Negative electrode sheet and preparation method therefor, battery, and electric device

Abstract

A negative electrode sheet and a preparation method therefor, a battery, and an electric device. The negative electrode sheet comprises a current collector and a negative electrode active layer arranged on at least one surface of the current collector, wherein the negative electrode active layer comprises a negative active material and a molecular sieve, and the pore diameter D of the molecular sieve satisfies: D≤10 nm. When the negative electrode sheet is used for preparing a battery, the fast-charging performance and cycling stability of the battery can be improved.

Description

Negative electrode sheet and preparation method thereof, battery and electrical device

[0001] Related applications

[0002] This application claims priority to Chinese patent application number 2024104054305, filed with the Patent Office of China on April 3, 2024, entitled “Negative electrode sheet and preparation method thereof, battery and electrical device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present invention relates to the technical field of batteries, and in particular to a negative electrode sheet and a preparation method thereof, a battery and an electrical device. Background Art

[0004] Alkali metal ion batteries such as lithium-ion batteries are becoming increasingly popular due to their clean and renewable characteristics. They have been widely used in many fields such as consumer electronics, electric vehicles and energy storage.

[0005] Traditional alkali metal ion batteries are prone to concentration polarization during charging, especially during rapid charging. This causes alkali metal ions to accumulate on the negative electrode surface, i.e., the liquid phase potential is too large, leading to the precipitation of alkali metals and the formation of alkali metal dendrites. Taking lithium-ion batteries as an example, due to the excellent conductivity and low potential of lithium metal, lithium metal ions will continue to preferentially gather near lithium dendrites and further reduce to form lithium dendrites. This process is accompanied by volume changes, which can easily cause the SEI film to rupture and lead to the loss of active lithium. The continuously deposited lithium metal will also fall off the negative electrode surface, thus forming "dead lithium" that can no longer participate in the reaction, resulting in reduced energy density and cycle performance of the secondary battery. In severe cases, sharp features will form that pierce the separator and cause a short circuit in the battery, which may cause catastrophic consequences such as combustion and explosion.

[0006] Therefore, traditional technologies still need to be further improved.

[0007] Summary of the Invention

[0008] Based on this, it is necessary to provide a negative electrode sheet and its preparation method, a battery and an electrical device, aiming to improve the fast charging performance and cycle stability of the battery.

[0009] In a first aspect of the present application, a negative electrode sheet is provided, comprising a current collector and a negative electrode active layer provided on at least one surface of the current collector, wherein the negative electrode active layer comprises a negative electrode active material and a molecular sieve;

[0010] Wherein, the pore size D of the molecular sieve satisfies: D≤10 nm.

[0011] In the above-mentioned negative electrode sheet, a molecular sieve is added to the negative electrode active layer. The molecular sieve has abundant nanopores and a large number of charge-rich centers. By controlling its specific pore size range, when applied to the preparation of batteries, taking alkali metal ion batteries as an example, the following effects can be produced: the molecular sieve of a specific pore size can have an electrostatic attraction effect on the solvated alkali metal ions on the surface of the negative electrode active layer, that is, the pores of the specific pore size in the molecular sieve nano-confine the solvated alkali metal ions, prompting the solvated alkali metal ions to remove some solvent molecules, reducing the coordination number of the solvent molecules or reducing the interaction force with the solvent molecules, which is equivalent to reducing the desolvation energy barrier at the interface of the negative electrode active layer and improving the transmission of alkali metal ions in the negative electrode active layer; and the partially desolvated lithium ions, due to the reduction of organic solvent molecules gathered around them, reduce the organic components in the solid electrolyte membrane (SEI) produced by reduction decomposition, which is equivalent to increasing the proportion of inorganic components, thereby increasing the diffusion rate of lithium ions in the SEI membrane. As a result, the above-mentioned negative electrode sheet can reduce the probability of metal dendrites and improve the fast charging performance and cycle stability of the battery.

[0012] Furthermore, the porous structure of the molecular sieve facilitates the infiltration of the electrolyte into the negative electrode, thereby improving the negative electrode's liquid retention capacity and lithium conductivity.

[0013] In some embodiments, 0.3 nm ≤ D ≤ 10 nm.

[0014] In some embodiments, 0.3 nm ≤ D ≤ 1 nm.

[0015] Further control the pore size of the molecular sieve to enhance the promoting effect on the desolvation process.

[0016] In some embodiments, the molecular sieve includes at least one of a silicon-aluminum molecular sieve, a phosphorus-aluminum molecular sieve, and a silicon-phosphorus-aluminum molecular sieve.

[0017] In some embodiments, the molecular sieve comprises a silicon-aluminum molecular sieve, and the silicon-aluminum molecular sieve comprises at least one of the compound represented by formula (1) and a hydrate of the compound represented by formula (1);

[0018] zQ·Al2O3·xSiO2(1); Q includes M + 2O and M 2+ At least one of O;

[0019] Among them, M + Including H + 、Li + , K + 、Na + At least one of M 2+ Including Ca 2+ and Ba 2+At least one of; 0≤z≤1,0 <x≤2000。

[0020] In some embodiments, 20≤x≤1700.

[0021] In some embodiments, 100≤x≤500.

[0022] Further regulating x is essentially regulating the molar ratio of silicon and aluminum atoms in the molecular sieve, so that the molecular sieve contains more negatively charged centers, further enhancing the promoting effect on the desolvation process.

[0023] In some embodiments, the silica-alumina molecular sieve includes at least one of potassium A-type molecular sieve, sodium A-type molecular sieve, calcium A-type molecular sieve, calcium Z-type molecular sieve, sodium Z-type molecular sieve, sodium Y-type molecular sieve, sodium mordenite molecular sieve, ZSM-5 molecular sieve and TS-1 molecular sieve.

[0024] In some embodiments, the volume average particle size Dv50 of the molecular sieve satisfies: 0.1 μm <Dv50≤20μm。

[0025] In some embodiments, 0.3 μm ≤ Dv50 ≤ 13 μm.

[0026] In some embodiments, 1 μm ≤ Dv50 ≤ 3 μm.

[0027] Research has found that, on the one hand, smaller molecular sieve particle size increases the contact surface with the negative electrode active material, making it more conducive for active ions to combine with electrons and then embed into the negative electrode material. On the other hand, if the molecular sieve particle size is too small, it is more likely to agglomerate, making dispersion difficult, and the raw material production is more difficult and costly. Therefore, further controlling the molecular sieve particle size Dv50 can further improve the battery's cycling stability.

[0028] In some embodiments, the specific surface area S of the molecular sieve satisfies: <S≤1500m 2 / g.

[0029] In some embodiments, the specific surface area S of the molecular sieve satisfies: 200m 2 / g≤S≤500m 2 / g.

[0030] In some embodiments, in the negative electrode active layer, the mass ratio of the molecular sieve to the negative electrode active material is (0.001-0.1):1.

[0031] In some embodiments, in the negative electrode active layer, the mass ratio of the molecular sieve to the negative electrode active material is (0.005-0.03):1.

[0032] In some embodiments, in the negative electrode active layer, the molecular sieve and the negative electrode active material are mixed with each other.

[0033] In a second aspect of the present application, a method for preparing a negative electrode sheet is provided, comprising the following steps:

[0034] A negative electrode active slurry is used to form a negative electrode active layer on at least one side of a current collector; the negative electrode active slurry includes a negative electrode active material and a molecular sieve, and the pore size D of the molecular sieve satisfies: D≤10nm.

[0035] In some embodiments, the steps of preparing the negative electrode active slurry include the following steps:

[0036] The negative electrode active material, the molecular sieve and a solvent are mixed.

[0037] In a third aspect of the present application, a battery is provided, comprising the negative electrode sheet of the first aspect or the negative electrode sheet prepared by the method for preparing the negative electrode sheet of the second aspect.

[0038] In a fourth aspect of the present application, an electrical device is provided, comprising the battery according to the third aspect.

[0039] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the disclosed drawings without any creative work.

[0041] FIG1 is a schematic diagram of the solvation and desolvation process of lithium ions during charge and discharge of a conventional lithium-ion battery;

[0042] FIG2 is a schematic diagram of the solvation and desolvation process of lithium ions during charge and discharge of a lithium ion battery prepared using the negative electrode sheet of the present application;

[0043] FIG3 is a schematic diagram of the state in which the molecular sieve and the negative electrode active material are mixed in the negative electrode active layer of the negative electrode sheet of the present application;

[0044] FIG4 is a schematic diagram of an embodiment of a battery cell;

[0045] FIG5 is an exploded view of FIG4;

[0046] FIG6 is a schematic diagram of an embodiment of a battery pack;

[0047] FIG7 is an exploded view of FIG6;

[0048] FIG8 is a schematic diagram of an embodiment of an electrical device using a battery as a power source;

[0049] FIG9 is a comparison of charging curves of the batteries prepared in Example 1 and Comparative Example 1; wherein (a) is the charging curve of the battery prepared in Example 1, and (b) is the charging curve of the battery prepared in Comparative Example 1;

[0050] FIG10 is a comparison of electrochemical impedance spectra of the batteries prepared in Example 1 and Comparative Example 1, wherein (a) is the electrochemical impedance spectra of the battery prepared in Example 1, and (b) is the electrochemical impedance spectra of the battery prepared in Comparative Example 1;

[0051] Figure 11 is a physical picture of the negative electrode sheets disassembled after cyclic charge and discharge of the batteries prepared in Example 1 and Comparative Example 1, wherein (a) is a physical picture of the negative electrode sheet of Example 1, and (b) is a physical picture of the negative electrode sheet of Comparative Example 1.

[0052] Description of reference numerals:

[0053] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery cell; 41. Shell; 42. Electrode assembly; 43. Cover; 5. Electrical device. DETAILED DESCRIPTION

[0054] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0055] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0056] " scope " disclosed in the present application can be limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 are also listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is expressed as an integer selected from "2-10", this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0057] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "one or more" means one or more than or equal to two.

[0058] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0059] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0060] It will be appreciated by those skilled in the art that, in the methods of various embodiments or examples, the order in which the steps are written does not imply a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible inherent logic. Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0061] In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0062] In this application, the terms "optionally," "optional," and "optional" are optional and refer to either option being present or absent. If a technical solution contains multiple "options," each option is considered independent unless otherwise specified and there are no conflicts or constraints.

[0063] In traditional technology, secondary batteries are prone to produce metal elements during the charging and discharging process, especially during fast charging. For example, lithium-ion batteries are prone to produce dead lithium such as lithium metal dendrites, which reduces the battery's cycle stability. Traditional technology often suppresses the generation of lithium dendrites by optimizing the electrolyte composition or improving the active materials, but the inhibitory effect is limited.

[0064] Research has found that during the battery charging process, the transfer of metals between the positive and negative electrodes is mainly achieved by the solvent in the electrolyte. Taking alkali metal ion batteries as an example, during the transfer process, alkali metal ions will undergo solvation and desolvation processes: during charging, alkali metal ions diffuse from the lattice on the positive electrode side into the electrolyte. The alkali metal ions attract solvent molecules to gather around them through coordination bonds, hydrogen bonds, or dipole interactions, which is equivalent to forming "wings" called "solvation". This will accelerate the diffusion of alkali metal ions in the solution, and the solvation structure of alkali metal ions will affect the structure and composition of the SEI formed during formation. When reaching the SEI position on the negative electrode surface, the solvated alkali metal ion "wings" are too large, and the resistance to transfer through the pores of the SEI into the negative electrode active layer is too great, so the solvent molecules adsorbed on the surface have to be removed. This process is called desolvation. After passing through the SEI membrane, the alkali metal ions combine with electrons and embed into the negative electrode material, completing the charging process.

[0065] Further research found that the desolvation process is a decomposition coordination process with a certain energy barrier (the kinetic energy barrier is as high as 50-70 kJ / mol). Its difficulty is related to the magnitude of the interaction force formed during solvation, and is specifically related to the type of solvent molecules, additives, concentration and metal salts in the electrolyte. If the desolvation process is too difficult, it will cause some alkali metal ions to accumulate and produce polarization, forming alkali metal dendrites, resulting in a decrease in battery performance.

[0066] Based on this, after a lot of experimental research, the technical solution of this application was obtained.

[0067] In one embodiment of the present application, a negative electrode sheet is provided, comprising a current collector and a negative electrode active layer disposed on at least one surface of the current collector, wherein the negative electrode active layer comprises a negative electrode active material and a molecular sieve.

[0068] The pore size D of the molecular sieve satisfies: D≤10 nm.

[0069] In the above-mentioned negative electrode sheet, a molecular sieve is added to the negative electrode active layer. The molecular sieve has abundant nanopores and negative charge centers. By controlling its specific pore size range, taking alkali metal ion batteries as an example, the following effects can be produced: the molecular sieve of a specific pore size has an electrostatic attraction effect on the solvated alkali metal ions on the surface of the negative electrode active layer, that is, the pores of a specific pore size in the molecular sieve nano-confine the solvated alkali metal ions, prompting the solvated lithium alkali metal ions to remove some solvent molecules, reducing the coordination number of the solvent molecules or reducing the interaction force with the solvent molecules, which is equivalent to reducing the desolvation energy barrier at the interface of the negative electrode active layer and improving the transmission of alkali metal ions in the negative electrode active layer; and the partially desolvated alkali metal, due to the reduction of organic solvent molecules gathered around it, reduces the organic components in the solid electrolyte membrane (SEI) produced by reduction decomposition, which is equivalent to increasing the proportion of inorganic components, thereby increasing the diffusion rate of lithium ions in the SEI membrane. Therefore, the above-mentioned negative electrode sheet can reduce the probability of alkali metal dendrites and improve the fast charging performance and cycle stability of the battery.

[0070] The following uses a lithium-ion battery system as an example to illustrate the solvation and desolvation processes during charge and discharge. The electrolyte contains ethylene carbonate (EC). Please refer to Figures 1 and 2 for details.

[0071] Figure 1 illustrates the solvation and desolvation processes of lithium ions during charge and discharge in a conventional lithium-ion battery. During charging, lithium ions diffuse from the lattice of the positive electrode into the electrolyte. Lithium ions and the electrolyte solvent, such as ethylene carbonate (EC), attract solvent molecules through coordination bonds and other forces, causing them to gather around the lithium ions to form highly coordinated complexes, such as Li(EC)4. This is called "solvation." When the lithium ions reach the SEI (solvation interface) on the negative electrode surface, the solvated metal ions have excessively large "wings," creating significant resistance to transport through the SEI pores into the negative electrode active layer. Only a portion of these "wings" can be removed from the adsorbed solvent molecules, a process known as desolvation. The ions then pass through the SEI membrane, combine with electrons, and become embedded in the negative electrode material, completing the charging process. A higher coordination number, equivalent to more wings around the lithium ions, increases the energy barrier for desolvation.

[0072] Further referring to FIG. 2 , FIG. 2 is a schematic diagram of the solvation and desolvation process of lithium ions during charge and discharge of a lithium-ion battery prepared by the negative electrode sheet of the present application. The solvation of lithium ions is the same as the process in FIG. 1 above. When the lithium ions reach the SEI position on the negative electrode surface, the molecular sieve in the negative electrode active layer uses its nanopores to nano-confine the solvated alkali metal ions, prompting the solvated lithium alkali metal ions to remove some solvent molecules (i.e., sieving and desolvation), thereby reducing the coordination number of the solvent molecules (e.g., Li(EC) n , n<4), which is equivalent to reducing the desolvation energy barrier at the interface of the negative electrode active layer and reducing the transmission resistance of alkali metal ions in the negative electrode active layer, thereby improving the fast charging performance and cycle stability of the battery.

[0073] In some of these embodiments, 0.3 nm ≤ D ≤ 10 nm.

[0074] In some embodiments, 0.3 nm ≤ D ≤ 1 nm.

[0075] Further control the pore size of the molecular sieve to enhance the promoting effect on the desolvation process.

[0076] In the above “0.3nm≤D≤10nm”, the specific value of D includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiment and the following point values: 0.3nm, 0.4nm, 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1nm, 1.1nm, 1.2nm, 1.3nm, 1.4nm, 1.5nm, 1.6nm, 1.7nm, 1.8nm, 1.9nm, 2.0nm, 2.1nm, 2.2nm, 2.3nm, 2.4nm, 2.5nm, 2.6nm, 2.7nm, 2.8nm, 2.9nm, 3.0nm, 3.1nm, 3.2nm, 3.3nm, 3.4nm, 3.5nm, 3.6nm, 3.7nm, 3.8nm, 3.9nm, 4.1nm, 4.1nm, 4.2nm, 4.3nm, 4.4nm, 4.5nm, 4.6nm, 4.7nm, 4.8nm, 4.9nm, 5.9nm, 5.1nm, 5.1nm, 5. nm, 1.8nm, 1.9nm, 2nm, 2.1nm, 2.2nm, 2.3nm, 2.4nm, 2.5nm, 2.6nm, 2.7nm, 2.8nm, 2.9nm, 3nm, 3.1nm, 3.2nm, 3.3nm, 3.4nm, 3.5nm, 3.6nm, 3.7nm, 3.8nm, 3.9nm, 4nm, 4.1nm, 4.2nm, 4.3nm, 4.4nm, 4.5nm, 4 .6nm, 4.7nm, 4.8nm, 4.9nm, 5nm, 5.1nm, 5.2nm, 5.3nm, 5.4nm, 5.5nm, 5.6nm, 5.7nm, 5.8nm, 5.9nm, 6 nm, 6.1nm, 6.2nm, 6.3nm, 6.4nm, 6.5nm, 6.6nm, 6.7nm, 6.8nm, 6.9nm, 7nm, 7.1nm, 7.2nm, 7.3nm, 7.4n m, 7.5nm, 7.6nm, 7.7nm, 7.8nm, 7.9nm, 8nm, 8.1nm, 8.2nm, 8.3nm, 8.4nm, 8.5nm, 8.6nm, 8.7nm, 8.8nm, 8.9nm, 9nm, 9.1nm, 9.2nm, 9.3nm, 9.4nm, 9.5nm, 9.6nm, 9.7nm, 9.8nm, 9.9nm, 10nm; or a range consisting of any two values.

[0077] In some embodiments, the molecular sieve includes at least one of a silicon-aluminum molecular sieve, a phosphorus-aluminum molecular sieve, and a silicon-phosphorus-aluminum molecular sieve.

[0078] In some embodiments, the molecular sieve includes a silicon-aluminum molecular sieve, and the silicon-aluminum molecular sieve includes at least one of the compound represented by formula (1) and a hydrate of the compound represented by formula (1):

[0079] zQ·Al2O3·xSiO2 (1); Q is selected from M + 2O and M 2+ At least one of O;

[0080] Among them, M + Including H + 、Li + , K + 、Na+ at least one of, M 2+ includes Ca 2+ and Ba 2+ at least one of; 0 ≤ z ≤ 1, 0 < x ≤ 2000.

[0081] The hydrate of the compound shown in formula (1) is formed after the compound shown in formula (1) absorbs water, and the specific molecular formula can be expressed as: zQ·Al2O3·xSiO2·yH2O, where the meanings of z and x are the same as above. Due to the excellent water absorption of aluminosilicate molecular sieves, in this field, y can take any value greater than 0, and will not be elaborated here.

[0082] In some of these embodiments, Q includes M + 2O, M + includes Li + or Na + . Further, M can be preferably selected according to the specific battery system to be applied. + , for example, for a lithium-ion battery, M + is selected from Li + , and for a sodium-ion battery, M + is selected from Na + . [[ID=三十二]]

[0083] It can be understood that the value of x above can represent the molar ratio of SiO2 and Al2O3 in the aluminosilicate molecular sieve.

[0084] In some of these embodiments, 20 ≤ x ≤ 1700.

[0085] In some of these embodiments, 100 ≤ x ≤ 500.

[0086] Furthermore, x essentially regulates the molar ratio of SiO2 and Al2O3 in the molecular sieve (also known as the silica-alumina ratio), making the molecular sieve contain more negatively charged centers and further enhancing the promotion effect on the desolvation process. In the above "0 < x ≤ 2000", the specific values of x include the minimum and maximum values of this range, as well as every value between this minimum and maximum value. Specific examples include but are not limited to the point values in the embodiments and the following point values: 10, 30, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000; or a range composed of any two numerical values.

[0087] In some embodiments, the silica-alumina molecular sieve includes at least one of potassium A-type molecular sieve, sodium A-type molecular sieve, calcium A-type molecular sieve, calcium Z-type molecular sieve, sodium Z-type molecular sieve, sodium Y-type molecular sieve, sodium mordenite molecular sieve, ZSM-5 molecular sieve and TS-1 molecular sieve.

[0088] Specifically, the silica-alumina molecular sieves include at least one of 3A molecular sieve (potassium A type), 4A molecular sieve (sodium A type), 5A molecular sieve (calcium A type), 10Z molecular sieve (calcium Z type), 13Z molecular sieve (sodium Z type), Y type molecular sieve (sodium Y type), sodium mordenite type, ZSM-5 and TS-1 type molecular sieves.

[0089] It should be noted that the pore size of the molecular sieve refers to the pore size of the channel formed by its crystal skeleton and elements, which is mainly determined by the type of crystal skeleton and elements. The types of molecular sieves are mainly divided into: A type, X type, Y type and Z type according to their crystal structure. The number in front of the model represents the pore size. For example, the effective pore size of 4A molecular sieve (sodium A type) is 0.4nm. 2+ Exchange of Na in 4A molecular sieve + , forming a pore size of 5A, which is 5A molecular sieve (also known as calcium A type) molecular sieve; using K + Na exchange of 4A molecular sieve + , forming a pore size of 3A, which is 3A (also known as potassium A type) molecular sieve.

[0090] In some embodiments, the volume average particle size Dv50 of the molecular sieve satisfies: 0.1 μm <Dv50≤20μm。

[0091] In some embodiments, 0.3 μm ≤ Dv50 ≤ 13 μm.

[0092] In some embodiments, 1 μm ≤ Dv50 ≤ 3 μm.

[0093] Research has found that, on the one hand, smaller molecular sieve particle size increases the contact surface with the negative electrode active material, making it more conducive for active metal ions to combine with electrons and then embed into the negative electrode material. On the other hand, if the molecular sieve particle size is too small, it is more likely to agglomerate, making dispersion difficult, and the raw material production is more difficult and costly. Therefore, further controlling the molecular sieve particle size Dv50 can further improve the battery's cycling stability.

[0094] It is understandable that the above average particle size Dv50 refers to the volume average particle size, that is, it represents: according to the particle size volume distribution of the material, starting from the small particle size, the particle size corresponding to the cumulative volume distribution percentage reaching 50% can be measured by instruments and methods known in the art. For example, it can be conveniently measured by referring to GB / T 19077-2016 Laser Diffraction Method for Particle Size Distribution and using a laser particle size analyzer. The test instrument can be the Mastersizer 2000E type laser particle size analyzer of Malvern Instruments Limited, UK.

[0095] In the above “0.1μm < Dv50 ≤ 20μm”, the specific values of Dv50 include the minimum and maximum values of this range, as well as each value between this minimum and maximum value. Specific examples include but are not limited to the point values in the examples and the following point values: 0.1μm, 0.15μm, 0.2μm, 0.25μm, 0.3μm, 0.35μm, 0.4μm, 0.45μm, 0.5μm, 0.55μm, 0.6μm, 0.65μm, 0.7μm, 0.75μm, 0.8μm, 0.85μm, 0.9μm, 0.95μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm; or a range composed of any two numerical values.

[0096] In some of the embodiments, the specific surface area S of the molecular sieve satisfies: 0 < S ≤ 1500m 2 / g.

[0097] In some of the embodiments, the specific surface area S of the molecular sieve satisfies: 200m 2 / g < S ≤ 500m 2 / g.

[0098] In the above “0 < S ≤ 1500m 2 / g”, the specific values of S include the minimum and maximum values of this range, as well as each value between this minimum and maximum value. Specific examples include but are not limited to the point values in the examples and the following point values: 100m 2 / g, 150m 2 / g, 200m 2 / g, 250m 2 / g, 300m 2 / g, 350m 2 / g, 400m 2 / g, 450m 2 / g、500m 2 / g、550m 2 / g、600m 2 / g、650m 2 / g、700m 2 / g、750m 2 / g、800m 2 / g、850m 2 / g、900m 2 / g、950m 2 / g、1000m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g、1400m 2 / g、1500m 2 / g; or a range consisting of any two values.

[0099] In some embodiments, in the negative electrode active layer, the mass ratio of the molecular sieve to the negative electrode active material is (0.001-0.1):1.

[0100] In some embodiments, in the negative electrode active layer, the mass ratio of the molecular sieve to the negative electrode active material is (0.005-0.03):1.

[0101] In some embodiments, in the negative electrode active layer, the negative electrode active material accounts for 90% to 99% by mass.

[0102] In some embodiments, in the negative electrode active layer, the molecular sieve and the negative electrode active material are mixed with each other.

[0103] The term "intermixing" as described above means that the molecular sieve and the negative electrode active material do not need to have a specific distribution pattern within the negative electrode active layer; rather, the two are physically mixed. Part of the surface of a portion of the negative electrode active material is in direct contact with the molecular sieve, and the molecular sieve can be considered to be dispersed within the negative electrode active material. For details, please refer to Figure 3, which is a schematic diagram illustrating the intermixing of the molecular sieve and the negative electrode active material within the negative electrode active layer of a negative electrode sheet provided in one embodiment of the present application.

[0104] The negative electrode active material may be any commonly used negative electrode active material in this application.

[0105] In any embodiment of the present application, the above-mentioned negative electrode active material includes at least one of mesocarbon microbeads, graphite, glassy carbon, carbon nanotubes, carbon-carbon composite materials, carbon fibers, hard carbon, soft carbon, silicon-based materials, tin-based materials, magnesium-based materials or iron-based materials.

[0106] Optionally, specific examples of the above-mentioned negative electrode active materials include, but are not limited to: at least one of mesophase carbon microbeads, natural graphite, artificial graphite, graphene, glassy carbon, carbon nanotubes, carbon fibers, hard carbon, soft carbon, iron oxide, tin oxide, silicon oxide, magnesium oxide, silicon-carbon composites, lithium metal or lithium metal alloys.

[0107] In some embodiments, the volume average particle size Dv50 of the negative electrode active material is 0.5 μm to 50 μm. The specific value of Dv50 includes the minimum and maximum values ​​of the range, as well as each value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1 .5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm; or a range consisting of any two values.

[0108] In some embodiments, the volume average particle size Dv50 of the negative electrode active material is larger than the volume average particle size Dv50 of the molecular sieve.

[0109] In some embodiments, the negative electrode active layer further includes a conductive agent.

[0110] In some embodiments, the conductive agent accounts for 0.1% to 1% by mass in the negative electrode active layer.

[0111] In any embodiment of the present application, the conductive agent may be any commonly used conductive agent in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, or graphene. Specifically, the conductive agent may be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs, and graphene, or composite conductive agents thereof.

[0112] In some embodiments, the negative electrode active layer further includes a binder.

[0113] In any embodiment of the present application, the above-mentioned binder can be a binder commonly used in the art, which can be selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, hydrogenated nitrile rubber, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS) and at least one of fluorine-containing acrylate resins.

[0114] Furthermore, it can be understood that the current collector has two surfaces arranged opposite to each other in its own thickness direction, and a negative electrode active layer is provided on at least one surface, which can be one of the surfaces or both surfaces.

[0115] In some embodiments, the current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on a polymer substrate.

[0116] In some embodiments, the metal material includes at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.

[0117] In some embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0118] In one embodiment of the present application, a method for preparing a negative electrode sheet is further provided, comprising the following step S10.

[0119] Step S10: forming a negative electrode active layer on at least one side of the current collector using a negative electrode active slurry; the negative electrode active slurry includes a negative electrode active material and a molecular sieve, and the pore size D of the molecular sieve satisfies: D≤10 nm.

[0120] The selection and addition amount of the molecular sieve and the negative electrode active material are as described above and will not be repeated here.

[0121] In some embodiments, the steps of preparing the negative electrode active slurry include the following steps:

[0122] The negative electrode active material, molecular sieve and solvent are mixed.

[0123] Furthermore, the mixing step is carried out under stirring conditions.

[0124] In some embodiments, the negative electrode active slurry includes a solvent; further, the negative electrode active slurry has a solid content of 40 wt % to 80 wt %, and a viscosity at 25° C. adjusted to 5000 mPa·s to 25000 mPa·s.

[0125] In some embodiments, the solvent includes, but is not limited to, water.

[0126] In one embodiment of the present application, a battery is further provided, comprising the above-mentioned negative electrode sheet or the negative electrode sheet prepared by the above-mentioned method for preparing the negative electrode sheet.

[0127] In some embodiments, the battery comprises an alkali metal ion battery, including but not limited to at least one of a lithium ion battery, a sodium ion battery, and a potassium ion battery.

[0128] Furthermore, the above-mentioned battery includes a positive electrode sheet and a separator, and the negative electrode sheet, the separator and the positive electrode sheet can be wound to form a battery assembly.

[0129] The separator and the positive electrode sheet can be alkali metal ion batteries applicable to various types of alkali metal ion batteries in the art. The separator and the positive electrode sheet are introduced here in a non-restrictive manner, but are not limited to the following systems.

[0130] Positive electrode sheet: includes a current collector and a positive electrode active layer provided on at least one surface of the current collector, and the positive electrode active layer includes a positive electrode material.

[0131] The positive electrode active material may be any positive electrode active material commonly used in the art, including but not limited to: positive electrode active materials for lithium ion batteries, positive electrode active materials for sodium ion batteries, and positive electrode active materials for potassium ion batteries.

[0132] The positive electrode active material of a lithium ion battery, the positive electrode active material of a sodium ion battery and the positive electrode active material of a potassium ion battery are hereinafter referred to as lithium ion active material, sodium ion active material or potassium ion active material, respectively.

[0133] Further, as an example, the lithium ion active material may include at least one of the following materials: lithium phosphates containing olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to: lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn1 / 3 O2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) or its modified compounds. Examples of lithium phosphates containing olivine structures may include but are not limited to at least one of lithium iron phosphate (such as LiFePO4, referred to as LFP), lithium manganese phosphate (such as LiMnPO4) or lithium manganese iron phosphate. In any embodiment of the present application, the molecular formula of the lithium ion active material is: LiFe x Mn (1-x) PO4, x is any number from 0 to 1.

[0134] It can be understood that when x is 0, LiFe x Mn (1-x) PO4 is LiMnPO4 lithium manganese phosphate. When x is 1, LiFe x Mn (1-x) PO4 is LiFePO4 lithium iron phosphate (LFP).

[0135] It should be noted that the lithium content in the positive electrode material exemplified above refers to its content when it is not in use. During the use of the battery, it will be repeatedly used as a battery, and the Li in the positive electrode active material will change during the charge and discharge process. That is, the molar subscript of Li in the positive electrode active material in the battery product will not always remain at 1, but will change; further, the range of change can be (0 to 1.2).

[0136] For example, LiFe x Mn (1-x) PO4 can be further expressed as Li y Fe x Mn (1-x) PO4, y is 0~1.1.

[0137] For example, for the ternary material Li y (Ni a Co bMn c ) 1-d M d O 2-x A x , y is 0.2~1.2, a+b+c=1, 0≤d≤1, 0≤x<2; M is one or more of Zr, Sr, B, Ti, Mg, Sn or Al, and A is one or more of S, N, F, Cl, Br or I.

[0138] The battery is accompanied by Li intercalation and deintercalation and consumption during the charge and discharge process. The molar content of Li varies when the battery is discharged to different states. The above definition of y includes the molar content of Li under different charge and discharge states of the battery. Furthermore, the battery voltage is usually between 2-5V.

[0139] In some embodiments, the above-mentioned active material includes a high-voltage positive electrode active material; further, the above-mentioned active material includes a nickel-containing active material; for example, it can be at least one of a nickel-containing ternary material, lithium nickel cobalt oxide, lithium nickel manganese oxide or lithium nickel cobalt manganese oxide; more specifically, it can be at least one of lithium nickel manganese cobalt oxide, nickel manganese spinel or nickel-rich lithium manganese oxide.

[0140] As an example, the sodium ion active material may include at least one of the following materials: a sodium transition metal oxide, a polyanionic compound, or a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as sodium ion battery positive electrode active materials may also be used.

[0141] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr or Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M includes at least one or more of Ti, V, Mn, Co, Ni, Fe, Cr or Cu, and 0<x≤1.

[0142] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr or Ce; Y includes at least one of P, S or Si; n represents (YO4) n- valence.

[0143] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n-A class of compounds containing anion units and halogen anions. The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, or Ce; Y includes at least one of P, S, or Si, and n represents (YO4) n- valence state; the halogen may be at least one of F, Cl or Br.

[0144] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and a class of compounds containing an optional halogen anion. Y includes at least one of P, S or Si, and n represents (YO4) n- valence state; Z represents a transition metal, including at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr or Ce, m represents (ZO y ) m+ valence state; the halogen may be at least one of F, Cl or Br.

[0145] Polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7)(NFPP), NaM1PO4F or Na3(VO y )2(PO4)2F (3-2y) At least one of .

[0146] M1 is at least one of V, Fe, Mn or Ni, and 0≤y≤1.

[0147] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ). The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr or Ce. Prussian blue compounds are, for example, Na a M2 b M3 c (CN)6, wherein M2 and M3 are each independently selected from at least one of Ni, Cu, Fe, Mn, Co or Zn, 0<a≤2, 0<b<1, 0<c<1.

[0148] In any embodiment of the present application, the current collector may be a metal foil or a composite current collector. For example, the positive electrode sheet may be aluminum foil as the metal foil.

[0149] The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on a polymer substrate.

[0150] In some embodiments, the metal material is selected from any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver or silver alloy.

[0151] In some embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE).

[0152] It can be understood that the current collector has two surfaces arranged opposite to each other in its own thickness direction, and the positive electrode active layer is sequentially provided on at least one surface, which can be one of the surfaces or both surfaces at the same time.

[0153] In some embodiments, the battery further includes an electrolyte. Examples of the electrolyte are described below, including but not limited to the following.

[0154] Diaphragm: The diaphragm is placed between the positive electrode and the negative electrode.

[0155] The type of the diaphragm of the present application can be any known porous structure diaphragm with good chemical stability and mechanical stability.

[0156] In some embodiments, the separator can be made of at least one of fiberglass, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different.

[0157] The thickness of the diaphragm is controlled to be 2 μm to 15 μm; optionally, the thickness of the diaphragm is controlled to be 2 μm to 13 μm.

[0158] Generally, the electrolyte solution includes an electrolyte salt and a solvent.

[0159] In some embodiments, the electrolyte salt may be selected from electrolyte salts commonly used in the art, such as lithium ion electrolyte salts.

[0160] As an example, the lithium ion electrolyte salt includes, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) or lithium tetrafluorooxalatophosphate (LiTFOP).

[0161] In some embodiments, the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) or diethyl sulfone (ESE).

[0162] In some embodiments, the concentration of the electrolyte salt in the electrolyte solution is generally 0.5 mol / L to 15 mol / L.

[0163] The present application has no particular limitation on the shape of the battery, and the battery of the present application can be cylindrical, square, or any other shape. For example, FIG4 shows a square-structured battery cell 4 as an example.

[0164] In some embodiments, referring to FIG5 , the housing may include a shell 41 and a cover 43. Shell 41 may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing a receiving cavity. Shell 41 may have an opening communicating with the receiving cavity, and cover 43 may be positioned over the opening to seal the receiving cavity.

[0165] The positive electrode sheet, separator and negative electrode sheet can be wound or laminated to form an electrode assembly 42, which is encapsulated in the receiving cavity. The number of electrode assemblies 42 included in the battery cell 4 can be one or more, which can be adjusted according to needs.

[0166] The battery includes one or more battery cells 4 .

[0167] The battery may be a battery module or a battery pack; the battery module or battery pack includes at least one battery cell 4. The number of battery cells contained in the battery module may be one or more, and those skilled in the art may select an appropriate number based on the application and capacity of the battery module.

[0168] Figures 6 and 7 illustrate an exemplary battery pack 1. Battery pack 1 includes a battery case and one or more battery cells 4 disposed within the battery case. The battery case comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for the battery cells 4.

[0169] The plurality of battery cells 4 can be arranged in the battery box in any manner.

[0170] The present application also provides an electrical device, which includes the above-mentioned battery.

[0171] Furthermore, in the above-mentioned electrical device, the battery may exist in the form of a battery cell, or may be further assembled into a battery pack.

[0172] The above-mentioned battery or the battery pack assembled therefrom can be used as a power source for an electrical device, or as an energy storage unit for an electrical device.

[0173] The above-mentioned electrical devices may be, but are not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc.

[0174] In some embodiments, the mobile device may be a mobile phone or a laptop computer, etc.

[0175] In some embodiments, electric vehicles include, but are not limited to, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, and the like.

[0176] FIG8 shows an example of an electric device 5. The electric device 5 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device 5's requirements for high power and high energy density of the battery, a battery pack may be used.

[0177] As another example, the power-consuming device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0178] The present application will be described below in conjunction with specific embodiments, but the present application is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present application. Under the guidance of the concept of the present application, those skilled in the art should realize that certain changes made to the various embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0179] The following are specific examples.

[0180] The raw materials used in the following examples and comparative examples were all purchased from the market unless otherwise specified.

[0181] Example 1

[0182] S1: Preparation of negative electrode sheet

[0183] Provide ZSM-5 molecular sieve: ZSM-5 zeolite has a two-dimensional ten-membered ring pore, part of which is a straight pore and the other part is a zigzag pore. Therefore, the molecular sieve has two pore sizes D: 0.55nm and 0.56nm respectively, the silicon-aluminum ratio (molar ratio of silicon dioxide to aluminum oxide) x = 1100, the volume average particle size Dv50 = 12μm, and the specific surface area S = 351m 2 / g.

[0184] The negative electrode active material (graphite, with a volume average particle size Dv50 of 12 μm), the conductive agent acetylene black, the binder SBR, the dispersant sodium carboxymethyl cellulose CMC-Na, and the above molecular sieves were mixed and dispersed in a solvent deionized water at a mass ratio of 94:1:1:1:3, and stirred and mixed until uniformly mixed to prepare a negative electrode active slurry;

[0185] The negative electrode slurry was pressurized at 7 mg / cm 2 The negative electrode active layer is formed by uniformly coating the negative electrode current collector aluminum foil with a coating density of 100 nm and drying the negative electrode active layer to obtain a negative electrode sheet. The molecular sieve content in the prepared negative electrode active layer is 3% by mass, and the mass ratio of the molecular sieve to the negative electrode active material is a1 = 0.032:1.

[0186] Among them, the physical property parameter test of the molecular sieve in the negative electrode sheet can be carried out by the following method:

[0187] If the negative electrode active material is a carbon-based active material, the pole piece is first scraped and powdered, and a sample is calcined to 500℃~600℃ in an oxygen atmosphere to complete the sintering of the binder and negative electrode active material in the pole piece. The remaining particles are the molecular sieve.

[0188] If the negative electrode active material is a silicon-based active material: first scrape the pole piece and take a sample to calcine to 500℃~600℃ in an oxygen atmosphere, then mix the sintered product with sodium hydroxide solution for reaction, and the powder after filtration is the molecular sieve.

[0189] Structural pore size test of molecular sieve: The separated molecular sieve is subjected to X-ray diffraction (XRD) test using the Bruker D8 DISCOVER instrument model. The characteristic peaks of the molecular sieve are tested and compared with the standard spectrum of the molecular sieve to obtain the type of molecular sieve (such as ZSM-5), and the structural pore size corresponding to the molecular sieve type can be obtained.

[0190] The volume average particle size Dv50 of the separated molecular sieve is obtained by testing in accordance with the standard GB / T19077-2016;

[0191] The specific surface area S is obtained by testing in accordance with the standard GB / T 19587-2004.

[0192] S2: Preparation of positive electrode

[0193] The nickel-cobalt-manganese ternary material NCM811, a conductive agent (conductive carbon black), and a binder (PVDF) were mixed in a mass ratio of 98:1:1, N-methylpyrrolidone was added, and the mixture was stirred for 6 hours to obtain a positive electrode slurry with a solid content of 50wt%. The slurry was coated on a positive electrode current collector aluminum foil (thickness of 13μm), and then dried and cold pressed to form a positive electrode active layer with a thickness of 35μm to obtain a positive electrode sheet.

[0194] Isolation membrane: A PE film (thickness of 7 μm) was used as a porous isolation membrane to obtain an isolation membrane.

[0195] S3: Diaphragm

[0196] S4: Preparation of electrolyte: The electrolyte salt LiPF6 is mixed with a mixed solvent and an additive VC (vinylene carbonate) to obtain an electrolyte, wherein the concentration of the electrolyte salt in the mixed solvent is 1 mol / L, the mixed solvent includes EC (ethylene carbonate), DMC (dimethyl carbonate) and EMC (ethyl methyl carbonate) in a mass ratio of 33:33:34, and the mass proportion of the additive Vc in the electrolyte is 2 wt%.

[0197] S5: Preparation of batteries

[0198] The positive electrode sheet, separator and negative electrode sheet were wound and wrapped with an aluminum-plastic film bag, and then injected with the configured electrolyte, vacuum-sealed, and left to stand at room temperature for 6 hours to obtain a battery for subsequent testing.

[0199] S6: Performance Test

[0200] (1) Fast charging performance test, as follows:

[0201] At 25°C, the battery was charged at a constant current of 0.33C to a charge cut-off voltage of 4.4V, then charged at a constant voltage to a current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33C to a discharge cut-off voltage of 2.8V. The actual capacity was recorded as C0.

[0202] Then the battery is charged with a constant current of 0.5C0, 1C0, 1.5C0, 2C0, 2.5C0, 3C0, 3.5C0, 4C0, 4.5C0, and 5C0 in sequence to the full battery charge cut-off voltage of 4.4V or the negative electrode cut-off potential of 0V (whichever is reached first). After each charge is completed, it is necessary to discharge with 1C0 to the full battery discharge cut-off voltage of 2.8V. Record the state of charge (SOC) at different charge rates to 10%, 20%, 30%, ... 80% SOC. The SOC-negative electrode potential curves at different rates were drawn. The charge rate corresponding to the negative electrode potential of 0 V under different SOC states was obtained after linear fitting. The charge rate is the charging window under that SOC state, which is recorded as C10%SOC, C20%SOC, C30%SOC, C40%SOC, C50%SOC, C60%SOC, C70%SOC, and C80%SOC, respectively. The charging time T for charging the battery from 10% SOC to 80% SOC is calculated according to the formula: (60 / C20%SOC + 60 / C30%SOC + 60 / C40%SOC + 60 / C50%SOC + 60 / C60%SOC + 60 / C70%SOC + 60 / C80%SOC) × 10%. For details, please see Table 1. The shorter the charging time T, the better the rapid charging performance of the secondary battery.

[0203] The charging curve obtained with the corresponding charging rate at different SOC states in the above test process as the vertical axis and SOC as the horizontal axis is shown in Figure 9 (a), where the vertical axis is the charging rate (Rate, C) and the horizontal axis is the state of charge (SOC).

[0204] (2) Charging resistance test, as follows:

[0205] At 25°C, the battery prepared above was discharged to 50% capacity, allowed to stand for 30 minutes, and then charged for 10 seconds at a current corresponding to a 4C rate. The electrochemical impedance spectrum during the charging process was obtained by flow impedance testing (frequency range of 500kHz to 30mHz, perturbation voltage of 5mV), as shown in Figure 10 (a), where the horizontal axis is the real part of the impedance (Z'), in ohms, and the vertical axis is the imaginary part of the impedance (-Z"), in ohms.

[0206] (3) Fast charging cycle performance test

[0207] At 25°C, the battery prepared above was charged to 10% SOC at 0.33C, and then charged at 5C to the SOC corresponding to 0V at 5C in the SOC-negative electrode potential curve at different rates in the fast charging performance test, and then charged at 4.5C to the SOC corresponding to 0V at 4.5C in the SOC-negative electrode potential curve at different rates in the fast charging performance test, and then charged at 4C to the SOC corresponding to 0V at 4C in the SOC-negative electrode potential curve at different rates in the fast charging performance test, and so on, until it was charged to 80% SOC, and then charged to 100% SOC at 0.33C, and then discharged to 0% SOC at a rate of 1C. One charge-discharge cycle was considered a cycle, until the capacity of the battery was less than 80% of the initial capacity, and the number of cycles Cy was recorded. For details, see Table 1.

[0208] Note: In the above fast charge cycle performance test, the SOC-negative electrode potential curve used is the SOC-negative electrode potential curve of Comparative Example 1.

[0209] (4) Circulating lithium deposition detection:

[0210] The battery that was cyclically charged and discharged in step (3) above until its capacity was less than 80% of the initial capacity was fully charged and then disassembled to observe the lithium deposition on the negative electrode sheet. The actual picture of the negative electrode sheet is shown in (b) of FIG11 , where only a very small amount of lithium deposition was observed.

[0211] Example 2

[0212] Example 2 is essentially the same as Example 1, differing only in that the molecular sieve used in step S1 is ZSM-5 molecular sieve, with a silicon-to-aluminum ratio x = 200. During the preparation of the negative electrode sheet, the negative electrode active material (graphite), conductive agent acetylene black, binder SBR, dispersant sodium carboxymethyl cellulose (CMC-Na), and the molecular sieve are prepared in a mass ratio of 96:1:1:1:1. The mass content of the molecular sieve in the resulting negative electrode active layer is 1%, and the mass ratio of the molecular sieve to the negative electrode active material, a1, is 0.01.

[0213] The other steps are the same as those in Example 1. Please see Tables 1 to 3 for specific parameters and results.

[0214] Example 3

[0215] Example 3 is essentially the same as Example 2, differing only in that, in step S1, during the preparation of the negative electrode sheet, the negative electrode active material (graphite), conductive agent acetylene black, binder SBR, dispersant sodium carboxymethyl cellulose (CMC-Na), and the aforementioned molecular sieve are prepared in a mass ratio of 96.7:1:1:1:0.3. The mass content of the molecular sieve in the resulting negative electrode active layer is 0.3%, and the mass ratio of the molecular sieve to the negative electrode active material, a1, is 0.0031.

[0216] The other steps are the same as those in Example 2. Please see Table 1 for specific parameters and results.

[0217] Examples 4 to 6

[0218] Examples 4 to 6 are basically the same as Example 2, except that the parameters listed in Table 1 are different. Please see Table 1 for specific values.

[0219] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters and results.

[0220] Examples 7 to 10

[0221] Examples 7 to 10 are basically the same as Example 2, except that the parameters listed in Table 1 are different. Please see Table 1 for specific values.

[0222] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters and results.

[0223] Examples 11 to 15

[0224] Examples 11 to 15 are basically the same as Example 1, except that the molecular sieve parameters listed in Table 1 are different, and in the preparation process of the negative electrode sheet, the negative electrode active material (graphite), the conductive agent acetylene black, the binder SBR, the dispersant sodium carboxymethyl cellulose CMC-Na, and the above molecular sieve are in a mass ratio of 96:1:1:1:1, the mass content of the molecular sieve in the obtained negative electrode active layer is 1%, and the mass ratio of the molecular sieve to the negative electrode active material a1=0.01. Please see Table 1 for specific values.

[0225] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters and results.

[0226] Comparative Example 1

[0227] Comparative Example 1 is substantially the same as Example 1, except that the negative electrode sheet is prepared as follows in step S1:

[0228] The negative electrode active material (graphite), conductive agent acetylene black, binder SBR, and dispersant sodium carboxymethyl cellulose CMC-Na were mixed and dispersed in deionized water solvent at a mass ratio of 97:1:1:1, and stirred and mixed to prepare a negative electrode active slurry;

[0229] The negative electrode slurry was pressurized at 7 mg / cm 2 The coating density is evenly coated on the negative electrode current collector aluminum foil, and after drying, a negative electrode active layer is formed to obtain a negative electrode sheet.

[0230] The other steps are the same as those in Example 1. Please see Tables 1 to 3 for specific parameters and results.

[0231] Among them, the charging curve obtained by the fast charging performance test of the battery prepared in Comparative Example 1 is shown in Figure 9 (b). Comparative analysis of Figure 9 (a) and (b) shows that compared with the charging curve of the battery prepared in Comparative Example 1, the fast charging capability of the battery of Example 1 is significantly improved.

[0232] The electrochemical impedance spectrum of the battery prepared in Comparative Example 1 obtained through the charge resistance test is shown in Figure 10(b). Comparative analysis of Figures 10(a) and (b) shows that the impedance of the battery in Example 1 is significantly lower than that of the battery prepared in Comparative Example 1.

[0233] When the battery prepared in Comparative Example 1 was subjected to a cycle lithium deposition test, a physical image of the disassembled negative electrode sheet is shown in Figure 11 (a). Comparative analysis of Figures 11 (a) and (b) shows that the amount of lithium deposition on the surface of the disassembled negative electrode sheet of the battery prepared in Example 1 is significantly less than that of the disassembled negative electrode sheet of the battery prepared in Comparative Example 1.

[0234] Comparative Example 2

[0235] Comparative Example 2 is basically the same as Example 2, except that the molecular sieve used in step S1 is different and the parameters listed in Table 1 are different. Please see Table 1 for specific values.

[0236] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters and results.

[0237] The relevant parameters and performance test results of each embodiment and comparative example are shown in Table 1. Here, the pore size of the molecular sieve is denoted as D, the molar ratio of SiO2 to Al2O3 is denoted as x, the volume average particle size is denoted as Dv50, and the specific surface area is denoted as S. In the negative electrode active layer, the mass ratio of the molecular sieve to the negative electrode active material is a1, the fast charging time of the battery is denoted as T, and the number of cycles is denoted as Cy.

[0238] Table 1

[0239] In Table 1, “\” represents the absence of the substance or parameter.

[0240] By analyzing the data in Table 1 and comparing the data of Examples 1 to 15 with those of Comparative Examples 1 to 2, it can be seen that the impedance of the battery prepared by using the negative electrode sheet in the present application is reduced and the amount of lithium deposition is reduced, which means that by adding a molecular sieve with a specific pore size to the negative electrode active layer, the desolvation energy barrier of metal ions during charging and discharging can be reduced, thereby reducing the probability of lithium dendrite formation and improving the fast charging performance and cycle stability of the battery.

[0241] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0242] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A negative electrode sheet comprising a current collector and a negative electrode active layer disposed on at least one surface of the current collector, wherein the negative electrode active layer comprises a negative electrode active material and a molecular sieve; in, The pore size D of the molecular sieve satisfies: D≤10 nm.

2. The negative electrode sheet according to claim 1, wherein: 0.3nm≤D≤10nm.

3. The negative electrode sheet according to claim 1, wherein: 0.3nm≤D≤1nm.

4. The negative electrode sheet according to any one of claims 1 to 3, wherein: The molecular sieve includes at least one of a silicon-aluminum molecular sieve, a phosphorus-aluminum molecular sieve, and a silicon-phosphorus-aluminum molecular sieve.

5. The negative electrode sheet according to any one of claims 1 to 4, wherein: The molecular sieve includes a silicon-aluminum molecular sieve, and the silicon-aluminum molecular sieve includes at least one of the compound represented by formula (1) and a hydrate of the compound represented by formula (1); zQ·Al2O3·xSiO2(1); Q includes M + 2O and M 2+ At least one of O; Among them, M + Including H + 、Li + , K + and Na + At least one of M 2+ Including Ca 2+ and Ba 2+ At least one of; 0≤z≤1,0 <x≤2000。 6. The negative electrode sheet according to claim 5, wherein: 20≤x≤1700。 7. The negative electrode sheet according to claim 5, wherein: 100≤x≤500。 8. The negative electrode sheet according to any one of claims 4 to 7, wherein: The silicon-alumina molecular sieve includes at least one of potassium A-type molecular sieve, sodium A-type molecular sieve, calcium A-type molecular sieve, calcium Z-type molecular sieve, sodium Z-type molecular sieve, sodium Y-type molecular sieve, sodium mordenite molecular sieve, ZSM-5 molecular sieve and TS-1 molecular sieve.

9. The negative electrode sheet according to any one of claims 1 to 8, wherein: The volume average particle size Dv50 of the molecular sieve satisfies: 0.1 μm <Dv50≤20μm。 10. The negative electrode sheet according to claim 9, wherein: 0.3μm≤Dv50≤13μm.

11. The negative electrode sheet according to claim 9, wherein: 1μm≤Dv50≤3μm.

12. The negative electrode sheet according to any one of claims 1 to 11, wherein: The specific surface area S of the molecular sieve satisfies: <S≤1500m 2 / g.

13. The negative electrode sheet according to any one of claims 1 to 11, wherein: The specific surface area S of the molecular sieve satisfies: 200m 2 / g≤S≤500m 2 / g.

14. The negative electrode sheet according to any one of claims 1 to 13, wherein: In the negative electrode active layer, the mass ratio of the molecular sieve to the negative electrode active material is (0.001-0.1):

1.

15. The negative electrode sheet according to any one of claims 1 to 13, wherein: In the negative electrode active layer, the mass ratio of the molecular sieve to the negative electrode active material is (0.005-0.03):

1.

16. The negative electrode sheet according to any one of claims 1 to 15, wherein: In the negative electrode active layer, the molecular sieve and the negative electrode active material are mixed with each other.

17. A method for preparing a negative electrode sheet, comprising the following steps: A negative electrode active slurry is used to form a negative electrode active layer on at least one side of a current collector; the negative electrode active slurry includes a negative electrode active material and a molecular sieve, and the pore size D of the molecular sieve satisfies: D≤10nm.

18. The method for preparing a negative electrode sheet according to claim 17, wherein: The steps of preparing the negative electrode active slurry include the following steps: The negative electrode active material, the molecular sieve and a solvent are mixed.

19. A battery comprising the negative electrode sheet according to any one of claims 1 to 16 or the negative electrode sheet prepared by the method for preparing the negative electrode sheet according to any one of claims 17 to 18.

20. An electrical device, wherein: It comprises the battery as claimed in claim 19.

Images