Single crystal high-entropy prussian blue positive electrode material and preparation method and application thereof

Abstract

The application provides a single crystal type high-entropy Prussian blue positive electrode material and a preparation method and application thereof, and the preparation method comprises the following steps: mixing a transition metal salt solution, a sodium ferrocyanide solution, a complexing agent solution, a base solution and a precipitant, performing a co-precipitation reaction under the condition that the pH value is 10-13, then performing standing and aging, and sequentially performing filtration, washing and drying to obtain the single crystal type high-entropy Prussian blue positive electrode material. The single crystal type high-entropy Prussian blue positive electrode material obtained by the application has a high material thermal decomposition temperature and excellent thermal stability; vacancies in the positive electrode material and a small amount of water content can inhibit the dissolution of metals; in addition, the single crystal type high-entropy Prussian blue positive electrode material obtained by the application has excellent morphology.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to a cathode material, particularly a single-crystal high-entropy Prussian blue cathode material and its preparation method and application. Background Technology

[0002] The core components of a sodium-ion battery consist of four parts: the positive electrode, the electrolyte, the separator, and the negative electrode. During charging, Na... + Electrons are released from the sodium-rich positive electrode, pass through the electrolyte and membrane, and enter the negative electrode; while electrons move along the external circuit to the negative electrode for charge compensation; the discharge process is the opposite of the former, and the two are highly reversible, thus enabling the sodium-ion battery to have charge and discharge functions.

[0003] The mainstream anode materials for sodium-ion batteries are hard carbon and NaTi2(PO4)3, both of which are characterized by long cycle life and high capacity. The electrolyte in sodium-ion batteries mainly consists of sodium salts such as NaPF6 and NaClO4, along with ester solvents, and its properties are similar to those of electrolytes in lithium-ion batteries.

[0004] Unlike the negative electrode and electrolyte, the positive electrode material remains a bottleneck in the development of sodium-ion batteries. Currently, widely studied sodium-ion positive electrode materials include transition metal oxides, polyanionic compounds, and Prussian blue-like materials (PBAs). Transition metal oxides and polyanionic compounds, due to the presence of fluorine and oxygen bonds in their crystal structures, make Na… + Transport processes within the crystal lattice are subject to significant chemical binding energy, which affects insertion / extraction on the cathode, resulting in low rate performance of the cathode material. Furthermore, transition metal oxides undergo uncontrollable phase transitions during charge and discharge, leading to a severe reduction in the material's cycle life; polyanionic compounds generally have low specific capacity due to the large molecular weight of their anions.

[0005] The general chemical formula for Prussian blue-like materials is A x M a [M b (CN)6] 1-y Each transition metal atom in this complex is linked by a cyanide ion, forming a rigid and open cubic framework. Due to its large porous structure, it can accommodate the free transport and storage of alkali metal ions. Because it contains no oxygen or fluorine, Na... + The transport process within the crystal lattice is subject to low chemical binding energy, resulting in outstanding rate performance. The average sodium storage potential of Prussian blue-like materials is higher than 3V, and when all transition metals in the structure are electrochemically active, they possess a theoretical capacity of 170 mAh / g. Furthermore, the preparation methods for Prussian blue-like materials are typically co-precipitation, hydrothermal methods, and ball milling, which are energy-efficient and operate under mild conditions.

[0006] However, mono-based Prussian blue-like compounds have some insurmountable problems due to their inherent physicochemical properties. For example, in Fe-based Prussian blue, the low average voltage is a problem that pure iron-based Prussian blue cannot solve. Mn, Co, and Cu-based Prussian blue materials are severely affected by the Jan Taylor effect due to their corresponding transition metal elements, and the transition metals are prone to dissolution during charge and discharge, causing structural damage and reducing the cycle stability of the material. Ni-based Prussian blue materials have a relatively low specific capacity because Ni is electrochemically inert in the system.

[0007] Therefore, there is a need to provide a single-crystal high-entropy Prussian blue cathode material with high discharge specific capacity, high cycle stability, and high safety, as well as its preparation method and application. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a single-crystal high-entropy Prussian blue cathode material, its preparation method, and its application. The single-crystal high-entropy Prussian blue cathode material obtained by the present invention has a high thermal decomposition temperature and excellent thermal stability; moreover, the cathode material has fewer vacancies and less water content, which can inhibit the dissolution of metals; in addition, the single-crystal high-entropy Prussian blue cathode material obtained by the present invention has excellent morphology.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a single-crystal high-entropy Prussian blue cathode material, the method comprising the following steps:

[0011] A mixed transition metal salt solution, sodium ferrocyanide solution, complexing agent solution, base liquid and precipitant are subjected to a co-precipitation reaction at a pH of 10-13, followed by static aging, and then filtration, washing and drying to obtain the single-crystal high-entropy Prussian blue cathode material.

[0012] The metal ions in the transition metal salt solution include Fe. 2+ Mn 2+ Co 2+ Ni 2+ and Cu 2+ .

[0013] This invention provides a method for preparing a single-crystal high-entropy Prussian blue cathode material. The high-entropy properties of the obtained single-crystal high-entropy Prussian blue cathode material enhance the Na... +The diffusion is unrestricted, inhibiting metal dissolution. The micron-sized single crystals help increase tap density and reduce structural degradation during cycling. In addition, by controlling the pH value of the co-precipitation reaction to 10-13, the obtained single-crystal high-entropy Prussian blue cathode material has a high thermal decomposition temperature and excellent thermal stability. Moreover, the cathode material has fewer vacancies and less water content, which can inhibit metal dissolution. Furthermore, the obtained single-crystal high-entropy Prussian blue cathode material has excellent morphology.

[0014] Preferably, the transition metal salt solution contains Fe 2+ Mn 2+ Co 2+ Ni 2+ and Cu 2+ The molar ratio is (0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2).

[0015] Preferably, the transition metal salt solution contains Fe 2+ The concentration is 50-80 mmol / L.

[0016] Preferably, the transition metal salt solution contains Mn 2+ The concentration is 50-80 mmol / L.

[0017] Preferably, the transition metal salt solution contains Co. 2+ The concentration is 50-80 mmol / L.

[0018] Preferably, the Ni in the transition metal salt solution 2+ The concentration is 50-80 mmol / L.

[0019] Preferably, the Cu in the transition metal salt solution 2+ The concentration is 50-80 mmol / L.

[0020] Preferably, the transition metal salt solution further includes sodium citrate.

[0021] Preferably, the concentration of sodium citrate in the transition metal salt solution is 80-120 mmol / L.

[0022] Preferably, in the transition metal salt solution, the anions that coordinate with the metal ions include at least one or a combination of at least two of oxalate, chloride, nitrate, sulfate, or carbonate.

[0023] Preferably, the concentration of the sodium ferrocyanide solution is 20-120 mmol / L.

[0024] Preferably, the complexing agent concentration of the complexing agent solution is 6-12 mmol / L.

[0025] Preferably, the complexing agent in the complexing agent solution includes any one or a combination of at least two of sodium citrate, trisodium citrate, sodium oxalate, sulfosalicylic acid, oxalic acid, or salicylic acid.

[0026] Preferably, the pH value of the base solution is 10-13.

[0027] Preferably, a surfactant is added to the base liquid.

[0028] Preferably, the concentration of the surfactant in the substrate is 6-12 mmol / L.

[0029] Preferably, the molar ratio of the complexing agent to the surfactant in the base liquid is (20-500):1.

[0030] Preferably, the surfactant comprises any one or a combination of at least two of polyvinyl alcohol, polyvinylpyrrolidone, or sodium dodecylbenzenesulfonate.

[0031] Preferably, the precipitant comprises sodium hydroxide and / or potassium hydroxide.

[0032] Preferably, the preparation method includes: adding a transition metal salt solution, a sodium ferrocyanide solution, a complexing agent solution, and a precipitant to a bottom liquid, carrying out a co-precipitation reaction under stirring and a pH value of 10-13, then allowing it to stand for aging, and then filtering, washing, and drying in sequence to obtain the single-crystal high-entropy Prussian blue cathode material.

[0033] Preferably, the flow rate of the transition metal salt solution is 50-200 L / h;

[0034] Preferably, the flow rate of the sodium ferrocyanide solution is 50-200 L / h;

[0035] Preferably, the flow rate of the complexing agent solution is 25-100 L / h;

[0036] Preferably, the temperature of the co-precipitation reaction is 15-45℃;

[0037] Preferably, the stirring speed is 400-800 rpm.

[0038] As a preferred embodiment of the preparation method described in the first aspect, the preparation method includes the following steps:

[0039] A transition metal salt solution, sodium ferrocyanide solution, complexing agent solution, and precipitant were added to the bottom liquid. A co-precipitation reaction was carried out under stirring and pH 10-13 conditions. The mixture was then allowed to stand and age. After filtration, washing, and drying, the monocrystalline high-entropy Prussian blue cathode material was obtained.

[0040] The metal ions in the transition metal salt solution include Fe in a molar ratio of (0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2). 2+ Mn 2+ Co 2+ Ni 2+ and Cu 2+ The transition metal salt solution also includes sodium citrate at a concentration of 80-120 mmol / L; the anions that coordinate with the metal ions in the transition metal salt solution include at least one or a combination of at least two of oxalate, chloride, nitrate, sulfate or carbonate.

[0041] The temperature for the coprecipitation reaction is 15-45℃;

[0042] The stirring speed is 400-800 rpm.

[0043] In a second aspect, the present invention provides a single-crystal high-entropy Prussian blue cathode material, wherein the single-crystal high-entropy Prussian blue cathode material is obtained by the preparation method described in the first aspect.

[0044] Thirdly, the present invention provides an application of the single-crystal high-entropy Prussian blue cathode material as described in the second aspect, wherein the single-crystal high-entropy Prussian blue cathode material is used in sodium-ion batteries.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] This invention provides a method for preparing a single-crystal high-entropy Prussian blue cathode material. The high-entropy properties of the obtained single-crystal high-entropy Prussian blue cathode material enhance the Na... + The diffusion is unrestricted, inhibiting metal dissolution. The micron-sized single crystals help increase tap density and reduce structural degradation during cycling. In addition, by controlling the pH value of the co-precipitation reaction to 10-13, the obtained single-crystal high-entropy Prussian blue cathode material has a high thermal decomposition temperature and excellent thermal stability. Moreover, the cathode material has fewer vacancies and less water content, which can inhibit metal dissolution. Furthermore, the obtained single-crystal high-entropy Prussian blue cathode material has excellent morphology. Attached Figure Description

[0047] Figure 1 This is a SEM image of the single-crystal high-entropy Prussian blue cathode material obtained in Example 1. Detailed Implementation

[0048] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0049] An embodiment of the present invention provides a method for preparing a single-crystal high-entropy Prussian blue cathode material, the method comprising the following steps:

[0050] A mixed transition metal salt solution, sodium ferrocyanide solution, complexing agent solution, base liquid and precipitant were subjected to a co-precipitation reaction at a pH of 10-13. The mixture was then allowed to stand for aging, and then filtered, washed and dried to obtain a single-crystal high-entropy Prussian blue cathode material.

[0051] Metal ions in transition metal salt solutions include Fe 2+ Mn 2+ Co 2+ Ni 2+ and Cu 2+ .

[0052] This invention provides a method for preparing a single-crystal high-entropy Prussian blue cathode material. The high-entropy properties of the obtained single-crystal high-entropy Prussian blue cathode material enhance the Na... + The diffusion is unrestricted, inhibiting metal dissolution. The micron-sized single crystals help increase tap density and reduce structural degradation during cycling. In addition, by controlling the pH value of the co-precipitation reaction to 10-13, the obtained single-crystal high-entropy Prussian blue cathode material has a high thermal decomposition temperature and excellent thermal stability. Moreover, the cathode material has fewer vacancies and less water content, which can inhibit metal dissolution. Furthermore, the obtained single-crystal high-entropy Prussian blue cathode material has excellent morphology.

[0053] In some embodiments, Fe in the transition metal salt solution 2+ Mn 2+ Co 2+ Ni 2+ and Cu 2+ The molar ratio is (0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2), for example, it can be 0.8:1.2:0.8:1.2:1, 1.2:0.8:1.2:0.8:1, 1:1:1:1:1, 0.8:0.8:0.8:0.8:1.2 or 1.2:1.2:1.2:1.2:0.8, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] In some embodiments, Fe in the transition metal salt solution 2+The concentration is 50-80 mmol / L, for example, it can be 50 mmol / L, 55 mmol / L, 60 mmol / L, 65 mmol / L, 70 mmol / L, 75 mmol / L or 80 mmol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0055] In some embodiments, Mn in transition metal salt solutions 2+ The concentration is 50-80 mmol / L, for example, it can be 50 mmol / L, 55 mmol / L, 60 mmol / L, 65 mmol / L, 70 mmol / L, 75 mmol / L or 80 mmol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0056] In some embodiments, Co in the transition metal salt solution 2+ The concentration is 50-80 mmol / L, for example, it can be 50 mmol / L, 55 mmol / L, 60 mmol / L, 65 mmol / L, 70 mmol / L, 75 mmol / L or 80 mmol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] In some embodiments, Ni in the transition metal salt solution 2+ The concentration is 50-80 mmol / L, for example, it can be 50 mmol / L, 55 mmol / L, 60 mmol / L, 65 mmol / L, 70 mmol / L, 75 mmol / L or 80 mmol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0058] In some embodiments, Cu in the transition metal salt solution 2+ The concentration is 50-80 mmol / L, for example, it can be 50 mmol / L, 55 mmol / L, 60 mmol / L, 65 mmol / L, 70 mmol / L, 75 mmol / L or 80 mmol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] In some embodiments, the transition metal salt solution also includes sodium citrate.

[0060] In some embodiments, the concentration of sodium citrate in the transition metal salt solution is 80-120 mmol / L, for example, it can be 80 mmol / L, 90 mmol / L, 100 mmol / L, 110 mmol / L or 120 mmol / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0061] In some embodiments, in the transition metal salt solution, the anion that coordinates with the metal ion includes at least one or a combination of at least two of oxalate, chloride, nitrate, sulfate, or carbonate. Typical but non-limiting combinations include combinations of oxalate and chloride, chloride and nitrate, sulfate and carbonate, nitrate, sulfate, and carbonate, or oxalate, chloride, nitrate, sulfate, and carbonate.

[0062] In some embodiments, the concentration of the sodium ferrocyanide solution is 20-120 mmol / L, for example, it can be 20 mmol / L, 40 mmol / L, 50 mmol / L, 80 mmol / L, 100 mmol / L or 120 mmol / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0063] In some embodiments, the complexing agent concentration of the complexing agent solution is 6-12 mmol / L, for example, it can be 6 mmol / L, 8 mmol / L, 9 mmol / L, 10 mmol / L or 12 mmol / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0064] In some embodiments, the complexing agent in the complexing agent solution includes any one or a combination of at least two of sodium citrate, trisodium citrate, sodium oxalate, sulfosalicylic acid, oxalic acid, or salicylic acid. Typical but non-limiting combinations include combinations of sodium citrate and trisodium citrate, combinations of salicylic acid and sulfosalicylic acid, combinations of oxalic acid and sodium oxalate, combinations of sodium citrate, trisodium citrate, oxalic acid, and sodium oxalate, combinations of oxalic acid, sodium oxalate, salicylic acid, and sulfosalicylic acid, or combinations of sodium citrate, trisodium citrate, sodium oxalate, sulfosalicylic acid, oxalic acid, and salicylic acid.

[0065] The base liquid of this invention contains a complexing agent and a precipitant. The amount of precipitant added is sufficient to ensure that the pH value of the base liquid meets the process requirements.

[0066] In some embodiments, the pH value of the substrate is 10-13, for example, it can be 10, 11, 12 or 13, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0067] In some embodiments, a surfactant is added to the base liquid.

[0068] In some embodiments, the concentration of the surfactant in the substrate is 6-12 mmol / L, for example, it can be 6 mmol / L, 7 mmol / L, 8 mmol / L, 10 mmol / L or 12 mmol / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0069] In some embodiments, the molar ratio of the complexing agent added to the surfactant in the base liquid is (20-500):1, for example, it can be 20:1, 50:1, 100:1, 200:1, 300:1, 400:1 or 500:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0070] In some embodiments, the surfactant comprises any one or a combination of at least two of polyvinyl alcohol, polyvinylpyrrolidone, or sodium dodecylbenzenesulfonate. Typical but non-limiting combinations include combinations of polyvinyl alcohol and polyvinylpyrrolidone, combinations of polyvinylpyrrolidone and sodium dodecylbenzenesulfonate, combinations of polyvinyl alcohol and sodium dodecylbenzenesulfonate, or combinations of polyvinyl alcohol, polyvinylpyrrolidone, and sodium dodecylbenzenesulfonate.

[0071] In some embodiments, the precipitant includes sodium hydroxide and / or potassium hydroxide.

[0072] This invention does not specify the amount of precipitant to be added, as long as the pH value of the coprecipitation reaction is maintained at the value required by the process.

[0073] In some embodiments, the preparation method includes the following steps:

[0074] A transition metal salt solution, sodium ferrocyanide solution, complexing agent solution, and precipitant were added to the bottom liquid. A co-precipitation reaction was carried out under stirring and pH 10-13 conditions. The mixture was then allowed to stand and age. After filtration, washing, and drying, a single-crystal high-entropy Prussian blue cathode material was obtained.

[0075] In some embodiments, the flow rate of the transition metal salt solution is 50-200 L / h, for example, it can be 50 L / h, 80 L / h, 100 L / h, 120 L / h, 150 L / h, 180 L / h or 200 L / h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0076] In some embodiments, the flow rate of the sodium ferrocyanide solution is 50-200 L / h, for example, it can be 50 L / h, 80 L / h, 100 L / h, 120 L / h, 150 L / h, 180 L / h or 200 L / h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0077] In some embodiments, the flow rate of the complexing agent solution is 25-100 L / h, for example, it can be 25 L / h, 40 L / h, 50 L / h, 60 L / h, 80 L / h or 100 L / h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0078] In some embodiments, the temperature of the coprecipitation reaction is 15-45°C, for example, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C or 45°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0079] In some embodiments, the stirring rate is 400-800 rpm, for example, 400 rpm, 500 rpm, 600 rpm, 700 rpm or 800 rpm, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0080] In some embodiments, the coprecipitation reaction time is 8-12 hours, for example, 8, 9, 10, 11, or 12 hours, but not limited to the listed values; other unlisted values ​​within the range are also applicable. The coprecipitation reaction time described in this invention is the stirring time.

[0081] In some embodiments, the drying is vacuum drying, and the vacuum drying temperature is 90-110°C, for example, 90°C, 95°C, 100°C, 105°C or 110°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0082] The vacuum drying time is 10-15 hours, for example, 10 hours, 12 hours, 13 hours, 14 hours or 15 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0083] In some embodiments, the preparation method includes the following steps:

[0084] A transition metal salt solution, sodium ferrocyanide solution, complexing agent solution, and precipitant were added to the bottom liquid. A co-precipitation reaction was carried out under stirring and pH 10-13 conditions. The mixture was then allowed to stand and age. After filtration, washing, and drying, a single-crystal high-entropy Prussian blue cathode material was obtained.

[0085] The metal ions in the transition metal salt solution include Fe in a molar ratio of (0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2). 2+ Mn 2+ Co 2+ Ni 2+ and Cu2+ The transition metal salt solution also includes sodium citrate at a concentration of 80-120 mmol / L; the anions that coordinate with the metal ions in the transition metal salt solution include at least one or a combination of at least two of oxalate, chloride, nitrate, sulfate or carbonate.

[0086] The temperature for coprecipitation reactions is 15-45℃;

[0087] The stirring speed is 400-800 rpm.

[0088] One embodiment of the present invention provides a single-crystal high-entropy Prussian blue cathode material, which is obtained by the preparation method in some embodiments.

[0089] This invention provides an application of a single-crystal high-entropy Prussian blue cathode material, as in some embodiments, for use in sodium-ion batteries.

[0090] Example 1

[0091] This embodiment provides a method for preparing a single-crystal high-entropy Prussian blue cathode material, the method comprising the following steps:

[0092] A transition metal salt solution, sodium ferrocyanide solution, complexing agent solution, and precipitant were added to the bottom liquid, and a co-precipitation reaction was carried out under stirring and pH 12 conditions. The mixture was then allowed to stand and age, followed by filtration, washing, and vacuum drying to obtain the product shown below. Figure 1 The image shows a single-crystal high-entropy Prussian blue cathode material;

[0093] The metal ions in the transition metal salt solution include Fe in a molar ratio of 1:1:1:1:1. 2+ Mn 2+ Co 2+ Ni 2+ and Cu 2+ Fe 2+ The concentration of Mn was 50 mmol / L. 2+ The concentration was 50 mmol / L, Co 2+ The concentration was 50 mmol / L, Ni 2+ The concentration was 50 mmol / L and Cu 2+ The concentration of the transition metal salt solution is 50 mmol / L; the transition metal salt solution also contains sodium citrate at a concentration of 100 mmol / L; in the transition metal salt solution, the anion that coordinates with the metal ion is sulfate.

[0094] The concentration of the sodium ferrocyanide solution was 80 mmol / L;

[0095] The complexing agent concentration of the complexing agent solution was 9 mmol / L, and the complexing agent was 5-sulfosalicylic acid;

[0096] The precipitant is sodium hydroxide;

[0097] The pH value of the substrate is 12, and the substrate contains polyvinyl alcohol at a concentration of 10 mmol / L. The molar ratio of complexing agent (5-sulfosalicylic acid) to polyvinyl alcohol in the substrate is 200:1.

[0098] The flow rate of the transition metal salt solution was 100 L / h, the flow rate of the sodium ferrocyanide solution was 100 L / h, and the flow rate of the complexing agent solution was 50 L / h; the temperature of the coprecipitation reaction was 30 °C, and the time was 10 h; the stirring speed was 400 rpm.

[0099] The vacuum drying temperature is 100℃ and the time is 12h.

[0100] Example 2

[0101] This embodiment provides a method for preparing a single-crystal high-entropy Prussian blue cathode material. Except for the complexing agent being salicylic acid, the rest is the same as in Example 1.

[0102] Example 3

[0103] This embodiment provides a method for preparing a single-crystal high-entropy Prussian blue cathode material, which is the same as in Example 1 except that the complexing agent is oxalic acid.

[0104] Example 4

[0105] This embodiment provides a method for preparing a single-crystal high-entropy Prussian blue cathode material, which is the same as in Example 1 except that the complexing agent is sodium oxalate.

[0106] Example 5

[0107] This embodiment provides a method for preparing a single-crystal high-entropy Prussian blue cathode material, which is the same as in Example 1 except that the complexing agent is sodium citrate.

[0108] Example 6

[0109] This embodiment provides a method for preparing a single-crystal high-entropy Prussian blue cathode material, the method comprising the following steps:

[0110] A transition metal salt solution, sodium ferrocyanide solution, complexing agent solution, and precipitant were added to the bottom liquid. A co-precipitation reaction was carried out under stirring and pH 12 conditions. The mixture was then allowed to stand and age. After filtration, washing, and vacuum drying, a single-crystal high-entropy Prussian blue cathode material was obtained.

[0111] The metal ions in the transition metal salt solution include Fe in a molar ratio of 1:1:1:1:1. 2+ Mn 2+ Co 2+ Ni 2+ and Cu 2+ Fe 2+ The concentration was 65 mmol / L, Mn 2+ The concentration was 65 mmol / L, Co 2+ The concentration was 65 mmol / L, Ni 2+ The concentration was 65 mmol / L and Cu 2+ The concentration of the transition metal salt solution is 65 mmol / L; the solution also contains sodium citrate at a concentration of 80 mmol / L; the anion that combines with the metal ion in the transition metal salt solution is nitrate.

[0112] The concentration of the sodium ferrocyanide solution was 20 mmol / L;

[0113] The complexing agent concentration of the complexing agent solution is 6 mmol / L, and the complexing agent is 5-sulfosalicylic acid;

[0114] The precipitant is sodium hydroxide;

[0115] The pH value of the substrate is 12, and the substrate contains polyvinylpyrrolidone at a concentration of 6 mmol / L. The molar ratio of complexing agent (5-sulfosalicylic acid) to polyvinylpyrrolidone in the substrate is 500:1.

[0116] The flow rate of the transition metal salt solution was 50 L / h, the flow rate of the sodium ferrocyanide solution was 50 L / h, and the flow rate of the complexing agent solution was 25 L / h; the temperature of the coprecipitation reaction was 15 °C, and the time was 12 h; the stirring speed was 500 rpm.

[0117] The vacuum drying temperature is 90℃ and the time is 15 hours.

[0118] Example 7

[0119] This embodiment provides a method for preparing a single-crystal high-entropy Prussian blue cathode material, the method comprising the following steps:

[0120] A transition metal salt solution, sodium ferrocyanide solution, complexing agent solution, and precipitant were added to the bottom liquid. A co-precipitation reaction was carried out under stirring and pH 12 conditions. The mixture was then allowed to stand and age. After filtration, washing, and vacuum drying, a single-crystal high-entropy Prussian blue cathode material was obtained.

[0121] The metal ions in the transition metal salt solution include Fe in a molar ratio of 1:1:1:1:1. 2+ Mn 2+Co 2+ Ni 2+ and Cu 2+ Fe 2+ The concentration of Mn was 80 mmol / L. 2+ The concentration was 80 mmol / L, Co 2+ The concentration was 50 mmol / L, Ni 2+ The concentration was 50 mmol / L and Cu 2+ The concentration of the transition metal salt solution is 80 mmol / L; the solution also contains sodium citrate at a concentration of 120 mmol / L; the anion that coordinates with the metal ion in the transition metal salt solution is chloride ion;

[0122] The concentration of the sodium ferrocyanide solution was 120 mmol / L;

[0123] The complexing agent concentration of the complexing agent solution was 12 mmol / L, and the complexing agent was 5-sulfosalicylic acid;

[0124] The precipitant is sodium hydroxide;

[0125] The pH value of the base solution is 12, and the base solution contains sodium dodecylbenzenesulfonate at a concentration of 12 mmol / L. The molar ratio of complexing agent (5-sulfosalicylic acid) to sodium dodecylbenzenesulfonate in the base solution is 20:1.

[0126] The flow rate of the transition metal salt solution was 200 L / h, the flow rate of the sodium ferrocyanide solution was 200 L / h, and the flow rate of the complexing agent solution was 100 L / h; the temperature of the coprecipitation reaction was 45 °C, and the time was 8 h; the stirring speed was 600 rpm.

[0127] The vacuum drying temperature was 110℃ and the time was 10 hours.

[0128] Example 8

[0129] This embodiment provides a method for preparing a single-crystal high-entropy Prussian blue cathode material, which is the same as in Example 1 except that sodium citrate is not added to the transition metal salt solution.

[0130] Example 9

[0131] This embodiment provides a method for preparing a single-crystal high-entropy Prussian blue cathode material. Except for adjusting the amount of precipitant and carrying out the co-precipitation reaction at a pH of 10, the rest is the same as in Example 1.

[0132] Example 10

[0133] This embodiment provides a method for preparing a single-crystal high-entropy Prussian blue cathode material. Except for adjusting the amount of precipitant and carrying out the co-precipitation reaction at a pH of 13, the rest is the same as in Example 1.

[0134] Comparative Example 1

[0135] This comparative example provides a method for preparing Prussian blue cathode material. Except for adjusting the amount of precipitant and carrying out the co-precipitation reaction at pH 9, the rest is the same as in Example 1.

[0136] Comparative Example 2

[0137] This comparative example provides a method for preparing Prussian blue cathode material. Except for adjusting the amount of precipitant and carrying out the co-precipitation reaction at pH 14, the rest is the same as in Example 1.

[0138] Comparative Example 3

[0139] This comparative example provides a method for preparing Prussian blue cathode material, which is the same as in Example 1 except that a complexing agent solution is not used.

[0140] Performance Characterization

[0141] The particle size distribution of the single-crystal high-entropy Prussian blue cathode material provided in the examples and the Prussian blue cathode material provided in the comparative examples was determined. The test method was to use a Malvern particle size analyzer to test the D50 particle size range of 0.5μm-4μm for single-crystal materials.

[0142] The single-crystal high-entropy Prussian blue cathode material provided in the examples and the Prussian blue cathode material provided in the comparative examples were coated on aluminum foil with conductive carbon black SP and 5 wt% polyvinylidene fluoride solution at a mass ratio of 8:1:1 to form cathode sheets. A sodium metal sheet was used as the anode, and a Celgard 2400 separator was used. The electrolyte was 1 mol / L NaPF6 (the solvents were ethylene carbonate and diethyl carbonate, with a volume ratio of 1:1). After the battery was left to stand for 12 hours, the initial discharge capacity, capacity retention rate after 100 cycles, and capacity retention rate after 1000 cycles were tested on a LandCT2001A battery tester.

[0143] The test method for the first discharge capacity is as follows: charge at a constant current and constant voltage of 1C to 3.7V, and then discharge at a constant current of 1C to 2V;

[0144] The test method for capacity retention rate after 100 cycles is as follows: charge at a constant current and constant voltage of 1C to 3.7V, then discharge at a constant current of 1C to 2V. After 100 cycles, record the discharge capacity. The ratio of the discharge capacity of 100 cycles to the initial discharge capacity is the capacity retention rate after 100 cycles.

[0145] The results are shown in Table 1.

[0146] Table 1

[0147]

[0148]

[0149] In summary, this invention provides a method for preparing a single-crystal high-entropy Prussian blue cathode material. The high-entropy properties of the obtained single-crystal high-entropy Prussian blue cathode material enhance the Na... + The diffusion is unrestricted, inhibiting metal dissolution. The micron-sized single crystals help increase tap density and reduce structural degradation during cycling. In addition, by controlling the pH value of the co-precipitation reaction to 10-13, the obtained single-crystal high-entropy Prussian blue cathode material has a high thermal decomposition temperature and excellent thermal stability. Moreover, the cathode material has fewer vacancies and less water content, which can inhibit metal dissolution. Furthermore, the obtained single-crystal high-entropy Prussian blue cathode material has excellent morphology.

[0150] 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 method for preparing a single-crystal high-entropy Prussian blue cathode material, characterized in that, The preparation method includes the following steps: A transition metal salt solution, sodium ferrocyanide solution, complexing agent solution, and precipitant were added to a base solution with a pH of 12. A co-precipitation reaction was carried out under the condition of pH 12, followed by static aging. The mixture was then filtered, washed, and dried to obtain the single-crystal high-entropy Prussian blue cathode material. The temperature for the coprecipitation reaction is 15-45℃; The complexing agent in the complexing agent solution is any one or a combination of at least two of the following: trisodium citrate, sodium oxalate, sulfosalicylic acid, oxalic acid, or salicylic acid. The complexing agent concentration of the complexing agent solution is 6-12 mmol / L; The base liquid contains a surfactant; The flow rate of the transition metal salt solution is 50-200 L / h; the flow rate of the sodium ferrocyanide solution is 50-200 L / h; and the flow rate of the complexing agent solution is 25-100 L / h. The precipitant is sodium hydroxide and / or potassium hydroxide; The metal ions in the transition metal salt solution include Fe. 2+ Mn 2+ Co 2+ Ni 2+ and Cu 2+ ; The transition metal salt solution also includes sodium citrate; the concentration of sodium citrate in the transition metal salt solution is 80-120 mmol / L.

2. The preparation method according to claim 1, characterized in that, Fe in transition metal salt solution 2+ Mn 2+ Co 2 + Ni 2+ and Cu 2+ The molar ratio is (0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2).

3. The preparation method according to claim 1, characterized in that, Fe in transition metal salt solution 2+ The concentration is 50-80 mmol / L.

4. The preparation method according to claim 1, characterized in that, Mn in the transition metal salt solution 2+ The concentration is 50-80 mmol / L.

5. The preparation method according to claim 1, characterized in that, Co in transition metal salt solution 2+ The concentration is 50-80 mmol / L.

6. The preparation method according to claim 1, characterized in that, Ni in transition metal salt solution 2+ The concentration is 50-80 mmol / L.

7. The preparation method according to claim 1, characterized in that, Cu in transition metal salt solution 2+ The concentration is 50-80 mmol / L.

8. The preparation method according to claim 1, characterized in that, In the transition metal salt solution, the anions that coordinate with the metal ions include at least one or a combination of at least two of the following: oxalate, chloride, nitrate, sulfate, or carbonate.

9. The preparation method according to claim 1, characterized in that, The concentration of the sodium ferrocyanide solution is 20-120 mmol / L.

10. The preparation method according to claim 1, characterized in that, The concentration of surfactant in the substrate is 6-12 mmol / L.

11. The preparation method according to claim 1, characterized in that, The molar ratio of the complexing agent to the surfactant in the base liquid is (20-500):

1.

12. The preparation method according to claim 1, characterized in that, The surfactant includes any one or a combination of at least two of polyvinyl alcohol, polyvinylpyrrolidone, or sodium dodecylbenzenesulfonate.

13. The preparation method according to claim 1, characterized in that, The preparation method includes: A transition metal salt solution, sodium ferrocyanide solution, complexing agent solution, and precipitant were added to the bottom liquid. A co-precipitation reaction was carried out under stirring and pH 12 conditions. The mixture was then allowed to stand and age. After filtration, washing, and drying, the monocrystalline high-entropy Prussian blue cathode material was obtained. The precipitant is sodium hydroxide and / or potassium hydroxide; The metal ions in the transition metal salt solution include Fe. 2+ Mn 2+ Co 2+ Ni 2+ and Cu 2+ The transition metal salt solution also includes sodium citrate; the concentration of sodium citrate in the transition metal salt solution is 80-120 mmol / L. The flow rate of the transition metal salt solution is 50-200 L / h; The flow rate of the sodium ferrocyanide solution is 50-200 L / h; The flow rate of the complexing agent solution is 25-100 L / h; The temperature for the coprecipitation reaction is 15-45℃; The stirring speed is 400-800 rpm.

14. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: A transition metal salt solution, sodium ferrocyanide solution, complexing agent solution, and precipitant were added to a bottom solution with a pH of 12. A co-precipitation reaction was carried out under stirring and pH 12 conditions. The mixture was then allowed to stand and age. After filtration, washing, and drying, the monocrystalline high-entropy Prussian blue cathode material was obtained. The metal ions in the transition metal salt solution include Fe in a molar ratio of (0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2). 2+ Mn 2+ Co 2+ Ni 2+ and Cu 2+ The transition metal salt solution also includes sodium citrate at a concentration of 80-120 mmol / L. In the transition metal salt solution, the anions that coordinate with the metal ions include at least one or a combination of at least two of the following: oxalate, chloride, nitrate, sulfate, or carbonate. The flow rate of the transition metal salt solution is 50-200 L / h; the flow rate of the sodium ferrocyanide solution is 50-200 L / h; the flow rate of the complexing agent solution is 25-100 L / h; and the precipitant is sodium hydroxide and / or potassium hydroxide. The temperature for the coprecipitation reaction is 15-45℃; The stirring speed is 400-800 rpm; The complexing agent in the complexing agent solution includes any one or a combination of at least two of the following: trisodium citrate, sodium oxalate, sulfosalicylic acid, oxalic acid, or salicylic acid. The complexing agent concentration of the complexing agent solution is 6-12 mmol / L.

15. A single-crystal high-entropy Prussian blue cathode material, characterized in that, The single-crystal high-entropy Prussian blue cathode material is obtained by the preparation method described in any one of claims 1-14.

16. An application of the single-crystal high-entropy Prussian blue cathode material as described in claim 15, characterized in that, The single-crystal high-entropy Prussian blue cathode material is used in sodium-ion batteries.

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