Inorganic-organic composite solid electrolyte, membrane material thereof, preparation method and solid-state battery

Abstract

The invention relates to the technical field of solid-state batteries, and particularly discloses an inorganic-organic composite solid-state electrolyte, a membrane material thereof, a preparation method and a solid-state battery. The electrolyte comprises a polymer matrix, inorganic solid electrolyte particles, a surface modifier, a cross-linking agent and a heat conduction enhancer. The preparation method of the membrane material comprises the following steps: inorganic particle surface modification treatment; compounding the slurry; gradient curing; and forming the film. The obtained membrane is high in ionic conductivity, low in interface impedance and high in thermal decomposition temperature. And the assembled total battery is high in capacity retention rate after being circulated for 500 times at 0.5 C, and a hot box test is qualified. According to the technology, the core problem of poor interface compatibility of the solid-state battery is solved, and meanwhile, the thermal runaway risk of the solid-state battery is reduced.

Description

Technical Field

[0001] The present invention provides an inorganic-organic composite solid electrolyte, a membrane material thereof, a preparation method and a solid-state battery, and relates to the technical field of solid-state batteries. Background Art

[0002] The current development of solid-state batteries is facing three interrelated key technical bottlenecks that need to be overcome urgently. The first is the severe challenge of uncontrolled interface impedance. Among the core components of solid-state batteries, there is a significant interface compatibility problem between oxide electrolytes such as LLZO and polymer electrolytes PEO. Due to differences in crystal structure, surface energy and chemical stability, a dense impedance layer and a large number of defect structures are easily formed at the contact interface, resulting in a sharp increase in interface impedance. According to research data in the literature, this interface impedance has exceeded 500Ω·cm 2 , far exceeding the acceptable range of ideal solid-state battery interface impedance. Such high interface impedance greatly hinders the efficient migration of lithium ions between the electrolyte and the electrode, causing a significant decrease in ion transmission efficiency during high-rate charge and discharge, which in turn severely limits the battery's rate performance, making it difficult to meet practical application requirements in scenarios such as fast charging and high power output. Secondly, there is the prominent problem of insufficient thermal safety. Traditional polyolefin separators will quickly melt when the temperature rises to 180°C, losing their physical isolation effect on the positive and negative electrodes, directly causing the risk of short circuits. At the same time, the thermal conductivity of polymer electrolytes is extremely low. Studies have shown that their thermal conductivity is generally less than 0.2W / mK, making it difficult for the heat generated by the battery during charge and discharge to be effectively dissipated. It is very easy to accumulate in local areas to form hot spots. As the temperature continues to rise, it may induce side reactions such as electrolyte decomposition and electrode material phase change, ultimately causing thermal runaway, leading to serious safety accidents such as battery combustion or even explosion. This has greatly restricted the application and promotion of solid-state batteries in fields with extremely high safety requirements, such as electric vehicles and energy storage systems. In addition, poor process adaptability is also an important bottleneck restricting the industrialization of solid-state batteries. In the preparation process of electrolyte membranes, the dry film forming technology has poor uniformity and low adaptability to various materials. The wet curing process is difficult to accurately control the crystallization conditions during the solvent removal process, which often leads to excessive crystallinity of the electrolyte membrane, forming a large number of ordered crystal structures that are not conducive to ion migration, making the ionic conductivity generally lower than 10. -4 More critically, the industry currently lacks a systematic solution that can simultaneously balance high ion conductivity, low interfacial impedance, and intrinsic safety. This means that improvements in a single technology are unlikely to break through the overall performance bottleneck. Collaborative research from multiple dimensions, including material molecular design, interface modification technology, preparation process optimization, and battery structure innovation, is needed to effectively address the multiple challenges facing solid-state batteries in practical applications, including interface, safety, and process. Summary of the Invention

[0003] To solve the above problems, the present invention provides an inorganic-organic composite solid electrolyte material, which includes a polymer matrix, inorganic solid electrolyte particles, a surface modifier, a cross-linking agent and a thermal conductivity enhancer.

[0004] Preferably, the polymer matrix is ​​selected from polyethylene oxide (PEO), polyacrylonitrile (PAN) or polyacrylates;

[0005] The polyacrylate monomer is selected from a combination of hydroxyethyl acrylate and methyl methacrylate in a mass ratio of (2-4):1.

[0006] Preferably, the inorganic solid electrolyte particles are oxide-type Li1.3Al0.3Ti1.7(PO4)3(LATP) or sulfide-type Li 10 GeP2S 12 (LGPS), particle size 10-5000nm; surface modifier is a silane coupling agent containing diamino group.

[0007] Preferably, the silane coupling agent is N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), and the addition amount is 0.5-10 wt % of the mass of the inorganic particles.

[0008] Preferably, the crosslinking agent is a mixture of ethylene glycol dimethacrylate and adipic acid dihydrazide in a mass ratio of (4-6):1, and the total addition amount is 0.5-10% of the polymer mass; the thermal conductivity enhancer is carboxylated nanodiamond with a particle size of 5-100 nm and a carboxylation degree ≥1.5 mmol / g, and the addition amount is 0.5-10 wt% of the total mass of the composite system.

[0009] The present invention also provides a method for preparing an inorganic-organic composite solid electrolyte membrane comprising the above-mentioned inorganic-organic composite solid electrolyte material, comprising the following steps:

[0010] (1) Surface modification of inorganic particles;

[0011] (2) Slurry compounding;

[0012] (3) Gradient curing;

[0013] (4) Film forming.

[0014] Preferably, in step (1), the inorganic particles are dispersed in an ethanol / water mixed solvent (volume ratio 3-5:1); a silane coupling agent is added, and the mixture is refluxed at 75-85° C. for 1.5-2.5 hours.

[0015] Preferably, in step (2), the solid content is controlled at 35-45 wt%; the ball milling parameters are: zirconia ball milling beads, rotation speed 250-350 rpm, time 3-5 h.

[0016] Preferably, in step (3), UV pre-curing: wavelength 365nm, intensity 45-55mW / cm 2 , time 20-40s; step-by-step temperature curing: first 60±2℃ / 1h, then 80±2℃ / 2h, and finally 100±5℃ / 1h.

[0017] Preferably, in step (4), the film thickness of the blade coating is 10-50 μm; dry composite alternative: the modified inorganic particles are dry-mixed with the polymer powder and then hot-pressed at a pressure of 10-20 MPa and a temperature of 120-150°C.

[0018] Preferably, the solvent in step (2) can be N-methylpyrrolidone (NMP) or water; and the aqueous slurry needs to be added with 0.1-0.5 wt% of ammonium polyacrylate dispersant.

[0019] Preferably, 0.05-0.2 wt % of photoinitiator Irgacure 819 is added before UV curing; and the step-by-step temperature increase process is carried out under an inert atmosphere.

[0020] Preferably, 1-3 wt% of polytetrafluoroethylene (PTFE) is added as a binder during dry compounding; and a secondary annealing treatment is required after hot pressing: 180° C. / 2 h.

[0021] The present invention also provides a solid-state lithium-ion battery comprising the membrane material prepared by the above method, comprising:

[0022] Positive electrode: lithium nickel cobalt manganese oxide (NCM) or lithium iron phosphate (LFP);

[0023] Negative electrode: silicon-carbon composite material or metallic lithium;

[0024] Electrolyte layer: the above-mentioned composite solid electrolyte membrane;

[0025] Interface buffer layer: provided between the electrolyte membrane and the electrode.

[0026] Preferably, the interface buffer layer is a sputtered Li3PO4 film with a thickness of 150-250nm; the positive electrode active material loading is ≥20mg / cm 2 .

[0027] Preferably, the mass ratio of the polymer matrix to the inorganic particles is (30-70):(70-30); and the polyacrylate contains 0.5-1 wt% of acrylic acid functional monomer.

[0028] Preferably, the battery structure is a sandwich-type stacked or wound type; the battery capacity is ≥5Ah.

[0029] Preferably, the wound battery adopts a ceramic-coated current collector; the tab welding points are coated with high-temperature resistant insulating glue.

[0030] The beneficial effects of the present invention are:

[0031] 1. Breakthrough in interface engineering:

[0032] The double amino structure of KH-792 (-NH-CH2-CH2-NH2) simultaneously bonds with the surface hydroxyl groups of LATP and the carboxyl groups of the polymer, reducing the interfacial impedance to 38Ω·cm 2 (92% decrease);

[0033] The sputtered Li3PO4 buffer layer (200nm) inhibits side reactions, and the capacity decay rate is <9% after 500 cycles.

[0034] 2. Thermal management innovation:

[0035] Carboxylated nanodiamonds (5nm) construct a three-dimensional thermal conductive network, increasing thermal conductivity to 1.8W / mK (0.18W / mK for traditional systems);

[0036] The synergistic cross-linking network makes the thermal decomposition temperature reach 315℃, and the passing temperature of the hot box test is 60℃ higher than the national standard.

[0037] 3. Process innovation advantages:

[0038] UV pre-curing (30s) locks the molecular conformation, and step-wise thermal curing eliminates internal stress, controlling the crystallinity at 23±2%;

[0039] It is compatible with both wet and dry processes, and the film thickness can be adjusted from 3 to 100 μm, making it suitable for mass production of wound batteries. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0042] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and the experimental materials used in the following examples, unless otherwise specified, are all purchased from commercial channels.

[0043] Example 1: Preparation of composite electrolyte membrane (oxide system)

[0044] Raw material formula:

[0045] Li1.3Al0.3Ti1.7(PO4)3 (LATP) nanoparticles (particle size 150nm) are used as the oxide skeleton, with an amount of 60 parts; hydroxyethyl acrylate (HEA) and methyl methacrylate (MMA) are used as the polymer matrix, with a mass ratio of 3:1 (45 parts and 15 parts respectively); KH-792 (N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, bisaminosilane coupling agent) is used as the interface modifier, with an amount of 2% of the mass of LATP (i.e. 1.2 parts); carboxylated nanodiamond (particle size 5nm) is used as the reinforcing phase, with an amount of 1.2 parts; ethylene glycol dimethacrylate (EGDMA) is used as the crosslinker, with an amount of 0.48 parts; adipic acid dihydrazide (ADH) is used as the auxiliary crosslinker, with an amount of 0.096 parts; and Irgacure819 is used as the photoinitiator, with an amount of 0.12 parts.

[0046] Preparation process:

[0047] Surface modification: LATP particles were dispersed in an ethanol / water mixed solvent (volume ratio of 4:1), KH-792 was added, and the mixture was refluxed and stirred at 80°C for 2 hours. Diamino functional groups were grafted on the LATP surface through the hydrolysis and condensation reaction of the silane coupling agent. Subsequently, the surface-modified LATP particles were obtained by centrifugation (speed 8000 rpm, time 15 minutes) and vacuum drying (60°C, 12 hours).

[0048] Slurry compounding: Modified LATP, hydroxyethyl acrylate, methyl methacrylate, EGDMA, ADH, carboxylated nanodiamond and Irgacure819 were added to N-methylpyrrolidone (NMP) in sequence and mixed for 4 hours using a planetary ball mill (speed 300 rpm, ball-to-material ratio 5:1) to control the solid content to 40% to form a uniformly dispersed composite slurry.

[0049] Gradient curing: The slurry was prepared into a 25 μm thick wet film by a doctor blade coating process, and then UV cured (wavelength 365 nm, light intensity 50 mW / cm 2 , time 30 seconds) to form a preliminary cross-linked structure, and then transferred to a nitrogen-protected oven for step-by-step thermal curing. The specific procedure is: 60°C for 1 hour → 80°C for 2 hours → 100°C for 1 hour, and finally a composite electrolyte membrane with both high ion conductivity and mechanical strength is obtained.

[0050] Example 2: Preparation of composite electrolyte membrane (sulfide system)

[0051] Recipe Adjustment:

[0052] The oxide electrolyte LATP was replaced with the sulfide electrolyte Li6PS5Cl (LGPS, particle size 100 nm), and the dosage was increased to 70 parts; the amount of KH-792 was adjusted to 3% (i.e., 2.1 parts) of the mass of LATP to enhance the interaction with the sulfide surface; the curing procedure was adjusted to: 50°C for 2 hours → 70°C for 3 hours. The remaining raw material composition and preparation process were consistent with Example 1.

[0053] Example 3: Dry process composite membrane preparation

[0054] Process changes:

[0055] The composite membrane was prepared by a dry hot pressing process. The specific steps are as follows: surface-modified LATP particles (60 parts) and polyacrylate powder (40 parts) were dry-mixed in a planetary mixer for 30 minutes, 2 parts of polytetrafluoroethylene (PTFE) were added as a binder, and mixing was continued for 15 minutes; the mixture was then transferred to a hot pressing mold and hot-pressed at a pressure of 15 MPa and a temperature of 130°C for 10 minutes to obtain a preliminary formed composite membrane; finally, the membrane was placed in a vacuum oven for annealing (180°C, 2 hours) to eliminate internal stress and promote interface fusion, and finally a self-supporting composite electrolyte membrane with a thickness of 30 μm was obtained.

[0056] Example 4: Battery Assembly (Laminated)

[0057] Structural configuration:

[0058] The positive electrode uses NCM811 (LiNi0.8Co0.1Mn0.1O2) active material with a loading of 22 mg / cm 2 A 200 nm thick Li3PO4 protective layer was deposited on the surface of the positive electrode by radio frequency magnetron sputtering technology (sputtering power 50 W, Ar / O2 flow ratio 9:1, working pressure 0.5 Pa); the electrolyte membrane adopted the composite membrane prepared in Example 1; the negative electrode selected SiC composite material (silicon content 30%); a sandwich structure was adopted during assembly, and the positive electrode sheet, electrolyte membrane and negative electrode sheet were stacked in sequence, and hot pressed at 80°C and 10 MPa pressure for 10 minutes to form a solid-state battery with close contact.

[0059] Example 5: Battery Assembly (Wound Type)

[0060] Special process:

[0061] The positive electrode current collector is made of aluminum foil coated with a 5μm thick Al2O3 ceramic layer (prepared by atomic layer deposition technology) to enhance interface stability; the tab welding is coated with polyimide high-temperature resistant glue (curing conditions: 150℃ / 1h→200℃ / 2h) to prevent welding heat damage; the battery is assembled using a winding process, and after winding, the sulfide composite electrolyte membrane prepared in Example 2 is fixed inside the battery by injection molding packaging technology (injection molding temperature 180℃, pressure 8MPa) to form a wound solid-state battery structure.

[0062] Example 6: High Capacity Battery

[0063] Parameter design:

[0064] The positive electrode uses high-load NCM811 (35 mg / cm 2 ), the electrolyte membrane is the dry composite membrane (thickness 50 μm) prepared in Example 3, and a winding structure design is adopted. By optimizing the electrode area (10 cm×10 cm) and the active material utilization rate (85%), combined with the theoretical specific capacity of NCM811 (210 mAh / g), the battery capacity is calculated to be 8 Ah (8 A×1 h), which meets the requirements of high energy density applications.

[0065] Comparative Example 1 (monoaminosilane):

[0066] The KH-792 in Example 1 was replaced with KH-550 (γ-aminopropyltrimethoxysilane, monoaminosilane coupling agent), and the amount was maintained at 2% of the mass of LATP. The remaining raw material composition, preparation process and battery assembly method were completely consistent with Examples 1 and 4, and were used to compare the effects of diamino and monoaminosilane on the interface modification effect.

[0067] Comparative Example 2 (without nanodiamond):

[0068] The carboxylated nanodiamonds were completely removed from the formulation of Example 1, and the remaining raw material compositions, preparation processes, and battery assembly methods were consistent with those of Examples 1 and 4, to evaluate the effects of nanodiamond reinforcement on the mechanical properties and ion conductivity of the composite electrolyte membrane.

[0069] Comparative Example 3 (constant temperature curing):

[0070] The UV curing step in Example 1 was eliminated, and the wet film was directly placed in an 80°C oven for constant temperature curing for 4 hours. The rest of the preparation process and battery assembly method were consistent with Examples 1 and 4, and were used to compare the effects of gradient curing and constant temperature curing on the membrane structure and performance.

[0071] Comparative Example 4 (commercial reference):

[0072] A commercial liquid electrolyte system was used as a control, specifically a Celgard 2325 polyolefin separator (25 μm thickness, PP / PE / PP three-layer structure) immersed in a 1M LiPF6 / EC:DEC (volume ratio 1:1) electrolyte. The battery structure configuration was exactly the same as that in Example 4, and was used to evaluate the electrochemical performance differences between the solid electrolyte system and the traditional liquid electrolyte system.

[0073] The above and comparative examples were tested for performance according to the following standards, and the results are shown in Table 1.

[0074] ① Ionic conductivity: GB / T36363-2018 "Test method for conductivity of electrolytes for lithium-ion batteries"

[0075] ②Interface impedance: GB / T39287-2020 "Test method for interface impedance of solid-state lithium batteries"

[0076] ③ Thermal decomposition temperature: GB / T19466.2-2004 "Plastic Differential Scanning Calorimetry"

[0077] ④ Cycle retention rate: GB / T18287-2013 "General Specification for Lithium-ion Batteries for Mobile Phones" 0.5C cycle

[0078] ⑤Hot box test: GB / T31485-2015 "Safety Requirements for Power Batteries for Electric Vehicles" thermal abuse test

[0079] Table 1 Test results

[0080]

[0081]

[0082] Based on the above data, we analyze as follows:

[0083] Core value of interface modification (Comparative Example 1 vs Example 4): The diamino structure of KH-792 reduces the interface impedance by 76% (162→38Ω·cm 2 ), the cycle retention rate increased by 15.2%, proving its irreplaceable role in enhancing interface compatibility;

[0084] Nanodiamond dual function (Comparative Example 2 vs. Example 4): After the loss, the thermal decomposition temperature dropped by 67°C (315→248°C), and the failure temperature in the hot box test dropped by 40°C, confirming its key role in thermal management; the ionic conductivity still reached 9.36×10 - 4 S / cm, indicating that LATP itself contributes mainly;

[0085] Advantages of gradient curing process (Comparative Example 3 vs Example 4): Constant temperature curing leads to a 46.7% decrease in ionic conductivity (1.28×10 -3 →6.82×10 -4 S / cm), the cycle retention rate plummeted by 23.1%, reflecting the necessity of stress control;

[0086] Industrial application value (Example 6): 50μm thick film supports 35mg / cm 2 With high-load electrodes, the 8Ah battery cycle retention rate is 86.7%, verifying the feasibility of the scheme in high energy density scenarios.

[0087] Therefore, the present invention achieves ionic conductivity > 10 through the triple innovation of bisaminosilane interface bridging, nanodiamond thermal conductive network and UV-step thermal synergistic curing. -3 S / cm, interface impedance <40Ω·cm 2 , and a synergistic breakthrough in thermal stability > 300°C, with comprehensive performance far exceeding the existing technology (Comparative Example 4).

[0088] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

[0089] The above description of the present invention and its embodiments is non-limiting and is only one embodiment of the present invention. The actual application is not limited to this. In short, if a person skilled in the art is inspired by this description and, without departing from the purpose of the present invention, designs methods and embodiments similar to this technical solution without creatively designing, they shall fall within the scope of protection of the present invention.

Claims

1. An inorganic-organic composite solid electrolyte material, characterized in that: The invention comprises a polymer matrix, inorganic solid electrolyte particles, a surface modifier, a cross-linking agent and a thermal conductivity enhancer.

2. The material according to claim 1, characterized in that: The polymer matrix is ​​selected from polyethylene oxide (PEO), polyacrylonitrile (PAN) or polyacrylates; the polyacrylate monomer is selected from a combination of hydroxyethyl acrylate and methyl methacrylate in a mass ratio of (2-4):

1.

3. The material according to claim 1, wherein: The inorganic solid electrolyte particles are oxide-type Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP) or sulfide-type Li 10 GeP2S 12 (LGPS), particle size 10-5000nm; surface modifier is a silane coupling agent containing diamino group.

4. The material according to claim 3, characterized in that: The silane coupling agent is N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and the addition amount is 0.5-10 wt % of the mass of the inorganic particles.

5. The material according to claim 1, wherein: The crosslinking agent is a mixture of ethylene glycol dimethacrylate and adipic acid dihydrazide in a mass ratio of (4-6):1, and the total addition amount is 0.5-10% of the polymer mass; the thermal conductivity enhancer is carboxylated nanodiamond with a particle size of 5-100nm and a carboxylation degree of ≥1.5mmol / g, and the addition amount is 0.5-10wt% of the total mass of the composite system.

6. A method for preparing an inorganic-organic composite solid electrolyte membrane comprising the material according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Surface modification of inorganic particles; (2) Slurry compounding; (3) Gradient curing; (4) Film forming.

7. The method according to claim 6, wherein: In the step (1), the inorganic particles are dispersed in an ethanol / water mixed solvent (volume ratio 3-5:1); a silane coupling agent is added, and the mixture is refluxed at 75-85° C. for 1.5-2.5 hours; in the step (2), the solid content is controlled at 35-45 wt %; the ball milling parameters are: zirconia ball milling beads, a rotation speed of 250-350 rpm, and a time of 3-5 hours; in the step (3), UV pre-curing is performed: a wavelength of 365 nm, an intensity of 45-55 mW / cm 2 , time 20-40s; step temperature curing: first 60±2℃ / 1h, then 80±2℃ / 2h, and finally 100±5℃ / 1h; in the step (4), the film thickness of the scraping is 10-50μm; dry composite alternative: dry mix the modified inorganic particles with the polymer powder and then hot press mold them at a pressure of 10-20MPa and a temperature of 120-150℃.

8. An inorganic-organic composite solid electrolyte membrane prepared according to the method of claim 6 or 7.

9. A solid-state lithium-ion battery comprising the solid electrolyte membrane according to claim 8, characterized in that: Include: Positive electrode: lithium nickel cobalt manganese oxide or lithium iron phosphate; Negative electrode: silicon-carbon composite material or metallic lithium; Electrolyte layer: the composite solid electrolyte membrane according to any one of claims 7-8; Interface buffer layer: provided between the electrolyte membrane and the electrode.

10. The solid-state lithium-ion battery according to claim 9, wherein: The interface buffer layer is a sputtered Li3PO4 film with a thickness of 150-250nm; the positive electrode active material loading is ≥20mg / cm 2 ; The mass ratio of polymer matrix to inorganic particles is (30-70): (70-30); the polyacrylate contains 0.5-50wt% of acrylic acid functional monomer.

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