CN116864669A - Positive electrode active material, preparation method thereof, positive electrode plate and sodium ion battery - Google Patents

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

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CN116864669A
CN116864669A CN202310790102.7A CN202310790102A CN116864669A CN 116864669 A CN116864669 A CN 116864669A CN 202310790102 A CN202310790102 A CN 202310790102A CN 116864669 A CN116864669 A CN 116864669A
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positive electrode
active material
electrode active
ion battery
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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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • 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
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • 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
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
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  • Battery Electrode And Active Subsutance (AREA)
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Abstract

The invention provides a positive electrode active material, a preparation method thereof, a positive electrode plate and a sodium ion battery, wherein the structural general formula of the positive electrode active material is Na n [Ni x Fe y Mn z ]O 2 Wherein, the value range of n is 0.67-1.0, the value range of x is 0.05-0.95, the value range of y is 0.05-0.65, and the value range of z is 0.05-0.65. The positive electrode active material has higher gram capacity exertion, energy density and excellent multiplying power performance, the cycle life can reach more than 3000 times, and the cost of the prepared sodium ion battery material is lower than that of a lithium ion battery.

Description

Positive electrode active material, preparation method thereof, positive electrode plate and sodium ion battery
Technical Field
The invention relates to the field of secondary batteries, in particular to a positive electrode active material, a preparation method thereof, a positive electrode plate and a sodium ion battery.
Background
Due to the scarcity of lithium resources, sodium ion batteries have the characteristics of sufficient resources, low cost, safety and excellent cycle, and in recent years, sodium ion batteries are receiving more attention as substitutes for lithium ion batteries.
The positive electrode active material is one of the key materials of sodium ion batteries, including oxides (layered and tunnel), prussian blue analogues, and polyanion compounds. Wherein the layered oxide is in contact with existing lithium ionsThe process equipment of the ternary positive electrode material of the sub-battery has higher compatibility, is the best technical route for industrialization at present, and is characterized in that Na in oxide + At low ratios to transition metal ions (in general<0.5 Stably exist in the form of a three-dimensional tunnel structure, but Na + The inherent deficiency results in low specific capacity, low practical application value, and when Na + When the ratio of the transition metal ions is larger than 0.5, the catalyst generally presents a layered structure, has the characteristics of simple preparation method, high specific capacity and high voltage, but has the phase change problem of the layered structure under high voltage, and has poor stability and poorer cycle performance.
Layered oxide according to Na + The positions are different and are divided into four structures of O2, O3, P2 and P3, wherein 'O' represents Na + In the octahedral position, "P" represents Na + In the position of the triangular prism, the number indicates the close-packed repetition period of the minimum oxygen atom, wherein the P2 structure has wider Na+ transmission channel and lower migration energy barrier, the rate performance and the cycle performance are excellent, and the Na of the O3 structure + The content is higher, the specific capacity is higher than that of the P2 structure, and the energy density of the prepared sodium ion battery is also higher.
The layered oxide based on the O3 structure has a simpler production process, higher energy density and multiplying power performance, and longer cycle life than 2000 times, and has wide application prospects in the fields of electric two-wheeled vehicles, electric automobiles below A00 level, outdoor energy storage, household energy storage and the like.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the positive electrode active material has higher gram capacity, energy density, excellent multiplying power performance and longer cycle life.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a positive electrode active material has a general structural formula of Na n [Ni x Fe y Mn z ]O 2 Wherein, the value range of n is 0.67-1.0, the value range of x is 0.05-0.95, the value range of y is 0.05-0.65, and the value range of z is 0.05-0.65.
The second purpose of the invention is to provide a preparation method of the positive electrode active material, which is simple and has good controllability and good quality of the prepared material.
A method for preparing a positive electrode active material, comprising the steps of:
step S1, weighing a sodium source, a nickel source, an iron source and a manganese source according to stoichiometric ratio, wherein the molar ratio is 1-3: 2 to 5:2 to 5: 1-3, and mixing to obtain a mixture;
step S2, sintering the mixture at 700-800 ℃ for the first time in an air atmosphere, cooling and crushing to obtain a first crushed material;
and S3, performing secondary sintering on the primary crushed material at 900-1000 ℃ in an air atmosphere, cooling and crushing to obtain the anode active material.
The third object of the present invention is to provide a positive electrode sheet having excellent rate performance and a long cycle life.
The positive plate comprises a positive current collector and a positive active material coating arranged on at least one surface of the positive current collector, wherein the positive active material coating comprises the positive active material.
Wherein the positive electrode active material comprises a first material and a second material, and the particle diameter D of the first material 50 The grain diameter D of the second material is 10.5-15.5 mu m 50 1.5-4.5 μm.
Wherein the mass ratio of the first material to the second material is 1-5: 1 to 2.
Wherein the positive electrode active material coating further comprises a conductive agent and a binder, and the mass ratio of the positive electrode active material to the conductive agent to the binder is 92-97: 1 to 6:2 to 7.
The conductive agent is one or more of conductive carbon black, conductive graphite, carbon nanotubes, single-walled carbon nanotubes, carbon fibers and graphene.
Wherein the binder is polyvinylidene fluoride.
Wherein the compaction density of the positive plate ranges from 2.8g/cm to 3.4g/cm 3 。
Wherein the coating surface density of the positive electrode active material coating layer is in the range of 10-35 mg/cm 2 。
The invention aims at providing a sodium ion battery with good multiplying power performance and cycle life.
The sodium ion battery comprises a negative plate, an isolating film, electrolyte, a shell and the positive plate, wherein the isolating film is arranged between the negative plate and the positive plate, and the shell is used for mounting and packaging the positive plate, the negative plate, the isolating film and the electrolyte.
Wherein the upper limit voltage of charge of the sodium ion battery is less than or equal to 4.05V.
Compared with the prior art, the invention has the beneficial effects that: the positive electrode active material has higher gram capacity exertion, energy density and excellent multiplying power performance, the cycle life can reach more than 3000 times, and the cost of the prepared sodium ion battery material is lower than that of a lithium ion battery. The positive electrode active material has nickel element, can provide high capacity, has iron element and manganese element, has relatively low price and low cost, in addition, the iron element has good conductivity, can improve the conductivity, the manganese element has electrochemical inertia, can play a role of a supporting structure, and three metal elements are mutually matched to form the positive electrode active material with good electrochemical performance and high structural stability.
Drawings
Fig. 1 is an SEM image of the positive electrode active material of this example 1.
Fig. 2 is a charge-discharge curve of the sodium ion battery of this example 1.
Fig. 3 is a normal temperature cycle life graph of the sodium ion battery of this example 1.
Detailed Description
The positive electrode active material has the structural general formula of Na n [Ni x Fe y Mn z ]O 2 Wherein, the value range of n is 0.67-1.0, the value range of x is 0.05-0.95, the value range of y is 0.05-0.65, and the value range of z is 0.05-0.65.
The positive electrode activity of the present inventionThe material is doped with a plurality of metal elements, and the plurality of metals have corresponding characteristics respectively, and can play a synergistic effect at the same time, so that the stability and the circulation performance are improved. Preferably, the valence of the metal element is set within a certain range, so that the stability of the positive electrode active material is better and the electrochemical performance is higher. The positive electrode active material of the invention is O3 type multi-element oxide material, ni 2+ Most of oxidation-reduction reaction occurs, high specific capacity of the material is ensured, fe 3+ Can contribute to partial capacity, can improve conductivity, and Mn < 4+ > is an electrochemical inert substance, can play a role of supporting a material structure, and the prepared sodium ion battery material has low cost and combines energy density and cycle performance.
The positive electrode active material has large and small particle size distribution, and the morphology is spherical or spheroid, so that the matching of the particle size and the morphology can ensure that small particles are fully filled in gaps among large particles, thereby obtaining higher compaction density and further improving the energy density of the sodium ion battery.
The upper limit voltage of the sodium ion battery is not more than 4.05V, so that redundant O' monoclinic phase change under high voltage can be avoided, and the prepared sodium ion battery has better reversibility, and further the cycle life is greatly prolonged.
The preparation method of the positive electrode active material is simple, and has good controllability and good quality of the prepared material.
A method for preparing a positive electrode active material, comprising the steps of:
step S1, weighing a sodium source, a nickel source, an iron source and a manganese source according to stoichiometric ratio, wherein the molar ratio is 1-3: 2 to 5:2 to 5: 1-3, and mixing to obtain a mixture;
step S2, sintering the mixture at 700-800 ℃ for the first time in an air atmosphere, cooling and crushing to obtain a first crushed material;
and S3, performing secondary sintering on the primary crushed material at 900-1000 ℃ in an air atmosphere, cooling and crushing to obtain the anode active material.
The preparation method of the positive electrode active material provided by the invention is used for carrying out twice sintering, the mixture is fully dried by one-time sintering, and then the temperature is increased for carrying out twice sintering, so that the positive electrode active material is obtained, and the performance of the positive electrode active material is more uniformly mixed.
The positive plate comprises a positive current collector and a positive active material coating arranged on at least one surface of the positive current collector, wherein the positive active material coating comprises the positive active material.
The positive plate provided by the invention has excellent multiplying power performance and longer cycle life.
Wherein the positive electrode active material comprises a first material and a second material, and the particle diameter D of the first material 50 The grain diameter D of the second material is 10.5-15.5 mu m 50 1.5-4.5 μm. The morphology of the positive electrode active material is spherical or spheroidic. Particle diameter D of positive electrode active material 10 In the range of 2 to 5 μm, the particle diameter D of the positive electrode active material 50 In the range of 8 to 14 μm, the particle diameter D of the positive electrode active material 90 Particle diameter D of particles 90 The range of (2) is 16 to 20. Mu.m. The particle size of the positive electrode active material is set within a certain range, so that the positive electrode plate has certain compaction density and surface density, and the positive electrode plate has better energy density and rate capability.
Wherein the mass ratio of the first material to the second material is 1-5: 1 to 2. The mass ratio of the first material to the second material is set within a certain range, so that the filled positive plate has better energy density and rate capability and better cycle performance. Only one particle size material is used in the positive plate, so that gaps are easily formed between the particle sizes, and the purpose of the small particle size is to fill the gaps, so that the positive plate has higher compaction density and energy density.
Wherein the positive electrode active material coating further comprises a conductive agent and a binder, and the mass ratio of the positive electrode active material to the conductive agent to the binder is 92-97: 1 to 6:2 to 7. And mixing the positive electrode active material, the conductive agent and the binder according to a certain mass ratio to obtain positive electrode slurry, and coating the positive electrode slurry on the surface of a positive electrode current collector to obtain the positive electrode plate. The positive electrode slurry can have a certain cohesiveness by mixing a certain positive electrode active material, a conductive agent and a binder.
The conductive agent is one or more of conductive carbon black, conductive graphite, carbon nanotubes, single-walled carbon nanotubes, carbon fibers and graphene. The conductive agent has good conductivity and can improve the conductivity of the lower positive electrode slurry.
Wherein the binder is polyvinylidene fluoride.
Wherein the compaction density of the positive plate ranges from 2.8g/cm to 3.4g/cm 3 . Preferably, the positive electrode sheet has a compacted density in the range of 2.8 to 3.2g/cm 3 、2.9～3.2g/cm 3 、3.0～3.2g/cm 3 . The positive plate has a compacted density in the range of 2.8g/cm 3 、2.9g/cm 3 、3.0g/cm 3 、3.1g/cm 3 、3.2g/cm 3 、3.4g/cm 3 。
Wherein the coating surface density of the positive electrode active material coating layer is in the range of 10-35 mg/cm 2 . Preferably, the coating surface density of the positive electrode active material coating layer is in the range of 10 to 35mg/cm 2 、12～32mg/cm 2 、15～30mg/cm 2 、20～28mg/cm 2 . Specifically, the coating surface density of the positive electrode active material coating layer was in the range of 10mg/cm 2 、15mg/cm 2 、20mg/cm 2 、25mg/cm 2 、28mg/cm 2 、30mg/cm 2 、35mg/cm 2 。
The sodium ion battery comprises a negative plate, an isolating film, electrolyte, a shell and the positive plate, wherein the isolating film is arranged between the negative plate and the positive plate, and the shell is used for mounting and packaging the positive plate, the negative plate, the isolating film and the electrolyte.
Wherein the negative plate and the positive plate of the sodium ion battery have different capacities in unit area, the ratio of the capacity of the negative plate to the capacity of the positive plate in unit area is defined as N/P, and the value of N/P is preferably 1.03-1.20. N/P is the ratio of the capacity of the negative electrode to the capacity of the positive electrode, and when N/P is too large, more negative electrode materials are needed, so that the cost is increased, and the potential of the positive electrode is increased, so that the high-temperature circulation and the storage performance are not facilitated; when N/P is too small, the negative electrode does not have enough sodium intercalation capacity, which may cause interfacial sodium precipitation and affect the battery performance. And assembling the positive plate and the negative plate 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 negative plate to avoid contact short circuit between the positive plate and the negative plate.
Wherein the upper limit voltage of charge of the sodium ion battery is less than or equal to 4.05V. The upper limit voltage of charging is controlled to be less than or equal to 4.05V, so that the phase change of the material under high voltage is avoided, irreversible change occurs, and the cycle life is further prolonged.
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 method for preparing a positive electrode active material, comprising the steps of:
step S1, weighing a sodium source, a nickel source, an iron source and a manganese source according to stoichiometric ratio, wherein the molar ratio is 1:5:5:3, mixing the mixture in a molar ratio to obtain a mixture;
step S2, sintering the mixture at 780 ℃ for the first time in an air atmosphere, cooling and crushing to obtain a first crushed material;
and S3, performing secondary sintering on the primary crushed material at 980 ℃ in an air atmosphere, cooling and crushing to obtain the positive electrode active material.
Wherein the sodium source is sodium chloride, the nickel source is nickel chloride, the iron source is ferric chloride, and the manganese source is manganese dioxide. The primary sintering time is 5 hours, the cooling time is 1.2 hours, the secondary sintering time is 12 hours, and the cooling time is 3 hours.
Wherein the positive electrode active material comprises a first material and a second material, the first material and the second material respectively have different particle size distribution, and the first material has a large particle size D 50 Particle diameter D 50 The second material had a small particle diameter D of 13.5. Mu.m 50 Particle diameter D 50 3.1 μm, the mass ratio of large and small particle size is 5:2.
the mass ratio of the positive electrode active material, the conductive agent and the polyvinylidene fluoride (PVDF) binder prepared in the embodiment is 95.2 percent: 2.0%:2.8%. The positive electrode active material is a multi-element oxide comprising Ni, fe and Mn, wherein the molar ratio of nickel, iron and manganese elements is x: y: z=1: 1:1. particle diameter D of positive electrode active material 10 3.2 μm, D 50 12.5 μm, D 90 18.5 μm.
Wherein the conductive agent is the combination of super. P and CNTs, and the mass ratio is 4:1.
the positive electrode active material, the conductive agent and the binder are mixed and dispersed in a solvent according to mass ratio, wherein the solvent is N-methyl pyrrolidone (NMP), so that positive electrode slurry is obtained. The positive electrode slurry was coated on a positive electrode current collector, which was made of Al foil with a thickness of 10 μm and a single-layer coating surface density of 20mg/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, 13% 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 10 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. The membrane of this example uses a combination of a 12 μm PE base membrane with a 4 μm 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 core is arranged in the shell, and after necessary manufacturing procedures, the energy is finally obtainedElectrochemical devices for storage and release, i.e., sodium ion batteries. The sodium ion battery housing is a steel housing.
Example 2
Unlike example 1, the following is: in the step S1, the weight ratio of the sodium source to the nickel source to the iron source to the manganese source is 1:5:5:2.
the remainder is the same as in example 1 and will not be described again here.
Example 3
Unlike example 1, the following is: in the step S1, the weight ratio of the sodium source to the nickel source to the iron source to the manganese source is 1:3:3:3.
the remainder is the same as in example 1 and will not be described again here.
Example 4
Unlike example 1, the following is: in the step S1, the weight ratio of the sodium source to the nickel source to the iron source to the manganese source is 1:5:5:3.
the remainder is the same as in example 1 and will not be described again here.
Example 5
Unlike example 1, the following is: in the step S1, the weight ratio of the sodium source to the nickel source to the iron source to the manganese source is 2:5:5:3.
the remainder is the same as in example 1 and will not be described again here.
Example 6
Unlike example 1, the following is: in the step S1, the weight ratio of the sodium source to the nickel source to the iron source to the manganese source is 2:3:4:3.
the remainder is the same as in example 1 and will not be described again here.
Example 7
Unlike example 1, the following is: the primary sintering temperature is 720 ℃, and the secondary sintering temperature is 920 ℃.
The remainder is the same as in example 1 and will not be described again here.
Example 8
Unlike example 1, the following is: the primary sintering temperature is 740 ℃, and the secondary sintering temperature is 940 ℃.
The remainder is the same as in example 1 and will not be described again here.
Example 9
Unlike example 1, the following is: the primary sintering temperature is 760 ℃, and the secondary sintering temperature is 960 ℃.
The remainder is the same as in example 1 and will not be described again here.
Example 10
Unlike example 1, the following is: the primary sintering temperature is 800 ℃, and the secondary sintering temperature is 1000 ℃.
The remainder is the same as in example 1 and will not be described again here.
Example 11
Unlike example 1, the following is: the structural general formula of the positive electrode active material is Na n [Ni x Fe y Mn z ]O 2 Wherein, the value range of n is 0.67-0.8, the value range of x is 0.05-0.4, the value range of y is 0.05-0.4, and the value range of z is 0.05-0.4.
The remainder is the same as in example 1 and will not be described again here.
Example 12
Unlike example 1, the following is: the structural general formula of the positive electrode active material is Na n [Ni x Fe y Mn z ]O 2 Wherein, the value range of n is 0.8-0.9, the value range of x is 0.05-0.2, the value range of y is 0.05-0.3, and the value range of z is 0.05-0.2.
The remainder is the same as in example 1 and will not be described again here.
Example 13
Unlike example 1, the following is: the structural general formula of the positive electrode active material is Na n [Ni x Fe y Mn z ]O 2 Wherein, the value range of n is 0.9-1.0, the value range of x is 0.5-0.8, the value range of y is 0.4-0.65, and the value range of z is 0.05-0.1.
The remainder is the same as in example 1 and will not be described again here.
Comparative example 1
A positive electrode active material having the chemical formula: na (Na) x Fe y Mn 1-y O 2 Wherein, the value range of x is 0.67-1.0, and the value range of y is 0.05-0.65.
Positive electrode active materials obtained in examples 1 to 10 and comparative example 1 were prepared into positive electrode sheets and sodium ion batteries, and the prepared sodium ion batteries were tested for capacity retention after 3000 charge and discharge cycles, 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 81% or more after 3000 charge and discharge cycles, whereas the capacity retention rate of comparative example 1 is only 72%, and the electrochemical performance is poor.
As shown by comparison of examples 1-6, when a sodium source, a nickel source, an iron source and a manganese source are arranged, the weight ratio of the components is 1:5:5:3, the preparation method of the prepared positive electrode active material is better.
As can be seen from the comparison of examples 1 and 7 to 10, the performance of the prepared positive electrode active material was better when the primary sintering temperature was 780℃and the secondary sintering temperature was 980 ℃.
As can be seen from the comparison of examples 1, 11 to 13, the positive electrode active material has a structural formula of Na n [Ni x Fe y Mn z ]O 2 Wherein, the n value range is 0.9-1.0, the x value range is 0.5-0.8, the y value range is 0.4-0.65, and the z value range is 0.05-0.1, the performance of the positive electrode active material is better.
As can be seen from fig. 1, the positive electrode active material prepared according to the present invention has a clear profile, and the positive electrode active material has large particles and small particles, the small particles being disposed around the large particles. As can be seen from FIG. 2, the positive electrode active material prepared by the invention has higher energy density when being applied to a sodium ion battery, and the reversible specific capacity of the positive electrode active material is up to 170.9mAh/g at 4.2V-2.0V discharge. As can be seen from fig. 3, the sodium ion battery of the present invention has excellent cycle performance, and has a capacity retention rate of about 83% after 3000 cycles.
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 (11)

1. A positive electrode active material is characterized in that the structural general formula is Na n [Ni x Fe y Mn z ]O 2 Wherein, the value range of n is 0.67-1.0, the value range of x is 0.05-0.95, the value range of y is 0.05-0.65, and the value range of z is 0.05-0.65.
2. A method for preparing a positive electrode active material, comprising the steps of:
step S1, weighing a sodium source, a nickel source, an iron source and a manganese source according to stoichiometric ratio, wherein the molar ratio is 1-3: 2 to 5:2 to 5: 1-3, and mixing to obtain a mixture;
step S2, sintering the mixture at 700-800 ℃ for the first time in an air atmosphere, cooling and crushing to obtain a first crushed material;
and S3, performing secondary sintering on the primary crushed material at 900-1000 ℃ in an air atmosphere, cooling and crushing to obtain the anode active material.
3. A positive electrode sheet comprising a positive electrode current collector and a positive electrode active material coating layer provided on at least one surface of the positive electrode current collector, the positive electrode active material coating layer comprising the positive electrode active material according to claim 1.
4. The positive electrode sheet according to claim 3, wherein the positive electrode active material packComprises a first material and a second material, wherein the particle size D of the first material 50 In the range of 10.5 to 15.5 mu m, and the particle diameter D of the second material 50 The mass ratio of the first material to the second material is 1-5: 1 to 2.
5. The positive electrode sheet according to claim 3, wherein the positive electrode active material coating layer further comprises a conductive agent and a binder, the mass ratio of the positive electrode active material, the conductive agent and the binder being 92 to 97:1 to 6:2 to 7.
6. The positive electrode sheet of claim 5, wherein the conductive agent is one or more of conductive carbon black, conductive graphite, carbon nanotubes, single-walled carbon nanotubes, carbon fibers, graphene.
7. The positive electrode sheet according to claim 5, wherein the binder is polyvinylidene fluoride.
8. The positive electrode sheet according to claim 3, wherein the compacted density of the positive electrode sheet is in the range of 2.8 to 3.4g/cm 3 。
9. The positive electrode sheet according to claim 3, wherein the coating surface density of the positive electrode active material coating layer is in the range of 10 to 35mg/cm 2 。
10. The sodium ion battery is characterized by comprising a negative plate, a separation film, electrolyte, a shell and the positive plate according to any one of claims 3-9, wherein the separation film is arranged between the negative plate and the positive plate, and the shell is used for installing and packaging the positive plate, the negative plate, the separation film and the electrolyte.
11. The sodium ion battery of claim 10, wherein the upper charge voltage of the sodium ion battery is less than or equal to 4.05V.
CN202310790102.7A 2023-06-29 2023-06-29 Positive electrode active material, preparation method thereof, positive electrode plate and sodium ion battery Pending CN116864669A (en)

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