A method for preparing low-cost, high-strength biomass fiber-based polymer solid electrolytes based on gamma irradiation

Abstract

The present invention belongs to the field of chemical energy storage and discloses a method for preparing low-cost, high-strength biomass fiber-based cellulose-based polymer composite solid electrolytes based on gamma irradiation. The polymer solid electrolyte uses biomass materials as raw materials, and adopts a combination of chemical treatment and mechanical treatment to prepare nanocellulose, which is then compounded with a polymer solid electrolyte matrix material by a blending method to prepare a polymer solid electrolyte membrane. The biomass fiber-based polymer solid electrolyte is irradiated with gamma rays, and its long polymer chains undergo shear and cross-linking reactions. At the same time, oxygen-containing functional groups and nitrogen-containing functional groups are chemically grafted on the fiber surface to form a uniformly dispersed and firmly anchored fiber-based polymer solid electrolyte. These processes cause the polymer chain segments to become shorter, increase the proportion of the amorphous phase, and thereby promote the formation of a higher ion migration number and a wider electrochemical window, thereby improving the safety of the battery.

Description

Technical Field

[0001] The present invention belongs to the field of chemical energy storage, and in particular relates to a method for preparing low-cost, high-strength biomass fiber-based polymer solid electrolytes based on gamma irradiation. Background Art

[0002] In order to meet the urgent demand for high-performance lithium-ion batteries in electric vehicles, hybrid vehicles and high-end energy storage systems, it is necessary to develop new energy storage technologies that are efficient, environmentally friendly and economical. Electrochemical energy storage has the characteristics of high efficiency and flexibility. In particular, lithium metal batteries, as one of the most common secondary batteries, have excellent rate performance and cycle life. Guo Shumin and others used wood powder as a raw material to explore its possibility as a lithium-ion battery separator. Lithium metal batteries usually use organic solvents as electrolytes, but this has safety hazards such as flammability and corrosion. In addition, the formation of lithium dendrites can pierce the separator, causing the battery to short-circuit and cause serious safety problems. In order to solve the above-mentioned disadvantages of liquid batteries, polymer solid electrolytes provide a new solution. It uses solid electrolytes instead of liquid electrolytes, essentially eliminating the hazards of flammability and leakage.

[0003] In addition, polymer solid electrolytes themselves have plasticity, can stabilize the electrode structure, and have better interfacial compatibility. Polymer blending technology is an effective strategy to combine the advantages of different polymers, balancing key properties such as ionic conductivity, mechanical strength, thermal stability and electrochemical window. Compared with copolymerization technology, it has lower costs, simpler and more efficient operation. At the same time, biomass materials, as an environmentally friendly, renewable, and easily biodegradable natural polymer, have the advantages of high aspect ratio, high specific surface area and strong network structure. Against the background of increasingly serious resource consumption and environmental pollution problems, the chemical modification and application development of plant cellulose have received widespread attention.

[0004] Although polymer matrices have many advantages, their ion migration numbers are relatively low. When the migration number of electrolyte salts is low, it will cause their concentration to form a gradient inside the electrolyte, thereby causing concentration polarization. This limitation seriously restricts its practical application range. + The conduction mainly occurs in the amorphous region of the complex, so it is key to explore various methods to increase the proportion of amorphous regions to promote the migration of lithium ions.

[0005] Patent CN 114106378 A proposes a method for preparing a natural cellulose gel polymer electrolyte, but its ion migration number is 0.46, which still produces a high polarization voltage and reduces the service life of the battery. Cross-linking, as a technical means, can effectively reduce the proportion of crystalline regions in the polymer matrix and improve the conductivity of the material through this change. When the polymer solid electrolyte is irradiated with gamma rays, it causes the shearing and cross-linking of its long polymer chains, and chemical groups containing oxygen and nitrogen functional groups are grafted on the fiber surface to obtain a uniformly dispersed and firmly anchored fiber-based polymer solid electrolyte, forming shorter polymer chain segments. This process destroys the crystalline structure of the polymer matrix, thereby increasing the proportion of the amorphous phase, promoting a higher ion migration number and a wider electrochemical window. Summary of the Invention

[0006] In response to the safety hazards of liquid batteries such as flammability and corrosion, as well as the low ion migration number of polymer solid electrolytes, the present invention provides a method for preparing low-cost, high-strength biomass fiber-based polymer solid electrolytes based on γ irradiation.

[0007] The plant cellulose used as the raw material for the preparation method provided by the present invention is a natural polymer material that is abundant in resources, environmentally friendly, renewable and biodegradable in nature. Its main structure is a linear macromolecular polysaccharide composed of D-pyranose glucose rings linked to each other by β-1,4 glycosidic bonds, including but not limited to corn cobs, beet pulp, banana peels, apocynum venetum, ramie, etc. The method first uses conventional, easily available and inexpensive biomass materials as raw materials, uses sodium chlorite to remove lignin from the fiber under acidic conditions, and uses an alkaline solution of sodium hydroxide to remove hemicellulose. The purified cellulose obtained by the above method is further dispersed into nano-scale microfibrillated cellulose by sulfuric acid treatment and mechanical treatment.

[0008] The technical solution of the present invention is achieved by the following steps:

[0009] (1) pre-treating the biomass material, washing the degummed biomass material with deionized water multiple times and drying it;

[0010] (2) The dried biomass short fibers are placed in a Soxhlet extractor for dewaxing. The extracting liquid is a benzene-alcohol mixture with a volume ratio of 2:1. The extraction time is controlled at 4-8 hours and the temperature range is 100-130°C. After dewaxing, the fibers are washed with anhydrous ethanol and dried.

[0011] (3) Place the dewaxed and dried biomass material in a 0.7 w / v% sodium chlorite solution at a bath ratio of 1:50. Add glacial acetic acid to maintain the solution acidic conditions. The pH is controlled at 3-6, the temperature range is 75-90°C, and the water bath heating time is controlled at 1-4 hours. After heating, wash repeatedly with deionized water and dry at room temperature.

[0012] (4) The dried fiber is placed in a 16-20 w / v% sodium hydroxide solution with a bath ratio of 1:50, a temperature range of 70-90°C, and a water bath heating time controlled to be 1-4 hours. After heating, the fiber is repeatedly washed with deionized water and dried at room temperature;

[0013] (5) Dilute 98% analytical grade sulfuric acid to 50%, place the dried fiber in 50% sulfuric acid with a bath ratio of 1:50, and heat and stir on a magnetic heating stirrer at 45°C for 2-4 hours;

[0014] (6) Centrifuging the solution hydrolyzed with sulfuric acid, placing the precipitate in deionized water, and centrifuging it again using a centrifugal device, repeating this process several times until the solution becomes neutral;

[0015] (7) Use an ultrasonic cell crusher to crush cells in an ice bath for 0.5-1.5 h;

[0016] (8) casting a composite film of the prepared nanocellulose and a polymer solid electrolyte matrix material by a blending method, including but not limited to one or more of polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), and drying them under vacuum for 24-48 hours;

[0017] (9) Place the polymer solid electrolyte membrane 60 The sample is irradiated with gamma rays under a radiation source of Co. The sample is placed in an environment with a temperature of 30 to 80° C., an irradiation dose rate is controlled at 0.5 to 100 Gy / min, and a total irradiation dose is 1 to 100 KGy.

[0018] The present invention has the following beneficial effects:

[0019] This polymer solid electrolyte uses biomass materials as raw materials, and adopts a combination of chemical and mechanical treatments to prepare nanocellulose. It is then compounded with the polymer solid electrolyte matrix material through a blending method to prepare a polymer solid electrolyte membrane. The biomass fiber-based polymer solid electrolyte is irradiated with gamma rays, and its long polymer chains undergo shear and cross-linking reactions. At the same time, oxygen-containing functional groups and nitrogen-containing functional groups are chemically grafted on the fiber surface to form a uniformly dispersed and firmly anchored fiber-based polymer solid electrolyte. These processes shorten the polymer chain segments, which in turn promotes the formation of a higher ion transfer number and a wider electrochemical window, thereby improving the safety of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 a is a scanning electron microscope (SEM) image of the biomass fiber of the present invention;

[0021] Figure 1 b is a scanning electron microscope (SEM) image of the degummed biomass fiber of the present invention;

[0022] Figure 1 c is a scanning electron microscope (SEM) image of the nanocellulose after degumming and dewaxing treatment of the present invention;

[0023] Figure 2 a is a scanning electron microscope (SEM) image of the composite film of the biomass fiber and the polymer solid electrolyte matrix material of the present invention;

[0024] Figure 2 b is a scanning electron microscope (SEM) image of the composite film of the degummed biomass fiber and the polymer solid electrolyte matrix material of the present invention;

[0025] Figure 2 c is a scanning electron microscope (SEM) image of the composite film of nanocellulose and polymer solid electrolyte matrix material after degumming and dewaxing treatment of the present invention;

[0026] Figure 3 LSV diagrams of different electrolytes at 60°C of the present invention;

[0027] Figure 4 The current density of the present invention at room temperature is 0.1 mA cm -2 Cycling curves of lithium-lithium symmetric batteries with different electrolytes.

[0028] Figure 5 It curve diagram of the symmetrical cell with nanocellulose and polymer solid electrolyte matrix material composite film under DC polarization voltage (EIS diagram of the embedded symmetrical cell before and after polarization) DETAILED DESCRIPTION

[0029] The method for preparing a low-cost, high-strength cellulose-based polymer composite solid electrolyte based on gamma irradiation provided by the present invention is described in detail below with reference to specific embodiments.

[0030] Example 1:

[0031] The pretreated apocynum venetum was extracted in a Soxhlet extractor with a 2:1 volume ratio of benzene and alcohol at 110°C for 8 hours. The dried fibers were then placed in a 0.7 w / v% sodium chlorite solution at a bath ratio of 1:50, controlled at a pH of 4, and heated in a 90°C waterbath for 1 hour. After heating, the fibers were repeatedly washed with deionized water and dried at room temperature. The treated fibers were then placed in a 17 w / v% sodium hydroxide solution at a bath ratio of 1:50, heated in a 90°C waterbath for 1 hour, repeatedly washed with deionized water, and dried at room temperature. The dried fibers were then placed in 50% sulfuric acid at a bath ratio of 1:50, heated and stirred at 45°C on a magnetic stirrer for 2 hours. After hydrolysis with sulfuric acid, the solution was repeatedly centrifuged until neutral. The resulting composite film was then dried in a vacuum environment for 24 hours. After drying, the fibers were irradiated with gamma rays at room temperature with a dose of 60 kGy at a rate of 1.0 Gy / min. After the irradiation is completed, the sample is washed and separated and then placed in an oven at 60° C. to dry for 12 h to obtain the Apocynum venetum / PEO composite material.

[0032] Example 2:

[0033] The pretreated corncobs were extracted in a Soxhlet extractor with a 2:1 volume ratio of benzene and alcohol at 120°C for 6 hours. The dried corncobs were then placed in a 0.7 w / v% sodium chlorite solution at a bath ratio of 1:50, controlled at a pH of 5, and heated in an 80°C waterbath for 2 hours. After heating, they were repeatedly washed with deionized water and dried at room temperature. The treated fibers were then placed in an 18 w / v% sodium hydroxide solution at an 80°C waterbath for 2 hours, repeatedly washed with deionized water, and dried at room temperature. The dried fibers were then placed in a 1:50 bath ratio of 50% sulfuric acid at 45°C on a magnetic stirrer for 3 hours. After hydrolysis with sulfuric acid, the solution was repeatedly centrifuged until neutral. The resulting composite film was then dried in a vacuum environment for 36 hours. After drying, the fibers were irradiated with gamma rays at room temperature with a dose of 80 kGy at a rate of 2.0 Gy / min. After irradiation, the sample was washed and separated and then dried in an oven at 60°C for 12 h to obtain a corncob / PAN composite material.

[0034] Example 3:

[0035] The pretreated sugar beet pulp was extracted in a Soxhlet extractor with a 2:1 volume ratio of benzene and alcohol at 130°C for 4 hours. The dried sugar beet pulp was then placed in a 0.7 w / v% sodium chlorite solution at a bath ratio of 1:50, controlled at a pH of 6, and heated in a 75°C waterbath for 3 hours. After heating, it was repeatedly washed with deionized water and dried at room temperature. The treated fiber was then placed in a 17.5 w / v% sodium hydroxide solution at a bath ratio of 75°C for 3 hours, repeatedly washed with deionized water, and dried at room temperature. 98% analytical grade sulfuric acid was diluted to 50%, and the dried fiber was placed in 60% sulfuric acid at a bath ratio of 1:50, heated and stirred at 45°C on a magnetic stirrer for 4 hours. After hydrolysis with sulfuric acid, the solution was repeatedly centrifuged until neutral. The resulting composite was then coated with PVDF to form a membrane, dried under vacuum for 48 hours, and then irradiated with gamma rays at room temperature with a dose of 100 kGy at a rate of 10 Gy / min. After the irradiation is completed, the sample is washed and separated and then placed in an oven at 60°C for 12 hours to obtain the beet pulp / PVDF composite material.

Claims

1. A method for preparing low-cost, high-strength biomass fiber-based polymer solid electrolytes based on gamma irradiation, characterized in that The fiber-based polymer solid electrolyte uses biomass materials as raw materials. The main structure of the selected biomass materials is a linear macromolecular polysaccharide formed by D-pyranose glucose rings linked to each other by β-1,4-glycosidic bonds. Nanocellulose is prepared by combining chemical treatment and mechanical treatment, and then compounded with a polymer solid electrolyte matrix material by a blending method to prepare a polymer solid electrolyte membrane. The polymer solid electrolyte membrane is irradiated by gamma rays to cause shear and cross-linking reactions of the long polymer chains. At the same time, oxygen-containing functional groups and nitrogen-containing functional groups are chemically grafted on the fiber surface to form a uniformly dispersed and firmly anchored fiber-based polymer solid electrolyte. These processes cause the polymer chain segments to become shorter, thereby promoting the formation of a higher ion migration number and a wider electrochemical window, thereby improving the safety of the battery. The method includes the following steps: (1) Pretreatment of biomass materials; (2) forming a composite film of the prepared nanocellulose and polymer solid electrolyte matrix material under a vacuum environment; (3) Place the polymer solid electrolyte membrane in a 60 γ-ray irradiation was performed under a Co irradiation source.

2. The method for preparing low-cost, high-strength biomass fiber-based polymer solid electrolyte based on gamma irradiation according to claim 1, characterized in that The pretreatment method of the biomass material comprises the following steps: Step 1: Degumming of biomass materials. Step 2: Dewaxing the biomass material. (1) washing the degummed hemp fibers with deionized water for multiple times and drying them; (2) dewaxing the dried biomass material, washing it with anhydrous ethanol, and drying it; Step 3: Preparation of nanocellulose, (1) The dewaxed and dried biomass material was placed in a 0.7 w / v% sodium chlorite solution with a bath ratio of 1:

50. Glacial acetic acid was added to maintain the solution in an acidic condition. The solution was heated in a water bath and then repeatedly washed with deionized water and dried at room temperature. (2) The dried fiber was placed in a 17-18 w / v% sodium hydroxide solution with a bath ratio of 1:50, heated in a water bath, and then repeatedly washed with deionized water and dried at room temperature; (3) Dilute 98% analytical grade sulfuric acid to 60%, place the dried fiber in 60% sulfuric acid with a bath ratio of 1:50, and heat and stir on a magnetic heating stirrer at 45°C; (4) centrifuging the solution hydrolyzed with sulfuric acid, placing the precipitate in deionized water, and centrifuging it again using a centrifugal device, repeating this process several times until the solution becomes neutral; (5) Use an ultrasonic cell crusher to crush the cells in an ice bath for 0.5-1.5 hours.

3. The method for preparing low-cost, high-strength biomass fiber-based polymer solid electrolyte based on gamma irradiation according to claim 2, characterized in that In the step 2, the dried biomass material is placed in a Soxhlet extractor for dewaxing treatment. The extracting liquid is a benzene-alcohol mixture with a volume ratio of 2:

1. The extraction time is controlled at 4-8 hours and the temperature range is 100-130°C.

4. The method for preparing low-cost, high-strength biomass fiber-based polymer solid electrolyte based on gamma irradiation according to claim 2, characterized in that In the step 3, the dried biomass material is placed in a 0.7 w / v.% sodium chlorite solution and heated in a water bath. The pH value of the acidic condition is controlled at 3-6, the temperature range is 75-90° C., and the heating time is controlled at 1-4 hours.

5. The method for preparing low-cost, high-strength biomass fiber-based polymer solid electrolyte based on gamma irradiation according to claim 2, characterized in that In the step 3, the dried biomass material is placed in a 17-18 w / v.% sodium hydroxide solution and heated in a water bath at a temperature of 70-90° C. for 1-4 hours.

6. The method for preparing low-cost, high-strength biomass fiber-based polymer solid electrolyte based on gamma irradiation according to claim 2, characterized in that In the step 3, the dried biomass material is placed in 60% sulfuric acid with a bath ratio of 1:50, and the heating and stirring time is 2-4 hours.

7. The method for preparing low-cost, high-strength biomass fiber-based polymer solid electrolyte based on gamma irradiation according to claim 1, characterized in that The polymer solid electrolyte matrix material is compositely formed into a film, which includes polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP). The environment is vacuum and the drying time is 24-48 hours.

8. The method for preparing low-cost, high-strength biomass fiber-based polymer solid electrolyte based on gamma irradiation according to claim 1, characterized in that The polymer solid electrolyte membrane gamma irradiation dose rate is 0.5-100 Gy / min, the irradiation dose is 1-100 KGy, and the irradiation environment temperature is 30-80°C.

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