Halide solid electrolyte with multi-layer hierarchical core-shell structure and preparation method of halide solid electrolyte

Abstract

The invention discloses a halide solid electrolyte with a multilayer hierarchical core-shell structure, which sequentially comprises an inner core halide solid electrolyte, a first conductive polymer high-molecular coating layer and a second hydrophobic polymer high-molecular coating layer from inside to outside, the first conductive polymer high-molecular coating layer is formed by copolymerizing conductive polymer monomers with ether oxygen groups-O-or carbonyl C = O, and the second hydrophobic polymer high-molecular coating layer is prepared by ball-milling, sintering and coating a high-molecular hydrophobic material on the surface of the first conductive polymer high-molecular coating layer; and a chemical bonding interface is formed between the first conductive polymer high-molecular coating layer and the inner core halide solid electrolyte through an ether oxygen group-O-or carbonyl C = O in a molecular chain segment. The thickness of the prepared halide solid electrolyte membrane can be reduced to be less than 100 microns, the growth of lithium dendrites is inhibited by the interface self-adaptive characteristic, and the capacity retention rate is gt after 200 cycles; 80%; the sintering temperature is less than or equal to 300 DEG C, the energy consumption is reduced, and lattice distortion is avoided.

Description

Technical Field

[0001] This invention relates to the field of solid electrolytes, specifically to a multi-layered hierarchical core-shell structured halide solid electrolyte and its preparation method. Background Technology

[0002] Solid-state electrolytes, as one of the core components of all-solid-state batteries, directly determine the energy density, cycle life, and safety performance of the battery system through their synergistic effect with electrode materials. Among various solid-state electrolyte systems, inorganic solid-state electrolytes, due to their unique single-ion conductivity and excellent intrinsic stability, have become the mainstream direction for the development of high-safety, long-life solid-state batteries. Inorganic solid-state electrolytes are mainly divided into three major systems: oxides, sulfides, and halides. The performance characteristics of each system are as follows: Oxide solid-state electrolytes: represented by garnet type (such as LLZO) and perovskite type (such as LLTO), although they have a wide electrochemical window (>5 V vs. Li+ / Li) and high room temperature ionic conductivity (10 V / Li), they are still widely used in solid-state batteries. -4 ~10 - ³ S / cm) Among them, oxide inorganic solid electrolytes usually require high-temperature sintering (>1000℃) to achieve densification. Sulfide solid electrolytes: such as LPS, LPSCl, etc., although they have excellent interfacial contact characteristics (densification can be achieved by cold pressing) and ultra-high ionic conductivity (>10 S / cm) - While its chemical stability is high (2 S / cm), it is sensitive to humidity (H2O→H2S release) and requires a harsh, dry environment to operate. It also has poor interfacial compatibility with high-voltage oxide cathodes (such as NCM, LCO) and lithium metal anodes, and is prone to sulfur redox reactions. Halogen solid electrolytes, on the other hand, are considered to be a promising next-generation solid electrolyte material due to their advantages such as high lithium-ion mobility, good mechanical flexibility, high electrochemical oxidation voltage, good compatibility with high-voltage oxide cathode materials, and simple synthesis methods.

[0003] However, halide solid electrolytes still face a key bottleneck: insufficient intrinsic air stability, and their crystal structure is prone to hydrolysis with water molecules in the environment. This defect severely restricts the large-scale preparation, storage, and universal development of battery assembly processes for halide electrolytes. CN202011593230.5 discloses a superhydrophobic material capable of conducting lithium ions, its preparation method, and its application. This technical solution is obtained by coating lithium-ion conductive nanomaterials with a low surface energy hydrophobic material, achieving both superhydrophobicity and lithium-ion conductivity. This can be used to improve the air stability of the protective material coated with it. However, it uses a single layer of low surface energy material to coat the electrolyte solid particles, and the outer hydrophobic polymer film can easily reduce the battery energy density and affect cycle life during the coating process, thus lacking universality. Summary of the Invention

[0004] To address the aforementioned issues, this invention aims to provide a multi-layered, hierarchical core-shell halide solid electrolyte and its preparation method. This halide solid electrolyte achieves a technological breakthrough through a gradient coating structure of "halide core - functionalized polymer shell." The organic polymer shell acts as a physical barrier, blocking direct contact between the halide core and water and oxygen components in the environment, suppressing hydrolysis side reactions, and ensuring that the conductivity decay rate is less than 5% after 24 hours of exposure in an environment with humidity >30%. Furthermore, the mechanical flexibility and adaptability of the shell enable close conformal contact with the inner electrolyte material, constructing low-impedance ion channels. Simultaneously, this invention further provides a universal preparation method for this halide solid electrolyte. By controlling the polymer precursor composition, solvent polarity gradient, and thermal treatment kinetic parameters, the chemical composition (e.g., a single-layer dense sealing layer + an outer ion-conducting layer), thickness (10-200 nm), and functional properties (e.g., self-healing, dendrite suppression) of the shell can be precisely customized, overcoming the "stability-conductivity" inversion caused by traditional coating techniques, and providing a material foundation for the industrialization of high-safety, high-energy-density solid-state batteries.

[0005] This invention is achieved through the following technical solution:

[0006] A multi-layered hierarchical core-shell structured halide solid electrolyte comprises, from the inside out, a core halide solid electrolyte, a first conductive polymer coating layer, and a second hydrophobic polymer coating layer. The first conductive polymer coating layer is copolymerized from conductive polymer monomers having etheroxy groups (-O-) or carbonyl groups (C=O). The second hydrophobic polymer coating layer is prepared by ball milling and sintering a hydrophobic polymer material onto the surface of the first conductive polymer coating layer. The first conductive polymer coating layer forms a chemical bonding interface with the core halide solid electrolyte through the etheroxy groups (-O-) or carbonyl groups (C=O) in the molecular chain segments. In this invention, the first conductive polymer coating layer is composed of an ion-conducting polymer containing polar functional groups (such as polyethylene oxide (PEO) or polycarbonate (PC)). Through the ether oxygen groups (-O-) or carbonyl groups (C=O) in the molecular chain segments, it forms a chemically bonded interface with the halide surface, providing a flexible ion transport channel and relieving interfacial stress. The second hydrophobic polymer coating layer is composed of a fluorinated polymer (such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE)) or a silane coupling agent (such as diaminosilane or octadecyltrimethoxysilane). Through the hydrophobic groups (-CF2-, long-chain alkyl groups), it forms a dense barrier, inhibiting water molecule penetration while retaining the selective transport capability of lithium ions. Furthermore, a synergistic effect is formed between the first conductive polymer coating layer and the second hydrophobic polymer coating layer, generating flexible organic molecular chains at their interface to provide low-energy-barrier Li-ion transport. +Jumping sites, collaboratively addressing mechanical performance deficiencies: Volume changes during charging and discharging can easily cause electrolyte particles to break down, affecting battery cycle life.

[0007] The conductive polymers include one or more of polyacrylonitrile (PAN), polyaniline, polyamide, polyazine, polypyrrole (PPy), polythiophene, polythiophene vinylidene, and polypyridinocatechinamine; the hydrophobic polymers include one or more of polytetrafluoroethylene, vinylidene fluoroethylene, polytetrafluoroethylene-perfluoroalkyl vinyl ether, diaminosilane coupling agent, imidazole tetrafluoroborate, n-octadecyl phosphoric acid, 1-undecyl mercaptan, phosphate oleyl ester, fluorinated isopropylene copolymer resin, and fluorinated ethylene / tetrafluoroethylene copolymer resin.

[0008] The chemical formula of the halide solid electrolyte is Li a MX b Where M is at least one of Group IIIB and Group IIIA metals, X is at least one of F, Cl, Br, and I, 0 < a ≤ 10, 1 ≤ b ≤ 13.

[0009] The conductive polymer monomer content is 0 wt% to 5 wt% of the halide solid electrolyte mass, and contains no 0 wt%; the polymer hydrophobic material content is 0 wt% to 5 wt% of the halide solid electrolyte mass, and contains no 0 wt%.

[0010] The total thickness of the first conductive polymer coating layer and the second hydrophobic polymer coating layer is 200-300 nm. The preparation method of the halide solid electrolyte as described above includes the following steps: S1, in an alkaline solution environment, ...

[0011] Conductive polymer monomers are in situ self-polymerized on the surface of the halide solid electrolyte to form a first-level conductive polymer polymer coating layer, thus obtaining a first-level halide solid electrolyte composite material; S2, a hydrophobic coating polymer material is added to form a second hydrophobic polymer polymer coating layer in situ on the surface of the first-level halide solid electrolyte composite material, thus obtaining a second-level halide solid electrolyte composite material.

[0012] In S1, the halide solid electrolyte and the conductive polymer monomer are mixed in a first solvent, which is at least one of alkane solvents, benzene solvents, ether solvents and ketone solvents, and is selected from at least one of dichloromethane, n-heptane, n-decane, p-xylene, trimethylbenzene, anisole, monochlorobenzene and cyclohexanone.

[0013] Post-treatment is performed, which involves low-temperature sintering at 120℃~250℃ to further remove adsorbed moisture or impurities from the material surface, reduce electrochemical side reactions, and improve interfacial side reactions. Sintering is divided into three sequential sintering stages, with the sintering temperature of each subsequent stage being higher than that of the preceding stage. The first sintering stage involves heating from room temperature to the first sintering temperature at a heating rate of 3℃ / min~8℃ / min and holding at that temperature for 1h~3h. The second sintering stage involves heating at a rate of 5℃ / min~30℃ / min... The heating rate is from the first sintering temperature to the second sintering temperature and held for 2 to 4 hours; the third sintering stage is: heating from the second sintering temperature to the third sintering temperature at a heating rate of 3°C / min to 8°C / min and held for 3 to 5 hours; the first sintering temperature is 120°C to 170°C, the second sintering temperature is 200°C to 220°C, and the third sintering temperature is 250°C to 300°C; after the third sintering stage, the temperature is lowered from the third sintering temperature at a rate of 1°C / min to 3°C / min.

[0014] An electrode prepared from a halide solid electrolyte as described above.

[0015] A battery prepared from a halide solid electrolyte as described above.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] The halide solid electrolyte membrane prepared by this invention can be reduced to a thickness of less than 100 μm. Its interface adaptive properties suppress lithium dendrite growth, and its capacity retention rate is >80% after 200 cycles. The sintering temperature is ≤300℃, which reduces energy consumption and avoids lattice distortion. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0019] Figure 1 The X-ray diffraction patterns of the Li3InCl6 solid electrolytes prepared in Example 1 and Comparative Example 1 of this invention are shown below.

[0020] Figure 2 The performance diagram for the air-stabilized type of Example 1 is shown.

[0021] Figure 3 This is a performance diagram of the air-stabilized type in Example 2;

[0022] Figure 4 The performance diagram for the air-stabilized type of Example 3 is shown.

[0023] Figure 5This is a SEM image of the Li3InCl6 solid electrolyte prepared in Example 1 of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0025] Example 1

[0026] (1) Weigh 5g of Li3InCl according to a mass ratio of 1:0.1wt%. 6、 5 mg PEO and 10 ml n-decane dispersant were added to a glass container for in-situ polymerization to coat the conductive polymer layer. (2) After stirring for a certain time, 5 mg 1-butyl-3-methylimidazolium tetrafluoroborate (organic polymer hydrophobic agent) was added to the system. The weighed raw materials, 10 ml n-decane dispersant, 200 μl, and 1 l polydimethylsiloxane dispersant were added to a ball mill jar and ball milled for 8 hours. 100g of ball milling beads (Φ1mm (30g); Φ3mm (50g); Φ5mm (20g). (3) The slurry after ball milling was heated to 180℃ at a heating rate of 5℃ / min in the first sintering stage and sintered for 2h; in the second sintering stage, the heating rate was increased from 180℃ to 230℃ at a heating rate of 5℃ / min and sintered for 3h; in the third sintering stage, the heating rate was increased from 200℃ to 250℃ at a heating rate of 5℃ / min and sintered for 3h; then the temperature was reduced from 250℃ to room temperature at a cooling rate of 2℃ / min. (4) After the heat treatment, the sample was naturally cooled to room temperature to obtain a graded core-shell structure polymer-coated Li3InCl6 solid electrolyte. Figure 2 The air-stabilized performance diagram of Example 1 is shown.

[0027] Example 2

[0028] (1) Weigh 5g of Li3InCl according to a mass ratio of 1:0.1wt%. 6、5 mg PVDF and 10 ml n-decane dispersant were added to a glass container for in-situ polymerization to coat the conductive polymer layer; (2) After stirring for a certain time, 5 mg diaminosilane coupling agent (organic polymer hydrophobic agent) was added to the system. The weighed raw materials, 10 ml n-decane dispersant, and 200 μl polydimethylsiloxane dispersant were added to a ball mill jar and ball milled for 8 hours. 100g of ball milling beads (Φ1mm (30g); Φ3mm (50g); Φ5mm (20g). (3) The slurry after ball milling was heated to 180℃ at a heating rate of 5℃ / min in the first sintering stage and sintered for 2h; in the second sintering stage, the heating rate was increased from 180℃ to 230℃ at a heating rate of 5℃ / min and sintered for 3h; in the third sintering stage, the heating rate was increased from 200℃ to 250℃ at a heating rate of 5℃ / min and sintered for 3h; then the temperature was reduced from 250℃ to room temperature at a cooling rate of 2℃ / min; (4) After the heat treatment was completed, the sample was naturally cooled to room temperature to obtain a graded core-shell structure polymer-coated Li3InCl6 solid electrolyte. Figure 3 The performance graph of the air-stabilized version of Example 2 is shown.

[0029] Example 3

[0030] (1) Weigh 5g of Li3InCl according to a mass ratio of 1:0.1wt%. 6、 5 mg PPy and 10 ml n-decane dispersant were added to a glass container for in-situ polymerization to coat the conductive polymer layer; (2) After stirring for a certain time, 5 mg n-octadecyl phosphoric acid (organic polymer hydrophobic agent) was added to the system. The weighed raw materials, 10 ml n-decane dispersant, and 200 μl polydimethylsiloxane dispersant were added to a ball mill jar and ball milled for 8 hours. 100g of ball milling beads (Φ1mm (30g); Φ3mm (50g); Φ5mm (20g). (3) The slurry after ball milling was heated to 180℃ at a heating rate of 5℃ / min in the first sintering stage and sintered for 2h; in the second sintering stage, the heating rate was increased from 180℃ to 230℃ at a heating rate of 5℃ / min and sintered for 3h; in the third sintering stage, the heating rate was increased from 200℃ to 250℃ at a heating rate of 5℃ / min and sintered for 3h; then the temperature was reduced from 250℃ to room temperature at a cooling rate of 2℃ / min; (4) After the heat treatment was completed, the sample was naturally cooled to room temperature to obtain a graded core-shell structure polymer-coated Li3InCl6 solid electrolyte. Figure 4 The performance graph of the air-stabilized version of Example 3 is shown.

[0031] Comparative Example 1

[0032] Similar to Example 1, (1) 5g of the weighed raw material, 10ml of n-decane dispersant, and 200ul of polydimethylsiloxane dispersant were added to a ball mill jar and milled for 8 hours. 100g of milling beads (Φ1mm (30g); Φ3mm (50g); Φ5mm (20g).

[0033] (2) The slurry after ball milling was heated to 180°C at a heating rate of 5°C / min in the first sintering stage and sintered for 2 hours; in the second sintering stage, the temperature was increased from 180°C to 230°C at a heating rate of 5°C / min and sintered for 3 hours; in the third sintering stage, the temperature was increased from 200°C to 250°C at a heating rate of 5°C / min and sintered for 3 hours; and then the temperature was reduced from 250°C to room temperature at a cooling rate of 2°C / min.

[0034] (3) After the heat treatment, the sample was naturally cooled to room temperature to obtain ball-milled Li3InCl6 solid electrolyte.

[0035] Comparative Example 2

[0036] (1) Weigh out 5g of Li3InCl 6、 5 mg PEO, 10 ml n-decane dispersant, and 200 μL polydimethylsiloxane dispersant were added to a ball mill jar and ball milled for 8 hours. The ball milling beads were 100 g each (Φ1 mm (30 g); Φ3 mm (50 g); Φ5 mm (20 g).

[0037] (2) The slurry after ball milling was heated to 180°C at a heating rate of 5°C / min in the first sintering stage and sintered for 2 hours; in the second sintering stage, the temperature was increased from 180°C to 230°C at a heating rate of 5°C / min and sintered for 3 hours; in the third sintering stage, the temperature was increased from 200°C to 250°C at a heating rate of 5°C / min and sintered for 3 hours; and then the temperature was reduced from 250°C to room temperature at a cooling rate of 2°C / min.

[0038] (3) After the heat treatment, the sample was naturally cooled to room temperature to obtain ball-milled Li3InCl6 solid electrolyte.

[0039] The difference between the Li3InCl6 material in this comparative example and that in Example 1 is that it is only coated with the first polymer conductive coating layer.

[0040] Comparative Example 3

[0041] The difference from Example 1 is that only the second hydrophobic polymer coating layer is applied.

[0042] 1. X-ray diffraction analysis: The phase composition of the Li3InCl6 solid electrolytes prepared in Examples 1-1 and Comparative Example 1 was analyzed using an X-ray diffractometer. The results are as follows: Figure 1As shown in the figure, the diffraction peaks of the Li3InCl6 solid electrolyte prepared in Example 1 are consistent with those of the standard card PDF#97-008-9617, and the high intensity and narrow half-peak width indicate high purity and good crystallinity of the product. It is essentially consistent with the fine powder of the Li3InCl6 solid electrolyte prepared in Comparative Example 1. The method of this invention achieves a coating thickness accuracy of ±400 nm and a coating coverage of ≥50% by selecting different coating materials, matching the solvent polarity gradient (non-polar → polar), and ball milling parameters (speed, time). Simultaneously, the outer hydrophobic encapsulation layer, through a dense physical barrier and chemical passivation, ensures that the conductivity decay rate of the composite material is ≤50% after exposure to an environment with ≤40% humidity for 9 hours, effectively blocking the penetration of H2O molecules. Furthermore, the gradient coating structure inhibits the side reactions of halides with O2 in the air. After storage at 25℃ / 60% humidity for 12 days, the XRD characteristic peak intensity change is ≤5%, and there is no crystalline phase decomposition. In terms of cost and environmental advantages, the ball milling-in-situ polymerization process enables the utilization rate of coating materials to be ≥90%, reducing waste generation; at the same time, the spray drying and vacuum sintering processes ensure that the solvent residue is ≤10 ppm, which complies with RoHS standards.

[0043] 2. SEM Analysis: SEM images are displayed as follows Figure 5 As shown, the Li3InCl6 particles prepared by ball milling and coating are spherical with uniform particle size distribution and an average particle size of about 400 nm.

[0044] 3. Ionic Conductivity Test: The ionic conductivity of the Li3InCl6 solid electrolytes prepared in Examples 1-3 and Comparative Examples 1-2 was tested using the AC impedance method. The test results are shown in Table 1. Air stability results are as follows: Figure 2-4 As shown in Table 2.

[0045] The effectiveness of electrolytes can be evaluated based on the following indicators:

[0046] a. Ionic conductance: Measured using AC impedance spectroscopy with an electrochemical workstation;

[0047] b. Particle size distribution: Measured using a dry laser particle size analyzer.

[0048] Table 1. Ion conductivity test results for examples and comparative examples.

[0049]

[0050] Table 2. Results of Air Stability Tests for Examples and Comparative Examples

[0051]

[0052] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-layered hierarchical core-shell structured halide solid electrolyte, characterized in that, From the inside out, the structure consists of a core halide solid electrolyte, a first conductive polymer coating layer, and a second hydrophobic polymer coating layer. The first conductive polymer coating layer is copolymerized from conductive polymer monomers having etheroxy groups (-O-) or carbonyl groups (C=O). The second hydrophobic polymer coating layer is prepared by ball milling and sintering a hydrophobic polymer material onto the surface of the first conductive polymer coating layer. The first conductive polymer coating layer forms a chemical bonding interface with the core halide solid electrolyte through the etheroxy groups (-O-) or carbonyl groups (C=O) in the molecular chain segments.

2. The halide solid electrolyte according to claim 1, characterized in that, The conductive polymer monomers include one or more of polyacrylonitrile, polyaniline, polyamide, polyazine, polypyrrole, polythiophene, polythiophene vinylidene, and polypyridinocatechinamine; the hydrophobic polymer materials include one or more of polytetrafluoroethylene, vinylidene fluoroethylene, polytetrafluoroethylene-perfluoroalkyl vinyl ether, diaminosilane coupling agent, imidazole tetrafluoroborate, n-octadecyl phosphoric acid, 1-undecyl mercaptan, phosphate oleyl ester, fluorinated isopropylene copolymer resin, and fluorinated ethylene / tetrafluoroethylene copolymer resin.

3. The multi-layered hierarchical core-shell structured halide solid electrolyte according to claim 1, characterized in that, The chemical formula of the halide solid electrolyte is Li a MX b Where M is at least one of Group IIIB and Group IIIA metals, X is at least one of F, Cl, Br, and I, 0 < a ≤ 10, 1 ≤ b ≤ 13.

4. The halide solid electrolyte according to claim 1, characterized in that, The conductive polymer monomer content is 0 wt% to 5 wt% of the halide solid electrolyte mass, and contains no 0 wt%; the polymer hydrophobic material content is 0 wt% to 5 wt% of the halide solid electrolyte mass, and contains no 0 wt%.

5. The halide solid electrolyte according to claim 1, characterized in that, The total thickness of the first conductive polymer coating layer and the second hydrophobic polymer coating layer is 200-300 nm.

6. The method for preparing a halide solid electrolyte according to claim 1, characterized in that, Includes the following steps: S1. In an alkaline solution environment, conductive polymer monomers are in situ self-polymerized on the surface of the halide solid electrolyte to form a first-level conductive polymer polymer coating layer, thereby obtaining a first-level halide solid electrolyte composite material; S2. A hydrophobic coating polymer material is added to form a second hydrophobic polymer polymer coating layer in situ on the surface of the first-level halide solid electrolyte composite material, thereby obtaining a second-level halide solid electrolyte composite material.

7. The method for preparing a halide solid electrolyte according to claim 1, characterized in that, In S1, the halide solid electrolyte and the conductive polymer monomer are mixed in a first solvent, which is at least one of alkane solvents, benzene solvents, ether solvents and ketone solvents, and is selected from at least one of dichloromethane, n-heptane, n-decane, p-xylene, trimethylbenzene, anisole, monochlorobenzene and cyclohexanone.

8. The method for preparing a halide solid electrolyte according to claim 1, characterized in that, Post-treatment is performed, which involves low-temperature sintering at 120℃~250℃ to further remove adsorbed moisture or impurities from the material surface, reduce electrochemical side reactions, and improve interfacial side reactions. Sintering is divided into three sequential sintering stages, with the sintering temperature of each subsequent stage being higher than that of the preceding stage. The first sintering stage involves heating from room temperature to the first sintering temperature at a heating rate of 3℃ / min~8℃ / min and holding at that temperature for 1h~3h. The second sintering stage involves heating at a rate of 5℃ / min~30℃ / min... The heating rate is from the first sintering temperature to the second sintering temperature and held for 2 to 4 hours; the third sintering stage is: heating from the second sintering temperature to the third sintering temperature at a heating rate of 3°C / min to 8°C / min and held for 3 to 5 hours; the first sintering temperature is 120°C to 170°C, the second sintering temperature is 200°C to 220°C, and the third sintering temperature is 250°C to 300°C; after the third sintering stage, the temperature is lowered from the third sintering temperature at a rate of 1°C / min to 3°C / min.

9. An electrode prepared from a halide solid electrolyte as described in any one of claims 1-5.

10. A battery prepared from a halide solid electrolyte as described in any one of claims 1-5.

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