electrode; 11: First single-sided area; 12: First double-sided area; 20: Second electrode; 21: Second single-sided area; 22: Second double-sided area; 30: First separator; 30: First separator; 40: Second separator; 50: Opposite two corner regions of the wound battery cell; 100: First current collector; 101: First active material layer; 102: First blank area; 200: Second current collector; 201: Second active material layer; 202: First blank area. Detailed implementation manners

[0043] To further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the preparation method of the secondary battery and the specific implementation manners and effects thereof proposed according to the present invention.

[0044] The present invention provides a method for preparing a secondary battery. In the process of preparing the stacked battery, by combining the advantages of preparing a wound battery, first a wound battery cell is prepared by a winding process, and then the opposite corners of the wound battery cell are cut to remove the connection of the electrode tabs at the corners, so as to obtain a stacked battery cell. On the one hand, it can ensure the accuracy of the alignment of the separator and the positive and negative electrode tabs, and ensure the yield of the preparation of the stacked secondary battery. On the other hand, it can improve the preparation rate of the stacked secondary battery and the production efficiency of the stacked secondary battery.

[0045] In some embodiments, with reference to Figure 1 as shown, the method includes:

[0046] Step S10: Provide a stacked structure.

[0047] In this step, the provided stacked structure includes a first electrode 10, a first separator 30, and a second electrode 20 that are sequentially stacked.

[0048] In one embodiment, as Figure 3 shown, the first electrode 10 includes a first current collector 100 and a plurality of first active material layers 101 that are sequentially spaced along the length direction of the first current collector 100, and a first blank area 102 is formed between adjacent first active material layers 101.

[0049] In one embodiment, as Figure 4 shown, the second electrode 20 includes a second current collector 200 and a plurality of second active material layers 201 that are sequentially spaced along the length direction of the second current collector 200, and a second blank area 202 is formed between adjacent second active material layers 201.

[0050] In one embodiment, the first electrode 10 is a positive electrode tab, the first current collector 100 is a positive current collector, the first active material layer 101 is a positive active material layer, the second electrode 20 is a negative electrode tab, the second current collector 200 is a negative current collector, and the second active material layer is a negative active material layer.

[0051] In another embodiment, the first electrode 10 is a negative electrode tab, the first current collector 100 is a negative current collector, the first active material layer 101 is a negative active material layer, the second electrode 20 is a positive electrode tab, the second current collector 200 is a positive current collector, and the second active material layer is a positive active material layer.

[0052] In some embodiments, the positive active material layer includes a positive active material, and the positive active material includes at least one of a lithium nickel transition metal oxide and a phosphate.

[0053] In some embodiments, the lithium nickel transition metal oxide includes LiNi x Co y M (1-x-y) O2, where M includes at least one of manganese, iron, chromium, titanium, zinc, vanadium, aluminum, zirconium, cerium, magnesium, calcium, molybdenum, strontium, tungsten, copper, yttrium, lanthanum, gallium, silver, and niobium, 0.5 ≤ x ≤ 1, 0 ≤ y ≤ 0.5, and x + y ≤ 1.

[0054] In some embodiments, x is 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or any value therebetween. In some embodiments, y is 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or any value therebetween.

[0055] In some embodiments, the positive active material includes at least one of a lithium nickel oxide, a lithium nickel cobalt aluminum oxide, a lithium nickel cobalt manganese oxide, a lithium nickel manganese cobalt magnesium oxide, and a lithium nickel manganese oxide. In some embodiments, the positive active material includes at least one of NCA, NCM111, NCM523, NCM622, NCM811, Ni90, Ni92, and Ni95.

[0056] In some embodiments, the phosphate includes LiMn k B (1-k)At least one of PO4, where 0 ≤ k ≤ 1, and the B element includes at least one of iron, cobalt, magnesium, calcium, zinc, chromium, and lead. In some embodiments, k is 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or any value between them. In some embodiments, the phosphate includes at least one of lithium iron phosphate and lithium manganese iron phosphate. In some embodiments, the phosphate includes LiMn 0.6 Fe 0.4 PO4 and LiMn 0.8 Fe 0.2 At least one of PO4.

[0057] In some embodiments, the positive electrode active material layer further includes a binder and a conductive material. The binder improves the binding between the positive electrode active material particles and also improves the binding between the positive electrode active material and the current collector.

[0058] In some embodiments, the binder includes: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon, etc.

[0059] In some embodiments, the conductive material includes: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based materials include natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based materials include metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0060] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, aluminum foil can be used. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate.

[0061] In some embodiments, the negative electrode active material layer includes a negative electrode active material. In some embodiments, the negative electrode active material includes at least one of carbon-based materials, silicon-based materials, tin-based materials, phosphorus-based materials, and metallic lithium. In some embodiments, the negative electrode active material includes a silicon-based material, or a mixture of a silicon-based material and at least one material selected from carbon-based materials, tin-based materials, phosphorus-based materials, and metallic lithium.

[0062] In some embodiments, the silicon-based material includes at least one of silicon, silicon alloy, silicon oxide compound, and silicon carbide compound. In some embodiments, the carbon-based material includes at least one of natural graphite, artificial graphite, soft carbon, hard carbon, carbon nanotube, and graphene. In some embodiments, the tin-based material includes at least one of tin, tin oxide, and tin alloy. In some embodiments, the phosphorus-based material includes phosphorus and / or phosphorus complex.

[0063] In some embodiments, based on the mass of the negative electrode active material, the mass percentage z% of the silicon-based material satisfies: 10 ≤ z ≤ 100. In some embodiments, z is 10, 11, 13, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 or any value therebetween.

[0064] In some embodiments, the negative electrode active material layer further includes a binder and a conductive agent. In some embodiments, the binder includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon, etc.

[0065] In some embodiments, the conductive agent includes: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based materials include natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based materials include metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0066] In some embodiments, the negative electrode current collector includes: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal, or any combination thereof.

[0067] In a specific embodiment, the method for preparing the positive electrode sheet includes:

[0068] Dissolve the positive electrode active material LiNi 0.9 Co 0.05 Mn 0.05 O2, the conductive agent acetylene black and multi-walled carbon nanotubes, and the binder polyvinylidene fluoride (PVDF) in a weight ratio of 95:2:1:2 in the solvent N-methylpyrrolidone (NMP), and after fully homogenizing and mixing evenly, obtain the positive electrode slurry; coat the positive electrode slurry evenly on the positive electrode current collector aluminum foil according to the gap coating method, and then through baking, cold pressing, and laser tab die-cutting, obtain the positive electrode sheet.

[0069] In a specific embodiment, the method for preparing the negative electrode sheet includes:

[0070] Dissolve artificial graphite as the negative electrode active material, acetylene black as the conductive agent, polyacrylic acid (PAA), styrene-butadiene rubber (SBR) as the binder, and sodium carboxymethyl cellulose (CMC) in deionized water as the solvent according to a weight ratio of 95:0.5:1.5:2:1, and fully stir and mix evenly to obtain a negative electrode slurry; coat the negative electrode slurry on the negative electrode current collector copper foil with a gap, and then through baking, cold pressing, and laser tab die-cutting, obtain the negative electrode sheet.

[0071] In an embodiment, as Figure 5 and Figure 6 shown, the provided laminated structure further includes a second separator 40, wherein the second separator 40 is disposed on a side of the first electrode 10 away from the first separator 30, and / or, the second separator 40 is disposed on a side of the second electrode 20 away from the first separator 30. In a specific embodiment, the second separator 40 is disposed on a side of the first electrode 10 away from the first separator 30.

[0072] In this embodiment, as Figure 5 and Figure 6 shown, through the setting of the second separator 40, after laminating the first electrode 10, the second electrode 20, the first separator 30, and the second separator 40, there will be a first separator 30 or a second separator 40 between each adjacent first electrode 10 and second electrode 20, avoiding the contact between the first electrode 10 and the second electrode 20, and thus ensuring the insulation between the first electrode 10 and the second electrode 20.

[0073] Step S20: Wind the laminated structure along the length direction of the laminated structure.

[0074] In this step, after winding the laminated structure to obtain a wound battery cell, the first blank area 102 and the second blank area 202 will be located in two opposite corner regions 50 of the formed wound battery cell.

[0075] In an embodiment, as Figure 3 shown, along the winding direction of the laminated structure, the distance between adjacent first active material layers 101 on the first electrode 10 will gradually increase, that is, along the winding direction of the laminated structure, the length of the first blank area 102 will gradually increase.

[0076] In an embodiment, as Figure 4 shown, along the winding direction of the laminated structure, the distance between adjacent second active material layers 201 on the second electrode 20 will gradually increase, that is, along the winding direction of the laminated structure, the length of the second blank area 202 will gradually increase.

[0077] In this embodiment, along the winding direction of the stacked structure, by setting the lengths of the first blank area 102 and / or the second blank area 202 to gradually increase, after winding is completed, only the first blank area 102 and the second blank area 202 exist in the two opposite corner regions 50 of the obtained wound battery cell, and the first active material layer 101 and the second active material layer 201 do not exist, effectively reducing the manufacturing cost of the laminated secondary battery. It should be noted that after the first blank area 102 is wound, it forms a curved arc. Along the winding direction of the stacked structure, the length of the first blank area 102 is equal to the length of this curved arc. This curved arc divided by π gives the bending diameter corresponding to this curved arc, and this bending diameter is equal to the total thickness of the adjacent first active material layers 101 (the two first active material layers 101 adjacent to the above-mentioned first blank area 102) and the structure therebetween after winding. Similarly, the curved arc formed after the second blank area 202 is wound is divided by π to obtain the bending diameter, and this bending diameter is equal to the total thickness of the adjacent second active material layers 201 (the two second active material layers 201 adjacent to the above-mentioned second blank area 202) and the structure therebetween after winding.

[0078] In one embodiment, along the winding direction of the stacked structure, the length of the first blank area 102 is 1.2 mm to 50.8 mm. In one embodiment, along the winding direction of the stacked structure, the length of the first blank area 102 is 1.2 mm, 2 mm, 5 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 50.8 mm or any value therebetween.

[0079] In one embodiment, along the winding direction of the stacked structure, the length of the second blank area 202 is 1.2 mm to 50.8 mm. In one embodiment, along the winding direction of the stacked structure, the length of the second blank area 202 is 1.2 mm, 2 mm, 5 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 50.8 mm or any value therebetween.

[0080] In one embodiment, along the winding direction of the stacked structure, the length of the first active material layer 101 is the same as the length of the second active material layer 201.

[0081] In one embodiment, in the wound battery cell, the orthographic projection of the first active material layer 101 on the innermost first separator 30 is located within the orthographic projection area of the second active material layer 201 on the innermost first separator 30. In one embodiment, in the wound battery cell, the orthographic projection of the first active material layer 101 on the innermost first separator 30 coincides with the orthographic projection of the second active material layer 201 on the innermost first separator 30.

[0082] In this embodiment, by setting the length of the first active material layer 101 to be the same as the length of the second active material layer 201, or by making the projections of the first active material layer 101 and the second active material layer 201 coincide on the first separator 30 which is the innermost layer of the wound battery after winding, the situation of misalignment between the first active material layer 101 and the second active material layer 201 can be prevented, ensuring that the first active material layer 101 and the second active material layer 201 are precisely aligned after winding is completed.

[0083] In one embodiment, along the winding direction of the laminated structure, the length of the first active material layer 101 is 12 mm to 800 mm. In one embodiment, along the winding direction of the laminated structure, the length of the first active material layer 101 is 12 mm, 20 mm, 50 mm, 100 mm, 200 mm, 400 mm, 600 mm, 800 mm, or any value between them. In one embodiment, the thickness of the first active material layer is 80 μm to 300 μm. In one embodiment, the thickness of the first active material layer is 80 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, or any value between them.

[0084] In one embodiment, along the winding direction of the laminated structure, the length of the second active material layer 201 is 12 mm to 800 mm. In one embodiment, along the winding direction of the laminated structure, the length of the second active material layer 201 is 12 mm, 20 mm, 50 mm, 100 mm, 200 mm, 400 mm, 600 mm, 800 mm, or any value between them. In one embodiment, the thickness of the second active material layer is 80 μm to 300 μm. In one embodiment, the thickness of the second active material layer is 80 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, or any value between them.

[0085] In one embodiment, as Figure 5 and Figure 6 shown, the first electrode 10 includes a first single-sided region 11 with the first active material layer 101 disposed on one side and a first double-sided region 12 with the first active material layer 101 disposed on both sides, and the second electrode 20 includes a second single-sided region 21 with the second active material layer 201 disposed on one side and a second double-sided region 22 with the second active material layer 201 disposed on both sides. In one embodiment, the first single-sided region 11 is located at the end of the first active material layer 101. In one embodiment, the second single-sided region 21 is located at the end of the second active material layer 201. It should be noted that disposing the active material layer on one side means that the active material layer is disposed on one surface of the current collector, and disposing the active material layer on both sides means that the active material layer is disposed on both opposite surfaces of the current collector.

[0086] In this embodiment, the step of winding the stacked structure along the length direction of the stacked structure to form a wound battery cell includes:

[0087] After the first single-sided region 11 of the first electrode 10 and the first separator 30 are wound half a turn, the first double-sided region 12 of the first electrode 10, the second double-sided region 22 of the second electrode 20, and the first separator 30 are wound, and the winding is ended by the second single-sided region of the second electrode 20 and the first separator 30 to form a wound battery cell.

[0088] In a specific embodiment, the stacked structure further includes a second separator 40 disposed on a side of the first electrode 10 away from the first separator 30. In this embodiment, the step of winding the stacked structure along the length direction of the stacked structure to form a wound battery cell includes: after the first single-sided region 11 of the first electrode 10 and the first separator 30 and the second separator 40 are wound half a turn, the first double-sided region 12 of the first electrode 10, the second double-sided region 22 of the second electrode 20, the first separator 30, and the second separator 40 are wound, and the winding is ended by the second single-sided region of the second electrode 20 and the first separator 30 to form a wound battery cell.

[0089] Step S30: Cut off and remove two opposite corner regions 50 of the wound battery cell.

[0090] After the stacked structure is wound through step S20, a wound battery cell will be formed. The cross-section of the wound battery cell is similar to a racetrack structure, and two corner regions 50 will be formed at two opposite ends of the wound battery cell.

[0091] In this step, as Figure 5 and Figure 6 shown, two opposite corner regions 50 of the wound battery cell will be cut off and removed. After the corner regions 50 are cut off and removed, the remaining part is a laminated battery cell, and a laminated secondary battery can be obtained after subsequent processing of the laminated battery cell.

[0092] In order to prevent the first current collector 100 and the second current collector 200 from coming into contact with each other when cutting the corner regions 50 of the wound battery cell, resulting in a short circuit, an insulating layer will be formed by coating on the first blank region 102 of the first electrode 10 and / or the second blank region 202 of the second electrode 20.

[0093] In one embodiment, an insulating layer is provided in the first blank region 102 of the first electrode 10. Then, the steps of forming the first electrode 10 are as follows: First, a first active material layer 101 is sequentially and spacedly coated on the first current collector 100, and the first blank region 102 is between adjacent first active material layers 101. Then, an insulating layer is sequentially coated in the first blank region 102. Alternatively, the first active material layer 101 and the insulating layer are alternately coated on the first current collector 100.

[0094] In one embodiment, an insulating layer is formed on the second blank area 202 of the second electrode 20. Then, the steps of forming the second electrode 20 are as follows: First, a second active material layer 201 is sequentially and spacedly coated on the second current collector 200, and the second blank area 202 is between adjacent second active material layers 201, and then an insulating layer is sequentially coated on the second blank area 202. Alternatively, the second active material layer 201 and the insulating layer are alternately coated on the second current collector 200 to form them.

[0095] In one embodiment, insulating layers are formed on both the first blank area 102 of the first electrode 10 and the second blank area 202 of the second electrode 20. The methods of forming the first electrode 10 and the second electrode 20 have been described in the above embodiments and will not be elaborated here.

[0096] In one embodiment, the insulating layer includes ceramic particles, a stabilizer, and a binder. Among them, the ceramic particles include at least one of alumina, boehmite, silica, and aluminum hydroxide, the stabilizer includes at least one of gelatin, methyl cellulose, carboxymethyl cellulose, sodium polyacrylate, polyethylene oxide, and polyvinyl alcohol, and the binder includes at least one of acrylic acid, styrene-butadiene rubber, polystyrene, and polyacrylate. Based on the mass of the insulating layer, the weight percentage of the ceramic particles is 45% - 65%, the weight percentage of the stabilizer is 15% - 20%, and the weight percentage of the binder is 10% - 40%. Based on the mass of the insulating layer, the weight percentage of the ceramic particles is 45%, 48%, 50%, 55%, 60%, 65% or any value between them, the weight percentage of the stabilizer is 15%, 16%, 17%, 18%, 19%, 20% or any value between them, and the weight percentage of the binder is 10%, 15%, 20%, 25%, 30%, 35%, 40% or any value between them.

[0097] In a specific embodiment, the insulating layer includes alumina as the ceramic particles, carboxymethyl cellulose as the stabilizer, and polyacrylate as the binder. In the insulating layer, the weight percentage of the ceramic particles is 48%, the weight percentage of the stabilizer is 18%, and the weight percentage of the binder is 34%.

[0098] In one embodiment, the thickness of the insulating layer is 1 - 5 microns. In one embodiment, the thickness of the insulating layer is 1 micron, 2 microns, 3 microns, 4 microns, 5 microns or any value between them. In one embodiment, the thickness of the insulating layer is 2 microns.

[0099] In one embodiment, the preparation method of the secondary battery further includes:

[0100] Step S40: Weld the tabs of the first electrode 10 and the tabs of the second electrode 20 respectively.

[0101] In this step, after cutting the two corner regions 50 of the wound electric core, the tabs of the first electrode 10 and the tabs of the second electrode 20 are welded respectively by ultrasonic welding, and a stacked electric core is obtained after the welding is completed.

[0102] Step S50: Post-process the stacked electric core.

[0103] In this step, after post-processing such as baking, packaging, injecting electrolyte, forming, degassing, and measuring the capacity of the stacked electric core, a final stacked secondary battery is obtained.

[0104] In a pair of ratios, taking the production speed of preparing a 75 Ah stacked electric core as an example, the stacking speed of the Z-type stacking process is 2 PPM (Pages Per Minute), while the stacking speed of the method for preparing the secondary battery of the present invention is 6 PPM. Compared with the Z-type stacking process, the stacking speed of the method for preparing the secondary battery of the present invention is increased by 300%.

[0105] The embodiment of the present invention also provides a secondary battery, which is prepared by the above method for preparing a secondary battery. Thus, the secondary battery has all the features and advantages of the method described above, and will not be elaborated here.

[0106] The method for preparing the secondary battery of the present invention introduces the method for preparing a wound battery into the production process of a stacked secondary battery, greatly improving the production speed of the stacked secondary battery. Compared with the Z-type stacking process, the method of the present invention only needs to control the alignment of the positive and negative electrode plates in the width direction of the electrode plate, reducing the requirement for controlling the misalignment of the electrode plates and the cost of misalignment control.

[0107] The above is only a preferred embodiment of the present invention, and does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to make equivalent embodiments with equivalent changes. However, as long as it does not depart from the technical content of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a secondary battery, characterized in that, Comprising: Providing a stacked structure, the stacked structure including a first electrode, a first separator, and a second electrode which are sequentially stacked. The first electrode includes a first current collector and a plurality of first active material layers sequentially arranged at intervals along the length direction of the first current collector. A first blank area is between adjacent first active material layers. The second electrode includes a second current collector and a plurality of second active material layers sequentially arranged at intervals along the length direction of the second current collector. A second blank area is between adjacent second active material layers; Winding the stacked structure along the length direction of the stacked structure to form a wound battery cell, where the first blank area and the second blank area are located in two opposite corner areas of the wound battery cell; Cutting and removing two opposite corner areas of the wound battery cell to obtain the secondary battery.

2. The method for preparing a secondary battery according to claim 1, characterized in that, Along the winding direction of the stacked structure, the distance between adjacent first active material layers gradually increases; and / or Along the winding direction of the stacked structure, the distance between adjacent second active material layers gradually increases; and / or Along the winding direction of the stacked structure, the length of the first active material layer is the same as the length of the second active material layer; and / or In the wound battery cell, the orthographic projection of the first active material layer on the innermost first separator is within the orthographic projection area of the second active material layer on the innermost first separator.

3. The method for preparing a secondary battery according to claim 1 or 2, characterized in that, In the wound battery cell, the orthographic projection of the first active material on the innermost first separator coincides with the orthographic projection of the second active material layer on the innermost first separator; and / or Along the winding direction of the stacked structure, the length of the first active material layer is 12 mm to 800 mm; and / or Along the winding direction of the stacked structure, the length of the second active material layer is 12 mm to 800 mm; and / or Along the winding direction of the stacked structure, the length of the first blank area is 1.2 mm to 50.8 mm; and / or Along the winding direction of the stacked structure, the length of the second blank area is 1.2 mm to 50.8 mm; and / or The thickness of the first active material layer is 80 μm to 300 μm; and / or The thickness of the second active material layer is 80 μm to 300 μm.

4. The method for preparing a secondary battery according to claim 1, characterized in that, An insulating layer is provided on the first blank area. The first electrode is formed by the following steps: sequentially and intermittently coating on the first current collector to form the first active material layers, with the first blank area between adjacent first active material layers, and sequentially coating on the first blank area to form the insulating layer; or, sequentially and alternately coating on the first current collector to form the first active material layers and the insulating layer; and / or An insulating layer is provided on the second blank area, and the second electrode is formed through the following steps: sequentially and spacedly coating on the second current collector to form the second active material layer, with the second blank area between adjacent second active material layers, and sequentially coating on the second blank area to form the insulating layer; alternatively, sequentially and alternately coating on the second current collector to form the second active material layer and the insulating layer.

5. The method for preparing a secondary battery according to claim 4, characterized in that, The insulating layer includes ceramic particles, a stabilizer, and a binder; wherein, the ceramic particles include at least one of alumina, boehmite, silica, and aluminum hydroxide, the stabilizer includes at least one of gelatin, methyl cellulose, carboxymethyl cellulose, sodium polyacrylate, polyethylene oxide, and polyvinyl alcohol, and the binder includes at least one of acrylic acid, styrene-butadiene rubber, polystyrene, and polyacrylate; Based on the mass of the insulating layer, the weight percentage of the ceramic particles is 45% - 65%, the weight percentage of the stabilizer is 15% - 20%, and the weight percentage of the binder is 10% - 40%.

6. The method for preparing a secondary battery according to claim 1, characterized in that, The laminated structure further includes a second separator, and the second separator is disposed on a side of the first electrode away from the first separator, and / or, the second separator is disposed on a side of the second electrode away from the first separator.

7. The method for preparing a secondary battery according to claim 1 or 6, characterized in that, The first electrode includes a first single-sided area with the first active material layer disposed on one side and a first double-sided area with the first active material layer disposed on both sides, and the second electrode includes a second single-sided area with the second active material layer disposed on one side and a second double-sided area with the second active material layer disposed on both sides; The step of winding the laminated structure along the length direction of the laminated structure to form a wound battery cell includes: After winding half a turn of the first single-sided area of the first electrode and the first separator, winding the first double-sided area of the first electrode, the second double-sided area of the second electrode, and the first separator, and finishing by winding the second single-sided area of the second electrode and the first separator to form the wound battery cell.

8. The method for preparing a secondary battery according to claim 1, characterized in that, After the step of cutting two opposite corner areas of the wound battery cell, the following steps are further included: Welding the electrode tab of the first electrode and the electrode tab of the second electrode respectively to obtain a stacked battery cell; Performing post-treatment on the stacked battery cell to obtain the secondary battery.

9. The method for preparing a secondary battery according to claim 1, characterized in that, The first electrode is one of a positive electrode plate and a negative electrode plate, and the second electrode is the other of the positive electrode plate and the negative electrode plate.

10. A secondary battery, characterized in that,The secondary battery is prepared by the preparation method of the secondary battery according to any one of claims 1 - 9.

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