Halide-based solid electrolyte, preparation method thereof and application of halide-based solid electrolyte in solid-state lithium ion battery

Abstract

The invention discloses a halide-based solid electrolyte, a preparation method thereof and application of the halide-based solid electrolyte in a solid-state lithium ion battery. The halide-based solid electrolyte is composed of a halide solid electrolyte Li2ZrCl6 and a three-dimensional perfluoroalkyl chain modified covalent organic framework partially coated on the surface of the halide solid electrolyte Li2ZrCl6, and is prepared by high-speed ball milling. According to the halide-based solid electrolyte disclosed by the invention, the contact among solid electrolyte particles and the interface contact between the solid electrolyte and a positive electrode are improved, and a solid lithium ion battery assembled by the halide-based solid electrolyte has higher ionic conductivity and more excellent cycle performance and shows good electrochemical performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of solid-state lithium ion batteries, and particularly relates to a halide-based solid-state electrolyte, a preparation method thereof and application thereof in solid-state lithium ion batteries. BACKGROUND

[0002] In recent years, all-solid-state lithium batteries have become a promising next-generation energy storage technology due to their high energy density and high safety. As a key material, solid-state electrolytes with high room-temperature lithium ion conductivity, electrochemical stability and electrode material compatibility are crucial for practical applications. However, polymer solid-state electrolytes (such as polyethylene oxide) have poor thermal stability, oxide solid-state electrolytes (such as Li7La3Zr2O12) require high-temperature sintering and have poor processing performance, and sulfide solid-state electrolytes (such as Li10GeP2S12) have poor compatibility with positive electrodes and are prone to moisture decomposition to produce toxic gases, which limits their further application (Wu J, Li J, Yao X. Exploring the Potential of Halide Electrolytes for Next-Generation All-Solid-State Lithium Batteries [J]. Advanced Functional Materials, 2025, 35(10): 2416671.). 12 10 12 However, the high room-temperature ion conductivity (> 10 -4 S cm -1 ), good deformability, simple synthesis, stability to 4V high-voltage positive electrodes, and theoretically monovalent halide anions compared to divalent S 2- 、O 2- ​​Lithium ions have less binding and larger ionic radius, and the anion lattice lithium ion migration barrier has intrinsic advantages (Li C, Du Y. Building a Better All-Solid-State Lithium-Ion Battery with Halide Solid-State Electrolyte[J]. ACS nano, 2025, 19(4): 4121-4155.). Zirconium-based halide solid-state electrolytes represented by Li2ZrCl6 have outstanding cost advantages and certain humidity resistance, but the contact between halide solid-state electrolytes and positive electrodes is poor, which limits the cycle stability (Wang K, Ren Q, Gu Z, et al. A cost-effective and humidity-tolerant chloride solid electrolyte for lithium batteries[J]. Nature Communications, 2021, 12(1):4410.).

[0003] Stable and flexible contact between electrolyte-electrolyte and electrode-electrolyte interfaces can avoid electrode and electrolyte structure damage and prolong battery cycle life, which plays an important role in achieving high energy density batteries. Previous studies have shown that the gas-solid reaction to construct fluoride-coated Li2ZrCl6 (i.e. LiF-ZrF4@Li2ZrCl6) stabilizes the interface contact and has excellent cycle stability and rate capability (Liu H, Li Y, Dong C, et al. Fluorinated coating stabilizing halide solid electrolytes for all-solid-state lithium metal batteries[J]. Energy Storage Materials, 2025, 75: 104107.). Chinese patent CN 117976967 A discloses a polymer-coated halide solid-state electrolyte, which improves the stability of halide solid-state electrolyte to metal lithium. However, these coatings have problems such as complex process and the interface contact with the positive electrode is expected to be further improved.

[0004] Covalent organic frameworks (COF) are porous crystalline materials constructed from light-weight organic building blocks (including C, N, O, H, B, etc.) connected by dynamic covalent bonds, with characteristics of regular directional channels, high specific surface area and structural functionalization. Covalent organic frameworks have excellent ion conductivity, and the covalently cross-linked polymer skeleton endows the material with excellent mechanical properties and low electronic conductivity, which is expected to become an ideal coating layer, thereby realizing stable long-cycle behavior and good reversible rate performance of the battery (Zhao Z, Wang R, Peng C, et al. Horizontally arranged zinc plateletelectrodeposits modulated by fluorinated covalent organic framework film for high-rate and durable aqueous zinc ion batteries[J]. Nature communications, 2021, 12(1): 6606.). Chinese patent CN 115926080 A discloses a three-dimensional perfluoroalkyl chain modified covalent organic framework, which is a three-dimensional quadrilateral topological structure synthesized by connecting two aldehyde groups of 2,5-bis (perfluoroalkyl) -triphenyl-para-dimethyl formaldehyde and four amino groups of tetra (4-aminophenyl) methane to form a -C=N- covalent bond. It has good flexibility and better ability to promote lithium salt dissociation, but there is no research report on using it as a coating layer. SUMMARY

[0005] The present application aims to provide a halide-based solid-state electrolyte and its preparation method and application in solid-state lithium ion batteries. By coating a covalent organic framework on the halide solid-state electrolyte, the present application improves the contact between solid-state electrolyte particles and the interface stability between the solid-state electrolyte and the positive electrode material, thereby improving the cycle performance of the prepared solid-state battery.

[0006] The technical solution to achieve the purpose of the present application is as follows:

[0007] A halide-based solid-state electrolyte, which is composed of a halide solid-state electrolyte and a covalent organic framework coated on the surface of the halide solid-state electrolyte, wherein the halide solid-state electrolyte is Li2ZrCl6, and the covalent organic framework is a three-dimensional perfluoroalkyl chain modified covalent organic framework (3D-COF-F4 or 3D-COF-F6), and its structural formula is:

[0008] (3D-COF-F4) or

[0009] (3D-COF-F6).

[0010] Preferably, the added mass fraction of the covalent organic framework is 1%-3%.

[0011] The preparation method of the halide-based solid-state electrolyte comprises the following steps: grinding and mixing the halide solid-state electrolyte and the covalent organic framework, and then performing high-energy ball milling to obtain the halide-based solid-state electrolyte.

[0012] Preferably, the rotation speed of the high-energy ball milling is 450-700 rpm.

[0013] Preferably, the high-energy ball milling time is 6-12 h.

[0014] The halide-based solid-state electrolyte is applied to a solid-state lithium ion battery.

[0015] A solid-state lithium ion battery comprises a positive electrode, the halide-based solid-state electrolyte, and a negative electrode.

[0016] The positive electrode is a common positive electrode material in a solid-state lithium ion battery, and is preferably a positive electrode composed of LiCoO2, Li2ZrCl6, vapor-grown carbon fiber, and a binder. In the specific embodiment of the present application, the mass ratio of LiCoO2, Li2ZrCl6, and vapor-grown carbon fiber is 50:50:5, the binder is polytetrafluoroethylene, and the added amount of the binder is 1wt.%.

[0017] The negative electrode is a common negative electrode material in a solid-state lithium ion battery, and is preferably a Li-In alloy.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] (1) The halide-based solid-state electrolyte of the present application at least partially coats the covalent organic framework on the basis of the halide solid-state electrolyte, and through the synergistic effect of the halide solid-state electrolyte and the covalent organic framework, it has a relatively ideal ionic conductivity.

[0020] (2) The present application uses a high-energy ball milling process to partially coat the covalent organic framework on the surface of the halide solid-state electrolyte. This method has the advantages of simplicity, low cost, and ease of improvement, and can obtain a solid-state electrolyte with higher ionic conductivity.

[0021] (3) The solid-state lithium ion battery of the present application has improved contact between solid-state electrolyte particles and interface contact between the solid-state electrolyte and the positive electrode, improved cycle performance, and good electrochemical performance. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1XRD pattern of Li2ZrCl6 without coating 3D-COF-F6 in Comparative Example 1;

[0023] Figure 2 XRD refinement pattern of 3D-COF-F6 in Example 1;

[0024] Figure 3 XRD pattern of Li2ZrCl6 coated with 1 wt.% 3D-COF-F6 in Example 1;

[0025] Figure 4 EDS pattern of Li2ZrCl6 coated with 1 wt.% 3D-COF-F6 in Example 1;

[0026] Figure 5 Temperature-dependent ionic conductivity plot of Li2ZrCl6 without coating 3D-COF-F6 in Comparative Example 1;

[0027] Figure 6 Temperature-dependent ionic conductivity plot of Li2ZrCl6 coated with 1 wt.% 3D-COF-F6 in Example 1;

[0028] Figure 7 Temperature-dependent EIS plot of Li2ZrCl6 coated with 1 wt.% 3D-COF-F6 in Example 1;

[0029] Figure 8 XRD refinement pattern of 3D-COF-F4 in Example 2;

[0030] Figure 9 Temperature-dependent ionic conductivity plot of Li2ZrCl6 coated with 1 wt.% 3D-COF-F4 in Example 2;

[0031] Figure 10 Temperature-dependent ionic conductivity plot of Li2ZrCl6 coated with 3 wt.% 3D-COF-F6 in Example 3;

[0032] Figure 11 SEM image of 3D-COF-F6 mixed phase with Li2ZrCl6 without high-energy ball milling in Comparative Example 2;

[0033] Figure 12 Temperature-dependent EIS plot of Li2ZrCl6 coated with 10 wt.% 3D-COF-F6 in Comparative Example 3;

[0034] Figure 13 Full-cell long cycle plot of solid-state lithium-ion battery assembled based on Li2ZrCl6 without coating 3D-COF-F6 in Comparative Example 2 at 25 °C, 0.2C rate;

[0035] Figure 14 Full cell long cycle plots of the solid-state lithium ion battery assembled based on the Li2ZrCl6 coated with 3D-COF-F6 in Example 2 at 25℃, 0.2C cycled for 50 cycles, 0.33C cycled for 100 cycles. DETAILED DESCRIPTION

[0036] The technical solutions of the present application will be further described in detail below in combination with several embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor shall fall within the scope of protection of the present application.

[0037] The three-dimensional perfluoroalkyl chain modified covalent organic frameworks (3D-COF-F4, 3D-COF-F6) used in the following examples were prepared according to Chinese Patent CN 115926080 A, and were formed by Schiff base reaction of tetra(4-aminophenyl)methane and 2,5-bis(perfluorobutyl)-terphenyl-p-diform, tetra(4-aminophenyl)methane and 2,5-bis(perfluorohexyl)-terphenyl-p-diform, respectively, and their structures are shown as follows:

[0038]

[0039]

[0040] Example 1

[0041] A halide-based solid-state electrolyte composed of Li2ZrCl6 and 3D-COF-F6 partially coated on the surface of Li2ZrCl6 was prepared by the following steps:

[0042] (1) Preparation of halide solid-state electrolyte Li2ZrCl6: Anhydrous LiCl and ZrCl4 were weighed according to the stoichiometric ratio, and the mass ratio of zirconia milling beads to powder was 30:1. The mixture was placed in a zirconia milling jar under inert atmosphere protection, and was ball-milled at a speed of 500 rpm for 5 minutes, then stopped for 10 minutes, and the cycle was repeated. The total time was 40 hours.

[0043] (2) Preparation of covalent organic framework 3D-COF-F6: Refer to Chinese Patent CN 115926080 A for preparation.

[0044] ​​(3) Coating: A certain amount of 3D-COF-F6 was weighed in an agate mortar and ground for 5 minutes, then Li2ZrCl6 was added to make the mass ratio of 3D-COF-F6 to Li2ZrCl6 1:99, and the mixture was ground for 15 minutes. Zirconium oxide balls with a mass ratio of 30:1 to the powder were placed in a zirconium oxide ball mill tank under inert atmosphere protection, and the mixture was ball milled at a speed of 700 rpm for 12 h to obtain a halide-based solid-state electrolyte, labeled as 3D-COF-F6@Li2ZrCl6.

[0045] Example 2

[0046] A halide-based solid-state electrolyte composed of Li2ZrCl6 and 3D-COF-F4 partially coated on the surface of Li2ZrCl6, prepared in the same way as Example 1, the only difference being that the coating layer was changed from 3D-COF-F6 to 3D-COF-F4.

[0047] Example 3

[0048] A halide-based solid-state electrolyte composed of Li2ZrCl6 and 3D-COF-F6 partially coated on the surface of Li2ZrCl6, prepared in a similar manner to Example 1, with the difference being that the mass ratio of 3D-COF-F6 to Li2ZrCl6 was 3:97, the high-energy ball milling speed was 450 rpm, and the high-energy ball milling time was 6 h.

[0049] Comparative Example 1

[0050] Comparative Example 1 differs from Example 1 in that the halide solid-state electrolyte Li2ZrCl6 is not coated with covalent organic framework 3D-COF-F6.

[0051] Comparative Example 2

[0052] Comparative Example 2 differs from Example 1 in that the halide solid-state electrolyte Li2ZrCl6 and the covalent organic framework 3D-COF-F6 are mixed by manual grinding in an agate mortar for 15 minutes, without high-energy ball milling.

[0053] Comparative Example 3

[0054] Comparative Example 3 differs from Example 1 in that the mass ratio of 3D-COF-F6 to Li2ZrCl6 is 10:90.

[0055] Example 4

[0056] A solid-state lithium ion battery comprising a positive electrode, a solid-state electrolyte, and a negative electrode, constructed by the following steps:

[0057] (1) Preparation of positive electrode material: LiCoO2 (LCO), Li2ZrCl6 and vapor-grown carbon fiber with a mass ratio of 50:50:5 were weighed and ground in an agate mortar for 30 minutes to mix thoroughly. Then, 1% by mass of polytetrafluoroethylene was added and rolled into a film with a thickness of about 100 μm. The film was cut into 8 mm diameter discs for later use. The mass of positive electrode active material was about 4 mg.

[0058] (2) The solid electrolyte is the halide-based solid electrolyte prepared in Example 1.

[0059] (3) The negative electrode is a Li-In alloy.

[0060] (4) Solid-state battery assembly: The positive electrode film, 60 mg of halide-based solid electrolyte powder, 35 mg of LiPSCl6 powder, and In foil were stacked sequentially in a slit mold and held under pressure of 3 tons for 5 minutes. Finally, Li foil was stacked on top of the In foil and assembled into a button cell, which was then placed in a test fixture. A torque of 3 N / m was applied using a torque wrench, allowing the solid-state battery to undergo charge-discharge testing at approximately 0.4 tons of pressure. The entire process was conducted inside a glove box.

[0061] Comparative Example 4

[0062] A solid-state lithium-ion battery, with the same composition and preparation method as Example 4, except that the halide-based solid electrolyte 3D-COF-F6@Li2ZrCl6 is replaced with the Li2ZrCl6 halide solid electrolyte prepared in Comparative Example 1.

[0063] The conductivity of the solid electrolytes prepared in Examples 1, 2, 3, and Comparative Example 1 was tested. The specific testing method was as follows: 100 mg of solid electrolyte material was placed in a ceramic sleeve, and a pressure of 3 tons was applied using a mold pressurizing device. The powder impedance was then measured. According to the formula... , where σ is the conductivity, l is the thickness of the powder after compression, S is the surface area of ​​the powder after compression, and R is the measured impedance value.

[0064] like Figure 1 As shown, the XRD pattern of Li2ZrCl6 in Example 1 contains the corresponding characteristic peaks, indicating successful synthesis.

[0065] like Figure 2 As shown, the XRD pattern of 3D-COF-F6 in Example 1 contains the corresponding characteristic peaks and the test results are consistent with the simulation results, indicating that the synthesis was successful.

[0066] like Figure 3 As shown, the XRD pattern of the halide-based solid electrolyte after coating in Example 1 contains characteristic peaks of 3D-COF-F6 and Li2ZrCl6, indicating that both maintain structural stability during high-energy ball milling.

[0067] like Figure 4 As shown, the halide-based solid electrolyte coated with 3D-COF-F6 in Example 1 exhibits good and uniform coating effect under EDS spectroscopy.

[0068] like Figure 5 As shown, the ionic conductivity of the halide solid electrolyte in Comparative Example 1 is 0.31 mS / cm at room temperature.

[0069] like Figure 6 As shown, the ionic conductivity of the halide-based solid electrolyte in Example 1 increased to 0.54 mS / cm at room temperature compared to Comparative Example 1. This is because the 3D-COF-F6 coating provides better interfacial contact and improves ion transport to some extent.

[0070] like Figure 7 As shown, the EIS spectrum of the halide-based solid electrolyte in Example 1 shows that it has a small impedance when cold-pressed into sheets. This is because the 3D-COF-F6 coating layer provides a certain degree of flexibility, which improves the contact between electrolyte particles.

[0071] like Figure 8 As shown, the XRD pattern of 3D-COF-F4 in Example 2 contains the corresponding characteristic peaks and the test results are consistent with the simulation results, indicating that the synthesis was successful.

[0072] like Figure 9 As shown, the ionic conductivity of the halide-based solid electrolyte in Example 2 increased to 0.52 mS / cm at room temperature compared to Comparative Example 1. This is because the 3D-COF-F4 coating layer is similar to 3D-COF-F6 and can provide better interfacial contact. However, the shorter F side chain makes the flexibility of the covalent organic framework slightly lower than that of 3D-COF-F6, so the room temperature ionic conductivity is slightly lower than that of Example 1.

[0073] like Figure 10 As shown, the ionic conductivity of the halide-based solid electrolyte in Example 3 increased to 0.40 mS / cm at room temperature compared to Comparative Example 1. This is because the 3D-COF-F6 coating layer provided better interfacial contact. The improvement effect was slightly lower than that in Example 1 because the 3D-COF-F6, which has a relatively low ionic conductivity, occupied a larger mass fraction. The lower ball milling speed and shorter time resulted in a poorer coating effect, and the overall improvement effect was not as good as that in Example 1.

[0074] like Figure 11As shown, the SEM image of the halide-based solid electrolyte in Comparative Example 2, which was mixed only by manual grinding without high-energy ball milling, shows that the 3D-COF-F6 is not fine enough and is inserted into the surface of the cold-pressed Li2ZrCl6 particles in a large sheet-like form, without forming a coating effect.

[0075] like Figure 12 As shown in the EIS spectrum of Comparative Example 3, adding excessive covalent organic frameworks will have a significant negative impact on the overall ionic conductivity due to the relatively low ionic conductivity of the covalent organic frameworks, resulting in increased impedance.

[0076] like Figure 13 As shown, the full cell in Comparative Example 1 exhibits high capacity decay after 70 cycles at 25°C and a 0.2C rate, with a capacity retention rate (CRR) of 70.28%. This is due to poor contact at the solid electrolyte interface under lower pressure (0.4 T) and the significant negative impact of volume changes in the cathode particles during cycling.

[0077] like Figure 14 As shown, the solid-state lithium-ion battery in Example 1 retained 81.12% of its capacity after 50 cycles at 0.2C and 100 cycles at 0.33C at 25°C. This is because the 3D-COF-F6 coating layer improves the contact between the solid electrolytes, stabilizes the interface between the electrolyte and the positive electrode, and avoids adverse interfacial reactions and mechanical failures, thus significantly improving the battery's cycle performance.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. 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 halide-based solid electrolyte, characterized in that, It consists of a halide solid electrolyte and a covalent organic framework partially coated on its surface. The halide solid electrolyte is Li₂ZrCl₆, and the covalent organic framework is a three-dimensional perfluoroalkyl chain modified covalent organic framework 3D-COF-F₄ or 3D-COF-F₆, with the following structural formula: or 。 2. The halide-based solid electrolyte according to claim 1, characterized in that, The mass fraction of added covalent organic frameworks is 1%-3%.

3. The method for preparing a halide-based solid electrolyte according to claim 1 or 2, characterized in that, Includes the following steps: The halide-based solid electrolyte was prepared by grinding and mixing the halide solid electrolyte with a covalent organic framework and then ball milling it with high energy.

4. The preparation method according to claim 3, characterized in that, The high-energy ball mill speed is 450-700 rpm.

5. The preparation method according to claim 3, characterized in that, The high-energy ball milling time is 6-12 hours.

6. The application of the halide-based solid electrolyte according to claim 1 or 2 in solid-state lithium-ion batteries.

7. A solid-state lithium-ion battery, characterized in that, It includes a positive electrode, a halide-based solid electrolyte as described in claim 1 or 2, and a negative electrode.

8. The solid-state lithium-ion battery according to claim 7, characterized in that, The cathode is composed of LiCoO2, Li2ZrCl6, vapor-grown carbon fibers and binder.

9. The solid-state lithium-ion battery according to claim 8, characterized in that, The mass ratio of LiCoO2, Li2ZrCl6, and vapor-grown carbon fiber is 50:50:5, and the binder is polytetrafluoroethylene, with an addition amount of 1 wt.%.

10. The solid-state lithium-ion battery according to claim 7, characterized in that, The negative electrode is a Li-In alloy.

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