Integrated separator-anode 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

(19) State Intellectual Property Office (12) Invention Patent Application (10) Application Publication Number (43) Application Publication Date (21) Application Number 202411173171.4 (22) Application Date 2024.08.23 (71) Applicant Yichang Nanomaterials Technology (Guangdong) Co., Ltd. Address 510095, Room 2411, South Building, No. 371-375, Huanshi East Road, Guangzhou, Guangdong Province (72) Inventors Wang Qiong, Huang Yang, Chen Zhaocheng, Zheng Sihan, Zhang Dezhi (74) Patent Agency Beijing Gecheng Intellectual Property Agency Co., Ltd. 11314 Patent Attorney Cheng Wei (51) Int.Cl. H01M 10 / 052 (2010.01) H01M 10 / 058 (2010.01) H01M 50 / 429 (2021.01) H01M 4 / 36 (2006.01) H01M 4 / 38(2006.01) H01M 4 / 583(2010.01) H01M 4 / 62(2006.01) H01M 50 / 403(2021.01) H01M 50 / 491(2021.01) H01M 4 / 137(2010.01) H01M 4 / 1399(2010.01) H01M 4 / 04(2006.01) (54) Invention Title: Integrated Separator-Positive Electrode and Preparation Method Thereof (57) Abstract: This disclosure provides an integrated separator-positive electrode, comprising a bacterial cellulose membrane and an aqueous positive electrode layer formed on the surface of the bacterial cellulose membrane by calcium ion crosslinking. The aqueous positive electrode layer is formed by crosslinking a polymerized colloid, alginate, and calcium ions in the presence of a sulfur-carbon nanotube composite material, wherein the 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. The integrated separator-positive electrode of this disclosure can be applied in lithium-sulfur batteries, enabling the lithium-sulfur batteries to exhibit high discharge specific capacity, high coulombic efficiency, and stable cycle performance. Claims (2 pages), Description (7 pages), Drawings (1 page), CN 121601731 A 2026.03.03 CN 1 21 60 17 31 A 1. 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, wherein the aqueous positive electrode layer is formed by a crosslinking reaction of a polymerized colloid, alginate, and calcium ions in the presence of a sulfur-carbon nanotube composite material; wherein 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 separator-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 separator-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 separator-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 / cm². 5. The integrated separator-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 separator-positive electrode according to claim 5, characterized in that the sulfur is sublimated 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 phenyl-2,4,6-trimethylbenzoyl lithium phosphite (LAP). 7. The integrated separator-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 membrane-positive electrode according to claim 1, characterized in that it comprises 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, the alginate and the calcium ions undergo a crosslinking reaction in the presence of the sulfur-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, wherein the mass ratio of sulfur to carbon nanotubes is 1:0.5 to 1.5. (Claims 1 / 2 page 2 CN 121601731 A) 11. The preparation method according to claim 8, wherein 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, wherein 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 phenyl-2,4,6-trimethylbenzoyl lithium phosphite (LAP). 13. The preparation method according to claim 8, wherein 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 preparation method of the aqueous dispersion in step (1) is as follows: grinding the sulfur and the carbon nanotubes 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 composite material of sulfur and carbon nanotubes; and mixing the composite material of sulfur and carbon nanotubes into water by ultrasonic dispersion to form the aqueous dispersion. 15. The preparation method according to claim 8, characterized in that the method of the film coating in step (3) is as follows: coating the aqueous positive electrode slurry onto the surface of the bacterial cellulose membrane with a scraper with a travel speed of 4 to 6 mm / s, wherein 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: irradiating the coated aqueous positive electrode slurry with ultraviolet light of wavelength 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 crosslinking in step (4) is as follows: 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, so that the polymerized colloid, the alginate and the calcium ions undergo a crosslinking reaction in the presence of the sulfur and carbon nanotube composite material to form the integrated separator-positive electrode. Claims 2 / 2 pages 3 CN 121601731 A Integrated separator-positive electrode and its preparation method Technical Field

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

[0002] Since the successful commercial production of lithium-ion batteries by Sony Corporation in 1991, they have been recognized by the industry and the scientific community as secondary batteries with relatively good comprehensive performance. At present, lithium-ion batteries have been widely used in various types of portable mobile terminals and electric vehicles. In recent years, the "carbon neutrality" development goal has put forward higher requirements for the storage and utilization of large-scale renewable energy. Because conventional lithium-ion rechargeable batteries have limited theoretical capacity, they cannot meet the demand for high energy density and large capacity energy storage. Therefore, it is necessary to seek new electrode active systems with high specific energy and high efficiency.

[0003] Compared with traditional lithium-ion batteries, lithium-sulfur batteries are assembled with a sulfur-containing conductive substrate as the positive electrode and metallic lithium as the negative electrode. They have very high theoretical energy density (2567Wh / kg) and theoretical specific capacity (1675mAh / g), which far exceed the values ​​of various commercially available lithium-ion batteries. In addition, elemental sulfur has a low environmental burden, is non-toxic to humans and animals, and is relatively abundant in the earth's crust. Lithium-sulfur batteries have attracted widespread attention from researchers as a promising new generation of high-energy rechargeable batteries. However, before large-scale commercial development can be achieved, lithium-sulfur batteries still need to solve several key problems. Among them, the "shuttle effect" caused by dissolved polysulfides and the lithium dendrite phenomenon caused by uneven lithium-ion deposition have the most significant impact 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, and therefore have 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), and is 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) were the first to use bacterial cellulose membranes as separator materials for lithium-sulfur batteries. Their results showed that bacterial cellulose membranes can promote uniform deposition of lithium ions on the lithium metal surface and prevent the formation of lithium dendrites. Compared with commercially available Celgard membranes, bacterial cellulose membranes exhibit superior electrolyte absorption and retention capabilities, as well as excellent thermal stability. However, how to utilize the properties of bacterial cellulose to improve the interfacial relationship between the electrode and the separator, inhibit polysulfide diffusion, and mitigate puncture short circuits caused by lithium dendrites remains a problem that the industry urgently needs to overcome.

[0005] In view of the various deficiencies 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, wherein the aqueous positive electrode layer is formed by cross-linking a polymerized colloid, alginate, and calcium ions in the presence of a sulfur-carbon nanotube composite material; wherein 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. Specification 1 / 7 pages 4 CN 121601731 A

[0006] In a specific embodiment, the aqueous positive electrode layer comprises a sulfur-carbon nanotube composite material 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 from 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 may be from 1:0.5 to 1.5. The mass ratio of sulfur to carbon nanotubes may 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 embodiment, the sulfur loading per unit area of ​​the aqueous positive electrode layer can be 1 to 2 mg / cm². The sulfur loading per unit area can 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 / cm².

[0013] In one specific embodiment, the sulfur can be elemental sulfur. In one specific embodiment, the elemental sulfur is sublimed sulfur or high-purity sulfur.

[0014] In one specific embodiment, the carbon nanotube may be a multi-walled carbon nanotube. In one 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 embodiment, the preparation method of the sulfur-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 a 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-carbon nanotube composite material; and mixing the sulfur-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. Instruction manual, page 2 / 7, CN 121601731 A

[0016] In a specific embodiment, 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

[0017] In a specific embodiment, the method of film coating in step (3) can be: coating the aqueous positive electrode slurry on the surface of the bacterial cellulose membrane with 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. In this specific embodiment, the distance may 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 may 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 gelatin 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 photoinitiator. In this specific embodiment, the ultraviolet photoinitiator is lithium phenyl-2,4,6-trimethylbenzoyl phosphite (LAP).

[0020] In one specific embodiment, 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; the irradiation time of the ultraviolet light 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 may be 2 to 20 mg / mL. In one specific embodiment, the mass concentration of the calcium-containing substance may 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) is as follows: 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, so that the polymerized colloid, the alginate and the calcium ions undergo a crosslinking reaction in the presence of the sulfur and carbon nanotube composite material to form the integrated membrane-positive electrode.In this specific embodiment, the soaking 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 alginate content can be 2 to 10 mg / mL, the photopolymerizable material content can be 5 to 30 mg / mL, the amount of photopolymerization initiator added can be 10% by weight of the photopolymerizable material content, 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-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.

[0028] The embodiments of this disclosure are illustrated by way of the accompanying drawings:

[0029] FIG1 shows a schematic diagram of the integrated separator-positive electrode structure fabrication process of this disclosure. Detailed Description

[0030] The embodiments of this disclosure are described below through specific examples. Those skilled in the art can easily understand the advantages and effects of this disclosure from the content described in this specification. 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 in this disclosure. In addition, 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 for a 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 rich network structure inside the bacterial cellulose provides a large number of channels for the transport of lithium ions. 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 alleviating 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 the rapid conduction of lithium ions, this disclosure utilizes the aforementioned 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 positive electrode slurry, a lithium-sulfur battery with an integrated membrane-positive electrode structure is obtained. After the alginate aqueous slurry is fully dried, it 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 integrated bacterial cellulose membrane-cathode composite structure and its preparation method based on an aqueous system provided in this disclosure utilizes bacterial cellulose as a multifunctional membrane for lithium-sulfur batteries, and leverages the surface affinity between alginate-based aqueous cathode slurry and cellulose to achieve an integrated membrane-electrode design. This allows the integrated bacterial cellulose membrane-cathode structure constructed based on an aqueous system to significantly improve the interfacial compatibility between the electrode and the membrane, reduce the resistance to interfacial ion and electron transfer, and thus minimize 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.Instruction manual, pages 4 / 7, CN 121601731 A

[0035] As shown in Figure 1, this disclosure provides a method for preparing an integrated separator-positive electrode as described above, comprising: grinding sulfur and carbon nanotubes in a mortar for 10 to 30 minutes to mix and form powder, and placing the powder into a sealed high-pressure reactor. A sulfur-carbon nanotube composite material was obtained by heat treatment at 140-170°C for 11-13 hours and then cooling to 20-35°C. This composite material was then uniformly mixed into water using ultrasonic dispersion to form an aqueous dispersion. Alginate, a photopolymerizable material, and a photopolymerization initiator were added to the aqueous dispersion and thoroughly mixed to form an aqueous positive electrode slurry. Next, a blade was used to uniformly coat the aqueous positive electrode slurry onto the surface of a freeze-dried bacterial cellulose membrane at a travel speed of 4-6 mm / s, with a distance of 140-160 μm between the blade and the membrane. Subsequently, a wavelength of [wavelength missing] was used to [text missing]. Irradiation with 360 to 370 nm ultraviolet light for 3 to 10 minutes initiates a photopolymerization reaction, causing the photopolymerizable material in the aqueous positive electrode slurry to form a polymerized colloid with carboxyl groups. This allows the aqueous positive electrode slurry to undergo cross-linking and pre-gelling through the carboxyl groups, forming 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 is not limited by the examples.

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

[0038] Equal masses of sublimed sulfur (S) and 99.5% pure carboxylated carbon nanotubes (CNTs) (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 simultaneously dissolved in the aqueous dispersion to obtain an aqueous positive electrode slurry.

[0040] A freeze-dried bacterial cellulose membrane was provided. The aqueous positive electrode slurry was uniformly coated onto the surface of the bacterial cellulose membrane using a coating method, with the distance between the coating blade and the bacterial cellulose membrane being 150 μm and the coating blade traveling at a speed of 5 mm / s. Then, the membrane was irradiated with a 365 nm ultraviolet lamp for 5 minutes to initiate a GelMA photocrosslinking reaction to form a three-dimensional crosslinked network structure, causing the aqueous positive electrode slurry to pre-gel, resulting in 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 immersed in a calcium chloride (CaCl2) aqueous solution at room temperature for 4 hours, allowing sodium alginate to undergo a deep crosslinking reaction via calcium ions and gel, resulting in a composite material. The composite material was thoroughly washed and freeze-dried again to obtain a membrane-positive electrode 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 using the mass concentrations shown in Table 1 below.

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

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

[0045] Based on the battery model selected in Preparation Example 2, the aforementioned separator-positive electrode product with an integrated structure was assembled into the battery, replacing the positive electrode and separator material, 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 if the amount of alginate and photopolymerizable polymer (GelMA) added is small, the capacity decay of the battery is more serious. This is mainly because when the amount of the above polymers is too small, the three-dimensional network structure constructed by polymer interpenetration inside the electrode has not yet been 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 conditions 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 (as specified in page 6 / 7 of the specification, CN 121601731 A) for 4 hours is sufficient to complete the 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 if the amount of alginate and photopolymerizable material (GelMA) added is too high, it will significantly affect the battery's discharge specific capacity, cycle stability, and coulombic efficiency, among which the increase in the amount of GelMA added has a more significant impact on battery performance. This is mainly because alginate and GelMA are both non-conductive materials, and excessive addition of these materials will affect the overall electronic conductivity of the electrode, thereby affecting the electrochemical performance. The results of Example 7 in Table 1 show that when the content of non-conductive components is too high, the impact on the battery's electrochemical performance is very serious.

[0053] The results of Example 3, Comparative Example 1 and Comparative Example 2 in Table 1 show that although high initial discharge capacity of the battery 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 the interpenetrating network structure of polymers. From the data of Comparative Example 2, it can be found that alginate plays a more critical role in forming a stable electrode structure.

[0054] In summary, the integrated separator-positive electrode of this disclosure, which includes a bacterial cellulose membrane as a supporting matrix, further includes an aqueous positive electrode layer with alginate 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. In addition, compared with traditional electrodes, the integrated separator-positive electrode of this disclosure uses only water in its manufacturing process without any other organic solvents, which has the dual advantages of safety and environmental protection, and has promising application prospects.

[0055] The above embodiments are only illustrative and are not intended to limit this disclosure. Any person skilled in the art may 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.Description Page 7 / 7 Page 10 CN 121601731 A Figure 1 Description of the Drawings Page 1 / 1 Page 11 CN 121601731 A Abstract The present disclosure provides an integrated separator-anode, including a bacterial cellulose membrane and an aqueous anode layer formed on a surface of the bacterial cellulose membrane by cross-linking via calcium ions. The aqueous anode layer is formed from a cross-linking reaction of a polymerized colloid, an alginate, and calcium ions in a presence of a sulfur-carbon nanotube composite, and the sulfur-carbon nanotube composite, the alginate, and the polymerized colloid have a concentration ratio of 1:0.06-0.33:0.16-1. The integrated separator-anode of the present disclosure is applicable for a lithium-sulfur battery which would exhibit a high discharge specific capacity, a high coulombic efficiency and a stable cycle performance.。

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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