Inorganic-based composite electrolyte thin film and preparation thereof and solid-state battery comprising same

Abstract

The application provides an inorganic compound electrolyte thin film and a preparation method thereof and a solid-state battery formed by the inorganic compound electrolyte thin film, and belongs to the technical field of battery electrolytes. The compound electrolyte thin film comprises a sulfide or halide solid-state electrolyte framework and a polymer electrolyte filled in the framework. By applying a specific pore-forming agent, controlling the particle size of the sulfide or halide and the pore-forming agent and the volume ratio of the sulfide or halide and the pore-forming agent, a self-supporting sulfide or halide solid-state electrolyte framework with uniform and interconnected pore distribution is constructed on the basis of ensuring that no high-temperature phase change or decomposition occurs at a low temperature. The inorganic compound electrolyte thin film significantly improves the air stability of the sulfide and halide solid-state electrolyte, the ion conductivity is greater than or equal to 1.8 mS cm ‑1 at 30 DEG C, the ion transference number is 0.6-0.8, and the electrochemical window is greater than or equal to 4.3 V vs. Li + / Li, the energy density of the solid-state battery of the inorganic compound electrolyte is significantly improved, and the problems of poor contact between the sulfide solid-state electrolyte and the electrode, serious interface side reactions and a narrow electrochemical window are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery electrolyte, and particularly relates to an inorganic-based composite electrolyte film comprising a sulfide solid electrolyte and a halide solid electrolyte, a preparation method thereof and a solid-state battery formed by the inorganic-based composite electrolyte film. BACKGROUND

[0002] At present, sulfides and halides are highly concerned in many kinds of solid electrolytes due to their higher ionic conductivity. It is reported that Li 10 GeP2S 12 The ionic conductivity at room temperature is 1.2*10 -2 S cm -1 (Nature Materials, 2011, 10(9) 682-686), Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The ionic conductivity at room temperature reaches 2.5*10 -2 S cm -1 (Nature Energy, 2016, 1, 16030), and the low-temperature sintering method guarantees that no phase transition occurs between-25 DEG C and 75 DEG C, and the ionic conductivity of the halide solid electrolyte Li3InCl6 at room temperature also reaches 1.49*10 -3 S / cm (Energy & Environmental Science, 2019, 12(9) 2665-2671). Moreover, the sulfide and halide electrolytes also have good plasticity and lower hardness, and have better contact with electrode materials under pressure. However, the application of sulfide solid electrolytes and halide solid electrolytes in solid-state batteries has serious technical obstacles: (1) phase transition or thermal decomposition at high temperature leads to sharp decrease of ionic conductivity, so the material preparation conditions are harsh and processing is difficult. The ionic conductivity of the beta phase Li3PS4 is the highest, and the irreversible transition from beta phase to alpha phase occurs at 500 DEG C, and the gamma phase Li3PS4 is spontaneously formed during the cooling process, and the ionic conductivity decreases to 3*10 - 7 S / cm (Solid State Ionics, 2011, 182(1): 53-58). Li 10 GeP2S 12stable at 500-600℃, and decomposed into Li4GeS4 and Li / P / S liquid phase materials at 700℃ (Nature Materials, 2011, 10(9): 682-686). (2) Sulfide and halide solid-state electrolytes are very sensitive to air, and contact with water and oxygen in the air leads to decomposition and complete destruction of the electrolyte structure. As the contact area increases, the degradation rate in the air increases, the ionic conductivity of the material decreases significantly, and the electrochemical performance decays (Electrochemical Energy Review, 2022, 5(3): 3), and toxic gas H2S is also produced, as well as strong corrosive degradation products that corrode aluminum current collectors. 1g of Li2S-25P2S5 sulfide solid-state electrolyte powder will produce 0.26cm 3 of toxic gas H2S in 1min under the condition of relative humidity of 40%-45% (Journal Material Science, 2013, 48(11)4137-4142). (3) Poor electrochemical stability, narrow electrochemical window, and unstable matching with lithium metal negative electrode or high-voltage positive electrode, which increases the interfacial impedance. For example, the electrochemical window of Li6PS5Cl is 1.71-2.01V, and the electrochemical window of Li 10 GeP2S 12 is 1.71-2.14V (Advanced Science, 2017, 4(8)1600517). (4) Sulfide and halide solid-state electrolytes have a brittle fracture problem in the process of large-scale and thin-film preparation, which leads to difficulty in processing and brings technical challenges to material production and practical application. Among them, the commonly used method is to introduce a polymer binder or a flexible support, but it will sacrifice the high ionic conductivity advantage of sulfide and halide; if the proportion of the polymer binder or the flexible support is controlled, the brittle fracture problem will be serious, and it is impossible to prepare a self-supporting sulfide and halide solid-state electrolyte film (Journal of The Chinese Ceramic Society, 2022, 50(1): 110-120). Therefore, further research and development is needed to propose new technical solutions to solve the application problems of sulfide and halide solid-state electrolytes. SUMMARY

[0003] The purpose of this invention is to provide a flexible, high-ionic-conductivity composite electrolyte thin film based on sulfides and halides, its preparation method, and a solid-state battery thereof. This invention enables the preparation of a porous sulfide or halide solid electrolyte framework at relatively low temperatures, achieving a self-supporting framework with uniform and interconnected pores while ensuring that the solid electrolyte material does not undergo high-temperature phase transitions or decomposition. By filling the framework pores with a polymer electrolyte, a rich and continuous organic-inorganic phase interface is constructed, resulting in an inorganic-based composite electrolyte thin film with high flexibility, high ionic conductivity, and a wide electrochemical window. This further improves the air stability of sulfide or halide solid electrolytes, thus solving the technical challenges of large-scale, thin-film preparation of sulfide and halide solid electrolytes and their application in solid-state batteries.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] An inorganic-based composite electrolyte film comprises at least a porous inorganic solid electrolyte framework and a polymer electrolyte filling the pores of the framework. The inorganic solid electrolyte is one or more of a sulfide solid electrolyte and a halide solid electrolyte; the inorganic solid electrolyte has a mass fraction of 50%-90%, and the polymer electrolyte has a mass fraction of 10%-50%.

[0006] The sulfide solid electrolyte is preferably Li6PS5X (X = one or more of Cl, Br or I), Li 10 M x P 3- x S 12 (0≤x≤2, M=Si, Sn or Ge or more), Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Li3PS4, Li7P3S 11 , Li2S: (1-x)P2S5 (0.7≤x≤0.8).

[0007] The halide solid electrolyte is preferably one or more of LiI, Li2ZnI4, Li3OCl, and Li3InCl6.

[0008] The polymer electrolyte includes one or more of the following: polymer-soluble salt type polymer electrolyte, salt-soluble polymer type polymer electrolyte, salt-soluble salt type polymer electrolyte, single-ion conductor polymer electrolyte, and gel polymer electrolyte.

[0009] The application discloses a preparation method of an inorganic compound electrolyte film, and particularly relates to the preparation of a porous inorganic solid electrolyte framework.

[0010] The pore-forming agent is ammonium bicarbonate, ammonium carbonate or one or more inorganic compounds which are gaseous and decomposed at 50-150 DEG C.

[0011] The inorganic compound solid electrolyte flexible film obtained by the preparation method is used to form a solid-state battery.

[0012] The application has the following characteristics and advantages:

[0013] The application is an inorganic compound electrolyte film based on sulfides and halides, a preparation method thereof and a solid-state battery formed by the film.

[0014] The application controls the particle size of the inorganic solid electrolyte powder and the pore-forming agent particles and controls the volume ratio of the inorganic solid electrolyte and the pore-forming agent to be 1:4-1:1.5, i.e. the volume ratio of the pore-forming agent is 60-80%. When the volume fraction of the pore-forming agent is less than 60%, the pores in the prepared inorganic solid electrolyte framework are mainly macropores generated by the removal of the pore-forming agent, which results in low strength and small specific surface area of the inorganic solid electrolyte framework. When the volume fraction of the pore-forming agent is increased to 60-80%, the pore size is uniform, the pore connectivity is increased and the pores are obviously in a three-dimensional interconnected state. Furthermore, under the premise that the inorganic solid electrolyte framework has self-supporting property, the sulfide and halide inorganic electrolyte framework has the characteristics of high pore volume, large specific surface area, suitable pore size, uniform pore distribution and interconnection. The polymer electrolyte is easy to fill the pores of the framework, forms rich three-dimensional continuous inorganic-organic phase interfaces, provides a fast ion transmission channel composed of three-dimensional continuous organic-inorganic phase interfaces and obtains an inorganic compound electrolyte film which is flexible and has high ionic conductivity. When the volume fraction of the pore-forming agent is more than 80%, even in the low-temperature pore-forming process, the volume change is relatively serious and even the framework structure is collapsed, so that the complete framework structure cannot be obtained. The sulfide or halide in the composite solid electrolyte is in the form of a film, which significantly reduces the amount of inorganic electrolyte in the solid-state battery and improves the energy density of the inorganic solid-state battery.

[0015] The composite solid electrolyte comprises an inorganic sulfide or halide solid electrolyte framework with three-dimensional continuous pores, and a polymer electrolyte filling the framework, which improves the water and oxygen stability of the sulfide and halide solid electrolyte, guarantees the high ionic conductivity of the sulfide or halide in the system, and improves the electrochemical stability, widens the electrochemical window, and obtains a stable interface with a lithium metal negative electrode or a high-voltage positive electrode.

[0016] The inorganic solid electrolyte framework is prepared by a low-temperature pore-forming process, which avoids high-temperature phase transition and high-temperature decomposition of the inorganic solid electrolyte, effectively avoids the problem of sharp decline of ionic conductivity of the sulfide or halide caused by high-temperature processing. On the one hand, the water and oxygen stability of the electrolyte is effectively improved, and the degree of hydration and oxidation in the air is reduced; on the other hand, the polymer electrolyte directly contacts the positive and negative electrode materials, effectively solving the problems of poor contact of the inorganic solid electrolyte with the electrode, serious interface side reaction, existence of space charge layer and narrow electrochemical window, solving the brittle fracture problem of the sulfide and halide solid electrolyte in the large-scale and thin-film preparation process, and the preparation process is simple and the equipment requirement is low.

[0017] The inorganic material-based composite electrolyte film in the solid-state battery has an ionic conductivity of 1.8*10 -3 Scm -1 at 30 DEG C, a room temperature ionic mobility of 0.6-0.8, and an electrochemical window of 4.3V vs.Li + / Li. The application provides a technical solution for the application of sulfide and halide solid electrolytes. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The figure is a cross-sectional scanning electron microscope photo of the inorganic solid electrolyte framework of the inorganic material-based composite electrolyte film prepared in Example 1.

[0019] Figure 2 The figure is a cross-sectional scanning electron microscope photo of the inorganic material-based composite electrolyte film prepared in Example 1.

[0020] Figure 3 The figure is a graph of the relationship between the ionic conductivity and temperature of the inorganic material-based composite electrolyte film prepared in Example 2.

[0021] Figure 4 The figure is a graph of the relationship between the ionic conductivity and temperature of the inorganic material-based composite electrolyte film prepared in Example 3.

[0022] Figure 5 The figure is an LSV curve of the inorganic material-based composite electrolyte film prepared in Example 4 at room temperature.

[0023] The application will be described in detail below with reference to specific implementation examples.

[0024] Example 1

[0025] Sulfide electrolyte Li6PS5Cl powder with an average particle size of 5 μm and ammonium bicarbonate powder with an average particle size of 10 μm were mixed uniformly in a volume ratio of 3:7, 50 mg of which was placed in a circular mold with a diameter of 10 mm, and then the mixed powder was pressed into a circular sheet with a thickness of about 0.3 mm by vibration and then applying a pressure of 300 MPa. The circular sheet was placed in a heating jacket, and set at 60 °C for 4 h to obtain a self-supporting porous Li6PS5Cl inorganic solid-state electrolyte framework. Figure 1 The scanning electron microscope photograph of the cross section of the prepared Li6PS5Cl inorganic solid-state electrolyte framework shows that the pore distribution is uniform, the pore size is concentrated, and the pores are interconnected.

[0026] A polymer-salt-type polymer electrolyte was used. LITFSI (lithium bis-trifluoromethylsulfonylimide) and PEO (polyethylene oxide, Mv = 600000) were configured into a 10 wt% acetonitrile solution in a ratio of [EO] / [Li + ] = 10:1, and the solution was mixed uniformly by magnetic stirring at 30 °C for 24 h. A small amount of PEO-LITFSI solution was uniformly dropped on the upper surface of the Li6PS5Cl inorganic electrolyte framework, which was then moved into a vacuum device and dried at 60 °C for 60 min. Then a small amount of PEO-LITFSI solution was uniformly dropped on the other surface of the Li6PS5Cl inorganic electrolyte framework, which was then moved into a vacuum device and dried at 60 °C for 60 min. The above steps were repeated until the pores in the Li6PS5Cl inorganic electrolyte framework were filled with the polymer electrolyte, and an inorganic-based composite electrolyte film was obtained, in which the mass fraction of Li6PS5Cl inorganic electrolyte was 55%, and the mass fraction of PEO-LITFSI polymer-salt-type polymer electrolyte was 45%. Figure 2 The scanning electron microscope photograph of the cross section of the prepared sulfide-based composite electrolyte flexible film shows that the polymer-salt-type polymer electrolyte fills the pores of the framework, and the two phases are tightly combined. The composite electrolyte film has an ionic conductivity of 3.2 x 10 -3 S cm -1 at 30 °C, and a lithium ion transference number as high as 0.8, and an electrochemical window of 4.6 V vs. Li + / Li.

[0027] Example 2

[0028] Sulfide electrolyte Li6PS5Cl powder with an average particle size of 2 μm and ammonium bicarbonate powder with an average particle size of 10 μm were mixed uniformly in a volume ratio of 3:7, 50 mg of which was placed in a circular mold with a diameter of 10 mm, and then the mixed powder was pressed into a circular sheet with a thickness of about 0.3 mm by vibration and then applying a pressure of 300 MPa. The circular sheet was placed in a heating jacket, and set at 60 °C for 4 h to obtain a self-supporting porous Li6PS5Cl inorganic solid-state electrolyte framework. 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3The powder and the ammonium carbonate powder with an average particle size of 5 μm are mixed uniformly at a volume ratio of 1:4. 150 mg of the mixed powder is placed in a circular mold with a diameter of 20 mm, and a circular sheet with a thickness of about 0.8 mm is prepared by applying a pressure of 400 MPa after vibration. The circular sheet is placed in a heating jacket, and a self-supporting porous Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The inorganic solid electrolyte framework is obtained.

[0029] A single-ion conductor type polymer electrolyte, specifically poly(styrene-trifluoromethane-sulfonimide lithium)-polyethylene oxide block copolymer (P(STFSILi)-PEO-P(STFSILi)), is prepared into a 10 wt% acetonitrile solution, and the solution is mixed uniformly by magnetic stirring at 30°C for 24 h. A small amount of the polymer electrolyte solution is uniformly dropped on the upper surface of the inorganic electrolyte framework, and the inorganic electrolyte framework is moved into a vacuum device and dried at 60°C for 60 min, and then the above step is repeated until the Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The other surface of the inorganic electrolyte framework is also uniformly dropped with a small amount of the P(STFSILi)-PEO-P(STFSILi) solution, and the inorganic electrolyte framework is moved into a vacuum device and dried at 60°C for 60 min, and the above step is repeated until the Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The other surface of the inorganic electrolyte framework is also uniformly dropped with a small amount of the P(STFSILi)-PEO-P(STFSILi) solution, and the inorganic electrolyte framework is moved into a vacuum device and dried at 60°C for 60 min, and the above step is repeated until the Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The pores in the inorganic electrolyte framework are filled with the polymer electrolyte, and an inorganic-based composite electrolyte film is obtained, in which the mass fraction of Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The mass fraction of the inorganic electrolyte is 80%, and the mass fraction of the P(STFSILi)-PEO-P(STFSILi) single-ion conductor type polymer electrolyte is 20%. Figure 3 The ion conductivity-temperature relationship of the prepared composite electrolyte film is shown in the graph, and the composite electrolyte film has a high ion conductivity of 2.83 x 10 -3 S cm -1 at 30°C, and an electrochemical window of 4.3 V vs. Li + / Li.

[0030] Example 3

[0031] Halide electrolyte Li3InCl6 powder with an average particle size of 6 μm and ammonium bicarbonate powder with an average particle size of 10 μm were mixed uniformly in a volume ratio of 1:1.85. 50 mg of the mixed powder was placed in a circular mold with a diameter of 10 mm, and then the mixed powder was pressed into a circular sheet with a thickness of about 0.3 mm by applying a pressure of 300 MPa after vibration. The circular sheet was placed in a heating jacket, and then the temperature was set to 50 °C for 6 h to obtain a self-supporting porous Li3InCl6 inorganic electrolyte skeleton.

[0032] A salt-dissolving salt-type polymer electrolyte, specifically, lithium bis(trifluoromethylsulfonyl)imide-lithiated polyvinylformal (LiTFSI-LiPVFM), was configured into a 10 wt% dimethyl sulfoxide (DMSO) solution, and the solution was mixed uniformly by magnetic stirring at 30 °C for 24 h. A small amount of the LiTFSI-LiPVFM solution was uniformly dropped on the upper surface of the Li3InCl6 inorganic electrolyte skeleton, and then the Li3InCl6 inorganic electrolyte skeleton was moved into a vacuum device and dried at 60 °C for 60 min. Then, a small amount of the LiTFSI-LiPVFM solution was uniformly dropped on the other surface of the Li3InCl6 inorganic electrolyte skeleton, and then the Li3InCl6 inorganic electrolyte skeleton was moved into the vacuum device and dried at 60 °C for 60 min. The above steps were repeated until the pores in the Li3InCl6 inorganic electrolyte skeleton were filled with the polymer electrolyte, and thus an inorganic material-based composite electrolyte thin film was obtained, in which the mass fraction of the Li3InCl6 inorganic electrolyte was 62%, and the mass fraction of the LiTFSI-LiPVFM salt-dissolving salt-type polymer electrolyte was 38%. Figure 4 The ion conductivity-temperature relationship of the prepared composite solid electrolyte thin film was measured, and the ion conductivity of the composite electrolyte thin film was 3.54 x 10 -3 S cm -1 at 30 °C. The electrochemical window was 4.6 V vs. Li + / Li, and the ion transference number reached 0.8.

[0033] Example 4

[0034] Sulfide electrolyte Li7P3S 11 powder with an average particle size of 2 μm and ammonium carbonate powder with an average particle size of 8 μm were mixed uniformly in a volume ratio of 1:1.5. 150 mg of the mixed powder was placed in a circular mold with a diameter of 20 mm, and then the mixed powder was pressed into a circular sheet with a thickness of about 0.8 mm by applying a pressure of 400 MPa after vibration. The circular sheet was placed in a heating jacket, and then the temperature was set to 150 °C for 2 h to obtain a self-supporting porous Li7P3S 11 inorganic electrolyte skeleton.

[0035] A gel polymer electrolyte was used. Specifically, a DEC (diethyl carbonate):EC (ethylene carbonate) = 1:1 (v / v) solution was prepared. Lithium perchlorate (LiClO4) was added to the solution and stirred for 2 hours. Then, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) was added and magnetically stirred at 30°C for 24 hours to mix thoroughly. A small amount of the gel polymer electrolyte solution was then uniformly added dropwise to Li7P3S. 11 The upper surface of the inorganic electrolyte framework was transferred into a vacuum apparatus and dried at 60°C for 60 min, followed by drying in Li7P3S. 11 A small amount of gel polymer electrolyte solution was uniformly dropped onto the other surface of the inorganic electrolyte framework, and then transferred to a vacuum device to dry at 60°C for 60 min. The above steps were repeated until Li7P3S was dried. 11 The pores in the inorganic electrolyte framework are filled with polymer electrolyte to obtain an inorganic-based composite electrolyte film, in which Li7P3S 11 The inorganic electrolyte comprises 85% by mass, and the gel polymer electrolyte comprises 15% by mass. The composite electrolyte membrane has an ionic conductivity of 1.80 × 10⁻⁶ at 30°C. -3 S cm -1 . Figure 5 The LSV curves of the prepared inorganic-based composite electrolyte flexible film at room temperature indicate that its electrochemical window is higher than 4.3V vs. Li. + / Li.

[0036] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. An inorganic-based composite electrolyte thin film, characterized by: The inorganic solid-state electrolyte is one or more of sulfide solid-state electrolyte and halide solid-state electrolyte; the mass fraction of the inorganic solid-state electrolyte is 50%-90%, and the mass fraction of the polymer electrolyte is 10%-50%; The sulfide solid-state electrolyte is Li6PS5X, where X = one or several of Cl, Br, or I, Li 10 M x P 3-x S 12 where 0 < x < 2, M = one or several of Si, Sn, or Ge, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li3PS4, Li7P3S 11 , Li2S:(1-x)P2S5, where 0.7 < x < 0.8; The halide solid-state electrolyte is one or more of LiI, Li2ZnI4, Li3OCl and Li3InCl6; The inorganic-based composite electrolyte thin film has an ion conductivity ≥ 1.8 × 10 -3 Scm -1 , a room temperature ion transference number 0.6-0.8, and an electrochemical window ≥ 4.3 V vs. Li + / Li.

2. The inorganic-based composite electrolyte film according to claim 1, wherein: The polymer electrolyte includes one or more of polymer-salt type polymer electrolyte, salt-solvent polymer type polymer electrolyte, salt-solvent-salt type polymer electrolyte, single-ion conductor polymer electrolyte and gel polymer electrolyte.

3. A method for preparing an inorganic-based composite electrolyte thin film according to claim 1, characterized in that: The preparation of the porous inorganic solid-state electrolyte framework specifically includes: using inorganic solid-state electrolyte powder with an average particle size of 2-8 μm and pore-forming agent particles with an average particle size of 1.5-4 times the average particle size of the inorganic solid-state electrolyte powder; uniformly mixing the inorganic solid-state electrolyte and the pore-forming agent at a volume ratio of 1:4-1:1.5; then pressing into a sheet, and keeping the temperature at 50-150 ℃ for 2-6 h; the above process is completed in an atmosphere filled with argon, thereby obtaining the porous inorganic solid-state electrolyte framework. The pore-forming agent is one or more of ammonium bicarbonate, ammonium carbonate or inorganic substances that are gaseous and decomposed at 50-150 ℃.

4. A solid-state battery using the inorganic solid-state electrolyte film according to claim 1 or 3.

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