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

Abstract

A positive electrode active material and a preparation method therefor, a positive electrode sheet, a battery, and an electric device. The positive electrode active material comprises: NaxMnaFebMcNdO2+δ-eFe, wherein 0.5≤x≤1.1, a≥0, b≥0, c≥0, d>0, a+b+c+d=1, -0.1≤δ≤0.1, and e≥0; an M ion comprises at least one of Ni2+, Ni3+, Cu2+, Cu+, Zn2+, Mg2+, Y3+, La3+, In3+, Sb3+, Li+, Sn2+ and Ag+; and ∑Bi×Ii 4≥1500 Å-4, where Bi is the molar fraction of cations, Ii is the ionic potential of the cations, the unit is Å-1, the cations comprise manganese ions, iron ions, M ions and N ions, and the ionic potential of the N ions is greater than or equal to 5 Å-1.

Description

Positive electrode active material and preparation method thereof, positive electrode sheet, battery and electrical equipment Technical Field

[0001] The present application belongs to the technical field of secondary batteries, and specifically relates to a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery and an electrical device. Background Art

[0002] Secondary batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as in military equipment, aerospace and other fields.

[0003] Sodium-ion batteries are a type of secondary battery, and layered transition metal oxides are commonly used as positive electrode active materials in sodium-ion batteries. However, existing sodium-ion batteries containing layered transition metal oxides have poor initial efficiency and cycle performance.

[0004] Public content

[0005] In view of the technical problems existing in the background technology, the present application provides a positive electrode active material, aiming to solve the problems of low first efficiency and cycle performance of batteries containing the positive electrode active material.

[0006] In order to achieve the above-mentioned object, the first aspect of the present application provides a positive electrode active material, wherein the positive electrode active material comprises: Na x Mn a Fe b M c N d O 2+δ-e F e ,

[0007] 0.5≤x≤1.1, a≥0, b≥0, c≥0, d>0, a+b+c+d=1, -0.1≤δ≤0.1, e≥0, M ions include Ni 2+ 、Ni 3+ 、Cu 2+ 、Cu + 、Zn 2+ Mg 2+ 、Y 3+ 、La 3+ 、In 3+ 、Sb 3+ 、Li + 、Sn 2+ and Ag + At least one of B i is the molar fraction of cations, I i is the ionic potential of the cation in units of The cations include manganese ions, iron ions, M ions and N ions, and the ion potential of the N ions is greater than or equal to

[0008] The positive electrode active material of the present application has a stable structure during the process of sodium insertion and extraction, thereby improving the initial efficiency and cycle performance of the battery.

[0009] In some embodiments of the present application, Thereby, the first efficiency and cycle performance of the battery can be improved.

[0010] In some embodiments of the present application, the N ions include B 3+ 、Ti 4+ 、Al 3+ 、Si 4+ 、Sn 4+ 、Sb 5+ 、Zr 4+ and Nb 5+ At least one of, optionally, the N ions include B 3+ 、Ti 4+ 、Zr 4+ and Al 3+ Thus, the first efficiency and cycle performance of the battery can be improved.

[0011] In some embodiments of the present application, the M ions include Ni 2+ 、Ni 3+ 、Cu 2+ 、Cu + 、Zn 2+ and Mg 2+ At least one of .

[0012] In some embodiments of the present application, the positive electrode active material satisfies one or more of the following conditions: x is 0.7≤x≤1, and may be 0.8≤x≤1; a is 0.3≤a≤0.7, and may be 0.35≤a≤0.55; b is 0.1≤b≤0.4, and may be 0.2≤b≤0.3; c is 0.2≤c≤0.5, and may be 0.3≤c≤0.4; d is 0.005≤d≤0.1, and may be 0.01≤d≤0.05; δ is -0.05≤δ≤0.05, and may be -0.02≤δ≤0.02; e is 0≤e≤0.01, and may be 0.001≤e≤0.005.

[0013] In some embodiments of the present application, 0.005≤d / (a+b+c)≤0.1, and optionally 0.01≤d / (a+b+c)≤0.05, thereby improving the initial efficiency and cycle performance of the battery.

[0014] In some embodiments of the present application, the phase of the positive electrode active material includes an O3 phase, a space group includes R3m, and an interlayer spacing of 0.53 nm to 0.54 nm, thereby increasing the capacity of the battery.

[0015] In some embodiments of the present application, the positive electrode active material satisfies one or more of the following conditions:

[0016] The positive electrode active material D v 50 is 2μm-30μm, optional is 4μm-12μm;

[0017] The specific surface area of ​​the positive electrode active material is 0.1 m 2 / g-2m 2 / g, optional 0.3m 2 / g-1m 2 / g;

[0018] The compaction density of the positive electrode active material under 8 tons of pressure is 3g / cm 3 -5g / cm 3 , optional 3.5g / cm 3 -4.5g / cm 3 .

[0019] Therefore, when the D of the positive electrode active material v 50. When one or more of the specific surface area and the compacted density is within the above range, the conduction distance of Na ions in the positive electrode active material is short and the surface side reactions are few, which promotes the positive electrode active material to exert its specific capacity and improves the capacity retention rate of the battery containing it.

[0020] The second aspect of the present application provides a method for preparing the positive electrode active material according to the first aspect, comprising:

[0021] Mixing a Na source, an Fe source, a Mn source, an M source, and a N source to obtain a precursor;

[0022] The precursor is calcined to obtain a positive electrode active material.

[0023] Thus, the present application can prepare the above-mentioned positive electrode active material with excellent structural stability, thereby improving the first efficiency and cycle stability of the battery.

[0024] The third aspect of the present application provides another method for preparing the positive electrode active material described in the first aspect, comprising:

[0025] mixing an Fe source, a Mn source, an M source, and a N source with water to obtain a mixed solution;

[0026] reacting the mixed solution with a precipitant to obtain a precursor;

[0027] The precursor is mixed with a Na source and calcined to obtain a positive electrode active material.

[0028] Thus, the present application can prepare the above-mentioned positive electrode active material with excellent structural stability, thereby improving the first efficiency and cycle stability of the battery.

[0029] The fourth aspect of the present application provides a positive electrode plate, which includes the positive electrode active material described in the first aspect of the present application, the positive electrode active material prepared by the method described in the second aspect, or the positive electrode active material prepared by the method described in the third aspect.

[0030] The fifth aspect of the present application provides a battery comprising the positive electrode sheet according to the fourth aspect of the present application, thereby having an excellent capacity retention rate.

[0031] A sixth aspect of the present application provides an electrical device comprising the battery described in the fifth aspect.

[0032] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0034] FIG1 is a schematic structural diagram of a battery according to an embodiment of the present application;

[0035] FIG2 is a schematic structural diagram of a battery module according to an embodiment of the present application;

[0036] FIG3 is a schematic structural diagram of a battery pack according to an embodiment of the present application;

[0037] FIG4 is an exploded view of FIG3 ;

[0038] FIG5 is a schematic diagram of an embodiment of an electric device using a battery as a power source;

[0039] FIG6 is a comparison of the charge and discharge curves of the button cells prepared in Example 1 and Comparative Example 1 at 10 mA / g in the first cycle;

[0040] FIG7 is a comparison chart of the capacity retention rates of button batteries prepared in Example 1 and Comparative Example 1.

[0041] Description of reference numerals:

[0042] 1: Secondary battery; 2: Battery module; 3: Battery pack; 4: Upper case; 5: Lower case. DETAILED DESCRIPTION

[0043] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0044] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0045] For the sake of clarity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0046] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0048] With the technological advancements and increasing demand for electric vehicles and rechargeable mobile devices, secondary batteries, as a representative of the new energy sector, are experiencing rapid growth in research. Sodium-ion batteries offer significant price advantages over traditional lithium-ion batteries and hold broad application prospects in large-scale energy storage systems.

[0049] Layered metal oxides have become one of the popular positive active materials for sodium-ion batteries due to their high electrical conductivity, high energy density, large capacity, and long cycle life. Before the battery is charged and discharged, the sodium content in the layered metal oxide is high, and there are positively charged sodium ions between oxygen and oxygen, which shield the negative electrical repulsion between oxygen and oxygen. As the first charge progresses, the sodium ions on the surface of the layered metal oxide are released, and the negative electrical repulsion between oxygen and oxygen increases. The layered metal oxide undergoes irreversible structural changes, which reduces the number of sodium insertion sites in the layered metal oxide, resulting in a decrease in the first efficiency of the battery. At the same time, as the negative electrical repulsion between oxygen and oxygen in the layered metal oxide increases, its local structure becomes unstable and is prone to reconstruction to form new phases, such as rock salt phase or spinel phase. At the same time, as the sodium ions decrease, the activity of oxygen will also increase, which is prone to side reactions with the electrolyte, resulting in the loss of cations and oxygen ions, forming cracks, and thus reducing the cycle performance of the battery.

[0050] In this application, the positive electrode active material includes an ion potential greater than or equal to N ions, and manganese ions, iron ions, M ions and N ions meet The resulting positive electrode active material has a strong covalent bond with oxygen, resulting in a strong interaction that effectively stabilizes the structural changes of the positive electrode active material during sodium intercalation and deintercalation, thereby improving the initial efficiency of the battery. At the same time, due to the strong interaction between the cations and oxygen in the resulting positive electrode active material, the repulsive force between oxygen and oxygen is weak, making the structure of the positive electrode active material stable and the activity of oxygen weakened, thereby inhibiting side reactions between the layered oxide and the electrolyte and improving the battery's cycling performance.

[0051] The positive electrode active material disclosed in the embodiments of the present application is suitable for secondary batteries, and the battery disclosed in the embodiments of the present application can be used in electrical devices that use batteries as power sources or various energy storage systems that use batteries as energy storage elements. Electrical devices may include but are not limited to mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys and electric airplane toys, etc., and spacecraft may include airplanes, rockets, space shuttles and spacecraft, etc.

[0052] In a first aspect, the present application proposes a positive electrode active material, wherein the positive electrode active material comprises: Na x Mn a Fe b M c N d O 2+δ-e F e ,

[0053] 0.5≤x≤1.1, a≥0, b≥0, c≥0, d>0, a+b+c+d=1, -0.1≤δ≤0.1, e≥0, M ions include Ni 2+ 、Ni 3+ 、Cu 2+ 、Cu + 、Zn 2+ Mg 2+ 、Y 3+ 、La 3+ 、In 3+ 、Sb 3+ 、Li + 、Sn 2+ and Ag + At least one of B i is the molar fraction of cations, I i is the ionic potential of the cation in units of The cations include manganese ions, iron ions, M ions and N ions, and the ion potential of the N ions is greater than or equal to

[0054] The present application at least includes the following beneficial effects: the positive electrode active material includes an ion potential greater than or equal to N ions, and manganese ions, iron ions, M ions and N ions meet The resulting positive electrode active material has a strong covalent bond with oxygen, resulting in a strong interaction that effectively stabilizes the structural changes of the positive electrode active material during sodium intercalation and deintercalation, thereby improving the initial efficiency of the battery. At the same time, due to the strong interaction between the cations and oxygen in the resulting positive electrode active material, the repulsive force between oxygen and oxygen is weak, making the structure of the positive electrode active material stable and the activity of oxygen weakened, thereby inhibiting side reactions between the layered oxide and the electrolyte and improving the battery's cycling performance.

[0055] In this application, the ionic potential of the cation I i It is defined as the cation charge number / cation radius, where the cation charge number is equal to its valence and the unit of cation radius is B i is the molar fraction of cations, which is equal to the molar number of cations in the positive electrode active material / (molar number of manganese ions a + molar number of iron ions b + molar number of M ions c + molar number of N ions d) × 100%, where molar number of manganese ions a + molar number of iron ions b + molar number of M ions c + molar number of N ions d = 1, and Σ represents the sum, for example, ΣB in this application i ×I i 4 =B Mn ×I Mn4 +B Fe ×I Fe 4 +B M ×I M 4 +B n ×I n 4 .

[0056] In some embodiments of the present application, the positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e middle In other embodiments of the present application, the positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e middle Therefore, in this application, the positive electrode active material is added with an ion potential greater than or equal to N ions and cations (including manganese ions, iron ions, M ions and N ions) ΣB i ×I i 4 Meeting the above conditions results in a strong covalent bond between the cations and oxygen in the resulting positive electrode active material, resulting in a strong interaction, which can effectively stabilize the structural changes of the positive electrode active material during the sodium intercalation and deintercalation process, thereby improving the initial efficiency of the battery. At the same time, due to the strong interaction between the cations and oxygen in the resulting positive electrode active material, the repulsive force between oxygen and oxygen is weak, making the structure of the positive electrode active material stable and the activity of oxygen weakened, thereby inhibiting the side reactions between the layered oxide and the electrolyte and improving the battery cycle performance.

[0057] In some embodiments of the present application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e Where x can be 0.5≤x≤1.1, for example, 0.6≤x≤1.1, 0.7≤x≤1, 0.8≤x≤1.1, 1≤x≤1.1, etc. Thus, the positive electrode active material includes the sodium element at this content, so that the battery has a higher capacity. In other embodiments of the present application, the positive electrode active material Nax Mn a Fe b M c N d O 2+δ-e F e Here, x can be 0.7≤x≤1, for example, 0.8≤x≤1.

[0058] It should be noted that in the positive electrode, battery, or electrical device, sodium ions are consumed during the battery formation and cycling processes, so the measured sodium content x in the positive electrode active material may be less than 1. Furthermore, if a sodium supplement is used in the positive and negative electrode sheets, the measured sodium content x in the positive electrode active material may be greater than 1 after the battery formation and cycling processes.

[0059] In some embodiments of the present application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e Where a can be a≥0, for example, 0.001≤a<1, 0.005≤a≤0.9, 0.1≤a≤0.8, 0.2≤a≤0.7, 0.3≤a≤0.6, 0.4≤a≤0.5, etc. Therefore, the positive electrode active material includes this content of manganese, which can effectively improve the structural stability of the positive electrode active material and improve the cycle stability of the battery containing it. In other embodiments of the present application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e Here, a can be 0.3≤a≤0.7, for example, 0.35≤a≤0.55.

[0060] In some embodiments of the present application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e Where b can be b≥0, for example, 0.001≤b<1, 0.005≤b≤0.9, 0.1≤b≤0.8, 0.2≤b≤0.7, 0.3≤b≤0.6, 0.4≤b≤0.5, etc. Therefore, the positive electrode active material includes this content of Fe, which can increase the specific capacity of the material. In other embodiments of the present application, the above-mentioned positive electrode active material Na x Mna Fe b M c N d O 2+δ-e F e Here, b can be 0.1≤b≤0.4, for example, 0.2≤b≤0.3.

[0061] In some embodiments of the present application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e The M ions may include Ni 2+ 、Ni 3+ 、Cu 2+ 、Cu + 、Zn 2+ Mg 2+ 、Y 3+ 、La 3+ 、In 3+ 、Sb 3+ 、Li + 、Sn 2+ and Ag + In some other embodiments of the present application, the positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e The M ions may include Ni 2+ 、Ni 3+ 、Cu 2+ 、Cu + 、Zn 2+ and Mg 2+ At least one of .

[0062] In some embodiments of the present application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e Where c is 0≤c, for example, 0.001≤c<1, 0.005≤c≤0.9, 0.1≤c≤0.8, 0.2≤c≤0.7, 0.3≤c≤0.6, 0.4≤c≤0.5, etc. Thus, the positive electrode active material includes the M ions in this content, which can improve the structural stability of the material. In other embodiments of the present application, the above-mentioned positive electrode active material Na x Mna Fe b M c N d O 2+δ-e F e Here, c can be 0.2≤c≤0.5, for example, 0.3≤c≤0.4.

[0063] In some embodiments of the present application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e The ionic potential of N ions in the Therefore, in this application, the positive electrode active material is added with an ion potential greater than or equal to N ions and cations (including manganese ions, iron ions, M ions and N ions) ΣB i ×I i 4 Meeting the above conditions results in a strong covalent bond between the cations and oxygen in the resulting positive electrode active material, resulting in a strong interaction, which can effectively stabilize the structural changes of the positive electrode active material during the sodium intercalation and deintercalation process, thereby improving the initial efficiency of the battery. At the same time, due to the strong interaction between the cations and oxygen in the resulting positive electrode active material, the repulsive force between oxygen and oxygen is weak, making the structure of the positive electrode active material stable and the activity of oxygen weakened, thereby inhibiting the side reactions between the layered oxide and the electrolyte and improving the battery cycle performance.

[0064] As an example, the N ions include B 3+ 、Ti 4+ 、Al 3+ 、Si 4+ 、Sn 4+ 、Sb 5+ 、Zr 4+ and Nb 5+ In some other embodiments of the present application, the N ions include B 3+ 、Ti 4+ 、Zr 4+ and Al 3+ At least one of .

[0065] The ionic potentials of common ions are shown in Table 1:

[0066] Table 1 Ionic potentials of common ions

[0067] In some embodiments of the present application, the above-mentioned positive electrode active material Na x Mn a Feb M c N d O 2+δ-e F e Where d is d>0, for example, 0.001≤c≤1, 0.005≤c≤0.9, 0.1≤c≤0.8, 0.2≤c≤0.7, 0.3≤c≤0.6, 0.4≤c≤0.5. In other embodiments of the present application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e Where d is 0.005≤d≤0.1, for example 0.01≤d≤0.05. Thus, by adding the N ion content in the positive electrode active material, and the cations (including manganese ions, iron ions, M ions and N ions) ΣB i ×I i 4 Meeting the above conditions results in a strong covalent bond between the cations and oxygen in the resulting positive electrode active material, resulting in a strong interaction, which can effectively stabilize the structural changes of the positive electrode active material during the sodium intercalation and deintercalation process, thereby improving the initial efficiency of the battery. At the same time, due to the strong interaction between the cations and oxygen in the resulting positive electrode active material, the repulsive force between oxygen and oxygen is weak, making the structure of the positive electrode active material stable and the activity of oxygen weakened, thereby inhibiting the side reactions between the layered oxide and the electrolyte and improving the battery cycle performance.

[0068] In some embodiments of the present application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e 0.005≤d / (a+b+c)≤0.1, for example, 0.007≤d / (a+b+c)≤0.1, 0.01≤d / (a+b+c)≤0.095, 0.015≤d / (a+b+c)≤0.09, 0.02≤d / (a+b+c)≤0.085, 0.025≤d / (a+b+c)≤0.08, 0.03≤d / (a+b+c)≤0.075, 0.035≤d / (a+b+c)≤0.07, 0.04≤d / (a+b+c)≤0.065, 0.045≤d / (a+b+c)≤0.06, 0.05≤d / (a+b+c)≤0.055, etc. In some embodiments of the present application, the above-mentioned positive electrode active material Na x Mn a Fe b M cN d O 2+δ-e F e 0.01≤d / (a+b+c)≤0.05. Therefore, the molar amount of N and the sum of the molar amounts of Mn ions, Fe ions, and M ions in the positive electrode active material of the present application satisfy the above relationship, which can improve the structural stability of the positive electrode active material, thereby improving the initial efficiency and cycle stability of the battery.

[0069] In some embodiments of the present application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e Where δ is -0.1≤δ≤0.1, and e is e≥0, for example, -0.09≤δ≤0.09, -0.08≤δ≤0.08, -0.07≤δ≤0.07, -0.06≤δ≤0.06, -0.05≤δ≤0.05, -0.04≤δ≤0.04, -0.03≤δ≤0.03, -0.02≤δ≤0.02, -0.01≤δ≤0.01, -0.01≤δ≤0, 0≤δ≤0.01, etc., 0.01≤e≤0.09, 0.02≤e≤0.08, 0.03≤e≤0.07, 0.04≤e≤0.06, 0.05≤e≤0.06, etc. In other embodiments of the present application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e Here, the value of δ is -0.05≤δ≤0.05, for example, -0.02≤δ≤0.02; the value of e is 0≤e≤0.01, for example, 0.001≤e≤0.005.

[0070] Specifically, doping the oxygen sites in the positive electrode active material of the present application with this content of F can effectively stabilize the oxygen in the positive electrode active material, thereby reducing the structural damage caused by lattice oxygen release in the positive electrode active material, improving the stability of the material, and further improving the cycle stability of the battery.

[0071] It should be noted that in the positive electrode sheet, battery or electrical device, due to the battery cycling process, the oxygen element in the positive electrode active material is lost, so the measured oxygen element content 2+δ-e in the positive electrode active material may be less than 2.

[0072] In some embodiments of the present application, the phase of the positive electrode active material includes O3 phase, and the space group includes The interlayer spacing is 0.53nm-0.54nm, for example, the interlayer spacing can be 0.532nm-0.54nm, 0.535nm-0.54nm, 0.537nm-0.54nm, etc. Specifically, the formed O3 phase has a high Na content in the positive electrode active material, which can release more Na ions, thereby increasing the battery capacity.

[0073] It should be noted that the phase state, space group and interlayer spacing of the positive electrode active material in the present application can be characterized by X-ray diffraction.

[0074] Specifically, the interlayer spacing d of the 003 crystal plane of the positive electrode active material is 003 The space group test method includes: grinding the sample to be tested in an agate mortar in a dry room or glove box and then passing it through a 350 mesh sieve. Taking an appropriate amount of the sieved sample, place it in the middle of the groove of the sample holder so that the loose sample powder is slightly higher than the plane of the sample holder; taking a glass slide and gently pressing the sample surface to make the sample surface flat and consistent with the frame plane, and scraping off the excess powder. After the sample preparation is completed, a Brucker D8A_A25 X-ray powder diffractometer from Brucker AxS, Germany, is used to measure the CuK α The ray is the radiation source, and the wavelength of the ray is The scanning 2θ angle range is 5°-60°, and the scanning rate is 4° / min. After the test is completed, the angle corresponding to the 003 crystal plane is obtained according to the Bragg equation 2d·sinθ=λ, and each unit cell of the 003 crystal plane contains three layers of transition metal layers, and the interlayer spacing d of the 003 crystal plane can be obtained. 003 By comparing the XRD diffraction peaks of the sample with the standard card of the XRD analysis software, the space group of the sample can be confirmed. At the same time, in the XRD spectrum, the characteristic peak in the range of 40.5° to 42.5° indicates that the positive electrode active material is O3 phase.

[0075] In some embodiments of the present application, the D of the positive electrode active material v 50 is 2 μm-30 μm, for example, the D v 50 can be 2μm-29μm, 4μm-28μm, 5μm-15μm, 6μm-14μm, 8μm-13μm, 9μm-12μm, 10μm-11μm, etc. In other embodiments of the present application, the D of the positive active material v 50 is 4μm-12μm.

[0076] In this application, D v 50 refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 50%, for example, with reference to the standard GB / T 19077-2016, and is measured using a laser particle size analyzer (such as Malvern Master Size 3000).

[0077] In some embodiments of the present application, the specific surface area of ​​the positive electrode active material is 0.1 m 2 / g-2m 2 / g, for example, the specific surface area of ​​the positive electrode active material can be 0.1m 2 / g-1.5m 2 / g,0.2m 2 / g-1m 2 / g,0.3m 2 / g-0.8m 2 / g,0.3m 2 / g-0.5m 2 In other embodiments of the present application, the specific surface area of ​​the positive electrode active material is 0.3 m 2 / g-1m 2 / g.

[0078] In this application, the specific surface area of ​​the positive electrode active material can be tested by referring to the following method: using the American Microelectronics multi-station fully automatic specific surface area and pore analyzer GeminiVII2390, take about 7g of the sample and put it into a 9cc long tube with a bulb, degas at 200℃ for 2h, and then put it into the host for testing to obtain the BET (specific surface area) data of the positive electrode active material.

[0079] In some embodiments of the present application, the compaction density of the positive electrode active material at a pressure of 300 MPa is 3.0 g / cm 3 -5.0g / cm 3 For example, the compaction density of the positive electrode active material at a pressure of 300 MPa can be 3.0 g / cm 3 -4.9g / cm 3 , 3.2g / cm 3 -4.8g / cm 3 , 3.5g / cm 3 -4.5g / cm 3 , 3.7g / cm 3 -4.2g / cm 3 , 4g / cm 3 -4.2g / cm 3 In some embodiments of the present application, the compaction density of the positive electrode active material under a pressure of 300 MPa is 3 g / cm 3 -4g / cm 3 .

[0080] In this application, "compacted density" has a meaning well known in the art and can be measured using instruments and methods well known in the art. For example, the following test method can be used: a fixed amount m of powder is placed in a special compaction mold, the mold is placed on a compaction density instrument, a pressure of 300 MPa is set, and the volume v of the powder under a pressure of 300 MPa is measured on the equipment. The compacted density is calculated by density = mass m / volume v (see GB / T24533-2009 for details).

[0081] Specifically, when the D of the positive electrode active material of the present application is v 50. When one or more of the specific surface area and the compaction density under a pressure of 300 MPa is within the above range, the conduction distance within the positive electrode active material is small and the surface side reactions are few, which promotes the positive electrode active material to exert its specific capacity and improves the capacity retention rate of the battery containing it.

[0082] The second aspect of the present application provides a method for preparing the positive electrode active material according to the first aspect, comprising:

[0083] S100: Mixing Na source, Fe source, Mn source, M source and N source to obtain a precursor

[0084] In some embodiments of the present application, a Na source, a Fe source, a Mn source, an M source, and a N source are mixed to obtain a precursor, which is then mixed according to the above-mentioned positive electrode active material composition.

[0085] It should be noted that, due to the loss of Na source during the subsequent calcination process, the amount of Na added will be slightly higher than the required Na content in the above-mentioned positive electrode active material composition.

[0086] The Na source, Fe source, Mn source, M source and N source in this application are conventional materials in the field, and those skilled in the art can select them according to actual conditions. For example, the Na source may include at least one of Na2CO3, NaHCO3, NaOH and Na2O2; the Fe source may include at least one of FeO, Fe2O3 and Fe3O4; the Mn source may include at least one of Mn2O3, Mn3O4, MnO and MnO2; the M source may include at least one of M oxides, salts containing M and other compounds; the N source may include at least one of N oxides, salts containing N and other compounds.

[0087] It should be noted that if it is necessary to dope the positive electrode active material with F element, at least one of the Na source, Fe source, Mn source, M source and N source adopts at least one of its corresponding fluorine-containing salts and other compounds, such as sodium fluoride, iron fluoride, iron fluoride, manganese fluoride, M fluoride (fluoride salt of M) and N fluoride (fluoride salt of N).

[0088] S200: calcining the precursor

[0089] In some embodiments of the present application, the above-mentioned precursor is placed in a muffle furnace and calcined in an air atmosphere, and then cooled to room temperature and mechanically crushed to obtain the positive electrode active material, wherein the calcination temperature can be 600℃-1200℃, for example, it can be 600℃-1100℃, 700℃-1000℃, 800℃-900℃, etc., and the holding time is 10h-20h, for example, it can be 10h-19h, 11h-18h, 12h-17h, 13h-16h, 14h-15h, etc.

[0090] In addition, as needed, the precursor can be pre-calcined and kept warm before calcining the precursor. The pre-calcination temperature can be 600℃-900℃, for example, 600℃-850℃, 650℃-800℃, 600℃-750℃, 550℃-700℃, 500℃-650℃, 550℃-600℃, etc., and the holding time is 10h-20h, for example, 10h-19h, 11h-18h, 12h-17h, 13h-16h, 14h-15h, etc.

[0091] Therefore, the solid-phase method can be used to prepare the above-mentioned positive electrode active material with stable structure, thereby improving the first efficiency and cycle stability of the battery.

[0092] The third aspect of the present application provides another method for preparing the positive electrode active material described in the first aspect, comprising:

[0093] Sa: Mix Fe source, Mn source, M source and N source with water to obtain a mixed solution

[0094] In some embodiments of the present application, the Fe source, the Mn source, the M source and the N source are mixed with water to obtain a mixed solution, and the positive electrode active material composition is mixed with water to obtain a mixed solution.

[0095] It should be noted that the Fe source, Mn source, M source and N source in the present application are conventional materials in the field, and those skilled in the art can select them according to actual conditions. For example, the Fe source may include at least one of ferric chloride, ferric sulfate and ferric nitrate; the Mn source may include at least one of manganese chloride, manganese sulfate and manganese nitrate; the M source may include at least one of chloride, sulfate and nitrate of M; and the N source may include at least one of chloride, sulfate and nitrate of N.

[0096] Sb: The mixed solution is reacted with a precipitant to obtain a precursor

[0097] In some embodiments of the present application, the mixed solution obtained in step Sa is reacted with a solution containing a precipitant to obtain a precursor, wherein the solution containing the precipitant includes at least one of hydroxide, carbonate and oxalate, for example, the solution containing the precipitant includes at least one of ammonia water, carbonic acid and oxalic acid.

[0098] Sc: Mix the precursor with the Na source and calcine

[0099] In some embodiments of the present application, the obtained precursor and the Na source are mixed according to the above-mentioned positive electrode active material composition, ball milled or mechanically stirred to mix uniformly, placed in a muffle furnace for calcination, then cooled to room temperature, and mechanically crushed to obtain the positive electrode active material, wherein the calcination temperature is 600°C-1200°C, for example, 700°C-1100°C, 800°C-1000°C, 900°C-950°C, etc., the calcination atmosphere can be air or oxygen atmosphere, and the holding time is 10h-20h, for example, 10h-19h, 11h-18h, 12h-17h, 13h-16h, 14h-15h, etc. Wherein, the Na source can include at least one of Na2CO3, NaHCO3, NaOH and Na2O2.

[0100] It should be noted that, as needed, before the precursor and the Na source are mixed and calcined, the precursor Na source can be pre-calcined and kept warm in advance. The pre-calcination temperature can be 600°C-900°C, for example, 600°C-850°C, 650°C-800°C, 600°C-750°C, 550°C-700°C, 500°C-650°C, 550°C-600°C, etc., and the holding time can be 10h-20h, for example, 10h-19h, 11h-18h, 12h-17h, 13h-16h, 14h-15h, etc.

[0101] In the present application, if the corresponding N source is water-insoluble, such as N oxide (N oxide), the N source is not added in step Sa, and the precursor is mixed with the Na source and the N source and sintered in step Sc.

[0102] It should be noted that if it is necessary to dope the positive electrode active material with F element, at least one of the Na source, Fe source, Mn source, M source and N source adopts at least one of its corresponding fluorine-containing salts and other compounds, such as sodium fluoride, iron fluoride, manganese fluoride, M fluoride (fluoride salt of M) and N fluoride (fluoride salt of N).

[0103] It should be noted that, due to the loss of Na source during the calcination process, the amount of Na added will be slightly higher than the required Na content in the above-mentioned positive electrode active material composition.

[0104] Therefore, the co-precipitation method can be used to prepare the above-mentioned positive electrode active material with stable structure, thereby improving the initial efficiency and cycle stability of the battery.

[0105] In a fourth aspect, the present application provides a positive electrode plate, which includes the positive electrode active material described in the first aspect of the present application or the positive electrode active material prepared by the method described in the second aspect.

[0106] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0107] The positive electrode current collector may be a conventional metal foil or a composite current collector (a metal material may be disposed on a polymer substrate to form a composite current collector). As an example, the positive electrode current collector may include at least one of copper foil, aluminum foil, nickel foil, stainless steel foil, stainless steel mesh, and carbon-coated aluminum foil.

[0108] The positive electrode active material layer may also optionally include a conductive agent and a binder. The conductive agent is used to improve the conductivity of the positive electrode active material layer, and the binder is used to firmly bond the positive electrode active material and the binder to the positive electrode current collector. This application does not specifically limit the types of conductive agent and binder, and they can be selected according to actual needs.

[0109] As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers; the binder may include at least one of styrene-butadiene rubber (SBR), water-based acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA) and polyvinyl alcohol (PVA).

[0110] These materials are all commercially available.

[0111] The fifth aspect of the present application provides a battery comprising the positive electrode sheet according to the fourth aspect of the present application, thereby having an excellent capacity retention rate.

[0112] A battery is a battery that can be recharged to activate the active materials after discharge and continue to be used.

[0113] It will be understood that the battery proposed in this application is a sodium ion battery.

[0114] Typically, a battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The separator is placed between the positive and negative electrodes to isolate them. The electrolyte conducts ions between the positive and negative electrodes.

[0115] [Negative electrode]

[0116] In a battery, the negative electrode sheet generally includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0117] The negative electrode current collector may be a conventional metal foil or a composite current collector (for example, a metal material may be disposed on a polymer substrate to form a composite current collector). As an example, the negative electrode current collector may be a copper foil.

[0118] There is no limitation on the specific type of the negative electrode active material. Active materials known in the art that can be used for the negative electrode of sodium ion batteries can be used, and those skilled in the art can select according to actual needs. As an example, the negative electrode active material may include but is not limited to at least one of sodium metal, carbon material, alloy material, transition metal oxide and / or sulfide, phosphorus-based material, and titanate material. Specifically, the carbon material may include at least one of hard carbon, soft carbon, amorphous carbon, and nanostructured carbon material; the alloy material may include an alloy material formed by at least one of Si, Ge, Sn, Pb, and Sb; the general formula of the transition metal oxide and sulfide is M x N y , wherein M includes at least one of Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V, and N includes O or S; the phosphorus-based material may include at least one of red phosphorus, white phosphorus, and black phosphorus; the titanate material may include Na2Ti3O7, Na2Ti6O 13 、Na4Ti5O 12 、Li4Ti5O 12 , NaTi2(PO4)3. These materials can be obtained through commercial channels.

[0119] The negative electrode active material layer typically also optionally includes a binder and a conductive agent. The conductive agent is used to improve the conductivity of the negative electrode active material layer, and the binder is used to firmly bond the negative electrode active material and the binder to the negative electrode current collector. This application does not specifically limit the types of conductive agent and binder, and they can be selected according to actual needs.

[0120] As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0121] As an example, the binder may include at least one of styrene-butadiene rubber (SBR), styrene-butadiene rubber (SBCs), water-based acrylic resin, and carboxymethyl cellulose (CMC).

[0122] The negative electrode active material layer may optionally include a thickener, such as carboxymethyl cellulose (CMC). However, the present application is not limited thereto, and other materials that can be used as thickeners for sodium ion battery negative electrode sheets may also be used.

[0123] [Electrolyte]

[0124] The electrolyte solution may include an electrolyte salt and a solvent.

[0125] As an example, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethylsulfonyl)imide.

[0126] As an example, the solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0127] In some embodiments, the electrolyte further includes additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives capable of improving certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance.

[0128] [Isolation film]

[0129] As the above-mentioned isolation membrane, the present application has no special restrictions and any known porous structure isolation membrane with electrochemical stability and mechanical stability can be selected according to actual needs. For example, it can include a single-layer or multi-layer film containing at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0130] The embodiment of the present application has no particular limitation on the shape of the battery, which can be cylindrical, square or any other shape. FIG1 shows a secondary battery 1 with a square structure as an example.

[0131] In some embodiments, the battery may include an outer packaging for encapsulating the positive electrode sheet, the negative electrode sheet, and the electrolyte.

[0132] In some embodiments, the outer packaging may include a housing and a cover. The housing may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing a receiving cavity. The housing may have an opening communicating with the receiving cavity, and the cover may be positioned over the opening to seal the receiving cavity.

[0133] The positive electrode sheet, negative electrode sheet, and separator can be wound or laminated to form an electrode assembly. The electrode assembly is encapsulated in the housing. The number of electrode assemblies in a battery can include one or more, which can be adjusted according to needs.

[0134] In some embodiments, the outer packaging of the battery may include a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.

[0135] The outer packaging of the battery may also include a soft bag, such as a bag-type soft bag. The material of the soft bag may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0136] In some embodiments, batteries may be assembled into a battery module. The battery module may contain multiple batteries, and the specific number may be adjusted according to the application and capacity of the battery module.

[0137] Figure 2 shows an example battery module 2. Referring to Figure 2 , within the battery module 2, multiple secondary batteries 1 may be arranged sequentially along the length of the battery module 2. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 1 may be secured together using fasteners.

[0138] The battery module 2 may further include a housing having a housing space, wherein the housing space accommodates a plurality of secondary batteries 1. In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0139] Figures 3 and 4 illustrate an example battery pack 3. Referring to Figures 3 and 4 , the battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box comprises an upper case 4 and a lower case 5. The upper case 4 can be placed over the lower case 5 to form an enclosed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0140] In a sixth aspect, the present application provides an electrical device comprising the battery described in the fifth aspect. Specifically, the battery can serve 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), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships, satellites, and energy storage systems.

[0141] FIG5 shows an example of an electric device, which includes a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0142] As another example, electric devices may include mobile phones, tablet computers, and laptop computers. These electric devices are generally required to be lightweight and thin, and may use batteries as power sources.

[0143] In order to make the technical problems, technical solutions, and beneficial effects solved by the embodiments of the present application more clear, the following will be further described in detail with reference to the embodiments and drawings. Obviously, the described embodiments are only some of the embodiments of the present application, not all of them. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0144] Example 1

[0145]

【NaNi 0.24 Fe 0.26 Mn 0.39 Mg 0.1 Si 0.01 O2 preparation].

[0146] Na2CO3, NiO, Fe2O3, Mn2O3, MgO, SiO2 were weighed in a total of 30 g of sample according to the molar ratio of Na:Ni:Fe:Mn:Mg:Si of 1:0.24:0.26:0.39:0.1:0.01. The obtained sample was pre-ground in an agate mortar and added to a planetary ball mill for ball milling for 1 hour to obtain a precursor mixture. The obtained precursor mixture was then evenly placed in an open crucible, and then heated from room temperature to 950 ° C at a heating rate of 5 ° C / min in a muffle furnace, and kept at a constant temperature of 950 ° C for 15 hours. After cooling naturally, the positive electrode active material NaNi 0.24 Fe 0.26 Mn 0.39 Mg 0.1 Si 0.01 O2.

[0147]

Preparation of positive electrode sheet

[0148] NaNi 0.24 Fe 0.26 Mn 0.39 Mg 0.1 Si 0.01 O2, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in the solvent NMP in a mass ratio of 80:15:5 to form a uniform positive electrode slurry. The positive electrode slurry is evenly coated on the surface of the positive electrode current collector aluminum foil. After drying and cold pressing, it is punched into a disc with a diameter of 14 mm to obtain a positive electrode sheet.

[0149]

Preparation of negative electrode sheet

[0150] The negative electrode is made of metallic sodium.

[0151] Preparation of electrolyte

[0152] Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in equal volumes to obtain an organic solvent, and then NaClO4 was dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0153]

Isolation film

[0154] A porous polyethylene film was used as the separator.

[0155]

Preparation of button battery

[0156] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation layer. The prepared electrolyte is added to obtain a button battery.

[0157] The button cells containing positive electrode active materials of Examples 2-20 and Comparative Examples 1-4 are the same as those of Example 1 except for the different parameters in the process of preparing the positive electrode active materials (see Table 1).

[0158] The compositions of the positive electrode active materials in the batteries of Examples 1-20 and Comparative Examples 1-4 of the present application are shown in Table 2.

[0159]

[0160]

[0161] The phase state, space group and interlayer spacing of the positive electrode active materials in Examples 1-20 and Comparative Examples 1-4, as well as the first efficiency and cycle performance of the obtained button batteries were characterized. The characterization results are shown in Table 3.

[0162] Testing methods:

[0163] (1) Phase state of positive electrode active material and interlayer spacing d of 003 crystal plane 003 And space group test:

[0164] In a dry room or glove box, grind the sample to be tested in an agate mortar and pass it through a 350 mesh sieve. Take an appropriate amount of the sieved sample and place it in the middle of the groove of the sample holder so that the loose sample powder is slightly higher than the plane of the sample holder. Take a glass slide and gently press the sample surface until the sample surface is flattened and aligned with the frame plane, and scrape off the excess powder. After the sample is prepared, use a Brucker D8A_A25 X-ray powder diffractometer from Brucker AxS, Germany, with CuK α The ray is the radiation source, and the wavelength of the ray is The scanning 2θ angle range is 5°-60°, and the scanning rate is 4° / min. After the test is completed, the angle corresponding to the 003 crystal plane is obtained according to the Bragg equation 2d·sinθ=λ, and each unit cell of the 003 crystal plane contains three layers of transition metal layers, and the interlayer spacing d of the 003 crystal plane can be obtained. 003 By comparing the XRD diffraction peaks of the sample with the standard card of the XRD analysis software, the space group of the sample can be confirmed. At the same time, in the XRD spectrum, the characteristic peak in the range of 40.5° to 42.5° indicates that the positive electrode active material is O3 phase.

[0165] (2) First cycle coulombic efficiency test of button cell

[0166] At 25°C, charge the button cell at a current density of 10 mA / g to 4.3 V (C0), and then discharge it at a current density of 10 mA / g to 1.5 V (C1). The first cycle coulombic efficiency of the battery = C1 / C0 × 100%.

[0167] (3) Cyclic performance test

[0168] At 25°C, charge the button cell at a constant current density of 10 mA / g to 4.2 V, then discharge it at a constant current density of 10 mA / g to 1.5 V. This yields the specific discharge capacity C2 of the button cell. The cell is then cycled 50 times at a constant current density of 10 mA / g, with the specific discharge capacity C3 at the 50th cycle being obtained. Capacity retention after 50 cycles = C2 / C3 × 100%.

[0169] Figure 6 is a comparison of the charge and discharge curves of the button batteries prepared in Example 1 and Comparative Example 1 at the first cycle of 10 mA / g. It can be seen from the figure that the first cycle coulombic efficiency of the button battery in Example 1 is 98%, and the first cycle coulombic efficiency of the button battery in Comparative Example 1 is 81%. Obviously, the first cycle coulombic efficiency of the button battery in Example 1 is higher than that of the button battery in Comparative Example 1.

[0170] FIG7 is a comparison chart of the capacity retention rates of button batteries prepared in Example 1 and Comparative Example 1. It can be seen from the figure that the capacity retention rate of the battery in Example 1 after 50 cycles is significantly better than that in Comparative Example 1.

[0171] Table 3

[0172] Conclusion: From the data in Table 3, it can be seen that the first cycle coulombic efficiency and the capacity retention rate of the batteries of Examples 1-20 are significantly higher than those of the batteries of Comparative Examples 1-4, which shows that the positive electrode active material of the present application includes an ion potential greater than or equal to N ions, and manganese ions, iron ions, M ions and N ions satisfy ΣB i ×I i 4 ≥1500, which can improve the first-cycle coulombic efficiency and cycle performance of the battery.

[0173] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A positive electrode active material, wherein include: So x Mr a Feb b M c N d O 2+δ-e F e , 0.5≤x≤1.1, a≥0, b≥0, c≥0, d>0, a+b+c+d=1, -0.1≤δ≤0.1, e≥0, M ions include Ni 2+ 、Ni 3+ , Cu 2+ , Cu + 、Zn 2+ Mg 2+ , Y 3+ ,La 3+ 、In 3+ , Sb 3+ , Li + Sn 2+ and Ag + At least one of B i is the molar fraction of the cation, I i is the ionic potential of the cation in units of The cations include manganese ions, iron ions, M ions and N ions, and the ion potential of the N ions is greater than or equal to 2. The positive electrode active material according to claim 1, wherein 3. The positive electrode active material according to claim 1 or 2, wherein The N ions include B 3+ 、Ti 4+ 、Al 3+ 、Si 4+ Sn 4+ , Sb 5+ 、Zr 4+ and Nb 5+ At least one of, optionally, the N ions include B 3+ 、Ti 4+ 、Zr 4+ and Al 3+ At least one of .

4. The positive electrode active material according to any one of claims 1 to 3, wherein The M ions include Ni 2+ 、Ni 3+ , Cu 2+ , Cu + 、Zn 2+ and Mg 2+ At least one of .

5. The positive electrode active material according to any one of claims 1 to 4, wherein The positive electrode active material satisfies one or more of the following conditions: The value of x is 0.7≤x≤1, and can be 0.8≤x≤1; The value of a is 0.3≤a≤0.7, and can be 0.35≤a≤0.55; The value of b is 0.1≤b≤0.4, and can be 0.2≤b≤0.3; The value of c is 0.2≤c≤0.5, and can be 0.3≤c≤0.4; The value of d is 0.005≤d≤0.1, and can be selected as 0.01≤d≤0.05; The value of δ is -0.05≤δ≤0.05, and can be -0.02≤δ≤0.02; The value of e is 0≤e≤0.01, and can be selected as 0.001≤e≤0.

005.

6. The positive electrode active material according to any one of claims 1 to 5, wherein 0.005≤d / (a+b+c)≤0.1, which can be optionally 0.01≤d / (a+b+c)≤0.

05.

7. The positive electrode active material according to any one of claims 1 to 6, wherein The phase state of the positive electrode active material includes an O3 phase, and the space group includes The interlayer spacing is 0.53nm-0.54nm.

8. The positive electrode active material according to any one of claims 1 to 7, wherein The positive electrode active material satisfies one or more of the following conditions: The positive electrode active material D v 50 is 2μm-30μm, optional is 4μm-12μm; The specific surface area of ​​the positive electrode active material is 0.1 m 2 / g-2m 2 / g, optional 0.3m 2 / g-1m 2 / g; The compaction density of the positive electrode active material under a pressure of 300 MPa is 3 g / cm 3 -5g / cm 3 , which can be 3g / cm 3 -4g / cm 3 。 9. A method for preparing the positive electrode active material according to any one of claims 1 to 8, wherein: include: Mixing a Na source, a Fe source, a Mn source, an M source, and a N source to obtain a precursor; The precursor is calcined to obtain a positive electrode active material.

10. A method for preparing the positive electrode active material according to any one of claims 1 to 8, wherein: include: Mixing the Fe source, the Mn source, the M source and the N source with water to obtain a mixed solution; reacting the mixed solution with a precipitant to obtain a precursor; The precursor is mixed with a Na source and calcined to obtain a positive electrode active material.

11. A positive electrode sheet, wherein: The positive electrode sheet comprises the positive electrode active material according to any one of claims 1 to 8 or the positive electrode active material prepared by the method according to claim 9 or 10.

12. A battery, wherein: The battery comprises the positive electrode sheet according to claim 11.

13. An electrical device, wherein: Comprising the battery as claimed in claim 12.

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