Preparation method and application of aqueous zinc ion battery positive electrode coating material

Abstract

The invention belongs to the technical field of water-based zinc ion battery positive electrode materials, and particularly relates to a preparation method and application of a water-based zinc ion battery positive electrode coating material. The method comprises the following steps: by taking NH4 < + >-V2O5 as a raw material, carrying out heat treatment to obtain black solid powder; the black solid powder, conductive carbon black and PVDF are mixed and ground according to the mass ratio, N-methyl pyrrolidone (NMP) is dropwise added for ultrasonic treatment, polyimide is added and stirred to be in a coating state, and the positive electrode coating material is obtained. The positive electrode coating material has relatively high mechanical property and chemical stability, has rich zinc-loving active sites, and can induce zinc ions to uniformly deposit and inhibit dendritic crystal reaction.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of positive electrode materials of aqueous zinc ion batteries, and particularly relates to a preparation method and application of a positive electrode coating material of an aqueous zinc ion battery. BACKGROUND

[0002] Aqueous zinc ion batteries (ZIBs) have shown great application potential in large-scale energy storage due to their high safety, environmental friendliness, low cost, and high theoretical capacity. In recent years, researchers have made great progress in the key components of ZIBs, including the design of new negative electrode structures, the development of high-performance electrolytes, and the exploration of diversified positive electrode materials. However, despite the improvement in overall performance, ZIBs still face many challenges in their path to practical application, especially in the development of positive electrode materials, where the bottleneck effect is particularly prominent.

[0003] Zn 2+ With a high charge valence (+2) and a large ion mass, Zn + This characteristic produces strong electrostatic interactions within the positive electrode material. During charging and discharging, the insertion / deinsertion of Zn 2+ In the positive electrode lattice, it can cause significant lattice strain and strong electrostatic repulsion. This not only severely hinders the diffusion of Zn 2+ In the material bulk phase (mass transfer limitation), it also limits the effective transport of electrons (electron conduction limitation), ultimately resulting in poor rate performance and actual specific capacity lower than the theoretical value.

[0004] Most potential ZIBs positive electrode materials (such as manganese-based oxides, vanadium-based oxides, etc.) inevitably have dissolution phenomena in aqueous environments. This dissolution not only directly leads to irreversible loss of active materials, reducing battery capacity and energy density, but also the dissolved metal ions can cause uncontrollable deposition or side reactions on the negative electrode (zinc metal) surface, destroying the stability of the negative electrode / electrolyte interface and accelerating the overall failure of the battery. The dissolution problem seriously restricts the cycle life of ZIBs.

[0005] During repeated Zn 2+ insertion / deinsertion processes, the positive electrode material often undergoes severe volume changes and complex phase transition processes. Due to the strong electrostatic interaction and lattice stress caused by Zn 2+ insertion, some phase transitions may be irreversible. This irreversible structural evolution can lead to lattice collapse, reduction of active sites, blockage of ion diffusion channels, and even complete loss of electrochemical activity of the material. Structural degradation is one of the fundamental reasons for the continuous capacity decay (poor cycle stability) and rate performance decline of ZIBs.

[0006] In summary, existing aqueous zinc-ion battery cathode materials generally face the problem of Zn 2+ Core issues include slow diffusion kinetics, poor material structural stability (dissolution and irreversible phase transition), and the resulting poor rate performance and short cycle life. These issues are interrelated and jointly restrict the improvement of the overall performance and practical application of ZIBs. Therefore, it is necessary to develop a material that can effectively inhibit the dissolution of the cathode material, stabilize its crystal structure, and improve the Zn 2+ New modification strategies for transport kinetics or high-performance cathode materials have become key hotspots and urgent needs in the current research field of aqueous zinc-ion batteries. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the present invention provides a preparation method and application of a positive electrode coating material for an aqueous zinc ion battery.

[0008] The technical solution of the present invention is: The present invention discloses a method for preparing a positive electrode coating material for an aqueous zinc ion battery, comprising the following steps: (1) NH4 + -V2O5 is used as raw material and black solid powder is obtained by heat treatment; (2) The black solid powder obtained in step (1), conductive carbon black and PVDF are mixed and ground according to a mass ratio, N-methylpyrrolidone (NMP) is added dropwise and ultrasonicated, and polyimide is added and stirred until it becomes a coating to obtain a positive electrode coating material.

[0009] Furthermore, in the above preparation method, the heat treatment conditions in step (1) are: + -V2O5 was placed in a tube furnace, heated to 300°C at a heating rate of 5-10°C / min, and calcined for 2 hours.

[0010] Furthermore, in the above preparation method, in step (2), the mass ratio of the black solid powder, the conductive carbon black and the PVDF is (7-8): (1-2): 1. Furthermore, in the above-mentioned preparation method, the mass ratio of the black solid powder, the conductive carbon black, and the PVDF is 8:1:1. Furthermore, in the above-mentioned preparation method, the mass ratio of the black solid powder, the conductive carbon black, and the PVDF is 7:2:1. Furthermore, in the above-mentioned preparation method, the amount of NMP added in step (2) is 5 mL / gram of mixed powder, the ultrasonication time is 10 minutes, the mass ratio of the polyimide to the black solid powder is 3:2, and the stirring time is 24 hours.

[0011] Polyimide is heated to produce graphene. Graphene oxide has a large specific surface area and exhibits electronegativity, which can adsorb positively charged vanadium ions (VO). 2+These vanadium ions attached to the graphene sheets begin to nucleate, crystallize and grow slowly under heat treatment, eventually forming a stable sandwich structure. On the other hand, the presence of V2O5 grains between graphene sheets can not only prevent graphene from agglomerating, but also promote the formation of small-sized V2O5 nanoparticles. It helps to stabilize the structural skeleton of V2O5 and promote the hydration of Zn 2+ The desolvation of zinc is beneficial to the long-term and efficient storage of zinc. The present invention also discloses the use of the positive electrode coating material prepared by the above method in preparing the positive electrode of an aqueous zinc ion battery, wherein the coating material is coated on the surface of carbon paper to form a protective layer.

[0012] Furthermore, in the above application, a coating machine is used to evenly coat the coating material on the substrate, and the coating thickness is 20 μm.

[0013] Furthermore, in the above application, the coated material is placed in an oven and heated to 280 degrees for 4 hours.

[0014] Advantages and beneficial effects of the present invention: (1) The positive electrode coating material has a large specific surface area and strong electronegativity, and can adsorb positively charged vanadium ions (VO) 2+ These vanadium ions attached between graphene sheets begin to nucleate, crystallize and grow slowly under heat treatment, eventually forming a stable sandwich-like structure.

[0015] (2) The presence of V2O5 grains between graphene sheets in the cathode coating material not only prevents graphene from agglomerating, but also promotes the formation of small-sized V2O5 nanoparticles. This helps stabilize the structural skeleton of V2O5 and promotes the hydration of Zn 2+ Desolvation of Zn 2+ The high charge density leads to strong electrostatic interactions, which directly affects the ion diffusion rate and thus increases the battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The cyclic charge and discharge diagrams of the full batteries prepared in Example 1, Example 2 and the comparative example. DETAILED DESCRIPTION

[0017] The present invention is described in detail below with reference to the accompanying drawings and examples, but the scope of protection of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0018] Example 1

[0019] A method for preparing a positive electrode coating material for an aqueous zinc ion battery according to this embodiment comprises the following steps: (1) NH4 + -V2O5 as raw material was placed in a crucible and heat treated in a tube furnace, heated to 300°C at a heating rate of 5°C / min, calcined for 2 hours to obtain a black solid, and ground to powder to obtain a black solid powder named g-V2O5; (2) 0.32g of g-V2O5, 0.04g of conductive carbon black and 0.04g of PVDF were mixed and placed in a mortar for grinding, 2ml of NMP was added dropwise, ultrasonic treatment was performed for 10min, 0.48g of polyimide was added dropwise and stirred for 24h to form a coating, the coating was coated on carbon paper using a coating machine to prepare a positive electrode material, the coating thickness was 20μm, and the coated material was placed in an oven and heated to 280 degrees for 4 hours. The prepared material is named V2O5@Zn.

[0020] The V2O5@Zn was used as the positive electrode of the battery, and pure zinc was used as the negative electrode to form a full battery. The full battery was tested under the experimental conditions of a current density of 5mA·cm 2

[0021] Example 2

[0022] The preparation method of the aqueous zinc ion battery positive electrode coating material of the present embodiment comprises the following steps: (1) NH4 + -V2O5 as raw material was placed in a crucible and heat treated in a tube furnace, heated to 300°C at a heating rate of 10°C / min, calcined for 2 hours to obtain a black solid, and ground to powder to obtain a black solid powder named g-V2O5-1; (2) 0.28g of g-V2O5-1, 0.08g of conductive carbon black and 0.04g of PVDF were mixed and placed in a mortar for grinding, 2ml of NMP was added dropwise, ultrasonic treatment was performed for 10min, 0.42g of polyimide was added dropwise and stirred for 24h to form a coating, the coating was coated on titanium foil using a coating machine to prepare a positive electrode material, the coating thickness was 20μm, and the prepared positive electrode material was named V2O5@Zn-1.

[0023] The V2O5@Zn-1 was used as the positive electrode of the battery, and pure zinc was used as the negative electrode to form a full battery. The full battery was tested under the experimental conditions of a current density of 5mA·cm².

[0024] Comparative Example 1 The preparation method of the aqueous zinc ion battery positive electrode coating material of the present embodiment comprises the following steps: (1) NH4 + ​-V2O5 was placed in a crucible and heat treated in a tube furnace, heated to 300°C at a heating rate of 10°C / min, calcined for 2 hours to obtain a black solid, and ground to powder to obtain a black solid powder named g-V2O5-2; (2) 0.32 g of g-V2O5-2, 0.04 g of conductive carbon black and 0.04 g of PVDF were mixed and placed in a mortar and ground thoroughly, 2 ml of NMP was added dropwise, stirred for 24 h to form a coating, the coating was coated on carbon paper using a coating machine to prepare a positive electrode material, the coating thickness was 20 μm, and the coated material was placed in an oven and heated to 280 degrees for 4 hours. The prepared positive electrode material was named V2O5@Zn-2.

[0025] The V2O5@Zn-2 was used as the battery positive electrode, and pure zinc was used as the battery negative electrode to form a full battery, and the full battery was tested under the experimental conditions of a current density of 5 mA·cm².

[0026] From the above data, it can be seen that the charge-discharge capacity of Example 1 remained very high after 6000 cycles, the capacity of Example 2 decreased slightly compared with Comparative Example 1, the efficiency fluctuated slightly, but the capacity was still relatively high, and Comparative Example 1 short-circuited at 4200 cycles and the capacity decreased significantly. Figure 1 It can be seen that the charge-discharge capacity of Example 1 remained very high after 6000 cycles, the capacity of Example 2 decreased slightly compared with Comparative Example 1, the efficiency fluctuated slightly, but the capacity was still relatively high, and Comparative Example 1 short-circuited at 4200 cycles and the capacity decreased significantly.

Claims

1. A method for preparing a positive electrode coating material for aqueous zinc-ion batteries, characterized by, Comprising the following steps: (1) NH4 + - V2O5 as raw material, by heat treatment to obtain black solid powder; (2) The black solid powder obtained in step (1), conductive carbon black and PVDF are mixed and ground according to the mass ratio, N-methyl pyrrolidone (NMP) is added dropwise for ultrasonic, polyimide is added and stirred until the coating is obtained, to obtain a positive electrode coating material.

2. The production method according to claim 1, characterized by, The conditions for the heat treatment in step (1) are: NH4 + -V2O5 is placed in a tube furnace and heated to 300°C at a rate of 5-10°C / min and calcined for 2 hours.

3. The production method according to claim 1, characterized by, The mass ratio of the black solid powder, conductive carbon black and PVDF in step (2) is (7-8):(1-2):

1.

4. The production method according to claim 3, characterized by, The mass ratio of the black solid powder, conductive carbon black and PVDF is 8:1:

1.

5. The preparation method according to claim 3, characterized in that The mass ratio of the black solid powder, conductive carbon black and PVDF is 7:2:

1.

6. The method of claim 1, wherein, The amount of NMP added in step (2) is 5mL per gram of mixed powder, the ultrasonic time is 10 minutes, the mass ratio of polyimide to black solid powder is 3:2, and the stirring time is 24 hours.

7. Use of the positive electrode coating material prepared by the method of any one of claims 1-6 in the preparation of a positive electrode of a water-based zinc ion battery, characterized in that, The coating material is coated on the surface of carbon paper to form a protective layer.

8. Use according to claim 7, characterized in that, The coating material is uniformly coated on the substrate by using a coating machine, and the coating thickness is 20μm.

9. Use according to claim 8, characterized in that, The coated material is heated to 280 degrees in an oven for 4 hours.

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