Prussian blue cathode material, method of manufacturing the same, cathode plate, and sodium ion battery

Abstract

The present invention provides a Prussian blue cathode material, a method for manufacturing the same, a cathode plate, and a sodium ion battery. The Prussian blue cathode material comprises a Prussian blue compound having the general chemical formula NaxFe[Fe(CN)6]y·nH2O. The Prussian blue cathode material according to the present invention has a simple synthesis method and low raw material costs. Furthermore, when applied to a sodium ion battery, it is advantageous for improving the performance of the sodium ion battery in terms of specific capacity, Coulomb efficiency, scaling performance, and long cycle stability.

Description

Technology Field

[0001] [Cross-reference of related applications]

[0002] This application claims priority to a Chinese patent application filed with the Chinese Intellectual Property Administration on June 27, 2023, with application number 202310772356.6 and application title “Prussian blue cathode material, method of manufacturing the same and application thereof,” all of which are incorporated herein by reference.

[0003] [Technology Field]

[0004] The present invention belongs to the field of battery and electrochemical energy storage technology, and in particular relates to a Prussian blue cathode material, a method for manufacturing the same, a cathode plate, and a sodium ion battery. Background Technology

[0005] Energy storage has established itself as a key challenge in modern society for utilizing renewable energy and promoting smart grids. Room-temperature sodium-ion batteries (SIBs), which operate under chemical conditions similar to lithium-ion batteries (LIBs), are emerging as promising candidates for energy storage systems (ESSs) due to the global abundance and low cost of sodium. Rechargeable sodium-ion batteries (SIBs) are emerging as highly promising candidates for large-scale energy storage system applications due to their abundant resources and controllable costs. Prussian blue (PB) and its analogs (PBAs) have been considered potential cathodes and are receiving increasing attention due to their unique rigid open framework, large gap sodium storage sites, high theoretical capacity, and non-toxic properties. Furthermore, the convenient synthesis process and low cost of PBAs are also very attractive for potential large-scale applications. However, PBAs exhibit low scaling capability and cycle stability due to low electronic conductivity and defects in the PBAs framework.

[0006] In a typical PB framework, the iron center is low-spin (Fe) depending on whether the iron atom is located on the carbon side or the nitrogen side of the cyanide ligand. LS (C)) or high spin (Fe HS It exists in the (N)) structure. Fe LS (C) and Fe HS (N) participates in redox reactions for sodium storage at different potentials, and since the number of Fe sites is the same in a perfect PB framework, it theoretically provides the same number of Coulombs. However, in existing literature, Fe HS (N) Compared to a redox couple, Fe LS (C) Shows that the capacity contribution of the redox pair is much lower. In addition, these insufficiently activated low-spin Fe LS (C) Redox pairs are electrochemically active at high potentials, which inevitably affects the average potential platform of PBA-based anodes. By reducing with water or doping with other transition metals, Fe LS (C) Activating redox pairs has been reported, but in this case, cycle stability is optimized while capacity is sacrificed. Therefore, resolving these issues is urgent to realize the full potential of PBA-based cathode materials, and unsatisfactory scaling capability is another obstacle to the commercialization of PBA materials.

[0007] In light of this, the objective of the present invention is to provide a Prussian blue cathode material having high magnification performance and excellent cycle stability, a method for manufacturing the same, and an application thereof, in order to solve the problem of capacity degradation caused by the optimization of cycle stability when existing Prussian blue materials are applied to sodium-ion batteries.

[0008] In light of this, the objective of the present invention is to provide a Prussian blue cathode material having high magnification performance and excellent cycle stability, a method for manufacturing the same, and an application, in order to solve the problem of capacity degradation caused by the optimization of cycle stability of existing Prussian blue materials.

[0009] In a first aspect, the present invention relates to a Prussian blue cathode material having the following general chemical formula,

[0010] Na x Formula I of Fe[Fe(CN)]6·nH2O

[0011] In Equation I, x ranges from 0.01 to 3, and

[0012] n is 0.01 to 3.

[0013] In an embodiment of the present invention, x can be selected from 0.05, 0.1, 0.5, 1, 1.5, 2, and 2.5, and the Prussian blue cathode material obtained when x < 1.5 has better cycle stability, has a low Na ion content which is in a sodium-deficient state, has a fast reaction rate, and has lower lattice defects and moisture content, thus having better performance; n can be selected from 0.05, 0.1, 0.5, 1, 1.5, 2, and 2.5; and both x and n are molar ratios.

[0014] The Prussian blue cathode material according to the present invention has a block-type structure.

[0015] In an embodiment of the present invention, the nanocubic size of the Prussian blue cathode material is 500 nm to 2000 nm.

[0016] In a second aspect, the present invention provides a method for manufacturing a Prussian blue cathode material, said manufacturing method, said manufacturing method

[0017] A step of mixing solution A and solution B to obtain a solid precipitate; and

[0018] The method includes the step of washing and drying the above-mentioned solid precipitate to obtain a Prussian blue cathode material;

[0019] The above solution A comprises a carbonaceous material, sodium ferrocyanide, and a first solvent;

[0020] The above solution B contains an iron salt, sodium citrate, and a second solvent.

[0021] In an embodiment of the present invention, the carbonaceous material may be selected from conductive carbon black, activated carbon, etc., and, for example, Ketjen black may be used.

[0022] In an embodiment of the present invention, the first solvent may comprise water and solvent A; water may be selected from deionized water; solvent A may be one or more selected from ethylene glycol, N,N-dimethylformamide, ethanol, and glycerol, for example, ethylene glycol; and the volume ratio of water to solvent A may be selected from 1:(0.01 to 100), for example, 1:(0.05 to 90), 1:(0.1 to 80), 1:(0.5 to 70), 1:(1 to 60), 1:(5 to 50), 1:(10 to 40), and 1:(20 to 30). In an embodiment of the present invention, a method for preparing the first solvent may include the step of uniformly mixing water and solvent A; Mixing is performed under stirring conditions, and the stirring time can be selected from 1 min to 100 min, for example, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min.

[0023] In an embodiment of the present invention, the concentration of sodium ferrocyanide in solution A can be selected from 0.1 g / L to 100 g / L, for example, 0.5 g / L, 1 g / L, 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, and 90 g / L.

[0024] In an embodiment of the present invention, the method for preparing solution A is,

[0025] The method may include the step of dispersing a carbonaceous material in a first solvent to obtain a dispersion, and then dissolving sodium ferrocyanide in the dispersion to obtain solution A.

[0026] In an embodiment of the present invention, ultrasonic stirring may be used for dispersion.

[0027] In an embodiment of the present invention, the iron salt may be one or more selected from divalent iron salts, for example, FeSO4·7H2O, Fe(NO3)2, and FeCl2·4H2O.

[0028] In an embodiment of the present invention, sodium citrate may be one or more selected from anhydrous sodium citrate, sodium citrate dihydrate, and sodium citrate pentahydrate.

[0029] In an embodiment of the present invention, the second solvent may comprise water and solvent B; water may be selected from deionized water; solvent B may be one or more selected from ethylene glycol, N,N-dimethylformamide, ethanol, and glycerol, for example, ethylene glycol; and the volume ratio of water and solvent B may be selected from 1:(0.01~100), for example 1:(0.05~90), 1:(0.1~80), 1:(0.5~70), 1:(1~60), 1:(5~50), 1:(10~40), and 1:(20~30). In an embodiment of the present invention, a method for preparing the second solvent may include the step of uniformly mixing water and solvent B; Mixing is performed under stirring conditions, and the stirring time can be selected from 1 min to 100 min, for example, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min.

[0030] In an embodiment of the present invention, the method for preparing solution B is,

[0031] It may include the step of obtaining solution B by dissolving iron salt and sodium citrate in a second solvent.

[0032] In an embodiment of the present invention, a uniform solution B can be obtained through stirring and dissolution.

[0033] In an embodiment of the present invention, the molar ratio of a carbonaceous material to sodium ferrocyanide can be selected from 1:(1 to 100), for example, 1:(5 to 90), 1:(10 to 80), 1:(20 to 70), 1:(30 to 60), and 1:(40 to 50); the molar ratio of sodium ferrocyanide to an iron salt can be selected from 1:(1 to 3), for example, 1:2; and the molar ratio of an iron salt to sodium citrate can be selected from 1:(1 to 100), for example, 1:(5 to 90), 1:(10 to 80), 1:(20 to 70), 1:(30 to 60), and 1:(40 to 50); The volume ratio of solution A to solution B can be selected from 1:(0.1~10), e.g. 1:(0.5~9), 1:(1~8), 1:(2~7), 1:(3~6), 1:(4~5).

[0034] In an embodiment of the present invention, sodium ferrocyanide is sparingly soluble in both solvent A and solvent B, and the action of solvent A and solvent B controls solubility and reaction rate to control defect formation during the crystal growth process.

[0035] In an embodiment of the present invention, mixing may be adding solution A dropwise to solution B or adding solution B dropwise to solution A; the dropwise addition rate may be selected from 0.1 mL / min to 100 mL / min, for example, 0.5 mL / min, 1 mL / min, 10 mL / min, 20 mL / min, 30 mL / min, 40 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min.

[0036] In an embodiment of the present invention, the action of mixing solution A and solution B controls the dissolution rate and the reaction rate.

[0037] In an embodiment of the present invention, mixing may be a reaction; the mixing temperature may be selected from 5°C to 100°C, for example, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, and 90°C; the mixing may be performed under stirring conditions, and the stirring speed may be selected from 100 rpm to 1500 rpm, for example, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, and 1400 rpm; and the mixing time may be selected from 12h to 72h, for example, 24h, 36h, 48h, and 60h.

[0038] In an embodiment of the present invention, the washing reagent may be selected from water or ethanol, and the water may be selected from deionized water; the ethanol may be selected from anhydrous ethanol; washing may be performed using water and ethanol alternately, and the number of water washes may be two, and the number of ethanol washes may be one.

[0039] In an embodiment of the present invention, the drying temperature may be selected from 60°C to 120°C, for example, 70°C, 80°C, 90°C, 100°C, and 110°C; and the drying time may be greater than 2h.

[0040] In an embodiment of the present invention, the method for manufacturing a Prussian blue cathode material is,

[0041] Deionized water and ethylene glycol are stirred and uniformly mixed in a volume ratio of 1:(0.01~50), with a stirring time of 10~60 minutes; then, Ketjen black is added to the mixture and ultrasonic stirring is performed until uniformly dispersed; then, the raw material sodium ferrocyanide (Na4Fe(CN)6·10H2O) is added to the dispersion and stirred for 30 minutes to obtain a sodium ferrocyanide dispersion with a concentration of 5g / L~50g / L; In addition, a step of weighing the divalent iron salt and sodium citrate according to the ratio of the amount of material of the divalent iron salt to sodium citrate 1:(0.01~100) and the ratio of the amount of material of the sodium ferrocyanide to the total metal salt 1:(1~2), adding them to a certain volume of a mixed solution of deionized water and ethylene glycol, ensuring that the volume ratio of the sodium ferrocyanide dispersion to the mixed metal salt solution is 1:(0.1~10), and then stirring and sufficiently dissolving to obtain a transparent mixed metal salt solution;

[0042] A step of slowly adding the mixed solution obtained above dropwise to another mixed solution through a constant pressure funnel or peristaltic pump at a dropwise addition rate of 1 mL / min to 100 mL / min, and simultaneously reacting for 12 to 72 hours at a reaction temperature of 5℃ to 100℃ with a stirring speed of 100 rpm to 1500 rpm, and then filtering or centrifuging to obtain a blue Prussian blue precipitate; and

[0043] The method may include the step of obtaining the Prussian blue cathode material for the sodium ion battery of the present invention by washing the Prussian blue precipitate obtained above thoroughly with a detergent, then placing it in a vacuum oven at 60℃ to 120℃ and drying it for a drying time > 2h.

[0044] In an embodiment of the present invention, the divalent iron salt is one or more selected from FeSO4·7H2O, Fe(NO3)2 or FeCl2·4H2O, and the sodium citrate is one or more selected from anhydrous sodium citrate, sodium citrate dihydrate, and sodium citrate pentahydrate; and the detergent is selected from deionized water or anhydrous ethanol.

[0045] The present invention also provides a Prussian blue cathode material comprising a Prussian blue compound having the following general chemical formula, and

[0046] Na x Fe[Fe(CN)6] y ·nH2O Formula I,

[0047] In Equation I, x is 0.01 to 3, and 0 <y<1이며,

[0048] n is 0.01 to 3.5.

[0049] When the Prussian blue cathode material according to the present invention is applied to a sodium ion battery, it is advantageous for improving the performance of the sodium ion battery in terms of specific capacity, Coulomb efficiency, scaling performance, and long cycle stability.

[0050] The present invention also provides a method for manufacturing a Prussian blue cathode material, said manufacturing method, said manufacturing method

[0051] A step of obtaining a solid precipitate by mixing a first dispersion and a second dispersion; and

[0052] The method includes the step of washing and drying the above-mentioned solid precipitate to obtain a Prussian blue anode material.

[0053] Here, the first dispersion comprises a ferrocyanide source, a first sodium source, and a first dispersant;

[0054] The second dispersion above includes a divalent iron source, a complexing agent, and a second dispersant.

[0055] The method for manufacturing a Prussian blue cathode material according to the present invention is to obtain a Prussian blue cathode material by mixing a ferrocyanide source, a first sodium source, and a divalent iron source and co-precipitating them to produce a Prussian blue compound, wherein the addition of a complexing agent causes a strong complexing reaction with the ferrous ion provided by the divalent iron source, thereby controlling the rate of formation of the Prussian blue compound, reducing defects in the Prussian blue compound, improving the yield of the Prussian blue compound, and improving the performance of the Prussian blue cathode material, and thus is advantageous for improving performance such as cycle stability, specific capacity, Coulomb efficiency, and magnification performance of a sodium ion battery using the manufactured Prussian blue cathode material.

[0056] The present invention also provides an anode plate comprising the aforementioned Prussian blue anode material; or, a Prussian blue anode material obtained by the method for manufacturing the aforementioned Prussian blue anode material.

[0057] The anode plate according to an embodiment of the present invention comprises the aforementioned Prussian blue anode material or a Prussian blue anode material obtained by the method of manufacturing the aforementioned Prussian blue anode material, and when applied to a sodium ion battery, it is advantageous for improving the performance of the sodium ion battery in terms of specific capacity, Coulomb efficiency, magnification performance, and long cycle stability.

[0058] The present invention provides a sodium ion battery comprising: a Prussian blue cathode material according to the technical solution; a Prussian blue cathode material manufactured by the method according to the technical solution; or a cathode plate according to the technical solution.

[0059] In an embodiment of the present invention, the sodium ion battery comprises a positive electrode, a negative electrode, a separator, and an electrolyte.

[0060] In an embodiment of the present invention, the method for manufacturing the anode is,

[0061] A step of obtaining a slurry by mixing a cathode material, a binder, a conductive agent, and a solvent; and

[0062] The method may include the step of applying the above slurry to an aluminum foil and then drying it to obtain an anode.

[0063] In an embodiment of the present invention, the cathode material is a Prussian blue cathode material according to the technical solution; the binder may be selected from polyvinylidene fluoride (PVDF); the conductive agent may be selected from Super P; the mass ratio of the cathode material, binder, and conductive agent may be selected from (6~8):(1~3):(0.5~1.5), or from (6.5~7.5):(1.5~2.5):(0.8~1.2), and may be 7:2:1; and the solvent is selected from dimethylpyrrolidone.

[0064] In an embodiment of the present invention, the cathode may be selected from metallic sodium; the separator may be selected from a glass fiber membrane; and the electrolyte may be selected from 1.0 mol / L NaClO4 / EC (ethylene carbonate) + PC (polycarbonate) + FEC (fluoroethylene carbonate) (EC:PC:FEC = 0.45:0.45:0.05, vol).

[0065] In an embodiment of the present invention, a CR2032 button cell battery can be assembled with an anode, a cathode, a separator, and an electrolyte inside a glove box.

[0066] The present invention provides a high-capacity, high-magnification Prussian blue cathode material for sodium ion batteries, wherein the chemical composition of the cathode material is Na xFe[Fe(CN)]6·nH2O has a stable and highly dispersible hierarchical structure (through scanning electron microscopy, it can be observed that the Prussian blue material is not a regular cube but a quasi-cubic shape formed by stacked layers), thereby ensuring high magnification performance and good cycle stability. The method for manufacturing the Prussian blue cathode material for sodium-ion batteries according to the present invention is suitable for industrialization and widespread adoption because the raw material cost is low, the manufacturing process is simple, control is easy, and energy consumption is low.

[0067] The present invention provides a normal-phase Prussian blue cathode material for a sodium ion battery, wherein the cathode material of the present invention is an Fe-based Prussian blue material, and its general chemical formula is Na x The present invention utilizes the characteristic that sodium ferrocyanide is sparingly soluble in organic solvents and easily soluble in water to induce differences in the solubility of sodium ferrocyanide in mixed solvents with different volume ratios of organic solution to water, thereby causing the reaction system to exhibit two phases, solid and liquid, and forming a new synthesis mechanism for Prussian blue; since an organic solvent is present in the reaction system, the reaction rate between each ion is slowed down to some extent; and an excess amount of sodium citrate not only causes strong complexing with ferros ions but also effectively increases the content of sodium ions in the solution, significantly delaying the formation rate of precipitates and effectively increasing the content of sodium ions in the elemental composition of the precipitates. By combining the above characteristics, the reaction mechanism of the present invention can effectively control the formation rate of Prussian blue and effectively increase the yield; thus, Prussian blue produced by the method according to the present invention has fewer defects and a higher yield.

[0068] The reaction mechanism of the Prussian blue cathode material for a sodium ion battery according to the present invention is as follows: first, a small amount of solid sodium ferrocyanide is partially dissolved in an organic solvent to form Na +and [Fe(CN)6] 4- After generating ions, Na + and [Fe(CN)6] 4 and water-soluble Fe 2+ a includes causing a co-precipitation reaction in the liquid phase. In the two-phase synthesis manufacturing process, the novel synthesis mechanism of Prussian blue helps to slow down the reaction rate and control the crystal growth process. Since it tends to grow on the surface of the precipitate formed when Prussian blue crystals are formed, the manufactured Prussian blue is a stable and highly dispersible hierarchical micro-nano structure assembled into micron cubes. It possesses characteristics such as appropriate grain size, a large specific surface area, and a high sodium ion migration velocity, thereby ensuring high magnification performance and good cycle stability. According to the study of specific embodiments, the 200-cycle capacity of the battery obtained in the present invention is 100 mA g -1 It is greater than, and the specific capacity after 800 cycles is 84 mA g -1 In the present invention, a certain amount of Ketjen black is added to a Prussian blue cathode material for sodium ion batteries to significantly improve the disadvantage of low conductivity of a single Prussian blue cathode material. Furthermore, since Ketjen black is a general conductive carbon black, it is difficult to obtain and costs can be controlled. The raw materials used in the method according to the present invention are inexpensive and easy to obtain, the synthesis process is safe and controllable, energy consumption is low, and the difficulty of recovering waste liquid generated in the reaction system is low, thus having large-scale production capacity. Brief explanation of the drawing

[0069] Part (a) of Fig. 1 is the X-ray diffraction pattern of the cathode material prepared in Example 1. Part (b) of Fig. 1 is a scanning electron microscope image of the cathode material prepared in Example 1. Part (a) of Fig. 2 is the X-ray diffraction pattern of the cathode material prepared in Example 2. Part (b) of Fig. 2 is a scanning electron microscope image of the cathode material prepared in Example 2. Part (a) of Fig. 3 is the X-ray diffraction pattern of the cathode material prepared in Example 3. Part (b) of Fig. 3 is a scanning electron microscope image of the cathode material prepared in Example 3. Part (a) of Fig. 4 is the X-ray diffraction pattern of the cathode material prepared in Comparative Example 1. Part (b) of Fig. 4 is a scanning electron microscope image of the cathode material prepared in Comparative Example 1. Part (a) of Fig. 5 is the X-ray diffraction pattern of the cathode material prepared in Comparative Example 2. Part (b) of Fig. 5 is a scanning electron microscope image of the cathode material prepared in Comparative Example 2. Figure 6 is a charge / discharge performance diagram of the cathode material prepared in Example 1. Part (a) of Fig. 7 is the charge / discharge performance of the cathode material prepared in Example 2. Part (b) of Fig. 7 is a magnification performance diagram of the cathode material prepared in Example 2. Part (c) of Fig. 7 is the cycle performance diagram of the cathode material prepared in Example 2. Figure 8 is a charge / discharge performance diagram of the cathode material prepared in Example 3. Figure 9 is a charge / discharge performance graph of the cathode material prepared in Comparative Example 1. Figure 10 is a charge / discharge performance graph of the cathode material prepared in Comparative Example 2. Specific details for implementing the invention

[0070] Hereinafter, the technical means of the embodiments of the present invention will be described clearly and completely. It is obvious that the described embodiments are only some of the embodiments of the present invention and not all of them. All other embodiments obtained by a person skilled in the art without creative effort based on the embodiments of the present invention fall within the scope of protection of the present invention.

[0071] An embodiment of the present invention provides a Prussian blue cathode material comprising a Prussian blue compound having the following general chemical formula, and

[0072] Na x Fe[Fe(CN)6] y ·nH2O Formula I

[0073] In Equation I, x is 0.01 to 3, and 0 <y<1이며,

[0074] n is 0.01 to 3.5.

[0075] When the Prussian blue cathode material according to the present invention is applied to a sodium ion battery, it is advantageous for improving the performance of the sodium ion battery in terms of specific capacity, Coulomb efficiency, scaling performance, and long cycle stability.

[0076] In some embodiments, x may be selected from any value between 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, or between 0.01 and 3. Preferably, when x < 1.5, the Na ion content is low, which corresponds to a sodium-deficient state, and the reaction rate is fast, which is advantageous for reducing lattice defects and moisture content of the Prussian blue compound, thus providing better performance and being advantageous for improving performance such as cycle stability, specific capacity, Coulomb efficiency, and magnification performance of a sodium-ion battery using the Prussian blue cathode material. More preferably, when x < 1, the Prussian blue compound is further controlled to a sodium-deficient state, the reaction rate is further accelerated, and the lattice defects and moisture content of the Prussian blue compound are reduced, which is advantageous for further improving performance such as cycle stability, specific capacity, Coulomb efficiency, and magnification performance of a sodium-ion battery using the Prussian blue cathode material. At the same time, when x > 0.5, the sodium ion content of the Prussian blue compound is controlled to a more appropriate range, so it is more advantageous to improve performance such as cycle stability, specific capacity, Coulomb efficiency, and magnification performance of a sodium ion battery using the Prussian blue cathode material.

[0077] In some embodiments, n can be selected from any value between 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.1, 3.2, or between 0.01 and 3.5, so that better performance can be obtained by controlling the moisture content of the Prussian blue compound, which is advantageous for improving performance such as cycle stability, specific capacity, Coulomb efficiency, and magnification performance of a sodium ion battery using the Prussian blue cathode material.

[0078] In some embodiments, 0 <y<1, y는 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.5, 0.6, 0.65, 0.7, 0.8, 0.85, 0.9, 0.93, 0.95, 0.97, 0.99, 또는 0 초과 1 미만 사이의 임의의 값으로부터 선택될 수 있다.

[0079] In some embodiments, y may be represented as y=1-δ, wherein δ represents the vacancy content of ferrocyanide ions. Here, 0<δ<1, and δ may be selected from 0.01, 0.02, 0.03, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.5, 0.6, 0.7, 0.8, 0.9, etc.

[0080] Preferably, 0.8 <y<1, 즉, 0<δ<0.2이므로, 상기 프러시안 블루 화합물의 격자 결함이 적은 상태로 제어되고, 상기 프러시안 블루 화합물의 성능이 개선되어 상기 프러시안 블루 양극재를 응용하는 나트륨 이온 전지의 사이클 안정성, 비용량, 쿨롱 효율, 배율 성능 등 성능을 향상시키는 데 유리하다.

[0081] In some embodiments, where y is represented as y=1-δ, the general chemical formula of the Prussian blue compound may be represented by the following Formula II, and

[0082] Na x Fe[Fe(CN)6] 1-δ Y δ ·nH2O Formula II

[0083] Here, Y represents the void of the ferrocyanide ion. The range of values ​​for x, n, and δ is as described above.

[0084] In some embodiments, at least some of the crystals of the Prussian blue compound are in a quasi-cubic form; that is, when the crystals of the Prussian blue compound are observed under a scanning electron microscope, the crystals of the Prussian blue compound form a distinct cubic structure, with the difference being that the intersections of the edges of the crystals of the Prussian blue compound form an arc.

[0085] In some embodiments, at least some of the crystals of the Prussian blue compound form a sphere-like shape, and the difference from the Prussian blue compound forming a cubic shape is that when the crystals of the Prussian blue compound forming a sphere-like shape are observed under a scanning electron microscope, the edges of the crystals of the Prussian blue compound form an arc shape.

[0086] In some embodiments, the crystal size of the Prussian blue compound is 0.1 μm or more and 2.5 μm or less, and, for example, the crystal size of the Prussian blue compound may be 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.3 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.3 μm, or any other size value between 0.1 μm and 2.5 μm.

[0087] In some embodiments, the chemical formula of the Prussian blue compound is Na 0.647 Fe[Fe(CN)6] 0.93 ·2.6H2O and Na 0.517 Fe[Fe(CN)6] 0.85 Since it is at least one selected from 3.15H2O, a Prussian blue compound with excellent performance can be obtained, which is advantageous for improving the performance of sodium ion batteries using the above Prussian blue cathode material, such as cycle stability, specific capacity, Coulomb efficiency, and magnification performance.

[0088] In some embodiments, the Prussian blue cathode material further comprises a carbonaceous material, and at least a portion of the carbonaceous material is attached to the crystal surface of the Prussian blue compound. The addition of the carbonaceous material is advantageous for suppressing defects during the formation process of the Prussian blue compound and for improving the conductivity of the Prussian blue cathode material, and is advantageous for improving performance such as cycle stability, specific capacity, Coulomb efficiency, and magnification performance of a sodium ion battery using the Prussian blue cathode material.

[0089] In some embodiments, the carbonaceous material is selected from conductive carbon black materials, for example, Ketjen black. Since the conductive carbon black material is a general conductive carbon black material, it is advantageous for suppressing defects during the formation process of the Prussian blue compound, while simultaneously improving the conductivity of the Prussian blue cathode material and reducing costs.

[0090] An embodiment of the present invention also provides a method for manufacturing a Prussian blue cathode material, said manufacturing method,

[0091] Step S100 of obtaining a solid precipitate by mixing the first dispersion and the second dispersion; and

[0092] The method includes step S200 of washing and drying the above solid precipitate to obtain a Prussian blue cathode material.

[0093] Here, the first dispersion comprises a ferrocyanide source, a first sodium source, and a first dispersant;

[0094] The second dispersion above includes a divalent iron source, a complexing agent, and a second dispersant.

[0095] The method for manufacturing a Prussian blue cathode material according to the present invention is to obtain a Prussian blue cathode material by mixing a ferrocyanide source, a first sodium source, and a divalent iron source and co-precipitating them to produce a Prussian blue compound, wherein the addition of a complexing agent causes a strong complexing reaction with the ferros ions provided by the divalent iron source, thereby controlling the rate of formation of the Prussian blue compound, reducing defects in the Prussian blue compound, improving the yield of the Prussian blue compound, and improving the performance of the Prussian blue cathode material, and thus is advantageous for improving the performance of a sodium ion battery using the manufactured Prussian blue cathode material, such as cycle stability, specific capacity, Coulomb efficiency, and magnification performance.

[0096] In some embodiments, the Prussian blue cathode material produced by the method for producing the Prussian blue cathode material is as described above.

[0097] In some embodiments, step S100 is,

[0098] Step S110 of dispersing a ferrocyanide source and a first sodium source in the first dispersant to obtain a first dispersion;

[0099] Step S120 of obtaining a second dispersion by dispersing a divalent iron source and a complexing agent in the second dispersant; and

[0100] It includes step S130 of mixing the first dispersion and the second dispersion to obtain a solid precipitate.

[0101] In some embodiments, the order of steps S110 and S120 does not matter, and step S110 may be performed before step S120, step S120 may be performed before step S110, or step S110 and step S120 may be performed simultaneously.

[0102] In some embodiments, the ferrocyanide source and the first sodium source may be dispersed in the first dispersant by stirring. The stirring time may be controlled to 5 to 30 minutes, for example, 6 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or any time value between 5 and 30 minutes.

[0103] In some embodiments, the ferrocyanide source and the first sodium source are derived from sodium ferrocyanide, that is, sodium ferrocyanide provides ferrocyanide ions and sodium ions simultaneously.

[0104] In some embodiments, sodium ferrocyanide may be Na4Fe(CN)6·10H2O.

[0105] In some embodiments, the concentration of sodium ferrocyanide in the first dispersant may be 5 g / L to 50 g / L, for example, 8 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, or any concentration value between 5 g / L and 50 g / L.

[0106] In some embodiments, the first dispersant comprises deionized water and a first solvent, wherein the ferrocyanide source is sparingly soluble in the first solvent. When the ferrocyanide source is derived from sodium ferrocyanide, the first solvent is selected from a solvent in which sodium ferrocyanide is sparingly soluble. By using a solvent in which the ferrocyanide source is sparingly soluble, the reaction system exhibits two phases, solid and liquid, because the solubility of the ferrocyanide source in the mixed solvent differs. Additionally, by using an organic solvent as the first solvent, it is advantageous to slow down the reaction rate to control the rate of formation of the Prussian blue compound, reduce defects in the Prussian blue compound, and improve the yield of the Prussian blue compound.

[0107] In some embodiments, the first solvent is one or more selected from ethylene glycol, N,N-dimethylformamide, ethanol, and glycerol.

[0108] In some embodiments, the volume ratio of deionized water to the first solvent in the first dispersant is selected from 1:(0.01 to 100), for example, the volume ratio of deionized water to the first solvent in the first dispersant may be 1:0.05, 1:0.1, 1:0.2, 1:0.5, 1:1, 1:5, 1:10, 1:20, 1:50, 1:80, 1:90, or any ratio between 1:0.01 and 1:100.

[0109] In some embodiments, the first dispersant can be obtained by stirring and uniformly mixing the deionized water in the first dispersant and the first solvent. Here, the stirring time after mixing the deionized water in the first dispersant and the first solvent can be controlled to 1 minute to 100 minutes, for example, 2 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 45 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes, or any time value between 1 minute and 100 minutes.

[0110] In some embodiments, the first dispersion further comprises a carbonaceous material. The carbonaceous material is selected from conductive carbon black materials, for example, Ketjen black. Since the conductive carbon black material is a general conductive carbonaceous material, it is advantageous for suppressing defects during the formation process of the Prussian blue compound, while simultaneously improving the conductivity of the Prussian blue cathode material and reducing costs. When the first dispersion further comprises a carbonaceous material, step S110 is,

[0111] Step S111 of dispersing a carbonaceous material in the first dispersant; and

[0112] It includes the step S112 of dispersing the ferrocyanide source and the first sodium source in the first dispersant.

[0113] In some embodiments, when the first dispersion comprises the carbonaceous material, the first solvent is preferably ethylene glycol, which is advantageous for uniformly dispersing the carbonaceous material in the first dispersant.

[0114] In some embodiments, when the first dispersion comprises the carbonaceous material, the concentration of the carbonaceous material is 0.1 g / L to 10 g / L, for example, 0.2 g / L, 0.5 g / L, 1 g / L, 2 g / L, 5 g / L, 6 g / L, 8 g / L, 9 g / L, or any concentration value between 0.1 g / L and 10 g / L.

[0115] In some embodiments, the carbonaceous material can be uniformly dispersed in the first dispersant through ultrasonic dispersion. The ultrasonic dispersion time may be 5 to 30 minutes, for example, 6 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or any time value between 5 minutes and 30 minutes.

[0116] In some embodiments, the ratio of the amount of the carbonaceous material to the amount of the ferrocyanide source material is selected from 1:(0.01 to 100), for example, the ratio of the amount of the carbonaceous material to the amount of the ferrocyanide source material may be 1:0.02, 1:0.05, 1:0.08, 1:0.1, 1:0.5, 1:0.8, 1:1, 1:2, 1:5, 1:10, 1:20, 1:50, 1:60, 1:80, or any ratio between 1:0.01 and 1:100.

[0117] In some embodiments, the divalent iron source and the complexing agent can be dispersed in the second dispersant by stirring. The stirring time can be controlled to 5 to 30 minutes, for example, 6 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or any time value between 5 and 30 minutes.

[0118] In some embodiments, the divalent iron source is derived from a divalent iron salt, and the divalent iron salt is one or more selected from FeSO4·7H2O, Fe(NO3)2, and FeCl2·4H2O.

[0119] In some embodiments, the complexing agent is one or more selected from anhydrous sodium citrate, sodium citrate dihydrate, sodium citrate pentahydrate, sodium oxalate, sodium tartrate, and sodium malate. The complexing agent causes a strong complexing reaction with ferros ions provided by a divalent iron source, and when the complexing agent is selected from the compounds, the complexing agent can also be used as a second sodium source. Therefore, it is advantageous to effectively improve the sodium ion concentration in a solution mixed with the first dispersion and the second dispersion, control the generation rate of the Prussian blue compound, effectively improve the sodium ion content in the Prussian blue compound, reduce defects in the Prussian blue compound, improve the yield of the Prussian blue compound, and improve the performance of the Prussian blue cathode material, thereby improving the performance of the sodium ion battery using the manufactured Prussian blue cathode material, such as cycle stability, specific capacity, Coulomb efficiency, and scaling performance.

[0120] In some embodiments, the ratio of the amount of the material of the divalent iron source to the amount of the material of the complexing agent is selected from 1:(1 to 100), for example, the ratio of the amount of the material of the divalent iron source to the amount of the material of the complexing agent may be 1:2, 1:4, 1:5, 1:10, 1:20, 1:50, 1:60, 1:80, 1:90, or any ratio between 1:1 and 1:100.

[0121] In some embodiments, the ratio of the amount of the ferrocyanide source material to the amount of the divalent iron source material is selected from 1:(1 to 3), for example, the ratio of the amount of the ferrocyanide source material to the amount of the divalent iron source material may be 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, 1:2.8, or any ratio between 1:1 and 1:3.

[0122] In some embodiments, the second dispersant comprises deionized water and a second solvent, wherein the ferrocyanide source is sparingly soluble in the second solvent. When the ferrocyanide source is derived from sodium ferrocyanide, the second solvent is selected from a solvent in which sodium ferrocyanide is sparingly soluble. By using a solvent in which the ferrocyanide source is sparingly soluble, the reaction system exhibits two phases, solid and liquid, because the solubility of the ferrocyanide source differs in the solvent in which the first dispersion and the second dispersion are mixed. Additionally, by using an organic solvent as the second solvent, it is advantageous to slow down the reaction rate to control the rate of formation of the Prussian blue compound, reduce defects in the Prussian blue compound, and improve the yield of the Prussian blue compound.

[0123] In some embodiments, the second solvent is one or more selected from ethylene glycol, N,N-dimethylformamide, ethanol, and glycerol.

[0124] In some embodiments, the volume ratio of deionized water to the second solvent in the second dispersant is selected from 1:(0.01 to 100), for example, the volume ratio of deionized water to the second solvent in the second dispersant may be 1:0.05, 1:0.1, 1:0.2, 1:0.5, 1:1, 1:5, 1:10, 1:20, 1:50, 1:80, 1:90, or any ratio between 1:0.01 and 1:100.

[0125] In some embodiments, since the first solvent and the second solvent are the same, it is advantageous to reduce the types of solvents used in the manufacturing process and to reduce manufacturing process costs.

[0126] In some embodiments, step S130 is,

[0127] Step S131 of obtaining a mixture by mixing the first dispersion and the second dispersion; and

[0128] The method includes step S132 of obtaining the solid precipitate by allowing the mixture to stand for a first standing time after undergoing a first stirring time at a first reaction temperature.

[0129] In some embodiments, the first dispersion and the second dispersion may be mixed by dropwise addition. For example, the first dispersion may be mixed by dropwise addition to the second dispersion, or the second dispersion may be mixed by dropwise addition to the first dispersion. Here, dropwise addition may be performed using a constant pressure funnel or a peristaltic pump. The dropwise addition rate may be 1 mL / min to 100 mL / min, for example, 2 mL / min, 5 mL / min, 10 mL / min, 15 mL / min, 20 mL / min, 50 mL / min, 60 mL / min, 75 mL / min, 80 mL / min, 90 mL / min, or any dropwise addition rate value between 1 mL / min and 100 mL / min.

[0130] In some embodiments, the volume ratio of the first dispersion to the second dispersion is 1:(0.1 to 10), for example, 1:0.1, 1:0.2, 1:0.5, 1:1, 1:3, 1:5, 1:6, 1:9, or any ratio between 1:0.1 and 1:10.

[0131] In some embodiments, the first reaction temperature may be 5°C to 100°C, for example, 10°C, 15°C, 20°C, 25°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or any temperature value between 5°C and 100°C.

[0132] In some embodiments, the first stirring time may be 12 to 72 hours, for example, 18 hours, 24 hours, 36 hours, 40 hours, 48 ​​hours, 56 hours, 60 hours, 64 hours, or any time value between 12 hours and 72 hours. Within the first stirring time, the mixture may react sufficiently through stirring. The stirring speed of the mixture may be 100 rpm to 1500 rpm, for example, 200 rpm, 300 rpm, 500 rpm, 600 rpm, 800 rpm, 1000 rpm, 1200 rpm, 1300 rpm, 1400 rpm, or any stirring speed between 100 rpm and 1500 rpm.

[0133] In some embodiments, the first resting time may be 12 to 36 hours, for example, 16 hours, 20 hours, 24 hours, 28 hours, 32 hours, or any time value between 12 hours and 36 hours.

[0134] In some embodiments, the solid precipitate can be obtained by separating it through a general solid-liquid separation method, for example, suction filtration, filtration, etc.

[0135] In some embodiments, step S200 is,

[0136] Step S210 of washing the solid precipitate with a first detergent to obtain a drying object; and

[0137] The method includes step S220 of obtaining the Prussian blue cathode material by drying the above-mentioned object.

[0138] In some embodiments, the first detergent may be selected from deionized water and / or anhydrous ethanol. The solid precipitate may be washed once or multiple times (e.g., two, three times, etc.) with the first detergent to obtain the object to be dried. When the first detergent is selected from deionized water and anhydrous ethanol, the solid precipitate is washed with deionized water and anhydrous ethanol, respectively.

[0139] In some embodiments, the drying treatment may adopt a general drying method such as vacuum drying. In some embodiments, vacuum drying may be performed at a temperature of 60°C to 120°C, for example, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 98°C, 100°C, 102°C, 105°C, 108°C, or any temperature value between 90°C and 110°C; the vacuum drying time may be greater than 2 hours, and furthermore, the vacuum drying time may be 12 hours to 36 hours, for example, 16 hours, 20 hours, 24 hours, 28 hours, 32 hours, or any time value between 12 hours and 36 hours.

[0140] In some embodiments, when the first dispersion contains a carbonaceous material, at least a portion of the carbonaceous material is attached to the crystal surface of the Prussian blue compound. That is, the Prussian blue anode material comprises a Prussian blue compound and the carbonaceous material, of which at least a portion is attached to the crystal surface of the Prussian blue compound.

[0141] A method for manufacturing a Prussian blue cathode material according to an embodiment of the present invention is to obtain a Prussian blue cathode material by mixing a ferrocyanide source, a first sodium source, and a divalent iron source and co-precipitating them to produce a Prussian blue compound, wherein the addition of a complexing agent causes a strong complexing reaction with the ferros ions provided by the divalent iron source, thereby controlling the rate of formation of the Prussian blue compound, reducing defects in the Prussian blue compound, improving the yield of the Prussian blue compound, and improving the performance of the Prussian blue cathode material, and thus is advantageous for improving performance such as cycle stability, specific capacity, Coulomb efficiency, and magnification performance of a sodium ion battery using the manufactured Prussian blue cathode material.

[0142] An embodiment of the present invention also provides an anode plate comprising the aforementioned Prussian blue anode material; or, a Prussian blue anode material obtained by the method for manufacturing the aforementioned Prussian blue anode material.

[0143] The anode plate according to an embodiment of the present invention comprises the aforementioned Prussian blue anode material or a Prussian blue anode material obtained by the method of manufacturing the aforementioned Prussian blue anode material, and when applied to a sodium ion battery, it is advantageous for improving the performance of the sodium ion battery in terms of specific capacity, Coulomb efficiency, magnification performance, and long cycle stability.

[0144] An embodiment of the present invention also provides a sodium ion battery comprising the aforementioned Prussian blue cathode material, or a Prussian blue cathode material obtained by the method of manufacturing the aforementioned Prussian blue cathode material, or the aforementioned cathode plate.

[0145] A sodium ion battery according to an embodiment of the present invention includes the aforementioned Prussian blue cathode material or the Prussian blue cathode material obtained by the method of manufacturing the aforementioned Prussian blue cathode material or the aforementioned cathode plate, thereby improving performance in terms of specific capacity, Coulomb efficiency, magnification performance, and long cycle stability.

[0146] In some embodiments, the sodium ion battery comprises a positive plate, a negative plate, a separator, and an electrolyte.

[0147] In some embodiments, the method for manufacturing the anode plate is,

[0148] A step of obtaining a slurry by mixing a Prussian blue cathode material, a binder, a conductive agent, and a solvent; and

[0149] The method may include the step of applying the above slurry to an aluminum foil and then drying it to obtain an anode plate.

[0150] In some embodiments, the cathode material is the aforementioned Prussian blue cathode material; the binder may be selected from polyvinylidene fluoride (PVDF); the conductive agent may be selected from Super P (conductive carbon black); the mass ratio of the cathode material, binder, and conductive agent may be selected from (6-8):(1-3):(0.5-1.5), or from (6.5-7.5):(1.5-2.5):(0.8-1.2), or 7:2:1; and the solvent is selected from dimethylpyrrolidone.

[0151] In some embodiments, the cathode may be selected from metallic sodium; the separator may be selected from a glass fiber membrane; and the electrolyte may be selected from 1.0 mol / L NaClO4 / EC (ethylene carbonate) + PC (polycarbonate) + FEC (fluoroethylene carbonate) (the volume ratio of EC:PC:FEC is 0.45:0.45:0.05).

[0152] In some embodiments, a CR2032 button cell battery can be assembled with an anode, a cathode, a separator, and an electrolyte inside a glove box.

[0153] While some specific examples are listed below, it should be noted that the examples described below are illustrative and are intended only to interpret the invention and should not be understood as limiting the invention. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature of the art or product descriptions shall apply. Where the manufacturer of the reagents or equipment used is not indicated, they are all general products available on the market.

[0154] Example 1

[0155] 100 mg of Ketjen black was weighed and added to a mixed solution of 100 mL of deionized water and ethylene glycol (volume ratio of deionized water to ethylene glycol: 3:1), and ultrasonically stirred for 5 to 30 minutes to obtain a uniformly dispersed solution, then 0.968 g of sodium ferrocyanide (Na4Fe(CN)6·10H2O) was weighed and added to it, and stirred for 5 to 30 minutes to obtain a 9.68 g / L sodium ferrocyanide dispersion; additionally, 5 g of anhydrous sodium citrate and 0.834 g of ferrous sulfate (FeSO4·7H2O) were weighed and dissolved in a mixed solution of 100 mL of deionized water and ethylene glycol (volume ratio of deionized water to ethylene glycol: 3:1), then stirred and dissolved to obtain a transparent mixed metal salt solution.

[0156] The mixed metal salt solution obtained above was slowly added dropwise to a sodium ferrocyanide dispersion through a constant pressure funnel at 25°C at a dropwise addition rate of 3.33 mL / min. After the addition was complete, the mixture was stirred at 500 rpm at 25°C for 4 hours, then allowed to stand for 24 hours. After the standing was complete, the mixture was filtered by suction to obtain a blue Prussian blue precipitate.

[0157] The obtained Prussian blue precipitate is washed alternately with water and ethanol, washing twice with water and once with ethanol until impurities are completely removed; and then vacuum dried at 100°C for 24 hours to obtain a Prussian blue cathode material for a sodium ion battery, wherein the chemical formula of the Prussian blue compound is Na 0.647 Fe[Fe(CN)6] 0.93 Y 0.07 ·2.6H2O (molecular formula confirmed using XRD detection), meaning the chemical formula of the Prussian blue compound is Na 0.647 Fe[Fe(CN)6] 0.93 It is ·2.6H2O.

[0158] Example 2

[0159] 200 mg of Ketjen black was weighed and added to a mixed solution of 100 mL of deionized water and ethylene glycol (volume ratio of deionized water to ethylene glycol is 2:1), and ultrasonically stirred for 5 to 30 minutes to obtain a uniformly dispersed solution, then 0.968 g of sodium ferrocyanide (Na4Fe(CN)6·10H2O) was weighed and added to it, and stirred for 5 to 30 minutes to obtain a 9.68 g / L sodium ferrocyanide dispersion; additionally, 5 g of anhydrous sodium citrate and 0.834 g of ferrous sulfate (FeSO4·7H2O) were weighed and dissolved in a mixed solution of 100 mL of deionized water and ethylene glycol (volume ratio of deionized water to ethylene glycol is 2:1), then stirred and dissolved to obtain a transparent mixed metal salt solution.

[0160] The mixed metal salt solution obtained above was slowly added dropwise to a sodium ferrocyanide dispersion through a constant pressure funnel at 25°C at a dropwise addition rate of 3.33 mL / min. After the addition was complete, the mixture was stirred at 500 rpm at 25°C for 4 hours, then allowed to stand for 24 hours. After the standing was complete, the mixture was filtered by suction to obtain a blue Prussian blue precipitate.

[0161] The Prussian blue precipitate obtained above is washed alternately with water and ethanol, washing twice with water and once with ethanol until impurities are completely removed; then, it is vacuum dried at 100°C for 24 hours to obtain a Prussian blue cathode material for a sodium-ion battery, wherein the chemical formula of the Prussian blue compound is Na 0.647 Fe[Fe(CN)6] 0.93 Y 0.07 Since ·2.6H2O, that is, the chemical formula of the Prussian blue compound is Na 0.647 Fe[Fe(CN)6] 0.93 It is ·2.6H2O.

[0162] Example 3

[0163] 0.968 g of sodium ferrocyanide (Na4Fe(CN)6·10H2O) was weighed and added to a mixed solution of 100 mL of deionized water and ethylene glycol (volume ratio of deionized water to ethylene glycol 1:1) and stirred for 5 to 30 minutes to obtain a dispersion of 9.68 g / L of sodium ferrocyanide; in addition, 5 g of anhydrous sodium citrate and 0.834 g of ferrous sulfate (FeSO4·7H2O) were weighed and dissolved in a mixed solution of 100 mL of deionized water and ethylene glycol (volume ratio of deionized water to ethylene glycol 1:1), then stirred and dissolved to obtain a transparent mixed metal salt solution.

[0164] The mixed metal salt solution obtained above was slowly added dropwise to a sodium ferrocyanide dispersion through a constant pressure funnel at 25°C at a dropwise addition rate of 3.33 mL / min. After the addition was complete, the mixture was stirred at 500 rpm at 25°C for 4 hours, then allowed to stand for 24 hours. After the standing was complete, the mixture was filtered by suction to obtain a blue Prussian blue precipitate.

[0165] The Prussian blue precipitate obtained above is washed alternately with water and ethanol, washing twice with water and once with ethanol until impurities are completely removed; then, it is vacuum dried at 100°C for 24 hours to obtain a Prussian blue cathode material for a sodium-ion battery, wherein the chemical formula of the Prussian blue compound is Na 0.517 Fe[Fe(CN)6] 0.85 □ 0.15 Since ·3.15H2O, that is, the chemical formula of the Prussian blue compound is Na 0.517 Fe[Fe(CN)6] 0.85 It is 3.15H2O.

[0166] Comparative Example 1

[0167] 100 mg of Ketjen black was weighed and added to 100 mL of deionized water and ultrasonically stirred for 5 to 30 minutes to obtain a uniformly dispersed dispersion, then 0.968 g of sodium ferrocyanide (Na4Fe(CN)6·10H2O) was weighed and added to the solution and stirred for 5 to 30 minutes to obtain a 9.68 g / L sodium ferrocyanide dispersion; additionally, 5 g of anhydrous sodium citrate and 0.834 g of ferrous sulfate (FeSO4·7H2O) were weighed and dissolved in 100 mL of deionized water, then stirred and dissolved to obtain a transparent mixed metal salt solution.

[0168] The mixed metal salt solution obtained above was slowly added dropwise to a sodium ferrocyanide dispersion through a constant pressure funnel at 25°C at a dropwise addition rate of 3.33 mL / min. After the addition was complete, the mixture was stirred at 500 rpm at 25°C for 4 hours, then allowed to stand for 24 hours. After the standing was complete, the mixture was filtered by suction to obtain a blue Prussian blue precipitate.

[0169] The Prussian blue precipitate obtained above was washed alternately with water and ethanol, twice with water and once with ethanol until impurities were completely removed; and then vacuum dried at 100°C for 24 hours to obtain a Prussian blue cathode material for a sodium ion battery.

[0170] Comparative Example 2

[0171] 200 mg of Ketjen black was weighed and added to 100 mL of deionized water and ultrasonically stirred for 5 to 30 minutes to obtain a uniformly dispersed dispersion, then 0.968 g of sodium ferrocyanide (Na4Fe(CN)6·10H2O) was weighed and added to the solution and stirred for 5 to 30 minutes to obtain a 9.68 g / L sodium ferrocyanide dispersion; additionally, 5 g of anhydrous sodium citrate and 0.834 g of ferrous sulfate (FeSO4·7H2O) were weighed and dissolved in 100 mL of deionized water, then stirred and dissolved to obtain a transparent mixed metal salt solution.

[0172] The mixed metal salt solution obtained above was slowly added dropwise to a sodium ferrocyanide dispersion through a constant pressure funnel at 25°C at a dropwise addition rate of 3.33 mL / min. After the addition was complete, the mixture was stirred at 500 rpm at 25°C for 4 hours, then allowed to stand for 24 hours. After the standing was complete, the mixture was filtered by suction to obtain a blue Prussian blue precipitate.

[0173] The Prussian blue precipitate obtained above was washed alternately with water and ethanol, twice with water and once with ethanol until impurities were completely removed; and then vacuum dried at 100°C for 24 hours to obtain a Prussian blue cathode material for a sodium ion battery.

[0174] Performance detection

[0175] (1) X-ray diffraction (XRD) test

[0176] Tests were performed using a D8 Focus type X-ray powder diffractometer from Bruker, Germany, with Cu-Kα as the radiation source and a wavelength of 1.5046λ; a Ni filter was used, the tube flow was 40 mA, the tube pressure was 40 KV, the scan range was 5°–90°, the scan speed was 5° / min, and the step size was 0.05°. The cathode materials prepared in the examples and comparative examples were placed on a glass slide, flattened, and the glass slide was embedded in the center of the experimental tank of the apparatus for testing; the phase identification and crystal structure information of the material were analyzed using JADE 6.0 software.

[0177] (2) Scanning electron microscope characterization

[0178] The morphology of the material was observed using an SU-3500 type scanning electron microscope tester manufactured by HITACHI at an acceleration voltage of 15 KV.

[0179] The detection results are as follows.

[0180] Part (a) of FIG. 1 is the X-ray diffraction pattern of the semi-spherical Prussian blue cathode material for a sodium-ion battery prepared in Example 1, where the X-axis is the X-ray scanning angle 2θ and the vertical axis is the X-ray intensity. As can be seen in FIG. 1, the Prussian blue cathode material has a characteristic peak on the (200) crystal plane at a scanning angle of 16.92°, a characteristic peak on the (220) crystal plane at a scanning angle of 24.12°, a characteristic peak on the (400) crystal plane at a scanning angle of 34.18°, a characteristic peak on the (420) crystal plane at a scanning angle of 38.56°, a characteristic peak on the (422) crystal plane at a scanning angle of 42.46°, a characteristic peak on the (440) crystal plane at a scanning angle of 49.39°, a characteristic peak on the (600) crystal plane at a scanning angle of 52.78°, and a characteristic peak on the (620) crystal plane at a scanning angle of 55.77°. The presence of a peak, belonging to the Fm-3m space group, and the absence of impurity peaks in the X-ray diffraction pattern indicate that the corresponding cathode material is a normal-phase material.

[0181] Part (b) of Fig. 1 is a scanning electron microscope image of the Prussian blue cathode material for a sodium ion battery prepared in Example 1, and it can be observed that the Prussian blue cathode material has a cubic block structure composed of nano-grade cubic crystal grains, and the size of the nano-cubes is about 2 μm.

[0182] Part (a) of FIG. 2 is the X-ray diffraction pattern of the Prussian blue cathode material for a sodium-ion battery prepared in Example 2, where the X-axis is the X-ray scanning angle 2θ and the vertical axis is the X-ray intensity. As can be seen from this, the Prussian blue cathode material has a characteristic peak on the (200) crystal plane at a scanning angle of 16.88°, a characteristic peak on the (220) crystal plane at a scanning angle of 24.06°, a characteristic peak on the (400) crystal plane at a scanning angle of 34.1°, a characteristic peak on the (420) crystal plane at a scanning angle of 38.42°, a characteristic peak on the (422) crystal plane at a scanning angle of 42.38°, a characteristic peak on the (440) crystal plane at a scanning angle of 49.4°, a characteristic peak on the (600) crystal plane at a scanning angle of 52.62°, and a characteristic peak on the (620) crystal plane at a scanning angle of 55.67°. It belongs to the Fm-3m space group, and the absence of impurity peaks in the X-ray diffraction pattern indicates that the corresponding cathode material is a normal-phase material.

[0183] Part (b) of Fig. 2 is a scanning electron microscope image of the Prussian blue cathode material for a sodium ion battery obtained in Example 2, and it can be observed that the Prussian blue material has a porous hierarchical semi-spherical structure composed of nanocubes, the size of the nanocubes is about 100 nm, the size of the hierarchical semi-spherical structure is about 2 μm, and the dispersibility is good.

[0184] Part (a) of FIG. 3 is the X-ray diffraction pattern of the Prussian blue cathode material for a sodium-ion battery prepared in Example 3, where the X-axis is the X-ray scanning angle 2θ and the vertical axis is the X-ray intensity. As can be seen from this, the Prussian blue cathode material has a characteristic peak on the (200) crystal plane at a scanning angle of 17.48°, a characteristic peak on the (220) crystal plane at a scanning angle of 24.84°, a characteristic peak on the (400) crystal plane at a scanning angle of 34.44°, a characteristic peak on the (420) crystal plane at a scanning angle of 38.53°, a characteristic peak on the (422) crystal plane at a scanning angle of 42.03°, a characteristic peak on the (440) crystal plane at a scanning angle of 49.61°, a characteristic peak on the (600) crystal plane at a scanning angle of 50.94°, and a characteristic peak on the (620) crystal plane at a scanning angle of 55.67°. It belongs to the Fm-3m space group, and the absence of impurity peaks in the X-ray diffraction pattern indicates that the corresponding cathode material is a normal-phase material.

[0185] Part (b) of Fig. 3 is a scanning electron microscope image of the Prussian blue cathode material for a sodium ion battery prepared in Example 3, and it can be observed that the Prussian blue material has a structure composed of nanocubic particles, but is somewhat broken, and the nanocubic particle size is 500 nm.

[0186] Part (a) of FIG. 4 is the X-ray diffraction pattern of the cubic Prussian blue cathode material for a sodium-ion battery prepared in Comparative Example 1, where the X-axis is the X-ray scanning angle 2θ and the vertical axis is the intensity of the X-ray; As can be seen from this, the Prussian blue cathode material has a characteristic peak on the (200) crystal plane at a scanning angle of 16.94°, a characteristic peak on the (220) crystal plane at a scanning angle of 24.08°, a characteristic peak on the (400) crystal plane at a scanning angle of 34.34°, a characteristic peak on the (420) crystal plane at a scanning angle of 38.56°, a characteristic peak on the (422) crystal plane at a scanning angle of 42.38°, a characteristic peak on the (440) crystal plane at a scanning angle of 49.4°, a characteristic peak on the (600) crystal plane at a scanning angle of 52.36°, and a characteristic peak on the (620) crystal plane at a scanning angle of 55.67°, belongs to the Fm-3m space group, and there are no impurity peaks in the X-ray diffraction pattern, indicating that the cathode material is a normal phase material.

[0187] Part (b) of Fig. 4 is a scanning electron microscope image of a cubic Prussian blue cathode material for a sodium ion battery prepared in Comparative Example 1, and it can be observed that the shape of the Prussian blue material is a cubic shape aggregated by nanoparticles, and the nanoparticle size is about 1 μm.

[0188] Part (a) of FIG. 5 is the X-ray diffraction pattern of the Prussian blue cathode material for a sodium-ion battery prepared in Comparative Example 2, where the X-axis is the X-ray scanning angle 2θ and the vertical axis is the intensity of the X-ray; As can be seen from this, the Prussian blue cathode material has a characteristic peak on the (200) crystal plane at a scanning angle of 16.82°, a characteristic peak on the (220) crystal plane at a scanning angle of 23.96°, a characteristic peak on the (400) crystal plane at a scanning angle of 34.1°, a characteristic peak on the (420) crystal plane at a scanning angle of 38.35°, a characteristic peak on the (422) crystal plane at a scanning angle of 42.19°, a characteristic peak on the (440) crystal plane at a scanning angle of 49.17°, a characteristic peak on the (600) crystal plane at a scanning angle of 52.26°, and a characteristic peak on the (620) crystal plane at a scanning angle of 55.42°, belongs to the Fm-3m space group, and there are no impurity peaks in the X-ray diffraction pattern, indicating that the cathode material is a normal phase material.

[0189] Part (b) of Fig. 5 is a scanning electron microscope image of the Prussian blue cathode material for a sodium ion battery prepared in Comparative Example 2, and it can be observed that the Prussian blue material has a cubic block structure composed of nanocubic particles, and the size of the nanocubic particles is about 1 μm.

[0190] As can be seen from the XRD diffraction results of the example and comparative example, the diffraction peak intensity of the Prussian blue material prepared in the example is stronger than that of the comparative example, the crystallinity of the material prepared in the example is higher, and the quality is superior.

[0191] At the same time, the small particle material attached to the surface of the Prussian blue compound shown in Fig. 1(b) and Fig. 2(b) indicates that at least a portion of the Ketjen black added in Examples 1 and 2 is attached to the surface of the Prussian blue compound in the manufactured Prussian blue cathode material.

[0192] The Prussian blue cathode material for sodium ion batteries prepared in the examples and comparative examples was used as the positive active material of the sodium ion battery, and the positive active material, binder (polyvinylidene fluoride (PVDF)), and conductive agent (Super P) were mixed in a mass ratio of 7:2:1, and then dimethylpyrrolidone (NMP) was added as a solvent and mixed and stirred to form a uniform slurry; the slurry was uniformly coated onto aluminum foil, dried, and cut into thin sheets to be used as the positive plate, metallic sodium was used as the negative plate, and a glass fiber membrane was used as the separator, and a CR2032 button cell battery was assembled in an argon glove box using 1.0 mol / L NaClO4 / EC (ethylene carbonate) + PC (polycarbonate) + FEC (fluoroethylene carbonate) (EC:PC:FEC = 0.45:0.45:0.05, vol) as the electrolyte.

[0193] The assembled button cell battery was tested using a Land battery tester manufactured by Wuhan Jinnuo Electronics Co., Ltd., and the test conditions and results are as follows. A constant current charge / discharge test was performed on the button cell battery, with a charge / discharge voltage range of 2V to 4.2V. Among Examples 1 to 3, the electrochemical performance of the Prussian blue electrode manufactured from the cathode material of Example 2 was the best, and at a current density of 100mA / g, the initial charge specific capacity and initial discharge specific capacity of the battery were 113.3mAh / g and 137mAh / g, respectively, and the discharge specific capacity retention rate after 200 cycles was 87.1%, whereas Comparative Example 1 and Comparative Example 2 had capacities of only 42% and 30% after 200 cycles. In addition, the Prussian blue electrode manufactured from the cathode material of Example 2 had a discharge specific capacity retention rate of 77% even after 800 cycles, and the Coulomb efficiency of each cycle approached 99%. The detection results are as follows (see Table 1 and Figures 6–10).

[0194] Current density 100mA g -1 Initial discharge capacity (mAh g) -1 ) Discharge capacity after 200 cycles (mAh g) -1 ) Discharge capacity after 800 cycles (mAh g) -1 ) Coulomb efficiency (%) Example 1 118.5 100.7 84.2 98.3 Example 2 137 119.3 106.2 99.5 Example 3 122.7 103.1 104.3 99.2 Comparative Example 1 110.7 46.5 98.1 Comparative Example 2 116.2 34.8 98.6

[0195] Here, FIG. 6 is a schematic diagram of the charge-discharge specific capacity results of the first to third cycles of the Prussian blue cathode material prepared in Example 1; parts of FIG. 7 (a) to FIG. 7 (c) are schematic diagrams of the charge-discharge performance of the Prussian blue cathode material prepared in Example 2, part of FIG. 7 (a) is a schematic diagram of the charge-discharge specific capacity results of the first to fifth cycles of the Prussian blue cathode material prepared in Example 2, and parts of FIG. 7 (b) and FIG. 7 (c) are schematic diagrams of the magnification performance and cycle performance results of the Prussian blue cathode material prepared in Example 2, respectively; FIG. 8 is a schematic diagram of the charge-discharge specific capacity results of the first to fourth cycles of the Prussian blue cathode material prepared in Example 3; FIG. 9 is a schematic diagram of the charge-discharge specific capacity results of the first to third cycles of the cathode material prepared in Comparative Example 1; Figure 10 is a schematic diagram of the charge-discharge specific capacity results of the first to third cycles of the cathode material prepared in Comparative Example 2. By combining the results of Figures 6 to 10 and Table 1, it can be seen that when the Prussian blue cathode material obtained in the embodiment of the present invention is applied to a sodium ion battery, the sodium ion battery is superior in terms of cycle stability, charge-discharge specific capacity, Coulomb efficiency, and scaling performance.

[0196] In the present invention, it was observed through scanning electron microscope images that Prussian blue and Ketjen black are uniformly distributed and that sodium ferrocyanide can be dissolved in an ethylene glycol solution. When an organic solvent is introduced into the reaction system, a mixed phase is formed because ferrous sulfate and sodium citrate are insoluble in the organic solvent. However, since the reaction must be carried out with the participation of water, the growth process of Prussian blue crystals can be controlled by introducing an organic solvent to further control the reaction rate. Consequently, aged Prussian blue has fewer defects, and the addition of Ketjen black can improve the problem of low conductivity of Prussian blue. Furthermore, after introducing Ketjen black, the conductivity of the Prussian blue and Ketjen black composite material can be significantly improved. In the present invention, the introduction of ethylene glycol, an organic solvent, causes two phases to exist in the reaction system and further increases the concentration of sodium ions in the aqueous reaction system. The organic solution introduced in the present invention does not participate in the reaction but only achieves the purpose of controlling the reaction rate, and the present invention can fully realize closed-loop recovery and recycling without waste after the reaction is completed, and the recovery method can be carried out through vacuum distillation at 80°C, making it environmentally friendly and safe.

[0197] Although the present invention has been described and explained with reference to specific embodiments of the invention, such description and explanation do not limit the invention. It will be apparent to those skilled in the art that various modifications may be made to suit the purpose, spirit, and scope of the invention, specific situations, materials, compositions of materials, materials, methods, or processes without departing from the true spirit and scope of the invention as defined by the appended claims. All such modifications are intended to be within the scope of the appended claims. Although the methods disclosed herein have been described with reference to specific actions performed in a specific order, it should be understood that these actions may be combined, subdivided, or rearranged to form equivalent methods without departing from the teachings of the invention. Accordingly, unless specifically stated in this specification, the order and grouping of actions do not limit the invention.

Claims

Claim 1 As a Prussian blue cathode material, comprising a Prussian blue compound having the following general chemical formula, wherein Na x Fe[Fe(CN)6] y ·nH2O Equation I, from Equation I, 0.5 <x<1.5이고, 0.8<y<1 이며, n은 0.01~3.5이고;상기 프러시안 블루 양극재는 적어도 일부가 상기 프러시안 블루 화합물의 결정 표면에 부착된 탄소질 물질을 더 포함하는 것을 특징으로 하는 프러시안 블루 양극재. Claim 2 In paragraph 1, 0.5 <x<1인 것을 특징으로 하는 프러시안 블루 양극재. Claim 3 A Prussian blue cathode material according to claim 1, characterized in that at least some of the crystals of the Prussian blue compound are in a quasi-cubic form. Claim 4 A Prussian blue cathode material according to claim 1, characterized in that the crystal size of the Prussian blue compound is 0.1 μm or more and 2.5 μm or less. Claim 5 In claim 1, the chemical formula of the Prussian blue compound is Na 0.647 Fe[Fe(CN)6] 0.93 ·2.6H2O and Na 0.517 Fe[Fe(CN)6] 0.85 Prussian blue cathode material characterized by being at least one selected from 3.15H2O. Claim 6 A Prussian blue cathode material according to claim 1, characterized in that the carbonaceous material is selected from a conductive carbon black material. Claim 7 A method for manufacturing a Prussian blue cathode material according to claim 1, comprising the steps of: mixing a first dispersion and a second dispersion to obtain a solid precipitate; and washing and drying the solid precipitate to obtain a Prussian blue cathode material, wherein the first dispersion comprises a ferrocyanide source, a first sodium source, and a first dispersant; the second dispersion comprises a divalent iron source, a complexing agent, and a second dispersant; and the first dispersion further comprises a carbonaceous material. Claim 8 A method for manufacturing a Prussian blue cathode material according to claim 7, wherein the ferrocyanide source and the first sodium source are derived from sodium ferrocyanide; and / or, the divalent iron source is derived from a divalent iron salt, wherein the divalent iron salt is one or more selected from FeSO4·7H2O, Fe(NO3)2, and FeCl2·4H2O; and / or, the complexing agent is one or more selected from anhydrous sodium citrate, sodium citrate dihydrate, sodium citrate pentahydrate, sodium oxalate, sodium tartrate, and sodium malate. Claim 9 A method for manufacturing a Prussian blue cathode material according to claim 7, wherein the first dispersant comprises deionized water and a first solvent, and the ferrocyanide source is sparingly soluble in the first solvent; and / or, the second dispersant comprises deionized water and a second solvent, and the ferrocyanide source is sparingly soluble in the second solvent; and / or, the first solvent and the second solvent are each independently one or more selected from ethylene glycol, N,N-dimethylformamide, ethanol, and glycerol. Claim 10 A method for manufacturing a Prussian blue cathode material according to claim 9, wherein the volume ratio of deionized water to the first solvent in the first dispersant is selected from 1:(0.01 to 100); and / or, the volume ratio of deionized water to the second solvent in the second dispersant is selected from 1:(0.01 to 100). Claim 11 A method for manufacturing a Prussian blue cathode material according to claim 7, wherein the ratio of the amount of the carbonaceous material to the amount of the ferrocyanide source material is selected from 1:(0.01 to 100); and / or, the ratio of the amount of the ferrocyanide source material to the amount of the divalent iron source material is selected from 1:(1 to 3); and / or, the ratio of the amount of the divalent iron source material to the amount of the complexing agent material is selected from 1:(1 to 100). Claim 12 An anode plate characterized by comprising a Prussian blue cathode material according to claim 1; or, a Prussian blue cathode material obtained by a method for manufacturing a Prussian blue cathode material according to claim 7. Claim 13 A sodium ion battery comprising a Prussian blue cathode material according to claim 1, or a Prussian blue cathode material obtained by the method for manufacturing a Prussian blue cathode material according to claim 7. Claim 14 delete Claim 15 delete Claim 16 delete

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