Negative electrode sheet, secondary battery, battery module, battery pack, and power consumption device

Abstract

The present application provides a negative electrode sheet, a secondary battery, a battery module, a battery pack, and a power consuming device. The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector, the negative electrode film layer includes first negative electrode active material particles and second negative electrode active material particles, the first negative electrode active material particles include a plurality of adsorption holes, and the first negative electrode active material particles have a tap density of 0.4 g / cm. 3 ~1.4g / cm 3 where the difference d between the median diameters of the first negative electrode active material particles and the second negative electrode active material particles satisfies 3 μm≦d≦19 μm, and the compaction density PD of the negative electrode film layer is 0.8 g / cm 3 ≦PD≦1.4g / cm 3 Meet the following.

Description

[Technical Field]

[0001] The present application relates to the technical field of batteries, and in particular to negative electrode sheets, secondary batteries, battery modules, battery packs, and power consuming devices. [Background technology]

[0002] As energy and environmental issues become more apparent every day, the new energy industry is attracting increasing attention. Lithium-ion batteries have been widely used as important new energy storage devices in recent years due to their high energy density and excellent cycle performance. However, the active material resources related to lithium-ion batteries are scarce, which has led to high battery costs and serious problems such as the depletion of related resources. Therefore, the development of other low-cost metal-ion secondary battery systems is required.

[0003] Sodium-ion batteries have become a popular research direction in recent years due to their advantages of low cost, abundant resources, and similar manufacturing process to that of lithium-ion batteries.

[0004] However, due to the low capacity per gram and voltage platform limitations of current cathode and anode materials in sodium-ion batteries, the energy density of sodium-ion batteries is still significantly lower than that of lithium-ion batteries, making it difficult to achieve practical commercial applications. The initial coulombic efficiency and power multiplier performance of sodium-ion batteries also need to be improved. Summary of the Invention

[0005] The present application has been made in view of the above-mentioned problems, and aims to provide a negative electrode sheet, a secondary battery, a battery module, a battery pack, and a power consumption device that can effectively improve the energy density and multiplication performance of a sodium ion battery.

[0006] A first aspect of the present application provides a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector, the negative electrode film layer including first negative electrode active material particles and second negative electrode active material particles, the first negative electrode active material particles including a plurality of adsorption holes, and the tap density of the first negative electrode active material particles being 0.4 g / cm 3 ~1.4g / cm 3 and selectable 0.6g / cm 3 ~1.0g / cm 3 a negative electrode film layer in which the difference d in median diameter between the first negative electrode active material particles and the second negative electrode active material particles satisfies 3 μm≦d≦19 μm, and the compaction density PD of the negative electrode film layer is 0.8 g / cm 3 ≦PD≦1.4g / cm 3 , selectable, 1.0g / cm 3 ≦PD≦1.2g / cm 3 To provide a negative electrode sheet that satisfies the above requirements.

[0007] Thus, the present invention provides a method for blending first and second negative electrode active material particles that satisfy the above conditions, thereby providing a negative electrode film layer with a high degree of compaction and a high porosity within the negative electrode film layer. Specifically, the first negative electrode active material particles contain a plurality of adsorption holes, and the tap density is within the above-mentioned appropriate range, so that even after cold pressing, the first negative electrode active material particles can have a sufficient number of adsorption holes within them. As a result, Na + is smoothly adsorbed to the first negative electrode active material particles during charging and smoothly desorbed during discharging. Furthermore, when the difference between the median diameter of the first negative electrode active material particles and the median diameter of the second negative electrode active material particles is within the above-mentioned appropriate range, it is advantageous for the second negative electrode active material particles to fill the gaps between the multiple first negative electrode active material particles, thereby providing the negative electrode active material particles with a high bulk density and, further, providing the negative electrode film layer with an appropriate compaction density after cold pressing. This allows the negative electrode active material particles in the negative electrode film layer to be in close contact with each other, thereby improving the electron and sodium ion transmission performance of the negative electrode sheet and further improving the power conversion performance of the sodium ion battery.

[0008] In any embodiment, the median diameter D of the first negative electrode active material particles 1 50 is 4 μm to 50 μm, optionally 4 μm to 25 μm, and the median diameter D of the second negative electrode active material particles 2 50 is between 1 μm and 40 μm, and optionally between 1 μm and 20 μm.

[0009] D 1 50, D 2 50 is within the appropriate range, while D 1 50 and D 2 50 is advantageous to control within the range specified in the present application, which is advantageous for the second negative electrode active material particles to fill the gaps between the first negative electrode active material particles and further advantageous for improving the compaction degree of the negative electrode film layer, and on the other hand, it is possible to provide good electron and sodium ion transmission performance within the first negative electrode active material particles and the second negative electrode active material particles, as well as to provide low particle interface resistance between the first negative electrode active material particles and the second negative electrode active material particles. As a result, when the negative electrode sheet of the present application is applied to a sodium ion battery, it allows the sodium ion battery to have high energy density and low impedance, and the sodium ion battery can have high capacity, good power supply performance, and good cycle performance.

[0010] In any embodiment, the mass percentage content of the first negative electrode active material particles relative to the total mass of the first negative electrode active material particles and the second negative electrode active material particles is 5% to 95%, and optionally 70% to 95%.

[0011] When the mass percentage content of the first negative electrode active material particles and the second negative electrode active material particles is within the above appropriate range, the second negative electrode active material particles can be ensured to fill the voids between the first negative electrode active material particles, while the negative electrode active material particles can have an appropriate specific surface area, thereby improving the compaction density of the negative electrode film layer, increasing the contact area between particles, improving the transmission path between particles, and preventing the occurrence of broken bridges between particles, resulting in a sodium-ion battery with high energy density and cycle performance.

[0012] In any embodiment, the elongation percentage E of the negative electrode sheet satisfies 0.1%≦E≦0.2%, and optionally 0.1%≦E≦0.15%.

[0013] When the difference in median diameter between the first and second negative electrode active material particles is within an appropriate range, the negative electrode active material particles can have a high bulk density. Therefore, when the cold-pressing parameters are the same, the negative electrode sheet can have a lower elongation than negative electrode active material particles with a lower bulk density.

[0014] In any embodiment, the coating weight CW of the negative electrode film layer on one side is 2 mg / cm 2 ~13mg / cm 2 and selectable at 5 mg / cm 2 ~12mg / cm 2 is.

[0015] When the coating weight of the negative electrode film layer is within the above-mentioned appropriate range, it is advantageous to control the thickness of the negative electrode film layer within an appropriate range. This not only provides an appropriate migration path for electrons and sodium ions in the negative electrode sheet, but also allows the negative electrode sheet to have an appropriate capacity. Therefore, when the negative electrode sheet of the present application is applied to a sodium ion battery, the sodium ion battery can have good charging performance and high energy density.

[0016] In any embodiment, the negative electrode film layer satisfies 30%≦P≦60%, optionally 45%≦P≦55%, where P=[1−CW / (d1*PA)]*100% and d1=d2 / (1+E), where CW represents the coating weight of one side of the negative electrode film layer, PA represents the true density of the negative electrode film layer on one side, E represents the elongation of the negative electrode sheet, and d2 represents the thickness of the negative electrode film layer on one side.

[0017] When the parameter P of the negative electrode layer satisfies the above condition, the increase in the compaction degree of the negative electrode layer is mainly due to the increase in the bulk density of the negative electrode active material particles, which is thought to have no significant effect on the porosity of the negative electrode layer. This not only improves the compaction degree of the negative electrode layer, but also maintains the electrolyte wettability of the negative electrode layer, ensuring that the secondary battery has high energy density and good power storage performance.

[0018] In any embodiment, the pore size of the adsorption pores in the first negative electrode active material particles is 0.1 nm to 16 nm, and optionally 1 nm to 7 nm. When the pore size distribution of the adsorption pores is within the above appropriate range, Na + This is advantageous for the adsorption and desorption of the compound, and is also advantageous for improving the multiplication performance of the secondary battery.

[0019] Optionally, the specific surface area of ​​the first negative electrode active material particles is 1 m 3 / g~40m 3 / g, selectable, 1.5m 3 / g~10m 3 / g. When the specific surface area of ​​the first negative electrode active material particles is within an appropriate range, the negative electrode sheet not only has good sodium ion transmission performance, but also reduces the loss of active ions at the solid electrolyte interface (SEI) membrane, thereby ensuring the initial coulombic efficiency of the sodium ion battery.

[0020] Optionally, the interplanar spacing of the (002) plane of the first negative electrode active material particles is 0.34 nm to 0.45 nm, and optionally 0.35 nm to 0.4 nm. When the interplanar spacing of the first negative electrode active material particles is within an appropriate range, Na + The electrode can be smoothly inserted and removed, thereby improving the multiplication performance of the sodium ion battery.

[0021] Optionally, the true density of the first negative electrode active material particles is 1.3 g / cm 3 ~2.0g / cm 3 and selectable 1.4g / cm 3 ~1.8g / cm 3 When the true density of the first negative electrode active material particles is within the above range and the tap density is within the range defined in the present application, it is considered that the first negative electrode active material particles contain a sufficient number of adsorption holes. + can be smoothly adsorbed and desorbed, and the sodium ion battery can have good power-saving performance.

[0022] In any embodiment, the first negative electrode active material particles are one or more types selected from hard carbon, soft carbon, and mesocarbon microbeads, and the second negative electrode active material particles are one or more types selected from hard carbon, soft carbon, and mesocarbon microbeads. The production process for particles selected from the above types of materials is mature, and first negative electrode active material particles and second negative electrode active material particles that meet the requirements of the present application can be easily obtained by processing.

[0023] In either embodiment, the first negative electrode active material particles have an irregular shape and / or a microspherical shape, and the second negative electrode active material particles have an irregular shape and / or a microspherical shape.

[0024] Optionally, the mass percentage content of the first negative electrode active material particles having an irregular shape relative to the total mass of the first negative electrode active material particles and the second negative electrode active material particles is 5% to 95%, and optionally 70% to 95%.

[0025] When the difference in median diameter between the first and second negative electrode active material particles is within the range of the present application, the negative electrode film layer can have a high degree of compaction regardless of the morphology of the first and second negative electrode active material particles, which improves the process flexibility of the negative electrode sheet and enables the sodium-ion battery to have a high energy density.

[0026] In any embodiment, the first negative electrode active material particles are selected from irregularly shaped hard carbon particles, and the second negative electrode active material particles are selected from microspherical hard carbon particles, and the mass percentage content of the first negative electrode active material particles is 70% to 95% with respect to the total mass of the first negative electrode active material particles and the second negative electrode active material particles.

[0027] When the second negative electrode active material particles are microspherical hard carbon particles, they can not only fill the gaps between the first negative electrode active material particles, but also improve the compaction degree of the negative electrode film layer, the adhesive strength of the adhesive to the negative electrode active material particles, and the conductive performance of the negative electrode film layer, and further exert a certain sliding effect, further improving the compaction degree of the negative electrode film layer.When the ratio of the first negative electrode active material particles to the second negative electrode active material particles is within an appropriate range, the negative electrode active material particles have an appropriate specific surface area, so that the surface of the negative electrode active material particle has an appropriate number of active sites for electrochemical reactions, and the coulombic efficiency of the sodium-ion battery can be ensured.

[0028] In any embodiment, the first negative electrode active material particles are selected from microspherical hard carbon particles, and the median diameter D of the first negative electrode active material particles is 1 50 is 10 μm to 50 μm, the second negative electrode active material particles are selected from microspherical hard carbon particles, and the median diameter D of the second negative electrode active material particles is 2 50 is 5 μm to 40 μm, where the mass percentage content of the first negative electrode active material particles relative to the total mass of the first negative electrode active material particles and the second negative electrode active material particles is 5% to 95%, optionally 70% to 95%.

[0029] When the microspherical hard carbon particles themselves have a high bulk density and the median diameters of the first and second negative electrode active material particles satisfy the above range, the bulk density of the negative electrode active material particles can be further improved. Furthermore, the microspherical second negative electrode active material particles can simultaneously perform void filling and sliding functions, thereby significantly improving the compaction degree of the negative electrode film layer. Therefore, when the negative electrode sheet of the present application is applied to a sodium-ion battery, it can significantly improve the energy density, power supply performance, and cycle stability of the sodium-ion battery.

[0030] In any embodiment, the compaction density PD of the negative electrode film layer is 1.0 g / cm 3 ≦PD≦1.2g / cm 3 and the negative electrode film layer satisfies 30%≦P≦60%, optionally 45%≦P≦55%, where P=[1−CW / (d1*PA)]*100% and d1=d2 / (1+E), where CW represents the coating weight of one side of the negative electrode film layer, PA represents the true density of the negative electrode film layer on one side, E represents the elongation of the negative electrode sheet, and d2 represents the thickness of the negative electrode film layer on one side.

[0031] When the parameter P of the anode film layer satisfies the above condition, the increased compaction of the anode film layer is believed to be mainly due to the increased bulk density of the anode active material particles. Therefore, the hard carbon particles can provide a high compaction in the anode film layer without distortion or slippage. This makes it possible to apply hard carbon materials to sodium-ion batteries, thereby expanding the potential for widespread application of sodium-ion batteries.

[0032] In any embodiment, the negative electrode film layer further includes a slip-increasing component, the ratio of the mass of the slip-increasing component to the sum of the mass of the first negative electrode active material particles and the second negative electrode active material particles is 100:2 to 100:1, and the slip-increasing component includes one or more of artificial graphite, natural graphite, and graphene.

[0033] When the negative electrode film layer contains a small amount of slip-increasing component, the slip-increasing component can exert a slipping effect during the cold pressing process, thereby further improving the compaction degree of the negative electrode film layer. In addition, the slip-increasing component also has good electrical conductivity, and when applied to a negative electrode sheet, it can further improve the electron transmission performance of the negative electrode sheet.

[0034] In any embodiment, the negative electrode film layer further includes a flexible adhesive, and the flexible adhesive includes one or more of a styrene acrylic emulsion, a copolymer of vinylidene fluoride and tetrafluoroethylene, a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and acrylic esters, polytetrafluoroethylene, nitrile rubber, and hydrogenated nitrile rubber.

[0035] The negative electrode film layer includes the flexible adhesive, which allows the negative electrode film layer to have good flexibility, which allows the negative electrode film layer to have less stress during cold pressing and allows the negative electrode sheet to have a lower elongation rate, which further improves the compaction degree of the negative electrode film layer and improves the energy density of the sodium-ion battery.

[0036] A second aspect of the present application provides a secondary battery including the negative electrode sheet of the first aspect of the present application.

[0037] The secondary battery of the present application can have high energy density and good multiplier performance by including the negative electrode sheet of the first aspect of the present application.

[0038] A third aspect of the present application provides a battery module including the secondary battery of the second aspect of the present application.

[0039] A fourth aspect of the present application provides a battery pack including the battery module of the third aspect of the present application.

[0040] A fifth aspect of the present application provides a power consumption device including at least one selected from the secondary battery of the second aspect of the present application, the battery module of the third aspect of the present application, or the battery pack of the fourth aspect of the present application.

[0041] The battery module, battery pack, and power consumption device of the present application include the secondary battery of the present application, and therefore have at least the same advantages as the secondary battery. [Brief explanation of the drawings]

[0042] [Figure 1] FIG. 2 is a schematic diagram of an elongation test of a negative electrode sheet according to an embodiment of the present application. [Figure 2] 1 is a schematic diagram of a secondary battery according to an embodiment of the present application. [Figure 3] FIG. 3 is an exploded view of the secondary battery shown in FIG. 2 according to the embodiment of the present invention. [Figure 4] 1 is a schematic diagram of a battery module according to an embodiment of the present application. [Figure 5] 1 is a schematic diagram of a battery pack according to an embodiment of the present application; [Figure 6] FIG. 6 is an exploded view of the battery pack shown in FIG. 5 according to the embodiment of the present invention. [Figure 7] 1 is a schematic diagram of a power consumption device that uses a secondary battery as a power source according to an embodiment of the present application. [Figure 8] 1 is a scanning electron microscope photograph (SEM image) of the negative electrode sheet according to Example 1 of the present application. 1 Battery pack, 2 Upper housing, 3 Lower housing, 4 Battery module, 5 Secondary battery, 51 Case, 52 Electrode assembly, 53 Cover plate DETAILED DESCRIPTION OF THE INVENTION

[0043] Hereinafter, specific embodiments of the present application will be described in detail with reference to the accompanying drawings. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters or redundant description of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to make it easier for those skilled in the art to understand. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0044] The "ranges" disclosed herein are defined in the form of lower and upper limits. A given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of that particular range. Such defined ranges may be inclusive or exclusive of the end values, and may be arbitrarily combined; i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are recited for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​1 and 2 and maximum range values ​​3, 4, and 5 are recited, the following ranges may also be contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. Unless otherwise specified, the numerical range "a to b" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 and 5" are listed in this specification, and "0 to 5" is an abbreviation for combinations of these numerical values. Furthermore, when a parameter is expressed as an integer of 2 or greater, this is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] Unless otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all technical features and optional technical features of the present application may be combined with each other to form a new technical solution.

[0047] Unless otherwise specified, all steps herein can be performed in sequence, randomly, and preferably in sequence. For example, when a method includes steps (a) and (b), it means that the method can include steps (a) and (b) performed in sequence, or can include steps (b) and (a) performed in sequence. For example, when a method can further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can include steps (a), (c), and (b), or can further include steps (c), (a), and (b), etc.

[0048] Unless otherwise specified, the terms "having," "comprising," and "including" referred to in this application may be open-ended or closed-ended. For example, the terms "having," "comprising," and "comprising" indicate that the term may further comprise, include, or contain other components not listed, or may only comprise or contain the listed components.

[0049] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or A and B are both true (or exist).

[0050] In order to improve the energy density and multiplier performance of sodium ion batteries, it is important to select the negative electrode active material of the sodium ion battery.

[0051] As a result of extensive research, the inventors have found that, unlike the lithium insertion reaction of lithium ion batteries, the negative electrode of a sodium ion battery undergoes a sodium insertion reaction during the charging process. + Not only does the intercalation of Na occur, but the Na in the negative electrode active material + By selecting negative electrode active material particles with multiple adsorption pores, it was found that Na adsorption also occurs during long-term cycling. + However, after the negative electrode active material particles with multiple adsorption holes are prepared in the negative electrode membrane layer, the compaction density of the negative electrode membrane layer is low, which not only affects the energy density of the sodium ion battery, but also leads to a longer transmission path for electrons and sodium ions in the negative electrode sheet, thereby reducing the transmission performance of electrons and sodium ions in the negative electrode sheet and further deteriorating the power supply performance of the sodium ion battery.

[0052] Based on this, the inventors have conducted extensive research and experiments to propose a negative electrode sheet, a secondary battery, a battery module, a battery pack, and a power consumption device.

[0053] Negative electrode sheet

[0054] A first aspect of the present application provides a negative electrode sheet including a negative electrode current collector and a negative electrode film layer. The negative electrode film layer is located on at least one surface of the negative electrode current collector, the negative electrode film layer including first negative electrode active material particles and second negative electrode active material particles, the first negative electrode active material particles including a plurality of adsorption holes, and the first negative electrode active material particles having a tap density of 0.4 g / cm. 3 ~1.4g / cm 3 and selectable, 0.6g / cm 3 ~1.0g / cm 3Here, the difference d in median diameter between the first negative electrode active material particles and the second negative electrode active material particles satisfies the relationship 3 μm≦d≦19 μm, 3 μm≦d≦15 μm, 3 μm≦d≦10 μm, 3 μm≦d≦5 μm, 5 μm≦d≦19 μm, 5 μm≦d≦15 μm, 5 μm≦d≦10 μm, 10 μm≦d≦19 μm, 10 μm≦d≦15 μm, or 15 μm≦d≦19 μm. The compaction density PD of the negative electrode film layer is 0.8 g / cm 3 ≦PD≦1.4g / cm 3 , 0.8g / cm 3 ≦PD≦1.2g / cm 3 , 0.8g / cm 3 ≦PD≦1.0g / cm 3 , 1.0g / cm 3 ≦PD≦1.4g / cm 3 , or 1.0 g / cm 3 ≦PD≦1.2g / cm 3 Meet the following.

[0055] Although the mechanism is unclear, the inventors of the present application unexpectedly discovered that the present negative electrode membrane layer contains first and second negative electrode active material particles that satisfy the above conditions, and by combining two types of negative electrode active material particles, the negative electrode membrane layer has a high compaction density and high porosity inside the negative electrode membrane layer. As a result, when the present negative electrode sheet is applied to a sodium ion battery, it can provide the sodium ion battery with high energy density and good power conversion performance.

[0056] Specifically, without being limited to any theory or interpretation, the first negative electrode active material particles have a plurality of adsorption pores, and the tap density is within the above-mentioned appropriate range, so that even after cold pressing, the first negative electrode active material particles can have a sufficient number of adsorption pores inside. +is smoothly adsorbed to the first negative electrode active material particles during charging and smoothly desorbed during discharging. Furthermore, when the difference between the median diameter of the first negative electrode active material particles and the median diameter of the second negative electrode active material particles is within the above-mentioned appropriate range, it is advantageous for the second negative electrode active material particles to fill the gaps between the multiple first negative electrode active material particles, thereby providing the negative electrode active material particles with a high bulk density and, further, providing the negative electrode film layer with an appropriate compaction density after cold pressing. This allows the negative electrode active material particles in the negative electrode film layer to be in close contact with each other, thereby improving the electron and sodium ion transmission performance of the negative electrode sheet and further improving the power conversion performance of the sodium ion battery.

[0057] In some embodiments, the median diameter D of the first negative electrode active material particles 1 50 may be 4 μm to 50 μm, and optionally 4 μm to 25 μm, and the median diameter D of the second negative electrode active material particles 2 50 may be 1 μm to 40 μm, and optionally 1 μm to 20 μm. For example, D 1 50 may be 4 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 35 μm, 45 μm, 50 μm, or any value within a range thereof; 2 50 may be 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, or a range of any of the foregoing values.

[0058] Without being limited to any theory or interpretation, 1 50, D 2 When D 50 is in the above appropriate range, it is advantageous not only to improve the compaction degree of the negative electrode film layer but also to improve the contact between particles and reduce the impedance of the sodium ion battery. 1 50, D 2 If 50 is within the appropriate range above, D 1 50 and D 250 is advantageous to control within the range specified in the present application, which is advantageous for the second negative electrode active material particles to fill the voids between the first negative electrode active material particles and further advantageous for improving the compaction degree of the negative electrode film layer, while the first negative electrode active material particles and the second negative electrode active material particles have an appropriate particle size, which not only allows the first negative electrode active material particles and the second negative electrode active material particles to have good electron and sodium ion transmission performance within the particles, but also allows the first negative electrode active material particles and the second negative electrode active material particles to have low particle interface resistance. As a result, when the negative electrode sheet of the present application is applied to a sodium ion battery, it allows the sodium ion battery to have high energy density and low impedance, and the sodium ion battery to have high capacity, good power supply performance, and good cycle performance.

[0059] In some embodiments, the mass percentage content of the first negative electrode active material particles relative to the total mass of the first negative electrode active material particles and the second negative electrode active material particles may be 5% to 95%, or optionally 70% to 95%. For example, the mass percentage content of the first negative electrode active material particles relative to the total mass of the first negative electrode active material particles and the second negative electrode active material particles may be 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, or any range of the above values.

[0060] Without being limited by any theory or interpretation, when the mass percentage content of the first negative electrode active material particles and the second negative electrode active material particles is within the above appropriate range, the second negative electrode active material particles can be ensured to fill the voids between the first negative electrode active material particles, while the negative electrode active material particles can have an appropriate specific surface area, thereby improving the compaction density of the negative electrode film layer, increasing the contact area between the particles, improving the transmission path between the particles, and preventing the occurrence of broken bridges between the particles, resulting in a sodium-ion battery with high energy density and cycle performance.

[0061] In some embodiments, the elongation percentage E of the negative electrode sheet satisfies 0.1%≦E≦0.2%, and optionally 0.1%≦E≦0.15%. For example, E may be 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, or any range of the foregoing values.

[0062] Without being limited to any theory or explanation, when the difference in median diameter between the first negative electrode active material particles and the second negative electrode active material particles is within an appropriate range, the negative electrode active material particles can have a high bulk density. Therefore, when the cold-pressing parameters are the same, the negative electrode sheet of the present invention can have a lower elongation rate than negative electrode active material particles with a lower bulk density.

[0063] In some embodiments, the single-side coating weight CW of the negative electrode film layer is 2 mg / cm 2 ~13mg / cm 2 may be selected to be 5 mg / cm 2 ~12mg / cm 2 For example, CW is 2 mg / cm 2 , 5 mg / cm 2 , 8 mg / cm 2 , 10 mg / cm 2 , 12 mg / cm 2 , 13 mg / cm 2 Or it may be within a range of any of the above values.

[0064] The single-sided coating weight of the negative electrode membrane layer can indicate the solid content in the negative electrode slurry coated on the single-sided negative electrode membrane layer within a unit area, and the value may be equal to the areal density of the single-sided negative electrode membrane layer.

[0065] Without being limited by any theory or explanation, when the coating weight of the negative electrode film layer is within the above-mentioned appropriate range, it is advantageous to control the thickness of the negative electrode film layer within an appropriate range. This not only provides an appropriate migration path for electrons and sodium ions in the negative electrode sheet, but also allows the negative electrode sheet to have an appropriate capacity. Therefore, when the negative electrode sheet of the present application is applied to a sodium ion battery, the sodium ion battery can have good power-conversion performance and high energy density.

[0066] In some embodiments, the negative electrode film layer can satisfy 30%≦P≦60%. Optionally, 45%≦P≦55%.

[0067] Here, P = [1-CW / (d1*PA)]*100%, d1 = d2 / (1+E), CW indicates the coating weight of one side of the negative electrode film layer, PA indicates the true density of one side of the negative electrode film layer, and PA = 1 / (Σx i / ρ i ) can be calculated using the formula, where x i indicates the mass ratio of the i-th component constituting the negative electrode film layer in the negative electrode film layer, and ρ i indicates the density of the i-th component, E indicates the elongation of the negative electrode sheet, and d2 indicates the thickness of the single-sided negative electrode film layer.

[0068] Without being limited by any theory or explanation, the inventors unexpectedly found that when the parameter P of the negative electrode layer satisfies the above conditions, the increase in compaction degree of the negative electrode layer is mainly achieved by increasing the bulk density of the negative electrode active material particles, without significantly affecting the porosity of the negative electrode layer, which not only improves the compaction degree of the negative electrode layer but also maintains the electrolyte wettability of the negative electrode layer, ensuring that the secondary battery has high energy density and good power consumption.

[0069] In some embodiments, the pore size of the adsorption pores in the first negative electrode active material particles may be 0.1 nm to 16 nm, and optionally 1 nm to 7 nm. When the pore size distribution of the adsorption pores is within the above appropriate range, Na + This is advantageous for the adsorption and desorption of the compound, and is advantageous for improving the multiplication performance of the secondary battery.

[0070] Optionally, the specific surface area of ​​the first negative electrode active material particles is 1 m 3 / g~40m 3 / g, selectable 1.5m 3 / g~10m 3 / g. When the specific surface area of ​​the first negative electrode active material particles is within an appropriate range, the negative electrode sheet not only has good sodium ion transmission performance, but also reduces the loss of active ions at the solid electrolyte interface (SEI), thereby ensuring the initial coulombic efficiency of the sodium ion battery.

[0071] Optionally, the interplanar spacing of the (002) plane of the first negative electrode active material particles may be 0.34 nm to 0.45 nm, or alternatively, 0.35 nm to 0.4 nm. When the interplanar spacing of the first negative electrode active material particles is within an appropriate range, Na + The electrode can be smoothly inserted and removed, thereby improving the multiplication performance of the sodium ion battery.

[0072] Optionally, the true density of the first negative electrode active material particles is 1.3 g / cm 3 ~2.0g / cm 3 It may be selectable to 1.4g / cm 3 ~1.8g / cm 3 When the true density of the first negative electrode active material particles is within the above range and the tap density is within the range defined in the present application, it is considered that the first negative electrode active material particles contain a sufficient number of adsorption holes. + can be smoothly adsorbed and desorbed, and the sodium ion battery can have good power-saving performance.

[0073] In the present application, the materials of the first negative electrode active material particles and the second negative electrode active material particles are not limited. In some embodiments, the first negative electrode active material particles may be one or more of hard carbon, soft carbon, and mesocarbon microbeads (MCMB), and the second negative electrode active material particles may be one or more of hard carbon, soft carbon, and MCMB.

[0074] The particle production process for particles selected from the above types of materials is mature, and first negative electrode active material particles and second negative electrode active material particles that meet the requirements of the present application can be easily obtained by processing.

[0075] The present application does not limit the morphology of the first and second negative electrode active material particles. In some embodiments, the first negative electrode active material particles may have an irregular shape and / or a microspherical shape, and the second negative electrode active material particles may have an irregular shape and / or a microspherical shape.

[0076] Optionally, the mass percentage content of the first negative electrode active material particles having an irregular shape relative to the total mass of the first negative electrode active material particles and the second negative electrode active material particles may be 5% to 95%, and optionally 70% to 95%.

[0077] The morphology of the first negative electrode active material particles and the morphology of the second negative electrode active material particles may be the same or different.

[0078] In the negative electrode sheet of the present application, when the difference in median diameter between the first negative electrode active material particles and the second negative electrode active material particles is within the range of the present application, the negative electrode film layer can have a high degree of compaction regardless of the morphology of the first negative electrode active material particles and the second negative electrode active material particles, which improves the process flexibility of the negative electrode sheet and enables the sodium ion battery to have a high energy density.

[0079] In some embodiments, the first negative electrode active material particles and the second negative electrode active material particles can both be hard carbon particles.

[0080] After extensive investigation, the inventors discovered that hard carbon materials have low storage voltage, high capacity, and good cycle stability. Furthermore, hard carbon materials are abundantly available and easy to prepare. More importantly, the hard carbon particles themselves have a large lattice spacing and are highly porous, making them an ideal choice for the first anode active material particles of the present invention. Conventional hard carbon materials have high hardness and little distortion or slippage during cold pressing. When applied to anode membrane layers, the compaction density of the anode membrane layer is usually low. However, in the anode membrane layer of the present invention, the small-sized second anode active material particles can fill the voids of the first anode active material particles, eliminating the need for deformation of the first anode active material particles and providing a high compaction density for the anode membrane layer. Therefore, when both the first and second anode active material particles are hard carbon particles, the application of the anode sheet of the present invention to a sodium-ion battery can reduce the cost of the sodium-ion battery and improve the energy density, power supply performance, and cycle stability of the sodium-ion battery.

[0081] In some embodiments, the first negative electrode active material particles may be selected from irregularly shaped hard carbon particles, and the second negative electrode active material particles may be selected from microspherical hard carbon particles. The mass percentage content of the first negative electrode active material particles may be 70% to 95% based on the total mass of the first negative electrode active material particles and the second negative electrode active material particles.

[0082] Without being limited by any theory or interpretation, when the second negative electrode active material particles are microspherical hard carbon particles, they can not only fill the gaps between the first negative electrode active material particles, but also improve the compaction degree of the negative electrode film layer, the adhesive strength of the adhesive to the negative electrode active material particles, and the conductive performance of the negative electrode film layer, and further exert a certain sliding effect, further improving the compaction degree of the negative electrode film layer.When the ratio of the first negative electrode active material particles to the second negative electrode active material particles is within an appropriate range, the negative electrode active material particles have an appropriate specific surface area, thereby providing the negative electrode active material particle surface with an appropriate number of active sites for electrochemical reactions, and ensuring the Coulombic efficiency of the sodium-ion battery.

[0083] In some embodiments, the first negative electrode active material particles are selected from microspherical hard carbon particles, and the median diameter D 1 50 is 10 μm to 50 μm, the second negative electrode active material particles are selected from microspherical hard carbon particles, and the median diameter D of the second negative electrode active material particles is 2 50 is 5 μm to 40 μm, where the mass percentage content of the first negative electrode active material particles relative to the total mass of the first negative electrode active material particles and the second negative electrode active material particles may be 5% to 95%, or optionally 70% to 95%.

[0084] Without being limited by any theory or interpretation, it is believed that when the microspherical hard carbon particles themselves have a high bulk density and the median diameters of the first and second negative electrode active material particles satisfy the above range, the bulk density of the negative electrode active material particles can be further improved. Furthermore, the microspherical second negative electrode active material particles can simultaneously perform void filling and sliding functions, thereby significantly improving the compaction degree of the negative electrode film layer. Therefore, when the negative electrode sheet of the present application is applied to a sodium-ion battery, it can significantly improve the energy density, power supply performance, and cycle stability of the sodium-ion battery.

[0085] In some embodiments, the first negative electrode active material particles and the second negative electrode active material particles may both be hard carbon particles. The density of compaction (PD) of the negative electrode film layer is 1.0 g / cm. 3 ≦PD≦1.2g / cm 3 The negative electrode film layer may satisfy 30%≦P≦60%, and optionally 45%≦P≦55%, where P=[1−CW / (d1*PA)]*100%, d1=d2 / (1+E), CW represents the coating weight of one side of the negative electrode film layer, PA represents the true density of one side of the negative electrode film layer, and PA=1 / (Σx i / ρ i ) is calculated by the formula, where x i indicates the mass ratio of the i-th component constituting the negative electrode film layer in the negative electrode film layer, and ρ i indicates the density of the i-th component, E indicates the elongation of the negative electrode sheet, and d2 indicates the thickness of the single-sided negative electrode film layer.

[0086] Without being limited to any theory or interpretation, it is believed that when the parameter P of the negative electrode film layer satisfies the above condition, the increased compaction of the negative electrode film layer is mainly achieved by increasing the bulk density of the negative electrode active material particles. Therefore, the hard carbon particles can provide a high compaction of the negative electrode film layer without generating distortion or slippage. This enables the application of hard carbon materials to sodium-ion batteries, thereby enhancing the potential for broad application of sodium-ion batteries.

[0087] In some embodiments, the negative electrode film layer may further include a slip-increasing component, and the ratio of the mass of the slip-increasing component to the sum of the mass of the first negative electrode active material particles and the second negative electrode active material particles may be 100:2 to 100:1. The slip-increasing component may include one or more of artificial graphite, natural graphite, and graphene.

[0088] Without being limited to any theory or explanation, it is believed that if the negative electrode film layer contains a small amount of slip-increasing component, the slip-increasing component can exert a slipping effect during the cold pressing process, thereby further improving the compaction degree of the negative electrode film layer. In addition, the slip-increasing component also has good electrical conductivity, and when applied to a negative electrode sheet, it can further improve the electronic transmission performance of the negative electrode sheet.

[0089] In some embodiments, the negative electrode membrane layer may further include a flexible adhesive, which may include one or more of a styrene acrylic emulsion, a copolymer of vinylidene fluoride and tetrafluoroethylene, a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and acrylic esters, polytetrafluoroethylene, nitrile rubber, and hydrogenated nitrile rubber.

[0090] Without being limited by any theory or explanation, the negative electrode film layer includes the flexible adhesive, which allows the negative electrode film layer to have good flexibility, which allows the negative electrode film layer to have less stress during cold pressing, which makes it easier for the negative electrode active material particles to accumulate, and allows the negative electrode sheet to have a lower elongation rate, which further improves the compaction degree of the negative electrode film layer and improves the energy density of the sodium ion battery.

[0091] Note that the negative electrode film layer parameters in this application all refer to the parameter range of one negative electrode film layer. When negative electrode film layers are provided on both sides of the negative electrode current collector, if either one of the negative electrode film layer parameters satisfies the specified range, it is considered to be within the protection range of this application.

[0092] The first negative electrode active material particles and the second negative electrode active material particles in the present application can be obtained by various methods, including but not limited to, for example, the first negative electrode active material particles and the second negative electrode active material particles can be obtained commercially or homemade.

[0093] For example, the first and second negative electrode active material particles may be hard carbon particles having an irregular shape, and the first and second negative electrode active material particles may be produced by subjecting coconut shells to a pre-carbonization process by placing the coconut shells at 300°C, and by using a double-roll molding machine. The carbon particles can be prepared by the following steps: crushing coconut shells after pre-carbonization treatment into particles with a diameter of about 2 mm using a carbonization machine and removing impurities by sieving; heat-treating the particles at 400°C to 800°C and, if necessary, introducing halogen or hydrogen halide gas to remove ash and obtain particles that are easy to process by ball milling; ball milling the particles to obtain carbon particles with Dv50 = 50 μm / 40 μm / 25 μm / 20 μm / 9 μm / 5 μm / 3 μm / 1 μm; placing the ball-milled particles in an inert atmosphere, maintaining the temperature at 1150°C, carbonizing the ball-milled particles, and, if necessary, introducing acetylene gas to coat the ball-milled particles by vapor phase growth, thereby preparing first and second negative electrode active material particles having irregular shapes.

[0094] As another example, the first and second negative electrode active material particles may be microspherical hard carbon particles. The first and second negative electrode active material particles are prepared by the following steps. A step of dehydrating and carbonizing starch and / or lignin at 200°C or less to obtain pre-carbonized particles with a fixed initial shape (for example, pre-carbonized particles obtained from lignin for papermaking, potato starch, corn starch, and rice starch, Dv50 of which are 50 μm, 25 μm, 10 μm, and 6 μm, respectively, and spherical or nearly spherical in shape), adding a salt or polymer dehydrating agent containing N, P, S, or a halogen, such as an ammonium salt, phosphate, sulfate, sulfite, persulfate, a halide, or a polymer of the above salt, to the starch and / or lignin as needed, and heat-treating the pre-carbonized particles at 400 to 800°C to obtain carbonized particles that are easily pulverized by ball milling or airflow pulverization; and a step of pulverizing the carbonized particles by ball milling or airflow pulverization, and further pulverizing the carbonized particles by ball milling or airflow pulverization to obtain particles of other particle sizes close to spherical or cullet shapes (for example, potato starch carbon particles with a particle size of 25 μm). (In this example, rice starch having a particle size of 6 μm is pulverized by primary ball milling to 20 μm so that the shape remains nearly spherical, and then by tertiary ball milling to 5 μm so that the shape remains nearly spherical, and then by tertiary ball milling to 5 μm particles so that the shape remains nearly spherical, and then by tertiary ball milling to 1.5 μm particles so that the shape remains nearly spherical, and then by tertiary ball milling to 1.5 μm particles so that the shape remains nearly spherical, and then by corn starch carbon particles having a particle size of 10 μm are pulverized by airflow milling to obtain cullet-shaped carbon particles having a particle size of 1 μm.) The method also includes the steps of: (1) placing the particles in an inert atmosphere and maintaining the temperature at 1150°C to carbonize the ball-milled particles; and (2) introducing acetylene gas as needed to coat the ball-milled particles by vapor deposition to prepare first and second negative electrode active material particles having a microspherical shape.

[0095] In this application, tap density has a meaning well known in the art and can be measured by methods well known in the art, for example, by testing using a powder tap density tester (e.g., Dandong Baite BT-310) in accordance with standards GB / T5162-2006 and GB / T24533-2009.

[0096] In this application, the median diameter has the meaning known in the art and can refer to the particle diameter corresponding to the cumulative particle size distribution percentage of particles reaching 50%. The median diameter can be measured by a method and device known in the art. For example, it can be measured using a laser particle size analyzer (e.g., Mastersizer 2000E, UK) in accordance with GB / T19077-2016 Particle Size Distribution Laser Diffraction Method.

[0097] In this application, the compaction degree of the negative electrode film layer has a meaning well known in the art and can be measured by a method well known in the art. For example, after the negative electrode sheet is cold-pressed, a press is used to punch out a wafer with a surface area S1 completely coated with slurry and a wafer without a surface area S1, which are then weighed to obtain average masses W2 and W1, and measured to obtain average thicknesses T2 and T1, thereby obtaining the compaction degree of the negative electrode film layer PD=(W2-W1) / (T2-T1) / S1.

[0098] In this application, the term "elongation E" of a negative electrode sheet has a meaning well known in the art and can refer to the rate of change in length in the machine direction of a negative electrode sheet before and after cold pressing. The elongation E can be measured using methods and equipment well known in the art. For example, as shown in FIG. 1, a 2-m-long coated and dried negative electrode sheet is taken. Two marks A1 and A2 are selected. The connecting line between A1 and A2 is parallel to the length direction of the negative electrode sheet. The distance between marks A1 and A2 is accurately measured with a ruler and denoted as L1. After the negative electrode sheet is cold-pressed with a certain pressure, the distance between A1 and A2 is measured and denoted as L2. Therefore, E = (L2 - L1) / L1.

[0099] In this application, the single-sided coating weight of the negative electrode film layer has a meaning well known in the art and can be measured by a method well known in the art. For example, after the negative electrode sheet is cold-pressed, a press is used to punch out a wafer with an area S2 completely coated with slurry and a wafer with no slurry coated, and these are weighed to obtain average masses M2 and M1, and the single-sided coating weight of the negative electrode sheet CW = (M2 - M1) / nS2, where n represents the number of negative electrode film layers. If the negative electrode sheet is coated on one side, n = 1. If the negative electrode sheet is coated on both sides, n = 2.

[0100] In this application, the thickness d2 of the single-sided negative electrode film layer can be measured using a micrometer. For example, after the negative electrode sheet is cold-pressed, the thickness d3 of the negative electrode sheet is measured using a micrometer. The negative electrode film layer on the surface of the negative electrode sheet is scraped off and washed with a solvent. Then, the thickness d4 of the negative electrode current collector is measured using a micrometer, and d4 = (d3 - d4) / n, where n represents the number of negative electrode film layers. If the negative electrode sheet is single-sided coated, n = 1. If the negative electrode sheet is double-sided coated, n = 2.

[0101] In this application, the pore size and pore size distribution of the adsorption pores of the negative electrode material have meanings well known in the art and can be measured by a method well known in the art, for example, by a specific surface area analyzer (e.g., Tristar II 3020M).

[0102] In this application, the specific surface area of ​​the negative electrode active material particles has a meaning well known in the art and can be measured by a method well known in the art. For example, the specific surface area of ​​the negative electrode active material can be measured by a nitrogen adsorption / desorption method using a specific surface area analyzer (e.g., Tristar II 3020M).

[0103] In this application, the interplanar spacing has a meaning well known in the art and can be measured by a method well known in the art, for example, by analyzing particles of the negative electrode active material by X-ray diffraction (e.g., Equinox 100).

[0104] In this application, the true density of the negative electrode active material particles has a meaning well known in the art and can be measured by a method known in the art, for example, using a true density tester (e.g., AccuPycII1340).

[0105] The secondary battery, battery module, battery pack, and power consuming device according to the present application will be described with reference to the drawings as appropriate.

[0106] secondary battery

[0107] A second aspect of the present application provides a secondary battery, which in some embodiments may be a sodium ion battery.

[0108] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are inserted and removed between the positive electrode sheet and the negative electrode sheet. The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The separator, located between the positive electrode sheet and the negative electrode sheet, serves to prevent short-circuiting between the positive and negative electrodes while allowing ions to pass through.

[0109] [Positive electrode sheet]

[0110] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer including the positive electrode active material of the first aspect of the present application.

[0111] As an example, the positive electrode current collector has opposite surfaces facing each other in its thickness direction, and the positive electrode film layer is provided on one or both of the opposing surfaces of the positive electrode current collector.

[0112] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. For example, aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymeric base layer and a metal layer formed on at least one surface of the polymeric base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymeric substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0113] In some embodiments, when the secondary battery is a sodium ion battery, the positive electrode active material can be a positive electrode active material known in the art and used in sodium ion batteries. For example, the positive electrode active material may be a single material or a combination of two or more materials. The positive electrode active material may be, for example, sodium iron composite oxide (NaFeO2), sodium cobalt composite oxide (NaCoO2), sodium chromium composite oxide (NaCrO2), sodium manganese composite oxide (NaMnO2), sodium nickel composite oxide (NaNiO2), sodium nickel titanium composite oxide (NaNi 1 / 2 Ti 1 / 2 O2), sodium nickel manganese composite oxide (NaNi 1 / 2 Mn 1 / 2 O2), sodium iron manganese composite oxide (Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2), sodium nickel cobalt manganese composite oxide (NaNi 1 / 3 Co 1 / 3 Mn 1 / 3O2), sodium iron phosphate compound (NaFePO4), sodium manganese phosphate compound (NaMnPO4), sodium cobalt phosphate compound (NaCoPO4), Prussian blue-based materials, polyanion materials (phosphates, fluorophosphates, pyrophosphates, sulfates), etc., but the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may also be used.

[0114] In some embodiments, the positive electrode membrane layer may further include an adhesive, as needed. For example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0115] In some embodiments, the positive electrode film layer may further include a conductive agent, for example, at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0116] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the adhesive, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, and applying the positive electrode slurry to a positive electrode current collector, followed by steps such as drying and cold pressing, to obtain a positive electrode sheet.

[0117] [Negative electrode sheet]

[0118] In the secondary battery of the present application, the negative electrode sheet includes the negative electrode sheet of the first aspect of the present application.

[0119] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0120] As an example, the negative electrode current collector has opposite surfaces facing each other in its thickness direction, and the negative electrode film layer is provided on one or both of the opposing surfaces of the negative electrode current collector.

[0121] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, copper foil or aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0122] In some embodiments, the negative electrode film layer may further include a conductive agent, if necessary, which may be at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0123] In some embodiments, the negative electrode membrane layer may further include other auxiliary agents, such as a thickener (eg, carboxymethylcellulose sodium (CMC-Na)), as needed.

[0124] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-described components for preparing the negative electrode sheet, such as first negative electrode active material particles, second negative electrode active material particles, an optional slip extender component, a conductive agent, an adhesive, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry, and applying the negative electrode slurry to a negative electrode current collector, followed by processes such as drying and cold pressing, to obtain a negative electrode sheet.

[0125] [Electrolyte]

[0126] The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte used in the present application is not particularly limited and can be selected according to needs. The electrolyte may be, for example, liquid, gel, or all-solid.

[0127] In some embodiments, the electrolyte uses an electrolytic solution, which includes an electrolyte salt and a solvent.

[0128] In some embodiments, the electrolyte salt is one or more of NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3.

[0129] In some embodiments, the solvent may be at least one selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0130] In some embodiments, the electrolyte solution may further contain additives as needed. For example, the additives may include a negative electrode film-forming additive and a positive electrode film-forming additive, and may also include additives that improve certain battery performance, such as an additive that improves the overcharge performance of the battery or an additive that improves the high-temperature or low-temperature performance of the battery.

[0131] [Separator]

[0132] In some embodiments, the secondary battery further includes a separator. The type of separator used in the present application is not particularly limited, and any known porous structure separator having good chemical and mechanical stability can be selected.

[0133] In some embodiments, the separator is made of at least one material selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers may be the same or different, and are not particularly limited.

[0134] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be prepared into an electrode assembly by a winding or lamination process.

[0135] In some embodiments, the secondary battery may include an outer casing, which is used to seal the electrode assembly and electrolyte.

[0136] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, or a steel case. Alternatively, the exterior of the secondary battery may be a soft package, such as a bag soft package. The soft package may be made of plastic, such as polypropylene, polybutylene terephthalate, or polybutylene succinate.

[0137] The shape of the secondary battery of the present application is not particularly limited, and may be cylindrical, rectangular, or any other shape. For example, Fig. 2 shows a secondary battery 5 having a rectangular structure as an example.

[0138] In some embodiments, referring to FIG. 3 , the exterior may include a case 51 and a cover plate 53. The case 51 includes a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving cavity. The case 51 has an opening communicating with the receiving cavity, and the cover plate 53 can cover the opening to seal the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is sealed in the receiving cavity. An electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be selected by those skilled in the art according to specific actual needs.

[0139] Battery modules and battery packs

[0140] In some embodiments, the secondary battery may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and those skilled in the art can select the specific number depending on the application and capacity of the battery module.

[0141] Fig. 4 shows an example of a battery module 4. Referring to Fig. 4, in the battery module 4, the plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0142] Optionally, the battery module 4 further includes a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in the accommodating space.

[0143] In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and those skilled in the art can select the specific number depending on the application and capacity of the battery pack.

[0144] 5 and 6 show an example of a battery pack 1. Referring to FIGS. 5 and 6, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 is attached to the lower housing 3 as a lid, forming an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0145] power consumption equipment The present application also provides a power consuming device including at least one of the secondary battery, battery module, or battery pack according to the present application. The secondary battery, battery module, or battery pack may be used as a power source for the power consuming device or as an energy storage means for the power consuming device. The power consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships, satellites, energy storage systems, etc.

[0146] The power consumption device can be selected from a secondary battery, a battery module, or a battery pack depending on the usage needs.

[0147] 7 shows an example of a power consuming device, such as 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 secondary battery of the power consuming device, a battery pack or a battery module can be adopted.

[0148] Other exemplary devices may be mobile phones, tablet computers, laptop computers, etc. These devices are generally required to be thin and can employ secondary batteries as their power source.

[0149] Example The following examples of the present application are provided. The examples described below are illustrative and are intended to aid in the interpretation of the present application and should not be construed as limitations on the present application. Unless specific techniques or conditions are specified in the examples, the techniques, conditions, or instructions are those described in the literature in this field. Unless the manufacturer of the reagents or equipment used is specified, they are all commercially available products.

[0150] Example 1 1) Preparation of the positive electrode sheet The positive electrode active material is sodium nickel manganese composite oxide (NaNi 1 / 2 Mn 1 / 2 O2), acetylene black as a conductive agent, and polyvinylidene fluoride (PVDF) as an adhesive are thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) in a weight ratio of 92:5:3 and stirred to form a uniform positive electrode slurry. The positive electrode slurry is then applied to a 13 μm thick positive electrode current collector aluminum foil, dried at 100°C, and pressed to obtain a positive electrode sheet.

[0151] 2) Preparation of negative electrode sheet Anode active material particles, acetylene black as a conductive agent, styrene acrylic emulsion as an adhesive, and sodium hydroxymethylcellulose (CMC-Na) as a thickener are thoroughly mixed with an appropriate amount of deionized water in a weight ratio of 94:1:4:1 and stirred to form a uniform anode slurry. The anode slurry is then applied to both sides of an 8μm-thick anode current collector copper foil, dried at 100°C, and pressed to obtain a cathode sheet.

[0152] Here, the negative electrode active material particles include first negative electrode active material particles and second negative electrode active material particles, and the first negative electrode active material particles and the second negative electrode active material particles are both hard carbon particles having irregular shapes, and the median diameter D of the first negative electrode active material is 1 50 is 25 μm, and the median diameter D of the first negative electrode active material particles 2 50 is 22 μm. The mass percentage content Q1 of the first negative electrode active material particles relative to the total mass of the negative electrode active material particles is 70%. The coating weight CW of one side of the negative electrode sheet is 8 mg / cm 2 is.

[0153] 3) Separator A polyethylene PE separator (Celgard) is used.

[0154] 4) Preparation of electrolyte Equal volumes of ethylene carbonate (EC) and propylene carbonate (PC) are uniformly mixed to obtain an organic solvent, and then NaPF6 is uniformly dissolved in the organic solvent to obtain an electrolyte solution, where the concentration of NaPF6 is 1 mol / L.

[0155] 5) Battery preparation The positive electrode sheet, separator, and negative electrode sheet are laminated in this order, the electrolyte solution is added, and the resulting laminate is sealed to obtain a sodium ion battery.

[0156] Examples 2 to 14 Based on the preparation method of Example 1, 1 50, D 2 50 to prepare the sodium ion batteries of Examples 2 to 14.

[0157] Examples 15 to 22 Based on the preparation method of Example 1, 1 50, D 2 50 and Q1 are adjusted to prepare the sodium ion batteries of Examples 15 to 22.

[0158] Examples 23 to 26 Based on the preparation method of Example 1, 1 50, D2 50 and Q1 are adjusted, and a slip increase component is separately added to the negative electrode slurry to prepare the sodium ion batteries of Examples 23 to 26.

[0159] Examples 27 to 29 Based on the preparation method of Example 1, the CW of the negative electrode sheet is adjusted to prepare the sodium ion batteries of Examples 27 to 29.

[0160] Example 30 Based on the preparation method of Example 1, 1 50, D 2 50, and replace the second negative electrode active material particles with microspherical hard carbon particles to prepare a sodium ion battery of Example 30.

[0161] Example 31 Based on the preparation method of Example 1, 1 50, D 2 50, and the first negative electrode active material particles and the second negative electrode active material particles are both replaced with microspherical hard carbon particles to prepare a sodium ion battery of Example 31.

[0162] Example 32 Based on the preparation method of Example 1, 1 50, D 2 50, and replace the first negative electrode active material particles with microspherical hard carbon particles to prepare the sodium ion battery of Example 32.

[0163] Example 33 Based on the preparation method of Example 1, 1 50, D 2 50, and replace the second negative electrode active material particles with soft carbon particles having irregular shapes to prepare a sodium ion battery of Example 33.

[0164] Example 34 Based on the preparation method of Example 1, 1 50, D 250, and replace the second negative electrode active material particles with spherical-like MCMB particles to prepare the sodium ion battery of Example 34.

[0165] Example 35 Based on the preparation method of Example 1, D 1 50, D 2 50, and replace the first negative electrode active material particles with soft carbon particles having irregular shapes to prepare a sodium ion battery of Example 35.

[0166] Example 36 Based on the preparation method of Example 1, D 1 50, D 2 50, and replace the first negative electrode active material particles with spherical MCMB particles to prepare the sodium ion battery of Example 36.

[0167] Examples 37 to 41 Based on the preparation method of Example 1, 1 50, D 2 The types of adhesives used for the negative electrode sheet and the negative electrode sheet are adjusted to prepare the sodium ion batteries of Examples 37 to 41. Here, the adhesive used for the negative electrode sheet of Example 37 is styrene butadiene rubber (SBR), the adhesive used for the negative electrode sheet of Example 38 is hydrogenated nitrile rubber, the adhesive used for the negative electrode sheet of Example 39 is a copolymer of vinylidene fluoride and hexafluoropropylene, the adhesive used for the negative electrode sheet of Example 40 is a copolymer of vinylidene fluoride and acrylic esters, and the adhesive used for the negative electrode sheet of Example 41 is polytetrafluoroethylene.

[0168] Examples 42 to 45 Based on the preparation method of Example 1, D 1 50, D 2 50, and the tap density of the first negative electrode active material particles are adjusted to prepare the sodium ion batteries of Examples 32 to 45.

[0169] Comparative Example 1 According to the preparation method of Example 1, the negative electrode active material particles are replaced with irregularly shaped hard carbon particles with a median diameter of 5 μm to prepare a sodium ion battery of Comparative Example 1.

[0170] Comparative Example 2 Based on the preparation method of Example 1, the negative electrode active material particles are replaced with microspherical hard carbon particles with a median diameter of 5 μm to prepare a sodium ion battery of Comparative Example 2.

[0171] Comparative Example 3 Based on the preparation method of Example 1, D 1 50, D 2 50 to prepare a sodium ion battery of Comparative Example 3.

[0172] The relevant preparation parameters for the negative electrode sheets of Examples 1 to 45 and Comparative Examples 1 to 3 are shown in Table 1 below. Here, Q1 represents the mass ratio of the first negative electrode active material particles to the total mass of the negative electrode active material particles, Q2 represents the mass ratio of the second negative electrode active material particles to the total mass of the negative electrode active material particles, and Q3 represents the mass ratio of the slip-increasing component to the negative electrode active material particles. The tap density ρ and D of the first negative electrode active material particles are 1 50, D 2 50 can be tested according to the methods described herein, and d, PA can be calculated according to the methods described herein.

[0173] The relevant test parameters for the negative electrode sheets of Examples 1 to 45 and Comparative Examples 1 to 3 are shown in Table 2 below, where CW, d2, E, and PD can be tested according to the methods described herein, and P can be calculated according to the methods described herein.

[0174] The negative electrode sheet of Example 1 was subjected to an SEM test, and the resulting SEM image is shown in FIG.

[0175] Preparation parameters of negative electrode sheets in Examples 1 to 45 and Comparative Examples 1 to 3 [Table 1]

[0176] Test parameters for negative electrode sheets of Examples 1 to 45 and Comparative Examples 1 to 3 [Table 2]

[0177] Furthermore, performance tests were carried out on the sodium ion batteries obtained in Examples 1 to 45 and Comparative Examples 1 to 3. The test results are shown in Table 3 below.

[0178] (1) Energy density test At 25°C, the secondary battery was charged at a constant current of 0.33C until the voltage reached 4.2V, and then at a constant voltage of 0.05C at 4.2V. At this point, the secondary battery reached a fully charged state. After leaving it for 5 minutes, it was discharged at a constant current of 0.33C until the voltage reached 2.5V, and then left for another 5 minutes. The capacity and voltage platform were recorded when the secondary battery was discharged at a constant current of 0.5C, and finally the mass of the secondary battery was measured.

[0179] Energy density of secondary battery (Wh / kg) = (Capacity when secondary battery is discharged at a constant current of 0.33C × Voltage platform when secondary battery is discharged at a constant current of 0.33C) / Mass of secondary battery.

[0180] (2) (Cycle life test) At 25°C, the secondary battery was charged at a constant current of 1 / 3C to 4.2V, then charged at a constant voltage of 4.2V until the current reached 0.05C, left for 5 minutes, and then discharged at 1 / 3C to 2.8V. The resulting capacity was designated as the initial capacity C0. The above steps were repeated for the same battery, and the discharge capacity C of the battery after the nth cycle was also recorded. n When recording the battery capacity retention rate P after each cycle n =C n / C0*100%, and P n The minimum n value corresponding to the case of ≦80% is taken as the cycle life of the secondary battery.

[0181] Performance test results for Examples 1 to 45 and Comparative Examples 1 to 3 [Table 3]

[0182] Summarizing Examples 1 to 6, when the median diameter of the first negative electrode active material particles remains constant, as the median diameter of the second negative electrode active material particles decreases, the difference in median diameter between the first and second negative electrode active material particles increases, and the bulk density of the negative electrode active material particles also increases accordingly. As shown in FIG. 8, the second negative electrode active material particles with a smaller median diameter can fill the gaps between the first negative electrode active material particles, thereby providing a high degree of compaction for the negative electrode film layer. Summarizing Examples 7 to 11, when the median diameter of the second negative electrode active material particles remains constant, as the median diameter of the first negative electrode active material particles increases, the difference in median diameter between the first and second negative electrode active material particles also increases, and the bulk density of the negative electrode active material particles also increases accordingly. This allows the negative electrode film layer to also have a high degree of compaction. Summarizing Examples 4, 10, 12, and 13 and Examples 1, 7, 14, and 19, it can be seen that when the difference between the median diameter of the first negative electrode active material particles and the median diameter of the second negative electrode active material particles is constant, the median diameters of the first negative electrode active material particles and the second negative electrode active material particles both have a certain effect on the compaction degree of the negative electrode film layer. Summarizing Examples 1 to 14 and 19, it can be seen that when the difference between the median diameters of the first negative electrode active material particles and the second negative electrode active material particles is within the range specified in the present application, the compaction degree of the negative electrode film layer can be effectively improved and the parameter P of the negative electrode film layer can be maintained within an appropriate range. This can improve the energy density and cycle life of sodium-ion batteries.

[0183] Summarizing Examples 15 to 22, it can be seen that the compaction index of the anode film layer generally increases and then decreases as the mass percentage content Q1 of the first anode active material particles decreases. This is because when Q1 is high, the mass percentage content Q2 of the second anode active material is relatively low, limiting the improvement in bulk density after mixing and limiting the increase in compaction index after cold pressing, resulting in a low compaction index of the anode film layer. When Q1 is low, Q2 is relatively high, and after the second anode active material particles fill the voids between the first anode active material particles, excess second anode active material particles remain. The compaction index of these second anode active material particles is difficult to increase even after cold pressing, and the median diameter of the second anode active material particles is small, resulting in a low compaction index of the anode film layer. When the contents of Q1 and Q2 are within an appropriate range, not only can the compaction degree of the negative electrode film layer be effectively improved, but also the parameter P corresponding to the negative electrode film layer can be maintained within an appropriate range, allowing the sodium-ion battery to combine high energy density with long cycle life.

[0184] Examples 19, 23, 24, 25, 26, and 27 show that adding a slip-increasing component to the negative electrode slurry can further improve the compaction degree of the negative electrode film layer. This is because the slip-increasing component exerts a sliding effect during the cold-pressing process of the negative electrode sheet, allowing the second negative electrode active material particles to more fully fill the voids between the first negative electrode active material particles. Examples 23 and 26 show that, although the tap density of the negative electrode film layer increases with increasing amounts of the slip-increasing component, the difference in energy density of the sodium-ion battery is not significant. This is because the slip-increasing component itself makes it difficult for sodium ions to intercalate, and while the slip-increasing component improves the compaction degree of the negative electrode film layer, it also reduces the theoretical capacity per gram of the negative electrode film layer.

[0185] Summarizing Examples 19, 27, and 29, it can be seen that the single-sided coating weight of the negative electrode film layer does not significantly affect the compaction degree of the negative electrode film layer. When the difference in median size between the first and second negative electrode active material particles is within the range of this application, negative electrode film layers with different single-sided coating weights all have a high compaction degree, an appropriate parameter P, and a long cycle life.

[0186] To summarize Examples 19 and 30 to 32, it can be seen that when at least one of the first negative electrode active material particles and the second active material particles is microspherical hard carbon particles, the compaction degree of the negative electrode film layer can be further improved.

[0187] Summarizing Examples 33 to 36, it can be seen that hard carbon has higher theoretical capacity per gram and cycle stability for sodium ion batteries compared to soft carbon and MCMB.

[0188] Summarizing Examples 19, 37 to 41, it can be seen that compared with the conventional negative electrode adhesive SBR, the flexible adhesive can improve the compaction degree of the negative electrode membrane layer, improve the long-term cycle performance of the sodium ion battery, and improve the energy density and cycle life of the sodium ion battery.

[0189] To summarise Examples 19 and 42 to 45, it can be seen that as the tap density of the first negative electrode active material particles increases, the compaction degree of the negative electrode film layer also increases.

[0190] In contrast, Comparative Examples 1 and 2 used only hard carbon particles with a median diameter of 5 μm as the negative electrode active material particles, resulting in a low compaction degree of the negative electrode film layer. As a result, the negative electrode sheet not only had a low energy density but also long electron and sodium ion transmission paths, resulting in low energy density and cycle life of the sodium-ion battery. In Comparative Example 3, negative electrode active material particles with different median diameters were used, but the difference in median diameter between the first and second negative electrode active material particles was smaller than the range specified in the present application, limiting the improvement in the compaction degree of the negative electrode film layer. Therefore, the sodium-ion battery of Comparative Example 3 also had poor energy density and cycle life.

[0191] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea of ​​the technical solution of the present application and achieves similar effects is included within the technical scope of the present application. In addition, various modifications that a person skilled in the art can conceive of may be made to the embodiments within the scope that does not deviate from the spirit of the present application, and other forms constructed by combining some of the components of the embodiments are also included within the scope of the present application.

Claims

1. a negative electrode current collector; a negative electrode film layer located on at least one surface of the negative electrode current collector, the negative electrode film layer including first negative electrode active material particles and second negative electrode active material particles, the first negative electrode active material particles including a plurality of adsorption holes, and a tap density of the first negative electrode active material particles being 0.4 g / cm ３ ~1.4g / cm ３ and a negative electrode film layer, a difference d between the median diameters of the first negative electrode active material particles and the second negative electrode active material particles satisfies 3 μm≦d≦19 μm; the first negative electrode active material particles are one or more types selected from hard carbon, soft carbon, and mesocarbon microbeads, and the second negative electrode active material particles are one or more types selected from hard carbon, soft carbon, and mesocarbon microbeads; The compaction density PD of the negative electrode film layer is 0.8 g / cm ３ ≦PD≦1.4 g / cm 3 .

2. The median diameter D of the first negative electrode active material particles １ 50 is 4 μm to 50 μm, The median diameter D of the second negative electrode active material particles ２ 50 is 1 μm to 40 μm, the negative electrode sheet according to claim 1.

3. 2. The negative electrode sheet according to claim 1, wherein the mass percentage content of the first negative electrode active material particles is 5% to 95% relative to the total mass of the first negative electrode active material particles and the second negative electrode active material particles.

4. The coating weight CW of the negative electrode film layer on one side is 2 mg / cm ２ ~13 mg / cm ２ The negative electrode sheet according to claim 1 ,

5. The negative electrode sheet according to claim 1 , wherein the first negative electrode active material particles satisfy at least one of the following: (1) The pore diameter of the adsorption holes is 0.1 nm to 16 nm. (2) The specific surface area of ​​the first negative electrode active material particles is 1 m ３ / g to 40m ３ / g. (3) The spacing between the (002) planes of the first negative electrode active material particles is 0.34 nm to 0.45 nm. (4) The true density of the first negative electrode active material particles is 1.3 g / cm ３ ~2.0 g / cm ３ is.

6. 2. The negative electrode sheet according to claim 1, wherein the first negative electrode active material particles have an irregular shape and / or a microspherical shape, and the second negative electrode active material particles have an irregular shape and / or a microspherical shape.

7. 2. The negative electrode sheet according to claim 1, wherein the first negative electrode active material particles are selected from irregularly shaped hard carbon particles, and the second negative electrode active material particles are selected from microspherical hard carbon particles, and a mass percentage content of the first negative electrode active material particles is 70% to 95% relative to a total mass of the first negative electrode active material particles and the second negative electrode active material particles.

8. The first negative electrode active material particles are selected from microspherical hard carbon particles, and the median diameter D of the first negative electrode active material particles is １ 50 is 10 μm to 50 μm, The second negative electrode active material particles are selected from microspherical hard carbon particles, and the median diameter D of the second negative electrode active material particles is ２ 50 is 5 μm to 40 μm, 2. The negative electrode sheet according to claim 1, wherein the mass percentage content of the first negative electrode active material particles is 5% to 95% with respect to the total mass of the first negative electrode active material particles and the second negative electrode active material particles.

9. 9. The negative electrode sheet according to claim 7, wherein the negative electrode film layer further comprises a slip-increasing component, wherein a ratio of the mass of the slip-increasing component to the sum of the mass of the first negative electrode active material particles and the mass of the second negative electrode active material particles is 100:2 to 100:1, and the slip-increasing component comprises one or more of artificial graphite, natural graphite, and graphene.

10. 2. The negative electrode sheet according to claim 1, wherein the negative electrode film layer further comprises a flexible adhesive, the flexible adhesive comprising one or more of a styrene-acrylic emulsion, a copolymer of vinylidene fluoride and tetrafluoroethylene, a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and an acrylic ester, polytetrafluoroethylene, nitrile rubber, and hydrogenated nitrile rubber.

11. A secondary battery comprising the negative electrode sheet according to claim 1.

12. A battery module comprising the secondary battery according to claim 11.

13. A battery pack comprising the battery module according to claim 12.

14. A power consuming device comprising at least one selected from the group consisting of the secondary battery according to claim 11, the battery module according to claim 12, and the battery pack according to claim 13.

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