Electrode active material, secondary battery, and electric device

Abstract

The application provides an electrode active material, comprising a layered metal oxide, the layered metal oxide has the following general formula: Na x Zn a Ni b Mn c M1 d O2M2 e ; wherein, 0.6<=x<=0.85, 0.95<=a+b+c+d<=1.05, 0<=d<=0.05, 0<=e<=0.067; wherein, 0.04<=a / c<=0.1, 0.23<=b / c<=0.45; wherein, M1 is selected from one or more of alkali metal elements, alkaline earth metal elements or transition metal elements except Zn, Ni and Mn; wherein, M2 is selected from non-metal elements except O.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to an electrode active material, a secondary battery, and an electrical device. Background Technology

[0002] In recent years, with the increasingly wide application of secondary batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. Due to the significant development of secondary batteries, higher requirements have been placed on their energy density and cycle performance.

[0003] Layered metal oxides are considered one of the promising cathode materials for sodium-ion batteries, mainly due to their simple preparation, high specific capacity, and high ionic conductivity. Currently, based on the different occupancy modes of sodium ions between transition metal layers and the different stacking modes of the oxygen layers in the transition metal layers, the structures of these layered metal oxides can be mainly divided into P2 type and O3 type. In P2 type and O3 type transition metal oxides, a single sodium ion occupies a triangular prism (P) position and an octahedral (O) position between the layers, respectively.

[0004] Current technology requires sodium-ion battery cathode materials with better performance. Summary of the Invention

[0005] In view of the above-mentioned issues, this application provides a novel electrode active material, a secondary battery, and an electrical device, which are described below.

[0006] In a first aspect, this application improves an electrode active material comprising a layered metal oxide, wherein the layered metal oxide

[0007] Compounds have the following general formula:

[0008] Na x Zn a Ni b Mn c M1 d O2M2 e

[0009] Where, 0.6≤x≤0.85, 0.95≤a+b+c+d≤1.05, 0≤d≤0.05, 0≤e≤0.067x;

[0010] Where, 0.04≤a / c≤0.1, 0.23≤b / c≤0.45;

[0011] M1 is selected from one or more alkali metal elements, alkaline earth metal elements, or transition metal elements other than Zn, Ni, and Mn.

[0012] wherein M2 is selected from non-metallic elements other than O.

[0013] The electrode active material based on the above-mentioned scheme has improved phase structure stability, and the electrode active material is used in a secondary battery, which exhibits one or more of the following advantages: improved discharge voltage, improved discharge specific capacity, and / or improved cycle performance.

[0014] In some embodiments, the electrode active material has one or more of the following characteristics:

[0015] (1) 0.03≤a≤0.075;

[0016] (2) 0.18≤b≤0.28;

[0017] (3) 0.67≤c≤0.75;

[0018] (4) 0.03≤d≤0.05;

[0019] (5) 0≤e≤0.05.

[0020] In some embodiments, the layered metal oxide belongs to a P2 phase hexagonal crystal system P63 / mmc space group.

[0021] In some embodiments, the powder XRD diffraction pattern of the layered metal oxide has one or more of the following characteristic peaks:

[0022] (1) a first characteristic peak at a 2θ value of 15.75°-15.90°;

[0023] (2) a second characteristic peak at a 2θ value of 31.95°-32.10°;

[0024] (3) a third characteristic peak at a 2θ value of 35.80°-35.95°;

[0025] (4) a fourth characteristic peak at a 2θ value of 36.75°-36.90°;

[0026] (5) a fifth characteristic peak at a 2θ value of 39.40°-39.55°.

[0027] In some embodiments, the powder XRD diffraction pattern of the layered metal oxide has one or more of the following characteristics:

[0028] (1) a ratio of diffraction intensity of the second characteristic peak to the first characteristic peak is 9.5%-13.5%;

[0029] (2) a ratio of diffraction intensity of the third characteristic peak to the first characteristic peak is 10.5%-14.5%;

[0030] (3) the ratio of the diffraction intensity of the fourth characteristic peak to the first characteristic peak is 0.5% to 1.5%;

[0031] (4) the ratio of the diffraction intensity of the fifth characteristic peak to the first characteristic peak is 16.5% to 21.5%.

[0032] In some embodiments, the powder XRD diffraction pattern of the layered metal oxide has one or more of the following characteristics:

[0033] (1) the first characteristic peak corresponds to (002) crystal face;

[0034] (2) the second characteristic peak corresponds to (004) crystal face;

[0035] (3) the third characteristic peak corresponds to (100) crystal face;

[0036] (4) the fourth characteristic peak corresponds to (101) crystal face;

[0037] (5) the fifth characteristic peak corresponds to (012) crystal face.

[0038] In some embodiments, the powder XRD diffraction pattern of the layered metal oxide further has the following characteristic peaks:

[0039] (6) the sixth characteristic peak with a 2θ value of 27.15°-27.25°;

[0040] (7) the seventh characteristic peak with a 2θ value of 28.35°-28.45°.

[0041] In some embodiments, the powder XRD diffraction pattern of the layered metal oxide has one or more of the following characteristics:

[0042] (1) the ratio of the diffraction intensity of the sixth characteristic peak to the seventh characteristic peak is 0.3-0.9:1;

[0043] (2) the ratio of the diffraction intensity of the sixth characteristic peak to the first characteristic peak is 0.2% to 1.2%;

[0044] (3) the ratio of the diffraction intensity of the seventh characteristic peak to the first characteristic peak is 0.3% to 1.3%.

[0045] In some embodiments, the measurement conditions of the powder XRD diffraction pattern of the layered metal oxide are as follows:

[0046] (1) the volume average particle size of the powder sample is: 5-15 μm

[0047] (2) the radiation source: Cu K-ray;

[0048] (3) the scanning mode: step scanning;

[0049] (4) Scanning conditions: 0.01-0.05° / step;

[0050] (5) Incident slit: 2-3 mm, Anti-scattering slit: 15-20 mm, Receiving slit: 0.2-0.4 mm.

[0051] In some embodiments, the electrode active material has one or more of the following characteristics:

[0052] (1) M1 is selected from one or more of alkali metal elements, alkaline earth metal elements or transition metal elements other than Zn, Ni, Mn, and M1 belongs to the second period, the third period, the fourth period or the fifth period;

[0053] (2) M2 is selected from non-metal elements other than O, and M2 belongs to the second period, the third period or the fourth period.

[0054] In some embodiments, the electrode active material has one or more of the following characteristics:

[0055] (1) M1 is selected from one or more of Li, K, Mg, Fe, Cu, V, Cr, Co, Ti, Sc;

[0056] (2) M2 is selected from one or more of F, Cl, B, C, N.

[0057] In some embodiments, the intensity of the characteristic peak corresponding to the (002) crystal face of the XRD diffraction pattern of the layered metal oxide powder satisfies the following relationship:

[0058] I / I0≥0.8;

[0059] I0 is the intensity of the characteristic peak of the (002) crystal face of the layered metal oxide without water immersion;

[0060] I is the intensity of the characteristic peak of the (002) crystal face of the layered metal oxide after water immersion for 24 hours.

[0061] In a second aspect, the present application provides a secondary battery comprising a positive electrode, wherein the positive electrode comprises the electrode active material described above.

[0062] In a third aspect, the present application provides an electric device comprising the secondary battery described above.

[0063] Advantages

[0064] One or more embodiments of the present application have one or more of the following advantages:

[0065] (1) The layered metal oxide of the present application has enhanced phase structure stability, and can maintain phase structure stability in water environment and atmospheric environment;

[0066] (2) The electrode active material of the present application is used for a secondary battery having an improved discharge middle voltage or discharge voltage;

[0067] (3) The electrode active material of the present application is used for a secondary battery having an improved specific capacity;

[0068] (4) The electrode active material of the present application is used for a secondary battery having an improved cycle stability. BRIEF DESCRIPTION OF DRAWINGS

[0069] Figure 1 (a), (b), (c) of FIG. 1 show XRD spectra of freshly prepared layered metal oxide of Example 1, water washed layered metal oxide of Example 1, and standard phase card (00-054-0894), respectively.

[0070] Figure 2 (a), (b), (c) of FIG. 2 show XRD spectra of freshly prepared layered metal oxide of Comparative Example 1, water washed layered metal oxide of Comparative Example 1, and standard phase card (00-054-0894), respectively.

[0071] Figure 3 (a) and (b) of FIG. 3 show scanning electron microscope photographs of layered metal oxide of Example 1 before and after water washing, respectively.

[0072] Figure 4 (a) of FIG. 4 shows a discharge specific capacity curve of layered metal oxide of Example 1; (b) shows a discharge specific capacity curve of layered metal oxide of Comparative Example 1.

[0073] Figure 5 is a schematic view of a secondary battery of an embodiment of the present application.

[0074] Figure 6 is a schematic view of a secondary battery of an embodiment of the present application. Figure 5 is an exploded view of a secondary battery of an embodiment of the present application.

[0075] Figure 7 is a schematic view of a battery module of an embodiment of the present application.

[0076] Figure 8 is a schematic view of a battery pack of an embodiment of the present application.

[0077] Figure 9 is an exploded view of a battery pack of an embodiment of the present application. Figure 8 is an exploded view of a battery pack of an embodiment of the present application.

[0078] Figure 10 is a schematic view of an electric device using a secondary battery of an embodiment of the present application as a power source.

[0079] BRIEF DESCRIPTION OF REFERENCE NUMERALS

[0080] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0081] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the negative electrode active material and its manufacturing method, positive electrode sheet, negative electrode sheet, secondary battery, battery module, battery pack, and device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0082] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0083] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0084] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0085] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0086] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0087] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0088] [Rechargeable Battery]

[0089] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged after being discharged to activate the active materials and continue to be used.

[0090] Typically, a secondary battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During charging and discharging, active ions (such as sodium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing active ions to pass through. The electrolyte, also positioned between the positive and negative electrodes, mainly serves to conduct active ions.

[0091] Secondary batteries, such as sodium-ion batteries, mainly consist of a positive electrode, a negative electrode, a separator, and an electrolyte. The positive and negative electrodes are separated by a separator to prevent short circuits, and the electrolyte wets both electrodes to ensure ion conduction. During charging, Na... +Sodium ions are extracted from the positive electrode, pass through the electrolyte and the membrane, and embed into the negative electrode, placing the positive electrode in a high-potential, sodium-deficient state and the negative electrode in a low-potential, sodium-rich state. The discharge process is the reverse: Na+ ions are extracted from the negative electrode, pass through the electrolyte and the membrane, and embed into the positive electrode material, restoring the positive electrode to a sodium-rich state. To maintain charge balance, an equal number of electrons are transferred through the external circuit during charging and discharging, migrating between the positive and negative electrodes along with Na+ ions, causing oxidation and reduction reactions at the positive and negative electrodes, respectively. Sodium ions can reversibly migrate between the positive and negative electrodes in the electrolyte; both the positive and negative electrodes are constructed of insertable materials that allow for the reversible insertion and extraction of sodium ions.

[0092] [Negative electrode plate]

[0093] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material, the negative electrode active material being any of the negative electrode active materials of this application.

[0094] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0095] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0096] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: hard carbon, heteroatom-doped carbon, metal oxides, metal sulfides, etc., which exhibit long cycle life as negative electrode materials for sodium-ion batteries, but their application is limited by low sodium storage capacity and energy density. Phosphorus-based materials, including elemental phosphorus (P) and metal phosphides (M... x P y (M = Fe, Co, Ni, Cu, Sn, Mo, etc.). However, this application is not limited to these materials; other conventional materials that can be used as negative electrode active materials in batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0097] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0098] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0099] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0100] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0101] [Positive electrode plate]

[0102] In some embodiments, the positive electrode typically includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0103] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0104] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0105] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0106] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0107] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0108] [Positive electrode active material]

[0109] In a first aspect, this application provides an electrode active material comprising a layered metal oxide having the following general formula:

[0110] Na x Zn a Ni b Mn c M1 d O2M2 e

[0111] Where, 0.6≤x≤0.85, 0.95≤a+b+c+d≤1.05, 0≤d≤0.05, 0≤e≤0.067x;

[0112] Where, 0.04≤a / c≤0.1, 0.23≤b / c≤0.45;

[0113] M1 is selected from one or more alkali metal elements, alkaline earth metal elements, or transition metal elements other than Zn, Ni, and Mn.

[0114] M2 is selected from nonmetallic elements other than O.

[0115] The electrode active material based on the above scheme exhibits improved phase structure stability, and when used in secondary batteries, it demonstrates one or more of the following advantages: increased discharge voltage, increased discharge specific capacity, and improved cycle performance. Without theoretical limitations, 0.04 ≤ a / c ≤ 0.1 and 0.23 ≤ b / c ≤ 0.45 are crucial for the material's stability and electrochemical performance. Under these conditions, Zn, Ni, and Mn elements achieve a synergistic effect, improving the material's phase structure stability.

[0116] In some implementations, the value of a / c can be 0.04-0.06, 0.06-0.08, or 0.08-0.1. The electrode active material of the above scheme exhibits further improved phase structure stability. Based on the improved phase structure stability of the electrode active material, when used in a secondary battery, the secondary battery exhibits one or more of the following advantages: increased discharge voltage, increased discharge specific capacity, and improved cycle performance.

[0117] In some implementations, the value of b / c can be 0.23-0.25, 0.25-0.3, 0.3-0.35, 0.35-0.4, or 0.4-0.45. The electrode active material of the above scheme exhibits further improved phase structure stability. Based on the improved phase structure stability of the electrode active material, when used in a secondary battery, the secondary battery exhibits one or more of the following advantages: increased discharge voltage, increased discharge specific capacity, and improved cycle performance.

[0118] In some implementations, 0.03 ≤ a ≤ 0.075, and the value of a can be 0.03-0.04, 0.04-0.05, 0.05-0.06, 0.06-0.07, or 0.07-0.075. The electrode active material of the above scheme exhibits further improved phase structure stability. Based on the improved phase structure stability of the electrode active material, when used in a secondary battery, the secondary battery exhibits one or more of the following advantages: increased discharge voltage, increased discharge specific capacity, and improved cycle performance.

[0119] In some implementations, 0.18 ≤ b ≤ 0.28, and the value of b can be 0.18-0.2, 0.2-0.22, 0.22-0.24, 0.24-0.26, or 0.26-0.28. The electrode active material of the above scheme exhibits further improved phase structure stability. Based on the improved phase structure stability of the electrode active material, when used in a secondary battery, the secondary battery exhibits one or more of the following advantages: increased discharge voltage, increased discharge specific capacity, and improved cycle performance.

[0120] In some implementations, 0.67 ≤ c ≤ 0.75, and the value of c can be 0.67-0.69, 0.69-0.71, 0.71-0.73, or 0.73-0.75. The electrode active material of the above scheme exhibits further improved phase structure stability. Based on the improved phase structure stability of the electrode active material, when used in a secondary battery, the secondary battery exhibits one or more of the following advantages: increased discharge voltage, increased discharge specific capacity, and improved cycle performance.

[0121] In some implementations, 0.03 ≤ d ≤ 0.05. The electrode active material of the above-described scheme has further improved phase structure stability. Based on the improved phase structure stability of the electrode active material, and when used in a secondary battery, the secondary battery exhibits one or more of the following advantages: increased discharge voltage, increased discharge specific capacity, and improved cycle performance.

[0122] In some implementations, the value of d can be 0, 0.01-0.02, 0.02-0.03, 0.03-0.04, or 0.04-0.05. The electrode active material of the above scheme exhibits further improved phase structure stability. Based on the improved phase structure stability of the electrode active material, when used in a secondary battery, the secondary battery exhibits one or more of the following advantages: increased discharge voltage, increased discharge specific capacity, and improved cycle performance.

[0123] In some implementations, 0 ≤ e ≤ 0.05, where e can take values ​​of 0, 0.01–0.02, 0.02–0.03, 0.03–0.04, or 0.04–0.05. The electrode active material of the above scheme exhibits further improved phase structure stability. Based on the improved phase structure stability of the electrode active material, when used in a secondary battery, the secondary battery exhibits one or more of the following advantages: increased discharge voltage, increased discharge specific capacity, and improved cycle performance.

[0124] In some implementations, the layered metal oxide belongs to the P2 phase hexagonal crystal system, space group P63 / mmc.

[0125] In some implementations, in layered metal oxides belonging to the P2 phase hexagonal crystal system P63 / mmc space group, the transition metal element (Me) forms a transition metal layer by sharing edges with the six surrounding oxygen atoms to create MeO6 octahedrons. Sodium ions are located between the transition metal layers, occupying prismatic positions between the MeO6 layers. In the P2 structure, sodium ions occupy two types of prismatic positions between the MeO6 layers: one where both the top and bottom sides of the prismatic octahedron are connected to the transition metal MeO6 octahedron by sharing edges, and another where they are connected to the transition metal MeO6 octahedron by sharing a plane.

[0126] In some embodiments, the powder XRD diffraction pattern of the layered metal oxide has one or more of the following characteristic peaks:

[0127] (1) The first characteristic peak with 2θ value is 15.75°-15.90°. The 2θ value of the first characteristic peak is, for example, 15.75°-15.80°, 15.80°-15.85°, and 15.85°-15.90°.

[0128] (2) The second characteristic peak with 2θ value is 31.95°-32.10°. For example, the 2θ value of the second characteristic peak is 31.95°-32.00°, 32.00°-32.05°, and 32.05°-32.10°.

[0129] (3) The third characteristic peak with a 2θ value of 35.80°-35.95°, for example, 35.80°-35.85°, 35.85°-35.90°, and 35.90°-35.95°.

[0130] (4) The fourth characteristic peak with 2θ values ​​of 36.75°-36.90°, for example, 36.75°-36.80°, 36.80°-36.85°, and 36.85°-36.90°.

[0131] (5) The fifth characteristic peak with 2θ values ​​of 39.40°-39.55°, for example, 39.40°-39.45°, 39.45°-39.50°, and 39.50°-39.55°.

[0132] In some embodiments, the powder XRD diffraction pattern of the layered metal oxide has one or more of the following characteristics:

[0133] (1) The ratio of the diffraction intensity of the second characteristic peak to that of the first characteristic peak is 9.5% to 13.5%, for example, 10% to 11%;

[0134] (2) The ratio of the diffraction intensity of the third characteristic peak to that of the first characteristic peak is 10.5% to 14.5%, for example, 12% to 13%;

[0135] (3) The ratio of the diffraction intensity of the fourth characteristic peak to that of the first characteristic peak is 0.5% to 1.5%, for example, 0.8% to 1.2%;

[0136] (4) The ratio of the diffraction intensity of the fifth characteristic peak to that of the first characteristic peak is 16.5% to 21.5%, for example, 17% to 18%.

[0137] In some embodiments, the powder XRD diffraction pattern of the layered metal oxide has one or more of the following characteristics:

[0138] (1) The first characteristic peak corresponds to the (002) crystal plane;

[0139] (2) The second characteristic peak corresponds to the (004) crystal plane;

[0140] (3) The third characteristic peak corresponds to the (100) crystal plane;

[0141] (4) The fourth characteristic peak corresponds to the (101) crystal plane;

[0142] (5) The fifth characteristic peak corresponds to the (012) crystal plane.

[0143] In some embodiments, the powder XRD diffraction pattern of the layered metal oxide also has the following characteristic peaks:

[0144] (6) The sixth characteristic peak with a 2θ value of 27.15°-27.25°, for example, the 2θ value of the sixth characteristic peak is 27.15°-27.20° or 27.20°-27.25°;

[0145] (7) The seventh characteristic peak with a 2θ value of 28.35°-28.45°. For example, the 2θ value of the seventh characteristic peak is 28.35°-28.40° or 28.40°-28.45°.

[0146] The electrode active material of the above scheme has further improved phase structure stability. Based on the improved phase structure stability of the electrode active material, and when used in a secondary battery, the secondary battery exhibits one or more of the following advantages: increased discharge voltage, increased discharge specific capacity, and improved cycle performance.

[0147] In some embodiments, the powder XRD diffraction pattern of the layered metal oxide has one or more of the following characteristics:

[0148] (1) The ratio of the diffraction intensity of the sixth characteristic peak to that of the seventh characteristic peak is 0.3-0.9:1;

[0149] (2) The ratio of the diffraction intensity of the sixth characteristic peak to that of the first characteristic peak is 0.2% to 1.2%, for example, 0.4% to 0.7%;

[0150] (3) The ratio of the diffraction intensity of the seventh characteristic peak to that of the first characteristic peak is 0.3% to 1.3%, for example, 0.5% to 0.8%.

[0151] The electrode active material of the above scheme has further improved phase structure stability. Based on the improved phase structure stability of the electrode active material, and when used in a secondary battery, the secondary battery exhibits one or more of the following advantages: increased discharge voltage, increased discharge specific capacity, and improved cycle performance.

[0152] In some embodiments, the measurement conditions for the powder XRD diffraction pattern have one or more of the following characteristics:

[0153] (1) The volume average particle size of the powder sample is 5-15 μm, for example 8-10 μm.

[0154] (2) Radiation source: CuK rays;

[0155] (3) Scanning mode: Step scan;

[0156] (4) Scanning conditions: 0.01-0.05° / step, for example 0.01-0.02° / step;

[0157] (5) Entrance slit: 2-3mm, anti-scattering slit: 15-20mm, receiving slit: 0.2-0.4mm.

[0158] In some implementations, the measurement range of the powder XRD diffraction pattern of the layered metal oxide is 2θ = 10 to 80°.

[0159] In some implementation schemes, the distinction between characteristic peaks and diffraction background peaks is subject to the following constraints: using the least second derivative calculation method, minimum effective value = 2, minimum peak width ≥ 0.01, maximum peak width ≤ 1, and peak width = 2.

[0160] In some embodiments, the term "average particle size" refers to the volume average particle size Dv50, such as the volume average particle size Dv50 measured using a powder laser particle size analyzer. In this application, the volume average particle size of the layered oxide cathode active material has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, in accordance with GB / T19077-2016 Particle Size Distribution Laser Diffraction Method.

[0161] In some implementations, the intensities of the characteristic peaks corresponding to the (002) crystal plane in the XRD diffraction pattern of the layered metal oxide powder conform to the following relationship:

[0162] I / I0 ≥ 0.8;

[0163] I0 represents the intensity of the characteristic peak of the (002) crystal plane of a layered metal oxide that has not been soaked in water;

[0164] I represents the intensity of the characteristic peak of the (002) crystal plane of the layered metal oxide after immersion in water for 24 hours.

[0165] In some implementations, 0.8 ≤ I / I0 ≤ 1.

[0166] In some implementations, 0.9 ≤ I / I0 ≤ 1.

[0167] In this application, the characteristic peaks and intensities of the (002) crystal plane of the layered oxide cathode active material are of a well-known meaning in the art. X-ray diffraction spectra can be determined using an X-ray powder diffractometer according to JIS K0131-1996 General Rules for X-ray Diffraction Analysis to obtain the characteristic peaks of the (002) crystal plane, and their peak heights can be measured, which are the intensities of the (002) crystal plane characteristic peaks. For example, a Bruker D8 Discover X-ray powder diffractometer from Bruker AxS, Germany, can be used with CuKα rays as the radiation source, and the ray wavelength... The scanning 2θ angle range was 10° to 80°. The X-ray diffraction analysis parameters were as follows: average particle size of powder sample: 9 μm; radiation source: CuK rays; scanning mode: step scan; scanning conditions: 0.016358° / step; entrance slit: 2.5 mm, anti-scattering slit: 18 mm, receiving slit: 0.30 mm.

[0168] In some embodiments, the electrode active material is a powder material. The particle size of the powder is from 0.5 μm to 15 μm, for example 0.5-1 μm, 1 μm-3 μm, 3 μm-5 μm, 5 μm-7 μm, 7 μm-9 μm, 9 μm-11 μm, 11 μm-13 μm, or 13 μm-15 μm.

[0169] In a second aspect, this application provides a secondary battery including a positive electrode comprising the aforementioned electrode active material. The aforementioned secondary battery is, for example, a sodium-ion battery.

[0170] In a third aspect, this application provides an electrical device including the aforementioned secondary battery.

[0171] [Electrolytes]

[0172] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0173] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0174] In some embodiments, the electrolyte salt is selected from sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, and sodium hexafluoroarsenate.

[0175] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0176] In some embodiments, the electrolyte may optionally include additives. As examples, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0177] [Isolation membrane]

[0178] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0179] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0180] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0181] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0182] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0183] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 5 This is an example of a square-structured secondary battery 5.

[0184] In some implementations, refer to Figure 6 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0185] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0186] Figure 7 This is battery module 4, used as an example. (See reference...) Figure 7 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0187] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0188] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0189] Figure 8 and Figure 9 This is battery pack 1 as an example. (See reference...) Figure 8 and Figure 9The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0190] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0191] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0192] Figure 10 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0193] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0194] The layered metal oxides prepared in the following examples and comparative examples have the general formula:

[0195] Na x Zn a Ni b Mn c M1 d O2M2 e

[0196] In the following examples and comparative examples, if element M1 is present, element M1 is selected from one or more of the following elements: Cu, Fe, Mg, Ti.

[0197] In the following examples and comparative examples, if there is an element M2, the element M2 is selected from one or more of the following elements: B, F.

[0198] The values ​​of x, a, b, c, d, and e in each embodiment and comparative example can be found in Table 1.

[0199] Example 1

[0200] Target general formula: Na 0.78 Zn 0.05 Ni 0.2 Mn 0.75 O2 F 0.01

[0201] According to the stoichiometric ratio of the target formula, 16.873 g of Na₂CO₃ (99%), 6.097 g of NiO (98%), 1.66 g of ZnO (98%), 24.17 g of Mn₂O₃, and 0.17 g of NaF (98%) were mixed in the agate ball mill jar of a planetary ball mill. The raw materials were thoroughly ground at a speed of 400 r / min. Then, the temperature was increased to 850 °C in a muffle furnace at a heating rate of 3 °C / min, and then calcined at that temperature for 24 h before naturally cooling to room temperature to obtain black Na. 0.78 Zn 0.05 Ni 0.2 Mn 0.75 O2 F 0.01 Material.

[0202] Examples 2-16

[0203] The difference between Examples 2-16 and Example 1 lies in the different target general formulas of the layered metal oxides. See Table 1 for details of the differences.

[0204] In Examples 9-16, elements M1 and M2 were introduced into the product in the following ways: element M1 is selected from one or more of the following elements: Fe, Cu, Mg, Ti; element M2 is selected from one or more of the following elements: B, F;

[0205] (1) Cu element is introduced into the product by introducing CuO into the raw material.

[0206] (2) Fe element is introduced into the product by introducing Fe2O3 into the raw material.

[0207] (3) By introducing MgO into the raw materials, Mg element is introduced into the product.

[0208] (4) By introducing TiO2 into the raw materials, Ti elements are introduced into the products.

[0209] (5) By introducing B2O3 into the raw materials, the element B is introduced into the product.

[0210] (6) By introducing NaF into the raw materials, F element is introduced into the product.

[0211] Comparative Examples 1-8

[0212] The difference between Comparative Examples 1-8 and Example 1 lies in the different target general formulas of the layered metal oxides. See Table 1 for details of the differences.

[0213] Preparation of secondary batteries

[0214] Preparation of the positive electrode sheet: The positive electrode active material, conductive agent carbon black, binder polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) were mixed evenly at a weight ratio of 80:15:5 to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto a positive electrode aluminum foil current collector, followed by drying, cold pressing, and slitting to obtain the positive electrode sheet. The positive electrode active material used was the P2-type layered metal oxide prepared in the above examples and comparative examples.

[0215] Preparation of the negative electrode: The negative electrode is an active thin sodium sheet with a diameter of 16 mm.

[0216] Preparation of electrolyte: In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), diethyl carbonate (DEC) and ethylene carbonate (EC) were mixed evenly at a volume ratio of 1 / 1, and an appropriate amount of sodium NaPF6 was added. After being fully dissolved and stirred evenly, a NaPF6 solution with a concentration of 1mol / L was prepared, which is the electrolyte of Example 1.

[0217] Separator membrane: Glass fiber is used as the separator membrane.

[0218] Battery assembly: In a glove box, place the foamed nickel, negative electrode sodium sheet, separator, and positive electrode sheet into the button cell case in sequence. Then, add electrolyte to the battery case and finally seal the battery case to obtain the button cell.

[0219] Analysis and testing

[0220] 1. X-ray diffraction analysis

[0221] Freshly prepared layered metal oxides were soaked in deionized water for 24 hours to obtain water-washed layered metal oxides.

[0222] X-ray diffraction analysis was performed on freshly prepared layered metal oxides and water-washed layered metal oxides to obtain XRD spectra. The intensity of the characteristic peak of the (002) crystal plane was collected and calculated.

[0223] I / I0 ≥ 0.8;

[0224] I0 represents the intensity of the characteristic peak of the (002) crystal plane of a freshly prepared (unsoaked in water) layered metal oxide.

[0225] I represents the intensity of the characteristic peak of the (002) crystal plane of the layered metal oxide after immersion in water for 24 hours.

[0226] The X-ray diffraction analysis parameters are as follows:

[0227] The average particle size of the powder sample is 9 μm;

[0228] Radiation source: CuK rays;

[0229] Scanning mode: Step scan;

[0230] Scanning conditions: 0.016358° / step;

[0231] Entrance slit: 2.5mm, anti-scattering slit: 18mm, receiving slit: 0.30mm.

[0232] 2. Scanning electron microscopy analysis

[0233] The layered metal oxides of Example 1 before and after water washing were analyzed using scanning electron microscopy.

[0234] 3. Battery Analysis

[0235] 3.1 Discharge specific capacity analysis

[0236] 2-4.5V specific capacity test: At 25℃, charge the battery to 4.5V at a constant current of 0.1C, let it rest for 5 minutes, and then discharge it to 2V at 0.1C. The resulting capacity is recorded as the 2-4.5V specific capacity.

[0237] 1.5-4.3V specific capacity test: At 25℃, charge the battery to 4.3V at a constant current of 0.1C, let it rest for 5 minutes, and then discharge it to 1.5V at 0.1C. The resulting capacity is recorded as the 1.5-4.3V specific capacity.

[0238] 3.2 Cyclic specific capacity analysis

[0239] At 25°C, the battery was charged to 4.5V at a constant current of 0.1C, rested for 5 minutes, and then discharged to 2V at 0.1C. The resulting capacity was recorded as the initial capacity C0. Next, the same battery was charged to 4.5V at a constant current of 1C, rested for 5 minutes, and then discharged to 2V at a constant current of 1C. The resulting capacity was recorded as the initial capacity C1. The same battery was then charged and discharged at a constant current of 1C, and the discharge capacity C50 of the battery was recorded after the 50th charge-discharge cycle at a constant current of 1C.

[0240] 50-week capacity retention rate = C50 / C1

[0241] 3.3 Discharge Medium Voltage

[0242] At 25°C, the battery is charged to 4.5V at a constant current of 0.1C, left to stand for 5 minutes, and then discharged to 2V at 0.1C. The resulting discharge voltage is recorded as the 2-4.5V discharge voltage.

[0243] 3.4 Average Discharge Voltage

[0244] At 25°C, the battery is charged to 4.5V at a constant current of 0.1C, left to stand for 5 minutes, and then discharged to 2V at 0.1C. The ratio of the discharge specific energy to the discharge specific capacity of 2-4.5V is recorded as the average discharge voltage.

[0245] The test results for the examples and comparative examples can be found in Table 2.

[0246]

[0247]

[0248]

[0249]

[0250] Results and Discussion

[0251] 1. Phase analysis

[0252] In Example 1, the ratio (I / I0) of the 002 characteristic peak of the layered metal oxide before and after water washing ranged from 0.85 to 1.05. In the comparative examples, the ratio (I / I0) of the 002 characteristic peak of the layered metal oxide before and after water washing ranged from 0.63 to 0.96. Specifically, in the comparative examples containing only Ni and Mn and no Zn, the ratio (I / I0) of the 002 characteristic peak before and after water washing ranged from 0.63 to 0.8. However, in the comparative examples containing Zn, the ratio of the 002 characteristic peak before and after water washing was above 0.8. This indicates the indispensability of Zn. The layered metal oxides with appropriate Zn / Ni / Mn ratios in the examples exhibited superior phase structure stability.

[0253] Figure 1 (a), (b), and (c) respectively show the freshly prepared layered metal oxide (Na) of Example 1. 0.78 Zn 0.05 Ni 0.2 Mn 0.75 O2F 0.01 Layered metal oxides (Na) after water washing 0.78 Zn 0.05 Ni 0.2 Mn 0.75 O2F 0.01 ) and standard P2 phase (Na) 0.67 Ni0.33 Mn 0.67 The XRD pattern of the PDF card (00-054-0894) for O2 is shown in the figure. As shown in the figure, the characteristic peaks of the XRD before and after water washing in Example 1 coincide with the characteristic peaks of (002), (004), (100), (101), and (012) in the standard XRD pattern, showing a single P2 phase. It is worth noting that the XRD pattern of the product of Example 1 shows two small characteristic peaks (marked with ※) near 27.2° and 28.4°, which are different from those of the standard card. These two characteristic peaks reflect the phase structure characteristics of Na and vacancy arranged in an orderly manner. In addition, the peak intensities of the XRD characteristic peaks before and after water washing are almost unchanged. For example, the (I / I0) of the 002 peak near 15.8° is 0.97, and the two characteristic peaks near 27.2° and 28.4° do not disappear. This indicates that the overall structure of Example 1 has excellent structural stability in water and air.

[0254] Figure 2 (a), (b), and (c) show the freshly prepared layered metal oxide (Na) of Comparative Example 1, respectively. 0.78 Ni 0.25 Mn 0.75 O2), layered metal oxides after water washing (Na) 0.78 Ni 0.25 Mn 0.75 O2) and standard P2 phase (Na) 0.67 Ni 0.33 Mn 0.67 The XRD spectrum of the PDF card (00-054-0894) for O2 is shown in the figure. As shown in the figure, the characteristic peaks of the XRD before washing in Comparative Example 1 coincide with the characteristic peaks of the standard XRD spectrum (002), (004), (100), (101), (012), etc. However, very weak impurity peaks appear near 20° and 40°, among which the impurity peak around 40° belongs to NiO impurity peaks. After washing, in addition to the characteristic peaks of the P2 phase and the weak impurity peaks of NiO before washing, new strong impurity peaks appear near 12° and 25°, which do not belong to the characteristic peaks of the P2 phase. This indicates that some structural side reactions occurred in the material after washing, and the phase structure was unstable during the washing process.

[0255] The XRD characteristic peaks of the freshly prepared layered metal oxide in Example 1 are shown below:

[0256] XRD characteristic peaks of layered metal oxides in Example 1

[0257] Serial number Characteristic peak 2 theta ° Relative intensity % Corresponding crystal face 1 15.85 100 (002) 2 32.02 10.69 (004) 3 35.82 12.16 (100) 4 36.77 1.05 (101) 5 39.44 17.81 (012) 6 27.17 0.57 Na / vacancy ordered superlattice peak 7 28.34 0.66 Na / vacancy ordered superlattice peak

[0258] The XRD characteristic peaks of the freshly prepared layered metal oxide of Comparative Example 1 are shown below:

[0259] XRD characteristic peaks of layered metal oxides in Comparative Example 1

[0260] Serial number Characteristic peak 2 theta ° Relative intensity % Corresponding crystal face 1 15.90 100 (002) 2 32.12 9.88 (004) 3 35.94 13.12 (100) 4 36.87 0.36 (101) 5 39.52 21.24 (012) 6 22.03 0.27 By-product miscellaneous peak 7 41.34 1.54 By-product miscellaneous peak

[0261] 2. Morphological analysis

[0262] Figure 3 Images (a) and (b) show scanning electron microscope (SEM) images of the layered metal oxide of Example 1 before and after water washing, respectively. As shown in the figure, the morphology of the layered metal oxide of Example 1 is an irregular hexagonal prism with smooth edges, which are unevenly aggregated together, with an average particle size distribution of 3-15 μm.

[0263] Compare Figure 3 The photos (a) and (b) before and after washing show that the surface, shape and size of the material did not change significantly before and after washing.

[0264] 3. Battery performance analysis

[0265] Figure 4 (a) shows the discharge specific capacity curves of the layered metal oxide of Example 1 at 2-4.5V / 1.5-4.3V; (b) shows the discharge specific capacity curves of the layered metal oxide of Comparative Example 1 at 2-4.5V / 1.5-4.3V.

[0266] The specific capacities of the layered metal oxide in Example 1 at 2-4.5V and 1.5-4.3V were 127.3 and 167.8 mAh / g, respectively, while those of the layered metal oxide in Comparative Example 1 were 125.1 and 161.4 mAh / g. Although Example 1 had a lower proportion of active variable-valence Ni, it exhibited higher capacity in both voltage ranges than the layered metal oxide in the Comparative Example, which contained more impurities.

[0267] The layered metal oxide of Example 1 exhibited a cycle retention rate of 98.3%@50 cycles, while the layered metal oxide of Comparative Example 1 had a cycle retention rate of 65.2%@50 cycles. Example 1 demonstrated a higher cycle retention rate compared to Comparative Example 1, indicating that the layered metal oxide of Example 1 possessed excellent cycling performance.

[0268] The average discharge voltage of the layered metal oxide in Example 1 was 3.61 V (average discharge voltage: 3.53 V), while the average discharge voltage of the layered metal oxide in Comparative Example 1, which contained impurities, was 3.60 V (average discharge voltage: 3.52 V). The layered metal oxide in Example 1 exhibited a higher average discharge voltage.

[0269] In Examples 1-8, the a / c ratio of the layered metal oxide is in the range of 0.04-0.10, and the b / c ratio is in the range of 0.23-0.45. The Zn, Ni, and Mn elements have a synergistic effect, which effectively improves the phase structure stability of the layered metal oxide. The battery exhibits improved specific capacity, discharge voltage, average discharge voltage, and / or capacity retention.

[0270] In Examples 9-16, doping elements Fe, Cu, Mg, Ti, B, or F were introduced. These elements had a synergistic effect with Zn, Ni, and Mn elements, further improving the phase structure stability of the layered metal oxide. The battery exhibited improved specific capacity, discharge voltage, average discharge voltage, and / or capacity retention.

[0271] In Comparative Examples 1-4, the a / c value of the layered metal oxide was 0.00, and the battery did not exhibit improved specific capacity, discharge voltage, average discharge voltage, and / or capacity retention.

[0272] In Comparative Examples 6-7, the b / c values ​​of the layered metal oxides were 0.06 and 0.90 (outside the range of 0.23-0.45), and the batteries did not exhibit improved specific capacity, discharge voltage, average discharge voltage, and / or capacity retention.

[0273] In Comparative Example 8, the x value for the layered metal oxide was 1 (outside the range of 0.6-0.85), and the battery did not exhibit improved specific capacity, discharge voltage, average discharge voltage, and / or capacity retention.

[0274] In summary, this application optimizes the layered metal oxide Na... x Zn a Ni b Mn c M1 d O2M2 e The composition was adjusted so that the content / ratio of each element was 0.6≤x≤0.85, 0.95≤a+b+c+d≤1.05, 0≤d≤0.05, 0≤e≤0.067x, 0.04≤a / c≤0.1, and 0.23≤b / c≤0.45, resulting in a good synergistic relationship between the elements and unexpectedly improving the layered metal oxide Na. x Zn a Ni b Mn c M1 d O2M2 e Due to its stable phase structure, this material, when used as a cathode material in sodium-ion batteries, results in improved specific capacity, discharge voltage, average discharge voltage, and / or capacity retention.

[0275] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. An electrode active material comprising a layered metal oxide, said layered metal oxide having the following general formula: So x Zn a Ni b Mr c M1 d O2M2 e in, 0.6≤x≤0.85, 0.95≤a+b+c+d ≤1.05, 0<d≤0.05, 0≤e≤0.067x; Where, 0.04≤a / c≤0.1, 0.23≤b / c≤0.45; M1 is selected from one or more of Li, K, Mg, V, Cr, Ti, and Sc; M2 is selected from nonmetallic elements other than O; or Where, 0.6≤x≤0.85, 0.95≤a+b+c+d ≤1.05, 0≤d≤0.05, 0<e≤0.067x; Where, 0.04≤a / c≤0.1, 0.23≤b / c≤0.45; M1 is selected from one or more of Li, K, Mg, V, Cr, Ti, and Sc; M2 is selected from nonmetallic elements other than O.

2. The electrode active material according to claim 1, having one or more of the following characteristics: （1）0.03≤a≤0.075； （2）0.18≤b≤0.28； （3）0.67≤c≤0.75； （4）0.03≤d≤0.05； （5）0≤e≤0.05。 3. The electrode active material according to claim 1 or 2, wherein, The layered metal oxide belongs to the P2 phase hexagonal crystal system, space group P63 / mmc.

4. The electrode active material according to any one of claims 1 to 3, wherein, The powder XRD diffraction pattern of the layered metal oxide has one or more of the following characteristic peaks: (1) The first characteristic peak with 2θ values ​​of 15.75°-15.90°; (2) The second characteristic peak with a 2θ value of 31.95°-32.10°; (3) The third characteristic peak with a 2θ value of 35.80°-35.95°; (4) The fourth characteristic peak with 2θ values ​​of 36.75°-36.90°; (5) The fifth characteristic peak with a 2θ value of 39.40°-39.55°.

5. The electrode active material according to claim 4, having one or more of the following characteristics: (1) The ratio of the diffraction intensity of the second characteristic peak to that of the first characteristic peak is 9.5%~13.5%; (2) The ratio of the diffraction intensity of the third characteristic peak to that of the first characteristic peak is 10.5%~14.5%; (3) The ratio of the diffraction intensity of the fourth characteristic peak to that of the first characteristic peak is 0.5%~1.5%; (4) The ratio of the diffraction intensity of the fifth characteristic peak to that of the first characteristic peak is 16.5% to 21.5%.

6. The electrode active material according to claim 4 or 5, having one or more of the following characteristics. (1) The first characteristic peak corresponds to the (002) crystal plane; (2) The second characteristic peak corresponds to the (004) crystal plane; (3) The third characteristic peak corresponds to the (100) crystal plane; (4) The fourth characteristic peak corresponds to the (101) crystal plane; (5) The fifth characteristic peak corresponds to the (012) crystal plane.

7. The electrode active material according to any one of claims 4 to 6, wherein, The powder XRD diffraction pattern of the layered metal oxide also has the following characteristic peaks: (6) The sixth characteristic peak with a 2θ value of 27.15°-27.25°; (7) The seventh characteristic peak with a 2θ value of 28.35°-28.45°.

8. The electrode active material according to claim 7, having one or more of the following characteristics: (1) The ratio of the diffraction intensity of the sixth characteristic peak to that of the seventh characteristic peak is 0.3~0.9:1; (2) The ratio of the diffraction intensity of the sixth characteristic peak to that of the first characteristic peak is 0.2%~1.2%; (3) The ratio of the diffraction intensity of the seventh characteristic peak to that of the first characteristic peak is 0.3% to 1.3%.

9. The electrode active material according to any one of claims 4 to 8, wherein the measurement conditions of the powder XRD diffraction pattern have one or more of the following characteristics: (1) The volume average particle size of the powder sample is 5-15 μm; (2) Radiation source: CuK rays; (3) Scanning mode: Step scan; (4) Scanning conditions: 0.01-0.05° / step; (5) Entrance slit: 2-3 mm, anti-scattering slit: 15-20 mm, receiving slit: 0.2-0.4 mm.

10. The electrode active material according to any one of claims 1 to 9, wherein, M2 is selected from nonmetallic elements other than O, and M2 belongs to the second, third or fourth period.

11. The electrode active material according to any one of claims 1 to 10, wherein, M2 is selected from one or more of F, Cl, B, C, and N.

12. The electrode active material according to any one of claims 1-11, wherein the intensity of the characteristic peak of the corresponding (002) crystal plane in the XRD diffraction pattern of the layered metal oxide powder conforms to the following relationship: I / I0 ≥ 0.8; I0 represents the intensity of the characteristic peak of the (002) crystal plane of a layered metal oxide that has not been soaked in water; I represents the intensity of the characteristic peak of the (002) crystal plane of the layered metal oxide after immersion in water for 24 hours.

13. A secondary battery, comprising a positive electrode, said positive electrode comprising the electrode active material according to any one of claims 1-12.

14. An electrical device comprising a secondary battery according to claim 13.

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