Negative pole piece, preparation method of negative pole piece, secondary battery and electric device

Abstract

The invention provides a negative pole piece which comprises a three-dimensional porous current collector and an insulating layer attached to one side of the three-dimensional porous current collector, the insulating layer extends from the surface of the three-dimensional porous current collector to the inside, and the thickness of the insulating layer is smaller than that of the three-dimensional porous current collector; the invention also relates to a preparation method of the corresponding negative pole piece, a secondary battery and an electric device. The negative pole piece can effectively avoid the growth of lithium dendrites on the surface of the negative pole piece and inhibit the volume expansion of the electrode, so that the cycle performance and the safety performance of the battery can be improved.

Description

Negative electrode sheet and preparation method thereof, secondary battery and electric device Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a negative electrode plate and a preparation method thereof, a secondary battery and an electrical device. Background Art

[0002] In recent years, as the application scope of secondary batteries has become increasingly wider, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0003] As secondary batteries have made great progress, higher requirements have been placed on their cycle performance and safety performance. Lithium metal secondary batteries have extremely high market competitiveness in the carbon neutral era due to their high energy density and low carbon emissions. However, there are still many problems to be solved in the current research on lithium metal batteries. One of the most important problems is that during the charging and discharging process of lithium metal batteries, lithium ions will be deposited on the surface of the negative electrode, generating lithium dendrites and dead lithium, causing the volume of the electrode to expand. As the number of cycles increases, lithium dendrites may pierce the isolation membrane, causing internal short circuits, thermal failure or explosions in the battery, causing safety problems.

[0004] Therefore, seeking a solution that can better improve the cycle performance and safety of secondary batteries is one of the key areas of focus for those skilled in the art.

[0005] Summary of the Invention

[0006] The present application is made in view of the above-mentioned problems, and one of its purposes is to provide a negative electrode sheet that can effectively suppress the volume expansion of the electrode, thereby improving the cycle performance and safety performance of the battery.

[0007] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a negative electrode plate, including a three-dimensional porous current collector and an insulating layer attached to one side of the three-dimensional porous current collector, the insulating layer extending from the surface of the three-dimensional porous current collector through the porous structure to the interior, and the thickness of the insulating layer is less than the thickness of the three-dimensional porous current collector.

[0008] The negative electrode plate of the present application adopts a three-dimensional porous current collector and attaches an insulating layer on the three-dimensional porous current collector so that the insulating layer extends from the surface of the three-dimensional porous current collector to a certain thickness inside; when the negative electrode plate is used to assemble a battery, the side of the negative electrode plate with the insulating layer is facing the isolation membrane, which can effectively cut off the surface electron channels of the three-dimensional porous current collector and reduce the electron concentration on the surface of the current collector, so that lithium ions cannot be deposited on the surface of the three-dimensional porous current collector during the deposition process, and are forced to enter the pores inside the three-dimensional porous current collector for deposition, which can effectively inhibit the growth of lithium dendrites on the surface of the negative electrode plate, avoid lithium dendrites piercing the isolation membrane and causing internal short circuits, thermal failures or explosions in the battery, thereby improving the safety of the battery and improving the cycle performance of the battery.

[0009] In addition, the insulating layer in the negative electrode plate of the present application extends from the surface of the three-dimensional porous current collector to the inside, which can reduce the volume of the negative electrode plate compared to the method of providing an insulating layer outward from the surface of the current collector.

[0010] In any embodiment, the thickness of the insulating layer is 5 μm to 20 μm, and the thickness of the three-dimensional porous current collector is 50 μm to 500 μm. This can further inhibit the growth of lithium dendrites on the surface of the negative electrode, further improving the safety and cycle performance of the battery.

[0011] In any embodiment, the insulating layer has through holes, so that when the insulating layer is made of a material that does not conduct ions, lithium ions can pass through the through holes and enter the internal pores of the three-dimensional porous current collector.

[0012] In any embodiment, the insulating layer comprises a polymer attached to the mesh of the three-dimensional porous current collector, that is, the insulating layer is formed by attaching a polymer insulating layer material to the mesh of the three-dimensional porous current collector.

[0013] In any embodiment, the thickness of the high molecular weight polymer attached to the mesh is less than 10 μm.

[0014] In any embodiment, the polymer comprises one or more of a polymer that is non-conductive of electrons and ions, and a polymer that is non-conductive of electrons but conductive of ions. These polymers can effectively inhibit the growth of lithium dendrites on the surface of the negative electrode, thereby improving the safety and cycle performance of the battery.

[0015] In any embodiment, the high molecular polymer that does not conduct electrons and ions includes one or more of polypropylene, polytetrafluoroethylene, and polyperfluoroethylene propylene.

[0016] In any embodiment, the electron-non-conductive but ion-conductive high molecular polymer includes one or more of polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, polydiallyldimethylammonium chloride and polyethyleneimine.

[0017] In any embodiment, the three-dimensional porous current collector includes one or more three-dimensional porous current collectors made of stainless steel, molybdenum, titanium, nickel, copper, and carbon materials.

[0018] In any embodiment, the pore diameter of the three-dimensional porous current collector is 50 μm to 600 μm.

[0019] In any embodiment, the porosity of the three-dimensional porous current collector is 50% to 90%.

[0020] The second aspect of the present application provides a method for preparing the negative electrode sheet of the first aspect of the present application, comprising the following steps:

[0021] providing a three-dimensional porous current collector;

[0022] Adhere an insulating paste on one surface of the three-dimensional porous current collector, and allow the insulating paste to penetrate into the interior of the three-dimensional porous current collector; the penetration depth of the insulating paste is less than the thickness of the three-dimensional porous current collector; and

[0023] The insulating paste is dried to form an insulating layer.

[0024] In this way, by attaching an insulating slurry to the surface of a three-dimensional porous current collector and allowing the insulating slurry to penetrate the interior of the three-dimensional porous current collector, an insulating layer can be formed on the three-dimensional porous current collector after the insulating slurry dries. This preparation method is simple to operate and suitable for large-scale industrial production.

[0025] In any embodiment, the insulating paste includes a solvent and one or more of a high molecular polymer that does not conduct electrons and ions and a high molecular polymer that does not conduct electrons but conducts ions.

[0026] In any embodiment, the high molecular polymer that does not conduct electrons and ions includes one or more of polypropylene, polytetrafluoroethylene, and polyperfluoroethylene propylene.

[0027] In any embodiment, the electron-non-conductive but ion-conductive high molecular polymer includes one or more of polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, polydiallyldimethylammonium chloride and polyethyleneimine.

[0028] In any embodiment, the solvent includes one or more of N-methylpyrrolidone, tetrahydrofuran, dimethyl sulfoxide, toluene, ethylene carbonate, and propylene carbonate.

[0029] In any embodiment, the solid content of the insulating paste is 1% to 25%.

[0030] In any embodiment, the solid content of the insulating paste is 9% to 15%.

[0031] The third aspect of the present application further provides a secondary battery comprising a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet, the negative electrode sheet being the negative electrode sheet of the first aspect of the present application or the negative electrode sheet prepared by the preparation method of the second aspect of the present application, and the side of the electrode sheet provided with the insulating layer is adjacent to the separator. Thus, the insulating layer on the negative electrode sheet can inhibit the deposition of lithium ions on the surface of the negative electrode sheet during charge and discharge to form lithium dendrites, effectively improving the safety and cycle performance of the battery.

[0032] The fourth aspect of the present application further provides an electrical device comprising the secondary battery of the third aspect of the present application.

[0033] The negative electrode plate of the present application is formed by attaching an insulating layer to one side of a three-dimensional porous current collector, and extending the insulating layer from the surface of the three-dimensional porous current collector to the inside; assembling the negative electrode plate into a secondary battery can effectively inhibit the growth of lithium dendrites on the surface of the negative electrode plate, avoid lithium dendrites piercing the isolation membrane and causing internal short circuits, thermal failure or explosions in the battery, thereby improving the safety of the battery and enhancing the cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to better describe and illustrate the embodiments and / or examples of the present application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the presently described embodiments and / or examples, and any of the best modes currently understood for these applications.

[0035] FIG1 is a schematic diagram of the arrangement of a positive electrode sheet, a negative electrode sheet, and a separator in a secondary battery in one embodiment of the present application;

[0036] FIG2 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0037] FIG3 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG2 ;

[0038] FIG. 4 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0039] Description of reference numerals:

[0040] 1. Negative electrode sheet; 11. Three-dimensional porous current collector; 12. Insulating layer; 2. Separator; 3. Positive current collector; 4. Positive active material layer; 5. Secondary battery; 51. Housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device. DETAILED DESCRIPTION

[0041] Below, the embodiments of the negative electrode sheet and its preparation method, secondary battery and electric device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0042] The "ranges" disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive and can be combined arbitrarily, 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 minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 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 this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0043] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0044] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0045] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0046] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0047] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0048] The weights described in this specification may be weight units known in the chemical industry, such as μg, mg, g, and kg.

[0049] At present, due to the great development of secondary batteries, higher requirements are also placed on the safety performance and cycle performance of secondary batteries. During the charge and discharge process of traditional lithium secondary batteries, lithium ions will be deposited on the surface of the negative electrode plate, generating lithium dendrites and dead lithium, causing the volume expansion of the electrode, affecting the cycle performance of the battery; as the number of cycles increases, phenomena such as lithium dendrites piercing the isolation membrane may occur, causing the battery to have an internal short circuit, thermal failure or explosion, causing safety problems. Therefore, seeking a plate that can improve the safety performance and cycle performance of the battery is one of the key areas of focus for those skilled in the art. In this regard, the inventors have discovered a negative electrode plate that can effectively inhibit the growth of lithium dendrites on the surface of the negative electrode plate, thereby improving the safety performance and cycle performance of the battery.

[0050] Please refer to Figure 1. In some embodiments, the first aspect of the present application provides a negative electrode plate 1, including a three-dimensional porous current collector 11 and an insulating layer 12 attached to one side of the three-dimensional porous current collector 11, wherein the insulating layer 12 extends from the surface of the three-dimensional porous current collector 11 through the porous structure to the interior, and the thickness of the insulating layer 12 is less than the thickness of the three-dimensional porous current collector 11.

[0051] The negative electrode plate 1 of the present application adopts a three-dimensional porous current collector 11 and attaches an insulating layer 12 on one side of the three-dimensional porous current collector 11, so that the insulating layer 12 extends from the surface of the three-dimensional porous current collector 11 to a certain thickness inside; when the negative electrode plate 1 is used to assemble a battery, the side of the negative electrode plate 1 with the insulating layer 12 is facing the isolation membrane 2, which can effectively cut off the surface electron channel of the three-dimensional porous current collector 11 and reduce the electron concentration on the surface of the current collector, so that lithium ions cannot be deposited on the surface of the three-dimensional porous current collector 11 during the deposition process, and are forced to enter the internal pores of the three-dimensional porous current collector 11 for deposition, which can effectively inhibit the growth of lithium dendrites on the surface of the negative electrode plate 1, avoid lithium dendrites piercing the isolation membrane 2 and causing internal short circuit, thermal failure or explosion of the battery, thereby improving the safety of the battery and improving the cycle performance of the battery. In addition, the insulating layer 12 in the negative electrode plate 1 of the present application extends from the surface of the three-dimensional porous current collector 11 to the inside, which can reduce the volume of the negative electrode plate 1 compared to the method of setting the insulating layer 12 outward on the surface of the current collector.

[0052] In some embodiments, the thickness of the insulating layer 12 is 5 μm to 20 μm, and the thickness of the three-dimensional porous current collector 11 is 50 μm to 500 μm. Thus, setting the thickness of the insulating layer 12 to 5 μm to 20 μm and the thickness of the three-dimensional porous current collector 11 to 50 μm to 500 μm can further inhibit the growth of lithium dendrites on the surface of the negative electrode sheet 1, further improving the safety and cycle performance of the battery.

[0053] It is understood that the thickness of the insulating layer 12 may be, but is not limited to, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, or 20 μm. The thickness of the three-dimensional porous current collector 11 may be, but is not limited to, 50 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, 300 μm, 320 μm, 340 μm, 360 μm, 380 μm, 400 μm, 420 μm, 440 μm, 460 μm, 480 μm, or 500 μm.

[0054] In some embodiments, the insulating layer 12 has through-holes. Thus, when the insulating layer 12 is made of a material that does not conduct ions, lithium ions can pass through the through-holes and thus penetrate the insulating layer 12 into the internal pores of the three-dimensional porous current collector 11. It should be noted that when the insulating layer 12 is made of a material that can conduct ions, the insulating layer 12 may not have through-holes.

[0055] In some embodiments, the insulating layer 12 comprises a polymer attached to the mesh of the three-dimensional porous current collector 11. That is, the insulating layer 12 is formed by attaching the polymer insulating layer 12 material to the mesh of the three-dimensional porous current collector 11. It is understood that the insulating layer 12 material can be coated on the mesh of the three-dimensional porous current collector 11 in the form of a slurry, which is then dried to form the insulating layer 12.

[0056] In some embodiments, the thickness of the polymer attached to the mesh is less than 10 μm. That is, the thickness of the polymer on each mesh of the three-dimensional porous current collector 11 is less than 10 μm. It is understood that the thickness of the polymer attached to the mesh can be, but is not limited to, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or 9 μm. The mesh is the filamentary material in the three-dimensional porous current collector 11 that is interconnected and encloses the holes. The three-dimensional porous structure of the current collector is formed by interweaving multiple meshes.

[0057] In some embodiments, the polymer of the insulating layer 12 includes one or more of a polymer that does not conduct electrons and ions and a polymer that does not conduct electrons but conducts ions. The material of the insulating layer 12 can be a polymer material that can conduct ions or cannot conduct ions. Among them, when using a polymer that does not conduct electrons but conducts ions, a polymer that also has other functions such as promoting electrolyte film formation can also be used. The above-mentioned types of polymers have excellent dielectric properties, can effectively cut off the surface electron channels of the three-dimensional porous current collector 11, and inhibit the deposition of lithium ions on the surface of the three-dimensional porous current collector 11, thereby effectively inhibiting the growth of lithium dendrites on the surface of the negative electrode plate 1, and improving the safety and cycle performance of the battery.

[0058] It is understood that the terms "insulating" and "non-conducting electrons" in this application do not mean that they are completely unable to conduct electrons, but rather that they have extremely low electron conductivity. For example, in some embodiments, the electron conductivity of the insulating layer 12 is less than 10 -10 S / cm.

[0059] In some embodiments, the electron- and ion-nonconducting polymer includes one or more of polypropylene, polytetrafluoroethylene, and polyperfluoroethylene propylene. These polymers, as insulating layer 12, can block electrons and lithium ions from passing through insulating layer 12. It is understood that when using such insulating layer 12 materials, insulating layer 12 should have through-holes to facilitate the passage of lithium ions through insulating layer 12 into the internal pores of three-dimensional porous current collector 11.

[0060] In some embodiments, the electron-non-conducting but ion-conducting polymer includes one or more of polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, polydiallyldimethylammonium chloride, and polyethyleneimine. The above-mentioned polymer composition as the insulating layer 12 can block electrons but cannot block lithium ions from passing through the insulating layer 12. It is understandable that when such an insulating layer 12 material is used, no through-holes may be provided in the insulating layer 12, and lithium ions can enter the internal pores of the three-dimensional porous current collector 11 through the insulating layer 12. Among them, polydiallyldimethylammonium chloride and polyethyleneimine are also polymers that have the function of promoting electrolyte film formation, which can effectively promote electrolyte film formation.

[0061] In some embodiments, the three-dimensional porous current collector 11 includes one or more of stainless steel, molybdenum, titanium, nickel, copper, and carbon materials. That is, the three-dimensional porous current collector 11 can be one or more of stainless steel porous current collector, molybdenum porous current collector, titanium porous current collector, nickel porous current collector, copper porous current collector, and carbon material porous current collector.

[0062] In some embodiments, the pore diameter of the three-dimensional porous current collector 11 is 50 μm to 600 μm. It is understood that the pore diameter of the three-dimensional porous current collector 11 refers to the average pore diameter. The pore diameter of the three-dimensional porous current collector 11 can be, but is not limited to, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm, and 600 μm.

[0063] In some embodiments, the porosity of the three-dimensional porous current collector 11 is 50% to 90%. It is understood that the porosity of the three-dimensional porous current collector 11 can be, but is not limited to, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%.

[0064] The second aspect of the present application provides a method for preparing the negative electrode sheet 1 of the first aspect of the present application. The preparation method comprises the following steps:

[0065] Providing a three-dimensional porous current collector 11;

[0066] Attaching an insulating paste to one side surface of the three-dimensional porous current collector 11 and allowing the insulating paste to penetrate into the interior of the three-dimensional porous current collector 11; the penetration depth of the insulating paste is less than the thickness of the three-dimensional porous current collector 11; and

[0067] The insulating paste is dried to form the insulating layer 12 .

[0068] In this way, by attaching an insulating slurry to one surface of the three-dimensional porous current collector 11 and allowing the insulating slurry to penetrate the interior of the three-dimensional porous current collector 11, an insulating layer 12 can be formed on the three-dimensional porous current collector 11 after the insulating slurry dries, thereby obtaining the negative electrode sheet 1 of the present application that can improve battery safety and cycle performance. This preparation method is simple to operate and is suitable for large-scale industrial production.

[0069] In some embodiments, the insulating paste includes a solvent and one or more of a polymer that is non-conductive to electrons and ions, and a polymer that is non-conductive to electrons but conductive to ions. It is understood that the polymer is dispersed in the solvent to form the insulating paste. The amounts of the solvent and polymer used can be determined based on actual conditions to ensure that the polymer is uniformly and stably dispersed in the solvent and has a suitable viscosity for easy coating.

[0070] In some embodiments, the high molecular polymer that does not conduct electrons and ions includes one or more of polypropylene, polytetrafluoroethylene, and polyperfluoroethylene propylene.

[0071] In some embodiments, the high molecular weight polymer that is non-electron-conducting but ion-conducting includes one or more of polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, polydiallyldimethylammonium chloride, and polyethyleneimine.

[0072] In some embodiments, the solvent includes one or more of N-methylpyrrolidone, tetrahydrofuran, dimethyl sulfoxide, toluene, ethylene carbonate, and propylene carbonate.

[0073] In some embodiments, the solid content of the insulating paste is 1% to 25%. It is understood that the solid content of the insulating paste can be, but is not limited to, 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, or 25%.

[0074] Referring to FIG. 1 , the third aspect of the present application further provides a secondary battery comprising a positive electrode sheet, a separator 2, a negative electrode sheet 1, and an electrolyte. The separator 2 is disposed between the positive electrode sheet and the negative electrode sheet 1. The negative electrode sheet 1 is the negative electrode sheet 1 of the first aspect of the present application or the negative electrode sheet 1 prepared by the preparation method of the second aspect of the present application. The side of the negative electrode sheet 1 provided with the insulating layer 12 is close to the separator 2. In this way, the growth of lithium dendrites on the surface of the negative electrode sheet 1 close to the separator 2 can be suppressed, effectively improving the safety and cycle performance of the battery.

[0075] In some embodiments, the positive electrode plate is a conventional plate structure, and the positive electrode plate includes a positive electrode collector 3 and a positive electrode active material layer 4 provided on the positive electrode collector 3 , and the positive electrode collector 3 is provided on the side of the positive electrode active material layer 4 away from the isolation membrane 2 .

[0076] The fourth aspect of the present application further provides an electrical device comprising the secondary battery of the third aspect of the present application.

[0077] The secondary battery and the electric device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0078] Unless otherwise specified, the components, material types, or contents of the batteries mentioned are applicable to both lithium-ion secondary batteries and sodium-ion secondary batteries.

[0079] In one embodiment of the present application, a secondary battery is provided.

[0080] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0081]

Positive electrode

[0082] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector.

[0083] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0084] In some embodiments, the positive electrode current collector may be a metal foil, for example, aluminum foil.

[0085] In some embodiments, the positive electrode active material may include a positive electrode active material for a battery known in the art.

[0086] As an example, the positive electrode active material of a lithium-ion secondary battery may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0087] As an example, the positive electrode active material of a sodium ion secondary battery may include at least one of the following materials: a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may also be used.

[0088] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0089] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be at least one of P, S and Si; n represents (YO4) n- valence.

[0090] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds containing anion units and halogen anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4) n- valence state; the halogen may be at least one of F, Cl and Br.

[0091] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be at least one of P, S and Si, and n represents (YO4) n- Z represents a transition metal, which may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents (ZO y ) m+ valence state; the halogen may be at least one of F, Cl and Br.

[0092] Polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0093] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ) compounds. The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0094] The weight ratio of the positive electrode active material in the positive electrode film layer is 80 to 100 weight percent based on the total weight of the positive electrode film layer.

[0095] In some embodiments, the positive electrode film layer may further optionally include 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 fluorine-containing acrylate resin. The weight ratio of the binder in the positive electrode film layer is 0 to 20 weight%, based on the total weight of the positive electrode film layer.

[0096] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. For 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 film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.

[0097] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, wherein the positive electrode slurry has a solid content of 40% by mass (wt%) to 80% by weight, and the viscosity at room temperature is adjusted to 5000 mPa·s to 25000 mPa·s, the positive electrode slurry is coated on the surface of the positive electrode collector, and after drying, the positive electrode sheet is formed by cold rolling; the positive electrode powder coating unit area density is 150 mg / m2 (mg / m 2 )~350mg / m 2 The compacted density of the positive electrode is 3.0 g / cm3 (g / cm 3 )~3.6g / cm 3 , optional 3.3g / cm 3 ~3.5g / cm 3 .

[0098] The calculation formula of the compacted density is:

[0099] Compaction density = coating surface density / (thickness of the electrode after extrusion - thickness of the current collector).

[0100] The mass M of the positive electrode active material per unit area of ​​the positive electrode membrane can be obtained by weighing using a standard balance.

[0101] The thickness T of the positive electrode film can be measured using a micrometer, for example, a Mitutoyo 293-100 with an accuracy of 0.1 μm. It should be noted that the thickness of the positive electrode film described in this application refers to the thickness of the positive electrode film in the positive electrode sheet after cold pressing and used in battery assembly.

[0102]

Negative electrode

[0103] The negative electrode sheet adopts the negative electrode sheet of the first aspect of the present application or the negative electrode sheet prepared by the preparation method of the second aspect of the present application.

[0104] Electrolytes

[0105] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0106] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0107] In some embodiments, the electrolyte salt of the lithium ion secondary battery can be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0108] The electrolyte salt of the sodium ion secondary battery can be selected from one or more of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, and sodium chloride.

[0109] The concentration of the electrolyte salt is generally 0.5 mol / L to 5 mol / L.

[0110] In some embodiments, the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl 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).

[0111] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0112]

Isolation film

[0113] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0114] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0115] In some embodiments, the isolation film has a thickness of 6 μm to 40 μm, and may optionally be 12 μm to 20 μm.

[0116] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0117] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0118] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0119] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG2 shows a secondary battery 5 having a square structure as an example.

[0120] In some embodiments, referring to Figure 3, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0121] In some embodiments, the secondary batteries 5 can be assembled into a battery module. The number of secondary batteries 5 contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0122] In the battery module, the plurality of secondary batteries 5 can be arranged in sequence along the length of the battery module. Of course, they can also be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 can be fixed by fasteners.

[0123] Optionally, the battery module may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0124] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0125] A battery pack may include a battery box and multiple battery modules disposed within the box. The battery box comprises an upper case and a lower case. The upper case can be placed over the lower case to form an enclosed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0126] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric 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.

[0127] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0128] Figure 4 shows an example of an electric device. This device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0129] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0130] The following are some examples.

[0131] In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0132] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0133] 1. Preparation Example

[0134] Preparation Example 1:

[0135] A 150μm thick copper foam produced by Shenzhen Yunfei New Materials Co., Ltd. was used as a three-dimensional porous current collector; the pore diameter of the copper foam was about 500μm.

[0136] Using polyvinylidene fluoride as a non-conductive high molecular polymer and N-methylpyrrolidone as a solvent, polyvinylidene fluoride is dissolved in N-methylpyrrolidone to prepare an insulating slurry; the solid content of the insulating slurry is 12%;

[0137] The insulating slurry is evenly coated on one surface of the copper foam; the insulating slurry is allowed to penetrate into the copper foam and adhere to the mesh of the copper foam;

[0138] The copper foam sample coated with the insulating slurry was placed in an 80°C oven and dried for 5 hours to obtain a three-dimensional porous current collector with an insulating layer on its surface, namely the negative electrode sheet of the present application. The insulating layer had a thickness of 14 μm, and the thickness of the insulating layer attached to the mesh was 8 μm.

[0139] Preparation Example 2:

[0140] This preparation example is basically the same as Preparation Example 1, except that the type of high molecular polymer in the insulating paste is different. In this preparation example, the non-conductive high molecular polymer is polytetrafluoroethylene.

[0141] Preparation Example 3:

[0142] This preparation example is basically the same as Preparation Example 1, except that the type of high molecular polymer in the insulating paste is different. In this preparation example, the non-conductive high molecular polymer is polydiallyldimethylammonium chloride.

[0143] Preparation Example 4:

[0144] This preparation example is basically the same as Preparation Example 1, except that the thickness of the insulating layer on the three-dimensional porous current collector is different. In this preparation example, the thickness of the insulating layer on the three-dimensional porous current collector is 8 μm.

[0145] Preparation Example 5:

[0146] This preparation example is basically the same as Preparation Example 1, except that the thickness of the insulating layer on the three-dimensional porous current collector is different. In this preparation example, the thickness of the insulating layer on the three-dimensional porous current collector is 20 μm.

[0147] Preparation Example 6:

[0148] This preparation example is basically the same as Preparation Example 1, except that the three-dimensional porous current collector is made of a different material. In this preparation example, the three-dimensional porous current collector is made of foamed nickel.

[0149] Preparation Example 7:

[0150] This preparation example is basically the same as Preparation Example 1, except that the three-dimensional porous current collector is made of a different material. In this preparation example, the three-dimensional porous current collector is made of carbon material.

[0151] Preparation Example 8:

[0152] This preparation example is basically the same as Preparation Example 1, except that the solid content of the insulating paste is different. The solid content of the insulating paste in this preparation example is 9%.

[0153] Preparation Example 9:

[0154] This preparation example is basically the same as Preparation Example 1, except that the solid content of the insulating paste is different. The solid content of the insulating paste in this preparation example is 15%.

[0155] 2. Preparation Comparative Example

[0156] Preparation Comparative Example 1:

[0157] In the comparative example of preparation, the three-dimensional porous current collector adopts blank foam copper, and no insulating layer is provided on the foam copper three-dimensional porous current collector.

[0158] 3. Negative electrode performance test

[0159] 1) Negative electrode surface resistance test:

[0160] In the resistance mode of the multimeter, use a stylus to measure the surface resistance of one side of the negative electrode sheet insulation layer prepared in each of the above preparation examples and the surface resistance of the blank foam copper prepared in the comparative example. Measure three times at different positions and record the average value.

[0161] 2) Negative electrode / Li half-cell performance test:

[0162] A discharge test was performed using a button cell. The positive electrode of the battery used the negative electrode sheet with a surface insulating layer prepared in each preparation embodiment; the negative electrode used a lithium sheet; the electrolyte used a LiFSI solution dissolved in DME with an electrolyte concentration of 1 M; and the isolation membrane used a PE film with a thickness of 12 μm.

[0163] Discharge conditions: The half-cell was discharged at a constant current density of 1 mA / cm at room temperature. 2 , continue discharging until a short circuit signal appears, that is, the battery voltage jumps to 0V.

[0164] Record the time from the start of discharge to short circuit.

[0165] 3) LFP / negative electrode full battery performance test:

[0166] A button cell was used for the cycle test. Lithium iron phosphate (LFP) was used as the positive active material of the battery. The weight ratio of lithium iron phosphate: conductive carbon black: PVDF binder in the positive active material layer was 8:1:1. Aluminum foil was used as the positive current collector. The negative electrode pole piece was the negative electrode pole piece prepared in each preparation embodiment. The electrolyte was a LiFSI solution dissolved in DME with an electrolyte concentration of 1 M. The isolation membrane was a PE film with a thickness of 12 μm.

[0167] Charging conditions: The battery was charged at room temperature using the constant current-constant voltage (CC-CV) mode. First, charge at a fixed rate of 0.2C in the constant current mode until the voltage reached 3.65V. Then, switch to the constant voltage mode with a cutoff current of 0.05C to fully charge the battery.

[0168] Discharge conditions: Discharge in constant current mode at a discharge rate of 0.5C to 2V and cycle 200 times.

[0169] The number of cycles at which the discharge capacity retention rate reached 50% was recorded.

[0170] The performance test results of the negative electrode sheets prepared in each preparation example and preparation comparative example are shown in Table 1.

[0171] Table 1

[0172] It can be seen from the data of the above-mentioned preparation examples and preparation comparison examples that by setting a surface insulating layer on the three-dimensional porous current collector, the surface resistance of the current collector is significantly increased compared with the blank foam copper sample, indicating that the resistance of electrons reaching the surface of the current collector is increased, effectively cutting off the electron channel on the surface of the current collector, thereby inhibiting the deposition of lithium ions on the surface of the negative electrode, achieving half-cell short circuit suppression and improving the cycle performance of the full battery.

[0173] 4. Application Examples

[0174] Application Example 1:

[0175] 1) Preparation of positive electrode sheet

[0176] The positive electrode active material lithium iron phosphate, conductive carbon black and binder PVDF were dispersed in the solvent NMP in a weight ratio of 8:1:1 and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained. The coating amount per unit area was 0.4g / 1540.25mm 2 .

[0177] 2) Preparation of negative electrode sheet

[0178] The negative electrode sheet prepared in Example 1 of the present application was prepared.

[0179] 3) Isolation film

[0180] A PE film having a thickness of 12 μm was used as a separator.

[0181] 4) Preparation of electrolyte

[0182] The electrolyte is a LiFSI solution dissolved in DME, and the concentration of the electrolyte is 1M.

[0183] 5) Preparation of batteries

[0184] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is placed between the positive and negative electrode sheets to play an isolating role, and the side of the negative electrode sheet with the insulating layer is close to the separator. Then, they are wound into a square bare battery cell and loaded with aluminum-plastic film. After baking at 80°C to remove water, 10g of the corresponding non-aqueous electrolyte is injected and sealed. After standing, hot and cold pressing, formation, clamping, capacity separation and other processes, the finished battery is obtained.

[0185] The secondary batteries of Application Examples 2 to 9 and the secondary battery of Application Comparative Example 1 were prepared in a similar manner to the secondary battery of Application Example 1, but used the negative electrode sheets of the corresponding Preparation Examples and Preparation Comparative Example.

[0186] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A negative electrode plate, comprising a three-dimensional porous current collector and an insulating layer attached to one side of the three-dimensional porous current collector, wherein the insulating layer extends from the surface of the three-dimensional porous current collector through a porous structure to the inside, and the thickness of the insulating layer is less than the thickness of the three-dimensional porous current collector.

2. The negative electrode sheet according to claim 1, characterized in that: The thickness of the insulating layer is 5 μm to 20 μm, and the thickness of the three-dimensional porous current collector is 50 μm to 500 μm.

3. The negative electrode sheet according to claim 1 or 2, characterized in that: The insulating layer has a through hole therein.

4. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: The insulating layer includes a high molecular polymer attached to the mesh of the three-dimensional porous current collector.

5. The negative electrode sheet according to claim 4, characterized in that: The adhesion thickness of the high molecular polymer on the mesh is less than 10 μm.

6. The negative electrode sheet according to claim 4 or 5, characterized in that: The high molecular polymer includes one or more of a high molecular polymer that does not conduct electrons and ions and a high molecular polymer that does not conduct electrons but conducts ions.

7. The negative electrode sheet according to claim 6, characterized in that: The high molecular polymer that does not conduct electrons and ions includes one or more of polypropylene, polytetrafluoroethylene and polyperfluoroethylene-propylene.

8. The negative electrode sheet according to claim 6 or 7, characterized in that: The high molecular polymer which does not conduct electrons but conducts ions includes one or more of polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, polydiallyldimethylammonium chloride and polyethyleneimine.

9. The negative electrode sheet according to any one of claims 1 to 8, characterized in that: The three-dimensional porous current collector includes one or more of three-dimensional porous current collectors made of stainless steel, molybdenum, titanium, nickel, copper, and carbon materials.

10. The negative electrode sheet according to any one of claims 1 to 9, characterized in that: The negative electrode sheet satisfies at least one of the following (1) to (2): (1) The pore diameter of the three-dimensional porous current collector is 50 μm to 600 μm; (2) The porosity of the three-dimensional porous current collector is 50% to 90%.

11. A method for preparing a negative electrode sheet, characterized in that: The steps include: Providing a three-dimensional porous current collector; Adhere an insulating slurry on one side surface of the three-dimensional porous current collector, and allow the insulating slurry to penetrate into the interior of the three-dimensional porous current collector; the penetration depth of the insulating slurry is less than the thickness of the three-dimensional porous current collector; as well as The insulating paste is dried to form an insulating layer.

12. The method for preparing a negative electrode sheet according to claim 11, characterized in that: The insulating paste includes a solvent and one or more of a high molecular polymer that does not conduct electrons and ions and a high molecular polymer that does not conduct electrons but conducts ions.

13. The method for preparing a negative electrode sheet according to claim 12, characterized in that: The preparation method satisfies at least one of the following (3) to (4): (3) The high molecular polymer that does not conduct electrons and ions includes one or more of polypropylene, polytetrafluoroethylene and polyperfluoroethylene propylene; (4) The high molecular polymer that does not conduct electrons but conducts ions includes one or more of polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, polydiallyldimethylammonium chloride and polyethyleneimine.

14. The method for preparing a negative electrode sheet according to claim 12 or 13, characterized in that: The solvent includes one or more of N-methylpyrrolidone, tetrahydrofuran, dimethyl sulfoxide, toluene, ethylene carbonate and propylene carbonate.

15. The method for preparing a negative electrode sheet according to any one of claims 11 to 14, characterized in that: The solid content of the insulating slurry is 1% to 25%; Optionally, the solid content of the insulating slurry is 9% to 15%.

16. A secondary battery, characterized in that: It includes a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte, wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet, the negative electrode sheet is the negative electrode sheet according to any one of claims 1 to 10 or the negative electrode sheet prepared by the preparation method according to any one of claims 11 to 15, and the side of the negative electrode sheet provided with the insulating layer is close to the separator.

17. An electrical device, characterized in that: Includes the secondary battery as claimed in claim 16.

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