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

Abstract

The invention discloses a positive electrode material composition and a preparation method thereof, a positive electrode, a sodium battery and an electric device. The positive electrode material composition comprises at least two nickel-iron-manganese-based sodium battery positive electrode active materials, the nickel-iron-manganese-based sodium battery positive electrode active materials are physically mixed, and the mixture of the nickel-iron-manganese-based sodium battery positive electrode active materials further contains a Cu element and a Q element. The positive electrode contains the positive electrode material composition, and the sodium battery contains the positive electrode. The electric device comprises the sodium battery. The positive electrode material composition can improve the direct-current internal resistance stability of the electrical property of the battery in the charging and discharging process.

Description

Technical Field

[0001] This application belongs to the technical field of sodium batteries, and particularly relates to a cathode material composition, a preparation method thereof, a cathode, a sodium battery, and an electrical device. Background Art

[0002] Sodium-ion batteries have the advantages of rich raw material reserves, low price, relatively stable chemical properties, and good safety, and are expected to replace lithium-ion batteries in the market. With the continuous development of new energy vehicles and the increasing proportion of clean energy, higher requirements are put forward for the energy conversion efficiency, energy density, and cycle stability of ion batteries.

[0003] Among them, the impedance and impedance stability of the battery cell are one of the important factors affecting the energy conversion efficiency of the cell. However, the impedance stability of current battery cells such as sodium batteries still needs to be further improved to better meet the current market needs for battery applications. Summary of the Invention

[0004] In view of the above problems, this application provides a cathode material composition, a preparation method thereof, a cathode containing the cathode material composition, and a sodium battery containing the cathode, so as to solve the technical problem that the impedance stability of the existing battery cell is not ideal.

[0005] In a first aspect, an embodiment of this application provides a cathode material composition. The cathode material composition in the embodiment of this application includes at least two nickel-iron-manganese-based sodium battery cathode active materials, and the nickel-iron-manganese-based sodium battery cathode active materials are physically mixed. The mixture of the nickel-iron-manganese-based sodium battery cathode active materials also contains Cu element and Q element. In the cathode material composition with a unit molar amount, the total molar content of Na is 0.78 - 1 moL;

[0006] The total molar content of Ni is 0.12 - 0.38 moL;

[0007] The total molar content of Mn is 0.18 - 0.48 moL;

[0008] The total molar content of Fe is 0.18 - 0.35 moL;

[0009] The total molar content of Q is 0.01 - 0.12 moL;

[0010] The total molar content of Cu is 0.01 - 0.14 moL;

[0011] The Q includes at least one element of Zn, Mg, and Ti.

[0012] In the positive electrode material composition of the embodiment of the present application, two or more nickel-iron-manganese-based sodium-ion battery positive electrode active materials are used to form a physical mixture, and the contents of metal elements such as Na, Ni, Mn, Fe, Cu, and Q elements contained in the mixture are controlled within the above ranges, so that the direct current internal resistance (DCR) of the battery cell containing the positive electrode material composition of the embodiment of the present application is relatively stable during charge and discharge, and the growth rate of DCR of the battery cell during charge and discharge can be significantly reduced. On this basis, the energy density and cycle performance of the battery cell can also be improved.

[0013] In some embodiments, in one unit mole of the positive electrode material composition, the molar content of at least one of the elements Na, Ni, Mn, Fe, Cu, and Y is:

[0014] The total molar content of Na is 0.8 to 1 mol;

[0015] The total molar content of Ni is 0.15 to 0.35 mol;

[0016] The total molar content of Mn is 0.20 to 0.45 mol;

[0017] The total molar content of Fe is 0.20 to 0.33 mol;

[0018] The total molar content of Q is 0.01 to 0.06 mol;

[0019] The total molar content of Cu is 0.02 to 0.09 mol.

[0020] By selectively controlling the total molar content of at least one of the metal elements Na, Ni, Mn, Fe, Cu, and the metal element represented by Q within the above ranges, the disordered arrangement of metal elements in the transition metal layer contained in each nickel-iron-manganese-based sodium-ion battery positive electrode active material can be further adjusted, and the spacing between the transition metal layer and the sodium layer can be adjusted to further improve the stability of the direct current internal resistance (DCR) of the battery cell containing the positive electrode material composition of the embodiment of the present application during charge and discharge. In particular, the Cu element and the metal element represented by Q within the above range of contents can improve the synergistic effect on the DCR stability of the battery cell, and further improve the DCR stability of the battery cell. At the same time, the cycle performance and the utilization of specific capacity of each nickel-iron-manganese-based sodium-ion battery positive electrode active material are further improved.

[0021] In some embodiments, at least one of the nickel-iron-manganese-based sodium-ion battery cathode active materials further contains active and / or inert doped metal elements. In the positive electrode material composition per unit mole, the total molar content of the doped metal elements is greater than 0 and less than or equal to 0.13 mol, and may be selected to be greater than 0 and less than or equal to 0.1 mol. The doped metal elements within this content range can participate in the disordered arrangement among the metal elements in the transition metal layer contained in the nickel-iron-manganese-based sodium-ion battery cathode active material and can adjust the spacing between the transition metal layer and the sodium layer, and can also improve the relevant electrochemical properties of each nickel-iron-manganese-based sodium-ion battery cathode 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 charge and discharge, so as to alleviate the increase in DCR of the battery cell during charge and discharge. At the same time, it can also improve the structural stability and / or the discharge capacity of the nickel-iron-manganese-based sodium-ion battery cathode active material.

[0022] In the demonstration example, the doped metal elements include at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ru, and Ir. These types of doped metal elements dope the transition metal layer contained in the nickel-iron-manganese-based sodium-ion battery cathode active material containing the doped metal elements, adjust the disordered arrangement of the metal elements in the transition metal layer and can adjust the spacing 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 charge and discharge, so as to alleviate the increase in DCR of the battery cell during charge and discharge and improve the structural stability and / or the discharge capacity of the nickel-iron-manganese-based sodium-ion battery cathode active material.

[0023] In some embodiments, in the positive electrode material composition per unit mole, the molar content ratio of the Na element to the total molar content of other metal elements is (0.81 - 0.89):1, and may be selected to be (0.82 - 0.89):1. Controlling the molar total content ratio 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 intercalated and deintercalated in the nickel-iron-manganese-based sodium-ion battery cathode active material, thereby increasing the reversible capacity of the positive electrode material composition; and it can also improve the structural stability of the nickel-iron-manganese-based sodium-ion battery cathode active material to improve its cycle performance.

[0024] In some embodiments, the Cu element and the Q element are distributed in different nickel-iron-manganese-based sodium-ion battery cathode active materials. By mixing the nickel-iron-manganese-based sodium-ion battery cathode active material containing the Cu element and the nickel-iron-manganese-based sodium-ion battery cathode active material containing the Q element to form a mixture, it is possible to balance the discharge capacity and cycle performance of the positive electrode material composition of the embodiment of the present application, and at the same time, it 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 charge and discharge, so as to alleviate the increase in DCR of the battery cell during charge and discharge.

[0025] In the examples, the nickel-iron-manganese-based sodium-ion battery positive electrode active material containing the Q element includes at least one of the following (1) to (4):

[0026] (1) The Dv50 particle size is 3 to 8 μm, and may be 4 to 6.5 μm;

[0027] (2) The Dv90 particle size is 8 to 16 μm, and may be 10 to 14 μm;

[0028] (3) The tap density under 3 tons of pressure is higher than 3.1 g / cm 3 , and may be 3.1 to 3.4 g / cm 3 ;

[0029] (4) The specific surface area is 0.4 to 1.0 m 2 / g, and may be 0.6 to 0.9 m 2 / g.

[0030] In the examples, the nickel-iron-manganese-based sodium-ion battery positive electrode active material containing the Cu element includes at least one of the following (5) to (8):

[0031] (5) The Dv50 particle size is 5 to 11 μm, and may be 6.5 to 10 μm;

[0032] (6) The Dv90 particle size is 13 to 19 μm, and may be 14.5 to 18 μm;

[0033] (7) The tap density under 3 tons of pressure is 3.0 to 3.3 g / cm 3 , and may be 3.0 to 3.25 g / cm 3 ;

[0034] (8) The specific surface area is 0.4 to 0.7 m 2 / g, and may be 0.5 to 0.6 m 2 / g.

[0035] The nickel-iron-manganese-based sodium-ion battery positive electrode active material containing the Q element and the nickel-iron-manganese-based sodium-ion battery positive electrode active material containing the Cu element have the above range characteristics, which can improve the performance such as the stability of the contact interface between the positive electrode material composition of the examples of the present application and the electrolyte, and improve the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the examples of the present application during charge and discharge. At the same time, it can also improve the specific capacity and cycle performance of the positive electrode material composition of the examples of the present application.

[0036] In some examples, each of the nickel-iron-manganese-based sodium-ion battery positive electrode active materials independently includes at least one of the following (1) to (2):

[0037] (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

[0038] (2) It includes a single crystal, and the morphology of the single crystal is blocky.

[0039] The selected O3-phase nickel-iron-manganese-based sodium-ion battery cathode active material has relatively high structural stability, improving the cycling performance of the battery cell.

[0040] In some embodiments, the discharge specific capacity of the cathode material composition is 115-128 mAh / g at 1.5-4.2 V and 0.1 C, and can be optionally 120-128 mAh / g.

[0041] In a second aspect, an embodiment of the present application provides a method for preparing a cathode material composition. The method for preparing the cathode material composition according to the embodiment of the present application includes the following steps:

[0042] According to the molar content ratios of Na, Ni, Mn, Fe, Q, and Cu contained in the cathode material composition described above per unit molar amount, at least two nickel-iron-manganese-based sodium-ion battery cathode active materials are physically mixed to form a cathode material composition.

[0043] The method for preparing the cathode material composition according to the embodiment of the present application mixes at least two nickel-iron-manganese-based sodium-ion battery cathode active materials according to the ratios of the content ranges of Na, Ni, Mn, Fe, Cu, and Q elements, so that the growth rate of the direct current internal resistance (DCR) of the battery cell containing the cathode material composition according to the embodiment of the present application during charge and discharge is small, and the cathode material composition according to the embodiment of the present application also has a high specific capacity and cycling performance.

[0044] In a third aspect, an embodiment of the present application provides a cathode. The cathode according to the embodiment of the present application includes a cathode active material layer, and the cathode active material layer includes the cathode material composition according to the embodiment of the present application or the cathode material composition prepared by the method for preparing the cathode material composition according to the embodiment of the present application.

[0045] Since the cathode active material layer of the cathode according to the embodiment of the present application contains the cathode material composition according to the above embodiment of the present application. Therefore, the growth rate of the direct current internal resistance (DCR) of the battery cell containing the cathode according to the embodiment of the present application during charge and discharge is small. At the same time, the battery cell has a high energy density and good cycling performance.

[0046] In some embodiments, the content of the cathode active material layer on a single side of the current collector is 260-350 mg / 1540.25 mm 2 , and can be optionally 280-320 mg / 1540.25 mm 2 .

[0047] In some embodiments, the compaction density of the positive electrode sheet is 2.6 to 3.4 g / cm 3 , optionally 2.8 to 3.2 g / cm 3 .

[0048] In some embodiments, the porosity of the positive electrode active material layer is 40% to 70%, optionally 50% to 65%.

[0049] In some embodiments, the positive electrode is a sheet, and the ratio of the thickness from one surface of the sheet to the opposite surface to the thickness of the current collector is 7 to 15:1, optionally 8 to 14:1.

[0050] In some embodiments, the positive electrode is a sheet, and the sheet resistance of the sheet is 0.5 to 5 mΩ, optionally 0.5 to 3 mΩ.

[0051] When the positive electrode in the embodiment of the present application has the above range characteristics, the stability of the contact interface between the sheet and the electrolyte enables the direct current internal resistance (DCR) of the battery cell containing the positive electrode in the embodiment of the present application to be relatively stable during charge and discharge, the battery cell has a high energy density and good cycling performance

[0052] In some embodiments, the conductive agent contained in the positive electrode active material layer includes a linear conductive agent.

[0053] In the embodiment, the linear conductive agent includes at least one of the following (1) to (5):

[0054] (1) The mass content ratio in the positive electrode active material layer is 0.1% to 2.5%, optionally 0.3 to 0.7%;

[0055] (2) The aspect ratio is 40 to 3000:1, optionally 50 to 2500:1;

[0056] (3) The length is 0.5 to 5 μm, optionally 0.5 to 2 μm;

[0057] (4) The diameter is 2 to 10 nm, optionally 3 to 7 nm;

[0058] (5) Includes at least one of carbon nanotubes, carbon fibers, and conductive oxide nanowires.

[0059] 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, and the type, aspect ratio, length, diameter, etc. of the linear conductive agent are selected and controlled within the above 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 wound around the surface of flat single crystal particles. The particulate conductive agent can be effectively dispersed in the gaps of the positive electrode material composition. In this way, the linear conductive agent effectively improves the conductivity of the positive electrode active material layer, can significantly reduce the internal resistance of the positive electrode, and is also beneficial to improving the DCR stability of the battery performance during charge and discharge.

[0060] In a fourth aspect, an embodiment of the present application provides a sodium battery. The sodium battery in the embodiment of the present application includes the positive electrode in the above embodiment of the present application. The stability of the contact interface between the electrode assembly and the electrolyte contained in the sodium battery monomer in the embodiment of the present application is good, and the direct current internal resistance (DCR) stability during charge and discharge is good. On this basis, the battery cell also has electrochemical performances such as high energy density and good cycle performance.

[0061] In some embodiments, the sodium battery is a sodium battery monomer, and the sodium battery monomer includes at least one of the following (1) to (3):

[0062] (1) The working voltage is 1.5 to 4.0 V; and / or

[0063] (2) The energy density at 1.5 to 4.0 V is 120 to 130 Wh / Kg;

[0064] (3) After 1000 cls, the growth rate of the direct current resistance of the sodium battery monomer cell is lower than 180%.

[0065] In a fifth aspect, an embodiment of the present application provides an electrical device, and the embodiment of the present application includes the sodium battery in the embodiment of the present application.

[0066] The electrical device in the embodiment of the present application has a long standby or battery life and a long service life.

[0067] The above description is only an overview of the technical solution of the present application. In order to be able to understand the technical means of the present application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present application more obvious and understandable, the following specifically illustrates the specific implementation manners of the present application. Description of the Drawings

[0068] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. And in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0069] Figure 1 Schematic diagram of a structure of the positive electrode in some embodiments of the present application;

[0070] Figure 2 Another schematic diagram of the structure of the positive electrode in some embodiments of the present application;

[0071] Figure 3 Schematic diagram of a structure of an embodiment of a sodium battery cell in an embodiment of the present application;

[0072] Figure 4 is Figure 3 Schematic diagram of the disassembly of the sodium battery cell shown;

[0073] Figure 5 Schematic diagram of a structure of an embodiment of a battery module in an embodiment of the present application;

[0074] Figure 6 Schematic diagram of a structure of an embodiment of a battery pack in an embodiment of the present application;

[0075] Figure 7 is Figure 6 Schematic diagram of the disassembled structure of the battery pack shown;

[0076] Figure 8 Schematic diagram of an embodiment of an electrical device including the battery in an embodiment of the present application as a power source.

[0077] The reference numerals in the specific embodiments are as follows:

[0078] 10 - positive electrode, 11 - current collector, 12 - positive electrode active material layer;

[0079] 20 - battery cell, 21 - housing, 22 - electrode assembly, 23 - cover plate;

[0080] 30 - battery module;

[0081] 40 - battery pack, 41 - upper box body, 42 - lower box body. Specific embodiments

[0082] Hereinafter, 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 thus are only examples and should not be used to limit the protection scope of the present application.

[0083] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "including" and "having" and any variations thereof in the specification and claims of the present application and the above accompanying drawings are intended to cover non-exclusive inclusion.

[0084] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is more than two, unless otherwise specifically and clearly defined.

[0085] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments may be included in at least one embodiment of the present application. The phrase appearing at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0086] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0087] In the description of the embodiments of the present application, the term "a plurality of" refers to more than two (including two). Similarly, "a plurality of groups" refers to more than two groups (including two groups), and "a plurality of pieces" refers to more than two pieces (including two pieces).

[0088] In the description of the embodiments of the present application, the orientation or positional relationship indicated by technical terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the indicated device or element 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.

[0089] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may also be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0090] Sodium-ion batteries (SIBs) have become ideal candidates for energy storage systems due to their abundant raw material reserves and low cost. Moreover, there is also a huge application space in the new energy vehicle market. With the rapid development of energy storage systems and new energy vehicles, the market's requirements for the performance of batteries, including sodium-ion batteries, such as energy conversion efficiency, energy density, and cycle stability, are also getting higher and higher.

[0091] Among them, the impedance and impedance stability of the battery cell are one of the important factors affecting the energy conversion efficiency of the battery cell. Currently, reducing the impedance of the battery cell or improving the impedance stability generally mainly includes methods such as optimizing the electrode design, improving the electrolyte wettability, and adopting advanced manufacturing processes. Although these can improve the impedance of the battery cell and the impedance stability to a certain extent, the improvement effect of these methods on the impedance and impedance stability of the battery cell is not particularly ideal, and at the same time, it will also lead to a decrease in the chemical properties such as the energy density or cycle performance of the battery cell or an increase in cost.

[0092] For sodium-ion batteries, the positive electrode material of sodium-ion batteries can provide active sodium ions and is an important component of sodium-ion batteries. Among the positive electrode materials of sodium-ion batteries, sodium-based layered oxides have attracted much attention due to their high specific capacity and a structure similar to that of the positive electrode material of lithium-ion batteries.

[0093] Based on the structure of the sodium-based layered oxide positive electrode material, it is currently considered that the sodium-based layered oxide positive electrode material is closely related to the energy density and cycle performance of the sodium battery cell. Therefore, the current industry is also adjusting and improving the electrochemical properties such as the specific capacity and structural stability of the sodium-based layered oxide positive electrode material by adjusting the crystal stability and doping of the sodium-based layered oxide positive electrode material to achieve the purpose of improving the energy density and cycle performance of the sodium battery cell.

[0094] In the process of researching and improving the energy conversion efficiency of batteries such as sodium batteries, a composition of sodium-based layered oxide positive electrode material is proposed. By physically mixing and compounding at least two types of sodium-based layered oxide positive electrode materials, a composition of sodium-based layered oxide positive electrode material is formed, and the types and contents of transition metal elements in the composition are regulated. After using it as the battery cell, it is found that it can significantly improve the impedance of the battery cell, such as significantly improving the stability of the direct current internal resistance (DCR) of the battery cell during charge and discharge, reducing the rising rate of DCR of the battery cell during charge and discharge, thereby improving the energy conversion efficiency of the battery cell. On this basis, the electrochemical properties such as the energy density and cycle performance of the battery cell can also be improved. Based on the above research, the embodiments of this application propose the following technical solutions.

[0095] Positive electrode material composition

[0096] In a first aspect, embodiments of the present application provide a cathode material composition. In some embodiments, the cathode material composition of the embodiments of the present application includes at least two nickel-iron-manganese-based sodium-ion cathode active materials, and the nickel-iron-manganese-based sodium-ion cathode active materials are physically mixed. The mixture formed by the nickel-iron-manganese-based sodium-ion cathode active materials further contains Cu element and Q element. And in one unit mole of the cathode material composition, the contents of Na, Ni, Mn, Fe, Cu, and Q elements are as follows:

[0097] The total molar content of Na is 0.78 to 1 moL;

[0098] The total molar content of Ni is 0.12 to 0.38 moL;

[0099] The total molar content of Mn is 0.18 to 0.48 moL;

[0100] The total molar content of Fe is 0.18 to 0.35 moL;

[0101] The total molar content of Q is 0.01 to 0.12 moL;

[0102] The total molar content of Cu is 0.01 to 0.14 moL;

[0103] Among them, Q includes at least one element of Zn, Mg, and Ti.

[0104] In the cathode material composition of the embodiments of the present application, the nickel-iron-manganese-based sodium-ion cathode active material refers to a sodium-ion layered oxide cathode material containing nickel element, iron element, and manganese element. The sodium-ion layered oxide cathode material refers to a cathode material composed of alternately arranged transition metal layers (TMO 6 ) containing Ni, Mn, Fe, etc. and sodium layers (NaO 6 ). Physical mixing means physically mixing at least two of the above-mentioned nickel-iron-manganese-based sodium-ion cathode active materials, and non-crystalline phase doping, such as without treatment such as sintering treatment after mixing.

[0105] The cathode material composition of the embodiments of the present application physically mixes two or more nickel-iron-manganese-based sodium-ion cathode active materials and controls the contents of metal elements such as Na, Ni, Mn, Fe, Cu, and Q elements in the mixture within the above ranges, so that the direct current internal resistance (DCR) of the battery cell containing the cathode material composition of the embodiments of the present application is 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. Among them, the Cu element and the metal elements represented by Q within the above range contents can play a synergistic effect on the DCR stability of the battery cell and can significantly improve the DCR stability of the battery cell.

[0106] On this basis, since at least one nickel-iron-manganese-based sodium-ion battery cathode active material contains Cu and Q elements within the above molar content ranges, the Cu and Q elements participate in the disordered arrangement among the metal elements in the transition metal layer contained in the nickel-iron-manganese-based sodium-ion battery cathode active material and can adjust the spacing between the transition metal layer and the sodium layer, improving the structural stability and / or the full utilization of the specific capacity of the nickel-iron-manganese-based sodium-ion battery cathode active material during the sodiation / delithiation process, enhancing the specific capacity and cycling performance of the cathode material composition of the embodiments of the present application, and thus correspondingly improving the energy density and cycling performance of the battery cell.

[0107] In some embodiments, in a unit molar amount of the cathode material composition, the total molar content of Na element can be 0.78 - 1 mol, optionally 0.8 - 1 mol, and further can be 0.89 - 0.91 mol. In exemplary embodiments, the total molar content of Na element can be 0.78 mol, 0.8 mol, 0.82 mol, 0.85 mol, 0.88 mol, 0.89 mol, 0.9 mol, 0.91 mol, 0.92 mol, 0.95 mol, 0.98 mol, 1.0 mol, etc., which are typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values. The Na element within this content range improves the reversible capacity of the cathode material composition.

[0108] In some embodiments, in a unit molar amount of the cathode material composition, the total molar content of Ni element can be 0.12 - 0.38 mol, optionally 0.15 - 0.35 mol, and further can be 0.2 - 0.3 mol. In exemplary embodiments, the total molar content of 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, etc., which are typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values.

[0109] In some embodiments, in a unit molar amount of the cathode material composition, the total molar content of Fe element can be 0.18 - 0.35 mol, optionally 0.20 - 0.33 mol, and further can be 0.24 - 0.28 mol. In exemplary embodiments, the total molar content of 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, etc., which are typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values.

[0110] At least one of the Ni element and the Fe element within the above content range can participate in the disordered arrangement among the metal elements in the transition metal layer contained in each nickel-iron-manganese-based sodium-ion battery cathode active material together with at least one of the Cu element or the Q element including the above content and elements such as the Mn element, and can adjust the spacing between the transition metal layer and the sodium layer, etc., thereby improving the relevant electrochemical properties of each nickel-iron-manganese-based sodium-ion battery cathode active material, further improving the DC internal resistance (DCR) stability performance of the battery cell containing the cathode material composition of the embodiment of the present application during charge and discharge, and further alleviating the increase in DCR of the battery cell during charge and discharge. On this basis, the specific capacity of the nickel-iron-manganese-based sodium-ion battery cathode active material can also be increased to increase the specific capacity of the cathode material composition of the embodiment of the present application. Further, the structural stability of the nickel-iron-manganese-based sodium-ion battery cathode active material during the sodiation / delithiation process can be improved, and the cycle performance of the cathode material composition of the embodiment of the present application can be improved.

[0111] In some embodiments, in the positive electrode material composition per unit mole amount, the total molar content of the Mn element can be 0.18 to 0.48 moL, optionally 0.20 to 0.45 moL, and further can be 0.39 to 0.41 moL. In exemplary embodiments, the total molar content of the Mn element can 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, etc., which are typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values. The Mn element within this content range can participate in the relevant electrochemical properties of each nickel-iron-manganese-based sodium-ion battery cathode active material together with at least one of the Cu element or the Q element including the above content, the Ni element, the Fe element, etc., further improving the DC internal resistance (DCR) stability performance of the battery cell containing the cathode material composition of the embodiment of the present application during charge and discharge, and further alleviating the increase in DCR of the battery cell during charge and discharge. On this basis, the structural stability of each nickel-iron-manganese-based sodium-ion battery cathode active material during the sodiation / delithiation process is improved, and the cycle performance of each nickel-iron-manganese-based sodium-ion battery cathode active material is improved.

[0112] In some embodiments, in a unit molar amount of the cathode material composition, the total molar content of the Q element may be 0.01 to 0.12 mol, optionally 0.01 to 0.1 mol, and further may be 0.01 to 0.06 mol. In exemplary embodiments, the total molar content of the Q 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, etc., which are typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values. When the nickel-iron-manganese-based sodium-ion cathode active material contains the Q element within this content range, the Q element can also participate in the disordered arrangement among the metal elements in the transition metal layer of the nickel-iron-manganese-based sodium-ion cathode active material containing the Q element, adjust the spacing between the transition metal layer and the sodium layer, thereby improving the relevant electrochemical properties of each nickel-iron-manganese-based sodium-ion cathode active material, and further improving the DC internal resistance (DCR) stability performance of the battery cell containing the cathode material composition of the embodiments of the present application during charge and discharge, so as to alleviate the increase in DCR of the battery cell during charge and discharge. Moreover, the metal element represented by Q within the above content range can further play a synergistic effect on the DCR stability of the battery cell with the Cu element within the above range content in the composition, further improving the DCR stability of the battery cell.

[0113] At the same time, it can also further improve the full utilization of the specific capacity of the nickel-iron-manganese-based sodium-ion cathode active material containing the Q element during the sodiation / desodiation process, improving the specific capacity of the cathode material composition of the embodiments of the present application; it can also reduce the migration of the Fe element in the nickel-iron-manganese-based sodium-ion cathode active material containing the Q element, improve the structural stability of each nickel-iron-manganese-based sodium-ion cathode active material during the sodiation / desodiation process, and improve the cycle performance of the cathode material composition of the embodiments of the present application.

[0114] In some embodiments, in a unit molar amount of the positive electrode material composition, the total molar content of the Cu element can be 0.01 to 0.14 moL, optionally 0.01 to 0.12 moL, and further can be 0.02 to 0.09 moL, 0.02 to 0.07 moL. In exemplary embodiments, the total molar content of the Cu 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, 0.13 moL, 0.14 moL and other typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values. When the nickel-iron-manganese-based sodium-ion battery positive electrode active material contains the Cu element within this content range, the Cu element can also participate in the disordered arrangement among the metal elements in the transition metal layer of the nickel-iron-manganese-based sodium-ion battery positive electrode active material containing the Cu element, adjust the spacing between the transition metal layer and the sodium layer, and can also improve the relevant electrochemical properties of each nickel-iron-manganese-based sodium-ion battery 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 charge and discharge, so as to alleviate the increase of DCR during charge and discharge of the battery cell. Similarly, the Cu element within the above content range can further play a synergistic effect on the DCR stability of the battery cell with the metal element represented by Q within the above range content, and further improve the DCR stability of the battery cell. At the same time, it can further improve the structural stability of the nickel-iron-manganese-based sodium-ion battery positive electrode active material containing the Cu element during the sodiation and desodiation process.

[0115] In some embodiments, at least one nickel-iron-manganese-based sodium-ion battery cathode active material contained in the cathode material composition of the embodiments of the present application further contains active and / or inert doped metal elements. In one mole of the cathode material composition, the total molar content of the doped metal elements is greater than 0 and less than or equal to 0.13 mol; optionally greater than 0 and less than or equal to 0.1 mol; in exemplary embodiments, the total molar content of the doped 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., which are typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values. The doped metal elements within this content range can participate in the disordered arrangement among the metal elements in the transition metal layer contained in the nickel-iron-manganese-based sodium-ion battery cathode active material containing doped metal elements and can adjust the spacing between the transition metal layer and the sodium layer. Together with at least one of the above-mentioned Ni, Mn, Fe, or further Cu element or Q element, they can also improve the relevant electrochemical properties of each nickel-iron-manganese-based sodium-ion battery cathode active material, thereby further improving the DC internal resistance (DCR) stability performance of the battery cell containing the cathode material composition of the embodiments of the present application during charge and discharge, so as to alleviate the increase in DCR of the battery cell during charge and discharge. At the same time, according to the type of the doped metal element represented by R, the structural stability and / or the discharge capacity per gram of the nickel-iron-manganese-based sodium-ion battery cathode active material containing the doped metal element can be further improved. When it is an active doped metal element, the content of the Ni element can be reduced, thereby reducing the economic cost of the nickel-iron-manganese-based sodium-ion battery cathode active material containing the doped metal element.

[0116] In the embodiments, the above-mentioned doped metal elements may include at least one of V, Cr, Ca, Al, Sc, Sn, Sb, Zr, Nb, Ru, and Ir. Among them, the active doped metal elements may include at least one metal element such as V, Cr, Sc, Sn, Sb, Nb, Ca, etc., and the inert doped metal elements may include at least one metal element such as Al, Zr, Ir, Ru, etc. These types of doped metal elements dope the transition metal layer contained in the nickel-iron-manganese-based sodium-ion battery cathode active material containing doped metal elements, adjust the disordered arrangement of metal elements in the transition metal layer, and can adjust the spacing between the transition metal layer and the sodium layer, which can further improve the DC internal resistance (DCR) stability performance of the battery cell of the cathode material composition of the present application embodiment during charge and discharge, so as to alleviate the growth of DCR during charge and discharge of the battery cell. In addition, according to the type of doped metal element, such as the inert doped metal element can also reduce the sensitivity to iron sites, and can assist the Mn element to further improve the structural stability of the nickel-iron-manganese-based sodium-ion battery cathode active material containing doped metal elements during the sodiation / desodiation process, and further improve the cycle performance of the nickel-iron-manganese-based sodium-ion battery cathode active material containing doped metal elements. For example, the active doped metal element can also further improve the specific capacity of the nickel-iron-manganese-based sodium-ion battery cathode active material containing doped metal elements with the Fe element, so as to correspondingly improve the energy density of the battery monomer.

[0117] Based on the molar content ranges of at least one of Cu and Q and Na, Ni, Mn, Fe or further doped metal elements contained in the cathode material composition of the present application embodiment per unit molar amount in the above embodiments, in some embodiments, in the cathode material composition per unit molar amount, the total molar contents of Na, Ni, Mn, Fe, Cu, Q, and doped metal elements may be as follows:

[0118] The total molar content of Na is 0.8 to 1 moL;

[0119] The total molar content of Ni is 0.15 to 0.35 moL;

[0120] The total molar content of Mn is 0.20 to 0.45 moL;

[0121] The total molar content of Fe is 0.20 to 0.33 moL;

[0122] The total molar content of Q is 0.01 to 0.06 moL;

[0123] The total molar content of Cu is 0.02 to 0.09 moL;

[0124] The total molar content of the doped metal element is 0 to 0.13 moL, and may be optionally 0 to 0.1 moL.

[0125] By controlling the total molar content of Na, Ni, Mn, Fe, Cu elements and the metal element shown by Q or further doped metal elements within this range, the disordered arrangement of metal elements in the transition metal layer and the spacing between the transition metal layer and the sodium layer in each nickel-iron-manganese-based sodium-ion battery cathode active material can be further adjusted, so as to further improve the DC internal resistance (DCR) stability performance of the battery cell containing the cathode material composition of the embodiment of the present application during charge and discharge. At the same time, the cycle performance and the utilization of specific capacity of each nickel-iron-manganese-based sodium-ion battery cathode active material are further improved.

[0126] In some embodiments, in the unit molar amount of the cathode material composition, the molar ratio of the total content of Na element to the total content of other metal elements in the cathode material composition of the embodiment of the present application in the above embodiments is (0.81 - 0.89):1, and can be selected as (0.82 - 0.89):1. In exemplary examples, it can be typical but non-limiting molar ratios such as 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 or the range between any two molar ratios. Controlling the molar ratio of the total content of Na element to the total 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 intercalated and deintercalated in the nickel-iron-manganese-based sodium-ion battery cathode active material, thereby increasing the reversible capacity of the cathode material composition of the embodiment of the present application; moreover, the sodium ions within this content range can increase the O3 crystal phase content of each nickel-iron-manganese-based sodium-ion battery cathode active material, making each nickel-iron-manganese-based sodium-ion battery cathode active material mainly present as the O3 crystal, thereby improving the structural stability of the nickel-iron-manganese-based sodium-ion battery cathode active material to improve its cycle performance.

[0127] In addition, since the nickel-iron-manganese-based sodium-ion battery cathode active material contained in the cathode material composition of the embodiment of the present application in the above embodiments is a sodium-ion layered oxide cathode material. Therefore, each nickel-iron-manganese-based sodium-ion battery cathode active material also contains oxygen atoms. The content of the oxygen atoms can be within the conventional content range of the sodium-ion layered oxide cathode material. The element types and contents in the cathode material composition and the nickel-iron-manganese-based sodium-ion battery cathode active material contained therein in the above embodiments can all be detected by using inductively coupled plasma emission spectroscopy (ICP) obtained by Agilent ICP-OES730 below.

[0128] In addition, the physical mixing ratio of at least two nickel-iron-manganese-based sodium-ion battery cathode active materials contained in the cathode material composition of the embodiment of the present application in the above embodiments can be adjusted according to the total molar amount content range of each element in the unit molar amount of the cathode material composition of the embodiment of the present application above.

[0129] In some embodiments, the Cu element and the Q element contained in the positive electrode material composition of the embodiments of the present application are distributed in different nickel-iron-manganese-based sodium-ion battery positive electrode active materials. In this way, the nickel-iron-manganese-based sodium-ion battery positive electrode active material containing the Cu element has relatively high structural stability during charge and discharge, thereby improving the cycle performance of the positive electrode material composition of the embodiments of the present application; the nickel-iron-manganese-based sodium-ion battery positive electrode active material containing the Q element has a relatively high specific capacity, thereby improving the specific capacity of the positive electrode material composition of the embodiments of the present application. Therefore, the compounding of the nickel-iron-manganese-based sodium-ion battery positive electrode active material containing the Cu element and the nickel-iron-manganese-based sodium-ion battery positive electrode active material containing the Q element forms a mixture, which can balance the specific capacity and cycle performance of the positive electrode material composition of the embodiments of the present application, thereby correspondingly balancing the energy density and cycle performance of the battery electric property. At the same time, it can further improve the DC internal resistance (DCR) stability performance of the battery cell containing the positive electrode material composition of the embodiments of the present application during charge and discharge, so as to alleviate the increase of DCR during charge and discharge of the battery cell.

[0130] Of course, the above Cu element and Q element can also be distributed in the same nickel-iron-manganese-based sodium-ion battery positive electrode active material.

[0131] In some embodiments, when the Cu element and the Q element are distributed in different nickel-iron-manganese-based sodium-ion battery positive electrode active materials, it is detected that in the embodiments, the Dv50 particle size of the powder of the nickel-iron-manganese-based sodium-ion battery positive electrode active material containing the above Q element can be 3 to 8 μm, and can be selected as 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 the range between any two particle size values. The Dv90 particle size of the nickel-iron-manganese-based sodium-ion battery positive electrode active material containing the above Q element can be 8 to 16 μm, and can be selected as 10 to 14 μm. In the demonstration example, 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 the range between any two particle size values.

[0132] In the examples, the Dv50 particle size of the nickel-iron-manganese-based sodium-ion battery cathode active material containing the above-mentioned Cu element can be 5-11 μm, preferably 6.5-10 μm. In the demonstration examples, 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 Dv90 particle size of the nickel-iron-manganese-based sodium-ion battery cathode active material containing the above-mentioned Cu element can be 13-19 μm, preferably 14.5-18 μm. In the demonstration examples, 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 the range between any two particle size values.

[0133] Among them, the Dv50 particle size refers to the particle size corresponding to when the cumulative particle size distribution percentage in the nickel-iron-manganese-based sodium-ion battery cathode active material powder containing the above-mentioned Q element or Cu element reaches 50%. The Dv90 particle size refers to the particle size corresponding to when the cumulative particle size distribution percentage in the nickel-iron-manganese-based sodium-ion battery cathode active material powder containing the above-mentioned Q element or Cu element reaches 90%. Dv50 and Dv90 can be measured separately for the Dv50 and Dv90 particle sizes of each nickel-iron-manganese-based sodium-ion battery cathode active material according to the method steps in GB / T16418.

[0134] The Dv50 particle size and Dv90 particle size within the above ranges can improve the compounding effect between nickel-iron-manganese-based sodium-ion battery cathode active materials such as the nickel-iron-manganese-based sodium-ion battery cathode active material containing the above-mentioned Q element and the nickel-iron-manganese-based sodium-ion battery cathode active material containing the above-mentioned Cu element, and further improve the DC internal resistance (DCR) stability performance of the battery cell of the cathode material composition of the present application embodiment during charge and discharge, so as to alleviate the increase of DCR during charge and discharge of the battery cell. At the same time, it has a suitable specific surface area and improves the stability of the contact interface between the positive electrode sheet and the electrolyte.

[0135] In some examples, when the Cu element and the Q element are distributed in different nickel-iron-manganese-based sodium-ion battery cathode active materials, in the examples, the specific surface area (BET) of the nickel-iron-manganese-based sodium-ion battery cathode active material particles containing the above-mentioned Q element is 0.4-1.0 m 2 / g, preferably 0.6-0.9 m 2 / g. In the demonstration examples, it can be 0.4 m 2 / g, 0.5 m 2 / g, 0.6 m 2 / g, 0.7 m 2 / g, 0.8 m 2 / g, 0.9 m 2 / g, 1.0 m 2Typical but non-limiting specific surface areas such as / g or the range between any two specific surface area values.

[0136] In the examples, the specific surface area (BET) of the nickel-iron-manganese-based sodium-ion battery cathode active material particles containing the above Cu element is 0.4 - 0.7 m 2 / g, and can be optionally 0.5 - 0.6 m 2 / g. In the demonstration examples, it can be 0.4 m 2 / g, 0.5 m 2 / g, 0.55 m 2 / g, 0.6 m 2 / g, 0.7 m 2 Typical but non-limiting specific surface areas such as / g or the range between any two specific surface area values.

[0137] The specific surface areas of the nickel-iron-manganese-based sodium-ion battery cathode active material containing the Q element and the nickel-iron-manganese-based sodium-ion battery cathode active material powder containing the Cu element in this range can improve the stability and other properties of the contact interface between the nickel-iron-manganese-based sodium-ion battery cathode active material containing the Q element and the nickel-iron-manganese-based sodium-ion battery cathode 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 cathode material composition of the embodiments of the present application during charge and discharge.

[0138] In some examples, when the Cu element and the Q element are distributed in different nickel-iron-manganese-based sodium-ion battery cathode active materials, in the examples, the tap density of the nickel-iron-manganese-based sodium-ion battery cathode active material powder containing the above Q element under a pressure of 3 tons is higher than 3.1 g / cm 3 , and can be optionally 3.1 - 3.4 g / cm 3 . In the demonstration examples, the tap density under a pressure of 3 tons can be 3.1 g / cm 3 , 3.2 g / cm 3 , 3.3 g / cm 3 , 3.4 g / cm 3 Typical but non-limiting tap densities such as or the range between any two tap density values.

[0139] In the examples, the tap density of the nickel-iron-manganese-based sodium-ion battery cathode active material powder containing the above Cu element under a pressure of 3 tons can be 3.0 - 3.3 g / cm 3 , and can be optionally 3.0 - 3.25 g / cm 3 . In the demonstration examples, the tap density under a pressure of 3 tons can be 3 g / cm 3 , 3.1 g / cm 3 , 3.15 g / cm 3 , 3.2 g / cm 3 , 3.25 g / cm 3 , 3.3 g / cm3 Typical but non-limiting compacted densities or ranges between any two compacted density values.

[0140] The specific surface areas of the nickel-iron-manganese-based sodium-ion battery cathode active materials containing element Q and the nickel-iron-manganese-based sodium-ion battery cathode active materials containing element Cu within this range can improve properties such as the stability of the contact interface between the nickel-iron-manganese-based sodium-ion battery cathode active materials containing element Q and the nickel-iron-manganese-based sodium-ion battery cathode active materials containing element Cu and the electrolyte, and further improve the DC internal resistance (DCR) stability performance of the battery cell containing the cathode material composition of the present application embodiment during charge and discharge. At the same time, the specific capacity per gram of the battery containing the nickel-iron-manganese-based sodium-ion battery cathode active materials containing element Q and the nickel-iron-manganese-based sodium-ion battery cathode active materials containing element Cu can be further improved.

[0141] Among them, the compacted density of the cathode material composition and each nickel-iron-manganese-based sodium-ion battery cathode active material powder contained therein in each of the above embodiments can be detected according to the following detection method:

[0142] Detect according to the test method of GB / T24533-2019 standard. Specifically, the following test steps can be referred to:

[0143] (1) Wipe the upper and lower gaskets, the top post and the metal cylindrical sleeve of the compacted density tester with a clean soft cloth (paper towel). If necessary, wipe with a soft cloth dipped in anhydrous ethanol and air dry.

[0144] (2) Place the gasket, the top post, the metal cylindrical sleeve, and the pad in the order of testing on the digital display thickness gauge and press the zero key.

[0145] (3) Remove the top post and the upper gasket, weigh 1 g of the nickel-iron-manganese-based sodium-ion battery cathode active material samples contained in Examples A1 to A12 and Comparative Examples A1 to A2 in the sleeve, accurate to 0.0001 g, and record the weight as m.

[0146] (4) Then slowly slide the gasket and the top post down from the hole, install them on the compacted density tester together with the pad, and tighten the pressure control knob.

[0147] (5) Shake the pressure bar, and at the same time observe the value on the digital display pressure gauge on the compacted density tester. After reaching the specified value of 2200 Ib, start the stopwatch; after 30 s, loosen the pressure control knob, remove the pressure, let the pad drop to a certain height, and then tighten the pressure control knob.

[0148] (6) Remove the top post, the sleeve and the negative film together with the pad, place them on the digital display thickness gauge, and read the value on the digital display thickness gauge within 10 s, and record it as H.

[0149] r = 10m / (S×H);

[0150] Then, calculate the powder compaction density r of the sample according to the formula r = 10m / (S×H).

[0151] 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 post in square centimeters (cm 2 ).

[0152] In some embodiments, at least two nickel-iron-manganese-based sodium-ion battery cathode active materials contained in the cathode material composition of the embodiments of the present application can be physically mixed in a molar ratio of the nickel-iron-manganese-based sodium-ion battery cathode active material containing Cu element to the nickel-iron-manganese-based sodium-ion battery cathode active material containing Q element of 0.5-28:1, optionally 0.5-18:1. Demonstration examples can be typical but non-limiting molar ratios such as 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 range between any two molar ratios. In the embodiments, when the Cu element and the Q element are distributed in different nickel-iron-manganese-based sodium-ion battery cathode active materials, the total molar ratio of the nickel-iron-manganese-based sodium-ion battery cathode active material containing the Cu element to the total molar ratio of the nickel-iron-manganese-based sodium-ion battery cathode active material containing the Q element is within the above physical mixing molar ratio range.

[0153] By controlling the physical mixing molar ratio of at least two nickel-iron-manganese-based sodium-ion battery cathode active materials within the above range, the compounding effect between each nickel-iron-manganese-based sodium-ion battery cathode active material can be fully exerted, and the DCR stability performance of the battery cell containing the cathode material composition of the embodiments of the present application during charge and discharge can be improved. At the same time, the specific capacity and cycle performance of the battery of the cathode material composition of the embodiments of the present application can be further balanced, thereby improving the energy density and cycle performance of the corresponding battery cell.

[0154] 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 phase layered metal oxide. Among them, the O3 phase layered metal oxide refers to a layered oxide with a crystalline 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 positive electrode active material makes each nickel-iron-manganese-based sodium positive electrode active material 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.

[0155] In some embodiments, through electron microscope analysis, the above nickel-iron-manganese-based sodium cathode active material crystals include single crystals, and the single crystals are in block shape.

[0156] Based on the type, content and mixing ratio of elements in the nickel-iron-manganese-based sodium positive electrode active material contained in the positive electrode material composition of the embodiments of the present application in the above-mentioned embodiments, as well as the morphology, crystal type, particle size, etc., it has been tested that in some embodiments, the discharge capacity in grams of the positive electrode material composition of the embodiments of the present application at 1.5-4.2V and 0.1C in the above-mentioned embodiments can reach 115-128mAh / g, and can be optionally 120-128mAh / g.

[0157] The charge gram capacity and discharge gram capacity of the positive electrode material composition of the embodiment of the present application are specifically prepared by preparing the positive electrode material composition of the embodiment of the present application into a positive electrode, and assembling it with the negative electrode into a sodium ion button battery, and detecting the gram capacity of the sodium ion button battery.

[0158] In the embodiment, the sodium ion button cell used to detect 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:

[0159] Positive electrode sheet: The positive electrode material composition of the embodiment of the present application is used as the positive electrode active material, and the conductive agent carbon nanotubes, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed 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 the 13μm positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained;

[0160] Negative electrode sheet: Hard carbon, conductive agent SP, and CMC binder were added to deionized water at a weight ratio of 8:1:1 and stirred thoroughly to form a uniform negative electrode slurry; the negative electrode slurry was evenly coated on the surface of a 6-μm copper foil, and after drying and cold pressing, a negative electrode sheet was obtained;

[0161] Electrolyte: 1M NaPF 6 / (EC / DEC, volume ratio 1:1);

[0162] Separator: Glass fiber;

[0163] Sodium ion button battery assembly: The above-mentioned positive electrode sheet, glass fiber film, and negative electrode sheet were stacked in sequence, and after assembly, a button battery assembly was formed. The electrode assembly was placed in a packaging shell, and 1M NaPF 6 / (EC / DEC, volume ratio 1:1) electrolyte was added. After processes such as encapsulation, formation, and standing, a sodium ion button battery was obtained.

[0164] Preparation method of the positive electrode material composition

[0165] In a second aspect, the embodiments of the present application provide the preparation method of the positive electrode material composition in the above text. In some embodiments, the preparation method of the positive electrode material composition in the embodiments of the present application includes the following steps:

[0166] S10: According to the molar content ratio of Na, Ni, Mn, Fe, Q, and Cu contained in the positive electrode material composition per unit molar amount, at least two nickel-iron-manganese-based sodium battery positive electrode active materials were physically mixed to form a positive electrode material composition.

[0167] In step S10 of the preparation method of the positive electrode material composition in the embodiments of the present application, the nickel-iron-manganese-based sodium battery positive electrode active material is the nickel-iron-manganese-based sodium battery positive electrode active material contained in the positive electrode material composition in the above text. Therefore, the physical mixing of at least two nickel-iron-manganese-based sodium battery 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 battery positive electrode active materials needs to satisfy that in the positive electrode material composition in the embodiments of the present application per unit molar amount, the contents of Na, Ni, Mn, Fe, Cu, and Q elements satisfy the ranges described above. Specifically:

[0168] The total molar content of Na is 0.78 - 1 moL, and can be optionally 0.8 - 1 moL;

[0169] The total molar content of Ni is 0.12 - 0.38 moL, and can be optionally 0.15 - 0.35 moL;

[0170] The total molar content of Mn is 0.18 - 0.48 moL, and can be optionally 0.20 - 0.45 moL;

[0171] The total molar content of Fe is 0.18 to 0.35 moL, and can be optionally 0.20 to 0.33 moL;

[0172] The total molar content of Q is 0.01 to 0.12 moL, and can be optionally 0.01 to 0.1 moL;

[0173] The total molar content of Cu is 0.01 to 0.14 moL, and can be optionally 0.01 to 0.12 moL.

[0174] In this way, in the preparation method of the positive electrode material composition of the embodiment of the present application, by mixing at least two nickel-iron-manganese-based sodium-ion battery positive electrode active materials according to the proportion of the content ranges of Na, Ni, Mn, Fe, Cu, and Q elements, the direct current internal resistance (DCR) of the battery cell containing the positive electrode material composition of the embodiment of the present application is relatively stable during the charge and discharge process, and the growth rate of DCR of the battery cell during the charge and discharge process can be significantly reduced. It also enables the positive electrode material composition of the embodiment of the present application to have high specific capacity and cycling performance.

[0175] The nickel-iron-manganese-based sodium-ion battery positive electrode active material in step S10 can obtain existing nickel-iron-manganese-based sodium-ion battery positive electrode active materials, and of course, can also be a nickel-iron-manganese-based sodium-ion battery positive electrode active material improved according to the element types and contents contained in the positive electrode material composition of the embodiment of the present application.

[0176] In some embodiments, the nickel-iron-manganese-based sodium-ion battery positive electrode active material in step S10 can be prepared according to the following method:

[0177] S11: Provide a precursor of each nickel-iron-manganese-based sodium-ion battery positive electrode active material respectively according to the element ratio contained in each nickel-iron-manganese-based sodium-ion battery positive electrode active material;

[0178] S12: Sinter each nickel-iron-manganese-based sodium-ion battery positive electrode active material separately to obtain each nickel-iron-manganese-based sodium-ion battery positive electrode active material.

[0179] In step S11 of the preparation method of the positive electrode material composition of the embodiment of the present application, the precursor of the nickel-iron-manganese-based sodium-ion battery positive electrode active material can be a proportional mixture containing a sodium source, a nickel source, a manganese source, an iron source, and further a copper source and a metal element source represented by Q, or further contains a doping metal source contained in the nickel-iron-manganese-based sodium-ion battery positive electrode active material in the positive electrode material composition of the embodiment of the present application above.

[0180] As in the embodiment, the precursor of the nickel-iron-manganese-based sodium-ion battery positive electrode active material can be a precursor of the nickel-iron-manganese-based sodium-ion battery positive electrode active material prepared by a solid-phase method or a precipitation method.

[0181] When preparing the precursor of the nickel-iron-manganese-based sodium-ion battery positive electrode active material by the solid-phase method, in the embodiment, the precursor of the nickel-iron-manganese-based sodium-ion battery positive electrode active material can be prepared according to a method including the following steps:

[0182] Step S111: According to the elemental stoichiometric ratio in the nickel-iron-manganese-based sodium-ion battery cathode active material, at least one of a sodium source, a nickel source, a manganese source, an iron source, a copper source, and a metal element source shown by Q, or further a doping element source is subjected to solid-phase mixing treatment to obtain a precursor of the nickel-iron-manganese-based sodium-ion battery cathode active material.

[0183] When preparing the precursor of the nickel-iron-manganese-based sodium-ion battery cathode active material by the solid-phase method, the solid-phase mixing treatment is relative to the liquid-phase mixing. Generally, it means that no solvent is added during the mixing treatment, such as no water is added, and it is also a dry mixing treatment of the solid substances of each source in step S111 under the condition of no solvent.

[0184] In order to improve the mixing uniformity of each source in step S111 during the solid-phase mixing treatment, in the embodiment, other source compounds except the sodium source in step S111 can be first subjected to mixing treatment, and then the sodium source is added for re-mixing treatment. This can improve the mixing uniformity of each source and improve the safety of the solid-phase mixing treatment.

[0185] In the embodiment, the solid-phase mixing treatment can include but is not limited to ball milling treatment. As long as it can improve the mixing uniformity 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 speed of the ball milling can be controlled to be 300 - 1000 revolutions per minute, and can be optionally 400 - 600 revolutions per minute; the time of the ball milling treatment can be 1h - 6h, and can be optionally 2h - 4h. Through this ball milling treatment, the mixing uniformity of each source can be improved, and thus the stability of the structure and electrochemical properties of the nickel-iron-manganese-based sodium-ion battery cathode active material in step S12 can be finally improved.

[0186] In the exemplary example, the sodium source can be a sodium salt, such as at least one of sodium carbonate, sodium hydroxide, etc.

[0187] In the exemplary example, the nickel source can be a soluble or insoluble nickel compound, such as nickel oxide (NiO) or nickel salt, etc. Among them, the nickel salt can include at least one of nickel nitrate, nickel carbonate, nickel hydroxide, nickel sulfate, etc.

[0188] In the exemplary example, the manganese source can be a soluble or insoluble manganese compound, such as manganese oxide (Mn 2 O 3 ) or manganese salt, etc. Among them, the manganese salt can include at least one of manganese nitrate, manganese carbonate, manganese hydroxide, manganese sulfate, etc.

[0189] In the exemplary example, the iron source can be a soluble or insoluble iron compound, such as an iron oxide (such as Fe 2 O 3) or iron salts, etc. Among them, the iron salts may include at least one of iron nitrate, iron carbonate, iron hydroxide, iron sulfate, etc.

[0190] In the demonstration example, the copper source may be a soluble or insoluble copper compound, such as a copper oxide (such as CuO) or a copper salt, etc. Among them, the copper salts may include at least one of copper nitrate, copper carbonate, copper hydroxide, copper sulfate, etc.

[0191] In the demonstration example, the metal element source and the doped metal element source represented by Q may be soluble or insoluble compounds of the metal element and the doped metal element represented by Q, such as oxides of the metal element and the doped metal element represented by Q or salts of the metal element and the doped metal element represented by Q, etc. Among them, the salts of the metal element and the doped metal element represented by Q may include at least one of nitrates, carbonates, hydroxides, sulfates, etc. of the metal element and the doped metal element represented by Q.

[0192] The types of the above-mentioned sodium source, nickel source, manganese source, iron source, copper source, and the metal element source and the doped metal element source represented by Q can be effectively mixed evenly during the mixing process, respectively improving the structural and chemical stability of the nickel-iron-manganese-based sodium-ion battery cathode active material precursor to form the nickel-iron-manganese-based sodium-ion battery cathode active material.

[0193] When preparing the nickel-iron-manganese-based sodium-ion battery cathode active material precursor by the precipitation method, it can be prepared according to the method including the following steps:

[0194] Step S113: According to the element stoichiometric ratio in the nickel-iron-manganese-based sodium-ion battery cathode active material, a mixed solution is prepared by mixing a soluble nickel source, a soluble manganese source, a soluble iron source, and at least one of a copper source and the metal element source represented by Q, or further adding a doping element source, and then at least one of a precipitating agent and a complexing agent is added for coprecipitation treatment to obtain a precipitate mixture;

[0195] Step S114: The precipitate mixture is mixed with the sodium source to obtain the nickel-iron-manganese-based sodium-ion battery cathode active material precursor.

[0196] In step S113, at least one of the precipitating agent and the complexing agent should be a compound capable of precipitating nickel, manganese, iron, copper, the metal element represented by Q, and the doping element in the nickel source, soluble manganese source, soluble iron source, soluble copper source, the metal element source represented by Q, and the doping element source. The precipitating agent and the complexing agent in step S113 can be the same or different. In the examples, the precipitating agent can include at least one of hydroxides and carbonates of alkali metals. In the examples, the complexing agent can include inorganic or organic complexing agents. In the exemplary examples, 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, disodium ethylenediaminetetraacetate, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), etc.

[0197] These types of precipitating agents and complexing agents can effectively precipitate nickel, manganese, iron, copper, the metal element represented by Q, and the doping element.

[0198] In the examples, at least one of the precipitating agent 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-ion battery cathode active material precursor.

[0199] In the exemplary examples, the soluble nickel source can include at least one of nickel acetate, nickel chloride, nickel nitrate, nickel sulfate, etc.

[0200] In the exemplary examples, the soluble manganese source can include at least one of manganese nitrate, manganese sulfate, halides, etc.

[0201] In the exemplary examples, the soluble iron source can include at least one of iron nitrate, manganese sulfate, halides, etc.

[0202] In the exemplary examples, the soluble copper source can include at least one of iron nitrate, manganese sulfate, halides, etc.

[0203] In the exemplary examples, the soluble metal element represented by Q and the doping metal element source can include at least one of nitrates, manganese sulfate, halides, etc. of the metal element represented by Q and the doping metal element.

[0204] The types of the above-mentioned soluble nickel source, soluble manganese source, soluble iron source, soluble copper source, soluble metal element represented by Q, and doping element source all have good solubility, and the stoichiometric ratio of each metal element in the precipitation mixture can be quantitatively controlled.

[0205] The mixing ratio between the sodium source and the precipitation mixture in step S114 should satisfy the sodium ion content in the nickel-iron-manganese-based sodium-ion battery cathode active material, that is, the sodium-ion battery layered oxide, specifically the stoichiometric ratio required for sodium in the O3-phase layered oxide. This mixing treatment can be a solid-phase mixing treatment or dissolving the soluble sodium source and then mixing it with the precipitation mixture, followed by removing the solvent.

[0206] In addition, the sodium source in step S114 can be a sodium salt, such as at least one of sodium carbonate, sodium hydroxide, etc.

[0207] Step S12:

[0208] After separately sintering at least two nickel-iron-manganese-based sodium-ion battery cathode active material precursors in step S11 in step S12, each nickel-iron-manganese-based sodium-ion battery cathode active material will be generated respectively. In the research, it is found that the sintering treatment conditions have a certain influence on the structural stability and electrochemical performance of the generated nickel-iron-manganese-based sodium-ion battery cathode active material. In some embodiments, the sintering treatment temperature can be controlled at 700-980 °C, preferably 750-950 °C. In exemplary embodiments, it can be 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, 950 °C, 980 °C and other typical but non-limiting temperatures or the range between any two temperature values.

[0209] At the above sintering temperature, the sintering treatment time can be 4 h to 20 h, preferably 6 h to 12 h. In exemplary embodiments, it can be 4 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h, 20 h and other typical but non-limiting hours or the range between any two hours.

[0210] By controlling the stability and time of the sintering treatment within the above range, each nickel-iron-manganese-based sodium-ion battery cathode active material precursor in step S11 can react to generate each nickel-iron-manganese-based sodium-ion battery cathode active material respectively, and further improve the synergistic effect after physical mixing and compounding of each nickel-iron-manganese-based sodium-ion battery cathode active material, further improving the DC internal resistance (DCR) stability of the battery cell containing the cathode material composition of the embodiments of the present application during charge and discharge, and at the same time, the energy density and cycle performance and other electrochemical performances of the battery cell can also be improved.

[0211] In the 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 the demonstration example, the heating rate can be 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 and other typical but non-limiting rates or the range between any two rate values. By controlling the heating rate of the sintering treatment, such as controlling within this heating rate range, the crystal perfection of each nickel-iron-manganese-based sodium-ion battery cathode active material can be improved, such as improving the uniformity of the crystal morphology.

[0212] In addition, it should be understood that the sintering treatment in the above step S12 is carried out in an oxygen-containing environment. For example, in the embodiment, it can be sintering treatment in air or carried out in an oxygen-containing protective atmosphere, such as sintering treatment in oxygen-containing nitrogen or an inert gas.

[0213] Cathode

[0214] In a third aspect, an embodiment of the present application provides a cathode. In some embodiments, the cathode of the embodiment of the present application includes a current collector and a cathode active material layer. Among them, the cathode active material layer is combined with the current collector, and the cathode active material layer contains the cathode material composition of the above embodiment of the present application.

[0215] In the cathode of the embodiment of the present application, the current collector refers to a structure for collecting current and is used to transmit electrons. The cathode active material layer refers to a layer structure containing a cathode active material, and the cathode active material is a key substance participating in the battery chemical reaction in the cathode. Among them, the cathode active material includes the cathode material composition of the above embodiment of the present application. The combination of the cathode active material layer and the current collector means that the cathode active material layer is at least combined on the surface of the current collector. In addition, the cathode can be a pole piece, and the pole piece refers to a sheet-like morphology of the cathode. Of course, it can also be set into other morphologies according to needs.

[0216] Since the cathode active material layer of the cathode of the embodiment of the present application contains the cathode material composition of the above embodiment of the present application. After testing, the direct current internal resistance (DCR) of the battery cell containing the cathode of the embodiment of the present application is relatively stable during the charge and discharge process, and the DCR growth rate of the battery cell during the charge and discharge process can be significantly reduced. At the same time, the battery cell has a high energy density and good cycle performance.

[0217] In the embodiments, the current collector included in the positive electrode of the embodiments of the present application includes, but is not limited to, a metal current collector, a carbon current collector, a conductive resin current collector, a composite current collector of metal and resin, etc. More specifically, for example, aluminum, copper, nickel, titanium, iron and their respective alloys, stainless steel, carbon fiber, carbon nanotube (CNT), graphite, etc. In the embodiments, the current collector may also be a dense film layer or a film layer with a porous structure. In the embodiments, the current collector may be, but is not limited to, aluminum foil or porous aluminum foil, etc.

[0218] In the embodiments, the positive electrode active material layer included in the positive electrode of the embodiments of the present application may be combined with the current collector by at least laminating on the surface of the current collector. When the surface layer of the current collector contains a porous structure or the current collector itself is a porous structure, the positive electrode active material layer may be at least partially embedded in the current collector.

[0219] In some embodiments, the positive electrode active material layer being at least combined on the surface of the current collector may be a structure as Figure 1 shown, 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 as a whole is a porous structure, in addition to being laminated and combined on the surface of the current collector 11, the positive electrode active material layer 12 may further extend into the porous structure of the current collector 11.

[0220] In other embodiments, the positive electrode active material layer being at least combined on the surface of the current collector may be a structure as Figure 2 shown, where the current collector 11 has two relatively arranged surfaces, and the positive electrode active material layer 12 is laminated on the two relatively arranged 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 is a porous structure, in addition to being laminated and combined on the two surfaces of the current collector 11, the positive electrode active material layer 12 may further extend into the porous structure of the current collector 11.

[0221] As an embodiment of the present application, in the above positive electrode active material layer, the mass content of the positive electrode material composition in the total mass of the positive electrode active material layer of the embodiments of the present application above may be 90% to 97%, optionally 94% to 96.5%. In exemplary examples, it may be typical but non-limiting contents such as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, etc. or the range between any two content values. The positive electrode material composition within this content range can effectively improve the energy density of the positive electrode and has good cycle performance.

[0222] In the positive electrode active material layer of each of the above application examples, in addition to the positive electrode active material components described above, it generally further includes components such as a binder and a conductive agent. This 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.

[0223] In the embodiment, the mass content of the binder contained in the above positive electrode active material layer can be 0.5% - 5%, optionally 1% - 3%. In the exemplary examples, 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 the range between any two content values.

[0224] In the embodiment, the binder can include one or more of oil-soluble binders, water-soluble binders, emulsion binders, etc. In the exemplary examples, the oil-soluble binder can include one or more of polyvinylidene fluoride, polyimide, polytetrafluoroethylene, butyl acrylate, polyacrylonitrile, etc.; in the exemplary examples, the water-soluble binder can include one or more of carboxymethyl cellulose, carboxymethyl cellulose salts, polyacrylic acid, polyacrylate salts, polyvinyl alcohol, sodium alginate, cyclodextrin, etc.; in the exemplary examples, the emulsion binder includes one or more of styrene-butadiene rubber, vinyl acetate resin, acrylic resin, chlorinated rubber.

[0225] The binder with the above range of content and the above types can effectively enhance the mechanical properties of the positive electrode active material layer and the bonding strength with the current collector, and can effectively improve the cycling performance of the positive electrode.

[0226] In the embodiment, the mass content of the conductive agent contained in the above positive electrode active material layer can be 0.5% - 5%, optionally 1% - 3%. In the exemplary examples, 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 the range between any two content values.

[0227] In the embodiment, the conductive agent can include at least one of particulate conductive agents, linear conductive agents, etc. Among them, the particulate conductive agent can include one or more of acetylene black (SP), conductive carbon black (super-P), Ketjen black, graphene, etc. The linear conductive agent can include one or more of carbon nanotubes, carbon fibers, conductive oxide nanowires, etc. The particulate conductive agent is a conductive agent with a non-linear particulate morphology relative to the linear conductive agent. The linear conductive agent refers to a conductive agent with a one-dimensional fibrous morphology.

[0228] The conductive agent with such a range of content and the above types can effectively improve the conductivity of the positive electrode active material layer.

[0229] In the examples, the conductive agent contained in the positive electrode active material layer of the positive electrodes in the above examples includes a linear conductive agent and a particulate conductive agent. Among them, the mass content of the linear conductive agent in the positive electrode active material layer is in the ratio of 0.1% to 2.5%, optionally 0.3% to 0.7%. In exemplary examples, it can 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% and other typical but non-limiting contents or the range between any two content values. Since the crystal of the nickel-iron-manganese-based sodium-ion battery positive electrode active material contained in the positive electrode material composition of the present application in the above text includes single crystals, and the morphology of the single crystals is in a block shape, therefore, adding a linear conductive agent to the positive electrode active material layer and controlling the content of the linear conductive agent within this range enables the linear conductive agent to form a rich conductive network structure in the positive electrode active material layer, and the linear conductive agent can also wind around the surface of the block-shaped single crystal particles. The particulate 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 particulate conductive agent constitutes a short-range conductive structure. Therefore, the conductive synergistic effect of the linear conductive agent and the particulate 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 beneficial to improving the DCR stability of the battery performance during charge and discharge.

[0230] In the examples, the aspect ratio of the above linear conductive agent can be controlled to be 40 to 3000:1, optionally 50 to 2500:1. In exemplary examples, it can be 40:1, 50:1, 100:1, 500:1, 1000:1, 1500:1, 2000:1, 2500:1, 3000:1 and other typical but non-limiting aspect ratios or the range between any two aspect ratio values. The aspect ratio refers to the ratio of the length to the diameter of the above linear conductive agent.

[0231] In a further example, the length of the above linear conductive agent can be controlled to be 0.5 to 5 μm, optionally 0.5 to 2 μm. In exemplary examples, it can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm and other typical but non-limiting lengths or the range between any two length values.

[0232] In a further embodiment, the diameter of the above linear conductive agent can be selectively controlled to be 2 to 10 nm, preferably 3 to 7 nm. In exemplary embodiments, typical but non-limiting diameters such as 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm or ranges between any two diameter values can be selected.

[0233] By selectively controlling the aspect ratio of the above linear conductive agent within the above range, or further selectively controlling the length and diameter of the above linear conductive agent within the above range, a richer long-range conductive network structure can be constructed by the linear conductive agent in the positive electrode active material layer, further enhancing the conductive synergistic effect of the linear conductive agent and the particulate conductive agent, so as to further improve the conductivity of the positive electrode active material layer.

[0234] In the embodiments, in addition to components such as the positive electrode active material, binder, and conductive agent, the positive electrode active material layer in the positive electrodes of the above embodiments may further contain other additives. In the embodiments, the additive may include but is not limited to functional components such as sodium supplement additives.

[0235] In some embodiments, the content of the positive electrode active material layer on a single side of the current collector in the above embodiments, that is, the coating weight (CW), is 260 to 350 mg / 1540.25 mm 2 , preferably 280 to 320 mg / 1540.25 mm 2 , and in exemplary embodiments, it can be 260 mg / 1540.25 mm 2 , 270 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm 2 , 290 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 , 310 mg / 1540.25 mm 2 , 320 mg / 1540.25 mm 2 , 330 mg / 1540.25 mm 2 , 340 mg / 1540.25 mm 2 , 350 mg / 1540.25 mm 2 and other typical but non-limiting contents or ranges between any two content values. The coating weight refers to the weight of the positive electrode active material layer per unit area. The coating weight within this range can effectively keep the direct current internal resistance (DCR) of the battery cell relatively stable during charge and discharge and improve the energy density of the battery cell.

[0236] In some embodiments, the tap density of the positive electrode active material layer in the above embodiments, that is, the tap density of the positive electrode sheet, can be 2.6 to 3.4 g / cm 3, optionally 2.8 to 3.2 g / cm 3 , in the demonstration example, it can be 2.6 g / cm 3 、2.7 g / cm 3 、2.8 g / cm 3 、2.9 g / cm 3 、3.0 g / cm 3 、3.1 g / cm 3 、3.2 g / cm 3 、3.3 g / cm 3 、3.4 g / cm 3 and other typical but non-limiting compaction densities or ranges between any two compaction density values. The compaction density refers to the weight of the positive electrode active material layer per unit volume. The compaction density within this range can effectively improve the stability of the contact interface between the positive electrode and the electrolyte, and make the DC internal resistance (DCR) of the battery cell relatively stable during charge and discharge and improve the energy density of the battery cell.

[0237] In some embodiments, the porosity of the positive electrode active material layer in the above embodiments can be 40% - 70%, optionally 50% - 65%. In the demonstration example, it can be 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 63%, 65%, 70% and other typical but non-limiting porosities or ranges between any two porosity values. The porosity refers to the percentage of the total volume of the pores contained in the positive electrode active material layer per unit volume to the unit volume of the positive electrode active material layer. The porosity within this range can enable the positive electrode active material layer to have the above-mentioned compaction density, further improve the wettability of the positive electrode with the electrolyte and improve the stability of the contact interface with the electrolyte, and make the DC internal resistance (DCR) of the battery cell relatively stable during charge and discharge and improve the energy density of the battery cell. Among them, the porosity of the positive electrode active material layer (electrode sheet) in the above embodiments can be detected according to the following method:

[0238] It is detected by the gas displacement method. Specifically, refer to GB / T24586 - 2009. The specific steps of the electrode sheet porosity detection method: Immerse the positive electrodes in each battery monomer in Examples B1 to B17 and Comparative Examples B1 to B2 in ethylene methyl carbonate (EMC) for cleaning, and then test according to the method specified in GB / T24586 - 2009. Using the gas displacement method, combined with Archimedes' principle and Boyle's law, accurately measure the true volume of the tested material as the true volume of the sample, so as to obtain the porosity of the sample to be tested. Among them, the percentage of the pore volume in a single electrode sheet to the total volume of the electrode sheet is the electrode sheet porosity, and the calculation formula: porosity = (V - V0) / V × 100%, where V0 is the true volume and V is the apparent volume.

[0239] In some embodiments, in the above embodiments, the positive electrode is a pole piece. The sheet resistance of the positive electrode active material layer in the above embodiments can be 0.5 to 5 mΩ, optionally 0.5 to 3 mΩ. In exemplary embodiments, 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 the range between any two sheet resistance values. The pole piece has the sheet-like morphology described above, and thus has two opposite surfaces. The sheet resistance refers to the resistance value between one surface of the sheet-like positive electrode and the opposite surface. The sheet resistance within this range can effectively improve the performance of the battery, including efficiency and lifespan. Among them, the sheet resistance of the above pole piece can be detected according to the following method:

[0240] Detect according to the method of GB / T 30835-2014 or T / CASAS 019—2021; for the tester verification regulation, please refer to the method of JJG 508-2004 for detection. Specifically, the four-probe method is used for detection: Immerse the positive electrodes in each battery cell in Examples B1 to B17 and Comparative Examples B1 to B2 in ethylene methyl carbonate (EMC) for cleaning, and test using the method specified in GB / T 30835-2014 or T / CASAS 019—2021. Fix four copper plates with a length of 1.5 cm * width of 1 cm * thickness of 2 mm equidistantly on a line, and the distance between the middle two copper plates is L (1 cm to 2 cm). The base material for fixing the copper plates is an insulating material. During the test, press the lower end surfaces of the four copper plates on the pole piece to be measured, connect the direct current I to the two end copper plates, measure the voltage V between the middle two copper plates, read the I and V values three times, and take the average of I and V. V / I is the pole piece resistance at the test location.

[0241] In some embodiments, in the above embodiments, the positive electrode is a pole piece, and the ratio of the thickness from one surface of the pole piece to the 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 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, etc., which are typical but non-limiting ratios or the range between any two ratios. The thickness refers to the perpendicular distance from one surface of the layer structure to the opposite surface. When a positive electrode active material layer is provided on one surface of the current collector as shown in Figure 1 , the thickness from one surface of the pole piece to the opposite surface refers to the sum of the thickness of one layer of the positive electrode active material layer and the thickness of the current collector; when positive electrode active material layers are provided on both surfaces of the current collector as shown in Figure 2 , the thickness from one surface of the pole piece to the opposite surface refers to the sum of the thicknesses of two layers of the positive electrode active material layer plus the total thickness of the current collector.

[0242] In the embodiment, the thickness of the positive electrode active material layer contained in the electrode can be controlled to be 85 to 221 μm, further 117 to 182 μm. In the exemplary embodiment, it 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, etc., typical but non-limiting thicknesses or ranges between any two thickness values. In the embodiment, the thickness of the current collector can be but is not limited to 13 to 15 μm.

[0243] By controlling the total thickness of the electrode and the thickness of the current collector within the above 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, film resistance, capacity and other properties 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, and improving the electrochemical properties such as the relative stability of the direct current internal resistance (DCR) during the charge and discharge process of the battery cell, the energy density of the battery cell, and the cycle performance.

[0244] Preparation method of the positive electrode:

[0245] The embodiment of the present application also provides a preparation method of the positive electrode in the above embodiment. In some embodiments, the preparation method of the positive electrode in the above embodiment includes the following steps:

[0246] S20: Mix components including a positive electrode active material, a binder, a conductive agent, etc. in proportion in a solvent to prepare a positive electrode slurry;

[0247] S30: Form a positive electrode active material layer by film-forming treatment of the positive electrode slurry on the current collector to obtain a positive electrode.

[0248] Step S20:

[0249] The positive electrode active material in step S20 includes the positive electrode material composition in the embodiment of the present application above.

[0250] The components such as the positive electrode active material, the binder, and the conductive agent in step S20 can be mixed according to the content ratio of the corresponding components contained in the positive electrode active material layer of the positive electrode above. The solvent can be an organic solvent suitable for preparing the positive electrode slurry, water, etc.

[0251] The mixing treatment in step S20 can be carried out according to the conventional method for preparing electrode slurries, such as including but not limited to stirring treatment until the components are uniformly dispersed to form a stable positive electrode slurry. Of course, the properties such as the viscosity of the positive electrode slurry should meet the requirements of the film-forming process so as to form a positive electrode active material layer meeting the quality requirements on the current collector.

[0252] Step S30:

[0253] Based on the positive electrode paste 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 above-mentioned embodiment of the present application.

[0254] In step S30, the film-forming treatment of the positive electrode paste on the current collector can be carried out according to the conventional method for forming the positive electrode active material layer. As in the embodiment, the electrode paste can first form a wet film on the current collector; then perform a drying treatment to volatilize the solvent, so that the wet film dries; then perform a rolling treatment on the dried film layer to form the positive electrode active material layer, thereby obtaining the positive electrode.

[0255] Of course, it can also be a method obtained by improving the conventional method for preparing the positive electrode active material layer, or a new method for preparing the positive electrode active material layer. As long as the electrode paste in step S20 is used to prepare the positive electrode active material layer on the current collector, it is within the scope disclosed in the specification of the embodiment of the present application.

[0256] In addition, the film-forming treatment conditions in S30 can be controlled and adjusted, such as controlling and adjusting the conditions for forming a wet film of the positive electrode paste prepared in step S20 on the current collector, the conditions for the rolling treatment, etc., so as to control and adjust the relevant properties of the formed positive electrode active material layer. For example, the content of the positive electrode active material layer on the single side of the current collector can be controlled and adjusted to the range of 250 - 330 mg / 1540.25 mm as described above 2 range, the tap density is controlled and adjusted to the range of 2.6 - 3.2 g / cm 3 range, the porosity is controlled and adjusted to the range of 35% - 65% as described above, and the film resistance of the electrode sheet is controlled and adjusted to the range of 0.5 - 5 mΩ as described above, etc.

[0257] Battery

[0258] Fourthly, the embodiment of the present application also provides a sodium battery.

[0259] In the embodiment, the sodium battery of the embodiment of the present application can include any one of a sodium battery cell, a battery module, and a battery pack.

[0260] Sodium battery cell:

[0261] The sodium battery cell, also known as the sodium battery core, refers to a battery including a battery outer package and an electrode assembly encapsulated in the battery outer package. The number of electrode assemblies contained in the battery cell can be one or more, which can be adjusted according to actual needs.

[0262] Among them, the outer packaging of the sodium battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.; it can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate, etc. The shape of the outer packaging can be cylindrical, square, or any other shape. The shape of the outer packaging endows the shape of the sodium battery cell. Therefore, the shape of the sodium battery cell can also be cylindrical, square, or any other shape corresponding to the outer packaging. In the demonstration example, the sodium battery cell can be, for example, Figure 3 the battery cell 20 with a square structure as shown.

[0263] In some embodiments, as Figure 4 shown, the outer packaging of the battery cell 20 may include a housing 21 and a cover plate 23. The housing 21 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose 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 to close the receiving cavity. One or more electrode assemblies 22 are encapsulated in the receiving cavity.

[0264] In the embodiments, the sodium battery cell can be a sodium battery cell containing an electrolyte solution, or a sodium battery cell containing a solid electrolyte.

[0265] When it is a sodium battery cell containing an electrolyte solution, the electrode assembly contained in the sodium battery cell generally includes a positive electrode, a negative electrode, and a separator. The positive electrode and the negative electrode are alternately stacked, and the separator is stacked between the positive electrode and the negative electrode to play a role of isolation, separating the positive electrode and the negative electrode. The positive electrode, the separator layer, and the negative electrode can form a laminated electrode assembly through a lamination process, or can form a wound core structure electrode assembly through a winding process. The electrode assembly containing the separator is placed in the outer packaging, electrolyte is injected and infiltrates the electrode assembly, and after encapsulation, a sodium battery cell is obtained.

[0266] When it is a sodium battery cell containing a solid electrolyte, the electrode assembly contained in the sodium battery cell generally includes a positive electrode, a negative electrode, and a solid electrolyte. The positive electrode and the negative electrode are alternately stacked, and the solid electrolyte is stacked between the positive electrode and the negative electrode to play a role of isolation, separating the positive electrode and the negative electrode. The electrode assembly containing the solid electrolyte is placed in the outer packaging, and after encapsulation, a sodium battery cell is obtained.

[0267] In each of the above sodium battery cells, the positive electrode contained in the electrode assembly is the positive electrode of the embodiment of the present application, that is, the positive electrode material composition of the embodiment of the present application is contained in its positive electrode active material layer. In this way, the stability of the contact interface between the electrode assembly contained in the sodium battery cell of the embodiment of the present application and the electrolyte is relatively stable, the direct current internal resistance (DCR) during the charge and discharge process is relatively stable, and the growth rate of the DCR of the battery cell core during the charge and discharge process is small. On this basis, the battery core also has electrochemical properties such as high energy density and good cycle performance.

[0268] In each of the above sodium battery monomers, the negative electrode included in the electrode assembly includes a negative electrode current collector, and may optionally include a negative electrode active material layer provided on the surface of the negative electrode current collector. The negative electrode active material layer contains a negative electrode active material. In the examples, the negative electrode current collector may include, but is not limited to, a metal or a composite current collector. For example, as the metal, sodium, sodium alloy, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc. may be used. When sodium or sodium alloy is used as the negative electrode current collector, since sodium or sodium alloy itself can also be used as the negative electrode active material, the negative electrode plate may not contain a negative electrode active material layer, and sodium or sodium alloy is both the current collector and the negative electrode active material.

[0269] The composite current collector may include a composite material of a polymer material and a metal. The polymer material therein 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 alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy. The composite current collector may be obtained by intermixing a polymer material and a metal, or may be coated on at least one side of the polymer material by electroplating, coating or other means.

[0270] 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, any one or more of carbon-based materials, alloy materials, titanium-based materials, and sodium metal to form a mixed or composite material. Among them, the carbon-based materials include, but are not limited to, one or more of graphite, soft carbon, hard carbon, carbon microspheres, and carbon fibers; the alloy materials include, but are not limited to, one or more of sodium tin alloy, sodium germanium alloy, and sodium antimony alloy; the titanium-based materials include, but are not limited to, one or more of titanium dioxide, titanate, and titanium phosphate.

[0271] The mass content of the negative electrode active material in the negative electrode active material layer may be 85% to 98%, optionally 95% to 98%. In the demonstration examples, it may be 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, etc., typical but non-limiting contents or ranges between any two content values.

[0272] The negative electrode active material layer may further 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 material and the current collector, improve the electronic conductivity, and at the same time, the conductive agent can also promote the infiltration of the electrolyte into the negative electrode plate. The binder can improve the bonding strength between the substances in the negative electrode active material layer and between the active layer and the current collector.

[0273] In the embodiments, the mass content of the conductive agent in the negative electrode active material layer can be 0.5% to 10%. In the exemplary embodiments, it can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% and other typical but non-limiting contents or the range between any two content values, and can also be set to other contents as needed. In the exemplary embodiments, the conductive agent includes one or more of acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fiber, and graphene.

[0274] In the embodiments, the mass content of the binder in the negative electrode active material layer can be 0.5% to 10%. In the exemplary embodiments, it can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% and other typical but non-limiting contents or the range between any two content values, and can also be set to other contents as needed. In the exemplary embodiments, the binder includes, but is not limited to, one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyimide, polytetrafluoroethylene, butyl 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.

[0275] In the embodiments, a thickener can optionally be included in the negative electrode active material layer, such as, but not limited to, carboxymethyl cellulose (CMC). The mass content of the thickener in the negative electrode active layer can be set to 0.5% to 5%. In the exemplary embodiments, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% and other typical but non-limiting contents or the range between any two content values.

[0276] In the embodiments, when each of the above sodium battery monomers contains a separator, the separator, as described above, is disposed between the positive electrode and the negative electrode to separate the positive electrode and the negative electrode. The separator can prevent electrons in the battery from freely passing through, preventing contact short circuit between the electrodes, but can allow sodium ions in the electrolyte to freely pass between the positive electrode and the negative electrode. The separator can be any known porous structure separator with electrochemical stability and mechanical stability. In the exemplary embodiments, the separator includes at least one monolayer or multilayer film of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), etc.

[0277] In the embodiments, when each of the above sodium battery monomers 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 can include at least one of polymer solid electrolytes, oxide electrolytes, sulfide electrolytes, borohydride electrolytes, composite solid electrolytes, etc.

[0278] After testing, in the examples, after 1000 cls charge-discharge cycles of the above-mentioned sodium battery single-cell core in each embodiment of the present application, the DCR growth rate of the battery single-cell core is lower than 180%. Therefore, the direct current internal resistance (DCR) of the sodium battery single-cell containing the positive electrode material composition in the above embodiment of the present application is stable during charge and discharge, and the DCR growth rate is small. Among them, the DCR detection method of the sodium battery single-cell core is detected according to the method in the following examples.

[0279] After further testing, as in the examples, the working voltage of the sodium battery single-cell in the embodiment of the present application is 1.5 - 4.0 V, that is, the sodium battery single-cell in the embodiment of the present application can be discharged at 1.5 - 4.0 V. In the examples, the energy density of the sodium battery single-cell in the embodiment of the present application can reach 120 - 130 Wh / K at 1.5 - 4.0 V. Therefore, the sodium battery single-cell in the embodiment of the present application also has a high energy density.

[0280] Among them, the performance detection methods such as DCR and energy density of the sodium battery single-cell core are detected according to the methods in the following examples.

[0281] Battery module:

[0282] When the sodium battery in the embodiment of the present application is a battery module, the battery module refers to being assembled by the above-mentioned sodium battery single-cells, that is, it can contain multiple above-mentioned sodium battery single-cells, and the specific number can be adjusted according to the application and capacity of the battery module.

[0283] In some embodiments, Figure 5 is a schematic diagram of a battery module 30 as an example. As Figure 5 shown, in the battery module 30, multiple sodium battery single-cells 20 can be arranged in sequence along the length direction of the battery module 30. Of course, they can also be arranged in any other way. Further, the multiple battery single-cells 20 can be fixed by fasteners.

[0284] Optionally, the battery module 30 can further include a housing with an accommodation space, and multiple sodium battery single-cells 20 are accommodated in the accommodation space.

[0285] Battery pack:

[0286] When the sodium battery in the embodiment of the present application is a battery pack, the battery pack refers to being assembled by the above-mentioned sodium battery single-cells, that is, it can contain multiple sodium battery single-cells, and the multiple sodium battery single-cells are assembled into the above-mentioned battery module. The specific number of battery single-cells or battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0287] In some embodiments, Figure 6 and Figure 7It is a schematic diagram of a battery pack 40 as an example. The battery pack 40 may include a battery box and a plurality of battery modules 30 disposed in the battery box. The battery box includes an upper box body 41 and a lower box body 42. The upper box body 41 is used to cover the lower box body 42 and form a closed space for accommodating the battery modules 30. The plurality of battery modules 30 can be arranged in the battery box in any manner.

[0288] Power-consuming device

[0289] In a fifth aspect, an embodiment of the present application further provides a power-consuming device. The power-consuming device in the embodiment of the present application includes a power supply unit or an energy storage unit, and of course, other auxiliary components or necessary components may also be included. Among them, the power supply unit or the energy storage unit contains the sodium battery in the above-mentioned embodiment of the present application. For example, it may be the above-mentioned sodium battery cell, battery module or battery pack. Since the power-consuming device in the embodiment of the present application contains the sodium battery in the above-mentioned embodiment of the present application, therefore, the power supply unit or the energy storage unit of the power-consuming device in the embodiment of the present application has good cycling performance, high energy density, long service life, and long standby or battery life of the power-consuming device in the embodiment of the present application.

[0290] In the embodiment, the power-consuming device may include, but is not limited to, mobile phones, tablets, laptop computers, electric toys, electric tools, battery cars, electric vehicles, ships, spacecrafts, etc. Among them, the electric toys may include fixed or mobile electric toys, for example, game consoles, electric vehicle toys, electric ship toys, electric airplane toys, etc., and the spacecrafts may include airplanes, rockets, space shuttles, spaceships, etc. As a power-consuming device, the battery cells, battery modules or battery packs in the battery can be selected according to its usage requirements.

[0291] Figure 8 It is a schematic diagram of a power-consuming device as an example. The power-consuming device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the power-consuming device for high power and high energy density, a battery pack or a battery module can be adopted.

[0292] In the embodiment, when the power-consuming device includes an energy storage unit, the power-consuming device can be an energy storage device. The energy storage device includes an energy storage unit, and of course, other auxiliary components or necessary components may also be included. Among them, the energy storage unit contains the battery in the above-mentioned embodiment of the present application. The battery contained in the energy storage unit can be one or more. When there are multiple batteries, the multiple batteries can form a battery module or a battery pack. Since the energy storage device in the embodiment of the present application contains the battery in the above-mentioned embodiment of the present application, therefore, the energy storage device has high energy density, good cycling performance, long service life, and further high energy density.

[0293] Embodiment

[0294] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those technologies or conditions not specified in the embodiments, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchases.

[0295] 1. Embodiment of Cathode Material Composition and Its Preparation Method

[0296] Embodiment A1

[0297] This embodiment provides a cathode material composition and its preparation method. The cathode material composition includes two sodium-ion battery cathode active materials based on nickel, iron, and manganese, and a mixture formed by physically mixing the two sodium-ion battery cathode active materials based on nickel, iron, and manganese in the proportions shown in Table 1 below.

[0298] The preparation method of the cathode material composition includes the following steps:

[0299] S1: According to the molar ratio of metal elements contained in the chemical formula Ⅰ, Na 0.88 Ni 0.21 Fe 0.30 Mn 0.38 Zn 0.08 Ca 0.03 O 2 grind NiO, ZnO, Mn 2 O 3 , Fe 2 O 3 , CaO at a rotation speed of 800 revolutions per minute for 5 hours, and then add sodium carbonate in proportion for mixing treatment to obtain a precursor of chemical formula Ⅰ; according to the molar ratio of metal elements contained in the chemical formula Ⅱ, Na 0.91 Ni 0.26 Fe 0.24 Mn 0.41 Cu 0.08 Al 0.01 O 2 grind NiO, ZnO, Mn 2 O 3 , Fe 2 O 3 , CuO, Al 2 O 3 at a rotation speed of 800 revolutions per minute for 5 hours, and then add sodium carbonate in proportion for mixing treatment to obtain a precursor of chemical formula Ⅱ;

[0300] S2: The precursors of Chemical Formula I and Chemical Formula II are respectively subjected to sintering treatment in a muffle furnace, pulverized, and nickel-iron-manganese-based sodium-ion battery positive electrode active materials shown in Chemical Formula I and Chemical Formula II are respectively obtained, and then dry-mixed to form a mixture according to the molar ratio of Formula II to Formula I of 0.5:1; wherein, the conditions of the sintering treatment are: temperature: 800 °C; time: 8 h; heating rate: 10 °C / min; oxygen atmosphere.

[0301] Examples A2 to A7

[0302] Examples A2 to A7 respectively provide a positive electrode material composition and a preparation method thereof. Compared with Example A1, the difference of this positive electrode material composition is that the physical mixing ratios of the two nickel-iron-manganese-based sodium-ion battery positive electrode active materials are different, and the others 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.

[0303] The preparation method of the positive electrode material composition in Examples A2 to A7 is prepared with reference to the preparation method of the positive electrode material composition in Example A1.

[0304] Example A8

[0305] This example provides a positive electrode material composition and a preparation method thereof. This positive electrode material composition includes two nickel-iron-manganese-based sodium-ion battery positive electrode active materials, and a mixture formed by physically mixing the two nickel-iron-manganese-based sodium-ion battery positive electrode active materials according to the ratio in Table 1 below.

[0306] The preparation method of this positive electrode material composition includes the following steps:

[0307] S1: According to the molar ratio of the metal elements contained in Na 0.88 Ni 0.21 Fe 0.25 Mn 0.38 Zn 0.13 Ca 0.03 O 2 NiO, ZnO, Mn 2 O 3 , Fe 2 O 3 , CaO are subjected to ball milling treatment at a rotation speed of 800 revolutions per minute for 5 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain the precursor of Chemical Formula I; according to the Na shown in Chemical Formula II 0.91 Ni 0.26 Fe0.24 Mn 0.35 Cu 0.14 Al 0.01 O 2 The molar ratio of the contained metal elements makes NiO, ZnO, Mn 2 O 3 , Fe 2 O 3 , CuO, Al 2 O 3 be ball-milled at a rotation speed of 800 revolutions per minute for 5 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain the precursor of Chemical Formula II;

[0308] S2: The precursors of Chemical Formula I and Chemical Formula II are respectively subjected to sintering treatment in a muffle furnace, crushed, and the nickel-iron-manganese-based sodium-ion battery positive electrode active materials shown in Chemical Formula I and Chemical Formula II are respectively obtained, and then dry-mixed in a ratio of 6.3:1 according to the molar ratio of Formula II to Formula I to form a mixture; among them, the conditions of the sintering treatment are: temperature: 800 °C; time: 8 h; heating rate: 10 °C / min; oxygen atmosphere.

[0309] Example A9

[0310] This example provides a positive electrode material composition and a preparation method thereof. The positive electrode material composition includes two nickel-iron-manganese-based sodium-ion battery positive electrode active materials, and a mixture formed by physically mixing the two nickel-iron-manganese-based sodium-ion battery positive electrode active materials according to the ratio in Table 1 below.

[0311] The preparation method of the positive electrode material composition includes the following steps:

[0312] S1: According to the molar ratio of the contained metal elements in Na 0.88 Ni 0.15 Fe 0.30 Mn 0.38 Zn 0.14 Ca 0.03 O 2 The molar ratio of the contained metal elements makes NiO, ZnO, Mn 2 O 3 , Fe 2 O 3 , CaO be ball-milled at a rotation speed of 800 revolutions per minute for 5 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain the precursor of Chemical Formula I; According to the molar ratio of the contained metal elements in Na 0.91 Ni 0.26 Fe 0.24 Mn 0.46 Cu 0.04 Al 0.01 O 2 The molar ratio of the contained metal elements makes NiO, ZnO, Mn 2 O3 , Fe 2 O 3 , CuO, Al 2 O 3 are ball-milled at a rotation speed of 800 revolutions per minute for 5 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain a precursor of Chemical Formula II;

[0313] S2: The precursors of Chemical Formula I and Chemical Formula II are respectively subjected to sintering treatment in a muffle furnace, crushed, and the nickel-iron-manganese-based sodium-ion battery positive electrode active materials shown in Chemical Formula I and Chemical Formula II are respectively obtained, and then dry-mixed in a ratio of 0.5:1 of the molar ratio of Formula II to Formula I to form a mixture; wherein, the conditions for the sintering treatment are: temperature: 800 °C; time: 8 h; heating rate: 10 °C / min; oxygen atmosphere.

[0314] Example A10

[0315] This example provides a positive electrode material composition and a preparation method thereof. The positive electrode material composition includes two nickel-iron-manganese-based sodium-ion battery positive electrode active materials, and a mixture formed by physically mixing the two nickel-iron-manganese-based sodium-ion battery positive electrode active materials according to the proportions in Table 1 below.

[0316] The preparation method of the positive electrode material composition includes the following steps:

[0317] S1: According to the molar ratio of the metal elements contained in Na 0.88 Ni 0.21 Fe 0.30 Mn 0.38 Ti 0.08 Zr 0.03 O 2 , NiO, TiO 2 , Mn 2 O 3 , Fe 2 O 3 , Ir 2 O 3 are ball-milled at a rotation speed of 800 revolutions per minute for 5 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain a precursor of Chemical Formula I; According to the molar ratio of the metal elements contained in Na 0.91 Ni 0.26 Fe 0.24 Mn 0.41 Cu 0.08 Al 0.01 O 2 , NiO, ZnO, Mn 2 O 3 , Fe 2 O 3 , CuO, Al 2 O3 Perform ball milling treatment at a rotation speed of 800 revolutions per minute for 5 hours, and then add sodium carbonate in proportion for mixing treatment to obtain a precursor of Chemical Formula II;

[0318] S2: Sinter the precursors of Chemical Formula I and Chemical Formula II in a muffle furnace respectively, crush them, and obtain nickel-iron-manganese-based sodium-ion battery cathode active materials shown in Chemical Formula I and Chemical Formula II respectively. Then, dry-mix them in a ratio of 3:1 by molar ratio of Formula II to Formula I to form a mixture; among them, the conditions for the sintering treatment are: temperature: 800 °C; time: 8 h; heating rate: 10 °C / min; oxygen atmosphere.

[0319] Example A11

[0320] This example provides a cathode material composition and a preparation method thereof. The cathode material composition includes two nickel-iron-manganese-based sodium-ion battery cathode active materials, and a mixture formed by physically mixing the two nickel-iron-manganese-based sodium-ion battery cathode active materials according to the ratio in Table 1 below.

[0321] The preparation method of the cathode material composition includes the following steps:

[0322] S1: According to the molar ratio of metal elements contained in Na 0.88 Ni 0.21 Fe 0.30 Mn 0.38 Mg 0.08 Sn 0.03 O 2 Perform ball milling treatment on NiO, TiO 2 , Mn 2 O 3 , Fe 2 O 3 , SnO 2 at a rotation speed of 800 revolutions per minute for 5 hours, and then add sodium carbonate in proportion for mixing treatment to obtain a precursor of Chemical Formula I; According to the molar ratio of metal elements contained in Na 0.91 Ni 0.26 Fe 0.24 Mn 0.41 Cu 0.08 Al 0.01 O 2 Perform ball milling treatment on NiO, ZnO, Mn 2 O 3 , Fe 2 O 3 , CuO, Al 2 O 3 at a rotation speed of 800 revolutions per minute for 5 hours, and then add sodium carbonate in proportion for mixing treatment to obtain a precursor of Chemical Formula II;

[0323] S2: The precursors of Chemical Formula I and Chemical Formula II are respectively subjected to sintering treatment in a muffle furnace, crushed, and the sodium-ion battery positive electrode active materials shown in Chemical Formula I and Chemical Formula II are respectively obtained. Then, they are dry-mixed to form a mixture according to the molar ratio of Formula II to Formula I of 3:1. Among them, the conditions of the sintering treatment are: temperature: 800 °C; time: 8 h; heating rate: 10 °C / min; oxygen atmosphere.

[0324] Comparative Example A1

[0325] This comparative example provides a positive electrode material composition and a preparation method thereof. The positive electrode material composition includes two sodium-ion battery positive electrode active materials, and a mixture formed by physically mixing the two sodium-ion battery positive electrode active materials according to the proportions in Table 1 below.

[0326] The preparation method of the positive electrode material composition includes the following steps:

[0327] S1: According to the molar ratio of the metal elements contained in Na 0.88 Ni 0.15 Fe 0.30 Mn 0.38 Zn 0.14 Ca 0.03 O 2 NiO, ZnO, Mn 2 O 3 Fe 2 O 3 CaO are subjected to ball milling treatment at a rotation speed of 800 revolutions per minute for 5 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain the precursor of Chemical Formula I; according to the molar ratio of the metal elements contained in Na 0.91 Ni 0.26 Fe 0.24 Mn 0.37 Cu 0.12 Al 0.01 O 2 NiO, ZnO, Mn 2 O 3 Fe 2 O 3 CuO, Al 2 O 3 are subjected to ball milling treatment at a rotation speed of 800 revolutions per minute for 5 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain the precursor of Chemical Formula II;

[0328] S2: The precursors of Chemical Formula I and Chemical Formula II are respectively sintered in a muffle furnace, crushed, and nickel-iron-manganese-based sodium-ion battery cathode active materials shown in Chemical Formula I and Chemical Formula II are respectively obtained. Then, they are dry-mixed to form a mixture according to the molar ratio of Formula II to Formula I of 1:10. Among them, the conditions for the sintering treatment are: temperature: 800 °C; time: 8 h; heating rate: 10 °C / min; oxygen atmosphere.

[0329] 2. Cathode and sodium-ion battery monomer examples

[0330] Examples B1 to B11

[0331] Examples B1 to B11 of this embodiment respectively provide a sodium-ion battery monomer. Each sodium-ion battery monomer includes an electrode assembly formed by a positive electrode sheet, a separator, and a negative electrode sheet, and also includes an electrolyte.

[0332] Among them, the sodium-ion battery monomers in Examples B1 to B11 are assembled as follows:

[0333] Positive electrode sheet: The sodium-ion cathode active material, conductive agent carbon nanotubes, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an appropriate amount of solvent NMP according to a weight ratio of 95:0.5:2:2.5 to form a uniform positive electrode slurry; the positive electrode slurry is uniformly 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. Among them, the sodium-ion cathode active materials are respectively the positive electrode material compositions in the above Examples A1 to A10; the positive electrode sheet contained in Example B11 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 its content is controlled to be 0.8%. As shown in Table 2, the total content of the conductive agents in the positive electrode sheet contained in Example B1 is the same as the total content of the conductive agents in the positive electrode sheet of Example B1.

[0334] Negative electrode sheet: Hard carbon, conductive agent SP, and CMC binder are added to deionized water according to a weight ratio of 8:1:1 and fully stirred and mixed to form a uniform negative electrode slurry; the negative electrode slurry is uniformly coated on the surface of a 6-μm copper foil, and after drying and cold pressing, a negative electrode sheet is obtained.

[0335] Electrolyte: In an environment with a water content of less than 10 ppm, ethylene carbonate EC and diethyl carbonate DMC, non-aqueous organic solvents, are mixed according to 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.

[0336] Separator: A porous polyethylene (PE) membrane is used as the separator.

[0337] Battery assembly: Stack the above-mentioned positive electrode sheets, separator films, and negative electrode sheets in sequence, with the separator film positioned between the positive electrode sheet and the negative electrode sheet to play a separating role, and obtain an electrode assembly through the lamination process. Place each electrode assembly in an outer package, inject electrolyte after drying, and obtain the sodium-ion battery monomers in Examples B1 to B11 through processes such as vacuum packaging, standing, formation, and shaping. Among them, the sodium-ion positive electrode active material contained in Example B1 is the positive electrode material composition in the above-mentioned Example A1, the sodium-ion positive electrode active material contained in Example B2 is the positive electrode material composition in the above-mentioned Example A2, and so on. The sodium-ion positive electrode active material contained in Example B11 is the positive electrode material composition in the above-mentioned Example A11.

[0338] Comparative Example B1

[0339] This Comparative Example B1 provides a sodium-ion battery monomer. Each sodium-ion battery monomer includes an electrode assembly formed by a positive electrode sheet, a separator film, and a negative electrode sheet, and also includes an electrolyte.

[0340] Among them, the sodium-ion battery monomers in Comparative Example B1 are all prepared with reference to the sodium-ion battery monomers in Example B1. The difference lies in:

[0341] In the sodium-ion battery monomers of Comparative Example B1, the sodium-ion positive electrode active material contained in the positive electrode sheet of the sodium-ion battery monomer is the positive electrode material composition in Comparative Example A1.

[0342] 2. Detection of relevant properties of the positive electrode material composition and sodium-ion battery monomer in each example:

[0343] 2.1 Characterization and relevant property testing of the positive electrode material composition in each example:

[0344] The positive electrode material compositions provided in the above-mentioned Examples A1 to A11 and Comparative Example A1 are respectively subjected to the detection of relevant characteristics in Table 1 below according to the following method, and the detection results are shown in Table 1:

[0345] Detection method for the element content of the nickel-iron-manganese-based sodium battery positive electrode active material: Obtain an inductively coupled plasma emission spectrum (ICP) using an Agilent ICP-OES730, and then calculate the content of each metal element in the positive electrode material compositions provided in Examples A1 to A11 and Comparative Example A1 based on the ICP results. According to the molar mixing ratio of each nickel-iron-manganese-based sodium battery positive electrode active material in each composition, convert the molar content of each metal element in the positive electrode material composition per unit molar amount.

[0346] Charge / discharge specific capacity detection method: The charge / discharge specific capacities of the cathode material compositions provided in Examples A1 to A11 and Comparative Example A1 were measured respectively according to the charge / discharge specific capacity detection method of the cathode material composition in the above text application examples.

[0347] 2.2 Performance tests of sodium-ion battery monomers and their contained cathode sheets in each example:

[0348] The sodium-ion battery monomers and their contained cathode sheets provided in Examples B1 to B11 and Comparative Example B1 above were respectively subjected to the relevant performance detections in Table 2 below according to the following method, and the detection results are shown in Table 2:

[0349] CW detection method: The cathodes in each battery monomer in Examples B1 to B17 and Comparative Examples B1 to B2 were respectively punched into 1540.25 mm 2 of pole pieces by a punching machine. By weighing and subtracting the weight of the aluminum foil, the weight of the pure active material layer was obtained, denoted as the weight of the active material layer / 1540.25 mm 2 .

[0350] Cathode sheet compaction density detection method: The cathode sheet compaction density can specifically refer to the test method for the first discharge specific capacity and the first charge-discharge efficiency of lithium manganese oxide, a cathode material for lithium-ion batteries, for details, see the GB / T 39864-2021 standard or GB / T42161-2022. The test steps with the following parameters can be specifically referred to:

[0351] The cathodes in each battery monomer in Examples B1 to B17 and Comparative Examples B1 to B2 were respectively punched into cathode sheets with a diameter of 14 mm using a punching machine, and the mass m c and thickness d c of the cathode sheets were measured respectively using an electronic balance and a desktop digital thickness gauge; A sufficient number of aluminum foil substrates with a diameter of 14 mm were punched out using a punching machine, and the mass m Al and thickness d Al of the aluminum foil substrates were measured respectively using an electronic balance and a desktop digital thickness gauge; The compaction density of each cathode sheet was calculated respectively according to the following formula:

[0352] Cathode sheet compaction density

[0353] where: ρ c is the compaction density of the cathode sheet, with the unit of grams per cubic centimeter (g / cm 3 );

[0354] m c is the mass of the cathode sheet, with the unit of grams (g);

[0355] m Alis the mass of the aluminum foil substrate, in grams (g);

[0356] is the diameter of the positive electrode plate, in millimeters (mm);

[0357] d c is the thickness of the positive electrode plate, in micrometers (μm);

[0358] d Al is the thickness of the aluminum foil substrate, in micrometers (μm).

[0359] Cycle retention rate (%): At 25°C, each battery cell in Examples B1 to B17 and Comparative Examples B1 to B2 is charged at a constant current of 0.33C to 3.85V, then charged at a constant voltage of 3.85V until the current is 0.05C, and then discharged at a constant current of 1C to 1.5V. This is one charge-discharge cycle. Taking the capacity of the first discharge as 100%, calculate the capacity retention rate after 1000 cycles of the battery. The capacity retention rate after 1000 cycles of the battery (%) = discharge capacity of the 1000th cycle / capacity of the first discharge × 100%.

[0360] Energy density: Each battery cell in Examples B1 to B17 and Comparative Examples B1 to B2 is charged at a rate of 0.33C to a voltage equal to 4.2V at room temperature, and then discharged at a rate of 0.33C to a voltage equal to 2.0V to measure the discharge energy S0. Then measure the mass M of the battery cell corresponding to S0, and calculate the energy density (mass energy density) of the battery cell according to the formula S0 / M.

[0361] Growth rate of resistance value (DCR) (%): At 25°C, the battery cell is charged at a constant current of 0.33C to a voltage of 4.1V, left standing for 5 min, discharged at 1C to 1.5V, left standing for 15 min, then charged at a constant current of 0.33C to a voltage of 4.1V again and discharged at 0.33C to 50% SOC, left standing for 30 min, then record the voltage, and perform a 4C pulsed discharge for 30 s and record the voltage after the pulsed discharge.

[0362] At 25°C, after 1000 cls of cycling, the battery cell is charged at a constant current of 0.33C to a voltage of 4.1V, left standing for 5 min, discharged at 1C to 1.5V, left standing for 15 min, then charged at a constant current of 0.33C to a voltage of 4.1V again and discharged at 0.33C to 50% SOC, left standing for 30 min, then record the voltage, and perform a 4C pulsed discharge for 30 s and record the voltage after the pulsed discharge.

[0363] Calculate DCR according to the formula. The calculation formula is: DCR = (voltage at the end of standing - voltage after pulsed discharge) / pulsed current.

[0364] DCR growth rate = DCR of the battery cell after 1000 cycles / initial DCR of the battery cell.

[0365] Table 1

[0366]

[0367]

[0368] Table 2

[0369]

[0370] Based on Table 1 and Table 2 above, it can be seen from the comparison between the examples and the comparative examples that by adjusting and controlling the total molar content of each raw material of nickel element, manganese element and copper element and the single metal element shown by Q in the positive electrode material composition of the embodiments of the present application within a certain range, the stability of the direct current resistance (DCR) of the corresponding sodium-ion battery single cell can be improved, and under the same charge and discharge conditions, the DCR growth rate of the sodium-ion battery single cell is controlled within the corresponding range.

[0371] By further comparing Example A1 to Example A7 with Example A8 to Example A9, and Comparative Example B1 to Example B7 with Example B8 to Example B9, it can be seen that simultaneously adjusting the copper element and zinc element in the positive electrode material composition can relatively significantly affect the stability of the DCR of the corresponding sodium-ion battery single cell. For example, when the copper element and zinc element in a single mole amount of the positive electrode material composition are adjusted to Example A8 and Example A9 respectively, the DCR growth rate of the sodium-ion battery single cell corresponding to the battery cell is higher than that of the sodium-ion battery single cell in Comparative Example B1 to Example B7. Therefore, in the positive electrode material composition, the total molar content of copper element and zinc element can improve the DCR growth of the battery cell.

[0372] It can be seen from Example A4, Example A10 to Example A11 and Example B4, Example B10 to Example B11 that when the zinc element contained in the positive electrode material composition of the embodiments of the present application is replaced with magnesium element and titanium element, the DCR of the sodium-ion battery single cell containing the corresponding positive electrode material composition can be kept relatively stable during charge and discharge. For example, under the same charge and discharge conditions, the DCR growth rates of the sodium-ion battery single cells in Example B10 to Example B11 are all lower than 180%.

[0373] On this basis, based on Table 1 and Table 2, it can be seen that the positive electrode material composition containing the embodiments of the present application has a relatively high specific capacity, and the corresponding sodium-ion battery single cell has good energy density and cycle performance at the same time.

[0374] As can be seen from Table 2, the positive electrode sheet containing the positive electrode material composition of the embodiment of the present application can achieve a relatively high tap density. Therefore, the positive electrode material composition of the embodiment of the present application can make the electrode sheet have a relatively high tap density.

[0375] 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 foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be covered within the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A cathode material composition, characterized in that, it comprises at least two nickel-iron-manganese-based sodium-ion cathode active materials, and the nickel-iron-manganese-based sodium-ion cathode active materials are physically mixed. The mixture of the nickel-iron-manganese-based sodium-ion cathode active materials further contains Cu element and Q element. In one unit mole of the cathode material composition, the total molar content of Na is 0.78 - 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 - 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 cathode material composition according to claim 1, characterized in that, in one unit mole of the cathode material composition, 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 - 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 - 0.06 moL; the total molar content of Cu is 0.02 - 0.09 moL; and / or at least one of the nickel-iron-manganese-based sodium-ion cathode active materials further contains active and / or inert doped metal elements. In one unit mole of the cathode material composition, the total molar content of the doped metal elements is greater than 0 and less than or equal to 0.13 moL, and can be selected to be greater than 0 and less than or equal to 0.1 moL; and / or in one unit mole of the cathode material composition, the ratio of the molar content of Na element to the total molar content of other metal elements is (0.81 - 0.89):1, and can be selected to be (0.82 - 0.89):1; and / or the Cu element and the Q element are distributed in different nickel-iron-manganese-based sodium-ion cathode active materials.

3. The cathode material composition according to claim 2, characterized in that, the doped metal elements include at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ru, and Ir; and / or the nickel-iron-manganese-based sodium-ion cathode active material containing the Q element includes at least one of the following (1) to (4): (1) The Dv50 particle size is 3 - 8 μm, and can be selected to be 4 - 6.5 μm; (2) The Dv90 particle size is 8 - 16 μm, and can be selected to be 10 - 14 μm; (3) The compaction density under a pressure of 3 tons is higher than 3.1 g / cm 3 , and can be optionally 3.1 - 3.4 g / cm 3 ; (4) The specific surface area is 0.4 to 1.0 m 2 / g, and can be optionally 0.6 to 0.9 m 2 / g; and / or the nickel-iron-manganese-based sodium-ion cathode active material containing the Cu element includes at least one of the following (5) to (8): (5) The Dv50 particle size is 5 - 11 μm, and can be selected to be 6.5 - 10 μm; (6) The Dv90 particle size is 13 - 19 μm, and can be selected to be 14.5 - 18 μm; (7) The compaction density under 3 tons of pressure is 3.0 - 3.3 g / cm 3 , and it can be optionally 3.0 - 3.25 g / cm 3 ; (8) The specific surface area is 0.4 to 0.7 m 2 / g, and it can be optionally 0.5 to 0.6 m 2 / g.

4. The cathode material composition according to any one of claims 1 - 3, characterized in that, Each of the nickel-iron-manganese-based sodium-ion battery cathode active materials independently includes 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) It includes a single crystal, and the morphology of the single crystal is blocky; and / or The discharge specific capacity of the cathode material composition is 115-128 mAh / g at 1.5-4.2 V and 0.1 C, and can be optionally 120-128 mAh / g.

5. A method for preparing the cathode material composition according to any one of claims 1 to 4, characterized in that, it includes the following steps: According to the molar content ratio of Na, Ni, Mn, Fe, Q, and Cu contained in the cathode material composition per unit molar amount, at least two nickel-iron-manganese-based sodium-ion battery cathode active materials are physically mixed to form a cathode material composition.

6. A cathode, including a cathode active material layer, characterized in that: The cathode active material layer includes the cathode material composition according to any one of claims 1 to 4.

7. The cathode according to claim 6, characterized in that: The content of the positive electrode active material layer on a single side of the current collector is 260 to 350 mg / 1540.25 mm 2 , optionally 280 to 320 mg / 1540.25 mm 2 ; and / or The compaction density of the positive electrode sheet is 2.6 to 3.4 g / cm 3 , and can be optionally 2.8 to 3.2 g / cm 3 ; and / or The porosity of the cathode active material layer is 40%-70%, and can be optionally 50%-65%; and / or The cathode is a pole piece, and the ratio of the thickness from one surface of the pole piece to the opposite surface to the thickness of the current collector is 7-15:1, and can be optionally 8-14:1; and / or The cathode is a pole piece, and the film resistance of the pole piece is 0.5-5 mΩ, and can be optionally 0.5-3 mΩ; and / or The conductive agent contained in the cathode active material layer includes a linear conductive agent.

8. The cathode according to claim 7, characterized in that: The linear conductive agent includes at least one of the following (1) to (5): (1) The mass content ratio in the cathode active material layer is 0.1%-2.5%, and can be optionally 0.3%-0.7%; (2) The aspect ratio is 40-3000:1, and can be optionally 50-2500:1; (3) The length is 0.5-5 μm, and can be optionally 0.5-2 μm; (4) The diameter is 2-10 nm, and can be optionally 3-7 nm; (5) It includes at least one of carbon nanotubes, carbon fibers, and conductive oxide nanowires.

9. A sodium battery, characterized in that, it includes the cathode according to any one of claims 6 to 8.

10. The sodium battery according to claim 9, characterized in that: The sodium battery is a sodium battery monomer, and the sodium battery monomer includes at least one of the following (1) to (3): (1) The working voltage is 1.5-4.0 V; and / or (2) The energy density at 1.5-4.0 V is 120-130 Wh / Kg; (3) After 1000 cls, the growth rate of the DC resistance of the sodium battery monomer cell is lower than 180%.

11. An electrical device, characterized in that: it includes the sodium battery according to claim 9 or 10.

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