Molecular sieve, secondary battery and method for manufacturing the same, battery device, power consuming device

Abstract

The application relates to the technical field of batteries, and provides a molecular sieve, a secondary battery and a preparation method thereof, a battery device and a power utilization device. The secondary battery comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, and the negative electrode film layer comprises a molecular sieve which has a porous structure and is doped with nitrogen elements. The secondary battery provided by the application has higher conductivity due to the nitrogen elements doped in the molecular sieve, so that the electrons can be transmitted in the negative electrode sheet at a faster speed, so that a more stable electric field environment is constructed in the negative electrode sheet, and lithium ions can be more orderly migrated in the negative electrode sheet under the action of the electric field. The good conductivity and excellent ion transmission environment can better inhibit the occurrence of side reactions in the cycle process of the battery, and further prolong the cycle life of the battery.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and particularly relates to a molecular sieve, a secondary battery and its preparation method, a battery device, and an electrical device. Background Technology

[0002] Rechargeable batteries, such as lithium-ion batteries, are widely used in smartphones, wearable devices, consumer drones, and electric vehicles due to their advantages such as high energy density, long cycle life, and no memory effect. With the widespread application of lithium-ion batteries in these fields, market demands for battery performance are becoming increasingly stringent. However, the cycle performance of rechargeable batteries remains relatively poor and requires further improvement.

[0003] The above statements are for the purpose of providing background information in relation to this application only and do not necessarily constitute prior art. Summary of the Invention

[0004] The purpose of this application is to provide a molecular sieve, a secondary battery and its preparation method, a battery device and an electrical device, in order to solve the problem of poor battery cycle performance.

[0005] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0006] In a first aspect, this application provides a secondary battery, including a negative electrode sheet, the negative electrode sheet including a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, the negative electrode film layer including a molecular sieve, the molecular sieve having a porous structure, and the molecular sieve being doped with nitrogen element.

[0007] In this application's technical solution, molecular sieves are used in the negative electrode film layer of the negative electrode sheet. Because the molecular sieves are doped with nitrogen, they possess high conductivity, significantly enriching the electron conduction channels in the negative electrode sheet. This allows electrons to transport through the negative electrode sheet at a faster speed, thus creating a more stable electric field environment. Under the influence of this electric field, lithium ions can migrate more orderly within the negative electrode sheet. The excellent conductivity and superior ion transport environment enable the battery to better suppress side reactions during cycling, reducing the risk of battery performance degradation due to side reactions and further extending the battery's cycle life.

[0008] Because nitrogen has a strong electronegativity, it creates a local electric field distortion around the nitrogen atom, thereby adjusting the intensity and direction distribution of the electric field on the negative electrode. At the same time, there is a strong attraction between the highly electronegative nitrogen atoms and the positively charged lithium ions in the electrolyte. Driven by the electric field, the lithium ions are more orderly distributed in the negative electrode. This means that lithium ions can be deposited more uniformly on the negative electrode, completing the insertion and extraction of lithium ions. This can effectively suppress the occurrence of lithium plating problems. As a result, the battery can maintain a relatively stable structure and performance during charge and discharge cycles, thus effectively extending the battery's cycle performance.

[0009] Furthermore, molecular sieves possess a porous structure. Due to the physical limitations of their pore size and the interactions between them and solvent molecules in the electrolyte, such as van der Waals forces and electrostatic interactions, they facilitate the gradual stripping of solvent molecules from the solvated lithium. This stripping effect significantly reduces the number of solvent molecules reaching the negative electrode surface to participate in the reaction. This means fewer solvent molecules undergo reduction reactions on the negative electrode surface, resulting in a marked decrease in organic components and a significant increase in inorganic components in the SEI film formed by the reduction reaction. This significantly improves the stability of the SEI film at high temperatures and has a marked positive effect on the battery's cycle performance.

[0010] In some embodiments, the molecular sieve comprises a composite formed of a non-aluminum metal oxide, alumina, and silicon oxide, wherein nitrogen element replaces part of the oxygen element in the non-aluminum metal oxide in the composite to form nitrogen doping.

[0011] In each mole of non-aluminum metal oxide, the molar amount of nitrogen doping is 0.012 mol to 0.018 mol.

[0012] The oxygen atoms in non-aluminum metal oxides are in a more reactive chemical environment, making them easier to be replaced by nitrogen to form nitrogen doping, thereby effectively improving the conductivity and stability of molecular sieves.

[0013] In some embodiments, at least a portion of the nitrogen doping element in the non-aluminum metal oxide is connected to the silicon element in the silicon oxide by at least one chemical bond, namely ionic bond or covalent bond;

[0014] Alternatively, at least some of the nitrogen doping elements in non-aluminum metal oxides are connected to the aluminum elements in alumina through at least one chemical bond, namely ionic or covalent bonds.

[0015] Because nitrogen has high electronegativity, it can easily form stable chemical bonds with other elements such as silicon and aluminum. This can effectively improve the structural stability of molecular sieves, thus having a significant positive effect on the cycle performance of batteries.

[0016] In some embodiments, the molecular sieve is also doped with lithium, wherein the lithium replaces part of the metal element in the non-aluminum metal oxide in the composite to form lithium doping.

[0017] The molar amount of lithium doping in each mole of non-aluminum metal oxide is 0.1 mol to 0.4 mol.

[0018] The chemical environment of metal atoms in non-aluminum metal oxides is relatively more active, making them easier to be replaced by lithium to form lithium doping, which significantly improves the ionic conductivity of molecular sieves.

[0019] In some embodiments, in the XRD diffraction pattern of the molecular sieve, the first diffraction angle 2θ corresponding to the molecular sieve (220) crystal plane satisfies: 9.95° < first diffraction angle 2θ ≤ 10.08°, and the second diffraction angle 2θ corresponding to the molecular sieve (533) crystal plane satisfies: 23.20° < second diffraction angle 2θ ≤ 23.50°.

[0020] The diffraction angles of the (220) and (533) crystal planes of the molecular sieve are within the above range, which means that the cell parameters of the molecular sieve gradually decrease and the interplanar spacing gradually decreases, that is, the molecular sieve has undergone cell shrinkage.

[0021] In some embodiments, the chemical formula of the molecular sieve is M z Li 2y O (1-2p / 3) N p ·Al2O3·xSiO2, where M includes at least one of K and Ca, z=(2 / n)(1-y), n represents the valence of M, 1.1≤x≤1.3, 0.05≤y≤0.2, 0.012≤p≤0.018.

[0022] As shown in the above molecular formula, molecular sieves have high thermal and chemical stability, making them less prone to framework collapse or crystal phase transformation. This allows them to function effectively during long-term battery cycling and extend battery cycle life.

[0023] In some embodiments, the molecular sieve satisfies at least one of the following features (1)-(3):

[0024] (1) The pore size of the porous structure of molecular sieve is 0.1 nm-0.3 nm;

[0025] (2) The particle size of the molecular sieve is 3μm-5μm;

[0026] (3) The specific surface area of ​​the molecular sieve is 600-900 m². 2 / g.

[0027] By controlling the pore size, particle size, and specific surface area of ​​the molecular sieve within the above-mentioned range, the molecular sieve can more easily exert its stripping effect on solvent molecules, that is, gradually stripping solvent molecules from the solvated lithium. This helps to reduce the number of solvent molecules participating in the reduction reaction on the negative electrode surface, thereby optimizing the SEI film and improving the cycle performance of the battery.

[0028] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on at least one surface of the negative electrode current collector, and the second negative electrode film layer is disposed on the surface of the first negative electrode film layer away from the negative electrode current collector. The molecular sieve is distributed in the second negative electrode film layer.

[0029] The molecular sieve is located in the second negative electrode film layer, which is conducive to the formation of an SEI film with a higher content of inorganic components and a lower content of organic components in the second negative electrode film layer. This significantly improves the stability of the SEI film and makes it less prone to cracking, thus enabling the battery to exhibit high cycle performance.

[0030] In some embodiments, the molecular sieve content is 1%-5% based on the total mass of the second negative electrode film. Within this range, the molecular sieve can play a full role, not only enabling lithium ions to be deposited relatively uniformly on the negative electrode, reducing the risk of lithium plating, but also enabling solvated lithium to undergo effective desolvation, thereby optimizing the formation of the SEI film and improving the cycle performance of the battery.

[0031] In some embodiments, the molecular sieve content ρ1 in the second negative electrode film layer per unit area and the areal density ρ2 of the negative electrode film layer satisfy the following ratio: ρ1:ρ2=0.8-1.5:100, where the unit of ρ1 is g / mm². 2 The unit of ρ2 is g / mm². 2 .

[0032] Within this range, not only can the ion transport channels in the negative electrode film be effectively optimized, enabling ions to migrate more quickly in the negative electrode sheet, but the electron conduction path can also be balanced, allowing electrons to be uniformly conducted between the second and first negative electrode films. This can effectively improve the ion transport performance and electron conduction capability of the entire negative electrode film, thereby enhancing the electrochemical performance of the battery.

[0033] In some embodiments, the first negative electrode film layer includes a first negative electrode active material, a first conductive agent, a first binder, and a first dispersant.

[0034] In some embodiments, the second negative electrode film layer further includes at least one of a second negative electrode active material, a second conductive agent, a second binder, and a second dispersant.

[0035] In some embodiments, based on the total mass of the second negative electrode film, the content of the second negative electrode active material is 92%-97%, the content of the second conductive agent is 0.5%-2%, the content of the second binder is 1%-1.5%, and the content of the second dispersant is 0.5%-0.8%.

[0036] By controlling the content of each component within the above range, the components can fully exert their synergistic effect, thereby constructing a second negative electrode film with excellent ionic conductivity and electronic conductivity, as well as high specific capacity and good stability.

[0037] In some embodiments, the negative electrode sheet further includes an SEI film, which includes a first SEI film and a second SEI film. The first SEI film covers at least a portion of the surface of the first negative electrode active material, and the second SEI film covers at least a portion of the surface of the second negative electrode active material.

[0038] The organic component content in the first SEI membrane is greater than that in the second SEI membrane, and the inorganic component content in the second SEI membrane is greater than that in the first SEI membrane.

[0039] The first SEI film with a higher content of organic components has better flexibility, while the second SEI film with a higher content of inorganic components has better thermal stability. The combination of these two materials gives the negative electrode sheet high flexibility and stability, making the battery less prone to side reactions and thus effectively improving the battery's cycle performance.

[0040] Secondly, this application provides a method for preparing a secondary battery, comprising the following steps:

[0041] A starting molecular sieve is provided, and the starting molecular sieve is nitrided to dope nitrogen elements in the starting molecular sieve in order to prepare a molecular sieve;

[0042] A negative electrode slurry containing molecular sieves is prepared, and the negative electrode slurry is coated on at least one side of the negative electrode current collector to form a negative electrode film layer, so as to prepare a negative electrode sheet.

[0043] The negative electrode and the positive electrode are assembled to prepare a secondary battery.

[0044] The preparation method provided in this application involves forming nitrogen doping in a molecular sieve through nitriding treatment, then coating a negative electrode slurry containing the molecular sieve onto the surface of the negative electrode current collector to form a negative electrode film layer, thereby obtaining a negative electrode sheet. The negative electrode sheet is then assembled with a positive electrode sheet to effectively prepare a secondary battery with the performance described above.

[0045] In some embodiments, prior to nitriding the initial molecular sieve, the following steps are also included:

[0046] The initial molecular sieve is heat-treated with a lithium-containing compound in a solution system to dope the initial molecular sieve with lithium.

[0047] Lithium doping is formed in the molecular sieve by heat treatment, thereby improving the ionic conductivity of the molecular sieve and making the negative electrode containing the molecular sieve less prone to polarization.

[0048] In some embodiments, the specific process of preparing a negative electrode slurry containing molecular sieves and coating the negative electrode slurry onto at least one side of the negative electrode current collector to form a negative electrode film layer is as follows:

[0049] A first negative electrode slurry containing a first negative electrode active material, a first conductive agent, a first binder and a first dispersant is prepared, and the first negative electrode slurry is coated on at least one surface of a negative electrode current collector to form a first negative electrode film layer.

[0050] A second negative electrode slurry containing molecular sieve, second negative electrode active material, second conductive agent, second binder and second dispersant is prepared, and the second negative electrode slurry is coated on the surface of the first negative electrode film layer away from the negative electrode current collector to form the second negative electrode film layer.

[0051] Thirdly, this application provides a molecular sieve, which includes the molecular sieve contained in the secondary battery provided in the first aspect.

[0052] This molecular sieve exhibits high thermal and chemical stability, thus better maintaining structural stability at high temperatures and significantly improving its resistance to chemical corrosion. When applied to battery systems, it can effectively enhance the transport capacity of ions and electrons, resulting in batteries exhibiting higher charge-discharge capacity and cycle performance.

[0053] Fourthly, this application provides a battery device including a plurality of secondary batteries as described in the above embodiments.

[0054] Fifthly, this application provides an electrical device, including a secondary battery or a battery device as described in the above embodiments, wherein the secondary battery or battery device is used to store or provide electrical energy. Attached Figure Description

[0055] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0056] Figure 1 This is an exploded view of the battery device provided in the embodiments of the present invention / application;

[0057] Figure 2This is an exploded view of the secondary battery provided in the embodiments of the present invention / application;

[0058] Figure 3 This is a schematic diagram of one embodiment of an electrical device that uses a secondary battery as a power source, as described in the present application.

[0059] The following are the labeling elements in the figure:

[0060] 100. Battery device;

[0061] 10. Box body; 11. First box body; 12. Second box body;

[0062] 20. Secondary battery assembly;

[0063] 30. Secondary battery; 31. Housing; 32. Electrode assembly; 33. Cover plate. Detailed Implementation

[0064] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0066] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0067] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0068] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0069] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0070] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0071] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0072] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0073] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0074] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0075] Unless otherwise specified, all steps of 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.

[0076] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0077] In the embodiments of this application, SEI film is short for "solid electrolyte interface", which refers to a solid electrolyte interface film with the characteristics of a solid electrolyte. That is, during the first charge and discharge process of a liquid lithium-ion battery, a passivation layer formed by the reaction between the electrode material and the electrolyte at the solid-liquid interface is formed and covers the surface of the negative electrode material.

[0078] In this embodiment of the application, a secondary battery refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0079] From a market perspective, the application of power batteries is becoming increasingly widespread. Power batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars. As the application areas of power batteries continue to expand, people are placing higher demands on the lifespan of new energy vehicles. This demand translates into requirements for battery cycle performance.

[0080] As a crucial component of a battery, the performance of the negative electrode directly impacts its cycle life, energy density, and power output. Due to its low potential, the solvent components in the electrolyte inevitably undergo reduction reactions on the surface of the negative electrode active material, forming a solid electrolyte interphase (SEI) film. During battery operation, the temperature continuously rises. For the SEI film, high temperatures destabilize the organic components within it. Simultaneously, the negative electrode potential may increase with battery operation. This combined effect of potential and temperature increases accelerates the reactions of organic components in the SEI film, such as oxidation and decomposition. This leads to continuous cracking and repair of the SEI film, a process that continuously consumes active lithium, reducing the battery's lithium reserves and affecting cycle stability. Furthermore, the continuous changes in the SEI film and the consumption of electrolyte solvent result in a significant increase in resistance to current flow (DCR), potentially leading to increased battery polarization, a deteriorated charging window, and further shortened cycle life.

[0081] Based on the above background, embodiments of this application provide a secondary battery, including a negative electrode sheet, the negative electrode sheet including a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, the negative electrode film layer including a molecular sieve, the molecular sieve having a porous structure, and the molecular sieve being doped with nitrogen element.

[0082] In this application's technical solution, a molecular sieve is used in the negative electrode film layer of the negative electrode sheet. Because the molecular sieve is doped with nitrogen, it exhibits high conductivity. The main reasons for this are: First, nitrogen atoms can adjust the band structure of the molecular sieve, reducing the band gap between its valence band and conduction band, allowing more electrons to be excited to the conduction band, thus improving the molecular sieve's conductivity. Second, the introduction of nitrogen, with its high electronegativity, will draw electrons from surrounding atoms or chemical bonds, creating defect sites within the molecular sieve. These defect sites can serve as centers for electron scattering, which to some extent facilitates electron transport, thereby increasing carrier mobility. Thus, the molecular sieve possesses good conductivity. Due to the high conductivity of the molecular sieve, the conductive channels for electrons in the negative electrode sheet are significantly enriched, allowing electrons to transport through the negative electrode sheet at a faster speed. This creates a more stable electric field environment in the negative electrode sheet, enabling lithium ions to migrate more orderly under the influence of the electric field. Good conductivity and excellent ion transport environment enable the battery to better suppress side reactions during cycling, reduce the risk of battery performance degradation caused by side reactions, and further extend the battery's cycle life.

[0083] Because nitrogen has a strong electronegativity, it creates a local electric field distortion around the nitrogen atom, thereby adjusting the intensity and direction distribution of the electric field on the negative electrode. At the same time, there is a strong attraction between the highly electronegative nitrogen atoms and the positively charged lithium ions in the electrolyte. Driven by the electric field, the lithium ions are more orderly distributed in the negative electrode. This means that lithium ions can be deposited more uniformly on the negative electrode, completing the insertion and extraction of lithium ions. This can effectively suppress the occurrence of lithium plating problems. As a result, the battery can maintain a relatively stable structure and performance during charge and discharge cycles, thus effectively extending the battery's cycle performance.

[0084] Furthermore, molecular sieves possess a porous structure. Due to the physical limitations of their pore size and the interactions between them and solvent molecules in the electrolyte, such as van der Waals forces and electrostatic interactions, they facilitate the gradual stripping of solvent molecules from lithium solvation. This significantly reduces the radius of lithium solvation, effectively increasing the migration rate of lithium ions and greatly improving the battery's rate performance. Simultaneously, the stripping effect of molecular sieves on solvent molecules greatly reduces the number of solvent molecules reaching the negative electrode surface to participate in the reaction, meaning fewer solvent molecules undergo reduction reactions on the negative electrode surface. The organic components in the SEI film mainly originate from solvent molecules in the electrolyte. As the participation of fewer solvent molecules in the SEI film formation process decreases, the organic component content in the SEI film also decreases accordingly. This significantly improves the stability of the SEI film at high temperatures, allowing it to maintain relative structural integrity during battery cycling. This enables the battery to maintain high capacity during long-term cycling, thereby improving the battery's cycle performance.

[0085] The aforementioned negative electrode current collector refers to the structure or component in a battery used to collect current at the negative electrode. For example, the negative electrode current collector can be a metal foil or a composite current collector. The metal foil can be copper foil. The composite current collector can be a polymer matrix material and a metal layer formed on at least one surface of the polymer matrix material. The composite current collector can be formed on the surface of the polymer matrix material using copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, or silver alloys. The polymer matrix material can be polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.

[0086] The aforementioned negative electrode film layer refers to a film layer disposed on the negative electrode current collector and containing negative electrode active material. The negative electrode active layer can be disposed on one side of the negative electrode current collector or on both sides of the negative electrode current collector.

[0087] In some embodiments, the molecular sieve comprises a composite formed of a non-aluminum metal oxide, alumina, and silicon oxide, wherein nitrogen element replaces part of the oxygen element in the non-aluminum metal oxide in the composite to form nitrogen doping.

[0088] In each mole of non-aluminum metal oxide, the molar amount of nitrogen doping is 0.012 mol to 0.018 mol.

[0089] For example, the molar amount of nitrogen doping per mole of non-aluminum metal oxide can be typical but not limiting values ​​such as 0.012 mol, 0.013 mol, 0.014 mol, 0.015 mol, 0.016 mol, 0.017 mol, 0.018 mol.

[0090] The oxygen atoms in non-aluminum metal oxides are in a more reactive chemical environment, making them easier to be replaced by nitrogen to form nitrogen doping, thereby effectively improving the conductivity and stability of molecular sieves.

[0091] In some embodiments, at least a portion of the nitrogen doping element in the non-aluminum metal oxide is connected to the silicon element in the silicon oxide by at least one chemical bond, namely ionic bond or covalent bond;

[0092] Alternatively, at least some of the nitrogen doping elements in non-aluminum metal oxides are connected to the aluminum elements in alumina through at least one chemical bond, namely ionic or covalent bonds.

[0093] Nitrogen's strong electronegativity gives it a powerful ability to form stable chemical bonds with other atoms. Nitrogen atoms form chemical bonds with surrounding atoms, such as silicon and aluminum atoms in the molecular sieve framework. These bonds effectively enhance the structural stability of the molecular sieve, especially when it is immersed in electrolyte for extended periods. These stable bonds effectively resist the electrolyte's erosion, preventing the molecular sieve from easily crumbling. Thus, the molecular sieve can continue to function effectively during battery cycling, significantly improving the battery's cycle life.

[0094] In some embodiments, the molecular sieve is also doped with lithium, wherein the lithium replaces part of the metal element in the non-aluminum metal oxide in the composite to form lithium doping.

[0095] The molar amount of lithium doping in each mole of non-aluminum metal oxide is 0.1 mol to 0.4 mol.

[0096] For example, the molar amount of lithium doping per mole of non-aluminum metal oxide can be typical but not limiting values ​​such as 0.1 mol, 0.15 mol, 0.2 mol, 0.25 mol, 0.3 mol, 0.35 mol, 0.4 mol.

[0097] The chemical environment of metal atoms in non-aluminum metal oxides is relatively more active, making them easier to be replaced by lithium to form lithium doping, which significantly improves the ionic conductivity of molecular sieves.

[0098] Because nitrogen has a high electronegativity, it readily forms high-energy coordination bonds with lithium doped in the molecular sieve, significantly enhancing the structural stability of the sieve and making it less susceptible to electrolyte corrosion and breakage. Simultaneously, the stable chemical bonds between nitrogen and lithium atoms effectively slow down lithium outflow during battery cycling, ensuring a sufficient amount of lithium is available for ion conduction and maintaining good ionic conductivity. This further improves the overall electrochemical performance of the battery, including cycle performance and rate capability.

[0099] In some embodiments, in the XRD diffraction pattern of the molecular sieve, the first diffraction angle 2θ corresponding to the molecular sieve (220) crystal plane satisfies: 9.95° < first diffraction angle 2θ ≤ 10.08°, and the second diffraction angle 2θ corresponding to the molecular sieve (533) crystal plane satisfies: 23.20° < second diffraction angle 2θ ≤ 23.50°.

[0100] In some embodiments, in the XRD diffraction pattern of the molecular sieve, the first diffraction angle 2θ corresponding to the molecular sieve (220) crystal plane satisfies: 10.01°≤ first diffraction angle 2θ≤10.08°, and the second diffraction angle 2θ corresponding to the molecular sieve (533) crystal plane satisfies: 23.25°≤ second diffraction angle 2θ≤23.50°.

[0101] The diffraction angles corresponding to the (220) crystal plane and the (533) crystal plane of the molecular sieve are within the above range, which means that the cell parameters of the molecular sieve gradually decrease and the interplanar spacing gradually decreases. That is, the molecular sieve has undergone cell shrinkage. This may be due to the doping of lithium ions. After lithium atoms enter the molecular sieve lattice, the lattice shrinks. Moreover, as the amount of lithium atom doping increases, the effect on the lattice becomes more obvious, which makes the diffraction angles corresponding to the (220) crystal plane and the (533) crystal plane increase accordingly.

[0102] In some embodiments, the chemical formula of the molecular sieve is M z Li 2y O (1-2p / 3) N p ·Al2O3·xSiO2, where M includes at least one of K and Ca, z=(2 / n)(1-y), n represents the valence of M, 1.1≤x≤1.3, 0.05≤y≤0.2, 0.012≤p≤0.018.

[0103] By controlling the x-value, i.e., the silicon-to-aluminum ratio, within the aforementioned range, the aluminum content in the molecular sieve is relatively high. The presence of aluminum atoms generates more negative charge centers, requiring the molecular sieve to have more cations to balance the charge. At this point, metal ions (such as calcium and potassium ions) more easily enter the molecular sieve framework to act as cations balancing the charge. Therefore, with the x-value within the aforementioned range, the molecular sieve contains a suitable amount of compounds formed by metal ions. When calcium or potassium ions enter the molecular sieve, because their radii differ from the original ions in the molecular sieve, the metal element (calcium or potassium) can adjust the pore size of the molecular sieve. This allows the molecular sieve to fully exert its stripping effect on solvent molecules, effectively improving the lithium-ion transport rate and thus the battery's charge-discharge capability. It also optimizes the formation of the SEI film, effectively enhancing its thermal stability and reducing the likelihood of rupture, thereby significantly improving the battery's cycle performance.

[0104] Nitrogen is doped into the molecular sieve to improve its electronic conductivity, while lithium is also doped into it to improve its ionic conductivity. This dual-doped molecular sieve creates a favorable ion transport environment, which significantly suppresses the occurrence of side reactions in the battery and further extends the battery's cycle life.

[0105] In some embodiments, the pore size of the porous structure of the molecular sieve is 0.1 nm to 0.3 nm. For example, the pore size can be typical but not limiting values ​​such as 0.1 nm, 0.15 nm, 0.2 nm, 0.25 nm, and 0.3 nm.

[0106] The pore size of the molecular sieve can be determined using instruments and methods known in the art, such as by combining BET with BJH (Barrett-Joyner-Halenda) testing.

[0107] By controlling the pore size of the molecular sieve within the aforementioned range, on the one hand, the physical limitation of the molecular sieve pore size allows solvent molecules to be gradually stripped from the solvated lithium, significantly reducing the radius of the solvated lithium. This effectively increases the migration rate of lithium ions, enabling them to more directly interact with the negative electrode active material through intercalation and deintercalation reactions, thus improving the battery's charge and discharge performance. On the other hand, this pore size can be well matched with the size of water molecules, allowing residual water molecules in the electrolyte to be effectively adsorbed into the molecular sieve. This prevents the electrolyte from decomposing or reacting adversely with the negative electrode active material, thereby improving the stability of the electrolyte's composition and performance, and effectively extending the battery's lifespan. Furthermore, this porous structure can effectively capture gases generated during battery cycling, preventing gas accumulation inside the battery, thereby improving battery safety and lifespan.

[0108] In some embodiments, the particle size of the molecular sieve is 3 μm-5 μm. For example, the particle size of the molecular sieve can be typical but not limiting values ​​such as 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm.

[0109] The particle size of molecular sieves can be obtained by testing the following methods:

[0110] Cross-sectional images of the negative electrode sheet were obtained using a Zeiss Sigma 300 SEM / TEM. Then, molecular sieve particles were identified through mapping, and the particle size of the molecular sieve particles was determined. Typically, the particle size of multiple (>50) molecular sieve particles can be tested, and the average diameter of all molecular sieve particles was calculated. The average diameter was then used as the particle size of the molecular sieve.

[0111] Within the aforementioned particle size range, molecular sieves can be more easily and uniformly mixed with other components, and can exert a good synergistic effect with other components to construct good ion transport channels and electron conduction networks, thereby enabling the battery to have excellent electrochemical performance.

[0112] In some embodiments, the specific surface area of ​​the molecular sieve is 600-900 m². 2 / g. For example, the specific surface area of ​​a molecular sieve can be 600 m². 2 / g、650m 2 / g、700m 2 / g、750m 2 / g、800m 2 / g、850m 2 / g、900m 2 / g and other typical but non-restrictive values.

[0113] Specific surface area refers to the total surface area per unit mass of a substance. It can be determined using instruments and methods known in the art, based on principles such as low-temperature nitrogen adsorption and / or static volumetric methods. For example, the specific surface area of ​​solid substances can be determined using the gas adsorption BET method (GB / T+19587-2004), conveniently measured using a pore size analyzer. As an example, a JW-BK122F analyzer is used for testing.

[0114] Controlling the specific surface area of ​​the molecular sieve within the above range means that the molecular sieve has an appropriate amount of pore structure, which can effectively play the role of the porous structure, realize the stripping of solvent molecules, and effectively absorb gases and water, thereby effectively improving the cycle performance of the battery.

[0115] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on at least one surface of the negative electrode current collector, and the second negative electrode film layer is disposed on the surface of the first negative electrode film layer away from the negative electrode current collector. The molecular sieve is distributed in the second negative electrode film layer.

[0116] The molecular sieve is located in the second negative electrode film layer, which is conducive to the formation of an SEI film with a higher content of inorganic components and a lower content of organic components in the second negative electrode film layer. This significantly improves the stability of the SEI film and makes it less prone to cracking, thus enabling the battery to exhibit high cycle performance.

[0117] In some embodiments, the molecular sieve content is 1%-5% based on the total mass of the second negative electrode membrane layer. Exemplarily, the molecular sieve content can be typical but not limiting values ​​such as 1%, 2%, 3%, 4%, 5%.

[0118] Within this range, molecular sieves can play a full role, not only enabling lithium ions to be deposited relatively uniformly on the negative electrode, reducing the risk of lithium plating, but also enabling solvated lithium to undergo effective desolvation, thereby optimizing the formation of the SEI film and improving the cycle performance of the battery.

[0119] In some embodiments, the molecular sieve content ρ1 in the second negative electrode film layer per unit area and the areal density ρ2 of the negative electrode film layer satisfy the following ratio: ρ1:ρ2=0.8-1.5:100, where the unit of ρ1 is g / mm². 2 The unit of ρ2 is g / mm². 2 .

[0120] "Area density" refers to the mass per unit area, usually expressed as weight per unit area (e.g., mg / m³). 2 mg / cm2, mg / mm 2 It is expressed as (). Areal density reflects the weight of active material loaded per unit area in the negative electrode film. The method for testing areal density is as follows:

[0121] In online testing, beta rays are used to measure the surface density. When beta rays penetrate the positive electrode sheet, some energy is absorbed, and the intensity attenuation of the rays has a negative exponential relationship with the surface density of the target. By detecting the intensity of the rays before and after penetration, the thickness and surface density of the positive electrode sheet can be estimated. In offline testing, a certain number of circular electrode sheets of a certain area are obtained by a stamping machine. The weight of the circular electrode sheets (excluding the weight of the positive current collector) is measured using a high-precision electronic scale. The surface density of the electrode sheet is obtained by dividing the weight of the circular electrode sheet by its area.

[0122] ρ1 refers to the mass of the molecular sieve contained per unit area of ​​the second negative electrode film layer.

[0123] Controlling the ratio of ρ1 to ρ2 within the above range can not only effectively optimize the ion transport channels in the negative electrode film, enabling ions to migrate more quickly in the negative electrode sheet, but also balance the electron conduction path, allowing electrons to be uniformly conducted between the second and first negative electrode films. This can effectively improve the ion transport performance and electron conduction capability of the entire negative electrode film, thereby enhancing the electrochemical performance of the battery.

[0124] In some embodiments, the second negative electrode film layer further includes at least one of a second negative electrode active material, a second conductive agent, a second binder, and a second dispersant.

[0125] In some embodiments, based on the total mass of the second negative electrode film, the content of the second negative electrode active material is 92%-97%, the content of the second conductive agent is 0.5%-2%, the content of the second binder is 1%-1.5%, and the content of the second dispersant is 0.5%-0.8%.

[0126] For example, the content of the second negative electrode active material can be typical but not limiting values ​​such as 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%.

[0127] For example, the content of the second conductive agent can be a typical but non-limiting value such as 0.5%, 0.8%, 1%, 1.5%, 2%.

[0128] For example, the content of the second adhesive can be typical but not limiting values ​​such as 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%.

[0129] For example, the content of the second dispersant can be a typical but non-limiting value such as 0.5%, 0.6%, 0.7%, 0.8%.

[0130] By controlling the content of each component within the above range, the components can fully exert their synergistic effect, thereby constructing a second negative electrode film with excellent ionic conductivity and electronic conductivity, as well as high specific capacity and good stability.

[0131] In some embodiments, the first negative electrode film layer includes a first negative electrode active material, a first conductive agent, a first binder, and a first dispersant.

[0132] Based on the total mass of the first negative electrode film layer, the content of the first negative electrode material is 90%-99%, the content of the first conductive agent is 0.5%-3%, the content of the first binder is 1.5%-2.5%, and the content of the first dispersant is 0.5%-1%.

[0133] In some embodiments, the first negative electrode active material may be a negative electrode active material known in the art for use in batteries. The second negative electrode active material may also be a negative electrode active material known in the art for use in batteries.

[0134] As an example, the first and second negative electrode active materials each independently include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. 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.

[0135] In some embodiments, the first adhesive may be a battery adhesive known in the art. The second adhesive may also be a battery adhesive known in the art.

[0136] As an example, the first adhesive and the second adhesive are each independently including, but not limited to, at least one of styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid and carboxymethyl chitosan.

[0137] In some embodiments, the first conductive agent may be a conductive agent for batteries known in the art. The second conductive agent may also be a conductive agent for batteries known in the art.

[0138] As an example, the first conductive agent and the second conductive agent may each independently include, but are not limited to, at least one of superconducting carbon, carbon black (e.g., acetylene black or Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0139] In some embodiments, the first dispersant may be a battery dispersant known in the art. The second dispersant may also be a battery dispersant known in the art.

[0140] As an example, the first dispersant and the second dispersant are, independently, including but not limited to, sodium carboxymethyl cellulose.

[0141] In some embodiments, the negative electrode sheet further includes an SEI film, which includes a first SEI film and a second SEI film. The first SEI film covers at least a portion of the surface of the first negative electrode active material, and the second SEI film covers at least a portion of the surface of the second negative electrode active material.

[0142] The organic component content in the first SEI membrane is greater than that in the second SEI membrane, and the inorganic component content in the second SEI membrane is greater than that in the first SEI membrane.

[0143] Because the molecular sieves are distributed within the second negative electrode film, they effectively strip solvent molecules, significantly reducing the number of solvent molecules reaching the surface of the second negative electrode active material to participate in the reaction. Since the organic components in the SEI film mainly originate from the reaction of solvent molecules in the electrolyte, this reduction in solvent molecules results in a significant decrease in the organic components and a significant increase in the inorganic components within the second SEI film formed on the surface of the second negative electrode active material. This significantly improves the thermal stability of the second SEI film, making it less prone to rupture during cycling, thereby enhancing the battery's cycle performance.

[0144] Since the first negative electrode film layer does not contain molecular sieves, the organic component content in the first SEI film formed on the surface of the first negative electrode active material is higher than that in the second SEI film, while the inorganic component content in the second SEI film is higher than that in the first SEI film. The first SEI film with a higher organic component content has better flexibility, while the second SEI film with a higher inorganic component content has better thermal stability. This combination gives the negative electrode sheet high flexibility and stability, making the battery less prone to side reactions and effectively improving the battery's cycle performance.

[0145] In some embodiments, the secondary battery includes a positive electrode and a separator disposed between the positive and negative electrodes, in addition to the negative electrode. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, disposed between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0146] [Positive electrode plate]

[0147] 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 aforementioned "positive electrode film layer disposed on at least one surface of the positive current collector" means that the positive electrode film layer can be disposed on one surface of the positive current collector along its own thickness direction, or it can be disposed on two surfaces of the positive current collector along its own thickness direction.

[0148] This application does not impose any particular limitation on the positive electrode current collector, as long as it can achieve the purpose of this application. In some embodiments, the positive electrode 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. 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 substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0149] In some embodiments, the positive electrode film contains a positive electrode active material, which may include positive electrode active materials known in the art for use in batteries. As an example, the positive electrode active material of a lithium-ion secondary battery may include at least one of the following materials: olivine-structured lithium-containing phosphates, lithium transition non-aluminum 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 non-aluminum metal oxides include, but are not limited to, at least one of lithium cobalt oxide, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, nickel-cobalt-manganese-aluminum quaternary materials, lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate, lithium manganese oxide, and their modified compounds. Examples of olivine-structured lithium-containing phosphates include, but are not limited to, at least one of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. The weight ratio of the positive electrode active material in the positive electrode active layer is 80wt%-100wt%, based on the total weight of the positive electrode active layer.

[0150] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder in the positive electrode film layer may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin. The binder accounts for 0-20 wt% of the positive electrode film layer based on the total weight of the positive electrode active layer.

[0151] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, carbon black (e.g., acetylene black or Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent comprises 0-20 wt% of the positive electrode film, based on the total weight of the positive electrode film.

[0152] 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 on the surface of the positive current collector, drying it and then cold pressing it through a cold rolling mill to form the positive electrode sheet.

[0153] [Isolation membrane]

[0154] The separator is used to separate the positive electrode and the negative electrode, prevent short circuits inside the secondary battery, allow electrolyte ions to pass freely, and does not affect the electrochemical charging and discharging process.

[0155] This application does not impose any particular restrictions on the separator membrane; as long as it can achieve the purpose of this application, any well-known porous separator membrane with good chemical and mechanical stability can be selected.

[0156] In some embodiments, the material of the separator can be selected from at least one 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.

[0157] [Electrolytes]

[0158] 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.

[0159] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0160] Taking lithium-ion batteries as an example, in some embodiments, the electrolyte salt may be selected from at least one 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.

[0161] In some embodiments, the solvent may 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, 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.

[0162] 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.

[0163] The second aspect of this application provides a method for preparing a secondary battery, comprising the following steps:

[0164] Step S10: Provide an initial molecular sieve and nitrid the initial molecular sieve to dope it with nitrogen element in order to prepare a molecular sieve.

[0165] Step S20: Prepare a negative electrode slurry containing molecular sieves, and coat the negative electrode slurry onto at least one side of the negative electrode current collector to form a negative electrode film layer, so as to prepare a negative electrode sheet;

[0166] Step S30: Assemble the negative electrode and the positive electrode to prepare a secondary battery.

[0167] The preparation method provided in this application involves forming nitrogen doping in a molecular sieve through nitriding treatment, then coating a negative electrode slurry containing the molecular sieve onto the surface of the negative electrode current collector to form a negative electrode film layer, thereby obtaining a negative electrode sheet. The negative electrode sheet is then assembled with a positive electrode sheet to effectively prepare a secondary battery with the performance described above.

[0168] In some embodiments, in step S10, the molecular formula of the initial molecular sieve is M. z O·Al₂O₃·xSiO₂, where M includes at least one of K and Ca, z = (2 / n), n represents the valence of M, 1.1 ≤ x ≤ 1.3, can be prepared by the following method:

[0169] Aluminum source, silicon source, M source and pH adjuster are added to deionized water and mixed. The mixture is stirred at 450 rpm to 620 rpm for 6 to 10 hours. The resulting mixture is then dried at 100℃ to 120℃ for 25 to 40 hours to obtain a gel-like mixture. The gel-like mixture is then washed with deionized water 3 to 5 times to obtain a solid mixture. Finally, the solid mixture is calcined at 600℃ to 650℃ for 10 to 12 hours to obtain the initial molecular sieve.

[0170] For example, the aluminum source includes soluble salts corresponding to the element aluminum, such as aluminum sulfate (Al2(SO4)3·18H2O).

[0171] For example, the silicon source includes, but is not limited to, silica dispersions. Specifically, the silica dispersion has a solid content of 10-15% and a Dv50 particle size of 15nm-35nm.

[0172] For example, the M source includes at least one of a potassium source and a calcium source, wherein the potassium source includes, but is not limited to, potassium hydroxide, and the calcium source includes, but is not limited to, calcium hydroxide.

[0173] For example, pH adjusters include, but are not limited to, potassium hydroxide and sodium hydroxide.

[0174] For example, the mass ratio of aluminum source, silicon source, M source, pH adjuster and deionized water can be 1-1.4:12-16:0.1-0.13:7-10:100.

[0175] In some embodiments, before nitriding the initial molecular sieve in step S10, the following steps are also included:

[0176] The initial molecular sieve is heat-treated with a lithium-containing compound in a solution system to dope the initial molecular sieve with lithium.

[0177] Lithium doping is formed in the molecular sieve by heat treatment, thereby improving the ionic conductivity of the molecular sieve and making the negative electrode containing the molecular sieve less prone to polarization.

[0178] For example, lithium-containing compounds include, but are not limited to, lithium hydroxide.

[0179] For example, the solution system includes, but is not limited to, an aqueous solution system. The concentration of lithium hydroxide in the solution system can be 2 mol / L to 4 mol / L.

[0180] For example, the heat treatment conditions are: temperature of 95℃-120℃, time of 6h-12h, and rotation speed of 50rpm-100rpm.

[0181] For example, heat treatment can be performed using an oil bath.

[0182] In some embodiments, in step S10, the nitriding treatment includes sintering under ammonia conditions at a flow rate of 0.15-0.25 L / min, and the sintering treatment includes sintering at 340℃-450℃ for 5h-8h, followed by sintering at 500℃-600℃ for 3h-5h.

[0183] In some embodiments, the specific process of preparing the negative electrode slurry containing molecular sieves and coating the negative electrode slurry onto at least one side of the negative electrode current collector to form a negative electrode film layer in step S20 is as follows:

[0184] A first negative electrode slurry containing a first negative electrode active material, a first conductive agent, a first binder and a first dispersant is prepared, and the first negative electrode slurry is coated on at least one surface of a negative electrode current collector to form a first negative electrode film layer.

[0185] A second negative electrode slurry containing molecular sieve, second negative electrode active material, second conductive agent, second binder and second dispersant is prepared, and the second negative electrode slurry is coated on the surface of the first negative electrode film layer away from the negative electrode current collector to form the second negative electrode film layer.

[0186] In some embodiments, in step S30, the negative electrode sheet, separator, and positive electrode sheet can be formed into an electrode assembly through a winding or stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a secondary battery is obtained. The shape of the secondary battery is not particularly limited; it can be cylindrical, square, or any other arbitrary shape.

[0187] A third aspect of this application provides a molecular sieve, which includes the molecular sieve contained in the secondary battery provided in the first aspect.

[0188] Nitrogen doping can improve the conductivity and stability of molecular sieves, which is more conducive to the promotion and application of molecular sieves.

[0189] Lithium doping can improve the ionic conductivity of molecular sieves, which helps to expand the application range of molecular sieves.

[0190] In some embodiments, in the XRD diffraction pattern of the molecular sieve, the first diffraction angle 2θ corresponding to the molecular sieve (220) crystal plane satisfies: 9.95° < first diffraction angle 2θ ≤ 10.08°, and the second diffraction angle 2θ corresponding to the molecular sieve (533) crystal plane satisfies: 23.20° < second diffraction angle 2θ ≤ 23.50°.

[0191] In some embodiments, in the XRD diffraction pattern of the molecular sieve, the first diffraction angle 2θ corresponding to the molecular sieve (220) crystal plane satisfies: 10.01°≤ first diffraction angle 2θ≤10.08°, and the second diffraction angle 2θ corresponding to the molecular sieve (533) crystal plane satisfies: 23.25°≤ second diffraction angle 2θ≤23.50°.

[0192] The diffraction angles corresponding to the (220) crystal plane and the (533) crystal plane of the molecular sieve are within the above range, which means that the cell parameters of the molecular sieve gradually decrease and the interplanar spacing gradually decreases. That is, the molecular sieve has undergone cell shrinkage. This may be due to the doping of lithium ions. After lithium atoms enter the molecular sieve lattice, the lattice shrinks. Moreover, as the amount of lithium atom doping increases, the effect on the lattice becomes more obvious, which makes the diffraction angles corresponding to the (220) crystal plane and the (533) crystal plane increase accordingly.

[0193] In some embodiments, the chemical formula of the molecular sieve is M z Li 2y O (1-2p / 3) Np ·Al2O3·xSiO2, where M includes at least one of K and Ca, z=(2 / n)(1-y), n represents the valence of M, 1.1≤x≤1.3, 0.05≤y≤0.2, 0.012≤p≤0.018.

[0194] The molecular sieve formed by this chemical formula has high thermal and chemical stability, which allows it to better maintain structural stability at high temperatures and significantly improves its resistance to chemical corrosion. When applied to battery systems, it can effectively improve the transport capacity of ions and electrons, enabling the battery to exhibit higher charge-discharge capacity and cycle performance.

[0195] In some embodiments, the pore size of the porous structure of the molecular sieve is 0.1 nm to 0.3 nm. For example, the pore size can be typical but not limiting values ​​such as 0.1 nm, 0.15 nm, 0.2 nm, 0.25 nm, and 0.3 nm.

[0196] In some embodiments, the particle size of the molecular sieve is 3 μm-5 μm. For example, the particle size of the molecular sieve can be typical but not limiting values ​​such as 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm.

[0197] In some embodiments, the specific surface area of ​​the molecular sieve is 600-900 m². 2 / g. For example, the specific surface area of ​​a molecular sieve can be 600 m². 2 / g、650m 2 / g、700m 2 / g、750m 2 / g、800m 2 / g、850m 2 / g、900m 2 / g and other typical but non-restrictive values.

[0198] A fourth aspect of this application provides a battery device including a plurality of secondary batteries described in the above embodiments.

[0199] The battery device mentioned in the embodiments of this application may include one or more secondary battery assemblies for providing voltage and capacity. The secondary battery assembly may include multiple secondary batteries, which are connected in series, parallel, or mixed connections via a busbar.

[0200] In some embodiments, the secondary battery assembly is typically formed by arranging multiple secondary batteries.

[0201] As an example, a secondary battery assembly can be a battery module, which consists of multiple secondary batteries arranged and fixed together to form an independent module. As another example, a battery module can be formed by bundling multiple secondary batteries together with cable ties.

[0202] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more secondary battery components housed within the housing.

[0203] As an example, the secondary battery assembly can be a battery module, which can be housed in the housing by fixing the battery module in the housing.

[0204] As an example, a secondary battery assembly can also be housed in a housing by directly fixing multiple secondary batteries to the housing.

[0205] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the secondary battery assembly. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0206] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the secondary battery assembly.

[0207] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0208] The fifth aspect of this application provides an electrical device, including a secondary battery or a battery device as described in the above embodiments, wherein the secondary battery or battery device is used to store or provide electrical energy.

[0209] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use secondary batteries, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0210] The secondary battery, battery device, and power-consuming device provided in the embodiments of this application will be described below with appropriate reference to the accompanying drawings.

[0211] Figure 1This is an exploded view of a battery device 100 as an example. The battery device 100 includes a housing 10 and a secondary battery assembly 20, which is housed within the housing 10. The housing 10 provides a space for the secondary battery assembly 20 and can have various structures. In some embodiments, the housing 10 may include a first housing 11 and a second housing 12, which overlap each other, collectively defining a closed space for accommodating the secondary battery assembly 20. Of course, the housing 10 formed by the first housing 11 and the second housing 12 can have various shapes, such as a cylinder, a cuboid, etc. Multiple secondary battery assemblies 20 can be arranged in any manner within the battery housing.

[0212] In the battery device 100, there can be one or more secondary battery components 20. These secondary battery components 20 can be connected in series, in parallel, or in a mixed configuration. A mixed configuration means that some of the secondary battery components 20 are connected in series and others in parallel. The multiple secondary battery components 20 can be directly connected in series, in parallel, or in a mixed configuration, and then the entire assembly of the multiple secondary battery components 20 is housed within the housing 10. Alternatively, the battery device 100 can also consist of multiple secondary battery components 20 first connected in series, in parallel, or in a mixed configuration to form battery modules, such as battery modules or battery packs. These battery modules are then connected in series, in parallel, or in a mixed configuration to form an entire assembly, which is then housed within the housing 10.

[0213] The secondary battery assembly 20 includes multiple secondary batteries 30. Figure 2 This is an exploded view of a secondary battery 30 as an example. The secondary battery 30 includes a housing 31, a cover plate 33, an electrode assembly 32, and other functional components.

[0214] The housing 31 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 31 is a hollow structure with an opening at one end, and the housing 31 is used to cooperate with the cover plate 33 to form an internal environment for accommodating the electrode assembly 32, electrolyte, and other functional components. The housing 31 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 31 can be determined according to the specific shape and size of the electrode assembly 32. The material of the housing 31 can be, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and is not limited here. The cover plate 33 is a component that covers the opening of the housing 31 to isolate the internal environment of the secondary battery 30 from the external environment. The material of the cover plate 33 can be, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and is not limited here.

[0215] Figure 3This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0216] Example

[0217] 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.

[0218] The following description is based on specific embodiments.

[0219] Example 1

[0220] This embodiment provides a molecular sieve and a secondary battery.

[0221] Molecular sieve

[0222] A type of molecular sieve, specifically a nitrogen-doped molecular sieve with the molecular formula CaO. 0.988 N 0.018 ·Al2O3·1.2SiO2.

[0223] The preparation method of the above-mentioned molecular sieve includes the following steps:

[0224] Step 1: Calcium hydroxide (Ca(OH)2), aluminum sulfate (Al2(SO4)3·18H2O), silica dispersion (silica with a Dv50 particle size of 15-35nm and a solid content of 10%), potassium hydroxide (KOH), and deionized water were mixed at a mass ratio of 0.11:1.2:14:9:100. After mixing, the mixture was stirred at 550 rpm for 8 hours using a magnetic stirrer. The resulting liquid was then dried in a forced-air drying oven at 100℃ for 30 hours to obtain a gel-like mixture. The gel-like mixture was then washed four times with deionized water and centrifuged to obtain a solid mixture. Finally, the solid mixture was calcined in a tube furnace at 600℃ for 12 hours to obtain an initial molecular sieve with the molecular formula CaO·Al2O3·1.2SiO2.

[0225] Step 2: Place the initial molecular sieve in a tubular furnace and pretreat it with ammonia gas. Control the ammonia gas flow rate to 0.2 L / min. First, purge for 30 min to make the tubular furnace completely filled with ammonia gas atmosphere. Then, heat the tubular furnace. First, heat it to 400℃ at a rate of 5℃ / min and hold for 8 h. Then, heat it to 600℃ at a rate of 2℃ / min and hold for 5 h to obtain the above-mentioned molecular sieve.

[0226] Secondary batteries

[0227] [Preparation of the negative electrode sheet]

[0228] The first negative electrode active material graphite, the first conductive agent carbon black, the first binder styrene polybutadiene rubber and the first dispersant sodium carboxymethyl cellulose are mixed in a weight ratio of 97:0.5:2:0.5, added to the solvent water, and stirred and mixed evenly to obtain the first negative electrode slurry; the first negative electrode slurry is evenly coated on the two opposite surfaces of the negative electrode current collector copper foil, and dried to form the first negative electrode film layer;

[0229] The second negative electrode active material (graphite), the second conductive agent (carbon black), the second binder (polyethylene styrene-butadiene rubber), the second dispersant (sodium carboxymethyl cellulose), and the molecular sieve prepared in Example 1 were mixed in a weight ratio of 96.5:0.8:1.2:0.5:1. The mixture was then added to a solvent of water and stirred until homogeneous to obtain the second negative electrode slurry. The second negative electrode slurry was uniformly coated onto the surface of the first negative electrode film layer away from the negative electrode current collector. After drying, cold pressing, and cutting, the negative electrode sheet was obtained. The molecular sieve content ρ1 per unit area of ​​the second negative electrode film layer and the areal density ρ2 of the negative electrode film layer (including the first and second negative electrode film layers) satisfy the following: ρ1:ρ2=1:100, where the unit of ρ1 is g / mm². 2 The unit of ρ2 is g / mm². 2 .

[0230] [Preparation of the positive electrode sheet]

[0231] The positive electrode active material lithium iron phosphate, the conductive agent acetylene black, and the binder PVDF (polyvinylidene fluoride) were mixed in a mass ratio of 97:1:2. The solvent NMP (N-methylpyrrolidone) was added and stirred until the system was homogeneous to obtain the positive electrode slurry. The positive electrode slurry was uniformly coated on both sides of the positive electrode current collector aluminum foil, dried at room temperature, transferred to an oven for further drying, cold pressed, and cut to obtain the positive electrode sheet.

[0232] [Isolation membrane]

[0233] Separator: A polyethylene film (PE) with a thickness of 7μm is used as the separator.

[0234] Electrolyte

[0235] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in the mixed solvent to obtain an electrolyte in which the concentration of lithium salt was 1 mol / L.

[0236] Preparation of the secondary battery: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes. The cells are then wound to obtain a bare cell. Tabs are welded to the bare cell, which is then placed in an aluminum casing and baked at 100°C to remove water. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. The non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation, and aging to obtain the secondary battery.

[0237] Example 2

[0238] This embodiment provides a molecular sieve and a secondary battery. The difference from Embodiment 1 is that the proportions of the components in the second negative electrode film are different. Specifically, the weight ratio of the second negative electrode active material graphite, the second conductive agent carbon black, the second binder polyethylene polystyrene-butadiene rubber, the second dispersant sodium carboxymethyl cellulose, and the molecular sieve prepared in Embodiment 1 is 94.5:0.8:1.2:0.5:3.

[0239] Example 3

[0240] This embodiment provides a molecular sieve and a secondary battery. The difference from Embodiment 1 is that the proportions of the components in the second negative electrode film are different. Specifically, the weight ratio of the second negative electrode active material graphite, the second conductive agent carbon black, the second binder polyethylene polystyrene-butadiene rubber, the second dispersant sodium carboxymethyl cellulose, and the molecular sieve prepared in Embodiment 1 is 92.5:0.8:1.2:0.5:5.

[0241] Example 4

[0242] This embodiment provides a molecular sieve and a secondary battery. The difference from Embodiment 1 is that the coating weights of the first and second negative electrode films are different. Specifically, the molecular sieve content ρ1 per unit area of ​​the second negative electrode film and the areal density ρ2 of the negative electrode films (including the first and second negative electrode films) satisfy the following: ρ1:ρ2 = 0.8:100, where ρ1 is in g / mm². 2 The unit of ρ2 is g / mm². 2 .

[0243] Example 5

[0244] This embodiment provides a molecular sieve and a secondary battery. The difference from Embodiment 1 is that the coating weights of the first and second negative electrode films are different. Specifically, the molecular sieve content ρ1 per unit area of ​​the second negative electrode film and the areal density ρ2 of the negative electrode films (including the first and second negative electrode films) satisfy the following: ρ1:ρ2 = 1.5:100, where ρ1 is in g / mm². 2 The unit of ρ2 is g / mm². 2 .

[0245] Example 6

[0246] This embodiment provides a molecular sieve and a secondary battery. The difference from Embodiment 1 is that the molecular sieve is different; specifically, the molecular formula of the molecular sieve is CaO. 0.99 N 0.015 ·Al2O3·1.2SiO2.

[0247] Example 7

[0248] This embodiment provides a molecular sieve and a secondary battery. The difference from Embodiment 1 is that the molecular sieve is different; specifically, the molecular formula of the molecular sieve is CaO. 0.992 N 0.012 ·Al2O3·1.2SiO2.

[0249] Example 8

[0250] This embodiment provides a molecular sieve and a secondary battery. The difference from Embodiment 1 is that the molecular sieve is different; specifically, the molecular sieve is simultaneously doped with nitrogen and lithium elements, and its molecular formula is Ca. 0.9 Li 0.2 O 0.988 N 0.018 ·Al2O3·1.2SiO2.

[0251] The preparation method of the above-mentioned molecular sieve includes the following steps:

[0252] Step 1 is the same as the steps in Example 1.

[0253] Step 2: Add the initial molecular sieve to a lithium hydroxide solution with a concentration of 3 mol / L, and then place it in an oil bath at 100℃ and 80 rpm for 8 hours. After that, the treated sample is centrifuged and washed repeatedly with deionized water 2-3 times to obtain the lithium-doped initial molecular sieve.

[0254] Step 3: Place the lithium-doped initial molecular sieve in a tube furnace and pretreat it with ammonia gas. Control the ammonia gas flow rate to 0.2 L / min. First, purge for 30 min to make the tube furnace completely filled with ammonia gas atmosphere. Then, heat the tube furnace. First, heat it to 400℃ at a rate of 5℃ / min and hold for 8 h. Then, heat it to 600℃ at a rate of 2℃ / min and hold for 5 h to obtain the above molecular sieve.

[0255] Example 9

[0256] This embodiment provides a molecular sieve and a secondary battery. The difference from Example 8 is that the proportions of the components in the second negative electrode film are different. Specifically, the weight ratio of the second negative electrode active material graphite, the second conductive agent carbon black, the second binder polyethylene polystyrene-butadiene rubber, the second dispersant sodium carboxymethyl cellulose, and the molecular sieve prepared in Example 8 is 94.5:0.8:1.2:0.5:3.

[0257] Example 10

[0258] This embodiment provides a molecular sieve and a secondary battery. The difference from Example 8 is that the proportions of the components in the second negative electrode film are different. Specifically, the weight ratio of the second negative electrode active material graphite, the second conductive agent carbon black, the second binder polyethylene polystyrene-butadiene rubber, the second dispersant sodium carboxymethyl cellulose, and the molecular sieve prepared in Example 8 is 92.5:0.8:1.2:0.5:5.

[0259] Example 11

[0260] This embodiment provides a molecular sieve and a secondary battery. The difference from Embodiment 8 is that the coating weights of the first and second negative electrode films are different. Specifically, the molecular sieve content ρ1 per unit area of ​​the second negative electrode film and the areal density ρ2 of the negative electrode films (including the first and second negative electrode films) satisfy the following: ρ1:ρ2 = 0.8:100, where ρ1 is in g / mm². 2 The unit of ρ2 is g / mm². 2 .

[0261] Example 12

[0262] This embodiment provides a molecular sieve and a secondary battery. The difference from Embodiment 8 is that the coating weights of the first and second negative electrode films are different. Specifically, the molecular sieve content ρ1 per unit area of ​​the second negative electrode film and the areal density ρ2 of the negative electrode film (including the first and second negative electrode films) satisfy the following: ρ1:ρ2 = 1.5:100, where ρ1 is in g / mm². 2 The unit of ρ2 is g / mm². 2 .

[0263] Example 13

[0264] This embodiment provides a molecular sieve and a secondary battery. The difference from Embodiment 8 is that the molecular sieve is different; specifically, the molecular formula of the molecular sieve is Ca. 0.8 Li 0.4 O 0.988 N 0.018 ·Al2O3·1.2SiO2.

[0265] Example 14

[0266] This embodiment provides a molecular sieve and a secondary battery. The difference from Embodiment 8 is that the molecular sieve is different; specifically, the molecular formula of the molecular sieve is Ca. 0.95 Li 0.1 O 0.988 N 0.018 ·Al2O3·1.2SiO2.

[0267] Example 15

[0268] This embodiment provides a molecular sieve and a secondary battery. The difference from Embodiment 8 is that the molecular sieve is different; specifically, the molecular formula of the molecular sieve is Ca. 0.9 Li 0.2 O 0.99 N 0.015 ·Al2O3·1.2SiO2.

[0269] Example 16

[0270] This embodiment provides a molecular sieve and a secondary battery. The difference from Embodiment 8 is that the molecular sieve is different; specifically, the molecular formula of the molecular sieve is Ca. 0.9 Li 0.2 O 0.992 N 0.012 ·Al2O3·1.2SiO2.

[0271] Comparative Example 1

[0272] This comparative example provides a secondary battery. The difference from Example 1 is that the negative electrode is different; specifically, the negative electrode does not contain molecular sieves.

[0273] Comparative Example 2

[0274] This comparative example provides a secondary battery. The difference from Example 1 is that the negative electrode is different, specifically: the molecular sieve in the negative electrode is not nitrogen-doped, and its molecular formula is CaO·Al2O3·1.2SiO2.

[0275] Performance testing

[0276] (1) Initial lithium intercalation capacity test

[0277] The negative electrode sheets provided in Examples 1-16 and Comparative Examples 1-2 were combined with lithium metal sheets to form a button cell. The button cell was discharged at 0.1C to 0.005V, then charged at 0.1C to 2.0V, and this cycle was repeated 3 times. The discharge capacity of the last cycle was recorded as the lithium intercalation capacity. The ratio of the lithium intercalation capacity to the mass of the negative electrode active material is the lithium intercalation amount, which reflects the rate performance of the negative electrode active material.

[0278] Since the negative electrode prepared in Comparative Example 1 does not contain molecular sieves, the initial lithium intercalation amount obtained from the test in Comparative Example 1 is used as a reference value, and the initial lithium intercalation degradation rate can be calculated according to formula (I).

[0279]

[0280] In Formula (I), the reference value for the initial lithium intercalation amount refers to the initial lithium intercalation amount obtained by testing the secondary battery prepared in Comparative Example 1 according to the above method, and the test value for the initial lithium intercalation amount refers to the initial lithium intercalation amount obtained by testing the secondary batteries prepared in Examples 1-16 and Comparative Example 2 according to the above method.

[0281] (2) Cyclic capacity retention

[0282] In a constant temperature environment of 60°C, the secondary batteries provided in Examples 1-16 and Comparative Examples 1-2 were charged to 3.65V at 0.1C, then charged at a constant voltage of 3.65V to 0.05C, and then discharged at 1C to 2.5V. After standing for 5 minutes, they were discharged at 0.05C to 2.0V to obtain the discharge capacity. The above process was repeated for charge-discharge cycles for a total of 1000 cycles. The discharge capacity of the last cycle was divided by the discharge capacity of the third cycle to obtain the cycle capacity retention rate after 1000 cycles.

[0283] Since the negative electrode prepared in Comparative Example 1 does not contain molecular sieves, the capacity retention rate at 60℃ / 1000 cycles obtained from the test in Comparative Example 1 is used as a reference value, and the capacity retention rate growth rate can be calculated according to formula (II).

[0284] Capacity retention rate growth rate = Capacity retention rate test value - Capacity retention rate reference value (II).

[0285] In Formula (II), the capacity retention rate reference value refers to the capacity retention rate of the secondary battery prepared in Comparative Example 1, which was tested according to the above method. The capacity retention rate test values ​​refer to the capacity retention rates of the secondary batteries prepared in Examples 1-16 and Comparative Example 2, which were tested according to the above method.

[0286] (3) Gas production

[0287] In a constant temperature environment of 45°C, the secondary batteries provided in Examples 1-16 and Comparative Examples 1-2 were charged to 3.65V at 0.1C, then charged at a constant voltage of 3.65V to 0.05C, and then discharged at 1C to 2.5V. After standing for 5 minutes, they were discharged at 0.05C to 2.0V to obtain the discharge capacity. Charge-discharge cycles were performed according to the above process. During the cycle, a pressure gauge was used to test the internal pressure of the secondary battery to measure the amount of gas generated during the cycle.

[0288] Since the negative electrode sheet prepared in Comparative Example 1 does not contain molecular sieves, the gas production rate at 45℃ / 1000 cycles obtained from the test in Comparative Example 1 is used as a reference value, and the gas production rate reduction rate can be calculated according to formula (III).

[0289]

[0290] In Formula (III), the reference value for gas production refers to the gas production obtained by testing the secondary battery prepared in Comparative Example 1 according to the above method, and the test value for gas production refers to the gas production obtained by testing the secondary batteries prepared in Examples 1-16 and Comparative Example 2 according to the above method.

[0291] The performance parameters of the secondary batteries provided in Examples 1-16 and Comparative Examples 1-2 are shown in Table 1.

[0292] Table 1

[0293]

[0294]

[0295] As can be clearly seen from Table 1, the addition of molecular sieves to the negative electrode slightly reduces the specific capacity of the secondary battery, specifically manifested in a deterioration in the initial lithium intercalation capacity, since the molecular sieves do not contribute additional energy storage function. However, the presence of molecular sieves can improve the high-temperature stability of the SEI film and suppress lithium plating, thus playing a positive role in the cycle performance of the secondary battery, specifically manifested in an improvement in cycle capacity retention. At the same time, the porous structure of molecular sieves can effectively capture the gas generated during cycling, specifically manifested in a reduction in gas production.

[0296] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery, characterized in that, The device includes a negative electrode sheet, which includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a molecular sieve, which has a porous structure and is doped with nitrogen.

2. The secondary battery as described in claim 1, characterized in that, The molecular sieve comprises a composite formed from a non-aluminum metal oxide, alumina, and silicon oxide, wherein the nitrogen element replaces part of the oxygen element in the non-aluminum metal oxide in the composite to form nitrogen doping; In each mole of the non-aluminum metal oxide, the molar amount of nitrogen doping is 0.012 mol to 0.018 mol.

3. The secondary battery as described in claim 2, characterized in that, At least a portion of the nitrogen-doped elements in the non-aluminum metal oxides are connected to the silicon elements in the silicon oxides by at least one chemical bond, namely ionic bonds or covalent bonds; Alternatively, at least a portion of the nitrogen dopant in the non-aluminum metal oxide is connected to the aluminum in the alumina by at least one chemical bond, either ionic or covalent.

4. The secondary battery according to any one of claims 2 to 3, characterized in that, The molecular sieve is also doped with lithium, wherein the lithium replaces part of the metal element in the non-aluminum metal oxide in the composite to form lithium doping; In each mole of the non-aluminum metal oxide, the molar amount of lithium doping is 0.1 mol to 0.4 mol.

5. The secondary battery according to any one of claims 1-4, characterized in that, In the XRD diffraction pattern of the molecular sieve, the first diffraction angle 2θ corresponding to the molecular sieve (220) crystal plane satisfies: 9.95° < first diffraction angle 2θ ≤ 10.08°, and the second diffraction angle 2θ corresponding to the molecular sieve (533) crystal plane satisfies: 23.20° < second diffraction angle 2θ ≤ 23.50°.

6. The secondary battery according to any one of claims 1 to 5, characterized in that, The chemical formula of the molecular sieve is M z Li 2y O (1-2p / 3) N p ·Al2O3·xSiO2, where M includes at least one of K and Ca, z=(2 / n)(1-y), n represents the valence of M, 1.1≤x≤1.3, 0.05≤y≤0.2, 0.012≤p≤0.

018.

7. The secondary battery according to any one of claims 1 to 6, characterized in that, The molecular sieve satisfies at least one of the following characteristics (1)-(3): (1) The pore size of the porous structure of the molecular sieve is 0.1 nm-0.3 nm; (2) The particle size of the molecular sieve is 3μm-5μm; (3) The BET specific surface area of ​​the molecular sieve is 600-900 m². 2 / g.

8. The secondary battery according to any one of claims 1 to 7, characterized in that, The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on at least one surface of the negative electrode current collector, and the second negative electrode film layer is disposed on the surface of the first negative electrode film layer away from the negative electrode current collector. The molecular sieve is distributed in the second negative electrode film layer.

9. The secondary battery as described in claim 8, characterized in that, Based on the total mass of the second negative electrode film layer, the content of the molecular sieve is 1%-5%.

10. The secondary battery according to any one of claims 8 to 9, characterized in that, The content ρ1 of the molecular sieve in the second negative electrode film layer per unit area and the areal density ρ2 of the negative electrode film layer satisfy the following: ρ1:ρ2=0.8-1.5:100, where the unit of ρ1 is g / mm². 2 The unit of ρ2 is g / mm². 2 .

11. The secondary battery according to any one of claims 8 to 10, characterized in that, The first negative electrode film layer includes a first negative electrode active material, a first conductive agent, a first binder, and a first dispersant; and / or The second negative electrode film layer also includes at least one of the following: a second negative electrode active material, a second conductive agent, a second binder, and a second dispersant.

12. The secondary battery as described in claim 11, characterized in that, Based on the total mass of the second negative electrode film, the content of the second negative electrode active material is 92%-97%, the content of the second conductive agent is 0.5%-2%, the content of the second binder is 1%-1.5%, and the content of the second dispersant is 0.5%-0.8%.

13. The secondary battery as described in claim 11 or 12, characterized in that, The negative electrode sheet also includes an SEI film, which includes a first SEI film and a second SEI film. The first SEI film covers at least a portion of the surface of the first negative electrode active material, and the second SEI film covers at least a portion of the surface of the second negative electrode active material. The organic component content in the first SEI membrane is greater than that in the second SEI membrane, and the inorganic component content in the second SEI membrane is greater than that in the first SEI membrane.

14. A method for preparing a secondary battery, characterized in that, Includes the following steps: A starting molecular sieve is provided, and the starting molecular sieve is subjected to nitriding treatment to dope the starting molecular sieve with nitrogen element in order to prepare a molecular sieve; A negative electrode slurry containing the molecular sieve is prepared, and the negative electrode slurry is coated on at least one side of the negative electrode current collector to form a negative electrode film layer, so as to prepare a negative electrode sheet. The negative electrode and the positive electrode are assembled to prepare a secondary battery.

15. The method for preparing a secondary battery as described in claim 14, characterized in that, Before subjecting the initial molecular sieve to nitriding treatment, the following steps are also included: The initial molecular sieve is heat-treated with a lithium-containing compound in a solution system to dope the initial molecular sieve with lithium.

16. The method for preparing a secondary battery as described in claim 14 or 15, characterized in that, The specific process for preparing a negative electrode slurry containing the molecular sieve and coating the negative electrode slurry onto at least one side of the negative electrode current collector to form a negative electrode film layer is as follows: A first negative electrode slurry containing a first negative electrode active material, a first conductive agent, a first binder, and a first dispersant is prepared, and the first negative electrode slurry is coated on at least one surface of the negative electrode current collector to form a first negative electrode film layer. A second negative electrode slurry containing the molecular sieve, the second negative electrode active material, the second conductive agent, the second binder, and the second dispersant is prepared, and the second negative electrode slurry is coated on the surface of the first negative electrode film layer away from the negative electrode current collector to form the second negative electrode film layer.

17. A molecular sieve, characterized in that, Includes the molecular sieve contained in the secondary battery as described in any one of claims 1-13.

18. A battery device, characterized in that, It includes multiple secondary batteries as described in any one of claims 1-13 or multiple secondary batteries prepared by the preparation method as described in any one of claims 14-16.

19. An electrical appliance, characterized in that, This includes the secondary battery as described in any one of claims 1-13, the secondary battery prepared by the preparation method as described in any one of claims 14-16, or the battery device as described in claim 18.

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