A secondary zinc-manganese battery cathode material, preparation method, and secondary zinc-manganese battery

Abstract

This invention relates to the field of battery cathode materials technology, and discloses a secondary zinc-manganese battery cathode material, its preparation method, and a secondary zinc-manganese battery. The secondary zinc-manganese battery cathode material includes manganese dioxide, graphite, calcium stearate, polypyrrole, and niobium pentoxide nanomaterials. The polypyrrole is coated onto the surface of the manganese dioxide via in-situ polymerization, and the niobium pentoxide nanomaterials are integrated into the polypyrrole-coated manganese dioxide composite material via in-situ growth. This invention provides a secondary zinc-manganese battery cathode material that, by employing a manganese dioxide / polypyrrole / niobium pentoxide composite material, constructs a stable conductive network and ion channels, significantly improving the conductivity and structural stability of the cathode material at low temperatures.

Description

Technical Field

[0001] This invention relates to the field of battery cathode material technology, and more specifically, to a secondary zinc-manganese battery cathode material, a preparation method thereof, and a secondary zinc-manganese battery. Background Technology

[0002] Rechargeable zinc-manganese batteries, as a type of recyclable electrochemical energy storage device, offer advantages such as being environmentally friendly and resource-saving. Compared to disposable zinc-manganese batteries, they can have their lifespan extended through multiple charge-discharge cycles, thereby reducing the generation of waste batteries and lessening the burden on the environment. By recycling and reusing battery materials, the use of natural resources such as zinc and manganese dioxide is reduced, energy consumption is lowered, and this aligns with the green and low-carbon development strategy.

[0003] Conventional rechargeable zinc-manganese batteries typically use potassium hydroxide (KOH) as the electrolyte, which has a relatively low freezing point and can maintain electrochemical activity below -18°C under certain concentration conditions, thus facilitating battery operation in low-temperature environments. However, traditional zinc-manganese batteries still face significant challenges at low temperatures, such as substantial capacity decay, voltage plateau decline, increased internal resistance, and intensified electrode polarization, limiting their application in cold regions or specific low-temperature conditions. This is particularly true in northern my country, where winter outdoor temperatures often drop to -10°C or even lower, placing even higher demands on the battery's low-temperature performance.

[0004] CN116072989A discloses a manganese-based oxide cathode aqueous rechargeable zinc-manganese battery with added solid acid. Although the patent document mentions doping Nb2O5 into MnO2 to improve its electrochemical performance, it does not clearly disclose the specific implementation method of the material combination or its applicability in low-temperature environments.

[0005] Therefore, zinc-manganese secondary batteries still struggle to achieve long-term stable operation under low-temperature conditions (such as -10°C and below), especially in terms of capacity retention, rate performance, and cycle stability. Further research is needed on electrode materials and matching electrolyte systems that combine excellent low-temperature performance and reversibility to promote the practical application of this type of battery in extreme environments. Summary of the Invention

[0006] This invention aims to address the poor performance of existing rechargeable zinc-manganese batteries at low temperatures and the issues of uniformity, conductivity, and stability in the preparation of cathode materials. This invention proposes a cathode material for rechargeable zinc-manganese batteries that utilizes a manganese dioxide / polypyrrole / niobium pentoxide composite material to construct a stable conductive network and ion channels, significantly improving the conductivity and structural stability of the cathode material at low temperatures.

[0007] To address the aforementioned technical problems, this invention provides a novel positive electrode material for secondary zinc-manganese batteries, comprising manganese dioxide, graphite, calcium stearate, polypyrrole, and niobium pentoxide nanomaterials. The polypyrrole is coated onto the surface of the manganese dioxide via in-situ polymerization, and the niobium pentoxide nanomaterials are integrated into the polypyrrole-coated manganese dioxide composite material via in-situ growth.

[0008] The technical solution provided by this invention brings significant beneficial effects:

[0009] 1. Significantly Improved Low-Temperature Performance: By using polypyrrole to conductively coat manganese dioxide and integrating niobium pentoxide nanomaterials in situ, the electronic conductivity and ion transport kinetics of the cathode material are synergistically enhanced through the tunnel structure of the niobium pentoxide TT crystal phase. Polypyrrole, acting as both a conductive and protective layer, effectively suppresses the dissolution and structural degradation of manganese dioxide at low temperatures. Niobium pentoxide, through its inherent tunnel structure, promotes rapid ion diffusion and contributes pseudocapacitance, jointly overcoming the problems of limited ion transport and slow charge transfer at low temperatures. This allows the battery prepared by this invention to maintain excellent discharge capacity, a stable voltage plateau, and good cycle stability even at low temperatures such as -10℃ or even -15℃, far exceeding the level of existing technologies.

[0010] 2. Enhanced Conductivity Network and Structural Stability: In-situ coating of polypyrrole on the manganese dioxide surface forms a dense conductive network, effectively reducing the internal resistance of the electrode. The in-situ integration of niobium pentoxide nanomaterials further optimizes ion and electron transport pathways, while its high chemical stability enhances the overall structural stability of the composite material, extending the battery's lifespan.

[0011] 3. Achieving uniform dispersion and efficient integration: Advanced integration technologies such as in-situ polymerization and in-situ growth are adopted to ensure highly uniform dispersion and close interfacial contact of polypyrrole and niobium pentoxide nanomaterials on manganese dioxide matrix, solving the problem of uneven distribution of additives in traditional physical mixing and maximizing the synergistic effect between components.

[0012] 4. Synergistic pseudocapacitive effect: Manganese dioxide, conductive polymers and niobium pentoxide can all contribute to pseudocapacitance. Through rapid surface Faraday reactions, they effectively overcome the bulk diffusion limitation at low temperatures and improve the power density and energy density of the battery.

[0013] 5. By adopting a mercury-free and cadmium-free environmentally friendly system, this invention significantly reduces the amount of heavy metal elements used in batteries, avoids the environmental pollution problems caused by them, and improves the green and environmentally friendly performance of the product.

[0014] According to one embodiment of the present invention, the cathode material contains the following components in parts by weight: 75-90 parts manganese dioxide; 6-11 parts graphite; 0.075-0.15 parts calcium stearate; 0.37-9 parts polypyrrole; and 0.75-6 parts niobium pentoxide nanomaterials. This preferred range of component proportions ensures a balance in material performance, further optimizing the battery's power output and cycle stability while maintaining high energy density.

[0015] According to one embodiment of the present invention, the positive electrode material contains the following components in parts by weight: 90 parts manganese dioxide; 9 parts graphite; 0.1 parts calcium stearate; 5 parts polypyrrole; and 2 parts niobium pentoxide nanomaterials. This specific ratio represents an experimentally verified optimal combination that enables the battery to achieve excellent discharge capacity and long cycle life at low temperatures, and is the preferred solution with the most outstanding performance in practical applications of the present invention.

[0016] According to one embodiment of the present invention, the niobium pentoxide is niobium pentoxide nanoparticles or nanofibers in the TT crystal phase. The TT crystal phase niobium pentoxide has a unique tunnel-like structure (approximately...). (diameter), can significantly promote the growth of ions, such as Zn 2+ and OH - The rapid diffusion of ions, especially in low-temperature environments, can effectively alleviate ion transport limitations, thereby further improving the battery's high-rate discharge performance and low-temperature response capability.

[0017] According to one embodiment of the present invention, the manganese dioxide is a manganese dioxide nanostructure.

[0018] The present invention also provides a method for preparing the secondary zinc-manganese battery cathode material according to any of the above descriptions, comprising the following steps:

[0019] S1. Manganese dioxide / polypyrrole composite material is obtained by in-situ oxidative polymerization of pyrrole monomer on the surface of manganese dioxide;

[0020] S2. Niobium pentoxide nanoparticles or nanofibers are synthesized by sol-gel method and then calcined at low temperature to obtain TT-niobium pentoxide;

[0021] S3. The manganese dioxide / polypyrrole composite material obtained in step S1 and the niobium pentoxide nanomaterial obtained in step S2 are subjected to in-situ growth or drop-in integration treatment to form a manganese dioxide / polypyrrole / niobium pentoxide composite material.

[0022] S4. Positive electrode powder is prepared by combining manganese dioxide / polypyrrole / niobium pentoxide composite material with graphite and calcium stearate.

[0023] According to one embodiment of the present invention, step S4 specifically includes: mixing the composite material obtained in step S3 with graphite and calcium stearate, dry mixing, pressing, granulating and sieving to prepare positive electrode powder.

[0024] According to an embodiment of the present invention, step S3 specifically includes: mixing the manganese dioxide / polypyrrole composite material obtained in step S1 with graphite and calcium stearate, and then performing in-situ growth or drop-in integration treatment with the niobium pentoxide nanomaterial obtained in step S2 to form a manganese dioxide / polypyrrole / niobium pentoxide composite material.

[0025] The present invention also provides a secondary zinc-manganese battery, comprising a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode adopts the secondary zinc-manganese battery positive electrode material described in any of the above-mentioned embodiments.

[0026] According to one embodiment of the present invention, the electrolyte is a 26%-45% (w / w) aqueous solution of potassium hydroxide. Detailed Implementation

[0027] The technical solution of the present invention will now be clearly and completely described. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. All experiments used analytical grade reagents and deionized water.

[0028] This invention provides a novel cathode material for secondary zinc-manganese batteries, which improves battery performance in low-temperature environments.

[0029] Specifically, the cathode material comprises manganese dioxide, graphite, calcium stearate, polypyrrole, and niobium pentoxide nanomaterials. Manganese dioxide, as the active material, is the core component responsible for the electrochemical reaction and energy delivery in the battery. Graphite, as a conductive agent, constructs an efficient electron transport network within the cathode material, ensuring electrons flow rapidly to reaction sites and reducing internal resistance. Calcium stearate, as a lubricant and processing aid, improves the flowability and formability of the cathode powder during pressing and granulation, enhancing production efficiency. Polypyrrole, as a conductive polymer, is tightly coated onto the surface of the manganese dioxide through in-situ polymerization, forming a uniform conductive coating and protective layer. This coating not only significantly improves the electronic conductivity of manganese dioxide but also effectively inhibits its dissolution and structural degradation in the electrolyte, thereby enhancing the cycle stability and lifespan of the cathode material. Niobium pentoxide nanomaterials are integrated into the polypyrrole-coated manganese dioxide composite material through in-situ growth. Their unique crystal structure and pseudocapacitive properties can significantly promote ion transport and provide an additional charge storage mechanism.

[0030] Furthermore, the cathode material contains the following components in parts by mass: 75-90 parts manganese dioxide; 6-11 parts graphite; 0.075-0.15 parts calcium stearate; 0.37-9 parts polypyrrole; and 0.75-6 parts niobium pentoxide nanomaterials.

[0031] Specifically, the niobium pentoxide is niobium pentoxide nanoparticles or nanofibers in the TT crystal phase. The TT crystal phase niobium pentoxide has a unique tunnel-like crystal structure, with a diameter of approximately [missing information] along the b-axis. The open tunnel.

[0032] Furthermore, the manganese dioxide is a manganese dioxide nanostructure.

[0033] Example 1

[0034] In this embodiment, the battery fabrication steps are as follows:

[0035] 1. Raw material preparation

[0036] Electrolytic manganese dioxide (EMD): Commercially available, purity ≥99%.

[0037] Expanded graphite: Commercially available, purity ≥99%.

[0038] Calcium stearate: Commercially available, purity ≥99%.

[0039] Potassium permanganate (KMnO4): analytical grade.

[0040] Pyrrole monomer: analytical grade, purified by vacuum distillation before use.

[0041] Perchloric acid (HClO4): analytical grade.

[0042] Ethanol: analytical grade.

[0043] Niobium pentaethoxy (Nb(OEt)5): analytical grade.

[0044] Potassium hydroxide (KOH): analytical grade.

[0045] Zinc powder: Commercially available, purity ≥99.9%.

[0046] Sodium polyacrylate: Commercially available.

[0047] Nano-indium oxide: nanoparticles <100nm, commercially available.

[0048] 2. Preparation of cathode materials

[0049] Pretreatment: Preparation of manganese dioxide nanostructures

[0050] Method: Hydrothermal synthesis.

[0051] Specific operations:

[0052] Weigh 3.0g of potassium permanganate (KMnO4) and dissolve it in 250mL of deionized water.

[0053] Transfer the solution to a 500 mL beaker and stir at 300 rpm for 30 minutes on a magnetic stirrer to ensure that the KMnO4 is completely dissolved.

[0054] The above solution was transferred to a 300 mL stainless steel autoclave lined with polytetrafluoroethylene.

[0055] Seal the autoclave and place it in an electric heating drying oven preheated to 150°C for a constant temperature reaction of 6 hours.

[0056] After the reaction is complete, allow the autoclave to cool naturally to room temperature.

[0057] The black precipitate obtained from the reaction was collected by vacuum filtration and was identified as MnO2. It was then washed repeatedly with a large amount of deionized water until the pH of the filtrate was neutral, approximately pH 6-7, and subsequently washed once with anhydrous ethanol.

[0058] The washed MnO2 precipitate was dried in a vacuum oven at 80°C for 12 hours.

[0059] The product obtained is porous hydrated manganese dioxide nanosheets. Layered manganese oxide is extremely unstable under high temperature and high pressure, and its layered structure will collapse and transform into tunnel-type porous manganese dioxide nanostructures.

[0060] Step S1: Pyrrole monomers are polymerized in situ on the surface of manganese dioxide to obtain a manganese dioxide / polypyrrole composite material;

[0061] Method: In-situ oxidative polymerization initiated by manganese dioxide.

[0062] Specific operations:

[0063] S11. Weigh 90 parts by mass of porous MnO2 nanosheets, with a mass of 9.0g. Disperse them in 200mL of deionized water and magnetically stir at 400rpm for 1 hour in a 500mL beaker to ensure uniform dispersion of MnO2.

[0064] S12. In a separate beaker, weigh 5 portions of pyrrole monomer, each with a mass of 0.5g, and dissolve them in 25mL of deionized water to prepare a pyrrole monomer solution.

[0065] S13. While continuously stirring the MnO2 dispersion, add 0.1M perchloric acid solution dropwise to adjust the pH of the dispersion to 2-3 and maintain it stable within this pH range.

[0066] S14. The pyrrole monomer solution prepared in step S12 is slowly added dropwise to the MnO2 dispersion through a constant pressure dropping funnel while continuously stirring at 400 rpm and maintaining pH 2-3. The dropping time is controlled at 30 minutes.

[0067] S15. After the addition is complete, continue stirring the reaction mixture at room temperature (25°C) for 6 hours to ensure complete polymerization of the pyrrole monomer. During this process, the solution color will gradually turn brownish-black, indicating the formation of the MnO2 / PPy composite material.

[0068] S16. Collect the obtained MnO2 / PPy composite material by centrifugation at 8000 rpm for 10 minutes.

[0069] S17. Wash the precipitate three times with deionized water and then three times with anhydrous ethanol to remove unreacted monomers and byproducts.

[0070] S18. Dry the washed MnO2 / PPy composite material in a vacuum oven at 100℃ overnight for about 12-16 hours.

[0071] S19. The product obtained is a porous manganese dioxide nanocomposite powder coated with polypyrrole.

[0072] Step S2: Niobium pentoxide nanoparticles or nanofibers are synthesized by sol-gel method and then calcined at low temperature to obtain TT-niobium pentoxide;

[0073] Method: Sol-gel method combined with low-temperature calcination.

[0074] Specific operations:

[0075] S21. Under a glove box or inert atmosphere, weigh an appropriate amount of niobium pentaethoxy, which will eventually be converted into 2 parts of TT-Nb2O5 nanomaterial with a mass of 0.2g. Dissolve the niobium pentaethoxy in 20mL of anhydrous ethanol and stir at 300rpm for 15 minutes on a magnetic stirrer to ensure complete dissolution.

[0076] S22. While stirring continuously at 300 rpm, slowly add 5 mL of deionized water dropwise at a rate of 0.5 mL / min using a syringe pump. The deionized water serves as the hydrolysing agent, and the addition time is approximately 10 minutes. Continue stirring for 2 hours to promote the hydrolysis and condensation reactions, forming a transparent sol that gradually gels.

[0077] S23. Transfer the obtained sol / gel to a drying oven and dry at 80°C for 24 hours to obtain gel powder.

[0078] S24. Grind the gel powder into a fine powder.

[0079] S25. Place the fine powder in a ceramic crucible and put it into a muffle furnace. Heat to 500°C at a heating rate of 5°C / min, and calcine at this temperature for 3 hours.

[0080] S26. After calcination, allow the muffle furnace to cool naturally to room temperature.

[0081] S27. The product obtained is TT-niobium pentoxide nanoparticles.

[0082] Step S3: The manganese dioxide / polypyrrole composite material obtained in step S1 and the niobium pentoxide nanomaterial obtained in step S2 are subjected to in-situ growth or drop-addition integration treatment to form a manganese dioxide / polypyrrole / niobium pentoxide composite material.

[0083] Method: Hydrothermal integration method.

[0084] Specific operations:

[0085] S31. Weigh the MnO2 / PPy composite material obtained in step S1, disperse it in 50 mL of deionized water, and stir it at 300 rpm for 30 minutes on a magnetic stirrer to ensure uniform dispersion.

[0086] S32. In a separate beaker, weigh an appropriate amount of the TT-Nb2O5 nanoparticles obtained in step S2, so that the final integrated amount is 2 portions, with a mass of 0.2g. Disperse or dissolve them in 20mL of deionized water and stir until homogeneous.

[0087] S33. Slowly add the Nb2O5 nanoparticle dispersion prepared in step S32 dropwise to the MnO2 / PPy dispersion while stirring at 300 rpm. After the addition is complete, continue stirring for 1 hour to ensure uniform mixing.

[0088] S34. Transfer the mixture to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene.

[0089] S35. Seal the high-pressure reactor and place it in an electric heating drying oven preheated to 160°C for 12 hours of constant temperature reaction.

[0090] S36. After the reaction is complete, allow the autoclave to cool naturally to room temperature.

[0091] S37. Collect the MnO2 / PPy / Nb2O5 composite material obtained from the reaction by vacuum filtration, wash it repeatedly with a large amount of deionized water, and then wash it once with anhydrous ethanol.

[0092] S38. Dry the washed composite material in a vacuum oven at 80°C for 12 hours.

[0093] S39. The product obtained is a ternary composite powder of manganese dioxide / polypyrrole / niobium pentoxide.

[0094] Step S4: The positive electrode powder is prepared by combining manganese dioxide / polypyrrole / niobium pentoxide composite material with graphite and calcium stearate. The process involves dry mixing, tableting, granulation, and sieving.

[0095] Specific operations:

[0096] S41. Weigh the MnO2 / PPy / Nb2O5 composite material, expanded graphite, and calcium stearate obtained in step S3 above, according to the required proportions. For example, weigh the MnO2 / PPy / Nb2O5 composite material, 9 parts of expanded graphite, and 0.1 parts of calcium stearate, wherein the MnO2 / PPy / Nb2O5 composite material contains 90 parts of MnO2, 5 parts of PPy, and 2 parts of Nb2O5.

[0097] S42. Place the weighed materials into a high-speed mixer and dry mix at 1000 rpm for 3 hours to ensure that all solid components are evenly dispersed.

[0098] S43. The dry-mixed powder is made into tablets using a conventional tableting process.

[0099] S 44. Granulate the sheet material using a granulator to form particles of the required size.

[0100] S45. Finally, the granulated material is sieved through a screen to collect positive electrode powder with a particle size range of 20-80 mesh.

[0101] 3. Preparation of negative electrode material and electrolyte

[0102] The negative electrode material uses existing conventional technology: zinc powder, sodium polyacrylate, and nano-indium oxide are mixed and dry-stirred at a mass ratio of 80:12:8 for 2.5 hours. Subsequently, electrolyte is added and wet-stirred for 2 hours, and finally degassing is performed to prepare the negative electrode zinc paste.

[0103] Electrolyte: 32% (w / w) potassium hydroxide aqueous solution.

[0104] 4. Battery assembly and performance testing

[0105] Battery assembly: Following the standard secondary zinc-manganese battery production line process, the above-prepared positive electrode powder, negative electrode zinc paste, and electrolyte are assembled into an AA-type secondary zinc-manganese battery.

[0106] Example 2

[0107] This embodiment prepares a secondary zinc-manganese battery using the same steps as in Example 1, but differs from Example 1 in the proportions of the components in the cathode material. In this embodiment, the cathode material contains the following components in parts by mass: 75 parts manganese dioxide; 11 parts graphite; 0.15 parts calcium stearate; 9 parts polypyrrole; and 5 parts niobium pentoxide nanomaterials.

[0108] In other embodiments, the niobium pentoxide nanomaterials are present in the following mass fractions: 0.17 parts, 1 part, 3 parts, or 6 parts.

[0109] Example 3

[0110] This embodiment prepares a secondary zinc-manganese battery using the same steps as in Example 1, but differs from Example 1 in the proportions of the components in the cathode material. In this embodiment, the cathode material contains the following components in parts by mass: 90 parts manganese dioxide; 5 parts graphite; 0.1 parts calcium stearate; 4 parts polypyrrole; and 1.5 parts niobium pentoxide nanomaterials.

[0111] Example 4

[0112] This embodiment differs from Embodiment 1 in that, in this embodiment, Nb₂O₅ is added dropwise to coat MnO₂ / PPy composite material, expanded graphite, and calcium stearate.

[0113] The cathode material composition is as follows: 90 parts electrolytic manganese dioxide, 5 parts polypyrrole, 2 parts TT-Nb2O5 nanomaterials, 9 parts expanded graphite, and 0.1 parts calcium stearate.

[0114] The preparation method of a secondary zinc-manganese battery includes the following steps:

[0115] 1. Preparation of MnO2 / PPy composite material: Porous MnO2 nanostructures were prepared according to the general pretreatment steps described above, and then MnO2 / PPy composite material was prepared according to the general step S1.

[0116] 2. Dry mixing: Mix the MnO2 / PPy composite material, 9 parts of expanded graphite, and 0.15 parts of calcium stearate in a dry mixer at 1000 rpm for 3 hours.

[0117] 3. Preparation of TT-Nb2O5 nanomaterial dispersion: Prepare TT-Nb2O5 nanoparticles according to the general step S2 above. Weigh 2 portions of TT-Nb2O5 nanoparticles and disperse them in 50 mL of deionized water. Sonicate the dispersion for 30 minutes to form a uniform nanoparticle dispersion.

[0118] 4. Nb₂O₅ Droplet Coating: While continuously stirring the dry mixture obtained in step 2 at 500 rpm, slowly add the TT-Nb₂O₅ nanoparticle dispersion prepared in step 3 dropwise into the mixture through a constant pressure dropping funnel. The dropping time is controlled between 30 and 60 minutes. Maintain room temperature (approximately 25°C) during the dropping process.

[0119] 5. Vibration and Drying: After the addition is complete, continue vibration and stirring for 2 hours to ensure that the Nb2O5 nanoparticles are uniformly coated on the surface of the cathode powder. Then, dry the mixture in a vacuum oven at 80°C for 12 hours.

[0120] 6. Final preparation of positive electrode powder: The dried material is pressed, granulated, and sieved to produce positive electrode powder with a particle size of 20-80 mesh. An AA-type secondary zinc-manganese battery is assembled using the same negative electrode zinc paste and electrolyte as in Example 1.

[0121] Comparative Example 1

[0122] This comparative example uses a conventional positive electrode material comprising 90 parts by weight of electrolytic manganese dioxide, 9 parts by weight of expanded graphite, and 0.1 parts by weight of calcium stearate. The material is dry-mixed, compressed, granulated, and sieved, but no polypyrrole or niobium pentoxide nanomaterials are added. An AA-type secondary zinc-manganese battery is assembled using the same negative electrode zinc paste and electrolyte as in Example 1.

[0123] Comparative Example 2

[0124] This comparative example differs from Example 1 in that it does not contain niobium pentoxide. The cathode material composition is: 90 parts electrolytic manganese dioxide, 5 parts polypyrrole, 9 parts expanded graphite, and 0.1 parts calcium stearate. Porous MnO2 nanostructures and MnO2 nanostructures were prepared sequentially using the same preparation steps as in Example 1. 2 / The PPy composite material was then mixed with expanded graphite and calcium stearate in the above proportions, followed by dry mixing, pressing, granulation, and sieving to obtain the positive electrode powder. An AA-type secondary zinc-manganese battery was then assembled using the same negative electrode zinc paste and electrolyte as in Example 1.

[0125] Comparative Example 3

[0126] The difference between this comparative example and Example 1 is that this comparative example uses a physical mixing method to contain only niobium pentoxide modification.

[0127] The cathode material composition consists of 90 parts electrolytic manganese dioxide, 2 parts TT-Nb2O5 nanomaterials, 9 parts expanded graphite, and 0.1 parts calcium stearate.

[0128] The preparation method of a secondary zinc-manganese battery includes the following steps:

[0129] 1. Prepare porous MnO2 nanostructures according to the pretreatment steps.

[0130] 2. Prepare TT-Nb2O5 nanomaterials according to step S2.

[0131] 3. The obtained porous MnO2 nanostructures, TT-Nb2O5 nanomaterials, expanded graphite, and calcium stearate are directly dry-mixed, pressed, granulated, and sieved (skipping steps S1 and S3) to finally obtain the positive electrode powder. An AA-type secondary zinc-manganese battery is assembled using the same negative electrode zinc paste and electrolyte as in Example 1.

[0132] Comparative Example 4

[0133] The difference between this comparative example and Example 1 is that this comparative example uses in-situ growth on bare MnO2 to contain only niobium pentoxide modification.

[0134] The cathode material composition consists of 90 parts electrolytic manganese dioxide, 2 parts TT-Nb2O5 nanomaterials, 9 parts expanded graphite, and 0.1 parts calcium stearate.

[0135] The preparation method of a secondary zinc-manganese battery includes the following steps:

[0136] 1. Prepare porous MnO2 nanostructures according to the pretreatment steps.

[0137] 2. Prepare TT-Nb2O5 nanomaterials according to step S2.

[0138] 3. The obtained porous MnO2 nanostructure and the TT-Nb2O5 nanomaterial obtained in step S2 are grown and integrated in situ under the hydrothermal conditions described in step S3 to form MnO2 / Nb2O5 composite material, i.e., step S1 is skipped.

[0139] The obtained MnO2 / Nb2O5 composite material was dry-mixed, pressed, granulated, and sieved with expanded graphite and calcium stearate to finally obtain the positive electrode powder. An AA-type secondary zinc-manganese battery was assembled using the same negative electrode zinc paste and electrolyte as in Example 1.

[0140] Comparative Example 5

[0141] The difference between this comparative example and Example 1 is that polypyrrole and niobium pentoxide are used for synergistic modification in this comparative example.

[0142] The cathode material composition is as follows: 90 parts electrolytic manganese dioxide, 5 parts polypyrrole, 2 parts TT-Nb2O5 nanomaterials, 9 parts expanded graphite, and 0.1 parts calcium stearate.

[0143] The preparation method of a secondary zinc-manganese battery includes the following steps:

[0144] 1. Prepare porous MnO2 nanostructures according to the pretreatment steps.

[0145] 2. Prepare MnO2 / PPy composite material according to step S1.

[0146] 3. Prepare TT-Nb2O5 nanomaterials according to step S2.

[0147] 4. The obtained MnO2 / PPy composite material, TT-Nb2O5 nanomaterial, expanded graphite, and calcium stearate are directly dry-mixed, pressed, granulated, and sieved, skipping step S3, to finally obtain the positive electrode powder. An AA-type secondary zinc-manganese battery is then assembled using the same negative electrode zinc paste and electrolyte as in Example 1.

[0148] Test case

[0149] To verify the electrochemical performance of the secondary zinc-manganese batteries prepared in each embodiment and comparative example, assembled AA-type secondary zinc-manganese battery samples were selected and subjected to low-temperature discharge performance tests under constant temperature conditions. Specific test items included discharge capacity, voltage plateau, and cycle life. The test conditions were as follows: the batteries were placed in low-temperature test chambers at -10℃ and -15℃ for at least 6 hours for constant temperature equilibration, and then discharged using a constant current discharge method with a current set to 100mA and a discharge cutoff voltage of 0.9V. The voltage-time curve and termination capacity during discharge were recorded, and the plateau voltage was extracted. Cycle life tests were conducted at -10℃ and -15℃ using a constant current charge-discharge cycle mode, testing the capacity retention rate of the batteries after 50 cycles. At least 9 batteries were selected for each sample group for testing, and the average value was taken as the final data. Testing instruments included an IT5101 battery internal resistance tester from ITECH Electronics and a PA15A / 2 ammeter from Shanghai Precision Instruments Co., Ltd., ensuring the accuracy and repeatability of the testing process.

[0150] Table 1 shows the effect of different cathode materials on battery performance in Examples 1-4 and Comparative Examples 1-5.

[0151]

[0152]

[0153] Results Analysis

[0154] As can be seen from the table, the battery prepared in Example 1 exhibits optimal discharge performance at both -10°C and -15°C. At -10°C, the battery of Example 1 achieves a discharge capacity of 1450 mAh, a plateau voltage of 1.12 V, and a cycle life of 92%. At the even lower temperature of -15°C, its discharge capacity remains at 1210 mAh, the voltage plateau is 1.05 V, and the cycle life reaches 88%, demonstrating significant low-temperature adaptability and electrochemical stability.

[0155] Compared to Comparative Example 1, Example 1 showed a discharge capacity increase of over 50%, as well as significant improvements in plateau voltage and cycle life. This indicates that traditional unmodified MnO2 cathode materials suffer from severe electron and ion transport bottlenecks at low temperatures. In contrast, this invention, through polypyrrole coating and in-situ integration of niobium pentoxide, significantly enhances electronic conductivity and structural stability, ensuring efficient energy release at low temperatures.

[0156] Further comparison with Comparative Examples 2 and 3 reveals that the introduction of either polypyrrole or niobium pentoxide alone can improve low-temperature performance to some extent, with polypyrrole showing a more significant effect on voltage plateau improvement. However, due to the lack of good interfacial bonding and synergistic network formation, the overall performance improvement is limited. Comparative Example 4 employed an in-situ coating method of niobium pentoxide onto MnO2, which improved the structural compactness and electrode stability to some extent. Its performance was superior to Comparative Example 3 (physical mixing) and Comparative Example 2 (PPy coating only), but still lower than Example 1, indicating that in-situ modification of a single functional material is insufficient to fully realize its low-temperature potential.

[0157] Although Comparative Example 5 simultaneously introduced polypyrrole and niobium pentoxide, exhibiting a certain synergistic effect and significantly outperforming all the aforementioned single-modification schemes in discharge capacity and cycle life, it employed a physical mixing method, resulting in a loose composite structure interface and discontinuous electron and ion channels. Therefore, it still falls short of the ternary composite system constructed through in-situ assembly in Example 1. Consequently, Example 1 maintains a significant advantage in overall performance, demonstrating that the composite strategy employed in this invention—the synergistic mechanism of polypyrrole coating and in-situ integration of niobium pentoxide—possesses stronger electrochemical reactivity and stability at low temperatures.

[0158] Furthermore, the comparison between Example 1 and Example 4 further confirms the superiority of the in-situ construction method. Both examples have the same cathode material composition, differing only in the introduction method of niobium pentoxide. Example 4, employing a drop-addition coating process, can also achieve a certain degree of uniform distribution of niobium pentoxide. While its low-temperature performance is superior to all comparative examples, it is still slightly inferior to Example 1 in key indicators such as discharge capacity, voltage plateau, and cycle life. This indicates that the in-situ hydrothermal integration method constructs a more stable and denser composite interface at the material microstructure level, which is beneficial for the efficient transport of electrons and ions and is key to further improving low-temperature performance.

[0159] In summary, the experimental results fully demonstrate that the cathode material design of "polypyrrole coating + niobium pentoxide in-situ integration" adopted in this invention can effectively improve the discharge capacity, voltage plateau stability and cycle life of secondary zinc-manganese batteries in low-temperature environments such as -10℃ and -15℃, which is significantly better than traditional cathode systems and various comparative technical solutions, and has outstanding technological progress and practical application value.

[0160] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0161] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A secondary zinc-manganese battery cathode material, characterized in that, The material includes manganese dioxide, graphite, calcium stearate, polypyrrole, and niobium pentoxide nanomaterials. The polypyrrole is coated on the surface of the manganese dioxide by in-situ polymerization, and the niobium pentoxide nanomaterials are added to the manganese dioxide / polypyrrole composite material by hydrothermal integration to form a manganese dioxide / polypyrrole / niobium pentoxide composite material. The niobium pentoxide nanomaterial is niobium pentoxide nanoparticles or nanofibers in the TT crystal phase. The manganese dioxide is a manganese dioxide nanostructure; The positive electrode material contains the following components in parts by mass: 75-90 parts manganese dioxide; 6-11 parts graphite; 0.075-0.15 parts calcium stearate; 0.37-9 parts polypyrrole; 0.75-6 parts of niobium pentoxide nanomaterials.

2. The secondary zinc-manganese battery cathode material according to claim 1, characterized in that: The positive electrode material contains the following components in parts by mass: 90 parts manganese dioxide; 9 parts graphite; 0.1 part calcium stearate; 5 parts polypyrrole; Two portions of niobium pentoxide nanomaterials.

3. A method for preparing a secondary zinc-manganese battery cathode material as described in any one of claims 1-2, characterized in that: Includes the following steps: S1. Manganese dioxide / polypyrrole composite material is obtained by in-situ oxidative polymerization of pyrrole monomer on the surface of manganese dioxide; S2. Niobium pentoxide nanoparticles or nanofibers were synthesized by sol-gel method and calcined at 500℃ to obtain TT-niobium pentoxide nanomaterials. S3. The manganese dioxide / polypyrrole composite material obtained in step S1 is hydrothermally integrated with the niobium pentoxide nanomaterial obtained in step S2 to form a manganese dioxide / polypyrrole / niobium pentoxide composite material. S4. Positive electrode powder is prepared by combining manganese dioxide / polypyrrole / niobium pentoxide composite material with graphite and calcium stearate.

4. The method for preparing a secondary zinc-manganese battery cathode material according to claim 3, characterized in that: Step S4 specifically includes: mixing, dry-mixing, pressing, granulating and sieving the manganese dioxide / polypyrrole / niobium pentoxide composite material obtained in step S3 with graphite and calcium stearate to prepare positive electrode powder.

5. A secondary zinc-manganese battery, characterized in that: It includes a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode uses the secondary zinc-manganese battery positive electrode material according to any one of claims 1-2.

6. A secondary zinc-manganese battery according to claim 5, characterized in that: The electrolyte is a 26%-45% (w / w) aqueous solution of potassium hydroxide.

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