Collagen-based solid electrolyte as well as preparation method and application thereof

Abstract

The invention discloses a collagen-based solid electrolyte as well as a preparation method and application thereof. The preparation method comprises the following steps: S1, preparing a collagen solution; s2, carrying out electrostatic spinning by adopting the collagen solution to obtain an electrospun membrane; s3, carrying out washing and vacuum drying on the electrospun membrane to obtain a dried membrane; s4, the dried film is rolled and shaped, and a rolled film is obtained; s5, the rolled film is soaked in a metal salt solution, and a wet film is obtained; and S6, carrying out extrusion liquid discharge on the wet film, and carrying out vacuum drying to obtain the collagen-based solid electrolyte. The invention can provide the solid electrolyte which takes protein as a main body, does not use synthetic macromolecules, is environment-friendly, degradable and high-voltage-resistant, and can be matched with conventional positive and negative electrodes, so that technical support is provided for a solid-state battery.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to a collagen-based solid electrolyte and a preparation method and application thereof. Background Art

[0002] Solid-state batteries are a new type of battery that uses solid electrolytes to replace separators and organic electrolytes. Compared with conventional lithium-ion batteries, solid-state batteries have the following advantages: (1) Good safety. There are no large amounts of organic liquid components in the solid electrolyte, which means that even if the solid-state battery is damaged, it will not catch fire or explode. (2) High energy density. Compared with organic electrolytes, solid electrolytes are more resistant to high voltages. Therefore, solid-state batteries can use high-performance materials such as high-voltage positive electrodes and metal negative electrodes to achieve a high energy density of more than 500Wh / kg.

[0003] As the core component of solid-state batteries, solid electrolytes are the key to improving the energy density, stability and safety of solid-state batteries. In order to meet the requirements of practical applications, solid electrolytes must meet the following conditions: (1) high ionic conductivity (more than 1mS / cm at room temperature); (2) good deformability; (3) sufficiently low cost. At present, the developed solid electrolytes mainly include two categories: inorganic solid electrolytes and polymer solid electrolytes. Among them, inorganic solid electrolytes have high ionic conductivity (more than 1mS / cm at room temperature), but poor deformability, and require the use of expensive raw materials such as rare earth, lithium sulfide or indium chloride for synthesis, and the cost of large-scale manufacturing is high. In contrast, polymer solid electrolytes have good flexibility, easy processing, low raw material cost, and have the potential for large-scale production, but they also have low ionic conductivity (10 at room temperature). -5 -10 -2 mS / cm), difficult to degrade and regenerate, etc. Therefore, the development of high-performance, economical, and environmentally friendly polymer solid electrolytes will help promote the practical application of solid-state batteries. Summary of the invention

[0004] In view of the above problems, the present invention aims to provide a collagen-based solid electrolyte and a preparation method and application thereof.

[0005] The technical solution of the present invention is as follows:

[0006] On the one hand, a method for preparing a collagen-based solid electrolyte is provided, comprising the following steps:

[0007] S1: prepare collagen solution;

[0008] S2: using the collagen solution to perform electrospinning to obtain an electrospun membrane;

[0009] S3: washing and vacuum drying the electrospun membrane to obtain a dry membrane;

[0010] S4: rolling and shaping the dried film to obtain a rolled film;

[0011] S5: soaking the rolled film in a metal salt solution to obtain a wet film;

[0012] S6: Extruding and draining the wet film, and vacuum drying the wet film to obtain the collagen-based solid electrolyte.

[0013] Preferably, in step S1, preparing the collagen solution specifically comprises the following sub-steps: dissolving the collagen product in glacial acetic acid, and then heating at 80-90° C. for 5-8 hours to obtain the collagen solution.

[0014] Preferably, the collagen product is skin collagen or gelatin, and the concentration of the collagen solution is 16-20%.

[0015] Preferably, in step S2, when electrospinning is performed, the applied voltage is 25-29 kV and the feeding speed is 0.3-0.4 mL / h.

[0016] Preferably, in step S3, the electrospun membrane is washed with anhydrous ethanol and then vacuum dried at 20-30° C. for 10-12 h, and the weight of the obtained dry membrane is 100-105% of the weight of the electrospun membrane.

[0017] Preferably, in step S4, when the dried film is rolled and shaped, the thickness of the rolled film is controlled to be 85±15 μm.

[0018] Preferably, in step S5, the solute used in the metal salt solution is any one of lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide, sodium bis(trifluoromethanesulfonyl imide), sodium bis(fluorosulfonyl imide, potassium bis(trifluoromethanesulfonyl imide), and potassium bis(fluorosulfonyl imide); and the solvent used in the metal salt solution is tetrahydrofuran or a mixture of ethylene glycol dimethyl ether and 1,3-dioxolane in a volume ratio of 1:1.

[0019] Preferably, the concentration of the metal salt solution is 1-2 mol / L, and the soaking time is 1-2 h.

[0020] On the other hand, a collagen-based solid electrolyte prepared by any of the above-mentioned preparation methods for a collagen-based solid electrolyte and its application in a solid-state battery are also provided.

[0021] The beneficial effects of the present invention are:

[0022] 1. Environmentally friendly and degradable. The present invention is a solid electrolyte with protein as the main body, without adding synthetic polymer materials and containing almost no liquid.

[0023] 2. Good electrochemical performance: The present invention has a wide electrochemical window and can work stably under high voltage conditions.

[0024] 3. Can match conventional electrodes. The present invention can match lithium iron phosphate or ternary material positive electrodes and lithium metal negative electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 these drawings without paying creative labor.

[0026] Figure 1 It is a schematic flow chart of the preparation method of the collagen-based solid electrolyte of the present invention;

[0027] Figure 2 Schematic diagram of film-forming test results of different proteins;

[0028] Figure 3 This is a schematic diagram of the thermogravimetric test results of Example 1;

[0029] Figure 4 is an optical photograph of Example 1;

[0030] Figure 5 It is a schematic diagram of the performance comparison results of lithium-lithium iron phosphate (Li-LiFePO4) batteries;

[0031] Figure 6 Schematic diagram of performance comparison results of lithium-ternary material (Li-NCM 811) batteries;

[0032] Figure 7 Schematic diagram of the test results of the degradability of Example 1 and commercial polypropylene diaphragm. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, in the absence of conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those generally understood by those of ordinary skill in the art to which this application belongs. The words "including" or "comprising" and the like used in the disclosure of the present invention mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0034] On the one hand, if Figure 1 As shown, the present invention provides a method for preparing a collagen-based solid electrolyte, comprising the following steps:

[0035] S1: Prepare collagen solution.

[0036] In a specific embodiment, preparing the collagen solution specifically includes the following sub-steps: dissolving the collagen product in glacial acetic acid, and then heating at 80-90° C. for 5-8 hours to obtain the collagen solution. Optionally, the collagen product is skin collagen or gelatin, and the concentration of the collagen solution is 16-20%.

[0037] In the above embodiment, glacial acetic acid is used as a solvent to prepare the collagen solution, which is environmentally friendly. Moreover, the collagen product can only be fully dissolved by heating in glacial acetic acid to obtain a spinning solution with good fluidity; it is also difficult to dissolve by heating in other solvents such as deionized water, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), anhydrous ethanol, dimethyl sulfoxide, chloroform, acetone, tetrahydrofuran, and acetonitrile.

[0038] In the present invention, the prepared protein solution is a collagen solution. The collagen used has the characteristics of large output and low price. Compared with other large-scale produced proteins, such as soy protein, pea protein, wheat protein, egg protein, etc., it has better film-forming properties and better flexibility of the protein film. Figure 2 shown.

[0039] S2: using the collagen solution to perform electrospinning to obtain an electrospun membrane.

[0040] In a specific embodiment, during electrospinning, the applied voltage is 25-29 kV and the feeding rate is 0.3-0.4 mL / h. It should be noted that electrospinning is a prior art, and the parameters used in this embodiment are only preferred parameters of the present invention. The present invention can also perform electrospinning under other parameter conditions to obtain the electrospun membrane.

[0041] S3: washing and vacuum drying the electrospun membrane to obtain a dry membrane.

[0042] In a specific embodiment, the electrospun membrane is washed with anhydrous ethanol and then vacuum dried at 20-30° C. for 10-12 h, and the weight of the obtained dry membrane is 100-105% of the weight of the electrospun membrane.

[0043] It should be noted that the washing and vacuum drying parameters in the above-mentioned embodiment are only preferred parameters of the present invention. The present invention can also perform washing and vacuum drying under other parameter conditions to obtain the dried film.

[0044] S4: rolling the dried film to obtain a rolled film.

[0045] In a specific embodiment, when the dry film is subjected to roller pressing and shaping, the thickness of the rolled film is controlled to be 85±15 μm.

[0046] It should be noted that the thickness of the rolled film is controlled to ensure the performance and safety of the battery. If the film thickness is too large, the internal resistance of the prepared solid electrolyte membrane will increase and the performance will be reduced. If the film thickness is too small, the stability of the prepared solid electrolyte membrane will be reduced, and the battery will short-circuit during use.

[0047] S5: soaking the rolled film in a metal salt solution to obtain a wet film.

[0048] In a specific embodiment, the solute used in the metal salt solution is any one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium bis(fluorosulfonyl)imide (NaFSI), potassium bis(trifluoromethanesulfonyl)imide (KTFSI), and potassium bis(fluorosulfonyl)imide (KFSI); the solvent used in the metal salt solution is tetrahydrofuran (THF) or a mixture of ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1.

[0049] In the above embodiments, the solvent used in the present invention can be fully removed during the drying process to obtain a solid electrolyte with collagen and metal salt as the main body. Other solvents in the prior art, such as carbonate solvents (ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), etc.) have high boiling points and low volatility, and are difficult to remove during the drying process, and the required solid electrolyte cannot be obtained.

[0050] In a specific embodiment, the concentration of the metal salt solution is 1-2 mol / L, and the immersion time is 1-2 h. It should be noted that too low a metal salt concentration will increase the residual solvent content and prolong the subsequent vacuum drying time. Too high a metal salt concentration cannot ensure effective dissolution of the metal salt in the solvent. Too short an immersion time cannot ensure sufficient contact between the metal salt and collagen, and too long an immersion time has no significant improvement in the performance of the prepared solid electrolyte membrane.

[0051] S6: Extruding and draining the wet film, and vacuum drying the wet film to obtain the collagen-based solid electrolyte.

[0052] In a specific embodiment, when the wet film is squeezed to drain the liquid, the weight of the wet film is ensured to be 280-300% of the initial dry film weight, and the wet film after squeezing and draining the liquid is vacuum dried at 20-30° C. for 1-2 hours.

[0053] It should be noted that the extrusion drainage and vacuum drying parameters in the above-mentioned embodiment are only preferred parameters of the present invention. The present invention can also perform extrusion drainage and vacuum drying under other parameter conditions to obtain the solid electrolyte.

[0054] On the other hand, a collagen-based solid electrolyte prepared by any of the above-mentioned preparation methods for a collagen-based solid electrolyte and its application in a solid-state battery are also provided.

[0055] Example 1

[0056] A collagen-based solid electrolyte is prepared by the following steps:

[0057] (1) Dissolve skin collagen in glacial acetic acid and then heat at 80°C for 5 h to obtain a collagen solution with a concentration of 20%.

[0058] (2) The collagen solution is subjected to electrospinning at a voltage of 25 kV and a feed rate of 0.4 mL / h to obtain an electrospun membrane. The electrospun membrane is collected on a release paper attached to a metal drum.

[0059] (3) The electrospun membrane was washed with anhydrous ethanol and then vacuum dried at 25° C. for 12 h to obtain a dry membrane.

[0060] (4) The dried film is subjected to roller pressing to obtain a roller pressed film with a thickness controlled at 85±15 μm.

[0061] (5) Soaking the rolled film in a metal salt solution for 1 hour to obtain a wet film; the solute used in the metal salt solution is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), the solvent is a mixture of ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1, and the concentration of the metal salt solution is 1 mol / L.

[0062] (6) The wet film is squeezed to drain the liquid, and vacuum dried at 25° C. for 1 hour to obtain the collagen-based solid electrolyte.

[0063] Example 2

[0064] Different from Example 1, the collagen product used in step (1) of this example is gelatin.

[0065] Example 3

[0066] Different from Example 1, the heating condition in step (1) of this example is 85°C.

[0067] Example 4

[0068] Different from Example 1, the heating condition in step (1) of this example is 90°C.

[0069] Example 5

[0070] Different from Example 1, the heating time in step (1) of this example is 6 hours.

[0071] Example 6

[0072] Different from Example 1, the heating time in step (1) of this example is 7 hours.

[0073] Example 7

[0074] Different from Example 1, the heating time in step (1) of this example is 8 hours.

[0075] Example 8

[0076] The difference from Example 1 is that the concentration in step (1) of this example is 16%.

[0077] Example 9

[0078] The difference from Example 1 is that the concentration in step (1) of this example is 18%.

[0079] Example 10

[0080] Different from Example 1, the voltage in step (2) of this example is 27 kV.

[0081] Embodiment 11

[0082] Different from Example 1, the voltage in step (2) of this example is 29 kV.

[0083] Example 12

[0084] Different from Example 1, the feeding rate in step (2) of this example is 0.3 mL / h.

[0085] Example 13

[0086] Different from Example 1, the feeding rate in step (2) of this example is 0.35 mL / h.

[0087] Embodiment 14

[0088] Different from Example 1, the vacuum drying temperature in step (3) of this example is 20°C.

[0089] Embodiment 15

[0090] Different from Example 1, the vacuum drying temperature in step (3) of this example is 30°C.

[0091] Example 16

[0092] Different from Example 1, the vacuum drying time in step (3) of this example is 10 hours.

[0093] Embodiment 17

[0094] Different from Example 1, the vacuum drying time in step (3) of this example is 11 hours.

[0095] Embodiment 18

[0096] Different from Example 1, the soaking time in step (5) of this example is 1.5 hours.

[0097] Embodiment 19

[0098] Different from Example 1, the soaking time in step (5) of this example is 2 hours.

[0099] Embodiment 20

[0100] Different from Example 1, the solute of the metal salt solution used in step (5) of this example is lithium bis(fluorosulfonyl)imide (LiFSI).

[0101] Embodiment 21

[0102] Different from Example 1, the solute of the metal salt solution used in step (5) of this example is sodium bis(trifluoromethanesulfonyl)imide (NaTFSI).

[0103] Embodiment 22

[0104] Different from Example 1, the solute of the metal salt solution used in step (5) of this example is sodium bis(fluorosulfonyl)imide (NaFSI).

[0105] Embodiment 23

[0106] Different from Example 1, the solute of the metal salt solution used in step (5) of this example is potassium bis(trifluoromethanesulfonyl)imide (KTFSI).

[0107] Embodiment 24

[0108] Different from Example 1, the solute of the metal salt solution used in step (5) of this example is potassium bis(fluorosulfonyl)imide (KFSI).

[0109] Embodiment 25

[0110] Different from Example 1, the solvent of the metal salt solution used in step (5) of this example is tetrahydrofuran.

[0111] Embodiment 26

[0112] Different from Example 1, the concentration of the metal salt solution used in step (5) of this example is 1.5 mol / L.

[0113] Embodiment 27

[0114] Different from Example 1, the concentration of the metal salt solution used in step (5) of this example is 2 mol / L.

[0115] Embodiment 28

[0116] Different from Example 1, the vacuum drying time in step (6) of this example is 1.5 h.

[0117] Embodiment 29

[0118] Different from Example 1, the vacuum drying time in step (6) of this example is 2 hours.

[0119] Embodiment 30

[0120] Different from Example 1, the vacuum drying temperature in step (6) of this example is 20°C.

[0121] Embodiment 31

[0122] Different from Example 1, the vacuum drying temperature in step (6) of this example is 30°C.

[0123] Comparative Example 1

[0124] Different from Example 1, this comparative example is a conventional commercial electrolyte, which is in a liquid state and plays the role of conducting the battery. The solute is lithium hexafluorophosphate, and the solvent is a mixture of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1:1. When assembling the battery, the electrolyte needs to be injected into the polypropylene diaphragm to ensure that the battery does not short-circuit.

[0125] Test Example 1

[0126] The solid electrolyte of Example 1 was subjected to a thermogravimetric test, and the results were as follows: Figure 3 As shown. Figure 3 It can be seen that the mass fraction of the present invention decreases by less than 10% before 100°C, which means that the residual liquid content is less than 10%, and it is mainly solid, which meets the conditions of solid electrolyte. However, the conventional electrolyte in Comparative Example 1 is mainly liquid and does not belong to the category of solid electrolyte.

[0127] Test Example 2

[0128] The optical photograph of the solid electrolyte of Example 1 is as follows Figure 4 The performance of Example 1 and Comparative Example 1 is shown in Table 1:

[0129] Table 1 Performance test results of the solid electrolyte of Example 1 and the conventional electrolyte of Comparative Example 1

[0130] product Electrolyte status Electrochemical Window (V) Ionic conductivity (mS / cm) Migration number Example 1 Solid State 4.7 1.1 0.8 Comparative Example 1 Liquid 4.3 10.5 0.37

[0131] It can be seen from Table 1 that the solid electrolyte of the present invention has a higher electrochemical window than conventional electrolytes, can maintain better working stability at high voltages, and has an ionic conductivity greater than 1 mS / cm, and has reached a relatively high level of performance among solid electrolytes.

[0132] In addition to the performance of the above-mentioned embodiment 1, the solid electrolytes of other embodiments of the present invention have an electrochemical window in the range of 3.7-4.7 V, an ionic conductivity in the range of 0.6-1.1 mS / cm, and a migration number in the range of 0.7-0.8.

[0133] Test Example 3

[0134] The solid electrolyte of Example 1 and the conventional electrolyte of Comparative Example 1 were used to assemble a lithium-iron phosphate (Li-LiFePO4) battery, and the performance test was carried out. The results are as follows: Figure 5 As shown. Figure 5 It can be seen that within the operating voltage range of 2.5-4V of the lithium-lithium iron phosphate battery, Example 1 is more stable in discharge specific capacity and coulombic efficiency than Comparative Example 1, which indicates that Example 1 can better match the lithium metal negative electrode and the lithium iron phosphate positive electrode.

[0135] Test Example 4

[0136] The solid electrolyte of Example 1 and the conventional electrolyte of Comparative Example 1 were used to assemble a lithium-ternary material (Li-NCM 811) battery, and the performance test was performed. The results are as follows: Figure 6 As shown. Figure 6 It can be seen that within the operating voltage range of 2.8-4.3V of the lithium-ternary material battery, Example 1 is more stable in discharge specific capacity and coulombic efficiency than Comparative Example 1, which indicates that Example 1 can better match the lithium metal negative electrode and the ternary material positive electrode.

[0137] Test Example 5

[0138] The degradability test was carried out using the solid electrolyte of Example 1 and the commercial polypropylene separator. The results are as follows: Figure 7 As shown. Figure 7It can be seen that the present invention has good degradability and can be completely degraded in a natural environment in 2 weeks, while the commercial polypropylene diaphragm has no obvious changes after 2 weeks.

[0139] It should be noted that the above test examples are only partial test results of the present invention. The collagen-based solid electrolytes obtained by the preparation method of the present invention have good electrochemical properties and can match conventional electrodes.

[0140] In summary, the present invention can provide a solid electrolyte that is protein-based, does not use synthetic polymers, is environmentally friendly and degradable, is high-voltage resistant, and can match conventional positive and negative electrodes. Compared with the prior art, the present invention has significant progress.

[0141] The above description is only a representative embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, uses the above-disclosed technical contents to make some changes or modifications to the embodiments are equivalent embodiments of the present invention. However, any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a collagen-based solid electrolyte, characterized in that: The following steps are involved: S1: prepare collagen solution; S2: using the collagen solution to perform electrospinning to obtain an electrospun membrane; S3: washing and vacuum drying the electrospun membrane to obtain a dry membrane; S4: rolling and shaping the dried film to obtain a rolled film; S5: soaking the rolled film in a metal salt solution to obtain a wet film; S6: Extruding and draining the wet film, and vacuum drying the wet film to obtain the collagen-based solid electrolyte.

2. The method for preparing the collagen-based solid electrolyte according to claim 1, characterized in that: In step S1, preparing the collagen solution specifically includes the following sub-steps: dissolving the collagen product in glacial acetic acid, and then heating at 80-90° C. for 5-8 hours to obtain the collagen solution.

3. The method for preparing the collagen-based solid electrolyte according to claim 2, characterized in that: The collagen product is skin collagen or gelatin, and the concentration of the collagen solution is 16-20%.

4. The method for preparing the collagen-based solid electrolyte according to claim 1, characterized in that: In step S2, during electrospinning, the applied voltage is 25-29 kV and the feeding rate is 0.3-0.4 mL / h.

5. The method for preparing the collagen-based solid electrolyte according to claim 1, characterized in that: In step S3, the electrospun membrane is washed with anhydrous ethanol and then vacuum dried at 20-30° C. for 10-12 h, and the weight of the obtained dry membrane is 100-105% of the weight of the electrospun membrane.

6. The method for preparing the collagen-based solid electrolyte according to claim 1, characterized in that: In step S4, when the dried film is rolled and shaped, the thickness of the rolled film is controlled to be 85±15 μm.

7. The method for preparing the collagen-based solid electrolyte according to claim 1, characterized in that: In step S5, the solute used in the metal salt solution is any one of lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide, sodium bis(trifluoromethanesulfonyl imide), sodium bis(fluorosulfonyl imide, potassium bis(trifluoromethanesulfonyl imide), and potassium bis(fluorosulfonyl imide); the solvent used in the metal salt solution is tetrahydrofuran or a mixture of ethylene glycol dimethyl ether and 1,3-dioxolane in a volume ratio of 1:

1.

8. The method for preparing the collagen-based solid electrolyte according to claim 7, characterized in that: The concentration of the metal salt solution is 1-2 mol / L, and the soaking time is 1-2 hours.

9. A collagen-based solid electrolyte, characterized in that: The collagen-based solid electrolyte is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the collagen-based solid electrolyte as claimed in claim 9 in a solid-state battery.

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