Cathode material and method of manufacturing the same, positive electrode plate and sodium ion battery

Abstract

The present application provides a positive electrode material belonging to the field of batteries, a method for manufacturing the same, a positive electrode plate, a sodium-ion battery, and an electric device; the positive electrode material comprises a core and a carbon-containing coating layer covering at least a portion of the surface of the core, and the core comprises sodium vanadium fluorophosphate; a Nth charge-discharge test is performed on a button-type battery manufactured using the positive electrode material, and in the discharge curve of the Nth charge-discharge test, the discharge specific capacity is C0, the total discharge specific capacity of the discharge platform corresponding to a voltage of 3.3V to 3.4V is C1, satisfying C1 / C0 < 6.7%, and N is an integer greater than or equal to 1, and the condition of the Nth charge-discharge test is to charge the button-type battery to 4.3V with a constant current of 0.2C at a temperature of 20℃ to 30℃, and then discharge it to 2V with a constant current of 0.2C. The positive electrode material provided in the present application has a high discharge specific capacity and electronic conductivity.

Description

Technology Field

[0001] The present invention relates to the field of battery technology, and specifically to a positive electrode material, a method for manufacturing the same, a positive electrode plate, and a sodium ion battery. Background Technology

[0002] Sodium-ion batteries (SIBs) are secondary batteries with the next-largest application prospects after lithium-ion batteries (e.g., applicable to fields such as new energy vehicles), and their electrochemical performance is primarily determined by the performance of the cathode. Among the various cathode materials for sodium-ion batteries, sodium vanadium fluorophosphate (Na3V2(PO4)2F3, NVPF) has a theoretical operating voltage of approximately 3.85 V and a theoretical specific capacity of 128.3 mAh / g, making it a cathode material for sodium-ion batteries with very high application prospects. However, currently manufactured NVPF materials still suffer from poor capacity, resulting in low energy density for sodium-ion batteries; furthermore, while the NVPF material itself possesses excellent ionic conductivity, it has poor electronic conductivity.

[0003] Taking into account the technical problems existing in the background technology, the present application provides a positive electrode material, a method for manufacturing the same, a positive electrode plate, and a sodium ion battery to solve the problem of insufficient capacity and poor electronic conductivity of currently manufactured NVPF materials.

[0004] According to the first aspect, the anode material provided in an embodiment of the present application comprises a core and a carbon-containing coating layer covering at least a portion of the surface of the core, wherein the core comprises sodium vanadium fluorophosphate (Na3V2(PO4)2F3);

[0005] A Nth charge-discharge test is performed on a button-type battery manufactured using the above-mentioned positive electrode material, and in the discharge curve of the Nth charge-discharge test, the discharge specific capacity is C0, the discharge specific capacity of the discharge platform corresponding to a voltage of 3.3V to 3.4V is C1, satisfying C1 / C0 < 6.7%, and N is an integer greater than or equal to 1, and

[0006] The condition of the above Nth charge / discharge test is to charge the button-type battery to 4.3V with a constant current of 0.2C at a temperature of 20℃ to 30℃, and then discharge it to 2V with a constant current of 0.2C.

[0007] In the technical means according to the embodiment of the present application, by controlling C1 / C0 to < 6.7%, the core of the anode material contains high-purity Na3V2(PO4)2F3, and the mass ratio of impurities such as Na3V2(PO4)3 is low, thereby effectively improving the capacity of the anode material and the energy density of the sodium-ion battery. In addition, the carbon-containing coating layer within the anode material effectively improves the electronic conductivity of the NVPF, thereby further improving the capacity of the material.

[0008] In some embodiments, the anode material is,

[0009] (1) Condition where C1 / C0≤3.5%;

[0010] (2) Condition in which the carbon-containing coating layer covers the surface of the core with a coating rate of 89% to 100%, preferably 95% to 100%;

[0011] (3) At least one of the following conditions is satisfied: the porosity of the anode material is 10% to 69%, preferably 15% to 30%.

[0012] In the technical means according to the embodiment of the present application, if the porosity is within the above range, it is advantageous to ensure the entry and exit of sodium ions while increasing the density of the carbon-containing coating layer and to improve the compaction density of the anode material. If C1 / C0 is within the above range, the purity of the NVPF phase in the anode material is increased, thereby more effectively improving the capacity of the anode material and the energy density of the sodium ion battery. If the carbon-containing coating layer covers the surface of the core with a coating rate within the above range, it is advantageous to improve the capacity and corrosion resistance of the anode material and to enable the anode material to have excellent electronic conductivity.

[0013] In some embodiments, the mass fraction of carbon elements in the anode material is 1.25% to 6%, and preferably 1.5% to 3.5%.

[0014] In the technical means according to the embodiment of the present application, if the mass fraction of carbon elements in the anode material is within the above range, the anode material may have high compaction density and electronic conductivity; and if a carbon-containing coating layer covers the surface of the core with a coating rate within the above range, it is advantageous for improving the capacity and corrosion resistance of the anode material and enables the anode material to have excellent electronic conductivity.

[0015] In some embodiments, the compaction density of the anode material is 1.4 g / cm³ 3 ~2g / cm 3 and preferably 1.53 g / cm³ 3 ~1.99g / cm 3 am.

[0016] In the technical means according to the embodiment of the present application, since the compaction density of the anode material is relatively high, the sodium ion battery can have a higher energy density.

[0017] In a second aspect, the method for manufacturing an anode material provided in the embodiment of the present application is.

[0018] A step of preparing a mixed slurry containing a sodium source, a fluorine source, a vanadium source, a phosphorus source, and a carbon source;

[0019] A step of obtaining a precursor by drying the above-mentioned mixed slurry;

[0020] The method includes the step of obtaining the anode material by calcining the above precursor;

[0021] The above-mentioned positive electrode material comprises a core and a carbon-containing coating layer covering at least a portion of the surface of the core, wherein the core comprises sodium vanadium fluorophosphate (Na3V2(PO4)2F3); the Nth charge-discharge test is performed on a button-type battery manufactured using the above-mentioned positive electrode material, and in the discharge curve of the Nth charge-discharge test, the discharge specific capacity is C0, the discharge specific capacity of the discharge platform corresponding to a voltage of 3.3V to 3.4V is C1, satisfying C1 / C0 < 6.7%, and N is an integer greater than or equal to 1, and the condition of the Nth charge-discharge test is to charge the button-type battery to 4.3V with a constant current of 0.2C at a temperature of 20℃ to 30℃, and then discharge it to 2V with a constant current of 0.2C.

[0022] The cathode material obtained through the manufacturing method provided in this application contains a core of high purity Na3V2(PO4)2F3 and has a low mass ratio of impurity phases such as Na3V2(PO4)3, so the capacity of the cathode material and the energy density of the sodium-ion battery can be effectively improved. In addition, the carbon-containing coating layer in the cathode material obtained by the above manufacturing method can effectively improve the electronic conductivity of the NVPF, thereby further improving the capacity of the material.

[0023] In some embodiments, the carbon source comprises at least one of citric acid, polyvinyl alcohol, glucose, sucrose, and oxalic acid, optionally comprises citric acid and / or polyvinyl alcohol, and also optionally comprises citric acid and polyvinyl alcohol;

[0024] Optionally, if the carbon source is citric acid and polyvinyl alcohol, the mass ratio of the citric acid to the polyvinyl alcohol is 2:1 to 1:4;

[0025] Optionally, the polyvinyl alcohol comprises at least one of polyvinyl alcohol 2000, polyvinyl alcohol 3000, polyvinyl alcohol 4000, and polyvinyl alcohol 6000.

[0026] In the technical means according to the embodiment of the present application, when the carbon source includes citric acid and polyvinyl alcohol, the combination of citric acid and polyvinyl alcohol can produce a mutually promoting effect, thereby further improving the compaction density, which is advantageous for improving the energy density of the sodium ion battery to which the anode material is applied.

[0027] In some embodiments, the manufacturing method is,

[0028] (1) The sodium source comprises at least one of sodium fluoride, sodium phosphate, sodium bicarbonate and sodium nitrate, and optionally, conditions comprising sodium fluoride;

[0029] (2) The above fluorine source comprises at least one of sodium fluoride, ammonium fluoride, potassium fluoride and lithium fluoride, and optionally, a condition comprising sodium fluoride;

[0030] (3) The above vanadium source is a condition in which vanadium pentoxide and / or ammonium metavanadate is included;

[0031] (4) The above phosphorus source satisfies at least one of the following conditions: containing at least one of ammonium dihydrogen phosphate, sodium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and triammonium phosphate.

[0032] In the technical means according to the embodiment of the present application, when sodium fluoride is used as a sodium source and / or a fluoride source, sodium can be provided while fluoride can also be provided. This is advantageous for reducing raw material input and waste compared to a method of providing sodium and fluoride separately.

[0033] In some embodiments, the method for preparing the mixed slurry is,

[0034] A step of taking the sodium source, the fluorine source, the vanadium source, and the phosphorus source according to the stoichiometric ratio of Na3V2(PO4)2F3, and mixing with a solvent and the carbon source to form a first slurry;

[0035] The method comprises the step of adjusting the pH value of the first slurry to 6 to 7 using a pH adjuster, and then obtaining the mixed slurry through a grinding process.

[0036] Optionally, the pH adjuster comprises at least one of ammonia water, sodium hydroxide, sodium carbonate, sodium bicarbonate, and ammonium bicarbonate, and optionally also comprises ammonia water.

[0037] In the technical means according to an embodiment of the present application, by adjusting the pH value of the first slurry to 6 to 7 using a pH adjuster, F in the mixed slurry - The hydrolysis of can be effectively suppressed, the generation of HF can be suppressed to effectively reduce F loss, and the generation of impurities such as sodium vanadium phosphate in the final product can be reduced, thereby effectively improving the purity (content) of Na3V2(PO4)2F3, and thus the capacity of the manufactured cathode material can be improved.

[0038] In some embodiments, the mixed slurry further includes a fluoride supplement;

[0039] Optionally, the fluoride supplement comprises ammonium fluoride and / or sodium fluoride, and also optionally, comprises ammonium fluoride;

[0040] Optionally, the molar amount of the fluoride supplement is 1% to 5% of the molar amount of the fluoride source.

[0041] In the technical means according to the embodiment of the present application, when a fluorine supplement is included in the mixed slurry, the fluorine supplement compensates for some of this F loss and effectively reduces the formation of impurity phases such as sodium vanadium phosphate in the final product, thereby effectively improving the purity (content) of Na3V2(PO4)2F3 and thus improving the capacity of the manufactured anode material.

[0042] In some embodiments, the temperature of the calcination treatment is 550°C to 800°C, preferably 650°C to 800°C; the holding time of the calcination treatment is 3h to 10h, preferably 4h to 9h; and the calcination treatment is performed in a protective atmosphere;

[0043] Optionally, the protective atmosphere comprises nitrogen and / or argon.

[0044] In the technical means according to the embodiment of the present application, if the temperature of the calcination treatment or the holding time is set within the respective ranges, the density of the carbon-containing coating layer can be improved, while the purity of Na3V2(PO4)2F3 in the anode material can also be improved. If the temperature of the calcination treatment is low or the holding time is short, the carbonization of the carbon source forming the carbon-containing coating layer is incomplete and the degree of graphitization tends to be low, resulting in reduced electronic conductivity and lower capacity of the manufactured anode material. Furthermore, if the temperature of the calcination treatment is relatively low, the formed carbon-containing coating layer becomes somewhat loose, resulting in lower compaction density of the anode material. If the sintering temperature is relatively high or the holding time is relatively long, F loss tends to increase and the purity of the Na3V2(PO4)2F3 phase in the anode material decreases, resulting in lower capacity of the anode material.

[0045] According to a third aspect, the positive electrode plate provided in an embodiment of the present application comprises a positive material according to the first aspect of the present application or a positive material manufactured by a manufacturing method according to the second aspect of the present application.

[0046] In this embodiment, the positive electrode plate includes the aforementioned positive material, so it has high capacity and energy density.

[0047] According to the fourth aspect, the sodium ion battery provided in the embodiment of the present application includes a positive electrode plate according to the third aspect of the present application.

[0048] In this embodiment, the sodium ion battery includes the aforementioned positive electrode plate, so it has high capacity and energy density.

[0049] According to the fifth aspect, the electric device provided in the embodiment of the present application includes a sodium ion battery according to the fourth aspect of the present application.

[0050] The electric device of the present application includes a sodium ion battery provided in the present application, and thus has at least the same advantages as a sodium ion battery.

[0051] The above description is merely an overview of the technical solution of the present application. To understand the technical means of the present application more thoroughly, it may be implemented in accordance with the contents of the specification. Furthermore, to enable a clearer understanding of the purpose, features, and advantages of the present application, specific embodiments of the present application are described below. Brief explanation of the drawing

[0052] Hereinafter, to more clearly explain the technical means of the present application, the drawings used in the description of the present application are briefly introduced. The drawings described below are merely some embodiments of the present application, and it is obvious to those skilled in the art that other drawings can be obtained based on these drawings without creative work. FIG. 1 is a diagram showing the manufacturing process flow of the anode material provided in the present application. FIG. 2 is a diagram showing the shape of an anode material manufactured according to Example 8 of the present application. FIG. 3 is a diagram showing the form of an anode material manufactured according to Example 13 of the present application. FIG. 4 is a diagram showing the shape of an anode material manufactured according to Example 13 of the present application. FIG. 5 is a drawing showing the first charge-discharge curve of a button-type battery made of a positive electrode material according to Example 6 of the present application. FIG. 6 is a drawing showing the first charge-discharge curve of a button-type battery made of a positive electrode material according to Comparative Example 3 of the present application. Specific details for implementing the invention

[0053] Hereinafter, embodiments of the technical means of the present application will be described in detail with reference to the attached drawings. The following embodiments are used merely to more clearly explain the technical means of the present application and are therefore illustrative; the scope of protection of the present application is not to be limited thereto.

[0054] All technical and scientific terms used in this specification have the same meaning as generally understood by those skilled in the art to which the present invention pertains, unless otherwise defined; terms used in this specification are intended to specifically describe embodiments and are not to be interpreted as limiting the scope of this application; and terms "comprising," "having," and all variations thereof as used in the description of the invention, claims, and drawings in this application are interpreted to cover non-exclusive inclusions.

[0055] In the embodiments of this application, terms such as "first," "second," etc. are used merely to distinguish different objects and should not be interpreted as indicating or implying relative importance, or as implicitly indicating the number of technical features being modified, a specific order, or a subject-object relationship. In the embodiments of this application, "plural" means two or more unless specifically defined otherwise.

[0056] In this specification, "Examples" means that specific features, structures, or characteristics described in combination with the Examples may be included in at least one Example of this application. As stated in various places in this specification, this phrase does not necessarily refer to the same Example, nor are they independent or alternative Examples mutually exclusive from other Examples. Those skilled in the art will understand clearly and implicitly that the Examples described in this specification may be combined with other Examples.

[0057] In the embodiments of this application, the term "and / or" merely describes the association between related objects and indicates that three relationships may exist; for example, “A and / or B” may represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, in this specification, the symbol " / " generally indicates that the related objects before and after it have an "or" relationship.

[0058] In the embodiments of the present application, the term “plural” means two or more (including two), likewise, “plural group” means two or more groups (including two groups), and “plural piece” means two or more pieces (including two pieces).

[0059] In the description of the embodiments of the present application, the directional or positional relationships indicated by technical terms such as “center,” “longitudinal,” “transverse,” “length,” “width,” “thickness,” “top,” “bottom,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inside,” “outside,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circular” are based on the directional or positional relationships illustrated in the attached drawings and are merely intended to easily and briefly explain the embodiments of the present application. They do not indicate or imply that the mentioned devices or components must have a specific direction or be configured and operated in a specific direction, and therefore should not be interpreted as limiting the present application.

[0060] Unless otherwise specifically stated in the description of the embodiments of this application, technical terms such as “mounting,” “connecting to each other,” “connecting,” and “fixing” should be interpreted in a broad sense, for example, they may be fixedly connected, detachably connected, or integrally formed; or they may be mechanically connected or electrically connected; or they may be directly connected or indirectly connected through an intermediate element; or the interiors of two components may be in communication or there may be an interaction relationship between two components. A person skilled in the art to which this application pertains will be able to readily understand the specific meaning that the said terms have in the embodiments of this application depending on the specific circumstances.

[0061] Currently, the discharge curves of already manufactured NVPF materials generally have three voltage platforms (Na + Although approximately 4.1V, 3.6V, and 3.3V–3.4V for / Na exist, theoretically, NVPF materials have two platforms (Na +There are only about 4.1V and 3.6V for / Na, where the presence of a low voltage platform of 3.3V to 3.4V reduces the average discharge voltage and discharge capacity of the cathode material and the sodium ion battery using said material, thereby lowering the energy density of the battery.

[0062] Based on the above phenomenon, according to the inventors' research, the reason a low-voltage platform of 3.3V to 3.4V exists in currently manufactured NVPF materials is that the solid-state method is generally used in the manufacture of NVPF materials. Since this method is prone to causing significant F loss during the manufacturing process, impurity phases such as sodium vanadium phosphate (Na3V2(PO4)3) are present in the final product. Consequently, the purity (content) of Na3V2(PO4)2F3 in the material is reduced, and as a result, a low-voltage platform of 3.3V to 3.4V is generated, which lowers the capacity of the product and reduces the energy density of the sodium-ion battery.

[0063] In order to solve the technical problems of insufficient capacity and poor electronic conductivity of currently existing NVPF materials, the present application provides a positive electrode material and a method for manufacturing the same, a positive electrode plate, a sodium ion battery, and an electric device. By improving the current NVPF material and the method for manufacturing the same, technical effects of improving electronic conductivity and capacity can be obtained, and through this, the capacity and energy density of the positive electrode plate, secondary battery, and electric device can also be improved.

[0064] According to the first aspect, the anode material provided in the present application comprises a core and a carbon-containing coating layer covering at least a portion of the surface of the core, wherein the core comprises sodium vanadium fluorophosphate (Na3V2(PO4)2F3); and a Nth charge-discharge test is performed on a button-type battery manufactured using the anode material, wherein in the discharge curve of the Nth charge-discharge test, the discharge specific capacity is C0, the total discharge specific capacity of the discharge platform corresponding to a voltage of 3.3V to 3.4V is C1, satisfying C1 / C0 < 6.7%, where N is an integer greater than or equal to 1, and the condition of the Nth charge-discharge test is to charge the button-type battery to 4.3V with a constant current of 0.2C at a temperature of 20℃ to 30℃, and then discharge it to 2V with a constant current of 0.2C.

[0065] In some embodiments, the manufacturing process of the button-type battery is as follows. The positive electrode material, conductive agent, and binder provided in this application are mixed in a specific mass ratio, and a suitable amount of solvent is added to form a uniform electrode slurry. Then, the electrode slurry is uniformly coated onto aluminum foil, and after vacuum drying, it is cut into a circular electrode plate of a specific diameter and immediately transferred to a glove box to stand by. A button-type battery is assembled by using metallic sodium as the counter electrode and glass fiber as the separator, and by adding an electrolyte. The entire assembly process is performed in a glove box filled with argon gas.

[0066] In some embodiments, the conductive agent comprises one or more of carbon black, acetylene black, kethon black, and carbon nanotubes.

[0067] In some embodiments, the binder comprises polyvinylidene fluoride (PVDF).

[0068] In some embodiments, the mass ratio of the anode material, conductive agent, and binder in the electrode slurry is (80:10:10) to (90:5:5).

[0069] In some embodiments, the solvent of the electrode slurry comprises at least one of N-methylpyrrolidone (NMP) and water.

[0070] In some embodiments, the diameter of the circular electrode plate is 15 mm to 20 mm.

[0071] In some embodiments, the electrolyte comprises an electrolyte, an organic solvent, and an optional additive, and the electrolyte is sodium perchlorate ( ) and sodium hexafluorophosphate ( It includes at least one of ), the organic solvent includes one or more of propylene carbonate, ethylene carbonate, and dimethyl carbonate, and the additive includes fluoroethylene carbonate (FEC).

[0072] In some embodiments, the concentration of the electrolyte contained in the electrolyte is 1 mol / L to 1.5 mol / L. For example, the manufacturing process of the button battery provided in this application is as follows. The positive electrode material provided in this application, conductive carbon black, and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 85:8:7, and a suitable amount of N-methylpyrrolidone (NMP) is added to form a uniform electrode slurry, then the electrode slurry is evenly spread on aluminum foil, vacuum dried, cut into a circular electrode plate with a diameter of 15 mm, and then immediately transferred to a glove box for later use. A CR2032 button-type battery is assembled using metallic sodium as the counter electrode and glass fiber as the separator, sodium perchlorate as the solute of the electrolyte, propylene carbonate, ethylene carbonate, and fluoroethylene carbonate (volume ratio 1:1:0.05) as the solvent of the electrolyte, and the concentration of sodium perchlorate in the electrolyte is 1 mol / L, and the entire assembly process is carried out in a glove box filled with argon gas.

[0073] For reference, the above discharge curve generally has the specific capacity (unit is mAh / g) as the horizontal coordinate and the voltage (unit is V) as the vertical coordinate; in this discharge curve, there exists a discharge platform that is nearly parallel to the horizontal axis in the section where the voltage of the vertical coordinate is 3.3V to 3.4V, and if we assume that the specific capacities corresponding to each end point of the discharge platform are C1' and C2', then C1 = C1' - C2', which is the absolute value of the difference between C1' and C2'; and C0 is the value of the intersection point of the discharge curve and the horizontal coordinate, which is the specific capacity corresponding when the voltage is 0.

[0074] In some embodiments, N may be an integer such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, etc.

[0075] In some embodiments, C1 / C0 may be 0, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 6.7%, or may be within a range consisting of any of the above values.

[0076] The cathode material provided in the present application includes Na3V2(PO4)2F3 and selectable Na3V2(PO4)3, and after manufacturing the cathode material into a button battery, when the cathode material includes Na3V2(PO4)3, a discharge platform exists in the voltage range of 3.3V to 3.4V in the Nth discharge curve, and this discharge platform corresponds to the discharge process of Na3V2(PO4)3, and C1 / C0, which is the ratio of the discharge specific capacity corresponding to this discharge platform to the Nth discharge specific capacity, can reflect the mass ratio of the Na3V2(PO4)3 impurity phase in the cathode material, and the lower C1 / C0 is, the lower the mass ratio of the Na3V2(PO4)3 impurity phase in the cathode material.

[0077] This application indicates that the core of the cathode material contains high-purity Na3V2(PO4)2F3 by setting C1 / C0 < 6.7%, and the low mass ratio of impurity phases such as Na3V2(PO4)3 is advantageous for effectively improving the capacity of the cathode material and the energy density of the sodium-ion battery. In addition, the carbon-containing coating layer within the cathode material can effectively improve the electronic conductivity of the NVPF, thereby further improving the capacity of the material.

[0078] In some embodiments, C1 / C0 ≤ 3.5%. For example, C1 / C0 may be 0, 0.1%, 0.3%, 0.7%, 0.9%, 1.1%, 1.3%, 1.7%, 2.1%, 2.3%, 2.7%, 3.1%, 3.3%, 3.5%, or may be within a range consisting of any of the above values.

[0079] In the technical means according to the embodiment of the present application, C1 / C0 is controlled within the above range, that is, the mass ratio of the Na3V2(PO4)3 impurity phase in the cathode material is controlled to be lower, so the mass ratio of Na3V2(PO4)2F3 in the cathode material is higher, that is, the purity of the NVPF phase in the cathode material is higher, which is advantageous for more effectively improving the capacity of the cathode material and the energy density of the sodium ion battery.

[0080] In some embodiments, the carbon-containing coating layer covers the surface of the core with a coating rate of 89% to 100%, preferably 95% to 100%, which is advantageous for improving the capacity and corrosion resistance of the anode material and enables the anode material to have excellent electronic conductivity. For example, in the anode material, the carbon-containing coating layer may cover the surface of the core with a coating rate within a range consisting of 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or any of the above values.

[0081] It can be understood that the "coverage rate" described in this application refers to the ratio of the area of ​​the core surface covered by the carbon-containing coating layer to the surface area of ​​the core.

[0082] In some embodiments, the mass fraction of carbon elements in the anode material is 1.25% to 6%, preferably 1.5% to 3.5%. For example, the mass fraction of carbon elements in the anode material may be 1.25%, 1.5%, 1.7%, 1.9%, 2.1%, 2.3%, 2.5%, 2.7%, 2.9%, 3.1%, 3.3%, 3.5%, 3.7%, 4%, 4.3%, 4.5%, 4.7%, 5%, 5.3%, 5.5%, 5.7%, 6%, or may be within a range consisting of any of the above values.

[0083] It can be understood that the mass fraction of carbon elements in the anode material refers to the mass percentage content of carbon elements in the anode material.

[0084] In the technical means according to the embodiment of the present application, if the mass fraction of carbon elements in the anode material is within the above range, it is advantageous to consider both compaction density and electronic conductivity. If the mass fraction of carbon elements in the anode material is relatively high, a brittle porous carbon layer is prone to forming excessively on the surface of the anode material, resulting in lower compaction density. If the mass fraction of carbon elements in the anode material is relatively low, electronic conductivity decreases and the capacity of the material decreases.

[0085] In some embodiments, the porosity of the anode material is 10% to 69%, preferably 15% to 30%. For example, the porosity of the anode material may be 10%, 15%, 17%, 19%, 21%, 23%, 25%, 27%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 69%, or may be within a range consisting of any of the above values. The porosity is advantageous for ensuring the entry and exit of sodium ions while increasing the density of the carbon-containing coating layer and is advantageous for improving the compaction density of the anode material.

[0086] In some embodiments, the compaction density of the anode material is 1.4 g / cm³ 3 ~2g / cm 3 and preferably 1.53 g / cm³ 3 ~1.99g / cm 3 is. For example, the above compaction density is 1.4 g / cm³ 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 , 2g / cm 3 It may be, or may be within a range consisting of any of the above values.

[0087] For reference, the compaction density of the anode material refers to the compaction density of the anode material measured under a pressure of 30 kN.

[0088] In the technical means according to the embodiment of the present application, since the compaction density of the anode material is relatively high, the sodium ion battery can have a higher energy density.

[0089] According to a second aspect, a method for manufacturing an anode material provided in the present application can be used to manufacture an anode material according to a first aspect of the present application and includes the following steps S1 to S3.

[0090] S1 Step: Prepare a mixed slurry, said mixed slurry including a sodium source, a fluorine source, a vanadium source, a phosphorus source, and a carbon source.

[0091] S2 Step: The above mixed slurry is dried to obtain a precursor.

[0092] Step S3: The above precursor is calcined to obtain the above anode material, wherein the above anode material comprises a core and a carbon-containing coating layer covering at least a portion of the surface of the core, wherein the core comprises sodium vanadium fluorophosphate (Na3V2(PO4)2F3); the Nth charge / discharge test is performed on a button-type battery manufactured using the above anode material, wherein in the Nth discharge curve, the discharge specific capacity is C0, the total discharge specific capacity of the discharge platform corresponding to a voltage of 3.3V to 3.4V is C1, satisfying C1 / C0 < 6.7%, and N is an integer greater than or equal to 1, and the condition of the Nth charge / discharge test is to charge the button-type battery to 4.3V with a constant current of 0.2C at a temperature of 20℃ to 30℃, and then discharge it to 2V with a constant current of 0.2C.

[0093] The cathode material obtained through the manufacturing method provided in this application contains a core of high purity Na3V2(PO4)2F3 and has a low mass ratio of impurities such as Na3V2(PO4)3, so the capacity of the cathode material and the energy density of the sodium ion battery can be effectively improved. In addition, the carbon-containing coating layer in the cathode material obtained by the above manufacturing method can effectively improve the electronic conductivity of the cathode material, thereby further improving the capacity of the material.

[0094] In some embodiments, the carbon source comprises at least one of citric acid, polyvinyl alcohol, glucose, sucrose, and oxalic acid, and optionally comprises citric acid and / or polyvinyl alcohol (PEG).

[0095] In the technical means according to the embodiment of the present application, when the carbon source includes citric acid, the mixed slurry includes a vanadium source, wherein the citric acid acts as a reducing agent to lower the valence state of vanadium, and V 4+ and / or V 5+ By igniting and increasing the solubility of vanadium in the mixed slurry, it is possible to realize ionic-level mixing of various elements. Therefore, the elemental distribution in the precursor obtained after drying treatment becomes more uniform, and the movement and fusion of ions during calcination treatment are facilitated, which is advantageous for improving the purity of the Na3V2(PO4)2F3 phase in the product.

[0096] In the technical means according to the embodiment of the present application, when the carbon source includes polyvinyl alcohol, the carbon-containing coating layer formed by sintering the polyvinyl alcohol is more dense, which is advantageous for improving the compaction density of the anode material and for improving the energy density of the sodium ion battery.

[0097] In some embodiments, the carbon source includes citric acid and polyvinyl alcohol.

[0098] In the technical means according to the embodiment of the present application, when the carbon source includes citric acid and polyvinyl alcohol, the combination of citric acid and polyvinyl alcohol can produce a mutually promoting effect, thereby further improving the compaction density, which is advantageous for improving the energy density of the sodium ion battery to which the anode material is applied.

[0099] In some embodiments, when the carbon source is citric acid and polyvinyl alcohol, the mass ratio of citric acid to polyvinyl alcohol is 2:1 to 1:4, preferably 2:1 to 1:3. For example, the mass ratio of citric acid to polyvinyl alcohol may be 2:1, 1:1, 1:2, 1:3, or 1:4, or may be within a range consisting of any of the above values, which is advantageous for further improving the compaction density of the anode material.

[0100] In some embodiments, the polyvinyl alcohol comprises at least one of polyvinyl alcohol 2000, polyvinyl alcohol 3000, polyvinyl alcohol 4000, and polyvinyl alcohol 6000.

[0101] “Polyvinyl alcohol 2000” as described in this application means that the weight-average molecular weight of polyvinyl alcohol is 2000, and other polyvinyl alcohols similarly mean that the weight-average molecular weights of polyvinyl alcohol are 3000, 4000, and 6000, respectively.

[0102] In some embodiments, the sodium source comprises at least one of sodium fluoride, sodium phosphate, sodium bicarbonate, and sodium nitrate, and optionally comprises sodium fluoride.

[0103] In some embodiments, the fluoride source comprises at least one of sodium fluoride, ammonium fluoride, potassium fluoride, and lithium fluoride, and optionally includes sodium fluoride.

[0104] In the technical means according to the embodiment of the present application, when sodium fluoride is used as a sodium source and / or a fluoride source, sodium can be provided while fluoride can also be provided. This is advantageous for reducing raw material input and waste compared to a method of providing sodium and fluoride separately.

[0105] In some embodiments, the vanadium source comprises vanadium pentoxide and / or ammonium metavanadate.

[0106] In some embodiments, the phosphorus source comprises at least one of ammonium dihydrogen phosphate, sodium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and triammonium phosphate.

[0107] In some embodiments, the method for preparing the mixed slurry may include the following steps.

[0108] Step S10: The sodium source, the fluorine source, the vanadium source, and the phosphorus source are taken according to the stoichiometric ratio of Na3V2(PO4)2F3, and mixed with a solvent and the carbon source to form a first slurry.

[0109] S20 Step: After adjusting the pH value of the first slurry to 6-7 using a pH adjuster, the mixed slurry is obtained through grinding treatment.

[0110] In the technical means according to the embodiment of the present application, by grinding the mixed slurry, the particle size of the particles in the mixed slurry is reduced, thereby increasing the solubility of each raw material and realizing ionic-level mixing of various elements. Consequently, the elemental distribution in the obtained precursor becomes more uniform, and the movement and fusion of ions during calcination treatment are facilitated, which is advantageous for improving the purity of the Na3V2(PO4)2F3 phase in the product.

[0111] In some embodiments, the drying treatment is spray drying.

[0112] According to the inventors' research, a mixed slurry contains a fluorine source, and F in the fluorine source - It is partially hydrolyzed to produce HF, which is prone to corroding spray drying equipment. More importantly, some HF volatilizes during the spray drying process, causing a loss of F, which leads to the formation of many impurity phases such as sodium vanadium phosphate in the final product, a decrease in the purity (content) of Na3V2(PO4)2F3, and consequently, a 3.3V low-voltage platform appears, resulting in a lower product capacity.

[0113] The manufacturing method provided in this application controls the pH value of the mixed slurry to 6 to 7, thereby controlling F in the mixed slurry -The hydrolysis of can be effectively suppressed, the generation of HF can be suppressed to effectively reduce F loss, and the generation of impurities such as sodium vanadium phosphate in the final product can be reduced, thereby effectively improving the purity (content) of Na3V2(PO4)2F3, and thus the capacity of the manufactured cathode material can be improved.

[0114] It can be understood that the “purity of Na3V2(PO4)2F3 (phase)” described in this application refers to the mass percentage content of Na3V2(PO4)2F3 in the anode material.

[0115] In some embodiments, the pH value of the mixed slurry may be 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, or 7, or may be within a range consisting of any of the above values.

[0116] In some embodiments, the pH adjuster comprises at least one of ammonia water, sodium hydroxide, sodium carbonate, sodium bicarbonate, and ammonium bicarbonate, and optionally comprises ammonia water.

[0117] In the technical means according to the embodiment of the present application, when ammonia water is used as a pH adjuster, the ammonia water is prone to volatilizing by generating ammonia gas during the subsequent calcination process, so other impurity elements are not introduced, thereby improving the purity of Na3V2(PO4)2F3 in the manufactured anode material.

[0118] In some embodiments, the type of solvent is not limited, and at least one of water commonly used in the art to which the present invention belongs, for example, purified water, deionized water, and distilled water, may be used as the solvent.

[0119] In some embodiments, the mixed slurry further includes a fluoride supplement.

[0120] In the process of calcining the precursor in the above S3 step, some F is generally lost. When a fluoride supplement is included in the mixed slurry, the fluoride supplement compensates for this partial loss of F, thereby effectively reducing the formation of impurities such as sodium vanadium phosphate in the final product, and thus effectively improving the purity (content) of Na3V2(PO4)2F3, which can improve the capacity of the manufactured anode material.

[0121] In some embodiments, the fluoride supplement comprises ammonium fluoride and / or sodium fluoride, and also comprises ammonium fluoride.

[0122] In the technical means according to the embodiment of the present application, when ammonium fluoride is used as a fluoride supplement, F - While it is possible to replenish it, ammonium ions can volatilize in the form of ammonia gas during the subsequent calcination process, so other impurity elements are not introduced, thereby improving the purity of Na3V2(PO4)2F3 in the manufactured anode material.

[0123] In some embodiments, the molar amount of the fluoride supplement is 1% to 5% of the molar amount of the fluoride source, preferably 3% to 5%. For example, the molar amount of the fluoride supplement may be 1%, 1.5%, 2%, 2.5%, 3%, 3.1%, 3%, 3.3%, 3.5%, 3.7%, 4%, 4.1%, 4.3%, 4.5%, 4.7%, or 5% of the molar amount of the fluoride source, or may be within a range consisting of any of the above figures, and accordingly F - While effectively replenishing it, it is possible to minimize negative effects such as excessive impurity phase in the final product or degraded electrochemical performance caused by an increased molar amount of fluoride supplement.

[0124] In some embodiments, the temperature of the calcination treatment is 550°C to 800°C, preferably 650°C to 800°C. For example, the temperature of the calcination treatment may be 550°C, 600°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, or 800°C, or may be within a range consisting of any of the above values.

[0125] In some embodiments, the holding time of the calcination treatment is 3h to 10h, preferably 4h to 9h. For example, the holding time of the calcination treatment may be 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, or may be within a range consisting of any of the above values.

[0126] Here, it can be understood that the holding time for the calcination treatment refers to the time for holding the temperature at that temperature after raising the temperature to the calcination treatment temperature.

[0127] In the technical means according to the embodiment of the present application, if the temperature of the calcination treatment or the holding time is set within the respective ranges, the density of the carbon-containing coating layer can be improved, while the purity of Na3V2(PO4)2F3 in the anode material can also be improved. If the temperature of the calcination treatment is low or the holding time is short, the carbonization of the carbon source forming the carbon-containing coating layer is incomplete and the degree of graphitization tends to be low, resulting in reduced electronic conductivity and lower capacity of the manufactured anode material. Furthermore, if the temperature of the calcination treatment is relatively low, the formed carbon-containing coating layer becomes somewhat loose, resulting in lower compaction density of the anode material. If the sintering temperature is relatively high or the holding time is relatively long, F loss tends to increase and the purity of the Na3V2(PO4)2F3 phase in the anode material decreases, resulting in lower capacity of the anode material.

[0128] In some embodiments, the heating process for raising the temperature to the calcination temperature includes the following procedure.

[0129] Procedure 1: By raising the temperature from room temperature to 120°C to 150°C and maintaining it at 120°C to 150°C for 2 to 4 hours, the precursor is consumed as much as possible, thereby preventing excessive consumption of the carbon source due to the moisture content becoming too high in the higher temperature range.

[0130] Procedure 2: The temperature is raised from 120°C to 150°C to 400°C to 550°C, and the temperature is maintained at 400°C to 550°C for 1 to 3 hours. This procedure can promote the decomposition of organic matter in the precursor and the reduction of vanadium.

[0131] Procedure 3: Raise the temperature from 400℃ to 550℃ to 550℃ to 800℃, and maintain the temperature at 550℃ to 800℃ for 5 to 9 hours.

[0132] For reference, the room temperature described in this application means 25℃ to 35℃.

[0133] In some embodiments, the temperature for keeping warm in Procedure 1 may be 120°C, 130°C, 140°C, or 150°C, or may be within a range consisting of any of the above values, and the time for keeping warm may be 2h, 3h, or 4h, or may be within a range consisting of any of the above values.

[0134] In some embodiments, the temperature for keeping warm in procedure 2 may be 400°C, 450°C, 500°C, or 550°C, or may be within a range consisting of any of the above values, and the time for keeping warm may be 1h, 2h, or 3h, or may be within a range consisting of any of the above values.

[0135] In some embodiments, the temperature for keeping warm in procedure 3 may be 550°C, 600°C, 650°C, 700°C, 750°C, or 800°C, or may be within a range consisting of any of the above values, and the time for keeping warm may be 5h, 6h, 7h, 8h, or 9h, or may be within a range consisting of any of the above values.

[0136] In some embodiments, the calcination treatment is performed in a protective atmosphere. Optionally, the protective atmosphere comprises nitrogen and / or argon.

[0137] According to a third aspect, the positive electrode plate provided in an embodiment of the present application comprises a positive material according to the first aspect of the present application or a positive material manufactured by a manufacturing method according to the second aspect of the present application.

[0138] The positive electrode plate comprises a positive material according to the first aspect of the present application or a positive material manufactured by the manufacturing method according to the second aspect of the present application, and thus has a higher capacity and energy density.

[0139] According to the fourth aspect, the sodium ion battery provided in the embodiment of the present application includes a positive electrode plate according to the third aspect of the present application.

[0140] The sodium ion battery includes a positive electrode plate according to the third aspect of the present application, and thus has a higher capacity and energy density.

[0141] According to the fifth aspect, the electric device provided in the embodiment of the present application includes a sodium ion battery according to the fourth aspect of the present application.

[0142] The electric device includes a sodium ion battery according to the fourth aspect of the present application, and thus has at least the same advantages as a sodium ion battery.

[0143] In some embodiments, the electric device may be, but is not limited to, a mobile phone, tablet, laptop computer, electric toy, electric tool, electric cart vehicle, electric automobile, ship, spacecraft, etc. Here, electric toys may include stationary or mobile electric toys, and may include, for example, game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, and spacecraft may include airplanes, rockets, space shuttles, spacecraft, etc.

[0144] Some specific embodiments are listed below. It should be noted that the embodiments described below are illustrative and used merely to explain the present application, and should not be construed as limiting the application. Where specific techniques or conditions are not specified in the embodiments, the invention shall be performed in accordance with the techniques or conditions described in literature of the art to which the invention pertains or in product descriptions. Unless the manufacturer is specified, all reagents or equipment used are ordinary products available on the market.

[0145] I. Manufacturing Method

[0146] [Example 1]

[0147] (1) Sodium fluoride (257.07 g), vanadium pentoxide (365.59 g) and ammonium dihydrogen phosphate (464.28 g) are dispersed in water according to the stoichiometric ratio of Na3V2(PO4)2F3, and citric acid and polyvinyl alcohol (the mass ratio of the two is 2:1, and the weight-average molecular weight of polyvinyl alcohol is 2000, where the ratio of the total mass = (sum of the masses of citric acid and polyvinyl alcohol) / (total mass of sodium fluoride, vanadium pentoxide, ammonium dihydrogen phosphate, citric acid, and polyvinyl alcohol)) are added as carbon sources to form a first slurry; ammonia water is added to the first slurry to adjust the pH value to 6; Next, the mixture is fed into a sand mill to perform circulating grinding, the rotation speed of the sand mill is 1000 r / min, and the mixture is ground for 3 hours to obtain a mixed slurry.

[0148] (2) A precursor is obtained by spray-drying the mixed slurry.

[0149] (3) The precursor is transferred into a sintering furnace and calcined under an argon protective atmosphere, and the oxygen content in the sintering furnace is controlled to ≤10 ppm, the moisture content in the maximum temperature holding section is controlled to ≤10 ppm, the CO content is controlled to ≤10 ppm, and the H2 content is controlled to ≤10 ppm; the heating process in the sintering furnace is to raise the temperature from room temperature to 140°C, hold at 140°C for 3 hours, raise the temperature from 140°C to 500°C, hold at 500°C for 2 hours, raise the temperature from 500°C to 705°C, and maintain the temperature of the calcination treatment at 705°C for 6.5 hours, thereby obtaining an anode material.

[0150] [Example 2]

[0151] The manufacturing process is similar to that of Example 1, the main difference being that the pH value is adjusted to 7 in step (1).

[0152] [Examples 3 to 7]

[0153] The manufacturing process is similar to that of Example 1, the main difference being that ammonium fluoride, a fluoride supplement, is added to the mixed solution of step (1), and the molar amount of ammonium fluoride is 1%, 2%, 3%, 5%, and 8% of the molar amount of sodium fluoride, respectively.

[0154] [Examples 8 to 11]

[0155] The manufacturing process is similar to that of Example 1, the main difference being that the mass ratio of citric acid to polyvinyl alcohol in step (1) is 1:1, 1:2, 1:3, and 1:4, respectively.

[0156] [Example 12]

[0157] The manufacturing process is similar to that of Example 1, the main difference being that polyvinyl alcohol is replaced with an equal mass of citric acid in step (1).

[0158] [Example 13]

[0159] The manufacturing process is similar to that of Example 1, the main difference being that in step (1), citric acid is replaced with an equal mass of polyvinyl alcohol.

[0160] [Example 14]

[0161] The manufacturing process is similar to that of Example 1, the main difference being that in step (1), citric acid and polyvinyl alcohol are replaced with an equal mass of glucose.

[0162] [Examples 15 to 21]

[0163] The manufacturing process is similar to that of Example 1, the main difference being that in step (1), the ratio of citric acid to polyvinyl alcohol to the total mass is adjusted so that the mass fraction of carbon atoms in the manufactured anode material is 1.25%, 1.5%, 2%, 2.3%, 3%, 5%, and 6%, respectively, and the corresponding mass sum of citric acid and polyvinyl alcohol is 152.17g, 182.61g, 243.48g, 280g, 365.22g, 608.70g, and 730.43g, respectively.

[0164] [Examples 22 to 27]

[0165] The manufacturing process is similar to that of Example 1, with the main difference being that the calcination temperature in step (3) is 500°C, 600°C, 650°C, 750°C, 700°C, and 800°C, respectively.

[0166] [Examples 28 to 35]

[0167] The manufacturing process is similar to that of Example 1, with the main difference being that the holding time of the calcination treatment in step (3) is 3h, 4h, 5h, 6h, 7h, 8h, 9h, and 10h, respectively.

[0168] [Examples 36 to 37]

[0169] The manufacturing process is similar to that of Example 1, the main difference being that the weight-average molecular weight of polyvinyl alcohol in step (1) is 6000 and 4000, respectively.

[0170] [Comparative Examples 1 to 2]

[0171] The manufacturing process is similar to that of Example 1, the main difference being that the pH values ​​in step (1) are adjusted to 4 and 5, respectively.

[0172] [Comparative Example 3]

[0173] The manufacturing process is similar to that of Example 1, the main difference being that the pH value is adjusted to 8 in step (1).

[0174] II. Test Method

[0175] 1. The mass fraction of carbon elements in the cathode material can be tested by the following method. Refer to Part 4 "Measurement of Carbon Content" of the chemical analysis method for lithium iron phosphate in YS / T 1028.4-2015, and test by the high-frequency combustion infrared absorption method.

[0176] 2. The compaction density of the anode material was measured using a compaction density meter, with a test pressure of 3 tons (T) and a compression time of 30 seconds (S).

[0177] 3. For the porosity test of the anode material, refer to TCSTM 00553-2022 Method for measuring porosity of light porous materials.

[0178] 4. The coverage rate of the carbon-containing coating layer is measured using a transmission electron microscope (TEM) and an X-ray energy spectrometer (EDX).

[0179] 5. Characteristics Test of Sodium Ion Battery

[0180] (1) Manufacturing of button-type batteries

[0181] Preparation of a positive electrode plate: The positive material prepared in the above example or comparative example, sodium alginate as a binder, and acetylene black as a conductive agent are dispersed and dissolved in an N-methylpyrrolidone (NMP) solvent in a mass ratio of 8:1:1 to obtain a positive electrode slurry. The positive electrode slurry is applied to both surfaces of an aluminum foil current collector, and a positive electrode plate is obtained through drying, cold pressing, and cutting.

[0182] Battery Assembly: A CR2032 button-type battery is assembled using metallic sodium as the counter electrode and glass fiber as the separator, sodium perchlorate as the solute of the electrolyte, propylene carbonate, ethylene carbonate, and fluoroethylene carbonate (volume ratio 1:1:0.05) as the solvents of the electrolyte, and the concentration of sodium perchlorate in the electrolyte is set to 1 mol / L. The entire assembly process is performed in a glove box filled with argon gas. After being left for 6 hours, the button-type battery is used for subsequent electrochemical performance testing.

[0183] (2) Test of the first charging capacity and the first discharging capacity

[0184] The test is performed using a battery tester (CT2001A) from Wuhan Land Electronics. Under atmospheric pressure conditions and at a temperature of 20°C to 30°C, the button battery is charged to 4.3V at a fixed rate of 0.2C and then discharged to 2V at a fixed rate of 0.2C, with the humidity of the test environment being less than 15%. 500 cycles are performed in this charge / discharge mode, and the discharge capacity and capacity retention rate of the 500th cycle are measured.

[0185] Coulomb efficiency of the first cycle = First discharge capacity / First charge capacity × 100%

[0186] [Table 1]

[0187]

[0188] [Table 2]

[0189]

[0190] III. Analysis of Test Results for Each Example and Comparative Example

[0191] As shown in FIGS. 2 to 4, the anode material manufactured in the present application has a core-shell shape and a relatively uniform particle size distribution.

[0192] In the discharge curve of Fig. 5, there is almost no voltage platform in the voltage range of 3.3V to 3.4V, which means that the content of the Na3V2(PO4)3 impurity phase in the anode material is very low. In the discharge curve of Fig. 6, the discharge specific capacity of the discharge platform corresponding to 3.3V to 3.4V is (98-89) mAh / g, and the first discharge specific capacity is 111 mAh / g; therefore, in Comparative Example 3, C1 / C0=8.1%, and the content of the Na3V2(PO4)3 impurity phase is relatively high.

[0193] As shown in Table 1, the anode materials prepared in each example all have a mass fraction of carbon elements between 1.25% and 6%, a coverage rate of the carbon-containing coating layer between 89% and 100%, a porosity of the anode material between 10% and 69%, and a compaction density of 1.4 g / cm³ 3 ~2g / cm 3 Between them, C1 / C0 are both less than 6.7%, and furthermore, C1 / C0 are both 6.1% or less; the cathode materials prepared in Comparative Examples 1 to 3 have C1 / C0 of 6.7% or more.

[0194] In addition, since each example adjusted the pH value to 6 to 7 by adding ammonia water to the first slurry, F in the slurry -The hydrolysis of can be effectively suppressed, and the generation of HF can be suppressed to effectively reduce F loss, thereby reducing the formation of impurity phases such as sodium vanadium phosphate in the final product. Consequently, the mass ratio of the Na3V2(PO4)3 impurity phase in the cathode material is relatively low, and the purity of the NVPF phase is high, resulting in a final C1 / C0 ratio of less than 6.7%. When referring to the first charge specific capacity, first discharge specific capacity, discharge specific capacity of the 500th cycle, and capacity retention rate of the 500th cycle in Table 2, the cathode material provided in the embodiment of the present application has a higher capacity, a higher capacity retention rate, and a higher energy density. On the other hand, in the case of Comparative Examples 1 to 3, since the pH is less than 6 or greater than 7, it is difficult to suppress HF generation and F loss; consequently, the mass ratio of the Na3V2(PO4)3 impurity phase in the cathode material is relatively high, and the purity of the NVPF phase is low, resulting in a final C1 / C0 ratio of 6.7% or higher. When referring to the first charge capacity, first discharge capacity, discharge capacity of the 500th cycle, and capacity retention rate of the 500th cycle in Table 2, the anode materials obtained in Comparative Examples 1 to 3 have low capacity and capacity retention rate, and low energy density.

[0195] In addition, as can be seen from the results of Examples 1 and 3 to 7 shown in Tables 1 and 2, Examples 3 to 6 are based on Example 1 and add an appropriate amount of ammonium fluoride as a fluoride supplement to compensate for F loss and reduce the formation of impurity phases such as sodium vanadium phosphate in the final product, which is advantageous for improving the purity of Na3V2(PO4)2F3. Consequently, the C1 / C0 value is found to be equivalent to or lower than that of Example 1, and thus the discharge capacity of the 500th cycle is equivalent to or higher than that of Example 1. In Example 7, because a relatively large molar amount of ammonium fluoride was added, the impurity phase in the final product became too large, and the discharge capacity of the 500th cycle is lower than that of Examples 1 and 3 to 6.

[0196] As can be seen by combining the results of Example 1 and Example 12 shown in Tables 1 and 2, compared to Example 12, which used citric acid alone as a carbon source, Example 1 improves compaction density by adding polyvinyl alcohol, making the carbon-containing coating layer denser. As can be seen by combining the results of Example 1 and Example 13 shown in Tables 1 and 2, compared to Example 13, which used polyvinyl alcohol alone as a carbon source, Example 1 can improve the purity of the NVPF phase to some extent by adding citric acid, and achieves a lower C1 / C0 ratio and an improved discharge capacity for the 500th cycle. As can be seen by combining the results of Example 1 and Example 14 shown in Tables 1 and 2, compared to Example 14, which used glucose as a carbon source, Example 1 can improve compaction density by using a combination of citric acid and polyvinyl alcohol.

[0197] As can be seen by combining the results of Example 1 and Examples 8 to 11 shown in Tables 1 and 2, when the mass ratio of citric acid to polyvinyl alcohol is within the range of 2:1 to 1:3, the corresponding button-type battery has a superior discharge capacity at the 500th cycle. As can be seen by combining the results of Example 1 and Examples 15 to 21 shown in Tables 1 and 2, when the mass fraction of carbon elements in the cathode material is between 1.5% and 3.5%, the corresponding button-type battery has a superior discharge capacity at the 500th cycle. As can be seen from the combined results of Examples 1, 22 to 27, and 28 to 35 shown in Tables 1 and 2, the temperature and time of the calcination treatment both affect the purity of the NVPF in the cathode material and the compaction density of the cathode material, and thus affect the performance of the corresponding button-type battery. Specifically, when the calcination temperature is 650°C to 800°C and the calcination time is 5h to 9h, the corresponding button-type battery has a relatively higher discharge capacity at the 500th cycle.

[0198] In summary, through C1 / C0 < 6.7%, the cathode material and the battery using said cathode material can exhibit superior performance in terms of capacity and capacity retention rate.

[0199] It should be noted that the present application is not limited to the embodiments described above. The embodiments described above are merely examples, and any embodiment having substantially the same configuration as the technical concept and achieving the same functional effect within the scope of the technical solution of the present application is included within the technical scope of the present application. Furthermore, any various modifications that a person skilled in the art may make to the embodiments without departing from the essence of the present application, or any other forms formed by combining some components of the embodiments, are all included within the scope of the present application.

Claims

Claim 1 An anode material comprising a core and a carbon-containing coating layer covering at least a portion of the surface of the core, wherein the core comprises sodium vanadium fluorophosphate; A positive electrode material is characterized by performing an Nth charge-discharge test on a button-type battery manufactured using the above positive electrode material, wherein in the discharge curve of the Nth charge-discharge test, the discharge specific capacity is C0, the discharge specific capacity of the discharge platform corresponding to a voltage of 3.3V to 3.4V is C1, satisfying C1 / C0 < 6.7%, and N is an integer greater than or equal to 1, and the manufacturing process of the above button-type battery is to mix the above positive electrode material, a conductive agent, and a binder, add a solvent to form an electrode slurry, apply the electrode slurry to aluminum foil, cut it into a circular electrode plate after vacuum drying, use metallic sodium as a counter electrode and glass fiber as a separator, and assemble the above button-type battery by adding an electrolyte, and the condition of the above Nth charge-discharge test is to charge the above button-type battery to 4.3V with a constant current of 0.2C at a temperature of 20℃ to 30℃, and then discharge it to 2V with a constant current of 0.2C. Claim 2 In claim 1, (1) a condition in which C1 / C0 ≤ 3.5%; (2) a condition in which the carbon-containing coating layer covers the surface of the core with a coating rate of 89% to 100%; (3) a condition in which the porosity of the anode material is 10% to 69%; (4) a condition in which the mass fraction of carbon elements in the anode material is 1.25% to 6%; and (5) a compaction density of the anode material of 1.4 g / cm³ 3 ~2g / cm 3 A positive electrode material characterized by satisfying at least one of the following conditions. Claim 3 A method for manufacturing an anode material comprises the steps of: preparing a mixed slurry containing a sodium source, a fluorine source, a vanadium source, a phosphorus source, and a carbon source; drying the mixed slurry to obtain a precursor; and calcining the precursor to obtain the anode material, wherein the anode material comprises a core and a carbon-containing coating layer covering at least a portion of the surface of the core, and the core comprises sodium vanadium fluorophosphate. A manufacturing method comprising: performing an Nth charge-discharge test on a button-type battery manufactured using the above-mentioned positive electrode material; wherein, in the discharge curve of the Nth charge-discharge test, the discharge specific capacity is C0, the discharge specific capacity of the discharge platform corresponding to a voltage of 3.3V to 3.4V is C1, satisfying C1 / C0 < 6.7%, and N is an integer greater than or equal to 1; wherein the manufacturing process of the above-mentioned button-type battery comprises mixing the above-mentioned positive electrode material, a conductive agent, and a binder, adding a solvent to form an electrode slurry, applying the electrode slurry to aluminum foil, cutting it into a circular electrode plate after vacuum drying, using metallic sodium as a counter electrode and glass fiber as a separator, and adding an electrolyte to assemble the above-mentioned button-type battery; wherein the condition of the above-mentioned Nth charge-discharge test is to charge the above-mentioned button-type battery to 4.3V with a constant current of 0.2C at a temperature of 20℃ to 30℃, and then discharge it to 2V with a constant current of 0.2C. Claim 4 A method for manufacturing according to claim 3, wherein the carbon source comprises at least one of citric acid, polyvinyl alcohol, glucose, sucrose, and oxalic acid; where the carbon source comprises citric acid and polyvinyl alcohol, the mass ratio of the citric acid to the polyvinyl alcohol is 2:1 to 1:4; and the polyvinyl alcohol comprises at least one of polyvinyl alcohol 2000, polyvinyl alcohol 3000, polyvinyl alcohol 4000, and polyvinyl alcohol 6000. Claim 5 A method for manufacturing according to claim 3 or 4, wherein the sodium source comprises at least one of sodium fluoride, sodium phosphate, sodium bicarbonate, and sodium nitrate; the fluoride source comprises at least one of sodium fluoride, ammonium fluoride, potassium fluoride, and lithium fluoride; the vanadium source comprises vanadium pentoxide and / or ammonium metavanadate; and the phosphorus source comprises at least one of ammonium dihydrogen phosphate, sodium phosphate, diammonium hydrogen phosphate, and triammonium phosphate. Claim 6 A method for manufacturing according to claim 3 or 4, wherein the step of preparing the mixed slurry comprises: taking the sodium source, the fluorine source, the vanadium source, and the phosphorus source according to the stoichiometric ratio of sodium vanadium fluorophosphate, and mixing with a solvent and the carbon source to form a first slurry; and adjusting the pH value of the first slurry to 6 to 7 using a pH adjuster, and then obtaining the mixed slurry through a grinding treatment; wherein the pH adjuster comprises at least one of ammonia water, sodium hydroxide, sodium carbonate, sodium bicarbonate, and ammonium bicarbonate. Claim 7 A method of manufacturing according to claim 3 or 4, wherein the mixed slurry further comprises a fluoride supplement; the fluoride supplement comprises ammonium fluoride and / or sodium fluoride; and the molar amount of the fluoride supplement is 1% to 5% of the molar amount of the fluoride source. Claim 8 A manufacturing method according to claim 3 or 4, wherein the temperature of the calcination treatment is 550℃ to 800℃; the holding time of the calcination treatment is 3h to 10h; the calcination treatment is performed in a protective atmosphere; and the protective atmosphere comprises nitrogen and / or argon. Claim 9 A positive electrode plate characterized by comprising a positive electrode material according to claim 1 or 2, or a positive electrode material manufactured by a manufacturing method according to any one of claims 3 to 4. Claim 10 A sodium ion battery characterized by including a positive electrode plate according to claim 9.

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