Composite positive electrode material, preparation method and proton battery

Abstract

The invention aims to provide a composite positive electrode material, a preparation method and a proton battery. The lithium ion battery cathode material comprises the following components in percentage by mass: 70%-99.7% of a cathode active material and 0%-30% of a coating material, the positive electrode activity is a protonation product MnOOHx of MnO2, and the coating material is a proton conductor; wherein the coating layer comprises a first coating layer and a second coating layer, and the first coating layer comprises AgCl, amorphous carbon and calcium sulfate hydrate; the second coating layer comprises sulfate hydrate, hydrosulfate, dihydric phosphate, pyrophosphate, phosphate hydrate, a sulfate-aluminum oxide compound, a nitrate-aluminum oxide compound, imidazole proton salt, pyridine proton salt, sulfimide proton salt and chloro-lithium borate. The invention is applied to the technical field of electrochemistry.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, and particularly to a composite cathode material, its preparation method, and a proton battery. Background Technology

[0002] Lithium-ion batteries face numerous challenges, including resource constraints, environmental pollution, and safety issues. Therefore, researchers are dedicated to developing batteries that utilize other charge carriers. Proton batteries possess the smallest mass and ionic radius, enabling faster diffusion kinetics; the smallest hydrated radius of protons reduces charge transfer resistance, enhancing reaction kinetics; and the use of aqueous electrolytes improves battery safety and stability. Consequently, proton batteries have become an important development direction for high-power, low-cost, highly safe, and environmentally friendly energy storage systems.

[0003] However, proton batteries are still in the early stages of research and face many challenges, mainly including high corrosion, high hydrogen evolution, and high cathode requirements. Currently, the widely studied metal oxide cathode, MnO2, is easily corroded and dissolved in acidic solutions. Furthermore, the current dissolution-precipitation mechanism of MnO2 makes it difficult to simultaneously meet the requirements of high capacity and high stability, limiting the battery's cycle life and necessitating the continuous replenishment of MnSO4 to compensate for Mn2+ loss. Initially, MnO2 was primarily studied for its application in Zn2+ batteries, where the storage mechanism involves the co-intercalation of H+ and Zn2+. Therefore, protons can reversibly intercalate / extract from MnO2. Modification methods can be used to reversibly intercalate / extract H+ from MnO2 as a proton battery cathode material. This intercalation / extraction mechanism can effectively ensure the structural stability of MnO2 and significantly improve the cycle life of the MnO2 cathode.

[0004] The mechanism by which MnO2, the cathode material for proton batteries, stores H+ is the dissolution and release mechanism of MnO2. Although this mechanism provides the cathode material with an ultra-high theoretical specific capacity (~616 mAh / g), the continuous dissolution of Mn2+ will cause continuous loss of MnO2 in the cathode. With the accumulation of cycles, this will lead to problems such as rapid capacity decay, decreased coulombic efficiency, lag in charge and discharge plateau, increased side reactions, and shortened cycle life.

[0005] By protonating and coating MnO2 materials, the dissolution-deposition channels of MnO2 are effectively blocked, forcing MnO2 to undergo reversible H+ insertion / extraction through the insertion / extraction mechanism, stabilizing the intercrystalline structure of MnO2, and effectively improving the cycle stability of the cathode material.

[0006] For example, Chinese patent CN1290216C discloses a method for preparing a positive electrode composite electrode to reduce the negative differential effect of proton exchange membrane fuel cells. However, this electrode is easily corroded and dissolved in acidic solutions. Moreover, the dissolution-precipitation mechanism of MnO2 makes it difficult to meet the requirements of high capacity and high stability. In addition, the current mechanism by which MnO2, the positive electrode material of proton batteries, stores H+ is through the dissolution and precipitation mechanism of MnO2. Although this mechanism provides the positive electrode material with an ultra-high theoretical specific capacity (~616 mAh / g), the continuous dissolution of Mn2+ will cause continuous loss of MnO2 in the positive electrode. With the accumulation of cycles, this will lead to problems such as rapid capacity decay, decreased coulombic efficiency, lag in charge and discharge plateau, increased side reactions, and shortened cycle life.

[0007] Therefore, it is necessary to provide a composite cathode material, preparation method, and proton battery. By protonating and surface coating MnO2 material, the dissolution-deposition channel of MnO2 is effectively blocked, forcing MnO2 to reversibly insert / extract H+ through the insertion / extraction mechanism, stabilizing the intercrystalline structure of MnO2, and effectively improving the cycle stability of the cathode material. The reversible storage of H+ is achieved by utilizing the insertion / extraction mechanism of MnO2. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a composite cathode material, preparation method and proton battery. By protonation and surface coating of MnO2 material, the dissolution-deposition channel of MnO2 is effectively blocked, forcing MnO2 to reversibly insert / extract H+ through the insertion / extraction mechanism, stabilizing the intercrystalline structure of MnO2, effectively improving the cycle stability of the cathode material, and utilizing the insertion / extraction mechanism of MnO2 to achieve reversible storage of H+.

[0009] The technical solution adopted in this invention is as follows: the composite cathode material, by mass percentage, comprises the following components: the cathode active material accounts for 70%-99.7%, and the coating material accounts for 0.3%-30%; the cathode active material is MnOOHx, a protonation product of MnO2, and the coating material is a proton conductor; the coating material coats the cathode active material to form a coating layer, wherein the coating layer includes a first coating layer and a second coating layer, the first coating layer includes AgCl, amorphous carbon, and calcium sulfate hydrate; the second coating layer includes sulfate hydrate, hydrogen sulfate, dihydrogen phosphate, pyrophosphate, phosphate hydrate, sulfate-alumina complex, nitrate-alumina complex, imidazole proton salt, pyridine proton salt, sulfonamide proton salt, and lithium chloroborate.

[0010] Furthermore, the value of x in MnOOHx of the positive electrode active material is 0.8-1.5; the thickness of the first coating layer is 1-50 nm; preferably 3-20 nm; the thickness of the second coating layer is 5-300 nm; preferably 10-150 nm; the mass ratio of the first coating layer to the second coating layer is (0.01-0.4):1, preferably (0.01-0.1):1.

[0011] Furthermore, a method for preparing the composite cathode material includes the following steps: Step S1: Add the manganese source to the alkaline solution, and gradually add the oxidant while controlling the pH value of the solution to obtain MnOOHx; Step S2: The obtained positive electrode active material MnOOHx is coated with a first coating layer on its surface by co-precipitation, chemical vapor deposition, or magnetron sputtering. Step S3: Add the cathode material with the first coating layer and the second coating layer material with proton conduction capability to the solvent, and obtain the composite cathode material by stirring, drying and high temperature treatment.

[0012] Furthermore, during the preparation of MnOOHx, the pH value of the solution needs to be controlled to be 8-9; the manganese source includes manganese sulfate, manganese chloride, manganese nitrate, manganese acetate, and manganese perchlorate; the alkaline solution includes sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, and ammonia; the oxidant includes hydrogen peroxide aqueous solution, potassium persulfate (K2S2O8), chloric acid, potassium peroxymonosulfate, potassium dichromate, potassium permanganate, and sodium hypochlorite. Further, the proton battery includes a positive electrode, an electrolyte, and a negative electrode; the positive electrode includes a composite positive electrode material, conductive carbon, and a binder; the negative electrode includes a negative electrode material, conductive carbon, and a binder; the conductive carbon includes conductive carbon black, acetylene black, conductive graphite, carbon nanotubes, carbon nanofibers, graphene, and Ketjen black; the binder includes polyvinylidene fluoride, polyvinylidene fluoride copolymer, nitrile rubber, hydrogenated nitrile rubber, polytetrafluoroethylene, and styrene-butadiene rubber; the electrolyte includes sulfuric acid electrolyte, phosphoric acid electrolyte, and gel electrolyte; the negative electrode material includes MoO3, WO3, TiO2, MXene, and 3,4,9,10-perylenetetracarboxylic dianhydride.

[0013] The beneficial effects of this invention are: 1. Reversible storage of H+ is achieved through the insertion / extraction mechanism of MnO2. By protonating and surface coating MnO2, the contact between the MnO2 cathode material and the acidic electrolyte is effectively blocked, ensuring the structural stability of MnO2 during charging and discharging, thereby significantly improving its cycle life. 2. The coating material is a proton conductor and can exist stably in acidic solutions. Since the composite cathode material itself contains protons, it can directly deprotonate to provide H+ during charging and discharging, thus avoiding excessive consumption of H+ in the electrolyte. 3. The first coating layer can effectively inhibit the dissolution of manganese and reduce interfacial impedance; the second coating layer can realize the rapid transport of protons, and promote the rapid transport of protons while isolating the acidic electrolyte and the positive electrode active material, thus ensuring the rate performance of the material. 4. By protonating and coating MnO2 materials, the dissolution-deposition channels of MnO2 are effectively blocked, forcing MnO2 to undergo reversible insertion / extraction of H+ through the insertion / extraction mechanism, stabilizing the intercrystalline structure of MnO2 and effectively improving the cycle stability of the cathode material. Detailed Implementation

[0014] Example 1: The preparation method of the composite cathode material includes the following steps: (1) Synthesis of positive electrode active material MnOOHx: Prepare 100 mL of 1 mol / L sodium hydroxide aqueous solution. Weigh 7.55 g of manganese sulfate and dissolve it in 50 mL of water. Control the stirring speed at 1000 rpm / min. Gradually add the MnSO4 solution dropwise to the sodium hydroxide aqueous solution, forming a milky white suspension. Sonicate the suspension for 10 min. While stirring at 1000 rpm / min, add 5 mL of 30% hydrogen peroxide aqueous solution dropwise. Observe the emulsion color gradually turning brownish-red. During the addition of hydrogen peroxide aqueous solution, continuously test the pH value of the solution and control it at 9-10. After the hydrogen peroxide is completely added, continue stirring for 3 h to allow the generated MnOOHx to gradually stabilize. Finally, filter, wash, and vacuum dry to obtain the positive electrode active material. (2) The first coating layer of the positive electrode active material: Prepare 10 ml of a 0.02 mol / L NaCl solution; Prepare 10 ml of 0.02 mol / L AgNO3 solution; Dissolve 1.5g of dehydrated sorbitan monooleate in 80ml of cyclohexane, then add 5g of MnOOHx, sonicate for 10min, and stir at 1000rpm for 20min; add the above AgNO3 solution to the mixture and stir at 1000rpm for 30min; place the mixture in an ice-water bath and control the temperature between 0-5℃.

[0015] Then, NaCl solution was slowly added dropwise to the above mixed solution while stirring at 1000 rpm, and then stirred for 30 min. After centrifugation, washing, and vacuum drying, the intermediate product coated with the first layer of coating material was obtained. (3) The second coating layer of the positive electrode active material: Weigh 0.1 g of di(methanesulfonyl)imide and dissolve it in 50 mL of N,N-dimethylformamide solvent. Then, place the intermediate product in the mixture and stir for 30 min. Then, use a rotary evaporator to evaporate the solvent at 50 °C. Finally, treat the powder in an Ar environment at 100 °C for 1 h to obtain sample 1.

[0016] Example 2: The concentrations of NaCl solution and AgNO3 solution in Example 1 were adjusted to 0.01 mol / L, and the other conditions remained unchanged. The resulting sample was named Sample 2.

[0017] Example 3: The concentrations of NaCl solution and AgNO3 solution in Example 1 were adjusted to 0.05 mol / L, and the sample obtained under the same conditions was named Sample 3.

[0018] Example 4: The mass of di(methanesulfonyl)imide in Example 1 was adjusted to 0.2 g, and the sample obtained under the same conditions was named Sample 4.

[0019] Comparative Example 1: The pH of the solution in Example 1 was adjusted to 7-8, and the other conditions remained unchanged. The resulting sample was named Control Sample 1. Comparative Example 2: The MnOOHx prepared in Example 1 was directly used as control sample 2; Comparative Example 3: The intermediate product coated with the first layer of coating material obtained in Example 1 was used as control sample 3.

[0020] Electrochemical Measurement: The composite positive electrode, conductive carbon, and PVDF were weighed in a weight ratio of 9:0.5:0.5 and placed in an agate mortar. An appropriate amount of N-methylpyrrolidone was added as a dispersant and the mixture was ground for 20 minutes to obtain a uniformly dispersed positive electrode slurry. The slurry was then evenly coated onto the surface of the carbon cloth using a scraper and dried in a vacuum oven at 100°C for 12 hours. Finally, the dried electrode was cut into round pieces with a diameter of 9 mm for later use.

[0021] MoO3, conductive carbon, and PVDF were weighed in a weight ratio of 9:0.5:0.5 and placed in an agate mortar. An appropriate amount of N-methylpyrrolidone was added as a dispersant and the mixture was ground for 20 minutes to obtain a uniformly dispersed negative electrode slurry. The slurry was then evenly coated onto the surface of carbon cloth using a scraper and dried in a vacuum oven at 100°C for 12 hours. Finally, the dried electrode was cut into round pieces with a diameter of 10 mm for later use.

[0022] A battery was assembled in a Swagelok electrochemical test cell using a composite positive electrode as the positive electrode, a MoO3 electrode as the negative electrode, glass fiber filter paper as the separator, and 1 mol / L H2SO4 as the electrolyte. Electrochemical performance was then tested. Charge-discharge tests were performed using a Newway testing system, with a voltage range of 0.4V-1.5V and a cycle rate of 10C (1C = 200mA / g).

[0023] Product effectiveness test: Swagelok batteries prepared in the examples and comparative examples were tested for their first-cycle charge specific capacity (calculated based on the positive electrode mass), efficiency, and cycle stability. The test method was as follows: the batteries were placed in a 25°C constant temperature chamber for testing. The first-cycle charge-discharge rate was 0.1C, followed by cycle testing at a rate of 10C, with a voltage range of 0.4-1.5V. Table 1: First-cycle charge specific capacity, first-cycle charge-discharge efficiency, and capacity retention rate after 1000 cycles for samples 1-4 and control samples 1-3.

[0024] As can be seen from Table 1, the composite cathode materials prepared in Examples 1-4 of this invention, when used in proton batteries, exhibit significantly better first-cycle charge-discharge efficiency and cycle stability than comparative samples 1-3.

[0025] Although the embodiments of the present invention are described with reference to actual solutions, they do not constitute a limitation on the meaning of the present invention. Modifications to the embodiments and combinations with other solutions based on this specification will be obvious to those skilled in the art.

Claims

1. A composite cathode material, characterized in that, The composite cathode material comprises the following components by mass percentage: 70%-99.7% cathode active material and 0.3%-30% coating material; the cathode active material is MnOOHx, a protonation product of MnO2, and the coating material is a proton conductor; the coating material coats the cathode active material to form a coating layer.

2. The composite cathode material according to claim 1, characterized in that: The first coating layer comprises AgCl, amorphous carbon, and calcium sulfate hydrate.

3. The composite cathode material according to claim 1, characterized in that: The coating layer includes a first coating layer and a second coating layer. The second coating layer includes sulfate hydrate, hydrogen sulfate, dihydrogen phosphate, pyrophosphate, phosphate hydrate, sulfate-alumina complex, nitrate-alumina complex, imidazole proton salt, pyridine proton salt, sulfonamide proton salt, and lithium chloroborate.

4. The composite cathode material according to claim 1, characterized in that: The value of x in the MnOOHx of the positive electrode active material is 0.8-1.5; the thickness of the first coating layer is 1-50 nm; the thickness of the second coating layer is 5-300 nm; and the mass ratio of the first coating layer to the second coating layer is (0.01-0.4):

1.

5. A method for preparing the composite cathode material according to any one of claims 1 to 4, characterized in that: The preparation method includes the following steps: Step S1: Add the manganese source to the alkaline solution, and gradually add the oxidant while controlling the pH value of the solution to obtain MnOOHx; Step S2: The obtained positive electrode active material MnOOHx is used to form the first coating layer on its surface by co-precipitation, chemical vapor deposition or magnetron sputtering; Step S3: Add the positive electrode material with the first coating layer and the second coating layer material with proton conduction capability to a solvent, and obtain the composite positive electrode material by stirring, drying and high temperature treatment.

6. The preparation method according to claim 1, characterized in that: During the preparation of MnOOHx, the pH value of the solution needs to be controlled, with a pH value of 8-9; the manganese source includes manganese sulfate, manganese chloride, manganese nitrate, manganese acetate, and manganese perchlorate; the alkaline solution includes sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, and ammonia; the oxidant includes hydrogen peroxide aqueous solution, potassium persulfate (K2S2O8), chloric acid, potassium peroxymonosulfate, potassium dichromate, potassium permanganate, and sodium hypochlorite.

7. A proton battery, comprising a positive electrode, an electrolyte, and a negative electrode, characterized in that, The positive electrode sheet includes conductive carbon, a binder, and a composite positive electrode material as described in claim 1, wherein the composite positive electrode material is connected to the conductive carbon via the binder, and the negative electrode sheet includes a negative electrode material, conductive carbon, and a binder.

8. The proton battery according to claim 7, characterized in that, The conductive carbon includes conductive carbon black, acetylene black, conductive graphite, carbon nanotubes, carbon nanofibers, graphene, and Ketjen black.

9. The proton battery according to claim 7, characterized in that, The adhesive includes polyvinylidene fluoride, polyvinylidene fluoride copolymer, nitrile rubber, hydrogenated nitrile rubber, polytetrafluoroethylene, and styrene-butadiene rubber.

10. The proton battery according to claim 7, characterized in that, The electrolyte includes sulfuric acid electrolyte, phosphoric acid electrolyte, and gel electrolyte; the negative electrode material includes MoO3, WO3, TiO2, MXene, and 3,4,9,10-perylenetetracarboxylic dianhydride.

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