A positive electrode material, a preparation method and application thereof

Abstract

This invention discloses a cathode material, its preparation method, and its application, belonging to the technical field of cathode materials for sodium-ion batteries. The cathode material has a core-shell structure, with a core of sodium manganese ferrocyanide and a shell of potassium manganese ferrocyanide; a manganese ferrocyanide intermediate layer is also present between the core and the shell. The intermediate layer contains Mn... 2+ The ionic radius is greater than that of the Na core. + Larger K atoms, with higher valence states, can reduce lattice spacing, thus supporting the structure and improving the material's cycling stability while inhibiting the absorption of water molecules; the K atoms in the outer shell... + Not only can it provide capacity, but also K + The ionic radius is also larger than that of Na. + Larger and wider ion transport channels result in a more stable structure, which also helps reduce the material's water absorption. The presence of the aforementioned intermediate layer and outer shell significantly improves the structural stability of the cathode material during charge and discharge, reduces side reactions between the cathode and electrolyte, and enhances interfacial stability, cycle performance, and rate performance.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery cathode materials technology, and more specifically, to a cathode material, its preparation method, and its application. Background Technology

[0002] As a major category of sodium-ion cathode materials, Prussian white is highly favored due to its simple processing and high capacity. However, in recent years, research on Prussian white sodium-ion cathode materials, especially in the direction of industrialization, has been significantly limited. The main reason is that Prussian white has strong water absorption and high difficulty in wastewater treatment, which seriously restricts its industrialization process. Currently, sodium-ion batteries prepared from Prussian white sodium-ion cathode materials have poor cycle performance and rate performance.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a cathode material, its preparation method, and its application, so as to solve or improve the above-mentioned technical problems.

[0005] This invention can be implemented as follows:

[0006] In a first aspect, the present invention provides a positive electrode material having a core-shell structure, wherein the core of the core-shell structure is sodium manganese ferrocyanide and the outer shell is potassium manganese ferrocyanide; and a manganese ferrocyanide intermediate layer is also provided between the core and the outer shell.

[0007] In an optional embodiment, the cathode material further has at least one of the following characteristics:

[0008] Feature 1: The molecular formula of the kernel is Na. x Mn[Fe(CN)6] y , of which 1 <x≤2,0.7≤y≤1;

[0009] Feature 2: D of the cathode material 50 Not less than 2.3 μm, preferably 2.3 μm to 3.0 μm;

[0010] Feature 3: The water content of the cathode material does not exceed 0.6 wt%.

[0011] Secondly, the present invention provides a method for preparing a positive electrode material as described in the foregoing embodiments, comprising the following steps: preparing a sodium manganese ferrocyanide core; forming a manganese ferrocyanide intermediate layer on the surface of the sodium manganese ferrocyanide core; and forming a potassium manganese ferrocyanide shell on the surface of the manganese ferrocyanide intermediate layer.

[0012] In an optional embodiment, the preparation of the sodium manganese ferrocyanide core includes reacting a sodium ferrocyanide solution, a first soluble manganese salt solution, and a complexing agent solution together.

[0013] In an optional embodiment, the preparation of the sodium manganese ferrocyanide core includes at least one of the following characteristics:

[0014] Feature 4: The reaction temperature is 30℃~90℃;

[0015] Feature 5: The reaction pH is 6–9;

[0016] Feature 6: Reaction time is 12h to 72h;

[0017] Feature 7: The concentration of the sodium ferrocyanide solution is 0.3 mol / L to 0.6 mol / L, and the concentration of the first soluble manganese salt solution is 0.5 mol / L to 2 mol / L; the molar ratio of sodium ferrocyanide in the sodium ferrocyanide solution to the first soluble manganese salt in the first soluble manganese salt solution is 0.97:1 to 1.03:1;

[0018] Feature 8: The concentration of the complexing agent solution is 0.002 mol / L to 14 mol / L; the molar ratio of the complexing agent in the complexing agent solution to the first soluble manganese salt in the first soluble manganese salt solution is 0.001:1 to 4:1;

[0019] Feature 9: The complexing agent includes at least one of citric acid, maleic acid, citric acid, ethylenediaminetetraacetic acid, sodium citrate, and ammonia water;

[0020] Feature 10: The reaction atmosphere is a protective atmosphere;

[0021] Feature 11: The reaction process is carried out under stirring conditions, preferably at a stirring speed of 200 rpm to 600 rpm.

[0022] In an optional embodiment, the preparation of the manganese ferrocyanide intermediate layer includes: adding a second soluble manganese salt solution to the material obtained from the preparation of the sodium manganese ferrocyanide core, mixing and reacting.

[0023] In an optional embodiment, the preparation of the manganese ferrocyanide interlayer includes at least one of the following characteristics:

[0024] Feature 12: The amount of the second soluble manganese salt in the second soluble manganese salt solution is 3% to 30% of the amount of the first soluble manganese salt in the first soluble manganese salt solution, and the concentration of the second soluble manganese salt solution is 0.5 mol / L to 2 mol / L;

[0025] Feature 13: The addition time of the second soluble manganese salt solution is 0.25h to 1h.

[0026] In an optional embodiment, the preparation of the potassium manganese ferrocyanide shell includes: performing solid-liquid separation and washing on the material obtained from the preparation of the manganese ferrocyanide intermediate layer; adding water to the washed solid to slurry to obtain Prussian white slurry; and mixing and reacting the Prussian white slurry with a potassium ferrocyanide solution.

[0027] In an optional embodiment, the preparation of the potassium manganese ferrocyanide shell includes at least one of the following features:

[0028] Feature 14: The concentration of the potassium ferrocyanide solution is 0.3 mol / L to 0.6 mol / L;

[0029] Feature 15: The amount of potassium ferrocyanide in the potassium ferrocyanide solution is 3% to 30% of the amount of ferrocyanide in the Prussian white slurry;

[0030] Feature 16: The average residence time of the potassium manganese ferrocyanide generated in the reaction in the aqueous solution does not exceed 15 min.

[0031] In an optional embodiment, the preparation of the potassium manganese ferrocyanide shell further includes: continuously discharging the mixed slurry generated by the reaction and spray drying it.

[0032] In an optional embodiment, the liquid feed rate for spray drying is 5L / h to 30L / h, and the temperature of the main tower for spray drying is 150℃ to 200℃.

[0033] In an optional embodiment, the volume of the container used for reacting Prussian white slurry with potassium ferrocyanide solution is 1 / 10 to 1 / 5 of the hourly feed volume of the spray dryer.

[0034] In an optional implementation, the container has a volume of 1L to 3L.

[0035] In an optional implementation, the container is a container with a stirring function.

[0036] In an optional embodiment, the Prussian white slurry and potassium ferrocyanide solution are mixed through a three-way pipe with a check valve and then fed into a spray dryer; preferably, the three-way pipe is ultrasonically dispersed.

[0037] Thirdly, the present invention provides a positive electrode sheet, wherein the active material in the positive electrode sheet includes the positive electrode material of the aforementioned embodiments.

[0038] Fourthly, the present invention provides a battery comprising the positive electrode sheet of the aforementioned embodiments.

[0039] The beneficial effects of this invention include:

[0040] In the cathode material provided by this invention, the manganese ferrocyanide intermediate layer can reduce the lattice spacing and play a supporting role in the structure, thereby improving the cycle stability of the material and inhibiting the absorption of water molecules; the potassium ferrocyanide outer shell contains K + Not only can it provide capacity, but also K + The ionic radius is also larger than that of Na. + The core has a large, wide ion transport channel and a more stable structure, which also helps reduce the material's water absorption. The presence of both an intermediate layer and a shell on the outside of the core significantly improves the structural stability of the cathode material during charging and discharging, reduces side reactions between the cathode and the electrolyte, and enhances interfacial stability, cycle performance, and rate performance. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 Here is a SEM image of the cathode material obtained in Example 1;

[0043] Figure 2 This is a TEM image of the cathode material obtained in Example 1;

[0044] Figure 3 The image shows the SEM image of the cathode material obtained in Comparative Example 1. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0046] The cathode material, its preparation method, and its application provided by this invention will be described in detail below.

[0047] The present invention provides a cathode material having a core-shell structure, wherein the core of the core-shell structure is sodium manganese ferrocyanide and the outer shell is potassium manganese ferrocyanide; and there is also a manganese ferrocyanide intermediate layer between the core and the outer shell.

[0048] The molecular formula of the above-mentioned kernel is Na. x Mn[Fe(CN)6] y , of which 1 <x≤2,0.7≤y≤1。

[0049] In some optional implementations, the molar ratio of the core, intermediate layer, and outer shell can be (54–94):(1–26):(5–45), such as 85:5:20 (i.e., 17:1:4), 90:5:10 (i.e., 19:1:2), 85:10:10 (i.e., 17:2:2), 90:2:16 (i.e., 45:1:8), 85:7:16, 94:3:6, or 70:10:40 (i.e., 7:1:4), etc. Furthermore, other molar ratios can be set according to actual needs.

[0050] In some alternative embodiments, the D of the above-mentioned positive electrode material 50 The micrometer diameter (D) is not less than 2.3 μm, and can be, for example, between 2.3 μm and 3.0 μm, such as 2.3 μm, 2.5 μm, 2.55 μm, 2.56 μm, 2.58 μm, 2.63 μm, 2.64 μm, 2.66 μm, 2.8 μm, or 3.0 μm, or other values ​​within the range of 2.3 μm to 3.0 μm. In some specific embodiments, the D of the above-mentioned cathode material... 50 The range is 2.55μm to 2.66μm.

[0051] In some optional embodiments, the water content of the above-mentioned positive electrode material does not exceed 0.6 wt%, such as 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, or 0.6 wt%, or other values ​​within the range not exceeding 0.6 wt%. In some specific embodiments, the water content of the above-mentioned positive electrode material can be from 0.3 wt% to 0.6 wt%.

[0052] In some typical implementations, the core of the above-mentioned cathode material is Na2Mn[Fe(CN)6], the intermediate layer is Mn2[Fe(CN)6], and the outer shell is K2Mn[Fe(CN)6].

[0053] Continuing from the above, in the cathode material provided by this invention, the manganese ferrocyanide intermediate layer can reduce the lattice spacing, acting as a structural support, thereby improving the cycle stability of the material and simultaneously inhibiting the absorption of water molecules. The potassium ferrocyanide in the potassium ferrocyanide outer shell... + Not only can it provide capacity, but also K + The ionic radius is also larger than that of Na. + The large size and wide ion transport channels contribute to a more stable structure and also help reduce the material's water absorption. The presence of these intermediate and outer layers significantly improves the structural stability of the cathode material during charge and discharge, reduces side reactions between the cathode and electrolyte, and enhances interfacial stability, cycle performance, and rate performance.

[0054] Accordingly, the present invention provides a method for preparing the above-mentioned cathode material, comprising the following steps:

[0055] Step S1: Prepare sodium manganese ferrocyanide core.

[0056] The preparation of the sodium manganese ferrocyanide core involves reacting a sodium ferrocyanide solution, a first soluble manganese salt solution, and a complexing agent solution together.

[0057] The above process can be carried out in a reactor. Sodium ferrocyanide solution, first soluble manganese salt solution and complexing agent solution are simultaneously introduced into the reactor to synthesize sodium manganese ferrocyanide under certain reaction atmosphere, stirring speed, reaction temperature, reaction pH value and reaction time.

[0058] In some optional embodiments, the reaction temperature can be between 30°C and 90°C, such as 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C, or other values ​​within the range of 30°C to 90°C. In some specific embodiments, the reaction temperature can be between 40°C and 90°C.

[0059] The reaction pH can be 6–9, such as 6, 6.5, 7, 7.5, 8, 8.5, or 9, or other values ​​within the range of 6–9. In some specific embodiments, the pH can be 6.6–9.0.

[0060] The reaction time can be from 12h to 72h, such as 12h, 24h, 36h, 48h, 60h or 72h, or other values ​​within the range of 12h to 72h.

[0061] In some alternative embodiments, the concentration of the sodium ferrocyanide solution can be 0.3 mol / L to 0.6 mol / L, such as 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, or 0.6 mol / L, or other values ​​within the range of 0.3 mol / L to 0.6 mol / L.

[0062] The concentration of the first soluble manganese salt solution can be 0.5 mol / L to 2 mol / L, such as 0.5 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L or 2 mol / L, or other values ​​within the range of 0.5 mol / L to 2 mol / L.

[0063] The aforementioned first soluble manganese salt solution may, by way of example, be at least one of manganese sulfate solution, manganese chloride solution, manganese nitrate solution, and manganese acetate solution.

[0064] In some optional embodiments, the molar ratio of sodium ferrocyanide in the sodium ferrocyanide solution to the first soluble manganese salt in the first soluble manganese salt solution can be from 0.97:1 to 1.03:1, such as 0.97:1, 0.98:1, 0.99:1, 1.00:1, 1.01:1, 1.02:1, or 1.03:1, or other values ​​within the range of 0.97:1 to 1.03:1. In some specific embodiments, the molar ratio of sodium ferrocyanide in the sodium ferrocyanide solution to the first soluble manganese salt in the first soluble manganese salt solution can be 1:1.

[0065] In some alternative embodiments, the concentration of the complexing agent solution can be from 0.002 mol / L to 14 mol / L, such as 0.002 mol / L, 0.01 mol / L, 0.1 mol / L, 1 mol / L, 2 mol / L, 5 mol / L, 8 mol / L, 10 mol / L, 12 mol / L, or 14 mol / L, or other values ​​within the range of 0.002 mol / L to 14 mol / L.

[0066] The molar ratio of the complexing agent in the complexing agent solution to the first soluble manganese salt in the first soluble manganese salt solution can be from 0.001:1 to 4:1, such as 0.001:1, 0.01:1, 0.1:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, or 4:1, or other values ​​within the range of 0.001:1 to 4:1. In some specific embodiments, the molar ratio of the complexing agent in the complexing agent solution to the first soluble manganese salt in the first soluble manganese salt solution can be from 0.5:1 to 2:1.

[0067] The complexing agent described above may, by way of example but not by way of limitation, include at least one of citric acid, maleic acid, citric acid, ethylenediaminetetraacetic acid, sodium citrate and ammonia.

[0068] In some alternative implementations, the reaction atmosphere for this step is a protective atmosphere, such as nitrogen and / or argon.

[0069] In some optional embodiments, the reaction process of this step is carried out under stirring conditions, wherein the stirring speed can be 200 rpm to 600 rpm, such as 200 rpm, 300 rpm, 400 rpm, 500 rpm or 600 rpm, or other values ​​in the range of 200 rpm to 600 rpm.

[0070] Taking the first soluble manganese salt solution as a manganese sulfate solution as an example, the reaction equations involved in step S1 include: MnSO4 + Na4Fe(CN)6 = Na2Mn[Fe(CN)6]↓ + Na2SO4.

[0071] The formation of the manganese ferrocyanide interlayer originates from Mn 2+ To Na + The substitution reaction, due to Mn 2+ Than Na + The large ionic radius and higher valence state of the ions can reduce the lattice spacing, thus playing a supporting role in the structure and improving the cycling stability of the material.

[0072] Step S2: Form a manganese ferrocyanide intermediate layer on the surface of the sodium manganese ferrocyanide core.

[0073] The preparation of the manganese ferrocyanide intermediate layer includes: adding a second soluble manganese salt solution to the material obtained from the preparation of the sodium manganese ferrocyanide core, mixing and reacting.

[0074] In some optional embodiments, the amount of the second soluble manganese salt in the second soluble manganese salt solution is 3% to 30% of the amount of the first soluble manganese salt in the first soluble manganese salt solution, such as 3%, 5%, 10%, 15%, 20%, 25%, or 30%, or other values ​​within the range of 3% to 30%.

[0075] The concentration of the second soluble manganese salt solution can be 0.5 mol / L to 2 mol / L, such as 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L, or other values ​​within the range of 0.5 mol / L to 2 mol / L.

[0076] The addition time of the second soluble manganese salt solution can be 0.25h to 1h, such as 0.25h, 0.5h, 0.75h or 1h, or other values ​​within the range of 0.25h to 1h.

[0077] In some typical embodiments, the second soluble manganese salt solution and the first soluble manganese salt solution are the same soluble manganese salt solution, for example, both can be manganese sulfate solutions with a concentration of 0.5 mol / L to 2 mol / L.

[0078] Since sodium ferrocyanide has completely reacted with manganese sulfate solution in step S1, the addition of manganese sulfate solution in step S2, within a short period (0.25 h to 1 h), constitutes an excess of sodium ferrocyanide. This excess manganese sulfate solution reacts with the sodium ferrocyanide core generated in step S1, forming manganese ferrocyanide on the surface of the sodium ferrocyanide core. The reaction equations include:

[0079] MnSO4+Na2Mn[Fe(CN)6]=Mn2[Fe(CN)6]+Na2SO4.

[0080] It should be noted that, due to the short reaction time, manganese ferrocyanide mainly accumulates on the surface of the sodium manganese ferrocyanide core to form a coating layer, and does not have time to penetrate into the interior of the sodium manganese ferrocyanide core.

[0081] Step S3: Form a potassium ferrocyanide shell on the surface of the manganese ferrocyanide intermediate layer.

[0082] The preparation of potassium manganese ferrocyanide shell includes: solid-liquid separation and washing of the material obtained from the preparation of manganese ferrocyanide intermediate layer; adding water to the washed solid phase to slurry to obtain Prussian white slurry; and mixing and reacting the Prussian white slurry with potassium ferrocyanide solution.

[0083] In some alternative embodiments, the material obtained from the preparation of the manganese ferrocyanide intermediate layer is filtered through a centrifuge, then washed to remove impurities, and the filter cake is then slurried with water to obtain Prussian white slurry. Subsequently, the Prussian white slurry and potassium ferrocyanide solution are continuously fed into a reaction vessel, causing the manganese ferrocyanide on the surface of the Prussian white slurry to react with the potassium ferrocyanide in the potassium ferrocyanide solution to form a potassium manganese ferrocyanide shell.

[0084] The chemical formula for the reaction between manganese ferrocyanide and potassium ferrocyanide in the above solution is:

[0085] Mn2[Fe(CN)6]+K4Fe(CN)6=2K2Mn[Fe(CN)6].

[0086] In some alternative embodiments, the concentration of the potassium ferrocyanide solution can be 0.3 mol / L to 0.6 mol / L, such as 0.3 mol / L, 0.4 mol / L, 0.5 mol / L or 0.6 mol / L, or other values ​​within the range of 0.3 mol / L to 0.6 mol / L.

[0087] In some optional embodiments, the amount of potassium ferrocyanide in the potassium ferrocyanide solution can be 3% to 30% of the amount of ferrocyanide in Prussian white slurry, such as 3%, 5%, 10%, 15%, 20%, 25% or 30%, or other values ​​within the range of 3% to 30%.

[0088] In some optional embodiments, the average residence time of the potassium manganese ferrocyanide generated in the aqueous solution does not exceed 15 min, such as 15 min, 12 min, 10 min, 8 min, 5 min, 2 min or 1 min, or other values ​​within the range not exceeding 15 min.

[0089] In some alternative embodiments, the preparation of the potassium manganese ferrocyanide shell further includes: continuously discharging the mixed slurry generated from the reaction and spray drying it. The spray drying is carried out in a spray dryer.

[0090] The feed rate for spray drying can be 5L / h to 30L / h, such as 5L / h, 10L / h, 15L / h, 20L / h, 25L / h or 30L / h, or other values ​​within the range of 5L / h to 30L / h.

[0091] The temperature of the main tower for spray drying can be 150℃~200℃, such as 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃, or other values ​​within the range of 150℃~200℃.

[0092] In some alternative embodiments, the volume of the container used for the reaction of Prussian white slurry with potassium ferrocyanide solution can be 1 / 10 to 1 / 5 of the hourly feed rate of the spray dryer, such as 1 / 10, 1 / 9, 1 / 8, 1 / 7, 1 / 6 or 1 / 5, or other values ​​within the range of 1 / 10 to 1 / 5.

[0093] In some alternative implementations, the volume of the container can be 1L to 3L, such as 1L, 1.5L, 2L, 2.5L or 3L, or other values ​​within the range of 1L to 3L.

[0094] In some alternative implementations, the container is a container with a stirring function, such as a stirrer.

[0095] In some alternative embodiments, the Prussian white slurry and potassium ferrocyanide solution are mixed through a tee pipe equipped with a check valve and then fed into a spray dryer. In some more typical embodiments, the tee pipe can be ultrasonically dispersed to prevent material from adhering to the pipe wall, thereby shortening the residence time of potassium manganese ferrocyanide in the aqueous solution.

[0096] It should be noted that the mixing of Prussian white slurry and potassium ferrocyanide solution in this invention can include two methods: one is to mix in a mixing tank and then enter the spray dryer through a one-way pipe; the other is to mix directly through a three-way pipe and enter the spray dryer.

[0097] Continuing from the above, in step S3, manganese ferrocyanide reacts rapidly with potassium ferrocyanide in the solution, quickly forming potassium manganese ferrocyanide without any byproducts. However, if the solution remains in the aqueous solution for too long, Prussian white will undergo dissolution-recrystallization. +Gradually penetrating into the material, it destroys the protective layer. Furthermore, the container volume for synthesizing potassium ferrocyanide should not be too large; it should ideally be 1 / 10 to 1 / 5 of the hourly feed volume for spray drying. During continuous feeding and discharging, this ensures both the ongoing reaction and that the average residence time of potassium ferrocyanide in the aqueous solution does not exceed 15 minutes. By mixing Prussian white slurry and potassium ferrocyanide solution through a three-way pipe equipped with a check valve and then introducing them into the spray dryer, and ultrasonically dispersing the mixture, the moisture is rapidly evaporated during spray drying, reducing the interstitial water content of the material. The potassium ferrocyanide on the material surface quickly solidifies, avoiding K... + It penetrates into the material, maintaining the integrity of the protective layer.

[0098] The method for preparing the above-mentioned cathode material provided by the present invention is simple to operate, low in cost, highly controllable, and suitable for industrial production.

[0099] In addition, the present invention also provides a positive electrode sheet, wherein the active material in the positive electrode sheet includes the above-mentioned positive electrode material.

[0100] The present invention also provides a battery cell comprising the above-mentioned positive electrode sheet.

[0101] For example, the aforementioned battery cells can be used, but are not limited to, in electrical devices such as vehicles, ships, or aircraft.

[0102] The present invention also provides a battery comprising the above-described battery cells.

[0103] The present invention also provides an electrical device comprising the aforementioned battery cell and / or battery. As examples, the electrical device may include, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., while spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0104] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0105] Example 1

[0106] This embodiment provides a cathode material, the preparation method of which includes:

[0107] Step S1: Prepare sodium manganese ferrocyanide core.

[0108] Sodium manganese ferrocyanide was synthesized by simultaneously introducing 0.5 mol / L sodium ferrocyanide solution, 2 mol / L manganese sulfate solution, and 2 mol / L sodium citrate solution into a reaction vessel under nitrogen atmosphere, stirring speed of 400 rpm, reaction temperature of 65℃, and reaction pH of 8.2. The molar ratio of sodium ferrocyanide to manganese sulfate was 1:1, and the molar ratio of sodium citrate to manganese sulfate was 2:1. Each solution was introduced into the reaction vessel for 24 hours.

[0109] Step S2: Prepare the manganese ferrocyanide intermediate layer.

[0110] Add manganese sulfate solution (concentration of 2 mol / L) to the material obtained in step S1. The amount of manganese sulfate added is 10% of the amount of manganese sulfate in step S1. The infusion time is 0.3 h, so that manganese ferrocyanide is generated on the surface of sodium manganese ferrocyanide.

[0111] Step S3: Prepare the potassium manganese ferrocyanide shell.

[0112] The slurry obtained in step S2 was filtered and washed in a centrifuge to remove impurities. The filter cake was then slurried with water to obtain Prussian white slurry. This Prussian white slurry was fed together with a 0.4 mol / L potassium ferrocyanide solution into a 1 L small stirred tank. The amount of potassium ferrocyanide was 5% of the amount of Prussian white ferrocyanide in the slurry. This caused the manganese ferrocyanide on the surface of the Prussian white to react with the potassium ferrocyanide in the solution, forming a potassium manganese ferrocyanide shell. Simultaneously, the slurry in the stirred tank was fed into a spray dryer (main tower temperature 180℃) at a rate of 10 L / h for drying to obtain the cathode material. The average residence time of the potassium manganese ferrocyanide generated in the aqueous solution was calculated by dividing the volume of the stirred tank by the feed rate of the spray dryer, which is 1 L / (10 L / h) = 0.1 h = 6 min.

[0113] The SEM and TEM images of the cathode material obtained in this embodiment are as follows: Figure 1 and Figure 2 As shown, by Figure 1 It can be seen that the cathode material has two protective layers, and a small amount of coating material can be seen on the surface of the cathode material. Figure 2 It can be seen that the cathode material has a three-layer structure, specifically including a core, an intermediate layer, and an outer shell from the inside out. The intermediate layer and the outer shell are both protective layers. The core is composed of Na2Mn[Fe(CN)6], the intermediate layer is composed of Mn2[Fe(CN)6], and the outer shell is composed of K2Mn[Fe(CN)6]. The molar ratio of the core, intermediate layer and outer shell is 90:5:10 (i.e. 19:1:2).

[0114] Example 2

[0115] This embodiment provides a cathode material, the preparation method of which includes:

[0116] Step S1: Prepare sodium manganese ferrocyanide core.

[0117] Sodium manganese ferrocyanide was synthesized by simultaneously introducing 0.4 mol / L sodium ferrocyanide solution, 2 mol / L manganese sulfate solution, and 2 mol / L sodium citrate solution into a reaction vessel under nitrogen atmosphere, stirring speed of 350 rpm, reaction temperature of 75℃, and reaction pH of 8.2. The molar ratio of sodium ferrocyanide to manganese sulfate was 1:1, and the molar ratio of sodium citrate to manganese sulfate was 1.5:1. Each solution was introduced into the reaction vessel for 40 h.

[0118] Step S2: Prepare the manganese ferrocyanide intermediate layer.

[0119] Add manganese sulfate solution (concentration of 2 mol / L) to the material obtained in step S1. The amount of manganese sulfate added is 15% of the amount of manganese sulfate in step S1. The infusion time is 0.4 h, so that manganese ferrocyanide is generated on the surface of sodium manganese ferrocyanide.

[0120] Step S3: Prepare the potassium manganese ferrocyanide shell.

[0121] The slurry obtained in step S2 was filtered and washed in a centrifuge to remove impurities. The filter cake was then slurried with water to obtain Prussian white slurry. This Prussian white slurry was then fed together with a 0.5 mol / L potassium ferrocyanide solution into a 1 L small stirred tank. The amount of potassium ferrocyanide was 10% of the amount of Prussian white ferrocyanide in the slurry. This caused the manganese ferrocyanide on the surface of the Prussian white slurry to react with the potassium ferrocyanide in the solution to form a potassium manganese ferrocyanide shell. Simultaneously, the slurry in the stirred tank was fed into a spray dryer (main tower temperature 160℃) at a rate of 10 L / h for drying to obtain the cathode material.

[0122] The cathode material obtained in this embodiment includes a core, an intermediate layer, and a shell, from the inside out. The core is composed of Na2Mn[Fe(CN)6], the intermediate layer is composed of Mn2[Fe(CN)6], and the shell is composed of K2Mn[Fe(CN)6]. The molar ratio of the core, intermediate layer, and shell is 85:5:20 (i.e., 17:1:4).

[0123] Example 3

[0124] This embodiment provides a cathode material, the preparation method of which includes:

[0125] Step S1: Prepare sodium manganese ferrocyanide core.

[0126] Sodium manganese ferrocyanide was synthesized by simultaneously introducing 0.5 mol / L sodium ferrocyanide solution, 1.6 mol / L manganese sulfate solution, and 2 mol / L sodium citrate solution into a reaction vessel under nitrogen atmosphere, stirring speed of 350 rpm, reaction temperature of 75℃, and reaction pH of 8.1. The molar ratio of sodium ferrocyanide to manganese sulfate was 1:1, and the molar ratio of sodium citrate to manganese sulfate was 1.3:1. Each solution was introduced into the reaction vessel for 48 hours.

[0127] Step S2: Prepare the manganese ferrocyanide intermediate layer.

[0128] Add manganese sulfate solution (concentration of 1.6 mol / L) to the material obtained in step S1. The amount of manganese sulfate added is 15% of the amount of manganese sulfate in step S1. The infusion time is 0.5 h, so that manganese ferrocyanide is generated on the surface of sodium manganese ferrocyanide.

[0129] Step S3: Prepare the potassium manganese ferrocyanide shell.

[0130] The slurry obtained in step S2 was filtered and washed in a centrifuge to remove impurities. The filter cake was then slurried with water to obtain Prussian white slurry. This Prussian white slurry was then fed together with a 0.4 mol / L potassium ferrocyanide solution into a 1 L small stirred tank. The amount of potassium ferrocyanide was 5% of the amount of Prussian white ferrocyanide in the slurry. This caused the manganese ferrocyanide on the surface of the Prussian white slurry to react with the potassium ferrocyanide in the solution to form a potassium manganese ferrocyanide shell. Simultaneously, the slurry in the stirred tank was fed into a spray dryer (main tower temperature 180℃) at a rate of 10 L / h for drying to obtain the cathode material.

[0131] The cathode material obtained in this embodiment includes a core, an intermediate layer, and a shell, from the inside out. The core is composed of Na2Mn[Fe(CN)6], the intermediate layer is composed of Mn2[Fe(CN)6], and the shell is composed of K2Mn[Fe(CN)6]. The molar ratio of the core, intermediate layer, and shell is 85:10:10 (i.e., 17:2:2).

[0132] Example 4

[0133] This embodiment provides a cathode material, the preparation method of which includes:

[0134] Step S1: Prepare sodium manganese ferrocyanide core.

[0135] Sodium manganese ferrocyanide was synthesized by simultaneously introducing 0.5 mol / L sodium ferrocyanide solution, 2 mol / L manganese sulfate solution, and 2 mol / L sodium citrate solution into a reaction vessel under nitrogen atmosphere, stirring speed of 400 rpm, reaction temperature of 85℃, and reaction pH of 8.0. The molar ratio of sodium ferrocyanide to manganese sulfate was 1:1, and the molar ratio of sodium citrate to manganese sulfate was 2:1. The reaction time for each solution was 48 h.

[0136] Step S2: Prepare the manganese ferrocyanide intermediate layer.

[0137] Add manganese sulfate solution (concentration of 2 mol / L) to the material obtained in step S1. The amount of manganese sulfate added is 10% of the amount of manganese sulfate in step S1. The infusion time is 0.5 h, so that manganese ferrocyanide is generated on the surface of sodium manganese ferrocyanide.

[0138] Step S3: Prepare the potassium manganese ferrocyanide shell.

[0139] The slurry obtained in step S2 was filtered and washed in a centrifuge to remove impurities. The filter cake was then slurried with water to obtain Prussian white slurry. This Prussian white slurry was then fed together with a 0.5 mol / L potassium ferrocyanide solution into a 1 L small stirred tank. The amount of potassium ferrocyanide was 8% of the amount of ferrocyanide in the Prussian white slurry. This caused the manganese ferrocyanide on the surface of the Prussian white slurry to react with the potassium ferrocyanide in the solution to form a potassium manganese ferrocyanide shell. Simultaneously, the slurry in the stirred tank was fed into a spray dryer (main tower temperature 180℃) at a rate of 10 L / h for drying to obtain the cathode material.

[0140] The cathode material obtained in this embodiment includes a core, an intermediate layer, and a shell, from the inside out. The core is composed of Na2Mn[Fe(CN)6], the intermediate layer is composed of Mn2[Fe(CN)6], and the shell is composed of K2Mn[Fe(CN)6]. The molar ratio of the core, intermediate layer, and shell is 90:2:16 (i.e., 45:1:8).

[0141] Example 5

[0142] This embodiment provides a cathode material, the preparation method of which includes:

[0143] Step S1: Prepare sodium manganese ferrocyanide core.

[0144] Sodium manganese ferrocyanide was synthesized by simultaneously introducing 0.5 mol / L sodium ferrocyanide solution, 1.8 mol / L manganese sulfate solution, and 2 mol / L sodium citrate solution into a reaction vessel under nitrogen atmosphere, stirring speed of 400 rpm, reaction temperature of 65℃, and reaction pH of 8.3. The molar ratio of sodium ferrocyanide to manganese sulfate was 1:1, and the molar ratio of sodium citrate to manganese sulfate was 2:1. Each solution was introduced into the reaction vessel for 60 h.

[0145] Step S2: Prepare the manganese ferrocyanide intermediate layer.

[0146] Add manganese sulfate solution (concentration of 1.8 mol / L) to the material obtained in step S1. The amount of manganese sulfate added is 15% of the amount of manganese sulfate in step S1. The infusion time is 0.6 h, so that manganese ferrocyanide is generated on the surface of sodium manganese ferrocyanide.

[0147] Step S3: Prepare the potassium manganese ferrocyanide shell.

[0148] The slurry obtained in step S2 was filtered and washed in a centrifuge to remove impurities. The filter cake was then slurried with water to obtain Prussian white slurry. This Prussian white slurry was then fed into a 1L small stirred tank along with a 0.5mol / L potassium ferrocyanide solution. The amount of potassium ferrocyanide was 8% of the amount of ferrocyanide in the Prussian white slurry. This caused the manganese ferrocyanide on the surface of the Prussian white slurry to react with the potassium ferrocyanide in the solution to form a potassium manganese ferrocyanide shell. Simultaneously, the slurry in the stirred tank was fed into a spray dryer (main tower temperature 160℃) at a rate of 10L / h for drying to obtain the cathode material.

[0149] The cathode material obtained in this embodiment includes a core, an intermediate layer, and a shell, from the inside out. The core is composed of Na2Mn[Fe(CN)6], the intermediate layer is composed of Mn2[Fe(CN)6], and the shell is composed of K2Mn[Fe(CN)6]. The molar ratio of the core, intermediate layer, and shell is 85:7:16, respectively.

[0150] Example 6

[0151] This embodiment provides a cathode material, the preparation method of which includes:

[0152] Step S1: Prepare sodium manganese ferrocyanide core.

[0153] Sodium manganese ferrocyanide was synthesized by simultaneously introducing a 0.3 mol / L sodium ferrocyanide solution, a 0.5 mol / L manganese sulfate solution, a 1 mol / L sodium citrate solution, and a 0.002 mol / L ethylenediaminetetraacetic acid (EDTA) complexing agent solution into a reactor under nitrogen atmosphere, stirring speed of 200 rpm, reaction temperature of 90 °C, and reaction pH of 6.6. The molar ratio of sodium ferrocyanide to manganese sulfate was 1:1, and the molar ratio of complexing agent to manganese sulfate was 0.5:1. Each solution was introduced into the reactor for 72 hours.

[0154] Step S2: Prepare the manganese ferrocyanide intermediate layer.

[0155] Add manganese sulfate solution (concentration of 0.5 mol / L) to the material obtained in step S1. The amount of manganese sulfate added is 6% of the amount of manganese sulfate in step S1. The infusion time is 0.25 h, so that manganese ferrocyanide is generated on the surface of sodium manganese ferrocyanide.

[0156] Step S3: Prepare the potassium manganese ferrocyanide shell.

[0157] The slurry obtained in step S2 was filtered and washed in a centrifuge to remove impurities. The filter cake was then slurried with water to obtain Prussian white slurry. This Prussian white slurry was then fed together with a 0.3 mol / L potassium ferrocyanide solution into a 1 L small stirred tank. The amount of potassium ferrocyanide was 3% of the amount of Prussian white ferrocyanide in the slurry. This caused the manganese ferrocyanide on the surface of the Prussian white slurry to react with the potassium ferrocyanide in the solution to form a potassium manganese ferrocyanide shell. Simultaneously, the slurry in the stirred tank was fed into a spray dryer (main tower temperature 150℃) at a rate of 5 L / h for drying to obtain the cathode material.

[0158] The cathode material obtained in this embodiment includes a core, an intermediate layer, and a shell, from the inside out. The core is composed of Na2Mn[Fe(CN)6], the intermediate layer is composed of Mn2[Fe(CN)6], and the shell is composed of K2Mn[Fe(CN)6]. The molar ratio of the core, intermediate layer, and shell is 94:3:6.

[0159] Example 7

[0160] This embodiment provides a cathode material, the preparation method of which includes:

[0161] Step S1: Prepare sodium manganese ferrocyanide core.

[0162] A mixed complexing agent solution of 0.6 mol / L sodium ferrocyanide, 2 mol / L manganese sulfate, 3 mol / L sodium citrate, and 0.5 mol / L ammonia was simultaneously introduced into a reactor. Sodium manganese ferrocyanide was synthesized under a nitrogen atmosphere, with a stirring speed of 600 rpm, a reaction temperature of 40℃, and a reaction pH of 9.0. The molar ratio of sodium ferrocyanide to manganese sulfate was 1:1, and the molar ratio of the complexing agent to manganese sulfate was 2:1. Each solution was introduced into the reactor for 12 hours.

[0163] Step S2: Prepare the manganese ferrocyanide intermediate layer.

[0164] Add manganese sulfate solution (concentration of 2 mol / L) to the material obtained in step S1. The amount of manganese sulfate added is 30% of the amount of manganese sulfate in step S1. The infusion time is 1 hour, so that manganese ferrocyanide is generated on the surface of sodium manganese ferrocyanide.

[0165] Step S3: Prepare the potassium manganese ferrocyanide shell.

[0166] The slurry obtained in step S2 was filtered and washed in a centrifuge to remove impurities. The filter cake was then slurried with water to obtain Prussian white slurry. This Prussian white slurry was then fed into a 3L small stirred tank along with a 0.6mol / L potassium ferrocyanide solution. The amount of potassium ferrocyanide was 20% of the amount of Prussian white ferrocyanide in the slurry. This caused the manganese ferrocyanide on the surface of the Prussian white slurry to react with the potassium ferrocyanide in the solution to form a potassium manganese ferrocyanide shell. Simultaneously, the slurry in the stirred tank was fed into a spray dryer (main tower temperature 200℃) at a rate of 30L / h for drying to obtain the cathode material.

[0167] The cathode material obtained in this embodiment includes a core, an intermediate layer, and a shell, from the inside out. The core is composed of Na2Mn[Fe(CN)6], the intermediate layer is composed of Mn2[Fe(CN)6], and the shell is composed of K2Mn[Fe(CN)6]. The molar ratio of the core, intermediate layer, and shell is 70:10:40 (i.e., 7:1:4).

[0168] Example 8

[0169] The difference between this embodiment and Embodiment 1 is that in step S3, the Prussian white slurry and the 0.4 mol / L potassium ferrocyanide solution are mixed through a three-way pipe with a check valve and ultrasonic dispersion and then immediately enter the spray dryer.

[0170] Comparative Example 1

[0171] After synthesizing sodium manganese ferrocyanide according to step S1 of Example 1, the subsequent preparation of the intermediate layer and outer shell is not carried out. The product is directly obtained by filtration, washing, pulping and spray drying.

[0172] The SEM image of the cathode material obtained in this comparative example is shown below. Figure 3 As shown, by Figure 3 It can be seen that the cathode material consists only of sodium manganese ferrocyanide, and there are no adhering substances on its surface.

[0173] Comparative Example 2

[0174] Sodium manganese ferrocyanide was synthesized according to steps S1 and S2 of Example 1 and coated with manganese ferrocyanide. The product was then directly filtered, washed, slurried, and spray-dried to obtain the final product. The subsequent preparation of potassium manganese ferrocyanide shell was not required.

[0175] In this cathode material, the molar ratio of Na2Mn[Fe(CN)6] to Mn2[Fe(CN)6] is 9:1.

[0176] Comparative Example 3

[0177] The difference between this comparative example and Example 1 is that no intermediate layer is provided, and the positive electrode material consists of a sodium manganese ferrocyanide core and a potassium manganese hydride shell with a molar ratio of 19:2.

[0178] Comparative Example 4

[0179] The difference between this comparative example and Example 1 is that in step S2, the addition time of the second soluble manganese salt solution is 0.1 h.

[0180] Comparative Example 5

[0181] The difference between this comparative example and Example 1 is that in step S2, the addition time of the second soluble manganese salt solution is 2 hours.

[0182] Comparative Example 6

[0183] The difference between this comparative example and Example 1 is that in step S3, the average residence time of the potassium manganese ferrocyanide generated in the aqueous solution is 20 min.

[0184] Comparative Example 7

[0185] The difference between this comparative example and Example 1 is that in step S3, the volume of the reaction vessel (stirred tank) is 1 / 2 of the hourly liquid feed rate of the spray dryer.

[0186] Comparative Example 8

[0187] The difference between this comparative example and Example 1 is that in step S3, the potassium manganese ferrocyanide generated by the reaction is not continuously discharged and spray-dried, but the material is discharged and spray-dried after the reaction is completely finished.

[0188] Test case

[0189] ① The particle size D of the cathode materials obtained in Examples 1-8 and Comparative Examples 1-8 50 And moisture content were tested. Among them, particle size D... 50 The tests were conducted using a Malvern particle size analyzer, and the moisture content was tested using an automatic moisture analyzer. The results are shown in Table 1.

[0190] ② The positive electrode materials obtained in Examples 1-8 and Comparative Examples 1-8 were respectively prepared into positive electrode sheets. Sodium metal was used as the negative electrode, and a NaPF6 ethylene carbonate (EC) / diethyl carbonate (DEC) solution was used as the electrolyte. These were assembled into coin cell half-cells in a glove box. Then, charge-discharge tests were conducted within a voltage range of 2.0V to 4.0V at rates of 0.1C and 5C, respectively, followed by 500 cycles at 0.1C. The discharge specific capacity and capacity retention are shown in Table 1. The physicochemical parameters of the positive electrode materials are shown in Table 1.

[0191] Table 1. Data for Examples and Comparative Samples

[0192]

[0193] As can be seen from Table 1, Comparative Example 1 is a simple sodium manganese ferrocyanide, which has the highest water content, the worst specific capacity at 5C discharge, and a low capacity retention rate after 500 cycles at 0.1C.

[0194] Comparative Example 2 had a layer of manganese ferrocyanide coated on the surface of sodium manganese ferrocyanide. Compared with Comparative Example 1, the water content of Comparative Example 2 was reduced, and the discharge specific capacity at 0.1C was slightly reduced. However, the discharge specific capacity at 5C and the capacity retention rate after 500 cycles at 0.1C were improved. This indicates that coating with manganese ferrocyanide has a certain effect on improving rate performance and cycle performance, but it will sacrifice some capacity.

[0195] Examples 1-8 all underwent double-layer coating. Compared to Comparative Example 1, the particle size was not significantly different, but the moisture content of the material was greatly reduced. The 0.1C discharge specific capacity remained almost unchanged compared to Comparative Example 1, while the 5C discharge specific capacity was significantly improved. Furthermore, after 500 cycles at 0.1C, the capacity retention rate was significantly enhanced. Compared to Comparative Example 2, Examples 1-8 had lower moisture content and higher capacity, indicating that the potassium manganese ferrocyanide on the surface played a role in reducing moisture and increasing capacity.

[0196] The results from Examples 1-8 and Comparative Examples 1-3 show that the three-layer Prussian white has better cycle performance and rate performance.

[0197] Furthermore, a comparison between Example 1 and Comparative Example 3 shows that Comparative Example 3 lacks an intermediate layer, has a higher water content, and exhibits slightly lower specific capacity at 5C discharge and capacity retention after 500 cycles at 0.1C.

[0198] A comparison of Example 1 and Comparative Examples 4-5 shows that the liquid ingress time of S2 has a certain impact on the discharge specific capacity and capacity retention of the material. Both excessively short and excessively long liquid ingress times are detrimental to the stability and permeability of the intermediate layer, leading to deterioration of electrical performance.

[0199] A comparison of Example 1 and Comparative Examples 6-8 shows that the average residence time of potassium manganese ferrocyanide in aqueous solution should not be too long, and spray drying should be performed as quickly as possible. The longer the residence time, the more potassium ions penetrate into the material, and the greater the destructive effect on rate performance (discharge specific capacity).

[0200] In summary, the positive electrode material provided by this invention has poor water absorption and stable structure during charging and discharging, which helps to reduce side reactions between the positive electrode and the electrolyte, and improves the interface stability, cycle performance and rate performance of the battery.

[0201] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A positive electrode material, characterized by, The positive electrode material has a core-shell structure, wherein the inner core of the core-shell structure is sodium ferrocyanide manganese, and the outer shell is potassium ferrocyanide manganese; and the inner core and the outer shell further have a manganese ferrocyanide intermediate layer.

2. The positive electrode material of claim 1, wherein, The positive electrode material further has at least one of the following characteristics: Feature 1 : the formula of the core is Na x Mn[Fe(CN)6] y wherein 1 < x < 2, 0.7 < y < 1 ; Feature 2: D50 of the positive electrode material is not more than 2.3 pm 50 not less than 2.3 pm; Characteristic 3: The water content of the positive electrode material is not more than 0.6wt%.

3. The positive electrode material according to claim 2, characterized in that, D of the positive electrode material is 2.3 μm to 3.0 μm. 50 2.3 μm to 3.0 μm.

4. A method for producing the positive electrode material according to any one of claims 1 to 3, characterized by, The method comprises the following steps: Preparation of a sodium ferrocyanide manganese inner core; formation of a manganese ferrocyanide intermediate layer on the surface of the sodium ferrocyanide manganese inner core; and formation of a potassium ferrocyanide manganese outer shell on the surface of the manganese ferrocyanide intermediate layer.

5. The preparation method according to claim 4, characterized in that, Preparation of the sodium ferrocyanide manganese inner core comprises: co-reaction of a sodium ferrocyanide solution, a first soluble manganese salt solution, and a complexing agent solution.

6. The preparation method according to claim 5, characterized in that, Preparation of the sodium ferrocyanide manganese inner core comprises at least one of the following characteristics: Characteristic 4: The reaction temperature is 30-90°C; Characteristic 5: The reaction pH value is 6-9; Characteristic 6: The reaction time is 12-72h; Characteristic 7: The concentration of the sodium ferrocyanide solution is 0.3-0.6mol / L, the concentration of the first soluble manganese salt solution is 0.5-2mol / L, and the molar ratio of sodium ferrocyanide in the sodium ferrocyanide solution to the first soluble manganese salt in the first soluble manganese salt solution is 0.97:1 to 1.03:1; Characteristic 8: The concentration of the complexing agent solution is 0.002-14mol / L, and the molar ratio of the complexing agent in the complexing agent solution to the first soluble manganese salt in the first soluble manganese salt solution is 0.001:1 to 4:1; Characteristic 9: The complexing agent comprises at least one of citric acid, maleic acid, citric acid, ethylenediaminetetraacetic acid, sodium citrate, and ammonia; Characteristic 10: The reaction atmosphere is a protective atmosphere; Characteristic 11: The reaction process is carried out under stirring.

7. The production method according to claim 6, characterized by, The stirring speed is 200-600rpm.

8. The method of any one of claims 5 to 7, wherein the method further comprises the step of: Preparation of the manganese ferrocyanide intermediate layer comprises: adding a second soluble manganese salt solution to the material obtained in the preparation of the sodium ferrocyanide manganese inner core, mixing, and reacting.

9. The production method according to claim 8, characterized by, Preparation of the manganese ferrocyanide intermediate layer comprises at least one of the following characteristics: Characteristic 12: The amount of the second soluble manganese salt in the second soluble manganese salt solution is 3-30% of the amount of substance of the first soluble manganese salt in the first soluble manganese salt solution, and the concentration of the second soluble manganese salt solution is 0.5-2mol / L; Characteristic 13: The second soluble manganese salt solution is added for 0.25-1h.

10. The preparation method according to claim 8, characterized in that, Preparation of the potassium ferrocyanide manganese outer shell comprises: solid-liquid separation and washing of the material obtained in the preparation of the manganese ferrocyanide intermediate layer, slurry of the obtained solid phase with water to obtain Prussian white slurry; and mixing and reacting of the Prussian white slurry with a potassium ferrocyanide solution.

11. The method of claim 10, wherein, Preparation of the potassium ferrocyanide manganese outer shell comprises at least one of the following characteristics: Characteristic 14: The concentration of the potassium ferrocyanide solution is 0.3-0.6mol / L; Characteristic 15: The amount of potassium ferrocyanide in the potassium ferrocyanide solution is 3-30% of the amount of substance of ferrocyanide in the Prussian white slurry; Feature 16: the average time for the reaction-generated manganese potassium ferrocyanide to stay in the aqueous solution is no more than 15 minutes.

12. The production method according to claim 10 or 11, characterized by, The preparation of the manganese potassium ferrocyanide shell further comprises continuously discharging the reaction-generated mixed slurry and performing spray drying.

13. The method of claim 12, wherein, The liquid feeding amount for the spray drying is 5-30 L / h, and the main tower temperature for the spray drying is 150-200 ℃.

14. The method of claim 12, wherein, The volume of the container for the reaction of the Prussian white slurry with the potassium ferrocyanide solution is 1 / 10-1 / 5 of the liquid feeding amount per hour for the spray drying.

15. The preparation method according to claim 14, characterized in that, The volume of the container is 1-3 L.

16. The method of claim 15, wherein, The container is a container with stirring function.

17. The method of claim 12, wherein, The Prussian white slurry and the potassium ferrocyanide solution are mixed through a three-way pipeline with a check valve and then enter the spray dryer.

18. The method of claim 17, wherein, The three-way pipeline is subjected to ultrasonic dispersion.

19. A positive electrode sheet characterized by comprising: The active material in the positive electrode sheet comprises the positive electrode material according to any one of claims 1-3.

20. A battery, characterized by The battery contains the positive electrode sheet according to claim 19.

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