CN117525393A - Sodium ion polyanion positive electrode material, preparation method thereof and battery pole piece - Google Patents

Sodium ion polyanion positive electrode material, preparation method thereof and battery pole piece Download PDF

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CN117525393A
CN117525393A CN202311663543.7A CN202311663543A CN117525393A CN 117525393 A CN117525393 A CN 117525393A CN 202311663543 A CN202311663543 A CN 202311663543A CN 117525393 A CN117525393 A CN 117525393A
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positive electrode
sodium
electrode material
sodium ion
carbon
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张孟
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Ningbo Xinghang Energy Technology 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
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
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  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention belongs to the technical field of new energy. The invention discloses a sodium ion polyanion positive electrode material, which comprises a sodium ion polyanion positive electrode material with an empirical formula of Na h Fe i (PO 4 ) j (P 2 O 7 ) k An electroactive material of/C, wherein h is a number from 4.05 to 4.15, i is a number from 2.89 to 2.95, j is a number from 1.96 to 1.98, k is a number from 1.01 to 1.04, and the empirical formula is Na h Fe i (PO 4 ) j (P 2 O 7 ) k The relationship among h, i, j and k in the electroactive material of/C is 9.7<(h+2i+3j+4k)/2<10. The invention discloses a sodium ion polyanion anodeA preparation method of the material. The invention discloses a battery pole piece. The preparation method of the sodium ion polyanion positive electrode material adopts a solid-liquid nanocrystallization method, the method is easy for scale production, no waste water and waste gas are discharged, the adopted raw materials are easy to obtain, and meanwhile, the prepared sodium ion polyanion positive electrode material has high specific capacity and higher dynamics performance under higher discharge rate.

Description

Sodium ion polyanion positive electrode material, preparation method thereof and battery pole piece
Technical Field
The invention belongs to the technical field of new energy, and particularly relates to a sodium ion polyanion positive electrode material, a preparation method thereof and a battery pole piece.
Background
Sodium ion batteries are considered ideal electrochemical energy storage candidates due to their high abundance of sodium elements, wide availability and low cost. However, developing sodium ion batteries with high energy density and high cycling stability in the most cost-effective manner remains a significant challenge. Sodium iron phosphate, which is a sodium ion polyanion positive electrode material, is used as one of sodium ion battery materials, and has poor conductivity and insufficient material dynamics performance, and the synthesis reaction of sodium iron phosphate is complex, and the synthesis condition is limited, so that the specific capacity of the sodium iron phosphate is low, and the application of the sodium ion battery is influenced. Research and development of a sodium ion polyanion positive electrode material with high capacity density and high performance and a preparation method of the green high-efficiency sodium ion polyanion positive electrode material of the material have important values.
The existing sodium ion battery iron-based phosphate sodium ion polyanion positive electrode material, such as ferric sodium phosphate, has low energy density, complex synthesis reaction, and is easy to generate impurities without chemical activity at high synthesis temperature, so that the specific capacity of the sodium ion battery iron-based phosphate sodium ion polyanion positive electrode material is insufficient, and the sodium ion polyanion positive electrode material in the prior art is prepared by adopting a solid phase method and a liquid phase method, wherein the liquid phase method is prepared by forming a salt solution into gel or directly drying and then sintering, the yield of the method is lower and the energy consumption is higher, the solid phase method is prepared by directly sintering at high temperature after mixing and ball milling solid raw materials, and the method is simple, but the prepared product has lower performance.
Disclosure of Invention
In order to solve the defects in the prior art, the invention discloses a preparation method of a sodium ion polyanion positive electrode material, which realizes nanocrystallization and uniform mixing of the material through solid-liquid reaction, is simple, and the material prepared by the method is the sodium ion polyanion positive electrode material with higher discharge rate and higher dynamic performance.
A sodium ion polyanionic positive electrode material is disclosed that is made from starting materials that deviate from stoichiometry, yet still provide high specific capacity and good cycle life at high discharge rates.
The invention discloses a sodium ion polyanion anode material, the sodiumThe ionic polyanionic positive electrode material includes a material having an empirical formula Na h Fe i (PO 4 ) j (P 2 O 7 ) k An electroactive material of/C, wherein h is a number from 4.05 to 4.15, i is a number from 2.89 to 2.95, j is a number from 1.96 to 1.98, k is a number from 1.01 to 1.04, and the empirical formula is Na h Fe i (PO 4 ) j (P 2 O 7 ) k The relationship among h, i, j and k in the electroactive material of/C is 9.7<(h+2i+3j+4k)/2<10。
Further, at least a portion of the electroactive material has a triclinic crystal structure. The partial triclinic crystal structure can increase the stability of the electroactive material and prolong the service life of the electroactive material. The ion diffusion rate of the sodium ion polyanion positive electrode material can be improved by the partial triclinic crystal structure, namely, the ionic conductivity of the electroactive material arranged by the partial triclinic crystal structure can be improved, and the conductivity of the sodium ion polyanion positive electrode material can be improved.
Further, the content of C in the electroactive material affects the electronic conductivity, stability and mechanical properties of the electroactive material, and when the content of C in the electroactive material is less than 1.0wt%, the conductivity of the electroactive material is poor, the conductivity of the sodium ion polyanion cathode material is affected, and when the content of C in the electroactive material is greater than 2.8wt%, the improved conductivity is relatively limited, and the specific surface area of the electroactive material is increased, affecting the processability of the material. In summary, the content of C in the electroactive material is 1.0wt% or more and 2.8wt% or less. Further, the content of C in the electroactive material is 1.4wt% or more and 2.4wt% or less. Preferably, the content of C in the electroactive material is 1.4wt% or more and 2.0wt% or less.
The invention also provides a preparation method of the sodium ion polyanion positive electrode material, the method realizes nanocrystallization and uniform mixing of the material through solid-liquid reaction, and the material prepared by the method has the characteristics of environmental protection, high yield and low cost, and has high product performance.
The invention disclosesA method for preparing a sodium ion polyanionic positive electrode material, the method comprising S1: mixing an iron source compound, a carbon source and a phosphorus source compound with water to form a precursor mixture a, S2: mixing the precursor mixture a with a sodium source compound to form a precursor mixture B, S3: and drying the precursor mixture B, calcining in a non-oxidizing atmosphere, and cooling to obtain the sodium ion polyanion positive electrode material. In the calcination process in a non-oxidizing atmosphere, the carbonaceous material or organic compound in the precursor mixture B is converted into a carbon material, i.e. empirical Na h Fe i (PO 4 ) j (P 2 O 7 ) k C in/C. The amounts of the iron source compound, the phosphorus source compound and the sodium source compound are calculated according to stoichiometric numbers (h, i, j, k) of Fe, P and Na in the general formula. The iron source compound, the carbon source, the phosphorus source, the sodium source and the like in the reactants can be selected in a plurality of types, and more types of reactants can provide more synthesis paths and methods, so that the synthesis process is more flexible, and the most suitable reactant can be selected according to the needs. If certain reactants are more expensive or difficult to obtain, the cost may be reduced by selecting other reactants that are less expensive or more readily available. Some reactants may be environmentally friendly, while other more environmentally friendly reactants may be selected to reduce environmental pollution.
Further, the mixing process in S1 specifically comprises dispersing an iron source compound, a carbon source compound and a phosphorus source compound in water, uniformly mixing to obtain an intermediate mixture, and dispersing for 1-7 h under the condition that the temperature of the intermediate mixture is more than or equal to 50 ℃ and less than or equal to 80 ℃ to form a precursor mixture A.
Further, the iron source compound in S1 is selected from one or more of ferrous oxalate, ferric acetate, ferric phosphate (trivalent), ferric phosphate (divalent), ferric oxide, ferrous carbonate, ferrous oxide, ferrous hydroxide, or ferric hydroxide (trivalent). Still further, the iron source compound in S1 is preferably selected from one or more of the group consisting of ferric oxide, ferrous carbonate, or ferric carbonate. The carbon source in S1 is at least one of inorganic carbon and carbon-containing organic matter, wherein the inorganic carbon is selected from conductive carbon black and carbonNanotube, ethylene-fast carbon black, graphene or graphite, and the carbon-containing organic matter is selected from glucose, sucrose, vitamin C, citric acid, tartaric acid, oxalic acid, polyvinyl alcohol or polyacrylic acid. The source of the phosphorus source in S1 is selected from one or two of phosphoric acid, sodium dihydrogen phosphate, ferric phosphate (trivalent) or ferric phosphate (divalent). Preferably, the source of the phosphorus source in S1 is selected from phosphoric acid and sodium dihydrogen phosphate, more preferably, the source of the phosphorus source in S1 is selected from phosphoric acid. In the S1 process, if a soluble substance such as phosphoric acid is used, a solid-liquid reaction between the raw materials usually occurs with an exothermic reaction and an increase in viscosity of the mixture of the precursor mixture A and the phosphorus source, wherein the intermediate reaction product may be a mixture of compounds composed of phosphorus, iron or hydrogen elements, such as FePO 4 、NaH 2 PO 4 And mixtures of phosphosiderite and the like. In the S1 process, the temperature of the mixture is controlled, preferably, the temperature of the mixture is 50 ℃ or higher and 80 ℃ or lower. In the S1 process, means such as high-speed dispersion and ball milling can be assisted, uniform mixing and nanocrystallization of materials are facilitated, and the dispersion or ball milling time is 1-7 h. The sodium source compound in S2 is selected from one or more of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium pyrophosphate or sodium hydrogen pyrophosphate. In the S2 process, the viscosity of the mixture of precursor mixture A and sodium source compound generally increases, and sodium carbonate or sodium bicarbonate, when used as a sodium source, reacts to form gaseous CO in the presence of a Lewis acid in the system 2 The product, precursor mixture B, is left for a period of time or assisted by dispersion or ball milling, CO 2 The product was removed. Sodium dihydrogen phosphate or sodium monohydrogen phosphate in S2 can be prepared according to the initial metering ratio specified in the empirical formula, and sodium dihydrogen phosphate or sodium monohydrogen phosphate can also be formed by partially neutralizing phosphoric acid with sodium hydroxide, sodium carbonate or sodium bicarbonate.
Further, in S2, the mixing temperature is controlled to be 50 ℃ or higher and 80 ℃ or lower. Further, the mixing temperature is controlled to 55 ℃ or higher and 70 ℃ or lower in S2, and preferably, the mixing temperature is controlled to 55 ℃ or higher and 65 ℃ or lower in S2.
Further, in S3, the calcination temperature is 400 ℃ or higher and 600 ℃ or lower, and the calcination time is 5h or higher and 20h or lower.
Further, the drying mode of the precursor mixture B in S3 is preferably spray drying, and the non-oxidizing atmosphere in S3 is an inert atmosphere or a reducing atmosphere, which are both used for preventing oxidation of the iron element in the precursor. The precursor mixture B can be dried into powder or particles in a short time by spray drying, and the drying speed is high and the production efficiency is high. The spray drying can uniformly disperse the precursor mixture B into fine liquid drops, thereby realizing uniform drying and avoiding the problems of local overheating or incomplete drying. Spray drying can result in high quality powders or granules with good flowability, dispersibility and solubility, and uniform precursor mixture B secondary spherical particles are formed by spray drying. The precursor mixture B secondary spherical particles are calcined under a non-oxidizing atmosphere, and the non-oxidizing atmosphere is preferably an inert atmosphere or a reducing atmosphere. Further, the non-oxidizing atmosphere is a pure nitrogen atmosphere.
The invention discloses a battery pole piece, which comprises a sodium ion polyanion positive electrode material as any one of the above.
The mixing mode in the invention is not particularly limited, and the technical schemes of dispersing, stirring or grinding, which are well known to those skilled in the art, can be adopted, so as to uniformly mix the components. The mixing mode in the invention can be wet grinding, the equipment of the wet grinding is stirring grinding or sand grinding or circulating stirring grinding, and the like, the grinding step can be carried out according to one or more steps to achieve smaller particle diameter, two-step ball milling can be carried out, wherein the grinding balls with the diameter of 0.5mm to 1.2mm are adopted in the first step, and the grinding balls with the diameter of 0.1mm to 0.5mm are adopted in the second step.
In the synthesis process of the sodium ion polyanion positive electrode material, nanocrystallization and uniform mixture of the material are realized through solid-liquid reaction, synthesis conditions are simple, and the prepared sodium ion polyanion positive electrode material has high specific capacity, high discharge capacity and high discharge rate, and has higher dynamic performance at higher discharge rate.
Drawings
Fig. 1 is a schematic diagram of X-ray diffraction analysis of example 6, example 7 and comparative example 2 in the embodiment of the present application.
Fig. 2 is a schematic diagram of example 9 and comparative example 3 in the present embodiment under a field emission electron microscope.
Detailed Description
In order to better understand the solution of the present invention, the following description will clearly and completely describe the solution of the present invention in the specific embodiment.
Preparation of sodium ion polyanion positive electrode material:
example 1
(1) 261g of ferrous oxalate dihydrate, 40.8g of glucose and 27g of multi-wall carbon nano tube aqueous slurry (5 wt%) are dispersed in 400g of deionized water and uniformly mixed to obtain an intermediate mixture, the temperature of the intermediate mixture is controlled to be 60 ℃, 144g of sodium dihydrogen phosphate is added, and the mixture is ground and dispersed for 6 hours by using a ball mill to form a precursor mixture A.
(2) 144g of sodium dihydrogen phosphate was added to the precursor mixture A obtained in the step (1) and dispersed for 2 hours to form a precursor mixture B.
(3) Spray drying the precursor mixture B obtained in the step (2) to obtain powder, calcining the powder at high temperature under the protection of argon, wherein the calcining temperature is 490 ℃, the calcining time is 16h, and cooling to obtain the ferric sodium pyrophosphate material, wherein the ferric sodium pyrophosphate material is a sodium ion polyanion positive electrode material co-coated by carbon, and the general formula of the ferric sodium pyrophosphate material is Na 4.05 Fe 2.9 (PO 4 ) 1.98 (P 2 O 7 ) 1.02 and/C, the carbon content of the ferric pyrophosphate sodium material is about 2.5wt%.
Example 2
(1) 271.8g of ferric orthophosphate and 45g of glucose were dispersed in 400g of deionized water and mixed uniformly to obtain an intermediate mixture, the temperature of the intermediate mixture was controlled to 60 ℃, 69.4g of phosphoric acid (85 wt%) was added, and the mixture was stirred and dispersed at high speed for 5 hours to form a precursor mixture A.
(2) 63.9g of sodium bicarbonate was added to the precursor mixture A obtained in the step (1) and dispersed for 3 hours to form a precursor mixture B.
(3) Spray drying the precursor mixture B obtained in the step (2) to obtain powder, calcining the powder at high temperature under the protection of pure nitrogen at 550 ℃ for 10 hours, and cooling to obtain a sodium ferric pyrophosphate material which is a sodium ion polyanion anode material co-coated with carbon, wherein the general formula of the sodium ferric pyrophosphate material is Na 4.08 Fe 2.92 (PO 4 ) 1.965 (P 2 O 7 ) 1.026 The carbon content of the carbon/C is about 2.1% by weight.
Example 3
(1) 140.1g of ferroferric oxide and 41g of glucose are dispersed in 40g of deionized water and uniformly mixed to obtain an intermediate mixture, the temperature of the intermediate mixture is controlled to be 60 ℃, 285g of phosphoric acid (85 wt%) is added to disperse for 4 hours, and a precursor mixture A is formed.
(2) 132.3g of sodium carbonate was added to the precursor mixture A obtained in the step (1) and dispersed for 4 hours to form a precursor mixture B.
(3) Spray drying the precursor mixture B obtained in the step (2) to obtain powder, calcining the powder at a high temperature under the protection of a mixed gas (hydrogen gas 5%) of argon and hydrogen at a calcining temperature of 500 ℃ for 12 hours, and cooling to obtain a sodium ferric pyrophosphate material, wherein the sodium ferric pyrophosphate material is a sodium ion polyanion positive electrode material co-coated with carbon, and the general formula of the sodium ferric pyrophosphate material is Na 4.1 Fe 2.89 (PO 4 ) 1.97 (P 2 O 7 ) 1.03 and/C, wherein the carbon content is 1.8wt%.
Example 4
The difference from example 3 is that the initial input metering ratio of the raw materials is different, the metering ratio is shown in the table 1, and finally the ferric sodium pyrophosphate material is obtained, the ferric sodium pyrophosphate material is a sodium ion polyanion positive electrode material coated by carbon, and the general formula of the ferric sodium pyrophosphate material is Na 4.06 Fe 2.91 (PO 4 ) 1.975 (P 2 O 7 ) 1.015 /C。
Example 5
The difference from example 3 is that the initial input metering ratio of the raw materials is different, the metering ratio is shown in the table 1, and finally the ferric sodium pyrophosphate material is obtained, the ferric sodium pyrophosphate material is a sodium ion polyanion positive electrode material coated by carbon, and the general formula of the ferric sodium pyrophosphate material is Na 4.15 Fe 2.94 (PO 4 ) 1.96 (P 2 O 7 ) 1.02 /C。
Example 6
Example 6 was prepared using the procedure described in example 1, with the difference from example 1 that: example 6 the sintering temperature in step 3 was 450 degrees.
Example 7
Example 7 was prepared using the procedure described in example 1, with the difference from example 1 that: example 7 the sintering temperature in step 3 was 550 degrees.
Example 8
Example 8 was prepared using the procedure described in example 3, with the difference from example 3 that: whereas the sintering time in step 3 was 6 hours in example 8.
Example 9
Example 9 was prepared using the procedure described in example 3, with the difference from example 3 that: example 9 the sintering time in step 3 was 20 hours.
Comparative example 1
The difference from example 3 is that the initial input metering ratio of the raw materials is different, the metering ratio is shown in the table 1, and finally the ferric sodium pyrophosphate material is obtained, the ferric sodium pyrophosphate material is a sodium ion polyanion positive electrode material coated by carbon, and the general formula of the ferric sodium pyrophosphate material is Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) 1 /C。
Comparative example 2
Comparative example 2 was prepared in the same manner as described in example 1, except that the sintering temperature was 600 degrees.
Comparative example 3
Comparative example 3 was prepared using the procedure described in example 3, with the difference from example 3 that: example 9 the sintering time in step 3 was 30 hours.
Comparative example 4
Comparative example 4 was carried out as described in example 2, except that the intermediate mixture temperature in step 1 was controlled to 40 ℃.
The values of h, i, j and k and the values of (h+2i+3j+4k)/2 in examples 1 to 5 and comparative example 1 are shown in Table 1.
TABLE 1
Application test:
the sodium ferric pyrophosphate materials prepared in the examples 1 to 5 and the comparative example 1 are respectively mixed with an acetylene black conductive agent and a polyvinylidene fluoride binder according to a mass ratio of 92:4:4, and with a proper amount of N-methyl pyrrolidone (NMP), and then coated on an aluminum foil after being uniformly mixed, and then dried, and a positive plate is punched by a punching machine after being dried.
Sodium sheet is used as a negative electrode, a fibrous membrane is used as a separation membrane, and an electrolyte is NaClO containing 1mol/L 4 The positive electrode, the negative electrode, the separator and the electrolyte are assembled into a button cell in a glove box (water and oxygen content is less than lpppm).
Electrochemical tests are carried out on the prepared button cell by adopting a cell test system, the current density is calculated according to 1 C=129 mAh/g, the ambient temperature is room temperature, and the charge-discharge voltage interval is 2V to 3.8V (for sodium cathode).
Comparative example 1 has a discharge capacity of 84.4mAh/g at 0.1C in the charge-discharge interval of 2V to 3.8V, and examples 1 to 5 have a discharge capacity of 95.5 to 102.2, and specific capacity data as shown in table 2 (C is a discharge rate in the table).
TABLE 2
Examples 1 to 5 in the present invention show a higher discharge capacity and higher dynamic performance at a higher discharge rate, and example 2 achieves a specific discharge capacity of about 100mAh/g at 0.2C charge and discharge. Comparative example 1 was not prepared in stoichiometric ratio, exhibiting poor discharge capacity. Example 3 the capacity was about 84mAh/g at a discharge rate of 3C, and the capacity retention was about 82% after 1000 cycles. As is evident from Table 2, the empirical formula of this application is Na h Fe i (PO 4 ) j (P 2 O 7 ) k The sodium ion polyanion battery prepared by the electroactive material of/C has higher discharge capacity.
XRD analysis and detection were carried out on example 6, example 7 and comparative example 2, and the results are shown in FIG. 1. When the analysis is carried out on fig. 1, three sample phases all conform to standard cards, but at a diffraction angle of 11 degrees, tiny hetero peaks appear, wherein the hetero peaks of the example 6 and the example 7 are stronger and weaker, the hetero peaks are obvious compared with the example 6 and the example 7 when the temperature is increased to 600 degrees of the comparative example 2, and the surface temperature is increased to have direct influence on the purity of the phases, so that the invention selects 450 ℃ to 600 ℃ as a preferable synthesis temperature.
The abscissa in fig. 1 represents the diffraction angle, and the ordinate in fig. 1 represents the diffraction intensity. The uppermost peak in FIG. 1 is the peak generated in example 6, the middle peak in FIG. 1 is the peak generated in example 7, the lowermost peak in FIG. 1 is the peak generated in comparative example 2,
the sintering times of example 3, example 8, example 9 and comparative example 3 were 12h, 6h, 20h and 30h, respectively, and the specific capacity data of each sample was as shown in table 3 (in table C, discharge rate).
TABLE 3 Table 3
The shortest sintering time for the sample of example 8, with a capacity of 89.5mah/g, which is lower than 100.8 of example 3, indicates that example 8 already gives a sample with better performance, but the active phase has slightly less crystalline integrity due to the short sintering time. Whereas the comparative example had a sintering time of 30 hours, which had the lowest specific capacity and was lower than that of example 9 having a sintering time of 20 hours, the primary particles of comparative example 3 were larger than those of example 9 by analysis with a scanning electron microscope, and had an agglomeration phenomenon due to the fact that the excessively long sintering time caused crystal growth and agglomeration, and the electron conduction path became long and the conductivity and kinetic properties became poor, and the preferred sintering time of the present invention was 6 to 20 hours. The images of example 9 and comparative example 3 under the electron microscope are shown in fig. 2.
Comparative example 4 has a lower viscosity of the slurry during step 1 than 100mAh/g of example 2, and has an electrochemical capacity of 92mAh/g as measured under the same conditions, because the raw material particles have a larger particle size at a lower temperature, and the prepared material has relatively poor properties.
It will be understood that modifications and variations will be apparent to those skilled in the art from the foregoing description, and it is intended that all such modifications and variations be included within the scope of the following claims.

Claims (10)

1. A sodium ion polyanionic positive electrode material, comprising:
has an empirical formula of Na h Fe i (PO 4 ) j (P 2 O 7 ) k An electroactive material of/C, wherein h is a number from 4.05 to 4.15, i is a number from 2.89 to 2.95, j is a number from 1.96 to 1.98, k is a number from 1.01 to 1.04, and the empirical formula is Na h Fe i (PO 4 ) j (P 2 O 7 ) k The relationship among h, i, j and k in the electroactive material of/C is 9.7<(h+2i+3j+4k)/2<10。
2. The sodium ion polyanionic positive electrode material according to claim 1, characterized in that:
electroactive material Na h Fe i (PO 4 ) j (P 2 O 7 ) k At least a part of the component (C) has a triclinic crystal structure.
3. The sodium ion polyanionic positive electrode material according to claim 1, characterized in that:
the content of C in the electroactive material is 1.0wt% or more and 2.8wt% or less.
4. A preparation method of a sodium ion polyanion positive electrode material is characterized by comprising the following steps:
s1: mixing an iron source compound, a carbon source and a phosphorus source compound with water to form a precursor mixture A;
s2: mixing the precursor mixture A with a sodium source compound to form a precursor mixture B;
s3: and drying the precursor mixture B, calcining in a non-oxidizing atmosphere, and cooling to obtain the sodium ion polyanion positive electrode material.
5. The method for preparing a sodium ion polyanionic positive electrode material according to claim 4, wherein: the mixing process in the step S1 is specifically to disperse an iron source compound, a carbon source compound and a phosphorus source compound in water and mix the iron source compound, the carbon source compound and the phosphorus source compound uniformly to obtain an intermediate mixture, and disperse the intermediate mixture for 1-7 h after controlling the temperature of the intermediate mixture to be more than or equal to 50 ℃ and less than or equal to 80 ℃ to form a precursor mixture A.
6. The method for preparing a sodium ion polyanionic positive electrode material according to claim 5, wherein: the iron source compound in S1 is selected from one or more of ferrous oxalate, ferric acetate, ferric phosphate (trivalent), ferric phosphate (divalent), ferric oxide, ferrous carbonate, ferrous oxide, ferrous hydroxide or ferric hydroxide (trivalent);
the carbon source in S1 is at least one of inorganic carbon and carbon-containing organic matters, wherein the inorganic carbon is selected from conductive carbon black, carbon nano tube, ethylene-fast carbon black, graphene or graphite, and the carbon-containing organic matters are selected from glucose, sucrose, vitamin C, citric acid, tartaric acid, oxalic acid, polyvinyl alcohol or polyacrylic acid;
the source of the phosphorus source in S1 is selected from one or two of phosphoric acid, sodium dihydrogen phosphate, ferric phosphate (trivalent) or ferric phosphate (divalent);
the sodium source compound in S2 is selected from one or more of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium pyrophosphate or sodium hydrogen pyrophosphate.
7. The method for preparing a sodium ion polyanionic positive electrode material according to claim 5, wherein: in S1, the mixing temperature is controlled to be more than or equal to 50 ℃ and less than or equal to 80 ℃.
8. The method for preparing a sodium ion polyanionic positive electrode material according to claim 5, wherein:
and S3, calcining at 400 ℃ or higher and 600 ℃ or lower for 5h or higher and 20h or lower.
9. The method for preparing a sodium ion polyanionic positive electrode material according to claim 5, wherein:
the drying mode of the precursor mixture B in the step S3 is spray drying;
the non-oxidizing atmosphere in S3 is an inert atmosphere or a reducing atmosphere.
10. A battery pole piece, characterized in that:
a battery pole piece comprising a polyanionic sodium ion polyanionic positive electrode material as defined in any one of claims 1-9.
CN202311663543.7A 2023-12-06 2023-12-06 Sodium ion polyanion positive electrode material, preparation method thereof and battery pole piece Pending CN117525393A (en)

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