A method for preparing a composite solid electrolyte having a soft filler
By combining lithium cellulose with polymers, a composite solid electrolyte was prepared, which solved the problems of lithium dendrite growth and insufficient mechanical properties in the existing technology, and achieved efficient lithium-ion transport and improved battery safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING INST OF TECH
- Filing Date
- 2023-05-29
- Publication Date
- 2026-06-26
AI Technical Summary
Existing composite solid electrolytes exhibit poor electrochemical performance at room temperature, lithium dendrite growth is not effectively suppressed, and mechanical properties are insufficient, resulting in inadequate battery safety and lifespan.
A composite solid electrolyte was prepared by using lithium cellulose as a soft filler and combining it with a polymer through a specific process. The lithium cellulose exposed oxygen-containing groups promoted lithium ion migration, anchored lithium salt anions, avoided filler agglomeration, and improved mechanical properties and ion transport efficiency.
The prepared composite solid electrolyte has high lithium-ion conductivity, excellent electrochemical performance and a wide electrochemical stability window, which significantly improves the cycle stability and safety of the battery.
Smart Images
Figure CN116826159B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing a composite solid electrolyte with soft filler, belonging to the field of metal secondary batteries. Background Technology
[0002] Lithium-ion batteries are widely used in mobile electronic devices and new energy electric vehicles due to their excellent stability and high energy density. However, with the increasing demand for high-energy-density and high-safety energy storage technologies, the development of new energy storage devices is urgently needed. Lithium metal, due to its ultra-high theoretical capacity (3860 mAh g⁻¹), is a suitable alternative. -1 Low mass density (0.534 g cm³) -3 With its low electrochemical potential (-3.04 V, relative to the standard hydrogen electrode), it is considered the most promising alternative to lithium-ion battery anodes. However, the organic electrolytes currently used in lithium-ion batteries are not stably compatible with metallic lithium, easily forming lithium dendrites, which can lead to short circuits and even safety hazards (leakage, explosion). Therefore, changing the electrolyte type, expanding battery application scenarios, and addressing battery safety hazards have become the current research focus for lithium-ion batteries.
[0003] Solid-state electrolytes have attracted increasing attention due to their high mechanical strength and safety, which effectively solve existing problems of electrolytes. Solid-state electrolytes can generally be classified into inorganic solid-state electrolytes, polymer solid-state electrolytes, and composite solid-state electrolytes. Organic polymer electrolytes possess high ionic conductivity in their elastic state and exhibit outstanding flexibility, but their low room-temperature ionic conductivity severely limits their large-scale application. Pure inorganic solid-state electrolytes have high room-temperature conductivity and good mechanical properties, but their poor interfacial contact performance and low flexibility prevent their widespread use. Adding different types of modified fillers to the polymer matrix can improve the polymer's room-temperature ionic conductivity while enhancing its mechanical properties, thereby achieving the goals of suppressing lithium dendrite growth and improving battery safety and energy density.
[0004] Therefore, composite solid electrolytes, which combine the advantages of both organic and inorganic electrolytes, can not only suppress the growth of lithium dendrites during solid-state battery cycling, but also improve battery safety and lifespan, which is of great significance for the development of next-generation lithium batteries.
[0005] Numerous patents have been published regarding composite solid-state electrolytes, most of which utilize inert fillers (silicon dioxide, titanium dioxide, etc.) that cannot conduct lithium ions and active fillers (garnet, perovskite, etc.) that can transport lithium ions, combined with polymers and lithium salts. However, due to the tendency of inorganic ceramic particles to agglomerate and the lack of stable lithium-ion transport pathways, the electrochemical performance of these composite electrolytes does not meet the requirements for operation at room temperature. To improve these composite solid-state electrolytes, many research patents have explored adding a small amount of electrolyte between the composite solid-state electrolyte and the battery's positive and negative electrodes, forming crystals, or directly immersing the electrolyte to form gel or semi-solid electrolytes. However, these electrolytes exhibit significantly reduced mechanical properties and cannot effectively suppress lithium dendrite growth, resulting in reduced battery cycle life. Therefore, there is an urgent need to explore new, highly efficient fillers, which is of great significance for the development of composite solid-state electrolytes. Summary of the Invention
[0006] The purpose of this invention is to provide a method for preparing a composite solid electrolyte with a soft filler, using lithium cellulose, which can transport lithium ions and restrict the movement of lithium salt anions, as a soft filler. The composite solid electrolyte has good mechanical properties and interfacial chemical stability, high lithium ion conductivity, and excellent electrochemical performance.
[0007] The objective of this invention is achieved through the following technical solution:
[0008] A method for preparing a composite solid electrolyte with soft filler involves adding lithium cellulose to a polymer slurry, stirring to obtain a composite solid electrolyte slurry, coating it onto a glass plate with a scraper and drying it to obtain the composite solid electrolyte.
[0009] The polymer slurry is obtained by adding a polymer and a lithium salt to a solvent;
[0010] The molar concentration of the lithium salt is between 0.125 and 0.5 mol / L, preferably 0.22 mol / L;
[0011] The mass ratio of the polymer to the solvent is between 1:100 and 3:10, preferably 1:10;
[0012] The content of the lithium cellulose in the polymer does not exceed 8 wt% by weight.
[0013] The preparation method of the polymer slurry is as follows: the polymer and lithium salt are added to a solvent and magnetically stirred overnight, with the stirring time controlled between 6 and 36 h, preferably 24 h; the stirring rate is controlled between 200 and 1500 r / min, preferably 800 r / min.
[0014] The height of the scraper is between 50 and 3000 μm, preferably 1000 μm, the drying temperature is maintained between 50 and 120 °C, preferably 80 °C, and the drying time is controlled between 6 and 36 h, preferably 24 h.
[0015] The polymer is one or more of polyethylene oxide, polyvinylidene fluoride (PVDF), polyacrylonitrile, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate, polyethylene succinate, polypropylene oxide, polyethyleneimine, and polyvinylidene chloride, preferably PVDF;
[0016] The lithium salt is one or more of lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium hexafluoroarsenate, and lithium hexafluorophosphate, with LiTFSI being preferred.
[0017] The solvent is one or more of N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide (DMAc), triethyl phosphate, dimethyl sulfoxide, ethanol, methanol, acetonitrile, and acetone, preferably DMAc.
[0018] A method for preparing a composite solid electrolyte with soft filler, wherein the method for preparing the lithium-ionized cellulose includes the following steps:
[0019] Step 1: Add nanocellulose particles to DMAc solvent and stir magnetically until the cellulose layer on the surface of the nanocellulose particles is detached; then centrifuge to obtain wet pre-dissolved nanocellulose; after drying, obtain pre-dissolved nanocellulose particles; the mass ratio of nanocellulose particles to DMAc is between 0.05 and 0.2, preferably 0.1;
[0020] Step 2: Add anhydrous lithium chloride (LiCl) to the DMAc solvent and stir until the LiCl is completely dissolved to obtain a DMAc / LiCl solution; the LiCl / DMAc molar ratio is between 0:1 and 0.22:1, preferably 0.17:1;
[0021] Step 3: Add the pre-dissolved nanocellulose particles obtained in Step 1 to the DMAc / LiCl solution obtained in Step 2, stir evenly, and obtain lithium cellulose; the mass fraction of the pre-dissolved nanocellulose particles is between 4 wt% and 30 wt%, preferably 20 wt%.
[0022] Its features are:
[0023] The stirring rate in step one is controlled between 200 and 1500 r / min, preferably 800 r / min; the time is controlled between 6 and 36 h, preferably 24 h.
[0024] The centrifugal speed for centrifugation in step one is controlled within 2000~12000 r / min, preferably 10000 r / min;
[0025] The drying temperature in step one is maintained between 50 and 120 °C, preferably 80 °C; the drying time is controlled between 6 and 36 hours, preferably 24 hours.
[0026] The stirring rate in step two is controlled between 200 and 1500 r / min, preferably 800 r / min, and the stirring time is controlled between 6 and 36 h, preferably 24 h.
[0027] The stirring rate in step three is controlled between 200 and 1500 r / min, preferably 800 r / min, and the stirring time is controlled between 6 and 36 h, preferably 24 h.
[0028] The nanocellulose particles are prepared and purified from various types of cellulose nanocrystals, cellulose nanofibers, cellulose nanosheets, and nanocellulose particles from trees, bamboo, cotton, crops, marine algae, and marine bacteria, with nanocellulose particles preferably prepared from cotton. Beneficial effects
[0029] 1. The lithium cellulose prepared by this invention removes the dense hydrogen bond structure inside the cellulose particles, exposing numerous oxygen-containing groups. When dissolved in a solvent, it can effectively promote the rapid migration of lithium ions in a composite solid electrolyte.
[0030] 2. The lithium-ion cellulose prepared by this invention can promote the dissociation of lithium salts and anchor lithium salt anions, thereby improving lithium-ion transport efficiency;
[0031] 3. The composite solid electrolyte prepared by this invention uses lithium cellulose as a soft filler to combine polymer and lithium salt, which avoids filler agglomeration and can better reduce the crystallinity of polymer to promote lithium ion transport. The resulting composite solid electrolyte has excellent electrochemical performance and is of great significance to the research and development of solid-state batteries.
[0032] 4. The lithium-ionized cellulose introduced in this invention has good flexibility and can interact with the polymer substrate, promoting the movement of polymer chain segments and greatly improving the ion transport efficiency of solid-state batteries.
[0033] 5. This invention provides a high-safety composite solid electrolyte. The lithium-ionized cellulose in the composite solid electrolyte not only improves the mechanical strength of the composite solid electrolyte and inhibits the growth of lithium dendrites, but also greatly promotes the ion transport efficiency of the composite solid electrolyte, improves the interface stability of the solid battery, and enhances the performance of the metal secondary battery.
[0034] 6. This invention provides a composite solid electrolyte with excellent electrochemical performance. The composite solid electrolyte has ideal ionic conductivity, a wide electrochemical stability window and a high lithium-ion transference number, which can significantly improve the cycle stability of solid lithium secondary batteries. Attached Figure Description
[0035] Figure 1 This is a SEM image of a composite solid electrolyte containing 1.5% lithium cellulose.
[0036] Figure 2 SEM image of a composite solid electrolyte containing 5.5% lithium cellulose;
[0037] Figure 3 SEM image of a composite solid electrolyte containing 7.2% lithium-ionized cellulose;
[0038] Figure 4 SEM image of a composite solid electrolyte containing 8% lithium cellulose;
[0039] Figure 5 SEM image of a composite solid electrolyte that does not contain lithium-ionized cellulose. Detailed Implementation
[0040] The present invention will be further described in detail below with reference to the embodiments. However, the present invention is not limited to the following embodiments.
[0041] The analytical testing methods used in the following embodiments include:
[0042] AC impedance spectroscopy, electrochemical stability window testing, lithium-ion transference number testing: Electrochemical workstation (CHI660D), Shanghai;
[0043] Scanning electron microscope (SEM) test: Model HITACHI S-4800, Japan
[0044] Stress-strain testing of solid electrolytes: INSTRON 3343, USA;
[0045] Electrochemical performance testing: LAND, Wuhan; Example 1
[0046] 15g of nanocellulose particles were added to 100 mL of DMAc and magnetically stirred for 24 h. The mixture was then centrifuged at 10000 r / min and transferred to a vacuum oven at 80℃ for 12 h to obtain pre-dissolved nanocellulose particles. A certain amount of anhydrous lithium chloride was added to the DMAc solvent until the anhydrous lithium chloride was completely dissolved and stirred continuously for 24 h, maintaining a molar ratio of 0.1:1 to obtain a DMAc / LiCl solution. 8g of the pre-dissolved nanocellulose particles were added to 50 mL of the DMAc / LiCl solution and stirred evenly to obtain lithium-ionized cellulose. 0.8 g of PVDF and 0.22 mol / L LiTFSI were added to 8 mL of DMAc solvent and magnetically stirred for 24 h. Then, 1.5% (w / w) of lithium cellulose PVDF was added, and the mixture was stirred for 24 h to obtain a composite solid electrolyte slurry. The slurry was coated onto a glass plate and placed in an 80 ℃ vacuum oven to dry for 24 h to obtain a composite solid electrolyte. Then, it was transferred to an argon-filled glove box and dried on an 80 ℃ heating plate for 12 h for later use.
[0047] The composite solid electrolyte with soft filler prepared in this experimental example was tested, and the results are as follows:
[0048] like Figure 1 As shown, the solid electrolyte prepared in this example has certain pores and is relatively flat, which is beneficial for the rapid migration of lithium ions at the solid-state battery interface. Tests show that the solid electrolyte prepared in this example has a conductivity of 3.7 × 10⁻⁶ at 25 °C. -5 S / cm, electrochemical window is 0–4.4 V (vs Li / Li + The lithium-ion transference number is 0.55. Example 2
[0049] 10 g of nanocellulose particles were added to 100 mL of DMAc and magnetically stirred for 20 h. The mixture was then centrifuged at 10000 r / min and transferred to a vacuum oven at 80 °C for 20 h to obtain pre-dissolved nanocellulose particles. A certain amount of anhydrous lithium chloride was added to the DMAc solvent until the anhydrous lithium chloride was completely dissolved and stirred continuously for 24 h, maintaining a molar ratio of 0.2:1 to obtain a DMAc / LiCl solution. 10 g of the pre-dissolved nanocellulose particles were taken and added to 50 mL of the DMAc / LiCl solution and stirred evenly to obtain lithium-ionized cellulose. 1 g of PVDF and 0.22 mol / L LiTFSI were added to 8 mL of DMAc solvent and magnetically stirred for 24 h. Then, 5.5% lithium cellulose of PVDF was added and the mixture was stirred for 24 h to obtain a composite solid electrolyte slurry. The slurry was coated onto a glass plate and placed in an 80 ℃ vacuum oven to dry for 24 h to obtain a composite solid electrolyte. Then, it was transferred to an argon-filled glove box and dried on a heating plate at 80 ℃ for 12 h for later use.
[0050] The composite solid electrolyte with soft filler prepared in this experimental example was tested, and the results are as follows:
[0051] like Figure 2 As shown, the solid electrolyte prepared in this example has fine pores and is relatively flat, which is beneficial for the rapid migration of lithium ions at the solid-state battery interface. Tests show that the solid electrolyte prepared in this example has a conductivity of 1.02 × 10⁻⁶ at 25 °C. -4 S / cm, electrochemical window is 0–4.8 V (vs Li / Li + The lithium-ion transference number is 0.67; the solid-state lithium iron phosphate battery prepared using a solid electrolyte with soft filler can stably cycle 300 times at room temperature and 0.5 C. Example 3
[0052] 18 g of nanocellulose particles were added to 100 mL of DMAc and magnetically stirred for 24 h. The mixture was then centrifuged at 10000 r / min and transferred to a vacuum oven at 80 °C for 24 h to obtain pre-dissolved nanocellulose particles. A certain amount of anhydrous lithium chloride was added to the DMAc solvent until the anhydrous lithium chloride was completely dissolved, and the mixture was stirred continuously for 24 h, maintaining a molar ratio of 0.15:1 to obtain a DMAc / LiCl solution. 10 g of the pre-dissolved nanocellulose particles were taken and added to 50 mL of the DMAc / LiCl solution and stirred evenly to obtain lithium-ionized cellulose. 0.8 g of PVDF and 0.22 mol / L LiTFSI were added to 8 mL of DMAc solvent and magnetically stirred for 24 h. Then, 7.2% (w / w) of lithium cellulose PVDF was added, and the mixture was stirred for 24 h to obtain a composite solid electrolyte slurry. The slurry was coated onto a glass plate and placed in an 80 ℃ vacuum oven to dry for 24 h to obtain a composite solid electrolyte. Then, it was transferred to an argon-filled glove box and dried on an 80 ℃ heating plate for 12 h for later use.
[0053] The composite solid electrolyte with soft filler prepared in this experimental example was tested, and the results are as follows:
[0054] like Figure 3 As shown, the solid electrolyte prepared in this example has almost no pores and is flat, which is conducive to the rapid migration of lithium ions at the solid-state battery interface. Tests show that the solid electrolyte prepared in this example has a conductivity of 1.85 × 10⁻⁶ at 25°C. -4 S / cm, electrochemical window is 0–5.3 V (vs Li / Li + The lithium-ion transference number is 0.79; the solid-state lithium iron phosphate battery prepared using a solid electrolyte with soft filler can stably cycle 500 times at room temperature and 0.5 C. Example 4
[0055] 16 g of nanocellulose particles were added to 100 mL of DMAc and magnetically stirred for 24 h. The mixture was then centrifuged at 10000 r / min and transferred to a vacuum oven at 80 °C for 24 h to obtain pre-dissolved nanocellulose particles. A certain amount of anhydrous lithium chloride was added to the DMAc solvent until the anhydrous lithium chloride was completely dissolved, and the mixture was stirred continuously for 24 h, maintaining a molar ratio of 0.12:1 to obtain a DMAc / LiCl solution. 12 g of the pre-dissolved nanocellulose particles were taken and added to 50 mL of the DMAc / LiCl solution and stirred evenly to obtain lithium-ionized cellulose. 0.6 g of PVDF and 0.22 mol / L LiTFSI were added to 8 mL of DMAc solvent and magnetically stirred for 24 h. Then, 8% (w / w) of lithium cellulose PVDF was added, and the mixture was stirred for 24 h to obtain a composite solid electrolyte slurry. The slurry was coated onto a glass plate and placed in an 80 ℃ vacuum oven for drying for 24 h to obtain a composite solid electrolyte. The electrolyte was then transferred to an argon-filled glove box and dried on an 80 ℃ heating plate for 12 h for later use.
[0056] The composite solid electrolyte with soft filler prepared in this experimental example was tested, and the results are as follows:
[0057] like Figure 4 As shown, the solid electrolyte prepared in this example has no obvious pores and is flat, which is conducive to the rapid migration of lithium ions at the solid-state battery interface. Tests show that the solid electrolyte prepared in this example has a conductivity of 1.36 × 10⁻⁶ at 25 °C. -4 S / cm, electrochemical window is 0–5.1 V (vs Li / Li + The lithium-ion transference number is 0.68; the solid-state lithium iron phosphate battery prepared using a solid electrolyte with soft filler can stably cycle 400 times at room temperature and 0.5 C. Comparative Example 1
[0058] 0.8 g of PVDF and 0.22 mol / L LiTFSI were added to 8 mL of DMAc solvent and magnetically stirred for 24 h. The mixture was stirred for 24 h to obtain a composite solid electrolyte slurry. The slurry was coated onto a glass plate and placed in a vacuum oven at 80 ℃ for 24 h to obtain a composite solid electrolyte. Then, it was transferred to a glove box filled with argon gas and dried on a heating plate at 80 ℃ for 12 h for later use.
[0059] The composite solid electrolyte prepared in this experimental example was tested, and the results are as follows:
[0060] like Figure 5As shown, the solid electrolyte prepared in this example has obvious surface pores, which is detrimental to the migration of lithium ions at the solid-state battery interface. Tests show that the solid electrolyte prepared in this example has a conductivity of 4.7 × 10⁻⁶ at 25 °C. -6 S / cm, electrochemical window is 0–4.3 V (vs Li / Li + The lithium-ion transference number is 0.16.
[0061] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.
Claims
1. A method for preparing a composite solid electrolyte with soft filler, characterized in that: Lithium-ionized cellulose was added to the polymer slurry, stirred to obtain a composite solid electrolyte slurry, and dried to obtain the composite solid electrolyte. The polymer slurry is obtained by adding a polymer and a lithium salt to a solvent; The mass ratio of the polymer to the solvent is between 1:100 and 3:10; The molar concentration of the lithium salt is between 0.125 and 0.5 mol / L; The content of the lithium cellulose as a percentage of the polymer weight does not exceed 8 wt%. The method for preparing the lithium-ionized cellulose includes the following steps: Step 1: Add nanocellulose particles to DMAc solvent and stir magnetically until the cellulose layer on the surface of the nanocellulose particles is detached; then centrifuge to obtain wet pre-dissolved nanocellulose; after drying, obtain pre-dissolved nanocellulose particles; the mass ratio of nanocellulose particles to DMAc is between 0.05 and 0.
2. Step 2: Add anhydrous lithium chloride to DMAc solvent and stir until LiCl is completely dissolved to obtain DMAc / LiCl solution; the molar ratio of LiCl / DMAc is between 0:1 and 0.22:
1. Step 3: Add the pre-dissolved nanocellulose particles obtained in Step 1 to the DMAc / LiCl solution obtained in Step 2, stir evenly, and obtain lithium cellulose; the mass fraction of the pre-dissolved nanocellulose particles is between 4wt% and 30wt%.
2. The method for preparing a composite solid electrolyte with soft filler as described in claim 1, characterized in that: The preparation method of the polymer slurry is as follows: the polymer and lithium salt are added to a solvent and magnetically stirred overnight, with the stirring time controlled between 6 and 36 hours and the stirring rate controlled between 200 and 1500 r / min.
3. The method for preparing a composite solid electrolyte with soft filler as described in claim 1, characterized in that: The drying temperature is maintained between 50 and 120°C, and the drying time is controlled between 6 and 36 hours.
4. The method for preparing a composite solid electrolyte with soft filler as described in claim 1, characterized in that: The polymer is one or more of the following: polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate, polyethylene succinate, polypropylene oxide, polyethyleneimine, and polyvinylidene chloride. The lithium salt is one or more of lithium perchlorate, lithium bis(trifluoromethanesulfonylimide) and lithium bis(fluorosulfonylimide), lithium tetrafluoroborate, lithium hexafluoroarsenate and lithium hexafluorophosphate. The solvent is one or more selected from N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide, triethyl phosphate, dimethyl sulfoxide, ethanol, methanol, acetonitrile, and acetone.
5. The method for preparing a composite solid electrolyte with soft filler as described in claim 1, characterized in that: The stirring rate in step one is controlled between 200 and 1500 r / min, and the time is controlled between 6 and 36 h. The centrifugal speed for centrifugation in step one is controlled within 2000–12000 r / min; The drying temperature in step one is maintained between 50 and 120°C, and the drying time is controlled between 6 and 36 hours. The stirring rate in step two is controlled between 200 and 1500 r / min, and the stirring time is controlled between 6 and 36 h. The stirring rate in step three is controlled between 200 and 1500 r / min, and the stirring time is controlled between 6 and 36 h.
6. The method for preparing a composite solid electrolyte with soft filler as described in claim 1, characterized in that: The nanocellulose particles are one of various cellulose nanofibers, cellulose nanosheets, and nanocellulose particles prepared and purified from trees, bamboo, cotton, marine algae, and marine bacteria.