F-doped Li-Y-Zr-Cl-S mixed halogen sulfide solid electrolyte material and preparation method and application thereof

Abstract

The invention relates to the technical field of solid electrolyte materials, in particular to an F-doped Li-Y-Zr-Cl-S mixed halogen sulfide solid electrolyte material and a preparation method and application thereof.The F-doped Li-Y-Zr-Cl-S mixed halogen sulfide solid electrolyte material comprises a solid electrolyte A and a solid electrolyte B, the chemical formula of the solid electrolyte A is as shown in a formula (I): Li Y < m > Zr < n > Cl F < q > Sb; wherein: egt; 0, mgt; 0, ngt; 0, pgt; 0, bgt; 0; 0 lt; q < = 0.6, and m + n > = 1; the solid electrolyte B is a sulfide solid electrolyte and accounts for 10-40% of the total mass, and a composite passivation layer composed of LiF, Li2S and LiCl is formed on the surface of a negative electrode in situ. The F-doped Li-Y / Zr-Cl-S mixed electrolyte material has the advantages that the F-doped Li-Y / Zr-Cl-S mixed electrolyte material is used as a composite layer, the composite layer has both ionic conductivity and electronic insulativity, the interface resistance is reduced, and the F-doped Li-Y / Zr-Cl-S mixed electrolyte material shows a wide electrochemical stability window (about 0-3.5 V), low interface impedance and excellent cycling stability and can meet the application requirement of a high-energy-density all-solid-state lithium metal battery.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte materials technology, and in particular to an F-doped Li–Y–Zr–Cl–S mixed halide sulfide solid electrolyte material, its preparation method and application. Background Technology

[0002] Halide solid electrolytes (such as Li3YCl6, Li2ZrCl6, etc.) have high oxidative decomposition voltages, but they are prone to reductive decomposition when in contact with lithium metal anodes, forming an interface layer with high impedance and instability. For example, direct contact between YCl3 and lithium metal may result in a reaction: YCl3 + 3Li → 3LiCl + Y(s), where (s) indicates that the product is a solid, and the same applies below.

[0003] This results in the formation of insulating LiCl and metallic Y deposits on the lithium anode surface, leading to increased interfacial impedance and decreased cycle life. In contrast, sulfide solid electrolytes (such as Li3PS4 and its derivatives) can form a sulfur-rich passivation layer (mainly composed of Li2S, etc.) in situ on the lithium anode surface, exhibiting low interfacial impedance; however, sulfides are easily oxidized and decomposed under high-voltage cathode conditions. For example, Li3PS4 at >2.4 V (for Li / Li + When it undergoes an oxidation reaction, it produces byproducts such as elemental sulfur and phosphorus-containing sulfides, which limits its stability under high-voltage positive electrode conditions.

[0004] To balance high-voltage stability and anode interface stability, researchers have recently attempted to combine Li–Y–Cl–S and Li–Zr–Cl–S systems. By adjusting the Y / Zr ratio and introducing sulfide components, a balance between interfacial compatibility and ionic conductivity can be achieved. However, this hybrid system still faces the challenge of simultaneously achieving both oxidation stability and interfacial stability. Some studies have reported that in the presence of PS4... 3- Introducing an appropriate amount of fluorine (F) into the sulfide electrolyte can form a fluorine-rich passivation layer inside the material and at the interface, increasing the actual oxidation decomposition voltage from approximately 2.4 V to approximately 3.5 V. Simultaneously, a stable interfacial phase mainly composed of LiF and metal fluorides is formed in situ at the positive electrode interface. Furthermore, the fluorine-rich interfacial layer contains species such as LiF and transition metal fluorides, which possess electrochemical inertness, significantly improving interfacial stability and suppressing side reactions. These findings suggest that doping the Li–Y–Zr–Cl–S mixed halide sulfide system with fluorine can synergistically improve the compatibility of the positive and negative electrode interfaces and the stability of the main material structure. Summary of the Invention

[0005] The object of the present invention is to solve the drawbacks existing in the prior art, and to provide a fluorine-doped Li–Y–Zr–Cl–S mixed halogen sulfide solid electrolyte material, its preparation method and application.

[0006] A fluorine-doped Li–Y–Zr–Cl–S mixed halogen sulfide solid electrolyte material, comprising solid electrolyte A and solid electrolyte B, the chemical formula of the solid electrolyte A is shown in formula (I): Li a Y m Zr n Cl p F q S b ; where: a > 0, m > 0, n > 0, p > 0, b > 0; 0 < q ≤ 0.6, and m + n ≥ 1; The solid electrolyte B is a sulfide solid electrolyte, and the solid electrolyte B accounts for 10% - 40% of the total mass.

[0007] Preferably, the solid electrolyte B is Li6PS5Cl or a sulfide containing a PS4 3- group.

[0008] Preferably, by partially substituting the Cl - sites to form an outer passivation layer rich in LiF and metal fluorides at the positive electrode interface, and a composite passivation layer coexisting with LiF–Li2S–LiCl at the negative electrode interface, thereby synergistically improving the compatibility and structural stability of the positive and negative electrode interfaces.

[0009] Preferably, the molar ratio of Y to Zr is 1:0 to 0.8:0.2.

[0010] Preferably, a preparation method of a fluorine-doped Li–Y–Zr–Cl–S mixed halogen sulfide solid electrolyte material comprises the following steps: Weigh lithium source, yttrium source, zirconium source, chlorine source, fluorine source, sulfur source and solid electrolyte B according to the stoichiometric ratio, and ball-mill and mix them in an inert atmosphere to obtain a precursor; heat the precursor to 500–600 °C in an inert atmosphere and hold for 8 - 12 hours to cause a solid-phase reaction of each component to generate a fluorine-doped Li–Y–Zr–Cl–S mixed halogen sulfide; after cooling, press the product powder into a mold under pressure to obtain a dense sheet of the solid electrolyte material.

[0011] Preferably, the lithium source is selected from LiCl, LiF and Li2S; the yttrium source is selected from YCl3; the zirconium source is selected from ZrCl4; the chlorine source is selected from LiCl and YCl3; the fluorine source is selected from LiF; the sulfur source is selected from Li2S.

[0012] Preferably, the ball milling time is 20–60 h and the rotation speed is 300–500 rpm.

[0013] Preferably, during the pressing and forming process, cold pressing is carried out under a pressure of 50–100 MPa.

[0014] Preferably, a all-solid-state battery, the all-solid-state battery includes the above-mentioned mixed halogen sulfide solid electrolyte material.

[0015] Preferably, the capacity retention rate of the all-solid-state battery after 300 cycles within a working voltage window of 2.0–3.5 V is not less than 85%.

[0016] The beneficial effects of the present invention are: In the present invention, a composite passivation layer composed of LiF, Li2S and LiCl is in-situ formed on the surface of the negative electrode. This composite layer has both ionic conductivity and electronic insulation: Li2S and LiCl come from the sulfide and halide components in the electrolyte, which helps to reduce the interfacial resistance; LiF, due to its chemical stability and high mechanical strength, can inhibit the penetration growth of lithium dendrites. In summary, the F-doped Li–Y / Zr–Cl–S mixed electrolyte material exhibits a wide electrochemical stability window (about 0–3.5 V), low interfacial impedance and excellent cycle stability, which can meet the application requirements of high energy density all-solid-state lithium metal batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the XRD pattern of the material obtained in Example 1 proposed by the present invention and that before F doping. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0019] A F-doped Li–Y–Zr–Cl–S mixed halogen sulfide solid electrolyte material, comprising solid electrolyte A and solid electrolyte B, the chemical formula of solid electrolyte A is shown in formula (I): Li a Y m Zr n Cl p F q S b ; wherein: a>0, m>0, n>0, p>0, b>0; 0<q≤0.6, and m + n≥1; Solid electrolyte B is a sulfide solid electrolyte, and solid electrolyte B accounts for 10%-40% of the total mass.

[0020] Solid electrolyte B is Li6PS5Cl or contains PS4 3- Sulfides of functional groups.

[0021] By partially replacing Cl with F element - The site is designed to form an outer passivation phase rich in LiF and metal fluorides at the positive electrode interface and a composite passivation layer in which LiF–Li2S–LiCl coexist at the negative electrode interface, thereby synergistically improving the compatibility and structural stability of the positive and negative electrode interfaces.

[0022] The molar ratio of Y to Zr is 1:0 to 0.8:0.2.

[0023] A method for preparing an F-doped Li–Y–Zr–Cl–S mixed halide sulfide solid electrolyte material includes the following steps: Lithium source, yttrium source, zirconium source, chlorine source, fluorine source, sulfur source, and solid electrolyte B were weighed according to stoichiometric ratio and ball-milled in an inert atmosphere to obtain a precursor. The precursor was heated to 500–600℃ in an inert atmosphere and held for 8–12 hours to allow the components to undergo a solid-phase reaction to generate F-doped Li–Y-Zr–Cl–S mixed halosulfides. After cooling, the product powder was pressed into a dense sheet of solid electrolyte material under pressure. The lithium source was selected from LiCl, LiF, and Li2S; the yttrium source was selected from YCl3; the zirconium source was selected from ZrCl4; the chlorine source was selected from LiCl and YCl3; the fluorine source was selected from LiF; and the sulfur source was selected from Li2S.

[0024] The ball milling time is 20–60 hours, and the rotation speed is 300–500 rpm. During the pressing process, the electrolyte sheet is cold-pressed at a pressure of 50–100 MPa to obtain a circular sheet electrolyte membrane with a diameter of 10 mm and a thickness of about 1 mm. If necessary, the cold-pressed sheet can be hot-pressed at 200 °C for 2 hours to further improve the density and mechanical strength. The prepared electrolyte sheet can be directly used for the assembly of all-solid-state batteries.

[0025] An all-solid-state battery, comprising the aforementioned mixed halide sulfide solid electrolyte material.

[0026] The all-solid-state battery retains no less than 85% of its capacity after 300 cycles within a working voltage window of 2.0–3.5V.

[0027] At the interface of high-voltage cathodes (such as LiCoO2, nickel-rich layered oxides, etc.), due to the presence of fluorine (F), the electrolyte basically does not undergo oxidative decomposition within approximately 3.5 V. The strong electronegativity generated by fluorine doping reduces the amount of PS4 in the electrolyte. 3-The groups are less likely to lose electrons, thus increasing the upper limit of the material's oxidation resistance. Simultaneously, an interfacial phase mainly composed of LiF and metal fluorides is formed in situ at the cathode interface, acting as an electron barrier to prevent further side reactions. For example, unreacted YCl3 and ZrCl4 components in the electrolyte can undergo exchange reactions with LiF at the interface, forming stable YF3, ZrF4, and other metal fluoride deposits (e.g., YCl3 + 3 LiF → YF3 + 3 LiCl; ZrCl4 + 4 LiF → ZrF4 + 4 LiCl). These fluorides exhibit high stability, protecting the cathode from electrolyte oxidation and improving interfacial contact stability.

[0028] At the lithium metal anode interface, fluorine (F) doping also plays a crucial role: during lithium deposition / stripping, F... - Ions react with lithium on the negative electrode surface to form a stable and dense LiF passivation layer: Li (metal) + F - →LiF(s).

[0029] Simultaneously, halogens and sulfur anions also react with lithium at the negative electrode interface to generate LiCl and Li2S, respectively. Li + +Cl - →LiCl(s), 2Li + +S 2- →Li2S(s).

[0030] Electrolyte sheet preparation: In a dry glove box, the electrolyte powder obtained above is placed in a mold and cold-pressed under a pressure of about 50–100 MPa.

[0031] Example 1: Preparation of a mixed halosulfide electrolyte with Y:Zr = 0.8:0.2 and F doping amount q = 0.2. LiCl, Li₂S, YCl₃, ZrCl₄, LiF, and Li₆PS₅Cl raw materials were weighed, with Li₆PS₅Cl accounting for 20% of the total mass, and LiF added to ensure that F occupies 20% of the halogen sites. Electrolyte sheets were prepared by ball milling, solid-state reaction at 550 °C for 10 hours, and cold pressing. XRD analysis showed that the obtained material mainly exhibited Li₃Y. 0.8 Zr 0.2 Cl 5.8 S 1.0 F 0.2 The halogen sulfide crystal phase characteristics were observed, with no obvious impurity phase peaks (such as...). Figure 1(As shown). This electrolyte sheet was assembled into an all-solid-state battery with a commercial LiCoO2 cathode (uncoated) and a lithium metal anode (cathode active material: electrolyte: conductive carbon = 70:20:10, no interfacial coating added). Cyclic voltammetry tests showed no significant oxidation current in the 2.0–3.5 V range, demonstrating that the electrolyte has a stable oxidation upper limit of approximately 3.5 V. Electrochemical impedance spectroscopy (EIS) measured the initial interfacial impedance of the battery to be approximately 50 Ω·cm. 2 After 100 charge-discharge cycles, the impedance increased only slightly, indicating good interface stability. The Li|electrolyte|Li symmetric cell exhibited a impedance of 0.1 mA·cm⁻¹. -2 Repeated lithium plating / stripping with current maintained a voltage polarization of approximately 50 mV, and no short circuit or significant voltage rise occurred after more than 1000 hours of continuous cycling. Constant current charge-discharge tests were performed on the LiCoO2|electrolyte|Li full cell at a cutoff voltage of 3.5 V, and the initial discharge specific capacity was approximately 150 mAh·g. -1 (At 0.1 C), the capacity retention rate is 88% after 300 cycles, demonstrating excellent long cycle life and capacity retention capability.

[0032] Example 2: A comparative electrolyte with Y:Zr = 1:0 (Zr-free, Y-only system) and F doping amount q = 0.2 was prepared (no Zr component compared to Example 1). The Li–Y–Cl–S:F electrolyte was prepared using the same method as in Example 1 (where the sulfide Li6PS5Cl content was 20 wt%). XRD showed that the material corresponds to Li3YCl. 5.8 S 1.0 F 0.2 The electrolyte is a halosulfide phase. When used in LiCoO2|Li batteries, slight signs of oxidation and decomposition were observed above 3.5 V, presumably due to a slight decrease in lattice stability in the absence of the Zr component. However, the battery remained stable for over 200 cycles below 3.5 V, retaining approximately 80% of its capacity. The initial interfacial impedance of the Li|electrolyte|Li symmetric battery was approximately 60 Ω·cm. 2 After 500 hours of cycling, it increases to approximately 80 Ω·cm. 2 The interfacial stability was slightly worse than that of Example 1 containing Zr. This result indicates that introducing a small amount of Zr helps to further improve the oxidation stability and cycling performance of the material.

[0033] Example 3: A high-F-content mixed electrolyte was prepared with a Y:Zr ratio of 0.8:0.2 and an F doping amount of q = 0.4. Except for increasing the LiF content to make F occupy 40% of the halogen sites, the remaining processes were the same as in Example 1. The XRD main peak position of the obtained material was slightly shifted compared to Example 1, indicating that the higher F doping caused slight lattice shrinkage. Electrochemical tests revealed that this electrolyte exhibited a lower polarization voltage (approximately 40 mV) and a longer cycle life (>1200 hours without short circuit) in Li|Li symmetric cells. However, in LiCoO2 cathode cycling at 3.5 V, excessively high F doping led to a slight increase in interfacial byproducts, and the capacity retention after 300 cycles was approximately 85%, comparable to Example 1. In summary, a suitable amount of F doping (approximately 20% halogen sites) is sufficient to form a stable LiF-rich interfacial layer, and excessively high F content does not significantly improve the stability of the cathode interface.

[0034] Comparative Example 1: A Li–Zr–Cl halide electrolyte without F doping and Y content was prepared as a control (i.e., a pure Li₂ZrCl₆ halide electrolyte). LiCl and ZrCl₄ raw materials were ball-milled at a 2:1 molar ratio and reacted in a solid-state environment at 400 °C for 4 hours to obtain Li₂ZrCl₆ powder, which was then pressed into tablets for electrochemical testing. The material exhibited an ionic conductivity of approximately 0.5 mS·cm at room temperature. -1 It possesses a wide electrochemical stability window >4 V. However, due to the lack of sulfide components and a LiF passivation layer, its interfacial stability is poor. In Li|Li symmetric cells, the initial polarization voltage is approximately 100 mV, and the interfacial impedance rapidly increases and short-circuit failure occurs within less than 200 hours of cycling. When Li₂ZrCl₆ is used in LiCoO₂|Li full cells, even with the charging cutoff voltage limited to 3.5 V, the battery capacity decays by more than 40% within 100 cycles, and the interfacial impedance increases significantly. In contrast, the F-doped Li–Y–Zr–Cl–S electrolyte used in Example 1 of this invention exhibits lower polarization, a more stable voltage plateau, and a capacity retention of nearly 90% after 300 cycles under the same test conditions.

[0035] Therefore, only by simultaneously introducing three measures—F doping, Y–Zr bimetal, and sulfide synergy—can the electrolyte achieve compatibility and stability at the interface between the high-voltage cathode and the lithium anode, thereby improving the overall performance of all-solid-state batteries.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An F-doped Li-Y-Zr-Cl-S mixed halosulfide solid-state electrolyte material comprising a solid-state electrolyte A and a solid-state electrolyte B, characterized in that, The chemical formula of the solid-state electrolyte A is shown as formula (I): Li a Y m Zr n Cl p F q S b ; wherein: a > 0, m > 0, n ≥ 0, p > 0, b > 0; 0 < q ≤ 0.6, and m + n ≥ 1; The solid-state electrolyte B is a sulfide solid-state electrolyte, and the solid-state electrolyte B accounts for 10% to 40% of the total mass.

2. The F-doped Li-Y-Zr-Cl-S mixed halosulfide solid-state electrolyte material of claim 1, wherein, The solid-state electrolyte B is Li6PS5Cl or contains PS4 3- sulfides of the group of the phosphorus 3. The F-doped Li-Y-Zr-Cl-S mixed halosulfide solid-state electrolyte material of claim 1, wherein, by partial substitution of F for Cl - The site is substituted by F element to form an outer layer of LiF and metal fluoride passivation phase at the positive electrode interface, and a composite passivation layer of LiF-Li2S-LiCl coexisting at the negative electrode interface, thereby synergistically improving the compatibility and structural stability of the positive and negative electrode interfaces.

4. The F-doped Li-Y-Zr-Cl-S mixed halosulfide solid-state electrolyte material of claim 1, wherein, The molar ratio of Y to Zr is 1:0 to 0.8:0.

2.

5. A method of producing the F-doped Li-Y-Zr-Cl-S mixed halosulfide solid-state electrolyte material according to claims 1-4, characterized in that, The method comprises the following steps: The lithium source, yttrium source, zirconium source, chlorine source, fluorine source, sulfur source, and solid-state electrolyte B are weighed in stoichiometric ratios, mixed in a ball mill in an inert atmosphere to obtain a precursor, the precursor is heated to 500-600°C in an inert atmosphere and held for 8-12 hours, so that the components undergo solid-phase reaction to generate F-doped Li-Y-Zr-Cl-S mixed halosulfide, and after cooling, the product powder is pressed into a dense sheet of the solid-state electrolyte material under pressure.

6. A method of producing a F-doped Li-Y-Zr-Cl-S mixed halosulfide solid-state electrolyte material according to claim 5, characterized in that, The lithium source is selected from LiCl, LiF, and Li2S; the yttrium source is selected from YCl3; the zirconium source is selected from ZrCl4; the chlorine source is selected from LiCl and YCl3; the fluorine source is selected from LiF; and the sulfur source is selected from Li2S.

7. A method of producing a F-doped Li-Y-Zr-Cl-S mixed halosulfide solid-state electrolyte material according to claim 5, characterized in that, The ball milling time is 20-60 h, and the rotation speed is 300-500 rpm.

8. A method of producing a F-doped Li-Y-Zr-Cl-S mixed halosulfide solid-state electrolyte material according to claim 5, characterized in that, During the pressing process, cold pressing is performed at a pressure of 50-100 MPa.

9. An all-solid battery, characterized by, The all-solid-state battery comprises the mixed halosulfide solid-state electrolyte material according to any one of claims 1-4.

10. The all-solid battery according to claim 9, wherein The all-solid-state battery has a capacity retention rate of no less than 85% after 300 cycles in a working voltage window of 2.0-3.5 V.

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