Composition of positive electrode material, method of preparation thereof, positive electrode, sodium battery and electrical device.

Abstract

A positive electrode material composition, a method for its preparation, a positive electrode, a sodium battery, and an electrical device are described. The positive electrode material composition includes at least two active positive electrode materials for a nickel-iron-manganese sodium-ion battery, and these active positive electrode materials are physically mixed. A mixture of the active positive electrode materials for a nickel-iron-manganese sodium-ion battery further includes a copper element (Cu) and a copper element (Q). The positive electrode includes the positive electrode material composition, and the sodium battery includes the positive electrode. The electrical device includes the sodium battery.The composition of the positive electrode material can improve the stability of the battery cell's DC resistance during charging and discharging processes.

Description

Positive electrode material composition and preparation method thereof, positive electrode, sodium battery and electrical device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on November 30, 2023, with application number 202311641701.9 and invention name “Positive electrode material composition and preparation method thereof, positive electrode, sodium battery and electrical device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the technical field of sodium batteries, and specifically relates to a positive electrode material composition and a preparation method thereof, a positive electrode, a sodium battery, and an electrical device. Background Art

[0003] Sodium-ion batteries, with their abundant raw material reserves, low price, relatively stable chemical properties, and good safety, are expected to replace lithium-ion batteries in the market. The continuous development of new energy vehicles and the increasing proportion of clean energy are placing higher demands on the energy conversion efficiency, energy density, and cycle stability of sodium-ion batteries.

[0004] The impedance and stability of battery cells are important factors affecting their energy conversion efficiency. However, the impedance stability of current battery cells, such as sodium batteries, needs to be further improved to better meet the current market demand for battery applications.

[0005] Summary of the Invention

[0006] In view of the above problems, the present application provides a positive electrode material composition and a preparation method thereof, a positive electrode containing the positive electrode material composition, and a sodium battery containing the positive electrode, so as to solve the technical problem of unsatisfactory impedance stability of existing battery cells.

[0007] In a first aspect, an embodiment of the present application provides a positive electrode material composition. The positive electrode material composition of the embodiment of the present application includes at least two nickel-iron-manganese-based sodium positive electrode active materials, each of the nickel-iron-manganese-based sodium positive electrode active materials is physically mixed, and the mixture of the nickel-iron-manganese-based sodium positive electrode active materials further contains Cu and Q elements. In the unit molar amount of the positive electrode material composition, the total molar content of Na is 0.78 to 1 mol;

[0008] The total molar content of Ni is 0.12 to 0.38 moL;

[0009] The total molar content of Mn is 0.18 to 0.48 moL;

[0010] The total molar content of Fe is 0.18 to 0.35 moL;

[0011] The total molar content of Q is 0.01 to 0.12 moL;

[0012] The total molar content of Cu is 0.01 to 0.14 moL;

[0013] The Q includes at least one element of Zn, Mg, and Ti.

[0014] The positive electrode material composition of the present embodiment uses two or more nickel-iron-manganese-based sodium cathode active materials to form a physical mixture, and the content of metal elements such as Na, Ni, Mn, Fe, Cu, and Q in the mixture is controlled within the above-mentioned range. This makes the direct current internal resistance (DCR) of the battery cell containing the positive electrode material composition of the present embodiment relatively stable during the charge and discharge process, and can significantly reduce the DCR growth rate of the battery cell during the charge and discharge process. On this basis, the energy density and cycle performance of the battery cell can also be improved.

[0015] In some embodiments, the molar content of at least one element among Na, Ni, Mn, Fe, Cu and Y in the positive electrode material composition per unit mole is:

[0016] The total molar content of Na is 0.8 to 1 moL;

[0017] The total molar content of Ni is 0.15 to 0.35 mol;

[0018] The total molar content of Mn is 0.20 to 0.45 mol;

[0019] The total molar content of Fe is 0.20 to 0.33 mol;

[0020] The total molar content of Q is 0.01 to 0.06 moL;

[0021] The total molar content of Cu is 0.02-0.09 mol.

[0022] By selecting and controlling the total molar content of at least one of the elements Na, Ni, Mn, Fe, Cu and the metal element shown in Q within the above range, the disordered arrangement of the metal elements in the transition metal layer contained in each nickel-iron-manganese-based sodium cathode active material can be further adjusted, and the distance between the transition metal layer and the sodium layer can be adjusted to further improve the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process. In particular, the Cu element and the metal element shown in Q in the above range can enhance the synergistic effect on the DCR stability of the battery cell, further improving the DCR stability of the battery cell. At the same time, the cycle performance and gram capacity of each nickel-iron-manganese-based sodium cathode active material are further improved.

[0023] In some embodiments, at least one of the nickel-iron-manganese-based sodium positive electrode active materials further contains active or / and inert doping metal elements. In the positive electrode material composition per unit mole, the total molar content of the doping metal elements is greater than 0 and less than or equal to 0.13 moL, and can be optionally greater than 0 and less than or equal to 0.1 moL. The doping metal elements in this content range can participate in the disordered arrangement between the metal elements in the transition metal layer contained in the nickel-iron-manganese-based sodium positive electrode active material and can adjust the distance between the transition metal layer and the sodium layer. It can also improve the relevant electrochemical properties of each nickel-iron-manganese-based sodium positive electrode active material, and further improve the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process, so as to alleviate the growth of the DCR of the battery cell during the charge and discharge process. At the same time, it can also improve the structural stability and / or gram capacity of the nickel-iron-manganese-based sodium positive electrode active material.

[0024] In an exemplary embodiment, the doping metal element includes at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ru, and Ir. These types of doping metal elements dope the transition metal layer contained in the nickel-iron-manganese-based sodium cathode active material containing the doping metal element, adjust the disordered arrangement of the metal elements in the transition metal layer, and adjust the distance between the transition metal layer and the sodium layer, which can further improve the DC internal resistance (DCR) stability of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process, thereby alleviating the increase in the DCR of the battery cell during the charge and discharge process and improving the structural stability and / or specific capacity of the nickel-iron-manganese-based sodium cathode active material.

[0025] In some embodiments, in the positive electrode material composition per unit molar amount, the ratio of the molar content of the Na element to the total molar content of other metal elements is (0.81-0.89):1, and can be optionally (0.82-0.89):1. Controlling the ratio of the total molar content of the Na element to the total molar content of other metal elements within this range can further adjust the content of sodium ions, increase the content of sodium ions that can be inserted and removed from the nickel-iron-manganese-based sodium cathode active material, thereby increasing the reversible capacity of the positive electrode material composition; and can also improve the structural stability of the nickel-iron-manganese-based sodium cathode active material, thereby improving its cycle performance.

[0026] In some embodiments, the Cu element and the Q element are distributed in different nickel-iron-manganese-based sodium cathode active materials. By compounding the nickel-iron-manganese-based sodium cathode active material containing the Cu element and the nickel-iron-manganese-based sodium cathode active material containing the Q element to form a mixture, the gram capacity and cycle performance of the positive electrode material composition of the embodiment of the present application can be balanced, and the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process can be further improved to alleviate the increase of the DCR of the battery cell during the charge and discharge process.

[0027] In an embodiment, the nickel-iron-manganese-based sodium cathode active material containing the Q element comprises at least one of the following (1) to (4):

[0028] (1) Dv50 particle size is 3-8 μm, and can be selected as 4-6.5 μm;

[0029] (2) Dv90 particle size is 8-16 μm, and can be selected as 10-14 μm;

[0030] (3) The compaction density under 3 tons of pressure is higher than 3.1g / cm 3 , can be selected as 3.1~3.4g / cm 3 ;

[0031] (4) Specific surface area is 0.4 to 1.0 m 2 / g, optional range is 0.6~0.9m 2 / g.

[0032] In an embodiment, the nickel-iron-manganese-based sodium cathode active material containing the Cu element comprises at least one of the following (1) to (4):

[0033] (1) Dv50 particle size is 5-11 μm, and can be selected as 6.5-10 μm;

[0034] (2) Dv90 particle size is 13-19 μm, and can be selected as 14.5-18 μm;

[0035] (3) The compaction density under 3 tons of pressure is 3.0-3.3 g / cm 3 , can be selected from 3.0 to 3.25 g / cm 3 ;

[0036] (4) Specific surface area is 0.4 to 0.7 m 2 / g, optional range is 0.5~0.6m 2 / g.

[0037] The nickel-iron-manganese-based sodium cathode active material containing the Q element and the nickel-iron-manganese-based sodium cathode active material containing the Cu element have the characteristics within the above ranges, which can improve the stability of the contact interface between the cathode material composition of the embodiment of the present application and the electrolyte, and improve the DC internal resistance (DCR) stability of the battery cell containing the cathode material composition of the embodiment of the present application during the charge and discharge process. At the same time, it can also improve the specific capacity and cycle performance of the cathode material composition of the embodiment of the present application.

[0038] In some embodiments, each of the nickel-iron-manganese-based sodium cathode active materials independently comprises at least one of the following (1) to (2):

[0039] (1) The crystal structure includes an O3 phase layered metal oxide, and the O3 phase layered metal oxide accounts for more than 95% of the total weight of the layered oxide; and / or

[0040] (2) It includes a single crystal, and the morphology of the single crystal is block-shaped.

[0041] The single crystal O3 phase nickel-iron-manganese-based sodium cathode active material has relatively high structural stability and improves the cycle performance of the battery cell.

[0042] In some embodiments, the positive electrode material composition has a discharge capacity of 115 to 128 mAh / g at 1.5 to 4.2 V and 0.1 C, and can optionally be 120 to 128 mAh / g.

[0043] In a second aspect, the present invention provides a method for preparing a positive electrode material composition. The method for preparing a positive electrode material composition according to the present invention comprises the following steps:

[0044] At least two nickel-iron-manganese-based sodium cathode active materials are physically mixed according to the molar content ratio of Na, Ni, Mn, Fe, Q and Cu contained in the above-mentioned cathode material composition per unit mole to form a cathode material composition.

[0045] The preparation method of the positive electrode material composition of the embodiment of the present application is to mix at least two nickel-iron-manganese-based sodium positive electrode active materials in a proportion within the content range of Na, Ni, Mn, Fe, Cu, and Q, so that the battery cell containing the positive electrode material composition of the embodiment of the present application has a small increase rate of direct current internal resistance (DCR) during the charge and discharge process, and also makes the positive electrode material composition of the embodiment of the present application have high gram capacity and cycle performance.

[0046] In a third aspect, the embodiments of the present application provide a positive electrode, which includes a positive electrode active material layer, wherein the positive electrode active material layer includes the positive electrode material composition of the embodiments of the present application or a positive electrode material composition prepared by the method for preparing the positive electrode material composition of the embodiments of the present application.

[0047] Since the positive electrode active material layer of the positive electrode of the embodiment of the present application contains the positive electrode material composition of the embodiment of the present application, the battery cell containing the positive electrode of the embodiment of the present application has a small increase in DC internal resistance (DCR) during the charge and discharge process. At the same time, the battery cell has a high energy density and good cycle performance.

[0048] In some embodiments, the content of the positive electrode active material layer on a single surface of the current collector is 260 to 350 mg / 1540.25 mm 2 , optional: 280~320mg / 1540.25mm 2 .

[0049] In some embodiments, the positive electrode has a compaction density of 2.6 to 3.4 g / cm 3 , can be selected as 2.8~3.2g / cm 3 .

[0050] In some embodiments, the porosity of the positive electrode active material layer is 40% to 70%, and can be optionally 50% to 65%.

[0051] In some embodiments, the positive electrode is a pole piece, and the ratio of the thickness from one surface of the pole piece to the other opposite surface to the thickness of the current collector is 7 to 15:1, and can be optionally 8 to 14:1.

[0052] In some embodiments, the positive electrode is a pole piece, and the membrane resistance of the pole piece is 0.5 to 5 mΩ, and can be optionally 0.5 to 3 mΩ.

[0053] When the positive electrode of the embodiment of the present application has the characteristics within the above range, the contact interface between the electrode and the electrolyte is stable, so that the direct current internal resistance (DCR) of the battery cell containing the positive electrode of the embodiment of the present application is relatively stable during the charge and discharge process, and the energy density of the battery cell is high and the cycle performance is good.

[0054] In some embodiments, the conductive agent contained in the positive electrode active material layer includes a linear conductive agent.

[0055] In an embodiment, the linear conductive agent includes at least one of the following (1) to (5):

[0056] (1) The mass content of the positive electrode active material layer is 0.1% to 2.5%, and can be 0.3% to 0.7%;

[0057] (2) The aspect ratio is 40 to 3000:1, and can be selected as 50 to 2500:1;

[0058] (3) The length is 0.5 to 5 μm, and can be optionally 0.5 to 2 μm;

[0059] (4) The diameter is 2 to 10 nm, and can be 3 to 7 nm;

[0060] (5) Includes at least one of carbon nanotubes, carbon fibers, and conductive oxide nanowires.

[0061] By adding a linear conductive agent to the positive electrode active material layer and controlling its content within the specified range, and by selecting and controlling its type, aspect ratio, length, and diameter within the aforementioned ranges, the linear conductive agent can form a rich conductive network structure within the positive electrode active material layer, and can also wrap around the surface of the flat single crystal particles. The particulate conductive agent can be effectively dispersed in the gaps within the positive electrode material composition. This effectively improves the conductivity of the positive electrode active material layer, significantly reduces the internal resistance of the positive electrode, and also helps improve the DCR stability of the battery's electrical properties during charge and discharge.

[0062] Fourthly, embodiments of the present application provide a sodium battery. These sodium batteries include the positive electrode described in the preceding embodiments. The electrode assembly in the sodium battery cell exhibits stable interface contact with the electrolyte, and good DC resistance (DCR) stability during charge and discharge. Furthermore, the battery cell also exhibits electrochemical properties such as high energy density and excellent cycling performance.

[0063] In some embodiments, the sodium battery is a sodium battery cell, and the sodium battery cell includes at least one of the following (1) to (3):

[0064] (1) The operating voltage is 1.5 to 4.0 V; and / or

[0065] (2) Energy density of 120-130 Wh / Kg at 1.5-4.0 V;

[0066] (3) After 1000 cls, the DC resistance growth rate of the sodium battery cell is less than 180%.

[0067] In a fifth aspect, an embodiment of the present application provides an electrical device, and the embodiment of the present application includes a sodium battery according to an embodiment of the present application.

[0068] The electrical device in the embodiment of the present application has a long standby or battery life and a long service life.

[0069] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0071] FIG1 is a schematic structural diagram of a positive electrode in some embodiments of the present application;

[0072] FIG2 is another schematic structural diagram of a positive electrode according to some embodiments of the present application;

[0073] FIG3 is a schematic structural diagram of an embodiment of a sodium battery cell according to an embodiment of the present application;

[0074] FIG4 is an exploded schematic diagram of the sodium battery cell shown in FIG3 ;

[0075] FIG5 is a schematic structural diagram of an embodiment of a battery module according to the present application;

[0076] FIG6 is a schematic structural diagram of an embodiment of a battery pack according to the present application;

[0077] FIG7 is a schematic diagram of the exploded structure of the battery pack shown in FIG6 ;

[0078] FIG8 is a schematic diagram of an embodiment of an electrical device including a battery according to an embodiment of the present application as a power source.

[0079] The accompanying drawings in the specific implementation manner are as follows:

[0080] 10-positive electrode, 11 current collector, 12-positive electrode active material layer;

[0081] 20-battery cell, 21-housing, 22-electrode assembly, 23-cover plate;

[0082] 30-battery module;

[0083] 40-battery pack, 41-upper box, 42-lower box. DETAILED DESCRIPTION

[0084] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0085] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0086] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0087] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0088] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0089] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0090] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0091] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0092] Sodium-ion batteries (SIBs) are ideal candidates for energy storage systems due to their abundant raw material reserves and low cost. They also have enormous potential for application in the new energy vehicle market. With the rapid development of energy storage systems and new energy vehicles, market demands for battery performance, including that of sodium-ion batteries, are increasing, including in terms of energy conversion efficiency, energy density, and cycle stability.

[0093] Among them, the impedance and impedance stability of battery cells are important factors affecting their energy conversion efficiency. Current methods for reducing battery cell impedance or improving impedance stability generally include optimizing electrode design, improving electrolyte wettability, and adopting advanced manufacturing processes. While these methods can improve battery cell impedance and impedance stability to a certain extent, the improvement effect of these methods on battery cell impedance and impedance stability is not particularly ideal. Furthermore, they can lead to reduced chemical properties such as battery cell energy density and cycle performance, or increased costs.

[0094] For sodium-ion batteries, sodium-ion battery cathode materials can provide active sodium ions and are an important component of sodium-ion batteries. Among sodium-ion battery cathode materials, sodium-electrolyte layered oxides have attracted much attention due to their high gram capacity and structure similar to that of lithium-ion battery cathode materials.

[0095] Based on the structure of sodium-based layered oxide cathode materials, it is currently believed that these materials have a significant impact on the energy density and cycle performance of sodium battery cells. Therefore, the industry is currently adjusting the crystal stability and doping of sodium-based layered oxide cathode materials to improve their electrochemical properties, such as gram capacity and structural stability, in order to achieve the goal of improving the energy density and cycle performance of sodium-based battery cells.

[0096] In the process of studying how to improve the energy conversion efficiency of batteries such as sodium batteries, a composition of sodium-based layered oxide positive electrode materials was proposed. By physically mixing and compounding at least two types of sodium-based layered oxide positive electrode materials to form a composition of sodium-based layered oxide positive electrode materials, and regulating the type and content of transition metal elements in the composition, and using it as a battery cell, it was found that it can significantly improve the impedance of the battery cell, such as significantly improving the DC internal resistance (DCR) stability of the battery cell during the charge and discharge process, and reducing the rate of increase of the DCR of the battery cell during the charge and discharge process, thereby improving the energy conversion efficiency of the battery cell. On this basis, the electrochemical properties of the battery cell, such as energy density and cycle performance, can also be improved. Based on the above research, the following technical solutions are proposed in the embodiments of the present application.

[0097] Positive electrode material composition

[0098] In the first aspect, the embodiments of the present application provide a positive electrode material composition. In some embodiments, the positive electrode material composition of the embodiments of the present application includes at least two nickel-iron-manganese-based sodium positive electrode active materials, each nickel-iron-manganese-based sodium positive electrode active material is physically mixed, and the mixture formed by the nickel-iron-manganese-based sodium positive electrode active material also contains Cu and Q elements. And in the positive electrode material composition per unit mole, the contents of Na, Ni, Mn, Fe, Cu, and Q elements are as follows:

[0099] The total molar content of Na is 0.78 to 1 moL;

[0100] The total molar content of Ni is 0.12 to 0.38 moL;

[0101] The total molar content of Mn is 0.18 to 0.48 moL;

[0102] The total molar content of Fe is 0.18 to 0.35 moL;

[0103] The total molar content of Q is 0.01 to 0.12 moL;

[0104] The total molar content of Cu is 0.01 to 0.14 moL;

[0105] Wherein, Q includes at least one element selected from Zn, Mg, and Ti.

[0106] In the positive electrode material composition of the embodiment of the present application, the nickel-iron-manganese-based sodium-based positive electrode active material refers to a sodium-based layered oxide positive electrode material containing nickel, iron and manganese elements. The sodium-based layered oxide positive electrode material refers to a positive electrode material composed of alternating transition metal layers (TMO6) and sodium layers (NaO6) including Ni, Mn, Fe, etc. Physical mixing refers to physically mixing at least two of the above-mentioned nickel-iron-manganese-based sodium-based positive electrode active materials, doping the amorphous phase, and not undergoing treatment such as sintering after mixing.

[0107] The positive electrode material composition of the embodiment of the present application is prepared by physically mixing two or more nickel-iron-manganese-based sodium cathode active materials, and controlling the content of metal elements such as Na, Ni, Mn, Fe, Cu, and Q in the mixture within the above-mentioned ranges. This allows the battery cell containing the positive electrode material composition of the embodiment of the present application to have a relatively stable DC internal resistance (DCR) during the charge and discharge process, and can significantly reduce the DCR growth rate of the battery cell during the charge and discharge process. Among them, the Cu element and the metal element represented by Q in the above-mentioned range of content can play a synergistic role in the DCR stability of the battery cell in the electrode material composition, and can significantly improve the DCR stability of the battery cell.

[0108] On this basis, since at least one nickel-iron-manganese-based sodium positive electrode active material contains Cu and Q elements in the above-mentioned molar content range, the Cu and Q elements participate in the disordered arrangement between the metal elements in the transition metal layer contained in the nickel-iron-manganese-based sodium positive electrode active material and can adjust the distance between the transition metal layer and the sodium layer, thereby improving the structural stability and / or gram capacity of the nickel-iron-manganese-based sodium positive electrode active material in the process of sodium insertion and extraction, and improving the gram capacity and cycle performance of the positive electrode material composition of the embodiment of the present application, thereby correspondingly improving the energy density and cycle performance of the battery cell.

[0109] In some embodiments, the total molar content of the Na element per unit mole of the positive electrode material composition may be 0.78 to 1 mole, optionally 0.8 to 1 mole, and further 0.89 to 0.91 mole. In exemplary embodiments, the total molar content of the Na element may be 0.78 mole, 0.8 mole, 0.82 mole, 0.85 mole, 0.88 mole, 0.89 mole, 0.9 mole, 0.91 mole, 0.92 mole, 0.95 mole, 0.98 mole, 1.0 mole, or other typical but non-limiting stoichiometric contents or a range between any two stoichiometric content values. The Na element in this content range improves the reversible capacity of the positive electrode material composition.

[0110] In some embodiments, the total molar content of the Ni element in the unit molar amount of the positive electrode material composition can be 0.12-0.38 moL, optionally 0.15-0.35 moL, and further can be 0.2-0.3 moL. In the exemplary embodiment, the total molar content of the Ni element can be 0.12 moL, 0.15 moL, 0.18 moL, 0.20 moL, 0.22 moL, 0.25 moL, 0.28 moL, 0.30 moL, 0.32 moL, 0.35 moL, 0.38 moL and other typical but non-limiting stoichiometric contents or the range between any two stoichiometric content values.

[0111] In some embodiments, in the positive electrode material composition per unit molar amount, the total molar content of the Fe element can be 0.18 to 0.35 moL, optionally 0.20 to 0.33 moL, and further 0.24 to 0.28 moL. In the exemplary embodiment, the total molar content of the Fe element can be 0.18 moL, 0.20 moL, 0.22 moL, 0.24 moL, 0.25 moL, 0.28 moL, 0.30 moL, 0.32 moL, 0.33 moL, and other typical but non-limiting stoichiometric contents or the range between any two stoichiometric content values.

[0112] At least one of the Ni element and the Fe element in the above-mentioned content range can participate in the disordered arrangement between the metal elements in the transition metal layer contained in each nickel-iron-manganese-based sodium positive electrode active material together with the Cu element or Q element including the above-mentioned content, the Mn element and other elements contained in each nickel-iron-manganese-based sodium positive electrode active material and can adjust the distance between the transition metal layer and the sodium layer, thereby improving the relevant electrochemical properties of each nickel-iron-manganese-based sodium positive electrode active material, thereby further improving the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process, and further alleviating the growth of the DCR of the battery cell during the charge and discharge process. On this basis, the gram capacity of the nickel-iron-manganese-based sodium positive electrode active material can also be increased to increase the gram capacity of the positive electrode material composition of the embodiment of the present application. The structural stability of the nickel-iron-manganese-based sodium positive electrode active material in the process of sodium insertion and extraction can be further improved, and the cycle performance of the positive electrode material composition of the embodiment of the present application can be improved.

[0113] In some embodiments, the total molar content of the Mn element per unit mole of the positive electrode material composition may be 0.18 to 0.48 moL, optionally 0.20 to 0.45 moL, and further 0.39 to 0.41 moL. In exemplary embodiments, the total molar content of the Mn element may be 0.18 moL, 0.20 moL, 0.22 moL, 0.25 moL, 0.28 moL, 0.30 moL, 0.32 moL, 0.35 moL, 0.38 moL, 0.39 moL, 0.40 moL, 0.41 moL, 0.42 moL, 0.45 moL, 0.48 moL, and other typical but non-limiting stoichiometric contents or a range between any two stoichiometric content values. The Mn element in this content range can participate in the relevant electrochemical properties of each nickel-iron-manganese-based sodium positive electrode active material together with the elements such as Cu element or Q element, Ni element, Fe element, etc. contained in each nickel-iron-manganese-based sodium positive electrode active material, further improving the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process, and further alleviating the growth of the DCR of the battery cell during the charge and discharge process. On this basis, the structural stability of each nickel-iron-manganese-based sodium positive electrode active material in the process of sodium insertion and deinsertion is improved, and the cycle performance of each nickel-iron-manganese-based sodium positive electrode active material is improved.

[0114] In some embodiments, in the unit molar amount of the positive electrode material composition, the total molar content of the Q element can be 0.01 to 0.12 moL, optionally 0.01 to 0.1 moL, and further can be 0.01 to 0.06 moL. In the exemplary embodiment, the total molar content of the Q element can be 0.01 moL, 0.02 moL, 0.03 moL, 0.04 moL, 0.05 moL, 0.06 moL, 0.07 moL, 0.08 moL, 0.09 moL, 0.10 moL, 0.11 moL, 0.12 moL and other typical but non-limiting stoichiometric contents or the range between any two stoichiometric content values. When the nickel-iron-manganese-based sodium cathode active material contains the Q element in this content range, the Q element can also participate in the disordered arrangement between the metal elements in the transition metal layer of the nickel-iron-manganese-based sodium cathode active material containing the Q element, and adjust the distance between the transition metal layer and the sodium layer, thereby improving the relevant electrochemical properties of each nickel-iron-manganese-based sodium cathode active material, and further improving the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process, so as to alleviate the growth of the DCR of the battery cell during the charge and discharge process. Moreover, the metal element shown by Q in the above content range can also further play a synergistic role in the stability of the DCR of the battery cell with the Cu element in the above range in the composition, thereby further improving the DCR stability of the battery cell.

[0115] At the same time, it can also further improve the full utilization of the gram capacity of the nickel-iron-manganese-based sodium cathode active material containing the Q element in the process of sodium deintercalation, thereby improving the gram capacity of the positive electrode material composition of the embodiment of the present application; it can also reduce the migration of the Fe element in the nickel-iron-manganese-based sodium cathode active material containing the Q element, improve the structural stability of each nickel-iron-manganese-based sodium cathode active material in the process of sodium deintercalation, and improve the cycle performance of the positive electrode material composition of the embodiment of the present application.

[0116] In some embodiments, the total molar content of the Cu element in the positive electrode material composition per unit molar amount may be 0.01 to 0.14 moL, optionally 0.01 to 0.12 moL, further 0.02 to 0.09 moL, 0.02 to 0.07 moL. In an exemplary embodiment, the total molar content of the Cu element may be 0.01 moL, 0.02 moL, 0.03 moL, 0.04 moL, 0.05 moL, 0.06 moL, 0.07 moL, 0.08 moL, 0.09 moL, 0.10 moL, 0.11 moL, 0.12 moL, 0.13 moL, 0.14 moL, and the like, or a range between any two stoichiometric content values. When the nickel-iron-manganese-based sodium positive electrode active material contains the Cu element in this content range, the Cu element can also participate in the disordered arrangement between the metal elements in the transition metal layer of the nickel-iron-manganese-based sodium positive electrode active material containing the Cu element, adjust the distance between the transition metal layer and the sodium layer, and also improve the relevant electrochemical properties of each nickel-iron-manganese-based sodium positive electrode active material, thereby further improving the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process, so as to alleviate the growth of the DCR of the battery cell during the charge and discharge process. Similarly, the Cu element in the above content range can also further play a synergistic role in the stability of the DCR of the battery cell in the composition with the metal element shown in the Q content range above, thereby further improving the DCR stability of the battery cell. At the same time, the structural stability of the nickel-iron-manganese-based sodium positive electrode active material containing the Cu element during the sodium intercalation and deintercalation process can also be further improved.

[0117] In some embodiments, at least one nickel-iron-manganese-based sodium cathode active material contained in the cathode material composition of the embodiment of the present application further contains active and / or inert doping metal elements. In the unit molar amount of the cathode material composition, the total molar content of the doping metal elements is greater than 0 and less than or equal to 0.13 moL; it can be optionally greater than 0 and less than or equal to 0.1 moL; in the exemplary embodiment, the total molar content of the doping metal elements can be 0.01 moL, 0.02 moL, 0.03 moL, 0.04 moL, 0.05 moL, 0.06 moL, 0.07 moL, 0.08 moL, 0.09 moL, 0.10 moL, 0.11 moL, 0.12 moL, 0.13 moL, etc., typical but non-limiting stoichiometric contents or the range between any two stoichiometric content values. The doping metal element in this content range can participate in the disordered arrangement between the metal elements in the transition metal layer contained in the nickel-iron-manganese-based sodium positive electrode active material containing doped metal elements and can adjust the distance between the transition metal layer and the sodium layer. Together with at least one of the above-mentioned Ni, Mn, Fe or further Cu elements or Q elements, it can also improve the relevant electrochemical properties of each nickel-iron-manganese-based sodium positive electrode active material, thereby further improving the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process, so as to alleviate the growth of the DCR of the battery cell during the charge and discharge process. At the same time, according to the type of doping metal element shown in R, the structural stability and / or gram capacity of the nickel-iron-manganese-based sodium positive electrode active material containing doped metal elements can be further improved. When it is an active doping metal element, the content of the Ni element can be reduced, thereby reducing the economic cost of the nickel-iron-manganese-based sodium positive electrode active material containing doped metal elements.

[0118] In an embodiment, the above-mentioned doping metal elements may include at least one of V, Cr, Ca, Al, Sc, Sn, Sb, Zr, Nb, Ru, and Ir. Among them, the active doping metal elements may include at least one metal element of V, Cr, Sc, Sn, Sb, Nb, Ca, etc., and the inert doping metal elements may be at least one metal element of Al, Zr, Ir, Ru, etc. These types of doping metal elements dope the transition metal layer contained in the nickel-iron-manganese-based sodium positive electrode active material containing doping metal elements, adjust the disordered arrangement of the metal elements in the transition metal layer, and adjust the distance between the transition metal layer and the sodium layer, which can further improve the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process, so as to alleviate the growth of the DCR of the battery cell during the charge and discharge process. In addition, depending on the type of doped metal element, inert doped metal elements can also reduce sensitivity to iron sites, and can assist the Mn element to further improve the structural stability of the nickel-iron-manganese-based sodium cathode active material containing doped metal elements during the sodium intercalation and deintercalation process, further improving the cycle performance of the nickel-iron-manganese-based sodium cathode active material containing doped metal elements. For example, active doped metal elements can also further enhance the specific capacity of the nickel-iron-manganese-based sodium cathode active material containing doped metal elements with the Fe element, thereby correspondingly increasing the energy density of the battery cell.

[0119] Based on the molar content ranges of at least one of Cu and Q and Na, Ni, Mn, Fe, or further doping metal elements contained in the positive electrode material composition of the present application per unit mole in the above embodiments, in some embodiments, the total molar content of Na, Ni, Mn, Fe, Cu, Q, and doping metal elements per unit mole in the positive electrode material composition can be as follows:

[0120] The total molar content of Na is 0.8 to 1 moL;

[0121] The total molar content of Ni is 0.15 to 0.35 moL;

[0122] The total molar content of Mn is 0.20-0.45 moL;

[0123] The total molar content of Fe is 0.20-0.33 moL;

[0124] The total molar content of Q is 0.01 to 0.06 moL;

[0125] The total molar content of Cu is 0.02 to 0.09 moL;

[0126] The total molar content of the doped metal elements is 0 to 0.13 moL, and can be optionally 0 to 0.1 moL.

[0127] By selecting and controlling the total molar content of Na, Ni, Mn, Fe, Cu and the metal element represented by Q or further doped metal elements within this range, the disordered arrangement of the metal elements in the transition metal layer contained in each nickel-iron-manganese-based sodium cathode active material and the distance between the transition metal layer and the sodium layer can be further adjusted to further improve the DC internal resistance (DCR) stability of the battery cell containing the cathode material composition of the embodiment of the present application during the charge and discharge process. At the same time, the cycle performance and gram capacity of each nickel-iron-manganese-based sodium cathode active material are further improved.

[0128] In some embodiments, in the unit molar amount of the positive electrode material composition, the ratio of the total molar content of the Na element to the total molar content of other metal elements in the positive electrode material composition of the embodiment of the present application in the above embodiments is (0.81~0.89):1, which can be (0.82~0.89):1. In the exemplary embodiment, it can be 0.81:1, 0.82:1, 0.83:1, 0.84:1, 0.85:1, 0.86:1, 0.87:1, 0.88:1, 0.89:1 and other typical but non-limiting molar ratios or the range between any two molar ratios. By controlling the ratio of the total molar content of the Na element to the total molar content of other metal elements within this range, the content of sodium ions can be further adjusted, and the content of sodium ions that can be inserted and removed from the nickel-iron-manganese-based sodium positive electrode active material can be increased, thereby improving the reversible capacity of the positive electrode material composition of the embodiment of the present application; moreover, the sodium ions in this content range can increase the O3 crystal phase content of each nickel-iron-manganese-based sodium positive electrode active material, so that each nickel-iron-manganese-based sodium positive electrode active material mainly presents O3 crystals, thereby improving the structural stability of the nickel-iron-manganese-based sodium positive electrode active material, thereby improving its cycle performance.

[0129] In addition, the nickel-iron-manganese-based sodium positive electrode active material contained in the positive electrode material composition of the embodiment of the present application in the above-mentioned embodiments is a sodium layered oxide positive electrode material. Therefore, each nickel-iron-manganese-based sodium positive electrode active material also contains oxygen atoms. The content of the oxygen atoms can be the conventional content range of the sodium layered oxide positive electrode material. The types and contents of elements in the positive electrode material composition and the nickel-iron-manganese-based sodium positive electrode active material contained therein in the above-mentioned embodiments can be detected by inductively coupled plasma emission spectroscopy (ICP) obtained by the Agilent ICP-OES730 below.

[0130] In addition, the physical mixing ratio of at least two nickel-iron-manganese-based sodium cathode active materials contained in the cathode material composition of the embodiment of the present application in the above-mentioned embodiments can be adjusted according to the total molar content range of each element in the cathode material composition of the embodiment of the present application per unit mole.

[0131] In some embodiments, the Cu element and Q element contained in the positive electrode material composition of the embodiment of the present application in the above-mentioned embodiments are distributed in different nickel-iron-manganese-based sodium positive electrode active materials. In this way, the nickel-iron-manganese-based sodium positive electrode active material containing the Cu element has a relatively high structural stability during the charge and discharge process, thereby improving the cycle performance of the positive electrode material composition of the embodiment of the present application; the nickel-iron-manganese-based sodium positive electrode active material containing the Q element has a relatively high gram capacity, thereby improving the gram capacity of the positive electrode material composition of the embodiment of the present application. Therefore, the nickel-iron-manganese-based sodium positive electrode active material containing the Cu element and the nickel-iron-manganese-based sodium positive electrode active material containing the Q element form a mixture, which can balance the gram capacity and cycle performance of the positive electrode material composition of the embodiment of the present application, thereby corresponding to the energy density and cycle performance of the balanced battery electrical properties. At the same time, it can also further improve the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process to alleviate the growth of the DCR of the battery cell during the charge and discharge process.

[0132] Of course, the above-mentioned Cu element and Q element can also be distributed in the same nickel-iron-manganese-based sodium cathode active material.

[0133] In some embodiments, when the Cu element and the Q element are distributed in different nickel-iron-manganese-based sodium cathode active materials, it has been tested that in the embodiment, the powder Dv50 particle size of the nickel-iron-manganese-based sodium cathode active material containing the above-mentioned Q element can be 3 to 8 μm, and can be optionally 4 to 6.5 μm. In the demonstration example, the Dv50 particle size can be 3 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm and other typical but non-limiting particle sizes or a range between any two particle size values. The Dv90 particle size of the nickel-iron-manganese-based sodium cathode active material containing the above-mentioned Q element can be 8 to 16 μm, and can be optionally 10 to 14 μm. In the exemplary embodiment, the Dv90 particle size can be 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm and other typical but non-limiting particle sizes or a range between any two particle size values.

[0134] In the embodiment, the powder Dv50 particle size of the nickel-iron-manganese-based sodium cathode active material containing the above-mentioned Cu element can be 5 to 11 μm, and can be optionally 6.5 to 10 μm. In the exemplary embodiment, the Dv50 particle size can be 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm and other typical but non-limiting particle sizes or the range between any two particle size values. The powder Dv90 particle size of the nickel-iron-manganese-based sodium cathode active material containing the above-mentioned Cu element can be 13 to 19 μm, and can be optionally 14.5 to 18 μm. In the exemplary embodiment, the Dv90 particle size can be 13 μm, 14 μm, 14.5 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm and other typical but non-limiting particle sizes or a range between any two particle size values.

[0135] The Dv50 particle size refers to the particle size corresponding to the cumulative particle size distribution percentage of the nickel-iron-manganese-based sodium cathode active material powder containing the above-mentioned Q element or Cu element when it reaches 50%. The Dv90 particle size refers to the particle size corresponding to the cumulative particle size distribution percentage of the nickel-iron-manganese-based sodium cathode active material powder containing the above-mentioned Q element or Cu element when it reaches 90%. The Dv50 and Dv90 particle sizes of each nickel-iron-manganese-based sodium cathode active material can be measured separately according to the method steps in GB / T16418.

[0136] The Dv50 particle size and Dv90 particle size within the above range can enhance the composite effect between the nickel-iron-manganese-based sodium cathode active material containing the Q element and the nickel-iron-manganese-based sodium cathode active material containing the Cu element, and further enhance the DC internal resistance (DCR) stability of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process, thereby alleviating the increase in the DCR of the battery cell during the charge and discharge process. At the same time, it has a suitable specific surface area to improve the stability of the contact interface between the positive electrode sheet and the electrolyte.

[0137] In some embodiments, when the Cu element and the Q element are distributed in different nickel-iron-manganese-based sodium cathode active materials, in the embodiment, the specific surface area (BET) of the nickel-iron-manganese-based sodium cathode active material particles containing the Q element is 0.4 to 1.0 m 2 / g, optional range is 0.6~0.9m 2 / g, in the example, it can be 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2Typical but non-limiting specific surface areas such as 1,4,6,7,8,9 or 1,4,7,9,10 ...

[0138] In the embodiment, the specific surface area (BET) of the nickel-iron-manganese-based sodium positive electrode active material particles containing the Cu element is 0.4 to 0.7 m 2 / g, optional range is 0.5~0.6m 2 / g, in the example, it can be 0.4m 2 / g, 0.5m 2 / g, 0.55m 2 / g, 0.6m 2 / g, 0.7m 2 Typical but non-limiting specific surface areas such as 1,4,6,7,8,9 or 1,4,7,9,10 ...

[0139] The specific surface area of ​​the nickel-iron-manganese-based sodium positive electrode active material containing the Q element and the nickel-iron-manganese-based sodium positive electrode active material containing the Cu element in this range can improve the stability of the contact interface between the nickel-iron-manganese-based sodium positive electrode active material containing the Q element and the nickel-iron-manganese-based sodium positive electrode active material containing the Cu element and the electrolyte, and further improve the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process.

[0140] In some embodiments, when the Cu element and the Q element are distributed in different nickel-iron-manganese-based sodium cathode active materials, in the embodiment, the compaction density of the nickel-iron-manganese-based sodium cathode active material powder containing the Q element under a pressure of 3 tons is higher than 3.1 g / cm 3 , can be selected as 3.1~3.4g / cm 3 In this example, the compacted density under 3 tons of pressure is 3.1 g / cm 3 、3.2g / cm 3 , 3.3g / cm 3 、3.4g / cm 3 Typical but non-limiting compacted densities or ranges between any two compacted density values.

[0141] In the embodiment, the compaction density of the nickel-iron-manganese-based sodium cathode active material powder containing the Cu element under a pressure of 3 tons can be 3.0-3.3 g / cm 3 , can be selected from 3.0 to 3.25 g / cm 3 In this example, the compacted density under 3 tons of pressure is 3g / cm 3 , 3.1g / cm 3 、3.15g / cm 3 、3.2g / cm 3 , 3.25g / cm 3 , 3.3g / cm3 Typical but non-limiting compacted densities or ranges between any two compacted density values.

[0142] The specific surface area of ​​the nickel-iron-manganese-based sodium positive electrode active material containing the Q element and the nickel-iron-manganese-based sodium positive electrode active material containing the Cu element in this range can improve the stability of the contact interface between the nickel-iron-manganese-based sodium positive electrode active material containing the Q element and the nickel-iron-manganese-based sodium positive electrode active material containing the Cu element and the electrolyte, and further improve the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process. At the same time, the gram capacity of the battery containing the nickel-iron-manganese-based sodium positive electrode active material containing the Q element and the nickel-iron-manganese-based sodium positive electrode active material containing the Cu element can be further improved.

[0143] The compacted density of the positive electrode material composition and the nickel-iron-manganese-based sodium positive electrode active material powders contained therein in the above embodiments can be tested according to the following test method:

[0144] Refer to the GB / T24533-2019 standard test method for testing. Please refer to the following test steps for details:

[0145] (1) Use a clean soft cloth (paper towel) to wipe the upper and lower gaskets, top column and metal cylindrical sleeve of the compaction density meter. If necessary, wipe them with a soft cloth dipped in anhydrous ethanol and air dry them;

[0146] (2) Place the gasket, top column, metal cylindrical sleeve, and pad in the order of the test and place them on the digital thickness gauge, and press the zero key;

[0147] (3) Remove the top post and upper gasket, weigh 1 g of the nickel-iron-manganese-based sodium cathode active material sample contained in Examples A1 to A12 and Comparative Examples A1 to A2 in the sleeve to the nearest 0.0001 g, and record the weight as m;

[0148] (4) Slowly slide the gasket and the top column down from the hole, install them together with the pad on the compaction density meter, and tighten the pressure control knob;

[0149] (5) Shake the pressure bar and observe the value on the digital pressure gauge on the compaction density meter at the same time. Start the stopwatch after reaching the specified value of 2200Ib; loosen the pressure control knob after 30 seconds to remove the pressure, lower the pad to a certain height, and then tighten the pressure control knob;

[0150] (6) Take out the top post, sleeve and film together with the pad, place them on the digital thickness gauge, and read the value on the digital thickness gauge within 10 seconds, which is recorded as H; r = 10m / (S×H);

[0151] Then calculate the powder compaction density r of the sample according to the above formula r=10m / (S×H).

[0152] Where mm is the sample weight in grams (g); HH is the thickness of the sample after compaction in millimeters (mm); SS is the cross-sectional area of ​​the top column in square centimeters (cm 2 ).

[0153] In some embodiments, the at least two nickel-iron-manganese-based sodium positive electrode active materials contained in the positive electrode material composition of the present application in each of the above embodiments can be physically mixed according to a molar ratio of nickel-iron-manganese-based sodium positive electrode active material containing Cu element to nickel-iron-manganese-based sodium positive electrode active material containing Q element of 0.5 to 28:1, optionally 0.5 to 18:1. For example, it can be a typical but non-limiting molar ratio of 0.5:1, 1:1, 3:1, 5:1, 8:1, 10:1, 13:1, 15:1, 18:1, 20:1, 23:1, 25:1, 28:1 or the like, or a range between any two molar ratios. In the embodiment, when the Cu element and the Q element are distributed in different nickel-iron-manganese-based sodium positive electrode active materials, the total molar ratio of the nickel-iron-manganese-based sodium positive electrode active material containing Cu element to the total molar ratio of the nickel-iron-manganese-based sodium positive electrode active material containing Q element is within the above-mentioned physical mixing molar ratio range.

[0154] By controlling the physical mixing molar ratio of at least two nickel-iron-manganese-based sodium cathode active materials within the above range, the compounding effect between the nickel-iron-manganese-based sodium cathode active materials can be fully utilized, thereby improving the DCR stability performance of the battery cell containing the cathode material composition of the embodiment of the present application during the charge and discharge process. At the same time, the gram capacity and cycle performance of the battery containing the cathode material composition of the embodiment of the present application can be further balanced, thereby improving the energy density and cycle performance of the corresponding battery cell.

[0155] In some embodiments, the nickel-iron-manganese-based sodium positive electrode active material contained in the positive electrode material composition of the embodiment of the present application in the above-mentioned embodiments is selected from O3 layered metal oxides. Wherein, the O3 layered metal oxide refers to a layered oxide with a crystal structure in which the oxygen contained therein is stacked in an ABCABC type manner. In the embodiments, the nickel-iron-manganese-based sodium positive electrode active material contained in the positive electrode material composition of the embodiment of the present application in the above-mentioned embodiments is mainly O3 crystal phase, and the weight content of the O3 crystal phase in each nickel-iron-manganese-based sodium positive electrode active material can be more than 95%, further more than 98%, and can also reach 100%. The higher the weight proportion of the O3 crystal phase in each nickel-iron-manganese-based sodium positive electrode active material, the more desirable it is. The O3 crystal phase contained in each nickel-iron-manganese-based sodium cathode active material enables each nickel-iron-manganese-based sodium cathode active material to have a relatively high structural stability, such as a relatively high structural stability relative to the P2 phase layered metal oxide, and its cycle performance is higher. At the same time, it can further improve the stability of the DCR of the battery cell containing the positive electrode material composition of the embodiment of the present application during the charge and discharge process.

[0156] In some embodiments, electron microscopic analysis shows that each of the nickel-iron-manganese-based sodium cathode active material crystals comprises a single crystal, and the single crystal is in a block shape.

[0157] Based on the element types, contents and mixing ratios of the nickel-iron-manganese-based sodium cathode active materials contained in the cathode material compositions of the embodiments of the present application in the above-mentioned embodiments, as well as the morphology, crystal form, particle size, etc., it has been tested that in some embodiments, the discharge gram capacity of the cathode material compositions of the embodiments of the present application in the above-mentioned embodiments at 1.5-4.2V and 0.1C can reach 115-128mAh / g, and can be optionally 120-128mAh / g.

[0158] The charge and discharge gram capacities of the positive electrode material compositions of the above-mentioned examples are specifically prepared by preparing the positive electrode material compositions of the present invention examples into positive electrodes, which are then assembled with the negative electrodes into sodium ion button batteries. The gram capacities of the sodium ion button batteries are then measured.

[0159] In the embodiment, the sodium ion button cell used to test the charge gram capacity and discharge gram capacity of the positive electrode material composition of the embodiment of the present application is assembled according to the following method:

[0160] Positive electrode sheet: The positive electrode material composition of the embodiment of the present application is used as the positive electrode active material, and is thoroughly stirred and mixed with the conductive agent carbon nanotubes, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) in an appropriate amount of solvent NMP at a weight ratio of 95:0.5:2:2.5 to form a uniform positive electrode slurry; the positive electrode slurry is evenly coated on the surface of a 13 μm positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained;

[0161] Negative electrode sheet: Add hard carbon, conductive agent SP, and CMC binder to deionized water in a weight ratio of 8:1:1 and stir thoroughly to form a uniform negative electrode slurry. The negative electrode slurry is evenly coated on the surface of a 6μm copper foil, dried, and cold pressed to obtain a negative electrode sheet.

[0162] Electrolyte: 1 M NaPF6 / (EC / DEC, volume ratio 1:1);

[0163] Diaphragm: Glass fiber;

[0164] Sodium ion button battery assembly: The above-mentioned positive electrode sheet, glass fiber film and negative electrode sheet are stacked in order to form a button battery assembly after assembly. The electrode assembly is placed in a packaging shell, and 1M NaPF6 / (EC / DEC, volume ratio 1:1) electrolyte is added. After packaging, formation, and static standing, a sodium ion button battery is obtained.

[0165] Preparation method of positive electrode material composition

[0166] In a second aspect, the present invention provides a method for preparing the positive electrode material composition of the above-mentioned embodiment. In some embodiments, the method for preparing the positive electrode material composition of the present invention comprises the following steps:

[0167] S10: Physically mixing at least two nickel-iron-manganese-based sodium cathode active materials according to the molar content ratio of Na, Ni, Mn, Fe, Q and Cu contained in the unit molar amount of the cathode material composition to form a cathode material composition.

[0168] In step S10 of the method for preparing the positive electrode material composition of the embodiment of the present application, the nickel-iron-manganese-based sodium positive electrode active material is the nickel-iron-manganese-based sodium positive electrode active material contained in the positive electrode material composition of the embodiment of the present application. Therefore, the physical mixing of at least two nickel-iron-manganese-based sodium positive electrode active materials also refers to physical intermixing and amorphous phase doping. The mixing ratio of at least two nickel-iron-manganese-based sodium positive electrode active materials needs to satisfy the content of Na, Ni, Mn, Fe, Cu, and Q elements in the positive electrode material composition of the embodiment of the present application per unit mole, specifically:

[0169] The total molar content of Na is 0.78 to 1 moL, and can be selected as 0.8 to 1 moL;

[0170] The total molar content of Ni is 0.12-0.38 moL, and can be selected as 0.15-0.35 moL;

[0171] The total molar content of Mn is 0.18 to 0.48 moL, and can be optionally 0.20 to 0.45 moL;

[0172] The total molar content of Fe is 0.18-0.35 moL, and can be selected as 0.20-0.33 moL;

[0173] The total molar content of Q is 0.01 to 0.12 moL, and can be optionally 0.01 to 0.1 moL;

[0174] The total molar content of Cu is 0.01 to 0.14 moL, and can be optionally 0.01 to 0.12 moL.

[0175] Thus, the method for preparing the positive electrode material composition of the embodiment of the present application, by mixing at least two nickel-iron-manganese-based sodium cathode active materials according to the proportions of the elements Na, Ni, Mn, Fe, Cu, and Q within the range of the content, makes the direct current internal resistance (DCR) of the battery cell containing the positive electrode material composition of the embodiment of the present application relatively stable during the charge and discharge process, and can significantly reduce the DCR growth rate of the battery cell during the charge and discharge process. This also makes the positive electrode material composition of the embodiment of the present application have high specific capacity and cycle performance.

[0176] The nickel-iron-manganese-based sodium cathode active material in step S10 can be an existing nickel-iron-manganese-based sodium cathode active material, and of course it can also be a nickel-iron-manganese-based sodium cathode active material improved according to the type and content of elements contained in the cathode material composition of the embodiment of the application.

[0177] In some embodiments, the nickel-iron-manganese-based sodium cathode active material in step S10 can be prepared according to the following method:

[0178] S11: providing each nickel-iron-manganese-based sodium cathode active material precursor according to the ratio of elements contained in each nickel-iron-manganese-based sodium cathode active material;

[0179] S12: sintering each nickel-iron-manganese-based sodium cathode active material separately to obtain each nickel-iron-manganese-based sodium cathode active material.

[0180] In step S11 of the method for preparing the positive electrode material composition of the embodiment of the present application, the nickel-iron-manganese-based sodium positive electrode active material precursor can be a mixture in proportion containing a sodium source, a nickel source, a manganese source, an iron source and further containing a copper source and a metal element source represented by Q, or further containing the doped metal source contained in the nickel-iron-manganese-based sodium positive electrode active material in the positive electrode material composition of the embodiment of the present application.

[0181] As described in the embodiment, the nickel-iron-manganese-based sodium cathode active material precursor can be prepared by a solid phase method or a precipitation method.

[0182] When a solid phase method is used to prepare a nickel-iron-manganese-based sodium cathode active material precursor, in an embodiment, the nickel-iron-manganese-based sodium cathode active material precursor can be prepared according to a method comprising the following steps:

[0183] Step S111: According to the stoichiometric ratio of elements in the nickel-iron-manganese-based sodium cathode active material, a sodium source, a nickel source, a manganese source, an iron source, a copper source, at least one of the metal element sources represented by Q, or further a doping element source is subjected to solid-phase mixing treatment to obtain a nickel-iron-manganese-based sodium cathode active material precursor.

[0184] When a solid-phase method is used to prepare a nickel-iron-manganese-based sodium cathode active material precursor, solid-phase mixing treatment is relative to liquid-phase mixing, and generally refers to not adding a solvent during the mixing process, such as not adding water, and also dry mixing the source solids in step S111 under solvent-free conditions.

[0185] To improve the uniformity of mixing of the various sources during the solid-phase mixing process in step S111, in an embodiment, the source compounds other than the sodium source in step S111 may be mixed first, and then the sodium source may be added and mixed again. This improves the uniformity of mixing of the various sources and enhances the safety of the solid-phase mixing process.

[0186] In the embodiment, the solid-phase mixing treatment can be coated with but not limited to ball milling treatment. As long as it is a method that can improve the uniform mixing of the source compounds in step S111, it is within the scope disclosed in the embodiments of the present application. In the embodiment, when the mixing treatment is ball milling treatment, the ball milling rate can be controlled to be 300 to 1000 rpm, optionally 400 to 600 rpm; the ball milling time can be 1h to 6h, optionally 2h to 4h. By using this ball milling treatment, the mixing uniformity of each source can be improved, thereby ultimately improving the stability of the structure and electrochemical properties of the nickel-iron-manganese-based sodium cathode active material in step S12.

[0187] In an exemplary embodiment, the sodium source may be a sodium salt, such as at least one of sodium carbonate, sodium hydroxide, and the like.

[0188] In an exemplary embodiment, the nickel source may be a soluble or insoluble nickel compound, such as nickel oxide (NiO) or a nickel salt, etc. The nickel salt may include at least one of nickel nitrate, nickel carbonate, nickel hydroxide, nickel sulfate, etc.

[0189] In an exemplary embodiment, the manganese source may be a soluble or insoluble manganese compound, such as manganese oxide (Mn2O3) or a manganese salt, etc. The manganese salt may include at least one of manganese nitrate, manganese carbonate, manganese hydroxide, manganese sulfate, etc.

[0190] In an exemplary embodiment, the iron source may be a soluble or insoluble iron compound, such as iron oxide (eg, Fe2O3) or an iron salt, etc. The iron salt may include at least one of iron nitrate, iron carbonate, iron hydroxide, iron sulfate, etc.

[0191] In an exemplary embodiment, the copper source may be a soluble or insoluble copper compound, such as copper oxide (eg, CuO) or a copper salt, etc. The copper salt may include at least one of copper nitrate, copper carbonate, copper hydroxide, copper sulfate, etc.

[0192] In an exemplary embodiment, the metal element source and the doping metal element source represented by Q may be soluble or insoluble compounds of the metal element represented by Q and the doping metal element, such as oxides of the metal element represented by Q and the doping metal element, or salts of the metal element represented by Q and the doping metal element. The salts of the metal element represented by Q and the doping metal element may include at least one of nitrates, carbonates, hydroxides, sulfates, and the like of the metal element represented by Q and the doping metal element.

[0193] The types of the above-mentioned sodium source, nickel source, manganese source, iron source, copper source and the metal elements and doped metal element sources shown in Q can be effectively mixed evenly during the mixing process, thereby improving the structure and chemical stability of each nickel-iron-manganese-based sodium cathode active material precursor to generate nickel-iron-manganese-based sodium cathode active material.

[0194] When the nickel-iron-manganese-based sodium cathode active material precursor is prepared by precipitation method, it can be prepared according to the method including the following steps:

[0195] Step S113: preparing a mixed solution of a soluble nickel source, a soluble manganese source, a soluble iron source, a copper source, at least one of the metal element sources represented by Q, or further a doping element source according to the stoichiometric ratio of elements in the nickel-iron-manganese-based sodium cathode active material, and then adding at least one of a precipitant and a complexing agent to perform co-precipitation treatment to obtain a precipitated mixture;

[0196] Step S114: mixing the precipitated mixture with a sodium source to obtain a nickel-iron-manganese-based sodium cathode active material precursor.

[0197] In step S113, at least one of the precipitant and the complexing agent should be a compound that can cause the nickel, manganese, iron, copper and the metal element shown in Q and the doping metal element in the nickel source, soluble manganese source, soluble iron source, soluble copper source and the metal element source shown in Q and the doping element source to precipitate. The precipitant and complexing agent in step S113 can be the same or different. For example, in the embodiment, the precipitant can include at least one of alkali metal hydroxides, carbonates, etc. In the embodiment, the complexing agent can include an inorganic or organic complexing agent. In the exemplary embodiment, the inorganic complexing agent can include at least one of ammonia water, ammonium bicarbonate, ammonium sulfate, ammonium carbonate, etc.; the organic complexing agent can include at least one of citric acid, tartaric acid and disodium ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid (EDTA), aminotriacetic acid (NTA), etc.

[0198] These types of precipitants and complexing agents can effectively precipitate nickel, manganese, iron, copper, the metal elements represented by Q, and doping elements.

[0199] In the embodiment, at least one of the precipitant and the complexing agent should be in excess relative to the total amount of metal elements contained in the mixed solution, such as the total molar amount, to ensure that all metal elements contained in the mixed solution are fully precipitated, so as to improve the accuracy of the stoichiometric ratio of the metal elements contained in the nickel-iron-manganese-based sodium cathode active material precursor.

[0200] In an exemplary embodiment, the soluble nickel source may include at least one of nickel acetate, nickel chloride, nickel nitrate, and nickel sulfate.

[0201] In an exemplary embodiment, the soluble manganese source may include at least one of manganese nitrate, manganese sulfate, and manganese halide.

[0202] In an exemplary embodiment, the soluble iron source may include at least one of iron nitrate, manganese sulfate, and halide.

[0203] In an exemplary embodiment, the soluble copper source may include at least one of iron nitrate, manganese sulfate, halide, and the like.

[0204] In an exemplary embodiment, the soluble metal element Q and the doping metal element source may include at least one of the metal element Q and the doping metal element's nitrate, manganese sulfate, halide, etc.

[0205] The types of the above-mentioned soluble nickel source, soluble manganese source, soluble iron source, soluble copper source and soluble metal element represented by Q and doping element source all have good solubility and can quantitatively control the stoichiometric ratio of each metal element in the precipitation mixture.

[0206] The mixing ratio of the sodium source and the precipitation mixture in step S114 should satisfy the sodium ion content in the nickel-iron-manganese-based sodium cathode active material, i.e., the sodium layered oxide, specifically the stoichiometric ratio required for the sodium element in the O3 crystalline layered oxide. The mixing process can be a solid phase mixing process or a process in which a soluble sodium source is dissolved and mixed with the precipitation mixture, followed by removal of the solvent.

[0207] In addition, the sodium source in step S114 may be a sodium salt, such as at least one of sodium carbonate, sodium hydroxide, etc.

[0208] Step S12:

[0209] In step S12, after the at least two nickel-iron-manganese-based sodium cathode active material precursors in step S11 are sintered separately, each nickel-iron-manganese-based sodium cathode active material will be generated. In the study, it was found that the sintering conditions have a certain influence on the structural stability and electrochemical properties of the generated nickel-iron-manganese-based sodium cathode active material. In some embodiments, the sintering temperature can be controlled at 700-980°C, optionally 750-950°C. In the exemplary embodiment, it can be 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 980°C, etc., typical but non-limiting temperatures or a range between any two temperature values.

[0210] At the above sintering temperature, the sintering treatment time can be 4h to 20h, optionally 6h to 12h. In the exemplary embodiment, it can be 4h, 5h, 8h, 10h, 12h, 15h, 18h, 20h and other typical but non-limiting hours or any range between two hours.

[0211] By controlling the stability and time of the sintering treatment within the above range, the precursors of the nickel-iron-manganese-based sodium cathode active materials in step S11 can be reacted to generate the nickel-iron-manganese-based sodium cathode active materials respectively, and the synergistic effect of the physical mixing and compounding of the nickel-iron-manganese-based sodium cathode active materials can be further improved, and the DC internal resistance (DCR) stability of the battery cell containing the cathode material composition of the embodiment of the present application during the charge and discharge process can be further improved, while also improving the electrochemical properties of the battery cell, such as the energy density and cycle performance.

[0212] In an embodiment, the temperature of the sintering treatment can be increased to the temperature of the sintering treatment at a heating rate of 2 to 20°C / min. The heating rate can be further controlled to be 5 to 15°C / min. In an exemplary embodiment, the heating rate can be a typical but non-limiting rate such as 2°C / min, 4°C / min, 5°C / min, 6°C / min, 8°C / min, 10°C / min, 12°C / min, 15°C / min, 17°C / min, 18°C / min, 20°C / min, or a range between any two rate values. By controlling the heating rate of the sintering treatment, such as controlling it within this heating rate range, the crystal perfection of each nickel-iron-manganese-based sodium cathode active material can be improved, such as improving the uniformity of the crystal morphology.

[0213] In addition, the sintering process in the above step S12 should be understood to be carried out in an oxygen environment. For example, in the embodiment, the sintering process can be carried out in air or in an oxygen-containing protective atmosphere, such as oxygen-containing nitrogen or other inert atmospheres.

[0214] positive electrode

[0215] In a third aspect, embodiments of the present application provide a positive electrode. In some embodiments, the positive electrode of the present application includes a current collector and a positive electrode active material layer. The positive electrode active material layer is combined with the current collector, and the positive electrode active material layer contains the positive electrode material composition of the embodiments of the present application.

[0216] In the positive electrode of the embodiment of the present application, the current collector refers to a structure for collecting current and for transmitting electrons. The positive electrode active material layer refers to a layer structure containing a positive electrode active material, which is a key substance participating in the battery chemical reaction in the positive electrode. Among them, the positive electrode active material includes the positive electrode material composition of the embodiment of the present application. The positive electrode active material layer is combined with the current collector, which means that the positive electrode active material layer is at least combined with the surface of the current collector. In addition, the positive electrode can be a pole piece, which means that the positive electrode has a sheet-like morphology. Of course, it can also be set to other morphologies as needed.

[0217] Because the positive electrode active material layer of the positive electrode of the present embodiment contains the positive electrode material composition of the present embodiment, testing has shown that the direct current internal resistance (DCR) of the battery cell containing the positive electrode of the present embodiment is relatively stable during the charge and discharge process, significantly reducing the DCR growth rate of the battery cell during the charge and discharge process. At the same time, the battery cell has a high energy density and good cycle performance.

[0218] In the embodiments, the current collector contained in the positive electrode of the present application includes, but is not limited to, a metal current collector, a carbon current collector, a conductive resin current collector, a metal and resin composite current collector, and more specifically, aluminum, copper, nickel, titanium, iron, and their respective alloys, stainless steel, carbon fiber, carbon nanotubes (CNTs), graphite, and the like. In the embodiments, the current collector can also be a dense film layer or a porous film layer. In the embodiments, the current collector can be, but is not limited to, aluminum foil or porous aluminum foil.

[0219] In the embodiments, the positive electrode active material layer contained in the positive electrode of the present application and the current collector can be at least laminated on the surface of the current collector. When the surface layer of the current collector has a porous structure or the current collector itself has a porous structure, the positive electrode active material layer can be at least partially embedded in the current collector.

[0220] In some embodiments, the positive electrode active material layer may be bonded to at least the surface of the current collector as shown in FIG1 , where the positive electrode active material layer 12 is laminated on one surface of the current collector 11. When the surface of the current collector 11 has a porous structure or the current collector 11 is porous as a whole, the positive electrode active material layer 12 may not only be laminated and bonded to the surface of the current collector 11 but may also further extend into the porous structure of the current collector 11.

[0221] In other embodiments, the positive electrode active material layer may be bonded to at least the surface of the current collector as shown in FIG2 , where the current collector 11 has two opposing surfaces, and the positive electrode active material layer 12 is laminated on the two opposing surfaces of the current collector 11. When at least one of the two surfaces of the current collector 11 has a porous structure or the current collector 11 as a whole has a porous structure, the positive electrode active material layer 12 may not only be laminated and bonded to the two surfaces of the current collector 11 but may also further extend into the porous structure of the current collector 11.

[0222] As an embodiment of the present application, in the above-mentioned positive electrode active material layer, the mass content of the total mass of the positive electrode material composition of the above-mentioned embodiment of the present application in the positive electrode active material layer can be 90% to 97%, optionally 94% to 96.5%. In the exemplary embodiment, it can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% and other typical but non-limiting contents or a range between any two content values. The positive electrode material composition in this content range can effectively improve the energy density of the positive electrode and has good cyclability.

[0223] The positive electrode active material layer contained in each of the above-mentioned embodiments generally includes, in addition to the above-mentioned positive electrode active material components, a binder, a conductive agent, and other components. The binder can enhance the mechanical properties between the positive electrode active material layer itself and the current collector. The conductive agent can effectively improve the conductivity of the positive electrode, such as reducing the resistance of the positive electrode.

[0224] In an embodiment, the mass content of the binder contained in the above-mentioned positive electrode active material layer can be 0.5% to 5%, optionally 1% to 3%. In an exemplary embodiment, it can be 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, 3.5%, 4%, 4.5%, 5% and other typical but non-limiting contents or a range between any two content values.

[0225] In an embodiment, the binder may include one or more of an oil-soluble binder, a water-soluble binder, an emulsion-type binder, etc. In an exemplary embodiment, the oil-soluble binder may include one or more of polyvinylidene fluoride, polyimide, polytetrafluoroethylene, polybutyl acrylate, polyacrylonitrile, etc.; in an exemplary embodiment, the water-soluble binder may include one or more of carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylic acid salt, polyvinyl alcohol, sodium alginate, cyclodextrin, etc.; in an exemplary embodiment, the emulsion-type binder may include one or more of styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0226] The content within this range and the above-mentioned types of binders can effectively enhance the mechanical properties of the positive electrode active material layer and the bonding strength between the positive electrode active material layer and the current collector, and can effectively improve the cycle performance of the positive electrode.

[0227] In an embodiment, the mass content of the conductive agent contained in the above-mentioned positive electrode active material layer can be 0.5% to 5%, optionally 1% to 3%. In a demonstration example, it can be 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, 3.5%, 4%, 4.5%, 5% and other typical but non-limiting contents or a range between any two content values.

[0228] In an embodiment, the conductive agent may include at least one of a granular conductive agent and a linear conductive agent. The granular conductive agent may include one or more of acetylene black (SP), conductive carbon black (super-P), Ketjen black, graphene, and the like. The linear conductive agent may include one or more of carbon nanotubes, carbon fibers, and conductive oxide nanowires. The granular conductive agent is a conductive agent with a nonlinear particle morphology, as opposed to a linear conductive agent. A linear conductive agent is a conductive agent with a one-dimensional fiber morphology.

[0229] The content within this range and the above-mentioned type of conductive agent can effectively improve the conductivity of the positive electrode active material layer.

[0230] In the embodiments, the conductive agent contained in the positive electrode active material layer of each of the above embodiments includes a linear conductive agent and a granular conductive agent. The linear conductive agent has a mass content in the positive electrode active material layer of 0.1% to 2.5%, optionally 0.3% to 0.7%. In exemplary embodiments, the linear conductive agent may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, or any other typical but non-limiting content, or a range between any two of these content values. Since the crystals of the nickel-iron-manganese-based sodium positive electrode active material contained in the positive electrode material composition of the above-mentioned application embodiment include single crystals, and the morphology of the single crystals is blocky, a linear conductive agent is added to the positive electrode active material layer, and the content of the linear conductive agent is controlled within this range, so that the linear conductive agent can form a rich conductive network structure in the positive electrode active material layer, and the linear conductive agent can also be entangled on the surface of the blocky single crystal particles. The granular conductive agent can be effectively dispersed in the gaps of the positive electrode material composition. In this way, the linear conductive agent constructs a long-range conductive network structure in the positive electrode active material layer, and the granular conductive agent constitutes a short-range conductive structure. Therefore, the conductive synergistic effect of the linear conductive agent and the granular conductive agent in the positive electrode active material layer effectively improves the conductivity of the positive electrode active material layer, can significantly reduce the internal resistance of the positive electrode, and is also conducive to improving the DCR stability of the battery electrical properties during the charge and discharge process.

[0231] In an embodiment, the aspect ratio of the linear conductive agent can be controlled to be 40 to 3000:1, or optionally 50 to 2500:1. In exemplary embodiments, typical but non-limiting aspect ratios such as 40:1, 50:1, 100:1, 500:1, 1000:1, 1500:1, 2000:1, 2500:1, and 3000:1 can be used, or ranges between any two aspect ratios. The aspect ratio refers to the ratio of the length of the linear conductive agent to its diameter.

[0232] In a further embodiment, the length of the linear conductive agent can be selected to be 0.5 to 5 μm, or optionally 0.5 to 2 μm. In the exemplary embodiment, the length can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or other typical but non-limiting lengths or a range between any two length values.

[0233] In a further embodiment, the diameter of the linear conductive agent can be selected to be 2 to 10 nm, or optionally 3 to 7 nm. In the exemplary embodiment, the diameter can be 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or other typical but non-limiting diameters, or a range between any two diameter values.

[0234] By controlling the aspect ratio of the linear conductive agent within the above range, or further controlling the length and diameter of the linear conductive agent within the above range, the linear conductive agent can construct a richer long-range conductive network structure in the positive electrode active material layer, further enhancing the conductive synergistic effect of the linear conductive agent and the particulate conductive agent, thereby further improving the conductivity of the positive electrode active material layer.

[0235] In the embodiments, the positive electrode active material layer in the positive electrode of each embodiment above may contain other additives in addition to the positive electrode active material, binder, conductive agent and other components. In the embodiments, the additives may include but are not limited to functional components such as sodium supplement additives.

[0236] In some embodiments, the content of the positive electrode active material layer on a single surface of the current collector in each of the above embodiments, i.e., the coating weight (CW), is 260-350 mg / 1540.25 mm 2 , optional: 280~320mg / 1540.25mm 2 In the example, it can be 260mg / 1540.25mm 2 、270mg / 1540.25mm 2 、280mg / 1540.25mm 2 、290mg / 1540.25mm 2 、300mg / 1540.25mm 2 、310mg / 1540.25mm2 、320mg / 1540.25mm 2 、330mg / 1540.25mm 2 、340mg / 1540.25mm 2 、350mg / 1540.25mm 2 Typical but non-limiting content values, or ranges between any two content values, are provided. The coating weight refers to the weight of the positive electrode active material layer per unit area. A coating weight within this range can effectively stabilize the direct current resistance (DCR) of the battery cell during charge and discharge and improve the energy density of the battery cell.

[0237] In some embodiments, the compaction density of the positive electrode active material layer in the above embodiments, that is, the compaction density of the positive electrode sheet, can be 2.6 to 3.4 g / cm 3 , can be selected as 2.8~3.2g / cm 3 In the example, it can be 2.6g / cm 3 , 2.7g / cm 3 , 2.8g / cm 3 , 2.9g / cm 3 , 3.0g / cm 3 , 3.1g / cm 3 、3.2g / cm 3 , 3.3g / cm 3 、3.4g / cm 3 Typical but non-limiting compacted densities, such as [ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ], [ 6 ], [ 7 ], [ 8 ], [ 9 ], [ 10 ], [ 11 ], [ 12 ], [ 13 ], [ 14 ], [ 15 ], [ 16 ], [ 17 ], [ 18 ], [ 19 ], [ 20 ], [ 21 ], [ 22 ], [ 23 ], [ 24 ], [ 25 ], [ 26 ], [ 27 ], [ 28 ], [ 29 ], [ 30 ], [ 31 ], [ 32 ], [ 33 ], [ 34 ], [ 35 ], [ 36

[0238] In some embodiments, the porosity of the positive electrode active material layer in the above embodiments may be 40% to 70%, optionally 50% to 65%. In the exemplary embodiment, it may be 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 63%, 65%, 70% or other typical but non-limiting porosities or a range between any two porosity values. The porosity refers to the total volume of pores contained in the unit volume of the positive electrode active material layer and the percentage of the unit volume of the positive electrode active material layer. The porosity in this range can enable the positive electrode active material layer to have the above-mentioned compaction density, further improve the electrolyte wettability of the positive electrode and improve the stability of the interface contact with the electrolyte, and improve the relative stability of the DC internal resistance (DCR) of the battery cell during the charge and discharge process and the energy density of the battery cell. Among them, the porosity of the positive electrode active material layer (pole piece) in the above embodiments can be detected according to the following method:

[0239] The test is conducted by gas displacement method, with specific reference to GB / T24586-2009. The specific steps of the electrode porosity test method are as follows: the positive electrode of each battery cell in Examples B1 to B17 and Comparative Examples B1 to B2 is immersed in ethyl methyl carbonate (EMC) for cleaning, and then tested using the method specified in GB / T24586-2009. The gas displacement method is combined with Archimedes' principle and Bohr's law to accurately measure the true volume of the material being tested, which is the true volume of the sample, thereby obtaining the porosity of the sample to be tested. Among them, the percentage of the pore volume in a single electrode to the total volume of the electrode is the electrode porosity, calculated as follows: Porosity = (V-V0) / V×100%, where V0 is the true volume and V is the apparent volume.

[0240] In some embodiments, the positive electrode in each of the above embodiments is a pole piece, and the sheet resistance of the positive electrode active material layer in each of the above embodiments can be 0.5 to 5 mΩ, optionally 0.5 to 3 mΩ. In the exemplary embodiment, it can be 0.5 mΩ, 1 mΩ, 1.5 mΩ, 2 mΩ, 2.5 mΩ, 3 mΩ, 3.5 mΩ, 4 mΩ, 4.5 mΩ, 5 mΩ, etc., which are typical but non-limiting or ranges between any two sheet resistance values. The pole piece has the sheet-like morphology described above, and therefore, it has two opposite surfaces. The sheet resistance refers to the resistance value between one surface of the sheet-like positive electrode to the other opposite surface. The sheet resistance in this range can effectively improve the performance of the battery, including efficiency and life. Among them, the sheet resistance of the above pole piece can be detected according to the following method:

[0241] Refer to GB / T 30835-2014 or T / CASAS 019-2021 for testing; for the tester verification procedure, please refer to JJG 508-2004 for testing. Specifically, the four-probe method is used for detection: the positive electrode of each battery cell in Examples B1 to B17 and Comparative Examples B1 to B2 is respectively immersed in ethyl methyl carbonate (EMC) for cleaning, and tested by the method specified in GB / T 30835-2014 or T / CASAS 019-2021. Four copper plates with a length of 1.5 cm, a width of 1 cm, and a thickness of 2 mm are fixed equidistantly in a line, and the spacing between the two middle copper plates is L (1 cm to 2 cm). The substrate for fixing the copper plates is an insulating material. During the test, the lower end faces of the four copper plates are pressed against the electrode to be tested, and a direct current I is connected to the copper plates at both ends. The voltage V is measured at the two middle copper plates. The I and V values ​​are read three times, and the average of I and V is taken. V / I is the electrode resistance at the test point.

[0242] In some embodiments, the positive electrode is a pole piece in each of the above embodiments, and the ratio of the thickness from one surface of the pole piece to the other opposite surface to the thickness of the current collector is 7 to 15:1, optionally 8 to 14:1. In exemplary embodiments, it can be a typical but non-limiting ratio such as 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, or a range between any two ratios. The thickness refers to the vertical distance from one surface of the layer structure to the other opposite surface. When a positive electrode active material layer is provided on one surface of the current collector as shown in FIG1 , the thickness from one surface of the pole piece to the other opposite surface refers to the sum of the thickness of one positive electrode active material layer plus the thickness of the current collector; when both surfaces of the current collector as shown in FIG2 contain positive electrode active material layers, the thickness from one surface of the pole piece to the other opposite surface refers to the sum of the thickness of two positive electrode active material layers plus the total thickness of the current collector.

[0243] In an embodiment, the thickness of the positive electrode active material layer contained in the electrode sheet can be controlled to be 85 to 221 μm, and further can be 117 to 182 μm. In exemplary embodiments, the thickness can be 85 μm, 90 μm, 100 μm, 110 μm, 117 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 182 μm, 190 μm, 200 μm, 210 μm, 220 μm, 221 μm, or other typical but non-limiting thicknesses, or ranges between any two thickness values. In an embodiment, the thickness of the current collector can be, but is not limited to, 13 to 15 μm.

[0244] By controlling the total thickness of the electrode and the thickness of the current collector within the above-mentioned ratio range or specific thickness range, the structure of the positive electrode active material layer contained in the electrode can be effectively improved, such as regulating the pore structure, membrane resistance and capacity of the positive electrode active material layer, thereby further improving the electrolyte wettability of the positive electrode and improving the stability of the contact interface with the electrolyte, thereby improving the relative stability of the direct current internal resistance (DCR) of the battery cell during the charge and discharge process and the energy density and cycle performance of the battery cell and other electrochemical properties.

[0245] Preparation method of positive electrode:

[0246] The present application also provides a method for preparing the positive electrode of the above embodiment. In some embodiments, the method for preparing the positive electrode of the above embodiment includes the following steps:

[0247] S20: Mixing the components including the positive electrode active material, the binder, the conductive agent and the like in a solvent in proportion to prepare a positive electrode slurry;

[0248] S30: The positive electrode slurry is subjected to a film-forming treatment on the current collector to form a positive electrode active material layer to obtain a positive electrode.

[0249] Step S20:

[0250] The positive electrode active material in step S20 includes the positive electrode material composition of the embodiment of the present application.

[0251] In step S20, the positive electrode active material, binder, conductive agent and other components can be mixed according to the content ratio of the corresponding components in the positive electrode active material layer of the positive electrode. The solvent can be an organic solvent or water suitable for preparing the positive electrode slurry.

[0252] The mixing process in step S20 can be performed according to conventional electrode slurry preparation methods, such as, but not limited to, stirring, until the components are evenly dispersed to form a stable positive electrode slurry. Of course, the viscosity and other properties of the positive electrode slurry should meet the requirements of the film forming process so that a positive electrode active material layer that meets the quality requirements can be formed on the current collector.

[0253] Step S30:

[0254] Based on the positive electrode slurry components prepared in step S20, the positive electrode active material layer prepared in step S30 is the positive electrode active material layer contained in the positive electrode of the embodiment of the present application.

[0255] In step S30, the positive electrode slurry is formed into a film on the current collector using conventional methods for forming a positive electrode active material layer. For example, in the embodiment, the electrode slurry may be first formed into a wet film on the current collector; then, a drying process is performed to evaporate the solvent, thereby drying the wet film; and then, the dried film layer is roller-pressed to form a positive electrode active material layer, thereby obtaining a positive electrode.

[0256] Of course, the positive electrode active material layer can also be prepared by improving the conventional positive electrode active material layer preparation method, or by adopting a new method. As long as the electrode slurry in step S20 is used to prepare the positive electrode active material layer on the current collector, it is within the scope of the embodiments disclosed in the present application.

[0257] In addition, the film forming conditions in S30 can be controlled and adjusted, such as the conditions for forming a wet film on the current collector of the positive electrode slurry configured in step S20, the conditions for the roller pressing process, etc., and the related properties of the formed positive electrode active material layer can be controlled and adjusted, such as controlling and adjusting the content of the positive electrode active material layer on a single side of the current collector to 250-330 mg / 1540.25 mm as mentioned above. 2 Range, compaction density control and adjustment to 2.6 ~ 3.2g / cm 3 range, the porosity is controlled and adjusted to the range of 35% to 65% as mentioned above, and the diaphragm resistance of the electrode is controlled and adjusted to the range of 0.5 to 5 mΩ as mentioned above.

[0258] Battery

[0259] In a fourth aspect, an embodiment of the present application also provides a sodium battery.

[0260] In an embodiment, the sodium battery of the present application may include any one of a sodium battery cell, a battery module, and a battery pack.

[0261] Sodium battery cells:

[0262] A sodium battery cell, also known as a sodium battery cell, refers to a battery cell that includes the outer battery packaging and the electrode assembly encapsulated within the outer battery packaging. The number of electrode assemblies contained in a battery cell can be one or more, and can be adjusted according to actual needs.

[0263] The outer packaging of the sodium battery cell can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell; or a soft shell, such as a bag-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate. The outer packaging can be cylindrical, square, or any other shape. The outer packaging shape embodies the shape of the sodium battery cell, so the shape of the sodium battery cell can also be cylindrical, square, or any other shape that corresponds to the outer packaging. In this example, the sodium battery cell can be a square-shaped battery cell 20 as shown in Figure 3.

[0264] In some embodiments, as shown in FIG4 , the outer packaging of a battery cell 20 may include a housing 21 and a cover plate 23 . The housing 21 may include a bottom plate and side plates connected to the bottom plate, which together form a receiving cavity. The housing 21 has an opening communicating with the receiving cavity, and the cover plate 23 is used to cover the opening, thereby sealing the receiving cavity. One or more electrode assemblies 22 are enclosed in the receiving cavity.

[0265] In the embodiment, the sodium battery cell may be a sodium battery cell containing an electrolyte, or a sodium battery cell containing a solid electrolyte.

[0266] In the case of a sodium battery cell containing an electrolyte, the electrode assembly contained in the sodium battery cell generally includes a positive electrode, a negative electrode, and a separator. The positive and negative electrodes are alternately stacked, and the separator is stacked between the positive and negative electrodes to isolate the positive and negative electrodes. The positive electrode, separator layer, and negative electrode can be formed into a laminated electrode assembly through a lamination process, or a wound electrode assembly through a winding process. The separator-containing electrode assembly is placed in an outer packaging, and the electrolyte is injected to soak the electrode assembly. After packaging, the sodium battery cell is obtained.

[0267] In the case of a sodium battery cell containing a solid electrolyte, the electrode assembly typically includes a positive electrode, a negative electrode, and a solid electrolyte. The positive and negative electrodes are alternately stacked, with the solid electrolyte layered between them to act as an insulator, separating the positive and negative electrodes. The electrode assembly containing the solid electrolyte is placed in an outer packaging, and encapsulated to form a sodium battery cell.

[0268] In each of the aforementioned sodium battery cells, the electrode assembly contains the positive electrode of the embodiment described above, meaning that its positive electrode active material layer contains the positive electrode material composition of the embodiment described above. This ensures that the interface between the electrode assembly and the electrolyte in the sodium battery cells of the embodiment described above is stable, and the DC internal resistance (DCR) during charge and discharge is relatively stable, with a low DCR growth rate for the battery cells during charge and discharge. Furthermore, the battery cells also exhibit electrochemical properties such as high energy density and excellent cycle performance.

[0269] In each of the above-mentioned sodium battery cells, the negative electrode contained in the electrode assembly includes a negative electrode current collector and, optionally, a negative electrode active material layer disposed on the surface of the negative electrode current collector, wherein the negative electrode active material layer contains a negative electrode active material. In embodiments, the negative electrode current collector may include, but is not limited to, a metal or a composite current collector. For example, the metal may include sodium, sodium alloys, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, silver alloys, etc. When sodium or a sodium alloy is used as the negative electrode current collector, since the sodium or sodium alloy itself can also serve as the negative electrode active material, the negative electrode plate may not contain a negative electrode active material layer, and the sodium or sodium alloy serves as both the current collector and the negative electrode active material.

[0270] The composite current collector may include a composite material of a polymer and a metal. The polymer may include, but is not limited to, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc., and the metal may include, but is not limited to, sodium, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may be obtained by blending the polymer and the metal, or may be coated on at least one side of the polymer by electroplating, coating, or other methods.

[0271] When the negative electrode includes a negative electrode active material layer, the negative electrode active material in the negative electrode active material layer may include, but is not limited to, a mixture or composite material of any one or more of a carbon-based material, an alloy material, a titanium-based material, and sodium metal. Carbon-based materials include, but are not limited to, one or more of graphite, soft carbon, hard carbon, carbon microspheres, and carbon fibers; alloy materials include, but are not limited to, one or more of sodium-tin alloy, sodium-germanium alloy, and sodium-antimony alloy; and titanium-based materials include, but are not limited to, one or more of titanium dioxide, titanates, and titanium phosphates.

[0272] The mass content of the negative electrode active material in the negative electrode active material layer can be 85% to 98%, optionally 95% to 98%. In the exemplary embodiment, it can be 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% and other typical but non-limiting contents or a range between any two content values.

[0273] The negative electrode active material layer may also include at least one of a conductive agent and a binder. The conductive agent is used to collect current between the negative electrode active materials and between the active materials and the current collector, improving electronic conductivity. It also promotes electrolyte wetting of the negative electrode sheet. The binder improves the bonding strength between the various substances in the negative electrode active material layer and between the active layer and the current collector.

[0274] In an embodiment, the conductive agent may comprise 0.5% to 10% by weight of the negative electrode active material layer. In exemplary embodiments, the conductive agent may comprise 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any other typical but non-limiting content, or a range between any two content values. Other content values ​​may also be used as needed. In exemplary embodiments, the conductive agent comprises one or more of acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fiber, and graphene.

[0275] In an embodiment, the binder content in the negative electrode active material layer may be 0.5% to 10% by weight. In exemplary embodiments, the binder content may be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or other typical but non-limiting content, or a range between any two content values. Other content values ​​may also be set as needed. In exemplary embodiments, the binder includes, but is not limited to, one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyimide, polytetrafluoroethylene, polybutyl acrylate, polyacrylonitrile, carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylate, polyvinyl alcohol, sodium alginate, cyclodextrin, styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0276] In an embodiment, the negative electrode active material layer may optionally include a thickener, such as, but not limited to, carboxymethyl cellulose (CMC). The mass content of the thickener in the negative electrode active layer may be set to 0.5% to 5%. In exemplary embodiments, the content may be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or other typical but non-limiting content, or a range between any two content values.

[0277] In the embodiments, when each of the aforementioned sodium battery cells includes a separator, the separator, as described above, is disposed between the positive and negative electrodes to separate them. The separator prevents electrons from freely passing through the battery, preventing contact and short circuits between the electrodes, while allowing sodium ions in the electrolyte to freely pass between the positive and negative electrodes. The separator can be any known porous structure separator with electrochemical and mechanical stability. In exemplary embodiments, the separator comprises a single or multilayer film of at least one of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF).

[0278] In an embodiment, when each of the sodium battery cells contains a solid electrolyte, the solid electrolyte, as described above, is disposed between the positive electrode and the negative electrode to separate the positive electrode and the negative electrode. The solid electrolyte may include at least one of a polymer solid electrolyte, an oxide electrolyte, a sulfide electrolyte, a borohydride electrolyte, a composite solid electrolyte, and the like.

[0279] Testing has shown that after 1000 cls of charge-discharge cycles, the DC resistance (DCR) growth rate of each sodium battery cell in each of the above-described embodiments of the present application has been less than 180%. Therefore, the sodium battery cells containing the positive electrode material compositions of the above-described embodiments of the present application exhibit stable DC resistance (DCR) during the charge-discharge process, with a low DCR growth rate. The DCR of these sodium battery cells was tested using the method described in the following examples.

[0280] Further testing, as shown in the examples, shows that the operating voltage of the sodium battery cells of the present application examples is 1.5-4.0V, which means that the sodium battery cells of the present application examples can be discharged at 1.5-4.0V. In the examples, the energy density of the sodium battery cells of the present application examples at 1.5-4.0V can reach 120-130Wh / K. Therefore, the sodium battery cells of the present application examples also have high energy density.

[0281] The performance testing methods of the sodium battery single cell, such as DCR and energy density, are carried out according to the methods in the following examples.

[0282] Battery Module:

[0283] When the sodium battery in the embodiment of the present application is a battery module, the battery module refers to being assembled from the above-mentioned sodium battery cells, that is, it can contain multiple of the above-mentioned sodium battery cells, and the specific number can be adjusted according to the application and capacity of the battery module.

[0284] In some embodiments, FIG5 is a schematic diagram of an exemplary battery module 30. As shown in FIG5 , within the battery module 30, multiple sodium battery cells 20 may be arranged sequentially along the length of the battery module 30. Of course, any other arrangement is also possible. Furthermore, the multiple battery cells 20 may be secured together using fasteners.

[0285] Optionally, the battery module 30 may further include a housing having an accommodation space, and the plurality of sodium battery cells 20 are accommodated in the accommodation space.

[0286] Battery Pack:

[0287] When the sodium battery in the embodiments of the present application is a battery pack, the battery pack is assembled from the aforementioned sodium battery cells, that is, it may contain multiple sodium battery cells, and the multiple sodium battery cells are assembled into the aforementioned battery module. The specific number of battery cells or battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0288] In some embodiments, Figures 6 and 7 are schematic diagrams of an exemplary battery pack 40. The battery pack 40 may include a battery box and multiple battery modules 30 disposed within the battery box. The battery box includes an upper box body 41 and a lower box body 42. The upper box body 41 covers the lower box body 42 and forms an enclosed space for accommodating the battery modules 30. The multiple battery modules 30 may be arranged in any manner within the battery box.

[0289] Electrical devices

[0290] In a fifth aspect, the embodiments of the present application also provide an electric device. The electric device of the embodiments of the present application includes a power supply unit or an energy storage unit, and of course may also include other auxiliary components or necessary components. Among them, the power supply unit or energy storage unit contains the sodium battery of the above-mentioned embodiments of the present application. For example, it can be the above-mentioned sodium battery cell, battery module or battery pack. Since the electric device of the embodiments of the present application contains the sodium battery of the above-mentioned embodiments of the present application, the power supply unit or energy storage unit of the electric device of the embodiments of the present application has good cycle performance, high energy density, long service life, and the standby or endurance time of the electric device of the embodiments of the present application is long.

[0291] In the embodiments, the power-consuming device may include, but is not limited to, mobile phones, tablets, laptop computers, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, and the like. Among these, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft. As power-consuming devices, battery cells, battery modules, or battery packs may be selected based on their usage requirements.

[0292] FIG8 is a schematic diagram of an exemplary electric device. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device, a battery pack or battery module may be used.

[0293] In the embodiment, when the electrical device contains an energy storage unit, the electrical device can be an energy storage device, and the energy storage device includes the energy storage unit, and of course can also include other auxiliary components or necessary components. Among them, the energy storage unit contains the battery of the embodiment of the above text application. The battery contained in the energy storage unit can be one or more. When there are multiple batteries, multiple batteries can form a battery module or battery pack. Since the energy storage device of the embodiment of the present application contains the battery of the embodiment of the above text application, the energy storage device has high energy density, good cycle performance, long service life, and further high energy density.

[0294] Example

[0295] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0296] 1. Examples of Positive Electrode Material Compositions and Preparation Methods Thereof

[0297] Example A1

[0298] This embodiment provides a positive electrode material composition and a preparation method thereof. The positive electrode material composition includes two nickel-iron-manganese-based sodium cathode active materials, which are physically mixed in the proportions shown in Table 1 to form a mixture.

[0299] The method for preparing the positive electrode material composition comprises the following steps:

[0300] S1: Na as shown in chemical formula I 0.88 Ni 0.21 Fe 0.30 Mn 0.38 Zn 0.08 Ca 0.03 The molar ratio of metal elements contained in O2 is 800 rpm. NiO, ZnO, Mn2O3, Fe2O3 and CaO are ball-milled for 5 hours, and then sodium carbonate is added in proportion to mix them to obtain the precursor of chemical formula I; according to chemical formula II, Na 0.91 Ni 0.26 Fe 0.24 Mn 0.41 Cu0.08 Al 0.01 The molar ratio of the metal elements contained in O2 is 800 rpm. NiO, ZnO, Mn2O3, Fe2O3, CuO, and Al2O3 are ball-milled for 5 hours, and sodium carbonate is added in proportion to mix the mixture to obtain a precursor of chemical formula II.

[0301] S2: The precursors of Chemical Formula I and Chemical Formula II are sintered in a muffle furnace and crushed to obtain nickel-iron-manganese-based sodium cathode active materials represented by Chemical Formula I and Chemical Formula II, respectively, and then dry-mixed in a molar ratio of Formula II to Formula I of 0.5:1 to form a mixture; wherein the sintering conditions are: temperature: 800°C; time: 8h; heating rate: 10°C / min; oxygen atmosphere.

[0302] Example A2 to Example A7

[0303] Examples A2 to A7 provide a positive electrode material composition and a preparation method thereof. Compared with Example A1, the difference between the positive electrode material composition and Example A1 is that the physical mixing ratio of the two nickel-iron-manganese-based sodium positive electrode active materials is different, and the other aspects are the same as the positive electrode material composition in Example A1. Among them, the molar ratio of Formula II to Formula I in Example A2 is 0.6:1, the molar ratio of Formula II to Formula I in Example A3 is 1.5:1, the molar ratio of Formula II to Formula I in Example A4 is 3:1, the molar ratio of Formula II to Formula I in Example A5 is 4:1, the molar ratio of Formula II to Formula I in Example A6 is 5:1, and the molar ratio of Formula II to Formula I in Example A7 is 6:1.

[0304] The preparation methods of the positive electrode material compositions in Examples A2 to A7 are prepared with reference to the preparation method of the positive electrode material composition in Example A1.

[0305] Example A8

[0306] This embodiment provides a positive electrode material composition and a preparation method thereof. The positive electrode material composition includes two nickel-iron-manganese-based sodium cathode active materials, which are physically mixed in the proportions shown in Table 1 to form a mixture.

[0307] The method for preparing the positive electrode material composition comprises the following steps:

[0308] S1: Na as shown in chemical formula I 0.88 Ni 0.21 Fe 0.25 Mn 0.38 Zn 0.13 Ca 0.03The molar ratio of metal elements contained in O2 is 800 rpm. NiO, ZnO, Mn2O3, Fe2O3 and CaO are ball-milled for 5 hours, and then sodium carbonate is added in proportion to mix them to obtain the precursor of chemical formula I; according to chemical formula II, Na 0.91 Ni 0.26 Fe 0.24 Mn 0.35 Cu 0.14 Al 0.01 The molar ratio of the metal elements contained in O2 is 800 rpm. NiO, ZnO, Mn2O3, Fe2O3, CuO, and Al2O3 are ball-milled for 5 hours, and sodium carbonate is added in proportion to mix the mixture to obtain a precursor of chemical formula II.

[0309] S2: The precursors of Chemical Formula I and Chemical Formula II are sintered in a muffle furnace and crushed to obtain nickel-iron-manganese-based sodium cathode active materials represented by Chemical Formula I and Chemical Formula II, respectively, and then dry-mixed in a molar ratio of Formula II to Formula I of 6.3:1 to form a mixture; wherein the sintering conditions are: temperature: 800°C; time: 8h; heating rate: 10°C / min; oxygen atmosphere.

[0310] Example A9

[0311] This embodiment provides a positive electrode material composition and a preparation method thereof. The positive electrode material composition includes two nickel-iron-manganese-based sodium cathode active materials, which are physically mixed in the proportions shown in Table 1 to form a mixture.

[0312] The method for preparing the positive electrode material composition comprises the following steps:

[0313] S1: Na as shown in chemical formula I 0.88 Ni 0.15 Fe 0.30 Mn 0.38 Zn 0.14 Ca 0.03 The molar ratio of metal elements contained in O2 is 800 rpm. NiO, ZnO, Mn2O3, Fe2O3 and CaO are ball-milled for 5 hours, and then sodium carbonate is added in proportion to mix them to obtain the precursor of chemical formula I; according to chemical formula II, Na 0.91 Ni 0.26 Fe 0.24 Mn 0.46 Cu 0.04 Al 0.01The molar ratio of the metal elements contained in O2 is 800 rpm. NiO, ZnO, Mn2O3, Fe2O3, CuO, and Al2O3 are ball-milled for 5 hours, and sodium carbonate is added in proportion to mix the mixture to obtain a precursor of chemical formula II.

[0314] S2: The precursors of Chemical Formula I and Chemical Formula II are sintered in a muffle furnace and crushed to obtain nickel-iron-manganese-based sodium cathode active materials represented by Chemical Formula I and Chemical Formula II, respectively, and then dry-mixed in a molar ratio of Formula II to Formula I of 0.5:1 to form a mixture; wherein the sintering conditions are: temperature: 800°C; time: 8h; heating rate: 10°C / min; oxygen atmosphere.

[0315] Example A10

[0316] This embodiment provides a positive electrode material composition and a preparation method thereof. The positive electrode material composition includes two nickel-iron-manganese-based sodium cathode active materials, which are physically mixed in the proportions shown in Table 1 to form a mixture.

[0317] The method for preparing the positive electrode material composition comprises the following steps:

[0318] S1: Na as shown in chemical formula I 0.88 Ni 0.21 Fe 0.30 Mn 0.38 Ti 0.08 Zr 0.03 The molar ratio of the metal elements contained in O2 is 800 rpm. NiO, TiO2, Mn2O3, Fe2O3 and Ir2O3 are ball-milled for 5 hours, and then sodium carbonate is added in proportion to mix the mixture to obtain the precursor of chemical formula I. According to chemical formula II, Na 0.91 Ni 0.26 Fe 0.24 Mn 0.41 Cu 0.08 Al 0.01 The molar ratio of the metal elements contained in O2 is 800 rpm. NiO, ZnO, Mn2O3, Fe2O3, CuO, and Al2O3 are ball-milled for 5 hours, and sodium carbonate is added in proportion to mix the mixture to obtain a precursor of chemical formula II.

[0319] S2: The precursors of Chemical Formula I and Chemical Formula II are sintered in a muffle furnace and crushed to obtain nickel-iron-manganese-based sodium cathode active materials represented by Chemical Formula I and Chemical Formula II, respectively, and then dry-mixed in a molar ratio of 3:1 of Formula II to Formula I to form a mixture; wherein the sintering conditions are: temperature: 800°C; time: 8h; heating rate: 10°C / min; oxygen atmosphere.

[0320] Example A11

[0321] This embodiment provides a positive electrode material composition and a preparation method thereof. The positive electrode material composition includes two nickel-iron-manganese-based sodium cathode active materials, which are physically mixed in the proportions shown in Table 1 to form a mixture.

[0322] The method for preparing the positive electrode material composition comprises the following steps:

[0323] S1: Na as shown in chemical formula I 0.88 Ni 0.21 Fe 0.30 Mn 0.38 Mg 0.08 Sn 0.03 The molar ratio of the metal elements contained in O2 is 800 rpm. NiO, TiO2, Mn2O3, Fe2O3, and SnO2 are ball-milled for 5 hours, and then sodium carbonate is added in proportion to mix the mixture to obtain the precursor of chemical formula I; according to chemical formula II, Na 0.91 Ni 0.26 Fe 0.24 Mn 0.41 Cu 0.08 Al 0.01 The molar ratio of the metal elements contained in O2 is 800 rpm. NiO, ZnO, Mn2O3, Fe2O3, CuO, and Al2O3 are ball-milled for 5 hours, and sodium carbonate is added in proportion to mix the mixture to obtain a precursor of chemical formula II.

[0324] S2: The precursors of Chemical Formula I and Chemical Formula II are sintered in a muffle furnace and crushed to obtain nickel-iron-manganese-based sodium cathode active materials represented by Chemical Formula I and Chemical Formula II, respectively, and then dry-mixed in a molar ratio of 3:1 of Formula II to Formula I to form a mixture; wherein the sintering conditions are: temperature: 800°C; time: 8h; heating rate: 10°C / min; oxygen atmosphere.

[0325] Comparative Example A1

[0326] This comparative example provides a positive electrode material composition and a preparation method thereof. The positive electrode material composition comprises two nickel-iron-manganese-based sodium positive electrode active materials, which are physically mixed in the proportions shown in Table 1 to form a mixture.

[0327] The method for preparing the positive electrode material composition comprises the following steps:

[0328] S1: Na as shown in chemical formula I 0.88 Ni 0.15 Fe0.30 Mn 0.38 Zn 0.14 Ca 0.03 The molar ratio of the metal elements contained in O2 is 800 rpm. NiO, ZnO, Mn2O3, Fe2O3, and CaO are ball-milled for 5 hours, and then sodium carbonate is added in proportion to mix the mixture to obtain the precursor of chemical formula I; according to chemical formula II, Na 0.91 Ni 0.26 Fe 0.24 Mn 0.37 Cu 0.12 Al 0.01 The molar ratio of the metal elements contained in O2 is 800 rpm. NiO, ZnO, Mn2O3, Fe2O3, CuO, and Al2O3 are ball-milled for 5 hours, and sodium carbonate is added in proportion to mix the mixture to obtain a precursor of chemical formula II.

[0329] S2: The precursors of Chemical Formula I and Chemical Formula II are sintered in a muffle furnace and crushed to obtain nickel-iron-manganese-based sodium cathode active materials represented by Chemical Formula I and Chemical Formula II, respectively, and then dry-mixed in a molar ratio of Formula II to Formula I of 1:10 to form a mixture; wherein the sintering conditions are: temperature: 800°C; time: 8h; heating rate: 10°C / min; oxygen atmosphere.

[0330] 2. Examples of positive electrodes and sodium-ion battery cells

[0331] Example B1 to Example B11

[0332] Embodiments B1 to B11 each provide a sodium ion battery cell. Each sodium ion battery cell includes an electrode assembly formed by a positive electrode sheet, a separator, and a negative electrode sheet, and also includes an electrolyte.

[0333] The sodium ion battery cells in Examples B1 to B11 are assembled as follows:

[0334] Positive electrode sheet: Sodium ion positive electrode active material, conductive agent carbon nanotubes, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are thoroughly stirred and mixed in an appropriate amount of solvent NMP in a weight ratio of 95:0.5:2:2.5 to form a uniform positive electrode slurry; the positive electrode slurry is evenly coated on the surface of a 13 μm positive electrode current collector aluminum foil, and after drying and cold pressing, the positive electrode sheets contained in Examples B1 to B10 are obtained; wherein the sodium ion positive electrode active material is the positive electrode material composition in the above-mentioned Examples A1 to A10 respectively; the positive electrode sheet contained in Example B1 is the positive electrode sheet contained in Example B1 using the positive electrode material composition in Example A11 as the positive electrode material, and the carbon nanotubes contained therein are replaced with carbon fibers, and the content thereof is controlled to be 0.8%. As shown in Table 2, the total content of the conductive agent in the positive electrode sheet contained in Example B1 is the same as the total content of the conductive agent contained in the positive electrode sheet of Example B1.

[0335] Negative electrode sheet: Add hard carbon, conductive agent SP, and CMC binder into deionized water in a weight ratio of 8:1:1 and stir thoroughly to form a uniform negative electrode slurry; evenly apply the slurry on the surface of 6μm copper foil, dry and cold press to obtain the negative electrode sheet.

[0336] Electrolyte: In an environment with a water content of less than 10 ppm, the non-aqueous organic solvents ethylene carbonate (EC) and diethyl carbonate (DMC) are mixed in a volume ratio of 1:1 to obtain an electrolyte solvent. Subsequently, sodium hexafluorophosphate and the mixed solvent are mixed to prepare an electrolyte with a sodium salt concentration of 1 mol / L.

[0337] Isolation membrane: porous polyethylene (PE) film is used as the isolation membrane.

[0338] Battery assembly: The aforementioned positive electrode sheets, separators, and negative electrode sheets are stacked in sequence, with the separators positioned between the positive and negative electrode sheets to provide isolation. The electrode assemblies are then laminated to obtain an electrode assembly. Each electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum packaging, standing, forming, and shaping, the sodium-ion battery cells of Examples B1 to B11 are obtained. The sodium-ion positive electrode active material in Example B1 is the positive electrode material composition of Example A1, the sodium-ion positive electrode active material in Example B2 is the positive electrode material composition of Example A2, and so on. The sodium-ion positive electrode active material in Example B11 is the positive electrode material composition of Example A11.

[0339] Comparative Example B1

[0340] This comparative example B1 provides a sodium ion battery cell, each of which includes an electrode assembly formed by a positive electrode sheet, a separator and a negative electrode sheet, and also includes an electrolyte.

[0341] The sodium ion battery monomers in Comparative Example B1 were prepared with reference to the sodium ion battery monomers in Example B1. The differences are:

[0342] In the sodium ion battery cell of Comparative Example B1, the sodium ion positive electrode active material contained in the positive electrode sheet of the sodium ion battery cell is the positive electrode material composition of Comparative Example A1.

[0343] 2. Related performance tests of the positive electrode material composition and sodium ion battery monomer in each embodiment:

[0344] 2.1 Characterization and related performance tests of the positive electrode material compositions of each embodiment:

[0345] The positive electrode material compositions provided in Examples A1 to A11 and Comparative Example A1 were tested for the relevant characteristics listed in Table 1 according to the following methods. The test results are shown in Table 1:

[0346] Method for detecting the element content of nickel-iron-manganese-based sodium cathode active material: Agilent ICP-OES730 was used to obtain inductively coupled plasma emission spectroscopy (ICP), and then the ICP results were used to calculate the content of each metal element in the cathode material compositions provided in Examples A1 to A11 and Comparative Example A1, respectively. The molar content of each metal element in the cathode material composition per unit mole was converted according to the molar mixing ratio of each nickel-iron-manganese-based sodium cathode active material in each composition.

[0347] Charge / discharge gram capacity detection method: The charge / discharge gram capacity of the positive electrode material compositions provided in Examples A1 to A11 and Comparative Example A1 was measured according to the charge / discharge gram capacity detection method of the positive electrode material compositions in the above application examples.

[0348] 2.2 Performance tests of sodium ion battery cells and the positive electrode sheets contained therein in each embodiment:

[0349] The sodium ion battery cells and the positive electrode sheets contained therein provided in Examples B1 to B11 and Comparative Example B1 were subjected to the relevant performance tests listed in Table 2 according to the following methods. The test results are shown in Table 2:

[0350] CW detection method: The positive electrodes of the battery cells in Examples B1 to B17 and Comparative Examples B1 to B2 were punched and filled into 1540.25 mm 2 The weight of the electrode is obtained by weighing and subtracting the weight of the aluminum foil, which is recorded as the weight of the active material layer / 1540.25mm 2 .

[0351] Positive electrode sheet compaction density test method: The specific compaction density of the positive electrode sheet can refer to the first discharge specific capacity and first charge and discharge efficiency test method of lithium manganese oxide, the positive electrode material of lithium-ion batteries, for details, see GB / T 39864-2021 or GB / T 42161-2022. For specific reference, please refer to the test steps of the following parameters:

[0352] The positive electrodes of the battery cells in Examples B1 to B17 and Comparative Examples B1 to B2 were punched out into positive electrode sheets with a diameter of 14 mm using a punching machine, and the mass m of the positive electrode sheets was measured using an electronic balance and a desktop digital display thickness gauge. c , thickness d c Use a punching machine to punch out a sufficient number of aluminum foil substrates with a diameter of 14 mm, and use an electronic balance and a desktop digital thickness gauge to measure the mass m of the aluminum foil substrates respectively Al , thickness d Al ; Calculate the compaction density of each positive electrode sheet according to the following formula:

[0353] Positive electrode compaction density

[0354] Where: c is the compacted density of the positive electrode, in grams per cubic centimeter (g / cm 3 );

[0355] m c is the mass of the positive electrode, in grams (g);

[0356] m Al is the mass of the aluminum foil substrate, in grams (g);

[0357] is the diameter of the positive electrode sheet, in millimeters (mm);

[0358] d c is the thickness of the positive electrode sheet, in micrometers (μm);

[0359] d Al is the thickness of the aluminum foil substrate, in micrometers (μm).

[0360] Cycle Retention (%): At 25°C, each battery cell in Examples B1 to B17 and Comparative Examples B1 to B2 was charged at a constant current of 0.33C to 3.85V, then charged at a constant voltage of 3.85V to a current of 0.05C, and then discharged at a constant current of 1C to 1.5V. This constituted one charge-discharge cycle. Taking the initial discharge capacity as 100%, the capacity retention after 1000 cycles was calculated. Capacity retention (%) after 1000 cycles = discharge capacity at the 1000th cycle / initial discharge capacity × 100%.

[0361] Energy density: Each battery cell in Examples B1 to B17 and Comparative Examples B1 and B2 was charged at a rate of 0.33C at room temperature to a voltage of 4.2V, then discharged at a rate of 0.33C to a voltage of 2.0V. The discharge energy, S0, was measured. The mass, M, of the battery cell corresponding to S0 was then measured, and the battery cell energy density (mass energy density) was calculated using the formula, S0 / M.

[0362] Resistance value (DCR) growth rate (%): At 25°C, the battery cell was charged at a constant current rate of 0.33C to a voltage of 4.1V, allowed to stand for 5 minutes, discharged at 1C to 1.5V, allowed to stand for 15 minutes, and then charged at a constant current rate of 0.33C to a voltage of 4.1V and discharged at 0.33C to 50% SOC. After standing for 30 minutes, the voltage was recorded. The battery cell was pulse discharged at 4C for 30 seconds, and the voltage after the pulse discharge was recorded.

[0363] At 25°C, after cycling for 1000cls, the cell was charged at a constant current rate of 0.33C to a voltage of 4.1V, allowed to stand for 5 minutes, discharged at 1C to 1.5V, allowed to stand for 15 minutes, charged at a constant current rate of 0.33C to a voltage of 4.1V again, and discharged at 0.33C to 50% SOC. After standing for 30 minutes, the voltage was recorded, and the cell was pulse discharged at 4C for 30 seconds, and the voltage after pulse discharge was recorded.

[0364] The DCR is calculated according to the formula: DCR = (static end voltage - pulse discharge voltage) / pulse current.

[0365] DCR growth rate = cell DCR after 1000 cycles / initial cell DCR.

[0366] Table 1

[0367] Table 2

[0368] Based on Tables 1 and 2 above, it can be seen from the comparison of the embodiments and the comparative examples that the total molar content of the raw materials of nickel, manganese and copper elements and the metal element represented by Q in the positive electrode material composition of the embodiment of the present application is adjusted and controlled within a certain range. The stability of the direct current resistance (DCR) of the corresponding sodium ion battery single cell can be improved. Under the same charge and discharge conditions, the DCR growth rate of the sodium ion battery single cell is controlled within the corresponding range.

[0369] Further comparisons of Examples A1 to A7 with Examples A8 to A9, and of Examples B1 to B7 with Examples B8 to B9, show that simultaneously adjusting the copper and zinc elements in the positive electrode material composition can significantly affect the stability of the DCR of the corresponding sodium-ion battery cells. For example, when the copper and zinc elements in the positive electrode material composition are adjusted to the molar amounts of Examples A8 and A9, respectively, the DCR growth rate of the corresponding sodium-ion battery cells is higher than the DCR growth rate of the sodium-ion battery cells in Examples B1 to B7. Therefore, the total molar content of copper and zinc in the positive electrode material composition can improve the DCR growth of the battery cells.

[0370] It can be seen from Examples A4, A10 to A11 and B4, B10 to B11 that when the zinc element contained in the positive electrode material composition of the embodiment of the present application is replaced with magnesium and titanium, the DCR of the sodium ion battery cell containing the corresponding positive electrode material composition can be kept relatively stable during the charge and discharge process. For example, under the same charge and discharge conditions, the DCR growth rate of the sodium ion battery cell in Examples B10 to B11 is less than 180%.

[0371] On this basis, based on Table 1 and Table 2, it can be seen that the positive electrode material composition containing the embodiment of the present application has a relatively high gram capacity, and the corresponding sodium ion battery single cell also has good energy density and cycle performance.

[0372] Based on Table 2, it can be seen that the positive electrode sheet containing the positive electrode material composition of the embodiment of the present application can achieve a higher compaction density. Therefore, the positive electrode material composition of the embodiment of the present application can enable the electrode sheet to have a relatively high electrode sheet compaction density.

[0373] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A positive electrode material composition, characterized in that: The invention comprises at least two nickel-iron-manganese-based sodium positive electrode active materials, each of which is physically mixed, and the mixture of the nickel-iron-manganese-based sodium positive electrode active materials further contains Cu element and Q element, and the total molar content of Na in the positive electrode material composition per unit mole is 0.78 to 1 mol; The total molar content of Ni is 0.12-0.38 mol; The total molar content of Mn is 0.18-0.48 mol; The total molar content of Fe is 0.18-0.35 mol; The total molar content of Q is 0.01 to 0.12 moL; The total molar content of Cu is 0.01-0.14 mol; The Q includes at least one element of Zn, Mg, and Ti.

2. The positive electrode material composition according to claim 1, characterized in that In the positive electrode material composition per unit mole, the molar content of at least one element among Na, Ni, Mn, Fe, Cu and Y is: The total molar content of Na is 0.8 to 1 mol; The total molar content of Ni is 0.15-0.35 mol; The total molar content of Mn is 0.20-0.45 mol; The total molar content of Fe is 0.20-0.33 mol; The total molar content of Q is 0.01 to 0.06 moL; The total molar content of Cu is 0.02-0.09 mol.

3. The positive electrode material composition according to claim 1 or 2, characterized in that: At least one of the nickel-iron-manganese-based sodium positive electrode active materials further contains active and / or inert doping metal elements, and the total molar content of the doping metal elements in the unit molar amount of the positive electrode material composition is greater than 0 and less than or equal to 0.13 mol; and / or In the positive electrode material composition per unit mole, the molar content of the Na element and the total molar content of other metal elements are in a ratio of (0.81 to 0.89):1; and / or The Cu element and the Q element are distributed in different nickel-iron-manganese-based sodium positive electrode active materials.

4. The positive electrode material composition according to any one of claims 1 to 3, characterized in that: At least one of the nickel-iron-manganese-based sodium positive electrode active materials further contains active and / or inert doping metal elements, and the total molar content of the doping metal elements in the unit molar amount of the positive electrode material composition is greater than 0 and less than or equal to 0.1 mol; and / or In the positive electrode material composition per unit mole, the ratio of the molar content of the Na element to the total molar content of other metal elements is (0.82-0.89):

1.

5. The positive electrode material composition according to claim 3 or 4, characterized in that: The doping metal element includes at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ru, and Ir.

6. The positive electrode material composition according to any one of claims 1 to 5, characterized in that: The nickel-iron-manganese-based sodium positive electrode active material containing the Q element includes at least one of the following (1) to (4): (1) Dv50 particle size is 3 to 8 μm; (2) Dv90 particle size is 8 to 16 μm; (3) The compaction density under 3 tons of pressure is higher than 3.1g / cm 3 ; (4) Specific surface area is 0.4 to 1.0 m 2 / g.

7. The positive electrode material composition according to any one of claims 1 to 6, characterized in that: The nickel-iron-manganese-based sodium positive electrode active material containing the Q element includes at least one of the following (1) to (4): (1) Dv50 particle size is 4 to 6.5 μm; (2) Dv90 particle size is 10-14 μm; (3) The compaction density under 3 tons of pressure is 3.1-3.4 g / cm 3 ; (4) Specific surface area is 0.6 to 0.9 m 2 / g.

8. The positive electrode material composition according to any one of claims 1 to 7, characterized in that: The nickel-iron-manganese-based sodium positive electrode active material containing the Cu element includes at least one of the following (1) to (4): (1) Dv50 particle size is 5 to 11 μm; (2) Dv90 particle size is 13-19 μm; (3) The compaction density under 3 tons of pressure is 3.0-3.3 g / cm 3 ; (4) Specific surface area is 0.4 to 0.7 m 2 / g.

9. The positive electrode material composition according to any one of claims 1 to 8, characterized in that: The nickel-iron-manganese-based sodium positive electrode active material containing the Cu element includes at least one of the following (1) to (4): (1) Dv50 particle size is 6.5 to 10 μm; (2) Dv90 particle size is 14.5-18 μm; (3) The compaction density under 3 tons of pressure is 3.0-3.25 g / cm 3 ; (4) Specific surface area is 0.5 to 0.6 m 2 / g.

10. The positive electrode material composition according to any one of claims 1 to 9, characterized in that: Each of the nickel-iron-manganese-based sodium positive electrode active materials independently comprises at least one of the following (1) to (2): (1) The crystal structure includes an O3 phase layered metal oxide, and the O3 phase layered metal oxide accounts for more than 95% of the total weight of the layered oxide; (2) comprising a single crystal, wherein the single crystal has a block-like morphology; and / or The positive electrode material composition has a discharge capacity of 115 to 128 mAh / g at 1.5 to 4.2 V and 0.1 C.

11. The positive electrode material composition according to any one of claims 1 to 10, characterized in that: The positive electrode material composition has a discharge capacity of 120 to 128 mAh / g at 1.5 to 4.2 V and 0.1 C.

12. A method for preparing the positive electrode material composition according to any one of claims 1 to 11, characterized in that: The steps include: At least two nickel-iron-manganese-based sodium positive electrode active materials are physically mixed according to the molar content ratio of Na, Ni, Mn, Fe, Q and Cu contained in the positive electrode material composition per unit mole to form a positive electrode material composition.

13. A positive electrode, comprising a positive electrode active material layer, characterized in that: The positive electrode active material layer comprises the positive electrode material composition according to any one of claims 1 to 11.

14. The positive electrode according to claim 13, characterized in that: The content of the positive electrode active material layer on a single surface of the current collector is 260-350 mg / 1540.25 mm 2 ; and / or The compaction density of the positive electrode is 2.6-3.4 g / cm 3 ; and / or The porosity of the positive electrode active material layer is 40% to 70%; and / or The positive electrode is a pole piece, and the ratio of the thickness from one surface of the pole piece to the other opposite surface to the thickness of the current collector is 7 to 15:1; and / or The positive electrode is a pole piece, and the film resistance of the pole piece is 0.5-5 mΩ; and / or The conductive agent contained in the positive electrode active material layer includes a linear conductive agent.

15. The positive electrode according to claim 13 or 14, characterized in that: The content of the positive electrode active material layer on a single surface of the current collector is 280-320 mg / 1540.25 mm 2 ; and / or The compaction density of the positive electrode is 2.8-3.2 g / cm 3 ; and / or The porosity of the positive electrode active material layer is 50% to 65%; and / or The positive electrode is a pole piece, and the ratio of the thickness from one surface of the pole piece to the other opposite surface to the thickness of the current collector is 8 to 14:1; and / or The positive electrode is a pole piece, and the membrane resistance of the pole piece is 0.5-3 mΩ.

16. The positive electrode according to claim 14, characterized in that: The linear conductive agent includes at least one of the following (1) to (5): (1) The mass content of the positive electrode active material layer is 0.1% to 2.5%; (2) Aspect ratio of 40 to 3000:1; (3) Length: 0.5 to 5 μm; (4) Diameter is 2 to 10 nm; (5) Includes at least one of carbon nanotubes, carbon fibers, and conductive oxide nanowires.

17. The positive electrode according to claim 16, characterized in that: The linear conductive agent includes at least one of the following (1) to (4): (1) The mass content of the positive electrode active material layer is 0.3 to 0.7%; (2) Aspect ratio of 50 to 2500:1; (3) Length: 0.5 to 2 μm; (4) The diameter is 3 to 7 nm.

18. A sodium battery, characterized in that: The positive electrode comprises the positive electrode according to any one of claims 13 to 17.

19. The sodium battery according to claim 18, characterized in that: The sodium battery is a sodium battery cell, and the sodium battery cell includes at least one of the following (1) to (3): (1) The operating voltage is 1.5 to 4.0 V; and / or (2) Energy density of 120-130Wh / Kg at 1.5-4.0V; (3) After 1000 cls, the DC resistance growth rate of the sodium battery cell is less than 180%.

20. An electrical device, characterized in that: Including the sodium battery according to claim 18 or 19.