Electrolyte film, method for manufacturing the same, and solid-state battery

Abstract

The application discloses an electrolyte film, a preparation method thereof and a solid-state battery. The electrolyte film has a three-layer stacked structure, comprising: a positive electrode stable layer doped with an F element in a host material; a fast ion conductive layer doped with an O element in the host material; and a negative electrode stable layer doped with an N element in the host material; wherein the fast ion conductive layer is located between the positive electrode stable layer and the negative electrode stable layer; and the host materials of the positive electrode stable layer, the fast ion conductive layer and the negative electrode stable layer are the same solid-state halide electrolyte. The application uses the same solid-state halide electrolyte as the host material, constructs a three-layer stacked structure of a positive electrode stable layer-fast ion conductive layer-negative electrode stable layer through layered doping of different elements (F, O and N), uses the same host material, can effectively inhibit side reactions between electrolyte layers and maintain good contact, and realizes performance complementation through functionalized doping of each layer, and both high ion conductivity and a wide electrochemical window are considered.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery technology, specifically relating to an electrolyte thin film, its preparation method, and a solid-state battery. Background Technology

[0002] With the increasing demands for power energy density and safety from next-generation electronic products, new energy vehicles, electric vertical take-off and landing aircraft, traditional lithium-ion batteries with organic solutions as electrolytes cannot meet future needs due to problems such as easy leakage and flammability. Developing solid-state batteries with higher safety and compatibility with high-energy-density electrodes has become one of the current focuses of battery development.

[0003] Solid electrolytes are a key component of solid-state batteries, making them a hot research topic. Among them, halide solid electrolytes (such as Li3MCl6, where M represents a metal element) are particularly popular due to their high ionic conductivity (>1×10⁻⁶). -3 Its advantages, such as S / cm and wide electrochemical window, have attracted much attention.

[0004] However, when solid halide electrolytes come into contact with lithium metal anodes, non-self-limiting side reactions occur, leading to poor interfacial stability. Taking ternary halides Li3MCl6 (M = Sc, Er, In, etc.) as an example, the side reaction equation is shown in equation (1):

[0005]

[0006] Doping is an important means of improving the intrinsic properties of materials. However, while single doping can improve a certain property (such as redox stability), it often sacrifices ionic conductivity, making it difficult to meet multiple performance requirements. For example, when the reduction stability of solid halide electrolytes is improved, their ionic conductivity generally decreases. To suppress side reactions at the electrolyte-anode interface, solid sulfide electrolytes (such as Li6PS5Cl) are often used as a buffer layer between the lithium metal anode and the solid halide electrolyte in practical applications. A bilayer electrolyte composed of two different substances, solid halide electrolyte and solid sulfide electrolyte, is called a heterogeneous bilayer solid electrolyte. However, the different chemical properties of the components in a heterogeneous bilayer solid electrolyte lead to side reactions at the interface. Taking the ternary halide Li3InCl6 as an example, the side reaction products include In2S3, InP, etc. These side reactions consume electrolyte, produce an inhomogeneous interface, and cause excessively high local current density, thereby inducing lithium dendrites.

[0007] In addition, existing solid electrolyte powders are usually made into thin films using a cold pressing process. However, the multilayer electrolyte prepared by the cold pressing method has a large thickness (~600 μm), which leads to an increase in the internal resistance of the battery and makes it difficult to achieve a balance between performance and thickness.

[0008] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art. Summary of the Invention

[0009] The purpose of this invention is to provide a homogeneous three-layer solid halide electrolyte thin film and its preparation process. By designing a homogeneous multilayer structure, the side reaction problem at the heterogeneous interface can be solved, which can balance high ionic conductivity and interface stability, and achieve thin film formation to reduce battery internal resistance.

[0010] To achieve the above objectives, the present invention provides an electrolyte thin film having a three-layer stacked structure, comprising:

[0011] The positive electrode stabilizing layer is doped with fluorine (F) in the main material;

[0012] Fast ion conductivity layer, which is doped with O element in the host material;

[0013] The negative electrode stabilizing layer is doped with nitrogen (N) in the host material;

[0014] The fast ion conductivity layer is located between the positive electrode stabilization layer and the negative electrode stabilization layer; the main materials of the positive electrode stabilization layer, the fast ion conductivity layer and the negative electrode stabilization layer are the same solid halide electrolyte.

[0015] For example, the total thickness of the electrolyte film is 150 μm to 250 μm, and the ionic conductivity is not less than 1 × 10⁻⁶. -3 S / cm.

[0016] For example, the solid halide electrolyte is one of Li3InCl6, Li3YCl6 or Li2ZrCl6.

[0017] The present invention also provides a method for preparing an electrolyte thin film, comprising the following steps:

[0018] Step 1: Provide a solid halide electrolyte as the host material;

[0019] Step 2: Based on the same host material, dop it with F, O and N elements respectively to obtain host materials doped with F, host materials doped with O and host materials doped with N.

[0020] Step 3: Prepare slurries from the F-doped host material, the O-doped host material, and the N-doped host material, respectively;

[0021] Step 4: Three slurries are sequentially coated and dried on the substrate to form an electrolyte film with a three-layer stacked structure. The slurry of the O-doped host material is coated in the middle and dried to form a fast ion conductivity layer. The slurry of the F-doped host material is dried to form a positive electrode stabilizing layer. The slurry of the N-doped host material is dried to form a negative electrode stabilizing layer.

[0022] For example, in step 1, the method for synthesizing the solid halide electrolyte includes: dissolving and dispersing lithium halide and metal halide evenly, evaporating and drying to obtain a precursor, and then calcining the precursor under an inert atmosphere to obtain the final product.

[0023] For example, the lithium halide is LiCl, and the metal halide is one of InCl3, YCl3, or ZrCl4.

[0024] For example, when the metal halide is InCl3 or YCl3, its molar ratio with LiCl is 1:3; when the metal halide is ZrCl4, its molar ratio with LiCl is 1:2.

[0025] For example, the calcination temperature is 240-260°C and the calcination time is 3-5 hours.

[0026] For example, in step 2, the doping is performed by ball milling.

[0027] The present invention also provides a solid-state battery comprising a positive electrode, a negative electrode and the above-described electrolyte film.

[0028] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0029] This invention uses the same halide electrolyte as the main material and constructs a three-layer stacked structure of positive electrode stabilization layer - fast ion conductivity layer - negative electrode stabilization layer by layering different elements (F, O, N). Taking advantage of the similar mechanical properties of homogeneous materials and the fact that their electrochemical stability windows largely overlap, side reactions between electrolyte layers can be effectively suppressed and good contact can be maintained. At the same time, the performance can be complemented by functional doping of each layer.

[0030] Specifically, doping the positive electrode stabilizing layer with F near the positive electrode significantly increases the oxidation potential of the material, thereby enhancing its oxidation resistance. Doping the negative electrode stabilizing layer with N near the negative electrode significantly reduces the reduction potential of the negative electrode stabilizing layer material, thereby enhancing its reduction resistance and extending the material's stability window towards lower potentials. Compared with heterobilayer electrolytes, the Young's moduli of each layer are similar, and the interface bonding is tight, avoiding heterogeneous interface side reactions, thus improving interface stability. Furthermore, the electrochemical windows of each layer partially overlap, ensuring interface compatibility. The centrally located fast ion conductivity layer doped with O helps form an amorphous phase and a low-coordination Li-Cl structure, giving the fast ion conductivity layer high ionic conductivity. This compensates for the loss of ionic conductivity in the stabilizing layers (positive and negative electrode stabilizing layers), maintaining the overall ionic conductivity of the film at ~1×10⁻⁶. -3S / cm can replace the role of separator and electrolyte in traditional batteries, simplifying the battery structure and reducing the manufacturing cost and packaging difficulty.

[0031] This invention employs a solution coating method, resulting in a film thickness (200 μm) significantly lower than that of cold-pressed ceramic sheets (600 μm), effectively reducing the battery's internal resistance. More importantly, by introducing a nitrogen-doped negative electrode stabilizing layer, interfacial stability with the lithium metal negative electrode is achieved, thus retaining excellent resistance to lithium dendrite formation while achieving thin-film fabrication. Furthermore, the reduced electrolyte film thickness helps to decrease the mass and volume of the solid-state battery.

[0032] The preparation process of this invention features a simple flow, basic equipment, and easy operation control, thus improving the efficiency of solid halide electrolyte and its thin-film device fabrication. This invention employs a liquid-phase synthesis route to prepare solid halide electrolytes, which has lower energy consumption compared to solid-phase synthesis routes and allows for the recovery of In from waste liquid. 3+ Y 3+ It utilizes metal resources, reduces resource waste, and has good economic benefits. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a solid-state battery provided by the present invention.

[0034] Figure 2 Electrochemical impedance spectroscopy (EIS) of the electrolyte film prepared for the embodiments of the present invention. Detailed Implementation

[0035] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of the electrolyte film, its preparation method, and the solid-state battery proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the embodiments of this invention. Please refer to the drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0036] The main material described in this article refers to undoped, basic solid halide electrolytes. Specifically, it is formed by combining lithium halides (such as LiCl) and metal halides (such as InCl3, YCl3, or ZrCl4). For example, Li3InCl6 can be prepared from LiCl and InCl3 in a molar ratio of 3:1; Li3YCl6 can be prepared from LiCl and YCl3 in a molar ratio of 3:1; and Li2ZrCl6 can be prepared from LiCl and ZrCl4 in a molar ratio of 2:1.

[0037] The homogeneity mentioned in this article refers to the fact that all three thin films use the same host material (e.g., all use Li3InCl6), but different compounds (LiF, Li2O, Li3N) are added to achieve the doping of F, O or N elements, thereby giving each layer different functions (antioxidant, high ionic conductivity, anti-reduction), but the host substances of the electrolytes in each layer are the same or similar.

[0038] In homogeneous multilayer solid electrolyte films, the chemical properties of each layer are similar, such as the Young's modulus between layers being similar, thus allowing them to maintain good contact. However, the materials of different layers have some differences in certain specific properties, resulting in the electrolyte device as a whole possessing multiple properties.

[0039] This invention uses the same halide electrolyte (such as Li3InCl6) as a substrate and constructs a three-layer stacked structure—a positive electrode stabilizing layer, a fast ion conductivity layer, and a negative electrode stabilizing layer—by layering different elements (F, O, N) through layer-by-layer doping. The similar mechanical properties of the homogeneous materials ensure close contact between the layers, while functional doping of each layer achieves complementary performance. Specifically, each electrolyte layer is based on the same halide substrate, has similar chemical properties, and achieves close contact between the layers through van der Waals forces and mechanical interlocking. The doping elements function by altering the crystal structure: F doping raises the valence band position to enhance oxidation resistance; O doping introduces a disordered phase to promote lithium-ion migration; and N doping lowers the conduction band position to improve reduction resistance. When the three layers work synergistically, lithium ions are efficiently transported in the fast ion conductivity layer, while the stabilizing layers respectively block the oxidation / reduction reactions of the positive and negative electrodes, achieving a balance between high ion conductivity and interfacial stability.

[0040] like Figure 1 As shown, the present invention provides an electrolyte film with a three-layer stacked structure, disposed between the positive electrode 1 and the negative electrode 2, constituting a solid-state battery. The electrolyte film includes, in sequence, a positive electrode stabilizing layer 10, a fast ion conductivity layer 20, and a negative electrode stabilizing layer 30.

[0041] The positive electrode stabilizing layer 10 is disposed adjacent to the positive electrode 1. The positive electrode stabilizing layer 10 is doped with F, which can significantly increase the oxidation potential of the positive electrode stabilizing layer, thereby enhancing its oxidation resistance.

[0042] The fast ion conductivity layer 20 is located between the positive electrode stabilizing layer 10 and the negative electrode stabilizing layer 30. The fast ion conductivity layer 20 is doped with oxygen in the host material, which helps to form an amorphous phase and a low-coordination Li-Cl structure, thereby improving lithium-ion transport capability. This is sufficient to compensate for the ion transport capability sacrificed by the positive electrode stabilizing layer 10 and the negative electrode stabilizing layer 30 to enhance stability, so that the overall electrolyte film balances interfacial stability and high ion transport capability (not less than 1×10⁻⁶). -3 S / cm).

[0043] The negative electrode stabilizing layer 30 is disposed adjacent to the negative electrode. The doping of N in the negative electrode stabilizing layer 30 significantly reduces its reduction potential, thereby enhancing its resistance to reduction. Consequently, the electrolyte material in this layer (especially at the interface) is more difficult to be reduced by the lithium metal anode, resulting in a more stable interface between the negative electrode stabilizing layer 30 and the lithium metal anode 2. This stable interface not only prevents continuous electrolyte consumption and maintains the integrity of the interface structure, but also facilitates the uniform deposition / dissolution of lithium ions across the entire interface plane (rather than concentrating at certain weak points), fundamentally preventing excessively high local current densities and thus suppressing the nucleation and growth of lithium dendrites.

[0044] The positive electrode stabilizing layer 10, the fast ion conductivity layer 20, and the negative electrode stabilizing layer 30 are all made of the same solid halide electrolyte. This homogeneous three-layer stacked structure ensures that the mechanical properties (such as Young's modulus) of each layer are similar and that the interfaces are tightly bonded, avoiding the formation of new, fragile heterogeneous interfaces between layers. If the interlayer bonding is poor, lithium dendrites may grow along the interlayer gaps. Therefore, the homogeneous three-layer stacked structure provides a stable supporting environment for the effective functioning of the negative electrode stabilizing layer. This invention, through material design (different functional doping and homogeneous structure), reduces the total thickness of the electrolyte film while maintaining sufficient mechanical strength (such as high Young's modulus) to physically block dendrite penetration, i.e., retains the ability to resist lithium dendrite formation.

[0045] The total thickness of the electrolyte film is 150 μm to 250 μm, the thickness of the positive electrode stabilizing layer 10 is 20 μm to 50 μm, and the thickness of the negative electrode stabilizing layer 30 is 20 μm to 50 μm. The thickness ratio of the fast ion conductivity layer 20 to the positive electrode stabilizing layer 10 is 1.5:1 to 3:1; the thickness ratio of the fast ion conductivity layer 20 to the negative electrode stabilizing layer 30 is also 1.5:1 to 3:1. For example, the thickness of the fast ion conductivity layer 20 is 100 μm, the thickness of the positive electrode stabilizing layer 10 is 50 μm, and the thickness of the negative electrode stabilizing layer 30 is 50 μm.

[0046] The present invention also provides a method for preparing an electrolyte thin film, comprising the following steps:

[0047] Step 1: Provide a solid halide electrolyte as the host material.

[0048] The method for synthesizing the solid halide electrolyte includes: dissolving and dispersing lithium halide and metal halide evenly; for example, deionized water can be added for dissolution and dispersion. Then, the precursor is obtained by evaporation and drying, and subsequently calcined under an inert atmosphere. The calcination temperature is 240-260℃, and the calcination time is 3-5 hours.

[0049] The lithium halide is LiCl, and the metal halide is one of InCl3, YCl3, or ZrCl4. When the metal halide is InCl3 or YCl3, its molar ratio with LiCl is 1:3; when the metal halide is ZrCl4, its molar ratio with LiCl is 1:2.

[0050] Step 2 involves doping the same host material with F, O, and N elements respectively to obtain F-doped host materials, O-doped host materials, and N-doped host materials. As an example, the doping is performed using a ball milling method.

[0051] Step 3: Prepare slurries from the F-doped, O-doped, and N-doped host materials, respectively. For example, a binder and a solvent can be added to the doped host materials, and the mixture can be dispersed and mixed to form a slurry.

[0052] Step 4: Three slurries are sequentially coated and dried on the substrate to form an electrolyte film with a three-layer stacked structure. The slurry of the O-doped host material is coated in the middle and dried to form a fast ion conductivity layer. The slurry of the F-doped host material is dried to form a positive electrode stabilizing layer. The slurry of the N-doped host material is dried to form a negative electrode stabilizing layer.

[0053] In some embodiments, a slurry of a host material doped with F can be coated first and dried to form a positive electrode stabilizing layer; then a slurry of a host material doped with O can be coated and dried to form a fast ion conductivity layer; finally, a slurry of a host material doped with N can be coated and dried to form a negative electrode stabilizing layer.

[0054] In other embodiments, a slurry of N-doped host material may be applied first and dried to form a negative electrode stabilizing layer; then an O-doped host material slurry may be applied and dried to form a fast ion conductivity layer; finally, an F-doped host material slurry may be applied and dried to form a positive electrode stabilizing layer.

[0055] The following detailed description is provided in conjunction with specific examples.

[0056] Example

[0057] Weigh out LiCl and InCl3 in a molar ratio of LiCl:InCl3 = 3:1 and dissolve them in deionized water. Place the solution in a vacuum oven at 80 °C and let it stand for 4 h until the liquid is completely evaporated. Then, turn on the vacuum system to a vacuum level of −0.1 MPa and maintain the temperature at 80 °C for another 4 h. After removing the container, immediately place it in a vacuum bag and evacuate it. Transfer it to a dry environment and open it. Place the solid in a mortar and grind it into powder. Transfer it to a crucible and place it in a tube furnace. Heat the furnace under an argon atmosphere at a rate of 2 °C / min to 250 °C and maintain the temperature for 4 h to obtain Li3InCl6 solid halide electrolyte, which will be used as the main material.

[0058] Li3InCl6 and LiF were weighed at a mass ratio of 10:1 and placed in a ZrO2 ball mill jar. The mixture was then ball-milled at 1000 rpm for 4 hours in a planetary ball mill to obtain a Li-In-Cl-F (F-doped) solid halide electrolyte. Subsequently, two equal masses of Li3InCl6 were weighed, and Li2O and Li3N were weighed at mass ratios of Li3InCl6:Li2O = 10:1 and Li3InCl6:Li3N = 10:1, respectively. These were then placed in ZrO2 ball mill jars, and the above operation was repeated to obtain Li-In-Cl-O (O-doped) and Li-In-Cl-N (N-doped) solid halide electrolytes, respectively.

[0059] Weigh ACN, PVDF, and Li-In-Cl-F solid halide electrolyte at a mass ratio of ACN:PVDF:doped solid halide electrolyte = 10:1:1. Mix PVDF and Li-In-Cl-F, then add ACN. Stir at 500 rpm for 12 h on a magnetic stirring table until a pale yellow viscous liquid forms a slurry. Pour the slurry onto a PET plate, adjust the thickness of the adjustable coating tool to 50 μm, and coat evenly. Then place the PET plate in a vacuum oven, evacuate to a vacuum level of −0.1 MPa, and place at 60℃ for 4 h. The resulting Li-In-Cl-F solid halide electrolyte film is then obtained. Subsequently, Li-In-Cl-O and Li-In-Cl-N are sequentially coated onto the surface of the solid electrolyte film with the same thickness parameters to obtain a homogeneous multilayer solid halide electrolyte film.

[0060] The EIS image of the electrolyte film prepared in the embodiments of the present invention is shown below. Figure 2 As shown. The equivalent circuit obtained by fitting the EIS diagram using specialized software shows the charge transfer resistance R of the thin film. ct The Ω is 24.68, and the calculated ionic conductivity is 1.03 × 10⁻⁶. -3The S / cm figure demonstrates that the bulk ionic conductivity of the same host material (Li-In-Cl based halide electrolyte) can be significantly modulated by doping it with different elements (F, O, N).

[0061] In summary, the homogeneous multifunctional electrolyte thin film prepared by this invention, through doping the same host material with F, O, and N functional elements respectively, forms a three-layer stacked structure thin film with different functional divisions. It possesses the advantages of both high ionic conductivity and a wide electrochemical window, making it suitable for the manufacture of high-energy-density, high-safety solid-state batteries. Furthermore, the liquid-phase synthesis method has low energy consumption, the waste liquid can be recycled for metal resources, and the coating process is simple and controllable.

[0062] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0063] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0064] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. An electrolyte film, characterized by, The electrolyte thin film has a three-layer stacked structure, comprising: a positive electrode stabilizing layer doped with F elements in a host material; a fast ion conductive layer doped with O elements in a host material; a negative electrode stabilizing layer doped with N elements in a host material; wherein the fast ion conductive layer is located between the positive electrode stabilizing layer and the negative electrode stabilizing layer; the host materials of the positive electrode stabilizing layer, the fast ion conductive layer and the negative electrode stabilizing layer are the same solid-state halide electrolyte; the thickness ratio of the fast ion conductive layer to the positive electrode stabilizing layer is 1.5:1-3:1; the thickness ratio of the fast ion conductive layer to the negative electrode stabilizing layer is 1.5:1-3:

1.

2. The electrolyte film according to claim 1, wherein The total thickness of the electrolyte thin film is 150 μm-250 μm.

3. The electrolyte film of claim 1, wherein The solid-state halide electrolyte is one of Li3InCl6, Li3YCl6 or Li2ZrCl6.

4. A method for producing the electrolyte film according to any one of claims 1 to 3, characterized by, The method comprises the following steps: Step 1, providing a solid-state halide electrolyte as a host material; Step 2, doping F elements, O elements and N elements in the same host material respectively to obtain the host material doped with F elements, the host material doped with O elements and the host material doped with N elements; Step 3, preparing slurries of the host material doped with F elements, the host material doped with O elements and the host material doped with N elements respectively; Step 4, coating and drying the three kinds of slurries on a substrate in sequence to form an electrolyte thin film with a three-layer stacked structure, wherein the slurry of the host material doped with O elements is coated in the middle, and the slurry of the host material doped with F elements is dried to form a positive electrode stabilizing layer, and the slurry of the host material doped with N elements is dried to form a negative electrode stabilizing layer.

5. The method for producing an electrolyte film according to claim 4, wherein In step 1, the synthesis method of the solid-state halide electrolyte comprises: dissolving and dispersing lithium halide and metal halide uniformly, drying to obtain a precursor, and calcining the precursor under an inert atmosphere.

6. The method for producing an electrolyte film according to claim 5, wherein The lithium halide is LiCl, and the metal halide is one of InCl3, YCl3 or ZrCl4.

7. The method for producing an electrolyte film according to claim 6, wherein When the metal halide is InCl3 or YCl3, the molar ratio of the metal halide to LiCl is 1:3; when the metal halide is ZrCl4, the molar ratio of the metal halide to LiCl is 1:

2.

8. The method for producing an electrolyte film according to claim 5, wherein The calcination temperature is 240-260°C, and the calcination time is 3-5h.

9. The method for producing an electrolyte film according to claim 4, wherein In step 2, the doping is performed by a ball milling method.

10. A solid state battery, characterized by The battery comprises a positive electrode, a negative electrode and an electrolyte thin film as described in any one of claims 1-3.

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