Sulfide solid electrolyte and preparation method and application thereof

Abstract

The invention relates to the technical field of solid-state battery electrolyte materials, in particular to a sulfide solid-state electrolyte and a preparation method and application thereof. The sulfide solid-state electrolyte comprises a core layer and a gradient coating layer from inside to outside; the core layer is a Li7P3S11-LiI-Li3N composite phase, the doping amount of LiI is 5%-10% of the mass of Li7P3S11, and the doping amount of Li3N is 2%-5% of the mass of Li7P3S11; the gradient coating layer is an Al2O3-Li3PO4 composite layer, the thickness of the gradient coating layer is 50-200 nm, the content of Al2O3 is gradually reduced from inside to outside, and the content of Li3PO4 is gradually increased from inside to outside; a low-temperature solvothermal-mechanochemical activation composite process is adopted to replace a traditional high-temperature solid-phase method, the preparation temperature is reduced to 350 DEG C or below, energy consumption is reduced by 40% or above, meanwhile, component segregation caused by high temperature is avoided, and component uniformity of the core layer is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery electrolyte materials technology, specifically to a sulfide solid electrolyte, its preparation method, and its application. Background Technology

[0002] Sulfide solid electrolytes have high room temperature ionic conductivity (up to 10). -3 With its high efficiency (on the order of S / cm), good machinability, and excellent contact compatibility with lithium metal anodes, lithium-ion battery electrolytes have become one of the core research directions for next-generation solid-state battery electrolytes. Currently, mainstream sulfide electrolytes such as Li... 10 GeP2S 12 (LGPS), Li7P3S 11 While exhibiting excellent ion conduction performance, these electrolytes still suffer from three major drawbacks: First, the preparation process largely relies on high-temperature solid-state reactions (typically 600-800℃), resulting in high energy consumption and a tendency for uneven product composition and grain agglomeration. Second, pure sulfide electrolytes have poor chemical stability and readily react with water and oxygen in the air to generate toxic H2S gas, increasing production and usage risks. Third, when in contact with lithium metal anodes, they are prone to interfacial side reactions that form a high-resistivity layer, while also failing to effectively suppress lithium dendrite growth, leading to insufficient battery cycle stability.

[0003] In existing improvement technologies, halide doping (such as LiI, LiBr) can improve ionic conductivity, but it will exacerbate the hygroscopicity of the electrolyte; surface coating with oxides (such as Al2O3) can improve stability, but the interfacial impedance between the coating layer and the electrolyte bulk is high. Therefore, a sulfide solid electrolyte, its preparation method and application are proposed. Summary of the Invention

[0004] In view of this, the present invention provides a sulfide solid electrolyte, its preparation method and application, to solve or alleviate the technical problems existing in the prior art, and at least provide a beneficial alternative.

[0005] The technical solution of this invention is implemented as follows: a sulfide solid electrolyte, comprising a core layer and a gradient coating layer from the inside out; the core layer is Li7P3S. 11 -LiI-Li3N composite phase, with LiI doping concentration of Li7P3S 11 5%–10% by mass, Li3N doping amount is Li7P3S 11 The content of Al2O3 is 2%-5% of the mass; the gradient coating layer is an Al2O3-Li3PO4 composite layer with a thickness of 50-200nm, and the content of Al2O3 gradually decreases and the content of Li3PO4 gradually increases from the inside to the outside.

[0006] Further preferred, room temperature ionic conductivity ≥1×10 -3S / cm, conductivity retention rate ≥85% after being placed in air for 24 hours.

[0007] A method for preparing a sulfide solid electrolyte includes the following steps:

[0008] Step 1: Raw material pretreatment: Dry Li2S, P2S5, LiI, Li3N, Al(NO3)3·9H2O and LiH2PO4 respectively to remove water, and pass them through a 200-mesh sieve to obtain pretreated raw materials;

[0009] Step 2, Low-temperature solvothermal synthesis: according to Li7P3S 11 Li2S and P2S5 were weighed in a stoichiometric ratio, and LiI and Li3N were added. Anhydrous acetonitrile was used as a solvent to carry out a solvothermal reaction. After the reaction, the product was separated, washed and dried to obtain the core layer precursor.

[0010] Step 3, Mechanochemical activation: The core layer precursor is ball-milled at a temperature controlled at ≤40℃ to obtain core layer powder;

[0011] Step 4, Gradient Coating: An Al2O3-Li3PO4 gradient layer is deposited on the surface of the core layer powder using atomic layer deposition technology to obtain the initial product;

[0012] Step 5, Low-temperature sintering: The initial product is sintered under pressure to obtain a sulfide solid electrolyte.

[0013] More preferably, in step 1, Li2S is dried at 120°C under vacuum for 4 hours, P2S5 is dried at 80°C for 2 hours under inert gas protection, and LiI, Li3N, Al(NO3)3·9H2O, and LiH2PO4 are dried at 60°C under vacuum for 1 hour.

[0014] More preferably, in step 2, the solid-liquid ratio of the solvothermal reaction is 1:5 g / mL, the heating rate is 5℃ / min, the reaction temperature is 120-150℃, the holding time is 6-8h, and the reaction atmosphere is an inert gas.

[0015] In a further preferred embodiment, in step 3, a planetary ball mill is used for ball milling, with a ball-to-material ratio of 20:1, a rotation speed of 300-400 r / min, a ball milling time of 2-3 h, and an inert gas atmosphere for ball milling.

[0016] More preferably, in step 4, the vacuum degree of atomic layer deposition is ≤1×10⁻⁶. -3 Pa, substrate temperature 150℃; Al2O3 deposition source is trimethylaluminum and deionized water, Li3PO4 deposition source is trimethyl phosphate and LiOtBu; gradient layer deposition includes pure Al2O3 layer (50-80 cycles), transition layer (40-60 cycles), pure Li3PO4 layer (50-80 cycles).

[0017] More preferably, in step 5, the sintering temperature is 300-350℃, the heating rate is 2℃ / min, the pressure is 10-15MPa, the holding time is 1h, and the sintering atmosphere is an inert gas.

[0018] An application of a sulfide solid electrolyte includes the following steps for an electrolyte layer in an all-solid-state lithium metal battery, wherein the battery uses lithium nickel cobalt manganese oxide or lithium iron phosphate as the positive electrode and lithium metal as the negative electrode.

[0019] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions:

[0020] I. This invention adopts a low-temperature solvothermal-mechanical-chemical activation composite process to replace the traditional high-temperature solid-phase method, reducing the preparation temperature to below 350℃ and reducing energy consumption by more than 40%. At the same time, it avoids component segregation caused by high temperature and significantly improves the uniformity of the core layer components.

[0021] Second, the LiI-Li3N composite doping of this invention constructs a fast ion conduction channel, and Li3N can also suppress the hygroscopicity of the electrolyte. Combined with the Al2O3-Li3PO4 gradient coating layer, the Al2O3 enhances the bonding force with the core layer, and the Li3PO4 improves the interfacial compatibility with the lithium metal anode, effectively suppressing the growth of lithium dendrites.

[0022] III. The sulfide solid electrolyte prepared by this invention can achieve a room temperature ionic conductivity of 1×10⁻⁶. -3 With a conductivity of over S / cm, it retains ≥85% of its conductivity after being placed in air for 24 hours, exhibiting excellent chemical stability. When applied to solid-state batteries, it demonstrates outstanding cycle performance. The preparation process is simple and controllable, making it suitable for industrial production.

[0023] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the invention will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a flowchart of the sulfide solid electrolyte preparation process of the present invention. Detailed Implementation

[0026] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0027] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0028] like Figure 1 As shown, this embodiment of the invention provides a sulfide solid electrolyte, comprising a core layer and a gradient coating layer from the inside out; the core layer is Li7P3S. 11 -LiI-Li3N composite phase, with LiI doping concentration of Li7P3S 11 5%–10% by mass, Li3N doping amount is Li7P3S 11 2%–5% of the mass; the gradient coating layer is an Al2O3-Li3PO4 composite layer with a thickness of 50–200 nm, and the Al2O3 content gradually decreases and the Li3PO4 content gradually increases from the inside to the outside.

[0029] In one embodiment, the room temperature ionic conductivity is ≥1×10⁻⁶. -3 S / cm, conductivity retention rate ≥85% after being placed in air for 24 hours.

[0030] A method for preparing a sulfide solid electrolyte includes the following steps:

[0031] Step 1: Raw material pretreatment: Dry Li2S, P2S5, LiI, Li3N, Al(NO3)3·9H2O and LiH2PO4 respectively to remove water, and pass them through a 200-mesh sieve to obtain pretreated raw materials;

[0032] Step 2, Low-temperature solvothermal synthesis: according to Li7P3S 11 Li2S and P2S5 were weighed in a stoichiometric ratio, and LiI and Li3N were added. Anhydrous acetonitrile was used as a solvent to carry out a solvothermal reaction. After the reaction, the product was separated, washed and dried to obtain the core layer precursor.

[0033] Step 3, Mechanochemical activation: The core layer precursor is ball-milled at a temperature controlled at ≤40℃ to obtain core layer powder;

[0034] Step 4, Gradient Coating: An Al2O3-Li3PO4 gradient layer is deposited on the surface of the core layer powder using atomic layer deposition technology to obtain the initial product;

[0035] Step 5, Low-temperature sintering: The initial product is sintered under pressure to obtain a sulfide solid electrolyte.

[0036] In one embodiment, in step 1, Li2S is dried at 120°C under vacuum for 4 hours, P2S5 is dried at 80°C for 2 hours under inert gas protection, and LiI, Li3N, Al(NO3)3·9H2O, and LiH2PO4 are dried at 60°C under vacuum for 1 hour.

[0037] In one embodiment, in step 2, the solid-liquid ratio of the solvothermal reaction is 1:5 g / mL, the heating rate is 5℃ / min, the reaction temperature is 120-150℃, the holding time is 6-8h, and the reaction atmosphere is an inert gas.

[0038] In one embodiment, in step 3, a planetary ball mill is used for ball milling, with a ball-to-material ratio of 20:1, a rotation speed of 300-400 r / min, a ball milling time of 2-3 h, and an inert gas atmosphere for ball milling.

[0039] In one embodiment, in step 4, the vacuum degree of atomic layer deposition is ≤1×10⁻⁶. -3 Pa, substrate temperature 150℃; Al2O3 deposition source is trimethylaluminum and deionized water, Li3PO4 deposition source is trimethyl phosphate and LiOtBu; gradient layer deposition includes pure Al2O3 layer (50-80 cycles), transition layer (40-60 cycles), pure Li3PO4 layer (50-80 cycles).

[0040] In one embodiment, in step 5, the sintering temperature is 300-350℃, the heating rate is 2℃ / min, the pressure is 10-15MPa, the holding time is 1h, and the sintering atmosphere is an inert gas.

[0041] An application of a sulfide solid electrolyte includes the following steps for use as an electrolyte layer in an all-solid-state lithium metal battery, wherein the battery uses lithium nickel cobalt manganese oxide or lithium iron phosphate as the positive electrode and lithium metal as the negative electrode.

[0042] In one embodiment, a method for preparing a sulfide solid electrolyte includes the following steps:

[0043] Raw material pretreatment: Select Li2S, P2S5, LiI, Li3N, Al(NO3)3·9H2O, and LiH2PO4 with a purity of 99.9%. Li2S was dried under vacuum at 120℃ for 4 hours, P2S5 was dried under argon protection at 80℃ for 2 hours, and the remaining raw materials were dried under vacuum at 60℃ for 1 hour. All materials were passed through a 200-mesh sieve and set aside for later use.

[0044] Low-temperature solvothermal synthesis: according to Li7P3S 11Li₂S (4.2 g) and P₂S₅ (5.8 g) were weighed out in a stoichiometric ratio, and LiI (0.8 g, 8 wt%) and Li₃N (0.3 g, 3 wt%) were added. The mixture was placed in a polytetrafluoroethylene reactor, and 50 mL of anhydrous acetonitrile was added. Under an argon atmosphere, the temperature was increased to 130 °C at a rate of 5 °C / min and held for 7 h. After cooling, the mixture was centrifuged, washed three times with anhydrous acetonitrile, and dried under vacuum at 60 °C for 2 h to obtain the core layer precursor.

[0045] Mechanochemical activation: The precursor was placed in a zirconia ball mill jar with a ball-to-material ratio of 20:1 and ball-milled at 350 r / min for 2.5 h under argon protection, with circulating water temperature controlled at ≤40℃, to obtain core layer powder. The measured ionic conductivity was 6.2 × 10⁻⁶. -4 S / cm.

[0046] Gradient coating: In ALD devices, 150℃, 1×10 -3 Under Pa conditions, TMA and water were first passed through for 60 cycles to deposit an Al2O3 layer; then, the deposition source was alternately passed through, with reduced TMA and increased TMP, for 50 cycles to deposit a transition layer; finally, TMP and LiOtBu were passed through for 60 cycles to deposit a Li3PO4 layer, with a total coating thickness of 120 nm.

[0047] Low-temperature sintering: Argon gas protection in graphite mold, temperature increased to 320℃ at 2℃ / min, pressure of 12MPa applied, and heat and pressure held for 1h; cooling and demolding to obtain electrolyte sheet with diameter of 14mm and thickness of 2mm.

[0048] Performance testing: The electrolyte has a room temperature ionic conductivity of 1.2 × 10⁻⁶. -3 S / cm, conductivity after being placed in air for 24 hours is 1.02×10 -3 S / cm; Assembled NCM811 / / electrolyte / / Li battery, initial discharge capacity at 0.2C rate is 192mAh / g, capacity retention after 500 cycles is 93.5%.

[0049] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A sulfide solid electrolyte, characterized in that: From the inside out, it consists of a core layer and a gradient coating layer; the core layer is Li7P3S. 11 -LiI-Li3N composite phase, with LiI doping amount of 5%-10% of Li7P3S11 mass and Li3N doping amount of Li7P3S11. 11 The content of Al2O3 is 2%-5% of the mass; the gradient coating layer is an Al2O3-Li3PO4 composite layer with a thickness of 50-200nm, and the content of Al2O3 gradually decreases and the content of Li3PO4 gradually increases from the inside to the outside.

2. A sulfide solid electrolyte, characterized in that: The room temperature ionic conductivity is ≥1×10-3S / cm, and the conductivity retention rate is ≥85% after being placed in air for 24 hours.

3. A method for preparing a sulfide solid electrolyte, in conjunction with the sulfide solid electrolyte as described in claims 1-2, characterized in that: Includes the following steps: Step 1: Raw material pretreatment: Dry Li2S, P2S5, Li I, Li3N, Al(NO3)3·9H2O and Li H2PO4 respectively to remove water, and pass them through a 200-mesh sieve to obtain pretreated raw materials; Step 2, Low-temperature solvothermal synthesis: according to Li7P3S 11 Li2S and P2S5 were weighed in a stoichiometric ratio, and Li I and Li3N were added. Anhydrous acetonitrile was used as a solvent to carry out a solvothermal reaction. After the reaction, the product was separated, washed and dried to obtain the core layer precursor. Step 3, Mechanochemical activation: The core layer precursor is ball-milled at a temperature controlled at ≤40℃ to obtain core layer powder; Step 4, Gradient Coating: An Al2O3-Li3PO4 gradient layer is deposited on the surface of the core layer powder using atomic layer deposition technology to obtain the initial product; Step 5, Low-temperature sintering: The initial product is sintered under pressure to obtain a sulfide solid electrolyte.

4. The method for preparing a sulfide solid electrolyte according to claim 2, characterized in that: In step 1, Li2S is dried at 120℃ under vacuum for 4 hours, P2S5 is dried at 80℃ for 2 hours under inert gas protection, and Li I, Li3N, Al(NO3)3·9H2O, and LiH2PO4 are dried at 60℃ under vacuum for 1 hour.

5. The method for preparing a sulfide solid electrolyte according to claim 2, characterized in that: In step 2, the solid-liquid ratio of the solvothermal reaction is 1:5 g / mL, the heating rate is 5℃ / min, the reaction temperature is 120-150℃, the holding time is 6-8h, and the reaction atmosphere is an inert gas.

6. The method for preparing a sulfide solid electrolyte according to claim 2, characterized in that: In step 3, a planetary ball mill is used for ball milling, with a ball-to-material ratio of 20:1, a rotation speed of 300-400 r / min, a milling time of 2-3 h, and an inert gas atmosphere.

7. The method for preparing a sulfide solid electrolyte according to claim 2, characterized in that: In step 4, the vacuum degree of atomic layer deposition is ≤1×10-3Pa and the substrate temperature is 150℃; the Al2O3 deposition source is trimethylaluminum and deionized water, and the Li3PO4 deposition source is trimethyl phosphate and LiOtBu; the gradient layer deposition includes a pure Al2O3 layer (50-80 cycles), a transition layer (40-60 cycles), and a pure Li3PO4 layer (50-80 cycles).

8. The method for preparing a sulfide solid electrolyte according to claim 3, characterized in that: In step 5, the sintering temperature is 300-350℃, the heating rate is 2℃ / min, the pressure is 10-15MPa, the holding time is 1h, and the sintering atmosphere is an inert gas.

9. An application of a sulfide solid electrolyte, used in conjunction with the sulfide solid electrolyte as described in claims 1-2, characterized in that: The method includes the following steps for an electrolyte layer in an all-solid-state lithium metal battery, wherein the battery uses lithium nickel cobalt manganese oxide or lithium iron phosphate as the positive electrode and lithium metal as the negative electrode.

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