A method and application of magnetic field-assisted construction of a double-layer interface of a lithium negative electrode in a solid-state battery

Abstract

A method and application for constructing a double-layer interface of a lithium negative electrode of a solid-state battery with the assistance of a magnetic field, belonging to the field of solid-state battery technology, includes the following steps: Step 1, grinding and polishing the surface of a solid electrolyte sheet; Step 2, modifying the polished surface of the solid electrolyte sheet with a magnetic metal halide to obtain a solid electrolyte sheet modified with a magnetic metal halide; Step 3, compounding a lithium negative electrode with the surface of the solid electrolyte sheet modified with a magnetic metal halide, applying a magnetic field, and heating the reaction at 180 to 400°C for 15 to 60 minutes to obtain a double-layer modified interface of a solid electrolyte / lithium negative electrode comprising lithium halide and a magnetic metal, wherein the magnetic metal is close to the lithium negative electrode side and the lithium halide is close to the solid electrolyte side. The operation method of the present invention is simple, efficient, and reliable, does not require the use of complex precision instruments, and has excellent improvement effects, making it easy to promote and apply on a large scale.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and specifically relates to a method for modifying the interface of a solid-state lithium battery negative electrode, and more particularly to a method and application of constructing a double-layer interface of a solid-state battery lithium negative electrode with the assistance of a magnetic field. Background Art

[0002] Solid-state lithium batteries (SSLBs) have higher theoretical energy density and excellent safety compared to traditional liquid lithium-ion batteries, and therefore have attracted widespread attention. Solid electrolytes (SSEs) are key components of SSLBs. Garnet-type solid electrolytes represented by LLZO have high lithium ion conductivity (10 -4 ~10 -3 Scm -1 ), excellent thermal stability, good electrochemical stability and stability to lithium anode, showing excellent comprehensive performance. However, the poor interface contact between garnet-type solid electrolyte and lithium negative electrode leads to the growth of lithium dendrites at the interface. In addition, the electronic conductivity of garnet-type solid electrolyte is not low enough (~10 -8 Scm -1 ), causing lithium to nucleate and grow in defects inside the electrolyte and at grain boundaries to form lithium dendrites, which seriously hinders the practical application of solid-state lithium batteries. Summary of the Invention

[0003] The present invention addresses the problems of poor interface contact between garnet-type solid electrolytes and lithium negative electrodes, high interface impedance, and growth of lithium dendrites at the interface and inside the electrolyte. It provides a method and application for using a magnetic field to assist in constructing a double-layer interface of the lithium negative electrode of a solid-state battery.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for constructing a double-layer interface of a lithium negative electrode of a solid-state battery with the assistance of a magnetic field comprises the following steps:

[0006] Step 1: grinding and polishing the surface of the solid electrolyte sheet;

[0007] Step 2: modifying the polished surface of the solid electrolyte sheet with a magnetic metal halide to obtain a solid electrolyte sheet modified with a magnetic metal halide;

[0008] Step 3: Composite the lithium negative electrode with the surface of a solid electrolyte sheet modified with a magnetic metal halide, apply a magnetic field, and heat the reaction at 180-400°C for 15-60 minutes to obtain a double-layer modified interface of a solid electrolyte / lithium negative electrode containing lithium halide and magnetic metal, wherein the magnetic metal single layer is close to the lithium negative electrode side, and the lithium halide layer is close to the solid electrolyte side.

[0009] Furthermore, the solid electrolyte is a garnet-type solid electrolyte Li 7-x La3Zr 2-x M x O 12 , and at least one of its doped compounds, wherein M is Nb or Ta, wherein 0≤x<2.

[0010] Furthermore, in step 2, the method of modifying the polished surface of the solid electrolyte sheet with the magnetic metal halide is: coating the polished surface of the solid electrolyte sheet with the magnetic metal halide.

[0011] Furthermore, the coating method includes at least one of drop coating, spin coating, and sputtering.

[0012] Furthermore, in the magnetic metal halide, the magnetic metal element includes at least one of iron (Fe), cobalt (Co), and nickel (Ni).

[0013] Furthermore, in the magnetic metal halide, the halide element includes at least one of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0014] Furthermore, the magnetic metal halide may or may not contain hydrated molecules. When it contains hydrated molecules, the lithium halide layer in the reaction product will contain lithium oxide, which can also transport lithium ions.

[0015] Furthermore, the mass of the magnetic metal halide coated on the surface of the solid electrolyte sheet per unit area is 0.002-0.05 mg / cm 2 .

[0016] The above method is applied in the preparation process of a solid-state lithium battery to obtain a solid-state lithium battery.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] After the magnetic metal halide and molten metallic lithium undergo an in-situ conversion reaction, lithium halide and magnetic metal elemental substance are formed. Under the traction of the magnetic field, the two are separated into layers, with the magnetic metal elemental substance layer close to the lithium negative electrode side and the lithium halide layer close to the electrolyte side. The lithium halide modified layer has good lithium ion conductivity and excellent electronic insulation properties. It can effectively transport lithium ions at the interface and block the transmission of electrons into the electrolyte, preventing lithium ions from nucleating and growing at internal defects and grain boundaries in the electrolyte, forming lithium dendrites within the electrolyte. The magnetic metal elemental substance layer combines with lithium metal, transporting lithium ions while having good electron conductivity. It can make the surface electric field uniformly distributed, allowing lithium to be uniformly deposited / stripped, and preventing lithium from preferentially depositing and forming lithium dendrites at high current density areas on the electrode surface due to uneven surface electric field distribution. Based on the inhibitory effect of the double-layer interface between the solid electrolyte and the lithium metal negative electrode on the growth of lithium dendrites, the prepared solid-state battery can achieve long-life stable cycling.

[0019] The operation method of the present invention is simple, efficient and reliable, does not require the use of complex precision instruments, has excellent improvement effects, and is easy to promote and apply on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 For the comparative example, unmodified Li 6.5 La3Zr 1.5 Ta 0.5 O 12 Impedance diagram of the assembled symmetrical battery;

[0021] Figure 2 is the Li modified by FeF3 in Example 1 6.5 La3Zr 1.5 Ta 0.5 O 12 Impedance diagram of the assembled symmetric battery. In the figure, GBIL is the abbreviation of Gradient bilayer interface layer, which means gradient bilayer interface layer.

[0022] Figure 3 is the Li modified by FeF3 in Example 1 6.5 La3Zr 1.5 Ta 0.5 O 12 In the time-current curve of the assembled blocking cell, GBIL is the abbreviation of Gradient bilayer interface layer, which means gradient bilayer interface layer;

[0023] Figure 4 is the Li modified by FeF3 in Example 1 6.5 La3Zr 1.5 Ta 0.5 O12 Long-cycle performance diagram of the assembled symmetric battery. DETAILED DESCRIPTION

[0024] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] Example 1

[0026] A method for constructing a double-layer interface of a lithium negative electrode of a solid-state battery with the assistance of a magnetic field comprises the following steps:

[0027] Step 1: Solid electrolyte sheet Li 6.5 La3Zr 1.5 Ta 0.5 O 12 Grind and polish the two surfaces;

[0028] Step 2: Spin coat 5 μl of a 0.2% FeF3 methanol dispersion onto the surface of a polished solid electrolyte sheet with a diameter of 12 mm using a spin coater to obtain a FeF3-modified solid electrolyte sheet.

[0029] Step 3: Place lithium sheets on the upper and lower surfaces of the FeF3-modified solid electrolyte sheet to build a solid-state lithium symmetrical battery, then place it on a heating table, apply a magnetic field and heat it at 300°C for 20 minutes to obtain a double-layer modified interface of solid electrolyte / lithium negative electrode containing lithium fluoride (LiF) and magnetic metal iron (Fe), wherein the magnetic metal elemental iron is close to the lithium negative electrode side, and lithium fluoride is close to the solid electrolyte side.

[0030] Example 2

[0031] A method for constructing a double-layer interface of a lithium negative electrode of a solid-state battery with the assistance of a magnetic field comprises the following steps:

[0032] Step 1: Solid electrolyte sheet Li 6.5 La3Zr 1.5 Ta 0.5 O 12 Grind the two surfaces;

[0033] Step 2: 5 μl of a 0.15% FeF3·6H2O methanol dispersion droplet was applied to the surface of a polished solid electrolyte sheet with a diameter of 12 mm to obtain a FeF3·6H2O-modified solid electrolyte sheet;

[0034] Step 3. Lithium sheets are placed on the upper and lower surfaces of the FeF3·6H2O-modified solid electrolyte sheet to build a solid-state lithium symmetrical battery. The battery is then placed on a heating table and heated at 300°C for 25 minutes after applying a magnetic field to obtain a double-layer modified interface of a solid electrolyte / lithium negative electrode containing lithium fluoride, lithium oxide, and magnetic metal iron. The magnetic metal elemental iron (Fe) is close to the lithium negative electrode side, and lithium fluoride (LiF) and lithium oxide (Li2O) are close to the solid electrolyte side.

[0035] Example 3

[0036] A method for constructing a double-layer interface of a lithium negative electrode of a solid-state battery with the assistance of a magnetic field comprises the following steps:

[0037] Step 1: Solid electrolyte sheet Li 6.5 La3Zr 1.5 Nb 0.5 O 12 Grind the two surfaces;

[0038] Step 2: Spin coat 5 μl of a 0.4% NiBr2 anhydrous ethanol dispersion onto the surface of a polished solid electrolyte sheet with a diameter of 12 mm using a spin coater to obtain a NiBr2-modified solid electrolyte sheet;

[0039] Step 3: Place lithium sheets on the upper and lower surfaces of the NiBr2-modified solid electrolyte sheet to build a solid-state lithium symmetrical battery, then place it on a heating table, apply a magnetic field and heat it at 400°C for 30 minutes to obtain a double-layer modified interface of solid electrolyte / lithium negative electrode containing lithium bromide (LiBr) and magnetic metal nickel (Ni), wherein the magnetic metal elemental nickel is close to the lithium negative electrode side, and lithium bromide is close to the solid electrolyte side.

[0040] Example 4

[0041] A method for constructing a double-layer interface of a lithium negative electrode of a solid-state battery with the assistance of a magnetic field comprises the following steps:

[0042] Step 1: Solid electrolyte sheet Li 6.5 La3Zr 1.5 Nb 0.5 O 12 Grind the two surfaces;

[0043] Step 2: Spin coat 5 μl of a 0.4% CoI2 methanol dispersion onto the surface of a polished solid electrolyte sheet with a diameter of 12 mm using a spin coater to obtain a CoI2-modified solid electrolyte sheet.

[0044] Step 3: Place lithium sheets on the upper and lower surfaces of the CoI2-modified solid electrolyte sheet to build a solid-state lithium symmetrical battery, then place it on a heating table, apply a magnetic field and heat it at 400°C for 40 minutes to obtain a double-layer modified interface of solid electrolyte / lithium negative electrode containing lithium iodide (LiI) and magnetic metal cobalt (Co), wherein the magnetic metal element cobalt is close to the lithium negative electrode side, and lithium iodide is close to the solid electrolyte side.

[0045] Example 5

[0046] A method for constructing a double-layer interface of a lithium negative electrode of a solid-state battery with the assistance of a magnetic field comprises the following steps:

[0047] Step 1: Solid electrolyte sheet Li 6.5 La3Zr 1.5 Ta 0.5 O 12 Grind and polish the two surfaces;

[0048] Step 2: FeF3 is sputtered on the surface of a polished solid electrolyte sheet with a diameter of 12 mm by magnetron sputtering to a thickness of about 200 nm to obtain a FeF3-modified solid electrolyte sheet;

[0049] Step 3: Place lithium sheets on the upper and lower surfaces of the FeF3-modified solid electrolyte sheet to build a solid-state lithium symmetrical battery, then place it on a heating table, apply a magnetic field and heat it at 300°C for 15 minutes to obtain a double-layer modified interface of solid electrolyte / lithium negative electrode containing lithium fluoride (LiF) and magnetic metal iron (Fe), wherein the magnetic metal elemental iron is close to the lithium negative electrode side, and lithium fluoride is close to the solid electrolyte side.

[0050] Example 6

[0051] A method for constructing a double-layer interface of a lithium negative electrode of a solid-state battery with the assistance of a magnetic field comprises the following steps:

[0052] Step 1: Solid electrolyte sheet Li 6.5 La3Zr 1.5 Ta 0.5 O 12 Grind and polish the two surfaces;

[0053] Step 2: Spin coat 10 μl of a 0.3% FeF3 methanol dispersion onto the surface of a polished solid electrolyte sheet with a diameter of 12 mm using a spin coater to obtain a FeF3-modified solid electrolyte sheet.

[0054] Step 3: Place lithium sheets on the upper and lower surfaces of the FeF3-modified solid electrolyte sheet to build a solid-state lithium symmetrical battery, then place it on a heating table, apply a magnetic field and heat it at 180°C for 60 minutes to obtain a double-layer modified interface of solid electrolyte / lithium negative electrode containing lithium fluoride (LiF) and magnetic metal iron (Fe), wherein the magnetic metal elemental iron is close to the lithium negative electrode side, and lithium fluoride is close to the solid electrolyte side.

[0055] Example 7

[0056] A method for constructing a double-layer interface of a lithium negative electrode of a solid-state battery with the assistance of a magnetic field comprises the following steps:

[0057] Step 1: Solid electrolyte sheet Li 6.5 La3Zr 1.5 Ta 0.5 O 12 Grind the two surfaces;

[0058] Step 2: Spin coat 10 μl of a 0.6% FeF3·6H2O methanol dispersion onto the surface of a polished solid electrolyte sheet with a diameter of 12 mm using a spin coater to obtain a FeF3·6H2O-modified solid electrolyte sheet.

[0059] Step 3. Lithium sheets are placed on the upper and lower surfaces of the FeF3·6H2O-modified solid electrolyte sheet to build a solid-state lithium symmetrical battery. The battery is then placed on a heating table and heated at 300°C for 40 minutes after applying a magnetic field to obtain a double-layer modified interface of a solid electrolyte / lithium negative electrode containing lithium fluoride, lithium oxide, and magnetic metal iron. The magnetic metal elemental iron (Fe) is close to the lithium negative electrode side, and lithium fluoride (LiF) and lithium oxide (Li2O) are close to the solid electrolyte side.

[0060] Comparative Example

[0061] The difference between this comparative example and Example 1 is that: 6.5 La3Zr 1.5 Ta 0.5 O 12 Lithium sheets are placed on the upper and lower surfaces of the solid electrolyte sheet to assemble a solid-state lithium symmetrical battery.

[0062] Figure 2 and Figure 1 The comparison shows that the impedance of the symmetrical battery modified with magnetic metal halide is significantly reduced. Figure 3 Calculations show that the electronic conductivity is nearly two orders of magnitude lower than that of the unmodified LLZTO, indicating that the modified layer has excellent insulation properties and can effectively inhibit the growth of lithium dendrites inside the electrolyte. Figure 4It shows that the symmetrical battery modified with magnetic metal halide has excellent long-cycle performance and good resistance to lithium dendrite growth.

[0063] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for constructing a double-layer interface of a lithium negative electrode of a solid-state battery with the assistance of a magnetic field, characterized in that: The following steps are involved: Step 1: grinding and polishing the surface of the solid electrolyte sheet; Step 2: modifying the polished surface of the solid electrolyte sheet with a magnetic metal halide to obtain a solid electrolyte sheet modified with a magnetic metal halide; Step 3: Composite the lithium negative electrode with the surface of a solid electrolyte sheet modified with a magnetic metal halide, apply a magnetic field, and heat the reaction at 180-400°C for 15-60 minutes to obtain a double-layer modified interface of a solid electrolyte / lithium negative electrode containing lithium halide and magnetic metal, wherein the magnetic metal is close to the lithium negative electrode side and the lithium halide is close to the solid electrolyte side.

2. The method according to claim 1, wherein: The solid electrolyte is garnet-type solid electrolyte Li 7-x La3Zr 2-x M x O 12 , and at least one of its doped compounds, wherein M is Nb or Ta, wherein 0≤x<2.

3. The method for constructing a double-layer interface of a lithium negative electrode of a solid-state battery with the assistance of a magnetic field according to claim 1, characterized in that: In step 2, the method for modifying the polished surface of the solid electrolyte sheet with the magnetic metal halide is as follows: coating the polished surface of the solid electrolyte sheet with the magnetic metal halide.

4. The method according to claim 3, wherein: The coating method includes at least one of drop coating, spin coating, and sputtering.

5. The method of claim 1, wherein: In the magnetic metal halide, the magnetic metal element includes at least one of iron, cobalt and nickel.

6. The method according to claim 1, wherein: In the magnetic metal halide, the halogen element includes at least one of fluorine, chlorine, bromine and iodine.

7. The method of claim 1, wherein: The magnetic metal halide may or may not contain hydrated molecules. When the magnetic metal halide contains hydrated molecules, the lithium halide layer in the reaction product contains lithium oxide.

8. The method of claim 1, wherein: The mass of magnetic metal halide coated on the surface of solid electrolyte sheet per unit area is 0.002~0.05mg / cm 2 .

9. A solid-state lithium battery obtained by applying the method according to any one of claims 1 to 8 to a preparation process of a solid-state lithium battery.

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