Solid electrolyte-negative electrode interface and preparation method therefor

Abstract

Disclosed in the present invention is a setter plate for preparing a ceramic solid electrolyte membrane. The setter plate comprises a lithium-containing ceramic layer and a high-temperature-resistant ceramic layer. The lithium-containing ceramic layer and the high-temperature-resistant ceramic layer are tightly bonded together by sintering, and the setter plate has a substantially flat surface. Also disclosed in the present invention are a preparation method for the setter plate and a method for using the setter plate to prepare a flat solid electrolyte membrane. In the present invention, when the setter plate is used for preparing the solid electrolyte membrane, the flatness and ionic conductivity of the solid electrolyte membrane can be improved, and the solid electrolyte membrane having a flat surface, a compact structure and high ionic conductivity is obtained.

Description

Solid-state electrolyte-negative electrode interface and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to a solid-state electrolyte-negative electrode interface and a preparation method thereof, and belongs to the field of solid-state batteries. The present application also relates to a solid-state electrolyte-negative electrode assembly comprising the solid-state electrolyte-negative electrode interface, and a solid-state lithium metal battery comprising the solid-state electrolyte-negative electrode assembly. BACKGROUND

[0002] Solid-state batteries are considered as the next generation of lithium batteries due to their safety and high energy density. Traditional lithium-ion batteries use liquid electrolytes, which may cause fire or explosion under high temperature or extreme conditions, and the safety performance is not ideal. Solid-state lithium batteries use solid-state electrolytes, which have high ionic conductivity, high temperature resistance and chemical stability, etc., can prevent lithium dendrite growth, improve the safety of the battery, and greatly reduce the safety hazards caused by electrolyte problems.

[0003] Currently, the negative electrode of a solid-state battery using a ceramic solid-state electrolyte is usually lithium metal or graphite combined with a current collector (copper foil), and a small amount of electrolyte is needed to soak the interface. Such a battery assembly method will generate SEI (solid-state electrolyte interface) with the lithium metal or graphite negative electrode due to the use of a small amount of electrolyte, resulting in an increase in interface impedance and a decrease in maximum current density, which is not conducive to improving the coulomb efficiency and cycle stability of the battery.

[0004] Therefore, there is a need for an improved solid-state electrolyte-negative electrode interface without electrolyte to optimize the interface contact and effectively improve the energy density of the solid-state battery.

[0005] SUMMARY

[0006] The technical problem to be solved by the present application is to improve the solid-state electrolyte-negative electrode interface of the prior art, improve the interface contact between the solid-state electrolyte and the lithium negative electrode, reduce the interface impedance, and improve the maximum current density and the energy density of the battery.

[0007] To solve the above technical problems, the present application provides a processing method for a solid-state electrolyte-negative electrode interface without electrolyte. The improved processing of the solid-state electrolyte-negative electrode interface uses an evaporation method to evaporate a layer of silver-nickel alloy on the negative side surface of the solid-state electrolyte, and then the solid-state electrolyte and the lithium negative electrode are subjected to hot pressing treatment to form a solid-state electrolyte-negative electrode interface without electrolyte, which effectively improves the interface contact and energy density of the solid-state battery.

[0008] The first aspect of the present application provides a preparation method for a solid-state electrolyte-negative electrode interface, characterized in that the method comprises the following steps:

[0009] evaporating a layer of silver-nickel alloy on the negative side surface of the solid-state electrolyte,

[0010] The solid-state electrolyte after evaporation is subjected to a hot-pressing treatment with the negative electrode to form the solid-state electrolyte-negative electrode interface.

[0011] In some embodiments, the silver-nickel alloy is evaporated with a content of metallic nickel of 5-50wt%, preferably 15-40wt%, more preferably 25-35wt%.

[0012] In some embodiments, the silver-nickel alloy is evaporated under the following conditions:

[0013] The nano-powder of metallic silver and metallic nickel is used,

[0014] The evaporation current is 40-60A, preferably 45-55A, more preferably about 50A,

[0015] The evaporation time is 30-60s, preferably 40-55s, more preferably about 50s.

[0016] In some embodiments, the thickness of the evaporated silver-nickel alloy layer is 50-300nm, preferably 100-200nm.

[0017] In some embodiments, the hot-pressing treatment is performed at a temperature of 200-500°C, preferably 250-450°C, more preferably 300-400°C, still more preferably 300-375°C, and / or

[0018] The hot-pressing treatment is performed at a pressure of 5-20MPa, preferably 8-15MPa, more preferably 9-12MPa.

[0019] In some embodiments, the hot-pressing treatment causes the surface of the evaporated silver-nickel alloy of the solid-state electrolyte to tightly adhere to the negative electrode.

[0020] In some embodiments, the preparation method further comprises a step of polishing the negative electrode side surface of the solid-state electrolyte before the evaporation step.

[0021] In some embodiments, the surface flatness of the negative electrode side surface of the solid-state electrolyte after polishing is ≤1μm.

[0022] In some embodiments, the solid-state electrolyte comprises one or more materials selected from lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, germanium aluminum lithium phosphate, or titanium aluminum lithium phosphate.

[0023] In some embodiments, the negative electrode is metallic lithium.

[0024] In some specific embodiments, the interfacial impedance of the solid electrolyte-negative electrode interface is ≤40Ω, preferably ≤30Ω, and more preferably ≤20Ω.

[0025] A second aspect of the present invention provides a solid electrolyte-anode assembly, comprising a solid electrolyte, a lithium metal anode, and a solid electrolyte-anode interface located between the solid electrolyte and the anode, wherein the solid electrolyte-anode interface is prepared by the preparation method of the first aspect of the present invention.

[0026] In some specific embodiments, the thickness of the solid electrolyte is 30-1000 μm, preferably 50-500 μm, and more preferably 100-200 μm.

[0027] In some specific embodiments, the thickness of the lithium metal anode is 5-500 μm, preferably 10-200 μm, and more preferably 15-100 μm.

[0028] The third aspect of the present invention provides the application of the solid electrolyte-anode assembly described in the second aspect of the present invention in a solid lithium metal battery.

[0029] A fourth aspect of the present invention provides a solid-state lithium metal battery, which includes the solid electrolyte-anode assembly described in the second aspect of the present invention.

[0030] This invention provides a method for preparing a solid electrolyte-anode interface, which improves the interfacial contact between the solid electrolyte and the lithium anode without using a current collector or electrolyte, reduces the interfacial impedance, and increases the maximum current density. This is beneficial for improving the coulombic efficiency and energy density of solid lithium metal batteries using the solid electrolyte-anode interface of this invention. Attached Figure Description

[0031] Figure 1 shows a graph of the critical current density test of the solid electrolyte-anode interface in Test Example 2 of the present invention. (A) shows the test results of the solid electrolyte-anode interface after vapor deposition and hot pressing treatment, and (B) shows the test results of the solid electrolyte-anode interface without vapor deposition treatment.

[0032] Figure 2 shows the capacity retention and coulombic efficiency curves of the lithium metal battery of Test Example 3 of the present invention during room temperature cycling performance testing. Detailed Implementation

[0033] The present invention will be further described below through specific embodiments. Unless otherwise specified, the terminology used herein has the same meaning as commonly understood by one of ordinary skill in the art. Numerical limits or ranges stated herein include endpoints, specifically including all values ​​and subranges within the numerical limits or ranges.

[0034] The term "about" when used in reference to a value means that the value contains variations, such as ±10%, ±5%, ±1%, or ±0.1% of the specified value.

[0035] The term "substantially the same" when used in reference to two values means that the difference between the two values is less than 10%, 5%, or 1% of the average of the two values.

[0036] The first aspect of the present application provides a method for preparing a solid-state electrolyte-negative electrode interface, characterized in that the method comprises the following steps:

[0037] evaporating a layer of silver-nickel alloy on the negative electrode side surface of the solid-state electrolyte,

[0038] thermally pressing the solid-state electrolyte after evaporation and the negative electrode to form the solid-state electrolyte-negative electrode interface.

[0039] In the present application, the term "evaporation" refers to vacuum evaporation, which is a process method of evaporating and vaporizing plating film materials under vacuum conditions using a certain heating evaporation method, and particles fly to the substrate surface to condense into a film. The physical process of evaporation includes: deposition material evaporation or sublimation into gaseous particles → rapid transportation of gaseous particles from the evaporation source to the substrate surface → nucleation and growth of gaseous particles on the substrate surface into a solid thin film → thin film atom reconstruction or chemical bonding. During the evaporation process, the device using a mechanical pump controls the gas pressure in the evaporation chamber to be close to vacuum, and by adjusting the evaporation current and evaporation time, the thickness of the plating layer can be controlled.

[0040] In the specific embodiments of the present application, the substrate used for evaporation is a solid-state electrolyte ceramic sheet, and the plating film material is metal silver and metal nickel, preferably nano-powder of metal silver and metal nickel, i.e. nano-silver-nickel powder.

[0041] In some embodiments, the content of metal nickel in the evaporated silver-nickel alloy is about 5-50wt%, preferably about 15-40wt%, and more preferably about 25-35wt%. For example, the content of metal nickel can be about 5wt%, 10wt%, 15wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, 45wt%, 50wt%, etc., or any content ratio within the above range.

[0042] In some embodiments, the silver-nickel alloy is deposited using a nanometer-sized powder of silver and nickel, at a pressure of 1 Pa or less, a current of 50 A, preferably 45-55 A, more preferably about 50 A, and a deposition time of 50 s, preferably 40-55 s, more preferably about 50 s. Under these deposition conditions, the nanometer-sized silver-nickel powder is sufficiently vaporized and deposited onto the surface of the solid electrolyte. Thus, the ratio of silver to nickel in the nanometer-sized powder of silver and nickel is substantially the same as the ratio of silver to nickel in the silver-nickel alloy layer deposited onto the surface of the solid electrolyte.

[0043] In some embodiments, the silver-nickel alloy layer is deposited to a thickness of about 50-300 nm, preferably about 100-200 nm. For example, the silver-nickel alloy layer can be deposited to a thickness of about 50 nm, 75 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 220 nm, 240 nm, 250 nm, 275 nm, 300 nm, or any thickness within the above ranges.

[0044] In the present application, the heat-pressing of the solid electrolyte after deposition and the negative electrode can be performed in an atmosphere furnace. The heat-pressing is performed by placing the surface of the solid electrolyte on which the silver-nickel alloy layer is deposited in contact with a lithium foil, and heating and applying pressure to the stack in the atmosphere furnace for a certain period of time, so that the solid electrolyte and the negative electrode are adhered to each other. In some embodiments, the pressure applied in the heat-pressing is a mechanical pressure, for example, by using a heavy weight press to apply a mechanical pressure to the stack of the solid electrolyte and the negative electrode lithium foil.

[0045] In some embodiments, the heat-pressing is performed at a temperature of about 200-500°C, preferably about 250-450°C, more preferably about 300-400°C, and still more preferably about 300-375°C. For example, the heat-pressing can be performed at a temperature of about 200°C, 225°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 475°C, 500°C, or any temperature within the above ranges.

[0046] In some embodiments, the hot-pressing process is performed at a pressure of about 5-20 MPa, preferably about 8-15 MPa, and more preferably about 9-12 MPa. For example, the hot-pressing process can be performed at a pressure of about 5 MPa, 6 MPa, 7 MPa, 8 MPa, 8.5 MPa, 9 MPa, 9.5 MPa, 10 MPa, 10.5 MPa, 11 MPa, 11.5 MPa, 12 MPa, 12.5 MPa, 13 MPa, 14 MPa, 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, 20 MPa, or any pressure within the above ranges.

[0047] In some embodiments, the hot-pressing process is performed for a time period of 1-30 minutes, preferably 5-20 minutes, and more preferably 8-15 minutes.

[0048] In some embodiments, the hot-pressing process causes the surface of the solid-state electrolyte layer of the vapor-deposited silver-nickel alloy to tightly adhere to the anode.

[0049] In the preparation method of the present application, the inventors have found that by adjusting the silver-nickel ratio in the vapor-deposited silver-nickel alloy layer, the interface impedance of the solid-state electrolyte-anode interface can be optimized. Unlike the resistance performance of macroscopic metals or alloys, when a certain amount of metallic nickel is added to the nano-vapor-deposited layer of pure silver, the interface impedance can be further reduced. The inventors have also found that by adjusting the pressure and temperature of the hot-pressing process, the interface impedance of the solid-state electrolyte-anode interface can be further reduced. A certain degree of hot-pressing process can make the adhesion between the solid-state electrolyte-silver-nickel alloy layer-lithium anode more tightly, reduce and eliminate the voids between the layers of substances, thereby forming more ion channels in the interface, reducing the interface impedance, and being conducive to improving the critical current density and the coulombic efficiency of the battery.

[0050] In some embodiments, the preparation method further comprises a step of polishing the anode-side surface of the solid-state electrolyte before the vapor-deposition step.

[0051] In some embodiments, the anode-side surface of the solid-state electrolyte has a surface flatness of ≤1 μm after polishing. In the present application, the surface flatness is defined as the maximum value of the height difference of each point on the measured surface in the direction perpendicular to the surface. The smaller the surface flatness value, the higher the flatness of the surface. A flat solid-state electrolyte surface is conducive to forming a flat vapor-deposited layer and improving the adhesion to the lithium anode. In preferred embodiments, the anode-side surface of the solid-state electrolyte has a surface flatness of ≤900 nm, ≤800 nm, ≤700 nm, ≤600 nm, ≤500 nm, ≤400 nm, ≤300 nm, ≤200 nm, or ≤100 nm after polishing.

[0052] In some embodiments, the solid state electrolyte comprises one or more materials selected from lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide (LLZTO), lithium lanthanum zirconium aluminum oxide (LLAZO), lithium lanthanum zirconium gallium oxide (LLGZO), lithium lanthanum titanium oxide (LLTO), lithium aluminum germanium phosphate (LAGP), or lithium aluminum titanium phosphate (LATP). In preferred embodiments, the solid state electrolyte consists of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, lithium aluminum germanium phosphate, or lithium aluminum titanium phosphate. More preferably, the solid state electrolyte is lithium lanthanum zirconium tantalum oxide (LLZTO).

[0053] The above materials are solid state electrolyte materials known in the art. For example, in certain embodiments, lithium lanthanum zirconium oxide (LLZO) has the chemical formula Li7La3Zr2O12. 12 ;

[0054] Lithium lanthanum zirconium tantalum oxide (LLZTO) has the chemical formula Li7La3Zr2-xTaxO12, where x is a number between 0 and 2. For example, when x = 0.5, the chemical formula is Li7La3Zr1.5TaxO12, when x = 0.6, the chemical formula is Li7La3Zr1.4TaxO12, and when x = 0.7, the chemical formula is Li7La3Zr1.3TaxO12. 7-x La3Zr 2-x Ta x O 12 , for example when x = 0.5, the chemical formula is Li7La3Zr1.5TaxO12, when x = 0.6, the chemical formula is Li7La3Zr1.4TaxO12, and when x = 0.7, the chemical formula is Li7La3Zr1.3TaxO12. 6.5 La3Zr 1.5 Ta 0.5 O 12 , for example when x = 0.5, the chemical formula is Li7La3Zr1.5TaxO12, when x = 0.6, the chemical formula is Li7La3Zr1.4TaxO12, and when x = 0.7, the chemical formula is Li7La3Zr1.3TaxO12. 6.4 La3Zr 1.4 Ta 0.6 O 12 , for example when x = 0.5, the chemical formula is Li7La3Zr1.5TaxO12, when x = 0.6, the chemical formula is Li7La3Zr1.4TaxO12, and when x = 0.7, the chemical formula is Li7La3Zr1.3TaxO12.

[0055] Lithium lanthanum zirconium aluminum oxide (LLAZO) has the chemical formula Li7La3AlxZr2-xO12, where x is a number between 0 and 2. For example, when x = 0.1, the chemical formula is Li7La3Al0.1Zr1.9O12, when x = 0.2, the chemical formula is Li7La3Al0.2Zr1.8O12, and when x = 0.3, the chemical formula is Li7La3Al0.3Zr1.7O12. 7-3x La3Al x Zr2O 12 , for example when x = 0.1, the chemical formula is Li7La3Al0.1Zr1.9O12, when x = 0.2, the chemical formula is Li7La3Al0.2Zr1.8O12, and when x = 0.3, the chemical formula is Li7La3Al0.3Zr1.7O12. 6.7 La3Al 0.1 Zr2O 12 , for example when x = 0.1, the chemical formula is Li7La3Al0.1Zr1.9O12, when x = 0.2, the chemical formula is Li7La3Al0.2Zr1.8O12, and when x = 0.3, the chemical formula is Li7La3Al0.3Zr1.7O12. 6.4 La3Al 0.2 Zr2O 12 ;

[0056] Lithium lanthanum zirconium gallium oxide (LLGZO) has the chemical formula Li7La3GaxZr2-xO12, where x is a number between 0 and 2. For example, when x = 0.2, the chemical formula is Li7La3Ga0.2Zr1.8O12, when x = 0.3, the chemical formula is Li7La3Ga0.3Zr1.7O12, and when x = 0.4, the chemical formula is Li7La3Ga0.4Zr1.6O12. 7-3x La3Ga x Zr2O 12 , for example when x = 0.2, the chemical formula is Li7La3Ga0.2Zr1.8O12, when x = 0.3, the chemical formula is Li7La3Ga0.3Zr1.7O12, and when x = 0.4, the chemical formula is Li7La3Ga0.4Zr1.6O12. 6.4 La3Ga 0.2 Zr2O 12 , for example when x = 0.2, the chemical formula is Li7La3Ga0.2Zr1.8O12, when x = 0.3, the chemical formula is Li7La3Ga0.3Zr1.7O12, and when x = 0.4, the chemical formula is Li7La3Ga0.4Zr1.6O12. 6.1 La3Ga 0.3 Zr2O 12 ;

[0057] Lithium lanthanum titanium oxide (LLTO) has the chemical formula Li 2-3x La x TiO3, for example, when x = 0.4, the chemical formula is Li 0.8 La 0.4 TiO3, when x = 0.5, the chemical formula is Li 0.5 La 0.5 TiO3;

[0058] Lithium aluminum germanium phosphate (LAGP) has the chemical formula Li 1.5 Al 0.5 Ge 1.5 (PO4)3;

[0059] Lithium aluminum titanium phosphate (LATP) has the chemical formula Li 1.3 Al 0.3 Ti 1.7 (PO4)3.

[0060] The method of preparing the solid-state electrolyte-cathode interface of the present application is suitable for forming a low-impedance interface between various solid-state electrolytes and lithium battery cathodes, thereby improving the interface contact and energy density of the solid-state battery.

[0061] In some embodiments, the solid-state electrolyte has a thickness of 30-1000 pm, preferably 50-500 pm, and more preferably 100-200 pm. Depending on the specific embodiment, the solid-state electrolyte can have a thickness of 30 pm, 40 pm, 50 pm, 60 pm, 70 pm, 80 pm, 90 pm, 100 pm, 110 pm, 120 pm, 130 pm, 140 pm, 150 pm, 160 pm, 170 pm, 180 pm, 190 pm, 200 pm, 250 pm, 300 pm, 350 pm, 400 pm, 450 pm, 500 pm, 600 pm, 700 pm, 800 pm, 900 pm, 1000 pm, or any thickness within the above ranges.

[0062] In some embodiments, the negative electrode is lithium metal. In some embodiments, the lithium metal negative electrode has a thickness of 5-500 pm, preferably 10-200 pm, more preferably 15-100 pm. According to specific embodiments, the lithium metal negative electrode has a thickness of 5 pm, 10 pm, 15 pm, 20 pm, 25 pm, 30 pm, 35 pm, 40 pm, 45 pm, 50 pm, 60 pm, 70 pm, 80 pm, 90 pm, 100 pm, 110 pm, 120 pm, 130 pm, 140 pm, 150 pm, 160 pm, 170 pm, 180 pm, 190 pm, 200 pm, 250 pm, 300 pm, 350 pm, 400 pm, 450 pm, 500 pm, or any thickness within the above ranges.

[0063] In some embodiments, the interface impedance of the solid-state electrolyte-negative electrode interface is ≤ 40 Ω, preferably ≤ 30 Ω, more preferably ≤ 20 Ω.

[0064] In the present application, the solid-state electrolyte-negative electrode interface prepared by the preparation method of the first aspect of the present application is tightly attached to the solid-state electrolyte and the negative electrode on both sides to form a whole. Therefore, the first aspect of the present application also provides a preparation method of a solid-state electrolyte-negative electrode assembly, which comprises a solid-state electrolyte, a negative electrode, and a solid-state electrolyte-negative electrode interface between the solid-state electrolyte and the negative electrode, the method comprising the following steps:

[0065] evaporating a layer of silver-nickel alloy on the negative electrode side surface of the solid-state electrolyte,

[0066] subjecting the evaporated solid-state electrolyte and the negative electrode to hot-pressing treatment to form the solid-state electrolyte-negative electrode interface between the solid-state electrolyte and the negative electrode, thereby obtaining the solid-state electrolyte-negative electrode assembly.

[0067] The second aspect of the present application provides a solid-state electrolyte-negative electrode assembly, which comprises a solid-state electrolyte, a lithium metal negative electrode, and a solid-state electrolyte-negative electrode interface between the solid-state electrolyte and the negative electrode, the solid-state electrolyte-negative electrode interface being prepared by the preparation method of the first aspect of the present application. Therefore, the solid-state electrolyte-negative electrode interface contained in the solid-state electrolyte-negative electrode assembly of the second aspect of the present application has one or more features described in the first aspect of the present application.

[0068] The third aspect of the present application provides the use of the solid-state electrolyte-negative electrode assembly of the second aspect of the present application described above in a solid-state lithium metal battery.

[0069] The fourth aspect of the present application provides a solid-state lithium metal battery, which comprises the solid-state electrolyte-negative electrode assembly of the second aspect of the present application described above.

[0070] Examples

[0071] The present application is described in detail below by way of examples, which are not intended to limit the present application. The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0072] In the following examples, dry-synthesized LLZTO is used as the solid-state electrolyte material for illustrative purposes only. It should be understood that the solid-state electrolyte material of the solid-state electrolyte-negative electrode interface of the present application is not limited to LLZTO.

[0073] Preparation Example: Preparation of LLZTO solid-state electrolyte.

[0074] To prepare the LLZTO solid-state electrolyte with the chemical formula of Li 6.4 La3Zr 1.4 Ta 0.6 O 12 To prepare the LLZTO solid-state electrolyte with the chemical formula of Li

[0075] The weighed element precursor powders were placed in a zirconium oxide ball mill jar, and an appropriate amount of zirconium oxide ball milling beads and isopropanol were added. The mixture was wet ball milled at a speed of 350 rpm for 12 h to obtain a mixed powder. The mixed powder was then placed in an oven for drying to completely remove the solvent isopropanol. The dried powder was placed in a tube furnace and sintered at 900 °C for 10 h with a heating rate of 5 °C / min. After the reaction was completed, the sample was naturally cooled in the tube furnace to obtain the LLZTO solid-state electrolyte powder.

[0076] The LLZTO solid-state electrolyte powder was taken for powder refinement, and then placed in a zirconium oxide ball mill jar, and an appropriate amount of zirconium oxide ball milling beads and isopropanol were added. The mixture was wet ball milled at a speed of 350 rpm for 12 h, and then dried and sieved to obtain LLZTO solid-state electrolyte powder with a size of about 300 nm. The LLZTO powder was uniaxially pressed at a pressure of 40 MPa for 3 min. The compacted ceramic sheet was sintered in a muffle furnace at a sintering temperature of 1300 °C for 10 min with a heating rate of 10 °C / min. After the reaction was completed, the sample was naturally cooled in the muffle furnace to obtain the LLZTO solid-state electrolyte. The cooled LLZTO solid-state electrolyte was polished to have a surface flatness of ≤1 μm.

[0077] The polished LLZTO solid-state electrolyte was used to prepare the solid-state electrolyte-negative electrode interface in the following examples.

[0078] Example 1: Preparation of solid-state electrolyte-negative electrode interface.

[0079] The negative side surface of the polished LLZTO solid electrolyte was evaporated with a silver-nickel alloy (thickness 150 nm), using nano silver-nickel powder as raw material (with nickel content of 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt% respectively), and the gas pressure in the evaporation chamber was controlled to be below 1 Pa. The evaporation conditions were: evaporation current 50 A, evaporation time 50 s.

[0080] The LLZTO after evaporation and a lithium foil with a thickness of 20 μm were placed in an atmosphere furnace for hot pressing, and the hot pressing temperature was 200°C, 250°C, 300°C, 350°C, 400°C respectively, the pressure was 10 MPa, and the pressure was maintained for 10 minutes, forming a solid electrolyte-negative interface with the lithium foil and the LLZTO closely adhered.

[0081] According to different combinations of nickel content and hot pressing temperature, a plurality of solid electrolyte-negative interface samples were prepared for subsequent performance testing.

[0082] Test Example 1: Interface impedance test.

[0083] The LLZTO-lithium foil negative electrode prepared in the example was assembled into a battery with an NCM811 positive electrode, and the interface impedance was tested. The test conditions were: using a high-precision electrochemical workstation with model ZF1260-1287 to test the alternating current impedance, and the intrinsic bulk impedance of the sample was tested by electrochemical impedance spectroscopy (EIS). The impedance test frequency range was from 1 Hz to 1 MHz, the alternating current amplitude was 0.01 V, and the test temperature was room temperature.

[0084] The test results of the interface impedance are shown in Table 1.

[0085] Table 1: Interface impedance (Ω) of LLZTO-lithium negative electrode prepared under different nickel content and hot pressing temperature conditions

[0086] As shown in the test results of Table 1, compared with the LLZTO without evaporation treatment, after evaporation of silver or silver-nickel alloy, the interface impedance can be reduced, and the evaporation of silver-nickel alloy reduces the impedance more, and when the nickel content is 25-35wt%, the interface impedance is the lowest. At the same time, hot pressing treatment can further reduce the interface impedance, and when the hot pressing temperature is 300-400°C, the interface impedance is the lowest.

[0087] The results of the orthogonal experiment show that when the nickel content is 30wt% and the hot pressing temperature is 350°C, compared with the blank sample without evaporation treatment, the interface impedance is reduced by 115Ω, and the reduction amplitude is more than 90%. Therefore, this parameter combination is used for subsequent testing.

[0088] Test Example 2: Critical current density test.

[0089] According to the preparation method of the embodiment, a silver-nickel alloy layer with a nickel content of 30wt% is evaporated on both sides of the LLZTO solid-state electrolyte, and a lithium foil is attached for hot pressing (hot pressing temperature 350°C) to obtain a lithium symmetric battery for detecting the critical current density. As a comparison, a lithium foil-LLZTO-lithium foil without evaporation treatment and only hot pressing is used as a blank control. The test results are shown in Table 2 and Figure 1.

[0090] Table 2 Critical current density of LLZTO-lithium negative electrode interface

[0091] As shown in the test results of Table 2 and Figure 1, the LLZTO-lithium negative electrode interface treated by evaporation and hot pressing can withstand a current density of 1.8mA / cm 2 , while the blank sample without evaporation treatment is 0.8mA / cm 2 , with an increase of at least 125%.

[0092] Test Example 3: Charge-discharge cycle test.

[0093] The LLZTO-lithium foil negative electrode prepared in the embodiment with a nickel content of 30wt% and a hot pressing temperature of 350°C is assembled into a battery with an NCM811 positive electrode for charge-discharge cycle test. The test conditions are: positive electrode load 17.2mg, first circle capacity 3.1556mAh, specific capacity 183.5mAh / g, charge-discharge interval 3-4.2V. After 200 cycles of charge-discharge cycle, the capacity retention rate is 91.8%. The capacity change and coulomb efficiency of the battery during the test are shown in Figure 2. In Figure 2, the upper curve is the coulomb efficiency, and the lower curve is the battery capacity.

[0094] According to the above charge-discharge cycle test, the solid-state lithium metal battery using the solid-state electrolyte-negative electrode interface of the present application has excellent cycle life and can maintain excellent coulomb efficiency during multiple cycles, which is beneficial to the industrial application of solid-state lithium metal batteries.

[0095] Example 2: Test results of other solid-state electrolyte-negative electrode interfaces.

[0096] In addition to the LLZTO solid-state electrolyte, referring to the preparation method of Example 1, the solid-state electrolyte-negative electrode interfaces were prepared using the solid-state electrolytes listed in Table 3 under the conditions of a nickel content of 30wt% and a hot pressing temperature of 350°C, and the interface impedance and critical current density were tested according to the methods of Test Examples 1-2, and the results are shown in Table 3 (with the results of the same solid-state electrolyte-negative electrode interface without evaporation treatment as a control). The results of the interfaces containing LLZTO obtained in Test Examples 1-2 are also listed in the table.

[0097] Table 3 Interface impedance and critical current density of solid electrolyte-negative electrode interface

[0098] From the above test results, it can be seen that the preparation method of the solid electrolyte-negative electrode interface of the present application is also applicable to other types of solid electrolytes. Compared with the untreated solid electrolyte-negative electrode interface, the solid electrolyte-negative electrode interface of the present application after evaporation of silver-nickel alloy and heat pressing treatment can greatly reduce the interface impedance and improve the critical current density, thereby improving the coulomb efficiency and energy density of the solid-state lithium metal battery.

[0099] The above describes the exemplary embodiments of the present application through the examples, but the present application is not limited thereto. Those skilled in the art should understand that the above examples are for illustrative purposes only, and the specific embodiments and examples of the present application should not be considered as limiting the scope of the present application. Changes and modifications can be made to the embodiments within the scope of the present application, and such changes and modifications should be considered as falling within the scope of the present application.

Claims

1. A method of preparing a solid-state electrolyte-anode interface, characterized by, The method comprises the following steps: evaporating a layer of silver-nickel alloy on the negative side surface of the solid-state electrolyte, subjecting the evaporated solid-state electrolyte and the negative electrode to hot-pressing treatment to form the solid-state electrolyte-negative electrode interface.

2. The production method according to claim 1, characterized by, The content of metallic nickel in the evaporated silver-nickel alloy is 5-50wt%, preferably 15-40wt%, and more preferably 25-35wt%.

3. The preparation method according to claim 1, characterized in that, The evaporation conditions of the silver-nickel alloy are that nanometer powders of metallic silver and metallic nickel are used, the evaporation current is 40-60A, preferably 45-55A, the evaporation time is 30-60s, preferably 40-55s.

4. The method of claim 1, wherein, The thickness of the evaporated silver-nickel alloy layer is 50-300nm, preferably 100-200nm.

5. The preparation method according to claim 1, characterized in that, The temperature of the hot-pressing treatment is 200-500℃, preferably 250-450℃, more preferably 300-400℃, and still more preferably 300-375℃, and / or The pressure of the hot-pressing treatment is 5-20MPa, preferably 8-15MPa, and more preferably 9-12MPa.

6. The method of claim 1, wherein, The hot-pressing treatment causes the evaporated silver-nickel alloy surface of the solid-state electrolyte to tightly adhere to the negative electrode.

7. The preparation method according to claim 1, characterized in that, The method further comprises a step of polishing the negative side surface of the solid-state electrolyte before the evaporation step.

8. The preparation method according to claim 7, characterized in that, The surface flatness of the polished negative side surface of the solid-state electrolyte is ≤1μm.

9. The method of claim 1, wherein, The solid-state electrolyte comprises one or more materials selected from lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, germanium aluminum lithium phosphate, or titanium aluminum lithium phosphate.

10. The method of claim 1, wherein, The negative electrode is metallic lithium.

11. The method of claim 1, wherein, The interface impedance of the solid-state electrolyte-negative electrode interface is ≤40Ω, preferably ≤30Ω, and more preferably ≤20Ω.

12. A solid-state electrolyte-anode assembly comprising a solid-state electrolyte, a lithium metal anode, and a solid-state electrolyte-anode interface located between the solid-state electrolyte and the anode, characterized in that, The solid-state electrolyte-negative electrode interface is prepared by the preparation method of any one of claims 1-11.

13. The solid-state electrolyte-anode assembly of claim 12, wherein, The thickness of the solid-state electrolyte is 30-1000μm, preferably 50-500μm, and more preferably 100-200μm.

14. The solid-state electrolyte-anode assembly of claim 12, wherein, The thickness of the lithium metal negative electrode is 5-500μm, preferably 10-200μm, and more preferably 15-100μm.

15. Use of the solid-state electrolyte-negative electrode assembly of any one of claims 12-14 in a solid-state lithium metal battery.

16. A solid-state lithium metal battery comprising the solid-state electrolyte-negative electrode assembly of any one of claims 12-14.

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