Zinc manganese pyrophosphate composite zinc manganese phosphate material, preparation method and application thereof

Abstract

The application belongs to the technical field of zinc ion batteries, and mainly discloses a pyrophosphate zinc manganese composite zinc manganese phosphate material and a preparation method thereof.The pyrophosphate zinc manganese composite zinc manganese phosphate material has the following specific structure: a pyrophosphate zinc manganese coating layer is arranged on the surface of the zinc manganese phosphate.The manganese nitrate is arranged at the upper wind port of a calcining furnace, the zinc salt is uniformly mixed with the pyrophosphate and then is arranged at the lower wind port of the calcining furnace, and then calcination is performed, and the pyrophosphate zinc manganese composite zinc manganese phosphate material is obtained.The coating layer of the pyrophosphate zinc manganese on the surface of the zinc manganese phosphate can significantly widen the voltage interval of the zinc manganese phosphate, improve the reversible capacity of the material, and improve the structural stability of the material.The pyrophosphate zinc manganese composite zinc manganese phosphate material can be prepared by using a one-step solid-phase sintering method, and the process is simple and easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of zinc-ion battery material technology, specifically relating to the positive electrode material of zinc-ion batteries and its preparation method. Background Technology

[0002] For over 20 years, lithium-ion batteries have experienced rapid growth and widespread application in the charging market. However, their vulnerability to high temperatures and susceptibility to fire have remained weaknesses. Aqueous zinc-ion batteries, with their key advantages such as safety and flexibility, are poised to challenge the dominance of lithium-ion batteries in areas like wearable electronics.

[0003] Cathode materials for zinc-ion batteries fall into two main categories: manganese-based and vanadium-based. Among them, manganese-based materials are the most promising cathode materials for zinc-ion batteries due to their low cost and lack of pollution. Chinese patent CN112340720B discloses a zinc-ion battery cathode material based on a doped zinc-manganese phosphate structure and its synthesis method. The doped zinc-manganese phosphate cathode material mainly includes doping of Zn sites with alkali metal ions and doping of Mn sites with polyvalent metal ions. However, simple metal doping has limited effect on modifying zinc-manganese phosphate, resulting in poor overall structural stability and phase optimization of the material. Moreover, simple doping modification cannot improve the voltage range of the zinc-manganese phosphate material itself. Summary of the Invention

[0004] The main objective of this invention is to provide a zinc-manganese phosphate cathode material composed of zinc-manganese pyrophosphate and manganese phosphate, which can both broaden the voltage range of zinc-manganese phosphate and improve the structural stability of zinc-manganese phosphate.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned cathode material.

[0006] A third objective of this invention is to provide a zinc-ion battery.

[0007] To achieve the above objectives, the present invention provides the following specific technical solutions.

[0008] First, the present invention provides a zinc manganese pyrophosphate composite material, specifically having a zinc manganese pyrophosphate coating layer on the surface of the zinc manganese phosphate.

[0009] Secondly, the present invention provides a method for preparing the above-mentioned zinc manganese pyrophosphate composite zinc manganese phosphate material, comprising the following steps: Manganese nitrate is placed at the upper air vent of the calcining furnace, and zinc salt and pyrophosphate are mixed evenly and placed at the lower air vent of the calcining furnace for calcination to obtain the final product.

[0010] In a further preferred embodiment, an oxidizing atmosphere is continuously introduced into the calcining furnace. The oxidizing atmosphere is preferably air.

[0011] The flow rate of the oxidizing atmosphere is further optimized to be 10~30 m / s.

[0012] In a further preferred embodiment, the zinc salt is at least one of zinc nitrate, zinc acetate, and zinc oxalate.

[0013] In a further preferred embodiment, the molar ratio of zinc salt, manganese salt, and pyrophosphate in the calcining furnace is 1:2~3:1~2.

[0014] In a further preferred embodiment, the calcination temperature is 300~900℃, and the calcination time is 1~10h.

[0015] Furthermore, the present invention provides a zinc-ion battery in which the positive electrode active material comprises the above-mentioned zinc manganese pyrophosphate composite zinc manganese phosphate material.

[0016] The present invention has the following significant advantages: (1) By coating the surface of zinc manganese phosphate with a zinc manganese pyrophosphate coating, the voltage range of zinc manganese phosphate can be significantly widened, the reversible capacity of the material can be improved, and the structural stability of the material can be improved.

[0017] (2) The present invention can prepare zinc manganese pyrophosphate composite material by one-step solid-state sintering method, which is simple and easy to implement.

[0018] (3) The preparation method provided by the present invention does not require complicated equipment and can be directly used with existing calcination furnaces or other equipment that can achieve heating, which is low in cost. Attached Figure Description

[0019] Figure 1 This is a TEM image of the composite material obtained in Example 1.

[0020] Figure 2 The image shows the HRTEM image of the composite material obtained in Example 1. Detailed Implementation

[0021] To broaden the voltage range of zinc manganese phosphate materials and improve the structural stability of zinc manganese phosphate, this invention provides a zinc manganese phosphate cathode material with zinc manganese pyrophosphate coating modification, specifically having a zinc manganese pyrophosphate coating layer on the surface of zinc manganese phosphate.

[0022] Pyrophosphate is resistant to high pressure and can maintain its structural stability under high pressure. Using pyrophosphate as a composite layer can ensure the high-pressure stability of both itself and the main material.

[0023] The present invention further provides a method for preparing the above-mentioned zinc manganese pyrophosphate composite zinc manganese phosphate material, comprising the following steps: Manganese nitrate is placed at the upper air vent of the calcining furnace, and zinc salt and pyrophosphate are mixed evenly and placed at the lower air vent of the calcining furnace for calcination to obtain the final product.

[0024] In the above preparation method, there is no specific requirement for the type of zinc salt or manganese salt used as the raw materials, as long as they can decompose at high temperatures without generating impurities. In a specific embodiment of the present invention, the zinc salt is at least one of zinc nitrate, zinc acetate, and zinc sulfate.

[0025] The amounts of zinc salt, manganese salt, and pyrophosphate are rationally configured based on the generated phases ZnMn2(PO4)2 and ZnMn3(P2O7)2. In a specific embodiment of the present invention, the molar ratio of zinc salt, manganese salt, and pyrophosphate in the calcining furnace is 1:2~3:1~2.

[0026] In the above preparation method, the calcination temperature is crucial for the content of the generated zinc manganese phosphate and zinc manganese pyrophosphate phases. Generally, the calcination temperature is 300-900℃, and the calcination time is 1-10 hours. However, different calcination temperatures will affect the content ratio of zinc manganese phosphate and zinc manganese pyrophosphate in the product. The calcination temperature determines the degree of oxidative decomposition of pyrophosphate. The higher the calcination temperature, the higher the proportion of pyrophosphate oxidized and decomposed to produce phosphoric acid, and thus the higher the amount of zinc manganese phosphate generated. The lower the calcination temperature, the lower the proportion of pyrophosphate oxidized and decomposed to produce phosphoric acid, and the higher the amount of zinc manganese pyrophosphate generated. However, the reaction process also needs to consider the application of materials; that is, the amount of zinc manganese phosphate and zinc manganese pyrophosphate in the product can be determined based on their relationship with the properties of the materials. In this invention, a calcination temperature of 800-900℃ is further preferred.

[0027] Furthermore, in the above preparation method, an oxidizing atmosphere is continuously introduced into the calcining furnace. The oxidizing atmosphere is preferably air. More preferably, the flow rate of the oxidizing atmosphere is 10~30 m / s. If the flow rate is too high, excess oxygen will not participate in the reaction, resulting in oxygen consumption. Moreover, if the flow rate is too high, the material at the upwind end cannot fully react with the material at the downwind end; if the flow rate is too low, the oxidation reaction will be incomplete, affecting the product yield.

[0028] The present invention also provides a zinc-ion battery, wherein the positive electrode active material comprises the above-mentioned zinc manganese pyrophosphate composite zinc manganese phosphate material.

[0029] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0030] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0031] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0032] Example 1 In a muffle furnace, 0.45 mol of manganese nitrate was placed at the air inlet, and 0.2 mol of zinc nitrate and 0.25 mol of pyrophosphate crystals were placed at the air outlet. Air was introduced into the muffle furnace at a flow rate of 10 m / s, and the temperature was raised to 400℃ for sintering for 4 hours. The composite material was then prepared by washing with water, washing with alcohol, and drying.

[0033] Figure 1 This is a TEM image of the composite material, which shows that the composite material has a coating layer.

[0034] Figure 2 The image is an HRTEM image of the composite material, which shows that the material is composed of two phases, ZnMn2(PO4)2 and ZnMn3(P2O7)2, forming a composite structure.

[0035] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the sintering temperature is 200°C.

[0036] In a muffle furnace, 0.45 mol of manganese nitrate was placed at the air inlet, and 0.2 mol of zinc nitrate and 0.25 mol of pyrophosphate crystals were placed at the air outlet. Air was introduced into the muffle furnace at a flow rate of 10 m / s. After sintering at 200℃ for 4 hours, the mixture was washed with water, alcohol, and dried to obtain the composite material.

[0037] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the sintering temperature is 1000℃.

[0038] In a muffle furnace, 0.45 mol of manganese nitrate was placed at the air inlet, and 0.2 mol of zinc nitrate and 0.25 mol of pyrophosphate crystals were placed at the air outlet. Air was introduced into the muffle furnace at a flow rate of 10 m / s. After sintering at 1000℃ for 4 hours, the mixture was washed with water, alcohol, and dried to obtain the composite material.

[0039] Comparative Example 3 In a muffle furnace, 0.02 mol zinc nitrate, 0.04 mol manganese nitrate and 0.04 mol diammonium hydrogen phosphate are uniformly mixed and calcined at 700℃ for 5 h to obtain ZnMn2(PO4)2 material.

[0040] Example 2 In a muffle furnace, 0.44 mol of manganese nitrate was placed at the air inlet, and 0.22 mol of zinc nitrate and 0.22 mol of pyrophosphate crystals were placed at the air outlet. Air was introduced into the muffle furnace at a flow rate of 20 m / s, and sintering was carried out at 300℃ for 8 hours. Then, the mixture was washed with water, alcohol, and dried to obtain the composite material.

[0041] Example 3 In a muffle furnace, 0.6 mol of manganese nitrate was placed at the air inlet, and 0.2 mol of zinc oxalate and 0.4 mol of pyrophosphate crystals were placed at the air outlet. Air was introduced into the muffle furnace at a flow rate of 300 m / s, and sintering was carried out at 600℃ for 6 hours. Then, the mixture was washed with water, alcohol, and dried to obtain the composite material.

[0042] Example 4 In a muffle furnace, 0.45 mol of manganese nitrate was placed at the air inlet, and 0.2 mol of zinc nitrate and 0.25 mol of pyrophosphate crystals were placed at the air outlet. Air was introduced into the muffle furnace at a flow rate of 20 m / s, and the furnace was sintered at 800℃ for 4 hours. The resulting composite material was then washed with water, alcohol, and dried.

[0043] Example 5 In a muffle furnace, 0.5 mol of manganese nitrate was placed at the air inlet, and 0.2 mol of zinc acetate and 0.3 mol of pyrophosphate crystals were placed at the air outlet. Air was introduced into the muffle furnace at a flow rate of 20 m / s. The mixture was sintered at 900℃ for 1 hour, and then washed with water, alcohol, and dried to obtain the composite material.

[0044] Battery assembly is completed using the following method: The composite materials obtained in Examples 1-5 and Comparative Examples 1-2, as well as the zinc manganese phosphate material in Comparative Example 3, were used as positive electrode materials. These materials were mixed with conductive agent acetylene black (AB) and binder polyvinylidene fluoride (PVDF) at a mass ratio of 7:2:1, using N-methylpyrrolidone (NMP) as solvent. The mixture was stirred at 800 rpm for 2 hours in a small beaker to obtain a slurry. The slurry was coated onto a stainless steel current collector using an automatic coating machine, laid flat on tempered glass, and dried in a vacuum drying oven at 85°C for 4 hours. The resulting electrode sheets were then die-cut into 12 mm diameter plates and dried in a vacuum drying oven at 105°C for 4 hours. Finally, a CR2032 coin cell was assembled. This cell uses a 16 mm diameter, 0.5 mm thick pure zinc sheet as the negative electrode, a mixture of 3M zinc sulfate and 0.05M manganese sulfate as the electrolyte, and a 18 mm diameter Whatman GF / D glass fiber membrane as the separator.

[0045] After the battery assembly was completed and aged for 12 hours, charge-discharge tests were conducted at different potentials. The discharge specific capacity of the samples after 100 cycles at a current density of 100 mA / g under voltages of 0.8-1.95V is shown in Table 1.

[0046] Table 1 The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A zinc-manganese pyrophosphate composite material, characterized in that, The specific structure is as follows: zinc manganese pyrophosphate coating layer is present on the surface of zinc manganese phosphate.

2. The preparation method of the zinc manganese pyrophosphate composite material as described in claim 1, characterized in that, Includes the following steps: Manganese nitrate is placed at the upper air vent of the calcining furnace, and zinc salt and pyrophosphate are mixed evenly and placed at the lower air vent of the calcining furnace for calcination to obtain the final product.

3. The preparation method according to claim 2, characterized in that, An oxidizing atmosphere is continuously introduced into the calcining furnace.

4. The preparation method according to claim 3, characterized in that, The flow rate of the oxidizing atmosphere is 10~30 m / s.

5. The preparation method according to claim 2, characterized in that, The zinc salt is at least one of zinc nitrate, zinc acetate, and zinc oxalate.

6. The preparation method according to any one of claims 2-5, characterized in that, In the calcining furnace, the molar ratio of zinc salt, manganese salt, and pyrophosphate is 1:2~3:1~2.

7. The preparation method according to claim 6, characterized in that, The calcination temperature is 300~900℃, and the calcination time is 1~10h.

8. A zinc-ion battery, characterized in that, The zinc-manganese phosphate material comprising zinc-manganese pyrophosphate composite as described in claim 1 or zinc-manganese phosphate material comprising zinc-manganese pyrophosphate composite prepared by any one of claims 2-7.

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