Coated halide solid electrolyte and preparation method and application thereof

Abstract

The invention discloses a coated halide solid electrolyte as well as a preparation method and application thereof, and relates to the technical field of battery materials. The solid electrolyte comprises a halide electrolyte and a composite coating material coated on the surface of the halide electrolyte, the halide electrolyte is trilithiated indium hexachloroindate, and the composite coating material comprises lithium zirconate and lithium fluoride in a mass ratio of (1-2): (2-1). The lithium zirconate-lithium fluoride composite coating layer is constructed on the surface of the halide electrolyte, so that moisture-proof sealing and interface isolation of the LIC are realized, the problem that the halide electrolyte in a dry-method positive electrode is easy to lose efficacy is solved, and the comprehensive performance of the all-solid-state battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery materials, in particular to a coated halide solid-state electrolyte and a preparation method and application thereof. BACKGROUND

[0002] Among solid-state electrolyte materials, sulfide solid-state electrolytes (such as lithium phosphorus sulfide chloride Li6PS5Cl, LPSC) have a room-temperature ionic conductivity as high as 10 -3 -10 -2 S / cm and good mechanical compliance, but have the problem of insufficient electrochemical stability at the high-voltage positive electrode interface, which is prone to side reactions with high-potential positive electrode materials, resulting in increased interface impedance and cycle performance degradation. Halide solid-state electrolytes (such as Li3InCl6, LIC) are of interest due to their wide electrochemical stability window and good compatibility with high-nickel positive electrode materials. The use of halide electrolytes in combination with sulfide electrolytes can take into account both high ionic conductivity and interface stability. The introduction of halide electrolyte LIC is expected to improve the interface contact and stability between NCM positive electrodes and LPSC electrolytes.

[0003] However, LIC is highly sensitive to environmental humidity, and Li3InCl6 exposed to air will rapidly absorb moisture, undergo hydrolysis to generate byproducts such as In2O3, LiCl and HCl, and the remaining portion forms hydrate Li3InCl6·xH2O, resulting in a decrease in ionic conductivity and corrosion of the positive electrode interface. Secondly, in the presence of trace amounts of moisture, halide and sulfide contact may occur anion exchange or decomposition reaction to generate non-conductive products such as indium sulfide (In2S3), which weakens the ion transport channel, increases the interface impedance, and leads to battery capacity attenuation. Existing interface modification methods cannot effectively solve the problem of moisture absorption of LIC and its interface side reactions when coexisting with sulfide electrolytes.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The present application aims to provide a coated halide solid-state electrolyte and a preparation method and application thereof. By constructing a lithium zirconate-lithium fluoride composite coating layer on the surface of the halide electrolyte, the moisture-proof sealing and interface isolation of the halide electrolyte are achieved, the problem of easy failure of halide electrolytes in dry positive electrodes is solved, and the comprehensive performance of the all-solid-state battery is improved.

[0006] The present application is implemented as follows: In a first aspect, the present application provides a coated halide solid-state electrolyte, the solid-state electrolyte comprising a halide electrolyte and a composite coating material coated on the surface of the halide electrolyte, wherein the halide electrolyte is trilithiated indium hexachloroindate, and the composite coating material comprises lithium zirconate and lithium fluoride in a mass ratio of (1-2):(2-1).

[0007] In some preferred embodiments, the mass ratio of the composite coating material to the halide electrolyte is (1-10):100.

[0008] In some preferred embodiments, the thickness of the composite coating material is 50-100 nm.

[0009] In a second aspect, the present application provides a preparation method of a coated halide solid-state electrolyte, comprising the following steps: After the anhydrous lithium carbonate and the zirconium oxide powder are uniformly mixed and ground, they are calcined in air at 800-1000℃ for 5-10 hours, and then ball-milled after cooling to obtain lithium zirconate powder; After the lithium zirconate powder and the lithium fluoride powder are mixed in a certain proportion, they are ball-mixed to obtain a composite powder; Under the protection of an inert gas, the halide electrolyte powder and the composite powder are uniformly mixed in a certain proportion, and high-speed dispersion mixing is performed to make the composite powder adhere to the surface of the halide electrolyte particles to form a coating structure, thereby obtaining the coated halide solid-state electrolyte.

[0010] In some preferred embodiments, the mixing speed of the high-speed dispersion mixing is 1500-3000 rpm, and the mixing time is >24 h.

[0011] In some preferred embodiments, the preparation method further comprises the following step: adding a volatile organic solvent spray during the high-speed dispersion mixing, and performing drying treatment after the mixing is completed to obtain the coated halide solid-state electrolyte.

[0012] In some preferred embodiments, the volatile organic solvent is anhydrous ethanol, and the addition amount is 40-60 ml; the drying treatment is vacuum drying, the drying temperature is 100-120℃, and the drying time is 4-6 h.

[0013] In some preferred embodiments, the temperature during the high-speed dispersion mixing process is 25-100℃.

[0014] In a third aspect, the present application provides a use of a coated halide solid-state electrolyte in the preparation of a positive electrode.

[0015] In some preferred embodiments, the step of preparing the positive electrode comprises: mixing the positive electrode material, the coated halide solid-state electrolyte, the sulfide solid-state electrolyte, the conductive agent and the binder in proportion, uniformly grinding by dry method, then laying and cold-pressing to form a composite positive electrode sheet.

[0016] The present application has the following beneficial effects: The present application realizes the moisture-proof sealing and interface isolation of the halide electrolyte by constructing a lithium zirconate-lithium fluoride composite coating layer on the surface of the halide electrolyte, while ensuring efficient transmission of lithium ions and preventing the interface impedance from rising due to a single insulating coating, so that the halide electrolyte after composite coating can still maintain stable cycle performance and low interface resistance under high SOC conditions, and finally realizes the synergistic improvement of energy density, cycle life and safety of the all-solid-state battery. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0018] Figure 1 The above is the schematic diagram of the coating effect in the embodiments of the present application and the scanning electron microscope image of the halide electrolyte after coating. Figure 2 The above is the X-ray powder diffraction pattern (XRD) of the battery positive electrode in the embodiments of the present application. Figure 3 The above is the X-ray photoelectron spectroscopy (XPS) of the battery positive electrode in the embodiments of the present application. Figure 4 The above is the cathode-electrolyte interface phase analysis diagram (RIS) in the embodiments of the present application. Figure 5 The above is the electrochemical impedance spectrogram (EIS) of the embodiments of the present application and the comparative examples. Figure 6 The above is the voltage-capacity curve of the embodiments of the present application and the comparative examples. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely. The specific conditions are not specified in the embodiments, and are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be purchased on the market.

[0020] According to research findings, halide solid-state electrolytes (such as Li3InCl6, LIC) exposed to air will rapidly absorb moisture and undergo hydrolysis to generate byproducts such as In2O3, LiCl, and HCl, and the remaining portion forms hydrate Li3InCl6 xH2O, resulting in a significant decrease in ionic conductivity. Although LIC exhibits relatively good stability in a low-humidity dry environment, it is difficult to completely avoid the presence of trace amounts of moisture during battery manufacturing and use. Once LIC absorbs moisture and decomposes, not only does its own conductivity decrease, but the corrosive products such as HCl released also damage the positive electrode component interface. LIC and sulfide solid-state electrolytes (such as lithium phosphorus sulfide chloride Li6PS5Cl, LPSC) and positive electrode active materials NCM still have the risk of interface side reactions. Especially in the presence of trace amounts of moisture, halide and sulfide contact may occur anion exchange or decomposition reaction, generating non-conductive products such as indium sulfide (In2S3), weakening the ion transport channel, increasing the interface impedance, and leading to battery capacity attenuation. The problem of moisture sensitivity and hygroscopic decomposition of halide electrolyte LIC in existing dry method composite cathodes, as well as the problem of performance degradation caused by interface reactions between LIC and sulfide electrolyte LPSC and positive electrode active material NCM have not been effectively solved.

[0021] Based on the above problems, the present application provides a coated halide solid-state electrolyte, the coating effect is as shown in Figure 1 The solid-state electrolyte includes a halide electrolyte and a composite coating material coated on the surface of the halide electrolyte, wherein the halide electrolyte is lithium triindate hexachloroindate (Li3InCl6, LIC), and the composite coating material includes lithium zirconate (Li2ZrO3) and lithium fluoride (LiF) with a mass ratio of (1-2): (2-1), preferably 1:1.

[0022] LiF has extremely low water chemical reactivity and excellent compactness, which can act as a moisture barrier to prevent moisture from the environment from invading the LIC particles. At the same time, Li2ZrO3 is an alkaline oxide that can undergo a neutralization reaction with trace amounts of moisture or acidic by-products such as HCl, generating stable lithium salts and inert oxides (such as LiCl and ZrO2), thereby consuming the invading moisture / acid and protecting the internal LIC from decomposition. Second, lithium zirconate (Li2ZrO3) belongs to lithium transition metal oxides and has good electrochemical stability, which can be used as a positive electrode coating material to inhibit the interfacial reaction between high-nickel positive electrodes and sulfide electrolytes. Coating Li2ZrO3 and LiF on the surface of LIC can act as a "buffer layer" to prevent LIC from directly contacting LPSC, thereby blocking the harmful reaction between halides and sulfides, inhibiting possible anion exchange and side phase generation at the interface. At the same time, Li2ZrO3 and LiF themselves are chemically inert to NCM positive electrode materials, which can avoid side reactions with NCM under high pressure and stabilize the positive electrode interface. Therefore, the presence of Li2ZrO3 in the composite coating layer provides a transmission path for lithium ions, which can compensate for the insulating properties of LiF to some extent, making the coating layer as a whole remain ion permeable. In addition, the addition of LiF can fill the pores between Li2ZrO3 particles, forming a more continuous and dense protective film. Under the synergistic action of the two, the composite layer is stable in structure during the cycle process and is not easy to crack and peel off, thereby continuously playing a protective role and realizing the capacity stability of the battery during long-term cycling.

[0023] In some preferred embodiments, the mass ratio of the composite coating material to the halide electrolyte is (1-10): 100; and the thickness of the composite coating material is 50-100 nm, which is sufficient to form a continuous coverage without being too thick to affect ion transmission.

[0024] In a second aspect, the application provides a preparation method of a coated halide solid-state electrolyte, comprising the following steps: S1, mixing and grinding anhydrous lithium carbonate (Li2CO3) and zirconium oxide (ZrO2) powders uniformly, then calcining at 800-1000°C in air for 5-10 hours, and then ball milling after cooling to obtain lithium zirconate powder.

[0025] In some embodiments of the application, the ratio of the anhydrous lithium carbonate to the zirconium oxide is 1:1, and the mixture is calcined at 700°C for 10h.

[0026] S2, mixing the lithium zirconate powder and the lithium fluoride powder in proportion, and then ball milling to obtain a composite powder.

[0027] It should be noted that the ratio of the lithium zirconate powder to the lithium fluoride powder is (1-2):(2-1) as described above.

[0028] In some embodiments of the present application, the ball milling is carried out in a planetary ball mill at a speed of 300 rpm for 2 hours to mix the two powders evenly, and the resulting composite powder has a particle size of submicron and presents a certain agglomeration.

[0029] S3. Under the protection of inert gas, the halide electrolyte powder and the composite powder are mixed uniformly at a certain ratio, and high-speed dispersion mixing is carried out to make the composite powder adhere to the surface of the halide electrolyte particles to form a coating structure, i.e. to obtain a coated halide solid-state electrolyte.

[0030] In some preferred embodiments, the mixing speed of the high-speed dispersion mixing is 1500-3000 rpm, and the mixing time is > 24 h. In the process of mechanical coating, Li2ZrO3 and LiF particles are embedded in the micro-roughness of the LIC surface under high-speed collision, and adhesion is achieved through van der Waals force and mechanical embedding. Li2ZrO3 is an oxide, which can react with the trace amount of oxide or water molecules that may exist on the surface of LIC to form a firm transition layer; LiF may exchange a small amount of ions with the surface of LIC under frictional heating to generate a transition layer containing F⁻ (such as Li3InCl 6-x F x ) in situ, which is beneficial to the combination of the coating and the substrate. Finally, the LIC electrolyte powder with the surface uniformly covered by the Li2ZrO3-LiF composite layer is obtained.

[0031] It should be noted that the sample is taken every 1 hour during the ball milling process to observe that the surface of the LIC particles is gradually coated with white composite powder and is basically bare, so as to determine that the coating of the halide electrolyte particles is completed.

[0032] In some preferred embodiments, the present application further comprises a step S4 of adding a volatile organic solvent spray in the high-speed dispersion mixing, and drying treatment is carried out after the mixing is completed to obtain a coated halide solid-state electrolyte.

[0033] In the above preparation method, the volatile organic solvent is anhydrous ethanol, and the addition amount is 40-60 ml. A small amount of volatile organic solvent is added to assist atomization, so that the coating is more uniform and the coating layer is more densely attached; the drying treatment is vacuum drying, the drying temperature is 100-120 ℃, and the drying time is 4-6 h. The solvent is quickly removed through drying treatment.

[0034] In some preferred embodiments, the temperature in the high-speed dispersion mixing process in the above preparation method is 25-100 ℃, and the temperature in the entire coating process is kept within room temperature to 100 ℃ to prevent LIC from decomposing.

[0035] In a third aspect, the present application provides a use of a coated halide solid-state electrolyte in the preparation of a positive electrode.

[0036] In some preferred embodiments, the step of preparing the positive electrode comprises: mixing the positive electrode material, the coated halide solid-state electrolyte, the sulfide solid-state electrolyte, the conductive agent, and the binder in proportion, uniformly grinding by dry method, then laying and cold-pressing to form a composite positive electrode sheet. In the positive electrode sheet, the coating layer ensures that the LIC does not decompose due to moisture absorption during subsequent mixing and sheet pressing, and the interface is stable when the positive electrode is in contact with the LPSC and NCM. Then, the LPSC-based separator and the negative electrode sheet are assembled into a full solid-state battery, which is packaged and tested under a certain pressure. Through the above scheme, the stability of the halide electrolyte in the dry positive electrode environment is greatly improved without changing the original composition and process of the battery, so that the halide electrolyte can more fully play a role in interface adjustment, thereby significantly improving the cycle performance and safety and reliability of the full solid-state battery.

[0037] The features and performances of the present application are further described in detail below in combination with embodiments.

[0038] Embodiment 1 The present embodiment provides a preparation method of a coated halide solid-state electrolyte, which comprises the following steps: S1, weigh anhydrous lithium carbonate (Li2CO3) and zirconium oxide (ZrO2) powder in a molar ratio of 1:1, uniformly grind, and calcine at 700°C in air for 10 hours to obtain Li2ZrO3 ceramic powder. After ball milling and sieving, Li2ZrO3 powder with a particle size D 50 about 1 microns is prepared for use.

[0039] S2, mix the above Li2ZrO3 powder and analytical pure lithium fluoride (LiF) powder in a mass ratio of 50:50, and place them in a planetary ball mill at a speed of 300 rpm for 2 hours to fully mix and uniformly mix the two powders. The obtained composite powder has a particle size in the submicron level and presents a certain agglomeration.

[0040] S3, in an Ar atmosphere glove box, mix 5g of Li3InCl6 (LIC) solid-state electrolyte powder with 0.25g of the above Li2ZrO3-LiF composite powder (equivalent to a coating amount of 5wt%), and place them in a grinding tank with zirconia ball medium. Dry ball mill at a speed of 400 rpm for 3 hours to uniformly coat the composite powder on the surface of the LIC particles. During the ball milling process, take samples every 1 hour to observe that the surface of the LIC particles is gradually coated with white composite powder, and there is basically no bareness. Add a small amount of anhydrous ethanol to continue grinding 15 minutes before the end of the ball milling to promote the dense adhesion of the coating layer. Then, take out the slurry and dry it in a vacuum at 40°C for 1 hour to remove the ethanol, and obtain the LIC powder coated with a Li2ZrO3-LiF composite layer on the surface.

[0041] The application of the halide solid-state electrolyte prepared in this example in the preparation of positive electrode sheets. The preparation of the positive electrode includes the following steps: placing NCM positive electrode active material, the above-mentioned coated LIC powder, LPSC electrolyte, VGCF conductive agent and PTFE fibrous binder in a mixing tank, and mixing at high speed for 5 minutes under an argon atmosphere to uniformly disperse the components. The mixed powder is laid in a mold and pressed under a pressure of 8 MPa to obtain a composite positive electrode sheet with a thickness of 100 μm. The LIC particles in the obtained positive electrode sheet are coated with a composite coating, and no obvious crystal precipitation is observed on the surface.

[0042] This example also provides a battery assembly and test. The positive electrode sheet, electrolyte separator and pre-prepared silicon-based negative electrode sheet (ternary carbon-coated nano-Si and graphite composite material) are stacked and assembled in a glove box, and packaged into a 2032 button cell under a pressure of 10 MPa. The battery is aged at room temperature for 12 hours, and then subjected to constant current charge and discharge test (4.3 V voltage window). After two cycles of formation at a rate of 0.1 C, the battery is cycled at a rate of 0.5 C for 50 cycles, and the performance indicators such as discharge specific capacity and coulombic efficiency are recorded. At the same time, the AC impedance spectrum of the battery is measured every 10 cycles (frequency range 0.1 Hz-1 MHz), and the change of interface impedance is tracked. The positive electrode of the disassembled battery is analyzed by X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).

[0043] As shown in Figure 2 , XRD shows that Example 1 maintains the main diffraction peak positions at 2θ ≈ 18.6°, 36.5° and 44.8°, and no In2S3 or other sulfur-containing by-product peaks are detected, indicating that the interface side reaction is effectively inhibited. As shown in Figure 3 , XPS survey scanning shows Li, Zr, In, F and other element peaks, and no significant peak value is observed in the S 2p high-resolution region, further confirming that no In2S3 or other sulfur-containing by-products are formed. Figure 2 and Figure 3 It is shown that the composite coating effectively inhibits the interface side reaction and significantly improves the interface stability. As shown in Figure 4 , according to the analysis of the cathode-electrolyte interface phase, a small semicircle (film / contact impedance, R HF ≈6Ω) is present in the high frequency region, followed by a main semicircle in the medium frequency region, and the horizontal diameter of the main semicircle corresponds to the interface charge transfer resistance R ct ≈80Ω; the left intercept gives the solution resistance R s ≈5Ω, and the right total intercept is about 90Ω (≈R s +R HF +R ct ). The low frequency end is a Warburg diffusion line with an angle of about 45° and a short length, indicating that the diffusion is weakly limited and the polarization is small. Overall, the interface impedance after cycling increases from about 60Ω to -80Ω, which is 230 mAhg-1 , 50 cycles capacity retention ≈80%, average coulombic efficiency >80% consistent stable electrochemical performance. As shown in Figure 6 -a, the battery voltage-capacity curve in Example 1 shows that the specific discharge capacity of the first cycle reaches 230 mAh / g (based on the positive active material) at 0.2C, the capacity retention rate is about 80% after 50 cycles, the average coulombic efficiency is more than 80%, the green / red curve is only slightly left-shifted compared with the blue / orange, and the platform is relatively flat, indicating that the interface is stable after composite coating and the polarization growth is small.

[0044] Comparative Example 1 This comparative example provides a preparation method of a coated halide solid-state electrolyte, and the remaining steps are the same as Example 1, the only difference is that the mass ratio of Li2ZrO3 to LiF is adjusted to 70:30, and the total coating amount is about 3wt%.

[0045] The prepared coated halide solid-state electrolyte is used to prepare a battery and test.

[0046] The results are shown in Figure 6 -b, after reducing the LiF proportion and coating thickness, the initial capacity of the battery is slightly improved (about 255 mAh / g), but the capacity retention rate after 50 cycles is reduced to about 75%, although the performance is still better than that of the uncoated control group, but it is slightly lower than that of Example 1. This shows that when the LiF content and coating thickness are insufficient, the moisture-proof and isolation effect is weakened, and the optimization of the composite coating needs to balance between ion conduction and protection performance.

[0047] Comparative Example 2 This comparative example provides a preparation method of a coated halide solid-state electrolyte, and the remaining steps are the same as Example 1, the only difference is that the halide solid-state electrolyte is not coated, and the halide solid-state electrolyte is not subjected to any surface coating treatment, and is directly added to the positive electrode mixture to prepare a battery, and the cycle performance is tested.

[0048] The results are shown in Figure 5 -a, the R interface ≈200Ω, the medium frequency half circle is significant, and the low frequency diffusion tail is long, indicating that the interface is severely deteriorated and the polarization is increased; as shown in Figure 6 -c, the first cycle capacity at 0.1C is about 150 mAh / g, but after 30 cycles, the capacity rapidly decreases to less than 100 mAh / g, the capacity retention rate is only about 39.8% at 50 cycles, the interface impedance increases from the initial 50Ω to about 200Ω, and the battery shows obvious polarization increase. It is shown that the uncoated LIC gradually fails in the cycle, and it is speculated that it has a severe side reaction with LPSC and absorbs moisture to decompose, and the interface stability is extremely poor.

[0049] Comparative Example 3 A comparative example is provided for a preparation method of a coated halide solid-state electrolyte, and the remaining steps are the same as those of Example 1, the only difference being that a single Li2ZrO3 coating is used, and only a 5wt% Li2ZrO3 powder is used to coat the surface of the LIC.

[0050] The prepared coated halide solid-state electrolyte is used to prepare a battery and test it.

[0051] The results are shown in Figure 5 -b, R interface ≈130Ω, the mid-frequency semicircle is significantly smaller than that of the control, indicating that the interface reaction is partially inhibited; as shown in Figure 6 -d, the capacity retention rate is increased to 61.2%, and the interface impedance is increased to about 130Ω, which is better than the uncoated control. This is due to the fact that the Li2ZrO3 coating inhibits the direct contact between NCM and LPSC to some extent, slowing down the interface reaction. However, due to the lack of hydrophobic LiF protection, the coating itself may gradually fail in the presence of moisture, and there is still a gap between Li2ZrO3 and LIC, which cannot completely block the invasion of moisture, so the performance improvement is limited.

[0052] Comparative Example 4 A comparative example is provided for a preparation method of a coated halide solid-state electrolyte, and the remaining steps are the same as those of Example 1, the only difference being that a single Li2ZrO3 coating is used, and only a 5wt% LiF powder is used to coat the surface of the LIC.

[0053] The prepared coated halide solid-state electrolyte is used to prepare a battery and test it.

[0054] The results are shown in Figure 5 -c, R interface ≈110Ω, the mid-frequency semicircle is smaller and the low-frequency tail is shorter, indicating that the initial interface is stable but long-term cycling may be limited by the coating's ion conductivity and adhesion; as shown in Figure 6 -e, the battery has a retention rate of nearly 75% in the first 20 cycles, and the initial effect is good, but as the cycle progresses, the capacity retention rate decreases to about 55% after 50 cycles, and the interface impedance increases to about 110Ω. The LiF dense layer effectively blocks moisture and harmful substances, making the early interface more stable, but since LiF is an ionic insulator, a thick coating may cause poor interface ion conduction, and the adhesion of the pure LiF coating to the LIC is weak, which may cause local peeling after long-term cycling, resulting in a performance decline.

[0055] In summary, the two-component Li2ZrO3-LiF composite coating material of the present application has significant advantages in various electrochemical performances. First, the cycle life is significantly prolonged, and the capacity retention rate is greatly improved. After long cycling, the capacity of the composite coated sample can still be maintained at about 80%, which is much higher than the less than 40% of the uncoated control. Second, the interface impedance growth is inhibited. Electrochemical impedance spectroscopy (EIS) results show that the interface impedance of the coated electrode of the present application only increases slightly after multiple cycles, while the interface impedance of the uncoated electrode increases significantly, indicating that the two-component coating effectively reduces the interface side reaction and maintains a low resistance stable interface. Third, the material's resistance to moisture stability is greatly improved. The present application can be placed in the air for a long time without significant performance degradation, and almost no by-products such as Li2CO3 and LiOH are generated on the surface as detected by XRD / XPS; in contrast, the uncoated material has obvious by-products after short exposure. The chemical inertness and hydrophobicity of LiF combined with the ion conductivity and structural stability of Li2ZrO3 make the composite coating layer effectively block the invasion of moisture and CO2 in the air. Fourth, the initial discharge capacity remains at a high level. Due to the thin coating layer and the lithium ion conductivity of Li2ZrO3, the initial specific capacity of the composite coated sample is basically the same as that of the uncoated sample, indicating that the present application does not lose capacity while improving stability. Fifth, the electrochemical stability window is widened. Thanks to the excellent stability of Li2ZrO3 and LiF, the composite coated electrode can be safely cycled at a higher voltage (≥4.5V) without severe capacity decay. Therefore, compared with the uncoated and single-layer coated Li2ZrO3 or LiF, the two-component composite coating of the present application achieves the best comprehensive performance through synergistic effect: Li2ZrO3 provides ion conduction and structural stability, LiF provides corrosion resistance and moisture resistance protection, and the combination of the two is significantly better than any single coating effect. In addition, the coating method is simple and easy to produce in batches by dry method, and has good commercialization prospects.

[0056] The preferred embodiments of the present application have been described above with the aid of drawing; the present application is not limited to the preferred embodiments and can be variously changed and modified by those skilled in the art. 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 coated halide solid electrolyte, characterized in that, The solid electrolyte includes a halide electrolyte and a composite coating material coated on the surface of the halide electrolyte, wherein the halide electrolyte is indium trilithium hexachloroindium, and the composite coating material includes lithium zirconate and lithium fluoride in a mass ratio of (1-2):(2-1).

2. The coated halide solid electrolyte according to claim 1, characterized in that, The mass ratio of the composite coating material to the halide electrolyte is (1-10):

100.

3. The coated halide solid electrolyte according to claim 1, characterized in that, The thickness of the composite coating material is 50-100 nm.

4. A method for preparing a coated halide solid electrolyte as described in any one of claims 1-3, characterized in that, Includes the following steps: Anhydrous lithium carbonate and zirconium oxide powder are mixed and ground evenly, then calcined in air at 800-1000℃ for 5-10 hours, cooled, and then ball-milled to obtain lithium zirconate powder. Lithium zirconate powder and lithium fluoride powder were mixed in a certain proportion and then ball-milled to obtain composite powder. Under inert gas protection, halide electrolyte powder and composite powder are mixed in proportion and dispersed at high speed, so that the composite powder adheres to the surface of halide electrolyte particles to form a coating structure, thus obtaining a coated halide solid electrolyte.

5. The method for preparing a coated halide solid electrolyte according to claim 4, characterized in that, The mixing speed of the high-speed dispersion mixer is 1500-3000 rpm, and the mixing time is >24h.

6. The method for preparing a coated halide solid electrolyte according to claim 4, characterized in that, The preparation method further includes the following steps: adding volatile organic solvents by spraying into a high-speed dispersion mixture, and drying the mixture after it is completed to obtain a coated halide solid electrolyte.

7. The method for preparing a coated halide solid electrolyte according to claim 6, characterized in that, The volatile organic solvent is anhydrous ethanol, and the amount added is 40-60 ml; the drying treatment is vacuum drying, the drying temperature is 100-120℃, and the drying time is 4-6 h.

8. A method for preparing a coated halide solid electrolyte according to any one of claims 4-7, characterized in that, The temperature during the high-speed dispersion and mixing process is 25-100℃.

9. The application of a coated halide solid electrolyte as described in any one of claims 1-3 in the preparation of a positive electrode.

10. The application according to claim 9, characterized in that, The steps for preparing the positive electrode include: mixing the positive electrode material, coated halide solid electrolyte, sulfide solid electrolyte, conductive agent and binder in proportion, dry grinding uniformly, laying the mixture into sheets and cold pressing to obtain the composite positive electrode sheet.

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