A high-capacity aqueous zinc-ion battery manganese-based positive electrode material and a preparation method and application thereof

Abstract

This invention relates to a high-capacity manganese-based cathode material for aqueous zinc-ion batteries, its preparation method, and its application. The invention utilizes a one-step hydrothermal method, adding an appropriate amount of bismuth ions during synthesis to obtain a heterojunction cathode material composed of bismuth oxide and manganese oxide. The reaction conditions are mild, the preparation process is simple, and the equipment requirements are low. The resulting cathode material exhibits an irregular nanosheet morphology with disordered stacking. This cathode material is the first to be applied to aqueous zinc-ion batteries, demonstrating ultra-high discharge specific capacity and excellent electrochemical performance, including cycle stability.

Description

Technical Field

[0001] This invention relates to a high-capacity aqueous zinc-ion battery manganese-based cathode material, its preparation method and application, belonging to the field of zinc-ion battery technology. Background Technology

[0002] With the increasing prominence of energy and environmental issues, the effective utilization of clean and renewable energy sources such as wind and solar power has received widespread attention. Consequently, higher demands are being placed on renewable energy storage devices. Lithium-ion batteries are widely used due to their long lifespan and high energy density, but their flammable and toxic organic electrolytes pose potential safety hazards, limiting their further development. Therefore, exploring alternative and safe energy storage devices is crucial.

[0003] In aqueous zinc-ion batteries, zinc, as the anode, has a theoretically high capacity (820 mA hg). -1 It has a low redox potential (-0.76V compared to the standard hydrogen electrode) and a low cost (Zn ~ 2.4 kg). -1 vs Li ~ 19.2 kg -1 With advantages such as high efficiency, environmental friendliness, and safety, aqueous zinc-ion batteries have attracted widespread attention from researchers in recent years. However, the development of aqueous zinc-ion batteries has been limited by the lack of suitable high-capacity cathode materials with good cycle stability.

[0004] Manganese oxides, represented by manganese dioxide, are considered one of the most promising cathode materials for aqueous zinc batteries. Manganese dioxide possesses multiple valence states (+2, +3, and +4), a high discharge voltage (approximately 1.3V), and an excellent theoretical capacity (616 mAh g⁻¹). -1 The advantages of MnO2, such as low manganese atom solubility, low conductivity, and irreversible phase transition, have attracted the interest of researchers. However, MnO2 has problems such as low manganese atom solubility, low conductivity, and irreversible phase transition. Therefore, aqueous zinc-ion batteries assembled with MnO2 electrode sheets exhibit limited cycle life and poor specific capacity at low current densities.

[0005] Chinese patent document CN112582602A discloses a manganese dioxide / graphite nanosheet composite zinc-ion cathode material and its preparation method. The method includes: combining commercial manganese dioxide with graphite nanosheets using a mechanical ball milling method, allowing manganese dioxide to be dispersed on the surface of the graphite nanosheets, thus constructing a conductive network and improving electron transport efficiency. Furthermore, the addition of graphite nanosheets significantly suppresses the volume change of manganese dioxide during the reaction process, resulting in a high-performance and durable zinc-ion battery cathode material. Test results show that the manganese dioxide / graphite nanosheet composite exhibits excellent electrochemical performance as an electrode material. At a current density of 0.1 A / g, the manganese dioxide / graphite nanosheet composite has a specific capacity of 210 mAh / g, and retains 83.8% of this capacity after 1000 cycles at a current density of 1 A / g. However, the specific capacity of this cathode material remains low at low current densities, indicating limited improvement.

[0006] Therefore, developing novel cathode materials remains the key to improving the performance of aqueous zinc batteries, in order to achieve high capacity and long cycle stability of MnO2-based electrode materials at low current densities. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a high-capacity manganese-based cathode material for aqueous zinc-ion batteries, its preparation method, and its application.

[0008] The preparation method of this invention is simple, and the resulting cathode material has an irregular microstructure of nanosheets that do not require stacking. When applied to aqueous zinc-ion batteries, the cathode material exhibits exceptionally high discharge capacity and excellent cycle stability, particularly under low current conditions. At a current density of 0.1 A / g, the highest discharge specific capacity reaches 720.6 mAh g. -1 The above results show that, at a current density of 2 A / g, the discharge specific capacity does not decrease after 2000 cycles.

[0009] The technical solution of the present invention is as follows:

[0010] A method for preparing a high-capacity manganese-based cathode material for aqueous zinc-ion batteries includes the following steps:

[0011] Take KMnO4 and Bi(NO3)3·5H2O and fully disperse them in water, stir magnetically, and then add citric acid solution to form a uniform mixture. The mixture is then subjected to hydrothermal reaction at 90-200℃ for 6-24 hours. After centrifugation or filtration, washing, and drying, a high-capacity aqueous zinc-ion battery manganese-based cathode material is obtained.

[0012] According to a preferred embodiment of the present invention, the molar ratio of KMnO4 to Bi(NO3)3·5H2O is (2-6):10.

[0013] More preferably, the molar ratio of KMnO4 to Bi(NO3)3·5H2O is (2-4):10.

[0014] According to a preferred embodiment of the present invention, the mass ratio of potassium permanganate to water is (0.02-0.05):1.

[0015] According to a preferred embodiment of the present invention, the concentration of the citric acid solution is 0.1 mol / L to 0.5 mol / L.

[0016] According to a preferred embodiment of the present invention, the molar ratio of potassium permanganate to citric acid is (7-15):1.

[0017] According to a preferred embodiment of the present invention, the hydrothermal reaction temperature is 120℃-190℃, and the reaction time is 10h-24h.

[0018] The most preferred hydrothermal reaction temperature is 180℃ and the reaction time is 12h.

[0019] According to a preferred embodiment of the invention, the washing is performed with deionized water or anhydrous ethanol.

[0020] According to a preferred embodiment of the present invention, the drying is performed by vacuum drying at 40-80°C for 8-20 hours.

[0021] Most preferably, the drying is performed under vacuum at 60°C for 12 hours. Excessive drying temperature will damage the structure of the cathode material, causing a significant decrease in its electrochemical performance.

[0022] A high-capacity manganese-based cathode material for aqueous zinc-ion batteries was prepared using the method described above.

[0023] According to a preferred embodiment of the present invention, the high-capacity aqueous zinc-ion battery manganese-based cathode material is bismuth oxide (Bi). 12.53 Mn 0.47 O 19.85 Heterojunction materials composed of manganese oxide R-MnO2.

[0024] According to a preferred embodiment of the present invention, the high-capacity aqueous zinc-ion battery manganese-based cathode material has an irregular nanosheet morphology, and the nanosheets are stacked in a disordered manner.

[0025] According to a preferred embodiment of the present invention, the high-capacity aqueous zinc-ion battery manganese-based cathode material exhibits a discharge specific capacity of up to 720.6 mAh g at a current density of 0.1 A / g. -1 The above results show that, at a current density of 2 A / g, the discharge specific capacity does not decrease after 2000 cycles.

[0026] The preparation method of this invention involves directly mixing bismuth oxide and manganese oxide to synthesize manganese-based cathode materials via a one-step hydrothermal method. During the synthesis process, a portion of the manganese reacts with the bismuth oxide, meaning that the manganese element in the manganese oxide replaces the bismuth in the bismuth oxide to generate Bi. 12.53 Mn 0.47 O 19.85 Bismuth oxide (Bi) was obtained. 12.53 Mn 0.47 O 19.85 In heterojunction materials with uniform distribution of manganese oxide (R-MnO2), bismuth oxide acts as an in-situ metal ion pool, continuously supplying Bi metal ions to R-MnO2 during application. 3+ The active substance Bi2Mn4O is formed. 10 This stabilizes the structure of MnO2. The preparation method has mild reaction conditions, simple preparation process, and low equipment requirements.

[0027] The aforementioned high-capacity aqueous zinc-ion battery manganese-based cathode material is used as a cathode material in rechargeable aqueous zinc-ion batteries.

[0028] A high-capacity aqueous zinc-ion battery, wherein the negative electrode is zinc foil, the electrolyte is a mixed solution of zinc sulfate and manganese sulfate, and the separator is a glass fiber membrane.

[0029] The positive electrode sheet is prepared by the following method:

[0030] The positive electrode material, activated carbon, and polyvinylidene fluoride (PVDF) dissolved in N-methylpyrrolidone are mixed evenly to form a slurry, which is then coated onto a titanium foil with a coating thickness of 200-600 μm. After drying, a positive electrode sheet is obtained. The mass ratio of the positive electrode material, activated carbon, and polyvinylidene fluoride is 7:1.5:1.5.

[0031] According to a preferred embodiment of the present invention, the thickness of the titanium foil is 20 μm.

[0032] According to a preferred embodiment of the present invention, the concentration of zinc sulfate in the electrolyte is 1-3 mol / L, and the concentration of manganese sulfate is 0.1-0.5 mol / L.

[0033] According to the present invention, the amount of N-methylpyrrolidone added can be determined according to existing technology.

[0034] Technical features and beneficial effects of the present invention:

[0035] 1. The preparation method of the present invention directly mixes bismuth oxide and manganese oxide, and the final cathode material can be prepared by a simple one-step hydrothermal method; the reaction conditions of the present invention are mild, the preparation process is simple, and the equipment requirements are low; the microstructure of the obtained cathode material is an irregularly stacked nanosheet.

[0036] 2. The negative electrode raw materials used in the aqueous zinc-ion battery of this invention are abundant and inexpensive; the electrolyte is zinc sulfate / manganese sulfate, which is inexpensive, safe, and environmentally friendly. The zinc-ion battery prepared from the positive electrode material of this invention has ultra-high discharge specific capacity and excellent cycle stability, as well as good rate performance; the discharge specific capacity can reach up to 720.6 mAh g at a current density of 0.1 A / g. -1 The above results show that, at a current density of 2 A / g, the discharge specific capacity does not decrease after 2000 cycles.

[0037] 3. In this invention, for a series of cathodes such as heterojunctions composed of bismuth oxide / manganese dioxide, the bismuth oxide acts as a metal ion pool during battery cycling, continuously supplying Bi metal ions to R-MnO2 in situ. 3+ The active substance Bi2Mn4O is formed. 10 This process stabilizes the structure of MnO2. This dynamic transformation also creates more active sites, resulting in ultra-high capacity and excellent cycle stability in the battery, providing a promising cathode material for future applications of aqueous zinc batteries. Attached Figure Description

[0038] Figure 1 The X-ray diffraction (XRD) pattern of the zinc-ion battery cathode material prepared in Example 1.

[0039] Figure 2 This is a scanning electron microscope (SEM) image of the zinc-ion battery cathode material prepared in Example 1.

[0040] Figure 3 The image shows the elemental analysis of the zinc-ion battery cathode material prepared in Example 1.

[0041] Figure 4 The graph shows the cycling performance of the zinc-ion battery cathode material prepared in Example 1 under a constant current of 0.3 A / g.

[0042] Figure 5 The graph shows the cycling performance of the zinc-ion battery cathode material prepared in Example 1 under a constant current of 2A / g.

[0043] Figure 6 The graph shows the rate performance of the zinc-ion battery cathode material prepared in Example 1, and the cycle performance after rate testing under a constant current of 0.1 A / g.

[0044] Figure 7 The graph shows the cycling performance of the zinc-ion battery cathode material prepared in Comparative Example 1 under a constant current of 0.3 A / g.

[0045] Figure 8 The graph shows the cycling performance of the zinc-ion battery cathode material prepared for Comparative Example 1 under a constant current of 2A / g.

[0046] Figure 9 The rate performance diagram of the zinc-ion battery cathode material prepared for Comparative Example 1 is shown.

[0047] Figure 10 The graph shows the cycling performance of the zinc-ion battery cathode material prepared in Comparative Example 2 under a constant current of 0.3 A / g.

[0048] Figure 11 The graph shows the cycling performance of the zinc-ion battery cathode material prepared for Comparative Example 2 under a constant current of 2 A / g. Detailed Implementation

[0049] The present invention will be further described below with reference to specific embodiments, but is not limited thereto.

[0050] Furthermore, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods; and unless otherwise specified, the reagents, materials and equipment are all commercially available.

[0051] Example 1

[0052] A method for preparing a high-capacity manganese-based cathode material for aqueous zinc-ion batteries includes the following steps:

[0053] 10 mmol of KMnO4 and 33 mmol of Bi(NO3)3·5H2O were weighed and thoroughly dispersed in 60 mL of water. The mixture was magnetically stirred for 60 min, and then 10 mL of 0.1 mol / L citric acid solution (CA) was added and stirred to form a homogeneous mixture. The mixture was transferred to a 100 mL reactor with a polytetrafluoroethylene liner and reacted at 180 °C for 12 h. The reaction product was allowed to cool naturally to room temperature. The precipitate after the hydrothermal reaction was separated by centrifugation, washed with anhydrous ethanol, and vacuum dried at 60 °C for 12 h to obtain a high-capacity aqueous zinc-ion battery manganese-based cathode material.

[0054] The X-ray diffraction (XRD) pattern of the zinc-ion battery cathode material prepared in this embodiment is as follows: Figure 1 As shown, its structure is Bi after XRD analysis. 12.53 Mn 0.47 O 19.85 / R-MnO2.

[0055] The scanning electron microscope (SEM) image of the zinc-ion battery cathode material prepared in this embodiment is shown below. Figure 2 As shown, Figure 2 It can be seen from the results that the microstructure of the obtained cathode material is an irregular, disordered stack of nanosheets.

[0056] The mapping elemental analysis diagram of the zinc-ion battery cathode material prepared in this embodiment is shown below. Figure 3,pass Figure 3 It can be seen that Bi and Mn elements are evenly distributed.

[0057] The zinc-ion battery cathode material prepared in this embodiment is used as a cathode material in a rechargeable aqueous zinc-ion battery.

[0058] Preparation of rechargeable aqueous zinc-ion batteries:

[0059] (1) Preparation of positive electrode sheet

[0060] The prepared positive electrode material, activated carbon, and polyvinylidene fluoride (PVDF) dissolved in N-methylpyrrolidone were mixed evenly to form a slurry, which was then coated onto a titanium foil with a thickness of 20 μm and a coating thickness of 400-600 μm. After drying, a positive electrode sheet was obtained. The mass ratio of the positive electrode material, activated carbon, and polyvinylidene fluoride was 7:1.5:1.5.

[0061] (2) Preparation of negative electrode sheet

[0062] The negative electrode is a zinc foil with a thickness of 20 μm. The oxide layer is removed by sanding with sandpaper, then rinsed with ethanol and dried to obtain the negative electrode sheet.

[0063] (3) Preparation of electrolyte

[0064] Weigh out 8.63g of zinc sulfate heptahydrate and 0.85g of manganese sulfate monohydrate and dissolve them in 10ml of deionized water to prepare the electrolyte.

[0065] (4) Battery manufacturing

[0066] The electrode plates are placed in the battery casing, and a glass fiber separator is placed between the positive and negative electrode plates. 70 μL of electrolyte is added, and then the battery is encapsulated to obtain a rechargeable aqueous zinc-ion battery.

[0067] The first charge-discharge curve of the zinc-ion battery assembled from the zinc-ion battery cathode material prepared in this embodiment at a constant current of 0.3 A / g is shown below. Figure 3 As shown, based on the mass of the positive electrode active material, the first-cycle discharge specific capacity is 171.3 mAh g. -1 After 160 cycles, it gradually increased to 474.4 mAh g. -1 The capacity does not decrease during cycling. This indicates that the cathode material of this invention has a large specific capacity when applied to zinc-ion batteries.

[0068] The cycling performance of the zinc-ion battery assembled from the zinc-ion battery cathode material prepared in this embodiment at a constant current of 2A / g is shown in the figure below. Figure 4 As shown, the initial discharge specific capacity is 113.5 mAh g. -1 After 2000 cycles, the capacity gradually increased to 161mAh.-1 The capacity does not decrease during the recycle process, indicating that the cathode material of this invention has good cycle stability when applied to zinc-ion batteries.

[0069] The zinc-ion battery cathode material prepared in this embodiment exhibits good rate performance when assembled into a zinc-ion battery. Testing was conducted after five cycles of pre-activation at a current density of 0.1 A / g. Figure 5 As shown, at a current density of 0.25 A / g, the initial discharge specific capacity is 504 mAh g. -1 When the current density increases from 0.25 A / g to 4 A / g, the average specific capacity remains at 221.6 mAh g. -1 When the current density recovers to 0.25 A / g, the specific capacity recovers to 572.9 mAh g. -1 After measuring the rate performance, further testing was conducted at a low current density of 0.1 A / g. After 20 cycles, the specific capacity reached a high of 720.6 mAh g. -1 .

[0070] Comparative Example 1

[0071] The preparation method of the manganese-based cathode material for aqueous zinc-ion batteries described in Example 1 differs from that in:

[0072] KMnO4 and Bi(NO3)3·5H2O were fully dispersed in 60 ml of water at a molar ratio of 1:10, and the rest was carried out as in Example 1.

[0073] A rechargeable aqueous zinc-ion battery was prepared according to the method in Example 1.

[0074] The zinc-ion battery assembled from Bi-doped MnO2 cathode material prepared in this comparative example exhibits the following cycling performance under a constant current of 0.3 A / g: Figure 7 At a low current density of 0.3 A / g, the initial capacity is 237.1 mAh g. -1 After 160 cycles, only 89.3 mAh g remained. -1 Its capacity is limited, but its performance is poor.

[0075] The zinc-ion battery assembled from Bi-doped MnO2 cathode material prepared in this comparative example exhibits the following cycling performance at a constant current of 2 A / g: Figure 8 At a current density of 2 A / g, the initial capacity is 181.4 mAh g. -1 After 2000 cycles, only 7.8 mAh g remained. -1 The capacity.

[0076] The rate performance of the zinc-ion battery assembled from the Bi-doped MnO2 cathode material prepared in this comparative example is shown in [reference needed]. Figure 9 Its rate capability is average; under the same test conditions, the discharge specific capacity at a current density of 0.25 A / g is 320.36 mAh / g. -1 The discharge specific capacity is 230.4 mAh g at a current density of 0.5 A / g. -1 The discharge specific capacity is 91.1 mAh g at a current density of 1 A / g. -1 The discharge specific capacity is 32.7 mAh g at a current density of 2 A / g. -1 The discharge specific capacity is 9.0 mAh g at a current density of 4 A / g. -1 .

[0077] The comparison shows that the stability, capacity, and rate performance of the Bi-doped MnO2 in Comparative Example 1 are inferior to those in Example 1 of this invention. This is because the amount of bismuth oxide formed during hydrothermal synthesis from a small amount of Bi doping is too small, resulting in insufficient ion supply to manganese dioxide, thus leading to poor stability and capacity. In contrast, Example 1 of this invention, by adding an appropriate amount of Bi ions, provides sufficient metal ion supply to manganese dioxide during charge and discharge, thereby improving the overall structural stability and capacity.

[0078] Comparative Example 2

[0079] The preparation method of the manganese-based cathode material for aqueous zinc-ion batteries described in Example 1 differs from that in:

[0080] KMnO4 and Bi(NO3)3·5H2O were fully dispersed in 60 ml of water at a molar ratio of 5:10, and the rest was carried out as in Example 1.

[0081] A rechargeable aqueous zinc-ion battery was prepared according to the method in Example 1.

[0082] The zinc-ion battery assembled from Bi-doped MnO2 cathode material prepared in this comparative example exhibits the following cycling performance under a constant current of 0.3 A / g: Figure 10 At a low current density of 0.3 A / g, the initial capacity is 115.8 mAh g. -1 After 160 cycles, only 52.6 mAh g remained. -1 Its capacity is limited, but its performance is poor.

[0083] The zinc-ion battery assembled from Bi-doped MnO2 cathode material prepared in this comparative example exhibits the following cycling performance at a constant current of 2 A / g: Figure 11 At a current density of 2 A / g, the initial capacity is 7.3 mAh g. -1 After 2000 cycles, only 30.66 mAh g remained. -1 The capacity.

[0084] The comparison shows that the stability and capacity of the Bi-doped MnO2 are inferior to those of Example 1 of this invention. This is because the excessive amount of bismuth oxide formed during hydrothermal synthesis from the large amount of Bi doping results in a relatively reduced proportion of manganese dioxide. Consequently, the portion of manganese dioxide that can provide capacity as an active material is reduced, leading to poor capacity. Example 1 of this invention, by adding an appropriate amount of Bi, achieves a suitable ratio of manganese dioxide to bismuth oxide, ensuring both a sufficient supply of metal ions for manganese dioxide during charging and discharging, and maximizing the zinc ion storage capacity of manganese dioxide, thus improving the overall structural stability and capacity.

[0085] In summary, it can be seen that both excessive and insufficient bismuth oxide content will reduce the electrochemical performance of the material.

[0086] Table 1 shows a comparison of the performance data of the cathode materials prepared in the embodiments and comparative examples of the present invention.

[0087] Table 1 Comparison of Partial Electrical Performance

[0088]

[0089] Example 2

[0090] The preparation method of the manganese-based cathode material for aqueous zinc-ion batteries described in Example 1 differs from that in:

[0091] Weigh 10 mmol of KMnO4 and 50 mmol of Bi(NO3)3·5H2O and disperse them thoroughly in 60 ml of water. Other steps are carried out as in Example 1.

[0092] A rechargeable aqueous zinc-ion battery was prepared according to the method in Example 1.

[0093] Example 3

[0094] The preparation method of the manganese-based cathode material for aqueous zinc-ion batteries described in Example 1 differs from that in:

[0095] Weigh 10 mmol of KMnO4 and 25 mmol of Bi(NO3)3·5H2O and disperse them thoroughly in 60 ml of water. Other steps are carried out as in Example 1.

[0096] A rechargeable aqueous zinc-ion battery was prepared according to the method in Example 1.

Claims

1. A method for preparing a high-capacity manganese-based cathode material for aqueous zinc-ion batteries, comprising the following steps: Disperse KMnO4 and Bi(NO3)3•5H2O thoroughly in water, stir magnetically, and then add citric acid solution to form a homogeneous mixture. Perform a hydrothermal reaction at 90-200℃ for 6-24 hours. After centrifugation or filtration, washing, and drying, a high-capacity aqueous zinc-ion battery manganese-based cathode material is obtained. The high-capacity aqueous zinc-ion battery manganese-based cathode material is bismuth oxide (Bi). 12.53 Mn 0.47 O 19.85 The heterojunction material composed of manganese oxide R-MnO2 has an irregular nanosheet morphology with disordered stacking. At a current density of 0.1 A / g, it achieves a discharge specific capacity of up to 720.6 mAh g. -1 The above results show that, at a current density of 2 A / g, the discharge specific capacity does not decrease after 2000 cycles.

2. The preparation method according to claim 1, characterized in that, The molar ratio of KMnO4 to Bi(NO3)3•5H2O is (2-6):

10.

3. The preparation method according to claim 1, characterized in that, The mass ratio of potassium permanganate to water is (0.02 - 0.05):

1.

4. The preparation method according to claim 1, characterized in that, The concentration of the citric acid solution is 0.1 mol / L-0.5 mol / L.

5. The preparation method according to claim 1, characterized in that, The molar ratio of potassium permanganate to citric acid is (7-15):

1.

6. The preparation method according to claim 1, characterized in that, The hydrothermal reaction temperature is 120℃-190℃, and the reaction time is 10h-24h.

7. The preparation method according to claim 1, characterized in that, The washing is performed with deionized water or anhydrous ethanol, and the drying is performed under vacuum at 40-80°C for 8-20 hours.

8. A high-capacity aqueous zinc-ion battery manganese-based cathode material, prepared by any one of the methods described in claims 1-7, wherein the high-capacity aqueous zinc-ion battery manganese-based cathode material is bismuth oxide (Bi). 12.53 Mn 0.47 O 19.85 The heterojunction material composed of manganese oxide R-MnO2 has an irregular nanosheet morphology with disordered stacking. At a current density of 0.1 A / g, it achieves a discharge specific capacity of up to 720.6 mAh g. -1 The above results show that, at a current density of 2 A / g, the discharge specific capacity does not decrease after 2000 cycles.

9. The application of the high-capacity aqueous zinc-ion battery manganese-based cathode material as described in claim 8, used as a cathode material in a rechargeable aqueous zinc-ion battery.

10. A high-capacity aqueous zinc-ion battery, wherein the negative electrode is zinc foil, the electrolyte is a mixed solution of zinc sulfate and manganese sulfate, the concentration of zinc sulfate in the electrolyte is 1-3 mol / L, the concentration of manganese sulfate is 0.1-0.5 mol / L, and the separator is a glass fiber separator. The positive electrode sheet is prepared by the following method: The positive electrode material as described in claim 8, activated carbon, and polyvinylidene fluoride (PVDF) dissolved in N-methylpyrrolidone are mixed evenly to form a slurry, which is then coated onto a titanium foil with a coating thickness of 200-600 μm. After drying, a positive electrode sheet is obtained; the mass ratio of the positive electrode material, activated carbon, and polyvinylidene fluoride is 7:1.5:1.5.

Images