A multilayer composite solid electrolyte membrane and a method of preparation and a solid state battery prepared

Abstract

The application discloses a kind of multilayer composite solid electrolyte membrane and preparation method and prepared solid-state battery, the multilayer composite solid electrolyte membrane is three-dimensional polymer network solid electrolyte, LiPON layer, polydopamine layer in turn, the three-dimensional polymer network solid electrolyte thickness is 20-40 μm, the thickness of the polydopamine layer is <100nm.The application can provide better ion transmission coordination effect by using silane coupling agent modified LLZO and degradation chitosan synergistic effect, improve the efficiency of ion channel.Crystal inhibition efficiency is improved, obvious crack is avoided after 1000 cycles, applied in solid-state battery, prolong the cycle life of battery, 1000 cycles have 95% capacity retention rate.Improve the mechanical toughness of solid electrolyte, and the elongation at break can reach 130%.Preparation whole process uses aqueous solvent, avoids the use of organic solvent, reduces 40% energy consumption, and there is no VOC emission in whole process, green and safe environmental protection.

Description

Technical Field

[0001] This invention relates to the field of electrolyte materials, specifically to a multilayer composite solid electrolyte membrane, its preparation method, and the solid-state battery prepared therefrom. Background Technology

[0002] With the development of science and technology, solid-state batteries are considered a strong candidate for next-generation energy storage technology due to their high safety and high energy density. Solid-state electrolytes are the core component of solid-state batteries, determining the battery's ion conductivity, interface stability, and cycle life. Existing solid-state electrolytes exhibit low ion conductivity at room temperature, insufficient mechanical strength, and poor stability against the lithium metal anode, easily leading to lithium dendrite growth and posing safety hazards. Furthermore, most existing rechargeable batteries use organic solvents, whose manufacturing processes are not environmentally friendly and consume high energy. Therefore, developing a solid-state electrolyte with excellent ion conductivity, long cycle life, and the ability to be produced in a green and energy-efficient manner is crucial.

[0003] Chinese invention patent application CN118511348A discloses a method for manufacturing a composite solid electrolyte. By forming a ceramic ion conductor containing a first polymer with cross-linked functional groups and a ceramic compound, the ionic conductivity of lithium ions can be effectively improved. Furthermore, the ionic conductivity of the composite solid electrolyte can be increased by using the ceramic ion conductor, but the improvement in ionic conductivity is not significant. Chinese invention patent application CN117813712A discloses a polymer solid electrolyte laminate and its preparation method, comprising a protective layer formed on at least one surface of the polymer solid electrolyte. In the continuous process of laminating the polymer solid electrolyte with electrodes after preparation, and in processes such as transportation, this protective layer can prevent changes in the physical properties of the polymer solid electrolyte caused by moisture and external air; however, its ionic conductivity performance is poor. Summary of the Invention

[0004] To develop a solid electrolyte with excellent ion conductivity, long cycle life, and green production with low energy consumption, the first aspect of this invention provides a multilayer composite solid electrolyte membrane, wherein the multilayer composite solid electrolyte membrane comprises, in sequence, a three-dimensional polymer network solid electrolyte, a LiPON (lithium phosphorus oxygen nitrogen) layer, and a polydopamine layer, wherein the thickness of the three-dimensional polymer network solid electrolyte is 20-40 μm, and the thickness of the polydopamine layer is <100 nm; the three-dimensional polymer network solid electrolyte includes modified LLZO with chitosan as the backbone.

[0005] In one embodiment, the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 20-40% polyethylene oxide, 10-30% degraded chitosan, 20-30% modified LLZO, 15-40% lithium salt, 6-10% crosslinking agent, and solvent percentages totaling 100%.

[0006] In one embodiment, the number average molecular weight of the polyethylene oxide (PEO) is 300-2500.

[0007] In one embodiment, the molecular weight of the degraded chitosan is 9000-11000.

[0008] As one embodiment, the method for preparing the degraded chitosan includes the following steps:

[0009] High-polymerization-degree chitosan powder was dissolved in a peroxy acid aqueous solution to form a transparent and viscous solution, and the degradation reaction was carried out by continuous stirring.

[0010] After degradation, LiOH solution was added to neutralize the residue, and the insoluble matter was removed by filtration.

[0011] The filtrate was mixed with ethanol to form a turbid chitosan solution, which was then freeze-dried to obtain degraded chitosan.

[0012] As one implementation, the degradation reaction conditions satisfy at least one of the ad conditions:

[0013] a: High-polymerization-degree chitosan has a deacetylation degree greater than 90% and a molecular weight > 100,000;

[0014] b: Degradation temperature is 40-60℃;

[0015] c: Degradation time is 10-20 hours;

[0016] d: The mass-to-volume ratio of highly polymerized chitosan to peroxy acid aqueous solution is (5-15) g: 1 L.

[0017] In one embodiment, the peroxyacid aqueous solution has a mass fraction of 1-5%.

[0018] In one embodiment, the peroxyacid aqueous solution has a mass fraction of 1%.

[0019] In one embodiment, the peroxy acid includes at least one of peroxy organic acid or peroxy inorganic acid.

[0020] In one embodiment, the peroxyacid includes at least one of peroxyformic acid, peroxyacetic acid, peroxytrifluoroacetic acid, peroxypropionic acid, peroxybutyric acid, peroxyisovaleric acid, long-chain peroxy fatty acids, peroxybenzoic acid, m-chloroperoxybenzoic acid, nitroperoxybenzoic acid, monoperoxyphthalic acid, persulfate, persulfate, pernitric acid, pernitric acid, perphosphoric acid, perphosphoric acid, percarbonic acid, and perboric acid.

[0021] In one embodiment, the degradation temperature is 60°C and the degradation time is 20 hours.

[0022] In one embodiment, the LiOH solution has a mass fraction of 5-15%.

[0023] In one embodiment, the LiOH solution has a mass fraction of 10%.

[0024] In one embodiment, the filtrate is mixed with ethanol at a ratio of 40 vol.

[0025] As one embodiment, the modified LLZO (lithium lanthanum zirconium oxide Li7La3Zr2O) 12 The LLZO modified with a silane coupling agent is prepared by means of the following steps:

[0026] LLZO is dried, ground, and sieved to obtain LLZO powder;

[0027] The silane coupling agent was dissolved in anhydrous ethanol, stirred and dispersed evenly, and acetic acid solution was added dropwise. After hydrolysis, a hydrolyzed solution of the silane coupling agent was obtained.

[0028] LLZO powder was added to the silane coupling agent hydrolysis solution and stirred until homogeneous, resulting in a modification reaction.

[0029] After the reaction was completed, the mixture was separated by filtration, washed, and dried to obtain silane coupling agent modified LLZO.

[0030] As one implementation, the conditions for the modification reaction satisfy at least one of the following conditions:

[0031] e: The pH after adding acetic acid solution is 4-5;

[0032] f: The hydrolysis reaction temperature is 30-40℃, and the hydrolysis reaction time is 1-5h;

[0033] g: The temperature of the modification reaction is 50-80℃, and the modification reaction time is 6-12h.

[0034] As one implementation, the conditions for the modification reaction satisfy at least one of the following conditions:

[0035] e: The pH after adding acetic acid solution is 4.5;

[0036] f: The hydrolysis reaction temperature is 40℃, and the hydrolysis reaction time is 4h;

[0037] g: The temperature of the modification reaction is 80℃, and the modification reaction time is 12h.

[0038] In one embodiment, the drying temperature of the LLZO is 120-150℃, and the drying time is 12-24h.

[0039] In one embodiment, the LLZO is dried at a temperature of 135°C for 24 hours, which thoroughly removes physically adsorbed water and trace amounts of Li2CO3.

[0040] In one embodiment, the LLZO is sieved with a mesh size of 400 mesh.

[0041] In one embodiment, the silane coupling agent is dissolved in anhydrous ethanol to form a 1-3 wt% solution.

[0042] In one embodiment, the silane coupling agent is dissolved in anhydrous ethanol to form a 2wt% solution.

[0043] In one embodiment, the concentration of the acetic acid solution is 4-6 wt%.

[0044] In one embodiment, the concentration of the acetic acid solution is 5 wt%.

[0045] In one embodiment, the mass ratio of the LLZO powder to the silane coupling agent hydrolysis solution is 1:(80-100).

[0046] In one embodiment, the mass ratio of the LLZO powder to the silane coupling agent hydrolysis solution is 1:90.

[0047] As one embodiment, the drying temperature of the silane coupling agent modified LLZO is 60-80℃, and the drying time is 12-24h.

[0048] In one embodiment, the drying temperature of the silane coupling agent modified LLZO is 80°C, and the drying time is 24 hours.

[0049] In one embodiment, the lithium salt includes at least one of lithium bisfluorosulfonylimide (LiFSi) or lithium bistrifluoromethanesulfonylimide (LiTFSi).

[0050] In one embodiment, the crosslinking agent includes at least one of polyethylene glycol diglycidyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, glycerol polyglycidyl ether, or sorbitol polyglycidyl ether.

[0051] In one embodiment, the crosslinking agent is polyethylene glycol diglycidyl ether (PEGDE).

[0052] In one embodiment, the number-average molecular weight of the polyethylene glycol diglycidyl ether is 1500-2500.

[0053] In one embodiment, the number-average molecular weight of the polyethylene glycol diglycidyl ether is 2000.

[0054] In one embodiment, the solvent is a mixture of water and acetonitrile, wherein the volume ratio of water to acetonitrile is (5-10):(1-5).

[0055] In one embodiment, the solvent is a mixture of water and acetonitrile, wherein the volume ratio of water to acetonitrile is 7:3.

[0056] A second aspect of the present invention provides a method for preparing a multilayer composite solid electrolyte membrane, comprising the following steps:

[0057] Polyethylene oxide, degraded chitosan, modified LLZO, lithium salt, and crosslinking agent are dissolved in a solvent and cast into a three-dimensional polymer network solid electrolyte.

[0058] A LiPON layer was deposited by magnetron sputtering on the surface of a three-dimensional polymer networked solid electrolyte.

[0059] The LiPON layer was densified by hot pressing, and the surface was coated with a polydopamine layer to obtain a multilayer composite solid electrolyte membrane.

[0060] As one implementation method, the parameters of the magnetron sputtering are: power 200-400 W, working gas is a mixture of Ar and N2, the volume ratio of Ar to N2 is 1:1, and vacuum degree <5×10⁻⁶. -3 Pa.

[0061] In one implementation, the thickness of the magnetron sputtered LiPON layer is controllable, and 0.5 μm is sufficient to effectively block electrons.

[0062] In one embodiment, the hot pressing temperature is 90-110°C.

[0063] In one embodiment, the hot pressing temperature is 100°C.

[0064] A third aspect of the present invention provides a solid-state battery comprising the above-described multilayer composite solid electrolyte membrane.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] (1) The multilayer composite solid electrolyte membrane of the present invention can provide a better ion transport coordination effect and improve the efficiency of ion channels by using silane coupling agent to modify LLZO and degraded chitosan synergistically.

[0067] (2) The multilayer composite solid electrolyte membrane of the present invention improves dendrite suppression efficiency by using silane coupling agent to modify LLZO and degrade chitosan in a synergistic effect. It avoids obvious cracks after 1000 cycles and, when applied to solid batteries, greatly improves the cycle life of the battery. It has a 95% capacity retention rate after 1000 cycles.

[0068] (3) The multilayer composite solid electrolyte membrane of the present invention improves the mechanical toughness of the solid electrolyte by introducing polyethylene glycol diglycidyl ether as a crosslinking agent, and the elongation at break can reach 130%.

[0069] (4) The multilayer composite solid electrolyte membrane of the present invention uses aqueous solvent throughout the preparation process, avoiding the use of organic solvents, reducing energy consumption by 40%, and has no VOC emissions throughout the process, making it green, safe and environmentally friendly.

[0070] (5) The multilayer composite solid electrolyte membrane of the present invention uses chitosan instead of PVDF in the traditional process, which reduces the production cost. Furthermore, the thickness of the LiPON layer can be controlled by magnetron sputtering, and only 0.5 μm is needed to achieve effective electron blocking, thus reducing the production cost. Attached Figure Description

[0071] Figure 1 This is a flowchart illustrating the fabrication process of a solid-state battery according to the present invention.

[0072] Figure 2 This is a schematic diagram of the structure of the multilayer composite solid electrolyte membrane of the present invention.

[0073] Figure 3 This is a diagram illustrating the lithium-ion transport mechanism of the multilayer composite solid electrolyte membrane of the present invention.

[0074] Figure 4 This is a schematic diagram of the solid-state battery structure of the present invention.

[0075] In the figure: 1. Three-dimensional polymer network solid electrolyte; 2. LiPON layer; 3. Polydopamine layer; 4. Lithium-ion transport channel; 5. Three-dimensional polymer network with chitosan as the backbone; 6. KH-550 modified LLZO; 7. Polymer segments formed by PEO and PEGDE; 8. NCM positive electrode; 9. Positive electrode current collector (aluminum foil); 10. Lithium negative electrode.

[0076] Figure 5The graph shows the cycle performance test results of the solid-state batteries prepared by the solid electrolyte membranes prepared in Example 4 and Comparative Example 2 of this invention. The test conditions were: constant temperature at 60°C and charge / discharge at 0.5C. Detailed Implementation

[0077] The flowchart for the preparation of solid-state batteries according to this invention is shown below. Figure 1 .

[0078] The lithium-ion transport mechanism in the multilayer composite solid electrolyte membrane of the present invention is described in [reference needed]. Figure 3 To facilitate the transport of lithium ions, chitosan-NH2-anchored LLZO (modified with KH-550) is used, and PEO segments transport lithium ions. This application utilizes a three-dimensional polymer network 5 with chitosan as the backbone to degrade the chitosan-NH2-anchored KH-550-modified LLZO 6, synergistically forming polymer segments 7 from PEO and PEGDE, thereby creating lithium ion transport channels 4.

[0079] Example 1

[0080] like Figure 2 As shown: A multilayer composite solid electrolyte membrane, wherein the multilayer composite solid electrolyte membrane comprises, in sequence, a three-dimensional polymer network solid electrolyte 1, a LiPON layer 2, and a polydopamine layer 3, wherein the thickness of the three-dimensional polymer network solid electrolyte 1 is 30 μm, and the thickness of the polydopamine layer is <100 nm.

[0081] The raw materials for preparing the three-dimensional polymer network solid electrolyte 1 include, by weight percentage, 20% polyethylene oxide, 30% degraded chitosan, 25% modified LLZO, 15% lithium salt, 10% crosslinking agent, and solvent.

[0082] The solvent, polyethylene oxide, degraded chitosan, modified LLZO, lithium salt, and crosslinking agent are in a weight ratio of 1:1.

[0083] The solvent is a mixture of water and acetonitrile in a volume ratio of 7:3.

[0084] The polyethylene oxide had a number average molecular weight of 400 and was purchased from Sigma-Aldrich 202398.

[0085] The degraded chitosan has a molecular weight of 9000-11000, a degree of deacetylation greater than 90%, and a solubility greater than 30 g / L;

[0086] The method for preparing the degraded chitosan includes the following steps:

[0087] High-polymerization-degree chitosan powder was dissolved in a peroxy acid aqueous solution to form a transparent and viscous solution, and the degradation reaction was carried out by continuous stirring.

[0088] After degradation, LiOH solution was added to neutralize the residue, and the insoluble matter was removed by filtration.

[0089] The filtrate was mixed with ethanol to form a turbid chitosan solution, which was then freeze-dried to obtain degraded chitosan.

[0090] The high degree of polymerization chitosan has a degree of deacetylation greater than 90% and a molecular weight greater than 100,000. It was purchased from Sigma Aldrich-419419.

[0091] The degradation temperature was 60℃, and the degradation time was 20 hours.

[0092] The mass-to-volume ratio of highly polymerized chitosan to peroxy acid aqueous solution is 10 g: 1 L.

[0093] The peroxyacid aqueous solution has a mass fraction of 1%. The peroxyacid aqueous solution is an aqueous solution of peroxyformic acid.

[0094] The LiOH solution has a mass fraction of 10%.

[0095] The filtrate was mixed with ethanol at a ratio of 40 vol.

[0096] The modified LLZO is a silane coupling agent modified LLZO, and the preparation method of the silane coupling agent modified LLZO includes the following steps:

[0097] LLZO is dried, ground, and sieved to obtain LLZO powder;

[0098] The silane coupling agent was dissolved in anhydrous ethanol, stirred and dispersed evenly, and acetic acid solution was added dropwise. After hydrolysis, a hydrolyzed solution of the silane coupling agent was obtained.

[0099] LLZO powder was added to the silane coupling agent hydrolysis solution and stirred until homogeneous, resulting in a modification reaction.

[0100] After the reaction was completed, the mixture was separated by filtration, washed, and dried to obtain silane coupling agent modified LLZO.

[0101] The pH after adding acetic acid solution was 4.5;

[0102] The hydrolysis reaction was carried out at a temperature of 40℃ for 4 hours.

[0103] The modification reaction was carried out at a temperature of 80℃ for 12 hours.

[0104] The LLZO was dried at 135°C for 24 hours.

[0105] The LLZO has a sieve aperture of 400 mesh.

[0106] The silane coupling agent is dissolved in anhydrous ethanol to form a 2 wt% solution.

[0107] The concentration of the acetic acid solution is 5 wt%.

[0108] The mass ratio of the LLZO powder to the silane coupling agent hydrolysis solution is 1:90.

[0109] The drying temperature of the silane coupling agent modified LLZO is 80℃, and the drying time is 24h.

[0110] The lithium salt is LiFSi;

[0111] The crosslinking agent is polyethylene glycol diglycidyl ether, with a number average molecular weight of 2000, purchased from Sigma-Aldrich 731811.

[0112] The solvent is a mixture of water and acetonitrile, with a volume ratio of water to acetonitrile of 7:3.

[0113] A method for preparing a multilayer composite solid electrolyte membrane includes the following steps:

[0114] Polyethylene oxide, degraded chitosan, modified LLZO, lithium salt, and crosslinking agent are dissolved in a solvent and cast into a three-dimensional polymer network solid electrolyte.

[0115] A LiPON layer was deposited by magnetron sputtering on the surface of a three-dimensional polymer networked solid electrolyte.

[0116] The LiPON layer was densified by hot pressing, and the surface was coated with a polydopamine layer to obtain a multilayer composite solid electrolyte membrane.

[0117] The magnetron sputtering parameters are: power 300 W, working gas is a mixture of Ar and N2, Ar to N2 volume ratio is 1:1, and vacuum degree <5×10⁻⁶. -3 Pa.

[0118] The hot pressing temperature is 100℃.

[0119] Example 2

[0120] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 30% polyethylene oxide, 20% degraded chitosan, 25% modified LLZO, 15% lithium salt, 10% crosslinking agent, and solvent.

[0121] Example 3

[0122] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 40% polyethylene oxide, 10% degraded chitosan, 25% modified LLZO, 15% lithium salt, 10% crosslinking agent, and solvent.

[0123] Example 4

[0124] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 40% polyethylene oxide, 10% degraded chitosan, 25% modified LLZO, 17% lithium salt, 8% crosslinking agent, and solvent.

[0125] Example 5

[0126] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 40% polyethylene oxide, 10% degraded chitosan, 25% modified LLZO, 19% lithium salt, 6% crosslinking agent, and solvent.

[0127] Example 6

[0128] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 40% polyethylene oxide, 10% degraded chitosan, 20% modified LLZO, 22% lithium salt, 8% crosslinking agent, and solvent.

[0129] Example 7

[0130] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 40% polyethylene oxide, 10% degraded chitosan, 15% modified LLZO, 27% lithium salt, 8% crosslinking agent, and solvent.

[0131] Example 8

[0132] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 40% polyethylene oxide, 10% degraded chitosan, 10% modified LLZO, 32% lithium salt, 8% crosslinking agent, and solvent.

[0133] Example 9

[0134] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 40% polyethylene oxide, 10% degraded chitosan, 5% modified LLZO, 37% lithium salt, 8% crosslinking agent, and solvent.

[0135] The lithium salt is LiTFSi.

[0136] Example 10

[0137] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 40% polyethylene oxide, 10% degraded chitosan, 25% modified LLZO, 17% lithium salt, 8% crosslinking agent, and solvent.

[0138] The lithium salt is LiTFSi.

[0139] Comparative Example 1

[0140] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 10, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 40% polyethylene oxide, 10% degraded chitosan, 25% modified LLZO, 25% lithium salt, and solvent.

[0141] Comparative Example 2

[0142] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 40% polyethylene oxide, 25% modified LLZO, 27% lithium salt, 8% crosslinking agent, and solvent.

[0143] Comparative Example 3

[0144] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 40% polyethylene oxide, 10% chitosan, 25% modified LLZO, 17% lithium salt, 8% crosslinking agent, and solvent.

[0145] The chitosan has a molecular weight >100,000 and was purchased from Sigma Aldrich-419419.

[0146] Comparative Example 4

[0147] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 40% polyethylene oxide, 10% degraded chitosan, 25% LLZO, 17% lithium salt, 8% crosslinking agent, and solvent.

[0148] The LLZO was unmodified.

[0149] Comparative Example 5

[0150] A multilayer composite solid electrolyte membrane and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 40% polyethylene oxide, 10% degraded chitosan, 42% lithium salt, 8% crosslinking agent, and solvent.

[0151] Performance testing

[0152] 1. Elongation at break: Tensile specimens of the multilayer composite solid electrolyte membranes used in the examples and comparative examples were prepared according to ASTM D638 standard, with five parallel samples. Tensile tests were conducted under constant temperature and humidity conditions: 25℃, 40%RH. The experimental results are the average values ​​of the five sets of results. The test results are shown in Table 1.

[0153] 2. Ionic conductivity: Following the blocked electrode method (ASTM D257), the multilayer composite solid electrolyte membranes of the examples and comparative examples were cut into 10 mm diameter discs. Lithium metal electrodes were hot-pressed onto both sides of the membrane in a glove box (25°C, H₂O / O₂ < 0.1 ppm). Frequency range: 0.1 Hz - 1.0 MHz, amplitude: 10 mV. The experimental results are the average of five sets of experimental values. The test results are shown in Table 1.

[0154] 3. Electronic Conductivity: Following the electron blocking electrode method (J. Electrochem. Soc. standard procedure), the multilayer composite solid electrolyte membranes of the examples and comparative examples were cut into 10 mm diameter discs. In a glove box (25℃, H2O / O2 < 0.1 ppm), lithium and metal electrodes were hot-pressed onto both sides of the membrane to form a Li|electrolyte|Au structure. A constant small voltage (0.1-0.5 V) was applied, and the membrane was polarized for a long time (1-24 hours). The current decay curve was recorded until the steady-state electronic current was reached. The experimental results are the average of five sets of experimental values. The test results are shown in Table 1.

[0155] 4. Cycle performance testing of solid-state batteries: See the structural diagram of solid-state batteries. Figure 4 .

[0156] Figure 4 middle

[0157] NCM cathode 8: 80 wt% active material (NCM811) + 10 wt% conductive carbon black + 10 wt% solid electrolyte. A cathode sheet with a thickness of 80-100 μm is formed by wet coating with Al cathode current collector 9. A cathode disc with a diameter of 14 mm is punched out (compatible with CR2032 battery case). The solid electrolyte is a slurry formed by dissolving polyethylene oxide, degraded chitosan, modified LLZO, lithium salt, and crosslinking agent in a solvent, as described in Examples 4 and 2.

[0158] Solid electrolyte membrane: Multilayer composite solid electrolyte membranes prepared in Example 4 and Comparative Example 2 (CR2032 battery case adapter).

[0159] Lithium anode 10: 50μm thick lithium foil, anode with a punched diameter of 14 mm (CR2032 battery case compatible).

[0160] Packaging: The positive electrode, solid electrolyte membrane and negative electrode are stacked in that order, and then hot-pressed at 80℃ for 10 min (pressure 10MPa), and packaged with a stainless steel CR2032 battery case to obtain a complete solid-state battery.

[0161] Test: 60℃ constant temperature chamber, 0.5C charge and discharge, cutoff voltage range: 2.8-4.3 V.

[0162] Test results are available Figure 5 .

[0163] Depend on Figure 5 It can be seen that the solid-state battery in Comparative Example 2 has a greater cycle degradation than the solid-state battery in Example 4.

[0164] Table 1

[0165]

Claims

1. A multilayer composite solid electrolyte membrane, characterized in that, The multilayer composite solid electrolyte membrane consists of a three-dimensional polymer network solid electrolyte, a LiPON layer, and a polydopamine layer. The thickness of the three-dimensional polymer network solid electrolyte is 20-40 μm, and the thickness of the polydopamine layer is <100 nm. The three-dimensional polymer network solid electrolyte includes modified LLZO with chitosan as the backbone. The raw materials for preparing the three-dimensional polymer network solid electrolyte include, by weight percentage, 20-40% polyethylene oxide, 10-30% degraded chitosan, 20-30% modified LLZO, 15-40% lithium salt, 6-10% crosslinking agent, and solvent, with the total percentages being 100%. The molecular weight of the degraded chitosan is 9000-11000; The crosslinking agent includes at least one of polyethylene glycol diglycidyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, glycerol polyglycidyl ether, or sorbitol polyglycidyl ether. The modified LLZO is silane coupling agent modified LLZO.

2. The multilayer composite solid electrolyte membrane according to claim 1, characterized in that, The method for preparing the degraded chitosan includes the following steps: High-polymerization-degree chitosan powder was dissolved in a peroxy acid aqueous solution to form a transparent and viscous solution, and the degradation reaction was carried out by continuous stirring. After degradation, LiOH solution was added to neutralize the residue, and the insoluble matter was removed by filtration. The filtrate was mixed with ethanol to form a turbid chitosan solution, which was then freeze-dried to obtain degraded chitosan.

3. The multilayer composite solid electrolyte membrane according to claim 2, characterized in that, The degradation reaction is subject to at least one of the following conditions: a: High-polymerization-degree chitosan has a deacetylation degree greater than 90% and a molecular weight > 100,000; b: Degradation temperature is 40-60℃; c: Degradation time is 10-20 hours; d: The mass-to-volume ratio of highly polymerized chitosan to peroxy acid aqueous solution is (5-15) g: 1 L.

4. The multilayer composite solid electrolyte membrane according to claim 2, characterized in that, The preparation method of the silane coupling agent modified LLZO includes the following steps: LLZO is dried, ground, and sieved to obtain LLZO powder; The silane coupling agent was dissolved in anhydrous ethanol, stirred and dispersed evenly, and acetic acid solution was added dropwise. After hydrolysis, a hydrolyzed solution of the silane coupling agent was obtained. LLZO powder was added to the silane coupling agent hydrolysis solution and stirred until homogeneous, resulting in a modification reaction. After the reaction was completed, the mixture was separated by filtration, washed, and dried to obtain silane coupling agent modified LLZO.

5. The multilayer composite solid electrolyte membrane according to claim 4, characterized in that, The conditions for the modification reaction satisfy at least one of the following conditions: e: The pH after adding acetic acid solution is 4-5; f: The hydrolysis reaction temperature is 30-40℃, and the hydrolysis reaction time is 1-5h; g: The temperature of the modification reaction is 50-80℃, and the modification reaction time is 6-12h.

6. A method for preparing a multilayer composite solid electrolyte membrane according to any one of claims 2-5, characterized in that, Includes the following steps: Polyethylene oxide, degraded chitosan, modified LLZO, lithium salt, and crosslinking agent are dissolved in a solvent and cast into a three-dimensional polymer network solid electrolyte. A LiPON layer was deposited by magnetron sputtering on the surface of a three-dimensional polymer networked solid electrolyte. The LiPON layer was densified by hot pressing, and the surface was coated with a polydopamine layer to obtain a multilayer composite solid electrolyte membrane.

7. A solid-state battery, characterized in that, Includes the multilayer composite solid electrolyte membrane as described in any one of claims 1-5.

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