Preparation method of interface modification layer between lithium metal electrode and garnet solid electrolyte and solid lithium metal battery

Abstract

The invention provides a preparation method of an interface modification layer between lithium metal and a garnet solid electrolyte. The preparation method comprises the following steps: 1) preparing a tantalum-doped garnet solid electrolyte; 2) co-sputtering a SnO2-Al layer on the surface of the tantalum-doped garnet solid electrolyte; and 3) co-sputtering a SnO2-Al layer on the surface of the tantalum-doped garnet type solid electrolyte, and then carrying out in-situ reaction on the tantalum-doped garnet type solid electrolyte and molten lithium metal to obtain an interface modification layer between the lithium metal and the garnet type solid electrolyte. The interface modification layer between the lithium metal and the garnet type solid electrolyte effectively inhibits the interface reaction between the garnet type solid electrolyte and the lithium metal, a double-layer conductive interface with a stable ion / electron transmission channel is formed in situ, and the stability of the garnet type solid electrolyte to the lithium metal is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and specifically relates to a method for preparing an interface modification layer between a lithium metal electrode and a garnet solid electrolyte and a solid lithium metal battery. Background Art

[0002] In recent years, the application of lithium-ion batteries has taken root in people's lives, and mobile devices widely use lithium-ion batteries. Today, most electric vehicles developed also use lithium-ion batteries as driving energy, and lithium-ion batteries with higher energy density are urgently needed. Metallic lithium anode, as the "holy grail" anode of secondary lithium batteries, exhibits high theoretical specific capacity (3860mAh g-1) and low electrochemical potential (-3.04V vs. hydrogen standard electrode), which can be suitable for replacing graphite electrodes. However, during the repeated deposition and precipitation of Li+ in liquid electrolytes, Li dendrites easily grow and propagate on the surface of Li metal anodes, forming dead lithium and even short-circuiting the battery, which may cause serious safety hazards such as combustion and explosion.

[0003] All-solid-state lithium metal batteries are considered to be one of the most promising next-generation battery systems. Solid-state electrolytes can significantly reduce safety risks by replacing liquid organic electrolytes that are limited by their potential leakage and flammability. In addition, the high mechanical modulus of solid-state electrolytes can help suppress lithium dendrites to achieve high-performance lithium metal batteries. Therefore, replacing traditional liquid electrolytes with non-flammable solid electrolytes is expected to fundamentally solve the safety issues of liquid lithium metal batteries.

[0004] Among different solid electrolytes, garnet-based electrolytes have advantages in ionic conductivity, energy density, chemical stability, electrochemical stability, environmental stability, and safety. Therefore, it is considered to be one of the most promising and important electrolytes for achieving high energy density and high safety solid-state lithium batteries. Unfortunately, there are still several key challenges in the practical progress of garnet-based solid-state lithium batteries: (1) poor interfacial contact between garnet electrolyte and Li anode, which is attributed to the rapid generation of lithium-phobic Li on the garnet surface in air. 2 CO 3 layers, resulting in hundreds or even thousands of Ω / cm 2 (2) Due to poor interfacial contact, the current or charge distribution at the interface is uneven, which significantly increases the battery polarization. Especially at high current density, severe Li dendrite growth and subsequent penetration of the solid electrolyte eventually lead to battery failure. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing an interface modification layer between a lithium metal electrode and a garnet solid electrolyte. The prepared interface modification layer inhibits the interface reaction between the garnet solid electrolyte and lithium metal.

[0006] A method for preparing an interface modification layer between lithium metal and garnet solid electrolyte comprises the following steps:

[0007] 1) preparing tantalum-doped garnet solid electrolyte;

[0008] 2) Co-sputtering SnO on the surface of the tantalum-doped garnet solid electrolyte 2 -Al layer;

[0009] 3) Co-sputtering SnO on the surface of the tantalum-doped garnet solid electrolyte 2 -Al layer is then reacted in situ with molten lithium metal to obtain an interface modification layer between lithium metal and garnet solid electrolyte.

[0010] Further, step 2 includes using a 99.99% high purity Al target as a direct frequency target, a 99.99% high purity SnO 2 The target material is a radio frequency target, argon is used as the sputtering atmosphere, and SnO is co-sputtered on the surface of the garnet electrolyte by magnetron sputtering. 2 -Al layer.

[0011] Furthermore, the pressure of the magnetron sputtering is 0.25Pa-2Pa, and the magnetron sputtering time is 10s-120s.

[0012] Preferably, the pressure of the magnetron sputtering is 0.5Pa.

[0013] Preferably, the magnetron sputtering time is 30 s.

[0014] Furthermore, step 1 includes the following steps:

[0015] 1.1) mixing a lithium source, a lanthanum source, a zirconium source, and a tantalum source in a molar ratio of 6.5:3:1.5:0.5 in a ball mill tube, and ball milling is performed to obtain a mixed raw material, wherein 15 wt% of a lithium source is added to the slurry;

[0016] 1.2) drying and sieving the mixed electrolyte raw material and then calcining it, refining the calcined powder by ball milling, and then drying and sieving it to obtain a precursor powder;

[0017] 1.3) The precursor powder is pressed into tablets and then sintered to obtain the tantalum-doped garnet solid electrolyte.

[0018] Further, the calcination treatment conditions include: heating to 950°C at a heating rate of 2-10°C / min, and then keeping the temperature for 6 hours;

[0019] The sintering treatment conditions include: heating to 1280-1320° C. at a heating rate of 5° C. / min, and then keeping the temperature for 10-60 minutes.

[0020] Furthermore, the temperature of the in-situ reaction in step 3 is 200-400°C.

[0021] Furthermore, the time of the in-situ reaction in step 3 is 0.5-2 min.

[0022] Another subject is a solid-state lithium metal battery, comprising a positive electrode, a negative electrode and a garnet solid electrolyte, wherein the garnet solid electrolyte is located between the positive electrode and the negative electrode, the garnet solid electrolyte is a tantalum-doped garnet solid electrolyte, the negative electrode is a lithium metal negative electrode, and an interface modification layer prepared by the above-mentioned preparation method is provided between the tantalum-doped garnet solid electrolyte and the lithium metal negative electrode.

[0023] The beneficial effects of the present invention are:

[0024] The present invention provides a method for preparing an interface modification layer between lithium metal and garnet-type solid electrolyte and a solid lithium metal battery. 2 The in-situ reaction of the SnO-Al layer with the molten lithium should form a stable interface modification layer. 2 When the -Al layer comes into contact with molten lithium, it will undergo a decomposition reaction to generate lithium-philic products. The decomposition products and undecomposed SnO 2 -Al layer forms a stable interface modification layer between garnet-type solid electrolyte and lithium metal. The interface modification layer between lithium metal and garnet-type solid electrolyte effectively inhibits the interface reaction between garnet-type solid electrolyte and lithium metal, forms a double-layer conductive interface with a stable ion / electron transmission channel in situ, ensures the stability of garnet-type solid electrolyte to lithium metal, and is expected to promote the development of all-solid-state lithium metal batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0026] Figure 1 is an AC impedance spectrum of the tantalum-doped garnet solid electrolyte obtained in specific Example 1 of the present invention;

[0027] Figure 2 is a cross-sectional scanning electron microscope image of the tantalum-doped garnet solid electrolyte obtained in specific Example 1 of the present invention;

[0028] Figure 3 The SnO obtained in the specific embodiment 1 of the present invention 2 -AC impedance spectrum of Al sputtered layer;

[0029] Figure 4 The SnO obtained in the specific embodiment 2 of the present invention 2 -AC impedance spectrum of Al sputtered layer;

[0030] Figure 5 The SnO obtained in the specific embodiment 2 of the present invention 2 -Scanning electron microscopy image of the interface between Al-sputtered tantalum-doped garnet-type solid electrolyte and lithium metal;

[0031] Figure 6 Li|SnO in the specific embodiment 2 of the present invention 2 -Al LLZTO SnO 2 - Cycling performance diagram of Al|Li symmetric battery. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and beneficial technical effects of the present invention clearer, the following is a detailed description of the preparation method of the interface modification layer between the lithium metal electrode and the garnet solid electrolyte and the beneficial effects of the solid-state lithium metal battery in combination with the accompanying drawings and specific embodiments. The embodiments in this specification are only for explaining the present invention, not for limiting the present invention, and the parameters, proportions, etc. of the embodiments are selected according to actual conditions and have no substantial effect on the results.

[0033] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0034] The present invention provides a method for modifying the interface between lithium metal and garnet-type solid electrolyte, comprising the following steps:

[0035] 1. Provide garnet solid electrolyte;

[0036] 2. Co-sputtering SnO on the surface of the garnet solid electrolyte 2 -Al layer;

[0037] 3. Co-sputtering SnO on the surface of the garnet-type solid electrolyte2 -Al layer reacts in situ with molten lithium metal to obtain an interface modification layer between the lithium metal and the garnet solid electrolyte;

[0038] In step 2, the magnetron sputtering pressure is 0.25Pa-2Pa (eg, 0.25Pa, 0.5Pa, 1Pa or 2Pa), and the magnetron sputtering time is 10s-120s (eg, 10s, 30s, 60s or 120s).

[0039] The present invention firstly adopts solid phase sintering to prepare garnet type solid electrolyte, and then adopts magnetron sputtering to deposit a layer of SnO on the surface of garnet type solid electrolyte. 2 -Al film, and finally SnO coated on the surface of garnet-type solid electrolyte 2 -Al film reacts with molten lithium in situ to form a stable interface modification layer. The interface modification layer between lithium metal and garnet-type solid electrolyte effectively inhibits the interface reaction between garnet-type solid electrolyte and lithium metal, and in situ forms a double-layer conductive interface with a stable ion / electron transmission channel, ensuring the stability of garnet-type solid electrolyte to lithium metal, which is expected to promote the development of all-solid-state lithium metal batteries.

[0040] Example 1

[0041] A method for modifying the interface between lithium metal and garnet-type solid electrolyte comprises the following steps:

[0042] 1) Preparation of tantalum-doped garnet solid electrolyte by solid phase sintering:

[0043] 1.1) Cubic LLZTO was prepared by using LiOH·H 2 O(AR), La 2 O 3 (99.99%), ZrO 2 (AR), Ta 2 O 3 (99.99%) raw materials were prepared according to a molar ratio of 6.5:3:1.5:0.5. An excess of 15 wt% LiOH·H 2 O is added to compensate for lithium loss during sintering.

[0044] 1.2) Heat treatment at 900℃ for 12 hours to remove La 2 O 3 Trace amounts of water and adsorbed CO 2 The raw materials were mixed by a wet milling process using yttrium-stabilized zirconia (YSZ) balls and isopropyl alcohol (IPA) as grinding media. The mixture was dried and calcined in an alumina crucible at 950 °C for 6 h to obtain a precursor powder.

[0045] 1.3) The precursor powder was pressed into a green blank with a diameter of 12.5 mm, covered with gravel in a magnesium oxide crucible, and sintered at 1320° C. for 10 min to obtain a tantalum-doped garnet solid electrolyte, wherein the heating and cooling rate was 5° C. / min.

[0046] 2) Sputtering SnO on the surface of tantalum-doped garnet solid electrolyte 2 Preparation of Al layer: The tantalum-doped garnet solid electrolyte (sheet) prepared in step 1 is used as the sputtering substrate, 99.99% high-purity Al target is used as the direct frequency target, and 99.99% high-purity SnO 2 The target material is used as a radio frequency target, argon is used as the sputtering atmosphere, and SnO is co-sputtered on the surface of tantalum-doped garnet solid electrolyte by magnetron sputtering. 2 -Al layer. The measurement and control sputtering conditions are direct frequency power of 15W, radio frequency power of 100W, magnetron sputtering temperature of room temperature, and vacuum degree of about 3×10 -4 Pa, the magnetron sputtering pressure is 0.5 Pa, and the magnetron sputtering time is 60 s.

[0047] 3) Formation of an interface modification layer between tantalum-doped garnet-type solid electrolyte with surface sputtered SnO2-Al layer and lithium metal: The SnO2-Al film deposited on the surface of the tantalum-doped garnet-type solid electrolyte reacts in situ with molten lithium at 300°C for 1 min to form a stable interface modification layer between the lithium metal and the tantalum-doped garnet-type solid electrolyte.

[0048] Example 2

[0049] A method for modifying the interface between lithium metal and garnet-type solid electrolyte comprises the following steps:

[0050] 1) Preparation of tantalum-doped garnet solid electrolyte by solid phase sintering:

[0051] 1.1) Cubic LLZTO was prepared by using LiOH·H 2 O(AR), La 2 O 3 (99.99%), ZrO 2 (AR), Ta 2 O 3 (99.99%) raw materials were prepared according to a molar ratio of 6.5:3:1.5:0.5. An excess of 15 wt% LiOH·H 2 O is added to compensate for lithium loss during sintering.

[0052] 1.2) Heat treatment at 900℃ for 12 hours to remove La 2 O 3 Trace amounts of water and adsorbed CO2 The raw materials were mixed by a wet milling process using yttrium-stabilized zirconia (YSZ) balls and isopropyl alcohol (IPA) as grinding media. The mixture was dried and calcined in an alumina crucible at 950 °C for 6 h to obtain a precursor powder.

[0053] 1.3) The precursor powder was pressed into a green blank with a diameter of 12.5 mm, covered with gravel in a magnesium oxide crucible, and sintered at 1320° C. for 10 min to obtain a tantalum-doped garnet solid electrolyte, wherein the heating and cooling rate was 5° C. / min.

[0054] 2) Sputtering SnO on the surface of tantalum-doped garnet solid electrolyte 2 Preparation of Al layer: The tantalum-doped garnet solid electrolyte (sheet) prepared in step 1 is used as the sputtering substrate, 99.99% high-purity Al target is used as the direct frequency target, and 99.99% high-purity SnO 2 The target material is used as a radio frequency target and argon is used as the sputtering atmosphere. The SnO is co-sputtered on the surface of the garnet electrolyte by magnetron sputtering. 2 -Al layer. The control sputtering conditions are: direct frequency power 15W, radio frequency power 100W, magnetron sputtering temperature is room temperature, and vacuum degree is about 3×10 -4 Pa, the magnetron sputtering pressure was 0.5 Pa, and the magnetron sputtering time was 30 s.

[0055] 3) Surface sputtering SnO 2 Formation of interface modification layer between tantalum-doped garnet-type solid electrolyte and lithium metal: SnO deposited on the surface of tantalum-doped garnet-type solid electrolyte 2 The -Al film reacts in situ with molten lithium at 300°C for 1 min to form a stable interface modification layer between the interface of lithium metal and tantalum-doped garnet-type solid electrolyte.

[0056] Comparative Example 1

[0057] The preparation process of this comparative example is the same as that of the above-mentioned Example 2, except that there is no sputtered intermediate layer on the surface of the tantalum-doped garnet solid electrolyte.

[0058] Material characterization and performance testing

[0059] In step 1, the tantalum-doped garnet solid electrolyte (LLZTO) was prepared. Silver was plated on both sides by magnetron sputtering as blocking electrodes. The AC impedance test was performed at 30°C. The AC impedance spectrum is shown in Figure 1 As shown in the test results, the ionic conductivity of the prepared LLZTO is 2.93×10 -4 S / cm.

[0060] Material characterization and performance testing

[0061] In step 1, the tantalum-doped garnet solid electrolyte (LLZTO) was prepared. Silver was plated on both sides by magnetron sputtering as blocking electrodes. The AC impedance test was performed at 30°C. The AC impedance spectrum is shown in Figure 1 As shown in the test results, the ionic conductivity of the prepared LLZTO is 2.93×10 -4 S / cm.

[0062] Depend on Figure 2 The scanning electron micrograph shown shows that the LLZTO particles are closely packed and present a cubic phase structure.

[0063] Depend on Figure 3 It can be seen that the interface impedance R of the lithium symmetric battery assembled in Example 1 at 25°C Li-LLZTO =42Ω; Figure 4 It can be seen that the interface impedance R of the lithium symmetric battery assembled in Example 2 at 25°C Li-LLZTO =9Ω. This shows that the interface modification layer in Example 1 and Example 2 greatly reduces the interface impedance between Li and LLZTO and improves the interface wettability between Li and LLZTO. However, due to the long sputtering time in Example 1, the SnO 2 -The Al layer is thicker, and may not react completely during the in-situ reaction with lithium metal, introducing additional interface impedance. Therefore, appropriate sputtering time will achieve the best interface impedance effect.

[0064] Depend on Figure 5 The scanning electron microscope shown shows that the SnO 2 -Al reacts in situ with molten lithium metal to form a uniform and stable interface modification layer between lithium metal and LLZTO.

[0065] The LLZTO with the interface modification layer on the surface in Example 2 was used to assemble a lithium symmetric battery and a cycle test was performed. The test results are as follows: Figure 6 As shown, at a current density of 0.2 mA cm -2 Under this condition, the battery cycle is stable, proving that the interface modification layer ensures the stable battery cycle performance.

[0066] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing an interface modification layer between lithium metal and garnet solid electrolyte, It is characterized in that The following steps are involved: 1) preparing tantalum-doped garnet solid electrolyte; 2) Co-sputtering SnO on the surface of the tantalum-doped garnet solid electrolyte 2 -Al layer; 3) Co-sputtering SnO on the surface of the tantalum-doped garnet solid electrolyte 2 -Al layer is then reacted in situ with molten lithium metal to obtain an interface modification layer between lithium metal and garnet solid electrolyte.

2. The method for preparing the interface modification layer between lithium metal and garnet solid electrolyte according to claim 1, It is characterized in that Step 2 includes using 99.99% high purity Al target as direct frequency target, 99.99% high purity SnO 2 The target material is a radio frequency target, argon is used as the sputtering atmosphere, and SnO is co-sputtered on the surface of the garnet electrolyte by magnetron sputtering. 2 -Al layer.

3. The method for preparing the interface modification layer between lithium metal and garnet solid electrolyte according to claim 2, It is characterized in that The pressure of the magnetron sputtering is 0.25Pa-2Pa, and the time of the magnetron sputtering is 10s-120s.

4. The method for preparing the interface modification layer between lithium metal and garnet solid electrolyte according to claim 3, It is characterized in that The pressure of the magnetron sputtering is 0.5Pa.

5. The method for preparing the interface modification layer between lithium metal and garnet solid electrolyte according to claim 3, It is characterized in that The magnetron sputtering time is 30 s.

6. The method for preparing the interface modification layer between lithium metal and garnet solid electrolyte according to claim 1, It is characterized in that Wherein step 1 comprises the following steps: 1.1) mixing a lithium source, a lanthanum source, a zirconium source, and a tantalum source in a molar ratio of 6.5:3:1.5:0.5 in a ball mill tube, and ball milling is performed to obtain a mixed raw material, wherein 15 wt% of a lithium source is added to the slurry; 1.2) drying and sieving the mixed electrolyte raw material and then calcining it, refining the calcined powder by ball milling, and then drying and sieving it to obtain a precursor powder; 1.3) The precursor powder is pressed into tablets and then sintered to obtain the tantalum-doped garnet solid electrolyte.

7. The method for preparing the interface modification layer between lithium metal and garnet solid electrolyte according to claim 6, It is characterized in that The calcination treatment conditions include: heating to 950°C at a heating rate of 2-10°C / min, and then keeping the temperature for 6 hours; The sintering treatment conditions include: heating to 1280-1320° C. at a heating rate of 5° C. / min, and then keeping the temperature for 10-60 minutes.

8. The method for preparing the interface modification layer between lithium metal and garnet solid electrolyte according to claim 1, It is characterized in that The temperature of the in-situ reaction in step 3 is 200-400°C.

9. The method for preparing the interface modification layer between lithium metal and garnet solid electrolyte according to claim 1, It is characterized in that The time of the in-situ reaction in step 3 is 0.5-2 min.

10. A solid-state lithium metal battery, It is characterized in that The invention comprises a positive electrode, a negative electrode and a garnet solid electrolyte, wherein the garnet solid electrolyte is located between the positive electrode and the negative electrode, the garnet solid electrolyte is a tantalum-doped garnet solid electrolyte, the negative electrode is a lithium metal negative electrode, and an interface modification layer prepared by the preparation method according to any one of claims 1 to 9 is provided between the tantalum-doped garnet solid electrolyte and the lithium metal negative electrode.

Images