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

Abstract

A positive electrode material and a preparation method therefor, a positive electrode (10), a sodium battery, and an electric device. The positive electrode material comprises a layered oxide represented by chemical formula NaqNixMnyFezZnpMiOj, 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 or / and inert doped metal element. The preparation method for the positive electrode material comprises a step for sintering a precursor of NaqNixMnyFezZnpMiOj. The positive electrode (10) comprises a layered oxide represented by the described chemical formula, and the sodium battery comprises the positive electrode (10). The electric device comprises the sodium battery.

Description

Organic compound and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on September 28, 2023, with application number 202311277081.5 and application name “Positive electrode material and preparation method thereof, positive electrode, sodium battery and electrical device”. It also claims priority to the Chinese patent application filed with the Patent Office of China on February 28, 2024, with application number 202410222045.7 and application name “Positive electrode material and preparation method thereof, positive electrode, sodium battery and electrical device”. The entire contents of these patent applications are incorporated herein by reference. Technical Field

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

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

[0004] Among sodium-ion battery cathode materials, layered oxides have become a research hotspot due to their relatively high energy density. However, layered oxides have poor structural stability and are prone to phase transitions during sodium intercalation and deintercalation, leading to structural deformation. This results in a significant decrease in the reversible capacity of layered oxides during cycling, leading to rapid cycling degradation in sodium-ion batteries. Technical issues

[0005] In view of the above problems, the present application provides a positive electrode material and a preparation method thereof, a positive electrode containing the positive electrode material, and a sodium battery containing the positive electrode, 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 attenuation. Technical Solutions

[0006] In a first aspect, the present invention provides a positive electrode material. The positive electrode material of the present invention 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 ;

[0007] Among them, 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 doping metal element.

[0008] The layered oxide contained in the positive electrode material of the embodiment of the present application is doped with the transition metal layer (TMO6) containing Ni, Fe, and Mn elements by Zn element or Zn element and the doping metal element shown in M, and the Zn element is controlled at the above-mentioned low content, which can suppress the Jahn-Teller effect of the layered oxide itself due to the Mn and Ni elements, and effectively adjust the arrangement between the transition metal elements in the transition metal layer (TMO6), thereby significantly reducing the structural distortion and irreversible phase change of the layered oxide shown in the chemical formula during the sodium deintercalation process, and significantly improving the structural stability of the layered oxide, so as to significantly improve the cycle stability of the reversible capacity of the layered oxide. Further, by controlling the content ratio of each metal element, on the basis of effectively improving the structural stability of the layered oxide, the gram capacity of the layered oxide can be further improved. Further, the low content of Zn element can also significantly reduce the segregation phenomenon of the transition metal element on the surface of the layered oxide shown in the chemical formula, improve the air stability of the layered oxide shown in the chemical formula in the air, avoid slurry agglomeration and gelation, improve the electrical properties, and improve the processing performance of the layered oxide shown in the chemical formula.

[0009] In some embodiments, at least one of q, x, y, z, p and i is in the following value 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.

[0010] By further selecting and controlling the stoichiometric ratio of at least one element among Na, Ni, Mn, Fe, Zn and M within this range, the doping of the transition metal layer in the layered oxide shown in the chemical formula by the Zn element or the doping metal element shown by the Zn element and M can be further improved, so as to further adjust the arrangement between the metal elements in the transition metal layer, thereby further improving the structural stability of the layered oxide shown in the chemical formula during the process of sodium insertion and deinsertion, and improving the specific capacity of the layered oxide and the cyclic stability of the reversible capacity.

[0011] In some embodiments, the stoichiometric ratio of the total stoichiometric amount of Ni, Mn, Fe, Zn and the doping metal element to the stoichiometric ratio of the Na element is 1:(0.8-1), and can be optionally 1:(0.83-0.95).

[0012] By controlling the stoichiometric ratio of the Na element to other metal elements contained in the layered oxide shown in the chemical formula within this range, the cycle stability of the specific capacity and reversible capacity of the layered oxide can be further improved.

[0013] In some embodiments, the stoichiometric ratio of the Zn element to the Ni element is 1:(3-15), and can be optionally 1:(3.1-11).

[0014] The stoichiometric ratio of the Zn element to the Ni element is controlled within this range. The stoichiometric ratio of the Zn element to the Ni element within this range can reduce costs while increasing the gram capacity of the layered oxide represented by the chemical formula.

[0015] In some embodiments, the stoichiometric ratio of the Zn element to the Mn element is 1:(4-25), and can be optionally 1:(5-15).

[0016] 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 gram capacity, further reducing the structural distortion and irreversible phase transition of the layered oxide shown in the chemical formula during the sodium insertion and deinsertion process, thereby further improving the structural stability of the layered oxide.

[0017] In some embodiments, the doping metal element includes at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, and Ir. The doping metal element M can be used together with a low content of Zn to further dope the transition metal layer contained in the layered oxide represented by the chemical formula, thereby adjusting the arrangement of the metal elements in the transition metal layer. Depending on the type of the doping metal element M, the structural stability and / or specific capacity of the layered oxide represented by the chemical formula during the sodium insertion and extraction process can be further improved.

[0018] 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 Fe0.3 Zn 0.05 O2、Na 0.89 Ni 0.23 Mr 0.41 Feb 0.3 Zn 0.06 O2、Na 0.89 Ni 0.23 Mr 0.42 Feb 0.285 Zn 0.065 O2、Na 0.89 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.07 O2、Na 0.9 Ni 0.23 Mr 0.4 Feb 0.3 Zn 0.075 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 V 0.02 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 Cr 0.02 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 Al 0.02 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 Sc 0.02 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 Mr 0.02 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 Sb 0.02 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 Zr 0.02 O2、Na0.85 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 0.02 O 1.8 At least one of .

[0019] The layered oxide represented by the chemical formula has a low Zn content, and this low Zn content interacts with other metal elements to form a specific arrangement between the metal elements in the transition metal layer contained in the layered oxide. This further improves the structural stability of the layered oxide during sodium insertion and extraction, and improves the cyclic stability of the specific capacity and reversible capacity of the layered oxide. Furthermore, while increasing the specific capacity of the layered oxide represented by the chemical formula, it can also improve electrochemical performance and processing performance.

[0020] In some embodiments, the layered oxide includes at least one of the following features (1) to (3):

[0021] (1) The crystal structure includes an O3 phase layered metal oxide, and the O3 phase layered metal oxide accounts for more than 95% of the total weight of the layered oxide;

[0022] (2) Dv50 particle size is 3 to 11 μm, and can be selected as 4 to 8 μm;

[0023] (3) It includes a single crystal, and the single crystal has a flat morphology.

[0024] In an embodiment, the characteristics of the single crystal include at least one of the following (1) to (4):

[0025] (1) The ratio of length, width and thickness is 1-8:1-5:0.5-2.5, and can be 2-6:2-4:1-2;

[0026] (2) Length is 1 to 8 μm, optionally 2 to 6 μm;

[0027] (3) Width is 1 to 5 μm, and can be 2 to 4 μm;

[0028] (4) The thickness is 0.5 to 2.5 μm, and can be optionally 1 to 2 μm.

[0029] The layered oxides shown in the chemical formulas in the above embodiments are mainly O3 phase layered metal oxides and include single crystal structures.

[0030] In some embodiments, the layered oxide includes at least one of the following features (1) to (3):

[0031] (1) The compaction density under 2 tons of pressure is 2.8 to 3.1 g / cm 3 , can be selected from 2.9 to 3.09 g / cm 3 ;

[0032] (2) The compaction density under 3 tons of pressure is 3.1 to 3.3 g / cm 3 , can be selected from 3.15 to 3.28 g / cm 3 ;

[0033] (3) Specific surface area is 0.5 to 1.3 m 2 / g, optional range is 0.6~0.9m 2 / g.

[0034] Based on the Dv50 particle size of the layered oxide shown in the above chemical formula (I) and the size distribution range of the O3 phase layered metal oxide single crystals contained therein, 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 contact interface between the layered oxide and the electrolyte and other properties, thereby improving the electrochemical properties such as the cycle performance.

[0035] In some embodiments, the layered oxide comprises at least one of the following (1) to (3) at 1.5-4.2 V and 0.1 C:

[0036] (1) The charging capacity is 164-174 mAh / g, and can be selected as 165-172 mAh / g;

[0037] (2) The discharge capacity is 158-165 mAh / g, and can be selected as 160-163 mAh / g;

[0038] (3) The initial efficiency is 92% to 98%, which can be selected as 92% to 95%.

[0039] The structural stability of the layered oxide shown in the above chemical formula has been significantly improved, the structural stability in the process of sodium insertion and extraction, high specific capacity, and good cyclic stability of reversible capacity.

[0040] In a second aspect, the present invention provides a method for preparing a positive electrode material. The method for preparing a positive electrode material in the present invention comprises the following steps:

[0041] Provides Na q Ni x Mn y Fe z Zn p M i O j precursors;

[0042] The precursor is sintered to obtain a chemical formula of Na q Ni x Mn y Fe z Zn p M i O j layered oxides;

[0043] Among them, 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 doping metal element.

[0044] The positive electrode material preparation method of the present application embodiment is to q Ni x Mn y Fe z Zn p M i O j The precursor is sintered to generate a chemical formula of Na q Ni x Mn y Fe z Zn p M i O jTherefore, the layered oxide prepared by the positive electrode material preparation method of the present invention has a low zinc content and high structural stability during the sodium insertion and removal process, which makes the prepared layered oxide have a high gram capacity and a cyclic stability of its reversible capacity. At the same time, it also has high air stability and diffusion rate. In addition, for Na q Ni x Mn y Fe z Zn p M i O j The sintering conditions of the precursor can be effectively controlled, thereby improving the q Ni x Mn y Fe z Zn p M i O j The stability of the structure and electrochemical properties of layered oxides.

[0045] In some embodiments, the doping metal element includes at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, and Ir. These doping metal elements, together with a low content of Zn, can further dope the transition metal layer contained in the layered oxide represented by the chemical formula, adjust the arrangement of the 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 represented by the chemical formula during the sodium insertion and extraction process.

[0046] In some embodiments, at least one of q, x, y, z, p, and i is within the following value ranges:

[0047] 0.15≤x≤0.25, 0.25≤y≤0.45, 0.25≤z≤0.32, 0.04≤p≤0.07, 0≤i≤0.05.

[0048] By adding Na q Ni x Mn y Fe z Zn p M i O j The ratio of these metal elements in the precursor is further controlled within this range, which can further adjust the arrangement of the metal elements in the prepared layered oxide, thereby further improving the structural stability of the prepared layered oxide during the process of sodium insertion and deinsertion, and improving the specific capacity of the layered oxide and the cyclic stability of the reversible capacity.

[0049] In some embodiments, the sintering process includes at least one of the following conditions (1) to (4):

[0050] (1) The temperature is 700-980°C, and can be selected as 750-950°C;

[0051] (2) The duration is 4 to 20 hours, and can be selected as 6 to 12 hours;

[0052] (3) The temperature is raised to the sintering temperature at a heating rate of 2 to 15°C / min.

[0053] By controlling the sintering conditions within the above range, the Na q Ni x Mn y Fe z Zn p M i O j The structural stability of the layered oxide during the process of sodium insertion and removal further improves the high specific capacity of the layered oxide and the cycle stability of its reversible capacity. q Ni x Mn y Fe z Zn p M i O j The content of O3 phase layered metal oxide and the single crystal content in the layered oxide control the single crystal size and the particle size of the layered oxide, thereby increasing the compaction density of the layered oxide.

[0054] In some embodiments, the Na q Ni x Mn y Fe z Zn p M i O j The precursor is prepared according to a method comprising the following steps:

[0055] According to Na q Ni x Mn y Fe z Zn p M i O j The precursor is obtained by solid-phase mixing the sodium source, nickel source, manganese source, iron source, zinc source and the doping metal element source shown by M in the stoichiometric ratio of the elements contained.

[0056] The solid-phase method was used to prepare Na q Ni x Mn y Fe z Znp M i O j The precursor can effectively control the stoichiometric ratio of each element and improve the preparation effect of the precursor.

[0057] In some embodiments, the Na q Ni x Mn y Fe z Zn p M i O j The precursor is prepared according to a method comprising the following steps:

[0058] According to Na q Ni x Mn y Fe z Zn p M i O j A soluble nickel source, a soluble manganese source, a soluble iron source, a soluble zinc source and a soluble doping metal element source represented by M are prepared into a mixed solution in a stoichiometric ratio of elements, and at least one of a precipitant and a complexing agent is added to perform a coprecipitation treatment to obtain a precipitated mixture;

[0059] The precipitation mixture is mixed with a sodium source to obtain the precursor.

[0060] The coprecipitation method was used to prepare Na q Ni x Mn y Fe z Zn p M i O j It is a precursor to improve the stoichiometric ratio accuracy of each element.

[0061] In a third aspect, embodiments of the present application provide a positive electrode. The positive electrode of the embodiment of the present application includes a current collector and a positive electrode active material layer disposed on a surface of the current collector, wherein the positive electrode active material layer includes the positive electrode material of the embodiment of the present application or a positive electrode material prepared by the positive electrode material preparation method of the embodiment of the present application.

[0062] Since the positive electrode active material layer of the positive electrode of the embodiment of the present application contains the positive electrode material of the embodiment of the present application, the positive electrode has a relatively high gram capacity and good cycle performance.

[0063] In some embodiments, the content of the positive electrode active material layer on the single surface of the current collector is 260-350 mg / 1540.25 mm 2 , optional: 280~320mg / 1540.25mm 2The positive electrode active material layer within this content range can effectively increase the gram capacity of the positive electrode and thus increase the energy density of the battery.

[0064] In some embodiments, the compaction density of the positive electrode active material layer is 2.8 to 3.4 g / cm 3 , can be selected as 2.9~3.2g / cm 3 The compaction density in this range can effectively increase the gram capacity of the positive electrode, thereby increasing the energy density of the battery, and has good interface stability with the electrolyte.

[0065] In some embodiments, the porosity of the positive electrode active material layer is 40% to 65%, and can be optionally 45% to 60%. Porosity within this range enables the positive electrode active material layer to have the aforementioned compaction density, thereby increasing the gram capacity of the positive electrode and thus the energy density of the battery, and improving the wettability of the electrolyte.

[0066] In some embodiments, the positive electrode is a pole piece, and the pole piece has a sheet resistance of 0.5 to 5 mΩ, and optionally 0.5 to 3 mΩ. The sheet resistance within this range can effectively improve performance including efficiency and lifespan.

[0067] In some embodiments, the positive electrode is a pole piece, and the ratio of the thickness from one surface of the pole piece to the other opposite surface to the thickness of the current collector is 6 to 15:1, and can be optionally 8 to 14:1.

[0068] By controlling the total thickness of the electrode and the thickness of the current collector within the above ratio range, the gram capacity of the electrode can be effectively increased, thereby increasing the energy density of the battery, and increasing the bonding strength between the positive electrode active material layer and the current collector, thereby increasing the mechanical strength of the electrode structure and improving the cycle performance of the electrode.

[0069] In some embodiments, the conductive agent contained in the positive electrode active material layer includes a linear conductive agent.

[0070] In an embodiment, the mass content of the linear conductive agent in the positive electrode active material layer is 0.1% to 2.5%, and can be optionally 0.2% to 0.8%.

[0071] In the embodiment, the aspect ratio of the linear conductive agent is 40 to 3000:1, and can be optionally 50 to 2500:1.

[0072] In an embodiment, the length of the linear conductive agent is 0.5 to 5 μm, and can be optionally 0.5 to 2 μm.

[0073] In an embodiment, the diameter of the linear conductive agent is 2 to 10 nm, and can be optionally 3 to 7 nm.

[0074] In an exemplary embodiment, the linear conductive agent includes at least one of carbon nanotubes, carbon fibers, and conductive oxide nanowires.

[0075] By adding a linear conductive agent to the positive electrode active material layer, and controlling the content of the linear conductive agent within the above range and selecting and controlling the type, aspect ratio, length, and diameter of the linear conductive agent within the above range, the linear conductive agent can form a rich conductive network structure in the positive electrode active material layer, and the linear conductive agent can also be wrapped around the surface of the flat single crystal particles. The granular 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, and the granular conductive agent constitutes a short-range conductive structure. Therefore, the conductive synergistic effect of the linear conductive agent and the granular conductive agent in the positive electrode active material layer effectively improves the conductivity of the positive electrode active material layer and can significantly reduce the internal resistance of the positive electrode.

[0076] In a fourth aspect, an embodiment of the present application provides a sodium battery. The sodium battery of the embodiment of the present application includes the positive electrode of the embodiment of the present application.

[0077] Since the sodium battery of the embodiment of the present application contains the positive electrode of the embodiment of the present application, the sodium battery of the embodiment of the present application has high energy density and good cycle performance.

[0078] In a fifth aspect, an embodiment of the present application provides an electrical device, and the embodiment of the present application includes a sodium battery according to an embodiment of the present application.

[0079] The electrical device in the embodiment of the present application has a long standby or battery life and a long service life.

[0080] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0082] FIG1 is a scanning electron microscope (SEM) image of a layered oxide provided in Example A6 of the present application;

[0083] FIG2 is a schematic diagram of the single crystal structure of the layered oxide contained in the positive electrode material of some embodiments of the present application;

[0084] FIG3 is a schematic structural diagram of a positive electrode in some embodiments of the present application;

[0085] FIG4 is another schematic structural diagram of a positive electrode according to some embodiments of the present application;

[0086] FIG5 is a schematic structural diagram of an embodiment of a sodium battery cell according to an embodiment of the present application;

[0087] FIG6 is an exploded schematic diagram of the sodium battery cell shown in FIG5 ;

[0088] FIG7 is a schematic structural diagram of an embodiment of a battery module according to the present application;

[0089] FIG8 is a schematic structural diagram of an embodiment of a battery pack according to the present application;

[0090] FIG9 is a schematic diagram of the exploded structure of the battery pack shown in FIG8 ;

[0091] FIG10 is a schematic diagram of an embodiment of an electrical device including a battery according to an embodiment of the present application as a power source.

[0092] The reference numerals in the specific embodiments are as follows: 10 - positive electrode, 11 - current collector, 12 - positive electrode active material layer; 20 - battery cell, 21 - housing, 22 - electrode assembly, 23 - cover plate; 30 - battery module; 40 - battery pack, 41 - upper case, 42 - lower case.

[0093] Implementation Methods of the Application

[0094] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0095] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0096] In the description of the embodiments of this application, the technical terms "first," "second," etc. are used only to distinguish different objects and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise specifically defined.

[0097] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0098] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0099] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0100] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0101] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0102] Sodium-ion batteries (SIBs) are ideal candidates for energy storage systems due to their abundant raw material reserves and low cost. They also have enormous potential for application in the new energy vehicle market. With the rapid development of energy storage systems and new energy vehicles, the requirements for the energy density and cycle stability of sodium-ion batteries are becoming increasingly stringent.

[0103] For sodium-ion batteries, cathode materials are an important component of sodium-ion batteries, providing active sodium ions. They are also one of the key factors affecting the energy density and cycle performance of sodium-ion batteries. Among sodium-ion battery cathode materials, layered oxides have attracted much attention due to their high gram capacity and structure similar to that of lithium-ion battery cathode materials.

[0104] According to the arrangement and stacking order of oxygen atoms in layered oxides, the layered oxides are currently mainly divided into P2 type and O3 type. For example, the current more representative P2 layered oxide Na 2 / 3 Ni 1 / 3 Mn 2 / 3 Although O2 has a high capacity, it is prone to P2-O2 phase transition during the process of sodium insertion and removal. This phase transition leads to Na 2 / 3 Ni 1 / 3 Mn 2 / 3 The structure of O2 is destroyed, causing its capacity to decay and reducing the cycle life. Compared with P2-type layered oxides, O3-type layered oxides can store more Na + , can also play a higher reversible capacity in the same voltage range, so it has better commercial application prospects. However, Na + The diffusion of O3-type layered oxides such as NaMn requires additional energy to pass the diffusion barrier. 0.5 Ni 0.5 O2 layered oxides undergo complex phase transitions during the charge and discharge process, especially the irreversible P3″ phase transition that occurs when charged to a high voltage above 4.1V. This phase transition destroys the structure of the O3 layered oxide, causing its capacity to decay and shortening its cycle life.

[0105] Therefore, the structural stability of the layered oxide is poor. It is easy to undergo phase change during the sodium deintercalation process, resulting in structural deformation, which causes the reversible capacity of the layered oxide to decay severely during the cycle, thereby causing the sodium ion battery to decay quickly. In order to improve the crystal structure stability of the layered oxide during the sodium deintercalation process and the electrochemical properties including reversible capacity and cycle performance, it is currently reported that the layered oxide is subjected to heterogeneous element doping treatment. Although the electrochemical properties such as the crystal structure stability and cycle performance of the layered oxide after doping are improved, they are not obvious. As is currently generally believed, when zinc is doped into the layered oxide, because the zinc element does not participate in the redox reaction of the layered oxide during the charge and discharge process, it can play the role of a stabilizer to reduce the structural distortion and slip phenomenon of the layered oxide during the charge and discharge process, thereby improving the structural stability of the layered oxide to improve its reversible capacity and cycle performance. At the same time, it is also generally believed that as the doping amount of the zinc element increases, its role as a stabilizer is also obvious, which can further reduce the structural distortion and slip phenomenon of the layered oxide during the charge and discharge process and improve the structural stability of the layered oxide. Therefore, it is generally believed that controlling the doping amount of zinc to a relatively high level is beneficial to the structural stability of the layered oxide. In layered oxides, the molar doping amount of zinc is generally above 8%.

[0106] However, research unexpectedly discovered that reducing the zinc doping content can effectively alleviate the premature structural phase transition of nickel-manganese layered oxides, reduce the phase transition of nickel-manganese layered oxides during charge and discharge, and significantly improve the crystal structure stability of nickel-manganese layered oxides during sodium insertion and extraction, thereby improving the specific capacity and reversible capacity stability of nickel-manganese layered oxides during cycling. Based on the above research, the following technical solutions are proposed in the embodiments of this application.

[0107] cathode materials

[0108] In one aspect, the present invention provides a low-zinc-doped cathode material. In some embodiments, the cathode material of the present invention comprises a layered oxide represented by the following chemical formula (I): Na q Ni x Mn y Fe z Zn p M i O j (Ⅰ);

[0109] 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 doping metal element.

[0110] In the chemical formula (I) of the layered oxide contained in the positive electrode material of the embodiment of the present application, q, x, y, z, p, i and j represent the stoichiometric content ratios of the doping metal elements represented by Na, Ni, Mn, Fe, Zn and M and O in the layered oxide, respectively. Therefore, the stoichiometric content ratio of Na, Ni, Mn, Fe, Zn and M and O contained 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; wherein, 0≤t<0.1. In addition, the stoichiometric ratio of the doping metal elements represented by Na, Ni, Mn, Fe, Zn and M and O can be a molar ratio or a mass ratio converted according to the molar ratio. The active doping metal element represented by M refers to a type of metal element that has electrochemical redox activity in the layered oxide and mainly contributes to the gram capacity of the layered oxide. The inert doping metal element, represented by M, refers to a metal element that is relatively stable in electrochemical redox activity in the layered oxide relative to the active doping metal element and primarily contributes to the stability of the layered oxide's crystal structure. The layered oxide is a cathode material composed of alternating octahedral transition metal layers (TMO6) containing Ni, Mn, and Fe, and alkali metal layers (NaO6).

[0111] The layered oxide contained in the positive electrode material of the embodiment of the present application is doped with the transition metal layer (TMO6) containing Ni, Fe, and Mn elements by Zn element or Zn element further with the doping metal element shown in M, and the doping amount of Zn element is controlled within the low content range shown in p, so that Zn element and Fe element or Zn element further with Fe element and the doping metal element shown in M ​​can jointly participate in the arrangement between the metal elements in the transition metal layer contained in the layered oxide crystal, mainly in a disordered arrangement, which can inhibit the layered oxide shown in chemical formula (I) itself from undergoing more phase changes due to the Jahn-Teller effect brought by the Mn element and the structure brought by excessive nickel element. Compared with the current layered oxide with a high zinc content, it can reduce the structural phase change of the layered oxide shown in chemical formula (I), can significantly reduce the structural distortion and irreversible phase change of the layered oxide shown in chemical formula (I) during the sodium insertion and extraction process, and can significantly improve the structural stability of the layered oxide, so as to improve the cycle stability of the reversible capacity of the layered oxide. At the same time, by controlling the content ratio of each metal element, the specific capacity of the layered oxide can be further increased on the basis of effectively improving the structural stability of the layered oxide. 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 can also improve the structural distortion and irreversible phase transition of the layered oxide during the sodium insertion and extraction process, which can significantly improve the structural stability of the layered oxide.

[0112] Furthermore, the low content of Zn in the layered oxide represented by the chemical formula (I) can also significantly reduce the segregation of transition metal elements on the surface of the layered oxide represented by the chemical formula (I), improve the air stability of the layered oxide represented by the chemical formula (I) in the air, avoid the occurrence of slurry agglomeration and gelation, improve the electrical properties, and at the same time improve the processing performance and electrical properties of the layered oxide represented by the chemical formula (I). In addition, the low content of Zn or Zn further doping with the doping metal element represented by M on the transition metal layer (TMO6) containing Ni, Fe, and Mn elements can effectively inhibit the Na deposition of the layered oxide during the charge and discharge process. + and vacancies, reducing the Na + The diffusion energy barrier of the layered oxide increases the diffusion rate of sodium ions contained in the layered oxide.

[0113] In an exemplary embodiment, in the layered oxide of chemical formula (I) contained in the positive electrode material of the present invention, the stoichiometric content q of the 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. The Na element in this content range increases the reversible capacity of the layered oxide represented by chemical formula (I).

[0114] In some embodiments, in the chemical formula (I) of the layered oxide contained in the positive electrode material of the embodiment of the present application, the stoichiometric content x of the Ni element can be further 0.15≤x≤0.25. Based on the value range of x in chemical formula (I), in the exemplary embodiment, x can be a typical but non-restrictive stoichiometric content such as 0.1, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.25, 0.3, or a range between any two stoichiometric content values. On the one hand, the 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 and deintercalation 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 the Ni element to reduce the content of Ni, thereby reducing the cost of the layered oxide without reducing the gram capacity of the layered oxide shown in chemical formula (I).

[0115] In some embodiments, in the chemical formula (I) of the layered oxide contained in the positive electrode material of the embodiment of the present application, the stoichiometric content y of the Mn element can be further 0.25≤y≤0.45. Based on the value range of y in chemical formula (I), in the exemplary embodiment, 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 by the Mn element and the Ni element 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 and extraction process; on the other hand, it can also make the layered oxide shown in chemical formula (I) have a larger average oxidation state and lattice space, thereby increasing the diffusion rate of Na ions.

[0116] In some embodiments, in the chemical formula (I) of the layered oxide contained in the positive electrode material of the embodiment of the present application, the stoichiometric content z of the Fe element can be further 0.25≤z≤0.32. Based on the value range of z in the chemical formula (I), in the exemplary embodiment, 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 a range between any two stoichiometric content values. The Fe element in this stoichiometric content range can be co-doped with the Zn element or the Zn element and the doping metal element shown in M ​​to the transition metal layer in the layered oxide shown in the chemical formula (I), thereby further improving the structural stability of the layered oxide shown in the chemical formula (I) during the sodium insertion and extraction process; at the same time, the Fe element replaces part of the Ni element, thereby reducing the content of the Ni element and reducing the cost of the layered oxide shown in the chemical formula (I) on the basis of increasing the gram capacity of the layered oxide shown in the chemical formula (I).

[0117] In some embodiments, in the chemical formula (I) of the layered oxide contained in the positive electrode material of the present 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 value range of p in chemical formula (I), in exemplary embodiments, p can be 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, 0.06, 0.065, 0.07, 0.075, or other typical but non-limiting stoichiometric contents or a range between any two stoichiometric content values. The Zn element in this stoichiometric content range can, or the Zn element can be further combined with the doping metal element shown in M, improve the doping of the transition metal layer contained in the layered oxide shown in chemical formula (I), further improve the structural stability of the layered oxide shown in chemical formula (I) during the sodium insertion and deinsertion process; and at the same time, further balance the electrical properties and processing properties of the positive electrode material.

[0118] In some embodiments, in the chemical formula (I) of the layered oxide contained in the positive electrode material of the embodiment of the present application, the stoichiometric content i of the doping metal element shown in M ​​can be further 0≤i≤0.05. Based on the value range of i in chemical formula (I), in the exemplary embodiment, 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 a range between any two stoichiometric content values. The doping metal element shown in M ​​in this stoichiometric content range can assist the low-content Zn element to further improve the doping of the transition metal layer contained in the layered oxide shown in chemical formula (I), adjust the arrangement between the metal elements in the transition metal layer, so as to further improve the structural stability of the layered oxide shown in chemical formula (I) during the sodium insertion and extraction process, and further improve the cycle stability of its specific capacity and / or reversible capacity.

[0119] In an exemplary embodiment, in the chemical formula (I) of the layered oxide contained in the positive electrode material of the present embodiment, the stoichiometric content j of O can be typical but non-limiting stoichiometric contents such as 1.8, 1.9, 2, or a range between any two stoichiometric content values.

[0120] In an embodiment, the active or / and inert doping metal element shown in M ​​may include at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, Ir, etc. Among them, the active doping metal element shown in M ​​may include at least one metal element among V, Ca, Cr, Nb, Cu, Sc, Sn, Sb, etc., and the inert doping metal element shown in M ​​may be at least one metal element among Zr, Mg, Ru, Ir, Al, Ti, etc. Selecting and controlling the active or / and inert doping metal element shown in M ​​to be among these elements can further improve the doping of the transition metal layer contained in the layered oxide shown in chemical formula (I) together with the low content of Zn element, adjust the arrangement between the metal elements in the transition metal layer, and according to the type of doping metal element shown in M, further improve the structural stability and / or gram capacity of the layered oxide shown in chemical formula (I) during the sodium insertion and extraction process.

[0121] Based on the value ranges of q, x, y, z, p, and i in the above embodiments, in some embodiments, the value ranges of q, x, y, z, p, and i in the chemical formula (I) of the layered oxide are as follows:

[0122] 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 content ratio of Na, Ni, Mn, Fe, Zn and the doping metal element represented by M contained in the layered oxide represented by chemical formula (I) may be 0.8-1:0.15-0.25:0.25-0.45:0.25-0.32:0.04-0.065:t-0.05; wherein 0≤t<0.05. By selecting and controlling the stoichiometric ratio of Na, Ni, Mn, Fe, Zn, or the doping metal elements represented by Na, Ni, Mn, Fe, Zn, and M within this range, the doping of the transition metal layer in the layered oxide represented by chemical formula (I) by the Zn element or the Zn element and the doping metal element represented by M can be further improved, further improving the structural stability of the layered oxide represented by chemical formula (I) during the sodium insertion and extraction process, adjusting the arrangement between the metal elements in the transition metal layer, and improving the cycle stability of the specific capacity and reversible capacity of the layered oxide. In addition, the electrochemical properties and processing properties of the layered oxide can also be further improved.

[0123] Based on the value ranges of q, x, y, z, p, and i in the above embodiments, in some embodiments, the stoichiometric ratio of the total stoichiometric amount of the doping metal elements represented by Ni, Mn, Fe, Zn, and M to the stoichiometric ratio of the Na element in the chemical formula (I) of the layered oxide is 1:(0.8-1), optionally 1:(0.85-0.95), and further 1:(0.85-0.92). In exemplary embodiments, the molar ratios may be 1:0.8, 1:0.82, 1:0.85, 1:0.88, 1:0.9, 1:0.95, 1:1, or any range between any two stoichiometric ratios. The stoichiometric ratio may be in terms of moles or mass converted to moles. Controlling the stoichiometric ratio of the Na element to other metal elements contained in the layered oxide represented by chemical formula (I) within this range can further increase the content of sodium ions, increase the content of sodium ions that can be inserted and removed from the layered oxide, and thus the gram capacity of the layered oxide; moreover, the sodium ions in this content range can increase the O3 crystal phase content of the layered oxide represented by chemical formula (I), so that the layered oxide represented by chemical formula (I) mainly presents O3 crystals, thereby improving the structural stability of the layered oxide represented by chemical formula (I) and improving the cyclic stability of its reversible capacity.

[0124] In some embodiments, the stoichiometric ratio of the Zn element to the Ni element in the chemical formula (I) of the layered oxide is 1:(3-15), optionally 1:(3.1-11). In exemplary embodiments, it can be a typical but non-limiting molar ratio of 1:3, 1:3.1, 1:5, 1:8, 1:10, 1:11, 1:12, 1:15, or a range between any two stoichiometric ratios. The stoichiometric ratio of the Zn element to the Ni element can be a molar number and a mass converted based on the molar number. The stoichiometric ratio of the Zn element to the Ni element in the chemical formula (I) is controlled within this range. The stoichiometric ratio of the Zn element to the Ni element in this range can further increase the gram capacity of the layered oxide shown in the chemical formula. If it is within the range, appropriately increasing the ratio, that is, appropriately increasing the zinc content, can further increase the gram capacity of the layered oxide shown in the chemical formula.

[0125] In some embodiments, the stoichiometric ratio of Zn to Mn is 1:(4-25), optionally 1:(5-15). In exemplary embodiments, the stoichiometric ratio may be 1:4, 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, 1:20, 1:22, 1:25, or any range between any two stoichiometric ratios. Similarly, the stoichiometric ratio of Zn to Mn may be in moles or in terms of mass converted to moles. Controlling the stoichiometric ratio of Zn to Mn within this range can further adjust the Mn content in the transition metal layer of the layered oxide shown in the chemical formula, thereby further reducing the Jahn-Teller effect between Mn and Ni in the transition metal layer, further reducing the structural distortion and irreversible phase transition of the layered oxide shown in the chemical formula during sodium insertion and extraction, and further improving the structural stability of the layered oxide. Of course, the above-mentioned stoichiometric ratio range of the Zn element and the Mn element can also take into account the gram capacity of the layered oxide represented by the chemical formula (I).

[0126] In addition, the stoichiometric ratios of Zn and Ni, and Zn and Mn in chemical formula (I) can be controlled separately within the aforementioned stoichiometric ratio ranges. In one embodiment, they can be controlled simultaneously within the aforementioned stoichiometric ratio ranges. Simultaneously controlling the stoichiometric ratios of Zn and Ni, and Zn and Mn within the aforementioned stoichiometric ratio ranges can allow the layered oxide represented by chemical formula (I) to better balance structural stability and specific capacity. This means that the layered oxide represented by chemical formula (I) has a relatively high specific capacity while having better cycle stability of reversible capacity.

[0127] Based on the value ranges of q, x, y, z, p, and i in the above embodiments, in the embodiments, the layered oxides represented by chemical formula (I) in the above embodiments may include 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 Ni0.23 Mr 0.41 Feb 0.3 Zn 0.06 O2、Na 0.89 Ni 0.23 Mr 0.42 Feb 0.285 Zn 0.065 O2、Na 0.89 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.07 O2、Na 0.9 Ni 0.23 Mr 0.4 Feb 0.3 Zn 0.075 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 V 0.02 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 Cr 0.02 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 Al 0.02 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 Sc 0.02 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 Mr 0.02 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 Sb 0.02 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28 Zn 0.04 Zr 0.02 O2、Na 0.85 Ni 0.23 Mr 0.42 Feb 0.28Zn 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 0.02 O 1.8 At least one of the above. The layered oxides shown in these chemical formulas have a low content of Zn element, and the low content of Zn element works together with other contents of metal elements to significantly improve the doping of the transition metal layer contained in the layered oxide shown in chemical formula (I), so that the metal elements in the transition metal layer contained in the layered oxide form a specific arrangement, further improving the structural stability of the layered oxide during the sodium insertion and extraction process, and improving the cycle stability of the specific capacity and reversible capacity of the layered oxide. At the same time, by controlling the doping content of the Zn element and the Fe element or further with the doping metal element shown in M, the content of the Ni element can also be reduced, thereby reducing the economic cost of the layered oxide on the basis of increasing the specific capacity of the layered oxide shown in chemical formula (I). In addition, the electrochemical properties and processing properties of the layered oxide can be further improved.

[0128] After testing, in some embodiments, the crystal structure of the layered oxide represented by chemical formula (I) in the above embodiments includes O3-phase layered metal oxide. The O3-phase layered metal oxide refers to a layered oxide with a crystal structure in which the oxygen contained therein is stacked in an ABCABC type. In the embodiments, the layered oxide represented by chemical formula (I) in the above embodiments is mainly O3-phase layered metal oxide. Mainly O3-phase layered metal oxide means that in the layered oxide represented by chemical formula (I), the weight proportion of O3-phase layered metal oxide, that is, the O3-phase layered metal oxide accounts for more than 95% of the total weight of the layered oxide represented by chemical formula (I), and further more than 98%. Of course, the weight proportion of O3-phase layered metal oxide in the layered oxide represented by chemical formula (I) can reach 100%. The higher the weight proportion of the O3-phase layered metal oxide in the layered oxide represented by chemical formula (I), the more desirable it is. 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 relative to P2 phase layered metal oxide, and has higher specific capacity and better cycle stability of reversible capacity.

[0129] In some embodiments, electron microscopic analysis shows that the layered oxide crystals represented by chemical formula (I) in the above embodiments include single crystals, which are flat, as shown in Figure 1. Since the layered oxide is mainly an O3 phase layered metal oxide, the O3 phase layered metal oxide is a single crystal.

[0130] Further electron microscopic analysis of the single crystal revealed that, in some embodiments, as shown in FIG2 , the ratio of length L, width W, and thickness H of the single crystal of the layered oxide represented by chemical formula (I) is 1-8:1-5:0.5-2.5, optionally 2-6:2-4:1-2, and in exemplary embodiments, can be 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 any two ratios. The length L and width W are shown as L and W in FIG2 , respectively, and are the length L and width W of the large surface of the flat single crystal; the thickness is shown as H in FIG2 , and is the thickness of the flat single crystal.

[0131] Based on the above-mentioned ratio of length L, width W, and thickness H, in the embodiment, the length L of the single crystal can be 1 to 8 μm, optionally 2 to 6 μm. In the demonstration example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm and other typical but non-limiting lengths or a range between any two length values.

[0132] In an embodiment, the width W of the single crystal may be 1 to 5 μm, optionally 2 to 4 μm. In an exemplary embodiment, the width W may be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or other typical but non-limiting widths, or a range between any two width values.

[0133] In an embodiment, the thickness H of the single crystal can be 0.5 to 2.5 μm, optionally 1 to 2 μm. In an exemplary embodiment, 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 a range between any two thickness values.

[0134] In the embodiments, the layered oxides represented by chemical formula (I) in the above embodiments have been tested to have a Dv50 particle size of 3 to 11 μm, optionally 4 to 8 μm. In exemplary embodiments, the Dv50 particle size can be a typical but non-limiting particle size of 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, or a range between any two particle size values. The Dv50 particle size refers to the particles of the layered oxide powder represented by chemical formula (I).

[0135] The Dv50 particle size of the layered oxide represented by Chemical Formula (I) in each of the above-mentioned embodiments and the size distribution range of the O3 phase layered metal oxide single crystals therein provide the layered oxide with a high compaction density, thereby increasing the compaction density of the positive electrode material of the present application embodiment and improving the energy density of the battery. This also provides the layered oxide with a suitable specific surface area.

[0136] According to the test, the specific surface area (BET) of the layered oxides represented by the chemical formula (I) in the above embodiments is 0.5 to 1.3 m 2 / g, optional range is 0.6~0.9m 2 / g, in the example, it 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 Typical but non-limiting specific surface areas such as 1000 nm / g or a range between any two specific surface area values ​​can be used. 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 properties such as cycling performance.

[0137] According to the test, the compacted density of the layered oxide represented by chemical formula (I) in the above embodiments under a pressure of 2 tons is 2.8-3.1 g / cm 3, can be selected from 2.9 to 3.09 g / cm 3 In this example, the compaction density under 2 tons of pressure is 2.8g / cm 3 , 2.9g / cm 3 , 3g / cm 3 、3.09g / cm 3 , 3.1g / cm 3 Typical but non-limiting compacted densities or ranges between any two compacted density values.

[0138] In the embodiments, the layered oxide represented by chemical formula (I) in the above embodiments has a compaction density of 3.1 to 3.3 g / cm2 under a pressure of 3 tons. 3 , can be selected from 3.15 to 3.28 g / cm 3 In the example, the compaction density under 3 tons of pressure is 3.1g / cm 3 、3.15g / cm 3 、3.2g / cm 3 , 3.25g / cm 3 、3.28g / cm 3 , 3.3g / cm 3 Typical but non-limiting compacted densities or ranges between any two compacted density values.

[0139] The above compaction density range can improve the energy density and corresponding electrochemical performance of the battery containing the layered oxide represented by the above chemical formula (I).

[0140] Based on the morphology, crystal form, particle size, and compacted density of the layered oxide represented by chemical formula (I) in the above embodiments, in the embodiments, the layered oxide has a charge capacity of 164 to 174 mAh / g at 1.5 to 4.2 V and 0.1 C, and can be optionally 165 to 172 mAh / g; a discharge capacity of 158 to 165 mAh / g, and can be optionally 160 to 163 mAh / g. In other embodiments, the layered oxide has a first efficiency of 92% to 98% at 1.5 to 4.2 V and 0.1 C, and can be optionally 92% to 95%.

[0141] The charge gram capacity, discharge gram capacity and first effect of the layered oxide refer to the gram capacity and first effect of the layered oxide, specifically, the layered oxide is prepared as a positive electrode for sodium ion buckle battery, and assembled with the negative electrode into a sodium ion buckle battery. The gram capacity and first effect are obtained by testing the sodium ion buckle battery. It can be seen from the gram capacity and first effect range of the layered oxide that the structural stability of the layered oxide crystal has been significantly improved, the structural stability during the sodium insertion and deintercalation process, the high gram capacity, and the good cyclic stability of the reversible capacity.

[0142] In the embodiment, the sodium ion button cell used to test the charge gram capacity and discharge gram capacity and the first effect of the layered oxide is assembled according to the following method:

[0143] Positive electrode sheet: The layered oxide represented by the above chemical formula (I) is used as the positive electrode active material, and is thoroughly stirred and mixed with a conductive agent carbon nanotube, a conductive agent carbon black, and a binder polyvinylidene fluoride (PVDF) in a weight ratio of 95:0.5:2:2.5 in an appropriate amount of solvent NMP to form a uniform positive electrode slurry; the positive electrode slurry is evenly coated on the surface of a 13 μm positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained;

[0144] Negative electrode sheet: Add hard carbon, conductive agent SP, and CMC binder to deionized water in a weight ratio of 8:1:1 and stir thoroughly to form a uniform negative electrode slurry. The negative electrode slurry is evenly coated on the surface of a 6μm copper foil, dried, and cold pressed to obtain a negative electrode sheet.

[0145] Electrolyte: 1 M NaPF6 / (EC / DEC, volume ratio 1:1);

[0146] Diaphragm: Glass fiber;

[0147] Sodium ion button cell assembly: The above-mentioned positive electrode sheet, glass fiber film and negative electrode sheet are stacked in order to form a button cell assembly after assembly. The electrode assembly is placed in a packaging shell, and 1M NaPF6 / (EC / DEC, volume ratio 1:1) electrolyte is added. After packaging, formation, and static standing, a sodium ion battery is obtained.

[0148] Based on the above embodiments, the positive electrode material of the present application can only contain the layered oxide represented by chemical formula (I) in the above embodiments. Of course, it can also further include other positive electrode materials, such as one or more of polyanion compounds, Prussian blue compounds, and other layered oxides.

[0149] In an exemplary embodiment, the polyanion compound may include at least one of sodium vanadium phosphate, sodium iron pyrophosphate, sodium iron phosphate, sodium fluoroferric phosphate, and the like.

[0150] In an exemplary embodiment, the Prussian blue compound may include at least one of Na2Fe[Fe(CN)6](FeHCF), Na2Mn[Fe(CN)6](MnHCF), and the like.

[0151] The above-mentioned other positive electrode materials can, together with the layered oxide represented by the above-mentioned chemical formula (I), further improve the electrochemical properties such as energy density, reversible capacity, and cycle performance of the battery containing the positive electrode material of the embodiment of the present application.

[0152] Preparation method of positive electrode material

[0153] In a second aspect, the present invention provides a method for preparing the positive electrode material of the above-mentioned embodiment. In some embodiments, the method for preparing the positive electrode material of the present invention comprises the following steps:

[0154] S10: Provides Na q Ni x Mn y Fe z Zn p M i O j precursors;

[0155] S20: The precursor is sintered to obtain a chemical formula of Na q Ni x Mn y Fe z Zn p M i O j layered oxides.

[0156] In step S10 of the method for preparing the positive electrode material according to the embodiment of the present application, Na q Ni x Mn y Fe z Zn p M i O j The precursor of is the precursor of the layered oxide represented by the chemical formula (I) contained in the positive electrode material of the above-mentioned embodiment of the application. q Ni x Mn y Fe z Zn p M i O j The contained q, x, y, z, p, i and j are respectively in the following ranges:

[0157] 0.8≤q≤1; 0.1≤x≤0.3, optionally 0.15≤x≤0.25; 0.2≤y≤0.5, optionally 0.25≤y≤0.45; 0.2≤z≤0.35, optionally 0.25≤z≤0.32; 0.02≤p≤0.075, optionally 0.04≤p≤0.07, 0.04≤p≤0.065; 0≤i≤0.1, optionally 0≤i≤0.05; 1.8≤j≤2; and x+y+z+p+i≤1; M is an active or / and inert doping metal element, in an exemplary embodiment, the doping 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 the Na in step S10 qNi x Mn y Fe z Zn p M i O j The precursor is reacted to generate the layered oxide represented by the chemical formula (I) contained in the positive electrode material of the above application embodiment.

[0158] The positive electrode material preparation method of the present application embodiment is to q Ni x Mn y Fe z Zn p M i O j The precursor is sintered to generate the positive electrode material of the above-mentioned embodiment of the application containing the chemical formula Na q Ni x Mn y Fe z Zn p M i O j Therefore, the layered oxide prepared by the positive electrode material preparation method of the present invention has a low zinc content and high structural stability during the sodium insertion and removal process, which makes the prepared layered oxide have a high gram capacity and a cyclic stability of its reversible capacity. At the same time, it also has high air stability and diffusion rate. In addition, for Na q Ni x Mn y Fe z Zn p M i O j The sintering conditions of the precursor can be effectively controlled, thereby improving the q Ni x Mn y Fe z Zn p M i O j The stability of the structure and electrochemical properties of layered oxides.

[0159] Step S10:

[0160] 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 zZn p M i O j The sodium source, nickel source, manganese source, iron source, zinc source and the doping element source represented by M are prepared by a solid phase method or a precipitation method according to the stoichiometric amount of the elements contained, such as moles or mass ratios converted based on moles.

[0161] When the solid phase method was used to prepare Na q Ni x Mn y Fe z Zn p M i O j When the precursor is Na q Ni x Mn y Fe z Zn p M i O j The precursor can be prepared according to a method comprising the following steps:

[0162] Step S11: According to Na q Ni x Mn y Fe z Zn p M i O j The sodium source, nickel source, manganese source, iron source, zinc source and the doping element source shown in M ​​are solid-phase mixed to obtain Na q Ni x Mn y Fe z Zn p M i O j precursor.

[0163] In step S11, solid-phase mixing treatment is relative to liquid-phase mixing, and generally refers to not adding a solvent during the mixing process, such as not adding water. It also refers to dry mixing of the sodium source, nickel source, manganese source, iron source and zinc source or further containing the doping element source shown by M under solvent-free conditions.

[0164] In order to improve the uniformity of mixing of the sodium source, nickel source, manganese source, iron source, and zinc source, or a source further containing a doping element represented by M, during the solid-phase mixing process, in an embodiment, the nickel source, manganese source, iron source, and zinc source, or a source further containing a doping element represented by M, can be mixed first, and then the sodium source can be added and mixed again. This improves the uniformity of mixing of the sources and improves the safety of the solid-phase mixing process.

[0165] In the embodiment, the mixing treatment can be covered but not limited to ball milling treatment, as long as it can improve the uniformity of the mixing of the sodium source, nickel source, manganese source, iron source and zinc source or further contain the doping element source shown by M, it is within the scope disclosed in the embodiment of the present application. In the embodiment, when the mixing treatment is ball milling treatment, the speed of the ball mill can be controlled to be 300 to 1000 rpm, optionally 400 to 600 rpm; the time of the ball milling treatment can be 1h to 6h, optionally 2h to 4h. By using this ball milling treatment, the mixing uniformity of each source can be improved, thereby ultimately improving the 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.

[0166] In an exemplary embodiment, the sodium source may be a sodium salt, such as at least one of sodium carbonate, sodium hydroxide, and the like.

[0167] In an exemplary embodiment, the nickel source may be a soluble or insoluble nickel compound, such as nickel oxide (NiO) or a nickel salt, etc. The nickel salt may include at least one of nickel nitrate, nickel carbonate, nickel hydroxide, nickel sulfate, etc.

[0168] In an exemplary embodiment, the manganese source may be a soluble or insoluble manganese compound, such as manganese oxide (Mn2O3) or a manganese salt, etc. The manganese salt may include at least one of manganese nitrate, manganese carbonate, manganese hydroxide, manganese sulfate, etc.

[0169] In an exemplary embodiment, the iron source may be a soluble or insoluble iron compound, such as iron oxide (eg, Fe2O3) or an iron salt, etc. The iron salt may include at least one of iron nitrate, iron carbonate, iron hydroxide, iron sulfate, etc.

[0170] In an exemplary embodiment, the zinc source may be a soluble or insoluble zinc compound, such as zinc oxide (such as ZnO) or a zinc salt, etc. The zinc salt may include at least one of zinc nitrate, zinc carbonate, zinc hydroxide, zinc sulfate, etc.

[0171] In an exemplary embodiment, the source of the doping metal element shown in M ​​may be a soluble or insoluble compound of the doping metal element shown in M, such as an oxide of the doping metal element shown in M ​​or a salt of the doping metal element shown in M. The salt of the doping metal element shown in M ​​may include at least one of a nitrate, carbonate, hydroxide, sulfate, etc. of the doping metal element shown in M.

[0172] The above sodium source, nickel source, manganese source, iron source and zinc source or further containing the doping element source shown by M can be effectively mixed uniformly during the mixing process to improve Na q Ni x Mn y Fe z Zn p M i O j The precursor to generate Na q Ni x Mn y Fe z Zn p M i O j Structure and chemical stability of layered oxides.

[0173] When the precipitation method is used to prepare Na q Ni x Mn y Fe z Zn p M i O j When the precursor is Na q Ni x Mn y Fe z Zn p M i O j The precursor can be prepared according to a method comprising the following steps:

[0174] Step S12: According to Na q Ni x Mn y Fe z Zn p M i O j A soluble nickel source, a soluble manganese source, a soluble iron source, a soluble zinc source or a soluble doping element source represented by M is prepared into a mixed solution in a stoichiometric ratio of elements, and at least one of a precipitant and a complexing agent is added to perform a coprecipitation treatment to obtain a precipitated mixture;

[0175] Step S13: Mixing the precipitated mixture with a sodium source to obtain Na q Ni x Mn y Fe z Zn p M i O j precursor.

[0176] In step S12, at least one of the precipitant and the complexing agent should be a compound that can precipitate nickel, manganese, iron, zinc and the doping metal element shown in M ​​in the nickel source, soluble manganese source, soluble iron source, soluble zinc source and the soluble doping element source shown in M. For example, in the embodiment, the precipitant may include at least one of alkali metal hydroxides, carbonates, etc.

[0177] In an embodiment, the complexing agent may include an inorganic or organic complexing agent. In a demonstration example, the inorganic complexing agent may include at least one of ammonia water, ammonium bicarbonate, ammonium sulfate, ammonium carbonate, etc.; the organic complexing agent may include at least one of citric acid, tartaric acid and disodium ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid (EDTA), aminotriacetic acid (NTA), etc.

[0178] These types of precipitants and complexing agents can effectively precipitate nickel, manganese, iron, zinc and the doping elements represented by M.

[0179] In the embodiment, at least one of the precipitant and the complexing agent should be in excess relative to the total amount of metal elements contained in the mixed solution, such as the total molar amount, to ensure that all metal elements contained in the mixed solution are fully precipitated to increase the Na 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.

[0180] In an exemplary embodiment, the soluble nickel source may include at least one of nickel acetate, nickel chloride, nickel nitrate, and nickel sulfate.

[0181] In an exemplary embodiment, the soluble manganese source may include at least one of manganese nitrate, manganese sulfate, and manganese halide.

[0182] In an exemplary embodiment, the soluble iron source may include at least one of iron nitrate, manganese sulfate, and halide.

[0183] In an exemplary embodiment, the soluble zinc source may include at least one of zinc nitrate, manganese sulfate, and halides.

[0184] In an exemplary embodiment, the soluble doping metal element source M may include at least one of nitrates, manganese sulfate, halides, and the like of the doping metal element M.

[0185] The above-mentioned soluble nickel source, soluble manganese source, soluble iron source, soluble zinc source and soluble doping element source represented by M all have good solubility and can quantitatively control the stoichiometric ratio of each metal element in the precipitation mixture.

[0186] The mixing ratio between the sodium source and the precipitation mixture in step S13 should satisfy Na q Ni x Mn y Fe z Zn p M i O j The mixing process can be a solid phase mixing process or a process in which a soluble sodium source is dissolved and mixed with the precipitation mixture, and then the solvent is removed.

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

[0188] In addition, there is no sequential order between the above step S11, step S12 and step S13.

[0189] Step S20:

[0190] In step S20, Na in step S10 is q Ni x Mn y Fe z Zn p M i O j After the precursor is sintered, a chemical formula of Na q Ni x Mn y Fe z Zn p M i O j The study found that the sintering conditions have a great influence on the formation of Na q Ni x Mn y Fe z Zn p M i O j The structural stability and electrochemical performance of the layered oxide are affected to a certain extent. In some embodiments, the sintering temperature can be controlled within a range of 700°C to 980°C, optionally 750°C to 950°C. In exemplary embodiments, the sintering temperature can be 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 980°C, or any other typical but non-limiting temperature range, or any temperature range between any two values.

[0191] At the above sintering temperature, the sintering treatment time can be 4h to 20h, optionally 6h to 12h. In the exemplary embodiment, it can be 4h, 5h, 8h, 10h, 12h, 15h, 18h, 20h and other typical but non-limiting hours or any range between two hours.

[0192] By controlling the stability and time of the sintering process within the above range, the Na q Ni x Mn y Fe z Zn p M i O j The precursor reacts to generate Na q Ni x Mn y Fe z Zn p M i O j layered oxides, and can further increase the Na q Ni x Mn y Fe z Zn p M i O j The structural stability of the layered oxide during the process of sodium insertion and removal further improves the high specific capacity of the layered oxide and the cycle stability of its reversible capacity. q Ni x Mn y Fe z Zn p M i O j The content of O3 phase layered metal oxide and the single crystal content in the layered oxide control the single crystal size and the particle size of the layered oxide, thereby increasing the compaction density of the layered oxide.

[0193] In an embodiment, the temperature of the sintering process can be increased to the temperature of the sintering process at a heating rate of 2 to 15°C / min. The heating rate can be further controlled to be 4 to 10°C / min. In an exemplary embodiment, the heating rate can be a typical but non-limiting rate such as 2°C / min, 4°C / min, 6°C / min, 8°C / min, 10°C / min, 12°C / min, 15°C / min, 17°C / min, 18°C / min, 20°C / min, or a range between any two rate values. By controlling the heating rate of the sintering process, such as controlling it in this heating rate range, the Na q Ni x Mn y Fe z Zn p M i O j The crystals of the layered oxide are perfect and complete, such as improving the uniformity of the crystal morphology.

[0194] In addition, the sintering process in the above step S20 should be understood to be carried out in an oxygen environment. For example, in the embodiment, the sintering process can be carried out in air or in an oxygen-containing protective atmosphere, such as oxygen-containing nitrogen or other inert atmospheres.

[0195] positive electrode

[0196] In a third aspect, embodiments of the present application provide a positive electrode. In some embodiments, the positive electrode of the present application includes a current collector and a positive electrode active material layer. The positive electrode active material layer and the current collector are stacked, and the positive electrode active material layer contains the positive electrode material of the above-mentioned embodiments of the present application.

[0197] In the positive electrode of the embodiment of the present application, the current collector refers to a structure for collecting current and for transmitting electrons. The positive electrode active material layer refers to a layer structure containing a positive electrode active material, which is a key substance participating in the battery chemical reaction in the positive electrode. Among them, the positive electrode active material includes the positive electrode material of the embodiment of the above text application. The positive electrode active material layer and the current collector are stacked in layers, which means that the positive electrode active material layer is at least stacked on the surface of the current collector. In addition, the positive electrode can be a pole piece, which means that the positive electrode has a sheet-like morphology. Of course, it can also be set to other morphologies as needed.

[0198] Since the positive electrode active material layer of the positive electrode of the embodiment of the present application contains the positive electrode material of the embodiment of the present application, the positive electrode has a relatively high gram capacity and good cycle performance.

[0199] In the embodiments, the current collector contained in the positive electrode of the present application includes, but is not limited to, a metal current collector, a carbon current collector, a conductive resin current collector, a metal and resin composite current collector, and more specifically, aluminum, copper, nickel, titanium, iron, and their respective alloys, stainless steel, carbon fiber, carbon nanotubes (CNTs), graphite, and the like. In the embodiments, the current collector can also be a dense film layer or a porous film layer. In the embodiments, the current collector can be, but is not limited to, aluminum foil or porous aluminum foil.

[0200] In the embodiments, the positive electrode active material layer contained in the positive electrode of the present invention may be at least laminated on the surface of the current collector when disposed 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.

[0201] In some embodiments, the positive electrode active material layer is provided at least on the surface of the current collector, and the structure may be as shown in FIG3 , where the positive electrode active material layer 12 is laminated on one surface of the current collector 11. When the surface of the current collector 11 has a porous structure or the current collector 11 is a porous structure as a whole, the positive electrode active material layer 12 may not only be provided on the surface of the current collector 11 but may also further extend into the porous structure of the current collector 11.

[0202] In other embodiments, the positive electrode active material layer is disposed at least on the surface of the current collector, and the structure may be as shown in FIG4 , where the current collector 11 has two opposing surfaces, and the positive electrode active material layer 12 is laminated on the two opposing surfaces of the current collector 11. When at least one of the two surfaces of the current collector 11 has a porous structure or the current collector 11 as a whole has a porous structure, the positive electrode active material layer 12 may not only be disposed on the two surfaces of the current collector 11 but may also further extend into the porous structure of the current collector 11.

[0203] As an embodiment of the present application, in the above-mentioned positive electrode active material layer, the mass content of the layered oxide represented by chemical formula (I) contained in the positive electrode material of the above-mentioned embodiment of the present application in the positive electrode active material layer can be 90% to 98%, optionally 92% to 96%. In the exemplary embodiment, it can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% and other typical but non-limiting contents or a range between any two content values. The layered oxide in this content range can effectively increase the gram capacity of the positive electrode, thereby increasing the energy density of the battery, and has good cyclability. Since the layered oxide also has good processing properties, it also effectively improves the film quality of the positive electrode active material layer.

[0204] The positive electrode active material layer contained in each of the above-mentioned embodiments generally includes, in addition to the above-mentioned positive electrode active material components, a binder, a conductive agent, and other components. The binder can enhance the mechanical properties between the positive electrode active material layer itself and the current collector. The conductive agent can effectively improve the conductivity of the positive electrode, such as reducing the resistance of the positive electrode.

[0205] In an embodiment, the mass content of the binder contained in the above-mentioned positive electrode active material layer can be 0.5% to 5%, optionally 1% to 3%. In a demonstration example, it can be 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3% and other typical but non-limiting contents or a range between any two content values.

[0206] In an embodiment, the binder may include one or more of an oil-soluble binder, a water-soluble binder, an emulsion-type binder, etc. In an exemplary embodiment, the oil-soluble binder may include one or more of polyvinylidene fluoride, polyimide, polytetrafluoroethylene, polybutyl acrylate, polyacrylonitrile, etc.; in an exemplary embodiment, the water-soluble binder may include one or more of carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylic acid salt, polyvinyl alcohol, sodium alginate, cyclodextrin, etc.; in an exemplary embodiment, the emulsion-type binder may include one or more of styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0207] The content within this range and the above-mentioned types of binders can effectively enhance the mechanical properties of the positive electrode active material layer and the bonding strength between the positive electrode active material layer and the current collector, and can effectively improve the cycle performance of the positive electrode.

[0208] In an embodiment, the mass content of the conductive agent contained in the above-mentioned positive electrode active material layer can be 0.5% to 5%, optionally 1% to 3%. In a demonstration example, it can be 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3% and other typical but non-limiting contents or a range between any two content values.

[0209] In an embodiment, the conductive agent may include at least one of a granular conductive agent and a linear conductive agent. The granular conductive agent may include one or more of acetylene black (SP), conductive carbon black (super-P), Ketjen black, graphene, and the like. The linear conductive agent may include one or more of carbon nanotubes, carbon fibers, and conductive oxide nanowires. The granular conductive agent is a conductive agent with a nonlinear particle morphology, as opposed to a linear conductive agent. A linear conductive agent is a conductive agent with a one-dimensional fiber morphology.

[0210] The content within this range and the above-mentioned type of conductive agent can effectively improve the conductivity of the positive electrode active material layer.

[0211] In the embodiments, the conductive agent contained in the positive electrode active material layer of each of the above embodiments includes a linear conductive agent and a granular conductive agent. The linear conductive agent has a mass content of 0.1% to 2.5% in the positive electrode active material layer, and can optionally be 0.2% to 0.8%. In exemplary embodiments, the linear conductive agent can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, or other typical but non-limiting content, or a range between any two content values. Since the crystals of the layered oxide shown in the chemical formula (I) contained in the positive electrode material of the above-mentioned embodiment of the application include single crystals, and the morphology of the single crystals is flat, a linear conductive agent is added to the positive electrode active material layer, and the content of the linear conductive agent is controlled within this range, so that the linear conductive agent can form a rich conductive network structure in the positive electrode active material layer, and the linear conductive agent can also be wrapped around the surface of the flat single crystal particles. The granular 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, and the granular conductive agent constitutes a short-range conductive structure. Therefore, the conductive synergistic effect played by the linear conductive agent and the granular conductive agent in the positive electrode active material layer effectively improves the conductivity of the positive electrode active material layer and can significantly reduce the internal resistance of the positive electrode.

[0212] In an embodiment, the aspect ratio of the linear conductive agent can be controlled to be 40 to 3000:1, or optionally 50 to 2500:1. In exemplary embodiments, typical but non-limiting aspect ratios such as 40:1, 50:1, 100:1, 500:1, 1000:1, 1500:1, 2000:1, 2500:1, and 3000:1 can be used, or ranges between any two aspect ratios. The aspect ratio refers to the ratio of the length of the linear conductive agent to its diameter.

[0213] In a further embodiment, the length of the linear conductive agent can be selected to be 0.5 to 5 μm, or optionally 0.5 to 2 μm. In the exemplary embodiment, the length can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or other typical but non-limiting lengths or a range between any two length values.

[0214] In a further embodiment, the diameter of the linear conductive agent can be selected to be 2 to 10 nm, or optionally 3 to 7 nm. In the exemplary embodiment, the diameter can be 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or other typical but non-limiting diameters, or a range between any two diameter values.

[0215] By controlling the aspect ratio of the linear conductive agent within the above range, or further controlling the length and diameter of the linear conductive agent within the above range, the linear conductive agent can construct a richer long-range conductive network structure in the positive electrode active material layer, further enhancing the conductive synergistic effect of the linear conductive agent and the particulate conductive agent, thereby further improving the conductivity of the positive electrode active material layer.

[0216] In the embodiments, the positive electrode active material layer in the positive electrode of each embodiment above may contain other additives in addition to the positive electrode active material, binder, conductive agent and other components. In the embodiments, the additives may include but are not limited to functional components such as sodium supplement additives.

[0217] In some embodiments, the content of the positive electrode active material layer on a single surface of the current collector in each of the above embodiments, that is, the coating weight (CW), is 260-350 mg / 1540.25 mm 2 , optional: 280~320mg / 1540.25mm 2 In the example, it can be 260mg / 1540.25mm 2 、270mg / 1540.25mm 2 、280mg / 1540.25mm 2 、290mg / 1540.25mm 2 、300mg / 1540.25mm 2 、310mg / 1540.25mm2 、320mg / 1540.25mm 2 、330mg / 1540.25mm 2 、340mg / 1540.25mm 2 、350mg / 1540.25mm 2 Typical but non-limiting contents or ranges between any two content values ​​are provided. The coating weight refers to the weight of the positive electrode active material layer per unit area. A coating weight within this range can effectively increase the gram capacity of the positive electrode and thus improve the energy density of the battery.

[0218] In some embodiments, the compaction density of the positive electrode active material layer in the above embodiments may be 2.8 to 3.4 g / cm 3 , can be selected as 2.9~3.2g / cm 3 In the example, it can be 2.8g / cm 3 , 2.9g / cm 3 , 3.0g / cm 3 , 3.1g / cm 3 、3.2g / cm 3 , 3.3g / cm 3 、3.4g / cm 3 Typical but non-limiting compacted densities, such as [ 0.05 ], or a range between any two compacted density values, are provided. The compacted density refers to the weight of the positive electrode active material layer per unit volume. A compacted density within this range can effectively increase the gram capacity of the positive electrode, thereby improving the energy density of the battery, while also providing good interfacial stability with the electrolyte.

[0219] In some embodiments, the porosity of the positive electrode active material layer in the above embodiments may be 40% to 65%, optionally 45% to 60%. In exemplary embodiments, it may be 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 63%, 65%, or other typical but non-limiting porosities or a range between any two porosity values. The porosity refers to the percentage of the total volume of pores contained in the unit volume of the positive electrode active material layer to the unit volume of the positive electrode active material layer. The porosity in this range enables the positive electrode active material layer to have the above-mentioned compaction density, thereby increasing the gram capacity of the positive electrode and thus increasing the energy density of the battery, and also improving the wettability of the electrolyte.

[0220] In some embodiments, the positive electrode in each of the above embodiments is a pole piece. The sheet resistance of the positive electrode active material layer in each of the above embodiments can be 0.5 to 5 mΩ, optionally 0.5 to 3 mΩ. In exemplary embodiments, it can be a typical but non-limiting sheet 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 a range between any two sheet resistance values. The pole piece has a sheet-like morphology as described above, and therefore has two opposing surfaces. The sheet resistance refers to the resistance value between one surface of the sheet-like positive electrode and the other opposing surface. A sheet resistance in this range can effectively improve battery performance, including efficiency and life.

[0221] In some embodiments, the positive electrode is a pole piece in each of the above embodiments, and the ratio of the thickness from one surface of the pole piece to the other opposite surface to the thickness of the current collector is 6 to 15:1, optionally 8 to 14:1. In exemplary embodiments, it can be a typical but non-limiting ratio such as 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, or a range between any two ratios. The thickness refers to the vertical distance from one surface of the layer structure to the other opposite surface. When a positive electrode active material layer is provided on one surface of the current collector as shown in FIG3 , the thickness from one surface of the pole piece to the other opposite surface refers to the sum of the thickness of one positive electrode active material layer plus the thickness of the current collector; when both surfaces of the current collector as shown in FIG4 contain positive electrode active material layers, the thickness from one surface of the pole piece to the other opposite surface refers to the sum of the thickness of the two positive electrode active material layers plus the total thickness of the current collector.

[0222] In an embodiment, the thickness of the positive electrode active material layer contained in the electrode sheet can be controlled to be 104 to 182 μm, and further can be 110 to 170 μm. In exemplary embodiments, the thickness can be 104 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 182 μm, or other typical but non-limiting thicknesses, or a range between any two thickness values. In an embodiment, the thickness of the current collector can be, but is not limited to, 13 μm.

[0223] By controlling the total thickness of the electrode and the thickness of the current collector within the above-mentioned ratio range or specific thickness range, the gram capacity of the electrode can be effectively increased, thereby increasing the energy density of the battery, and increasing the bonding strength between the positive electrode active material layer and the current collector, thereby increasing the mechanical strength of the electrode structure and improving the cycle performance of the electrode.

[0224] Preparation method of positive electrode:

[0225] The present application also provides a method for preparing the positive electrode of the above embodiment. In some embodiments, the method for preparing the positive electrode of the above embodiment includes the following steps:

[0226] S30: Mixing the components including the positive electrode active material, the binder, the conductive agent and the like in a solvent in proportion to prepare a positive electrode slurry;

[0227] S40: The positive electrode slurry is subjected to a film-forming treatment on the current collector to form a positive electrode active material layer to obtain a positive electrode.

[0228] Step S30:

[0229] The positive electrode active material in step S30 includes the positive electrode material of the above-mentioned embodiment of the application, specifically, includes the layered oxide represented by the above-mentioned chemical formula (I).

[0230] In step S30, the positive electrode active material, binder, conductive agent and other components can be mixed according to the content ratio of the corresponding components in the positive electrode active material layer of the positive electrode. The solvent can be an organic solvent or water suitable for preparing positive electrode slurry.

[0231] The mixing process in step S30 can be performed according to conventional electrode slurry preparation methods, such as, but not limited to, stirring, until the components are evenly dispersed to form a stable positive electrode slurry. Of course, the viscosity and other properties of the positive electrode slurry should meet the requirements of the film forming process so that a positive electrode active material layer that meets the quality requirements can be formed on the current collector.

[0232] Step S40:

[0233] 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 embodiment of the present application.

[0234] The positive electrode slurry is formed into a film on the current collector in step S40 according to conventional methods for forming a positive electrode active material layer. For example, in the embodiment, the electrode slurry may be first formed into a wet film on the current collector; then, a drying process is performed to evaporate the solvent, thereby drying the wet film; and then, the dried film layer is roller-pressed to form a positive electrode active material layer, thereby obtaining a positive electrode.

[0235] Of course, the positive electrode active material layer can also be prepared by improving the conventional positive electrode active material layer preparation method, or by adopting a new method. As long as the electrode slurry in step S30 is used to prepare the positive electrode active material layer on the current collector, it is within the scope of the embodiments disclosed in the present application.

[0236] In addition, the film forming processing conditions in S40 can be controlled and adjusted, such as the conditions for forming a wet film on the current collector of the positive electrode slurry configured in step S30, the conditions for the roller pressing process, etc., and the related properties of the formed positive electrode active material layer can be controlled and adjusted, such as controlling and adjusting the content of the positive electrode active material layer on the single side of the current collector to 260-350 mg / 1540.25 mm as described above. 2 Range, compaction density control and adjustment to 2.8 ~ 3.4g / cm 3 range, the porosity is controlled and adjusted to the range of 40% to 65% as mentioned above, and the diaphragm resistance of the electrode is controlled and adjusted to the range of 0.5 to 5 mΩ as mentioned above.

[0237] Battery

[0238] In a fourth aspect, an embodiment of the present application also provides a sodium battery.

[0239] In an embodiment, the sodium battery of the present application may include any one of a sodium battery cell, a battery module, and a battery pack.

[0240] Sodium battery cells:

[0241] A sodium battery cell, also known as a sodium battery cell, refers to a battery cell that includes the outer battery packaging and the electrode assembly encapsulated within the outer battery packaging. The number of electrode assemblies contained in a battery cell can be one or more, and can be adjusted according to actual needs.

[0242] The outer packaging of the sodium battery cell can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell; or a soft shell, such as a bag-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate. The outer packaging can be cylindrical, square, or any other shape. The outer packaging shape embodies the shape of the sodium battery cell, so the shape of the sodium battery cell can also be cylindrical, square, or any other shape that corresponds to the outer packaging. In this example, the sodium battery cell can be a square-shaped battery cell 20 as shown in Figure 5.

[0243] In some embodiments, as shown in FIG6 , the outer packaging of a battery cell 20 may include a housing 21 and a cover plate 23 . The housing 21 may include a bottom plate and side plates connected to the bottom plate, which together form a receiving cavity. The housing 21 has an opening communicating with the receiving cavity, and the cover plate 23 is used to cover the opening, thereby sealing the receiving cavity. One or more electrode assemblies 22 are enclosed in the receiving cavity.

[0244] In the embodiment, the sodium battery cell may be a sodium battery cell containing an electrolyte, or a sodium battery cell containing a solid electrolyte.

[0245] In the case of a sodium battery cell containing an electrolyte, the electrode assembly contained in the sodium battery cell generally includes a positive electrode, a negative electrode, and a separator. The positive and negative electrodes are alternately stacked, and the separator is stacked between the positive and negative electrodes to isolate the positive and negative electrodes. The positive electrode, separator layer, and negative electrode can be formed into a laminated electrode assembly through a lamination process, or a wound electrode assembly through a winding process. The separator-containing electrode assembly is placed in an outer packaging, and the electrolyte is injected to soak the electrode assembly. After packaging, the sodium battery cell is obtained.

[0246] In the case of a sodium battery cell containing a solid electrolyte, the electrode assembly typically includes a positive electrode, a negative electrode, and a solid electrolyte. The positive and negative electrodes are alternately stacked, with the solid electrolyte layered between them to act as an insulator, separating the positive and negative electrodes. The electrode assembly containing the solid electrolyte is placed in an outer packaging, and encapsulated to form a sodium battery cell.

[0247] In each of the above-mentioned sodium battery cells, the positive electrode contained in the electrode assembly is the positive electrode of the embodiment of the above-mentioned application, that is, its positive electrode active material layer contains the positive electrode material of the embodiment of the above-mentioned application, specifically, the layered oxide represented by the above-mentioned chemical formula (I).

[0248] In this way, the sodium battery cell has high energy density and good cycle performance.

[0249] As shown in the embodiment, the energy density of the sodium battery cell can reach 110-160Wh / kg, and can be optionally 120-155Wh / kg. The capacity retention rate after 1000 cycles under 0.5C / 1C charge and discharge conditions in the range of 1.5-4.05V can reach 70%-95%, and can be optionally 80%-90%.

[0250] In each of the above-mentioned sodium battery cells, the negative electrode contained in the electrode assembly includes a negative electrode current collector and, optionally, a negative electrode active material layer disposed on the surface of the negative electrode current collector, wherein the negative electrode active material layer contains a negative electrode active material. In embodiments, the negative electrode current collector may include, but is not limited to, a metal or a composite current collector. For example, the metal may include sodium, sodium alloys, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, silver alloys, etc. When sodium or a sodium alloy is used as the negative electrode current collector, since the sodium or sodium alloy itself can also serve as the negative electrode active material, the negative electrode plate may not contain a negative electrode active material layer, and the sodium or sodium alloy serves as both the current collector and the negative electrode active material.

[0251] The composite current collector may include a composite material of a polymer and a metal. The polymer may include, but is not limited to, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc., and the metal may include, but is not limited to, sodium, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may be obtained by blending the polymer and the metal, or may be coated on at least one side of the polymer by electroplating, coating, or other methods.

[0252] When the negative electrode includes a negative electrode active material layer, the negative electrode active material in the negative electrode active material layer may include, but is not limited to, a mixture or composite material of any one or more of a carbon-based material, an alloy material, a titanium-based material, and sodium metal. Carbon-based materials include, but are not limited to, one or more of graphite, soft carbon, hard carbon, carbon microspheres, and carbon fibers; alloy materials include, but are not limited to, one or more of sodium-tin alloy, sodium-germanium alloy, and sodium-antimony alloy; and titanium-based materials include, but are not limited to, one or more of titanium dioxide, titanates, and titanium phosphates.

[0253] The mass content of the negative electrode active material in the negative electrode active material layer can be 85% to 98%, optionally 95% to 98%. In the exemplary embodiment, it can be 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% and other typical but non-limiting contents or a range between any two content values.

[0254] The negative electrode active material layer may also include at least one of a conductive agent and a binder. The conductive agent is used to collect current between the negative electrode active materials and between the active materials and the current collector, improving electronic conductivity. It also promotes electrolyte wetting of the negative electrode sheet. The binder improves the bonding strength between the various substances in the negative electrode active material layer and between the active layer and the current collector.

[0255] In an embodiment, the conductive agent may comprise 0.5% to 10% by weight of the negative electrode active material layer. In exemplary embodiments, the conductive agent may comprise 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any other typical but non-limiting content, or a range between any two content values. Other content values ​​may also be used as needed. In exemplary embodiments, the conductive agent comprises one or more of acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fiber, and graphene.

[0256] In an embodiment, the binder content in the negative electrode active material layer may be 0.5% to 10% by weight. In exemplary embodiments, the binder content may be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or other typical but non-limiting content, or a range between any two content values. Other content values ​​may also be set as needed. In exemplary embodiments, the binder includes, but is not limited to, one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyimide, polytetrafluoroethylene, polybutyl acrylate, polyacrylonitrile, carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylate, polyvinyl alcohol, sodium alginate, cyclodextrin, styrene-butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0257] In an embodiment, the negative electrode active material layer may optionally include a thickener, such as, but not limited to, carboxymethyl cellulose (CMC). The mass content of the thickener in the negative electrode active layer may be set to 0.5% to 5%. In exemplary embodiments, the content may be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or other typical but non-limiting content, or a range between any two content values.

[0258] In the embodiments, when each of the aforementioned sodium battery cells includes a separator, the separator, as described above, is disposed between the positive and negative electrodes to separate them. The separator prevents electrons from freely passing through the battery, preventing contact and short circuits between the electrodes, while allowing sodium ions in the electrolyte to freely pass between the positive and negative electrodes. The separator can be any known porous structure separator with electrochemical and mechanical stability. In exemplary embodiments, the separator comprises a single or multilayer film of at least one of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF).

[0259] In an embodiment, when each of the sodium battery cells contains a solid electrolyte, the solid electrolyte, as described above, is disposed between the positive electrode and the negative electrode to separate the positive electrode and the negative electrode. The solid electrolyte may include at least one of a polymer solid electrolyte, an oxide electrolyte, a sulfide electrolyte, a borohydride electrolyte, a composite solid electrolyte, and the like.

[0260] Battery Module:

[0261] When the sodium battery in the embodiment of the present application is a battery module, the battery module refers to being assembled from the above-mentioned sodium battery cells, that is, it can contain multiple of the above-mentioned sodium battery cells, and the specific number can be adjusted according to the application and capacity of the battery module.

[0262] In some embodiments, FIG7 is a schematic diagram of an exemplary battery module 30. As shown in FIG7 , within the battery module 30, multiple sodium battery cells 20 may be arranged sequentially along the length of the battery module 30. Of course, any other arrangement is also possible. Furthermore, the multiple battery cells 20 may be secured together using fasteners.

[0263] Optionally, the battery module 30 may further include a housing having an accommodation space, and the plurality of sodium battery cells 20 are accommodated in the accommodation space.

[0264] Battery Pack:

[0265] When the sodium battery in the embodiments of the present application is a battery pack, the battery pack is assembled from the aforementioned sodium battery cells, that is, it may contain multiple sodium battery cells, and the multiple sodium battery cells are assembled into the aforementioned battery module. The specific number of battery cells or battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0266] In some embodiments, Figures 8 and 9 are schematic diagrams of an exemplary battery pack 40. The battery pack 40 may include a battery box and multiple battery modules 30 disposed within the battery box. The battery box includes an upper box body 41 and a lower box body 42. The upper box body 41 covers the lower box body 42 and forms an enclosed space for accommodating the battery modules 30. The multiple battery modules 30 may be arranged in any manner within the battery box.

[0267] Electrical devices

[0268] In a fifth aspect, the embodiments of the present application also provide an electric device. The electric device of the embodiments of the present application includes a power supply unit or an energy storage unit, and of course may also include other auxiliary components or necessary components. Among them, the power supply unit or energy storage unit contains the sodium battery of the above-mentioned embodiments of the present application. For example, it can be the above-mentioned sodium battery monomer, battery module or battery pack. Since the electric device of the embodiments of the present application contains the sodium battery of the above-mentioned embodiments of the present application, the power supply unit or energy storage unit of the electric device of the embodiments of the present application has high energy density, good cycle performance, long service life, and the electric device of the embodiments of the present application has a long standby or battery life.

[0269] In the embodiments, the electrical device may include, but is not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, a battery-powered vehicle, an electric car, a ship, a spacecraft, and the like. The electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, and the spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft. The battery may be a single cell, a battery module, or a battery pack, depending on the intended use of the electrical device.

[0270] FIG10 is a schematic diagram of an exemplary electric device. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device, a battery pack or battery module may be used.

[0271] In the embodiment, when the electrical device contains an energy storage unit, the electrical device can be an energy storage device, and the energy storage device includes the energy storage unit, and of course can also include other auxiliary components or necessary components. Among them, the energy storage unit contains the battery of the embodiment of the above text application. The battery contained in the energy storage unit can be one or more. When there are multiple batteries, multiple batteries can form a battery module or battery pack. Since the energy storage device of the embodiment of the present application contains the battery of the embodiment of the above text application, the energy storage device has high energy density, good cycle performance, long service life, and further high energy density. Example

[0272] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0273] 1. Examples of positive electrode materials and preparation methods thereof

[0274] Example A1

[0275] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.89 Ni 0.23 Mn 0.45 Fe 0.3 Zn 0.02 Layered oxides of O2.

[0276] The positive electrode material preparation method comprises the following steps:

[0277] S1: According to Na 0.89 Ni 0.23 Mn 0.45 Fe 0.3 Zn 0.02 The molar ratio of the metal elements contained in O2 was 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3 and Fe2O3, and then an excess amount of sodium carbonate was added in proportion for mixing to obtain a precursor;

[0278] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.89 Ni 0.23 Mn0.45 Fe 0.3 Zn 0.02 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 850 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0279] Example A2

[0280] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 Layered oxides of O2.

[0281] The positive electrode material preparation method comprises the following steps:

[0282] S1: According to Na 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 The molar ratio of the metal elements contained in O2 was 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3 and Fe2O3, and then sodium carbonate was added in proportion for mixing to obtain a precursor;

[0283] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 860 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0284] Example A3

[0285] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cu 0.02 Layered oxides of O2.

[0286] The positive electrode material preparation method comprises the following steps:

[0287] S1: According to Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04Cu 0.02 The molar ratio of the metal elements contained in O2 is 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3, Fe2O3 and CuO, and then sodium carbonate is added in proportion for mixing to obtain a precursor;

[0288] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cu 0.02 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 865 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0289] Example A4

[0290] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 Layered oxides of O2.

[0291] The positive electrode material preparation method comprises the following steps:

[0292] S1: According to Na 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 The molar ratio of the metal elements contained in O2 was 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3 and Fe2O3, and then sodium carbonate was added in proportion for mixing to obtain a precursor;

[0293] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 865 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0294] Example A5

[0295] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.89 Ni 0.23 Mn 0.41 Fe0.3 Zn 0.06 Layered oxides of O2.

[0296] The positive electrode material preparation method comprises the following steps:

[0297] S1: According to Na 0.89 Ni 0.23 Mn 0.41 Fe 0.3 Zn 0.06 The molar ratio of the metal elements contained in O2 was 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3 and Fe2O3, and then sodium carbonate was added in proportion for mixing to obtain a precursor;

[0298] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.89 Ni 0.23 Mn 0.41 Fe 0.3 Zn 0.06 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 865 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0299] Example A6

[0300] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.89 Ni 0.23 Mn 0.42 Fe 0.285 Zn 0.065 Layered oxides of O2.

[0301] The positive electrode material preparation method comprises the following steps:

[0302] S1: According to Na 0.89 Ni 0.23 Mn 0.42 Fe 0.285 Zn 0.065 The molar ratio of the metal elements contained in O2 was 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3 and Fe2O3, and then sodium carbonate was added in proportion for mixing to obtain a precursor;

[0303] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.89 Ni 0.23 Mn 0.42 Fe 0.285 Zn 0.065O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 865 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0304] Example A7

[0305] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 Layered oxides of O2.

[0306] The positive electrode material preparation method comprises the following steps:

[0307] S1: According to Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 The molar ratio of the metal elements contained in O2 was 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3 and Fe2O3, and then sodium carbonate was added in proportion for mixing to obtain a precursor;

[0308] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 880 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0309] Example A8

[0310] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 Layered oxides of O2.

[0311] The positive electrode material preparation method comprises the following steps:

[0312] S1: According to Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075The molar ratio of the metal elements contained in O2 was 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3 and Fe2O3, and then sodium carbonate was added in proportion for mixing to obtain a precursor;

[0313] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 880 ℃; time: 10h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0314] Example A9

[0315] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 Layered oxides of O2.

[0316] The positive electrode material preparation method comprises the following steps:

[0317] S1: According to Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 The molar ratio of the metal elements contained in O2 is such that nickel nitrate, zinc nitrate, manganese nitrate and iron nitrate are fully dissolved to prepare a mixed solution; and a sufficient amount of ammonium carbonate is added to the mixed solution for co-precipitation to obtain a precipitate mixture;

[0318] S2: According to Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 The molar content of sodium in O2 is higher than that of sodium carbonate, and the precipitation mixture is mixed with sodium carbonate to obtain Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 Precursor of O2.

[0319] 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 crushed to obtain Na0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 850 ℃; time: 14h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0320] Example A10

[0321] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Al 0.02 Layered oxides of O2.

[0322] The positive electrode material preparation method comprises the following steps:

[0323] S1: According to Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Al 0.02 The molar ratio of the metal elements contained in O2 was 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3 and Al2O3, and then sodium carbonate was added in proportion for mixing to obtain a precursor;

[0324] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Al 0.02 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 850 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0325] Example A11

[0326] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 Layered oxides of O2.

[0327] The positive electrode material preparation method comprises the following steps:

[0328] S1: According to Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 The molar ratio of the metal elements contained in O2 is 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3 and SnO2, and then sodium carbonate is added in proportion for mixing to obtain a precursor;

[0329] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 850 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0330] Example A12

[0331] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ti 0.02 Layered oxides of O2.

[0332] The positive electrode material preparation method comprises the following steps:

[0333] S1: According to Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ti 0.02 The molar ratio of the metal elements contained in O2 is 500 rpm. NiO, ZnO, Mn2O3 and TiO2 are ball-milled for 6 hours, and then sodium carbonate is added in proportion to mix them to obtain a precursor;

[0334] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ti 0.02 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 850 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0335] Example A13

[0336] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Mg 0.02 Layered oxides of O2.

[0337] The positive electrode material preparation method comprises the following steps:

[0338] S1: According to Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Mg 0.02 The molar ratio of the metal elements contained in O2 was 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3 and MgO, and then sodium carbonate was added in proportion for mixing to obtain a precursor;

[0339] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Mg 0.02 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 850 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0340] Example A14

[0341] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 Layered oxides of O2.

[0342] The positive electrode material preparation method comprises the following steps:

[0343] S1: According to Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02The molar ratio of the metal elements contained in O2 was 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3 and IrO2, and then sodium carbonate was added in proportion for mixing to obtain a precursor;

[0344] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 850 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0345] Example A15

[0346] This embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material includes a chemical formula of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O 1.8 layered oxides.

[0347] The positive electrode material preparation method comprises the following steps:

[0348] 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 molar ratio of the metal elements contained is to ball-mill NiO, ZnO, Mn2O3, and IrO2 at a rotation speed of 500 rpm for 6 hours, and then sodium carbonate is added in proportion and mixed to obtain a precursor;

[0349] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O 1.8 layered oxide; wherein the sintering conditions are: temperature: 700 ° C; time: 20h; heating rate: 15 ° C / min; oxygen atmosphere.

[0350] Comparative Example A1

[0351] This comparative example provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a chemical formula of Na 0.92 Ni 0.33 Mn 0.33 Fe 0.33 Zn 0.01 Layered oxides of O2.

[0352] The positive electrode material preparation method comprises the following steps:

[0353] S1: According to Na 0.92 Ni 0.33 Mn 0.33 Fe 0.33 Zn 0.01 The molar ratio of the metal elements contained in O2 was 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3 and Fe2O3, and then sodium carbonate was added in proportion for mixing to obtain a precursor;

[0354] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.92 Ni 0.33 Mn 0.33 Fe 0.33 Zn 0.01 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 900 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0355] Comparative Example A2

[0356] This comparative example provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a chemical formula of Na 0.92 Ni 0.25 Mn 0.33 Fe 0.33 Zn 0.08 Layered oxides of O2.

[0357] The positive electrode material preparation method comprises the following steps:

[0358] S1: According to Na 0.92 Ni 0.25 Mn 0.33 Fe 0.33 Zn 0.08 The molar ratio of the metal elements contained in O2 was 500 rpm for 6 hours by ball milling NiO, ZnO, Mn2O3 and Fe2O3, and then sodium carbonate was added in proportion for mixing to obtain a precursor;

[0359] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.92 Ni 0.25 Mn0.33 Fe 0.33 Zn 0.08 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 900 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0360] Comparative Example A3

[0361] This comparative example provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a chemical formula of Na 0.94 Ni 0.33 Mn 0.33 Fe 0.33 Layered oxides of O2.

[0362] The positive electrode material preparation method comprises the following steps:

[0363] S1: According to Na 0.94 Ni 0.33 Mn 0.33 Fe 0.33 The molar ratio of the metal elements contained in O2 was 500 rpm for 6 hours by ball milling NiO, Mn2O3 and Fe2O3, and then sodium carbonate was added in proportion for mixing to obtain a precursor;

[0364] S2: The precursor is sintered in a muffle furnace and crushed to obtain Na 0.92 Ni 0.25 Mn 0.33 Fe 0.33 O2 layered oxide; wherein, the sintering treatment conditions are: temperature: 900 ℃; time: 12h; heating rate: 5 ℃ / min; oxygen atmosphere.

[0365] Characterization of layered oxides and related performance tests in each example:

[0366] The layered oxides provided in Examples A1 to A15 and Comparative Examples A1 to A3 were tested for the relevant characteristics listed in Table 1 according to the following methods. The test results are shown in Table 1:

[0367] Method for detecting the element content of layered oxides: Inductively coupled plasma emission spectroscopy (ICP) was obtained using an Agilent ICP-OES730. The content of each metal element was then calculated from the ICP results, and the mass percentage of each component was then calculated.

[0368] Single crystal morphology detection method: Scanning electron microscopy (SEM) was performed on the layered oxides provided in each example using the micron-scale SEM measurement method according to GB / T 16594-1996. The SEM image of the layered oxide provided in Example A6 is shown in FIG1 .

[0369] Crystalline phase characterization method: The layered oxides were analyzed using an XRD diffractometer at a scanning rate of 0.5°C / min.

[0370] Dv50 detection method: Detect layered oxides according to the method steps in GB / T16418.

[0371] BET specific surface area detection method: Detect the specific surface area of ​​layered oxides according to the method steps in GB / T19587-2017.

[0372] Compacted density test method: Refer to the GB / T24533-2019 standard test method for testing. For details, please refer to the following test steps:

[0373] (1) Use a clean soft cloth (paper towel) to wipe the upper and lower gaskets, top column and metal cylindrical sleeve of the compaction density meter. If necessary, wipe them with a soft cloth dipped in anhydrous ethanol and air dry them;

[0374] (2) Place the gasket, top column, metal cylindrical sleeve, and pad in the order of the test and place them on the digital thickness gauge, and press the zero key;

[0375] (3) Remove the top column and upper gasket, weigh 1g of sample in the sleeve to the nearest 0.0001g, and record the weight as m;

[0376] (4) Slowly slide the gasket and the top column down from the hole, install them together with the pad on the compaction density meter, and tighten the pressure control knob;

[0377] (5) Shake the pressure bar and observe the value on the digital pressure gauge on the compaction density meter at the same time. Start the stopwatch after reaching the specified value of 2200Ib; loosen the pressure control knob after 30 seconds to remove the pressure, lower the pad to a certain height, and then tighten the pressure control knob;

[0378] (6) Take out the top column, sleeve and film together with the pad, place them on the digital thickness gauge, and read the value on the digital thickness gauge within 10 seconds, which is recorded as H;

[0379] r = 10 m / (S × H);

[0380] Then calculate the powder compaction density r of the sample according to the above formula r=10m / (S×H).

[0381] Where mm is the sample weight in grams (g); HH is the thickness of the sample after compaction in millimeters (mm); SS is the cross-sectional area of ​​the top column in square centimeters (cm 2 ).

[0382] Charge / discharge gram capacity detection method: The charge / discharge gram capacity detection method of the layered oxide in the above application example was used for detection.

[0383] Table 1

[0384] From the test results of the relevant properties of the layered oxides provided in each embodiment in Table 1 above, it can be seen that the layered oxides with low zinc content provided in Examples A1 to A15 have similar crystal forms and particle sizes as those in Comparative Examples A1 to A3; however, the material compaction density of the layered oxides in Examples A1 to A15 is slightly higher than that in Comparative Examples A1 to A3. Further testing shows that the specific surface areas of the layered oxide particles provided in Examples A1 to A15 are respectively 0.5 to 1.3 m 2 / g, further 0.6~0.9m 2 The charge / discharge gram 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, combined with the data in Table 3 below, it can be seen that 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.

[0385] 2. Examples of positive electrodes and sodium-ion battery cells

[0386] Example B1 to Example B15

[0387] Embodiments B1 to B15 provide a sodium ion battery cell, respectively. Each sodium ion battery cell includes an electrode assembly formed by a positive electrode sheet, a separator, and a negative electrode sheet, and also includes an electrolyte.

[0388] The sodium ion battery cells in Examples B1 to B15 are assembled as follows:

[0389] Positive electrode sheet: Sodium ion positive electrode active material, conductive agent carbon nanotube, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an appropriate amount of solvent NMP in a weight ratio of 95:0.5:2:2.5 to form a uniform positive electrode slurry; the positive electrode slurry is evenly coated on the surface of a 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 the above-mentioned Examples A1 to A15, respectively, and the positive electrode materials in the above-mentioned Examples A1 to A15 are prepared respectively. Among them, the conductive agent carbon nanotube content in Example B15 is 0 (the conductive agent is all conductive agent carbon black), that is, the conductive agent carbon nanotubes in Example B1 are replaced by conductive agent carbon black. Compared with the positive electrode sheet in Example B1, 0.5% of the carbon nanotube conductive agent in Example B1 is replaced by conductive agent carbon black, but the total content of the conductive agent contained in the positive electrode sheet in Example B1 is the same as the total content of the conductive agent contained in the positive electrode sheet of Example B1.

[0390] Negative electrode sheet: Add hard carbon, conductive agent SP, and CMC binder to deionized water in a weight ratio of 8:1:1 and stir thoroughly to form a uniform negative electrode slurry; evenly apply the negative electrode slurry on the surface of a 6μm copper foil, dry, and cold press to obtain a negative electrode sheet.

[0391] Electrolyte: In an environment with a water content of less than 10 ppm, the non-aqueous organic solvents ethylene carbonate (EC) and diethyl carbonate (DMC) are mixed in a volume ratio of 1:1 to obtain an electrolyte solvent. Subsequently, sodium hexafluorophosphate and the mixed solvent are mixed to prepare an electrolyte with a sodium salt concentration of 1 mol / L.

[0392] Isolation membrane: porous polyethylene (PE) film is used as the isolation membrane.

[0393] Battery Assembly: The aforementioned positive electrode sheets, separators, and negative electrode sheets are stacked in sequence, with the separators positioned between the positive and negative electrodes to provide isolation. The electrode assemblies are then laminated to obtain an electrode assembly. Each electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum packaging, standing, forming, and shaping, the sodium-ion battery cells of Examples B1 to B10 are obtained. The sodium-ion positive electrode active material in Example B1 is the positive electrode material of Example A1, the sodium-ion positive electrode active material in Example B2 is the positive electrode material of Example A2, and so on. The sodium-ion positive electrode active material in Example B15 is the positive electrode material of Example A15.

[0394] Example B16 to Example B24

[0395] Embodiments B16 to B24 each provide a sodium ion battery cell. Each sodium ion battery cell includes an electrode assembly formed by a positive electrode sheet, a separator, and a negative electrode sheet, and also includes an electrolyte.

[0396] The sodium ion battery monomers in Examples B16 to B24 were prepared with reference to the sodium ion battery monomer in Example B3. The differences were:

[0397] In the sodium ion battery cells of Example B16 to Example B18, the content (CW) of the positive electrode active material layer on one side of the current collector contained in the positive electrode sheet of each sodium ion battery cell is controlled as shown in Table 2.

[0398] In the sodium ion battery cells of Example B19 to Example 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.

[0399] In the sodium ion battery cells of Examples B22 and B23, the carbon nanotube content in the positive electrode sheets of each sodium ion battery cell was controlled as shown in Table 2. The total content of the conductive agent in the positive electrode sheets of Examples B22 and B23 was the same as that in the positive electrode sheet of Example B1.

[0400] In the sodium ion battery cell of Example B24, the carbon nanotubes contained in the positive electrode sheet of the sodium ion battery cell are replaced with 1% carbon fibers, as shown in Table 2. The total content of the conductive agent contained in the positive electrode sheet of Example B24 is the same as the total content of the conductive agent contained in the positive electrode sheet of Example B1.

[0401] Comparative Examples B1 to B3

[0402] Comparative Examples B1 to B3 provide a sodium ion battery cell, respectively. Each sodium ion battery cell includes an electrode assembly formed by a positive electrode sheet, a separator, and a negative electrode sheet, and also includes an electrolyte.

[0403] The sodium ion battery monomers in Comparative Examples B1 to B3 were prepared with reference to the sodium ion battery monomer in Example B1. The differences were:

[0404] 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 sodium ion positive electrode material in Comparative Example A1, as shown in Table 1.

[0405] 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 sodium ion positive electrode material in Comparative Example A2, as shown in Table 1.

[0406] 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 sodium ion positive electrode material in Comparative Example A3, as shown in Table 1.

[0407] Related performance tests of the positive electrode sheets contained in the sodium ion battery cells in each embodiment:

[0408] The positive electrode sheets contained in the sodium ion battery cells provided in Examples B1 to B24 and Comparative Examples B1 to B3 were respectively subjected to the relevant performance tests in Table 2 according to the following methods. The test results are shown in Table 2:

[0409] Positive electrode slurry gel test method: After the positive electrode slurry used to prepare the positive electrode sheets contained in the sodium ion battery monomers of the above embodiments is placed at room temperature for 12 hours, the gelation of the positive electrode slurry is observed with the naked eye.

[0410] CW detection method: the electrode is punched into 1540.25mm 2 The weight of the electrode is obtained by weighing and subtracting the weight of the aluminum foil, which is recorded as the weight of the active material layer / 1540.25mm 2 .

[0411] Positive electrode sheet compaction density test method: The specific compaction density of the positive electrode sheet can refer to the first discharge specific capacity and first charge and discharge efficiency test method of lithium manganese oxide, the positive electrode material of lithium-ion batteries, for details, see GB / T 39864-2021 or GB / T 42161-2022. For specific reference, please refer to the test steps of the following parameters:

[0412] Obtain battery electrodes that meet the machinability requirements, use a punch to punch out positive electrodes with a diameter of 14 mm, and use an electronic balance and a desktop digital thickness gauge to measure the mass m of the positive electrodes. c , thickness d c Use a punching machine to punch out a sufficient number of aluminum foil substrates with a diameter of 14 mm, and use an electronic balance and a desktop digital thickness gauge to measure the mass m of the aluminum foil substrates respectively Al , thickness d Al ; Calculate the positive electrode compaction density according to the following formula:

[0413] Positive electrode compaction density

[0414] Where: c is the compacted density of the positive electrode, in grams per cubic centimeter (g / cm 3 );

[0415] m c is the mass of the positive electrode, in grams (g);

[0416] mAl is the mass of the aluminum foil substrate, in grams (g);

[0417] is the diameter of the positive electrode sheet, in millimeters (mm);

[0418] d c is the thickness of the positive electrode sheet, in micrometers (μm);

[0419] d Al is the thickness of the aluminum foil substrate, in micrometers (μm).

[0420] The charge capacity, discharge capacity and first efficiency of layered oxides are tested in accordance with the aforementioned national standards: GB / T 39864-2021 or GB / T 42161-2022:

[0421] According to the battery treatment method in GB / T 39864-2021 or Section 7.4 of GB / T 42161-2022, place the assembled sodium ion button battery in a constant temperature box at 23°C ± 2°C, let it stand for 2 to 12 hours, and then charge and discharge it under the following conditions:

[0422] Charging: constant current charging at a rate of 0.1C to 3.75V, then constant voltage charging, constant voltage charging dielectric current 0.05C; Discharging: constant current discharge at a rate of 0.1C to 2.0V;

[0423] After charging and discharging the sodium ion button cell assembled above for one cycle according to GB / T 39864-2021 or Section 7.5 of GB / T 42161-2022 as described in Section 7.4, record the charge and discharge capacity of the sodium ion button cell and the mass of the layered oxide in the corresponding sodium ion button cell, and calculate the first discharge capacity in grams and the first charge and discharge efficiency of the layered oxide.

[0424] The first discharge capacity in grams is calculated according to formula (4) in section 8.1 of GB / T 39864-2021 or GB / T 42161-2022, and the first charge and 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)

[0425] In formula 4:

[0426] C - first discharge capacity in gram, in milliampere hours per gram (mA.h / g);

[0427] Q ID —First discharge capacity in gram, in milliampere hours per gram (mA.h / g);

[0428] m is the mass of the layered oxide in the tested sodium ion button cell, in grams (g);

[0429] In formula 5:

[0430] η——first charge and discharge efficiency;

[0431] Q ID —First discharge capacity, in milliampere-hours (mA.h);

[0432] Q IC —The initial charge capacity, in milliampere hours (mA.h).

[0433] Electrode porosity test method: The test is carried out by gas replacement method, with specific reference to GB / T24586-2009. The specific steps of the electrode porosity test method 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. The gas replacement method is combined with Archimedes' principle and Bohr's law to accurately measure the true volume of the material being tested, which is the true volume of the sample, thereby obtaining the porosity of the sample to be tested. Among them, the percentage of the pore volume in the electrode to the total volume of the electrode is the electrode porosity, and the calculation formula is: Porosity = (V-V0) / V×100%, where V0 is the true volume and V is the apparent volume.

[0434] Diaphragm resistance test method: Refer to GB / T 30835-2014 or T / CASAS 019-2021 for testing; for tester verification procedures, refer to JJG 508-2004. Specifically, the four-probe method is used: the electrode is cleaned by immersing it in ethyl methyl carbonate (EMC). Testing is performed using the method specified in GB / T 30835-2014 or T / CASAS 019-2021. Four copper plates, 1.5 cm long, 1 cm wide, and 2 mm thick, are fixed equidistantly in a line. The spacing between the two center plates is L (1 cm to 2 cm). The substrate used to secure the plates is insulating material. During testing, the lower ends of the four copper plates are pressed against the electrode to be tested. A DC current I is applied to the two end plates. A voltage V is measured across the two center plates. The I and V values ​​are read three times, and the average of I and V is taken. V / I is the electrode resistance at the test point.

[0435] Table 2

[0436] Electrochemical performance test of sodium ion battery monomer in each embodiment:

[0437] The sodium ion battery cells provided in the above-mentioned Examples B1 to B24 and Comparative Examples B1 to B3 were respectively subjected to electrochemical performance tests as shown in Table 3 below according to the following methods. The test results are shown in Table 3:

[0438] Sodium ion battery monomer related performance testing methods:

[0439] Cyclic DCR test: The DCR test is carried out according to the normal temperature test method in the "High Power Lithium-ion Power Battery Performance Test Specification for HEV":

[0440] The battery cell to be tested is discharged at a constant current of 1C to a cutoff voltage (3.0V). After standing at 20±2°C for 1 hour, it is then charged at 1C for 18 minutes, adjusting the SOC to 30%, and standing for 1 hour. It is then charged at 3C for 1.5 minutes, standing for 1 hour, then discharged at 9C for 0.5 minutes, standing for 1 hour, and then charged at 1C for 6 minutes, adjusting the SOC to 40%, and standing for 1 hour. This cycle is repeated until the SOC reaches 70%. The DCR value is calculated using the formula.

[0441] Energy density: Measure the discharge energy, S0, of each battery cell at room temperature by charging it at a rate of 0.33C to a voltage of 4.2V, then discharging it at a rate of 0.33C to a voltage of 2.0V. Then, measure the mass, M, of the battery cell corresponding to S0, and calculate the mass energy density of the battery cell using the formula, S0 / M.

[0442] Cycle Retention (%): At 25°C, a 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 initial discharge capacity as 100%, calculate the capacity retention after 1000 cycles. Capacity retention (%) after 1000 cycles = discharge capacity at the 1000th cycle / initial discharge capacity × 100%.

[0443] Table 3

[0444] It can be seen from the data in Table 2 and Table 3 that in the sodium ion battery of the present application, the compaction density of the positive electrode active material layer contained in the positive electrode sheet in the sodium ion battery monomer provided by Examples B1 to B24 can reach 2.8 to 3.4 g / cm 3 , the CW of the positive electrode active material layer can reach 260~350mg / 1540.25mm 2Furthermore, 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% to 65%, and the sheet resistance is 0.5 to 5 mΩ. Specifically, the porosity and sheet resistance of the positive electrode active material layer can be adjusted according to the CW and compaction density of the positive electrode active material layer and the conductive agent contained therein.

[0445] From Example B1 to Example B8 in the comparison table, it can be seen that as the content of zinc in the layered oxide shown in Chemical Formula (I) gradually increases, the energy density of the battery cell of the sodium ion battery monomer gradually increases. Of course, the overall trend of the cycle performance of the corresponding sodium ion battery monomer is a downward trend. In the layered oxide shown in Chemical Formula (I), as the zinc content increases, it can increase the gram capacity of the layered oxide, but at the same time it is not conducive to the structural stability of the layered oxide, which reduces the cycle performance of its reversible capacity. However, compared with Comparative Examples 1 and 2, it can be seen that the zinc element is controlled in an appropriate range and satisfies the appropriate stoichiometric ratio of Zn to Ni and Mn. The layered oxide shown in Chemical Formula (I) can effectively take into account both high gram capacity and good reversible capacity cycle stability.

[0446] From the comparison of Example B3 with 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 the 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.

[0447] Comparing Example B14 and Example B15, the type of conductive agent contained in the positive electrode active material layer contained in the positive electrode sheet has a certain influence on the capacity of the positive electrode sheet. When the conductive agent contains linear carbon nanotubes, the energy density of the corresponding sodium ion battery cell is higher than that of Example B15.

[0448] Comparing Examples B1 to B15 with Comparative Examples B1 to B3, when the layered oxide zinc content is too low, such as in Comparative Examples B1 and B3, not only does it lead to a significant decrease in the energy density of the sodium ion battery monomer, but it also significantly reduces the cycle retention rate of the sodium ion battery monomer. When the layered oxide zinc content is too high, such as in Comparative Example B2, although the energy density of the sodium ion battery monomer can be maintained without a significant decrease, the cycle retention rate of the sodium ion battery monomer is significantly reduced. It can be seen that the zinc element and other metal elements in the layered oxide shown in Chemical Formula (I) and the content of each metal element can significantly affect the disordered arrangement of the metal elements in the transition metal layer contained in the layered oxide, thereby significantly affecting the comprehensive performance of the gram capacity and cycle stability of the layered oxide.

[0449] It can be seen from this that the layered oxide of the embodiment of the present application controls the zinc element within a suitably low content range, and controls the content of zinc and metal elements such as Ni, Fe, and Mn, so that the transition metal layer contained in the layered oxide of the embodiment of the present application has a specific arrangement. On the basis of effectively improving the gram capacity of the layered oxide, it also takes into account and balances the structural stability of the layered oxide, thereby improving the cycle performance of the layered oxide and the sodium ion battery. It also shows that in the layered oxide of the embodiment of the present application, it is not that the higher the zinc content, the higher the gram capacity of the layered oxide and the better the cycle performance, but when the zinc content exceeds a certain amount, its gram capacity does not continue to increase, and is not conducive to the structural stability of the layered oxide, which reduces the cycle performance of the layered oxide.

[0450] In addition, it can be seen from the data in Table 3 that the cell DCR of the sodium ion battery cells in Examples B1 to B24 does not vary much, and the cell DCR differences of the sodium ion battery cells in Examples B1 to B24 are in the range of 0mΩ to 0.8mΩ. Moreover, the cell DCR of the sodium ion battery cells in Examples B1 to B24 is significantly lower than the cell DCR values ​​of the sodium ion battery cells in Comparative Examples B1 to B3. Therefore, the layered oxide represented by chemical formula (I) controls the zinc content within the content range of chemical formula (I). On the one hand, by controlling the low zinc content and adjusting the arrangement of other metal elements in the transition metal layer to improve the stability of the layered oxide structure, it can also stabilize the transition metal interlayer channel, improve the sodium ion transmission rate, and improve the DCR growth of the battery cell.

[0451] Further comparison of the positive electrode slurries of Examples B1 to B24 with those of Comparative Examples B1 and B3 reveals that the gelation of the positive electrode slurries of Examples B1 to B24 is significantly less than that of the positive electrode slurries of Comparative Examples B1 and B3. Therefore, the layered oxides of the present application control the zinc content within a suitably low range, effectively increasing the specific capacity and cycle performance of the layered oxide while also improving its processability.

[0452] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A positive electrode material, characterized in that: Includes layered oxides of the following chemical formula: Na q Ni x Mn y Fe z Zn p M i O j ; Among them, 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 doping metal element.

2. The positive electrode material according to claim 1, characterized in that At least one of q, x, y, z, p and i is in the following value 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 positive electrode material according to claim 1 or 2, characterized in that: The stoichiometric ratio of the total stoichiometric amount of the Ni element, the Mn element, the Fe element, the Zn element and the doping metal element to the Na element is 1:(0.8-1), and can be optionally 1:(0.83-0.95).

4. The positive electrode material according to any one of claims 1 to 3, characterized in that: The stoichiometric ratio of the Zn element to the Ni element is 1:(3-15), and can be optionally 1:(3.1-11); and / or The stoichiometric ratio of the Zn element to the Mn element is 1:(4-25), and can be optionally 1:(5-15).

5. The positive electrode material according to any one of claims 1 to 4, characterized in that: The doping metal element includes at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, and Ir.

6. The positive electrode material according to any one of claims 1 to 5, characterized in that The above-mentioned lamellar compound inclusive Na 0.89 Ni 0.23 Mn 0.45 Fe 0.3 Zinc 0.02 O2, Na 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zinc 0.03 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 Cu 0.02 O2, Na 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zinc 0.05 O2, Na 0.89 Ni 0.23 Mn 0.41 Fe 0.3 Zinc 0.06 O2, Na 0.89 Ni 0.23 Mn 0.42 Fe 0.285 Zinc 0.065 O2, Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.07 O2, Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zinc 0.075 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 V 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 Cr 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 Al 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 Sc 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 Sn 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 Sb 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 Zr 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 Nb 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 Ti 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 Mg 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 Ru 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 Ir 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zinc 0.04 Ir 0.02 O 1.8 Very little in the middle.

7. The positive electrode 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 an O3 phase layered metal oxide, and the O3 phase layered metal oxide accounts for more than 95% of the total weight of the layered oxide; (2) Dv50 particle size is 3 to 11 μm, and can be 4 to 8 μm; (3) It includes a single crystal, wherein the single crystal has a flat morphology.

8. The positive electrode material according to claim 7, characterized in that: The single crystal has the following characteristics: (1) The ratio of length, width and thickness is 1-8:1-5:0.5-2.5, which can be 2-6:2-4:1-2; (2) Length is 1 to 8 μm, and can be 2 to 6 μm; (3) Width is 1 to 5 μm, and can be 2 to 4 μm; (4) The thickness is 0.5 to 2.5 μm, and can be optionally 1 to 2 μm.

9. The positive electrode material according to any one of claims 1 to 7, 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 to 3.1 g / cm 3 , optional: 2.9~3.09g / cm 3 ; (2) The compaction density under 3 tons of pressure is 3.1-3.3 g / cm 3 , can be selected as 3.15~3.28g / cm 3 ; (3) Specific surface area is 0.5 to 1.3 m 2 / g, optional range is 0.6~0.9m 2 / g.

10. The positive electrode material according to any one of claims 1 to 9, characterized in that: The layered oxide comprises at least one of the following (1) to (3) at 1.5 to 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 efficiency is 92% to 98%, which can be selected as 92% to 95%.

11. A method for preparing a positive electrode material, characterized in that: The steps include: Provide Na q Ni x Mn y Fe z Zn p M i O j Precursor of The precursor is sintered to obtain a product having a chemical formula of Na q Ni x Mn y Fe z Zn p M i O j Layered oxides; Among them, 0.8≤q≤1, 0.1≤x≤0.3, 0.2≤y≤0.5, 0.2≤z≤0.35, 0.02≤p≤0.07, 0≤i≤0.1, 1.8≤j≤2, and x+y+z+p+i≤1; M is an active and / or inert doping metal element.

12. The preparation method according to claim 11, characterized in that: The doping metal element includes at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, and Ir; and / or At least one of q, x, y, z, p and i is in the following value 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.

13. The preparation method according to claim 11 or 12, characterized in that: The sintering process includes at least one of the following conditions (1) to (4): (1) The temperature is 700-980°C, and can be 750-950°C; (2) The time is 4 to 20 hours, and can be 6 to 12 hours; (3) The temperature is raised to the sintering temperature at a heating rate of 2 to 15°C / min.

14. The preparation method according to any one of claims 11 to 12, characterized in that: The Na q Ni x Mn y Fe z Zn p M i O j The precursor is prepared according to 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 a sodium source, a nickel source, a manganese source, an iron source, a zinc source and a doping metal element source represented by M according to the stoichiometric ratio of the elements contained therein; and / or The Na q Ni x Mn y Fe z Zn p M i O j The precursor is prepared according to a method comprising the following steps: According to Na q Ni x Mn y Fe z Zn p M i O j A soluble nickel source, a soluble manganese source, a soluble iron source, a soluble zinc source and a soluble doping metal element source represented by M are prepared into a mixed solution according to the stoichiometric ratio of the elements, and at least one of a precipitant and a complexing agent is added to perform a coprecipitation treatment to obtain a precipitated mixture; The precipitation mixture is mixed with a sodium source to obtain the precursor.

15. A positive electrode, comprising a current collector and a positive electrode active material layer disposed on the surface of the current collector, characterized in that: The positive electrode active material layer comprises the positive electrode material according to any one of claims 1 to 10 or the positive electrode material prepared by the preparation method according to any one of claims 11 to 14.

16. The positive electrode according to claim 15, characterized in that: The content of the positive electrode active material layer on the single surface of the current collector is 260-350 mg / 1540.25 mm 2 , optional: 280~320mg / 1540.25mm 2 ; and / or The compaction density of the positive electrode active material layer is 2.8 to 3.4 g / cm 3 , can be selected as 2.9~3.2g / cm 3 .

17. The positive electrode according to claim 15 or 16, characterized in that: The porosity of the positive electrode active material layer is 40% to 65%, and can be 45% to 60%; and / or The positive electrode is a pole piece, and the membrane resistance of the pole piece is 0.5 to 5 mΩ, and can be optionally 0.5 to 3 mΩ.

18. The positive electrode according to any one of claims 15 to 17, characterized in that: The positive electrode is a pole piece, and the ratio of the thickness from one surface of the pole piece to the other opposite surface to the thickness of the current collector is 6 to 15:1, and can be optionally 8 to 14:

1.

19. The positive electrode according to any one of claims 15 to 18, characterized in that: The conductive agent contained in the positive electrode active material layer includes a linear conductive agent.

20. The positive electrode according to claim 19, characterized in that: The mass content of the linear conductive agent in the positive electrode active material layer is 0.1% to 2.5%, and can be 0.2% to 0.8%; and / or The linear conductive agent has an aspect ratio of 40 to 3000:1, and can be optionally 50 to 2500:1; The length of the linear conductive agent is 0.5 to 5 μm, and can be 0.5 to 2 μm; and / or The diameter of the linear conductive agent is 2 to 10 nm, and can be 3 to 7 nm; and / or The linear conductive agent includes at least one of carbon nanotubes, carbon fibers, and conductive oxide nanowires.

21. A sodium battery, characterized in that: The positive electrode comprises the positive electrode according to any one of claims 15 to 20.

22. An electrical device, characterized in that: Including the sodium battery as claimed in claim 21.

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