Positive electrode active material and preparation method thereof, positive electrode plate, battery and electric equipment

Abstract

The positive electrode active material comprises NaxMnaFebMcNdO2 + delta-eFe, 0.5 < = x < = 1.1, a > = 0, b > = 0, c > = 0, d > 0, a + b + c + d = 1,-0.1 < = delta < = 0.1, e > = 0, M ions comprise at least one of Ni < 2 + >, Ni < 3 + >, Cu < 2 + >, Cu < + >, Zn < 2 + >, Mg < 2 + >, Y < 3 + >, La < 3 + >, In < 3 + >, Sb < 3 + >, Li < + >, Sn < 2 + > and Ag < + >, sigma Bi * Ii4 > is greater than or equal to 1500-4, Bi is the mole fraction of cations, Ii is the ion potential of the cations, the unit is-1, and the cations comprise manganese ions, iron ions, M ions and N ions, and the ion potential of the N ions is greater than or equal to 5-1. The positive electrode active material provided by the invention is stable in structure in a sodium intercalation and deintercalation process, so that the first efficiency and cycle performance of the battery can be improved.

Description

[0001] This application is a divisional application of the original patent application (i.e., the parent application) with the application date of June 19, 2023, application number 2023107286598, and invention title "[Positive electrode active material and preparation method thereof, positive electrode sheet, battery and electrical device]". Technical Field

[0002] This application belongs to the field of secondary battery technology, specifically relating to a positive electrode active material and its preparation method, a positive electrode sheet, a battery, and an electrical device. Background Technology

[0003] Secondary batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles and electric cars, as well as in military equipment and aerospace and other fields.

[0004] Sodium-ion batteries are a type of rechargeable battery, and layered transition metal oxides are commonly used 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.

[0005] Public content In view of the technical problems existing in the background art, this application provides a positive electrode active material, which aims to solve the problems of low first efficiency and low cycle performance of batteries containing it.

[0006] To achieve the above objectives, a first aspect of this application provides a positive electrode active material, the positive electrode active material comprising: Na x Mn a Fe 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 them, ΣB i ×Ii 4 ≥1500Å -4 B i I is the mole fraction of cations. i The ionic potential of the cation is given in Å. -1 The cations include manganese ions, iron ions, M ions, and N ions, wherein the ionic potential of the N ions is greater than or equal to 5 Å. -1 .

[0007] The positive electrode active material of this application has a stable structure during the sodium insertion / extraction process, which can improve the first efficiency and cycle performance of the battery.

[0008] In some embodiments of this application, 1500 Å -4 ≤ΣB i ×I i 4 ≤1900Å -4 This can improve the battery's initial efficiency and cycle performance.

[0009] In some embodiments of this application, the N ion includes B 3+ Ti 4+ Al 3+ Si 4+ Sn 4+ Sb 5+ Zr 4+ and Nb 5 + At least one of them, optionally, the N ion includes B 3+ Ti 4+ Zr 4+ And Al 3+ At least one of them. This can improve the battery's initial efficiency and cycle performance.

[0010] In some embodiments of this application, the M ion includes Ni. 2+ Ni 3+ Cu 2+ Cu + Zn 2+ and Mg 2+ At least one of them.

[0011] In some embodiments of this application, the positive electrode active material satisfies at least one of the following conditions: x is 0.7≤x≤1, optionally 0.8≤x≤1; a is 0.3≤a≤0.7, optionally 0.35≤a≤0.55; b is 0.1≤b≤0.4, optionally 0.2≤b≤0.3; c is 0.2≤c≤0.5, optionally 0.3≤c≤0.4; d is 0.005≤d≤0.1, optionally 0.01≤d≤0.05; δ is -0.05≤δ≤0.05, optionally -0.02≤δ≤0.02; e is 0≤e≤0.01, optionally 0.001≤e≤0.005.

[0012] In some embodiments of this application, 0.005 ≤ d / (a+b+c) ≤ 0.1, and can be optionally 0.01 ≤ d / (a+b+c) ≤ 0.05. This can improve the battery's initial efficiency and cycle performance.

[0013] In some embodiments of this application, the phase state of the positive electrode active material includes the O3 phase, and the space group includes The interlayer spacing is 0.53nm-0.54nm. This can improve the battery capacity.

[0014] In some embodiments of this application, the positive electrode active material satisfies at least one of the following conditions: The positive electrode active material D v 50 is 2μm-30μm, and can be selected from 4μm-12μm; The specific surface area of ​​the positive electrode active material is 0.1 m². 2 / g-2m 2 / g, optionally 0.3m 2 / g-1m 2 / g; The compaction density of the positive electrode active material under 8 tons of pressure is 3 g / cm³. 3 -5g / cm 3 3.5g / cm³ is an option. 3 -4.5g / cm 3 .

[0015] Therefore, when the D of the positive electrode active material v 50. When at least one of the specific surface area and compaction density is within the above range, the conduction distance of Na ions in 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.

[0016] The second aspect of this application provides a method for preparing the positive electrode active material described in the first aspect, comprising: The precursor was obtained by mixing Na source, Fe source, Mn source, M source and N source; The precursor is calcined to obtain the positive electrode active material.

[0017] Therefore, this 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.

[0018] A third aspect of this application provides another method for preparing the positive electrode active material described in the first aspect, comprising: A mixed solution was obtained by mixing Fe source, Mn source, M source and N source with water; The mixed solution is reacted with a precipitant to obtain a precursor; The precursor was mixed with a Na source and calcined to obtain the positive electrode active material.

[0019] Therefore, this 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.

[0020] The fourth aspect of this application provides a positive electrode sheet, which includes the positive electrode active material described in the first aspect of this 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.

[0021] A fifth aspect of this application provides a battery comprising the positive electrode sheet described in the fourth aspect of this application. Consequently, the battery exhibits excellent capacity retention.

[0022] The sixth aspect of this application provides an electrical device that includes the battery described in the fifth aspect.

[0023] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0024] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a schematic diagram of the structure of a battery according to one embodiment of this application; Figure 2 This is a schematic diagram of the structure of a battery module according to one embodiment of this application; Figure 3 This is a schematic diagram of the structure of a battery pack according to one embodiment of this application; Figure 4 yes Figure 3 Exploded view; Figure 5 This is a schematic diagram of one embodiment of an electrical device that uses a battery as a power source; Figure 6 A comparison of the charge-discharge curves of the coin cells prepared in Example 1 and Comparative Example 1 at 10 mA / g in the first cycle; Figure 7 This is a comparison chart of the capacity retention rates of the coin cells prepared in Example 1 and Comparative Example 1.

[0025] Explanation of reference numerals in the attached figures: 1: Secondary battery; 2: Battery module; 3: Battery pack; 4: Upper casing; 5: Lower casing. Detailed Implementation

[0026] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] For the sake of brevity, this article only discloses some specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0029] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0031] With the technological advancements and increasing demands for electric vehicles and rechargeable mobile devices, secondary batteries, as a representative of the new energy field, have seen rapid development in related research. Sodium-ion batteries offer a significant price advantage over traditional lithium-ion batteries and have broad application prospects in large-scale energy storage systems.

[0032] Layered metal oxides (LMOs) have become a popular cathode active material for sodium-ion batteries due to their high conductivity, high energy density, large capacity, and long cycle life. Before charging and discharging, LMOs have a high sodium content, and positively charged sodium ions shield the negative repulsion between oxygen atoms. During the first charge, sodium ions are released from the LMO surface, increasing the negative repulsion between oxygen atoms and causing irreversible structural changes. This reduces the number of sodium intercalation sites, leading to a decrease in the battery's initial efficiency. Simultaneously, the increased negative repulsion between oxygen atoms in LMOs makes their local structure unstable, making them prone to reconstruction and the formation of new phases, such as rock salt or spinel phases. Furthermore, the decrease in sodium ions increases oxygen activity, making them more susceptible to side reactions with the electrolyte, resulting in the loss of cations and oxygen ions and the formation of cracks, thus reducing the battery's cycle performance.

[0033] In this application, the positive electrode active material includes materials with an ionic potential greater than or equal to 5 Å. -1 The N ions, and the manganese ions, iron ions, M ions and N ions satisfy ΣB i ×I i 4 ≥1500Å -4 The resulting positive electrode active material exhibits strong covalent bonding and interaction between cations and oxygen, effectively stabilizing the structural changes during sodium insertion / extraction and thus improving the battery's initial efficiency. Simultaneously, the strong interaction between cations and oxygen in the resulting positive electrode active material weakens the repulsive force between oxygen atoms, resulting in structural stability and reduced oxygen activity. This suppresses side reactions between layered oxides and the electrolyte, improving battery cycle performance.

[0034] The positive electrode active material disclosed in this application is suitable for secondary batteries, and the battery disclosed in this application can be used in electrical devices that use batteries as a power source or in 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, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0035] The first aspect of this application discloses a positive electrode active material, said positive electrode active material comprising: Na x Mn a Fe 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 them, ΣB i ×I i 4 ≥1500Å -4 B i I is the mole fraction of cations. i The ionic potential of the cation is given in Å. -1 The cations include manganese ions, iron ions, M ions, and N ions, wherein the ionic potential of the N ions is greater than or equal to 5 Å. -1 .

[0036] This application includes at least the following beneficial effects: the positive electrode active material contains ions with an ion potential greater than or equal to 5 Å. -1 The N ions, and the manganese ions, iron ions, M ions and N ions satisfy ΣB i ×I i 4 ≥1500Å -4The resulting positive electrode active material exhibits strong covalent bonding and interaction between cations and oxygen, effectively stabilizing the structural changes during sodium insertion / extraction and thus improving the battery's initial efficiency. Simultaneously, the strong interaction between cations and oxygen in the resulting positive electrode active material weakens the repulsive force between oxygen atoms, resulting in structural stability and reduced oxygen activity. This suppresses side reactions between layered oxides and the electrolyte, improving battery cycle performance.

[0037] In this application, the ionic potential I of the cation i Defined as cation charge number / cation radius, where the cation charge number equals its valence, and the cation radius is in Å (1 Å = 10⁻⁶). -10 m); B i The mole fraction of cations is equal to the number of moles of cations in the positive electrode active material / (moles of manganese ions a + moles of iron ions b + moles of M ions c + moles of N ions d) × 100%, where the number of moles of manganese ions a + moles of iron ions b + moles of M ions c + moles of N ions d = 1, and Σ represents summation, for example, ΣB in this application. i ×I i 4 =B Mn ×I Mn 4 +B Fe ×I Fe 4 +B M ×I M 4 +B n ×I n 4 .

[0038] In some embodiments of this application, the positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e ΣB i ×I i 4 ≥1500Å -4 For example, 1500Å -4 -3000Å -4 1600Å -4 -2900Å -4 1700Å -4 -2800Å -4 1800Å -4 -2700Å -4 1900Å -4-2600Å -4 2000Å -4 -2500Å -4 2100Å -4 -2400Å -4 2200Å -4 -2300Å -4 In other embodiments of this application, the positive electrode active material Na... x Mn a Fe b M c N d O 2+δ-e F e 1500Å -4 ≤ΣB i ×I i 4 ≤1900Å -4 Therefore, the positive electrode active material in this application has an ion potential greater than or equal to 5 Å. -1 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 positive electrode active material with strong covalent bonding and interaction between cations and oxygen. This effectively stabilizes the structural changes of the positive electrode active material during sodium insertion / extraction, thereby improving the battery's initial efficiency. Simultaneously, the strong interaction between cations and oxygen in the obtained positive electrode active material weakens the repulsive force between oxygen molecules, stabilizing the structure of the positive electrode active material and reducing oxygen activity. This suppresses side reactions between layered oxides and the electrolyte, improving battery cycle performance.

[0039] In some embodiments of this 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 value of 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. Therefore, the positive electrode active material includes this amount of sodium, resulting in a higher battery capacity. In other embodiments of this application, the above-mentioned positive electrode active material Na... x Mn a Fe b M c N d O 2+δ-e F e In this case, x can take values ​​of 0.7 ≤ x ≤ 1, for example, 0.8 ≤ x ≤ 1.

[0040] It should be noted that in the positive electrode, battery, or electrical device, sodium ions are consumed during the formation and cycling processes, which may result in the measured sodium content (x) in the positive electrode active material being less than 1. Conversely, if sodium replenishment agents are used in both the positive and negative electrode plates, the measured sodium content (x) in the positive electrode active material may be greater than 1 after the battery undergoes formation and cycling.

[0041] In some embodiments of this application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e In this context, 'a' can be greater than or equal to 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, including this amount of manganese in the positive electrode active material can effectively improve the structural stability of the positive electrode active material and enhance the cycle stability of batteries containing it. In other embodiments of this application, the above-mentioned positive electrode active material Na... x Mn a Fe b M c N d O 2+δ-e F e In this case, 'a' can take values ​​of 0.3 ≤ a ≤ 0.7, for example, 0.35 ≤ a ≤ 0.55.

[0042] In some embodiments of this application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e In this context, b can be greater than or equal to 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, including this amount of Fe in the positive electrode active material can improve the specific capacity of the material. In other embodiments of this application, the above-mentioned positive electrode active material Na... x Mn a Fe b M c N d O 2+δ-e F e In this case, b can take values ​​of 0.1 ≤ b ≤ 0.4, for example, 0.2 ≤ b ≤ 0.3.

[0043] In some embodiments of this application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e 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 + At least one of them. In other embodiments of this application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e M ions may include Ni 2+ Ni 3+ Cu 2 + Cu + Zn 2+ and Mg 2+ At least one of them.

[0044] In some embodiments of this application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e In this context, c is set to 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. Therefore, including this amount of M ions in the positive electrode active material can improve the structural stability of the material. In other embodiments of this application, the above-mentioned positive electrode active material Na... x Mn a Fe b M c N d O 2+δ-e F e In this case, c can take values ​​of 0.2≤c≤0.5, for example, 0.3≤c≤0.4.

[0045] In some embodiments of this 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 is greater than or equal to 5 Å. -1 Therefore, the positive electrode active material in this application has an ion potential greater than or equal to 5 Å. -1 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 positive electrode active material with strong covalent bonding and interaction between cations and oxygen. This effectively stabilizes the structural changes of the positive electrode active material during sodium insertion / extraction, thereby improving the battery's initial efficiency. Simultaneously, the strong interaction between cations and oxygen in the obtained positive electrode active material weakens the repulsive force between oxygen molecules, stabilizing the structure of the positive electrode active material and reducing oxygen activity. This suppresses side reactions between layered oxides and the electrolyte, improving battery cycle performance.

[0046] As an example, 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 them. In other embodiments of this application, the N ion includes B. 3+ Ti 4+ Zr 4+ And Al 3+ At least one of them.

[0047] The ionic potentials of common ions are shown in Table 1:

[0048] In some embodiments of this application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F eIn this context, d is taken as 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 this application, the above-mentioned positive electrode active material Na... x Mn a Fe b M c N d O 2+δ-e F e In this case, d is taken as 0.005 ≤ d ≤ 0.1, for example, 0.01 ≤ d ≤ 0.05. Therefore, by adding this amount of N ions to 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 positive electrode active material with strong covalent bonding and interaction between cations and oxygen. This effectively stabilizes the structural changes of the positive electrode active material during sodium insertion / extraction, thereby improving the battery's initial efficiency. Simultaneously, the strong interaction between cations and oxygen in the obtained positive electrode active material weakens the repulsive force between oxygen molecules, stabilizing the structure of the positive electrode active material and reducing oxygen activity. This suppresses side reactions between layered oxides and the electrolyte, improving battery cycle performance.

[0049] In some embodiments of this application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e In some embodiments of this application, the above-mentioned positive electrode active material Na... x Mn a Fe b M c N d O 2+δ-e F eIn this application, 0.01 ≤ d / (a+b+c) ≤ 0.05. Therefore, the molar amount of N in the positive electrode active material satisfies the above relationship with the sum of the molar amounts of Mn, Fe, and M ions, which can improve the structural stability of the positive electrode active material, thereby improving the battery's initial efficiency and cycle stability.

[0050] In some embodiments of this application, the above-mentioned positive electrode active material Na x Mn a Fe b M c N d O 2+δ-e F e In this context, δ takes values ​​of -0.1 ≤ δ ≤ 0.1, and e takes values ​​of 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., and 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 this application, the above-mentioned positive electrode active material Na... x Mn a Fe b M c N d O 2+δ-e F e In this case, δ takes the value of -0.05≤δ≤0.05, for example -0.02≤δ≤0.02; e takes the value of 0≤e≤0.01, for example 0.001≤e≤0.005.

[0051] Specifically, the oxygen sites in the positive electrode active material of this application are doped with this amount of F, which can effectively stabilize the oxygen in the positive electrode active material, thereby reducing the structural damage caused by the release of oxygen from the lattice in the positive electrode active material, improving the stability of the material, and thus improving the cycle stability of the battery.

[0052] It should be noted that in positive electrode sheets, batteries, or electrical devices, due to the cycling process, oxygen elements in the positive electrode active material are lost, which may result in the measured oxygen content 2+δ-e in the positive electrode active material being less than 2.

[0053] In some embodiments of this application, the phase state of the positive electrode active material includes the O3 phase, and the space group includes The interlayer spacing is 0.53nm-0.54nm, for example, it can be 0.532nm-0.54nm, 0.535nm-0.54nm, 0.537nm-0.54nm, etc. Specifically, the positive electrode active material formed by O3 phase has a high Na content, which can release more Na ions, resulting in a high battery capacity.

[0054] It should be noted that the phase state, space group, and interlayer spacing of the positive electrode active material in this application can be characterized by X-ray diffraction.

[0055] Specifically, the interlayer spacing d of the 003 crystal plane of the positive electrode active material 003 The space group testing method includes: grinding the sample to be tested in an agate mortar and pestle in a drying room or glove box, then passing it through a 350-mesh sieve. A suitable amount of the sieved sample is placed in the center of the sample holder groove, ensuring the loose sample powder is slightly higher than the sample holder plane. A glass slide is then gently pressed against the sample surface to level it with the frame plane, and excess powder is scraped off. After sample preparation, a Brucker D8A_A25 X-ray powder diffractometer from Brucker AxS (Germany) is used with CuK... α The radiation source is X-ray with a wavelength of λ = 1.5406 Å. The scanning angle range is 5°-60°, and the scanning rate is 4° / min. After the test, the interlayer spacing d of the 003 crystal plane can be obtained by passing the angle corresponding to the 003 crystal plane, according to Bragg's equation 2d•sinθ = λ, and the fact that each unit cell of the 003 crystal plane contains three transition metal layers. 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, the characteristic peaks in the XRD pattern in the range of 40.5° to 42.5° indicate that the positive electrode active material is the O3 phase.

[0056] In some embodiments of this application, the D of the positive electrode active material v 50 is 2μm-30μm, for example, the D of the positive electrode active material v 50 can be 2μm-29μm, 4μm-28μm, 5μm-15μm, 6μm-14μm, 8μm-13μm, 9μm-12μm, 10μm-11μm, etc. In some other embodiments of this application, the D of the positive electrode active material... v 50 is 4μm-12μm.

[0057] In this application, D v 50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50%, for example, measured using a laser particle size analyzer (e.g., Malvern Master Size 3000) according to standard GB / T 19077-2016.

[0058] In some embodiments of this application, the specific surface area of ​​the positive electrode active material is 0.1 m². 2 / g-2m 2 / g, for example, the specific surface area of ​​the positive electrode active material can be 0.1m². 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 / g, etc. In some other embodiments of this application, the specific surface area of ​​the positive electrode active material is 0.3m². 2 / g-1m 2 / g.

[0059] In this application, the specific surface area of ​​the positive electrode active material can be obtained by the following method: using a US-made Gemini VII2390 multi-station fully automated specific surface area and porosity analyzer, take about 7g of sample and put it into a 9cc long tube with a bulb, degas at 200℃ for 2h, and then put it into the main unit to test and obtain the BET (specific surface area) data of the positive electrode active material.

[0060] In some embodiments of this application, the compaction density of the positive electrode active material under a pressure of 300 MPa is 3.0 g / cm³. 3 -5.0g / cm 3 For example, the compaction density of the positive electrode active material under a pressure of 300 MPa can be 3.0 g / cm³. 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 Etc. In some embodiments of this application, the compaction density of the positive electrode active material under a pressure of 300 MPa is 3 g / cm³. 3 -4g / cm 3 .

[0061] In this application, "compacted density" has a well-known meaning in the art and can be determined using instruments and methods well-known in the art. For example, the following test method can be used: a quantitative amount of powder m is placed in a compaction mold, the mold is placed on a compaction density instrument, a pressure of 300 MPa is set, the volume v of the powder under the pressure of 300 MPa is measured on the instrument, and the compacted density is calculated by using density = mass m / volume v (refer to GB / T24533-2009 for details).

[0062] Specifically, when the D of the positive electrode active material of this application v 50. When at least one of the specific surface area and the compaction density at 300 MPa pressure 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.

[0063] The second aspect of this application provides a method for preparing the positive electrode active material described in the first aspect, comprising: S100: A precursor is obtained by mixing Na source, Fe source, Mn source, M source and N source. In some embodiments of this application, a precursor is obtained by mixing a Na source, an Fe source, a Mn source, an M source, and an N source according to the above-described positive electrode active material composition.

[0064] 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.

[0065] The Na source, Fe source, Mn source, M source, and N source in this application are conventional materials in the art, and those skilled in the art can select them according to actual needs. 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 oxides of M, salts containing M, and other compounds; and the N source may include at least one of oxides of N, salts containing N, and other compounds.

[0066] It should be noted that if F element needs to be doped in the positive electrode active material, at least one of the Na source, Fe source, Mn source, M source and N source shall be at least one of its corresponding fluorine-containing salt 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).

[0067] S200: Calcine the precursor. In some embodiments of this application, the precursor obtained above is placed in a muffle furnace and calcined in an air atmosphere, then cooled to room temperature, and mechanically pulverized to obtain the positive electrode active material. The calcination temperature can be 600℃-1200℃, for example, 600℃-1100℃, 700℃-1000℃, 800℃-900℃, etc., and the holding time is 10h-20h, for example, 10h-19h, 11h-18h, 12h-17h, 13h-16h, 14h-15h, etc.

[0068] In addition, the precursor can be pre-calcined and kept at a certain temperature before calcining, as needed. The pre-calcination temperature can be 600℃-900℃, for example, 600℃-850℃, 650℃-800℃, 600℃-750℃, 550℃-700℃, 500℃-650℃, 550℃-600℃, etc. The holding time is 10h-20h, for example, 10h-19h, 11h-18h, 12h-17h, 13h-16h, 14h-15h, etc.

[0069] Therefore, the above-mentioned structurally stable positive electrode active material can be prepared by using the solid-state method, thereby improving the first-cycle efficiency and cycle stability of the battery.

[0070] A third aspect of this application provides another method for preparing the positive electrode active material described in the first aspect, comprising: Sa: A mixed solution is obtained by mixing Fe source, Mn source, M source and N source with water. In some embodiments of this application, a mixed solution is obtained by mixing Fe source, Mn source, M source and N source with water according to the above-described positive electrode active material composition.

[0071] It should be noted that the Fe source, Mn source, M source and N source in this application are conventional materials in the art, and those skilled in the art can select them according to actual needs. 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 the chloride, sulfate and nitrate of M; and the N source may include at least one of the chloride, sulfate and nitrate of N.

[0072] Sb: The precursor is obtained by reacting the mixed solution with a precipitant. In some embodiments of this 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, carbonic acid and oxalic acid.

[0073] Sc: The precursor is mixed with the Na source and calcined. In some embodiments of this application, the obtained precursor and Na source are mixed evenly by ball milling or mechanical stirring according to the above-mentioned positive electrode active material composition, then calcined in a muffle furnace, cooled to room temperature, and mechanically pulverized to obtain the positive electrode active material. The calcination temperature is 600℃-1200℃, for example, 700℃-1100℃, 800℃-1000℃, 900℃-950℃, etc. The calcination atmosphere can be air or oxygen, and the holding time is 10h-20h, for example, 10h-19h, 11h-18h, 12h-17h, 13h-16h, 14h-15h, etc. The Na source may include at least one of Na₂CO₃, NaHCO₃, NaOH, and Na₂O₂.

[0074] It should be noted that, as needed, before mixing and calcining the precursor and Na source, the precursor and Na source can be pre-calcined and kept at a certain temperature. The pre-calcination temperature can be 600℃-900℃, for example, 600℃-850℃, 650℃-800℃, 600℃-750℃, 550℃-700℃, 500℃-650℃, 550℃-600℃, etc. The holding time can be 10h-20h, for example, 10h-19h, 11h-18h, 12h-17h, 13h-16h, 14h-15h, etc.

[0075] In this application, if the corresponding N source is non-water-soluble, such as N oxide (an oxide of N), then 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.

[0076] It should be noted that if it is necessary to dope the F element in the positive electrode active material, at least one of the Na source, Fe source, Mn source, M source and N source shall be at least one of its corresponding fluorine-containing salt and other compounds, such as sodium fluoride, iron fluoride, manganese fluoride, M fluoride (fluoride salt of M) and N fluoride (fluoride salt of N).

[0077] It should be noted that, due to the loss of Na source during calcination, the amount of Na added will be slightly higher than the required Na content in the above-mentioned positive electrode active material composition.

[0078] Therefore, the co-precipitation method can be used to prepare the above-mentioned structurally stable positive electrode active material, thereby improving the battery's initial efficiency and cycle stability.

[0079] The fourth aspect of this application provides a positive electrode sheet, which includes the positive active material described in the first aspect of this application or the positive active material prepared by the method described in the second aspect.

[0080] The positive electrode typically includes a positive current collector and a positive active material layer disposed on the positive current collector, wherein the positive active material layer includes a positive active material.

[0081] The positive electrode current collector can be a conventional metal foil or a composite current collector (a composite current collector can be formed by setting metal materials on a polymer substrate). 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.

[0082] 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 agents and binders, and they can be selected according to actual needs.

[0083] 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).

[0084] These materials can all be obtained through commercial means.

[0085] A fifth aspect of this application provides a battery comprising the positive electrode sheet described in the fourth aspect of this application. Consequently, the battery exhibits excellent capacity retention.

[0086] A battery is a device that can be recharged after being discharged, allowing its active materials to be reactivated and continue to be used.

[0087] It is understood that the battery proposed in this application is a sodium-ion battery.

[0088] Typically, a battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The separator, positioned between the positive and negative electrodes, serves as a barrier. The electrolyte, acting as a conductor of ions, lies between the positive and negative electrodes.

[0089] [Negative electrode plate] In a battery, the negative electrode typically includes a negative current collector and a negative active material layer disposed on the negative current collector, wherein the negative active material layer includes a negative active material.

[0090] The negative electrode current collector can be a conventional metal foil or a composite current collector (for example, a metal material can be disposed on a polymer substrate to form a composite current collector). As an example, the negative electrode current collector can be a copper foil.

[0091] The specific type of the negative electrode active material is not limited; any active material known in the art that can be used as a negative electrode in sodium-ion batteries can be used. 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 materials, alloy materials, transition metal oxides and / or sulfides, phosphorus-based materials, and titanate materials. Specifically, the carbon material may include at least one of hard carbon, soft carbon, amorphous carbon, and nanostructured carbon materials; the alloy material may include an alloy material formed from at least one of Si, Ge, Sn, Pb, and Sb; the general formula of the transition metal oxides and sulfides is M. x N y 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 or Na2Ti6O7. 13 Na4Ti5O 12 Li4Ti5O 12 At least one of NaTi2(PO4)3. These materials are all commercially available.

[0092] The negative electrode active material layer may also optionally include 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 agents and binders, which can be selected according to actual needs.

[0093] 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.

[0094] As an example, the adhesive may include at least one of styrene-butadiene rubber (SBR), styrene-butadiene rubber (SBCs), water-based acrylic resin, and carboxymethyl cellulose (CMC).

[0095] The negative electrode active material layer may also optionally include a thickener, such as carboxymethyl cellulose (CMC). However, this application is not limited to this, and other materials that can be used as thickeners for sodium-ion battery negative electrode sheets may also be used.

[0096] Electrolyte The electrolyte may include an electrolyte salt and a solvent.

[0097] As an example, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium dioxalate borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

[0098] As an example, the solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl 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), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0099] In some embodiments, the electrolyte also includes additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance.

[0100] [Isolation membrane] As for the aforementioned separator, this application does not have any particular limitations. Any known porous structure separator with electrochemical and mechanical stability can be selected according to actual needs. For example, it may include a single-layer or multi-layer film containing at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0101] This application does not impose any particular limitation on the shape of the battery; it can be cylindrical, square, or any other arbitrary shape. Figure 1 This is an example of a square-structured secondary battery 1.

[0102] In some embodiments, the battery may include an outer packaging. This outer packaging is used to encapsulate the positive electrode, the negative electrode, and the electrolyte.

[0103] In some embodiments, the outer packaging may include a shell and a cover. The shell may include a base plate and side plates attached to the base plate, the base plate and side plates enclosing a receiving cavity. The shell has an opening communicating with the receiving cavity, and the cover can be placed over the opening to close the receiving cavity.

[0104] The positive electrode, negative electrode, and separator can be formed into an electrode assembly using a winding or stacking process. The electrode assembly is encapsulated within the receiving cavity. The number of electrode assemblies contained in the battery can be one or more, and can be adjusted as needed.

[0105] In some implementations, the outer packaging of the battery may include a rigid shell, such as a rigid plastic shell, an aluminum shell, or a steel shell.

[0106] The outer packaging of the battery may also include a pouch, such as a soft pouch. The material of the pouch may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0107] In some implementations, batteries can be assembled into battery modules, and the number of batteries contained in a battery module can be multiple, with the specific number adjustable according to the application and capacity of the battery module.

[0108] Figure 2 This is battery module 2 as an example. (See reference...) Figure 2 In battery module 2, multiple secondary batteries 1 can be arranged sequentially along the length of battery module 2. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 1 can be fixed in place using fasteners.

[0109] The battery module 2 may also include a housing with a receiving space in which multiple secondary batteries 1 are housed. In some embodiments, the battery modules may also be assembled into a battery pack, the number of battery modules contained in the battery pack being adjustable according to the application and capacity of the battery pack.

[0110] Figure 3 and 4 This is battery pack 3 as an example. (See reference...) Figure 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 includes an upper body 4 and a lower body 5, with the upper body 4 covering the lower body 5 to form a closed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0111] A sixth aspect of this 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 and satellites, and energy storage systems.

[0112] Figure 5 This is an example of an electrical appliance. The electrical appliance includes pure electric vehicles, hybrid electric vehicles, or plug-in hybrid electric vehicles.

[0113] Another example of a power-consuming device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and may use batteries as their power source.

[0114] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0115] Example 1 NaNi 0.24 Fe 0.26 Mn 0.39 Mg 0.1 Si 0.01 O2 preparation.

[0116] A total of 30 g of sample was weighed, consisting of Na₂CO₃, NiO, Fe₂O₃, Mn₂O₃, MgO, and SiO₂ in a molar ratio of Na:Ni:Fe:Mn:Mg:Si of 1:0.24:0.26:0.39:0.1:0.01. The sample was pre-ground in an agate mortar and then ball-milled in a planetary ball mill for 1 hour to obtain a precursor mixture. This precursor mixture was then evenly placed in an open crucible and heated from room temperature to 950 °C in a muffle furnace at a heating rate of 5 °C / min, and held at 950 °C for 15 hours. After natural cooling, the positive electrode active material NaNi was obtained. 0.24 Fe 0.26 Mn 0.39 Mg 0.1 Si 0.01 O2.

[0117] Preparation of the positive electrode sheet NaNi 0.24 Fe 0.26 Mn 0.39 Mg 0.1 Si 0.01O2, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in NMP solvent at a mass ratio of 80:15:5 to form a uniform positive electrode slurry. The positive electrode slurry is then uniformly coated onto 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 the positive electrode sheet.

[0118] Preparation of the negative electrode sheet The negative electrode is made of metallic sodium.

[0119] Preparation of Electrolyte Equal volumes of ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed to obtain an organic solvent. NaClO4 was then dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0120]

Isolation Film

[0121] [Preparation of button cells] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The prepared electrolyte is then added to obtain a coin cell.

[0122] The coin cells containing positive electrode active materials in Examples 2-20 and Comparative Examples 1-4 are the same as those in Example 1, except for the different parameters in the preparation of the positive electrode active material (see Table 1).

[0123] The composition of the positive electrode active material in the batteries of Examples 1-20 and Comparative Examples 1-4 of this application is shown in Table 2.

[0124]

[0125]

[0126] 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 resulting coin cells, were characterized. The characterization results are shown in Table 3.

[0127] Testing methods: (1) Phase state of the positive electrode active material and interlayer spacing d of the 003 crystal plane 003 and space group testing: Grind the sample to be tested into a fine powder in an agate mortar and pestle in a drying room or glove box, then pass it through a 350-mesh sieve. Take an appropriate amount of the sieved sample and place it in the center of the sample holder groove, ensuring the loose sample powder is slightly higher than the sample holder plane. Gently press a glass slide onto the sample surface to level it with the frame plane, and scrape off any excess powder. After sample preparation, use a Brucker D8A_A25 X-ray powder diffractometer (Brucker AxS, Germany) with CuK... α The radiation source is X-ray with a wavelength of λ = 1.5406 Å. The scanning angle range is 5°-60°, and the scanning rate is 4° / min. After the test, the interlayer spacing d of the 003 crystal plane can be obtained by passing the angle corresponding to the 003 crystal plane, according to Bragg's equation 2d•sinθ = λ, and the fact that each unit cell of the 003 crystal plane contains three transition metal layers. 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, the characteristic peaks in the XRD pattern in the range of 40.5° to 42.5° indicate that the positive electrode active material is the O3 phase.

[0128] (2) First-cycle coulombic efficiency test of button cell At 25℃, the coin cell was charged to 4.3V at a constant current density of 10mA / g, yielding the charging specific capacity C0. It was then discharged to 1.5V at a constant current density of 10mA / g, yielding the discharging specific capacity C1. The first-cycle coulombic efficiency of the battery = C1 / C0 × 100%.

[0129] (3) Cyclic performance test At 25℃, the coin cell was charged to 4.2V at a constant current density of 10mA / g, and then discharged to 1.5V at a constant current density of 10mA / g. The discharge specific capacity C2 of the coin cell was obtained. Subsequently, it was charged and discharged at a constant current density of 10mA / g for 50 cycles, and the discharge specific capacity C3 of the 50th cycle was taken. The capacity retention rate of the battery after 50 cycles = C2 / C3 × 100%.

[0130] Figure 6 The graph shows a comparison of the charge-discharge curves of the coin cells prepared in Example 1 and Comparative Example 1 at 10 mA / g in the first cycle. As can be seen from the graph, the coulombic efficiency of the coin cell in Example 1 is 98% in the first cycle, while that of the coin cell in Comparative Example 1 is 81%. Obviously, the coulombic efficiency of the coin cell in Example 1 is higher than that of the coin cell in Comparative Example 1.

[0131] Figure 7 The graph shows a comparison of the capacity retention rates of the coin cells prepared in Example 1 and Comparative Example 1. As can be seen from the graph, the capacity retention rate of the battery in Example 1 after 50 cycles is significantly better than that in Comparative Example 1.

[0132] Table 3

[0133] In conclusion, as shown in Table 3, the batteries of Examples 1-20 exhibit significantly higher first-cycle coulombic efficiency and capacity retention after 50 cycles compared to the batteries of Comparative Examples 1-4. This indicates that the positive electrode active material of this application contains components with an ion potential greater than or equal to 5 Å. -1 The N ions, and the manganese ions, iron ions, M ions and N ions satisfy ΣB i ×I i 4 A value of ≥1500 can improve the first-cycle coulombic efficiency and cycle performance of the battery.

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A positive electrode active material, characterized in that, 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 them, ΣB i ×I i 4 ≥1500Å -4 B i I is the mole fraction of cations. i The ionic potential of the cation is given in Å. -1 The cations include manganese ions, iron ions, M ions, and N ions, wherein the ionic potential of the N ions is greater than or equal to 5 Å. -1 The positive electrode active material includes an O3 phase and a space group including... The interlayer spacing d of the 003 crystal plane 003 The wavelength is 0.53nm-0.54nm.

2. The positive electrode active material according to claim 1, characterized in that, 1500Å -4 ≤ΣB i ×I i 4 ≤1900Å -4 。 3. The positive electrode active material according to claim 1 or 2, characterized in that, 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 them.

4. The positive electrode active material according to claim 1 or 2, characterized in that, The N ions include B 3+ Ti 4+ Zr 4+ And Al 3+ At least one of them.

5. The positive electrode active material according to any one of claims 1-4, characterized in that, The M ion includes Ni 2+ Ni 3+ Cu 2+ Cu + Zn 2+ and Mg 2+ At least one of them.

6. The positive electrode active material according to any one of claims 1-5, characterized in that, The positive electrode active material satisfies at least one of the following conditions: x takes values ​​of 0.7 ≤ x ≤ 1; The value of a is 0.3 ≤ a ≤ 0.7; The value of b is 0.1 ≤ b ≤ 0.4; The value of c is 0.2 ≤ c ≤ 0.5; The value of d is 0.005 ≤ d ≤ 0.1; The value of δ is -0.05 ≤ δ ≤ 0.05; The value of e is 0 ≤ e ≤ 0.

01.

7. The positive electrode active material according to any one of claims 1-6, characterized in that, The positive electrode active material satisfies at least one of the following conditions: x takes the value 0.8 ≤ x ≤ 1; The value of a is 0.35 ≤ a ≤ 0.55; The value of b is 0.2 ≤ b ≤ 0.3; The value of c is 0.3 ≤ c ≤ 0.4; The value of d is 0.01 ≤ d ≤ 0.05; The value of δ is -0.02 ≤ δ ≤ 0.02; The value of e is 0.001 ≤ e ≤ 0.

005.

8. The positive electrode active material according to any one of claims 1-7, characterized in that, 0.005≤d / (a+b+c)≤0.

1.

9. The positive electrode active material according to any one of claims 1-7, characterized in that, 0.01≤d / (a+b+c)≤0.

05.

10. The positive electrode active material according to any one of claims 1-9, characterized in that, The positive electrode active material satisfies at least one of the following conditions: The positive electrode active material D v 50 represents 2μm-30μm; The specific surface area of ​​the positive electrode active material is 0.1 m². 2 / g-2m 2 / g; The compaction density of the positive electrode active material under 300 MPa pressure is 3 g / cm³. 3 -5g / cm 3 .

11. The positive electrode active material according to any one of claims 1-10, characterized in that, The positive electrode active material satisfies at least one of the following conditions: The positive electrode active material D v 50 is 4μm-12μm; The specific surface area of ​​the positive electrode active material is 0.3 m². 2 / g-1m 2 / g; The compaction density of the positive electrode active material under 300 MPa pressure is 3 g / cm³. 3 -4g / cm 3 .

12. A method for preparing the positive electrode active material according to any one of claims 1-11, characterized in that, include: The precursor was obtained by mixing Na source, Fe source, Mn source, M source and N source; The precursor is calcined to obtain the positive electrode active material.

13. A method for preparing the positive electrode active material according to any one of claims 1-11, characterized in that, include: A mixed solution was obtained by mixing Fe source, Mn source, M source and N source with water; The mixed solution is reacted with a precipitant to obtain a precursor; The precursor was mixed with a Na source and calcined to obtain the positive electrode active material.

14. A positive electrode plate, characterized in that, The positive electrode sheet comprises the positive active material according to any one of claims 1-11 or the positive active material prepared by the method according to claim 12 or 13.

15. A battery, characterized in that, The battery includes the positive electrode sheet as described in claim 14.

16. An electrical appliance, characterized in that, Includes the battery as described in claim 15.

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