Positive electrode material of secondary zinc-manganese battery, preparation method of positive electrode material and secondary zinc-manganese battery

Abstract

The invention relates to the technical field of battery positive electrode materials, and discloses a secondary zinc-manganese battery positive electrode material, a preparation method and a secondary zinc-manganese battery, the secondary zinc-manganese battery positive electrode material comprises manganese dioxide, graphite, calcium stearate, polypyrrole and a niobium pentoxide nanometer material, the polypyrrole is coated on the surface of the manganese dioxide in an in-situ polymerization mode, and the niobium pentoxide nano material is integrated in the polypyrrole coated manganese dioxide composite material in an in-situ growth mode. According to the secondary zinc-manganese battery positive electrode material provided by the invention, a stable conductive network and an ion channel are constructed by adopting a manganese dioxide / polypyrrole / niobium pentoxide composite material, so that the conductivity and the structural stability of the positive electrode material at a low temperature are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery positive electrode materials, and more particularly to a secondary zinc-manganese battery positive electrode material, a preparation method and a secondary zinc-manganese battery. Background Art

[0002] As a recyclable electrochemical energy storage device, secondary zinc-manganese batteries offer the advantages of environmental friendliness and resource conservation. Compared to disposable zinc-manganese batteries, they can be recharged and discharged multiple times to extend their service life, thereby reducing the generation of waste batteries and lowering the environmental burden. By recycling and reusing battery materials, the use of natural resources such as metallic zinc and manganese dioxide is reduced, lowering energy consumption and aligning with green and low-carbon development strategies.

[0003] Conventional secondary zinc-manganese batteries mostly 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, which is beneficial for the battery's operation in low-temperature environments. However, traditional zinc-manganese batteries still have serious problems under low-temperature conditions, such as significant discharge capacity degradation, voltage plateau drop, internal resistance increase, and increased electrode polarization, which limits their application in cold regions or specific low-temperature conditions. This is especially true in northern my country, where outdoor temperatures often drop to -10°C or even lower in winter. Such environments place higher demands on the battery's low-temperature performance.

[0004] CN116072989A discloses a manganese-based oxide positive electrode 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 of the material combination or its applicability in low-temperature environments.

[0005] Therefore, under low temperature conditions (such as -10°C and below), zinc-manganese secondary batteries are still difficult to achieve long-term stable operation, especially in terms of capacity retention, rate performance and cycle stability. There is a need to further explore electrode materials and supporting electrolyte systems that have both excellent low-temperature performance and reversibility to promote the practical application of such batteries in extreme environments. Summary of the Invention

[0006] This invention aims to address the poor performance of existing secondary zinc-manganese batteries at low temperatures, as well as the uniformity, conductivity, and stability issues encountered in the preparation of positive electrode materials. This invention proposes a secondary zinc-manganese battery positive electrode material 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 positive electrode material at low temperatures.

[0007] To solve the above technical problems, the present invention provides a new secondary zinc-manganese dioxide battery positive electrode material, including manganese dioxide, graphite, calcium stearate, polypyrrole and niobium pentoxide nanomaterial, wherein the polypyrrole is coated on the surface of the manganese dioxide by in situ polymerization, and the niobium pentoxide nanomaterial is integrated into the polypyrrole-coated manganese dioxide composite material by in situ growth.

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

[0009] 1. Significantly improve low-temperature performance: Through the conductive coating of polypyrrole on manganese dioxide and the in-situ integration of niobium pentoxide nanomaterials, the tunnel structure of the TT crystal phase of niobium pentoxide is utilized to synergistically enhance the electronic conductivity and ion transport kinetics of the positive electrode material. Polypyrrole, as a conductive layer and protective layer, effectively inhibits the dissolution and structural degradation of manganese dioxide at low temperatures. Niobium pentoxide promotes rapid ion diffusion through its inherent tunnel structure and provides pseudocapacitance contribution, which together overcomes the problems of limited ion transport and slow charge transfer at low temperatures. This enables the battery prepared by the present invention to maintain excellent discharge capacity, stable voltage platform and good cycle stability in low temperature environments such as -10°C or even -15°C, far exceeding the existing technology level.

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

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

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

[0013] 5. The present invention significantly reduces the use of heavy metal elements in the battery by adopting a mercury-free and cadmium-free environmentally friendly system, avoids the environmental pollution problems caused by this, and improves the green environmental protection performance of the product.

[0014] According to one embodiment of the present invention, the positive electrode material contains the following components 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 nanomaterial. This preferred range of component ratios ensures a balanced material performance, further optimizing the battery's power output and cycling stability while maintaining high energy density.

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

[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 ions such as Zn 2+ and OH - The rapid diffusion of ions can effectively alleviate the ion transport limitations, especially in low temperature environments, thereby further improving the high-rate discharge performance and low-temperature response capability of the battery.

[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 any of the above-mentioned secondary zinc-manganese battery positive electrode materials, comprising the following steps:

[0019] S1, polymerizing pyrrole monomers on the surface of manganese dioxide by in-situ oxidation to obtain a manganese dioxide / polypyrrole composite material;

[0020] S2, synthesizing niobium pentoxide nanoparticles or nanofibers by a sol-gel method, and obtaining TT-niobium pentoxide by low-temperature calcination;

[0021] S3, in-situ growth or dropwise integration of the manganese dioxide / polypyrrole composite material obtained in step S1 and the niobium pentoxide nanomaterial obtained in step S2 to form a manganese dioxide / polypyrrole / niobium pentoxide composite material;

[0022] S4. A positive electrode powder is prepared by mixing a 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, tableting, granulating and screening to prepare positive electrode powder.

[0024] According to one 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 dropwise integrated processing 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 any of the above-mentioned secondary zinc-manganese battery positive electrode materials.

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

[0027] The technical solutions of the present invention are described below in a clear and complete manner. Obviously, the embodiments described are only some, not all, of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention. Analytical grade reagents and deionized water were used in all experiments.

[0028] The present invention provides a novel secondary zinc-manganese battery positive electrode material, which is used to improve the performance of the battery in a low-temperature environment.

[0029] Specifically, the components of the positive electrode material include manganese dioxide, graphite, calcium stearate, polypyrrole and niobium pentoxide nanomaterials. Among them, manganese dioxide, as the positive electrode active material, is the core component of the battery for electrochemical reactions and energy provision. Graphite, as a conductive agent, constructs an efficient electron transport network inside the positive electrode material to ensure that electrons can quickly flow to the reaction sites and reduce the internal resistance of the battery. Calcium stearate, as a lubricant and processing aid, helps the fluidity and formability of the positive electrode powder during tableting and granulation, thereby improving production efficiency. Polypyrrole, as a conductive polymer, is tightly coated on the surface of the manganese dioxide by in-situ polymerization to form a uniform conductive coating and protective layer. This coating not only greatly improves the electronic conductivity of manganese dioxide, but also effectively inhibits the dissolution and structural degradation of manganese dioxide in the electrolyte, thereby enhancing the cycle stability and life of the positive electrode 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] Further, the positive electrode material contains the following components in mass fraction: 75-90 parts of manganese dioxide; 6-11 parts of graphite; 0.075-0.15 parts of calcium stearate; 0.37-9 parts of polypyrrole; and 0.75-6 parts of niobium pentoxide nano-material.

[0031] Specifically, the niobium pentoxide is TT phase niobium pentoxide nanoparticles or nanofibers. The TT phase niobium pentoxide has a unique tunnel-like crystal structure, which has an open tunnel with a diameter of about 0.37-0.75 nm along the b-axis direction.

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

[0033] Embodiment 1

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

[0035] 1. Preparation of raw materials

[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 pure.

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

[0041] Perchloric acid (HCIO4): analytical pure.

[0042] Ethanol: analytical pure.

[0043] Niobium pentaethoxide (Nb(OEt)5): analytical pure.

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

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

[0046] Sodium polyacrylate: commercially available.

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

[0048] 2. Preparation of positive electrode material

[0049] Pre-treatment: preparation of manganese dioxide nanostructure

[0050] Method: hydrothermal synthesis method. ​

[0051] Specific operations:

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

[0053] The solution was transferred to a 500 mL beaker and stirred at 300 rpm on a magnetic stirrer for 30 min to ensure complete dissolution of KMnO4.

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

[0055] The autoclave was sealed and placed in an electric forced air drying oven preheated to 150° C. for constant temperature reaction for 6 hours.

[0056] After the reaction was completed, the autoclave was naturally cooled to room temperature.

[0057] The black precipitate obtained by the reaction is MnO2, which is collected by filtration and repeatedly washed with a large amount of deionized water until the pH value of the filtrate is neutral, about pH 6-7, and then washed once with anhydrous ethanol.

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

[0059] The resulting product is a porous birnessite-type manganese dioxide nanosheet. Layered manganese oxide is extremely unstable under high temperature and high pressure environments, and its layered structure will collapse and transform into a tunnel-type porous manganese dioxide nanostructure.

[0060] Step S1: polymerizing pyrrole monomers on the surface of manganese dioxide by in-situ oxidation 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 (9.0 g). Disperse them in 200 mL of deionized water and stir them magnetically in a 500 mL beaker at 400 rpm for 1 hour to ensure uniform dispersion of the MnO2.

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

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

[0066] S14, the prepared pyrrole monomer solution in step S12 is slowly added drop by drop into the MnO2 dispersion under the condition of continuous stirring at 400 rpm and maintaining pH 2-3, and the dropwise adding time is controlled within 30 minutes.

[0067] S15, after the dropwise adding is completed, the reaction mixture is continuously stirred at room temperature 25℃ for 6 hours to ensure the pyrrole monomers are fully polymerized. During this process, the solution color will gradually change to brown-black, indicating the formation of MnO2 / PPy composite material.

[0068] S16, the obtained MnO2 / PPy composite material is collected by centrifugation at a speed of 8000 rpm for 10 minutes.

[0069] S17, the precipitate is washed with deionized water for three times and then washed with anhydrous ethanol for three times to remove the unreacted monomers and by-products.

[0070] S18, the washed MnO2 / PPy composite material is dried in a vacuum oven at 100℃ overnight, and the drying time is about 12-16 hours.

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

[0072] Step S2: Synthesis of niobium pentoxide nanoparticles or nanofibers by sol-gel method, and TT-niobium pentoxide is obtained by low-temperature calcination;

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

[0074] Specific operation:

[0075] S21, under the protection of a glove box or inert atmosphere, an appropriate amount of pentaethoxy niobium is weighed so that it is finally converted into 2 parts of TT-Nb2O5 nanomaterial with a mass of 0.2g. The pentaethoxy niobium is dissolved in 20mL of anhydrous ethanol, and stirred at a speed of 300rpm on a magnetic stirrer for 15 minutes to ensure complete dissolution.

[0076] S22, under continuous stirring at 300rpm, 5mL of deionized water is slowly added drop by drop as a hydrolysis agent at a rate of 0.5mL / min by an injection pump, and the dropwise adding time is about 10 minutes. Continue stirring for 2 hours to promote the hydrolysis and condensation reaction, form a transparent sol, and gradually gel.

[0077] S23, the obtained sol / gel is transferred to a drying oven and dried at 80℃ for 24 hours to obtain a gel dry powder.

[0078] S24, the gel dry powder is ground into fine powder.

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

[0080] S26. After the calcination is completed, the muffle furnace is naturally cooled to room temperature.

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

[0082] Step S3: in-situ growth or dropwise integration of the manganese dioxide / polypyrrole composite material obtained in step S1 and the niobium pentoxide nanomaterial obtained in step S2 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 on a magnetic stirrer at 300 rpm for 30 minutes to ensure uniform dispersion.

[0086] S32. In a separate beaker, weigh an appropriate amount of the TT-Nb2O5 nanoparticles obtained in step S2 to a final total weight of 2 parts and a mass of 0.2 g. Disperse or dissolve the nanoparticles in 20 mL of deionized water and stir evenly.

[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 polytetrafluoroethylene-lined stainless steel autoclave.

[0089] S35. Seal the autoclave and place it in an electric forced air drying oven preheated to 160° C. for constant temperature reaction for 12 hours.

[0090] S36. After the reaction is completed, the autoclave is naturally cooled to room temperature.

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

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

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

[0094] Step S4: preparing the positive electrode powder by using the manganese dioxide / polypyrrole / niobium pentoxide composite material, graphite and calcium stearate: dry mixing, tableting, granulation and screening.

[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 desired ratio. 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 comprises 90 parts of MnO2, 5 parts of PPy, and 2 parts of Nb2O5.

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

[0098] S43, forming the mixed powder after dry mixing into tablets through a conventional tableting process.

[0099] S44. The flaky material is passed through a granulator to form granules of a desired size.

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

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

[0102] The negative electrode material is conventionally prepared using zinc powder, sodium polyacrylate, and nano-indium oxide in a mass ratio of 80:12:8, dry-mixed for 2.5 hours. Subsequently, electrolyte was added and wet-mixed for 2 hours, followed by degassing to produce a negative electrode zinc paste.

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

[0104] 4.Battery assembly and performance testing

[0105] Battery assembly: According to the standard secondary zinc-manganese battery production line process, the prepared positive electrode powder, negative electrode zinc paste and electrolyte are assembled into AA-sized secondary zinc-manganese batteries.

[0106] Example 2

[0107] This example prepared a secondary zinc-manganese battery using the same steps as Example 1, differing from Example 1 in the proportions of the components in the positive electrode material. The positive electrode material in this example contained the following components by weight: 75 parts manganese dioxide; 11 parts graphite; 0.15 parts calcium stearate; 9 parts polypyrrole; and 5 parts niobium pentoxide nanomaterial.

[0108] In other embodiments, the mass fraction of the niobium pentoxide nanomaterial is 0.17 parts, 1 parts, 3 parts, or 6 parts.

[0109] Example 3

[0110] This example prepared a secondary zinc-manganese battery using the same steps as Example 1. The difference from Example 1 lies in the ratio of the components in the positive electrode material. In this example, the positive electrode material contained the following components by weight: 90 parts manganese dioxide; 5 parts graphite; 0.1 parts calcium stearate; 4 parts polypyrrole; and 1.5 parts niobium pentoxide nanomaterial.

[0111] Example 4

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

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

[0114] A method for preparing a secondary zinc-manganese battery comprises the following steps:

[0115] 1. Preparation of MnO2 / PPy composite materials: Prepare porous MnO2 nanostructures according to the general pretreatment steps above, and then prepare MnO2 / PPy composite materials according to general step S1.

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

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

[0118] 4. Nb2O5 drop-coating: While continuously stirring the dry mixed mixture from step 2 at 500 rpm, slowly dropwise add the TT-Nb2O5 nanoparticle dispersion prepared in step 3 into the mixture through a constant pressure dropping funnel, the dropwise adding time is controlled in 30-60 minutes. Keep the room temperature at about 25°C during the dropwise adding process.

[0119] 5. Vibration stirring and drying: After the dropwise adding is completed, continue vibration stirring for 2 hours to ensure the Nb2O5 nanoparticles are evenly 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 the cathode powder: After drying, the material is pressed, granulated, and sieved to produce a cathode powder with a particle size of 20-80 mesh. The same negative zinc paste and electrolyte as in Example 1 are used to assemble AA type secondary zinc-manganese batteries.

[0121] Comparative Example 1

[0122] This comparative example uses a traditional cathode material, which includes 90 parts by mass of electrolytic manganese dioxide, 9 parts of expanded graphite, and 0.1 part of calcium stearate, which are dry mixed, pressed, granulated, and sieved, but without adding any polypyrrole or niobium pentoxide nanomaterial. The same negative zinc paste and electrolyte as in Example 1 are used to assemble AA type secondary zinc-manganese batteries.

[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 of electrolytic manganese dioxide, 5 parts of polypyrrole, 9 parts of expanded graphite, and 0.1 part of calcium stearate. The porous MnO2 nanostructure, MnO 2 / PPy composite material, and finally the obtained MnO2 / PPy composite material is dry mixed, pressed, granulated, and sieved with expanded graphite and calcium stearate according to the above proportions to obtain a cathode powder. The same negative zinc paste and electrolyte as in Example 1 are used to assemble AA type secondary zinc-manganese batteries.

[0125] Comparative Example 3

[0126] This comparative example differs from Example 1 in that it only contains niobium pentoxide modification by physical mixing.

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

[0128] The method for preparing 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 were directly dry-mixed, tableted, granulated, and sieved (skipping steps S1 and S3) to obtain a positive electrode powder. An AA-sized secondary zinc-manganese battery was assembled using the same negative electrode zinc paste and electrolyte as in Example 1.

[0132] Comparative Example 4

[0133] This comparative example is different from Example 1 in that in this comparative example, only niobium pentoxide is modified by in-situ growth on bare MnO2.

[0134] Positive electrode material composition: 90 parts of electrolytic manganese dioxide, 2 parts of TT-Nb2O5 nanomaterial, 9 parts of expanded graphite, and 0.1 part of calcium stearate.

[0135] A method for preparing a secondary zinc-manganese battery comprises 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 is in situ grown and integrated with the TT-Nb2O5 nanomaterial obtained in step S2 under the hydrothermal conditions described in step S3 to form a MnO2 / Nb2O5 composite material, i.e., step S1 is skipped.

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

[0140] Comparative Example 5

[0141] This comparative example is different from Example 1 in that polypyrrole and niobium pentoxide are used for synergistic modification in this comparative example.

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

[0143] A method for preparing a secondary zinc-manganese battery comprises 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 were directly dry-mixed, tableted, granulated, and sieved, i.e., step S3 was skipped to finally produce the positive electrode powder. AA-sized secondary zinc-manganese battery was assembled using the same negative electrode zinc paste and electrolyte as in Example 1.

[0148] Test example

[0149] To verify the electrochemical performance of the secondary zinc-manganese batteries prepared in each example and comparative example, assembled AA-sized secondary zinc-manganese battery samples were selected and subjected to low-temperature discharge performance testing under a constant temperature environment. Specific test items included discharge capacity, voltage plateau, and cycle life. The test conditions were as follows: After the batteries were placed in a low-temperature test chamber at -10°C and -15°C for constant temperature equilibration for at least 6 hours, a discharge test was conducted 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 the discharge process were recorded, and the plateau voltage was extracted. The cycle life test was conducted at -10°C and -15°C using a constant current charge-discharge cycle mode to test the capacity retention of the batteries after 50 cycles. At least 9 batteries were tested in each sample group, and the average value was taken as the final data. The testing instruments included the IT5101 battery internal resistance tester produced by Itech Electronics and the PA15A / 2 ammeter produced by Shanghai Precision Instruments Co., Ltd. to ensure the accuracy and repeatability of the testing process.

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

[0151]

[0152]

[0153] Result 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 in 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, the battery maintains a discharge capacity of 1210 mAh, a plateau voltage of 1.05 V, and a cycle life of 88%, demonstrating significant low-temperature adaptability and electrochemical stability.

[0155] Compared with Comparative Example 1, the discharge capacity of Example 1 is improved by more than 50%, and the platform voltage and cycle life are also significantly improved. This indicates that the traditional unmodified MnO2 cathode material has a serious bottleneck in electron and ion transmission under low temperature conditions, while the present application significantly improves the electronic conductivity and structural stability by in-situ integration of polyazole coating and niobium pentoxide, ensuring the energy release efficiency at low temperature.

[0156] Further compared with Comparative Examples 2 and 3, it can be found that the introduction of polyazole or niobium pentoxide alone can improve the low temperature performance to a certain extent, especially the polyazole has a more obvious effect on the voltage platform improvement. However, due to the lack of good interface combination and synergistic network, the overall performance improvement is limited. Comparative Example 4 adopts the in-situ coating method of niobium pentoxide on MnO2, which improves the structural compactness and electrode stability to a certain extent, and its performance is better than that of Comparative Examples 3 (physical mixing) and 2 (only PPy coating), but still lower than that of Example 1, indicating that the in-situ modification of single functional material is still insufficient to fully exert its low temperature potential.

[0157] Although Comparative Example 5 introduces polyazole and niobium pentoxide at the same time, it has a certain synergistic effect, and the discharge capacity and cycle life are obviously better than all the above single modification schemes, but it adopts a physical mixing method, the composite structure interface is loose, and the electron and ion channels are discontinuous, which is still difficult to match the ternary composite system constructed by in-situ assembly in Example 1. Therefore, Example 1 still maintains a significant advantage in comprehensive performance, which proves that the composite strategy adopted in the present application, i.e. the synergistic mechanism of polyazole coating and in-situ integration of niobium pentoxide, has stronger electrochemical reaction activity and stability under low temperature environment.

[0158] In addition, the comparison between Example 1 and Example 4 further proves the superiority of the in-situ construction method. The cathode material components of the two are the same, only the introduction method of niobium pentoxide is different. Example 4 adopts a drop coating process, which can also achieve uniform distribution of niobium pentoxide to a certain extent, and its low temperature performance is better than all the comparative examples, but it is still slightly inferior to Example 1 in terms of discharge capacity, voltage platform and cycle life, etc. This indicates that the in-situ hydrothermal integration method constructs a more stable and compact composite interface at the microstructure level of the material, which is beneficial to the efficient transmission of electrons and ions, and is the key to further improving the low temperature performance.

[0159] In summary, the test results fully show that the cathode material design of "polyazole coating + in-situ integration of niobium pentoxide" adopted in the present application can effectively improve the discharge capacity, voltage platform stability and cycle life of the secondary zinc-manganese battery under low temperature environment such as-10℃ and-15℃, which is significantly better than the traditional cathode system and various technical solutions of comparative examples, and has outstanding technical progress and practical application value.

[0160] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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 only express several implementation methods of the present application, which are convenient for understanding the technical solutions of the present application in a specific and detailed manner, but they cannot be understood as limiting the scope of protection of the patent application. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several variations and improvements can be made, which all fall within the scope of protection of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the scope of protection of the claims attached to the present application. Therefore, the scope of protection of the patent application of this application shall be based on the content of the attached claims, and the description can be used to interpret the content of the claims.

Claims

1. A secondary zinc-manganese battery positive electrode material, characterized in that: The composite material comprises manganese dioxide, graphite, calcium stearate, polypyrrole and niobium pentoxide nanomaterial, wherein the polypyrrole is coated on the surface of the manganese dioxide by in-situ polymerization, and the niobium pentoxide nanomaterial is integrated into the polypyrrole-coated manganese dioxide composite material by in-situ growth.

2. A secondary zinc-manganese battery positive electrode material according to claim 1, characterized in that: The positive electrode material contains the following components in parts by mass: 75-90 parts of manganese dioxide; 6-11 graphite; 0.075-0.15 parts of calcium stearate; 0.37-9 parts of polypyrrole; 0.75-6 parts of niobium pentoxide nanomaterial.

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

4. The positive electrode material for a secondary zinc-manganese battery according to claim 1, characterized in that: The niobium pentoxide is niobium pentoxide nanoparticles or nanofibers in the TT crystal phase.

5. The positive electrode material for a secondary zinc-manganese battery according to claim 1, characterized in that: The manganese dioxide is a manganese dioxide nanostructure.

6. A method for preparing a positive electrode material for a secondary zinc-manganese battery according to any one of claims 1 to 5, characterized in that: The steps include: S1, polymerizing pyrrole monomers on the surface of manganese dioxide by in-situ oxidation to obtain a manganese dioxide / polypyrrole composite material; S2, synthesizing niobium pentoxide nanoparticles or nanofibers by a sol-gel method, and obtaining TT-niobium pentoxide by calcining at a low temperature; S3, in-situ growth or dropwise integration of the manganese dioxide / polypyrrole composite material obtained in step S1 and the niobium pentoxide nanomaterial obtained in step S2 to form a manganese dioxide / polypyrrole / niobium pentoxide composite material; S4. A positive electrode powder is prepared by mixing a manganese dioxide / polypyrrole / niobium pentoxide composite material with graphite and calcium stearate.

7. The method for preparing a positive electrode material for a secondary zinc-manganese battery according to claim 6, characterized in that: The step S4 specifically includes: mixing the composite material obtained in step S3 with graphite and calcium stearate, dry-mixing, tableting, granulating and screening to prepare positive electrode powder.

8. The method for preparing a positive electrode material for a secondary zinc-manganese battery according to claim 6, characterized in that: The 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 dropwise integration treatment with the niobium pentoxide nanomaterial obtained in step S2 to form the manganese dioxide / polypyrrole / niobium pentoxide composite material.

9. A secondary zinc-manganese battery, characterized in that: The invention comprises a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode adopts the secondary zinc-manganese battery positive electrode material according to any one of claims 1 to 5.

10. The secondary zinc-manganese battery according to claim 9, characterized in that: The electrolyte is a 26%-45% (w / w) potassium hydroxide aqueous solution.

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