Electrode active material, secondary battery, and electric device

Abstract

The present application provides an electrode active material, comprising a layered metal oxide having the general formula: Na x M1 a M2 b Mn 1‑a‑b O 2‑z F z ; wherein 0.55≤x≤0.85, a≥0, b≥0, 0.1≤a+b≤0.33, 0.06≤z / (1-a-b)≤0.13; M1 is selected from one or more of an alkali metal element, an alkaline earth metal element, except Na; M2 is selected from one or more of a transition metal element, except Mn.

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 provides an electrode active material comprising a layered metal oxide having the following general formula:

[0007] Na x M1 a M2 b Mn 1-a-b O 2-z F z

[0008] Where 0.55≤x≤0.85, a≥0, b≥0, 0.1≤a+b≤0.33, 0.06≤z / (1-ab)≤0.13;

[0009] M1 is selected from one or more alkali metal elements other than Na and alkaline earth metal elements;

[0010] M2 is selected from one or more transition metal elements other than Mn.

[0011] The electrode active material described above exhibits improved phase structure stability. Furthermore, when used in secondary batteries, this electrode active material provides one or more of the following advantages: increased discharge voltage, increased discharge specific capacity, and improved cycle performance.

[0012] In some embodiments, the layered metal oxide is a P2-type layered metal oxide. Electrode active materials based on the above scheme exhibit improved phase structure stability, and when used in secondary batteries, these batteries demonstrate increased discharge voltage, increased specific capacity, and / or improved cycle retention.

[0013] In some implementations, the electrode active material has one or more of the following characteristics:

[0014] -The alkali metal element is selected from Li, K, or a combination thereof;

[0015] - The alkaline earth metal element is selected from Be, Mg, Ca, Sr, Ba or a combination thereof;

[0016] - The transition metal element is selected from Ni, Fe, Ti, V, Cr, Co, Cu, Zn or a combination thereof.

[0017] The electrode active material based on the above scheme has improved phase structure stability, and when used in a secondary battery, the secondary battery exhibits improved discharge voltage, improved specific capacity, and / or improved cycle retention.

[0018] In some implementations, the electrode active material has one or more of the following characteristics:

[0019] -The alkali metal element is Li;

[0020] -The alkaline earth metal element is Mg;

[0021] - The transition metal element is selected from Ni, Fe, Zn or a combination thereof.

[0022] The electrode active material based on the above scheme has improved phase structure stability, and when used in a secondary battery, the secondary battery exhibits improved discharge voltage, improved specific capacity, and / or improved cycle retention.

[0023] In some implementations, the electrode active material has one or more of the following characteristics:

[0024] (1) 0.65 ≤ x ≤ 0.75;

[0025] (2) 0.06 ≤ z / (1-ab) ≤ 0.08.

[0026] The electrode active material based on the above scheme has improved phase structure stability, and when used in a secondary battery, the secondary battery exhibits improved discharge voltage, improved specific capacity, and / or improved cycle retention.

[0027] In some embodiments, 0.25 ≤ (a+b) / (1-ab) ≤ 0.43. The electrode active material based on the above scheme exhibits improved phase structure stability, and when used in secondary batteries, the secondary batteries demonstrate increased discharge voltage, increased specific capacity, and / or improved cycle retention.

[0028] In some embodiments, in the electrode active material, the intensities of the characteristic peaks corresponding to the (002) crystal plane in the X-ray diffraction spectrum of the layered metal oxide conform to the following relationship:

[0029] I / I0 ≥ 0.8;

[0030] 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;

[0031] 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.

[0032] The electrode active material based on the above scheme has improved phase structure stability, and when used in a secondary battery, the secondary battery exhibits improved discharge voltage, improved specific capacity, and / or improved cycle retention.

[0033] In some implementations, the electrode active material includes

[0034] The core comprises the layered metal oxide;

[0035] A shell covering at least a portion of the surface of the core, the shell containing a first element A selected from: Ti, Al, Mg, Co, or combinations thereof;

[0036] The electrode active material has the following general formula:

[0037] Na x M1 a M2 b Mn 1-a-b O 2-z F z ·A n

[0038] Where n>0.

[0039] The electrode active material based on the above scheme has improved phase structure stability, and when used in a secondary battery, the secondary battery exhibits improved discharge voltage, improved specific capacity, and / or improved cycle retention.

[0040] In some embodiments, the electrode active material conforms to the following relationship: 0 < n ≤ 0.0006 / z. The electrode active material based on the above scheme exhibits improved phase structure stability, and when used in a secondary battery, the secondary battery demonstrates increased discharge voltage, increased specific capacity, and / or improved cycle retention.

[0041] In a second aspect, this application provides a secondary battery including a positive electrode, said positive electrode comprising the aforementioned electrode active material.

[0042] In a third aspect, this application provides an electrical device including the aforementioned secondary battery.

[0043] Beneficial effects

[0044] One or more embodiments of this application have one or more of the following beneficial effects:

[0045] (1) The layered metal oxide of this application has enhanced phase structure stability and can maintain phase structure stability in both aqueous and atmospheric environments;

[0046] (2) The electrode active material of this application is used in a secondary battery, which has an improved discharge voltage;

[0047] (3) The electrode active material of this application is used in a secondary battery, which has an improved specific capacity;

[0048] (4) The electrode active material of this application is used in secondary batteries, which have improved cycle stability. Attached Figure Description

[0049] Figure 1 (a), (b), and (c) show the XRD spectra of the freshly prepared layered metal oxide, the water-washed layered metal oxide, and the standard phase card (00-054-0894) of Example 1, respectively.

[0050] Figure 2 (a), (b) and (c) show the XRD spectra of the freshly prepared layered metal oxide, the water-washed layered metal oxide and the standard phase card (00-054-0894) of Comparative Example 1A.

[0051] Figure 3 (a) and (b) show scanning electron microscope images of the layered metal oxide of Example 1 at different magnifications.

[0052] Figure 4 (a) shows the discharge specific capacity curve of the layered metal oxide of Example 1; (b) shows the discharge specific capacity curve of the layered metal oxide of Comparative Example 1A.

[0053] Figure 5 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0054] Figure 6 yes Figure 5 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0055] Figure 7 This is a schematic diagram of a battery module according to one embodiment of this application.

[0056] Figure 8 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0057] Figure 9 yes Figure 8 An exploded view of a battery pack according to one embodiment of this application is shown.

[0058] Figure 10 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0059] Explanation of reference numerals in the attached figures:

[0060] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Top cover assembly Detailed Implementation

[0061] 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.

[0062] 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.

[0063] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0064] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0065] 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.

[0066] 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.

[0067] 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).

[0068] [Rechargeable Battery]

[0069] 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.

[0070] 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.

[0071] 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.

[0072] [Negative electrode plate]

[0073] 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.

[0074] 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.

[0075] 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.).

[0076] 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.

[0077] 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).

[0078] 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.

[0079] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0080] 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.

[0081] [Positive electrode plate]

[0082] 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.

[0083] 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.

[0084] 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.).

[0085] 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.

[0086] 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.

[0087] 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.

[0088] [Positive electrode active material]

[0089] In a first aspect, this application provides an electrode active material comprising a layered metal oxide having the following general formula:

[0090] Na x M1 a M2 b Mn 1-a-b O 2-z Fz

[0091] Where 0.55≤x≤0.85, a≥0, b≥0, 0.1≤a+b≤0.33, 0.06≤z / (1-ab)≤0.13;

[0092] M1 is selected from one or more alkali metal elements other than Na and alkaline earth metal elements;

[0093] M2 is selected from one or more transition metal elements other than Mn.

[0094] The electrode active material of the above-described scheme exhibits improved phase structure stability. Furthermore, the electrode active material, when used in a secondary battery, demonstrates one or more of the following advantages: increased discharge voltage, increased discharge specific capacity, and improved cycle performance.

[0095] Unrestricted by theory, 0.06 ≤ z / (1-ab) ≤ 0.13 is crucial for the stability and electrochemical performance of materials. When z / (1-ab) is within this range, the material exhibits the following advantages:

[0096] (1) The material exhibits improved phase structure stability. The phase structure of the material can remain stable in both aqueous and atmospheric environments. This property is beneficial for maintaining structural stability during the coating process to form electrodes (aqueous environment) and during atmospheric storage (atmospheric environment).

[0097] (2) The material has a high specific capacity.

[0098] (3) F doping can effectively enhance the ionic bond strength and structural stability of the material, thereby improving the reversibility of phase transition and cycle reversibility under high pressure, thus giving the material superior cycle performance.

[0099] (4) z / (1-ab) represents a specific F / Mn ratio that can suppress M1, M2 and Mn. 4+ The orderly arrangement of Mn stabilizes the valence change of Mn under low voltage, making the valence change of active transition metals such as Fe and Ni at higher voltages during charging significantly different from that of low-voltage Mn. This improves the overall utilization rate of M2 active transition metal elements such as Fe and Ni in the material and increases the discharge voltage of the material.

[0100] (5) Since the material has a high discharge voltage, the cycling problem caused by the low voltage Mn variable valence Jean Taylor effect can be suppressed by shortening the voltage window, thereby improving the energy density and cycling performance of the material.

[0101] When the ratio of F to Mn is too low, the proportion of Mn-O is much higher than that of Mn-F, resulting in minimal improvement on the series of water and air instability problems caused by Mn-O. Furthermore, even a very small proportion of F / Mn doping is insufficient to break the transition metal-Mn bond. 4+ The ordered structure is insufficient to suppress the two-phase transition in the low-voltage region, nor is it sufficient to ensure that the Mn valence change occurs entirely below 2V. As a result, the cycle decay defect caused by the Ginger-Taylor distortion during the 2-4.5V cycling process is caused by this.

[0102] When the ratio of F to Mn is too high, F will be mostly distributed on the surface of the structure due to its high electronegativity, forming a large number of complex fluoride layers on the surface uncontrollably. This makes it difficult for most Na ions to be removed during charging, resulting in low charging capacity, low discharge capacity in total charge, and thus low energy density.

[0103] In some embodiments, the layered metal oxide is a P2-type layered metal oxide.

[0104] In some implementations, in the P2-type layered metal oxide, 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.

[0105] In some embodiments, the layered P2 type layered metal oxide belongs to the hexagonal crystal system, space group P63 / mmc.

[0106] In some embodiments, the alkali metal element is selected from Li, K, or a combination thereof. Electrode active materials based on the above schemes exhibit improved phase structure stability, and when used in secondary batteries, these batteries demonstrate increased discharge voltage, increased specific capacity, and / or improved cycle retention.

[0107] In some implementations, the term "alkaline earth metals" refers to elements in Group 2 of the periodic table (IUPAC).

[0108] In some embodiments, the alkaline earth metal element is selected from Be, Mg, Ca, Sr, Ba, or combinations thereof. Electrode active materials based on the above schemes exhibit improved phase structure stability, and when used in secondary batteries, these batteries demonstrate increased discharge voltage, increased specific capacity, and / or improved cycle retention.

[0109] In some implementations, the term transition metal refers to elements in groups 3 to 12 of the periodic table (IUPAC).

[0110] In some embodiments, the transition metal other than Mn is selected from Ni, Fe, Ti, Cr, Co, Cu, Zn, or combinations thereof. Electrode active materials based on the above schemes exhibit improved phase structure stability, and when used in secondary batteries, these batteries demonstrate increased discharge voltage, increased specific capacity, and / or improved cycle retention.

[0111] In some embodiments, the alkali metal element is Li. The electrode active material based on the above scheme exhibits improved phase structure stability, and when used in a secondary battery, the secondary battery demonstrates increased discharge voltage, increased specific capacity, and / or improved cycle retention.

[0112] In some embodiments, the alkaline earth metal element is Mg. The electrode active material based on the above scheme exhibits improved phase structure stability, and when used in a secondary battery, the secondary battery demonstrates increased discharge voltage, increased specific capacity, and / or improved cycle retention.

[0113] In some embodiments, the transition metal element is selected from Ni, Fe, Zn, or combinations thereof. Electrode active materials based on the above schemes exhibit improved phase structure stability, and when used in secondary batteries, these batteries demonstrate increased discharge voltage, increased specific capacity, and / or improved cycle retention.

[0114] In some implementations, 0.06≤z / (1-ab)≤0.07, 0.07≤z / (1-ab)≤0.08, 0.08≤z / (1-ab)≤0.09, 0.09≤z / (1-ab)≤0.1, 0.01≤z / (1-ab)≤0.11, 0.11≤z / (1-ab)≤0.12, and 0.12≤z / (1-ab)≤0.13.

[0115] In some implementations, x takes values ​​of 0.55-0.6, 0.6-0.65, 0.65-0.7, 0.7-0.75, 0.75-0.8, or 0.8-0.85.

[0116] In some implementations, the value of 'a' is 0, 0-0.05, 0.05-0.1, 0.1-0.15, 0.15-0.2, 0.2-0.25, 0.25-0.3, or 0.3-0.33.

[0117] In some implementations, the value of b is 0, 0-0.05, 0.05-0.1, 0.1-0.15, 0.15-0.2, 0.2-0.25, 0.25-0.3, or 0.3-0.33.

[0118] In some implementations, a and b are not both 0.

[0119] In some implementation schemes, the value of a+b is 0.1-0.15, 0.15-0.2, 0.2-0.25, 0.25-0.3, or 0.3-0.33.

[0120] In some embodiments, 0.65 ≤ x ≤ 0.75. The electrode active material based on the above scheme exhibits improved phase structure stability, and when used in secondary batteries, the secondary batteries demonstrate increased discharge voltage, increased specific capacity, and / or improved cycle retention.

[0121] In some embodiments, 0.06 ≤ z / (1-ab) ≤ 0.08. The electrode active material based on the above scheme exhibits improved phase structure stability, and when used in a secondary battery, the secondary battery demonstrates increased discharge voltage, increased specific capacity, and / or improved cycle retention.

[0122] In some implementations, 0.25 ≤ (a+b) / (1-ab) ≤ 0.43. The ratio of (M1+M2) / Mn content is the main factor affecting the trivalent and tetravalent valence of Mn and the actual sodium content of the structure. When the Na content is determined, the valence composition of Mn depends on the content of (M1+M2). Trivalent Mn is a charge compensation element that provides low voltage (below 2V). The low voltage and the easy occurrence of the Jan Taylor effect are often the main factors leading to cycle decay. M1 or M2 are the elements that mainly provide (above 2V) charge compensation and affect the material structure type, playing a major role in the final overall capacity and average voltage of the material. If the (M1+M2) / Mn content ratio is too low, (a+b) / (1-ab) < 0.25, Mn is the main element providing charge compensation. To provide high capacity, excessive trivalent Mn participation easily leads to Gaines-Taylor distortion of the structure. If the (M1+M2) / Mn content ratio is too high, (a+b) / (1-ab) > 0.43, Mn accounts for a very small proportion of the structure of the central atomic framework of the transition metal layer. Therefore, the possibility of F doping to build Mn-F bonds is greatly reduced, and the benefit of F doping to stabilize the structure is greatly reduced. Therefore, the electrode active material based on the above scheme has improved phase structure stability, and when this electrode active material is used in secondary batteries, the secondary batteries exhibit improved discharge voltage, improved specific capacity, and / or improved cycle retention.

[0123] In some implementations, (a+b) / (1-ab) takes values ​​of 0.25-0.3, 0.3-0.35, 0.35-0.4, or 0.4-0.43.

[0124] In some embodiments, in the electrode active material, the intensities of the characteristic peaks corresponding to the (002) crystal plane in the X-ray diffraction spectrum of the layered metal oxide conform to the following relationship:

[0125] I / I0 ≥ 0.8;

[0126] 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;

[0127] 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.

[0128] 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...

[0129] In some embodiments, the measurement conditions for the powder XRD diffraction pattern have one or more of the following characteristics:

[0130] (1) The volume average particle size of the powder sample is 5-15 μm;

[0131] (2) Radiation source: CuK rays;

[0132] (3) Scanning mode: Step scan;

[0133] (4) Scanning conditions: 0.01-0.05° / step;

[0134] (5) Entrance slit: 1-5mm, anti-scattering slit: 10-20mm, receiving slit: 0.1-1mm.

[0135] In some implementations, 0.8 ≤ I / I0 ≤ 1.

[0136] In some implementations, 0.9 ≤ I / I0 ≤ 1.

[0137] In some implementations, the electrode active material includes

[0138] The core comprises the layered metal oxide;

[0139] A shell covering at least a portion of the surface of the core, the shell containing a first element A selected from: Ti, Al, Mg, Co, or combinations thereof;

[0140] The electrode active material has the following general formula:

[0141] Na x M1 a M2 b Mn 1-a-b O 2-z F z ·A n

[0142] Where n>0.

[0143] The electrode active material based on the above scheme has improved phase structure stability, and when used in a secondary battery, the secondary battery exhibits improved discharge voltage, improved specific capacity, and / or improved cycle retention.

[0144] In the above embodiments, the first element A exists in the shell in the form of an oxide containing only element A, or in the form of a composite oxide containing both element Na and element A.

[0145] In the above implementation scheme, the subscript n of the first element A indicates that the first element A is in Na x M1 a M2 b Mn 1-a-b O 2-z F z ·A n The percentage of molar content.

[0146] In some embodiments, the electrode active material conforms to the following relationship:

[0147] 0 < n ≤ 0.0006 / z.

[0148] The electrode active material based on the above scheme has improved phase structure stability, and when used in a secondary battery, the secondary battery exhibits improved discharge voltage, improved specific capacity, and / or improved cycle retention.

[0149] In some embodiments, the electrode active material is a powder material. The volume average particle size of the powder is from 0.5 μm to 15 μm, for example 0.5-1 μm, 1-1.5 μm, 1.5-2 μm, 2-2.5 μm, 2.5-3 μm, 3-3.5 μm, 3.5-4 μm, 4-4.5 μm, 4.5-5 μm, 5-7 μm, 7-9 μm, 9-11 μm, 11-13 μm, or 13-15 μm.

[0150] 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 / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0151] 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.

[0152] In a third aspect, this application provides an electrical device including the aforementioned secondary battery.

[0153] [Electrolytes]

[0154] 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.

[0155] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0156] In some embodiments, the electrolyte salt is selected from sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, and sodium hexafluoroarsenate.

[0157] 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.

[0158] 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.

[0159] [Isolation membrane]

[0160] 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.

[0161] 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.

[0162] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0170] 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.

[0171] Figure 8 and Figure 9 This is battery pack 1 as an example. (See reference...) Figure 8 and Figure 9 The 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.

[0172] 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.

[0173] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0174] Figure 10This 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.

[0175] 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.

[0176] The following examples demonstrate the preparation of layered metal oxides having the following general formula:

[0177] Na x M1 a M2 b Mn 1-a-b O 2-z F z

[0178] M1 is selected from one or more alkali metal elements other than Na and alkaline earth metal elements;

[0179] M2 is selected from one or more transition metal elements other than Mn.

[0180] Example 1

[0181] Target general formula: Na 0.75 Ni 0.25 Mn 0.75 O 1.95 F 0.05

[0182] According to the stoichiometric ratio of the target formula, 15.55 g of Na₂CO₃ (99% purity), 7.306 g of NiO (99% purity), 0.82 g of NaF (98% purity), and 23.16 g of Mn₂O₃ (98% purity) 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 a black P₂ type layered metal oxide, Na. 0.75 Ni 0.25 Mn 0.75 O 1.95 F 0.05 Material.

[0183] Example 2-12

[0184] The difference between Examples 2-12 and Example 1 lies in the target general formula of the layered metal oxide. See Table 1 for details of the differences.

[0185] Examples 12-14

[0186] Examples 12-14 will prepare the following electrode active materials, which include:

[0187] The core comprises the layered metal oxide;

[0188] A shell covering at least a portion of the surface of the core, the shell containing a first element A selected from: Ti, Al, Mg, Co, or combinations thereof;

[0189] The electrode active material has the following general formula:

[0190] Na x M1 a M2 b Mn 1-a-b O 2-z F z ·A n

[0191] M1 is selected from one or more alkali metal elements other than Na and alkaline earth metal elements;

[0192] M2 is selected from one or more transition metal elements other than Mn.

[0193] Example 12

[0194] Target general formula: Na 0.75 Ni 0.25 Mn 0.75 O 1.95 F 0.05 ·Mg 0.01

[0195] The difference between Example 12 and Example 1 is that after the material is synthesized, the product is ball-milled with nano MgO powder at a molar ratio of 100:1 and then calcined at a temperature of 400-600℃ for 4-10 hours.

[0196] Examples 13 and 14

[0197] The difference between Examples 13 and 14 and Example 12 is that the target general formula of the layered metal oxide varies depending on the amount of MgO coating. Apart from the difference in coating amount, the other preparation methods are the same as in Example 12.

[0198] Comparative Examples 1A, 1B, and 2-7

[0199] The difference between Comparative Examples 1A, 1B, and 2-7 and Example 1 lies in the different target general formulas of the layered metal oxides. See Table 1 for details of the differences.

[0200] Preparation of secondary batteries

[0201] 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.

[0202] Preparation of the negative electrode: The negative electrode is an active thin sodium sheet with a diameter of 16 mm.

[0203] 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. Then, an appropriate amount of NaPF6 was added and stirred until fully dissolved and homogeneous to prepare a NaPF6 solution with a concentration of 1mol / L, which is the electrolyte of Example 1.

[0204] Separator membrane: Glass fiber is used as the separator membrane.

[0205] 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.

[0206] Analysis and testing

[0207] 1. X-ray diffraction analysis

[0208] Freshly prepared layered metal oxides were soaked in deionized water for 24 hours to obtain water-washed layered metal oxides.

[0209] 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: I / I0≥0.8;

[0210] I represents the intensity of the characteristic peak of the (002) crystal plane of a freshly prepared layered metal oxide;

[0211] I0 represents the intensity of the characteristic peak of the (002) crystal plane of the layered metal oxide after water washing.

[0212] The XRD pattern was tested using a Bruker D8 Discover X-ray powder diffractometer from Bruker AxS, Germany. The X-ray diffraction parameters were as follows: average particle size of the 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. After obtaining the XRD diffraction pattern, the position of the characteristic peak of the (002) crystal plane was confirmed, and its peak height was measured, which is the intensity of the characteristic peak of the (002) crystal plane.

[0213] 2. Scanning electron microscopy analysis

[0214] The layered metal oxides of Example 1 were analyzed using scanning electron microscopy.

[0215] 3. Battery Analysis

[0216] 3.1 Discharge specific capacity analysis

[0217] 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.

[0218] 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.

[0219] 3.2 Cyclic specific capacity analysis

[0220] 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 above steps were then repeated for the same battery at a constant current of 1C, and the discharge capacity C of the battery was recorded after the 50th cycle of constant current charge-discharge at a 1C rate. 50 .

[0221] 50-week capacity retention rate = C 50 / C1

[0222] 3.3 Discharge Medium Voltage

[0223] 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.

[0224] 3.4 Average Discharge Voltage

[0225] 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.

[0226] The results of the above tests are detailed in Table 1.

[0227]

[0228] Results and Discussion

[0229] 1. Phase analysis

[0230] In the examples, the ratio (I / I0) of the 002 characteristic peak in the layered metal oxides before and after water washing ranged from 0.85 to 1.1. In the comparative examples, the ratio (I / I0) of the 002 characteristic peak in the layered metal oxides before and after water washing ranged from 0.5 to 0.8. The layered metal oxides in the examples exhibited superior phase structure stability.

[0231] Figure 1 Figures (a), (b), and (c) show the XRD spectra of the freshly prepared layered metal oxide, the water-washed layered metal oxide, and the standard phase card (00-054-0894) of Example 1. As shown in the figure, the characteristic peaks of the XRD before and after water washing in Example 1 coincide with multiple characteristic peaks of the standard XRD spectrum, such as 002, 004, 100, 101, and 012, indicating a single P2 phase. Furthermore, the peak intensities of the XRD characteristic peaks before and after water washing remain almost unchanged, for example, the 002 peak near 15°.

[0232] Figure 2 Figures (a), (b), and (c) show the XRD spectra of the freshly prepared layered metal oxide and the layered metal oxide after water washing in Comparative Example 1A. As shown in the figure: the characteristic peaks of the XRD before water washing in Example 1 coincide with the characteristic peaks of the standard XRD spectrum at 002, 004, 100, 101, and 012, etc., and low-intensity impurity peaks appear near 20° and 40°, with the 40° impurity peak belonging to NiO. After water washing, in addition to the characteristic peaks of the P2 phase and the weak impurity peaks of NiO before water 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 structures of the material underwent side reactions after water washing, and the water washing process was unstable.

[0233] 2. Morphological analysis

[0234] Figure 3Images (a) and (b) show scanning electron microscope images of the layered metal oxide of Example 1 at different magnifications. As shown in the figure, the morphology of the layered metal oxide of Example 1 is an irregular hexagonal prism with rounded edges, which are unevenly aggregated together, with an average particle size distribution of 3-15 μm.

[0235] 3. Battery performance analysis

[0236] 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 1A at 2-4.5V / 1.5-4.3V.

[0237] The specific capacities of the layered metal oxide in Example 1 at 2-4.5V and 1.5-4.3V were 145 mAh / g and 175 mAh / g, respectively, while the specific capacities of the layered metal oxide in Comparative Example 1A were 109 and 165 mAh / g. The layered metal oxide in Example 1 exhibited higher capacity in both voltage ranges.

[0238] The layered metal oxide of Example 1 exhibited a cycle retention rate of 83.72%@50 cycles, while the layered metal oxide of Comparative Example 1A had a cycle retention rate of 64.9%@50 cycles. The layered metal oxide of the Example 1 demonstrated a higher cycle retention rate.

[0239] The average discharge voltage of the layered metal oxide in Example 1 was 3.63V (average discharge voltage: 3.54V), while the average discharge voltage of the layered metal oxide in Comparative Example 1A was 3.41V (average discharge voltage: 3.30V). The layered metal oxide in the Example 1 exhibited a higher average discharge voltage.

[0240] As can be seen from Examples 1-3, when z / (1-ab) is in the range of 0.06-0.13, the layered metal oxide material exhibits improved stability, higher specific capacity, higher average discharge voltage, and cycle retention rate.

[0241] As can be seen from Examples 4-5, when x is between 0.6 and 0.85, the layered metal oxide material exhibits improved stability, higher specific capacity, higher average discharge voltage, and cycle retention rate.

[0242] As can be seen from Examples 6-11, M1 can be selected from one or more alkali metal elements (e.g., Li) or alkaline earth metal elements (e.g., Mg), and M2 can be selected from one or more transition metal elements (e.g., Ni, Zn, Fe). The layered metal oxide material exhibits improved stability, higher specific capacity, higher average discharge voltage, and cycle retention rate.

[0243] As can be seen from Examples 12-14, by providing an MgO coating layer (with a coating amount of 0.6%-1.5% molar percentage of the layered metal oxide material) on the surface of the layered metal oxide material, the coated layered metal oxide material exhibits improved stability, higher specific capacity, higher average discharge voltage, and cycle retention rate.

[0244] As can be seen from Comparative Examples 1A, 1B, and 3-5, the undoped layered metal oxides did not exhibit the aforementioned improved performance.

[0245] As can be seen from Comparative Example 2, when the Na content (i.e., the x value) reaches 1, the layered metal oxide does not exhibit the aforementioned improved performance.

[0246] As can be seen from Comparative Examples 6 and 7, when the values ​​of z / (1-ab) are 0.14 and 0.05, respectively, the layered metal oxides do not exhibit the aforementioned improved performance.

[0247] In summary, without theoretical constraints, when z / (1-ab) ranges from 0.06 to 0.13, there is a synergistic effect between Mn and F elements in the material. Appropriate F / Mn doping ratios can break the interaction between M1 and M2 metals and Mn. 4+ The formed ordered cationic structure not only stabilizes the valence change of Mn at low voltage, but also clearly distinguishes the valence changes of active transition metals such as Fe and Ni at higher voltages from those of low-voltage Mn during charging. This suppresses complex two-phase transitions in the low-voltage region while simultaneously increasing the discharge voltage and capacity. This allows the material to address the poor cycling performance caused by the Jan Taylor effect of low-voltage Mn valence changes by shortening the voltage window, thus improving the material's cycling performance and energy density. Furthermore, the addition of F significantly improves the poor water and air stability issues caused by the simple Me-O configuration in layered oxides, and addresses a series of common problems related to slurry preparation processes and storage.

[0248] 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 M1 a M2 b Mr 1-a-b O 2-z F z Where 0.55≤x≤0.85, a≥0, b≥0, 0.1≤a+b≤0.33, 0.06≤z / (1-ab)≤0.13; M1 is selected from one or more alkaline earth metal elements, and a > 0; M2 is selected from one or more transition metal elements other than Mn; or M1 is selected from one or more alkali metal elements other than Na and alkaline earth metal elements; M2 is a combination of Ni and Zn.

2. The electrode active material according to claim 1, wherein, The layered metal oxide is a P2-type layered metal oxide.

3. The electrode active material according to any one of claims 1-2, having one or more of the following characteristics: - The alkali metal element is selected from Li, K, or a combination thereof; - The alkaline earth metal element is selected from Be, Mg, Ca, Sr, Ba or a combination thereof; - The transition metal element is selected from Ni, Fe, Ti, Cr, Co, Cu, Zn or a combination thereof.

4. The electrode active material according to any one of claims 1-3, having one or more of the following characteristics: - The alkali metal element is Li; - The alkaline earth metal element is Mg; - The transition metal element is selected from Ni, Fe, Zn or a combination thereof.

5. The electrode active material according to any one of claims 1-4, wherein it has one or more of the following characteristics: （1） 0.65≤x≤0.75； (2) 0.06≤z / (1-ab)≤0.

08.

6. The electrode active material according to any one of claims 1-5, wherein, 0.25≤(a+b) / (1-ab)≤0.

43.

7. The electrode active material according to any one of claims 1-6, wherein, The intensity of the characteristic peaks corresponding to the (002) crystal plane in the X-ray diffraction pattern of the layered metal oxide 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.

8. The electrode active material according to any one of claims 1-7, comprising: The core comprises the layered metal oxide; A shell covering at least a portion of the surface of the core, the shell containing a first element A selected from: Ti, Al, Mg, Co, or combinations thereof; The electrode active material has the following general formula: So x M1 a M2 b Mr 1-a-b O 2-z F z A n in, n>0。 9. The electrode active material according to claim 8, wherein, The electrode active material conforms to the following relationship: 0 < n ≤ 0.0006 / z.

10. A secondary battery comprising a positive electrode, said positive electrode comprising the electrode active material according to any one of claims 1-9.

11. An electrical device comprising a secondary battery according to claim 10.

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