Preparation method and application of flexible current collector material

Abstract

The present invention discloses a preparation method and application of a flexible current collector material, which relates to the technical field of current collector preparation. The preparation method of the flexible current collector material comprises heating chitosan gel to a first temperature T1 for pretreatment, wherein the first temperature T1 is lower than the carbonization temperature of the chitosan gel; and carbonizing the chitosan gel after the pretreatment to obtain the flexible current collector material. The temperature increase pretreatment reduces the local damage to the basic carbon skeleton of chitosan caused by the internal stress of the molecules, which helps to maintain the structure of the basic carbon skeleton of the chitosan gel; the temperature increase below the carbonization temperature of the chitosan gel also reduces the excessive dehydration and excessive hardening of the chitosan gel, while causing the molecular chains of the chitosan gel to rearrange and adjust at a slower rate. The structure of the flexible current collector material formed is looser and more orderly, so that the material has better flexibility while maintaining a certain mechanical strength.

Description

Technical Field

[0001] The present invention relates to the technical field of current collector preparation, and in particular to a preparation method and application of a flexible current collector material. Background Art

[0002] Three-dimensional porous carbon, due to its unique three-dimensional network structure, high conductivity, and large specific surface area, facilitates mass transfer and electron diffusion, and has significant application prospects in the field of current collectors for advanced energy storage batteries such as lithium-ion batteries and sodium-ion batteries. Furthermore, considering diverse application scenarios such as wearables, flexible batteries are currently a key development direction, and corresponding flexible current collectors are also generating significant demand.

[0003] However, the preparation of existing high-performance three-dimensional porous carbon current collectors often requires complex and tedious preparation processes, which are costly and have low yields. Derivatives based on biomass raw materials such as cellulose and chitin are new environmentally friendly and low-carbon methods for preparing three-dimensional porous carbon that have been developed in recent years. However, the final product obtained after conventional high-temperature carbonization treatment is difficult to ensure good mechanical strength, has poor results, low pass rate, and poor repeatability of experimental operations. In addition, existing carbonized products are basically not flexible and cannot meet the practical application requirements of flexible electrodes. Summary of the Invention

[0004] The main purpose of the present invention is to propose a preparation method and application of a flexible current collector material, aiming to solve the problems of poor mechanical strength, low pass rate, poor flexibility and poor repeatability of flexible current collector materials prepared using biomass raw materials in the prior art.

[0005] To achieve the above object, the present invention provides a method for preparing a flexible current collector material, comprising the following steps:

[0006] heating the chitosan gel to a first temperature T1 for pretreatment, wherein the first temperature T1 is lower than the carbonization temperature of the chitosan gel;

[0007] The chitosan gel that has undergone the pretreatment is carbonized to obtain the flexible current collector material.

[0008] In one embodiment, the pretreatment of heating the chitosan gel to a first temperature T1 includes:

[0009] The chitosan gel is heated to T0 for a first pretreatment, and then heated to a first temperature T1 for a second pretreatment, wherein T0 < the first temperature T1 < the carbonization temperature of the chitosan gel.

[0010] In one embodiment, the chitosan gel is heated to T0 for a first pretreatment, and then heated to a first temperature T1 for a second pretreatment:

[0011] The value range of T0 is 280-320°C; and / or,

[0012] The heating rate to T0 is less than or equal to 1°C / min, and / or

[0013] The first pretreatment includes heat preservation at T0, the heat preservation time is 0.3 to 0.7 hours; and / or,

[0014] The first temperature T1 has a value range of 380-420° C.; and / or,

[0015] The heating rate to the first temperature T1 is less than or equal to 1°C / min;

[0016] The second pretreatment includes keeping the temperature at the first temperature T1 for 0.3 to 0.7 hours.

[0017] In one embodiment, the carbonizing the pretreated chitosan gel to obtain the flexible current collector material comprises:

[0018] The chitosan gel that has undergone the pretreatment is heated to a second temperature T2 for a first carbonization treatment, and then heated to a third temperature T3 for a second carbonization treatment to obtain the flexible current collector material.

[0019] In one embodiment, the chitosan gel that has completed the pretreatment is heated to a second temperature T2 for a first carbonization treatment, and then heated to a third temperature T3 for a second carbonization treatment to obtain the flexible current collector material:

[0020] The second temperature T2 has a value range of 580-620° C.; and / or,

[0021] The heating rate to the second temperature T2 is less than or equal to 2°C / min; and / or,

[0022] The first carbonization treatment includes holding at a second temperature T2 for 1.8 to 2.2 hours; and / or,

[0023] The third temperature T3 has a value range of 780-820° C.; and / or,

[0024] The heating rate to the third temperature T3 is less than or equal to 1°C / min; and / or,

[0025] The second carbonization treatment includes holding at a second temperature T2 for a time of 0.8 to 1.2 hours.

[0026] In one embodiment, the chitosan gel is prepared by the following steps:

[0027] S11, obtaining a chitosan solution;

[0028] S12, mixing the chitosan solution and a cross-linking agent to perform chemical cross-linking, so that at least a portion of the chitosan is chemically cross-linked to obtain a first chitosan gel;

[0029] S13, mixing the first chitosan gel and a solution containing monovalent hydrogen ions to perform physical crosslinking, so that at least a portion of the chitosan is physically crosslinked to obtain a second chitosan gel;

[0030] S14, washing the second chitosan gel with an alcohol reagent and water in sequence, cooling, and drying to obtain a chitosan gel.

[0031] In one embodiment, step S11 includes:

[0032] S111. Chitosan, alkali, urea, thiourea and water are mixed, and a cyclic freeze-thaw technique is used to prepare a chitosan solution.

[0033] In one embodiment, in step S111, the mass ratio of chitosan, alkali, urea, thiourea and water is (0.5-3): (9-11): (3-5): (0.5-1.5): (80-90); and / or,

[0034] The freezing temperature in the cyclic freeze-thaw technology is -40 to -60°C; and / or,

[0035] The freezing time in the cyclic freeze-thaw technique is 4 to 12 hours; and / or,

[0036] The thawing temperature in the freeze-thaw cycle technique is 20-25°C; and / or,

[0037] The thawing time in the freeze-thaw cycle technique is 2.5 to 3.5 hours; and / or,

[0038] The number of cycles in the cyclic freeze-thaw technique is 3 to 5 times.

[0039] In one embodiment, in step S12, the volume ratio of the chitosan solution to the cross-linking agent is (18-22):1; and / or,

[0040] In step S12, the chemical cross-linking time is 0.5 to 1 hour; and / or,

[0041] In step S12, the cross-linking agent includes any one of epichlorohydrin and epichlorohydrin, and / or,

[0042] In step S13, the physical cross-linking time is 15 to 25 seconds; and / or,

[0043] In step S13, the solution containing monovalent hydrogen ions includes any one of hydrochloric acid and acetic acid; and / or,

[0044] In step S14, the cooling method includes freezing with liquid nitrogen; and / or,

[0045] In step S14, the drying method includes freeze drying.

[0046] The present invention also proposes an application, in which the flexible current collector material prepared by the method for preparing the flexible current collector material is applied to a wearable device. The method for preparing the flexible current collector material comprises the following steps:

[0047] heating the chitosan gel to a first temperature T1 for pretreatment, wherein the first temperature T1 is lower than the carbonization temperature of the chitosan gel;

[0048] The chitosan gel that has completed the pretreatment is carbonized to obtain the flexible current collector material.

[0049] The present invention proposes a preparation method and application of a flexible current collector material, wherein, on the one hand, a heating pretreatment removes free water, some bound water, and volatile gases in the chitin gel in advance, causing it to slowly dehydrate and degas, reducing the generation of intramolecular stress and the local damage to the chitin basic carbon skeleton caused by intramolecular stress, thereby helping to maintain the structure of the chitin gel basic carbon skeleton; on the other hand, the heating temperature below the carbonization temperature of the chitin gel also reduces excessive dehydration and excessive hardening of the chitin gel, while causing the molecular chains of the chitin gel to rearrange and adjust at a slower rate, resulting in a looser and more ordered structure of the flexible current collector material, allowing the material to have better flexibility while maintaining a certain mechanical strength. This pretreatment procedure allows for more precise control of the stable structure and mechanical properties of the flexible current collector material, enhancing the repeatability and operability of the experimental process. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0051] Figure 1 This is a scanning electron microscope image of the flexible current collector material in Example 1 provided by the present invention;

[0052] Figure 2 This is a test diagram of the flexibility performance of the flexible current collector material in Example 1 provided by the present invention.

[0053] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. Where the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased commercially. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or schemes that A and B meet at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but must be based on the ability of ordinary technicians in this field to achieve. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that the combination of such technical solutions does not exist and is not within the scope of protection required by the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0055] Three-dimensional porous carbon, due to its unique three-dimensional network structure, high conductivity, and large specific surface area, facilitates mass transfer and electron diffusion, and has significant application prospects in the field of current collectors for advanced energy storage batteries such as lithium-ion batteries and sodium-ion batteries. Furthermore, considering diverse application scenarios such as wearables, flexible batteries are currently a key development direction, and corresponding flexible current collectors are also generating significant demand.

[0056] However, the preparation of existing high-performance three-dimensional porous carbon current collectors often requires complex and tedious preparation processes, which are high-cost and low-yield. Derivatives based on biomass raw materials such as cellulose and chitin are new environmentally friendly and low-carbon methods for preparing three-dimensional porous carbon that have been developed in recent years. However, the final product obtained after conventional high-temperature carbonization treatment is difficult to ensure good mechanical strength, with poor results and low pass rate; and conventional high-temperature carbonization treatment is usually an extensive heat treatment process, and the repeatability of experimental operations is poor. In addition, existing carbonization products are basically not flexible and cannot meet the actual application requirements of flexible electrodes.

[0057] In view of this, the present invention provides a method for preparing a flexible current collector material, comprising the following steps:

[0058] The chitosan gel is heated to a first temperature T1 for pretreatment, wherein the first temperature T1 is lower than the carbonization temperature of the chitosan gel; and the chitosan gel after the pretreatment is carbonized to obtain the flexible current collector material.

[0059] In the technical solution of the present invention, the chitin gel is subjected to a temperature pretreatment below the carbonization temperature of the chitin gel before being carbonized. The temperature pretreatment, on the one hand, removes the free water, part of the bound water and volatile gases in the chitin gel in advance, causing it to slowly dehydrate and degas, reducing the generation of molecular internal stress, reducing the local damage of the chitin basic carbon skeleton by molecular internal stress, and helping to maintain the structure of the chitin gel basic carbon skeleton; on the other hand, the temperature rise below the carbonization temperature of the chitin gel also reduces the excessive dehydration and excessive hardening of the chitin gel, while causing the molecular chains of the chitin gel to rearrange and adjust at a slower rate, resulting in a looser and more ordered structure of the flexible current collector material, so that the material has better flexibility while maintaining a certain mechanical strength. Through this pretreatment procedure, the stable structure and mechanical properties of the flexible current collector material can be more accurately controlled, enhancing the repeatability and operability of the experimental process.

[0060] It should be noted that the temperature pretreatment process of the present invention can be set to be completed in a single temperature increase mode or in a gradient temperature increase mode. As long as the temperature of the temperature pretreatment is higher than room temperature and lower than the carbonization temperature of the chitin gel, the effect of the present invention is finally achieved, and there is no strict restriction on the length of the pretreatment time and the number of temperature increases.

[0061] It should be noted that the carbonization treatment of the present invention can be completed in a single heating mode or in a gradient heating mode. As long as the temperature of the carbonization treatment is higher than the carbonization temperature of the chitin gel and the effect of the present invention is ultimately achieved, there is no strict restriction on the length of the pretreatment time and the number of heating times.

[0062] In some embodiments of the present invention, heating the chitosan gel to a first temperature T1 for pretreatment includes heating the chitosan gel to T0 for a first pretreatment, and then heating it to the first temperature T1 for a second pretreatment, wherein T0 < the first temperature T1 < the carbonization temperature of the chitosan gel. Dividing the pretreatment into two heating steps allows the chitosan molecular chains to rearrange under milder conditions, helps control the progression of physical and chemical changes within the chitosan molecules, facilitates obtaining a more structurally sound carbon skeleton, and improves the flexibility of the final flexible current collector material.

[0063] In some embodiments of the present invention, the chitosan gel is heated to T0 for the first pretreatment and then heated to the first temperature T1 for the second pretreatment: the value range of T0 is 280-320°C. T0 can be 280°C, 300°C, 310°C or 320°C. Within this range of T0, the chemical bonds within the chitosan gel molecules can be broken at a lower temperature, resulting in a relatively complete and stable basic carbon skeleton, which is beneficial to improving the flexibility of the final flexible current collector material.

[0064] In some embodiments of the present invention, the chitosan gel is heated to T0 for a first pretreatment and then heated to a first temperature T1 for a second pretreatment: the heating rate to T0 is less than or equal to 1°C / min. The heating rate to T0 can be 0.2°C / min, 0.6°C / min, 0.8°C / min or 1°C / min. The heating rate to T0 is within a suitable range to ensure that the chemical bonds within the chitosan gel molecules are broken at a slower rate, maintaining the basic carbon skeleton structure intact, which is beneficial to improving the flexibility of the final flexible current collector material.

[0065] In some embodiments of the present invention, the chitosan gel is heated to T0 for a first pretreatment, and then heated to a first temperature T1 for a second pretreatment: the first pretreatment includes holding the chitosan gel at T0 for a time of 0.3 to 0.7 hours. The holding time for the first pretreatment can be 0.3 hours, 0.5 hours, or 0.7 hours. Within an appropriate range, the holding time for the first pretreatment can ensure that the chemical bonds within the chitosan gel molecules are slowly broken over a longer period of time, thereby maintaining the basic carbon skeleton structure.

[0066] In some embodiments of the present invention, the chitosan gel is heated to T0 for a first pretreatment and then heated to a first temperature T1 for a second pretreatment: the first temperature T1 is in a range of 380°C to 420°C. The first temperature T1 can be 380°C, 400°C, or 420°C. A suitable range of the first temperature T1 can ensure a relatively stable and complete basic carbon skeleton, which is beneficial for improving the flexibility of the final flexible current collector material.

[0067] In some embodiments of the present invention, the chitosan gel is heated to T0 for a first pretreatment and then heated to a first temperature T1 for a second pretreatment: the heating rate to the first temperature T1 is less than or equal to 1°C / min. The heating rate to the first temperature T1 can be 0.2°C / min, 0.6°C / min, 0.8°C / min, or 1°C / min. The heating rate to the first temperature T1 is within a suitable range to ensure that a relatively stable and complete basic carbon skeleton is obtained, which is beneficial to improving the flexibility of the final flexible current collector material.

[0068] In some embodiments of the present invention, the chitosan gel is heated to T0 for a first pretreatment, and then heated to a first temperature T1 for a second pretreatment: the second pretreatment includes keeping the temperature at the first temperature T1 for 0.3 to 0.7 hours. The holding time of the second pretreatment can be 0.3 hours, 0.5 hours, or 0.7 hours. The holding time of the second pretreatment within an appropriate range can ensure that the chemical bonds within the chitosan gel molecules are slowly broken over a longer period of time, maintaining the carbon skeleton structure from being destroyed, and is conducive to improving the flexibility of the final flexible current collector material.

[0069] In some embodiments of the present invention, the carbonizing the pretreated chitin gel to obtain the flexible current collector material includes: heating the pretreated chitin gel to a second temperature T2 for a first carbonization treatment, and then heating it to a third temperature T3 for a second carbonization treatment to obtain the flexible current collector material.

[0070] In the technical solution of the present invention, the carbonization treatment is divided into two steps of heating, the purpose of which is to prevent the embrittlement of the carbonaceous structure during the high-temperature carbonization process, which is beneficial to improving the flexibility of the final flexible current collector material and making the preparation process also have good repeatability and operability.

[0071] In some embodiments of the present invention, the chitosan gel that has completed the pretreatment is heated to a second temperature T2 for a first carbonization treatment, and then heated to a third temperature T3 for a second carbonization treatment, to obtain the flexible current collector material: the second temperature T2 has a value range of 580 to 620°C. The second temperature T2 can be 580°C, 600°C, 615°C, or 620°C. The second temperature T2 within a suitable range can ensure that the first carbonization process is relatively mild, gradually removes the remaining moisture and volatile substances, and simultaneously begins to form a carbon structure, completing the initial carbonization degradation without causing structural damage too quickly, thereby reducing the probability of embrittlement of the carbonaceous structure during the high-temperature carbonization process.

[0072] In some embodiments of the present invention, the chitin gel that has completed the pretreatment is heated to a second temperature T2 for a first carbonization treatment, and then heated to a third temperature T3 for a second carbonization treatment, to obtain the flexible current collector material: the heating rate for heating to the second temperature T2 is less than or equal to 2°C / min. The heating rate for heating to the second temperature T2 can be 0.2°C / min, 0.6°C / min, 1.8°C / min or 2°C / min. The slower the heating rate, the better. This ensures that the first carbonization process is relatively mild, gradually removes the remaining moisture and volatile substances, and begins to form a carbon structure at the same time, but not too quickly to cause structural damage, thereby reducing the probability of brittle carbon structure during high-temperature carbonization.

[0073] In some embodiments of the present invention, the chitosan gel that has completed the pretreatment is heated to a second temperature T2 for a first carbonization treatment, and then heated to a third temperature T3 for a second carbonization treatment, to obtain the flexible current collector material: the first carbonization treatment includes holding the material at the second temperature T2 for a time of 1.8 to 2.2 hours. The holding time for the first carbonization treatment can be 1.8 hours, 2 hours, or 2.2 hours. The holding time for the first carbonization treatment within an appropriate range can ensure that the first carbonization treatment process fully removes residual moisture and volatile substances, forming a more stable carbon structure.

[0074] In some embodiments of the present invention, the chitosan gel that has completed the pretreatment is heated to a second temperature T2 for a first carbonization treatment, and then heated to a third temperature T3 for a second carbonization treatment, to obtain the flexible current collector material: the third temperature T3 has a value range of 780 to 820°C. The third temperature T3 can be 780°C, 800°C, or 820°C. Within an appropriate range, the third temperature T3 can effectively control the pyrolysis rate, promote deeper cross-linking between molecules and densification of the carbon structure, fully and stably carbonize the chitosan, and reduce internal stress, ensuring sufficient carbonization without over-carbonization, thereby obtaining a carbon material with a more uniform structure and better performance.

[0075] In some embodiments of the present invention, the chitosan gel that has completed the pretreatment is heated to a second temperature T2 for a first carbonization treatment, and then heated to a third temperature T3 for a second carbonization treatment, to obtain the flexible current collector material: the heating rate to the third temperature T3 is less than or equal to 1°C / min. The heating rate to the third temperature T3 can be 0.2°C / min, 0.6°C / min, 0.8°C / min or 1°C / min. The heating rate to the third temperature T3 can effectively control the pyrolysis rate within an appropriate range, promote deeper cross-linking between molecules and densification of the carbon structure, while reducing internal stress, ensuring sufficient carbonization but not over-burning, thereby obtaining a carbon material with a more uniform structure and better performance.

[0076] In some embodiments of the present invention, the chitosan gel that has completed the pretreatment is heated to a second temperature T2 for a first carbonization treatment, and then heated to a third temperature T3 for a second carbonization treatment to obtain the flexible current collector material: the second carbonization treatment includes holding the temperature at the second temperature T2 for a time of 0.8 to 1.2 hours. The holding time of the second carbonization treatment can be 1.2 hours, 1.2 hours, or 1.2 hours. The holding time of the second carbonization treatment within an appropriate range can ensure sufficient carbonization.

[0077] In some embodiments of the present invention, the chitosan gel is prepared by the following steps:

[0078] S11, obtaining a chitosan solution;

[0079] S12, mixing the chitosan solution and a cross-linking agent to perform chemical cross-linking, so that at least a portion of the chitosan is chemically cross-linked to obtain a first chitosan gel;

[0080] S13, mixing the first chitosan gel and a solution containing monovalent hydrogen ions to perform physical crosslinking, so that at least a portion of the chitosan is physically crosslinked to obtain a second chitosan gel;

[0081] S14, washing the second chitosan gel with an alcohol reagent and water in sequence, cooling, and drying to obtain a chitosan gel.

[0082] In the technical solution of the present invention, chemical crosslinking connects chitin molecules through covalent bonds, strengthening the chitin network structure and improving its mechanical strength and chemical resistance. In step S12, some chitin molecules react with the crosslinker to form stable chemical bonds. In step S13, the first chitin gel is mixed with a solution containing monovalent hydrogen ions. The role of the monovalent hydrogen ions may be to promote the formation of hydrogen bonds between chitin molecules, thereby achieving physical crosslinking. Physical crosslinking does not involve the formation of covalent bonds, but rather strengthens the internal connection of chitin through intermolecular forces such as hydrogen bonds and van der Waals forces. This process can complement chemical crosslinking, ensuring that even chitin parts that are not directly involved in chemical crosslinking can be tightly bound through physical interaction, further improving the overall stability and integrity of the chitin gel. In step S14, the gel is first washed with an alcohol reagent to remove unreacted crosslinking agent, low molecular weight substances and possible impurities, and then washed with water to remove alcohol residues. After washing, the gel needs to be cooled and dried. Cooling helps to stabilize the gel structure, while drying removes moisture, allowing the gel to reach the desired physical state for subsequent processing.

[0083] It should be noted that the molecular weight of chitosan in the present invention is (203.19)n, where 203.19 is the molecular weight of the chitosan monomer unit, that is, the molecular weight of chitosan is the molecular weight of its basic unit N-acetylamino-D-glucose 203.19 multiplied by the number of repeating units n, and the number of repeating units can be 100, 120, or 200. The mass concentration of chitosan in the chitosan solution is 30-35 g / L, and its mass concentration can be 30 g / L, 33 g / L, or 35 g / L. Its mass concentration within this range can ensure that a better carbonized skeleton is obtained.

[0084] It should be noted that the conditions for chemical cross-linking are: adding the cross-linking agent dropwise into the chitosan solution at 0° C. to obtain the first chitosan gel.

[0085] In some embodiments of the present invention, step S11 includes: S111, mixing chitosan, alkali, urea, thiourea and water, and preparing a chitosan solution by using a freeze-thaw cycle technology.

[0086] In the technical solution of the present invention, the freeze-thaw cycle technology is used to obtain a colorless and transparent chitosan solution without turbidity or impurities, thereby ensuring that the chitosan solution is fully dissolved.

[0087] In some embodiments of the present invention, in step S111, the mass ratio of chitosan, alkali, urea, thiourea, and water is (0.5-3):(9-11):(3-5):(0.5-1.5):(80-90). The mass ratio of chitosan, alkali, urea, thiourea, and water can be 0.5:9:3:0.5:80, 3:10:4:1:85, or 2:11:5:1.5:90. A mass ratio within an appropriate range can ensure that chitosan is fully dissolved to form a colorless and transparent chitosan solution.

[0088] In some embodiments of the present invention, in step S111, the freezing temperature in the cyclic freeze-thaw technology is -40 to -60°C. The freezing temperature in the cyclic freeze-thaw technology can be -40°C, -50°C, or -60°C. The freezing temperature in the cyclic freeze-thaw technology within an appropriate range can ensure that the chitosan solution freezes and solidifies quickly, and quickly forms uniform and fine ice crystals, thereby reducing damage to the molecular structure of the chitosan.

[0089] It should be noted that the freezing temperature provided by the present invention is a preferred solution. In actual operation, the effect of the present invention can be achieved as long as the temperature is lower than the freezing point of the chitosan solution.

[0090] In some embodiments of the present invention, in step S111, the freezing time in the cyclic freeze-thaw technique is 4 to 12 hours. The freezing time in the cyclic freeze-thaw technique can be 4 hours, 8 hours, or 12 hours. The freezing time in the cyclic freeze-thaw technique within an appropriate range can ensure that the chitosan solution is fully frozen.

[0091] In some embodiments of the present invention, in step S111, the thawing temperature in the cyclic freeze-thaw technique is 20-25° C. The thawing temperature in the cyclic freeze-thaw technique can be 20° C., 22° C., or 25° C. The thawing temperature in the cyclic freeze-thaw technique within an appropriate range may help promote closer aggregation or reorganization of chitin molecules through physical action, thereby increasing the stability of chitin in the solvent.

[0092] In some embodiments of the present invention, in step S111, the thawing time in the cyclic freeze-thaw technique is 2.5 to 3.5 hours. The thawing time in the cyclic freeze-thaw technique can be 2.5 hours, 3 hours, or 3.5 hours. The thawing time in the cyclic freeze-thaw technique within an appropriate range can ensure that the chitosan solution solid is fully thawed.

[0093] In some embodiments of the present invention, in step S111, the number of cycles in the cyclic freeze-thaw technique is 3 to 5. The number of cycles in the cyclic freeze-thaw technique can be 3, 4, or 5. The number of cycles in the cyclic freeze-thaw technique within an appropriate range can ensure that the chitosan solution is colorless and transparent, that is, the chitosan is fully dissolved in the solution.

[0094] In some embodiments of the present invention, in step S12, the volume ratio of the chitosan solution to the cross-linking agent is (18-22):1. The volume ratio of the chitosan solution to the cross-linking agent can be 18:1, 20:1, or 22:1. The volume ratio of the chitosan solution to the cross-linking agent within an appropriate range can ensure that during the chemical cross-linking process, the chitosan molecules can be appropriately interconnected, neither excessively nor insufficiently, to achieve an appropriate cross-linking density. Excessive cross-linking may cause the chitosan gel to become harder and more brittle, while insufficient cross-linking may loosen the chitosan gel structure and reduce its physical and chemical stability.

[0095] In some embodiments of the present invention, in step S12, the chemical cross-linking time is 0.5 to 1 hour. The chemical cross-linking time can be 0.5 hours, 0.7 hours or 1 hour. The chemical cross-linking time within a suitable range can ensure that the chitin molecules have a good cross-linking density.

[0096] In some embodiments of the present invention, in step S12, the crosslinking agent includes any one of epichlorohydrin and epichlorohydrin. The crosslinking agent can be epichlorohydrin or epichlorohydrin. Compared with other crosslinking agents, the above crosslinking agents have better efficiency in chemical reactions and good compatibility with chitin.

[0097] In some embodiments of the present invention, in step S13, the physical crosslinking time is 15 to 25 seconds. The physical crosslinking time can be 15 seconds, 20 seconds, or 25 seconds. The physical crosslinking time within a suitable range can cause some chitin molecular chains to be forced to parallelize and stack in the liquid environment through strong self-cohesion, forming a more compact structure.

[0098] In some embodiments of the present invention, in step S13, the solution containing monovalent hydrogen ions includes hydrochloric acid or acetic acid. Compared with other solutions containing monovalent hydrogen ions, the above solution can more accurately control the pH value of the solution, thereby controlling the degree of physical crosslinking.

[0099] In some embodiments of the present invention, in step S14, the cooling method includes liquid nitrogen freezing. Compared with other cooling methods, liquid nitrogen freezing can promote rapid cooling of the chitosan gel and maintain the microstructure unchanged.

[0100] In some embodiments of the present invention, in step S14, the drying method includes freeze drying. Compared with other drying methods, freeze drying directly removes water through a sublimation process, avoiding damage to the material structure during water evaporation, so that the dried chitosan gel maintains good porosity and looseness.

[0101] The present invention also proposes an application, in which the flexible current collector material prepared by the preparation method of the flexible current collector material is applied to a wearable device. It has all the technical solutions of the preparation method of the flexible current collector material, and therefore also has all the beneficial effects brought by the above technical solutions, which will not be repeated here.

[0102] The technical solutions of the present invention are further described in detail below in conjunction with specific embodiments and drawings. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0103] Example 1

[0104] A method for preparing a flexible current collector material comprises the following steps:

[0105] (1) Obtain chitosan solution: Mix crude chitosan raw material powder (purchased from Zhejiang Jinke Pharmaceutical Co., Ltd. without prior purification) with NaOH, urea, thiourea, and deionized water in a mass ratio of 3:10:4:1:85, and stir with a magnetic stirrer at room temperature for 30 minutes to dissolve NaOH, urea, and thiourea, thereby promoting uniform mixing of the raw materials. The mixture is then placed in a low-temperature box pre-cooled to -60°C for 12 hours, then taken out and thawed at room temperature for 3 hours, and then placed in a magnetic stirrer for 1 hour (the first stirring requires manual assistance with a glass rod). This cycle is repeated 5 times to form a colorless and transparent chitosan solution. The obtained transparent chitosan solution is centrifuged at 8000 rpm in a 0°C constant temperature centrifuge for 10 minutes to obtain a chitosan solution free of bubbles and impurities.

[0106] (2) Preparation of chitin gel: In a constant temperature ice water bath at 0°C, under continuous magnetic stirring at a constant speed of 500 rpm, 50 mL of the crosslinking agent epichlorohydrin was dripped dropwise into 1000 g of chitin solution through a constant pressure dropping funnel over 30 minutes for chemical crosslinking to obtain the first chitin gel. The first chitin gel was then quickly placed in a 0.1 M hydrochloric acid solution for 20 seconds for physical crosslinking to obtain the second chitin gel. The second chitin gel was then immersed in ethanol and deionized water tanks for 2 hours and 48 hours, respectively, keeping the liquid circulation continuously flowing to thoroughly wash away residual acid, alkali and other reagents.

[0107] The washed second chitosan gel was placed in liquid nitrogen for rapid cooling to maintain the microstructure unchanged, and then the frozen second chitosan gel was placed in a freeze drying box at -70°C for drying for 24 hours to obtain chitosan gel.

[0108] (3) Chitosan gel pretreatment and carbonization procedure: The freeze-dried chitosan gel was subjected to programmed temperature control in a N2 protected tube furnace. The procedure is as follows:

[0109] First pretreatment: heating from room temperature to 300°C at a rate of 1°C / min and holding for 0.5h;

[0110] Second pretreatment: heating from 300°C to 400°C at a heating rate of 1°C / min and holding for 0.5h;

[0111] First carbonization treatment: heating from 400°C to 600°C at a rate of 2°C / min and holding for 2 h;

[0112] Second carbonization treatment: heating from 600°C to 800°C at a heating rate of 1°C / min and keeping at this temperature for 1 h.

[0113] Example 2

[0114] A method for preparing a flexible current collector material comprises the following steps:

[0115] (1) Obtain chitosan solution: Mix crude chitosan raw material powder (purchased from Zhejiang Jinke Pharmaceutical Co., Ltd. without prior purification) with NaOH, urea, thiourea, and deionized water in a mass ratio of 0.5:11:5:1.5:90, and stir with a magnetic stirrer at room temperature for 30 minutes to dissolve NaOH, urea, and thiourea to promote uniform mixing of the raw materials. Then, place the mixture in a low-temperature box pre-cooled to -40°C for 4 hours, then take it out and thaw it at 20°C for 2.5 hours, and then place it in a magnetic stirrer and stir for 1 hour (the first stirring requires manual assistance with a glass rod). This cycle is repeated 3 times to form a colorless and transparent chitosan solution. The obtained transparent chitosan solution is centrifuged at 8000 rpm in a 0°C constant temperature centrifuge for 10 minutes to obtain a chitosan solution free of bubbles and impurities.

[0116] (2) Preparation of chitin gel: In a constant temperature ice water bath at 0°C, under continuous magnetic stirring at a constant speed of 500 rpm, the crosslinking agent epichlorohydrin was added dropwise to the chitin solution through a constant pressure dropping funnel for 45 minutes for chemical crosslinking, wherein the volume ratio of chitin solution to crosslinking agent was 18:1, to obtain the first chitin gel. The first chitin gel was then quickly placed in a 0.1M hydrochloric acid solution for 15 seconds for physical crosslinking to obtain the second chitin gel. The second chitin gel was then immersed in ethanol and deionized water tanks for 2 hours and 48 hours, respectively, and the liquid circulation was maintained to continuously flow to thoroughly wash away residual acid, alkali and other reagents.

[0117] The washed second chitosan gel was placed in liquid nitrogen for rapid cooling to maintain the microstructure unchanged, and then the frozen second chitosan gel was placed in a freeze drying box at -70°C for drying for 24 hours to obtain chitosan gel.

[0118] (3) Chitosan gel pretreatment and carbonization procedure: The freeze-dried chitosan gel was subjected to programmed temperature control in a N2 protected tube furnace. The procedure is as follows:

[0119] First pretreatment: heating from 20°C to 280°C at a rate of 0.1°C / min and holding for 0.3h;

[0120] Second pretreatment: heating from 280°C to 380°C at a rate of 0.1°C / min and holding for 0.3h;

[0121] First carbonization treatment: heating from 380°C to 580°C at a rate of 0.1°C / min and holding for 1.8 h;

[0122] Second carbonization treatment: heating from 580°C to 820°C at a heating rate of 0.1°C / min and keeping the temperature for 0.8h.

[0123] Example 3

[0124] A method for preparing a flexible current collector material comprises the following steps:

[0125] (1) Obtain chitosan solution: Mix crude chitosan raw material powder (purchased from Zhejiang Jinke Pharmaceutical Co., Ltd. without prior purification) with NaOH, urea, thiourea, and deionized water in a mass ratio of 3:9:3:0.5:80, and stir with a magnetic stirrer at room temperature for 30 minutes to dissolve NaOH, urea, and thiourea to promote uniform mixing of the raw materials. Then, place the mixture in a low-temperature box pre-cooled to -60°C for 12 hours, then take it out and thaw it at 25°C for 3.5 hours, and then place it in a magnetic stirrer and stir for 1 hour (the first stirring requires manual assistance with a glass rod). This cycle is repeated 5 times to form a colorless and transparent chitosan solution. The obtained transparent chitosan solution is centrifuged at 8000 rpm in a constant temperature centrifuge at 0°C for 10 minutes to obtain a chitosan solution free of bubbles and impurities.

[0126] (2) Preparation of chitin gel: In a constant temperature ice water bath at 0°C, under continuous magnetic stirring at a constant speed of 500 rpm, the crosslinking agent epichlorohydrin was added dropwise to the chitin solution through a constant pressure dropping funnel for 60 minutes for chemical crosslinking, wherein the volume ratio of chitin solution to crosslinking agent was 22:1, to obtain the first chitin gel. The first chitin gel was then quickly placed in a 0.1M acetic acid solution for 25 seconds for physical crosslinking to obtain the second chitin gel. The second chitin gel was then immersed in ethanol and deionized water tanks for 2 hours and 48 hours, respectively, and the liquid circulation was maintained to continuously flow to thoroughly wash away residual acid, alkali and other reagents.

[0127] The washed second chitosan gel was placed in liquid nitrogen for rapid cooling to maintain the microstructure unchanged, and then the frozen second chitosan gel was placed in a freeze drying box at -70°C for drying for 24 hours to obtain chitosan gel.

[0128] (3) Chitosan gel pretreatment and carbonization procedure: The freeze-dried chitosan gel was subjected to programmed temperature control in a N2 protected tube furnace. The procedure is as follows:

[0129] First pretreatment: heating from 25°C to 320°C at a rate of 0.5°C / min and holding for 0.7h;

[0130] Second pretreatment: heating from 320°C to 420°C at a rate of 0.5°C / min and holding for 0.7h;

[0131] First carbonization treatment: heating from 420°C to 620°C at a rate of 1.5°C / min and holding for 2.2h;

[0132] Second carbonization treatment: heating from 620°C to 820°C at a heating rate of 0.5°C / min and keeping the temperature for 1.2h.

[0133] Comparative Example 1

[0134] Compared with Example 1, Comparative Example 1 is the same as Example 1 except that the first carbonization treatment and the second carbonization treatment are directly performed.

[0135] Performance Testing

[0136] The flexible current collector material prepared in Example 1 was observed by scanning electron microscopy and its flexibility was characterized. The specific detection method is as follows:

[0137] 1) Scanning electron microscopy observation: The microscopic morphology of the current collector material obtained in Example 1 was observed by field emission scanning electron microscopy (FE-SEM, JEOL JSM-7500F) at an accelerating voltage of 5 kV and a magnification of 10,000. It was confirmed that the current collector material had a network-like porous structure composed of lamellar structural units connected to a three-dimensionally aligned fiber skeleton. The results are as follows: Figure 1 shown.

[0138] 2) Characterization of flexibility: Select a piece of prepared current collector material (size about 1.5*1.5cm 2 ), manually squeeze the two ends of the material sample toward the middle to make the middle bulge, then use tweezers to grab the material sample, and gently press the tweezers to make the sample bulge outward and bend. After the sample is bent by external force, it can still maintain its structural integrity without any structural damage such as fragmentation, showing good flexibility. The results are as follows Figure 2 shown.

[0139] In summary, the flexible current collector material prepared by the preparation method of the flexible current collector material provided by the present invention has a looser and more ordered structure, and has good flexibility while maintaining a certain mechanical strength; at the same time, the stable structure and mechanical properties of the flexible current collector material can be more accurately controlled, thereby enhancing the repeatability and operability of the experimental process.

[0140] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of the present invention.

Claims

1. A method for preparing a flexible current collector material, characterized in that: The following steps are involved: The chitosan gel is heated to T0 for a first pretreatment, and then heated to a first temperature T1 for a second pretreatment, wherein T0 < the first temperature T1 < the carbonization temperature of the chitosan gel; heating the pretreated chitosan gel to a second temperature T2 for a first carbonization treatment, and then heating it to a third temperature T3 for a second carbonization treatment to obtain the flexible current collector material; The chitosan gel is prepared by the following steps: S11, obtaining a chitosan solution; S12, mixing the chitosan solution and a cross-linking agent to perform chemical cross-linking, so that at least a portion of the chitosan is chemically cross-linked to obtain a first chitosan gel; S13, mixing the first chitosan gel and a solution containing monovalent hydrogen ions to perform physical crosslinking, so that at least a portion of the chitosan is physically crosslinked to obtain a second chitosan gel; S14, washing the second chitosan gel with an alcohol reagent and water in sequence, cooling, and drying to obtain a chitosan gel; The value range of T0 is 280-320°C; the heating rate to T0 is less than or equal to 1°C / min; the first pretreatment includes keeping warm at T0, and the holding time is 0.3-0.7h; the value range of the first temperature T1 is 380-420°C; the heating rate to the first temperature T1 is less than or equal to 1°C / min; the second pretreatment includes keeping warm at the first temperature T1, and the holding time is 0.3-0.7h; The second temperature T2 has a value range of 580 to 620° C.; the heating rate to the second temperature T2 is less than or equal to 2° C. / min; the first carbonization treatment includes holding at the second temperature T2 for 1.8 to 2.2 hours; the third temperature T3 has a value range of 780 to 820° C.; the heating rate to the third temperature T3 is less than or equal to 1° C. / min; the second carbonization treatment includes holding at the second temperature T2 for 0.8 to 1.2 hours; Step S11 includes: S111, mixing chitosan, alkali, urea, thiourea and water, and preparing a chitosan solution by freeze-thaw cycle technology; In step S111, the mass ratio of chitosan, alkali, urea, thiourea and water is (0.5-3): (9-11): (3-5): (0.5-1.5): (80-90); the freezing temperature in the cyclic freeze-thaw technology is -40--60° C.; the freezing time in the cyclic freeze-thaw technology is 4-12 hours; the thawing temperature in the cyclic freeze-thaw technology is 20-25° C.; the thawing time in the cyclic freeze-thaw technology is 2.5-3.5 hours; and the number of cycles in the cyclic freeze-thaw technology is 3-5 times; In step S12, the volume ratio of the chitosan solution to the cross-linking agent is (18-22):1; The chemical crosslinking time is 0.5 to 1 hour; the crosslinking agent includes any one of epichlorohydrin and epichlorohydrin; In step S13, the physical cross-linking time is 15 to 25 seconds; the solution containing monovalent hydrogen ions includes any one of hydrochloric acid and acetic acid; In step S14, the cooling method includes liquid nitrogen freezing; and the drying method includes freeze drying.

2. An application, wherein the flexible current collector material prepared by the method for preparing the flexible current collector material according to claim 1 is applied to a wearable device.

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