A solid electrolyte with a coated modification layer, its preparation method and application in a solid-state battery

Abstract

A solid electrolyte with a coated modification layer, its preparation method and application in a solid-state battery, which relates to the technical field of lithium batteries. It includes: a matrix material and a coated modification layer. The matrix material is a Ta-doped cubic garnet-type solid electrolyte with the general formula: Li 7‑x La3Zr 2‑x Ta x O 12 , where 0.375 ≤ x ≤ 1.5; the coated modification layer material is Mg, Zn, Al, Ge, Sn, Si, Au, Ag, etc.; the thickness of the coated modification layer is 10 to 50 nanometers. Within the thickness range of the coated layer material satisfying the above conditions, the interface contact and the effect of inhibiting dendrites can be further improved, and the interface impedance and critical current density perform better.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and particularly relates to a solid electrolyte with a coated modification layer, a preparation method thereof, and an application in a solid battery. Background Art

[0002] In recent years, electric vehicles have been gradually popularized, setting off an "automobile revolution" globally. However, the market share of electric vehicles is still at a low level, mainly due to problems such as short driving range and low safety performance. Therefore, developing high-energy-density and high-safety batteries has become the focus of the scientific community and the business community. Among them, one of the most promising ways is to develop solid-state lithium batteries. On the one hand, lithium metal batteries have a high specific capacity, and the theoretical specific capacity of their negative electrodes can reach 3860 mAh g -1 . On the other hand, compared with organic liquid electrolytes, solid electrolytes have stable performance, are not easy to burn, and can limit the growth of lithium dendrites to a certain extent, with high safety. Garnet-type solid electrolytes have a relatively high ionic conductivity (≈10 -3 S cm -1 ) and relatively stable chemical properties, and are very ideal solid electrolyte materials.

[0003] However, due to the hardness of the garnet-type solid electrolyte itself, its interface with the negative electrode metal lithium is mostly point contact, resulting in a large interfacial resistance. And poor contact with lithium metal will also lead to uneven flux of lithium ions through the interface, triggering adverse dendrite growth / expansion, especially at positions such as defects and cracks. In addition, during the electrochemical process, lithium ions are easily combined with electrons on the surface of the solid electrolyte grain boundaries to form metallic lithium, leading to the formation of lithium dendrites. Therefore, it is necessary to modify the interface of the garnet-type solid electrolyte to improve the interfacial wettability, reduce the interfacial impedance, and inhibit the growth of lithium dendrites. For example:

[0004] Patent CN202111436177.2 discloses a multi-layer composite solid electrolyte and a preparation method thereof, using one or more of metal zinc, indium, tin or aluminum, metal nitrides, metal fluorides, and metal oxides as raw materials for preparing the lithiumophilic layer, and using the raw materials for preparing the lithiumophilic layer as a target to be compounded on the surface of the electrolyte sheet layer by magnetron sputtering. Although this technical solution can alleviate the defect of high interfacial resistance caused by poor solid-solid contact at the interface, it does not pay attention to the influence of the thickness of the composite layer on the uniformity of lithium deposition. When the composite layer is too thin or too thick, lithium metal cannot be deposited uniformly, ultimately resulting in uncontrolled growth of lithium dendrites and battery short-circuit failure.

[0005] Therefore, there is an urgent need to provide an interfacial modification that can reduce the interfacial impedance between the solid electrolyte and lithium metal and inhibit the growth of lithium dendrites during the electrochemical process. Summary of the Invention

[0006] In view of this, the present invention first provides a garnet-type solid electrolyte with a coating modification layer, characterized in that it comprises: a base material and a coating modification layer, wherein the base material is a Ta-doped cubic garnet-type solid electrolyte with a general formula of: Li 7-x Ln3Z 2-x Ta x O 12 , wherein 0.375≤x≤1.5; the material of the coating modification layer is Mg, Zn, Al, Ge, Sn, Si, Au, Ag, etc.; the thickness of the coating modification layer is 10 to 50 nanometers.

[0007] The present invention has found through a large number of experimental investigations that by regulating the above-mentioned coating material and its thickness so that the coating thickness meets the above-mentioned range, the interface problem between the solid electrolyte and metallic lithium can be significantly improved, making it difficult for dendrites to grow, thereby achieving a reduction in interface impedance and an increase in critical current density.

[0008] As a preferred embodiment of the present invention, the coating layer material is Ag, Ge, Al and Zn, and the coating modification method can be magnetron sputtering, atomic layer deposition, vapor deposition, molecular layer deposition and the like. The present invention finds that when the thickness of the coating modification layer is reasonably controlled by the above method, an alloy layer will be formed through solid solution reaction during the electrochemical process, which can better achieve better interface contact and improve interface wettability.

[0009] As a preferred embodiment of the present invention, the coating layer material is Ag, and the coating layer thickness is 14 to 25 nanometers.

[0010] The present invention finds that in the above-mentioned coating layer material, the formation of the Ag film undergoes the process of nucleation, growth and film formation of Ag particles. Experiments have found that when the thickness of the Ag layer is less than 14nm, the particle size of the Ag particles shrinks significantly, and there are obvious gaps between the particles, resulting in the Ag film showing a discontinuous growth mode to form an island structure, causing the surface of the Ag film to become rough. The rough surface affects the uniform and rapid passage of lithium ions through the interface, inducing uneven lithium deposition; with the increase of the thickness of the Ag layer, when it reaches 20 nanometers, the particle size of the Ag particles meets the close contact between the particles, the Ag film begins to become continuous, dense and flat, the interface contact is better and uniform lithium deposition is induced; however, when the thickness of the Ag layer is further increased from 25nm, the sputtered Ag atoms are superimposed on the continuous Ag layer, the particle size of the Ag particles gradually increases, and the Ag particles are superimposed layer by layer, so that the Ag film begins to form large islands in a nuclear growth mode, and the Ag film becomes rough again, and the surface becomes rough again, which again induces uneven lithium deposition, affecting the electrochemical performance.

[0011] Within the thickness range of the above-mentioned coating material, the interface contact and the effect of suppressing dendrites can be further improved, and the interface impedance and the critical current density are better.

[0012] Furthermore, the present invention provides a method for preparing a garnet-type solid electrolyte with a coating modification layer in the above technical solution, including:

[0013] (1) Press the electrolyte powder into a garnet-type solid electrolyte wafer with a thickness of 300-400 microns under a pressure of 15-25 MPa;

[0014] (2) Embed the mother powder around and on the surface of the wafer for primary roasting and polishing to obtain the matrix material; (3) Coat the coating layer on the surface of the matrix material to obtain a modified matrix.

[0015] As a preferred embodiment of the present invention, step (2) is carried out for primary roasting at 1200 °C.

[0016] As a preferred embodiment of the present invention, the preparation method further includes: polishing the roasted matrix material.

[0017] Coat the coating modification layer material on the surface of the garnet-type solid electrolyte sheet according to different thicknesses by methods such as magnetron sputtering, atomic layer deposition, chemical vapor deposition, molecular layer deposition, etc.;

[0018] In addition, the present invention also provides a lithium battery, which includes the above-mentioned garnet-type solid electrolyte with a coating modification layer. When the lithium battery contains the garnet-type solid electrolyte with the coating layer of the present invention, it has excellent low interface impedance and high critical current density.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The present invention prepares a garnet-type solid electrolyte modified with a 20-nm-thick Ag layer coating, which can form a uniform and dense interface layer on the surface of the solid electrolyte, improve interface contact, reduce interface impedance, and form a Li-Ag alloy during the solid solution reaction in the electrochemical process, further improving interface wettability. The surface of the 20-nm-thick Ag layer is flat and smooth, which can make Li ions pass more uniformly, lithium ions deposit more uniformly, and it is easier to form a Li-Ag alloy layer, thereby significantly reducing the interface impedance, increasing the critical current density, and suppressing the growth of lithium dendrites. Description of the Drawings

[0021] Figure 1 It is a surface morphology diagram of a garnet solid electrolyte with a coating modification layer in Example 1.

[0022] Figure 2Interface impedance diagram of the garnet solid electrolyte with a coating modification layer in Example 1.

[0023] Figure 3 Critical current density diagram of the garnet solid electrolyte with a coating modification layer in Example 1. Detailed implementation mode

[0024] The following examples are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0025] For those not specified in the examples in terms of specific techniques or conditions, they are all conventional methods or carried out according to the techniques or conditions described in the literature in this field, or according to the product instructions. For reagents, instruments, etc. not specified in terms of the manufacturer, they are all conventional products that can be obtained through regular channels.

[0026] The garnet-type solid electrolyte Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The specific steps for making the electrolyte wafer from the powder are as follows:

[0027] (1) Press the above electrolyte powder into a wafer with a thickness of 350 microns using a pressure of 20 MPa;

[0028] (2) Embed the mother powder around and on the surface of the above wafer, and sinter it at 1200 °C for 12 hours to obtain a solid electrolyte wafer; (3) Polish the surface of the solid electrolyte wafer obtained in step (2) successively with 800-mesh, 1000-mesh, 1500-mesh, 2000-mesh, 3000-mesh, and 4000-mesh sandpapers to obtain the required solid electrolyte wafer.

[0029] Example 1

[0030] This example provides a garnet-type solid electrolyte wafer with a coating modification layer, and the chemical formula of its matrix material is Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ; The coating material is Ag; the thickness of the coating is 20 nanometers.

[0031] The preparation method of the garnet-type solid electrolyte wafer with a coating modification layer in this example is as follows:

[0032] (1) Prepare Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Solid electrolyte wafer with a thickness of 350 microns;

[0033] (2) Coat Ag on Li by magnetron sputtering6.4 La3Zr 1.4 Ta 0.6 O 12 On the surface of the solid electrolyte sheet, the thickness of the Ag layer was controlled to be 20 nm, and a garnet-type solid electrolyte with a coated modification layer was prepared.

[0034] The surface morphology diagram of the coated layer coating the garnet solid electrolyte in this example is as shown in Figure 1 shown; the interfacial impedance diagram is as shown in Figure 2 shown; the critical current density diagram is as shown in Figure 3 shown.

[0035] Example 2

[0036] This example provides a garnet-type solid electrolyte with a coated modification layer, which is only different from Example 1 in that the thickness of the coated layer is 25 nm.

[0037] Example 3

[0038] This example provides a garnet-type solid electrolyte with a coated modification layer, which is only different from Example 1 in that the thickness of the coated layer is 18 nm.

[0039] Example 4

[0040] This example provides a garnet-type solid electrolyte with a coated modification layer, which is only different from Example 1 in that the thickness of the coated layer is 14 nm.

[0041] Example 5

[0042] This example provides a garnet-type solid electrolyte with a coated modification layer, which is only different from Example 1 in that the thickness of the coated layer is 12 nm.

[0043] Example 6

[0044] This example provides a garnet-type solid electrolyte with a coated modification layer, which is only different from Example 1 in that the thickness of the coated layer is 10 nm.

[0045] Example 7

[0046] This example provides a garnet-type solid electrolyte with a coated modification layer, which is only different from Example 1 in that the thickness of the coated layer is 6 nm.

[0047] Example 8

[0048] This example provides a garnet-type solid electrolyte with a coated modification layer, which is only different from Example 1 in that the thickness of the coated layer is 35 nm.

[0049] Example 9

[0050] This embodiment provides a garnet-type solid electrolyte with a coated modification layer, which is only different from Embodiment 1 in that the thickness of the coating layer is 45 nanometers.

[0051] Embodiment 10

[0052] This embodiment provides a garnet-type solid electrolyte with a coated modification layer, which is only different from Embodiment 1 in that the thickness of the coating layer is 50 nanometers.

[0053] Embodiment 11

[0054] This embodiment provides a garnet-type solid electrolyte with a coated modification layer, which is only different from Embodiment 1 in that the thickness of the coating layer is 100 nanometers.

[0055] Embodiment 12

[0056] This embodiment provides a garnet-type solid electrolyte with a coated modification layer, which is only different from Embodiment 1 in that the coating layer material is Ge and the thickness of the coating layer is 16 nm.

[0057] Embodiment 13

[0058] This embodiment provides a garnet-type solid electrolyte with a coated modification layer, which is only different from Embodiment 1 in that the coating layer material is Al and the thickness of the coating layer is 20 nm.

[0059] Embodiment 14

[0060] This embodiment provides a garnet-type solid electrolyte with a coated modification layer, which is only different from Embodiment 1 in that the coating layer material is Zn and the thickness of the coating layer is 24 nm.

[0061] Comparative Example 1

[0062] This embodiment provides a garnet-type solid electrolyte with a coated modification layer, and the coating layer material is Mo. The specific preparation method is only different from Embodiment 1 in that: the coating layer material is Mo and the thickness of the coating layer is 50 nm.

[0063] Comparative Example 2

[0064] This embodiment provides a garnet-type solid electrolyte with a coating layer, and the coating layer material is Si. The specific preparation method is only different from Embodiment 1 in that: the coating layer material is Si and the thickness of the coating layer is 200 nm.

[0065] Comparative Example 3

[0066] This embodiment provides a garnet-type solid electrolyte with a coating layer, and the coating layer material is Au. The only difference in the specific preparation method from Example 1 is that: the coating layer material is Au, and the coating layer thickness is 100 nm.

[0067] Comparative Example 4

[0068] This embodiment provides a garnet-type solid electrolyte with a coating layer, and the coating layer material is Sn. The only difference in the specific preparation method from Example 1 is that: the coating layer material is Sn, and the coating layer thickness is 150 nm.

[0069] Comparative Example 5

[0070] This embodiment provides a garnet-type solid electrolyte with a coating layer, and the coating layer material is Cu. The only difference in the specific preparation method from Example 1 is that: the coating layer material is Cu, and the coating layer thickness is 100 nm.

[0071] Comparative Example 6

[0072] This embodiment provides a garnet-type solid electrolyte with an added coating layer, and the coating layer material is Mg. The only difference in the specific preparation method from Example 1 is that: the coating layer material is Mg, and the coating layer thickness is 100 nm.

[0073] Comparative Example 7

[0074] This embodiment provides a garnet-type solid electrolyte with a coating layer, and the coating layer material is In. The only difference in the specific preparation method from Example 1 is that: the coating layer material is In, and the coating layer thickness is 200 nm..

[0075] Comparative Example 8

[0076] This embodiment provides a garnet-type solid electrolyte with a coating layer, and the coating layer material is Cr. The only difference in the specific preparation method from Example 1 is that: the coating layer material is Cr, and the coating layer thickness is 300 nm.

[0077] Comparative Example 9

[0078] This embodiment provides a garnet-type solid electrolyte with a coating layer, and the coating layer material is Pt. The only difference in the specific preparation method from Example 1 is that: the coating layer material is Pt, and the coating layer thickness is 200 nm.

[0079] For the solid electrolyte sheets of the above embodiments and comparative examples, lithium metal sheets are placed on both sides thereof and then loaded into a mold battery to fabricate a symmetric lithium battery. An impedance analyzer is used to perform an interfacial impedance test on it, with the frequency ranging from 0.1 Hz to 10 6 Hz, and a Blue Power battery test system is used to perform a critical current density test on it, with the cut-off capacity being 1 mAh cm -2 .

[0080] The test performance includes interface impedance test and critical current density test, and the results are shown in Table 1.

[0081] Table 1

[0082] Item Matrix Material Coating Layer Coating Layer Thickness Interface Impedance Critical Current Density Example 1 LLZTO Ag 20nm <![CDATA[2Ωcm 2 > <![CDATA[5.1mA cm -2 > Example 2 LLZTO Ag 25nm <![CDATA[4Ωcm 2 > <![CDATA[4.7mA cm -2 > Example 3 LLZTO Ag 18nm <![CDATA[3Ωcm 2 > <![CDATA[5mA cm -2 > Example 4 LLZTO Ag 14nm <![CDATA[3.5Ωcm 2 > <![CDATA[4.2mA cm -2 > Example 5 LLZTO Ag 12nm <![CDATA[44Ωcm 2 > <![CDATA[2.2mA cm -2 > Example 6 LLZTO Ag 10nm <![CDATA[33Ωcm 2 > <![CDATA[1.3mA cm -2 > Example 7 LLZTO Ag 6nm <![CDATA[27Ωcm 2 > <![CDATA[3mA cm -2 > Example 8 LLZTO Ag 35nm <![CDATA[50Ωcm 2 > <![CDATA[2mA cm -2 > Example 9 LLZTO Ag 45nm <![CDATA[112Ωcm 2 > <![CDATA[1.5mA cm -2 > Example 10 LLZTO Ag 50nm <![CDATA[47Ωcm 2 > <![CDATA[2.6 mA cm -2 > Example 11 LLZTO Ag 100nm <![CDATA[1235Ωcm 2 > <![CDATA[2mA cm -2 > Example 12 LLZTO Ge 16nm <![CDATA[10Ωcm 2 > <![CDATA[3.5mA cm -2 > Example 13 LLZTO Al 20nm <![CDATA[15Ωcm 2 > <![CDATA[3.7mA cm -2 > Example 14 LLZTO Zn 24nm <![CDATA[13Ωcm 2 > <![CDATA[4mA cm -2 > Comparative Example 1 LLZTO Mo 50nm <![CDATA[93Ωcm 2 > <![CDATA[2.6 mA cm -2 > Comparative Example 2 LLZTO Si 200nm <![CDATA[1100Ωcm 2 > 1.3mA cm-2 Comparative Example 3 LLZTO Au 100nm <![CDATA[60Ωcm 2 > 2mA cm-2 Comparative Example 4 LLZTO Sn 150nm <![CDATA[1675Ωcm 2 > 2.1mA cm-2 Comparative Example 5 LLZTO Cu 100nm <![CDATA[66Ωcm 2 > <![CDATA[3.2mA cm -2 > Comparative Example 6 LLZTO Mg 100nm <![CDATA[79Ωcm 2 > <![CDATA[2mA cm -2 > Comparative Example 7 LLZTO In 200nm <![CDATA[285Ωcm 2 > <![CDATA[0.8mA cm -2 > Comparative Example 8 LLZTO Cr 300nm <![CDATA[356Ωcm 2 > <![CDATA[1.1mA cm -2 <!-- 5 -->]]> Comparative Example 9 LLZTO Pt 200nm <![CDATA[184Ωcm 2 > <![CDATA[1.3mA cm -2 > 。

Claims

1. A solid electrolyte with a coated modification layer, characterized in that, Comprising: Substrate material and coated modification layer, the substrate material is Ta-doped cubic garnet-type solid electrolyte, with the general formula: Li 7-x La3Zr 2-x Ta x O 12 , where x = 0.6; the coated modification layer material is Ag, and the thickness of the coated modification layer is 14 to 25 nanometers; a Li-Ag alloy is formed by a solid solution reaction during the electrochemical process; The thickness of the matrix material is 300 to 400 microns; The preparation method comprises the following steps: (1) Press the electrolyte powder into a garnet-type solid electrolyte wafer with a thickness of 300 to 400 microns under a pressure of 15 - 25 MPa; (2) Embed the mother powder around and on the surface of the wafer for primary calcination and polishing to obtain the matrix material; (3) Coating a coating modification layer material with the said thickness on the surface of the matrix material.

2. The application of a solid electrolyte with a coating modification layer as claimed in claim 1, as a solid electrolyte of a lithium battery, reducing the interfacial impedance and increasing the critical current density.

3. A solid-state lithium battery, characterized in that, Comprising a solid electrolyte with a coating modification layer as claimed in claim 1.

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