Positive electrode active material, method for manufacturing the same, positive electrode sheet, battery, and electric device

Abstract

The application discloses a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery and an electric device. The positive electrode active material comprises: Na x Mn a Cu b M1 c M2 d M3 e O 2+f‑g R g wherein M1 comprises an element capable of forming a cation with a valence less than or equal to positive divalent; M2 comprises an element capable of forming a cation with a valence of positive trivalent; M3 comprises an element capable of forming a cation with a valence greater than or equal to positive tetravalent, R comprises a group VIIA element, 0.67≤x≤1.2, a+b+c+d+e=1, a>0, b>0, c≥0, d≥0, e≥0, -0.1≤f≤0.1, 0≤g≤0.05, the positive electrode active material is beneficial to make more copper enter the crystal lattice of the positive electrode active material, reduce the content of CuO impurities while improving the cycle stability of the positive electrode active material, and improve the specific capacity of the positive electrode active material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and in particular, relates to a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery and an electric device. BACKGROUND

[0002] Lithium ion batteries have the characteristics of green, environmental protection, high energy, low carbon, etc. They are not only applied to energy storage power supply systems such as hydroelectric, thermal, wind and solar power stations, but also widely used in electric bicycles, electric motorcycles, electric vehicles and other electric vehicles, military equipment, aerospace and other fields. However, the content of lithium in the earth's crust is scarce, and as the demand for lithium resources exceeds the supply, its price has also risen rapidly. Sodium element has very similar physical and chemical properties to lithium element, and the sodium element is abundant in the earth's crust and has low cost. Sodium ion batteries developed by using sodium element instead of lithium element have attracted more and more attention.

[0003] DISCLOSURE

[0004] In view of the technical problems in the background art, the present application provides a positive electrode active material, which aims to improve the specific capacity of the positive electrode and the cycle stability of the battery.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a positive electrode active material, which comprises:

[0006] Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g ,

[0007] wherein M1 comprises an element capable of forming a cation with a valence less than or equal to positive two; M2 comprises an element capable of forming a cation with a valence of positive three; M3 comprises an element capable of forming a cation with a valence greater than or equal to positive four, R comprises a group VIIA element, 0.67≤x≤1.2, a+b+c+d+e=1, a>0, b>0, c≥0, d≥0, e≥0, -0.1≤f≤0.1, 0≤g≤0.05,

[0008] The positive electrode active material of the first aspect of the present application has at least the following beneficial effects: it is beneficial to make more copper enter the crystal lattice of the positive electrode active material, while improving the cycle stability of the positive electrode active material, reducing the content of CuO impurities, and improving the specific capacity of the positive electrode active material.

[0009] In some embodiments of the present application, M1 includes at least one of the following elements: Li, K, Mg, Ca, Zn, Ni, and optionally, Ni. M1 is selected from the elements in the given range, which can provide charge compensation during sodium deintercalation, or activate the redox charge compensation of the nearby oxygen, thereby improving the specific capacity of the positive electrode active material.

[0010] In some embodiments of the present application, M2 includes at least one of the following elements: Cr, Al, B, Fe, Co, In, Y, La, Bi, and optionally, at least one of Cr, Fe, and Co. M2 is selected from the elements in the given range, which can provide charge compensation during sodium deintercalation, or activate the redox charge compensation of the nearby oxygen, thereby improving the specific capacity of the positive electrode active material.

[0011] In some embodiments of the present application, M3 includes at least one of the following elements: Ti, Zr, Nb, Mo, W, Sn, Sb, Si, and Ce. M3 is selected from the elements in the given range, which is conducive to improving the cycle stability and specific capacity of the positive electrode active material.

[0012] In some embodiments of the present application, R includes at least one of the following elements: F and Cl, and optionally, F. R is selected from the elements in the given range, which is conducive to stabilizing the oxygen in the positive electrode active material, thereby reducing the structural damage caused by lattice oxygen release in the positive electrode active material, improving the stability of the positive electrode active material, and further improving the capacity retention rate of the battery.

[0013] In some embodiments of the present application, Satisfying the given conditions is conducive to further improving the specific capacity and cycle stability of the positive electrode active material.

[0014] In some embodiments of the present application, 0.7≤x≤1, and optionally, 0.8≤x≤1.

[0015] In some embodiments of the present application, 0.3≤a≤0.7, and optionally, 0.3≤a≤0.5.

[0016] In some embodiments of the present application, 0.05≤b≤0.2, and optionally, 0.1≤b≤0.15.

[0017] In some embodiments of the present application, 0.1≤c≤0.3, and optionally, 0.15≤c≤0.25.

[0018] In some embodiments of the present application, 0.1≤d≤0.4, and optionally, 0.2≤d≤0.3.

[0019] In some embodiments of the present application, 0≤e≤0.1, and optionally, 0.01≤e≤0.05.

[0020] In some embodiments of the present application, the phase state of the positive electrode active material includes a first phase, and the interlayer spacing of the first phase is 0.525 nm to 0.545 nm, or 0.53 nm to 0.54 nm. The first phase-based positive electrode active material has higher first-cycle coulomb efficiency.

[0021] In some embodiments of the present application, the phase state of the positive electrode active material includes a second phase, and the interlayer spacing of the second phase is 0.54 nm to 0.57 nm. The sodium ion in the second phase-based positive electrode active material migrates faster, and has better rate performance.

[0022] In some embodiments of the present application, the phase state of the positive electrode active material includes an O3 phase, and the space group includes The interlayer spacing is 0.53 nm to 0.54 nm. The positive electrode active material satisfying the O3 phase state has a higher content of sodium ions, which is beneficial to improve the first-cycle coulomb efficiency of the positive electrode active material and the battery.

[0023] In some embodiments of the present application, the phase state of the positive electrode active material includes a P2 phase, and the space group includes P63 / mmc, and the interlayer spacing is 0.54 nm to 0.57 nm. The positive electrode active material satisfying the P2 phase state has faster migration of sodium ions, which is beneficial to improve the rate performance and fast charging performance of the positive electrode active material and the battery.

[0024] In some embodiments of the present application, the phase state of the positive electrode active material includes an O3 phase and a P2 phase, and the mass ratio of the positive electrode active material in the O3 phase state to the positive electrode active material in the P2 phase state is (1-10):1. Satisfying the given condition is beneficial to exert the synergistic effect of the O3 phase and the P2 phase.

[0025] In some embodiments of the present application, the particle size D v 50 of the positive electrode active material is 2 μm to 30 μm, or 4 μm to 12 μm.

[0026] In some embodiments of the present application, the specific surface area of the positive electrode active material is 0.1 m 2 / g to 2 m 2 / g, or 0.3 m 2 / g to 1 m 2 / g.

[0027] In some embodiments of the present application, the compaction density of the positive electrode active material under a pressure of 300 MPa is 3 g / cm 3 ~ 5 g / cm 3 , or 3.0 g / cm 3 ~ 4.0 g / cm 3 .

[0028] The second aspect of the present application provides a method for preparing the positive electrode active material of the first aspect of the present application, comprising: calcining raw material components comprising a sodium source, a manganese source and a copper source.

[0029] The method for preparing the positive electrode active material of the second aspect of the present application has at least the following beneficial effects: not only simple process, but also the use of manganese and copper elements to improve the electrochemical performance of the positive electrode active material.

[0030] In some embodiments of the present application, the sodium source, the manganese source and the copper source each independently comprises at least one of an oxide, a hydroxide, a carbonate and a bicarbonate.

[0031] In some embodiments of the present application, the raw material components further comprise: at least one of an M1 source, an M2 source and an M3 source, and optionally, the M1 source, the M2 source and the M3 source each independently comprises at least one of an oxide, a hydroxide, a carbonate and a bicarbonate.

[0032] The third aspect of the present application provides a positive electrode tab, comprising: the positive electrode active material of the first aspect of the present application, or the positive electrode active material prepared by the method of the second aspect of the present application.

[0033] The fourth aspect of the present application provides a battery, comprising: the positive electrode tab of the third aspect of the present application, or the positive electrode active material prepared by the method of the second aspect of the present application, or the positive electrode active material of the first aspect of the present application.

[0034] The fifth aspect of the present application provides an electric device, comprising: the battery of the fourth aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0035] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the following drawings, in which:

[0036] Figure 1 is a structural schematic diagram of a battery of an embodiment of the present application;

[0037] Figure 2 is a structural schematic diagram of a battery module of an embodiment of the present application;

[0038] Figure 3 is a structural schematic diagram of a battery pack of an embodiment of the present application;

[0039] Figure 4 is an exploded view of Figure 3 ;

[0040] Figure 5 is a schematic diagram of an embodiment of an electric device using the battery of the present application as a power supply;

[0041] Figure 6 is an XRD comparison chart of the positive electrode active material prepared in Example 1 and Comparative Example 1 of the present application.

[0042] BRIEF DESCRIPTION OF DRAWINGS

[0043] 1: battery; 2: battery module; 3: battery pack; 4: upper case; 5: lower case. DETAILED DESCRIPTION

[0044] The present application will be further described with reference to the specific embodiments. It is to be understood that these embodiments are merely illustrative of the present application and do not limit the scope of the present application.

[0045] Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase "in one embodiment" or "an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another.

[0046] The ranges disclosed herein are inclusive of the endpoints and / or ranges based on the lower and / or upper limits. Ranges are inclusive of the endpoints, and are also inclusive of the absence of the end values, unless expressly limited by context. It is specifically intended that the scope of each range include the minimum and maximum values, unless expressly limited in the context, by the use of "from" or "to." Use of "from" indicates open- ended range; and "to" indicates closed- ended range. Other numerical ranges are contained herein, for example, one or more of the individual values or sub-ranges between the recited ranges are intended to be encompassed in this application, unless the context indicates otherwise.

[0047] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, unless otherwise specified, and such technical solutions should be considered to be included in the disclosure of the present application.

[0048] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, unless otherwise specified, and such technical solutions should be considered to be included in the disclosure of the present application.

[0049] If not specifically stated, "including" and "comprising" mentioned in the present application are open-ended. For example, "including" and "comprising" can mean that other components not listed can also be included or contained. In addition, in the present application, the terms "a plurality of" and "a plurality of" mean two or more.

[0050] If there is no special indication, in this application, the term "and / or" is only a description of the association relationship of the associated object, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0051] Unless otherwise defined, all technical and scientific terms used in the application have the same meaning as commonly understood by one of ordinary skill in the art to which the application belongs; the terms used in the application are only for the purpose of describing specific embodiments and are not intended to limit the application; the terms "include" and "have" and any variations thereof in the specification and claims of the application are intended to cover non-exclusive inclusion. Unless otherwise stated, the terms used in the application have the commonly understood meaning understood by those skilled in the art. Unless otherwise stated, the values of the parameters mentioned in the application can be measured by various measurement methods commonly used in the art (for example, tests can be performed according to the methods given in the examples of the application).

[0052] At present, with the continuous rise of lithium resource price, the development of sodium ion battery by replacing lithium element with sodium element has attracted more and more attention. Copper doping is beneficial to improve the electrochemical performance of layered sodium ion positive active material. When Cu ions enter the crystal lattice of layered oxide in the copper-containing layered sodium ion battery layered oxide positive active material, the structure can be effectively stabilized and the cycle stability can be increased. However, if the layered oxide product contains a large amount of CuO impurity phase, the specific capacity of the product will decrease, and the lower Cu content in the crystal lattice will reduce the cycle stability of the layered oxide.

[0053] In view of the above problems, in the present application, by adjusting the ratio of each component in the positive active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g More Cu ions can enter the crystal lattice of the layered oxide, the content of CuO impurity phase can be reduced, and the specific capacity can be improved while improving the cycle stability of the positive active material.

[0054] The positive electrode active material disclosed by the embodiments of the present application is suitable for secondary batteries, and the battery disclosed by the embodiments of the present application can be used in an electric device using the battery as a power source or a variety of energy storage systems using the battery as an energy storage element. The electric device can include, but is not limited to, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric automobile, a ship, a spacecraft, and the like. Among them, the electric toy can include a fixed or mobile electric toy, for example, a game machine, an electric automobile toy, an electric ship toy, and an electric aircraft toy, and the like, and the spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, and the like.

[0055] The first aspect of the present application provides a positive electrode active material, comprising: Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g , wherein M1 comprises an element capable of forming a cation with a valence less than or equal to positive divalent; M2 comprises an element capable of forming a cation with a valence of positive trivalent; M3 comprises an element capable of forming a cation with a valence greater than or equal to positive tetravalent, R comprises a group VIIA element, 0.67≤x≤1.2, a+b+c+d+e=1, a>0, b>0, c≥0, d≥0, e≥0, -0.1≤f≤0.1, 0≤g≤0.05,

[0056] As some specific examples, x can have values of 0.67, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, etc., or can be within a range defined by any of these values. As some more specific examples, a can have values of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc., or can be within a range defined by any of these values. As some further specific examples, b can have values of 0.05, 0.15, 0.25, 0.35, 0.45, 0.55, 0.65, 0.75, 0.85, 0.95, etc., or can be within a range defined by any of these values. As yet some further specific examples, c can have values of 0, 0.05, 0.15, 0.25, 0.35, 0.45, 0.55, 0.65, 0.75, 0.85, 0.95, etc., or can be within a range defined by any of these values. As yet some further specific examples, d can have values of 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc., or can be within a range defined by any of these values. As yet some further specific examples, e can have values of 0, 0.05, 0.15, 0.25, 0.35, 0.45, 0.55, 0.65, 0.75, 0.85, 0.95, etc., or can be within a range defined by any of these values. As yet some further specific examples, f can have values of -0.1, -0.08, -0.06, -0.05, -0.03, -0.02, -0.01, 0, 0.01, 0.02, 0.03, 0.05, 0.08, 0.1, etc., or can be within a range defined by any of these values. As yet some further specific examples, g can have values of 0, 0.001, 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, etc., or can be within a range defined by any of these values. As yet some further specific examples, can have values of 0.001, 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, etc., or can be within a range defined by any of these values. It will be appreciated that in the “manganese site” doping described herein, the manganese site represents the position of the manganese element or the M3 element in the crystal lattice of the positive active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g the position of the manganese element or the M3 element in the crystal lattice of the positive active material Na

[0057] In the present application, when analyzing the composition and element types and valence states of the positive electrode active material, the test methods used include but are not limited to XRD test, X-ray photoelectron spectroscopy (XPS), EDS energy spectrum analysis, etc. The molar amount of each element in the positive electrode active material can be obtained by inductively coupled plasma emission spectrometry (i.e. ICP test), and the instrument standard can refer to EPA6010D-2014 "Inductively Coupled Plasma Atomic Emission Spectrometry". Specifically, the sample to be tested can be treated and digested into a solution by chemical methods, atomized into plasma and excited to emit characteristic spectral lines of elements, and the element content can be qualitatively and quantitatively analyzed according to the wavelength and intensity (proportional to concentration) of the spectral lines.

[0058] It should be noted that in the positive electrode plate, the battery or the electric device, due to the formation and cycle of the battery and other processes, sodium ions will be consumed, so the measured sodium element content x in the positive electrode active material will be less than 1. In addition, if the positive electrode plate and the negative electrode plate use a sodium supplement agent, after the battery is formed and cycled, the measured sodium element content x in the positive electrode active material will be greater than 1. In addition, the battery will be accompanied by Na deintercalation and consumption during charging and discharging, and the molar content of Na will be different when the battery is discharged to different states. In the present application, the molar content of Na in the positive electrode active material is the initial state of the material, i.e. the state before feeding, and the positive electrode active material is applied to the battery system, and after charging and discharging cycle, the molar content of Na will change.

[0059] In addition, due to different process controls such as oxygen content or factors such as lattice oxygen release during the preparation of the positive electrode active material, the oxygen element content in the positive electrode active material will also differ, and in the present application, the molar content of oxygen in the positive electrode active material is only the theoretical state value, and the actual molar content of oxygen will fluctuate.

[0060] It can be understood that in the present application, the Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R gis a layered oxide. In the layered oxide, Cu is more difficult to enter the oxygen octahedron in the transition metal layer. By increasing the content of elements that are prone to form high-valence ions, such as Mn, Ti, Zr, etc., while reducing the content of low-valence ions, more deformed oxygen octahedra can be formed in the local structure of the layered oxide, and then more lattice distortion buffers are provided for Cu to enter the oxygen octahedron, so that more Cu can enter the layered oxide lattice. Among the elements prone to form low-valence ions, elements prone to form lower valence, i.e., monovalent and divalent ions, such as Cu, Li, Mg, Ni, etc., have a lower probability of forming deformed oxygen octahedra in adjacent structures, while elements prone to form trivalent ions, such as Al, have a slightly higher probability of forming deformed oxygen octahedra.

[0061] In the embodiments of the present application, M1 can be selected as an element prone to form low-valence cations with a valence less than or equal to positive two, M2 can be selected as an element prone to form cations with a valence of positive three, and M3 can be selected as an element prone to form high-valence cations with a valence greater than or equal to positive four. The Cu element, the M1 element, and the M2 element have a lower valence, which can provide charge compensation during sodium extraction or activate the oxidation and reduction of the surrounding oxygen to provide charge compensation, thereby increasing the amount of sodium that can be extracted from the layered oxide and increasing the specific capacity. However, the introduction of the M1 element and the M2 element can cause Cu to precipitate, reducing the Cu content in the layered oxide lattice. Compared to the M2 element, the introduction of the M1 element with a lower valence has a relatively weak effect on promoting Cu precipitation. In addition, the M3 element can be considered as manganese doping. When the content of the M1 element and the M2 element decreases and the content of the M3 element increases, it is beneficial to cause local lattice deformation in the layered oxide, especially the Mn-O6 octahedron near the manganese element, which will deform, greatly buffering the lattice deformation caused by Cu entering the lattice, and thereby accommodating more Cu. The entry of more Cu into the layered oxide lattice not only helps to stabilize the structure of the layered oxide and improve the cycle stability, but also reduces the content of CuO impurities and acts as an active element to provide charge compensation during sodium extraction, thereby improving the specific capacity. Among them, In the formula, the ratio of the numerator to the denominator to some extent reflects the difficulty and the amount of deformed oxygen octahedra formed by the change in the content of low-valence elements and high-valence elements, and the exponents of b, b+c, and b+d in the numerator and the exponent of a+e in the denominator to some extent reflect the probability of Cu elements, M1 elements, M2 elements, and M3 forming deformed oxygen octahedra. By comprehensively adjusting the content of the elements in the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g the ratio of the elements in the formula, and Satisfy the range requirements, help a large number of Cu into the lattice of layered oxide, while improving the cycle stability, reduce the content of CuO impurity phase, and then increase the specific capacity.

[0062] The positive electrode active material of the first aspect of the application has at least the following beneficial effects: it is beneficial to make more copper enter the crystal lattice of the positive electrode active material, while improving the cycle stability of the positive electrode active material, reducing the content of CuO impurity phase, and improving the specific capacity of the positive electrode active material.

[0063] In some embodiments of the application, the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g Among them, M1, M2, M3 and R can each independently include one or more elements. Unless otherwise specified, when one or more of M1, M2, M3 and R includes two or more elements, the numerical range of the corresponding stoichiometric number in the chemical formula is not only a limitation of the stoichiometric number of each element as the site, but also a limitation of the sum of the stoichiometric numbers of each element as the site. For example, taking M1 as an example, when M1 is two or more elements M11, M12……M1 n , the stoichiometric numbers c1, c2……c n of M11, M12……M1 n each need to fall within the numerical range limited by the application to c, and the sum of c1, c2……c n also needs to fall within the numerical range. Similarly, for the case where M2, M3 and R are two or more elements, the numerical range of the stoichiometric number of M2, M3 and R limited by the application also has the above meaning.

[0064] In some embodiments of the application, the positive electrode active material can include but is not limited to the Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g For example, the positive electrode active material can only include Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g , and can also include Nax Mn a Cu b M1 c M2 d M3 e O 2+f-g R g and other types of positive electrode active materials; for example, the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g The surface can further include a coating layer, wherein the specific type of the other type of positive electrode active material and the coating layer material is not particularly limited, and can be selected by a person skilled in the art as needed, and will not be described in detail here.

[0065] In some embodiments of the present application, M1 can include at least one of the following elements: Li, K, Mg, Ca, Zn, Ni, and optionally can include Ni.

[0066] The M1 element in the given range is prone to form low-valence cations with a valence less than or equal to positive divalent, such as the Li element which is prone to form cations Li + The introduction of the M1 active element in the given range can provide charge compensation during the process of deintercalating sodium, or activate the redox charge compensation of the nearby oxygen, which is conducive to improving the specific capacity of the positive electrode active material. Optionally, M1 can include the Ni element, for example, can only include the Ni element, or can include the Ni element and one or more elements selected from Li, K, Mg, Ca, Zn, and the selection of the Ni element is conducive to further improving the specific capacity of the positive electrode active material.

[0067] In some embodiments of the present application, M2 can include at least one of the following elements: Cr, Al, B, Fe, Co, In, Y, La, Bi, and optionally can include at least one of Cr, Fe, Co.

[0068] The M2 element in the given range is also prone to form low-valence cations with a valence less than or equal to positive divalent, and the introduction of the M2 active element in the given range can also provide charge compensation during the process of deintercalating sodium, or activate the redox charge compensation of the nearby oxygen, which is conducive to improving the specific capacity of the positive electrode active material. Optionally, M2 can include at least one of Cr, Fe, Co, for example, M2 can include one of Cr, Fe, Co, and the selection of at least one of the Cr, Fe, Co elements is conducive to further improving the specific capacity of the positive electrode active material. Further optionally, when M2 includes at least one of Cr, Fe, Co, M1 can include the Ni element.

[0069] In some embodiments of the present application, M3 can include at least one of the following elements: Ti, Zr, Nb, Mo, W, Sn, Sb, Si, Ce.

[0070] The M3 element in the given range is prone to form high-valence cations with valence greater than or equal to +4. In the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g The introduction of the M3 element in the positive electrode active material is conducive to promoting the local deformation of the crystal lattice of the layered oxide by regulating the relative amount of the M3 element and the M1 and M2 elements, and then more Cu can enter the crystal lattice of the layered oxide, while reducing the content of CuO impurities, and the copper entering the crystal lattice of the layered oxide can also provide charge compensation as an active element in the sodium extraction process, thereby improving the specific capacity. The selection of the M3 element in the given range is conducive to improving the cycle stability and specific capacity of the positive electrode active material.

[0071] In some embodiments of the present application, R can include at least one of the following elements: F, Cl, and optionally, can include F.

[0072] The oxygen site doping of the R element in the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g is conducive to stabilizing oxygen in the positive electrode active material, thereby reducing the structural damage caused by lattice oxygen release in the positive electrode active material, improving the stability of the positive electrode active material, and further improving the capacity retention rate of the battery. Optionally, R can include a fluorine element, for example, can only be a fluorine element.

[0073] It can be understood that the positive electrode active material of the present application can include Na x Mn a Cu b Fe d Nb e O 2+f-g F g , Na x Mn a Cu b Ni c Fe d O 2+f , Nax Mn a Cu b Fe d O2, Na x Mn a Cu b Li c Co d Zr e O 2+f , Na x Mn a Cu b Ni c Cr d O2, etc. all of which are consistent with the general formula Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g , for example, as one specific example, the positive active material can include, but is not limited to, Na 0.94 Mn 0.45 Cu 0.15 Ni 0.25 Fe 0.15 O2, Na 0.93 Mn 0.4 Cu 0.1 Ni 0.2 Fe 0.2 Al 0.1 O2, Na 0.94 Mn 0.45 Cu 0.1 Zn 0.05 Ni 0.2 Fe 0.15 Al 0.05 O2, Na 0.93 Mn 0.45 Cu 0.15 Ni 0.2 Fe 0.2 Ti 0.05 O2, Na 0.94 Mn 0.5 Cu 0.2 Ni 0.1 Fe 0.1 Zr 0.1 O2.

[0074] In some embodiments of the present application,

[0075] As some specific examples, The value of x can be 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, or a range formed by any of the above values. In the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g Among them, Cu, M1, M2 elements can provide charge compensation or activate the oxidation and reduction charge compensation of the surrounding oxygen in the sodium extraction process, but M1 and M2 elements generally have a lower valence state, which can easily induce the precipitation of CuO, The value of x in the given range is beneficial to further improve the specific capacity of the positive electrode active material, and at the same time, more Cu can enter the crystal lattice of the layered oxide, effectively stabilizing the structure and improving the cycle stability of the positive electrode active material.

[0076] Control The value of x meets the given range condition, which is beneficial to further improve the specific capacity and cycle stability of the positive electrode active material.

[0077] In some embodiments of the present application, 0.7≤x≤1, which can be 0.8≤x≤1.

[0078] As some specific examples, the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g Among them, the value of x can be 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or a range formed by any of the above values. The value of x meets the given range condition, which is beneficial to obtain a higher capacity. Optionally, 0.8≤x≤1.

[0079] In some embodiments of the present application, 0.3≤a≤0.7, which can be 0.3≤a≤0.5.

[0080] As some specific examples, the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R gIn some embodiments, a can be 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, or the like, or a range defined by any of these values. The value of a satisfies the given range, which is conducive to reducing the risk of sodium overflow and improving the cycle stability of the positive electrode active material. Alternatively, 0.3≤a≤0.5.

[0081] In some embodiments of the present application, 0.05≤b≤0.2, or 0.1≤b≤0.15.

[0082] As some specific examples, the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g In some embodiments, b can be 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, or the like, or a range defined by any of these values. The value of b satisfies the given range, which is conducive to stabilizing the structure of the layered oxide and improving the cycle stability of the positive electrode active material. Alternatively, 0.1≤b≤0.15.

[0083] In some embodiments of the present application, 0.1≤c≤0.3, or 0.15≤c≤0.25.

[0084] As some specific examples, the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g In some embodiments, c can be 0.1, 0.12, 0.15, 0.18, 0.2, 0.2, 0.22, 0.25, 0.28, 0.3, or the like, or a range defined by any of these values. The value of c satisfies the given range, which can provide charge compensation during sodium extraction or activate the oxidation and reduction of nearby oxygen, and also reduce the risk of CuO precipitation, thereby improving both the specific capacity and the cycle stability of the positive electrode active material. Alternatively, 0.15≤c≤0.25.

[0085] In some embodiments of the present application, 0.1≤d≤0.4, or 0.2≤d≤0.3.

[0086] As some specific examples, the positive electrode active material Na x Mn a Cub M1 c M2 d M3 e O 2+f-g R g In some embodiments, d can be 0.1, 0.12, 0.15, 0.18, 0.2, 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, or a range defined by any of these values. The value of d satisfies the given range, which can provide charge compensation during sodium deintercalation, or activate the oxidation and reduction of oxygen in the vicinity, while reducing the risk of CuO precipitation, and is conducive to improving the specific capacity and cycle stability of the positive active material. Alternatively, 0.2≤d≤0.3.

[0087] In some embodiments of the present application, 0≤e≤0.1, which can be 0.01≤e≤0.05.

[0088] As some specific examples, the positive active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g In some embodiments, e can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or a range defined by any of these values. The value of e satisfies the given range, which is conducive to allowing more Cu to enter the layered oxide lattice, stabilizing the structure of the layered oxide, and reducing the content of CuO impurities, thereby improving the specific capacity and cycle stability of the positive active material. Alternatively, 0.01≤e≤0.05.

[0089] In some embodiments of the present application, the phase state of the positive active material can include a first phase, and the interlayer spacing of the first phase is 0.525nm-0.545nm, which can be 0.53nm-0.54nm.

[0090] The positive active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R gIn some embodiments, the first phase has a layer spacing of 0.525 nm to 0.545 nm. The layer spacing of the first phase is defined as the spacing between transition metal layers in a direction perpendicular to the (001) crystal plane, which can be obtained by X-ray diffraction test on the positive electrode active material. The layer spacing of the first phase can be 0.525 nm to 0.545 nm, 0.528 nm to 0.544 nm, 0.532 nm to 0.544 nm, 0.534 nm to 0.542 nm, 0.536 nm to 0.542 nm, 0.538 nm to 0.542 nm, or 0.539 nm to 0.541 nm, or a range consisting of any of the above values. Alternatively, the layer spacing of the first phase can be 0.53 nm to 0.54 nm. When the layer spacing of the first phase satisfies the given range, the sodium ion content in the layered oxide is higher, and the first coulombic efficiency of the positive electrode active material based on such a layered oxide is higher. The positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g The phase state of the first phase includes the first phase is beneficial to improve the first coulombic efficiency of the positive electrode active material and the battery. It should be noted that in the present application, the "first" in the first phase is only for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of phase states included in the first phase. In the present application, the first phase is understood to be the phase state of the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g All phase states satisfying the layer spacing of 0.525 nm to 0.545 nm in the first phase, for example, the first phase can include but is not limited to the O3 phase, and the space group of the first phase can include but is not limited to

[0091] In some embodiments of the present application, the phase state of the positive electrode active material can include a second phase, and the layer spacing of the second phase is 0.54 nm to 0.57 nm.

[0092] The positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R gIn some embodiments, the interlayer spacing of the second phase is defined as the spacing between transition metal layers in the direction perpendicular to the (001) crystal plane, which can be obtained by X-ray diffraction test of the positive electrode active material. The interlayer spacing of the second phase can be 0.54 nm-0.57 nm, 0.542 nm-0.568 nm, 0.544 nm-0.566 nm, 0.546 nm-0.562 nm, 0.548 nm-0.56 nm, 0.55 nm-0.56 nm, or 0.552 nm-0.558 nm, or a range consisting of any of the above values. When the interlayer spacing of the second phase meets the given range, the migration of sodium ions in the layered oxide is faster, and the rate performance is better. The positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g The phase state of the second phase includes the second phase, which is beneficial to improve the rate performance and fast charging performance of the positive electrode active material and the battery. It should be noted that in the second phase described in the present application, "second" is only for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of phase states included in the second phase. In the present application, the second phase is understood to be the phase state of the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g All phase states that meet the interlayer spacing of 0.54 nm-0.57 nm, for example, the second phase can include but is not limited to P2 phase, and the space group of the second phase can include but is not limited to P63 / mmc.

[0093] Optionally, the phase state of the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g The phase state of the positive electrode active material can include both the first phase and the second phase, which is beneficial to make the positive electrode active material and the battery have both high first-cycle coulomb efficiency and high rate performance.

[0094] In some embodiments of the present application, the phase state of the positive electrode active material can include O3 phase, the space group can include R3m, and the interlayer spacing can be 0.53 nm-0.54 nm.

[0095] The space group of the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g The space group of the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g The interlayer spacing of the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g The sodium ion content is high, which is beneficial to improve the first coulomb efficiency of the positive electrode active material and the battery.

[0096] In some embodiments of the present application, the phase state of the positive electrode active material can include P2 phase, the space group can include P63 / mmc, and the interlayer spacing can be 0.54nm-0.57nm.

[0097] The space group of the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g The space group of the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g The interlayer spacing of the positive electrode active material Na x Mn a Cu b M1 cM2 d M3 e O 2+f-g R g The migration of sodium ions is faster, which is beneficial to improve the rate performance and fast charging performance of the positive active material and the battery.

[0098] Optionally, the positive active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g The phase state of the positive active material can simultaneously include the O3 phase and the P2 phase, and meeting this condition is beneficial to make the positive active material and the battery have higher first cycle coulomb efficiency and higher rate performance. Making the positive active material simultaneously include the O3 phase and the P2 phase is not only beneficial to make the positive active material and the battery have higher first cycle coulomb efficiency and better rate performance, but also the interface contact of the O3 phase and the P2 phase will exist small stress, form interlocking effect, so that the O3 phase and the P2 phase have synergistic effect, can increase the structural stability, and improve the cycle stability of the positive active material and the battery.

[0099] In some embodiments of the present application, the phase state of the positive active material can include the O3 phase and the P2 phase, and the mass ratio of the positive active material in the O3 phase state to the positive active material in the P2 phase state can be (1-10):1.

[0100] For example, the positive active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g and the positive active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R gThe mass ratio can be 1 / 1, 2 / 1, 3 / 1, 4 / 1, 5 / 1, 6 / 1, 7 / 1, 8 / 1, 9 / 1, 10 / 1, or any range of these values. The mass ratio of the O3 phase to the P2 phase can be calculated by first determining the elemental composition of the O3 and P2 phases using transmission electron microscopy and energy dispersive spectroscopy, and then combining this with the average elemental composition obtained from ICP testing of the sample. Ensuring that the content of the O3 and P2 phases in the positive electrode active material meets the given range requirements is beneficial for further leveraging the synergistic effect of the O3 and P2 phases, enabling the positive electrode active material and battery to possess both good first-cycle coulombic efficiency, rate performance, and cycle stability.

[0101] In some embodiments of this application, the phase state, interlayer spacing, and space group tests of the positive electrode active material can be performed as follows: The sample to be tested is ground finely in an agate mortar and passed through a 350-mesh sieve in a drying room or glove box. An appropriate amount of the sieved sample is placed in the center of the sample holder groove, ensuring the loose sample powder is slightly higher than the sample holder plane. A glass slide is gently pressed against the sample surface to level it with the frame plane, and excess powder is scraped off. After sample preparation, a Brucker D8A_A25 X-ray powder diffractometer from Brucker AxS (Germany) is used with CuK... α X-rays are the radiation source, and the wavelength of the X-rays is... The 2θ angle is scanned within the range of 5° to 60° at a scanning rate of 4° / min. After the test, the interlayer spacing (e.g., d) of the selected crystal plane (e.g., the 003 crystal plane) can be obtained by using the angle corresponding to the selected crystal plane (e.g., the 003 crystal plane) and applying the Bragg equation 2d·sinθ=λ, as well as the fact that each unit cell of the selected crystal plane (e.g., the 003 crystal plane) contains three transition metal layers. 003 By comparing the XRD diffraction peaks of the sample with the standard card of the XRD analysis software, the space group of the sample can be confirmed. Note: For phases such as O3, O3', and P3, the 003 crystal plane can be used, while for phases such as P2, O2, and O2', the 002 crystal plane can be used. Generally, the 2θ angle peak position is within 15° to 17°, and they all represent the first-order diffraction of X-rays by the transition metal layer / sodium layer in the layered oxide.

[0102] In some embodiments of this application, the particle size D of the positive electrode active material v 50 can be 2μm to 30μm, or 4μm to 12μm.

[0103] For example, the particle size D of the positive electrode active material v 50 can be 2μm, 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm, etc., or can be a range of any of the above values. In this application, D v50 refers to the particle size corresponding to the cumulative volume distribution percentage of 50%, which can be determined by referring to the standard GB / T 19077-2016 / ISO 13320:2009, using a laser particle size analyzer (Malvern Master Size 2000). The specific test process can include: taking an appropriate amount of sample to be tested (the sample concentration ensures that the light intensity is 8%-12%), adding 20 ml of deionized water, and simultaneously ultrasonicating for 5 min (53 KHz / 120 W) to ensure that the sample is completely dispersed, and then determining the sample according to the standard GB / T 19077-2016 / ISO 13320:2009. Alternatively, the particle size D50 of the positive electrode active material can be 4 μm-12 μm. v 50 can be 4 μm-12 μm.

[0104] In some embodiments of the present application, the specific surface area of the positive electrode active material can be 0.1 m 2 / g-2 m 2 / g, and can be 0.3 m 2 / g-1 m 2 / g.

[0105] For example, the specific surface area of the positive electrode active material can be 0.1 m 2 / g, 0.2 m 2 / g, 0.5 m 2 / g, 0.8 m 2 / g, 1 m 2 / g, 1.2 m 2 / g, 1.5 m 2 / g, 1.8 m 2 / g, 2 m 2 / g, etc., or can be a range consisting of any of the above values. In the present application, the specific surface area of the positive electrode active material can be determined by a conventional method in the art, such as by nitrogen physical adsorption method; for another example, BET (specific surface area) data of the positive electrode active material can be obtained by using the American McDougal full-automatic specific surface area and pore analyzer Gemini VII 2390. Alternatively, the specific surface area of the positive electrode active material can be 0.3 m 2 / g-1 m 2 / g.

[0106] In some embodiments of the present application, the compaction density of the positive electrode active material under a pressure of 300 MPa can be 3 g / cm 3 -5 g / cm 3 , and can be 3.0 g / cm 3 -4.0 g / cm 3 .

[0107] For example, the compaction density of the positive electrode active material under a pressure of 8 tons can be 3 g / cm3 3.2 g / cm3 3 3.4 g / cm3 3 3.6 g / cm3 3 3.8 g / cm3 3 4 g / cm3 3 4.2 g / cm3 3 4.4 g / cm3 3 4.6 g / cm3 3 4.8 g / cm3 3 5 g / cm3 3 or a range consisting of any of the above values. In the present application, the tap density of the positive electrode active material under a pressure of 300 MPa can be measured by using an apparatus and a method known in the art, for example, an electronic pressure testing machine, such as a UTM7305 electronic pressure testing machine, etc. Alternatively, the tap density of the positive electrode active material under a pressure of 300 MPa can be 3.0 g / cm3 3 4.0 g / cm3 3 .

[0108] Specifically, when at least one of the D v 50, the specific surface area and the tap density under a pressure of 300 MPa of the positive electrode active material of the present application is within the above range, the conduction distance in the positive electrode active material is small, the surface side reaction is less, and the capacity of the positive electrode active material is promoted to improve the capacity retention rate of the battery containing the same.

[0109] The second aspect of the present application provides a method for preparing the positive electrode active material of the first aspect of the present application, which comprises: calcining raw material components comprising a sodium source, a manganese source and a copper source.

[0110] For example, the raw material components can be mixed according to a predetermined stoichiometric ratio, and then calcined to obtain a positive electrode active material containing Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g It should be noted that the process parameters for calcining the raw material components are not particularly limited, and can be selected flexibly by those skilled in the art according to actual needs. In addition, it should be noted that since there is a loss of sodium source during calcination, the amount of sodium source added can be slightly higher than the required content of sodium in the composition of the positive electrode active material obtained.

[0111] The method for preparing the positive electrode active material according to the second aspect of the present application has at least the following beneficial effects: not only simple process, but also the use of manganese and copper elements to improve the electrochemical performance of the positive electrode active material.

[0112] In some embodiments of the present application, the sodium source, the manganese source and the copper source can each independently include at least one of an oxide, a hydroxide, a carbonate and a bicarbonate.

[0113] The method for preparing the positive electrode active material including Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g When the positive electrode active material including Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R g is prepared, the forms and specific types of the sodium source, the manganese source and the copper source are not particularly limited, and a person skilled in the art can flexibly select them according to actual needs, as long as they can provide the corresponding sodium element, manganese element and copper element for the positive electrode active material, and can be conventional materials in the art, for example, the sodium source, the manganese source and the copper source can be provided in the form of an oxide or a precursor capable of forming the corresponding oxide. For example, the sodium source can include but is not limited to at least one of sodium oxide, sodium hydroxide, sodium carbonate and sodium bicarbonate, and correspondingly, the manganese source and the copper source can each independently include at least one of an oxide, a hydroxide, a carbonate and a bicarbonate. Alternatively, the sodium source, the manganese source and the copper source are provided in the form of the given range type, which is not only conducive to obtaining the positive electrode active material Na x Mn a Cu b by mixing and calcining, but also facilitates the regulation of the proportions of the components, and the source of each raw material component is wide and easy to obtain. c d In some embodiments of the present application, the raw material components can further include at least one of an M1 source, an M2 source and an M3 source, and optionally, the M1 source, the M2 source and the M3 source each independently include at least one of an oxide, a hydroxide, a carbonate and a bicarbonate. e 2+f-g At least one of M1, M2 and M3 can be doped in the positive electrode active material containing sodium, manganese and copper elements to improve the performance of the positive electrode active material, for example, by regulating the element selection and doping amount of M1, M2 and M3, and the stoichiometric number relationship thereof with the corresponding elements in other raw material components, to increase the specific capacity of the positive electrode active material Na x Mn a Cu bM1 c M2 d M3 e O 2+f-g The content of Cu element in the R crystal lattice reduces the content of CuO impurity phase, and improves the specific capacity of the positive electrode active material while increasing the cycle stability of the positive electrode active material. The selection range of the optional elements M1, M2 and M3 has been described in detail in the foregoing part, and will not be repeated here. The sources of M1, M2 and M3 can be conventional materials in the art, and the forms thereof can independently include, but are not limited to, oxides, hydroxides, carbonates and bicarbonates, so as to facilitate obtaining the positive electrode active material Na x Mn a Cu b M1 c M2 d M3 e O 2+f-g R by mixed calcination, and facilitate the regulation of the proportion of each component, and the sources of each raw material component are wide and easy to obtain.

[0116] In some embodiments of the present application, before calcining each raw material component, the method can further include: grinding and / or ball milling the raw material components to improve the mixing uniformity and calcination efficiency of each raw material component. For example, as some specific examples, after mixing, grinding and / or ball milling each raw material component, the raw material components can be placed in an open crucible, and then the muffle furnace is heated to 800-1200°C at a heating rate of 3-8°C / min, and held at 900-1000°C for 12-17h, and after natural cooling, the positive electrode active material is obtained.

[0117] The third aspect of the present application provides a positive electrode tab, which includes the positive electrode active material of the first aspect of the present application, or the positive electrode active material prepared by the method of the second aspect of the present application.

[0118] In a battery, the positive electrode tab generally includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.

[0119] The positive electrode current collector can be a conventional metal foil or a composite current collector (a metal material can be disposed on a polymer substrate to form a composite current collector). As an example, the positive electrode current collector can include at least one of a copper foil, an aluminum foil, a nickel foil, a stainless steel foil, a stainless steel mesh and a carbon-coated aluminum foil.

[0120] The positive electrode active material layer can also optionally include at least one of a binder, a conductive agent, and other optional additives. As an example, the conductive agent can include, but is not limited to, one or more of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. As an example, the binder can include, but is not limited to, one or more of styrene butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0121] These materials are all commercially available.

[0122] The fourth aspect of the present application provides a battery, which includes the positive electrode tab of the third aspect of the present application, or the positive electrode active material prepared by the method of the second aspect of the present application, or the positive electrode active material of the first aspect of the present application. Thus, the battery can have good cycle stability and specific capacity.

[0123] The battery refers to a battery that can be activated by charging after discharging and continue to be used.

[0124] It can be understood that the battery proposed in the present application is a sodium ion battery.

[0125] Generally, the battery includes a positive electrode tab, a negative electrode tab, a separator, and an electrolyte. During the charging and discharging process of the battery, active ions are inserted and extracted between the positive electrode tab and the negative electrode tab. The separator is arranged between the positive electrode tab and the negative electrode tab and plays a role of isolation. The electrolyte plays a role of ion conduction between the positive electrode tab and the negative electrode tab.

[0126] [Negative electrode tab]

[0127] In the battery, the negative electrode tab generally includes a negative electrode current collector and a negative electrode active material layer arranged on the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material. The negative electrode current collector can be a conventional metal foil or a composite current collector (for example, a metal material can be arranged on a polymer substrate to form a composite current collector). As an example, the negative electrode current collector can be a copper foil.

[0128] In some embodiments of the present application, the battery of the fourth aspect of the present application can be a lithium ion battery, in which case the specific type of negative electrode active material is not limited, and active materials known in the art that can be used in the negative electrode of a sodium ion battery can be used, and a person skilled in the art can select according to actual needs. As an example, the negative electrode active material can 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, titanate material. Specifically, the carbon material can include at least one of hard carbon, soft carbon, amorphous carbon, nanostructured carbon material; the alloy material can include an alloy material formed by at least one of Si, Ge, Sn, Pb, Sb; the general formula of the transition metal oxide and sulfide is M x N y , wherein M includes at least one of Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, V, and N includes O or S; the phosphorus-based material can include at least one of red phosphorus, white phosphorus, black phosphorus; the titanate material can include at least one of Na2Ti3O7, Na2Ti6O 13 , Na4Ti5O 12 , Li4Ti5O 12 , NaTi2(PO4)3. These materials can all be obtained through commercial channels.

[0129] The negative electrode active material layer can also optionally include a binder and a conductive agent, the conductive agent is used to improve the conductivity of the negative electrode active material layer, and the binder is used to firmly bond the negative electrode active material and the binder to the negative electrode current collector. The present application does not make specific limitations on the types of conductive agent and binder, which can be selected according to actual needs. As an example, the conductive agent can include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. As an example, the binder can include at least one of styrene butadiene rubber (SBR), styrene-butadiene rubber (SBCs), water-based acrylic resin and carboxymethyl cellulose (CMC).

[0130] The negative electrode active material layer can also optionally include a thickening agent, such as carboxymethyl cellulose (CMC). However, the present application is not limited thereto, and other materials that can be used as a thickening agent for the negative electrode of a sodium ion battery can also be used.

[0131] In some embodiments of the present application, the battery of the fourth aspect of the present application can be a sodium metal battery, in which case the negative electrode active material thereof can include, but is not limited to, metallic sodium alone. For example, the negative electrode active material can also be an alloy formed by metallic sodium and other various metal or non-metal elements.

[0132] In some embodiments of the present application, the battery of the fourth aspect of the present application can also be a negative electrode-free sodium metal battery, in which case the negative electrode only has a metal foil current collector and no sodium metal on the surface thereof, and only sodium in the positive electrode is used during the cycle, and sodium metal is precipitated and stripped on the negative electrode side.

[0133] [Electrolyte]

[0134] The electrolyte can include an electrolyte salt and a solvent.

[0135] As an example, the electrolyte salt can include at least one of sodium hexafluorophosphate, sodium difluoro oxalate borate, sodium tetrafluoroborate, sodium bisoxalate borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate, and sodium bis(trifluoromethylsulfonyl)imide.

[0136] As an example, the solvent can include at least one of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), 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), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0137] In some embodiments, an additive can also be included in the electrolyte. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and an additive capable of improving certain properties of the battery, such as an additive capable of improving overcharge performance, an additive capable of improving high-temperature performance, and an additive capable of improving low-temperature performance.

[0138] [Separator]

[0139] As the separator described above, the present application is not particularly limited and any known porous structure separator having electrochemical stability and mechanical stability can be used according to the actual needs, for example, a single layer or a multi-layer film including at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride can be used.

[0140] The shape of the battery according to the embodiments of the present application is not particularly limited and can be a cylindrical shape, a square shape, or any other shape. For example, Figure 1 FIG. 1 is a battery 1 having a square structure as an example.

[0141] In some embodiments, the battery can include an outer package. The outer package is used to encapsulate the positive electrode sheet, the negative electrode sheet, and the electrolyte.

[0142] In some embodiments, the outer package can include a housing and a cover plate. The housing can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The housing has an opening communicating with the receiving cavity, and the cover plate can be arranged on the opening to close the receiving cavity.

[0143] The positive electrode sheet, the negative electrode sheet, and the separator film can be formed into an electrode assembly through a rolling process or a stacking process. The electrode assembly is encapsulated in the receiving cavity. The number of electrode assemblies contained in the battery can include one or several, which can be adjusted according to requirements.

[0144] In some embodiments, the outer package of the battery can include a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.

[0145] The outer package of the battery can also include a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, such as polypropylene (PP), polybutylene terephthalate (PBT), or polybutylene succinate (PBS).

[0146] In some embodiments, the battery can be a battery monomer or a battery module or a battery pack assembled by the battery monomer. The number of batteries contained in the battery module or the battery pack can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0147] Figure 2 The battery module 2 is an example. Referring to Figure 2 In the battery module 2, the plurality of batteries 1 can be arranged in sequence along the length direction of the battery module 2. Of course, they can also be arranged in any other manner. Further, the plurality of batteries 1 can be fixed by fasteners.

[0148] The battery module 2 can also include a housing having a receiving space, and the plurality of batteries 1 are received in the receiving space. In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0149] Figure 3 and 4 The battery pack 3 is an example. Referring to Figure 3 and 4 In the battery pack 3, a battery box and a plurality of battery modules 2 arranged in the battery box can be included. The battery box includes an upper box body 4 and a lower box body 5, and the upper box body 4 can be arranged on the lower box body 5 to form a closed space for receiving the battery modules 2. The plurality of battery modules 2 can be arranged in the battery box in any manner.

[0150] The fifth aspect of the present application provides a power consuming device comprising the battery of the fourth aspect of the present application.

[0151] Specifically, the battery can be used as a power source of the power consuming device, or as an energy storage unit of the power consuming device. The power consuming device can include, but is not limited to, mobile devices (such as mobile phones, notebook computers), electric vehicles (such as 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, energy storage systems.

[0152] Figure 5 The power consuming device is an example. The power consuming device includes a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. Another example of the power consuming device can include a mobile phone, a tablet computer, a notebook computer. The power consuming device generally requires thinning, and a battery can be used as a power source.

[0153] Hereinafter, the embodiments of the present application are described. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. If the specific technology or condition is not specified in the embodiments, it is performed according to the technology or condition described in the literature in the art or according to the product instruction. If the reagent or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained by purchase.

[0154] Example 1

[0155] (I) Preparation of the battery

[0156] (1) Preparation of the positive active material of the sodium-ion battery

[0157] Na2CO3, Mn2O3, CuO, NiO, Fe2O3, TiO2 were weighed and mixed. The obtained sample was pre-ground in an agate mortar and then ball-milled in a planetary ball mill for 1 h to obtain a precursor mixture. The obtained precursor mixture was uniformly placed in an open crucible, and then heated in a muffle furnace at a temperature increasing rate of 5 ℃ / min from room temperature to 950 ℃ and kept for 15 h, and then naturally cooled to obtain the positive active material Na 0.86 Mn 0.4 Cu 0.11 Ni 0.19 Fe 0.28 Ti 0.02 O2. The metal composition was tested by inductively coupled plasma emission spectrometry.

[0158] (2) Preparation of the positive electrode sheet

[0159] The positive active material Na 0.86Mn 0.4 Cu 0.11 Ni 0.19 Fe 0.28 Ti 0.02 O2, conductive agent carbon black (Super P), binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 80:15:5 in an appropriate amount of solvent NMP to form a uniform positive electrode slurry; the positive electrode slurry was uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, it was punched into a circular sheet with a diameter of 14 mm to obtain a positive electrode tab.

[0160] (3) Preparation of negative electrode tab: the negative electrode tab used metal sodium sheet.

[0161] (4) Preparation of electrolyte: equal volume of ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed to obtain an organic solvent, then NaClO4 was dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0162] (5) Isolation film: a porous polyethylene film was used as the isolation film.

[0163] (6) Preparation of button cell

[0164] The above positive electrode tab, isolation film, negative electrode tab were stacked in order, with the isolation film between the positive electrode tab and the negative electrode tab to play a role of isolation, and the above prepared electrolyte was added, to complete the preparation of the button cell.

[0165] Examples 2-13 and Comparative Examples 1-2

[0166] Examples 2-13 and Comparative Examples 1-2 are different from the examples in that the composition of each component of the raw materials and the molar ratio of the related elements are different when preparing the positive electrode active material, and the positive electrode active material prepared is different (see Table 2 for details). Among them, the positive electrode active material prepared in Examples 2-13 and Comparative Examples 1-2 all meet the general formula Na x Mn a Cu b M1 c M2 d M3 e O2. Zn source was ZnO, Zr source was ZrO2, and Al source was Al2O3.

[0167] (ii) Test method

[0168] (a) Inductively coupled plasma emission spectrometry for testing the elemental composition of the positive electrode active material

[0169] Instrument standard reference EPA6010D-2014 "Inductively Coupled Plasma Atomic Emission Spectrometry". The positive electrode active material sample is digested into solution by chemical method, atomized into plasma to excite the characteristic spectrum of elements, and the element content is qualitatively and quantitatively analyzed according to the wavelength and intensity (proportional to concentration) of the spectrum.

[0170] (b) Capacity retention rate test of button cell after 50 cycles

[0171] 25℃, 10mA / g current density constant current charging to 4.2V, then 10mA / g current density constant current discharging to 2V, to get the discharge specific capacity C0 of button cell, then 10mA / g current density constant current charging and discharging for 50 cycles, take the discharge specific capacity C1 of the 50th cycle. Cycle 50 cycles capacity retention rate = C1 / C0 x 100%.

[0172] (c) Specific capacity test of button cell

[0173] At 25℃, the button cell is charged to 4.2V at a rate of 0.1C, and then discharged to 1.5V at a rate of 0.1C, to get the specific capacity of the battery, and the nominal specific capacity is 140mAh / g.

[0174] The relevant tests were carried out on examples 1-13 and comparative examples 1-2, and the test results are shown in Figure 6 and Table 1.

[0175]

[0176] Results and conclusions:

[0177] Figure 6 XRD comparison chart of the positive electrode active material prepared in example 1 and comparative example 1 of the present application. In combination with example 1, comparative example 1 and Figure 6 It can be seen that, under the condition that the content of Cu component is 0.15, the positive electrode active material prepared in example 1 of the present application has very low CuO impurity phase content, while the CuO impurity phase content in comparative example 1 is relatively high. Further, in combination with examples 1-13 and comparative examples 1-2 and Table 1, it can be seen that the positive electrode active material prepared in the above examples of the present application can obtain good cycle stability and discharge specific capacity when used in batteries. The reason may be that the regulation of the element ratio in the positive electrode active material prepared in the present application is conducive to the entry of Cu into the lattice, thereby reducing the CuO impurity phase content. Further, in combination with examples 8-13, it can be seen that, under the premise of meeting the value range, even if the types of M1 element and M2 element are changed, good cycle stability and discharge specific capacity can also be obtained.

[0178] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced equivalently. Such modifications or replacements do not change the essence of the corresponding technical solutions, which should be covered in the scope of the claims and the specification of the present application. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A positive electrode active material, characterized in that, include: So x Mr a Cu b M1 c M2 d M3 e O 2+f-g R g , Among them, M1 includes elements that can form cations with a valence less than or equal to +2; M2 includes elements that can form cations with a valence of +3; M3 includes elements that can form cations with a valence greater than or equal to +4; R includes group VIIA elements; 0.67≤x≤1.2; a+b+c+d+e=1; a>0; b>0; c≥0; d≥0; e≥0; -0.1≤f≤0.1; 0<g≤0.

05. .

2. The positive electrode active material according to claim 1, characterized in that, At least one of the following conditions must be met: M1 includes at least one of the following elements: Li, K, Mg, Ca, Zn, Ni; M2 includes at least one of the following elements: Cr, Al, B, Fe, Co, In, Y, La, Bi; M3 includes at least one of the following elements: Ti, Zr, Nb, Mo, W, Sn, Sb, Si, Ce; R includes at least one of the following elements: F, Cl.

3. The positive electrode active material according to claim 2, characterized in that, M1 includes Ni; M2 includes at least one of Cr, Fe, and Co; R includes F.

4. The positive electrode active material according to any one of claims 1-3, characterized in that, 。 5. The positive electrode active material according to any one of claims 1 to 3, characterized in that, At least one of the following conditions must be met: 0.7≤x≤1； 0.3≤a≤0.7； 0.05≤b≤0.2； 0.1≤c≤0.3； 0.1≤d≤0.4； 0≤e≤0.1。 6. The positive electrode active material according to claim 5, characterized in that, 0.8≤x≤1； 0.3≤a≤0.5； 0.1≤b≤0.15； 0.15≤c≤0.25； 0.2≤d≤0.3； 0.01≤e≤0.05。 7. The positive electrode active material according to any one of claims 1 to 3, characterized in that, The positive electrode active material includes a first phase, and the interlayer spacing of the first phase is 0.525 nm to 0.545 nm.

8. The positive electrode active material according to claim 7, characterized in that, The interlayer spacing of the first phase is 0.53 nm to 0.54 nm.

9. The positive electrode active material according to any one of claims 1 to 3, characterized in that, The positive electrode active material includes a second phase, and the interlayer spacing of the second phase is 0.54 nm to 0.57 nm.

10. The positive electrode active material according to any one of claims 1 to 3, characterized in that, The positive electrode active material includes an O3 phase and a space group including [missing information]. The interlayer spacing is 0.53 nm to 0.54 nm; and / or, the phase state of the positive electrode active material includes the P2 phase, the space group includes P63 / mmc, and the interlayer spacing is 0.54 nm to 0.57 nm.

11. The positive electrode active material according to claim 10, characterized in that, The positive electrode active material comprises an O3 phase and a P2 phase, and the mass ratio of the positive electrode active material in the O3 phase to the positive electrode active material in the P2 phase is (1~10):

1.

12. The positive electrode active material according to any one of claims 1 to 3, characterized in that, At least one of the following conditions must be met: The volumetric particle size distribution D of the positive electrode active material v 50 represents 2μm~30μm; The specific surface area of ​​the positive electrode active material is 0.1 m². 2 / g~2m 2 / g; The compaction density of the positive electrode active material under 300 MPa pressure is 3 g / cm³. 3 ~5g / cm 3 .

13. The positive electrode active material according to claim 12, characterized in that, The volumetric particle size distribution D of the positive electrode active material v 50 has a thickness of 4μm to 12μm; The specific surface area of ​​the positive electrode active material is 0.3 m². 2 / g~1m 2 / g; The compaction density of the positive electrode active material under a pressure of 300 MPa is 3.0 g / cm³. 3 ~ 4.0g / cm 3 .

14. A method for preparing the positive electrode active material according to any one of claims 1 to 13, characterized in that, include: The raw material components, including sodium, manganese and copper sources, are roasted.

15. The method according to claim 14, characterized in that, At least one of the following two conditions must be met: The sodium source, the manganese source, and the copper source each independently comprise at least one of oxides, hydroxides, carbonates, and bicarbonates; The raw material components further include at least one of M1 source, M2 source and M3 source, wherein each of the M1 source, M2 source and M3 source independently includes at least one of oxide, hydroxide, carbonate and bicarbonate.

16. A positive electrode plate, characterized in that, include: The positive electrode active material according to any one of claims 1 to 13, or the positive electrode active material prepared by the method according to claim 14 or 15.

17. A battery, characterized in that, include: The positive electrode sheet according to claim 16, or the positive electrode active material prepared by the method according to claim 14 or 15, or the positive electrode active material according to any one of claims 1 to 13.

18. An electrical appliance, characterized in that, include: The battery of claim 17.

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