Composite solid electrolyte and preparation method thereof

Abstract

The invention relates to a composite solid electrolyte and a preparation method thereof, the composite solid electrolyte comprises: a lithium zirconium phosphate (LZP) oligomer: a chain nanocluster with a polymerization degree of 5-10, the surface of which is modified by trimethyl phosphate (TMP) to form a phosphate group; a polymer matrix, namely PVDF-HFP; the lithium salt is lithium bis (trifluoromethanesulfonimide) LiFSI or LiDFOB, and the molar ratio of the lithium salt to the polymer repeating unit is (1: 8)-(1: 12); wherein the LZP oligomer and a-CF2 group of the PVDF-HFP form a hydrogen bond through a phosphate group of the TMP, and the LZP oligomer and the-CF2 group of the PVDF-HFP interact with each other through a dipole, so that molecular-level interface bonding is realized; the LZP oligomer constructs a continuous three-dimensional ion channel in the electrolyte, and the dielectric constant is 60-80; the electrolyte forms a film at 60 DEG C or below by a solution casting method.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery material technology, and specifically relates to a composite solid electrolyte and its preparation method. Background Technology

[0002] Solid electrolytes are the core material for next-generation high-safety lithium batteries, and they need to have both high ionic conductivity (>10). -4 The electrolytes possess high dielectric constant (S / cm), low interfacial impedance, and excellent mechanical strength. Traditional solid-state electrolytes (such as LLZO and LATP) suffer from high interfacial impedance and dendrite growth due to insufficient contact between rigid particles and the electrode interface. Existing composite electrolytes often use inorganic fillers (such as SiO2 and Al2O3) blended with polymers (PEO and PVDF). However, the poor interfacial compatibility between inorganic fillers and polymer matrices easily creates ion transport bottlenecks. Furthermore, the low dielectric constant of the fillers (<10) makes it difficult to effectively shield lithium salt ion pairs, thus limiting the improvement of ion mobility. The shortcomings of existing technologies include: poor dispersibility of the inorganic component in solvents: due to a lack of sufficient functional groups, inorganic fillers exhibit poor dispersibility in organic solvents, leading to layering and aggregation, which significantly affects the uniformity of the composite electrolyte membrane and makes it difficult to construct unobstructed lithium-ion migration pathways; poor interfacial contact: the physical mixing between the inorganic filler and the polymer matrix results in micron-sized voids at the electrolyte interface, causing discontinuous ion transport pathways; insufficient dielectric constant: traditional inorganic fillers have low dielectric constants, failing to fully dissociate lithium salts (such as LiFSI), thus limiting ionic conductivity (<10). -4 (S / cm); Complex process: requires high-temperature sintering or high-pressure molding, making it difficult to achieve large-area uniform film preparation. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a method that eliminates physical interface voids between inorganic fillers and the polymer matrix, reduces interfacial impedance, and solves the problem of poor interfacial contact. It overcomes the limitation of traditional fillers with low dielectric constants (ε < 10), enhances lithium salt dissociation capabilities, and improves dielectric properties. It avoids high-temperature sintering / high-pressure molding, achieving low-temperature, large-area uniform film formation, thus simplifying the preparation process. Simultaneously, it increases ionic conductivity to > 5 × 10⁻⁵. -4 A composite solid electrolyte with optimized overall performance, including S / cm, lithium-ion transference number >0.65, and cycling stability, and its preparation method.

[0004] The first technical solution of the present invention is the composite solid electrolyte, which is characterized by comprising:

[0005] Lithium zirconium phosphate (LiZr2(PO4)3LZP) oligomer: chain-like nanoclusters with a degree of polymerization of 5-10, the surface of which is modified with trimethyl phosphate (TMP) to form phosphate groups, accounting for 20-40% by mass;

[0006] Polymer matrix: Fluorinated ethylene-propylene copolymer PVDF-HFP, degree of polymerization 600,000, mass percentage 50-70%;

[0007] Lithium salt: Lithium bis(trifluoromethanesulfonyl)imide (LiFSI), purity >99%, mass percentage 5-20%;

[0008] Lithium zirconium phosphate (LZP) oligomers form hydrogen / covalent interfacial bonds and dipole interactions with the -CF2 groups of trimethyl phosphate (TMP) and fluorinated ethylene-propylene copolymer (PVDF-HFP). The dielectric constant of lithium zirconium phosphate (LZP) oligomers is 60–80, which can construct continuous three-dimensional ion channels in the electrolyte.

[0009] The electrolyte is formed into a film at a temperature below 60°C using a solution casting method, and has an ionic conductivity >5×10⁻⁻¹. 4 S / cm, 25℃, interfacial impedance <50Ω·cm 2 The lithium-ion transference number is >0.65.

[0010] Preferably, the lithium zirconium phosphate (LZP) oligomer has a particle size of 2–200 nm and is a molecular-level composite with the polymer matrix; the molar ratio of lithium salt bis(trifluoromethanesulfonyl)imide (LiFSI) to the repeating unit of fluorinated ethylene-propylene copolymer (PVDF-HFP) is 1:8–1:12; and lithium lanthanum titanate (LLTO) nanowires are added at a mass ratio of 1–10% to construct an electron-ion dual-conductivity network.

[0011] Preferably, the phosphorus-oxygen double bond and phosphate / phosphonate structure in the trimethyl phosphate (TMP) molecule interact with the metal ions on the surface of lithium zirconium phosphate (LiZr2(PO4)3) LZP oligomer to form a stable interface; the phosphate / phosphonate groups can improve the dispersibility and binding force between the inorganic filler and the fluorinated ethylene-propylene copolymer (PVDF-HFP) matrix.

[0012] Preferably, the fluorinated ethylene-propylene copolymer PVDF-HFP is replaced with polyethylene oxide (PEO) or polyacrylonitrile (PAN); the lithium salts are lithium bis(trifluoromethanesulfonyl)imide (LiFSI) and lithium difluorooxalate borate (LiDFOB) to suit high and low temperature scenarios; and the fibrous composite electrolyte is prepared by electrospinning technology.

[0013] The second technical solution of the present invention is a method for preparing the composite solid electrolyte, characterized by comprising the following steps:

[0014] (1) Sol-gel method for synthesizing lithium zirconium phosphate (LZP) oligomers: Zirconium source and lithium source were dissolved in ethanol, triethylamine was added to adjust the pH to 8-10, and after stirring to form a gel, phosphorus source was added, aged for 60 h, and dried and ground at 70 °C.

[0015] (2) Trimethyl phosphate TMP modification: The lithium zirconium phosphate LZP oligomer obtained in step (1) was dispersed in ethanol, and trimethyl phosphate TMP was added at a mass ratio of 1:5 to 1:10 of trimethyl phosphate TMP to lithium zirconium phosphate LZP oligomer. After stirring and reacting, the solvent was evaporated.

[0016] (3) Ligand exchange: The trimethyl phosphate (TMP) modified lithium zirconium phosphate (LZP) oligomer was dispersed in N,N-dimethylacetamide (DMAC) solvent and ultrasonically treated for 2 h to replace the triethylamine ligand with N,N-dimethylacetamide (DMAC);

[0017] (4) Film formation: Add polymer matrix PVDF-HFP and lithium bis(trifluoromethanesulfonyl)imide (LiFSI) to the dispersion in step (3), stir at 60°C for 4 hours and then cast, and vacuum dry at 60°C for 24 hours to obtain a self-supporting solid electrolyte film with molecular-level interfacial contact and high dielectric constant.

[0018] The third technical solution of this invention is the application of the composite solid electrolyte in solid-state lithium batteries, characterized in that, using the aforementioned electrolyte, the ionic conductivity is >5×10⁻⁶. -4 S / cm, 25℃, lithium-ion transference number ≥0.65.

[0019] The fourth technical solution of the present invention is a composite solid electrolyte modified with the silane coupling agent, characterized in that it includes:

[0020] Polymer matrix: fluorinated ethylene-propylene copolymer PVDF-HFP or polyethylene oxide PEO, accounting for 50-70% by mass;

[0021] Lithium salt: Lithium difluorooxalate borate (LiDFOB), with a mass percentage of 5-30%, and the molar ratio of lithium salt to repeating units in the polymer matrix is ​​1:8-1:12;

[0022] Interface modifier: γ-aminopropyltriethoxysilane KH550; lithium zirconium phosphate (LZP) oligomers are modified with γ-aminopropyltriethoxysilane KH550, the amount of γ-aminopropyltriethoxysilane KH550 being 5-30% of the mass of the lithium zirconium phosphate (LZP) oligomers; the siloxane groups of γ-aminopropyltriethoxysilane KH550 hydrolyze and condense with the hydroxyl groups on the surface of the lithium zirconium phosphate (LZP) oligomers, and the amino groups form hydrogen bonds / covalent bonds with the -CF2 groups of the polymer matrix PVDF-HFP;

[0023] Lithium zirconium phosphate (LZP) oligomers, after modification with γ-aminopropyltriethoxysilane (KH550), achieved molecular-level dispersion in N,N-dimethylacetamide (DMAC) solvent and formed a chemically bonded interface with the polymer matrix, resulting in an electrolyte membrane with an ionic conductivity ≥5×10⁻⁶. -4S / cm, 25℃, interfacial impedance ≤50Ω·cm 2 The lithium-ion transference number is >0.65.

[0024] The fifth technical solution of the present invention is a method for preparing the silane coupling agent-modified composite solid electrolyte, characterized by the following steps:

[0025] (1) Preparation of lithium zirconium phosphate (LZP) oligomers by sol-gel method: zirconium source, lithium source and phosphorus source are reacted in ethanol, confined by triethylamine, aged for 60 h, dried and ground.

[0026] (2) γ-aminopropyltriethoxysilane KH550 modified lithium zirconium phosphate LZP oligomer: Lithium zirconium phosphate LZP oligomer was dispersed in ethanol, γ-aminopropyltriethoxysilane KH550 was added, hydrolysis and condensation were carried out at 60℃ for 4h, and the solvent was evaporated to obtain the composite system of lithium zirconium phosphate LZP oligomer material and silicon LZP@Si;

[0027] (3) The composite system of lithium zirconium phosphate (LZP) oligomer material and silicon, LZP@Si, was dispersed in N,N-dimethylacetamide (DMAC) and ultrasonically treated for 2 hours.

[0028] (4) Add fluorinated ethylene-propylene copolymer PVDF-HFP and lithium difluorooxalate borate LiDFOB, stir at 60℃ for 4h, cast into a film, and vacuum dry.

[0029] In step (2), the hydrolysis and condensation are carried out in an ammonia buffer system with pH 8 to 9 to control the partial hydrolysis state of γ-aminopropyltriethoxysilane KH550.

[0030] The sixth technical solution of the present invention is the ionic liquid-bridged composite solid electrolyte, which is characterized by comprising:

[0031] Lithium zirconium phosphate (LZP) oligomers, with a mass percentage of 20–40 wt%;

[0032] The polymer matrix is ​​PVDF-HFP, with a mass percentage of 50–70 wt%.

[0033] Lithium salt LiFSI, with a mass percentage of 5–20 wt%;

[0034] The interface bridging agent EMIM-TFSI, with a mass ratio of 5-15 wt%, is a cationic EMIM. + The TFSI- anion coordinates with oxygen atoms on the LZP surface and undergoes a dipole interaction with the -CF2 group of PVDF-HFP.

[0035] The seventh technical solution of the present invention is a method for preparing the ionic liquid-bridged composite solid electrolyte, characterized by comprising the following steps:

[0036] (1) The lithium zirconium phosphate (LiZr2(PO4)3LZP) oligomer was reacted with the interfacial bridging agent EMIM-TFSI in acetonitrile at 60°C for 2 h.

[0037] (2) Disperse the product from step (1) in N,N-dimethylacetamide (DMAC) solvent and sonicate it.

[0038] (3) Add fluorinated ethylene-propylene copolymer PVDF-HFP and lithium bis(trifluoromethanesulfonyl)imide (LiFSI), and stir at 50°C to form a film.

[0039] The eighth technical solution of the present invention is the application of the ionic liquid-bridged composite solid electrolyte in solid-state lithium batteries. Its special feature is that, using the electrolyte, the ionic conductivity in the solid-state lithium battery is ≥6.0 × 10⁻⁶. -4 S / cm.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] (1) The phosphate / phosphonate groups of this invention can also improve the dispersibility and binding force between the inorganic filler and the polymer (PVDF-HFP) matrix, resulting in better interfacial contact of the composite solid electrolyte. Through the molecular-level contact solid electrolyte interface design and ultra-high dielectric constant characteristics, lithium-ion transport efficiency and interfacial stability are significantly improved, making it suitable for high-energy-density, high-safety solid-state lithium battery systems. LZP functionalization: Modification of LZP with TMP ensures both the size uniformity of lithium zirconium phosphate and the molecular-level dispersion of lithium zirconium phosphate clusters.

[0042] (2) Ultra-low degree of polymerization LZP oligomers: Low degree of polymerization (5-10) chain-like LZP was synthesized via the sol-gel method, achieving uniform dispersion at the nanoscale. The confinement effect of triethylamine avoided the traditional particle agglomeration problem. Molecular-level composites could be achieved between LZP and the polymer matrix; the molecular-level interface design eliminated interfacial voids, constructing continuous ion transport channels. The ultra-high dielectric constant (ε=60-80) of LZP oligomers efficiently shielded lithium salt ion pairs, increasing the lithium ion transference number (t). + >0.6); Self-supporting films (10-50 μm thick) can be prepared at room temperature by solution casting without the need for high temperature and high pressure treatment.

[0043] (3) This invention synthesizes low-polymerization-degree 5-10 chain LZP through the sol-gel method, achieving uniform dispersion at the nanoscale. Through the confinement effect of triethylamine, the problem of particle agglomeration in traditional methods is avoided.

[0044] (4) Molecular-level composite interface design: LZP oligomers are bonded to the fluoropolymer matrix via hydrogen bonds / dipole interactions, forming a defect-free ion transport interface. Dielectric constant regulation: The dielectric constant of LZP oligomers is >60, providing a strong polarization field for lithium salt dissociation and increasing ion mobility by more than 30%.

[0045] (5) Inorganic / organic bonding interface, molecular modification, ionic conductivity > 5 × 10⁻⁻⁶ 4 S / cm (25℃), lithium-ion transference number >0.65.

[0046] (6) Cyclic performance data: >1000 cycles, 0.5C, capacity retention 85%.

[0047] (7) In the prior art, the poor dispersibility of inorganic fillers leads to interfacial voids. The present invention achieves molecular-level interfacial bonding through TMP modification.

[0048] (7) Traditional fillers have a dielectric constant of <10, while the present invention uses LZP oligomers with a dielectric constant >60, which provides a strong polarization field for lithium salt dissociation and increases the ion transference number by more than 30%.

[0049] (9) LZP oligomers modified with TMP form hydrogen bonds with PVDF-HFP, eliminating interfacial voids and resulting in an interfacial impedance of <50Ω·cm. 2 The high dielectric constant LZP promotes lithium salt dissociation, resulting in an ion transference number >0.65.

[0050] Table 1: Technical Logic Chain Table, which intuitively shows the correspondence between objective, solution, and effect:

[0051] Existing technological defects Invention Solution Technical effect Interface gaps TMP molecular bonding <![CDATA[Interface impedance < 50 Q-cm 2 > low dielectric constant LZP dielectric s = 60-80 Ion transport number > 0.65 High temperature process 60C solution casting Large-area film formation Ionic conductivity <![CDATA[<10 -4 S / cm]]> <![CDATA[>5×10 -4 S / cm]]> Attached Figure Description

[0052] Figures 1-1 to 1-3 These are transmission electron microscope images of lithium zirconium phosphate-PVDF-HFP at different scales according to the present invention;

[0053] Figure 2 This is the infrared contrast spectrum of the present invention;

[0054] Figure 3 This is an Arrhenius curve of ionic conductivity between Example 1 and the comparative example of the present invention;

[0055] Figure 4 This is a comparison chart of the ionic conductivity of the present invention. Detailed Implementation

[0056] The present invention will be further described in detail below with reference to embodiments:

[0057] Example 1:

[0058] Composite solid electrolytes, including:

[0059] Lithium zirconium phosphate (LZP) oligomer: 2-50 wt%; chain-like nanoclusters with a degree of polymerization of 5-10, the surface of which is modified with trimethyl phosphate (TMP) to form phosphate groups; the LZP oligomer has a particle size of 2-200 nm and a mass percentage of 20-40%;

[0060] The polymer matrix is ​​fluorinated ethylene-propylene copolymer PVDF-HFP;

[0061] The lithium salt is 5-20 wt%, which is lithium bis(trifluoromethanesulfonyl)imide (LiFSI) or lithium difluorooxalate borate (LiDFOB), and the molar ratio of the lithium salt to the polymer repeating unit is 1:8 to 1:12; the molar ratio of the lithium salt lithium bis(trifluoromethanesulfonyl)imide (LiFSI) to the fluorinated ethylene-propylene copolymer PVDF-HFP repeating unit is 1:8 to 1:12.

[0062] Among them, lithium zirconium phosphate (LiZr2(PO4)3,LZP) oligomers achieve molecular-level interfacial bonding through hydrogen bonds and dipole interactions between the phosphate groups of trimethyl phosphate (TMP) and the -CF2 groups of fluorinated ethylene-propylene copolymer (PVDF-HFP); correspondingly Figure 1-2 / 1-3TEM images and Figure 2 Infrared peak shift (1020cm) -1 );

[0063] Lithium zirconium phosphate (LiZr2(PO4)3,LZP) oligomers construct continuous three-dimensional ion channels in an electrolyte with a dielectric constant of 60–80; the electrolyte is formed into a film at a temperature below 60°C by solution casting.

[0064] The polymer matrix is ​​replaced with polyethylene oxide (PEO) or polyacrylonitrile (PAN); lithium titanate lanthanum (LLTO) nanowires are added to construct an electron-ion dual-conductivity network.

[0065] The preparation method of composite solid electrolyte includes the following steps:

[0066] (1) Sol-gel method for synthesizing lithium zirconium phosphate (LZP) oligomers: Zirconium source and lithium source are dissolved in ethanol, triethylamine is added to adjust the pH to 8-10, and after stirring to form a gel, phosphorus source is added, aged for 60 h, and dried and ground at 70 °C; the amount of triethylamine added in step (1) is controlled to control the pH to 8-10; the mass ratio of TMP to LZP in step (b) is 1:5-1:10;

[0067] (2) TMP modification: Disperse lithium zirconium phosphate LiZr2(PO4)3,LZP oligomers in ethanol, add TMP at a mass ratio of TMP to LZP of 1:5 to 1:10, stir the reaction and then evaporate the solvent.

[0068] (3) Ligand exchange: The trimethyl phosphate (TMP) modified lithium zirconium phosphate (LZP) oligomer was dispersed in N,N-dimethylacetamide (DMAC) solvent and ultrasonically treated for 2 h to replace the triethylamine ligand with N,N-dimethylacetamide (DMAC);

[0069] (4) Film formation:

[0070] Add polymer matrix PVDF-HFP and lithium bis(trifluoromethanesulfonyl)imide (LiFSI) to the dispersion in step (3), stir at 60°C for 4 hours, then cast and vacuum dry at 60°C for 24 hours to obtain a self-supporting solid electrolyte film with molecular-level interfacial contact and high dielectric constant.

[0071] Working principle:

[0072] Ligand exchange: The lithium zirconium phosphate (LiZr2(PO4)3,LZP) oligomer is initially confined by triethylamine to maintain its size stability and uniformity. The phosphorus-oxygen double bond and phosphate group in the trimethyl phosphate (TMP) molecule can interact with the metal ions on the surface of the LiZr2(PO4)3,LZP oligomer to form a stable interface. Simultaneously, the phosphate groups can improve the dispersibility and binding force between the inorganic filler and the fluorinated ethylene-propylene copolymer (PVDF-HFP) matrix, resulting in better interfacial contact of the composite solid electrolyte and preparing it for subsequent molecular-level interfacial contact with the PVDF-HFP.

[0073] Molecular-level interfacial contact: The phosphate group in trimethyl phosphate (TMP) can bond with lithium zirconium phosphate (LiZr2(PO4)3,LZP) oligomers to modify them. Simultaneously, the end groups (-OH, -PO4) of the oligomers form hydrogen bonds and dipole interactions with the -CF2 groups of the fluorinated ethylene-propylene copolymer (PVDF-HFP), achieving chemical bonding between the inorganic and organic phases and eliminating interfacial defects.

[0074] Dielectric enhancement effect: The high dielectric constant (ε=60-80) of lithium zirconium phosphate (LiZr2(PO4)3,LZP) oligomers significantly reduces the lithium salt dissociation energy and increases the free Li... + concentration;

[0075] Three-dimensional ion channels: Lithium zirconium phosphate (LiZr2(PO4)3) oligomers form a continuous network in the polymer, which promotes Li transport by coordinating polymer chain segment movement.

[0076] Test results: Ionic conductivity 0.52 mS / cm (see [link]). Figure 4 As shown in the image, the infrared spectrum shows that the P=O peak has shifted to 1020 cm⁻¹. -1 (See also) Figure 2As shown in the figure, it is confirmed that trimethyl phosphate (TMP) is bonded to -CF2.

[0077] Example 2:

[0078] By replacing the fluorinated ethylene-propylene copolymer PVDF-HFP with polyethylene oxide (PEO), using lithium difluorooxalate borate (LiDFOB) as the lithium salt, and adding lithium titanate lanthanum (LLTO) nanowires (5 wt%), the ionic conductivity was maintained at >4.5 × 10⁻⁶. -4 S / cm.

[0079] Film formation process: Electrospinning technology is used (voltage 15kV, receiving distance 15cm);

[0080] Effect: Ionic conductivity remains at 1.8 × 10⁻⁶ at -20℃. -4 S / cm.

[0081] Comparative Example 1 (without silane modification):

[0082] Electrolytes of unmodified lithium zirconium phosphate (LiZr2(PO4)3)2,LZP oligomers: Trimethyl phosphate TEM showed agglomeration ( Figure 1-1 ), ionic conductivity <1×10 -4 S / cm; Using γ-aminopropyltriethoxysilane KH550 instead of trimethyl phosphate TMP (Example 3): Ionic conductivity maintained >5×10 -4 S / cm"

[0083] Example 3:

[0084] Silane coupling agent modified composite solid electrolytes include:

[0085] Lithium zirconium phosphate oligomers (degree of polymerization 5-10, particle size 2-50 nm), with a mass percentage of 20-40%;

[0086] Polymer matrix: fluorinated ethylene-propylene copolymer PVDF-HFP or polyethylene oxide PEO, accounting for 50-70% by mass;

[0087] Lithium salt: Lithium bis(trifluoromethanesulfonyl)imide (LiFSI), with a molar ratio of lithium salt to polymer repeating unit of 1:8 to 1:12;

[0088] Interface modifier: amino-containing silane coupling agent (KH550), whose siloxane groups form covalent bonds with the hydroxyl groups on the surface of lithium zirconium phosphate LiZr2(PO4)3,LZP oligomers through hydrolysis and condensation, and the amino groups form hydrogen bonds with the fluorine / oxygen atoms of the polymer matrix;

[0089] Among them, lithium zirconium phosphate (LiZr2(PO4)3,LZP) oligomers, after modification with silane coupling agents, achieve molecular-level dispersion in DMAC solvent and form a chemically bonded interface with the polymer matrix, resulting in an ionic conductivity of the electrolyte membrane ≥5×10⁻⁶. -4 S / cm (25℃), interfacial impedance ≤50Ω·cm 2 .

[0090] The silane coupling agent is γ-aminopropyltriethoxysilane (KH550), and its amount is 5-15% of the mass of lithium zirconium phosphate (LZP) oligomer.

[0091] A method for preparing a silane coupling agent modified composite solid electrolyte includes:

[0092] (1) Preparation of lithium zirconium phosphate (LiZr2(PO4)3,LZP oligomers by sol-gel method: zirconium source, lithium source and phosphorus source are reacted in ethanol, confined by triethylamine, aged for 60 h, dried and ground.

[0093] (2) Silane-modified lithium zirconium phosphate LiZr2(PO4)3,LZP oligomer: LiZr2(PO4)3,LZP oligomer was dispersed in ethanol, γ-aminopropyltriethoxysilane KH550 was added, and hydrolysis and condensation were carried out at 60℃ for 4h. The solvent was evaporated to obtain LZP@Si; the hydrolysis and condensation in step (b) were carried out in an ammonia buffer system with pH=8-9 to control the partial hydrolysis state of silane;

[0094] (3) The composite system of lithium zirconium phosphate (LZP) oligomer material and silicon, LZP@Si, was dispersed in N,N-dimethylacetamide (DMAC) and ultrasonically treated for 2 hours.

[0095] (4) Add fluorinated ethylene-propylene copolymer PVDF-HFP and lithium difluorooxalate borate LiDFOB, stir at 60℃ for 4h, cast into a film, and vacuum dry.

[0096] In the application of composite solid-state electrolytes in solid-state lithium batteries, the electrolyte satisfies the following:

[0097] Ionic conductivity >5×10 -4 S / cm (25℃); Lithium-ion transference number ≥ 0.65; Interfacial impedance < 50 Ω·cm 2 .

[0098] Table 2: Performance Data Completeness

[0099] Example Ionic conductivity (25℃) Number of migrations Interface impedance 1 (TMP) <![CDATA[5.3×10 -4 S / cm]]> 0.68 <![CDATA[42Ω·cm 2 ]]> 3(KH550) <![CDATA[6.1×10 -4 S / cm]]> 0.72 <![CDATA[35Ω·cm 2 ]]> Comparative Example <![CDATA[2.1×10 -4 S / cm]]> 0.41 <![CDATA[>100Ω·cm 2 ]]>

[0100] Table 3: Comparison of dielectric properties of electrolyte membranes with unmodified LZP, TMP-modified LZP, and Al2O3 fillers

[0101] sample Dielectric constant ε <![CDATA[Ionic transference number t * > LZP / TMP 75 0.68 Unmodified LZP 40 0.52 <![CDATA[Al2O3]]> 9 0.35

[0102] In summary, the main contents of this invention are summarized in the following table:

[0103] Table 4: Innovation of Technical Solutions

[0104]

[0105] Table 5: Technical Effects

[0106]

[0107] Table 6: Verification of Consistency between Objective-Solution-Effect

[0108]

[0109] Example 4:

[0110] Ionic liquid-bridged composite solid electrolytes include:

[0111] Lithium zirconium phosphate (LZP) oligomers, with a mass percentage of 20-40 wt%;

[0112] The polymer matrix is ​​PVDF-HFP, with a mass percentage of 50-70 wt%.

[0113] Lithium salt LiFSI, with a mass percentage of 5-20 wt%;

[0114] Interfacial bridging agent EMIM-TFSI, with a mass ratio of 5-15 wt%, is a cationic EMIM. + The TFSI- anion coordinates with oxygen atoms on the LZP surface and undergoes a dipole interaction with the -CF2 group of PVDF-HFP.

[0115] The preparation method of the ionic liquid-bridged composite solid electrolyte includes the following steps:

[0116] (1) The lithium zirconium phosphate (LiZr2(PO4)3LZP) oligomer was reacted with the interfacial bridging agent EMIM-TFSI in acetonitrile at 60°C for 2 h.

[0117] (2) Disperse the product from step (1) in N,N-dimethylacetamide (DMAC) solvent and sonicate it.

[0118] (3) Add fluorinated ethylene-propylene copolymer PVDF-HFP and lithium bis(trifluoromethanesulfonyl)imide (LiFSI), and stir at 50°C to form a film.

[0119] Mechanism of action:

[0120] EMIM + The cations form coordination bonds with oxygen atoms on the LZP surface;

[0121] TFSI- The anion generates a strong dipole interaction with the -CF2 group of PVDF-HFP;

[0122] Mass percentage: Ionic liquids account for 5-15% of the total electrolyte mass;

[0123] Performance metrics:

[0124] Ionic conductivity ≥ 6.0 × 10 -4 S / cm (25℃)

[0125] Lithium-ion transference number > 0.70

[0126] Interface impedance ≤30Ω·cm 2 .

[0127] Performance advantages comparison (supported by data)

[0128] parameter Silane solution (KH550) Ionic liquid scheme Ionic conductivity (25℃) <![CDATA[6.1×10 -4 S / cm]]> <![CDATA[7.2×10 -4 S / cm]]> Interface impedance <![CDATA[35Ω·cm 2 ]]> <![CDATA[28Ω·cm 2 ]]> thermal stability Decomposes at 180℃ Decomposes at >250℃ Low temperature performance (-20℃) <![CDATA[1.8×10 -4 S / cm]]> <![CDATA[3.5×10 -4 S / cm]]>

[0129] Example 5:

[0130] The application of ionic liquid-bridged composite solid-state electrolytes in solid-state lithium batteries, wherein the ionic conductivity of the solid-state lithium battery using the aforementioned ionic liquid-bridged composite solid-state electrolyte is ≥6.0×10⁻⁶. -4 S / cm.

[0131] This invention systematically solves three major pain points of solid electrolytes (described in the background art) through an innovative chain of molecular-level interface design (Objective 1) → high-dielectric LZP oligomers (Objective 2) → low-temperature solution processing (Objective 3), ultimately achieving a high-performance, high-stability, and low-cost composite solid electrolyte (Objective 4). All technical effects are rigorously supported by data from the examples (Tables 2-3, Figures 1-3). Figure 4 This forms a complete logical closed loop.

[0132] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.

Claims

1. A composite solid-state electrolyte, characterized by, Comprise: Zirconium lithium phosphate LiZr2(PO4)3 LZP oligomer: chain-like nanoclusters with a degree of polymerization of 5-10, the surface is modified with trimethyl phosphate TMP to form phosphate groups, and the mass fraction is 20-40%; Polymer matrix: fluorinated ethylene-propylene copolymer PVDF-HFP, degree of polymerization 600000, mass fraction 50-70%; Lithium salt: lithium bis(trifluoromethanesulfonyl)imide LiFSI, purity > 99%, mass fraction 5-20%; Zirconium lithium phosphate LZP oligomer forms hydrogen bond / covalent bond interfacial bonding and dipole interaction with trimethyl phosphate TMP and -CF2 group of fluorinated ethylene-propylene copolymer PVDF-HFP, the dielectric constant of zirconium lithium phosphate LZP oligomer is 60-80, and a continuous three-dimensional ion channel is constructed in the electrolyte; The electrolyte is formed by solution casting method below 60℃, ion conductivity >5×10 -4 S / cm, 25℃, interface impedance <50Ω·cm 2 , lithium ion transfer number >0.65; the lithium zirconium phosphate LZP oligomer particle size is 2-200nm, and is molecularly compounded with the polymer matrix; the molar ratio of lithium bis-trifluoromethanesulfonimide LiFSI and fluorinated ethylene-propylene copolymer PVDF-HFP repeating units is 1:8-1:12; lithium lanthanum titanate LLTO nanowires are added, the mass ratio is 1-10%, and an electron-ion dual conduction network is constructed.

2. The composite solid-state electrolyte of claim 1, wherein The phosphorus-oxygen double bond and phosphate / phosphonate structure in the trimethyl phosphate TMP molecule interact with the metal ions on the surface of zirconium lithium phosphate LiZr2(PO4)3, LZP oligomer to form a stable interface; the phosphate / phosphonate group can improve the dispersibility and bonding force of the inorganic filler and the fluorinated ethylene-propylene copolymer PVDF-HFP matrix; the fluorinated ethylene-propylene copolymer PVDF-HFP is replaced by polyethylene oxide PEO or polyacrylonitrile PAN; lithium salt: lithium bis(trifluoromethanesulfonyl)imide LiFSI, lithium difluoro(oxalato)borate LiDFOB is suitable for high and low temperature scenes; electrospinning technology is used to prepare fibrous composite electrolyte.

3. A method of producing the composite solid-state electrolyte according to claim 1, characterized by, Comprise the following steps: (1) Sol-gel synthesis of zirconium lithium phosphate LZP oligomer: dissolve zirconium source and lithium source in ethanol, add triethylamine to adjust pH to 8-10, stir to form gel, then add phosphorus source, age for 60 h, dry at 70°C and grind; (2) Trimethyl phosphate TMP modification: disperse the zirconium lithium phosphate LZP oligomer obtained in step (1) in ethanol, add trimethyl phosphate TMP at a mass ratio of 1:5-1:10, stir and react, then evaporate the solvent; (3) Ligand exchange: disperse the trimethyl phosphate TMP modified zirconium lithium phosphate LZP oligomer in N,N-dimethylacetamide DMAC solvent, ultrasonic treatment for 2 h, and replace triethylamine ligand with N,N-dimethylacetamide DMAC; (4) Film formation: add polymer matrix PVDF-HFP and lithium bis(trifluoromethanesulfonyl)imide LiFSI to the dispersion liquid of step (3), stir at 60°C for 4 h, then cast, and vacuum dry at 60°C for 24 h to obtain a self-supporting solid electrolyte film with molecular-level interfacial contact and high dielectric constant.

4. Use of a composite solid-state electrolyte in a solid-state lithium battery, characterized in that: The electrolyte according to any one of claims 1-2 has an ionic conductivity > 5 x 10 -4 S / cm, 25°C, with a lithium ion transference number > 0.

65.

5. A silane coupling agent-modified composite solid electrolyte characterized by comprising a solid electrolyte and a silane coupling agent. Comprise: Polymer matrix: fluorinated ethylene-propylene copolymer PVDF-HFP or polyethylene oxide PEO, mass fraction 50-70%; Lithium salt: lithium difluoro(oxalato)borate LiDFOB, mass fraction 5-30%, and the molar ratio of lithium salt to polymer matrix repeat unit is 1:8-1:12; Interface modifier: γ-aminopropyl triethoxysilane KH550; zirconium lithium phosphate LZP oligomer is modified by γ-aminopropyl triethoxysilane KH550, the amount of γ-aminopropyl triethoxysilane KH550 is 5-30% of the mass of zirconium lithium phosphate LZP oligomer; the siloxane group of γ-aminopropyl triethoxysilane KH550 is hydrolyzed and condensed with the surface hydroxyl group of zirconium lithium phosphate LZP oligomer, and the amino group forms a hydrogen bond / covalent bond with the -CF2 group of the polymer matrix PVDF-HFP; After the modification of lithium zirconium phosphate LZP oligomer by gamma-aminopropyl triethoxysilane KH550, the molecular dispersion is realized in N,N-dimethylacetamide DMAC solvent, and a chemical bonding interface is formed with the polymer matrix, so that the ionic conductivity of the electrolyte membrane is ≥5×10 -4 S / cm, 25℃, interface impedance ≤50Ω·cm 2 , lithium ion migration number >0.

65.

6. A method of producing a composite solid-state electrolyte modified with a silane coupling agent according to claim 5, characterized by, Comprising the steps of: (1) preparing zirconium lithium phosphate LZP oligomer by sol-gel method: zirconium source, lithium source and phosphorus source are reacted in ethanol, limited by triethylamine, aged for 60 h, dried and ground; (2) modifying zirconium lithium phosphate LZP oligomer with γ-aminopropyl triethoxysilane KH550: disperse zirconium lithium phosphate LZP oligomer in ethanol, add γ-aminopropyl triethoxysilane KH550, hydrolyze and condense at 60°C for 4 h, evaporate the solvent to obtain a composite system LZP@Si of zirconium lithium phosphate LZP oligomer material and silicon; (3) disperse the composite system LZP@Si of zirconium lithium phosphate LZP oligomer material and silicon in N,N-dimethylacetamide DMAC and ultrasonic treat for 2 h; (4) add fluorinated ethylene-propylene copolymer PVDF-HFP and lithium difluoro(oxalato)borate LiDFOB, stir at 60°C for 4 h, and cast into a film, and vacuum dry.

7. The silane coupling agent modified composite solid-state electrolyte according to claim 6, wherein, The hydrolysis and condensation in step (2) is carried out in an ammonia buffer system with pH 8-9, and the partial hydrolysis state of γ-aminopropyl triethoxysilane KH550 is controlled.

8. An ion-liquid-bridged composite solid-state electrolyte, characterized by, Comprising: zirconium lithium phosphate LZP oligomer, mass ratio 20-40 wt%; polymer matrix PVDF-HFP, mass ratio 50-70 wt%; lithium salt LiFSI, mass ratio 5-20 wt%; Interface bridging agent EMIM-TFSI, mass ratio 5-15wt%, its cation EMIM + Coordinated with the surface oxygen atoms of LZP, and the anion TFSI- interacts with the -CF2 group dipole of PVDF-HFP.

9. A method of producing the composite solid-state electrolyte bridged by the ionic liquid according to claim 8, characterized by, Comprising the following steps: (1) zirconium lithium phosphate LiZr2(PO4)3 LZP oligomer and interface bridging agent EMIM-TFSI are reacted in acetonitrile at 60°C for 2 h; (2) disperse the product of step (1) in N,N-dimethylacetamide DMAC solvent and ultrasonic treat; (3) add fluorinated ethylene-propylene copolymer PVDF-HFP and lithium bis(trifluoromethanesulfonyl)imide LiFSI, and stir at 50°C to form a film.

10. Use of an ionic liquid-bridged composite solid-state electrolyte in a solid-state lithium battery, characterized in that: The solid-state lithium battery has an ionic conductivity of ≥ 6.0 x 10 -4 S / cm using the electrolyte of any one of claims 8-9.

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