A sulfide solid electrolyte and its preparation method and application

Abstract

The present invention discloses a sulfide solid electrolyte, its preparation method, and application. The sulfide solid electrolyte comprises Li7Si2S7X, where X is one or more of Cl, Br, and I. The sulfide solid electrolyte provided by the present invention has high ionic conductivity and high stability to lithium metal in all-solid-state lithium batteries. This allows the use of lithium metal, which has a high energy density, as the negative electrode material, improving the electrochemical performance of solid-state batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and in particular relates to a sulfide solid electrolyte and a preparation method and application thereof. Background Art

[0002] All-solid-state batteries have a solid electrolyte layer between the positive and negative electrodes. They utilize solid electrolytes instead of the liquid electrolytes found in traditional lithium-ion batteries, reducing flammability and improving cycle life. They also enable the use of alkali metal anodes, further improving the energy density and safety of lithium-ion batteries, making them the most promising next-generation lithium-ion batteries.

[0003] Currently, solid-state electrolytes can be divided into three major categories: inorganic solid-state electrolytes, polymer solid-state electrolytes, and composite solid-state electrolytes. Inorganic solid-state electrolytes include oxide inorganic solid-state electrolytes and sulfide inorganic solid-state electrolytes. Sulfur has a large atomic radius and polarizability, which causes lattice distortion and forms large ion channels. Furthermore, the binding force between sulfur and lithium ions is weak, resulting in a large number of mobile carriers within the system. Therefore, sulfide solid-state electrolytes exhibit good ionic conductivity and have become the main research focus.

[0004] However, current sulfide solid electrolytes have low ionic conductivity and low stability to lithium metal, which limits their application in high-energy-density batteries. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a sulfide solid electrolyte and its preparation method and application, so as to solve the problems of low ionic conductivity and low stability to lithium metal of the existing sulfide solid electrolyte.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In one aspect, the present invention provides a sulfide solid electrolyte, wherein the composition of the sulfide solid electrolyte is Li7Si2S7X, wherein X is one or more of Cl, Br, and I.

[0008] Preferably, the composition of the sulfide solid electrolyte is Li7Si2S7I a X (1-a) , wherein X is one or more of Cl and Br, and 0<a≤1. More preferably, 0.4≤a≤0.6, for example, a can be 0.4, 0.5, 0.6, etc.

[0009] Preferably, the sulfide solid electrolyte has an argyrodite-type crystal phase structure.

[0010] On the other hand, the present invention also provides a method for preparing the sulfide solid electrolyte according to the first aspect, comprising the following steps:

[0011] (1) According to the stoichiometric ratio of elements in Li7Si2S7X, a lithium source, a silicon source, a sulfur source, and an X source are mixed in an inert gas atmosphere to obtain a mixture;

[0012] (2) ball milling the mixture in an inert gas atmosphere to obtain a precursor powder;

[0013] (3) The precursor powder is calcined in an inert gas atmosphere to obtain a sulfide solid electrolyte.

[0014] Preferably, in step (1), the lithium source is one or more of Li2S, LiI, LiCl, and LiBr; the silicon source is SiS2; and the sulfur source is one or more of Li2S, SiS2, and Li2S2.

[0015] Preferably, in step (1), the X source is one or more of LiI, LiCl, and LiBr.

[0016] Preferably, the ball milling speed in step (2) is 300-700 rpm, and the ball milling time is 5-20 h.

[0017] Preferably, the calcination temperature in step (3) is 350-700° C., and the calcination time is 1-5 h.

[0018] In a third aspect, the present invention provides an all-solid-state battery, comprising a positive electrode layer, a negative electrode layer and a solid electrolyte layer, wherein the solid electrolyte layer is the sulfide solid electrolyte described in the first aspect.

[0019] Preferably, the positive electrode of the all-solid-state battery comprises LiNi 0.7 Mn 0.1 Co 0.2 O2 and the sulfide solid electrolyte described in the first aspect, the negative electrode is a lithium metal sheet.

[0020] The beneficial effects of the present invention are:

[0021] The sulfide electrolyte provided by the present invention has high ionic conductivity and high stability to lithium metal in all-solid-state lithium batteries, thereby enabling the use of lithium metal with high energy density as the negative electrode material, thereby improving the electrochemical performance of solid-state batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the XRD pattern of the sulfide solid electrolyte prepared in Examples 1 to 3;

[0023] Figure 21 is a conductivity diagram of the sulfide solid electrolyte prepared in Examples 1 to 3;

[0024] Figure 3 Graph showing the cycle performance of all-solid-state batteries prepared using the sulfide solid electrolytes prepared in Examples 1 to 3. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] The embodiment of the present invention provides a sulfide solid electrolyte, the composition of the sulfide solid electrolyte is Li7Si2S7X, wherein X is one or more of Cl, Br, and I. Preferably, the composition of the sulfide solid electrolyte is Li7Si2S7I a X (1-a) , wherein X is one or more of Cl, Br, and 0<a≤1.

[0027] In some embodiments, the sulfide solid state electrolyte has an argyrodite-type crystal phase structure.

[0028] The present invention also provides a method for preparing a sulfide solid electrolyte, comprising the following steps:

[0029] (1) According to the stoichiometric ratio of elements in Li7Si2S7X, a lithium source, a silicon source, a sulfur source, and an X source are mixed in an inert gas atmosphere to obtain a mixture;

[0030] (2) In an inert gas atmosphere, the mixture is ball-milled at a speed of 300-700 rpm for 5-20 h to obtain a precursor powder;

[0031] (3) In an inert gas atmosphere, the precursor powder is calcined at 350-700°C for 1-5 hours to obtain a sulfide solid electrolyte.

[0032] Wherein, in step (1), the lithium source is one or more of Li2S, LiI, LiCl, and LiBr; the silicon source is SiS2; the sulfur source is one or more of Li2S, SiS2, and Li2S2; and the X source is one or more of LiI, LiCl, and LiBr.

[0033] In order to further illustrate the present invention, a sulfide solid electrolyte provided by the present invention, its preparation method and application are described in detail below with reference to examples, but they should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1

[0035] Li2S, SiS2, and LiI were mixed in a glove box at a molar ratio of 3:2:1 to obtain a mixture. The mixture was placed in a 50mL zirconia milling jar, along with zirconia balls. The jar was sealed and transferred to a ball mill. Milling was performed at 500 rpm for 15 hours. The milled sample was collected and sealed in a vacuum quartz tube for calcination at 700°C for 5 hours to obtain the Li7Si2S7I solid electrolyte material.

[0036] Example 2

[0037] Li2S, SiS2, LiI, and LiCl were mixed in a glove box at a molar ratio of 3:2:0.5:0.5 to obtain a mixture. The mixture was placed in a 50mL zirconium dioxide ball milling jar, and zirconium dioxide balls were added. The mixture was sealed and transferred to a ball mill. The ball mill was milled at 500 rpm for 15 hours. The milled sample was collected and sealed in a vacuum quartz tube for calcination. The calcination temperature was 700℃ and the calcination time was 5 hours to obtain Li7Si2S7I 0.5 Cl 0.5 Solid electrolyte materials.

[0038] Example 3

[0039] Li2S, SiS2, LiI, and LiBr were mixed in a glove box at a molar ratio of 3:2:0.5:0.5 to obtain a mixture. The mixture was placed in a 50mL zirconium dioxide ball milling jar, and zirconium dioxide balls were added. The mixture was sealed and transferred to a ball mill. The ball mill was milled at 500 rpm for 15 hours. The ball-milled sample was collected and sealed in a vacuum quartz tube for calcination. The calcination temperature was 700°C and the calcination time was 5 hours to obtain Li7Si2S7I 0.5 Br 0.5 Solid electrolyte materials.

[0040] Example 4

[0041] Li2S, SiS2, and LiCl were mixed in a glove box at a molar ratio of 3:2:1 to obtain a mixture. The mixture was placed in a 50mL zirconia milling jar, along with zirconia balls. The jar was sealed and transferred to a ball mill. Milling was performed at 500 rpm for 15 hours. The milled sample was collected and sealed in a vacuum quartz tube for calcination at 700°C for 5 hours to obtain the Li7Si2S7Cl solid electrolyte material.

[0042] Example 5

[0043] Li2S, SiS2, and LiBr were mixed in a glove box at a molar ratio of 3:2:1 to obtain a mixture. The mixture was placed in a 50mL zirconia milling jar, along with zirconia balls. The jar was sealed and transferred to a ball mill. Milling was performed at 500 rpm for 15 hours. The milled sample was collected and sealed in a vacuum quartz tube for calcination at 700°C for 5 hours to obtain the Li7Si2S7Br solid electrolyte material.

[0044] Example 6

[0045] Li2S, SiS2, LiI, and LiCl were mixed in a glove box at a molar ratio of 3:2:0.4:0.6 to obtain a mixture. The mixture was placed in a 50mL zirconium dioxide ball milling jar, and zirconium dioxide balls were added. The mixture was sealed and transferred to a ball mill. The ball mill was milled at 500 rpm for 15 hours. The ball-milled sample was collected and sealed in a vacuum quartz tube for calcination. The calcination temperature was 700°C and the calcination time was 5 hours to obtain Li7Si2S7I 0.4 Cl 0.6 Solid electrolyte materials.

[0046] Example 7

[0047] Li2S, SiS2, LiI, and LiCl were mixed in a glove box at a molar ratio of 3:2:0.2:0.8 to obtain a mixture. The mixture was placed in a 50mL zirconium dioxide ball milling jar, and zirconium dioxide balls were added. The mixture was sealed and transferred to a ball mill. The ball mill was milled at 500 rpm for 15 hours. The ball-milled sample was collected and sealed in a vacuum quartz tube for calcination. The calcination temperature was 700°C and the calcination time was 5 hours to obtain Li7Si2S7I 0.2 Cl 0.8 Solid electrolyte materials.

[0048] Example 8

[0049] Li2S, SiS2, LiI, and LiBr were mixed in a glove box at a molar ratio of 3:2:0.4:0.6 to obtain a mixture. The mixture was placed in a 50mL zirconium dioxide ball milling jar, and zirconium dioxide balls were added. The mixture was sealed and transferred to a ball mill. The ball mill was milled at 500 rpm for 15 hours. The ball-milled sample was collected and sealed in a vacuum quartz tube for calcination. The calcination temperature was 700°C and the calcination time was 5 hours to obtain Li7Si2S7I 0.4 Br 0.6 Solid electrolyte materials.

[0050] Example 9

[0051] Li2S, SiS2, LiI, and LiBr were mixed in a glove box at a molar ratio of 3:2:0.6:0.4 to obtain a mixture. The mixture was placed in a 50mL zirconium dioxide ball milling jar, and zirconium dioxide balls were added. The mixture was sealed and transferred to a ball mill. The ball milling was carried out at 500 rpm for 15 hours. The ball-milled sample was collected and sealed in a vacuum quartz tube for calcination. The calcination temperature was 700℃ and the calcination time was 5 hours to obtain Li7Si2S7I 0.6 Br 0.4 Solid electrolyte materials.

[0052] Example 10

[0053] Li2S, SiS2, LiI, and LiBr were mixed in a glove box at a molar ratio of 3:2:0.2:0.8 to obtain a mixture. The mixture was placed in a 50mL zirconium dioxide ball milling jar, and zirconium dioxide balls were added. The mixture was sealed and transferred to a ball mill. The ball mill was milled at 500 rpm for 15 hours. The milled sample was collected and sealed in a vacuum quartz tube for calcination. The calcination temperature was 700°C and the calcination time was 5 hours to obtain Li7Si2S7I 0.2 Br 0.8 Solid electrolyte materials.

[0054] Performance Testing

[0055] (1) XRD test

[0056] Figure 1 2 is the XRD pattern of the sulfide solid electrolyte obtained in Examples 1 to 3. As can be seen from the figure, the main diffraction peaks of the obtained solid electrolyte are sharp, which proves that the solid electrolyte has good crystallinity. At the same time, the synthesized sample has a argyrodite-type crystal phase structure.

[0057] (2) Ionic conductivity test

[0058] Assemble stainless steel / electrolyte / stainless steel cells and use Admo electrochemical workstation to measure the cell -1 ~10 6 The AC impedance spectrum (EIS) in the Hz frequency range was then fitted to obtain the impedance values ​​corresponding to each embodiment. Finally, the ionic conductivity was calculated according to the formula: σ = L / (R×S), where L is the thickness of the electrolyte sheet, R is the bulk impedance of the electrolyte, and S is the surface area of ​​the electrolyte. The test results are shown in Figure 2. Figure 2 and as shown in Table 1.

[0059] Table 1 Ionic conductivity of sulfide electrolytes prepared in Examples 1 to 3

[0060]

[0061] (3) Lithium metal stability test

[0062] Preparation of all-solid-state lithium-ion battery: First, 120 mg of sulfide solid electrolyte material was pressed into a sheet with a thickness of about 0.70 mm under a pressure of 360 MPa, and pressure was applied to the groove of the battery mold for 1 minute to obtain the electrolyte sheet. 0.7 Mn 0.1 Co 0.2 O2, sulfide solid electrolyte material, and VGCF were mixed uniformly in a mass ratio of 7:2.8:0.2 to produce a cathode composite material. Subsequently, 2 mg of the cathode composite material was evenly distributed on one side of the electrolyte sheet and subjected to a pressure of 300 MPa for 30 seconds. Finally, a lithium metal anode was placed on the other side of the electrolyte sheet and a pressure of 60 MPa was applied to produce an all-solid-state lithium battery.

[0063] The cycle performance of solid-state lithium batteries was tested at 0.5C and room temperature. The results are as follows Figure 3 As shown. Figure 3 It can be seen that the all-solid-state batteries assembled using the solid electrolytes of Examples 1 to 3 have excellent discharge capacity and cycle stability, indicating that the sulfide solid electrolyte provided by the present invention has good lithium metal stability and can be used to prepare high energy density lithium batteries.

[0064] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0065] The above-described embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A sulfide solid electrolyte, characterized in that: The composition of the sulfide solid electrolyte is Li7Si2S7I 0.5 Br 0.5 .

2. The sulfide solid electrolyte according to claim 1, characterized in that The sulfide solid electrolyte has an argyrodite-type crystal phase structure.

3. The method for preparing a sulfide solid electrolyte according to any one of claims 1 to 2, characterized in that: The following steps are involved: Li2S, SiS2, LiI, and LiBr were mixed in a glove box at a molar ratio of 3:2:0.5:0.5 to obtain a mixture; the mixture was placed in a 50 mL zirconium dioxide ball milling jar, and zirconium dioxide balls were added, sealed, and transferred to a ball mill; ball milling was carried out at 500 rpm for 15 h, and the ball-milled sample was collected and sealed in a vacuum quartz tube for calcination; the calcination temperature was 700 ° C, and the calcination time was 5 h to obtain Li7Si2S7I 0.5 Br 0.5 Solid electrolyte materials.

4. An all-solid-state battery comprising a positive electrode layer, a negative electrode layer and a solid electrolyte layer, characterized in that: The solid electrolyte layer comprises the sulfide solid electrolyte according to any one of claims 1 to 2.

5. The all-solid-state battery according to claim 4, characterized in that The positive electrode includes LiNi 0.7 Mn 0.1 Co 0.2 O2 and the sulfide solid electrolyte, and the negative electrode is a lithium metal sheet.

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