A prussian blue-based positive electrode material, a preparation method, a positive electrode sheet, a secondary battery and an electric device

Abstract

The present application relates to a kind of prussian blue positive material, preparation method, positive pole piece, secondary battery and electric device, the prussian blue positive material includes primary particle, the primary particle is spherical particle, the sphericity of the spherical particle is 0.6-1, the average particle size D50 of the prussian blue positive material is 0.5 μm-20 μm;The prussian blue positive material described in the present application has spherical morphology, can improve the tap density of material, and then improve the compaction density of positive pole piece, improve the ion conductivity and electronic conductivity of pole piece, be favorable to the construction high energy density prussian blue battery;In addition, spheroidization particle can also improve particle flow and slurry processing performance, help to improve slurry dispersibility, particle is more difficult to gather and adhere between, flow well, easy to material delivery, batch mixing and battery processing.

Description

[0001] This application claims priority to prior application 2024118089600, filed on December 10, 2024, which was received by the China National Intellectual Property Administration and is entitled "A Prussian blue cathode material, preparation method, cathode sheet, secondary battery and power-consuming device". Technical Field

[0002] This invention relates to the field of electrode materials technology, and in particular to a Prussian blue-based cathode material, its preparation method, cathode sheet, secondary battery, and power-consuming device. Background Technology

[0003] Prussian blue is a cathode material with a three-dimensional open structure, possessing advantages such as large ion channels, high voltage plateau, low cost, and ease of preparation, making it a promising candidate for electrochemical energy storage. These materials have a face-centered cubic structure, with a three-dimensional framework composed of metal ions and ferricyanides, providing open ion channels that facilitate rapid ion transport. They exhibit high specific capacity and good cycle stability in sodium-ion batteries, making them ideal candidates to replace traditional lithium-ion batteries. With the growing global demand for sustainable energy storage systems, Prussian blue-based materials have attracted widespread attention due to their low cost, environmental friendliness, and high safety. Researchers are working to improve their electrochemical performance through structural optimization and synthesis methods to meet the increasing energy storage needs.

[0004] Prussian blue cathode materials are metal-organic framework materials with a special structure, whose chemical formula can be represented as A. x M1[M2(CN)6] y ·nH₂O (0≤x≤2, 0≤y<1). Where A represents an alkali metal ion, such as Na. + K + M1 and M2 are different coordinated transition metal ions, such as Mn, Fe, Co, Ni, Cu, Zn, Cr, etc. These materials typically have a face-centered cubic structure, where the metal M and ferricyanide ions are arranged in a Fe-C≡NM configuration to form a three-dimensional framework. Fe and M ions are arranged cubically at the vertices, C≡N ions are located on the edges of the cube, and embedded ions A... + The H₂O molecules are located within the cubic voids of the lattice. This structure endows Prussian blue-like materials with a unique electronic structure and high specific capacity, enabling them to exhibit excellent electrochemical performance in sodium-ion batteries.

[0005] Currently, most synthesized Prussian blue-based material particles are cubic in shape, resulting in low tap density, which is detrimental to the construction of high-energy-density battery cells. Researchers have attempted to improve the tap density of Prussian blue-based materials by embedding primary particles to form secondary spherical or near-spherical particles, or by combining particles of different sizes. However, these secondary particles formed by embedding primary single-crystal particles are prone to breakage during processing, affecting electrode compaction and making it difficult to achieve high-compaction characteristics. Furthermore, during cycling, the randomly oriented primary particles within the polycrystalline secondary particles cause grain boundary cracks due to anisotropic expansion / contraction, resulting in poor cycling stability.

[0006] Therefore, given the problem of low tap density in existing Prussian blue cathode materials, it is of great significance to provide a Prussian blue cathode material with primary spherical or near-spherical particles and its preparation method. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a Prussian blue cathode material, a preparation method, a cathode sheet, a secondary battery, and an electrical device. The Prussian blue cathode material of the present invention has a near-spherical morphology, which can increase the tap density of the material, thereby increasing the compaction density of the cathode sheet, improving the ionic and electronic conductivity of the sheet, and facilitating the construction of high-energy-density Prussian blue battery cells. In addition, spherical particles can also improve particle flowability and slurry processing performance, helping to improve slurry dispersibility, making it less prone to particle aggregation and adhesion, resulting in good flowability and facilitating material transport, batch mixing, and battery cell processing.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a Prussian blue-based cathode material, the Prussian blue-based cathode material comprising primary particles, the primary particles being spherical particles, the sphericity of the spherical particles being 0.6-1, for example, being 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99 or 1, but not limited to the listed values, other unlisted values ​​within the range are also applicable.

[0010] The average particle size D50 of the Prussian blue cathode material is 0.5μm-20μm, for example, it can be 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm or 20μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0011] The Prussian blue cathode material of this invention consists of primary spherical or near-spherical particles. Primary particles have higher mechanical strength than secondary particles, and spherical particles are easier to form a dense packing than square particles, exhibiting high tap density and good material flowability and dispersibility. When used in secondary batteries and electrical devices, the electrode sheet is less prone to breakage during processing, achieving high tap density and improving energy density. During cycling, the absence of intergranular interfaces within the primary particles makes them less prone to cracking during charge and discharge, resulting in good cycle stability.

[0012] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0013] Preferably, the molecular formula of the Prussian blue-type cathode material is A x M[M'(CN)6] y ·zH2O, wherein 0<x≤2, 0<y<1, 0<z≤3; A is an alkali metal, and M and M' are transition metals; A is selected from any one or at least two combinations of Na, K or Li, preferably Na; M and M' are each independently selected from any one or at least two combinations of Mn, Fe, Co, Ni, Cu or Zn, with M preferably Mn and / or Fe, and M' preferably Fe.

[0014] Preferably, the sphericity of the quasi-spherical particles is 0.8-1, for example, it can be 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99 or 1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, the average particle size D50 of the Prussian blue cathode material is 1μm-10μm, for example, it can be 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm or 10μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0016] In a second aspect, the present invention provides a preparation method for a Prussian blue-type cathode material as described in the first aspect, the preparation method comprising the following steps:

[0017] A first solution is obtained by mixing the cyanide alkali metal salt of transition metal M' with a first solvent; a second solution is obtained by mixing the transition metal M salt with a second solvent; the first solution, the second solution and the reaction substrate are mixed and reacted to generate a precipitate, which is then aged, washed and dried to obtain a Prussian blue cathode material.

[0018] The reaction substrate contains any one or a combination of at least two of the following: a complexing agent, a sodium supplement, a reducing agent, a pH adjuster, an alkali metal cyanide salt of transition metal M', and a salt of transition metal M.

[0019] This invention obtains spherical or near-spherical morphology of single particles by controlling the material configuration and material ratio to regulate the reaction micro-zone environment. Sphericalization has the characteristics of high tapping material, and the material has good dispersibility and flowability, making it easy to transport, batch mix and process for battery cells, and suitable for industrial mass production. The single particle material has good structural stability and good cycle performance.

[0020] Preferably, the complexing agent comprises any one or a combination of at least two of sodium hexametaphosphate, triethanolamine, sodium citrate, ascorbic acid, tartaric acid, glucose, or sodium ethylenediaminetetraacetate, wherein typical but non-limiting combinations include a combination of sodium hexametaphosphate and triethanolamine, a combination of sodium citrate and ascorbic acid, a combination of glucose and ethylenediaminetetraacetic acid, a combination of sodium hexametaphosphate, triethanolamine, and sodium citrate, and a combination of ascorbic acid, tartaric acid, and glucose.

[0021] Preferably, the sodium supplement comprises any one or a combination of at least two of sodium sulfate, sodium nitrate, sodium acetate, sodium chloride, or sodium carbonate, wherein typical but non-limiting combinations include a combination of sodium sulfate and sodium nitrate, a combination of sodium acetate and sodium chloride, a combination of sodium chloride and sodium carbonate, a combination of sodium sulfate, sodium nitrate, and sodium acetate, or a combination of sodium nitrate, sodium acetate, sodium chloride, and sodium carbonate.

[0022] Preferably, the reducing agent comprises any one or a combination of at least two of butylated hydroxyanisole, butylated hydroxytoluene, tert-butylhydroquinone, glucose, sodium sulfite, or ascorbic acid, wherein typical but non-limiting combinations include a combination of butylated hydroxyanisole and butylated hydroxytoluene, a combination of butylated hydroxytoluene and tert-butylhydroquinone, a combination of tert-butylhydroquinone and ascorbic acid, a combination of butylated hydroxyanisole, butylated hydroxytoluene, and tert-butylhydroquinone, and a combination of butylated hydroxytoluene, tert-butylhydroquinone, and ascorbic acid.

[0023] Preferably, the pH adjuster comprises any one or a combination of at least two of sulfuric acid, hydrochloric acid, sodium bicarbonate, disodium bicarbonate, sodium hydroxide, or ammonia.

[0024] Preferably, the first solvent comprises water and / or ethanol.

[0025] Preferably, the concentration of the alkali metal cyanide salt of the transition metal M' is 0.1 mol / L to 5 mol / L, for example, it can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the M salt comprises any one or a combination of at least two of sulfates, nitrates, acetates and chlorides, wherein typical but non-limiting combinations include combinations of sulfates and nitrates, combinations of nitrates and acetates, combinations of acetates and chlorides, combinations of sulfates, nitrates and acetates, and combinations of nitrates, acetates and chlorides.

[0027] Preferably, the second solvent comprises water and / or ethanol.

[0028] Preferably, the concentration of the transition metal M salt in the second solution is 0.1 mol / L to 10 mol / L, for example, it can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the reaction temperature is 10℃-100℃, for example, it can be 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0030] Preferably, the pH of the reaction is 5-9, for example, it can be 5, 6, 7, 8 or 9, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the reaction time is 1h-24h, for example, it can be 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the solution used for washing is water and / or ethanol.

[0033] Preferably, the drying temperature is 80℃-250℃, for example, it can be 80℃, 90℃, 100℃, 120℃, 140℃, 150℃, 160℃, 180℃, 200℃, 220℃, 240℃ or 250℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0034] Preferably, the drying time is 1h-72h, for example, it can be 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 25h, 30h, 35h, 40h, 45h, 50h, 55h, 60h, 65h, 70h or 72h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Thirdly, the present invention provides a positive electrode sheet comprising the Prussian blue cathode material described in the first aspect, or a Prussian blue cathode material prepared by the preparation method of the Prussian blue cathode material described in the second aspect.

[0036] The positive electrode sheet prepared using the Prussian blue-based positive electrode material of the present invention has high compaction density, higher mechanical strength, and higher stability. During processing, the electrode sheet is not easily broken, which can achieve high compaction density and improve energy density.

[0037] Fourthly, the present invention provides a secondary battery comprising the positive electrode sheet described in the third aspect.

[0038] The secondary battery assembled using the positive electrode sheet of the present invention has high energy density, good cycle performance, and long cycle life.

[0039] Fifthly, the present invention provides an electrical device comprising the secondary battery described in the fourth aspect.

[0040] Electrical devices assembled using the secondary batteries of this invention have high energy density and long service life, significantly reducing manufacturing costs.

[0041] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0042] Compared with the prior art, the present invention has at least the following beneficial effects:

[0043] (1) The Prussian blue cathode material provided by the present invention is a primary spherical or near-spherical particle. The primary particle has higher mechanical strength than the secondary particle, and the spherical particle is easier to form a dense filling than the square particle, and has the characteristics of high tap density.

[0044] (2) The Prussian blue cathode material provided by the present invention has good flowability and dispersibility, and is easy to transport, batch mix and cell process; the preparation method is simple and easy to industrialize and mass-produce.

[0045] (3) The positive electrode sheet prepared from the Prussian blue-based positive electrode material provided by this invention has high compaction density, higher mechanical strength, and higher stability. The secondary battery assembled from the positive electrode sheet provided by this invention has high energy density and good cycle stability. Attached Figure Description

[0046] Figure 1 This is a SEM image of the Prussian blue cathode material prepared in Example 1 of this invention. Detailed Implementation

[0047] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0048] In the following examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used are conventional methods and techniques in the art.

[0049] Example 1

[0050] This embodiment provides a Prussian blue-based cathode material, which comprises near-spherical primary particles with a sphericity of 0.85 and an average particle size D50 of 5.6 μm. The molecular formula of the Prussian blue-based cathode material is Na. 1.98 Mn 0.45 Fe 0.55 [Fe(CN)6] 0.98 ·1.5H2O;

[0051] The method for preparing Prussian blue-type cathode materials provided in this embodiment includes the following steps:

[0052] (1) Prepare the reaction solution: Dissolve 1 mol of sodium ferrocyanide in 0.5 L of water to obtain the first solution; dissolve 0.5 mol of manganese sulfate and 0.5 mol of ferrous sulfate in 1 L of water to obtain the second solution.

[0053] (2) Prepare the reaction base solution: Mix 1 mol of complexing agent sodium hexametaphosphate, 1 mol of sodium supplement agent sodium chloride, 0.1 mol of reducing agent butylated hydroxyanisole, and 0.1 mol of ferrous sulfate and dissolve them in water to obtain the reaction base solution.

[0054] (3) Reaction and post-processing: The reaction base liquid was added to the reaction vessel, and the first and second solutions were slowly added to the reaction vessel. The reaction temperature was controlled at 50°C and the reaction time was controlled at 12h. After the reaction was completed, the reaction slurry was separated and washed to obtain solid material. The solid material was vacuum dried at 160°C for 36h to obtain Prussian blue cathode material.

[0055] SEM images of the prepared Prussian blue-type cathode material are shown below. Figure 1 As shown in the figure, the primary particles of the Prussian blue cathode material are spherical.

[0056] Example 2

[0057] This embodiment provides a Prussian blue-based cathode material, which comprises near-spherical primary particles with a sphericity of 0.83 and an average particle size D50 of 8.2 μm. The molecular formula of the Prussian blue-based cathode material is Na. 1.96 Mn 0.5 Fe 0.5 [Fe(CN)6] 0.96 0.9H2O;

[0058] The method for preparing Prussian blue-type cathode materials provided in this embodiment includes the following steps:

[0059] (1) Prepare the reaction solution: Dissolve 1 mol of sodium ferrocyanide in 0.5 L of ethanol to obtain the first solution; dissolve 0.7 mol of manganese chloride and 0.7 mol of ferrous chloride in 1 L of ethanol to obtain the second solution.

[0060] (2) Prepare the reaction base solution: Mix 1 mol of complexing agent sodium citrate, 0.2 mol of sodium supplement agent sodium sulfate, 0.3 mol of reducing agent ascorbic acid, 0.1 mol of ferrous sulfate and 0.1 mol of manganese sulfate and dissolve them in ethanol to obtain the reaction base solution.

[0061] (3) Reaction and post-processing: The reaction base liquid was added to the reaction vessel, and the first and second solutions were slowly added to the reaction vessel. The reaction temperature was controlled at 30°C and the reaction time was controlled at 18h. After the reaction was completed, the reaction slurry was separated and washed to obtain solid material. The solid material was vacuum dried at 150°C for 24h to obtain Prussian blue cathode material.

[0062] Example 3

[0063] This embodiment provides a Prussian blue-based cathode material, which comprises near-spherical primary particles with a sphericity of 0.88 and an average particle size D50 of 2.7 μm. The molecular formula of the Prussian blue-based cathode material is Na.1.95 Mn 0.5 Fe 0.5 [Mn(CN)6] 0.97 0.6H2O;

[0064] The method for preparing Prussian blue-type cathode materials provided in this embodiment includes the following steps:

[0065] (1) Prepare the reaction solution: Dissolve 1 mol of sodium manganese cyanide in 0.5 L of water to obtain the first solution; dissolve 0.45 mol of manganese sulfate and 0.45 mol of ferrous sulfate in 1 L of water to obtain the second solution.

[0066] (2) Prepare the reaction base solution: Mix 1 mol of complexing agent ascorbic acid, 1 mol of sodium supplement sodium carbonate, 0.1 mol of reducing agent dibutylhydroxytoluene, and 0.3 mol of sodium manganese cyanide and dissolve them in water to obtain the reaction base solution.

[0067] (3) Reaction and post-processing: The reaction base liquid was added to the reaction vessel, and the first and second solutions were slowly added to the reaction vessel. The reaction temperature was controlled at 50°C and the reaction time was controlled at 12h. After the reaction was completed, the reaction slurry was separated and washed to obtain solid material. The solid material was vacuum dried at 180°C for 48h to obtain Prussian blue cathode material.

[0068] Example 4

[0069] This embodiment provides a Prussian blue cathode material. The only difference from Example 1 is that, when preparing this Prussian blue cathode material, the amount of manganese sulfate and ferrous sulfate added in the second solution in step (1) is 0.1 mol.

[0070] Example 5

[0071] This embodiment provides a Prussian blue-based cathode material. The only difference from Example 1 is that, when preparing this Prussian blue-based cathode material, the amount of sodium chloride added as a sodium supplement in the reaction substrate in step (2) is 0.005 mol.

[0072] Example 6

[0073] This embodiment provides a Prussian blue-based cathode material. The only difference from Example 1 is that, when preparing this Prussian blue-based cathode material, the amount of sodium hexametaphosphate, a complexing agent, added to the reaction substrate in step (2) is 12 mol.

[0074] Comparative Example 1

[0075] This comparative example provides a Prussian blue-based cathode material, which differs from Example 1 only in that sodium hexametaphosphate, a complexing agent, was not added to the reaction substrate in step (2) when preparing the Prussian blue-based cathode material.

[0076] Comparative Example 2

[0077] This comparative example provides a Prussian blue-based cathode material. The only difference from Example 1 is that sodium chloride, a sodium supplement, was not added to the reaction substrate in step (2) when preparing the Prussian blue-based cathode material.

[0078] Comparative Example 3

[0079] This comparative example provides a Prussian blue-based cathode material, which differs from Example 1 only in that the specific steps for preparing this Prussian blue-based cathode material are as follows:

[0080] (1) Mixing MnSO4 with water yields Mn 2+ The first solution has a concentration of 2 mol / L; the second solution is obtained by mixing Na4Fe(CN)6 with a concentration of 0.5 mol / L and Na2SO4 with a concentration of 0.1 mol / L.

[0081] (2) Place the second solution in the reactor and keep the temperature constant at 60°C. At the same time, control the stirring speed to 700 r / min. During this process, continuously introduce nitrogen into the reactor to make the oxygen content of the reaction atmosphere lower than 0.8% and create a non-oxidizing atmosphere. Then, introduce the first solution into the reactor at a flow rate of 0.225% / h of the available volume of the reactor to carry out the first reaction. When the seed crystal size reaches 2.5 μm, the first reaction stage ends.

[0082] After the first reaction stage is completed, the first solution and sodium citrate solution are simultaneously and slowly introduced into the reactor to carry out the second reaction. During this period, the total concentration of metal ions in the reactor is controlled to be 0.2 mol / L and the pH is 6-9 by adjusting the flow rate of sodium citrate solution. In the second reaction stage, the oxygen content of the reaction atmosphere is maintained below 0.8%, and the stirring speed is 600 r / min until the reaction product is obtained.

[0083] (3) The product from the crystallization process is vacuum dried at 100℃ for 24 hours. The dried powder is then ground in a mortar for 10 minutes and sieved to obtain the product with the molecular formula Na. 1.98 Mn 0.45 Fe 0.55 [Fe(CN)6] 0.97 ·1.5H₂O, D50 is 5.3μm, TD = 0.53g / cm 3 Prussian blue-based cathode materials.

[0084] Battery preparation and testing: The positive electrode material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were weighed and dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 and mixed thoroughly. Then, the slurry was coated onto aluminum foil using a coater and dried in a vacuum drying oven at 80°C for 8 hours. Finally, the aluminum foil was stamped into 1.13 cm thick sheets. 2 A circular positive electrode sheet was obtained. Using this electrode sheet as the positive electrode and a sodium metal sheet as the counter electrode, a porous polypropylene membrane (Celgard 2400, USA) was used as a separator to separate the positive and counter electrodes. The button cell was assembled in an argon-filled glove box. Cyclic performance tests were conducted using a battery testing system at 0.1C and 0.5C rates at 2-4V and 25℃. The test results are shown in Table 1.

[0085] Table 1

[0086]

[0087]

[0088] The test results show that:

[0089] (1) As can be seen from Examples 1-3, the Prussian blue cathode material of the present invention has a spherical morphology of primary particles. The particles are evenly distributed, and the spherical morphology helps to improve the tap density of the cathode material. The particles can be in close contact with each other, which reduces the barrier to ion / electron transport. The coin capacity is high, and the single particles are not easy to crack, resulting in good cycle performance.

[0090] (2) By comparing Example 1 with Examples 4-5, it can be seen that the present invention obtains a positive electrode material with stable crystal structure and quasi-spherical morphology of primary particles by further optimizing the mass ratio range of complexing agent, sodium supplement, reducing agent, pH adjuster, cyanide alkali metal salt of transition metal M' and transition metal M salt in the reaction base liquid. When the molar amount of transition metal M salt is too low, the sphericity is poor and the cycle performance is reduced; when the molar amount of sodium supplement is too low, it will be difficult to maintain sphericity and the specific capacity will be reduced.

[0091] (3) By comparing Example 1 and Example 6, it can be seen that the present invention can achieve better sphericity and excellent electrochemical performance by further optimizing the amount of complexing agent.

[0092] (4) As can be seen from Example 1 and Comparative Example 1, if no complexing agent is added, the present invention cannot achieve sphericity and the tap density decreases significantly.

[0093] (5) As can be seen from Example 1 and Comparative Example 2, if the sodium supplement is not added, the present invention cannot achieve sphericity and the tap density is significantly reduced.

[0094] (6) As can be seen from Example 1 and Comparative Example 3, the present invention can obtain high tap and excellent electrochemical performance by synthesizing single-particle spherical materials. However, the conventional method for preparing Prussian blue cathode materials cannot obtain cathode materials with spherical primary particles, and the tap density of the materials is significantly reduced.

[0095] In summary, the Prussian blue cathode material of this invention has a near-spherical morphology, which improves the tap density of the material and enhances the ionic and electronic conductivity of the electrode, thus facilitating the construction of high-energy-density Prussian blue battery cells. Furthermore, the spherical particles improve particle flowability and slurry processing performance, contributing to better slurry dispersibility, reducing particle aggregation and adhesion, and ensuring good flowability, making material transport, batch mixing, and battery cell processing easier. The Prussian blue cathode material of this invention has a spherical or near-spherical single-particle morphology. Sphericalization provides high tap density, and the material exhibits good dispersibility and flowability, facilitating material transport, batch mixing, and battery cell processing, making it suitable for industrial mass production. The single-particle material also demonstrates good structural stability and cycle performance.

[0096] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A Prussian blue-based cathode material, characterized in that, The Prussian blue cathode material comprises primary particles, which are spherical particles with a sphericity of 0.6-1 and an average particle size D50 of 0.5μm-20μm.

2. The Prussian blue-based cathode material according to claim 1, characterized in that, The molecular formula of the Prussian blue-based cathode material is A. x M[M'(CN)6] y ·zH₂O, where 0 < x ≤ 2, 0 < y < 1, 0 < z ≤ 3; A is an alkali metal, and M and M' are transition metals; A is selected from any one or at least two of Na, K or Li, preferably Na; M and M' are each independently selected from any one or at least two of Mn, Fe, Co, Ni, Cu or Zn, with M preferably Mn and / or Fe, and M' preferably Fe; Preferably, the sphericity of the quasi-spherical particles is 0.8-1; Preferably, the average particle size D50 of the Prussian blue cathode material is 1 μm-10 μm.

3. A method for preparing a Prussian blue-based cathode material as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: A first solution is obtained by mixing the alkali metal cyanide salt of transition metal M' with a first solvent; a second solution is obtained by mixing the transition metal M salt with a second solvent; the first solution, the second solution and the reaction substrate are mixed and reacted to generate a precipitate, which is then washed and dried to obtain a Prussian blue cathode material. The reaction substrate contains any one or a combination of at least two of the following: a complexing agent, a sodium supplement, a reducing agent, a pH adjuster, an alkali metal cyanide salt of transition metal M', and a salt of transition metal M.

4. The preparation method according to claim 3, characterized in that, The complexing agent comprises any one or a combination of at least two of the following: sodium hexametaphosphate, triethanolamine, sodium citrate, ascorbic acid, tartaric acid, glucose, or sodium ethylenediaminetetraacetate. Preferably, the sodium supplement comprises any one or a combination of at least two of sodium sulfate, sodium nitrate, sodium acetate, sodium chloride, or sodium carbonate; Preferably, the reducing agent comprises any one or a combination of at least two of butylated hydroxyanisole, butylated hydroxytoluene, tert-butylhydroquinone, glucose, sodium sulfite, or ascorbic acid; Preferably, the pH adjuster comprises any one or a combination of at least two of sulfuric acid, hydrochloric acid, sodium bicarbonate, disodium bicarbonate, sodium hydroxide, or ammonia.

5. The preparation method according to claim 3 or 4, characterized in that, The first solvent contains water and / or ethanol; Preferably, the concentration of the alkali metal cyanide salt of the transition metal M' is 0.1 mol / L to 5 mol / L.

6. The preparation method according to any one of claims 3-5, characterized in that, The transition metal M salt comprises any one or a combination of at least two of sulfate, nitrate, acetate and chloride salts; Preferably, the second solvent comprises water and / or ethanol; Preferably, the concentration of the transition metal M salt in the second solution is 0.1 mol / L to 10 mol / L.

7. The preparation method according to any one of claims 3-6, characterized in that, The reaction temperature is 10℃-100℃; Preferably, the pH of the reaction is 5-9; Preferably, the reaction time is 1 hour to 24 hours; Preferably, the solution used for washing is water and / or ethanol; Preferably, the drying temperature is 80℃-250℃; Preferably, the drying time is 1 hour to 72 hours.

8. A positive electrode sheet, characterized in that, The positive electrode sheet comprises the Prussian blue-based positive electrode material as described in claim 1 or 2, or the Prussian blue-based positive electrode material prepared by the method for preparing the Prussian blue-based positive electrode material as described in any one of claims 3-7.

9. A secondary battery, characterized in that, The secondary battery comprises the positive electrode sheet as described in claim 8.

10. An electrical appliance, characterized in that, The electrical device includes the secondary battery as described in claim 9.

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