Integrated diaphragm-positive electrode and preparation method thereof

Abstract

The invention provides an integrated diaphragm-positive electrode which comprises a bacterial cellulose membrane and a water-based positive electrode layer formed on the surface of the bacterial cellulose membrane through calcium ion crosslinking, the aqueous positive electrode layer is formed by a cross-linking reaction of a polymerized colloid, alginate and calcium ions in the presence of a composite material of sulfur and carbon nanotubes, and the concentration ratio of the composite material of sulfur and carbon nanotubes to the alginate to the polymerized colloid is 1: 0.06-0.33: 0.16-1. The integrated diaphragm-positive electrode disclosed by the invention can be applied to a lithium-sulfur battery, so that the lithium-sulfur battery shows high specific discharge capacity, high coulombic efficiency and stable cycle performance.

Description

Technical Field

[0001] This disclosure belongs to the field of lithium-sulfur battery technology, and particularly relates to an integrated separator-cathode used in lithium-sulfur batteries and its preparation method. Background Technology

[0002] Since its successful commercial production by Sony in 1991, lithium-ion batteries have been recognized by both industry and the scientific community as a high-performance rechargeable battery. Currently, lithium-ion batteries are widely used in various portable mobile devices and electric vehicles. In recent years, the goal of "carbon neutrality" has placed higher demands on the large-scale storage and utilization of renewable energy. Because conventional lithium-ion rechargeable batteries have limited theoretical capacity, they cannot meet the demands for high energy density and large capacity energy storage. Therefore, it is necessary to seek new electrode activity systems with high specific energy and high efficiency.

[0003] Compared to traditional lithium-ion batteries, lithium-sulfur batteries, assembled with a sulfur-containing conductive substrate as the positive electrode and metallic lithium as the negative electrode, possess very high theoretical energy density (2567 Wh / kg) and theoretical specific capacity (1675 mAh / g), far exceeding those of currently commercialized lithium-ion batteries. Furthermore, elemental sulfur has a low environmental impact, is non-toxic to humans and animals, and is relatively abundant in the Earth's crust. Lithium-sulfur batteries, as a promising next-generation high-energy rechargeable battery, have attracted widespread attention from researchers. However, before achieving large-scale commercial development, lithium-sulfur batteries still need to solve several key challenges. Among these, the "shuttle effect" caused by dissolved polysulfides and the lithium dendrite phenomenon caused by uneven lithium-ion deposition have the most significant impacts on the capacity, stability, and coulombic efficiency of lithium-sulfur batteries.

[0004] As is well known, biomass materials are abundant, inexpensive, readily available, renewable, and environmentally friendly. In the process of achieving the goal of "carbon neutrality," biomass resources are the most important substitute for petrochemical resources, thus possessing very good development and application value. Bacterial cellulose, as a typical biomass material, is mainly produced by the secondary metabolism of certain bacteria. Bacterial cellulose has many advantages such as abundant hydroxyl groups, ultrafine nanofibers, high mechanical strength, and three-dimensional macroporous structure (see Huang et al. (2014), Recent advances in bacterial cellulose, Cellulose, 21(1), 1-30), making it very suitable as a multifunctional membrane material for lithium-sulfur batteries. For example, Yu et al. (Cellulose-Based Porous Membrane for Suppressing Li Dendrite Formation in Lithium–Sulfur Battery, ACS Energy Letters, 2016) first used bacterial cellulose membranes as membrane materials for lithium-sulfur batteries. The results showed that bacterial cellulose membranes can promote the uniform deposition of lithium ions on the surface of metallic lithium and prevent the formation of lithium dendrites. Compared to commercially available Celgard membranes, bacterial cellulose membranes exhibit superior electrolyte absorption and retention capabilities, as well as excellent thermal stability. However, leveraging the properties of bacterial cellulose to improve the interfacial relationship between the electrode and the membrane, inhibit polysulfide diffusion, and mitigate puncture short circuits caused by lithium dendrites remains a pressing issue for the industry. Summary of the Invention

[0005] To address the shortcomings of the prior art, this disclosure provides an integrated membrane-positive electrode, comprising a bacterial cellulose membrane and an aqueous positive electrode layer formed on the surface of the bacterial cellulose membrane. The aqueous positive electrode layer is formed by a cross-linking reaction of polymerized colloid, alginate, and calcium ions in the presence of a sulfur-carbon nanotube composite material. The mass concentration ratio of the sulfur-carbon nanotube composite material, the alginate, and the polymerized colloid is 1:0.06 to 0.33:0.16 to 1.

[0006] In one specific embodiment, the aqueous positive electrode layer comprises a composite material of sulfur and carbon nanotubes and a colloid cross-linked with methacryloyl colloid, alginate, and calcium ions. The methacryloyl colloid may be methacryloyl gelatin (GelMA) or methacryloyl hyaluronic acid gelatin (HAMA).

[0007] This disclosure also provides a method for preparing an integrated membrane-positive electrode as described in the foregoing embodiments, comprising the following steps: (1) mixing a sulfur-carbon nanotube composite material with water to form an aqueous dispersion; (2) adding alginate, a photopolymerizable material and a photopolymerization initiator to the aqueous dispersion and mixing to form an aqueous positive electrode slurry; (3) coating the aqueous positive electrode slurry onto the surface of a freeze-dried bacterial cellulose membrane by a coating method, and initiating a photopolymerization reaction under ultraviolet light irradiation, so that the photopolymerizable material forms a polymerized colloid and the aqueous positive electrode slurry is pregelled to form an aqueous positive electrode layer; and (4) immersing the aqueous positive electrode layer together with the bacterial cellulose membrane in an aqueous solution containing calcium ions so that the polymerized colloid, alginate and calcium ions undergo a crosslinking reaction in the presence of the sulfur-carbon nanotube composite material to form the integrated membrane-positive electrode.

[0008] In one specific embodiment, the mass concentration of the sulfur-carbon nanotube composite material can be 20 to 40 mg / mL, for example, but not limited to 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 or 40 mg / mL, preferably 30 mg / mL.

[0009] In one specific embodiment, the mass concentration of the alginate can be 2 to 10 mg / mL, for example, but not limited to 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 4, 5, 6, 7, 8, 9 or 10 mg / mL.

[0010] In one specific embodiment, the mass concentration of the polymerized colloid may be 5 to 30 mg / mL, for example, but not limited to 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 mg / mL.

[0011] In one specific embodiment, the mass ratio of sulfur to carbon nanotubes can be from 1:0.5 to 1.5. The mass ratio of sulfur to carbon nanotubes can be, for example, but not limited to, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4 or 1:1.5.

[0012] In one specific implementation, the sulfur loading per unit area of ​​the aqueous positive electrode layer can be 1 to 2 mg / cm³. 2The sulfur loading per unit area may be, for example, but not limited to, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0 mg / cm³. 2 .

[0013] In one specific embodiment, the sulfur may be elemental sulfur. In another specific embodiment, the elemental sulfur is sublimated sulfur or high-purity sulfur.

[0014] In one specific embodiment, the carbon nanotube may be a multi-walled carbon nanotube. In another specific embodiment, the multi-walled carbon nanotube may be a carboxylated multi-walled carbon nanotube, for example, a carboxylated multi-walled carbon nanotube with a purity greater than 95%.

[0015] In one specific implementation, the preparation method of the sulfur and carbon nanotube composite material in step (1) may be as follows: grinding the sulfur and the carbon nanotube in a mortar for 10 to 30 minutes to form powder; placing the powder in a sealed high-pressure autoclave and heat-treating the powder at 140 to 170°C for 11 to 13 hours; cooling the heat-treated powder to 20 to 35°C to obtain the sulfur and carbon nanotube composite material; and mixing the sulfur and carbon nanotube composite material into water by ultrasonic dispersion to form the aqueous dispersion. In this specific embodiment, the mortar can be an agate mortar; the grinding time can be, for example, but not limited to, 10, 11, 12, 13, 14, 15, 16, 17, 19, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 minutes; the temperature of the autoclave placed in the constant temperature chamber can be, for example, but not limited to, 140, 145, 150, 155, 160, 165 or 170°C; and the time for placing the autoclave in the constant temperature chamber can be, for example, but not limited to, 11, 11.5, 12, 12.5 or 13 hours.

[0016] In one specific embodiment, the mass concentration of the sulfur-carbon nanotube composite material in step (1) is 20 to 40 mg / mL, the mass concentration of the alginate in the aqueous positive electrode slurry in step (3) is 2 to 10 mg / mL, and the mass concentration of the polymerized colloid is 5 to 30 mg / mL.

[0017] In one specific embodiment, the coating method in step (3) can be as follows: the aqueous positive electrode slurry is coated onto the surface of the bacterial cellulose membrane using a doctor blade with a travel speed of 4 to 6 mm / s, and the distance between the doctor blade and the bacterial cellulose membrane is 140 to 160 μm. In this specific embodiment, the distance can be, for example, but not limited to, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159 or 160 μm; the travel speed can be, for example, but not limited to, 4, 4.2, 4.4, 4.6, 4.8, 5, 5.2, 5.4, 5.6, 5.8 or 6 mm / s.

[0018] In one specific embodiment, the polymerized colloid may be a colloid obtained by photopolymerization of a photopolymerizable material such as double-bond modified gelatin. In this specific embodiment, the double-bond modified gelatin is gelatin methacryloyl (GelMA) or hyaluronic acid methacryloyl (HAMA), preferably GelMA.

[0019] In one specific embodiment, the photopolymerization is carried out in the presence of a photopolymerization initiator. The photopolymerization initiator may be an ultraviolet (UV) photoinitiator. In this specific embodiment, the UV photoinitiator is lithium phenyl-2,4,6-trimethylbenzoyl phosphinate (LAP).

[0020] In one specific implementation, the photopolymerization is carried out in the presence of water. The water is preferably deionized water.

[0021] In one specific embodiment, the alginate is selected from at least one of the group consisting of sodium alginate, potassium alginate, magnesium alginate, and ammonium alginate.

[0022] In one specific embodiment, the ultraviolet irradiation in step (3) may be: irradiating the coated aqueous positive electrode slurry with ultraviolet light of a wavelength of 360 to 370 nm for 3 to 10 minutes. In this specific embodiment, the wavelength of the ultraviolet light may be, for example, but not limited to, 360, 361, 362, 363, 364, 365, 366, 367, 368, 369, or 370 nm; and the irradiation time may be, for example, but not limited to, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 minutes.

[0023] In one specific embodiment, the calcium-containing aqueous solution in step (4) may be a solution prepared by dissolving a calcium-containing substance selected from at least one of calcium chloride, calcium lactate, and calcium hydroxide in water, wherein the concentration ratio of the alginate to the calcium-containing substance is 1:1 to 2. In one specific embodiment, the calcium-containing substance is preferably calcium chloride.

[0024] In one specific embodiment, the amount of calcium-containing substance added can be 2 to 20 mg / mL. In one specific embodiment, the mass concentration of the calcium-containing substance can be, for example, but not limited to, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 mg / mL.

[0025] In one specific embodiment, the crosslinking in step (4) involves immersing the aqueous positive electrode layer together with the bacterial cellulose membrane in an aqueous solution containing calcium ions at 20 to 35°C for 3 to 5 hours. This allows the polymerized colloid, the alginate, and the calcium ions to undergo a crosslinking reaction in the presence of the sulfur and carbon nanotube composite material, thereby forming the integrated membrane-positive electrode. In this specific embodiment, the immersion time is, for example, but not limited to, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5 hours.

[0026] In one specific embodiment, the mass concentration of the sulfur-carbon nanotube composite material can be 20 to 40 mg / mL, the content of the alginate can be 2 to 10 mg / mL, the content of the photopolymerizable material can be 5 to 30 mg / mL, the amount of the photopolymerization initiator added can be 10% by weight of the content of the photopolymerizable material, and the mass concentration of the calcium ion-containing aqueous solution can be 2 to 20 mg / mL. These concentration ranges are beneficial for achieving appropriate pre-gelling or cross-linking and further gelation.

[0027] Compared with the prior art, the beneficial effects of this disclosure are as follows: (1) This disclosure uses green, renewable, and degradable natural biomass bacterial cellulose as the membrane matrix, which effectively improves the mechanical strength and thermal stability of the battery membrane; (2) The bacterial cellulose used in this disclosure has a rich macroporous network structure and a large number of hydroxyl groups on the surface of the cellulose, which can ensure the rapid transport of lithium ions on the one hand and effectively alleviate the shuttle effect of polysulfides on the other hand; (3) The aqueous positive electrode slurry uses only water as a dispersant and solvent in the preparation and coating process, without using any other organic solvents, which has the dual advantages of safety and environmental protection compared with traditional electrodes and their preparation process; (4) The integrated structure design of the membrane and positive electrode has a significant positive effect on improving the flexibility of the battery and reducing the resistance of ion / electron interface transport; (5) The lithium-sulfur battery assembled using the bacterial cellulose membrane-positive electrode integrated composite structure material exhibits high specific capacity, high coulombic efficiency and stable cycle performance. Attached Figure Description

[0028] Embodiments of this disclosure are illustrated with reference to the accompanying drawings:

[0029] Figure 1 This diagram shows the fabrication process of the integrated separator-cathode structure disclosed herein. Detailed Implementation

[0030] The following specific embodiments illustrate the implementation of this disclosure. Those skilled in the art can easily understand the advantages and effects of this disclosure from the content described herein. This disclosure can also be implemented or applied through other different embodiments, and the details in this specification can also be modified and changed based on different viewpoints and applications without departing from the spirit described herein. Furthermore, all ranges and values ​​herein are inclusive and can be combined. Any numerical value or point falling within the ranges described herein, such as any integer, can be used as a minimum or maximum value to derive a lower range, etc.

[0031] Specifically, this disclosure provides an integrated structure design of separator-electrode, mainly involving an integrated composite structure of bacterial cellulose separator-cathode based on an aqueous system and its preparation method, and the composite structure can be applied to lithium-sulfur batteries.

[0032] The naturally formed three-dimensional continuous structure of bacterial cellulose can be directly used as a flexible separator for batteries. The abundant pore structure inside the bacterial cellulose provides a large number of channels for lithium ion transport. The hydroxyl groups on the surface of the bacterial cellulose not only help to improve the wettability of the electrolyte but also inhibit the "shuttle effect" of soluble polysulfides. Furthermore, the good mechanical strength of the bacterial cellulose plays a positive role in mitigating the puncture short circuit caused by lithium dendrites.

[0033] Because the abundant hydroxyl groups in bacterial cellulose help inhibit polysulfide shuttle, its high mechanical strength resists the piercing effect of lithium dendrites, and its high porosity facilitates rapid lithium-ion conduction, this disclosure utilizes bacterial cellulose with high porosity, high mechanical strength, and a nanofiber spatial network structure as a supporting matrix. Furthermore, by coating the supporting matrix with an alginate-based aqueous cathode slurry, a lithium-sulfur battery with an integrated membrane-cathode structure is obtained. After thorough drying, the alginate aqueous slurry will form a strong interfacial interaction with the bacterial cellulose membrane, which is beneficial to the stability of the electrode structure and ion interfacial transport.

[0034] Therefore, the aqueous bacterial cellulose membrane-cathode integrated composite structure and its preparation method provided in this disclosure utilize bacterial cellulose as a multifunctional membrane for lithium-sulfur batteries, and leverage the surface affinity between alginate-based aqueous cathode slurry and cellulose to achieve an integrated membrane-electrode design. This aqueous bacterial cellulose membrane-cathode integrated structure significantly improves the interfacial compatibility between the electrode and the membrane, reduces the resistance to interfacial ion and electron transfer, and thus minimizes the interfacial transport resistance of ions and electrons. Furthermore, after assembling the integrated membrane-cathode into a lithium-sulfur battery, the battery exhibits high specific capacity, high coulombic efficiency, and stable cycle performance.

[0035] like Figure 1As shown, this disclosure provides a method for preparing an integrated separator-cathode as described above, comprising: grinding sulfur and carbon nanotubes in a mortar for 10 to 30 minutes to form a powder; placing the powder in a sealed autoclave and heat-treating it at 140 to 170°C for 11 to 13 hours; cooling it to 20 to 35°C to obtain a sulfur-carbon nanotube composite material; uniformly mixing the sulfur-carbon nanotube composite material into water by ultrasonic dispersion to form an aqueous dispersion; adding alginate, a photopolymerizable material, and a photopolymerization initiator to the aqueous dispersion and mixing them thoroughly to form an aqueous cathode slurry; and then uniformly coating the aqueous cathode slurry onto the surface of a freeze-dried bacterial cellulose membrane using a doctor blade with a travel speed of 4 to 6 mm / s using a doctor blade. The distance between the scraper and the bacterial cellulose membrane is 140 to 160 μm. Subsequently, the material is irradiated with ultraviolet light with a wavelength of 360 to 370 nm for 3 to 10 minutes to initiate a photopolymerization reaction. This causes the photopolymerizable material in the aqueous positive electrode slurry to form a polymerized colloid with carboxyl groups. The aqueous positive electrode slurry is then cross-linked and pre-gelled through the carboxyl groups to form an aqueous positive electrode layer. Finally, the aqueous positive electrode layer, together with the bacterial cellulose membrane, is immersed in an aqueous solution containing calcium ions at 20 to 35 °C for 3 to 5 hours. In the presence of the sulfur and carbon nanotube composite material, the polymerized colloid, the alginate, and the calcium ions undergo a cross-linking reaction and further gelation. After thorough washing and freeze-drying, the integrated membrane-positive electrode is formed.

[0036] The present disclosure will be further described in detail below through specific preparation examples and embodiments, but the scope of the present disclosure shall not be limited by the embodiments.

[0037] Preparation Example 1 (Integrated Separator-Positive Electrode):

[0038] Equal masses of sublimed sulfur (S) and carboxylated carbon nanotubes (CNTs) with a purity of 99.5% (Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.) were ground in an agate mortar for 20 minutes to obtain powder. The powder was placed in an autoclave, sealed, and then placed in a constant temperature oven at 155°C for 12 hours. After cooling, a sulfur-carbon nanotube composite material (S / CNTs) was obtained.

[0039] S / CNTs were ultrasonically dispersed with deionized water for 30 minutes to obtain an aqueous dispersion. Sodium alginate (Shanghai Maclean Biochemical Technology Co., Ltd.), GelMA (Suzhou Intelligent Manufacturing Research Institute Co., Ltd.), and LAP (Suzhou Intelligent Manufacturing Research Institute Co., Ltd.) were then dissolved in the aqueous dispersion to obtain an aqueous positive electrode slurry.

[0040] A freeze-dried bacterial cellulose membrane is provided. Using a scraping coating method, with the distance between the scraper and the bacterial cellulose membrane at 150 μm and the scraper travel speed at 5 mm / s, an aqueous positive electrode slurry is uniformly coated onto the surface of the bacterial cellulose membrane. Then, the membrane is irradiated with a 365 nm ultraviolet lamp for 5 minutes to initiate a reaction that forms a three-dimensional cross-linked network structure via GelMA photocrosslinking, thereby pre-gelling the aqueous positive electrode slurry. This yields a semi-finished product comprising a pre-gelled aqueous positive electrode layer and a bacterial cellulose membrane as a substrate.

[0041] The semi-finished product was soaked in an aqueous solution of calcium chloride (CaCl2) at room temperature for 4 hours to allow sodium alginate to undergo a deep cross-linking reaction and gelation through calcium ions, resulting in a composite material. The composite material was then thoroughly washed and freeze-dried again to obtain a membrane-cathode product with an integrated structure.

[0042] Based on the method of Preparation Example 1 described above, the membrane-positive electrode products of Examples 1 to 7 and Comparative Examples 1 and 2 were prepared according to the mass concentrations shown in Table 1 below.

[0043] Preparation Example 2 (Lithium-sulfur battery):

[0044] The CR2032 coin cell model was selected. Its positive electrode material is a composite material of sulfur and carbon nanotubes, the negative electrode material is lithium metal sheet, the separator material is Celgard 2250, and the electrolyte contains 1M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as electrolyte, 1wt% lithium nitrate (LiNO3) as additive, and a mixed solution of ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1 as solvent.

[0045] Based on the battery model selected in Preparation Example 2, the aforementioned integrated separator-cathode product was used to replace the cathode and separator materials and assembled into the battery to obtain lithium-sulfur battery samples of Examples 1 to 7 and Comparative Examples 1 and 2.

[0046] Experimental Example: Electrochemical Testing and Analysis

[0047] Using a battery testing device (LAND CT-2001A, Wuhan Landian Electronics Co., Ltd.), constant current charge / discharge tests were performed on the electrodes of lithium-sulfur battery samples of Examples 1 to 7 and Comparative Examples 1 and 2 at a current density of 800 mA / g. The results of discharge specific capacity and average coulombic efficiency are recorded in Table 1 below.

[0048] Table 1

[0049]

[0050] The results of Examples 1, 2, and 3 in Table 1 show that the battery capacity decays significantly when the amount of alginate and photopolymerizable material (GelMA) added is low. This is mainly because when the amount of the above polymers is too small, the three-dimensional network structure built by polymer interpenetration inside the electrode has not yet formed, and the electrode micro / nano structure is not stable enough.

[0051] The results of Examples 3 and 4 in Table 1 show that, under the condition that other factors remain unchanged, simply increasing the concentration of the CaCl2 aqueous solution used for calcium ion crosslinking does not further improve the electrochemical performance of the battery. This also indicates that soaking in a CaCl2 aqueous solution with a mass concentration of 10 mg / mL for 4 hours is sufficient to complete calcium ion crosslinking, and there is no need to further increase the concentration of the CaCl2 aqueous solution.

[0052] The results of Examples 3, 5, and 6 in Table 1 show that excessive addition of alginate and photopolymerizable polymer (GelMA) significantly affects the battery's discharge specific capacity, cycle stability, and coulombic efficiency, with the increase in GelMA addition having a more significant impact on battery performance. This is mainly because both alginate and GelMA are non-conductive materials; excessive addition of these materials affects the overall electronic conductivity of the electrode, thereby impacting electrochemical performance. The results of Example 7 in Table 1 show that excessively high levels of non-conductive components have a very serious impact on the battery's electrochemical performance.

[0053] The results in Table 1 for Example 3, Comparative Example 1, and Comparative Example 2 show that although high initial discharge capacity can be obtained without UV irradiation pre-gelation or without alginate calcium ion gelation, the battery degradation during subsequent cycles is very severe. This is mainly because a stable electrode micro / nano structure relies on an interpenetrating polymer network structure. Data from Comparative Example 2 reveals that alginate plays a more crucial role in forming a stable electrode structure.

[0054] In summary, the integrated separator-cathode disclosed herein, comprising a bacterial cellulose membrane as a supporting substrate, further includes an aqueous alginate-containing cathode layer cross-linked on the surface of the bacterial cellulose membrane. When applied to lithium-sulfur batteries, it can effectively improve the battery's discharge specific capacity, coulombic efficiency, and cycle performance. Furthermore, compared to traditional electrodes, the integrated separator-cathode of this disclosure uses only water in its fabrication process without any other organic solvents, offering both safety and environmental advantages, and thus demonstrating promising application prospects.

[0055] The above embodiments are merely illustrative and not intended to limit this disclosure. Any person skilled in the art can modify and alter the above embodiments without departing from the spirit and scope of this disclosure. Therefore, the scope of protection of this disclosure is defined by the appended claims, and should be covered by the technical content of this disclosure as long as it does not affect the effect and purpose of this disclosure.

Claims

1. An integrated separator-positive electrode, comprising: Bacterial cellulose membrane; as well as An aqueous positive electrode layer is formed on the surface of the bacterial cellulose membrane, wherein the aqueous positive electrode layer is formed by cross-linking of polymerized colloid, alginate and calcium ions in the presence of a composite material of sulfur and carbon nanotubes. The mass concentration ratio of the sulfur-carbon nanotube composite material, the alginate, and the polymerized colloid is 1:0.06 to 0.33:0.16 to 1.

2. The integrated diaphragm-positive electrode according to claim 1, characterized in that, The mass concentration of the sulfur-carbon nanotube composite material is 20 to 40 mg / mL, the mass concentration of the alginate is 2 to 10 mg / mL, and the mass concentration of the polymerized colloid is 5 to 30 mg / mL.

3. The integrated diaphragm-positive electrode according to claim 1, characterized in that, The mass ratio of sulfur to carbon nanotubes is 1:0.5 to 1.

5.

4. The integrated diaphragm-positive electrode according to claim 1, characterized in that, The sulfur loading per unit area of ​​the aqueous positive electrode layer is 1 to 2 mg / cm³. 2 .

5. The integrated diaphragm-positive electrode according to claim 1, characterized in that, The sulfur is elemental sulfur, the carbon nanotubes are multi-walled carbon nanotubes, and the polymerized colloid is a colloid obtained by photopolymerization of double-bond modified gelatin, wherein the photopolymerization is carried out in the presence of a photopolymerization initiator.

6. The integrated diaphragm-positive electrode according to claim 5, characterized in that, The sulfur is sublimed sulfur or high-purity sulfur, the carbon nanotubes are carboxylated multi-walled carbon nanotubes, the double-bond modified gelatin is methacrylamide gelatin (GelMA) or methacrylamide hyaluronic acid gelatin (HAMA), and the photopolymerization initiator is lithium phenyl-2,4,6-trimethylbenzoyl phosphite (LAP).

7. The integrated diaphragm-positive electrode according to claim 1, characterized in that, The alginate is selected from at least one of the group consisting of sodium alginate, potassium alginate, magnesium alginate, and ammonium alginate.

8. A method for preparing an integrated separator-positive electrode according to claim 1, characterized in that, Includes the following steps: (1) The composite material of sulfur and carbon nanotubes is mixed with water to form an aqueous dispersion. liquid; (2) Add alginate, photopolymerizable material and photopolymerization initiator to the aqueous dispersion and mix to form an aqueous positive electrode slurry; (3) The aqueous positive electrode slurry is coated onto the surface of a freeze-dried bacterial cellulose membrane by a scraping coating method. Under ultraviolet light irradiation, a photopolymerization reaction is initiated, which causes the photopolymerizable material to form a polymerized colloid and pregel the aqueous positive electrode slurry to form an aqueous positive electrode layer. as well as (4) The aqueous positive electrode layer together with the bacterial cellulose membrane is immersed in an aqueous solution containing calcium ions so that the polymerized colloid, the alginate and the calcium ions undergo a cross-linking reaction in the presence of the sulfur and carbon nanotube composite material to form the integrated membrane-positive electrode.

9. The preparation method according to claim 8, characterized in that, The mass concentration of the sulfur and carbon nanotube composite material in step (1) is 20 to 40 mg / mL, the mass concentration of the alginate in the aqueous positive electrode slurry in step (3) is 2 to 10 mg / mL, and the mass concentration of the polymerized colloid is 5 to 30 mg / mL.

10. The preparation method according to claim 8, characterized in that, The mass ratio of sulfur to carbon nanotubes is 1:0.5 to 1.

5.

11. The preparation method according to claim 8, characterized in that, The sulfur is elemental sulfur, the carbon nanotubes are multi-walled carbon nanotubes, and the polymerized colloid is a colloid obtained by photopolymerization of double-bond modified gelatin.

12. The preparation method according to claim 11, characterized in that, The sulfur is sublimed sulfur or high-purity sulfur, the carbon nanotubes are carboxylated multi-walled carbon nanotubes, the double-bond modified gelatin is methacrylamide gelatin (GelMA) or methacrylamide hyaluronic acid gelatin (HAMA), and the photopolymerization initiator is lithium phenyl-2,4,6-trimethylbenzoyl phosphite (LAP).

13. The preparation method according to claim 8, characterized in that, The alginate is selected from at least one of the group consisting of sodium alginate, potassium alginate, magnesium alginate, and ammonium alginate.

14. The preparation method according to claim 8, characterized in that, The method for preparing the aqueous dispersion in step (1) is as follows: the sulfur and the carbon nanotubes are ground in a mortar for 10 to 30 minutes to form a powder; the powder is placed in a sealed high-pressure reactor and heat-treated at 140 to 170°C for 11 to 13 hours; the heat-treated powder is cooled to 20 to 35°C to obtain the composite material of sulfur and carbon nanotubes; and the composite material of sulfur and carbon nanotubes is mixed into water by ultrasonic dispersion to form the aqueous dispersion.

15. The preparation method according to claim 8, characterized in that, The method of coating the film in step (3) is as follows: the aqueous positive electrode slurry is coated on the surface of the bacterial cellulose membrane using a scraper with a travel speed of 4 to 6 mm / s, and the distance between the scraper and the bacterial cellulose membrane is 140 to 160 μm.

16. The preparation method according to claim 8, characterized in that, The ultraviolet irradiation in step (3) is as follows: the coated aqueous positive electrode slurry is irradiated with ultraviolet light with a wavelength of 360 to 370 nm for 3 to 10 minutes.

17. The preparation method according to claim 8, characterized in that, The calcium-containing aqueous solution in step (4) is a solution prepared by dissolving a calcium-containing substance selected from at least one of calcium chloride, calcium lactate and calcium hydroxide in water, wherein the concentration ratio of the alginate to the calcium-containing substance is 1:1 to 2.

18. The preparation method according to claim 17, characterized in that, The amount of calcium-containing substance added is 2 to 20 mg / mL.

19. The preparation method according to claim 8, characterized in that, The cross-linking process described in step (4) involves immersing the aqueous positive electrode layer together with the bacterial cellulose membrane in an aqueous solution containing calcium ions at 20 to 35°C for 3 to 5 hours, so that the polymerized colloid, the alginate and the calcium ions undergo a cross-linking reaction in the presence of the sulfur and carbon nanotube composite material to form the integrated membrane-positive electrode.

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