CN115188951A - Carbon composite iron-based polyanion positive electrode material and preparation method thereof - Google Patents

Carbon composite iron-based polyanion positive electrode material and preparation method thereof Download PDF

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CN115188951A
CN115188951A CN202210980380.4A CN202210980380A CN115188951A CN 115188951 A CN115188951 A CN 115188951A CN 202210980380 A CN202210980380 A CN 202210980380A CN 115188951 A CN115188951 A CN 115188951A
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carbon
iron
slurry
carbon composite
carbon material
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李云峰
段华玲
罗传军
周阳
任小磊
孙振航
郭玉玥
齐振君
周晓飞
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Duofudo New Material Co ltd
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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
    • H01M4/581—Chalcogenides or intercalation compounds thereof
    • H01M4/5815—Sulfides
    • 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
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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

Abstract

The invention provides a carbon composite iron-based polyanion positive electrode material, which is of a spherical structure with a hollow interior; the spherical structure comprises an iron-based polyanion compound and a carbon material embedded in the iron-based polyanion compound. Compared with the prior art, the carbon material in the carbon composite iron-based polyanionic cathode material provided by the invention uniformly penetrates through the iron-based polyanionic compound fused particles, so that the electronic conductivity of the fused particles is effectively enhanced, the carbon source part of the fused particles is penetrated out, the connection is generated among the particles, and the overall conductivity of the material is improved; the cross and staggered distribution of the carbon material in the material enhances the stability of the spherical structure of the material; in addition, the smaller specific surface area of the spherical structure enhances the stability of the spherical structure in the surrounding environment, so that the shape integrity of the spherical structure is kept good in the long-term continuous charging and discharging process.

Description

Carbon composite iron-based polyanion positive electrode material and preparation method thereof
Technical Field
The invention belongs to the technical field of sodium ion batteries, and particularly relates to a carbon composite iron-based polyanion positive electrode material and a preparation method thereof.
Background
Compared with a lithium ion battery, the sodium ion battery has the advantages of rich resources, low cost, high cost performance and the like, and is considered to be an ideal energy storage device of a large-scale energy storage system in the future. The key to commercial application of sodium ion batteries is how to achieve increased energy density, and efficient and inexpensive cathode materials are a major problem. Therefore, the development of a novel positive electrode material with high voltage, high capacity and stable structure has important application value.
The positive electrode material of the sodium ion battery mainly comprises transition metal oxide, polyanion type compound, transition metal cyanide and the like. The polyanion type anode material has the advantages of stable structure, high working voltage, long cycle life, good thermal stability, high safety performance and very wide application prospect. Among polyanionic anode materials, the iron-based polyanionic anode material has the advantages of rich resources, low cost, high safety, environmental friendliness and the like, is easy for large-scale production and application, and is an ideal choice for the low-cost high-performance sodium ion battery anode material.
However, pure phase Na x Fe y (SO 4 ) z The material has the problem of low electronic conductivity, which greatly limits the exertion of the electrochemical performance. In order to improve the electronic conductivity of the material, an in-situ carbon coating method is generally adopted. However, since it contains SO 4 2- The polyanion material is easy to be thermally decomposed at the temperature of more than 400 ℃, the temperature of carbon coating is usually higher than 800 ℃, and the carbon coating is not suitable for processing Na x Fe y (SO 4 ) z A material. Thus, how to combine the conductive carbon material with Na x Fe y (SO 4 ) z The uniform and efficient compounding of materials to obtain the cathode material with high conductivity is a problem to be solved in the field.
Although, the high energy ball milling combined with low temperature sintering method can mix the conductive carbon source with Na x Fe y (SO 4 ) z The material is compounded, and the process route is very simple. However, since there is a problem that the material is often seriously adhered to the wall, the ball milling method used in the method has its limitation in both crushing and dispersing effects, resulting in that various raw materials are difficult to be efficiently crushed and uniformly dispersed. This will affect the ratio of key elements in the material, and further it is difficult to ensure the stability of the electrochemical properties of the material.
The coating can also be carried out by a spray granulation method. The spray granulation is to disperse the raw materials in the solvent uniformly, atomize the raw materials into mist drops, simultaneously introduce dry heating gas, evaporate the solvent at the moment of contact of the raw materials and the solvent, and obtain dry micron-sized or nano-sized spherical particles through gas-solid separation. Although the method is simple to operate, high in continuity, high in preparation efficiency, easy to obtain materials with uniform components and controllable shapes, for the iron-based polyanionic material, the active element ferrous ions in the iron-based polyanionic material are very easy to oxidize under the conditions of oxygen content and high temperature, so that the application of the process in the materials is limited.
Disclosure of Invention
In view of this, the technical problem to be solved by the present invention is to provide a carbon composite iron-based polyanionic cathode material and a preparation method thereof, wherein the carbon-based material in the carbon composite iron-based polyanionic cathode material obtained by the method is uniformly distributed, and has high stability and charge transport capability.
The invention provides a carbon composite iron-based polyanion positive electrode material, which is of a spherical structure with a hollow interior; the spherical structure comprises an iron-based polyanion compound and a carbon material embedded in the iron-based polyanion compound; the iron-based polyanion compound is Na x Fe y (SO 4 ) z (ii) a Wherein 1 is<x≤10，1<y≤10，z＝x/2+y。
Preferably, the particle size D50 of the carbon composite iron-based polyanionic cathode material is 1 to 10 μm.
The invention also provides a preparation method of the carbon composite iron-based polyanion positive electrode material, which comprises the following steps:
s1) mixing sodium sulfate, ferrous sulfate and carbon material slurry with a solvent to obtain precursor slurry;
s2) carrying out spray granulation on the precursor slurry in a protective atmosphere to obtain a precursor of the anode material;
and S3) sintering the precursor of the cathode material at a low temperature in a protective atmosphere to obtain the carbon composite iron-based polyanion cathode material.
Preferably, the molar ratio of the sodium sulfate to the ferrous sulfate is 1: 2-2: 1.
preferably, the total mass of the sodium sulfate and the ferrous sulfate is 10-40% of the total mass of the sodium sulfate, the ferrous sulfate and the solvent.
Preferably, the carbon material slurry comprises a carbon material, a dispersant and a solvent; the mass concentration of the carbon material in the carbon material slurry is 4-5%;
the carbon material in the carbon material slurry is selected from one or more of carbon nanotubes, carbon fibers, reduced graphene oxide and graphene.
Preferably, the mass of the carbon material in the carbon material slurry is 1% to 10% of the total mass of the sodium sulfate and the ferrous sulfate.
Preferably, a reducing agent is also added in the step S1); the molar ratio of the reducing agent to the ferrous sulfate is 1-1:1; the reducing agent is selected from L-ascorbic acid and/or citric acid.
Preferably, the air inlet temperature of the spray granulation is 120-250 ℃; the feeding speed of the precursor slurry during spray granulation is 5-100 mL/min.
Preferably, the low-temperature sintering temperature is 300-450 ℃; the low-temperature sintering time is 1-24 h; the heating rate of the low-temperature sintering is 2-20 ℃/min.
The invention provides a carbon composite ironThe carbon composite iron-based polyanionic positive electrode material is of a spherical structure with a hollow interior; the spherical structure comprises an iron-based polyanion compound and a carbon material embedded in the iron-based polyanion compound; the iron-based polyanion compound is Na x Fe y (SO 4 ) z (ii) a Wherein 1 is<x≤10，1<y is less than or equal to 10, z = x/2+y. Compared with the prior art, the carbon material in the carbon composite iron-based polyanionic cathode material provided by the invention uniformly penetrates through the iron-based polyanionic compound fused particles, so that the electronic conductivity of the fused particles is effectively enhanced, the carbon source part of the fused particles is penetrated out, the connection is generated between the particles, and the overall conductivity of the material is improved; the cross and staggered distribution of the carbon material in the material enhances the stability of the spherical structure of the material; in addition, the smaller specific surface area of the spherical structure enhances the stability of the spherical structure in the surrounding environment, so that the shape integrity of the spherical structure is kept good in the long-term continuous charging and discharging process.
The invention also provides a preparation method of the carbon composite iron-based polyanion cathode material, which comprises the following steps: s1) mixing sodium sulfate, ferrous sulfate, a reducing agent, carbon material slurry and a solvent to obtain precursor slurry; s2) carrying out spray granulation on the precursor slurry in a protective atmosphere to obtain a precursor of the anode material; and S3) sintering the precursor of the cathode material at a low temperature in a protective atmosphere to obtain the carbon composite iron-based polyanion cathode material. Compared with the prior art, the preparation method has the advantages that the spray granulation is combined with the low-temperature sintering technology, the pretreatment steps such as pre-drying and the like are not needed for the raw materials, the preparation method is simple, the operation flow is short, the carbon material is added in a slurry form, so that the carbon material is dispersed more uniformly, the precursor slurry has better stability, and the uniformity of the prepared anode material is further ensured; meanwhile, protective atmosphere is introduced in the spray drying and low-temperature sintering processes for protection, so that materials are prevented from being oxidized, and the performance of the anode material obtained by the method is stable.
Drawings
Fig. 1 is a scanning electron microscope image of the carbon composite iron-based polyanion positive electrode material obtained in example 1 of the present invention;
fig. 2 is an XRD pattern of the carbon composite iron-based polyanionic positive electrode material obtained in example 1 of the present invention;
fig. 3 is a first charge-discharge curve diagram of a battery assembled by the carbon composite iron-based polyanion positive electrode material obtained in example 1 of the present invention;
fig. 4 is a charge-discharge curve diagram of a battery assembled by the carbon composite iron-based polyanion positive electrode material obtained in example 1 of the present invention;
fig. 5 is a first charge-discharge curve diagram of assembled batteries of carbon composite iron-based polyanion cathode materials 1 and 2 obtained in comparative examples of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a carbon composite iron-based polyanion positive electrode material, which is of a spherical structure with a hollow interior; the spherical structure comprises an iron-based polyanion compound and a carbon material embedded in the iron-based polyanion compound; the iron-based polyanion compound is Na x Fe y (SO 4 ) z (ii) a Wherein 1 is<x≤10，1<y≤10，z＝x/2+y。
The carbon composite iron-based polyanion positive electrode material provided by the invention is a spherical structure which is hollow inside and is formed by iron-based polyanion compound fused particles, has good dispersibility and is not easy to agglomerate, the micro-nano structure formed by secondary particles is beneficial to shortening the transfer distance of sodium ions in a solid phase, and meanwhile, carbon materials are uniformly dispersed in the micro-nano particles, so that the electronic conductivity among the particles is greatly enhanced; in the invention, the particle size D50 of the carbon composite iron-based polyanion cathode material is 1-10 μm.
Said ironPolyanionic compounds being Na x Fe y (SO 4 ) z (ii) a Wherein x is preferably 3 to 9, more preferably 4 to 8, and still more preferably 5 to 6; the y is preferably 3 to 9, more preferably 4 to 8, and still more preferably 5 to 6.
The carbon material is embedded in molten particles formed by an iron-based polymer anionic compound; the mass of the carbon material is 1% to 10%, more preferably 3% to 8%, still more preferably 4% to 6%, and most preferably 5% of the mass of the iron-based polymer anionic compound.
The carbon material in the carbon composite iron-based polyanionic cathode material provided by the invention uniformly penetrates through the iron-based polyanionic compound fused particles, so that the electronic conductivity of the fused particles is effectively enhanced, the carbon source part of the fused particles is penetrated out, the connection is generated among the particles, and the overall conductivity of the material is improved; the cross and staggered distribution of the carbon material in the material enhances the stability of the spherical structure of the material; in addition, the smaller specific surface area of the spherical structure enhances the stability of the spherical structure in the surrounding environment, so that the shape integrity of the spherical structure is kept good in the long-term continuous charging and discharging process.
The invention also provides a preparation method of the carbon composite iron-based polyanion positive electrode material, which comprises the following steps: s1) mixing sodium sulfate, ferrous sulfate and carbon material slurry with a solvent to obtain precursor slurry; s2) carrying out spray granulation on the precursor slurry in a protective atmosphere to obtain a precursor of the anode material; and S3) sintering the precursor of the cathode material at a low temperature in a protective atmosphere to obtain the carbon composite iron-based polyanion cathode material.
In the present invention, the sources of all raw materials are not particularly limited, and they may be commercially available.
Mixing sodium sulfate, ferrous sulfate, carbon material slurry and a solvent to obtain precursor slurry; the ferrous sulfate can be ferrous sulfate with crystal water, and is preferably ferrous sulfate heptahydrate; the solvent is preferably water; in the invention, preferably, the sodium sulfate and the ferrous sulfate are dissolved in the solvent and then added into the carbon material slurry for mixing; the molar ratio of the sodium sulfate to the ferrous sulfate is preferably 1:2 to 2:1, more preferably 1: 1.8-1.8: 1, more preferably 1: (1.6 to 1.8), most preferably 1: (1.66-1.69); the total mass of the sodium sulfate and the ferrous sulfate is preferably 10-40%, more preferably 20-35%, still more preferably 24-30%, and most preferably 26-27% of the total mass of the sodium sulfate, the ferrous sulfate and the solvent; the solvent is a solvent well known to those skilled in the art, and is not particularly limited, and in the present invention, one or more of water, ethanol, and N-methylpyrrolidone (NMP) are preferable; the carbon material slurry preferably comprises a carbon material, a dispersant and a solvent; according to the invention, the carbon material slurry is used as a raw material, contains a certain amount of dispersing agent, and is more easily and uniformly dispersed in a solution containing a sodium source and an iron source, the rearrangement and occupation of atoms in the crystallization process are more ordered, the overall appearance is more regular and uniform, the final particle growth is more complete, and the electrochemical performance is more excellent; the carbon material is preferably one or more of carbon nanotube, carbon fiber, reduced graphene oxide and graphene; the particle size of the carbon material is preferably 1 to 10 μm; the mass concentration of the carbon material in the carbon material slurry is 4-5%; the dispersant is any dispersant known to those skilled in the art, and is not particularly limited, and in the present invention, CMC and/or PVP is preferred; the mass concentration of the dispersing agent in the carbon material slurry is preferably 0.5-2%; the solvent in the carbon material slurry is not particularly limited as long as it is well known to those skilled in the art, and in the present invention, one or more of water, ethanol, and N-methylpyrrolidone (NMP) are preferable; the dispersant uniformly disperses the carbon material; the mass of the carbon material in the carbon material slurry is 1-10% of the total mass of the sodium sulfate and the ferrous sulfate; in order to prevent the slurry from being oxidized in the subsequent process, a reducing agent is preferably added; the molar ratio of the reducing agent to the ferrous sulfate is preferably 1: 10-1: 1, more preferably 1: 8-1: 2, preferably 1:5-1:6; the reducing agent is a reducing agent well known to those skilled in the art, and is not particularly limited, and in the present invention, an organic reducing agent is preferable, and ascorbic acid and/or citric acid is more preferable; the mixing method is not particularly limited, but in the present invention, it is preferable to uniformly mix and disperse the raw materials by stirring, dispersing, ball milling, or sand milling to obtain a precursor slurry; the mixing time is preferably 1 to 3 hours, more preferably 2 hours.
Carrying out spray granulation on the precursor slurry in a protective atmosphere to obtain a precursor of the anode material; the protective atmosphere is not particularly limited as long as it is known to those skilled in the art, and nitrogen and/or argon is preferable in the present invention; the oxygen content of the protective atmosphere is preferably less than 1ppm; the feeding speed of the precursor slurry during spray granulation is preferably 5-100 mL/min; the air inlet temperature of the spray granulation is preferably 120-250 ℃, more preferably 150-250 ℃, and further preferably 180-220 ℃; the air outlet temperature of the spray granulation is preferably 85-120 ℃, and more preferably 95-105 ℃.
Sintering the precursor of the positive electrode material at low temperature in a protective atmosphere to obtain a carbon composite iron-based polyanion positive electrode material; the protective atmosphere is not particularly limited as long as it is known to those skilled in the art, and nitrogen and/or argon is preferable in the present invention; the oxygen content of the protective atmosphere is preferably less than 1ppm; the temperature of the low-temperature sintering is preferably 300-450 ℃, more preferably 350-420 ℃, further preferably 370-400 ℃, further preferably 380-390 ℃, and most preferably 385 ℃; the time of the low-temperature sintering, namely the heat preservation time, is preferably 1 to 24 hours, more preferably 5 to 20 hours, still more preferably 10 to 14 hours, and most preferably 12 hours; the heating rate of the low-temperature sintering is preferably 2-20 ℃/min, more preferably 2-15 ℃/min, still more preferably 2-10 ℃/min, and most preferably 2-5 ℃/min.
According to the invention, the spray granulation is combined with the low-temperature sintering technology, the pretreatment steps such as pre-drying and the like are not needed for the raw materials in the method, the preparation method is simple, the operation flow is short, and the carbon material is added in a slurry form, so that the carbon material is dispersed more uniformly, the precursor slurry has better stability, and the uniformity of the prepared anode material is further ensured; meanwhile, protective atmosphere is introduced in the spray drying and low-temperature sintering processes for protection, so that materials are prevented from being oxidized, and the performance of the anode material obtained by the method is stable.
In the spray granulation process, the carbon material is uniformly dispersed in an iron source and a sodium source, and after low-temperature sintering, the carbon material is uniformly distributed between solid solutions formed by ferrous sulfate and sodium sulfate step by step; on one hand, the carbon-based skeleton plays a role in stabilizing the structure of the material; on the other hand, na is bonded by the carbon material x Fe y (SO 4 ) z The particles are connected in series in the reticular carbon-based framework, so that a good bridging effect is achieved for electron transfer, the charge transfer capacity among the particles of the anode material can be obviously improved, the defect of poor conductivity of the material is overcome, and the electrochemical performance of the material is improved.
In order to further illustrate the present invention, the following describes in detail a carbon composite iron-based polyanionic positive electrode material and a method for preparing the same, which are provided by the present invention, with reference to examples.
The reagents used in the following examples are all commercially available.
Example 1
46.2g of Na 2 SO 4 Adding the mixture into 540.5g of water, placing the mixture on a magnetic stirrer to be completely dissolved, and then adding 149.79g of FeSO 4 ·7H 2 Dissolving O in the solution to obtain a blue-green solution; to the above blue-green solution was added 160.05g CNT slurry (4% CNT,1% dispersant CMC and H) 2 O), dispersing for 2h to obtain a sprayed precursor mixed feed liquid; introducing the mixed feed liquid into a spray dryer at N 2 Under atmosphere (oxygen content)<0.1 ppm) was sprayed and granulated, setting the inlet air temperature at 220 deg.C, the inlet speed at about 5mL/min, and the outlet air temperature at 100 deg.C to obtain Na 6 Fe 5 (SO 4 ) 8 A precursor powder of @ CNT; transferring the precursor powder obtained above to a sintering furnace in N 2 Under atmosphere (oxygen content)<0.1 ppm), setting the heating rate of 2 ℃/min, and keeping the temperature at 385 ℃ for 12 hours to obtain the carbon composite iron-based polyanion positive electrode material Na 6 Fe 5 (SO 4 ) 8 @ CNT cathode material.
The carbon composite iron-based polyanionic cathode material obtained in example 1 was analyzed by a scanning electron microscope, and a Scanning Electron Microscope (SEM) image thereof was shown in fig. 1. As can be seen from FIG. 1, the carbon nanotubes are clearly embedded in the middle of the particles to form a compact shell, and the whole body has a hollow spherical structure of 1-10 μm.
The XRD pattern of the carbon composite iron-based polyanionic positive electrode material obtained in example 1 was shown in fig. 2 by analyzing the material by X-ray diffraction. From FIG. 2, na can be seen 6 Fe 5 (SO 4 ) 8 The material shows high crystallinity, and the carbon nanotubes are tightly embedded in Na 6 Fe 5 (SO 4 ) 8 The bulk structure of the material.
In the carbon composite iron-based polyanion positive electrode material prepared by the method, carbon is embedded in the positive electrode material, and Na is added x Fe y (SO 4 ) z The particles are connected in the network-shaped carbon-based framework, so that the charge transport capability among the particles of the positive electrode material can be obviously improved.
Na prepared in example 1 6 Fe 5 (SO 4 ) 8 The method comprises the following steps of mixing a @ CNT positive electrode material, a conductive agent SUPER-P and a binder PVDF into slurry (solid content is 27.4%) respectively according to a mass ratio of 90 4 (the solvent is propylene carbonate) as an electrolyte, and the electrolyte is assembled into a CR2032 battery in a glove box.
And (3) carrying out charge and discharge tests on the assembled battery on a charge and discharge tester, wherein the tested charge and discharge interval is 1.5-4.5V. Testing the cycle performance of the assembled battery at 0.5C, and testing the rate performance of the assembled battery at 0.1C, 0.2C, 0.5C, 1C and 2C to obtain a first charge-discharge curve chart shown in FIG. 3; the charging and discharging curve chart is shown in figure 4; the obtained charge and discharge related data are shown in table 1. Through fig. 3, fig. 4 and table 1, it can be found that the carbon composite sodium ion cathode material prepared by the invention has good stability and rate capability.
TABLE 1 Battery Charge and discharge test results
Figure BDA0003800195260000081
Comparative example
46.2g of Na 2 SO 4 Adding into 540.5g water, placing on a magnetic stirrer to completely dissolve, and then adding 149.79g FeSO 4 ·7H 2 Dissolving O in the solution to obtain a blue-green solution; 160.05g CNT slurry (4% CNT,1% dispersant CMC and H) was added to the above cyan solution 2 O composition and the content of each component) and dispersing for 2 hours to obtain sprayed precursor mixed feed liquid; introducing the mixed liquid into a spray dryer, respectively in N 2 Under atmosphere (oxygen content)<0.1 ppm) and air atmosphere, and the precursors obtained in both atmospheres were respectively designated as 1 and 2. Setting the air inlet temperature to be 220 ℃, the feeding speed to be about 5mL/min and the air outlet temperature to be 100 ℃ to obtain precursor powder of Na6Fe5 (SO 4) 8@ CNT; the two precursor powders obtained above were transferred to a sintering furnace respectively under an N2 atmosphere (oxygen content)<0.1 ppm), setting the heating rate of 2 ℃/min, and keeping the temperature at 385 ℃ for 12 hours to obtain the carbon composite iron-based polyanion positive electrode material Na 6 Fe 5 (SO 4 ) 8 @ CNT cathode materials 1 and 2.
Na prepared by the above comparative example 6 Fe 5 (SO 4 ) 8 The @ CNT positive electrode materials 1 and 2 are respectively mixed with a conductive agent SUPER-P and a binder PVDF to prepare slurry (solid content is 27.4%) according to a mass ratio of 90 4 (the solvent is propylene carbonate) as an electrolyte, and the electrolyte is assembled into a CR2032 battery in a glove box.
And (3) carrying out charge and discharge tests on the assembled battery on a charge and discharge tester, wherein the tested charge and discharge interval is 1.5-4.5V. The capacity of the assembled battery was tested at 0.1C to obtain its first charge and discharge curve, as shown in fig. 5. It is clear from this that the atmosphere protection conditions for spray drying are very necessary.
Example 2
0.900kg of Na was weighed 2 SO 4 Dissolving in 10.782kg water, stirring in disperser to dissolve completely, and adding 2.937kg FeSO 4 ·7H 2 Dissolving O in the solution to obtain a blue-green solution; to the above blue-green solution was added 3.133kg of CNT slurry (4% CNT,1% dispersant CMC and H) 2 O), dispersing for 2h to prepare spray-dried precursor slurry to obtain sprayed precursor mixed feed liquid; introducing the mixed material liquid into a spray dryer for spray granulation, setting the air inlet temperature at 220 ℃, the feeding speed at about 70mL/min and the air outlet temperature at 100 ℃ to obtain black Na 6 Fe 5 (SO 4 ) 8 A precursor powder of @ CNT; transferring the precursor powder to a sintering furnace in N 2 Under atmosphere (oxygen content)<0.1 ppm), setting the heating rate of 2 ℃/min, and keeping the temperature at 385 ℃ for 12h to obtain Na 6 Fe 5 (SO 4 ) 8 The @ CNT positive electrode material is the carbon composite iron-based polyanion positive electrode material.
The carbon composite iron-based polyanionic cathode material obtained in example 2 was analyzed by a scanning electron microscope, and it was found that the carbon nanotubes of the obtained cathode material were uniformly embedded in the middle of the particles to form a compact shell, and the whole was in a hollow spherical structure of 1 μm to 10 μm. Na (Na) 6 Fe 5 (SO 4 ) 8 The material shows high crystallinity, and the carbon nanotubes are tightly embedded in Na 6 Fe 5 (SO 4 ) 8 The bulk structure of the material.
Na prepared in example 2 6 Fe 5 (SO 4 ) 8 The method comprises the following steps of mixing and preparing a @ CNT positive electrode material, a conductive agent SUPER-P and a binder PVDF into slurry (solid content is 27.4%) by mass ratio of 90 4 (the solvent is propylene carbonate) as an electrolyte, and the electrolyte is assembled into a CR2032 battery in a glove box.
And (3) carrying out charge and discharge tests on the assembled battery on a charge and discharge tester, wherein the tested charge and discharge interval is 1.5-4.5V. The capacity of the assembled battery was measured at 0.1C to obtain a specific first-cycle discharge capacity of 82.26mAh/g.
Example 3
15.4g of Na 2 SO 4 Added to 232g of water, placed on a magnetic stirrer to be completely dissolved, and 49.93g of FeSO 4 ·7H 2 Dissolving O in the solution to obtain a blue-green solution; then adding 31.61g of VC to dissolve the VC in the solution; finally, 53.35g of CNT paste (4% CNT,1% dispersant CMC and H) was added to the above solution 2 O), dispersing for 2h to obtain a sprayed precursor mixed feed liquid; introducing the mixed feed liquid into a spray dryer at N 2 Under atmosphere (oxygen content)<0.1 ppm) was sprayed and granulated, setting the inlet air temperature at 220 deg.C, the inlet speed at about 5mL/min, and the outlet air temperature at 100 deg.C to obtain Na 6 Fe 5 (SO 4 ) 8 A precursor powder of @ CNT; transferring the precursor powder obtained above to a sintering furnace in N 2 Under atmosphere (oxygen content)<0.1 ppm), setting a heating rate of 2 ℃/min, and keeping the temperature at 385 ℃ for 12 hours to obtain a carbon composite iron-based polyanion positive electrode material, namely Na 6 Fe 5 (SO 4 ) 8 @ CNT cathode material.
In the carbon composite iron-based polyanionic cathode material prepared by the method, carbon is embedded in the cathode material, and Na is added x Fe y (SO 4 ) z The particles are connected in the network-shaped carbon-based framework, so that the charge transport capability among the particles of the positive electrode material can be obviously improved.
Na prepared in example 3 6 Fe 5 (SO 4 ) 8 The @ CNT positive electrode material, the conductive agent SUPER-P and the binder PVDF are respectively mixed into slurry (solid content is 27.4%) according to the mass ratio of 90 4 (the solvent is propylene carbonate) as an electrolyte, and the electrolyte is assembled into a CR2032 battery in a glove box.
And (3) carrying out charge and discharge tests on the assembled battery on a charge and discharge tester, wherein the tested charge and discharge interval is 1.5-4.5V. The capacity of the assembled battery was measured at 0.1C to obtain a specific first cycle discharge capacity of 85.03mAh/g.

Claims (10)

1. The carbon composite iron-based polyanionic positive electrode material is characterized in that the carbon composite iron-based polyanionic positive electrode material is of a spherical structure with a hollow interior; the spherical structure comprises an iron-based polyanion compound and a carbon material embedded in the iron-based polyanion compound; the iron-based polyanion compound is Na x Fe y (SO 4 ) z (ii) a Wherein 1 is<x≤10，1<y≤10，z＝x/2+y。
2. The carbon composite iron-based polyanionic cathode material according to claim 1, wherein the particle size D50 of the carbon composite iron-based polyanionic cathode material is 1 to 10 μm.
3. A method for preparing the carbon composite iron-based polyanionic positive electrode material according to claim 1, comprising the steps of:
s1) mixing sodium sulfate, ferrous sulfate and carbon material slurry with a solvent to obtain precursor slurry;
s2) carrying out spray granulation on the precursor slurry in a protective atmosphere to obtain a precursor of the anode material;
and S3) sintering the precursor of the cathode material at a low temperature in a protective atmosphere to obtain the carbon composite iron-based polyanion cathode material.
4. The preparation method according to claim 3, wherein the molar ratio of the sodium sulfate to the ferrous sulfate is 1: 2-2: 1.
5. the method according to claim 3, wherein the total mass of the sodium sulfate and the ferrous sulfate is 10 to 40% of the total mass of the sodium sulfate, the ferrous sulfate and the solvent.
6. The production method according to claim 3, wherein the carbon material slurry comprises a carbon material, a dispersant and a solvent; the mass concentration of the carbon material in the carbon material slurry is 4-5%;
the carbon material in the carbon material slurry is selected from one or more of carbon nanotubes, carbon fibers, reduced graphene oxide and graphene.
7. The production method according to claim 3, wherein the mass of the carbon material in the carbon material slurry is 1% to 10% of the total mass of the sodium sulfate and the ferrous sulfate.
8. The method according to claim 3, wherein a reducing agent is further added in the step S1); the molar ratio of the reducing agent to the ferrous sulfate is 1-1:1; the reducing agent is selected from L-ascorbic acid and/or citric acid.
9. The preparation method according to claim 3, wherein the inlet air temperature for the spray granulation is 120-250 ℃; the feeding speed of the precursor slurry during spray granulation is 5-100 mL/min.
10. The preparation method according to claim 3, wherein the temperature of the low-temperature sintering is 300-450 ℃; the low-temperature sintering time is 1-24 h; the heating rate of the low-temperature sintering is 2-20 ℃/min.
CN202210980380.4A 2022-08-16 2022-08-16 Carbon composite iron-based polyanion positive electrode material and preparation method thereof Pending CN115188951A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116154154A (en) * 2023-04-13 2023-05-23 深圳珈钠能源科技有限公司 Pure-phase polyanion type sulfate sodium ion battery positive electrode material and preparation method thereof
CN116417617A (en) * 2023-05-26 2023-07-11 宁德新能源科技有限公司 Positive electrode material, positive electrode sheet, sodium ion secondary battery and electricity utilization device

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116154154A (en) * 2023-04-13 2023-05-23 深圳珈钠能源科技有限公司 Pure-phase polyanion type sulfate sodium ion battery positive electrode material and preparation method thereof
CN116417617A (en) * 2023-05-26 2023-07-11 宁德新能源科技有限公司 Positive electrode material, positive electrode sheet, sodium ion secondary battery and electricity utilization device
CN116417617B (en) * 2023-05-26 2023-10-24 宁德新能源科技有限公司 Positive electrode material, positive electrode sheet, sodium ion secondary battery and electricity utilization device

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