Negative plate and preparation method thereof, battery and power utilization device

Abstract

The invention discloses a negative plate and a preparation method thereof, a battery and an electric device. The negative plate comprises a negative current collector, a porous layer is laminated on the surface of the negative current collector, the porous layer comprises a metal oxide, and the metal oxide comprises an alkali metal element and a metal element with electronegativity greater than 1.3. The battery comprises the negative plate. The electric device comprises the battery. According to the negative plate disclosed by the invention, crystals can be deposited in the pores of the porous layer, and the crystals are disorderly deposited in the pores, so that the generation of dendritic crystals is obviously relieved, and the performances such as the safety performance of the battery are improved. And direct deposition of devitrification on the surface, deviating from the negative electrode current collector, of the porous layer can be obviously reduced, and the stability of a contact interface between the porous layer and electrolyte is good, so that the cycle performance and other electrochemical performance of the battery are improved.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and specifically relates to a negative electrode sheet and a preparation method thereof, a battery, and an electrical device. Background Art

[0002] During the charge and discharge process, ion batteries such as lithium and sodium batteries are prone to crystallization at the negative electrode due to structural changes in the electrode materials and ion migration. This can occur as lithium (lithium batteries) or sodium (sodium batteries) precipitation. When this crystallization, such as lithium or sodium precipitation, occurs unevenly, its continued accumulation can lead to bulges in certain areas and even the formation of dendrites. This can damage the solid electrolyte interface (SEI) and, in worse cases, lead to safety issues such as short circuits, thermal runaway, and even explosions.

[0003] Therefore, how to improve battery safety and suppress the occurrence of battery dendrites has always been a problem that the field has been trying to solve. Summary of the Invention

[0004] In view of the above problems, the present application provides a negative electrode sheet and a preparation method thereof, as well as a battery and an electrical device containing the negative electrode sheet, to alleviate the technical problem that dendrites are prone to occur in the negative electrode sheet of existing batteries.

[0005] In a first aspect, embodiments of the present application provide a negative electrode sheet. The negative electrode sheet of the embodiments of the present application includes a negative electrode current collector, a porous layer laminated on the surface of the negative electrode current collector, the porous layer including a three-dimensional inorganic skeleton, the three-dimensional inorganic skeleton including a metal oxide, and the metal oxide including a first metal element and a second metal element; wherein the first metal element is an alkali metal element, and the second metal element is a metal element having an electronegativity greater than 1.5.

[0006] Since the porous layer in the negative electrode sheet of the embodiment of the present application includes a metal oxide containing a first metal element and a second metal element, on the one hand, it can reduce the phenomenon of electron exchange in the porous layer, so that the electron exchange on the negative electrode sheet will occur on the negative electrode current collector to the greatest extent. When crystallization occurs in the negative electrode sheet, the crystals begin to deposit from the surface of the negative electrode current collector exposed in the pores contained in the porous layer, and deposit layer by layer along the pores, significantly reducing the probability of crystallization directly depositing on the surface of the porous layer away from the negative electrode current collector. Moreover, the porous layer causes disordered deposition of crystallization in its pores, significantly alleviating the formation of dendrites, and improving battery safety performance and other performance. On the other hand, the metal oxide containing the first metal element and the second metal element makes the porous layer have good electrical insulation, improves the stability of the contact interface between the porous layer and the electrolyte, thereby improving the electrochemical performance of the battery, such as the cycle performance.

[0007] In some embodiments, the electrical conductivity of the metal oxide is ≤10-5 S / m. This conductivity range can further improve the electrical insulation of the porous layer, thereby further reducing the probability of electron exchange in the porous layer and increasing the probability of crystallization deposition layer by layer in the pores of the porous layer, thereby further alleviating the formation of dendrites; at the same time, it further improves the stability of the contact interface between the porous layer and the electrolyte.

[0008] In some embodiments, the alkali metal element contained in the metal oxide includes at least one element selected from the group consisting of Li, Na, and K.

[0009] In some embodiments, the second metal element contained in the metal oxide includes at least one metal element selected from the group consisting of Mg, Sn, Zn, Ti, Ag, and Al.

[0010] In an exemplary embodiment, the alkali metal element includes Li, and the metal oxide includes at least one of Li5AlO4, LiAl5O8, Li2MgO2, Li2SnO3, LiAgO, Li2ZnO2, Li2TiO3, Li2Al4O7, and LiAlO2.

[0011] In an exemplary embodiment, the alkali metal element includes Na, and the metal oxide includes at least one of Na5AlO4 and Na2SnO3.

[0012] In an exemplary embodiment, the alkali metal element includes K, and the metal oxide includes at least one of KSbO, KSbO 3 , K 2 SnO 2 , and K 2 SnO 3 .

[0013] The selection of metal oxides, specifically the above-mentioned types or further the above-mentioned specific compounds as the material of the porous layer, can, on the one hand, increase the pore content and pore structure in the porous layer, and improve the structural stability of the three-dimensional inorganic skeleton, so as to further increase the amount of crystallization carried by the porous layer, and increase the disordered deposition of crystallization in the pores, so as to further slow down the formation of dendrites. On the other hand, due to the presence of alkali metal elements in the oxide, the porous layer has at least one of lithium-philic sites, sodium-philic sites, and potassium-philic sites, which can deposit crystallization in the pores of the porous layer while improving the stability of the crystallization in the pores, reducing the crystallization (including the formed dendrites) from falling off the pores and migrating to the surface of the porous layer away from the negative electrode current collector, thereby ensuring that the crystallization is deposited in the pores of the porous layer to the greatest extent, so as to further reduce the formation of dendrites and improve the safety performance of the battery.

[0014] In some embodiments, the porous layer comprises a three-dimensional inorganic framework.

[0015] In some embodiments, the three-dimensional inorganic skeleton includes at least one structure selected from the group consisting of a fiber skeleton, a sheet skeleton, and a rod skeleton.

[0016] These three-dimensional inorganic skeletons can improve the structural stability of the porous layer and form a rich three-dimensional pore network structure, thereby effectively slowing down the formation of dendrites.

[0017] In an embodiment, the three-dimensional inorganic skeleton includes the fiber skeleton, and the fibers of the fiber skeleton include one or more of the following (1) to (2):

[0018] (1) The length of the fiber is 2 to 100 μm;

[0019] (2) The diameter of the fiber is 10 to 100 nm.

[0020] The aspect ratio, length and diameter of the fibers used to form the fiber skeleton are controlled within the above-mentioned ranges, and the pores formed thereby present a rich three-dimensional pore network structure. The porous layer can also be adjusted to have a porosity in the range of 25% to 60%, which can further slow down the formation of dendrites and improve the mechanical properties of the fiber skeleton.

[0021] In some embodiments, the second metal element is a metal element with an electronegativity greater than 1.5. The metal element with an electronegativity greater than 1.5 can further improve the electrical insulation of the porous layer and further enhance the deposition of crystals in the pores of the porous layer 12 .

[0022] In some embodiments, the porous layer includes one or more of (1) to (3):

[0023] (1) The thickness of the porous layer is 10 to 80 μm, and can be optionally 20 to 30 μm;

[0024] (2) The porosity of the porous layer is 25% to 60%, and can be optionally 30% to 50%;

[0025] (3) The pore diameter of the porous layer is 200 to 800 nm, and can be optionally 200 to 450 nm.

[0026] By controlling at least one of the thickness, porosity, pore diameter, etc. of the porous layer within the above-mentioned range, the depth of the pores, the pore structure, etc. can be adjusted, the amount of the metal represented by the first metal element contained in the pore-loaded metal oxide of the porous layer can be increased, and the disordered deposition of the atoms of the first metal element can be increased to further slow down the formation of dendrites and improve the safety performance of the battery.

[0027] In some embodiments, the porous layer further includes an ion supplement, and the ion supplement includes at least one of a lithium supplement, a sodium supplement, and a potassium supplement.

[0028] In an embodiment, the ion supplementer is filled in the pores of the porous layer.

[0029] In an embodiment, the ion supplementer is filled in the pores of the porous layer, and the total filling volume of the ion supplementer in the pores accounts for 10% to 80% of the total volume of the pores.

[0030] In an exemplary embodiment, the lithium supplement includes at least one of metallic lithium, lithium alloy, and lithium-containing inorganic salt.

[0031] In an exemplary embodiment, the sodium supplement comprises at least one of metallic sodium, sodium alloy, and sodium-containing inorganic salt.

[0032] In an exemplary embodiment, the potassium supplement comprises at least one of metallic potassium, potassium alloy, and potassium-containing inorganic salt.

[0033] By providing an ion supplementer in the porous layer, or further controlling the position of the ion supplementer in the porous layer or the filling amount thereof, at least one of active lithium, active sodium, and active potassium can be provided, which can participate in the formation or repair of the SEI film during the battery charge and discharge process, thereby improving the reversible capacity of the battery.

[0034] In some embodiments, the negative electrode current collector comprises a metal current collector or a composite current collector; wherein the metal contained in the metal current collector or the composite current collector comprises at least one of copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. Negative electrode current collectors made of these materials can enhance the strength of the porous layer bonded to the negative electrode, improving the structural stability of the negative electrode sheet.

[0035] In a second aspect, the present invention also provides a method for preparing a negative electrode sheet. The method for preparing a negative electrode sheet in the present invention comprises the following steps:

[0036] forming a porous layer on the surface of the negative electrode current collector;

[0037] The porous layer includes a metal oxide, and the metal oxide includes a first metal element and a second metal element; the first metal element is an alkali metal element; and the second metal element is a metal element with an electronegativity greater than 1.3.

[0038] The method for preparing the negative electrode sheet of the embodiment of the present application directly forms a porous layer of metal oxide containing a first metal element and a second metal element on the surface of the negative electrode current collector, thereby giving the porous layer good electrical insulation and a rich pore structure such as high porosity. When crystallization occurs on the negative electrode sheet, the crystals can be directly deposited in the pores contained in the porous layer, and the crystals can be disorderly deposited in the pores, thereby significantly alleviating the formation of dendrites and improving the electrochemical stability and safety performance of the battery. Moreover, the porous layer is directly formed on the surface of the negative electrode current collector. Therefore, the formed porous layer has a strong bonding force with the negative electrode current collector, and the preparation method conditions are controllable, thereby improving the quality stability of the negative electrode sheet.

[0039] In some embodiments, the electrical conductivity of the metal oxide is ≤10 -5 The metal oxides in this conductivity range have good electrical insulation, thus giving the formed three-dimensional inorganic skeleton good electrical insulation and reducing the phenomenon of electron exchange in the porous layer.

[0040] In some embodiments, the method for forming a porous layer on the surface of the negative electrode current collector comprises the following steps:

[0041] preparing a material or precursor material for forming a three-dimensional inorganic framework into a slurry;

[0042] The slurry is subjected to the film-forming treatment on the surface of the negative electrode current collector.

[0043] The material or precursor material for forming the three-dimensional inorganic skeleton is prepared into a slurry so as to facilitate film formation by coating. A relatively mature coating film forming process can be used to form the film to improve the quality of the porous layer, such as thickness uniformity, pore distribution uniformity, etc.

[0044] In the embodiment, the viscosity of the slurry at 28° C. is 5000-12000 mPa.s.

[0045] The slurry within this viscosity range can effectively control the porosity of the porous layer to 25% to 60%, and the pore diameter can be within the range of 200 to 800 nm.

[0046] In some embodiments, the precursor material is prepared according to a method comprising the following steps:

[0047] Carrying out an etching reaction on the AX alloy in an alcohol solution to generate the precursor material, wherein the concentration of the alcohol solution is 95% to 100%;

[0048] Wherein, A in the AX alloy is the first metal element, and X is the second metal element.

[0049] By using alcohol to etch the AX alloy, the generated precursor material can form linear materials including fibers and other morphologies, thereby forming skeletons including three-dimensional fiber skeletons, which can enrich the three-dimensional pore network structure contained in the porous layer.

[0050] In some embodiments, the method further comprises the step of loading an ion supplementing agent in the porous layer.

[0051] In an embodiment, the ion supplementer is filled in the pores of the porous layer, and a method of filling the ion supplementer into the pores includes at least one of a slurry infusion method and a melt infusion method.

[0052] In a third aspect, an embodiment of the present application provides a battery, comprising the negative electrode sheet of the embodiment of the present application or a negative electrode sheet prepared by the method for preparing the negative electrode sheet of the embodiment of the present application.

[0053] Because the battery of the present embodiment includes the negative electrode sheet of the present embodiment, when crystallization occurs in the battery cell, the crystals will randomly deposit within the pores of the porous layer of the negative electrode sheet, significantly alleviating the formation of dendrites and improving battery safety and other performance. This also improves the stability of the interface between the negative electrode sheet and the electrolyte, thereby enhancing the battery's electrochemical performance, such as cycling performance.

[0054] In a fourth aspect, an embodiment of the present application provides an electrical device, including a battery according to an embodiment of the present application.

[0055] Since the electrical device of the embodiment of the present application contains the battery of the embodiment of the present application, the power supply unit or energy storage unit of the electrical device of the embodiment of the present application has high safety, good cycle performance and long service life.

[0056] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0058] Figure 1 A schematic structural diagram of a negative electrode sheet according to some embodiments of the present application;

[0059] Figure 2 This is another structural schematic diagram of the negative electrode sheet in some embodiments of the present application;

[0060] Figure 3 A surface scanning electron microscope (SEM) image of the porous layer contained in the negative electrode sheet provided in some embodiments of the present application;

[0061] Figure 4 This is a schematic structural diagram of an embodiment of a battery cell of the present application;

[0062] Figure 5 for Figure 4 An exploded schematic diagram of the battery cell shown;

[0063] Figure 6This is a schematic structural diagram of an embodiment of a battery module of the present application;

[0064] Figure 7 This is a schematic structural diagram of an embodiment of a battery pack of the present application;

[0065] Figure 8 for Figure 7 Schematic diagram of the exploded structure of the battery pack shown;

[0066] Figure 9 Schematic diagram of an embodiment of an electrical device including a battery according to an embodiment of the present application as a power source;

[0067] Figure 10 The charge and discharge curve of the lithium-ion battery cell containing the negative electrode sheet in Example 1 is shown;

[0068] Figure 11 This is a charge and discharge curve diagram of a lithium-ion battery cell containing the negative electrode sheet in Example 6.

[0069] The accompanying drawings in the specific implementation manner are as follows:

[0070] 10-negative electrode sheet, 11-negative electrode current collector, 12-porous layer, 121-three-dimensional inorganic skeleton, 122-pores;

[0071] 20-battery cell, 21-housing, 22-electrode assembly, 23-cover plate;

[0072] 30-battery module;

[0073] 40-battery pack, 41-upper box, 42-lower box. DETAILED DESCRIPTION

[0074] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0076] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0077] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of 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.

[0078] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0079] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0080] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0081] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0082] Batteries, as portable power sources, are widely used in various electronic devices. For example, lithium batteries, due to their high energy density, long cycle life, and low self-discharge rate, have found widespread application in smartphones, laptops, electric vehicles, and other fields. Sodium batteries, with their higher theoretical specific capacity and lower cost compared to lithium batteries, have already found initial application in energy storage systems, solar streetlights, and other fields.

[0083] However, there are still some problems in practical applications of batteries. For example, during the charge and discharge process of lithium batteries and sodium batteries, due to structural changes in the electrode materials and ion migration, crystallization phenomena such as lithium deposition (lithium batteries) or sodium deposition (sodium batteries) are prone to occur at the negative electrode of the battery. When crystallization such as lithium deposition or sodium deposition occurs unevenly, continuous accumulation causes bulges in certain areas and even forms dendrite structures, which may lead to the destruction of the solid electrolyte interface (SEI) and even worse, cause safety issues such as short circuit, thermal runaway, and even explosion.

[0084] To mitigate the phenomenon of crystallization, including the formation of dendrites, in batteries, current improvements are mainly made by optimizing negative electrode materials, improving electrolytes, and controlling charge and discharge conditions. Although these existing methods can mitigate the development of crystallization, including dendrites, to a certain extent, the effect is not ideal.

[0085] In order to effectively slow down crystallization, including dendrite formation, at the negative electrode and improve the battery's cycling performance and safety, a composite negative electrode sheet is proposed, which includes a porous layer on the surface of the negative electrode current collector. The porous layer is controlled to contain metal oxides, and the metal oxides include alkali metal elements and metal elements with an electronegativity greater than 1.3. The porous layer is added to the surface of the negative electrode current collector, and the material of the porous layer is selected so that the porous layer is inert to electrons, reducing the exchange of electrons between the porous layer and the negative electrode. This allows crystallization at the negative electrode to deposit directly on the exposed current collector surface within the pores of the porous layer to the greatest extent possible, reducing the amount of crystallization directly deposited on the porous layer surface. This significantly reduces the destructive effect of crystallization on the SEI membrane and improves the battery's cycling performance. Furthermore, the porous layer allows crystallization to deposit in a disordered manner, significantly slowing down the formation of dendrites and reducing the amount of dendrite formation, thereby improving the battery's safety. At the same time, the porous layer also reduces side reactions at the interface between the negative electrode sheet and the electrolyte, further improving the battery's cycling performance.

[0086] Based on the above research, the embodiments of this application propose the following technical solutions.

[0087] negative electrode

[0088] In the first aspect, the present invention provides a negative electrode sheet. In some embodiments, the negative electrode sheet structure of the present invention is as follows: Figures 1 to 2 As shown, the negative electrode sheet 10 includes a negative electrode current collector 11 and a porous layer 12 laminated on the surface of the negative electrode current collector. The porous layer 12 includes a metal oxide, and the metal oxide includes a first metal element and a second metal element; the first metal element is an alkali metal element; the second metal element is a metal element with an electronegativity greater than 1.3, optionally greater than 1.5.

[0089] In the negative electrode sheet 10 of the embodiment of the present application, the negative electrode current collector 11 refers to a structure for collecting current and for transmitting electrons. In the embodiment of the present application, the negative electrode current collector 11 also serves as a negative electrode material. The porous layer 12 refers to a layer structure with a pore structure. Metal oxide refers to an ionic compound formed by covalent bonds between a metal element containing a first metal element and a second metal element and an oxygen element. There are no free electrons in its crystal structure, and electrons cannot flow freely and cannot conduct current, that is, it has electrical insulation. Among them, electrical insulation means that the porous layer 12 has low electron transfer performance or electron exchange performance or almost no electron transfer and electron exchange characteristics. The alkali metal element (that is, the first metal element) in the metal oxide should be understood as a metal element in Group IA of the periodic table. Electronegativity refers to the scale of the ability of the atoms of the second metal element to attract electrons in the metal oxide, and is based on the electronegativity of fluorine specified by Pauling as 4.0, and the electronegativity values of these metal elements are determined based on this standard. In addition, based on the electronegativity value range of the second metal element, the second metal element and the first metal element are different types of metal elements.

[0090] The negative electrode current collector 11 contained in the negative electrode sheet 10 of the embodiment of the present application can play the role of a conventional negative electrode. The porous layer 12 contains a metal oxide containing the first metal element and the second metal element, which has good electrical insulation. On the one hand, it can reduce the phenomenon of electron exchange in the porous layer 12. When crystallization occurs in the negative electrode sheet 10, the crystallization is deposited from the surface of the negative electrode current collector 11 exposed in the pores contained in the porous layer 12 to the greatest extent, and deposited layer by layer along the pores, significantly reducing the probability of crystallization directly depositing on the surface of the porous layer 12 away from the negative electrode current collector 11. Moreover, the porous layer 12 allows the crystallization to deposit disorderly in the pores of the porous layer 12, significantly alleviating the formation of dendrites and improving battery safety performance and other performance. On the other hand, since the porous layer 12 contains the above-mentioned metal oxide containing the first metal element and the second metal element, it has good electrical insulation, improves the stability of the contact interface between the porous layer 12 and the electrolyte, thereby improving the electrochemical performance of the battery, such as the cycle performance.

[0091] [Negative electrode current collector contained in negative electrode sheet]

[0092] In some embodiments, such as Figures 1 to 2The thickness of the negative electrode current collector 11 included in the negative electrode sheet 10 of the embodiment of the present application can be 20 to 50 μm. This thickness range can effectively ensure the mechanical strength of the negative electrode sheet 10 while effectively controlling the overall thickness of the negative electrode sheet 10, thereby improving the volume energy density of the battery.

[0093] In some embodiments, the negative electrode current collector 11 included in the negative electrode sheet 10 of the present invention may include, but is not limited to, a metal or composite current collector. For example, the metal may include copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.

[0094] The composite current collector may include a composite material of a polymer and a metal. The polymer may include, but is not limited to, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc., and the metal may include, but is not limited to, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may be obtained by blending the polymer and the metal, or may be coated on at least one side of the polymer by electroplating, coating, or other methods.

[0095] These metal or composite current collectors have good electrical conductivity, good mechanical properties, and flexible thickness control. Furthermore, these negative electrode current collectors can enhance the strength of the porous layer 12 and improve the structural stability of the negative electrode sheet 10.

[0096] In the embodiment, the negative electrode current collector 11 may have a conventional structure and morphology, such as a sheet. When the negative electrode current collector 11 is in the sheet shape, it has two opposite surfaces.

[0097] [Porous layer contained in the negative electrode sheet]

[0098] The porous layer 12 contained in the negative electrode sheet 10 of the present embodiment can be stacked on the surface of the negative electrode current collector 11 in any manner. For example, in the embodiment, it can be a non-fixed stacking arrangement or a fixed stacking arrangement. When a fixed stacking arrangement is used, it can include but is not limited to bonding, pressing, or in-situ film formation. As long as the porous layer 12 can be stacked and bonded to the surface of the negative electrode current collector 11 and can play the role of the negative electrode current collector 11 in transporting electrons and exchanging charges, it can be used.

[0099] In some embodiments, when the negative electrode current collector 11 is in sheet form (having two opposite surfaces), the porous layer 12 contained in the negative electrode sheet 10 of the present embodiment can be combined on one surface of the negative electrode current collector 11, such as Figure 1 Of course, the porous layer 12 can also be combined on the two opposite surfaces of the negative electrode current collector 11, as shown in FIG. Figure 2 shown.

[0100] In some embodiments, the thickness of the porous layer 12 included in the negative electrode sheet 10 of the present application can be controlled to be 10-80 μm, optionally 20-50 μm, and further 20-30 μm. In exemplary embodiments, the thickness can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, or any other typical but non-limiting thickness, or a range between any two thickness values. Controlling the thickness of the porous layer 12 within a range can adjust the depth of the pores in the porous layer 12. When crystallization occurs in the negative electrode sheet 10, the crystals can be fully deposited in the pores, reducing or preventing the crystal deposition from filling the pores and overflowing the pores, resulting in deposition on the surface of the porous layer 12. In addition, this thickness can improve the mechanical properties of the negative electrode sheet 11 together with the negative electrode current collector 11 , and can also improve the volume energy density of the battery.

[0101] In some embodiments, the porosity of the porous layer 12 contained in the negative electrode sheet 10 of the present application embodiment can be 25% to 60%, optionally 30% to 50%, and further optionally 30% to 40%. In exemplary embodiments, it can be 25%, 27%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, 50%, 60%, and other typical but non-limiting porosities or a range between any two porosity values. Controlling the porosity of the porous layer 12 within this range can increase the amount of pore-loaded crystallization contained in the porous layer 12 and increase the disordered deposition of crystallization to further slow down the formation of dendrites and improve the safety performance of the battery. Moreover, the porosity in this range can enable the pores in the porous layer 12 to form a rich three-dimensional pore structure, so that the pores can form a rich three-dimensional pore network channel in the porous layer 12, increase the disordered deposition of crystallization, to further slow down the formation of dendrites and improve the safety performance of the battery. The porosity of the porous layer 12 may be measured according to the method of GB / T24586-2009 below.

[0102] In some embodiments, the diameter of the pores in the porous layer 12 contained in the negative electrode sheet 10 of the embodiment of the present application can be 200 to 800 nm, optionally 200 to 450 nm. In the exemplary embodiment, it can be a typical but non-limiting pore diameter such as 200 nm, 300 nm, 400 nm, 450 nm, 500 nm, 600 nm, 700 nm, 800 nm, or a range between any two pore diameter values. The diameter of the pore can be the gap distance between two adjacent pore skeletons in the porous layer 12, which can be calibrated and detected using a scanning electron microscope (SEM). Controlling the diameter of the pore within this range can increase the porosity of the porous layer 12, thereby increasing the amount of crystallization loaded by the porous layer 12; at the same time, the pore diameter in this range can increase the disordered deposition of crystallization in the pores 122, so as to further slow down the formation of dendrites and reduce the amount of dendrite formation.

[0103] In some embodiments, the structure of the porous layer 12 can be as follows: Figure 3 As shown, it includes a three-dimensional inorganic skeleton 121. Figure 3 In the porous layer 12 shown, the three-dimensional inorganic skeleton 121 constitutes the layer skeleton of the porous layer 12, and adjacent three-dimensional inorganic skeletons 121 constitute pores 122 in the porous layer 12. Since the three-dimensional inorganic skeleton 121 is a three-dimensional skeleton, the pores 122 formed by the three-dimensional inorganic skeleton 121 can also be a three-dimensional porous structure, that is, at least some of the pores are interconnected.

[0104] In some embodiments, such as Figure 3 The three-dimensional inorganic skeleton 121 in the porous layer 12 may include at least one of a fiber skeleton, a sheet skeleton, and a rod skeleton. The fiber skeleton refers to a skeleton that is fibrous, or a skeleton formed by fibers in a certain regular or irregular manner, such as interweaving; Figure 3 As shown, when the three-dimensional inorganic skeleton 121 is a fibrous skeleton, the fibrous skeleton forms abundant pores 122 in the porous layer 12, and the abundant pores 122 present a three-dimensional pore network. Similarly, a sheet-like skeleton refers to a skeleton that is sheet-like, or is formed by sheet-like materials stacked in a certain regular or irregular manner, such as stacking. A rod-like skeleton refers to a skeleton that is rod-like, or is formed by rod-like materials in a certain regular or irregular manner.

[0105] The three-dimensional inorganic skeletons 121 of the above-mentioned morphologies can improve the structural stability of the porous layer 12 and form a rich three-dimensional pore network structure, thereby effectively slowing down the formation of dendrites.

[0106] When the three-dimensional inorganic skeleton 121 includes Figure 3When the fiber skeleton is shown, in the embodiment, the aspect ratio of the fibers of the fiber skeleton can be (2-100): (10-100), optionally (30-80): (20-80), and in the exemplary embodiment, it can be (2-40): (70-80), (2-40): (60-70), (40-60): (50-60), (60-80): (40-50) and other typical but non-limiting aspect ratios or ranges between any aspect ratio values.

[0107] In an embodiment, the length of the fibers of the fiber skeleton can be 2 to 100 μm, and can further be 30 to 80 μm. In a demonstration example, it can be 2 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, and other typical but non-restrictive lengths or a range between any two length values.

[0108] In an embodiment, the fiber diameter of the fiber skeleton can be selected as 10 to 100 nm, and further selected as 20 to 80 nm. In a demonstration example, it can be a typical but non-limiting diameter such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or a range between any two diameter values.

[0109] The aspect ratio, length and diameter of the fibers of the fiber skeleton are controlled within the above ranges respectively, and the pores 122 formed thereby present a rich three-dimensional pore network structure. The porous layer 12 can also be adjusted to have a porosity in the range of 25% to 60% as mentioned above, which can further slow down the formation of dendrites and improve the mechanical properties of the fiber skeleton.

[0110] When the three-dimensional inorganic skeleton 121 includes a rod-shaped skeleton, in an embodiment, the aspect ratio of the rod-shaped material of the rod-shaped skeleton can be (5-100):1, and can be optionally (10-20):1. In an exemplary embodiment,

[0111] Typical but non-limiting aspect ratios include 80:1, 90:1, 100:1, or any range between aspect ratio values.

[0112] In an embodiment, the length of the rod-shaped material of the rod-shaped skeleton can be 10 to 50 μm, optionally 20 to 30 nm. In an exemplary embodiment, it can be a typical but non-limiting length such as 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, or a range between any two length values.

[0113] In an embodiment, the diameter of the rod-shaped material of the rod-shaped skeleton can be 20 to 500 nm, optionally 20 to 400 nm. In an exemplary embodiment, it can be a typical but non-limiting diameter such as 20 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, or a range between any two diameter values.

[0114] The aspect ratio, length and diameter of the rod-shaped material of the rod-shaped skeleton are controlled within the above-mentioned ranges respectively, and the pores 122 formed therein also have a rich three-dimensional pore network structure. The porous layer 12 can also be adjusted to have a rich porosity of 25% to 60% as mentioned above, which can further slow down the formation of dendrites and improve the mechanical properties of the rod-shaped skeleton.

[0115] When the three-dimensional inorganic skeleton 121 includes a sheet-like skeleton, in an embodiment, the plane area of the sheet-like material of the sheet-like skeleton can be 400 to 10000 nm. 2 , optional 600~2500nm 2 , in this example, it can be 400nm 2 , 600nm 2 , 800nm 2 , 1000nm 2 , 2000nm 2 , 2500nm 2 , 3000nm 2 , 4000nm 2 , 5000nm 2 , 6000nm 2 , 7000nm 2 , 8000nm 2 , 9000nm 2 , 10000nm 2 Typical but non-limiting areas or ranges between any two area values.

[0116] In an embodiment, the thickness of the sheet material of the sheet skeleton can be 20 to 100 nm, optionally 30 to 60 nm. In a demonstration example, it can be a typical but non-limiting thickness such as 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or a range between any two thickness values.

[0117] The planar area and thickness of the sheet material of the sheet skeleton are controlled within the above ranges respectively, and the pores 122 formed therein also have rich porosity and three-dimensional pore network structure as well as good mechanical properties, thereby further slowing down dendrites and improving the structural stability of the porous layer 12.

[0118] Since the metal oxide in the porous layer 12 in each of the above embodiments includes the first metal element and the second metal element, the metal oxide should have good electrical insulation. In some embodiments, the electrical conductivity of the metal oxide contained in the porous layer 12 is ≤10 -5 S / m, optional ≤10 -8 S / m, and the lower the conductivity, the more desirable it is. Among them, conductivity can also be called electrical conductivity, which is the inverse of resistivity. The lower the conductivity of the metal oxide, the more desirable it is. Controlling the conductivity of the metal oxide contained in the porous layer 12 to be below this conductivity can improve the electrical insulation of the porous layer 12, reduce the probability of electron exchange in the porous layer 12, and enable the crystallization of the negative electrode sheet 10 to be deposited in the pores of the porous layer 12 to the greatest extent, and increase the disordered deposition of crystallization, further slowing down the formation of dendrites, and improving the safety performance of the battery. At the same time, further improve the stability of the contact interface between the porous layer 12 and the electrolyte. Among them, the conductivity of the porous layer 12 can be obtained by first using a four-probe inspection technique to detect the resistivity of the porous layer 12, and then calculating the inverse of the conductivity to obtain the conductivity.

[0119] In the embodiments, the metal oxide in the porous layer 12 of the above embodiments can be referred to as AXO oxide. The AXO oxide represents an oxide containing three elements: the element represented by A, the element represented by X, and O (oxygen). A represents the first metal element. In an exemplary embodiment, the first metal element represented by A can include any one of Li, Na, and K. X represents the second metal element. In an exemplary embodiment, the metal element represented by X can include at least one of Mg, Sn, Zn, Ti, Ag, and Al. The metal element represented by X is optionally a metal element that can form an alloy with the element represented by A.

[0120] Based on the first metal element and the second metal element contained in the above metal oxide, such as the types of elements A and X contained in the oxide represented by AXO, in an exemplary embodiment, the above metal oxide such as the oxide represented by AXO may include at least the following types and specific compounds:

[0121] In an exemplary embodiment, when A is Li, the AXO oxide may include at least one of Li5AlO4, LiAl5O8, Li2MgO2, Li2SnO3, LiAgO, Li2ZnO2, and Li2TiO3.

[0122] In an exemplary embodiment, when A is Na, the AXO oxide includes at least one of Na5AlO4 and Na2SnO3.

[0123] In an exemplary embodiment, when A is K, the AXO oxide includes at least one of KSbO, KSbO 3 , K 2 SnO 2 , and K 2 SnO 3 .

[0124] Selecting metal oxides such as oxides shown in AXO, specifically selecting the above types or further the above specific compounds as the material of the porous layer 12, on the one hand, can increase the pore content and pore structure in the porous layer 12, such as forming Figure 3 The three-dimensional inorganic skeleton 121 shown can make the three-dimensional inorganic skeleton 121 a fiber skeleton, and of course it can also be a rod-shaped skeleton or a sheet-shaped skeleton and other morphological structures. When the three-dimensional inorganic skeleton 121 is formed, it can form abundant pores 122 in the porous layer 12, and at least part of the pores 122 are interconnected to form a rich three-dimensional pore network structure, thereby effectively improving the porosity of the porous layer 12, so as to further increase the amount of crystallization loaded by the porous layer 12, and increase the disordered deposition of crystallization in the pores 122, so as to further slow down the formation of dendrites. On the other hand, the porous layer 12 formed by the metal oxide such as AXO oxide has good mechanical properties. When formed as Figure 3 When the three-dimensional inorganic skeleton 121 is shown, the three-dimensional inorganic skeleton 121 has good mechanical properties, thereby improving the structural stability of the porous layer 12, so that the crystallization of the negative electrode sheet 10 can be better disorderly deposited in the pores of the porous layer 12. Secondly, due to the presence of alkali metal elements in the metal oxide, the porous layer 12 has at least one of lithium-loving sites, sodium-loving sites, and potassium-loving sites. For example, when the alkali metal elements in the metal oxide include lithium, the metal oxide such as AXO oxide has lithium-loving sites; when the alkali metal elements in the metal oxide include sodium, the metal oxide such as AXO oxide has sodium-loving sites; when the alkali metal elements in the metal oxide include potassium, the metal oxide such as AXO oxide has potassium-loving sites. Because the porous layer 12 has at least one of the following sites: a lithium-loving site, a sodium-loving site, and a potassium-loving site, when crystallization occurs in the negative electrode sheet 10, the crystals are deposited in the pores of the porous layer 12 while improving the stability of the crystals in the pores, reducing the risk of crystals (including formed dendrites) falling out of the pores and migrating to the surface of the porous layer 12 facing away from the negative electrode current collector 11. In this way, the deposition of subsequent crystals on the surface of the crystals that migrate to the surface of the porous layer 12 is reduced, thereby ensuring that the crystals are deposited in the pores of the porous layer 12 to the greatest extent possible, further reducing the formation of dendrites and improving the safety performance of the battery.

[0125] On the basis of the above embodiments, as some embodiments of the present application, the porous layer 12 in the above embodiments further includes an ion supplement. The ion supplement may include at least one of a lithium supplement, a sodium supplement, and a potassium supplement. The ion supplement may be doped into the skeleton of the porous layer 12, such as being doped into the above metal oxide, or may be filled into the pores contained in the porous layer 12. For example, in the embodiment, the ion supplement is filled into Figure 3 In the pores 122 of the porous layer 12 shown. By filling the pores of the porous layer 12 with the ion supplement as in the embodiment, at least one of active lithium, active sodium, and active potassium can be provided, such as participating in the formation or repair of the SEI film during the battery charge and discharge process, thereby improving the reversible capacity of the battery. In the embodiment, when the ion supplement includes a lithium supplement, the negative electrode sheet 10 of the embodiment of the present application can be used as a negative electrode sheet of a lithium battery; when the ion supplement includes a sodium supplement, the negative electrode sheet 10 of the embodiment of the present application can be used as a negative electrode sheet of a sodium battery; when the ion supplement includes a potassium supplement, the negative electrode sheet 10 of the embodiment of the present application can be used as a negative electrode sheet of a potassium battery. Of course, it can also contain both a lithium supplement and a sodium supplement, such as a negative electrode sheet for a sodium battery.

[0126] When the metal oxide material in the porous layer 12 includes the above-mentioned metal oxides such as AXO oxide, the skeleton of the porous layer 12 is as follows: Figure 3The three-dimensional inorganic framework 121 in the porous layer 12 shown has sites that are lithium-, sodium-, and potassium-philic. This effectively enhances the binding force between the aforementioned ion-supplementing agent, such as at least one of the lithium, sodium, and potassium supplements, and the framework of the porous layer 12, thereby improving the stability of the aforementioned ion-supplementing agent, such as at least one of the lithium, sodium, and potassium supplements, within the porous layer 12. In embodiments, when the aforementioned ion-supplementing agent is filled in the pores of the porous layer 12, the stability of the ion-supplementing agent within the pores can be improved, thereby enhancing the stability of the negative electrode sheet 11 in replenishing at least one of lithium, sodium, and potassium. More importantly, when at least one of the aforementioned ion-supplementing agents, such as a lithium supplement, a sodium supplement, or a potassium supplement, has good electrical conductivity and is filled in the pores of the porous layer 12, the skeleton of the porous layer 12 has sites that are affinitive for lithium, sodium, or potassium, which can reduce the concentration of at least one of the lithium supplement, sodium supplement, or potassium supplement, thereby reducing the risk of the ion-supplementing agent falling out of the pores of the porous layer 12 and migrating to the surface of the porous layer 12 facing away from the negative electrode current collector 11. In this way, when crystallization occurs in the battery, the crystals will not deposit on the conductive surface of the lithium supplement, sodium supplement, or potassium supplement that has migrated to the surface of the porous layer 12 facing away from the negative electrode current collector 11. Therefore, the crystals can be deposited in the pores of the porous layer 12 to the greatest extent possible, further reducing the formation of dendrites and thus improving the safety of the battery. Therefore, when at least one of the lithium supplement, sodium supplement, and potassium supplement has good electrical conductivity, in the embodiment, the at least one of the lithium supplement, sodium supplement, and potassium supplement is filled in the pores of the porous layer 12, that is, it does not overflow the pores to the surface of the porous layer 12, so as to avoid crystallization and deposition on the at least one of the lithium supplement, sodium supplement, and potassium supplement bound to the surface of the porous layer 12.

[0127] For example, in the embodiment, when the metal oxide such as AXO oxide is a lithium-containing oxide, the ion supplement contained in the porous layer 12 may include a lithium supplement. In an exemplary embodiment, the ion supplement is filled in the pores of the porous layer 12. When the metal oxide such as AXO oxide is a sodium-containing oxide, the ion supplement contained in the porous layer 12 may include a sodium supplement. In an exemplary embodiment, the ion supplement is filled in the pores of the porous layer 12. When the metal oxide such as AXO oxide is a potassium-containing oxide, the ion supplement contained in the porous layer 12 may include a potassium supplement. In an exemplary embodiment, the ion supplement is filled in the pores of the porous layer 12. In this way, the lithium supplement corresponds to the lithium-philic site of the skeleton of the porous layer 12, the sodium supplement corresponds to the sodium-philic site of the skeleton of the porous layer 12, and the potassium supplement corresponds to the potassium-philic site of the skeleton of the porous layer 12. This can further enhance the binding force between at least one of the ion supplements, such as the lithium supplement, the sodium supplement, and the potassium supplement, and the porous layer 12, thereby improving the stability of the lithium supplement, the sodium supplement, and the potassium supplement, respectively.

[0128] In an exemplary embodiment, the lithium supplement may include at least one of metallic lithium, a lithium alloy, and a lithium-containing inorganic salt. The sodium supplement may include at least one of metallic sodium, a sodium alloy, and a sodium-containing inorganic salt. The potassium supplement may include at least one of metallic potassium, a potassium alloy, and a potassium-containing inorganic salt. These lithium, sodium, and potassium supplements can each provide abundant active ions, such as active lithium ions, active sodium ions, and active potassium ions, during the battery's charge and discharge processes.

[0129] In the embodiment, the total weight of at least one of the ion supplements, such as lithium supplements, sodium supplements, and potassium supplements, contained in the porous layer 12 satisfies: the product of the total capacity of the battery cell and the value of the capacity retention rate improvement divided by the constant a, specifically satisfying the following formula relationship:

[0130] G = C × T / a.

[0131] In the formula, G is the total weight of at least one of the ion supplements, such as lithium supplements, sodium supplements, and potassium supplements, loaded in the negative electrode sheet 10; C is the total capacity of the battery cell containing the negative electrode sheet 10 according to the embodiment of the present application, in mAh; T is the expected SOH improvement value of the battery cell containing the negative electrode sheet 10 according to the embodiment of the present application, in %, SOH refers to the percentage of the remaining capacity of the battery cell to the initial capacity; a refers to the total theoretical gram capacity constant of any one or more of the ion supplements, such as lithium supplements, sodium supplements, and potassium supplements, wherein, when the ion supplement is lithium metal, a(lithium metal) is 3860 mAh / g, when the ion supplement is sodium metal, a(sodium metal) is 1166 mAh / g, and when the ion supplement is potassium metal, a(potassium metal) is 686 mAh / g.

[0132] In an embodiment, when the ion-replenishing agent is filled in the pores of the porous layer 12, the filling volume of the ion-replenishing agent in the pores accounts for 10% to 80% of the filled pore volume. The filling volume of the ion-replenishing agent in the pores as a percentage of the filled pore volume can be checked according to the method described below in "Method for Determining the Filling Amount of the Ion-Replenishing Agent in the Porous Layer."

[0133] By controlling the content of the ion-supplementing agent in the porous layer 12 within the above range, at least one of active lithium, active sodium, and active potassium can be provided during the charge and discharge process, thereby participating in the formation or repair of the SEI film during the battery's charge and discharge process, thereby improving the battery's reversible capacity. When the ion-supplementing agent is filled in the pores of the porous layer 12, this volume ratio of the ion-supplementing agent not only fully provides at least one of active lithium, active sodium, and active potassium, but also provides space for the deposition of crystals that may occur in the negative electrode sheet 10. This allows the crystals to be deposited in the pores of the porous layer 12 as much as possible, significantly reducing the formation of dendrites on the surface of the negative electrode sheet 10 and improving battery safety and other performance.

[0134] Preparation method of negative electrode sheet

[0135] The present application also provides a method for preparing the negative electrode sheet of the above embodiment. In some embodiments, the method for preparing the negative electrode sheet of the above embodiment includes the following steps:

[0136] S10: forming a porous layer on the surface of the negative electrode current collector.

[0137] In the preparation method of the negative electrode sheet of the embodiment of the present application, the negative electrode current collector refers to the above Figure 1 and Figure 2 The negative electrode current collector 11 in the negative electrode sheet 10 of the embodiment of the present application is shown. The porous layer includes the metal oxide described above in the porous layer of the negative electrode sheet of the embodiment of the present application. Therefore, the metal oxide includes a first metal element and a second metal element; the first metal element is an alkali metal element; the second metal element is a metal element with an electronegativity greater than 1.3, optionally greater than 1.5.

[0138] The method for preparing the negative electrode sheet of the embodiment of the present application directly forms a porous layer of metal oxide containing a first metal element and a second metal element on the surface of the negative electrode current collector, thereby giving the porous layer a rich pore structure such as high porosity. When crystallization occurs on the negative electrode sheet, the crystals can be directly deposited in the pores contained in the porous layer, and the crystals can be deposited disorderly in the pores, thereby significantly alleviating the formation of dendrites and improving the electrochemical stability and safety performance of the battery. Moreover, the porous layer is directly formed on the surface of the negative electrode current collector. Therefore, the formed porous layer has a strong bonding force with the negative electrode current collector, and the preparation method conditions are controllable, thereby improving the quality stability of the negative electrode sheet.

[0139] In some embodiments, the electrical conductivity of the metal oxide contained in the formed porous layer may be ≤10 -5 In the S / m material, in an embodiment, the metal oxide containing the first metal element and the second metal element may be the electrically insulating AXO oxide described above.

[0140] In some embodiments, the porous layer formed contains a three-dimensional inorganic skeleton. In this case, the porous layer can be Figure 3 The porous layer 12 shown contains a three-dimensional inorganic skeleton 121 and pores 122.

[0141] In the embodiment, when the porous layer formed contains a three-dimensional inorganic skeleton, the method for forming the porous layer on the surface of the negative electrode current collector in step S10 includes the following steps:

[0142] S11: preparing a material or precursor material for forming a three-dimensional inorganic framework into a slurry;

[0143] S12: performing film forming treatment on the surface of the negative electrode current collector using the slurry.

[0144] In step S11, the material or precursor material for forming the three-dimensional inorganic framework is prepared into a slurry so as to form a wet film on the surface of the negative electrode current collector using a relatively mature coating film forming method, thereby improving the layer structure quality of the porous layer, such as thickness uniformity, uniformity of pore distribution, etc. In an embodiment, the viscosity of the slurry prepared in step S11 at 28° C. can be controlled to be 5000 to 12000 mPa.s, optionally 6000 to 9000 mPa.s. In exemplary embodiments, the viscosity can be 5000 mPa.s, 6000 mPa.s, 7000 mPa.s, 8000 mPa.s, 9000 mPa.s, 10000 mPa.s, 11000 mPa.s, 12000 mPa.s, or a range between any two viscosity values. By controlling and adjusting the viscosity of the slurry, the solid content concentration in the slurry can be controlled, thereby adjusting the skeleton distribution and morphology in the porous layer, thereby adjusting the pore diameter and porosity range of the porous layer. At the same time, the slurry in this viscosity range can effectively control the porous layer to have a porosity of 25% to 60% and a pore diameter of 200 to 800 nm in the negative electrode sheet 10 of the above-mentioned embodiment.

[0145] In the embodiment, when the material directly used to form the three-dimensional inorganic skeleton in step S11 is prepared into a slurry, the slurry contains the above-mentioned metal oxide having the first metal element and the second metal element; as in the embodiment, the metal oxide containing the first metal element and the second metal element can be the electrically insulating AXO oxide including the above-mentioned.

[0146] In the embodiment, when the precursor material directly used to form the three-dimensional inorganic skeleton in step S11 is prepared into a slurry, the slurry contains the above-mentioned metal oxide precursor material having the first metal element and the second metal element; as in the embodiment, the metal oxide precursor material can be the electrically insulating AXO oxide precursor material including the above-mentioned.

[0147] In the embodiment, the precursor material for forming the three-dimensional inorganic framework is prepared according to a method comprising the following steps:

[0148] The AX alloy is subjected to an etching reaction in an alcohol solution to generate the precursor material;

[0149] The concentration of the alcohol solution is 95% to 100%. A in the AX alloy is the first metal element contained in the metal oxide described above, specifically an alkali metal element; X is the second metal element contained in the metal oxide described above, specifically a metal element with an electronegativity greater than 1.3, optionally greater than 1.5. In embodiments, when the metal oxide described above is an AXO oxide, A in the AX alloy is the alkali metal element represented by A in the AXO oxide described above, such as any one of Li, Na, and K; and X in the AX alloy is the metal element represented by X in the AXO oxide described above, with an electronegativity greater than 1.3, optionally greater than 1.5, such as at least one of Mg, Sn, Zn, Ti, Ag, and Al. In this case, the precursor material is the precursor material for the electrically insulating AXO oxide described above. Etching the AX alloy with alcohol allows the resulting precursor material to form linear materials with morphologies such as fibers, thereby forming a framework including a three-dimensional fibrous skeleton, enriching the three-dimensional pore network structure contained in the porous layer.

[0150] In an embodiment, the AX alloy and the alcohol solution can be mixed in a molar ratio of a:b, where a:b = the ratio of the total moles of hydroxyl groups (-OH) contained in the alcohol to the total moles of the metal elements represented by A and X. By mixing the AX alloy and the alcohol solution in a molar ratio of a:b, the AX alloy and the alcohol can fully react to form a metal oxide precursor, such as the AXO oxide precursor described above. The alcohol can be present in a suitable excess relative to the AX alloy to ensure sufficient reaction between the AX alloy and the alcohol and to adjust the viscosity of the precursor solution containing the AXO oxide.

[0151] In the embodiment, the alcohol solution can be any alcohol solvent as long as it contains -OH, such as but not limited to at least one of ethanol, methanol, propanol, etc.

[0152] In an exemplary embodiment, when A is lithium and X is aluminum, that is, when the AX alloy is a LiAl alloy such as a Li2Al3 alloy, and the alcohol solvent is propanol (C3H7OH), the etching reaction of Li2Al3 and C3H7OH includes the following reactions:

[0153] Li2Al3+11C3H7OH=2Li(C3H7O)+3Al(C3H7O)3+11 / 2H2

[0154] The resulting components, such as Li(C3H7O) + Al(C3H7O)3, constitute the precursor material for Li-Al-O. The molar ratio of Li2Al3 to C3H7OH is a:b = 1:11 (specifically, the ratio of the total number of moles of hydroxyl groups (-OH) contained in propanol, 1, to the total number of moles of the metal represented by Li2Al3, 11). Of course, this a:b ratio can be less than 1:11 to ensure a moderate excess of C3H7OH relative to Li2Al3, ensuring sufficient reaction of the Li2Al3.

[0155] In the embodiment, the solvent of the slurry may be an alcohol solvent, and of course may also be other solvents, as long as any solvent that can ensure the stability of the three-dimensional inorganic framework material is acceptable.

[0156] The film forming process in step S12 includes the steps of coating the slurry on the surface of the negative electrode current collector to form a wet film and then heat-treating the wet film.

[0157] In an embodiment, when the slurry contains a material for forming a three-dimensional inorganic skeleton, the heat treatment may be a drying treatment to remove a solvent such as an alcohol solvent in the wet film, so that the material forms a three-dimensional inorganic skeleton, thereby forming the porous layer described above.

[0158] In an embodiment, when the slurry contains a precursor material for forming a three-dimensional inorganic framework, the heat treatment causes the precursor material to react to generate a material for forming a three-dimensional inorganic framework, and simultaneously serves as a drying agent to remove solvents such as alcohol solvents in the wet film.

[0159] For example, when the slurry contains the precursor material generated by etching an AX alloy in an alcohol solution, during the heat treatment process, the precursor material reacts to generate the AXO oxide described above, while the solvent is removed, such as by evaporation. In an exemplary embodiment, when the precursor material contains the precursor material generated by the LiAl alloy and containing Li(C3H7O)3, the precursor material containing Li(C3H7O)3 undergoes the following reactions during the heat treatment process to generate Li5AlO4:

[0160] 5Li(C3H7O)+Al(C3H7O)3+32O2=Li5AlO4+24CO2+28H2O

[0161] In an embodiment, the heat treatment temperature can be 250-400°C, optionally 290-330°C. The heat treatment time should be sufficient to allow the slurry to completely dry and solidify into a film on the surface of the negative electrode current collector, such as for 20-100 minutes. When the slurry contains the aforementioned precursor material, the precursor material can react to form the material for forming the three-dimensional inorganic framework, while the slurry can also completely dry and solidify into a film on the surface of the negative electrode current collector.

[0162] In some embodiments, after step S10 of the method for preparing the negative electrode sheet of the embodiment of the present application, the method further includes the following step S20:

[0163] S20: loading an ion supplementer in the porous layer.

[0164] In the embodiment, the ion supplementer is the same as the ion supplementer contained in the negative electrode sheet 10 of the embodiment of the present application, and may include at least one of a lithium supplementer, a sodium supplementer, and a potassium supplementer. In the embodiment, the amount of the ion supplementer loaded into the porous layer may also be the same as described above for the negative electrode sheet, with the total volume of the ion supplementer in the pores of the porous layer being controlled to account for 10% to 80% of the total volume of the pores of the porous layer.

[0165] In an embodiment, the ion supplementer is filled in the pores of the porous layer, and the method of filling the ion supplementer into the pores of the porous layer can be achieved by at least one of slurry infusion, melt infusion, etc.

[0166] The slurry infusion process involves dispersing or dissolving a powder of at least one of a lithium supplement, a sodium supplement, and a potassium supplement in a solvent to form a slurry, which is then infused into the pores of the porous layer by grouting or other methods, and then removing the solvent. The slurry infusion process can be performed in a protective atmosphere such as argon or nitrogen, based on the inherent properties of the material of the at least one of the lithium supplement, a sodium supplement, and a potassium supplement, and stability considerations including processing and material stability. The solvent can be a non-aqueous solvent.

[0167] Melt infusion is a process in which an ion-replenishing agent, such as at least one of a lithium supplement, a sodium supplement, or a potassium supplement, is heated and melted, and then the melted ion-replenishing agent, such as at least one of a lithium supplement, a sodium supplement, or a potassium supplement, is infused or infiltrated into the pores of the porous layer, followed by cooling. During the melt infusion process, the process can be performed in a protective atmosphere, such as argon or nitrogen, based on the inherent properties of the at least one of the ion-replenishing agent, such as at least one of a lithium supplement, a sodium supplement, or a potassium supplement, and considerations such as material stability. The heating and melting temperature should ensure that the at least one of the ion-replenishing agent, such as at least one of a lithium supplement, a sodium supplement, or a potassium supplement, melts, and does not destroy the structure of the porous layer and the stability of the material, such as by not causing decomposition of the porous layer material.

[0168] As in the embodiment, when the lithium supplement agent, the sodium supplement agent, and the potassium supplement agent are metallic lithium, metallic sodium, and metallic potassium, respectively, at least one of the metallic lithium, metallic sodium, and metallic potassium is subjected to a heat-melting treatment in a protective atmosphere, and then the hot molten metal liquid is poured into the pores of the porous layer and then cooled.

[0169] In the exemplary embodiment, the metallic lithium element and the metallic sodium element can be lithium ribbons, sodium ribbons, potassium ribbons, etc., respectively, which are laid on the surface of the porous layer and then heat-melted together to melt at least one of the lithium ribbons, sodium ribbons, and potassium ribbons. In this way, the molten metal liquid can be poured or infiltrated into the pores of the porous layer by its own gravity or with the help of external forces such as hot wind.

[0170] Battery

[0171] In a third aspect, an embodiment of the present application also provides a battery.

[0172] In an embodiment, the battery of the embodiment of the present application may include any one of a battery cell, a battery module, and a battery pack.

[0173] [Battery Cell]

[0174] A battery cell, also known as a battery core, refers to the battery packaging and the electrode assembly encapsulated within it. A battery cell can contain one or more electrode assemblies, which can be adjusted based on actual needs.

[0175] The outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.; or it can be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate. The outer packaging shape can be cylindrical, square, or any other shape. The outer packaging shape gives the battery cell a shape, so the shape of the battery cell can also be cylindrical, square, or any other shape corresponding to the shape of the outer packaging. In the exemplary embodiment, the battery cell can be as follows Figure 4 The battery cell 20 shown has a square structure.

[0176] In some embodiments, as Figure 5 As shown, the outer packaging of the battery cell 20 may include a housing 21 and a cover plate 23. The housing 21 may include a bottom plate and side plates connected to the bottom plate, which together form a receiving cavity. The housing 21 has an opening communicating with the receiving cavity, and the cover plate 23 is used to cover the opening, thereby sealing the receiving cavity. One or more electrode assemblies 22 are enclosed in the receiving cavity.

[0177] In the embodiment, the battery cell may be a battery cell containing an electrolyte or a battery cell containing a solid electrolyte.

[0178] In the case of a battery cell containing an electrolyte, the electrode assembly contained in the battery cell generally includes a positive electrode sheet, a negative electrode sheet, and a separator. The positive electrode sheets and the negative electrode sheets are alternately stacked, and the separator is stacked between the positive electrode sheets and the negative electrode sheets to isolate the positive electrode sheets from the negative electrode sheets. The positive electrode sheet, the separator layer, and the negative electrode sheet can be formed into an electrode assembly with a laminated structure through a lamination process, or can be formed into an electrode assembly with a core structure through a winding process. The electrode assembly containing the separator is placed in an outer packaging, and the electrolyte is injected and the electrode assembly is soaked, and the battery cell is obtained by packaging.

[0179] In the case of a battery cell containing a solid electrolyte, the electrode assembly typically includes a positive electrode sheet, a negative electrode sheet, and a solid electrolyte. The positive and negative electrode sheets are alternately stacked, with the solid electrolyte layered between them to act as an insulator, separating the positive and negative electrodes. The electrode assembly containing the solid electrolyte is placed in an outer packaging, and then packaged to form a battery cell.

[0180] Negative electrode sheet of the electrode assembly:

[0181] In each of the aforementioned battery cells, the electrode assembly contains the negative electrode sheet described in the previous application examples. Thus, when crystallization occurs in the battery cell, it begins to deposit disorderly from the surface of the negative electrode current collector exposed in the pores of the porous layer, significantly alleviating dendrite formation and improving the safety and other performance of the battery cell. This also enhances the stability of the interface between the negative electrode sheet and the electrolyte, thereby improving the battery's electrochemical performance, including cycling performance.

[0182] In some embodiments, the weight per unit area of the porous layer contained in the negative electrode sheet on the surface of the current collector (coating weight) can be equal to: (the amount of ion supplement added in the porous layer 12 of the negative electrode sheet 10 above / density + (the gram capacity of the positive electrode sheet contained in the battery cell*the coating weight of the positive electrode active layer / B / the density of the positive electrode active layer)) / (the thickness of the porous layer 12×the porosity per unit area of the porous layer 12).

[0183] The thickness of the porous layer 12 is in μm, the porosity per unit area of the porous layer 12 is in %, and the density of the ion supplement is in g / cm 3 The unit of gram capacity of positive electrode active material is mAh / g, where B refers to a constant. B is the theoretical gram capacity of the alkali metal atom (such as lithium, sodium, etc.) in the positive electrode active layer, such as 3860 mAh / g for lithium metal and 1166 mAh / g for sodium metal.

[0184] Positive electrode of the electrode assembly:

[0185] In each of the above-mentioned battery cells, the positive electrode sheet contained in the electrode assembly includes a positive electrode current collector and a positive electrode active material layer bonded to at least one surface of the positive electrode current collector.

[0186] In embodiments, the positive electrode current collector contained in the positive electrode sheet may include, but is not limited to, a metal current collector, a carbon current collector, a conductive resin current collector, a metal-resin composite current collector, and more specifically, aluminum, copper, nickel, titanium, iron, and their respective alloys, stainless steel, carbon fiber, carbon nanotubes (CNTs), graphite, and the like. In embodiments, the current collector may also be a dense film layer or a porous film layer. In embodiments, the current collector may be, but is not limited to, aluminum foil or porous aluminum foil.

[0187] In the embodiments, the positive electrode active material layer contained in the positive electrode sheet may be bonded to one surface of the positive electrode current collector, or may be bonded to both opposing surfaces of the positive electrode current collector. When the surface layer of the positive electrode current collector has a porous structure or the positive electrode current collector itself has a porous structure, the positive electrode active material layer may be at least partially embedded in the current collector.

[0188] In an embodiment, the mass content of the positive electrode active material contained in the positive electrode active material layer of the positive electrode sheet can be 90% to 98%, optionally 92% to 96%. In exemplary embodiments, the mass content can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or other typical but non-limiting values, or a range between any two values. Positive electrode active material in this content range can effectively improve the energy density of the positive electrode sheet.

[0189] In the embodiment, the positive electrode active material may include a sodium ion positive electrode active material or a lithium ion positive electrode active material, and of course it can also be a positive electrode material used in a potassium ion battery. For example, when containing a sodium ion positive electrode active material, the battery cell of the embodiment of the present application may be a sodium battery cell. At this time, the electrolyte contained in the corresponding sodium battery cell is a sodium ion electrolyte, and the pores in the porous layer of the negative electrode sheet of the above text application embodiment may also contain a sodium supplement. When containing a lithium ion positive electrode active material, the battery cell of the embodiment of the present application may be a lithium battery cell. At this time, the electrolyte contained in the corresponding lithium battery cell is a lithium ion electrolyte, and the pores in the porous layer of the negative electrode sheet of the above text application embodiment may also contain a lithium supplement.

[0190] In an exemplary embodiment, the sodium ion positive electrode active material may include one or more of sodium layered oxides, polyanion compounds, and Prussian blue compounds. For example, the layered oxide may include Na x MO2, M=one or more of Fe, Mn, Ni, Co, Cr, Sc, Ti, V, Cr, Cu, Zn, 0.4≤x≤1, for example, NaFe 0.33 Mn 0.33 Ni 0.33 O2、NaFe 0.5 Ni 0.5 O2、Na0.6 MnO2、Na 0.44 MnO2、Na 0.65 Mn 0.75 Ni 0.25 O2、NaNi 0.5 Mn 0.5 O2、Na 0.78 Ni 0.23 Mn 0.69 O2, NaVO2, NaFeO2, Na 0.7 CoO2, etc. Polyanion compounds may include one or more of phosphate, pyrophosphate, sulfate type, anion doping type, such as olivine type NaFePO4, Na2FeP2O7, NaFePO4F, Na3V2(PO4)3, NaFeSO4. Prussian blue compounds may include Na 0.61 Fe[Fe(CN)6] 0.94 ,BR-FeHCF,Na 1.48 Ni[Fe(CN)6] 0.89 、NaNi 0.05 Mn 0.95 [Fe(CN)6] or more.

[0191] In an exemplary embodiment, the lithium ion positive electrode active material may include but is not limited to LiFePO4, Li3V2(PO4)3, LiMn2O4, LiMnO2, LiNiO2, LiCoO2, LiVPO4F, LiFeO2, Li 1+x L 1-y-z M 1 y M 2 z One or more of O2, wherein -0.1≤x≤0.2, 0≤y≤1, 0≤z≤1, 0≤y+z≤1, L, M 1 、M 2 Each independently includes one or more of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Mg, and Ga.

[0192] The aforementioned types of sodium ion positive electrode active materials or lithium ion positive electrode active materials have high specific capacity, or further have high structural stability and good cycle performance.

[0193] In the embodiments, the positive electrode active material layer contained in the positive electrode sheet generally includes, in addition to the aforementioned positive electrode active material components, a binder, a conductive agent, and other components. The binder can enhance the mechanical properties between the positive electrode active material layer itself and the current collector. The conductive agent can effectively improve the conductivity of the positive electrode, such as by reducing the resistance of the positive electrode.

[0194] In an embodiment, the mass content of the binder contained in the above-mentioned positive electrode active material layer can be 0.5% to 5%, optionally 1% to 3%. In a demonstration example, it can be 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3% and other typical but non-limiting contents or a range between any two content values.

[0195] In an embodiment, the binder may include one or more of an oil-soluble binder, a water-soluble binder, an emulsion-type binder, etc. In an exemplary embodiment, the oil-soluble binder may include one or more of polyvinylidene fluoride, polyimide, polytetrafluoroethylene, polybutyl acrylate, polyacrylonitrile, etc.; in an exemplary embodiment, the water-soluble binder may include one or more of carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylic acid salt, polyvinyl alcohol, sodium alginate, cyclodextrin, etc.; in an exemplary embodiment, the emulsion-type binder may include one or more of styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0196] The content within this range and the above-mentioned types of binders can effectively enhance the mechanical properties of the positive electrode active material layer and the bonding strength between the positive electrode active material layer and the current collector, and can effectively improve the cycle performance of the positive electrode.

[0197] In an embodiment, the mass content of the conductive agent contained in the positive electrode active material layer may be 0.5% to 5%, optionally 1% to 3%. In an exemplary embodiment, it may be 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, or a typical but non-limiting content or a range between any two content values. In an embodiment, the conductive agent may include one or more of acetylene black (SP), conductive carbon black (super-P), Ketjen black, graphene, etc. This range of content and the above-mentioned types of conductive agents can effectively improve the conductivity of the positive electrode active material layer.

[0198] Isolation film:

[0199] In the embodiments, when each of the battery cells includes a separator, the separator, as described above, is disposed between the positive electrode and the negative electrode to separate the positive and negative electrodes. The separator prevents electrons from freely passing through the battery, preventing contact and short circuits between the electrodes, but allows sodium ions in the electrolyte to freely pass between the positive and negative electrodes. The separator can be any known porous structure separator with electrochemical and mechanical stability. In exemplary embodiments, the separator includes a single or multilayer film of at least one of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF).

[0200] Solid electrolyte:

[0201] In the embodiments, when each of the battery cells contains a solid electrolyte, the solid electrolyte, as described above, is disposed between the positive electrode and the negative electrode to separate the positive electrode from the negative electrode. The solid electrolyte may include at least one of a polymer solid electrolyte, an oxide electrolyte, a sulfide electrolyte, a borohydride electrolyte, a composite solid electrolyte, and the like.

[0202] [Battery Module]

[0203] When the battery of the present embodiment is a battery module, the battery module is assembled from the aforementioned battery cells, which means that it can contain multiple battery cells, the specific number of which can be adjusted according to the application and capacity of the battery module. Because the battery module of the present embodiment contains the battery cells of the present embodiment, the battery module of the present embodiment has high safety performance and stable electrochemical properties such as cycling performance.

[0204] In some embodiments, Figure 6 FIG is a schematic diagram of a battery module 30 as an example. Figure 6 As shown, in the battery module 30, the plurality of battery cells 20 may be arranged in sequence along the length direction of the battery module 30. Of course, they may also be arranged in any other manner. The plurality of battery cells 20 may further be fixed by fasteners.

[0205] Optionally, the battery module 30 may further include a housing having an accommodation space, and the plurality of battery cells 20 may be accommodated in the accommodation space.

[0206] [Battery Pack]

[0207] When the battery of the present application is a battery pack, it is composed of the aforementioned battery cells, which can contain multiple battery cells, and these multiple battery cells are assembled into the aforementioned battery module. The specific number of battery cells or battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack. Therefore, the battery pack of the present application has high safety performance and stable electrochemical properties such as cycle performance.

[0208] In some embodiments, Figure 7 and Figure 8 Figure 4 is a schematic diagram of an example battery pack 40. The battery pack 40 may include a battery box and multiple battery modules 30 disposed within the battery box. The battery box comprises an upper case 41 and a lower case 42. The upper case 41 covers the lower case 42 and forms an enclosed space for accommodating the battery modules 30. The multiple battery modules 30 may be arranged in any manner within the battery box.

[0209] Electrical devices

[0210] On the fourth aspect, the embodiments of the present application also provide an electric device. The electric device of the embodiments of the present application includes a power supply unit or an energy storage unit, and of course may also include other auxiliary components or necessary components. Among them, the power supply unit or energy storage unit contains the battery of the above-mentioned embodiment of the text application. For example, it can be the above-mentioned battery cell, battery module or battery pack. Since the electric device of the embodiments of the present application contains the battery of the above-mentioned embodiment of the text application, the power supply unit or energy storage unit of the electric device of the embodiments of the present application has high safety, good cycle performance, and long service life, and the electric device of the embodiments of the present application is safe to use, and the standby or battery life can also be extended.

[0211] In the embodiments, the electrical device may include, but is not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, a battery-powered vehicle, an electric car, a ship, a spacecraft, and the like. The electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, and the spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft. The battery may be a single cell, a battery module, or a battery pack, depending on the intended use of the electrical device.

[0212] Figure 9 The figure is a schematic diagram of an exemplary electric device. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device, a battery pack or battery module can be used.

[0213] In the embodiment, when the electrical device contains an energy storage unit, the electrical device can be an energy storage device, and the energy storage device includes the energy storage unit, and of course can also include other auxiliary components or necessary components. Among them, the energy storage unit contains the battery of the embodiment of the above text application. The battery contained in the energy storage unit can be one or more. When there are multiple batteries, multiple batteries can form a battery module or battery pack. Since the energy storage device of the embodiment of the present application contains the battery of the embodiment of the above text application, the energy storage device has high energy density, good cycle performance, long service life, and further high energy density.

[0214] Example

[0215] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0216] 1. Negative Electrode Sheet and Preparation Method Example

[0217] Example 1

[0218] This embodiment provides a negative electrode sheet and a method for preparing the same. The negative electrode sheet comprises a copper foil current collector and a porous layer laminated on two opposing surfaces of the copper foil current collector. The porous layer comprises a three-dimensional inorganic framework and a three-dimensional pore network structure formed by the framework. The three-dimensional inorganic framework is composed of electrically insulating Li5AlO4 inorganic nanofibers. The copper foil current collector has a thickness of 6 μm. Parameters such as the thickness, porosity, and fiber size of the porous layer forming the three-dimensional inorganic framework are shown in Table 1 below.

[0219] The method for preparing the negative electrode sheet comprises the following steps:

[0220] S1. Preparation of Li5AlO4 precursor:

[0221] Li2Al3 alloy and propanol (purity> 95%) are placed in a reaction tank at a molar ratio of 1:9. The reaction tank is kept at 50°C and is not connected to the outside world. The inorganic skeleton precursor is obtained by reacting for 50 hours. The viscosity of the precursor is controlled to be 5000 mPa.s.

[0222] S2. Forming a porous layer on the copper foil current collector:

[0223] The Li5AlO4 precursor prepared in step S1 is adjusted to a viscosity within the specification range and then extrusion coated on two opposite surfaces of a 6μm copper foil current collector. The coated current collector is heat treated at 320°C in an oven in an air atmosphere until dry. The Li5AlO4 precursor reacts to form Li5AlO4 nanofibers, which constitute a three-dimensional inorganic skeleton and form a porous layer.

[0224] Example 2 to Example 5

[0225] Examples 2 to 5 provide a negative electrode sheet and a method for preparing the same. These negative electrode sheets differ from the negative electrode sheet in Example 1 in that the porosity of the porous layer is different and the fiber size forming the three-dimensional inorganic skeleton is different. All other parameters are the same as those in Example 1. Parameters such as the thickness, porosity, and fiber size forming the three-dimensional inorganic skeleton of the porous layer in the negative electrode sheets in Examples 2 to 5 are shown in Table 1 below.

[0226] The preparation methods of the negative electrode sheets in Examples 2 to 5 are respectively adjusted by adjusting the relevant conditions of Step S1 and Step S2 in Example 1, so that the parameters such as the thickness, porosity and fiber size of the three-dimensional inorganic skeleton formed on the surface of the copper foil current collector are shown in Table 1 below.

[0227] Example 6

[0228] This embodiment 6 provides a negative electrode sheet and a preparation method thereof. Compared with the negative electrode sheet in embodiment 1, the negative electrode sheet is different in that the porosity of the porous layer contained in the negative electrode sheet is filled with lithium metal.

[0229] The method for preparing the negative electrode sheet comprises the following steps:

[0230] S1. Preparation of Li5AlO4 precursor:

[0231] Same as step S1 in Example 1;

[0232] S2. Forming a porous layer on the copper foil current collector:

[0233] Same as step S2 in Example 1;

[0234] S3. Filling the porous layer with an ion-replenishing agent:

[0235] According to the weight content of metallic lithium in the negative electrode sheet, a certain amount of metallic lithium strip is covered on the surface of the porous layer in step S2 by transfer coating, and placed in an argon protective atmosphere at 200°C for 30 minutes. Based on the capillary action and the gravity of the molten lithium metal, the metallic lithium melts and infiltrates into the pores of the porous layer, and then cools.

[0236] Example 7 to Example 15

[0237] Examples 7 to 15 provide a negative electrode sheet and a method for preparing the same. These negative electrode sheets differ from the negative electrode sheet in Example 3 in that the material of the three-dimensional inorganic framework in the porous layer of the negative electrode sheet is replaced with the corresponding three-dimensional inorganic framework materials in Examples 7 to 15, as shown in Table 1. The thickness, porosity, and fiber size of the porous layer of the negative electrode sheets in Examples 7 to 15, as well as the type and content of the ion supplement filled in the porous layer, are shown in Table 1.

[0238] In the preparation methods of the negative electrode sheets in Examples 7 to 15, the Li2Al3 alloy in step S1 of Example 1 is replaced with Li2Mg alloy (corresponding to Example 7), Li2Sn alloy (corresponding to Example 8), LiAg alloy (corresponding to Example 9), Li2Zn alloy (corresponding to Example 10), and Li4Ti alloy (corresponding to Examples 11 to 15), respectively, and the etching reaction is carried out with the alcohol solution in step S1 of Example 1 to prepare each precursor respectively;

[0239] Each precursor was then applied to two opposing surfaces of the copper foil current collector to form porous layers according to the method of step S2 in Example 1, thereby preparing the negative electrode sheets of Examples 7 to 13. In Examples 7 to 8 and Examples 10 to 15, the porous layers were filled with the corresponding lithium alloy or elemental lithium listed in Table 1 using the melt infusion method of step S3 in reference to Example 6. In Example 9, a lithium-containing inorganic salt was dissolved into a solution and infused into the pores of the porous layer of the negative electrode sheet of Example 9, with the infusion amount shown in Table 1.

[0240] Comparative Example 1

[0241] This comparative example provides a negative electrode sheet and a method for preparing the same. This negative electrode sheet differs from the negative electrode sheet in Example 3 in that the metal oxide material in the porous layer of the negative electrode sheet is replaced with the corresponding zinc oxide in Comparative Example 1 as shown in Table 1. Parameters such as the thickness, porosity, and fiber size forming the three-dimensional inorganic framework of the porous layer of the negative electrode sheet in Comparative Example 1 are shown in Table 1 below.

[0242] The method for preparing the negative electrode sheet comprises the following steps:

[0243] This comparative example provides a method for preparing a three-dimensional zinc oxide inorganic framework using electrospinning technology. Zinc acetate is dissolved in nitrogen-nitrogen dimethylformamide to form a saturated solution, and 15% polyvinyl pyrrolidone is added to adjust the solution viscosity to 5000 mPa.s. The resulting composite electrospinning solution is then sprayed onto the surface of a foil via electrospinning to produce zinc acetate@polyvinyl pyrrolidone composite fibers. The composite fibers are dried at 60°C and sintered at 500°C to produce an inorganic three-dimensional zinc oxide nanolayer. The fiber diameter and porosity of this inorganic layer can be controlled by the equipment power supply and the electrospinning solution propulsion speed, as shown in Table 1 below.

[0244] Comparative Example 2

[0245] This comparative example provides a negative electrode sheet. Compared with the negative electrode sheet in Example 1, the negative electrode sheet in this comparative example only contains the copper foil current collector in Example 1 (without the porous layer).

[0246] Comparative Example 3

[0247] This comparative example provides a negative electrode sheet. Compared to the negative electrode sheet in Example 1, the three-dimensional inorganic framework material in the porous layer of the negative electrode sheet is replaced with conductive carbon nanotubes. The corresponding parameters of the porous layer of the negative electrode sheet in Comparative Example 3, such as thickness and porosity, and the size of the conductive carbon nanotubes forming the three-dimensional inorganic framework, are shown in Table 1 below.

[0248] The method for preparing the negative electrode sheet comprises the following steps:

[0249] Carbon nanotubes, SBR, and a dispersant (such as sodium carboxymethyl cellulose) are mixed in a ratio of 97%:2.3%:0.7%. After mixing, deionized water is used as a solvent and stirred to form a slurry. The slurry is stirred to a solid content of 54% and a viscosity of 8000 mPa.s. The slurry is then coated on both sides of a copper foil and dried to obtain a porous carbon nanotube layer. The porosity can be adjusted by the solid content and viscosity and can be selected to be 20-40%.

[0250] 2. Lithium-ion battery cell example

[0251] The electrode assemblies formed by the negative electrode sheets provided in Examples 1 to 15 and Comparative Examples 1 to 3, the separators, and the positive electrode sheets are assembled into lithium-ion battery cells according to the following method:

[0252] Positive electrode sheet: The lithium iron phosphate active material, carbon black conductive agent, and polyvinylidene fluoride (PVDF) binder are thoroughly stirred and mixed in an appropriate amount of NMP solvent at a weight ratio of 95:2.5:2.5 to form a uniform positive electrode slurry; the positive electrode slurry is evenly coated on the surface of a 13μm positive electrode current collector aluminum foil, dried, and cold pressed to obtain a positive electrode sheet;

[0253] Negative electrode sheets: the negative electrode sheets provided in the above-mentioned Examples A1 to A15 and Comparative Examples 1 to 3 respectively.

[0254] Electrolyte: In an environment with a water content of less than 10 ppm, the non-aqueous organic solvents ethylene carbonate (EC) and diethyl carbonate (DMC) are mixed in a volume ratio of 1:1 to obtain an electrolyte solvent. Subsequently, lithium hexafluorophosphate and the mixed solvent are mixed to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0255] Isolation membrane: porous polyethylene (PE) film is used as the isolation membrane.

[0256] Battery Assembly: The positive electrode sheets, separators, and negative electrode sheets are stacked in sequence, with the separators positioned between the positive and negative electrodes to provide insulation. The stacking process yields the electrode assemblies. Each electrode assembly is placed in an outer packaging, dried, and then filled with electrolyte. After vacuum packaging, resting, forming, and shaping, each lithium-ion battery cell is obtained.

[0257] 3. Related performance testing of negative electrode sheets and lithium-ion battery cells in each embodiment:

[0258] 3.1 Characterization of the porous layer contained in the negative electrode sheet in each embodiment:

[0259] The porous layers in the negative electrode sheets provided in Examples 1 to 15 and Comparative Examples 1 to 3 were tested, including parameters such as thickness, porosity, and the dimensions of the three-dimensional inorganic framework material forming the porous layers. The test results are shown in Table 1 below for the relevant data for each example.

[0260] Among them, the thickness detection method of the porous layer is: the thickness of the porous layer can be tested using a micrometer or SEM cross-sectional scanning.

[0261] Porosity test method for porous layers: See GB / T 24586-2009. Principle: Utilizing the displacement method with an inert gas (helium) of small molecular diameter, combined with Archimedes' principle and Bohr's law (PV = nRT), the true volume of the material being tested is accurately measured, thereby determining the porosity of the composite membrane sample being tested.

[0262] Calculation formula: Apparent volume V2 = S*H*c; Porosity P = (V2-V1) / V2*100%;

[0263] Where: S-area, cm 2 ; H-thickness, cm; c-sample number, EA; V1-true volume of the sample, cm 3 ; V2-apparent volume of the sample, cm 3 ; P-porosity of sample, %.

[0264] The dimensions of the three-dimensional inorganic skeleton material of the porous layer were measured by scanning electron microscopy (SEM) of the porous layer of the negative electrode sheet in each embodiment using the scanning electron microscopy measurement method of GB / T 16594-1996 for micrometer-level length. At the same time, the length and diameter data of the three-dimensional inorganic skeleton material formed in each porous layer can be obtained based on the SEM photos. Among them, the SEM image of the porous layer contained in the negative electrode sheet in Example 1 is as follows: Figure 3 shown.

[0265] Pore diameter detection method of the porous layer: The porous layer contained in the negative electrode sheet of each embodiment is subjected to scanning electron microscopy (SEM) using the micron-level length scanning electron microscopy measurement method of GB / T 16594-1996 to calculate the distance between two adjacent skeletons.

[0266] Method for detecting the electrical conductivity of the three-dimensional skeleton in the porous layer: first, the resistivity ρ of the three-dimensional inorganic skeleton is detected using a four-probe inspection technique, and then the electrical conductivity is calculated according to the 1 / ρ formula.

[0267] Method for detecting the amount of ion replenisher filled in the porous layer: cut the negative electrode sheet perpendicular to the thickness direction of the current collector to make a cross-sectional sample, measure the total thickness D1 of the porous layer on one side of the negative electrode sheet, and measure the ion replenisher filling thickness D2 in the porous layer on one side. Calculate the ratio of the total filling volume of the pores in the porous layer of the negative electrode sheet to the total volume of the pores according to the formula D2 / D1, and record it as the ion replenisher filling amount in the porous layer.

[0268] 3.2 Relevant performance test methods for each lithium-ion battery cell:

[0269] The lithium-ion battery cells prepared above were subjected to the relevant performance tests listed in Table 1 below according to the following methods. The test results are shown in Table 1:

[0270] Cycle retention rate (%): At 25°C, charge the battery cell to 3.7V at a constant current of 0.33C, then charge at a constant voltage of 3.7V to a current of 0.05C, and then discharge at a constant current of 1C to 2.0V. This is one charge and discharge cycle. Taking the capacity of the first discharge as 100%, calculate the capacity retention rate of the battery after 500 cycles. Capacity retention rate (%) after 1000 cycles = discharge capacity of the 1000th cycle / capacity of the first discharge × 100%. Among them, the charge and discharge curve of the lithium-ion battery cell containing the negative electrode sheet in Example 1 is as follows: Figure 10 As shown, the charge and discharge curves of the lithium-ion battery cell containing the negative electrode sheet in Example 6 are as follows: Figure 11 shown.

[0271] First efficiency test method: At 25°C, let the battery cell stand for 30 minutes; then charge it at a constant current rate of 0.33C to 3.7V, then charge it at a constant voltage rate of 3.7V to a current of 0.05C; then let it stand for 30 minutes; discharge it at a constant current rate of 0.33C to 2V, and then let it stand for another 30 minutes. This is a cycle of charge and discharge. Record the charge capacity C during the first cycle of charge and discharge. 10 and discharge capacity C 20 , the first effect is calculated using the formula: first effect = C 20 / C 10 ×100%.

[0272] Safety test method for battery cell overcharge thermal runaway: Charge the battery cell to 3.7V at 0.33C, then overcharge at 1C for 12 minutes. After charging, activate the heating film to heat the large surface of the cell to 300°C, and then observe the temperature rise of the large surface of the cell and whether it will catch fire or explode.

[0273] Table 1

[0274]

[0275]

[0276]

[0277] Combine Figure 3 、 Figures 10 and 11 From the data in Table 1, compared with Examples 1 to 5, it can be seen that when the porous layer material in the negative electrode sheet is the same, as the porosity of the porous layer increases from 25% to 60%, the battery cells containing the negative electrode sheets of Examples 1 and 2 rise in temperature after being heated to 300°C on the large surface. The large surface temperature of the cell containing the negative electrode sheet of Example 1 is higher than that of the cell containing the negative electrode sheet of Example 2. When the porosity reaches 40%, the battery cell temperature remains stable.

[0278] Further comparison of Examples 2 to 4 with Example 1 shows that when the porosity of the porous layer in the negative electrode sheet is less than 30%, the safety and cycle performance of the battery cell are reduced. Comparison of Examples 2 to 4 with Example 5 shows that when the porosity of the porous layer in the negative electrode sheet is greater than 50%, the cycle performance of the battery cell is reduced relative to Examples 2 to 4.

[0279] This indicates that a moderate increase in the porosity of the porous layer in the negative electrode sheet can improve the safety performance of the battery cell. Simultaneously, the porosity of the porous layer in the corresponding battery cell also gradually increases from 25% to 40%. Therefore, a porous layer porosity of 30% to 50% is relatively excellent.

[0280] By comparing Example 1 with Example 6, it can be seen that when the porous layer contained in the negative electrode sheet is filled with lithium metal as a lithium supplement, it is tested that the cycle performance of the battery cell is improved. After further testing, the first efficiency of the battery cell is improved. This is because the metallic lithium provides active lithium during the charge and discharge process of the battery cell.

[0281] By comparing Examples 3, 7 to 15, it can be seen that when the skeleton material of the porous layer in the negative electrode sheet is other AXO skeleton materials, it can effectively play its role and improve the safety performance and cycle performance of the battery cell.

[0282] By comparing Example 6 with Comparative Example 1, it can be seen that when the skeleton material of the porous layer in the negative electrode sheet is replaced by the AXO skeleton material with the non-AXO skeleton material, the safety performance and cycle performance of the battery cell containing the non-AXO skeleton material are significantly reduced compared with the battery cell containing the AXO skeleton material.

[0283] Comparing Example 1 with Comparative Examples 2 and 3, it can be seen that when the copper foil current collector is directly used as the negative electrode, the temperature of the battery cells corresponding to Comparative Examples 2 and 3 rises significantly relative to that of the battery cells in Example 1 after the large surface is heated to 300°C. This indicates that the battery cells corresponding to Comparative Examples 2 and 3 continue to experience thermal runaway reactions after 300°C, which significantly reduces the safety performance of the battery cells corresponding to Comparative Examples 2 and 3. At the same time, the cycle performance of the battery cells corresponding to Comparative Examples 2 and 3 is also significantly reduced relative to that of the battery cells in Example 1. When a porous layer with conductivity is added to the surface of the copper foil current collector, although the safety performance and cycle performance of the battery cells in Comparative Example 2 are improved, they are still significantly lower than those of the battery cells in Example 1. Disassembling the battery cells revealed that there was obvious crystallization on the surface of the electrode of Comparative Example 3. This may be due to the conductivity of the carbon nanotubes themselves, which causes the crystals to be directly deposited on the surface of the porous layer of carbon nanotubes.

[0284] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A negative electrode sheet, comprising a negative electrode current collector, characterized in that: A porous layer is provided on at least one side of the negative electrode current collector, and the porous layer includes a metal oxide, and the metal oxide includes a first metal element and a second metal element; wherein the first metal element is an alkali metal element; and the second metal element is a metal element with an electronegativity greater than 1.

3.

2. The negative electrode sheet according to claim 1, wherein: The electrical conductivity of the metal oxide is ≤10 -5 S / m.

3. The negative electrode sheet according to claim 1 or 2, characterized in that: The alkali metal element includes at least one element selected from the group consisting of Li, Na, and K; and / or The second metal element includes at least one metal element selected from the group consisting of Mg, Sn, Zn, Ti, Ag, and Al.

4. The negative electrode sheet according to any one of claims 1 to 3, wherein: The alkali metal element includes Li, and the metal oxide includes at least one of Li5AlO4, Li2MgO2, Li2SnO3, LiAgO, Li2Zn2O2, Li2TiO3, LiAl5O8, Li2Al4O7, and LiAlO2.

5. The negative electrode sheet according to any one of claims 1 to 3, wherein: The alkali metal element includes Na, and the metal oxide includes at least one of Na5AlO4 and Na2SnO3.

6. The negative electrode sheet according to any one of claims 1 to 3, wherein: The alkali metal element includes K, and the metal oxide includes at least one of KSbO, KSbO3, K2SnO2, and K2SnO3.

7. The negative electrode sheet according to any one of claims 1 to 6, wherein: The porous layer comprises a three-dimensional inorganic skeleton; and / or The second metal element is a metal element with an electronegativity greater than 1.

5.

8. The negative electrode sheet according to claim 7, wherein: The three-dimensional inorganic skeleton includes at least one structure of a fiber skeleton, a sheet skeleton, and a rod skeleton.

9. The negative electrode sheet according to claim 8, wherein: The three-dimensional inorganic skeleton includes the fiber skeleton, and the fibers of the fiber skeleton include one or more of the following (1) to (2): (1) The length of the fiber is 2 to 100 μm; (2) The diameter of the fiber is 10 to 100 nm.

10. The negative electrode sheet according to any one of claims 8 to 9, characterized in that: The three-dimensional inorganic skeleton includes the fiber skeleton, and the fibers of the fiber skeleton include one or more of the following (1) to (3): (4) The thickness of the porous layer is 20 to 30 μm; (5) The porosity of the porous layer is 30% to 50%; (6) The pore diameter of the porous layer is 200 to 450 nm.

11. The negative electrode sheet according to any one of claims 1 to 10, wherein: The porous layer includes one or more of (1) to (3): (1) The thickness of the porous layer is 10 to 80 μm; (2) The porosity of the porous layer is 25% to 60%; (3) The pore diameter of the porous layer is 200 to 800 nm.

12. The negative electrode sheet according to any one of claims 1 to 11, wherein: The porous layer further includes an ion supplement, and the ion supplement includes at least one of a lithium supplement, a sodium supplement, and a potassium supplement.

13. The negative electrode sheet according to claim 12, wherein: The ion supplement agent is filled in the pores of the porous layer; and / or The ion supplementer is filled in the pores of the porous layer, and the total filling volume of the ion supplementer in the pores accounts for 10% to 80% of the total volume of the pores.

14. The negative electrode sheet according to claim 12 or 13, wherein: The lithium supplement comprises at least one of metallic lithium, lithium alloy, and lithium-containing inorganic salt; The sodium supplement comprises at least one of metallic sodium, sodium alloy, and sodium-containing inorganic salt; The potassium supplement comprises at least one of metallic potassium, potassium alloy, and potassium-containing inorganic salt.

15. The negative electrode sheet according to any one of claims 1 to 14, wherein: The negative electrode current collector includes a metal current collector or a composite current collector; wherein the metal contained in the metal current collector and the composite current collector includes at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.

16. A method for preparing a negative electrode sheet, characterized in that: The steps include: forming a porous layer on the surface of the negative electrode current collector; The porous layer includes a metal oxide; the metal oxide includes a first metal element and a second metal element; the first metal element is an alkali metal element; and the second metal element is a metal element with an electronegativity greater than 1.

3.

17. The preparation method according to claim 16, wherein The electrical conductivity of the metal oxide is ≤10 -5 S / m; and / or The method for forming the porous layer on the surface of the negative electrode current collector comprises the following steps: preparing a material or precursor material for forming a three-dimensional inorganic framework into a slurry; The slurry is subjected to a film-forming treatment on the surface of the negative electrode current collector to form the porous layer.

18. The preparation method according to claim 17, wherein The film forming treatment comprises coating the slurry on the surface of the negative electrode current collector to form a wet film and then heat treating the wet film at 280-400° C. for 20-100 minutes; and / or The viscosity of the slurry at 28° C. is 5000-12000 mPa.s.

19. The preparation method according to any one of claims 17 to 18, characterized in that: The precursor material is prepared according to a method comprising the following steps: Carrying out an etching reaction on the AX alloy in an alcohol solution to generate the precursor material, wherein the concentration of the alcohol solution is 95% to 100%; Wherein, A in the AX alloy is the first metal element, and X is the second metal element.

20. The preparation method according to any one of claims 16 to 19, characterized in that: The method further includes the step of loading an ion supplement agent in the porous layer.

21. The preparation method according to claim 20, characterized in that The ion supplementer is filled in the pores of the porous layer, and a method of filling the ion supplementer into the pores includes at least one of a slurry infusion method and a melt infusion method.

22. A battery, characterized in that: The negative electrode sheet comprises the negative electrode sheet according to any one of claims 1 to 15 or the negative electrode sheet prepared by the preparation method according to any one of claims 16 to 21.

23. An electrical device, characterized in that: Including the battery of claim 22.

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