CN118575294A

CN118575294A - Electrode plate and preparation method thereof, secondary battery and preparation method thereof, battery module, battery pack and electricity utilization device

Info

Publication number: CN118575294A
Application number: CN202280089602.1A
Authority: CN
Inventors: 田亚西; 唐代春
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-10-11
Filing date: 2022-10-11
Publication date: 2024-08-30
Also published as: WO2024077476A1

Abstract

The application provides an electrode plate and a preparation method thereof, a secondary battery and a preparation method thereof, a battery module, a battery pack and an electric device. The electrode plate (7) comprises a current collector (71), a first active layer (72) and a second active layer (73), wherein the first active layer (72) is positioned on at least one surface of the current collector (71), the second active layer (73) is positioned on the first active layer (72), and the electronic conductivity of the first active layer (72) is smaller than that of the second active layer (73).

Description

Electrode plate and preparation method thereof, secondary battery and preparation method thereof, battery module, battery pack and electricity utilization device

Technical Field

The application relates to the field of secondary batteries, in particular to an electrode plate and a preparation method thereof, a secondary battery and a preparation method thereof, a battery module, a battery pack and an electric device.

Background

In the use process of the secondary battery, the problem of lithium precipitation on the surface of the electrode plate is unavoidable. The occurrence of the problem of lithium precipitation can generate lithium dendrites on the surface of the electrode sheet. And growth of lithium dendrites may damage a Solid Electrolyte Interface (SEI) film, reducing cycle performance of the battery. Therefore, inhibiting the lithium precipitation on the surface of the electrode plate has important significance for improving the cycle performance of the battery.

Disclosure of Invention

Based on the above problems, the application provides an electrode plate and a preparation method thereof, a secondary battery and a preparation method thereof, a battery module, a battery pack and an electric device, which can effectively inhibit the problem of lithium precipitation on the surface of the electrode plate and improve the cycle performance of the secondary battery.

In order to achieve the above object, a first aspect of the present application provides an electrode tab including a current collector, a first active layer on at least one surface of the current collector, and a second active layer on the first active layer, the first active layer having an electron conductivity smaller than that of the second active layer.

In the electrode tab provided in the first aspect of the present application, by forming the first active layer on at least one surface of the current collector, forming the second active layer on the surface of the first active layer, and making the electron conductivity of the first active layer smaller than that of the second active layer, it is possible to suppress the transport kinetics of electrons in the first active layer, to aggregate electrons in the first active layer, and to make lithium ions have a larger concentration polarization on the surface of the first active layer. At this time, lithium dendrite generated by lithium precipitation mainly grows on the surface of the first active layer, so that the lithium dendrite can be effectively prevented from growing on the surface of the electrode plate, and further, the lithium precipitation on the surface of the electrode plate can be restrained, thereby improving the cycle performance of the secondary battery.

In some of these embodiments, the first active layer comprises a first active material and an electron conductance inhibitor.

Optionally, the electron conductivity inhibitor includes at least one of styrene-butadiene rubber, barium titanate, and lithium titanate.

In some embodiments, the electron conductivity inhibitor comprises 0.3% to 10% by mass of the first active layer.

In some of these embodiments, the first active layer further comprises a lithium-philic material.

Optionally, the lithium-philic material includes at least one of zinc oxide, magnesium oxide, silver, and tin.

In some embodiments, the lithium-philic material comprises 1-5% by mass of the first active layer.

In some of these embodiments, the second active layer comprises a second active material that is the same as or different from the first active material.

The second aspect of the application provides a preparation method of the electrode slice of the first aspect, comprising the following steps:

the first active layer is formed over at least one surface of the current collector, and the second active layer is formed over the first active layer.

In some of these embodiments, the first active layer and the second active layer are each independently formed using a respective active paste, optionally by means of coating.

A third aspect of the present application provides a secondary battery comprising the electrode tab of the first aspect or the electrode tab prepared by the preparation method of the electrode tab of the second aspect.

A fourth aspect of the present application provides a method for manufacturing a secondary battery of the third aspect, comprising the steps of:

and performing formation treatment on the secondary battery preform provided with the electrode plate.

In some of these embodiments, after the forming process, further comprising:

And charging the product after the formation treatment from the lower limit of the voltage window to the upper limit of the voltage window at 40-50 ℃, and then discharging to the lower limit of the voltage window.

In some of these embodiments, the lower voltage window limit is 2.3V to 2.7V.

In some of these embodiments, the upper limit of the voltage window is 4.4V to 4.6V.

In some of these embodiments, the charging current is 1C to 3C.

In some of these embodiments, the discharge current is 1C to 3C.

In some of these embodiments, between the charging and the discharging further comprises:

Standing the charged product;

optionally, the standing time is 5 min-30 min.

A fifth aspect of the present application provides a battery module comprising the secondary battery of the third aspect or the secondary battery prepared by the method for preparing a secondary battery of the fourth aspect.

A sixth aspect of the present application provides a battery pack comprising the secondary battery of the third aspect, or the secondary battery prepared by the method for preparing a secondary battery of the fourth aspect, or the battery module of the fifth aspect.

A seventh aspect of the present application provides an electric device including at least one of the secondary battery of the third aspect, the secondary battery prepared by the method of preparing the secondary battery of the fourth aspect, the battery module of the fifth aspect, and the battery pack of the sixth aspect.

Drawings

In order to more clearly illustrate the technical solution of the present application, the following description will briefly explain the drawings used in the present application. It is apparent that the drawings described below are only some embodiments of the present application, and that other drawings may be obtained from the drawings without inventive work for those skilled in the art.

Fig. 1 is a schematic view of an electrode sheet according to an embodiment of the present application.

Fig. 2 is a schematic view of an electrode sheet according to another embodiment of the present application.

Fig. 3 is a schematic view of a secondary battery according to an embodiment of the present application.

Fig. 4 is an exploded view of the secondary battery according to an embodiment of the present application shown in fig. 3.

Fig. 5 is a schematic view of a battery module according to an embodiment of the present application.

Fig. 6 is a schematic view of a battery pack according to an embodiment of the present application.

Fig. 7 is an exploded view of the battery pack of the embodiment of the present application shown in fig. 6.

Fig. 8 is a schematic view of an electric device in which a secondary battery according to an embodiment of the present application is used as a power source.

Reference numerals illustrate:

1. A battery pack; 2. an upper case; 3. a lower box body; 4. a battery module; 5. a secondary battery; 51. a housing; 52. an electrode assembly; 53. a cover plate; 6. an electric device; 7. electrode pole pieces; 71. a current collector; 72. a first active layer; 73. and a second active layer.

For a better description and illustration of embodiments and/or examples of those inventions disclosed herein, reference may be made to one or more of the accompanying drawings. Additional details or examples used to describe the drawings should not be construed as limiting the scope of the disclosed invention, the presently described embodiments and/or examples, and any of the presently understood modes of carrying out the invention.

Detailed Description

In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. Preferred embodiments of the present application are shown in the drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

The "range" disclosed herein is defined in terms of lower and upper limits, with the given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4,1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise indicated, the numerical ranges "a-b" represent a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is only a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6,7, 8, 9, 10, 11, 12 or the like.

All embodiments of the application and alternative embodiments may be combined with each other to form new solutions, unless otherwise specified.

All technical features and optional technical features of the application may be combined with each other to form new technical solutions, unless specified otherwise.

All the steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise specified. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

The terms "comprising" and "including" as used herein mean open ended or closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.

The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).

Unless otherwise indicated, terms used in the present application have well-known meanings commonly understood by those skilled in the art. Unless otherwise indicated, the numerical values of the parameters set forth in the present application may be measured by various measurement methods commonly used in the art (e.g., may be tested according to the methods set forth in the examples of the present application).

The application provides an electrode plate and a preparation method thereof, a secondary battery and a preparation method thereof, a battery module, a battery pack and an electric device. Such secondary batteries are suitable for various electric devices using batteries, such as cellular phones, portable devices, notebook computers, battery cars, electric toys, electric tools, electric automobiles, ships, and spacecraft, etc., including, for example, airplanes, rockets, space shuttles, and spacecraft, etc.

The first aspect of the application provides an electrode sheet. The electrode sheet includes a current collector, a first active layer, and a second active layer. The first active layer is located on at least one surface of the current collector, the second active layer is located on the first active layer, and the electronic conductivity of the first active layer is smaller than that of the second active layer.

In the electrode tab of the present embodiment, by forming the first active layer on at least one surface of the current collector, forming the second active layer on the surface of the first active layer, and making the electron conductivity of the first active layer smaller than that of the second active layer, it is possible to suppress the transport kinetics of electrons in the first active layer, to aggregate electrons in the first active layer, and to simultaneously polarize lithium ions with a larger concentration on the surface of the first active layer. At this time, lithium dendrite generated by lithium precipitation mainly grows on the surface of the first active layer, so that the lithium dendrite can be effectively prevented from growing on the surface of the electrode plate, and further, the lithium precipitation on the surface of the electrode plate can be restrained, thereby improving the cycle performance of the secondary battery. In addition, in the electrode plate of the embodiment, the problem of lithium precipitation is effectively avoided on the surface of the electrode plate, so that the influence of growth of lithium dendrites on the diaphragm is effectively avoided, the problem of thermal runaway of the battery caused by the fact that the lithium dendrites pierce the diaphragm is avoided, and the safety performance of the battery can be effectively improved.

In one embodiment, the electron conductivity may be tested by: the prepared electrode plate can be placed in a resistance meter, and the conductivity of the electrode plate can be obtained by using a formula sigma=U, wherein sigma is electronic conductivity, U is detection voltage, I is loading current, delta is plate thickness, and delta is the thickness change value of the plate after pressurization.

Referring to fig. 1, as a specific embodiment, the electrode tab 7 includes a current collector 71, a first active layer 72, and a second active layer 73. The first active layer 72 is located on one surface of the current collector 71, and the second active layer 73 is located on the first active layer 72, and the electron conductivity of the first active layer 72 is smaller than that of the second active layer 73. In the present embodiment, the first active layer 71 and the second active layer 72 are each one layer, and the current collector 71, the first active layer 72, and the second active layer 73 are stacked in this order.

Referring to fig. 2, as another embodiment, the electrode tab 7 includes a current collector 71, a first active layer 72, and a second active layer 73. The first active layer 72 is located on both surfaces of the current collector 71, and the second active layer 73 is located on the first active layer 72, and the electron conductivity of the first active layer 72 is smaller than that of the second active layer 73. In the present embodiment, the first active layer 71 and the second active layer 72 are each two layers, and the second active layer 73, the first active layer 72, the current collector 71, the first active layer 72, and the second active layer 73 are stacked in this order.

In some embodiments, the first active layer includes a first active material and an electron conductance inhibitor. The electron conductivity of the first active layer can be reduced by the use of an electron conductivity inhibitor, such that the electron conductivity of the first active layer is less than the electron conductivity of the second active layer. Optionally, the electron conductivity inhibitor comprises at least one of styrene-butadiene rubber, barium titanate, and lithium titanate. Alternatively, the electron conductivity inhibitor accounts for 0.3-10% of the mass of the first active layer. When the addition amount of the electron conductivity inhibitor is too small, the effect of reducing the electron conductivity of the first active layer is limited. When the addition amount of the electron conductivity inhibitor is too large, the duty ratio of the first active material is correspondingly reduced, and part of the energy density of the electrode plate is sacrificed to be unfavorable for improving the energy density of the battery. Specifically, the percentage by mass of the electron conductivity inhibitor in the first active layer may be, but is not limited to, 0.3%, 0.5%, 0.7%, 1%, 1.2%, 1.5%, 1.7%, 2%, 2.2%, 2.5%, 2.7%, 3%, 3.2%, 3.5%, 3.7%, 4%, 5%, 7%, 10%, etc.

In some embodiments, the first active layer further comprises a lithium-philic material. Through the use of the lithium-philic material, the nucleation energy barrier of lithium on the first active layer can be reduced, lithium precipitation on the surface of the first active layer is promoted, the growth of lithium dendrites on the surface of the electrode plate is further inhibited, and the cycle performance and the safety performance of the secondary battery can be further improved. As an alternative example of the lithium-philic material, the lithium-philic material includes at least one of zinc oxide, magnesium oxide, silver, and tin.

Optionally, when the first active layer includes a lithium-philic material, the lithium-philic material accounts for 1% -5% of the mass of the first active layer. When the addition amount of the lithium philic material is too small, the effect of lowering the nucleation energy barrier for lithium is limited. When the addition amount of the lithium-philic material is too large, the duty ratio of the first active material is correspondingly reduced, and part of the energy density of the electrode plate is sacrificed, so that the improvement of the energy density of the battery is not facilitated. Alternatively, as some specific examples of the weight percentage of the lithium-philic material to the first active layer, the weight percentage of the lithium-philic material to the first active layer may be, but is not limited to, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, etc.

It is understood that the second active layer includes a second active material. The second active material is the same as or different from the first active material.

It is also understood that the first active layer may further include at least one of a binder, a conductive agent, and a thickener. The second active layer may further include at least one of a binder, a conductive agent, and a thickener. Alternatively, the binder, the conductive agent, and the thickener of the first active layer may be the same or different from the binder, the conductive agent, and the thickener of the second active layer, respectively.

In some embodiments, the electrode sheet in the present application is a positive electrode sheet or a negative electrode sheet. Optionally, the negative electrode of the battery is mainly affected by the lithium precipitation problem, and the electrode plate is the negative electrode plate in the application.

The second aspect of the application provides a method for preparing the electrode slice of the first aspect. The preparation method of the electrode plate comprises the following steps: a first active layer is formed on at least one surface of a current collector, and a second active layer is formed on the surface of the first active layer.

Alternatively, as an example of the formation manner of the first active layer and the second active layer, the first active layer and the second active layer are each independently formed using a corresponding active paste, optionally by coating. For example, the first active paste is transferred onto at least one surface of the current collector by coating to form a first active layer. The second active slurry is transferred onto the first active layer by coating to form a second active layer.

It is understood that after the first active material is coated on at least one surface of the current collector, a drying process is performed to form the first active layer. And then coating the second active slurry on the dried first active layer, and performing drying treatment again to form a second active layer.

A third aspect of the present application provides a secondary battery comprising the electrode tab of the first aspect or the electrode tab prepared by the method of preparing the electrode tab of the second aspect. In the process of charging and discharging, lithium dendrite grows on the surface of the first active layer of the electrode pole piece preferentially, so that adverse effects of a lithium precipitation problem on the SEI film and the isolation film can be effectively restrained, and therefore, the secondary battery can keep good cycle performance and safety performance. Optionally, the electrode tab of the first aspect or the electrode tab prepared by the method for preparing an electrode tab of the second aspect is used as a negative electrode tab of a secondary battery.

A fourth aspect of the present application provides a method of manufacturing a secondary battery of the third aspect. The preparation method of the secondary battery comprises the following steps: the secondary battery preform equipped with the electrode tab of the first aspect or the electrode tab prepared by the electrode tab preparation method of the second aspect is subjected to a chemical conversion treatment. The active material in the secondary battery preform is activated by the formation process, so that the battery starts to be able to charge and discharge normally.

In some embodiments, after the forming process, further comprising: and charging the product after the formation treatment from the lower limit of the voltage window to the upper limit of the voltage window at 40-50 ℃, and then discharging to the lower limit of the voltage window. And (3) charging and discharging the product after the formation treatment at a higher temperature of 40-50 ℃, promoting lithium ions to move from the second active layer to the first active layer of the electrode plate, promoting the growth of lithium dendrites on the surface of the first active layer, and reducing the influence of lithium precipitation on the surface of the electrode plate. Alternatively, as a temperature selection at the time of charge and discharge at a higher temperature, the temperature may be, but is not limited to 41 ℃, 42 ℃,43 ℃,44 ℃, 45 ℃, 46 ℃, 47 ℃,48 ℃, 49 ℃, or the like.

In some embodiments, the voltage of the secondary battery preform is brought to its lower voltage window limit by the formation process.

Optionally, the product after the formation treatment is charged from its lower limit to its upper limit and then discharged to its lower limit, the lower limit being 2.3V-2.7V. For example, the lower voltage window limit may be selected to be 2.3V, 2.4V, 2.5V, 2.6V, 2.7V, or the like. The upper limit of the voltage window is 4.4V-4.6V. For example, the lower voltage window limit may be selected to be 4.4V, 4.5V, 4.6V, or the like.

Optionally, the product after the formation treatment is charged from the lower limit of the voltage window to the upper limit of the voltage window and then discharged to the lower limit of the voltage window, and the charged current is 1-3C. For example, the charging current may be 1C, 2C, 3C, or the like. The discharge current is 1-3C. For example, the current of discharge may be 1C, 2C, 3C, or the like. Alternatively, the charging process may be performed in a segmented charging or a direct charging manner.

It will be appreciated that the voltage window represents a voltage range within which the material has a relatively stable structure and performance, which may be determined by the type of material. For example, the voltage window of the product after the formation treatment is shown in the voltage range of the voltage window, and the structure and the performance of the product are stable. When charged beyond the upper voltage window limit, or discharged below the lower voltage window limit, the product may suffer from structural and performance instability. The upper and lower limits of the voltage window of the product after the formation process may be identified based on the material and structural properties of the product.

In some embodiments, between charging and discharging further comprises: and standing the charged product. Optionally, the standing time is 5 min-30 min. For example, the time of standing may be, but is not limited to, 5min, 8min, 10min, 15min, 20min, 25min, 30min, or the like.

A fifth aspect of the present application provides a battery module. The battery module includes the secondary battery of the third aspect or the secondary battery prepared by the method of preparing the secondary battery of the fourth aspect.

A sixth aspect of the present application provides a battery pack. The battery pack includes the secondary battery of the third aspect, or the secondary battery prepared by the method of preparing the secondary battery of the fourth aspect, or the battery module of the fifth aspect.

A seventh aspect of the application provides an electrical device. The electric device includes at least one of the secondary battery of the third aspect, the secondary battery prepared by the method for preparing a secondary battery of the fourth aspect, the battery module of the fifth aspect, and the battery pack of the sixth aspect.

The secondary battery, the battery module, the battery pack, and the electric device of the present application will be described below with reference to the accompanying drawings as appropriate.

In general, a secondary battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. During the charge and discharge of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The isolating film is arranged between the positive pole piece and the negative pole piece, and mainly plays a role in preventing the positive pole piece and the negative pole piece from being short-circuited, and meanwhile ions can pass through the isolating film.

Positive electrode plate

The positive electrode plate comprises a positive electrode current collector and a positive electrode active layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active layer comprises a positive electrode active material.

As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode active layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.

In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

As an example, the positive electrode active material may include a positive electrode active material for a battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (e.g., liCoO ₂), lithium nickel oxide (e.g., liNiO ₂), lithium manganese oxide (e.g., liMnO ₂、LiMn ₂O ₄), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, Lithium nickel cobalt manganese oxide (such as LiNi _1/3Co _1/3Mn _1/3O ₂ (which may also be abbreviated as NCM ₃₃₃)、LiNi _0.5Co _0.2Mn _0.3O ₂ (which may also be abbreviated as NCM ₅₂₃)、LiNi _0.5Co _0.25Mn _0.25O ₂ (which may also be abbreviated as NCM ₂₁₁)、LiNi _0.6Co _0.2Mn _0.2O ₂ (which may also be abbreviated as NCM ₆₂₂)、LiNi _0.8Co _0.1Mn _0.1O ₂ (which may also be abbreviated as NCM ₈₁₁)), a metal oxide, At least one of lithium nickel cobalt aluminum oxide (such as LiNi _0.85Co _0.15Al _0.05O ₂) and modified compounds thereof, and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO ₄ (which may also be referred to simply as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO ₄), a composite of lithium manganese phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon. The weight ratio of the positive electrode active material in the positive electrode film layer is 80-100 wt%, based on the total weight of the positive electrode active layer.

In some embodiments, the positive electrode active layer further optionally includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin. The weight ratio of the binder in the positive electrode active layer is 0 to 20% by weight based on the total weight of the positive electrode active layer.

In some embodiments, the positive electrode active layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The weight ratio of the conductive agent in the positive electrode active layer is 0 to 20% by weight based on the total weight of the positive electrode active layer.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the components for preparing the positive electrode plate, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methyl pyrrolidone) to form positive electrode slurry, wherein the solid content of the positive electrode slurry is 40-80 wt%, the viscosity of the positive electrode slurry at room temperature is adjusted to 5000-25000 mPa.s, the positive electrode slurry is coated on the surface of a positive electrode current collector, and the positive electrode slurry is formed after being dried and cold-pressed by a cold rolling mill; the unit surface density of the positive electrode powder coating is 150-350 mg/m ², the compacted density of the positive electrode plate is 3.0-3.6 g/cm ³, and the compacted density of the positive electrode plate is 3.3-3.5 g/cm ³. The calculation formula of the compaction density is as follows: compacted density = coated area density/(post-extrusion pole piece thickness-current collector thickness).

It is understood that the positive electrode tab in an embodiment of the present application may include a first active layer on at least one surface of the positive electrode current collector and a second active layer on the first active layer, and the first active layer has an electron conductivity smaller than that of the second active layer.

Negative pole piece

The negative electrode tab includes a negative electrode current collector and a negative electrode active layer disposed on at least one surface of the negative electrode current collector, the negative electrode active layer including a negative electrode active material.

As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode active layer is provided on either one or both of the two surfaces opposing the anode current collector.

In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the anode active material may employ an anode active material for a battery, which is well known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more. The weight ratio of the anode active material in the anode active layer is 70 to 100% by weight based on the total weight of the anode active layer.

In some embodiments, the negative active layer further optionally includes a binder. The binder may be at least one selected from Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS). The weight ratio of the binder in the anode active layer is 0 to 30% by weight based on the total weight of the anode active layer.

In some embodiments, the anode active layer further optionally includes a conductive agent. The conductive agent is at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. The weight ratio of the conductive agent in the anode active layer is 0 to 20% by weight based on the total weight of the anode active layer.

In some embodiments, the anode active layer may optionally further include other adjuvants, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like. The weight ratio of the other auxiliary agent in the negative electrode film layer is 0-15% by weight based on the total weight of the negative electrode active layer.

In some embodiments, the negative electrode sheet may be prepared by: dispersing the components for preparing the negative electrode plate, such as the negative electrode active material, the conductive agent, the binder and any other components, in a solvent (such as deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70wt%, and the viscosity of the negative electrode slurry at room temperature is adjusted to 2000-10000 mPa.s; and (3) coating the obtained negative electrode slurry on a negative electrode current collector, and performing a drying procedure, cold pressing, such as a pair roller, to obtain a negative electrode plate. The unit area density of the negative electrode powder coating is 75-220 mg/m ², and the compacted density of the negative electrode plate is 1.2-2.0 g/m ³.

It is understood that the anode tab in an embodiment of the present application may include a first active layer and a second active layer, wherein the first active layer is located on at least one surface of the anode current collector, the second active layer is located on the first active layer, and the electron conductivity of the first active layer is less than the electron conductivity of the second active layer.

Electrolyte composition

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The application is not particularly limited in the kind of electrolyte, and may be selected according to the need. For example, the electrolyte may be liquid, gel, or all solid.

In some embodiments, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF ₆), lithium tetrafluoroborate (LiBF ₄), lithium perchlorate (LiClO ₄), lithium hexafluoroarsenate (LiAsF ₆), lithium bis-fluorosulfonimide (LiFSI), lithium bis-trifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalato borate (lipfob), lithium dioxaato borate (LiBOB), lithium difluorophosphate (LiPO ₂F ₂), lithium difluorodioxaato phosphate (LiDFOP), and lithium tetrafluorooxalato phosphate (LiTFOP). The concentration of the electrolyte salt is usually 0.5 to 5mol/L.

In some embodiments, the solvent may be selected from one or more of fluoroethylene carbonate (FEC), ethylene Carbonate (EC), propylene Carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl Propyl Carbonate (MPC), ethylene Propyl Carbonate (EPC), butylene Carbonate (BC), methyl Formate (MF), methyl Acetate (MA), ethyl Acetate (EA), propyl Acetate (PA), methyl Propionate (MP), ethyl Propionate (EP), propyl Propionate (PP), methyl Butyrate (MB), ethyl Butyrate (EB), 1, 4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, and the like.

Isolation film

In some embodiments, a separator is further included in the secondary battery. The type of the separator is not particularly limited, and any known porous separator having good chemical stability and mechanical stability can be used.

In some embodiments, the material of the isolating film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.

In some embodiments, the secondary battery may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte described above.

In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The exterior package of the secondary battery may also be a pouch type pouch, for example. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate. The shape of the secondary battery is not particularly limited in the present application, and may be cylindrical, square, or any other shape. For example, fig. 3 is a secondary battery 5 of a square structure as one example.

In some embodiments, referring to fig. 4, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is enclosed in the accommodating chamber. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art may select according to specific practical requirements.

In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number may be selected by one skilled in the art according to the application and capacity of the battery module.

Fig. 5 is a battery module 4 as an example. Referring to fig. 5, in the battery module 4, a plurality of secondary batteries 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of secondary batteries 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a case having an accommodating space in which the plurality of secondary batteries 5 are accommodated.

In some embodiments, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and a specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

Fig. 6 and 7 are battery packs 1 as an example. Referring to fig. 6 and 7, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

In addition, the application also provides an electric device which comprises at least one of the secondary battery, the battery module or the battery pack. The secondary battery, the battery module, or the battery pack may be used as a power source of the power consumption device, and may also be used as an energy storage unit of the power consumption device. The power utilization device may include mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric-only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

As the electricity consumption device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirements thereof.

Fig. 8 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the secondary battery by the power consumption device, a battery pack or a battery module may be employed.

As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a secondary battery can be used as a power source.

Examples

In order to make the technical problems, technical schemes and beneficial effects solved by the application more clear, the application will be further described in detail below with reference to the embodiments and the accompanying drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the application, its application, or uses. All other embodiments, which can be made by a person skilled in the art based on the embodiments of the application without any inventive effort, are intended to fall within the scope of the application.

The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1:

preparing a positive electrode plate main body:

The weight ratio of the Nickel Cobalt Manganese (NCM) ternary material, the conductive agent carbon black and the binder polyvinylidene fluoride (PVDF) is 97.44:1.3:1.3, stirring and mixing uniformly to obtain positive electrode slurry; and uniformly coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and cutting to obtain the positive electrode plate.

Preparing a cathode pole piece main body:

Artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR), thickener sodium carboxymethylcellulose (CMC) and electron conductivity inhibitor are mixed according to the weight ratio of 93.1:0.7:2.3:1.2:2.7, dissolving the mixture in deionized water serving as a solvent, and uniformly mixing the mixture to prepare first active slurry. Wherein the electron conductivity inhibitor is styrene butadiene rubber.

Artificial graphite, conductive agent carbon black, binder styrene butadiene rubber and thickener sodium hydroxymethyl cellulose are mixed according to the weight ratio of 97.3:0.7:0.8:1.2, dissolving the mixture in deionized water serving as a solvent, and uniformly mixing the mixture to prepare second active slurry.

And coating the first active slurry on the surface of the current collector copper foil, and drying to form a first active layer. And then coating a second slurry on the first active layer, drying, cold pressing and cutting to obtain the negative electrode plate.

Preparation of electrolyte:

In an argon atmosphere glove box (H ₂O<0.1ppm,O ₂ <0.1 ppm), uniformly mixing an organic solvent of Ethylene Carbonate (EC)/ethylmethyl carbonate (EMC) according to a volume ratio of 3/7, adding 1mol/L LiPF6 lithium salt, uniformly dispersing, and uniformly stirring to obtain an electrolyte.

Isolation film:

A polypropylene film was used as a separator.

Preparation of secondary battery:

And sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, enabling the isolating film to be positioned between the positive electrode plate main body and the negative electrode plate main body to play a role of isolation, then winding to obtain a bare cell, welding a tab for the bare cell, loading the bare cell into an aluminum shell, baking at 80 ℃ to remove water, injecting electrolyte, and sealing to obtain the uncharged battery. And (3) sequentially standing, hot-cold pressing the uncharged battery to obtain a secondary battery preform, and performing formation treatment on the secondary battery preform, wherein the voltage of a battery product after the formation treatment is 2.5V.

Example 2

Compared with example 1, the difference of example 2 is that artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR), thickener sodium hydroxymethyl cellulose (CMC) and electron conductivity inhibitor are mixed according to the weight ratio of 96.1:0.7:1.7:1.2: and 0.3, dissolving the mixture in deionized water serving as a solvent, and uniformly mixing the mixture to prepare first active slurry. Wherein the electron conductivity inhibitor is styrene butadiene rubber.

Example 3

Example 3 is different from example 1 in that artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), thickener sodium hydroxymethyl cellulose (CMC), electron conductivity inhibitor are mixed in a weight ratio of 95.1:0.7:2.3:1.2:0.7 is dissolved in deionized water, and the mixture is uniformly mixed to prepare the first active slurry. Wherein the electron conductivity inhibitor is butyl rubber.

Example 4

Example 4 is different from example 1 in that artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), thickener sodium hydroxymethyl cellulose (CMC), electron conductivity inhibitor are mixed in a weight ratio of 92.1:0.7:2.3:1.2:3.7, dissolving the mixture in deionized water serving as a solvent, and uniformly mixing the mixture to prepare first active slurry. Wherein the electron conductivity inhibitor is styrene butadiene rubber.

Example 5

Example 5 is different from example 1 in that the electron conduction inhibitor is barium titanate.

Example 6

Example 6 differs from example 1 in that the electron conductivity inhibitor is lithium titanate.

Example 7

Example 7 is different from example 1 in that artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR), thickener sodium hydroxymethyl cellulose (CMC), electron conductivity inhibitor, and lithium philic material are mixed in a weight ratio of 93.1:0.7:2.3:1.2:1.7:1 is dissolved in deionized water, and is evenly mixed to prepare the first active slurry. Wherein the electron conductivity inhibitor is styrene butadiene rubber, and the lithium-philic material is zinc oxide.

Example 8

Example 8 differs from example 7 in that the lithium-philic material is magnesium oxide.

Example 9

Example 9 differs from example 7 in that the lithium-philic material is silver.

Example 10

Example 10 differs from example 7 in that the lithium-philic material is tin.

Example 11

Compared with example 5, the difference of example 11 is that artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR), thickener sodium hydroxymethyl cellulose (CMC), electron conductivity inhibitor and lithium-philic material are mixed according to the weight ratio of 93.1:0.7:2.3:1.2:1.7:1 is dissolved in deionized water, and is evenly mixed to prepare the first active slurry. Wherein the electron conductivity inhibitor is barium titanate and the lithium-philic material is zinc oxide.

Example 12

Example 12 differs from example 11 in that the lithium-philic material is magnesium oxide.

Example 13

Example 13 differs from example 11 in that the lithium-philic material is silver.

Example 14

Example 14 differs from example 11 in that the lithium-philic material is tin.

Example 15

Compared with example 6, the difference of example 15 is that the weight ratio of the artificial graphite as the first active material, the carbon black as the conductive agent, the styrene-butadiene rubber (SBR) as the first binder, the sodium carboxymethylcellulose (CMC) as the thickener, the electron conductivity inhibitor and the lithium-philic material is 93.1:0.7:2.3:1.2:1.7:1 is dissolved in deionized water, and is evenly mixed to prepare the first active slurry. Wherein the electron conductivity inhibitor is lithium titanate and the lithium-philic material is zinc oxide.

Example 16

Example 16 differs from example 15 in that the lithium-philic material is magnesium oxide.

Example 17

Example 17 differs from example 15 in that the lithium-philic material is silver.

Example 18

Example 18 differs from example 15 in that the lithium-philic material is tin.

Example 19

Compared with example 9, the difference of this example is that artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR), thickener sodium hydroxymethyl cellulose (CMC), electron conductivity inhibitor and lithium-philic material are mixed according to the weight ratio of 94.5:0.7:2.3:1.2:0.3:1 is dissolved in deionized water, and is evenly mixed to prepare the first active slurry. Wherein the electron conductivity inhibitor is styrene butadiene rubber, and the lithium-philic material is silver.

Example 20

Compared with example 19, the difference of this example is that artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR), thickener sodium hydroxymethyl cellulose (CMC), electron conductivity inhibitor and lithium-philic material are mixed according to the weight ratio of 92.1:0.7:2.3:1.2:2.7:1 is dissolved in deionized water, and is evenly mixed to prepare the first active slurry.

Example 21

Compared with example 19, the difference of this example is that artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR), thickener sodium hydroxymethyl cellulose (CMC), electron conductivity inhibitor and lithium philic material are mixed according to the weight ratio of 84.8:0.7:2.3:1.2:10:1 is dissolved in deionized water, and is evenly mixed to prepare the first active slurry.

Example 22

Compared with example 19, the difference of this example is that artificial graphite, conductive agent carbon black, binder Ding Benxiang glue (SBR), thickener sodium hydroxymethyl cellulose (CMC), electron conductivity inhibitor and lithium-philic material are mixed according to the weight ratio of 83.8:0.7:2.3:1.2:10:2, dissolving the mixture in deionized water serving as a solvent, and uniformly mixing the mixture to prepare first active slurry.

Example 23

Compared with example 19, the difference of this example is that artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR), thickener sodium hydroxymethyl cellulose (CMC), electron conductivity inhibitor and lithium-philic material are mixed according to the weight ratio of 80.8:0.7:2.3:1.2:10: and 5, dissolving in deionized water serving as a solvent, and uniformly mixing to prepare the first active slurry.

Comparative example 1

Compared with example 1, comparative example 1 is different in that:

Artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR) and thickener sodium hydroxymethyl cellulose (CMC) are mixed according to the weight ratio of 95.8:0.7:2.3:1.2, dissolving the mixture in deionized water serving as a solvent, and uniformly mixing the mixture to prepare first active slurry.

Artificial graphite, conductive agent carbon black, binder Styrene Butadiene Rubber (SBR) and thickener sodium hydroxymethyl cellulose (CMC) are mixed according to the weight ratio of 97.3:0.7:0.8:1.2, dissolving the mixture in deionized water serving as a solvent, and uniformly mixing the mixture to prepare second active slurry.

Comparative example 2

Comparative example 2 differs from example 1 in that the electron-conducting agent was replaced with zinc oxide.

Comparative example 3

The comparative example was different from example 9 in that artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), thickener sodium carboxymethylcellulose (CMC), electron conductivity inhibitor, and lithium philic material were mixed in a weight ratio of 95.2:0.7:2.3:1.2:0.1:0.5 is dissolved in deionized water, and the mixture is uniformly mixed to prepare the first active slurry. Wherein the electron conductivity inhibitor is styrene butadiene rubber, and the lithium-philic material is silver.

Comparative example 4

The comparative example was different from example 9 in that artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), thickener sodium carboxymethylcellulose (CMC), electron conductivity inhibitor, and lithium philic material were mixed in a weight ratio of 74.8:0.7:2.3:1.2:15:6, dissolving the mixture in deionized water serving as a solvent, and uniformly mixing to prepare the first active slurry. Wherein the electron conductivity inhibitor is styrene butadiene rubber, and the lithium-philic material is silver.

Test example 1

The secondary batteries in examples and comparative examples were charged to 4.4V at 3C at 45C, left to stand for 10min, and discharged to 2.5V at 1C. Meanwhile, the condition was cycled 1000 times, and the capacity retention rate was measured 1000 times.

Test example 2

The secondary batteries in examples and comparative examples were charged to 4.4V at 1C at 25 ℃, left for 10min, and discharged to 2.5V at 1C. Meanwhile, the condition was cycled 1000 times, and the capacity retention rate was measured 1000 times.

The test results of the examples and comparative examples are shown in table 1.

TABLE 1

As can be seen from table 1, the battery is better cycled by incorporating the electron conductivity inhibitor and/or the lithium-philic material in the examples in the appropriate amounts.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims

The electrode plate is characterized by comprising a current collector, a first active layer and a second active layer, wherein the first active layer is positioned on at least one surface of the current collector, the second active layer is positioned on the first active layer, and the electronic conductivity of the first active layer is smaller than that of the second active layer.
The electrode pad of claim 1, wherein the first active layer comprises a first active material and an electron conductance inhibitor;

Optionally, the electron conductivity inhibitor includes at least one of styrene-butadiene rubber, barium titanate, and lithium titanate.
The electrode pad of claim 2, wherein the electron conductivity inhibitor comprises 0.3-10% by mass of the first active layer.
The electrode pad of any one of claims 2-3, wherein the first active layer further comprises a lithium-philic material;

optionally, the lithium-philic material includes at least one of zinc oxide, magnesium oxide, silver, and tin.
The electrode pad of claim 4, wherein the lithium-philic material comprises 1-5% by mass of the first active layer.
The electrode pad of any one of claims 2-5, wherein the second active layer comprises a second active material that is the same or different than the first active material.
The method for preparing the electrode sheet according to any one of claims 1 to 6, comprising the steps of:

the first active layer is formed over at least one surface of the current collector, and the second active layer is formed over the first active layer.
The method of manufacturing an electrode sheet according to claim 7, wherein the first active layer and the second active layer are each independently formed using a respective active paste, optionally by means of coating.
A secondary battery comprising the electrode sheet according to any one of claims 1 to 6 or the electrode sheet produced by the electrode sheet production method according to any one of claims 7 to 8.
The method for manufacturing a secondary battery according to claim 9, comprising the steps of:

and performing formation treatment on the secondary battery preform provided with the electrode plate.
The method of manufacturing a secondary battery according to claim 10, further comprising, after the formation process:

And charging the product after the formation treatment from the lower limit of the voltage window to the upper limit of the voltage window at 40-50 ℃, and then discharging to the lower limit of the voltage window.
The method for manufacturing a secondary battery according to claim 11, wherein the product after the pairing process is charged from its lower voltage window limit to its upper voltage window limit and then discharged to its lower voltage window limit satisfying at least one of the following characteristics:

(1) The lower limit of the voltage window is 2.3V-2.7V;

(2) The upper limit of the voltage window is 4.4V-4.6V;

(3) The charging current is 1-3C;

(4) The discharge current is 1-3C.
The method of manufacturing a secondary battery according to any one of claims 11 to 12, characterized by further comprising, between the charging and the discharging:

Standing the charged product;

optionally, the standing time is 5 min-30 min.
A battery module comprising the secondary battery according to claim 9 or a secondary battery produced by the method for producing a secondary battery according to any one of claims 10 to 13.
A battery pack comprising the secondary battery according to claim 9, or the secondary battery produced by the method for producing a secondary battery according to any one of claims 10 to 13, or the battery module according to claim 14.
An electric device comprising at least one of the secondary battery according to claim 9, the secondary battery produced by the method for producing a secondary battery according to any one of claims 10 to 13, the battery module according to claim 14, and the battery pack according to claim 15.