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

Abstract

The application discloses a positive electrode material and a preparation method thereof, a positive electrode, a sodium battery and an electric device. q Ni x Mn y Fe z Zn p M i O j The layered oxide shown in the formula, 0.8<=q<=1, 0.1<=x<=0.3, 0.2<=y<=0.5, 0.2<=z<=0.35, 0.02<=p<=0.075, 0<=i<=0.1; M is a doped metal element. The positive electrode material preparation method comprises the step of sintering treatment of Na q Ni x Mn y Fe z Zn p M i O j The precursor. The positive electrode contains the layered oxide shown in the formula, and the sodium battery contains the positive electrode. The electric device contains the sodium battery. The positive electrode material contains the layered oxide with stable structure, high specific capacity and good cycle stability of reversible capacity. The sodium battery has high energy density and good cycle performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium battery, and particularly relates to a positive electrode material and a preparation method thereof, a positive electrode, a sodium battery and an electric device. BACKGROUND

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

[0003] Among sodium ion battery positive electrode materials, layered oxides have high energy density and are currently one of the research hotspots of sodium ion battery positive electrode materials. However, the structure of layered oxides is poor in stability, and it is easy to cause phase change and structural deformation during sodium extraction and insertion, which leads to serious attenuation of the reversible capacity of layered oxides during the cycle process, thereby causing fast cycle attenuation of sodium ion batteries. SUMMARY

[0004] In view of the above problems, the application provides a positive electrode material and a preparation method thereof, and a positive electrode containing the positive electrode material and a sodium battery containing the positive electrode, to solve the technical problems that the existing layered oxides have poor structure stability, which leads to fast cycle attenuation of the specific capacity of the layered oxides and the battery.

[0005] In a first aspect, the embodiments of the application provide a positive electrode material. The positive electrode material of the embodiments of the application comprises a layered oxide shown in the following chemical formula:

[0006] Na q Ni x Mn y Fe z Zn p M i O j ;

[0007] 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 doping metal element.

[0008] The layered oxide contained in the positive electrode material of the embodiments of the present application is doped with Zn element or Zn element and a doping metal element represented by M to the transition metal layer (TMO6) containing Ni, Fe and Mn elements, and the Zn element is controlled to the above low content, which can inhibit the Jahn-Teller effect of the layered oxide represented by the formula itself due to Mn and Ni elements, effectively adjust the arrangement between transition metal elements in the transition metal layer (TMO6), thereby significantly reducing the structural distortion and irreversible phase change of the layered oxide represented by the formula in the sodium extraction process, and significantly improving the structural stability of the layered oxide 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 specific capacity of the layered oxide can be further improved. Further, the low content of Zn element can also significantly reduce the segregation phenomenon of transition metal elements on the surface of the layered oxide represented by the formula, improve the air stability of the layered oxide represented by the formula in air, avoid slurry agglomeration and gelation, improve the electrical performance, and improve the processability of the layered oxide represented by the formula.

[0009] In some embodiments, at least one of q, x, y, z, p and i is in the following range: 0.15≤x≤0.25, 0.25≤y≤0.45, 0.25≤z≤0.32, 0.04≤p≤0.07, 0≤i≤0.05.

[0010] By further selecting and controlling the stoichiometric ratio of at least one element of Na, Ni, Mn, Fe, Zn and M in the range, the doping of Zn element or Zn element and the doping metal element represented by M to the transition metal layer of the layered oxide represented by the formula can be further improved to further adjust the arrangement between metal elements in the transition metal layer, thereby further improving the structural stability of the layered oxide represented by the formula in the sodium extraction process, and improving the specific capacity and cycle stability of the reversible capacity of the layered oxide.

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

[0012] Controlling the stoichiometric ratio of Na element to other metal elements contained in the layered oxide represented by the formula in the range can further improve the specific capacity and cycle stability of the reversible capacity of the layered oxide.

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

[0014] controlling the stoichiometric ratio of the Zn element to the Ni element in the range can improve the gram capacity of the layered oxide shown in the chemical formula while reducing the cost.

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

[0016] controlling the stoichiometric ratio of the Zn element to the Mn element in the range can improve the gram capacity while adjusting the Jahn-Teller effect in which Mn participates in the transition metal layer, further reducing the structural distortion and irreversible phase change of the layered oxide shown in the chemical formula during the sodium deintercalation process, to further improve 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 further dope the transition metal layer contained in the layered oxide shown in the chemical formula together with a low content of Zn element, adjust the arrangement between metal elements in the transition metal layer, and according to the type of the doping metal element M, further improve the structural stability and / or gram capacity of the layered oxide shown in the chemical formula during the sodium deintercalation process.

[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 Fe 0.3 Zn 0.05 O2、Na 0.89 Ni 0.23 Mn 0.41 Fe 0.3 Zn 0.06 O2、Na 0.89 Ni 0.23 Mn 0.42 Fe0.285 Zn 0.065 O2, Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 O2, Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 V 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cr 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Al 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sc 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sb 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Zr 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Nb 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28Zn 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 Zn, O2, Na, Ni, Mn, Fe, Ru, Ir, and O.

[0019] The content of Zn element in the layered oxide shown in the chemical formula is low, and the low content of Zn element and other content of metal elements jointly act to form a specific arrangement between the metal elements in the transition metal layer contained in the layered oxide, thereby further improving the structural stability of the layered oxide in the sodium deintercalation process, and improving the cycle stability of the specific capacity and reversible capacity of the layered oxide. At the same time, on the basis of being able to improve the specific capacity of the layered oxide shown in the chemical formula, the electrochemical performance and processing performance can be improved.

[0020] In some embodiments, the layered oxide includes at least one feature of the following (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) the Dv50 particle size is 3-11 μm, and optionally 4-8 μm;

[0023] (3) including a single crystal, and the morphology of the single crystal is flat.

[0024] In embodiments, the single crystal includes at least one of the following features (1) to (4):

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

[0026] (2) The length is 1-8 μm, and can be 2-6 μm;

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

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

[0029] The layered oxides shown 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 2.8–3.1 g / cm³. 3 The selectable value is 2.9–3.09 g / cm³. 3 ;

[0032] (2) The compaction density under 3 tons of pressure is 3.1–3.3 g / cm³. 3 The selectable value is 3.15–3.28 g / cm³. 3 ;

[0033] (3) Specific surface area is 0.5–1.3 m² 2 / g, which can be selected from 0.6 to 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 single crystal of the layered metal oxide containing the O3 phase, the layered oxide has a high compaction density, thereby improving the energy density of the battery; at the same time, the layered oxide has a suitable specific surface area, which can improve the stability of the interface between the layered oxide and the electrolyte, thereby improving the electrochemical performance such as cycle performance.

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

[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) First-time efficacy 92-98%, 92-95% can be selected.

[0039] The structure stability of the layered oxide shown in the above formula is obviously improved, the structure stability in the sodium deintercalation process is high, the specific capacity is high, and the cycle stability of the reversible capacity is good.

[0040] In a second aspect, the embodiments of the present application provide a preparation method of the positive electrode material. The preparation method of the positive electrode material provided by the embodiments of the present application comprises the following steps:

[0041] providing a precursor of Na q Ni x Mn y Fe z Zn p M i O j ;

[0042] sintering the precursor to obtain a layered oxide with a chemical formula of Na q Ni x Mn y Fe z Zn p M i O j ;

[0043] 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; and M is an active or / and inert doped metal element.

[0044] The preparation method of the positive electrode material provided by the embodiments of the present application sinter the precursor of Na q Ni x Mn y Fe z Zn p M i O j to obtain a low-zinc layered oxide with a chemical formula of Na q Ni x Mn y Fe z Zn p M i O j . Therefore, the layered oxide prepared by the preparation method of the positive electrode material provided by the embodiments of the present application has a low content of zinc element, high structure stability in the sodium deintercalation process, high specific capacity of the prepared layered oxide, and good cycle stability of the reversible capacity. Meanwhile, the layered oxide also has high air stability and diffusion rate and other performances. In addition, the precursor of Na q Ni x Mn y Fe z Zn p Mi O j The conditions of the sintering treatment of the precursor of the layered oxide of the chemical formula Na q Ni x Mn y Fe z Zn p M i O j The structure and the stability of the electrochemical performance of the layered oxide of the chemical formula Na

[0045] In some embodiments, the doping metal elements include at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, Ir. The doping metal elements can further dope the transition metal layers of the layered oxide of the chemical formula Na

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

[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 further regulating the proportions of the metal elements in the precursor of the layered oxide of the chemical formula Na q Ni x Mn y Fe z Zn p M i O j to be in the above range, the arrangement of the metal elements in the prepared layered oxide can be further adjusted, so as to further improve the structural stability of the prepared layered oxide in the sodium deintercalation process, and improve the cycle stability of the specific capacity and the reversible capacity of the layered oxide.

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

[0050] (1) the temperature is 700-980℃, and is optionally 750-950℃;

[0051] (2) the time is 4-20h, and is optionally 6-12h;

[0052] (3) the temperature is raised to the sintering treatment temperature at a temperature raising rate of 2-15℃ / min.

[0053] By controlling the conditions of the sintering treatment in 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 sodium extraction, further improves the high specific capacity of the layered oxide and the cycle stability of its reversible capacity. At the same time, it can also improve the Na q Ni x Mn y Fe z Zn p M i O j The content of O3 phase layered metal oxide in the layered oxide and the content of single crystal, control the size of single crystal and the particle size of the layered oxide, so as to improve 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 the stoichiometric ratio of the elements contained in 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 M indicated doped metal element source are solid-phase mixed to obtain the precursor.

[0056] The precursor of Na q Ni x Mn y Fe z Zn p M i O j By this solid-phase method, the stoichiometric ratio of each element can be effectively controlled, and the preparation effect of the precursor can be improved.

[0057] In some embodiments, the Na q Ni x Mn y Fe z Zn p M i O jThe precursor of Na

[0058] According to Na q Ni x Mn y Fe z Zn p M i O j The soluble nickel source, the soluble manganese source, the soluble iron source, the soluble zinc source and the soluble M-doped metal element source are mixed to prepare a mixed solution, at least one of the precipitating agent and the complexing agent is added to perform a co-precipitation treatment to obtain a precipitate mixture;

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

[0060] The precursor of Na q Ni x Mn y Fe z Zn p M i O j The precursor of Na

[0061] In a third aspect, the embodiments of the present application provide a positive electrode. The positive electrode comprises a current collector and a positive electrode active material layer combined with the current collector, and the positive electrode active material layer comprises the positive electrode material of the embodiments of the present application or is prepared by the preparation method of the positive electrode material of the embodiments of the present application.

[0062] Since the positive electrode active material layer of the positive electrode of the embodiments of the present application contains the positive electrode material of the embodiments 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 one side of the current collector is 260-350 mg / 1540.25 mm 2 , and optionally 280-320 mg / 1540.25 mm 2 . The positive electrode active material layer in the content range can effectively improve the gram capacity of the positive electrode and thus improve the energy density of the battery.

[0064] In some embodiments, the compaction density of the positive electrode active material layer is 2.8-3.4 g / cm 3 , and optionally 2.9-3.2 g / cm 3 . The compaction density in the range can effectively improve the gram capacity of the positive electrode and thus improve the energy density of the battery, and the contact interface with the electrolyte has good stability.

[0065] In some embodiments, the porosity of the positive electrode active material layer is 40% to 65%, or 45% to 60%. The porosity in this range allows the positive electrode active material layer to have the above-mentioned tap density, improves the gram capacity of the positive electrode, thereby improving the energy density of the battery, and improves the wettability of the electrolyte.

[0066] In some embodiments, the positive electrode is a pole piece, and the sheet resistance of the pole piece is 0.5 to 5 mΩ, or 0.5 to 3 mΩ. The sheet resistance in this range effectively improves the performance, including the efficiency and the life.

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

[0068] By controlling the total thickness of the pole piece and the thickness of the current collector to be in the above-mentioned ratio range, the gram capacity of the pole piece is effectively improved, thereby improving the energy density of the battery, improving the bonding strength between the positive electrode active material layer and the current collector, improving the mechanical strength of the pole piece structure, and improving the cycle performance of the pole piece.

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

[0070] In some embodiments, the mass content of the linear conductive agent in the positive electrode active material layer is 0.1% to 2.5%, or 0.2% to 0.8%.

[0071] In some embodiments, the aspect ratio of the linear conductive agent is 40 to 3000:1, or 50 to 2500:1.

[0072] In some embodiments, the length of the linear conductive agent is 0.5 to 5 μm, or 0.5 to 2 μm.

[0073] In some embodiments, the diameter of the linear conductive agent is 2 to 10 nm, or 3 to 7 nm.

[0074] In some embodiments, the linear conductive agent includes at least one of a carbon nanotube, a carbon fiber, and a conductive oxide nanowire.

[0075] By adding a linear conductive agent to the positive electrode active material layer, and controlling the content, type, aspect ratio, length, and diameter of the linear conductive agent within a specified range, the linear conductive agent can form a rich conductive network structure within the positive electrode active material layer. Furthermore, the linear conductive agent can be wound around the surface of flattened single-crystal particles. The particulate conductive agent can be effectively dispersed in the gaps between the positive electrode material. Thus, the linear conductive agent constructs a long-range conductive network structure in the positive electrode active material layer, while the particulate conductive agent constitutes a short-range conductive structure. Therefore, the conductivity-enhancing effect of both the linear and particulate conductive agents in the positive electrode active material layer effectively improves the conductivity of the positive electrode active material layer and significantly reduces the internal resistance of the positive electrode.

[0076] Fourthly, embodiments of this application provide a sodium battery. The sodium battery of this application includes the positive electrode described in the embodiments above.

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

[0078] Fifthly, embodiments of this application provide an electrical device, including the sodium battery of this application.

[0079] The electrical devices in this application have long standby or battery life and a long service life.

[0080] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0081] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0082] Figure 1 This is a scanning electron microscope (SEM) image of the layered oxide provided in Embodiment A6 of this application;

[0083] Figure 2 This is a schematic diagram of the single-crystal structure of the layered oxide contained in the cathode material of some embodiments of this application;

[0084] Figure 3 This is a schematic diagram of the structure of the positive electrode in some embodiments of this application;

[0085] Figure 4 Another structural schematic diagram of a positive electrode for some embodiments of the present application;

[0086] Figure 5 A structural schematic diagram of an embodiment of a sodium battery cell of the present application;

[0087] Figure 6 A structural schematic diagram of Figure 5 A structural schematic diagram of a disassembled sodium battery cell;

[0088] Figure 7 A structural schematic diagram of an embodiment of a battery module of the present application;

[0089] Figure 8 A structural schematic diagram of an embodiment of a battery pack of the present application;

[0090] Figure 9 A structural schematic diagram of Figure 8 A structural schematic diagram of a disassembled battery pack;

[0091] Figure 10 A schematic diagram of an embodiment of an electrical device comprising a battery of the present application as a power source.

[0092] Reference signs in the detailed description of the embodiments are as follows:

[0093] 10 - positive electrode, 11 - current collector, 12 - positive electrode active material layer;

[0094] 20 - battery cell, 21 - shell, 22 - electrode assembly, 23 - cover plate;

[0095] 30 - battery module;

[0096] 40 - battery pack, 41 - upper box, 42 - lower box. DETAILED DESCRIPTION

[0097] The embodiments of the technical solutions of the present application will be described in detail below in conjunction with the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0098] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0099] In the description of the embodiments of the present application, the technical terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise explicitly specified and limited.

[0100] Reference herein to "embodiments" means that the particular features, structures, or characteristics described in connection with the embodiments can 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 all refer to the same embodiment, nor is it necessarily a separate or alternative embodiment to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0101] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " herein generally represents an "or" relationship between the front and rear associated objects.

[0102] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two), and similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0103] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the embodiments of the present application.

[0104] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0105] Sodium-ion batteries (SIBs) have become an ideal candidate for energy storage systems due to the abundant reserves and low prices of raw materials. Moreover, there is a huge application space 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 also increasing.

[0106] For sodium-ion batteries, the positive electrode material of sodium-ion batteries can provide active sodium ions, which is an important part of sodium-ion batteries and one of the important factors affecting the energy density and cycle performance of sodium-ion batteries. Among the positive electrode materials of sodium-ion batteries, layered oxides are of great concern due to their high specific capacity and structure similar to that of lithium-ion battery positive electrode materials.

[0107] According to the stacking order of the arrangement of oxygen atoms in the layered oxide, the layered oxide is currently mainly divided into P2 type and O3 type. For example, the currently more representative P2 layered oxide Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2 has a high capacity, but it is prone to P2-O2 phase transition during sodium extraction and insertion. This phase transition leads to the structural destruction of Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2, causing its capacity to decay and reducing the cycle life. Compared with P2-type layered oxides, O3-type layered oxides can store more Na + , and can also exhibit higher reversible capacity within the same voltage range, thus having better commercial application prospects. However, the diffusion of Na + in O3-type layered oxides requires additional energy to pass through the diffusion energy barrier. Therefore, most O3-type layered oxides such as NaMn 0.5 Ni 0.5 O2 layered oxides will undergo a complex phase transition process during charging and discharging, especially the irreversible P3" phase transition that occurs when charged to a high voltage of 4.1 V or above. This phase transition leads to the structural destruction of O3-type layered oxides, causing its capacity to decay and reducing the cycle life.

[0108] Therefore, the crystal structure of the layered oxide is poor in stability, and the layered oxide is prone to phase transition during sodium extraction, resulting in structural deformation, which leads to a serious decrease in the reversible capacity of the layered oxide during the cycle process, thereby causing the sodium-ion battery to cycle rapidly. In order to improve the crystal structure stability of the layered oxide during sodium extraction and the electrochemical properties including the reversible capacity and the cycle performance, it is reported that the layered oxide is doped with a hetero element. Although the crystal structure stability and the electrochemical properties such as the cycle performance of the layered oxide after doping are improved, the improvement is not obvious. It is generally believed that when the layered oxide is doped with zinc element, the zinc element does not participate in the redox reaction of the layered oxide during the charging and discharging process, and thus can act as a stabilizer to reduce the structural distortion and sliding phenomenon of the layered oxide during the charging and discharging process, thereby improving the structural stability of the layered oxide and improving the reversible capacity and the cycle performance. It is also generally believed that with the increase of the doping amount of the zinc element, the role of the stabilizer is also obvious, which can further reduce the structural distortion and sliding phenomenon of the layered oxide during the charging and discharging process, and improve the structural stability of the layered oxide. Therefore, it is generally believed that controlling the high doping amount of the zinc element is beneficial to the structural stability of the layered oxide. In the layered oxide, the molar doping amount of the zinc element is generally more than 8%.

[0109] However, through research, it is found that reducing the doping amount of the zinc element can effectively alleviate the premature structural phase transition of the nickel-manganese layered oxide, reduce the phase transition of the nickel-manganese-containing layered oxide during the charging and discharging process, and obviously improve the crystal structure stability of the nickel-manganese-containing layered oxide during the sodium extraction process, thereby improving the specific capacity and the reversible capacity stability of the nickel-manganese-containing layered oxide during the cycle process. Based on the above research, the embodiments of the present application provide the following technical solutions.

[0110] Positive electrode material

[0111] In the first aspect, the embodiments of the present application provide a low-zinc-doped positive electrode material. In some embodiments, the positive electrode material of the embodiments of the present application comprises a layered oxide represented by the following chemical formula (I):

[0112] Na q Ni x Mn y Fe z Zn p M i O j (I);

[0113] In the 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 or / and inactive doping metal element.

[0114] In the formula (I), q, x, y, z, p, i and j represent the stoichiometric content ratios of Na, Ni, Mn, Fe, Zn and M, and O in the layered oxide, respectively. Therefore, the stoichiometric content ratios of Na, Ni, Mn, Fe, Zn and M, and O in the layered oxide can be 0.8-1:0.1-0.3:0.2-0.5:0.2-0.35:0.02-0.075:t-0.1:1.8-2; wherein 0≤t<0.1. In addition, the stoichiometric ratios of the doping metal elements of Na, Ni, Mn, Fe, Zn and M, and O can be molar ratios, or mass ratios converted from the molar ratios. The active doping metal element of M refers to a type of metal element having electrochemical redox activity in the layered oxide, and mainly contributing to the capacity of the layered oxide. The inactive doping metal element of M refers to a type of metal element having relatively stable electrochemical redox activity in the layered oxide, and mainly contributing to the stability of the crystal structure of the layered oxide. The layered oxide refers to a type of positive electrode material composed of transition metal layer (TMO6) octahedron containing Ni, Mn and Fe elements and sodium layer (NaO6) alkali metal layer arranged alternately.

[0115] The layered oxide contained in the positive electrode material of the embodiment of the present application is doped with Zn element or Zn element and further doped with M indicated doping metal element into transition metal layer (TMO6) containing Ni, Fe and Mn elements, and the amount of Zn element is controlled in a low content range indicated by p, so that Zn element and Fe element or Zn element and Fe element and M indicated doping metal element can jointly participate in the arrangement between metal elements in the transition metal layer contained in the layered oxide crystal, mainly disordered arrangement, can inhibit the Jahn-Teller effect of the layered oxide itself indicated by formula (I) due to Mn element and the phase transition of the structure caused by too much nickel element, compared with the current layered oxide with high content of zinc element, can reduce the structure phase transition of the layered oxide indicated by formula (I), can significantly reduce the structure distortion and irreversible phase transition of the layered oxide indicated by formula (I) in the process of deintercalating sodium, can significantly improve the structure 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, on the basis of effectively improving the structure stability of the layered oxide, the specific capacity of the layered oxide can be further improved. Moreover, the content ratio of each metal element can also effectively adjust the distance between the transition metal elements in the transition metal layer (TMO6), so as to control the amount of deintercalating sodium, and can also improve the structure distortion and irreversible phase transition of the layered oxide in the process of deintercalating sodium, and can significantly improve the structure stability of the layered oxide.

[0116] Further, the low content of Zn element in the layered oxide indicated by formula (I) above can also significantly reduce the segregation phenomenon of transition metal elements on the surface of the layered oxide indicated by formula (I), improve the air stability of the layered oxide indicated by formula (I) in air, avoid slurry agglomeration and gelation, improve the electrical performance, and at the same time improve the processing performance and electrical performance of the layered oxide indicated by formula (I). In addition, the low content of Zn element or Zn element and further doped with M indicated doping metal element into transition metal layer (TMO6) containing Ni, Fe and Mn elements can effectively inhibit the Na + and vacancy ordering transition of the layered oxide in the charging and discharging process, reduce the diffusion energy barrier of Na + , and improve the diffusion rate of sodium ions contained in the layered oxide.

[0117] In the exemplary embodiment, 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 q of Na element can be 0.8, 0.85, 0.9, 0.95, 1.0 and other typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values. The content range of Na element improves the reversible capacity of the layered oxide indicated by formula (I).

[0118] In some embodiments, in the chemical formula (I) of the layered oxide contained in the positive electrode material of the embodiments of the present application, the stoichiometric content x of the element Ni can further be 0.15≤x≤0.25. Based on the value range of x in the chemical formula (I), in exemplary examples, x can be 0.1, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.25, 0.3, etc., typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values. The Ni element in this content range, on the one hand, can effectively reduce the content of non-active impurity phases such as NiO in the layered oxide under the co-doping of the elements Zn and Fe or the elements Zn, Fe and the doping metal elements represented by M, thereby further improving the structural stability of the layered oxide in the process of deintercalating sodium. At the same time, the elements Zn and Fe or the elements Zn, Fe and the doping metal elements represented by M can also replace part of the element Ni, thereby reducing the content of Ni, so that the cost of the layered oxide can be reduced without reducing the capacity of the layered oxide represented by the chemical formula (I).

[0119] In some embodiments, in the chemical formula (I) of the layered oxide contained in the positive electrode material of the embodiments of the present application, the stoichiometric content y of the element Mn can further be 0.25≤y≤0.45. Based on the value range of y in the chemical formula (I), in exemplary examples, y can be 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, etc., typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values. The Mn element in this stoichiometric content range, on the one hand, can reduce the Jahn-Teller effect caused by the elements Mn and Ni under the co-doping of the elements Zn and Fe or the elements Zn, Fe and the doping metal elements represented by M, thereby further improving the structural stability of the layered oxide in the process of deintercalating sodium; on the other hand, can also make the layered oxide represented by the chemical formula (I) have a larger average oxidation state and lattice space, thereby improving the diffusion rate of Na ions.

[0120] In some embodiments, in the chemical formula (I) of the layered oxide contained in the positive electrode material of the embodiments of the present application, the stoichiometric content z of the Fe element can further be 0.25≤z≤0.32. Based on the range of the value of z in the chemical formula (I), in exemplary examples, z can be 0.2, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, etc., typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values. The Fe element in this stoichiometric content range can jointly dope the transition metal layer in the layered oxide shown in the chemical formula (I) with the Zn element or the Zn element and the doping metal element M shown, further improving the structural stability of the layered oxide shown in the chemical formula (I) in the process of deintercalating sodium; at the same time, the Fe element replaces part of the Ni element, reducing the content of the Ni element on the basis of improving the specific capacity of the layered oxide shown in the chemical formula (I), and reducing the cost of the layered oxide shown in the chemical formula (I).

[0121] In some embodiments, in the chemical formula (I) of the layered oxide contained in the positive electrode material of the embodiments of the present application, the stoichiometric content p of the Zn element can be 0.04≤p≤0.07, further 0.04≤p≤0.065. Based on the range of the value of p in the chemical formula (I), in exemplary examples, 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, etc., typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values. The Zn element in this stoichiometric content range can further dope the transition metal layer contained in the layered oxide shown in the chemical formula (I) with the doping metal element M shown, further improving the structural stability of the layered oxide shown in the chemical formula (I) in the process of deintercalating sodium; at the same time, further balancing the electrical performance and processing performance of the positive electrode material.

[0122] In some embodiments, in the chemical formula (I) of the layered oxide contained in the positive electrode material of the embodiments of the present application, the stoichiometric content i of the doped metal element represented by M can further be 0≤i≤0.05. Based on the range of the value of i in the chemical formula (I), in exemplary embodiments, i can be 0, 0.01, 0.02, 0.03, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, and the like, which are typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values. The doped metal element represented by M in the stoichiometric content range can assist the low content of Zn element to further improve the doping of the transition metal layer contained in the layered oxide represented by the chemical formula (I), adjust the arrangement between the metal elements in the transition metal layer, and further improve the structural stability of the layered oxide represented by the chemical formula (I) during the sodium extraction process, and further improve the cycle stability of the specific capacity and / or reversible capacity.

[0123] In exemplary embodiments, in the chemical formula (I) of the layered oxide contained in the positive electrode material of the embodiments of the present application, the stoichiometric content j of O can be 1.8, 1.9, 2, and the like, which are typical but non-limiting stoichiometric contents or ranges between any two stoichiometric content values.

[0124] In embodiments, the active or / and inactive doped metal element represented by M can include at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, Ir, and the like. Among them, the active doped metal element represented by M can include at least one of V, Ca, Cr, Nb, Cu, Sc, Sn, Sb, and the like, and the inactive doped metal element represented by M can include at least one of Zr, Mg, Ru, Ir, Al, Ti, and the like. Selecting the active or / and inactive doped metal element represented by M from these elements can further improve the doping of the transition metal layer contained in the layered oxide represented by the 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 the doped metal element represented by M, further improve the structural stability and / or specific capacity of the layered oxide represented by the chemical formula (I) during the sodium extraction process.

[0125] Based on the range of the values of q, x, y, z, p, and i in the above embodiments, in some embodiments, the values of q, x, y, z, p, and i in the chemical formula (I) of the layered oxide are simultaneously in the following ranges:

[0126] 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. At this time, the stoichiometric content ratio of Na, Ni, Mn, Fe, Zn and the doping metal elements represented by M contained in the layered oxide represented by the chemical formula (I) can be 0.8-1:0.15-0.25:0.25-0.45:0.25-0.32:0.04-0.065:t-0.05; wherein 0≤t<0.05. By selecting and controlling the stoichiometric ratio of Na, Ni, Mn, Fe, Zn or Na, Ni, Mn, Fe, Zn and the doping metal elements represented by M within the range, the doping of Zn element or Zn element and the doping metal elements represented by M to the transition metal layer in the layered oxide represented by the chemical formula (I) can be further improved, the structural stability of the layered oxide represented by the chemical formula (I) in the sodium extraction process can be further improved, the arrangement between the metal elements in the transition metal layer can be adjusted, and the cycle stability of the specific capacity and reversible capacity of the layered oxide can be improved. In addition, the electrochemical performance and processing performance of the layered oxide can be further improved.

[0127] Based on the value range of q, x, y, z, p and i in each of the above embodiments, in some embodiments, the total stoichiometric amount of the doping metal elements represented by Ni, Mn, Fe, Zn and M and the stoichiometric amount of Na in the chemical formula (I) of the layered oxide is 1:(0.8-1), which can be selected as 1:(0.85-0.95), further as 1:(0.85-0.92), and in exemplary examples, it can be 1:0.8, 1:0.82, 1:0.85, 1:0.88, 1:0.9, 1:0.95, 1:1, etc. Typical but non-limiting molar ratio or range between any two stoichiometric ratio values. Among them, the stoichiometric amount can be the number of moles and the mass converted according to the number of moles. By controlling the stoichiometric ratio of Na and other metal elements contained in the layered oxide represented by the chemical formula (I) within the range, the content of sodium ions can be further improved, the content of sodium ions that can be extracted and inserted by the layered oxide can be improved, thereby the specific capacity of the layered oxide; and the sodium ions within the content range can improve the O3 crystal phase content of the layered oxide represented by the chemical formula (I), so that the layered oxide represented by the chemical formula (I) mainly presents O3 crystal, thereby improving the structural stability of the layered oxide represented by the chemical formula (I), to improve the cycle stability of its reversible capacity.

[0128] In some embodiments, the stoichiometric ratio of Zn to Ni in the chemical formula (I) of the layered oxide is 1:(3-15), optionally 1:(3.1-11). In exemplary cases, typical but non-limiting molar ratios such as 1:3, 1:3.1, 1:5, 1:8, 1:10, 1:11, 1:12, and 1:15, or any range between two stoichiometric ratios, are possible. The stoichiometric ratio of Zn to Ni can be the number of moles or the mass converted from the number of moles. Controlling the stoichiometric ratio of Zn to Ni in chemical formula (I) within this range can further increase the specific capacity of the layered oxide shown in the chemical formula. For example, appropriately increasing this ratio within the range, i.e., appropriately increasing the zinc content, can further increase the specific capacity of the layered oxide shown in the chemical formula.

[0129] In some embodiments, the stoichiometric ratio of Zn to Mn is 1:(4-25), optionally 1:(5-15). In exemplary cases, typical but non-limiting stoichiometric ratios such as 1:4, 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, 1:20, 1:22, and 1:25, or any range between two stoichiometric ratios, are possible. Similarly, the stoichiometry of Zn to Mn can be the number of moles and the mass converted from the number of moles. Controlling the stoichiometric ratio of Zn to Mn within this range allows for further adjustment of the Mn content in the transition metal layer of the layered oxide shown in the chemical formula. This further enhances the Jahn-Teller effect between Mn and Ni elements in the transition metal layer, further reducing structural distortion and irreversible phase transitions during sodium insertion / extraction in the layered oxide shown in the chemical formula, thereby further improving the structural stability of the layered oxide. Of course, the above-mentioned stoichiometric ratio range of Zn and Mn can also take into account the specific capacity of the layered oxide shown in chemical formula (Ⅰ).

[0130] Furthermore, in chemical formula (I), the Zn and Ni elements and the Zn and Mn elements can be controlled within the aforementioned stoichiometric ratio ranges, respectively. In one embodiment, they can be controlled simultaneously within the aforementioned stoichiometric ratio ranges. Simultaneously controlling the stoichiometric ratios of Zn and Ni elements and Zn and Mn elements within the aforementioned stoichiometric ratio ranges allows the layered oxide shown in chemical formula (I) to better balance structural stability and specific capacity. That is, it allows the layered oxide shown in chemical formula (I) to have better reversible capacity and cycle stability while also possessing a relatively high specific capacity.

[0131] Based on the value ranges of q, x, y, z, p, and i in the above embodiments, the layered oxide represented by chemical formula (Ⅰ) in the above embodiments may include Na. 0.89 Ni 0.23 Mn0.45 Fe 0.3 Zn 0.02 O2, Na 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cu 0.02 O2, Na 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 O2, Na 0.89 Ni 0.23 Mn 0.41 Fe 0.3 Zn 0.06 O2, Na 0.89 Ni 0.23 Mn 0.42 Fe 0.285 Zn 0.065 O2, Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 O2, Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 V 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cr 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Al 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sc 0.02 O2, Na 0.85 Ni0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 O2 、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sb 0.02 O2 、 Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Zr 0.02 O2 、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Nb 0.02 O2 、 Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ti 0.02 O2 、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Mg 0.02 O2 、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ru 0.02 O2 、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O2、Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O 1.8The layered oxide shown in the chemical formula (I) is mainly an O3 phase layered metal oxide. The O3 phase layered metal oxide refers to a type of crystal structure of layered oxide in which the oxygen contained therein is stacked in an ABCABC type. In the embodiments, the layered oxide shown in the chemical formula (I) in each of the above embodiments is mainly an O3 phase layered metal oxide. Mainly an O3 phase layered metal oxide means that in the layered oxide shown in the chemical formula (I), the weight ratio of the 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 shown in the chemical formula (I), further more than 98%, and of course, the weight ratio of the O3 phase layered metal oxide in the layered oxide shown in the chemical formula (I) can reach 100%. The higher the weight ratio of the O3 phase layered metal oxide in the layered oxide shown in the chemical formula (I) is, the more desirable it is. The layered oxide shown in the chemical formula (I) mainly exists in the form of an O3 phase layered metal oxide or a pure O3 phase layered metal oxide, which makes the layered oxide have relatively high structural stability, such as relatively high structural stability compared with a P2 phase layered metal oxide, and higher specific capacity and better cycle stability of reversible capacity.

[0132] It is detected that in some embodiments, the crystal structure of the layered oxide shown in the chemical formula (I) in each of the above embodiments includes an O3 phase layered metal oxide. The O3 phase layered metal oxide refers to a type of crystal structure of layered oxide in which the oxygen contained therein is stacked in an ABCABC type. In the embodiments, the layered oxide shown in the chemical formula (I) in each of the above embodiments is mainly an O3 phase layered metal oxide. Mainly an O3 phase layered metal oxide means that in the layered oxide shown in the chemical formula (I), the weight ratio of the 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 shown in the chemical formula (I), further more than 98%, and of course, the weight ratio of the O3 phase layered metal oxide in the layered oxide shown in the chemical formula (I) can reach 100%. The higher the weight ratio of the O3 phase layered metal oxide in the layered oxide shown in the chemical formula (I) is, the more desirable it is. The layered oxide shown in the chemical formula (I) mainly exists in the form of an O3 phase layered metal oxide or a pure O3 phase layered metal oxide, which makes the layered oxide have relatively high structural stability, such as relatively high structural stability compared with a P2 phase layered metal oxide, and higher specific capacity and better cycle stability of reversible capacity.

[0133] In some embodiments, the crystal of the layered oxide shown in the chemical formula (I) in each of the above embodiments includes a single crystal, which is 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.

[0134] Further electron microscopy analysis of the single crystal shows that in some embodiments, as shown in Figure 2As shown, the ratio of the length L, the width W and the thickness H of the single crystal of the layered oxide shown in the chemical formula (I) is 1-8: 1-5: 0.5-2.5, which can be selected as 2-6: 2-4: 1-2, and in the exemplary embodiment, it can be 1: 1: 0.5, 3: 2: 0.5, 5: 3: 1, 7: 4: 2, 8: 5: 2.5, 8: 2: 1, and the like, which are typical but not limited ratios or a range between any two ratios. Among them, the length L and the width W are respectively as shown in Figure 2 the length L and the width W of the flat single crystal; and the thickness is as shown in Figure 2 the thickness of the flat single crystal.

[0135] On the basis of the ratio of the length L, the width W and the thickness H, in the embodiment, the length L of the single crystal can be 1-8 μm, which can be selected as 2-6 μm, and in the exemplary embodiment, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, and the like, which are typical but not limited lengths or a range between any two length values.

[0136] In the embodiment, the width W of the single crystal can be 1-5 μm, which can be selected as 2-4 μm, and in the exemplary embodiment, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, and the like, which are typical but not limited widths or a range between any two width values.

[0137] In the embodiment, the thickness H of the single crystal can be 0.5-2.5 μm, which can be selected as 1-2 μm, and in the exemplary embodiment, it can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, and the like, which are typical but not limited thicknesses or a range between any two thickness values.

[0138] In the embodiment, it is detected that the Dv50 particle size of the layered oxide shown in the chemical formula (I) in the above embodiments is 3-11 μm, which can be selected as 4-8 μm, and in the exemplary embodiment, the Dv50 particle size can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, and the like, which are typical but not limited particle sizes or a range between any two particle size values. Among them, the Dv50 particle size refers to the particle of the layered oxide powder shown in the chemical formula (I).

[0139] The Dv50 particle size of the layered oxide shown in the chemical formula (I) in the above embodiments and the size distribution range of the O3 phase layered metal oxide single crystal contained therein make the layered oxide have a high compaction density, thereby improving the compaction density of the positive electrode material of the present application, and improving the energy density of the battery. At the same time, the layered oxide has a suitable specific surface area.

[0140] It is detected that in the embodiment, the specific surface area (BET) of the layered oxide shown in the chemical formula (I) in the above embodiments is 0.5-1.3 m 2 / g, optionally 0.6 to 0.9 m 2 / g, in an exemplary embodiment, 0.5 m 2 / g, 0.6 m 2 / g, 0.7 m 2 / g, 0.8 m 2 / g, 0.9 m 2 / g, 1 m 2 / g, 1.1 m 2 / g, 1.2 m 2 / g, 1.3 m 2 / g, etc., and a range between any two of the specific surface areas. The range of the specific surface area can improve the stability of the interface between the layered oxide and the electrolyte, and the like, and thus can improve the electrochemical properties such as the cycle performance.

[0141] It was confirmed that the layered oxide represented by Chemical Formula (I) in each of the embodiments had a compaction density of 2.8 to 3.1 g / cm 3 , optionally 2.9 to 3.09 g / cm 3 , in an exemplary embodiment, 2.8 g / cm 3 , 2.9 g / cm 3 , 3 g / cm 3 , 3.09 g / cm 3 , 3.1 g / cm 3 , etc., and a range between any two of the compaction densities.

[0142] It was confirmed that the layered oxide represented by Chemical Formula (I) in each of the embodiments had a compaction density of 3.1 to 3.3 g / cm 3 , optionally 3.15 to 3.28 g / cm 3 , in an exemplary embodiment, 3.1 g / cm 3 , 3.15 g / cm 3 , 3.2 g / cm 3 , 3.25 g / cm 3 , 3.28 g / cm 3 , 3.3 g / cm 3 , etc., and a range between any two of the compaction densities.

[0143] The range of the compaction density can improve the energy density and the corresponding electrochemical properties of the battery containing the layered oxide represented by Chemical Formula (I).

[0144] Based on the properties of the layered oxide represented by Chemical Formula (I) in each of the above embodiments, such as morphology, crystal form, particle size, and compaction density, the layered oxide has a charge specific capacity of 164-174 mAh / g, optionally 165-172 mAh / g, and a discharge specific capacity of 158-165 mAh / g, optionally 160-163 mAh / g, at 1.5-4.2 V and 0.1 C. In other embodiments, the layered oxide has an initial efficiency of 92-98%, optionally 92-95%, at 1.5-4.2 V and 0.1 C.

[0145] The charge specific capacity and discharge specific capacity and initial efficiency of the layered oxide refer to the specific capacity and initial efficiency of the layered oxide, specifically, the layered oxide is prepared into a positive electrode of a sodium ion button cell, assembled with a negative electrode into a sodium ion button cell, and the specific capacity and initial efficiency of the sodium ion button cell are detected. From the range of the specific capacity and initial efficiency of the layered oxide, it can be seen that the structural stability of the layered oxide crystal has been significantly improved, the structural stability during sodium extraction and insertion is high, and the cycle stability of reversible capacity is good.

[0146] In the embodiments, the above-mentioned sodium ion button cell for testing the charge specific capacity and discharge specific capacity and initial efficiency of the layered oxide is assembled according to the following method:

[0147] Positive electrode sheet: the layered oxide represented by Chemical Formula (I) is used as a positive active material, and a conductive agent carbon nanotube, a conductive agent carbon black, and a binder polyvinylidene fluoride (PVDF) are mixed 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 uniformly 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;

[0148] Negative electrode sheet: hard carbon, conductive agent SP, and CMC binder are added to deionized water in a weight ratio of 8:1:1 and stirred to form a uniform negative electrode slurry; the negative electrode slurry is uniformly coated on the surface of a 6 μm copper foil, and after drying and cold pressing, a negative electrode sheet is obtained;

[0149] Electrolyte: 1M NaPF6 / (EC / DEC, volume ratio 1:1);

[0150] Separator: glass fiber;

[0151] 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, the electrode assembly is put into a packaging shell, 1M NaPF6 / (EC / DEC, volume ratio 1:1) electrolyte is added, and after packaging, formation, and standing processes, a sodium ion battery is obtained.

[0152] Based on the above embodiments, the positive electrode material of the embodiments of the present application can only contain the layered oxide shown in the chemical formula (I) in the above embodiments. Of course, other positive electrode materials such as polyanion compounds, Prussian blue compounds, and other layered oxides can also be further included.

[0153] In the examples, the polyanion compound can include at least one of sodium vanadate, sodium iron pyrophosphate, sodium iron phosphate, sodium iron fluoride phosphate, and the like.

[0154] In the examples, the Prussian blue compound can include at least one of Na2Fe[Fe(CN)6] (FeHCF), Na2Mn[Fe(CN)6] (MnHCF), and the like.

[0155] The above other positive electrode materials can be used together with the layered oxide shown in the chemical formula (I) above, and can further improve the energy density, reversible capacity, cycle performance, and other electrochemical properties of the battery containing the positive electrode material of the embodiments of the present application.

[0156] Method for preparing a positive electrode material

[0157] In a second aspect, the embodiments of the present application provide a method for preparing the above positive electrode material. In some embodiments, the method for preparing the positive electrode material of the embodiments of the present application includes the following steps:

[0158] S10: providing a precursor of Na q Ni x Mn y Fe z Zn p M i O j ;

[0159] S20: sintering the precursor to obtain a layered oxide with a chemical formula of Na q Ni x Mn y Fe z Zn p M i O j .

[0160] In step S10 of the method for preparing the positive electrode material of the embodiments of the present application, the precursor of Na q Ni x Mn y Fe z Zn p M i O j is the precursor of the layered oxide shown in the chemical formula (I) of the above positive electrode material. Therefore, the Na q Nix Mn y Fe z Zn p M i O j q, x, y, z, p, i and j are respectively as follows:

[0161] 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 inactive 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, Ir. The sintering treatment in step S20 is to make the precursor of Na q Ni x Mn y Fe z Zn p M i O j react to generate the layered oxide shown in the chemical formula (I) contained in the positive electrode material of the embodiments of the present application.

[0162] The positive electrode material preparation method of the embodiments of the present application generates the precursor of Na q Ni x Mn y Fe z Zn p M i O j by sintering. The positive electrode material of the embodiments of the present application contains the chemical formula Na q Ni x Mn y Fe z Zn p M i O j low-zinc layered oxide. Therefore, the zinc element content in the layered oxide prepared by the positive electrode material preparation method of the embodiments of the present application is low, the structural stability is high in the process of deintercalating sodium, the specific capacity of the prepared layered oxide is high, and the cycle stability of the reversible capacity is high. At the same time, it also has high air stability and diffusion rate and other performances. In addition, the precursor of Na q Ni x Mn y Fe z Zn pM i O j The conditions of the sintering treatment of the precursor of Na q Ni x Mn y Fe z Zn p M i O j The structure and the stability of the electrochemical performance of the layered oxide of Na

[0163] Step S10:

[0164] The precursor of Na q Ni x Mn y Fe z Zn p M i O j The precursor of Na q Ni x Mn y Fe z Zn p M i O j The sodium source, the nickel source, the manganese source, the iron source and the zinc source and the source of the doping element represented by M are prepared by a solid phase method or a precipitation method according to the stoichiometric ratio of the elements contained in Na

[0165] When the precursor of Na q Ni x Mn y Fe z Zn p M i O j is prepared by a solid phase method, in the embodiment, the precursor of Na q Ni x Mn y Fe z Zn p M i O j The precursor of Na

[0166] Step S11: The sodium source, the nickel source, the manganese source, the iron source and the zinc source and the source of the doping element represented by M are solid phase mixed according to the stoichiometric ratio of the elements in Na q Ni x Mn y Fe z Zn p M i O j The precursor of Na q Ni xMn y Fe z Zn p M i O j precursor of M.

[0167] In step S11, the solid phase mixing treatment is generally referred to as a dry mixing treatment of the sodium source, the nickel source, the manganese source, the iron source, the zinc source, or the further source of the doping element M without adding a solvent, such as water, under a solvent-free condition.

[0168] In order to improve the mixing uniformity of the sodium source, the nickel source, the manganese source, the iron source, the zinc source, or the further source of the doping element M in the solid phase mixing treatment, in the embodiments, the nickel source, the manganese source, the iron source, and the zinc source, or the further source of the doping element M can be first mixed and treated, and then the sodium source is added for further mixing treatment. In this way, the mixing uniformity of the sources can be improved, and the safety of the solid phase mixing treatment can be improved.

[0169] In the embodiments, the mixing treatment can be, but is not limited to, a ball milling treatment. As long as the mixing uniformity of the sodium source, the nickel source, the manganese source, the iron source, and the zinc source, or the further source of the doping element M can be improved, it is within the scope disclosed in the embodiments. In the embodiments, when the mixing treatment is a ball milling treatment, the rotating speed of the ball milling can be controlled to be 300-1000 rpm, and can be optionally 400-600 rpm. The ball milling treatment time can be 1 h-6 h, and can be optionally 2 h-4 h. Through the ball milling treatment, the mixing uniformity of the sources can be improved, so that the Na q Ni x Mn y Fe z Zn p M i O j the structure and the stability of the electrochemical performance of the layered oxide.

[0170] In the exemplary embodiments, the sodium source can be a sodium salt, such as at least one of sodium carbonate and sodium hydroxide.

[0171] In the exemplary embodiments, the nickel source can be a soluble or insoluble nickel compound, such as nickel oxide (NiO) or a nickel salt. The nickel salt can include at least one of nickel nitrate, nickel carbonate, nickel hydroxide, and nickel sulfate.

[0172] In the exemplary embodiments, the manganese source can be a soluble or insoluble manganese compound, such as manganese oxide (Mn2O3) or a manganese salt. The manganese salt can include at least one of manganese nitrate, manganese carbonate, manganese hydroxide, and manganese sulfate.

[0173] In the exemplary embodiment, the iron source can be a soluble or insoluble iron compound, such as an iron oxide (e.g., Fe2O3) or an iron salt, etc. The iron salt can include at least one of iron nitrate, iron carbonate, iron hydroxide, iron sulfate, etc.

[0174] In the exemplary embodiment, the zinc source can be a soluble or insoluble zinc compound, such as zinc oxide (e.g., ZnO) or a zinc salt, etc. The zinc salt can include at least one of zinc nitrate, zinc carbonate, zinc hydroxide, zinc sulfate, etc.

[0175] In the exemplary embodiment, the source of the doping metal element represented by M can be a soluble or insoluble compound of the doping metal element represented by M, such as an oxide of the doping metal element represented by M or a salt of the doping metal element represented by M, etc. The salt of the doping metal element represented by M can include at least one of a nitrate, a carbonate, a hydroxide, a sulfate, etc. of the doping metal element represented by M.

[0176] The above-mentioned types of the sodium source, the nickel source, the manganese source, the iron source, the zinc source, and the further source of the doping element represented by M can be effectively mixed uniformly during the mixing process, thereby improving the Na q Ni x Mn y Fe z Zn p M i O j precursor to generate a Na q Ni x Mn y Fe z Zn p M i O j layered oxide.

[0177] When the precursor of the Na q Ni x Mn y Fe z Zn p M i O j is prepared by the precipitation method, in the exemplary embodiment, the precursor of the Na q Ni x Mn y Fe z Zn p M i O j can be prepared according to a method including the following steps:

[0178] Step S12: The Na q Ni x Mn y Fe z Znp M i O j The soluble nickel source, the soluble manganese source, the soluble iron source, the soluble zinc source, or the further soluble M-doped element source are mixed to form a mixed solution, and at least one of a precipitant and a complexing agent is added to perform a co-precipitation treatment to obtain a precipitate mixture.

[0179] Step S13: mixing the precipitate mixture with a sodium source to obtain a Na q Ni x Mn y Fe z Zn p M i O j precursor.

[0180] In step S12, the at least one of the precipitant and the complexing agent should be a compound capable of precipitating nickel, manganese, iron, zinc, and the M-doped metal element in the nickel source, the soluble manganese source, the soluble iron source, the soluble zinc source, and the soluble M-doped element source. In the embodiment, the precipitant can include at least one of a hydroxide, a carbonate, or the like of an alkali metal.

[0181] In the embodiment, the complexing agent can include an inorganic or organic complexing agent. In the exemplary embodiment, the inorganic complexing agent can include at least one of ammonia, ammonium bicarbonate, ammonium sulfate, ammonium carbonate, or the like; and the organic complexing agent can include at least one of citric acid, tartaric acid, ethylenediaminetetraacetic acid disodium salt, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), or the like.

[0182] The precipitant and the complexing agent of these types can effectively precipitate nickel, manganese, iron, zinc, and the M-doped element.

[0183] In the embodiment, the at least one of the precipitant and the complexing agent should be in excess relative to the total amount of metal elements, such as the total molar amount, contained in the mixed solution to ensure that all the metal elements contained in the mixed solution are sufficiently precipitated to improve the accuracy of the stoichiometric ratio of the metal elements in the Na q Ni x Mn y Fe z Zn p M i O j precursor.

[0184] In the exemplary embodiment, the soluble nickel source can include at least one of nickel acetate, nickel chloride, nickel nitrate, and nickel sulfate.

[0185] In the exemplary embodiment, the soluble manganese source can include at least one of a nitrate of manganese, manganese sulfate, a halide, or the like.

[0186] In an exemplary embodiment, the soluble iron source can include at least one of a nitrate, a sulfate, a halide, and the like of iron.

[0187] In an exemplary embodiment, the soluble zinc source can include at least one of a nitrate, a sulfate, a halide, and the like of zinc.

[0188] In an exemplary embodiment, the soluble M-doped metal element source can include at least one of a nitrate, a sulfate, a halide, and the like of the M-doped metal element.

[0189] The above-mentioned soluble nickel source, soluble manganese source, soluble iron source, soluble zinc source, and soluble M-doped metal element source all have good solubility, and can quantitatively control the stoichiometric ratio of each metal element in the precipitated mixture.

[0190] The mixing ratio between the sodium source in step S13 and the precipitated mixture should satisfy Na q Ni x Mn y Fe z Zn p M i O j stoichiometric ratio of sodium element. The mixing process can be a solid-phase mixing process or the soluble sodium source is dissolved and then mixed with the precipitated mixture, and then the solvent is removed.

[0191] In an exemplary embodiment, the sodium source can be a sodium salt, which can include at least one of sodium carbonate, sodium hydroxide, and the like.

[0192] In addition, the above-mentioned step S11 and step S12 and step S13 do not have a sequential relationship.

[0193] Step S20:

[0194] After the precursor of Na q Ni x Mn y Fe z Zn p M i O j in step S10 is sintered in step S20, a layered oxide with a chemical formula of Na q Ni x Mn y Fe z Zn p M i O j is generated. In the research, it is found that the sintering process conditions affect the generated Na q Ni x Mn y Fe z Znp M i O j The structural stability and electrochemical performance of the layered oxide are influenced. In some embodiments, the sintering treatment temperature can be controlled at 700-980°C, optionally 750-950°C, and in exemplary embodiments, can be at 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 980°C, or any range between any two of the temperatures.

[0195] At the above sintering temperature, the sintering treatment time can be 4-20h, optionally 6-12h, and in exemplary embodiments, can be at 4h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, or any range between any two of the hours.

[0196] By controlling the sintering treatment temperature and time in the above ranges, the precursor of Na q Ni x Mn y Fe z Zn p M i O j reacts to form Na q Ni x Mn y Fe z Zn p M i O j layered oxide, and the content of O3 phase layered metal oxide and single crystal content in the Na q Ni x Mn y Fe z Zn p M i O j layered oxide can be further improved, and the structural stability of the layered oxide during sodium deintercalation, the high gravimetric capacity of the layered oxide and the cycle stability of the reversible capacity are further improved. At the same time, the content of O3 phase layered metal oxide and single crystal content in the Na q Ni x Mn y Fe z Zn p M i O j layered oxide can be controlled, and the single crystal size and the particle size of the layered oxide are controlled, so as to improve the compaction density of the layered oxide.

[0197] In embodiments, the sintering process can be performed at a temperature increasing rate of 2-15 ℃ / min. The temperature increasing rate can be further controlled to be 4-10 ℃ / min. In exemplary embodiments, the temperature increasing rate can be 2 ℃ / min, 4 ℃ / min, 6 ℃ / min, 8 ℃ / min, 10 ℃ / min, 12 ℃ / min, 15 ℃ / min, 17 ℃ / min, 18 ℃ / min, 20 ℃ / min, or any other typical but non-limiting rate or a range between any two rate values. By controlling the temperature increasing rate of the sintering process, such as controlling the temperature increasing rate within the range, the Na q Ni x Mn y Fe z Zn p M i O j The crystal of the layered oxide is perfect and complete, such as improving the uniformity of the crystal morphology.

[0198] In addition, the sintering process in step S20 should be understood to be performed in an oxygen-containing environment, such as sintering in air or in an oxygen-containing protective atmosphere, such as sintering in oxygen-containing nitrogen or inert other.

[0199] Positive electrode

[0200] In some embodiments, the positive electrode of the embodiments of the present application comprises a current collector and a positive active material layer. The positive active material layer is combined with the current collector, and the positive active material layer contains the positive electrode material of the embodiments of the present application described above.

[0201] In the positive electrode of the embodiments of the present application, the current collector refers to a structure for collecting current and transmitting electrons. The positive active material layer refers to a layer structure containing a positive active material, which is a key substance participating in the chemical reaction of the battery in the positive electrode. The positive active material includes the positive electrode material of the embodiments of the present application described above. The positive active material layer is combined with the current collector, which means that the positive active material layer is at least combined on the surface of the current collector. In addition, the positive electrode can be a pole piece, which refers to a sheet-like morphology of the positive electrode. Of course, it can also be set to other morphologies as needed.

[0202] Since the positive active material layer of the positive electrode of the embodiments of the present application contains the positive electrode material of the embodiments of the present application described above, the specific capacity of the positive electrode is relatively high, and the cycle performance is good.

[0203] In the embodiments of this application, the current collector included in the positive electrode includes, but is not limited to, metal current collectors, carbon current collectors, conductive resin current collectors, and composite current collectors of metal and resin, and more specifically, aluminum, copper, nickel, titanium, iron and their respective alloys, stainless steel, carbon fiber, carbon nanotubes (CNTs), graphite, etc. In the embodiments, the current collector can also be a dense film layer or a porous film layer. In the embodiments, the current collector can be, but is not limited to, aluminum foil or porous aluminum foil.

[0204] In the embodiments of this application, the positive electrode active material layer contained in the positive electrode may be at least stacked on the surface of the current collector. When the surface layer of the current collector has a porous structure or the current collector itself has a porous structure, the positive electrode active material layer may be at least partially embedded in the current collector.

[0205] In some embodiments, the positive electrode active material layer is at least bonded to the surface of the current collector, and may be as follows: Figure 3 In the structure shown, the positive electrode active material layer 12 is stacked on one surface of the current collector 11. When the surface of the current collector 11 has a porous structure or the current collector 11 as a whole has a porous structure, the positive electrode active material layer 12 can extend further into the porous structure of the current collector 11 in addition to being stacked on the surface of the current collector 11.

[0206] In other embodiments, the positive electrode active material layer is at least bonded to the surface of the current collector, and may be as follows: Figure 4 The structure shown has a current collector 11 with two opposing surfaces, and the positive electrode active material layer 12 is stacked on the two opposing surfaces of the current collector 11. When at least one of the two surfaces of the current collector 11 has a porous structure or the current collector 11 as a whole is a porous structure, the positive electrode active material layer 12 can extend further into the porous structure of the current collector 11 in addition to being stacked on the two surfaces of the current collector 11.

[0207] As an embodiment of this application, in the above-mentioned positive electrode active material layer, the mass content of the layered oxide of chemical formula (Ⅰ) contained in the positive electrode material of the above-mentioned embodiment of this application can be 90% to 98%, optionally 92% to 96%, and in exemplary examples, it can be typical but non-limiting contents such as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or any range between two contents. The layered oxide in this content range can effectively improve the specific capacity of the positive electrode, thereby improving the energy density of the battery, and has good cycle performance. Since the layered oxide also has good processing performance, it also effectively improves the film quality of the positive electrode active material layer.

[0208] The positive electrode active material layer of the positive electrode of each of the above embodiments generally includes, in addition to the positive electrode active material component described above, a binder, a conductive agent, and the like. The binder can enhance the mechanical properties of 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.

[0209] In the embodiments, the mass content of the binder included in the positive electrode active material layer can be 0.5% to 5%, optionally 1% to 3%, and in exemplary embodiments, can be 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, and the like, or a range between any two of the content values.

[0210] In the embodiments, the binder can include one or more of an oil-soluble binder, a water-soluble binder, an emulsion-type binder, and the like. In exemplary embodiments, the oil-soluble binder can include one or more of polyvinylidene fluoride, polyimide, polytetrafluoroethylene, polybutyl acrylate, polyacrylonitrile, and the like; in exemplary embodiments, the water-soluble binder can include one or more of carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylic acid salt, polyvinyl alcohol, sodium alginate, cyclodextrin, and the like; and in exemplary embodiments, the emulsion-type binder includes one or more of styrene-butadiene rubber, vinyl acetate resin, acrylic resin, chlorinated rubber, and the like.

[0211] The range of content and the types of binder described above 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.

[0212] In the embodiments, the mass content of the conductive agent included in the positive electrode active material layer can be 0.5% to 5%, optionally 1% to 3%, and in exemplary embodiments, can be 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, and the like, or a range between any two of the content values.

[0213] In the embodiments, the conductive agent can include at least one of a particulate conductive agent, a linear conductive agent, and the like. The particulate conductive agent can include one or more of acetylene black (SP), conductive carbon black (super-P), Ketjen black, graphene, and the like. The linear conductive agent can include one or more of carbon nanotubes, carbon fibers, conductive oxide nanowires, and the like. The particulate conductive agent is a non-linear, particulate morphology conductive agent relative to the linear conductive agent. The linear conductive agent refers to a one-dimensional fiber morphology conductive agent.

[0214] The range of content and the types of conductive agent described above can effectively improve the conductivity of the positive electrode active material layer.

[0215] In the embodiments, the conductive agent contained in the positive electrode active material layer in the positive electrode of the above embodiments includes linear conductive agents and particulate conductive agents. The mass content of the linear conductive agent in the positive electrode active material layer is 0.1% to 2.5%, optionally 0.2% to 0.8%. In exemplary examples, it can be a typical but non-limiting content or a range between any two content values, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, and 2.5%. Since the layered oxide crystals of chemical formula (Ⅰ) contained in the cathode material of the above-described embodiments include single crystals, and these single crystals have a flattened morphology, adding a linear conductive agent to the cathode active material layer and controlling the content of the linear conductive agent within this range allows the linear conductive agent to form a rich conductive network structure in the cathode active material layer, and the linear conductive agent can also be wrapped around the surface of the flattened single crystal particles. The particulate conductive agent can be effectively dispersed in the gaps of the cathode material. In this way, the linear conductive agent constructs a long-range conductive network structure in the cathode active material layer, and the particulate conductive agent constitutes a short-range conductive structure. Therefore, the conductivity enhancement effect played by the linear conductive agent and the particulate conductive agent in the cathode active material layer effectively improves the conductivity of the cathode active material layer and can significantly reduce the internal resistance of the cathode.

[0216] In the embodiments, the aspect ratio of the linear conductive agent can be selected from 40 to 3000:1, or from 50 to 2500:1. In exemplary cases, typical but non-limiting aspect ratios such as 40:1, 50:1, 100:1, 500:1, 1000:1, 1500:1, 2000:1, 2500:1, and 3000:1, or any range between two aspect ratios, can be used. This aspect ratio refers to the ratio of the length to the diameter of the linear conductive agent.

[0217] In a further embodiment, the length of the linear conductive agent can be selected to be 0.5 to 5 μm, or 0.5 to 2 μm. In the example, typical but non-limiting lengths such as 0.5 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm, or any range between two length values, can be used.

[0218] In a further embodiment, the diameter of the linear conductive agent can be selected to be 2 to 10 nm, or 3 to 7 nm. In the example, typical but non-limiting diameters such as 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm, or any range between two diameter values, can be used.

[0219] By selecting the aspect ratio of the linear conductive agent in the above range, or further selecting the length and diameter of the linear conductive agent in the above range, the linear conductive agent can construct a more abundant 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, so as to further improve the conductivity of the positive electrode active material layer.

[0220] In the embodiments, the positive electrode active material layer in the positive electrode of each of the above embodiments can further contain other additives in addition to the components such as the positive electrode active material, the binder, and the conductive agent.

[0221] In some embodiments, the content of the positive electrode active material layer on the single side of the current collector in each of the above embodiments, i.e., the coating weight (CW) is 260-350 mg / 1540.25 mm 2 , and can be 280-320 mg / 1540.25 mm 2 , and in exemplary examples, can be 260 mg / 1540.25 mm 2 , 270 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm 2 , 290 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 , 310 mg / 1540.25 mm 2 , 320 mg / 1540.25 mm 2 , 330 mg / 1540.25 mm 2 , 340 mg / 1540.25 mm 2 , 350 mg / 1540.25 mm 2 , or a range between any two content values. The coating weight refers to the weight of the positive electrode active material layer per unit area. The coating weight in the range can effectively improve the gram capacity of the positive electrode and thus improve the energy density of the battery.

[0222] In some embodiments, the compaction density of the positive electrode active material layer in each of the above embodiments can be 2.8-3.4 g / cm 3 , and can be 2.9-3.2 g / cm 3 , and in exemplary examples, can be 2.8 g / cm 3 , 2.9 g / cm 3 , 3.0 g / cm 3 , 3.1 g / cm 3 , 3.2 g / cm 3 , 3.3 g / cm 3 , 3.4 g / cm3 Some embodiments, the porosity of the positive electrode active material layer in each of the above embodiments can be 40% to 65%, optionally 45% to 60%, and in exemplary embodiments, can be 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 63%, 65%, and the like, typical but non-limiting porosities or ranges between any two of the porosities. The porosity refers to the total volume of the pores contained in the positive electrode active material layer per unit volume and the percentage of the positive electrode active material layer per unit volume. The range of porosity can make the positive electrode active material layer have the above-mentioned compacted density, increase the gram capacity of the positive electrode, thereby increasing the energy density of the battery, and improve the wettability of the electrolyte.

[0223] Some embodiments, the porosity of the positive electrode active material layer in each of the above embodiments can be 40% to 65%, optionally 45% to 60%, and in exemplary embodiments, can be 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 63%, 65%, and the like, typical but non-limiting porosities or ranges between any two of the porosities. The porosity refers to the total volume of the pores contained in the positive electrode active material layer per unit volume and the percentage of the positive electrode active material layer per unit volume. The range of porosity can make the positive electrode active material layer have the above-mentioned compacted density, increase the gram capacity of the positive electrode, thereby increasing the energy density of the battery, and improve the wettability of the electrolyte.

[0224] Some embodiments, the porosity of the positive electrode active material layer in each of the above embodiments can be 40% to 65%, optionally 45% to 60%, and in exemplary embodiments, can be 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 63%, 65%, and the like, typical but non-limiting porosities or ranges between any two of the porosities. The porosity refers to the total volume of the pores contained in the positive electrode active material layer per unit volume and the percentage of the positive electrode active material layer per unit volume. The range of porosity can make the positive electrode active material layer have the above-mentioned compacted density, increase the gram capacity of the positive electrode, thereby increasing the energy density of the battery, and improve the wettability of the electrolyte.

[0225] Some embodiments, the porosity of the positive electrode active material layer in each of the above embodiments can be 40% to 65%, optionally 45% to 60%, and in exemplary embodiments, can be 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 63%, 65%, and the like, typical but non-limiting porosities or ranges between any two of the porosities. The porosity refers to the total volume of the pores contained in the positive electrode active material layer per unit volume and the percentage of the positive electrode active material layer per unit volume. The range of porosity can make the positive electrode active material layer have the above-mentioned compacted density, increase the gram capacity of the positive electrode, thereby increasing the energy density of the battery, and improve the wettability of the electrolyte. Figure 3 The thickness of the electrode sheet from one surface to the opposite surface refers to the thickness of the positive electrode active material layer plus the thickness of the current collector when the positive electrode active material layer is disposed on one surface of the current collector as shown in FIG. 1. Figure 4 The thickness of the electrode sheet from one surface to the opposite surface refers to the thickness of the positive electrode active material layer plus the thickness of the current collector when the positive electrode active material layer is disposed on one surface of the current collector as shown in FIG. 1. The thickness of the electrode sheet from one surface to the opposite surface refers to the thickness of the positive electrode active material layer plus the thickness of the current collector when the positive electrode active material layer is disposed on one surface of the current collector as shown in FIG. 1.

[0226] In embodiments, the thickness of the positive electrode active material layer contained in the pole piece can be controlled to be 104-182 μm, further to be 110-170 μm, and in exemplary embodiments, can be 104 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 182 μm, and the like typical but non-limiting thicknesses or ranges between any two thickness values. In embodiments, the thickness of the current collector can be, but is not limited to, 13 μm.

[0227] By controlling the total thickness of the pole piece and the thickness of the current collector to be within the above ratio range or specific thickness range, the gram capacity of the pole piece can be effectively improved to increase the energy density of the battery, and the bonding strength between the positive electrode active material layer and the current collector can be improved, the mechanical strength of the pole piece structure can be improved, and the cycle performance of the pole piece can be improved.

[0228] Preparation method of the positive electrode:

[0229] The embodiments of the present application also provide a preparation method of the above-mentioned positive electrode. In some embodiments, the preparation method of the above-mentioned positive electrode comprises the following steps:

[0230] S30: mixing and processing the components including the positive electrode active material, the binder, the conductive agent, and the like in the solvent in proportion to prepare a positive electrode slurry;

[0231] S40: forming a film of the positive electrode slurry on the current collector to form a positive electrode active material layer to obtain a positive electrode.

[0232] Step S30:

[0233] The positive electrode active material in step S30 includes the positive electrode material of the above-mentioned embodiments, and specifically includes the layered oxide represented by the chemical formula (I).

[0234] The positive electrode active material, the binder, the conductive agent, and the like in step S30 can be mixed and processed according to the content proportion of the corresponding components contained in the positive electrode active material layer of the above-mentioned positive electrode. The solvent can be selected from organic solvents or water suitable for preparing the positive electrode slurry.

[0235] The mixing and processing in step S30 can be mixed and processed according to the preparation method of the conventional electrode slurry, such as but not limited to stirring processing, until the components are uniformly 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 to form a positive electrode active material layer meeting the quality requirements on the current collector.

[0236] Step S40:

[0237] Based on the positive electrode slurry component 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 application example above.

[0238] The film formation treatment of the positive electrode slurry on the current collector in step S40 can be carried out according to the method for forming a conventional positive electrode active material layer. As in the example, it can be that the electrode slurry is first formed into a wet film on the current collector; then drying treatment is carried out to volatilize the solvent, so that the wet film is dried; and then the dried film layer is subjected to rolling treatment to form a positive electrode active material layer, thereby obtaining a positive electrode.

[0239] Of course, the positive electrode active material layer can also be prepared by a method improved from the conventional method for preparing a positive electrode active material layer, or by a new method. As long as the electrode slurry in step S30 is used to prepare a positive electrode active material layer on a current collector, it is within the scope disclosed in the specification of the application example.

[0240] In addition, the film formation treatment conditions in S40 can be controlled and adjusted, such as the conditions for forming a wet film of the positive electrode slurry prepared in step S30 on the current collector, the conditions for rolling treatment, etc., so as to control and adjust the related properties of the positive electrode active material layer formed, such as controlling and adjusting the content of the positive electrode active material layer on one side of the current collector to the range of 260-350 mg / 1540.25 mm 2 as above, controlling and adjusting the compaction density to the range of 2.8-3.4 g / cm 3 as above, controlling and adjusting the porosity to the range of 40%-65% as above, controlling and adjusting the sheet resistance of the electrode tab to the range of 0.5-5 mΩ as above, etc.

[0241] Battery

[0242] In a fourth aspect, the application example also provides a sodium battery.

[0243] In the example, the sodium battery of the application example can include any one of a sodium battery monomer, a battery module, and a battery pack.

[0244] Sodium battery monomer:

[0245] The sodium battery monomer, also known as a sodium battery cell, refers to a battery outer package and an electrode assembly packaged in the battery outer package. The number of electrode assemblies contained in the battery monomer can be one or more, which can be adjusted according to actual needs.

[0246] The outer package of the sodium battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. or a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as polypropylene, polybutylene terephthalate, polybutylene succinate, etc. The outer package can be in a cylindrical shape, a square shape, or any other shape. The outer package determines the shape of the sodium battery cell, and thus, the sodium battery cell can also be in a cylindrical shape, a square shape, or any other shape corresponding to the shape of the outer package. In an exemplary embodiment, the sodium battery cell can be a square-shaped battery cell 20 as shown in FIG. 1. Figure 5

[0247] In some embodiments, as shown in FIG. 2, the outer package of the battery cell 20 can include a shell 21 and a cover plate 23. The shell 21 can include a bottom plate and side plates connected to the bottom plate, which enclose a receiving cavity. The shell 21 has an opening communicating with the receiving cavity, and the cover plate 23 is used to cover the opening to seal the receiving cavity. One or more electrode assemblies 22 are encapsulated in the receiving cavity. Figure 6

[0248] In an embodiment, the sodium battery cell can be a sodium battery cell containing electrolyte or a sodium battery cell containing solid-state electrolyte.

[0249] When the sodium battery cell contains electrolyte, the electrode assembly contained in the sodium battery cell generally includes a positive electrode, a negative electrode, and a separator. The positive electrode and the negative electrode are alternately stacked, and the separator is stacked between the positive electrode and the negative electrode to play a separating role and separate the positive electrode and the negative electrode. The positive electrode, the separator layer, and the negative electrode can form a laminated structure of the electrode assembly through a lamination process, or form a roll core structure of the electrode assembly through a winding process. The electrode assembly containing the separator is placed in the outer package, electrolyte is injected and infiltrates the electrode assembly, and the sodium battery cell is obtained after encapsulation.

[0250] When the sodium battery cell contains solid-state electrolyte, the electrode assembly contained in the sodium battery cell generally includes a positive electrode, a negative electrode, and a solid-state electrolyte. The positive electrode and the negative electrode are alternately stacked, and the solid-state electrolyte is stacked between the positive electrode and the negative electrode to play a separating role and separate the positive electrode and the negative electrode. The electrode assembly containing the solid-state electrolyte is placed in the outer package, and the sodium battery cell is obtained after encapsulation.

[0251] In each of the above sodium battery cells, the positive electrode contained in the electrode assembly is the positive electrode of the above embodiment, i.e., contains the positive electrode material of the above embodiment in the positive electrode active material layer, specifically contains the layered oxide represented by Formula (I) above.

[0252] In this way, the sodium battery cell has high energy density and good cycle performance.

[0253] ​​As detected in the examples, the energy density of the sodium battery cell can reach 110-160 Wh / kg, optionally 120-155 Wh / kg. The capacity retention rate at 1000 cycles under 0.5C / 1C charge-discharge conditions in the range of 1.5-4.05 V can reach 70-95%, optionally 80-90%.

[0254] In each of the above 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, the negative electrode active material layer containing a negative electrode active material. In the examples, the negative electrode current collector can include but is not limited to a metal or a composite current collector. For example, as the metal, sodium, sodium alloy, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc. can be used. In the case of using sodium or sodium alloy as the negative electrode current collector, since sodium or sodium alloy itself can also serve as the negative electrode active material, the negative electrode tab can not contain the negative electrode active material layer, and sodium or sodium alloy is both the current collector and the negative electrode active material.

[0255] The composite current collector can include a composite of a polymer material and a metal, wherein the polymer material can include but is not limited to polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc., and the metal can include but is not limited to sodium, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy. The composite current collector can be obtained by mixing the polymer material and the metal with each other, or by plating, coating or other means to cover at least one side of the polymer material.

[0256] When the negative electrode includes the negative electrode active material layer, the negative electrode active material in the negative electrode active material layer can include but is not limited to a mixed or composite material formed by any one or more of a carbon-based material, an alloy material, a titanium-based material, and sodium metal. The carbon-based material includes but is not limited to one or more of graphite, soft carbon, hard carbon, carbon microspheres, and carbon fibers; the alloy material includes but is not limited to one or more of sodium-tin alloy, sodium-germanium alloy, and sodium-antimony alloy; the titanium-based material includes but is not limited to one or more of titanium dioxide, titanate, and titanium phosphate.

[0257] The mass content of the negative electrode active material in the negative electrode active material layer can be 85%-98%, optionally 95%-98%, and in the examples, can be 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, etc. typical but non-limiting contents or ranges between any two content values.

[0258] The negative active material layer can further include at least one of a conductive agent and a binder. The conductive agent serves to collect electric current between the negative active materials and between the active material and the current collector, improving electronic conductivity, while the conductive agent can also facilitate impregnation of the electrolyte into the negative electrode sheet. The binder can improve the binding strength between the substances in the negative active material layer and between the active layer and the current collector.

[0259] In an embodiment, the conductive agent can have a mass content of 0.5% to 10% in the negative active material layer. In an exemplary embodiment, the conductive agent can have a mass content of 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two of the above values, or any other value as needed. In an exemplary embodiment, the conductive agent includes one or more of acetylene black (SP), carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fibers, and graphene.

[0260] In an embodiment, the binder can have a mass content of 0.5% to 10% in the negative active material layer. In an exemplary embodiment, the binder can have a mass content of 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two of the above values, or any other value as needed. In an exemplary embodiment, the binder includes one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyimide, polytetrafluoroethylene, polybutyl acrylate, polyacrylonitrile, carboxymethyl cellulose, carboxymethyl cellulose salt, polyacrylic acid, polyacrylic acid salt, polyvinyl alcohol, sodium alginate, cyclodextrin, styrene butadiene rubber, vinyl acetate resin, acrylic resin, and chlorinated rubber.

[0261] In an embodiment, the negative active material layer can further include a thickening agent, such as, but not limited to, carboxymethyl cellulose (CMC). The mass content of the thickening agent in the negative active layer can be set to 0.5% to 5%. In an exemplary embodiment, the mass content of the thickening agent can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range between any two of the above values, or any other value as needed.

[0262] In the embodiment, when each of the above sodium battery cells contains a separator, the separator is disposed between the positive electrode and the negative electrode to separate the positive electrode and the negative electrode, as described above. The separator can prevent the electrodes from being in contact with each other to prevent a short circuit, but can allow sodium ions in the electrolyte to pass freely between the positive electrode and the negative electrode. The separator can be any porous separator known to have electrochemical stability and mechanical stability, and in an exemplary embodiment, the separator includes a single layer or multiple layers of at least one of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF).

[0263] In the embodiment, when each of the above sodium battery cells contains a solid-state electrolyte, the solid-state electrolyte is disposed between the positive electrode and the negative electrode to separate the positive electrode and the negative electrode, as described above. The solid-state electrolyte can include at least one of a polymer solid-state electrolyte, an oxide electrolyte, a sulfide electrolyte, a borohydride electrolyte, and a composite solid-state electrolyte.

[0264] Battery module:

[0265] When the sodium battery of the embodiment is a battery module, the battery module refers to a module assembled from the above sodium battery cells, i.e., can contain a plurality of the above sodium battery cells, and the number of the sodium battery cells can be adjusted according to the application and capacity of the battery module.

[0266] In some embodiments, Figure 7 is a schematic view of a battery module 30 as an example. As shown in Figure 7 In the battery module 30, a plurality of sodium battery cells 20 can be arranged in sequence along the length direction of the battery module 30. Of course, the sodium battery cells 20 can also be arranged in any other manner. Further, the plurality of sodium battery cells 20 can be fixed by fasteners.

[0267] Optionally, the battery module 30 can further include a housing having an accommodation space, and the plurality of sodium battery cells 20 are accommodated in the accommodation space.

[0268] Battery pack:

[0269] When the sodium battery of the embodiment is a battery pack, the battery pack refers to a pack assembled from the above sodium battery cells, i.e., can contain a plurality of sodium battery cells, and the plurality of sodium battery cells are assembled into the above battery module. The number of the sodium battery cells or the battery module contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0270] In some embodiments, Figure 8 and Figure 9is a schematic diagram of a battery pack 40 as an example. In the battery pack 40, a battery case and a plurality of battery modules 30 disposed in the battery case can be included. The battery case includes an upper case 41 for covering a lower case 42 and forms an enclosed space for accommodating the battery modules 30. The plurality of battery modules 30 can be arranged in the battery case in any manner.

[0271] Electric device

[0272] In a fifth aspect, the embodiments of the present application further 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 can also include other auxiliary components or necessary components. The power supply unit or the energy storage unit contains the sodium battery of the embodiments of the present application. It can be the sodium battery cell, the battery module or the battery pack of the embodiments of the present application. Since the electric device of the embodiments of the present application contains the sodium battery of the embodiments of the present application, the power supply unit or the 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 long standby or endurance time of the electric device of the embodiments of the present application.

[0273] In the embodiments, the electric device can include but is not limited to a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric car, a ship, a spacecraft, etc. The electric toy can include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, an electric plane toy, etc. The spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, etc. As the electric device, the battery cell, the battery module or the battery pack in the battery can be selected according to the use requirement of the electric device.

[0274] Figure 10 is a schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the electric device, the battery pack or the battery module can be used.

[0275] In the embodiments, when the electric device contains an energy storage unit, the electric device can be an energy storage device. The energy storage device includes an energy storage unit, and of course can also include other auxiliary components or necessary components. The energy storage unit contains the battery of the embodiments of the present application. The battery contained in the energy storage unit can be one or more. When there are a plurality of batteries, the plurality of batteries can form a battery module or a battery pack. Since the energy storage device of the embodiments of the present application contains the battery of the embodiments of the present application, the energy storage device has high energy density, good cycle performance, long service life, and further high energy density.

[0276] Embodiments

[0277] Hereinafter, the examples of the present application will be described. The examples described below are illustrative and are intended to explain the present application, and are not to be understood as limiting the present application. In the examples, unless a specific technique or condition is mentioned, the technique or condition described in the literature in the art or according to the product manual is used. Unless the manufacturer is mentioned, the reagent or instrument used is a general product available on the market.

[0278] 1. Positive electrode material and method for producing the same

[0279] Example A1

[0280] The present example provides a positive electrode material and a method for producing the same. The positive electrode material includes a layered oxide of the chemical formula Na 0.89 Ni 0.23 Mn 0.45 Fe 0.3 Zn 0.02 O2.

[0281] The method for producing the positive electrode material includes the following steps:

[0282] S1: NiO, ZnO, Mn2O3, Fe2O3 are ball-milled at a rotation speed of 500 rpm for 6 hours according to the molar ratio of the metal elements contained in Na 0.89 Ni 0.23 Mn 0.45 Fe 0.3 Zn 0.02 O2, and then mixed with excess sodium carbonate in proportion to obtain a precursor;

[0283] S2: The precursor is sintered in a muffle furnace, and then crushed to obtain a layered oxide of Na 0.89 Ni 0.23 Mn 0.45 Fe 0.3 Zn 0.02 O2; wherein the sintering conditions are: temperature: 850°C; time: 12h; heating rate: 5°C / min; oxygen atmosphere.

[0284] Example A2

[0285] The present example provides a positive electrode material and a method for producing the same. The positive electrode material includes a layered oxide of the chemical formula Na 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 O2.

[0286] The method for producing the positive electrode material includes the following steps:

[0287] S1: NiO, ZnO, Mn2O3, Fe2O3 are ball-milled at a rotation speed of 500 rpm for 6 hours according to the molar ratio of the metal elements contained in Na 0.89Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 O2 of the precursor is Na

[0288] S2: sintering the precursor in a muffle furnace, and crushing to obtain a Na 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 O2 layered oxide; wherein the sintering condition is: temperature: 860°C; time: 12h; heating rate: 5°C / min; oxygen atmosphere.

[0289] Example A3

[0290] The present embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cu 0.02 O2.

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

[0292] S1: according to the molar ratio of metal elements contained in Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cu 0.02 O2, NiO, ZnO, Mn2O3, Fe2O3 and CuO are ball milled at 500 rpm for 6 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain a precursor;

[0293] S2: sintering the precursor in a muffle furnace, and crushing to obtain a Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cu 0.02 O2 layered oxide; wherein the sintering condition is: temperature: 865°C; time: 12h; heating rate: 5°C / min; oxygen atmosphere.

[0294] Example A4

[0295] The embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide with a chemical formula of Na 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 O2.

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

[0297] S1: according to the molar ratio of metal elements contained in Na 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 O2, NiO, ZnO, Mn2O3 and Fe2O3 are subjected to ball milling treatment at a rotating speed of 500 revolutions per minute for 6 hours, and then sodium carbonate is added in proportion to be mixed to obtain a precursor;

[0298] S2: the precursor is subjected to sintering treatment in a muffle furnace, and is crushed to obtain a layered oxide of Na 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 O2; wherein the sintering treatment condition is as follows: temperature: 865 DEG C; time: 12h; temperature rising rate: 5 DEG C / min; oxygen atmosphere.

[0299] Example A5

[0300] The embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide with a chemical formula of Na 0.89 Ni 0.23 Mn 0.41 Fe 0.3 Zn 0.06 O2.

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

[0302] S1: according to the molar ratio of metal elements contained in Na 0.89 Ni 0.23 Mn 0.41 Fe 0.3 Zn 0.06 O2, NiO, ZnO, Mn2O3 and Fe2O3 are subjected to ball milling treatment at a rotating speed of 500 revolutions per minute for 6 hours, and then sodium carbonate is added in proportion to be mixed to obtain a precursor;

[0303] S2: the precursor is subjected to sintering treatment in a muffle furnace, and is crushed to obtain a layered oxide of Na 0.89 Ni 0.23 Mn0.41 Fe 0.3 Zn 0.06 O2 of the layered oxide; wherein the sintering treatment is at a temperature of 865°C, for a time of 12h, at a heating rate of 5°C / min, in an oxygen atmosphere.

[0304] Example A6

[0305] The present example provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide of Na 0.89 Ni 0.23 Mn 0.42 Fe 0.285 Zn 0.065 O2.

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

[0307] S1: according to the molar ratio of the metal elements contained in Na 0.89 Ni 0.23 Mn 0.42 Fe 0.285 Zn 0.065 O2, NiO, ZnO, Mn2O3 and Fe2O3 are ball milled at a speed of 500 revolutions per minute for 6 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain a precursor;

[0308] S2: the precursor is subjected to sintering treatment in a muffle furnace, and is crushed to obtain a layered oxide of Na 0.89 Ni 0.23 Mn 0.42 Fe 0.285 Zn 0.065 O2; wherein the sintering treatment is at a temperature of 865°C, for a time of 12h, at a heating rate of 5°C / min, in an oxygen atmosphere.

[0309] Example A7

[0310] The present example provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide of Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 O2.

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

[0312] S1: according to the molar ratio of the metal elements contained in Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07S1: according to the molar ratio of metal elements contained in Na

[0313] S2: the precursor is subjected to sintering treatment in a muffle furnace, and is crushed to obtain Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 O2layered oxide; wherein the sintering treatment is performed at a temperature of 880 ℃ for 12 h at a heating rate of 5 ℃ / min in an oxygen atmosphere.

[0314] Example A8

[0315] The embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide of Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2.

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

[0317] S1: according to the molar ratio of metal elements contained in Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2, NiO, ZnO, Mn2O3 and Fe2O3 are subjected to ball milling treatment at a rotating speed of 500 r / min for 6 h, and then sodium carbonate is added in proportion to be mixed to obtain a precursor;

[0318] S2: the precursor is subjected to sintering treatment in a muffle furnace, and is crushed to obtain Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2layered oxide; wherein the sintering treatment is performed at a temperature of 880 ℃ for 12 h at a heating rate of 5 ℃ / min in an oxygen atmosphere.

[0319] Example A9

[0320] The embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide of Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2.

[0321] The positive electrode material preparation method comprises the following steps:

[0322] S1: according to Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2The molar ratio of the metal elements contained in the nickel nitrate, zinc nitrate, manganese nitrate and iron nitrate is fully dissolved to prepare a mixed solution; then a sufficient amount of ammonium carbonate is added to the mixed solution for co-precipitation treatment to obtain a precipitate mixture;

[0323] S2: according to Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2The molar content of sodium element, the precipitate mixture is mixed with sodium carbonate to obtain Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2The precursor.

[0324] S3: the Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2The precursor is sintered in a muffle furnace, crushed to obtain Na 0.9 Ni 0.23 Mn 0.4 Fe 0.3 Zn 0.075 O2Layered oxide; wherein the sintering conditions are: temperature: 850℃; time: 14h; heating rate: 5℃ / min; oxygen atmosphere.

[0325] Example A10

[0326] The embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide with a chemical formula of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Al 0.02 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 Fe0.28 Zn 0.04 Al 0.02 O2so as to obtain a precursor;

[0329] S2: sintering the precursor in a muffle furnace, and crushing to obtain a Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Al 0.02 O2layered oxide; wherein the sintering condition is: temperature: 850°C; time: 12h; heating rate: 5°C / min; oxygen atmosphere.

[0330] Example A11

[0331] The present embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 O2.

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

[0333] S1: according to the molar ratio of metal elements contained in Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 O2, NiO, ZnO, Mn2O3 and SnO2 are ball milled at a speed of 500 rpm for 6 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain a precursor;

[0334] S2: sintering the precursor in a muffle furnace, and crushing to obtain a Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 O2layered oxide; wherein the sintering condition is: temperature: 850°C; time: 12h; heating rate: 5°C / min; oxygen atmosphere.

[0335] Example A12

[0336] The embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ti 0.02 O2.

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

[0338] S1: according to the molar ratio of metal elements contained in Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ti 0.02 O2, NiO, ZnO, Mn2O3 and TiO2 are subjected to ball milling treatment under a rotating speed of 500 revolutions per minute for 6 hours, and then sodium carbonate is added in proportion to be mixed to obtain a precursor;

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

[0340] Example A13

[0341] The embodiment provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Mg 0.02 O2.

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

[0343] S1: according to the molar ratio of metal elements contained in Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Mg 0.02 O2, NiO, ZnO, Mn2O3 and MgO are subjected to ball milling treatment under a rotating speed of 500 revolutions per minute for 6 hours, and then sodium carbonate is added in proportion to be mixed to obtain a precursor;

[0344] S2: the precursor is sintered in a muffle furnace, and is 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 is at a temperature of 850°C for 12 hours at a heating rate of 5°C / min in an oxygen atmosphere.

[0345] Example A14

[0346] The present example provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O2.

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

[0348] S1: according to the molar ratio of metal elements contained in Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O2, NiO, ZnO, Mn2O3 and IrO2 are ball milled at a speed of 500 revolutions per minute for 6 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain a precursor;

[0349] S2: the precursor is sintered in a muffle furnace, and is 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 is at a temperature of 850°C for 12 hours at a heating rate of 5°C / min in an oxygen atmosphere.

[0350] Example A15

[0351] The present example provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O 1.8 .

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

[0353] 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 contained metal elements is used to ball mill NiO, ZnO, Mn2O3 and IrO2 at a rotating speed of 500 revolutions per minute for 6 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain a precursor;

[0354] S2: the precursor is sintered in a muffle furnace, and is crushed to obtain a layered oxide of Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Ir 0.02 O 1.8 , wherein the sintering treatment conditions are: temperature: 700 DEG C; time: 20h; heating rate: 15 DEG C / min; oxygen atmosphere.

[0355] Comparative Example A1

[0356] The present comparative example provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide of chemical formula Na 0.92 Ni 0.33 Mn 0.33 Fe 0.33 Zn 0.01 O2.

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

[0358] S1: according to Na 0.92 Ni 0.33 Mn 0.33 Fe 0.33 Zn 0.01 O2, the molar ratio of the contained metal elements is used to ball mill NiO, ZnO, Mn2O3 and Fe2O3 at a rotating speed of 500 revolutions per minute for 6 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain a precursor;

[0359] S2: the precursor is sintered in a muffle furnace, and is crushed to obtain a layered oxide of Na 0.92 Ni 0.33 Mn 0.33 Fe 0.33 Zn 0.01A layered oxide of Na

[0360] Comparative Example A2

[0361] The present comparative example provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide of Na 0.92 Ni 0.25 Mn 0.33 Fe 0.33 Zn 0.08 O2.

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

[0363] S1: according to the molar ratio of metal elements contained in Na 0.92 Ni 0.25 Mn 0.33 Fe 0.33 Zn 0.08 O2, NiO, ZnO, Mn2O3 and Fe2O3 are ball milled at a speed of 500 revolutions per minute for 6 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain a precursor;

[0364] S2: the precursor is sintered in a muffle furnace, and then crushed to obtain a layered oxide of Na 0.92 Ni 0.25 Mn 0.33 Fe 0.33 Zn 0.08 O2; wherein the sintering treatment conditions are: temperature: 900°C; time: 12h; heating rate: 5°C / min; oxygen atmosphere.

[0365] Comparative Example A3

[0366] The present comparative example provides a positive electrode material and a preparation method thereof. The positive electrode material comprises a layered oxide of Na 0.94 Ni 0.33 Mn 0.33 Fe 0.33 O2.

[0367] The preparation method of the positive electrode material comprises the following steps:

[0368] S1: according to the molar ratio of metal elements contained in Na 0.94 Ni 0.33 Mn 0.33 Fe 0.33 O2, NiO, Mn2O3 and Fe2O3 are ball milled at a speed of 500 revolutions per minute for 6 hours, and then sodium carbonate is added in proportion for mixing treatment to obtain a precursor;

[0369] S2: sintering the precursor in a muffle furnace, crushing, to obtain Na 0.92 Ni 0.25 Mn 0.33 Fe 0.33 O2 layered oxide; wherein the sintering treatment condition is: temperature: 900℃; time: 12h; heating rate: 5℃ / min; oxygen atmosphere.

[0370] Characterization of layered oxide and related performance test in each embodiment:

[0371] The layered oxide provided in the above embodiments A1 to A15 and comparative examples A1 to A3 is respectively subjected to the following related characteristic detection in Table 1 below according to the following method, and the results of the detection are shown in Table 1:

[0372] Layered oxide element content detection method: inductively coupled plasma emission spectrum (ICP) is obtained by using Agilent ICP-OES730, and then the ICP result is used to calculate the content of each metal element, and the mass percentage content ratio of each component is calculated.

[0373] Single crystal morphology detection method: scanning electron microscope (SEM) of the layered oxide provided in each embodiment is measured by using GB / T 16594-1996 micron level length scanning electron microscope. The electron microscope graph of the layered oxide provided in embodiment A6 is shown in Figure 1 .

[0374] Crystal phase characterization method: the layered oxide is analyzed by using XRD diffractometer with a scanning speed of 0.5℃ / min.

[0375] Dv50 detection method: the layered oxide is detected according to the method steps in GB / T16418.

[0376] BET specific surface detection method: the specific surface of the layered oxide is detected according to the method steps in GB / T19587-2017.

[0377] Compacted density detection method: the test method is detected according to GB / T24533-2019 standard test method, and the specific test steps can be referred to as follows:

[0378] (1) wipe the upper and lower gaskets, top column and metal cylindrical sleeve of the compacted density instrument with a clean soft cloth (towel), and if necessary, wipe with soft cloth dipped in anhydrous ethanol and dry in the air;

[0379] (2) place the gaskets, top column, metal cylindrical sleeve and pad according to the order of testing, and place them on the digital thickness gauge, and press the zero key;

[0380] (3) Remove the top column and the upper gasket, weigh 1 g of the sample in the sleeve to the nearest 0.0001 g, and record the weight as m;

[0381] (4) Slowly slide the gasket and the top column out of the hole, respectively, and install them together with the pad on the compaction density instrument, and tighten the pressure control knob;

[0382] (5) Shake the pressure column while observing the value on the digital pressure gauge on the compaction density instrument, and start the stopwatch after the value reaches the specified value 2200 Ib. Loosen the pressure control knob after 30 s, remove the pressure, and lower the pad to a certain height, and then tighten the pressure control knob again;

[0383] (6) Take out the top column, the sleeve, and the bottom sheet together with the pad, and place them on the digital thickness gauge, and read the value on the digital thickness gauge within 10 s, and record it as H;

[0384] r = 10m / (S x H);

[0385] Then, the powder compaction density r of the sample is calculated according to the formula r = 10m / (S x H).

[0386] wherein mm is the weight of the sample, in grams (g); HH is the thickness of the sample after compaction, in millimeters (mm); and SS is the cross-sectional area of the top column, in square centimeters (cm 2 ).

[0387] Charging / discharging gram capacity detection method: The charging / discharging gram capacity detection method of the layered oxide in the above application embodiment is used for detection.

[0388] Table 1

[0389]

[0390]

[0391] As can be seen from the detection results of the properties of the layered oxides provided in the above Table 1, the layered oxides provided in Examples A1 to A15 have similar crystal forms and particle sizes compared with the layered oxides in Comparative Examples A1 to A3, but the material compaction densities of the layered oxides in Examples A1 to A15 are slightly higher than those of the layered oxides in Comparative Examples A1 to A3. Further detection shows that the specific surface areas of the layered oxides provided in Examples A1 to A15 are 0.5-1.3 m 2 / g, and further 0.6-0.9 m 2The charge / discharge capacities of the layered oxides in Comparative Examples A2 to A3 are higher than those of the layered oxides in Examples Al to A15, but as will be appreciated from the data in Table 3 below, the cycle performance of the layered oxides in Comparative Examples A2 to A3 is significantly lower than that of the layered oxides in Examples Al to A15 due to the poor structural stability of the layered oxides in Comparative Examples A2 to A3.

[0392] 2. Positive electrode and sodium-ion battery cell examples

[0393] Examples Bl to B15

[0394] Examples Bl to B15

[0395] The sodium-ion battery cells in Examples Bl to B15 are assembled as follows:

[0396] Positive electrode sheet: sodium-ion positive electrode active material, conductive agent carbon nanotube, conductive agent carbon black, binder polyvinylidene fluoride (PVDF) are mixed 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 uniformly 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; wherein the sodium-ion positive electrode active material is the positive electrode material in Examples Al to A15, respectively, and the positive electrode material in Examples Al to A15 is prepared. In Example B15, the content of conductive agent carbon nanotube is 0 (the conductive agent is all conductive agent carbon black), that is, the conductive agent carbon nanotube in Example Bl is replaced by conductive agent carbon black, and compared with the positive electrode sheet in Example Bl, 0.5% of carbon nanotube conductive agent in Example Bl is replaced by conductive agent carbon black, but the total content of conductive agent contained in the positive electrode sheet of Example Bl is the same as that of Example Bl.

[0397] Negative electrode sheet: hard carbon, conductive agent SP, CMC binder are added to deionized water in a weight ratio of 8:1:1 to form a uniform negative electrode slurry; the negative electrode slurry is uniformly coated on the surface of a 6 μm copper foil, and after drying and cold pressing, a negative electrode sheet is obtained.

[0398] Electrolyte: In an environment with a water content of less than 10 ppm, non-aqueous organic solvent ethylene carbonate EC and diethyl carbonate DMC are mixed in a volume ratio of 1:1 to obtain an electrolyte solvent, and then sodium hexafluorophosphate is mixed with the mixed solvent to prepare an electrolyte with a sodium salt concentration of 1 mol / L.

[0399] Separator: a porous polyethylene (PE) film is used as a separator.

[0400] Battery assembly: The above positive electrode sheet, separator and negative electrode sheet are stacked in order respectively, with the separator between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and the electrode assembly is obtained through the stacking process. Each electrode assembly is placed in an outer package, dried, and then injected with electrolyte, and then subjected to vacuum packaging, standing, formation, shaping and other processes to obtain sodium-ion battery cells in Examples B1 to B10 respectively. Among them, the sodium-ion positive electrode active material contained in Example B1 is the positive electrode material in Example A1 described above, the sodium-ion positive electrode active material contained in Example B2 is the positive electrode material in Example A2 described above, and so on. The sodium-ion positive electrode active material contained in Example B15 is the positive electrode material in Example A15 described above.

[0401] Examples B16 to B24

[0402] Examples B16 to B24 each provide a sodium-ion battery cell, each of which includes an electrode assembly formed by a positive electrode sheet, a separator and a negative electrode sheet, and further includes an electrolyte.

[0403] Among them, the sodium-ion battery cells in Examples B16 to B24 are all prepared with reference to the sodium-ion battery cell in Example B3. The difference is that:

[0404] In the sodium-ion battery cells of Examples B16 to B18, the content (CW) of the positive electrode active material layer on the single side of the current collector of the positive electrode sheet of each sodium-ion battery cell is controlled as shown in Table 2.

[0405] In the sodium-ion battery cells of Examples B19 to B21, the compaction density of the positive electrode active material layer contained in the positive electrode sheet of each sodium-ion battery cell is controlled as shown in Table 2.

[0406] In the sodium-ion battery cells of Examples B22 to B23, the content of carbon nanotubes contained in the positive electrode sheet of each sodium-ion battery cell is controlled as shown in Table 2. Among them, the total content of conductive agents contained in the positive electrode sheet of Examples B22 to B23 is the same as the total content of conductive agents contained in the positive electrode sheet of Example B1.

[0407] 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% content of carbon fibers, as shown in Table 2. Among them, the total content of conductive agents contained in the positive electrode sheet of Example B24 is the same as the total content of conductive agents contained in the positive electrode sheet of Example B1.

[0408] Comparative Examples B1 to B3

[0409] The sodium-ion battery cell of Comparative Example B1 to Comparative Example B3 each provides a sodium-ion battery cell including an electrode assembly formed by a positive electrode sheet, a separator, and a negative electrode sheet, and further including an electrolyte.

[0410] In the sodium-ion battery cell of Comparative Example B1 to Comparative Example B3, the sodium-ion battery cell is prepared with reference to the sodium-ion battery cell of Example B1. The difference lies in that:

[0411] 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 of Comparative Example A1, as shown in Table 1.

[0412] 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 of Comparative Example A2, as shown in Table 1.

[0413] 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 of Comparative Example A3, as shown in Table 1.

[0414] Performance test of the positive electrode sheet contained in the sodium-ion battery cell of each example:

[0415] The positive electrode sheet contained in the sodium-ion battery cell provided in each of the above-mentioned Example B1 to Example B24 and Comparative Example B1 to Comparative Example B3 is subjected to the performance test in Table 2 below according to the following method, and the test results are shown in Table 2:

[0416] Positive electrode slurry gel test method: after the positive electrode slurry used to prepare the positive electrode sheet contained in the sodium-ion battery cell of each of the above-mentioned examples is placed at room temperature for 12 hours, the gelation of the positive electrode slurry is observed by naked eye.

[0417] CW detection method: the electrode sheet is punched into a 1540.25mm 2 electrode sheet by a punching machine, and the weight of the pure active material layer 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 .

[0418] Positive electrode sheet compaction density detection method: the positive electrode sheet compaction density can be specifically referred to the first discharge specific capacity and first charge-discharge efficiency test method of lithium-ion battery positive electrode material lithium manganate, which is detailed in GB / T 39864-2021 standard or GB / T42161-2022. The test steps of the following parameters can be specifically referred to:

[0419] The battery electrode sheet meeting the processability requirement is punched into a 14mm diameter positive electrode sheet by a punching machine, and an electronic balance and a table type digital thickness gauge are used to measure the mass m c, thickness d c ; a sufficient number of aluminum foil substrates with a diameter of 14 mm were punched out by a puncher, and the mass m Al , thickness d Al ; the positive electrode sheet compaction density was calculated according to the following formula:

[0420] Positive electrode sheet compaction density

[0421] Wherein: p c is the positive electrode sheet compaction density, in units of grams per cubic centimeter (g / cm 3 );

[0422] m c is the mass of the positive electrode sheet, in units of grams (g);

[0423] m Al is the mass of the aluminum foil substrate, in units of grams (g);

[0424] is the diameter of the positive electrode sheet, in units of millimeters (mm);

[0425] d c is the thickness of the positive electrode sheet, in units of microns (pm);

[0426] d Al is the thickness of the aluminum foil substrate, in units of microns (pm).

[0427] The charge and discharge gram capacities of the layered oxide and the initial efficiency were detected according to the aforementioned national standards: GB / T 39864-2021 standard or GB / T 42161-2022:

[0428] According to the battery treatment method in Section 7.4 of GB / T 39864-2021 standard or GB / T 42161-2022, the above assembled sodium ion button cell was placed in a constant temperature oven, the temperature was controlled at 23℃±2℃, and after standing for 2h to 12h, it was charged and discharged under the following conditions:

[0429] Charging: constant current charging to 3.75V at 0.1C rate, then constant voltage charging, constant voltage charging medium current 0.05C; Discharging: constant current discharging to 2.0V at 0.1C rate;

[0430] According to Section 7.5 of GB / T 39864-2021 standard or GB / T 42161-2022, the battery was charged and discharged according to Section 7.4 after the above assembled sodium ion button cell was cycled for one week, the charge and discharge capacities of the sodium ion button cell and the mass of the layered oxide in the sodium ion button cell were recorded, and the first discharge gram capacity and the first charge-discharge efficiency of the layered oxide were calculated.

[0431] wherein the initial discharge gram capacity is calculated according to the formula (4) in Section 8.1 of GB / T 39864-2021 standard or GB / T 42161-2022, and the initial charge-discharge efficiency is calculated according to the formula (5) in Section 8.2 of GB / T 39864-2021 standard or GB / T 42161-2022:

[0432] C = Q ID / m (4)

[0433] η = Q ID / Q IC x 100% (5)

[0434] In formula 4:

[0435] C - initial discharge gram capacity, unit: milliampere-hour per gram (mA.h / g);

[0436] Q ID - initial discharge gram capacity, unit: milliampere-hour per gram (mA.h / g);

[0437] m is the mass of the layered oxide in the tested sodium ion button cell, unit: gram (g);

[0438] In formula 5:

[0439] η - initial charge-discharge efficiency;

[0440] Q ID - initial discharge capacity, unit: milliampere-hour (mA.h);

[0441] Q IC - initial charge capacity, unit: milliampere-hour (mA.h).

[0442] The method for detecting the porosity of the pole piece is detected by the gas displacement method, and the specific reference is GB / T24586-2009. The specific steps of the method for detecting the porosity of the pole piece are as follows: the pole piece is immersed in methyl ethyl carbonate (EMC) for cleaning, and then the method specified in GB / T24586-2009 is used for testing. The gas displacement method, combined with the Archimedes principle and Boyle's law, is used to accurately measure the true volume of the measured material, i.e. the true volume of the sample, so as to obtain the porosity of the sample to be tested. The percentage of the pore volume in the total volume of the pole piece is the porosity of the pole piece, and the calculation formula is: porosity = (V-V0) / V x 100%, wherein V0 is the true volume and V is the apparent volume.

[0443] Membrane resistance detection method: refer to GB / T 30835-2014 or T / CASAS 019-2021 method for detection; tester verification procedure please refer to JJG 508-2004 method for detection. Specifically, four-probe method is used for detection: the pole piece is immersed in methyl ethyl carbonate (EMC) for cleaning, and the method specified in GB / T 30835-2014 or T / CASAS 019-2021 is used for testing. Four copper plates with a length of 1.5 cm, a width of 1 cm and a thickness of 2 mm are fixed equidistantly on a line, and the distance between the middle two copper plates is L (1 cm to 2 cm). The base material for fixing the copper plates is insulating material. When testing, the lower end surface of the four copper plates is pressed on the measured pole piece, and the two end copper plates are connected to direct current I. The voltage V is measured at the middle two copper plates. Read I and V values three times, take the average value of I and V, and V / I is the resistance of the test pole piece.

[0444] Table 2

[0445]

[0446] Electrochemical performance test of sodium ion battery cell in each embodiment:

[0447] The sodium ion battery cells provided in Examples B1 to B24 and Comparative Examples B1 to B3 above were respectively subjected to the following electrochemical performance tests in Table 3 below according to the following methods, and the test results are shown in Table 3:

[0448] Sodium ion battery cell performance test method:

[0449] Cycle DCR test: test DCR according to the normal temperature test method in the "HEV high-power lithium ion power battery performance test specification":

[0450] The battery cell (cell) to be tested is discharged at 1C constant current to the cut-off voltage (3.0V), and after standing at 20±2℃ for 1h, it is charged at 1C current for 18min, the SOC is adjusted to 30%, and it is standing for 1h, then it is charged at 3C for 1.5min, standing for 1h, then it is discharged at 9C for 0.5min, standing for 1h, then it is charged at 1C for 6min, adjusting the SOC to 40%, and standing for 1h. Such cycle is repeated until the test is stopped when the SOC is 70%, and the DCR value is obtained by the calculation formula.

[0451] Energy density: measure the discharge energy S0 of each cell at room temperature charged at 0.33C rate to a voltage equal to 4.2V, and then discharged at 0.33C rate to a voltage equal to 2.0V. Then measure the mass M of the battery cell corresponding to S0, and calculate the mass energy density of the battery cell according to the formula S0 / M.

[0452] Cycle retention rate (%): the secondary battery was charged at 0.33C constant current to 3.85V at 25℃, then charged at 3.85V constant voltage to the current of 0.05C, then discharged at 1C constant current to 1.5V, which was one charge-discharge cycle. Taking the capacity of the first discharge as 100%, the capacity retention rate of the battery after 1000 cycles was calculated. The capacity retention rate (%) of the battery after 1000 cycles = the discharge capacity of the 1000th cycle / the capacity of the first discharge x 100%.

[0453] Table 3

[0454]

[0455] As can be seen from the data in Table 2 and Table 3, in the sodium ion battery of the present application, the positive electrode active material layer contained in the positive electrode sheet of examples B1 to B24 can achieve a compaction density of 2.8-3.4 g / cm 3 , and the CW of the positive electrode active material layer can reach 260-350 mg / 1540.25 mm 2 . Further, while controlling the CW and the compaction density of the positive electrode active material layer, the porosity of the positive electrode active material layer is 40%-65%, and the sheet resistance is 0.5-5 mΩ, which can be adjusted according to the CW and the compaction density of the positive electrode active material layer and the conductive agent contained therein.

[0456] As can be seen from the comparative examples B1 to B8 in the comparison table, as the content of zinc element in the layered oxide represented by formula (I) gradually increases, the cell energy density of the sodium ion battery cell gradually increases, and of course the overall trend of the cycle performance of the corresponding sodium ion battery cell is a decreasing trend. In the layered oxide represented by formula (I), as the content of zinc element increases, it can increase the gram capacity of the layered oxide, but is not conducive to the structural stability of the layered oxide, which reduces the cycle performance of the reversible capacity, but compared with Comparative Example 1 and Comparative Example 2, when the zinc element is controlled in an appropriate range and meets the appropriate stoichiometric ratio of Zn to Ni and Mn, the layered oxide represented by formula (I) can effectively balance the high gram capacity and good reversible capacity cycle stability.

[0457] As can be seen from the comparison between Example B3 and Examples B10 to B14 in the comparison table, the type of doped metal elements contained in the layered oxide represented by formula (I) also has a certain influence on the gram capacity and structural stability of the layered oxide, therefore, the doped metal element M participates in the disordered arrangement of the metal elements in the transition metal layer contained in the layered oxide, which can contribute to the gram capacity and / or structural stability of the layered oxide.

[0458] Comparative Example B14 and Example B15, the type of conductive agent contained in the positive electrode active material layer of the positive electrode sheet has a certain influence on the capacity exertion of the positive electrode sheet. When the conductive agent contains linear carbon nanotubes, the cell energy density of the corresponding sodium-ion battery cell is relatively high compared to Example B15.

[0459] Comparative Example B1 to Example B15 and Comparative Example B1 to Comparative Example B3, when the content of layered oxide zinc is too low, such as Comparative Example B1 and Comparative Example B3, not only does it significantly reduce the energy density of the sodium-ion battery cell, but it also significantly reduces the cycle retention rate of the sodium-ion battery cell. When the content of layered oxide zinc is too high, such as Comparative Example B2, although it can maintain the energy density of the sodium-ion battery cell without significant reduction, it can significantly reduce the cycle retention rate of the sodium-ion battery cell. Therefore, the zinc element and other metal elements in the layered oxide represented by chemical formula (I) and the content of each metal element can significantly affect the disordered arrangement of metal elements in the transition metal layer of the layered oxide, thereby significantly affecting the comprehensive performance of the specific capacity and cycle stability of the layered oxide.

[0460] Therefore, the layered oxide of the present application controls the content of zinc element in a proper low range, and controls the content of zinc element and Ni, Fe, Mn and other metal elements, so that the transition metal layer contained in the layered oxide of the present application has a specific arrangement. On the basis of effectively improving the specific capacity of the layered oxide, the structural stability of the layered oxide is also taken into account and balanced, thereby improving the cycle performance of the layered oxide and the sodium-ion battery. At the same time, it also shows that in the layered oxide of the present application, the higher the content of zinc element, the higher the specific capacity and the better the cycle performance of the layered oxide, but when the content of zinc element exceeds a certain amount, the specific capacity does not continue to increase, and it is not conducive to the structural stability of the layered oxide, which reduces the cycle performance of the layered oxide.

[0461] In addition, from the data in Table 3, it can be seen that the cell DCR of the sodium-ion battery cell in Example B1 to Example B24 does not change much, and the difference in cell DCR of each sodium-ion battery cell in Example B1 to Example B24 is in the range of 0 mΩ to 0.8 mΩ. Moreover, the cell DCR of the sodium-ion battery cell in Example B1 to Example B24 is significantly lower than the cell DCR value of the sodium-ion battery cell in Comparative Example B1 to Comparative Example B3. Therefore, by controlling the content of zinc in the layered oxide represented by chemical formula (I) within the content range in chemical formula (I), on the basis of improving the structural stability of the layered oxide by controlling the low zinc content and adjusting the arrangement of other metal elements in the transition metal layer, it can also stabilize the channel between the transition metal layers, improve the sodium-ion transmission rate, and improve the DCR growth of the battery cell.

[0462] It can be further known from the positive electrode slurries in Examples B1 to B24 and Comparative Examples B1 and B3 that the gelling phenomenon of the positive electrode slurries in Examples B1 to B24 is obviously lower than that of the positive electrode slurries in Comparative Examples B1 and B3. Therefore, the layered oxides in the embodiments of the present application control the zinc element in a proper low content range, which effectively improves the tap capacity and cycle performance of the layered oxides and also improves the processing performance of the layered oxides.

[0463] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the specification of the present application. Especially, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A positive electrode material, characterized by, A layered oxide comprising a chemical formula as follows: Na q Ni x Mn y Fe z Zn p M i O j ; wherein 0.8≤q≤1, 0.1≤x≤0.3, 0.2≤y≤0.5, 0.2≤z≤0.35, 0.02≤p≤0.075, 0≤i≤0.1, 1.8≤j≤2, and x+y+z+p+i≤1; M is an active or / and inactive doped metal element; a stoichiometric ratio of a total stoichiometry of the Ni element, the Mn element, the Fe element, the Zn element and the doped metal element to a stoichiometry of the Na element is 1:(0.8-0.89); a stoichiometric ratio of the Zn element to the Ni element is 1:(3-15); a stoichiometric ratio of the Zn element to the Mn element is 1:(4-25).

2. The positive electrode material of claim 1, wherein, at least one of the q, x, y, z, p and i is in a range as follows: 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: a stoichiometric ratio of a total stoichiometry of the Ni element, the Mn element, the Fe element, the Zn element and the doped metal element to a stoichiometry of the Na element is 1:(0.83-0.89).

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

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

6. The positive electrode material according to any one of claims 1 to 5, characterized by The layered oxide comprises Na 0.89 Ni 0.23 Mn 0.45 Fe 0.3 Zn 0.02 O2, Na 0.89 Ni 0.23 Mn 0.44 Fe 0.3 Zn 0.03 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cu 0.02 O2, Na 0.89 Ni 0.23 Mn 0.42 Fe 0.3 Zn 0.05 O2, Na 0.89 Ni 0.23 Mn 0.41 Fe 0.3 Zn 0.06 O2, Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 5Zn 0.065 O2, Na 0.89 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.07 O2,, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 V 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Cr 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Al 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sc 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sn 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Sb 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Zr 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 Zn 0.04 Nb 0.02 O2, Na 0.85 Ni 0.23 Mn 0.42 Fe 0.28 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 7. The positive electrode material according to any one of claims 1 to 6, characterized in that: the layered oxide comprises at least one feature of (1)-(3) as follows: (1) the crystal structure comprises an O3 phase layered metal oxide, and the O3 phase layered metal oxide accounts for more than 95% of a total weight of the layered oxide; (2) a Dv50 particle size is 3-11 μm; (3) comprising a single crystal, a morphology of the single crystal is flat.

8. The positive electrode material of claim 7, characterized in that: the Dv50 particle size is 4-8 μm.

9. The cathode material of claim 7, wherein: the single crystal comprises at least one feature of (1)-(4) as follows: (1) a ratio of length, width and thickness is 1-8:1-5:0.5-2.5; (2) the length is 1-8 μm; (3) the width is 1-5 μm; (4) the thickness is 0.5-2.5 μm.

10. The cathode material of claim 7, wherein: the single crystal comprises at least one feature of (1)-(4) as follows: (1) a ratio of length, width and thickness is 2-6:2-4:1-2; (2) the length is 2-6 μm; (3) the width is 2-4 μm; (4) the thickness is 1-2 μm.

11. The positive electrode material according to any one of claims 1 to 10, characterized in that: the layered oxide comprises at least one feature of (1)-(3) as follows: (1) Compacted density of 2.8-3.1 g / cm3 under 2 tons of pressure 3 ; (2) Compacted density of 3.1-3.3 g / cm3 under 3 tons of pressure 3 ; (3) the specific surface area is 0.5-1.3 m 2 / g.

12. The positive electrode material according to any one of claims 1 to 10, characterized in that: the layered oxide comprises at least one feature of (1)-(3) as follows: (1) Compacted density of 2.9-3.09 g / cm3 under 2 tons of pressure 3 ; (2) Compacted density at 3 tons pressure is 3.15-3.28 g / cm 3 ; (3) the specific surface area is 0.6-0.9 m 2 / g.

13. The positive electrode material according to any one of claims 1 to 12, characterized in that: the layered oxide comprises at least one of (1)-(3) as follows at 1.5-4.2 v and 0.1 C: (1) a charge gram capacity is 164-174 mAh / g; (2) a discharge gram capacity is 158-165 mAh / g; (3) a first efficiency is 92-98%.

14. The positive electrode material according to any one of claims 1 to 13, characterized in that: The layered oxide includes at least one of (1) to (3) below at 1.5 to 4.2 V and 0.1 C: (1) a charge gram capacity of 165 to 172 mAh / g; (2) a discharge gram capacity of 160 to 163 mAh / g; (3) a first efficiency of 92 to 95%.

15. A method of producing the positive electrode material according to any one of claims 1 to 14, characterized by, comprising the following steps: A precursor of Na q Ni x Mn y Fe z Zn p M i O j ; sintering the precursor to obtain a layered oxide of formula Na q Ni x Mn y Fe z Zn p M i O j ; wherein 0.8≤q≤1, 0.1≤x≤0.3, 0.2≤y≤0.5, 0.2≤z≤0.35, 0.02≤p≤0.07, 0≤i≤0.1, 1.8≤j≤2, and x+y+z+p+i≤1; M is an active or / and inactive doped metal element; a stoichiometric ratio of the total of the Ni element, the Mn element, the Fe element, the Zn element and the doped metal element to the stoichiometric ratio of the Na element is 1:(0.8-0.89); a stoichiometric ratio of the Zn element to the Ni element is 1:(3-15); a stoichiometric ratio of the Zn element to the Mn element is 1:(4-25).

16. The method of claim 15, wherein, the doped metal element includes at least one of V, Ca, Cr, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, Ir; and / or at least one of q, x, y, z, p and i is in the following range: 0.15≤x≤0.25, 0.25≤y≤0.45, 0.25≤z≤0.32, 0.04≤p≤0.07, 0≤i≤0.

05.

17. The method of manufacturing according to claim 15 or 16, characterized in that, the sintering treatment includes at least one of (1) to (3) below: (1) a temperature of 700-980℃; (2) a time of 4-20h; (3) a temperature rising rate of 2-15℃ / min.

18. The method of claim 17, wherein, the sintering treatment includes at least one of (1) to (2) below: (1) a temperature of 750-950℃; (2) a time of 6-12h.

19. The method of any one of claims 15-18, wherein, The Na q Ni x Mn y Fe z Zn p M i O j 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 element content ratio is measured, and the sodium source, nickel source, manganese source, iron source, zinc source and M doped metal element source are mixed by solid phase mixing treatment to obtain the precursor. and / or The Na q Ni x Mn y Fe z Zn p M i O j The precursor of the formula M1M2M3M4M5M6M7M8M9M10M11M12M13M14M15M16M17M18M19M20M21M22M23M24M25M26M27M28M29M30M31M32M33M34M35M36M37M38M39M40M41M According to Na q Ni x Mn y Fe z Zn p M i O j The soluble nickel source, the soluble manganese source, the soluble iron source, the soluble zinc source and the soluble M indicated doping metal element source are prepared into a mixed solution in a stoichiometric ratio of the intermediate elements, at least one of the precipitator and the complexing agent is added for co-precipitation treatment to obtain a precipitate mixture; mixing the precipitation mixture with a sodium source to obtain the precursor.

20. A positive electrode comprising a positive electrode active material, characterized by: The positive electrode active material layer includes the positive electrode material of any one of claims 1-14 or the positive electrode material prepared by the preparation method of any one of claims 15-19.

21. The positive electrode of claim 20, wherein: The content of the positive electrode active material on one side of the current collector is 260 to 350 mg / 1540.25 mm 2 ; and / or The compacted density of the positive electrode is 2.8 to 3.4 g / cm 3 .

22. The positive electrode of claim 21, wherein: The content of the positive electrode active material on one side of the current collector is 280 to 320 mg / 1540.25 mm 2 ; and / or The compacted density of the positive electrode is 2.9 to 3.2 g / cm 3 .

23. The positive electrode of any one of claims 20-22, wherein: The porosity of the positive electrode active material layer is 40-65%; and / or The positive electrode is a pole piece, and the sheet resistance of the pole piece is 0.5-5 mΩ.

24. The positive electrode of claim 23, wherein: The porosity of the positive electrode active material layer is 45-60%; and / or The positive electrode is a pole piece, and the sheet resistance of the pole piece is 0.5-3 mΩ.

25. The positive electrode of any one of claims 20-24, wherein: The positive electrode is a pole piece, and the ratio of the thickness from one surface to the opposite surface of the pole piece to the thickness of the current collector is 6-15:

1.

26. The positive electrode of claim 25, wherein: The positive electrode is a pole piece, and the ratio of the thickness from one surface to the opposite surface of the pole piece to the thickness of the current collector is 8-14:

1.

27. The positive electrode according to any one of claims 20 to 26, characterized by: The conductive agent contained in the positive electrode active material layer includes a linear conductive agent.

28. The positive electrode of claim 27, wherein: The mass content of the linear conductive agent in the positive electrode active material layer is 0.1%-2.5%; and / or The length of the linear conductive agent is 0.5-5 μm; and / or ​ the linear conductive agent has a diameter of 2 to 10 nm; and / or the linear conductive agent comprises at least one of carbon nanotubes, carbon fibers, and conductive oxide nanowires.

29. The positive electrode of claim 28, wherein: the linear conductive agent has a mass content in the positive electrode active material layer of 0.2 to 0.8%; and / or the linear conductive agent has an aspect ratio of 50 to 2500:1; the linear conductive agent has a length of 0.5 to 2 μm; and / or the linear conductive agent has a diameter of 3 to 7 nm.

30. A sodium battery, comprising: The sodium battery of claim 30.

31. An electrical device, comprising: The sodium battery of claim 30.

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