High-entropy layered oxide and preparation method and application thereof

Abstract

The invention relates to the technical field of sodium ion batteries, and discloses a high-entropy layered oxide and a preparation method and application thereof. According to the high-entropy layered oxide provided by the invention, the nickel-iron-manganese oxide is used as a basic system, and a specific amount of metal element B is used for replacing a part of sodium element in the high-entropy layered oxide; a specific amount of metal elements M, M 'and M' 'replace part of transition metal elements (Ni, Fe and Mn), and the proportional relation among the metal elements M, M 'and M' 'is limited, so that stable atom arrangement is constructed among the elements, the stability of a crystal structure is realized, phase change is relieved, and the material is used as a positive electrode active material, and the service life of the material is prolonged. The cycling stability of the material under high voltage or ultrahigh voltage can be ensured, and meanwhile, the average voltage, the specific discharge capacity and the energy density of the sodium electric material can be remarkably improved. In addition, compared with a copper-iron-manganese oxide system in the prior art, the nickel-cobalt-manganese oxide serving as a basic system has the cost advantage.

Description

Technical Field

[0001] This application relates to the field of sodium-ion battery technology, specifically to a high-entropy layered oxide, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries have gained significant attention since their introduction due to their lower raw material costs, higher discharge capacity, longer cycle life, lower self-discharge rate, and better environmental friendliness. However, with the rapid development of the new energy industry, power and energy storage batteries are facing higher requirements in terms of energy density, safety, and cycle life, posing a significant challenge to conventional sodium-ion batteries.

[0003] Currently, sodium-ion batteries are in the research stage, and there are no commercially available sodium-ion battery cathode materials. Sodium-ion layered oxides (Na₂O₃) are used. x MO2 (where M represents a 3d transition metal element, which may contain one or more elements such as Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Nb, Ru, Mo, Zn, etc.) has attracted widespread attention from researchers due to its rich compositional diversity and tunable electrochemical properties. Currently, researchers' research on sodium-ion batteries mainly focuses on layered oxide cathode materials.

[0004] However, sodium-electric layered oxide materials suffer from drawbacks such as low voltage plateau, low discharge capacity, short cycle life under high or ultra-high voltage, and poor safety. How to significantly improve the discharge voltage plateau of sodium-electric layered oxide materials to increase energy density while ensuring the material's cycle stability under high or ultra-high voltage has become a major challenge in the industry. Summary of the Invention

[0005] This application provides a high-entropy layered oxide, its preparation method, and its application, to solve the problems of low voltage plateau, low discharge capacity, short cycle life under high voltage or ultra-high voltage, and poor safety of sodium-electric layered oxide materials in the prior art.

[0006] In a first aspect, this application provides a high-entropy layered oxide having the following general formula: Na a B b (Ni x1 M x2 M' x3 Fe y Mn z M” z’ )O 2+cWherein, 0.8 < a < 1.0, 0 < b < 0.2, 0 < c < 0.2, 0.2 < x1 < 0.4, x2 > 0, x3 > 0, 0.2 < x1 + x2 + x3 < 0.6, 0 < y < 0.4, 0 < z < 0.5, 0 < z' < 0.3, 0.9 < x1 + x2 + x3 + y + z + z' < 1.1, and the ratio of (x2 + x3) to z' ranges from 0.75 to 1.0; B, M, M', and M” are metallic elements, B is selected from Li, K, and Ca; M and M' are selected from two different elements from Sr, Cd, Mg, Zn, Cu, Ba, and Co; and M” is selected from Zr, Ce, W, and Ti.

[0007] In some alternative embodiments, the high-entropy layered oxide has an α-NaFeO2 type layered structure, wherein element B is doped in the Na-O octahedral layer, and after doping with element B, the occupancy rate of element Na in the Na-O octahedral layer, Occ(Na), is between 75% and 95%.

[0008] In some alternative embodiments, elements M, M', and M'' are doped into the transition metal-oxygen (TM-O) octahedral layer, and the interlayer spacing d(O-TM-O) of the TM-O octahedral layer after doping with elements M, M', and M'' is between... between.

[0009] Secondly, this application provides a method for preparing the above-mentioned high-entropy layered oxide, comprising the following steps:

[0010] S1, mix nickel-iron-manganese hydroxide precursor A containing metal elements M, M', and M”, sodium source, and oxide of metal element B to obtain a mixture;

[0011] S2, the mixture is sintered in an oxygen-containing atmosphere to obtain a high-entropy layered oxide.

[0012] In some optional embodiments, in S1, the molar ratio of sodium element in the sodium source to the total amount of metal element in precursor A is 0.75:1 to 0.95:1;

[0013] And / or, taking metal element B as the basis, the molar ratio of the oxide of metal element B to the total amount of metal element in precursor A is 0.001 to 0.2:1.

[0014] In some alternative embodiments, in S2, the sintering temperature is 700℃~1000℃ and the sintering time is 3h~20h.

[0015] In some alternative embodiments, the sodium source includes at least one of sodium carbonate, sodium hydroxide, sodium nitrate, and sodium acetate.

[0016] Thirdly, this application provides a positive electrode sheet, comprising:

[0017] Positive current collector, and

[0018] A positive electrode active material layer disposed on at least one side of the positive electrode current collector, the positive electrode active material layer comprising the high-entropy layered oxide described above or the high-entropy layered oxide prepared by the above preparation method.

[0019] Fourthly, this application provides a sodium-ion battery, including the aforementioned positive electrode.

[0020] Fifthly, this application provides an electrical device including the aforementioned sodium-ion battery.

[0021] The technical solution of this application has the following advantages:

[0022] The high-entropy layered oxide provided in this application has the following general formula: Na a B b (Ni x1 M x2 M' x3 Fe y Mn z M” z’ )O 2+c Wherein, 0.8 < a < 1.0, 0 < b < 0.2, 0 < c < 0.2, 0.2 < x1 < 0.4, x2 > 0, x3 > 0, 0.2 < x1 + x2 + x3 < 0.6, 0 < y < 0.4, 0 < z < 0.5, 0 < z' < 0.3, 0.9 < x1 + x2 + x3 + y + z + z' < 1.1, and the ratio of (x2 + x3) to z' ranges from 0.75 to 1.0; B, M, M', and M” are metallic elements, B is selected from Li, K, and Ca; M and M' are selected from two different elements from Sr, Cd, Mg, Zn, Cu, Ba, and Co; and M” is selected from Zr, Ce, W, and Ti. The high-entropy layered oxide provided in this application uses nickel-iron-manganese oxide as its base system. By replacing a portion of the sodium element in the high-entropy layered oxide with a specific amount of metal element B, and by replacing a portion of the transition metal elements (Ni, Fe, Mn) with specific amounts of metal elements M, M', and M"", and by defining the proportional relationship between the metal elements M, M', and M", a stable atomic arrangement is constructed between the elements, thereby achieving crystal structure stability and helping to mitigate phase transitions. When used as a positive electrode active material, it can ensure the cycling stability of the material under high or ultra-high voltage, while also significantly improving the average voltage and discharge specific capacity of sodium-ion batteries. Furthermore, the nickel-cobalt-manganese oxide base system in this application has a cost advantage compared to the copper-iron-manganese oxide system in the prior art.

[0023] The high-entropy layered oxide provided in this application has an α-NaFeO2 type layered structure, wherein boron (B) is doped into the Na-O octahedral layer, and after B doping, the occupancy rate (Occ(Na)) of Na in the Na-O octahedral layer is between 75% and 95%. By limiting the occupancy rate, Na… + A reasonable ratio in the crystal structure is beneficial for achieving a balance between cycle stability and discharge specific capacity.

[0024] The high-entropy layered oxide provided in this application has M, M', and M” metal elements doped into a transition metal-oxygen (TM-O) octahedral layer, and the interlayer spacing d(O-TM-O) of the TM-O octahedral layer after doping with M, M', and M” elements is between Between. By limiting the octahedral interlayer spacing, the material can maintain a good α-NaFeO2 type layered structure, ensuring that the material also has good rate performance.

[0025] The method for preparing high-entropy layered oxides provided in this application includes the following steps: S1, mixing a nickel-iron-manganese hydroxide precursor A containing metal elements M, M', and M" with an oxide of metal element B to obtain a mixture; S2, sintering the mixture in an oxygen-containing atmosphere to obtain high-entropy layered oxides. This method is simple to operate, requires no adjustment to existing production line equipment, and is easy to promote and apply. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a SEM image of the high-entropy layered oxide provided in Example 1 of this application;

[0028] Figure 2 This is the XRD pattern of the high-entropy layered oxide provided in Example 1 of this application. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

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

[0031] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0032] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0033] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0034] In the description of the embodiments of this application, the term "at least one" refers to one or more (including one); the term "one or more" refers to two or more (including two).

[0035] Although there is a lot of research on layered oxide cathode materials in the existing technology, sodium-ion battery layered oxide materials have defects such as low voltage plateau, low discharge capacity, short cycle life at high voltage (4.1V) and poor safety.

[0036] To address the problems existing in the aforementioned related technologies, according to a first aspect of this application, a high-entropy layered oxide is provided, characterized in that the high-entropy layered oxide has the following general formula: Na a B b (Ni x1 M x2 M' x3 Fe y Mn z M” z’ )O 2+c Among them, 0.8 < a < 1.0, 0 < b < 0.2, 0 < c < 0.2, 0.2 < x1 < 0.4, x2 > 0, x3 > 0, 0.2 < x1 + x2 + x3 < 0.6, 0 < y < 0.4, 0 < z < 0.5, 0 < z' < 0.3, 0.9 < x1 + x2 + x3 + y + z + z' < 1.1, and the ratio of (x2 + x3) to z' is between 0.75 and 1.0; B, M, M', and M” are metallic elements, B is selected from Li, K, and Ca; M and M' are selected from two different elements from Sr, Cd, Mg, Zn, Cu, Ba, and Co; and M” is selected from Zr, Ce, W, and Ti.

[0037] In some optional implementations, the value of 'a' can be 0.81, 0.85, 0.9, 0.92, 0.95, 0.99, or within any range of the above values; the value of 'b' can be 0.001, 0.003, 0.01, 0.05, 0.08, 0.1, 0.12, 0.15, 0.17, 0.19, or within any range of the above values; the value of 'c' can be 0.01, 0.05, 0.08, 0.1, 0.12, 0.15, 0.17, 0.19, or within any range of the above values; x The value of 1 can be 0.21, 0.23, 0.27, 0.29, 0.31, 0.34, 0.36, 0.37, 0.39, or any value within the range of these values; the value of x1+x2+x3 can be 0.22, 0.24, 0.29, 0.33, 0.38, 0.42, 0.47, 0.51, 0.54, 0.57, 0.59, or any value within the range of these values; the value of y can be 0.01, 0.04, 0.06, 0.09, 0.11, 0.15, 0.17, 0.2, 0.23 The values ​​of z are 0.27, 0.29, 0.31, 0.34, 0.36, 0.37, 0.39, or any of the above values; the values ​​of z can be 0.01, 0.04, 0.06, 0.09, 0.11, 0.15, 0.17, 0.2, 0.23, 0.27, 0.29, 0.31, 0.34, 0.36, 0.37, 0.39, 0.42, 0.45, 0.47, 0.49, or any of the above values; the values ​​of z' can be 0.01, 0.04, 0.06, 0.09 ... The values ​​of x1+x2+x3+y+z+z' can be 0.93, 0.96, 0.97, 0.99, 1.01, 1.05, 1.07, 1.09, or any of the above values; the values ​​of (x2+x3) and z' can be 0.75, 0.80, 0.85, 0.90, 0.92, 0.94, 0.96, 0.98, 1.0, or any of the above values.

[0038] The high-entropy layered oxide provided in this application is based on nickel-iron-manganese oxide. By replacing part of the sodium element in the high-entropy layered oxide with a specific amount of metal element B, replacing part of the transition metal element with a specific amount of metal elements M, M', and M" and limiting the ratio between the doping metal elements M, M', and M" to construct a stable atomic arrangement among the elements, thereby achieving crystal structure stability and helping to alleviate phase transition. When used as a positive electrode active material, it can ensure the cycling stability of the material under high voltage or ultra-high voltage, and can also significantly improve the average voltage, discharge specific capacity and energy density of sodium electrode materials. Without the doping of high-entropy layered oxides with metal element B, the material's stability deteriorates. The absence of either metal element M or M' leads to a decline in electrochemical performance, while the addition of either increases the complexity of the fabrication process and raises costs. Without metal element M", the overall performance of the material cannot be guaranteed. If the ratio of (x2+x3) to z' is too low, the material's discharge specific capacity decreases significantly; if it is too high, the material's cycling performance under high or ultra-high voltage deteriorates. Furthermore, this application, using nickel-cobalt-manganese oxide as the base system, offers a cost advantage compared to the copper-iron-manganese oxide system in existing technologies.

[0039] In some alternative embodiments, the high-entropy layered oxide has an α-NaFeO2 type layered structure, wherein element B is doped in the Na-O octahedral layer, and after doping with element B, the occupancy rate of element Na in the Na-O octahedral layer, Occ(Na), is between 75% and 95%.

[0040] In some alternative implementations, the occupancy of Na in the Na-O octahedral layer, Occ(Na), can be 75%, 80%, 82%, 86%, 88%, 90%, 92%, 95%, or within any of the above values.

[0041] In this application, limiting the site occupancy rate helps to balance cycle stability and discharge specific capacity. If the site occupancy rate is below 75%, there will be a problem of low discharge specific capacity; if the site occupancy rate is above 95%, there will be a problem of deteriorated material stability.

[0042] In some alternative embodiments, elements M, M', and M'' are doped into the transition metal-oxygen (TM-O) octahedral layer, and the interlayer spacing d(O-TM-O) of the TM-O octahedral layer after doping with elements M, M', and M'' is between... between.

[0043] In some alternative implementations, the octahedral interlayer spacing d(O-TM-O) of the doped TM-O can be... Or it may fall within the range of any of the above values.

[0044] In this application, by limiting the octahedral interlayer spacing, the material can maintain a good α-NaFeO2 type layered structure, ensuring that the material also has good rate performance. If the octahedral interlayer spacing is lower than... The rate capability of the material will decrease; if the interlayer density of the octahedron is higher than that of the material... The cycling performance of the material under high or ultra-high voltage may be reduced.

[0045] Secondly, this application provides a method for preparing the above-mentioned high-entropy layered oxide, comprising the following steps:

[0046] S1, mix the nickel-iron-manganese hydroxide precursor A containing metal elements M, M', and M”, the sodium source, and the oxide of metal element B to obtain a mixture;

[0047] S2, the mixture is sintered in an oxygen-containing atmosphere to obtain a high-entropy layered oxide.

[0048] In some optional embodiments, in S1, the molar ratio of sodium element in the sodium source to the total amount of metal element in precursor A is 0.75:1 to 0.95:1; for example, the molar ratio of sodium element in the sodium source to the total amount of metal element in precursor A can be 0.75:1, 0.78:1, 0.80:1, 0.83:1, 0.85:1, 0.88:1, 0.90:1, 0.92:1, 0.95:1, or within any of the above values.

[0049] And / or, the sodium source includes at least one of sodium carbonate, sodium hydroxide, sodium nitrate, and sodium acetate;

[0050] And / or, in S2, the sintering temperature is 700℃~1000℃, and the sintering time is 3h~20h. For example, the sintering temperature can be 700℃, 750℃, 780℃, 800℃, 850℃, 900℃, 920℃, 950℃, 980℃, 1000℃, or within any range of the above values; the sintering time can be 3h, 5h, 8h, 10h, 13h, 15h, 17h, 19h, 20h, or within any range of the above values.

[0051] In some alternative embodiments, the precursor A structure has the general formula (Ni x1 M x2 M' x3 Fe y Mn z M” z’ (OH) z”, where 0.2 < x1 < 0.4, x2 > 0, x3 > 0, 0.2 < x1 + x2 + x3 < 0.6, 0 < y < 0.4, 0 < z < 0.5, 0 < z' < 0.3, 2 ≤ z” < 3.

[0052] In some optional embodiments, the value of x1 can be 0.21, 0.23, 0.27, 0.29, 0.31, 0.34, 0.36, 0.37, 0.39, or within any range of the above values; the value of x1+x2+x3 can be 0.22, 0.24, 0.29, 0.33, 0.38, 0.42, 0.47, 0.51, 0.54, 0.57, 0.59, or within any range of the above values; the value of y can be 0.01, 0.04, 0.06, 0.09, 0.11, 0.15, 0.17, 0.2, 0.23, 0.27, 0.29, 0.31, 0.34, 0.36, 0.37, 0.39, or within any range of the above values. The range of z is: z = 0.01, 0.04, 0.06, 0.09, 0.11, 0.15, 0.17, 0.2, 0.23, 0.27, 0.29, 0.31, 0.34, 0.36, 0.37, 0.39, 0.42, 0.45, 0.47, 0.49, or any of the above values; z' can be 0.01, 0.04, 0.06, 0.09, 0.11, 0.15, 0.17, 0.2, 0.23, 0.27, 0.29, or any of the above values; z” can be 2, 2.04, 2.06, 2.1, 2.3, 2.5, 2.7, 2.8, 2.9, or any of the above values.

[0053] In this application, precursor A is conventional in the field and can be prepared using methods known in the field, without any specific limitations.

[0054] In some alternative embodiments, the oxide of metal element B is one of K2O, CaO, Li2O, MgO, etc.

[0055] Thirdly, this application provides a positive electrode sheet, comprising:

[0056] Positive current collector, and

[0057] A positive electrode active material layer disposed on at least one side of the positive electrode current collector, the positive electrode active material layer comprising the high-entropy layered oxide described above or the high-entropy layered oxide prepared by the above preparation method.

[0058] Fourthly, this application provides a sodium-ion battery, including the aforementioned positive electrode.

[0059] Fifthly, this application provides an electrical device including the aforementioned sodium-ion battery.

[0060] The sodium-ion battery of this application is described below.

[0061] [Positive electrode plate]

[0062] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive active material layer includes a positive active material.

[0063] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0064] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0065] In this application, the cathode material is capable of reversibly inserting and de-inserting Na. + Compounds. For example, positive electrode active materials include transition metal oxides, polyanionic compounds, Prussian blue analogs, etc.

[0066] In some embodiments, the positive electrode active material is a transition metal oxide. The positive electrode active material layer in the positive electrode sheet of this application does not exclude other positive electrode active materials besides the high-entropy layered oxide provided in this application. As an example, Na can be cited. x MO2 or Na y M₂O₄ (where M is a transition metal, 0≤x≤1, 0≤y≤2) represents sodium-containing complex oxides, spinel-like oxides, layered metal chalcogenides, olivine structures, etc. Examples include sodium cobalt oxides such as NaCoO₂, sodium manganese oxides such as NaMn₂O₄, sodium nickel oxides such as NaNiO₂, and Na… 4 / 3 Ti 5 / 3 Sodium titanium oxides such as O4, sodium manganese nickel composite oxides, sodium manganese nickel cobalt composite oxides; materials with olivine-type crystal structures such as NaMPO4 (M=Fe, Mn, Ni), etc.

[0067] In some embodiments, the positive electrode active material may optionally be a layered or spinel-like sodium-containing composite oxide, such as NaCoO2, NaMn2O4, NaNiO2, or NaNi 1 / 2 Mn 1 / 2 Sodium-manganese-nickel composite oxides, represented by O2, etc., with NaNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, NaNi 0.6 Mn 0.2 Co 0.2 Sodium-manganese-nickel-cobalt composite oxides, represented by O2, or NaNi 1-x-y- z Co x Al y Mg z Sodium-containing composite oxides such as O2 (where 0≤x≤1, 0≤y≤0.1, 0≤z≤0.1, 0≤1-xyz≤1). Furthermore, sodium-containing composite oxides in which a portion of the constituent elements of the aforementioned sodium-containing composite oxides are replaced by additive elements such as Ge, Ti, Zr, Mg, Al, Mo, and Sn are also included within the scope of this application.

[0068] In some embodiments, the positive electrode active material is optionally a polyanionic compound. As an example, the polyanionic compound may be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4). n- The valence state. Polyanionic compounds can also have sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl, or Br. Polyanionic compounds can also have sodium ions, tetrahedral (YO4) valence states. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO)y ) m+ The valence state; the halogen can be at least one of F, Cl, and Br. Examples of polyanionic compounds include NaFePO4, Na3V2(PO4)3, NaM'PO4F (M' is one or more of V, Fe, Mn, and Ni), and Na3(VO4)2(PO4)3. y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0069] In some embodiments, the positive electrode active material is optionally a Prussian blue analogue. As an example, Prussian blue compounds may contain sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds include, for example, Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0070] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0071] In some embodiments, the binder may optionally comprise 0.1-3.5% of the total weight of the positive electrode active material layer, and optionally 0.5-2.5%.

[0072] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0073] In some embodiments, the conductive agent may optionally account for 0.05-5% of the total weight of the positive electrode active material layer, and optionally 0.5-3%.

[0074] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0075] [Negative electrode plate]

[0076] In a sodium-ion battery, the negative electrode typically includes a negative current collector and a layer of negative active material disposed on the negative current collector, wherein the negative active material layer includes a negative active material.

[0077] The negative electrode sheet may also consist only of a negative current collector, i.e., without a negative electrode active material. The negative electrode sheet may also include a pre-deposited metallic phase on the negative current collector. The negative current collector can be made of conventional metal foil, carbon-coated metal foil, or porous metal plate, etc. As an example, the negative current collector can be made of copper foil or aluminum foil.

[0078] The specific type of the negative electrode active material is not limited; any active material known in the art that can be used as a negative electrode in sodium-ion batteries can be used. Those skilled in the art can select according to actual needs. As an example, the negative electrode active material may include, but is not limited to, one or more of sodium metal, carbon materials, alloy materials, transition metal oxides and / or sulfides, phosphorus-based materials, and titanate materials. Specifically, the carbon material may include one or more of hard carbon, soft carbon, amorphous carbon, and nanostructured carbon materials; the alloy material may include alloys formed from one or more of Si, Ge, Sn, Pb, and Sb; the general formula of the transition metal oxides and sulfides is M. x N y M includes one or more of Fe, Co, Ni, Mn, Sn, Mo, Sb, and V, and N includes O or S; the phosphorus-based material may include one or more of red phosphorus, white phosphorus, and black phosphorus; the titanate material may include Na2Ti3O7 and Na2Ti6O7. 13 Na4Ti5O 12 Li4Ti5O 12 One or more of NaTi2(PO4)3. These materials are all commercially available.

[0079] The negative electrode active material layer may also optionally include a binder and a conductive agent. The conductive agent is used to improve the conductivity of the negative electrode active material layer, and the binder is used to firmly bond the negative electrode active material and the conductive agent to the negative electrode current collector. This application does not specifically limit the types of conductive agents and binders, which can be selected according to actual needs.

[0080] As an example, conductive agents may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0081] As an example, the adhesive may include one or more of styrene-butadiene rubber (SBR), styrene-butadiene rubber (SBCs), water-based acrylic resin, and carboxymethyl cellulose (CMC).

[0082] The negative electrode active material layer may also optionally include a thickener, such as carboxymethyl cellulose (CMC). However, this application is not limited to this, and other materials that can be used as thickeners for the negative electrode sheet of sodium-ion batteries may also be used.

[0083] [Isolation membrane]

[0084] As for the aforementioned separator, this application does not have any particular limitations. Any known porous structure separator with electrochemical and mechanical stability can be selected according to actual needs. For example, it can be a single-layer or multi-layer film containing one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0085] Electrolyte

[0086] The electrolyte acts as a conductor of ions between the positive and negative electrodes. The electrolyte may include an electrolyte salt and a solvent.

[0087] As an example, the electrolyte sodium salt includes at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium dioxalate borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

[0088] As an example, the solvent may include 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), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), and methyl butyrate. One or more of the following: (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), diethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, tetrahydrofuran, methyltetrahydrofuran, 1,3-dioxopentane, 1,3-dioxane, 1,4-dioxane, tetrahydropyran, methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0089] In some embodiments, the electrolyte further includes additives. For example, the additives can include negative electrode film-forming additives, or can include positive electrode film-forming additives, or can also include additives that can improve certain battery performance, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature performance of the battery, and additives for improving the low-temperature performance of the battery.

[0090] The sodium-ion solid electrolyte can be various sodium-ion solid electrolytes commonly used in the art.

[0091] In some embodiments, the sodium-ion solid electrolyte includes but is not limited to: NASICON type: Na (1+x9+2y5) Zr (2-y5) M y5 P (3-x9) Si x9 O 12 , 0≤x9≤3, 0≤y5≤1, M includes at least one of Zn, Mg, Ca; Na-β-Alumina type: Na2O·2Al2O3 or Na2O·3Al2O3, etc.; Na (3+x10) M y6 A (1-y6) Q (4-z6) T z6 type, where -1<x10<2, 0≤y6≤1, 0≤z6≤2, M includes at least one of B, Al, In, Si, Ge, Sn, Ti, W, Mo, A includes at least one of P, As, Sb, Bi, Q includes at least one of S, Se, T includes at least one of F, Cl, Br, I; Na (11+x11) M (2-y7) A (1+y7) Q (12-z7) T z7 type where -1<x11<1, 0≤y7≤2, 0≤z7≤2, M includes at least one of B, Al, In, Si, Ge, Sn, Ti, W, Mo, A includes P, As, Sb, Bi; Q = at least one of S, Se, and T includes at least one of F, Cl, Br, I; inverse perovskite type Na3OX, X includes at least one of Cl, Br, I, BH4.

[0092] In some embodiments, the positive electrode sheet, negative electrode sheet, and separator can be made into an electrode assembly through a winding process or a stacking process.

[0093] In some embodiments, the sodium-ion battery can include an outer package. The outer package can be used to encapsulate the above electrode assembly and electrolyte.

[0094] In some implementations, the outer packaging of a sodium-ion battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of a sodium-ion battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0095] This application does not impose any particular restrictions on the shape of the sodium-ion battery; it can be cylindrical, square, or any other arbitrary shape.

[0096] In some embodiments, sodium-ion batteries can be assembled into battery modules, and the number of sodium-ion batteries contained in a battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0097] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0098] In some embodiments, the aforementioned electrical device may also include a battery module or battery pack assembled from the aforementioned sodium-ion batteries. The sodium-ion battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0099] As the electrical device, sodium-ion batteries, battery modules, or battery packs can be selected according to their usage requirements. An example electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of sodium-ion batteries for such devices, battery packs or battery modules can be used.

[0100] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use sodium-ion batteries as their power source.

[0101] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0102] Example 1

[0103] This embodiment provides a high-entropy layered oxide, the specific composition of which and its preparation method are as follows:

[0104] (1) A mixed aqueous solution of nickel sulfate, ferrous sulfate, manganese sulfate, copper sulfate, magnesium sulfate, and zirconium sulfate with a total concentration of 2 mol / L was prepared according to the molar ratio of six elements Ni, Fe, Mn, Cu, Mg, and Zr of 30:30:30:2:4:8. A mixed aqueous solution of NH3·H2O with a concentration of 0.2 mol / L and sodium hydroxide with a concentration of 10 mol / L was added to adjust the pH of the solution to 10.6. The solution was stirred under an inert atmosphere and co-precipitated at 60℃ for 100 h to obtain a precursor Ni with an average particle size of 8 μm. 0.3 Fe 0.3 Mn 0.3 Cu 0.02 Mg 0.04 Zr 0.08 (OH) 2.24 .

[0105] (2) Sodium carbonate and CaO are added to the precursor respectively, and the mixing ratio is based on the molar ratio of precursor Ni. 0.3 Fe 0.3 Mn 0.3 Cu 0.02 Mg 0.04 Zr 0.08 (OH) 2.24 The total amount of metallic elements in the mixture is Na:Ca = 1:0.93:0.003. The mixture is then thoroughly mixed to obtain material A0. Subsequently, material A0 is sintered at 920℃ for 10 hours in an oxygen-containing atmosphere. After coarse crushing, fine crushing, sieving, and iron removal, the high-entropy layered oxide Na is finally obtained. 0.93 Ca 0.003 (Ni 0.3 Fe 0.3 Mn 0.3 Cu 0.02 Mg 0.04 Zr 0.08 )O 2.038 .

[0106] Figure 1 and Figure 2 The SEM morphology and XRD test curves of the material described in Example 1 are shown below. Figure 1 As can be seen, the material described in Example 1 exhibits a good single-crystal morphology; from Figure 2 It can be seen that the material described in Example 1 has a good α-NaFeO2 type layered structure.

[0107] Example 2

[0108] This embodiment provides a high-entropy layered oxide, the specific composition of which and its preparation method are as follows:

[0109] (1) A mixed aqueous solution of nickel sulfate, ferrous sulfate, manganese sulfate, strontium sulfate, zinc sulfate, and cerium sulfate with a total concentration of 2 mol / L was prepared according to the molar ratio of six elements Ni, Fe, Mn, Sr, Zn, and Ce of 30:30:30:2:4:8. A mixed aqueous solution of NH3·H2O with a concentration of 0.2 mol / L and sodium hydroxide with a concentration of 10 mol / L was added to adjust the pH of the solution to 10.5. The solution was stirred under an inert atmosphere and co-precipitated at 60℃ for 110 h to obtain a precursor Ni with an average particle size of 8 μm. 0.3 Fe 0.3 Mn 0.3 Sr 0.02 Zn 0.04 Ce 0.08 (OH) 2.24 .

[0110] (2) Sodium carbonate and Li₂O were added to the precursor respectively, and the mixing ratio was based on the molar ratio of Ni. 0.3 Fe 0.3 Mn 0.3 Sr 0.0 2Zn 0.04 Ce 0.08 (OH) 2.24 The total metal content of Na:Li was 1:0.94:0.006. The mixture was homogeneously prepared to obtain material A0. Then, under an oxygen-containing atmosphere, material A0 was sintered at 920℃ for 10 hours. After coarse crushing, fine crushing, sieving, and iron removal, the high-entropy layered oxide Na was finally obtained. 0.94 Li 0.006 (Ni 0.3 Fe 0.3 Mn 0.3 Sr 0.02 Zn 0.04 Ce 0.08 )O 2.043 .

[0111] Example 3

[0112] This embodiment provides a high-entropy layered oxide, the specific composition of which and its preparation method are as follows:

[0113] (1) A mixed aqueous solution of nickel sulfate, ferrous sulfate, manganese sulfate, copper sulfate, magnesium sulfate, and titanium oxysulfate with a total concentration of 2 mol / L was prepared according to the molar ratio of six elements Ni, Fe, Mn, Cu, Mg, and Ti of 25:27:44:3:2:5. A mixed aqueous solution of NH3·H2O with a concentration of 0.2 mol / L and sodium hydroxide with a concentration of 10 mol / L was added to adjust the pH of the solution to 10.6. The mixture was stirred under an inert atmosphere and co-precipitated at 60℃ for 105 h to obtain a precursor Ni with an average particle size of 8 μm. 0.25 Fe 0.27 Mn0.44 Cu 0.03 Mg 0.02 Ti 0.05 (OH) 2.22 .

[0114] (2) Sodium carbonate and K2O are added to the precursor respectively, and the mixing ratio is according to the molar ratio of Ni 0.25 Fe 0.27 Mn 0.44 Cu 0.03 Mg 0.02 Ti 0.05 (OH) 2.22 The total metal content of Na:K = 1:0.82:0.006 was uniformly mixed to obtain material A0. Then, under an oxygen-containing atmosphere, material A0 was sintered at 920℃ for 10 hours. After coarse crushing, fine crushing, sieving, and iron removal processes, the high-entropy layered oxide cathode material Na was finally obtained. 0.82 K 0.006 (Ni 0.25 Fe 0.27 Mn 0.44 Cu 0.03 Mg 0.02 Ti 0.05 )O 2.098 .

[0115] Example 4

[0116] This embodiment provides a high-entropy layered oxide, the specific composition of which and its preparation method are as follows:

[0117] (1) A mixed aqueous solution of nickel sulfate, ferrous sulfate, manganese sulfate, zinc sulfate, magnesium sulfate, and titanium oxysulfate with a total concentration of 2 mol / L was prepared according to the molar ratio of six elements Ni, Fe, Mn, Zn, Mg, and Ti of 25:27:44:3:2:5. A mixed aqueous solution of NH3·H2O with a concentration of 0.2 mol / L and sodium hydroxide with a concentration of 10 mol / L was added to adjust the pH of the solution to 10.5. The mixture was stirred under an inert atmosphere and co-precipitated at 60℃ for 102 h to obtain a precursor Ni with an average particle size of 8 μm. 0.25 Fe 0.27 Mn 0.44 Zn 0.03 Mg 0.02 Ti 0.05 (OH) 2.22 .

[0118] (2) Sodium carbonate and K2O are added to the precursor respectively, and the mixing ratio is according to the molar ratio of Ni 0.25 Fe 0.27 Mn 0.44 Zn 0.03 Mg 0.02 Ti0.05 (OH) 2.22 The total metal content of Na:K = 1:0.82:0.006 was uniformly mixed to obtain material A0. Then, under an oxygen-containing atmosphere, material A0 was sintered at 1000℃ for 3 hours. After processes such as coarse crushing, fine crushing, sieving, and iron removal, the high-entropy layered oxide cathode material Na was finally obtained. 0.82 K 0.006 (Ni 0.25 Fe 0.27 Mn 0.44 Zn 0.03 Mg 0.02 Ti 0.05 )O 2.098 .

[0119] Example 5

[0120] This embodiment provides a high-entropy layered oxide, the specific composition of which and its preparation method are as follows:

[0121] (1) A mixed aqueous solution of nickel sulfate, ferrous sulfate, manganese sulfate, copper sulfate, magnesium sulfate, and titanium oxysulfate with a total concentration of 2 mol / L was prepared according to the molar ratio of six elements Ni, Fe, Mn, Co, Ba, and Zr of 25:27:44:3:2:5. A mixed aqueous solution of NH3·H2O with a concentration of 0.2 mol / L and sodium hydroxide with a concentration of 10 mol / L was added to adjust the pH of the solution to 10.6. The mixture was stirred under an inert atmosphere and co-precipitated at 60℃ for 105 h to obtain a precursor Ni with an average particle size of 8 μm. 0.25 Fe 0.27 Mn 0.44 Co 0.03 Ba 0.02 Zr 0.05 (OH) 2.22 .

[0122] (2) Sodium carbonate and Li₂O were added to the precursor respectively, and the mixing ratio was based on the molar ratio of Ni. 0.25 Fe 0.27 Mn 0.44 Co 0.03 Ba 0.02 Zr 0.05 (OH) 2.22 The total metal content of Na:Li was 1:0.82:0.006. The mixture was homogeneously prepared to obtain material A0. Then, under an oxygen-containing atmosphere, material A0 was sintered at 880℃ for 13 hours. After coarse crushing, fine crushing, sieving, and iron removal, the high-entropy layered oxide cathode material Na was finally obtained. 0.82 Li 0.006 (Ni 0.25 Fe 0.27 Mn 0.44 Co 0.03 Ba0.02 Zr 0.05 )O 2.098 .

[0123] Example 6

[0124] This embodiment provides a high-entropy layered oxide, the specific composition of which and its preparation method are as follows:

[0125] (1) A mixed aqueous solution of nickel sulfate, ferrous sulfate, manganese sulfate, copper sulfate, magnesium sulfate, and zirconium sulfate with a total concentration of 2 mol / L was prepared according to the molar ratio of six elements Ni, Fe, Mn, Cu, Mg, and Zr of 21:25:45:2:4:2. A mixed aqueous solution of NH3·H2O with a concentration of 0.2 mol / L and sodium hydroxide with a concentration of 10 mol / L was added to adjust the pH of the solution to 10.6. The solution was stirred under an inert atmosphere and co-precipitated at 60℃ for 100 h to obtain a precursor Ni with an average particle size of 8 μm. 0.21 Fe 0.25 Mn 0.45 Cu 0.02 Mg 0.04 Zr 0.02 (OH) 2.02 .

[0126] (2) Sodium carbonate and CaO are added to the precursor respectively, and the mixing ratio is based on the molar ratio of precursor Ni. 0.21 Fe 0.25 Mn 0.45 Cu 0.02 Mg 0.04 Zr 0.02 (OH) 2.02 The total amount of metallic elements in the mixture is Na:Ca = 1:0.93:0.003. The mixture is then thoroughly mixed to obtain material A0. Subsequently, material A0 is sintered at 920℃ for 10 hours in an oxygen-containing atmosphere. After coarse crushing, fine crushing, sieving, and iron removal, the high-entropy layered oxide Na is finally obtained. 0.93 Ca 0.003 (Ni 0.21 Fe 0.25 Mn 0.45 Cu 0.02 Mg 0.04 Zr 0.02 )O 2.053 .

[0127] Comparative Example 1

[0128] This comparative example provides a high-entropy layered oxide, the specific composition and preparation method of which are as follows:

[0129] (1) A mixed aqueous solution of nickel sulfate, ferrous sulfate, and manganese sulfate was prepared according to the molar ratio of Ni, Fe, and Mn of 33:33:33. The pH of the solution was adjusted to 10.6 by adding a mixed aqueous solution of NH3·H2O (0.2 mol / L) and sodium hydroxide (10 mol / L). The mixture was stirred under an inert atmosphere and co-precipitated at 60°C for 100 h to obtain a precursor Ni with an average particle size of 8 μm. 0.33 Fe 0.33 Mn 0.33 (OH) 1.98 .

[0130] (2) Sodium carbonate was added to the precursor separately, and the mixing ratio was according to the molar ratio of Ni. 0.33 Fe 0.33 Mn 0.33 (OH) 1.98 The total amount of metallic elements in the mixture is Na = 1:1. The mixture is then homogenized to obtain material A0. Subsequently, material A0 is sintered at 930℃ for 10 hours in an oxygen-containing atmosphere. After coarse crushing, fine crushing, sieving, and iron removal, the high-entropy layered oxide Na(Ni) is finally obtained. 0.33 Fe 0.33 Mn 0.33 )O2.

[0131] Comparative Example 2

[0132] This comparative example provides a high-entropy layered oxide, the specific composition and preparation method of which are as follows:

[0133] (1) A mixed aqueous solution of nickel sulfate, ferrous sulfate, and manganese sulfate was prepared according to the molar ratio of Ni, Fe, and Mn of 26:28:46. The pH of the solution was adjusted to 10.6 by adding a mixed aqueous solution of NH3·H2O (0.2 mol / L) and sodium hydroxide (10 mol / L). The mixture was stirred under an inert atmosphere and co-precipitated at 60°C for 100 h to obtain a precursor Ni with an average particle size of 8 μm. 0.26 Fe 0.28 Mn 0.46 (OH)2.

[0134] (2) Sodium carbonate was added to the precursor separately, and the mixing ratio was according to the molar ratio of Ni. 0.26 Fe 0.28 Mn 0.46 The total metal content of (OH)₂ and Na is 1:1. After uniform mixing, material A0 is obtained. Then, under an oxygen-containing atmosphere, material A0 is sintered at 930℃ for 10 hours. Following coarse crushing, fine crushing, sieving, and iron removal processes, the high-entropy layered oxide Na(Ni)₂ is finally obtained. 0.26 Fe 0.28 Mn 0.46 )O2.

[0135] Comparative Example 3

[0136] This comparative example provides a high-entropy layered oxide, the specific composition and preparation method of which are as follows:

[0137] (1) A mixed aqueous solution of nickel sulfate, ferrous sulfate, and manganese sulfate was prepared according to the molar ratio of Ni, Fe, and Mn of 33:33:33. The pH of the solution was adjusted to 10.6 by adding a mixed aqueous solution of NH3·H2O (0.2 mol / L) and sodium hydroxide (10 mol / L). The mixture was stirred under an inert atmosphere and co-precipitated at 60°C for 100 h to obtain a precursor Ni with an average particle size of 8 μm. 0.33 Fe 0.33 Mn 0.33 (OH) 1.98 .

[0138] (2) Sodium carbonate and CaO are added to the precursor respectively, and the mixing ratio is based on the molar ratio of Ni. 0.33 Fe 0.33 Mn 0.33 (OH) 1.98 The total amount of metallic elements in the mixture was 1:1:0.003 (Na:Ca = 1:1:0.003), and the mixture was thoroughly mixed to obtain material A0. Then, under an oxygen-containing atmosphere, material A0 was sintered at 930℃ for 10 hours. After coarse crushing, fine crushing, sieving, and iron removal, the high-entropy layered oxide Na was finally obtained. 0.994 Ca 0.003 (Ni 0.33 Fe 0.33 Mn 0.33 )O2.

[0139] Comparative Example 4

[0140] This comparative example provides a high-entropy layered oxide, the specific composition and preparation method of which are as follows:

[0141] A mixed aqueous solution of nickel sulfate, ferrous sulfate, manganese sulfate, copper sulfate, and zirconium sulfate with a total concentration of 2 mol / L was prepared according to the molar ratio of six elements Ni, Fe, Mn, Cu, and Zr of 30:30:30:6:8. The pH of the solution was adjusted to 10.6 by adding a mixed aqueous solution of 0.2 mol / L NH3·H2O and 10 mol / L sodium hydroxide. The mixture was stirred under an inert atmosphere and co-precipitated at 60℃ for 100 h to obtain a precursor Ni with an average particle size of 8 μm. 0.3 Fe 0.3 Mn 0.3 Cu 0.02 Mg 0.04 Zr 0.08 (OH) 2.24 .

[0142] (2) Sodium carbonate and CaO are added to the precursor respectively, and the mixing ratio is based on the molar ratio of precursor Ni. 0.3 Fe 0.3 Mn 0.3 Cu 0.06 Zr 0.08 (OH) 2.24 The total amount of metallic elements in the mixture is Na:Ca = 1:0.93:0.003. The mixture is then thoroughly mixed to obtain material A0. Subsequently, material A0 is sintered at 920℃ for 10 hours in an oxygen-containing atmosphere. After coarse crushing, fine crushing, sieving, and iron removal, the high-entropy layered oxide Na is finally obtained. 0.93 Ca 0.003 (Ni 0.3 Fe 0.3 Mn 0.3 Cu 0.06 Zr 0.08 )O 2.038 .

[0143] Comparative Example 5

[0144] This comparative example provides a high-entropy layered oxide, the specific composition and preparation method of which are as follows:

[0145] A mixed aqueous solution of nickel sulfate, ferrous sulfate, manganese sulfate, copper sulfate, and magnesium sulfate with a total concentration of 2 mol / L was prepared according to the molar ratio of six elements Ni, Fe, Mn, Cu, and Mg of 30:30:30:2:4. The pH of the solution was adjusted to 10.6 by adding a mixed aqueous solution of 0.2 mol / L NH3·H2O and 10 mol / L sodium hydroxide. The mixture was stirred under an inert atmosphere and co-precipitated at 60℃ for 100 h to obtain a precursor Ni with an average particle size of 8 μm. 0.3 Fe 0.3 Mn 0.3 Cu 0.02 Mg 0.04 (OH) 2.06 .

[0146] (2) Sodium carbonate and CaO are added to the precursor respectively, and the mixing ratio is based on the molar ratio of precursor Ni. 0.3 Fe 0.3 Mn 0.3 Cu 0.02 Mg 0.04 (OH) 2.06 The total amount of metallic elements in the mixture is Na:Ca = 1:1:0.003. The mixture is then thoroughly mixed to obtain material A0. Subsequently, material A0 is sintered at 920℃ for 10 hours in an oxygen-containing atmosphere. After coarse crushing, fine crushing, sieving, and iron removal, the high-entropy layered oxide Na is finally obtained. 0.994 Ca 0.003 (Ni 0.3 Fe0.3 Mn 0.3 Cu 0.02 Mg 0.04 )O 2.06 .

[0147] Test case

[0148] The high-entropy layered oxides provided in the embodiments and comparative examples of this application are analyzed and evaluated using the following specific methods:

[0149] (1) Analysis of composition and crystal structure:

[0150] The composition of the material was determined by ICP (Agilent 720) emission spectroscopy, and the crystal structure was analyzed by X-ray diffractometer (Malvern Aeris benchtop). The data such as Na occupancy and octahedral interlayer spacing were obtained by refining the XRD data.

[0151] (2) Morphological characteristics:

[0152] The surface morphology of the material was observed using a scanning electron microscope, specifically a Phenom Pro electron microscope.

[0153] (3) Electrical performance testing

[0154] The high-entropy layered oxides provided in the various embodiments and comparative examples were used as positive electrode active materials to assemble batteries, which were then subjected to charge-discharge tests at 25°C. The battery assembly method is as follows:

[0155] 52.5 mg of positive electrode active material, 15 mg of acetylene black, and 7.5 mg of polyvinylidene fluoride (PVDF) were mixed with NMP as the solvent and the solid content was 50%. The mixture was coated onto an aluminum foil current collector and dried at 120°C for 12 hours. The dried electrode was then pressed into a positive electrode sheet with a diameter of 11 mm and a thickness of 100 μm using a roller press at a pressure of 100 MPa, with an areal density of 10 mg / cm³. 2 Then, using this positive electrode, a 2032-type coin cell was fabricated in a glove box under an Ar atmosphere with a dew point of -80°C. The negative electrode used sodium metal with a diameter of 17 mm and a thickness of 1 mm. The electrolyte was a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in equal volumes, with 1 M NaPF6 as the supporting electrolyte. The separator was a porous polyethylene membrane with a thickness of 25 μm. Additionally, the 2032 battery included gaskets and corrugated washers, and was assembled into a coin-shaped battery from the positive and negative electrode casings.

[0156] (3-1) Initial discharge specific capacity test:

[0157] The initial discharge specific capacity was set as follows: After the 2032 coin-shaped battery was manufactured (see Example 1 for the manufacturing process), it was placed for 24 hours. After the open circuit voltage (OCV) stabilized, the test temperature was adjusted to 25°C, and the current density at the positive electrode was set to 0.18 mA / mg (0.2C). It was charged until the termination voltage was 4.1V or 4.2V. After resting for 1 hour, it was discharged until the capacity at the termination voltage of 2.0V was measured.

[0158] (3-2) Capacity retention test after 50 laps:

[0159] The method for calculating the capacity retention rate after 50 cycles is as follows: Perform charge-discharge cycles under the above conditions, and calculate the discharge specific capacity on the 50th cycle ÷ the initial discharge specific capacity × 100%.

[0160] (3-3) Ratio Performance Test:

[0161] After the 2032 coin-shaped battery was placed for 24 hours and the open circuit voltage (OCV) stabilized, the test temperature was adjusted to 25°C, the current density of the positive electrode was set to 1.8mA / mg (2C), and it was charged until the termination voltage was 4.1V. After resting for 1 hour, it was discharged until the capacity at the termination voltage of 2.0V was reached.

[0162] The specific test results are shown in the table below:

[0163] Table 1

[0164] Table 2

[0165]

[0166]

[0167] As can be seen from the high-entropy layered oxide data (Table 1) and 2-4.2V ultra-high voltage cycling data (Table 2) provided in the embodiments and comparative examples above for 2-4.1V high-voltage cycling at 25°C, the high-entropy layered oxides in this application improve the high-voltage cycling performance, initial discharge specific capacity, and 2C high-rate discharge specific capacity of the material through the design of the high-entropy layered oxide composition. This indicates that the crystal structure of the material provided in this application has good stability, which is beneficial to the reversible and rapid insertion and extraction of sodium ions during charging and discharging, and maintains the stability of the crystal structure during long-term cycling. Furthermore, by adjusting the ratio and selection of metal elements, this application achieves the control of the TM-O octahedral interlayer spacing d(O-TM-O) and the octane fraction Occ(Na) in the Na-O octahedral layer of the crystal structure, further improving the various properties of the material.

[0168] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A high-entropy layered oxide, characterized in that, The high-entropy layered oxide has the following general formula: Na a B b (Ni x1 M x2 M' x3 Fe y Mn z M” z’ )O 2+c Wherein, 0.8 < a < 1.0, 0 < b < 0.2, 0 < c < 0.2, 0.2 < x1 < 0.4, x2 > 0, x3 > 0, 0.2 < x1 + x2 + x3 < 0.6, 0 < y < 0.4, 0 < z < 0.5, 0 < z' < 0.3, 0.9 < x1 + x2 + x3 + y + z + z' < 1.1, and the ratio of (x2 + x3) to z' ranges from 0.75 to 1.0; B, M, M', and M” are metallic elements, B is selected from Li, K, and Ca; M and M' are selected from two different elements from Sr, Cd, Mg, Zn, Cu, Ba, and Co; and M” is selected from Zr, Ce, W, and Ti.

2. The high-entropy layered oxide according to claim 1, characterized in that, The high-entropy layered oxide has an α-NaFeO2 type layered structure, wherein element B is doped in the Na-O octahedral layer, and after doping with element B, the occupancy rate of element Na in the Na-O octahedral layer, Occ(Na), is between 75% and 95%.

3. The high-entropy layered oxide according to claim 1, characterized in that, Elements M, M', and M” are doped into the transition metal-oxygen (TM-O) octahedral layer, and the interlayer spacing d(O-TM-O) of the TM-O octahedral layer after doping with M, M', and M” elements is between between.

4. A method for preparing a high-entropy layered oxide according to any one of claims 1-3, characterized in that, Includes the following steps: S1, mix nickel-iron-manganese hydroxide precursor A containing metal elements M, M', and M”, sodium source, and oxide of metal element B to obtain a mixture; S2, the mixture is sintered in an oxygen-containing atmosphere to obtain a high-entropy layered oxide.

5. The method for preparing high-entropy layered oxides according to claim 4, characterized in that, In S1, the molar ratio of sodium element in the sodium source to the total amount of metal element in precursor A is 0.75:1 to 0.95:1; And / or, taking metal element B as the basis, the molar ratio of the oxide of metal element B to the total amount of metal element in precursor A is 0.001 to 0.2:

1.

6. The method for preparing high-entropy layered oxides according to claim 4, characterized in that, In S2, the sintering temperature is 700℃~1000℃ and the sintering time is 3h~20h.

7. The method for preparing high-entropy layered oxides according to any one of claims 4-6, characterized in that, The sodium source includes at least one of sodium carbonate, sodium hydroxide, sodium nitrate, and sodium acetate.

8. A positive electrode sheet, characterized in that, include: Positive 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 comprises a high-entropy layered oxide as described in any one of claims 1-3 or a high-entropy layered oxide prepared by the preparation method described in any one of claims 4-7.

9. A sodium-ion battery, characterized in that, Includes the positive electrode sheet as described in claim 8.

10. An electrical device, characterized in that, Including the sodium-ion battery as described in claim 9.

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