A halide solid-state electrolyte of a multilayer hierarchical core-shell structure and a preparation method thereof

Abstract

The application discloses a kind of multilayer hierarchical core-shell structure halide solid electrolyte, from inside to outside include core halide solid electrolyte, first conductive polymer high molecular coating layer and second hydrophobic polymer high molecular coating layer in sequence, first conductive polymer high molecular coating layer is formed by the copolymerization of conductive polymer monomer with ether oxygen group-O or carbonyl C=O, second hydrophobic polymer high molecular coating layer is made by high molecular hydrophobic material ball milling sintering coating on the surface of first conductive polymer high molecular coating layer, first conductive polymer high molecular coating layer forms chemical bonding interface between core halide solid electrolyte by ether oxygen group-O or carbonyl C=O in molecular chain segment.The halide solid electrolyte film prepared by the application can be reduced to below 100 μm, the interface self-adapting characteristic inhibits lithium dendrite growth, capacity retention rate>80% after 200 cycles;Sintering temperature≤300℃, 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⁻⁻⁴ V), they are still widely used in solid-state batteries. 4 Oxide solid electrolytes (~10⁻³ S / cm) are inorganic solid electrolytes, but densification is usually achieved through high-temperature sintering (>1000℃). Sulfide solid electrolytes, such as LPS and LPSCl, although possessing excellent interfacial contact characteristics (densification is achieved through cold pressing) and ultra-high ionic conductivity (>10⁻² S / cm), have significant defects in chemical stability, are sensitive to humidity (H₂O→H₂S release), and require operation in a harsh, dry environment; they also have poor interfacial compatibility between high-voltage oxide cathodes (such as NCM and LCO) and lithium metal anodes, and are prone to sulfur redox reactions; while halide solid electrolytes are considered to be highly promising next-generation solid electrolyte materials 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 solve the above problems, the purpose of the present application is to provide a halide solid-state electrolyte with a multi-layer hierarchical core-shell structure and a preparation method. The halide solid-state electrolyte realizes a technical breakthrough by constructing a gradient coating structure of "halide core-functional polymer shell". The organic polymer shell layer acts as a physical barrier to block the direct contact between the halide core and the water and oxygen components in the environment, inhibits the hydrolysis side reaction, and makes the conductivity decay rate of the material less than 5% after 24 hours of exposure in an environment with humidity> 30%. In addition, the mechanical flexibility and self-adaptability of the shell layer realize close conformal contact with the inner electrolyte material, constructing a low-impedance ion channel. Meanwhile, the present application further provides a universal preparation method for the halide solid-state electrolyte. By adjusting the composition of the polymer precursor, the solvent polarity gradient, and the heat treatment kinetics parameters, the chemical composition (such as a single-layer dense sealing layer + an outer ion-conducting layer), the thickness (10-200 nm), and the functional properties (such as self-repairing and dendrite inhibition) of the shell layer can be precisely customized, breaking the "stability-conductivity" inversion relationship caused by traditional coating technology, and providing a material basis for the industrialization of high-safety and high-energy-density solid-state batteries.

[0005] The present application is realized by the following technical solutions:

[0006] A halide solid-state electrolyte with a multi-layer hierarchical core-shell structure, which comprises, from inside to outside, an inner core halide solid-state electrolyte, a first conductive polymer high molecular coating layer, and a second hydrophobic polymer high molecular coating layer. The first conductive polymer high molecular coating layer is co-polymerized from conductive polymer monomers with ether oxygen groups (-O-) or carbonyl groups (C=O). The second hydrophobic polymer high molecular coating layer is obtained by ball milling and sintering a hydrophobic polymer material on the surface of the first conductive polymer high molecular coating layer. The first conductive polymer high molecular coating layer forms a chemical bonding interface between the inner core halide solid-state electrolyte through the ether oxygen groups (-O-) or carbonyl groups (C=O) in the molecular chain segment. In the present application, the first conductive polymer high molecular coating layer is composed of ion-conductive polymers containing polar functional groups (such as polyethylene oxide (PEO) and polycarbonate (PC)), which form a chemical bonding interface with the halide surface through the ether oxygen groups (-O-) or carbonyl groups (C=O) in the molecular chain segment, providing flexible ion transport channels and relieving interface stress. The second hydrophobic polymer high molecular coating layer is composed of fluorinated polymers (such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE)) or silane coupling agents (such as bisamino silane and octadecyl trimethoxysilane), which form a dense barrier through hydrophobic groups (-CF2-, long-chain alkyl), inhibit the penetration of water molecules, and retain the selective transport ability of lithium ions. Moreover, the first conductive polymer high molecular coating layer and the second hydrophobic polymer high molecular coating layer form a synergistic effect, generating flexible molecular chains of organic compounds between the two interfaces to provide low-energy barrier Li⁺ hopping sites, and solving the problem of insufficient mechanical properties: the volume change during charging and discharging easily causes the rupture of electrolyte particles, affecting the cycle life of the battery.

[0007] The conductive polymer includes one or more of polyacrylonitrile (PAN), polyaniline, polyazepine, polypyrrole (PPy), polythiophene, polythiophene vinylene, and polyphenazine; and the hydrophobic polymer includes one or more of polytetrafluoroethylene, tetrafluoroethylene, polytetrafluoroethylene-perfluoroalkyl vinyl ether, bisamino silane coupling agent, imidazole tetrafluoroborate, n-octadecyl phosphoric acid, 1-undecyl mercaptan, phosphoric acid oleyl ester, fluorinated isopropylene copolymer resin, and fluorinated ethylene / tetrafluoroethylene copolymer resin.

[0008] The halide solid-state electrolyte has a chemical formula of Li a MX b wherein M is at least one of a Group III B metal element and a Group III A metal element, X is at least one of F, Cl, Br, and I, 0

[0009] The content of the conductive polymer monomer is 0wt% to 5wt% of the mass of the halide solid-state electrolyte, and the content of the hydrophobic polymer is 0wt% to 5wt% of the mass of the halide solid-state electrolyte.

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

[0011] The conductive polymer monomer is in-situ polymerized on the surface of the halide solid-state electrolyte to form a first-level conductive polymer coating layer, to obtain a first-level halide solid-state electrolyte composite material; S2, adding a hydrophobic coating polymer material to in-situ coat a second-level hydrophobic polymer coating layer on the surface of the first-level halide solid-state electrolyte composite material, to obtain a second-level halide solid-state electrolyte composite material.

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

[0013] The post-treatment is low-temperature sintering at 120-250 DEG C, which further removes the water or impurities adsorbed on the surface of the material, reduces the electrochemical side reaction, and improves the interface side reaction; the sintering is divided into three sintering stages which are sequentially performed, wherein the sintering temperature of the later sintering stage is greater than that of the former sintering stage; the first sintering stage is: using a heating rate of 3-8 DEG C / min to heat from room temperature to the first sintering temperature and keeping for 1-3 h; the second sintering stage is: using a heating rate of 5-30 DEG C / min to heat from the first sintering temperature to the second sintering temperature and keeping for 2-4 h; the third sintering stage is: using a heating rate of 3-8 DEG C / min to heat from the second sintering temperature to the third sintering temperature and keeping for 3-5 h; the first sintering temperature is 120-170 DEG C, the second sintering temperature is 200-220 DEG C, and the third sintering temperature is 250-300 DEG C; after the third sintering stage, the temperature is decreased from the third sintering temperature at a rate of 1-3 DEG C / min.

[0014] An electrode prepared from the halide solid-state electrolyte as described above.

[0015] A battery prepared from the halide solid-state electrolyte as described above.

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

[0017] The halide solid-state electrolyte film prepared by the present application has a thickness of less than 100 microns, the interface self-adapting property inhibits the growth of lithium dendrites, the capacity retention rate is greater than 80% after 200 cycles, the sintering temperature is less than or equal to 300 DEG C, the energy consumption is reduced, and the lattice distortion is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present application and are incorporated in and constitute a part of this application, illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application. In the drawings:

[0019] Figure 1 X-ray diffraction pattern of the Li3InCl6 solid-state electrolyte prepared in Example 1 and Comparative Example 1 of the present application;

[0020] Figure 2 Air stability performance chart of Example 1;

[0021] Figure 3 Air stability performance chart of Example 2;

[0022] Figure 4 Air stability performance chart of Example 3;

[0023] Figure 5SEM image of Li3InCl6 solid-state electrolyte prepared for Example 1 of the present application. DETAILED DESCRIPTION

[0024] In order to make the objects, technical solutions, and advantages of the present application clearer, further, the present application will be described in detail below with reference to examples and drawings. The schematic embodiments of the present application and the descriptions thereof are only used to explain the present application, and do not limit the present application.

[0025] Example 1

[0026] (1) 5g Li3InCl6 was weighed according to the mass ratio of 1:0.1wt%, 5mg PEO, and 10ml n-decane dispersant were added to the glassware in-situ polymerization to coat the conductive polymer layer. 6、 5mg PEO and 10ml n-decane dispersant were added to the glassware in-situ polymerization to coat the conductive polymer layer. (2) After stirring for a certain time, 5mg 1-butyl-3-methylimidazolium tetrafluoroborate (organic polymer hydrophobic agent) was added to the system. The weighed raw materials, 10ml n-decane dispersant, and 200μl, l polydimethylsiloxane dispersant were added to the ball mill tank, and ball milling was performed for 8 hours. The ball milling beads were 100g (Φ1mm (30g); Φ3mm (50g); Φ5mm (20g). (3) The ball-mixed slurry was heated to 180℃ at a heating rate of 5 ℃ / min in the first sintering stage, sintered for 2h; the temperature was raised from 180℃ to 230℃ at a heating rate of 5 ℃ / min in the second sintering stage, sintered for 3h; the temperature was raised from 200℃ to 250℃ at a heating rate of 5 ℃ / min in the third sintering stage, sintered for 3h; and then the temperature was lowered 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 hierarchical core-shell structure polymer-coated Li3InCl6 solid-state electrolyte. Figure 2 An air-stable performance graph of Example 1 is shown.

[0027] Example 2

[0028] (1) 5g Li3InCl6 was weighed according to the mass ratio of 1:0.1wt%, 5mg PEO, and 10ml n-decane dispersant were added to the glassware in-situ polymerization to coat the conductive polymer layer. 6、5mg PPy and 10 ml n-decane dispersant were added to a glassware to in-situ polymerize a conductive polymer layer; (2) After stirring for a certain period of time, 5 mg of octadecyl phosphoric acid (organic macromolecular hydrophobic agent) was added to the system. The weighed raw materials and 10 ml of n-decane dispersant, 200 ul of polydimethylsiloxane dispersant were added to the ball mill tank, and ball milling was carried out for 8 hours. The ball milling beads were 100 g (Φ1 mm (30 g); Φ3 mm (50 g); Φ5 mm (20 g). (3) The slurry after ball milling was heated to 180℃ at a heating rate of 5 ℃ / min in the first sintering stage, sintered for 2h; in the second sintering stage, it was raised from 180℃ to 230℃ at a heating rate of 5 ℃ / min, sintered for 3h; in the third sintering stage, it was raised from 200℃ to 250℃ at a heating rate of 5 ℃ / min, sintered for 3h; then it was cooled 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 hierarchical core-shell structure polymer-coated Li3InCl6 solid-state electrolyte. Figure 3 The air stable performance chart of Example 2 is shown.

[0029] Example 3

[0030] (1) 5 g of Li3InCl6 and 0.5 g of double amino silane coupling agent (organic macromolecular hydrophobic agent) were weighed according to the mass ratio of 1:0.1 wt%. 6、 5mg PPy and 10 ml n-decane dispersant were added to a glassware to in-situ polymerize a conductive polymer layer; (2) After stirring for a certain period of time, 5 mg of octadecyl phosphoric acid (organic macromolecular hydrophobic agent) was added to the system. The weighed raw materials and 10 ml of n-decane dispersant, 200 ul of polydimethylsiloxane dispersant were added to the ball mill tank, and ball milling was carried out for 8 hours. The ball milling beads were 100 g (Φ1 mm (30 g); Φ3 mm (50 g); Φ5 mm (20 g). (3) The slurry after ball milling was heated to 180℃ at a heating rate of 5 ℃ / min in the first sintering stage, sintered for 2h; in the second sintering stage, it was raised from 180℃ to 230℃ at a heating rate of 5 ℃ / min, sintered for 3h; in the third sintering stage, it was raised from 200℃ to 250℃ at a heating rate of 5 ℃ / min, sintered for 3h; then it was cooled 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 hierarchical core-shell structure polymer-coated Li3InCl6 solid-state electrolyte. Figure 4 The air stable performance chart 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 1The diffraction peaks of the Li3InCl6 solid electrolyte prepared in Example 1 are consistent with the standard card PDF #97-008-9617, and the diffraction peak intensity is high and the half-peak width is narrow, indicating that the product has high purity and good crystallinity. It is basically consistent with the Li3InCl6 solid electrolyte fine powder prepared in Comparative Example 1. The method of the application realizes the thickness precision of the coating layer ± 400 nm and the coating coverage rate ≥ 50% by selecting different coating materials, matching the solvent polarity gradient (non-polar → polar) and the ball milling parameters (rotation speed, time). At the same time, the outer hydrophobic packaging layer blocks the penetration of H2O molecules by the dense physical barrier and chemical passivation effect, so that the conductivity attenuation rate of the composite material is ≤ 50% after being exposed in an environment with humidity ≤ 40% for 9 hours. In addition, the gradient coating structure inhibits the side reaction of halide and O2 in the air, and the intensity change of the XRD characteristic peak of the material is ≤ 5% after being stored at 25°C / 60% humidity for 12 days, without decomposition of the crystal phase. In terms of cost and environmental protection advantages, the utilization rate of the coating material is ≥ 90% by using the ball milling-in-situ polymerization process to reduce waste generation; at the same time, the spray drying and vacuum sintering process ensures that the solvent residue is ≤ 10 ppm, which meets the RoHS standard.

[0043] 2. SEM analysis: The SEM image shows that the Li3InCl6 particles prepared by ball milling coating are spherical, and the particle size distribution is uniform, with an average particle size of about 400 nm, as shown in Figure 5

[0044] 3. Ion conductivity test: The ion conductivity of the Li3InCl6 solid electrolyte prepared in Examples 1-3 and Comparative Examples 1-2 was tested by alternating current impedance method. The test results are shown in Table 1. The air stability results are shown in Figures 2-4 and Table 2.

[0045] The effect of the electrolyte is evaluated according to the following indicators:

[0046] a. Ion conductance: measured by electrochemical workstation alternating current impedance method;

[0047] b. Particle size distribution: measured by laser particle size analyzer dry laser particle size analysis.

[0048] Table 1 Test results of ion conductance of examples and comparative examples

[0049]

[0050] Table 2 Test results of air stability of examples and comparative examples

[0051]

[0052] ​The above detailed description of the specific embodiments of the present application has been given to understand the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A multilayered hierarchical core-shell structured halide solid-state electrolyte, characterized in that, The inner core halide solid-state electrolyte, the first conductive polymer high molecular coating layer and the second hydrophobic polymer high molecular coating layer are sequentially arranged from the inside to the outside, the first conductive polymer high molecular coating layer is formed by copolymerization of conductive polymer monomers with ether oxygen groups -O- or carbonyl groups C=O, the second hydrophobic polymer high molecular coating layer is formed by ball milling and sintering of high molecular hydrophobic materials on the surface of the first conductive polymer high molecular coating layer, the first conductive polymer high molecular coating layer forms a chemical bonding interface between the inner core halide solid-state electrolyte through the ether oxygen groups -O- or carbonyl groups C=O in the molecular chain segments, the conductive polymer monomers include one or more of polyacrylonitrile, polyaniline, polyamide, polypyrrole, polythiophene, polythiophene ethylene and polyphenyl catechol amine, the high molecular hydrophobic materials include one or more of polytetrafluoroethylene, polytetrafluoroethylene-perfluoroalkyl vinyl ether, bisamino silane coupling agent, imidazole tetrafluoroborate, n-octadecyl phosphoric acid, 1-undecyl mercaptan, phosphoric acid oleyl ester, fluorinated isopropylene copolymer resin and fluorinated ethylene / tetrafluoroethylene copolymer resin, the content of the conductive polymer monomers is 0wt%-5wt% of the mass of the halide solid-state electrolyte and does not include 0wt%, and the content of the high molecular hydrophobic materials is 0wt%-5wt% of the mass of the halide solid-state electrolyte and does not include 0wt%.

2. The multilayered hierarchical core-shell structured halide solid-state electrolyte of claim 1, wherein, The chemical formula of the halide solid-state electrolyte is Li a MX b wherein M is at least one of a Group III B metal element and a Group III A metal element, X is at least one of F, Cl, Br, and I, 0 < a ≤ 10, and 1 ≤ b ≤ 13.

3. The halide solid state electrolyte of claim 1, wherein, The total thickness of the first conductive polymer high molecular coating layer and the second hydrophobic polymer high molecular coating layer is 200-300nm.

4. A method of producing the halide solid-state electrolyte according to claim 1, characterized by, The method comprises the following steps: S1, in an alkaline solution environment, the conductive polymer monomers are self-polymerized on the surface of the halide solid-state electrolyte to form a first conductive polymer high molecular coating layer, thereby obtaining a first halide solid-state electrolyte composite material; S2, the hydrophobic coating high molecular material is added to the surface of the first halide solid-state electrolyte composite material to form a second hydrophobic polymer high molecular coating layer, thereby obtaining a second halide solid-state electrolyte composite material.

5. The method of producing a halide solid-state electrolyte according to claim 4, characterized by, In S1, the halide solid-state electrolyte and the conductive polymer monomers are mixed in a first solvent, and the first solvent is at least one of an alkane solvent, a benzene solvent, an ether solvent and a ketone solvent.

6. The method of producing a halide solid-state electrolyte according to claim 4, characterized by, The post-treatment is low-temperature sintering at 120-250°C, which further removes the water or impurities adsorbed on the surface of the material, reduces the electrochemical side reaction, and improves the interface side reaction; the sintering is divided into three sintering stages in sequence, wherein the sintering temperature of the latter sintering stage is greater than that of the former sintering stage; the first sintering stage is: using a temperature rising rate of 3-8°C / min to rise from room temperature to the first sintering temperature and keeping for 1-3 h; the second sintering stage is: using a temperature rising rate of 5-30°C / min to rise from the first sintering temperature to the second sintering temperature and keeping for 2-4 h; the third sintering stage is: using a temperature rising rate of 3-8°C / min to rise from the second sintering temperature to the third sintering temperature and keeping for 3-5 h; the first sintering temperature is 120-170°C, the second sintering temperature is 200-220°C, and the third sintering temperature is 250-300°C; after the third sintering stage, the temperature is lowered from the third sintering temperature at a rate of 1-3°C / min.

7. An electrode prepared from a halide solid-state electrolyte comprising any one of claims 1-3.

8. A battery prepared from a halide solid-state electrolyte comprising any one of claims 1-3.

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