Modified HKUST-1 / cellulose reference solid electrolyte and preparation method thereof

Abstract

The invention discloses a modified HKUST-1 / cellulose-based solid electrolyte and a preparation method thereof, and belongs to the technical field of lithium metal batteries. The preparation method comprises the following steps: mixing HKUST-1 and a silane coupling agent, and carrying out reflux reaction to obtain a modified HKUST-1 nano filler; and adding the modified HKUST-1 nanofiller into a mixed solution of cellulose and lithium bis (trifluoromethanesulfonimide), adding a stable dispersant, carrying out film casting on the obtained dispersion liquid, and drying to obtain the modified HKUST-1 / cellulose-based solid electrolyte. The ionic conductivity of the quasi-solid electrolyte at 30 DEG C is 8.05 * 10 <-4 >-1.75 * 10 <-3 > S / cm, the electrochemical window is 4.4-4.6 V, the ionic conductivity is high, the ionic transference number is high, the mechanical property is good, the lithium dendrite resistance is strong, and the quasi-solid electrolyte has a very good application value in lithium metal batteries.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium metal batteries, and in particular relates to a modified HKUST-1 / cellulose-based solid electrolyte and a preparation method thereof. Background Art

[0002] With the rapid development of portable electronic devices, the market demand for safe, reliable and high-energy-density batteries continues to grow. Lithium metal batteries are regarded as promising candidate batteries due to their high specific capacity and low operating potential. However, traditional liquid electrolytes are prone to leakage, which may cause safety hazards; while inorganic solid-state batteries have the problem of poor interface stability. In contrast, quasi-solid-state electrolytes, as a highly promising polymer electrolyte, can not only effectively inhibit the growth of lithium dendrites, but also have the advantages of being non-leaky and non-flammable, and can meet the needs of high-safety batteries. However, most of the current polymer substrates cannot simultaneously meet the needs of high ionic conductivity and inhibition of lithium dendrites due to the limitations of lithium ion migration and mechanical properties. Therefore, it is crucial to find a polymer substrate that has both excellent mechanical and electrochemical properties.

[0003] Cellulose is a renewable and easily accessible natural resource that is harmless to the environment and shows great potential in the application field of new energy batteries with extremely high environmental protection requirements. Cellulose molecules have many polar groups with ion conductivity (such as -OH, -O-, etc.). These polar groups can interact with lithium ions and assist in the rapid transmission of lithium ions on the cellulose molecular chain. However, the dense hydrogen bond network between cellulose molecules will seriously hinder ion conduction, which to a certain extent restricts the research on cellulose-based electrolytes.

[0004] HKUST-1 is also known as Cu 3 (BTC) 2 , is a copper-based metal organic framework (MOF) material, which is self-assembled by copper ions and 1,3,5-benzenetricarboxylic acid ligands through coordination bonds to form a three-dimensional porous structure. This porous structure provides a channel for the transmission of lithium ions and promotes the migration of lithium ions. At the same time, the unsaturated copper ions inside HKUST-1 can open the dense hydrogen bond network inside cellulose. The synergistic effect of the two can significantly improve the various properties of cellulose-based solid electrolytes. However, after adding HKUST-1 to the cellulose system, due to surface energy reasons, particles are prone to agglomeration, which affects the performance of the quasi-solid electrolyte. Summary of the invention

[0005] To address the above problems, the present invention provides a modified HKUST-1 / cellulose-based solid electrolyte and its preparation method. By using a silane coupling agent to modify the surface of HKUST-1, the modified HKUST-1 is then introduced into the cellulose system, and a stable dispersant is added. After doctor-blading and drying, a modified HKUST-1 / cellulose-based solid electrolyte is obtained. This quasi-solid electrolyte has high ionic conductivity, high ion transference number, good mechanical properties, and strong lithium dendrite resistance.

[0006] The present invention is achieved through the following technical solutions:

[0007] A preparation method of a modified HKUST-1 / cellulose-based solid electrolyte, in which HKUST-1 and a silane coupling agent are mixed and subjected to a reflux reaction to obtain modified HKUST-1 nanocomposite fillers; the modified HKUST-1 nanocomposite fillers are added to a mixed solution of cellulose and lithium bis(trifluoromethanesulfonyl)imide, and a stable dispersant is added. The resulting dispersion is doctor-blade cast and dried to obtain a modified HKUST-1 / cellulose-based solid electrolyte.

[0008] Further, the preparation method specifically includes the following steps:

[0009] (1) Preparation of modified HKUST-1 nanocomposite fillers: Copper salts and 1,3,5-benzenetricarboxylic acid are dissolved in absolute ethanol and stirred at room temperature. After centrifugation, washing, and vacuum drying, HKUST-1 is obtained; HKUST-1 is added to toluene, stirred, and then a silane coupling agent is added. A reflux reaction is carried out under oil bath heating. After the reaction is completed, it is naturally cooled to room temperature, and then centrifuged, washed, and vacuum dried again to obtain modified HKUST-1 nanocomposite fillers;

[0010] (2) Preparation of modified HKUST-1 / cellulose-based solid electrolyte: Cellulose is dissolved in N-methylpyrrolidone and stirred at room temperature. Then, lithium bis(trifluoromethanesulfonyl)imide is added and stirred evenly to obtain a mixed solution; the modified HKUST-1 nanocomposite fillers are added to the mixed solution and stirred evenly at room temperature. Then, a stable dispersant is added and stirred. The resulting dispersion is cast into a film by doctor-blading and then vacuum dried to obtain a modified HKUST-1 / cellulose-based solid electrolyte.

[0011] Further, in step (1), the silane coupling agent is γ-glycidoxypropyltrimethoxysilane, and the mass ratio of HKUST-1 to the silane coupling agent is 20 - 30:1.

[0012] Further, in step (1), the temperature of the reflux reaction is 90 - 120 °C, and the time is 3 - 6 h.

[0013] Further, in step (1), the copper salt is one or a mixture of two of copper nitrate trihydrate and copper acetate, and the mass ratio of the copper salt to 1,3,5-benzenetricarboxylic acid is 2-5:1.

[0014] Further, in step (2), the stable dispersant is ethylenediamine tetraacetic dianhydride or glutaraldehyde.

[0015] Further, in step (2), the mass ratio of lithium bis(trifluoromethanesulfonyl)imide to cellulose is 1:2-5; the mass ratio of lithium bis(trifluoromethanesulfonyl)imide to the modified HKUST-1 nanofiller is 1:0.04-0.28; the mass ratio of the stable dispersant to the modified HKUST-1 nanofiller is 1:80-100.

[0016] Further, in step (2), the cellulose is one or more of methyl cellulose, ethyl cellulose, cellulose acetate, carboxymethyl cellulose, and hydroxypropyl methyl cellulose.

[0017] A modified HKUST-1 / cellulose-based solid electrolyte prepared by the preparation method as described above.

[0018] Further, the ionic conductivity of the modified HKUST-1 / cellulose-based solid electrolyte at 30 °C is 8.05×10 -4 ~1.75×10 -3 S / cm, and the electrochemical window is 4.4-4.6 V.

[0019] The preparation principle of the modified HKUST-1 / cellulose-based solid electrolyte of the present invention:

[0020] The present invention utilizes a silane coupling agent to modify the metal-organic framework material copper-based MOF (HKUST-1) to obtain modified HKUST-1. Functional groups with good affinity for cellulose are grafted onto the surface of the modified HKUST-1. Among them, the epoxy group can react with the hydroxyl groups in the cellulose molecule to form covalent bond connections, and at the same time, hydrogen bonds can also be formed to enhance the interaction; the silanol formed after the hydrolysis of the trimethoxysilyl group can condense with the hydroxyl groups on the cellulose surface to generate siloxane bonds. These effects jointly promote the binding between the modified HKUST-1 and cellulose, building a bridge that can stably transport lithium ions. At the same time, HKUST-1 itself has a unique pore structure, opening up more efficient transport channels for lithium ions. And by using the coordination effect between the unsaturated open copper metal sites in HKUST-1 and the hydroxyl groups (-OH) in the cellulose molecule, the dense hydrogen bond network inside the cellulose is broken, the intermolecular polymer structure is expanded, and the transport of lithium ions is decoupled from the relaxation of polymer segments. The synergistic effect of the three significantly improves the ionic conductivity, reduces the ionic migration resistance, increases the ionic transference number, and reduces the local polarization and uneven deposition caused by poor ionic transport. While breaking the original hydrogen bond network, the stability of the crystalline region is reduced, effectively reducing the original high crystallinity of cellulose, so as to prepare a quasi-solid-state electrolyte with more excellent performance.

[0021] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0022] 1. The present invention utilizes a silane coupling agent to graft functional groups with good affinity for cellulose onto the surface of HKUST-1, building a bridge that can stably transport lithium ions. At the same time, HKUST-1 itself has an adjustable porous structure, and its open and unsaturated copper ions can combine with the hydroxyl groups inside the cellulose to open the dense hydrogen bond network, thereby constructing a multi-level ion channel, and thus obtaining a cellulose-based quasi-solid-state electrolyte with both high ionic conductivity and excellent lithium dendrite resistance.

[0023] 2. The quasi-solid-state electrolyte of the present invention has high ionic conductivity and high lithium ion transference number. The ionic conductivity at 30 °C is 8.05×10 -4 ~1.75×10 -3S / cm. The silane coupling agent forms a uniform and ordered molecular layer on the surface of HKUST-1. These molecular layers can act as a "bridge" to guide the ordered arrangement and orientation of cellulose molecules on its surface, promote the interaction and entanglement between cellulose chains, and form a more continuous conductive channel. The epoxy group and trimethoxysilyl group contained in the silane coupling agent have good affinity with cellulose. The epoxy group can react with the hydroxyl group in the cellulose molecule to form a covalent bond, and at the same time can also form hydrogen bonds to enhance the interaction. The silanol formed after the hydrolysis of the trimethoxysilyl group can condense with the hydroxyl group on the cellulose surface to form a siloxane bond. These interactions further enhance the stability and coherence of the conductive channel. At the same time, HKUST-1 itself has a porous structure, and its addition provides more transport channels for lithium ions, improving the conductivity of lithium ions and the lithium ion transference number.

[0024] 3. In the present invention, HKUST-1 can reduce the crystallinity of cellulose and improve the lithium ion transport rate. HKUST-1 has unsaturated open copper ion sites, which can coordinate with the hydroxyl group (-OH) in the cellulose molecule, break the dense hydrogen bond network inside cellulose, improve the transport environment of Li + and reduce the activation energy, while reducing the crystallinity of cellulose.

[0025] 4. The quasi-solid-state electrolyte of the present invention has a wide electrochemical window, and the electrochemical window is 4.4 - 4.6V. Due to the successful construction of multi-level ion channels in the quasi-solid-state electrolyte, the growth of lithium dendrites caused by local electron aggregation is avoided, so it has a wide electrochemical window and is suitable for more high-voltage cathode materials, such as ternary cathode materials like lithium cobaltate and lithium nickel cobalt manganate.

[0026] 5. In the present invention, modified HKUST-1 is introduced into the cellulose system to improve the interface stability and resist the piercing of lithium dendrites. The introduction of modified HKUST-1 reduces the local polarization and uneven deposition caused by poor ion transport, and further improves the interface stability between the electrolyte membrane and the electrode.

[0027] 6. The modified HKUST-1 nanocomposite filler of the present invention binds more tightly to the cellulose substrate and is more uniformly dispersed. In the present invention, the surface of HKUST-1 is modified with a silane coupling agent, and the obtained modified HKUST-1 is grafted with functional groups having affinity with cellulose, improving its dispersibility in the cellulose solution; a stable dispersant is added to the mixed solution of cellulose and HKUST-1. The stable dispersant can react with the functional groups on the surface of cellulose or HKUST-1 to form a stable three-dimensional network, firmly fixing HKUST-1 in the cellulose solution substrate to prevent its aggregation or sedimentation.

[0028] 7. In the present invention, HKUST-1 can improve the flame retardancy of the quasi-solid electrolyte. As a porous metal-organic framework material, HKUST-1 has good thermal stability. Transition metal ions can promote the oxidation of carbon oxides and capture free radicals in the broken polymer chains, generating a dense and strong carbon layer, which can effectively block the diffusion of heat flow and smoke particles, improve the flame retardancy of the electrolyte, and provide guarantee for the safety performance of the battery.

[0029] 8. The electrolyte absorption rate of the quasi-solid electrolyte of the present invention is greatly improved. The modified HKUST-1 has a porous structure with a specific surface area as high as 893.02 m 2 / g and a large average adsorption pore diameter of 2.21 nm. The porous structure provides abundant adsorption sites, improves the liquid affinity of the electrolyte, and simultaneously forms a three-dimensional network structure synergistically, which is beneficial to the diffusion and absorption of the electrolyte.

[0030] 9. The lithium metal symmetric battery assembled with the quasi-solid electrolyte of the present invention can stably cycle for more than 2000 h, having good electrochemical stability and long-term cycle life. The initial discharge specific capacity of the full battery assembled with this electrolyte is 144 mAh·g -1 at a current density of 0.2 C, the initial Coulomb efficiency is 93.58%, and the capacity retention rate after 200 cycles is 97.29%; at a low current density of 0.1 C, the discharge specific capacity reaches 151.9 mAh·g -1 After five charge-discharge cycles at different current densities, the discharge specific capacity reaches 150.6 mAh·g -1 and the capacity retention rate can reach 99.14%. It can be seen that the full battery assembled with this electrolyte has excellent cycle discharge specific capacity and rate discharge specific capacity characteristics.

[0031] 10. The preparation method of the present invention is simple, the raw materials used are inexpensive, and the preparation cost is low, which is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 N of the modified HKUST-1 nanofiller in Example 4 2 adsorption / desorption curve.

[0033] Figure 2 Electrochemical impedance spectra of CLKH-10, Pure CL, and CLH-10 in Example 4 and Comparative Examples 1-2.

[0034] Figure 3 Electrochemical window diagrams of CLKH-10, Pure CL, and CLH-10 in Example 4 and Comparative Examples 1-2.

[0035] Figure 4Interface compatibility test diagram of CLKH-10 in Example 4.

[0036] Figure 5 Cycling diagram at the same magnification of CLKH-10, Pure CL, and CLH-10 in Example 4 and Comparative Examples 1-2.

[0037] Figure 6 Cycling diagrams at different magnifications of CLKH-10, Pure CL, and CLH-10 in Example 4 and Comparative Examples 1-2. Detailed implementation mode

[0038] The present invention will be further described in detail below through examples. These examples are only used to illustrate the present invention and do not limit the protection scope of the present invention.

[0039] Example 1

[0040] Preparation of modified HKUST-1 / cellulose-based solid electrolyte:

[0041] (1) Preparation of modified HKUST-1 nanofiller: Dissolve 0.5 g of Cu(NO 3 ) 2 ·3H 2 O and 0.25 g of 1,3,5-benzenetricarboxylic acid in 500 mL of absolute ethanol and stir at room temperature for 48 h. Then centrifuge at a speed of 9500 r / min for 8 min, centrifuge three times, and then wash three times with absolute ethanol. Place it in a vacuum oven and dry at 80 °C for 12 h to obtain HKUST-1. Slowly add 0.25 g of HKUST-1 to a three-necked flask containing toluene and stir for 30 min. Then slowly dropwise add 0.01 g of γ-glycidoxypropyltrimethoxysilane. Set the oil bath temperature to 110 °C to make the reaction system in a reflux state. React under this condition for 3 h. After the reaction is completed, naturally cool to room temperature, centrifuge at a high speed of 9500 r / min to precipitate the solid. After pouring off the upper toluene solution, wash three times with toluene, and place it in a vacuum oven and dry at 80 °C for 12 h to obtain the modified HKUST-1 nanofiller.

[0042] (2) Preparation of modified HKUST-1 / cellulose-based solid electrolyte: Dissolve 1 g of cellulose acetate in 3.88 mL of N-methylpyrrolidone, stir at room temperature to form a transparent solution, then add 0.5 g of lithium bis(trifluoromethanesulfonyl)imide and continue to stir evenly to obtain a mixed solution. Add 0.02 g of modified HKUST-1 nanofiller to this mixed solution, stir evenly at room temperature, then add 0.2 mg of ethylenediaminetetraacetic dianhydride and continue to stir evenly to obtain a dispersion. Pour this dispersion into a polytetrafluoroethylene mold, place it in a vacuum oven and dry at 90 °C for 12 h to obtain the modified HKUST-1 / cellulose-based solid electrolyte (denoted as CLKH-2).

[0043] Example 2

[0044] The difference between Example 2 and Example 1 is that in Example 2, the mass of the modified HKUST-1 nanofiller is 0.05 g, and the mass of ethylenediaminetetraacetic dianhydride is 0.5 mg. The remaining preparation processes and conditions are the same as those in Example 1, and the modified HKUST-1 / cellulose-based solid electrolyte is obtained (denoted as CLKH-5).

[0045] Example 3

[0046] The difference between Example 3 and Example 1 is that in Example 3, the mass of the modified HKUST-1 nanofiller is 0.08 g, and the mass of ethylenediaminetetraacetic dianhydride is 0.8 mg. The remaining preparation processes and conditions are the same as those in Example 1, and the modified HKUST-1 / cellulose-based solid electrolyte is obtained (denoted as CLKH-8).

[0047] Example 4

[0048] The difference between Example 4 and Example 1 is that in Example 4, the mass of the modified HKUST-1 nanofiller is 0.1 g, and the mass of ethylenediaminetetraacetic dianhydride is 1.0 mg. The remaining preparation processes and conditions are the same as those in Example 1, and the modified HKUST-1 / cellulose-based solid electrolyte is obtained (denoted as CLKH-10).

[0049] Comparative Example 1

[0050] The difference between Comparative Example 1 and Example 4 is that in Comparative Example 1, HKUST-1 is not added, and the remaining preparation processes and conditions are the same as those in Example 4, and the cellulose-based solid electrolyte (Pure CL) is obtained.

[0051] Comparative Example 2

[0052] The difference between Comparative Example 2 and Example 4 is that in Comparative Example 2, unmodified HKUST-1 is added, and the remaining preparation processes and conditions are the same as those in Example 4, and the HKUST-1 / cellulose-based solid electrolyte is obtained (denoted as CLH-10).

[0053] Example 5

[0054] Example 5 is different from Example 1 in that the mass of the modified HKUST-1 nanofiller in Example 5 is 0.12 g, and the mass of dianhydride of ethylenediaminetetraacetic acid is 1.2 mg. The remaining preparation processes and conditions are the same as those in Example 1, and the modified HKUST-1 / cellulose-based solid electrolyte (denoted as CLKH-12) is prepared.

[0055] Example 6

[0056] Example 6 is different from Example 1 in that the mass of the modified HKUST-1 nanofiller in Example 6 is 0.14 g, and the mass of dianhydride of ethylenediaminetetraacetic acid is 1.4 mg. The remaining preparation processes and conditions are the same as those in Example 1, and the modified HKUST-1 / cellulose-based solid electrolyte (denoted as CLKH-14) is prepared.

[0057] Example 7

[0058] Preparation of modified HKUST-1 / cellulose-based solid electrolyte:

[0059] (1) Preparation of modified HKUST-1 nanofiller: Dissolve 0.75 g of Cu(CH 3 COO) 2 ·H 2 O and 0.25 g of 1,3,5-benzenetricarboxylic acid in 500 mL of absolute ethanol, stir at room temperature for 48 h, then centrifuge at a speed of 9500 r / min for 8 min, centrifuge three times and then continue to wash three times with absolute ethanol, and place in a vacuum oven to dry at 80 °C for 12 h to obtain HKUST-1. Slowly add 0.20 g of HKUST-1 to a three-necked flask containing toluene and stir for 30 min, then slowly dropwise add 0.01 g of γ-glycidoxypropyltrimethoxysilane, set the oil bath temperature to 90 °C, keep the reaction system in a reflux state, react under this condition for 6 h, after the reaction is completed, naturally cool to room temperature, centrifuge at a high speed of 9500 r / min to precipitate the solid, pour off the upper toluene solution, wash three times with toluene, and place in a vacuum oven to dry at 80 °C for 12 h to obtain the modified HKUST-1 nanofiller.

[0060] (2) Preparation of modified HKUST-1 / cellulose-based solid electrolyte: Dissolve 1.5 g of hydroxypropyl methylcellulose in 4.0 mL of N-methylpyrrolidone. After stirring at room temperature, add 0.5 g of lithium bis(trifluoromethanesulfonyl)imide and continue stirring evenly to obtain a mixed solution. Add 0.05 g of modified HKUST-1 nanofiller to this mixed solution. After stirring evenly at room temperature, add 0.6 mg of glutaraldehyde and continue stirring evenly to obtain a dispersion. Pour this dispersion into a polytetrafluoroethylene mold and place it in a vacuum oven to dry at 90 °C for 12 h to obtain the modified HKUST-1 / cellulose-based solid electrolyte.

[0061] Example 8

[0062] Preparation of modified HKUST-1 / cellulose-based solid electrolyte:

[0063] (1) Preparation of modified HKUST-1 nanofiller: Dissolve 0.5 g of Cu(NO 3 ) 2 ·3H 2 O, 0.5 g of Cu(CH 3 COO) 2 ·H 2 O and 0.25 g of 1,3,5-benzenetricarboxylic acid in 500 mL of absolute ethanol and stir at room temperature for 48 h. Then centrifuge at a speed of 9500 r / min for 8 min. After centrifuging three times, continue to wash with absolute ethanol three times and place it in a vacuum oven to dry at 80 °C for 12 h to obtain HKUST-1. Slowly add 0.25 g of HKUST-1 to a three-necked flask containing toluene and stir for 30 min. Subsequently, slowly dropwise add 0.01 g of γ-glycidoxypropyltrimethoxysilane. Set the oil bath temperature to 120 °C to make the reaction system in a reflux state and react under this condition for 4 h. After the reaction is completed, naturally cool to room temperature, centrifuge at a high speed of 9500 r / min to precipitate the solid, pour out the upper toluene solution, wash with toluene three times, and place it in a vacuum oven to dry at 80 °C for 12 h to obtain the modified HKUST-1 nanofiller.

[0064] (2) Preparation of modified HKUST-1 / cellulose-based solid electrolyte: Dissolve 1 g of methylcellulose and 1 g of ethylcellulose in 4.5 mL of N-methylpyrrolidone. After stirring at room temperature, add 0.5 g of lithium bis(trifluoromethanesulfonyl)imide and continue stirring evenly to obtain a mixed solution. Add 0.075 g of modified HKUST-1 nanofiller to this mixed solution. After stirring evenly at room temperature, add 0.9 mg of ethylenediaminetetraacetic dianhydride and continue stirring evenly to obtain a dispersion. Pour this dispersion into a polytetrafluoroethylene mold and place it in a vacuum oven to dry at 90 °C for 12 h to obtain the modified HKUST-1 / cellulose-based solid electrolyte.

[0065] Example 9

[0066] Preparation of Modified HKUST-1 / Cellulose-Based Solid Electrolyte:

[0067] (1) Preparation of Modified HKUST-1 Nanofiller: Dissolve 1.25 g of Cu(NO 3 ) 2 ·3H 2 O and 0.25 g of 1,3,5-benzenetricarboxylic acid in 500 mL of absolute ethanol, stir at room temperature for 48 h, then centrifuge at a speed of 9500 r / min for 8 min, centrifuge three times and then wash with absolute ethanol three times, and place in a vacuum oven to dry at 80 °C for 12 h to obtain HKUST-1. Slowly add 0.30 g of HKUST-1 to a three-necked flask containing toluene and stir for 30 min, then slowly dropwise add 0.01 g of γ-glycidoxypropyltrimethoxysilane, set the oil bath temperature to 105 °C to make the reaction system in a reflux state, react under this condition for 5 h, after the reaction is completed, naturally cool to room temperature, centrifuge at a high speed of 9500 r / min to precipitate the solid, pour off the upper toluene solution, wash with toluene three times, and place in a vacuum oven to dry at 80 °C for 12 h to obtain the modified HKUST-1 nanofiller.

[0068] (2) Preparation of Modified HKUST-1 / Cellulose-Based Solid Electrolyte: Take 1 g of cellulose acetate, 1 g of carboxymethyl cellulose and 0.5 g of hydroxypropyl methyl cellulose and dissolve them in 5.0 mL of N-methylpyrrolidone, stir at room temperature, then add 0.5 g of lithium bis(trifluoromethanesulfonyl)imide and continue to stir evenly to obtain a mixed solution. Add 0.1 g of the modified HKUST-1 nanofiller to this mixed solution, stir evenly at room temperature, then add 1.0 mg of glutaraldehyde and continue to stir evenly to obtain a dispersion. Pour this dispersion into a polytetrafluoroethylene mold and place it in a vacuum oven to dry at 90 °C for 12 h to obtain the modified HKUST-1 / Cellulose-based solid electrolyte.

[0069] Material Property Detection and Analysis

[0070] (1) Detection of Specific Surface Area and Pore Size Distribution of Modified HKUST-1

[0071] Figure 1 This is the N 2 adsorption / desorption curve of the modified HKUST-1 nanofiller in Example 4. Evaluate the specific surface area and pore size distribution of the modified HKUST-1 nanofiller through N 2 adsorption / desorption curve test, and the results are as follows Figure 1As shown. The specific surface area and average adsorption pore diameter of the modified HKUST-1 nanofiller in Example 4 were compared with those of the unmodified HKUST-1 in Comparative Example 2, and the comparison data are shown in Table 1.

[0072] Table 1 Data table of specific surface area and pore diameter

[0073] Comparative Example 2 Example 4 <![CDATA[Specific surface area (m 2 / g)]]> 826.86 893.02 Average adsorption pore diameter (nm) 2.14 2.21

[0074] From Figure 1 the N of the modified HKUST-1 nanofiller 2 adsorption / desorption curve, it can be seen that the specific surface area of the modified HKUST-1 nanofiller is 893.02 m 2 / g, and the average adsorption pore diameter is 2.21 nm. And as can be seen from Table 1, the specific surface area of HKUST-1 without surface modification is 826.86 m 2 / g, and the average adsorption pore diameter is 2.14 nm.

[0075] By comparison, it can be seen that both the specific surface area and the average adsorption pore diameter of the modified HKUST-1 nanofiller are larger than those of the unmodified HKUST-1. This is because the organic group part of the silane coupling agent can form a covering layer on the surface of HKUST-1 during the modification process. This covering layer can prevent the shrinkage or collapse of the HKUST-1 pore channels through steric hindrance effects, and at the same time, some tiny voids can be formed between the organic groups, increasing the specific surface area and pore diameter of the material.

[0076] (2) Electrochemical performance detection of quasi-solid electrolyte

[0077] Figure 2 The electrochemical impedance spectra of CLKH-10, Pure CL, and CLH-10 of Example 4 and Comparative Examples 1-2 are as follows: The alternating current impedance spectra of the SS blocking electrode / quasi-solid electrolyte-LiPF 6 / SS blocking electrode (SS: stainless steel sheet) symmetrical battery were tested. During the test, the frequency range was set to 0.1 - 10 6 Hz, and the impedance diagram of the electrolyte was obtained. From Figure 2 Calculated, the ionic conductivity of CLKH-10 in Example 4 at 30 °C is 1.75×10 -3 S / cm, while the ionic conductivity of CLH-10 prepared by adding the same mass of unmodified HKUST-1 in Comparative Example 2 at 30 °C is 6.66×10 -4 S / cm, and the ionic conductivity of Pure CL prepared without adding HKUST-1 in Comparative Example 1 at 30 °C is only 4.10×10 -4S / cm. This indicates that the ionic conductivity of the cellulose-based solid electrolyte with the modified HKUST-1 nanofiller has been significantly improved.

[0078] The ionic conductivities of the quasi-solid electrolytes in Examples 1-6 and Comparative Examples 1-2 were statistically analyzed, and the data are shown in Table 2.

[0079] Table 2 Data table of ionic conductivity

[0080]

[0081]

[0082] As can be seen from Table 2, the ionic conductivities in Examples 1-6 were 8.05×10 -4 ~1.75×10 -3 S / cm, among which the ionic conductivity of CLKH-10 in Example 4 was the highest, reaching 1.75×10 -3 S / cm. Compared with Pure CL in Comparative Example 1 and CLH-10 in Comparative Example 2, the ionic conductivity of CLKH-10 in Example 4 increased by 326.83% and 162.76% respectively.

[0083] Figure 3 Figure of the electrochemical window of CLKH-10, Pure CL, and CLH-10 in Example 4 and Comparative Examples 1-2: Measured by the SS blocking electrode / quasi-solid electrolyte-LiPF 6 / Li semi-blocking battery using linear sweep voltammetry (LSV) at a scanning rate of 10 mV / s and a voltage range of 2-6 V. As Figure 3 can be seen, the electrochemical window of CLKH-10 in Example 4 was 4.5 V. The electrochemical window of CLH-10 in Comparative Example 2 was 4.2 V, and the electrochemical window of Pure CL in Comparative Example 1 was only 4.1 V. This shows that the cellulose-based solid electrolyte with the modified HKUST-1 nanofiller has a higher electrochemical window.

[0084] Figure 4 Figure of the interfacial compatibility test of CLKH-10 in Example 4: Cyclic testing was carried out by assembling a Li / quasi-solid electrolyte-LiPF 6 / Li lithium metal symmetric battery at a temperature of 30 °C and a current density of 0.1 mA / cm 2 . Figure 4Among them, due to the addition of modified HKUST-1, the local polarization and uneven deposition caused by poor ion transport are reduced, so that the polarization voltage of the lithium metal symmetric battery assembled by CLKH-10 of Example 4 is basically stable and less than 100 mV, and it can stably cycle for more than 2000 h, which fully reflects its good electrochemical stability and long-term cycle life.

[0085] Figure 5 The same-rate cycling diagrams of CLKH-10, Pure CL, and CLH-10 of Example 4 and Comparative Examples 1-2: By assembling the lithium iron phosphate / quasi-solid-state electrolyte-LiPF 6 / Li full battery was subjected to a rate cycling test at a current density of 0.2C. From Figure 5 It can be seen that the initial discharge specific capacity of the lithium iron phosphate / quasi-solid-state electrolyte-LiPF 6 / Li full battery composed of CLKH-10 of Example 4 at a current density of 0.2C is 144 mAh·g -1 , the initial Coulomb efficiency is 93.58%, and the capacity retention rate after 200 cycles is 97.29%. In contrast, the discharge specific capacity of the battery assembled with Pure CL of Comparative Example 1 after 200 cycles is only 112.9 mAh·g -1 , and the capacity retention rate is 87.38%. The capacity retention rate and initial Coulomb efficiency of the battery assembled with CLH-10 of Comparative Example 2 are not much different from those of CLKH-10, but it can be clearly seen that the discharge specific capacity of CLKH-10 is higher.

[0086] Figure 6 The different-rate cycling diagrams of CLKH-10, Pure CL, and CLH-10 of Example 4 and Comparative Examples 1-2: By assembling the lithium iron phosphate / quasi-solid-state electrolyte-LiPF 6 / Li full battery was subjected to different-rate cycling tests at current densities of 0.1C, 0.2C, 0.5C, 1C and then back to 0.1C. From Figure 6 It can be seen that the discharge specific capacity of the full battery assembled with CLKH-10 of Example 4 reaches 151.9 mAh·g at a low current density of 0.1C -1 . When the current density gradually increases to 0.2C, 0.5C, 1C, the discharge specific capacity decreases to 149.5, 138.5 and 80.6 mAh·g respectively -1 . However, after five charge-discharge cycles at different current densities, the discharge specific capacity reaches 150.6 mAh·g again -1When the current density returns to 0.1C again, the capacity retention rate can reach 99.14%. Although the measured capacity retention rate and Coulomb efficiency of the batteries composed of Pure CL in Comparative Example 1 and CLH-10 in Comparative Example 2 are not much different from those of CLKH-10, it can be clearly seen that the discharge specific capacity of CLKH-10 is better. It can be seen that the full battery assembled with CLKH-10 has more excellent cyclic discharge specific capacity and rate discharge specific capacity characteristics.

[0087] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a modified HKUST-1 / cellulose-based solid electrolyte, characterized in that: HKUST-1 and a silane coupling agent are mixed and subjected to a reflux reaction to obtain a modified HKUST-1 nanofiller; the modified HKUST-1 nanofiller is added to a mixed solution of cellulose and lithium bis(trifluoromethanesulfonyl)imide, and a stabilizing dispersant is added, and the obtained dispersion is subjected to cast film formation and then dried to obtain a modified HKUST-1 / cellulose reference solid electrolyte.

2. The method for preparing the modified HKUST-1 / cellulose-based solid electrolyte according to claim 1, characterized in that: The preparation method specifically comprises the following steps: (1) Preparation of modified HKUST-1 nanofiller: copper salt and 1,3,5-benzenetricarboxylic acid are dissolved in anhydrous ethanol, stirred at room temperature, centrifuged, washed and vacuum dried to obtain HKUST-1; HKUST-1 is added to toluene, stirred, and then a silane coupling agent is added, and reflux reaction is carried out under oil bath heating. After the reaction is completed, the mixture is naturally cooled to room temperature, centrifuged again, washed and vacuum dried to obtain a modified HKUST-1 nanofiller; (2) Preparation of modified HKUST-1 / cellulose-based solid electrolyte: cellulose was dissolved in N-methylpyrrolidone, stirred at room temperature, and then lithium bis(trifluoromethanesulfonyl imide) was added and stirred evenly to obtain a mixed solution; modified HKUST-1 nanofiller was added to the mixed solution, stirred evenly at room temperature, and then a stabilizing dispersant was added and stirred evenly, and the obtained dispersion was subjected to film casting and vacuum drying to obtain a modified HKUST-1 / cellulose-based solid electrolyte.

3. The method for preparing the modified HKUST-1 / cellulose-based solid electrolyte according to claim 2, characterized in that: In step (1), the silane coupling agent is γ-glycidyloxypropyltrimethoxysilane, and the mass ratio of HKUST-1 to the silane coupling agent is 20 to 30:

1.

4. The method for preparing the modified HKUST-1 / cellulose-based solid electrolyte according to claim 2, characterized in that: In step (1), the temperature of the reflux reaction is 90-120° C. and the time is 3-6 hours.

5. The method for preparing the modified HKUST-1 / cellulose-based solid electrolyte according to claim 2, characterized in that: In step (1), the copper salt is one or a mixture of copper nitrate trihydrate and copper acetate, and the mass ratio of the copper salt to 1,3,5-benzenetricarboxylic acid is 2 to 5:

1.

6. The method for preparing the modified HKUST-1 / cellulose-based solid electrolyte according to claim 2, characterized in that: In step (2), the stabilizing dispersant is ethylenediaminetetraacetic acid dianhydride or glutaraldehyde.

7. The method for preparing the modified HKUST-1 / cellulose-based solid electrolyte according to claim 2, characterized in that: In step (2), the mass ratio of the lithium bis(trifluoromethanesulfonyl imide) to the cellulose is 1:2-5; the mass ratio of the lithium bis(trifluoromethanesulfonyl imide) to the modified HKUST-1 nanofiller is 1:0.04-0.28; and the mass ratio of the stabilizing dispersant to the modified HKUST-1 nanofiller is 1:80-100.

8. The method for preparing the modified HKUST-1 / cellulose-based solid electrolyte according to claim 2, characterized in that: In step (2), the cellulose is one or more of methyl cellulose, ethyl cellulose, cellulose acetate, carboxymethyl cellulose and hydroxypropyl methyl cellulose.

9. A modified HKUST-1 / cellulose-based solid electrolyte prepared by the preparation method according to any one of claims 1 to 8.

10. The modified HKUST-1 / cellulose-based solid electrolyte according to claim 9, characterized in that: The ionic conductivity of the modified HKUST-1 / cellulose solid electrolyte at 30°C is 8.05×10 -4 ~1.75×10 -3 S / cm, and the electrochemical window is 4.4~4.6V.

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