High-stability composite solid electrolyte and preparation method thereof

Abstract

The invention provides a high-stability composite solid electrolyte and a preparation method thereof, and relates to a lithium ion battery technology. The invention provides a preparation method of a multilayer composite LLZO solid electrolyte, which comprises the following steps: respectively preparing an LLZO electrolyte layer and a LiAlO protective layer with high air stability and good lithium wettability by adopting a tape casting process, tightly compounding the LLZO electrolyte layer and the LiAlO protective layer by adopting a warm isostatic pressing process, and forming a compact multilayer structure after glue discharging and co-sintering. In the design, the LiAlO ceramic layer on the outer layer can effectively isolate erosion of water and carbon dioxide in the environment to LLZO, and the air stability of the material is remarkably improved; meanwhile, by utilizing the good wettability of LiAlO to lithium metal, the interface impedance between the solid electrolyte and the negative electrode can be greatly reduced, and the interface ion transmission efficiency is improved. The composite structure gives consideration to protectiveness and interface compatibility, and provides a new material and process thought for promoting the practical application of the high-safety and high-performance all-solid-state lithium battery.

Description

Technical Field

[0001] This invention relates to lithium-ion battery technology, and more particularly to a highly stable composite solid electrolyte and its preparation method. Background Technology

[0002] Lithium-ion batteries, as one of the most important electrochemical energy storage technologies, have been widely used in consumer electronics, electric vehicles, energy storage systems, and other fields, significantly promoting the transformation of the energy structure and the development of portable electronic devices. However, traditional lithium-ion batteries typically use flammable and leaky organic liquid electrolytes, which are prone to thermal runaway under abnormal conditions such as overcharging, short circuits, high temperatures, or mechanical damage, and may even lead to safety accidents such as fires and explosions, severely restricting their further application in scenarios with high safety requirements.

[0003] To fundamentally improve battery safety, solid-state lithium-ion battery technology has emerged. This technology replaces traditional organic electrolytes and separators with solid-state electrolytes, eliminating the risks of liquid leakage and combustion, and promising higher energy density (e.g., when combined with a lithium metal anode) and a wider operating temperature range. Based on different material systems, solid-state electrolytes are mainly classified into three categories: polymer-based, inorganic ceramic-based, and organic-inorganic composite systems. Among these, inorganic solid-state electrolytes have become a research hotspot due to their high ionic conductivity, good mechanical strength, and excellent thermal stability.

[0004] Among many inorganic solid electrolytes, garnet-type... (LLZO) is known for its high lithium-ion conductivity (reaching [value missing] at room temperature). (above), wide electrochemical window ( Due to its excellent chemical and electrochemical stability with lithium metal, LLZO is considered one of the most promising solid-state electrolyte materials. However, LLZO still faces several key challenges in practical applications: First, the material is sensitive to air, and its surface is easily exposed to humid air. The reaction produces insulation First, the layer leads to a decrease in interfacial ion transport capacity and an increase in interfacial impedance. Second, the solid-solid contact between LLZO and electrode materials (especially lithium metal) is poor, resulting in insufficient interfacial wettability, which causes high interfacial resistance and uneven current distribution, affecting the rate performance and cycle stability of the battery. Third, ceramic electrolytes are brittle and are prone to microcracks during preparation and assembly, affecting their mechanical integrity and interfacial contact during long-term cycling. Summary of the Invention

[0005] In order to reduce Ceramic membrane solid electrolytes are sensitive to air and have reduced impedance. This application provides a highly stable composite solid electrolyte and its preparation method.

[0006] Firstly, this application provides a highly stable composite solid electrolyte, comprising, in sequence, the following components: Ceramic membrane, Ceramic membrane and Ceramic membrane;

[0007] Ceramic membrane, Ceramic membrane and After the ceramic membrane is laminated, it is subjected to warm isostatic pressing and high-temperature sintering to bond the grains together, resulting in a dense membrane without pores.

[0008] High-stability composite solid electrolyte with impedance of 85-232 Ω and ionic conductivity. .

[0009] Furthermore, the aforementioned The thickness of the ceramic film is 5-20 micrometers. The thickness of the ceramic film is 60-80 micrometers.

[0010] Secondly, this application provides a method for preparing the aforementioned highly stable composite solid electrolyte, comprising the following preparation steps:

[0011] (1) Preparation of ceramic membranes: Organic solvents, dispersants, and... Ceramic powder, binder, and plasticizer are ball-milled to obtain a slurry, which is then subjected to a casting process to obtain... Ceramic membrane;

[0012] (2) Preparation of ceramic membranes: Organic solvents, dispersants, and... Ceramic powder, binder and plasticizer are ball-milled and then cast to obtain a ceramic film.

[0013] (3) Multi-story Preparation of solid electrolytes: In Ceramic membrane stacked on top and bottom surfaces Ceramic membranes are obtained by bonding membrane tapes together using a temperature isostatic pressing technique.

[0014] (4) The composite ceramic membrane is debonded to remove the adhesive; after cooling in the furnace, it is used. The mother powder was used to compensate for the Li atmosphere and then sealed and sintered at 1000-15000℃ to obtain the desired high-stability composite solid electrolyte.

[0015] After cooling in the furnace, to prevent During the solid electrolyte sintering process, the stoichiometric ratio of the solid electrolyte system shifts due to the volatilization of Li, resulting in a decrease in material performance. To address this, LLZO powder of the same composition is used to bury the ceramic membrane during the sintering process for sealed sintering. The buried powder compensates for the loss of Li atmosphere, reducing the impact of Li volatilization on the ceramic membrane composition.

[0016] Furthermore, the temperature range for warm isostatic pressing is 60-80℃, and the working pressure range is 10-30 MPa.

[0017] Furthermore, the adhesive removal temperature is 500-800℃, and the sintering holding time for the ceramic membrane is 1-6 hours.

[0018] Furthermore, the heating rate during the glue removal process is 1-5℃ / min.

[0019] Furthermore, in the preparation of the LLZO ceramic membrane, the solvent includes one or more of toluene, xylene, ethanol, butanol, isopropanol, methyl ethyl ketone, and acetone; and the dispersant is one or more of polyisobutylene, oleic acid, stearic acid, and triethyl phosphate.

[0020] Furthermore, in the preparation of LLZO ceramic membranes, organic solvents, dispersants, and The mass ratio of ceramic powder, binder and plasticizer is 100:1-10:30-60:2-12:1-10.

[0021] further, In the preparation of the ceramic membrane, the binder is one or more of polyvinyl alcohol, polyvinyl chloride, polyvinyl butyral, ethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose.

[0022] The plasticizer is one or more of dibutyl phthalate, dioctyl phthalate, and mixed phthalic acid esters.

[0023] further, In the preparation of ceramic membranes, organic solvents, dispersants, and The mass ratio of ceramic powder, binder and plasticizer is 100:1-10:10-50:2-12:1-10.

[0024] Beneficial effects: 1. This invention proposes a method for preparing a multilayer composite LLZO solid electrolyte, which uses a casting process to prepare an LLZO electrolyte layer and a layer with high air stability and good lithium wettability. A protective layer is formed, and the two are tightly bonded through a warm isostatic pressing process, resulting in a dense multilayer structure after debinding and co-sintering. In this design, the outer layer... The ceramic layer effectively isolates LLZO from the corrosive effects of water and carbon dioxide in the environment, significantly improving the material's air stability; simultaneously, utilizing Excellent wettability to lithium metal can significantly reduce the interfacial impedance between the solid electrolyte and the negative electrode, thereby improving interfacial ion transport efficiency. This composite structure balances protection and interfacial compatibility, providing new material and process ideas for advancing the practical application of high-safety, high-performance all-solid-state lithium batteries.

[0025] 2. Compared to the existing technology that introduces it through coating, As a protective / isolating layer, the oxide layer of LLZO readily reacts with air to form... Impurities are eliminated by using warm isostatic pressing (WIP) technology to bond the film layers through grains, resulting in a dense, non-porous bonding layer that effectively improves the air stability of the solid electrolyte and reduces the interfacial resistance. Attached Figure Description

[0026] Figure 1 This is the XRD pattern of the LLZO solid electrolyte in Example 1;

[0027] Figure 2 This is the XRD pattern of the LLZO solid electrolyte in Comparative Example 1. Detailed Implementation

[0028] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Example 1: A method for preparing a highly stable composite solid electrolyte, comprising the following preparation process:

[0030] (1) Preparation of LLZO ceramic membrane

[0031] A mixed solvent of toluene and isopropanol (7 / 3 by volume), 3 wt% triethyl phosphate, and Li7La3Zr2O were added. 12 (LLZO) ceramic powder was initially ball-milled (solid content 40wt%). After ball milling for 24 hours, 3wt% polyvinyl butyral and 2wt% dibutyl phthalate were added, and a second ball milling was performed to obtain LLZO casting slurry. The slurry was degassed, and finally a 70-micron thick LLZO film material was formed on the casting machine.

[0032] (2) Preparation of LiAlO2 ceramic film

[0033] A mixture of toluene and isopropanol (volume ratio 7 / 3), 3 wt% triethyl phosphate, and LiAlO2 ceramic powder were initially ball-milled (solid content 20 wt%). After ball milling for 24 hours, 3 wt% polyvinyl butyral and 2 wt% dibutyl phthalate were added, and a second ball milling was performed to obtain a LiAlO2 casting slurry. The slurry was degassed, and finally a 5-micron-thick LiAlO2 thick film material was formed on a casting machine.

[0034] (3) Preparation of high-stability composite solid electrolyte

[0035] The ceramic membranes obtained in steps (1) and (2) are cut into certain sizes, and LiAlO2 ceramic membranes are stacked on the upper and lower surfaces of the LLZO ceramic membrane. The membranes are then bonded together using a warm isostatic press under process conditions of 70°C and 10 MPa.

[0036] (4) The composite ceramic membrane is debonded at 700°C to remove the binder; after cooling in the furnace, LLZO master powder is used to compensate for the Li atmosphere and sealed sintering is carried out at 1200°C to obtain the desired high-stability composite solid electrolyte.

[0037] The XRD pattern of the LLZO solid electrolyte in Example 1 is as follows: Figure 1 .

[0038] Example 2, a method for preparing a highly stable composite solid electrolyte, comprising the following preparation process:

[0039] (1) Preparation of LLZO ceramic membrane

[0040] A mixed solvent of toluene and isopropanol (7 / 3 by volume), 3 wt% triethyl phosphate, and Li7La3Zr2O were added. 12 (LLZO) ceramic powder was initially ball-milled (solid content 40wt%). After ball milling for 24 hours, 3wt% polyvinyl butyral and 2wt% dibutyl phthalate were added, and a second ball milling was performed to obtain LLZO casting slurry. The slurry was degassed, and finally a 70-micron thick LLZO film material was formed on the casting machine.

[0041] (2) Preparation of LiAlO2 ceramic film

[0042] A mixture of toluene and isopropanol (volume ratio 7 / 3), 3 wt% triethyl phosphate, and LiAlO2 ceramic powder were initially ball-milled (solid content 20 wt%). After ball milling for 24 hours, 3 wt% polyvinyl butyral and 2 wt% dibutyl phthalate were added, and a second ball milling was performed to obtain a LiAlO2 casting slurry. The slurry was degassed, and finally a 7-micron-thick LiAlO2 thick film material was formed on a casting machine.

[0043] (3) Preparation of high-stability composite solid electrolyte

[0044] The ceramic membranes obtained in steps (1) and (2) are cut into certain sizes, and LiAlO2 ceramic membranes are stacked on the upper and lower surfaces of the LLZO ceramic membrane. The membranes are then bonded together using a warm isostatic press under process conditions of 70°C and 10 MPa.

[0045] (4) The composite ceramic membrane is debonded at 700°C to remove the binder; after cooling in the furnace, LLZO master powder is used to compensate for the Li atmosphere and sealed sintering is carried out at 1200°C to obtain the desired high-stability composite solid electrolyte.

[0046] Example 3: A method for preparing a highly stable composite solid electrolyte, comprising the following preparation process:

[0047] (1) Preparation of LLZO ceramic membrane

[0048] A mixed solvent of toluene and isopropanol (7 / 3 by volume), 3 wt% triethyl phosphate, and Li7La3Zr2O were added. 12 (LLZO) ceramic powder was initially ball-milled (solid content 40wt%). After ball milling for 24 hours, 3wt% polyvinyl butyral and 2wt% dibutyl phthalate were added, and a second ball milling was performed to obtain LLZO casting slurry. The slurry was degassed, and finally a 70-micron thick LLZO film material was formed on the casting machine.

[0049] (2) Preparation of LiAlO2 ceramic film

[0050] A mixture of toluene and isopropanol (volume ratio 7 / 3), 3 wt% triethyl phosphate, and LiAlO2 ceramic powder were initially ball-milled (solid content 20 wt%). After ball milling for 24 hours, 3 wt% polyvinyl butyral and 2 wt% dibutyl phthalate were added, and a second ball milling was performed to obtain a LiAlO2 casting slurry. The slurry was degassed, and finally a 10-micron-thick LiAlO2 thick film material was formed on a casting machine.

[0051] (3) Preparation of high-stability composite solid electrolyte

[0052] The ceramic membranes obtained in steps (1) and (2) are cut into certain sizes, and LiAlO2 ceramic membranes are stacked on the upper and lower surfaces of the LLZO ceramic membrane. The membranes are then bonded together using a warm isostatic press under process conditions of 70°C and 10 MPa.

[0053] (4) The composite ceramic membrane is debonded at 700°C to remove the binder; after cooling in the furnace, LLZO master powder is used to compensate for the Li atmosphere and sealed sintering is carried out at 1200°C to obtain the desired high-stability composite solid electrolyte.

[0054] Example 4: A method for preparing a highly stable composite solid electrolyte, comprising the following preparation process:

[0055] (1) Preparation of LLZO ceramic membrane

[0056] A mixture of toluene and isopropanol (7 / 3 by volume), 3 wt% triethyl phosphate, and Li7La3Zr2O were prepared.12 (LLZO) ceramic powder was initially ball-milled (solid content 40 wt%). After ball milling for 24 hours, 3 wt% polyvinyl butyral and 2 wt% dibutyl phthalate were added, and a second ball milling was performed to obtain LLZO casting slurry. The slurry was degassed, and finally a 70-micron thick LLZO film material was formed on the casting machine.

[0057] (2) Preparation of LiAlO2 ceramic film

[0058] A mixture of toluene and isopropanol (7 / 3) solvent, 3wt% triethyl phosphate, and LiAlO2 ceramic powder were initially ball-milled (solid content 20wt%). After ball milling for 24 hours, 3wt% polyvinyl butyral and 2wt% dibutyl phthalate were added, and a second ball milling was performed to obtain LiAlO2 casting slurry. The slurry was degassed, and finally a 15-micron-thick LiAlO2 thick film material was formed on a casting machine.

[0059] (3) Preparation of high-stability composite solid electrolyte

[0060] The ceramic membranes obtained in steps (1) and (2) are cut into certain sizes, and LiAlO2 ceramic membranes are stacked on the upper and lower surfaces of the LLZO ceramic membrane. The membranes are then bonded together using a warm isostatic press under process conditions of 70°C and 10 MPa.

[0061] (4) The composite ceramic membrane is debonded at 700°C to remove the binder; after cooling in the furnace, LLZO master powder is used to compensate for the Li atmosphere and sealed sintering is carried out at 1200°C to obtain the desired high-stability composite solid electrolyte.

[0062] Example 5: A method for preparing a highly stable composite solid electrolyte, comprising the following preparation process:

[0063] (1) Preparation of LLZO ceramic membrane

[0064] A mixed solvent of toluene and isopropanol (7 / 3 by volume), 3 wt% triethyl phosphate, and Li7La3Zr2O were added. 12 (LLZO) ceramic powder was initially ball-milled (solid content 40wt%). After ball milling for 24 hours, 3wt% polyvinyl butyral and 2wt% dibutyl phthalate were added, and a second ball milling was performed to obtain LLZO casting slurry. The slurry was degassed, and finally a 70-micron thick LLZO film material was formed on the casting machine.

[0065] (2) Preparation of LiAlO2 ceramic film

[0066] A mixture of toluene and isopropanol (volume ratio 7 / 3), 3 wt% triethyl phosphate, and LiAlO2 ceramic powder were initially ball-milled (solid content 20 wt%). After ball milling for 24 hours, 3 wt% polyvinyl butyral and 2 wt% dibutyl phthalate were added, and a second ball milling was performed to obtain a LiAlO2 casting slurry. The slurry was degassed, and finally a 20-micron-thick LiAlO2 thick film material was formed on a casting machine.

[0067] (3) Preparation of high-stability composite solid electrolyte

[0068] The ceramic membranes obtained in steps (1) and (2) are cut into certain sizes, and LiAlO2 ceramic membranes are stacked on the upper and lower surfaces of the LLZO ceramic membrane. The membranes are then bonded together using a warm isostatic press under process conditions of 70°C and 10 MPa.

[0069] (4) The composite ceramic membrane is debonded at 700°C to remove the binder; after cooling in the furnace, LLZO master powder is used to compensate for the Li atmosphere and sealed sintering is carried out at 1200°C to obtain the desired high-stability composite solid electrolyte.

[0070] Comparative Example 1: A method for preparing a solid electrolyte, comprising the following preparation process:

[0071] (1) Preparation of LLZO ceramic membrane

[0072] A mixed solvent of toluene and isopropanol (7 / 3 by volume), 3 wt% triethyl phosphate, and Li7La3Zr2O were added. 12 (LLZO) ceramic powder was initially ball-milled (solid content 40wt%). After ball milling for 24 hours, 3wt% polyvinyl butyral and 2wt% dibutyl phthalate were added, and a second ball milling was performed to obtain LLZO casting slurry. The slurry was degassed, and finally a 70-micron thick LLZO film material was formed on the casting machine.

[0073] (2) The LLZO ceramic membrane was debinded at 700°C to remove the binder; after cooling in the furnace, LLZO master powder was used to compensate for the Li atmosphere and sealed and sintered at 1200°C to obtain a solid electrolyte.

[0074] The XRD pattern of the LLZO solid electrolyte in Comparative Example 1 is shown below. Figure 2 .

[0075] Performance testing:

[0076] 1) XRD analysis was performed on the LLZO solid electrolytes in Example 1 and Comparative Example 1 after they were left to stand in air for 24 hours. The analysis results are as follows: Figure 1 and such Figure 2 .

[0077] from Figure 1 As can be seen from the XRD, the composite solid electrolyte obtained by stacking LiAlO2 ceramic films on both sides of the LLZO ceramic film and co-firing them only contains Li7La3Zr2O. 12 Two phases, (LLZO) and LiAlO2, were detected, and no other impurities were detected. Figure 2 The electrolyte shown does not have stacked LiAlO2, and Li2CO3 impurity phase was detected in the XRD pattern; Figure 1 and Figure 2 The comparison shows that stacking LiAlO2 ceramic layers can effectively protect Li7La3Zr2O2 ceramics, preventing them from coming into contact with air and generating impurities such as Li2CO3, thereby improving the air stability of LLZO solid electrolyte.

[0078] 2) Impedance and ionic conductivity of solid electrolytes in each embodiment and comparative example

[0079] Table 1. Impedance and ionic conductivity of solid electrolytes in each embodiment and comparative example.

[0080]

[0081] As shown in Table 1, the impedance of all examples with stacked LiAlO2 ceramic layers is lower than that of Comparative Example 1, indicating that LiAlO2 can effectively improve the wettability with Li metal, thereby reducing the contact resistance. Among the examples, the ionic conductivity of Comparative Example 1 is significantly higher than that of Examples 1-5. This is because the ionic conductivity of LLZO (>10) is much higher. -3 S / cm) is higher than that of LiAlO2 (>10) -11 (S / cm) An excessively thick LiAlO2 layer will severely reduce the ionic conductivity of the solid electrolyte.

[0082] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A highly stable composite solid electrolyte, characterized in that, The components are, in order, LiAlO2 ceramic membrane, LLZO ceramic membrane, and LiAlO2 ceramic membrane; After stacking LiAlO2 ceramic membrane, LLZO ceramic membrane and LiAlO2 ceramic membrane, the grains are bonded together by warm isostatic pressing and high-temperature sintering, resulting in a dense and pore-free membrane. The highly stable composite solid electrolyte exhibits an impedance of 85-232 Ω and an ionic conductivity of 1.09 × 10⁻⁶. -4 -3.11* 10 -4 S / cm.

2. The high-stability composite solid electrolyte according to claim 1, characterized in that, The thickness of the LiAlO2 ceramic film is 5-20 micrometers, and the thickness of the LLZO ceramic film is 60-80 micrometers.

3. A method for preparing the high-stability composite solid electrolyte according to claim 1 or 2, characterized in that, The preparation steps include the following: (1) Preparation of LLZO ceramic film: organic solvent, dispersant and Li7La3Zr2O 12 Ceramic powder, binder and plasticizer are ball-milled to obtain a slurry, which is then cast to obtain an LLZO ceramic film. (2) Preparation of LiAlO2 ceramic film: Organic solvent, dispersant, LiAlO2 ceramic powder, binder and plasticizer are ball-milled and then cast to obtain ceramic film; (3) Preparation of multilayer LLZO solid electrolyte: LiAlO2 ceramic films are stacked on the upper and lower surfaces of LLZO ceramic film, and the film strips are bonded together by warm isostatic pressing to obtain composite ceramic film. (4) The composite ceramic membrane is debonded and the binder is removed. After cooling in the furnace, LLZO master powder is used to compensate for the Li atmosphere and sealed sintering is carried out at 1000-15000℃ to obtain the required high-stability composite solid electrolyte.

4. The method for preparing a highly stable composite solid electrolyte according to claim 3, characterized in that, The temperature range for warm isostatic pressing is 60-80℃, and the working pressure range is 10-30 MPa.

5. A method for preparing a highly stable composite solid electrolyte according to claim 3 or 4, characterized in that, The adhesive removal temperature is 500-800℃, and the sintering holding time for the ceramic membrane is 1-6 hours.

6. The method for preparing a highly stable composite solid electrolyte according to claim 5, characterized in that, The heating rate during the glue removal process is 1-5℃ / min.

7. A method for preparing a highly stable composite solid electrolyte according to any one of claims 3, 4, and 6, characterized in that, In the preparation of LLZO ceramic membranes, the solvent includes one or more of toluene, xylene, ethanol, butanol, isopropanol, methyl ethyl ketone, and acetone; the dispersant is one or more of polyisobutylene, oleic acid, stearic acid, and triethyl phosphate.

8. The method for preparing a highly stable composite solid electrolyte according to claim 7, characterized in that, In the preparation of LLZO ceramic membranes, organic solvents, dispersants, and Li7La3Zr2O are used. 12 The mass ratio of ceramic powder, binder and plasticizer is 100:1-10:30-60:2-12:1-10.

9. A method for preparing a highly stable composite solid electrolyte according to any one of claims 3, 4, 6, and 8, characterized in that, In the preparation of the LiAlO2 ceramic membrane, the binder is one or more of polyvinyl alcohol, polyvinyl chloride, polyvinyl butyral, ethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. The plasticizer is one or more of dibutyl phthalate, dioctyl phthalate, and mixed phthalic acid esters.

10. The method for preparing a highly stable composite solid electrolyte according to claim 9, characterized in that, In the preparation of LiAlO2 ceramic membrane, the mass ratio of organic solvent, dispersant and LiAlO2 ceramic powder, binder and plasticizer is 100:1-10:10-50:2-12:1-10.

Images