A modified sulfide solid-state electrolyte and synthesis method and use

Abstract

The application relates to a structure electrolyte modified sulfide solid electrolyte and a synthesis method and application. In the electrolyte, a soft acid element based rich-iodine argyrodite type electrolyte is used as a nucleating agent and a dopant, and a phosphorus based argyrodite type solid electrolyte modified by multiple element synergic doping is synthesized. Since the dopant is similar to the matrix phase structure, the phase structure is beneficial to be maintained, and the multiple element doping is promoted. The introduction of multiple heterovalent soft acid elements can greatly improve the air stability of the phosphorus based argyrodite type solid electrolyte, the introduction of a large amount of iodine elements can also promote the improvement of the lithium stability, meanwhile, the introduction of multiple elements increases the anion mixed arrangement disorder degree and the lithium ion concentration, optimizes the matrix structure, reduces the lithium ion migration energy barrier, and improves the lithium ion conductivity. The application uses an optimized preparation process, and uses the electrolyte with the same structure as the matrix as the dopant, so that the sulfide solid electrolyte modified by multiple element synergic doping and having excellent comprehensive performance is synthesized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of all-solid-state lithium battery sulfide solid electrolyte, and particularly relates to a modified sulfide solid electrolyte and a synthesis method and application thereof. BACKGROUND

[0002] At present, liquid lithium battery technology has been widely applied in electric vehicles and power grid energy storage markets, and plays an important role in production and life. However, with the progress of science and technology, the vigorous development of various new electronic functional devices and smart grids, the energy density limit and thermal loss behavior of commercial liquid lithium battery technology are increasingly inconsistent with the growing market demand. The all-solid-state lithium ion battery technology replaces the organic separator and flammable and volatile organic electrolyte with solid-state electrolyte, thereby realizing higher energy density and safety, and is considered as one of the most promising next-generation energy storage device technologies.

[0003] As an intermediate carrier for rapid migration of lithium ions between positive active material and negative active material, the solid-state electrolyte should have high ionic conductivity and good mechanical properties, so as to realize good contact with the electrode material and efficient lithium ion transfer. Among the currently studied solid-state electrolyte directions, the sulfide solid electrolyte shows the highest ionic conductivity and better cold-pressing formability, and becomes the most potential system for industrialization. However, the reported sulfide solid electrolyte still faces problems such as narrow electrochemical window, instability to lithium metal, air sensitivity and the like, which limit its large-scale application. For example, the argyrodite-type sulfide solid electrolyte Li6PS5Cl has a relatively high ionic conductivity (>1 mS / cm), but it reacts with lithium metal to form an electron-insulating intermediate phase passivation layer, and the P-S bond contained therein is easy to hydrolyze to produce hydrogen sulfide when it contacts with trace moisture in the air, resulting in a sharp deterioration of performance. Therefore, the sulfide solid electrolyte needs to be modified. Doping modification is a common strategy to improve the performance of materials. Proper beneficial element doping, especially the synergistic doping of multiple beneficial elements, can increase the component diversity, adjust the microstructure, and thus effectively improve the performance of the matrix while maintaining the structure of the matrix parent phase. In the exploration of doping modification of sulfide solid electrolyte, doping agents containing soft acid elements such as As2S5 and Sb2S5 can enhance the humidity stability, and doping agents containing fluorine and iodine elements such as LiF and LiI can improve the stability to lithium. However, whether the elements can be doped into the matrix without destroying the structure of the matrix, and whether the doping of the elements can positively affect the performance of the matrix are uncontrollable. Especially when multiple elements are doped into the matrix, the ratio of element doping and other factors cause greater difficulty in predicting the structure and performance optimization of the matrix, and currently there are few reports on multiple element doping. SUMMARY

[0004] The application aims to provide a modified sulfide solid electrolyte and a synthesis method and use thereof, wherein a soft acid element-containing argyrodite sulfide solid electrolyte Li 7+b-c M b M’ 1-b S 6-c I c As a nucleating agent and a dopant, the phosphorus-based argyrodite solid electrolyte Li 7-a PS 6-a X a is doped and modified to synthesize a same-structure electrolyte-modified argyrodite solid electrolyte xLi 7-a PS 6-a X a ·yLi 7+b-c M b M’ 1-b S 6-c I c , wherein 1>x>y>0, x+y=1, 2>a>0, 1>b>0, 2>c>0, X is one or more of F, Cl and Br, M is one or more of Si, Ge and Sn, and M' is one or more of As, Sb and Bi. Since the dopant has a similar phase structure to the matrix, the matrix is doped with multiple beneficial elements while the matrix phase structure is also maintained, and the nucleation and growth are promoted. The introduction of multiple beneficial elements can effectively solve the problems of poor electrochemical stability, air sensitivity and instability to lithium of the phosphorus-based argyrodite sulfide solid electrolyte in the prior art, and promote the industrialization and application of high-performance sulfide solid electrolytes.

[0005] To solve the technical problem, the application provides a modified sulfide solid electrolyte, which is a same-structure electrolyte-modified sulfide solid electrolyte, and the same-structure electrolyte is an iodine-rich argyrodite electrolyte containing one or more soft acid elements of As, Sb and Bi.

[0006] The modified sulfide solid electrolyte has a chemical formula of xLi 7-a PS 6-a X a ·yLi 7+b-c M b M’ 1-b S 6-c I c , wherein 1>x>y>0, x+y=1, 2>a>0, 1>b>0, 2>c>0, X is one or more of F, Cl and Br, M is one or more of Si, Ge and Sn, and M' is one or more of As, Sb and Bi.

[0007] The modified sulfide solid electrolyte belongs to a cubic crystal system F 43(_)m Space group, halogen elements are located in the face center and vertex of the cubic structure, P, M, M' occupy the tetrahedral interstitial and octahedral interstitial formed by halogen doping, forming a skeleton composed of PS4, MS4, M'S4 tetrahedron, the tetrahedron is PS4, MS4, M'S4 tetrahedron, the tetrahedron occupies the body center and midpoint of each edge of the cube, S is distributed in the tetrahedral site and free sulfur site, Li occupies the remaining tetrahedral interstitial.

[0008] Further, the particle size of the modified sulfide solid electrolyte is 2-20 μm. Too large or too small particle size is not conducive to uniform mixing and effective contact with the positive active material, affecting the battery capacity and reducing the electrochemical cycle performance.

[0009] The second aspect of the application provides a synthesis method of the modified sulfide solid electrolyte. The same structure electrolyte modified sulfide solid electrolyte can be obtained by using one-step method or two-step method. The same structure electrolyte modified sulfide solid electrolyte prepared by using one-step method produces a small amount of impurities at a lower doping amount, and the same structure electrolyte modified sulfide solid electrolyte prepared by using two-step method produces a small amount of impurities at a higher doping amount.

[0010] The same structure electrolyte modified sulfide solid electrolyte is synthesized by using one-step method, which includes the following steps:

[0011] (1-1) Mix lithium sulfide, phosphorus pentasulfide, M source, M' source, sulfur powder, lithium iodide, LiX according to xLi 7-a PS 6-a X a ·yLi 7+b-c M b M' 1-b S 6-c I c molar ratio, to obtain a mixture, wherein 1>x≥y>0, x+y=1, 2≥a≥0, 1>b≥0, 2≥c>0, X is one or more of F, Cl, Br, M is one or more of Si, Ge, Sn, M' is one or more of As, Sb, Bi;

[0012] (1-2) The mixture obtained in step (1-1) is sintered under vacuum or inert atmosphere and heat treated for a period of time, and the obtained product is the same structure electrolyte modified sulfide solid electrolyte. The same structure electrolyte modified sulfide solid electrolyte prepared by one-step method is based on the thermal diffusion of doping elements to replace the corresponding occupation during the formation of the main phase by heat treatment.

[0013] The same structure electrolyte modified sulfide solid electrolyte is synthesized by using two-step method, which includes the following steps:

[0014] (2-1) Mix M source, M' source, sulfur powder, lithium iodide, LiX according to Li 7+b-c M b M' 1-b S 6-c I c in molar ratio to obtain a mixed raw material, wherein 1 > b ≥ 0, 2 ≥ c > 0, M is one or more of Si, Ge, Sn, M' is one or more of As, Sb, Bi, and X is one or more of F, Cl, Br;

[0015] (2-2) Heat and keep the mixed raw material obtained in step (2-1) in vacuum or inert atmosphere for a period of time, and the obtained product is a solid electrolyte of argyrodite structure doped with Li 7+b-c M b M' 1-b S 6-c I c wherein 1 > b ≥ 0, 2 ≥ c > 0, M is one or more of Si, Ge, Sn, M' is one or more of As, Sb, Bi, and X is one or more of F, Cl, Br;

[0016] (2-3) Mix lithium sulfide, phosphorus pentasulfide, LiX and the Li 7+b-c M b M' 1-b S 6-c I c obtained in step (2-2) according to xLi 7-a PS 6-a X a · yLi 7+b-c M b M' 1-b S 6-c I c in molar ratio to obtain a mixed raw material, wherein 1 > x ≥ y > 0, x + y = 1, 2 ≥ a ≥ 0, 1 > b ≥ 0, 2 ≥ c > 0, X is one or more of F, Cl, Br, M is one or more of Si, Ge, Sn, and M' is one or more of As, Sb, Bi;

[0017] (2-4) Heat and keep the mixed raw material obtained in step (2-3) in vacuum or inert atmosphere for a period of time, and the obtained product is a solid electrolyte of argyrodite structure doped with Li

[0018] Further, in the steps (1-1) and (2-1), the M source includes any one or a combination of at least two of M, MS, and MS2, and the M' source is any one or a combination of at least two of M', M'2S3, and M'2S5. M is one or more of Si, Ge, and Sn, and M' is one or more of As, Sb, and Bi.

[0019] Further, in the steps (1-1), (2-1), and (2-3), the mixing method can be sand grinding, grinding, ball milling, or solvent mixing. The solvent can be polar or nonpolar, and the mixing time is 0.1-75 h. The mixing process can occur in a vacuum, under inert atmosphere protection, or in a mixed atmosphere.

[0020] Further, in the steps (1-2), (2-2), and (2-4), the sintering temperature is 200-600 DEG C, the holding time is 0.5-68 h, and the heating rate is 1-20 DEG C / min. A sintering temperature that is too low or a holding time that is too short is not conducive to increasing the crystal phase content of the electrolyte, and a sintering temperature that is too high or a holding time that is too long can cause a large amount of S to volatilize in the electrolyte and increase energy consumption. A slow heating rate requires high equipment and consumes a long time, and a fast heating rate is not conducive to uniform element diffusion.

[0021] Further, in the steps (1-2), (2-2), and (2-4), the sintering temperature is 400-550 DEG C, the holding time is 5-15 h, and the heating rate is 1.5-10 DEG C / min.

[0022] In addition, the application also provides a use of the modified sulfide solid electrolyte and the synthesis method according to any one of the above.

[0023] Compared with the prior art, the application has the following advantages:

[0024] The modified sulfide solid electrolyte prepared by the application has a same structure as the electrolyte, the dopant used has a kesterite structure, and the same structure as the matrix phase. Therefore, compared with the commonly used dopant, the dopant can provide more nucleation sites in the nucleation and growth process of the matrix phase, promote the nucleation and growth of the matrix phase, maintain the phase structure, and introduce a doping modification element into the matrix phase.

[0025] In addition, the same-structure electrolyte-modified sulfide solid electrolyte prepared by the present application makes full use of the advantages of two structure-similar argyrodite-type electrolytes. The phosphorus-based argyrodite-type sulfide solid electrolyte has relatively low cost and high ionic conductivity. However, according to the hard-soft acid-base theory, phosphorus belongs to hard acid, and has weak combination ability with sulfur in the electrolyte. When exposed to moisture in the air, the phosphorus is easily hydrolyzed and oxidized, and hydrogen sulfide gas is released, and the performance rapidly deteriorates. In comparison, soft acid elements tend to combine with sulfur. The argyrodite solid electrolyte containing soft acid elements and rich in iodine has higher air stability. When the argyrodite sulfide solid electrolyte containing soft acid elements and rich in iodine contacts with lithium, a low-electronic-conductivity lithium iodide protective layer is formed, effectively inhibiting the occurrence of interface side reactions in the electrochemical cycle process. For the phosphorus-based argyrodite-type sulfide solid electrolyte, the elements contained in the argyrodite sulfide solid electrolyte containing soft acid elements and rich in iodine are all beneficial elements. The latter can be used as a dopant without damaging the matrix structure of the phosphorus-based argyrodite-type sulfide solid electrolyte, and can introduce multiple beneficial elements, reduce the lithium ion migration energy barrier, and synthesize a multi-element synergistically doped modified sulfide solid electrolyte with high ionic conductivity, high air stability, high electrochemical stability, and high stability to lithium. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 X-ray diffraction patterns of the samples prepared in Example 1, Example 5, Example 6, Comparative Example 1, and Comparative Example 2. DETAILED DESCRIPTION

[0027] In order to make the purposes, technical solutions and beneficial technical effects of the present application clearer, the present application will be described in detail below in combination with specific examples. It should be understood that the examples described in the present specification are only for the purpose of explaining the present application, and are not intended to limit the present application.

[0028] If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturers are used. If the manufacturers of the reagents used are not specified, the conventional products that can be purchased on the market are used. Example 1

[0029] Lithium sulfide, phosphorus pentasulfide, antimony sulfide, lithium iodide, lithium chloride, germanium sulfide, and sulfur powder were weighed in a glove box under the protection of argon atmosphere according to the molar ratio of 0.95Li6PS5Cl·0.05Li 6.3 Ge 0.3 Sb 0.7 S5I, and then were preliminarily mixed in a marquetry mortar for ten minutes. The preliminarily mixed powder was transferred into a ball mill tank containing zirconia balls, sealed, and ball-milled at a speed of 500 r / min for 20 hours to obtain the mixed powder.

[0030] The mixed powder was sealed in a quartz tube. The quartz tube was placed in a sintering furnace and heated to 500°C at a heating rate of 3°C / min and kept at this temperature for 12 hours. The product was allowed to cool naturally to room temperature and the quartz tube was taken out to obtain 0.95Li6PS5Cl·0.05Li 6.3 Ge 0.3 Sb 0.7 S5I sample. Example 2

[0031] Lithium sulfide, lithium chloride, antimony sulfide, lithium iodide, phosphorus pentasulfide, germanium sulfide, and sulfur powder were mixed in a glove box under argon atmosphere according to the conditions of 0.93Li6PS5Cl·0.07Li 6.3 Ge 0.3 Sb 0.7 The molar ratio of S5I was weighed, and then ground in an agate mortar for fifteen minutes to preliminarily mix. The preliminarily mixed powder was transferred to a ball mill filled with zirconia balls, sealed, and ball milled at a speed of 500 r / min for 24 hours to obtain a mixed powder.

[0032] The mixed powder was sealed in a quartz tube. The quartz tube was placed in a sintering furnace and heated to 500°C at a heating rate of 3°C / min and kept at this temperature for 12 hours. The product was allowed to cool naturally to room temperature and the quartz tube was taken out to obtain 0.93Li6PS5Cl·0.07Li 6.3 Ge 0.3 Sb 0.7 S5I sample. Example 3

[0033] Lithium sulfide, antimony sulfide, lithium iodide, sulfur powder and germanium sulfide were placed in a glove box under argon atmosphere according to the Li 6.3 Ge 0.3 Sb 0.7 The molar ratio of S5I was weighed, and then ground in an agate mortar for five minutes for preliminary mixing. The preliminarily mixed powder was transferred to a ball mill filled with zirconia balls, sealed, and ball milled at a speed of 350 r / min for 12 hours to obtain a mixed powder.

[0034] The mixed powder was sealed in a quartz tube. The quartz tube was placed in a sintering furnace and heated to 475°C at a heating rate of 5°C / min and kept at this temperature for 9 hours. The product was allowed to cool naturally to room temperature and the quartz tube was taken out to obtain Li 6.3 Ge 0.3 Sb 0.7 S5I sample.

[0035] Li 6.3 Ge 0.3 Sb 0.7S5I, lithium sulfide, lithium phosphorus pentasulfide, lithium chloride in a glove box under argon atmosphere protection were weighed according to 0.95Li6PS5Cl·0.05Li 6.3 Ge 0.3 Sb 0.7 The raw materials were weighed according to the molar ratio of S5I, and then were preliminarily mixed in a agate mortar for 15 minutes. The preliminarily mixed raw materials were transferred into a ball mill tank containing zirconia balls, and were sealed. The raw materials were ball-milled at a speed of 500 r / min for 20 hours to obtain mixed powder.

[0036] The obtained mixed powder was sealed in a quartz tube. The quartz tube was placed in a sintering furnace, and was heated to 500℃ at a heating rate of 3℃ / min, and was kept for 12 hours. The product was naturally cooled to room temperature to obtain 0.95Li6PS5Cl·0.05Li 6.3 Ge 0.3 Sb 0.7 S5I sample. Example 4

[0037] Antimony sulfide, germanium sulfide, lithium iodide, lithium sulfide, sulfur powder in a glove box under argon atmosphere protection were weighed according to Li 6.3 Ge 0.3 Sb 0.7 The raw materials were weighed according to the molar ratio of S5I, and then were preliminarily mixed in a agate mortar for 5 minutes. The preliminarily mixed powder was transferred into a ball mill tank containing zirconia balls, and was sealed. The raw materials were ball-milled at a speed of 350 r / min for 12 hours to obtain mixed powder.

[0038] The obtained mixed powder was sealed in a quartz tube. The quartz tube was placed in a sintering furnace, and was heated to 475℃ at a heating rate of 5℃ / min, and was kept for 9 hours. The product was naturally cooled to room temperature to obtain Li 6.3 Ge 0.3 Sb 0.7 S5I sample.

[0039] Li 6.3 Ge 0.3 Sb 0.7 S5I, lithium sulfide, lithium chloride, lithium phosphorus pentasulfide in a glove box under argon atmosphere protection were weighed according to 0.9Li6PS5Cl·0.1Li 6.3 Ge 0.3 Sb 0.7 The raw materials were weighed according to the molar ratio of S5I, and then were preliminarily mixed in a agate mortar for 15 minutes. The preliminarily mixed raw materials were transferred into a ball mill tank containing zirconia balls, and were sealed. The raw materials were ball-milled at a speed of 500 r / min for 20 hours to obtain mixed powder.

[0040] The mixed powder was sealed in a quartz tube. The quartz tube was placed in a sintering furnace and heated to 500°C at a heating rate of 3°C / min for 12 hours, and the product was naturally cooled to room temperature to obtain 0.9Li6PS5Cl·0.1Li 6.3 Ge 0.3 Sb 0.7 S5I sample. Example 5

[0041] Lithium sulfide, antimony sulfide, lithium iodide, sulfur powder, germanium sulfide were weighed in a glove box under argon atmosphere protection according to the molar ratio of 0.9Li6PS5Cl·0.1Li 6.3 Ge 0.3 Sb 0.7 S5I, and then ground in a marigold mortar for five minutes for preliminary mixing. The preliminary mixed powder was transferred into a ball mill tank containing zirconia balls and sealed, and ball milled at a speed of 350 r / min for 12 hours to obtain a mixed powder.

[0042] The obtained mixed powder was sealed in a quartz tube. The quartz tube was placed in a sintering furnace and heated to 475°C at a heating rate of 5°C / min for 9 hours, and the product was naturally cooled to room temperature to obtain Li 6.3 Ge 0.3 Sb 0.7 S5I sample.

[0043] Li 6.3 Ge 0.3 Sb 0.7 S5I, lithium sulfide, phosphorus pentasulfide, lithium chloride were weighed in a glove box under argon atmosphere protection according to the molar ratio of 0.85Li6PS5Cl·0.15Li 6.3 Ge 0.3 Sb 0.7 S5I, and then ground in a marigold mortar for fifteen minutes for preliminary mixing. The preliminary mixed raw materials were transferred into a ball mill tank containing zirconia balls and sealed, and ball milled at a speed of 500 r / min for 20 hours to obtain a mixed powder.

[0044] The obtained mixed powder was sealed in a quartz tube. The quartz tube was placed in a sintering furnace and heated to 500°C at a heating rate of 3°C / min for 12 hours, and the product was naturally cooled to room temperature to obtain 0.85Li6PS5Cl·0.15Li 6.3 Ge 0.3 Sb 0.7 S5I sample. Example 6

[0045] Lithium sulfide, antimony sulfide, lithium iodide, sulfur powder, germanium sulfide were weighed in a glove box under argon atmosphere protection according to the molar ratio of 0.9Li6PS5Cl·0.1Li 6.3 Ge 0.3 Sb0.7 S5I were weighed in molar ratio, and then were preliminary mixed in a marble mortar for five minutes. The preliminary mixed powder was transferred into a ball mill tank with zirconia balls, and was sealed. The powder was ball-milled at a speed of 350 r / min for 12 hours to obtain a mixed powder.

[0046] The obtained mixed powder was sealed in a quartz tube. The quartz tube was placed in a sintering furnace, and was heated to 475 °C at a heating rate of 5 °C / min, and was kept for 9 hours. The quartz tube was taken out after the product was naturally cooled to room temperature to obtain Li 6.3 Ge 0.3 Sb 0.7 S5I sample.

[0047] The Li 6.3 Ge 0.3 Sb 0.7 S5I, lithium sulfide, diphosphorus pentasulfide, lithium chloride were weighed in the glove box under the protection of argon atmosphere according to the molar ratio of 0.8Li6PS5Cl·0.2Li 6.3 Ge 0.3 Sb 0.7 S5I were weighed in molar ratio, and then were preliminary mixed in a marble mortar for fifteen minutes. The preliminary mixed powder was transferred into a ball mill tank with zirconia balls, and was sealed. The powder was ball-milled at a speed of 550 r / min for 24 hours to obtain a mixed powder.

[0048] The obtained mixed powder was sealed in a quartz tube. The quartz tube was placed in a sintering furnace, and was heated to 500 °C at a heating rate of 3 °C / min, and was kept for 12 hours. The quartz tube was taken out after the product was naturally cooled to room temperature to obtain 0.8Li6PS5Cl·0.2Li 6.3 Ge 0.3 Sb 0.7 S5I sample. Example 7

[0049] The difference between this example 7 and example 5 is only in the raw material part, and finally 0.85Li6PS5Cl·0.15Li6SbS5I sample is obtained.

[0050] Comparative Example 1

[0051] Lithium sulfide, diphosphorus pentasulfide, lithium chloride were weighed in the glove box under the protection of argon atmosphere according to the molar ratio of Li6PS5Cl, and then were preliminary mixed in a marble mortar for ten minutes. The preliminary mixed powder was transferred into a ball mill tank with zirconia balls, and was sealed. The powder was ball-milled at a speed of 500 r / min for 20 hours to obtain a mixed powder.

[0052] The mixed powder was sealed in a quartz tube. The quartz tube was placed in a sintering furnace and heated to 500℃ at a heating rate of 3℃ / min for 12 hours. The quartz tube was taken out after the product was naturally cooled to room temperature to obtain a Li6PS5Cl sample.

[0053] Comparative Example 2

[0054] Lithium sulfide, germanium sulfide, antimony sulfide, iodine sulfide and sulfur powder were weighed in a molar ratio of Li 6.3 Ge 0.3 Sb 0.7 S5I and then were preliminarily mixed in a corundum mortar for 10 minutes. The preliminarily mixed raw materials were transferred into a ball mill tank containing zirconia balls and sealed, and were ball-milled at a rotation rate of 500 r / min for 20 hours to obtain a mixed powder.

[0055] The mixed powder was sealed in a quartz tube. The quartz tube was placed in a sintering furnace and heated to 500℃ at a heating rate of 3℃ / min for 12 hours. The quartz tube was taken out after the product was naturally cooled to room temperature to obtain a Li 6.3 Ge 0.3 Sb 0.7 S5I sample.

[0056] Comparative Example 3

[0057] The difference between this comparative example 3 and example 3 is only that the temperature of the two sintering treatments is 180℃.

[0058] Comparative Example 4

[0059] The difference between this comparative example 4 and example 3 is only that the temperature of the two sintering treatments is 620℃.

[0060] Comparative Example 5

[0061] The difference between this comparative example 5 and example 3 is only that the holding time of the two sintering treatments is 0.4h.

[0062] Comparative Example 6

[0063] The difference between this comparative example 6 and example 3 is only that the holding time of the two sintering treatments is 70h.

[0064] Comparative Example 7

[0065] The difference between this comparative example 7 and example 3 is only that the heating rate of the two sintering treatments is 0.5℃ / min.

[0066] Comparative Example 8

[0067] The difference between this comparative example 8 and example 3 is only that the heating rate of the two sintering treatments is 25℃ / min.

[0068] The sulfide solid electrolytes synthesized in Examples 1 to 7 and Comparative Examples 1 to 8 were subjected to the following performance tests.

[0069] Ion conductivity test procedure: 110 mg of the test sample was loaded into a mold with a diameter of 10 mm, and stainless steel current collector rods were placed on the top and bottom, and a press was used to apply a pressure of 450 MPa on both ends to form an electrolyte sheet with a diameter of 10 mm, and an electrochemical workstation was used to perform an alternating current impedance test at 30°C. The amplitude of the alternating current was 10 mV, and the frequency range was 0.01 HZ to 1 MHz.

[0070] Lithium symmetric battery assembly and critical current density test procedure: 130 mg of the test sample was loaded into a mold with a diameter of 10 mm, and stainless steel rods were placed on the top and bottom, and a press was used to apply a pressure of 275 MPa on both ends of the stainless steel rods to form an electrolyte sheet with a diameter of 10 mm, and the mold was then opened and the stainless steel rods were removed, and a lithium sheet with a diameter of 10 mm was placed on both ends of the electrolyte sheet, and stainless steel rods were used as current collectors and were placed on the top and bottom, and a press was used to apply a pressure of 75 MPa on both ends of the stainless steel current collector rods. A Neware battery test system was used to test the critical current density of the assembled lithium symmetric battery, and the initial constant current was set to 0.1 mA / cm 2 , and the lithium plating and stripping time was 1 hour, and the lithium plating / stripping constant current was gradually increased, and the lithium plating and stripping constant current was increased by 0.1 mA / cm 2 every 1 hour.

[0071] The test results of the sulfide solid electrolytes synthesized in Examples 1 to 7 and Comparative Examples 1 to 8 are shown in Table 1.

[0072] Table 1 Test results of the sulfide solid electrolytes in Examples 1 to 7 and Comparative Examples 1 to 8.

[0073]

[0074] As can be seen from the data in the table, the ion conductivity of the sample 0.95Li6PS5Cl·0.05Li 6.3 Ge 0.3 Sb 0.7 S5I in Example 1 was higher than that of the sample Li6PS5Cl in Comparative Example 1 and the sample Li 6.3 Ge 0.3 Sb 0.7 S5I in Comparative Example 2, indicating that Li 6.3 Ge 0.3 Sb 0.7Ge, Sb, I elements in S5I doped into Li6PS5Cl can optimize the internal structure, reduce the lithium ion migration energy barrier, improve the ionic conductivity, and after air exposure, the ionic conductivity of the undoped comparative example 1 sample decreases to nearly one order of magnitude of the original, while the ionic conductivity of the doped example 1 sample attenuates significantly less, indicating that Li 6.3 Ge 0.3 Sb 0.7 Soft acid elements Ge, Sb in S5I doped into Li6PS5Cl can effectively improve the air stability, the critical current density of the lithium symmetric battery based on the example 1 sample is greater than that of the comparative example 1 sample and the comparative example 2 sample, and the doping of Ge, Sb, I elements effectively improves the stability of the electrolyte to lithium, because a more stable interface layer can be formed at the interface between the metal lithium and the solid-state electrolyte during the constant current charge and discharge process. With the increase of the doping amount of Ge, Sb, I elements, the ionic conductivity of the electrolyte is improved, and the ionic conductivity of the electrolyte is improved. 6.3 Ge 0.3 Sb 0.7 Further increase of the doping amount of S5I, the ionic conductivity of the example 2 sample decreases, which is caused by the increase of the insulating impurity phase SbSI, indicating that it is difficult to achieve the full doping of multiple elements in the Li6PS5Cl matrix by using the sulfide containing doping elements directly by one-step method, and the impurity phase is precipitated when the doping amount is 5%~7% by one-step method.

[0075] With the increase of the doping amount of Ge, Sb, I elements, the ionic conductivity of the electrolyte is improved, and the ionic conductivity of the electrolyte is improved. 6.3 Ge 0.3 Sb 0.7 S5I is precipitated only when the doping amount is higher, and the ionic conductivity is higher under the same composition. It is indicated that the two-step method uses Li 6.3 Ge 0.3 Sb 0.7 S5I as a nucleating agent and a dopant can effectively promote the nucleation and growth of the Li6PS5Cl matrix phase, inhibit the formation of impurity phases, maintain the phase structure, and increase the doping amount of Ge, Sb, I elements. The doping of Ge, Sb, I elements can form a more stable interface layer at the interface between the metal lithium and the solid-state electrolyte, effectively enhancing the stability of the electrolyte to lithium, and the lithium symmetric battery exhibits a higher critical current density.

[0076] The above shows general specific embodiments and comparative examples, and describes the basic principles, main preparation process features, and advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that modifications or improvements can be made thereto without departing from the principles or basic features of the present invention. Therefore, from all perspectives, the examples should be regarded as illustrative and non-limiting. The scope of the present invention is defined by the appended claims rather than the foregoing description. Modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A modified sulfide solid-state electrolyte, characterized by, The sulfide solid electrolyte is a homologous electrolyte-modified sulfide solid electrolyte, and the homologous electrolyte is an iodine-rich argyrodite-type electrolyte containing one or more soft acid elements of As, Sb and Bi. The modified sulfide solid electrolyte has a chemical formula: xLi 7-a PS 6-a X a ·yLi 7+b-c M b M’ 1-b S 6-c I c , wherein 1>x>y>0, x+y=1, 2>a>0, 1>b>0, 2>c>0, X is one or more of F, Cl, Br, M is one or more of Si, Ge, Sn, M' is one or more of As, Sb, Bi. The modified sulfide solid electrolyte belongs to a cubic system F 43(_) m Space group, halogen elements are located in the face center and vertex of the cubic structure, P, M, M' occupy the tetrahedral interstitial and octahedral interstitial formed by halogen doping, forming a skeleton composed of PS4, MS4, M'S4 tetrahedron, the tetrahedron is PS4, MS4, M'S4 tetrahedron, the tetrahedron occupies the body center and midpoint of each edge of the cube, S is distributed in the tetrahedral site and free sulfur site, Li occupies the remaining tetrahedral interstitial.

2. The sulfide solid-state electrolyte according to claim 1, characterized by, The modified sulfide solid electrolyte has a particle size of 2-20 μm.

3. A method for synthesizing the modified sulfide solid-state electrolyte according to claim 1 or 2, characterized by, The homologous electrolyte-modified sulfide solid electrolyte is obtained by using a one-step method or a two-step method.

4. The method of synthesis of claim 3, wherein, The homologous electrolyte-modified sulfide solid electrolyte is synthesized by using a one-step method, comprising the following steps: 1-1) mix lithium sulfide, phosphorus pentasulfide, M source, M' source, sulfur powder, lithium iodide, LiX according to xLi 7-a PS 6-a X a ·yLi 7+b- c M b M' 1-b S 6-c I c in a molar ratio to obtain a mixture, wherein 1>x≥y>0, x+y=1, 2≥a≥0, 1>b≥0, 2≥c>0, X is one or more of F, Cl, Br, M is one or more of Si, Ge, Sn, M' is one or more of As, Sb, Bi; 1-2) sintering and heat-insulating the mixture obtained in step 1-1) under vacuum or inert atmosphere for a period of time, and the obtained product is the homologous electrolyte-modified sulfide solid electrolyte.

5. The synthesis method according to claim 3, characterized in that The homologous electrolyte-modified sulfide solid electrolyte is synthesized by using a two-step method, comprising the following steps: 2-1) mixing M source, M' source, sulfur powder, lithium iodide, LiX according to Li 7+b-c M b M' 1-b S 6-c I c molar ratio, to obtain a mixed raw material, wherein 1 > b > 0, 2 > c > 0, M is one or more of Si, Ge, Sn, M' is one or more of As, Sb, Bi, and X is one or more of F, Cl, Br; 2-2) The mixed raw materials obtained in step 2-1) are heated and kept for a certain period of time under vacuum or inert atmosphere, and the obtained product is a 7+b-c M b M' 1-b S 6-c I c wherein 1 > b > 0, 2 > c > 0, M is one or more of Si, Ge, Sn, M' is one or more of As, Sb, Bi, and X is one or more of F, Cl, Br. 2-3) mixing lithium sulfide, phosphorus pentasulfide, LiX and the Li obtained in step 2-2) of the present application 7+b-c M b M’ 1-b S 6-c I c according to xLi 7-a PS 6- a X a ·yLi 7+b-c M b M’ 1-b S 6-c I c are mixed in a molar ratio to obtain a mixed raw material, wherein 1 > x > y > 0, x + y = 1, 2 > a > 0, 1 > b > 0, 2 > c > 0, X is one or more of F, Cl, Br, M is one or more of Si, Ge, Sn, and M' is one or more of As, Sb, Bi. 2-4) heating and heat-insulating the mixed raw materials obtained in step 2-3) under vacuum or inert atmosphere for a period of time, and the obtained product is the homologous electrolyte-modified sulfide solid electrolyte.

6. The method of synthesis according to claim 4 or 5, wherein, In the steps 1-1) and 2-1), the M source includes any one or a combination of at least two of the elements M, MS and MS2, and the M' source is any one or a combination of at least two of the elements M', M'2S3 and M'2S5.

7. The method of synthesis of claim 6, wherein, In the steps 1-1), 2-1) and 2-3), the mixing is performed by sand milling or grinding or ball milling or solvent mixing, and the mixing time is 0.1-75 h.

8. The method of synthesis of claim 7, wherein, In the steps 1-2), 2-2) and 2-4), the sintering temperature is 200-600 ℃, the heat-insulating time is 0.5-68 h, and the heating rate is 1-20 ℃ / min.

9. The method of synthesis of claim 8, wherein, In the steps 1-2), 2-2) and 2-4), the sintering temperature is 400-550 ℃, the heat-insulating time is 5-15 h, and the heating rate is 1.5-10 ℃ / min.

10. Use of a modified sulfide solid-state electrolyte, characterized in that, The modified sulfide solid electrolyte of any one of claims 1 or 2 or the modified sulfide solid electrolyte prepared by the synthesis method of any one of claims 3-9 is used in a lithium ion battery.

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