A collagen-based fibrous carbon-hydroxyapatite nanocomposite material, its preparation method and application

Abstract

This invention relates to the fields of nanomaterials and lithium-sulfur batteries, providing a collagen-based fibrous carbon-hydroxyapatite nanocomposite material, its preparation method, and its applications. Using fish scales as raw material, this invention removes some of the hydroxyapatite from the fish scales through a physical exfoliation method, leaving a collagen fiber-hydroxyapatite composite material. This material is then pre-oxidized and carbonized to obtain the collagen-based fibrous carbon / hydroxyapatite nanocomposite material. The nanocomposite material provided by this invention has a large specific surface area. Furthermore, the cross-linking between fibers during the pre-oxidation process and the maintenance of the long-range structure of the composite material after carbonization form a network structure that can efficiently capture polysulfides and suppress the shuttle effect. Using this nanocomposite material to modify the separator of a lithium-sulfur battery can effectively solve the problem of polysulfide shuttle during battery cycling, improving the cycle stability and coulombic efficiency of the lithium-sulfur battery.

Description

Technical Field

[0001] This invention relates to the fields of nanomaterials and lithium-sulfur battery technology, and in particular to a collagen-based fibrous carbon-hydroxyapatite nanocomposite material, its preparation method, and its application. Background Technology

[0002] With the development of electric vehicles and portable devices, existing lithium-ion batteries are struggling to meet the ever-increasing capacity and range requirements of battery systems. Among all newly developed battery systems, lithium-sulfur batteries stand out due to their ultra-high theoretical energy density (2600 Wh·kg⁻¹). -1 It stands out. Moreover, the low-cost nature of sulfur further enhances its application possibilities.

[0003] The separator is the most important core component in lithium-sulfur batteries besides the positive and negative electrodes, playing a crucial role in preventing contact between the positive and negative electrodes and providing a channel for lithium-ion transport. Lithium-sulfur batteries face challenges during use, including the low conductivity of sulfur and discharge products (Li₂S / Li₂S₂), the volume expansion of sulfur during cycling, the severe shuttle effect caused by dissolved LiPSs in the electrolyte, and the limitations imposed by irreversible Li₂S / Li₂S₂ deposition and phase transformation. The separator's role is primarily threefold: inhibiting the diffusion of lithium polysulfides, improving the utilization rate of sulfur-containing active materials, and accelerating the reaction rate. These correspond to three key issues in lithium-sulfur batteries: the dissolution of polysulfides, the insulation of active materials, and the slow solid-liquid-solid reaction rate.

[0004] However, the problem of polysulfide shuttle in lithium-sulfur batteries remains unsolved, which seriously hinders the practical application of lithium-sulfur batteries. The "shuttle effect" of soluble intermediate polysulfides (LiPSs) leads to the loss of active materials and anode passivation, resulting in poor cycle stability and low coulombic efficiency of lithium-sulfur batteries. Summary of the Invention

[0005] In view of this, the present invention provides a collagen-based fibrous carbon-hydroxyapatite nanocomposite material, its preparation method, and its application. The present invention uses fish scales as raw material to prepare a collagen-based fibrous carbon-hydroxyapatite nanocomposite material, which is then used to modify the separator of lithium-sulfur batteries. This effectively suppresses the shuttle effect of polysulfides and improves the long-cycle stability and coulombic efficiency of lithium-sulfur batteries.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A method for preparing a collagen-based fibrous carbon-hydroxyapatite nanocomposite material includes the following steps:

[0008] After crushing the fish scales, they were sieved to obtain a collagen fiber-hydroxyapatite composite material.

[0009] The collagen fiber-hydroxyapatite composite material was pre-oxidized and shaped in an oxygen-containing environment to obtain an oxidized collagen fiber-hydroxyapatite composite material.

[0010] The oxidized collagen fiber-hydroxyapatite composite material was carbonized under a protective atmosphere to obtain a collagen-based fibrous carbon-hydroxyapatite nanocomposite material.

[0011] Preferably, the pulverizing speed is 10,000 to 50,000 r / min, the pulverizing time is 2 to 10 min, the sieve mesh size is 0.03 to 0.018 mm, and the sieve residue is a collagen fiber-hydroxyapatite composite material.

[0012] After sieving, the obtained collagen fiber-hydroxyapatite composite material is dried at a temperature of 40–90°C for 12–72 hours.

[0013] Preferably, the temperature of the pre-oxidation and shaping treatment is 120-350℃, the holding time is 1-6h, the heating rate to the pre-oxidation and shaping treatment temperature is 2-15℃ / min, and the temperature is naturally cooled to 20-50℃ after the holding time is completed.

[0014] Preferably, the carbonization treatment temperature is 500-900℃, the holding time is 1-6h, the heating rate to the carbonization treatment temperature is 2-15℃ / min, and the temperature naturally drops to 20-50℃ after the holding time is completed.

[0015] The present invention also provides a collagen-based fibrous carbon-hydroxyapatite nanocomposite material prepared by the preparation method described above.

[0016] Preferably, the collagen-based fibrous carbon-hydroxyapatite nanocomposite material is used to modify the separator of the lithium-sulfur battery.

[0017] The present invention also provides a modified diaphragm, comprising a diaphragm and a modified layer disposed on the surface of the diaphragm; the modified layer comprises a conductive agent, a binder, and the collagen-based fibrous carbon-hydroxyapatite nanocomposite material described in the above embodiments.

[0018] Preferably, the mass ratio of the collagen-based fibrous carbon-hydroxyapatite nanocomposite material, the conductive agent, and the binder is 1–3:1–3:1.

[0019] The present invention also provides a method for preparing the modified diaphragm described above, comprising the following steps:

[0020] Collagen-based fibrous carbon-hydroxyapatite nanocomposite material was mixed with conductive agent, binder and solvent to obtain collagen-based fibrous carbon-hydroxyapatite nanocomposite material slurry.

[0021] The collagen-based fibrous carbon-hydroxyapatite nanocomposite slurry was coated onto the surface of the diaphragm and then dried to obtain the modified diaphragm.

[0022] The present invention also provides a lithium-sulfur battery, comprising a lithium metal anode, a sulfur cathode, a separator, and an electrolyte, wherein the separator is a modified separator as described in the above scheme or a modified separator prepared by the preparation method described in the above scheme.

[0023] This invention provides a method for preparing collagen-based fibrous carbon-hydroxyapatite nanocomposite materials. Using fish scales as raw material, a portion of the hydroxyapatite is removed from the fish scales via a physical exfoliation method (crushing), leaving a collagen fiber-hydroxyapatite composite material. The resulting collagen fiber-hydroxyapatite composite material is then pre-oxidized and shaped in an oxygen-containing environment, transforming the collagen fibers into oxidized collagen fibers and causing partial oxidative cross-linking between the fibers. Finally, it is carbonized in a protective atmosphere to maintain the original long-range structure of the material and achieve long-range conductivity, transforming the oxidized collagen fibers into oxidized collagen fibrous carbon, thus obtaining the collagen-based fibrous carbon-hydroxyapatite nanocomposite material. The main material used in this invention, collagen fiber, is a natural biological fiber material with excellent adsorption and biodegradability, as well as a good fibrous microstructure. After carbonization, the collagen-based fibrous carbon-hydroxyapatite nanocomposite material exhibits a large specific surface area. Furthermore, the cross-linking between fibers during the pre-oxidation and shaping process maintains the long-range structure of the composite material after carbonization, forming a network structure that efficiently captures polysulfides, suppresses the shuttle effect, and improves the long-cycle stability and safety of lithium-sulfur batteries, thereby increasing coulombic efficiency. Additionally, hydroxyapatite can chemically adsorb polysulfides during charge and discharge, helping the separator inhibit polysulfide transfer and thus improving the battery's cycle capacity. However, hydroxyapatite has poor conductivity, and excessive content can affect the battery's internal resistance. This invention removes some of the hydroxyapatite from the fish scales, which helps to ensure the full utilization of hydroxyapatite's function while avoiding its impact on the battery's internal resistance.

[0024] This invention also provides the application of collagen-based fibrous carbon-hydroxyapatite nanocomposite materials in lithium-sulfur batteries. This invention utilizes collagen-based fibrous carbon-hydroxyapatite nanocomposite materials to modify the separator of lithium-sulfur batteries, effectively solving the problem of polysulfide shuttle during battery cycling and improving the cycle stability and coulombic efficiency of lithium-sulfur batteries. Example results show that modifying commercial PP separators with the collagen-based fibrous carbon-hydroxyapatite nanocomposite materials prepared according to this invention, and applying the modified separator to lithium-sulfur batteries, results in a lithium-sulfur battery with an initial discharge specific capacity of 1105.3 mAh g at 1C. -1The initial coulombic efficiency reached 99.47%, and the cycle stability was high, with the discharge specific capacity still reaching 825.9 mAh g after 150 cycles. -1 The Coulomb efficiency can still reach 98.18%. Attached Figure Description

[0025] Figure 1 SEM image of the collagen-based fibrous carbon-hydroxyapatite nanocomposite material prepared in Example 1;

[0026] Figure 2 This is a comparison chart of the discharge specific capacity of lithium-sulfur batteries assembled using modified separators and ordinary separators in Example 1.

[0027] Figure 3 This is a comparison chart of the coulombic efficiencies of lithium-sulfur batteries assembled using modified and ordinary separators in Example 1. Detailed Implementation

[0028] This invention provides a method for preparing collagen-based fibrous carbon-hydroxyapatite nanocomposite materials, comprising the following steps:

[0029] After crushing the fish scales, they were sieved to obtain a collagen fiber-hydroxyapatite composite material.

[0030] The collagen fiber-hydroxyapatite composite material was pre-oxidized and shaped in an oxygen-containing environment to obtain an oxidized collagen fiber-hydroxyapatite composite material.

[0031] The oxidized collagen fiber-hydroxyapatite composite material was carbonized under a protective atmosphere to obtain a collagen-based fibrous carbon-hydroxyapatite nanocomposite material.

[0032] In this invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art.

[0033] This invention involves pulverizing fish scales and then sieving them to obtain a collagen fiber-hydroxyapatite composite material. The fish scales used in this invention have no special requirements; any common fish scales used in daily life are acceptable, including dried fish scales from species such as tilapia, grass carp, bass, silver carp, and mandarin fish. In this invention, the pulverizing speed is preferably 10,000–50,000 r / min, more preferably 25,000 r / min, and the pulverizing time is preferably 2–10 min, more preferably 3–8 min. The original hydroxyapatite content in the fish scales is 50–70%. This invention uses pulverization to physically peel away the hydroxyapatite, breaking down the physical cross-linking structure in the fish scales, causing some of the hydroxyapatite to detach from the collagen fiber structure. The remaining hydroxyapatite then combines with the collagen fibers to form a collagen fiber-hydroxyapatite composite material. Hydroxyapatite exhibits excellent chemisorption properties for polysulfides, helping the separator inhibit polysulfide transfer and thus improving battery cycle capacity. However, the poor conductivity of hydroxyapatite results in poor polysulfide reuse. This invention removes some hydroxyapatite, reducing its content and enabling it to effectively adsorb polysulfides without affecting the battery's cycle reuse process. This achieves the goal of both adsorbing polysulfides and improving battery cycle capacity, avoiding irreversible reduction of active materials due to fixed polysulfides no longer participating in the reaction.

[0034] In this invention, the aperture of the sieve used for sieving is preferably 0.03-0.018 mm, more preferably 0.08 mm-0.018 mm, and the sieve residue obtained is a collagen fiber-hydroxyapatite composite material; the content of hydroxyapatite in the collagen fiber-hydroxyapatite composite material is 20-40 wt%.

[0035] In this invention, after sieving, the process preferably includes drying the obtained collagen fiber-hydroxyapatite composite material. The drying temperature is preferably 40-90°C, more preferably 50-80°C, and the drying time is preferably 12-72 hours, more preferably 24-60 hours. The drying is preferably carried out in an oven.

[0036] After obtaining the collagen fiber-hydroxyapatite composite material, the present invention pre-oxidizes and shapes the collagen fiber-hydroxyapatite composite material in an oxygen-containing environment to obtain an oxidized collagen fiber-hydroxyapatite composite material. In the present invention, the temperature of the pre-oxidation and shaping treatment is preferably 120-350℃, more preferably 160-300℃, specifically preferably 160℃, 250℃ or 300℃; the holding time of the pre-oxidation treatment is preferably 1-6h, more preferably 2-5h; the heating rate to the pre-oxidation and shaping treatment temperature is preferably 2-15℃ / min, more preferably 2-8℃ / min; after the holding time, the temperature is naturally cooled to 20-50℃, more preferably to 20-30℃; the oxygen-containing environment is preferably an air environment; the pre-oxidation and shaping treatment is preferably carried out in a muffle furnace; the present invention, through the pre-oxidation and shaping treatment, transforms the collagen fibers in the composite material into oxidized collagen fibers, and partial oxidative cross-linking occurs between the fibers.

[0037] After obtaining the oxidized collagen fiber-hydroxyapatite composite material, the present invention carbonizes the oxidized collagen fiber-hydroxyapatite composite material under a protective atmosphere to obtain a collagen-based fibrous carbon-hydroxyapatite nanocomposite material. In the present invention, the carbonization temperature is preferably 500–900℃, more preferably 600–900℃, specifically preferably 600℃, 700℃, or 900℃; the holding time for the carbonization is preferably 1–6 h, more preferably 2–5 h; the heating rate to the carbonization temperature is preferably 2–15℃ / min, more preferably 5–10℃ / min; after the holding time, the temperature is naturally cooled to 20–50℃, more preferably to 20–30℃; the protective atmosphere is preferably nitrogen; and the carbonization is preferably carried out in a tube furnace. This invention transforms oxidized collagen fibers into oxidized collagen fibrous carbon through carbonization, resulting in a collagen-based fibrous carbon-hydroxyapatite nanocomposite material. The obtained collagen-based fibrous carbon-hydroxyapatite nanocomposite material retains its original long-range structure to achieve long-range conductivity. In this invention, after carbonization, it is preferable to further grind the obtained collagen-based fibrous carbon-hydroxyapatite nanocomposite material. This invention does not have specific requirements for the particle size of the ground material, as long as it is uniform and fine. In a specific embodiment of this invention, the particle size of the ground collagen-based fibrous carbon-hydroxyapatite nanocomposite material is preferably 0.1–10 μm.

[0038] The present invention also provides a collagen-based fibrous carbon-hydroxyapatite nanocomposite material prepared by the preparation method described above, wherein the content of hydroxyapatite in the collagen-based fibrous carbon-hydroxyapatite nanocomposite material is preferably 20-80 wt%, and more preferably 30-60 wt%.

[0039] The present invention also provides the application of the collagen-based fibrous carbon-hydroxyapatite nanocomposite material described above in lithium-sulfur batteries. The collagen-based fibrous carbon-hydroxyapatite nanocomposite material is used to modify the separator of the lithium-sulfur battery. Specifically, the ordinary separator is modified using the collagen-based fibrous carbon-hydroxyapatite nanocomposite material to prepare a modified separator and apply it to the lithium-sulfur battery. The modified separator and the lithium-sulfur battery will be described in detail below.

[0040] This invention also provides a modified diaphragm, comprising a diaphragm and a modified layer disposed on the surface of the diaphragm; the modified layer comprises a conductive agent, a binder, and the collagen-based fibrous carbon-hydroxyapatite nanocomposite material described in the above-described scheme. In this invention, the mass ratio of the collagen-based fibrous carbon-hydroxyapatite nanocomposite material, the conductive agent, and the binder is preferably 1-3:1-3:1, more preferably 1.5-2.5:1.5-2.5:1; the conductive agent is preferably acetylene black (AB), and the binder is preferably polyvinylidene fluoride (PVDF); in a specific embodiment of this invention, when the diameter of the diaphragm is 19 mm, the loading of the collagen-based fibrous carbon-hydroxyapatite nanocomposite material on the surface of the diaphragm is preferably 0.150-0.330 mg / piece; the diaphragm is preferably a PP diaphragm, and this invention does not have special requirements for the type of PP diaphragm, and commercially available PP diaphragms well known to those skilled in the art can be used.

[0041] The present invention also provides a method for preparing the modified diaphragm described above, comprising the following steps:

[0042] Collagen-based fibrous carbon-hydroxyapatite nanocomposite material was mixed with conductive agent, binder and solvent to obtain collagen-based fibrous carbon-hydroxyapatite nanocomposite material slurry.

[0043] The collagen-based fibrous carbon-hydroxyapatite nanocomposite slurry was coated onto the surface of the diaphragm and then dried to obtain the modified diaphragm.

[0044] This invention involves mixing collagen-based fibrous carbon-hydroxyapatite nanocomposite materials with a conductive agent, a binder, and a solvent to obtain a collagen-based fibrous carbon-hydroxyapatite nanocomposite material slurry. In this invention, the solvent is N,N-dimethylformamide (DMF); the amount of solvent used is controlled to ensure that the mass fraction of the binder in the obtained collagen-based fibrous carbon-hydroxyapatite nanocomposite material slurry is 1-5%; preferably, the collagen-based fibrous carbon-hydroxyapatite nanocomposite materials are first mixed with the conductive agent and the binder, and then the resulting mixture is dissolved in the solvent. The mixing time of the collagen-based fibrous carbon-hydroxyapatite nanocomposite materials with the conductive agent and the binder is preferably 12-72 hours.

[0045] After obtaining a collagen-based fibrous carbon-hydroxyapatite nanocomposite slurry, the present invention coats the collagen-based fibrous carbon-hydroxyapatite nanocomposite slurry onto the surface of a diaphragm and then dries it to obtain a modified diaphragm. In the present invention, the coating is preferably performed using a coater, and the coating height of the coater is preferably 30-250 μm, more preferably 30-200 μm; the drying temperature is preferably 50-80℃, the drying time is preferably 12-72 h, and the drying is preferably performed in a vacuum drying oven; the present invention removes excess solvent by drying.

[0046] The present invention also provides a lithium-sulfur battery, comprising a lithium metal anode, a sulfur cathode, a separator, and an electrolyte, wherein the separator is the modified separator described in the above scheme or the modified separator prepared by the preparation method described in the above scheme.

[0047] In this invention, the preferred method for preparing the sulfur positive electrode sheet is as follows: sublimed sulfur, conductive carbon black, and gelatin solution are mixed to obtain a viscous slurry; the viscous slurry is coated onto the surface of aluminum foil and then dried and pressed sequentially to obtain a sulfur positive electrode sheet; the mass fraction of the gelatin solution is preferably 1-5%, and the solvent is preferably water; the mass ratio of the sublimed sulfur, conductive carbon black, and gelatin solution is preferably 63:30:7; the mixing method is preferably mechanical mixing; the aluminum foil is preferably cleaned with alcohol before coating; in a specific embodiment of this invention, when the diameter of the aluminum foil is 12 mm, the sulfur loading on the surface of the aluminum foil is preferably 1.000-1.300 mg / sheet; the drying temperature is preferably 40-80℃, and the drying time is preferably 6-24 h; this invention does not have special requirements for the pressing, and the sulfur positive electrode sheet can be pressed into a specific size according to actual needs; in a specific embodiment of this invention, the sulfur positive electrode sheet is preferably a circular sheet with a diameter of 10-15 mm.

[0048] In this invention, the electrolyte preferably comprises a solvent and a solute. The solvent is preferably a mixed solvent of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME), and the volume ratio of DOL to DME in the mixed solvent is preferably 1:1. The solute preferably comprises lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and LiNO3. The concentration of LiTFSI in the electrolyte is preferably 1M, and the concentration of LiNO3 is preferably 0.4M.

[0049] In a specific embodiment of the present invention, it is preferred to assemble a button cell into a lithium metal anode, a sulfur cathode, a separator, and an electrolyte, and then let the resulting button cell stand for 8 to 12 hours before conducting a charge-discharge cycle test at a rate of 1C.

[0050] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0051] Example 1

[0052] (1) Preparation of collagen-based fibrous carbon-hydroxyapatite nanocomposite materials:

[0053] 30g of fish scales were weighed and placed in a pulverizer for physical peeling for 8 minutes (rotation speed of 25000r / min). The collagen fiber / hydroxyapatite composite material was separated using a mesh screen with a pore size of 0.18mm and then dried in an oven at 60℃ for 24 hours.

[0054] The collagen fiber-hydroxyapatite composite material prepared above was subjected to pre-oxidation and shaping treatment in a muffle furnace. The heating process ranged from room temperature to 160°C, with a heating rate of 2°C / min. The holding time at 160°C was 2 hours. After holding, the material was naturally cooled to 30°C and then removed to obtain the oxidized collagen fiber-hydroxyapatite composite material.

[0055] The oxidized collagen fiber-hydroxyapatite composite material was carbonized in a tube furnace. The heating temperature range was from room temperature to 600℃, the heating rate was 5℃ / min, and the holding time at 600℃ was 2h. After holding, the material was naturally cooled to 50℃ and taken out to obtain collagen-based fibrous carbon-hydroxyapatite nanocomposite material (the content of hydroxyapatite was tested to be 34wt%). The material was then ground and collected for later use.

[0056] Figure 1 This is a SEM image of the collagen-based fibrous carbon-hydroxyapatite nanocomposite material prepared in this embodiment. Figure 1 As can be seen, the obtained nanocomposite material has a distinct fibrous structure.

[0057] (2) Preparation of modified diaphragms:

[0058] The collagen-based fibrous carbon-hydroxyapatite nanocomposite material prepared above was mixed with conductive agent acetylene black and binder polyvinylidene fluoride for 24 hours and then dissolved in N,N-dimethylformamide (DMF) solution to obtain a uniformly dispersed slurry. The mass ratio of collagen-based fibrous carbon-hydroxyapatite nanocomposite material to conductive agent acetylene black (AB) and binder polyvinylidene fluoride (PVDF) was 1:3:1, so that the mass concentration of polyvinylidene fluoride in the final slurry was 2wt%.

[0059] The uniformly dispersed slurry prepared above was coated onto the surface of a commercial PP diaphragm using a coater with a height of 120 μm. The coated diaphragm was then transferred to a vacuum drying oven to remove excess solvent at a temperature of 60 °C for 24 h. The diaphragm was then cut into small round pieces with a diameter of 19 mm using a cutting machine.

[0060] (3) Assemble lithium-sulfur batteries

[0061] The aforementioned separator was assembled with a standard lithium metal negative electrode and a sulfur positive electrode in a glove box to form a CR2025 button cell. The electrolyte was DOL / DME = 1:1 (volume ratio) + 1M LiTFSI + 0.4M LiNO3. The assembled battery was left to stand for 8 hours. Similarly, a lithium-sulfur battery was assembled with a standard PP separator, a lithium metal sheet, and a sulfur positive electrode as a control.

[0062] The preparation method of sulfur positive electrode is as follows: sublimed sulfur, conductive carbon black and gelatin solution are mechanically mixed in a mass ratio of 63:30:7, the mass concentration of gelatin is 2%, and a viscous slurry is obtained. This slurry is coated on aluminum foil that has been cleaned with alcohol. The aluminum foil is dried in an oven at 40°C for 24 hours and then taken out. The aluminum foil is then cut into round pieces with a diameter of 12 mm using a tablet press.

[0063] (4) Electrochemical performance testing of lithium-sulfur batteries

[0064] The lithium-sulfur battery was subjected to cycle performance testing on a charge-discharge device under 1C conditions. The test results are as follows: Figures 2-3 As shown.

[0065] Figure 2 This is a comparison chart of the discharge specific capacity of lithium-sulfur batteries assembled using modified and ordinary separators. Figure 3 This is a comparison chart of the coulombic efficiencies of lithium-sulfur batteries assembled using modified and ordinary separators.

[0066] Depend on Figures 2-3 The data shows that the lithium-sulfur battery assembled using the modified separator prepared in this invention has a higher discharge specific capacity and a more stable cycle efficiency compared with the lithium-sulfur battery using a conventional separator. This indicates that modifying the separator with the collagen-based fibrous carbon-hydroxyapatite nanocomposite material of this invention can effectively suppress the shuttle effect of polysulfides and improve the coulombic efficiency and cycle performance of the lithium-sulfur battery.

[0067] Example 2

[0068] (1) Preparation of collagen-based fibrous carbon-hydroxyapatite nanocomposite materials:

[0069] 30g of fish scales were weighed and placed in a pulverizer for physical peeling for 10min (speed 25000r / min). Collagen fiber-hydroxyapatite composite material was separated using a 0.10mm mesh screen and dried in a 50℃ oven for 48h.

[0070] The collagen fiber-hydroxyapatite composite material prepared above was subjected to pre-oxidation and shaping treatment in a muffle furnace. The heating process ranged from room temperature to 300°C, with a heating rate of 4°C / min. The holding time at 300°C was 4 hours. After holding, the material was naturally cooled to 30°C and then removed to obtain the oxidized collagen fiber-hydroxyapatite composite material.

[0071] The oxidized collagen fiber-hydroxyapatite composite material was carbonized in a tube furnace. The heating temperature range was from room temperature to 700℃, with a heating rate of 10℃ / min. The material was held at 700℃ for 6 hours, then allowed to cool naturally to 50℃ before being removed. This yielded a collagen-based fibrous carbon-hydroxyapatite nanocomposite material (with a hydroxyapatite content of 36 wt%), which was then ground and collected for later use. Scanning electron microscopy revealed that the obtained collagen-based fibrous carbon-hydroxyapatite nanocomposite material exhibited a distinct fibrous structure.

[0072] (2) Preparation of modified membrane

[0073] The above-mentioned collagen-based fibrous carbon-hydroxyapatite nanocomposite material was mixed with conductive agent acetylene black and binder polyvinylidene fluoride for 36 hours and then dissolved in N,N-dimethylformamide (DMF) solution to obtain a uniformly dispersed slurry. The ratio of collagen-based fibrous carbon-hydroxyapatite nanocomposite material to conductive agent acetylene black (AB) and binder polyvinylidene fluoride (PVDF) was 2:2:1, resulting in a final polyvinylidene fluoride mass concentration of 2.5 wt%.

[0074] The uniformly dispersed slurry prepared above was coated onto the surface of a commercial PP diaphragm using a coater with a height of 90 μm. The coated diaphragm was then transferred to a vacuum drying oven to remove excess solvent at 50°C for 36 hours. Finally, it was cut into small round pieces with a diameter of 19 mm using a cutting machine.

[0075] (3) Assemble lithium-sulfur batteries

[0076] The modified separator described above was assembled with a standard lithium metal anode and a sulfur cathode in a glove box to form a CR2025 button cell. The electrolyte was DOL / DME = 1:1 (volume ratio) + 1M LiTFSI + 0.4M LiNO3. The assembled cells were allowed to stand for 10 hours. Similarly, a lithium-sulfur battery was assembled with a standard separator, lithium metal, and a sulfur cathode as a control. The preparation method of the sulfur cathode was the same as in Example 1.

[0077] (4) Electrochemical performance testing of lithium-sulfur batteries

[0078] The lithium-sulfur battery was subjected to cycle performance testing on a charge-discharge device under 1C conditions. The test results show that, compared with lithium-sulfur batteries using ordinary separators, the lithium-sulfur battery assembled using the modified separator prepared in this invention has a higher discharge specific capacity and a more stable cycle efficiency.

[0079] Example 3

[0080] (1) Preparation of collagen-based fibrous carbon-hydroxyapatite nanocomposite materials:

[0081] 30g of fish scales were weighed and crushed in a pulverizer for 3 minutes. The collagen fiber-hydroxyapatite composite material was separated using a 0.08mm mesh screen and dried in an 80℃ oven for 12 hours.

[0082] The collagen fiber-hydroxyapatite composite material prepared above was subjected to pre-oxidation and shaping treatment in a muffle furnace. The heating process ranged from room temperature to 250°C, with a heating rate of 8°C / min. The holding time at 250°C was 5 hours. After holding, the material was naturally cooled to 30°C and then removed to obtain the oxidized collagen fiber-hydroxyapatite composite material.

[0083] The prepared oxidized collagen fiber-hydroxyapatite composite fibers were carbonized in a tube furnace. The heating temperature range was from room temperature to 900℃, with a heating rate of 15℃ / min. The holding time at 900℃ was 6 hours. After holding, the material was naturally cooled to 50℃ and removed to obtain a collagen-based fibrous carbon-hydroxyapatite nanocomposite material (the hydroxyapatite content was found to be 43 wt%). This material was then ground and collected for later use. Scanning electron microscopy revealed that the obtained collagen-based fibrous carbon-hydroxyapatite nanocomposite material exhibited a distinct fibrous structure.

[0084] (2) Preparation of modified membrane

[0085] The above-mentioned collagen-based fibrous carbon-hydroxyapatite nanocomposite material was mixed with conductive agent acetylene black and binder polyvinylidene fluoride for 72 hours and then dissolved in N,N-dimethylformamide (DMF) solution to obtain a uniformly dispersed slurry. The ratio of the oxidized collagen-based fibrous carbon / hydroxyapatite nanocomposite material to conductive agent acetylene black (AB) and binder polyvinylidene fluoride (PVDF) was 1.5:2.5:1, resulting in a final polyvinylidene fluoride mass concentration of 4 wt%.

[0086] The uniformly dispersed slurry prepared above was coated onto the surface of a commercial PP diaphragm using a coater with a height of 200 μm. The coated diaphragm was then transferred to a vacuum drying oven to remove excess solvent at 80°C for 72 hours. Finally, it was cut into small round pieces with a diameter of 19 mm using a cutting machine.

[0087] (3) Assemble lithium-sulfur batteries

[0088] The modified separator described above was assembled with a standard lithium metal anode and a sulfur cathode in a glove box to form a CR2025 button cell. The electrolyte was DOL / DME = 1:1 (volume ratio) + 1M LiTFSI + 0.4M LiNO3. The assembled cells were allowed to stand for 12 hours. Similarly, a lithium-sulfur battery was assembled with a standard separator, lithium metal, and a sulfur cathode as a control. The preparation method of the sulfur cathode was the same as in Example 1.

[0089] (4) Electrochemical performance testing of lithium-sulfur batteries

[0090] The lithium-sulfur battery was subjected to cycle performance testing on a charge-discharge device under 1C conditions. The test results show that, compared with lithium-sulfur batteries using ordinary separators, the lithium-sulfur battery assembled using the modified separator prepared in this invention has a higher discharge specific capacity and a more stable cycle efficiency.

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing collagen-based fibrous carbon-hydroxyapatite nanocomposite, characterized by, The preparation steps are: The fish scales are crushed and sieved to obtain collagen fiber-hydroxyapatite composite material; the crushing speed is 10000-50000 r / min, and the crushing time is 2-10 min; the sieving is performed with a sieve having a mesh size of 0.03-0.018 mm, and the sieve residue is the collagen fiber-hydroxyapatite composite material; the content of hydroxyapatite in the collagen fiber-hydroxyapatite composite material is 20-40 wt%; The collagen fiber-hydroxyapatite composite material is subjected to pre-oxidation and shaping treatment in an oxygen-containing environment to obtain oxidized collagen fiber-hydroxyapatite composite material; the pre-oxidation and shaping treatment is performed at a temperature of 120-350 ℃ for 1-6 h, and the temperature is raised to the pre-oxidation and shaping treatment temperature at a rate of 2-15 ℃ / min; after the heat preservation is completed, the temperature is naturally lowered to 20-50 ℃; The oxidized collagen fiber-hydroxyapatite composite material is subjected to carbonization treatment in a protective atmosphere to obtain collagen-based fibrous carbon-hydroxyapatite nanocomposite material.

2. The production method according to claim 1, characterized by, After the sieving, the obtained collagen fiber-hydroxyapatite composite material is further dried; the drying temperature is 40-90 ℃, and the drying time is 12-72 h.

3. The production method according to claim 1, characterized by, The carbonization treatment is performed at a temperature of 500-900 ℃ for 1-6 h, and the temperature is raised to the carbonization treatment temperature at a rate of 2-15 ℃ / min; after the heat preservation is completed, the temperature is naturally lowered to 20-50 ℃.

4. The collagen-based fibrous carbon-hydroxyapatite nanocomposite material prepared by the preparation method of any one of claims 1-3.

5. Use of the collagen-based fibrous carbon-hydroxyapatite nanocomposite material according to claim 4 in lithium-sulfur batteries, characterized by the fact that, The collagen-based fibrous carbon-hydroxyapatite nanocomposite material is used for modifying the separator of the lithium-sulfur battery.

6. A modified separator, characterized by, The separator and a modified layer provided on the surface of the separator; the components of the modified layer include a conductive agent, a binder, and the collagen-based fibrous carbon-hydroxyapatite nanocomposite material of claim 5.

7. The modified separator of claim 6, wherein, The mass ratio of the collagen-based fibrous carbon-hydroxyapatite nanocomposite material, the conductive agent, and the binder is 1-3:1-3:

1.

8. The method of producing the modified separator according to claim 6 or 7, characterized by, The steps include: The collagen-based fibrous carbon-hydroxyapatite nanocomposite material, a conductive agent, a binder, and a solvent are mixed to obtain collagen-based fibrous carbon-hydroxyapatite nanocomposite material slurry; The collagen-based fibrous carbon-hydroxyapatite nanocomposite material slurry is coated on the surface of the separator and dried to obtain a modified separator.

9. A lithium-sulfur battery comprising a metal lithium negative electrode sheet, a sulfur positive electrode sheet, a separator, and an electrolyte, characterized by, The separator is the modified separator of claim 6 or 7 or the modified separator prepared by the preparation method of claim 8.

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