A cellulose-based gel electrolyte and a preparation method and application thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTH CHINA UNIV OF TECH
- Filing Date
- 2026-04-07
- Publication Date
- 2026-07-14
Smart Images
Figure CN122393400A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium metal battery technology, specifically to a cellulose-based gel electrolyte, its preparation method, and its application. Background Technology
[0002] Lithium metal batteries, which use lithium metal as the negative electrode material, have become a promising emerging force in the energy storage field. Lithium metal boasts an extremely high theoretical specific capacity (3860 mAh / g, far exceeding the 372 mAh / g of graphite anodes) and the lowest negative electrochemical potential (-3.04 V vs. standard hydrogen electrode (SHE)), indicating a broad application prospect. Furthermore, lithium is a relatively abundant metallic element in the Earth's crust, and with continuous advancements in lithium extraction technology, the production cost of lithium metal is expected to further decrease, thus lithium metal batteries also possess a potential low-cost advantage.
[0003] However, lithium metal anodes are prone to forming lithium dendrites during charge and discharge, which can puncture the separator and cause internal short circuits, leading to safety issues. Furthermore, side reactions between lithium metal and the electrolyte can cause battery capacity decay and reduced cycle life. Replacing liquid electrolyte with solid electrolyte is an effective solution to these problems, but the generally low ionic conductivity of solid electrolytes hinders improvements in battery cycle performance. Gel electrolytes, a semi-solid electrolyte, combine the advantages of both liquid and solid electrolytes, possessing both high ionic conductivity and high mechanical strength, and hold promise for effectively addressing the main problems of existing lithium metal batteries.
[0004] Therefore, it is of great significance to develop a gel electrolyte that can effectively suppress the growth of lithium dendrites, has high ionic conductivity, high mechanical strength, good thermal stability, and is safe and environmentally friendly. Summary of the Invention
[0005] The purpose of this invention is to provide a cellulose-based gel electrolyte, its preparation method, and its application.
[0006] The technical solution adopted in this invention is: A method for preparing a cellulose-based gel electrolyte includes the following steps: Allyl cellulose was dissolved in an organic solvent, and then a thiol-functionalized organolithium salt and an initiator were added before the first ultraviolet irradiation. The thiol-functionalized organolithium salt was prepared by reacting 1,4-butanediol bis(thioglycolate) (BBTG) with lithium 4-styrenesulfonyl(trifluoromethanesulfonyl)imine (LiSTFSI) or 1-[2-(acryloyloxypropyl)propylsulfonyl]-1-(trifluoromethanesulfonyl)imine (LiMTFSI). After adding a bis(thiol) crosslinking agent and an initiator, the product was subjected to a second ultraviolet irradiation and then purified to obtain a cellulose-based gel electrolyte.
[0007] Preferably, the molar ratio of the double bond in the allyl cellulose to the thiol group in the thiol-functionalized organolithium salt is 8:1 to 6.
[0008] Preferably, the degree of substitution of the allyl cellulose is 0.5 to 3.
[0009] Preferably, the allyl cellulose is prepared by modifying cellulose with an etherifying agent.
[0010] Preferably, the organic solvent is at least one of N,N-dimethylformamide (DMF) and acetonitrile (ACN).
[0011] Preferably, the duration of the first ultraviolet irradiation is 20 to 40 minutes.
[0012] Preferably, the amount of the initiator is 5% to 10% of the total mass of allyl cellulose and thiol-functionalized organolithium salt (for the first UV irradiation) and 5% to 10% of the total mass of allyl cellulose and dithiol crosslinking agent (for the second UV irradiation).
[0013] Preferably, the initiator is at least one of benzoin dimethyl ether (DMPA), 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.
[0014] Preferably, the mass ratio of allyl cellulose to dithiol crosslinking agent is 4.5 to 5.5:1.
[0015] Preferably, the bis(thioglycolic acid) crosslinking agent is at least one of 1,4-butanediol bis(thioglycolic acid) and 3,6-dioxa-1,8-octanedithiol (DODT).
[0016] Preferably, the duration of the second ultraviolet irradiation is 70 min to 110 min.
[0017] Preferably, the product purification includes the following operations: soaking the product in acetonitrile first, and then soaking it in a mixed solvent of ethylene carbonate and diethyl carbonate.
[0018] Preferably, the ethylene carbonate-diethyl carbonate mixed solvent is prepared by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1.5 to 2.5.
[0019] A cellulose-based gel electrolyte, which is prepared by the above-described method.
[0020] A lithium metal battery comprising the aforementioned cellulose-based gel electrolyte.
[0021] The principle of this invention: This invention covalently bonds anions to the main chain of allyl cellulose through a click chemical reaction between double bonds and thiol groups, making Li the only mobile substance. + Limited anion migration avoids the formation of concentration gradients, which is beneficial to Li. + Ions are uniformly deposited on the metal surface along the direction of the electric field, which effectively suppresses the growth of lithium dendrites. In addition, allyl cellulose as a matrix can also endow the gel electrolyte with high mechanical strength and excellent thermal stability.
[0022] The beneficial effects of the present invention are: the cellulose-based gel electrolyte of the present invention can effectively inhibit the growth of lithium dendrites, and has high ionic conductivity, high lithium ion transference number, high mechanical strength, good thermal stability, and is safe and environmentally friendly, making it suitable for lithium metal batteries. Moreover, its preparation process is simple, the reaction conditions are mild, and the production cost is low, making it suitable for large-scale industrial production and application.
[0023] Specifically: 1) The cellulose-based gel electrolyte of the present invention uses allyl cellulose as the matrix. Hydrogen bonds exist between the hydroxyl groups in the molecular chain structure of allyl cellulose, which can endow the gel electrolyte with high mechanical strength and excellent thermal stability. In addition, cellulose is a natural polymer with abundant reserves and is environmentally friendly. 2) This invention grafts a thiol-functionalized organolithium salt onto the main chain of allyl cellulose, thus covalently linking the thiol-functionalized organolithium salt to allyl cellulose. The anions in the thiol-functionalized organolithium salt are fixed to the polymer main chain, resulting in only Li ions being mobile in the system. + The addition of ions significantly reduces concentration polarization, which helps to reduce the growth of lithium dendrites, thereby improving the safety performance of lithium metal batteries. 3) This invention introduces a large number of alkoxy segments into the gel electrolyte system through a dithiol crosslinking agent, enabling Li... + Ions can be transported through alkoxy segments, which effectively improves the ionic conductivity of the gel electrolyte; 4) The synthesis process of the cellulose-based gel electrolyte of the present invention has mild reaction conditions, and ultraviolet light initiation can reduce energy consumption. Cellulose has low cost and is environmentally friendly, making it suitable for large-scale industrial production and application. Attached Figure Description
[0024] Figure 1 The Fourier transform infrared spectrum of the cellulose-based gel electrolyte in Example 4 is shown.
[0025] Figure 2 The tensile strength-strain curves are for the cellulose-based gel electrolytes in Examples 1-4.
[0026] Figure 3 The figures show the ionic conductivity-temperature relationship curves of the cellulose-based gel electrolytes in Examples 1-4.
[0027] Figure 4 The LSV curves are for batteries assembled with cellulose-based gel electrolytes from Examples 1 to 4.
[0028] Figure 5 The graph shows the cycle stability test results of the lithium-lithium symmetric battery assembled with the cellulose-based gel electrolyte of Example 4.
[0029] Figure 6 The graph shows the charge / discharge performance test results of the LFP battery assembled with the cellulose-based gel electrolyte of Example 4. Detailed Implementation
[0030] The present invention will be further explained and described below with reference to specific embodiments.
[0031] The preparation method of BBTG-Li in Examples 1-4 is as follows: 0.2g of 4-styrenesulfonyl (trifluoromethanesulfonyl)imine lithium (LiSTFSI) was stirred and dissolved in 1mL of acetonitrile, and then 6mg of benzoin dimethyl ether (DMPA) and 0.6mL of 1,4-butanediol bis(thioglycolate) (BBTG) were added and stirred evenly. The mixture was then irradiated under ultraviolet light for 6min. The product was precipitated repeatedly with diethyl ether 3 times, and the solid was collected and dried to obtain the thiol-functionalized organolithium salt (denoted as BBTG-Li).
[0032] Example 1: A cellulose-based gel electrolyte, the preparation method of which is as follows: 40 mg of allyl cellulose (degree of substitution 1.15) was dissolved in 1 g of DMF by stirring. Then, 15.9 mg of BBTG-Li and 4.5 mg of benzoin dimethyl ether were added. The molar ratio of the double bonds in allyl cellulose to the thiol groups in BBTG-Li was 8:1. The mixture was stirred until homogeneous and then poured into a polytetrafluoroethylene mold. The mixture was irradiated under ultraviolet light for 30 min. Then, 6 mg of 1,4-butanediol bis(thioglycolate) and 3 mg of benzoin dimethyl ether were added. The mixture was stirred until homogeneous and then irradiated under ultraviolet light for 1.5 h. The product was then soaked in acetonitrile and then soaked twice in a mixed solvent of ethylene carbonate and diethyl carbonate (EC:DEC volume ratio of 1:2). The product was then cut into discs to obtain the cellulose-based gel electrolyte (denoted as AC-S-1).
[0033] The preparation reaction of cellulose-based gel electrolyte is as follows: .
[0034] Example 2: A cellulose-based gel electrolyte, the preparation method of which is as follows: 40 mg of allyl cellulose (degree of substitution 1.15) was dissolved in 1 g of DMF by stirring. Then, 31.7 mg of BBTG-Li and 5.7 mg of benzoin dimethyl ether were added. The molar ratio of the double bonds in allyl cellulose to the thiol groups in BBTG-Li was 4:1. The mixture was stirred until homogeneous and then poured into a polytetrafluoroethylene mold. The mixture was irradiated under ultraviolet light for 30 min. Then, 6 mg of 1,4-butanediol bis(thioglycolate) and 3 mg of benzoin dimethyl ether were added. The mixture was stirred until homogeneous and then irradiated under ultraviolet light for 1.5 h. The product was then soaked in acetonitrile and then soaked twice in a mixed solvent of ethylene carbonate and diethyl carbonate (EC:DEC volume ratio of 1:2). The product was then cut into discs to obtain the cellulose-based gel electrolyte (denoted as AC-S-2).
[0035] Example 3: A cellulose-based gel electrolyte, the preparation method of which is as follows: 40 mg of allyl cellulose (degree of substitution 1.15) was dissolved in 1 g of DMF by stirring. Then, 63.5 mg of BBTG-Li and 8.3 mg of benzoin dimethyl ether were added. The molar ratio of the double bonds in allyl cellulose to the thiol groups in BBTG-Li was 2:1. The mixture was stirred until homogeneous and then poured into a polytetrafluoroethylene mold. The mixture was irradiated under ultraviolet light for 30 min. Then, 6 mg of 1,4-butanediol bis(thioglycolate) and 3 mg of benzoin dimethyl ether were added. The mixture was stirred until homogeneous and then irradiated under ultraviolet light for 1.5 h. The product was then soaked in acetonitrile and then soaked twice in a mixed solvent of ethylene carbonate and diethyl carbonate (EC:DEC volume ratio of 1:2). The product was then cut into discs to obtain the cellulose-based gel electrolyte (denoted as AC-S-3).
[0036] Example 4: A cellulose-based gel electrolyte, the preparation method of which is as follows: 40 mg of allyl cellulose (degree of substitution 1.15) was dissolved in 1 g of DMF by stirring. Then, 95.2 mg of BBTG-Li and 10.8 mg of benzoin dimethyl ether were added. The molar ratio of the double bonds in allyl cellulose to the thiol groups in BBTG-Li was 4:3. The mixture was stirred until homogeneous and then poured into a polytetrafluoroethylene mold. The mixture was irradiated under ultraviolet light for 30 min. Then, 6 mg of 1,4-butanediol bis(thioglycolate) and 3 mg of benzoin dimethyl ether were added. The mixture was stirred until homogeneous and then irradiated under ultraviolet light for 1.5 h. The product was then soaked in acetonitrile and then soaked twice in a mixed solvent of ethylene carbonate and diethyl carbonate (EC:DEC volume ratio of 1:2). The product was then cut into discs to obtain the cellulose-based gel electrolyte (denoted as AC-S-4).
[0037] Performance testing: 1) The Fourier transform infrared spectrum of the cellulose-based gel electrolyte (AC-S-4) in Example 4 is shown below. Figure 1 As shown.
[0038] Depend on Figure 1 It can be seen that at 1321cm -1 1165cm -1 1141cm -1 and 1093cm -1 A characteristic absorption peak was detected at 1321 cm⁻¹. -1 The absorption peak at 1165 cm⁻¹ is attributed to the stretching vibration of the CF bond in the -CF₃ group. -1 The absorption peak at 1141 cm⁻¹ is attributed to the asymmetric stretching vibration of S=O=S, while the peak at 1141 cm⁻¹ is attributed to the asymmetric stretching vibration of S=O=S. -1 and 1093cm -1 The absorption peaks at 1654 cm⁻¹ are attributed to the stretching vibrations of the SN and SNS bonds, respectively. Furthermore, the absorption peak at 1654 cm⁻¹... -1 and 1600cm -1 The absorption peak at that point is attributed to the skeletal vibration of the benzene ring (C=C). Based on the above attribution and analysis of the infrared characteristic peaks, it is concluded that BBTG-Li was successfully grafted onto the main chain of allyl cellulose.
[0039] 2) Tensile tests were performed on the cellulose-based gel electrolytes of Examples 1-4 at a tensile rate of 5 mm / min. The tensile strength-strain curves obtained are shown below. Figure 2 As shown.
[0040] Depend on Figure 2It can be seen that the tensile strengths of the cellulose-based gel electrolytes in Examples 1 to 4 are 20.9 MPa, 21.9 MPa, 24.2 MPa and 24.9 MPa respectively, all above 20 MPa, indicating high mechanical strength. Furthermore, the tensile strength gradually increases with the increase of BBTG-Li content. This may be because the benzene ring in the styrene-type lithium salt monomer provides rigid support, effectively compensating for the decrease in hydrogen bond density caused by BBTG crosslinking. A synergistic reinforcement effect is formed between the grafted monomer and the cellulose matrix. The steric hindrance and polar interaction of the macromolecular chain restrict the chain segment movement, thereby improving the structural stability.
[0041] 3) The cellulose-based gel electrolytes from Examples 1-4 were soaked in a mixed solvent of ethylene carbonate and diethyl carbonate (EC:DEC volume ratio of 1:2), then assembled into stainless steel symmetrical cells. The ionic conductivity was calculated using AC impedance spectroscopy, and the resulting ionic conductivity-temperature curves are shown below. Figure 3 As shown.
[0042] Depend on Figure 3 It can be seen that the ionic conductivity of the cellulose-based gel electrolytes in Examples 1-4 at room temperature was 0.12 mS / cm, 0.25 mS / cm, 0.57 mS / cm, and 1.03 mS / cm, respectively. With the increase of BBTG-Li content, the ionic conductivity of the cellulose-based gel electrolyte showed an increasing trend. Among them, the cellulose-based gel electrolyte in Example 4 had the highest ionic conductivity, reaching 1.03 mS / cm, demonstrating a generally high level of ionic conductivity. Furthermore, the ionic conductivity of the cellulose-based gel electrolytes in Examples 1-4 all increased significantly with increasing temperature.
[0043] 4) The cellulose-based gel electrolytes from Examples 1-4 were soaked in a mixed solvent of ethylene carbonate and diethyl carbonate (EC:DEC volume ratio 1:2), then assembled into batteries with stainless steel sheets (working electrodes) and lithium sheets (reference electrodes), and linear sweep voltammetry was performed. The sweep range was 3V-6V, and the sweep rate was 1mV / s. The obtained LSV curves are shown below. Figure 4 As shown.
[0044] Depend on Figure 4 It can be seen that the oxidative decomposition voltages (usually the voltage at which the current reaches 20 μA) of the cellulose-based gel electrolytes in Examples 1 to 4 are 5.1V, 5.3V, 5.3V and 5.4V, respectively, all higher than 5.0V. Among them, the decomposition voltage of Example 4 is as high as 5.4V. A high decomposition voltage means that it can be adapted to electrode materials with higher voltages, support higher charge and discharge voltages, and maintain chemical and electrochemical stability under high voltage, thereby making the battery safer, with higher energy density and longer life.
[0045] 5) The cellulose-based gel electrolyte from Example 4 was soaked in a mixed solvent of ethylene carbonate and diethyl carbonate (EC:DEC volume ratio of 1:2), then assembled into a lithium-lithium symmetric battery, and subjected to a constant current cycling test (to evaluate the electrolyte's ability to suppress lithium dendrite growth). The test temperature was 25°C, and the current density was 0.3 mA / cm². 2 The cycle mode was a 1-hour charge / discharge cycle (i.e., 1 hour of charging, 1 hour of discharging). The cycle stability test results are as follows: Figure 5 (The small images in the picture are enlarged views of a specific area.)
[0046] Depend on Figure 5 It can be seen that the voltage of the lithium-lithium symmetric battery is stable and can be maintained for at least 1400 hours, indicating that the interface stability between the cellulose-based gel electrolyte and metallic lithium in Example 4 is good, and the lithium deposition is uniform and stable.
[0047] 6) The cellulose-based gel electrolyte from Example 4 was soaked in a mixed solvent of ethylene carbonate and diethyl carbonate (EC:DEC volume ratio of 1:2), and then assembled into an LFP battery (the assembly sequence of the Li / LiFePO4 half-cell is negative electrode shell, corrugated spring sheet, stainless steel gasket, lithium metal sheet, gel electrolyte, lithium iron phosphate positive electrode sheet, and positive electrode shell). Charge-discharge tests were then conducted (to evaluate the battery's capacity and cycle stability) at 25°C and a rate of 1C. The charge-discharge performance test results are as follows: Figure 6 As shown.
[0048] Depend on Figure 6 It can be seen that the initial discharge specific capacity of the LFP battery is 132.6 mAh / g, which reaches a maximum capacity of 136.7 mAh / g after 6 cycles, and a discharge specific capacity of 125.6 mAh / g after 150 cycles, with a capacity retention rate of about 92% and a coulombic efficiency of up to 99.8%, demonstrating a comprehensive advantage of high capacity, long cycle life and high coulombic efficiency.
[0049] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
Claims
1. A method for preparing a cellulose-based gel electrolyte, characterized in that, Includes the following steps: Allyl cellulose was dissolved in an organic solvent, and then a thiol-functionalized organolithium salt and an initiator were added before the first ultraviolet irradiation. The thiol-functionalized organolithium salt was prepared by reacting 1,4-butanediol bis(thioglycolate) with lithium 4-styrenesulfonyl(trifluoromethanesulfonyl)imide or lithium 1-[2-(acryloyloxypropyl)propylsulfonyl]-1-(trifluoromethanesulfonyl)imide. After adding a bis(thiol) crosslinking agent and an initiator, the product was subjected to a second ultraviolet irradiation and then purified to obtain a cellulose-based gel electrolyte.
2. The preparation method according to claim 1, characterized in that: The molar ratio of the double bonds in the allyl cellulose to the thiol groups in the thiol-functionalized organolithium salt is 8:1 to 6.
3. The preparation method according to claim 1 or 2, characterized in that: The degree of substitution of the allyl cellulose is 0.5 to 3.
4. The preparation method according to claim 1 or 2, characterized in that: The duration of the first ultraviolet irradiation is 20 to 40 minutes.
5. The preparation method according to claim 1, characterized in that: The mass ratio of allyl cellulose to dithiol crosslinking agent is 4.5–5.5:
1.
6. The preparation method according to claim 1 or 5, characterized in that: The dithiolated crosslinking agent is at least one of 1,4-butanediol bis(thioglycolate) and 3,6-dioxa-1,8-octanedithiol; and / or, the initiator is at least one of benzoin dimethyl ether, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.
7. The preparation method according to claim 1 or 5, characterized in that: The second ultraviolet irradiation time is 70 min to 110 min.
8. The preparation method according to any one of claims 1, 2 and 5, characterized in that: The product purification includes the following steps: first soaking the product in acetonitrile, and then soaking it in a mixed solvent of ethylene carbonate and diethyl carbonate.
9. A cellulose-based gel electrolyte, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.
10. A lithium metal battery, characterized in that, It includes the cellulose-based gel electrolyte of claim 9.