Sodium layered metal oxide and its manufacturing method, secondary battery and power consumption device

Abstract

This application discloses sodium layered metal oxides, methods for producing the same, secondary batteries, and power consumption devices. The general chemical formula of sodium layered metal oxides is Na 1-x A x C y M 1-y O2, where M comprises a transition metal element, A comprises at least one of a Group IIA element, a Group V metal element, a Group VIA metal element, and a Group IIIB element, the ionic radius of A is greater than the ionic radius of M, C comprises at least one of a Period 3 metal element, a Period 4 metal element, and a Period 5 metal element, the valence of C is equal to or less than the valence of M, x = 0.001 to 0.150, y = 0.001 to 0.500. Doping the sodium layered metal oxide with A and C makes it less likely to undergo phase slippage or phase change in a sodium-free state, resulting in excellent stability and improved cycle performance and service life.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to a Chinese patent application filed with the China Patent Office on May 15, 2023, bearing application number 202310541146.6 and entitled "Sodium layered metal oxide and its manufacturing method, secondary battery and power consumption device," the entire contents of which are incorporated herein by reference.

[0002] The present application belongs to the field of battery material technology, and specifically relates to a sodium layered metal oxide and its manufacturing method, a secondary battery and a power consuming device. [Background technology]

[0003] Sodium-ion batteries have become an important candidate for large-scale energy storage systems due to the advantages of abundant sodium reserves, low cost, and unique battery safety characteristics. Sodium layered metal oxides, which may be represented as NaMO2, where M is a transition metal element, have characteristics such as high specific capacity, high compaction density, and tunable voltage range, and can be used as positive electrode materials for sodium-ion batteries.

[0004] However, sodium layered metal oxides have the defect of being structurally unstable, and sodium ion batteries are prone to undergo phase changes as the positive electrode material sodium layered metal oxide during the cycle charge-discharge process, thereby affecting their cycle life. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above problems, the present application aims to solve the technical problem of the unstable structure of sodium layered metal oxide, and provides a sodium layered metal oxide, a method for producing the same, a secondary battery and a power consumption device. [Means for solving the problem]

[0006] According to a first aspect, an embodiment of the present application provides a sodium layered metal oxide, the general chemical formula of which is Na 1-x A x C y M 1-y O2, where M comprises a transition metal element; A includes at least one of a Group IIA element, a Group V metal element, a Group VIA metal element, and a Group IIIB element, and the ionic radius of A is larger than the ionic radius of M; C includes at least one of a metal element of the third period, a metal element of the fourth period, and a metal element of the fifth period, and the valence of C is equal to or less than the valence of M; x=0.001~0.150, y=0.001~0.500.

[0007] By doping sodium layered metal oxide with specific element species A and C, A has a larger ionic radius than transition metal M and a larger valence than sodium ions. Therefore, the strong Coulomb interaction between the high-value element A and oxygen atoms makes it difficult for layer slippage and phase change to occur in the sodium layered metal oxide in a sodium-free state, thereby supporting the layered structure. Element C, which has a lower valence than transition metal M, balances the valence and reduces the increase in lattice stress caused by local valence changes. Therefore, the sodium layered metal oxide doped with element species A and C according to the embodiments of the present application has excellent stability and can improve its cycle performance and service life.

[0008] In one embodiment, A is a doping element for the sodium site and C is a doping element for M.

[0009] A-doping of the sodium site and C-doping of the M site form stable dual-site doped sodium layered metal oxides.

[0010] In some embodiments, the valence of A is +2 to +4.

[0011] After doping sodium layered metal oxide with A, which has a valence of +2 to +4, the strong Coulomb interaction between the doping element A and oxygen atoms with respect to +1 sodium ions makes it less likely for layer slippage to occur in a sodium-free state, and provides excellent structural pillar effects, thereby improving the crystal structure stability of the sodium layered metal oxide.

[0012] In some embodiments, the Group IIA element in A comprises at least one of calcium, strontium, and barium; the Group V metal element comprises at least one of antimony and bismuth; the Group VIA metal element comprises tellurium; the Group IIIB element comprises at least one of yttrium, cerium, and lanthanum; or A comprises calcium.

[0013] The ionic radii of calcium, strontium, barium, antimony, bismuth, yttrium, cerium, lanthanum, and tellurium are close to or slightly larger than the ionic radius of sodium ion, and have higher valences than sodium ion, so these doping elements can be used to dope the sodium sites of sodium layered metal oxides, and the strong Coulomb interaction with oxygen atoms can better suppress interlayer slippage of sodium layered metal oxides.On the other hand, calcium element not only dopes well at sodium sites, but also can make the crystal structure of sodium layered metal oxides more stable.

[0014] In some embodiments, the third period metal element in C includes at least one of magnesium and aluminum, the fourth period metal element includes at least one of zinc, gallium, and germanium, and the fifth period metal element includes zirconium, or C includes aluminum.

[0015] The ionic radii of zirconium, magnesium, aluminum, zinc, gallium, and germanium are close to or smaller than the ionic radius of the transition metal M, and their valences are equal to or less than that of the transition metal M. Therefore, they can be easily doped into the transition metal M site, balance the valence, and reduce the risk of an increase in lattice stress due to a relatively large local valence change. On the other hand, aluminum element can be well doped into the transition metal M site, and can better balance the valence.

[0016] In some embodiments, M includes at least two of nickel, manganese, copper, and iron, or M includes nickel, iron, and manganese.

[0017] Sodium layered metal oxides formed from various transition metals, namely nickel, manganese, copper, and iron, not only make it difficult for transition metal ions to move in the transition metal layer, but also bond with the doping element C at the sodium site, thereby better suppressing phase changes and improving electrochemical stability in the sodium-free state. Meanwhile, nickel, iron, and manganese jointly form the transition metal element M at the M site, and thus sodium layered metal oxides formed from the three transition metals of nickel, iron, and manganese not only have the characteristic of high specific capacity, but also allow easy doping with the doping element C.

[0018] In one embodiment, the molar ratio of nickel, iron, and manganese in M ​​is (0.2-0.4):(0.2-0.4):(0.2-0.6).

[0019] The sodium layered metal oxide formed by the three transition metals of nickel, iron and manganese under the above molar ratio conditions has a high specific capacity and good stability.

[0020] In one embodiment, x=0.01 to 0.02, and y=0.01 to 0.02.

[0021] By carrying out doping modification with doping element A and doping element C under the above doping mass conditions, the stability of the sodium layered metal oxide can be improved and the impact on the energy density of the sodium layered metal oxide is small.

[0022] In one embodiment, the sodium layered metal oxide has an O3 type crystal structure.

[0023] Sodium layered metal oxides with an O3-type crystal structure have a high specific capacity and can be commonly used as positive electrode materials for sodium-ion batteries.

[0024] In some embodiments, the chemical formula of the sodium layered metal oxide is Na 0.98 Ca 0.02 Ni 1 / 3 Fe 0.31 Al 0.02 Mn 1 / 3 It is O2.

[0025] The sodium layered metal oxide of the above formula not only has excellent structural stability, but also has high specific capacity and energy density, and has excellent overall performance when used as a positive electrode active material.

[0026] According to a second aspect, an embodiment of the present application provides a method for producing the sodium layered metal oxide, the method comprising the steps of: subjecting a mixture containing a source of a transition metal M and a source of a doping element C to a first polishing process and a first calcination process to obtain an intermediate product; mixing the intermediate product, the sodium source and the doping element A source to carry out a second polishing treatment, and then carrying out a second calcination treatment to obtain a sodium layered metal oxide.

[0027] In the process of preparing the sodium layered metal oxide, the transition metal M site is first doped with C, and then the sodium site is doped with A, thereby obtaining a sodium layered metal oxide doped with both the sodium site and the transition metal M site. This preparation method is not only simple, but also allows for easy doping, and the obtained sodium layered metal oxide has very good stability.

[0028] In some embodiments, the step of preparing a mixture comprising a source of a transition metal M and a source of a doping element C comprises: preparing an aqueous solution of a source of a transition metal M and an aqueous solution of a source of a doping element C, respectively; adding a complexing agent to the aqueous solution of the transition metal M source and the aqueous solution of the doping element C source to carry out a complexing reaction, thereby obtaining a first gel-like substance and a second gel-like substance, respectively; and mixing and drying the first gel-like substance and the second gel-like substance to obtain a mixture.

[0029] By adopting the sol-gel method, the transition metal M source and the doping element C source can be mixed uniformly, and uniform doping can be achieved more effectively.

[0030] In some embodiments, (1) the complexing agent includes at least one of citric acid, oxalic acid, glutamic acid, polypropylene alcohol, polyvinylidene fluoride, and polyacrylamide; (2) The temperature of the complexation reaction is 40 to 100°C; (3) The pH value of the complexation reaction is 7 to 11.

[0031] Depending on the type of the complexing agent and the complexing reaction conditions, a gel-like substance can be formed from the transition metal M source and the doping element C source, respectively.

[0032] In some embodiments, the first firing step comprises firing at 800-950°C for 6-10 hours, and then lowering the temperature to 200-600°C for 3-6 hours; and / or The second firing treatment involves firing at 800 to 950°C for 6 to 10 hours, and then lowering the temperature to 200 to 600°C for 3 to 6 hours.

[0033] The first calcination treatment conditions can realize C element doping at the M site, while the second calcination treatment conditions can realize A doping at the sodium site.

[0034] In some embodiments, (1) a source of a transition metal M comprising at least one of a soluble halide salt, acetate, carbonate, nitrate, sulfate, hydroxide, and oxide of M; (2) the source of doping element C includes at least one of soluble halogen salts, acetates, carbonates, nitrates, sulfates, hydroxides, and oxides of C; (3) the source of doping element A comprises at least one of a soluble halide salt, acetate, carbonate, nitrate, sulfate, hydroxide, and oxide of A; (4) The sodium source contains at least one of sodium halide, sodium acetate, sodium carbonate, sodium nitrate, sodium sulfate, sodium hydroxide, and sodium oxide.

[0035] The material type of the transition metal M source can provide the M element for the preparation of sodium layered metal oxide, the material type of the doping element C source can provide the C element for the preparation of sodium layered metal oxide, the material type of the doping element A source can provide the A element for the preparation of sodium layered metal oxide, and the sodium source can provide the sodium element for the preparation of sodium layered metal oxide.

[0036] According to a third aspect, an embodiment of the present application provides a secondary battery, wherein the positive electrode plate of the secondary battery contains the sodium layered metal oxide according to the first aspect of the embodiment of the present application and / or the sodium layered metal oxide obtained by the manufacturing method according to the second aspect of the embodiment of the present application.

[0037] By using the sodium layered metal oxide according to the first embodiment of the present application and / or the sodium layered metal oxide produced by the production method according to the second embodiment of the present application as the positive electrode active material in the positive electrode plate of a secondary battery, the material particles on the surface of the positive electrode active material layer are less likely to be damaged or shed due to the structural stability unique to the sodium layered metal oxide.In this way, side reactions on the surface of the positive electrode active material layer are reduced, thereby reducing the capacity fade phenomenon and improving cycle performance and service life.

[0038] According to a fourth aspect, an embodiment of the present application provides a power consuming device, the power consuming device including a secondary battery according to the third aspect of the embodiment of the present application.

[0039] By employing the secondary battery according to the third aspect of the embodiment of the present application, the power consuming device can operate for a longer period of time.

[0040] The above description is merely a summary of the technical solution of the present application. In order to make the technical solution of the present application more clearly understandable, and to implement it in accordance with the content of the specification, and to make the above and other objectives, features and advantages of the present application more clearly comprehensible, the following particularly cites specific embodiments of the present application to describe them. [Brief explanation of the drawings]

[0041] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments. The drawings are for the purpose of illustrating the preferred embodiments only and are not to be considered as limitations on the present application. And like drawing reference numerals represent like elements in all drawings. In the drawings: [Figure 1]1 is a schematic diagram of a sodium layered metal oxide of an example of the present application before and after doping. FIG. [Figure 2] 1 is a flowchart of a method for producing a sodium layered metal oxide according to an embodiment of the present application. [Figure 3] 1 is a structural schematic diagram of an embodiment of a secondary battery in an example of the present application; [Figure 4] FIG. 4 is an exploded schematic view of the secondary battery shown in FIG. [Figure 5] 1 is a structural schematic diagram of an embodiment of a battery module in an embodiment of the present application; [Figure 6] 1 is a structural schematic diagram of an embodiment of a battery pack in an example of the present application; [Figure 7] FIG. 7 is a schematic exploded view of the battery pack shown in FIG. 6. [Figure 8] 1 is a schematic diagram of one embodiment of a power consuming device including a battery as a power source according to an example of the present application. [Figure 9] FIG. 1 is an XRD curve diagram of an example of NaCaNiFeAlMnO in the present application. [Figure 10] FIG. 2 is an XRD curve diagram of NaNi1 / 3Fe1 / 3Mn1 / 3O2, a comparative example of the present application. [Figure 11] FIG. 2 is an XRD curve diagram of comparative example Na0.98Ca0.02Ni1 / 3Fe1 / 3Mn1 / 3O2 of the present application. [Figure 12] FIG. 2 is an XRD curve diagram of NaNi1 / 3Fe0.31Al0.02Mn1 / 3O2, a comparative example of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0042] The following describes in detail the embodiments of the technical solution of the present application in conjunction with the drawings. The following embodiments are only used to more clearly explain the technical solution of the present application, and are merely examples, which do not limit the protection scope of the present application.

[0043] 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 of this application, and the terms used herein are only for describing specific embodiments and are not intended to limit this application. The terms "comprises" and "having" and any variations thereof in the specification and claims of this application and the description of the drawings above are intended to cover a non-exclusive "comprise."

[0044] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only for distinguishing different objects, and should not be understood as indicating or implying the relative importance or the number, specific order, or hierarchical relationship of the technical features shown. In the description of the embodiments of the present application, unless otherwise expressly and specifically limited, the meaning of "plurality" is two or more.

[0045] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. Appearances of this phrase in various locations throughout the specification do not necessarily all refer to the same embodiment, nor are they mutually exclusive, independent, or alternative embodiments. Those skilled in the art can explicitly or implicitly understand that the embodiments described herein can be combined with other embodiments.

[0046] In the description of the embodiments of this application, the term "and / or" is merely a relation that describes related objects and indicates that three relations may exist. For example, A and / or B may represent three cases: A alone, a combination of A and B, and B alone. In addition, the character " / " in this specification generally indicates that the related objects before and after are in an "or" relationship.

[0047] In describing the embodiments of this application, the term "plurality" refers to two or more (including two); similarly, "sets" refers to two or more (including two sets); "plurality" refers to two or more (including two); "at least one" refers to one or more (including one, two, three, etc.).

[0048] In describing the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "center," "longitudinal direction," "lateral direction," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial direction," "radial direction," and "circumferential direction" are orientations or positional relationships shown in the drawings, and are intended only to facilitate the description and simplification of the embodiments of the present application. They do not indicate or imply that the devices or elements referred to have a specific orientation or must be configured and operated in a specific orientation, and therefore should not be understood as limitations of the embodiments of the present application.

[0049] In the description of the embodiments of the present application, unless otherwise clearly defined or limited, the technical terms "attached," "connected," "connected," "fixed," etc. should be understood in a broad sense, and may refer to, for example, a fixed connection, a detachable connection, or an integral connection, a mechanical connection, an electrical connection, a direct connection, an indirect connection via an intermediate medium, internal communication between two elements, or an interactive relationship between two elements. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application according to specific circumstances.

[0050] With the increasing scarcity of traditional energy resources, the development of new energy storage devices is receiving increasing attention. Secondary batteries have attracted much attention due to their high energy density, high theoretical capacity, good cycle stability, and environmental protection properties. Secondary batteries can be used in energy storage power systems such as hydroelectric, thermal, wind, and solar power plants, and are also widely used in electric transportation tools such as electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As the application fields of secondary batteries as power batteries continue to expand, their market demand is constantly increasing, and performance requirements such as battery cycle performance are also becoming increasingly higher.

[0051] Lithium-ion batteries, as a type of secondary battery, have the characteristics of high energy density, long service life, energy saving and environmental protection. However, due to the global lithium resource limitation and increasing cost, there are challenges to using lithium-ion batteries for large-scale energy storage. Sodium-ion batteries have already become an important candidate for large-scale energy storage systems due to the advantages of abundant sodium reserves in the earth, low cost, and unique battery safety characteristics. Therefore, the development of resource-unlimited, low-cost sodium-ion batteries has the potential for further development in the field of energy storage.

[0052] Sodium layered metal oxides can be used as positive electrode materials for sodium-ion batteries because they have characteristics such as high specific capacity, high compaction density, and adjustable voltage range. However, the structure of sodium layered metal oxides is unstable, and sodium layered metal oxides used as positive electrode materials for sodium-ion batteries are prone to phase changes during the cycle charge-discharge process.

[0053] In the commonly used sodium layered metal oxides, the separation of sodium ions during charging weakens the interlayer interaction, increasing the interlayer spacing. As the interlayer spacing increases, phase stability decreases and layer slippage occurs under thermodynamic driving. This phase change can reoccur at the end of discharge, resulting in stress accumulation and particle fracture in the sodium layered metal oxide particles, reducing structural stability. Furthermore, after the sodium layered metal oxide particles are broken, new surfaces are formed, and side reactions, such as surface oxygen deficiency phase changes, oxidation of solvent molecules, and interfacial side reactions such as transition metal elution, can occur on these new surfaces, potentially leading to rapid battery capacity degradation.

[0054] To solve the problem of structural instability of sodium layered metal oxides, related art has modified sodium layered metal oxides, such as by coating or doping. Surface coating modification is difficult to fundamentally improve the phase change of the internal structure of sodium layered metal oxides, and the effect of inhibiting layer slippage is small. Doping modification tends to ignore the ionic radius parameter of sodium ions, and the ionic radius of commonly used doping elements is close to that of transition metals, making it easy to form doping at the transition metal site. However, excessive doping of inactive elements at the transition metal site tends to reduce the overall capacity. Furthermore, doping of low-valence doping elements at the sodium site also tends to cause phase change problems under sodium-free conditions, leading to insufficient stability.

[0055] Based on the above considerations, in order to solve the problem of the unstable structure of sodium layered metal oxide, the embodiments of the present application combine theoretical calculations and experiments to research and design a new type of doped sodium layered metal oxide, and perform dual-site doping at the sodium site and the transition metal M site of sodium layered metal oxide, thereby making the sodium layered metal oxide more stable and significantly improving its cycle performance and service life.Therefore, the following technical solution is proposed:

[0056] Sodium Layered Metal Oxide According to a first aspect, the present application provides a sodium layered metal oxide. In one embodiment of the present application, the sodium layered metal oxide of the present application has the general chemical formula: Na 1-x A x C y M 1-y It is O2.

[0057] Na 1-x A x C y M 1-y In O2, M includes a transition metal element; A includes at least one of a Group IIA element, a Group V metal element, a Group VIA metal element, and a Group IIIB element; the ionic radius of A is larger than the ionic radius of M; C includes at least one of a third period metal element, a fourth period metal element, and a fifth period metal element; the valence of C is equal to or less than the valence of M; and x is 0.001 to 0.150, and y is 0.001 to 0.500.

[0058] It should be noted that the elements A, C, and M are different from each other, and for example, when an element appears at the A site, C and M do not include this element at the A site. In the embodiments of the present application, the above chemical elements are classified based on the periodic table of elements known in the art, that is, based on the list of chemical elements arranged in ascending order of the charge number of the element nucleus. The periodic table has 7 periods and 16 groups. Each row is called a period, and each column is called a group (Group VIII has three columns).

[0059] By doping sodium layered metal oxide with specific A and C element species, the sodium layered metal oxide can be endowed with excellent stability, thereby enhancing its cycle performance and service life.

[0060] General chemical formula Na 1-x A x C y M 1-yIn O2, A and C are doping elements, where A is the doping element of the sodium site and C is the doping element of M.

[0061] Doping refers to modifying a material with a doping element, substituting the doping site with the doping element. Generally, the lattice constant of the material or the valence of the element in the material is changed to improve the material performance. In the embodiment of the present application, the doping element is used to replace and modify the sodium site and the transition metal M site.

[0062] The doping element A can satisfy the following requirements: (1) its ionic radius is larger than that of the transition metal M, and (2) the valence after doping with the doping element A is larger than the valence of the sodium ion (i.e., +1). After the doping element A is doped into the sodium site of the sodium layered metal oxide, there is a strong Coulomb interaction between the high-valence doping element A and oxygen atoms. When the sodium layered metal oxide is in a sodium-free state, the strong Coulomb interaction between the doping element A and oxygen atoms can suppress the occurrence of interlayer slippage in the sodium layered metal oxide, thereby making it less likely to undergo a phase change and thus supporting the layered structure.

[0063] The doping element C can satisfy the condition that the valence after doping is equal to or less than the valence of the transition metal M. Since the valence after doping with the doping element A is higher than the valence of the sodium ion, doping the transition metal M site with the doping element C having such a low valence can achieve a good balance of valence and reduce the change in lattice stress due to the change in valence after A doping.

[0064] Therefore, in the sodium layered metal oxide of the present application, the sodium site is doped with doping element A and the transition metal M site is doped with doping element C. This dual-site doped sodium layered metal oxide has very good stability, and also has very good cycle performance and service life.

[0065] In some embodiments, the valence after doping with the doping element A is +2 to +4. For example, it may be +2, +3, or +4. As shown in FIG. 1 , doping the sodium layered metal oxide with a doping element A having a doping valence of +2 to +4 results in a stronger Coulomb interaction between the doping element A and oxygen atoms with respect to the +1 sodium ion. This makes the sodium layered metal oxide less susceptible to layer slippage in a sodium-free state, and provides excellent structural pillaring, thereby improving the stability of the crystal structure of the sodium layered metal oxide.

[0066] In some embodiments, the doping element A includes a group IIA element comprising at least one of calcium, strontium, and barium, a group V metal element comprising at least one of antimony and bismuth, a group VIA metal element comprising tellurium, and a group IIIB element comprising at least one of yttrium, cerium, and lanthanum.

[0067] It should be noted that the metallic elements in this application are elements having metallic properties, including metalloids that lie between metals and non-metals, such as tellurium.

[0068] Specifically, the doping element A includes at least one of calcium (Ca), strontium (Sr), barium (Ba), antimony (Sb), bismuth (Bi), yttrium (Y), cerium (Ce), lanthanum (La), and tellurium (Te). Calcium, strontium, and barium can be doped with a valence of +2. Antimony, bismuth, yttrium, and lanthanum can be doped with a valence of +3. Cerium and tellurium can be doped with a valence of +4. Because the ionic radii of calcium, strontium, barium, antimony, bismuth, yttrium, cerium, lanthanum, and tellurium are close to the ionic radius of sodium and have higher valences than sodium ions, these doping elements can be used to dope the sodium sites of sodium-layered metal oxides relatively easily, and the strong Coulomb interaction between these elements and oxygen atoms can suppress interlayer slippage of sodium-layered metal oxides.

[0069] In some embodiments, the doping element A necessarily contains calcium. The calcium ion radius is closer to the sodium ion radius, making it easier to dope into the sodium site. After calcium doping, the risk of additional structural distortion due to doping can be reduced, which is more advantageous for enhancing structural stability. Therefore, the calcium element not only dopes well into the sodium site, but also makes the crystal structure of the sodium-layered metal oxide more stable.

[0070] In some embodiments, the third period metal element of the doping element C comprises at least one of magnesium and aluminum, the fourth period metal element comprises at least one of zinc, gallium, and germanium, and the fifth period metal element comprises zirconium.

[0071] Specifically, the doping element C includes at least one of zirconium (Zr), magnesium (Mg), aluminum (Al), zinc (Zn), gallium (Ga), and germanium (Ge). The ionic radii of zirconium, magnesium, aluminum, zinc, gallium, and germanium are close to or smaller than the ionic radius of the transition metal M, and their valences are equal to or less than the valence of the transition metal M. For example, when the transition metal M is trivalent iron or tetravalent manganese, the doping element can be selected from magnesium, aluminum, zinc, etc. The doping element C can be easily doped into the transition metal M site, and can also balance the valence and reduce changes in lattice stress caused by relatively large local valence changes.

[0072] In some embodiments, the doping element C necessarily contains aluminum, which can not only dope well into the transition metal M sites but also achieve better valence balance.

[0073] In some embodiments, M comprises at least two of nickel (Ni), manganese (Mn), copper (Cu), and iron (Fe). It should be noted that when M comprises various elements, the valence of the transition metal M after doping with the doping element C is equal to or less than the valence of at least one of the transition metals M. The sodium-layered metal oxide formed from various transition metals, i.e., nickel, manganese, copper, and iron, not only makes it difficult for transition metal ions to move in the transition metal layer, but also binds with the doping element C at the sodium site, thereby better suppressing phase change and improving the electrochemical stability in the sodium-free state.

[0074] In some embodiments, M includes nickel, iron, and manganese. Nickel, iron, and manganese form transition metal elements at the M site, and thus, a sodium layered metal oxide formed from three transition metals, nickel, iron, and manganese, not only has a high specific capacity, but also allows easy doping with the doping element C.

[0075] In one embodiment, the molar ratio of nickel, iron, and manganese in M ​​is (0.2-0.4):(0.2-0.4):(0.2-0.6). For example, the molar ratio of nickel, iron, and manganese is 0.2:0.2:0.6, or the molar ratio of nickel, iron, and manganese is 0.25:0.25:0.5, or the molar ratio of nickel, iron, and manganese is 0.3:0.3:0.4, or the molar amounts of nickel, iron, and manganese are the same. A sodium layered metal oxide formed from three transition metals, nickel, iron, and manganese, under the above molar ratio conditions has a high specific capacity and good stability.

[0076] As an example of the present application, 1-x A x C y M 1-y In O2, x is the doping amount of doping element A, y is the doping amount of doping element C, x = 0.001 to 0.150, y = 0.001 to 0.400, and in examples, x is 0.001, 0.005, 0.010, 0.015, 0.020, 0.030, 0.050, 0.080, 0.100, 0.120, 0. x and y may be typical but non-limiting values ​​such as 150, and y may be typical but non-limiting values ​​such as 0.001, 0.005, 0.010, 0.015, 0.020, 0.030, 0.050, 0.080, 0.100, 0.120, 0.150, 0.200, 0.250, 0.350, 0.380, and 0.400. At the same time, the magnitudes of x and y must maintain the electroneutrality requirement of the system. For example, if the valence of doping element A is a, the valence of doping element C is b, and the valence of transition metal M is c, then (1-x) + ax + by + c(1-y) = 4. After doping with doping element A, the valence balance can be maintained by changing the valence of transition metal M.

[0077] Furthermore, x=0.01 to 0.02 and y=0.01 to 0.02. By performing doping modification with doping element A and doping element C under the above doping mass conditions, the stability of the sodium layered metal oxide can be significantly improved and the effect on the energy density of the sodium layered metal oxide is small.

[0078] In one embodiment, the sodium layered metal oxide has an O3 type crystal structure.

[0079] Sodium layered metal oxides may have a variety of different structures and phases, such as O3, P3, O'3, and P2, where O and P represent the octahedral and prismatic coordination structures of sodium ions, respectively. Sodium layered metal oxides with the O3 structure have a high specific capacity and can be commonly used as positive electrode materials for sodium-ion batteries.

[0080] In some embodiments, the chemical formula of the sodium layered metal oxide is Na 0.98 Ca 0.02 Ni 1 / 3 Fe 0.31 Al 0.02 Mn 1 / 3 After calcium doping, the valence balance is maintained by the valence change of the transition metal Mn. That is, the 0.02 valence that increased after calcium doping on the sodium site is reduced by the partial manganese valence change. Specifically, Na 0.98 Ca 0.02 Ni 1 / 3 Fe 0.31 Al 0.02 Mn 1 / 3In O2, Na is +1, Ca is +2, Ni is +2, Fe is +3, Al is +3, about 0.02 mol of Mn atoms are +3, the remaining about 0.31 mol of Mn atoms are +4, and O is -2, ultimately maintaining electrical neutrality of the system. The sodium layered metal oxide of the above chemical formula not only has very good structural stability, but also has high specific capacity, high energy density, and good overall performance when used as a positive electrode active material.

[0081] Method for producing sodium layered metal oxide According to a second aspect, the present application provides a method for preparing a sodium layered metal oxide, i.e., a layered metal oxide having the general chemical formula Na 1-x A x C y M 1-y The present invention provides a method for producing sodium layered metal oxide, which is O2. As shown in FIG. 2, the method for producing sodium layered metal oxide includes the following steps:

[0082] S01: A mixture containing a transition metal M source and a doping element C source is subjected to a first polishing treatment and a first firing treatment to obtain an intermediate product; S02: The intermediate product, the sodium source and the doping element A source are mixed and subjected to a second polishing treatment, and then a second calcination treatment to obtain a sodium layered metal oxide.

[0083] In the process for producing the sodium layered metal oxide in the examples of the present application, the transition metal M site is first doped with C, and then the sodium site is doped with A, thereby obtaining a sodium layered metal oxide doped with both the sodium site and the transition metal M site. 1-x A x C y M 1-ySince the purpose of the present invention is to produce and obtain a sodium layered metal oxide material, which is O2, the polishing and calcination steps are used to dope the doping element C and the doping element A into the transition metal M site and the sodium site, respectively. The production method of the present invention not only facilitates doping, but also has a simple process, and the obtained sodium layered metal oxide has very good stability.

[0084] Step S01: The transition metal M source may be understood as a soluble compound capable of providing a source of the doping element M. Specifically, the transition metal M source includes at least one of soluble halides, acetates, carbonates, nitrates, sulfates, hydroxides, and oxides of M. For example, if the transition metal M is iron, the iron source may be iron halide, iron acetate, iron carbonate, iron nitrate, iron sulfate, etc. Similarly, for other transition metal elements, soluble compounds corresponding to M can be prepared as solutions. The above types of transition metal M sources can effectively provide the M element for the production of sodium layered metal oxides.

[0085] The doping element C source may be understood as a compound that can provide the source of the doping element C. Specifically, the doping element C source includes at least one of soluble halogen salts, acetates, carbonates, nitrates, sulfates, hydroxides, and oxides of C. For example, if the doping element C is zinc, the zinc source may be zinc halide, zinc acetate, zinc carbonate, zinc nitrate, zinc sulfate, etc. Other doping elements C can be similarly prepared by preparing soluble compounds corresponding to C as solutions. The above-mentioned types of materials for the doping element C source can effectively provide the C element for the production of sodium layered metal oxides.

[0086] In some embodiments, the steps for preparing a mixture comprising a source of a transition metal M and a source of a doping element C include:

[0087] S011: Prepare an aqueous solution of a transition metal M source and an aqueous solution of a doping element C source, S012: Adding a complexing agent to the aqueous solution of the transition metal M source and the aqueous solution of the doping element C source to carry out a complexing reaction, thereby obtaining a first gel-like substance and a second gel-like substance, respectively; S013: A first gel-like substance and a second gel-like substance are mixed and dried to obtain a mixture.

[0088] In the examples of the present application, a sol-gel method is adopted, in which the transition metal M source and the doping element C source are prepared as solutions, and then complexed with a complexing agent to form a gel-like substance. By mixing the gel-like M source and C source in this way, uniform doping can be achieved.

[0089] In step S011, a solution of a transition metal M source is prepared by dissolving a transition metal M source in water at a certain ratio, where the M concentration is 0.2-0.8 mol / L. A solution of a doping element C source is prepared by dissolving a doping element C source in water at a certain ratio, where the C concentration is 0.2-2 mol / L.

[0090] In step S012, a complexing agent is added to the solution of the transition metal M source, and the reaction temperature and pH value are controlled so that the reaction system forms a first gel-like substance through a complexing reaction; a complexing agent is added to the solution of the doping element C source, and the reaction temperature and pH value are controlled so that the reaction system forms a second gel-like substance through a complexing reaction;

[0091] In some embodiments, the complexing agent is an organic complexing agent, including at least one of citric acid, oxalic acid, glutamic acid, polypropylene alcohol, polyvinylidene fluoride, and polyacrylamide, and the manner of adding the complexing agent may be mixing a solution of the complexing agent with a solution of the transition metal M source or a solution of the doping element C source.

[0092] In some embodiments, the complexation reaction conditions include a temperature of 40-100°C, which may be, for example, typical but non-limiting temperatures such as 45°C, 50°C, 60°C, 70°C, and 80°C, and a pH value of 7-11, which may be, for example, typical but non-limiting pH values ​​such as 7.0, 7.5, 8, 9, 10, and 11.

[0093] By selecting the type of complexing agent and the complexing reaction conditions, the complexing reaction can be carried out gently, so that the transition metal M source and the doping element C source respectively form a first gel-like substance and a second gel-like substance, which are then mixed and dried to obtain a mixture, facilitating the subsequent doping process.

[0094] In step S013, drying is performed mainly to remove the solvent in the gel-like substance, and the drying temperature may be 100 to 120°C. Under these conditions, the drying can minimize the impact on the quality and stability of the mixture. After the mixture is dried, a first polishing treatment and a first firing treatment are performed in sequence to obtain an intermediate product that can be understood as a transition metal hydroxide modified by doping with a transition metal layer.

[0095] In some embodiments, the first polishing may be a ball milling process.

[0096] In some embodiments, the first firing process includes a two-stage firing process: (1) firing at 800-950°C for 6-10 hours, for example, at a temperature of, but not limited to, 800°C, 850°C, 900°C, 920°C, or 940°C, for a time period of, but not limited to, 6 hours, 8 hours, 9 hours, or 10 hours; and (2) firing at a temperature of, but not limited to, 200-600°C for 3-6 hours, for example, at a temperature of, but not limited to, 200°C, 250°C, 300°C, 400°C, or 500°C, for a time period of, but not limited to, 3 hours, 4 hours, 5 hours, or 6 hours. As described above, the first firing treatment conditions, in which firing is first performed at a high temperature for a long time, and then the temperature is lowered and firing is performed for a short time, can effectively achieve doping of the C element at the M site.

[0097] Step S02: The intermediate product obtained in step S01, a sodium source, and a doping element A source are mixed and subjected to a second polishing treatment, followed by a second calcination treatment, thereby obtaining a sodium layered metal oxide as a target product.

[0098] In the step of mixing the intermediate product, the sodium source, and the doping element A source, the sodium source and the doping element A source may be prepared as solutions, and a complexing agent may be added to carry out a complexing reaction to form a gel-like substance. The gel-like substance of the sodium source and the A source may then be dried and mixed with the intermediate product. Such a sol-gel method can more effectively achieve uniform doping.

[0099] The doping element A source may be understood as a soluble compound capable of providing the doping element A. Specifically, the doping element A source may include at least one of soluble halides, acetates, carbonates, nitrates, sulfates, hydroxides, and oxides of A. For example, if the doping element A is calcium, the calcium source may be calcium halide, calcium acetate, calcium nitrate, etc. Similarly, for other doping elements, the soluble compound corresponding to A can be prepared as a solution. The above-mentioned material type of the doping element A source can effectively provide the A element for the preparation of sodium layered metal oxides. Meanwhile, the sodium source may include at least one of sodium halide, sodium acetate, sodium carbonate, sodium nitrate, sodium sulfate, sodium hydroxide, and sodium oxide. The above-mentioned material type of the sodium source can effectively provide the sodium element for the preparation of sodium layered metal oxides.

[0100] In some embodiments, the second polishing may be a ball milling process.

[0101] In some embodiments, the second firing process includes a two-stage firing process: (1) firing at 800-950°C for 6-10 hours, for example, at a temperature of, but not limited to, 800°C, 850°C, 900°C, 920°C, or 940°C, for a typical but non-limiting time period, for example, 6 hours, 8 hours, 9 hours, or 10 hours; and (2) firing at a temperature of, but not limited to, 200-600°C for 3-6 hours, for example, at a temperature of, but not limited to, 200°C, 250°C, 300°C, 400°C, or 500°C, for a typical but non-limiting time period, for example, 3 hours, 4 hours, 5 hours, or 6 hours. As described above, the doping of the element A at the sodium site can be effectively achieved by the second firing treatment conditions of first firing at a high temperature for a long time and then firing at a lower temperature for a short time.

[0102] secondary battery According to a third aspect, an embodiment of the present application provides a secondary battery, wherein the positive electrode plate of the secondary battery contains the sodium layered metal oxide according to the first aspect of the embodiment of the present application and / or the sodium layered metal oxide obtained by the production method according to the second aspect of the embodiment of the present application.

[0103] The positive electrode plate of the secondary battery contains a compound having the general formula Na 1-x A x C y M 1-y By using sodium layered metal oxide (O2) as the positive electrode active material, the inherent structural stability of sodium layered metal oxide makes it difficult for material particles on the surface of the positive electrode active material layer to break or fall off. This reduces side reactions on the surface of the positive electrode active material layer, thereby reducing the capacity fade phenomenon and improving cycle performance and service life.

[0104] In one embodiment, the positive electrode plate in the secondary battery according to the embodiment of the present application includes (1) a current collector and (2) a positive electrode active material layer, the positive electrode active material layer being bonded to the current collector, wherein the positive electrode active material layer contains a positive electrode active material, the positive electrode active material being the sodium layered metal oxide according to the first embodiment of the present application and / or the sodium layered metal oxide obtained by the manufacturing method according to the second embodiment of the present application.

[0105] The positive electrode active material layer is an active layer included in the positive electrode plate in the examples of the present application, and contains at least a layer structure of a positive electrode material, which is bonded to a current collector. Meanwhile, by using the sodium layered metal oxide according to the first embodiment of the examples of the present application and / or the sodium layered metal oxide obtained by the production method according to the second embodiment as the positive electrode active material in the positive electrode plate, the material particles on the surface of the positive electrode active material layer are less likely to break or fall off due to the structural stability unique to the sodium layered metal oxide. As a result, side reactions on the surface of the positive electrode active material layer are reduced, thereby reducing the capacity fade phenomenon and improving cycle performance and service life.

[0106] In one embodiment, the positive electrode active material layer may be bonded to at least one surface of a current collector.

[0107] In some embodiments, the current collector of the positive electrode plate, also referred to as a positive electrode current collector, may be a metal foil sheet or a composite current collector. For example, the metal foil sheet may be aluminum foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymer substrate, such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE).

[0108] In some embodiments, the positive electrode active material layer optionally further comprises an adhesive. For example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0109] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent, such as superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0110] For example, the secondary battery of the present application includes a positive electrode plate, a separator, and a negative electrode plate. That is, the positive electrode plate included in the secondary battery is a cathode material having the general formula of Na 1-x A x C y M 1-yThe secondary battery of the present invention contains a layered metal oxide of sodium, which is O2. Thus, the secondary battery of the present invention has good cycle stability, low capacity decay during cycling, and significantly improved cycle performance.

[0111] Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charge and discharge process, active ions are absorbed and released back and forth between the positive and negative electrodes. The electrolyte functions to conduct ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes and allows ions to pass through.

[0112] In some embodiments, the electrolyte serves to conduct ions between the positive and negative plates. The embodiments of the present application are not specifically limited to the type of electrolyte, which can be selected as needed. For example, the electrolyte may be liquid, gel-like, or all-solid.

[0113] In some embodiments, the secondary battery of the embodiments of the present application may include any one of a battery cell, a battery module, and a battery pack.

[0114] Here, a battery cell includes a battery case and a battery core packaged in the battery case. There is no particular limitation on the shape of the battery cell, and it may be cylindrical, rectangular, or any other shape. For example, the battery cell 10 has a rectangular structure as shown in Figure 3.

[0115] In some embodiments, as shown in FIG. 4 , the exterior of the battery cell 10 may include a case 11 and a top cover assembly 12. The case 11 may include a bottom plate and side plates connected to the bottom plate, which together form a surrounding accommodating cavity. The case 11 has an opening communicating with the accommodating cavity, and the top cover assembly 12 is used to cover the opening to seal the accommodating cavity. The positive electrode plate, separator, and negative electrode plate included in the secondary battery of the present application are wound and / or stacked to form an electrode assembly 13. The electrode assembly 13 is packaged in the accommodating cavity. An electrolyte is impregnated into the electrode assembly 13. The number of electrode assemblies 13 included in the battery cell 10 may be one or more and can be adjusted according to actual needs.

[0116] Methods for manufacturing the battery cell 10 are well known. In some embodiments, the battery cell 10 may be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, the separator, and the negative electrode plate may be wound or stacked to form an electrode assembly 13, which may then be placed in an outer casing, dried, and then injected with an electrolyte. The battery cell 10 may then be obtained through processes such as vacuum packaging, standing, chemical conversion, and molding.

[0117] A battery module refers to an assembly of the battery cells 10, that is, it may include a plurality of the battery cells 10, the specific number of which can be adjusted according to the application and capacity of the battery module.

[0118] In some embodiments, FIG. 5 is a schematic diagram of an example battery module 20. As shown in FIG. 5, in the battery module 20, the plurality of battery cells 10 may be arranged in order along the longitudinal direction of the battery module 20. Of course, the plurality of battery cells 10 may be arranged in any other manner. The plurality of battery cells 10 may be further fixed by fasteners. Optionally, the battery module 20 may further include a housing having an accommodating space, and the plurality of battery cells 10 are accommodated in the accommodating space.

[0119] The battery pack refers to an assembly of the battery cells 10, i.e., may include a plurality of battery cells 10, and the plurality of battery cells 10 may be assembled into the battery module 20. The specific number of battery cells 10 or battery modules 20 included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0120] 6 and 7 are schematic diagrams of an exemplary battery pack 30. The battery pack 30 may include a battery box and a plurality of battery modules 20 installed in the battery box. The battery box includes an upper housing 31 and a lower housing 32, and the upper housing 31 covers the lower housing 32 to form a sealed space for accommodating the battery modules 20. The plurality of battery modules 20 may be arranged in the battery box in any manner.

[0121] power consumption equipment According to a fourth aspect, the present invention further provides a power consumption device, which includes the secondary battery of the above-mentioned embodiment of the present invention. The secondary battery may be used as a power source for the power consumption device or as an energy storage unit for the power consumption device. Therefore, the power consumption device of the embodiment of the present invention has a long standby or operating time.

[0122] The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and satellite, an energy storage system, etc. The power consuming device may select a secondary battery, a battery module, or a battery pack according to its usage needs.

[0123] 8 is a schematic diagram of an example power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, which may employ a battery pack or battery module to meet the high power and high energy density demands of the power consuming device.

[0124] Other examples of power consuming devices may be mobile phones, tablet computers, laptop computers, etc. These power consuming devices are generally required to be thin and may employ secondary batteries as their power source.

[0125] Example The following describes examples of the present application. The examples described below are illustrative and are intended to interpret the present application, but should not be understood as limitations on the present application. If no specific techniques or conditions are described in the examples, they are carried out according to the techniques, conditions, or product specifications described in documents within the field. If no manufacturer is specified for the reagents or equipment used, they are all ordinary products that are commercially available.

[0126] 1. Examples of sodium layered metal oxide and its manufacturing method Example A1 Sodium layered metal oxide, whose chemical formula is Na 0.98 Ca 0.02 Ni 1 / 3 Fe 0.31 Al 0.02 Mn 1 / 3 The method for producing sodium layered metal oxide includes the following steps:

[0127] S11: Preparation of intermediate products: Solution preparation: Nickel nitrate, iron nitrate, and manganese nitrate were dissolved in water in the molar ratios shown in the chemical formula to obtain a transition metal salt solution with a total transition metal M concentration of approximately 0.5 mol / L. Aluminum nitrate was dissolved in water to obtain an aluminum salt solution with a concentration of 2 mol / L. Citric acid was dissolved in water to obtain a complexing agent solution with a concentration of 0.5 mol / L.

[0128] The transition metal salt solution and the complexing agent solution were mixed and the temperature was controlled at 50°C and pH=8 until a first gel-like substance was obtained, and the aluminum salt solution and the complexing agent solution were mixed and the temperature was controlled at 50°C and pH=8 until a second gel-like substance was obtained.

[0129] The first and second gel-like substances were mixed, dried at 110°C for 10 minutes, and then ball-milled for 30 minutes. After ball-milling, the mixture was calcined at 800°C for 6 hours and then at 250°C for 3 hours to obtain the intermediate product (i.e., a transition metal hydroxide modified by doping with a transition metal layer).

[0130] S12: The intermediate product, sodium nitrate, and calcium nitrate were mixed in the proportions given in the formula and then ball-milled for a second time for 30 minutes. After ball-milling, the mixture was calcined at 800°C for 6 hours and then at 250°C for 3 hours. Finally, the sodium layered metal oxide of the formula above was obtained. Figure 9 shows its XRD pattern.

[0131] Example A2 Sodium layered metal oxide, whose chemical formula is Na 0.98 Bi 0.02 Ni 1 / 3 Fe 0.31 Al 0.02 Mn 1 / 3 The method for producing the sodium layered metal oxide is different from that of Example A1 in the amount of the corresponding raw materials used, but the rest is basically the same.

[0132] Example A3 Sodium layered metal oxide, whose chemical formula is Na 0.98 Ca 0.02 Ni 1 / 3 Fe 0.31 Mg 0.02 Mn 1 / 3 The method for producing the sodium layered metal oxide is different from that of Example A1 in the amount of the corresponding raw materials used, but the rest is basically the same.

[0133] Example A4 Sodium layered metal oxide, whose chemical formula is Na 0.98 Ca 0.02 Ni 1 / 3 Fe 0.31 W 0.02 Mn 1 / 3 The method for producing the sodium layered metal oxide is different from that of Example A1 in the amount of the corresponding raw materials used, but the rest is basically the same.

[0134] Example A5 Sodium layered metal oxide, whose chemical formula is Na 0.97 Ca 0.03 Ni 1 / 3 Fe 0.31 Al 0.02 Mn 1 / 3 The method for producing the sodium layered metal oxide is different from that of Example A1 in the amount of the corresponding raw materials used, but the rest is basically the same.

[0135] Example A6 Sodium layered metal oxide, whose chemical formula is Na 0.96 Ca 0.04 Ni 1 / 3 Fe 0.31 Al 0.02 Mn 1 / 3 The method for producing the sodium layered metal oxide is different from that of Example A1 in the amount of the corresponding raw materials used, but the rest is basically the same.

[0136] Comparative Example A1 Sodium layered metal oxide, whose chemical formula is NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 The sodium layered metal oxide is prepared in the same manner as in Example A1 except for the amount of raw materials used. Figure 10 shows the XRD diagram of the characteristic.

[0137] Comparative example A2 Sodium layered metal oxide, whose chemical formula is Na 0.98 Ca 0.02 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3O2. The method for producing the sodium layered metal oxide is basically the same as in Example A1, except for the corresponding raw materials and amounts used. Figure 11 shows the XRD diagram of the characterization.

[0138] Comparative example A3 Sodium layered metal oxide, whose chemical formula is NaNi 1 / 3 Fe 0.31 Al 0.02 Mn 1 / 3 O2. The method for producing the sodium layered metal oxide is different from that of Example A1 in the amount of the corresponding raw materials, but the rest is basically the same. Figure 12 shows the XRD diagram of the characterization.

[0139] Comparative example A4 Sodium layered metal oxide, whose chemical formula is Na 0.98 Li 0.02 Ni 1 / 3 Fe 0.31 Al 0.02 Mn 1 / 3 The method for producing the sodium layered metal oxide is different from that of Example A1 in the amount of the corresponding raw materials used, but the rest is basically the same.

[0140] Comparative Example A5 Sodium layered metal oxide, whose chemical formula is Na 0.8 Ca 0.2 Ni 1 / 3 Fe 0.31 Al 0.02 Mn 1 / 3 The method for producing sodium layered metal oxide is basically the same as that in Example A1, except that the corresponding raw materials and amounts used are different from those in Example A1.

[0141] 2. Secondary battery cell example Examples B1 to B6 and Comparative Examples B1 to B5 Examples B1 to B6 and Comparative Examples B1 to B5 each provide a secondary battery cell. Each secondary battery cell includes a battery core formed of a positive electrode plate, a separator, and a negative electrode plate, and further includes an electrolyte. The positive electrode active material in the positive electrode plates of Examples B1 to B6 and Comparative Examples B1 to B5 corresponds to the sodium layered metal oxide provided in Examples A1 to A6 and Comparative Examples A1 to A5, respectively. For example, the sodium layered metal oxide in Example A1 is used as the positive electrode active material in the battery core of the secondary battery of Example B1, and the sodium layered metal oxide in Example A2 is used as the positive electrode active material in the battery core of the secondary battery of Example B2. By analogy, the sodium layered metal oxide in Comparative Example A5 is used as the positive electrode active material in the battery core of the secondary battery of Comparative Example B5.

[0142] The positive electrode plate is manufactured according to the following method.

[0143] Methylpyrrolidone (NMP) was used as a solvent, and sodium layered metal oxide, a conductive agent (carbon nanotubes), and an adhesive (PVDF) were mixed in a mass ratio of 8:1:1 to prepare a positive electrode slurry. The positive electrode slurry was uniformly coated on an aluminum foil, and then coated on both sides, where the surface density on each side was 0.25 mg / mm 2 After thorough vacuum drying, cold pressing and slitting, a positive electrode plate was obtained.

[0144] Negative electrode plate: Metallic sodium was used as the counter electrode, i.e., the negative electrode plate.

[0145] Electrolyte: Ethylene carbonate (EC) / diethyl carbonate (DEC) were mixed at a volume ratio of 1:1 at room temperature, and NaPF6 was added to the mixed solution to obtain a solution with a concentration of 1 mol / L as an electrolyte.

[0146] Assembly of secondary battery: In a low-humidity, constant-temperature room, in an argon atmosphere glove box, the positive electrode plate and negative electrode plate manufactured above were stacked in the order of "positive electrode plate-separator-negative electrode", filled with an electrolyte, and assembled into a button-type battery.

[0147] Performance Test (1) Material characterization As can be seen from the comparative analysis of the XRD curve of the sodium layered metal oxide of Example A1 (FIG. 9), the XRD curve of the sodium layered metal oxide of Comparative Example A1 (FIG. 10), the XRD curve of the sodium layered metal oxide of Comparative Example A2 (FIG. 11), and the XRD curve of the sodium layered metal oxide of Comparative Example A3 (FIG. 12), Example A1 of the present application achieved doping with calcium and aluminum.

[0148] (2) Battery charge / discharge test The secondary battery cells of Examples B1 to B6 and Comparative Examples B1 to B5 were each tested.

[0149] The charge-discharge test conditions were a test temperature of 45°C, a charge-discharge ratio of 0.1 C, a charge-discharge cutoff voltage of 2.0 to 4.2 V (vs. Na+ / Na), and 300 cycles. The test results are shown in Table 1.

[0150] [Table 1]

[0151] As can be seen from the test results in Table 1, Compared with comparative examples in which the sodium layered metal oxide is undoped or doped at only one site, the examples of the present application effectively improve the cycle performance of secondary batteries by co-doping the sodium site and the transition metal M site, and the impact of small amounts of doping on the first charge capacity is relatively small. As can be seen from Examples B1, B5, B6, and Comparative Example B5, excessive Ca doping of 4% significantly affected the cycle performance and capacity of secondary batteries, but adjusting the Ca doping concentration from 4% to 2% increased the corresponding secondary battery capacity and the corresponding cycle capacity retention rate, indicating that a Ca doping concentration of 2% was more effective.

[0152] Finally, it should be noted that the above embodiments are merely intended to illustrate the technical solutions of the present application and are not intended to limit the same. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified or some or all of the technical features may be replaced with equivalents. Such modifications or replacements do not deviate from the essence of the relevant technical solutions from the scope of the technical solutions of the embodiments of the present application, and all of these should be included within the scope of the claims and description of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in the embodiments may be combined in any manner. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions within the scope of the claims. [Explanation of symbols]

[0153] 10—battery cell, 11—case, 12—top cover assembly, 13—electrode assembly, 20—battery module, 30—battery pack, 31—upper housing, 32—lower housing.

Claims

1. A sodium layered metal oxide, the general chemical formula of which is Na １－ｘ A ｘ C ｙ M １－ｙ O ２ where: M comprises a transition metal element; A includes at least one of a Group IIA element, a Group V metal element, a Group VIA metal element, and a Group IIIB element, and the ionic radius of A is larger than the ionic radius of M; C includes at least one of a metal element of the third period, a metal element of the fourth period, and a metal element of the fifth period, and the valence of the C is equal to or less than the valence of the M; A sodium layered metal oxide, characterized in that x=0.001 to 0.150 and y=0.001 to 0.

500.

2. 2. The sodium layered metal oxide according to claim 1, wherein A is a doping element for the sodium site, and C is a doping element for M.

3. 2. The sodium layered metal oxide according to claim 1, wherein the valence of A is +2 to +4.

4. The group IIA element in A includes at least one of calcium, strontium, and barium, the group V metal element includes at least one of antimony and bismuth, the group VIA metal element includes tellurium, and the group IIIB element includes at least one of yttrium, cerium, and lanthanum, or 2. The sodium layered metal oxide according to claim 1, wherein A contains calcium element.

5. The third period metal element in the C includes at least one of magnesium and aluminum, the fourth period metal element includes at least one of zinc, gallium, and germanium, and the fifth period metal element includes zirconium, or 2. The sodium layered metal oxide according to claim 1, wherein the C contains an aluminum element.

6. M includes at least two of nickel, manganese, copper, and iron, or 2. The sodium layered metal oxide of claim 1, wherein M comprises nickel, iron, and manganese.

7. 7. The sodium layered metal oxide according to claim 6, wherein the molar ratio of nickel, iron and manganese in M ​​is (0.2-0.4):(0.2-0.4):(0.2-0.6).

8. 2. The sodium layered metal oxide according to claim 1, wherein x is 0.01 to 0.02 and y is 0.01 to 0.

02.

9. 2. The sodium layered metal oxide according to claim 1, wherein the sodium layered metal oxide has an O3 type crystal structure.

10. The chemical formula of the sodium layered metal oxide is Na ０．９８ Ca ０．０２ Ni １／３ Fe ０．３１ Al ０．０２ Mn １／３ O ２ 2. The sodium layered metal oxide according to claim 1, wherein:

11. 2. The method for producing the sodium layered metal oxide according to claim 1, subjecting a mixture containing a source of a transition metal M and a source of a doping element C to a first polishing process and a first calcination process to obtain an intermediate product; and mixing the intermediate product, a sodium source, and a doping element A source to perform a second polishing treatment, and then performing a second calcination treatment to obtain the sodium layered metal oxide.

12. The step of preparing the mixture containing a source of a transition metal M and a source of a doping element C comprises: preparing an aqueous solution of the transition metal M source and an aqueous solution of the doping element C source, respectively; adding a complexing agent to both the aqueous solution of the transition metal M source and the aqueous solution of the doping element C source to carry out a complexing reaction to obtain a first gel-like substance and a second gel-like substance, respectively; 12. The method according to claim 11, further comprising the step of mixing the first gel-like substance and the second gel-like substance and drying the mixture.

13. (1) the complexing agent includes at least one of citric acid, oxalic acid, glutamic acid, polypropylene alcohol, polyvinylidene fluoride, and polyacrylamide; (2) The temperature of the complexation reaction is 40 to 100°C; (3) The pH value of the complexation reaction is 7 to 11.

14. The first firing treatment includes firing at 800 to 950 ° C for 6 to 10 hours, and then lowering the temperature to 200 to 600 ° C for 3 to 6 hours; and / or The method according to claim 11, wherein the second firing treatment comprises firing at 800 to 950°C for 6 to 10 hours, and then lowering the temperature to 200 to 600°C for 3 to 6 hours.

15. (1) the source of the transition metal M comprises at least one of a soluble halide salt, acetate salt, carbonate salt, nitrate salt, sulfate salt, hydroxide salt, and oxide salt of M; (2) the source of doping element C includes at least one of soluble halogen salts, acetates, carbonates, nitrates, sulfates, hydroxides, and oxides of C; (3) the source of doping element A comprises at least one of a soluble halide salt, acetate, carbonate, nitrate, sulfate, hydroxide, and oxide of A; (4) The method according to claim 11, wherein the sodium source includes at least one of sodium halide, sodium acetate, sodium carbonate, sodium nitrate, sodium sulfate, sodium hydroxide, and sodium oxide.

16. 12. A secondary battery, wherein a positive electrode plate of the secondary battery contains the sodium layered metal oxide according to any one of claims 1 to 10 and / or the sodium layered metal oxide obtained by the manufacturing method according to claim 11.

17. A power consuming device comprising the secondary battery of claim 16.

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