A double-coated Prussian electrode material and its preparation and application

Abstract

The present invention relates to the field of lithium-ion battery technology, and in particular to a double-coated Prussian-type electrode material and its preparation and application. The present invention first mixes Na4Fe(CN)6 with a sodium salt to obtain a first solution, dissolves the metal salt to obtain a second solution; then adds the second solution to the first solution for reaction to obtain a pre-treated mixed solution; then adds the pre-treated mixed solution to a reactor, and after reaction, performs post-treatment to obtain a Prussian-type positive electrode material; then, the Prussian-type positive electrode material is coated with ZnO or Al2O3 using a fluidized bed to form a coating layer to obtain a single-coated Prussian-type positive electrode material; finally, the single-coated Prussian-type positive electrode material is mixed with graphene, added to a reactor for reaction, and post-treated to obtain a double-coated Prussian-type positive electrode material. The double-coated Prussian-type electrode material of the present invention has good cycle stability and conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a double-coated Prussian-type electrode material and its preparation and application. Background Art

[0002] Energy is essential to the development of human society. With the development of society, energy issues have attracted widespread attention. With the increasing shortage of traditional fossil fuels, the development of new clean energy sources has become a hot topic. Among all the new energy sources being developed, electrochemical energy storage boasts high energy efficiency, long cycle life, low maintenance costs, and flexible power and energy characteristics. It has significant advantages in integrated power grids such as wind power and photovoltaic power generation.

[0003] In electrochemical energy storage, lithium-ion batteries (Li-ion batteries) are widely used due to their high energy density, high power density, high voltage, long life, and high safety. However, the development of cathode materials significantly constrains the energy density and cost of Li-ion batteries. However, as Li-ion batteries are increasingly used in electric vehicles, problems such as lithium resource shortages and high costs have emerged. Compared to lithium, sodium is abundant in the Earth's crust, simple to extract, and relatively inexpensive. Furthermore, the electrochemical working principles of Na-ion batteries are similar to those of Li-ion batteries. Therefore, Na-ion batteries offer a promising rechargeable alternative to Li-ion batteries.

[0004] Prussian blue and its analogs are three-dimensional frameworks whose large interstices facilitate the transport and storage of sodium ions, making them excellent cathode materials for sodium-ion batteries. Prussian blue cathode materials are typically prepared using a hydrothermal synthesis method: a solution containing sodium ferrocyanide (Na4Fe(CN)6) is mixed and heated with salt solutions of Mn, Fe, Co, Cu, and other salts. A reactor is then used to grow the crystals into a Prussian blue cathode material with a specific morphology. This synthesis method is simple and efficient, but the resulting Prussian blue cathode material exhibits poor electronic conductivity, which can easily lead to structural collapse during cycling, resulting in a reduced cycle life.

[0005] Therefore, in the research of Prussian-type positive electrode materials, Prussian white positive electrode materials and carbon materials are mixed and carbon-coated to improve the conductivity of Prussian-type positive electrode materials. Generally, carbon materials with good conductivity are mixed and sintered in an inert atmosphere to form a carbon coating. However, the use of high-temperature sintering may destroy the three-dimensional skeleton structure of the Prussian-type positive electrode material, causing the structure of the material to collapse more easily and reducing the cycle life. Summary of the Invention

[0006] To address the above-mentioned problems, the present invention aims to provide a double-coated Prussian-type electrode material and its preparation and application. The present invention first mixes Na4Fe(CN)6 with a sodium salt to obtain a first solution, dissolves the metal salt to obtain a second solution; then adds the second solution to the first solution for reaction to obtain a pre-treated mixed solution; then adds the pre-treated mixed solution to a reactor, and after reaction, performs post-treatment to obtain a Prussian-type cathode material; then, the Prussian-type cathode material is coated with ZnO or Al2O3 using a fluidized bed to form a coating layer, obtaining a single-coated Prussian-type cathode material; finally, the single-coated Prussian-type cathode material is mixed with graphene, added to a reactor for reaction, and post-treated to obtain a double-coated Prussian-type cathode material. The double-coated Prussian-type cathode material of the present invention has good cycle stability and conductivity.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] The first object of the present invention is to provide a method for preparing a double-coated Prussian cathode material, comprising the following steps:

[0009] (1) coating a Prussian cathode material with ZnO or Al2O3 using a fluidized bed to form a coating layer to obtain a single-coated Prussian cathode material;

[0010] (2) The single-coated Prussian cathode material prepared in step (1) is mixed with graphene and then added into a reactor for reaction, and then post-processed to obtain a double-coated Prussian cathode material.

[0011] In one embodiment of the present invention, in step (1), the preparation method of the Prussian cathode material is as follows:

[0012] 1) mixing Na4Fe(CN)6 and sodium salt to obtain a first solution;

[0013] 2) dissolving the metal salt to obtain a second solution;

[0014] 3) adding the second solution obtained in step 2) to the first solution prepared in step 1) to react to obtain a pretreated mixed solution;

[0015] 4) The pre-treated mixed solution obtained in step 3) is added into a reactor, and after the reaction, post-processed to obtain a Prussian cathode material.

[0016] In one embodiment of the present invention, in step 1), the mass ratio of Na4Fe(CN)6 to sodium salt is 2 to 6:3;

[0017] The sodium salt is selected from one or more of sodium carbonate, sodium chloride or sodium sulfate.

[0018] In one embodiment of the present invention, in step 2), the metal salt is selected from one or more of manganese salts, iron salts, copper salts, chromium salts, cobalt salts and nickel salts;

[0019] The manganese salt is selected from one or more of MnSO4 and MnCl2; the iron salt is selected from one or more of FeSO4 and FeCl2; the copper salt is selected from one or more of CuSO4 and CuCl2; the chromium salt is selected from one or more of CrSO4 and CrCl2; the cobalt salt is selected from one or more of CoSO4 and CoCl2; and the nickel salt is selected from one or more of NiSO4.

[0020] In one embodiment of the present invention, in step 3), the volume ratio of the first solution to the second solution is 2 to 3:1;

[0021] During the reaction, the reaction temperature is 60-100° C. and the reaction time is 1-5 hours.

[0022] In one embodiment of the present invention, in step 4), during the reaction, the reaction temperature is 150-200° C., and the reaction time is 18-25 h.

[0023] In one embodiment of the present invention, in step (1), the mass ratio of the Prussian cathode material to the oxide is 100:0.1-1;

[0024] In one embodiment of the present invention, in step (1), the oxide is selected from one or more of zinc oxide, lithium cobalt oxide or aluminum oxide;

[0025] The thickness of the coating layer is 20 to 30 mm.

[0026] In one embodiment of the present invention, in step (2), the ratio of the single-coated Prussian cathode material to the graphene is 50-100 g:50 mL;

[0027] During the reaction, the reaction temperature is 180-250° C. and the reaction time is 20-25 h.

[0028] In one embodiment of the present invention, in step (2), the post-treatment is freeze-drying;

[0029] During the freeze-drying process, the freeze-drying temperature is -20 to -30°C, and the freeze-drying time is 6 to 10 hours.

[0030] The second object of the present invention is to provide a double-coated Prussian cathode material prepared by the above method.

[0031] The third object of the present invention is to provide an application of a double-coated Prussian cathode material in the preparation of a lithium-ion battery.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The present invention adopts a double-layer coating method to coat the Prussian cathode material with oxides (Al2O3, ZnO, LiCoO2, etc.) and then wrap it in a three-dimensional network layer formed by graphene oxide (rGO) to form a double-layer coated Prussian cathode material.

[0034] (2) The oxide coating can effectively prevent the metal ions (Mn 2+ 、Fe 3+ / 2+ ) is dissolved and released during the battery cycle, which can effectively improve the cycle stability of the positive electrode material.

[0035] (3) Using graphene and positive electrode materials to form a composite of nanoparticles wrapped in a three-dimensional network layer formed by graphene oxide (rGO), the conductivity of the material is greatly improved. The three-dimensional network layer formed by graphene can act as a buffer layer for certain material expansion and prevent the cracking of the electrode during the battery cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is an SEM image of the double-coated Prussian cathode material prepared in Example 1;

[0037] Figure 2 This is a TEM image of the double-coated Prussian cathode material prepared in Example 1;

[0038] Figure 3 Schematic diagram of the charge and discharge curves of the double-coated Prussian cathode material prepared in Example 1;

[0039] Figure 4 Schematic diagram of the cycle curves of the uncoated Prussian cathode material prepared in Comparative Example 1, the single-coated Prussian cathode material prepared in Comparative Example 2, and the double-coated Prussian cathode material prepared in Example 1. DETAILED DESCRIPTION

[0040] The present invention provides a method for preparing a double-coated Prussian cathode material, comprising the following steps:

[0041] (1) coating a Prussian cathode material with ZnO or Al2O3 using a fluidized bed to form a coating layer to obtain a single-coated Prussian cathode material;

[0042] (2) The single-coated Prussian cathode material prepared in step (1) is mixed with graphene and then added into a reactor for reaction, and then post-processed to obtain a double-coated Prussian cathode material.

[0043] In one embodiment of the present invention, in step (1), the preparation method of the Prussian cathode material is as follows:

[0044] 1) mixing Na4Fe(CN)6 and sodium salt to obtain a first solution;

[0045] 2) dissolving the metal salt to obtain a second solution;

[0046] 3) adding the second solution obtained in step 2) to the first solution prepared in step 1) to react to obtain a pretreated mixed solution;

[0047] 4) The pre-treated mixed solution obtained in step 3) is added into a reactor, and after the reaction, post-processed to obtain a Prussian cathode material.

[0048] In one embodiment of the present invention, in step 1), the mass ratio of Na4Fe(CN)6 to sodium salt is 2 to 6:3;

[0049] The sodium salt is selected from one or more of sodium carbonate, sodium chloride or sodium sulfate.

[0050] In one embodiment of the present invention, in step 2), the metal salt is selected from one or more of manganese salts, iron salts, copper salts, chromium salts, cobalt salts and nickel salts;

[0051] The manganese salt is selected from one or more of MnSO4 and MnCl2; the iron salt is selected from one or more of FeSO4 and FeCl2; the copper salt is selected from one or more of CuSO4 and CuCl2; the chromium salt is selected from one or more of CrSO4 and CrCl2; the cobalt salt is selected from one or more of CoSO4 and CoCl2; and the nickel salt is selected from one or more of NiSO4.

[0052] In one embodiment of the present invention, in step 3), the volume ratio of the first solution to the second solution is 2 to 3:1;

[0053] During the reaction, the reaction temperature is 60-100° C. and the reaction time is 1-5 hours.

[0054] In one embodiment of the present invention, in step 4), during the reaction, the reaction temperature is 150-200° C., and the reaction time is 18-25 h.

[0055] In one embodiment of the present invention, in step (1), the mass ratio of the Prussian cathode material to the oxide is 100:0.1-1;

[0056] In one embodiment of the present invention, in step (1), the oxide is selected from one or more of zinc oxide, lithium cobalt oxide or aluminum oxide;

[0057] The thickness of the coating layer is 20 to 30 mm.

[0058] In one embodiment of the present invention, in step (2), the ratio of the single-coated Prussian cathode material to the graphene is 50-100 g:50 mL;

[0059] During the reaction, the reaction temperature is 180-250° C. and the reaction time is 20-25 h.

[0060] In one embodiment of the present invention, in step (2), the post-treatment is freeze-drying;

[0061] During the freeze-drying process, the freeze-drying temperature is -20 to -30°C, and the freeze-drying time is 6 to 10 hours.

[0062] The present invention provides a double-coated Prussian cathode material prepared by the above method.

[0063] The present invention provides an application of a double-coated Prussian cathode material in the preparation of a lithium-ion battery.

[0064] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] In the following examples, unless otherwise specified, all reagents used are commercially available reagents in the field; and all detection methods or means used are conventional detection methods or means in the field.

[0066] Example 1

[0067] This embodiment provides a double-coated Prussian cathode material and a preparation method thereof.

[0068] (1) Preparation of the first solution: Dissolve 200 g of Na4Fe(CN)6 and 150 g of Na2SO4 in 1 L of water to obtain a first solution;

[0069] (2) Preparation of the second solution: 90 g of MnSO4 was dissolved in 500 mL of water to obtain the second solution;

[0070] (3) Preparation of pretreatment mixed solution: adding the second solution obtained in step (2) to the first solution prepared in step (1), reacting at 90° C. for 3 h to obtain a pretreatment mixed solution;

[0071] (4) Preparation of Prussian cathode material: The pre-treated mixed solution obtained in step (3) was added to a reactor, reacted at 150° C. for 25 h, and then filtered to obtain a Prussian cathode material;

[0072] (5) The Prussian cathode material obtained in step (4) is coated with an oxide using a fluidized bed to form a coating layer with a thickness of 20 nm (Prussian cathode material: oxide = 100 g: 1 g), thereby obtaining a single-coated Prussian cathode material;

[0073] (6) 100 g of the single-coated Prussian cathode material prepared in step (5) was mixed with 50 mL of graphene and added to a reactor, reacted at 180° C. for 25 h, and freeze-dried at −30° C. for 6 h to obtain a double-coated Prussian cathode material.

[0074] The SEM image of the double-coated Prussian cathode material prepared in this embodiment is as follows Figure 1 As shown in the TEM image Figure 2 shown.

[0075] The charge and discharge curves of the double-coated Prussian cathode material prepared in this embodiment are as follows: Figure 3 As shown, its cycle curve is as follows Figure 4 shown.

[0076] Comparative Example 1

[0077] This comparative example provides a Prussian cathode material and a preparation method thereof.

[0078] (1) Preparation of the first solution: Dissolve 200 g of Na4Fe(CN)6 and 150 g of Na2SO4 in 1 L of water to obtain a first solution;

[0079] (2) Preparation of the second solution: 90 g of MnSO4 was dissolved in 500 mL of water to obtain the second solution;

[0080] (3) Preparation of pretreatment mixed solution: adding the second solution obtained in step (2) to the first solution prepared in step (1), reacting at 90° C. for 3 h to obtain a pretreatment mixed solution;

[0081] (4) Preparation of Prussian cathode material: The pretreated mixed solution obtained in step (3) was added to a reactor, reacted at 150° C. for 20 h, and then filtered to obtain a Prussian cathode material (uncoated Prussian cathode material).

[0082] The cycle curve of the uncoated Prussian cathode material prepared in this comparative example is as follows Figure 4 shown.

[0083] Comparative Example 2

[0084] This embodiment provides a double-coated Prussian cathode material and a preparation method thereof.

[0085] (1) Preparation of the first solution: Dissolve 200 g of Na4Fe(CN)6 and 150 g of Na2SO4 in 1 L of water to obtain a first solution;

[0086] (2) Preparation of the second solution: 90 g of MnSO4 was dissolved in 500 mL of water to obtain the second solution;

[0087] (3) Preparation of pretreatment mixed solution: adding the second solution obtained in step (2) to the first solution prepared in step (1), reacting at 90° C. for 3 h to obtain a pretreatment mixed solution;

[0088] (4) Preparation of Prussian cathode material: The pre-treated mixed solution obtained in step (3) was added to a reactor, reacted at 150° C. for 25 h, and then filtered to obtain a Prussian cathode material;

[0089] (5) The Prussian cathode material obtained in step (4) is coated with oxide using a fluidized bed to form a coating layer with a thickness of 20 nm to obtain a single-coated Prussian cathode material.

[0090] The single-coated Prussian cathode material ( Figure 4 -single wrap) cycle curve is as follows Figure 4 As shown, the double-coated Prussian cathode material prepared in Example 1 ( Figure 4 - double coating) and the uncoated Prussian cathode material ( Figure 4 -uncoated), the order of cycle stability from high to low is: double-coated Prussian-type positive electrode material, single-coated Prussian-type positive electrode material, and uncoated Prussian-type positive electrode material.

[0091] Example 2

[0092] This embodiment provides a double-coated Prussian cathode material and a preparation method thereof.

[0093] (1) Preparation of the first solution: Dissolve 100 g of Na4Fe(CN)6 and 150 g of NaCl in 1 L of water to obtain the first solution;

[0094] (2) Preparation of the second solution: 90 g of FeSO4 was dissolved in 400 mL of water to obtain a second solution;

[0095] (3) Preparation of pretreatment mixed solution: adding the second solution obtained in step (2) to the first solution prepared in step (1), reacting at 60° C. for 5 h to obtain a pretreatment mixed solution;

[0096] (4) Preparation of Prussian cathode material: The pre-treated mixed solution obtained in step (3) was added to a reactor, reacted at 180° C. for 20 h, and then filtered to obtain a Prussian cathode material;

[0097] (5) The Prussian cathode material obtained in step (4) is coated with an oxide using a fluidized bed to form a coating layer with a thickness of 25 nm (Prussian cathode material: oxide = 100 g: 0.1 g), thereby obtaining a single-coated Prussian cathode material;

[0098] (6) 80 g of the single-coated Prussian cathode material prepared in step (5) was mixed with 50 mL of graphene and added to a reactor, reacted at 200 ° C for 22 h, and freeze-dried at -25 ° C for 8 h to obtain a double-coated Prussian cathode material.

[0099] Example 3

[0100] This embodiment provides a double-coated Prussian cathode material and a preparation method thereof.

[0101] (1) Preparation of the first solution: 300 g of Na4Fe(CN)6 and 150 g of Na2CO3 were dissolved in 1.2 L of water to obtain the first solution;

[0102] (2) Preparation of the second solution: 90 g of NiSO4 was dissolved in 400 mL of water to obtain a second solution;

[0103] (3) Preparation of a pretreatment mixed solution: adding the second solution obtained in step (2) to the first solution prepared in step (1), reacting at 100° C. for 1 h to obtain a pretreatment mixed solution;

[0104] (4) Preparation of Prussian cathode material: The pre-treated mixed solution obtained in step (3) was added to a reactor, reacted at 200° C. for 18 h, and then filtered to obtain a Prussian cathode material;

[0105] (5) The Prussian cathode material obtained in step (4) is coated with an oxide using a fluidized bed to form a coating layer with a thickness of 30 nm (Prussian cathode material: oxide = 100 g: 0.5 g), thereby obtaining a single-coated Prussian cathode material;

[0106] (6) 50 g of the single-coated Prussian cathode material prepared in step (5) was mixed with 50 mL of graphene and added to a reactor, reacted at 250° C. for 20 h, and freeze-dried at −20° C. for 10 h to obtain a double-coated Prussian cathode material.

[0107] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing a double-coated Prussian cathode material, characterized in that: The following steps are involved: Mixing Na4Fe(CN)6 with sodium salt to obtain a first solution; dissolving the metal salt to obtain a second solution; adding the second solution to the first solution to react, thereby obtaining a pretreatment mixed solution, wherein the volume ratio of the first solution to the second solution is 2 to 3:1, and during the reaction, the reaction temperature is 60 to 100° C., and the reaction time is 1 to 5 hours; The pre-treated mixed solution is added to a reactor, and after the reaction, post-processing is performed to obtain a Prussian cathode material. During the reaction, the reaction temperature is 150-200° C. and the reaction time is 18-25 hours; The Prussian cathode material is coated with an oxide using a fluidized bed to form a coating layer to obtain a single-coated Prussian cathode material; the mass ratio of the Prussian cathode material to the oxide is 100:0.1-1; the oxide is selected from one or more of zinc oxide, lithium cobalt oxide, or aluminum oxide; and the coating layer has a thickness of 20-30 mm; The single-coated Prussian cathode material and graphene are mixed and added into a reactor for reaction at a reaction temperature of 180 to 250° C., and post-processed to obtain a double-coated Prussian cathode material; wherein the amount ratio of the single-coated Prussian cathode material to the graphene is 50 to 100 g:50 mL, and the reaction time is 20 to 25 h during the reaction process.

2. The method for preparing a double-coated Prussian cathode material according to claim 1, characterized in that: The mass ratio of Na4Fe(CN)6 to sodium salt is 2 to 6:3; The sodium salt is selected from one or more of sodium carbonate, sodium chloride or sodium sulfate.

3. The method for preparing a double-coated Prussian cathode material according to claim 1, characterized in that: The metal salt is selected from one or more of manganese salts, iron salts, copper salts, chromium salts, cobalt salts and nickel salts; The manganese salt is selected from one or more of MnSO4 and MnCl2; the iron salt is selected from one or more of FeSO4 and FeCl2; the copper salt is selected from one or more of CuSO4 and CuCl2; the chromium salt is selected from one or more of CrSO4 and CrCl2; the cobalt salt is selected from one or more of CoSO4 and CoCl2; and the nickel salt is selected from one or more of NiSO4.

4. A double-coated Prussian cathode material prepared by the method according to any one of claims 1 to 3.

5. Use of the double-coated Prussian cathode material according to claim 4 in the preparation of lithium-ion batteries.

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