Preparation method and application of dual-modified high-performance cellulose-based solid electrolyte membrane

Abstract

The invention discloses a preparation method and application of a dual-modified high-performance cellulose-based solid-state electrolyte membrane, the dual-modified high-performance cellulose-based solid-state electrolyte membrane is prepared through two strategies of grafting a zwitterionic compound and introducing metal ions to form a complex, and the dual-modified high-performance cellulose-based solid-state electrolyte membrane is applied to a solid-state lithium battery to test the lithium storage performance; according to the invention, the comprehensive performance of the solid electrolyte membrane, such as ionic conductivity, lithium ion transference number, stable voltage window and long cycle performance, is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of solid-state lithium batteries and relates to a preparation method and application of a double-modified high-performance cellulose-based solid electrolyte membrane. Background Art

[0002] Solid-state lithium batteries have the characteristics of high energy density and high safety, and are expected to solve major safety hazards and industry pain points such as leakage, explosion, and spontaneous combustion of traditional liquid lithium batteries. The research and development of high-performance solid electrolyte materials is crucial to the development of solid-state lithium batteries.

[0003] Polymer-based solid electrolytes are composed of polymer matrix and lithium salt complexes. They have many advantages such as light weight, easy processing and high flexibility, and have attracted widespread attention. Common polymer solid electrolyte matrices mainly include cellulose containing polar functional groups, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer and polyacrylonitrile. The mobility and flexibility of polymer molecular segments containing functional groups affect the performance of polymer solid electrolytes. However, the crystallinity of polymer-based solid electrolytes affects the Li + Migration leads to lower ionic conductivity, so the ionic conductivity of polymer-based solid electrolytes is often improved through doping, blending, structural design and other methods.

[0004] Cellulose is the most abundant natural polymer material in nature. It has many advantages such as low cost, renewable and degradable. It is a solid electrolyte matrix material with great development potential. In view of this, the present invention intends to use cellulose as the matrix, and adopt two strategies of grafting amphoteric compounds and forming metal complexes to improve its ionic conductivity, prepare cellulose-based solid electrolyte membrane, and test its application feasibility to promote the research and development of solid-state lithium batteries. Summary of the invention

[0005] The present invention mainly aims at the problems of low ionic conductivity and lithium ion migration number of fiber-based solid electrolytes, and adopts two strategies of chemical grafting of zwitterionic compounds and introduction of metal ion complexes, and utilizes their synergistic effect to improve the comprehensive performance of cellulose-based solid electrolytes such as ionic conductivity and lithium ion migration number.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a double-modified high-performance cellulose-based solid electrolyte membrane, the specific steps are as follows:

[0008] Step 1: immersing the cellulose membrane in a tannic acid solution for 16-24 hours to obtain a tannic acid-grafted cellulose membrane, and then immersing it in a sulfonic acid betaine solution for 8-12 hours to obtain a zwitterionic compound-modified cellulose membrane;

[0009] Step 2: immersing the cellulose membrane modified with the zwitterionic compound obtained in the above step 1 in a metal ion solution for 2-5 hours to obtain a cellulose membrane complexed with metal ions;

[0010] Step 3: Immerse the metal ion complexed cellulose membrane in step 2 in a lithium salt solution for 4-12 hours, vacuum dry at 60°C for 20-24 hours, and then press at 10-15 MPa for 30-50 minutes to obtain a smooth and flat dual-strategy modified cellulose-based solid electrolyte membrane.

[0011] The cellulose membrane described in step 1 includes a lignocellulose membrane, a cellulose acetate membrane, a carboxymethyl cellulose membrane or a methyl cellulose membrane, etc., with a thickness of 70-100 μm, all of which are conventional commercial products or can be prepared by conventional methods; the concentration of the tannic acid solution is 8-12 mg / mL, and the solvent of the tannic acid solution is Tris-HCL buffer with a concentration of 10-12 mmol / L and a pH of 8.0-8.5; the concentration of the sulfobetaine solution is 8-12 mg / mL.

[0012] The metal ion solution described in step 2 includes zinc gluconate solution, zinc acetate solution, zinc chloride solution, nickel gluconate solution, nickel acetate solution, nickel chloride solution, copper gluconate solution, copper acetate solution, copper chloride solution, ferric gluconate solution, ferric acetate solution or ferric chloride solution, etc., with a concentration of 10-15 mg / mL.

[0013] The lithium salt described in step 3 includes lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate or lithium perchlorate, etc. The concentration of the lithium salt solution is 10-20 mg / mL, and the solvent is N,N-dimethylformamide or N-methylpyrrolidone, etc.

[0014] The present invention also provides the application of assembling a solid-state lithium battery with the double-modified high-performance cellulose-based solid electrolyte membrane prepared by the preparation method and a positive electrode and a lithium metal negative electrode, and testing its electrochemical lithium storage performance.

[0015] Beneficial effects of the present invention:

[0016] The present invention adopts the synergistic effect of the dual strategies of surface modification and metal ion complexation. Sulfonate betaine can promote the dissociation of lithium salt and release more free Li + , metal ion complex, expanded the distance between cellulose molecular chains, reduced the crystallinity of cellulose, improved the mobility of chain segments, and constructed Li + Fast migration channels improve the overall performance of solid electrolytes. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the synergistic effect mechanism between the surface modification of cellulose-based composite solid electrolyte membrane and metal ion complex;

[0018] Figure 2 The surface morphology and elemental scan of the cellulose-based solid electrolyte membrane prepared in Example 3;

[0019] Figure 3 The first charge and discharge curve of the solid-state battery assembled with the cellulose-based solid electrolyte membrane, lithium iron phosphate positive electrode and lithium negative electrode prepared in Example 3 at a charge and discharge rate of 1.0C;

[0020] Figure 4 is the ionic conductivity of the cellulose-based solid electrolyte membrane prepared in Example 4 at 25-45°C;

[0021] Figure 5 The cyclic stability curve of the solid-state battery assembled with the cellulose-based solid electrolyte membrane, lithium iron phosphate positive electrode and lithium negative electrode prepared in Example 4 at 1.0C rate charge and discharge. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0023] Example 1

[0024] The cellulose acetate membrane was immersed in 8 mg / mL tannic acid solution (solvent: Tris-HCl buffer, 10 mmol / L, pH=8.5) for 18 h to obtain a cellulose acetate membrane grafted with tannic acid;

[0025] The cellulose acetate membrane grafted with tannic acid was immersed in a sulfobetaine solution with a concentration of 8 mg / mL for 12 hours to obtain a cellulose acetate membrane modified with a zwitterionic compound grafted with sulfobetaine;

[0026] The cellulose acetate membrane modified with zwitterionic compounds was immersed in a 10 mg / mL aqueous solution of zinc gluconate for 3 h to obtain Zn 2+ Complexed cellulose acetate membrane;

[0027] The cellulose acetate membrane complexed with metal ions was further immersed in a 12 mg / mL N,N-dimethylformamide solution of lithium bis(trifluoromethanesulfonyl)imide LiTFSI for 8 h, then vacuum dried at 60 °C for 24 h, and then pressed at 10 MPa for 30 min to obtain a smooth and flat dual-strategy modified cellulose acetate-based solid electrolyte membrane.

[0028] Figure 1Schematic diagram of the synergistic effect mechanism between the surface modification of cellulose-based solid electrolyte membranes and metal ion complexes. Zwitterions promote the dissociation of lithium salts and release more free lithium ions. After the metal ions are complexed with the hydroxyl groups on the cellulose molecular chains, the distance between the molecular chains is expanded, which is beneficial to the rapid migration of lithium ions. The synergistic effect of the two strategies constructs a stable and fast lithium ion migration channel.

[0029] The dual-strategy modified cellulose acetate-based composite solid electrolyte membrane prepared in this example was assembled into a solid-state lithium battery with a lithium iron phosphate positive electrode material and a lithium sheet negative electrode in a CR2032 or CR2025 stainless steel battery shell, and its electrochemical performance was tested.

[0030] Example 2

[0031] The methylcellulose membrane was immersed in a 12 mg / mL tannic acid solution (solvent: Tris-HCl buffer, 10 mmol / L, pH=8.5) for 16 h to obtain a tannic acid-grafted methylcellulose membrane;

[0032] The methyl cellulose membrane grafted with tannic acid was immersed in a 10 mg / mL sulfobetaine solution for 10 h to obtain a methyl cellulose membrane modified with a zwitterionic compound grafted with sulfobetaine;

[0033] The zwitterionic compound-modified methylcellulose membrane was immersed in a 15 mg / mL nickel chloride aqueous solution for 2 h to obtain Ni 2+ Complexed methylcellulose membrane;

[0034] The methyl cellulose membrane complexed with metal ions was further immersed in a 14 mg / mL N-methylpyrrolidone solution of lithium hexafluorophosphate for 6 h, then vacuum dried at 60 °C for 24 h, and then pressed at 10 MPa for 50 min to obtain a smooth and flat dual-strategy modified methyl cellulose-based solid electrolyte membrane.

[0035] The dual-strategy modified methyl cellulose-based composite solid electrolyte membrane prepared in this example was assembled into a solid-state lithium metal battery with a lithium iron phosphate positive electrode and a lithium sheet negative electrode, and its electrochemical performance was tested.

[0036] Example 3

[0037] The lignocellulose membrane was immersed in 8 mg / mL tannic acid solution (solvent: Tris-HCl buffer, 12 mmol / L, pH=8) for 24 h to obtain a tannic acid-grafted lignocellulose membrane;

[0038] The tannic acid-grafted cellulose membrane was immersed in a 12 mg / mL sulfonated betaine solution for 8 hours to obtain a sulfonated betaine-grafted zwitterionic compound-modified cellulose membrane.

[0039] The zwitterionic compound-modified lignocellulose membrane was immersed in a 10 mg / mL ferric acetate aqueous solution for 4 h to obtain Fe 3+ Complexed lignocellulose membranes;

[0040] The above-mentioned metal ion complexed cellulose membrane was further immersed in a 12 mg / mL N,N-dimethylformamide solution of lithium bis(trifluoromethanesulfonyl)imide LiTFSI for 12 h, then vacuum dried at 60 °C for 20 h, and then pressed at 12 MPa for 40 min to obtain a smooth and flat dual-strategy modified cellulose-based solid electrolyte membrane.

[0041] The surface morphology and elemental scanning of the dual strategy modified lignocellulose-based composite solid electrolyte membrane prepared in this example are shown in Figure 2. Figure 2 As shown in the figure, it can be seen that the prepared solid electrolyte membrane is composed of fibers with a diameter of 20-30 μm, and C, O, N, S, F and Fe elements are evenly distributed.

[0042] The dual strategy modified lignocellulose-based composite solid electrolyte membrane prepared in this embodiment is assembled with a lithium iron phosphate positive electrode and a lithium sheet negative electrode into a solid-state lithium metal battery, such as Figure 3 As shown, the initial specific capacity at 1.0C rate charge and discharge is close to 128.5mAh / g.

[0043] Example 4

[0044] The lignocellulose membrane was immersed in a 10 mg / mL tannic acid solution (solvent: Tris-HCl buffer, 11 mmol / L, pH=8.5) for 18 h to obtain a tannic acid-grafted lignocellulose membrane;

[0045] The tannic acid-grafted lignocellulose membrane was immersed in a sulfobetaine solution with a concentration of 8 mg / mL for 12 hours to obtain a sulfobetaine-grafted zwitterionic compound-modified lignocellulose membrane;

[0046] The cellulose membrane modified with zwitterionic compounds was immersed in a 12 mg / mL copper acetate aqueous solution for 5 h to obtain Cu 2+ Complexed lignocellulose membranes;

[0047] The above-mentioned cellulose membrane with complexed metal ions was further immersed in a 20 mg / mL N,N-dimethylformamide solution of lithium bis(trifluoromethanesulfonyl)imide LiTFSI for 4 h, then vacuum dried at 60 °C for 22 h, and then pressed at 15 MPa for 30 min to obtain a smooth and flat dual-strategy modified cellulose-based solid electrolyte membrane.

[0048] The ionic conductivity of the dual strategy modified lignocellulose-based composite solid electrolyte membrane prepared in this example was measured. Figure 4 As shown, the ionic conductivity at 25℃, 30℃, 35℃, 40℃, and 45℃ is 3.58×10 -4 5.65×10 -4 , 6.86×10 -4 ,8.28×10 -4 , 9.02×10 -4 S / cm.

[0049] The dual strategy modified lignocellulose-based composite solid electrolyte membrane prepared in this embodiment is assembled with lithium iron phosphate positive electrode and lithium sheet negative electrode to form a solid lithium metal battery with a reversible discharge specific capacity of 140.1 mAh / g at 1.0C charge and discharge. Figure 5 As shown in the figure, there is no obvious attenuation of the discharge capacity after 60 cycles.

[0050] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for preparing a double-modified high-performance cellulose-based solid electrolyte membrane, characterized in that: The specific steps are as follows: Step 1: immersing the cellulose membrane in a tannic acid solution for 16-24 hours to obtain a tannic acid-grafted cellulose membrane, and then immersing it in a sulfonic acid betaine solution for 8-12 hours to obtain a zwitterionic compound-modified cellulose membrane; Step 2: immersing the cellulose membrane modified by the zwitterionic compound in a metal ion solution for 2-5 hours to obtain a cellulose membrane complexed with metal ions; Step 3: Immerse the cellulose membrane complexed with metal ions in a lithium salt solution for 4-12 hours, vacuum dry it at 60°C for 20-24 hours, and press it at 10-15 MPa for 30-50 minutes to obtain a smooth and flat double-modified cellulose-based solid electrolyte membrane.

2. The method for preparing the double-modified high-performance cellulose-based solid electrolyte membrane according to claim 1, characterized in that: In step 1, the cellulose membrane is a lignocellulose membrane, a cellulose acetate membrane, a carboxymethyl cellulose membrane or a methyl cellulose membrane.

3. The method for preparing the double-modified high-performance cellulose-based solid electrolyte membrane according to claim 1, characterized in that: In step 1, the concentration of the tannic acid solution is 8-12 mg / mL, the solvent of the tannic acid solution is Tris-HCL buffer, the concentration of the Tris-HCL buffer is 10-12 mmol / L, and the pH is 8.0-8.

5.

4. The method for preparing the double-modified high-performance cellulose-based solid electrolyte membrane according to claim 1, characterized in that: The concentration of the sulfobetaine solution in step 1 is 8-12 mg / mL.

5. The method for preparing the double-modified high-performance cellulose-based solid electrolyte membrane according to claim 1, characterized in that: In step 2, the metal ion solution is zinc gluconate solution, zinc acetate solution, zinc chloride solution, nickel gluconate solution, nickel acetate solution, nickel chloride solution, copper gluconate solution, copper acetate solution, copper chloride solution, ferric gluconate solution, ferric acetate solution or ferric chloride solution, and the concentration is 10-15 mg / mL.

6. The method for preparing a double-modified high-performance cellulose-based solid electrolyte membrane according to claim 1, characterized in that: In step 3, the lithium salt is lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate or lithium perchlorate, the concentration of the lithium salt solution is 10-20 mg / mL, and the solvent is N,N-dimethylformamide or N-methylpyrrolidone.

7. Application of the double-modified high-performance cellulose-based solid electrolyte membrane prepared by the preparation method of claim 1, assembled with a positive electrode and a lithium metal negative electrode into a solid-state lithium battery.

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