Sodium-ion battery positive electrode material and preparation method thereof, positive electrode plate, secondary battery and electric device

Abstract

The invention provides a sodium ion battery positive electrode material and a preparation method thereof, a positive electrode plate, a secondary battery and an electric device, the positive electrode material has a layered structure, the chemical formula of the positive electrode material is NaxMnaMbAcO2, M comprises one or more of Fe, Ni, Co, Cu, Zr, Ti, Al, Mg, Zn, Cr, Sn, Nb and Sb; a comprises one or more of Bi, Te and V; 0 < x < = 1, 0 < a, 0 < b, and 0 < c < = 0.1. The doping of the element A enables the layered structure oxide to show a hydrophobic characteristic, and the adsorbability of the layered structure oxide to water molecules is reduced, so that the reaction between the layered structure oxide and the water molecules is reduced, and the water stability of the positive electrode material is improved.

Description

Technical Field

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

[0002] Sodium-ion batteries, developed based on sodium, are expected to replace lithium-ion batteries in some markets due to their low manufacturing cost and excellent safety, becoming a strong competitor to next-generation batteries. The cathode material of sodium-ion batteries is the primary factor affecting their performance. With their increasing application, higher requirements are being placed on their stability and other performance characteristics.

[0003] Therefore, further improving the stability and other performance of secondary batteries is an urgent problem to be solved. Summary of the Invention

[0004] The embodiments of the present application provide a sodium ion battery positive electrode material and a preparation method thereof, a positive electrode plate, a secondary battery, and an electrical device, aiming to provide a sodium ion battery positive electrode material with good stability.

[0005] In a first aspect, the present invention provides a positive electrode material for a sodium ion battery, wherein the positive electrode material has a layered structure and its chemical formula is: Na x Mn a M b A c O2, where

[0006] M includes one or more of Fe, Ni, Co, Cu, Zr, Ti, Al, Mg, Zn, Cr, Sn, Nb, and Sb;

[0007] A includes one or more of Bi, Te, and V;

[0008] 0<x≤1, 0<a, 0<b, 0<c≤0.1.

[0009] According to the embodiments of the present application, element A is doped into the positive electrode material of the present application, and A includes one or more of Bi, Te, and V. The incorporation of element A can improve the water stability of the layered structure oxide. Due to the low coordination characteristics of element A with oxygen, it is difficult for it to form a coordination structure with the oxygen atoms in the water molecules. After element A is doped into the layered structure oxide, element A can occupy part of the transition metal element sites in the layered structure oxide, and the adsorbable sites of water molecules on the layered structure oxide are reduced, so that the layered structure oxide exhibits hydrophobic properties, thereby reducing the adsorption of the layered structure oxide to water molecules, thereby reducing the reaction between the layered structure oxide and water molecules, and improving the water stability of the positive electrode material.

[0010] In some embodiments, A includes a Bi element.

[0011] In some embodiments, M includes one or more of Fe, Ni, Cu, and Co.

[0012] In some embodiments, 0.8≤x≤1, 0.25≤a≤0.5, 0.5≤b≤0.75, 0.01≤c≤0.05, and a+b+c=1.

[0013] According to the embodiments of the present application, the layered structure oxide with the above-mentioned ratio has a higher active ion storage capacity, and can embed and release more active ions including sodium ions, thereby providing a higher battery capacity, which enables the battery to store more electrical energy, have a higher capacity and a longer service life.

[0014] In some embodiments, the positive electrode material further contains element X, and the element X includes one or more of Se, Ce, Si, P, B, and F.

[0015] According to the embodiments of the present application, the X element can be introduced into the positive electrode material in the form of doping, coating or adsorption to improve the structural stability and electrochemical performance of the positive electrode material.

[0016] In some embodiments, the cathode material has any one of the following chemical formulas: NaMn 0.5 Ni 0.2 Fe 0.29 Bi 0.01 O2, NaMn 0.4 Ni 0.2 Fe 0.29 Cu 0.1 Bi 0.01 O2, NaMn 0.3 Co 0.3 Fe 0.29 Te 0.01 Zr 0.1 O2、NaMn 0.4 Ni 0.2 Fe 0.25 Bi 0.05 Cu 0.1 O2、NaMn 0.3 Co 0.25 Fe 0.24 Bi 0.01 Zr 0.1 Si 0.1 O2.

[0017] In some embodiments, the sodium interlayer spacing of the positive electrode material is 0.53 nm to 0.55 nm.

[0018] According to the embodiments of the present application, the sodium interlayer spacing in the layered oxide is within this range, which is beneficial to the conduction and diffusion of sodium ions. At the same time, it can reduce the exchange reaction of hydrogen ions and sodium ions caused by the reaction of the layered oxide with water, and has better water stability.

[0019] In some embodiments, the cathode material has an O3 phase, belonging to Space group.

[0020] According to the embodiments of the present application, the O3 phase positive electrode material has a higher initial Na content, can release more sodium ions, and has a higher capacity.

[0021] In some embodiments, the positive electrode material satisfies: 2θ0-2θ1≤0.1°, wherein 2θ1 is the diffraction angle corresponding to the characteristic peak (003) in the XRD spectrum obtained after the positive electrode material is immersed in water at 20°C to 30°C for 24 hours, and 2θ0 is the diffraction angle corresponding to the characteristic peak (003) in the XRD spectrum of the positive electrode material.

[0022] According to the embodiments of the present application, 2θ0-2θ1 represents the change in the sodium interlayer spacing of the above-mentioned layered oxide positive electrode material after being soaked in water for 24 hours. The smaller the 2θ0-2θ1 value is, the smaller the change in the sodium interlayer spacing of the layered oxide before and after soaking in water, the weaker the sensitivity to water and the better the water stability.

[0023] In a second aspect, the present invention provides a method for preparing a positive electrode material for a sodium ion battery according to the first aspect of the present invention, comprising:

[0024] According to the chemical formula Na x Mn a M b A c O2 provides precursors including Na source, Mn source, M source, and A source;

[0025] The precursor is calcined to obtain a positive electrode material for a sodium ion battery.

[0026] In some embodiments, providing a precursor comprising a Na source, a Mn source, an M source, and an A source comprises: ball milling and mixing materials comprising a Na source raw material, a Mn source raw material, an M source raw material, and an A source raw material to obtain the precursor.

[0027] In some embodiments, the Na source raw material includes one or more Na-containing compounds. Optionally, the Na source raw material includes one or more of Na2CO3, NaHCO3, NaOH, and Na2O2.

[0028] In some embodiments, the Mn source raw material includes one or more Mn-containing oxides; optionally, the Mn source raw material includes one or more of Mn2O3, Mn3O4, MnO, and MnO2.

[0029] In some embodiments, the M source raw material includes an oxide or hydroxide containing the M element; optionally, the M source raw material includes one or more of iron oxide, nickel oxide, cobalt oxide, copper oxide, magnesium oxide, zinc oxide, aluminum oxide, titanium dioxide, chromium oxide, iron hydroxide, nickel hydroxide, cobalt hydroxide, titanium hydroxide, and chromium hydroxide.

[0030] In some embodiments, the A source raw material includes one or more of the A element and a compound containing the A element; optionally, the A source raw material includes one or more of Bi element, Te element, V element, Cu element, bismuth oxide, tellurium oxide, vanadium pentoxide, and copper oxide.

[0031] In some embodiments, providing a precursor comprising a Na source, a Mn source, an M source, and an A source comprises:

[0032] reacting a Mn source raw material, an M source raw material, and an A source raw material with a precipitant to obtain a co-precipitate containing the Mn source, the M source, and the A source;

[0033] The coprecipitate and the Na source raw material are subjected to ball milling and mixing treatment to obtain the precursor.

[0034] In some embodiments, the Mn source material includes one or more of chlorides, sulfates, and nitrates containing Mn.

[0035] In some embodiments, the M source raw material includes one or more of chlorides, sulfates, and nitrates containing the M element.

[0036] In some embodiments, the A source material includes one or more of element A and a compound containing element A;

[0037] In some embodiments, the Na source raw material includes one or more Na-containing compounds. Optionally, the Na source includes one or more of Na2CO3, NaHCO3, NaOH, and Na2O2.

[0038] In some embodiments, the precipitant comprises one or more of a hydroxide precipitant, a phosphate precipitant, and an oxalate precipitant.

[0039] In some embodiments, the hydroxide precipitating agent comprises sodium hydroxide, calcium hydroxide, or a combination thereof.

[0040] In some embodiments, the phosphate precipitating agent comprises one or more of soluble phosphoric acid, sodium phosphate, and potassium phosphate.

[0041] In some embodiments, the oxalate precipitant comprises one or more of oxalic acid, ammonium oxalate, potassium oxalate, and sodium oxalate.

[0042] In some embodiments, the precursor further includes an X source, the X source includes a compound containing an X element, and the X element includes one or more of Se, Ce, Si, P, B, and F.

[0043] In some embodiments, the calcination temperature is 600°C to 1200°C.

[0044] In some embodiments, the calcination treatment time is 10 hours to 20 hours.

[0045] In a third aspect, an embodiment of the present application provides a positive electrode sheet, comprising the sodium ion battery positive electrode material of the embodiment of the first aspect of the present application or the sodium ion battery positive electrode material obtained according to the preparation method of the embodiment of the second aspect of the present application.

[0046] In a fourth aspect, an embodiment of the present application provides a secondary battery, comprising the positive electrode sheet of the embodiment of the third aspect of the present application.

[0047] In a fifth aspect, an embodiment of the present application provides an electrical device, comprising the secondary battery of the embodiment of the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0049] Figure 1 This is a schematic diagram of a possible reaction between a layered structured oxide and water in this application.

[0050] Figure 2 This is the XRD pattern of the positive electrode material provided in Example 1 of the present application before and after soaking in water.

[0051] Figure 3 yes Figure 2 A magnified view of the (003) characteristic peak position in the XRD pattern.

[0052] Figure 4 This is the XRD diagram of the positive electrode material provided in Comparative Example 1 of the present application before and after soaking in water.

[0053] Figure 5 is a schematic diagram of a secondary battery according to one embodiment of the present application;

[0054] Figure 6 yes Figure 5 FIG. 1 is an exploded view of a secondary battery according to an embodiment of the present application.

[0055] Figure 7 Schematic diagram of a battery module according to one embodiment of the present application.

[0056] Figure 8 Schematic diagram of a battery pack according to one embodiment of the present application.

[0057] Figure 9 yes Figure 8 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0058] Figure 10 FIG. 1 is a schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source.

[0059] Explanation of reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 housing; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0060] Below, with appropriate reference to the accompanying drawings, the embodiments of the sodium ion battery positive electrode material and its preparation method, the positive electrode sheet, the secondary battery and the electric device of the present application are specifically disclosed in detail. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0061] " range " disclosed in the application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The range limited in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a particular parameter, it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the application, unless otherwise specified, the numerical range " ab " represents an abbreviation of any real number combination between a and b, characterized in that a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0062] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0063] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0064] Unless otherwise specified, the terms "connected" and "connection" in this application should be understood broadly. For example, they can refer to fixed connection, detachable connection, or integral connection; they can refer to direct connection, indirect connection through an intermediate medium, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0065] Unless otherwise specified, in this application, the terms "first", "second", "third", "fourth", etc. are used to distinguish different objects rather than to describe a specific order or a primary-secondary relationship.

[0066] The term "plurality" used in this application refers to two or more.

[0067] The present invention relates to sodium-ion battery cathode materials. Sodium and lithium reside in adjacent periods within the same main group and have similar chemical properties. Preliminary research indicates that sodium-ion batteries and lithium-ion batteries operate similarly at room temperature. Furthermore, sodium resources are widely distributed, with an abundance nearly 1,000 times that of lithium, resulting in lower costs.

[0068] In sodium-ion battery systems, the cathode material is a key factor affecting the operating voltage, energy density, and other electrochemical properties of sodium-ion batteries. Layered oxides are one of the main cathode materials used in sodium-ion batteries. In such layered oxides, oxygen and coordinating elements, including transition metals (such as manganese, cobalt, nickel, and iron), stack to form multiple layers, with sodium ion layers between the layers. When used as cathode materials for sodium-ion batteries, sodium ions are intercalated and deintercalated between the layers during the battery's charge and discharge processes, maintaining the stability of the layered structure. However, layered oxides are highly susceptible to moisture absorption from the environment. The absorbed water molecules dissociate into hydrogen ions and hydroxide ions. The hydrogen ions exchange with sodium ions in the layered oxide, occupying the sites of the sodium ions, reducing the capacity of the cathode material and even destroying the layered structure. Furthermore, the adsorbed water molecules also react with the oxide, forming harmful byproducts on its surface. Therefore, layered oxides have poor water stability, which affects their performance and stability as cathode materials for sodium-ion batteries.

[0069] Figure 1 A schematic diagram shows a possible failure of a layered oxide by reaction with water. After water molecules are adsorbed on the surface of the layered oxide, the water dissociates. The hydrogen ions formed after dissociation exchange with the active ions (Li, Na, K) in the layered oxide, resulting in a decrease in the active ion content of the (003) layer in the layered oxide and an increase in the interlayer spacing of the (003) layer, which is manifested as the (003) peak shifting to the left in XRD characterization.

[0070] In this application, after in-depth research, a new layered oxide is provided by element doping modification of the layered oxide positive electrode material, which has high water stability, specific capacity and excellent cycle stability and can be used as a positive electrode material for sodium ion batteries.

[0071] Sodium ion battery cathode materials

[0072] The embodiment of the first aspect of the present application provides a sodium ion battery positive electrode material, the positive electrode material has a layered structure, and its chemical formula is: Na x Mn a M b A c O2, where

[0073] M includes one or more of Fe, Ni, Co, Cu, Zr, Ti, Al, Mg, Zn, Cr, Sn, Nb, and Sb;

[0074] A includes one or more of Bi, Te, and V;

[0075] 0<x≤1, 0<a, 0<b, 0<c≤0.1.

[0076] The study found that the above-mentioned layered oxide positive electrode material has a brand-new structure and composition, and has high structural stability. When used in sodium-ion batteries, it can improve the specific capacity and cycle stability of sodium-ion batteries.

[0077] According to the embodiments of the present application, the Mn element, the M element, and the O element can form a stable crystal structure. During the charge and discharge process, the Mn element can participate in the redox reaction, providing effective charge compensation for the deintercalation of sodium ions and maintaining the stability of the crystal structure, thereby enabling the positive electrode material to have good electrochemical properties, such as a higher capacity retention rate, an improved charge and discharge voltage platform, etc.

[0078] According to the sodium ion battery cathode material of the embodiment of the present application, 0<a, optionally, 0.25≤a≤0.5, thereby enabling the cathode material to have a stable crystal structure and further improving the electrochemical performance of the cathode material.

[0079] According to the sodium ion battery positive electrode material of the embodiment of the present application, 0 < b, optionally, 0.5 ≤ b ≤ 0.75. In these embodiments, the positive electrode material can be doped with one or more M elements including Fe, Ni, Co, Cu, Zr, Ti, Al, Mg, Zn, Cr, Sn, Nb, and S. By incorporating the M element, the Mn element in the positive electrode material can be partially replaced, so that the positive electrode material further has improved structural stability and electrochemical performance. In some embodiments, M can further be selected from one or more of Fe, Ni, Co, and Cu.

[0080] According to the sodium ion battery positive electrode material of the embodiment of the present application, it is further doped with an A element including Bi, Fe, V or a combination thereof, and the A element can be selected as Bi. The incorporation of the A element can effectively improve the water stability of the layered structure oxide. Due to the low coordination characteristics of the A element with oxygen, it is difficult for it to form a coordination structure with the oxygen atoms in the water molecules. After the A element is incorporated into the layered structure oxide, the A element can occupy some of the transition metal element sites in the layered structure oxide, and the adsorbable sites of the water molecules on the layered structure oxide are reduced, so that the layered structure oxide exhibits hydrophobic properties, thereby reducing the adsorption of the layered structure oxide to water molecules, thereby reducing the reaction of the layered structure oxide with water molecules, improving the water stability of the positive electrode material, and reducing the reaction of the positive electrode material with water molecules during synthesis and storage, reducing the formation of residual alkali on the surface of the positive electrode material and the resulting loss of sodium content.

[0081] According to an embodiment of the present application, 0<c<0.1, and optionally, 0.01≤c≤0.05. This can further reduce the reaction between the positive electrode material and water molecules, thereby improving the water stability of the positive electrode material.

[0082] According to the sodium ion battery positive electrode material of the embodiment of the present application, 0<x≤1, optionally 0.6≤x≤1, further optionally, 0.8≤x≤1. Based on the number of sodium elements in the molecular formula compound represented by the chemical formula of the positive electrode material in the above embodiment is less than or equal to 1, which is conducive to improving the physicochemical stability of the layered oxide positive electrode material, reducing the energy loss caused by structural damage of the positive electrode material during storage and charge and discharge cycles, thereby achieving a higher capacity retention rate. In the above embodiment, by adding predetermined elements to the positive electrode material with a layered structure, the water stability of the positive electrode material can be improved, the replacement of sodium ions in the layered oxide with hydrogen ions can be reduced, and the generation of by-products caused by the reaction of some elements in the positive electrode material with water or electrolyte can be reduced, thereby improving the structural stability and electrochemistry of the positive electrode material, so that the positive electrode material maintains a stable crystal structure during the sodium ion deintercalation process, so that the positive electrode material has improved capacity and cycle performance.

[0083] In some embodiments, a+b+c=1. The above-mentioned positive electrode material contains predetermined doping elements and composition ratios, which can obtain good electrochemical performance (such as higher capacity, stable charge and discharge voltage platform) and structural stability, thereby providing improved capacity utilization and cycle performance.

[0084] In some embodiments, b / (a+c)≤1.

[0085] According to the embodiments of the present application, excessively high M element content in the positive electrode material can easily cause the positive electrode material to react with water or electrolyte to produce excessive byproducts, thereby affecting the stability of the positive electrode material structure. By adjusting the M element content to a lower range and simultaneously incorporating a certain amount of A element including Bi, Te, V, or a combination thereof, the water stability of the positive electrode material and the structural stability during the electrochemical reaction can be enhanced, thereby achieving improved electrochemical performance.

[0086] In some embodiments of the present application, the sodium ion battery positive electrode material may further include a doping element X, where X includes one or more of Se, Ce, Si, P, B, and F. The X element may be incorporated into the positive electrode material in the form of doping, adsorption, or coating, which may further stabilize the crystal structure of the positive electrode material and enhance the stability of the crystal structure during the sodium ion insertion and extraction process.

[0087] In some embodiments, the positive electrode material has any one of the following chemical formulas: NaMn 0.5 Ni 0.2 Fe 0.29 Bi 0.01 O2、 NaMn 0.4 Ni 0.2 Fe 0.29 Cu 0.1 Bi 0.01 O2, NaMn 0.3 Co 0.3 Fe 0.29 Te 0.01 Zr 0.1 O2、NaMn 0.4 Ni 0.2 Fe 0.25 Bi 0.05 Cu 0.1 O2、NaMn 0.45 Ni 0.2 Fe 0.2 Bi 0.05 Cu 0.1 O2.

[0088] According to the embodiments of the present application, the positive electrode material having the above-mentioned chemical composition contains predetermined doping elements, which can obtain good electrochemical properties (such as higher capacity, stable charge and discharge voltage platform) and structural stability, thereby providing improved capacity utilization and cycle performance.

[0089] In some embodiments, the sodium interlayer spacing of the positive electrode material is 0.53 nm to 0.55 nm.

[0090] According to the embodiments of the present application, the sodium interlayer spacing of the positive electrode material is within the above-mentioned range, which is conducive to the conduction and diffusion of sodium ions within the layer. At the same time, it can reduce the exchange reaction of hydrogen ions and sodium ions when the layered structure oxide encounters water, so that the positive electrode material has higher water stability.

[0091] In some embodiments, the positive electrode material has an O3 phase, which is Space group.

[0092] According to the embodiment of the present application, the positive electrode material has The space group is face-centered cubic crystal structure. The positive electrode material with this crystal structure has a higher initial Na content, can release more sodium ions, and has a higher capacity.

[0093] In some embodiments, the positive electrode material satisfies: 2θ0-2θ1≤0.1°, wherein 2θ1 is the diffraction angle corresponding to the characteristic peak (003) in the XRD spectrum obtained after the positive electrode material is immersed in water at 20-30°C for 24 hours, and 2θ0 is the diffraction angle corresponding to the characteristic peak (003) in the XRD spectrum of the positive electrode material.

[0094] As can be understood by those skilled in the art, 2θ0-2θ1 represents the offset of the (003) characteristic peak of the above-mentioned layered oxide positive electrode material before and after soaking in deionized water at room temperature for 24 hours. The offset of the (003) characteristic peak can be used to know the change in the sodium interlayer spacing before and after soaking in water. The smaller the 2θ0-2θ1 value, the smaller the change in the sodium interlayer spacing of the layered oxide before and after soaking in water, the weaker the sensitivity to water and the better the water stability. The positive electrode material provided in the embodiment of the present application is doped with the A element, which is beneficial to reduce the production of by-products caused by the reaction of some elements in the positive electrode material with water or electrolyte, improve the structural stability and electrochemical performance of the positive electrode material, and enable the positive electrode material to maintain the stability of the crystal structure during the deintercalation and insertion of sodium ions, thereby making the positive electrode material have improved capacity and cycle performance.

[0095] Figure 2 and Figure 3 The XRD patterns of the positive electrode material doped with element A in one embodiment of the present application before and after immersion in deionized water at 25° C. are shown respectively. Figure 4 Shown are magnified views of the (003) characteristic peak position in the XRD patterns of the layered oxide cathode material undoped with element A before and after immersion in deionized water at 25°C. Comparison reveals that the (003) characteristic peak change (2θ0-2θ1) of the layered oxide cathode material modified by element A before and after immersion in deionized water at 25°C for 24 hours is ≤0.1°, indicating that element A doping can significantly improve the water stability of layered cathode materials.

[0096] Preparation method of sodium ion battery positive electrode material

[0097] The embodiment of the second aspect of the present application provides a method for preparing the sodium ion battery positive electrode material according to the embodiment of the first aspect of the present application, comprising:

[0098] According to the chemical formula Na x Mn a M b A c O2 provides Na source and precursor materials including Mn source, M source and A source;

[0099] The precursor material is calcined to obtain a positive electrode material for a sodium ion battery.

[0100] In the embodiments of the present application, any one of the solid-phase method and the co-precipitation method can be selected to prepare the sodium ion battery positive electrode material of the first embodiment of the present application, and a positive electrode material with good structural stability and electrochemical performance can be prepared.

[0101] Solid phase method

[0102] In some embodiments, a solid phase method is used to prepare the sodium ion battery cathode material of the first embodiment of the present application, and the method includes:

[0103] According to the chemical formula Na x Mn a M b A c O2 provides precursors including Na source, Mn source, M source, and A source;

[0104] The precursor materials are subjected to ball milling and mixing treatment to obtain a mixture;

[0105] The mixed material is calcined to obtain a positive electrode material for a sodium ion battery.

[0106] In some embodiments, providing a precursor comprising a Na source, a Mn source, an M source, and an A source includes: ball milling and mixing materials comprising a Na source raw material, a Mn source raw material, an M source raw material, and an A source raw material to obtain the precursor.

[0107] In some embodiments, the Na source raw material may include a Na-containing compound, which may be one or more of a sodium salt, a sodium-containing oxide, and a sodium-containing hydroxide, and may further be one or more of Na2CO3, NaHCO3, NaOH, and Na2O2.

[0108] In some embodiments, the Mn source material may include a Mn-containing oxide, which may be one or more of Mn2O3, Mn3O4, MnO, and MnO2.

[0109] In some embodiments, the M source raw material may include an oxide or hydroxide containing the M element, and the M element includes one or more of Fe, Ni, Co, Ti, Cr, Zr, Se, Nb, and Sb. Optionally, the M source raw material may include one or more of iron oxide, nickel oxide, cobalt oxide, titanium dioxide, chromium oxide, iron hydroxide, nickel hydroxide, cobalt hydroxide, titanium hydroxide, and chromium hydroxide.

[0110] In some embodiments, the A source material may include one or more of a simple substance of the A element, an oxide containing the A element, or a salt containing the A element, and the A element may include one or more of Bi, Te, and V. Alternatively, the A source material may include one or more of a simple substance of Bi, a simple substance of Te, a simple substance of V, bismuth oxide, tellurium oxide, and vanadium pentoxide.

[0111] In some embodiments, the precursor material may further include an X source, which may include one or more compounds containing element X, wherein element X includes one or more of Se, Ce, Si, P, B, and F. Alternatively, the X source may include one or more of an oxide containing element X, a hydroxide containing element X, and a salt containing element X.

[0112] In some embodiments, calcining the mixture to obtain a sodium ion battery cathode material includes:

[0113] The mixed material is placed in a muffle furnace and calcined at a preset temperature. After calcination, it is cooled to room temperature and crushed to obtain a positive electrode material.

[0114] In some embodiments, the preset temperature may be 600° C. to 1200° C. Optionally, the preset temperature may be 600° C., 700° C., 800° C., 900° C., 1000° C., 1100° C., 1200° C., or any range thereof.

[0115] In some embodiments, the calcination time can be 10 hours to 20 hours. Alternatively, the calcination time can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 12 hours, or any range thereof.

[0116] According to the embodiments of the present application, the preparation method of the present application adopts a solid-phase method to prepare the positive material. By comprehensively regulating the reaction conditions of the reactants, including the predetermined reaction temperature and reaction time, the positive electrode material has the specific chemical composition and structure described in the present application, which can greatly improve the electrochemical properties of the positive electrode material and ultimately improve the specific capacity, rate performance and cycle performance of the sodium ion battery.

[0117] Coprecipitation method

[0118] In some embodiments, the sodium ion battery positive electrode material of the first embodiment of the present application is prepared by a coprecipitation method, the method comprising:

[0119] reacting a Mn source raw material, an M source raw material, and an A source raw material with a precipitant to obtain a co-precipitate containing the Mn source, the M source, and the A source;

[0120] The coprecipitate and the Na source raw material are ball-milled to obtain a precursor.

[0121] The precursor is calcined to obtain a positive electrode material for a sodium ion battery.

[0122] In some embodiments, the Mn source material may include one or more of chlorides, sulfates, and nitrates containing Mn.

[0123] In some embodiments, the M source raw material may include one or more of chlorides, sulfates, and nitrates containing the M element, and the M element may include one or more of Fe, Ni, Co, Cu, Zr, Ti, Al, Mg, Zn, Cr, Sn, Nb, and Sb.

[0124] In some embodiments, the A source material may include one or more of a simple substance of the A element, an oxide containing the A element, and a salt containing the A element, and the A element includes one or more of Bi, Te, and V.

[0125] In some embodiments, the precipitant may include one or more of a hydroxide precipitant, a phosphate precipitant, and an oxalate precipitant.

[0126] In some embodiments, the hydroxide precipitating agent comprises sodium hydroxide, calcium hydroxide, or a combination thereof;

[0127] In some embodiments, the phosphate precipitant includes one or more of phosphoric acid, sodium phosphate, and potassium phosphate;

[0128] In some embodiments, the oxalate precipitant comprises one or more of oxalic acid, ammonium oxalate, potassium oxalate, and sodium oxalate.

[0129] In some embodiments, the Na source raw material may include a Na-containing compound, which may be one or more of a sodium salt, a sodium-containing oxide, and a sodium-containing hydroxide, and may further be one or more of Na2CO3, NaHCO3, NaOH, and Na2O2.

[0130] In some embodiments, the precursor may further include an X source. The X source raw material may include one or more compounds containing element X. Element X may include one or more of Se, Ce, Si, P, B, and F. Alternatively, the X source may be an oxide containing element X, a hydroxide containing element X, or a salt containing element X.

[0131] In some embodiments, the preset temperature may be 600° C. to 1200° C. Optionally, the preset temperature may be 600° C., 700° C., 800° C., 900° C., 1000° C., 1100° C., 1200° C., or any range thereof.

[0132] In some embodiments, the calcination time can be 10 to 20 hours. Alternatively, the calcination time can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 12 hours, or any range thereof.

[0133] Therefore, the preparation method of the present application adopts a co-precipitation method to prepare the positive electrode material. By comprehensively regulating the reaction conditions of the reactants, including the reaction temperature, reaction time, precipitant, etc., the positive electrode material has the specific chemical composition and structure described in the present application, which can greatly improve the electrochemical performance of the positive electrode material and ultimately improve the specific capacity, rate performance and cycle performance of the sodium ion battery.

[0134] Positive electrode

[0135] An embodiment of the third aspect of the present application provides a positive electrode plate, comprising the sodium ion battery positive electrode material of the first aspect of the present application or the sodium ion battery positive electrode material obtained according to the preparation method of the second aspect of the present application.

[0136] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode material layer includes the sodium ion battery positive electrode material of the first embodiment of the present application, or the sodium ion battery positive electrode material obtained by the preparation method of the second embodiment of the present application. As a result, the positive electrode plate of the present application has high comprehensive electrochemical performance.

[0137] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode material layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0138] In some embodiments, the positive electrode 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 material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0139] In some embodiments, the thickness of the positive electrode current collector is 4 μm to 20 μm, optionally 6 μm to 18 μm, and further optionally 8 μm to 16 μm.

[0140] In some embodiments, the positive electrode material layer comprises 80% to 98% by mass of the positive electrode material based on the total weight of the positive electrode material layer, thereby further improving the energy density.

[0141] secondary batteries

[0142] An embodiment of the fourth aspect of the present application provides a secondary battery, comprising the positive electrode sheet according to the embodiment of the third aspect of the present application.

[0143] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0144] [Positive electrode]

[0145] The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode material layer includes the positive electrode material of the first aspect of the present application.

[0146] The positive electrode material of the aforementioned positive electrode sheet may also include one or more of sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds, which are different from those of the present application. The sodium-ion battery of the embodiments of the present application may utilize a negative electrode sheet using hard carbon as the negative electrode active material, in combination with a positive electrode sheet including one or more of the positive electrode active materials selected from sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds, thereby enabling the sodium-ion battery to have higher capacity performance and energy density.

[0147] Examples of the sodium transition metal oxides include:

[0148] Na 1-x Cu h Fe k Mn l M 1 m O 2-y , where M 1One or more of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn and Ba, 0 <x≤0.33,0<h≤0.24,0≤k≤0.32,0<l≤0.68,0≤m<0.1,h+k+l+m=1,0≤y<0.2;

[0149] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 is one or more of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn and Ba, 0 <z≤0.1;

[0150] Na a Li b Ni c Mn d Fe e O2, of which 0.67 <a≤1,0<b<0.2,0<c<0.3,

[0151] 0.67 <d+e<0.8,b+c+d+e=1。

[0152] Examples of the polyanionic compound include:

[0153] A 1 f M 3 g (PO4) i O j X 1 3-j , wherein A is one or more of H, Li, Na, K and NH4, M 3 is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu and Zn, X 1 is one or more of F, Cl and Br, 0 <f≤4,0<g≤2,1≤i≤3,0≤j≤2;

[0154] Na n M 4 PO4X 2 , where M 4 is one or more of Mn, Fe, Co, Ni, Cu and Zn, X 2 is one or more of F, Cl and Br, 0 <n≤2;

[0155] Na p M 5 q(SO4)3, where M 5 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, 0 < p ≤ 2, 0 < q ≤ 2;

[0156] Na s Mn t Fe 3-t (PO4)2(P2O7), where 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2, or 3.

[0157] As an example of the above-mentioned Prussian blue compounds, for example, the following can be listed:

[0158] A u M 6 v [M 7 (CN)6] w ·xH2O, where A is H + , NH4 + , an alkali metal cation, or an alkaline earth metal cation, M 6 and M 7 are each independently one or more of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A is H + , Li + , Na + , K + , NH4 + , Rb + , Cs + , Fr + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , and Ra 2+ in one or more of them, M 6 and M 7 are each independently the cation of one or more of the transition metal elements Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, and W. Optionally, A is Li + , Na + , and K + in one or more of them, M 6 is the cation of one or more of the transition metal elements Mn, Fe, Co, Ni, and Cu, M 7 is the cation of one or more of the transition metal elements Mn, Fe, Co, Ni, and Cu.

[0159] In some embodiments, the positive electrode material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0160] In some implementations, the weight percentage of the binder in the positive electrode material layer is greater than or equal to 0.5 wt %, which is beneficial for obtaining good bonding performance.

[0161] In some embodiments, the positive electrode material layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0162] In some implementations, the weight percentage of the conductive agent in the positive electrode material layer is greater than or equal to 0.5 wt %, which is beneficial for constructing a better electronic conductive network.

[0163] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0164] [Negative electrode]

[0165] The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode material layer includes a negative electrode active material.

[0166] As an example, the negative electrode current collector has two surfaces that face each other in its thickness direction, and the negative electrode material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector. The negative electrode current collector can be made of materials such as metal foil, carbon-coated metal foil, or porous metal sheet, and copper foil is optionally used.

[0167] As an example, the negative electrode material layer includes a negative electrode active material, an optional conductive agent, and an optional binder. The conductive agent is used to improve the conductivity of the negative electrode material layer, and the binder is used to firmly bond the negative electrode active material and the binder to the negative electrode current collector. This application does not specifically limit the types of the conductive agent and binder, and they can be selected according to actual needs.

[0168] As an example, the negative electrode active material may be one or more of natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon and soft carbon.

[0169] As an example, the conductive agent can be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers; the binder can be one or more of styrene-butadiene rubber (SBR), styrene-butadiene rubber (SBCs), water-based acrylic resin and carboxymethyl cellulose (CMC).

[0170] The negative electrode material layer may also optionally include a thickener, such as carboxymethyl cellulose (CMC). However, the present application is not limited thereto, and the present application may also use other materials that can be used as thickeners for negative electrode sheets of sodium ion batteries.

[0171] [Electrolytes]

[0172] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0173] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0174] In some embodiments, the electrolyte may include an organic solvent and a sodium salt. Any organic solvent and sodium salt that can be used in sodium-ion batteries can be selected based on actual needs. For example, the organic solvent may be one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC); and the sodium salt may be one or more of NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3.

[0175] In some embodiments, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0176] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0177] [Isolation film]

[0178] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0179] In some embodiments, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0180] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0181] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0182] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0183] The present application has no particular restrictions on the shape of the secondary battery, which can be cylindrical, square or any other shape. For example, Figure 5 The secondary battery 5 is a square structure as an example.

[0184] In some embodiments, reference Figure 6 , the outer packaging may include a shell 51 and a top cover assembly 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a accommodating cavity. The shell 51 has an opening connected to the accommodating cavity, and the top cover assembly 53 can be covered on the opening to close the accommodating cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the accommodating cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0185] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0186] Figure 7 4 is an example of a battery module. Figure 7In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length of the battery module 4. Of course, they may also be arranged in any other manner. The plurality of secondary batteries 5 may further be fixed by fasteners.

[0187] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0188] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0189] Figure 8 and Figure 9 The battery pack 1 is used as an example. Figure 8 and Figure 9 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0190] Electrical devices

[0191] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, and battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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., but is not limited thereto.

[0192] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0193] Figure 10 This is an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0194] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0195] Example

[0196] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0197] Example 1

[0198] Preparation of positive electrode materials

[0199] S10, weighing a total of 30 g of Na2CO3, Mn2O3, NiO, Fe2O3, CuO, and Bi2O3 according to the molar ratio of Na:Mn:Ni:Fe:Cu:Bi=1:0.4:0.2:0.29:0.1:0.01;

[0200] S20, pre-grinding the obtained sample in an agate mortar and then adding it to a planetary ball mill for ball milling for 1 h to obtain a precursor mixture;

[0201] S30, the obtained precursor mixture is evenly placed in an open crucible, and then heated from room temperature to 950 ° C in a muffle furnace at a heating rate of 5 ° C / min, and kept at 950 ° C for 15 hours. After natural cooling, the positive electrode material NaMn 0.4 Ni 0.2 Fe 0.29 Cu 0.1 Bi 0.01 O2.

[0202] Examples 2 to 7

[0203] The preparation method is the same as that of Example 1, except that the components of the positive electrode material are adjusted, as shown in Table 1.

[0204] Example 8

[0205] The difference from Example 1 is that the method for preparing the positive electrode material is adjusted, specifically:

[0206] S10. Weigh a total of 30 g of sample, including NaOH, NiSO4, FeSO4, MnSO4·H2O, CuO, and Bi2O3, according to a molar ratio of Na:Ni:Fe:Mn:Cu:Bi=1:0.2:0.29:0.4:0.1:0.01;

[0207] S20, dispersing NiSO4, FeSO4, MnSO4·H2O, CuO, and Bi2O3 in deionized water to obtain a solution, adding a precipitant, sodium hydroxide, to the solution to react, filtering out the liquid after the reaction, and drying to obtain a precursor powder;

[0208] S30, the precursor powder was ball-milled with sodium carbonate, and then placed in a muffle furnace and heated from room temperature to 950 ° C at a heating rate of 5 ° C / min, and kept at 950 ° C for 15 hours. After natural cooling, the positive electrode material NaMn was obtained. 0.4 Ni 0.2 Fe 0.29 Cu 0.1 Bi 0.01 O2.

[0209] Comparative Examples 1 to 3

[0210] The preparation method is the same as that of Example 1, except that the components of the positive electrode material are adjusted, as shown in Table 1.

[0211] Table 1:

[0212]

[0213]

[0214] Test section

[0215] X-ray diffraction test:

[0216] The positive electrode materials obtained in each embodiment and comparative example were immersed in deionized water at 25°C for 24 hours, and the XRD patterns before and after immersion were measured, and the changes in the characteristic peak (003) in the XRD diffraction pattern were compared. The XRD diffraction pattern test method is as follows: an X-ray diffraction tester (PANalytical, the Netherlands, XPert Pro MPD) was used, and the test conditions were set as follows: Cu Kα radiation The working current was 250 mA, continuous scanning was adopted, the working voltage was 40 kV, the scanning range 2θ was 10° to 70°, the step length was 0.1°, and the scanning speed was 0.2 s / step.

[0217] The performance test results are detailed in Table 2.

[0218] Table 2:

[0219] cathode materials <![CDATA[2θ0(°)]]> <![CDATA[2θ1(°)]]> <![CDATA[2θ0-2θ1(°)]]> Example 1 <![CDATA[NaMn 0.4 Ni 0.2 Feb 0.29 Cu 0.1 Bi 0.01 O2]]> 16.40 16.32 0.08 Example 2 <![CDATA[NaMn 0.3 What 0.3 Fe 0.29 You 0.01 Zr 0.1 O2]]> 16.48 16.41 0.07 Example 3 <![CDATA[NaMn 0.3 What 0.25 Fe 0.24 Would 0.01 Zr 0.1 Yes 0.1 O2]]> 16.42 16.33 0.09 Example 4 <![CDATA[NaMn 0.4 Ni 0.2 Feb 0.25 Bi 0.05 Cu 0.1 O2]]> 16.39 16.33 0.06 Example 5 <![CDATA[NaMn 0.4 Ni 0.2 Feb 0.2 Bi 0.1 Cu 0.1 O2]]> 16.39 16.32 0.07 Example 6 <![CDATA[NaMn 0.45 Ni 0.2 Feb 0.2 Bi 0.05 Cu 0.1 O2]]> 16.42 16.35 0.07 Example 7 <![CDATA[NaMn 0.2 Ni 0.35 Feb 0.3 Bi 0.05 Cu 0.1 O2]]> 16.55 16.47 0.08 Example 8 <![CDATA[NaMn 0.4 Ni 0.2 Feb 0.29 Cu 0.1 Bi 0.01 O2]]> 16.44 16.36 0.07 Comparative Example 1 <![CDATA[NaMn 0.4 Ni 0.2 Feb 0.29 Cu 0.11 O2]]> 16.53 16.36 0.17 Comparative Example 2 <![CDATA[NaMn 0.4 Aunt 0.2 Fe 0.29 The 0.1 Zr 0.01 O2]]> 16.51 16.32 0.19 Comparative Example 3 <![CDATA[NaMn 0.4 Ni 0.2 Feb 0.29 Cu 0.1 Ga 0.01 O2]]> 16.59 16.41 0.18

[0220] From the test results in Table 2, it can be seen that when element A is incorporated into the layered oxide positive electrode material, the 2θ0-2θ1 value of the (003) characteristic peak of the positive electrode material before and after soaking in water is significantly reduced. This indicates that after the incorporation of element A, the offset of the (003) characteristic peak in the XRD spectrum of the positive electrode material is reduced, the change in the sodium interlayer spacing is reduced, and the sensitivity of the positive electrode material to water is weakened. Therefore, the incorporation of element A can effectively improve the water stability of the layered oxide positive electrode material, reduce the reaction between the positive electrode material and water, and keep the structure of the layered oxide positive electrode material stable.

[0221] The positive electrode material provided in the above embodiment can also be used to prepare a secondary battery. The specific preparation method is as follows:

[0222] Preparation of positive electrode sheet

[0223] The positive electrode material, binder PVDF and conductive agent conductive carbon black are mixed in a weight ratio of 90:5:5, and the solvent NMP is added to ensure that the solid content is 40%. The mixture is stirred under vacuum stirring until a uniform and transparent system is obtained to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and then transferred to an oven for drying at a drying temperature of 120°C, and then cold pressed and cut to obtain positive electrode sheets.

[0224] Preparation of negative electrode sheet

[0225] The negative electrode active material graphite, conductive agent Super P, thickener carboxymethyl cellulose (CMC), and binder styrene butadiene rubber (SBR) are mixed evenly in deionized water at a mass ratio of 80:15:3:2 to form a negative electrode slurry, and the solid content in the negative electrode slurry is 30wt%; the negative electrode slurry is evenly coated on the current collector copper foil and dried at 85°C, and then cold pressed, trimmed, cut into pieces, and slit, and then dried under vacuum conditions at 120°C for 12 hours to form a negative electrode sheet.

[0226] Isolation film

[0227] A 16 μm polyethylene film was used as the separator.

[0228] Preparation of electrolyte

[0229] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. 1 mol / L NaPF6 was dissolved in the organic solvent, and 5% fluoroethylene carbonate (FEC) was added based on the total mass of the electrolyte, and the mixture was mixed to obtain an electrolyte.

[0230] Preparation of secondary batteries

[0231] The positive electrode sheet, the separator, and the negative electrode sheet were stacked in sequence, the electrolyte was injected and the battery was sealed, and the battery was left to stand for 6 hours to obtain a sodium ion secondary button battery.

[0232] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A sodium ion battery cathode material, characterized in that The positive electrode material has a layered structure and its chemical formula is: Na x Mn a M b A c O2, where M includes one or more of Fe, Ni, Co, Cu, Zr, Ti, Al, Mg, Zn, Cr, Sn, Nb, and Sb; A includes one or more of Bi, Te, and V; 0<x≤1, 0<a, 0<b, 0<c≤0.

1.

2. The sodium ion battery positive electrode material according to claim 1, characterized in that M includes one or more of Fe, Ni, Cu, and Co.

3. The sodium ion battery positive electrode material according to claim 1, characterized in that A includes Bi element.

4. The sodium ion battery positive electrode material according to any one of claims 1 to 3, characterized in that 0.8≤x≤1, 0.25≤a≤0.5, 0.5≤b≤0.75, 0.01≤c≤0.05, a+b+c=1.

5. The sodium ion battery positive electrode material according to any one of claims 1 to 4, characterized in that The positive electrode material further contains an X element, and the X element includes one or more of Se, Ce, Si, P, B, and F.

6. The sodium ion battery cathode material according to any one of claims 1 to 5, characterized in that The positive electrode material includes any one of the following chemical formulas: NaMn 0.5 Ni 0.2 Fe 0.29 Bi 0.01 O2、NaMn 0.4 Ni 0.2 Fe 0.29 Cu 0.1 Bi 0.01 O2、NaMn 0.3 Co 0.3 Fe 0.29 Te 0.01 Zr 0.1 O2、NaMn 0.4 Ni 0.2 Fe 0.25 Bi 0.05 Cu 0.1 O2、NaMn 0.3 Co 0.25 Fe 0.24 Bi 0.01 Zr 0.1 Si 0.1 O2.

7. The sodium ion battery cathode material according to any one of claims 1 to 6, characterized in that The sodium interlayer spacing of the positive electrode material is 0.53nm to 0.55nm.

8. The sodium ion battery cathode material according to any one of claims 1 to 7, characterized in that The positive electrode material has an O3 phase, belonging to Space group.

9. The sodium ion battery cathode material according to any one of claims 1 to 8, characterized in that The positive electrode material satisfies: 2θ0-2θ1≤0.1°, wherein 2θ1 is the diffraction angle corresponding to the characteristic peak (003) in the XRD spectrum obtained after the positive electrode material is immersed in water at 20°C to 30°C for 24 hours, and 2θ0 is the diffraction angle corresponding to the characteristic peak (003) in the XRD spectrum of the positive electrode material.

10. A method for preparing a positive electrode material for a sodium ion battery according to any one of claims 1 to 9, characterized in that: include: According to the chemical formula Na x Mn a M b A c O2 provides precursors including Na source, Mn source, M source, and A source; The precursor is calcined to obtain a positive electrode material for a sodium ion battery.

11. The method for preparing a positive electrode material for a sodium ion battery according to claim 10, wherein: The precursor comprising a Na source, a Mn source, an M source, and an A source comprises: The materials including the Na source raw material, the Mn source raw material, the M source raw material and the A source raw material are subjected to ball milling and mixing treatment to obtain the precursor.

12. The method for preparing a positive electrode material for a sodium ion battery according to claim 11, wherein: The method satisfies at least one of the following: The Na source raw material includes one or more Na-containing compounds; The Mn source raw material includes one or more Mn-containing oxides; The M source raw material includes an oxide or hydroxide containing the M element; The A source raw material includes one or more of element A and compounds containing element A.

13. The method for preparing a positive electrode material for a sodium ion battery according to claim 12, wherein: The method satisfies at least one of the following: The Na source raw material includes one or more of Na2CO3, NaHCO3, NaOH, and Na2O2; The Mn source raw material includes one or more of Mn2O3, Mn3O4, MnO, and MnO2; The M source raw material includes one or more of iron oxide, nickel oxide, cobalt oxide, copper oxide, magnesium oxide, zinc oxide, aluminum oxide, titanium dioxide, chromium oxide, iron hydroxide, nickel hydroxide, cobalt hydroxide, titanium hydroxide, and chromium hydroxide; The A source material includes one or more of Bi, Te, V, Cu, bismuth oxide, tellurium oxide, vanadium pentoxide, and copper oxide.

14. The method for preparing a positive electrode material for a sodium ion battery according to claim 10, wherein: The precursor comprising a Na source, a Mn source, an M source, and an A source comprises: reacting a Mn source raw material, an M source raw material, and an A source raw material with a precipitant to obtain a co-precipitate containing the Mn source, the M source, and the A source; The coprecipitate and the Na source raw material are subjected to ball milling and mixing treatment to obtain the precursor.

15. The method for preparing a positive electrode material for a sodium ion battery according to claim 14, wherein: The method satisfies at least one of the following: The Mn source raw material includes one or more of chlorides, sulfates, and nitrates containing Mn; The M source raw material includes one or more of chloride, sulfate, and nitrate containing the M element; The A source raw material includes one or more of element A and compounds containing element A; The Na source raw material includes one or more Na-containing compounds; The precipitant includes one or more of a hydroxide precipitant, a phosphate precipitant and an oxalate precipitant.

16. The method for preparing a positive electrode material for a sodium ion battery according to claim 15, wherein: The hydroxide precipitant includes sodium hydroxide, calcium hydroxide or a combination thereof; The phosphate precipitant includes one or more of soluble phosphoric acid, sodium phosphate, and potassium phosphate; The oxalate precipitant includes one or more of oxalic acid, ammonium oxalate, potassium oxalate, and sodium oxalate.

17. The method for preparing a positive electrode material for a sodium ion battery according to any one of claims 10 to 16, characterized in that: The precursor further includes an X source, and the X source includes a compound containing an X element, and the X element includes one or more of Se, Ce, Si, P, B, and F.

18. The method according to any one of claims 10 to 17, characterized in that The method satisfies at least one of the following: The calcination temperature is 600°C to 1200°C; The calcination treatment time is 10 hours to 20 hours.

19. A positive electrode plate, characterized in that: The invention relates to a sodium ion battery positive electrode material according to any one of claims 1 to 9 or a sodium ion battery positive electrode material obtained by the preparation method according to any one of claims 10 to 18.

20. A secondary battery, characterized in that: Including the positive electrode sheet according to claim 19.

21. An electrical device, characterized in that: A secondary battery according to claim 20 is included.

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