Molecular network modified composite solid electrolyte as well as preparation method and application thereof

Abstract

The invention discloses a molecular network modified composite solid electrolyte as well as a preparation method and application thereof. The composite solid electrolyte is prepared from the following raw materials in percentage by weight: 5wt%-30wt% of solute salt, 5wt%-80wt% of inorganic filler and 10wt%-80wt% of a polymer matrix, and the polymer matrix consists of a compound A, a polymer B and a polymer C in a mass ratio of 10: 1: (1.5-4.5). The invention also specifically discloses a preparation method of the composite solid electrolyte and an application of the composite solid electrolyte in preparation of a lithium metal battery. The composite solid electrolyte prepared by the invention has high ionic conductivity and smooth morphology, and can be fully contacted with an electrode to realize stable circulation when being applied to a lithium metal battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium metal battery solid-state electrolyte, and particularly relates to a molecular network modified composite solid-state electrolyte and a preparation method and application thereof. BACKGROUND

[0002] In the field of energy storage technology, lithium ion batteries have long dominated the market with graphite negative materials. However, due to the theoretical capacity of graphite negative materials (372 mAh / g), the energy density of current commercial lithium ion batteries has reached the material limit, making it difficult to meet the urgent needs of the new energy industry for high-energy storage systems. In this context, lithium metal negative electrodes have become the focus of research again due to their excellent theoretical specific capacity (3860 mAh / g) and the lowest electrochemical potential (-3.040 V vs. SHE), driving lithium metal batteries to become the core development direction of the next generation of high-energy density secondary batteries.

[0003] Although liquid electrolyte systems exhibit good performance in laboratory research, they face double challenges in practical applications: first, the volatility of organic electrolytes poses safety risks such as leakage and combustion; second, lithium metal is prone to dendrite growth during cycling, which not only exacerbates capacity decay but also can cause internal short circuits. To solve this industry technical problem, solid-state electrolyte technology has emerged, which has the advantages of intrinsic safety and mechanical rigidity, can eliminate the safety risks of liquid systems, and effectively inhibit lithium dendrite penetration through physical barriers, providing a key breakthrough for the practical application of lithium metal negative electrodes.

[0004] Current solid-state electrolyte systems mainly present three major technical routes: inorganic ceramic electrolytes exhibit high ionic conductivity of 1 x 10 -3 ~ 1 x 10 -2 S / cm and a wide electrochemical window of more than 4.5 V, but the electrode / electrolyte contact resistance caused by its rigid interface and the side reaction of some systems with lithium metal need to be solved; polymer electrolytes achieve low impedance contact due to their excellent interface compatibility, but their room temperature ionic conductivity is generally less than 1 x 10 -4 S / cm and their electrochemical stability is insufficient; hybrid electrolyte systems constructed through organic-inorganic composite strategies inherit the high lithium conductivity of inorganic phases and have the flexible interface advantage of polymer phases, and their room temperature ionic conductivity can be improved to 1 x 10 -3The ionic conductivity of the composite solid-state electrolyte is on the order of 10-4S / cm, while exhibiting good interface stability and processability, and has become the most promising technology direction for industrialization. However, the composite solid-state electrolyte has very superior ionic transport performance, but when it is actually applied to the battery, it usually presents unsatisfactory cycle stability. The reasons for the poor cycle stability of the composite solid-state electrolyte are on the one hand the "short board effect" in the electrolyte: the polymer part of the composite electrolyte often cannot withstand the oxidation problem brought by high voltage, and is prone to decomposition after long-time charge-discharge cycle; on the other hand, the structure of the composite electrolyte is not as dense as the polymer electrolyte and not as solid as the inorganic ceramic electrolyte, which has a bad impact on the interface stability and resistance to dendrite of the composite electrolyte.

[0005] The patent document CN202410263514.X discloses a flexible composite solid-state electrolyte and its preparation method and application, wherein the flexible composite solid-state electrolyte is prepared from the following raw materials in weight percentage: 5wt%-30wt% of solute salt; 5wt%-80wt% of inorganic filler; 10wt%-80wt% of polymer substrate, which is composed of polymer A and compound B in a mass ratio of 1-10:1, polymer A is one or more of polyether-based polyurethane or polyester-based polyurethane, and compound B is one or more of fluorine-containing polymer ethylene-tetrafluoroethylene copolymer, polytetrafluoroethylene, fluorinated ethylene-propylene copolymer, perfluoroalkoxy resin, polychlorotrifluoroethylene, ethylene-chlorotrifluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride or polyvinylidene fluoride-hexafluoropropylene. The flexible composite solid-state electrolyte has a high voltage window of 5.0V, which can completely match the high voltage positive electrode material, and the assembled lithium iron phosphate / nickel cobalt manganese battery can realize stable cycle while having high specific capacity. However, the inorganic filler used in the flexible composite solid-state electrolyte mentioned in the patent document has poor compatibility with lithium metal, which leads to poor cycle stability when the electrolyte is used with lithium metal electrode, limiting the further application of the electrolyte in solid-state batteries.

[0006] The patent document CN202411831335.8 discloses a thermoplastic polyurethane elastomer flexible composite solid electrolyte and its preparation method and application. The flexible composite solid electrolyte is prepared from the following raw materials in the following weight percentage: 1wt%-30wt% of solute salt; 5wt%-50wt% of inorganic filler; 40wt%-90wt% of polymer matrix, wherein the inorganic filler is one or more of active filler or inert filler, the active filler is one or more of garnet type filler, perovskite type material, LISICON type filler or NASICON type filler, the inert filler is one or more of natural clay, SiO2 or Al2O3, the polymer A is one or more of polyether type polyurethane, polyester type polyurethane, polyimide type polyurethane or polyurea type polyurethane, and the compound B is one or more of polyethylene glycol diacrylate, pentaerythritol triacrylate or tetraacrylate. The polymer A usually has excellent mechanical properties, and the hard segment and soft segment of the polymer A can provide mechanical properties and ion conduction properties respectively, so that the use of the polymer A as the polymer matrix can prepare a flexible composite solid electrolyte with excellent mechanical properties. The compound B can be excited by external conditions (such as heating or ultraviolet treatment) to break the double bond and generate a polymer crosslinking network rich in ether oxygen groups, which can further enhance the ion transmission efficiency inside the polymer matrix. The prepared composite solid electrolyte has high flexibility and high ion conductivity, and is expected to be applied to wearable electronic devices. However, the composite solid electrolyte mentioned in the patent document is affected by the residual alkali substances (such as lithium carbonate and lithium hydroxide) on the surface of the garnet inorganic filler, which affects the interface stability of the electrolyte / electrode. At the same time, the polymer molecules used to form the polymer molecular network are prone to decomposition at high voltage, which leads to the decrease of the stability of the electrolyte during the charging and discharging process of the battery, which limits the practical application effect of the electrolyte.

[0007] Therefore, it is the top priority to develop a high practical performance composite solid electrolyte by designing and constructing an electrolyte with high ion transmission performance and high material stability. SUMMARY

[0008] The present application provides a molecular network modified composite solid electrolyte with high ion transmission performance and high material stability, and a preparation method thereof. The composite solid electrolyte has high ion conductivity and flat morphology, and can fully contact the electrode to realize stable circulation when applied in a lithium metal battery.

[0009] In order to achieve the above-mentioned application purposes, the present application adopts the following technical solutions:

[0010] A molecular network modified composite solid electrolyte is prepared from the following raw materials in the following weight percentage:

[0011] 5wt%~30wt% of solute salt, the solute salt being one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium difluoro(oxalato)borate (LiDFOB), lithium nitrate (LiNO3) and lithium tetrafluoroborate (LiBF4);

[0012] 5wt%~80wt% of inorganic filler, the inorganic filler being one or more of active filler and inert filler, wherein the active filler is one or more of NASICON type filler, garnet type filler and perovskite type filler, and the inert filler is one or more of SiO2, Al2O3, TiO2 and ZrO2;

[0013] 10wt%~80wt% of polymer matrix, the polymer matrix being composed of compound A, polymer B and polymer C in a mass ratio of 10:1:(1.5~4.5), wherein the compound A is one or more of butyl acrylate, methyl acrylate, isobutyl acrylate, hexafluorobutyl acrylate and hexafluorobutyl methacrylate; the polymer B is one or more of polymethyl methacrylate, polyethylene glycol diacrylate, polyethylene glycol succinate, diethylene glycol diacrylate and poly(ethylene glycol) methacrylate; and the polymer C is one or more of fluorine-containing polymer ethylene-tetrafluoroethylene copolymer, polytetrafluoroethylene, fluorinated ethylene-propylene copolymer, perfluoroalkoxy resin, polychlorotrifluoroethylene, ethylene-chlorotrifluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride and polyvinylidene fluoride-hexafluoropropylene.

[0014] In the technical solution of the present application, the compound A and the polymer B form a polymer network through ultraviolet light-induced radical polymerization, the compound A and the polymer B have a large number of sites available for lithium ion binding on one hand, and the large side chain of the compound A can help to disperse the polymer chain through steric hindrance on the other hand, thereby reducing the crystallinity of the composite solid-state electrolyte polymer part, improving the morphology and enhancing the ion transmission performance. The polymer C has a large number of fluorine-containing groups on the molecular chain, which can attract lithium ions through large electronegativity and has strong oxidation stability. The inorganic filler plays a role in regulating the structure and providing ion transmission channels in the electrolyte, and in addition, the presence of the inorganic filler can also inhibit the effect of lithium dendrites to a certain extent. Therefore, the solid-state electrolyte composed of the compound A, the polymer B and the polymer C and the inorganic filler has excellent room temperature ionic conductivity and cycle stability at the same time.

[0015] Preferably, the composite solid-state electrolyte is prepared from the following raw materials in the following weight percentage: 10wt%~20wt% of solute salt, 10wt%~40wt% of inorganic filler, and the balance being the polymer matrix.

[0016] Preferably, the NASICON type filler is Li1+x Al x Ti 2-x (PO4)3(LATP) and Li 1+x Al x Ge 2-x (PO4)3(LAGP); the garnet filler is Li 6.5 La3Zr 1.2 Ta 1.5 O 12 (LLZTO); the perovskite filler is Li 3x La 2 / 3-x TiO3(LLTO).

[0017] Preferably, the mass ratio of compound A, polymer B and polymer C in the polymer matrix is 10:1:3.5.

[0018] A preparation method of a molecular network modified composite solid-state electrolyte, the specific preparation steps of which are as follows:

[0019] Step S1: uniformly mixing compound A and polymer B to obtain a mixed solution;

[0020] Step S2: adding polymer C and solvent D to the mixed solution obtained in step S1 and uniformly mixing to obtain a mixed slurry;

[0021] Step S3: adding a solute salt to the mixed slurry obtained in step S2 and uniformly mixing to obtain a mixed slurry;

[0022] Step S4: mixing an inorganic filler with solvent D and ultrasonic dispersing for 30-120 min to obtain an inorganic filler dispersion liquid;

[0023] Step S5: adding the inorganic filler dispersion liquid obtained in step S4 to the mixed slurry obtained in step S3 and uniformly mixing to obtain a composite electrolyte precursor;

[0024] Step S6: fully stirring the composite electrolyte precursor obtained in step S5 under the condition of ultraviolet light irradiation treatment, then casting on a glass plate, and vacuum drying to obtain a molecular network modified composite solid-state electrolyte.

[0025] Preferably, the solvent D in step S1 is one or more of N-methylpyrrolidone, N,N-dimethylformamide and dimethyl sulfoxide.

[0026] Preferably, the mixing process in steps S1, S2, S3, S5 and S6 is carried out on a magnetic stirrer, and the stirring speed is 900-1200 r / min.

[0027] Preferably, the ultraviolet light irradiation treatment in step S6 is carried out under an ultraviolet light curing lamp, the wavelength of the ultraviolet light lamp is 365 nm, and the power is 20 W.

[0028] A lithium metal battery is assembled by using the above-mentioned molecular network modified composite solid electrolyte, lithium iron phosphate or nickel cobalt manganese positive electrode and lithium metal negative electrode.

[0029] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0030] The lithium metal battery assembled by the molecular network modified composite solid electrolyte prepared by the present application has an upper limit of the electrochemical stability window of 4.8 V or more, which can easily adapt to most high-voltage positive electrode materials on the market; after the compound A and the polymer B are treated by ultraviolet light, free radical polymerization occurs to form a polymer network structure, and the large side chain groups in the network structure improve the structure and surface morphology of the electrolyte and construct an ion-conducting network structure for lithium ion transmission in the electrolyte. The network composed of the compound A and the polymer B improves the interface contact between the electrolyte and the lithium metal electrode and forms a stable, uniform and firm SEI layer with the lithium metal electrode, promotes the uniform deposition of lithium ions at the interface and protects the electrolyte from being damaged by lithium dendrites, so that the battery equipped with the composite solid electrolyte prepared by the present application has an extraordinary cycle life and cycle stability. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Optical photograph of the composite solid electrolyte prepared for Example 1.

[0032] Figure 2 Linear sweep voltammogram of the composite solid electrolyte prepared for Example 1 and Comparative Examples 1 and 2.

[0033] Figure 3 Symmetric steel battery electrochemical impedance diagram of the composite solid electrolyte prepared for Example 1 and Comparative Examples 1 and 2.

[0034] Figure 4 Symmetric lithium battery electrochemical impedance diagram of the composite solid electrolyte prepared for Example 1 and Comparative Examples 1 and 2.

[0035] Figure 5 Symmetric lithium battery constant current charge-discharge polarization diagram of the composite solid electrolyte prepared for Example 1 and Comparative Examples 1 and 2.

[0036] Figure 6 Charge-discharge cycle diagram of the LFP||Li battery of the composite solid electrolyte prepared for Example 1 and Comparative Examples 1 and 2 at a 1C rate. DETAILED DESCRIPTION

[0037] The above content of the present application is further illustrated in detail by the following examples, but this should not be understood as the scope of the above subject matter of the present application being limited to the following examples only, and any technology realized based on the above content of the present application falls within the scope of the present application.

[0038] Example 1

[0039] Step S1: 1.0 g of butyl acrylate (Aldrich reagent, B100035) and 0.1 g of polyethylene glycol diacrylate (Aldrich reagent, P131592) were weighed into a sealed glass bottle and stirred on a magnetic stirrer at a speed of 600 r / min for 1 h; 0.35 g of polyvinylidene fluoride (PVDF, Duodde reagent) was weighed, 6 mL of N-methylpyrrolidone (NMP) was measured with a burette, and added to the glass bottle, and stirred on a magnetic stirrer at a speed of 600 r / min until the polyvinylidene fluoride was completely dissolved; 0.25 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) (25 wt% of butyl acrylate) was weighed, 2 mL of NMP was measured, and added to the above glass bottle, and stirred on a magnetic stirrer at a speed of 600 r / min until the LiTFSI was completely dissolved to obtain a mixed slurry; 0.2 g of LLZTO filler (20 wt% of butyl acrylate) was mixed with 2 mL of NMP, and was placed in a glass bottle and ultrasonically dispersed in an ultrasonic cleaner for 1 h to obtain an LLZTO-NMP suspension; the LLZTO-NMP suspension was poured into the glass bottle containing the mixed slurry, and stirred at a speed of 1200 r / min for 2 h until the two were uniformly mixed, and was then placed under an ultraviolet light lamp for ultraviolet light treatment for 1 h; after the treatment was completed, the electrolyte precursor was cast on a glass plate, and vacuum dried for 24 h to obtain a composite solid-state electrolyte.

[0040] Step S2: The completely dried composite solid-state electrolyte prepared in step S1 was cut into a solid-state electrolyte disc with a diameter of 19 mm, and was assembled into Li||SS and LFP||Li button cells in a glove box for subsequent testing.

[0041] Example 2

[0042] The preparation method of this example is the same as that of Example 1, except that the mass of PVDF in step S1 is replaced by 0.15 g, the solute salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is replaced by lithium hexafluorophosphate, the proportion of the filler LLZTO is replaced by 20 wt%, and the solvent N-methylpyrrolidone is replaced by DMF.

[0043] Example 3

[0044] The preparation method of this example is the same as that of Example 1, except that the PVDF mass in step S1 is replaced by 0.25 g, the solute salt lithium bis-trifluoromethanesulfonimide (LiTFSI) is replaced by lithium difluoro(oxalato)borate, the filler LLZTO proportion is replaced by 30 wt%, and the solvent DMF is replaced by dimethyl sulfoxide.

[0045] Example 4

[0046] The preparation method of this example is the same as that of Example 1, except that the solute salt lithium bis-trifluoromethanesulfonimide (LiTFSI) in step S1 is replaced by lithium difluoro(oxalato)borate, and the solute salt proportion is replaced by 20 wt%.

[0047] Example 5

[0048] The preparation method of this example is the same as that of Example 1, except that the PVDF in step S1 is replaced by polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and the mass is replaced by 0.45 g.

[0049] Example 6

[0050] The preparation method of this example is the same as that of Example 1, except that the polyvinylidene fluoride in step S1 is replaced by PVDF-HFP, the mass ratio is replaced by 5:1 (butyl acrylate: PVDF-HFP), and the filler LLZTO proportion is replaced by 10 wt%.

[0051] Example 7

[0052] The preparation method of this example is the same as that of Example 1, except that the polyvinylidene fluoride in step S1 is replaced by PVDF-HFP, and the solvent DMF is replaced by dimethyl sulfoxide.

[0053] Comparative Example 1

[0054] Step S1: 1.0 g of butyl acrylate (Aldrich Reagent, B100035) and 0.1 g of polyethylene glycol diacrylate (Aldrich Reagent, P131592) were weighed into a sealed glass bottle and stirred on a magnetic stirrer at a speed of 600 r / min for 1 h; 0.35 g of polyvinylidene fluoride (Duodde Reagent) was weighed, 8 mL of NMP was measured with a graduated cylinder, and added to the above glass bottle, and stirred on a magnetic stirrer at a speed of 600 r / min until the PVDF was completely dissolved; 0.25 g of LiTFSI (the proportion is 25 wt% of butyl acrylate) was weighed, 2 mL of NMP was measured, and added to the above glass bottle, and stirred on a magnetic stirrer at a speed of 600 r / min until the LTFSI was completely dissolved to obtain a mixed slurry; here, the comparative example 1 does not add inorganic fillers, which can illustrate that the addition of the garnet inorganic filler in example 1 does not affect the stability of the electrolyte, the polymer matrix and the inorganic filler have high compatibility, and the inorganic filler has great help to the performance improvement of the electrolyte in the battery. Pour the LLZTO-NMP suspension liquid into the glass bottle containing the mixed slurry, stir at a speed of 1200 r / min for 2 h until the two are uniformly mixed, and then transfer into an ultraviolet light lamp for ultraviolet light treatment for 1 h. After the treatment is completed, the electrolyte precursor is cast on a glass plate, vacuum dried for 24 h to obtain a composite solid-state electrolyte.

[0055] Step S2: The completely dried composite solid-state electrolyte prepared in step S1 was cut into a solid-state electrolyte disc with a diameter of 19 mm, and was assembled into Li||SS, LFP||Li button cells in a glove box for subsequent testing.

[0056] Comparative Example 2

[0057] Step S1: 0.35 g of polyvinylidene fluoride (Duodde Reagent) was weighed, 8 mL of NMP was measured with a graduated cylinder, and added to a glass bottle, and stirred on a magnetic stirrer at a speed of 600 r / min until the PVDF was completely dissolved; 0.25 g of LiTFSI (the proportion is 25 wt% of butyl acrylate) was weighed, 2 mL of NMP was measured, and added to the above glass bottle, and stirred on a magnetic stirrer at a speed of 600 r / min until the LTFSI was completely dissolved to obtain a mixed slurry; 0.2 g of LLZTO filler (the proportion is 20 wt% of butyl acrylate) was mixed with 2 mL of NMP, and was loaded into a glass bottle and treated with ultrasonic dispersion for 1 h in an ultrasonic cleaner to obtain a LLZTO-NMP suspension liquid; the LLZTO-NMP suspension liquid was poured into the glass bottle containing the mixed slurry, and stirred at a speed of 1200 r / min for 2 h until the two were uniformly mixed, and then transferred into an ultraviolet light lamp for ultraviolet light treatment for 1 h. After the treatment is completed, the electrolyte precursor is cast on a glass plate, vacuum dried for 24 h to obtain a composite solid-state electrolyte.

[0058] Step S2: The fully dried composite solid-state electrolyte prepared in step S1 was cut into solid-state electrolyte discs with a diameter of 19 mm, and Li||SS, LFP||Li button cells were assembled in a glove box for subsequent testing.

[0059] Performance test:

[0060] 1. Test method

[0061] (1) Linear sweep voltammetry test was performed on the Li||SS button cell prepared by Example 1 to analyze the oxidation potential thereof.

[0062] (2) The SS||SS button cells prepared by Example 1, Comparative Example 1 and Comparative Example 2 were tested for electrochemical impedance on an electrochemical workstation.

[0063] (3) The Li||Li button cells prepared by Example 1, Comparative Example 1 and Comparative Example 2 were tested for electrochemical impedance on an electrochemical workstation.

[0064] (4) The Li||Li button cells prepared by Example 1, Comparative Example 1 and Comparative Example 2 were tested for constant current charge-discharge polarization at a current density of 0.1 mA / cm 2 on the Blue Electron test software.

[0065] (6) The LFP||Li button cells prepared by Example 1, Comparative Example 1 and Comparative Example 2 were tested for constant current charge-discharge at a rate of 1C (1C = 170 mAh / g) on the Blue Electron test software.

[0066] 2. Test results

[0067] As shown in Figure 1 , the composite solid-state electrolyte film prepared in Example 1 has a light and thin bending morphology, and the flexible composite solid-state electrolyte can form ideal mechanical contact with the electrode in the battery when the battery is assembled, reducing the difficulty of lithium ion transmission at the electrode-electrolyte interface in the battery.

[0068] As shown in Figure 2 , the current of the composite solid-state electrolyte prepared in Example 1 begins to rise significantly after 4.8V, indicating that decomposition begins, indicating that the composite solid-state electrolyte obtained by Example 1 has ideal electrochemical stability and can be used with most high-voltage positive electrode materials on the market.

[0069] As shown in Figure 3As shown in Table 1, the SS||SS battery assembled by Example 1 has the lowest bulk charge transfer resistance (5.41 Ω), while the bulk charge transfer resistance of the SS||SS batteries assembled by Comparative Example 1 and Comparative Example 2 is 8.85 Ω and 5.95 Ω, respectively. The ionic conductivity is calculated by the formula, and the ionic conductivity of the composite solid electrolyte prepared by Example 1 is 4.61 x 10 -4 S / cm, and the ionic conductivity of the composite solid electrolyte prepared by Comparative Example 1 and Comparative Example 2 is 2.81 x 10 -4 S / cm and 4.18 x 10 -4 S / cm, respectively. The enhancement of ionic conductivity can be explained as the combined effect of the ion-conducting network composed of compound A and polymer B and the inorganic ion conductor.

[0070] As shown in Table 2, the interfacial charge transfer resistance of the Li||Li battery assembled by Example 1 is 185.4 Ω, while the interfacial charge transfer resistance of the Li||Li batteries assembled by Comparative Example 1 and Comparative Example 2 is 155.3 Ω and 201.3 Ω, respectively. The interfacial charge transfer resistance of the symmetric lithium battery of the electrolyte obtained by Example 1 is higher than that of Comparative Example 1 and lower than that of Comparative Example 2, which indicates that the polymer network composed of compound A and polymer B is beneficial to improve the interfacial contact between the electrolyte and the electrode, and the introduction of inorganic fillers, although enhancing the ionic conductivity, can adversely affect the interface between the electrode and the electrolyte. Figure 4 As shown in Table 3, the Li||Li coin battery assembled by Example 1 can be stably cycled for 2000 h without significant polarization increase at a current of 0.1 mA / cm 2 , and the symmetric batteries assembled by Comparative Example 1 and Comparative Example 2 are short-circuited after 89 h and 302 h of cycling, respectively, indicating that a stable and uniform interfacial layer is formed between the composite solid electrolyte prepared by Example 1 and the lithium metal electrode, which can ensure long-term stable cycling of the battery.

[0071] Figure 5 As shown in Table 4, the LFP||Li coin battery assembled by Example 1 can be stably cycled at a rate of 1C for 1600 cycles with a capacity retention rate of 88.73%, while the LFP||Li coin batteries assembled by Comparative Example 1 and Comparative Example 2 show significant capacity decay or coulombic efficiency decrease after less than 125 cycles.

[0072] As shown in Table 4, the LFP||Li coin battery assembled by Example 1 can be stably cycled at a rate of 1C for 1600 cycles with a capacity retention rate of 88.73%, while the LFP||Li coin batteries assembled by Comparative Example 1 and Comparative Example 2 show significant capacity decay or coulombic efficiency decrease after less than 125 cycles. Figure 6

[0073] ​​The application is illustrated by the above examples, but the application is not limited to the above detailed process equipment and process flow, that is, the application does not mean that the application must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any improvement of the application, equivalent replacement of each raw material of the product of the application, addition of auxiliary ingredients, selection of specific modes, etc. fall within the protection scope and disclosure scope of the application.

Claims

1. A molecular network modified composite solid electrolyte, characterized in that The composite solid electrolyte is prepared from the following raw materials in the following weight percentage ratios: 5 wt% to 30 wt% of a solute salt, wherein the solute salt is one or more of lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate, lithium difluorooxalatoborate, lithium nitrate, and lithium tetrafluoroborate; 5 wt% to 80 wt% of an inorganic filler, wherein the inorganic filler is one or more of an active filler and an inert filler, wherein the active filler is one or more of a NASICON filler, a garnet filler, and a perovskite filler, and the inert filler is one or more of SiO2, Al2O3, TiO2, and ZrO2; The polymer matrix comprises 10 wt% to 80 wt% of a compound A, a polymer B, and a polymer C in a mass ratio of 10:1:(1.5 to 4.5), wherein the compound A is one or more of butyl acrylate, methyl acrylate, isobutyl acrylate, hexafluorobutyl acrylate, and hexafluorobutyl methacrylate; the polymer B is one or more of polymethyl methacrylate, polyethylene glycol diacrylate, polyethylene succinate, diethylene glycol diacrylate, and poly(ethylene glycol) methacrylate; and the polymer C is one or more of a fluorine-containing polymer selected from ethylene-tetrafluoroethylene copolymer, polytetrafluoroethylene, fluorinated ethylene-propylene copolymer, perfluoroalkoxy resin, polychlorotrifluoroethylene, ethylene-chlorotrifluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, and polyvinylidene fluoride-hexafluoropropylene.

2. A molecular network modified composite solid electrolyte according to claim 1, characterized in that The composite solid electrolyte is prepared from the following raw materials in the following weight percentage ratios: 10wt% to 20wt% of solute salt, 10wt% to 40wt% of inorganic filler, and the balance being a polymer matrix.

3. The molecular network modified composite solid electrolyte according to claim 1, characterized in that: The NASICON type filler is Li 1+x Al x Ti 2-x (PO4)3 and Li 1+x Al x Ge 2-x (PO4) 3 one or more; garnet type filler is Li 6.5 La3Zr 1.2 Ta 1.5 O 12 ; Perovskite filler is Li 3x La 2 / 3-x TiO3.

4. The molecular network modified composite solid electrolyte according to claim 1, characterized in that: The mass ratio of compound A, polymer B and polymer C in the polymer matrix is ​​10:1:3.

5.

5. The method for preparing a molecular network modified composite solid electrolyte according to claims 1 to 4, characterized in that The specific preparation steps are: Step S1: mixing compound A and polymer B uniformly to obtain a mixed solution; Step S2: adding polymer C and solvent D to the mixed solution obtained in step S1 and mixing them uniformly to obtain a mixed slurry; Step S3: adding a solute salt to the mixed slurry obtained in step S2 and mixing them uniformly to obtain a mixed slurry; Step S4: mixing the inorganic filler and the solvent D and then ultrasonically dispersing them for 30 to 120 minutes to obtain an inorganic filler dispersion; Step S5: adding the inorganic filler dispersion obtained in step S4 to the mixed slurry obtained in step S3 and mixing them evenly to obtain a composite electrolyte precursor; Step S6: The composite electrolyte precursor obtained in step S5 is fully stirred under ultraviolet light irradiation conditions, cast on a glass plate, and vacuum dried to obtain a molecular network modified composite solid electrolyte.

6. The method for preparing a molecular network-modified composite solid electrolyte according to claim 5, characterized in that: In step S1 and step S4, the solvent D is one or more of N-methylpyrrolidone, N,N-dimethylformamide and dimethyl sulfoxide.

7. The method for preparing a molecular network-modified composite solid electrolyte according to claim 5, characterized in that: The mixing processes in step S1, step S2, step S3, step S5 and step S6 are all carried out on a magnetic stirrer with a stirring speed of 900-1200 r / min.

8. The method for preparing a molecular network modified composite solid electrolyte according to claim 5, characterized in that The ultraviolet light irradiation treatment in step S6 is performed under an ultraviolet curing lamp with a wavelength of 365 nm and a power of 20 W.

9. A lithium metal battery, characterized in that: A lithium metal button battery is assembled using the molecular network modified composite solid electrolyte according to claims 1 to 4, a lithium iron phosphate or nickel cobalt manganese positive electrode and a lithium metal negative electrode.

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