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

Abstract

The present application discloses a positive electrode active material and a preparation method therefor, a positive electrode sheet, a battery, and an electrical device. The positive electrode active material comprises a sodium manganese oxide; the sodium manganese oxide comprises a first phase and a second phase; the first phase comprises first sodium ion layers and first transition metal layers which are sequentially alternated, and the second phase comprises second sodium ion layers and second transition metal layers which are sequentially alternated; and the interlayer spacing of the adjacent first transition metal layers in the first phase in a direction perpendicular to a crystal plane (001) is d1, and the interlayer spacing of the adjacent second transition metal layers in the direction perpendicular to the crystal plane (001) is d2, wherein d1-d2 ranges from 0.01 nm to 0.02 nm.

Description

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

[0001] The present disclosure relates to the field of batteries, and in particular to a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery, and an electrical device. Background Art

[0002] Sodium-ion batteries are secondary batteries that rely primarily on the movement of sodium ions between the positive and negative electrodes to work. Secondary batteries represented by sodium-ion batteries have been used in energy storage power systems (such as hydropower, thermal, wind and solar power stations, etc.), as well as in many fields such as electric vehicles and aerospace. Compared with lithium-ion batteries, the reserves of sodium salts, which are the main components of the positive active materials of sodium-ion batteries, are more abundant, and the price of sodium salts is much lower than the price of lithium salts, which are the main components of the positive active materials of lithium-ion batteries. As a result, sodium-ion batteries have significant cost advantages in terms of raw materials. However, sodium-ion batteries still have problems such as low energy density and poor stability, which limit the practical application of sodium-ion batteries.

[0003] Application Contents

[0004] In a first aspect of the present application, a positive electrode active material is proposed, comprising sodium manganese oxide, wherein the sodium manganese oxide comprises a first phase and a second phase, wherein the first phase comprises a first sodium ion layer and a first transition metal layer alternating in sequence, and the second phase comprises a second sodium ion layer and a second transition metal layer alternating in sequence; the interlayer spacing of adjacent first transition metal layers in the first phase perpendicular to the (001) crystal plane is d1, and the interlayer spacing of adjacent second transition metal layers in the second phase perpendicular to the (001) crystal plane is d2, and d1-d2 is 0.01nm-0.02nm. Thus, the strain generated in the first phase and the second phase during the sodium insertion and extraction process can be reduced, the occurrence of defects and cracks in the crystal structure can be reduced, and the cycle stability of the positive electrode active material can be improved.

[0005] According to an embodiment of the present application, the sodium manganese oxide includes a doping element Q, and the doping element satisfies at least one of the following conditions: the doping element Q includes a first doping element Q1, and the first doping element partially replaces the sodium element in the sodium manganese oxide, and the first doping element includes at least one of Li, K, Ca, La, Sr; the doping element Q includes a second doping element Q2, and the second doping element partially replaces the manganese element in the sodium manganese oxide, and the second doping element includes at least one of Fe, Co, Ni, Cu, Zn, Ga, Li, B, Mg, Al, Si, Ti, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, Bi; the doping element Q includes a third doping element Q3, and the third doping element partially replaces the oxygen element in the sodium manganese oxide, and the third doping element includes at least one of F, Cl. Thus, the structural stability and specific capacity of the positive electrode active material can be further improved.

[0006] According to an embodiment of the present application, the sodium manganese oxide satisfies the chemical formula: Na d Q1 a aMn y bQ2 b cO z dQ3 c e, where 0.5 < x ≤ 1.2, 0 ≤ a ≤ 0.5, 0.5 < x + a ≤ 1.2; 0 < y, 0 ≤ b ≤ 0.6, y + b = 1; 1.8 ≤ z ≤ 2.2, 0 ≤ c ≤ 0.2, 1.8 ≤ z + c ≤ 2.2. Thus, the structural stability of the positive electrode active material during the cycling process can be improved.

[0007] According to an embodiment of the present application, the sodium manganese oxide satisfies the chemical formula: Na x Q1 a Mn y Fe d Ni e Q2 b O z Q3 c , where y + d + e + b = 1, 0.1 ≤ d ≤ 0.6, 0.1 ≤ e ≤ 0.6, the diffraction peak intensity of the first transition metal layer / the first sodium ion layer in the first phase for X-rays within 2θ of 13° - 16.2° is S1, and the diffraction peak intensity of the second transition metal layer / the second sodium ion layer in the second phase for X-rays within 2θ of 16.2° - 17° is S2, where S1 / (S2 + S1)×e ≤ 0.1. Thus, the specific capacity, average discharge voltage, and structural stability of the positive electrode active material during the cycling process can be improved.

[0008] According to an embodiment of the present application, 0.05 ≤ S1 / (S2 + S1), and optionally, 0.1 ≤ S1 / (S2 + S1). Thus, the structural stability and specific capacity of the positive electrode active material can be further improved.

[0009] According to an embodiment of the present application, the first phase in the sodium manganese oxide satisfies the chemical formula: Na x1 Q1 a1 Mn y1 Fe d1 Ni e1 Q2 b1 O z Q3 c1 , where 0.6 < x1 ≤ 0.8, 0 ≤ a1 ≤ 0.6, 0 ≤ b1 ≤ 0.6, y1 + d1 + e1 + c1 = 1, and 0 ≤ (d1 × e1) / (y1 2 ) ≤ 0.5; the second phase in the sodium manganese oxide satisfies the chemical formula: Na x2 Q1 a2 Mn y2 Fe d2 Ni e2 Q2 b2 O z Q3 c2 , where 0.7 < x2 ≤ 1, 0.1 ≤ a2 ≤ 0.6, 0.1 ≤ b2 ≤ 0.6, y2 + d2 + e2 + c2 = 1, and 0.1 ≤ (d2 × e2) / (y2 2 ) ≤ 1. Thus, the structural stability and specific capacity of the positive electrode active material can be further improved.

[0010] According to an embodiment of the present application, the intensity of the X-ray diffraction peak of the first transition metal layer / the first sodium ion layer in the first phase at 2θ of 13° - 16.2° is S1, and the intensity of the X-ray diffraction peak of the second transition metal layer / the second sodium ion layer in the second phase at 2θ of 16. – 17° is S2, and S1 and S2 satisfy 0.01 ≤ S1 / (S1 + S2) ≤ 0.5. Thus, while having high cycle stability, the positive electrode active material can also have a high specific capacity. Optionally, 0.05 ≤ S1 / (S1 + S2) ≤ 0.5. Thus, the structural stability and specific capacity of the positive electrode active material can be further improved.

[0011] According to an embodiment of the present application, 0.550 nm ≤ d1 ≤ 0.565 nm, 0.530 nm ≤ d2 ≤ 0.545 nm. Thus, the synergistic effect of the first phase and the second phase during cycling can be utilized to improve the structural stability of the positive electrode active material during cycling.

[0012] According to an embodiment of the present application, the first phase is a P2 phase with a space group of P63 / mmc, and the second phase is an O3 phase with a space group of R3m. Thus, the synergistic effect between the P2 and O3 phases can further improve the cycling stability and specific capacity of the positive electrode active material.

[0013] According to an embodiment of the present application, at 25°C, the pH of a deionized water solution of the positive electrode active material with a mass concentration of 2g / 18mL is 7-13; alternatively, the pH is 11-13. This facilitates the formation of a positive electrode slurry that is uniformly dispersed and easy to coat.

[0014] In a second aspect of the present application, a method for preparing the aforementioned positive electrode active material is proposed, comprising: providing a precursor; calcining the precursor to obtain the positive electrode active material, wherein the positive electrode active material comprises sodium manganese oxide, the sodium manganese oxide comprises a first phase and a second phase, the first phase comprises a first sodium ion layer and a first transition metal layer alternating in sequence; the second phase comprises a second sodium ion layer and a second transition metal layer alternating in sequence; the interlayer spacing of adjacent first transition metal layers in the first phase in a direction perpendicular to the (001) crystal plane is d1, and the interlayer spacing of adjacent second transition metal layers in the second phase in a direction perpendicular to the (001) crystal plane is d2, and d1-d2 is 0.01nm-0.02nm. Thus, the aforementioned positive electrode active material can be prepared by a relatively simple method.

[0015] According to an embodiment of the present application, providing a precursor includes: providing a mixture of a first sodium manganese oxide and a second sodium manganese oxide, wherein the molar number of the first sodium manganese oxide in the mixture is m1, and the molar number of the second sodium manganese oxide in the mixture is m2, m1:m2=(1:2)-(1:10), wherein the interlayer spacing of the first transition metal layers adjacent to each other in the first sodium manganese oxide in the direction perpendicular to the (001) crystal plane is 0.550nm-0.565nm, and the interlayer spacing of the second transition metal layers adjacent to each other in the second sodium manganese oxide in the direction perpendicular to the (001) crystal plane is 0.530nm-0.545nm. Thus, the aforementioned positive electrode active material can be obtained by a two-step calcination process, and the interlayer spacing d1 of the first transition metal layers adjacent to each other in the first phase in the direction perpendicular to the (001) crystal plane and the interlayer spacing d2 of the second transition metal layers adjacent to each other in the second phase in the direction perpendicular to the (001) crystal plane can be precisely controlled.

[0016] According to an embodiment of the present application, the calcination process satisfies at least one of the following conditions: the calcination process temperature is 800°C-900°C; and the calcination process time is 0.5h-20h. Thus, a positive electrode active material with a desired interlayer spacing can be obtained.

[0017] According to an embodiment of the present application, providing a first sodium manganese oxide includes: providing a mixture of a sodium source, a manganese oxide, and an oxide of a doping element, and performing a first calcination process, wherein the molar number of the sodium source in the mixture is m 1-1 The molar number of the manganese oxide in the mixture is m 2-1 The molar number of the doping element oxide in the mixture is m 3-1 , m 1-1 :m 2-1 :m 3-1 =(0.5-0.8):(0.6-0.95):(0-0.4) Thus, the first sodium manganese oxide with the desired interlayer spacing can be obtained.

[0018] According to an embodiment of the present application, the first calcination treatment satisfies at least one of the following conditions: the temperature of the first calcination treatment is 700° C.-900° C.; and the time of the first calcination treatment is 10 h-20 h.

[0019] According to an embodiment of the present application, providing a second sodium manganese oxide includes: providing a mixture of a sodium source, a manganese oxide, and an oxide of a doping element, and performing a second calcination process, wherein the molar number of the sodium source in the mixture is m 1-2 The molar number of the manganese oxide in the mixture is m 2-2 The molar number of the doping element oxide in the mixture is m 3-2 , m 1-2 :m 2-2 :m 3-2 =(0.8-1.1):(0.3-0.5):(0-0.6) Thus, a second sodium manganese oxide with a desired interlayer spacing can be obtained.

[0020] According to an embodiment of the present application, the second calcination treatment satisfies at least one of the following conditions: the temperature of the second calcination treatment is 800° C.-1100° C.; and the time of the second calcination treatment is 10 h-20 h.

[0021] In a third aspect of the present application, a positive electrode sheet is provided, comprising the aforementioned positive electrode active material and / or the positive electrode active material prepared using the aforementioned method. Thus, the positive electrode sheet possesses all the features and advantages of the aforementioned positive electrode active material and method for preparing the positive electrode active material, which will not be further elaborated here.

[0022] In a fourth aspect of the present application, a battery is provided, comprising the aforementioned positive electrode sheet. Thus, the battery has all the features and advantages of the aforementioned positive electrode sheet, which will not be described in detail here.

[0023] In a fifth aspect of the present application, the present application provides an electrical device comprising the aforementioned battery. Thus, the electrical device has all the features and advantages of the aforementioned battery, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings. The drawings are only for the purpose of illustrating the embodiments and are not to be considered as limiting the present application.

[0025] FIG1 is a schematic diagram of the interlayer spacing of sodium manganese oxide;

[0026] FIG2 shows a schematic diagram of a battery according to an embodiment of the present application;

[0027] FIG3 is an exploded view of the battery shown in FIG2 according to an embodiment of the present application;

[0028] FIG4 shows a schematic diagram of a battery module according to an embodiment of the present application;

[0029] FIG5 shows a schematic diagram of a battery pack according to an embodiment of the present application;

[0030] FIG6 is an exploded view of the battery pack shown in FIG5 according to an embodiment of the present application;

[0031] FIG7 shows a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application;

[0032] FIG8 shows the XRD diffraction spectrum of the positive electrode active material in Example 1 of the present application;

[0033] FIG9 shows the XRD diffraction spectrum of the positive electrode active material in Comparative Example 1 of the present application.

[0034] Explanation of reference numerals: 1: battery pack, 2: upper case, 3: lower case, 4: battery module, 5: battery, 51: housing, 52: electrode assembly, 53: top cover assembly. DETAILED DESCRIPTION

[0035] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0036] In the description of this application, "A and / or B" may include the case of A alone, the case of B alone, or any of the cases of A and B, where A and B are only used for example, and may be any technical feature connected by "and / or" in this application.

[0037] In the description of this application, “plurality” means two or more.

[0038] In the description of this application, regardless of whether the word "about" or "approximately" is used, all numbers disclosed herein are approximate values. The value of each number may vary by less than 10% or by a reasonable difference considered by a person skilled in the art, such as 1%, 2%, 3%, 4% or 5%.

[0039] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by those skilled in the art to which this application belongs. The terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application. Unless otherwise specified, the terms used in this application have the commonly understood meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0040] The terms "include" and "have" in the description and claims of this application and any variations thereof are open expressions, that is, including the contents specified in this application but not excluding other contents.

[0041] As the application of power batteries continues to expand, the demand for the power battery market is also growing. Secondary batteries, represented by sodium-ion batteries, have been applied in a variety of fields, including energy storage power systems, electric vehicles, and aerospace. However, current sodium-ion batteries suffer from significant degradation in cycle performance with increasing charge and discharge cycles, as well as a decrease in battery capacity due to deactivation of the positive electrode active material.

[0042] Taking sodium manganese oxide as an example, the layered structure of the positive electrode active material contains sodium manganese oxide, which continuously undergoes sodium ion intercalation and deintercalation during the charge-discharge cycle. Accordingly, during this process, the layered structure of the sodium manganese oxide shrinks and expands to complete the sodium ion intercalation and deintercalation. When the stress on the layered structure of the sodium manganese oxide during this shrinkage and expansion is too great, the layered structure of the sodium manganese oxide is damaged by the excessive stress, resulting in defects and cracks within the sodium manganese oxide particles, which in turn leads to poor cyclic stability of the positive electrode active material.

[0043] Based on the above considerations, the present application proposes a sodium manganese oxide positive electrode active material with a mixed phase, in which the interlayer spacing d1 of adjacent first transition metal layers in the first phase in the positive electrode active material in the direction perpendicular to the (001) crystal plane, and the interlayer spacing d2 of adjacent second transition metal layers in the second phase in the direction perpendicular to the (001) crystal plane, the difference between d1 and d2 is between 0.01nm and 0.02nm, thereby playing an "interlocking" role during the contraction and expansion process of the sodium manganese oxide layered structure, so that the stress to which the sodium manganese oxide layered structure is subjected during the sodium insertion and deinsertion process is relatively small, thereby reducing the strain of the crystal structure, reducing the occurrence of defects and cracks in the crystal structure caused by excessive strain, and improving the stability of the positive electrode active material during the charge and discharge cycle.

[0044] As an example, referring to FIG. 1 , the aforementioned interlayer spacing refers to the distance between two adjacent transition metal layers in the direction perpendicular to the (001) crystal plane in the sodium manganese layered oxide.

[0045] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions, such as sodium ions, are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0046] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located at least on one side of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0047] The battery disclosed in the embodiments of the present application can be used in an electrical device that uses a battery as a power source, or a power supply system that uses a battery disclosed in the present application to form the electrical device, or various energy storage systems that use batteries as energy storage elements. Electrical devices may include mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft.

[0048] It should be understood that the technical solutions described in the embodiments of the present application are not limited to the batteries and electrical devices described above, but can also be applied to all other electrical devices including batteries and using batteries. However, for the sake of simplicity, the following embodiments are explained using electric vehicles as an example.

[0049] In the first aspect of the present application, the present application proposes a positive electrode active material, including sodium manganese oxide, which includes a first phase and a second phase, the first phase including a first sodium ion layer and a first transition metal layer alternating in sequence, and the second phase including a second sodium ion layer and a second transition metal layer alternating in sequence; the interlayer spacing between adjacent first transition metal layers in the first phase in the direction perpendicular to the (001) crystal plane is d1, and the interlayer spacing between adjacent second transition metal layers in the second phase in the direction perpendicular to the (001) crystal plane is d2, and d1-d2 is 0.01nm-0.02nm. Since the interlayer spacing of the first phase is slightly larger than the interlayer spacing of the second phase, the strain generated in the first phase and the second phase during the sodium insertion and deinsertion process can be reduced, reducing the occurrence of defects and cracks in the crystal structure, thereby improving the cycle stability of the positive electrode active material.

[0050] In some embodiments, when d1-d2 is less than 0.01 nm, the "interlocking" effect between the first phase and the second phase is not obvious, and the cycle stability of the positive electrode active material cannot be improved; when d1-d2 is greater than 0.02 nm, the interlayer spacing between the first phase and the second phase is too large, and the synergistic effect between the two phases during the charge and discharge cycle is poor, which is not conducive to the deintercalation and extraction of sodium ions.

[0051] As an example, d1-d2 may be 0.01 nm, 0.011 nm, 0.012 nm, 0.013 nm, 0.014 nm, 0.015 nm, 0.016 nm, 0.017 nm, 0.018 nm, 0.019 nm, or 0.02 nm.

[0052] According to an embodiment of the present application, the sodium manganese oxide may include a doping element Q, thereby further improving the structural stability and specific capacity of the positive electrode active material.

[0053] In some embodiments, the doping element Q may include a first doping element Q1, which partially replaces the sodium element in the sodium manganese oxide. The first doping element includes at least one of Li, K, Ca, La, and Sr. This can increase the rate of sodium ion insertion and extraction.

[0054] In some embodiments, the doping element Q may include a second doping element Q2, which partially replaces the manganese element in the sodium manganese oxide. The second doping element includes at least one of Fe, Co, Ni, Cu, Zn, Ga, Li, B, Mg, Al, Si, Ti, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi. This can improve the specific capacity, average discharge voltage, structural stability, and other aspects of the positive electrode active material.

[0055] In some embodiments, the doping element Q may include a third doping element Q3, and the third doping element partially replaces the oxygen element in the sodium manganese oxide. The third doping element includes at least one of F and Cl. Thereby, the crystal structure stability of the cathode active material can be further improved.

[0056] According to an embodiment of the present application, the sodium manganese oxide may satisfy the chemical formula: Na x Q1 a Mn y Q2 b O z Q3 c , where 0.5 < x ≤ 1.2, 0 ≤ a ≤ 0.5, 0.5 < x + a ≤ 1.2; 0 < y, 0 ≤ b ≤ 0.6, y + b = 1; 1.8 ≤ z ≤ 2.2, 0 ≤ c ≤ 0.2, 1.8 ≤ z + c ≤ 2.2. Thereby, the structural stability of the cathode active material during cycling can be improved.

[0057] In some embodiments, when the cathode active material undergoes processes such as sodium supplementation and formation, and after long-term cycling use, the content of sodium element in the cathode active material may exceed the standard value due to the sodium supplementation process, or may be lower than the standard value after formation and long-term cycling use; the content of oxygen element in the cathode active material may also be lower than the standard value due to the release of lattice oxygen in the later stage of cycling.

[0058] In some embodiments, by controlling the content of each element in the sodium manganese oxide, the cathode active material can have a high specific capacity, and there is an appropriate difference between the layer spacing of adjacent first transition metal layers in the first phase of the sodium manganese oxide in the direction perpendicular to the (001) crystal plane and the layer spacing of adjacent second transition metal layers in the second phase in the direction perpendicular to the (001) crystal plane. There is a synergistic effect between the first phase and the second phase that satisfies the above layer spacing difference, further improving the cycle stability of the cathode active material.

[0059] According to an embodiment of the present application, the sodium manganese oxide satisfies the chemical formula: Na x Q1 a Mn y Fe d Ni e Q2 b O z Q3 c, where y + d + e + b = 1, 0.1 ≤ d ≤ 0.6, 0.1 ≤ e ≤ 0.6. The X-ray diffraction peak intensity of the first transition metal layer / first sodium ion layer in the first phase within 2θ of 13° - 16.2° is S1, and the X-ray diffraction peak intensity of the second transition metal layer / second sodium ion layer in the second phase within 2θ of 16.2° - 17° is S2, where S1 / (S2 + S1) × e ≤ 0.1. Thus, the specific capacity, average discharge voltage, and structural stability during cycling of the positive electrode active material can be improved.

[0060] In some embodiments, the phase with a larger layer spacing in the positive electrode active material is beneficial to the high-voltage phase transition of the positive electrode active material, thereby effectively improving the average discharge voltage of the positive electrode active material and further increasing the energy density of the positive electrode active material.

[0061] In other embodiments, the variable valence of Ni in the positive electrode active material during charge and discharge can provide charge compensation, thereby increasing the specific capacity of the positive electrode active material. However, during charge and discharge, Ni located in the transition metal layer in the sodium manganese oxide with a larger layer spacing easily migrates to the sodium ion layer, thereby causing the layered structure of the sodium manganese oxide to be damaged and the cycle stability to decrease.

[0062] As an example, when S1 / (S2 + S1) × e ≤ 0.1, the positive electrode active material has a high specific capacity, a high average discharge voltage, and excellent cycle stability.

[0063] According to an embodiment of the present application, 0.05 ≤ S1 / (S2 + S1), and optionally, 0.1 ≤ S1 / (S2 + S1). Thus, the average discharge voltage of the positive electrode active material and the structural stability during cyclic charge and discharge can be further improved.

[0064] According to an embodiment of the present application, the first phase in the sodium manganese oxide satisfies the chemical formula: Na x1 Q1 a1 Mn y1 Fe d1 Ni e1 Q2 b1 O z Q3 c1 , where 0.6 < x1 ≤ 0.8, 0 ≤ a1 ≤ 0.6, 0 ≤ b1 ≤ 0.6, y1 + d1 + e1 + c1 = 1, and 0 ≤ (d1 × e1) / (y1 2 ) ≤ 0.5; the second phase in the sodium manganese oxide satisfies the chemical formula: Na x2 Q1 a2 Mn y2 Fe d2 Ni e2 Q2 b2 O z Q3c2 , where 0.7 < x2 ≤ 1, 0.1 ≤ a2 ≤ 0.6, 0.1 ≤ b2 ≤ 0.6, y2 + d2 + e2 + c2 = 1, and 0.1 ≤ (d2 × e2) / (y2 2 ) ≤ 1. Thus, the structural stability and specific capacity of the positive electrode active material can be further improved.

[0065] In some embodiments, during the charge and discharge process, Ni and Fe in the first transition metal layer in the first phase with a larger interlayer spacing are likely to migrate into the first sodium ion layer, thereby causing the layered structure of sodium manganese oxide to be damaged and the cycle stability to decrease. By controlling the relatively low content of Fe and Ni that replace the manganese element in sodium manganese oxide in the first phase with a larger interlayer spacing, that is, satisfying 0 ≤ (d1 × e1) / (y1 2 ) ≤ 0.5, it helps to make the structure of the first phase more stable and not easily damaged due to the migration of Fe and Ni, and improves the structural stability of the positive electrode active material during the charge and discharge cycle.

[0066] In some examples, since Fe and Ni in the second transition metal layer in the second phase with a smaller interlayer spacing are not likely to migrate, by controlling the relatively high content of Fe and Ni, that is, 0.1 ≤ (d1 × e1) / (y1 2 ) ≤ 1, the specific capacity of the positive electrode active material can be improved.

[0067] According to the embodiments of the present application, the X-ray diffraction peak intensity of the first transition metal layer / first sodium ion layer in the first phase within 2θ of 13° - 16.2° is S1, and the X-ray diffraction peak intensity of the second transition metal layer / second sodium ion layer in the second phase within 2θ of 16.2° - 17° is S2. S1 and S2 satisfy 0.01 ≤ S1 / (S1 + S2) ≤ 0.5. Thus, while the positive electrode active material has high cycle stability, it can also have a high specific capacity. Optionally, 0.05 ≤ S1 / (S1 + S2) ≤ 0.5. Thus, the structural stability and specific capacity of the positive electrode active material can be further improved.

[0068] As an example, the X-ray diffraction peak intensity of the transition metal layer / sodium ion layer in the positive electrode active material within a specific 2θ range refers to the X-ray diffraction peak intensity of the crystal structure formed by adjacent transition metal layers and sodium ion layers in the positive electrode active material within the specific 2θ range.

[0069] As an example, the X-ray diffraction peak intensity S1 of the first transition metal layer / first sodium ion layer in the first phase and the X-ray diffraction peak intensity S2 of the second transition metal layer / second sodium ion layer in the second phase can be obtained by the following method: performing an XRD test on the positive electrode active material, using CuKα rays as the radiation source, and the ray wavelength The scanning 2θ angle range is 5°-60°, and the scanning rate is 4° / min for testing. The 2θ angle peak is within 15°-17°. The respective diffraction peak intensities can be obtained after full spectrum fitting and Rietveld peak separation. Generally, the diffraction peak intensity of the positive electrode active material to X-rays within 2θ of 13°-16.2° is S1, and the diffraction peak intensity of the positive electrode active material to X-rays within 2θ of 16.2°-17° is S2.

[0070] As an example, for the first phase, after the aforementioned XRD test is completed, the 2θ angle peak is generally within 15°-17° through the angle corresponding to the 002 crystal plane. According to the Bragg equation 2dsinθ=λ, and each unit cell of the 002 crystal plane contains three layers of the first transition metal, the interlayer spacing d of the 002 crystal plane can be obtained. 002 For the second phase, after the test is completed, the angle corresponding to the 003 crystal plane is generally within 15°-17°. According to the Bragg equation 2dsinθ=λ, and each unit cell of the 003 crystal plane contains three layers of the second transition metal layer, the interlayer spacing d of the 003 crystal plane can be obtained. 003 By d 002 and d 003 That is, the interlayer spacing between adjacent transition metal layers in the corresponding first phase and second phase in the direction perpendicular to the (001) crystal plane can be obtained.

[0071] According to an embodiment of the present application, 0.550 nm ≤ d1 ≤ 0.565 nm, and 0.530 nm ≤ d2 ≤ 0.545 nm. Thus, the synergistic effect of the first phase and the second phase during the cycle can be utilized to improve the structural stability of the positive electrode active material during the cycle.

[0072] As an example, the elemental composition of the positive electrode active material can be tested by inductively coupled plasma atomic emission spectrometry. Specifically, the instrument standard refers to EPA6010D-2014 "Inductively coupled plasma atomic emission spectrometry". After the sample to be tested is chemically treated and digested into a solution, it is atomized into a plasma and excited to produce characteristic spectral lines of the elements. The element content is qualitatively and quantitatively analyzed based on the wavelength and intensity of the spectral lines (which are proportional to the concentration). Among them, the composition of each of the two phases in the positive electrode active material can be obtained by ion polishing the cross section of the sample to be tested and performing elemental analysis on the particles of different phases.

[0073] According to the embodiments of the present application, the first phase is a P2 phase with a space group of P63 / mmc, and the second phase is an O3 phase with a space group of R3m. Due to the inconsistent arrangement of the oxygen layers between the P2 and O3 phases, this helps to enhance the "interlocking" effect between the first and second phases, thereby further improving the cycling stability of the positive electrode active material.

[0074] As an example, the space group of the positive electrode active material can be confirmed by comparing the XRD diffraction peaks of the positive electrode active material with the standard card of the XRD analysis software.

[0075] According to an embodiment of the present application, at 25° C., the pH of a deionized water solution of a positive electrode active material with a mass concentration of 2 g / 18 mL may be 7-13; alternatively, the pH is 11-12.5.

[0076] As an example, the pH value of the positive electrode active material may be 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, or 13.

[0077] As an example, the positive electrode active material can be weakly alkaline, thereby facilitating the subsequent formation of a positive electrode slurry suitable for coating, and the pH of the positive electrode active material is 7-13. Alternatively, the pH of the positive electrode active material can meet the pH range of 11-13, and further, the pH of the positive electrode active material can meet the pH range of 11-12.5, thereby reducing the occurrence of gelation during the slurry preparation process and improving the coating stability of the positive electrode slurry.

[0078] As an example, the pH of the positive electrode active material of the present application is measured by the following method: after determining the elemental composition of the positive electrode active material by ICP, 2 g of the positive electrode active material is added to 18 mL of deionized water, stirred at room temperature (25°C) until completely dissolved, and allowed to stand for 30 minutes. The pH of the obtained supernatant is tested, and the measured pH result is the pH of the positive electrode active material.

[0079] In a second aspect of the present application, a method for preparing the aforementioned positive electrode active material is proposed, comprising: providing a precursor; calcining the precursor to obtain the positive electrode active material, wherein the positive electrode active material comprises sodium manganese oxide, the sodium manganese oxide comprises a first phase and a second phase, the first phase comprises a first sodium ion layer and a first transition metal layer alternating in sequence; the second phase comprises a second sodium ion layer and a second transition metal layer alternating in sequence; the interlayer spacing between adjacent first transition metal layers in the first phase in a direction perpendicular to the (001) crystal plane is d1, the interlayer spacing between adjacent second transition metal layers in the second phase in a direction perpendicular to the (001) crystal plane is d2, and d1-d2 is 0.01nm-0.02nm. Thus, the aforementioned positive electrode active material can be prepared by a relatively simple method.

[0080] According to an embodiment of the present application, providing a precursor includes: providing a mixture of a first sodium manganese oxide and a second sodium manganese oxide, wherein the molar number of the first sodium manganese oxide in the mixture is m1, the molar number of the second sodium manganese oxide in the mixture is m2, and the molar ratio of the first sodium manganese oxide to the second sodium manganese oxide in the mixture is m1:m2=(1:2)-(1:10), wherein the interlayer spacing of adjacent transition metal layers in the first sodium manganese oxide in the direction perpendicular to the (001) crystal plane is 0.550nm-0.565nm, and the interlayer spacing of adjacent transition metal layers in the second sodium manganese oxide in the direction perpendicular to the (001) crystal plane is 0.530nm-0.545nm. Thus, the aforementioned positive electrode active material can be obtained by a two-step calcination process, and the interlayer spacing of adjacent first transition metal layers in the first phase in the direction perpendicular to the (001) crystal plane and the interlayer spacing of adjacent second transition metal layers in the second phase in the direction perpendicular to the (001) crystal plane can be precisely controlled.

[0081] According to an embodiment of the present application, the calcination treatment satisfies at least one of the following conditions: the calcination treatment temperature may be 800° C.-900° C.; and the calcination treatment time may be 0.5 h-20 h.

[0082] As an example, the temperature for calcining the mixture of the first sodium manganese oxide and the second sodium manganese oxide can be 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C or 900°C.

[0083] When the temperature for calcining the mixture of the first sodium manganese oxide and the second sodium manganese oxide is 800°C-900°C, the interlayer spacing d1 of adjacent first transition metal layers in the first phase in the positive electrode active material in the direction perpendicular to the (001) crystal plane and the interlayer spacing d2 of adjacent second transition metal layers in the second phase in the direction perpendicular to the (001) crystal plane can be more accurately controlled, so that the difference between d1 and d2 is within the aforementioned range, so that during the contraction and expansion of the sodium manganese oxide layered structure, the first phase and the second phase will play an "interlocking" role, so that the stress to which the sodium manganese oxide layered structure is subjected during the sodium insertion and deinsertion process is relatively small, thereby reducing the strain of the crystal structure, reducing the occurrence of defects and cracks in the crystal structure caused by excessive strain, and improving the stability of the positive electrode active material during the charge and discharge cycle.

[0084] As an example, the calcination time of the mixture of the first sodium manganese oxide and the second sodium manganese oxide can be 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h.

[0085] According to an embodiment of the present application, providing a first sodium manganese oxide includes: providing a mixture of a sodium source, a manganese oxide, and an oxide of a doping element, and performing a first calcination process, wherein the molar number of the sodium source in the mixture is m 1-1 , the number of moles of manganese oxide in the mixture is m 2-1 , the number of moles of the doping element oxide in the mixture is m 3-1 , m 1-1 :m 2-1 :m 3-1 =(0.5-0.8):(0.6-0.95):(0-0.4) Thus, the first sodium manganese oxide with the desired interlayer spacing can be obtained.

[0086] According to an embodiment of the present application, the first calcination treatment satisfies at least one of the following conditions: the temperature of the first calcination treatment may be 700° C.-900° C.; and the time of the first calcination treatment may be 10 h-20 h.

[0087] As an example, the temperature of the first calcination treatment when synthesizing the first sodium manganese oxide can be 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C or 900°C.

[0088] As an example, the first calcination treatment time during the synthesis of the first sodium manganese oxide may be 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, or 20 h.

[0089] In some embodiments, under the aforementioned ratio of sodium source, manganese oxide, and doping element oxide, and the conditions of the first calcination treatment, a first sodium manganese oxide can be obtained in which the interlayer spacing between adjacent transition metal layers in the direction perpendicular to the (001) crystal plane is 0.550 nm-0.565 nm.

[0090] According to an embodiment of the present application, providing a second sodium manganese oxide includes: providing a mixture of a sodium source, a manganese oxide, and an oxide of a doping element, and performing a second calcination process, wherein the molar number of the sodium source in the mixture is m 1-2 , the number of moles of manganese oxide in the mixture is m 2-2 , the number of moles of the doping element oxide in the mixture is m 3-2 , m 1-2 :m 2-2 :m 3-2 =(0.8-1.1):(0.3-0.5):(0-0.6).

[0091] According to an embodiment of the present application, the second calcination treatment satisfies at least one of the following conditions: the temperature of the second calcination treatment is 800° C.-1100° C.; and the time of the second calcination treatment is 10 h-20 h.

[0092] As an example, the temperature of the second calcination treatment when synthesizing the second sodium manganese oxide can be 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, 1050°C, 1060°C, 1070°C, 1080°C, 1090°C or 1100°C.

[0093] As an example, the second calcination treatment time when synthesizing the second sodium manganese oxide can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours or 20 hours.

[0094] In some embodiments, under the aforementioned ratio of sodium source, manganese oxide, and doping element oxide, and the conditions of the second calcination treatment, a second sodium manganese oxide can be obtained in which the interlayer spacing between adjacent transition metal layers in the direction perpendicular to the (001) crystal plane is 0.530 nm-0.545 nm.

[0095] As an example, the sodium source may include at least one of Na2CO3, NaHCO3, NaOH, and Na2O2.

[0096] As an example, the manganese oxide may include at least one of Mn2O3, Mn3O4, MnO, and MnO2.

[0097] It should be noted that the relevant parameters in the above-mentioned method for preparing positive electrode active materials can refer to some or all of the technical features in the aforementioned embodiments. The parts not described in the relevant embodiments of the method for preparing positive electrode active materials can also refer to the aforementioned embodiments and related drawings, and will not be repeated here.

[0098] The above description of the various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced with each other and will not be repeated herein for the sake of brevity.

[0099] In a third aspect of the present application, the present application proposes a positive electrode plate, comprising the aforementioned positive electrode active material, and / or the positive electrode active material prepared by the aforementioned method.

[0100] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer contains a positive electrode active material.

[0101] In the present application, the positive electrode current collector may be a metal foil or a composite current collector. The metal foil is, for example, aluminum foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one side of the polymer base layer. The metal layer may be made of, but is not limited to, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer material of the polymer base layer may be polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and the like.

[0102] In some embodiments, the positive electrode active material is the positive electrode active material in the positive electrode active material layer. In addition to the positive electrode active material, the positive electrode active material layer may optionally include a conductive agent and / or a binder. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0103] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0104] The present application does not particularly limit the preparation method of the positive electrode sheet, and the preparation can refer to existing methods. For example, the positive electrode slurry is coated on the positive electrode current collector, dried, and cold pressed to form the positive electrode sheet. The positive electrode slurry can be formed by dispersing the positive electrode active material, optional conductive agent, optional binder and other components in a solvent (e.g., N-methylpyrrolidone) and stirring them uniformly.

[0105] Furthermore, the positive electrode sheet of the present application does not exclude other additional functional layers in addition to the positive electrode active material layer. For example, the positive electrode sheet may further include a conductive primer layer (e.g., composed of a conductive agent and a binder) disposed between the positive electrode current collector and the positive electrode active material layer. For another example, the positive electrode sheet may further include a protective layer covering the surface of the positive electrode active material layer.

[0106] In the fourth aspect of the present application, the present application proposes a battery comprising the aforementioned positive electrode plate, the positive electrode plate comprising a positive electrode collector and a positive electrode active material layer located at least on one side of the positive electrode collector, the positive electrode active material layer comprising the aforementioned positive electrode active material, and / or, the positive electrode active material prepared by the aforementioned method.

[0107] In the embodiment of the present application, the battery may be a secondary battery. For example, the battery 5 in FIG2 may be a sodium ion battery.

[0108] In some embodiments, a battery includes a positive electrode sheet, a negative electrode sheet, and a separator. During the battery's charge and discharge processes, active ions are intercalated and released between the positive and negative electrode sheets. The electrolyte acts as an ion conductor between the positive and negative electrode sheets. The separator, positioned between the positive and negative electrode sheets, prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0109] In some embodiments, the electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet.

[0110] In some embodiments, the electrode assembly is a wound structure formed by winding the positive electrode sheet and the negative electrode sheet.

[0111] In some embodiments, the electrode assembly is a laminate structure.

[0112] As an example, multiple positive electrode sheets and multiple negative electrode sheets can be provided respectively, and the multiple positive electrode sheets and the multiple negative electrode sheets can be alternately stacked.

[0113] As an example, multiple positive electrode sheets may be provided, and the negative electrode sheet is folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0114] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form a plurality of stacked folded segments.

[0115] As an example, multiple separators may be provided, each of which is provided between any adjacent positive electrode sheets or negative electrode sheets.

[0116] As an example, the separator may be provided continuously, and may be provided between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0117] In some embodiments, the shape of the electrode assembly can be cylindrical, flat, or polygonal.

[0118] In some embodiments, the electrode assembly is provided with tabs that can conduct current from the electrode assembly. The tabs include a positive tab and a negative tab.

[0119] In some embodiments, the positive electrode plate can be the aforementioned positive electrode plate.

[0120] In some embodiments, the negative electrode plate may include a negative electrode current collector, which may be a metal foil, a metal foam, or a composite current collector. For example, the metal foil may include silver-surface-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, a carbon electrode, or titanium. The metal foam may include nickel foam, copper foam, aluminum foam, alloy foam, or carbon foam. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0121] In some embodiments, the negative electrode sheet may be a rolled metal foil or a surface coated inert layer of metal powder coated on a current collector.

[0122] In some embodiments, the negative electrode current collector may be a composite current collector, for example, the composite current collector may include at least one of carbon cloth, carbon film, carbonaceous, porous current collector, alloyed modified current collector, lithiophilic modified current collector and sodium-philic modified current collector.

[0123] In some embodiments, the negative electrode plate may include a negative electrode current collector and a negative electrode active material layer arranged on at least one side of the negative electrode current collector. The negative electrode active material layer may include a negative electrode active material. The negative electrode active material may be a material with a high gram capacity. For example, the negative electrode active material may include at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate.

[0124] As an example, the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon compound, silicon-nitrogen compound, and silicon alloy material; the tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material.

[0125] The present application has no particular limitation on the type of isolation membrane, and any porous isolation membrane with good chemical stability and mechanical stability can be selected.

[0126] As an example, the primary material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, ceramic, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. In the case of a multi-layer composite film, the materials of each layer may be the same or different. The separator may be a separate component positioned between the positive and negative electrode sheets, or it may be attached to the surface of the positive and / or negative electrode sheets.

[0127] As an example, referring to Figure 3 , the positive electrode sheet, the negative electrode sheet, and the separator can be wound or laminated to form an electrode assembly 52. ​​The electrode assembly 52 is encapsulated within a housing cavity, and the electrolyte fills the interior of the electrode assembly 52. ​​The battery 5 can contain one or more electrode assemblies 52, and those skilled in the art can select the number based on specific needs.

[0128] In this application, the electrolyte can be selected with reference to existing secondary batteries. As an example, the electrolyte includes an organic solvent, a sodium salt, and an optional additive. The sodium salt includes, but is not limited to, at least one of NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3. The organic solvent includes, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0129] In some embodiments, the additives in the electrolyte may include negative electrode film-forming additives and positive electrode film-forming additives; they may also include additives that can improve certain performance of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high temperature and / or low temperature performance of the battery, etc. As an example, the additives may include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), vinyl sulfate (DTD), propylene sulfate, vinyl sulfite (ES), 1,3-propane sultone (PS), 1,3-propene sultone (PST), sulfonate cyclic quaternary ammonium salt, succinic anhydride, succinonitrile (SN), adiponitrile (AND), tris(trimethylsilyl) phosphate (TMSP) and tris(trimethylsilyl) borate (TMSB). At least one of the group.

[0130] As an example, the present application has no particular restrictions on the shape of the battery, which can be cylindrical, square, or any other shape. For example, Figure 2 is a battery 5 with a square structure as an example. Specifically, with reference to Figure 3, the outer packaging of the battery 5 may include a shell 51 and a top cover assembly 53. Among them, the shell 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity.

[0131] As an example, batteries can be assembled into battery modules, and the number of batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module. Figure 4 is a battery module 4 as an example. Referring to Figure 4, in the battery module 4, the battery 5 shown in Figure 2 can be used as a battery cell, and a plurality of battery cells can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. The plurality of battery cells can further be fixed by fasteners. The battery module 4 can also include a housing having a accommodating space, and a plurality of battery cells are accommodated in the accommodating space.

[0132] As an example, the above-mentioned battery modules can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery pack. Figures 5 and 6 are battery packs 1 as an example. Referring to Figures 5 and 6, the battery pack 1 may include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 to form an enclosed space for accommodating the battery module 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0133] In a fifth aspect of the present application, the present application proposes an electrical device comprising the aforementioned battery 5. Therefore, the electrical device has all the features and advantages of the aforementioned battery 5, which will not be described in detail here.

[0134] Batteries, battery modules, or battery packs can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices may include, but are not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc. Electrical devices can select batteries, battery modules, or battery packs based on their usage requirements.

[0135] As an example, Figure 7 shows an example electrical device. This device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module can be used.

[0136] As an example, the power-consuming device may also be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0137] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0138] Example 1

[0139] Synthesis of the first sodium manganese oxide:

[0140] A total of 30 g of Na2CO3, Mn2O3, and NiO were weighed according to a Na:Mn:Ni molar ratio of 0.75:0.8:0.2. The obtained sample was pre-ground in an agate mortar and added to a planetary ball mill for 1 hour to obtain a precursor mixture. The obtained precursor mixture was evenly placed in an open crucible, and then heated from room temperature to 850°C in a muffle furnace at a heating rate of 5°C / min, and kept at a constant temperature of 850°C for 15 hours. After cooling naturally, the first sodium manganese oxide Na 0.7 Mn 0.8 Ni 0.2 O2.

[0141] Synthesis of the second sodium manganese oxide:

[0142] A total of 30 g of Na2CO3, Mn2O3, Fe2O3, NiO, and CuO were weighed according to the Na:Mn:Fe:Ni:Cu molar ratio of 0.95:0.4:0.3:0.2:0.1. The obtained sample was pre-ground in an agate mortar and added to a planetary ball mill for 1 hour to obtain a precursor mixture. The obtained precursor mixture was evenly placed in an open crucible, and then heated from room temperature to 950°C in a muffle furnace at a heating rate of 5°C / min, and kept at a constant temperature of 950°C for 15 hours. After cooling naturally, the second sodium manganese oxide Na 0.9 Mn 0.4 Fe 0.3 Ni 0.2 Cu 0.1 O2.

[0143] Synthesis of positive electrode active materials:

[0144] A 30g sample of the first and second sodium manganese oxides was prepared at a molar ratio of 1:3. The sample was pre-ground in an agate mortar and then ball-milled in a planetary ball mill for 1 hour to obtain a precursor mixture. The resulting precursor mixture was evenly placed in an open crucible and then heated from room temperature to 800°C in a muffle furnace at a heating rate of 5°C / min. The temperature was maintained at 800°C for 10 hours and allowed to cool naturally to obtain the positive electrode active material.

[0145] Example 2

[0146] The synthesis method of the first sodium manganese oxide in Example 2 is the same as the synthesis method of the first sodium manganese oxide in Example 1. The difference is that,

[0147] Synthesis of the second sodium manganese oxide:

[0148] A total of 30 g of Na2CO3, Mn2O3, Fe2O3, NiO, and TiO2 were weighed according to the Na:Mn:Fe:Ni:Ti molar ratio of 0.95:0.4:0.3:0.2:0.1. The obtained sample was pre-ground in an agate mortar and added to a planetary ball mill for 1 hour to obtain a precursor mixture. The obtained precursor mixture was evenly placed in an open crucible, and then heated from room temperature to 950°C in a muffle furnace at a heating rate of 5°C / min, and kept at a constant temperature of 950°C for 15 hours. After cooling naturally, the second sodium manganese oxide Na 0.9 Mn 0.4 Fe 0.3 Ni 0.2 Ti 0.1 O2.

[0149] Synthesis of positive electrode active materials:

[0150] A 30g sample of the first and second sodium manganese oxides was prepared at a molar ratio of 1:9. The sample was pre-ground in an agate mortar and then milled in a planetary ball mill for 1 hour to obtain a precursor mixture. The resulting precursor mixture was evenly placed in an open crucible and then heated from room temperature to 800°C in a muffle furnace at a heating rate of 5°C / min. The mixture was maintained at 800°C for 10 hours and allowed to cool naturally to obtain the positive electrode active material.

[0151] Example 3

[0152] The synthesis method of the first sodium manganese oxide in Example 3 is the same as the synthesis method of the first sodium manganese oxide in Example 1. The difference is that,

[0153] Synthesis of the second sodium manganese oxide:

[0154] A total of 30 g of Na2CO3, Mn2O3, Fe2O3, NiO, and ZnO were weighed according to the Na:Mn:Fe:Ni:Zn molar ratio of 0.95:0.4:0.3:0.2:0.1. The obtained sample was pre-ground in an agate mortar and added to a planetary ball mill for 1 hour to obtain a precursor mixture. The obtained precursor mixture was evenly placed in an open crucible, and then heated from room temperature to 950°C in a muffle furnace at a heating rate of 5°C / min, and kept at a constant temperature of 950°C for 15 hours. After cooling naturally, the second sodium manganese oxide Na 0.9 Mn 0.4 Fe 0.3 Ni 0.2 Zn 0.1 O2.

[0155] Synthesis of positive electrode active materials:

[0156] A 30g sample of the first and second sodium manganese oxides was prepared at a molar ratio of 1:3. The sample was pre-ground in an agate mortar and then ball-milled in a planetary ball mill for 1 hour to obtain a precursor mixture. The resulting precursor mixture was evenly placed in an open crucible and then heated from room temperature to 800°C in a muffle furnace at a heating rate of 5°C / min. The temperature was maintained at 800°C for 10 hours and allowed to cool naturally to obtain the positive electrode active material.

[0157] Example 4

[0158] The synthesis method of the first sodium manganese oxide and the second sodium manganese oxide in Example 4 is the same as the synthesis method of the first sodium manganese oxide and the second sodium manganese oxide in Example 1. The difference is that:

[0159] Synthesis of positive electrode active materials:

[0160] A 30g sample of the first and second sodium manganese oxides was prepared at a molar ratio of 1:4. The sample was pre-ground in an agate mortar and then milled in a planetary ball mill for 1 hour to obtain a precursor mixture. The resulting precursor mixture was evenly placed in an open crucible and then heated from room temperature to 800°C in a muffle furnace at a heating rate of 5°C / min. The mixture was maintained at 800°C for 10 hours and allowed to cool naturally to obtain the positive electrode active material.

[0161] Example 5

[0162] The synthesis method of the first sodium manganese oxide and the second sodium manganese oxide in Example 5 is the same as the synthesis method of the first sodium manganese oxide and the second sodium manganese oxide in Example 1. The difference is that:

[0163] Synthesis of positive electrode active materials:

[0164] A 30g sample of the first and second sodium manganese oxides was prepared at a molar ratio of 3:1. The sample was pre-ground in an agate mortar and then milled in a planetary ball mill for 1 hour to obtain a precursor mixture. The resulting precursor mixture was evenly placed in an open crucible and then heated from room temperature to 800°C in a muffle furnace at a heating rate of 5°C / min. The temperature was maintained at 800°C for 10 hours and allowed to cool naturally to obtain the positive electrode active material.

[0165] Example 6

[0166] The synthesis method of the first sodium manganese oxide and the second sodium manganese oxide in Example 6 is the same as the synthesis method of the first sodium manganese oxide and the second sodium manganese oxide in Example 2. The difference is that:

[0167] Synthesis of positive electrode active materials:

[0168] A 30g sample of the first and second sodium manganese oxides was prepared at a molar ratio of 0.5:99.5. The sample was pre-ground in an agate mortar and then milled in a planetary ball mill for 1 hour to obtain a precursor mixture. The resulting precursor mixture was evenly placed in an open crucible and then heated from room temperature to 800°C in a muffle furnace at a heating rate of 5°C / min. The mixture was maintained at 800°C for 10 hours and allowed to cool naturally to yield the positive electrode active material.

[0169] Comparative Example 1

[0170] The synthesis method of the first sodium manganese oxide and the second sodium manganese oxide in Comparative Example 1 is the same as the synthesis method of the first sodium manganese oxide and the second sodium manganese oxide in Example 1. The difference is that:

[0171] Synthesis of positive electrode active materials:

[0172] A 30g sample of the first and second sodium manganese oxides was prepared at a molar ratio of 1:3. The sample was pre-ground in an agate mortar and then ball-milled in a planetary ball mill for 1 hour to obtain a precursor mixture. The resulting precursor mixture was evenly placed in an open crucible and then heated from room temperature to 300°C in a muffle furnace at a heating rate of 5°C / min. The mixture was maintained at 300°C for 10 hours and allowed to cool naturally to obtain the positive electrode active material.

[0173] Comparative Example 2

[0174] The synthesis method of the first sodium manganese oxide and the second sodium manganese oxide in Comparative Example 2 is the same as the synthesis method of the first sodium manganese oxide and the second sodium manganese oxide in Example 1. The difference is that:

[0175] Synthesis of positive electrode active materials:

[0176] A 30g sample of the first and second sodium manganese oxides was prepared at a molar ratio of 1:3. The sample was pre-ground in an agate mortar and then ball-milled in a planetary ball mill for 1 hour to obtain a precursor mixture. The resulting precursor mixture was evenly placed in an open crucible and then heated from room temperature to 1000°C in a muffle furnace at a heating rate of 5°C / min. The mixture was maintained at 1000°C for 10 hours and allowed to cool naturally to obtain the positive electrode active material.

[0177] Comparative Example 3

[0178] Comparative Example 3 only includes the first sodium manganese oxide in Example 1.

[0179] Comparative Example 4

[0180] Comparative Example 4 only includes the second sodium manganese oxide in Example 1.

[0181]

Test part

[0182] 1. Characterization of positive electrode active materials

[0183] 1) Test of interlayer spacing and peak intensity

[0184] In a glove box, the sample to be tested was ground in an agate mortar and then passed through a 350-mesh sieve. An appropriate amount of the sieved sample was placed in the middle of the sample holder groove, so that the loose sample powder was slightly higher than the sample holder plane. A glass slide was used to gently press the sample surface until the sample surface was flattened and aligned with the frame plane, and the excess powder was scraped off. After the sample preparation was completed, a Brucker D8A_A25 X-ray powder diffractometer from Brucker AxS, Germany, was used to analyze the CuK α The ray is the radiation source, and the wavelength of the ray is The test was performed with a scanning 2θ angle range of 5°-60° and a scanning rate of 4° / min.

[0185] For the P2 phase, the 2θ angle peak is generally within 15°-17° according to the angle corresponding to the 002 crystal plane. 002 sinθ=λ, and the interlayer spacing d on the 002 crystal plane is obtained 002 ; By fitting the full spectrum with Rietveld, the diffraction peak intensity S1 corresponding to the 002 crystal plane in the range of 15°-17° was obtained;

[0186] For the O3 phase, the 2θ angle peak is generally within 15°-17° according to the 2d 003 sinθ=λ, and the interlayer spacing d on the 003 crystal plane is obtained 003 ; By fitting the full spectrum with Rietveld, the diffraction peak intensity S2 corresponding to the 003 crystal plane in the range of 15°-17° was obtained.

[0187] 2) pH test

[0188] 2 g of positive electrode active material was placed in a beaker, 18 mL of deionized water was added and stirred at 25 °C until completely dissolved. After standing for 30 min, the pH of the supernatant was tested with a pH meter.

[0189] 3) Element composition test

[0190] The instrument standard refers to EPA 6010D-2014, Inductively Coupled Plasma Atomic Emission Spectrometry. The sample is chemically treated and dissolved into a solution. This solution is then atomized and injected into the plasma, where it is excited to produce characteristic elemental spectral lines. The wavelength and intensity of these spectral lines (which are proportional to concentration) are used to qualitatively and quantitatively analyze the elemental content.

[0191] 2. Performance Testing

[0192] 1) Discharge specific capacity test, 50-cycle capacity retention test

[0193] At 25°C, the positive electrode active material was prepared into a button cell and then charged at a constant current density of 10 mA / g to 4.3 V. The cell was then discharged at a constant current density of 10 mA / g to 2.0 V, yielding a discharge specific capacity (C0) of the button cell. The cell was then subjected to 50 cycles of constant charge and discharge at a current density of 10 mA / g, with the discharge specific capacity (C1) at the 50th cycle being measured. The capacity retention rate of the sodium manganese oxide positive electrode active material after 50 cycles was calculated as (C1 / C0) × 100%.

[0194] The button cell is prepared according to the following steps.

[0195] Preparation of positive electrode sheets: The positive electrode active material, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are added to N-methylpyrrolidone (NMP) in a mass ratio of 80:15:5 and stirred evenly to form a positive electrode slurry; the positive electrode slurry is evenly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, it is punched into a disc with a diameter of 14 mm to obtain a positive electrode sheet.

[0196] Negative electrode: Sodium metal sheet.

[0197] Preparation of the 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 organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0198] Isolation membrane: porous polyethylene membrane is used as the isolation membrane.

[0199] Preparation of button battery: stack the above-mentioned positive electrode sheet, separator, and negative electrode sheet in order, so that the separator is between the positive electrode sheet and the negative electrode sheet, add the above-prepared electrolyte, and the preparation of the button battery is completed.

[0200] The characterization results of the positive electrode active materials are shown in Table 1:

[0201] Table 1

[0202] The XRD diffraction spectra of the positive electrode active materials in Example 1 and Comparative Example 1 can be seen in Figures 8 and 9.

[0203] The characterization results of the button battery are shown in Table 2:

[0204] Table 2

[0205] In the description of this specification, reference to the terms "one embodiment", "another embodiment", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0206] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and are not to be construed as limiting the present application. Persons of ordinary skill in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A positive electrode active material, wherein including sodium manganese oxide, The sodium manganese oxide comprises a first phase and a second phase, wherein the first phase comprises a first sodium ion layer and a first transition metal layer alternating in sequence, and the second phase comprises a second sodium ion layer and a second transition metal layer alternating in sequence; The interlayer spacing between adjacent first transition metal layers in the first phase in a direction perpendicular to the (001) crystal plane is d1, and the interlayer spacing between adjacent second transition metal layers in the second phase in a direction perpendicular to the (001) crystal plane is d2, and d1-d2 is 0.01nm-0.02nm.

2. The positive electrode active material according to claim 1, wherein The sodium manganese oxide includes a doping element Q, and the doping element satisfies at least one of the following conditions: The doping element Q includes a first doping element Q1, the first doping element partially replaces the sodium element in the sodium manganese oxide, and the first doping element includes at least one of Li, K, Ca, La, and Sr; The doping element Q includes a second doping element Q2, the second doping element partially replaces the manganese element in the sodium manganese oxide, and the second doping element includes at least one of Fe, Co, Ni, Cu, Zn, Ga, Li, B, Mg, Al, Si, Ti, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi; The doping element Q includes a third doping element Q3, the third doping element partially replaces the oxygen element in the sodium manganese oxide, and the third doping element includes at least one of F and Cl.

3. The positive electrode active material according to claim 1 or 2, wherein The sodium manganese oxide satisfies the chemical formula: Na x Q1 a Mn y Q2 b O z Q3 c , where 0.5 <x≤1.2,0≤a≤0.5,0.5<x+a≤1.2; 0<y,0≤b≤0.6,y+b=1; 1.8≤z≤2.2,0≤c≤0.2,1.8≤z+c≤2.2。 4. The positive electrode active material according to claim 3, wherein The sodium manganese oxide satisfies the chemical formula: Na x Q1 a Mn y Fe d Ni e Q2 b O z Q3 c , where y+d+e+b=1, 0.1≤d≤0.6, 0.1≤e≤0.6, The diffraction peak intensity of the first transition metal layer / the first sodium ion layer in the first phase to X-rays within 2θ of 13°-16.2° is S1, and the diffraction peak intensity of the second transition metal layer / the second sodium ion layer in the second phase to X-rays within 2θ of 16.2°-17° is S2, wherein S1 / (S2+S1)×e≤0.

1.

5. The positive electrode active material according to claim 4, wherein 0.05≤S1 / (S2+S1).

6. The positive electrode active material according to any one of claims 1 to 5, wherein The first phase in the sodium manganese oxide satisfies the chemical formula: Na x1 Q1 a1 Mn y1 Fe d1 Ni e1 Q2 b1 O z Q3 c1 ,in, 0.6 < x1 ≤ 0.8, 0 ≤ a1 ≤ 0.6, 0 ≤ b1 ≤ 0.6, y1 + d1 + e1 + c1 = 1, and 0 ≤ (d1 × e1) / (y1 2 ) ≤ 0.5; The second phase in the sodium manganese oxide satisfies the chemical formula: Na x2 Q1 a2 Mn y2 Fe d2 Ni e2 Q2 b2 O z Q3 c2 ,in, 0.7 < x2 ≤ 1, 0.1 ≤ a2 ≤ 0.6, 0.1 ≤ b2 ≤ 0.6, y2 + d2 + e2 + c2 = 1, and 0.1 ≤ (d2 × e2) / (y2 2 ) ≤ 1.

7. The positive electrode active material according to claim 6, wherein The diffraction peak intensity of the first transition metal layer / the first sodium ion layer in the first phase to X-rays within 2θ of 13°-16.2° is S1, and the diffraction peak intensity of the second transition metal layer / the second sodium ion layer in the second phase to X-rays within 2θ of 16.2°-17° is S2, and S1 and S2 satisfy 0.01≤S1 / (S1+S2)≤0.

5.

8. The positive electrode active material according to any one of claims 1 to 7, wherein 0.550nm≤d1≤0.565nm, 0.530nm≤d2≤0.545nm.

9. The positive electrode active material according to any one of claims 1 to 8, wherein The first phase is P2 phase, and the space group is P63 / mmc; the second phase is O3 phase, and the space group is 10. The positive electrode active material according to any one of claims 1 to 9, wherein: At 25° C., the pH of the deionized water solution of the positive electrode active material with a mass concentration of 2 g / 18 mL is 7-13.

11. A method for preparing the positive electrode active material according to any one of claims 1 to 10, wherein: include: Providing precursors; The precursor is calcined to obtain the positive electrode active material, wherein the positive electrode active material comprises sodium manganese oxide, The sodium manganese oxide includes a first phase and a second phase, the first phase includes a first sodium ion layer and a first transition metal layer alternating in sequence; the second phase includes a second sodium ion layer and a second transition metal layer alternating in sequence; the interlayer spacing of adjacent first transition metal layers in the first phase in a direction perpendicular to the (001) crystal plane is d1, and the interlayer spacing of adjacent second transition metal layers in the second phase in a direction perpendicular to the (001) crystal plane is d2, and d1-d2 is 0.01nm-0.02nm.

12. The method according to claim 11, wherein: The providing of the precursor comprises: providing a mixture of a first sodium manganese oxide and a second sodium manganese oxide, wherein the molar number of the first sodium manganese oxide in the mixture is m1, the molar number of the second sodium manganese oxide in the mixture is m2, and m1:m2=(1:2)-(1:10), Among them, the interlayer spacing of the first transition metal layers adjacent to each other in the first sodium manganese oxide in a direction perpendicular to the (001) crystal plane is 0.550nm-0.565nm, and the interlayer spacing of the second transition metal layers adjacent to each other in the second sodium manganese oxide in a direction perpendicular to the (001) crystal plane is 0.530nm-0.545nm.

13. The method according to claim 11 or 12, wherein: The calcination treatment satisfies at least one of the following conditions: The calcination temperature is 800°C-900°C; The calcination treatment time is 0.5h-20h.

14. The method according to claim 12, wherein: Providing a first sodium manganese oxide comprises: providing a mixture of a sodium source, a manganese oxide, and an oxide of a doping element, and performing a first calcination treatment, wherein the molar number of the sodium source in the mixture is m 1-1 The molar number of the manganese oxide in the mixture is m 2-1 The molar number of the doping element oxide in the mixture is m 3-1 , m 1-1 :m 2-1 :m 3-1 =(0.5-0.8):(0.6-0.95):(0-0.4).

15. The method according to claim 14, wherein: The first calcination treatment satisfies at least one of the following conditions: The temperature of the first calcination treatment is 700°C-900°C; The first calcination treatment time is 10h-20h.

16. The method according to claim 12, wherein: Providing a second sodium manganese oxide comprises: providing a mixture of a sodium source, a manganese oxide, and an oxide of a doping element, and performing a second calcination treatment, wherein the molar number of the sodium source in the mixture is m 1-2 The molar number of the manganese oxide in the mixture is m 2-2 The molar number of the doping element oxide in the mixture is m 3-2 , m 1-2 :m 2-2 :m 3-2 =(0.8-1.1):(0.3-0.5):(0-0.6).

17. The method according to claim 16, wherein: The second calcination treatment satisfies at least one of the following conditions: The temperature of the second calcination treatment is 800°C-1100°C; The second calcination treatment time is 10h-20h.

18. A positive electrode sheet, wherein: The invention comprises the positive electrode active material according to any one of claims 1 to 10, and / or the positive electrode active material prepared by the method according to any one of claims 11 to 17.

19. A battery, wherein: Including the positive electrode sheet as described in claim 18.

20. An electrical device, wherein: Comprising the battery of claim 19.

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