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

Abstract

This application discloses a cathode material and its preparation method, a cathode, a sodium battery, and an electrical device. The cathode material includes a material with the chemical formula Na... q Ni x Mn y Fe z Zn p M i O j The layered oxide shown has the following properties: 0.8 ≤ q ≤ 1, 0.1 ≤ x ≤ 0.3, 0.2 ≤ y ≤ 0.5, 0.2 ≤ z ≤ 0.35, 0.02 ≤ p ≤ 0.075, 0 ≤ i ≤ 0.1; M is a doped metal element. The cathode material preparation method includes adding Na... q Ni x Mn y Fe z Zn p M i O j The precursor undergoes a sintering process. The positive electrode contains the layered oxide shown in the chemical formula, and the sodium battery contains this positive electrode. The electrical device contains this sodium battery. The layered oxide contained in the positive electrode material of this application exhibits high structural stability, high specific capacity, and good cycle stability of reversible capacity. The sodium battery has high energy density and good cycle performance.

Description

[0001] This application is a divisional application of the invention entitled "Positive electrode material and preparation method thereof, positive electrode, sodium battery and power device", filed on February 28, 2024, with application number 202410222045.7. Technical Field

[0002] This application belongs to the field of sodium battery technology, specifically relating to a cathode material and its preparation method, a cathode, a sodium battery, and an electrical device. Background Technology

[0003] Sodium-ion batteries have advantages such as abundant raw material reserves, low price, relatively stable chemical performance, 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 being placed on the energy density and cycle stability of sodium-ion batteries.

[0004] In sodium-ion battery cathode materials, layered oxides have become a research hotspot due to their high energy density. However, layered oxides suffer from poor structural stability and are prone to phase transitions during sodium insertion / extraction, leading to structural deformation. This results in severe capacity decay during cycling, causing rapid capacity loss in sodium-ion batteries. Summary of the Invention

[0005] In view of the above problems, this application provides a cathode material and its preparation method, a cathode containing the cathode material, and a sodium battery containing the cathode, so as to solve the technical problem that the existing layered oxides have poor structural stability, resulting in their own specific capacity and rapid battery cycle decay.

[0006] Firstly, embodiments of this application provide a cathode material. The cathode material of this application comprises a layered oxide as shown in the following chemical formula: Na q Ni x Mn y Fe z Zn p M i O j ; Wherein, 0.8≤q≤1; 0.1≤x≤0.3, 0.2≤y≤0.5, 0.2≤z≤0.35, 0.02≤p≤0.075, 0≤i≤0.1, 1.8≤j≤2, and x+y+z+p+i≤1; M is an active and / or inert doped metal element.

[0007] In this embodiment, the layered oxide in the cathode material is doped with Zn or a combination of Zn and the doping metal element M to form a transition metal layer (TMO6) containing Ni, Fe, and Mn elements. By controlling the Zn content to the aforementioned low level, the Jahn-Teller effect caused by Mn and Ni elements in the layered oxide itself can be suppressed. This effectively regulates the arrangement of transition metal elements in the transition metal layer (TMO6), thereby significantly reducing structural distortion and irreversible phase transitions during sodium insertion / extraction of the layered oxide. This significantly improves the structural stability of the layered oxide, thus significantly enhancing the cycle stability of its reversible capacity. Furthermore, by controlling the content ratio of each metal element, the specific capacity of the layered oxide can be further improved while effectively enhancing its structural stability. Additionally, the low Zn content can significantly reduce the segregation of transition metal elements on the surface of the layered oxide, improving its air stability in air, preventing slurry agglomeration and gelation, and improving both electrical performance and processing performance.

[0008] In some embodiments, at least one of q, x, y, z, p and i is within the following range of values: 0.15≤x≤0.25, 0.25≤y≤0.45, 0.25≤z≤0.32, 0.04≤p≤0.07, 0≤i≤0.05.

[0009] By further controlling the stoichiometric ratio of at least one element among Na, Ni, Mn, Fe, Zn, and M within this range, it is possible to further increase the doping of the transition metal layer in the layered oxide shown in the chemical formula by Zn element or by the doping metal element shown by Zn element and M, so as to further adjust the arrangement between metal elements in the transition metal layer, thereby further improving the structural stability of the layered oxide shown in the chemical formula during sodium insertion / extraction, and improving the specific capacity and reversible capacity cycling stability of the layered oxide.

[0010] In some embodiments, the total stoichiometry of Ni, Mn, Fe, Zn and the doped metal elements to the stoichiometry of Na is 1:(0.8 to 1), or optionally 1:(0.83 to 0.95).

[0011] By controlling the stoichiometric ratio of Na to other metal elements contained in the layered oxide as shown in the chemical formula within this range, the cycling stability of the specific capacity and reversible capacity of the layered oxide can be further improved.

[0012] In some embodiments, the stoichiometric ratio of Zn to Ni is 1:(3-15), and can be optionally 1:(3.1-11).

[0013] By controlling the stoichiometric ratio of Zn to Ni within this range, the specific capacity of the layered oxide shown in the chemical formula can be increased while reducing costs.

[0014] In some embodiments, the stoichiometric ratio of the Zn element to the Mn element is 1:(4-25), and optionally 1:(5-15).

[0015] By controlling the stoichiometric ratio of Zn to Mn within this range, the Jahn-Teller effect involving Mn in the transition metal layer can be adjusted while increasing the specific capacity. This further reduces the structural distortion and irreversible phase transition of the layered oxides shown in the chemical formula during sodium insertion / extraction, thereby further improving the structural stability of the layered oxides.

[0016] In some embodiments, the doping metal element includes at least one selected from V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, and Ir. The doping metal element M, together with a low content of Zn, can further dope the transition metal layer of the layered oxide shown in the chemical formula, adjusting the arrangement of metal elements in the transition metal layer, and, depending on the type of doping metal element M, further improving the structural stability and / or specific capacity of the layered oxide shown in the chemical formula during sodium insertion / extraction processes.

[0017] In some embodiments, the layered oxide includes Na. 0.89 Ni 0.23 Mn 0.45 Fe 0.3 Zn 0.02 O2, Na 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cu 0.02 O2, Na 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 O2, Na 0.89 Ni 0.23 Mn 0.41 Fe 0.3 Zn 0.06 O2, Na 0.89 Ni 0.23 Mn 0.42 Fe0.285 Zn 0.065 O2、Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 O2、Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.0 4V 0.02 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cr 0.02 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Al 0.02 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sc 0.02 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sb 0.02 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Zr 0.02 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Nb 0.02 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn0.04 Ti 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Mg 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ru 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.0 2O 1.8 At least one of them.

[0018] The layered oxide shown in the chemical formula has a low Zn content, and this low Zn content interacts with other metal elements to create a specific arrangement among the metal elements in the transition metal layers of the layered oxide. This further improves the structural stability of the layered oxide during sodium insertion / extraction, and enhances the cycling stability of its specific capacity and reversible capacity. Simultaneously, in addition to improving the specific capacity of the layered oxide shown in the chemical formula, it also improves its electrochemical performance and processing performance.

[0019] In some embodiments, the layered oxide includes at least one of the following features (1) to (3): (1) The crystal structure includes 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) The particle size of Dv50 is 3-11 μm, and can be selected as 4-8 μm; (3) Includes single crystals, wherein the single crystals have a flat morphology.

[0020] In the embodiments, the single crystal features include at least one of the following (1) to (4): (1) The ratio of length, width and thickness is 1~8:1~5:0.5~2.5, and can be selected as 2~6:2~4:1~2; (2) The length is 1 to 8 μm, and can be 2 to 6 μm; (3) Width is 1-5 μm, and can be 2-4 μm; (4) The thickness is 0.5 to 2.5 μm, and can be 1 to 2 μm.

[0021] The layered oxides shown in the above embodiments are mainly O3 phase layered metal oxides, and include single crystal structures.

[0022] In some embodiments, the layered oxide includes at least one of the following features (1) to (3): (1) The compaction density under 2 tons of pressure is 2.8–3.1 g / cm³. 3 The selectable value is 2.9–3.09 g / cm³. 3 ; (2) The compaction density under 3 tons of pressure is 3.1–3.3 g / cm³. 3 The selectable value is 3.15–3.28 g / cm³. 3 ; (3) Specific surface area is 0.5–1.3 m² 2 / g, which can be selected from 0.6 to 0.9 m 2 / g.

[0023] Based on the Dv50 particle size of the layered oxide shown in the above chemical formula (Ⅰ) and the size distribution range of the single crystal of the layered metal oxide containing the O3 phase, the layered oxide has a high compaction density, thereby improving the energy density of the battery; at the same time, the layered oxide has a suitable specific surface area, which can improve the stability of the interface between the layered oxide and the electrolyte, thereby improving the electrochemical performance such as cycle performance.

[0024] In some embodiments, the layered oxide comprises at least one of (1) to (3) below at 1.5–4.2 V and 0.1 C: (1) The charging capacity is 164-174 mAh / g, and can be selected as 165-172 mAh / g; (2) The discharge capacity is 158-165 mAh / g, and can be selected as 160-163 mAh / g; (3) The initial efficacy is 92-98%, and 92-95% can be selected.

[0025] The structural stability of the layered oxide shown in the above chemical formula has been significantly improved. It exhibits structural stability during sodium insertion / extraction, high specific capacity, and good cyclic stability of reversible capacity.

[0026] Secondly, embodiments of this application provide a method for preparing a cathode material. The method for preparing the cathode material according to embodiments of this application includes the following steps: Provide Na q Ni x Mny Fe z Zn p M i O j Precursors; The precursor was sintered to obtain a product with the chemical formula Na. q Ni x Mn y Fe z Zn p M i O j Layered oxides; Wherein, 0.8≤q≤1; 0.1≤x≤0.3, 0.2≤y≤0.5, 0.2≤z≤0.35, 0.02≤p≤0.075, 0≤i≤0.1, 1.8≤j≤2, and x+y+z+p+i≤1; M is an active and / or inert doped metal element.

[0027] The cathode material preparation method in this application embodiment involves Na... q Ni x Mn y Fe z Zn p M i O j The precursor is sintered to produce Na q Ni x Mn y Fe z Zn p M i O j The layered oxide produced by the cathode material preparation method in this application has a low zinc content, resulting in high structural stability during sodium insertion / extraction, thus leading to high specific capacity and cycle stability of its reversible capacity. It also exhibits high air stability and diffusion rate. Furthermore, it is effective against Na... q Ni x Mn y Fe z Zn p M i O j The conditions for sintering the precursor can be effectively controlled, thereby improving the yield of the precursor with the chemical formula Na. q Ni x Mn y Fe z Zn p M i O j The stability of the structure and electrochemical properties of layered oxides.

[0028] In some embodiments, the doping metal element includes at least one selected from V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, and Ir. These doping metal elements, together with a low concentration of Zn, can further dope the transition metal layer of the layered oxide shown in the chemical formula, adjust the arrangement of metal elements in the transition metal layer, and, depending on the type of doping metal element, further improve the structural stability and / or specific capacity of the layered oxide shown in the chemical formula during sodium insertion / extraction processes.

[0029] In some embodiments, at least one of q, x, y, z, p, and i takes the following range of values: 0.15≤x≤0.25、0.25≤y≤0.45、0.25≤z≤0.32、0.04≤p≤0.07、0≤i≤0.05.

[0030] By Na q Ni x Mn y Fe z Zn p M i O j By further controlling the proportion of these metal elements in the precursor within this range, the arrangement of metal elements in the prepared layered oxide can be further adjusted, thereby further improving the structural stability of the prepared layered oxide during the sodium insertion / extraction process, and improving the specific capacity and reversible capacity cycling stability of the layered oxide.

[0031] In some embodiments, the sintering process includes at least one of the following conditions (1) to (4): (1) The temperature is 700~980℃, and 750~950℃ can be selected; (2) The time is 4 to 20 hours, and can be 6 to 12 hours; (3) The temperature is increased to the sintering temperature at a heating rate of 2 to 15 °C / min.

[0032] By controlling the sintering conditions within the above range, the Na content can be further increased. q Ni x Mn y Fe z Zn p M i O j The structural stability of layered oxides during sodium insertion / extraction further enhances their high specific capacity and the cycling stability of their reversible capacity. It also improves the Na... q Ni x Mn y Fe z Znp M i O j The content of O3 phase layered metal oxide and single crystal content in layered oxides are controlled to adjust the single crystal size and particle size of the layered oxides, thereby increasing the compaction density of the layered oxides.

[0033] In some embodiments, the Na q Ni x Mn y Fe z Zn p M i O j The precursor is prepared by a method comprising the following steps: According to Na q Ni x Mn y Fe z Zn p M i O j The precursor is obtained by solid-phase mixing of sodium, nickel, manganese, iron, zinc and the doped metal element source shown in M, according to the element stoichiometry of the contained elements.

[0034] Na was prepared by this solid-state method. q Ni x Mn y Fe z Zn p M i O j The precursor can effectively control the stoichiometric ratio of each element and improve the preparation effect of the precursor.

[0035] In some embodiments, the Na q Ni x Mn y Fe z Zn p M i O j The precursor is prepared by a method comprising the following steps: According to Na q Ni x Mn y Fe z Zn p M i O j In accordance with the elemental stoichiometry, a mixed solution is prepared by combining a soluble nickel source, a soluble manganese source, a soluble iron source, a soluble zinc source, and a soluble doped metal element source as shown in M. At least one of the precipitant and complexing agent is added for co-precipitation treatment to obtain a precipitate mixture. The precipitate mixture was mixed with a sodium source to obtain the precursor.

[0036] Na was prepared by this coprecipitation method. q Ni x Mn y Fe z Zn p M i O j The precursor can improve the accuracy of the stoichiometry of each element.

[0037] Thirdly, embodiments of this application provide a positive electrode. The positive electrode of this application includes a current collector and a positive electrode active material layer bonded to the current collector, wherein the positive electrode active material layer includes the positive electrode material of this application or a positive electrode material prepared by the positive electrode material preparation method of this application.

[0038] Because the positive electrode active material layer of the positive electrode in this embodiment contains the positive electrode material described in the above embodiment, the specific capacity of this positive electrode is relatively high, and its cycle performance is good.

[0039] In some embodiments, the content of the positive electrode active material layer on one side of the current collector is 260–350 mg / 1540.25 mm. 2 The dosage can be selected as 280–320 mg / 1540.25 mg. 2 A positive electrode active material layer with this content range can effectively increase the specific capacity of the positive electrode, thereby increasing the energy density of the battery.

[0040] In some embodiments, the compaction density of the positive electrode active material layer is 2.8–3.4 g / cm³. 3 The selectable value is 2.9–3.2 g / cm³. 3 This compaction density range can effectively increase the specific capacity of the positive electrode, thereby improving the energy density of the battery, and also provides good stability at the electrolyte interface.

[0041] In some embodiments, the porosity of the positive electrode active material layer is 40% to 65%, optionally 45% to 60%. This porosity range enables the positive electrode active material layer to have the aforementioned compaction density, increasing the specific capacity of the positive electrode and thus increasing the energy density of the battery, and also improving the wettability of the electrolyte.

[0042] In some embodiments, the positive electrode is a film resistivity of 0.5–5 mΩ, optionally 0.5–3 mΩ. This range of film resistivity effectively improves performance characteristics including efficiency and lifespan.

[0043] In some embodiments, the positive electrode is an electrode sheet, and the thickness ratio of the electrode sheet from one surface to the opposite surface to the current collector thickness is 6 to 15:1, optionally 8 to 14:1.

[0044] By controlling the total thickness of the electrode to the thickness of the current collector within the above-mentioned ratio range, the specific capacity of the electrode can be effectively increased, thereby increasing the energy density of the battery. It can also improve the bonding strength between the positive electrode active material layer and the current collector, improve the mechanical strength of the electrode structure, and improve the cycle performance of the electrode.

[0045] In some embodiments, the conductive agent contained in the positive electrode active material layer includes a linear conductive agent.

[0046] In the embodiments, the mass content of the linear conductive agent in the positive electrode active material layer is 0.1% to 2.5%, and can be selected as 0.2% to 0.8%.

[0047] In the embodiments, the aspect ratio of the linear conductive agent is 40 to 3000:1, and can be selected as 50 to 2500:1.

[0048] In the embodiments, the length of the linear conductive agent is 0.5 to 5 μm, and can be selected as 0.5 to 2 μm.

[0049] In the embodiments, the diameter of the linear conductive agent is 2 to 10 nm, and can be selected as 3 to 7 nm.

[0050] In the example, the linear conductive agent includes at least one of carbon nanotubes, carbon fibers, and conductive oxide nanowires.

[0051] By adding a linear conductive agent to the positive electrode active material layer, and controlling the content, type, aspect ratio, length, and diameter of the linear conductive agent within a specified range, the linear conductive agent can form a rich conductive network structure within the positive electrode active material layer. Furthermore, the linear conductive agent can be wound around the surface of flattened single-crystal particles. The particulate conductive agent can be effectively dispersed in the gaps between the positive electrode material. Thus, the linear conductive agent constructs a long-range conductive network structure in the positive electrode active material layer, while the particulate conductive agent constitutes a short-range conductive structure. Therefore, the conductivity-enhancing effect of both the linear and particulate conductive agents in the positive electrode active material layer effectively improves the conductivity of the positive electrode active material layer and significantly reduces the internal resistance of the positive electrode.

[0052] Fourthly, embodiments of this application provide a sodium battery. The sodium battery of this application includes the positive electrode described in the embodiments above.

[0053] Since the sodium battery of this application embodiment contains the positive electrode of the above application embodiment, the sodium battery of this application embodiment has high energy density and good cycle performance.

[0054] Fifthly, embodiments of this application provide an electrical device, including the sodium battery of this application.

[0055] The electrical devices in this application have long standby or battery life and a long service life.

[0056] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0057] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a scanning electron microscope (SEM) image of the layered oxide provided in Embodiment A6 of this application; Figure 2 This is a schematic diagram of the single-crystal structure of the layered oxide contained in the cathode material of some embodiments of this application; Figure 3 This is a schematic diagram of the structure of the positive electrode in some embodiments of this application; Figure 4 This is a schematic diagram of another structure of the positive electrode in some embodiments of this application; Figure 5 This is a schematic diagram of the structure of a sodium battery cell according to an embodiment of this application; Figure 6 for Figure 5 The diagram shows a breakdown of a sodium battery cell. Figure 7 This is a schematic diagram of one embodiment of the battery module of this application; Figure 8 This is a schematic diagram of one embodiment of the battery pack of this application; Figure 9 for Figure 8 The diagram shows the exploded structure of the battery pack. Figure 10 This is a schematic diagram of one embodiment of an electrical device that uses a battery as a power source, as described in the present application.

[0058] The reference numerals in the detailed embodiments are as follows: 10 - Positive electrode, 11 - Current collector, 12 - Positive electrode active material layer; 20-Battery cell, 21-Casing, 22-Electrode assembly, 23-Cover plate; 30-Battery Module; 40 - Battery pack, 41 - Upper casing, 42 - Lower casing. Detailed Implementation

[0059] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0061] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0062] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0063] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0064] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0065] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0066] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0067] Sodium-ion batteries (SIBs) have become an ideal candidate for energy storage systems due to their abundant raw material reserves and low price. They also have significant application potential in the new energy vehicle market. With the rapid development of energy storage systems and new energy vehicles, the requirements for the energy density and cycle stability of sodium-ion batteries are becoming increasingly stringent.

[0068] For sodium-ion batteries, the cathode material provides active sodium ions and is a crucial component, significantly influencing energy density and cycle performance. Among sodium-ion battery cathode materials, layered oxides have attracted considerable attention due to their high specific capacity and structure similar to lithium-ion battery cathode materials.

[0069] Based on the stacking order of oxygen atoms in layered oxides, these oxides are currently mainly classified into P2 type and O3 type. A representative example is the P2 layered oxide Na. 2 / 3 Ni 1 / 3 Mn 2 / 3 Although O2 has a high capacity, it is prone to P2 oxidation during sodium insertion / extraction. The O2 phase transition leads to Na 2 / 3 Ni 1 / 3 Mn 2 / 3 The structural disruption of O2 leads to capacity decay and reduced cycle life. Compared to P2-type layered oxides, O3-type layered oxides can store more Na. +It can also exhibit high reversible capacity within the same voltage range, thus showing better prospects for commercial applications. However, Na in O3-type layered oxides... + Diffusion requires additional energy to overcome the diffusion energy barrier. Therefore, most O3-type layered oxides such as NaMn 0.5 Ni 0.5 O2 layered oxides undergo complex phase transitions during charge and discharge, especially the irreversible P3″ phase transition that occurs when charged to a high voltage above 4.1V. This phase transition leads to the destruction of the structure of O3-type layered oxides, causing their capacity to decay and reducing cycle life.

[0070] Therefore, layered oxides currently suffer from poor structural stability. During sodium insertion / extraction, they are prone to phase transitions leading to structural deformation, resulting in severe capacity decay during cycling and consequently rapid capacity loss in sodium-ion batteries. To improve the crystal structure stability and electrochemical performance (including reversible capacity and cycle performance) of layered oxides during sodium insertion / extraction, heteroelement doping has been reported. While doping improves the crystal structure stability and cycle performance, the improvement is not significant. For example, it is generally believed that zinc doping of layered oxides can act as a stabilizer, reducing structural distortion and slippage during charge / discharge because zinc does not participate in the redox reactions. This improves structural stability and enhances reversible capacity and cycle performance. Furthermore, it is generally believed that the stabilizing effect of zinc increases with increasing doping concentration, further reducing structural distortion and slippage and improving structural stability. Therefore, it is generally believed that a higher zinc doping level is beneficial to the structural stability of layered oxides. In layered oxides, the molar doping level of zinc is typically above 8%.

[0071] However, research unexpectedly revealed that reducing the zinc doping content can effectively alleviate the premature structural phase transition phenomenon in nickel-manganese layered oxides, reduce phase transitions during charge-discharge processes, and significantly improve the crystal structure stability of nickel-manganese layered oxides during sodium insertion / extraction processes. This, in turn, enhances the specific capacity and reversible capacity stability of nickel-manganese layered oxides during cycling. Based on the above research, the embodiments of this application propose the following technical solutions.

[0072] cathode materials In one aspect, embodiments of this application provide a low-zinc-doped cathode material. In some embodiments, the cathode material of this application comprises a layered oxide as shown in the following chemical formula (Ⅰ): Naq Ni x Mn y Fe z Zn p M i O j (I); In the chemical formula (Ⅰ), 0.8≤q≤1, 0.1≤x≤0.3, 0.2≤y≤0.5, 0.2≤z≤0.35, 0.02≤p≤0.075, 0≤i≤0.1, 1.8≤j≤2, and x+y+z+p+i≤1; M is an active and / or inert doped metal element.

[0073] In the chemical formula (Ⅰ) of the layered oxide contained in the cathode material of this application embodiment, q, x, y, z, p, i, and j represent the stoichiometric proportions of the doped metal elements Na, Ni, Mn, Fe, Zn, and M, and O in the layered oxide, respectively. Therefore, the stoichiometric ratio of Na, Ni, Mn, Fe, Zn, M, and O in the layered oxide can be 0.8–1: 0.1–0.3: 0.2–0.5: 0.2–0.35: 0.02–0.075: t–0.1: 1.8–2; where 0 ≤ t < 0.1. Furthermore, the stoichiometric ratio of the doped metal elements Na, Ni, Mn, Fe, Zn, M, and O can be a molar ratio or a mass ratio converted from a molar ratio. The active doped metal element M refers to a class of metal elements that have electrochemical redox activity in the layered oxide and mainly contribute to the specific capacity of the layered oxide. The inert doped metal element indicated by M is relative to the active doped metal element. It refers to a class of metal elements that contribute primarily to the stability of the electrochemical redox activity in the layered oxide and are mainly responsible for the stability of the crystal structure of the layered oxide. The layered oxide is a cathode material composed of alternating transition metal layers (TMO6) octahedra containing Ni, Mn, and Fe elements and alkali metal layers (NaO6).

[0074] In this embodiment, the layered oxide containing the cathode material is doped with Zn element or Zn element further doped with the doping metal element M shown in the figure to form a transition metal layer (TMO6) containing Ni, Fe, and Mn elements. At the same time, the Zn element doping amount is controlled within the low content range shown in the figure p, so that Zn element and Fe element or Zn element further doped with Fe element and the doping metal element M shown in the figure can participate in the arrangement of metal elements in the transition metal layer contained in the layered oxide crystal. The arrangement is mainly disordered, which can suppress the structural phase transition of the layered oxide shown in the figure (I) due to the Jahn-Teller effect brought by Mn element and the excessive nickel element. Compared with the current layered oxide with high zinc content, it can reduce the structural phase transition of the layered oxide shown in the figure (I). It can significantly reduce the structural distortion and irreversible phase transition of the layered oxide shown in the figure (I) during the sodium insertion / extraction process, and can significantly improve the structural stability of the layered oxide, thereby improving the cycle stability of the reversible capacity of the layered oxide. Meanwhile, by controlling the content ratio of each metal element, the specific capacity of the layered oxide can be further improved while effectively enhancing its structural stability. Moreover, the content ratio of each metal element can also effectively adjust the spacing between transition metal elements in the transition metal layer (TMO6), thereby controlling the amount of sodium removal and improving the structural distortion and irreversible phase transition during the sodium insertion / extraction process of the layered oxide, thus significantly improving its structural stability.

[0075] Furthermore, the low Zn content in the layered oxide shown in formula (I) can significantly reduce the segregation of transition metal elements on the surface of the layered oxide shown in formula (I), improve the air stability of the layered oxide shown in formula (I) in air, avoid slurry agglomeration and gelation, and improve both the electrical properties and the processing performance and electrical properties of the layered oxide shown in formula (I). In addition, the low Zn content or Zn element further combined with the doping metal element shown in M ​​to dope the transition metal layer (TMO6) containing Ni, Fe, and Mn elements can effectively suppress the Na+ precipitation during the charging and discharging process of the layered oxide. + The ordered transformation of vacancies reduces Na + The diffusion barrier increases the diffusion rate of sodium ions contained in layered oxides.

[0076] In the exemplary embodiment, in the chemical formula (I) of the layered oxide contained in the cathode material of this application, the stoichiometric content q of Na element can be a typical but non-limiting stoichiometric content such as 0.8, 0.85, 0.9, 0.95, 1.0, or a range between any two stoichiometric content values. This range of Na element content improves the reversible capacity of the layered oxide shown in chemical formula (I).

[0077] In some embodiments, the stoichiometric content x of Ni element in the layered oxide contained in the cathode material of this application embodiment can be further 0.15≤x≤0.25. Based on the range of x values ​​in chemical formula (I), in the exemplary example, x can be a typical but non-limiting stoichiometric content such as 0.1, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.25, 0.3, or any range between two stoichiometric content values. Ni element in this content range can effectively reduce the content of inactive impurity phases such as NiO in the layered oxide under the co-doping of Zn element, Fe element, or Zn element, Fe element and the doping metal element shown in M, thereby further improving the structural stability of the layered oxide during the sodium insertion / extraction process. At the same time, Zn element, Fe element, or Zn element, Fe element and the doping metal element shown in M ​​can also replace part of Ni element, reducing the Ni content, thereby reducing the cost of the layered oxide without reducing the specific capacity of the layered oxide shown in chemical formula (I).

[0078] In some embodiments, the stoichiometric content y of Mn element in the layered oxide contained in the cathode material of this application embodiment can be further 0.25≤y≤0.45. Based on the range of values ​​of y in chemical formula (I), in the exemplary example, y can be a typical but non-limiting stoichiometric content such as 0.2, 0.23, 0.25, 0.28, 0.3, 0.33, 0.35, 0.38, 0.4, 0.43, 0.45, 0.48, 0.5, or a range between any two stoichiometric content values. On the one hand, the Mn element in this stoichiometric content range can reduce the Jahn-Teller effect brought about by Mn and Ni elements under the co-doping of Zn, Fe, or the doping metal elements shown by Zn, Fe, and M, further improving the structural stability of the layered oxide during the sodium insertion / extraction process; on the other hand, it can also make the layered oxide shown by chemical formula (I) have a larger average oxidation state and lattice space, thereby increasing the diffusion rate of Na ions.

[0079] In some embodiments, the stoichiometric content z of Fe element in the layered oxide contained in the cathode material of this application embodiment can be further 0.25≤z≤0.32. Based on the range of z values ​​in formula (I), in the exemplary example, z can be a typical but non-limiting stoichiometric content such as 0.2, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, or any range between two stoichiometric content values. Fe element within this stoichiometric content range can co-dope the transition metal layer in the layered oxide shown in formula (I) with Zn element or Zn element and the doping metal element shown in M, further improving the structural stability of the layered oxide shown in formula (I) during sodium insertion / extraction process; at the same time, Fe element replaces part of Ni element, reducing the Ni element content and lowering the cost of the layered oxide shown in formula (I) while increasing the specific capacity of the layered oxide shown in formula (I).

[0080] In some embodiments, in the chemical formula (I) of the layered oxide contained in the cathode material of this application, the stoichiometric content p of the Zn element can be 0.04≤p≤0.07, and further 0.04≤p≤0.065. Based on the range of p values ​​in chemical formula (I), in the exemplary example, p can be a typical but non-limiting stoichiometric content or a range between any two stoichiometric content values, such as 0.02, 0.025, 0.025, 0.03, 0.03, 0.035, 0.04, 0.045, 0.045, 0.05, 0.05, 0.055, 0.055, 0.06, 0.065, 0.07, 0.075. The Zn element within this stoichiometric range can, or the Zn element can, further enhance the doping of the transition metal layer contained in the layered oxide shown in chemical formula (I) with the doping metal element shown in M, thereby further improving the structural stability of the layered oxide shown in chemical formula (I) during the sodium insertion / extraction process; and at the same time further balancing the electrical performance and processing performance of the cathode material.

[0081] In some embodiments, in the chemical formula (I) of the layered oxide contained in the cathode material of this application, the stoichiometric content i of the doped metal element represented by M can be further 0 ≤ i ≤ 0.05. Based on the range of values ​​of i in chemical formula (I), in the exemplary example, i can be a typical but non-limiting stoichiometric content such as 0, 0.01, 0.02, 0.03, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any range between two stoichiometric content values. The doped metal element represented by M in this stoichiometric content range can assist the low content of Zn element in further increasing the doping of the transition metal layer contained in the layered oxide represented by chemical formula (I), adjusting the arrangement between metal elements in the transition metal layer, so as to further improve the structural stability of the layered oxide represented by chemical formula (I) during sodium insertion / extraction process, and further improve its specific capacity and / or reversible capacity cycle stability.

[0082] In the exemplary example, in the chemical formula (Ⅰ) of the layered oxide contained in the cathode material of this application embodiment, the stoichiometric content j of O can be a typical but non-limiting stoichiometric content such as 1.8, 1.9, 2, or a range between any two stoichiometric content values.

[0083] In the embodiments, the active and / or inert doping metal element represented by M may include at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, Ir, etc. The active doping metal element represented by M may include at least one of V, Ca, Cr, Nb, Cu, Sc, Sn, Sb, etc., and the inert doping metal element represented by M may include at least one of Zr, Mg, Ru, Ir, Al, Ti, etc. By selecting the active and / or inert doping metal element represented by M from these elements, it is possible to further enhance the doping of the transition metal layer contained in the layered oxide of chemical formula (I) together with a low content of Zn, adjust the arrangement of metal elements in the transition metal layer, and, depending on the type of doping metal element represented by M, further improve the structural stability and / or specific capacity of the layered oxide of chemical formula (I) during sodium insertion / extraction processes.

[0084] Based on the value ranges of q, x, y, z, p, and i in the above embodiments, in some embodiments, the simultaneous value ranges of q, x, y, z, p, and i in the chemical formula (Ⅰ) of the layered oxide are as follows: 0.8≤q≤1, 0.15≤x≤0.25, 0.25≤y≤0.45, 0.25≤z≤0.32, 0.04≤p≤0.07, 0≤i≤0.05. In this case, the stoichiometric ratio of Na, Ni, Mn, Fe, Zn, and M, the doping metal elements, in the layered oxide shown in chemical formula (Ⅰ) can be 0.8~1:0.15~0.25:0.25~0.45:0.25~0.32:0.04~0.065:t~0.05; where 0≤t<0.05. By controlling the stoichiometric ratio of the doping metal elements Na, Ni, Mn, Fe, Zn, or Na, Ni, Mn, Fe, Zn, and M within this range, the doping of the transition metal layer in the layered oxide of chemical formula (I) can be further improved, thereby enhancing the structural stability of the layered oxide during sodium insertion / extraction, regulating the arrangement of metal elements in the transition metal layer, and improving the cycling stability of the specific capacity and reversible capacity of the layered oxide. Furthermore, the electrochemical performance and processing performance of the layered oxide can also be further improved.

[0085] Based on the value ranges of q, x, y, z, p, and i in the above embodiments, in some embodiments, the total stoichiometry of the doped metal elements Ni, Mn, Fe, Zn, and M in the chemical formula (Ⅰ) of the layered oxide to the stoichiometry of Na is 1:(0.8~1), optionally 1:(0.85~0.95), and further 1:(0.85~0.92). In exemplary examples, it can be a typical but non-limiting molar ratio such as 1:0.8, 1:0.82, 1:0.85, 1:0.88, 1:0.9, 1:0.95, 1:1, or any range between two stoichiometric ratios. The stoichiometry can be the number of moles and the mass converted from the number of moles. By controlling the stoichiometric ratio of Na to other metal elements contained in the layered oxide shown in chemical formula (I) within this range, the content of sodium ions can be further increased, thereby increasing the content of sodium ions that can be inserted or extracted from the layered oxide, and thus increasing the specific capacity of the layered oxide. Moreover, the sodium ions within this range can increase the content of the O3 crystal phase in the layered oxide shown in chemical formula (I), so that the layered oxide shown in chemical formula (I) mainly exhibits O3 crystals, thereby improving the structural stability of the layered oxide shown in chemical formula (I) and thus improving the cycle stability of its reversible capacity.

[0086] In some embodiments, the stoichiometric ratio of Zn to Ni in the chemical formula (I) of the layered oxide is 1:(3-15), optionally 1:(3.1-11). In exemplary cases, typical but non-limiting molar ratios such as 1:3, 1:3.1, 1:5, 1:8, 1:10, 1:11, 1:12, and 1:15, or any range between two stoichiometric ratios, are possible. The stoichiometric ratio of Zn to Ni can be the number of moles or the mass converted from the number of moles. Controlling the stoichiometric ratio of Zn to Ni in chemical formula (I) within this range can further increase the specific capacity of the layered oxide shown in the chemical formula. For example, appropriately increasing this ratio within the range, i.e., appropriately increasing the zinc content, can further increase the specific capacity of the layered oxide shown in the chemical formula.

[0087] In some embodiments, the stoichiometric ratio of Zn to Mn is 1:(4-25), optionally 1:(5-15). Exemplary examples include typical but non-limiting stoichiometric ratios such as 1:4, 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, 1:20, 1:22, and 1:25, or any range between two stoichiometric ratios. Similarly, the stoichiometry of Zn to Mn can be the number of moles and the mass converted from the number of moles. Controlling the stoichiometric ratio of Zn to Mn within this range allows for further adjustment of the Mn content in the transition metal layer of the layered oxide shown in the chemical formula. This further enhances the Jahn-Teller effect between Mn and Ni elements in the transition metal layer, further reducing structural distortion and irreversible phase transitions during sodium insertion / extraction in the layered oxide shown in the chemical formula, thereby further improving the structural stability of the layered oxide. Of course, the above-mentioned stoichiometric ratio range of Zn and Mn elements can also take into account the specific capacity of the layered oxide shown in chemical formula (Ⅰ).

[0088] Furthermore, in chemical formula (I), the ratios of Zn to Ni and Zn to Mn can be controlled separately within the aforementioned stoichiometric ranges. In one embodiment, they can be controlled simultaneously within the aforementioned stoichiometric ranges. By simultaneously controlling the stoichiometric ratios of Zn to Ni and Zn to Mn within the aforementioned stoichiometric ranges, the layered oxide shown in chemical formula (I) can better balance structural stability and specific capacity. That is, the layered oxide shown in chemical formula (I) can have better reversible capacity and cycle stability while also having a relatively high specific capacity.

[0089] Based on the value ranges of q, x, y, z, p, and i in the above embodiments, the layered oxide represented by chemical formula (Ⅰ) in the above embodiments may include Na. 0.89 Ni 0.23 Mn0.45 Fe 0.3 Zn 0.02 O2、Na 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cu 0.02 O2、Na 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 O2、Na 0.89 Ni 0.23 Mn 0.41 Fe 0.3 Zn 0.06 O2、Na 0.89 Ni 0.23 Mn 0.42 Fe 0.285 Zn 0.065 O2、Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 O2、Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.0 4V 0.02 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cr 0.02 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Al 0.02 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sc 0.02 O2、Na 0.85 Ni0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sb 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Zr 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Nb 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ti 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Mg 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ru 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.0 20 1.8At least one of the following. The layered oxides shown in these chemical formulas have a low Zn content, and this low Zn content, in conjunction with other metal elements, can significantly enhance the doping of the transition metal layer in the layered oxide shown in chemical formula (I). This results in a specific arrangement of the metal elements in the transition metal layer of the layered oxide, further improving the structural stability of the layered oxide during sodium insertion / extraction, and enhancing the specific capacity and reversible capacity cycling stability of the layered oxide. Simultaneously, by controlling the doping content of Zn with Fe or further with the doping metal element shown in M, the Ni content can be reduced, thereby reducing the cost of the layered oxide while improving its specific capacity. Furthermore, the electrochemical performance and processing performance of the layered oxide can be further improved.

[0090] Upon testing, in some embodiments, the crystal structure of the layered oxides shown in chemical formula (I) in the above embodiments includes O3 phase layered metal oxides. The O3 phase layered metal oxides refer to layered oxides with a crystal structure in which the oxygen atoms are stacked in an ABCABC pattern. In the embodiments, the layered oxides shown in chemical formula (I) in the above embodiments are mainly O3 phase layered metal oxides. "Mainly O3 phase layered metal oxides" means that the weight percentage of O3 phase layered metal oxides in the layered oxides shown in chemical formula (I) is more than 95%, further more than 98%, and of course, the weight percentage of O3 phase layered metal oxides in the layered oxides shown in chemical formula (I) can reach 100%. A higher weight percentage of O3 phase layered metal oxides in the layered oxides shown in chemical formula (I) is desirable. The layered oxide shown in chemical formula (Ⅰ) mainly exists as O3 phase layered metal oxide or pure O3 phase layered metal oxide, which makes the layered oxide have relatively high structural stability, such as relatively high structural stability compared with P2 phase layered metal oxide, and higher specific capacity and better cycle stability of reversible capacity.

[0091] In some embodiments, electron microscopy analysis shows that the layered oxide crystals represented by chemical formula (I) in the above embodiments comprise single crystals, which are flat in shape, such as... Figure 1 As shown. Since this layered oxide is mainly an O3 phase layered metal oxide, it is a single crystal.

[0092] Further electron microscopy analysis of the single crystal revealed that in some embodiments, such as Figure 2As shown, the ratio of length L, width W, and thickness H of the single crystal of the layered oxide shown in chemical formula (Ⅰ) is 1–8:1–5:0.5–2.5, and can be selected as 2–6:2–4:1–2. In the example, it can be a typical but non-limiting ratio such as 1:1:0.5, 3:2:0.5, 5:3:1, 7:4:2, 8:5:2.5, 8:2:1, or any range between two ratios. Wherein, length L and width W are respectively as shown in the figure. Figure 2 As shown in L and W, these represent the length L and width W of a large facet of a flat single crystal; the thickness is as shown in the figure. Figure 2 As shown in H, this represents the thickness of a flattened single crystal.

[0093] Based on the above-mentioned length L, width W, and thickness H ratios, in the embodiments, the length L of the single crystal can be 1 to 8 μm, and can be selected as 2 to 6 μm. In the exemplary examples, it can be a typical but non-limiting length such as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or any range between two length values.

[0094] In the embodiments, the width W of the single crystal can be 1 to 5 μm, and can be selected as 2 to 4 μm. In the exemplary example, it can be a typical but non-limiting width such as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any range between two width values.

[0095] In the embodiments, the thickness H of the single crystal can be 0.5 to 2.5 μm, and can be selected as 1 to 2 μm. In the exemplary examples, it can be a typical but non-limiting thickness such as 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, or any range between two thickness values.

[0096] In the embodiments, the Dv50 particle size of the layered oxides represented by chemical formula (I) in the above embodiments was detected to be 3–11 μm, optionally 4–8 μm. In the exemplary examples, the Dv50 particle size can be a typical but non-limiting particle size such as 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, or any range between two particle size values. Here, the Dv50 particle size refers to the particle size of the layered oxide powder represented by chemical formula (I).

[0097] The Dv50 particle size of the layered oxide shown in chemical formula (Ⅰ) in the above embodiments and the size distribution range of the single crystals of the layered metal oxide containing the O3 phase result in a high compaction density of the layered oxide, thereby improving the compaction density of the cathode material in the embodiments of this application and increasing the energy density of the battery. Simultaneously, the layered oxide also possesses a suitable specific surface area.

[0098] Testing revealed that, in the embodiments described above, the specific surface area (BET) of the layered oxides represented by chemical formula (Ⅰ) was 0.5–1.3 m². 2 / g, which can be selected from 0.6 to 0.9 m 2 / g, in the example, can be 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g is a typical but not limiting specific surface area, or a range between any two specific surface area values. A specific surface area within this range can improve properties such as the stability of the interface between the layered oxide and the electrolyte, thereby improving electrochemical performance such as cycle performance.

[0099] Testing revealed that, in the embodiments, the compaction density of the layered oxides represented by chemical formula (Ⅰ) in the above embodiments was 2.8–3.1 g / cm³ under a pressure of 2 tons. 3 The selectable value is 2.9–3.09 g / cm³. 3 In the demonstration example, the compaction density under 2 tons of pressure is 2.8 g / cm³. 3 2.9g / cm 3 3g / cm 3 3.09 g / cm 3 3.1g / cm 3 Typical but non-restrictive compaction densities or the range between any two compaction density values.

[0100] In the embodiments, the compaction density of the layered oxide represented by chemical formula (Ⅰ) in the above embodiments is 3.1–3.3 g / cm³ under a pressure of 3 tons. 3 The selectable value is 3.15–3.28 g / cm³. 3 In the demonstration example, the compaction density under 3 tons of pressure is 3.1 g / cm³. 3 3.15g / cm 3 3.2g / cm 3 3.25g / cm 3 3.28g / cm 3 3.3g / cm 3 Typical but non-restrictive compaction densities or the range between any two compaction density values.

[0101] The above-mentioned compaction density range can improve the energy density and corresponding electrochemical performance of batteries containing the layered oxides shown in the above chemical formula (Ⅰ).

[0102] Based on the morphology, crystal form, grain size, and compaction density of the layered oxide represented by chemical formula (Ⅰ) in the above embodiments, in these embodiments, the specific charging capacity of the layered oxide at 1.5–4.2V and 0.1C is 164–174 mAh / g, optionally 165–172 mAh / g; the specific discharging capacity is 158–165 mAh / g, optionally 160–163 mAh / g. In other embodiments, the initial efficiency of the layered oxide at 1.5–4.2V and 0.1C is 92–98%, optionally 92–95%.

[0103] The charge capacity, discharge capacity, and first-efficiency of this layered oxide refer to its specific capacity and first-efficiency. Specifically, this layered oxide was prepared as the positive electrode of a sodium-ion coin cell and assembled with a negative electrode to form a sodium-ion coin cell. The specific capacity and first-efficiency of the sodium-ion coin cell were then measured. The specific capacity and first-efficiency range of this layered oxide indicate that the structural stability of the crystal structure is significantly improved, demonstrating structural stability during sodium insertion / extraction, high specific capacity, and good cycle stability of the reversible capacity.

[0104] In the embodiment, the sodium-ion coin cell used to test the charge capacity and discharge capacity of the layered oxide and its first-efficiency performance was assembled according to the following method: Positive electrode sheet: The layered oxide shown in the above chemical formula (Ⅰ) is used as the positive electrode active material. It is mixed with conductive carbon nanotubes, conductive carbon black, and binder polyvinylidene fluoride (PVDF) in an appropriate amount of solvent NMP at a weight ratio of 95:0.5:2:2.5 to form a uniform positive electrode slurry. The positive electrode slurry is uniformly coated on the surface of a 13μm positive electrode current collector aluminum foil. After drying and cold pressing, the positive electrode sheet is obtained. Negative electrode sheet: Hard carbon, conductive agent SP, and CMC binder are 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 is uniformly coated on the surface of a 6μm copper foil, and after drying and cold pressing, the negative electrode sheet is obtained. Electrolyte: 1M NaPF6 / (EC / DEC, volume ratio 1:1); Diaphragm: Glass fiber; Sodium-ion button cell assembly: The positive electrode, glass fiber film and negative electrode are stacked in sequence to form a button cell assembly. The electrode assembly is put into the packaging shell, and 1M NaPF6 / (EC / DEC, volume ratio 1:1) electrolyte is added. After encapsulation, formation and settling processes, sodium-ion battery is obtained.

[0105] Based on the above embodiments, the cathode material of this application may contain only the layered oxide shown in chemical formula (Ⅰ) in the above embodiments. Of course, it may further include other cathode materials, such as one or more of polyanionic compounds, Prussian blue compounds, and other layered oxides.

[0106] In the example, the polyanionic compound may include at least one of sodium vanadium phosphate, sodium iron pyrophosphate, sodium iron phosphate, sodium fluorophosphate, etc.

[0107] In the example, the Prussian blue compounds may include at least one of Na2Fe[Fe(CN)6] (FeHCF), Na2Mn[Fe(CN)6] (MnHCF), etc.

[0108] The other cathode materials mentioned above, together with the layered oxide shown in the above chemical formula (I), can further improve the electrochemical performance of batteries containing the cathode materials of the embodiments of this application, such as energy density, reversible capacity, and cycle performance.

[0109] Preparation method of positive electrode material Secondly, embodiments of this application provide a method for preparing the cathode material according to the above embodiments. In some embodiments, the method for preparing the cathode material according to this application includes the following steps: S10: Provides Na q Ni x Mn y Fe z Zn p M i O j Precursors; S20: The precursor is sintered to obtain Na q Ni x Mn y Fe z Zn p M i O j Layered oxides.

[0110] In step S10 of the cathode material preparation method in this application embodiment, Na q Ni x Mn y Fe z Zn p M i O j The precursor is the layered oxide precursor represented by chemical formula (Ⅰ) contained in the cathode material of the embodiments described above. Therefore, the Na in S10 q Ni x Mn y Fez Zn p M i O j The ranges of q, x, y, z, p, i, and j are as follows: 0.8≤q≤1; 0.1≤x≤0.3, which can be selected as 0.15≤x≤0.25; 0.2≤y≤0.5, which can be selected as 0.25≤y≤0.45; 0.2≤z≤0.35, which can be selected as 0.25≤z≤0.32; 0.02≤p≤0.075, which can be selected as 0.04≤p≤0.07, 0.04≤p≤0.065; 0≤i≤0.1, which can be selected as 0≤i≤0.05; 1.8≤j≤2; and x+y+z+p+i≤1; M is an active and / or inert doped metal element. In the example, the doped metal element includes at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, and Ir. The sintering treatment in step S20 is to make Na in step S10 q Ni x Mn y Fe z Zn p M i O j The precursor reacts to generate the layered oxide with chemical formula (Ⅰ) contained in the cathode material of the above application embodiment.

[0111] The cathode material preparation method in this application embodiment involves Na... q Ni x Mn y Fe z Zn p M i O j The precursor is sintered to produce the positive electrode material containing the chemical formula Na in the embodiments described above. q Ni x Mn y Fe z Zn p M i O j The layered oxide produced by the cathode material preparation method in this application has a low zinc content, resulting in high structural stability during sodium insertion / extraction, thus leading to high specific capacity and cycle stability of its reversible capacity. It also exhibits high air stability and diffusion rate. Furthermore, it is effective against Na... q Ni x Mn y Fe z Zn p M i O jThe conditions for sintering the precursor can be effectively controlled, thereby improving the yield of the precursor with the chemical formula Na. q Ni x Mn y Fe z Zn p M i O j The stability of the structure and electrochemical properties of layered oxides.

[0112] Step S10: Na in step S10 q Ni x Mn y Fe z Zn p M i O j The precursor can be based on Na q Ni x Mn y Fe z Zn p M i O j The sodium, nickel, manganese, iron, and zinc sources, as well as the dopant element source shown in M, are prepared using solid-state or precipitation methods, based on the stoichiometry of the elements, such as moles or the mass ratio converted from moles.

[0113] When Na is prepared by solid-state method q Ni x Mn y Fe z Zn p M i O j In the example, Na is used as a precursor. q Ni x Mn y Fe z Zn p M i O j The precursor can be prepared by a method including the following steps: Step S11: According to Na q Ni x Mn y Fe z Zn p M i O j By using the elemental stoichiometry, sodium, nickel, manganese, iron, and zinc sources, along with the dopant element source shown in M, are subjected to solid-state mixing to obtain Na. q Ni x Mn y Fe z Zn p Mi O j The precursor.

[0114] In step S11, solid-phase mixing is relative to liquid-phase mixing. It generally refers to the mixing process without adding solvents, such as water. It also means that the sodium source, nickel source, manganese source, iron source and zinc source or the source solid containing the doping element M is dry-mixed under solvent-free conditions.

[0115] To improve the uniformity of mixing of the sodium, nickel, manganese, iron, and zinc sources, or sources further containing doping elements as shown in M, during the solid-state mixing process, in this embodiment, the nickel, manganese, iron, and zinc sources, or sources further containing doping elements as shown in M, can be mixed first, and then the sodium source can be added for a second mixing process. This improves the mixing uniformity of each source and enhances the safety of the solid-state mixing process.

[0116] In this embodiment, the mixing process can include, but is not limited to, ball milling. Any method that improves the uniformity of mixing the sodium, nickel, manganese, iron, and zinc sources, or further includes dopant elements as shown in M, falls within the scope of this application. In this embodiment, when the mixing process is ball milling, the milling speed can be controlled to be 300–1000 rpm, optionally 400–600 rpm; the milling time can be 1–6 h, optionally 2–4 h. This ball milling process improves the uniformity of mixing among the sources, thereby ultimately increasing the Na content in step S20. q Ni x Mn y Fe z Zn p M i O j The stability of the structure and electrochemical properties of layered oxides.

[0117] In the example, the sodium source can be a sodium salt, such as at least one of sodium carbonate, sodium hydroxide, etc.

[0118] In the example, the nickel source can be a soluble or insoluble nickel compound, such as nickel oxide (NiO) or a nickel salt. The nickel salt can include at least one of nickel nitrate, nickel carbonate, nickel hydroxide, and nickel sulfate.

[0119] In the example, the manganese source can be a soluble or insoluble manganese compound, such as manganese oxide (Mn2O3) or a manganese salt. The manganese salt can include at least one of manganese nitrate, manganese carbonate, manganese hydroxide, and manganese sulfate.

[0120] In the example, the iron source can be a soluble or insoluble iron compound, such as an iron oxide (e.g., Fe₂O₃) or an iron salt. The iron salt can include at least one of ferric nitrate, ferric carbonate, ferric hydroxide, and ferric sulfate.

[0121] In the example, the zinc source can be a soluble or insoluble zinc compound, such as zinc oxide (e.g., ZnO) or a zinc salt. The zinc salt can include at least one of zinc nitrate, zinc carbonate, zinc hydroxide, and zinc sulfate.

[0122] In the example, the source of the doped metal element M can be a soluble or insoluble compound of the doped metal element M, such as an oxide or a salt of the doped metal element M. The salt of the doped metal element M can include at least one of the following: nitrate, carbonate, hydroxide, sulfate, etc.

[0123] The aforementioned sodium, nickel, manganese, iron, and zinc sources, or further sources containing the doping element shown in M, can effectively achieve uniform mixing during the mixing process, improving the Na... q Ni x Mn y Fe z Zn p M i O j The precursor generates Na q Ni x Mn y Fe z Zn p M i O j The structure and chemical stability of layered oxides.

[0124] When Na is prepared by precipitation method q Ni x Mn y Fe z Zn p M i O j In the example, Na is used as a precursor. q Ni x Mn y Fe z Zn p M i O j The precursor can be prepared by a method including the following steps: Step S12: According to Na q Ni x Mn y Fe z Zn p Mi O j In the elemental stoichiometry, a mixed solution is prepared by using a soluble nickel source, a soluble manganese source, a soluble iron source, a soluble zinc source, or a source containing a soluble dopant element as shown in M, and then at least one of a precipitant and a complexing agent is added for co-precipitation treatment to obtain a precipitate mixture. Step S13: Mix the precipitate mixture with a sodium source to obtain Na. q Ni x Mn y Fe z Zn p M i O j The precursor.

[0125] In step S12, at least one of the precipitant and complexing agent should be a compound that can cause nickel, manganese, iron, zinc and doped metal elements shown in M ​​from the nickel source, soluble manganese source, soluble iron source, soluble zinc source and soluble doped element source M to precipitate. For example, in the embodiment, the precipitant may include at least one of alkali metal hydroxide, carbonate and the like.

[0126] In the embodiments, the complexing agent may include inorganic or organic complexing agents. In the exemplary embodiment, the inorganic complexing agent may include at least one of ammonia, ammonium bicarbonate, ammonium sulfate, ammonium carbonate, etc.; the organic complexing agent may include at least one of citric acid, tartaric acid, disodium ethylenediaminetetraacetate, ethylenediaminetetraacetic acid (EDTA), aminotriacetic acid (NTA), etc.

[0127] These types of precipitants and complexing agents can effectively precipitate nickel, manganese, iron, zinc, and the dopant element shown in M.

[0128] In the embodiments, at least one of the precipitant and 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, thereby increasing the Na content. q Ni x Mn y Fe z Zn p M i O j The accuracy of the stoichiometric ratio of the metal elements contained in the precursor.

[0129] In the example, the soluble nickel source may include at least one of nickel acetate, nickel chloride, nickel nitrate, and nickel sulfate.

[0130] In the example, the soluble manganese source may include at least one of manganese nitrate, manganese sulfate, halide, etc.

[0131] In the example, the soluble iron source may include at least one of iron nitrates, manganese sulfate, halides, etc.

[0132] In the example, the soluble zinc source may include at least one of zinc nitrate, manganese sulfate, halide, etc.

[0133] In the example, the soluble doped metal element source shown in M ​​may include at least one of the doped metal element shown in M, such as nitrate, manganese sulfate, or halide.

[0134] The aforementioned soluble nickel source, soluble manganese source, soluble iron source, soluble zinc source, and soluble dopant source M all have good solubility, and the stoichiometric ratio of each metal element in the precipitate mixture can be quantitatively controlled.

[0135] The mixing ratio between the sodium source and the precipitate mixture in step S13 should satisfy Na q Ni x Mn y Fe z Zn p M i O j The stoichiometric ratio of sodium in the mixture. This mixing process can be a solid-phase mixing process or the soluble sodium source can be dissolved, mixed with the precipitate mixture, and then the solvent can be removed.

[0136] In the example, the sodium source can be a sodium salt, such as at least one of sodium carbonate, sodium hydroxide, etc.

[0137] Furthermore, there is no sequential relationship between the above steps S11, S12, and S13.

[0138] Step S20: In step S20, the Na in step S10 is... q Ni x Mn y Fe z Zn p M i O j After the precursor is sintered, it will produce a substance with the chemical formula Na. q Ni x Mn y Fe z Zn p M i O j Layered oxides. The study found that sintering conditions significantly affected the formation of Na. q Ni x Mn y Fe z Zn p M i Oj The structural stability and electrochemical performance of layered oxides are affected to some extent. In some embodiments, the sintering temperature can be controlled between 700 and 980°C, preferably between 750 and 950°C. In exemplary cases, it can be typical but non-limiting temperatures such as 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, and 980°C, or any range between two temperature values.

[0139] At the above sintering temperature, the sintering time can be 4h to 20h, or 6h to 12h. In the example, it can be a typical but non-limiting number of hours such as 4h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, or any range between two hours.

[0140] By stabilizing the sintering process and controlling the time within the above range, the Na in step S10 can be ensured to be within the specified range. q Ni x Mn y Fe z Zn p M i O j The precursor reaction generates Na q Ni x Mn y Fe z Zn p M i O j Layered oxides, and can further enhance Na q Ni x Mn y Fe z Zn p M i O j The structural stability of layered oxides during sodium insertion / extraction further enhances their high specific capacity and the cycling stability of their reversible capacity. It also improves the Na... q Ni x Mn y Fe z Zn p M i O j The content of O3 phase layered metal oxide and single crystal content in layered oxides are controlled to adjust the single crystal size and particle size of the layered oxides, thereby increasing the compaction density of the layered oxides.

[0141] In the embodiments, the sintering temperature can be increased to the sintering temperature at a heating rate of 2–15 °C / min. This heating rate can be further controlled to be 4–10 °C / min. In exemplary cases, the heating rate can be typical but not limiting rates such as 2 °C / min, 4 °C / min, 6 °C / min, 8 °C / min, 10 °C / min, 12 °C / min, 15 °C / min, 17 °C / min, 18 °C / min, and 20 °C / min, or a range between any two rate values. By controlling the heating rate of the sintering process, such as controlling it within this heating rate range, the Na… q Ni x Mn y Fe z Zn p M i O j Layered oxides have complete and well-formed crystals, which can improve the uniformity of crystal morphology.

[0142] In addition, the sintering process in step S20 above should be understood to be carried out in an oxygen-containing environment. For example, in the embodiment, it can be sintering in air or in an oxygen-containing protective atmosphere, such as oxygen-containing nitrogen or other inert atmospheres.

[0143] positive electrode Thirdly, embodiments of this application provide a positive electrode. In some embodiments, the positive electrode of this application includes a current collector and a positive electrode active material layer. The positive electrode active material layer is bonded to the current collector, and the positive electrode active material layer contains the positive electrode material described in the embodiments of this application.

[0144] In the positive electrode of this application embodiment, the current collector refers to a structure used to collect current and transport electrons. The positive electrode active material layer refers to a layer structure containing positive electrode active material, which is a key substance participating in the battery chemical reaction in the positive electrode. The positive electrode active material includes the positive electrode material of the above-described application embodiment. The bonding between the positive electrode active material layer and the current collector means that the positive electrode active material layer is at least bonded to the surface of the current collector. Furthermore, the positive electrode can be an electrode sheet, meaning the positive electrode has a sheet-like morphology. Of course, it can also be configured into other morphologies as needed.

[0145] Because the positive electrode active material layer of the positive electrode in this embodiment contains the positive electrode material described in the above embodiment, the specific capacity of this positive electrode is relatively high, and its cycle performance is good.

[0146] In the embodiments of this application, the current collector included in the positive electrode includes, but is not limited to, metal current collectors, carbon current collectors, conductive resin current collectors, and composite current collectors of metal and resin, and more specifically, aluminum, copper, nickel, titanium, iron and their respective alloys, stainless steel, carbon fiber, carbon nanotubes (CNTs), graphite, etc. In the embodiments, the current collector can also be a dense film layer or a porous film layer. In the embodiments, the current collector can be, but is not limited to, aluminum foil or porous aluminum foil.

[0147] In the embodiments of this application, the positive electrode active material layer contained in the positive electrode may be at least stacked on the surface of the current collector. When the surface layer of the current collector has a porous structure or the current collector itself has a porous structure, the positive electrode active material layer may be at least partially embedded in the current collector.

[0148] In some embodiments, the positive electrode active material layer is at least bonded to the surface of the current collector, and may be as follows: Figure 3 In the structure shown, the positive electrode active material layer 12 is stacked 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 has a porous structure, the positive electrode active material layer 12 can extend further into the porous structure of the current collector 11 in addition to being stacked on the surface of the current collector 11.

[0149] In other embodiments, the positive electrode active material layer is at least bonded to the surface of the current collector, and may be as follows: Figure 4 In the structure shown, the current collector 11 has two opposing surfaces, and the positive electrode active material layer 12 is stacked on the two opposing surfaces of the current collector 11. When at least one of the two surfaces of the current collector 11 has a porous structure or the current collector 11 as a whole is a porous structure, the positive electrode active material layer 12 can extend further into the porous structure of the current collector 11, in addition to being stacked on the two surfaces of the current collector 11.

[0150] As an embodiment of this application, in the above-mentioned positive electrode active material layer, the mass content of the layered oxide of chemical formula (Ⅰ) contained in the positive electrode material of the above-mentioned embodiment of this application can be 90% to 98%, optionally 92% to 96%, and in exemplary examples, it can be typical but non-limiting contents such as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or any range between two contents. The layered oxide in this content range can effectively improve the specific capacity of the positive electrode, thereby improving the energy density of the battery, and has good cycle performance. Since the layered oxide also has good processing performance, it also effectively improves the film quality of the positive electrode active material layer.

[0151] In addition to the positive electrode active material components described above, the positive electrode active material layer in the embodiments of the above applications generally also includes components such as binders and conductive agents. The binder enhances the mechanical properties between the positive electrode active material layer itself and the current collector. The conductive agent effectively improves the conductivity of the positive electrode, such as reducing its resistance.

[0152] In the embodiments, the mass content of the binder contained in the above-mentioned positive electrode active material layer can be 0.5% to 5%, optionally 1% to 3%, and in the exemplary examples, it can be a typical but non-limiting content such as 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, or any range between two content values.

[0153] In the embodiments, the adhesive may include one or more of oil-soluble adhesives, water-soluble adhesives, and emulsion adhesives. In the exemplary embodiments, the oil-soluble adhesive may include one or more of polyvinylidene fluoride, polyimide, polytetrafluoroethylene, polybutyl acrylate, and polyacrylonitrile; in the exemplary embodiments, the water-soluble adhesive may include one or more of carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylate, polyvinyl alcohol, sodium alginate, and cyclodextrin; in the exemplary embodiments, the emulsion adhesive may include one or more of styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0154] The content of this range and the types of binders mentioned above can effectively enhance the mechanical properties of the positive electrode active material layer and the bonding strength between it and the current collector, thereby effectively improving the cycle performance of the positive electrode.

[0155] In the embodiments, the mass content of the conductive agent contained in the above-mentioned positive electrode active material layer can be 0.5% to 5%, optionally 1% to 3%, and in the exemplary examples, it can be a typical but non-limiting content such as 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, or any range between two content values.

[0156] In this embodiment, the conductive agent may include at least one of particulate conductive agents and linear conductive agents. The particulate conductive agent may include one or more of acetylene black (SP), conductive carbon black (super-P), Ketjen black, and graphene. The linear conductive agent may include one or more of carbon nanotubes, carbon fibers, and conductive oxide nanowires. The particulate conductive agent is a conductive agent with a non-linear particle morphology, as opposed to a linear conductive agent. A linear conductive agent refers to a conductive agent with a one-dimensional fiber morphology.

[0157] The content of this range and the types of conductive agents mentioned above can effectively improve the conductivity of the positive electrode active material layer.

[0158] In the embodiments, the conductive agent contained in the positive electrode active material layer of the positive electrode in the above embodiments includes a linear conductive agent and a particulate conductive agent. The mass content of the linear conductive agent in the positive electrode active material layer is 0.1% to 2.5%, optionally 0.2% to 0.8%. In exemplary examples, it can be a typical but non-limiting content or a range between any two content values, such as 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%, and 2.5%. Since the layered oxide crystals of chemical formula (I) contained in the positive electrode material of the above embodiments include single crystals, and the morphology of these single crystals is flat, adding a linear conductive agent to the positive electrode active material layer and controlling the content of the linear conductive agent within this range allows 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 be wound around the surface of the flat single crystal particles. The particulate conductive agent can be effectively dispersed in the gaps of the positive electrode material. In this way, the linear conductive agent constructs a long-range conductive network structure in the positive electrode active material layer, while the particulate conductive agent constitutes a short-range conductive structure. Therefore, the conductivity enhancement effect of the linear and particulate conductive agents in the positive electrode active material layer effectively improves the conductivity of the positive electrode active material layer and can significantly reduce the internal resistance of the positive electrode.

[0159] In the embodiments, the aspect ratio of the linear conductive agent can be selected from 40 to 3000:1, or from 50 to 2500:1. In exemplary cases, typical but non-limiting aspect ratios such as 40:1, 50:1, 100:1, 500:1, 1000:1, 1500:1, 2000:1, 2500:1, and 3000:1, or any range between two aspect ratios, can be used. This aspect ratio refers to the ratio of the length to the diameter of the linear conductive agent.

[0160] In a further embodiment, the length of the linear conductive agent can be selected to be 0.5 to 5 μm, or 0.5 to 2 μm. In the example, typical but non-limiting lengths such as 0.5 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm, or any range between two length values, can be used.

[0161] In a further embodiment, the diameter of the linear conductive agent can be selected to be 2 to 10 nm, or 3 to 7 nm. In the exemplary example, it can be a typical but non-limiting diameter such as 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or any range between two diameter values.

[0162] By controlling the aspect ratio of the linear conductive agent within the aforementioned range, or further controlling the length and diameter of the linear conductive agent within the aforementioned range, the linear conductive agent can construct a richer long-range conductive network structure in the positive electrode active material layer, further enhancing the conductivity synergistic effect of the linear conductive agent and the particulate conductive agent, thereby further improving the conductivity of the positive electrode active material layer.

[0163] In the embodiments, the positive electrode active material layer in the positive electrode of the above embodiments may contain other additives in addition to components such as positive electrode active material, binder, and conductive agent. In the embodiments, the additives may include, but are not limited to, functional components such as sodium supplementation additives.

[0164] In some embodiments, the content of the positive electrode active material layer on one side of the current collector, i.e., the coating weight (CW), in the above embodiments is 260–350 mg / 1540.25 mm. 2 The dosage can be selected as 280–320 mg / 1540.25 mg. 2 In the example, it can be 260mg / 1540.25mm 2 270mg / 1540.25mm 2 280mg / 1540.25mm 2 290mg / 1540.25mm 2 300mg / 1540.25mm 2 310mg / 1540.25mm 2 320mg / 1540.25mm 2 330mg / 1540.25mm 2 340mg / 1540.25mm 2 350mg / 1540.25mm 2 Typical but non-limiting contents or a range between any two contents. The coating weight refers to the weight of the positive electrode active material layer per unit area. This range of coating weights can effectively increase the specific capacity of the positive electrode, thereby increasing the energy density of the battery.

[0165] In some embodiments, the compaction density of the positive electrode active material layer in the above embodiments can be 2.8–3.4 g / cm³. 3 The selectable value is 2.9–3.2 g / cm³. 3 In the example, it can be 2.8 g / cm³. 3 2.9g / cm 3 3.0g / cm 3 3.1g / cm 3 3.2g / cm 3 3.3g / cm 33.4g / cm 3 Typical but not limiting compaction densities, or any range between two compaction density values, are specified. This compaction density refers to the weight of the positive electrode active material layer per unit volume. Compaction densities within this range can effectively increase the specific capacity of the positive electrode, thereby improving the energy density of the battery, and also exhibit good stability at the electrolyte interface.

[0166] In some embodiments, the porosity of the positive electrode active material layer in the above embodiments can be 40% to 65%, optionally 45% to 60%. In exemplary examples, typical but non-limiting porosities such as 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 63%, and 65%, or any range between two porosity values, are possible. This porosity refers to the percentage of the total volume of pores per unit volume of the positive electrode active material layer to the unit volume of the positive electrode active material layer. A porosity within this range allows the positive electrode active material layer to have the aforementioned compaction density, increasing the specific capacity of the positive electrode and thus improving the energy density of the battery, and also improving the wettability of the electrolyte.

[0167] In some embodiments, the positive electrode in the above embodiments is the electrode sheet, and the film resistance of the positive electrode active material layer in the above embodiments can be 0.5–5 mΩ, optionally 0.5–3 mΩ. In exemplary examples, it can be a typical but non-limiting film resistance such as 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, or any range between two film resistance values. The electrode sheet has the sheet-like morphology described above, and therefore has two opposing surfaces. The film resistance refers to the resistance value between one surface of the sheet-like positive electrode and the opposing surface. This range of film resistance can effectively improve the battery's performance, including efficiency and lifespan.

[0168] In some embodiments, the positive electrode in the above embodiments is the electrode sheet, and the ratio of the thickness of the electrode sheet from one surface to the opposite surface to the thickness of the current collector is 6 to 15:1, optionally 8 to 14:1. In exemplary examples, typical but non-limiting ratios such as 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, and 15:1, or any range between two ratios, can be used. This thickness refers to the vertical distance from one surface of the layer structure to the opposite surface. When... Figure 3 When a positive electrode active material layer is disposed on one surface of the current collector, the thickness from one surface of the electrode to the opposite surface refers to the sum of the thickness of one positive electrode active material layer and the thickness of the current collector; when... Figure 4 When both surfaces of the current collector shown contain positive electrode active material layers, the thickness of one surface of the electrode to the opposite surface refers to the sum of the thicknesses of the two positive electrode active material layers plus the total thickness of the current collector.

[0169] In the embodiments, the thickness of the positive electrode active material layer contained in the electrode sheet can be controlled to be 104–182 μm, and more specifically 110–170 μm. In exemplary cases, typical but non-limiting thicknesses such as 104 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, and 182 μm, or any range between two thickness values, are possible. In the embodiments, the thickness of the current collector can be, but is not limited to, 13 μm.

[0170] By controlling the total thickness of the electrode to the thickness of the current collector within the aforementioned ratio range or a specific thickness range, the specific capacity of the electrode can be effectively increased, thereby increasing the energy density of the battery. It can also improve the bonding strength between the positive electrode active material layer and the current collector, enhance the mechanical strength of the electrode structure, and improve the cycle performance of the electrode.

[0171] Methods for preparing the positive electrode: This application also provides a method for preparing the positive electrode of the above embodiments. In some embodiments, the method for preparing the positive electrode of the above embodiments includes the following steps: S30: Mix components including positive electrode active material, binder, conductive agent and other components in a solvent in a certain proportion to prepare positive electrode slurry; S40: The positive electrode slurry is film-formed on the current collector to form a positive electrode active material layer, thus obtaining the positive electrode.

[0172] Step S30: The positive electrode active material in step S30 includes the positive electrode material of the above-described application embodiments, specifically including the layered oxide shown in the above chemical formula (Ⅰ).

[0173] In step S30, the positive electrode active material, binder, conductive agent, and other components can be mixed according to the corresponding component content ratios contained in the positive electrode active material layer of the positive electrode described above. The solvent can be an organic solvent or water suitable for preparing the positive electrode slurry.

[0174] The mixing process in step S30 can be carried out according to conventional electrode slurry preparation methods, such as, but not limited to, stirring, until the components are evenly dispersed to form a stable positive electrode slurry. Of course, the viscosity and other properties of this positive electrode slurry should meet the requirements of the film-forming process so as to form a positive electrode active material layer that meets quality requirements on the current collector.

[0175] Step S40: Based on the positive electrode slurry components prepared in step S30, the positive electrode active material layer prepared in step S40 is the positive electrode active material layer contained in the positive electrode of the above-described embodiment.

[0176] In step S40, the positive electrode slurry is deposited on the current collector in a film-forming process that follows conventional methods for forming positive electrode active material layers. For example, in this embodiment, the electrode slurry can first be deposited on the current collector to form a wet film; then dried to allow the solvent to evaporate, thus drying the wet film; finally, the dried film is rolled to form a positive electrode active material layer, thereby obtaining the positive electrode.

[0177] Of course, the positive electrode active material layer can also be prepared by an improved method of the conventional positive electrode active material layer preparation method, or by a new method. As long as the positive electrode active material layer is prepared by applying the electrode slurry in step S30 onto the current collector, it falls within the scope of the embodiments disclosed in this application.

[0178] Furthermore, the film-forming conditions in S40 can be controlled and adjusted, such as the conditions for the formation of a wet film of the positive electrode slurry on the current collector in step S30, and the conditions for the rolling process. This allows for the control and adjustment of the relevant properties of the formed positive electrode active material layer, such as controlling and adjusting the content of the positive electrode active material layer on a single surface of the current collector to 260–350 mg / 1540.25 mm as mentioned above. 2 The compaction density should be controlled and adjusted to the range of 2.8–3.4 g / cm³ as described above. 3 The porosity is controlled and adjusted to the range of 40% to 65% as mentioned above, and the film resistance of the electrode is controlled and adjusted to the range of 0.5 to 5 mΩ as mentioned above.

[0179] Battery Fourthly, embodiments of this application also provide a sodium battery.

[0180] In the embodiments of this application, the sodium battery may include any one of sodium battery cell, battery module, and battery pack.

[0181] Sodium battery cell: A sodium battery cell, also known as a sodium battery module, refers to the battery including its outer packaging and the electrode assembly encapsulated within it. A single battery cell can contain one or more electrode assemblies, which can be adjusted according to actual needs.

[0182] The outer packaging of the sodium battery cell can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell; or it can be a soft package, such as a pouch. The soft package material can be plastic, such as polypropylene, polybutylene terephthalate, or polybutylene succinate. The shape of the outer packaging can be cylindrical, square, or any other arbitrary shape. This outer packaging shape determines the shape of the sodium battery cell; therefore, the shape of the sodium battery cell can also be cylindrical, square, or any other arbitrary shape corresponding to the shape of the outer packaging. In the example, the sodium battery cell can be as follows: Figure 5The shown is a square-structured battery cell 20.

[0183] In some embodiments, such as Figure 6 As shown, the outer packaging of the battery cell 20 may include a housing 21 and a cover plate 23. The housing 21 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing 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 within the receiving cavity.

[0184] In the embodiments, the sodium battery cell can be a sodium battery cell containing electrolyte or a sodium battery cell containing solid electrolyte.

[0185] When the sodium battery cell contains an electrolyte, the electrode assembly typically includes a positive electrode, a negative electrode, and a separator. The positive and negative electrodes are alternately stacked, and the separator is stacked between them to provide isolation. This positive electrode, separator layer, and negative electrode can be formed into a laminated electrode assembly using a lamination process, or into a wound electrode assembly using a winding process. The electrode assembly containing the separator is placed in an outer package, injected with electrolyte to wet the electrode assembly, and then encapsulated to obtain the sodium battery cell.

[0186] When the sodium battery cell contains a solid electrolyte, the electrode assembly typically includes a positive electrode, a negative electrode, and a solid electrolyte. The positive and negative electrodes are alternately stacked, and the solid electrolyte is stacked between the positive and negative electrodes to provide insulation, separating them. The electrode assembly containing the solid electrolyte is placed in an outer package and then encapsulated to obtain the sodium battery cell.

[0187] In each of the above sodium battery cells, the positive electrode contained in the electrode assembly is the positive electrode of the above-described embodiment, that is, the positive electrode material of the above-described embodiment is contained in its positive electrode active material layer, specifically containing the layered oxide shown in the above chemical formula (Ⅰ).

[0188] In this way, the sodium battery cell has high energy density and good cycle performance.

[0189] As shown in the embodiment, the energy density of the sodium battery cell can reach 110–160 Wh / kg, optionally 120–155 Wh / kg. The capacity retention rate after 1000 cycles under 0.5C / 1C charge / discharge conditions within the range of 1.5–4.05V can reach 70–95%, optionally 80–90%.

[0190] In the aforementioned sodium battery cells, the negative electrode assembly includes a negative electrode current collector and optionally a negative electrode active material layer disposed on the surface of the negative electrode current collector, the negative electrode active material layer containing a negative electrode active material. In the embodiments, the negative electrode current collector may include, but is not limited to, a metal or composite current collector. For example, as a metal, sodium, sodium alloys, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, silver alloys, etc., can be used. When sodium or sodium alloys are used as the negative electrode current collector, since sodium or sodium alloys themselves can also serve as negative electrode active materials, the negative electrode sheet may not contain a negative electrode active material layer; sodium or sodium alloys are both the current collector and the negative electrode active material.

[0191] Composite current collectors can be composite materials of polymer materials and metals. The polymer materials may include, but are not limited to, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE), while the metals may include, but are not limited to, sodium, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Composite current collectors can be obtained by blending polymer materials and metals, or by electroplating, coating, or other methods to coat at least one side of the polymer material.

[0192] When the negative electrode includes a negative electrode active material layer, the negative electrode active material in the negative electrode active material layer can be a mixture or composite material formed from any one or more of carbon-based materials, alloy materials, titanium-based materials, and sodium metal. Among them, carbon-based materials include, but are not limited to, one or more of graphite, soft carbon, hard carbon, carbon microspheres, and carbon fibers; alloy materials include, but are not limited to, one or more of sodium-tin alloys, sodium-germanium alloys, and sodium-antimony alloys; and titanium-based materials include, but are not limited to, one or more of titanium dioxide, titanates, and titanium phosphates.

[0193] The mass content of the negative electrode active material in the negative electrode active material layer can be 85% to 98%, and can be selected as 95% to 98%. In the example, it can be a typical but non-limiting content such as 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or any range between two content values.

[0194] The negative electrode active material layer may also include at least one of a conductive agent and a binder. The conductive agent is used to collect current between the negative electrode active materials and between the active materials and the current collector, thereby improving electronic conductivity. Simultaneously, the conductive agent can also promote the wetting of the negative electrode sheet by the electrolyte. 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.

[0195] 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 examples, it can be a typical but non-limiting content such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two content values. Other contents can also be set as needed. In the exemplary examples, the conductive agent includes one or more of acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fiber, and graphene.

[0196] 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 examples, it can be a typical but non-limiting content such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two content values. Other contents can also be set as needed. In the exemplary examples, the binder includes, but is not limited to, one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyimide, polytetrafluoroethylene, polybutyl acrylate, polyacrylonitrile, carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylate, polyvinyl alcohol, sodium alginate, cyclodextrin, styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0197] In the embodiments, the negative electrode active material layer may optionally include a thickener, such as, but not limited to, carboxymethyl cellulose (CMC). The mass content of the thickener in the negative electrode active layer can be set to 0.5% to 5%, and in exemplary examples, it can be a typical but non-limiting content such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range between any two content values.

[0198] In the embodiments, when each of the above-mentioned sodium battery cells contains a separator, the separator, as described above, is disposed between the positive and negative electrodes, separating them. The separator prevents electrons in the battery from passing freely, thus preventing short circuits between the electrodes, but allows sodium ions in the electrolyte to pass freely between the positive and negative electrodes. The separator can be any known porous structure separator with electrochemical and mechanical stability. In the examples, the separator includes at least one single-layer or multi-layer film of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF).

[0199] In the embodiments, when each of the above-mentioned sodium battery cells contains a solid electrolyte, the solid electrolyte, as described above, is disposed between the positive and negative electrodes, separating the positive and negative electrodes. The solid electrolyte may include at least one of polymer solid electrolytes, oxide electrolytes, sulfide electrolytes, borohydride electrolytes, and composite solid electrolytes.

[0200] Battery module: When the sodium battery in the embodiments of this application is a battery module, the battery module refers to the assembly of the above-mentioned sodium battery cells, that is, it can contain multiple of the above-mentioned sodium battery cells, and the specific number can be adjusted according to the application and capacity of the battery module.

[0201] In some embodiments, Figure 7 This is a schematic diagram of battery module 30 as an example. (See diagram below.) Figure 7 As shown, in the battery module 30, multiple sodium battery cells 20 can be arranged sequentially along the length of the battery module 30. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 20 can be secured using fasteners.

[0202] Optionally, the battery module 30 may also include a housing with a receiving space in which a plurality of sodium battery cells 20 are received.

[0203] Battery pack: When the sodium battery in the embodiments of this application is a battery pack, the battery pack refers to the assembly of the sodium battery cells described above, that is, it can contain multiple sodium battery cells, and these multiple sodium battery cells are assembled into the battery module described above. The specific number of battery cells or battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0204] In some embodiments, Figure 8 and Figure 9 This is a schematic diagram of a battery pack 40 as an example. The battery pack 40 may include a battery compartment and multiple battery modules 30 disposed within the battery compartment. The battery compartment includes an upper compartment 41 and a lower compartment 42. The upper compartment 41 covers the lower compartment 42, forming a closed space for accommodating the battery modules 30. The multiple battery modules 30 can be arranged in any manner within the battery compartment.

[0205] Electrical appliances Fifthly, this application also provides an electrical device. The electrical device of this application includes a power supply unit or an energy storage unit, and may also include other auxiliary or necessary components. The power supply unit or energy storage unit contains the sodium battery described in the above application embodiment. For example, it may be a sodium battery cell, a battery module, or a battery pack. Because the electrical device of this application embodiment contains the sodium battery described in the above application embodiment, the power supply unit or energy storage unit of the electrical device of this application embodiment has high energy density, good cycle performance, and long service life, and the standby or battery life of the electrical device of this application embodiment is long.

[0206] In this embodiment, the electrical device may include, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc. As the electrical device, individual battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0207] Figure 10 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0208] In the embodiments, when the electrical device includes an energy storage unit, the electrical device can be an energy storage device, which includes the energy storage unit and may also include other auxiliary or necessary components. The energy storage unit contains the battery described in the above-described embodiment. The energy storage unit may contain one or more batteries. When there are multiple batteries, they can form a battery module or battery pack. Because the energy storage device of this embodiment includes the battery described in the above-described embodiment, the energy storage device has high energy density, good cycle performance, long service life, and further high energy density.

[0209] Example The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0210] 1. Examples of cathode materials and their preparation methods Example A1 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.89 Ni 0.23 Mn 0.45 Fe 0.3 Zn 0.02 Layered oxides of O2.

[0211] The method for preparing the cathode material includes the following steps: S1: According to Na 0.89 Ni 0.23 Mn 0.45 Fe 0.3 Zn0.02 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and Fe2O3 at 500 rpm for 6 hours, followed by mixing with excess sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.89 Ni 0.23 Mn 0.45 Fe 0.3 Zn 0.02 Layered oxides of O2; wherein the sintering conditions are: temperature: 850℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0212] Example A2 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 Layered oxides of O2.

[0213] The method for preparing the cathode material includes the following steps: S1: According to Na 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and Fe2O3 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 Layered oxides of O2; wherein the sintering conditions are: temperature: 860℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0214] Example A3 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cu 0.02 Layered oxides of O2.

[0215] The method for preparing the cathode material includes the following steps: S1: According to Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cu 0.02 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, Fe2O3, and CuO at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cu 0.02 Layered oxides of O2; wherein the sintering conditions are: temperature: 865℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0216] Example A4 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 Layered oxides of O2.

[0217] The method for preparing the cathode material includes the following steps: S1: According to Na 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and Fe2O3 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 Layered oxides of O2; wherein the sintering conditions are: temperature: 865℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0218] Example A5 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.89 Ni 0.23 Mn0.41 Fe 0.3 Zn 0.06 Layered oxides of O2.

[0219] The method for preparing the cathode material includes the following steps: S1: According to Na 0.89 Ni 0.23 Mn 0.41 Fe 0.3 Zn 0.06 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and Fe2O3 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.89 Ni 0.23 Mn 0.41 Fe 0.3 Zn 0.06 Layered oxides of O2; wherein the sintering conditions are: temperature: 865℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0220] Example A6 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.89 Ni 0.23 Mn 0.42 Fe 0.285 Zn 0.065 Layered oxides of O2.

[0221] The method for preparing the cathode material includes the following steps: S1: According to Na 0.89 Ni 0.23 Mn 0.42 Fe 0.285 Zn 0.065 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and Fe2O3 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.89 Ni 0.23 Mn 0.42 Fe 0.285 Zn 0.065 Layered oxides of O2; wherein the sintering conditions are: temperature: 865℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0222] Example A7 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 Layered oxides of O2.

[0223] The method for preparing the cathode material includes the following steps: S1: According to Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and Fe2O3 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 Layered oxides of O2; wherein the sintering conditions are: temperature: 880℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0224] Example A8 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 Layered oxides of O2.

[0225] The method for preparing the cathode material includes the following steps: S1: According to Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and Fe2O3 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075Layered oxides of O2; wherein the sintering conditions are: temperature: 880℃; time: 10h; heating rate: 5℃ / min; oxygen atmosphere.

[0226] Example A9 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 Layered oxides of O2.

[0227] The method for preparing the cathode material includes the following steps: S1: According to Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 The molar ratio of metal elements contained in O2 is used to fully dissolve nickel nitrate, zinc nitrate, manganese nitrate, and ferric nitrate to prepare a mixed solution; then, sufficient ammonium carbonate is added to the mixed solution for co-precipitation treatment to obtain a precipitate mixture; S2: According to Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 The molar ratio of sodium in O2 was determined by mixing the precipitate mixture with sodium carbonate to obtain Na. 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2 precursor.

[0228] S3: Put Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 The O2 precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 Layered oxides of O2; wherein the sintering conditions are: temperature: 850℃; time: 14h; heating rate: 5℃ / min; oxygen atmosphere.

[0229] Example A10 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.85 Ni 0.23 Mn 0.42Fe 0.28 Zn 0.04 Al 0.02 Layered oxides of O2.

[0230] The method for preparing the cathode material includes the following steps: S1: According to Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Al 0.02 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and Al2O3 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Al 0.02 Layered oxides of O2; wherein the sintering conditions are: temperature: 850℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0231] Example A11 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 Layered oxides of O2.

[0232] The method for preparing the cathode material includes the following steps: S1: According to Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and SnO2 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02Layered oxides of O2; wherein the sintering conditions are: temperature: 850℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0233] Example A12 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ti 0.02 Layered oxides of O2.

[0234] The method for preparing the cathode material includes the following steps: S1: According to Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ti 0.02 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and TiO2 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ti 0.02 Layered oxides of O2; wherein the sintering conditions are: temperature: 850℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0235] Example A13 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Mg 0.02 Layered oxides of O2.

[0236] The method for preparing the cathode material includes the following steps: S1: According to Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Mg 0.02The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and MgO at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Mg 0.02 Layered oxides of O2; wherein the sintering conditions are: temperature: 850℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0237] Example A14 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 Layered oxides of O2.

[0238] The method for preparing the cathode material includes the following steps: S1: According to Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and IrO2 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 Layered oxides of O2; wherein the sintering conditions are: temperature: 850℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0239] Example A15 This embodiment provides a cathode material and its preparation method. The cathode material includes materials with the chemical formula Na. 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O1.8 Layered oxides.

[0240] The method for preparing the cathode material includes the following steps: S1: According to Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O 1.8 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and IrO2 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O 1.8 Layered oxides; wherein the sintering conditions are: temperature: 700℃; time: 20h; heating rate: 15℃ / min; oxygen atmosphere.

[0241] Comparative Example A1 This comparative example provides a cathode material and its preparation method. The cathode material includes a component with the chemical formula Na. 0.92 Ni 0.33 Mn 0.33 Fe 0.33 Zn 0.01 Layered oxides of O2.

[0242] The method for preparing the cathode material includes the following steps: S1: According to Na 0.92 Ni 0.33 Mn 0.33 Fe 0.33 Zn 0.01 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and Fe2O3 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.92 Ni 0.33 Mn 0.33 Fe 0.33 Zn 0.01 Layered oxides of O2; wherein the sintering conditions are: temperature: 900℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0243] Comparative Example A2 This comparative example provides a cathode material and its preparation method. The cathode material includes a component with the chemical formula Na. 0.92 Ni 0.25 Mn 0.33 Fe 0.33 Zn 0.08 Layered oxides of O2.

[0244] The method for preparing the cathode material includes the following steps: S1: According to Na 0.92 Ni 0.25 Mn 0.33 Fe 0.33 Zn 0.08 The precursor was obtained by ball milling NiO, ZnO, Mn2O3, and Fe2O3 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.92 Ni 0.25 Mn 0.33 Fe 0.33 Zn 0.08 Layered oxides of O2; wherein the sintering conditions are: temperature: 900℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0245] Comparative Example A3 This comparative example provides a cathode material and its preparation method. The cathode material includes a component with the chemical formula Na. 0.94 Ni 0.33 Mn 0.33 Fe 0.33 Layered oxides of O2.

[0246] The method for preparing the cathode material includes the following steps: S1: According to Na 0.94 Ni 0.33 Mn 0.33 Fe 0.33 The precursor was obtained by ball milling NiO, Mn2O3, and Fe2O3 at 500 rpm for 6 hours, followed by mixing with sodium carbonate in a specific ratio. S2: The precursor was sintered in a muffle furnace and then pulverized to obtain Na. 0.92 Ni 0.25 Mn 0.33 Fe 0.33Layered oxides of O2; wherein the sintering conditions are: temperature: 900℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0247] Characterization and related performance tests of layered oxides in each embodiment: The layered oxides provided in Examples A1 to A15 and Comparative Examples A1 to A3 were subjected to the relevant feature detections shown in Table 1 below, respectively, according to the following methods. The detection results are shown in Table 1: Method for detecting elemental content in layered oxides: Inductively coupled plasma emission spectra (ICP) were obtained using an Agilent ICP-OES730, and the content of each metal element was calculated from the ICP results, thereby calculating the mass percentage of each component.

[0248] Single crystal morphology detection method: The layered oxides provided in each embodiment were subjected to scanning electron microscopy (SEM) using the scanning electron microscopy measurement method for micrometer-scale crystals as specified in GB / T 16594-1996. The SEM image of the layered oxide provided in Example A6 is shown below. Figure 1 As shown.

[0249] Crystal phase characterization method: The layered oxides were analyzed using an XRD diffractometer at a scan rate of 0.5℃ / min.

[0250] Dv50 testing method: The layered oxides shall be tested in accordance with the method and procedure in GB / T16418.

[0251] BET specific surface area testing method: The specific surface area of ​​layered oxides shall be tested according to the method and procedure in GB / T19587-2017.

[0252] Compacted density testing method: Refer to the test method of GB / T24533-2019 standard. Specific test steps are as follows: (1) Wipe the upper and lower pads, top column and metal cylindrical sleeve of the compaction density meter with a clean soft cloth (paper towel). If necessary, wipe with a soft cloth dipped in anhydrous ethanol and air dry. (2) Place the gasket, top column, metal cylindrical sleeve, and pad in the order of the test and place them on the digital thickness gauge, then press the zeroing button; (3) Remove the top column and the upper gasket, weigh 1g of sample into the sleeve, accurate to 0.0001g, and record the weight as m; (4) Slowly slide the gasket and top column out of the hole and install them together with the gasket on the compaction density meter, and tighten the pressure control knob; (5) Shake the pressure bar and observe the value on the digital pressure gauge on the compaction density meter. Start the stopwatch after the specified value of 2200 Ib is reached. After 30 seconds, release the pressure control knob to remove the pressure. The pad will drop to a certain height. Then tighten the pressure control knob. (6) Take out the top column, sleeve and bottom plate together with the pad, place them on the digital thickness gauge, and read the value on the digital thickness gauge within 10s, and record it as H; r = 10m / (S×H); Then, calculate the powder compaction density r of the sample according to the formula r=10m / (S×H).

[0253] Where mm is the sample weight in grams (g); HH is the compacted sample thickness in millimeters (mm); and SS is the cross-sectional area of ​​the top column in square centimeters (cm²). 2 ).

[0254] Charge / discharge specific capacity testing method: The charge / discharge specific capacity testing method for layered oxides in the above-described embodiments was used for testing.

[0255] Table 1 Example layered oxide chemical formula (Ni+Mn+Fe+Zn+M): Na molar ratio Zn:Ni, Zn:Mn molar ratio Crystal phase Dv50μm <![CDATA[Compaction density g / cm 3 > Charge / discharge capacity (mAh / g) Example A1 <![CDATA[Na 0.89 Ni 0.23 Mn 0.45 Fe 0.3 Zn 0.02 O2]]> 1: 0.89 Zn:Ni = 1:11.5 Zn:Mn = 1:10.5 O3 4.5 2T, 3.053T, 3.15 165 / 159 Example A2 <![CDATA[Na 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 O2]]> 1: 0.89 Zn:Ni = 1:7.67 Zn:Mn = 1:14.67 O3 5 2T, 3.063T, 3.15 165 / 159 Example A3 <![CDATA[Na 0.85 Aunt 0.23 Mn 0.42 Fe 0.28 Zn 0.04 The 0.02 O2]]> 0.99: 0.85 Zn:Ni = 1: 5.75 Zn:Mn = 1: 10.5 O3 5.2 2T, 3.053T, 3.17 167 / 160 Example A4 <![CDATA[Na 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 O2]]> 1: 0.89 Zn:Ni = 1:4.6 Zn:Mn = 1:8.4 O3 5.7 2T, 3.053T, 3.18 168 / 161 Example A5 <![CDATA[Na 0.89 Ni 0.23 Mn 0.41 Fe 0.3 Zn 0.06 O2]]> 1: 0.89 Zn:Ni = 1:3.83 Zn:Mn = 1:6.83 O3 6 2T, 3.053T, 3.2 169 / 161 Example A6 <![CDATA[Na 0.89 Ni 0.23 Mn 0.42 Fe 0.285 Zn 0.065 O2]]> 1: 0.89 Zn:Ni = 1:3.54 Zn:Mn = 1:6.46 O3 6.2 2T, 3.053T, 3.19 169 / 162 Example A7 <![CDATA[Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 O2]]> 1: 0.89 Zn:Ni=1:3.29 Zn:Mn=1:6 O3 6.5 2T, 3.053T, 3.2 170 / 162 Example A8 <![CDATA[Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2]]> 1.005: 0.9 Zn:Ni=1:3.07 Zn:Mn=1:5.33 O3 7 2T 3.053T3.12 171 / 163 Example A9 <![CDATA[Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2]]> 1.005: 0.9 Zn:Ni=1:3.07 Zn:Mn=1:5.33 O3 8 2T, 2.93T, 3.15 169 / 162 Example A10 <![CDATA[Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Al 0.02 O2]]> 0.99: 0.85 Zn:Ni = 1:5.75 Zn:Mn = 1:10.5 O3 5 2T, 3.053T, 3.17 167 / 159 Example A11 <![CDATA[Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 O2]]> 0.99: 0.85 Zn:Ni = 1:5.75 Zn:Mn = 1:10.5 O3 5.6 2T, 3.053T, 3.17 168 / 161 Example A12 <![CDATA[Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 The 0.02 O2]]> 0.99: 0.85 Zn:Ni = 1:5.75 Zn:Mn = 1:10.5 O3 5.8 2T, 3.053T, 3.17 166 / 159 Example A13 <![CDATA[Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 Mg 0.02 O2]]> 0.99: 0.85 Zn:Ni = 1:5.75 Zn:Mn = 1:10.5 O3 5.1 2T, 3.053T, 3.17 167 / 161 Example A14 <![CDATA[Na 0.85 What 0.23 Mr. 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O2]]> 0.99: 0.85 Zn:Ni = 1:5.75 Zn:Mn = 1:10.5 O3 5.6 2T, 3.053T, 3.17 168 / 160 Example A15 <![CDATA[Na 0.85 What 0.23 Mr. 0.42 Fe 0.28 Zn 0.04 Ir 0.02 Oh 1.8 ]]> 0.99: 0.85 Zn:Ni = 1:5.75 Zn:Mn = 1:10.5 O3 5.6 2T, 3.053T, 3.17 167 / 159 Comparative Example A1 <![CDATA[Na 0.92 Ni 0.33 Mn 0.33 Fe 0.33 Zn 0.01 O2]]> 1: 0.92 Zn:Ni=1:33 Zn:Mn=1:33 O3 5.2 2T, 2.93T, 3.05 160 / 155 Comparative Example A2 <![CDATA[Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.08 O2]]> 1.01: 0.95 Zn:Ni = 1:2.875 Zn:Mn = 1:5.25 O3 5.2 2T, 2.953T, 3.1 169 / 161 Comparative Example A3 <![CDATA[Na 0.94 Ni 0.33 Mr 0.33 Feb 0.33 O2]]> 0.99: 0.94 / O3 5.2 2T 2.83T 2.95 172 / 160 As shown in Table 1 above, the layered oxides with low zinc content provided in Examples A1 to A15 have similar crystal forms and particle sizes to those in Comparative Examples A1 to A3; however, the compacted density of the layered oxides in Examples A1 to A15 is slightly higher than that in Comparative Examples A1 to A3. Further testing revealed that the specific surface area of ​​the layered oxide particles in Examples A1 to A15 ranges from 0.5 to 1.3 m². 2 / g, further to 0.6–0.9m 2 / g range. The charge / discharge specific capacity of the layered oxides in Comparative Examples A2 to A3 is higher than that of the layered oxides in Examples A1 to A15. However, according to the data in Table 3 below, due to the poor structural stability of Comparative Examples A2 to A3, their cycle performance is significantly lower than that of the layered oxides in Examples A1 to A15.

[0256] 2. Examples of positive electrode and sodium-ion battery cell Examples B1 to B15 Examples B1 to B15 provide a sodium-ion battery cell, each sodium-ion battery cell including an electrode assembly formed by a positive electrode, a separator, and a negative electrode, and also including an electrolyte.

[0257] The sodium-ion battery cells in Examples B1 to B15 are assembled as follows: Positive electrode sheet: Sodium ion positive electrode active material, conductive agent carbon nanotubes, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are mixed thoroughly 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 uniformly coated on the surface of a 13μm positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained; wherein, the sodium ion positive electrode active material is the positive electrode material in Examples A1 to A15 above, and positive electrode materials containing the positive electrode materials in Examples A1 to A15 above are prepared respectively. In Example B15, the content of conductive carbon nanotubes is 0 (all conductive agents are conductive carbon black), which means that the conductive carbon nanotubes in Example B1 are replaced with conductive carbon black. Compared with the positive electrode in Example B1, the 0.5% carbon nanotube conductive agent in Example B1 is replaced with conductive carbon black. However, the total content of conductive agent in the positive electrode in Example B1 is the same as the total content of conductive agent in the positive electrode in Example B1.

[0258] Negative electrode sheet: Hard carbon, conductive agent SP, and CMC binder are added to deionized water at a weight ratio of 8:1:1 and thoroughly mixed to form a uniform negative electrode slurry; the negative electrode slurry is uniformly coated on the surface of a 6μm copper foil, and after drying and cold pressing, the negative electrode sheet is obtained.

[0259] Electrolyte: In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate EC and diethyl carbonate DMC are mixed at a volume ratio of 1:1 to obtain the electrolyte solvent. Then, sodium hexafluorophosphate is mixed with the mixed solvent to prepare an electrolyte with a sodium salt concentration of 1 mol / L.

[0260] Separator membrane: Porous polyethylene (PE) membrane is used as the separator membrane.

[0261] Battery Assembly: The positive electrode, separator, and negative electrode are stacked sequentially, with the separator positioned between the positive and negative electrode sheets to provide isolation. The electrode assembly is then formed through a stacking process. Each electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, the sodium-ion battery cells of Examples B1 to B10 are obtained. Specifically, the sodium-ion positive electrode active material in Example B1 is the same as the positive electrode material in Example A1, the sodium-ion positive electrode active material in Example B2 is the same as the positive electrode material in Example A2, and so on, with the sodium-ion positive electrode active material in Example B15 being the same as the positive electrode material in Example A15.

[0262] Examples B16 to B24 Examples B16 to B24 provide a sodium-ion battery cell, each sodium-ion battery cell including an electrode assembly formed by a positive electrode, a separator, and a negative electrode, and also including an electrolyte.

[0263] In these examples, the sodium-ion battery cells in Examples B16 to B24 were all prepared with reference to the sodium-ion battery cell in Example B3. The difference is: In the sodium-ion battery cells of Examples B16 to B18, the content (CW) of the positive active material layer on the current collector single surface of the positive electrode sheet of each sodium-ion battery cell is controlled as shown in Table 2.

[0264] In the sodium-ion battery cells of Examples B19 to B21, the compaction density of the positive electrode active material layer contained in the positive electrode sheet of each sodium-ion battery cell is controlled as shown in Table 2.

[0265] In the sodium-ion battery cells of Examples B22 to B23, the content of carbon nanotubes in the positive electrode of each sodium-ion battery cell was controlled as shown in Table 2. The total content of conductive agent in the positive electrode of Examples B22 to B23 was the same as the total content of conductive agent in the positive electrode of Example B1.

[0266] In the sodium-ion battery cell of Example B24, the carbon nanotubes in the positive electrode of the sodium-ion battery cell were replaced with 1% carbon fiber, as shown in Table 2. The total content of conductive agent in the positive electrode of Example B24 was the same as that in the positive electrode of Example B1.

[0267] Comparative Examples B1 to B3 Comparative Examples B1 to B3 each provide a sodium-ion battery cell, each sodium-ion battery cell including an electrode assembly formed by a positive electrode, a separator, and a negative electrode, and also including an electrolyte.

[0268] The sodium-ion battery cells in Comparative Examples B1 to B3 were all prepared using the same method as the sodium-ion battery cell in Example B1. The differences are: In the sodium-ion battery cell of Comparative Example B1, the sodium-ion positive electrode active material contained in the positive electrode sheet of the sodium-ion battery cell is the same as the sodium-ion positive electrode material in Comparative Example A1, as shown in Table 1.

[0269] In the sodium-ion battery cell of Comparative Example B2, the sodium-ion positive electrode active material contained in the positive electrode sheet of the sodium-ion battery cell is the same as the sodium-ion positive electrode material in Comparative Example A2, as shown in Table 1.

[0270] In the sodium-ion battery cell of Comparative Example B3, the sodium-ion positive electrode active material contained in the positive electrode sheet of the sodium-ion battery cell is the same as the sodium-ion positive electrode material in Comparative Example A3, as shown in Table 1.

[0271] Performance tests of the positive electrode in each sodium-ion battery cell in each embodiment: The positive electrode sheets contained in the sodium-ion battery cells provided in Examples B1 to B24 and Comparative Examples B1 to B3 were subjected to the relevant performance tests shown in Table 2 below, according to the following methods. The test results are shown in Table 2: Cathode slurry gelation test method: After the cathode slurry used to prepare the cathode sheet of the sodium-ion battery cell in the above embodiments is placed at room temperature for 12 hours, the gelation of the cathode slurry is observed by the naked eye.

[0272] CW testing method: The electrode sheet is punched to 1540.25mm using a punching machine. 2 The weight of the electrode is obtained by subtracting the weight of the aluminum foil from its weight, and is denoted as the weight of the active material layer / 1540.25mm. 2 .

[0273] Method for testing the compaction density of the positive electrode sheet: The specific method for testing the compaction density of the positive electrode sheet can be found in the test methods for the first discharge specific capacity and first charge / discharge efficiency of lithium manganese oxide, a positive electrode material for lithium-ion batteries, as detailed in GB / T 39864-2021 or GB / T42161-2022. The specific test steps for the following parameters can be referenced: To obtain processable battery electrode sheets, a positive electrode sheet with a diameter of 14mm was punched out using a stamping machine. The mass (m) of the positive electrode sheet was measured using an electronic balance and a benchtop digital thickness gauge. c Thickness d c A sufficient number of aluminum foil substrates with a diameter of 14mm were punched out using a punching machine. The mass (m) of the aluminum foil substrates was measured using an electronic balance and a benchtop digital thickness gauge. Al Thickness d Al Calculate the compaction density of the positive electrode using the following formula: Positive electrode compaction density ρ c = ( m c - m Al ) × 10 6 ÷ [π (φ / 2) × (d) c - d Al ) ]; Where: ρ c This refers to the compaction density of the positive electrode sheet, expressed in grams per cubic centimeter (g / cm³). 3 ); m c The mass of the positive electrode is expressed in grams (g). m Al The mass of the aluminum foil substrate is expressed in grams (g). φ is the diameter of the positive electrode plate, in millimeters (mm). d c The thickness of the positive electrode is expressed in micrometers (μm). d Al The thickness of the aluminum foil substrate is expressed in micrometers (μm).

[0274] The charging capacity, discharging capacity, and first-efficiency testing of layered oxides should refer to the aforementioned national standards: GB / T39864-2021 or GB / T 42161-2022. According to the battery treatment method in GB / T 39864-2021 or Section 7.4 of GB / T 42161-2022, the assembled sodium-ion button batteries were placed in a constant temperature chamber, with the temperature controlled at 23℃±2℃, and left to stand for 2 to 12 hours. Then, they were charged and discharged under the following conditions: Charging: Constant current charging at 0.1C rate to 3.75V, followed by constant voltage charging, with a dielectric current of 0.05C during constant voltage charging; Discharging: Constant current discharging at 0.1C rate to 2.0V; In accordance with GB / T 39864-2021 standard or GB / T 42161-2022, after the sodium-ion coin cell assembled above has undergone one charge-discharge cycle as described in Section 7.4, the charge-discharge capacity of the sodium-ion coin cell and the mass of the layered oxide in the corresponding sodium-ion coin cell are recorded, and the initial discharge specific capacity and initial charge-discharge efficiency of the layered oxide are calculated.

[0275] The initial discharge capacity is calculated according to formula (4) in section 8.1 of GB / T 39864-2021 or GB / T 42161-2022, and the initial charge-discharge efficiency is calculated according to formula (5) in section 8.2 of GB / T 39864-2021 or GB / T 42161-2022. C = Q ID / m(4) η = Q ID / Q IC ×100%(5) In Equation 4: C—First discharge capacity, in milliampere-hours per gram (mA.h / g). Q ID — Initial discharge capacity, in milliampere-hours per gram (mA.h / g). m represents the mass of the layered oxide in the sodium-ion coin cell, measured in grams (g). In Equation 5: η—Initial charge / discharge efficiency; Q ID — Initial discharge capacity, in milliampere-hours (mA.h); Q IC — Initial charge capacity, in milliampere-hours (mA.h).

[0276] Electrode porosity testing method: The porosity is tested using the gas displacement method, specifically referring to GB / T24586-2009. The specific steps are as follows: The electrode is immersed in ethyl methyl carbonate (EMC) for cleaning, and then tested using the method specified in GB / T24586-2009. Utilizing the gas displacement method, combined with Archimedes' principle and Bohr's law, the true volume of the material being tested is accurately measured, which is the true volume of the sample, thus obtaining the porosity of the sample. The porosity is the percentage of pore volume in the electrode to the total volume of the electrode. The calculation formula is: Porosity = (V - V0) / V × 100%, where V0 is the true volume and V is the apparent volume.

[0277] Diaphragm resistance testing method: Refer to GB / T 30835-2014 or T / CASAS 019—2021 for testing; for the instrument calibration procedure, refer to JJG 508-2004 for testing. Specifically, the four-probe method is used: the electrode is immersed in ethyl methyl carbonate (EMC) for cleaning, and tested according to the method specified in GB / T 30835-2014 or T / CASAS 019—2021, using four probes each 1.5cm long. 1cm wide Two-mm thick copper plates are fixed at equal intervals along a line. The distance between the two middle copper plates is L (1cm to 2cm). The substrate for fixing the copper plates is an insulating material. During the test, the lower ends of the four copper plates are pressed onto the electrode to be tested. A DC current I is connected to the copper plates at both ends. The voltage V is measured on the two middle copper plates. The values ​​of I and V are read three times. The average value of I and V is taken. V / I is the electrode resistance at the test point.

[0278] Table 2 Example <![CDATA[CWmg / 1540.25mm 2 ]]> <![CDATA[Compaction density g / cm 3 > Types and contents of conductive agents Positive electrode slurry gel 12h Example B1 310 3.2 Carbon nanotubes, content: 0.5% Slight Gel Example B2 310 3.2 Carbon nanotubes, content: 0.5% Slight Gel Example B3 310 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B4 310 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B5 310 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B6 310 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B7 310 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B8 310 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B9 310 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B10 310 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B11 310 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B12 310 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B13 310 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B14 310 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B15 310 3.2 It contains no carbon nanotubes and is entirely carbon black. Non-gel Example B16 260 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B17 300 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B18 350 3.2 Carbon nanotubes, content: 0.5% Non-gel Example B19 310 2.8 Carbon nanotubes, content: 0.5% Non-gel Example B20 310 3.1 Carbon nanotubes, content: 0.5% Non-gel Example B21 310 3.4 Carbon nanotubes, content: 0.5% Non-gel Example B22 310 3.2 Carbon nanotubes, content: 0.1% Non-gel Example B23 310 3.2 Carbon nanotubes, content: 2.5% Non-gel Example B24 310 3.2 Carbon fiber, content: 1% Non-gel Comparative Example B1 310 3.2 Carbon nanotubes, content: 0.5% moderate gel Comparative Example B2 310 3.2 Carbon nanotubes, content: 0.5% Non-gel Comparative Example B3 310 3.2 Carbon nanotubes, content: 0.5% moderate gel Electrochemical performance tests of sodium-ion battery cells in each embodiment: The sodium-ion battery cells provided in Examples B1 to B24 and Comparative Examples B1 to B3 were subjected to the relevant electrochemical performance tests shown in Table 3 below, according to the following methods. The test results are shown in Table 3: Methods for testing the relevant performance of sodium-ion battery cells: Cyclic DCR Test: The DCR was tested according to the room temperature test method in the "Performance Test Specification for High-Power Lithium-ion Power Batteries for HEVs". The battery cell under test was discharged at a constant current of 1C to the cutoff voltage (3.0V), and then placed at 20±2℃ for 1 hour. It was then charged at 1C for 18 minutes, the SOC was adjusted to 30%, and it was placed for 1 hour. Next, it was charged at 3C for 1.5 minutes and placed for 1 hour. Then, it was discharged at 9C for 0.5 minutes and placed for 1 hour. Finally, it was charged at 1C for 6 minutes, the SOC was adjusted to 40%, and it was placed for 1 hour. This cycle was repeated until the SOC reached 70%. The DCR value was then calculated using the formula.

[0279] Energy density: The discharge energy S0 of each individual cell is measured by charging it at a rate of 0.33C to 4.2V at room temperature and then discharging it at a rate of 0.33C to 2.0V. The mass M of the cell corresponding to S0 is then measured, and the mass energy density of the cell is calculated using the formula S0 / M.

[0280] Cycle retention rate (%): At 25℃, the secondary battery is charged at a constant current of 0.33C to 3.85V, then charged at a constant voltage of 3.85V to a current of 0.05C, and then discharged at a constant current of 1C to 1.5V. This constitutes one charge-discharge cycle. Taking the capacity of the first discharge as 100%, calculate the capacity retention rate after 1000 cycles. Capacity retention rate after 1000 cycles (%) = Discharge capacity of the 1000th cycle / Capacity of the first discharge × 100%.

[0281] Table 3 Example Single cell cycle DCR / mΩ Single cell energy density Wh / Kg Cycle retention rate % Example B1 1.0 136 85 Example B2 1.2 139 83 Example B3 1.3 141 84 Example B4 1.4 143 82 Example B5 1.2 144 82 Example B6 1.3 145 81 Example B7 1.5 146 81 Example B8 1.7 147 80 Example B9 1.8 147 78 Example B10 1.5 135 83 Example B11 1.6 139 80 Example B12 1.6 135 82 Example B13 1.4 136 83 Example B14 1.6 135 81 Example B15 1.5 125 81 Example B16 1.5 130 85 Example B17 1.7 139 84 Example B18 1.4 146 82 Example B19 1.6 125 87 Example B20 1.4 132 85 Example B21 1.7 145 80 Example B22 1.6 145 73 Example B23 1.4 130 87 Example B24 1.8 134 82 Comparative Example B1 2.1 123 64 Comparative Example B2 2.3 140 70 Comparative Example B3 2.2 122 63 As shown in Tables 2 and 3, in the sodium-ion batteries of this application, the compaction density of the positive electrode active material layer contained in the positive electrode sheet of the sodium-ion battery cell provided in Examples B1 to B24 can reach 2.8–3.4 g / cm³. 3 The CW of the positive electrode active material layer can reach 260–350 mg / 1540.25 mm. 2 Furthermore, while controlling the CW and compaction density of the positive electrode active material layer, the porosity of the positive electrode active material layer is 40%–65%, and the membrane resistance is 0.5–5 mΩ. Specifically, the porosity and membrane resistance of the positive electrode active material layer can be adjusted according to the CW, compaction density, and the conductive agent it contains.

[0282] Comparing Examples B1 to B8 in the table, it can be seen that as the zinc content in the layered oxide shown in chemical formula (I) gradually increases, the cell energy density of the sodium-ion battery cell gradually increases. However, the overall trend of the cycle performance of the corresponding sodium-ion battery cell is a decrease. In the layered oxide shown in chemical formula (I), as the zinc content increases, it can improve the specific capacity of the layered oxide, but it is detrimental to the structural stability of the layered oxide, resulting in a decrease in its reversible capacity cycle performance. However, compared with Comparative Examples B1 and B2, it can be seen that when the zinc content is controlled within an appropriate range and the stoichiometric ratio of Zn to Ni and Mn is within a suitable range, the layered oxide shown in chemical formula (I) can effectively balance high specific capacity and good reversible capacity cycle stability.

[0283] Comparing Examples B3 and Examples B10 to B14 in the table, it can be seen that the type of doped metal element contained in the layered oxide represented by chemical formula (Ⅰ) also has a certain influence on the specific capacity and structural stability of the layered oxide. Therefore, the doped metal element represented by M participates in the disordered arrangement of metal elements in the transition metal layer contained in the layered oxide, and can contribute to the specific capacity and / or structural stability of the layered oxide.

[0284] Comparing Examples B14 and B15, the type of conductive agent contained in the positive electrode active material layer has a certain impact on the capacity of the positive electrode. When the conductive agent contains linear carbon nanotubes, the cell energy density of the corresponding sodium-ion battery cell is higher than that of Example B15.

[0285] Comparing Examples B1 to B15 with Comparative Examples B1 to B3, when the zinc content of the layered oxide is too low, as in Comparative Examples B1 and B3, it not only significantly reduces the energy density of the sodium-ion battery cells but also significantly reduces their cycle retention rate. When the zinc content of the layered oxide is too high, as in Comparative Example B2, although the energy density of the sodium-ion battery cells is not significantly reduced, the cycle retention rate of the sodium-ion battery cells is significantly reduced. Therefore, it can be seen that the types and contents of zinc and other metal elements in the layered oxide represented by chemical formula (I) can significantly affect the disordered arrangement of metal elements in the transition metal layers of the layered oxide, thereby significantly affecting the overall performance of the layered oxide in terms of specific capacity and cycle stability.

[0286] Therefore, it can be seen that the layered oxide in this application controls the zinc content to an appropriately low range, and also controls the content of zinc and other metal elements such as Ni, Fe, and Mn. This results in a specific arrangement of the transition metal layers in the layered oxide, effectively improving the specific capacity of the layered oxide while also taking into account and balancing its structural stability, thereby improving the cycle performance of the layered oxide and the sodium-ion battery. It also indicates that in the layered oxide of this application, a higher zinc content does not necessarily lead to a higher specific capacity and better cycle performance. Rather, when the zinc content exceeds a certain amount, the specific capacity does not continue to increase, and it is detrimental to the structural stability of the layered oxide, thus reducing its cycle performance.

[0287] Furthermore, as shown in Table 3, the cell DCR variation range of the sodium-ion battery cells in Examples B1 to B24 is not large, and the cell DCR difference of each sodium-ion battery cell in Examples B1 to B24 is in the range of 0 mΩ to 0.8 mΩ. Moreover, the cell DCR of the sodium-ion battery cells in Examples B1 to B24 is significantly lower than that of the sodium-ion battery cells in Comparative Examples B1 to B3. Therefore, by controlling the zinc content in the layered oxide represented by chemical formula (I) within the range of chemical formula (I), the layered oxide structure can be stabilized by controlling the low zinc content and adjusting the arrangement of other metal elements in the transition metal layer, thereby improving the sodium-ion transport rate and the DCR growth of the battery cell.

[0288] Further comparison of the cathode slurries in Examples B1 to B24 with those in Comparative Examples B1 and B3 reveals that the gelation phenomenon in the cathode slurries of Examples B1 to B24 is significantly lower than that in Comparative Examples B1 and B3. Therefore, the layered oxides of this application, by controlling the zinc content to an appropriately low range, not only effectively improve the specific capacity and cycle performance of the layered oxides but also enhance their processing performance.

[0289] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A positive electrode material, characterized in that, Including layered oxides as shown in the following chemical formulas: So q Ni x Mr y Feb z Zn p M i O j ; Wherein, 0.8≤q≤1, 0.1≤x≤0.3, 0.2≤y≤0.5, 0.2≤z≤0.35, 0.02≤p≤0.075, 0≤i≤0.1, 1.8≤j≤2, and x+y+z+p+i≤1; M is an active and / or inert doped metal element.

2. The cathode material as described in claim 1, characterized in that, At least one of q, x, y, z, p, and i takes values ​​within the following range: 0.15≤x≤0.25、0.25≤y≤0.45、0.25≤z≤0.32、0.04≤p≤0.07、0≤i≤0.

05.

3. The cathode material as described in claim 1 or 2, characterized in that: The total stoichiometry of the Ni, Mn, Fe, Zn and doped metal elements to the stoichiometry of the Na element is 1:(0.8~1). and / or The stoichiometric ratio of Zn to Ni is 1:(3-15). and / or The stoichiometric ratio of Zn to Mn is 1:(4-25).

4. The cathode material according to any one of claims 1 to 3, characterized in that: The total stoichiometry of the Ni, Mn, Fe, Zn and doped metal elements to the stoichiometry of the Na element is 1:(0.83-0.95). and / or The stoichiometric ratio of Zn to Ni is 1:(3.1~11). and / or The stoichiometric ratio of Zn to Mn is 1:(5-15).

5. The cathode material according to any one of claims 1 to 4, characterized in that: The doped metal element includes Cu.

6. The cathode material as described in claim 5, characterized in that: The doped metal element also includes at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Ru, and Ir.

7. The cathode material according to any one of claims 1 to 6, characterized in that: The layered oxide includes at least one of the following features (1) to (3): (1) The crystal structure includes 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) The particle size of Dv50 is 3-11 μm; (3) Includes single crystals, wherein the single crystals have a flat morphology.

8. The cathode material as described in claim 7, characterized in that: The Dv50 particle size is 4–8 μm.

9. The cathode material as described in claim 7, characterized in that: The single crystal is characterized by at least one of the following (1) to (4): (1) The ratio of length, width and thickness is 1-8: 1-5: 0.5-2.5; (2) Length is 1–8 μm; (3) Width is 1–5 μm; (4) The thickness is 0.5 to 2.5 μm.

10. The cathode material as described in claim 7, characterized in that: The single crystal is characterized by at least one of the following (1) to (4): (1) The ratio of length, width and thickness is 2-6:2-4:1-2; (2) Length is 2-6 μm; (3) Width is 2–4 μm; (4) The thickness is 1 to 2 μm.

11. The cathode material according to any one of claims 1 to 10, characterized in that: The layered oxide includes at least one of the following features (1) to (3): (1) The compaction density under 2 tons of pressure is 2.8–3.1 g / cm³. 3 ; (2) The compaction density under 3 tons of pressure is 3.1–3.3 g / cm³. 3 ; (3) Specific surface area is 0.5–1.3 m² 2 / g.

12. The cathode material according to any one of claims 1 to 10, characterized in that: The layered oxide includes at least one of the following features (1) to (3): (1) The compaction density under 2 tons of pressure is 2.9–3.09 g / cm³. 3 ; (2) The compaction density under 3 tons of pressure is 3.15~3.28 g / cm³. 3 ; (3) Specific surface area is 0.6–0.9 m² 2 / g.

13. The cathode material according to any one of claims 1 to 12, characterized in that: The layered oxide comprises at least one of (1) to (3) below at 1.5–4.2 v and 0.1 C: (1) The charging capacity is 164-174 mAh / g; (2) The discharge capacity is 158–165 mAh / g; (3) The first-efficacy rate is 92-98%.

14. The cathode material according to any one of claims 1 to 13, characterized in that: The layered oxide comprises at least one of (1) to (3) below at 1.5–4.2 v and 0.1 C: (1) The charging capacity is 165-172 mAh / g; (2) The discharge capacity is 160-163 mAh / g; (3) The first-efficacy rate is 92-95%.

15. A positive electrode, comprising a positive electrode active material, characterized in that: The positive electrode active material layer comprises the positive electrode material according to any one of claims 1 to 14.

16. The positive electrode as described in claim 15, characterized in that: The content of the positive electrode active material on one side of the current collector is 260–350 mg / 1540.25 mm. 2 ; and / or The compaction density of the positive electrode is 2.8–3.4 g / cm³. 3 .

17. The positive electrode as described in claim 16, characterized in that: The content of the positive electrode active material on one side of the current collector is 280–320 mg / 1540.25 mm. 2 ; and / or The compaction density of the positive electrode is 2.9–3.2 g / cm³. 3 .

18. The positive electrode according to any one of claims 15-17, characterized in that: The porosity of the positive electrode active material layer is 40%–65%; and / or The positive electrode is a film plate, and the film resistance of the film plate is 0.5 to 5 mΩ.

19. The positive electrode as described in claim 18, characterized in that: The porosity of the positive electrode active material layer is 45%–60%; and / or The positive electrode is a film plate, and the film resistance of the film plate is 0.5 to 3 mΩ.

20. The positive electrode according to any one of claims 15-19, characterized in that: The positive electrode is an electrode sheet, and the thickness from one surface of the electrode sheet to the opposite surface is in the ratio of the thickness of the current collector to 6 to 15:

1.

21. The positive electrode as described in claim 20, characterized in that: The positive electrode is an electrode sheet, and the thickness from one surface of the electrode sheet to the opposite surface is in the ratio of the thickness of the current collector to 8 to 14:

1.

22. The positive electrode according to any one of claims 15-21, characterized in that: The conductive agent contained in the positive electrode active material layer includes a linear conductive agent.

23. The positive electrode as described in claim 22, characterized in that: The linear conductive agent has a mass content of 0.1% to 2.5% in the positive electrode active material layer; and / or The aspect ratio of the linear conductive agent is 40 to 3000:1; The linear conductive agent has a length of 0.5–5 μm; and / or The diameter of the linear conductive agent is 2–10 nm; and / or The linear conductive agent includes at least one of carbon nanotubes, carbon fibers, and conductive oxide nanowires.

24. The positive electrode as described in claim 23, characterized in that: The linear conductive agent has a mass content of 0.2% to 0.8% in the positive electrode active material layer; and / or The aspect ratio of the linear conductive agent is 50 to 2500:1; The linear conductive agent has a length of 0.5–2 μm; and / or The diameter of the linear conductive agent is 3–7 nm.

25. A sodium battery, characterized in that, Includes the positive electrode as described in any one of claims 15-24.

26. An electrical appliance, characterized in that: Including the sodium battery of claim 25.

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