Method for preparing prussian blue material with high tap density and controllable particle size and application thereof

Abstract

The application provides a preparation method of Prussian blue material with high tap density and controllable particle size and application thereof. The preparation method of the Prussian blue material provided by the application adopts a controlled crystallization precipitation method to synthesize the Prussian blue material, and comprises the following steps: adding a first raw material and a second raw material into a base solution, optionally adding a complexing agent, forming slurry containing primary particles, adding the slurry containing primary particles into the slurry containing primary particles after part of the slurry containing primary particles is optionally concentrated or without concentration, and forming polycrystalline particles after precipitation, so as to obtain the Prussian blue material. The Prussian blue material prepared by the application is applied to a battery as a positive electrode material, and excellent cycle performance and rate performance are exhibited.

Description

TECHNICAL FIELD

[0001] The present application relates to a process for controllably improving the first circle coulomb efficiency of lithium, sodium ion battery two-dimensional composite material, and belongs to the technical field of battery materials, relates to a preparation method and application of a prussian blue type positive electrode material with controllable high tap density and particle size, and particularly relates to a long precipitation period precipitation synthesis process for improving the tap density and particle size of a sodium, potassium, zinc ion battery positive electrode material. BACKGROUND

[0002] Compared with the traditional layered transition metal oxide positive electrode material, the prussian blue type positive electrode material used in sodium ion battery and other energy storage systems has the advantages of simple synthesis process, high reversible capacity, controllable voltage platform, stable cycle performance, good rate performance, low raw material cost and the like. The main disadvantage is that the material has low tap density and small particle size (nanoscale, generally less than 1-2 microns), and the particles are easy to agglomerate, which causes many difficulties in the actual production and processing and battery application of the material, such as low washing and sieving efficiency, mixing and coating difficulty, etc., resulting in high actual processing cost of the material, low battery quality energy density and volume energy density, and the like. Therefore, how to improve and increase the density and particle size of the prussian blue type material to make it controllable and reach or approach the level of layered materials is one of the key factors for the large-scale production and practical application of the prussian blue type material.

[0003] In addition, the current academic and industrial commonly used prussian blue type material synthesis method is a simple liquid phase precipitation method, which is usually carried out by one-pot co-precipitation. The precipitation is ended after the material is added to the full kettle. The precipitation period is short, the feeding speed is generally slow, the yield is low, and the product synthesized by the short period precipitation process has large batch-to-batch fluctuation in terms of particle size, tap density, specific surface area and the like, and the product consistency is poor. How to realize the stability of various indexes of products in different batches in the process of large-scale production is a problem that needs to be solved in the process of product practical application. SUMMARY

[0004] In view of the above problems, the present application provides a long precipitation period precipitation synthesis process for controllably improving the tap density and particle size of a sodium, potassium, zinc ion battery positive electrode material. By improving and optimizing the particle size and tap density of the material, the processing performance and battery energy density of the material in the actual application process are improved.

[0005] The present application provides a preparation method of a prussian blue material, wherein the preparation method synthesizes the prussian blue material by a controlled crystallization precipitation method, which comprises: adding a first raw material and a second raw material into a base solution, optionally adding a complexing agent to form a slurry containing primary particles, adding part of the slurry containing primary particles into the slurry containing primary particles after optional concentration or without concentration, and forming polycrystalline particles after precipitation to obtain the prussian blue material.

[0006] According to an embodiment of the present application, the primary particles have a single crystal structure.

[0007] Preferably, the particle size of the primary particles is not less than 0.5 μm.

[0008] Preferably, the polycrystalline particles are formed after agglomeration of the primary particles.

[0009] Preferably, the first raw material is selected from at least one of sodium and / or potassium hemifumarate.

[0010] Preferably, the first raw material is provided by a solution containing the first raw material, and the concentration is 0.1-1 mol / L.

[0011] Preferably, the second raw material is selected from at least one of a salt of a transition metal.

[0012] Preferably, the transition metal is selected from, but not limited to, iron, cobalt, nickel, manganese, copper, zinc, and the like.

[0013] Preferably, the second raw material is provided by a solution containing the second raw material, and the concentration is 0.1-3 mol / L.

[0014] Preferably, the solution containing the first raw material and the solution containing the second raw material further comprise a solvent.

[0015] According to an embodiment of the present application, the base solution comprises an alkali metal salt and a solvent. Preferably, in the base solution, the alkali metal salt is at a saturated or near-saturated concentration to provide an alkali metal-rich environment required for precipitation.

[0016] Preferably, the complexing agent is selected from at least one of trisodium citrate, sodium oxalate, sodium pyrophosphate, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, manganese sodium ethylenediaminetetraacetate, triethanolamine, urea, sodium succinate, sodium tartrate, polyvinylpyrrolidone, polyacrylamide, and the like.

[0017] Preferably, the molar ratio of the first raw material to the second raw material is 0.6-1.4.

[0018] Preferably, the molar ratio of the first raw material to the complexing agent is (5-50): 1.

[0019] Preferably, the first raw material and the second raw material are added in a manner of quantitative dropwise addition.

[0020] Preferably, the quantitative dropwise addition specifically refers to that the volume ratio of the hourly feeding amount of the solution containing the first raw material or the solution containing the second raw material to the base solution is 1:(5-20).

[0021] Preferably, the controlled crystallization precipitation method is selected from a batch precipitation method and / or a continuous precipitation method.

[0022] Preferably, when the batch precipitation method is used, the slurry containing primary particles is concentrated.

[0023] Preferably, when the continuous precipitation method is used, the slurry containing primary particles can be optionally concentrated or not concentrated.

[0024] Preferably, when the concentrated slurry containing primary particles is added, the variation of the solid content of the slurry containing primary particles is not more than 20wt% / h.

[0025] Preferably, in the preparation method, the solid content of the slurry containing primary particles is controlled to be 1wt% to 60wt%.

[0026] Preferably, the precipitation period of the precipitation is 1 to 720h.

[0027] According to the embodiments of the present application, the preparation method further comprises: before or after the precipitation, the primary particles and / or the polycrystalline particles can be further classified to improve the uniformity of the particle size distribution.

[0028] Preferably, when the index of the polycrystalline particles meets the requirements, the feeding is stopped, and the precipitation is ended.

[0029] Preferably, when the batch precipitation is used, the index of the polycrystalline particles comprises: the particle size distribution presents a normal distribution in a unimodal form or a bimodal distribution, and the particles are uniform.

[0030] Further preferably, the particle size distribution D50 of the polycrystalline particles is 4 to 40μm, and the laser particle size distribution consistency is not more than 0.4.

[0031] Preferably, when the continuous precipitation is used, the preparation of the polycrystalline particles comprises: the particle size distribution at least presents a bimodal distribution.

[0032] Further preferably, the particle size distribution D50 of the polycrystalline particles is 4 to 40μm, and the laser particle size distribution consistency is not less than 0.4.

[0033] According to an embodiment of the present application, the preparation method synthesizes the Prussian blue material by using a batch precipitation method, comprising: adding a first raw material, a second raw material and a complexing agent into a base solution to form a slurry containing primary particles, adding part of the slurry containing primary particles into the slurry containing primary particles after concentration, and forming polycrystalline particles after precipitation, and obtaining the Prussian blue material after aging treatment, washing and drying; preferably, when the slurry containing primary particles after concentration is added, the variation of solid content of the slurry containing primary particles is not more than 15wt% / h; preferably, the solid content of the slurry containing primary particles is controlled to be 10wt%-30wt%.

[0034] Exemplarily, the preparation method synthesizes the Prussian blue material by using a continuous precipitation method, comprising: adding a first raw material, a second raw material and a complexing agent into a base solution to form a slurry containing primary particles, adding part of the slurry containing primary particles into the slurry containing primary particles without concentration, and obtaining the Prussian blue material after precipitation; preferably, the solid content of the slurry containing primary particles is less than 5wt%.

[0035] The present application also provides a positive electrode material, which comprises a Prussian blue material prepared by the above preparation method; the chemical formula of the Prussian blue material is (M 1 ) x (M 2 ) y (M 3 (CN)6) z ·mH2O.

[0036] Preferably, in the chemical formula, M 1 may be at least one of Li, Na, K, Cs, Zn and the like.

[0037] Preferably, in the chemical formula, M 2 may be at least one of Fe, Mn, Ni, Co, V, Cu, Zn and the like, preferably two kinds.

[0038] Preferably, in the chemical formula, M 3 may be at least one of Fe and Mn.

[0039] Preferably, in the chemical formula, 0≤x≤2, 0≤y≤1, 0≤z≤1.

[0040] Preferably, in the chemical formula, m is an integer greater than or equal to 0.

[0041] Exemplarily, the Prussian blue material can be Na2Mn 1-x Fe x(Fe(CN)6)·mH2O.

[0042] According to an embodiment of the present application, the particle size D50 of the positive electrode material is 10-30 μm.

[0043] Preferably, the tap density of the positive electrode material is not less than 0.5 g / cm 3 .

[0044] Preferably, the loose bulk density of the positive electrode material is not less than 0.5 g / cm 3 .

[0045] The present application also provides the use of the above positive electrode material.

[0046] The present application also provides a positive electrode sheet, which comprises at least the above positive electrode material.

[0047] The present application also provides an ionic battery, which comprises at least the above positive electrode sheet.

[0048] Advantages

[0049] Compared with the prior art, the present application has the following advantages:

[0050] (1) The present application uses a controlled crystallization precipitation method to synthesize Prussian blue material, and by adjusting the type and amount of complexing agent, the generation rate of polycrystalline particles is slowed down, so as to realize accurate control of the particle size and tap density of the positive electrode material.

[0051] (2) When using an intermittent precipitation process, the supersaturation of the slurry in the reaction kettle and the precipitation period can be controlled to make the primary particles and polycrystalline particles slowly crystallize and grow, and at the same time, part of the slurry containing primary particles is filtered and returned to the slurry in the reaction kettle. Thus, the primary particles in the slurry in the reaction kettle continuously agglomerate and grow to obtain polycrystalline particles, and at the same time, the polycrystalline particles rub and collide with each other, so as to make the polycrystalline particles tend to form spherical or quasi-spherical morphology with high tap density and low specific surface area.

[0052] (3) When using a continuous precipitation process, the production cycle can be continuously extended, and during the crystallization and precipitation process, the reaction kettle can be in full-load production state. By adjusting the reaction process conditions, the overflow slurry can meet the requirements, at which time the feeding and discharging of the reaction kettle are carried out at the same time, and no concentration is carried out in the process. The Prussian blue material produced by using the continuous process is characterized by bimodal or multimodal distribution of laser particle size, and the size of the particles is large, and the compaction density is high.

[0053] (4) Using the controlled crystallization precipitation method, the material can be more conveniently coated with a concentration gradient. By adjusting the concentration and proportion of the raw materials in real time during the process, the proportion of each element in the material from the core to the surface can be changed during the precipitation process, thereby constructing a gradient core-shell structure with a high capacity and high voltage in the core, high stability in the outer core, and a uniform proportion from the core to the outer core.

[0054] (5) Using the controlled crystallization precipitation method, the particle size distribution, tap density, and morphology of the polycrystalline particles during the precipitation process can be monitored in real time. When the indicators meet the required specifications, the feeding is stopped, improving the stability between different batches, increasing the product pass rate, and avoiding fluctuations in product indicators caused by short cycles.

[0055] (6) By extending the reaction period, the operation rate of the reaction kettle is improved, the production efficiency and single-kettle output are increased, and the frequent reaction kettle discharge, cleaning of the reaction kettle, addition of water, and heating to continue feeding are avoided, thereby maximizing the production capacity of the reaction kettle.

[0056] (7) Using the controlled crystallization precipitation method, small-sized (e.g., not less than 0.5 pm) primary particles can be prepared as seeds in advance, and the precipitation period, particle growth rate, and morphology can be further improved by adding an appropriate amount of seeds in batches to start the precipitation, thereby ensuring the consistency of each batch of slurry and improving the product pass rate. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 It is a process flow diagram for Example 1.

[0058] Figure 2 It is a schematic diagram of the change in particles during the controlled crystallization intermittent precipitation process.

[0059] Figure 3 It is an SEM image of the finished product of Example 1.

[0060] Figure 4 It is a laser particle size distribution of the finished product of Example 1.

[0061] Figure 5 It is a 1C cycle performance diagram of a sodium ion half-cell assembled by the Prussian blue positive electrode material of Example 1.

[0062] Figure 6 It is an SEM image of the finished product of Example 2.

[0063] Figure 7 It is a laser particle size distribution of the finished product of Example 2.

[0064] Figure 8Rate performance and charge-discharge curve of the sodium-ion half battery assembled by the prussian blue cathode material of Example 2.

[0065] Figure 9 SEM image of the product of Example 3.

[0066] Figure 10 Laser particle size distribution of the product of Example 3.

[0067] Figure 11 Volume comparison chart of the slurries prepared by the controlled precipitation crystallization method and the common coprecipitation method of the application (same mass).

[0068] Figure 12 Tap density and loose bulk density of the prussian blue materials prepared by different precipitation methods.

[0069] Figure 13 2C cycle performance and charge-discharge curve of the zinc-ion half battery assembled by the prussian blue cathode material of Example 3.

[0070] Figure 14 1C cycle performance chart of the sodium-ion half battery assembled by the prussian blue cathode material of Comparative Example 1. DETAILED DESCRIPTION

[0071] [Prussian blue material]

[0072] The application provides a preparation method of a prussian blue material, which synthesizes the prussian blue material by a controlled crystallization precipitation method, and comprises the following steps: adding a first raw material and a second raw material into a base solution, optionally adding a complexing agent, forming a slurry containing primary particles, adding part of the slurry containing primary particles into the slurry containing primary particles after optional concentration or without concentration, and forming polycrystalline particles after precipitation to obtain the prussian blue material.

[0073] In the application, as the polycrystalline particles grow, the polycrystalline particles continuously collide, rub and adhere to each other, the solid content of the slurry increases, and the solid content of the slurry preferably increases as the precipitation time prolongs.

[0074] According to an embodiment of the application, the primary particles have a single crystal structure, preferably a cubic single crystal structure.

[0075] According to an embodiment of the application, the particle size of the primary particles is not less than 0.5 μm.

[0076] According to an embodiment of the application, the polycrystalline particles are formed after the agglomeration of the primary particles.

[0077] According to an embodiment of the application, the first raw material is selected from sodium ferricyanide and / or potassium ferricyanide.

[0078] According to embodiments of the present application, the first raw material is provided in a solution having a concentration of 0.1-1 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L.

[0079] According to embodiments of the present application, the second raw material is selected from at least one of a salt of a transition metal, such as at least one of a sulfate, a nitrate, an oxalate, an acetate, a chloride salt of a transition metal, and the like.

[0080] Preferably, the transition metal is selected from, but not limited to, iron, cobalt, nickel, manganese, copper, zinc salts, and the like.

[0081] Exemplarily, the second raw material is selected from at least one of an iron salt, such as at least one of ferrous sulfate, ferric nitrate, ferrous oxalate, ferrous acetate, ferrous chloride.

[0082] Exemplarily, the second raw material is selected from at least one of a manganese salt, such as at least one of manganese sulfate, manganese nitrate, manganese oxalate, manganese acetate, manganese chloride.

[0083] Exemplarily, the second raw material is selected from at least one of a salt, such as at least one of cobalt sulfate, cobalt nitrate, cobalt oxalate, cobalt chloride.

[0084] Exemplarily, the second raw material is selected from at least one of a nickel salt, such as at least one of nickel sulfate, nickel nitrate, nickel oxalate, nickel acetate, nickel chloride, and the like.

[0085] According to embodiments of the present application, the second raw material is provided in a solution having a concentration of 0.1-3 mol / L, such as 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L.

[0086] According to embodiments of the present application, the solution comprising the first raw material, the solution comprising the second raw material further comprise a solvent, which can be selected from any solvent known in the art, such as water.

[0087] According to embodiments of the present application, the base solution comprises an alkali metal salt and a solvent. Preferably, in the base solution, the alkali metal salt is at a saturated or near saturated concentration, to provide an alkali metal rich environment required for the precipitation.

[0088] Preferably, the solvent can be selected from any solvent known in the art, such as water.

[0089] Preferably, the alkali metal salt is selected from at least one of sodium salt, potassium salt, zinc salt. Further, the sodium salt is, for example, at least one of sodium chloride, sodium sulfate, sodium oxalate, sodium acetate, sodium nitrate. Further, the potassium salt is, for example, at least one of potassium chloride, potassium sulfate, potassium oxalate, potassium acetate, potassium nitrate. Further, the zinc salt is, for example, at least one of zinc chloride, zinc sulfate, zinc nitrate, zinc acetate, etc.

[0090] According to an embodiment of the present application, the complexing agent is selected from at least one of trisodium citrate, sodium oxalate, sodium pyrophosphate, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, triethanol ethylenediamine, urea, sodium succinate, sodium tartrate, polyvinylpyrrolidone, polyacrylamide, etc.

[0091] According to an embodiment of the present application, the molar ratio of the first raw material and the second raw material is 0.6-1.4, for example, 1:1.

[0092] According to an embodiment of the present application, the molar ratio of the first raw material and the complexing agent is (5-50):1, for example, 10:1, 6:1, 40:1.

[0093] According to an embodiment of the present application, the first raw material and the second raw material are added in a manner of quantitative dropping. The quantitative dropping in the present application can be performed by using a quantitative dropping device, for example, a peristaltic pump, a metering pump, a screw pump, or by a high tank gravity flow form, optionally, it is further provided with a flow control device, for example, an electromagnetic flowmeter, a rotor flowmeter, a valve, etc.

[0094] Preferably, the quantitative dropping specifically refers to the volume ratio of the feed amount of the solution containing the first raw material or the solution containing the second raw material to the volume of the bottom liquid per hour is 1:(5-20), for example, 1:(6-12).

[0095] According to an embodiment of the present application, the control crystallization precipitation method is selected from a batch precipitation method and / or a continuous precipitation method.

[0096] According to an embodiment of the present application, the concentration can be performed by using a concentration device, for example, at least one of a negative pressure microporous filter, a positive pressure microporous filter, a belt filter, a plate and frame filter press, a thickener, a centrifuge, etc.

[0097] According to an embodiment of the present application, when the batch precipitation method is used, the slurry containing the primary particles is further concentrated.

[0098] According to an embodiment of the present application, when the continuous precipitation method is used, the slurry containing the primary particles can be optionally concentrated or not concentrated, for example, the slurry containing the primary particles is intermittently concentrated.

[0099] According to the embodiment of the present application, when the slurry containing primary particles is added after concentration, the variation of the solid content of the slurry containing primary particles is not more than 20wt% / h, for example, not more than 15wt% / h, and further for example, not more than 10wt% / h.

[0100] According to the embodiment of the present application, in the preparation method, the solid content of the slurry containing primary particles is controlled to be 1wt% to 60wt%, preferably 10wt% to 30wt%.

[0101] According to the embodiment of the present application, the precipitation period of the precipitation is 1 to 720h, preferably 4 to 96h.

[0102] According to the embodiment of the present application, after concentration, a mother liquor containing alkali metal salt is produced, which can be recycled as the bottom liquor or directly discharged. The direct discharge in the present application refers to the discharge of the mother liquor after treatment by the methods known in the art, for example, the residual transition metal ions, complexing agents, alkali metal salts and the like in the mother liquor are subjected to precipitation filtration or evaporation crystallization, so that the impurity content reaches the national discharge standard and is discharged.

[0103] According to the embodiment of the present application, the preparation method is carried out under stirring; preferably, the stirring speed is 10rpm to 600rpm.

[0104] According to the embodiment of the present application, the preparation method further comprises: before or after the precipitation, the primary particles and / or the polycrystalline particles can be further classified to improve the uniformity of the particle size distribution.

[0105] Preferably, the classification comprises screening small particles in the slurry, for example, screening small particles in the slurry containing primary particles and / or the slurry of polycrystalline particles, and optionally recycling the small particles to the bottom liquor. The classification in the present application can be carried out by using classification equipment, for example, at least one of hydrocyclone classifier, thickener, ceramic filter or microporous filter.

[0106] Preferably, the particle size of the small particles is less than 2μm. In the present application, the particle size of the small particles corresponds to the particle size range corresponding to the first small peak (if the peak is more than two) in the laser particle size distribution graph.

[0107] According to the embodiment of the present application, the preparation method further comprises real-time and precise monitoring of the pH value of the slurry containing primary particles. Preferably, the pH value is 2 to 7, preferably 5 to 7.

[0108] According to the embodiment of the present application, the preparation method is carried out under the protection of inert atmosphere and / or reducing atmosphere to prevent the oxidation of transition metal ions.

[0109] Preferably, the inert atmosphere is selected from at least one of nitrogen, helium, neon, argon.

[0110] Preferably, the reducing atmosphere is selected from at least one of hydrogen, carbon monoxide.

[0111] According to an embodiment of the present application, the preparation method further comprises monitoring the oxygen content of the slurry containing primary particles in real time, preferably, the oxygen content of the slurry containing primary particles is 0-40wt%, for example, 0.1wt%, 0.5wt%, 0.8wt%, 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, 30wt%, 40wt%. In the present application, the oxygen content of the slurry containing primary particles can be monitored by using an oxygen content monitoring device, for example, an online dissolved oxygen meter.

[0112] According to an embodiment of the present application, the feeding is stopped when the index of the polycrystalline particles meets the requirements, and the precipitation is completed.

[0113] Preferably, when using intermittent precipitation, the index of the polycrystalline particles comprises: the particle size distribution presents a normal distribution in the form of unimodal or bimodal distribution, and the particles are uniform.

[0114] Further preferably, the particle size distribution D50 of the polycrystalline particles is 4-40μm, and the laser particle size distribution consistency is not more than 0.4. In the present application, the particle size distribution consistency represents the degree of deviation of the particle size distribution from the middle, and the lower the particle size distribution consistency, the lower the degree of deviation, and the better the consistency of the particle size.

[0115] Preferably, when using continuous precipitation, the preparation of the polycrystalline particles comprises: the particle size distribution at least presents a bimodal distribution.

[0116] Further preferably, the particle size distribution D50 of the polycrystalline particles is 4-40μm, and the laser particle size distribution consistency is not less than 0.4.

[0117] According to an embodiment of the present application, the preparation method further comprises: after the precipitation is completed, a ripening treatment is further required.

[0118] Preferably, the ripening temperature is 10-150℃, preferably 50-150℃.

[0119] Preferably, the ripening time is 1-72h, preferably 12-72h.

[0120] According to the embodiments of the present application, after the aging treatment, washing and / or drying can be further performed. The washing and drying in the present application can be performed by using washing equipment and drying equipment, for example, the washing equipment can be plate and frame filter press, centrifuge, etc.; and the drying equipment can be air drying oven, hot air circulation oven, rotary drying kiln, disc drying, spray drying, flash drying, vibration drying, etc.

[0121] Preferably, in the present application, the qualified judging standard of washing can be at least one of the judging standards known in the art, for example, washing time, washing times, mother liquor conductivity (≤10 μS / cm), slurry color, moisture content (≤20 wt%), impurity content (for example, Na, S content lower than 100 ppm), etc.

[0122] Further preferably, the washing medium is at least one of ultrapure water, dilute acid, dilute alkali. Further, the concentration of the dilute acid or dilute alkali is not more than 10 wt%.

[0123] Further preferably, the washing temperature is 10-90℃.

[0124] Preferably, in the present application, the qualified judging standard of drying is moisture content not more than 2%, slurry color, slurry caking state, etc.

[0125] Further preferably, the drying temperature is 50-200℃, preferably 50-120℃.

[0126] Further preferably, the drying atmosphere is at least one of air, nitrogen or vacuum.

[0127] According to the embodiments of the present application, the preparation method further comprises: after washing and / or drying, further performing crushing, which comprises crushing and / or sieving, crushing the caked large particles to qualified particle size.

[0128] Preferably, in the present application, the crushing can be performed by using crushing equipment, for example, at least one of ultrasonic vibrating screen, mechanical crusher, air flow crusher, disintegrator, etc.

[0129] Preferably, during sieving, the mesh number of the screen is 50-500 mesh, preferably 100-400 mesh.

[0130] According to an exemplary scheme of the present application, the preparation method employs a batch precipitation method to synthesize the Prussian blue material, comprising: adding a first raw material, a second raw material and a complexing agent into a base solution to form a slurry containing primary particles, returning part of the slurry containing primary particles after concentration into the slurry containing primary particles, and forming polycrystalline particles after precipitation, and obtaining the Prussian blue material after aging treatment, washing and drying; preferably, when the slurry containing primary particles after concentration is added, the change in solid content of the slurry containing primary particles is not more than 15wt% / h, for example, 10wt% / h; preferably, the solid content of the slurry containing primary particles is controlled to be 10wt% to 30wt%, for example, 10wt% / h, 20wt% / h.

[0131] According to an exemplary scheme of the present application, the preparation method employs a continuous precipitation method to synthesize the Prussian blue material, comprising: adding a first raw material, a second raw material and a complexing agent into a base solution to form a slurry containing primary particles, adding part of the slurry containing primary particles without concentration into the slurry containing primary particles, and forming polycrystalline particles after precipitation, and obtaining the Prussian blue material; preferably, the solid content of the slurry containing primary particles is less than 5wt%.

[0132] In the crystallization and precipitation method of the Prussian blue material, the supersaturation of the slurry is in the metastable state region between the supersaturation concentration C0 and the critical nucleation concentration C k At this time, basically no new nucleus is generated, and mainly the process of crystal growth and crystal type improvement. In addition, the inventors found that the commonly used complexing agents such as alkaline ammonia or ammonium bicarbonate are not suitable for the precipitation system of the Prussian blue material, because under alkaline conditions, the metal ions such as Fe 2+ , Mn 2+ in the Prussian blue raw material will form precipitates such as Fe(OH)2 and Mn(OH)2, so for the precipitation system of the Prussian blue material, a suitable neutral or weakly acidic complexing agent needs to be selected. In addition, in the crystallization and precipitation process, the particle size and tap density of the particles in the slurry mainly depend on the control of the precipitation period. The crystallization and precipitation can include continuous precipitation and batch precipitation, wherein the continuous precipitation is characterized by simultaneous feeding and discharging, and the solid content of the slurry is low, and if the particle size and other indicators of the particles at the discharging time are qualified, the precipitation period can be infinitely extended. The batch precipitation can increase the solid content of the slurry through concentration, so that the precipitation period can be controlled to be 3 to 10 days. Therefore, by adjusting the crystallization and precipitation method, for example, by adjusting, matching, combining and modifying the batch and continuous precipitation methods, Prussian blue materials with different particle sizes, different components and proportions, different surface and internal morphologies, and different tap densities can be produced to meet the needs of different batteries.

[0133] The application also provides a Prussian blue material prepared by the above preparation method.

[0134] [Positive electrode material]

[0135] The application also provides a positive electrode material comprising a Prussian blue material; the Prussian blue material has a chemical formula of (M 1 ) x (M 2 ) y (M 3 (CN)6) z ·mH2O.

[0136] According to an embodiment of the application, the Prussian blue material is prepared by the above preparation method.

[0137] According to an embodiment of the application, in the chemical formula, M 1 may be at least one of Li, Na, K, Cs, Zn, etc.

[0138] According to an embodiment of the application, in the chemical formula, M 2 may be at least one of Fe, Mn, Ni, Co, V, Cu, Zn, etc., preferably two kinds.

[0139] According to an embodiment of the application, in the chemical formula, M 3 may be at least one of Fe and Mn.

[0140] According to an embodiment of the application, in the chemical formula, 0≤x≤2, 0≤y≤1, 0≤z≤1.

[0141] According to an embodiment of the application, in the chemical formula, m is an integer greater than or equal to 0, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

[0142] Exemplarily, the Prussian blue material can be Na2Mn 1-x Fe x (Fe(CN)6)·mH2O.

[0143] According to an embodiment of the application, the particle size D50 of the positive electrode material is 10-30 μm, for example, 10-20 μm.

[0144] According to an embodiment of the application, the tap density of the positive electrode material is not less than 0.5 g / cm 3 , for example, 0.6-1 g / cm 3 , such as 0.6 g / cm 3 , 0.7 g / cm 3 , 0.8 g / cm3 0.9 g / cm3 3 .

[0145] According to an embodiment of the present application, the bulk density of the positive electrode material is not less than 0.5 g / cm3 3 , for example, 0.6-1 g / cm3 3 , such as 0.6 g / cm3 3 , 0.7 g / cm3 3 , 0.8 g / cm3 3 , 0.9 g / cm3 3 .

[0146] According to an embodiment of the present application, the positive electrode material has a spherical or quasi-spherical particle structure, such as having a particle structure substantially as shown in Figure 3 , Figure 6 or Figure 9 .

[0147] According to an exemplary embodiment of the present application, the positive electrode material is Na2Fe((Fe(CN)6)·H2O, having a particle size D50 of 15±1 μm, and a tap density of not less than 0.8 g / cm3 3 .

[0148] According to an exemplary embodiment of the present application, the positive electrode material is Na2Mn 0.5 Fe 0.5 ((Fe(CN)6)·2H2O, having a particle size D50 of 20±1 μm, and a tap density of not less than 0.72 g / cm3 3 .

[0149] According to an exemplary embodiment of the present application, the positive electrode material is K2Mn(Fe(CN)6)·4H2O, having a particle size D50 of 14±2 μm, and a tap density of not less than 0.6 g / cm3 3 .

[0150] [Application]

[0151] The present application also provides the use of the above-mentioned positive electrode material, preferably in a sodium-ion battery.

[0152] The present application also provides a positive electrode sheet, comprising at least the above-mentioned positive electrode material, and optionally a positive electrode current collector.

[0153] According to an embodiment of the present application, the positive electrode current collector can be selected from the positive electrode current collectors known in the art, for example, selected from a pure metal foil or a metal foil made of an alloy material, such as a carbon-coated aluminum foil, a titanium foil, a stainless steel foil. Preferably, the positive electrode current collector is selected from a pure metal foil, for example, an aluminum foil.

[0154] According to an embodiment of the present application, the battery cathode sheet further comprises a conductive agent and a binder.

[0155] According to an embodiment of the present application, the conductive agent is at least one of conductive carbon black, acetylene black, carbon black (Super-P), Ketjen black (KT-Black), conductive carbon sphere, conductive graphite, carbon nanotube, conductive carbon fiber, graphene.

[0156] According to an embodiment of the present application, the binder is at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), sodium alginate, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, carboxymethyl cellulose sodium, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate and polyhexafluoropropylene.

[0157] According to an embodiment of the present application, the mixing mass ratio of the active material, the conductive agent and the binder of the sheet-shaped battery cathode sheet is (6-9.8):(0.1-3):(0.1-2); preferably (8-9):(0.5-1):(0.5-1); exemplarily 9:0.5:0.5, 9.5:0.3:0.2.

[0158] The present application further provides a preparation method of the above-mentioned cathode sheet, comprising the following steps:

[0159] After mixing the active material of the battery cathode sheet, optionally with the conductive agent and / or the binder, adding a solvent to disperse to obtain a cathode slurry, coating the cathode slurry on a cathode current collector, drying, rolling, die cutting to obtain the battery cathode sheet.

[0160] According to an embodiment of the present application, the cathode current collector has the meaning as described above.

[0161] According to an embodiment of the present application, in the preparation method, the drying is preferably vacuum drying. Preferably, the drying temperature is 60-200℃, preferably 100-200℃, for example 100℃, 110℃, 140℃. Further, the drying time is 0.5-20h, preferably 12-20h, for example 12h, 14h, 20h.

[0162] The present application further provides an ionic battery, comprising at least the above-mentioned cathode sheet.

[0163] According to an embodiment of the present application, the ionic battery further comprises an electrolyte and a separator.

[0164] According to an embodiment of the present application, the electrolyte of the electrolyte is at least one of lithium salt, sodium salt, potassium salt, zinc salt.

[0165] Preferably, the lithium salt is selected from at least one of LiPF6, LiClO4, LiBOB, LiTSFI, LiFSI, preferably LiPF6.

[0166] Preferably, the sodium salt is selected from at least one of NaClO4, NaPF6, Na2SO4, NaNO3, NaTFSI and NaFSI, preferably NaClO4.

[0167] Preferably, the potassium salt is selected from at least one of KBF4, KClO4, KPF6, KFSI, KTFSI, K2SO4, KNO3, preferably KClO4.

[0168] Preferably, the zinc salt is selected from at least one of ZnSO4, ZnCl2, Zn(CF3SO3)2, ZnTFSI, ZnNO3, preferably Zn(CF3SO3)2.

[0169] Preferably, the concentration of the electrolyte is 0.3-30 mol / L, which is adjusted according to the solubility of different solutes in the solvent.

[0170] According to the embodiments of the present application, the solvent of the electrolyte can be an organic solvent and / or water.

[0171] Preferably, the organic solvent is selected from at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DEC), diethyl carbonate (DMC), ethyl methyl carbonate (EMC), etc., preferably two or three. Further, when the organic solvent is selected from two or three of the above-mentioned organic solvents, the volume ratio can be 1:1 or 1:1:1.

[0172] Preferably, the water is selected from ultrapure water, the ionic conductivity of which is less than 10 μS / cm. The ultrapure water in the present application can be prepared by methods known in the art, for example, by reverse osmosis.

[0173] According to the embodiments of the present application, the electrolyte further comprises an additive.

[0174] Preferably, the additive is selected from at least one of VC (vinylene carbonate), FEC (fluoroethylene carbonate), PS (propylene sulfite). Preferably, the additive is added in an amount of 0.2%-5% of the total volume of the solvent.

[0175] According to the exemplary embodiments of the present application, when the ion battery is a sodium ion battery, the electrolyte comprises: an electrolyte of 1 mol / L NaClO4, and a solvent of EC / PC+1% FEC in a volume ratio of 1:1.

[0176] According to the exemplary scheme of the present application, when the ion battery is a zinc ion battery, the electrolyte comprises: 3 mol / L of Zn(CF3SO3)2 as the electrolyte, and the above-mentioned ultrapure water as the solvent.

[0177] According to the embodiments of the present application, the ion battery is prepared by a method known in the art, for example, in a glove box or a dry room, and the atmosphere of the glove box or the dry room is inert gas (such as nitrogen or argon) or dry air. Exemplarily, the ion battery is prepared in a glove box under the protection of argon atmosphere.

[0178] According to the embodiments of the present application, the separator can be selected from the separators known in the art, and preferably is a glass fiber separator, for example, a GF / D type glass fiber separator.

[0179] The technical scheme of the present application will be further described in detail below with reference to specific examples. It should be understood that the following examples are only illustrative and explanatory of the present application, and should not be interpreted as limiting the scope of protection of the present application. Any technology achieved based on the above description of the present application is covered within the scope of protection intended by the present application.

[0180] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0181] Example 1

[0182] (1) Prussian blue material was prepared by a batch precipitation method: 1M (M refers to mol / L) aqueous solution of sodium ferricyanide (Na4Fe(CN)6) was prepared and 0.1M sodium citrate complexing agent was added as raw material 1, and 1M aqueous solution of FeSO4 was prepared as raw material 2. The raw materials were fed into a 10mL reaction kettle at a temperature of 80℃, and the pH value of the slurry in the reaction kettle was controlled between 6 and 7. The reaction kettle was equipped with an overflow port, and when the liquid level was full, the reaction kettle continued to overflow, and the overflow was pumped into a positive pressure micro-porous filter through a diaphragm pump to obtain primary particles with a particle size of D50≥0.5μm. The pressure during the concentration process was 1MPa, and the mother liquor containing alkali metal salt generated after concentration was collected in a mother liquor tank and recycled as the bottom liquid after filtration. The concentrated slurry flowed back into the reaction kettle by gravity. 3 The reaction kettle (double-layer stirring, upper layer propeller type, lower layer disc turbine type, with flow guide cylinder and 6 baffles) was pre-added with saturated Na2SO4 aqueous solution as the bottom liquid, and the volume of the bottom liquid was 40% of the full kettle volume. Water bath heating was used, and the precipitation temperature was 80℃. Nitrogen was pre-purified as a protective gas. When the oxygen content displayed by the dissolved oxygen meter was less than 1wt%, raw material 1 and raw material 2 were fed in, and the feeding speed of each was 1 / 30 of the volume of the reaction kettle per hour (i.e. the ratio of the hourly feeding amount to the volume of the bottom liquid was 1:12). The stirring speed was 30rpm, and the pH value of the slurry in the reaction kettle was controlled between 6 and 7. The reaction kettle was equipped with an overflow port, and when the liquid level was full, the reaction kettle continued to overflow, and the overflow was pumped into a positive pressure micro-porous filter through a diaphragm pump to obtain primary particles with a particle size of D50≥0.5μm. The pressure during the concentration process was 1MPa, and the mother liquor containing alkali metal salt generated after concentration was collected in a mother liquor tank and recycled as the bottom liquid after filtration. The concentrated slurry flowed back into the reaction kettle by gravity. Figure 1The slurry return velocity was adjusted by adjusting the concentration time and concentration pressure to ensure that the slurry return velocity was stable, and the solid content of the reactor fluctuated by less than 10 wt% per hour. After 72 hours of precipitation, the particle size D50 of the slurry was 15 ± 1 μm, and the tap density was greater than or equal to 0.8 g / cm 3 After the slurry in the reactor was concentrated to a solid content of greater than or equal to 20 wt%, the feed and concentration were stopped. The particle change process during the precipitation process is shown in FIG. 2. Figure 2 The slurry in the reactor was pumped into the aging tank for aging. The aging time was 12 hours, the nitrogen flow rate of the aging tank was 0.4 m 3 / h, and after aging, the slurry was washed by a centrifugal machine for 5 times. After washing, the slurry was dried in a hot air circulation drying box at 80°C for 24 hours. After the moisture content was less than or equal to 2 wt%, the slurry was sieved by an ultrasonic vibrating screen with a mesh size of 100 mesh. After sieving, the material was de-ironed by an electromagnetic de-ironing machine and was packaged by a double-cone mixer. Figure 3 The SEM and laser particle size distribution of the Prussian blue positive electrode material with the chemical formula Na2Fe((Fe(CN)6)·H2O prepared in this example are shown in FIGS. 3 and 4, respectively. Figure 4

[0183] (2) Preparation of an electrode sheet: the Prussian blue positive electrode material with the chemical formula Na2Fe((Fe(CN)6)·H2O prepared in step (1) was weighed according to a mass ratio of Prussian blue material: carbon black (Super-P): PVDF = 8: 1: 1, and NMP solvent was added to prepare a slurry with a solid content of 40 wt%. The slurry was uniformly coated on a carbon-coated aluminum foil according to a solid content of 2 mg / cm 2 , to form a positive electrode sheet with a coating thickness of 60 μm. After 20 MPa rolling and 140°C vacuum drying for 12 hours, the positive electrode sheet was cut into an electrode sheet with a diameter of 10 mm.

[0184] (3) Preparation of a half battery: the electrode sheet prepared in step (2) was assembled into a 2032 button-type half battery. The separator was GF / D (glass microfiber separator, purchased from Duoduo Reagent), the counter electrode was a sodium sheet (self-made), and the electrolyte was 1 M NaClO4, with a solvent of EC / DEC in a volume ratio of 1:1 + 1% FEC.

[0185] The half battery assembled in this example was charged and discharged at 1 C (i.e., 150 mA / g), and the cycle capacity was tested. The results are shown in FIG. 5. Figure 5 As can be seen from the figure, the charge and discharge range of the half battery assembled from the Prussian blue positive electrode material synthesized in this example was 2-4.2 V, the first cycle discharge capacity was 123.1 mAh / g, the first cycle charge and discharge efficiency was 95.9%, and the capacity after 280 cycles was 98.9 mAh / g, with a capacity retention rate of 80.3%. ​

[0186] Example 2

[0187] (1) Prussian blue cathode material was prepared by intermittent precipitation: a 0.6M sodium prussiatetraacetate (Na4Fe(CN)6) aqueous solution was prepared and a 0.1M EDTA complexing agent was added as raw material 1. A 0.3M MnSO4 + 0.3M FeSO4 aqueous solution was prepared as raw material 2. The mixture was then subjected to a 3m... 3 The reactor (double-layer stirred tank, upper layer paddle type, lower layer open turbine type, with guide tube and 3 baffles) is pre-filled with saturated NaCl aqueous solution as the bottom liquid, the volume of which is 30% of the full reactor volume. Oil bath heating is used, with a precipitation temperature of 60℃. Nitrogen gas is pre-purged as a protective gas. When the dissolved oxygen meter shows an oxygen content of less than 0.8wt%, raw material 1 and raw material 2 are fed separately, each at a rate of 1 / 20 of the reactor volume per hour (i.e., the ratio of hourly feed rate to bottom liquid volume is 1:6). The stirring speed is 50 rpm, and the pH value of the slurry in the reactor is controlled between 5 and 6. The reactor is equipped with an overflow port; when the liquid level is full, the overflow continues and is pumped through a diaphragm pump into a belt filter for concentration, obtaining primary particles with D50 ≥ 0.5μm. A belt filter is equipped with a water ring vacuum pump to provide vacuum suction. During the concentration process, the pressure of the water ring vacuum pump is <-0.06 MPa. The concentrated mother liquor is collected in a mother liquor tank. Metal ions in the mother liquor are precipitated and filtered before being directly discharged. The slurry, after concentration in the filter, forms a filter cake, which is scraped off by a scraper and falls into the reaction vessel by gravity. The return speed of the filter cake is adjusted by the feed, discharge, and filter cloth travel speeds of the filter to ensure a stable return speed. The hourly solid content fluctuation of the slurry in the reaction vessel is <15 wt%. After 100 hours of sedimentation, the particle size D50 of the slurry is tested to be 20 ± 1 μm, and the tap density is ≥0.72 g / cm³. 3 After passing the initial test, feeding and concentration were stopped. At this point, the solid content of the slurry in the reactor was ≥40wt%. All the slurry from the reactor and filter was pumped into an aging tank for aging for 16 hours at a stirring speed of 40 rpm and a nitrogen flow rate of 1 m³ / min. 3 After aging, the slurry is washed and dried using a plate and frame filter press, with each washing and air blowing occurring 6 times, alternating between the two processes. The washing water is ultrapure water, heated at 80℃ via a plate heat exchanger. After washing until the mother liquor conductivity is ≤20μS / cm, it is dried in a vacuum drying oven at 150℃ for 10 hours. When the moisture content is ≤1wt%, it is sieved using an ultrasonic vibrating screen with a mesh size of 400 mesh. After sieving, the material is batch-packaged using a permanent magnet iron separator and a double spiral mixer. This example yields a material with the chemical formula Na2Mn. 0.5 Fe 0.5 Prussian blue cathode material (Fe(CN)6).2H2O) has SEM and laser particle size distributions as shown in the figures.Figure 6 and Figure 7 as shown.

[0188] (2) Preparation of electrode sheet: the Prussian blue positive electrode material prepared in step (1) was mixed with PVDF and Ketjen black (KT-black) in a mass ratio of Prussian blue material: KT-black: PVDF = 7:2:1, and NMP solvent was added to prepare a slurry with a solid content of 30wt%, which was then uniformly coated on a conductive aluminum foil in an amount of 2mg / cm

[0189] Na2Mn 0.5 Fe 0.5 ((Fe(CN)6).2H2O) according to the mass ratio of Prussian blue material: KT-black: PVDF = 7:2:1, and NMP solvent was added to prepare a slurry with a solid content of 30wt%, which was then uniformly coated on a conductive aluminum foil in an amount of 2mg / cm 2 2 to form a positive electrode sheet with a coating thickness of 60μm, and then cut into an electrode sheet with a diameter of 12mm after 10MPa rolling and 110℃ vacuum drying for 14h;

[0190] (3) Preparation of half-cell: the electrode sheet prepared in step (2) was assembled into a 2016 button-type half-cell, the separator was Cellgard2400 (purchased from Duoduo Reagent), the counter electrode was a sodium sheet (self-made), and the electrolyte was: 1M NaPF6, the solvent was EC / DEC in a volume ratio of 1:1, and 2% VC was added as an additive.

[0191] The half-cell assembled in this example was charged and discharged at a current of 0.2C-10C (30-1500mA / g) to test the rate performance, and the results are shown in Figure 8 From Figure 8 it can be seen that the charge and discharge range of the half-cell assembled by the Prussian blue positive electrode material synthesized in this example is 2-4.2V, the first cycle discharge capacity at 0.2C is 140.5mAh / g, the first cycle discharge capacity at 10C is 111.4mAh / g, and the 10C capacity retention rate at 0.2C rate is 79.3%.

[0192] Example 3

[0193] (1) Preparation of Prussian blue positive electrode material by continuous precipitation method: a 0.4M potassium ferricyanide (K4Fe(CN)6) aqueous solution was prepared and 0.01M ethanedioic acid tetraacetate disodium complexing agent was added as raw material 1, and a 0.4M MnSO4 aqueous solution was prepared as raw material 2, and the two solutions were mixed at a flow rate of 1m 3A reactor (single-layer paddle stirring, without draft tube and 4 baffles) was pre-charged with saturated KNO3 aqueous solution as a bottom liquid, the volume of the bottom liquid was 20% of the full reactor volume, water bath heating was used, the precipitation temperature was 50°C, and nitrogen-hydrogen mixed gas (volume ratio of N2:H2=9:1) was pre-purged as a protective gas. When the oxygen content displayed by the dissolved oxygen meter was less than 0.5wt%, raw material 1 and raw material 2 were started to be fed, and the feeding amount per hour was 1 / 40 of the reactor volume (i.e. the volume ratio of the feeding amount per hour to the bottom liquid was 1:8). The stirring speed was 60 rpm, and the pH value of the slurry in the reactor was controlled between 5 and 7. The reactor was equipped with an overflow port, and when the liquid level was full, the reactor continued to overflow, and the overflow was qualified slurry, and the solid content of the slurry in the reactor was <5wt%. 3 The slurry was pumped into the aging tank for aging, saturated yellow blood potassium salt was added during the aging process for material defect repair, the aging time was 10h, the stirring speed was 40rpm, the nitrogen flow rate of the aging tank was 0.5m 3 / h, the slurry after aging was washed by a centrifugal machine, 1wt% dilute acid solution was used for washing, the washing times were 6 times, and after washing, disc drying equipment was used for drying, the drying temperature was 100°C, the drying time was 4h, and after drying, an ultrasonic vibrating screen was used for sieving, and the mesh size was 100 meshes. The prussian blue positive electrode material of the formula K2Mn(Fe(CN)6)·4H2O was prepared in this embodiment, and the SEM and laser particle size distribution diagram are shown in Figure 9 and Figure 10 .

[0194] (2) Preparation of the electrode sheet: the prussian blue positive electrode material K2Mn(Fe(CN)6)·4H2O prepared in step (1) was weighed according to the mass ratio of prussian blue material:KT-black:PTFE=6:2:2, NMP solvent was added to prepare a slurry with a solid content of 30wt%, and then the slurry was uniformly coated on a titanium foil according to the dosage of 1mg / cm 2 , so as to form a positive electrode sheet with a coating thickness of 40μm, and then the positive electrode sheet was cut into an electrode sheet with a diameter of 10mm after 8MPa rolling and 100°C vacuum drying for 20h.

[0195] (3) Preparation of the half battery: the electrode sheet prepared in step (2) was assembled into a 2032 button-type half battery, the separator was GF / A (purchased from Duoduo Reagent), the counter electrode was a zinc sheet, and the electrolyte was a 3M Zn(CF3SO3)2 aqueous solution.

[0196] The half battery assembled in this embodiment was subjected to charge and discharge at a current size of 2C (600mA / g), and the cycle performance was tested, and the results are shown in Figure 13As shown in the figure, the zinc-ion half-cell assembled from the Prussian blue cathode material synthesized in this embodiment has a charge / discharge range of 0.4–2.0 V, a first-cycle discharge capacity of 147.3 mAh / g at 2C, a discharge capacity of 112.8 mAh / g at the 200th cycle, and a cycle capacity retention rate of 76.6%.

[0197] Comparative Example 1

[0198] (1) In this comparative example, Prussian blue cathode material was prepared using a conventional coprecipitation method: a 1M (M refers to mol / L) aqueous solution of sodium prussiate (Na4Fe(CN)6) was prepared as raw material 1, and a 1M FeSO4 aqueous solution was prepared as raw material 2. The solution was prepared at 10m... 3 The reactor (double-layered stirring vessel, upper layer propeller type, lower layer disc turbine type, with guide tube and 6 baffles) is pre-filled with saturated Na2SO4 aqueous solution as the bottom liquid, the volume of which is 40% of the full reactor volume. Water bath heating is used, with a settling temperature of 80℃. Nitrogen gas is pre-purged as a protective gas. When the dissolved oxygen meter shows an oxygen content of less than 1wt%, raw material 1 and raw material 2 are fed separately, at a rate of 1 / 30 of the reactor volume per hour (i.e., the ratio of feed rate to bottom liquid volume is 1:12). The stirring speed is 30 rpm, and the pH value of the slurry in the reactor is controlled between 6 and 7. The reactor is equipped with an overflow port; the reaction is complete when the liquid level reaches the overflow port.

[0199] (2) Preparation of electrode: The electrode was prepared according to the method of Example 1, except that the Prussian blue cathode material was replaced with the Prussian blue cathode material prepared in step (1) of this comparative example.

[0200] (3) Preparation of half cell: Prepare half cell according to the method of Example 1, except that the electrode is replaced with the electrode prepared in step (2) of this comparative example.

[0201] The half-cell assembled in this comparative example was charged and discharged at 1C (i.e., 150mA / g) to test its cycle capacity. The results are as follows: Figure 14 As shown. From Figure 14 As can be seen from the results, the charge-discharge range of the half-cell assembled from the Prussian blue cathode material synthesized in this comparative example is 2 to 4.2V, the first-cycle discharge capacity is 135.0 mAh / g, the first-cycle charge-discharge efficiency is 91.8%, the capacity after 200 cycles is 95.6 mAh / g, and the capacity retention rate is 70.8%.

[0202] Test Example 1

[0203] Take 1.7g of each of the powders obtained after aging and drying the slurry from Examples 1, 3, and 1 (Comparative Example 1), and place them in a graduated cylinder, as follows: Figure 11As shown in the figure, from left to right, in order are the powder obtained after drying the slurry of Comparative Example 1, Example 3, and Example 1, and it can be seen from the figure that the powder obtained after drying the slurry prepared by the continuous precipitation method (i.e. Example 3) has the highest density, while the powder obtained after drying the slurry prepared by the common coprecipitation method (i.e. Comparative Example 1) has the lowest density.

[0204] Figure 12 The tap density and the loose bulk density of the Prussian blue materials prepared in Comparative Example 1, Example 1, and Example 3 are shown in the table below, wherein the tap density and the loose bulk density of Comparative Example 1 are 0.46 g / cm 3 , 0.47 g / cm 3 , respectively; the tap density and the loose bulk density of Example 1 are 0.62 g / g / cm 3 , 0.7 g / cm 3 , respectively; and the tap density and the loose bulk density of Example 3 are 0.7 g / cm 3 , 0.77 g / cm 3 , respectively. Figure 12 It can be seen that the Prussian blue positive electrode material prepared by the controlled crystallization precipitation method of the present application, especially by the continuous precipitation method, has higher tap density and loose bulk density. This is because the Prussian blue positive electrode material prepared by the continuous precipitation method includes particles of different particle sizes, such as large-particle-size particles and small-particle-size particles, and the small-particle-size particles help to fill the voids between the large-particle-size particles, thereby increasing the tap density of the material.

[0205] It can be seen from the half-cells of Comparative Example 1 and Example 1 that the first cycle discharge capacity of Comparative Example 1 is 135.0 mAh / g, which is higher than that of Example 1, but the first cycle charge-discharge efficiency, the capacity after 200 cycles, and the capacity retention rate of Example 1 are better. This is because the Prussian blue material of Comparative Example 1 has small particles and a large specific surface area, so its initial capacity is higher. However, the large specific surface area leads to an increase in side reactions on the electrode, thereby reducing its cycle performance. Moreover, the Prussian blue material of the present application is more conducive to improving the volumetric energy density of the battery.

[0206] The above describes exemplary embodiments of the present application. However, the scope of protection of the present application is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for preparing a Prussian blue material, characterized in that The preparation method adopts a controlled crystallization precipitation method to synthesize the Prussian blue material, including: adding a first raw material and a second raw material into a base solution, adding a complexing agent, forming a slurry containing primary particles, adding the slurry containing primary particles into a part of the slurry containing primary particles after optional concentration or without concentration, and forming polycrystalline particles after precipitation to obtain the Prussian blue material; the primary particles have a single crystal structure, and the particle size of the primary particles is not less than 0.5 μm; the polycrystalline particles are formed after agglomeration of the primary particles; the pH value of the slurry containing primary particles is 2-7; Before or after precipitation, the primary particles and / or the polycrystalline particles are also classified to improve the uniformity of the particle size distribution of the particles, and the feeding is stopped when the index of the polycrystalline particles meets the requirements, and the precipitation is ended; The molar ratio of the first raw material to the second raw material is 0.6-1.4, and the molar ratio of the first raw material to the complexing agent is 5-50:1; The solid content of the slurry containing primary particles is 1 wt%-60 wt%; when the slurry containing primary particles after concentration is added, the change value of the solid content of the slurry containing primary particles is not greater than 20 wt% / h; The first raw material is selected from sodium ferricyanide and / or potassium ferricyanide; the first raw material is provided by a solution containing the first raw material, and the concentration is 0.1-1 mol / L; the second raw material is selected from at least one of the salts of transition metals; the transition metal is selected from iron, cobalt, nickel, manganese, copper and zinc; the second raw material is provided by a solution containing the second raw material, and the concentration is 0.1-3 mol / L; the base solution includes an alkali metal salt and a solvent; in the base solution, the alkali metal salt is saturated or close to saturation concentration to provide an alkali-rich environment required for precipitation; The controlled crystallization precipitation method is selected from a batch precipitation method and / or a continuous precipitation method; When the batch precipitation method is used, the slurry containing primary particles is also concentrated; when the batch precipitation method is used, the index of the polycrystalline particles includes: the particle size distribution presents a normal distribution in a unimodal form or a bimodal distribution, and the particles are uniform; the particle size distribution D50 of the polycrystalline particles is 4-40 μm, and the laser particle size distribution consistency is not greater than 0.4; When the continuous precipitation method is used, the slurry containing primary particles is optionally concentrated or not concentrated; when the continuous precipitation method is used, the index of the polycrystalline particles includes: the particle size distribution at least presents a bimodal distribution; the particle size distribution D50 of the polycrystalline particles is 4-40 μm, and the laser particle size distribution consistency is not less than 0.

4.

2. The production method according to claim 1, characterized by, The solution containing the first raw material and the solution containing the second raw material also include a solvent.

3. The preparation method according to claim 1, characterized in that, The complexing agent is selected from at least one of trisodium citrate, sodium oxalate, sodium pyrophosphate, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, triethanol ethylenediamine, urea, sodium succinate, sodium tartrate, polyvinyl pyrrolidone and polyacrylamide.

4. The preparation method according to claim 1, characterized in that, The first raw material and the second raw material are added in a quantitative dropwise manner; specifically, the volume ratio of the feed amount of the solution containing the first raw material or the solution containing the second raw material to the volume of the bottom liquid is 1:5-20 per hour; The precipitation period of the precipitation is 1-720 hours.

5. The preparation method according to claim 1, characterized in that, The preparation method adopts a batch precipitation method to synthesize the Prussian blue material, and includes the following steps: adding a first raw material, a second raw material and a complexing agent into a bottom liquid to form slurry containing primary particles, returning part of the slurry containing primary particles to the slurry containing primary particles after concentration, forming polycrystalline particles after precipitation, and obtaining the Prussian blue material after aging treatment, washing, drying and the like. When the slurry containing primary particles after concentration is added, the change value of the solid content of the slurry containing primary particles is not greater than 15 wt% / h; and the solid content of the slurry containing primary particles is controlled to be 10 wt%-30 wt%.

6. The method of claim 1, wherein, The preparation method adopts a continuous precipitation method to synthesize the Prussian blue material, and includes the following steps: adding a first raw material, a second raw material and a complexing agent into a bottom liquid to form slurry containing primary particles, adding part of the slurry containing primary particles into the slurry containing primary particles without concentration, forming polycrystalline particles after precipitation, and obtaining the Prussian blue material; and the solid content of the slurry containing primary particles is less than 5 wt%.

7. A positive electrode material, characterized in that, The positive electrode material is a Prussian blue material, and the Prussian blue material is prepared by the preparation method according to any one of claims 1-6.

8. The positive electrode material according to claim 7, characterized in that, The chemical formula of the Prussian blue material is (M 1 ) x (M 2 ) y (M 3 (CN)6) z ·mH2O; In the formula, M 1 at least one selected from Li, Na, K, Cs, Zn; M 2 at least one selected from the group consisting of Fe, Mn, Ni, Co, V, Cu, Zn; M 3 at least one selected from the group consisting of Fe, Mn; 0≤x≤2, 0≤y≤1, 0≤z≤1; m is an integer greater than or equal to 0.

9. The cathode material of claim 8, wherein, The Prussian blue material is Na2Mn 1-x Fe x (Fe(CN)6) mH2O.

10. The positive electrode material of claim 8, wherein, The particle size D50 of the positive electrode material is 10-30 μm. The tap density of the positive electrode material is not less than 0.5 g / cm 3 ; The bulk density of the positive electrode material is not less than 0.5 g / cm 3 .

11. Use of the positive electrode material according to any one of claims 7-10 in the preparation of a positive electrode sheet or a sodium ion battery.

12. A positive electrode sheet characterized by comprising: The positive electrode sheet at least includes the positive electrode material according to any one of claims 7-10.

13. An ionic battery, characterized in that, The ion battery at least includes the positive electrode sheet according to claim 12.

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