Surface-modified sulfur-containing electrolyte as well as preparation method and application thereof
By forming an oxide modified layer on the surface of the sulfur-containing electrolyte, the problems of damage to sulfur-containing electrolyte and unstable humidity during the preparation process are solved, and the stability and high ionic conductivity in a high humidity environment are achieved, and the assembly cost of solid-state batteries is reduced.
Patent Information
- Application Number
- CN202510389981.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-31
- Publication Date
- 2025-07-11
AI Technical Summary
In the prior art, sulfur-containing electrolytes are easily damaged during the preparation process and are unstable to humid air, resulting in a decrease in ionic conductivity and high-cost production facilities.
Chemical substances such as LiBO2, B2O3, etc. are added to an inert atmosphere, and a modified layer is formed by low-temperature heating treatment and oxidizing gas is used to form a modified layer to repair the surface of the sulfur-containing electrolyte and improve its stability to humid air.
Without increasing the particle size of the electrolyte, the crystallinity and ionic conductivity of the sulfur-containing electrolyte are improved, its stability in a high humidity environment is enhanced, and the assembly cost of solid-state batteries is reduced.
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Abstract
Description
Technical Field
[0001] The present invention relates to the field of batteries, and particularly to a sulfur-containing electrolyte with surface modification, a preparation method thereof, and an application thereof. Background Art
[0002] All-solid-state batteries have high energy density and safety performance, which have attracted great interest from researchers. Compared with oxide glass and ceramic electrolytes, sulfur-containing electrolytes are widely used because they exhibit lower Young's modulus values.
[0003] However, the preparation of sulfur-containing electrolytes usually requires sintering at 400°C to 550°C, which will cause grain growth. Larger electrolyte particles in the battery system will lead to low utilization rate of active materials. Therefore, it is necessary to refine the sintered electrolyte material. Common methods such as wet ball milling and jet milling can reduce the particle size of the electrolyte to 3 μm or less, but the solvent or high-energy action will damage the surface of the electrolyte.
[0004] Moreover, due to the extremely poor stability of sulfur-containing electrolytes to water, toxic H2S gas will be generated after hydrolysis, and at the same time, the ionic conductivity will drop severely. This makes the preparation of solid electrolytes using sulfur-containing electrolytes require an inert glove box atmosphere with extremely low humidity (-80°C dew point), or in a dry room with a dew point less than -60°C. Compared with the -30°C dew point environment required for traditional lithium-ion batteries, the infrastructure required is much more expensive.
[0005] In summary, there is an urgent need in the prior art for a process that can both repair the damaged surface of sulfur-containing electrolytes and improve the stability of sulfur-containing electrolytes to wet air. Summary of the Invention
[0006] The embodiments of the present invention provide a sulfur-containing electrolyte with surface modification, a preparation method thereof, and an application thereof, which can both repair the surface of the refined sulfur-containing electrolyte and improve the stability of the sulfur-containing electrolyte to wet air, effectively overcoming the defects existing in the prior art.
[0007] In the first aspect of the present invention, a preparation method of the above-mentioned sulfur-containing electrolyte with surface modification is provided, including:
[0008] In an inert atmosphere, a chemical substance is added to the refined sulfur-containing electrolyte, and the sulfur-containing electrolyte and the chemical substance are mixed to obtain a composite, wherein the chemical substance includes at least one element of boron, nitrogen, fluorine, and sulfur;
[0009] The composite is placed in an atmosphere of a mixed gas for low-temperature heat treatment, so that the decomposition product or melting product of the chemical substance forms a coating layer on the surface of the sulfur-containing electrolyte, and the coating layer is oxidized by the oxidizing gas in the mixed gas to obtain a modified layer, thereby obtaining a sulfur-containing electrolyte with a surface modification. The mixed gas includes an inert gas and an oxidizing gas.
[0010] According to an embodiment of the present invention, the chemical substance is at least one of LiBO2, B2O3, H3BO3, B(OCH3)3, S, LiNO3, LiF, C2F6LiNO4S2, F2NO4S2.Li, and NH4F.
[0011] According to an embodiment of the present invention, the mass of the chemical substance is 0.1% to 10% of the mass of the sulfur-containing electrolyte.
[0012] According to an embodiment of the present invention, the inert gas is at least one of nitrogen, argon, helium, and neon.
[0013] According to an embodiment of the present invention, the oxidizing gas is at least one of oxygen, sulfur dioxide, ozone, chlorine, nitrogen dioxide, and hydrogen peroxide vapor.
[0014] According to an embodiment of the present invention, the content of the oxidizing gas is 1% to 10% of the content of the mixed gas.
[0015] According to an embodiment of the present invention, the heating temperature during the low-temperature heat treatment is 100 to 250 °C, and the heating time is 1 to 5 h.
[0016] In a second aspect of the present invention, there is provided a sulfur-containing electrolyte with a surface modification, wherein the sulfur-containing electrolyte is coated with a modified layer, and the modified layer includes oxides containing at least two elements of boron, nitrogen, and fluorine.
[0017] According to an embodiment of the present invention, the sulfur-containing electrolyte is a sulfide electrolyte.
[0018] According to an embodiment of the present invention, the sulfide electrolyte is at least one of those represented by Chemical Formula (1) and Chemical Formula (2);
[0019] Chemical Formula (1) is: Li x MP y S z , where M includes one or more of Sn, Ge, or Si, 0 < x ≤ 10, 0 < y ≤ 2, and 0 < z ≤ 12;
[0020] Chemical Formula (2) is: Li 7-x-y PS 6-x-y Clx X y , wherein X is a halogen element, 0 ≤ x ≤ 1.7, and 0 ≤ y ≤ 1.7.
[0021] According to an embodiment of the present invention, the thickness of the modification layer is less than or equal to 200 nm.
[0022] In a third aspect of the present invention, a battery is provided, including: a positive electrode, a solid electrolyte, and a negative electrode;
[0023] Wherein, the solid electrolyte includes: a surface-modified sulfur-containing electrolyte prepared by using the preparation method provided in the first aspect of the present invention, or the surface-modified sulfur-containing electrolyte provided in the second aspect of the present invention described above.
[0024] A surface-modified sulfur-containing electrolyte, a preparation method and an application thereof provided by the present invention. On the one hand, through a preparation method of performing low-temperature heat treatment on the refined sulfur-containing electrolyte included in the composite, while ensuring that the particle size of the sulfur-containing electrolyte grains does not increase significantly, the crystallinity of the sulfur-containing electrolyte is improved, the surface of the refined sulfur-containing electrolyte is repaired, and thus the ionic conductivity of the sulfur-containing electrolyte is enhanced. On the other hand, by performing low-temperature heating on a chemical substance including at least one element among boron, nitrogen, fluorine, and sulfur in the composite, the chemical substance is decomposed or melted, and the decomposition product or melting product is formed into a coating layer on the surface of the sulfur-containing electrolyte, and the coating layer is oxidized by the oxidizing property in the mixed gas to obtain a preparation method of a modification layer including oxides containing at least two elements among boron, nitrogen, and fluorine, and a surface-modified sulfur-containing electrolyte is obtained. Among them, the modification layer coated on the sulfur-containing electrolyte can avoid the direct contact between the sulfur-containing electrolyte and wet air, inhibit the damage of the structure of the electrolyte material by water in the air, and thus reduce the decomposition of the electrolyte and the generation of H2S gas, enhance the stability of the sulfide to wet air, and enable the sulfur-containing electrolyte to maintain a high ionic conductivity even in a high-humidity environment. Further, based on the sulfur-containing electrolyte prepared by the above method, the cycle performance of a solid-state battery assembled at a higher humidity can be ensured, and the assembly cost of the solid-state battery can be reduced. Detailed Embodiments
[0025] To enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below. The following specific embodiments listed are only used to describe the principles and features of the present invention, and the examples given are only used to explain the present invention, not to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.
[0026] To facilitate the understanding of the technical solutions in the present invention, the background technology will be introduced in detail below:
[0027] Solid-state batteries have high energy density and safety performance. Moreover, they also have higher interfacial stability and better mechanical properties, can inhibit the penetration of lithium dendrites, provide solutions for achieving high energy density of batteries, and have attracted great interest from researchers.
[0028] Currently, the mainstream inorganic solid electrolyte materials selected for solid electrolytes mainly include oxides, halides, and sulfur-containing electrolytes. Among these electrolytes, compared with oxide glasses and ceramic electrolytes, sulfur-containing electrolytes (such as Li 9.6 P3S 12 ,Li 10 GeP2S 12 ,and Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 etc.) have received extensive attention due to their ultra-high ionic conductivity (up to 10 -2 S / cm) and deformability, as well as their relatively low Young's modulus value (if the electrolyte has a low Young's modulus value, it indicates that the electrolyte is beneficial for the mutual contact between electrode materials in the battery system and reduces the interfacial impedance).
[0029] However, the preparation of sulfur-containing electrolytes usually requires sintering at 400°C - 550°C, which will lead to grain growth. Larger electrolyte particles in the battery system will result in low utilization rate of active materials. Therefore, it is necessary to refine the sintered electrolyte material. Common methods such as wet ball milling and air jet milling can reduce the particle size of the electrolyte to 3μm or less, but the solvent or high-energy action will damage the surface of the electrolyte.
[0030] Moreover, due to the extremely poor stability of sulfur-containing electrolytes to water, toxic H2S gas will be generated after hydrolysis, and at the same time, the ionic conductivity will drop severely. This makes the preparation of solid electrolytes using sulfur-containing electrolytes require an inert glove box atmosphere with extremely low humidity (-80°C dew point), or be carried out in a dry room with a dew point < -60°C. Compared with the -30°C dew point environment required for traditional lithium-ion batteries, the required infrastructure is much more expensive.
[0031] In summary, there is an urgent need in the prior art for a process that can both repair the damaged surface of sulfur-containing electrolytes and improve the stability of sulfur-containing electrolytes to humid air.
[0032] In view of the technical problems in the above background art, the present invention provides a method for preparing a surface-modified sulfur-containing electrolyte, including:
[0033] First, in an inert atmosphere, a chemical substance is added to the refined sulfur-containing electrolyte, and the sulfur-containing electrolyte and the chemical substance are mixed to obtain a composite. Among them, the chemical substance includes at least one element of boron, nitrogen, fluorine, and sulfur. Then, the composite is placed in a mixed gas atmosphere for low-temperature heat treatment, so that the decomposition product or melting product of the chemical substance forms a coating layer on the surface of the sulfur-containing electrolyte, and the coating layer is oxidized by the oxidizing gas in the mixed gas to obtain a modified layer, thus obtaining a surface-modified sulfur-containing electrolyte. Among them, the mixed gas includes an inert gas and an oxidizing gas.
[0034] In the above preparation process, the sulfur-containing electrolyte and the chemical substance can be fully mixed by dry or wet methods to obtain a composite. The chemical substance in the above preparation process is a substance that can decompose or melt in a low-temperature heating environment.
[0035] Based on the inventor's research foundation and experimental verification, since treating the sulfur-containing electrolyte in a high-temperature environment will cause the growth of the grain size of the sulfur-containing electrolyte crystals, and larger electrolyte particles in the battery system will result in low utilization rate of the active material and damage the conductivity of the sulfur-containing electrolyte. Therefore, the present invention uses low-temperature heating to treat the sulfur-containing electrolyte. And after observing the sulfur-containing electrolyte before and after modification by a scanning electron microscope (SEM), it is found that the grain size of the sulfur-containing electrolyte before and after modification has not changed significantly, verifying that treating the sulfur-containing electrolyte by the above method will not further damage the conductivity of the sulfur-containing electrolyte.
[0036] At the same time, it is known that treating the refined electrolyte by low-temperature heat treatment can repair the surface of the sulfur-containing electrolyte. And after observing the sulfur-containing electrolyte before and after modification by X-ray diffraction (XRD), it is found that the X-ray diffraction peak intensity of the sulfur-containing electrolyte after modification is significantly increased compared with that before modification, verifying that treating the sulfur-containing electrolyte by the above method will improve the crystallinity of the sulfur-containing electrolyte, significantly enhance the ionic conductivity of the sulfur-containing electrolyte, and achieve the effect of repairing the surface of the refined sulfur-containing electrolyte.
[0037] Furthermore, based on the inventor's research and experimental verification, it is found that since the modified layer on the surface of the surface-modified sulfur-containing electrolyte obtained by the above method is an oxide, this modified layer can effectively isolate the reaction between the surface of the sulfur-containing electrolyte and water, and can significantly improve the stability of the sulfur-containing electrolyte against humid air.
[0038] Therefore, based on the above description, the preparation method of the surface-modified sulfur-containing electrolyte provided by the present invention can not only repair the surface of the refined sulfur-containing electrolyte, but also improve the stability of the sulfur-containing electrolyte against moist air.
[0039] In some preferred embodiments, the chemical substance is at least one of LiBO2, B2O3, H3BO3, B(OCH3)3, S, LiNO3, LiF, C2F6LiNO4S2, F2NO4S2.Li, and NH4F.
[0040] It should be understood that both too thin and too thick modification layers will affect the performance of the obtained surface-modified sulfur-containing electrolyte. If the modification layer coated on the sulfur-containing electrolyte is too thin, the modification layer not only cannot effectively improve the stability of the sulfur-containing electrolyte against moist air, but also has a risk of being fragile, affecting the safety of use of the surface-modified sulfur-containing electrolyte during the preparation of the solid-state battery; if the modification layer coated on the sulfur-containing electrolyte is too thick, it will significantly reduce the overall ionic conductivity of the surface-modified sulfur-containing electrolyte and affect the ion transport performance. Therefore, corresponding means are needed to control the thickness of the modification layer coated on the prepared sulfur-containing electrolyte.
[0041] In some preferred embodiments, the mass of the chemical substance is 0.1% to 10% of the mass of the sulfur-containing electrolyte. The mass of the chemical substance is, for example, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% of the mass of the sulfur-containing electrolyte, or a new range is formed by selecting any two of the foregoing values, and the value taken within the new range. It should be understood that the more the mass of the chemical substance, the greater the thickness of the modification layer; the less the mass of the chemical substance, the smaller the thickness of the modification layer. Based on this, in this embodiment, the thickness of the modification layer coated on the sulfur-containing electrolyte is controlled by controlling the mass of the chemical substance.
[0042] In some preferred embodiments, the inert gas included in the mixed gas is at least one of nitrogen, argon, helium, and neon.
[0043] In some preferred embodiments, the oxidizing gas in the mixed gas is at least one of oxygen, sulfur dioxide, ozone, chlorine, nitrogen dioxide, and hydrogen peroxide vapor.
[0044] In some preferred embodiments, the content of the oxidizing gas in the mixed gas is 1% to 10% of the content of the mixed gas. The content of the oxidizing gas in the mixed gas is, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% of the content of the mixed gas, or any two of the foregoing values are selected to form a new range, and the value taken within the new range. It should be understood that the greater the content of the oxidizing gas in the mixed gas, the greater the thickness of the modified layer; the smaller the content of the oxidizing gas in the mixed gas, the smaller the thickness of the modified layer. Based on this, in this embodiment, the thickness of the modified layer coated on the sulfur-containing electrolyte is controlled by controlling the content of the oxidizing gas in the mixed gas. In addition, if the content of the oxidizing gas in the mixed gas is too large, it may also cause the original crystal structure of the sulfur-containing electrolyte to be damaged during the sintering process. By setting the maximum value of the proportion of the oxidizing gas in the mixed gas, this risk is effectively avoided.
[0045] In some preferred embodiments, the heating temperature during the low-temperature heat treatment is 100 to 250 °C, and the heating time is 1 to 5 h. The heating temperature during the low-temperature heat treatment is, for example, 100 °C, 125 °C, 150 °C, 175 °C, 200 °C, 225 °C, 250 °C, or any two of the foregoing values are selected to form a new range, and the value taken within the new range; the heating time is, for example, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, or any two of the foregoing values are selected to form a new range, and the value taken within the new range. It should be understood that controlling the temperature and time of low-temperature heating is the key to affecting the surface-modified sulfur-containing electrolyte obtained by preparation: if the heating temperature is too high, not only can the damage on the surface of the sulfur-containing electrolyte not be repaired, but also the grain size of the modified sulfur-containing electrolyte will increase significantly, and larger electrolyte particles will lead to low utilization rate of the active material, and then lead to a decrease in the conductivity of the electrolyte; if the heating temperature is too low, the chemical substances cannot be decomposed or melted. In addition, an appropriate heating time can ensure a moderate thickness of the modified layer. By using the heating time and heating temperature in the preferred embodiments provided by the present invention for preparation, it can effectively ensure that the grain size of the modified sulfur-containing electrolyte does not increase significantly, realize the repair of its damaged surface, and at the same time, a modified layer with a moderate thickness can be obtained, effectively improving the stability of the sulfur-containing electrolyte against moist air.
[0046] The present invention provides a surface-modified sulfur-containing electrolyte, comprising:
[0047] A modified layer is coated on the sulfur-containing electrolyte, and the modified layer includes an oxide containing at least two elements of boron, nitrogen, and fluorine.
[0048] It should be understood that the modified layer may include not only the elements contained in the chemical substance, but also any elements contained in the selected sulfur-containing electrolyte, such as lithium, sulfur, phosphorus, etc. This is because a part of the surface of the sulfur-containing electrolyte may also be oxidized by the oxidizing gas and become a part of the modified layer.
[0049] According to the research and experimental verification of the inventors, by observing the sulfur-containing electrolyte before and after modification through a scanning electron microscope and an X-ray energy spectrometer, it is proved that the particle size of the grains of the sulfur-containing electrolyte before and after modification has not changed significantly, and the crystallinity and ionic conductivity of the sulfur-containing electrolyte have been significantly improved, realizing the repair of the surface of the refined sulfur-containing electrolyte. In addition, the modified layer composed of oxides coated on the sulfur-containing electrolyte can effectively isolate the reaction between the surface of the sulfur-containing electrolyte and water, and significantly improve the stability of the sulfur-containing electrolyte to wet air and its tolerance to wet air.
[0050] In some preferred embodiments, the sulfur-containing electrolyte is a sulfide electrolyte.
[0051] It should be understood that the sulfur-containing electrolyte may also include other electrolytes containing sulfur elements, such as thioborate, sulfur-based glass ceramics, etc.
[0052] In some preferred embodiments, the sulfide electrolyte is at least one of the formulas (1) and (2);
[0053] Formula (1) is: Li x MP y S z , where M includes one or more of Sn, Ge or Si, 0 < x ≤ 10, 0 < y ≤ 2, 0 < z ≤ 12;
[0054] Formula (2) is: Li 7-x-y PS 6-x-y Cl x X y , where X is a halogen element, 0 ≤ x ≤ 1.7, 0 ≤ y ≤ 1.7.
[0055] In some preferred embodiments, the thickness of the modified layer is less than or equal to 200 nm. Exemplarily, the thickness of the modified layer is, for example, 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm and other values less than or equal to 200 nm. The influence of the modified layer thickness on the performance of the surface-modified sulfur-containing electrolyte has been described above and will not be elaborated here.
[0056] The present invention provides a solid-state battery, comprising: a positive electrode, a solid electrolyte and a negative electrode; wherein the solid electrolyte comprises: a surface-modified sulfur-containing electrolyte prepared by the preparation method provided above, or the surface-modified sulfur-containing electrolyte provided above.
[0057] According to the inventors' research and experimental verification, since the modification layer can improve the stability of the sulfur-containing electrolyte to humid air, after the surface-modified sulfur-containing electrolyte provided by the present invention is exposed to a high humidity environment (for example, a dew point of -50°C), the decomposition products of the sulfur-containing electrolyte are reduced, and the ionic conductivity retention rate of the sulfur-containing electrolyte is relatively high. Therefore, the sulfur-containing electrolyte prepared based on the above method can also ensure the cycle performance of the solid-state battery assembled under higher humidity. This shows that the surface-modified sulfur-containing electrolyte and the preparation method thereof provided by the present invention can provide a strong guarantee for assembling solid-state batteries using sulfur-containing electrolytes as materials under a high humidity environment, and can reduce the assembly cost of solid-state batteries.
[0058] The present invention is further described below through specific embodiments.
[0059] Example 1
[0060] The solid electrolyte was prepared by the following method:
[0061] In an inert atmosphere, weigh the gas-milled 50 3μm Li 5.5 PS 4.5 C 1.5 2g of sulfur-containing electrolyte, 0.01g of sulfur, 0.005g of C2F6LiNO4S2 and 0.005g of B2O3 were added into a 100mL ball mill, and the mixture was ball milled at 200rpm for 3h to fully mix the materials to obtain a composite. The composite was placed in a tubular furnace and sintered at a low temperature of 150°C for 3h in a mixed atmosphere of argon and ozone (where ozone accounts for 2% of the total gas content), so that the products of the chemical substances heated and decomposed or melted adhered to the surface of the sulfur-containing electrolyte, and the surface layer of the sulfur-containing electrolyte was oxidized by ozone to generate a modified layer including oxides containing lithium, sulfur, phosphorus, chlorine, oxygen, boron, nitrogen and fluorine elements.
[0062] Example 2
[0063] The solid electrolyte was prepared by the following method:
[0064] In an inert atmosphere, weigh the wet refined D 50 2μm Li 5.4 PS 4.4 C 1.63 g of sulfur-containing electrolyte, 0.01 g of F2NO4S2.Li and 0.01 g of LiNO3 were added to a 100 mL ball mill jar and ball milled at 250 rpm for 2 h to fully mix the materials and obtain a composite; the composite was placed in a tube furnace and sintered by low-temperature heating in a mixed atmosphere of argon and oxygen (where oxygen accounted for 5% of the total gas content), the heating temperature was 180 °C, and the heating time was 3 h, so that the products of the chemical substances decomposed or melted by heating adhered to the surface of the sulfur-containing electrolyte, and the surface layer of the sulfur-containing electrolyte was oxidized by oxygen to form a modified layer including oxides containing lithium, sulfur, phosphorus, chlorine, oxygen, nitrogen, and fluorine elements.
[0065] Example 3
[0066] The following method was used to prepare a solid electrolyte:
[0067] In an inert atmosphere, weigh D 50 with a particle size of 2 μm of Li 5.5 PS 4.5 C 1.5 4 g of sulfur-containing electrolyte, 0.02 g of sulfur, 0.005 g of LiF, 0.015 g of NH4F and 0.015 g of B(OCH3)3 were added to a 100 mL ball mill jar and ball milled at 300 rpm for 1 h to fully mix the materials and obtain a composite; the composite was placed in a tube furnace and sintered by low-temperature heating in a mixed atmosphere of argon and ozone (where ozone accounted for 5% of the total gas content), the heating temperature was 200 °C, and the heating time was 3 h, so that the products of the chemical substances that were easily decomposed or melted by heating adhered to the surface of the sulfur-containing electrolyte, and the surface layer of the sulfur-containing electrolyte was oxidized by ozone to form a modified layer including oxides containing lithium, sulfur, phosphorus, chlorine, oxygen, boron, and nitrogen elements.
[0068] Comparative Example 1
[0069] The following method was used to prepare a solid electrolyte:
[0070] Weigh D 50 with a particle size of 3 μm of Li 5.5 PS 4.5 C 1.5 2 g of sulfur-containing electrolyte was ball milled in a 100 mL ball mill jar at 200 rpm for 3 h; the ball milled sulfur-containing electrolyte was placed in a tube furnace and sintered at 150 °C for 3 h in an argon atmosphere.
[0071] Comparative Example 2
[0072] The following method was used to prepare a solid electrolyte:
[0073] Weigh D 50 with a particle size of 2 μm of Li 5.4 PS4.4 C 1.6 Weigh 3 g of sulfur-containing electrolyte, place it in a 100 mL ball mill jar, and ball mill it at 250 rpm for 2 h; place the ball-milled sulfur-containing electrolyte in a tube furnace and sinter it at 180 °C under argon for 2 h.
[0074] Comparative Example 3
[0075] The following method was used to prepare the solid electrolyte:
[0076] Weigh D 50 with a particle size of 2 μm of Li 5.5 PS 4.5 C 1.5 Weigh 4 g of sulfur-containing electrolyte, ball mill it at 300 rpm for 1 h; place the ball-milled sulfur-containing electrolyte in a tube furnace and sinter it at 200 °C under a nitrogen atmosphere for 1 h.
[0077] Performance test
[0078] (1) Perform performance tests on the wet air stability of the solid electrolytes of each example and comparative example (the test results are shown in Table 1):
[0079] Test the ionic conductivity of the solid electrolyte that has just been exposed to an environment with a dew point of -50 °C and the solid electrolyte that has been exposed to an environment with a dew point of -50 °C for 4 h, respectively. Among them, the test method for the ionic conductivity of the solid electrolyte is as follows: Weigh 200 mg of the solid electrolyte powder and place it in a battery mold (inner diameter 10 mm), apply a pressure of 300 MPa, and use an electrochemical workstation to test the AC impedance. Apply an external voltage of 10 mV in the frequency range of 1 Hz to 1 MHz, and calculate the ionic conductivity of the solid electrolyte after different exposure times according to the test results.
[0080] Table 1 Test results of the wet air stability of the solid electrolytes in the examples and comparative examples
[0081]
[0082] According to the data in Table 1, by comparing the 0 min ionic conductivity of Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3, it is found that the 0 min ionic conductivity of the examples is significantly higher than that of the comparative examples, which proves that the introduction of chemical substances and the treatment with oxidizing gases do not cause a decrease in the ionic conductivity of the electrolyte, and the influence of the modification layer on the ionic conductivity of the sulfur-containing electrolyte is small;
[0083] In addition, by comparing the ionic conductivity retention rates of Example 1 with Comparative Example 1, Example 2 with Comparative Example 2, and Example 3 with Comparative Example 3, it was found that the ionic conductivity retention rates of the examples were significantly higher than those of the comparative examples, indicating that the addition of the modification layer significantly improved the water stability of the sulfur-containing electrolyte.
[0084] In summary, the experiments demonstrate that the modification layer of the surface-modified sulfur-containing electrolyte provided by the present invention effectively improves the water stability of the sulfur-containing electrolyte while not affecting the overall ionic conductivity of the solid-state battery.
[0085] (2) Using the solid electrolytes, ternary cathode materials, and lithium metal anode materials after being exposed to an environment with a dew point of -50°C for 4 h in the above-mentioned examples and comparative examples, the corresponding solid-state batteries of the above-mentioned examples and comparative examples were prepared. Electrochemical performance tests were respectively carried out on the solid-state batteries corresponding to each of the examples and comparative examples (the test results are shown in Table 2):
[0086] Specifically, the preparation process of the solid-state battery is as follows:
[0087] Preparation of the positive electrode sheet: The ternary cathode material, the solid electrolyte after being exposed to an environment with a dew point of -50°C for 4 h, a conductive agent (VGCF), and a binder (PTFE) were mixed according to a mass ratio of 80:20:2:0.5 to prepare a positive electrode film; then the positive electrode film was combined with stainless steel to form a positive electrode sheet;
[0088] Lithium metal was used as the negative electrode sheet;
[0089] Preparation of the solid electrolyte membrane: The solid electrolyte after being exposed to an environment with a dew point of -50°C for 4 h and a binder (PTFE) were fully mixed according to a mass ratio of 100:0.5 to prepare an electrolyte membrane;
[0090] The above positive electrode sheet, negative electrode sheet, and solid electrolyte membrane were assembled into a solid-state battery.
[0091] Furthermore, electrochemical performance tests were carried out on the solid-state battery, including:
[0092] First charge-discharge test: In an environment of 25°C, the solid-state battery was subjected to a constant current charge-discharge test at 0.1C for 1 cycle, and the first discharge specific capacity and the first Coulombic efficiency of the solid-state battery were measured. During the charge-discharge process, the voltage range was 2.7 - 4.2 V.
[0093] Long-cycle test: In an environment of 25 °C, the solid-state battery was charged and discharged in a constant current of 0.1C for 100 cycles, and the discharge specific capacity of the solid-state battery after 100 cycles was measured. Among them, the voltage range was 2.7 - 4.2V; according to the first discharge specific capacity of the solid-state battery and the discharge specific capacity of the solid-state battery after 100 cycles, the capacity retention rate of the solid-state battery after 100 cycles was calculated.
[0094] Table 2 Comparison of Electrochemical Performance Tests of Solid-State Batteries Corresponding to Examples and Comparative Examples
[0095]
[0096] According to the data in Table 1, by comparing the first discharge specific capacity and the first Coulomb efficiency of Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3, it was found that the first discharge specific capacity and the first Coulomb efficiency of the solid-state battery corresponding to the example were both higher than those of the solid-state battery corresponding to the comparative example; by comparing the capacity retention rates of Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3 after 100 cycles, it was found that the capacity retention rates of the solid-state batteries corresponding to the examples after 100 cycles were also higher than those of the solid-state batteries corresponding to the comparative examples. The experiment shows that the electrochemical performance of the solid-state battery assembled with the surface-modified sulfur-containing electrolyte provided by the present invention is significantly better than that of the solid-state battery assembled with the unmodified sulfur-containing electrolyte, which further shows that the surface-modified sulfur-containing electrolyte and its preparation method provided by the present invention can provide strong guarantee for assembling solid-state batteries with sulfur-containing electrolytes as materials in an environment with relatively high humidity, and reduce the assembly cost of solid-state batteries.
[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A preparation method of a surface-modified sulfur-containing electrolyte, characterized in that, Comprising: In an inert atmosphere, a chemical substance is added to the refined sulfur-containing electrolyte, and the sulfur-containing electrolyte and the chemical substance are mixed to obtain a composite, wherein the chemical substance includes at least one element of boron, nitrogen, fluorine, and sulfur; The composite is placed in a mixed gas atmosphere for low-temperature heat treatment, so that the decomposition product or melting product of the chemical substance forms a coating layer on the surface of the sulfur-containing electrolyte, and the coating layer is oxidized by the oxidizing gas in the mixed gas to obtain a modified layer, thereby obtaining a sulfur-containing electrolyte with a surface modification. The mixed gas includes an inert gas and an oxidizing gas.
2. The preparation method according to claim 1, wherein: The chemical substance is at least one of LiBO2, B2O3, H3BO3, B(OCH3)3, S, LiNO3, LiF, C2F6LiNO4S2, F2NO4S2.Li, and NH4F.
3. The preparation method according to claim 1 or 2, characterized in that, The mass of the chemical substance is 0.1% to 10% of the mass of the sulfur-containing electrolyte.
4. The preparation method according to claim 1 or 2, characterized in that, The inert gas is at least one of nitrogen, argon, helium, and neon.
5. The preparation method according to claim 1 or 2, characterized in that, The oxidizing gas is at least one of oxygen, sulfur dioxide, ozone, chlorine, nitrogen dioxide, and hydrogen peroxide vapor.
6. The preparation method according to claim 1 or 2, characterized in that, The content of the oxidizing gas is 1% to 10% of the content of the mixed gas.
7. The preparation method according to claim 1 or 2, characterized in that, During the low-temperature heat treatment, the heating temperature is 100 to 250 °C, and the heating time is 1 to 5 h.
8. A surface-modified sulfur-containing electrolyte, characterized in that, Comprising: The sulfur-containing electrolyte is coated with a modified layer, and the modified layer includes oxides containing at least two elements of boron, nitrogen, and fluorine.
9. The surface-modified sulfur-containing electrolyte according to claim 8, wherein The sulfur-containing electrolyte is a sulfide electrolyte.
10. The surface-modified sulfur-containing electrolyte according to claim 9, wherein The sulfide electrolyte is at least one of those shown by chemical formula (1) and chemical formula (2); The chemical formula (1) is: Li x MP y S z , where M includes one or more of Sn, Ge, or Si, 0 < x ≤ 10, 0 < y ≤ 2, 0 < z ≤ 12; The chemical formula (2) is: Li 7-x-y PS 6-x-y Cl x X y , where X is a halogen element, 0 ≤ x ≤ 1.7, 0 ≤ y ≤ 1.
7.
11. The surface-modified sulfur-containing electrolyte according to claim 10, wherein, The thickness of the modified layer is less than or equal to 200 nm.
12. A solid-state battery, characterized in that, Comprising: A positive electrode, a solid electrolyte, and a negative electrode; Wherein, the solid electrolyte includes: the surface-modified sulfur-containing electrolyte prepared by using the preparation method according to any one of claims 1-7, or the surface-modified sulfur-containing electrolyte according to any one of claims 8-11.