Flexible transparent cobalt-doped manganese dioxide zinc ion battery positive pole piece and preparation method thereof

Abstract

The invention discloses a preparation method of a flexible transparent cobalt-doped manganese dioxide zinc ion battery positive pole piece, and belongs to the technical field of aqueous zinc ion batteries. Comprising the following steps: dispersing manganese acetate tetrahydrate, cobalt nitrate hexahydrate and sodium sulfate in deionized water to prepare an electrolyte; a nickel grid / PET current collector is used as a working electrode, a platinum sheet is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, a cobalt-doped manganese dioxide layer is deposited on the surface of the nickel grid / PET current collector in the electrolyte by adopting a constant-voltage electrochemical deposition method, and the positive pole piece is prepared. A flexible transparent cobalt-doped manganese dioxide positive pole piece with high transparency and excellent electrochemical performance is prepared on a flexible transparent grid current collector by adopting a low-cost and high-efficiency electro-deposition process, and the application of a high-performance flexible transparent zinc ion battery can be realized.

Description

Technical Field

[0001] This invention belongs to the field of aqueous zinc-ion battery technology, specifically relating to a flexible, transparent cobalt-doped manganese dioxide zinc-ion battery positive electrode sheet and its preparation method. Background Technology

[0002] With the rapid development of wearable electronic devices, smart packaging, and invisible electronic products, the demand for flexible transparent power systems is increasing. Aqueous zinc-ion batteries, due to their high safety, low cost, and environmental friendliness, have become highly promising candidates for transparent power sources. Among numerous zinc-ion battery cathode materials, manganese dioxide is one of the most promising cathode materials for flexible transparent zinc-ion batteries due to its low cost, environmental friendliness, good biocompatibility, and high theoretical specific capacity. However, traditional manganese dioxide cathode materials suffer from poor conductivity, structural instability during cycling, and manganese dissolution, leading to rapid battery capacity decay and short cycle life.

[0003] In recent years, researchers have attempted to improve the electrochemical performance of manganese dioxide through elemental doping. Cobalt doping has been shown to effectively modulate the electronic structure of manganese dioxide, improving its conductivity and structural stability. For example, patent application CN119390126A discloses a method for preparing cobalt-doped manganese dioxide nanosheets / core-shell structured powder materials in one step using Co3[Co(CN)6]2 as a hard template, combined with liquid-phase co-precipitation-hydrothermal conversion. Patent application CN114551874A discloses a one-pot hydrothermal reaction method for preparing cobalt-doped manganese dioxide powder materials using potassium permanganate, cobalt salt, and ammonium salt as raw materials. Patent application CN118645617A prepared cobalt-doped manganese tetroxide composite powder materials via a hydrothermal method to improve the specific capacity of zinc-ion battery cathodes. The cobalt-doped manganese dioxide cathode materials prepared by the aforementioned patented technologies are all powder materials. The electrode sheet preparation requires a binder-based film-forming process, resulting in opaque electrode sheets that cannot meet the application requirements of flexible transparent zinc-ion batteries. Furthermore, they fail to address the key issue in flexible transparent battery applications—how to maintain excellent electrochemical performance while maintaining high transparency. In addition, the preparation processes for these cobalt-doped manganese dioxide cathode materials involve complex steps, high reaction temperatures, high energy consumption, high costs, and the need to use hazardous chemicals, limiting large-scale production and application. Developing cobalt-doped manganese dioxide cathode materials with both high transparency and excellent electrochemical performance, along with a simple and low-cost preparation process, is of great significance for promoting the development and application of flexible transparent aqueous zinc-ion battery technology. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a flexible, transparent cobalt-doped manganese dioxide zinc-ion battery positive electrode sheet and its preparation method, thereby solving the problems in the prior art.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing a flexible, transparent cobalt-doped manganese dioxide zinc-ion battery positive electrode includes the following steps: An electrolyte was prepared by dispersing manganese acetate tetrahydrate, cobalt nitrate hexahydrate, and sodium sulfate in deionized water. Using a nickel mesh / PET current collector as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, a cobalt-doped manganese dioxide layer is deposited on the surface of the nickel mesh / PET current collector in the electrolyte using a constant voltage electrochemical deposition method to prepare a positive electrode sheet.

[0006] Furthermore, the concentration of manganese acetate in the electrolyte is 0.05-0.2 mol / L.

[0007] Furthermore, the concentration of cobalt nitrate in the electrolyte is 0.002-0.01 mol / L.

[0008] Furthermore, the concentration of sodium sulfate in the electrolyte is 0.1 mol / L.

[0009] Furthermore, the sheet resistance of the nickel mesh / PET current collector is 2-5 Ω / sq, and the light transmittance is 80-85%.

[0010] Furthermore, the deposition potential range of the constant voltage electrochemical deposition method is 0.4-1.6V, and the deposition time is 5-30 min.

[0011] Furthermore, the preparation process of the nickel mesh / PET current collector includes: After mixing acrylic resin and ethanol, the mixture is coated onto the surface of a PET substrate that has undergone plasma cleaning and then dried under vacuum to obtain an acrylic resin crack network template sample. The sample was subjected to vacuum deposition to deposit a nickel film on a PET substrate; The coated sample was immersed in acetic acid, ultrasonically treated to remove the acrylic resin template layer, and then cleaned and dried to obtain a nickel mesh / PET current collector. The flexible, transparent cobalt-doped manganese dioxide zinc-ion battery positive electrode sheet is prepared using the above-mentioned preparation method.

[0012] The above-mentioned positive electrode sheet is used in the assembly of flexible transparent aqueous zinc-ion batteries.

[0013] A flexible transparent aqueous zinc-ion battery includes: the aforementioned positive electrode, a transparent zinc metal mesh negative electrode, and a hydrogel electrolyte located between the positive and negative electrodes.

[0014] The beneficial effects of this invention are: 1. To address the problems of poor conductivity, poor light transmittance, and uneven stress distribution in standalone manganese dioxide thin film electrodes, this invention prepares cobalt-doped manganese dioxide thin film electrodes by one-step electrodeposition on a nickel grid surface. This significantly improves the intrinsic conductivity of the manganese dioxide thin film electrode, effectively suppresses cracking and delamination of the manganese dioxide thin film electrode, and yields a grid-structured cobalt-doped manganese dioxide positive electrode material with high transparency, high mechanical stability, and high electrochemical activity.

[0015] 2. This invention uses a simple and low-cost one-step electrodeposition process to prepare flexible transparent cobalt-doped manganese dioxide cathode thin film electrode material. It does not require high temperature and high pressure conditions or the introduction of external binder / conductive agent materials. The process is simple, highly controllable, and suitable for large-area, large-scale production processes.

[0016] 3. Regarding the concentration limit of manganese acetate tetrahydrate (0.05-0.2 mol / L): This concentration range ensures a sufficient supply of manganese source during the deposition process, enabling manganese dioxide to nucleate and grow uniformly on the current collector. Too low a concentration will result in a slow deposition rate, making it difficult to form a continuous film; too high a concentration will easily lead to an excessively thick deposition layer or agglomeration, reducing the transmittance of the electrode and increasing internal resistance.

[0017] 4. Regarding the concentration limit of cobalt nitrate hexahydrate (0.002-0.01 mol / L): This doping concentration range is crucial for achieving excellent electrochemical performance. Appropriate cobalt ion doping (0.002-0.01 mol / L) effectively increases oxygen vacancies in the material, improves conductivity, and acts as a "structural pillar" (as shown in Examples 1-5). If the concentration is too low (<0.002 mol / L), the doping effect is not significant; if the concentration is too high (>0.01 mol / L), as shown in the trend of Example 6, excessive cobalt ions may lead to excessive lattice distortion, destroying the layered structure and reducing cycle stability.

[0018] 5. Regarding the limitation of sodium sulfate concentration (0.1 mol / L): Sodium sulfate serves as a supporting electrolyte, and this concentration provides good ionic conductivity of the solution, ensuring uniform current distribution during electrodeposition and facilitating the acquisition of a deposited layer with uniform morphology.

[0019] 6. Regarding the limitations on current collector sheet resistance and light transmittance: A low sheet resistance of 2-5 Ω / sq and a high light transmittance of 80-85% for nickel mesh / PET current collectors are fundamental to achieving high-performance flexible transparent batteries. This parameter range balances the conductivity of the current collector (affecting rate performance) and optical transparency (requirements for specific application scenarios).

[0020] 7. Regarding the limitations of deposition potential and time: A potential range of 0.4-1.6V and a deposition time of 5-30 min enable precise control of the active material loading. Too short a deposition time results in insufficient active material and low capacity; too long a time (e.g., >30 min), although increasing the loading, will significantly reduce light transmittance and increase internal stress in the film, making it prone to detachment (as shown in the comparison between Example 4 and Comparative Example 2). Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 These are digital photographs, optical microscope images, and SEM images of the positive electrode sheet prepared in Example 1; Figure 2 This is a digital photograph of the flexible, transparent aqueous zinc-ion battery assembled with the positive electrode sheet of this invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] A method for preparing a flexible, transparent cobalt-doped manganese dioxide zinc-ion battery positive electrode includes the following steps: S1. Add manganese acetate tetrahydrate, cobalt nitrate hexahydrate and sodium sulfate to 100 mL of deionized water, stir and mix to prepare an electrolyte; S2 uses a nickel mesh / PET current collector as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode to construct a three-electrode structure. The electrolyte prepared in S1 is added, and a cobalt-doped manganese dioxide layer is deposited on the surface of the nickel mesh / PET current collector using a constant voltage electrochemical deposition method to prepare a cobalt-doped manganese dioxide / nickel mesh / PET composite flexible transparent positive electrode sheet.

[0025] In S1, the concentration of manganese acetate tetrahydrate in the electrolyte is 0.05-0.2 mol / L; the concentration of cobalt nitrate hexahydrate is 0.002-0.02 mol / L; and the concentration of sodium sulfate is 0.1 mol / L.

[0026] In S2, the sheet resistance of the nickel mesh / PET current collector is 2-5 Ω / sq, and the transmittance is 80-85%; the deposition potential range of the constant voltage electrochemical deposition method is 0.4-1.6V, and the deposition time is 5-30 min.

[0027] The nickel mesh / PET current collector was prepared in-house. A highly interconnected metal wire mesh was fabricated on a PET substrate using a crack template method and a vacuum deposition process to obtain the nickel mesh / PET. Specifically, the method for preparing nickel mesh / PET current collectors includes the following steps: Step 1: Mix acrylic resin and ethanol at a volume ratio of 2:1 to obtain a uniform mixture; apply the mixture to the surface of a PET substrate that has been plasma cleaned, and transfer it to a vacuum drying oven to dry at 80°C for 30 min to obtain an acrylic resin crack network template sample. Step 2: Place the sample in a high-vacuum metal evaporation coating system with a vacuum level of 2×10⁻⁶. -4 A 18 nm nickel film was vacuum deposited at Pa and a substrate temperature of 100 °C. Step 3: Immerse the coated sample in acetic acid, sonicate for 1 min to remove the acrylic resin template layer, then clean with ultrapure water and ethanol, and vacuum dry at 80℃ for 1 h to obtain the nickel mesh / PET current collector. The technical solution of the present invention will be described below through the following embodiments. In the embodiments, the sources of each raw material are as follows: Cobalt nitrate hexahydrate: Manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.; Specification: AR; CAS No.: 10026-22-9; Manganese acetate tetrahydrate: Manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.; Specification: AR; CAS No.: 6156-78-1; PET: Manufacturer: Zhejiang Guoyuan; Specification: Thickness 100 microns.

[0028] ITO / PET: Manufacturer: Luoyang Tengchang Xukun Biotechnology Co., Ltd.; Specification: Sheet resistance 7 ohms.

[0029] The nickel mesh / PET current collector was prepared in-house using the method described above. The raw materials used in this in-house preparation method are sourced from the following: Acrylic resin: Manufacturer: Sinopharm Chemical Reagent Co., Ltd.; Specification: AR; Ethanol: Manufacturer: Sinopharm Chemical Reagent Co., Ltd.; Specification: 99.9%; Acetic acid: Manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.; Specification: AR; Nickel granules: Manufacturer: Sinopharm Chemical Reagent Co., Ltd.; Specification: 99.99%.

[0030] Example 1 S1. Add 2.45g manganese acetate tetrahydrate (0.01 mol), 1.42g sodium sulfate (0.01 mol), and 0.145g cobalt nitrate hexahydrate (0.0005 mol) to 100 mL of deionized water to prepare the electrolyte. S2. Using a nickel mesh / PET (2.5 cm × 2.5 cm) as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, constant voltage electrochemical deposition was performed under a stirring condition of 300 r / min, with a deposition potential of 0.7 V and a deposition time of 15 min. The resulting samples were then washed sequentially with deionized water and dried in an oven at 50 °C for 2 h.

[0031] Figure 1 In the image, 'a' is a bending demonstration photograph of the cobalt-doped manganese dioxide composite positive electrode sheet of the prepared flexible transparent aqueous zinc-ion battery. Figure 1 Images b and c in the figures are optical microscope and SEM images of the positive electrode, respectively. From b and c, it can be seen that the cobalt-doped manganese dioxide composite thin film layer is uniformly grown on the nickel grid / PET current collector. Furthermore, from... Figure 1 As can be seen in c, the surface of the cobalt-doped manganese dioxide composite film is relatively rough, which is beneficial to reducing interfacial impedance and improving the storage capacity of zinc ions.

[0032] Example 2 S1. Add 2.45g manganese acetate tetrahydrate (0.01 mol), 1.42g sodium sulfate (0.01 mol), and 0.145g cobalt nitrate hexahydrate (0.0005 mol) to 100 mL of deionized water to prepare the electrolyte. S2. Using a nickel mesh / PET (2.5 cm × 2.5 cm) as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, constant voltage electrochemical deposition was performed under stirring conditions of 300 r / min, with a deposition potential of 0.7 V and a deposition time of 5 min. The resulting samples were then washed sequentially with deionized water and dried in an oven at 50 °C for 2 h.

[0033] Example 3 S1. Add 2.45g manganese acetate tetrahydrate (0.01 mol), 1.42g sodium sulfate (0.01 mol), and 0.145g cobalt nitrate hexahydrate (0.0005 mol) to 100 mL of deionized water to prepare the electrolyte. S2. Using a nickel mesh / PET (2.5 cm × 2.5 cm) as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, constant voltage electrochemical deposition was performed under a stirring condition of 300 r / min, with a deposition potential of 0.7 V and a deposition time of 10 min. The resulting samples were then washed sequentially with deionized water and dried in an oven at 50 °C for 2 h.

[0034] Example 4 S1. Add 2.45g manganese acetate tetrahydrate (0.01 mol), 1.42g sodium sulfate (0.01 mol), and 0.145g cobalt nitrate hexahydrate (0.0005 mol) to 100 mL of deionized water to prepare the electrolyte. S2. Using a nickel mesh / PET (2.5 cm × 2.5 cm) as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, constant voltage electrochemical deposition was performed under stirring conditions of 300 r / min, with a deposition potential of 0.7 V and a deposition time of 30 min. The resulting samples were then washed sequentially with deionized water and dried in an oven at 50 °C for 2 h.

[0035] Example 5 S1. Add 2.45g manganese acetate tetrahydrate (0.01 mol), 1.42g sodium sulfate (0.01 mol), and 0.058g cobalt nitrate hexahydrate (0.0002 mol) to 100 mL of deionized water to prepare the electrolyte. S2. Using a nickel mesh / PET (2.5 cm × 2.5 cm) as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, constant voltage electrochemical deposition was performed under a stirring condition of 300 r / min, with a deposition potential of 0.7 V and a deposition time of 15 min. The resulting samples were then washed sequentially with deionized water and dried in an oven at 50 °C for 2 h.

[0036] Example 6 S1. Prepare an electrolyte solution by adding 2.45 g manganese acetate tetrahydrate (0.01 mol), 1.42 g sodium sulfate (0.01 mol), and 0.291 g (0.001 mol) cobalt nitrate hexahydrate to 100 mL of deionized water. S2. Using a nickel mesh / PET (2.5 cm × 2.5 cm) as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, constant voltage electrochemical deposition was performed under a stirring condition of 300 r / min, with a deposition potential of 0.7 V and a deposition time of 15 min. The resulting samples were then washed sequentially with deionized water and dried in an oven at 50 °C for 2 h.

[0037] Example 7 S1. Add 1.23g manganese acetate tetrahydrate (0.005 mol), 1.42g sodium sulfate (0.01 mol), and 0.073g cobalt nitrate hexahydrate (0.00025 mol) to 100 mL of deionized water to prepare the electrolyte. S2. Using a nickel mesh / PET (2.5 cm × 2.5 cm) as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, constant voltage electrochemical deposition was performed under a stirring condition of 300 r / min, with a deposition potential of 0.7 V and a deposition time of 15 min. The resulting samples were then washed sequentially with deionized water and dried in an oven at 50 °C for 2 h.

[0038] Example 8 S1. Add 4.9g manganese acetate tetrahydrate (0.02 mol / L), 1.42g sodium sulfate (0.01 mol / L), and 0.291g (0.001 mol / L) cobalt nitrate hexahydrate to 100 mL of deionized water to prepare the electrolyte. S2. Using a nickel mesh / PET (2.5 cm × 2.5 cm) as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, constant voltage electrochemical deposition was performed under a stirring condition of 300 r / min, with a deposition potential of 0.7 V and a deposition time of 15 min. The resulting sample was then washed sequentially with deionized water and dried in an oven at 50 °C for 2 h. Comparative Example 1 S1. Add 2.45g manganese acetate tetrahydrate (0.01 mol) and 1.42g sodium sulfate (0.01 mol) to 100 mL of deionized water to prepare the electrolyte; S2. Using a nickel mesh / PET (2.5 cm × 2.5 cm) as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, constant voltage electrochemical deposition was performed under a stirring condition of 300 r / min, with a deposition potential of 0.7 V and a deposition time of 15 min. The resulting sample was then washed sequentially with deionized water and dried in an oven at 50 °C for 2 h. Comparative Example 2 S1. Add 2.45g manganese acetate tetrahydrate (0.01 mol) and 1.42g sodium sulfate (0.01 mol) to 100 mL of deionized water to prepare the electrolyte; S2. Using a nickel mesh / PET (2.5 cm × 2.5 cm) as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, constant voltage electrochemical deposition was performed under stirring conditions of 300 r / min, with a deposition potential of 0.7 V and a deposition time of 30 min. The resulting samples were then washed sequentially with deionized water and dried in an oven at 50 °C for 2 h.

[0039] Comparative Example 3 S1. Add 2.33g manganese acetate tetrahydrate (0.0095 mol), 1.42g sodium sulfate (0.01 mol), and 0.145g (0.0005 mol) cobalt nitrate hexahydrate to 100 mL of deionized water to prepare the electrolyte. S2. Using an ITO / PET (2.5 cm × 2.5 cm) electrode as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, constant voltage electrochemical deposition was performed under a stirring condition of 300 r / min, with a deposition potential of 0.7 V and a deposition time of 15 min. The resulting sample was then washed sequentially with deionized water and dried in an oven at 50 °C for 2 h.

[0040] Experimental Test 1) Preparation of negative electrode sheet and battery assembly of flexible transparent aqueous zinc-ion battery A zinc negative electrode electrolyte was prepared by dissolving 3 g zinc sulfate, 3 g sodium sulfate, 0.08 g PEI solution, and 0.5 g boric acid in 20 mL deionized water. A zinc foil was used as the anode, and a nickel mesh / PET (2.5 cm × 2.5 cm) was used as the working electrode. Electrodeposition was then performed at a constant voltage of −0.2 V for 1 h. The resulting sample was gently rinsed with deionized water and then air-dried for 2 h to obtain a transparent zinc metal mesh negative electrode sheet.

[0041] Conductive tape was attached to the edges of the transparent positive electrode (samples prepared in Examples 1-8 and Comparative Examples 1-3, respectively) and the negative electrode to facilitate electron transport. A piece of PAM / ZnSO4 / MnSO4 hydrogel electrolyte of suitable size was sandwiched between the positive and negative electrodes, and air was gently squeezed out. The entire device was then encapsulated with transparent acrylic tape to assemble a flexible transparent aqueous zinc-ion battery. The effective working area of ​​the flexible transparent aqueous zinc-ion battery is 4 cm². 2 (2 cm × 2 cm).

[0042] Using the transparent zinc metal mesh negative electrode sheet prepared through the above experimental process and the positive electrode sheets prepared in each embodiment and comparative example, a flexible transparent aqueous zinc-ion battery device was fabricated according to the above flexible transparent aqueous zinc-ion battery assembly process, as shown below. Figure 2 As shown, performance tests were conducted.

[0043] 2) Performance Testing The transmittance of the prepared electrode sheets and the assembled transparent aqueous zinc-ion battery was measured using a UV spectrophotometer. The transmittance was measured at 100 μA·cm⁻¹. -2 Under a charge / discharge current of 0.9–1.8 V, charge / discharge tests were conducted on the positive electrode prepared in Example 1 and the assembled flexible transparent aqueous zinc-ion battery device within a charge / discharge voltage window to obtain the discharge specific capacity data of the positive electrode and the zinc-ion battery device. Additionally, the assembled flexible transparent aqueous zinc-ion battery device was tested at 100 μA·cm⁻¹. -2 The battery capacity retention rate was obtained by cyclic testing for 200 cycles under the charge / discharge current. The assembled flexible transparent aqueous zinc-ion battery device was cyclically bent 500 times at a bending angle of 60°, and the discharge capacity retention rate of the battery after 500 cyclic bends at 60° was obtained.

[0044] 3) Test Result Analysis The test results are shown in the table below: Table 1. Summary of performance data of batteries assembled from electrodes prepared in each embodiment and comparative example. As can be seen from Table 1: Comparing the samples of Example 1 and Comparative Example 1, Comparative Example 1 deposited pure manganese dioxide on a nickel grid. Due to the high resistivity of manganese dioxide, the capacity retention rate of the assembled battery after 200 cycles was only 51%, and the sheet resistance reached 243.3 Ω / sq. In Example 1, cobalt was introduced as a dopant into manganese dioxide, which significantly improved the capacity retention rate to 71% and reduced the sheet resistance to 128.7 Ω / sq. At the same time, the discharge specific capacity and bending resistance were also improved. This indicates that the introduction of cobalt significantly improves the intrinsic electronic conductivity of the material at the electrochemical level by generating oxygen vacancies and modulating the electronic band structure. This not only reduces the charge transfer impedance, but more importantly, it homogenizes the current distribution of the electrochemical reaction. In Comparative Example 1, due to the poor conductivity of pure manganese dioxide, the charge and discharge current is concentrated in a few highly conductive areas, resulting in a high concentration of local charge and stress. At high rates, the active material cannot fully react, and irreversible structural collapse occurs during cycling. The uniform current distribution in Example 1 avoids such problems. Secondly, cobalt ions can act as additional nucleation sites in the early stages of electrodeposition, promoting the formation of finer, denser nanocrystalline structures of manganese dioxide. This structure has more grain boundaries, which can act as stress buffer regions, effectively dispersing and releasing internal stresses caused by zinc ion insertion / extraction or external mechanical bending, thus preventing crack initiation and propagation. At the atomic scale, cobalt doping achieves dynamic stress compensation. This is because cobalt ions (e.g., Co²⁺ ~0.74 Å) and manganese ions (e.g., Mn)... 4The radius difference (~0.53 Å) caused by the incorporation of cobalt ions leads to local lattice distortion and pre-strain. This lattice strain dynamically compensates for and counteracts the lattice contraction / expansion stress caused by zinc ion insertion during charging and discharging, thus avoiding high stress concentration locally (especially at grid corners). Cobalt ions act as "structural pillars" to embed and stabilize the structure of manganese dioxide. This effectively suppresses the drastic volume changes and interlayer collapse caused by repeated zinc ion insertion / extraction, fundamentally reducing the resulting destructive macroscopic stress and ensuring the long-term integrity of the electrode structure.

[0045] Comparing the samples of Example 4 and Comparative Example 2, both were deposited for 30 minutes. As shown in Table 1, the electrode of Example 4 (cobalt-doped manganese dioxide electrode sample) maintained a capacity retention rate of 69% and 90% after cycling and bending, respectively. In contrast, the capacity retention rate of the electrode of Comparative Example 2 (pure manganese dioxide electrode sample) plummeted to 47% and 55% after cycling and bending, respectively. Microscopic observation revealed extensive detachment of active material from the electrode surface of Comparative Example 2. This is because pure manganese dioxide has poor conductivity, resulting in uneven current distribution during deposition, concentrating in low-resistance areas such as corners. This leads to cracking and delamination of the deposited active material layer. As deposition time increases, the stress unevenness intensifies, causing extensive detachment of active material and severe damage to the mesh-like current collector structure. The sheet resistance reached 1225.8 Ω / sq. The combined effect of reduced active material quantity and increased sheet resistance resulted in a battery capacity of only 8 μAh·cm⁻¹. -2 In Example 4, cobalt ions were introduced for doping, which effectively improved conductivity and optimized stress distribution. This ensured that even a thicker deposition layer maintained excellent structural integrity and strong adhesion to the substrate, without significant detachment. The sheet resistance was 143.9 Ω / sq, and the assembled battery capacity was still 28 μAh·cm. -2 .

[0046] Comparing the samples of Example 1 and Comparative Example 3, Comparative Example 3 replaced the nickel mesh / PET substrate with ITO / PET. Due to the uniform conductivity of ITO / PET across its entire surface, cobalt-doped manganese dioxide is deposited on the entire electrode surface, rather than only in the mesh area as in nickel mesh / PET. The prepared positive electrode and the assembled battery have lower light transmittance. In addition, when ITO / PET is used as an aqueous zinc ion positive electrode current collector, it undergoes an oxidation reaction at high potential, leading to a decrease in conductivity and a battery cycle retention rate as low as 32%. Furthermore, due to the poor mechanical properties of ITO, the battery assembled from the Comparative Example 3 sample has very poor bending resistance. After 500 cycles of 60° bending, the ITO layer breaks, and the battery discharge capacity retention rate is as low as 15%. This indicates that the nickel mesh / PET, due to the mesh morphology of the metal layer and its strong adhesion to the substrate, as well as the good electrochemical stability of gold, contributes to the high cycle stability, high light transmittance, and high bending resistance of flexible transparent aqueous zinc ion batteries.

[0047] Compared to Examples 2, 3, and 4, the deposition time for cobalt-doped manganese dioxide in Example 1 was longer than that in Examples 2 and 3, but shorter than that in Example 4. The discharge specific capacity ranking of the assembled batteries was Example 2 < Example 3 < Example 1 < Example 4, while the transmittance ranking was the opposite: Example 2 > Example 3 > Example 1 > Example 4. The sheet resistance ranking of the electrodes was Example 2 < Example 3 < Example 1 < Example 4. This indicates that the deposition time of cobalt-doped manganese dioxide primarily affected the battery's discharge specific capacity and transmittance. A longer deposition time resulted in a greater deposition amount, thus leading to a higher battery capacity, but also a higher coverage of the active material on the electrodes, resulting in lower transmittance. Simultaneously, because the conductivity of the deposited Co-MnO2 was lower than that of the nickel mesh current collector, the overall sheet resistance of the composite electrode also tended to increase with its increased coverage.

[0048] Compared to Examples 5 and 6, the amount of cobalt nitrate hexahydrate added in Example 1 was more than in Example 5, but less than in Example 6. The capacity of the assembled batteries from each sample was ranked as Example 5 < Example 6 < Example 1, while the sheet resistance was ranked as Example 5 > Example 6 > Example 1. This indicates that there is an optimal range for cobalt doping. At lower concentrations, as the amount of cobalt introduced increases, the conductivity of the material improves (manifested as a decrease in sheet resistance), and correspondingly, the capacity of the assembled battery also increases. When the amount of cobalt introduced is large, excessive cobalt ions can lead to excessive lattice stretching, destroying the layered structure of manganese dioxide, which in turn compresses ion channels, making the active material more prone to irreversible collapse during cycling, thus affecting cycle life.

[0049] Compared to Examples 7 and 8, Example 1 demonstrates the effect of the overall electrolyte concentration on device performance. It is noteworthy that Examples 1, 7, and 8 maintained a constant manganese-cobalt molar ratio (Mn:Co = 20:1), only changing the total concentration of the precursor materials in the electrolyte. Experimental results show that as the electrolyte concentration increases (Example 7 < Example 1 < Example 8), the discharge specific capacity of the assembled battery increases (18 < 25 < 27 μAh·cm⁻²), while the cycle stability (capacity retention after 200 cycles) decreases (74% > 71% > 65%). This is mainly because the electrolyte concentration directly affects the kinetics of electrochemical deposition: at lower concentrations (Example 7), the deposition rate is slower, which is beneficial for the orderly arrangement and dense growth of grains, resulting in excellent structural stability and cycle life; however, the active material loading is relatively low, limiting the battery capacity. When the concentration is too high (Example 8), although the accelerated deposition rate significantly improves the loading of active material and the initial capacity, the excessively rapid growth rate can easily lead to large internal stress or structural defects in the deposited layer. This makes the layer more prone to structural degradation during subsequent charge-discharge cycles and bending, resulting in a decrease in capacity retention. The concentration parameters of Example 1 (0.1 mol / L Mn²⁺, 0.005 mol / L Co²⁺) achieved the best balance between deposition rate and film quality, balancing high specific capacity and good cycling stability. In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0050] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing a flexible transparent positive electrode sheet for a cobalt-doped manganese dioxide zinc ion battery, characterized by, Includes the following steps: An electrolyte was prepared by dispersing manganese acetate tetrahydrate, cobalt nitrate hexahydrate, and sodium sulfate in deionized water. Using a nickel mesh / PET current collector as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, a cobalt-doped manganese dioxide layer is deposited on the surface of the nickel mesh / PET current collector in the electrolyte using a constant voltage electrochemical deposition method to prepare a positive electrode sheet.

2. The method of making a flexible transparent positive electrode sheet for a zinc-ion battery of cobalt-doped manganese dioxide according to claim 1, characterized in that, The concentration of manganese acetate in the electrolyte is 0.05-0.2 mol / L.

3. The method of making a flexible transparent positive electrode of a cobalt-doped zinc-manganese dioxide zinc-ion battery as claimed in claim 1, wherein, The concentration of cobalt nitrate in the electrolyte is 0.002-0.01 mol / L.

4. The method of making a flexible transparent positive electrode of a cobalt-doped zinc-manganese dioxide zinc-ion battery of claim 1, wherein, The electrolyte contains sodium sulfate at a concentration of 0.1 mol / L.

5. The method of making a flexible transparent positive electrode of a cobalt-doped zinc-manganese dioxide zinc-ion battery of claim 1, wherein, The sheet resistance of the nickel mesh / PET current collector is 2-5 Ω / sq, and the light transmittance is 80-85%.

6. The method of making a flexible transparent positive electrode of a cobalt-doped zinc-manganese dioxide zinc-ion battery of claim 1, wherein, The deposition potential range of the constant voltage electrochemical deposition method is 0.4-1.6V, and the deposition time is 5-30 min.

7. The method for preparing the flexible transparent cobalt-doped manganese dioxide zinc-ion battery positive electrode sheet according to claim 1, characterized in that, The preparation process of the nickel mesh / PET current collector includes: After mixing acrylic resin and ethanol, the mixture is coated onto the surface of a PET substrate that has undergone plasma cleaning and then dried under vacuum to obtain an acrylic resin crack network template sample. The sample was subjected to vacuum deposition to deposit a nickel film on a PET substrate; The coated sample was immersed in acetic acid and ultrasonically treated to remove the acrylic resin template layer. After cleaning and drying, a nickel mesh / PET current collector was obtained.

8. A flexible, transparent cobalt-doped manganese dioxide zinc-ion battery positive electrode sheet, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The application of the positive electrode sheet according to claim 8 in the assembly of a flexible transparent aqueous zinc-ion battery.

10. A flexible, transparent, aqueous zinc-ion battery, characterized in that, include: The positive electrode, the transparent zinc metal mesh negative electrode, and the hydrogel electrolyte located between the positive and negative electrode as described in claim 8.

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