Secondary battery, method for preparing negative electrode sheet, battery module, battery pack, and electric device

Abstract

A secondary battery, a method for preparing a negative electrode sheet, a battery module, a battery pack, and an electric device. The secondary battery comprises a negative electrode sheet. The negative electrode sheet comprises: a negative electrode current collector; a negative electrode active material layer, located on at least one side of the negative electrode current collector; and a solid electrolyte interphase film, located on the side of the negative electrode active material layer away from the negative electrode current collector, wherein the solid electrolyte interphase film comprises a first compound, and the first compound satisfies the chemical formula M1aM2bXc, wherein M1 element comprises one or two of lithium element and sodium element, M2 element comprises one or more of titanium element, zirconium element, chromium element, iron element, nickel element, cobalt element, tantalum element, niobium element and lanthanum element, X comprises one or two of oxygen element and carbon element, a is 1-4, b is 0-5, and c is 1-12.

Description

Secondary batteries, methods for preparing negative electrode sheets, battery modules, battery packs, and electrical devices.

[0001] Cross-reference to related applications

[0002] This application is based on and claims priority to Chinese Patent Application No. 202510179513.1, filed on February 18, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of battery technology, and in particular to a secondary battery, a method for preparing a negative electrode sheet, a battery module, a battery pack, and an electrical device. Background Technology

[0004] Rechargeable batteries are widely used in energy storage systems for hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. As the application range of batteries expands, the performance requirements for rechargeable batteries are becoming increasingly stringent. Summary of the Invention

[0005] The present invention aims to at least partially solve one of the technical problems in the related art.

[0006] To achieve the above objectives, a first aspect of this application provides a secondary battery, including a negative electrode sheet, the negative electrode sheet comprising: a negative electrode current collector; a negative electrode active material layer located on at least one side of the negative electrode current collector; and a solid electrolyte interface (SEI) film located on the side of the negative electrode active material layer away from the negative electrode current collector; the solid electrolyte interface film comprising a first compound, the first compound satisfying the chemical formula M 1a M 2b X c Among them, M1 element includes one or two of lithium and sodium elements, M2 element includes one or more of titanium, zirconium, chromium, iron, nickel, cobalt, tantalum, niobium and lanthanum elements, X includes one or two of oxygen and carbon elements, a is 1-4, b is 0-5, and c is 1-12.

[0007] This application includes at least the following beneficial effects: the first compound has good ion transport capability, which can improve the transport efficiency of lithium ions and / or sodium ions in the SEI film, which is conducive to promoting the rapid insertion and extraction of lithium ions and / or sodium ions during the charging and discharging process, thereby improving the fast charging performance of the battery.

[0008] In some embodiments, the first compound includes one or more of LiTiO2, LiZrO3, LiCrO2, LiFeO3, LiNiO4, LiCoO2, LiTaO3, LiNbO3, LiLaO5, NaTiO2, NaZrO3, NaCrO2, NaFeO3, NaNiO4, NaCoO2, NaTaO3, NaNbO3, NaLaO5, Na2LaO6, Li2CO3, and Na2CO3. Therefore, these first compounds can improve the transport efficiency of lithium ions and / or sodium ions in the SEI film, thereby further improving the fast-charging performance of the battery.

[0009] In some embodiments, the solid electrolyte interphase (SEI) membrane contains 0.2 wt% to 2 wt% of the M2 element, based on the total mass of the elements contained in the SEI membrane. Therefore, by controlling the content of the M2 element in the SEI membrane, the transport capacity of lithium ions and / or sodium ions in the SEI membrane is improved, thereby enhancing the fast-charging performance of the battery.

[0010] In some embodiments, the solid electrolyte interphase (SEI) membrane contains 0.5 wt% to 1.5 wt% of the M2 element, based on the total mass of the elements contained in the SEI membrane. This further enhances the transport capacity of lithium ions and / or sodium ions in the SEI membrane, thereby further improving the fast-charging performance of the battery.

[0011] In some embodiments, the negative electrode further includes a coating layer located between the negative electrode active material layer and the solid electrolyte membrane, the coating layer comprising a second compound satisfying the chemical formula M. 2d X e Where d is 1-4 and e is 1-6. Thus, the coating can further isolate the negative electrode active material layer and the electrolyte, thereby further reducing electrolyte decomposition and active lithium consumption caused by direct contact between the two, so as to further improve the battery's storage performance and cycle performance.

[0012] In some embodiments, the second compound includes one or more of TiO2, TiC, ZrO2, ZrC, Cr2O3, Cr3C2, Fe2O3, Fe3O4, Fe3C, Ni2O3, Ni2C, Co3O4, Co2C, Ta2O5, Ta2C, Nb2O5, NbC, La2O3, and LaC2. Therefore, these second compounds can further improve battery performance.

[0013] In some embodiments, the coating thickness is 5 nm to 30 nm. Therefore, selecting an appropriate coating thickness aims to balance coating durability with battery storage performance and cycle performance.

[0014] In some embodiments, the coating thickness is 7nm-20nm. This allows for a further balance between coating durability and battery storage and cycle performance.

[0015] In some embodiments, the negative electrode active material layer includes a first portion and a second portion stacked together; the first portion is located on the side closer to the negative electrode current collector, and the second portion is located on the side closer to the coating layer, the second portion including the second compound. Thus, the second compound can further prevent direct contact between the electrolyte and the active sites of the negative electrode active material layer, further reducing side reactions between the electrolyte and the main or auxiliary materials, thereby further improving the battery's storage performance and cycle performance.

[0016] In some embodiments, the thickness of the second portion is 0.2 μm-1.5 μm. Therefore, controlling the thickness of the second portion is beneficial for obtaining better battery kinetic performance, and can further improve the battery's storage performance and cycle performance.

[0017] In some embodiments, the second portion contains 0.02 wt% to 0.5 wt% of the second compound, based on the total mass of the elements contained in the second portion. Therefore, by controlling the content of the second compound in the negative electrode active material layer, it is beneficial to obtain better battery kinetic performance, and the battery's storage and cycle performance can be further improved.

[0018] In some embodiments, the thickness of the negative electrode active material layer is 50 μm-90 μm. This optimizes the performance of the secondary battery.

[0019] In a second aspect, this application provides a method for preparing a negative electrode sheet for a secondary battery, comprising: forming a negative electrode sheet comprising a negative electrode active material layer on at least one side of a negative electrode current collector; and forming a coating layer on the side of the negative electrode active material layer away from the negative electrode current collector by a vapor deposition method, the coating layer comprising a second compound satisfying the chemical formula M 2d X e Among them, M2 element includes one or more of titanium, zirconium, chromium, iron, nickel, cobalt, tantalum, niobium, and lanthanum; X includes one or two of oxygen and carbon; d is 1-4; and e is 1-6.

[0020] In some embodiments, the vapor deposition method includes one or more of electron beam evaporation, magnetron sputtering, vacuum evaporation, and atomic layer deposition. Therefore, by selecting a suitable vapor deposition method, the second compound can be adhered to the surface of the negative electrode active material layer to form a coating.

[0021] In some embodiments, the electron beam evaporation method satisfies one or more of the following conditions: the vacuum degree of the electron beam evaporation method is 1.5 × 10⁻⁶. -1 Pa -2.5×10 -1 Pa; the operating current of the electron beam evaporation method is 300mA-500mA; the evaporation time of the electron beam evaporation method is 10s-100s. Therefore, by controlling the vacuum degree, operating current, and evaporation time of the electron beam evaporation method to suitable conditions, the thickness of the coating and the depth of the second compound penetrating into the negative electrode active material layer, i.e., the thickness of the second part, can be controlled.

[0022] In some embodiments, the electron beam evaporation method satisfies one or more of the following conditions: the vacuum degree of the electron beam evaporation method is 1.8 × 10⁻⁶. -1 Pa -2.3×10 -1 Pa; the operating current of the electron beam evaporation method is 400mA-450mA; the evaporation time of the electron beam evaporation method is 30s-70s. Therefore, the thickness of the coating and the thickness of the second part can be further controlled.

[0023] In some embodiments, before forming a coating on the side of the negative electrode active material layer away from the negative electrode current collector by vapor deposition, the process further includes pre-treating the negative electrode active material layer to obtain a pre-treated negative electrode active material layer. This removes surface impurities from the negative electrode active material layer, thereby increasing its surface roughness.

[0024] In some embodiments, the pretreatment includes plasma treatment. Plasma treatment can thus increase the surface roughness of the negative electrode active material layer.

[0025] In some embodiments, the plasma treatment satisfies one or more of the following conditions: the plasma treatment further includes introducing a carrier gas, the carrier gas including one or more of O2, N2, CO2, and NH3; the vacuum degree of the plasma treatment is less than or equal to 1 × 10⁻⁶. -3 Pa; the discharge power of the plasma treatment is 100W-1200W; the gas flow rate of the plasma treatment is 100mL / min-1000mL / min; the treatment time of the plasma treatment is 1min-20min. Therefore, it is necessary to control the carrier gas, vacuum degree, discharge power, gas flow rate, and treatment time of the plasma treatment to suitable conditions in order to control the roughness of the negative electrode active material layer to an appropriate level. This can improve the adhesion between the negative electrode active material layer and the coating while maintaining the uniformity of the SEI film.

[0026] In some embodiments, the plasma treatment satisfies one or more of the following conditions: the vacuum degree of the plasma treatment is 5 × 10⁻⁶. -4 Pa-1×10 -3 Pa; the discharge power of the plasma treatment is 200W-1000W; the gas flow rate of the plasma treatment is 200mL / min-800mL / min; the treatment time of the plasma treatment is 2min-10min. This allows for further control of the roughness of the negative electrode active material layer.

[0027] In some embodiments, the pretreated negative electrode active material layer satisfies one or more of the following conditions: the roughness of the pretreated negative electrode active material layer is 50 nm-200 nm; the surface of the pretreated negative electrode active material layer has active groups. This increases the adhesion between the negative electrode active material layer and the coating.

[0028] In some embodiments, the active groups include one or more of -OH, -NH2, -COOH, -C=O, and -SO3H. Therefore, by selecting different carrier gases, the surface of the pretreated negative electrode active material layer can have different active groups.

[0029] In a third aspect, this application provides a battery module, including the secondary battery of the first aspect of this application, or a secondary battery having a negative electrode sheet obtained by the preparation method of the second aspect of this application. Thus, the battery possesses all the features and advantages of the aforementioned negative electrode sheet, which will not be repeated here.

[0030] In a fourth aspect, this application provides a battery pack that includes the battery module of the third aspect of this application.

[0031] In a fifth aspect, this application provides an electrical device comprising one or more of the following: a secondary battery selected from the first aspect of this application, a secondary battery having a negative electrode sheet obtained using the preparation method of the second aspect of this application, a battery module of the third aspect of this application, and a battery pack of the fourth aspect of this application. Thus, the battery possesses all the features and advantages of the aforementioned negative electrode sheet, which will not be elaborated further here. Attached Figure Description

[0032] Figure 1 is a scanning electron microscope (SEM) image of the negative electrode sheet in Example 1. In Figure 1, (a) is a scanning electron microscope image of the negative electrode sheet, (b) is a Ti element distribution map at the corresponding position in (a), and (c) is an O element distribution map at the corresponding position in (a).

[0033] Figure 2 is an XPS analysis diagram of Ti element in the negative electrode sheet of Example 1.

[0034] Figure 3 is an XPS analysis diagram of the negative electrode sheet of the battery cell after formation in Example 1 and Comparative Example 1. In Figure 3(a), the chemical state change diagram of Ti element is shown, and in Figure 3(b), the chemical state change diagram of C element is shown.

[0035] Figure 4 is a schematic diagram of a secondary battery according to an embodiment of this application.

[0036] Figure 5 is an exploded view of the secondary battery according to one embodiment of this application, as shown in Figure 4.

[0037] Figure 6 is a schematic diagram of a battery module according to one embodiment of this application.

[0038] Figure 7 is a schematic diagram of a battery pack according to one embodiment of this application.

[0039] Figure 8 is an exploded view of a battery pack according to an embodiment of this application, as shown in Figure 7.

[0040] Figure 9 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of this application.

[0041] Figure 10 shows the electrochemical impedance spectroscopy (EIS) spectra of Example 1 and Comparative Example 1.

[0042] Figure 11 is a DC impedance (DCR) diagram for Example 1 and Comparative Example 1.

[0043] Figure 12 is a graph showing the SOC versus the scaling factor for Example 1 and Comparative Example 1.

[0044] Explanation of reference numerals in the attached diagram: 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0045] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the secondary battery, method for preparing the negative electrode sheet, battery module, battery pack, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0046] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0048] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0049] Unless otherwise specified, all steps in this 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 it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0050] The charging speed of rechargeable batteries is crucial for improving user experience, especially in the electric vehicle sector, where the demand for fast charging is increasingly urgent as the driving range of electric vehicles increases. Therefore, there is a pressing need to improve the fast-charging performance of rechargeable batteries.

[0051] To improve the charging speed of rechargeable batteries, carbon coating technology can be employed, such as using pitch-based soft carbon to coat graphite, increasing the interlayer spacing to provide channels for rapid lithium-ion insertion and extraction; heteroatom doping technology, such as nitrogen doping of graphite to form CN bonds, can improve the conductivity of the graphite carbon layer and expand the interlayer spacing; granulation technology, such as reducing the particle size of graphite to increase the contact area between active materials and improve the connectivity of the conductive network; and graphite end-face structure adjustment technology, such as increasing the proportion of graphite end faces to improve the lithium-ion insertion and extraction rate. However, all of the above methods involve modification at the powder level of the negative electrode active material, which usually involves adjusting the slurry formulation and optimizing process parameters, increasing the complexity of mass production processes. Therefore, how to improve the fast-charging performance of rechargeable batteries is an urgent problem to be solved.

[0052] Based on this, this application proposes a secondary battery, including a negative electrode sheet, the negative electrode sheet comprising: a negative electrode current collector; a negative electrode active material layer, the negative electrode active material layer being located on at least one side of the negative electrode current collector; a solid electrolyte interface (SEI) film, the solid electrolyte interface film being located on the side of the negative electrode active material layer away from the negative electrode current collector; the solid electrolyte interface film comprising a first compound, the first compound satisfying the chemical formula M 1a M 2b X c Among them, M1 element includes one or two of lithium and sodium elements, M2 element includes one or more of titanium, zirconium, chromium, iron, nickel, cobalt, tantalum, niobium and lanthanum elements, X includes one or two of oxygen and carbon elements, a is 1-4, b is 0-5, and c is 1-12.

[0053] For secondary batteries, lithium ions and / or sodium ions diffuse within the electrode material and electrolyte to complete the charging and discharging process. The ion diffusion coefficient can directly reflect the ease with which lithium ions and / or sodium ions are transported in the various components of the battery. That is, the larger the ion diffusion coefficient, the faster the ions diffuse in the material and the stronger the transport capability.

[0054] Commonly used methods for testing ion diffusion coefficients include the neutron method, girder-current intermittent titration (GITT), potentiostat-intermittent titration (PITT), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), pulsed current relaxation (CPR), potential step chronoamperometry (PSCA), and potential relaxation (PRT). Taking LiTiO2 as an example, the ion diffusion coefficient of LiTiO2 measured by the neutron method is approximately 10. -6 cm 2 / S, thus, the first compound has good ion transport capability, which can improve the transport efficiency of lithium ions and / or sodium ions in the SEI film, which is conducive to promoting the rapid insertion and extraction of lithium ions and / or sodium ions during the charging and discharging process, thereby improving the fast charging performance of the battery.

[0055] Meanwhile, solid electrolyte interface membranes can also be used to isolate the electrolyte and the negative electrode active material layer, thereby reducing electrolyte decomposition and active lithium consumption caused by direct contact between the two, so as to improve the battery's storage performance and cycle performance.

[0056] In some embodiments, the first compound includes one or more of LiTiO2, LiZrO3, LiCrO2, LiFeO3, LiNiO4, LiCoO2, LiTaO3, LiNbO3, LiLaO5, NaTiO2, NaZrO3, NaCrO2, NaFeO3, NaNiO4, NaCoO2, NaTaO3, NaNbO3, NaLaO5, Na2LaO6, Li2CO3, and Na2CO3. Therefore, these first compounds can improve the transport efficiency of lithium ions and / or sodium ions in the SEI film, thereby further improving the fast-charging performance of the battery.

[0057] In some embodiments, the solid electrolyte interphase (SEI) membrane contains 0.2 wt% to 2 wt% M2 element, based on the total mass of elements contained in the SEI membrane. The first compound can promote the rapid insertion and extraction of lithium ions and / or sodium ions during charging and discharging. However, if the M2 element content in the SEI membrane is too high, it will increase the interfacial impedance in the cell, thus affecting the transport capacity of lithium ions and / or sodium ions. Therefore, by controlling the M2 element content in the SEI membrane, the transport capacity of lithium ions and / or sodium ions in the SEI membrane can be improved, thereby improving the fast-charging performance of the battery.

[0058] In this application, the negative electrode of the formed battery cell is disassembled and subjected to X-ray photoelectron spectroscopy (XPS) testing. XPS testing is a surface analysis technique that obtains qualitative and quantitative information about the elements on the material surface by measuring the energy distribution of photoelectrons emitted when X-rays excite the sample surface, including the type, content, chemical state, and electronic state of the elements.

[0059] As an example, based on the total mass of elements contained in the solid electrolyte interface membrane, the solid electrolyte interface membrane contains 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, or 2.0wt% of element M2.

[0060] In other embodiments, the solid electrolyte interface membrane contains 0.5wt%-1.5wt% of M2 element, based on the total mass of elements contained in the solid electrolyte interface membrane.

[0061] In some embodiments, the negative electrode further includes a coating layer located between the negative electrode active material layer and the solid electrolyte membrane. The coating layer includes a second compound satisfying the chemical formula M. 2d X e Where d is 1-4 and e is 1-6. Thus, the coating can further isolate the negative electrode active material layer and the electrolyte, thereby further reducing electrolyte decomposition and active lithium consumption caused by direct contact between the two, so as to further improve the battery's storage performance and cycle performance.

[0062] Meanwhile, taking TiO2 as the second compound as an example, TiO2, as a high dielectric constant material, can reduce the energy transport barrier of lithium ions and / or sodium ions at the interface, improve the reaction kinetics of the cell, and further improve the storage performance and cycle performance of the battery.

[0063] In some embodiments, the second compound includes one or more of TiO2, TiC, ZrO2, ZrC, Cr2O3, Cr3C2, Fe2O3, Fe3O4, Fe3C, Ni2O3, Ni2C, Co3O4, Co2C, Ta2O5, Ta2C, Nb2O5, NbC, La2O3, and LaC2. Therefore, these second compounds can further improve the battery's storage and cycle performance.

[0064] In some implementations, the coating thickness is 5nm-30nm. If the coating thickness exceeds 30nm, the transport path of lithium ions and / or sodium ions becomes longer, leading to increased internal resistance of the battery; when the coating thickness is less than 5nm, the coating is prone to damage during charging and discharging. A coating thickness within 30nm is beneficial for achieving better battery kinetic performance, thereby improving the battery's storage and cycle performance. Therefore, selecting an appropriate coating thickness aims to balance coating durability with battery storage and cycle performance.

[0065] As an example, the thickness of the coating can be 5nm, 10nm, 15nm, 20nm, 25nm, or 30nm. In some other embodiments of this application, the thickness of the coating is 7nm-20nm.

[0066] In this application, the thickness of the coating can be obtained by focusing ion beam transmission electron microscopy (FIB-TEM). Specifically, before battery formation, the surface and side of the negative electrode sheet are thinned and sliced ​​using a dual-beam electron microscope (FIB, model: Thermo Fisher-Scios2 HiVac). Then, the surface film layer of the thinned sample is observed using a TEM microscope (model: Thermo Scientific-Talos F200S G2). n test sites are selected, and the average thickness of the n test sites is measured and calculated to obtain the thickness of the coating.

[0067] In some embodiments, the area of ​​the coating is greater than or equal to the area of ​​the negative electrode active material layer. Therefore, the coating can further isolate the negative electrode active material layer from the electrolyte.

[0068] In some embodiments, the negative electrode active material layer includes a first portion and a second portion stacked together; the first portion is located on the side closer to the negative electrode current collector, and the second portion is located on the side closer to the coating layer, the second portion including a second compound.

[0069] The negative electrode active material on the surface of the negative electrode sheet is damaged by the cold pressing process. Simultaneously, the negative electrode sheet surface comes into contact with more air, resulting in numerous defects or active sites. In the initial stage of SEI film formation, due to the SEI film's lack of density, some electrolyte may contact the active sites of the negative electrode active material layer. The second compound can further prevent direct contact between the electrolyte and the active sites of the negative electrode active material layer, further reducing side reactions between the electrolyte and the main or auxiliary materials, thereby further improving the battery's storage and cycle performance.

[0070] In some embodiments, the thickness of the second portion is 0.2 μm to 1.5 μm. Therefore, controlling the thickness of the second portion is beneficial for obtaining better battery kinetic performance, and can further improve the battery's storage performance and cycle performance.

[0071] As an example, the thickness of the second part can be 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.2μm, 1.3μm, 1.4μm or 1.5μm.

[0072] In this application, prior to battery formation, elemental analysis of the negative electrode sheet is performed using argon ion polishing technology-scanning electron microscopy (CP elemental surface scan analysis). Specifically, the depth of the negative electrode sheet containing the M2 element is determined by CP elemental surface scan analysis, and the thickness of the coating obtained above is subtracted to obtain the thickness of the second part.

[0073] In some embodiments, the second part contains 0.02 wt% to 0.5 wt% of a second compound, based on the total mass of the elements contained in the second part. If the content of the second compound in the negative electrode active material layer is too high, it will lead to an increase in the interfacial impedance of the cell, affecting the battery's kinetic performance. Therefore, by controlling the content of the second compound in the negative electrode active material layer, it is beneficial to obtain better battery kinetic performance, and further improve the battery's storage performance and cycle performance. In this application, the content of the second compound can be obtained by X-ray photoelectron spectroscopy (XPS).

[0074] As an example, based on the total mass of the elements contained in the second part, the second part may contain 0.02wt%, 0.04wt%, 0.06wt%, 0.08wt%, 0.10wt%, 0.12wt%, 0.14wt%, 0.16wt%, 0.18wt%, 0.20wt%, 0.22wt%, 0.24wt%, 0.26wt%, 0.28wt%, 0.30wt%, 0.32wt%, 0.34wt%, 0.36wt%, 0.38wt%, 0.40wt%, 0.42wt%, 0.44wt%, 0.46wt%, 0.48wt%, or 0.50wt% of a second compound.

[0075] In some embodiments, the thickness of the negative electrode active material layer is 50 μm-90 μm. This optimizes the performance of the secondary battery. In this application, the thickness of the negative electrode active material layer is measured using a micrometer. As an example, the thickness of the negative electrode active material layer can be 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, or 90 μm.

[0076] In some embodiments, the bond strength between the coating and the negative electrode active material layer is 8 MPa-20 MPa.

[0077] In this application, the bonding strength between the coating and the negative electrode active material layer refers to the bonding ability between the coating and the negative electrode active material layer. During the charging and discharging process of the battery, this bonding ability can make the coating firmly adhere to the surface of the negative electrode active material layer, thereby reducing the peeling of the coating.

[0078] In this application, the bonding strength can be tested using a nanoindentation test method. Specifically, a certain pressure is applied to the surface of the film layer using an indenter of a specific shape and size, causing deformation of the film layer and the graphite electrode sheet. By measuring parameters such as the size and shape of the indentation and the residual deformation after unloading, and combining them with the corresponding mechanical model, the mechanical properties of the film layer, such as hardness and elastic modulus, are calculated, thereby evaluating the bonding ability between the coating and the negative electrode active material layer.

[0079] As an example, the bonding strength between the coating and the negative electrode active material layer can be 10MPa, 11MPa, 12MPa, 13MPa, 14MPa, 15MPa, 16MPa, 17MPa, 18MPa, 19MPa, 20MPa, 21MPa, 22MPa, 23MPa, 24MPa or 25MPa.

[0080] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0081] In some embodiments, the negative electrode active material layer includes a negative electrode active material, which may be a negative electrode active material known in the art for use in batteries.

[0082] In some embodiments, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. As an example, the silicon-based material may be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0083] Furthermore, the negative electrode active material includes artificial graphite and / or natural graphite.

[0084] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder may be selected from one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0085] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0086] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0087] In some embodiments, the secondary battery proposed in this application further includes a positive electrode, an electrolyte, and a separator. During the charging and discharging process, active ions repeatedly insert and extract between the positive and negative electrode. The electrolyte acts as a conductor of ions between the positive and negative electrode. The separator, disposed between the positive and negative electrode, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0088] [Positive electrode plate]

[0089] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0090] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0091] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0092] In some embodiments, when the battery is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries.

[0093] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include one or more of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials 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 include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 One or more of the following: O2) and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0094] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before material addition. After charge-discharge cycles, the molar Li content changes when the positive electrode active material is applied to the battery system.

[0095] In the examples of positive electrode active materials for lithium-ion batteries in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0096] In some embodiments, when the battery is a sodium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for sodium-ion batteries.

[0097] As an example, the positive electrode active material may include one or more of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue sodium compounds, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. The modified compounds of the above materials may be for doping modification and / or surface coating modification of the materials.

[0098] In some embodiments, the transition metal in the sodium transition metal oxide can be one or more selected from Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, and Cu. The chemical formula of the sodium transition metal oxide can satisfy Na x MO2, wherein M includes one or more of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, and Cu, and 0 < x ≤ 1.

[0099] In some embodiments, the polyanionic compound may be a sodium ion, a transition metal ion, or a tetrahedral (YO4) compound. n- A class of compounds with anionic units. The transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include one or more of P, S, and Si; n represents (YO4). n- The price state.

[0100] In some embodiments, the polyanionic compound may also have sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds containing anionic units and halide anions. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include one or more of P, S, and Si, where n represents (YO4). n- The valence state of halogens can include one or more of F, Cl, and Br.

[0101] In some embodiments, the polyanionic compound may also be a tetrahedral compound containing sodium ions (YO4). n- Anionic unit, polyhedral unit (ZO) y) m+ And a class of compounds with optional halide anions. M may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may include one or more of P, S, and Si, and n represents (YO4). n- The valence state, Z represents transition metal, m represents (ZO) y ) m+ The valence state of halogens can include one or more of F, Cl, and Br.

[0102] As an example, polyanionic compounds can satisfy the chemical formulas NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2 (P2O7), NaM'PO4F (M' includes one or more of V, Fe, Mn and Ni), and Na3(VO4) y )2(PO4)2F 3-2y One or more of (0≤y≤1).

[0103] In some embodiments, Prussian blue compounds may contain sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds. Transition metals can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce.

[0104] As an example, Prussian blue compounds can satisfy the chemical formula Na a Me b Me' c (CN)6, wherein Me and Me' each independently include one or more of Ni, Cu, Fe, Mn, Co, and Zn, 0 < a ≤ 2, 0 < b < 1, and 0 < c < 1.

[0105] During the charging and discharging process of a battery, sodium (Na) undergoes insertion / extraction and consumption, resulting in varying molar Na content at different discharge states. In the examples of positive electrode active materials in this application, the molar Na content refers to the initial state of the material, i.e., the state before material addition. After charge-discharge cycles, the molar Na content changes when the positive electrode active material is applied to the battery system.

[0106] In the enumeration of positive electrode active materials for sodium-ion batteries in this application, the molar content of O is only a theoretical state value. The release of oxygen from the crystal lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0107] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0108] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0109] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0110] [Electrolytes]

[0111] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0112] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0113] In some embodiments, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0114] In some embodiments, the solvent may be selected from one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0115] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0116] [Isolation membrane]

[0117] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0118] In some embodiments, the material of the separator can be selected from one or more of glass fiber, nonwoven 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.

[0119] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0120] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0121] 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. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0122] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 shows a square-structured secondary battery 5 as an example.

[0123] In some embodiments, referring to FIG5, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0124] In a second aspect, this application provides a method for preparing a negative electrode sheet for a secondary battery, specifically comprising:

[0125] S100, A negative electrode sheet containing a negative electrode active material layer is formed on at least one side of the negative electrode current collector.

[0126] In some embodiments, the negative electrode active material, conductive agent, binder and any other components are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry; the negative electrode slurry is coated onto a negative electrode current collector, and after drying, cold pressing and other processes, a negative electrode active material layer is formed on the surface of the negative electrode current collector, thus obtaining the initial electrode sheet.

[0127] In some embodiments, the negative electrode active material layer is pretreated to obtain a pretreated negative electrode active material layer. This removes surface impurities from the negative electrode active material layer, thereby increasing its surface roughness.

[0128] In some implementations, pretreatment includes plasma treatment. Plasma treatment is a dry processing technique in which the plasma medium contains ions, electrons, neutrons, photons, free radicals, metastable excited particles, and molecules. Under the action of an electromagnetic field, these particles diffuse into the material surface in a gradient manner, resulting in surface activation, grafting of chemical structures and functional groups, and material volatilization and removal. This alters the chemical structure and morphology of the material surface, thereby improving the surface properties of the material.

[0129] In some embodiments, the plasma treatment satisfies one or more of the following conditions: the plasma treatment further includes the introduction of a carrier gas, said carrier gas including one or more of O2, N2, CO2, and NH3; the vacuum degree of the plasma treatment is less than or equal to 1 × 10⁻⁶. -3 Pa; the discharge power of the plasma treatment is 100W-1200W; the gas flow rate of the plasma treatment is 100mL / min-1000mL / min; the treatment time of the plasma treatment is 1min-20min.

[0130] During plasma treatment, plasma impacts the surface of the negative electrode active material layer, increasing its surface roughness. Simultaneously, active groups are introduced onto the surface of the negative electrode active material layer via a carrier gas. These active groups can then bond with the second compound and the solid electrolyte interphase (SEI) film. The increased roughness and the introduced active groups result in a tighter adhesion of the coating to the negative electrode active material layer surface, thus enhancing the bonding strength. This increased adhesion helps reduce coating peeling during battery use. However, excessive plasma treatment can lead to excessively high surface roughness of the negative electrode active material layer, resulting in an uneven surface and affecting the uniformity of the SEI film formation.

[0131] Therefore, it is necessary to control the carrier gas, vacuum degree, discharge power, gas flow rate, and processing time of plasma treatment to suitable conditions in order to control the roughness of the negative electrode active material layer to a suitable size, thereby improving the adhesion between the negative electrode active material layer and the coating while maintaining the uniformity of the SEI film.

[0132] In addition, plasma treatment can slightly increase the depth of the second compound penetrating into the negative electrode active material, that is, it can increase the thickness of the second part, thereby further protecting the negative electrode active material layer.

[0133] As an example, the vacuum level for plasma processing can be 1×10⁻⁶. -5 Pa, 0.5×10 -4 Pa, 1×10 -4 Pa, 0.2×10 -3 Pa, 0.4×10 -3 Pa, 0.6×10 -3 Pa, 0.8×10 -3 Pa or 1×10 -3 Pa.

[0134] As an example, the discharge power of plasma treatment can be 100W, 300W, 500W, 700W, 900W, or 1200W.

[0135] As an example, the gas flow rate for plasma treatment can be 100 mL / min, 200 mL / min, 400 mL / min, 600 mL / min, 800 mL / min, or 1000 mL / min.

[0136] As an example, the plasma treatment time can be 1 min, 5 min, 10 min, 15 min, or 20 min.

[0137] In other embodiments of this application, the plasma treatment satisfies one or more of the following conditions: the vacuum degree of the plasma treatment is 5 × 10⁻⁶. -4 Pa-1×10 -3 Pa; the discharge power of plasma treatment is 200W-1000W; the gas flow rate of plasma treatment is 200mL / min-800mL / min; the treatment time of plasma treatment is 2min-10min.

[0138] In some embodiments, the roughness of the pretreated negative electrode active material layer is 50 nm–200 nm. The roughness can be obtained by AFM atomic force microscopy. This increases the adhesion between the negative electrode active material layer and the coating.

[0139] As an example, the roughness of the pretreated negative electrode active material layer can be 50nm, 70nm, 90nm, 110nm, 130nm, 150nm, 170nm, 190nm or 200nm.

[0140] In some embodiments, the surface of the pretreated negative electrode active material layer has active groups. Therefore, plasma treatment of the carrier gas can transfer the corresponding active groups to the surface of the negative electrode active material layer.

[0141] In some embodiments, the active groups include one or more of -OH, -NH2, -COOH, -C=O, and -SO3H. Therefore, by selecting different carrier gases, the surface of the pretreated negative electrode active material layer can have different active groups. Taking TiO2 as an example, introducing active groups, such as unsaturated bonds like -OH and NH2, onto the surface of the negative electrode active material layer allows them to tightly bind with TiO2 molecules, forming -O:TiO2 and / or -N:TiO2 interface layers. This makes the coating adhere more tightly to the negative electrode active material layer, thereby improving the adhesion between the two.

[0142] S200. A coating layer is formed on the side of the negative electrode active material layer away from the negative electrode current collector by vapor deposition. The coating layer includes a second compound, which satisfies the chemical formula M. 2d X e Among them, M2 element includes one or more of titanium, zirconium, chromium, iron, nickel, cobalt, tantalum, niobium, and lanthanum; X includes one or more of oxygen and carbon; d is 1-4; and e is 1-6.

[0143] In some embodiments, the vapor deposition method includes one or more of electron beam evaporation, magnetron sputtering, vacuum evaporation, and atomic layer deposition. Therefore, by selecting a suitable vapor deposition method, the second compound can be adhered to the surface of the negative electrode active material layer to form a coating.

[0144] In some implementations, the electron beam evaporation method satisfies one or more of the following conditions: the vacuum level of the electron beam evaporation method is 1.5 × 10⁻⁶. -1 Pa -2.5×10 -1 Pa; the working current of electron beam evaporation is 300mA-500mA; the evaporation time of electron beam evaporation is 10s-100s.

[0145] Electron beam evaporation is a physical vapor deposition (PVD) technique that uses an electron gun to generate a high-energy electron beam. The electron gun includes a thermionic cathode (usually a heated tungsten filament) that emits electrons and an anode that accelerates the electrons. The electron beam strikes the target material, converting its energy into heat, heating the target material to its evaporation temperature. Atoms or molecules of the evaporated material fly to the substrate surface in a vacuum and condense, forming a coating. Therefore, by controlling the vacuum level, operating current, and evaporation time of electron beam evaporation to suitable conditions, the thickness of the coating and the depth to which the second compound penetrates the negative electrode active material layer, i.e., the thickness of the second part, can be controlled.

[0146] As an example, the vacuum level of electron beam evaporation can be 1.5 × 10⁻⁶. -1 Pa, 1.6 × 10 -1 Pa, 1.7××10 -1 Pa, 1.8××10 -1 Pa, 1.9 × 10 -1 Pa, 2.0×10 -1 Pa, 2.1×10 -1 Pa, 2.2×10 -1 Pa, 2.3×10 -1 Pa, 2.4 × 10 -1 Pa or 2.5 × 10 -1 Pa.

[0147] As an example, the operating current of the electron beam evaporation method can be 300mA, 320mA, 340mA, 360mA, 380mA, 400mA, 420mA, 440mA, 460mA, 480mA or 500mA.

[0148] As an example, the evaporation time for electron beam evaporation can be 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s, 60s, 65s, 70s, 75s, 80s, 85s, 90s, 95s, or 100s.

[0149] In other embodiments of this application, the electron beam evaporation method satisfies one or more of the following conditions: the vacuum degree of the electron beam evaporation method is 1.8 × 10⁻⁶. -1 Pa -2.3×10 -1 Pa; the working current of electron beam evaporation is 400mA-450mA; the evaporation time of electron beam evaporation is 30s-70s.

[0150] In a third aspect of this application, a battery module is provided, including the secondary battery of the first aspect of this application, or a secondary battery having a negative electrode sheet made using the method of the second aspect of this application.

[0151] In some implementations, the battery module may contain one or more secondary batteries, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0152] Figure 6 shows a battery module 4 as an example. Referring to Figure 6, in the battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple secondary batteries 5 can be fixed in place using fasteners.

[0153] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0154] In a fourth aspect, this application provides a battery pack that includes the battery module of the third aspect of this application.

[0155] In some implementations, the battery pack may contain one or more battery modules, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0156] Figures 7 and 8 show a battery pack 1 as an example. Referring to Figures 7 and 8, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0157] In a fifth aspect of this application, an electrical device is provided, comprising one or more of the following: a secondary battery selected from the first aspect of this application, a secondary battery having a negative electrode sheet manufactured using the method of the second aspect of this application, a battery module of the third aspect of this application, and a battery pack of the fourth aspect of this application.

[0158] Therefore, secondary batteries, battery modules, or battery packs can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices can include, but are not limited to, 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.

[0159] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0160] Figure 9 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0161] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0162] Example

[0163] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0164] Example 1

[0165] (1) Preparation of negative electrode sheet

[0166] S100: Artificial graphite (negative electrode active material), acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC-Na) (thickener) are thoroughly mixed in a deionized water solvent system at a weight ratio of 96.82:0.53:1.95:0.7. This mixture is then coated onto both surfaces of a 6 μm thick copper foil. After drying at 110°C for 20 min, it is cold-pressed to obtain an areal density of 10.71 mg / cm³. 2 The compacted density is 1.4 g / cm³. 3 The initial electrode sheet is a negative electrode current collector with a negative electrode active material layer and a thickness of 159 μm. The test results show that the porosity of the negative electrode active material layer in the initial electrode sheet is 40% and the roughness is 50 nm.

[0167] S200. Place the TiO2 source material in the crucible; cut the initial electrode into 40cm×40cm pieces, clean the initial electrode to remove surface impurities; place the initial electrode on the electron beam evaporation stage, start the vacuum pump, and evacuate the evaporation chamber to a vacuum level of 2×10⁻⁶. -1Pa; When the electron beam evaporation coating machine is turned on and the working current reaches 425mA, the focused electron beam strikes the source material in the crucible, converting its energy into heat energy, and heating the source material to the evaporation temperature; the evaporated material atoms or molecules fly to the surface of the initial electrode in the vacuum and condense to form a thin film, i.e., a coating; at the same time, TiO2 penetrates into the pores of the negative electrode active material layer to form the second part; after the predetermined evaporation time of 50s is reached, the power is turned off; the pressure in the evaporation chamber gradually returns to atmospheric pressure, and the initial electrode with the coating completed is taken out, which is the negative electrode used in this embodiment.

[0168] (2) Preparation of positive electrode sheet

[0169] Lithium iron phosphate (LiFePO4), carbon black (Super P), and polyvinylidene fluoride (PVDF) binder were thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) at a weight ratio of 97.2:0.7:2.1 to form a uniform positive electrode slurry. The positive electrode slurry was then coated onto both surfaces of an aluminum foil current collector. After drying, cold pressing, slitting, and cutting, the positive electrode sheet was obtained. The compacted density of the positive electrode sheet was 2.45 g / cm³. 3 Its surface density is 21.68 mg / cm³. 2 .

[0170] (3) Separating membrane

[0171] A 12μm thick polyethylene film was selected as the separator.

[0172] (4) Preparation of electrolyte

[0173] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1:1 to obtain a mixed solvent; lithium hexafluorophosphate (LiPF6) was dissolved in the above mixed solvent and stirred until homogeneous, with a molar concentration of 1 mol / L, to form an electrolyte.

[0174] (5) Battery manufacturing

[0175] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation, forming a battery cell. The bare cell is then placed in an outer package, filled with the prepared electrolyte, and sealed to obtain a secondary battery.

[0176] The difference between Comparative Example 1 and Example 1 is that the negative electrode sheet is not subjected to electron beam evaporation treatment.

[0177] The preparation methods of the batteries in Examples 2-23 are the same as those in Example 1, and the differences are detailed in Table 1.

[0178] Table 1

[0179] Example 24

[0180] The difference between Example 24 and Example 1 is that, before forming the TiO2 coating, the negative electrode active material layer is pretreated to obtain a pretreated initial electrode.

[0181] The pretreatment method is plasma treatment, specifically involving the following steps: cleaning the initial electrode to remove surface impurities; placing the cleaned initial electrode on the sample stage of the plasma reaction chamber; and starting the vacuum pump to evacuate the reaction chamber to a vacuum level of 0.75 × 10⁻⁶. -3 Pa; set the discharge power of the reaction chamber to 550W; after the reaction chamber produces glow, introduce carrier gas O2 at a flow rate of 450mL / min; after 6 minutes of plasma treatment, when the reaction chamber returns to normal pressure and there is no sound of air intake, the pretreated initial electrode can be removed.

[0182] The preparation methods of the batteries in Examples 25-48 are the same as those in Example 24, and the differences are detailed in Table 2.

[0183] Table 2

[0184] 1. Negative electrode structural parameter testing

[0185] (1) Coating thickness

[0186] The thickness of the coating can be obtained by focusing ion beam transmission electron microscopy (FIB-TEM). Specifically, before battery formation, the surface and sides of the electrode sample are thinned using a dual-beam electron microscope (FIB, model: Thermo Fisher-Scios 2HiVac). Then, the surface film of the thinned sample is observed using a TEM microscope (model: Thermo Scientific-Talos F200S G2). n test sites are selected, and the average thickness of the n test sites is measured and calculated to obtain the coating thickness.

[0187] (2) Thickness of the second part

[0188] Before battery formation, the electrode surface is analyzed using argon ion polishing technology-scanning electron microscopy (CP elemental surface scan analysis). Specifically, CP elemental surface scan analysis is used to determine the depth of the M2 element in the negative electrode. Subtracting the thickness of the coating layer gives the thickness of the second part.

[0189] (3) Roughness

[0190] Roughness was obtained through atomic force microscopy (AFM). Specifically, the tip scans the sample surface, and the surface morphology is obtained by measuring the change in the interaction force between the tip and the sample surface. The surface morphology is then reconstructed in three dimensions using software, and the surface roughness is calculated.

[0191] (4) Bond strength

[0192] The bonding strength can be tested using the nanoindentation test method. Specifically, a certain pressure is applied to the surface of the film layer using an indenter of a specific shape and size, causing deformation of the film layer and the graphite electrode sheet. By measuring parameters such as the size and shape of the indentation and the residual deformation after unloading, and combining them with the corresponding mechanical model, the mechanical properties of the film layer, such as hardness and elastic modulus, can be calculated, thereby evaluating the bonding ability between the coating and the negative electrode active material layer.

[0193] 2. Negative electrode plate composition detection

[0194] (1) CP element surface scan analysis

[0195] CP elemental surface scanning analysis refers to the process of analyzing the surface of an electrode using argon ion polishing (CP) combined with scanning electron microscopy (SEM). CP technology uses a high-energy argon ion beam to bombard the sample surface, removing a layer of material and exposing the internal structure, thus obtaining a smooth polished cross-section. Testing instrument: Zeiss Supra 55, reference standard GB / T 17359-2012.

[0196] CP elemental surface scan analysis was performed on the negative electrode sheet obtained in Example 1, referring to Figure 1. Figure 1(a) is a scanning electron microscope image of the negative electrode sheet. Energy-dispersive X-ray spectroscopy (EDS) surface scan was performed on the corresponding positions in Figure 1(a) to obtain the Ti element distribution map in Figure 1(b) and the O element distribution map in Figure 1(c). As can be seen from Figure 1(b) and Figure 1(c), Ti and O elements are enriched on the surface of the negative electrode sheet and dispersed inside the negative electrode sheet. Therefore, the negative electrode sheet of Example 1 has a coating containing titanium and oxygen elements on its surface, and the interior of the negative electrode sheet also contains titanium and oxygen elements.

[0197] (2) X-ray photoelectron spectroscopy (XPS) analysis

[0198] XPS testing is a surface analysis technique that uses X-ray photoelectron spectrometer (XPS) to measure the energy distribution of photoelectrons emitted when an X-ray excites the sample surface, thereby determining the elemental composition and relative concentration of elements. The instrument used is an Axis Supra / Supra+ X-ray photoelectron spectrometer, conforming to standard GB / T 33502-2017.

[0199] a. XPS analysis of the negative electrode plate

[0200] XPS analysis was performed on the negative electrode sheet of Example 1. The chemical state change diagram of Ti in Example 1 is shown in Figure 2. As shown in Figure 2, the TiO2 symmetric peaks are located at 458.2 eV and 464.2 eV. Therefore, the surface of the negative electrode sheet of Example 1 has a titanium-containing coating.

[0201] b. Perform XPS analysis on the negative electrode of the formed battery cell after disassembly.

[0202] After the cells of Example 1 and Comparative Example 1 were formed, the formed cells were disassembled to separate the negative electrode sheets, and XPS analysis was performed on the surface of the negative electrode sheets. Referring to Figure 3, the XPS patterns of Ti and C elements are shown in Figure (a) and Figure (b), respectively.

[0203] As shown in Figure 3(b), the CC peak is at 284.8 eV (used as a reference for charge correction), the CO peak is at 286 eV (representing organic CO), and the metal carbonate peak (representing inorganic matter) is between 288 eV and 290 eV. Therefore, comparing the peak areas of Example 1 and Comparative Example 1, it can be seen that the negative electrode sheet of the battery cell formed in Example 1 with the coating has a reduced organic content and an increased inorganic content. This is because TiO2 is a semiconductor and a high dielectric constant material, capable of conducting both electrons and lithium ions. Therefore, it can promote the formation of inorganic metal carbonates in the SEI, while simultaneously reducing the organic content.

[0204] In Figure 3(a), curve 1 represents Ti. 4+ The symmetrical peak of curve 2 is Ti. 3+ The symmetrical peaks are observed at 458.6 eV and 464.5 eV, respectively, representing Ti peaks. 4+ The peaks at 458 eV and 463.5 eV represent Ti. 3+ The peak indicates that the valence state of Ti changed during the cell formation process. The mechanism involved is that TiO2 is reduced to Ti at a low potential. 3+ Afterwards, with Li + The two electrodes combine to form LiTiO2. Ti can be detected on the surface of the formed negative electrode. 3+ The peak indicates the formation of LiTiO2. Furthermore, based on the total mass of elements contained in the solid electrolyte interface film, the solid electrolyte interface film contains 0.9 wt% titanium (M2).

[0205] 3. Battery performance testing

[0206] (1) Electrochemical impedance spectroscopy (EIS)

[0207] The testing method is as follows: The battery cell is fully discharged and then connected to the test fixture. An electrochemical workstation is used for testing, with a frequency range of 30 MHz to 500 kHz, a test temperature of 25°C, and a disturbance voltage of 5 mV. The test is started according to the set parameters, and the test data is obtained.

[0208] The ESI spectra of Example 1 and Comparative Example 1 are shown in Figure 10. Electrochemical impedance spectroscopy (EIS) is used to evaluate the fast-charging performance of batteries. Specifically, in the EIS spectra, the semicircle represents the charge transfer process at the electrode / electrolyte interface. The larger the diameter of the semicircle, the greater the resistance and the more difficult the charge transfer. Therefore, as shown in Figure 10, the semicircle of the cell in Example 1 is significantly smaller than that in Comparative Example 1, indicating that the lithium-ion transport rate at the negative electrode and electrolyte interface in Example 1 is faster than that in Comparative Example 1.

[0209] (2) DC resistance (DCR)

[0210] Test method: At 25℃, the battery is fully charged at 0.33C and discharged at 0.33C, and the capacity C0 is measured. Then, at 25℃, the battery is discharged at a rate of 0.33C to 90%, 70%, 50%, 20%, and 10% SOC. At each SOC, the battery is discharged and charged at a rate of 1C for 60 seconds. The voltage before discharge is marked as U0, the voltage after discharge is marked as U1, and the discharge rate of 1C is marked as I. The DC resistance DCR of the secondary battery at different SOCs is then calculated as (U0 - U1) / I.

[0211] Figure 11 shows the DCR diagrams for Example 1 and Comparative Example 1, specifically illustrating the effect of different SOCs on the discharge DC resistance (DCR). Fast charging performance is not only related to the charging process but also closely related to the discharging process. The negative DCR shift indicates that the battery's internal discharge resistance decreases under conditions of 90%, 70%, 50%, 20%, and 10% SOC, which helps to increase the discharge rate and thus affects fast charging performance. Therefore, the negative DCR shift in Example 1 indicates that the battery has lower internal discharge resistance under multiple SOC conditions, which helps to increase the discharge rate and thus improve fast charging performance; while the battery in Comparative Example 1 does not have a negative DCR shift, its discharge rate is relatively slow, and its fast charging performance is not as good as that of Example 1.

[0212] (3) Three-electrode test

[0213] Test method: At 25℃, the battery is charged to 3.65V at a rate of 0.33C, and then discharged to 2V at a rate of 0.33C. The measured discharge capacity is marked as C0. Then, lithium plating is performed at 25℃ using reference electrodes. For the positive electrode reference: the battery is charged at 0.00002A for 2 hours at 25℃; for the negative electrode reference: the battery is charged at 0.00002A for 2 hours at 25℃. The battery is then discharged to the initial voltage at a rate of 0.33C. Finally, the battery is charged to the cutoff voltage or the anode potential drops to 0V at rates of 0.5C, 0.8C, 1C, 2C, 2.5C, 3C, 3.5C, and 4C. The measured capacity is marked as Ci. The SOC is calculated as Ci / C0 × 100%, and the curve of SOC versus rate is obtained. The higher the curve, the better the fast charging performance.

[0214] Figure 12 shows the SOC versus rate curves for Example 1 and the comparative example. Compared to the curve of Comparative Example 1, the curve of Example 1 is higher, indicating that the fast charging performance of Example 1 is better than that of Comparative Example 1.

[0215] (4) Charging time

[0216] Points are selected based on the curves of SOC and magnification C. The multipliers corresponding to 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, and 80% are C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, and C15, respectively. The time t required to charge the battery cell to the same SOC is calculated using the formula: t = (60 / C1 + 60 / C2 + 60 / C3 + 60 / C4 + 60 / C5 + 60 / C6 + 60 / C7 + 60 / C8 + 60 / C9 + 60 / C10 + 60 / C11 + 60 / C12 + 60 / C13 + 60 / C14 + 60 / C15) × 0.05.

[0217] (5) Storage performance test

[0218] Test method: Allow to stand at a constant temperature of 25℃ for 5 minutes; charge at 0.33C0 to 3.65V, then charge at 3.65V to 0.05C0, allow to stand for 5 minutes; discharge at 0.33C to 2V, and record the capacitance at this point as C. z (The capacity of the cell after storage is the reversible capacity, marked as C) t(t is the storage time); charge at 0.33C0 to 3.65V, then charge at 3.65V constant voltage to 0.05C0, at which point the cell is fully charged; place the fully charged secondary battery in a 60℃ constant temperature environment and store for 30 days. Remove the cell and test according to the first step. Repeat the above operation until t = 180 days, then calculate the reversible capacity retention rate F, F = C t ÷C z ×100%.

[0219] (7) Cyclic performance test

[0220] Test method: At 60℃, the battery is charged at a constant current rate of 1C to the cutoff voltage of 3.65V, and then discharged at a rate of 1C to the cutoff voltage of 2V. The initial capacity is recorded as C0. After charging at a rate of 1C, the battery is discharged at a rate of 1C, and the discharge capacity C of each cycle is recorded. n Calculate the SOH value after each cycle. The formula for SOH is: SOH = C n / C0×100%. When the SOH value drops to 80%, record the number of cycles at this point. The more cycles, the longer the secondary battery maintains its healthy state and the longer its cycle life.

[0221] The test results of the negative electrode and battery in Examples 1-23 and Comparative Example 1 are shown in Table 3.

[0222] Table 3

[0223] The test results of the negative electrode and battery in Examples 24-48 are shown in Table 4.

[0224] Table 4

[0225] As shown in Tables 3 and 4, the batteries obtained in Examples 1 through 48 all exhibit short charging times, good storage life, and cycle life.

[0226] Examples 1-23 involve using electron beam evaporation to coat the surface of the negative electrode sheet. This coating, along with the SEI film, isolates the negative electrode sheet from the electrolyte, reducing the rate of battery aging and degradation, and extending the battery's storage and cycle life. Simultaneously, the first compound contained in the SEI film improves the ion transport efficiency within the SEI film, thereby shortening the battery's charging time. Further, as in Examples 24-48, plasma treatment is used to process the initial electrode sheet to improve the surface roughness of the negative electrode active material layer, facilitating the formation of the coating.

[0227] In contrast, Comparative Example 1, which did not undergo electron beam evaporation treatment, had a lower battery storage life and cycle life than Examples 1-48, and a longer charging time than Examples 1-48.

[0228] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

A secondary battery wherein, The negative electrode sheet includes: a negative electrode current collector; a negative electrode active material layer on at least one side of the negative electrode current collector; a solid-state electrolyte interface film on a side of the negative electrode active material layer away from the negative electrode current collector; The solid-state electrolyte interface film includes a first compound satisfying a chemical formula M 1a M 2b X c wherein the M1 element includes one or both of a lithium element and a sodium element, the M2 element includes one or more of a titanium element, a zirconium element, a chromium element, an iron element, a nickel element, a cobalt element, a tantalum element, a niobium element, and a lanthanum element, X includes one or both of an oxygen element and a carbon element, a is 1-4, b is 0-5, and c is 1-12. The secondary battery according to claim 1, wherein The first compound includes one or more of LiTiO2, LiZrO3, LiCrO2, LiFeO3, LiNiO4, LiCoO2, LiTaO3, LiNbO3, LiLaO5, NaTiO2, NaZrO3, NaCrO2, NaFeO3, NaNiO4, NaCoO2, NaTaO3, NaNbO3, NaLaO5, Na2LaO6, Li2CO3, Na2CO3. The secondary battery according to any one of claims 1-2, wherein The solid-state electrolyte interface film contains 0.2wt%-2wt% of the M2 element based on the total mass of elements contained in the solid-state electrolyte interface film. The secondary battery according to claim 3, wherein The solid-state electrolyte interface film contains 0.5wt%-1.5wt% of the M2 element based on the total mass of elements contained in the solid-state electrolyte interface film. The secondary battery according to any one of claims 1 to 4, wherein The negative electrode sheet further includes a coating layer between the negative electrode active material layer and the solid electrolyte film, the coating layer including a second compound satisfying a chemical formula M 2d X e ; wherein d is 1-4 and e is 1-6. The secondary battery according to claim 5, wherein The second compound includes one or more of TiO2, TiC, ZrO2, ZrC, Cr2O3, Cr3C2, Fe2O3, Fe3O4, Fe3C, Ni2O3, Ni2C, Co3O4, Co2C, Ta2O5, Ta2C, Nb2O5, NbC, La2O3, LaC2. The secondary battery according to any one of claims 5-6, wherein The thickness of the coating layer is 5nm-30nm. Optionally, the thickness of the coating layer is 7nm-20nm. The secondary battery according to any one of claims 5 to 7, wherein The negative electrode active material layer includes a first part and a second part arranged in a stack; the first part is located on a side close to the negative electrode current collector, and the second part is located on a side close to the coating layer, and the second part includes the second compound. The secondary battery according to claim 8, wherein The thickness of the second part is 0.2μm-1.5μm. The secondary battery according to any one of claims 8-9, wherein The second part contains 0.02wt%-0.5wt% of the second compound based on the total mass of elements contained in the second part. The secondary battery according to any one of claims 1 to 10, wherein The thickness of the negative electrode active material layer is 50μm-90μm. A method of manufacturing a negative electrode sheet for a secondary battery, wherein The negative electrode sheet includes: forming a negative electrode sheet including a negative electrode active material layer on at least one side of a negative electrode current collector; A coating layer is formed by a vapor deposition method on a side of the negative electrode active material layer distal from the negative electrode current collector, the coating layer including a second compound, the second compound satisfying the chemical formula M 2d X e ; wherein the M2 element includes one or more of a titanium element, a zirconium element, a chromium element, an iron element, a nickel element, a cobalt element, a tantalum element, a niobium element, and a lanthanum element, X includes one or both of an oxygen element and a carbon element, d is 1-4, and e is 1-6. The method of claim 12, wherein, The vapor deposition method includes one or more of an electron beam evaporation method, a magnetron sputtering method, a vacuum evaporation method, and an atomic layer deposition method. The method of claim 13, wherein, The electron beam evaporation method satisfies one or more of the following conditions: The vacuum degree of the electron beam evaporation method is 1.5 x 10 -1 Pa-2.5 x 10 -1 Pa; The working current of the electron beam evaporation method is 300mA-500mA. The evaporation time of the electron beam evaporation method is 10s-100s. The method of claim 14, wherein, The electron beam evaporation method satisfies one or more of the following conditions: The vacuum degree of the electron beam evaporation method is 1.8 x 10 -1 Pa-2.3 x 10 -1 Pa; The working current of the electron beam evaporation method is 400mA-450mA. The evaporation time of the electron beam evaporation method is 30 s-70 s. The method according to any one of claims 12-15, wherein Before the coating layer is formed on the side of the negative electrode active material layer away from the negative electrode current collector by the vapor deposition method, the method further comprises: pretreating the negative electrode active material layer to obtain a pretreated negative electrode active material layer. The method of claim 16, wherein, The pretreatment comprises plasma treatment. The method of claim 17, wherein, The plasma treatment satisfies one or more of the following conditions: The plasma treatment further comprises introducing a carrier gas, the carrier gas comprising one or more of O2, N2, CO2, NH3; The vacuum degree of the plasma treatment is less than or equal to 1 x 10 -3 Pa; The discharge power of the plasma treatment is 100 W-1200 W; The gas flow of the plasma treatment is 100 mL / min-1000 mL / min; The treatment time of the plasma treatment is 1 min-20 min. The method of claim 18, wherein, The plasma treatment satisfies one or more of the following conditions: The vacuum degree of the plasma treatment is 5x10 -4 Pa-1x10 -3 Pa; The discharge power of the plasma treatment is 200 W-1000 W; The gas flow of the plasma treatment is 200 mL / min-800 mL / min; The treatment time of the plasma treatment is 2 min-10 min. The method according to any one of claims 16-19, wherein The pretreated negative electrode active material layer satisfies one or more of the following conditions: The roughness of the pretreated negative electrode active material layer is 50 nm-200 nm; The surface of the pretreated negative electrode active material layer has active groups. The method of claim 20, wherein, The active groups comprise one or more of -OH, -NH2, -COOH, -C=O, -SO3H. A battery module, wherein, The secondary battery comprising the negative electrode active material layer of any one of claims 1-11, or the secondary battery comprising the negative electrode sheet prepared by the method of any one of claims 12-21. A battery pack, wherein, The battery module of claim 22. An electric power utilization device, wherein, One or more of the secondary battery of any one of claims 1-11, the secondary battery using the negative electrode sheet prepared by the method of any one of claims 12-21, the battery module of claim 22, and the battery pack of claim 23.

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