Secondary seawater battery positive electrode material, preparation method and application

Abstract

The invention discloses a secondary seawater battery positive electrode material, a preparation method and application, a copper-based Prussian blue analogue K0. 2Cu [Fe (CN) 6] 0.7. 4.05 H2O is used as the secondary seawater battery positive electrode material, and the secondary seawater battery positive electrode material has high discharge specific capacity, excellent rate capability and good cycle life. The material is prepared by a coprecipitation method, is simple to prepare and has the potential of large-scale production. The material can be used as a positive electrode material of a secondary seawater battery, and has important significance for developing an environment-friendly, safe, low-cost and sustainable energy storage technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage technology and material preparation technology, and in particular relates to a positive electrode material, a preparation method and an application of a secondary seawater battery. Background Art

[0002] Seawater is a natural multi-component electrolyte containing a variety of ions and exhibits a conductivity of about 50 mS cm -1 It has high ionic conductivity, and has the advantages of abundant reserves, renewable and easy access. When used as an electrolyte, it is expected to effectively reduce the production cost of the battery. However, the current seawater batteries are mainly primary batteries and are difficult to reuse (Progress and Applications of Seawater-Activated Batteries, Sustainability 2023, 15, 1635). The developed secondary seawater batteries can be divided into three parts: the positive electrode chamber, the negative electrode chamber and the solid electrolyte (Rechargeable seawater battery and its electrochemical mechanism, Chem Electro Chem, 2015, 2, 328). Among them, the positive electrode chamber contains seawater and the positive electrode, and the negative electrode chamber contains a sodium metal negative electrode and a non-aqueous electrolyte. However, this secondary seawater battery is a semi-seawater secondary battery (because the negative end cannot use seawater), has a complex structure, and requires the use of expensive components (such as ceramic diaphragms), which limits its application in the field of large-scale energy storage. The key to the research and development of secondary all-seawater batteries is the need to use low-cost methods to prepare high-capacity and long-cycle life electrode materials.

[0003] In view of the above problems, the K designed by the present invention 0.2 Cu[Fe(CN)6] 0.7 ·4.05H2O is used as the cathode material for secondary all-seawater batteries, and a feasible low-cost preparation method is proposed, which is of great significance to the field of large-scale energy storage technology and equipment. Summary of the invention

[0004] The purpose of the present invention is to provide a positive electrode material suitable for secondary seawater batteries in view of the shortcomings of the prior art. The material and the preparation process have the advantages of low cost, safety, sustainability, etc., and are suitable for large-scale energy storage.

[0005] To achieve the above object, the technical solution adopted by the present invention comprises the following steps:

[0006] A rechargeable seawater battery cathode material, based on K 0.2 Cu[Fe(CN)6] 0.74.05H2O as the positive electrode active material of rechargeable seawater batteries.

[0007] Furthermore, the K 0.2 Cu[Fe(CN)6] 0.7 4.05H2O is prepared by co-precipitation method.

[0008] Furthermore, the coprecipitation method comprises the following steps: mixing copper nitrate, potassium ferrocyanide, sodium citrate and potassium nitrate in a solution, allowing the mixture to stand for reaction, centrifuging the mixture and washing the mixture with deionized water, and drying the mixture to obtain the K 0.2 Cu[Fe(CN)6] 0.7 ·4.05H2O.

[0009] Furthermore, the molar ratio of copper nitrate, potassium ferrocyanide, sodium citrate and potassium nitrate is 2:1:2:25.

[0010] Furthermore, the coprecipitation reaction time is 10-15 h, preferably 12 h.

[0011] Furthermore, K 0.2 Cu[Fe(CN)6] 0.7 ·4.05H2O powder, a conductive agent, and a binder are mixed and dissolved with a solvent, and then coated on a cleaned current collector, and then dried to obtain the positive electrode material.

[0012] A rechargeable and dischargeable seawater battery comprises the positive electrode material as described in any one of the above items.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1) The present invention discloses a positive electrode material that can be applied to a rechargeable seawater battery. Compared with the "oxygen evolution (OER) / oxygen reduction (ORR)" mechanism of the air electrode (electrocatalyst) used in the traditional secondary seawater battery, its energy storage principle is the "cation insertion / deinsertion" mechanism, and the voltage polarization is small, which is suitable as a secondary seawater battery electrode material;

[0015] 2) Compared with supercapacitor and conversion type positive electrode materials, it has higher discharge capacity, excellent rate performance and good cycle life. It has a discharge capacity of 66.5mAh / g at a current density of 0.2A / g. It has a discharge capacity of 51.9mAh / g at a current density of 5A / g, showing excellent rate performance. At the same time, it still maintains 64.5% of the initial capacity after 1000 cycles at a current density of 2A / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 K obtained in Example 1 of the present invention 0.2Cu[Fe(CN)6] 0.7 ·SEM photo of 4.05H2O cathode material;

[0017] Figure 2 K obtained in Example 1 of the present invention 0.2 Cu[Fe(CN)6] 0.7 ·X-ray diffraction pattern of 4.05H2O cathode material;

[0018] Figure 3 K obtained in Example 1 of the present invention 0.2 Cu[Fe(CN)6] 0.7 ·Constant current charge and discharge curve of 4.05H2O cathode material;

[0019] Figure 4 K obtained in Example 1 of the present invention 0.2 Cu[Fe(CN)6] 0.7 ·4.05H2O rate performance curve of positive electrode material;

[0020] Figure 5 K obtained in Example 1 of the present invention 0.2 Cu[Fe(CN)6] 0.7 ·4.05H2O cycle stability curve of positive electrode material;

[0021] Figure 6 Cu[Fe(CN)6] prepared in the comparative example of the present invention 0.7 ·SEM photo of 3.47H2O cathode material;

[0022] Figure 7 Cu[Fe(CN)6] prepared in the comparative example of the present invention 0.7 ·3.47 Constant current charge and discharge curve of H2O cathode material;

[0023] Figure 8 Cu[Fe(CN)6] prepared in the comparative example of the present invention 0.7 ·3.47 Rate performance curve of H2O cathode material. DETAILED DESCRIPTION

[0024] In order to make the purpose and technical solution of the present invention clearer and easier to understand, the present invention is described in detail below in conjunction with embodiments. It should be noted that the specific embodiments described herein are only used to explain the present invention and are not used to limit the scope of protection of the present invention.

[0025] Example 1

[0026] A method for preparing a secondary seawater battery positive electrode material comprises the following steps:

[0027] 100 mL of a solution containing 0.04 mol / L copper nitrate and 0.04 mol / L sodium citrate and 100 mL of a 0.02 mol / L potassium ferrocyanide solution were mixed into 50 mL of a 1 mol / L potassium nitrate solution, allowed to stand for 12 h, centrifuged, washed with deionized water, and dried to obtain K 0.2 Cu[Fe(CN)6] 0.7 ·4.05H2O powder. 0.2 Cu[Fe(CN)6] 0.7 4.05H2O powder, Ketjen black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1 and dissolved in N-methylpyrrolidone, then coated on clean carbon paper and dried to obtain K loaded on carbon paper. 0.2 Cu[Fe(CN)6] 0.7 ·4.05H2O.

[0028] The K prepared in this example 0.2 Cu[Fe(CN)6] 0.7 ·SEM photos of 4.05H2O materials are shown in Figure 1 X-ray diffraction results ( Figure 2 ) indicates that it is a face-centered cubic Prussian blue analog. This material was used as a positive electrode material and its energy storage performance was tested in a three-electrode system with seawater as the electrolyte. Its constant current charge and discharge curve is shown in Figure 3 As shown, it has a discharge capacity of 66.5 mAh / g at a current density of 0.2 A / g. And has a discharge specific capacity of 51.9 mAh / g at a current density of 5 A / g, showing excellent rate performance ( Figure 4 ). At the same time, it has good cycle performance ( Figure 5 ), and it still maintained 64.5% of the initial capacity after 1000 cycles at a current density of 2 A / g.

[0029] Comparative Example

[0030] A method for preparing a secondary seawater battery positive electrode material comprises the following steps:

[0031] 100 mL of 0.04 mol / L copper nitrate solution and 100 mL of 0.02 mol / L potassium ferrocyanide solution were mixed in 50 mL of deionized water, allowed to stand for 12 h, centrifuged, washed with deionized water, and dried to obtain Cu[Fe(CN)6] 0.7 ·3.47H2O powder. Cu[Fe(CN)6] 0.7 ·3.47H2O powder, Ketjen black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1 and dissolved in N-methylpyrrolidone, then coated on clean carbon paper and dried to obtain Cu[Fe(CN)6] loaded on carbon paper.0.7 ·3.47H2O.

[0032] The Cu[Fe(CN)6] prepared in this comparative example 0.7 ·SEM photos of 3.47H2O materials are shown in Figure 6 As shown, the material has an irregular particle morphology, and its regularity and crystal quality are significantly lower than those of the sample prepared in Example 1. The material was used as a positive electrode material, and its energy storage performance was tested in a three-electrode system with seawater as the electrolyte. Its constant current charge and discharge curve is shown in Figure 7 As shown, it has a discharge capacity of 65.7 mAh / g at a current density of 0.2 A / g. However, it only has a discharge capacity of 41.6 mAh / g at a current density of 5 A / g ( Figure 8 ), the rate performance is obviously inferior to that of K prepared in Example 1 0.2 Cu[Fe(CN)6] 0.7 ·4.05H2O.

[0033] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art who is familiar with the present invention may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. A rechargeable and dischargeable seawater battery positive electrode material, characterized in that: K 0.2 Cu[Fe(CN)6] 0.7 4.05H2O as the positive electrode active material of rechargeable seawater batteries.

2. The rechargeable and dischargeable seawater battery positive electrode material according to claim 1, characterized in that: The K 0.2 Cu[Fe(CN)6] 0.7 4.05H2O is prepared by co-precipitation method.

3. The rechargeable and dischargeable seawater battery positive electrode material according to claim 2, characterized in that: The coprecipitation method comprises the following steps: mixing copper nitrate, potassium ferrocyanide, sodium citrate and potassium nitrate in a solution, allowing the mixture to stand for reaction, centrifuging the mixture and washing the mixture with deionized water, and drying the mixture to obtain the K 0.2 Cu[Fe(CN)6] 0.7 ·4.05H2O.

4. The rechargeable and dischargeable seawater battery positive electrode material according to claim 3, characterized in that: The molar ratio of the copper nitrate, potassium ferrocyanide, sodium citrate and potassium nitrate is 2:1:2:

25.

5. The rechargeable and dischargeable seawater battery positive electrode material according to claim 3, characterized in that: The coprecipitation reaction time is 10-15h.

6. The rechargeable and dischargeable seawater battery positive electrode material according to claim 1, characterized in that: K 0.2 Cu[Fe(CN)6] 0.7 ·4.05H2O powder, a conductive agent, and a binder are mixed and dissolved, and then coated on a cleaned current collector, and then dried to obtain the positive electrode material.

7. A rechargeable seawater battery, characterized in that: Comprising the positive electrode material as described in any one of claims 1 to 6.

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