Negative electrode sheet, method for manufacturing the same, and battery

Abstract

The application relates to the technical field of batteries, in particular to a negative electrode sheet, a preparation method thereof and a battery. The negative electrode sheet comprises a current collector, a first negative electrode coating arranged on at least one side surface of the current collector in the thickness direction, and a second negative electrode coating arranged on the surface of the first negative electrode coating away from the current collector, wherein the second negative electrode coating comprises layered multi-metal oxides, the layered multi-metal oxides contain at least two metal elements, and the layered multi-metal oxides satisfy at least one of the following characteristics: the capacity of the layered multi-metal oxides is greater than or equal to 100 mAh / g; the specific surface area of the layered multi-metal oxides is greater than or equal to 100 m 2 / g; the layered multi-metal oxides have a porous structure; and the interlayer spacing of the layered multi-metal oxides is greater than or equal to 0.15 nm. The application can improve the ion diffusion rate of the negative electrode sheet, facilitate the rapid transmission of sodium ions on the surface of the negative electrode sheet, and further improve the cycle stability and fast-charging performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a negative electrode sheet, a preparation method thereof and a battery. BACKGROUND

[0002] With the increasing market demand, the development of lithium ion batteries will be restricted by lithium resources. Lithium accounts for only 0.0065% of the elements in the earth's crust, and the reserves of lithium resources are not abundant, and the geographical distribution is also uneven. It can be predicted that the application of lithium ion batteries will be severely limited by lithium resources in a few decades.

[0003] Sodium ion batteries are another type of energy storage batteries with similar working mechanism and battery structure to lithium ion batteries. Recently, sodium ion batteries have received more and more attention. The abundance of sodium resources is much higher than that of lithium elements, and the global distribution is uniform, the price is low and stable, and there is no development bottleneck. Because sodium is easy to obtain and low in price, and the negative electrode current collector of sodium battery can use aluminum foil, instead of copper foil as in lithium battery, sodium ion battery has great potential price advantage. The material cost of sodium ion battery has a 30%-40% reduction space compared with lithium ion battery. With the continuous in-depth research, the potential advantages of sodium ion battery are constantly explored, especially the excellent performance at high and low temperatures and the high safety, which lays a good foundation for the application of sodium ion battery in energy storage and power fields.

[0004] In related technologies, the negative electrode sheet of the sodium ion battery mostly includes a current collector and a negative active material layer (also can be called a negative coating) arranged on the current collector. However, the structure or composition of the existing negative electrode sheet still has more or less shortcomings, for example, the ion diffusion rate or the transmission speed of sodium ions in the negative electrode sheet needs to be improved, so that the cycle stability and fast charging performance of the battery using the negative electrode sheet need to be further improved.

[0005] Therefore, it is urgent to develop a new type of negative electrode sheet for sodium ion battery, so as to improve the cycle performance and fast charging performance of the sodium ion battery. SUMMARY

[0006] Therefore, the present application aims to at least partially solve one of the technical problems in the related art. To this end, the present application provides a negative electrode sheet, a preparation method thereof and a battery, which can improve the ion diffusion rate, facilitate the rapid transmission of sodium ions on the surface of the negative electrode sheet, and further improve the cycle stability and fast charging performance of the battery using the negative electrode sheet.

[0007] In order to solve the above technical problems, the present application is implemented as follows:

[0008] According to one aspect of the present application, the embodiments of the present application provide a negative electrode sheet, which comprises:

[0009] current collector;

[0010] a first negative electrode coating layer disposed on at least one side surface of the current collector in the thickness direction, the first negative electrode coating layer comprising a negative electrode active material; and

[0011] a second negative electrode coating layer disposed on a surface of the first negative electrode coating layer away from the current collector, the second negative electrode coating layer comprising a layered multi-metal oxide, the layered multi-metal oxide comprising at least two metal elements, and the layered multi-metal oxide satisfying at least one of the following characteristics:

[0012] (I) the capacity of the layered multi-metal oxide is ≥ 100 mAh / g;

[0013] (II) the specific surface area of the layered multi-metal oxide is ≥ 100 m 2 / g;

[0014] (III) the layered multi-metal oxide has a porous structure;

[0015] (IV) the interlayer distance of the layered multi-metal oxide is ≥ 0.15 nm.

[0016] In some embodiments, the capacity of the layered multi-metal oxide is 100-800 mAh / g, preferably 100-750 mAh / g.

[0017] In some embodiments, the specific surface area of the layered multi-metal oxide is 100-200 m 2 / g, preferably 120-170 m 2 / g.

[0018] In some embodiments, the pore size of the porous structure is in the range of 10-20 nm, preferably 14-16 nm.

[0019] In some embodiments, the interlayer distance of the layered multi-metal oxide is 0.2-1.0 nm, preferably 0.3-0.8 nm.

[0020] In some embodiments, the chemical formula of the layered multi-metal oxide is M1 2+ x M2 3+ y O z , wherein M1 and M2 are each selected from transition metal elements, 0.4≤x≤0.8, 0.2≤y≤0.4, and z=(2x+3y) / 2.

[0021] In some embodiments, M1 includes at least one of Ni, Zn, Mn, Mg, Cu, or Co, M2 includes at least one of Fe, Bi, Al, V, or Co, and M1 and M2 are not simultaneously selected from Co.

[0022] In some embodiments, the negative active material includes at least one of graphite, soft carbon, or hard carbon.

[0023] In some embodiments, the first negative electrode coating further includes a first binder and a first conductive agent.

[0024] In some embodiments, the first binder includes at least one of polyvinylidene fluoride, styrene butadiene rubber, sodium hydroxymethyl cellulose, polyacrylic acid, polyacrylate, polyvinyl alcohol, polytetrafluoroethylene, polyethylene oxide, carboxypropyl methyl cellulose, or hexafluoropropylene.

[0025] In some embodiments, the first conductive agent includes at least one of conductive carbon black, conductive graphite, carbon nanotube, graphene, or vapor grown carbon fiber.

[0026] In some embodiments, the mass ratio of the negative active material, the first conductive agent, and the first binder is (90-94):(1-6):(2-4).

[0027] In some embodiments, the second negative electrode coating further includes a second binder and a second conductive agent.

[0028] In some embodiments, the second binder includes at least one of polyvinylidene fluoride, styrene butadiene rubber, sodium hydroxymethyl cellulose, polyacrylic acid, polyacrylate, polyvinyl alcohol, polytetrafluoroethylene, polyethylene oxide, carboxypropyl methyl cellulose, or hexafluoropropylene.

[0029] In some embodiments, the second conductive agent includes at least one of conductive carbon black, conductive graphite, carbon nanotube, graphene, or vapor grown carbon fiber.

[0030] In some embodiments, the mass ratio of the layered multi-metal oxide, the second conductive agent, and the second binder is (90-94):(2-6):(2-4).

[0031] In some embodiments, the thickness of the second negative electrode coating is 2-6 μm.

[0032] In some embodiments, the thickness ratio of the second negative electrode coating to the first negative electrode coating is 1:(10-30).

[0033] According to another aspect of the present application, the embodiments of the present application provide a preparation method of a negative electrode sheet, comprising the following steps:

[0034] coating a first negative electrode slurry on at least one side surface of the current collector to obtain a first negative electrode coating layer;

[0035] coating a second negative electrode slurry on the surface of the first negative electrode coating layer to obtain a second negative electrode coating layer;

[0036] The first negative electrode coating layer comprises a negative electrode active material, and the second negative electrode coating layer comprises a layered multi-metal oxide.

[0037] In some embodiments, the preparation of the layered multi-metal oxide comprises: mixing M1 salt, M2 salt, water and urea, and after hydrothermal reaction, washing, drying, calcination and ball milling, the layered multi-metal oxide is obtained.

[0038] In some embodiments, the anions of the M1 salt and the M2 salt respectively comprise at least one of nitrate ions, sulfate ions, chloride ions or acetate ions.

[0039] In some embodiments, the M1 element of the M1 salt comprises at least one of Ni, Zn, Mn, Mg, Cu or Co, and the M2 element of the M2 salt comprises at least one of Fe, Bi, Al or V.

[0040] In some embodiments, the molar ratio of the M1 salt, the M2 salt and the urea is (5-7) : (0.5-1.5) : 10.

[0041] In some embodiments, the temperature of the hydrothermal reaction is 120-180°C, and the time of the hydrothermal reaction is 8-12h.

[0042] In some embodiments, the temperature of the calcination is 450-500°C, and the time of the calcination is 1-2h.

[0043] In some embodiments, the rotation speed of the ball milling is 50-70r / min, and the time of the ball milling is 12-24h.

[0044] In some embodiments, the preparation of the first negative electrode slurry comprises: uniformly mixing a negative electrode active material, a first conductive agent and a first binder in a solvent to obtain the first negative electrode slurry.

[0045] The preparation of the second negative electrode slurry comprises: uniformly mixing a layered multi-metal oxide, a second conductive agent and a second binder in a solvent to obtain the second negative electrode slurry.

[0046] In some embodiments, the first negative electrode slurry is coated on the surface of the current collector to form a first negative electrode coating after drying; and the second negative electrode slurry is coated on the first negative electrode coating to form a second negative electrode coating on the surface of the first negative electrode coating after drying, thereby obtaining the negative electrode sheet.

[0047] According to yet another aspect of the present application, the embodiments of the present application provide a battery comprising a positive electrode sheet and a negative electrode sheet, wherein the negative electrode sheet is the aforementioned negative electrode sheet or is prepared according to the aforementioned method.

[0048] In some embodiments, the positive electrode sheet comprises a positive electrode coating, and the positive electrode coating comprises a positive electrode active material, wherein the positive electrode active material comprises a Prussian blue type positive electrode material.

[0049] In some embodiments, the Prussian blue type positive electrode material has a chemical formula of Na x M3[M4(CN)6] y ·zH2O, 0 < x < 2, 0.8 < y < 1, 0 < z < 20, M3 and M4 are respectively selected from transition metal elements.

[0050] In some embodiments, the positive electrode coating further comprises a positive electrode conductive agent and a positive electrode binder, and the mass ratio of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder is (90-94):(1-6):(2-4).

[0051] The technical solutions of the present application have at least the following beneficial effects:

[0052] In the embodiments of the present application, the negative electrode sheet is provided with a first negative electrode coating and a second negative electrode coating on the surface of the current collector in sequence, wherein the layered multi-metal oxide in the second negative electrode coating has a certain capacity, which can improve the performance of the negative electrode sheet and increase the capacity of the negative electrode sheet. In addition, the specific surface area of the layered multi-metal oxide is large or has a porous structure, and the stability is high, which can increase the ion diffusion rate of the negative electrode sheet while ensuring its cycle stability, thereby improving the cycle performance of the battery using the negative electrode sheet. In addition, the layered multi-metal oxide in the second negative electrode coating has a layered structure and a large interlayer spacing, which is beneficial to the rapid transmission of sodium ions on the surface of the negative electrode sheet during charging, and is beneficial to improving the fast charging performance of the battery.

[0053] Furthermore, the capacity, ion diffusion rate, cycle stability or transmission speed of sodium ions of the negative electrode sheet is improved by the layered multi-metal oxide in the second negative electrode coating, so that the capacity, cycle stability and fast charging performance of the battery using the negative electrode sheet can be improved.

[0054] Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or can be learned by practice of the application. DETAILED DESCRIPTION

[0055] The application will be further described with reference to the following examples. It should be understood that these examples are intended to illustrate the application and are not intended to limit the scope of the application.

[0056] The endpoints of the ranges and any values described herein are not limited to the precise values stated. The ranges and endpoints thereof can be readily adjusted to include values approximating the value stated. For numerical ranges, the end points are included within the range. The ranges and endpoints thereof can be readily adjusted to include values approximating the value stated.

[0057] If not specifically explained, all the embodiments and optional embodiments of the application can be combined with each other to form new technical solutions. If not specifically explained, all the technical features and optional technical features of the application can be combined with each other to form new technical solutions.

[0058] If not specifically explained, all the steps of the application can be performed in sequence or randomly, preferably in sequence. If not specifically explained, the "includes" and "contains" mentioned in the application means open, and can also be closed. For example, the "includes" and "contains" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0059] As described in the background, the sodium ion battery in the related art has the characteristics of abundant resources, easy to obtain and low price of sodium, and large price advantage. However, the negative electrode sheet in the existing sodium ion battery still has certain deficiencies. In addition, in the sodium ion battery, the positive electrode material is a key component of the cost reduction of the sodium ion battery, and has attracted much attention in recent years. Among them, the Prussian blue type positive electrode material has the characteristics of low cost, easy to obtain, simple process, high safety, etc., and is favored by many researchers. However, the Prussian blue type sodium ion battery has the following problems: first, the coordinated water in the lattice of the Prussian blue type positive electrode material may be transferred into the electrolyte and electrochemically decomposed, which destroys the electrolyte, affects the electrochemical performance of the battery, and even causes safety hazards; second, in the use process of the Prussian blue type material sodium ion battery, the transition metal may be dissolved out, which affects the negative electrode SEI film and further affects the electrochemical performance of the battery; third, the Prussian blue type positive electrode material sodium ion battery has poor fast charging performance, which is not conducive to the popularization and application of such batteries. Therefore, effective technical means are needed to improve the above-mentioned problems of the sodium ion battery containing the Prussian blue type positive electrode material.

[0060] The inventors of the present application have found, through research, that by improving the structure or composition of the negative electrode sheet, not only can some problems existing in the negative electrode sheet itself be improved, but also the electrochemical performance of sodium ion batteries using Prussian blue-based positive electrode materials can be improved. Thus, the inventors of the present application have developed a suitable negative electrode sheet that not only can improve the capacity, ion diffusion rate and other properties of the negative electrode sheet, but also can be used to improve the long cycle performance and safety performance of sodium ion batteries using Prussian blue-based positive electrode materials, thereby laying a firmer foundation for the commercial application of sodium ion batteries. The present application will be described in detail below.

[0061] [Negative electrode sheet]

[0062] In some embodiments, the present application provides a negative electrode sheet, which comprises:

[0063] a current collector;

[0064] a first negative electrode coating layer disposed on at least one side surface of the current collector in the thickness direction, the first negative electrode coating layer comprising a negative electrode active material; and

[0065] a second negative electrode coating layer disposed on the surface of the first negative electrode coating layer away from the current collector, the second negative electrode coating layer comprising a layered multi-metal oxide, the layered multi-metal oxide comprising at least two metal elements.

[0066] The provided negative electrode sheet has a multi-layer structure, which comprises a current collector, a first negative electrode coating layer and a second negative electrode coating layer arranged in sequence, i.e., the first negative electrode coating layer is disposed on at least one side surface of the current collector, and the second negative electrode coating layer is disposed on the surface of the first negative electrode coating layer. The first negative electrode coating layer can be a conventional negative electrode coating layer (also referred to as a negative electrode active material layer), and the second negative electrode coating layer can be used as a multifunctional coating layer to improve the electrochemical performance of the negative electrode sheet.

[0067] The above "the first negative electrode coating layer is disposed on at least one side surface of the current collector in the thickness direction" means that the first negative electrode coating layer can be disposed on one surface of the current collector in the thickness direction of the current collector, or can be disposed on both surfaces of the current collector in the thickness direction of the current collector. The "surface" here can be the entire area of the current collector, or can be a partial area of the current collector. In the present embodiment, the surface can be a partial area of the current collector, and the remaining area of the current collector can be used to connect the tab. The present application does not have a particular limitation in this regard, as long as the purpose of the present application can be achieved.

[0068] As an example, the current collector has two surfaces opposite in the thickness direction of the current collector itself, and the first negative electrode coating is arranged on the two opposite surfaces of the current collector. Further, the second negative electrode coating is formed on the surface of the first negative electrode coating on both sides. It can be understood that, in other embodiments, the first negative electrode coating can also be arranged on any one of the two surfaces of the current collector.

[0069] In the present application, the material of the current collector in the negative electrode tab is not specifically limited.

[0070] In the present application, the second negative electrode coating in the negative electrode tab contains a layered multi-metal oxide, and the layered multi-metal oxide contains two or more metal elements. Compared with a single-metal oxide, the layered multi-metal oxide has a strong coupled electric field by the coordination of two or more metal elements, can accelerate the migration of electrons, speed up the electrochemical reaction kinetics, and thus help to improve the electrochemical performance of the negative electrode tab using the layered multi-metal oxide.

[0071] Further, the layered multi-metal oxide satisfies at least one of the following characteristics:

[0072] (I) The capacity of the layered multi-metal oxide is ≥100 mAh / g;

[0073] (II) The specific surface area of the layered multi-metal oxide is ≥100 m 2 / g;

[0074] (III) The layered multi-metal oxide has a porous structure;

[0075] (IV) The interlayer spacing of the layered multi-metal oxide is ≥0.15 nm.

[0076] Preferably, the layered multi-metal oxide satisfies all the above characteristics, that is, the layered multi-metal oxide satisfies four of the above characteristics.

[0077] In some embodiments, the capacity of the layered multi-metal oxide is ≥100 mAh / g; preferably, the capacity of the layered multi-metal oxide is 100-800 mAh / g; more preferably, the capacity of the layered multi-metal oxide is 100-750 mAh / g; for example, the capacity of the layered multi-metal oxide can be 100 mAh / g, 150 mAh / g, 170 mAh / g, 200 mAh / g, 300 mAh / g, 500 mAh / g, 700 mAh / g, 720 mAh / g, 750 mAh / g, 800 mAh / g, or more than 800 mAh / g, etc. By containing a layered multi-metal oxide with a certain capacity in the second negative electrode coating of the negative electrode tab, the performance of the negative electrode material in the negative electrode tab can be improved, and the capacity of the negative electrode tab can be improved.

[0078] In some embodiments, the specific surface area of the layered multi-metal oxide is ≥100 m 2 / g; preferably, the specific surface area of the layered multi-metal oxide is 100-200 m 2 / g; more preferably, the specific surface area of the layered multi-metal oxide is 120-170 m 2 / g; for example, the specific surface area of the layered multi-metal oxide can be 100 m 2 / g, 120 m 2 / g, 130 m 2 / g, 140 m 2 / g, 150 m 2 / g, 160 m 2 / g, 170 m 2 / g, 200 m 2 / g or more than 200 m 2 / g, etc. By including the layered multi-metal oxide with a larger specific surface area (such as no less than 100 m 2 / g or no less than 120 m 2 / g) in the second negative electrode coating of the negative electrode sheet, more active sites can be provided, which helps to improve the ion diffusion rate while ensuring the cycle stability of the battery.

[0079] In some embodiments, the layered multi-metal oxide has a porous structure. Preferably, the pore size of the porous structure is in the range of 10-20 nm; more preferably, the pore size of the porous structure is in the range of 14-16 nm. For example, the pore size of the porous structure can be any one of 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm or a range value between any two of them. By including the layered multi-metal oxide with a porous structure in the second negative electrode coating of the negative electrode sheet, and by making the pore size of the porous structure in the above suitable range, the suitable pore size facilitates the transmission of ions and electrons while having a relatively stable structure, which improves the electrochemical reaction kinetics, helps to improve the ion diffusion rate while ensuring the cycle stability of the battery.

[0080] Therefore, in the negative electrode sheet of the present application, by including the layered multi-metal oxide with a certain capacity, a large specific surface area, and a porous structure in the second negative electrode coating, the performance of the negative electrode material in the negative electrode sheet can be improved, the capacity of the negative electrode sheet can be improved, and the ion diffusion rate can be improved while ensuring the cycle stability of the battery due to the characteristics of the porous structure, the large specific surface area, and the high stability.

[0081] In some embodiments, the interlayer spacing of the layered multi-metal oxide is ≥ 0.15 nm; preferably, the interlayer spacing of the layered multi-metal oxide is 0.2 nm to 1.0 nm; more preferably, the interlayer spacing of the layered multi-metal oxide is 0.3 nm to 0.8 nm. For example, the interlayer spacing of the layered multi-metal oxide can be 0.15 nm, 0.2 nm, 0.3 nm, 0.4 nm, 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, etc. The provided layered multi-metal oxide has a layered structure and a relatively wide interlayer spacing (preferably 0.3-0.8 nm), and the radius of sodium ion is 0.102 nm, so that the sodium ion can be rapidly transported on the surface of the negative electrode during charging, thereby improving the fast-charging performance of the battery.

[0082] It should be noted that the present application does not limit the testing method of the specific surface area, interlayer spacing, pore size, etc. of the layered multi-metal oxide, which can be tested by any method known in the art. For example, the specific surface area and pore size of the layered multi-metal oxide can be tested by a porosimetry (specific surface area and porosity analyzer); the interlayer spacing of the layered multi-metal oxide can be tested by an X-ray diffractometer.

[0083] In some preferred embodiments, the provided negative electrode sheet is applied in a sodium ion battery, and a Prussian blue-based positive electrode material is used as the positive active material in the sodium ion battery. Further, the negative electrode sheet of the present application not only can utilize the characteristics of the layered multi-metal oxide, such as a certain capacity, a porous structure, a large specific surface area, a wide interlayer spacing, and high stability, to improve the performance of the negative electrode material, increase the capacity, improve the ion diffusion rate while ensuring the cycle stability of the battery, increase the transport speed of sodium ions on the surface of the negative electrode sheet, and improve the fast-charging performance of the battery; but also can utilize the layered multi-metal oxide to absorb free water in the Prussian blue-based positive electrode material, and the layered multi-metal oxide becomes a layered multi-metal hydroxide after absorbing water, which has a certain flame retardancy and can be used to improve the safety and cycle life of the positive electrode material. At the same time, the layered multi-metal oxide and the layered multi-metal hydroxide formed after absorbing water have a strong adsorption effect on metal ions, which can be used to solve the problem of thickening of the negative electrode SEI film caused by the dissolution of transition metal, ensure the performance of the battery, and further improve the safety and service life of the battery. Further, the provided negative electrode sheet can effectively improve the above-mentioned problems (such as safety problems, transition metal dissolution problems, and poor fast-charging performance) of the sodium ion battery containing the Prussian blue-based positive electrode material by the arrangement of the layered multi-metal oxide in the second negative electrode coating.

[0084] In some embodiments, the chemical formula of the layered multi-metal oxide is M1 2+x M2 3+ y O z M1 and M2 are each selected from transition metal elements, wherein 0.4≤x≤0.8, 0.2≤y≤0.4, and z=(2x+3y) / 2. Optionally, x+y=1. It is worth noting that x, y, and z need to satisfy the charge balance.

[0085] The layered multi-metal oxide contains M1 metal elements and M2 metal elements, and M1 and M2 can each be selected from transition metal elements, and M1 is selected from transition metal elements with a positive valence of two, and M2 is selected from transition metal elements with a positive valence of three. In this application, the chemical formula of the layered multi-metal oxide can be denoted as M1M2-LDO.

[0086] It should be further pointed out that in M1M2-LDO, the value ranges of x, y, and z can satisfy the above ranges, and the specific values of x, y, and z can be selected and set according to actual application conditions, as long as the above ranges are satisfied, which is not limited in this application.

[0087] In some embodiments, M1 includes but is not limited to at least one of Ni, Zn, Mn, Mg, Cu, or Co, M2 includes but is not limited to at least one of Fe, Bi, Al, V, or Co, and M1 and M2 are not simultaneously selected from Co. That is, in this application, the layered multi-metal oxide can be selected from metal oxides formed by at least two of Ni, Zn, Mn, Fe, Mg, Cu, Co, Bi, Al, and V. The layered multi-metal oxide has a stronger coupled electric field than single metal oxides, which can accelerate the migration of electrons and speed up the electrochemical reaction kinetics.

[0088] Preferably, M1 is selected from at least one of Ni, Zn, Mn, or Co; more preferably, M1 is selected from at least one of Ni or Co. Preferably, M2 is selected from at least one of Fe, Al, or Co; more preferably, M2 is selected from at least one of Fe or Co. Exemplarily, the layered multi-metal oxide can be NiFe-LDO, NiCo-LDO, CoFe-LDO, or NiCoFe-LDO.

[0089] By using the layered multi-metal oxides formed by the above-mentioned transition metal elements such as Ni, Co, and Fe, the atomic radii of the metal elements are similar, the products are easy to prepare and the morphology is easy to control, and the synergistic effect between the metals is strong, which is beneficial to the transmission of electrons and ions.

[0090] In some embodiments, the first negative electrode coating further includes a first binder and a first conductive agent, that is, the first negative electrode coating includes a negative electrode active material, a first binder, and a first conductive agent.

[0091] In some embodiments, the second negative electrode coating further comprises a second binder and a second conductive agent, i.e., the second negative electrode coating comprises the layered multi-metal oxide, the second binder and the second conductive agent. The second binder in the second negative electrode coating serves to bind the layered multi-metal oxide and the second conductive agent together, while binding the first negative electrode coating and the second negative electrode coating.

[0092] It should be noted that the specific type of the negative active material in the negative electrode tab is not limited, and can be set according to conventional selection in the art.

[0093] As an example, in some embodiments, the negative active material comprises, but is not limited to, at least one of graphite, soft carbon or hard carbon. The graphite can be artificial graphite, natural graphite, modified graphite, etc.

[0094] In the present application, the negative active material can be a negative electrode material known in the prior art. For example, the negative active material can be graphite, can be soft carbon, can be hard carbon, can be a combination of graphite and soft carbon, can be a combination of graphite and hard carbon, or can be a combination of soft carbon and hard carbon, etc.

[0095] It should be noted that the structure and material selection of the negative electrode tab that are not specifically described are not limited, and can be set according to conventional selection in the art.

[0096] As an example, in some embodiments, the first conductive agent comprises, but is not limited to, at least one of conductive carbon black (Super P), graphene, conductive graphite, conductive carbon tube or conductive carbon fiber.

[0097] In some embodiments, the second conductive agent comprises, but is not limited to, at least one of conductive carbon black (Super P), graphene, conductive graphite, conductive carbon tube or conductive carbon fiber.

[0098] The conductive carbon black includes acetylene black, Ketjen black, etc. The conductive carbon tube includes carbon nanotube, carbon micrometer tube, etc. The conductive carbon fiber includes vapor phase growth carbon fiber.

[0099] In the present application, the first conductive agent and the second conductive agent can be of the same type or of different types, and are not limited in this regard.

[0100] In addition, in other embodiments, any conductive agent known in the art that can be applied in the negative electrode tab can also be used, which will not be listed one by one here.

[0101] Preferably, the first conductive agent and the second conductive agent are acetylene black or Ketjen black, which have small density and large specific surface area, have high adhesion to the negative electrode material with large specific surface area, and are beneficial to the performance of the porous material.

[0102] In some embodiments, the first binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylate (LA), polyvinyl alcohol, polytetrafluoroethylene, polyethylene oxide, carboxypropyl methyl cellulose, or hexafluoropropylene.

[0103] In some embodiments, the second binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylate (LA), polyvinyl alcohol, polytetrafluoroethylene, polyethylene oxide, carboxypropyl methyl cellulose, or hexafluoropropylene.

[0104] In the present application, the first binder and the second binder can be of the same type or of different types, and no limitation is made in this regard.

[0105] Preferably, the first binder and the second binder are selected from one or more of PVDF, SBR, CMC, PAA, and LA; more preferably, the first binder and the second binder are selected from one or more of CMC and PAA. CMC and PAA not only contain hydroxyl functional groups (-OH), but also contain carboxyl functional groups, which are conducive to improving the flowability of the porous material slurry with a large specific surface area.

[0106] In some embodiments, in the first negative electrode coating, the mass ratio of the negative electrode active material, the first conductive agent, and the first binder is (90-94):(1-6):(2-4), such as 90:6:4, 92:5:3, 93:4:4, 94:3:3, etc.

[0107] In some embodiments, in the second negative electrode coating, the mass ratio of the layered multi-metal oxide, the second conductive agent, and the second binder is (90-94):(2-6):(2-4), such as 90:6:4, 92:5:3, 93:4:4, 94:3:3, etc.

[0108] Preferably, the mass ratio of the layered multi-metal oxide and the second conductive agent is (90-94):(3-4).

[0109] Preferably, the mass ratio of the layered multi-metal oxide and the second binder is (90-94):(3-3.5).

[0110] It can be understood that the mass ratio of the negative active material, the first conductive agent and the first binder, and the mass ratio of the layered multi-metal oxide, the second conductive agent and the second binder are related to the electrical performance of the corresponding battery. By controlling the proportion of each substance in the first negative electrode coating and the second negative electrode coating within the above range, the negative active material and the layered multi-metal oxide can be fully utilized to effectively improve the cycle performance and fast charging performance of the negative electrode sheet.

[0111] In addition, in the present application, if the content of the layered multi-metal oxide in the second negative electrode coating is too small, such as less than 90% by mass, the performance of the negative electrode material cannot be effectively improved, the ion diffusion rate cannot be effectively improved, the cycle stability cannot be ensured, and the fast charging performance cannot be effectively improved. If the content of the layered multi-metal oxide in the second negative electrode coating is too large, such as greater than 94% by mass, the amount of the binder and other substances will be reduced, which will affect the adhesion effect and other properties of the first negative electrode coating and the second negative electrode coating.

[0112] In some embodiments, the thickness of the single-sided second negative electrode coating on the current collector is 2 μm to 6 μm. For example, the thickness of the second negative electrode coating can be any one of 2 μm, 3 μm, 4 μm, 5 μm, 6 μm or a range value between any two of them. If the thickness of the second negative electrode coating is too thin, such as less than 2 μm, the performance of the negative electrode material cannot be effectively improved, the ion diffusion rate cannot be effectively improved, the cycle stability cannot be ensured, and the fast charging performance cannot be effectively improved. If the thickness of the second negative electrode coating is too thick, such as greater than 6 μm, the electrochemical reaction will be affected and the impedance will be increased.

[0113] In some embodiments, the thickness ratio of the second negative electrode coating to the first negative electrode coating is 1:(10-30). For example, the thickness ratio of the second negative electrode coating to the first negative electrode coating can be 1:10, 1:15, 1:20, 1:25, 1:30, etc.

[0114] In the present application, since the layered multi-metal oxide has the characteristics of porosity and large specific surface area, if the thickness of the second negative electrode coating containing the layered multi-metal oxide is too thick, the electron transport distance will be increased, the electron resistance will be increased, the rate performance will be reduced, and the performance of the negative active material such as hard carbon will be affected. If the thickness of the second negative electrode coating containing the layered multi-metal oxide is too thin, the performance improvement of the full battery will not be obvious, the overall electrical performance and safety performance of the battery will not be further guaranteed and optimized, and the long cycle of the battery will be affected.

[0115] [Method for preparing negative electrode sheet]

[0116] In some embodiments, the present application provides a method for preparing a negative electrode sheet, which comprises the following steps:

[0117] coating a first negative electrode slurry on at least one side surface of the current collector to obtain a first negative electrode coating layer;

[0118] coating a second negative electrode slurry on the surface of the first negative electrode coating layer to obtain a second negative electrode coating layer;

[0119] The first negative electrode coating layer comprises a negative electrode active material, and the second negative electrode coating layer comprises a layered multi-metal oxide.

[0120] It should be understood that all the features and advantages described above for the "negative electrode sheet" also apply to the "method for manufacturing the negative electrode sheet", which will not be repeated here.

[0121] In the manufacturing process of the negative electrode sheet of the present application, the layered multi-metal oxide is first prepared, then the second negative electrode slurry containing the layered multi-metal oxide is prepared, the first negative electrode slurry containing the negative electrode active material is prepared, and then the first negative electrode coating layer and the second negative electrode coating layer are respectively formed by coating, drying, etc., to obtain the negative electrode sheet.

[0122] For example, in some embodiments, the preparation of the layered multi-metal oxide comprises: mixing M1 salt, M2 salt, water and urea, and after hydrothermal reaction, washing, drying, calcination and ball milling, the layered multi-metal oxide is obtained.

[0123] In the preparation process of the layered multi-metal oxide, the hydrothermal reaction is first carried out. During the hydrothermal reaction, the mixture of M1 salt, M2 salt, water and urea can react to generate a layered multi-metal hydroxide. Further, after the hydrothermal reaction, the obtained material can be washed to remove impurities, and after drying, the generated layered multi-metal hydroxide is calcined to prepare a layered multi-metal oxide powder. Then, the obtained layered multi-metal oxide powder is ball milled to obtain a layered multi-metal oxide of a target size (such as nanoscale).

[0124] In the present application, the size of the layered multi-metal oxide is nanoscale, so that the active sites are more and the reaction kinetics is faster. The specific size of the layered multi-metal oxide is not limited and can be selected according to actual needs, as long as it is nanoscale. Generally, since the layered multi-metal oxide is generally a micrometer-sized flaky material, the volume expansion is large during long cycle, which affects the life, therefore, in the preparation of the second negative electrode coating layer, the micrometer-sized layered multi-metal oxide is prepared into nanoscale material by means of high-energy ball milling, which can effectively reduce the influence of volume expansion.

[0125] In some embodiments, in the raw materials for preparing the layered multi-metal oxide, the anions of the M1 salt and the M2 salt each comprise at least one of nitrate ions, sulfate ions, chloride ions or acetate ions.

[0126] In some embodiments, the M1 element of the M1 salt comprises at least one of Ni, Zn, Mn, Mg, Cu or Co, and the M2 element of the M2 salt comprises at least one of Fe, Bi, Al, V or Co.

[0127] In some embodiments, the molar ratio of the M1 salt, the M2 salt and the urea is (5-7):(0.5-1.5):10. Preferably, the molar ratio of the M1 salt, the M2 salt and the urea is (5-7):(0.9-1.2):10. For example, the molar ratio of the M1 salt, the M2 salt and the urea is 5:1:10, 6:1:10, 7:1:10, 7:1.1:10, etc.

[0128] It should be understood that, in the preparation of the layered multi-metal oxide, the amount of the M1 salt and the M2 salt added as raw materials can be slightly different from the ratio of M1 and M2 in the final layered multi-metal oxide, because it is necessary to slightly over-amount the raw materials added in order to improve the reaction efficiency or yield, and after the reaction, the excess M1 salt or M2 salt can be removed by washing, etc., so as to obtain a layered multi-metal oxide containing M1 and M2 in the target ratio.

[0129] In some embodiments, the mass ratio of the M1 salt and water is (0.8-1.2):20. For example, the mass ratio of the M1 salt and water is 0.8:20, 0.9:20, 1:20, 1.2:20, etc.

[0130] In some embodiments, the temperature of the hydrothermal reaction is 120-180°C, and the time of the hydrothermal reaction is 8-12h. As an example, the temperature of the hydrothermal reaction can be 120°C, 130°C, 140°C, 150°C, 160°C, 180°C, etc., and of course can also be other values within the above range, which are not limited herein; the time of the hydrothermal reaction can be 8h, 9h, 10h, 11h, 12h, etc., and of course can also be other values within the above range, which are not limited herein. By controlling the temperature and time of the hydrothermal reaction within the above suitable ranges, a layered multi-metal hydroxide with good performance can be prepared.

[0131] The specific operation mode of the washing and drying steps performed after the hydrothermal reaction can be performed in a conventional manner, for example, using water, alcohol or other solvents for washing, and then drying at 50-100°C for 10-48h.

[0132] In some embodiments, the calcination temperature is 450-500℃, and the calcination time is 1-2h. For example, the calcination temperature can be 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, or other values within the above range. The calcination time can be 1h, 1.5h, 2h, or other values within the above range. The layered multi-metal oxide can be prepared by calcining the layered multi-metal hydroxide. If the calcination temperature is too high (e.g., greater than 500℃), the layered multi-metal oxide structure collapses and cannot be restored. If the calcination temperature is too low (e.g., less than 450℃), the layered multi-metal oxide cannot be formed.

[0133] In some embodiments, the ball milling speed is 50-70r / min, and the ball milling time is 12-24h. For example, the ball milling speed can be 50r / min, 60r / min, 70r / min, or other values within the above range. The ball milling time can be 12h, 16h, 18h, 20h, 22h, 24h, or other values within the above range. The appropriate nano-sized layered multi-metal oxide can be prepared by controlling the ball milling speed and time, which has more active sites and faster reaction kinetics.

[0134] In the present application, the layered multi-metal oxide is obtained by calcining the layered multi-metal hydroxide, has a large specific surface area and a porous structure. Preferably, the specific surface area of the layered multi-metal oxide is 120-170m 2 / g, and the pore size of the porous structure is 10-20nm. More preferably, the ball milling speed is 55-65r / min, and the ball milling time is 16-20h. In this way, the layered multi-metal oxide has a large specific surface area and a suitable pore size after ball milling while retaining the original layered structure. Preferably, the specific surface area of the layered multi-metal oxide is 140-170m 2 / g, and the pore size of the porous structure is 14-16nm. Therefore, the large specific surface area can provide more active sites, and the suitable pore size facilitates the transmission of ions and electrons while maintaining a stable structure, thereby improving the electrochemical reaction kinetics.

[0135] In the present application, the layered multi-metal oxide is preferably NiFe-LDO, NiCo-LDO, CoFe-LDO, or NiCoFe-LDO. The atomic radii of the metal elements in these layered multi-metal oxides are similar, the products are easy to prepare and the morphology is easy to control. In addition, the synergistic effect between the metals is strong, which is beneficial to the transmission of electrons and ions.

[0136] As an example, the preparation of the layered multi-metal oxide specifically includes: mixing M1 salt, M2 salt, water and urea, for example, mixing at least two of Ni, Zn, Mn, Fe, Mg, Cu, Co, Bi, Al, V salts (nitrate, sulfate, chloride, acetate) with urea, and performing a hydrothermal reaction at a temperature of 120-180 DEG C for 8-12 hours to prepare a layered multi-metal hydroxide; then, placing the layered multi-metal hydroxide in a ceramic boat and placing it in a tube furnace, and performing calcination at a temperature of 450-500 DEG C for 1-2 hours to prepare a layered multi-metal oxide powder; and then, adding the prepared powder into a planetary ball mill, setting the rotation speed of the ball mill to 50-70 r / min, and performing ball milling for 12-24 hours to prepare a nano-sized layered multi-metal oxide.

[0137] In some embodiments, the preparation of the negative electrode tab specifically includes:

[0138] S1, first preparing a first negative electrode slurry and a second negative electrode slurry;

[0139] S2, uniformly coating the first negative electrode slurry on the surface of the current collector, and after drying, forming a first negative electrode coating layer on the surface of the current collector; wherein, optionally, the coating thickness of the first negative electrode coating layer is 40-60 pm;

[0140] S3, coating the second negative electrode slurry on the first negative electrode coating layer, and after drying, forming a second negative electrode coating layer on the surface of the first negative electrode coating layer to obtain a negative electrode tab. Wherein, optionally, the ratio of the coating thickness of the second negative electrode coating layer to the coating thickness of the first negative electrode coating layer is 1:(10-30). By controlling the ratio of the coating thickness of the second negative electrode coating layer to the coating thickness of the first negative electrode coating layer within the above range, the electrochemical performance of the battery can be ensured, because the layered multi-metal oxide has the characteristics of porosity and large specific surface area. If the thickness of the second negative electrode coating layer is too thick, the electron transport distance increases, the electron resistance increases, the rate performance decreases, and the performance of the negative electrode active material such as hard carbon is affected. If the thickness of the second negative electrode coating layer is too thin, the performance improvement of the full battery is not obvious.

[0141] Optionally, in step S1, the preparation of the first negative electrode slurry includes: uniformly mixing the negative electrode active material, the first conductive agent and the first binder in a solvent to obtain the first negative electrode slurry.

[0142] Optionally, in step S1, the preparation of the second negative electrode slurry includes: uniformly mixing the layered multi-metal oxide, the second conductive agent and the second binder in a solvent to obtain the second negative electrode slurry.

[0143] The components and contents of the negative active material, the first conductive agent, the first binder, the second conductive agent, the second binder, and the like described herein refer to those of the first aspect, and will not be repeated here.

[0144] The solvent in the first negative electrode slurry and the second negative electrode slurry can be a solvent commonly used in the art for preparing a negative electrode slurry, such as water, an organic solvent, and the like, without limitation.

[0145] Optionally, in steps S2 and S3, the drying temperature is 100-150°C, and the drying time is 0.5-12 h. In steps S2 and S3, the purpose of drying is to remove the moisture in the negative electrode sheet.

[0146] [Battery]

[0147] In some embodiments, a battery is provided, which includes the negative electrode sheet described above.

[0148] The battery can exhibit good electrochemical performance, such as a high initial discharge specific capacity, good cycle stability, and good fast-charging performance, due to the inclusion of the negative electrode sheet provided in the embodiments.

[0149] In the present application, the battery can be a sodium-ion battery. The battery can be, for example, a wound or stacked battery, and can be, for example, a prismatic (aluminum can, steel can, etc.) battery, a pouch battery, or a cylindrical battery, without limitation. The battery has a high capacity, good cycle performance, a long service life, and good fast-charging performance.

[0150] In some embodiments, the battery described above further includes a positive electrode sheet, an electrolyte, and a separator. That is, the battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator.

[0151] In some embodiments, the positive electrode sheet includes a positive electrode coating layer, and the positive electrode coating layer includes a positive electrode active material, and the positive electrode active material includes a Prussian blue-based positive electrode material.

[0152] By way of example, the positive electrode sheet includes a positive electrode current collector and a positive electrode coating layer disposed on at least one surface of the positive electrode current collector, and the positive electrode coating layer includes a positive electrode active material, and the positive electrode active material includes a Prussian blue-based positive electrode material. By way of example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode coating layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0153] In the present embodiments, the materials, structures, and the like of the positive electrode current collector, the conductive agent, the binder, and the like in the positive electrode active material layer in the positive electrode sheet are not limited, and can be selected from the positive electrode sheet structures and components commonly used in the art for secondary batteries.

[0154] In particular, the positive active material in the positive electrode tab of the embodiments of the present application can include a Prussian blue type positive electrode material. By using the negative electrode tab provided by the present application, in combination with a sodium ion battery including a Prussian blue type positive electrode material, the free water in the Prussian blue type positive electrode material can be absorbed by the layered multi-metal oxide in the negative electrode tab, and the layered multi-metal oxide becomes layered multi-metal hydroxide after absorbing water. The layered multi-metal hydroxide has a certain flame retardancy, which can be used to improve the safety and cycle life of the positive electrode material. At the same time, the layered multi-metal oxide and the layered multi-metal hydroxide formed after absorbing water have a strong adsorption effect on metal ions, which can be used to solve the phenomenon of thickening of the negative electrode SEI film caused by the dissolution of transition metals, ensure the performance of the electric performance, and further improve the safety and service life of the battery. Further, the above-mentioned problems (such as safety problems, transition metal dissolution problems, poor fast charging performance, etc.) existing in the sodium ion battery containing the Prussian blue type positive electrode material can be effectively improved.

[0155] In some embodiments, the chemical formula of the Prussian blue type positive electrode material is Na x M3[M4(CN)6] y ·zH2O, 0 < x ≤ 2, 0.8 ≤ y ≤ 1, 0 < z ≤ 20, M3 and M4 are respectively selected from transition metal elements.

[0156] Optionally, M3 and M4 can be selected from one or more of Fe, Mn, Cu, Ni, Co, Zn or Cr.

[0157] In some embodiments, the positive electrode coating further includes a positive electrode conductive agent and a positive electrode binder, that is, the positive electrode coating includes the positive active material, the positive electrode conductive agent and the positive electrode binder. In the positive electrode coating, the specific types of the positive electrode conductive agent and the positive electrode binder are not limited and can be set according to the conventional selection in the art. As an example, the positive electrode conductive agent includes, but is not limited to, at least one of conductive carbon black, graphene, conductive graphite, conductive carbon tube or conductive carbon fiber. The conductive carbon black includes acetylene black, Ketjen black, etc. The conductive carbon tube includes carbon nanotube, carbon micrometer tube, etc. The conductive carbon fiber includes vapor phase growth carbon fiber. The positive electrode binder includes, but is not limited to, one or more of polyvinylidene fluoride, butadiene rubber, sodium hydroxymethyl cellulose, polyacrylic acid, polyacrylate, polyvinyl alcohol, polytetrafluoroethylene, polyethylene oxide, carboxypropyl methyl cellulose or hexafluoropropylene.

[0158] Optionally, the mass ratio of the positive active material, the positive electrode conductive agent and the positive electrode binder is (90-94):(1-6):(2-4), such as 90:6:4, 92:5:3, 93:4:4, 94:3:3, etc.

[0159] Optionally, the preparation of the positive electrode sheet comprises: first preparing the positive electrode slurry, then uniformly coating the positive electrode slurry on the positive electrode current collector, and after drying, forming a positive electrode coating on the surface of the positive electrode current collector to obtain the positive electrode sheet. For example, after the preparation of the positive electrode slurry, the coating machine parameters are set so that the coating thickness is 50 μm to 60 μm (such as 55 μm), the positive electrode slurry is uniformly coated on the positive electrode current collector aluminum foil, and after the coating is completed, the electrode sheet is dried at 110°C for 0.5 h to obtain the positive electrode sheet.

[0160] Optionally, the preparation of the positive electrode slurry comprises: uniformly mixing the positive electrode active material, the positive electrode conductive agent and the positive electrode binder in the solvent to obtain the positive electrode slurry.

[0161] Optionally, in the preparation process of the positive electrode sheet, the drying temperature is 100°C to 150°C, and the drying time is 0.5 h to 12 h. The purpose of drying is to remove the moisture in the positive electrode sheet.

[0162] In some embodiments, in the battery, the separator comprises, but is not limited to, a polypropylene separator (PP), a polyethylene separator (PE), and a multi-layer composite separator (PP / PE / PP). Preferably, the separator is a PE separator, so that the layered multi-metal oxide becomes a layered multi-metal hydroxide after absorbing water, the layered multi-metal hydroxide is alkaline, the PE separator has good chemical stability and can resist alkaline corrosion, and the high temperature resistance of the layered multi-metal hydroxide also compensates for the poor heat resistance of the PE separator.

[0163] It should be further pointed out that the battery of the present application does not limit the specific material or type of electrolyte, and components and types that can be used for secondary batteries known in the art can be selected as long as the purpose of the present application can be achieved.

[0164] Since the battery and the electronic device provided by the embodiments of the present application adopt all the technical solutions of the above-mentioned embodiments, they at least have all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described here.

[0165] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application and cannot be understood as a limitation of the present application. If the specific technology or condition is not specified in the embodiments, it is carried out according to the technology or condition described in the literature in the art or according to the product instruction. If the reagent, material or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained by purchase.

[0166] Example 1

[0167] 1. Preparation of the negative electrode sheet, comprising the following steps:

[0168] S1, respectively take hard carbon material, SP and PVDF according to the mass ratio of 90:6:4, add N-methyl pyrrolidone (NMP) according to the mass ratio of 1:2.2 of hard carbon material and N-methyl pyrrolidone (NMP), high-speed dispersion, mix evenly to prepare the first negative electrode slurry.

[0169] According to the mass ratio of 93:4:3, respectively take layered multi-metal oxide (NiFe-LDO), acetylene black and CMC, add N-methyl pyrrolidone (NMP) according to the mass ratio of 1:2 of NiFe-LDO and N-methyl pyrrolidone (NMP), high-speed dispersion, mix evenly to prepare the second negative electrode slurry.

[0170] S2, set the coating machine parameters, the coating thickness is 40μm, the first negative electrode slurry is uniformly coated on the surface of the current collector aluminum foil, the electrode piece after coating is dried at 110℃ for 0.5h, and the first negative electrode coating is formed on the surface of the current collector to obtain the electrode piece A.

[0171] S3, the second negative electrode slurry is coated on the first negative electrode coating of the electrode piece A, the coating thickness of the second negative electrode coating is 2μm, the coated electrode piece is dried at 110℃ for 12h, the second negative electrode coating is formed on the surface of the first negative electrode coating, and the negative electrode piece is obtained.

[0172] In the above step S1, the preparation of layered multi-metal oxide (NiFe-LDO) includes: taking nickel nitrate, iron nitrate and urea according to the molar ratio of 5:1:10, the mass ratio of nickel salt to distilled water is 1:20, mixing nickel nitrate, iron nitrate, urea and distilled water, stirring for 30min, then pouring into the reaction kettle, putting the hydrothermal kettle into the oven, hydrothermal reaction at 150℃, hydrothermal reaction time is 10h, preparing layered multi-metal hydroxide, collecting the sample with high-speed centrifuge, then washing the sample with water and ethanol for three times to remove excess impurities, then drying in the constant temperature 60℃ drying box for 24h to obtain powder sample; then, put it into the ceramic boat and put it into the tube furnace, calcine at 450℃, calcine time is 2h, prepare layered NiFe-LDO powder, then put the prepared powder into the planetary ball mill, set the rotation speed of the ball mill to 60r / min, ball mill for 18h, prepare nano-sized layered multi-metal oxide, namely NiFe-LDO.

[0173] The capacity of the NiFe-LDO is about 728mAh / g; the specific surface area is 165m 2 / g; the pore size of the porous structure is 15nm; the interlayer spacing is 0.45nm.

[0174] 2, the preparation of positive electrode piece, including the following steps:

[0175] Prussian blue type positive electrode material Na 1.73 Fe[Fe(CN)6]·3.8H2O, SP and PVDF, according to the mass ratio of 90:6:4, respectively, Prussian blue type positive electrode material Na 1.73 Fe[Fe(CN)6]·3.8H2O and NMP were added in an amount of 1:2.2 of NMP, and high-speed dispersion was carried out, and the positive electrode slurry was prepared after mixing uniformly;

[0176] The coating machine parameters were set so that the coating thickness was 35 μm, and the positive electrode slurry was uniformly coated on the positive electrode current collector aluminum foil. After the coating was completed, the pole piece was dried at 110°C for 0.5h by blowing, and the positive electrode pole piece was prepared.

[0177] Example 2

[0178] This embodiment is mainly used to illustrate the preparation of the negative electrode pole piece by using different layered multi-metal oxides.

[0179] Example 2-1

[0180] According to the method described in Example 1, the difference is that:

[0181] The preparation of the layered multi-metal oxide (NiCo-LDO) includes: nickel nitrate, cobalt nitrate and urea are weighed according to the molar ratio of 6:1:10, the mass ratio of nickel salt to distilled water is 1:20, nickel nitrate, cobalt nitrate, urea and distilled water are mixed and stirred for 30 min, then poured into a reaction kettle, the hydrothermal kettle is put into an oven, and the hydrothermal reaction is carried out at a temperature of 160°C, the hydrothermal reaction time is 10h, the layered multi-metal hydroxide is prepared, the sample is collected by high-speed centrifuge, and then the sample is washed with water and ethanol for three times to remove excess impurities, and then dried in a constant temperature 60°C drying box for 24h to obtain a powder sample; then, it is placed in a ceramic boat and put into a tube furnace, and calcined at a temperature of 450°C, the calcination time is 2h, the layered NiCo-LDO powder is prepared, and the prepared powder is added into a planetary ball mill, the rotation speed of the ball mill is set to 64r / min, and the ball milling time is 18h, and the nano-sized layered multi-metal oxide (NiCo-LDO) is prepared.

[0182] The capacity of the NiCo-LDO is about 720mAh / g; the specific surface area is 149m 2 / g; the pore size of the porous structure is 16nm; and the interlayer spacing is 0.43nm.

[0183] The rest is the same as Example 1.

[0184] Example 2-2

[0185] According to the method described in Example 1, the difference is that:

[0186] The preparation of the layered multi-metal oxide (NiCoFe-LDO) comprises: taking nickel nitrate, cobalt nitrate, iron nitrate and urea according to a molar ratio of 7:1:1:10, and a mass ratio of the nickel salt to distilled water being 1:20; mixing the nickel nitrate, cobalt nitrate, iron nitrate, urea and distilled water, stirring for 30 min, then pouring into a reaction kettle; placing the hydrothermal kettle into an oven, and performing a hydrothermal reaction at a temperature of 160°C for 11 h; collecting the sample by using a high-speed centrifuge, then washing the sample with water and ethanol three times to remove excess impurities, and then drying in a constant-temperature drying box at 60°C for 24 h to obtain a powder sample; then, placing the sample into a ceramic boat and placing it into a tube furnace, and performing calcination at a temperature of 450°C for 1.5 h to prepare a layered NiCoFe-LDO powder; and finally, adding the prepared powder into a planetary ball mill, setting the rotation speed of the ball mill to 62 r / min, and ball milling for 19 h to prepare a nano-sized layered multi-metal oxide, namely, NiCoFe-LDO.

[0187] The capacity of the NiCoFe-LDO is about 718 mAh / g; the specific surface area is 158 m 2 / g; the pore size of the porous structure is 14 nm; and the interlayer spacing is 0.41 nm.

[0188] The rest is the same as in Example 1.

[0189] Example 2-3

[0190] The operation is performed according to the method described in Example 1, except that:

[0191] The preparation of the layered multi-metal oxide (NiCoFe-LDO) comprises: taking nickel nitrate, cobalt nitrate, iron nitrate and urea according to a molar ratio of 7:1:1:10, and a mass ratio of the nickel salt to distilled water being 1:20; mixing the nickel nitrate, cobalt nitrate, iron nitrate, urea and distilled water, stirring for 30 min, then pouring into a reaction kettle; placing the hydrothermal kettle into an oven, and performing a hydrothermal reaction at a temperature of 160°C for 11 h; collecting the sample by using a high-speed centrifuge, then washing the sample with water and ethanol three times to remove excess impurities, and then drying in a constant-temperature drying box at 60°C for 24 h to obtain a powder sample; then, placing the sample into a ceramic boat and placing it into a tube furnace, and performing calcination at a temperature of 450°C for 1.5 h to prepare a layered NiCoFe-LDO powder; and finally, adding the prepared powder into a planetary ball mill, setting the rotation speed of the ball mill to 62 r / min, and ball milling for 19 h to prepare a nano-sized layered multi-metal oxide, namely, NiCoFe-LDO.

[0192] The capacity of the NiCoFe-LDO is about 718 mAh / g; the specific surface area is 169 m 2 / g; the pore size of the porous structure is 16 nm; and the interlayer spacing is 0.41 nm.

[0193] The rest is the same as that in Example 1.

[0194] Example 2-4

[0195] The method described in Example 1 is followed, except that:

[0196] The preparation of the layered multi-metal oxide (NiCoFe-LDO) comprises: nickel nitrate, cobalt nitrate, iron nitrate and urea are weighed according to a molar ratio of 7:1:1:10, the mass ratio of nickel salt to distilled water is 1:20, nickel nitrate, cobalt nitrate, iron nitrate, urea and distilled water are mixed, stirred for 30 min, then poured into a reaction kettle, the hydrothermal kettle is put into an oven, and hydrothermal reaction is carried out at a temperature of 160℃, the hydrothermal reaction time is 11h, the layered multi-metal hydroxide is prepared, the sample is collected by a high-speed centrifuge, then the sample is washed with water and ethanol for three times to remove excess impurities, and then dried in a constant-temperature drying box at 60℃ for 24h to obtain a powder sample; then, the powder sample is placed into a ceramic boat and put into a tube furnace, and calcination is carried out at a temperature of 500℃, the calcination time is 1h, the layered NiCoFe-LDO powder is prepared, and the prepared powder is added into a planetary ball mill, the rotation speed of the ball mill is set to 50r / min, and the ball milling time is 12h, so as to prepare the nano-sized layered multi-metal oxide, i.e. NiCoFe-LDO.

[0197] The capacity of the NiCoFe-LDO is about 718 mAh / g; the specific surface area is 142 m 2 / g; the pore size of the porous structure is 14 nm; and the interlayer spacing is 0.41 nm.

[0198] The rest is the same as that in Example 1.

[0199] Example 3

[0200] This example is mainly used to illustrate the preparation of the negative electrode sheet and the positive electrode sheet when the proportions of various substances in the first negative electrode slurry, the second negative electrode slurry or the positive electrode slurry are different.

[0201] Example 3-1

[0202] The method described in Example 1 is followed, except that:

[0203] The hard carbon material, SP and PVDF are weighed according to a mass ratio of 94:4:2, NMP is added according to a mass ratio of the hard carbon material to NMP of 1:2.2, high-speed dispersion is carried out, and the first negative electrode slurry is prepared after uniform mixing.

[0204] Layered multi-metal oxides (NiFe-LDO), acetylene black and CMC were weighed according to the mass ratio of 93:3:4, NMP was added according to the mass ratio of NiFe-LDO to NMP of 1:2, high-speed dispersion was carried out, and the second negative electrode slurry was prepared after mixing uniformly.

[0205] Prussian blue type positive electrode material Na4Fe(CN)6·10H2O, SP and PVDF were weighed according to the mass ratio of 94:4:2, NMP was added according to the mass ratio of Prussian blue type positive electrode material Na4Fe(CN)6·10H2O to NMP of 1:2.2, high-speed dispersion was carried out, and the positive electrode slurry was prepared after mixing uniformly.

[0206] The rest was the same as example 1.

[0207] Example 3-2

[0208] The method described in example 1 was operated, except that:

[0209] Hard carbon material, SP and PVDF were weighed according to the mass ratio of 92:5:3, NMP was added according to the mass ratio of hard carbon material to NMP of 1:2.2, high-speed dispersion was carried out, and the first negative electrode slurry was prepared after mixing uniformly.

[0210] Layered multi-metal oxides (NiFe-LDO), acetylene black and CMC were weighed according to the mass ratio of 93:3.5:3.5, NMP was added according to the mass ratio of NiFe-LDO to NMP of 1:2, high-speed dispersion was carried out, and the second negative electrode slurry was prepared after mixing uniformly.

[0211] Prussian blue type positive electrode material Na4Fe(CN)6·10H2O, SP and PVDF were weighed according to the mass ratio of 92:5:3, NMP was added according to the mass ratio of Prussian blue type positive electrode material Na4Fe(CN)6·10H2O to NMP of 1:2.2, high-speed dispersion was carried out, and the positive electrode slurry was prepared after mixing uniformly. 1.79 Fe[Fe(CN)6]·0.16H2O, SP and PVDF were weighed according to the mass ratio of 92:5:3, NMP was added according to the mass ratio of Prussian blue type positive electrode material Na4Fe(CN)6·10H2O to NMP of 1:2.2, high-speed dispersion was carried out, and the positive electrode slurry was prepared after mixing uniformly. 1.79 Fe[Fe(CN)6]·0.16H2O, SP and PVDF were weighed according to the mass ratio of 92:5:3, NMP was added according to the mass ratio of Prussian blue type positive electrode material Na4Fe(CN)6·10H2O to NMP of 1:2.2, high-speed dispersion was carried out, and the positive electrode slurry was prepared after mixing uniformly.

[0212] The rest was the same as example 1.

[0213] Example 3-3

[0214] The method described in example 1 was operated, except that:

[0215] The layered multi-metal oxide (NiFe-LDO), acetylene black and CMC were weighed according to the mass ratio of 90:5:5, NMP was added according to the mass ratio of NiFe-LDO to NMP of 1:2, high-speed dispersion was carried out, and the second negative electrode slurry was prepared after mixing uniformly.

[0216] The rest were the same as in Example 1.

[0217] Example 3-4

[0218] The method described in Example 1 was followed, except that:

[0219] The layered multi-metal oxide (NiFe-LDO), acetylene black and CMC were weighed according to the mass ratio of 94:3:3, NMP was added according to the mass ratio of NiFe-LDO to NMP of 1:2, high-speed dispersion was carried out, and the second negative electrode slurry was prepared after mixing uniformly.

[0220] The rest were the same as in Example 1.

[0221] Example 4

[0222] This example is mainly used to illustrate the preparation of negative electrode sheets and positive electrode sheets when the thicknesses of the first negative electrode coating, the second negative electrode coating or the positive electrode coating are different.

[0223] Example 4-1

[0224] The method described in Example 1 was followed, except that:

[0225] In the preparation of the negative electrode sheet, the coating thickness of the first negative electrode coating was 60 μm; the coating thickness of the second negative electrode coating was 4 μm.

[0226] In the preparation of the positive electrode sheet, the coating thickness of the positive electrode coating was 55 μm.

[0227] The rest were the same as in Example 1.

[0228] Example 4-2

[0229] The method described in Example 1 was followed, except that:

[0230] In the preparation of the negative electrode sheet, the coating thickness of the first negative electrode coating was 50 μm; the coating thickness of the second negative electrode coating was 5 μm.

[0231] In the preparation of the positive electrode sheet, the coating thickness of the positive electrode coating was 45 μm.

[0232] The rest were the same as in Example 1.

[0233] Comparative Example 1

[0234] The present comparative example is mainly used to illustrate the preparation of the negative electrode sheet without setting the second negative electrode coating on the negative electrode sheet.

[0235] The operation is performed according to the method described in Example 1, except that: no second negative electrode coating is set on the first negative electrode coating, that is, the negative electrode sheet of Comparative Example 1 only includes the current collector and the first negative electrode coating set on the current collector.

[0236] Comparative Example 2

[0237] The present comparative example is mainly used to illustrate the preparation of the negative electrode sheet when the existing material is used to replace the layered multi-metal oxide.

[0238] The operation is performed according to the method described in Example 1, except that: NiO is used to replace the layered multi-metal oxide;

[0239] The capacity of the NiO is about 718 mAh / g; the specific surface area is 115 m 2 / g; the pore size of the porous structure is 22 nm; and the interlayer spacing is 0.46 nm.

[0240] Performance test

[0241] 1. Preparation of sodium ion battery

[0242] (1) The positive electrode sheets prepared in each of the above examples and comparative examples are respectively rolled, and the positive electrode sheets are punched into positive electrode sheets with a diameter of φ 14 mm by a punching machine.

[0243] (2) The negative electrode sheets prepared in each of the above examples and comparative examples are respectively rolled, and the negative electrode sheets are punched into negative electrode sheets with a diameter of φ 14 mm by a punching machine.

[0244] (3) A PE separator is provided as a separation film.

[0245] (4) An electrolyte is provided, which is prepared by dissolving 1.0 mol / L of NaPF6 in an organic solvent of diglyme dimethyl ether.

[0246] (5) The full battery is assembled in the order of positive electrode shell, positive electrode sheet, separator, negative electrode sheet, foamed nickel, and negative electrode shell. The assembled full battery is clamped with an insulating tweezer and placed on a packaging machine for sealing treatment. Finally, the packaged full battery is left to stand for 24 h, so that the electrolyte fully infiltrates the electrode material before electrochemical test.

[0247] 2. Electrochemical performance test of the battery

[0248] (1) The first circle discharge specific capacity test: sodium ion batteries prepared from each example and comparative example were taken respectively, and the first circle discharge specific capacity test was carried out under the test conditions of 0.2C rate, charge cut-off voltage 4.8V, and discharge cut-off voltage 2.0V at 25℃ environment.

[0249] (2) Discharge specific capacity after 1000 cycles and capacity retention rate after 1000 cycles test: sodium ion batteries prepared from each example and comparative example were taken respectively, and discharged to 2.0V at 0.2C rate at 25℃ environment, and then charged to 4.8V at 0.2C rate, which was defined as one complete charge-discharge cycle, recorded as cycle 1, and the process was repeated until the cycle number was equal to 1000, and the test was ended. The discharge capacity of the last cycle was the discharge specific capacity after 1000 cycles; the capacity retention rate after 1000 cycles = discharge specific capacity after 1000 cycles / first circle discharge specific capacity*100%.

[0250] (3) 1C / 1C cycle life test: sodium ion batteries prepared from each example and comparative example were taken respectively, and the capacity was divided under the test conditions of 0.2C rate, charge cut-off voltage 4.8V, and discharge cut-off voltage 2.0V at 25℃ environment, and then 1C / 1C cycle test was carried out at 25℃ environment (charge cut-off voltage 4.8V, discharge cut-off voltage 2.0V), and the cycle number when the discharge specific capacity decreased to 0 was recorded.

[0251] (4) Test of charge transfer resistance of new battery: Autolab electrochemical workstation was used to test the charge transfer resistance of the half battery, and the test frequency was 0.01Hz-100kHz.

[0252] (5) Test of sodium ion diffusion coefficient of new battery: CT2001A blue battery system was used to carry out constant current intermittent titration test on the half battery, and the voltage range was 0.2-4.8V.

[0253] (6) Test of metal content of negative electrode sheet after 1000 cycles: the negative electrode material on the aluminum foil was scraped off from the negative electrode sheet after 1000 cycles, and the energy dispersive spectrometer was used to measure the metal content of the sample.

[0254] (7) Test of time required for 1C cycle to fully charge in the third cycle: the time required for 1C charging to 4.8V after discharging to 2.0V in the third cycle of 1C cycle was recorded.

[0255] The test results are shown in Table 1.

[0256] Table 1

[0257]

[0258]

[0259]

[0260] As can be seen from Table 1, compared with Comparative Example 1-2, the batteries prepared by using the negative electrode tab of the embodiments 1 to 4 of the present application have higher first circle discharge specific capacity, better cycle performance, lower charge transfer resistance, higher sodium ion diffusion coefficient, and lower metal content in the negative electrode layer after 1000 cycles, indicating that the multifunctional layered multi-metal oxide coating, i.e., the second negative electrode coating containing multi-metal oxide, can significantly improve the battery performance and the safety and life.

[0261] In addition, through the analysis and comparison of the embodiments 1 and 2, it can be seen that when the capacity of the layered multi-metal oxide of the present application is ≥100 mAh / g, such as in the range of 100-750 mAh / g, the specific surface area of the layered multi-metal oxide is in the range of 100-200 m 2 / g, preferably in the range of 120-170 m 2 / g, the pore size of the porous structure of the layered multi-metal oxide is in the range of 10 nm-20 nm, preferably in the range of 14 nm-16 nm, the interlayer distance of the layered multi-metal oxide is in the range of 0.2 nm-1.0 nm, preferably in the range of 0.3 nm-0.8 nm, the performance of the prepared negative electrode tab is not much different, and all have high initial discharge specific capacity, good cycle performance, and significantly reduced charge transfer resistance and significantly increased sodium ion diffusion coefficient, indicating that the electrochemical reaction kinetics is significantly improved, which is beneficial to the improvement of the electrical performance of the battery.

[0262] Through the analysis and comparison of the embodiments 1 and 3 and 4, it can be seen that the performance of the prepared negative electrode tab is not much different when the content and thickness of each substance in the first negative electrode coating and the second negative electrode coating defined in the present application are used, and all have high initial discharge specific capacity, good cycle performance, improved sodium ion diffusion coefficient, and improved electrical performance of the battery.

[0263] The part not described in detail in the present application is the technology known to those skilled in the art.

[0264] The basic principles of the present application are described above in combination with specific embodiments, but it should be pointed out that the advantages, advantages, effects, etc. mentioned in the present application are only examples and not limitations, and these advantages, advantages, effects, etc. cannot be considered as the must-have of each embodiment of the present application. In addition, the above specific details are only for the purpose of example and for the purpose of understanding, and are not limited to the above specific details. The present application must be implemented using the above specific details.

[0265] It should be noted that the terms "and / or" or " / " as used herein merely describes an associated relationship among associated objects, and indicates that there can be three relationships, for example, A and / or B, which can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0266] In the detailed description and in the claims, a list of items connected by the term "at least one of" or "one or more of" can mean any combination of the items in the list. For example, if the items in a list are A, B, and C, the phrase "at least one of A, B, and C" can mean A alone; B alone; C alone; A and B together; A and C together; B and C together; or A, B, and C together. The term "at least one of" can be limited to mean only one of the items in the list A, B, and C. For example, if the items in a list are A, B, and C, the phrase "at least one of A, B, and C" can mean A alone; B alone; or C alone.

[0267] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A sodium-ion battery negative electrode sheet, characterized by, The sodium ion battery negative electrode sheet comprises: a current collector; a first negative electrode coating layer arranged on at least one side surface of the current collector in the thickness direction, the first negative electrode coating layer comprising a negative electrode active material; the negative electrode active material comprising at least one of graphite, soft carbon and hard carbon; and A second negative electrode coating is disposed on a surface of the first negative electrode coating distal from the current collector, the second negative electrode coating comprising a layered multi-metal oxide having a general chemical formula of M1 2+ x M2 3+ y O z , the M1 comprising at least one of Ni, Zn, Mn, Mg, Cu, Co, the M2 comprising at least one of Fe, Bi, Al, V, Co, and M1 and M2 not being selected from Co at the same time, wherein 0.4≤x≤0.8, 0.2≤y≤0.4, z=(2x+3y) / 2, and the layered multi-metal oxide satisfies the following characteristics: (I) the capacity of the layered multi-metal oxide is ≥100 mAh / g; (II) the layered multimetal oxide has a specific surface area of > 100 m2 / g 2 / g; (III) the layered multi-metal oxide has a porous structure; (IV) the interlayer spacing of the layered multi-metal oxide is ≥0.15 nm.

2. The sodium-ion battery anode web of claim 1, wherein, The capacity of the layered multi-metal oxide is 100-800 mAh / g; and / or, The specific surface area of the layered multimetal oxide is 100 to 200 m 2 / g; and / or, The pore size range of the porous structure is 10-20 nm; and / or, The interlayer spacing of the layered multi-metal oxide is 0.2-1.0 nm.

3. The sodium-ion battery anode web of claim 2, wherein, The capacity of the layered multi-metal oxide is 100-750 mAh / g.

4. The sodium-ion battery anode web of claim 2, wherein, The specific surface area of the layered multimetal oxide is 120 to 170 m 2 / g.

5. The sodium-ion battery anode web of claim 2, wherein, The pore size range of the porous structure is 14-16 nm.

6. The sodium-ion battery anode web of claim 2, wherein, The interlayer spacing of the layered multi-metal oxide is 0.3-0.8 nm.

7. The sodium-ion battery anode web of claim 1, wherein, The first negative electrode coating layer further comprises a first binder and a first conductive agent; The first binder comprises at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium hydroxymethyl cellulose, polyacrylic acid, polyacrylate, polyvinyl alcohol, polytetrafluoroethylene, polyethylene oxide, carboxypropyl methyl cellulose and hexafluoropropylene; The first conductive agent comprises at least one of conductive carbon black, conductive graphite, carbon nanotubes, graphene and vapor-grown carbon fibers; The mass ratio of the negative electrode active material, the first conductive agent and the first binder is (90-94):(1-6):(2-4).

8. The sodium-ion battery anode web of any one of claims 1 to 7, wherein, The second negative electrode coating layer further comprises a second binder and a second conductive agent; The second binder comprises at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium hydroxymethyl cellulose, polyacrylic acid, polyacrylate, polyvinyl alcohol, polytetrafluoroethylene, polyethylene oxide, carboxypropyl methyl cellulose and hexafluoropropylene; The second conductive agent comprises at least one of conductive carbon black, conductive graphite, carbon nanotubes, graphene and vapor-grown carbon fibers; The mass ratio of the layered multi-metal oxide, the second conductive agent and the second binder is (90-94):(2-6):(2-4); The thickness of the second negative electrode coating layer is 2-6 μm; The thickness ratio of the second negative electrode coating layer to the first negative electrode coating layer is 1:(10-30).

9. The method of making a sodium-ion battery anode web of any one of claims 1 to 8, wherein, The method comprises the following steps: coating a first negative electrode slurry on at least one side surface of a current collector to obtain a first negative electrode coating layer; coating a second negative electrode slurry on the surface of the first negative electrode coating layer to obtain a second negative electrode coating layer; The first negative electrode coating layer comprises a negative electrode active material, and the second negative electrode coating layer comprises a layered multi-metal oxide.

10. The method of making a sodium-ion battery anode web of claim 9, wherein, The preparation of the layered multi-metal oxide comprises: mixing M1 salt, M2 salt, water and urea, and then performing hydrothermal reaction, washing, drying, calcination and ball milling to obtain the layered multi-metal oxide; The anions of the M1 salt and the M2 salt respectively comprise at least one of nitrate ions, sulfate ions, chloride ions and acetate ions; The M1 element of the M1 salt comprises at least one of Ni, Zn, Mn, Mg, Cu and Co, the M2 element of the M2 salt comprises at least one of Fe, Bi, Al, V and Co, and M1 and M2 are not simultaneously selected from Co; The molar ratio of the M1 salt, the M2 salt and urea is (5-7):(0.5-1.5):10; The temperature of the hydrothermal reaction is 120-180℃, and the time of the hydrothermal reaction is 8-12h; The temperature of the calcination is 450-500℃, and the time of the calcination is 1-2h; The rotation speed of the ball milling is 50-70 r / min, and the time of the ball milling is 12-24h.

11. The method of producing a sodium-ion battery anode web of claim 9 or 10, wherein, The preparation of the first negative electrode slurry comprises: uniformly mixing a negative electrode active material, a first conductive agent and a first binder in a solvent to obtain a first negative electrode slurry; The preparation of the second negative electrode slurry comprises: uniformly mixing a layered multi-metal oxide, a second conductive agent and a second binder in a solvent to obtain a second negative electrode slurry; The first negative electrode slurry is coated on the surface of the current collector, and after drying, a first negative electrode coating layer is formed on the surface of the current collector; the second negative electrode slurry is coated on the first negative electrode coating layer, and after drying, a second negative electrode coating layer is formed on the surface of the first negative electrode coating layer, thereby obtaining a sodium ion battery negative electrode sheet.

12. A battery comprising a positive electrode sheet and a negative electrode sheet, characterized by The negative electrode sheet is the sodium ion battery negative electrode sheet according to any one of claims 1-8 or the sodium ion battery negative electrode sheet prepared by the method according to any one of claims 9-11.

13. The battery of claim 12, wherein, The positive electrode sheet comprises a positive electrode coating layer, and the positive electrode coating layer comprises a positive electrode active material, wherein the positive electrode active material comprises a Prussian blue type positive electrode material; The Prussian blue type positive electrode material has a general chemical formula of Na x M3[M4(CN)6] y •zH2O, 0 < x < 2, 0.8 < y < 1, 0 < z < 20, M3and M4are respectively selected from transition metal elements. The positive electrode coating layer further comprises a positive electrode conductive agent and a positive electrode binder, and the mass ratio of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder is (90-94):(1-6):(2-4).

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