Secondary battery and method for manufacturing the same

Abstract

The invention relates to a secondary battery and a preparation method thereof. The preparation method of the secondary battery comprises the following steps: coating a first surface of a first current collector with first target slurry; drying the first target slurry on the first surface of the first current collector; coating the second surface of the first current collector with first target slurry to obtain a first electrode; the first surface and the second surface, deviating from each other, of a second current collector are both coated with second target slurry; drying the second target slurry on the first surface and the second surface of the second current collector to obtain a second electrode; and adhering the second surface of the second electrode into the first target slurry on the second surface of the first current collector by adopting a hot-pressing process to realize hot-pressing combination of the first electrode and the second electrode. Wherein the first electrode and the second electrode have the same polarity. The quality of the thick electrode can be improved, and meanwhile, the dynamic performance of the battery is improved, so that the capacity of the battery is further improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a secondary battery and a preparation method thereof. Background Art

[0002] Driven by the market, the mileage of lithium-ion battery vehicles is getting higher and higher, and the energy storage containers are getting bigger and bigger.

[0003] In the limited shell space, increasing the capacity of the battery lies in increasing the proportion of active materials. Increasing the thickness of the electrode and reducing the number of winding layers of the electrode can reduce the space occupied by the separator, thereby achieving the purpose of increasing the proportion of active materials. However, thick electrodes prepared by traditional preparation processes often have various problems.

[0004] Therefore, how to improve the quality of thick electrodes and at the same time improve the kinetic performance of the battery, thereby further increasing the capacity of the battery, is an urgent problem to be solved. Summary of the invention

[0005] Based on this, the embodiments of the present application provide a secondary battery and a method for preparing the same, which can improve the quality of thick electrodes while improving the dynamic performance of the battery, thereby further improving the capacity of the battery.

[0006] In some embodiments of the present application, the present application provides a method for preparing a secondary battery, comprising:

[0007] Coating a first target slurry on a first surface of a first current collector;

[0008] Drying the first target slurry on the first surface of the first current collector;

[0009] Coating a first target slurry on the second surface of the first current collector to obtain a first electrode;

[0010] Coating the second target slurry on the first surface and the second surface of the second current collector which are opposite to each other;

[0011] Drying the second target slurry on the first surface and the second surface of the second current collector to obtain a second electrode;

[0012] The second surface of the second electrode is adhered to the first target slurry on the second surface of the first current collector by a hot pressing process, so as to realize hot pressing bonding of the first electrode and the second electrode, wherein the first electrode and the second electrode have the same polarity.

[0013] In some embodiments of the present application, drying the first target slurry on the first surface of the first current collector includes: performing a first heat treatment process on the first target slurry on the first surface of the first current collector until the dryness of the first target slurry on the first surface of the first current collector reaches a first preset value. Wherein the process temperature of the first heat treatment process is: 70°C-130°C.

[0014] In some embodiments of the present application, coating the first target slurry on the second surface of the first current collector to obtain the first electrode includes:

[0015] coating a first target slurry on the second surface of the first current collector;

[0016] The first target slurry on the second surface of the first current collector is subjected to a second heat treatment process until the dryness of the first target slurry on the second surface of the first current collector reaches a second preset value, thereby obtaining a first electrode. The second preset value is less than the first preset value. The process temperature of the second heat treatment process is 70°C-130°C.

[0017] In some embodiments of the present application, drying the second target slurry on the first surface and the second surface of the second current collector includes: performing a third heat treatment process on the first surface of the second current collector that is opposite to each other and the second target slurry on the second surface, until the dryness of the first surface of the second current collector that is opposite to each other and the second target slurry on the second surface reach a third preset value, thereby obtaining a second electrode. The third preset value is greater than the second preset value; and the process temperature of the third heat treatment process is 70°C-130°C.

[0018] In some embodiments of the present application, the second surface of the second electrode is adhered to the first target slurry on the second surface of the first current collector by a hot pressing process, and the hot pressing bonding of the first electrode and the second electrode includes:

[0019] Pressing the first surface or the second surface of the second electrode into the first target slurry on the second surface of the first current collector by a roll pressing process;

[0020] The first target slurry on the second surface of the first current collector is subjected to a fourth heat treatment process until the dryness of the first target slurry on the second surface of the first current collector reaches a first preset value. The process temperature of the fourth heat treatment process is 70°C-130°C.

[0021] In some embodiments of the present application, the present application further provides a secondary battery, comprising: at least two layers of electrodes stacked in sequence along the thickness direction. The electrode comprises a current collector and a target slurry disposed on two surfaces of the current collector that are opposite to each other. Among them, the electrodes are all of the same polarity. The current collector comprises a microporous foil; the target slurry comprises at least a positive electrode active material or a negative electrode active material, a conductive agent and a binder.

[0022] In some embodiments of the present application, if the electrodes are all positive electrodes, the microporous foil material includes microporous aluminum foil. If the electrodes are all negative electrodes, the microporous foil material includes microporous copper foil.

[0023] In some embodiments of the present application, the thickness of the microporous aluminum foil is 10µm-25µm, and the thickness of the microporous copper foil is 2µm-20µm.

[0024] In some embodiments of the present application, the diameter of the micropores of the microporous foil is 0.2 mm to 0.8 mm, and the distance between any two adjacent micropores is 0.3 mm to 1 mm.

[0025] In some embodiments of the present application, the porosity of the microporous foil is greater than or equal to 15%.

[0026] In some embodiments of the present application, the target slurry thickness between two adjacent current collectors is 70 μm-200 μm. The target slurry thickness on two surfaces of the electrode sheet facing away from each other is 70 μm-200 μm.

[0027] In some embodiments of the present application, the present application further provides a secondary battery, including: a positive electrode, a negative electrode, a separator, an electrolyte, and a packaging structure that encapsulates the positive electrode, the negative electrode, the separator, and the electrolyte. The separator is arranged between the positive electrode and the negative electrode. The electrolyte is arranged between the separator and the positive electrode and the negative electrode. Among them, the positive electrode and the negative electrode are both the electrodes described in the above embodiments, or the electrodes prepared by the preparation method described in the above embodiments.

[0028] In some embodiments of the present application, the thickness of the positive electrode is: 70µm~200µm, and the number of layers of the positive electrode does not exceed 4. The thickness of the negative electrode is: 70µm~200µm, and the number of layers of the negative electrode does not exceed 4. Among them, the thickness of the positive electrode is negatively correlated with the number of layers of the positive electrode. The thickness of the negative electrode is negatively correlated with the number of layers of the negative electrode.

[0029] The secondary battery and the preparation method thereof provided in the present application may have / at least have the following advantages:

[0030] In the embodiment of the present application, after drying the first target slurry coated on the first surface of the first current collector, the first target slurry is then coated on the second surface of the first current collector, and the first target slurry on the second surface is not completely dried, that is, a first electrode with a completely dried first surface and an incompletely dried second surface is obtained. And, the second current collector with the second target slurry coated on both the first and second surfaces is dried to obtain a second electrode. Finally, the second surface of the second electrode is pressed into the incompletely dried first target slurry on the second surface of the first electrode, and then continued to dry, so that the second surface of the second electrode is physically bonded to the second surface of the first electrode, and the first electrode and the second electrode are hot-pressed. In this way, compared with the traditional preparation method of thick electrodes, the embodiment of the present application combines the coating process and the rolling process in the traditional preparation method into one process, making full use of the drying equipment in the coating process to control the drying state of the electrode, while reducing the floor space occupied by the rolling process, realizing the hot-pressing combination of the two electrodes, and solving the problems of cracking and poor adhesion of the traditional thick electrode.

[0031] In addition, in the embodiments of the present application, microporous foil is used instead of traditional foil, and the diffusion path of ions can be converted into three-dimensional all-round penetration through the micropores, thereby solving the problem of difficult ion diffusion in multi-layer electrodes and improving the kinetic efficiency of the battery.

[0032] Furthermore, compared with the dry process which has not yet been commercially applied, the wet process used in the embodiment of the present application has a better bonding effect and better uniformity of the target slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 A schematic diagram of a process for preparing a secondary battery provided in some embodiments of the present application;

[0035] Figure 2 A schematic flow chart of step S300 in a method for preparing a secondary battery provided in some embodiments of the present application;

[0036] Figure 3 A schematic flow chart of step S600 in a method for preparing a secondary battery provided in some embodiments of the present application;

[0037] Figure 4 A schematic diagram of a method for preparing a secondary battery provided in some embodiments of the present application;

[0038] Figure 5 A schematic structural diagram of a microporous foil in a method for preparing a secondary battery provided in some embodiments of the present application;

[0039] Figure 6 A schematic cross-sectional view of a structure obtained in step S620 in a method for preparing a secondary battery provided in some embodiments of the present application; and Figure 6 It is also a cross-sectional schematic diagram of a secondary battery provided by an embodiment.

[0040] Description of reference numerals:

[0041] 100 - microporous foil; 101 - micropores; 200 - active material; 11 - first electrode; 12 - second electrode; 2 - electrode drive roller; 31 - upper pressing roller; 32 - lower pressing roller. DETAILED DESCRIPTION

[0042] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0044] It should be understood that although the terms first and second can be used to describe various elements, components, regions, layers, collector structures and / or parts, these elements, components, regions, layers, collector structures and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, collector structure or part from another element, component, region, layer, collector structure or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer, collector structure or part discussed below can be represented as a second element, component, region, layer or part; for example, the first collector structure can be referred to as the second collector structure, and similarly, the second collector structure can be referred to as the first collector structure; the first collector structure and the second collector structure are different collector structures. It should be understood that in addition to the orientation shown in the figure, the spatial relationship terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as "below other elements" or "below" or "below" will be oriented as "on" other elements or features. Thus, the exemplary terms "below" and "beneath" can encompass both an orientation of above and below. Furthermore, the device can be included in alternative orientations (eg, rotated 90 degrees or at other orientations) and the spatial descriptors used herein interpreted accordingly.

[0045] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that when the terms "consisting of" and / or "comprising" are used in this specification, the presence of the features, integers, steps, operations, elements and / or parts can be determined, but the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups is not excluded. At the same time, when used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0046] Driven by the market, the mileage of lithium-ion battery vehicles is getting higher and higher, and the energy storage containers are getting bigger and bigger.

[0047] In the limited shell space, increasing the capacity of the battery lies in increasing the proportion of active materials. Increasing the thickness of the electrode and reducing the number of winding layers of the electrode can reduce the space occupied by the diaphragm, thereby achieving the purpose of increasing the proportion of active materials. However, thick electrodes prepared by traditional preparation processes often have various problems. For example: during the coating process of the pole piece, the solvent evaporates inconsistently after baking, causing the pole piece to dry and crack easily, resulting in defects in the battery cell interface, which affects the further thickness of the electrode. Furthermore, the adhesion of the active material deteriorates, and it is easy to drop the material during processing, and the active material is also easy to fall off during the cycle of the battery cell. In addition, as the electrode becomes thicker, the distance of electron transmission and ion transmission becomes longer, and the battery kinetic performance deteriorates. Therefore, how to improve the quality of thick electrodes and at the same time improve the kinetic performance of the battery, thereby further increasing the capacity of the battery, is an urgent problem to be solved.

[0048] Based on this, the present application provides a secondary battery and a preparation method thereof, which can improve the quality of thick electrodes and at the same time improve the dynamic performance of the battery, thereby further improving the capacity of the battery.

[0049] See also Figure 1 , the present application provides a method for preparing a secondary battery, comprising steps S100 to S600.

[0050] S100, coating a first target slurry on a first surface of a first current collector.

[0051] S200, drying the first target slurry on the first surface of the first current collector.

[0052] S300, coating a first target slurry on a second surface of a first current collector to obtain a first electrode.

[0053] S400 , coating a second target slurry on a first surface and a second surface of a second current collector that are opposite to each other.

[0054] S500, drying the second target slurry on the first surface and the second surface of the second current collector to obtain a second electrode.

[0055] S600, using a hot pressing process to adhere the second surface of the second electrode to the first target slurry on the second surface of the first current collector, thereby achieving hot pressing bonding of the first electrode and the second electrode, wherein the first electrode and the second electrode have the same polarity.

[0056] In the embodiment of the present application, after drying the first target slurry coated on the first surface of the first current collector, the first target slurry is then coated on the second surface of the first current collector, and the first target slurry on the second surface is not completely dried, that is, a first electrode with a completely dried first surface and an incompletely dried second surface is obtained. And, the second current collector coated with the second target slurry on both the first surface and the second surface is dried to obtain a second electrode. Finally, the second surface of the second electrode is pressed into the incompletely dried first target slurry on the second surface of the first electrode, and then continued to dry, so that the second surface of the second electrode is physically bonded to the second surface of the first electrode, and the first electrode and the second electrode are hot-pressed. In this way, compared with the traditional preparation method of thick electrodes, the embodiment of the present application combines the coating process and the rolling process in the traditional preparation method into one process, fully utilizing the drying equipment in the coating process to control the drying state of the electrode, while reducing the floor space of the rolling process, realizing the hot-pressing combination of the two electrodes, and solving the problems of cracking and poor adhesion of the traditional thick electrode. In addition, compared with the dry process that has not yet been commercialized, the embodiment of the present application uses a wet process with better bonding effect and better uniformity of the target slurry.

[0057] In some embodiments, step S200 of drying the first target slurry on the first surface of the first current collector includes: performing a first heat treatment process on the first target slurry on the first surface of the first current collector until the dryness of the first target slurry on the first surface of the first current collector reaches a first preset value. The process temperature of the first heat treatment process is: 70°C-130°C.

[0058] In some embodiments, see Figure 2 , step S300 is to coat the first target slurry on the second surface of the first current collector, and obtaining the first electrode includes steps S310~S320.

[0059] S310, coating a first target slurry on a second surface of the first current collector.

[0060] S320, performing a second heat treatment process on the first target slurry on the second surface of the first current collector until the dryness of the first target slurry on the second surface of the first current collector reaches a second preset value, thereby obtaining a first electrode.

[0061] The second preset value is smaller than the first preset value. The process temperature of the second heat treatment process is 70°C-130°C.

[0062] In some embodiments, step S500 of drying the second target slurry on the first surface and the second surface of the second current collector includes: performing a third heat treatment process on the first surface of the second current collector that is opposite to each other and the second target slurry on the second surface, until the dryness of the first surface of the second current collector that is opposite to each other and the second target slurry on the second surface reach a third preset value, thereby obtaining a second electrode. The third preset value is greater than the second preset value; and the process temperature of the third heat treatment process is 70°C-130°C.

[0063] In some embodiments, see Figure 3 Step S600 uses a hot pressing process to adhere the first surface or the second surface of the second electrode to the first target slurry on the second surface of the first current collector, and the hot pressing bonding of the first electrode and the second electrode includes steps S610~S620.

[0064] S610, using a roll pressing process to press the first surface or the second surface of the second electrode into the first target slurry on the second surface of the first current collector.

[0065] S620, performing a fourth heat treatment process on the first target slurry on the second surface of the first current collector until the dryness of the first target slurry on the second surface of the first current collector reaches a first preset value.

[0066] Among them, the process temperature of the fourth heat treatment process is: 70℃-130℃.

[0067] It should be noted that, in the above-mentioned embodiments, the execution of each step in the method is not strictly limited in order, and these steps may not necessarily be executed in the order described, but may be executed in other ways. Moreover, at least a part of any step may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but may be executed at different times, and the execution order of these sub-steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least a part of the sub-steps or stages of other steps. The method is limited to being able to realize the preparation of the corresponding memory.

[0068] In order to more clearly illustrate the method for preparing the semiconductor structure provided by the above embodiment, Figure 1 to Figure 6 The preparation method is described in detail.

[0069] In step S100, refer to Figure 4~Figure 6 , coating the first target slurry on the first surface of the first current collector.

[0070] In some embodiments, see Figure 5 and Figure 6The first current collector includes a microporous foil 100 . The first target slurry includes an active material 200 .

[0071] Accordingly, see for example Figure 4 , Figure 5 and Figure 6 The microporous foil 100 enters the coating area through the electrode driving roller 2 , and the first surface (eg, surface A) of the microporous foil 100 is coated with the active material 200 .

[0072] In the embodiment of the present application, microporous foil 100 is used instead of traditional foil, and the diffusion path of ions can be converted into three-dimensional all-round penetration through micropores 101, which solves the problem of difficult ion diffusion in multi-layer electrodes and improves the kinetic efficiency of the battery.

[0073] In some embodiments, if the electrodes are positive electrodes, the microporous foil 100 comprises a microporous aluminum foil. If the electrodes are negative electrodes, the microporous foil 100 comprises a microporous copper foil.

[0074] Further, for example, the thickness of the microporous aluminum foil is: 10µm-25µm.

[0075] For example, the thickness of the microporous aluminum foil is: 10µm-12µm, 12µm-14µm, 14µm-16µm, 16µm-18µm, 18µm-20µm, 20µm-22µm, 22µm-24µm or 24µm-25µm. For example, the thickness of the microporous aluminum foil can be: 10µm, 15µm, 20µm or 25µm, etc. The thickness of the microporous copper foil is: 2µm-20µm. For example, the thickness of the microporous copper foil can be: 2µm, 8µm, 12µm, 16µm or 20µm, etc.

[0076] In some embodiments, the micropore diameter of the microporous foil 100 is 0.2 mm-0.8 mm.

[0077] For example, the micropore diameter of the microporous foil 100 is 0.2 mm-0.35 mm, 0.35 mm-0.5 mm, 0.5 mm-0.65 mm or 0.65 mm-0.9 mm. For example, the micropore diameter of the microporous foil 100 can be 0.2 mm, 0.4 mm, 0.6 mm or 0.8 mm, etc.

[0078] In some embodiments, the distance between any two adjacent microholes 101 is 0.3 mm-1 mm.

[0079] For example, the distance between any two adjacent different microholes 101 is 0.3mm-0.45mm, 0.45mm-0.6mm, 0.6mm-0.75mm, 0.75mm-0.9mm or 0.9mm-1mm, etc. For example, the distance between any two adjacent different microholes 101 can be 0.3mm, 0.5mm, 0.7mm or 1mm, etc.

[0080] In some embodiments, the porosity of the microporous foil 100 is greater than or equal to 15%. For example, the porosity of the microporous foil 100 can be 15%, 20%, 25% or 30%, etc.

[0081] In step S200, refer to Figure 4~Figure 6 , a first heat treatment process is performed on the first target slurry on the first surface of the first current collector until the dryness of the first target slurry on the first surface of the first current collector reaches a first preset value. The process temperature of the first heat treatment process is: 70°C-130°C. Here, the process time of the first heat treatment process is adjusted according to the required dryness.

[0082] Illustratively, the first heat treatment process may employ an oven.

[0083] In some examples, if the first electrode is a positive electrode, the process temperature of the first heat treatment process is: 80°C-130°C. For example, the process temperature of the first heat treatment process is: 80°C-90°C, 90°C-100°C, 100°C-110°C, 110°C-120°C or 120°C-130°C. For example: the process temperature of the first heat treatment process is: 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, etc.

[0084] In some examples, if the first electrode is a negative electrode, the process temperature of the first heat treatment process is: 70°C-120°C. For example, the process temperature of the first heat treatment process is: 70°C-80°C, 80°C-90°C, 90°C-100°C, 100°C-110°C or 110°C-120°C. For example: the process temperature of the first heat treatment process is: 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, etc.

[0085] For example, see Figure 4 Under the action of the oven heat in the coating area, the first surface (eg, surface A) of the active material 200 is dried.

[0086] In step S310, refer to Figure 4~Figure 6 , coating the first target slurry on the second surface of the first current collector.

[0087] For example, see Figure 4 After the first surface (such as surface A) is dried, the second surface (such as surface B) is coated.

[0088] In step S320, refer to Figure 4~Figure 6 , a second heat treatment process is performed on the first target slurry on the second surface of the first current collector until the dryness of the first target slurry on the second surface of the first current collector reaches a second preset value, thereby obtaining a first electrode. The second preset value is less than the first preset value. The process temperature of the second heat treatment process is 70°C-130°C. Here, the process time of the second heat treatment process is adjusted according to the required dryness.

[0089] Illustratively, the second heat treatment process may employ an oven.

[0090] In some examples, if the first electrode is a positive electrode, the process temperature of the second heat treatment process is: 80°C-130°C. For example, the process temperature of the second heat treatment process is: 80°C-90°C, 90°C-100°C, 100°C-110°C, 110°C-120°C or 120°C-130°C. For example: the process temperature of the second heat treatment process is: 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, etc.

[0091] In some examples, if the second electrode is a negative electrode, the process temperature of the second heat treatment process is: 70°C-120°C. For example, the process temperature of the second heat treatment process is: 70°C-80°C, 80°C-90°C, 90°C-100°C, 100°C-110°C or 110°C-120°C. For example: the process temperature of the second heat treatment process is: 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, etc.

[0092] For example, see Figure 4 After the first surface (eg, surface A) is dried, the second surface (eg, surface B) is coated. The active material on surface B is not completely dried, and the first electrode 11 is obtained.

[0093] In step S400, refer to Figure 4~Figure 6 , the second target slurry is coated on the first surface and the second surface of the second current collector which are opposite to each other.

[0094] In some embodiments, see Figure 5 and Figure 6 The second current collector includes a microporous foil 100 . The second target slurry includes an active material 200 .

[0095] In step S500, refer to Figure 4~Figure 6 , the first surface of the second current collector facing away from each other and the second target slurry on the second surface are both subjected to a third heat treatment process until the dryness of the first surface of the second current collector facing away from each other and the second target slurry on the second surface both reach a third preset value, thereby obtaining a second electrode 12. The third preset value is greater than the second preset value; the process temperature of the third heat treatment process is: 70°C-130°C. Here, the process time of the third heat treatment process is adjusted according to the required dryness.

[0096] Illustratively, the third heat treatment process may employ an oven.

[0097] In some examples, if the first electrode is a positive electrode, the process temperature of the third heat treatment process is: 80°C-130°C. For example, the process temperature of the third heat treatment process is: 80°C-90°C, 90°C-100°C, 100°C-110°C, 110°C-120°C or 120°C-130°C. For example: the process temperature of the third heat treatment process is: 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, etc.

[0098] In some examples, if the second electrode is a negative electrode, the process temperature of the third heat treatment process is: 70°C-120°C. For example, the process temperature of the third heat treatment process is: 70°C-80°C, 80°C-90°C, 90°C-100°C, 100°C-110°C or 110°C-120°C. For example: the process temperature of the third heat treatment process is: 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, etc.

[0099] It should be particularly noted that the first electrode 11 and the second electrode 12 have the same polarity.

[0100] In step S610, refer to Figure 4~Figure 6 The second surface of the second electrode 12 is pressed into the first target slurry on the second surface of the first current collector by a roll pressing process.

[0101] In some embodiments, the second electrode 12 whose first surface and second surface are completely dried and the first electrode 11 whose second surface (e.g., surface B) is not completely dried are rolled together, and the second electrode 12 is pressed into the active material that is not completely dried on the second surface (e.g., surface B) of the first electrode 11 through the pressure of the upper pressing roller 31 and the lower pressing roller 32.

[0102] In step S620, refer to Figure 4~Figure 6, performing a fourth heat treatment process on the first target slurry on the second surface of the first current collector until the dryness of the first target slurry on the second surface of the first current collector reaches a first preset value.

[0103] The process temperature of the fourth heat treatment process is 70° C.-130° C. Here, the process time of the fourth heat treatment process is adjusted according to the required dryness.

[0104] Illustratively, the fourth heat treatment process may employ an oven.

[0105] In some examples, if the first electrode is a positive electrode, the process temperature of the fourth heat treatment process is: 80°C-130°C. For example, the process temperature of the fourth heat treatment process is: 80°C-90°C, 90°C-100°C, 100°C-110°C, 110°C-120°C or 120°C-130°C. For example: the process temperature of the fourth heat treatment process is: 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, etc.

[0106] In some examples, if the second electrode is a negative electrode, the process temperature of the fourth heat treatment process is: 70°C-120°C. For example, the process temperature of the fourth heat treatment process is: 70°C-80°C, 80°C-90°C, 90°C-100°C, 100°C-110°C or 110°C-120°C. For example: the process temperature of the fourth heat treatment process is: 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, etc.

[0107] In some embodiments, after continuing to be exposed to the heat of the oven, the second electrode 12 and the second surface (eg, surface B) of the first electrode 11 are physically bonded to achieve thermal compression bonding of the first electrode 11 and the second electrode 12 .

[0108] In some embodiments of this application, please refer to Figure 6 In one aspect, the present application also provides a secondary battery, comprising: at least two layers of electrodes stacked in sequence along the thickness direction. The electrode comprises a current collector and a target slurry disposed on two surfaces of the current collector that are opposite to each other. The electrodes are all of the same polarity. The current collector comprises a microporous foil 100; the target slurry comprises at least a positive electrode active material or a negative electrode active material, a conductive agent and a binder.

[0109] In the embodiment of the present application, microporous foil 100 is used instead of traditional foil, and the diffusion path of ions can be converted into three-dimensional all-round penetration through micropores 101, which solves the problem of difficult ion diffusion in multi-layer electrodes and improves the kinetic efficiency of the battery.

[0110] In some embodiments, if the electrodes are positive electrodes, the microporous foil 100 comprises a microporous aluminum foil. If the electrodes are negative electrodes, the microporous foil 100 comprises a microporous copper foil.

[0111] Further, for example, the thickness of the microporous aluminum foil is: 10µm-25µm. For example, the thickness of the microporous aluminum foil is: 10µm-12µm, 12µm-14µm, 14µm-16µm, 16µm-18µm, 18µm-20µm, 20µm-22µm, 22µm-24µm or 24µm-25µm. For example, the thickness of the microporous aluminum foil can be: 10µm, 15µm, 20µm or 25µm, etc. The thickness of the microporous copper foil is: 2µm-20µm. For example, the thickness of the microporous copper foil can be: 2µm, 8µm, 12µm, 16µm or 20µm, etc.

[0112] In some embodiments, the micropore diameter of the microporous foil 100 is: 0.2mm-0.8mm. For example, the micropore diameter of the microporous foil 100 is: 0.2mm-0.35mm, 0.35mm-0.5mm, 0.5mm-0.65mm or 0.65mm-0.9mm. For example: the micropore diameter of the microporous foil 100 can be: 0.2mm, 0.4mm, 0.6mm or 0.8mm, etc. The spacing between any two adjacent different micropores 101 is: 0.3mm-1mm. For example: the spacing between any two adjacent different micropores 101 can be: 0.3mm, 0.5mm, 0.7mm or 1mm, etc.

[0113] In some embodiments, the porosity of the microporous foil 100 is greater than or equal to 15%. For example, the porosity of the microporous foil 100 can be 15%, 20%, 25% or 30%, etc.

[0114] In some embodiments of the present application, if the electrodes are all positive electrodes, the microporous foil material 100 comprises a microporous aluminum foil. If the electrodes are all negative electrodes, the microporous foil material 100 comprises a microporous copper foil.

[0115] In some embodiments of the present application, the target slurry thickness between two adjacent current collectors is: 70µm-200µm. For example, the target slurry thickness between two adjacent current collectors is: 70µm-80µm, 80µm-90µm, 90µm-100µm, 100µm-110µm, 110µm-120µm, 120µm-130µm, 130µm-140µm, 140µm-150µm, 150µm-160µm, 160µm-170µm, 170µm-180µm, 180µm-190µm or 190µm-200µm. For example: the target slurry thickness between two adjacent current collectors is: 70µm, 100µm, 130µm, 160µm or 200µm, etc. The target slurry thickness of the two surfaces of the electrode sheet facing away from each other is: 70µm-200µm. For example, the target slurry thickness of the two surfaces of the electrode sheet facing away from each other is: 70µm-80µm, 80µm-90µm, 90µm-100µm, 100µm-110µm, 110µm-120µm, 120µm-130µm, 130µm-140µm, 140µm-150µm, 150µm-160µm, 160µm-170µm, 170µm-180µm, 180µm-190µm or 190µm-200µm. For example: the target slurry thickness of the two surfaces of the electrode sheet facing away from each other is: 70µm, 100µm, 130µm, 160µm or 200µm, etc.

[0116] In some embodiments of the present application, the present application also provides a secondary battery, including: a positive electrode, a negative electrode, a separator, an electrolyte, and a packaging structure that encapsulates the positive electrode, the negative electrode, the separator, and the electrolyte. The separator is arranged between the positive electrode and the negative electrode. The electrolyte is arranged between the separator and the positive electrode and the negative electrode. Among them, the positive electrode and the negative electrode are both the electrodes described in the above embodiments, or the electrodes prepared by the preparation method described in the above embodiments.

[0117] In the embodiment of the present application, microporous foil 100 is used instead of traditional foil, and the diffusion path of ions can be converted into three-dimensional all-round penetration through micropores 101, which solves the problem of difficult ion diffusion in multi-layer electrodes and improves the kinetic efficiency of the battery.

[0118] In some embodiments, the thickness of the positive electrode is 70µm to 200µm.

[0119] For example, the thickness of the positive electrode is: 70µm-80µm, 80µm-90µm, 90µm-100µm, 100µm-110µm, 110µm-120µm, 120µm-130µm, 130µm-140µm, 140µm-150µm, 150µm-160µm, 160µm-170µm, 170µm-180µm, 180µm-190µm or 190µm-200µm. For example, the thickness of the positive electrode can be: 70µm, 100µm, 130µm, 160µm or 200µm, etc. The number of layers of the positive electrode does not exceed 4. For example, the number of layers of the positive electrode can be 2 layers, 3 layers or 4 layers. The thickness of the negative electrode is: 70µm~200µm. For example, the thickness of the negative electrode is: 70µm-80µm, 80µm-90µm, 90µm-100µm, 100µm-110µm, 110µm-120µm, 120µm-130µm, 130µm-140µm, 140µm-150µm, 150µm-160µm, 160µm-170µm, 170µm-180µm, 180µm-190µm or 190µm-200µm. For example: the thickness of the negative electrode can be: 70µm, 100µm, 130µm, 160µm or 200µm, etc. The number of layers of the negative electrode does not exceed 4. For example, the number of layers of the negative electrode can be 2, 3 or 4. The thickness of the positive electrode is negatively correlated with the number of layers of the positive electrode. The thickness of the negative electrode is negatively correlated with the number of layers of the negative electrode.

[0120] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features of the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0121] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A method for preparing a secondary battery, characterized in that: include: Coating a first target slurry on a first surface of a first current collector; Drying the first target slurry on the first surface of the first current collector; coating the first target slurry on the second surface of the first current collector to obtain a first electrode; Coating the second target slurry on the first surface and the second surface of the second current collector which are opposite to each other; Drying the second target slurry on the first surface and the second surface of the second current collector to obtain a second electrode; Adhere the second surface of the second electrode to the first target slurry on the second surface of the first current collector by a hot pressing process, so as to achieve hot pressing bonding of the first electrode and the second electrode; Wherein, the first electrode and the second electrode have the same polarity.

2. The method for preparing a secondary battery according to claim 1, wherein: The first target slurry for drying the first surface of the first current collector includes: Performing a first heat treatment process on the first target slurry on the first surface of the first current collector until the dryness of the first target slurry on the first surface of the first current collector reaches a first preset value; Wherein, the process temperature of the first heat treatment process is: 70℃-130℃.

3. The method for preparing a secondary battery according to claim 2, characterized in that: The step of coating the first target slurry on the second surface of the first current collector to obtain the first electrode comprises: coating the first target slurry on the second surface of the first current collector; Performing a second heat treatment process on the first target slurry on the second surface of the first current collector until the dryness of the first target slurry on the second surface of the first current collector reaches a second preset value, thereby obtaining the first electrode; Among them, the second preset value is smaller than the first preset value; the process temperature of the second heat treatment process is: 70°C-130°C.

4. The method for preparing a secondary battery according to claim 1, wherein: The second target slurry dried on the first surface and the second surface of the second current collector includes: Performing a third heat treatment process on the second target slurry on the first surface and the second surface of the second current collector which are opposite to each other, until the dryness of the second target slurry on the first surface and the second surface of the second current collector which are opposite to each other reaches a third preset value, thereby obtaining the second electrode; Wherein, the third preset value is greater than the second preset value; and the process temperature of the third heat treatment process is: 70°C-130°C.

5. The method for preparing a secondary battery according to claim 1, wherein: Adhering the first surface or the second surface of the second electrode to the first target slurry on the second surface of the first current collector by a hot pressing process to achieve hot pressing bonding of the first electrode and the second electrode includes: Pressing the second surface of the second electrode into the first target slurry on the second surface of the first current collector by a roll pressing process; Performing a fourth heat treatment process on the first target slurry on the second surface of the first current collector until the dryness of the first target slurry on the second surface of the first current collector reaches a first preset value; Wherein, the process temperature of the fourth heat treatment process is: 70℃-130℃.

6. A secondary battery, characterized in that: The secondary battery is prepared by the method for preparing the secondary battery according to any one of claims 1 to 5, comprising: at least two layers of electrodes stacked in sequence along the thickness direction; the electrode comprises a current collector and a target slurry disposed on two surfaces of the current collector facing away from each other; Wherein, the electrodes are all of the same polarity; the current collector comprises a microporous foil; and the target slurry comprises at least a positive electrode active material or a negative electrode active material, a conductive agent and a binder.

7. The secondary battery according to claim 6, characterized in that: If the electrodes are all positive electrodes, the microporous foil material includes microporous aluminum foil; if the electrodes are all negative electrodes, the microporous foil material includes microporous copper foil.

8. The secondary battery according to claim 7, characterized in that The thickness of the microporous aluminum foil is 10µm-25µm; the thickness of the microporous copper foil is 2µm-20µm.

9. A secondary battery, characterized in that: include: positive electrode; Negative electrode; A separator, disposed between the positive electrode and the negative electrode; An electrolyte is disposed between the separator and the positive electrode and the negative electrode; and a packaging structure that packages the positive electrode, the negative electrode, the separator, and the electrolyte; Wherein, the positive electrode and the negative electrode are electrodes in the secondary battery according to any one of claims 6 to 8, or electrodes prepared by the preparation method according to any one of claims 1 to 5.

10. The secondary battery according to claim 9, characterized in that The thickness of the positive electrode is: 70µm~200µm, and the number of layers of the positive electrode does not exceed 4 layers; the thickness of the negative electrode is: 70µm~200µm, and the number of layers of the negative electrode does not exceed 4 layers; wherein, the thickness of the positive electrode is negatively correlated with the number of layers of the positive electrode; the thickness of the negative electrode is negatively correlated with the number of layers of the negative electrode.

Images