Double bond regulated cellulose-based gel polymer electrolyte and method for preparing the same
Patent Information
- Application Number
- CN202310381775.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-04-11
- Publication Date
- 2026-09-22
- Estimated Expiration
- 2043-04-11
AI Technical Summary
[0003]尽管已经报道了各类纤维素基凝胶聚合物电解质在锂离子电池中的应用，但是相比于其他聚合物而言，纤维素本身难以溶解，未改性时对商用的碳酸脂类电解液相溶性、浸润性较差，如何通过改性、复合、共混等方法对纤维素进行结构优化设计出可用于锂离子电池的凝胶聚合物电解质仍值得进一步探索
[0027](1)本发明使用的原料来源广泛，成本低廉，绿色可降解，是环境友好型材料。
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Figure CN116417683B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of modified cellulose gel polymer electrolytes and lithium-ion battery electrolytes, specifically relating to a method for preparing a double-bond regulated cellulose-based gel polymer electrolyte. Background Technology
[0002] Gel polymer electrolytes combine the advantages of all-solid polymer electrolytes and organic liquid electrolytes, exhibiting high ionic conductivity while being less prone to leakage due to the smaller electrolyte volume, thus providing high safety. Cellulose's flexible modifiability lays the foundation for its application in gel polymer electrolytes. Cellulose and its derivatives, such as methylcellulose, cellulose acetate, and hydroxyethylcellulose, have been used as substrates or incorporated into gel polymer electrolytes, opening up entirely new avenues for the application of natural macromolecular materials.
[0003] Although the application of various cellulose-based gel polymer electrolytes in lithium-ion batteries has been reported, cellulose itself is difficult to dissolve compared to other polymers. When unmodified, it has poor compatibility and wettability with commercially available carbonate electrolytes. Further exploration is needed to optimize the structure of cellulose through modification, compounding, blending and other methods to design gel polymer electrolytes that can be used in lithium-ion batteries. Summary of the Invention
[0004] To overcome the shortcomings of existing technologies, the present invention aims to provide a cellulose-based gel polymer electrolyte with high ionic conductivity and high capacity retention, regulated by double bonds, and its preparation method. Starting from the dissolution and etherification modification of cellulose, ester groups are introduced onto allyl cellulose via click reaction to prepare cellulose derivatives, significantly enhancing their compatibility in commercial carbonate electrolytes and obtaining an uncrosslinked gel polymer electrolyte with high ionic conductivity, high lithium-ion transference number, and high capacity retention. Furthermore, the performance of the gel polymer electrolyte is further optimized by adding 1,4-butanediol bis(thioglycolate) as a crosslinking agent. The high efficiency of click reaction enables stepwise regulation of double bonds, resulting in a crosslinked gel polymer electrolyte with high ionic conductivity, high lithium-ion transference number, and high capacity retention, and providing a new feasible approach for the targeted and quantitative substitution of cellulose.
[0005] This invention aims to improve the incompatibility of natural macromolecules with commercial ester electrolytes in lithium-ion batteries, thereby increasing ionic conductivity and interfacial compatibility, and ultimately enhancing the electrochemical performance of lithium-ion batteries. Furthermore, this invention discloses a method for preparing cellulose-based gel electrolytes, wherein uncrosslinked gel polymer electrolytes are obtained by direct dissolution and drying, and crosslinked gel polymer electrolytes are cured using ultraviolet light. The process is simple, rapid, and easy to operate, and has significant application prospects in the field of lithium-ion batteries.
[0006] The objective of this invention is achieved by at least one of the following technical solutions:
[0007] A method for preparing a double-bond regulated cellulose-based gel polymer electrolyte includes the following steps: S1, preparation of allyl cellulose:
[0008] (1) Prepare an alkali / urea solution by mixing a certain amount of sodium hydroxide, urea and deionized water in a mass ratio of (4-8): (10-12): (80-86). Add cellulose powder at -16℃ to -20℃ and stir at a speed of 1800-2400 r / min for 5-10 min to obtain a cellulose solution with a mass fraction of 3%-6%.
[0009] (2) Under a nitrogen atmosphere and at 30-35°C, allyl glycidyl ether is slowly added dropwise to the cellulose solution. Under light-protected conditions, the reaction is carried out under mechanical or magnetic stirring for 24-30 hours. The product after the reaction is precipitated and washed in acetone solvent, then placed in a dialysis bag for dialysis for 4-7 days, and then freeze-dried at -50 to -60°C for 48-72 hours to obtain allyl cellulose.
[0010] S2. Preparation of ester-containing cellulose derivatives:
[0011] (1) Dissolve the above allyl cellulose in a solvent and prepare an allyl cellulose solution with a mass fraction of 2-5%;
[0012] (2) A certain amount of methyl mercaptoacetate and initiator were slowly added dropwise to the allyl cellulose solution. The mixture was mechanically stirred at room temperature and reacted under 365 nm ultraviolet light for 2-3 hours. After the reaction was completed, the product was directly placed into a dialysis bag for dialysis for 4-7 days and then freeze-dried at -50 to -60℃ for 48-72 hours to obtain an allyl cellulose derivative containing ester groups.
[0013] S3. Preparation of uncrosslinked cellulose-based gel polymer electrolyte:
[0014] (1) The above-mentioned ester-containing cellulose derivatives are dissolved in a solvent and prepared into a solution with a mass fraction of 2-3%. The solution is centrifuged at a speed of 8000-10000 r / min to obtain a casting solution.
[0015] (2) Cast the casting solution into a plastic petri dish, dry it at 50-60°C and cut it to obtain a dry film. Dry it in a vacuum oven at 60-65°C for 4-6 hours to completely remove water and then transfer it to a glove box. Soak it in electrolyte for 8-24 hours to obtain an uncrosslinked cellulose-based gel polymer electrolyte.
[0016] S4. Preparation of cross-linked cellulose-based gel polymer electrolytes:
[0017] (1) Dissolve the above-mentioned ester-containing cellulose derivatives in a solvent to prepare a solution with a mass fraction of 3-4%, and centrifuge at a speed of 8000-10000 r / min to remove a small amount of undissolved cellulose derivatives.
[0018] (2) Add 1,4-butanediol bis(thioglycolate) and initiator, stir evenly to obtain casting solution;
[0019] (3) Cast the casting solution into a plastic petri dish, irradiate with 365nm ultraviolet light for 2-10 min to form a gel, dry at 50-60℃ and cut to obtain a dry film, dry in a vacuum oven at 60-65℃ for 4-6 h to completely remove water and then transfer to a glove box and soak in electrolyte for 8-24 h to obtain a cross-linked cellulose-based gel polymer electrolyte.
[0020] Further, in step S1(2), the molar ratio of allyl glycidyl ether to anhydrous glucose units of cellulose is (12-15):1; preferably, the molar ratio of allyl glycidyl ether to anhydrous glucose units of cellulose is 12:1.
[0021] Further, in steps S2(1), S3(1), and S4(1), the solvent should be one of dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide; preferably, the solvent is dimethyl sulfoxide.
[0022] Further, in step S2(2), the ratio of the amount of methyl mercaptoacetate to the amount of allyl cellulose double bond is (0.75~1.25):1;
[0023] Furthermore, in steps S2(2) and S4(2), the initiator is one of benzoin dimethyl ether and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, and the amount of initiator added is 7% to 14% of the amount of methyl mercaptoacetate.
[0024] Further, in steps S3(2) and S4(3), the electrolyte is a carbonate electrolyte, including one of the following: 1 mol / L lithium bis(trifluoromethanesulfonyl)aminoethylene carbonate / dimethyl carbonate (volume ratio 1:1) electrolyte, 1 mol / L lithium bis(trifluoromethanesulfonyl)aminoethylene carbonate / diethyl carbonate (volume ratio 1:2) electrolyte, and 1 mol / L lithium bis(trifluoromethanesulfonyl)aminoethylene carbonate / dimethyl carbonate (volume ratio 1:1). Preferably, the electrolyte is 1 mol / L lithium bis(trifluoromethanesulfonyl)aminoethylene carbonate / diethyl carbonate (volume ratio 1:2).
[0025] The gel polymer electrolyte obtained in this invention is green and pollution-free, exhibiting excellent swelling properties in electrolyte (Q = 563%), an ionic conductivity of 0.41 mS / cm at room temperature, and a high lithium-ion transference number of 0.63. A lithium iron phosphate / lithium battery assembled using this gel polymer electrolyte as a raw material has a discharge capacity of 118.3 mAh / g at 0.2C, and a capacity retention rate of 92.6% after 100 charge-discharge cycles. Furthermore, the ester-containing cellulose derivative can be further subjected to a click reaction with 1,4-butanediol bis(thioglycolate) to convert the remaining double bonds back into ester-containing segments, achieving stepwise control of the double bonds. After drying to form a dry film, it was immersed in a carbonate electrolyte to obtain a cross-linked cellulose-based gel polymer electrolyte. It exhibits high swelling capacity (Q = 324%) in the electrolyte, high ionic conductivity of 0.60 mS / cm and high lithium-ion transference number of 0.65 at room temperature. The lithium iron phosphate / lithium battery assembled with the gel polymer electrolyte prepared using it as raw material has a discharge capacity of 125.6 mAh / g at 0.2C and a capacity retention rate of 95.9% after 200 charge-discharge cycles.
[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0027] (1) The raw materials used in this invention are widely available, inexpensive, green and biodegradable, and are environmentally friendly materials.
[0028] (2) Allyl cellulose with active double bonds was prepared under mild conditions. Ester groups were efficiently and accurately introduced onto allyl cellulose by click reaction, which greatly improved the problem of poor compatibility between cellulose and commercial ester electrolytes and improved the electrochemical performance of gel polymer electrolyte.
[0029] (3) The double bonds can be clicked in steps to carry out multiple quantitative and qualitative reactions, realizing the step-by-step control of the double bonds, and further crosslinking the remaining double bonds on the ester-containing cellulose derivatives, improving the affinity with the electrolyte while enhancing the mechanical properties of the membrane.
[0030] (4) The cellulose-based gel polymer electrolyte prepared by this invention has high ionic conductivity, high capacity retention and high thermal stability, and has great application prospects in the field of lithium-ion batteries. Attached Figure Description
[0031] Figure 1 This is a graph showing the change in ionic conductivity of the uncrosslinked gel polymer electrolyte prepared by S3 in Implementation Case 2 at different temperatures;
[0032] Figure 2 This is a graph showing the change in ionic conductivity of the cross-linked gel polymer electrolyte prepared by S4 in Implementation Case 2 at different temperatures;
[0033] Figure 3 The circuit charge-discharge performance curve of the uncrosslinked gel polymer electrolyte prepared by S3 in Implementation Case 2 at 0.2C is shown.
[0034] Figure 4 The cross-linked gel polymer electrolyte prepared by S4 in Implementation Case 2 is shown in the cycle charge-discharge performance curve at 0.2C.
[0035] Figure 5 This is a graph showing the changes in the specific capacity and efficiency of the uncrosslinked gel polymer electrolyte prepared by S3 in Implementation Case 2 during the first 100 cycles at 0.2C.
[0036] Figure 6 This is a graph showing the changes in the specific capacity and efficiency of the uncrosslinked gel polymer electrolyte prepared by S4 in Implementation Case 2 during the first 100 cycles at 0.2C. Detailed Implementation
[0037] The following examples further illustrate specific implementations of the present invention, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described below are those that can be implemented or understood by those skilled in the art by referring to existing technology. Reagents or instruments whose manufacturers are not specified are considered to be conventional products that can be purchased commercially.
[0038] Example 1
[0039] S1, Preparation of allyl cellulose:
[0040] (1) Prepare an alkali / urea solution by mixing 19.95g sodium hydroxide, 34.2g urea and 230.85g deionized water in a mass ratio of 7:12:81. Add 15g cellulose powder at -18℃ and stir at 2000r / min for 5min to obtain a 5% cellulose solution.
[0041] (2) Under a nitrogen atmosphere and at 30°C, 116.11 g of allyl glycidyl ether was added dropwise to the cellulose solution. The reaction was carried out under light-protected conditions with mechanical or magnetic stirring for 24 h. The product after the reaction was poured into acetone solvent to precipitate and wash. Then it was placed in a dialysis bag for dialysis for 5 days and then freeze-dried at -52°C for 48 h to obtain allyl cellulose.
[0042] S2. Preparation of ester-containing cellulose derivatives:
[0043] (1) Dissolve 2g of allyl cellulose in 48g of dimethyl sulfoxide solvent to prepare an allyl cellulose solution with a mass fraction of 4%.
[0044] (2) 0.7741 g of methyl mercaptoacetate and 0.1269 g of dimethyl benzoate were slowly added dropwise to an allyl cellulose solution. The mixture was mechanically stirred at room temperature and reacted under 365 nm ultraviolet light for 2 h. After the reaction was completed, the product was directly placed into a dialysis bag and dialyzed for 7 days. Then it was freeze-dried at -52 °C for 48 h to obtain an allyl cellulose derivative containing ester groups.
[0045] S3. Preparation of uncrosslinked cellulose-based gel polymer electrolyte:
[0046] (1) Take 0.2g of the above-mentioned ester-containing cellulose derivative, dissolve it in 10g of dimethyl sulfoxide solvent to prepare a solution with a mass fraction of 2%, and centrifuge to obtain the casting solution;
[0047] (2) The casting solution was cast into a plastic petri dish, dried at 50°C and then cut to obtain a dry film. After being completely dehydrated by vacuum drying at 65°C for 4 hours, the film was transferred into a glove box and immersed in an electrolyte of 1 mol / L bis(trifluoromethanesulfonyl)aminolithium in ethylene carbonate / diethyl carbonate (volume ratio 1:2) for 8 hours to obtain an uncrosslinked cellulose-based gel polymer electrolyte.
[0048] S4. Preparation of cross-linked cellulose-based gel polymer electrolytes:
[0049] (1) Dissolve 0.22g of the ester-containing cellulose derivative in 10g of dimethyl sulfoxide solvent to prepare a 2.2% solution by mass fraction, and centrifuge to remove a small amount of undissolved cellulose derivative;
[0050] (2) Add 0.0908g of 1,4-butanediol bis(thioglycolate) and 0.01312g of benzoin dimethyl ether, stir evenly to obtain casting solution;
[0051] (3) The casting solution was cast into a plastic petri dish and irradiated with 365nm ultraviolet light for 2 min to form a gel. After drying at 50℃, the dry film was cut and dried under vacuum at 65℃ for 4 h to completely remove water. Then it was transferred to a glove box and immersed in an electrolyte of 1 mol / L bis(trifluoromethanesulfonyl)aminolithium in ethylene carbonate / diethyl carbonate (volume ratio 1:2) for 8 h to obtain a cross-linked cellulose-based gel polymer electrolyte.
[0052] Example 2
[0053] S1, Preparation of allyl cellulose:
[0054] (1) Prepare an alkali / urea solution by mixing 19.95g sodium hydroxide, 34.2g urea and 230.85g deionized water in a mass ratio of 7:12:81. Add 15g cellulose powder at -18℃ and stir at 2000r / min for 5min to obtain a 5% cellulose solution.
[0055] (2) Under a nitrogen atmosphere and at 30°C, 125.35 g of allyl glycidyl ether was added dropwise to the cellulose solution. The reaction was carried out under light-protected conditions with mechanical or magnetic stirring for 24 h. The product after the reaction was poured into acetone solvent to precipitate and wash. Then it was placed in a dialysis bag for dialysis for 5 days and then freeze-dried at -52°C for 48 h to obtain allyl cellulose.
[0056] S2. Preparation of ester-containing cellulose derivatives:
[0057] (1) Dissolve 2g of allyl cellulose in 48g of dimethyl sulfoxide solvent to prepare an allyl cellulose solution with a mass fraction of 4%.
[0058] (2) 1.0321 g of methyl mercaptoacetate and 0.1692 g of dimethyl benzoate were slowly added dropwise to an allyl cellulose solution. The mixture was mechanically stirred at room temperature and reacted under 365 nm ultraviolet light for 2 h. After the reaction was completed, the product was directly placed into a dialysis bag and dialyzed for 7 days. Then it was freeze-dried at -52 °C for 48 h to obtain an allyl cellulose derivative containing ester groups.
[0059] S3. Preparation of uncrosslinked cellulose-based gel polymer electrolyte:
[0060] (1) Take 0.2g of the above-mentioned ester-containing cellulose derivative, dissolve it in 10g of dimethyl sulfoxide solvent to prepare a solution with a mass fraction of 2%, and centrifuge to obtain the casting solution;
[0061] (2) The casting solution was cast into a plastic petri dish, dried at 50°C and then cut to obtain a dry film. After being completely dehydrated by vacuum drying at 65°C for 4 hours, it was transferred into a glove box and immersed in an electrolyte of 1 mol / L bis(trifluoromethanesulfonyl)aminolithium in ethylene carbonate / diethyl carbonate (volume ratio 1:2) for 8 hours to obtain an uncrosslinked cellulose-based gel polymer electrolyte.
[0062] S4. Preparation of cross-linked cellulose-based gel polymer electrolytes:
[0063] (1) Dissolve 0.24g of the ester-containing cellulose derivative in 10g of dimethyl sulfoxide solvent to prepare a 2.4% solution by mass fraction, and centrifuge to remove a small amount of undissolved cellulose derivative;
[0064] (2) Add 0.07782g of 1,4-butanediol bis(thioglycolate) and 0.011124g of benzoin dimethyl ether, stir evenly to obtain casting solution;
[0065] (3) The casting solution was cast into a plastic petri dish and irradiated with 365nm ultraviolet light for 4 min to form a gel. After drying at 50℃, the dry film was cut and dried under vacuum at 65℃ for 4 h to completely remove water. Then it was transferred to a glove box and immersed in an electrolyte of 1 mol / L bis(trifluoromethanesulfonyl)aminolithium in ethylene carbonate / diethyl carbonate (volume ratio 1:2) for 8 h to obtain a cross-linked cellulose-based gel polymer electrolyte.
[0066] Example 3
[0067] S1, Preparation of allyl cellulose:
[0068] (1) Prepare an alkali / urea solution by mixing 13.31g sodium hydroxide, 20.91g urea and 155.82g deionized water in a mass ratio of 7:11:82. Add 10g cellulose powder at -18℃ and stir at 2000r / min for 5min to obtain a 5% cellulose solution.
[0069] (2) Under a nitrogen atmosphere and at 30°C, 72.62 g of allyl glycidyl ether was added dropwise to the cellulose solution. The reaction was carried out under light-protected conditions with mechanical or magnetic stirring for 24 h. The product after the reaction was poured into acetone solvent to precipitate and wash. Then it was placed in a dialysis bag for dialysis for 5 days and then freeze-dried at -52°C for 48 h to obtain allyl cellulose.
[0070] S2. Preparation of ester-containing cellulose derivatives:
[0071] (1) Dissolve 2g of allyl cellulose in 48g of dimethyl sulfoxide solvent to prepare an allyl cellulose solution with a mass fraction of 4%.
[0072] (2) 1.1611 g of methyl mercaptoacetate and 0.1903 g of dimethyl benzoate were slowly added dropwise to an allyl cellulose solution. The mixture was mechanically stirred at room temperature and reacted under 365 nm ultraviolet light for 2 h. After the reaction was completed, the product was directly placed into a dialysis bag and dialyzed for 7 days. Then it was freeze-dried at -52 °C for 48 h to obtain an allyl cellulose derivative containing ester groups.
[0073] S3. Preparation of uncrosslinked cellulose-based gel polymer electrolyte:
[0074] (1) Take 0.2g of the above-mentioned ester-containing cellulose derivative, dissolve it in 10g of dimethyl sulfoxide solvent to prepare a solution with a mass fraction of 2%, and centrifuge to obtain the casting solution;
[0075] (2) The casting solution was cast into a plastic petri dish, dried at 50°C and then cut to obtain a dry film. After being completely dehydrated by vacuum drying at 65°C for 4 hours, the film was transferred into a glove box and immersed in an electrolyte of 1 mol / L bis(trifluoromethanesulfonyl)aminolithium in ethylene carbonate / diethyl carbonate (volume ratio 1:2) for 8 hours to obtain an uncrosslinked cellulose-based gel polymer electrolyte.
[0076] S4. Preparation of cross-linked cellulose-based gel polymer electrolytes:
[0077] (1) Dissolve 0.25g of the ester-containing cellulose derivative in 10g of dimethyl sulfoxide solvent to prepare a 2.5% solution by mass fraction, and centrifuge to remove a small amount of undissolved cellulose derivative;
[0078] (2) Add 0.06147g of 1,4-butanediol bis(thioglycolate) and 0.00888g of benzoin dimethyl ether, stir evenly to obtain casting solution;
[0079] (3) The casting solution was cast into a plastic petri dish and irradiated with 365nm ultraviolet light for 5 min to form a gel. After drying at 50℃, the dry film was cut and dried under vacuum at 65℃ for 4 h to completely remove water. Then it was transferred to a glove box and immersed in an electrolyte of 1 mol / L bis(trifluoromethanesulfonyl)aminolithium in ethylene carbonate / diethyl carbonate (volume ratio 1:2) for 8 h to obtain a cross-linked cellulose-based gel polymer electrolyte.
[0080] Example 4
[0081] S1, Preparation of allyl cellulose:
[0082] (1) Prepare an alkali / urea solution by mixing 14.42g sodium hydroxide, 28.81g urea and 196.83g deionized water in a mass ratio of 6:12:82. Add 10g cellulose powder at -18℃ and stir at 2000r / min for 5min to obtain a 4% cellulose solution.
[0083] (2) Under a nitrogen atmosphere and at 25°C, 75.58 g of allyl glycidyl ether was added dropwise to the cellulose solution. The reaction was carried out under light-protected conditions with mechanical or magnetic stirring for 24 h. The product after the reaction was poured into acetone solvent to precipitate and wash. Then it was placed in a dialysis bag for dialysis for 5 days and then freeze-dried at -52°C for 48 h to obtain allyl cellulose.
[0084] S2. Preparation of ester-containing cellulose derivatives:
[0085] (1) Dissolve 2g of allyl cellulose in 48g of dimethyl sulfoxide solvent to prepare an allyl cellulose solution with a mass fraction of 4%.
[0086] (2) 1.2901 g of methyl mercaptoacetate and 0.2115 g of dimethyl benzoate were slowly added dropwise to an allyl cellulose solution. The mixture was mechanically stirred at room temperature and reacted under 365 nm ultraviolet light for 2 h. After the reaction was completed, the product was directly placed into a dialysis bag and dialyzed for 7 days. Then it was freeze-dried at -52 °C for 48 h to obtain an allyl cellulose derivative containing ester groups.
[0087] S3. Preparation of uncrosslinked cellulose-based gel polymer electrolyte:
[0088] (3) Take 0.2g of the above-mentioned ester-containing cellulose derivative, dissolve it in 10g of dimethyl sulfoxide solvent to prepare a solution with a mass fraction of 2%, and centrifuge to obtain the casting solution;
[0089] (4) The casting solution was cast into a plastic petri dish, dried at 50°C and then cut to obtain a dry film. After being completely dehydrated by vacuum drying at 65°C for 4 hours, the film was transferred into a glove box and immersed in an electrolyte of 1 mol / L bis(trifluoromethanesulfonyl)aminolithium in ethylene carbonate / diethyl carbonate (volume ratio 1:2) for 8 hours to obtain an uncrosslinked cellulose-based gel polymer electrolyte.
[0090] S4. Preparation of cross-linked cellulose-based gel polymer electrolytes:
[0091] (4) Dissolve 0.24g of the ester-containing cellulose derivative in 10g of dimethyl sulfoxide solvent to prepare a 2.4% solution by mass fraction, and centrifuge to remove a small amount of undissolved cellulose derivative.
[0092] (5) Add 0.04675g of 1,4-butanediol bis(thioglycolate) and 0.00675g of benzoin dimethyl ether, stir evenly to obtain casting solution;
[0093] The casting solution was poured into a plastic petri dish and irradiated with 365nm ultraviolet light for 10 min to form a gel. After drying at 50℃, the gel was cut to obtain a dry film. After vacuum drying at 65℃ for 4 h to completely remove water, the film was transferred to a glove box and immersed in an electrolyte of 1 mol / L bis(trifluoromethanesulfonyl)aminolithium in ethylene carbonate / diethyl carbonate (volume ratio 1:2) for 8 h to obtain a cross-linked cellulose-based gel polymer electrolyte.
[0094] Test Analysis
[0095] The cellulose-based gel polymer electrolytes obtained in Examples 1-4 were sequentially assembled in the following order: CR2016 positive electrode shell, stainless steel sheet or lithium iron phosphate, gel polymer electrolyte, stainless steel sheet or lithium sheet, spring sheet, and negative electrode shell. After being covered with tweezers, the electrodes were sealed in a sealing machine at a pressure of 50 kg / cm² for 12-15 seconds. Two types of batteries, stainless steel / gel polymer electrolyte / stainless steel and lithium iron phosphate / gel polymer electrolyte / lithium, were assembled for testing of ionic conductivity and cycle performance.
[0096] The ionic conductivity was measured using AC impedance spectroscopy, employing a stainless steel / gel polymer electrolyte / stainless steel battery structure. The ionic conductivity of the uncrosslinked / crosslinked gel polymer prepared in Example 2 is as follows: Figure 1 , Figure 2 As shown, the uncrosslinked gel polymer electrolyte has an ionic conductivity of 0.41 mS / cm at room temperature, while the crosslinked gel polymer electrolyte has a high ionic conductivity of 0.60 mS / cm at room temperature.
[0097] Cycle performance was tested using a Blue Electric battery testing system employing a lithium iron phosphate / gel polymer electrolyte / lithium structure. The constant current charge / discharge voltage range was 2.5–3.65 V. The charge / discharge performance of the uncrosslinked / crosslinked gel polymer prepared in Example 2 at 0.2C is as follows: Figure 3 , Figure 4 As shown, the specific capacity and efficiency for the first 100 cycles at 0.2C are as follows: Figure 5 , Figure 6 As shown, the uncrosslinked gel polymer electrolyte has a discharge capacity of 118.3 mAh / g at 0.2C and a capacity retention rate of 92.6% after 100 charge-discharge cycles, while the crosslinked gel polymer electrolyte has a discharge capacity of 125.6 mAh / g at 0.2C and a capacity retention rate of 95.9% after 200 charge-discharge cycles.
[0098] It should be understood that the above embodiments are merely preferred embodiments of the present invention and are only used to explain the present invention, not to limit the present invention. Any changes, substitutions, modifications, etc., made by those skilled in the art without departing from the spirit and essence of the present invention should be within the protection scope of the present invention.
Claims
1. A method for preparing a double-bond-regulated cellulose-based gel polymer electrolyte, characterized in that, The steps include the following: S1, Preparation of allyl cellulose: (1) Prepare an alkali / urea solution by mixing sodium hydroxide, urea and water, and add cellulose powder at low temperature and stir to dissolve it to obtain a cellulose solution; (2) Under a nitrogen atmosphere, allyl glycidyl ether was added dropwise to the cellulose solution. The reaction was carried out under light-protected conditions with mechanical or magnetic stirring. The product was precipitated and washed in acetone solvent, then placed in a dialysis bag for dialysis. After dialysis, it was freeze-dried at low temperature to obtain allyl cellulose. S2. Preparation of ester-containing cellulose derivatives: (1) Take the allyl cellulose, add solvent and stir to dissolve it completely to obtain an allyl cellulose solution; (2) Add methyl mercaptoacetate and initiator dropwise to allyl cellulose solution, stir mechanically at room temperature, react under ultraviolet light, after the reaction is completed, put the product into a dialysis bag for dialyzing, and freeze dry at low temperature to obtain allyl cellulose derivatives containing ester groups. S3. Preparation of uncrosslinked cellulose-based gel polymer electrolyte: (1) The above-mentioned ester-containing cellulose derivatives were dissolved in a solvent and then prepared into a solution. After centrifugation, a casting solution was obtained. (2) Casting solution is poured into plastic petri dish, dried and cut to obtain dry film, vacuum dried to completely remove water and then transferred to glove box, and immersed in electrolyte to obtain non-crosslinked cellulose-based gel polymer electrolyte. S4. Preparation of cross-linked cellulose-based gel polymer electrolytes: (1) Dissolve the above-mentioned ester-containing cellulose derivatives in a solvent to prepare a solution, and centrifuge to remove a small amount of undissolved cellulose derivatives; (2) Add 1,4-butanediol bis(thioglycolate) and initiator, stir evenly to obtain casting solution; (3) Cast the casting solution into a plastic petri dish, irradiate it with ultraviolet light to form a gel, dry it and cut it to obtain a dry film. After vacuum drying to completely remove water, transfer it into a glove box and soak it in electrolyte to obtain a cross-linked cellulose-based gel polymer electrolyte.
2. The method for preparing the double-bond regulated cellulose-based gel polymer electrolyte according to claim 1, characterized in that, In step S1 (1), the mass ratio of sodium hydroxide, urea, and water is (4-8):(10-12):(80-86); the temperature for stirring and dissolving the cellulose powder is -16°C to -20°C, the stirring speed is 1800-2400 r / min, the stirring time is 5-10 min, and the mass percentage of the resulting cellulose solution is 3%-6%.
3. The method for preparing the double-bond regulated cellulose-based gel polymer electrolyte according to claim 1, characterized in that, In step S1(2), the molar ratio of allyl glycidyl ether to anhydrous glucose units of cellulose is (12-15):
1. The reaction time under mechanical or magnetic stirring is 24–30 h, the dialysis time in dialysis bags is 4–7 days, the freeze-drying temperature is -50 to -60°C, and the freeze-drying time is 48–72 h.
4. The method for preparing the double-bond regulated cellulose-based gel polymer electrolyte according to claim 1, characterized in that, In steps S2(1), S3(1), and S4(1), the solvent should be one of dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide; and be prepared into a solution with a mass fraction of 2-5%.
5. The method for preparing the double-bond regulated cellulose-based gel polymer electrolyte according to claim 1, characterized in that, In step S2 (2), the ratio of the amount of methyl mercaptoacetate to the amount of allyl cellulose double bond is (0.75-1.25):1; The initiator is one of benzoin dimethyl ether and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, and the amount of initiator added is 7% to 14% of the amount of methyl mercaptoacetate.
6. The method for preparing the double-bond regulated cellulose-based gel polymer electrolyte according to claim 1, characterized in that, In step S2 (2), the ultraviolet irradiation wavelength is 365nm, the reaction is carried out under mechanical stirring for 2-3 hours, the dialysis time is 4-7 days, the freeze-drying temperature is -50 to -60°C, and the freeze-drying time is 48-72 hours.
7. The method for preparing the double-bond regulated cellulose-based gel polymer electrolyte according to claim 1, characterized in that, In steps S3(2) and S4(3), the electrolyte is a carbonate electrolyte, including one of the following: 1 mol / L lithium bis(trifluoromethanesulfonyl)aminoethylene carbonate / dimethyl carbonate (volume ratio 1:1) electrolyte, 1 mol / L lithium bis(trifluoromethanesulfonyl)aminoethylene carbonate / diethyl carbonate (volume ratio 1:2) electrolyte, and 1 mol / L lithium bis(trifluoromethanesulfonyl)aminoethylene carbonate / dimethyl carbonate (volume ratio 1:1). The electrolyte soaking time is 8~24h.
8. The method for preparing the double-bond regulated cellulose-based gel polymer electrolyte according to claim 1, characterized in that, In step S4 (2), the initiator is one of benzoin dimethyl ether and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, and the amount of initiator added is 7% to 14% of the amount of 1,4-butanediol bis(thioglycolate).
9. The method for preparing the double-bond regulated cellulose-based gel polymer electrolyte according to claim 1, characterized in that, In steps S3 (2) and S4 (3), the temperature of the vacuum oven is set to 60-65°C and the drying time is 8-12 hours. In step S4 (3), the ultraviolet light irradiation wavelength is 365nm and the irradiation time is 2 to 10 minutes.
10. A cellulose-based gel polymer electrolyte with double bond regulation, high ionic conductivity, and high capacity retention obtained by the preparation method according to any one of claims 1-9.