CN116854066A - Sodium ion positive electrode active material, preparation method thereof, positive plate and sodium ion battery - Google Patents

Sodium ion positive electrode active material, preparation method thereof, positive plate and sodium ion battery Download PDF

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CN116854066A
CN116854066A CN202310790095.0A CN202310790095A CN116854066A CN 116854066 A CN116854066 A CN 116854066A CN 202310790095 A CN202310790095 A CN 202310790095A CN 116854066 A CN116854066 A CN 116854066A
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positive electrode
sodium ion
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陈晓艳
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
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    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
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Abstract

The invention provides a sodium ion positive electrode active material, a positive electrode plate and an electrochemical device, wherein the structural general formula of the sodium ion positive electrode active material is Na x V y (PO 4 ) z Wherein, the value of x is 2.5-3.5, the value of y is 1.5-2.0, and the value of z is 2.0-3.0. The preparation method of the material comprises the following steps: weighing a sodium source, a vanadium source and ammonium dihydrogen phosphate according to a stoichiometric ratio, wherein the molar ratio is 1-3: 2 to 5: 2-4, mixing and adding the mixture into a solvent, and stirring to obtain a mixed solution; stirring the mixed solution to form precursor wet gel; drying the precursor wet gel, heating and sintering to obtain the precursor with the structural general formula Na x V y (PO 4 ) z Sodium ion positive electrode active material of (a). The sodium ion positive electrode material has higher energy density, multiplying power performance and cycle life, can realize 0V storage, and greatly improves the transportation and storage safety. The preparation method is simple and has good operability.

Description

Sodium ion positive electrode active material, preparation method thereof, positive plate and sodium ion battery
Technical Field
The invention relates to the field of secondary batteries, in particular to a sodium ion positive electrode active material, a preparation method thereof, a positive electrode plate and a sodium ion battery.
Background
Sodium ion battery has similar working principle as lithium ion battery as a secondary batteryI.e. by Na+ intercalation and deintercalation between positive and negative electrode materials without Li + From the resource abundance, the lithium resource crust abundance is 0.0065%, the sodium resource crust abundance is 2.75%, the distribution is wider, and the price is lower, so that the development of the sodium ion battery has important strategic value.
The positive electrode material of the sodium ion battery mainly comprises three types: layered oxides, prussian blue analogues, polyanionic compounds. The layered oxidation and the existing lithium ion battery ternary cathode material process equipment have higher compatibility, are the fastest technical route of industrialization at present, have higher compaction density and specific capacity, but the ash material has strong moisture absorption, structural phase change problem and relatively poorer cycle performance. Face-centered cubic crystal structure and open channel frame structure of Prussian blue analog are Na + And a larger transmission channel is provided, so that the material has better multiplying power performance and theoretical specific capacity of 170mAh/g, but more vacancies and a large amount of crystal water exist in the crystal skeleton of the material, and the specific capacity and the cycle life of the material are greatly reduced. The polyanion compound has small volume change and phase change in the Na+ intercalation and deintercalation process, stable structure and better circulation and safety performance, but has relatively poor conductivity, lower specific capacity and low energy density. The existing polyanion compound has short cycle life and high cost, and is difficult to solve the application situations of large-scale energy storage, mobile power stations, low-speed vehicles and the like.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the sodium ion positive electrode active material has higher energy density, excellent multiplying power performance, good cycle performance and safety performance.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a sodium ion positive electrode active material has a structural general formula of Na x V y (PO 4 ) z Wherein, the value of x is 2.5-3.5, the value of y is 1.5-2.0, and the value of z is 2.0-3.0.
Wherein the value of y is 1.7-1.8.
Wherein the particle diameter D of the sodium ion positive electrode active material 10 The value range of the catalyst is 1-4 mu m, and the particle diameter D of the sodium ion positive electrode active material 50 The value range of the catalyst is 8-12 mu m, and the particle diameter D of the sodium ion positive electrode active material 90 The range of the value of (2) is 15-20 mu m.
The second purpose of the invention is to provide a preparation method of the sodium ion positive electrode active material, which is simple to operate and good in controllability.
A preparation method of a sodium ion positive electrode active material comprises the following steps:
step S1, weighing a sodium source, a vanadium source and ammonium dihydrogen phosphate according to a stoichiometric ratio, wherein the molar ratio of the sodium source to the vanadium source to the ammonium dihydrogen phosphate is 1-3: 2 to 5: 2-4, mixing and adding the mixture into a solvent, and stirring to obtain a mixed solution;
step S2, stirring the mixed solution to form precursor wet gel;
step S3, drying the precursor wet gel, and heating and sintering to obtain the precursor with the structural general formula Na x V y (PO 4 ) z Sodium ion positive electrode active material of (a).
The third object of the present invention is to provide a positive electrode sheet having excellent energy density, rate performance and cycle life.
The positive plate comprises a positive current collector and a positive coating arranged on at least one side surface of the positive current collector, wherein the positive coating comprises the sodium ion positive active material.
Wherein the positive electrode coating further comprises a conductive agent and a binder, and the mass ratio of the sodium ion positive electrode active material to the conductive agent to the binder is 90-98: 2 to 8:1 to 6.
Wherein the compaction density of the positive electrode coating ranges from 1.8g/cm to 2.6g/cm 3 。
Wherein the coating surface density of the positive electrode coating is 10-40 mg/cm 2 。
The invention aims at providing a sodium ion battery with good energy density, rate capability and cycle life.
A sodium ion battery comprises the positive plate. Specifically, the sodium ion battery comprises a negative plate, an isolating film, electrolyte, a shell and the positive plate. The isolating film is arranged between the negative plate and the positive plate.
The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material can be one or more of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microsphere, silicon-based material, tin-based material, lithium titanate or other metals capable of forming alloy with lithium. Wherein, the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be one or more selected from simple substance silicon, silicon oxygen compound, silicon carbon compound and silicon alloy; the tin-based material can be selected from one or more of elemental tin, tin oxide and tin alloy. The negative current collector is typically a structure or part that collects current, and may be any of a variety of materials suitable in the art for use as a negative current collector for a lithium ion battery, for example, the negative current collector may be a material including, but not limited to, a metal foil, etc., and more particularly may be a material including, but not limited to, a copper foil, etc.
The sodium ion battery also includes an electrolyte comprising an organic solvent, an electrolyte sodium salt, and an additive. Wherein the electrolyte sodium salt can be NaPF 6 、NaBF 4 、NaClO 4 、NaAsF 6 、NaSO 3 CF 3 、Na[(FSO 2 ) 2 N]And the organic solvent may be a cyclic carbonate, including PC, EC; chain carbonates, including DFC, DMC or EMC; carboxylic esters, including MF, MA, EA, MP, and the like, are also contemplated. And additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, overcharge prevention additives, and control of H in electrolytes 2 At least one of an additive for O and HF content, an additive for improving low temperature performance, and a multifunctional additive.
The separator may be a variety of materials suitable for lithium ion battery separators in the art, and may be, for example, a combination of one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fibers, and the like.
The shell is made of one of stainless steel and aluminum plastic films.
Compared with the prior art, the invention has the beneficial effects that:
1. the sodium ion positive electrode material has higher energy density, multiplying power performance and cycle life, can realize 0V storage, and greatly improves the transportation and storage safety.
2. The sodium ion positive electrode material is spherical or spheroid, has the particle diameter D50 of 8-12 mu m, has higher tap density and shorter Na + A transmission path, whereby a higher energy density and excellent rate performance can be obtained, and furthermore, na x V y (PO 4 ) z The positive electrode active material has a stable polyhedral framework structure, and the prepared sodium ion battery has good cycle performance and safety performance.
3. The formula of the positive plate electrode is designed as follows: NVP: conductive agent: binder = 90% -98%: 2-8%: the high conductive dosage can improve the charge exchange impedance of the active substances by 1 to 6 percent, and meanwhile, the preferable conductive agent is composed of super.P and CNTs, wherein the super.P is nano-sized particles, has larger specific surface area, can adsorb a large amount of electrolyte, has good short-range conductive performance, and the CNTs are carbon nanotubes with larger length-diameter ratio, so that the electric connection between the active particles can be better realized, and the long-range conductive performance is good. In addition, the adhesive can prevent the electrochemical device from falling off in a long-term circulation process, thereby avoiding the failure of the electrochemical device.
4. The current collectors of the electrochemical device are all made of aluminum foil, which has the difference with the lithium ion battery (the positive current collector is aluminum foil and the negative current collector is copper foil), so that the cost can be further reduced, the weight can be reduced, and the 0V storage can be realized, thereby greatly improving the transportation and storage safety, because of the electrochemistryNa when the device is overdischarged + The larger radius does not embed into Al crystal lattice, so that pulverization of the current collector is avoided.
Drawings
Fig. 1 is an SEM image of the sodium ion positive electrode active material of this example 1.
Fig. 2 is an XRD pattern of the sodium ion positive electrode active material of this example 1.
Fig. 3 is a normal temperature cycle life graph of the sodium ion battery of this example 1.
Fig. 4 is a graph of capacity retention rate of the sodium ion battery of example 1.
Detailed Description
A sodium ion positive electrode active material has a structural general formula of Na x V y (PO 4 ) z Wherein, the value of x is 2.5-3.5, the value of y is 1.5-2.0, and the value of z is 2.0-3.0.
The sodium ion positive electrode active material provided by the invention adopts phosphate groups, sodium elements and vanadium elements, so that the material has excellent electrochemical performance and cycle performance. The sodium ion positive electrode active material does not contain manganese element, so that the Jahn-Teller efficiency induced by manganese element is avoided, the unit cell volume change is avoided, the structural stability is avoided to be poor, and the sodium ion positive electrode active material has excellent cycle performance. And the sodium ion positive electrode active material can realize 0V storage, and greatly improves the transportation and storage safety.
Wherein the value of y is 1.7-1.8. The polyanion compound contains vanadium element, and can greatly improve the cycle performance. The content of vanadium element is set within a certain range, so that the positive electrode active material has the cycle performance, the multiplying power performance and the safety performance.
Wherein the particle diameter D of the sodium ion positive electrode active material 10 The value range of the catalyst is 1-4 mu m, and the particle diameter D of the sodium ion positive electrode active material 50 The value range of the catalyst is 8-12 mu m, and the particle diameter D of the sodium ion positive electrode active material 90 The range of the value of (2) is 15-20 mu m. The sodium ion positive electrode active material is spherical or spheroidic, and the particle size distribution of the sodium ion positive electrode active material is setIn a certain range, the positive electrode active materials with different particle sizes can be mixed with each other, the gaps among the sodium ion positive electrode active materials are reduced, and the energy density is improved.
The preparation method of the sodium ion positive electrode active material is simple to operate and good in controllability.
A preparation method of a sodium ion positive electrode active material comprises the following steps:
step S1, weighing a sodium source, a vanadium source and ammonium dihydrogen phosphate according to a stoichiometric ratio, wherein the molar ratio of the sodium source to the vanadium source to the ammonium dihydrogen phosphate is 1-3: 2 to 5: 2-4, mixing and adding the mixture into a solvent, and stirring to obtain a mixed solution;
step S2, stirring the mixed solution to form precursor wet gel;
step S3, drying the precursor wet gel, heating and sintering to obtain the precursor with the structural general formula Na x V y (PO 4 ) z Sodium ion positive electrode active material of (a).
A positive electrode sheet has excellent energy density, rate capability and cycle life.
The positive plate comprises a positive current collector and a positive coating arranged on at least one side surface of the positive current collector, wherein the positive coating comprises the sodium ion positive active material.
Wherein the positive electrode coating further comprises a conductive agent and a binder, and the mass ratio of the sodium ion positive electrode active material to the conductive agent to the binder is 90-98: 2 to 8:1 to 6. Wherein the conductive agent is selected from one or more of conductive carbon black, conductive graphite, carbon nanotubes, single-walled carbon nanotubes, carbon fibers and graphene. The binder is polyvinylidene fluoride. Preferably, the mass ratio of the sodium ion positive electrode active material, the conductive agent and the binder is 90:4: 6. 92:3: 5. 93:3: 4. 95:2: 3. 95:3: 2. 97:2: 1. 98:1:1.
wherein the compaction density of the positive electrode coating ranges from 1.8g/cm to 2.6g/cm 3 . The compacted density of the positive electrode coating was in the range of 1.8g/cm 3 、1.9g/cm 3 、2.0g/cm 3 、2.1g/cm 3 、2.2g/cm 3 、2.3g/cm 3 、2.4g/cm 3 、2.5g/cm 3 、2.6g/cm 3 。
Wherein the coating surface density of the positive electrode coating is 10-40 mg/cm 2 . Preferably, the method comprises the steps of. The density of the coating surface is 10mg/cm 2 、15mg/cm 2 、18mg/cm 2 、20mg/cm 2 、23mg/cm 2 、26mg/cm 2 、27mg/cm 2 、28mg/cm 2 、30mg/cm 2 、35mg/cm 2 、40mg/cm 2 。
A sodium ion battery has good energy density, rate capability and cycle life.
A sodium ion battery comprises the positive plate. Specifically, the sodium ion battery comprises a negative plate, an isolating film, electrolyte, a shell and the positive plate, wherein the negative plate and the positive plate are separated by the isolating film, and the shell is used for mounting and packaging the negative plate, the isolating film, the positive plate and the electrolyte. The sodium ion battery has higher energy density, rate capability and cycle life, can realize 0V storage, and greatly improves the transportation and storage safety.
The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material can be one or more of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microsphere, silicon-based material, tin-based material, lithium titanate or other metals capable of forming alloy with lithium. Wherein, the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be one or more selected from simple substance silicon, silicon oxygen compound, silicon carbon compound and silicon alloy; the tin-based material can be selected from one or more of elemental tin, tin oxide and tin alloy. The negative current collector is typically a structure or part that collects current, and may be any of a variety of materials suitable in the art for use as a negative current collector for a lithium ion battery, for example, the negative current collector may be a material including, but not limited to, a metal foil, etc., and more particularly may be a material including, but not limited to, a copper foil, etc.
The separator may be a variety of materials suitable for lithium ion battery separators in the art, and may be, for example, a combination of one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fibers, and the like, including but not limited to.
The sodium ion battery also includes an electrolyte comprising an organic solvent, an electrolyte sodium salt, and an additive. Wherein the electrolyte sodium salt can be NaPF 6 、NaBF 4 、NaClO 4 、NaAsF 6 、NaSO 3 CF 3 、Na[(FSO 2 ) 2 N]The organic solvent may be a cyclic carbonate, including PC, EC; chain carbonates, including DFC, DMC, or EMC; carboxylic esters, including MF, MA, EA, MP, and the like, are also contemplated. And additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, overcharge prevention additives, and control of H in electrolytes 2 At least one of an additive for O and HF content, an additive for improving low temperature performance, and a multifunctional additive.
Wherein, the material of casing is one of stainless steel, aluminium, plastic-aluminum membrane.
In order to make the technical solution and advantages of the present invention more apparent, the present invention and its advantageous effects will be described in further detail below with reference to the specific embodiments, but the embodiments of the present invention are not limited thereto.
Example 1
A preparation method of a sodium ion positive electrode active material comprises the following steps:
step S1, weighing sodium source sodium chloride, vanadium source vanadium pentoxide and phosphorus source monoammonium phosphate according to a stoichiometric ratio, wherein the molar ratio is 3:2:3, mixing and adding the mixture into an ethanol solvent, and stirring to obtain a mixed solution;
step S2, stirring the mixed solution to form precursor wet gel;
step S3, drying the precursor wet gel, heating to 850 ℃ and sintering to obtain the precursor with the structural general formula Na x V y (PO 4 ) z Sodium of (2)The ionic positive electrode active material has a structural general formula of Na 2.6 V 1.6 (PO 4 ) 2.2 . As shown in fig. 1, the sodium ion positive electrode active material has a clear and complete profile and has particle sizes of different sizes. As can be seen from the XRD pattern of the sodium ion positive electrode active material of fig. 2, the sodium ion positive electrode active material of the present invention has higher crystallinity without significant impurity peaks.
Grinding the sodium ion positive electrode active material to obtain the particle size D of the sodium ion positive electrode active material 10 The value range of (2) mu m, and the particle diameter D of the sodium ion positive electrode active material 50 The value range of (2) is 10 mu m, and the particle diameter D of the sodium ion positive electrode active material is 90 The range of the values of (2) is 16 μm.
The sodium ion positive electrode active material, the graphene conductive agent and the polyvinylidene fluoride binder are mixed according to the mass ratio of 94.7:2.8:2.5 mixing and dispersing the mixture in a solvent, wherein the solvent is N-methyl pyrrolidone, so as to obtain the positive electrode slurry.
The positive electrode slurry was coated on a positive electrode current collector, which was made of Al foil with a thickness of 12 μm and a single-layer coating surface density of 25mg/cm 2 Thereby obtaining the positive plate of the sodium ion battery.
And assembling the positive plate and the negative plate of the sodium ion battery into a semi-finished battery cell in a winding or lamination mode, and at least 1 layer of isolating film is arranged between the adjacent positive plate and the negative plate so as to avoid contact short circuit between the positive plate and the negative plate.
The capacity of the unit area of the negative electrode plate is 3% -20% higher than that of the unit area of the positive electrode plate, 15% is selected in the embodiment, and the Na of the positive electrode migration can be completely received by the higher capacity of the negative electrode + The phenomenon of sodium precipitation of the negative electrode is avoided, and in addition, the cycle life is also prolonged.
The negative plate current collector is made of Al foil and has a thickness of 12 mu m. The membrane can be PE, PP base membrane or multilayer composite membrane, non-woven fabric membrane, polyimide membrane, aramid membrane, and the membrane coating can be ceramic, boehmite, PVDF, PMMA, siO 2 、BaSO 4 Any one of aramid fibers. This embodimentThe membrane adopts a combination of a 16um PE base membrane and 4 mu m ceramic. And assembling the positive plate and the negative plate into a semi-finished battery cell in a winding or lamination mode, and arranging 1 layer of isolating film between the adjacent positive plate and negative plate to avoid contact short circuit between the positive plate and the negative plate. The semi-finished battery cell is arranged in the shell, and after necessary manufacturing procedures, an electrochemical device for energy storage and release, namely a sodium ion battery, is finally obtained. The sodium ion battery shell structure is a stainless steel shell.
Example 2
Unlike example 1, the following is: sodium ion positive electrode active material with structural general formula of Na 2.5 V 1.6 (PO 4 ) 2.2 。
The remainder is the same as embodiment 1 and will not be described here again.
Example 3
Unlike example 1, the following is: sodium ion positive electrode active material with structural general formula of Na 2.9 V 1.5 (PO 4 ) 2.0 。
The remainder is the same as embodiment 1 and will not be described here again.
Example 4
Unlike example 1, the following is: sodium ion positive electrode active material with structural general formula of Na 3.3 V 1.6 (PO 4 ) 2.6 。
The remainder is the same as embodiment 1 and will not be described here again.
Example 5
Unlike example 1, the following is: sodium ion positive electrode active material with structural general formula of Na 2.7 V 1.7 (PO 4 ) 2.8 。
The remainder is the same as embodiment 1 and will not be described here again.
Example 6
Unlike example 1, the following is: the molar ratio of the sodium source to the vanadium source to the ammonium dihydrogen phosphate is 1:3:2 mixing.
The remainder is the same as embodiment 1 and will not be described here again.
Example 7
Unlike example 1, the following is: the molar ratio of the sodium source to the vanadium source to the ammonium dihydrogen phosphate is 1:2:2 mixing.
The remainder is the same as embodiment 1 and will not be described here again.
Example 8
Unlike example 1, the following is: the molar ratio of the sodium source to the vanadium source to the ammonium dihydrogen phosphate is 1:3:3 mixing.
The remainder is the same as embodiment 1 and will not be described here again.
Example 9
Unlike example 1, the following is: the molar ratio of the sodium source to the vanadium source to the monoammonium phosphate is 2:3:3 mixing.
The remainder is the same as embodiment 1 and will not be described here again.
Example 10
Unlike example 1, the following is: the molar ratio of the sodium source to the vanadium source to the ammonium dihydrogen phosphate is 3:2:4, mixing.
The remainder is the same as embodiment 1 and will not be described here again.
Example 11
Unlike example 1, the following is: the molar ratio of the sodium source to the vanadium source to the monoammonium phosphate is 2:2:3 mixing.
The remainder is the same as embodiment 1 and will not be described here again.
Comparative example 1
A positive electrode active material having the chemical formula: na (Na) 0.7 Mn 0.3 O 2 。
Positive electrode active materials obtained in examples 1 to 11 and comparative example 1 were prepared into positive electrode sheets and sodium ion batteries, and the prepared sodium ion batteries were subjected to 10000 charge and discharge cycles to test the capacity retention rate of the base, and the results were recorded in table 1.
TABLE 1
As can be seen from the above table 1, the positive electrode active material prepared by the present invention is better in application to the positive electrode sheet and the sodium ion battery than the positive electrode sheet and the sodium ion battery of comparative example 1, and still has a capacity retention rate of 80% or more after 10000 charge and discharge cycles in combination with fig. 4, whereas the capacity retention rate of comparative example 1 is only 65%, and the electrochemical performance is poor. As can be seen from fig. 3, the gram capacity of the material in example 1 is close to that of the sodium ion battery at different multiplying powers, and the sodium ion battery has excellent multiplying power performance.
As shown by comparison of examples 1 to 5, when the structural formula of the sodium ion positive electrode active material is Na 2.6 V y (PO 4 ) 2.2 Wherein, when the value of x is 2.6, the value of y is 1.6, and the value of z is 2.2, the prepared sodium ion positive electrode active material has better performance.
As shown by comparison of examples 1 and 6-11, when a sodium source, a vanadium source and ammonium dihydrogen phosphate are arranged, the molar ratio is 1:3:2, the prepared sodium ion positive electrode active material has better performance.
Variations and modifications of the above embodiments will occur to those skilled in the art to which the invention pertains from the foregoing disclosure and teachings. Therefore, the present invention is not limited to the above-described embodiments, but is intended to be capable of modification, substitution or variation in light thereof, which will be apparent to those skilled in the art in light of the present teachings. In addition, although specific terms are used in the present specification, these terms are for convenience of description only and do not limit the present invention in any way.

Claims (9)

1. A sodium ion positive electrode active material is characterized in that the structural general formula is Na x V y (PO 4 ) z Wherein, the value of x is 2.5-3.5, the value of y is 1.5-2.0, and the value of z is 2.0-3.0.
2. The sodium ion positive electrode active material according to claim 1, wherein y has a value of 1.7 to 1.8.
3. The sodium ion positive electrode active material according to claim 1, wherein the sodium ion positive electrode active material has a particle size D 10 The value range of the catalyst is 1-4 mu m, and the particle diameter D of the sodium ion positive electrode active material 50 Is taken from (a)The value range is 8-12 mu m, and the particle diameter D of the sodium ion positive electrode active material 90 The range of the value of (2) is 15-20 mu m.
4. The preparation method of the sodium ion positive electrode active material is characterized by comprising the following steps of:
step S1, weighing a sodium source, a vanadium source and ammonium dihydrogen phosphate according to a stoichiometric ratio, wherein the molar ratio of the sodium source to the vanadium source to the ammonium dihydrogen phosphate is 1-3: 2 to 5: 2-4, mixing and adding the mixture into a solvent, and stirring to obtain a mixed solution;
step S2, stirring the mixed solution to form precursor wet gel;
step S3, drying the precursor wet gel, heating and sintering to obtain the precursor with the structural general formula Na x V y (PO 4 ) z Sodium ion positive electrode active material of (a).
5. A positive electrode sheet comprising a positive electrode current collector and a positive electrode coating layer provided on at least one side surface of the positive electrode current collector, the positive electrode coating layer comprising the sodium ion positive electrode active material according to any one of claims 1 to 3.
6. The positive electrode sheet according to claim 5, wherein the positive electrode coating further comprises a conductive agent and a binder, and the mass ratio of the sodium ion positive electrode active material, the conductive agent and the binder is 90 to 98:2 to 8:1 to 6.
7. The positive electrode sheet according to claim 5, wherein the positive electrode coating has a compacted density ranging from 1.8 to 2.6g/cm 3 。
8. The positive electrode sheet according to claim 5, wherein the coating surface density of the positive electrode coating layer has a value ranging from 10 to 40mg/cm 2 。
9. A sodium ion battery comprising the positive electrode sheet according to any one of claims 5 to 8.
CN202310790095.0A 2023-06-29 2023-06-29 Sodium ion positive electrode active material, preparation method thereof, positive plate and sodium ion battery Pending CN116854066A (en)

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