Secondary battery, preparation method for negative electrode plate, and electrical apparatus

Abstract

The present application provides a secondary battery, a preparation method for a negative electrode plate, and an electrical apparatus. The secondary battery comprises the negative electrode plate, the negative electrode plate comprises a negative electrode current collector, and the negative electrode current collector is a three-dimensional mesh conductive material comprising a pore structure; and a negative electrode active material, at least a portion of the negative electrode active material being attached to a side wall of the current collector pore structure. By using a three-dimensional mesh conductive material comprising a pore structure as a negative electrode current collector, the present application can make the current collector in the negative electrode plate more lightweight, which is beneficial to reducing the weight of the secondary battery. In addition, the mesh structure in the negative electrode current collector can provide deposition sites for the negative electrode active material, and the pore structure surrounded by the mesh structure provides deposition and expansion spaces for the negative electrode active material.

Description

Secondary battery, method for manufacturing negative electrode sheet, and electric device

[0001] Cross-reference to related applications

[0002] This application refers to the Chinese Patent Application No. 202410873826.2, filed on July 1, 2024, entitled "Secondary battery, method for manufacturing negative electrode sheet, and electric device", which is incorporated by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of secondary batteries, and in particular to a secondary battery, a method for manufacturing a negative electrode sheet, and an electric device. BACKGROUND

[0004] In recent years, lithium ion batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc.

[0005] With the increasing requirements for power performance and endurance of electric devices, it is necessary to further improve the energy density of secondary batteries. SUMMARY

[0006] The present application is made in view of the above-mentioned problems, and aims to provide a secondary battery with high energy density and an electric device.

[0007] A first aspect of the present application provides a secondary battery, comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector, the negative electrode current collector being a three-dimensional network conductive material comprising a pore structure; and a negative electrode active material, at least a portion of the negative electrode active material being attached to the sidewall of the pore structure of the negative electrode current collector.

[0008] Using a three-dimensional network conductive material comprising a pore structure as the negative electrode current collector can achieve lightweight of the current collector in the negative electrode sheet, which is beneficial to reduce the weight of the secondary battery, and the three-dimensional network structure in the negative electrode current collector can provide deposition sites for the negative electrode active material, and the pore structure surrounded by the network structure provides deposition and expansion space for the negative electrode active material. Even without adding auxiliary materials such as binders and dispersants in the negative electrode sheet, the attachment of the negative electrode active material on the negative electrode current collector can be achieved, which can not only improve the loading capacity of the negative electrode active material in the negative electrode sheet, but also make the negative electrode sheet immune to the negative effects such as kinetic decline caused by thick coating process, thereby comprehensively improving the energy density of the secondary battery.

[0009] In any embodiment, the average particle size of the negative electrode active material is 0.8 nm-600 nm.

[0010] The negative electrode active material with the average particle size in the above range can effectively play the capacity level and has good structural stability during the cycle process, which is beneficial to the improvement of the energy density of the secondary battery.

[0011] In any embodiment, the mass percentage of the negative electrode active material is 10%-70% based on the total mass of the negative electrode tab.

[0012] The negative electrode tab has a high negative electrode active material loading, which is beneficial to the improvement of the energy density of the secondary battery.

[0013] In any embodiment, the mass percentage of the negative electrode active material is 40%-60% based on the total mass of the negative electrode tab.

[0014] When the mass percentage of the negative electrode active material is 40%-60% based on the total mass of the negative electrode tab, the secondary battery can have low interface resistance and cycle expansion, and the initial efficiency and cycle life of the secondary battery are improved while the energy density is improved.

[0015] In any embodiment, the negative electrode active material comprises one or more of a carbon-based material and a silicon-based material.

[0016] The negative electrode active material is prone to expansion during the cycle process, and the pore structure of the negative electrode current collector reserves space for the expansion of the negative electrode active material, which is beneficial to reducing the expansion force on the secondary battery during the cycle process and improving the cycle life of the secondary battery.

[0017] In any embodiment, the negative electrode active material comprises a nano-silicon-based material.

[0018] In the prior art, nano-silicon is prone to agglomeration and is difficult to be stably dispersed in the negative electrode film layer, and therefore, hard carbon or other types of porous carbon is needed as a substrate for deposition. The capacity of hard carbon or other types of porous carbon is lower than the gram capacity of silicon material, and the advantages of high capacity and high energy density of silicon material cannot be fully utilized. The negative electrode tab provided in the embodiments of the present application provides deposition sites and deposition space for nano-silicon in the pore structure of the negative electrode current collector, and does not need to provide other deposition sites for nano-silicon in the negative electrode tab, which is beneficial to further improving the loading of the negative electrode active material and fully utilizing the advantages of high capacity of silicon material, and provides a possibility for breaking through the upper limit of the energy density of the secondary battery that can be achieved in the prior art.

[0019] In any embodiment, the negative electrode tab is composed of the negative electrode current collector and the negative electrode active material.

[0020] In any embodiment, the pore diameter of the pore structure in the current collector is 0.5-10 μm.

[0021] The current collector with the pore size in the above range can provide effective deposition sites for the negative active material, provide sufficient accommodation space for the expansion of the negative active material during the cycle process, and provide certain strength for the negative current collector, which is conducive to the simultaneous improvement of the cycle stability and energy density of the secondary battery.

[0022] In any embodiment, the porosity of the current collector is 60%-80%.

[0023] The current collector with the porosity in the above range can provide effective deposition sites for the negative active material, provide sufficient accommodation space for the expansion of the negative active material during the cycle process, and provide certain strength for the negative current collector, which is conducive to the simultaneous improvement of the cycle stability and energy density of the secondary battery.

[0024] In any embodiment, the current collector comprises one or more of foamed copper, foamed nickel, and foamed aluminum.

[0025] The above material can provide strength and flow capacity as a current collector, and has a suitable pore structure, which is conducive to the deposition of the negative active material.

[0026] In any embodiment, the negative electrode sheet further comprises a passivation layer, which is arranged on the outer surface of the current collector and the negative active material.

[0027] The nanomaterial has high chemical activity and is prone to cause safety hazards such as combustion in air, and the surface passivation layer can significantly improve the safety performance of the secondary battery.

[0028] In any embodiment, the mass content of the passivation layer is 1%-10% based on the total mass of the negative electrode sheet.

[0029] The passivation layer with the mass content in the above range can balance the safety performance and energy density of the secondary battery.

[0030] In any embodiment, the passivation layer comprises one or more of carbon and ceramic material.

[0031] The passivation layer comprising carbon material is conducive to the improvement of the conductivity of the negative electrode sheet of the secondary battery, and is conducive to the further improvement of the energy density of the secondary battery; the passivation layer comprising ceramic material is conducive to the improvement of the safety performance of the secondary battery.

[0032] In any embodiment, the mass content of oxygen at the attachment site of the negative active material in the current collector is 0.5%-5%.

[0033] The pore size in the current collector is large, and the deposition material of the silicon-based material such as hard carbon commonly used in the prior art is difficult to increase the adsorption amount of the precursor through capillary action. The mass content of oxygen elements at the attachment site of the negative active material in the current collector is within the above range, which indicates that the negative current collector has certain surface defects, is beneficial to providing sites for the deposition of the negative active material, can improve the adsorption amount of the negative active material precursor under the action of acid-base neutralization, increase the loading amount of the negative active material, and further improve the energy density of the secondary battery; at the same time, the above setting can also improve the bonding strength between the negative active material and the negative current collector, and improve the cycle stability of the secondary battery.

[0034] In any embodiment, the negative current collector surface comprises a deposition-inducing material, the deposition-inducing material comprising one or more of a Lewis acid, a Bronsted acid, the Lewis acid comprising one or more of aluminum oxide, zinc oxide, zirconium oxide, the Bronsted acid comprising one or more of aluminosilicate, aluminum zincate, aluminum zirconate.

[0035] The above deposition-inducing material can also improve the adsorption of the negative active material precursor on the current collector through electrophilicity or proton release, thereby increasing the loading amount of the negative active material and further improving the energy density of the secondary battery; at the same time, the above setting can also improve the bonding strength between the negative active material and the current collector, and improve the cycle stability of the secondary battery.

[0036] In any embodiment, the mass content of the deposition-inducing material is 1%-10% based on the total mass of the negative electrode sheet.

[0037] The negative electrode sheet with the mass content of the deposition-inducing material within the above range can provide an effective number of deposition sites without causing excessive sacrifice to the loading amount of the negative active material, which is beneficial to comprehensively improving the energy density of the secondary battery.

[0038] In any embodiment, the secondary battery further comprises a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive film layer arranged on at least one side of the positive current collector, the single-sided area density of the positive film layer being 7.0 g / cm 2 -9.0 g / cm 2 .

[0039] The thickness of the negative film layer on the surface of the negative current collector in the prior art is generally tens of microns, and the thickness of the positive film layer is difficult to be thickened and the area density is difficult to be further improved due to the limited space size of the secondary battery and the limited capacity of the negative film layer. The secondary battery negative electrode sheet occupies a small space in the secondary battery and has a high loading amount of negative active material, which provides space for the improvement of the area density of the positive electrode sheet, so that the secondary battery can achieve high single-sided area density and obtain a breakthrough in energy density.

[0040] The second aspect of the present application provides a method for preparing a negative electrode sheet, comprising: obtaining a current collector, the current collector being a three-dimensional network conductive material comprising a pore structure; and depositing a negative active material, at least a portion of the negative active material being deposited in the pore structure of the current collector.

[0041] In any embodiment, before the depositing of the negative active material, the method for preparing the negative electrode sheet further comprises: performing site modification on the current collector, the method for the site modification comprising one or more of ozone treatment, plasma treatment, atomic layer deposition, chemical vapor deposition, and physical vapor deposition.

[0042] The above-mentioned site modification method is advantageous for improving the specific adsorption of a negative active material precursor (e.g., silane) on the surface of the current collector, optimizing the adsorption site and amount of the negative active material precursor, and realizing the regulation of the deposition site of the negative active material.

[0043] In any embodiment, the method for depositing the negative active material comprises one or more of a silane cracking method, an evaporation method, and a sputtering deposition method.

[0044] In any embodiment, the method for preparing the negative electrode sheet further comprises surface passivation after the depositing of the negative active material, the method for the surface passivation comprising one or more of carbon coating, ceramic material coating, ozone treatment, and plasma treatment.

[0045] The third aspect of the present application provides an electric device comprising the secondary battery of the first aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0046] FIG. 1 is a schematic structural diagram of a negative electrode sheet in a secondary battery according to an embodiment of the present application.

[0047] FIG. 2 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0048] FIG. 3 is an exploded view of the secondary battery according to an embodiment of the present application shown in FIG. 2.

[0049] FIG. 4 is a schematic diagram of a battery module according to an embodiment of the present application.

[0050] FIG. 5 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0051] FIG. 6 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 5.

[0052] FIG. 7 is a schematic diagram of an electric device using the secondary battery according to an embodiment of the present application as a power source.

[0053] Explanation of Reference Numerals: 1: battery pack; 2: upper case; 3: lower case; 4: battery module; 5: secondary battery; 51: case; 52: electrode assembly; 53: top cap assembly. DETAILED DESCRIPTION

[0054] Hereinafter, embodiments of the secondary battery, the method of manufacturing a negative electrode sheet, and the electric device of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there can be cases where unnecessary detailed description is omitted. For example, there can be cases where detailed description of matters well known in the art, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0055] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also contemplated. In addition, 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: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise specified, the numerical range "a-b" represents a shorthand notation for any real combination of integers 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 herein, and "0-5" is just a shorthand notation for these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0056] If not specifically stated, all embodiments of the present application and optional embodiments can be combined with each other to form new technical solutions.

[0057] If not specifically stated, all technical features of the present application and optional technical features can be combined with each other to form new technical solutions.

[0058] If not specified otherwise, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c) means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0059] If not specified otherwise, the present application refers to "comprising" and "including" as open terms, which also can be closed terms. For example, "comprising" and "including" can mean that other components not listed can also be included or comprised.

[0060] If not specified otherwise, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": 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).

[0061] In the prior art, the negative active material is usually formulated into a negative electrode slurry and then coated on the surface of a negative electrode current collector to form a negative electrode film layer to prepare a negative electrode sheet. In order to improve the processing and coating performance of the negative electrode slurry, a binder, a dispersant and other auxiliary materials are added to the negative electrode slurry. The addition of other auxiliary materials reduces the loading amount of the negative active material, which is not conducive to the improvement of the energy density of the secondary battery.

[0062] Based on this, the present application provides a secondary battery with high energy density.

[0063] The first aspect of the present application provides a secondary battery, comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector, the negative electrode current collector being a three-dimensional network conductive material comprising a pore structure; and a negative active material, at least a part of the negative active material being attached to the sidewall of the current collector pore structure.

[0064] The three-dimensional network conductive material including the pore structure as the negative current collector can realize the lightweight of the negative current collector in the negative electrode sheet, which is beneficial to reduce the weight of the secondary battery, and the three-dimensional network structure in the negative current collector can provide deposition sites for the negative active material, and the pore structure surrounded by the network structure provides deposition and expansion space for the negative active material, even without adding auxiliary materials such as binders and dispersants in the negative electrode sheet to realize the adhesion of the negative active material on the negative current collector, which can not only improve the loading capacity of the negative electrode sheet, but also make the negative electrode sheet immune to the negative effects such as kinetic decline caused by thick coating process, thereby comprehensively improving the energy density of the secondary battery.

[0065] In some embodiments, the average particle size of the negative active material is 0.8 nm-600 nm.

[0066] The average particle size of the negative active material can be tested by a method known in the art. For example, the negative electrode sheet is cut along the thickness direction by using argon ion polishing technology (CP cross-section polishing technology), and the length diameter of the negative active material in the cross-section of the negative electrode sheet is observed, and the average value of the length diameter is taken as the average particle size.

[0067] In some embodiments, the average particle size of the negative active material can be 0.8 nm, 0.9 nm, 1 nm, 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, 1.9 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, or any numerical range between any two of them.

[0068] The negative active material with the average particle size in the above range can effectively exert the capacity level and has good structural stability during the cycle process, which is beneficial to improve the energy density of the secondary battery.

[0069] In some embodiments, the mass fraction of the negative active material is 10%-70% based on the total mass of the negative electrode sheet. In some embodiments, the mass fraction of the negative active material can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any numerical range between any two of them, based on the total mass of the negative electrode sheet.

[0070] The negative electrode sheet has a high loading capacity of the negative active material, which is beneficial to improve the energy density of the secondary battery.

[0071] In some embodiments, the mass percentage of the negative active material is 40%-60% based on the total mass of the negative electrode tab. When the mass percentage of the negative active material is 40%-60% based on the total mass of the negative electrode tab, the secondary battery can have low interfacial resistance and cycle expansion, and can improve the initial efficiency and cycle life of the secondary battery while improving the energy density.

[0072] In some embodiments, the negative active material comprises one or more of a carbon-based material and a silicon-based material.

[0073] In some embodiments, the carbon-based material comprises one or more of nanocarbon, artificial graphite, natural graphite, soft carbon, hard carbon, and composite carbon. In some embodiments, the silicon-based material comprises at least one of elemental silicon, silicon-oxygen material, silicon-carbon material, silicon-nitrogen material, and silicon alloy. The silicon-oxygen material refers to a material containing silicon and oxygen elements, and mainly comprises silicon-oxygen compounds. The silicon-carbon material refers to a material containing silicon and carbon elements, and mainly comprises silicon-carbon composite materials.

[0074] The negative active material described above is prone to expansion during the cycle process, and the pore structure of the negative current collector provides space for the expansion of the negative active material, which is conducive to reducing the expansion force on the secondary battery during the cycle process and improving the cycle life of the secondary battery.

[0075] In some embodiments, the negative active material comprises a nanosilicon-based material.

[0076] The nanosilicon-based material refers to a silicon-containing material with an aspect ratio less than 1000 nm. The nanosilicon-based material includes, but is not limited to, nanosilicon element, nanosilicon-oxygen material, and nanosilicon-carbon material. It should be understood that the nanosilicon-oxygen material and the nanosilicon-carbon material can be formed by simultaneously depositing different elements on the surface of the current collector, or can be formed by first depositing the nanosilicon element on the surface of the current collector and then performing carbon coating or ozone treatment to improve the stability of the silicon element.

[0077] In the prior art, nanosilicon elements are prone to agglomeration and are difficult to stably disperse in the negative film layer, and therefore, a hard carbon or other type of porous carbon is needed as a substrate for deposition. However, the capacity of the hard carbon or other type of porous carbon is lower than the gram capacity of the silicon material, and therefore, the advantages of high capacity and high energy density of the silicon material cannot be fully utilized. The negative electrode tab provided in the embodiments of the present application uses the pore structure in the negative current collector as a deposition site and deposition space for nanosilicon, and does not need to provide other hosts for nanosilicon in the negative electrode tab, which is conducive to further improving the loading capacity of the negative active material and fully utilizing the advantages of high capacity of the silicon material, and provides a possibility for breaking through the upper limit of the energy density of the secondary battery that can be achieved in the prior art.

[0078] In some embodiments, the negative electrode tab is composed of the negative current collector and the negative active material.

[0079] In some embodiments, the pore size of the pore structure in the current collector is 0.5-10 μm.

[0080] The pore size of the pore structure in the current collector can be tested by any known method in the art, for example, by observing and measuring the pore size of the pore structure in the current collector by optical microscopy.

[0081] In some embodiments, the pore size of the pore structure in the current collector can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any range between any two of these values.

[0082] The current collector with the pore size in the above range can provide effective deposition sites for the negative active material, sufficient accommodation space for the expansion of the negative active material during the cycle process, and certain strength for the negative current collector, which is conducive to the simultaneous improvement of the cycle stability and energy density of the secondary battery.

[0083] In some embodiments, the porosity of the current collector is 60-80%.

[0084] In some embodiments, the porosity of the current collector can be 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, or any range between any two of these values.

[0085] The porosity of the current collector can be tested by any known method in the art, for example, a calibrated measuring cylinder is taken, washed and dried. The measuring cylinder, a dropper, kerosene and the sample of the current collector to be tested are placed in a calibrated laboratory 4 h in advance, the room temperature of the calibrated laboratory is controlled to be 20±5°C, and the room temperature does not change by more than 1°C / h. During the test, the sample is first placed in the measuring cylinder, then the measuring cylinder is placed on a balance to remove the skin, then kerosene is dropped into the measuring cylinder using the dropper, and after the meniscus of the liquid level line of the kerosene is above the sample, the liquid level is accurately adjusted to a certain mark of the measuring cylinder by dropping kerosene drop by drop, then the indication V1 (unit: mL) of the measuring cylinder and the weight m3 (unit: g) displayed by the balance at this time are read, and the absolute compact volume of the sample is calculated according to the following formula:

[0086] wherein V represents the absolute compact volume of the sample, in cm 3 ; ε represents the correction coefficient of the measuring cylinder; and ρ represents the density of kerosene, in g / cm 3 .

[0087] The porosity of the sample is calculated by the following formula:

[0088] wherein P represents the porosity of the foamed metal; V0 represents the volume of the sample measured in a natural state, or apparent volume, in cm 3 ; V represents the absolute compact volume of the foamed metal, in cm 3 .

[0089] The current collector with the porosity in the above range can provide effective deposition sites for the negative active material, provide sufficient accommodation space for the expansion of the negative active material during the cycle process, and provide certain strength for the negative current collector, which is conducive to the simultaneous improvement of the cycle stability and energy density of the secondary battery.

[0090] In some embodiments, the current collector comprises one or more of foamed copper, foamed nickel, and foamed aluminum.

[0091] The above material can provide strength and flow capacity as a current collector, and has a suitable pore structure, which is conducive to the deposition of the negative active material.

[0092] In some embodiments, the negative electrode sheet further comprises a passivation layer, which is arranged on the outer surface of the current collector and the negative active material.

[0093] The nanomaterial has high chemical activity and is prone to cause safety hazards such as combustion in air, and the surface passivation layer can significantly improve the safety performance of the secondary battery.

[0094] In some embodiments, the mass content of the passivation layer is 1% to 10% based on the total mass of the negative electrode sheet.

[0095] In some embodiments, the mass content of the passivation layer can be selected as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any numerical range between any two of them, based on the total mass of the negative electrode sheet.

[0096] The passivation layer with the mass content in the above range can balance the safety performance and energy density of the secondary battery.

[0097] In some embodiments, the passivation layer comprises one or more of carbon and ceramic material.

[0098] In some embodiments, the ceramic material comprises one or more of aluminum oxide, copper oxide, nickel oxide, titanium oxide, zirconium oxide, magnesium oxide, beryllium oxide, aluminum nitride, titanium nitride, titanium carbide, zirconium carbide, zirconium boride, molybdenum silicide, zirconium silicide, silicon oxide, silicon nitride, boron nitride, boron carbide, and silicon carbide.

[0099] The passivation layer including the carbon material is beneficial to improve the conductivity of the negative electrode tab of the secondary battery, and is beneficial to further improve the energy density of the secondary battery; the passivation layer including the ceramic material is beneficial to improve the safety performance of the secondary battery.

[0100] In some embodiments, the mass content of oxygen element at the negative electrode active material adhesion site in the current collector is 0.5%-5%.

[0101] In some embodiments, the mass content of oxygen element at the negative electrode active material adhesion site in the current collector can be selected as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any numerical range between any two of them.

[0102] The mass content of oxygen element at the negative electrode active material adhesion site in the current collector can be tested by a method known in the art. As an example, a time-of-flight secondary ion mass spectrometer (such as a model ULVAC-PHI-PHI nano TOF3 time-of-flight secondary ion mass spectrometer) is used to analyze the components at the negative electrode active material adhesion site in the current collector, and the sample should be ensured to have a length and width of about 1x1 cm 2 in size, and a thickness of not more than 5 mm. Bi ions are used as primary pulsed ions to bombard the surface of the sample for spectrum acquisition to obtain the mass content of oxygen element on the surface.

[0103] The pore size in the current collector is large, and the deposition material such as hard carbon and silicon-based material commonly used in the prior art is difficult to increase the adsorption amount of the precursor by capillary action. The mass content of oxygen element at the negative electrode active material adhesion site in the current collector within the above range indicates that the negative electrode current collector has certain surface defects, which is beneficial to increase the deposition site of the negative electrode active material, to improve the adsorption amount of the negative electrode active material precursor under the action of acid-base neutralization, to increase the loading amount of the negative electrode active material, and to further improve the energy density of the secondary battery; at the same time, the above setting can also improve the bonding strength between the negative electrode active material and the negative electrode current collector, and improve the cycle stability of the secondary battery.

[0104] In some embodiments, the surface of the negative electrode current collector comprises a deposition-inducing material, the deposition-inducing material comprises one or more of a Lewis acid, a Bronsted acid, the Lewis acid comprises one or more of aluminum oxide, zinc oxide, zirconium oxide, and the Bronsted acid comprises one or more of aluminosilicate, aluminum zincate, and aluminum zirconate.

[0105] Lewis acid, also known as electrophile, refers to a substance (including ions, atomic groups or molecules) that can accept electron pairs. Bronsted acid refers to molecules or ions that can release protons. It should be pointed out that the location of the deposition inducing material is not limited, including but not limited to the outer surface of the negative current collector and the inner surface of the pore structure.

[0106] The above-mentioned Bronsted acid includes Al-O-Si, Al-O-Zn, Al-O-Zr and other covalent bonds, which can form a local acidic environment at the deposition site and release protons.

[0107] The above-mentioned deposition inducing material can also improve the adsorption of the negative active material precursor on the current collector by electrophilicity or proton release, thereby increasing the loading capacity of the negative active material and further improving the energy density of the secondary battery; at the same time, the above-mentioned setting can also improve the bonding strength between the negative active material and the current collector, and improve the cycle stability of the secondary battery.

[0108] In some embodiments, the mass content of the deposition inducing material is 1%-10% based on the total mass of the negative electrode sheet.

[0109] In some embodiments, the mass content of the deposition inducing material can be selected as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any numerical range between any two of them based on the total mass of the negative electrode sheet.

[0110] The negative electrode sheet with the mass content of the deposition inducing material in the above range can not only provide an effective number of deposition sites, but also not cause too much sacrifice to the loading capacity of the negative active material, which is beneficial to comprehensively improve the energy density of the secondary battery.

[0111] In some embodiments, the secondary battery further comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, and the single-sided area density of the positive electrode film layer is 7.0 g / cm 2 -9.0 g / cm 2 .

[0112] In this application, the area density of the positive electrode film layer is the meaning known in the art, which can be tested by known methods in the art. For example, a single-sided coated and cold-pressed positive electrode sheet (if it is a double-sided coated positive electrode sheet, the positive active layer on one side can be wiped off first) is punched into a small disc with an area of S1, and its mass is weighed and recorded as M1. Then the positive electrode film layer of the above-weighed positive electrode sheet is wiped off, and the mass of the positive electrode current collector is weighed and recorded as M0. The single-sided area density of the positive electrode film layer is (M1-M0) / S1.

[0113] In some embodiments, the single-sided area density of the positive electrode film layer can be selected from 7.0 g / cm 2 , 7.1 g / cm 2 , 7.2 g / cm 2 , 7.3 g / cm 2 , 7.4 g / cm 2 , 7.5 g / cm 2 , 7.6 g / cm 2 , 7.7 g / cm 2 , 7.8 g / cm 2 , 7.9 g / cm 2 , 8.0 g / cm 2 , 8.1 g / cm 2 , 8.2 g / cm 2 , 8.3 g / cm 2 , 8.4 g / cm 2 , 8.5 g / cm 2 , 8.6 g / cm 2 , 8.7 g / cm 2 , 8.8 g / cm 2 , 8.9 g / cm 2 , 9.0 g / cm 2 , or any numerical range between any two of the above values.

[0114] The thickness of the negative electrode film layer on the surface of the negative electrode current collector in the prior art is generally tens of microns. Due to the limited space size of the secondary battery and the limited capacity of the negative electrode film layer, it is difficult to thicken the positive electrode film layer. The secondary battery negative electrode sheet occupies a small space in the secondary battery and has a high negative active material loading capacity. The increase in the area density of the positive electrode sheet provides space for the secondary battery to achieve a high single-sided area density and obtain a breakthrough in energy density.

[0115] The second aspect of the present application provides a method for preparing a negative electrode sheet, comprising: obtaining a current collector, which is a three-dimensional network conductive material comprising a pore structure; and depositing a negative active material, at least a portion of which is deposited in the pore structure of the current collector.

[0116] In some embodiments, before the deposition of the negative active material, the method for preparing the negative electrode sheet further comprises: modifying the sites of the current collector, the method for modifying the sites comprising one or more of ozone treatment, plasma treatment, atomic layer deposition, chemical vapor deposition, and physical vapor deposition.

[0117] In some embodiments, the method for modifying the sites comprises depositing one or more of Lewis acids and Brønsted acids on the surface of the current collector using one or more of atomic layer deposition, chemical vapor deposition, and physical vapor deposition.

[0118] The above site modification method is beneficial to improve the specific adsorption of the negative active material precursor (e.g., silane) on the surface of the current collector, optimize the adsorption site and amount of the negative active material precursor, and realize the regulation of the deposition site of the negative active material.

[0119] In some embodiments, the method of depositing the negative active material includes one or more of a silane cracking method, an evaporation method, and a sputtering deposition method.

[0120] In some embodiments, the method of depositing the negative active material includes a silane cracking method.

[0121] Silane at high temperature is in an electron-deficient state, is easy to be adsorbed at electrophilic sites of the current collector, and is beneficial to the uniform and controllable deposition of nanosilicon on the surface of the current collector.

[0122] In some embodiments, the method of preparing the negative electrode sheet further includes surface passivation after the deposition of the negative active material, and the method of surface passivation includes one or more of carbon coating, ceramic material coating, ozone treatment, and plasma treatment.

[0123] In some embodiments, the positive electrode current collector can adopt a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be adopted. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0124] In some embodiments, the positive electrode active material can adopt a positive electrode active material for a battery known in the art. As an example, the positive electrode active material can include at least one of a lithium-containing phosphate of an olivine structure, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material for a battery can also be used. These positive electrode active materials can be used alone only in one kind, or two or more kinds can be used in combination. Among them, examples of the lithium transition metal oxide can 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 / 3 O2 (which can also be referred to as NCM 333 ), LiNi0.5 Co 0.2 Mn 0.3 O2(also can be referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(also can be referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(also can be referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2), and modified compounds thereof. Examples of lithium-containing phosphates of olivine structure can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4(also can be referred to as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon.

[0125] In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder can 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.

[0126] In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0127] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and after processes such as drying, cold pressing, etc., the positive electrode tab can be obtained.

[0128] In some embodiments, the secondary battery further includes an electrolyte.

[0129] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not particularly limited in the present application and can be selected as desired. For example, the electrolyte can be liquid, gel, or all-solid.

[0130] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0131] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0132] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0133] In some embodiments, the electrolyte solution can optionally further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0134] In some embodiments, the secondary battery further includes a separator. The type of separator is not particularly limited in the present application and any known porous separator having good chemical stability and mechanical stability can be used.

[0135] In some embodiments, 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, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0136] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be used to manufacture an electrode assembly through a roll-pressing process or a stacking process.

[0137] In some embodiments, the secondary battery can include an outer package. The outer package can be used to encapsulate the electrode assembly and the electrolyte described above.

[0138] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, or the like can be listed.

[0139] The present application does not have a particular limitation on the shape of the secondary battery, which can be cylindrical, square, or any other arbitrary shape. For example, FIG. 2 is a secondary battery 5 of a square structure as an example.

[0140] In some embodiments, referring to FIG. 3, the outer package can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and a side plate connected to the bottom plate, which enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, which can be selected by those skilled in the art according to the specific actual needs.

[0141] In some embodiments, the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0142] FIG. 4 is a battery module 4 as an example. Referring to FIG. 4, in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0143] Optionally, the battery module 4 can also include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0144] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0145] FIGS. 5 and 6 are a battery pack 1 as an example. Referring to FIGS. 5 and 6, the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be provided on the lower box body 3 to form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any arbitrary manner.

[0146] In addition, the application also provides a power utilization device comprising at least one of the secondary battery, the battery module, or the battery pack provided by the application. The secondary battery, the battery module, or the battery pack can be used as a power supply of the power utilization device, and can also be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0147] As the power utilization device, the secondary battery, the battery module, or the battery pack can be selected according to the use requirement thereof.

[0148] FIG. 7 is a power utilization device as an example. The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of the power utilization device for high power and high energy density of the secondary battery, the battery pack or the battery module can be used.

[0149] The device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thin and light, and the secondary battery can be used as a power supply.

[0150] Embodiment

[0151] Hereinafter, the embodiments of the application are described. The embodiments described below are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument used is not indicated by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0152] I. Preparation method

[0153] Embodiment 1

[0154] Preparation of the negative electrode tab:

[0155] The rolled foam copper is placed into a roll-to-roll chemical vapor deposition device, ozone is introduced for 10 min, and then silane is introduced for deposition at 560℃, the silane flow rate is 500 mL / min, and the gas inlet time is 90 min. Finally, the temperature is increased to 680℃, acetylene is introduced at a flow rate of 1000 mL / min for 60 min for carbon coating. The pore size of the foam copper is 5 microns, the porosity is 60%, the average particle size of the deposited nanosilicon is 500 nm, the mass content of the coated carbon layer is 5%, and the mass content of oxygen elements at the nanosilicon attachment site in the foam copper is 1%. After cold pressing and cutting, the deposited three-dimensional network structure is obtained to obtain the negative electrode sheet, and the thickness of the cold-pressed negative electrode sheet is 30 microns.

[0156] Preparation of the positive electrode sheet:

[0157] The nickel-cobalt-manganese (NCM) ternary material, conductive agent carbon black, binder polyvinylidene fluoride (PVDF), and N-methyl pyrrolidone (NMP) are stirred and mixed uniformly at a mass ratio of 94.7:1.5:2.7:1.1 to obtain a positive electrode slurry. Then the positive electrode slurry is uniformly coated on the positive electrode current collector, and then dried, cold-pressed, and cut to obtain the positive electrode sheet, and the area density of the positive electrode sheet is 8.4 g / cm 2 .

[0158] Preparation of the separator:

[0159] A polyethylene film with a thickness of 13 microns is used as the separator.

[0160] Preparation of the electrolyte:

[0161] A mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) is prepared at a volume ratio of 1:1:1, and LiPF6 lithium salt is added to make the concentration 1 mol / L.

[0162] Assembly of the battery:

[0163] According to the order of "separator-negative electrode sheet-separator-positive electrode sheet", the positive electrode sheet, the negative electrode sheet, and one end of the two separators are fixed on the discharge roller, and the other end is fixed on the winding shaft after being stacked together. The winding shaft is rotated by a motor to wind the positive electrode sheet, the negative electrode sheet, and the two separators to obtain a wound battery, and the volume of the secondary battery is 680 mL.

[0164] Example 2

[0165] Example 2 and Example 1 have basically the same preparation method, except that the gas inlet time of silane is adjusted to 60 min.

[0166] Example 3

[0167] Example 3 is substantially the same as the preparation method of Example 1, except that the silane gas inlet time is adjusted to 30 min.

[0168] Example 4

[0169] Example 4 is substantially the same as the preparation method of Example 1, except that the silane gas inlet time is adjusted to 40 min.

[0170] Example 5

[0171] Example 5 is substantially the same as the preparation method of Example 1, except that the foamed copper is placed into a roll-to-roll chemical vapor deposition device, 10 nm of aluminum oxide is deposited on the surface by atomic layer deposition, and then silane is introduced for deposition. The mass ratio of aluminum oxide to the negative electrode sheet is 1.2%.

[0172] Example 6

[0173] Example 6 is substantially the same as the preparation method of Example 1, except that the foamed copper is not subjected to ozone treatment before the introduction of silane for deposition in the preparation method of the negative electrode sheet.

[0174] Comparative Example 1

[0175] Comparative Example 1 is substantially the same as the battery preparation method of Example 1, except for the preparation method of the negative electrode sheet.

[0176] The preparation method of the negative electrode sheet in Comparative Example 1 is as follows: commercially available G14 silicon-carbon composite material, artificial graphite, conductive agent carbon black, SBR, and CMC are mixed in a mass ratio of 46.72:46.38:0.5:5.21.2 in an aqueous solvent to obtain a negative electrode slurry; then the negative electrode slurry is uniformly coated on a negative electrode current collector copper foil, followed by drying, cold pressing, and slitting to obtain a negative electrode sheet. The mass content of silicon in the G14 silicon-carbon composite material is 55%, the average particle size of silicon particles is 2 nm, and the carbon structure in the silicon-carbon composite material is biomass porous carbon. The areal density of the negative electrode sheet is 5.4 mAh / cm 2 , and the compacted density is 1.1 g / cm 3 .

[0177] The preparation method of the positive electrode sheet in Comparative Example 1 is substantially the same as that of Example 1, except that the areal density of the positive electrode sheet in Comparative Example 1 is 5.8 g / cm 2 .

[0178] II. Performance Test

[0179] 1. Test method for mass ratio of negative electrode active material

[0180] Take 1 g of negative electrode sheet in 3 mL of hydrofluoric acid and 1 mL of nitric acid for ablation, soak for 3 h, then add 5 mL of H2O, and then carefully suck into a 25 mL volumetric flask, continue to wash the bubble flask with water, and suck the washing liquid into the volumetric flask; the solution in the volumetric flask is filtered, and 10 mL of the filtrate is used for inductively coupled plasma optical emission spectrometry (ICP-OES) to obtain the mass content of silicon element in the test solution as Cm, unit: ppm, then the mass content M of silicon element in the sample is calculated by the following formula: M = Cm x 1 x 10 -3 × 25

[0181] 2. Battery capacity retention rate test

[0182] At 25°C, the prepared lithium ion battery is charged at 1 / 3C constant current to 4.3V, then charged at 4.3V constant voltage to 0.05C current, and then discharged at 1 / 3C to 2.5V. The obtained capacity is recorded as the initial capacity C0. The above steps are repeated for the same battery, and the discharge capacity Cn of the battery after the nth cycle is recorded. The battery capacity retention rate Pn = Cn / C0*100% after each cycle, and the capacity retention rate and cycle number curve of the lithium ion battery of Example 1 can be obtained with P1, P2, …, P100 as the vertical coordinate and the corresponding cycle number as the horizontal coordinate.

[0183] In this test process, the first cycle corresponds to n = 1, the second cycle corresponds to n = 2, and the 100th cycle corresponds to n = 100. P100 is the capacity retention rate of the battery after 100 cycles under the above test conditions.

[0184] 3. Initial efficiency test

[0185] At 25°C, the prepared secondary battery is charged at a constant current of 0.33C rate to a charge cut-off voltage of 5mV, then charged at a constant voltage until the current is less than or equal to 0.05C, and then left for 5 min. Then the prepared secondary battery is discharged at a constant current of 0.33C rate to a cut-off voltage of 1.0V, and then left for 5 min. The discharge capacity / charge capacity is taken as the initial efficiency.

[0186] 4. Energy density test

[0187] At 25°C, the prepared secondary battery is charged at a constant current of 0.33C rate to a charge cut-off voltage of 5mV, then charged at a constant voltage until the current is less than or equal to 0.05C, and then left for 5 min. Then the prepared secondary battery is discharged at a constant current of 0.33C rate to a cut-off voltage of 1.0V, and then left for 5 min. The above is one charge-discharge cycle of the battery.

[0188] The cell mass energy density (Wh / kg) = (the capacity of the third discharge in the cycle process x the discharge platform) / the mass of the cell.

[0189] The volume energy density of the battery cell (Wh / L) = (the capacity of the third discharge during the cycle process x the discharge platform) / the volume of the battery cell.

[0190] III. Test results

[0191] The negative electrode sheet provided in the embodiment includes a negative electrode current collector, the negative electrode current collector includes foamed copper, and the negative electrode active material silicon element is attached to the side wall of the pore structure of the foamed copper. Compared with the secondary battery prepared by coating the negative electrode slurry on the surface of the negative electrode current collector in the prior art, the energy density of the secondary battery is improved.

[0192] The negative electrode active material in the embodiment is deposited in the pore structure of the negative electrode current collector, so as to reduce the thickness of the negative electrode film layer while achieving high loading of the secondary battery, and further break through the maximum area density of the positive electrode sheet.

[0193] The volume energy density of the embodiment 1 is 900 Wh / L, and the volume energy density of the comparative example 1 is 600 Wh / L. According to the test results, when the mass ratio of the silicon content to the mass of the negative electrode film layer in the comparative example is 26.58%, the mass energy density is still lower than that of the secondary battery in the embodiment.

[0194] As can be seen from the comparison between the embodiment 1-5 and the embodiment 6, the modification of the surface sites of the negative electrode current collector is conducive to the improvement of the loading of the negative electrode active material, and helps to further improve the energy density and cycle life of the secondary battery.

[0195] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications of the embodiments, combination of part of the components in the embodiments to construct other ways, which can be thought by those skilled in the art, are also included in the scope of the present application.

Claims

1. A secondary battery characterized by comprising: The negative electrode sheet comprises a negative electrode current collector, which is a three-dimensional network conductive material comprising a pore structure; and a negative electrode active material, at least a portion of which is attached to the side wall of the negative electrode current collector pore structure.

2. The secondary battery according to claim 1, characterized by The average particle size of the negative electrode active material is 0.8 nm-600 nm.

3. The secondary battery according to claim 1 or 2, characterized by The mass percentage of the negative electrode active material based on the total mass of the negative electrode sheet is 10%-70%.

4. The secondary battery according to any one of claims 1 to 3, characterized by, The mass percentage of the negative electrode active material based on the total mass of the negative electrode sheet is 40%-60%.

5. The secondary battery according to any one of claims 1 to 4, characterized by, The negative electrode active material comprises one or more of a carbon-based material, a silicon-based material.

6. The secondary battery according to any one of claims 1 to 5, characterized by The negative electrode active material comprises a nano-silicon-based material.

7. The secondary battery according to any one of claims 1 to 6, characterized by, The negative electrode sheet is composed of the negative electrode current collector and the negative electrode active material.

8. The secondary battery according to any one of claims 1 to 7, characterized by, The pore size of the pore structure in the current collector is 0.5 μm-10 μm.

9. The secondary battery according to any one of claims 1 to 8, characterized by, The porosity of the current collector is 60%-80%.

10. The secondary battery according to any one of claims 1 to 9, characterized by The current collector comprises one or more of foamed copper, foamed nickel, and foamed aluminum.

11. The secondary battery according to any one of claims 1 to 10, characterized by The negative electrode sheet further comprises a passivation layer, which is arranged on the outer surface of the current collector and the negative electrode active material.

12. The secondary battery according to claim 11, characterized by The mass content of the passivation layer based on the total mass of the negative electrode sheet is 1%-10%.

13. The secondary battery according to claim 11 or 12, characterized by The passivation layer comprises one or more of carbon and a ceramic material.

14. The secondary battery according to any one of claims 1 to 13, characterized by The mass content of oxygen at the attachment site of the negative electrode active material in the current collector is 0.5%-5%.

15. The secondary battery according to any one of claims 1 to 14, characterized by, The surface of the negative electrode current collector comprises a deposition-inducing material, which comprises one or more of a Lewis acid and a Bronsted acid, the Lewis acid comprises one or more of aluminum oxide, zinc oxide, and zirconium oxide, and the Bronsted acid comprises one or more of aluminosilicate, aluminizincate, and aluminizirconate.

16. The secondary battery according to claim 15, characterized by The mass content of the deposition-inducing material based on the total mass of the negative electrode sheet is 1%-10%.

17. The secondary battery according to any one of claims 1 to 16, characterized by The secondary battery further comprises a positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector, the positive electrode film layer having a single side surface density of 7.0 g / cm 2 - 9.0 g / cm 2 .

18. A method for producing a negative electrode sheet, characterized by The method comprises: obtaining a current collector, which is a three-dimensional network conductive material comprising a pore structure; depositing a negative electrode active material, at least a portion of which is deposited in the pore structure of the current collector.

19. The method of claim 18, wherein, Before the deposition of the negative electrode active material, the preparation method further comprises: site modification of the current collector, the method of site modification comprising one or more of ozone treatment, plasma treatment, atomic layer deposition, chemical vapor deposition, and physical vapor deposition.

20. The method of manufacturing according to claim 18 or 19, wherein, The method of depositing the negative electrode active material comprises one or more of silane cracking, evaporation, and sputter deposition.

21. The production method according to any one of claims 18 to 20, characterized by, The preparation method of the negative electrode sheet further comprises surface passivation after the deposition of the negative electrode active material, the method of surface passivation comprising one or more of carbon coating, ceramic material coating, ozone treatment, and plasma treatment.

22. An electrical device, comprising: The secondary battery of any one of claims 1-17.

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