Positive electrode active material and method for manufacturing the same, positive electrode plate, battery and power consumption device

Abstract

This application discloses a positive electrode active material and a method for producing the same, a positive electrode plate, a battery and a power consumption device, wherein the positive electrode active material comprises a core and a coating layer, the core comprises a sodium ion transition metal oxide containing iron and / or nickel, where b is the molar amount of iron and c is the molar amount of nickel, and 0 ≤ b ≤ 0.4 and 0 ≤ c ≤ 0.4, the coating layer is provided on at least a portion of the surface of the core, the coating layer contains an alkaline sodium compound, and the mass percentage of the alkaline sodium compound is w% based on the total amount of the positive electrode active material, and satisfies 0.1 ≤ (b + c) / w ≤ 0.5.

Description

[Technical Field]

[0001] This application belongs to the technical field of secondary batteries and specifically relates to positive electrode active material and its manufacturing method, positive electrode plate, battery and power consumption device. [Background technology]

[0002] Rechargeable batteries are widely used in various home appliances and electric vehicles due to their excellent characteristics such as being lightweight, pollution-free, and having no memory effect.

[0003] Sodium-ion batteries are a type of rechargeable battery, and layered transition metal oxides are commonly used as positive electrode active materials in sodium-ion batteries. At high voltages, layered transition metal oxides can desorb and absorb more sodium ions, resulting in a relatively high specific capacity. However, conventional layered transition metal oxides are structurally unstable at high voltages, leading to relatively low cycle stability of the battery at high voltages. [Overview of the project] [Problems that the invention aims to solve]

[0004] Disclosure details In view of the technical problems present in the background technology, this application aims to provide a positive electrode active material that improves the cycle stability and energy density of batteries containing it at high voltages by solving the problem of the structural instability of positive electrode active materials at high voltages. [Means for solving the problem]

[0005] To achieve the above objective, a first aspect of this application provides a positive electrode active material, the positive electrode active material being a core, the core comprising a sodium ion transition metal oxide containing iron and / or nickel, wherein the molar amount of iron in the sodium ion transition metal oxide is denoted as b, the molar amount of nickel is denoted as c, and the core has 0 ≤ b ≤ 0.4 and 0 ≤ c ≤ 0.4. A coating layer is provided on at least a portion of the surface of the core, and the coating layer contains an alkaline sodium compound, wherein the mass percentage of the alkaline sodium compound is w% based on the total amount of the positive electrode active material, and the coating layer satisfies 0.1 ≤ (b+c) / w ≤ 0.5.

[0006] The positive electrode active material of this application exhibits structural stability at high voltages, thereby improving the high-voltage cycle stability and energy density of batteries containing it.

[0007] In some embodiments, 0.2 ≤ (b+c) / w ≤ 0.4. This improves the structural stability of the positive electrode active material at high voltages, thereby improving the high-voltage cycle stability and energy density of the battery containing it.

[0008] In some embodiments, the mass percentage w% of the alkaline sodium compound is 0.3 wt% to 5 wt%, and selectively 0.5 wt% to 2 wt%. This improves the structural stability of the positive electrode active material at high voltage, thereby improving the high-voltage cycle stability and energy density of the battery containing it.

[0009] In some embodiments, the alkaline sodium compound comprises at least one of sodium hydroxide and sodium carbonate, and is selectively sodium carbonate. This improves the structural stability of the positive electrode active material at high voltage, thereby improving the high-voltage cycle stability and energy density of the battery containing it.

[0010] In some embodiments, the mass ratio of sodium carbonate is 80% or more of the total mass of the coating layer. This improves the structural stability of the positive electrode active material at high voltage, thereby improving the high-voltage cycle stability and energy density of the battery containing it.

[0011] In some embodiments, based on the total mass of the coating layer, the mass ratio of the sodium hydroxide is 10% or less. Thereby, the structural stability of the positive electrode active material at high voltages can be improved, thereby improving the cycle stability and energy density of the battery containing the same at high voltages.

[0012] In some embodiments, the sodium ion transition metal oxide is Na , a , , x , e , d , 2-e+δ , b , c Mn a Fe b Ni c Q d O 2-e+δ F e and includes 0.5 ≦ x ≦ 1.2, 0 < a, 0 ≦ b ≦ 0.4, 0 ≦ c ≦ 0.4, 0 ≦ d, a + b + c + d = 1, 0 ≦ e ≦ 0.2, -0.1 ≦ δ ≦ 0.1, and Q includes at least one of Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi.

[0013] In some embodiments, the sodium ion transition metal oxide is Na x Mn a Fe b Ni c Q d O 2-e+δ F e and includes 0.7 ≦ x ≦ 1.2, 0 < a, 0.1 ≦ b ≦ 0.4, 0.1 ≦ c ≦ 0.4, 0 ≦ d ≦ 0.3, a + b + c + d = 1, 0 ≦ e ≦ 0.2, -0.1 ≦ δ ≦ 0.1, and Q includes at least one of Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi, and is selectively at least one of B, Mg, Al, Si, Ca, Ti, Co, Cu, Zn, Zr, Nb, Mo, La, and Bi. Based on the total amount of the positive electrode active material, the mass ratio of the alkaline sodium compound is 1 wt% - 2 wt%. Thereby, the structural stability of the positive electrode active material at high voltages can be improved, thereby improving the cycle stability and energy density of the battery containing the same at high voltages.

[0014] In some embodiments, at least one of the conditions of 0.3≤a≤0.6, 0.15≤b≤0.35, 0.15≤c≤0.35, 0.1≤d≤0.2 is satisfied.

[0015] In some embodiments, 0.5≤(b + c) / a≤2, and optionally 0.5≤(b + c) / a≤1.5. Thereby, the structural stability of the positive electrode active material at high voltage can be improved, and thereby the cycle stability and energy density of the battery containing the same at high voltage can be improved.

[0016] In some embodiments, the phase state of the sodium ion transition metal oxide includes an O3 phase, and the space group is

Number

[0017] In some embodiments, the sodium ion transition metal oxide is Na x Mn a Ni c Q d O 2-e+δ F e including, 0.5≤x≤1.2, 0 < a, 0.1≤c≤0.3, 0≤d≤0.3, a + c + d = 1, 0≤e≤0.2, -0.1≤δ≤0.1, Q includes at least one of Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W and Bi, and optionally is at least one of B, Mg, Al, Si, Ca, Ti, Co, Cu, Zn, Zr, Nb, Mo, La and Bi. Based on the total amount of the positive electrode active material, the mass ratio of the alkaline sodium compound is 0.5 wt% - 1.5 wt%. Thereby, the structural stability of the positive electrode active material at high voltage can be improved, and thereby the cycle stability and energy density of the battery containing the same at high voltage can be improved.

[0018] In some embodiments, at least one of the following conditions is satisfied: 0.5 ≤ a ≤ 0.8, 0.15 ≤ c ≤ 0.25, and 0.05 ≤ d ≤ 0.15.

[0019] In some embodiments, 0.125 ≤ c / a ≤ 0.45, and selectively 0.2 ≤ c / a ≤ 0.3. This improves the structural stability of the positive electrode active material at high voltages, thereby improving the high-voltage cycle stability and energy density of the battery containing it.

[0020] In some embodiments, the phase state of the sodium ion transition metal oxide includes a P2 phase, the space group includes P63 / mmc, and the layer spacing is 0.55 nm-0.57 nm. This can improve the rate performance and cycle stability of the battery.

[0021] In some embodiments, the BET specific surface area of ​​the positive electrode active material is Sm 2 The relationship is / g, and S and w satisfy 0.3 ≤ w / S ≤ 3, and selectively satisfy the relationship 0.5 ≤ w / S ≤ 2. This can improve battery cycle stability.

[0022] In some embodiments, the positive electrode active material is the D of the positive electrode active material. v The conditions are that 50 is 2μm-20μm, selectively 4μm-15μm, and the BET specific surface area of ​​the positive electrode active material is 0.2m². 2 / g-2m 2 It is / g, and selectively 0.3m 2 / g-2m 2 The conditions are that the density is / g and the compaction density of the positive electrode active material at a pressure of 300 MPa is 3.1 g / cm³. 3 -3.8g / cm 3 Therefore, selectively 3.2 g / cm³ 3 -3.6 g / cm³ 3 It satisfies at least one of the following conditions.

[0023] This results in the D of the positive electrode active material. v50. When at least one of the specific surface area and the compaction density at a pressure of 300 MPa is within the above range, the conduction distance of Na ions in the positive electrode active material is small, surface side reactions are few, the positive electrode active material is promoted to exert its gram capacity, and the capacity retention rate of the battery containing it is improved.

[0024] A second aspect of this application provides a method for producing the positive electrode active material described in the first aspect, To provide a sodium ion transition metal oxide containing iron and / or nickel, wherein in the sodium ion transition metal oxide, the molar amount of iron is denoted as b, the molar amount of nickel is denoted as c, and 0 ≤ b ≤ 0.4 and 0 ≤ c ≤ 0.4. The process includes mixing the sodium ion transition metal oxide and an alkaline sodium compound and sintering them to obtain a positive electrode active material. Here, the mass percentage of the alkaline sodium compound is w%, with respect to the total amount of the positive electrode active material, and 0.1 ≤ (b+c) / w ≤ 0.5.

[0025] This invention enables the production of a positive electrode active material with a stable structure at high voltages, thereby improving the cycle stability and energy density of batteries containing it at high voltages.

[0026] A third aspect of this application provides a positive electrode plate comprising a positive electrode active material described in the first aspect of this application or a positive electrode active material manufactured by the method described in the second aspect.

[0027] A fourth aspect of this application provides a battery including the positive electrode plate described in the third aspect of this application.

[0028] A fifth aspect of this application provides a power consumption device including the battery described in the fourth aspect.

[0029] Additional aspects and advantages of this application are partially shown in the following description, partially revealed in the following description, or understood through the practice of this application.

[0030] By reading the detailed description of the following optional embodiments, various other advantages and benefits will become apparent to those skilled in the art. The drawings are used solely to illustrate the purpose of the optional embodiments and are not to be considered limitations to this application. Note that in all drawings, the same drawing number indicates the same component. In the drawings, [Brief explanation of the drawing]

[0031] [Figure 1] This is a cross-sectional view of the positive electrode active material according to one embodiment of this application. [Figure 2] This is a schematic diagram of the structure of a battery according to one embodiment of this application. [Figure 3] This is a schematic diagram of the structure of a battery module according to one embodiment of this application. [Figure 4] This is a schematic diagram of the structure of a battery pack according to one embodiment of this application. [Figure 5] Figure 4 is an exploded view. [Figure 6] This is a schematic diagram of one embodiment of a power-consuming device that uses a battery as a power source. [Figure 7] This is a surface morphology diagram of the positive electrode active material manufactured in Example 1. [Figure 8] This is a surface morphology diagram of the positive electrode active material manufactured in Comparative Example 1. [Figure 9] This is a surface morphology diagram of the positive electrode active material obtained by disassembling the button-type battery of Example 1 after 50 cycles. [Figure 10] This is a surface morphology diagram of the positive electrode active material obtained by disassembling the button-type battery of Comparative Example 1 after 50 cycles. [Modes for carrying out the invention]

[0032] The following describes in detail embodiments of the technical invention of this application. The following embodiments are merely examples to clarify the technical invention of this application and should not be used to limit the scope of protection of this application.

[0033] The “Examples” as used herein mean that certain features, structures, or characteristics described in conjunction with the Examples may be included in at least one Example of this Application. The appearance of this phrase at each location in the Specification does not necessarily refer to the same Example, nor do they represent mutually exclusive or alternative Examples. Those skilled in the art will understand, both explicitly and implicitly, that the Examples described herein can be combined with other Examples.

[0034] For simplicity and clarity, this specification specifically discloses only a range of certain numerical values. However, any lower limit and any upper limit may be combined to form an unspecified range, and any lower limit and any other lower limit may be combined to form an unspecified range, and similarly, any upper limit and any other upper limit may be combined to form an unspecified range. Furthermore, each point or single numerical value disclosed individually may itself act as a lower or upper limit when combined with any other point or single numerical value, or when combined with other lower or upper limits, to form an unspecified range.

[0035] In the description of the embodiments of this application, the term "and / or" merely describes a relationship between related objects, indicating that three relationships may exist. For example, A and / or B may represent three cases: A alone, a combination of A and B, or B alone. In this specification, the letter " / " generally indicates that the preceding and succeeding related objects are in an "or" relationship.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art relating to the present application. The terms used herein are solely for the purpose of describing specific embodiments and are not intended to limit this application. The terms “including” and “having” and any variations thereof in the description of the specification, claims, and drawings of this application are intentionally intended to cover the non-exclusive “including.”

[0037] Secondary batteries are not only used in energy storage and power systems such as hydroelectric, thermal, wind, and solar power plants, but also widely applied in electric transportation such as electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. Sodium-ion batteries have a strong price advantage over conventional lithium-ion batteries and have the potential for a wide range of applications in large-scale power storage systems.

[0038] Layered transition metal oxides are a popular cathode active material for sodium-ion batteries due to their high conductivity, high energy density, relatively large capacity, and relatively long cycle life. Under high-voltage charging conditions, a relatively large amount of sodium ions are released from layered transition metal oxides, giving them a relatively high specific capacity. However, this also leads to relatively high oxygen activity in the layered transition metal oxides. This highly reactive oxygen readily reacts with the metal in the transition metal oxide, causing the metal to migrate to the electrolyte. Furthermore, the highly reactive oxygen readily reacts with the electrolyte, causing metal elution and oxygen deficiency in the transition metal oxide, leading to crack formation in the layered transition metal oxide and reducing its structural stability, thereby lowering the battery's cycle stability at high voltages.

[0039] In this application, the positive electrode active material includes a core and a coating layer provided on at least a portion of the surface of the core, the core includes a sodium ion transition metal oxide containing iron and / or nickel, where the molar amount of iron is denoted as b and the molar amount of nickel as c, with 0 ≤ b ≤ 0.4 and 0 ≤ c ≤ 0.4. Because the activity of nickel and iron in the sodium ion transition metal oxide is relatively high, it easily induces an increase in the oxygen activity of adjacent oxygen sites, and thus this application can control the values ​​of the molar amount of iron b and the molar amount of nickel c within the above range, thereby reducing the content of highly reactive oxygen species in the transition metal oxide. Simultaneously, the coating layer contains an alkaline sodium compound, and the mass ratio of the alkaline sodium compound is w% based on the total amount of the positive electrode active material, and the ratio of the iron element and / or nickel element in the sodium ion transition metal oxide in the core of this application to the alkaline sodium compound in the coating layer satisfies 0.1 ≤ (b + c) / w ≤ 0.5. A core and coating layer satisfying this composition can improve the specific capacity of the positive electrode active material while simultaneously reducing the surface activity of the sodium ion transition metal oxide. Furthermore, this coating layer effectively blocks contact between the sodium ion transition metal oxide and the electrolyte, reduces side reactions between the electrolyte and the transition metal oxide surface, reduces metal elution and oxygen deficiency, improves the structural stability of the positive electrode active material at high voltage, and thereby improves the cycle stability and energy density of the battery containing it at high voltage.

[0040] The positive electrode active material disclosed in the embodiments of this application is applicable to secondary batteries, and the battery disclosed in the embodiments of this application can be used in power-consuming devices that use the battery as a power source or in various energy storage systems that use the battery as an energy storage element. Power-consuming devices may include, but are not limited to, mobile phones, tablets, laptop computers, electric toys, power tools, electric bicycles, electric vehicles, ships, and spacecraft. Here, electric toys may include stationary or mobile electric toys, such as game consoles, electric vehicle toys, electric steamship toys and electric airplane toys, and spacecraft may include airplanes, rockets, spacecraft and spaceships.

[0041] A first aspect of this application provides a positive electrode active material, referring to Figure 1, wherein the positive electrode active material 1000 comprises a core 100 and a coating layer 200, wherein the core 100 comprises a sodium ion transition metal oxide containing iron and / or nickel, where b is the molar amount of iron and c is the molar amount of nickel, and 0 ≤ b ≤ 0.4 and 0 ≤ c ≤ 0.4, the coating layer 200 is provided on at least a portion of the surface of the core 100, the coating layer 200 contains an alkaline sodium compound, and the mass percentage of the alkaline sodium compound is w% based on the total amount of the positive electrode active material 1000, and satisfies 0.1 ≤ (b + c) / w ≤ 0.5.

[0042] The positive electrode active material 1000 of this application includes a core 100 and a coating layer 200 provided on at least a portion of the surface of the core 100. The core 100 contains a sodium ion transition metal oxide containing iron and / or nickel, where b is the molar amount of iron and c is the molar amount of nickel, with 0 ≤ b ≤ 0.4 and 0 ≤ c ≤ 0.4. Because the activity of nickel and iron in the sodium ion transition metal oxide is relatively high, it easily induces an increase in the oxygen activity of adjacent oxygen sites. Thus, this application can control the values ​​of the molar amount b of iron and the molar amount c of nickel within the above range, thereby reducing the content of highly reactive oxygen species in the transition metal oxide. Simultaneously, the coating layer 200 contains an alkaline sodium compound, and the mass ratio of the alkaline sodium compound is w% based on the total amount of the positive electrode active material, and the ratio of the iron element and / or nickel element in the sodium ion transition metal oxide in the core 100 of this application to the alkaline sodium compound in the coating layer 200 satisfies 0.1 ≤ (b + c) / w ≤ 0.5. The core 100 and coating layer 200 satisfying this composition can improve the specific capacity of the positive electrode active material 1000 while simultaneously reducing the surface activity of the sodium ion transition metal oxide. Furthermore, this coating layer 200 effectively blocks contact between the sodium ion transition metal oxide and the electrolyte, reduces side reactions between the electrolyte and the surface of the sodium ion transition metal oxide, reduces metal elution and oxygen deficiency, improves the structural stability of the positive electrode active material 1000 at high voltage, and thereby improves the cycle stability and energy density of the battery containing it at high voltage.

[0043] In some embodiments of this application, the core 100 comprises a sodium ion transition metal oxide containing iron and / or nickel, where b is the molar amount of iron and c is the molar amount of nickel, and 0≦b≦0.4 and 0≦c≦0.4, for example 0.001≦b≦0.4, 0.005≦b≦0.4, 0.01≦b≦0.4, 0.015≦b≦0.4, 0.02≦b≦0.4, 0.05≦b≦0.4, 0.07≦b≦0.4, 0.1≦b≦0.4, 0.12≦b≦0.4, 0.15≦b≦0.4, 0.17≦b≦0.4, 0.2≦b≦0.4, 0.22≦b≦0.4, 0. 25≦b≦0.4, 0.27≦b≦0.4, 0.3≦b≦0.4, 0.32≦b≦0.4, 0.35≦b≦0.4, 0.37≦b≦0.4, etc., and 0.001≦c≦0.4, 0.005≦c≦0.4, 0.01≦c≦0.4, 0.015≦c≦0.4, 0.02≦c≦0.4, 0.05≦c≦0.4, 0.07 Examples include ≤c≦0.4, 0.1≦c≦0.4, 0.12≦c≦0.4, 0.15≦c≦0.4, 0.17≦c≦0.4, 0.2≦c≦0.4, 0.22≦c≦0.4, 0.25≦c≦0.4, 0.27≦c≦0.4, 0.3≦c≦0.4, 0.32≦c≦0.4, 0.35≦c≦0.4, 0.37≦c≦0.4, etc. Specifically, because the activity of nickel and iron in sodium ion transition metal oxides is relatively high, it easily induces an increase in the oxygen activity of adjacent oxygen sites. As a result, this application can control the molar amounts b of iron and c of nickel within the above ranges, thereby reducing the content of highly reactive oxygen species in the transition metal oxide, thereby reducing metal elution and oxygen deficiency in the transition metal oxide and improving the structural stability of the positive electrode active material 1000 at high voltage.

[0044] In some embodiments of this application, the mass percentage of the alkaline sodium compound is w% with respect to the total amount of the positive electrode active material 1000, and satisfies 0.1 ≤ (b+c) / w ≤ 0.5, for example, 0.15 ≤ (b+c) / w ≤ 0.45, 0.2 ≤ (b+c) / w ≤ 0.4, 0.25 ≤ (b+c) / w ≤ 0.35, 0.25 ≤ (b+c) / w ≤ 0.3, etc. In some other embodiments of this application, the mass percentage of the alkaline sodium compound is w%, and satisfies 0.2 ≤ (b+c) / w ≤ 0.4. As a result, the core 100 and coating layer 200 satisfying this composition can improve the specific capacity of the positive electrode active material 1000 while simultaneously reducing the surface activity of the sodium ion transition metal oxide. Furthermore, the coating layer 200 effectively blocks contact between the sodium ion transition metal oxide and the electrolyte, reducing side reactions between the electrolyte and the surface of the sodium ion transition metal oxide, thereby reducing metal elution and oxygen deficiency, improving the structural stability of the positive electrode active material 1000 at high voltages, and thereby improving the cycle stability and energy density of the battery containing it at high voltages.

[0045] In some embodiments of this application, the mass percentage w% of the alkaline sodium compound is 0.3wt%-5wt%, for example 0.5wt%-4.5wt%, 0.8wt%-4.2wt%, 1wt%-4wt%, 1.2wt%-3.7wt%, 1.5wt%-3.5wt%, 1.8wt%-3.2wt%, 2wt%-3wt%, 2.2wt%-2.8wt%, 2.5wt%-2.7wt%, etc. In some other embodiments of this application, the mass percentage w% of the alkaline sodium compound is 0.5wt%-2wt%. As a result, the mass ratio of the alkaline sodium compound in the coating layer 200 of the positive electrode active material 1000 of this application satisfies the above range, effectively blocking contact between the sodium ion transition metal oxide and the electrolyte, reducing side reactions between the electrolyte and the surface of the sodium ion transition metal oxide, reducing metal elution and oxygen deficiency, improving the structural stability of the positive electrode active material 1000 at high voltage, and thereby improving the cycle stability and energy density of the battery containing it at high voltage.

[0046] In some embodiments of this application, the alkaline sodium compound comprises at least one of sodium hydroxide and sodium carbonate. In some other embodiments of this application, the alkaline sodium compound comprises sodium carbonate. As a result, the coating layer 200 made of the alkaline sodium compound effectively blocks contact between the sodium ion transition metal oxide and the electrolyte, reduces side reactions between the electrolyte and the surface of the sodium ion transition metal oxide, reduces metal elution and oxygen deficiency, improves the structural stability of the positive electrode active material 1000 at high voltage, and thereby improves the cycle stability and energy density of the battery containing it at high voltage.

[0047] In some embodiments of this application, the mass percentage of sodium carbonate is 80% or more based on the total mass of the coating layer 200, for example, 80%-100%, 82%-98%, 85%-95%, 87%-92%, 90%-92%, etc. As a result, the coating layer 200 contains the above-mentioned amount of sodium carbonate, the sodium carbonate is distributed relatively uniformly on the surface of the core 100, and the resulting coating layer 200 is more uniform, effectively blocking contact between the sodium ion transition metal oxide and the electrolyte, reducing side reactions between the electrolyte and the surface of the sodium ion transition metal oxide, reducing metal elution and oxygen deficiency, improving the structural stability of the positive electrode active material 1000 at high voltage, and thereby improving the high-voltage cycle stability and energy density of the battery containing it.

[0048] In some embodiments of the present application, based on the total mass of the coating layer 200, the mass ratio of sodium hydroxide is 10% or less, for example, 9% - 10%, 8% - 8.5%, 7% - 7.8%, 6% - 6.8%, 5% - 5.8%, 4% - 4.8%, 3% - 3.8%, 2% - 2.8%, 1% - 1.8%, 0% - 1%, etc. Specifically, sodium hydroxide in the coating layer 200 is likely to undergo a side reaction with the adhesive in the positive electrode slurry, severely gelling the slurry. Moreover, sodium hydroxide is likely to simultaneously generate water molecules during the process of conversion to form the coating layer 200, and the water molecules are likely to react with sodium hexafluorophosphate, which is the lithium salt of the battery electrolyte, to be converted into HF, thereby reducing the cycle stability of the battery. Thus, the mass ratio of sodium hydroxide in the coating layer 200 of the present application is within the above range, which can reduce the gelling of the positive electrode slurry and simultaneously improve the cycle stability of the battery containing it at high voltages.

[0049] In some embodiments of the present application, the sodium ion transition metal oxide in the core 100 is Na x Mn a Fe b Ni c Q d O 2-e+δ F e and includes 0.5 ≦ x ≦ 1.2, 0 < a, 0 ≦ b ≦ 0.4, 0 ≦ c ≦ 0.4, 0 ≦ d, a + b + c + d = 1, 0 ≦ e ≦ 0.2, -0.1 ≦ δ ≦ 0.1, and Q includes at least one of Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi.

[0050] In some specific embodiments of the present application, the sodium ion transition metal oxide in the core 100 is Na x Mn a Fe b Ni c Q<{ d O 2-e+δ F e and includes 0.7 ≤ x ≤ 1.2, 0 < a, 0.1 ≤ b ≤ 0.4, 0.1 ≤ c ≤ 0.4, 0 ≤ d ≤ 0.3, a + b + c + d = 1, 0 ≤ e ≤ 0.2, -0.1 ≤ δ ≤ 0.1, where Q contains at least one of Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi, and is selectively at least one of B, Mg, Al, Si, Ca, Ti, Co, Cu, Zn, Zr, Nb, Mo, La, and Bi. Based on the total amount of the positive electrode active material 1000, the mass ratio of the alkaline sodium compound is 1 wt% - 2 wt%, such as 1.2 wt% - 2 wt%, 1.5 wt% - 2 wt%, 1.8 wt% - 2 wt%, etc. Thereby, the mass ratio of the alkaline sodium compound in the coating layer 200 on the surface of the sodium ion transition metal oxide core 100 of the present application satisfies the above range, effectively blocking the contact between the sodium ion transition metal oxide and the electrolyte, reducing the side reaction between the electrolyte and the surface of the sodium ion transition metal oxide, reducing metal elution and oxygen deficiency, improving the structural stability of the positive electrode active material 1000 at high voltage, and thereby improving the cycle stability and energy density of the battery containing it at high voltage.

[0051] In some embodiments of the present application, in the above sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e x may take 0.7 ≤ x ≤ 1.2, for example, 0.7 ≤ x ≤ 1.1, 0.8 ≤ x ≤ 1, 0.85 ≤ x ≤ 1, 0.88 ≤ x ≤ 1, 0.9 ≤ x ≤ 1, 0.95 ≤ x ≤ 1, 0.98 ≤ x ≤ 1, etc. Thereby, this sodium ion transition metal oxide contains sodium element with this content, giving the battery a relatively high capacity.

[0052] It should be explained that in positive electrodes, batteries, or power-consuming devices, batteries consume sodium ions through processes such as chemical formation and cycling, resulting in situations where the measured sodium element content x in the sodium ion transition metal oxide is less than 1. At the same time, if sodium replenishment is used in both the positive and negative electrodes, after processes such as chemical formation and cycling, the measured sodium element content x in the sodium ion transition metal oxide will be greater than 1.

[0053] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e In this case, a may take the value a>0, for example, 0.001≦a<1, 0.005≦a≦0.9, 0.1≦a≦0.8, 0.2≦a≦0.7, 0.3≦a≦0.6, 0.4≦a≦0.5, etc. This allows the sodium ion transition metal oxide to contain this amount of manganese, effectively improving the structural stability of the sodium ion transition metal oxide and improving the cycle stability of the battery containing it. In some other embodiments of this application, the sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e In this case, a may take the range 0.3 ≤ a ≤ 0.6.

[0054] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F eIn this case, b may take a value of 0.1 ≦ b ≦ 0.4, for example, 0.1 ≦ b ≦ 0.35, 0.15 ≦ b ≦ 0.3, 0.2 ≦ b ≦ 0.25, 0.22 ≦ b ≦ 0.25, etc. Thereby, this sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e contains Fe at this content, which can not only reduce the high active oxygen content in the sodium ion transition metal oxide, but also improve the specific capacity of the positive electrode active material 1000. In some other embodiments of the present application, in the above sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e b may take a value of 0.15 ≦ b ≦ 0.35. <00千0588> In some embodiments of the present application, in the above sodium ion transition metal oxide Na x Mn a Fe b Ni<000千091>Q d O 2-e+δ F e c takes a value of 0.1 ≦ c ≦ 0.40, for example, 0.1 ≦ c ≦ 0.35, 0.15 ≦ c ≦ 0.3, 0.2 ≦ c ≦ 0.25, 0.22 ≦ c ≦ 0.25, etc. Thereby, this sodium ion transition metal oxide Na<0千00095>Mn a Fe b Ni c Q d O 2-e+δ F e contains Ni at this content, which can not only reduce the high active oxygen content in the sodium ion transition metal oxide, but also improve the specific capacity of the positive electrode active material 1000. In some other embodiments of the present application, in the above sodium ion transition metal oxide Na x [[ID=6​​​​c Q d O 2-e+δ F e In this case, c takes the value 0.15 ≤ c ≤ 0.35.

[0056] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e In this application, Q includes at least one of Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi. In some other embodiments of this application, the sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e In this equation, Q includes at least one of B, Mg, Al, Si, Ca, Ti, Co, Cu, Zn, Zr, Nb, Mo, La, and Bi.

[0057] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e In this case, d takes the range 0≦d≦0.3, for example, 0.001≦d≦0.3, 0.005≦d≦0.3, 0.01≦d≦0.3, 0.05≦d≦0.3, 0.1≦d≦0.3, 0.15≦d≦0.3, 0.17≦d≦0.27, 0.2≦d≦0.25, 0.2≦d≦0.22, etc. Thus, this sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F eThis contains the element Q in this amount, which can improve the structural stability of the positive electrode active material 1000. In some other embodiments of this application, the sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e In this case, d takes the range 0.1 ≤ d ≤ 0.2.

[0058] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e In this case, the value of δ is -0.1≦δ≦0.1, and the value of e is 0≦e≦0.2, 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≦0.2, 0.02≦e≦0.18, 0.05≦e≦0.15, 0.08≦e≦0.12, 0.1≦e≦0.12, etc.

[0059] Specifically, the sodium ion transition metal oxide Na of this application x Mn a Fe b Ni c Q d O 2-e+δ F e Doping the oxygen sites in this mixture with F effectively stabilizes the oxygen in the sodium ion transition metal oxide, thereby reducing structural breakdown due to lattice oxygen release in the sodium ion transition metal oxide, improving the stability of the positive electrode active material 1000, and further improving the battery's cycle stability.

[0060] It should be explained that in positive electrode plates, batteries, or power-consuming devices, as batteries undergo processes such as cycles, oxygen elements are lost from the sodium ion transition metal oxide, resulting in a situation where the measured oxygen element content 2+δ-e in the sodium ion transition metal oxide is less than 2.

[0061] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e In this case, 0.5 ≤ (b+c) / a ≤ 2, for example, 0.8 ≤ (b+c) / a ≤ 2, 1 ≤ (b+c) / a ≤ 1.8, 1.2 ≤ (b+c) / a ≤ 1.6, 1.5 ≤ (b+c) / a ≤ 1.6, etc. In some other embodiments of this application, the above sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e In this case, 0.5 ≤ (b+c) / a ≤ 1.5. Specifically, Ni can contribute to capacity, but tends to cause structural instability when Fe and Ni undergo valence changes. Mn, on the other hand, can stabilize the structure of the sodium ion transition metal oxide. As a result, the molar amounts a of Mn, b of Fe, and c of Ni in the sodium ion transition metal oxide of this application satisfy the above relationship, improving the specific capacity of the sodium ion transition metal oxide while simultaneously improving its structural stability at high voltages. This improves the cycle stability and energy density of batteries containing it at high voltages.

[0062] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e The phase state includes the O3 phase, and the space group is,

number

[0063] One thing to explain is the sodium ion transition metal oxide Na in this application. x Mn a Fe b Ni c Q d O 2-e+δ F e The phase states, space groups, and interlayer spacing can be characterized using X-ray diffraction.

[0064] Specifically, sodium ion transition metal oxide Na x Mn a Fe b Ni c Q d O 2-e+δ F e The interlayer spacing d of the 003 crystal plane 003The test method for the space group includes the following: After finely grinding the sample to be measured in an agate mortar in a drying room or glove box, it is sieved through a 350-mesh sieve. An appropriate amount of the sieved sample is taken and placed in the middle of the groove of the sample holder. The loosened sample powder is raised slightly above the plane of the sample holder. The slide glass is taken and the sample surface is gently pressed to flatten the sample surface, then it is aligned with the plane of the frame, and any excess powder is scraped off. After the sample preparation is complete, the test is performed using a Brucker D8A_A25 X-ray powder diffractometer from Brucker AxS GmbH in Germany, with CuKα radiation as the radiation source, radiation wavelength λ = 1.5406 Å, scanning angle 2θ range of 5°-60°, and scanning speed of 4° / min. After the test is complete, the Bragg equation 2d·sinθ=λ and the fact that each unit cell of the 003 crystal plane contains three transition metal layers are used to determine the interlayer spacing d of the 003 crystal plane based on the angle corresponding to the 003 crystal plane. 003 This allows us to obtain the XRD diffraction peaks of the sample and, by comparing them with the standard card of the XRD analysis software, confirm the space group and crystalline phase of the sample.

[0065] In some further specific embodiments of this application, the sodium ion transition metal oxide in the core 100 is Na x Mn a Ni c Q d O 2-e+δ F e Includes, 0.5 ≤ x ≤ 1.2, 0 < a, 0.1 ≤ c ≤ 0.3, 0 ≤ d ≤ 0.3, a + c + d = 1, 0 ≤ e ≤ 0.2, -0.1 ≤ δ ≤ 0.1, and Q contains at least one of Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi, and is selectively at least one of B, Mg, Al, Si, Ca, Ti, Co, Cu, Zn, Zr, Nb, Mo, La, and Bi. Based on the total amount of the positive electrode active material 1000, the mass ratio of the alkaline sodium compound is 0.5 wt% - 1.5 wt%, for example, 0.5 wt% - 1.3 wt%, 0.7 wt% - 1 wt%, 0.9 wt% - 1 wt%, etc. Thereby, the mass ratio of the alkaline sodium compound in the coating layer 200 on the surface of the sodium ion transition metal oxide core 100 according to the present application satisfies the above range, effectively blocks the contact between the sodium ion transition metal oxide and the electrolyte, reduces the side reaction between the electrolyte and the surface of the sodium ion transition metal oxide, reduces metal elution and oxygen deficiency, improves the structural stability of the positive electrode active material 1000, and thereby can improve the cycle stability and energy density at high voltage of the battery containing it.

[0066] In some embodiments of the present application, the above sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e where x may take 0.5 ≤ x ≤ 1.2, for example, 0.5 ≤ x ≤ 1.1, 0.6 ≤ x ≤ 1.1, 0.8 ≤ x ≤ 1, 0.85 ≤ x ≤ 1, 0.88 ≤ x ≤ 1, 0.9 ≤ x ≤ 1, 0.95 ≤ x ≤ 1, 0.98 ≤ x ≤ 1, etc. Thereby, this sodium ion transition metal oxide contains sodium element with this content, giving the battery a relatively high capacity.

[0067] It should be explained that in positive electrodes, batteries, or power-consuming devices, batteries consume sodium ions through processes such as chemical formation and cycling, resulting in situations where the measured sodium element content x in the sodium ion transition metal oxide is less than 1. At the same time, if sodium replenishment is used in both the positive and negative electrodes, after processes such as chemical formation and cycling, the measured sodium element content x in the sodium ion transition metal oxide will be greater than 1.

[0068] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e In this case, a may take the value a>0, for example, 0.001≦a<1, 0.005≦a≦0.9, 0.1≦a≦0.8, 0.2≦a≦0.7, 0.3≦a≦0.6, 0.4≦a≦0.5, etc. This allows the sodium ion transition metal oxide to contain this amount of manganese, effectively improving the structural stability of the sodium ion transition metal oxide and improving the cycle stability of the battery containing it. In some other embodiments of this application, the sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e In this case, a may take the range 0.5 ≤ a ≤ 0.8.

[0069] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e In this case, c takes the range 0.1 ≤ c ≤ 0.3, for example, 0.15 ≤ c ≤ 0.3, 0.2 ≤ c ≤ 0.25, 0.22 ≤ c ≤ 0.25, etc. Thus, this sodium ion transition metal oxide Na x Mn a Feb Ni c Q d O 2-e+δ F e This contains Ni in this amount, which can not only reduce the high reactive oxygen species content in sodium ion transition metal oxides but also improve the specific capacity of the positive electrode active material 1000. In some other embodiments of this application, the sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e In this case, c takes the value 0.15 ≤ c ≤ 0.25.

[0070] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e In this application, Q includes at least one of Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi. In some other embodiments of this application, the sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e In this equation, Q includes at least one of B, Mg, Al, Si, Ca, Ti, Co, Cu, Zn, Zr, Nb, Mo, La, and Bi.

[0071] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F eIn this case, d takes the range 0≦d≦0.3, for example, 0.001≦d≦0.3, 0.005≦d≦0.3, 0.01≦d≦0.3, 0.05≦d≦0.3, 0.1≦d≦0.3, 0.15≦d≦0.3, 0.17≦d≦0.27, 0.2≦d≦0.25, 0.2≦d≦0.22, etc. Thus, this sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e This contains the element Q in this amount, which can improve the structural stability of the positive electrode active material 1000. In some other embodiments of this application, the sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e In this case, d takes the value 0.05 ≤ d ≤ 0.15.

[0072] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e In this case, the value of δ is -0.1≦δ≦0.1, and the value of e is 0≦e≦0.2, 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≦0.2, 0.02≦e≦0.18, 0.05≦e≦0.15, 0.08≦e≦0.12, 0.1≦e≦0.12, etc.

[0073] Specifically, the sodium ion transition metal oxide Na of this application x Mn a Ni c Q d O 2-e+δ F eDoping the oxygen sites in this mixture with F effectively stabilizes the oxygen in the sodium ion transition metal oxide, thereby reducing structural breakdown due to lattice oxygen release in the sodium ion transition metal oxide, improving the stability of the positive electrode active material 1000, and further improving the battery's cycle stability.

[0074] It should be explained that in positive electrode plates, batteries, or power-consuming devices, as batteries undergo processes such as cycles, oxygen elements are lost from the sodium ion transition metal oxide, resulting in a situation where the measured oxygen element content 2+δ-e in the sodium ion transition metal oxide is less than 2.

[0075] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e In this case, 0.125 ≤ c / a ≤ 0.45, for example, 0.15 ≤ c / a ≤ 0.45, 0.175 ≤ c / a ≤ 0.425, 0.2 ≤ c / a ≤ 0.4, 0.225 ≤ c / a ≤ 0.375, 0.25 ≤ c / a ≤ 0.35, 0.275 ≤ c / a ≤ 0.325, 0.3 ≤ c / a ≤ 0.325, etc. In some other embodiments of this application, the above sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e In this case, 0.2 ≤ c / a ≤ 0.3. Specifically, Ni can contribute to capacity, but it tends to cause structural instability when its valence changes, while Mn can stabilize the structure of the sodium ion transition metal oxide. As a result, the molar amounts a of Mn and c of Ni in the sodium ion transition metal oxide of this application satisfy the above relationship, improving the specific capacity of the sodium ion transition metal oxide while simultaneously improving its structural stability at high voltage, thereby improving the cycle stability and energy density of the battery containing it at high voltage.

[0076] In some embodiments of this application, the sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e The phase state includes a P2 phase, the space group includes P63 / mmc, and the interlayer spacing is 0.55nm-0.57nm. For example, the interlayer spacing may be 0.552nm-0.57nm, 0.555nm-0.568nm, 0.557nm-0.565nm, 0.56nm-0.562nm, etc. Specifically, the large interlayer spacing of the sodium ion transition metal oxide in the formed P2 phase improves the transport rate of Na ions, maintains the integrity of the layered structure, and gives the battery excellent rate performance and cycle performance.

[0077] One thing to explain is the sodium ion transition metal oxide Na in this application. x Mn a Ni c Q d O 2-e+δ F e The phase states, space groups, and interlayer spacing can be characterized using X-ray diffraction.

[0078] Specifically, sodium ion transition metal oxide Na x Mn a Ni c Q d O 2-e+δ F e The interlayer spacing d of the 003 crystal plane 003The method for testing the space group includes the following: After finely grinding the sample to be measured in an agate mortar in a drying room or glove box, it is sieved through a 350-mesh sieve. An appropriate amount of the sieved sample is taken and placed in the middle of the groove of the sample holder. The loosened sample powder is raised slightly above the plane of the sample holder. The slide glass is taken and the sample surface is gently pressed to flatten the sample surface, then it is aligned with the plane of the frame, and any excess powder is scraped off. After the sample preparation is complete, the test is performed using a Brucker D8A_A25 X-ray powder diffractometer from Brucker AxS GmbH in Germany, with CuKα radiation as the radiation source, radiation wavelength λ = 1.5406 Å, scanning angle 2θ range of 5°-60°, and scanning speed of 4° / min. After the test is complete, the Bragg equation 2d·sinθ=λ and the fact that each unit cell of the 003 crystal plane contains three transition metal layers are used to determine the interlayer spacing d of the 003 crystal plane based on the angle corresponding to the 003 crystal plane. 003 This allows us to obtain the XRD diffraction peaks of the sample and, by comparing them with the standard card of the XRD analysis software, confirm the space group and crystalline phase of the sample.

[0079] In some embodiments of this application, the BET specific surface area of ​​the positive electrode active material 1000 is Sm 2 The ratio of w to w is / g, and S and w satisfy the following relationships: 0.3 ≤ w / S ≤ 3, for example, 0.5 ≤ w / S ≤ 2.8, 0.7 ≤ w / S ≤ 2.5, 1 ≤ w / S ≤ 2.2, 1.3 ≤ w / S ≤ 2, 1.5 ≤ w / S ≤ 1.8. In some other embodiments of this application, S and w in the positive electrode active material 1000 satisfy the relationship 0.5 ≤ w / S ≤ 2. Thus, S and W in the positive electrode active material 1000 described in this application satisfy the above relationship, improving the activity ratio capacity of the positive electrode, while effectively blocking contact between the sodium ion transition metal oxide and the electrolyte, reducing side reactions between the electrolyte and the transition metal oxide surface, reducing metal elution and oxygen deficiency, improving the structural stability of the positive electrode active material 1000, and thereby improving the high-voltage cycle stability and energy density of the battery containing it.

[0080] In some embodiments of this application, the D of the positive electrode active material 1000v 50 is 2μm-20μm, for example, the D of the positive electrode active material. v 50 may be 2μm-19μm, 4μm-18μm, 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 1000 v 50 corresponds to a range of 4 μm to 15 μm.

[0081] In this application, D v 50 refers to the particle size corresponding to the point when the cumulative volume distribution percentage reaches 50%, and is measured using a laser particle size analyzer (e.g., Malvern Master Size 3000), referring to, for example, the standard GB / T 19077-2016.

[0082] In some embodiments of this application, the BET specific surface area of ​​the positive electrode active material 1000 is 0.2 m². 2 / g-2m 2 The value is / g, and for example, the specific surface area of ​​the positive electrode active material is 0.2m². 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 It may also be / g, etc. In some other embodiments of this application, the specific surface area of ​​the positive electrode active material 1000 is 0.3m². 2 / g-2m 2 It is / g.

[0083] In this application, the BET specific surface area of ​​the positive electrode active material 1000 has a meaning known in the art and can be measured using instruments and methods known in the art. For example, it can be obtained by testing with reference to the following method: Using a Micromeritics Gemini VII 2390 multi-station fully automatic specific surface area and pore size analyzer, approximately 7 g of sample is taken and placed in a 9 cc long tube with bubbles, degassed at 200°C for 2 hours, and then tested by placing it in the main unit to obtain the BET specific surface area data of the positive electrode active material 1000.

[0084] In some embodiments of this application, the compaction density of the positive electrode active material 1000 at a pressure of 300 MPa is 3.1 g / cm³. 3 -3.8g / cm 3 For example, the compaction density of positive electrode active material 1000 at a pressure of 300 MPa is 3.0 g / cm³. 3 -3.8g / cm 3 3.2 g / cm³ 3 -3.5g / cm 3 3.2 g / cm³ 3 -3.4 g / cm³ 3 The following may also be the case. In some embodiments of this application, the compaction density of the positive electrode active material 1000 at a pressure of 300 MPa is 3.2 g / cm³. 3 -3.6 g / cm³ 3 That is the case.

[0085] In this application, "consolidation density" has the meaning known in the art and can be measured using instruments and methods known in the art. For example, the following test method can be used: A fixed amount m of powder is placed in a mold specifically for consolidation, the mold is placed in a consolidation density instrument, a pressure of 300 MPa is set, the instrument measures the thickness volume v of the powder under a pressure of 300 MPa, and the consolidation density is calculated using the formula density = mass m / volume v (see GB / T24533-2009 for specifics).

[0086] Specifically, the D of the positive electrode active material 1000 of this application v 50. When at least one of the specific surface area and the compaction density at a pressure of 300 MPa is within the above range, the conduction distance within the positive electrode active material 1000 is small, surface side reactions are few, promoting the positive electrode active material to exert its gram capacity and improving the capacity retention rate of the battery containing it.

[0087] In this application, the elemental composition of the positive electrode active material 1000 can be measured using instruments and methods known in the art, for example, by testing using inductively coupled plasma atomic emission spectroscopy, with the instrument standard referring to EPA6010D-2014 "Inductively Coupled Plasma Atomic Emission Spectroscopy". The sample was treated by a chemical method to decompose into a solution, atomized and entered into a plasma to excite characteristic spectral lines of the elements, and the elemental content was qualitatively and quantitatively analyzed based on the wavelength and intensity (proportional to concentration) of the spectral lines.

[0088] The content of the alkaline sodium compound Na2CO3 in the coating layer 200 of the positive electrode active material 1000 can be measured using instruments and methods known in the art, for example, by referring to the GB / T 9736-2008 standard. Under a carbon dioxide-free atmosphere, 30 g of the obtained positive electrode active material powder was weighed, 100 ml of pure water was added and stirred for 30 min, allowed to stand for 10 min, and then filtered by suction. A certain amount of filtrate was transferred, and a 0.05 mol / L hydrochloric acid standard solution was selected and titrated using a Mettler T5 titrator.

[0089] The content of the alkaline sodium compound NaOH in the coating layer 200 of the positive electrode active material 1000 can be measured using instruments and methods known in the art, for example, by referring to the GB / T 9736-2008 standard. Under a dehumidified atmosphere with carbon dioxide removed, 30 g of the obtained layered oxide powder was weighed, 100 ml of anhydrous ethanol was added and stirred for 30 min, then allowed to stand for 10 min and filtered by suction. 10 ml of the filtrate was then transferred, diluted with 50 ml of ultrapure water, and subsequently titrated with a 0.05 mol / L hydrochloric acid standard solution. The instrument used was a Mettler T5 titrator.

[0090] In this application, the sodium content in the composition of the sodium ion transition metal oxide in core 100 can be calculated by subtracting the total amount of alkaline sodium compounds NaOH and Na2CO3 in the coating layer obtained by the above test method from the total amount of sodium elements obtained by the above inductively coupled plasma atomic emission spectroscopy, and the content of other elements in the composition of the sodium ion transition metal oxide can be obtained by the above inductively coupled plasma atomic emission spectroscopy, thereby obtaining the composition of the sodium ion transition metal oxide. The mass percentage w% of alkaline sodium compounds in the above positive electrode active material 1000 can be obtained by adding the content of alkaline sodium compounds NaOH and Na2CO3 in the above coating layer.

[0091] A second aspect of this application provides a method for producing the positive electrode active material described in the first aspect, and includes: S100: Provides sodium ion transition metal oxides containing iron and / or nickel. In some embodiments of this application, in the sodium ion transition metal oxide, the molar amount of iron is denoted as b, the molar amount of nickel is denoted as c, and 0 ≤ b ≤ 0.4 and 0 ≤ c ≤ 0.4.

[0092] In this application, the sodium ion transition metal oxide is Na x Mn a Fe b Ni c Q d O 2-e+δ F e It may also contain, for example, the sodium ion transition metal oxide is the above Na x Mn a Fe b Ni c Q d O 2-e+δ F ecomprising, 0.7 ≤ x ≤ 1.2, 0 < a, 0.1 ≤ b ≤ 0.4, 0.1 ≤ c ≤ 0.4, 0 ≤ d ≤ 0.3, a + b + c + d = 1, 0 ≤ e ≤ 0.2, -0.1 ≤ δ ≤ 0.1, where Q comprises at least one of Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi, and for example, the sodium ion transition metal oxide is the above-mentioned Na x Mn a Ni c Q d O 2-e+δ F e comprising, 0.5 ≤ x ≤ 1.2, 0 < a, 0.1 ≤ c ≤ 0.3, 0 ≤ d ≤ 0.3, a + c + d = 1, 0 ≤ e ≤ 0.2, -0.1 ≤ δ ≤ 0.1, where Q comprises at least one of Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi.

[0093] In some embodiments of the present application, the method for manufacturing the sodium ion transition metal oxide may include the following: Mix a Na source, an Fe source, a Mn source, a Ni source, and a Q source according to the composition of the sodium ion transition metal oxide, then pre-grind in an agate mortar, and then add to a planetary ball mill for ball milling for 1 h - 8 h, such as 2 h - 7 h, 3 h - 6 h, 4 h - 5 h, etc., to obtain a precursor mixture I. Next, uniformly place the obtained precursor mixture I in an open crucible, and then heat in a muffler furnace at a heating rate of 2 °C / min - 5 °C / min (such as 2 °C / min - 3 °C / min, 2 °C / min - 3 °C / min, etc.) from room temperature to 900 °C - 1000 °C, for example, seal at 910 °C - 990 °C, 920 °C - 980 °C, 930 °C - 970 °C, 940 °C - 960 °C, 940 °C - 950 °C, and hold at a constant temperature for 10 h - 20 h, such as 11 h - 19 h, 12 h - 18 h, 13 h - 17 h, 14 h - 16 h, 14 h - 15 h, etc. The atmosphere used is air with moisture removed and carbon dioxide removed, and after natural cooling, a sodium ion transition metal oxide is obtained.

[0094] It should be explained that, due to the loss of the Na source during the subsequent calcination process, the amount of Na added is slightly higher than the required amount of Na in the composition of the sodium ion transition metal oxide described above.

[0095] The Na source, Fe source, Mn source, Ni source and Q source in this application are common materials in the art and can be selected by those skilled in the art as appropriate. 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 Ni source may include NiO; and the Q source may include at least one of Q oxides, Q-containing salts, and other compounds.

[0096] It should be explained that when it is necessary to dope the positive electrode active material with element F, at least one of the Na source, Fe source, Mn source, Ni source, and Q source is adopted as its corresponding fluorine-containing salt and at least one of the other components, such as sodium fluoride, iron fluoride, manganese fluoride, nickel fluoride, and Q fluoride (fluoride salt of Q).

[0097] S200: The sodium ion transition metal oxide and the alkaline sodium compound are mixed and sintered. In some embodiments of this application, the above-mentioned sodium ion transition metal oxide and alkaline sodium compound are mixed in a ratio of 0.1 ≤ (b + c) / w ≤ 0.5 (where b is the molar amount of iron in the sodium ion transition metal oxide, c is the molar amount of nickel, and w is the mass percentage of the alkaline sodium compound relative to the total amount of the positive electrode active material), then pre-polished in an agate mortar, and then added to a planetary ball mill and ball-milled for 1h-8h, for example, 2h-7h, 3h-6h, 4h-5h, etc., to obtain Precursor Mixture II Next, the obtained precursor mixture II was uniformly placed in an open crucible and subsequently heated in a muffle furnace at a heating rate of 2°C / min-5°C / min (e.g., 2°C / min-3°C / min, 2°C / min-3°C / min, etc.) from room temperature to 300°C-600°C, then further heated to, for example, 350°C-550°C, 400°C-500°C, 450°C-500°C, etc., and then held at a constant temperature for 1h-3h, for example, 1h-2h, 2h-3h, 1h-1.5h, etc., using dehumidified air from which carbon dioxide has been removed. After natural cooling, the positive electrode active material was obtained. This sintering process allows for more uniform distribution of alkaline sodium compounds on the surface of sodium ion transition metal oxides and better bonding between them, thereby forming a stable coating layer on the surface of sodium ion transition metal oxides, improving the structural stability of the positive electrode active material at high voltages, and thereby improving the cycle stability and energy density of batteries containing it at high voltages.

[0098] This makes it possible to obtain a positive electrode active material with a stable structure at high voltage by manufacturing it using the method of this application, thereby improving the cycle stability and energy density of batteries containing it at high voltage.

[0099] A third aspect of this application provides a positive electrode plate comprising a positive electrode active material described in the first aspect of this application or a positive electrode active material manufactured by the method described in the second aspect.

[0100] The positive electrode plate generally includes a positive electrode current collector and a positive electrode active material layer installed on the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.

[0101] The positive electrode current collector may be a conventional metal foil sheet or a composite current collector (a composite current collector may be formed by placing a metal material on a polymer substrate). For 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.

[0102] The positive electrode active material layer further selectively comprises a conductive agent and an adhesive, the conductive agent being used to improve the conductivity of the positive electrode active material layer, and the adhesive being used to firmly bond the positive electrode active material and the adhesive to the positive electrode current collector. This application does not specifically limit the types of conductive agent and adhesive, and they can be selected according to actual needs.

[0103] For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjenblack, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, and the adhesive may include at least one of styrene-butadiene rubber (SBR), water-based acrylic resin, carboxymethylcellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), and polyvinyl alcohol (PVA).

[0104] All of these materials can be obtained through commercial means.

[0105] A fourth aspect of this application provides a battery comprising a positive electrode plate as described in the third aspect of this application, thereby providing a battery with excellent cycle stability and energy density at high voltage.

[0106] A battery is a device that can be continuously used by activating its active material through a charging process after discharge.

[0107] To make it clear, the battery described in this application is a sodium-ion battery.

[0108] Generally, a battery consists of a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. During charging and discharging of the battery, active ions intermittently

[0109] [Negative electrode plate] In a battery, the negative electrode plate generally includes a negative electrode current collector and a negative electrode active material layer placed on the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0110] The negative electrode current collector may be a conventional metal foil sheet or a composite current collector (for example, a composite current collector may be formed by placing a metal material on a polymer substrate). For example, the negative electrode current collector may be made of copper foil.

[0111] The specific type of negative electrode active material is not limited, and any active material known in the art that can be used in sodium-ion battery negative electrodes may be used, and those skilled in the art can select according to their actual needs. For example, the negative electrode active material may include, but is not limited to, at least one of sodium metal, carbon material, alloy material, transition metal oxide and / or sulfide, phosphorus-based material, or titanate material. Specifically, the carbon material may include at least one of hard carbon, soft carbon, amorphous carbon, or nanostructured carbon material, the alloy material may include an alloy material formed from at least one of Si, Ge, Sn, Pb, or Sb, and the general formula for the transition metal oxide and sulfide is M x N y Here, M includes at least one of Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V, N includes O or S, the phosphorus-based material may include at least one of red phosphorus, white phosphorus, and black phosphorus, and the titanate material may be Na2Ti3O7, Na2Ti6O 13 Na4Ti5O12 Li4Ti5O 12 It may also contain at least one of NaTi2(PO4)3. All of these materials can be obtained by commercial means.

[0112] The negative electrode active material layer generally further selectively comprises an adhesive and a conductive agent, the conductive agent being used to improve the conductivity of the negative electrode active material layer, and the adhesive being used to firmly bond the negative electrode active material and the adhesive to the negative electrode current collector. This application does not specifically limit the types of conductive agent and adhesive, and they can be selected according to actual needs.

[0113] For example, the conductive agent may include at least one of the following: superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0114] For example, the adhesive may contain at least one of styrene-butadiene rubber (SBR), styrene-butadiene rubber (SBCs), water-based acrylic resin, and carboxymethylcellulose (CMC).

[0115] The negative electrode active material layer further selectively contains a thickening agent, such as carboxymethylcellulose (CMC). However, this application is not limited to this, and may further use other materials that can be used as thickening agents for the negative electrode plate of a sodium-ion battery.

[0116] [Electrolyte] The electrolyte may contain an electrolyte salt and a solvent.

[0117] For example, the electrolyte sodium salt may include at least one of the following: sodium hexafluorophosphate, sodium difluoro(oxalato)borate, sodium tetrafluoroborate, sodium bis(oxalato)borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate, and sodium di(trifluoromethylsulfonyl)imide.

[0118] For example, the solvent may include at least one of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0119] In some embodiments, the electrolyte further includes additives. For example, the additives may include negative electrode film forming additives, positive electrode film forming additives, and further additives that can improve some of the battery's performance characteristics, such as additives that improve the battery's overcharge performance, additives that improve the battery's high-temperature performance, and additives that improve the battery's low-temperature performance.

[0120] [Separator] As the separator described above, this application does not particularly limit it, and any known porous structure separator having electrochemical stability and mechanical stability can be selected and used according to actual needs, for example, it may include a single-layer or multi-layer film containing at least one of glass fibers, nonwoven fabrics, polyethylene, polypropylene, and polyvinylidene fluoride.

[0121] The embodiments of this application are not particularly limited to the shape of the battery, which may be cylindrical, rectangular, or any other shape. Figure 2 shows a rectangular secondary battery 1 as an example.

[0122] In some embodiments, the battery may include an casing used to package a positive electrode plate, a negative electrode plate, and an electrolyte.

[0123] In some embodiments, the exterior may include a case and a cover plate. Here, the case may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates enclosing and forming a housing cavity. The case has an opening that communicates with the housing cavity, and the cover plate can cover the opening so as to seal the housing cavity.

[0124] The positive electrode plate, negative electrode plate, and separator can be formed into an electrode assembly by a winding or lamination process. The electrode assembly is packaged in the housing cavity. The number of electrode assemblies included in the battery may be one or more and can be adjusted according to the requirements.

[0125] In some embodiments, the battery casing may include a rigid case, such as a rigid plastic case, an aluminum case, or a steel case.

[0126] The battery casing may include a pouch, such as a bag-shaped pouch. The material of the pouch may include at least one of the following plastics: polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0127] In some embodiments, the batteries can be assembled into a battery module, and the number of batteries included in the battery module may be multiple, with the specific number being adjustable depending on the application and capacity of the battery module.

[0128] Figure 3 shows an example of a battery module 2. Referring to Figure 3, multiple secondary batteries 1 may be installed in sequence along the longitudinal direction of the battery module 2. Of course, they may be arranged in any other manner. Furthermore, these multiple secondary batteries 1 may be fixed in place by fasteners.

[0129] The battery module 2 may further include a housing having a housing space, in which a plurality of secondary batteries 1 are housed. In some embodiments, the battery modules may further be assembled into a battery pack, the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0130] Figures 4 and 5 show an example of a battery pack 3. Referring to Figures 4 and 5, the battery pack 3 may include a battery box and a plurality of battery modules 2 installed in the battery box. The battery box includes an upper housing 4 and a lower housing 5, the upper housing 4 being lidable on the lower housing 5 and forming a sealed space for housing the battery modules 2. The plurality of battery modules 2 may be arranged in the battery box in any manner.

[0131] A fifth aspect of this application provides a power-consuming device including a battery as described in the fourth aspect. Specifically, the battery may serve as a power source for the power-consuming device or as an energy storage unit for the power-consuming device. The power-consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptop computers), 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.

[0132] Figure 6 shows an example of a power-consuming device. This power-consuming device includes pure electric vehicles, hybrid electric vehicles, or plug-in hybrid electric vehicles.

[0133] Other examples of power-consuming devices may include mobile phones, tablet computers, and laptop computers. These power-consuming devices generally require a thin design and may use batteries as their power source.

[0134] To clarify the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application, the embodiments are described in more detail below, linked to the drawings. Clearly, the embodiments described are only some, and not all, embodiments of this application. The following description of at least one exemplary embodiment is for illustrative purposes only and does not imply any limitation on this application or its applications. All other embodiments derived from the embodiments of this application without the creative effort of a person skilled in the art are all within the scope of protection of this application.

[0135] Example 1 Manufacturing of positive electrode active material A total of 30 g of Na2CO3, Mn2O3, Fe2O3, and NiO were weighed in a molar ratio of Na:Mn:Fe:Ni of 1:0.4:0.3:0.3. The resulting sample was pre-polished in an agate mortar and then added to a planetary ball mill and ball-milled for 1 hour to obtain precursor mixture I. The obtained precursor mixture I was then uniformly placed in an open crucible and subsequently heated in a muffle furnace from room temperature to 950°C at a heating rate of 5°C / min, and maintained at 950°C for 15 hours. The atmosphere used was dehumidified air from which carbon dioxide had been removed. After natural cooling, the composition was Na 0.89 Mn 0.4 Fe 0.3 Ni 0.3 A sodium ion transition metal oxide, which is O2, was obtained. Next, the obtained sodium ion transition metal oxide and 0.5 g of Na2CO3 were pre-polished in an agate mortar and then added to a planetary ball mill and ball-milled for 1 hour to obtain precursor mixture II. Next, the obtained precursor mixture II was uniformly placed in an open crucible and subsequently heated in a muffle furnace from room temperature to 500°C at a heating rate of 5°C / min, and then maintained at a constant temperature of 500°C for 2 hours. The atmosphere used was dehumidified air from which carbon dioxide had been removed. After natural cooling, a positive electrode active material having a coating layer on its surface was obtained.

[0136] Manufacturing of positive electrode plates The above-mentioned positive electrode active material, conductive agent carbon black (Super P), and adhesive polyvinylidene fluoride (PVDF) were thoroughly stirred and mixed in solvent NMP (N-methylpyrrolidone) in a mass ratio of 80:15:5 to form a uniform positive electrode slurry. The positive electrode slurry was uniformly applied to the upper and lower surfaces of the aluminum foil of the positive electrode current collector, dried, and cold-pressed, and then punched out into a wafer with a diameter of 14 mm to obtain a positive electrode plate.

[0137] Manufacturing of negative electrode plates The negative electrode plate uses a metallic sodium sheet.

[0138] Manufacturing of electrolyte Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in equal volumes to obtain an organic solvent, and then NaClO4 was dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0139] Separator A porous polyethylene membrane was used as the separator.

[0140] Manufacturing of button-type batteries The positive electrode plate, separator, and negative electrode plate were stacked in order, with the separator positioned between the positive and negative electrode plates to provide isolation. The manufactured electrolyte was then added to obtain a button-type battery.

[0141] The button-type batteries containing the positive electrode active material of Examples 2-30 are the same as those of Example 1, except that the parameters in the process of manufacturing the positive electrode active material are different (see Table 1-6), and element Q is added as an oxide of Q, and the F source is added in the form of a sodium source NaF.

[0142] The button-type battery containing the positive electrode active material of Comparative Example 1 is the same as that of Example 1, except that the process for manufacturing the positive electrode active material is different.

[0143] The process for producing the positive electrode active material of Comparative Example 1 involves weighing a total of 30 g of a sample containing Na2CO3, Mn2O3, Fe2O3, and NiO in a molar ratio of Na:Mn:Fe:Ni of 1:0.4:0.3:0.3, pre-polishing the obtained sample in an agate mortar, then adding it to a planetary ball mill and ball milling for 1 hour to obtain precursor mixture I, uniformly placing the obtained precursor mixture I into an open crucible, and subsequently heating it in a muffle furnace from room temperature to 950°C at a heating rate of 5°C / min, and maintaining a constant temperature of 950°C for 15 hours. The atmosphere used is dehumidified air from which carbon dioxide has been removed, and after natural cooling, the composition is Na 0.89 Mn 0.4 Fe 0.3 Ni 0.3 We obtained a positive electrode active material that is O2.

[0144] The button-type batteries containing the cathode active materials of Comparative Examples 2-3 and 6 are the same as Comparative Example 1 except that the parameters in the process of manufacturing the cathode active material are different (see Table 1-6), and the element Q is added as an oxide of Q, and the F source is added in the form of sodium source NaF.

[0145] The button-type batteries containing the cathode active materials of Comparative Examples 4-5 are the same as Example 1 except that the parameters in the process of manufacturing the cathode active material are different (see Table 1-6).

[0146] Considering that sodium element is lost during the sintering process, therefore, when it is desired to obtain a sodium ion transition metal oxide with the subscript x of Na element being 1, it is necessary to make the Na source 0.05 - 0.2 excessive in the mixing stage. For example, for NaMn 0.4 Fe 0.3 Ni 0.3 O2, when it is desired to obtain a sodium ion transition metal oxide, Na2CO3, Mn2O3, Fe2O3, and NiO are made in a molar ratio of Na:Mn:Fe:Ni of 1.05 - 1.2:0.4:0.3:0.3. At the same time, it should be noted that the alkaline sodium compounds in Examples 1-30 and Comparative Examples 4-5 all used sodium carbonate.

[0147] The compositions of the cathode active materials in the batteries of Examples 1-30 and Comparative Examples 1-6 of the present application are as shown in Table 1-6.

[0148]

Table 1

[0149]

Table 2

[0150]

Table 3

[0152] [Table 5]

[0153] [Table 6]

[0154] [Table 7]

[0155] The surface morphology, BET specific surface area, sodium ion transition metal oxide composition, phase state, space group and interlayer spacing, and proportion of alkaline sodium compounds of the positive electrode active materials in Examples 1-30 and Comparative Examples 1-6 were characterized, and the characterization results are shown in Table 1-6. Furthermore, the discharge ratio capacity in the first cycle and the cycle performance of the button-type battery obtained from the positive electrode active materials in Examples 1-30 and Comparative Examples 1-6 were characterized, and the characterization results are shown in Table 7.

[0156] Testing methods: (1) Characterization of the surface morphology of the positive electrode active material: The surface morphology of the positive electrode active material is characterized using a scanning electron microscope (SEM), for example, using a field emission scanning electron microscope (Zeiss Gemini360) in accordance with the JY / T010-1996 standard.

[0157] (2) Characterization of the BET specific surface area of ​​the positive electrode active material: Using a Micromeritics GeminiVII2390 multi-station fully automated specific surface area and pore size analyzer from the United States, approximately 7 g of sample was taken, placed in a 9 cc long tube with air bubbles, degassed at 200°C for 2 hours, and then tested in the analyzer to obtain BET specific surface area data for positive electrode active material 1000.

[0158] (3) Characterization of the composition of sodium ion transition metal oxides: The tests were performed using inductively coupled plasma atomic emission spectroscopy: the instrument standards were referred to EPA6010D-2014, "Inductively Coupled Plasma Atomic Emission Spectroscopy." The samples were treated by chemical methods to decompose into a solution, atomized, and entered into the plasma to excite characteristic spectral lines of the elements. The elemental content was then qualitatively and quantitatively analyzed based on the wavelength and intensity (proportional to concentration) of the spectral lines.

[0159] The content of the alkaline sodium compound Na2CO3 in the coating layer of the positive electrode active material can be measured using instruments and methods known in the art, for example, by referring to GB / T 9736-2008 standard. Under a carbon dioxide-free atmosphere, 30 g of the obtained positive electrode active material powder was weighed, 100 ml of pure water was added and stirred for 30 mins, allowed to stand for 10 mins, and then filtered by suction. A certain amount of filtrate was transferred, and a 0.05 mol / L hydrochloric acid standard solution was selected and titrated. The instrument used was a Mettler T5 titrator.

[0160] The content of the alkaline sodium compound NaOH in the coating layer of the positive electrode active material can be measured using instruments and methods known in the art, for example, by referring to GB / T 9736-2008 standard. Under a dehumidified atmosphere with carbon dioxide removed, 30 g of the obtained layered oxide powder was weighed, 100 ml of anhydrous ethanol was added and stirred for 30 min, then allowed to stand for 10 min and filtered by suction. 10 ml of the filtrate was then transferred, diluted with 50 ml of ultrapure water, and subsequently titrated with a 0.05 mol / L hydrochloric acid standard solution. The instrument used was a Mettler T5 titrator.

[0161] The sodium content in the composition of the sodium ion transition metal oxide can be calculated by subtracting the total amount of alkaline sodium compounds NaOH and Na2CO3 in the coating layer obtained by the above test method from the total amount of sodium obtained by the above inductively coupled plasma atomic emission spectroscopy. The content of other elements in the composition of the sodium ion transition metal oxide can be obtained by the above inductively coupled plasma atomic emission spectroscopy, thereby obtaining the composition of the sodium ion transition metal oxide.

[0162] (4) w% mass percentage test of alkaline sodium compounds in positive electrode active material: Obtained by adding the content of alkaline sodium compounds NaOH and Na2CO3 in the above coating layer.

[0163] (5) Phase state of sodium ion transition metal oxide, interlayer spacing d of the 003 crystal plane 003 and spatial group testing: After finely grinding the sample to be measured in an agate mortar in a drying room or glove box, it was sieved through a 350-mesh sieve. An appropriate amount of the sieved sample was taken and placed in the middle of the groove of the sample holder, so that the loosened sample powder was slightly higher than the plane of the sample holder. The slide glass was then removed and the sample surface was gently pressed to flatten the sample surface, then aligned with the plane of the frame, and any excess powder was scraped off. After the sample preparation was complete, CuK was measured using a Brucker D8A_A25 X-ray powder diffractometer from Brucker AxS GmbH, Germany. α The test was conducted using a radiation source with a radiation wavelength λ = 1.5406 Å, a scanning angle range of 2θ - 5° - 60°, and a scanning speed of 4° / min. After the test was completed, the Bragg equation 2d·sinθ = λ was used based on the angle corresponding to the 003 crystal plane, and based on the fact that each unit cell of the 003 crystal plane contains three transition metal layers, the interlayer spacing d of the 003 crystal plane was determined. 003 This allows us to obtain the XRD diffraction peaks of the sample and, by comparing them with the standard card of the XRD analysis software, confirm the space group and crystalline phase of the sample.

[0164] (6) Initial discharge specific capacity of the positive electrode active material and battery cycle performance test At 25 °C, the button-type battery was charged at a constant current of 10 mA / g to 4.2 V, and then discharged at a constant current of 10 mA / g to 1.5 V to obtain the initial discharge specific capacity C0 of the button-type battery. Subsequently, it was charged and discharged at a constant current of 10 mA / g for 50 cycles, and the discharge specific capacity C1 at the 50th cycle was obtained. The 50-cycle capacity retention rate of the battery = C1 / C0 × 100%.

[0165] Figure 7 is a surface morphology diagram of the positive electrode active material manufactured in Example 1, and Figure 8 is a surface morphology diagram of the positive electrode active material manufactured in Comparative Example 1. As can be seen from Figures 7-8, the surface of the positive electrode active material in Example 1 has a uniform coating layer, and the surface of the positive electrode active material in Comparative Example 1 is relatively clean and has no obviously continuously coated coating layer. Moreover, there is no obviously continuously coated coating layer on the surfaces of the positive electrode active materials in Comparative Examples 2-3 and 6. Figure 9 is a surface morphology diagram of the positive electrode active material decomposed after the button-type battery in Example 1 was cycled 50 times, and Figure 10 is a surface morphology diagram of the positive electrode active material decomposed after the button-type battery in Comparative Example 1 was cycled 50 times. As can be seen from Figures 9-10, the button-type battery in Example 1 still has a uniform coating layer on the surface of the positive electrode active material and no obvious cracks after 50 cycles, while the button-type battery in Comparative Example 1 has obvious cracks on the surface of the positive electrode active material after 50 cycles. This shows that the positive electrode active material in Example 1 has relatively high structural stability at high voltages compared to the positive electrode active material in Comparative Example 1, thereby indicating that the cycle performance and energy density of the battery in Example 1 can be improved.

[0166]

Table 8

[0167] Conclusion: As can be seen from the data in Table 1-6, sodium carbonate and sodium hydroxide were detected in the positive electrode active materials of Examples 1-31 and Comparative Examples 5-7. This sodium hydroxide may have been obtained by a water absorption reaction of sodium oxide on the surface of the positive electrode active material. Sodium carbonate and sodium hydroxide were also measured in the positive electrode active material of Comparative Example 1-4. This sodium carbonate may have originated from a sodium source in the mixing process, and the sodium hydroxide may similarly have been obtained by a water absorption reaction of sodium oxide on the surface of the positive electrode active material. As can be seen from the data in Table 7, Example 1-30 has a superior capacity retention rate at high voltage compared to the battery of Comparative Example 1-6, demonstrating that the positive electrode active material of this application can improve the cycle stability of the battery. At the same time, the initial discharge ratio capacity of the positive electrode active material of Example 1-30 of this application is 158 mAh / g or higher, demonstrating that the battery of this application has a superior energy density at high voltage. In summary, the positive electrode active material of this application can simultaneously improve the cycle stability and energy density of the battery at high voltage.

[0168] Finally, it should be noted that the above embodiments are merely for illustrative purposes and not limiting purposes. While the application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications can still be made to the embodiments described above, or equivalent substitutions can be made to some or all of the technical features thereof. Such modifications or substitutions should not cause the essence of the corresponding invention to deviate from the scope of the invention in each embodiment of this application, and should all be included within the scope of the claims and specification of this application. In particular, unless there is a structural conflict, the technical features referred to in each embodiment may be combined in any manner. This application is not limited to any specific embodiment disclosed in the specification, but includes all inventions that fall within the scope of the claims. [Explanation of Symbols]

[0169] 1000: Positive electrode active material 100: Cores 200: Covering layer 1: Secondary battery 2: Battery module 3: Battery pack 4: Upper cabinet 5: Lower cabinet

Claims

1. It is a positive electrode active material, A core comprising a sodium ion transition metal oxide containing iron and / or nickel, wherein the molar amount of iron in the sodium ion transition metal oxide is denoted as b, the molar amount of nickel is denoted as c, and the core has 0 ≤ b ≤ 0.4 and 0 ≤ c ≤ 0.

4. A positive electrode active material comprising a coating layer, the coating layer provided on at least a portion of the surface of the core, the coating layer containing an alkaline sodium compound, the mass ratio of the alkaline sodium compound being w% with respect to the total amount of the positive electrode active material, and the coating layer satisfying 0.1 ≤ (b + c) / w ≤ 0.

5.

2. The positive electrode active material according to claim 1, wherein 0.2 ≤ (b + c) / w ≤ 0.

4.

3. The positive electrode active material according to claim 1 or 2, wherein the mass percentage w% of the alkaline sodium compound is 0.3 wt% to 5 wt%, and selectively 0.5 wt% to 2 wt%.

4. The positive electrode active material according to any one of claims 1 to 3, wherein the alkaline sodium compound comprises at least one of sodium hydroxide and sodium carbonate, and is selectively sodium carbonate.

5. The positive electrode active material according to claim 4, wherein the mass ratio of sodium carbonate is 80% or more based on the total mass of the coating layer.

6. The positive electrode active material according to claim 4 or 5, wherein the mass ratio of sodium hydroxide is 10% or less based on the total mass of the coating layer.

7. The aforementioned sodium ion transition metal oxide is Na ｘ Mn ａ Fe ｂ Ni ｃ Q ｄ O ２－ｅ＋δ F ｅ Includes, The positive electrode active material according to any one of claims 1 to 6, wherein 0.5 ≤ x ≤ 1.2, 0 < a, 0 ≤ b ≤ 0.4, 0 ≤ c ≤ 0.4, 0 ≤ d, a + b + c + d = 1, 0 ≤ e ≤ 0.2, -0.1 ≤ δ ≤ 0.1, and Q comprises at least one of Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi.

8. The aforementioned sodium ion transition metal oxide is Na ｘ Mn ａ Fe ｂ Ni ｃ Q ｄ O ２－ｅ＋δ F ｅ and contains 0.7≦x≦1.2, 0<a, 0.1≦b≦0.4, 0.1≦c≦0.4, 0≦d≦0.3, a+b+c+d=1, 0≦e≦0.2, -0.1≦δ≦0.1, and Q contains at least one of Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi, and selectively contains at least one of B, Mg, Al, Si, Ca, Ti, Co, Cu, Zn, Zr, Nb, Mo, La, and Bi. The positive electrode active material according to any one of claims 1 to 7, wherein the mass ratio of the alkaline sodium compound is 1 wt% to 2 wt% based on the total amount of the positive electrode active material.

9. The conditions are 0.3 ≤ a ≤ 0.6 and The conditions are 0.15 ≤ b ≤ 0.35, The conditions are 0.15 ≤ c ≤ 0.35, The positive electrode active material according to claim 8, which satisfies at least one of the conditions 0.1 ≤ d ≤ 0.

2.

10. The positive electrode active material according to claim 8 or 9, wherein 0.5 ≤ (b + c) / a ≤ 2, and selectively 0.5 ≤ (b + c) / a ≤ 1.

5.

11. The phase state of the sodium ion transition metal oxide includes the O3 phase, and the space group is [Math 1] A positive electrode active material according to any one of claims 8 to 10, comprising and having a layer spacing of 0.53 nm to 0.55 nm.

12. The aforementioned sodium ion transition metal oxide is Na ｘ Mn ａ Ni ｃ Q ｄ O ２－ｅ＋δ F ｅ Includes, 0.5 ≤ x ≤ 1.2, 0 < a, 0.1 ≤ c ≤ 0.3, 0 ≤ d ≤ 0.3, a + c + d = 1, 0 ≤ e ≤ 0.2, -0.1 ≤ δ ≤ 0.1, and Q includes at least one of Li, B, Mg, Al, Si, K, Ca, Ti, Co, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi, and selectively includes at least one of B, Mg, Al, Si, Ca, Ti, Co, Cu, Zn, Zr, Nb, Mo, La, and Bi. The positive electrode active material according to any one of claims 1 to 7, wherein the mass ratio of the alkaline sodium compound is 0.5 wt% to 1.5 wt% based on the total amount of the positive electrode active material.

13. The conditions are 0.5 ≤ a ≤ 0.8 and The conditions are 0.15 ≤ c ≤ 0.25, The positive electrode active material according to claim 12, which satisfies at least one of the conditions 0.05 ≤ d ≤ 0.

15.

14. The positive electrode active material according to claim 12 or 13, wherein 0.125 ≤ c / a ≤ 0.45 and selectively 0.2 ≤ c / a ≤ 0.

3.

15. The positive electrode active material according to any one of claims 11 to 14, wherein the phase state of the sodium ion transition metal oxide includes a P2 phase, the space group includes P63 / mmc, and the interlayer spacing is 0.55 nm to 0.57 nm.

16. The BET specific surface area of ​​the positive electrode active material is Sm ２ The positive electrode active material according to any one of claims 1 to 15, wherein the ratio is / g, and S and w satisfy 0.3 ≤ w / S ≤ 3, and selectively satisfy the relationship 0.5 ≤ w / S ≤ 2.

17. The positive electrode active material is The D of the positive electrode active material ｖ The conditions are that 50 is 2 μm-20 μm, and selectively 4 μm-15 μm, The BET specific surface area of ​​the positive electrode active material is 0.2 m². ２ / g-2m ２ It is / g, and selectively 0.3m ２ / g-2m ２ The conditions for / g, The compaction density of the positive electrode active material at a pressure of 300 MPa is 3.1 g / cm³. ３ -3.8 g / cm ３ Therefore, selectively 3.2 g / cm³ ３ -3.6 g / cm ３ A positive electrode active material according to any one of claims 1 to 16, which satisfies at least one of the following conditions.

18. A method for producing a positive electrode active material, To provide a sodium ion transition metal oxide containing iron and / or nickel, wherein in the sodium ion transition metal oxide, the molar amount of iron is denoted as b, the molar amount of nickel is denoted as c, and 0 ≤ b ≤ 0.4 and 0 ≤ c ≤ 0.

4. The process includes mixing the sodium ion transition metal oxide and an alkaline sodium compound and sintering them to obtain a positive electrode active material. A method for producing a positive electrode active material, wherein, with respect to the total amount of the positive electrode active material, the mass ratio of the alkaline sodium compound is w%, and 0.1 ≤ (b + c) / w ≤ 0.

5.

19. A positive electrode plate, wherein the positive electrode plate contains a positive electrode active material described in any one of claims 1 to 17 or a positive electrode active material manufactured by the method described in claim 18.

20. A battery comprising the positive electrode plate described in claim 19.

21. A power-consuming device comprising the battery described in claim 20.

Images