Positive electrode active material, method for producing same, secondary battery, battery module, battery pack, and power-driven device

Abstract

The application provides a positive electrode active material and a preparation method thereof, a secondary battery, a battery module, a battery pack and a power utilization device. The positive electrode active material comprises a layered sodium composite oxide containing antimony, and the sodium composite oxide containing antimony has a chemical formula as shown in formula I, Na x Mn a Fe b Ni c Sb d L e O2(I) in the formula I, 0.7 < x < 1, 0 < a, 0 < b, 0.1 < c < 0.3, 0 < d < 0.1, 0 < e, a + b + c + d + e = 1, (b + c) / (a + d + e) < 1, and L is selected from one or more of Cu, Li, Ti, Zr, K, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Si, La, Ta, P and B. According to the application, the layered sodium composite oxide containing antimony can have high stability to water by being doped with the specific metal Sb.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a positive electrode active material, a preparation method thereof, a secondary battery, a battery module, a battery pack and a power utilization device. BACKGROUND

[0002] In recent years, as the application range of lithium ion batteries is more and more extensive, lithium ion batteries are widely used in energy storage power supply systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. With the shortage of resources needed for the manufacture of lithium ion batteries and the rising cost of raw materials such as Ni and Co, finding a low-cost substitute for lithium ion batteries has become a research hotspot in the field of new energy.

[0003] Sodium ion batteries have the advantages of abundant reserves, low cost, system safety, low temperature and high rate, and are excellent successors of lithium ion batteries. However, the existing sodium ion battery positive electrode active material has poor water stability and low specific capacity, which limits the development of sodium ion batteries. SUMMARY

[0004] The present application is made in view of the above-mentioned problems, and provides a positive electrode active material, a preparation method thereof, a secondary battery, a battery module, a battery pack and a power utilization device, for solving the problems of poor water stability and low specific capacity of sodium ion battery positive electrode active material.

[0005] To achieve the above-mentioned purpose, the first aspect of the present application provides a positive electrode active material, comprising a layered antimony-containing sodium composite oxide, the antimony-containing sodium composite oxide has a chemical formula as shown in formula I,

[0006] Na x Mn a Fe b Ni c Sb d L e O2(I)

[0007] In formula I, 0.7 < x ≤ 1, 0 < a, 0 ≤ b, 0.1 < c ≤ 0.3, 0 < d ≤ 0.1, 0 ≤ e, a + b + c + d + e = 1, (b + c) / (a + d + e) ≤ 1, and L is selected from one or more of Cu, Li, Ti, Zr, K, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Si, La, Ta, P and B.

[0008] According to this application, by doping with a specific metal Sb, layered antimony-containing sodium composite oxides can be made to have high stability to water. Furthermore, during the electrochemical reaction process, side reactions of antimony-containing sodium composite oxides can be effectively suppressed, resulting in high cycle stability and stable electrochemical performance of antimony-containing sodium composite oxides, thereby improving the specific capacity of sodium-ion batteries during the first charge and discharge cycle.

[0009] In any embodiment of the first aspect of this application, in formula I, 0.3≤a≤0.4, 0.2≤b≤0.3, 0.15≤c≤0.2, 0.05≤d≤0.1, 0.05≤e≤0.1, a+b+c+d+e=1, 0.4≤(b+c) / (a+d+e)≤1.

[0010] In these optional embodiments, the elemental ratios in the antimony-containing sodium composite oxide meet the above requirements, which improves the ordered arrangement of cations in the layered structure, ensuring high structural stability of the cathode active material and thus enhancing its water stability. On the other hand, according to these optional embodiments, the antimony-containing sodium composite oxide can contain higher amounts of Fe and Ni, resulting in sodium-ion batteries using such antimony-containing sodium composite oxide cathode active materials exhibiting higher initial charge-discharge specific capacity. Therefore, the antimony-containing sodium composite oxide according to this embodiment better balances water stability, cycle stability during electrochemical processes, and initial charge-discharge specific capacity.

[0011] In any embodiment of the first aspect of this application, L is selected from one or more of Cu, Li, Ti, Zr, Mg, Ca, Zn, Bi, Sn, Al, Si, La, Ta, P and B. Optionally, L is selected from one or more of Cu, Li, Mg, Zn, Al, Si and B.

[0012] These specific optional additional dopants can enhance the water stability of layered antimony-containing sodium composite oxides, as well as their cycling stability in electrochemical processes. Furthermore, these specific optional L examples exhibit good electrolyte stability and are beneficial for electrolyte wetting.

[0013] In any embodiment of the first aspect of this application, the antimony-containing sodium composite oxide includes an O3 phase, wherein the O3 phase has a space group It has a layered crystal structure.

[0014] In these alternative embodiments, O3 exhibits significant advantages over other phases in both specific capacity and specific energy. The antimony-containing sodium composite oxide of this application includes an O3 phase, which has a space group... The layered crystal structure of the sodium composite oxide containing antimony is stable, and the positive electrode active material has good capacity performance and cycle performance.

[0015] In any embodiment of the first aspect of the application, the interlayer spacing of the sodium composite oxide containing antimony is 0.53 nm to 0.54 nm.

[0016] In these optional embodiments, the interlayer spacing (d 003 ) of the sodium composite oxide containing antimony is controlled within this range, the structure of the positive electrode active material is more stable, and the positive electrode active material has better cycle performance. Meanwhile, sodium ions are more easily deintercalated between the layers, and the capacity of the positive electrode active material is better improved. In addition, the interlayer spacing of the sodium composite oxide containing antimony is between 0.53 nm and 0.54 nm, which is conducive to the conduction and diffusion of sodium ions between the layers, and can inhibit the exchange of hydrogen ions and sodium ions when the layered sodium composite oxide containing antimony is exposed to water, thereby making the sodium composite oxide containing antimony have higher stability to water.

[0017] In any embodiment of the first aspect of the application, the X-ray diffraction spectrum of the sodium composite oxide containing antimony satisfies I1 / I0≥0.2,

[0018] wherein I1 is the peak intensity of the X-ray diffraction peak of the 003 crystal plane of the O3 phase of the sodium composite oxide containing antimony after immersion in deionized water for 24 hours, and I0 is the peak intensity of the X-ray diffraction peak of the 003 crystal plane of the O3 phase of the sodium composite oxide containing antimony without immersion in deionized water.

[0019] In these optional embodiments, the use of antimony for doping enhances the interaction between transition metals and oxygen in the O3 phase layered sodium composite oxide containing antimony, thereby increasing the stability to water, which is reflected in the I1 / I0 parameter. The greater the ratio of I1 / I0, the less sensitive to water, indicating that the sodium composite oxide containing antimony has stronger stability to water.

[0020] In any embodiment of the first aspect of the application, the volume average particle size Dv50 of the positive electrode active material is 3 μm to 30 μm, and optionally 5 μm to 15 μm.

[0021] In these optional embodiments, the volume average particle size Dv50 of the positive electrode active material is within an appropriate range, which is conducive to obtaining a higher compaction density of the positive electrode active material layer, and at the same time has a suitable porosity to meet the required amount of electrolyte infiltration for electrochemical reaction, and has a shorter migration path of active ions and electrons within the particles, thereby improving the energy density and cycle performance of the positive electrode active material layer.

[0022] In any embodiment of the first aspect of the application, the specific surface area of the positive electrode active material is 0.1 m2 / g~5m 2 / g, optionally 0.3m 2 / g~3m 2 / g.

[0023] In these optional embodiments, the positive electrode active material has a proper specific surface area, which can reduce the liquid absorption phenomenon in the positive electrode slurry preparation process, improve the solid content and particle dispersion uniformity in the positive electrode slurry, thereby improving the particle dispersion uniformity and compaction density in the film layer containing the positive electrode active material, and further improving the specific capacity and energy density of the sodium ion battery and improving the cycle performance of the sodium ion battery.

[0024] In any embodiment of the first aspect of the application, the tap density of the positive electrode active material is 1 g / cm 3 ~3 g / cm 3 , optionally 1.5 g / cm 3 ~2.5 g / cm 3 .

[0025] In these optional embodiments, the positive electrode active material has a proper tap density, which is beneficial to make the positive electrode active material have a higher compaction density, so that the sodium ion battery has higher capacity performance and energy density.

[0026] In any embodiment of the first aspect of the application, the powder compaction density of the positive electrode active material under 8 tons of pressure is 3 g / cm 3 ~5 g / cm 3 , optionally 3.5 g / cm 3 ~4.5 g / cm 3 .

[0027] In these optional embodiments, the positive electrode active material has a higher compaction density, which is beneficial to make the sodium ion battery have higher capacity performance and energy density. Within this range, the higher the compaction density of the positive electrode active material, the higher the capacity performance and energy density of the sodium ion battery.

[0028] The second aspect of the application also provides a preparation method of the positive electrode active material, comprising:

[0029] providing raw materials, so that the element ratio in the raw materials meets the chemical formula shown in formula I of the first aspect of the application;

[0030] calcining the raw materials to obtain the positive electrode active material,

[0031] wherein the positive electrode active material comprises a layered sodium-containing composite oxide containing antimony, and the sodium-containing composite oxide containing antimony has a chemical formula as shown in formula I,

[0032] Na xMn a Fe b Ni c Sb d L e O2(I)

[0033] In formula I, 0.7 < x ≤ 1, 0 < a, 0 ≤ b, 0.1 < c ≤ 0.3, 0 < d < 0.1, 0 ≤ e, a + b + c + d + e = 1, (b + c) / (a ​​+ d + e) ​​≤ 1, and L is selected from one or more of Cu, Li, Ti, Zr, K, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Si, La, Ta, P, and B.

[0034] According to an embodiment of the method for preparing the positive electrode active material of this application, raw materials are first provided, and then the raw materials are calcined to obtain the positive electrode active material. The above-mentioned method for preparing the positive electrode active material is simple and has high manufacturability.

[0035] In any embodiment of the second aspect of this application, providing raw materials includes: mixing sodium source, manganese source, iron source, nickel source, antimony source and L source evenly to obtain raw materials, wherein the L source is selected from one or more of Cu source, Li source, Ti source, Zr source, K source, Nb source, Mg source, Ca source, Mo source, Zn source, Cr source, W source, Bi source, Sn source, Ge source, Al source, Si source, La source, Ta source, P source and B source.

[0036] In any embodiment of the second aspect of this application, the sodium source is selected from one or more of Na2CO3, NaHCO3, NaOH and Na2O2.

[0037] In any embodiment of the second aspect of this application, the iron source is selected from one or more of Fe2O3, Fe3O4 and FeO.

[0038] In any embodiment of the second aspect of this application, the manganese source is selected from one or more of Mn2O3, Mn3O4, MnO and MnO2.

[0039] In any embodiment of the second aspect of this application, the nickel source is selected from NiO or Ni(OH)2.

[0040] In any embodiment of the second aspect of this application, the antimony source is selected from one or more of elemental antimony, antimony-containing oxides, or antimony salts.

[0041] In any embodiment of the second aspect of this application, the provision of raw materials includes: mixing an iron source, a manganese source, a nickel source, an L source with water to obtain a mixed solution, wherein the L source is selected from one or more of a Cu source, a Li source, a Ti source, a Zr source, a K source, a Nb source, a Mg source, a Ca source, a Mo source, a Zn source, a Cr source, a W source, a Bi source, a Sn source, a Ge source, an Al source, a Si source, a La source, a Ta source, a P source, and a B source; mixing the mixed solution with a precipitant to form a precipitate; and stirring the precipitate, a sodium source, and an antimony source evenly to obtain the raw materials.

[0042] In any embodiment of the second aspect of this application, the sodium source is selected from one or more of Na2CO3, NaHCO3, NaOH and Na2O2.

[0043] In any embodiment of the second aspect of this application, the iron source is selected from one or more of iron-containing chlorides, sulfates and nitrates.

[0044] In any embodiment of the second aspect of this application, the manganese source is selected from one or more of manganese-containing chlorides, sulfates and nitrates.

[0045] In any embodiment of the second aspect of this application, the nickel source is selected from one or more of nickel-containing chlorides, sulfates, and nitrates.

[0046] In any embodiment of the second aspect of this application, the antimony source is selected from one or more of elemental antimony, antimony-containing oxides, or antimony salts.

[0047] In any embodiment of the second aspect of this application, the precipitant is selected from one or more of hydroxides, carbonates and oxalates.

[0048] The third aspect of the application also provides a secondary battery, including the positive electrode active material of the first aspect of the application or the positive electrode active material prepared by the preparation method of the second aspect of the application.

[0049] A fourth aspect of this application provides a battery module including the secondary battery of the third aspect of this application.

[0050] A fifth aspect of this application provides a battery pack that includes the battery module of the fourth aspect of this application.

[0051] A sixth aspect of this application provides an electrical device comprising at least one selected from the third aspect of this application, the fourth aspect of this application, or the fifth aspect of this application. Attached Figure Description

[0052] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0053] Figure 1 These are the X-ray diffraction spectra of the positive electrode active material of one embodiment of this application before and after soaking in deionized water for 24 hours;

[0054] Figure 2 This is the X-ray diffraction spectrum of the positive electrode active material of another embodiment of this application before and after soaking in deionized water for 24 hours;

[0055] Figure 3 The X-ray diffraction patterns of the antimony-free positive electrode active material before and after soaking in deionized water for 24 hours are shown.

[0056] Figure 4 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0057] Figure 5 yes Figure 4 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0058] Figure 6 This is a schematic diagram of a battery module according to one embodiment of this application.

[0059] Figure 7 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0060] Figure 8 yes Figure 7 An exploded view of a battery pack according to one embodiment of this application is shown.

[0061] Figure 9 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0062] Explanation of reference numerals in the attached figures:

[0063] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0064] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the adhesive, negative electrode sheet, secondary battery, battery module, battery pack, and power supply device for secondary batteries according to this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0065] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0066] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0067] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0068] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0069] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0070] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0071] Positive electrode active material

[0072] The first aspect of this application provides a positive electrode active material comprising a layered antimony-containing sodium composite oxide having a chemical formula as shown in Formula I.

[0073] Na x Mn a Fe b Ni c Sb d L e O2(I)

[0074] In formula I, 0.7 < x ≤ 1, 0 < a, 0 ≤ b, 0.1 < c ≤ 0.3, 0 < d ≤ 0.1, 0 ≤ e, a + b + c + d + e = 1, (b + c) / (a ​​+ d + e) ​​≤ 1, and L is selected from one or more of Cu, Li, Ti, Zr, K, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Si, La, Ta, P, and B.

[0075] The antimony-containing sodium composite oxide provided in this application has a specific chemical composition. The antimony-containing sodium composite oxide has the chemical formula shown in Formula I, Na... x Mn a Feb Ni c Sb d L e O2(I). In the positive electrode active material of this application, doping with a specific metal Sb enables the layered antimony-containing sodium composite oxide to have high stability to water. Furthermore, in the electrochemical reaction, it can effectively suppress the formation of byproducts due to undesirable chemical reactions on the particle surface of the antimony-containing sodium composite oxide, thereby enabling the antimony-containing sodium composite oxide to have high cycle stability and to stably exert its electrochemical performance.

[0076] It is not intended to be limited to any theory. The reasons for the structural stability of the antimony-containing sodium composite oxide according to the embodiments of this application are further explained below in order to better understand the purpose and intended effects of this application.

[0077] The inventors discovered that when a layered sodium composite oxide containing Ni and / or Fe (without Sb) comes into contact with water, sodium ions in the layered sodium composite oxide exchange with hydrogen ions. The hydrogen ions embed between the layers, causing the layered structure to collapse and break down. Furthermore, Ni and / or Fe react with water to form NiO and / or Fe. m O n (e.g., FeO, Fe2O3, Fe3O4), affecting the stability of the layered structure. Furthermore, during electrochemical processes, layered sodium composite oxides react with the electrolyte, generating NiO and / or Fe on the particle surface. m O n The electrochemical performance of layered sodium composite oxides is greatly reduced due to the presence of byproducts such as NiO and / or Fe3O4. The inventors further reduced the Ni and / or Fe content in the layered sodium composite oxides to suppress the formation of byproducts. However, as the Ni and / or Fe content decreased, the specific capacity of the sodium-ion battery formed using the layered sodium composite oxide as the positive electrode active material also decreased during the first charge and discharge cycle.

[0078] The inventors unexpectedly discovered that the antimony-containing sodium composite oxide doped with the specific element Sb of this application can significantly improve the stability of the positive electrode active material containing Ni and / or Fe to water without reducing the initial charge-discharge specific capacity. Not wishing to be limited by any theory, the inventors believe that the above-mentioned effect can be achieved by doping with a certain amount of Sb as follows: Specifically, when a layered sodium composite oxide containing Ni and / or Fe without Sb comes into contact with water, sodium ions in the interlayer exchange with hydrogen ions. Hydrogen ions embed between the layers. Since the atomic radius of hydrogen ions is significantly smaller than that of sodium ions, the interlayer spacing decreases, and may even lead to the collapse and destruction of the layered structure. When a certain amount of Sb is doped into such a layered sodium composite oxide, some of the Ni and / or Fe in the layered crystal structure is replaced by Sb. On the one hand, since Sb has a strong interaction with Na, and can even alloy with it, the degree of exchange between sodium ions and hydrogen ions in the interlayer is reduced when the Sb-doped layered sodium composite oxide comes into contact with water. On the other hand, due to its higher chemical stability, Sb is less likely to react with water to form oxides that would disrupt the layered crystal structure. Furthermore, during electrochemical reactions (such as battery charging and discharging), Sb-doped layered sodium composite oxides can effectively suppress side reactions with the electrolyte, resulting in high cycle stability and stable electrochemical performance.

[0079] In some embodiments of this application, the doping of antimony-containing sodium composite oxides with Mn, Sb, and L, wherein L is selected from one or more of Cu, Li, Ti, Zr, K, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Si, La, Ta, P, and B, can further enhance the stability of the layered antimony-containing sodium composite oxides to water and the cycling stability of the antimony-containing sodium composite oxides in electrochemical processes.

[0080] In some embodiments of this application, in Equation I, 0.7 < x ≤ 1, and x is 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, or 1 in any other range consisting of any two of the above endpoints.

[0081] In some embodiments of this application, 0 < d ≤ 0.1 in Formula I is used to control the content of Sb doping to be relatively low, so as to avoid excessive Sb doping, which would result in a reduced initial charge-discharge specific capacity of the sodium-ion battery containing the antimony-containing sodium composite oxide of this application.

[0082] In some embodiments of this application, (b+c) / (a+d+e)≤1 in Formula I is used to control the appropriate content of Fe and / or Ni doping. This prevents excessive Fe and / or Ni from reacting more readily with water and also prevents Fe and / or Ni in the antimony-containing sodium composite oxide from reacting with the electrolyte during electrochemical processes, thereby effectively suppressing the occurrence of side reactions. Furthermore, (b+c) / (a+d+e)≤1 in Formula I indicates that the total doping content of Sb, Mn, and L is greater than or equal to the total doping content of Fe and Ni, thus ensuring the structural stability of the antimony-containing sodium composite oxide.

[0083] According to this application, doping with a specific metal, Sb, can enhance the water stability of layered antimony-containing sodium composite oxides. Sb and O have a strong covalent interaction, which at least improves the local structural stability of the layered antimony-containing sodium composite oxides, suppresses side reactions such as proton exchange when the layered antimony-containing sodium composite oxides come into contact with water molecules, and thus increases their water stability. Furthermore, during the electrochemical reaction process, side reactions of the antimony-containing sodium composite oxides can be effectively suppressed, resulting in high cycle stability and stable electrochemical performance.

[0084] In some embodiments, in Equation I, 0.3≤a≤0.4, 0.2≤b≤0.3, 0.15≤c≤0.2, 0.05≤d≤0.1, 0.05≤e≤0.1, a+b+c+d+e=1, and 0.4≤(b+c) / (a+d+e)≤1.

[0085] Optionally, a is 0.4, b is 0.2, c is 0.2, d is 0.1, and e is 0.1.

[0086] In these optional embodiments, the antimony-containing sodium composite oxide, where the elemental ratios meet the above requirements, can improve the ordered arrangement of cations in the layered structure, ensuring higher structural stability of the cathode active material, thereby enhancing its water stability. On the other hand, according to these optional embodiments, the antimony-containing sodium composite oxide can contain higher amounts of Fe and Ni, enabling sodium-ion batteries using such cathode active materials to have higher initial charge-discharge specific capacity. Therefore, the antimony-containing sodium composite oxide according to this embodiment better balances water stability, cycle stability during electrochemical processes, and initial charge-discharge specific capacity.

[0087] In some embodiments, L is selected from one or more of Cu, Li, Ti, Zr, Mg, Ca, Zn, Bi, Sn, Al, Si, La, Ta, P, and B.

[0088] Optionally, L is selected from one or more of Cu, Li, Mg, Zn, Al, Si and B.

[0089] These specific optional additional dopants can enhance the water stability of layered antimony-containing sodium composite oxides, as well as their cycling stability in electrochemical processes. Furthermore, these specific optional L examples exhibit good electrolyte stability and also facilitate electrolyte wetting.

[0090] The layered antimony-containing sodium composite oxide of this application is used as a positive electrode active material. Based on the stable phase structure of the layered antimony-containing sodium composite oxide, it can be classified into layered metal oxides such as P2 phase and O3 phase.

[0091] In some embodiments, the antimony-containing sodium composite oxide includes an O3 phase, wherein the O3 phase has a space group... It has a layered crystal structure.

[0092] In these alternative embodiments, O3 exhibits significant advantages over other phases in both specific capacity and specific energy. The antimony-containing sodium composite oxide of this application includes an O3 phase, which has a space group... The layered crystal structure of the positive electrode active material has good structural stability, which is beneficial to improving the capacity performance and cycle performance of the positive electrode active material.

[0093] In some embodiments, the interlayer spacing of the antimony-containing sodium composite oxide is 0.53 nm to 0.54 nm.

[0094] Optionally, the interlayer spacing of the antimony-containing sodium composite oxide is 0.534 nm to 0.548 nm.

[0095] In these alternative embodiments, the interlayer spacing (d) of the antimony-containing sodium composite oxide 003 When controlled within this range, the structure of the positive electrode active material is more stable, resulting in better cycle performance. Simultaneously, sodium ions are more easily inserted and removed between layers, further improving the charge-discharge specific capacity of the positive electrode active material. Furthermore, the interlayer spacing of the antimony-containing sodium composite oxide is between 0.53 nm and 0.54 nm, which facilitates the conduction and diffusion of sodium ions between layers and inhibits the exchange reaction between hydrogen ions and sodium ions when the layered antimony-containing sodium composite oxide encounters water, thus giving it higher stability to water.

[0096] In some embodiments, the X-ray diffraction pattern of the antimony-containing sodium composite oxide satisfies I1 / I0 ≥ 0.2.

[0097] Wherein, I1 is the peak intensity of the X-ray diffraction peak of the O3 phase 003 crystal plane of the antimony-containing sodium composite oxide after soaking in deionized water for 24 hours, and I0 is the peak intensity of the X-ray diffraction peak of the O3 phase 003 crystal plane of the antimony-containing sodium composite oxide without soaking in deionized water.

[0098] In some embodiments of this application, the X-ray diffraction pattern of the antimony-containing sodium composite oxide satisfies 0.2≤I1 / I0<1, where I1 / I0 reflects the sensitivity of the antimony-containing sodium composite oxide in the O3 phase layer to water.

[0099] Optionally, the X-ray diffraction pattern of the antimony-containing sodium composite oxide satisfies 0.35 ≤ I1 / I0 < 1.

[0100] Alternatively, the X-ray diffraction pattern of the antimony-containing sodium composite oxide satisfies 0.6 ≤ I1 / I0 ≤ 0.9.

[0101] Figure 1 These are the X-ray diffraction spectra of the positive electrode active material of one embodiment of this application before and after soaking in deionized water for 24 hours; Figure 2 This is the X-ray diffraction spectrum of the positive electrode active material of another embodiment of this application before and after soaking in deionized water for 24 hours; Figure 3 These are the X-ray diffraction spectra of antimony-free positive electrode active materials before and after soaking in deionized water for 24 hours.

[0102] As an example, Figure 1 The antimony-containing sodium composite oxide NaNi is shown. 0.2 Fe 0.29 Mn 0.4 Cu 0.1 Sb 0.01 X-ray diffraction patterns of O2 before and after soaking in deionized water for 24 hours. Figure 1 The solid lines represent the X-ray diffraction pattern of the O3 phase of the antimony-containing sodium composite oxide before immersion in deionized water (before immersion), while the dashed lines represent the X-ray diffraction pattern after immersion in deionized water for 24 hours (after immersion). Figure 1 It can be seen that I1 / I0 is 0.35, and the positions of the characteristic peaks in the two X-ray diffraction patterns are basically the same, indicating that the antimony-containing sodium composite oxide NaNi 0.2 Fe 0.29 Mn 0.4 Cu 0.1 Sb 0.01 After soaking in deionized water for 24 hours, the crystal structure of O2 did not undergo substantial changes. Therefore, this antimony-containing sodium composite oxide is not sensitive to water, which can be understood as its strong stability to water.

[0103] As yet another example, Figure 2 The antimony-containing sodium composite oxide NaNi is shown.0.2 Fe 0.2 Mn 0.4 Cu 0.1 Sb 0.1 X-ray diffraction patterns of O2 before and after soaking in deionized water for 24 hours. Figure 2 The solid lines represent the X-ray diffraction pattern of the O3 phase of the antimony-containing sodium composite oxide before immersion in deionized water (before immersion), while the dashed lines represent the X-ray diffraction pattern after immersion in deionized water for 24 hours (after immersion). Figure 2 As can be seen from the data, I1 / I0 is 0.86, and the positions of the characteristic peaks in the two X-ray diffraction patterns are basically the same, indicating that the antimony-containing sodium composite oxide NaNi 0.2 Fe 0.2 Mn 0.4 Cu 0.1 Sb 0.1 After being soaked in deionized water for 24 hours, the crystal structure of O2 did not undergo any substantial change. Therefore, this antimony-containing sodium composite oxide is not sensitive to water and has stronger water stability.

[0104] In contrast. Figure 3 The antimony-free sodium composite oxide NaNi is shown. 0.2 Fe 0.29 Mn 0.4 Cu 0.11 X-ray diffraction patterns of O2 before and after soaking in deionized water for 24 hours. Figure 3 The solid lines represent the X-ray diffraction pattern of the O3 phase crystal of the sodium composite oxide before immersion in deionized water (before immersion), while the dashed lines represent the X-ray diffraction pattern after immersion in deionized water for 24 hours (after immersion). Figure 3 As can be seen, I1 / I0 is 0.08, and the positions of the characteristic peaks in the two X-ray diffraction patterns are deviated, indicating that the crystal structure of the antimony-free sodium composite oxide changes significantly after being soaked in deionized water for 24 hours. Therefore, the antimony-free sodium composite oxide is relatively sensitive to water and has poor stability in water.

[0105] In these alternative embodiments, antimony doping enhances the interaction between the transition metal and oxygen in the O3 phase layered antimony-containing sodium composite oxide, thereby increasing its stability to water. This is reflected in the I1 / I0 parameter; the larger the I1 / I0 ratio, the less sensitive it is to water, indicating that the antimony-containing sodium composite oxide has stronger water stability.

[0106] In some embodiments, the volume average particle size Dv50 of the positive electrode active material is 3 μm to 30 μm.

[0107] Optionally, the volume average particle size Dv50 of the positive electrode active material is 5 μm to 15 μm.

[0108] According to this application, the volume average particle size Dv50 of the positive electrode active material can be measured using conventional methods in the art. For example, it can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, in accordance with GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0109] In these alternative embodiments, the volume average particle size Dv50 of the positive electrode active material is within an appropriate range, which is beneficial for obtaining a high compaction density of the positive electrode active material layer, while having a suitable porosity to meet the electrolyte wetting amount required for electrochemical reactions, and also having a shorter migration path for active ions and electrons within the particles, thereby improving the energy density and cycle performance of the positive electrode active material layer.

[0110] In some embodiments, the specific surface area of ​​the positive electrode active material is 0.1 m². 2 / g~5m 2 / g.

[0111] Optionally, the specific surface area of ​​the positive electrode active material is 0.3 m². 2 / g~3m 2 / g.

[0112] According to this application, the specific surface area of ​​the positive electrode active material has a meaning known in the art and can be measured using instruments and methods known in the art. For example, the specific surface area of ​​solid materials can be determined by referring to the GB / T 19587-2017 standard for gas adsorption BET method, using the nitrogen adsorption specific surface area analysis test method, and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis test can be performed using a TriStarⅡ3020 specific surface area and porosity analyzer from Micromeritics, USA.

[0113] In these alternative embodiments, the positive electrode active material has an appropriate specific surface area, which can reduce liquid absorption during the preparation of the positive electrode slurry, increase the solid content and particle dispersion uniformity in the positive electrode slurry, thereby improving the particle dispersion uniformity and compaction density in the film layer containing the positive electrode active material, thereby improving the specific capacity and energy density of the sodium-ion battery, and improving the cycle performance of the sodium-ion battery.

[0114] In some embodiments, the tap density of the positive electrode active material is 1 g / cm³. 3 ~3g / cm 3 .

[0115] Optionally, the tap density of the positive electrode active material is 1.5 g / cm³. 3~2.5g / cm 3 .

[0116] According to this application, the tap density of the positive electrode active material has a well-known meaning in the art and can be measured using instruments and methods well-known in the art. For example, it can be measured by referring to GB / T5162-2006 Powder Tap Density Determination Method and using a tap density meter, such as the FZS4-4B type tap density meter.

[0117] In these alternative embodiments, the positive electrode active material has an appropriate tap density, which is beneficial to the positive electrode active material having a higher tap density, thereby enabling the sodium-ion battery to have higher capacity performance and energy density.

[0118] In some embodiments, the compaction density of the positive electrode active material powder under 8 tons of pressure is 3 g / cm³. 3 ~5g / cm 3 Optionally, it can be 3.5g / cm³. 3 ~4.5g / cm 3 .

[0119] According to this application, the compaction density of the positive electrode active material has a meaning known in the art and can be measured using instruments and methods known in the art, such as referring to the GB / T24533-2009 standard and using an electronic pressure testing machine, such as the UTM7305 electronic pressure testing machine.

[0120] In these alternative embodiments, the positive electrode active material has a high compaction density, which is beneficial for enabling the sodium-ion battery to have higher capacity performance and energy density. Within this range, the higher the compaction density of the positive electrode active material, the higher the capacity performance and energy density of the sodium-ion battery.

[0121] Preparation method of positive electrode active material

[0122] Methods for preparing positive electrode active materials include:

[0123] Provide raw materials such that the elemental ratios in the raw materials satisfy the chemical formula shown in Formula I of the first aspect of this application;

[0124] The raw materials are calcined to obtain the positive electrode active material.

[0125] The positive electrode active material includes a layered antimony-containing sodium composite oxide, which has the chemical formula shown in Formula I.

[0126] Na x Mn a Fe b Ni c Sb d L eO2(I)

[0127] In formula I, 0.7 < x ≤ 1, 0 < a, 0 ≤ b, 0.1 < c ≤ 0.3, 0 < d < 0.1, 0 ≤ e, a + b + c + d + e = 1, (b + c) / (a ​​+ d + e) ​​≤ 1, and L is selected from one or more of Cu, Li, Ti, Zr, K, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Si, La, Ta, P, and B.

[0128] In some embodiments, the raw materials for the positive electrode active material can be obtained by co-precipitation, gelation, or solid-phase methods.

[0129] According to an embodiment of the method for preparing the positive electrode active material of this application, raw materials are first provided, and then the raw materials are calcined to obtain the positive electrode active material. The above-mentioned method for preparing the positive electrode active material is simple and has high manufacturability.

[0130] In some embodiments, step S1, providing raw materials, includes: mixing sodium, manganese, iron, nickel, antimony, and L sources evenly to obtain the raw materials. A ball mill or a high-speed mixer can be used for mixing in step S1. As an example, sodium, manganese, iron, nickel, antimony, and L sources are added to a high-speed mixer according to stoichiometric ratios for mixing over a period of 0.5 to 2 hours. The raw materials are obtained by mixing the sodium, manganese, iron, nickel, antimony, and L sources through a solid-phase mixing method.

[0131] In some embodiments of this application, the L source is selected from one or more of the following: Cu source, Li source, Ti source, Zr source, K source, Nb source, Mg source, Ca source, Mo source, Zn source, Cr source, W source, Bi source, Sn source, Ge source, Al source, Si source, La source, Ta source, P source, and B source.

[0132] In some embodiments of this application, the sodium source is selected from one or more of Na2CO3, NaHCO3, NaOH, and Na2O2.

[0133] In some embodiments of this application, the iron source is selected from one or more of Fe2O3, Fe3O4 and FeO.

[0134] In some embodiments of this application, the manganese source is selected from one or more of Mn2O3, Mn3O4, MnO and MnO2.

[0135] In some embodiments of this application, the nickel source is selected from NiO or Ni(OH)2.

[0136] In some embodiments of this application, the antimony source is selected from one or more of elemental antimony, antimony-containing oxides, or antimony salts.

[0137] In some other embodiments, step S1, providing raw materials, includes: mixing an iron source, a manganese source, a nickel source, an L source, and water to obtain a mixture; mixing the mixture with a precipitant to form a precipitate; and stirring the precipitate, sodium source, and antimony source evenly to obtain the raw material. The manganese source, iron source, nickel source, and L source are precipitated using a co-precipitation method, and then mixed with the sodium source and antimony source using a ball mill or high-speed mixer to obtain the raw material.

[0138] In some embodiments of this application, the L source is selected from one or more of the following: Cu source, Li source, Ti source, Zr source, K source, Nb source, Mg source, Ca source, Mo source, Zn source, Cr source, W source, Bi source, Sn source, Ge source, Al source, Si source, La source, Ta source, P source, and B source.

[0139] In some embodiments of this application, the sodium source is selected from one or more of Na2CO3, NaHCO3, NaOH, and Na2O2.

[0140] In some embodiments of this application, the iron source is selected from one or more of iron-containing chlorides, sulfates, and nitrates.

[0141] In some embodiments of this application, the manganese source is selected from one or more of manganese-containing chlorides, sulfates, and nitrates.

[0142] In some embodiments of this application, the nickel source is selected from one or more of nickel-containing chlorides, sulfates, and nitrates.

[0143] In some embodiments of this application, the antimony source is selected from one or more of elemental antimony, antimony-containing oxides, or antimony salts.

[0144] In some embodiments of this application, the precipitant is selected from one or more of hydroxides, carbonates and oxalates.

[0145] In some embodiments, calcination in step S2 includes calcining the raw materials in a muffle furnace at a temperature of 600°C to 1200°C in an air or oxygen atmosphere for 10 to 20 hours. The calcination temperature significantly affects the performance of the positive electrode active material. At lower calcination temperatures, the reaction is incomplete, easily generating amorphous materials containing impurities, which significantly impacts the electrochemical performance of the positive electrode active material. As the calcination temperature increases, the diffusion coefficient of the material increases, promoting ion and vacancy diffusion, particle rearrangement, and other mass transfer processes, thus facilitating the obtaining of products with high structural stability. At higher calcination temperatures, oxygen-deficient compounds are easily generated, and the extraction and insertion of sodium ions into the positive electrode active material are hindered.

[0146] Optionally, the calcination temperature is 900℃~950℃, and the holding time is 15h~20h.

[0147] Optionally, pre-calcination can be carried out as needed before calcination. The pre-calcination temperature is 600℃~900℃, the atmosphere is air or oxygen, and the holding time is 10h~20h.

[0148] In some embodiments of this application, step S2, after calcination, further includes cooling and then mechanical pulverization to obtain the positive electrode active material. This results in a volume average particle size Dv50 of 3 μm to 30 μm for the positive electrode active material. This is beneficial for obtaining a final positive electrode active material with superior particle size distribution and specific surface area.

[0149] In addition, please refer to the appendix as appropriate below. Figures 4 to 9 This application describes the secondary battery, battery module, battery pack, and electrical device. Figure 4 This is a schematic diagram of a secondary battery according to one embodiment of this application. Figure 5 yes Figure 4 An exploded view of a secondary battery according to one embodiment of this application is shown. Figure 6 This is a schematic diagram of a battery module according to one embodiment of this application. Figure 7 This is a schematic diagram of a battery pack according to one embodiment of this application. Figure 8 yes Figure 7 An exploded view of a battery pack according to one embodiment of this application is shown. Figure 9 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0150] A third aspect of this application provides a secondary battery, including the positive electrode active material of the first aspect of this application or the positive electrode active material prepared by the preparation method of the second aspect of this application.

[0151] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0152] The positive electrode includes a positive current collector and a positive electrode film layer formed on at least a portion of the surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, which is the positive electrode active material of the first aspect of this application or a positive electrode active material prepared by the preparation method of the second aspect of this application. Therefore, the foregoing description of embodiments of the positive electrode active material according to this application is also applicable to the positive electrode active material in secondary batteries, and the same content will not be repeated.

[0153] In some embodiments, the positive electrode film layer may further include a conductive agent to improve the conductivity of the positive electrode. This application does not impose specific limitations on the type of conductive agent, which can be selected according to actual needs. As an example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers.

[0154] In some embodiments, the positive electrode film layer may further include an adhesive to firmly bond the positive electrode active material and optionally a conductive agent to the positive electrode current collector. This application does not impose specific limitations on the type of adhesive, which can be selected according to actual needs. As an example, the adhesive may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA), and carboxymethyl chitosan (CMCS).

[0155] In some embodiments, the positive electrode current collector can be a conductive carbon sheet, a metal foil, a carbon-coated metal foil, a porous metal plate, or a composite current collector. The conductive carbon material of the conductive carbon sheet can be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers. The metal material of the metal foil, carbon-coated metal foil, and porous metal plate can each be independently selected from at least one of copper, aluminum, nickel, and stainless steel. The composite current collector can be a composite current collector formed by combining a metal foil with a polymer base film. The positive electrode current collector is, for example, one or more of copper foil, aluminum foil, nickel foil, stainless steel foil, stainless steel mesh, and carbon-coated aluminum foil, with aluminum foil being preferred.

[0156] The above-mentioned positive electrode sheet is prepared according to conventional methods in the art. Typically, the positive electrode active material and optional conductive agent and binder are dispersed in a solvent (e.g., N-methylpyrrolidone, abbreviated as NMP) to form a uniform positive electrode slurry. The positive electrode slurry is coated on the positive electrode current collector, and after drying and cold pressing, the positive electrode sheet is obtained.

[0157] In some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0158] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0159] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0160] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0161] In some embodiments, the negative electrode film layer may optionally include an adhesive. The adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0162] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0163] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0164] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0165] In some embodiments of this application, the electrolyte acts as a conductor of ions between the positive and negative electrode plates. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0166] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0167] In some embodiments, the electrolyte salt may be selected from one or more of NaPF6, NaClO4, NaBF4, KPF6, KClO4, KBF4, LiPF6, LiClO4, LiBF4, Zn(PF6)2, Zn(ClO4)2, and Zn(BF4)2.

[0168] In some embodiments, the electrolyte salt may be selected from one or more of NaPF6, NaClO4, and NaBF4.

[0169] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0170] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0171] In some embodiments of this application, there are no particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0172] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0173] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0174] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0175] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0176] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 A square-structured secondary battery 5 is shown as an example.

[0177] In some implementations, refer to Figure 5 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0178] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0179] Figure 6 Battery module 4 is shown as an example. (See reference...) Figure 6 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0180] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0181] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0182] Figure 7 and Figure 8 Battery pack 1 is shown as an example. (See reference...) Figure 7 and Figure 8The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0183] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0184] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0185] Figure 9 An example electrical device is shown. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0186] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0187] Example

[0188] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0189] Example 1

[0190] Na₂CO₃, NiO, Mn₂O₃, CuO, and Sb₂O₃ were added in a molar ratio of Na:Mn:Ni:Cu:Sb = 1:0.2:0.5:0.2:0.1, and a total of 30g of each sample was weighed. Each sample was pre-ground in an agate mortar and then ball-milled in a planetary ball mill for 1 hour to obtain the raw material. The raw material was evenly placed in an open crucible and then heated from room temperature to 950℃ in a muffle furnace at a heating rate of 5℃ / min, and held at 950℃ for 15 hours. After natural cooling, the positive electrode active material was obtained, which was a layered NaNi₂O₃. 0.2 Mn 0.5 Cu 0.2 Sb 0.1 O2.

[0191] The positive electrode active materials of Examples 1-19 and Comparative Examples 1-6 were prepared according to Table 1 below.

[0192] Table 1. Parameter results of the positive electrode active materials of Examples 1-19 and Comparative Examples 1-6

[0193]

[0194]

[0195] Manufacturing of sodium-ion batteries

[0196] (1) Preparation of positive electrode sheet

[0197] The above-mentioned positive electrode active material, conductive carbon black (SP), and binder polyvinylidene fluoride (PVDF) were thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 80:15:5 to form a uniform positive electrode slurry. This slurry was coated onto the positive electrode current collector carbon-coated Al foil, dried, cold-pressed, and then punched into small round discs with a diameter of 14 mm.

[0198] (2) Preparation of electrolyte

[0199] Dissolve an equal volume of ethylene carbonate in propylene carbonate, and then uniformly dissolve an appropriate amount of sodium perchlorate in the mixed solvent to form a 1 mol / L electrolyte for later use.

[0200] (3) The negative electrode is made of sodium metal.

[0201] (4) The isolation membrane is made of porous polyethylene membrane.

[0202] (5) Stack and wind the positive electrode, separator, and negative electrode in sequence to obtain an electrode assembly. Place the electrode assembly in an outer packaging, add the electrolyte prepared above, and after processes such as encapsulation, standing, formation, and aging, obtain a secondary battery.

[0203] The positive electrode active materials and secondary batteries of each embodiment and comparative example were tested according to the following test methods.

[0204] (1) Interlayer spacing d of the 003 crystal plane of the positive electrode active material 003 and space group testing

[0205] 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 from Brucker AxS (Germany) with CuKα rays as the radiation source. The 2θ angle was scanned within the range of 10° to 70° at a scanning rate of 4° / min. After the test, the interlayer spacing d of the 003 crystal plane was obtained by using the angle corresponding to the 003 crystal plane and applying Bragg's equation 2d·sinθ=λ, as well as the fact that each unit cell of the 003 crystal plane contains three transition metal layers. 003 The space group of the sample can be confirmed by comparing the XRD diffraction peaks of the sample with the standard card of the XRD analysis software.

[0206] (2) Immersion test of positive electrode active material

[0207] Take 5g of positive electrode active material and place it in a beaker. Add 15mL of deionized water and stir vigorously for 1min. After standing for 24h, filter and dry under vacuum at 60℃ for 6h to obtain the soaked positive electrode active material.

[0208] The X-ray powder diffractometer used in test (1) above was used to observe the change in the intensity of the (003) characteristic peak in the X-ray diffraction spectrum of the positive electrode active material before and after immersion in water for 24 hours. I1 represents the intensity of the (003) characteristic peak in the X-ray diffraction spectrum of the positive electrode active material after immersion in water for 24 hours, and I0 represents the intensity of the (003) characteristic peak in the X-ray diffraction spectrum of the positive electrode active material before immersion. I1 / I0 can represent the water stability of the positive electrode active material. The smaller the I1 / I0, the worse the water stability of the positive electrode active material and the more sensitive it is to water.

[0209] (3) High humidity storage capacity change rate test

[0210] The positive electrode active material prepared in the above embodiment was placed in an air environment with 70% humidity and 25°C for one day, and placed in a conventional storage environment (humidity <1% and temperature 25°C) for one day. The positive electrode active materials under the two storage conditions were used to make batteries, and their capacity was tested. The high humidity storage capacity change rate of the positive electrode active material was calculated.

[0211] Specifically: At 25°C, after preparing a secondary battery using the positive electrode active material, it is charged at a constant current density of 10 mA / g to 4.3V, and then discharged at a constant current density of 10 mA / g to 1.5V, yielding the discharge specific capacity C0 of the secondary battery. The same positive electrode active material is placed in air at 70% humidity and 25°C for one day. Then, at 25°C, the obtained positive electrode active material is prepared into a coin cell, charged at a constant current density of 10 mA / g to 4.3V, and then discharged at a constant current density of 10 mA / g to 1.5V, yielding the discharge specific capacity C1 of the secondary battery. The rate of change is equal to C1 / C0.

[0212] Table 2 Test results of Examples 1-19 and Comparative Examples 1-6

[0213]

[0214] Based on the above results, Examples 1 to 19 all achieved good results, with moderate interlayer spacing, large I1 / I0 values, and high specific surface area, tap density, and powder compaction density under 8 tons of pressure for the positive electrode active material. Furthermore, the capacity change rate during high humidity storage was high; a higher change rate indicates better water stability. This application, by doping with a specific metal Sb, enables the layered antimony-containing sodium composite oxide to exhibit high water stability. Moreover, during the electrochemical reaction process, it effectively suppresses side reactions of the antimony-containing sodium composite oxide, thereby obtaining a high specific surface area, tap density, and powder compaction density under 8 tons of pressure. Consequently, the sodium-ion battery containing the positive electrode active material of this application exhibits a high specific capacity during the first charge-discharge cycle.

[0215] Comparative Example 1, without antimony doping, shows a low I1 / I0 value, indicating poor water stability. Comparative Examples 2, 3, and 4 have excessively high Fe and Ni content; excessive Fe and Ni react more readily with water, resulting in a low I1 / I0 value and further indicating poor water stability. Containing lower Fe and Ni content in the cathode active material results in a lower initial charge-discharge specific capacity in sodium-ion batteries, but also reduces the structural stability of the layered antimony-containing sodium composite oxide. Comparative Examples 5 and 6 show that excessive Sb doping leads to a lower initial charge-discharge specific capacity in sodium-ion batteries, while insufficient Sb doping fails to meet the water stability requirements of the cathode material.

[0216] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. 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 comprising a layered antimony-containing sodium composite oxide, said antimony-containing sodium composite oxide having a chemical formula as shown in Formula I. And x Mn a Fe b Yes c Sb d L e O2 (I) In Equation I, 0.7 < x ≤ 1, 0 < a, 0 < b, 0.1 < c ≤ 0.3, 0 < d ≤ 0.1, 0 ≤ e, a + b + c + d + e = 1, (b + c) / (a ​​+ d + e) ​​≤ 1, and L is selected from one or more of Cu, Li, Ti, Zr, K, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Si, La, Ta, P, and B.

2. The positive electrode active material according to claim 1, wherein, In Equation I, 0.3≤a≤0.4, 0.2≤b≤0.3, 0.15≤c≤0.2, 0.05≤d≤0.1, 0.05≤e≤0.1, a+b+c+d+e=1, and 0.4≤(b+c) / (a+d+e)≤1.

3. The positive electrode active material according to claim 1, wherein, The L is selected from one or more of Cu, Li, Ti, Zr, Mg, Ca, Zn, Bi, Sn, Al, Si, La, Ta, P, and B.

4. The positive electrode active material according to claim 3, wherein, The L is selected from one or more of Cu, Li, Mg, Zn, Al, Si and B.

5. The positive electrode active material according to claim 1, wherein, The antimony-containing sodium composite oxide includes an O3 phase, wherein the O3 phase has a space group R. m has a layered crystal structure.

6. The positive electrode active material according to claim 1, wherein, The interlayer spacing of the antimony-containing sodium composite oxide is 0.53 nm to 0.54 nm.

7. The positive electrode active material according to claim 1, wherein, The X-ray diffraction pattern of the antimony-containing sodium composite oxide satisfies I1 / I0≥0.

2. Wherein, I1 is the peak intensity of the X-ray diffraction peak of the O3 phase 003 crystal plane of the antimony-containing sodium composite oxide after soaking in deionized water for 24 hours, and I0 is the peak intensity of the X-ray diffraction peak of the O3 phase 003 crystal plane of the antimony-containing sodium composite oxide before soaking in deionized water.

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 (1) to (4): (1) The volume average particle size Dv50 of the positive electrode active material is 3μm to 30μm; (2) The specific surface area of ​​the positive electrode active material is 0.1 m². 2 / g~5m 2 / g; (3) The tap density of the positive electrode active material is 1 g / cm³. 3 ~3g / cm 3 ; (4) The compaction density of the positive electrode active material under 8 tons of pressure is 3 g / cm³. 3 ~5g / cm 3 .

9. The positive electrode active material according to claim 8, wherein, The positive electrode active material satisfies one or more of the following (5) to (8): (5) The volume average particle size Dv50 of the positive electrode active material is 5 μm to 15 μm; (6) The specific surface area of ​​the positive electrode active material is 0.3 m². 2 / g~3m 2 / g; (7) The tap density of the positive electrode active material is 1.5 g / cm³. 3 ~2.5g / cm 3 ; (8) The compacted density of the positive electrode active material under 8 tons of pressure is 3.5 g / cm³. 3 ~4.5g / cm 3 .

10. A method for preparing a positive electrode active material, comprising: Provide raw materials such that the elemental ratios in the raw materials satisfy the chemical formula shown in Formula I as described in any one of claims 1 to 9; The raw materials are calcined to obtain the positive electrode active material. The positive electrode active material comprises a layered antimony-containing sodium composite oxide, which has the chemical formula shown in Formula I. And x Mn a Fe b Yes c Sb d L e O2 (I) In Equation I, 0.7 < x ≤ 1, 0 < a, 0 < b, 0.1 < c ≤ 0.3, 0 < d < 0.1, 0 ≤ e, a + b + c + d + e = 1, (b + c) / (a ​​+ d + e) ​​≤ 1, and L is selected from one or more of Cu, Li, Ti, Zr, K, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Si, La, Ta, P, and B.

11. The method for preparing the positive electrode active material according to claim 10, wherein, The raw materials provided include: Sodium, manganese, iron, nickel, antimony, and L sources are mixed evenly to obtain the raw material. The L source is selected from one or more of the following: Cu source, Li source, Ti source, Zr source, K source, Nb source, Mg source, Ca source, Mo source, Zn source, Cr source, W source, Bi source, Sn source, Ge source, Al source, Si source, La source, Ta source, P source, and B source.

12. The method for preparing the positive electrode active material according to claim 11, wherein, The raw materials satisfy one or more of the following (9) to (13): (9) The sodium source is selected from one or more of Na2CO3, NaHCO3, NaOH and Na2O2; (10) The iron source is selected from one or more of Fe2O3, Fe3O4 and FeO; (11) The manganese source is selected from one or more of Mn2O3, Mn3O4, MnO and MnO2; (12) The nickel source is selected from NiO or Ni(OH)2; (13) The antimony source is selected from one or more of elemental antimony, antimony-containing oxides or antimony salts.

13. The method for preparing the positive electrode active material according to claim 10, wherein, The raw materials provided include: Iron source, manganese source, nickel source, L source are mixed with water to obtain a mixed solution, wherein the L source is selected from one or more of Cu source, Li source, Ti source, Zr source, K source, Nb source, Mg source, Ca source, Mo source, Zn source, Cr source, W source, Bi source, Sn source, Ge source, Al source, Si source, La source, Ta source, P source and B source; The mixture is then mixed with a precipitant to form a precipitate; The precipitate, sodium source, and antimony source are stirred evenly to obtain the raw material.

14. The method for preparing the positive electrode active material according to claim 13, wherein, The raw materials satisfy one or more of the following (14) to (19): (14) The sodium source is selected from one or more of Na2CO3, NaHCO3, NaOH and Na2O2; (15) The iron source is selected from one or more of iron-containing chlorides, sulfates and nitrates; (16) The manganese source is selected from one or more of manganese-containing chlorides, sulfates and nitrates; (17) The nickel source is selected from one or more of nickel-containing chlorides, sulfates and nitrates; (18) The antimony source is selected from one or more of elemental antimony, antimony-containing oxides or antimony salts; (19) The precipitant is selected from one or more of hydroxides, carbonates and oxalates.

15. A secondary battery, characterized in that, The positive electrode active material includes any one of claims 1 to 9 or the positive electrode active material prepared by the method of any one of claims 10 to 14.

16. A battery module comprising the secondary battery of claim 15.

17. A battery pack comprising the battery module of claim 16.

18. An electrical device comprising at least one selected from the secondary battery of claim 15, the battery module of claim 16, or the battery pack of claim 17.

Images