A two-dimensional high-entropy Prussian blue analog nanomaterial and its preparation method

Abstract

The application discloses a two-dimensional high-entropy Prussian blue analogue nanomaterial, and a preparation method of the two-dimensional high-entropy nanomaterial. The two-dimensional high-entropy nanomaterial is formed by assembling high-entropy Prussian blue analogue nanosol particles; wherein the high-entropy sol nanometer particles are obtained by coordinating five or more than five transition metal ions with ferrocyanide or ferricyanide. The application also discloses a preparation method of the two-dimensional high-entropy nanomaterial. The configuration entropy of the Prussian blue analogue is significantly improved by coordinating five or more than five transition metal cations with ferrocyanide or ferricyanide, the high-entropy effect helps to stabilize the crystal structure, reduces the dissolution of transition metals in the Prussian blue analogue, reduces the change of the unit cell volume in the charging and discharging process, and is beneficial to the reversible deintercalation of sodium ions. Meanwhile, the high-entropy sol nanometer particles are assembled into two-dimensional nanomaterial, the high-entropy material is fully contacted with the electrolyte, the diffusion path of ions in the electrode material is shortened and the diffusion energy barrier is reduced, so as to improve the diffusion rate of sodium ions.

Description

Technical Field

[0001] The present invention relates to a two-dimensional high-entropy Prussian blue analogue nanomaterial, and also relates to a preparation method of the above two-dimensional high-entropy Prussian blue analogue nanomaterial. Background Art

[0002] Sodium-ion batteries are gradually becoming a research hotspot in the field of energy storage batteries due to advantages such as rich sodium resources, high energy conversion efficiency, long cycle life, and good safety performance. Prussian blue analogues are coordination polymers with a three-dimensional open framework structure, and their general formula is A x M1[M2(CN)6] ym .nH2O(0<x≤2, 0<y≤1, y + m = 1), where A is Li + , Na + , K + and other alkali metal ions, and M1 and M2 are transition metal ions such as Fe, Co, Ni, etc. This type of material forms an octahedral configuration with six coordination using transition metal ions as the center and cyanide ions as the ligand, and the alkali metal ions are filled in the framework structure and coordination voids. Prussian blue analogues have the following main advantages as the cathode material for sodium-ion batteries: the rigid framework structure and open sites ensure that Na with a relatively large ionic radius + can be reversibly intercalated and deintercalated without changing the material structure; in addition, due to the two-electron redox reaction, Prussian blue analogues have a relatively high theoretical specific capacity. At present, the following problems still need to be solved urgently in the practical application of Prussian blue analogues: (1) A considerable number of Fe(CN)6 vacancy defects will be generated inside their crystal structure, and these vacancy defects are easily occupied by coordinated water, resulting in a decrease in the initial capacity, and water molecules will undergo certain side reactions during the electrochemical process, thereby seriously reducing the cycle life of the electrode material. (2) The electrical conductivity of Prussian blue analogues is poor, and the rate performance needs to be improved. Summary of the Invention

[0003] Object of the Invention: The object of the present invention is to provide a two-dimensional high-entropy Prussian blue analogue nanomaterial with good cycle life and rate performance, and another object of the present invention is to provide a preparation method of the above two-dimensional high-entropy Prussian blue analogue nanomaterial.

[0004] Technical Solution: The two-dimensional high-entropy Prussian blue analogue nanomaterial described in the present invention is formed by assembling high-entropy Prussian blue analogue nanosol particles into a two-dimensional sheet-like nanostructure; among them, the high-entropy sol nanoparticles are obtained by coordinating five or more transition metal ions with ferricyanide or ferrocyanide.

[0005] The preparation method of the above two-dimensional high-entropy Prussian blue analogue nanomaterial includes the following steps:

[0006] (1) Dissolve ferrocyanide or ferricyanide in deionized water to obtain precursor solution A, and dissolve no less than five transition metal salts in deionized water to obtain precursor solution B; add sodium chloride to precursor solution A and add a complexing agent to precursor solution B, or add sodium chloride to precursor solution A only, or add a complexing agent to precursor solution B only; mix precursor solution A and precursor solution B, and after reaction, obtain high-entropy Prussian blue analog sol C.

[0007] (2) Dialyze sol C until impurity ions are removed to obtain a homogeneous and stable sol D; freeze-dry sol D to obtain a two-dimensional high-entropy Prussian blue analog nanomaterial.

[0008] In step (1), the ferrocyanide is sodium ferrocyanide or potassium ferrocyanide; the ferrocyanide is potassium ferrocyanide.

[0009] In step (1), the transition metal ions in the transition metal salt are at least five of the following: iron ions, ferrous ions, manganese ions, cobalt ions, nickel ions, copper ions, zinc ions, or titanium ions.

[0010] In step (1), the complexing agent is sodium citrate or sodium ethylenediaminetetraacetate.

[0011] In step (1), the concentration of ferrocyanide or ferricyanide in the precursor solution A is 0.005-0.5 mol / L, and the concentration of sodium chloride is 0.01-2.5 mol / L.

[0012] In step (1), the precursor solution B is added with a molar ratio of at least five transition metal salts of metal ions such that the calculated configuration entropy is greater than 1.5R, and the concentration of the complexing agent is 0.01 to 1 mol / L.

[0013] In step (1), the volume ratio of precursor solution A to precursor solution B is 1:5 to 5:1, and the reaction time is 1 to 4 hours.

[0014] The above-mentioned two-dimensional high-entropy Prussian blue analog nanomaterials are used as cathode materials for sodium-ion batteries.

[0015] First, forming high-entropy materials, i.e., increasing the configurational entropy of the material, can promote the formation of single-phase solid solutions and slow down or suppress phase transitions during electrode material cycling, which is beneficial for promoting reversible structural evolution and improving cycling stability. Second, lattice distortion effects and electronic structure diversity improve the conductivity of the material. In addition, the hysteresis diffusion effect reduces the aggregation of secondary particles during charging and discharging, which is beneficial for maintaining the structural stability of the active material and the integrity of the electrode. Finally, increasing the configurational entropy of the material can also enhance the stability of the material in air and improve the mechanical strength of nanoparticles. Simultaneously, constructing two-dimensional nanomaterials gives the electrode material a large specific surface area and active sites, allowing for sufficient contact with the electrolyte. Furthermore, two-dimensional nanomaterials can effectively slow down the volume deformation of their own structure during ion insertion / extraction. Finally, two-dimensional nanomaterials provide sodium ions with a shorter diffusion path and a lower diffusion energy barrier in the electrode material, thereby effectively improving the rate performance of the electrode material.

[0016] Beneficial Effects: Compared with the prior art, the present invention has the following significant advantages: By coordinating five or more transition metal cations with ferrocyanide or ferricyanide, the configurational entropy of Prussian blue analogs is significantly increased. The high entropy effect helps stabilize the crystal structure, reduces the dissolution of transition metals in Prussian blue analogs, reduces the change in unit cell volume during charging and discharging, and facilitates the reversible insertion and extraction of sodium ions. Thus, the mutual coupling effect between multiple elements can further improve the comprehensive performance of the electrode material. At the same time, the high entropy sol nanoparticles are assembled into two-dimensional nanomaterials, allowing the high entropy material to fully contact the electrolyte, shortening the diffusion path of ions in the electrode material and reducing the diffusion energy barrier, thereby increasing the diffusion rate of sodium ions. The Prussian blue analogs of the present invention have good cycle life and rate performance. Attached Figure Description

[0017] Figure 1 The image shows the X-ray diffraction pattern of the two-dimensional high-entropy nanomaterial prepared in Example 1.

[0018] Figure 2 Transmission electron microscopy (TEM) image (1 μm) of the two-dimensional high-entropy nanomaterials prepared in Example 1;

[0019] Figure 3 The graph shows the cycling performance of the two-dimensional high-entropy nanomaterials prepared in Example 1.

[0020] Figure 4 The rate performance diagram of the two-dimensional high-entropy nanomaterials prepared in Example 1 is shown.

[0021] Figure 5 Transmission electron microscopy (TEM) image (1 μm) of the two-dimensional high-entropy nanomaterials prepared in Example 2;

[0022] Figure 6The graph shows the cycling performance of the two-dimensional high-entropy nanomaterials prepared in Example 2.

[0023] Figure 7 This is a rate performance diagram of the two-dimensional high-entropy nanomaterials prepared in Example 2. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0025] Example 1

[0026] The present invention discloses a method for preparing two-dimensional high-entropy Prussian blue analog nanomaterials, comprising the following steps:

[0027] (1) Sodium ferrocyanide was dissolved in deionized water to obtain precursor solution A, in which the concentration of sodium ferrocyanide was 0.08 mol / L. Ferrous chloride, manganese chloride, nickel chloride, cobalt chloride, and zinc sulfate were dissolved in deionized water to obtain precursor solution B, in which Fe... 2+ Mn 2+ Ni 2+ Co 2+ Zn 2+ The concentrations of all five transition metal salts were 0.01 mol / L (metal ions of the five transition metal salts were added in the above molar ratio, and the configurational entropy of the Prussian blue analog was calculated to be greater than 1.5R). Sodium chloride and sodium citrate were added to precursor solutions A and B, respectively, to increase the concentration of sodium ions and slow down the reaction rate (both increasing the concentration of sodium ions and slowing down the reaction rate can increase the sodium content in the final product, the Prussian blue analog, thereby increasing the specific capacity of the nanomaterial). The concentration of sodium chloride in precursor solution A was 1.28 mol / L, and the concentration of sodium citrate in precursor solution B was 0.07 mol / L. Precursor solutions A and B were mixed at a volume ratio of 1:1, and after reacting for 2 hours, high-entropy Prussian blue analog sol C was obtained.

[0028] (2) Dialyze sol C to remove impurity ions and obtain a homogeneous and stable sol D; freeze-dry sol D to obtain two-dimensional high-entropy nanomaterials.

[0029] From X-ray diffraction pattern ( Figure 1 As can be seen from the transmission electron microscopy (TEM) image, this two-dimensional high-entropy nanomaterial exhibits a distinct Prussian blue characteristic peak and is a cubic phase. Figure 2 The results show that the prepared high-entropy nanomaterials exhibit a two-dimensional sheet-like structure assembled from sol nanoparticles, and are rich in nanopores. To verify the efficacy of the two-dimensional high-entropy nanomaterials prepared in this invention in the field of sodium-ion battery cathodes, the nanomaterials prepared in Example 1 were fabricated as electrode materials, and electrochemical performance tests were performed. The results were obtained from the cycle performance diagram (…). Figure 3As can be seen, this two-dimensional high-entropy nanomaterial exhibits good cycle life and high reversible specific capacity, at 0.1 A·g -1 After 200 cycles at a current density, its discharge specific capacity remains as high as 80.2 mAh·g. -1 ;From the rate performance diagram ( Figure 4 As can be seen, this two-dimensional high-entropy nanomaterial exhibits high rate capability, reaching 1 A·g -1 Even at high current densities, its average discharge specific capacity remains as high as 74.8 mAh·g. -1 .

[0030] Example 2

[0031] The present invention discloses a method for preparing two-dimensional high-entropy Prussian blue analog nanomaterials, comprising the following steps:

[0032] (1) Sodium ferrocyanide was dissolved in deionized water to obtain precursor solution A, in which the concentration of sodium ferrocyanide was 0.08 mol / L. Ferrous chloride, manganese chloride, nickel chloride, cobalt chloride, and copper chloride were dissolved in deionized water to obtain precursor solution B, in which Fe... 2+ Mn 2+ Ni 2+ Co 2+ Cu 2+ The concentrations of both were 0.01 mol / L. Sodium chloride and sodium citrate were added to precursor solutions A and B, respectively, to increase the concentration of sodium ions and slow down the reaction rate. The concentration of sodium chloride in precursor solution A was 1.28 mol / L, and the concentration of sodium citrate in precursor solution B was 0.07 mol / L. Precursor solutions A and B were mixed at a volume ratio of 1:1 and reacted for 2 hours to obtain high-entropy Prussian blue analog sol C.

[0033] (2) Dialyze sol C to remove impurity ions and obtain a homogeneous and stable sol D; freeze-dry sol D to obtain two-dimensional high-entropy nanomaterials.

[0034] From transmission electron microscopy images ( Figure 5 As can be seen, the two-dimensional high-entropy nanomaterials prepared in Example 2 exhibit a two-dimensional sheet-like structure assembled from sol nanoparticles, similar to that in Example 1. (From the cycle performance diagram...) Figure 6 As can be seen, this two-dimensional high-entropy nanomaterial exhibits good cycle life and high reversible specific capacity, at 0.1 A·g -1 After 200 cycles at a current density, its discharge specific capacity remains as high as 77.3 mAh·g. -1 ;From the rate performance diagram ( Figure 7 As can be seen, this two-dimensional high-entropy nanomaterial exhibits high rate capability, reaching 1 A·g -1 Even at high current densities, its average specific capacity remains as high as 54.6 mAh·g.-1 .

[0035] Example 3

[0036] The present invention discloses a method for preparing two-dimensional high-entropy Prussian blue analog nanomaterials, comprising the following steps:

[0037] (1) Potassium ferrocyanide was dissolved in deionized water to obtain precursor solution A, in which the concentration of potassium ferrocyanide was 0.005 mol / L. Ferrous chloride, manganese chloride, nickel chloride, cobalt chloride, and zinc sulfate were dissolved in deionized water to obtain precursor solution B, in which the concentration of Fe was 0.005 mol / L. 2+ Mn 2+ Ni 2+ Co 2+ Zn 2+ The concentrations of the five transition metal salts were 0.002 mol / L, 0.003 mol / L, 0.002 mol / L, 0.0015 mol / L, and 0.0015 mol / L, respectively (the metal ions of the five transition metal salts were added in the above molar ratio, and the configurational entropy of the Prussian blue analog was calculated to be greater than 1.5R). Sodium chloride was added to precursor solution A to increase the concentration of sodium ions. The concentration of sodium chloride in precursor solution A was 2.5 mol / L. Precursor solution A and precursor solution B were mixed at a volume ratio of 5:1 and reacted for 4 hours to obtain high-entropy Prussian blue analog sol C.

[0038] (2) Dialyze sol C to remove impurity ions and obtain a homogeneous and stable sol D; freeze-dry sol D to obtain two-dimensional high-entropy nanomaterials.

[0039] The two-dimensional high-entropy nanomaterials prepared in Example 3 have essentially the same structure and electrochemical properties as the materials prepared in Example 1.

[0040] Example 4

[0041] The present invention discloses a method for preparing two-dimensional high-entropy Prussian blue analog nanomaterials, comprising the following steps:

[0042] (1) Sodium ferrocyanide was dissolved in deionized water to obtain precursor solution A, in which the concentration of sodium ferrocyanide was 0.5 mol / L. Ferric nitrate, manganese sulfate, cobalt chloride, nickel nitrate, copper chloride, and zinc sulfate were dissolved in deionized water to obtain precursor solution B, in which Fe... 3+ Mn 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+The concentrations of the six transition metal salts were 0.01 mol / L, 0.008 mol / L, 0.008 mol / L, 0.008 mol / L, 0.008 mol / L, and 0.008 mol / L, respectively (the metal ions of the six transition metal salts were added in the above molar ratio, and the configurational entropy of the Prussian blue analog was calculated to be greater than 1.5R). Sodium citrate was added to precursor solution B to slow down the reaction rate. The concentration of sodium citrate in precursor solution B was 1 mol / L. Precursor solution A and precursor solution B were mixed at a volume ratio of 1:5, and after reacting for 1 h, high-entropy Prussian blue analog sol C was obtained.

[0043] (2) Dialyze sol C to remove impurity ions and obtain a homogeneous and stable sol D; freeze-dry sol D to obtain two-dimensional high-entropy nanomaterials.

[0044] Example 4 yielded a two-dimensional high-entropy nanomaterial, which had a structure and properties that were basically the same as those of the material prepared in Example 1.

[0045] Example 5

[0046] The present invention discloses a method for preparing two-dimensional high-entropy Prussian blue analog nanomaterials, comprising the following steps:

[0047] (1) Potassium ferricyanide was dissolved in deionized water to obtain precursor solution A, in which the concentration of potassium ferricyanide was 0.08 mol / L. Ferrous chloride, manganese acetate, cobalt sulfate, nickel nitrate, and titanium chloride were dissolved in deionized water to obtain precursor solution B, in which the concentration of potassium ferricyanide was 0.08 mol / L. 2+ Mn 2+ Co 2+ Ni 2+ Ti 3+ The concentrations of both were 0.01 mol / L. Sodium chloride and sodium ethylenediaminetetraacetate were added to precursor solutions A and B, respectively, to increase the concentration of sodium ions and slow down the reaction rate. The concentration of sodium chloride in precursor solution A was 1.28 mol / L, and the concentration of sodium ethylenediaminetetraacetate in precursor solution B was 0.07 mol / L. Precursor solutions A and B were mixed at a volume ratio of 1:1 and reacted for 2 hours to obtain high-entropy Prussian blue analog sol C.

[0048] (2) Dialyze sol C to remove impurity ions and obtain a homogeneous and stable sol D; freeze-dry sol D to obtain two-dimensional high-entropy nanomaterials.

[0049] Example 5 yielded a two-dimensional high-entropy nanomaterial, which had a structure and properties that were basically the same as those of the material prepared in Example 1.

[0050] The present invention relates to a two-dimensional high-entropy nanomaterial. Structurally, the two-dimensional nanomaterial has a high specific surface area, more active sites, a shorter sodium ion diffusion path, and a lower diffusion energy barrier. In terms of composition, the lattice distortion effect and electronic structure diversity of the high-entropy material improve the conductivity of the material. At the same time, the high-entropy effect can slow down or suppress phase transitions, which is beneficial to promoting the reversible evolution of the structure and improving cycle stability.

Claims

1. A method for preparing a two-dimensional high-entropy Prussian blue analogue nanomaterial, characterized in that, The method comprises the following steps: (1) dissolving ferrocyanide or ferricyanide in deionized water to obtain precursor solution A, and dissolving not less than five kinds of transition metal salts in deionized water to obtain precursor solution B; adding sodium chloride to the precursor solution A and adding a complexing agent to the precursor solution B, or only adding sodium chloride to the precursor solution A, or only adding the complexing agent to the precursor solution B; mixing the precursor solution A and the precursor solution B, and obtaining high-entropy Prussian blue analogue sol C after reaction; the complexing agent is sodium citrate; in the precursor solution A, the concentration of the ferrocyanide or ferricyanide is 0.005-0.5 mol / L, and the concentration of the sodium chloride is 0.01-2.5 mol / L; in the precursor solution B, the molar ratio of metal ions of the at least five kinds of transition metal salts is added in an amount calculated to obtain a configurational entropy greater than 1.5R, and the concentration of the complexing agent is 0.01-1 mol / L; the volume ratio of the precursor solution A to the precursor solution B is 1:5-5:1; (2) dialyzing the sol C until impurity ions are removed to obtain uniform and stable sol D; freeze-drying the sol D to obtain two-dimensional high-entropy Prussian blue analogue nanomaterial; the two-dimensional high-entropy Prussian blue analogue nanomaterial is formed by assembling high-entropy Prussian blue analogue nanosol particles into a two-dimensional sheet-shaped nanostructure.

2. The method of claim 1, wherein: In step (1), the ferrocyanide is sodium ferrocyanide or potassium ferrocyanide; the ferricyanide is potassium ferricyanide.

3. The method of claim 1, wherein: In step (1), the transition metal ions in the transition metal salts are at least five kinds of iron ions, ferrous ions, manganese ions, cobalt ions, nickel ions, copper ions, zinc ions or titanium ions.

4. The method of claim 1, wherein: In step (1), the reaction time is 1-4 h.

5. The method of claim 1, wherein: In step (2), the high-entropy sol nanoparticles are obtained by coordination of five or more than five kinds of transition metal ions and ferrocyanide or ferricyanide.

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