A reactive solid polymer electrolyte, its preparation method and application

Abstract

This application discloses a reactive solid-state polymer electrolyte, its preparation method, and its applications, belonging to the field of electrolyte technology. The reactive solid-state polymer electrolyte provided in this application comprises a polyethylene oxide substrate and modified bacterial cellulose and a lithium salt dispersed on the polyethylene oxide substrate; wherein the modified bacterial cellulose is a reactive molecular brush formed by grafting alkylated polyvinyl imidazole side chains onto the surface of bacterial cellulose; the modified bacterial cellulose accounts for 5%-20% by mass. By designing the molecular structure of bacterial cellulose, rapid lithium-ion transport can be promoted and the ionic conductivity of the electrolyte can be improved. The rigid cellulose backbone can endow the solid-state polymer electrolyte with excellent mechanical properties. Simultaneously, a stable electrolyte / electrode interface can be formed, thereby significantly improving the cycle stability of lithium batteries.

Description

Technical Field

[0001] This application belongs to the field of electrolyte technology, and in particular relates to a reactive solid polymer electrolyte, its preparation method and application. Background Technology

[0002] Solid-state electrolytes replace the electrolyte and separator in traditional lithium-ion batteries, undertaking the functional roles of ion conduction and connection between the positive and negative electrodes. Solid-state electrolytes are mainly classified into three categories: solid polymer electrolytes, inorganic solid electrolytes, and organic-inorganic composite solid electrolytes. Among these, solid polymer electrolytes are widely used due to their good flexibility, processability, and thermal stability, with polyethylene oxide (PEO) being a particularly prevalent type. However, PEO solid polymer electrolytes generally suffer from low ionic conductivity, poor mechanical properties, and unstable electrolyte / electrode interfaces. Therefore, developing solid polymer electrolytes with excellent overall performance is a pressing technical challenge.

[0003] Currently, fillers are commonly added to improve the performance of PEO solid polymer electrolytes. Prior art, application publication number CN113471531 A, discloses a polymer solid electrolyte comprising a plant cellulose aerogel matrix, a comb-shaped PEO-based polymer, and a lithium salt, wherein the comb-shaped PEO-based polymer and the lithium salt fill the pores of the plant cellulose aerogel matrix.

[0004] However, the above-mentioned PEO solid polymer electrolyte has the following problems: First, while increasing the conductivity, it will reduce the mechanical strength of the polymer electrolyte, causing safety hazards; second, it is easy to cause instability at the electrolyte / electrode interface, resulting in a short battery life. Summary of the Invention

[0005] This application discloses a reactive solid polymer electrolyte, its preparation method, and its application, aiming to solve the technical problems of existing PEO solid polymer electrolytes, such as low ionic conductivity, poor mechanical properties, and unstable electrolyte / electrode interface.

[0006] To achieve the above objectives, the technical solution of this application is:

[0007] A first aspect of this application provides a reactive solid polymer electrolyte comprising a polyethylene oxide substrate and modified bacterial cellulose and a lithium salt dispersed on the polyethylene oxide substrate;

[0008] The modified bacterial cellulose is a reactive molecular brush formed by grafting alkylated polyvinyl imidazole side chains onto the surface of bacterial cellulose.

[0009] The modified bacterial cellulose accounts for 5%-20% of the mass of the polyethylene oxide substrate.

[0010] Preferably, in conjunction with the first aspect, the lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalateborate.

[0011] The second aspect of this application provides a method for preparing the reactive solid polymer electrolyte described in the first aspect, the method comprising:

[0012] Bacterial cellulose was dispersed in N,N-dimethylformamide, then 4-dimethylaminopyridine and triethylamine were added for reaction, followed by the addition of 2-bromoisobutyryl bromide. The mixture was then separated and collected to obtain intermediate product I.

[0013] Intermediate product I, 1-vinylimidazolium, ligand, catalyst, and reducing agent were polymerized in N,N-dimethylformamide, and then separated and collected to obtain intermediate product II.

[0014] The intermediate product II was subjected to an alkylation reaction with iodobutane to obtain the modified bacterial cellulose;

[0015] The modified bacterial cellulose, polyethylene oxide, and lithium salt are mixed and treated, volatilized to form a film, and then solidified to obtain the reactive solid polymer electrolyte.

[0016] Preferably, in conjunction with the second aspect, the ligand is one or a combination of N,N,N',N”,N”-pentamethyldiethylenetriamine, 2,2-bipyridine and tris(2-pyridinemethyl)amine.

[0017] In conjunction with the second aspect, preferably, the catalyst is one or more of copper bromide, copper chloride, cuprous bromide, and cuprous chloride.

[0018] In conjunction with the second aspect, preferably, the reducing agent is one or more of ascorbic acid, stannous isooctanoate, and thiourea dioxide.

[0019] In conjunction with the second aspect, preferably, the ratio of bacterial cellulose, 4-dimethylaminopyridine, triethylamine and 2-bromoisobutyryl bromide added is 2g:3g:46mL:34mL.

[0020] Preferably, in conjunction with the second aspect, the ratio of the amount of intermediate product I, 1-vinylimidazole, ligand, catalyst and reducing agent added is 50g:1500mL:20g:2.5g:23g.

[0021] Preferably, in conjunction with the second aspect, the mass ratio of the molecular brush modified bacterial cellulose, polyethylene oxide substrate, and lithium salt is (2-8):40:13.

[0022] The third aspect of this application provides the application of a reactive solid polymer electrolyte prepared by the preparation method described in the second aspect in lithium metal batteries.

[0023] Compared with the prior art, the advantages or beneficial effects of the embodiments of this application include at least the following:

[0024] The reactive solid polymer electrolyte provided in this application is made by uniformly distributing modified bacterial cellulose and lithium salt on a polyethylene oxide substrate. The modified bacterial cellulose is a reactive molecular brush formed by grafting alkylated polyvinyl imidazole side chains onto the surface of the bacterial cellulose. On the one hand, by designing the molecular structure of bacterial cellulose, the nitrogen cations in the polyvinyl imidazole side chains can fix the anions in the lithium salt, weakening their coordination with lithium ions, promoting rapid lithium ion transport, and thus improving the ionic conductivity of the polymer. On the other hand, the rigid cellulose backbone endows the solid polymer electrolyte with excellent mechanical properties, which can inhibit the growth of lithium dendrites. Thirdly, redox reactions occur during charging and discharging, forming a stable electrolyte / electrode interface, thereby significantly improving the cycle stability of the lithium battery. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 Scanning electron microscope image of the modified bacterial cellulose prepared in the embodiments of this application;

[0027] Figure 2 Scanning electron microscope images of 10% BC-g-PVIMI / PEO SPE and PEO SPE prepared for the embodiments of this application;

[0028] Among them, (a) 10% BC-g-PVIMI / PEO SPE; (b) PEO SPE;

[0029] Figure 3 XRD patterns of 10% BC-g-PVIMI / PEO SPE and PEO SPE prepared for the embodiments of this application;

[0030] Figure 4 Stress-strain curves of 10% BC-g-PVIMI / PEO SPE and PEO SPE prepared for the embodiments of this application;

[0031] Figure 5Impedance spectra of 10% BC-g-PVIMI / PEO SPE and PEO SPE prepared for the embodiments of this application at 60 °C;

[0032] Figure 6 Stress-strain curves of 5% BC-g-PVIMI / PEO SPE prepared for the embodiments of this application;

[0033] Figure 7 Impedance spectrum of 5% BC-g-PVIMI / PEO SPE prepared for the embodiments of this application at 60°C;

[0034] Figure 8 Stress-strain curves of 20% BC-g-PVIMI / PEO SPE prepared for the embodiments of this application;

[0035] Figure 9 Impedance spectrum of 20% BC-g-PVIMI / PEO SPE prepared for the embodiments of this application at 60°C;

[0036] Figure 10 The stress-strain curve of the 10% BC / PEO SPE prepared as a comparative example of this application is shown.

[0037] Figure 11 Impedance spectrum of 10% BC / PEO SPE prepared as a comparative example of this application at 60 °C;

[0038] Figure 12 The reactive solid polymer electrolyte prepared for the embodiments of this application was used to fabricate a lithium-lithium symmetric battery at 60°C and 0.1 mAh / cm². 2 Voltage-time curve under the given conditions;

[0039] Among them, (a) 10% BC-g-PVMI / PEO SPE was used to prepare a lithium-lithium symmetric battery LiI; (b) 5% BC-g-PVMI / PEOSPE was used to prepare a lithium-lithium symmetric battery LiⅡ; (c) 20% BC-g-PVMI / PEO SPE was used to prepare a lithium-lithium symmetric battery LiⅢ; and (d) PEOSPE was used to prepare a lithium-lithium symmetric battery LiⅣ.

[0040] Figure 13 Comparison of the cycling performance of lithium metal full cells prepared from 10% BC-g-PVIMI / PEO SPE and PEO SPE in the embodiments of this application at 60°C and 1C.

[0041] Figure 14 Cyclic voltammogram of a 10% BC-g-PVIMI / PEO SPE assembled half-cell for an embodiment of this application. Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0043] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0044] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0045] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0046] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0047] It should be noted that all raw materials and reagents in the embodiments of this application were purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0048] In a first aspect, embodiments of this application provide a reactive solid polymer electrolyte, comprising a polyethylene oxide substrate and modified bacterial cellulose and lithium salt dispersed on the polyethylene oxide substrate;

[0049] The modified bacterial cellulose is a reactive molecular brush formed by grafting alkylated polyvinyl imidazole side chains onto the surface of bacterial cellulose.

[0050] The modified bacterial cellulose accounts for 5%-20% of the mass of the polyethylene oxide substrate.

[0051] In one aspect, by designing the molecular structure of bacterial cellulose, the nitrogen cations in the polyvinyl imidazole side chain can fix the anions in the lithium salt, weakening their coordination with lithium ions, promoting rapid lithium ion transport, and thus improving the ionic conductivity of the polymer. In another aspect, the rigid cellulose skeleton endows the solid polymer electrolyte with excellent mechanical properties, which can inhibit the growth of lithium dendrites. In a third aspect, redox reactions occur during charging and discharging, forming a stable electrolyte / electrode interface, thereby significantly improving the cycle stability of the lithium battery.

[0052] It should be noted that the lithium salt is preferably one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalateborate. The nitrogen cation in the polyvinylimidazolium side chain can immobilize the anion in the lithium salt, weakening its coordination with lithium ions, promoting lithium ion transport, and thus improving the ionic conductivity of the polymer solid electrolyte.

[0053] The second aspect of this application provides a method for preparing the reactive solid polymer electrolyte described in the first aspect, the method comprising:

[0054] Bacterial cellulose was dispersed in N,N-dimethylformamide, then 4-dimethylaminopyridine and triethylamine were added for reaction, followed by the addition of 2-bromoisobutyryl bromide. The mixture was then separated and collected to obtain intermediate product I.

[0055] Intermediate product I, 1-vinylimidazolium, ligand, catalyst, and reducing agent were polymerized in N,N-dimethylformamide, and then separated and collected to obtain intermediate product II.

[0056] The intermediate product II was subjected to an alkylation reaction with iodobutane to obtain the modified bacterial cellulose;

[0057] The modified bacterial cellulose, polyethylene oxide, and lithium salt are mixed and treated, volatilized to form a film, and then solidified to obtain the reactive solid polymer electrolyte.

[0058] It should be noted that the aqueous solvent in the cellulose dispersion was replaced with N,N-dimethylformamide. After centrifugation, the cellulose was redispersed in N,N-dimethylformamide. 4-Dimethylaminopyridine and triethylamine were added, and 2-bromoisobutyryl bromide was added under an inert atmosphere and an ice-water bath. After a sealed reaction under an inert atmosphere, ethanol was added to quench the reaction. After centrifugation and washing, intermediate I was obtained. Intermediate I was dispersed in N,N-dimethylformamide, and 1-vinylimidazole, a ligand, a catalyst, and a reducing agent were added. The reaction was then carried out again under an inert atmosphere in a sealed environment. After heating, centrifugation, and washing, intermediate II was obtained, which was a one-dimensional molecular brush. Intermediate II was dispersed in N,N-dimethylformamide, and iodobutane was added for alkylation. The reaction was carried out under an inert atmosphere in a sealed environment. After heating, centrifugation, and washing, molecular brush-modified bacterial cellulose was obtained.

[0059] It should be noted that the molecularly modified bacterial cellulose, polyethylene oxide substrate and lithium salt are added to acetonitrile, stirred evenly and then cast onto a carrier mold. After vacuum drying, the reactive solid polymer electrolyte is obtained.

[0060] In this embodiment, the preferred ratio of bacterial cellulose, 4-dimethylaminopyridine, triethylamine, and 2-bromoisobutyryl bromide is 2g:3g:46mL:34mL. By controlling the amount of each raw material added, the hydroxyl groups on the bacterial cellulose can be converted into bromine-containing initiation sites, thereby forming a macromolecular initiator.

[0061] In the embodiments of this application, the ligand is preferably one or a combination of N,N,N',N”,N”-pentamethyldiethylenetriamine, 2,2-bipyridine and tris(2-pyridinemethyl)amine; the catalyst is preferably one or more of copper bromide, copper chloride, cuprous bromide and cuprous chloride; and the reducing agent is preferably one or more of ascorbic acid, stannous isooctanoate and thiourea dioxide.

[0062] In this embodiment, the preferred ratio of intermediate product I, 1-vinylimidazole, ligand, catalyst, and reducing agent is 50g:1500mL:20g:2.5g:23g. Through the action of these ligands, catalysts, and reducing agents, reversible atom transfer radical polymerization can be carried out, thereby grafting polyvinylimidazole side chains onto bacterial cellulose.

[0063] In this embodiment of the application, the preferred mass ratio of the molecular brush modified bacterial cellulose, polyoxyethylene substrate and lithium salt is (2-8):40:13.

[0064] The third aspect of this application provides the application of a reactive solid-state polymer electrolyte prepared by the method described in the second aspect in lithium metal batteries. This reactive solid-state polymer electrolyte possesses excellent mechanical properties, high ionic conductivity, and the ability to form a stable electrolyte / electrode interface, thereby endowing the lithium battery with excellent cycle stability.

[0065] The technical solution of this application will be further described below with reference to specific embodiments.

[0066] Example 1

[0067] The preparation method of A1-reactive solid polymer electrolyte (10% BC-g-PVMI / PEO SPE) provided in this embodiment specifically includes:

[0068] S101: Weigh 75g of bacterial cellulose aqueous dispersion with a mass fraction of 0.8wt%, wash with DMF at 8000rpm for 10min, repeat centrifugation and washing six times, then uniformly disperse in 150mL DMF, add 0.90g of 4-dimethylaminopyridine and 13.6mL of triethylamine, add 10.3mL of 2-bromoisobutyryl bromide under nitrogen atmosphere and ice bath, mix well, react at 25-30℃ for 24h, quench with ethanol, centrifuge with ethanol at 6000rpm for 5min, then centrifuge with DMF at 6000rpm for 5min, wash until the supernatant is colorless, to obtain intermediate product I;

[0069] S102: 0.20 g of intermediate product I was uniformly dispersed in 10 mL of DMF, and 6 mL of 1-vinylimidazole, 80 μL of N,N,N',N”,N”-pentamethyldiethylenetriamine, 10 mg of CuBr2 and 92 mg of ascorbic acid were added sequentially. The mixture was reacted at 70 °C under a nitrogen atmosphere for 24 h, and then centrifuged at 6000 rpm for 5 min with DMF. After centrifugation and washing three times, intermediate product II was obtained.

[0070] S103: 0.20 g of intermediate product II was uniformly dispersed in 20 mL of DMF, 6.3 mL of iodobutane was added, and the mixture was reacted at 70 °C under a nitrogen atmosphere for 24 h. The mixture was then centrifuged with ethanol at 6000 rpm for 5 min. After centrifugation and washing three times, molecular brush modified bacterial cellulose was obtained.

[0071] S104: 20 mg of molecular brush modified bacterial cellulose, 200 mg of polyethylene oxide and 65 mg of lithium bis(trifluoromethanesulfonyl)imide were uniformly dispersed in 8 mL of acetonitrile, and then poured into a polytetrafluoroethylene petri dish. The acetonitrile was volatilized at 40 °C and then dried under vacuum at 40 °C for 24 h to obtain Al-reactive solid polymer electrolyte, denoted as 10% BC-g-PVMI / PEO SPE.

[0072] Example 2

[0073] The preparation method of A2-reactive solid polymer electrolyte (5% BC-g-PVMI / PEO SPE) provided in this embodiment is basically the same as that in Example 1 in terms of component ratio, preparation operation and process parameters. The difference is that in this embodiment, 10 mg of molecular brush modified bacterial cellulose, 200 mg of polyethylene oxide and 65 mg of lithium bis(trifluoromethanesulfonyl)imide are added to react to obtain A2-reactive solid polymer electrolyte (5% BC-g-PVMI / PEO SPE).

[0074] Example 3

[0075] The preparation method of A3-reactive solid polymer electrolyte (20% BC-g-PVMI / PEO SPE) provided in this embodiment is basically the same as that in Example 1 in terms of component ratio, preparation operation, and process parameters. The difference is that in this embodiment, 40 mg of molecular brush modified bacterial cellulose, 200 mg of polyethylene oxide and 65 mg of lithium bis(trifluoromethanesulfonyl)imide are added to react to obtain A3-reactive solid polymer electrolyte (20% BC-g-PVMI / PEO SPE).

[0076] Meanwhile, to verify the comprehensive performance of the reactive solid polymer electrolytes prepared in the above embodiments, this application provides the following comparative examples for detailed illustration.

[0077] Comparative Example 1

[0078] The composition ratio, preparation operation, and process parameters of the B1-solid polymer electrolyte (PEO SPE) prepared in this embodiment are basically the same as those in Example 1. The difference is that bacterial cellulose is not added in this embodiment to prepare B1-solid polymer electrolyte (PEO SPE).

[0079] Comparative Example 2

[0080] The composition ratio, preparation operation, and process parameters of the B2-solid polymer electrolyte (10% BC / PEO SPE) prepared in this embodiment are basically the same as those in Example 1. The difference is that pure bacterial cellulose is added in this embodiment, and the bacterial cellulose is not modified to prepare the B2-solid polymer electrolyte (10% BC / PEO SPE).

[0081] The performance test results of the reactive solid polymer electrolytes prepared in the embodiments and comparative examples of this application are shown in Table 1.

[0082] Table 1. Overall performance of reactive solid polymer electrolytes

[0083]

[0084] To verify the appearance properties of the reactive solid polymer electrolyte prepared in the embodiments of this application, the reactive solid polymer electrolyte prepared in the embodiments was characterized, and the results were as follows: Figures 1 to 2 As shown; where, Figure 1 Scanning electron microscope image of molecular brush modified bacterial cellulose; Figure 2 Scanning electron microscope images of 10% BC-g-PVIMI / PEO SPE and PEO SPE.

[0085] according to Figure 1 As is known, molecular brush modified bacterial cellulose has a one-dimensional molecular brush microstructure, consisting of many fibers stacked together to form a porous structure.

[0086] according to Figure 2 As is known, (a) is a scanning electron microscope image of 10% BC-g-PVMI / PEO SPE; (b) is a scanning electron microscope image of PEO-SPE, which, compared with PEO SPE, has smaller grain diameter and relatively uniformly distributed reactive molecular brushes in the polyoxyethylene substrate.

[0087] To verify the structural properties of the reactive solid polymer electrolyte prepared in the embodiments of this application, the reactive solid polymer electrolyte prepared in the embodiments was characterized, and the results were as follows: Figures 3 to 4 As shown; where, Figure 3 XRD patterns of 10% BC-g-PVIMI / PEO-SPE and PEO-SPE; Figure 4 Stress-strain curves for 10% BC-g-PVIMI / PEO-SPE and PEO-SPE; Figure 5 Impedance spectra of 10% BC-g-PVIMI / PEO SPE and PEO SPE at 60 °C; Figure 6 Stress-strain curves for 5% BC-g-PVIMI / PEO SPE; Figure 7 Impedance spectrum of 5% BC-g-PVIMI / PEO SPE at 60℃; Figure 8 Stress-strain curves for 20% BC-g-PVIMI / PEO SPE; Figure 9 Impedance spectrum of 20% BC-g-PVIMI / PEO SPE at 60℃.

[0088] according to Figure 3 It is known that the diffraction peak intensity of 10% BC-g-PVMI / PEO SPE is significantly lower than that of PEO SPE, indicating that the introduction of BC-g-PVMI is beneficial to reducing crystallinity.

[0089] according to Figure 4 It is known that the tensile strength of 10% BC-g-PVMI / PEO SPE is 5.2 MPa, which is significantly higher than the tensile strength of PEO SPE of 2.1 MPa, indicating that the reactive solid polymer electrolyte provided in this application has good mechanical properties.

[0090] according to Figure 5 As is known, according to the calculation formula in Equation 1,

[0091]

[0092] Where: σ is the ionic conductivity, L is the electrolyte thickness, S is the steel sheet area, and R is the bulk resistance.

[0093] At 60℃, the ionic conductivity of 10% BC-g-PVMI / PEO SPE is 3.0 × 10⁻⁶. -4 The S / cm of PEOSPE is much higher than that of PEOSPE, which has an ionic conductivity of only 7.4 × 10⁻⁶. -5 S / cm. The reason may be the presence of nitrogen cations in the PVIMI side chain, which can fix anions, weakening cation coordination and promoting lithium-ion transport.

[0094] according to Figure 6 It is known that the tensile strength of 5% BC-g-PVMI / PEO SPE is 3.9 MPa, which is significantly higher than the tensile strength of PEO SPE of 2.1 MPa.

[0095] according to Figure 7 As is known, according to Equation 1, the ionic conductivity of 5% BC-g-PVMI / PEO SPE is 1.8 × 10⁻⁶ at 60°C. -4 S / cm.

[0096] according to Figure 8It is known that the tensile strength of 20% BC-g-PVMI / PEO SPE is 6.3 MPa, which is significantly higher than the tensile strength of PEO SPE of 2.1 MPa.

[0097] according to Figure 9 As is known, according to Equation 1, the ionic conductivity of 20% BC-g-PVMI / PEO SPE is 2.7 × 10⁻⁶ at 60°C. -4 S / cm.

[0098] according to Figure 10 It is known that the tensile strength of 10% BC / PEO SPE is 4.0 MPa, which is significantly higher than the tensile strength of PEO (2.1 MPa).

[0099] according to Figure 11 As is known, according to Equation 1, the ionic conductivity of 10% BC / PEO SPE is 1.1 × 10⁻⁶ at 60°C. -4 S / cm.

[0100] Given that the above-mentioned reactive solid polymer electrolyte has good mechanical properties and high ionic conductivity, it can be used as a solid electrolyte in lithium metal batteries.

[0101] The 10% BC-g-PVMI / PEO SPE prepared in Example 1 was applied to a lithium-lithium symmetric battery. In this battery, lithium sheets served as both the negative and positive electrodes, and the 10% BC-g-PVMI / PEO SPE was used as the solid electrolyte. The lithium-lithium symmetric battery was assembled in a glove box under an argon atmosphere, maintaining the moisture and oxygen content in the glove box below 0.1 ppm. The assembled button cell was designated CR2032 and denoted as the lithium-lithium symmetric battery LiI.

[0102] The 10% BC-g-PVMI / PEO SPE prepared in Example 1 was applied to a lithium metal full cell. In this lithium metal full cell, lithium foil was used as the negative electrode, lithium iron phosphate as the positive electrode, and 10% BC-g-PVMI / PEO SPE as the solid electrolyte. The lithium iron phosphate electrode was prepared by coating a mixture of lithium iron phosphate active material, conductive carbon black, polyvinylidene fluoride, polyethylene oxide, and lithium bis(trifluoromethanesulfonyl)imide in a mass ratio of 60:15:15:8:2 onto carbon-coated aluminum foil, drying it in a 60°C oven, and cutting it into 12mm diameter pieces. The assembled button cell was designated CR2032 and denoted as a lithium metal full cell (LFPI).

[0103] To evaluate the interfacial stability of solid electrolytes during cycling, this application used the 5% BC-g-PVMI / PEO SPE prepared in Example 2, the 20% BC-g-PVMI / PEO SPE prepared in Example 3, and the PEO SPE prepared in Comparative Example 1 as solid electrolytes, and assembled them into lithium-lithium symmetric batteries with lithium sheets as the negative and positive electrodes, respectively, and designated as lithium-lithium symmetric batteries LiII, LiIII, and LiIV. The lithium-lithium symmetric batteries LiI, LiII, LiIII, and LiIV differ only in the type of solid electrolyte; the preparation methods and the types and amounts of other raw materials are the same.

[0104] In order to evaluate the application potential of solid electrolytes, this application uses PEO SPE prepared in Comparative Example 1 as solid electrolyte, lithium iron phosphate as positive electrode and lithium sheet as negative electrode to assemble a lithium metal full cell, denoted as lithium metal full cell LFPⅡ.

[0105] This application measures, records, and plots the results of four types of lithium-ion symmetric batteries—LiI, LiII, LiIII, and LiIV—at 60°C and 0.1 mA / cm². 2 and 0.1mAh / cm 2 The voltage-time curve under cyclic conditions is shown in the following figure. Figure 12 As shown, (a) is the voltage-time curve of the lithium-lithium symmetric battery LiI, (b) is the voltage-time curve of the lithium-lithium symmetric battery LiⅡ, (c) is the voltage-time curve of the lithium-lithium symmetric battery LiⅢ, and (d) is the voltage-time curve of the lithium-lithium symmetric battery LiⅣ.

[0106] according to Figure 12 It can be seen that, compared with lithium-lithium symmetric cells assembled with 5% BC-g-PVMI / PEO SPE, 20% BC-g-PVMI / PEO SPE and PEO SPE, the lithium-lithium symmetric cell LiI assembled with 10% BC-g-PVMI / PEO SPE has a smaller overpotential and a longer cycle life, and exhibits more stable lithium deposition / stripping behavior.

[0107] This application also measures, records, and plots a comparison of the cycle performance of two types of lithium metal full cells, LFPI and LFPⅡ, under 30°C and 0.5C conditions, as shown in the figure below. Figure 13 As shown.

[0108] according to Figure 13It can be seen that, compared with lithium metal full cells assembled by PEO SPE, lithium metal full cells LFPI assembled by 10% BC-g-PVMI / PEO SPE have higher discharge specific capacity and exhibit good cycle performance.

[0109] To further explore the mechanism by which 10% BC-g-PVMI / PEO SPE improves battery cycle stability, this application assembled a half-cell using lithium foil as the negative electrode, a conductive carbon black and polyvinylidene fluoride mixed slurry as the positive electrode, and 10% BC-g-PVMI / PEO SPE as the electrolyte. Cyclic voltammetry tests were conducted using an electrochemical workstation, as detailed below. Figure 14 As shown.

[0110] according to Figure 14 As shown, 10% BC-g-PVIMI / PEO SPE exhibits a redox pair during charge and discharge, with I- being oxidized to I3 at 3.18V. - I3 at 3.68V and 3.84V - It is further oxidized to I2; at 3.59V, I2 is reduced to I3. - I3 at 3.04V - It is reduced to I-. The above results confirm that BC-g-PVIMI undergoes redox reactions during charge and discharge, forming a stable electrolyte / electrode interface, thereby significantly improving the cycle stability of the battery.

[0111] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0112] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A reactive solid polymer electrolyte, characterized in that, Includes a polyethylene oxide substrate and modified bacterial cellulose and lithium salt dispersed on the polyethylene oxide substrate; The modified bacterial cellulose is a reactive molecular brush formed by grafting alkylated polyvinyl imidazole side chains onto the surface of bacterial cellulose. The modified bacterial cellulose accounts for 5%-20% of the mass of the polyethylene oxide substrate.

2. The reactive solid polymer electrolyte according to claim 1, characterized in that, The lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalateborate.

3. A method for preparing a reactive solid polymer electrolyte according to any one of claims 1-2, characterized in that, The method includes: Bacterial cellulose was dispersed in N,N-dimethylformamide, then 4-dimethylaminopyridine and triethylamine were added for reaction, followed by the addition of 2-bromoisobutyryl bromide. The mixture was then separated and collected to obtain intermediate product I. Intermediate product I, 1-vinylimidazolium, ligand, catalyst, and reducing agent were polymerized in N,N-dimethylformamide, and then separated and collected to obtain intermediate product II. The intermediate product II was subjected to an alkylation reaction with iodobutane to obtain the modified bacterial cellulose; The modified bacterial cellulose, polyethylene oxide, and lithium salt are mixed and treated, and then volatilized to form a film to obtain the reactive solid polymer electrolyte.

4. The method for preparing the reactive solid polymer electrolyte according to claim 3, characterized in that, The ligand is one or a combination of N,N,N',N”,N”-pentamethyldiethylenetriamine, 2,2-bipyridine and tris(2-pyridinemethyl)amine.

5. The method for preparing the reactive solid polymer electrolyte according to claim 3, characterized in that, The catalyst is one or more of copper bromide, copper chloride, cuprous bromide, and cuprous chloride.

6. The method for preparing the reactive solid polymer electrolyte according to claim 3, characterized in that, The reducing agent is one or more of ascorbic acid, stannous isooctanoate, and thiourea dioxide.

7. The method for preparing the reactive solid polymer electrolyte according to claim 3, characterized in that, The ratio of bacterial cellulose, 4-dimethylaminopyridine, triethylamine and 2-bromoisobutyryl bromide added is 2g:3g:46mL:34mL.

8. The method for preparing the reactive solid polymer electrolyte according to claim 3, characterized in that, The ratio of intermediate product I, 1-vinylimidazole, ligand, catalyst and reducing agent added is 50g:1500mL:20g:2.5g:23g.

9. The method for preparing the reactive solid polymer electrolyte according to claim 3, characterized in that, The mass ratio of the molecular brush-modified bacterial cellulose, polyoxyethylene substrate, and lithium salt is (2-8):40:

13.

10. The application of a reactive solid polymer electrolyte prepared by any one of claims 3-9 in a lithium metal battery.

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