High-safety sulfide solid-state electrolyte and preparation method and application thereof

Abstract

The application belongs to the technical field of solid-state batteries, and particularly relates to a high-safety sulfide solid-state electrolyte and a preparation method and application thereof. The application utilizes decomposition of a lithium salt at high temperature to generate an inorganic composite interface on a surface of a sulfide electrolyte, which can isolate direct contact of the sulfide electrolyte with decomposition products of an NCM positive electrode and oxygen released by phase change, reduce reaction heat generation, and also prevent generation of SO2 gas, thereby significantly improving thermal stability of the sulfide electrolyte. The preparation method provided by the application is simple in steps, convenient in operation, low in energy consumption, low in cost and high in efficiency. The sulfide solid-state electrolyte provided by the application significantly improves thermal stability between the sulfide electrolyte and high-specific-energy positive and negative electrode materials, is suitable for lithium-ion batteries, and is particularly suitable for lithium-ion all-solid-state batteries.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery technology, specifically relating to a high-safety sulfide solid electrolyte, its preparation method, and its application. Background Technology

[0002] Compared to liquid batteries, lithium-ion all-solid-state batteries use non-flammable solid electrolytes, which have intrinsic material safety. At the same time, all-solid-state batteries are compatible with high-energy-density positive and negative electrode materials such as lithium metal, and have higher weight / volume energy density. In addition, the wide operating temperature range brought by solid electrolytes, all-solid-state batteries are expected to significantly improve the safety and range of new energy vehicles.

[0003] Sulfide solid electrolytes possess ultra-high room-temperature ionic conductivity comparable to liquid electrolytes, along with excellent mechanical properties, and can be directly cold-pressed, thus attracting widespread attention in the industry. However, recent research has revealed that all-solid-state batteries are not necessarily absolutely safe, and the risk of thermal runaway still exists.

[0004] Research by Li Hong et al. from the Institute of Physics, Chinese Academy of Sciences (Thermal Stability of Sulfide Solid Electrolyte with Lithium Metal, Yujing Wu, Adv. Energy Mater, 2023, 2301336.) has found that some sulfide electrolytes and Li metal can undergo violent combustion during heating or ball milling, generating a large amount of heat and posing a risk of thermal runaway.

[0005] Researchers at Tsinghua University, including Xinyu Rui (Distinct thermal runaway mechanisms of sulfide-based all-solid-state batteries, Energy Environ. Sci., 2023, 16, 3552-3563.), investigated the thermal failure mechanism between common sulfide electrolytes and the high-energy-density cathode material NCM811. Experimental results showed that some sulfide electrolytes react with O2 generated during the phase transition of NCM811 at high temperatures, releasing a large amount of heat and generating toxic and harmful SO2 gas, posing a safety hazard.

[0006] Bairav ​​S et al. from Purdue University (Interphases and Electrode Crosstalk Dictate the Thermal Stability of Solid-State Batteries, Bairav ​​S. Vishnugopi, ACSEnergy Lett, 2023, 8, 398-407.) studied the thermal stability of sulfides before and after cycling with lithium metal. Their results showed that the interface between the surface sulfide and the positive and negative electrode materials directly affects the onset temperature and maximum heat release rate of thermal runaway.

[0007] Currently, most research on the modification of sulfide electrolytes focuses only on the electrochemical performance and air stability of sulfide electrolyte materials, while research on improving the thermal stability of sulfide materials is relatively lacking. Summary of the Invention

[0008] The purpose of this invention is to provide a high-safety sulfide solid electrolyte, its preparation method, and its application. The preparation method provided by this invention improves the stability of the sulfide solid electrolyte.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] This invention provides a method for preparing a sulfide solid electrolyte, comprising the following steps:

[0011] The lithium source, phosphorus source, sulfur source, halogen source and lithium salt are ball-milled and mixed, and then pressed into tablets and calcined in sequence.

[0012] The lithium source does not include lithium salts;

[0013] The lithium salt includes one or more of organic lithium salts and inorganic lithium salts;

[0014] The calcination temperature is 400–600°C; the calcination is carried out under vacuum conditions.

[0015] Preferably, the mass ratio of the lithium salt to the total mass of the lithium source, phosphorus source, sulfur source and halogen source is 1 to 5:100.

[0016] Preferably, the lithium source is a lithium sulfide; the lithium sulfide includes one or more of Li2S and Li2S2.

[0017] Preferably, the phosphorus source is a phosphorus sulfide; the phosphorus sulfide includes P2S5 and P4S. 10 One or more of P4S9.

[0018] Preferably, the halogen source is a halogen salt; the halogen salt includes one or more of LiCl, LiBr and LiI.

[0019] Preferably, the organic lithium salt includes one or more of LiDFOB, LiFSI, LiTFSI, and LiBOB; and the inorganic lithium salt includes one or more of LiNO3, LiF, and LiPO2F2.

[0020] Preferably, the tablet compression pressure is 10-80 MPa, and the holding time is 2-10 min; the tablet compression is carried out in an inert atmosphere.

[0021] Preferably, the calcination temperature is 450–600°C, and the holding time is 5–20 h.

[0022] The present invention also provides a sulfide solid electrolyte obtained by the preparation method described above, comprising major elements and trace elements; the major elements include Li, P, S and X; X is one or more of the seventh group elements; the trace elements include B, C and O.

[0023] The present invention also provides the application of the sulfide solid electrolyte described above in lithium-ion batteries.

[0024] This invention provides a method for preparing a sulfide solid electrolyte. The invention utilizes the high-temperature decomposition of lithium salts to generate an inorganic composite interface on the surface of the sulfide electrolyte. This interface isolates the sulfide electrolyte from direct contact with the decomposition products of the NCM cathode and the oxygen released during phase transition, reducing heat generation and preventing SO2 gas formation, thereby significantly improving the thermal stability of the sulfide electrolyte. The preparation method provided by this invention is simple, convenient, energy-efficient, low-cost, and highly efficient.

[0025] This invention also provides a sulfide solid electrolyte obtained by the preparation method described above. The sulfide solid electrolyte provided by this invention comprises major and trace elements; the major elements include Li, P, S, and X; X is one or more elements from Group 7; the trace elements include B, C, and O. The sulfide solid electrolyte provided by this invention significantly improves the thermal stability between the sulfide electrolyte and high-energy-density positive and negative electrode materials.

[0026] This invention also provides the application of the sulfide solid electrolyte described above in lithium-ion batteries. The sulfide electrolyte provided by this invention has high thermal stability and is suitable for use in lithium-ion batteries, especially for all-solid-state lithium-ion batteries. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The DSC thermal curves of the sulfide solid electrolyte and the high-Ni cathode material prepared in Examples 1 and Comparative Examples 1-4 are shown.

[0029] Figure 2 The above are STA-MS curves of the sulfide solid electrolyte and the high-Ni cathode material prepared in Example 1.

[0030] Figure 3 The STA-MS curves of Comparative Example 2 and the high-energy-density cathode hybrid material are shown.

[0031] Figure 4 The STA-MS curves of Comparative Example 3 and the high-energy-density cathode hybrid material are shown.

[0032] Figure 5 The STA-MS curves are for Comparative Example 4 and the high-energy-density cathode hybrid material. Detailed Implementation

[0033] This invention provides a method for preparing a sulfide solid electrolyte, comprising the following steps:

[0034] The lithium source, phosphorus source, sulfur source, halogen source and lithium salt are ball-milled and mixed, and then pressed into tablets and calcined in sequence.

[0035] The lithium source does not include lithium salts;

[0036] The lithium salt includes one or more of organic lithium salts and inorganic lithium salts;

[0037] The calcination temperature is 400–600°C; the calcination is carried out under vacuum conditions.

[0038] This invention involves ball milling and mixing a lithium source, a phosphorus source, a sulfur source, a halogen source, and a lithium salt. In this invention, the lithium source is preferably a lithium sulfide; the lithium sulfide preferably includes one or more of Li₂S and Li₂S₂, more preferably Li₂S.

[0039] In this invention, the phosphorus source is preferably a phosphorus sulfide; the phosphorus sulfide preferably includes P2S5 and P4S. 10 One or more of P4S9, more preferably P2S5.

[0040] In this invention, the lithium source, phosphorus source, and sulfur source are more preferably lithium sulfide and phosphorus sulfide. This invention can simultaneously provide a lithium source, a phosphorus source, and a sulfur source using lithium sulfide and phosphorus sulfide.

[0041] In this invention, the halogen source is preferably a halogen salt; the halogen salt preferably includes one or more of LiCl, LiBr and LiI, and more preferably LiCl.

[0042] In this invention, the organic lithium salt preferably includes one or more of LiDFOB, LiFSI, LiTFSI and LiBOB, more preferably LiDOFB; the inorganic lithium salt preferably includes one or more of LiNO3, LiF and LiPO2F2.

[0043] In this invention, the molar ratio of the lithium source, phosphorus source, sulfur source and halogen source is preferably determined according to the chemical formula Li6PS5X.

[0044] In this invention, the mass ratio of the lithium salt to the total mass of the lithium source, phosphorus source, sulfur source and halogen source is preferably 1 to 5:100, more preferably 2 to 4:100, and even more preferably 3:100.

[0045] In this invention, the ball milling is preferably solid-phase ball milling; the ball milling is preferably carried out in an inert atmosphere; the inert atmosphere is preferably argon or nitrogen; the ball milling speed is preferably 400-800 rpm, more preferably 500-700 rpm, even more preferably 600 rpm, and the time is preferably 5-30 h, more preferably 8-24 h, even more preferably 15-20 h.

[0046] After ball milling and mixing, the present invention sequentially performs tableting and calcination. In the present invention, the tableting pressure is preferably 10-80 MPa, more preferably 20-50 MPa, and the holding time is preferably 2-10 min, more preferably 2-5 min; the tableting is preferably carried out in an inert atmosphere; the inert atmosphere is preferably argon or nitrogen.

[0047] In this invention, the calcination temperature is preferably 450–600°C, more preferably 500–600°C, and even more preferably 540–560°C; the holding time is preferably 5–20 h, more preferably 12–20 h, and even more preferably 15–17 h. Calcination under vacuum conditions in this invention can prevent the formation of impurities.

[0048] The present invention also provides a sulfide solid electrolyte obtained by the preparation method described above, comprising major elements and trace elements; the major elements include Li, P, S and X; X is one or more of the seventh group elements; the trace elements include B, C and O.

[0049] The sulfide solid electrolyte provided by this invention comprises major and trace elements, wherein B, C, and O are derived from the added lithium salt, and their specific content is related to the mass of lithium salt added. The surface of the sulfide solid electrolyte has an inorganic composite interface that can isolate the sulfide electrolyte from direct contact with the decomposition products of the NCM cathode and the oxygen released during phase transition, resulting in good thermal stability.

[0050] The present invention also provides the application of the sulfide solid electrolyte described above in lithium-ion batteries.

[0051] The sulfide solid electrolyte provided by this invention has high thermal stability and is suitable for use in lithium-ion batteries, especially for lithium-ion all-solid-state batteries.

[0052] To further illustrate the present invention, the following detailed description of the invention's solutions, in conjunction with the accompanying drawings and embodiments, is provided, but should not be construed as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] According to the chemical formula Li6PS5Cl, weigh Li2S, LiCl and P2S5, weigh 3% of the total mass of Li2S, LiCl and P2S5, and place the above raw materials in a ball mill jar. Add grinding balls at a ball-to-material mass ratio of 1:30 and ball mill for 16 hours at a speed of 600 rpm.

[0055] Under inert gas protection, the above mixed raw materials are collected and compressed into tablets. The resulting tablet mixture is placed in a tube furnace, the tube furnace is evacuated, the temperature is set to 550℃, and calcined for 15 hours to obtain a sulfide solid electrolyte.

[0056] Example 2

[0057] According to the chemical formula Li6PS5Cl, weigh Li2S, LiCl and P2S5, weigh 3% of the total mass of Li2S, LiCl and P2S5 in LiPO2F2, mix the above raw materials and place them in a ball mill jar, add ball milling beads at a ball-to-material mass ratio of 1:30 and ball mill at 600 rpm for 16 hours.

[0058] Under inert gas protection, the above mixed raw materials are collected and compressed into tablets. The resulting tablet mixture is placed in a tube furnace, the tube furnace is evacuated, the temperature is set to 550℃, and calcined for 15 hours to obtain a sulfide solid electrolyte.

[0059] Comparative Example 1

[0060] The sulfide solid electrolyte Li6PS5Cl was purchased from Ganfeng Lithium Group Co., Ltd.

[0061] Comparative Example 2

[0062] Sulfide solid electrolyte Li7P3S 11 The materials were purchased from Ganfeng Lithium Group Co., Ltd.

[0063] Comparative Example 3

[0064] The sulfide solid electrolyte Li3PS4 was purchased from Ganfeng Lithium Group Co., Ltd.

[0065] Comparative Example 4

[0066] Sulfide solid electrolyte Li 10 GeP 12 S2, the material was purchased from Ganfeng Lithium Group Co., Ltd.

[0067] Test Example 1

[0068] The sulfide solid electrolytes of Example 1 and Comparative Example 1 were respectively mixed with high-energy-density cathode materials, wherein the mass ratio of the high-energy-density cathode material to the sulfide solid electrolyte was 7:3, to obtain mixed materials. The heat generation characteristics of the obtained mixed materials were tested using differential scanning calorimetry (DSC), and the results are as follows. Figure 1 As shown.

[0069] according to Figure 1 It can be seen that the exothermic peak height of the mixed material obtained by the sulfide solid electrolyte and the high specific energy cathode material in Example 1 is lower, the exothermic onset temperature is higher, and the exothermic peak area is smaller. This indicates that the reaction intensity of the sulfide solid electrolyte and the high specific energy cathode in Example 1 is lower and the heat generation is less during heating, resulting in higher thermal stability.

[0070] Test Example 2

[0071] The sulfide solid electrolytes of Example 1 and Comparative Example 2 were respectively mixed with high-energy-density cathode materials, with a mass ratio of high-energy-density cathode material to sulfide solid electrolyte of 7:3, to obtain mixed materials. The gas production characteristics of the mixed materials were tested using simultaneous thermal analysis mass spectrometry (STA-MS), and the results are as follows. Figure 2 and Figure 3 As shown.

[0072] according to Figure 2 and Figure 3 It can be seen that in Example 1, no toxic or harmful SO2 gas is generated during the heating process of mixing the sulfide solid electrolyte with the high specific energy cathode material, while in Comparative Example 2, a large amount of SO2 gas is generated during the heating process, which poses a safety problem.

[0073] Test Example 3

[0074] The sulfide solid electrolyte of Comparative Example 3 was mixed with a high-energy-density cathode material at a mass ratio of 7:3 to obtain a mixed material. The gas production characteristics of the mixed material were tested using simultaneous thermal analysis mass spectrometry (STA-MS), and the results are as follows. Figure 4 As shown.

[0075] according to Figure 2 and Figure 4 It can be seen that in Example 1, no toxic or harmful SO2 gas is generated during the heating process of mixing the sulfide solid electrolyte with the high specific energy cathode material, while in Comparative Example 3, a large amount of SO2 gas is generated during the heating process, which poses a safety problem.

[0076] Test Example 4

[0077] The sulfide solid electrolyte of Comparative Example 4 was mixed with a high-energy-density cathode material at a mass ratio of 7:3 to obtain a mixed material. The gas production characteristics of the mixed material were tested using simultaneous thermal analysis mass spectrometry (STA-MS), and the results are as follows: Figure 5 As shown.

[0078] according to Figure 2 and Figure 5 It can be seen that in Example 1, no toxic or harmful SO2 gas is generated during the heating process of mixing the sulfide solid electrolyte with the high specific energy cathode material, while in Comparative Example 4, SO2 gas is generated during the heating process, which poses a safety problem.

[0079] As can be seen from the above embodiments, the sulfide solid electrolyte obtained by the preparation method provided by the present invention has significantly reduced heat and gas generation compared with the high specific energy cathode material, and has better safety.

[0080] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a sulfide solid electrolyte, characterized in that, Includes the following steps: According to the chemical formula Li6PS5Cl, weigh Li2S, LiCl and P2S5, weigh 3% of the total mass of Li2S, LiCl and P2S5 in LiDFOB or LiPO2F2, mix the above raw materials and place them in a ball mill jar, add ball milling beads at a ball-to-material mass ratio of 1:30 and ball mill at 600 rpm for 16 hours. Under inert gas protection, the above mixed raw materials were collected and compressed into tablets. The resulting tablet mixture was placed in a tube furnace, the tube furnace was evacuated, the temperature was set to 550℃, and calcined for 15 hours to obtain a sulfide solid electrolyte. The tablet compression pressure is 10~80MPa, and the holding time is 2~10min; the tablet compression is carried out in an inert atmosphere.

2. The sulfide solid electrolyte obtained by the preparation method of claim 1.

3. The application of the sulfide solid electrolyte of claim 2 in lithium-ion batteries.

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