CN109037759B - Sintering method for preparing compact garnet-type lithium ion solid electrolyte - Google Patents
Sintering method for preparing compact garnet-type lithium ion solid electrolyte Download PDFInfo
- Publication number
- CN109037759B CN109037759B CN201710433799.7A CN201710433799A CN109037759B CN 109037759 B CN109037759 B CN 109037759B CN 201710433799 A CN201710433799 A CN 201710433799A CN 109037759 B CN109037759 B CN 109037759B
- Authority
- CN
- China
- Prior art keywords
- solid electrolyte
- temperature heating
- temperature
- electrolyte material
- sintering
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
- H01M10/0562—Solid materials
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0065—Solid electrolytes
- H01M2300/0068—Solid electrolytes inorganic
- H01M2300/0071—Oxides
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
Disclosed herein is a sintering method for producing a dense garnet-type lithium ion solid electrolyte, the method comprising sintering a solid electrolyte material, the sintering comprising in sequence: at least one high temperature heating process, and at least one low temperature heating process, wherein the low temperature heating time is longer than the high temperature heating time. According to the method of the present invention, the grain size of the solid electrolyte can be controlled by adjusting the sintering time in the high-temperature heating process. Compared with a one-step sintering method, the multi-step sintering method provided by the invention has the advantage that the density, the conductivity and the bending strength of the solid electrolyte are higher.
Description
Technical Field
The invention belongs to the field of preparation of lithium ion solid electrolytes, and particularly relates to a preparation method of a compact garnet type lithium ion solid electrolyte material.
Background
Increasingly developed portable electronic devices and electric automobiles require lithium ion batteries with higher energy density, longer life, and better safety. Compared with the current commercial lithium ion battery based on the organic system electrolyte, the lithium sulfur battery and the lithium air battery based on the solid electrolyte have higher energy density, fundamentally reduce the potential safety hazard of the lithium battery, and are the research hotspots in the field of chemical power sources at home and abroad at present. The solid electrolyte is in various types, including phosphate ceramics and glass ceramics of NASICON structure, sulfides of LISICON structure, Li of perovskite structure3xLa1-xTiO3，Li3N，LixPOyNz(LiPON) and pomegranateLi of stone structure7La3Zr2O12(LLZO) and the like. Wherein, LLZO has the following advantages: (1) exhibits chemical and electrochemical stability in direct contact with metallic lithium; (2) the compactness and the strength are high, and the lithium can not be punctured by lithium dendrites, so that the metal lithium with high energy density can be used as a negative electrode material of a lithium battery; (3) the room temperature conductivity reaches 10-4More than S/cm; (4) the electrochemical window reaches 6V (relative to Li)+/Li), enabling the application of high voltage positive electrode materials; (5) the self-chemical stability is high, and the preparation is simple. LLZO is currently the hottest material system studied in lithium ion solid electrolytes. Different kinds of ion doping, such as Al, Ga and the like for replacing Li, Ca, Sr, Ba, Y and the like for replacing La, Nb, Ta, W, Si and the like for replacing Zr, F for replacing O and the like, play a role in stabilizing the room-temperature cubic phase of LLZO and improving the lithium ion conductivity thereof to a certain extent. Wherein the LLZO (LLZTO) material with Ta replacing Zr site has 1 × 10-3The lithium ion conductivity of S/cm is far higher than that of pure LLZO.
The energy density of lithium ion batteries and lithium sulfur batteries based on LLZO solid electrolytes is much higher than that of current commercial lithium ion batteries using organic electrolytes, but the thickness of practical solid electrolytes needs to be less than 100 μm. Within this thickness limit, the electrolyte must be very dense and possess sufficient strength to meet the requirements of device assembly. In addition, the compact ceramics have tighter grain boundary bonding and higher conductivity; the surface of the dense ceramic may completely block the growth of lithium dendrites. Currently, the published documents and patents employ one-step sintering of LLZO ceramics (e.g. WO210090301a1, CN104159869a1, etc.). However, in such a one-step sintering process, when the sintering temperature is high, overgrown LLZO grains are easily formed, and the size may reach 50 μm or more, resulting in low relative density and mechanical strength; when the sintering temperature is low, the grain boundary bonding is insufficient, resulting in large grain boundary resistance and insufficient strength.
Disclosure of Invention
Aiming at the defects of the existing LLZO-based solid electrolyte, the invention aims to develop a new preparation method to obtain a more compact LLZO material with higher lithium ion conductivity and higher strength.
Therefore, the invention adopts a sintering strategy of combining short-time high-temperature sintering and long-time low-temperature sintering to densify the product, thereby improving the comprehensive performance of the ceramic.
The invention provides a sintering method for preparing a compact solid electrolyte material, which comprises the following steps:
sintering the solid electrolyte material, wherein the sintering comprises the following steps:
at least one high-temperature heating process, and
at least one low-temperature heating process is carried out,
wherein the low temperature heating time is longer than the high temperature heating time.
In one embodiment of the present invention, the solid electrolyte material has a general formula of Li7-xLa3(Zr2-x,Mx)O12/SA, wherein M is selected from one or more of Al, Ga, In, Si, Ge, Sn, Sb, Bi, Sc, Y, Ti, Hf, V, Nb and Ta; SA is not present, or SA is selected from MgO, CaO, ZrO2And HfO2One or more of; 0<x<1。
In one embodiment of the present invention, M is Ta and x is 0.6.
In one embodiment of the present invention, SA is MgO.
In one embodiment of the present invention, the heating temperature in the high-temperature heating process is 1175 ℃ or more, preferably 1200 ℃ to 1400 ℃, more preferably 1000 ℃ to 1200 ℃, more preferably 1250 ℃ to 1280 ℃, provided that the heating temperature in the high-temperature heating process is higher than the heating temperature in the low-temperature heating process.
In one embodiment of the present invention, the heating temperature in the low-temperature heating process is 1200 ℃ or less, preferably 900 ℃ to 1200 ℃, more preferably 1000 ℃ to 1200 ℃, more preferably 1150 ℃ to 1180 ℃, provided that the heating temperature in the high-temperature heating process is higher than the heating temperature in the low-temperature heating process.
In one embodiment of the present invention, the high temperature heating time is 1 to 120 minutes, preferably 2 to 100 minutes, more preferably 5 to 90 minutes, and still more preferably 10 to 80 minutes.
In one embodiment of the present invention, the low-temperature heating time is 2.5 to 7.5 hours, preferably 3 to 6 hours, more preferably 3.5 to 5.5 hours, and still more preferably 4 to 5 hours.
According to the method of the present invention, the high-temperature heating step precedes the low-temperature heating step.
The invention also provides a solid electrolyte material prepared by the method.
In one embodiment of the present invention, a solid electrolyte material is provided having greater than 4.0 x 10-4Electrical conductivity of S/cm, compactness higher than 97%, and bending strength greater than 140 MPa.
According to the method of the present invention, the grain size of the solid electrolyte can be controlled by adjusting the sintering time in the high-temperature heating process. Compared with a one-step sintering method, the multi-step sintering method provided by the invention has the advantage that the density, the conductivity and the bending strength of the solid electrolyte are higher.
Drawings
FIG. 1 is an X-ray diffraction pattern of the samples of comparative examples 1-2 and examples 1-4.
FIGS. 2(A) - (F) are scanning electron micrographs showing cross-sectional microstructures of ceramic samples of comparative example 1, examples 1-4 and comparative example 2, respectively.
FIGS. 3(A) - (F) are scanning electron microscope photographs showing the microstructures of the cross-sections of the ceramic samples of comparative example 1, examples 1-4 and comparative example 2 after acid etching, respectively.
FIGS. 4(A) to (F) are scanning electron energy spectrograms showing the distribution of Mg element at the cross-section of the ceramic samples of comparative example 1, examples 1 to 4 and comparative example 2, respectively.
FIG. 5 is an AC impedance spectrum of the samples of comparative examples 1-2 and examples 1-4.
FIG. 6 shows the room temperature (25 ℃) conductivity and the compactness of the samples of comparative examples 1-2 and examples 1-4.
FIGS. 7(A) - (B) show the activation energies and Arrhenius fit straight lines for the samples of comparative examples 1-2 and examples 1-4, respectively.
FIG. 8 shows the flexural strength of the samples of comparative examples 1-2 and examples 1-4.
FIGS. 9(A) - (F) are microstructures of fresh sections of samples of comparative example 3, examples 5-8 and comparative example 4, respectively.
FIG. 10 is an AC impedance spectrum of the samples of comparative examples 3-4 and examples 5-8.
FIG. 11 shows the room temperature (25 ℃) conductivity and the compactness of the samples of comparative examples 3-4 and examples 5-8.
Detailed Description
Disclosed is a method for producing a solid electrolyte material, which comprises two or more sintering steps for sintering a solid electrolyte. The two or more sintering processes include at least a short-time high-temperature (e.g., 1250 ℃ or more) sintering process and a long-time low-temperature (e.g., 1150 ℃ or less) sintering process. The solid ceramic electrolyte obtained using the two-or more-step sintering process may simultaneously have a dense microstructure, high mechanical strength and high electrical conductivity. For example, solid ceramic electrolytes sintered by this method have high lithium ion conductivities (up to about 5X 10)-4S/cm), high density (up to about 98%), dense cross-sectional microstructure and high flexural strength (up to about 160 MPa).
In one aspect, the present invention provides a sintering method for producing a dense solid electrolyte material, the method comprising: sintering the solid electrolyte material, wherein the sintering comprises the following steps: at least one high temperature heating process, and at least one low temperature heating process, wherein the low temperature heating time is longer than the high temperature heating time.
In another aspect, the present invention provides a method of preparing a dense solid electrolyte material, the method comprising: providing a solid electrolyte material; sintering the solid electrolyte material to obtain a compact solid electrolyte material, wherein the sintering sequentially comprises: at least one high temperature heating process, and at least one low temperature heating process, wherein the low temperature heating time is longer than the high temperature heating time.
In yet another aspect, the present invention provides a method of making a dense solid electrolyte material, the method comprising: providing solid electrolyte material powder; forming the solid electrolyte material powder into a solid electrolyte material biscuit; sintering the solid electrolyte material biscuit to obtain a compact solid electrolyte material, wherein the sintering sequentially comprises: at least one high temperature heating process, and at least one low temperature heating process, wherein the low temperature heating time is longer than the high temperature heating time.
In the present invention, the solid electrolyte material is available in the general formula Li7-xLa3(Zr2-x,Mx)O12A LLZO series lithium ion solid electrolyte material represented by/SA, wherein M is selected from one or more of Al, Ga, In, Si, Ge, Sn, Sb, Bi, Sc, Y, Ti, Hf, V, Nb and Ta; SA is absent, or selected from MgO, CaO, ZrO2,HfO2One or more of; 0<x<1。
In a specific embodiment, x is 0.6.
In one embodiment, M is selected from Ta.
When SA is not present, the solid electrolyte material is a pure LLZO series lithium ion solid electrolyte material (Li)7-xLa3(Zr2-x,Mx)O12). In one embodiment, the LLZO solid electrolyte has a garnet crystal structure. In one embodiment, the LLZO garnet is cubic phase Li6.4La3Zr1.4Ta0.6O12(LLZTO)。
When SA is present, the solid electrolyte material is a composite electrolyte material. In one embodiment, SA is selected from MgO. In a specific embodiment, the solid electrolyte material is a LLZO garnet/MgO composite electrolyte material. In a more specific embodiment, the solid electrolyte material is a LLZTO garnet/MgO composite electrolyte material.
The sintering step of the method of the present invention comprises at least one high temperature heating step and at least one low temperature heating step. For example, a biscuit of the solid electrolyte material is first heated to a higher temperature T at a faster rate in a high temperature heating processHeight ofAnd kept for a short time tHeight ofThen quickly cooled to a lower temperature T in a low-temperature heating processIs low inAnd guaranteeFor a longer time tIs low inAnd finally naturally cooling to room temperature.
The heating temperature in the high-temperature heating process is 1175 ℃ or more, for example, 1200 ℃ or more, for example, 1250 ℃ or more, for example, 1280 ℃ or more, for example, 1300 ℃ or more, for example, 1175 ℃ to 1600 ℃, for example, 1200 ℃ to 1500 ℃, for example, 1200 ℃ to 1400 ℃, for example, 1200 ℃ to 1300 ℃, for example, 1250 ℃ to 1400 ℃, for example, 1250 ℃ to 1300 ℃, for example, 1250 ℃ to 1280 ℃, provided that the heating temperature in the high-temperature heating process is higher than the heating temperature in the low-temperature heating process.
The heating temperature in the low-temperature heating process is 1250 ℃ or less, such as 1200 ℃ or less, such as 1180 ℃ or less, such as 900 ℃ to 1200 ℃, such as 950 ℃ to 1200 ℃, such as 1000 ℃ to 1200 ℃, such as 1150 ℃ to 1200 ℃, such as 950 ℃ to 1180 ℃, such as 1000 ℃ to 1180 ℃, such as 1150 ℃ to 1180 ℃, provided that the heating temperature in the high-temperature heating process is higher than the heating temperature in the low-temperature heating process.
The high-temperature heating time in the high-temperature heating process is 1 to 120 minutes, such as 2 to 100 minutes, such as 5 to 90 minutes, such as 10 to 80 minutes, such as 20 to 80 minutes, such as 10 to 40 minutes, such as 20 to 40 minutes, such as 40 to 80 minutes, such as 10 minutes, 20 minutes, 40 minutes, 80 minutes, and the like.
In one embodiment of the invention, the low temperature heating time is 2.5 to 7.5 hours, such as 3 to 6 hours, such as 3.5 to 5.5 hours, such as 4 to 5 hours, such as 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, and the like.
In the method of producing a solid electrolyte material of the present invention, the sintering step may include a plurality of high-temperature heating processes and a plurality of low-temperature heating processes. For example, the method of the present invention may include two or more high temperature heating processes. For example, a green body of solid electrolyte material may first be heated to a higher temperature THeight 1And kept for a short time tHeight 1Then the biscuit is further heated to a higher temperature THeight 2And kept for a short time tHeight 2. In another embodiment, the biscuit of solid electrolyte material may be heated to a higher temperatureTemperature THeight 1And kept for a short time tHeight 1Then cooling the biscuit to a temperature THeight 2And kept for a short time tHeight 2. The sintering step of the method of the invention may comprise two or more low temperature heating processes. For example, after heating at an elevated temperature, the temperature of the biscuit is reduced to a lower temperature TLow 1And maintained for a longer time tLow 1Then further cooled to TLow 2And maintained for a longer time tLow 2。
Herein, "high temperature" in the "high temperature heating process" and "low temperature" in the "low temperature heating process" are relative to each other. That is, the heating temperature in the high-temperature heating step is higher than the heating temperature in the low-temperature heating step. In an embodiment including two or more high-temperature heating processes and/or two or more low-temperature heating processes, the lowest heating temperature in the high-temperature heating process is higher than the highest heating temperature in the low-temperature heating process.
Herein, "shorter time" in the "high-temperature heating process" and "longer time" in the "low-temperature heating process" are relative to each other. That is, the heating time in the high-temperature heating step is shorter than the heating time in the low-temperature heating step. In embodiments including two or more high-temperature heating processes and/or two or more low-temperature heating processes, the total heating time in the high-temperature heating process is shorter than the total heating time in the low-temperature heating process.
If the solid electrolyte material volatilizes during sintering, the buried powder can be used during sintering. Methods employing embedded powders are known in the art. For example, garnet solid electrolytes can be sintered at temperatures as high as 1000 ℃ or higher, where lithium oxide is highly volatile, and the buried powder can provide an additional lithium oxide atmosphere to protect the electrolyte.
The method for producing the solid electrolyte material powder is not particularly limited. The initial powder may be prepared by any suitable method known in the art by one skilled in the art. For example, the starting solid electrolyte material may be subjected to planetary ball milling to obtain a slurry, which is then dried and sieved to obtain the initial powder.
The method of molding the solid electrolyte material powder into a solid electrolyte material biscuit is not particularly limited. Any suitable shaping method known in the art may be employed by those skilled in the art. For example, the starting powder may be dry-pressed and then subjected to isostatic pressing, for example at a pressure of 200 MPa.
The invention also provides a solid electrolyte material prepared by the method. The density, the conductivity and the mechanical strength of the garnet electrolyte can be effectively improved by adopting a two-step or multi-step sintering method combining short-time high-temperature sintering and long-time low-temperature sintering. For example, a solid electrolyte material is provided having greater than 4.0 x 10-4Electrical conductivity of S/cm, compactness higher than 97%, and bending strength greater than 140 MPa. In some embodiments, the conductivity of the solid electrolyte material is greater than or equal to 4.2 x 10-4S/cm, greater than or equal to 4.5X 10-4S/cm, greater than or equal to 4.8X 10-4S/cm of 5.0X 10 or more-4S/cm of 5.2X 10 or more-4S/cm, or greater than or equal to 5.3X 10-4S/cm. In some embodiments, the density of the solid electrolyte material is greater than or equal to 97.5%, or greater than or equal to 98%. In some embodiments, the solid electrolyte material has a flexural strength greater than or equal to 145MPa, greater than or equal to 150MPa, greater than or equal to 155MPa, or equal to or greater than 160 MPa.
Examples
The following examples are given to further illustrate embodiments of the present invention, by way of example of pure LLZTO garnet and LLZTO garnet/MgO composite electrolyte material.
Preparation of the starting powder
The LLZTO garnet comprises cubic phase Li6.4La3Zr1.4Ta0.6O12. With LiOH. H2O (analytically pure, 10% excess), La2O3(purity 99.99%, pretreatment at 900 ℃ for 12 hours), ZrO2(analytically pure) and Ta2O5(purity: 99.99%) as a raw materialAccording to the stoichiometric ratio, Yttrium Stabilized Zirconia (YSZ) is used as a ball milling medium, isopropanol is used as a solvent, and the materials are ball milled and mixed uniformly. And after drying the slurry, grinding the slurry in an alumina mortar, then placing the slurry in an alumina crucible, calcining the slurry for 6 hours at 950 ℃, ball-milling the slurry again by adopting the same ball-milling parameters, and calcining the slurry for 6 hours at 950 ℃ to obtain pure cubic phase LLZTO garnet powder.
Pure LLTZO garnet samples: planetary ball milling is carried out for 12 hours at the speed of 250rpm to obtain slurry, and the slurry is dried, screened, collected and stored for later use.
LLZTO garnet/MgO composite electrolyte sample: to LLZTO powder, 6% by mass of nano MgO (50nm, purity 99.9%) was added, and the mixture was ball-milled using the same parameters as above. The slurry obtained by ball milling was transferred to a high speed sanding system and sanded at 1200-2400rpm for 1-2 hours. Drying the slurry to obtain the LLZTO/MgO composite fine powder. The powder is collected and stored for later use after being screened by a 200-mesh sieve.
Preparation of buried powder
In the present invention, Li is used6.4La3Zr1.4Ta0.6O12(LLZTO, Li excess 10%) and lower cost Li6.75La3Zr1.75Nb0.25O12(LLZNO, Li excess 20%) as a buried powder. With LiOH. H2O (analytically pure, 10% excess), La2O3(99.99%, pretreatment at 900 ℃ for 12 hours), ZrO2(analytically pure) and Ta2O5(99.99%) as precursor powder, and ball-milling and mixing according to stoichiometric ratio. After drying, grinding by an alumina mortar, placing in an alumina crucible, and calcining at 950 ℃ for 12 hours to obtain the LLZTO buried powder. The preparation process of the LLZNO buried powder is the same as that of the LLZTO buried powder, wherein LiOH. H2O is in excess of 20%.
Preparation of ceramic sheets and test strips
And (3) obtaining a round sheet biscuit and a test strip biscuit by utilizing the initial powder obtained above through dry pressing and 200MPa isostatic pressing, wherein the diameter of the round sheet biscuit is 18mm, the thickness of the round sheet biscuit is about 2mm, and the size of the test strip biscuit is 5mm multiplied by 7mm multiplied by 40 mm.
The biscuit was sintered in a covered platinum crucible. For the ceramic wafer sample, the ceramic wafer sample is placed above a woven platinum mesh, the embedded powder is LLZNO and is placed under a biscuit, and the biscuit is separated from the embedded powder; for the test strip sample, because the size is large and sintering is not easy to be dense, the sample is completely embedded in the LLZTO embedding powder and then sintered. And grinding the ceramic wafer and the test strip obtained by sintering to a set size, wherein the thickness of the ceramic wafer is 1-2mm, and the three-dimensional size of the test strip is 3mm multiplied by 4mm multiplied by 30mm, and polishing by abrasive paper to be tested for characterization analysis.
Characterization of the test
1) Phase analysis
Powder X-ray diffraction (PXRD) (japan, Ultima IV, nickel filtered copper ka radiation,
) The phase composition of the powder and ceramic synthesized at room temperature was determined. Scanning angle range: 10 degrees to 60 degrees; scanning speed: 0.1 deg./sec. The ceramic wafers were ground to powder for testing.
2) Electrochemical analysis
The ion conductivity of each ceramic wafer sample was analyzed by an ac impedance spectroscopy analyzer (Autolab, model PGSTAT 302N). The test mode is constant voltage variable frequency impedance spectroscopy, the frequency range is 10Hz-7MHz, and the bias voltage is set to 20 mV. And sputtering gold on the upper and lower parallel surfaces of the sample to serve as blocking electrodes for lithium ions. The conductivity of each sample was measured at different temperatures in the incubator, ranging from 10 ℃ to 85 ℃. From Arrhenius (Arrhenius) formula σ T ═ Aexp (-E)a/kT) fitting temperature-conductivity data and calculating to obtain activation energy, wherein sigma is conductivity, A is frequency factor, EaFor activation energy, k is the Boltzmann constant and T is the absolute temperature.
3) Analysis of Density and mechanical Properties
The density of each ceramic wafer sample was measured using the archimedes method. In this, the test was carried out with a Mettler-Toledo (Mettler-Toledo) densitometric assembly, using ethanol as solvent. The theoretical density of LLZTO calculated by XRD data was 5.5g/cm3The theoretical density of MgO is 3.58g/cm3. For the LLZTO/MgO composite ceramic electrolyte,the theoretical density calculation value is 5.338g/cm3. The density is calculated by dividing the density measurement by the theoretical density. The bending strength of the test bars was measured using a three-point bending method (Instron 3366). The test span was 20mm and the loading rate was 0.02 mm/min.
4) Analysis of microstructure of cross section
And observing the microstructure of the random section of the ceramic chip sample by adopting a scanning electron microscope (Hitachi, S-3400N). And soaking the section of the sample for 3min by using 2mol/L HCl to corrode the grain boundary, so that the sample shows the grain boundary. And detecting the distribution of Mg element in the sample by using a scanning electron spectrometer (Hitachi, S-3400N).
Example 1
The LLZTO/MgO composite ceramic was prepared according to the methods described in the section "preparation of initial powder" and "preparation of ceramic sheet and test bar" above, wherein in the sintering step, the sample was sintered at 1250 ℃ for 10 minutes and then incubated at 1150 ℃ for 5 hours.
Example 2
The LLZTO/MgO composite ceramic was prepared according to the methods described in the section "preparation of initial powder" and "preparation of ceramic sheet and test bar" above, wherein in the sintering step, the sample was sintered at 1250 ℃ for 20 minutes and then incubated at 1150 ℃ for 5 hours.
Example 3
The LLZTO/MgO composite ceramic was prepared according to the methods described in the section "preparation of initial powder" and "preparation of ceramic sheet and test bar" above, wherein in the sintering step, the sample was sintered at 1250 ℃ for 40 minutes and then incubated at 1150 ℃ for 5 hours.
Example 4
The LLZTO/MgO composite ceramic was prepared according to the methods described in the section "preparation of initial powder" and "preparation of ceramic sheet and test bar" above, wherein in the sintering step, the sample was sintered at 1250 ℃ for 80 minutes and then incubated at 1150 ℃ for 5 hours.
Example 5
Pure LLZTO ceramic was prepared according to the methods described in the "preparation of initial powder" and "preparation of ceramic sheet and test strip" section above, wherein in the sintering step, the sample was sintered at 1280 ℃ for 10 minutes, and then incubated at 1180 ℃ for 5 hours.
Example 6
Pure LLZTO ceramic was prepared according to the methods described in the "preparation of initial powder" and "preparation of ceramic sheet and test strip" section above, wherein in the sintering step, the sample was sintered at 1280 ℃ for 20 minutes, and then incubated at 1180 ℃ for 5 hours.
Example 7
Pure LLZTO ceramic was prepared according to the methods described in the "preparation of initial powder" and "preparation of ceramic sheet and test strip" section above, wherein in the sintering step, the sample was sintered at 1280 ℃ for 40 minutes, and then incubated at 1180 ℃ for 5 hours.
Example 8
Pure LLZTO ceramic was prepared according to the methods described in the "preparation of initial powder" and "preparation of ceramic sheet and test strip" section above, wherein in the sintering step, the sample was sintered at 1280 ℃ for 80 minutes, and then incubated at 1180 ℃ for 5 hours.
Comparative example 1
The LLZTO/MgO composite ceramic was prepared according to the methods described in the section "preparation of initial powder" and "preparation of ceramic sheet and test bar" above, wherein in the sintering step, the sample was sintered at 1150 ℃ for 5 hours.
Comparative example 2
The LLZTO/MgO composite ceramic was prepared according to the methods described in the section "preparation of initial powder" and "preparation of ceramic sheet and test bar" above, wherein in the sintering step, the sample was sintered at 1250 ℃ for 5 hours.
Comparative example 3
Pure LLZTO ceramic was prepared according to the methods described in the "preparation of initial powder" and "preparation of ceramic sheet and test strip" section above, wherein in the sintering step, the sample was sintered at 1180 ℃ for 5 hours.
Comparative example 4
Pure LLZTO ceramic was prepared according to the methods described in the "preparation of initial powder" and "preparation of ceramic sheet and test strip" section above, wherein in the sintering step, the sample was sintered at 1280 ℃ for 5 hours.
Specific properties of each example and comparative example are described below:
PXRD results for the ceramic sheets and strips of comparative examples 1-2 and examples 1-4 are shown in fig. 1, where (200) is the peak position of the MgO phase standard card (PDF #77-2179) in the bottom set of discrete vertical lines, and the remaining vertical lines are the reference peaks of the cubic garnet phase LLZO. All samples exhibited sharp diffraction peaks, both peak position and intensity consistent with LLZO standard peaks for the cubic garnet phase (c.a. geiger, e.alekseev, b.lazic, m.fish, t.armbruster, r.langner, m.fechtelkord, n.kim, t.pettke and w.weppner, incorg.chem., 2011,50, 1089-. A characteristic diffraction peak (42.9 degrees) corresponding to the diffraction surface (200) of the cubic MgO (PDF #77-2179) can be observed at the left shoulder of the diffraction peak (43 degrees) corresponding to the cubic LLZTO diffraction surface (532). No other miscellaneous peak except. In contrast to the one-step sintering method, which is the one-step sintering method and the two-step sintering method, which are the examples, no other impurity phase is generated by the two-step sintering method.
The fresh cross-sectional microstructures of the samples of comparative examples 1-2 and examples 1-4 are shown in FIG. 2. Wherein, the comparative example 2 and the example 4 both show clear grain boundary and partial transgranular phenomena; no distinct grain boundary (complete transgranular phenomenon) was observed in comparative example 1 and examples 1 to 3. This phenomenon results from the time of sintering in the high temperature section (1250 deg.C) for the different examples. When the time at high temperature is longer (example 4, 80 minutes; comparative example 2, 300 minutes), the grain boundary is clear; when the time is short in the high temperature period, the crystal passing phenomenon is obvious. All examples exhibited clear grain boundaries after acid etching (fig. 3), when the grain sizes of the different samples were clearly compared. Along with the prolonging of the heat preservation time in the high-temperature section, the crystal grains grow; the sample of comparative example 1 exhibited the smallest size of grains, while the sample of comparative example 2 exhibited the largest size of grains, with grain sizes in-between for the samples of examples 1-4 using the two-step sintering method. This phenomenon indicates that the grain size can be controlled by adjusting the two-step sintering regime. The distribution of the Mg element in the ceramic is shown in FIG. 4 (the black area indicates Mg). With the prolonging of the heat preservation time of the high temperature section, not only the LLZTO crystal grains grow up, but also the Mg element shows the enrichment trend. In addition, the Mg element is distributed at the LLZTO crystal boundary; while no Mg element was observed inside the LLZTO grains, it is said thatBright Mg2+Cannot enter the LLZTO crystal lattice, and LLZTO/MgO is a two-phase composite ceramic.
The AC impedance spectrum of comparative examples 1-2 and examples 1-4 is shown in FIG. 5 (lower right inset is the fitted circuit diagram). All the curves are formed by combining a high-frequency region semicircle and a low-frequency region long tail straight line. The Au electrode being Li+The straight line of the low frequency region is a semi-infinite diffusion response of lithium ions at the blocking electrode, and the occurrence of the straight line indicates that the material is Li+A conductor. Circuit model Rb(RgbQgb)(RelQel) For fitting impedance spectroscopy measurement data and is shown as a smooth fit curve in the figure, where Rb、RgbAnd RelCorresponding to bulk impedance, grain boundary impedance and Au blocking electrode impedance, QgbAnd QelRespectively corresponding to grain boundaries and the interface constant phase angle element between the ceramic and the electrode. The total impedance value is composed ofb+Rgb) The reciprocal is determined as the total conductivity value. The room temperature conductivity and density of the example samples are shown in figure 6. The sample of comparative example 1 has the lowest conductivity, the conductivity gradually increases along with the prolonged holding time of examples 1-4 in the high temperature section, and the sample of comparative example 2, which has the longest holding time in the high temperature section, has the highest conductivity. The density changes show completely opposite trends. Comparative example 1 sintered by one-step process has high density and low conductivity; comparative example 2 has high conductivity and low density. In contrast, examples 3 and 4, which were sintered in two steps, exhibited high conductivity (5X 10) simultaneously-4S/cm) and high density (-98%). The activation energies of all the samples of the examples are shown in FIG. 7A, with values floating between 0.42-0.45 eV. The fitted line in fig. 7B is highly linear, indicating that all samples obey arrhenius' law. The consistent activation energy indicates that the two-step sintering process has no significant impact on this property.
The flexural strength of the samples of comparative examples 1-2 and examples 1-4 is shown in FIG. 8. Examples 1, 2 and 4 exhibited higher bending strength than comparative examples 1 and 2. The embodiments obtained by the two-step sintering process possess simultaneously high density, high electrical conductivity, high mechanical strength and a dense microstructure, which properties are beneficial for the manufacture and long-term use of devices based on solid lithium-ion electrolytes.
To verify the universality of the method, green compacts were prepared using pure LLZTO powder that had only been subjected to planetary ball milling, without sand milling, and similar sintering experiments were performed. The powder obtained by planetary ball milling is thicker and has lower activity, and the sintering temperature is increased by 30-1180 ℃ and 1280 ℃. The fresh cross-section microstructures of comparative examples 3-4 and examples 5-8 are shown in FIG. 9. In comparative example 3, after the heat preservation at 1180 ℃ for 5 hours, very obvious grain boundaries can be observed among grains, and no transgranular fracture area exists. In comparative example 4, after the temperature of 1280 ℃ is kept for 5 hours, crystal grains excessively grow and the size exceeds 100 mu m, and the phenomenon can seriously reduce the strength of the ceramic. The grain boundaries of examples 5-8 obtained by the two-step sintering were well bonded, and numerous transgranular fracture zones were present. As the holding time in the high temperature zone was prolonged, excessively grown grains were developed in examples 5 to 8, and particularly, in example 8 (FIG. 9E) in which the holding time was as long as 80 minutes, grains having a size of about 50 μm were present in a partial region. For pure LLZTO, the two-step sintering can obtain a more compact cross-section microstructure and stronger grain boundary bonding, and simultaneously avoid the excessive growth of grains caused by long-time high-temperature sintering.
The impedance spectrum curves of comparative examples 3-4 and examples 5-8 are shown in FIG. 10 (lower right inset is the fitted circuit diagram). All curves are composed of a high-frequency area semicircle and a low-frequency area long tail. And fitting the circuit diagram and corresponding physical elements with the LLZTO/MgO composite ceramic sample. For pure LLZTO samples, comparative examples 3-4 were similar in impedance spectrum curve shape to examples 5-8. The conductivity of the electrolyte ceramic was calculated taking Rb + Rgb as the total resistance value. The conductivity and density of the sample are shown in fig. 11. Unlike composite ceramics, the conductivity and density of the pure LLZTO sample in comparative example 3 are simultaneously low, which is related to the relatively poor grain boundary bonding of the sample in the cross-sectional view. Examples 5-8, which were sintered in a two-step process, exhibited higher densification and electrical conductivity. The cross-sectional structure, conductivity and density analysis were combined and the samples of examples 5 and 6, i.e. the samples with shorter holding times in the high temperature section (10 and 20 minutes) were optimized. The performance characterization results of comparative examples 3-4 and examples 5-8 show that the two-step sintering method is helpful for improving the compactness and the conductivity of the high-purity LLZTO and optimizing the section microstructure, and is a universal sintering method.
TABLE 1 Performance parameters of the samples of comparative examples 1-2 and examples 1-4
From the foregoing, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. The embodiments described above are exemplary only, and should not be taken as limiting the scope of the invention, which is defined by the following claims.
Claims (17)
1. A method for producing a dense solid electrolyte material, the method comprising:
providing solid electrolyte material powder;
forming the solid electrolyte material powder into a solid electrolyte material biscuit;
sintering the solid electrolyte material biscuit to obtain a compact solid electrolyte material,
wherein the sintering comprises in sequence:
at least one high-temperature heating process, and
at least one low-temperature heating process is carried out,
wherein the heating temperature in the high-temperature heating procedure is 1200 ℃ to 1400 ℃, the heating temperature in the low-temperature heating procedure is 950 ℃ to 1180 ℃,
wherein the low temperature heating time is longer than the high temperature heating time,
wherein the solid electrolyte material has a general formula of Li7-xLa3(Zr2-x,Mx)O12/SA, where M is selected fromOne or more selected from Al, Ga, In, Si, Ge, Sn, Sb, Bi, Sc, Y, Ti, Hf, V, Nb and Ta; SA is not present, or SA is selected from MgO, CaO, ZrO2And HfO2One or more of; 0<x<1。
2. The method of claim 1, wherein M is Ta and x is 0.6.
3. The method of claim 1, wherein SA is MgO.
4. The method of any one of claims 1-3, wherein the solid electrolyte material has a garnet crystal structure.
5. The method according to any one of claims 1 to 3, wherein the heating temperature in the high-temperature heating process is 1200 ℃ to 1300 ℃.
6. A method according to any one of claims 1 to 3, wherein the heating temperature in the high-temperature heating process is 1250 ℃ to 1280 ℃.
7. The method according to any one of claims 1 to 3, wherein the heating temperature in the low-temperature heating process is 1000 ℃ to 1180 ℃.
8. The method as set forth in any one of claims 1 to 3, wherein the heating temperature in the low-temperature heating process is 1150 ℃ to 1180 ℃.
9. A process according to any one of claims 1 to 3 wherein the elevated temperature heating time is from 1 to 120 minutes.
10. A process according to any one of claims 1 to 3 wherein the elevated temperature heating time is from 2 to 100 minutes.
11. A process according to any one of claims 1 to 3 wherein the elevated temperature heating time is from 5 to 90 minutes.
12. A process according to any one of claims 1 to 3 wherein the elevated temperature heating time is from 10 to 80 minutes.
13. A process according to any one of claims 1 to 3 wherein the low temperature heating time is from 2.5 to 7.5 hours.
14. A process according to any one of claims 1 to 3 wherein the low temperature heating time is from 3 to 6 hours.
15. A process according to any one of claims 1 to 3 wherein the low temperature heating time is from 3.5 to 5.5 hours.
16. A process according to any one of claims 1 to 3 wherein the low temperature heating time is from 4 to 5 hours.
17. A solid electrolyte material prepared by the method of any one of claims 1-16, wherein the solid electrolyte material has a density of greater than 4.0 x 10-4Electrical conductivity of S/cm, compactness higher than 97%, and bending strength greater than 140 MPa.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710433799.7A CN109037759B (en) | 2017-06-09 | 2017-06-09 | Sintering method for preparing compact garnet-type lithium ion solid electrolyte |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710433799.7A CN109037759B (en) | 2017-06-09 | 2017-06-09 | Sintering method for preparing compact garnet-type lithium ion solid electrolyte |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109037759A CN109037759A (en) | 2018-12-18 |
| CN109037759B true CN109037759B (en) | 2021-03-02 |
Family
ID=64629815
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201710433799.7A Active CN109037759B (en) | 2017-06-09 | 2017-06-09 | Sintering method for preparing compact garnet-type lithium ion solid electrolyte |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109037759B (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109935901A (en) * | 2019-03-25 | 2019-06-25 | 武汉理工大学 | A kind of Nb, Ta are co-doped with carbuncle type LLZO solid electrolyte and preparation method thereof |
| CN110224146B (en) * | 2019-05-23 | 2021-02-26 | 湖北大学 | Low-temperature online densification method for fuel cell electrolyte |
| CN110311172B (en) * | 2019-06-04 | 2022-10-14 | 上海应用技术大学 | Preparation method and application of LiCuLaZrO solid electrolyte |
| CN111326787A (en) * | 2020-02-19 | 2020-06-23 | 北京化工大学 | Mixed ion-electron conductor of garnet structure and application thereof in energy storage device |
| CN113548893B (en) * | 2020-04-23 | 2022-08-09 | 中国科学院上海硅酸盐研究所 | Lithium garnet composite ceramic electrolyte |
| CN111795984B (en) * | 2020-06-22 | 2022-05-10 | 中国科学院上海硅酸盐研究所 | Sample preparation method for observing microstructure inside ceramic by scanning electron microscope |
| DE102020209708A1 (en) | 2020-07-31 | 2022-02-03 | Schott Ag | Mixture of sintering aids, solid-state ion conductors and method for producing solid-state ion conductors |
| US20220045355A1 (en) * | 2020-08-10 | 2022-02-10 | Corning Incorporated | Garnet-mgo composite thin membrane and method of making |
| CN113346127B (en) * | 2021-05-31 | 2022-08-30 | 东风汽车集团股份有限公司 | NASICON type lithium ion solid electrolyte, preparation method and battery |
| CN113402271B (en) * | 2021-06-04 | 2022-04-29 | 哈尔滨工业大学 | Method for improving density and conductivity of tantalum-doped garnet-type solid electrolyte |
| CN114243004A (en) * | 2021-12-13 | 2022-03-25 | 西安交通大学 | Garnet type solid electrolyte capable of effectively inhibiting lithium dendrites and preparation method thereof |
| CN114497714B (en) * | 2022-02-21 | 2023-11-17 | 西安交通大学 | Preparation method of garnet type solid electrolyte with high ion conductivity |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101394123B1 (en) * | 2012-06-26 | 2014-05-15 | 한국기계연구원 | Oxide solid electrolyte, method for manufacturing of the same and all-solid-state secondary battery using the same |
| CN104124467B (en) * | 2014-07-22 | 2016-06-01 | 武汉理工大学 | A kind of method utilizing lithium lanthanum zirconium oxygen presoma coated powder to prepare solid electrolyte |
| CN104143661B (en) * | 2014-07-31 | 2016-08-24 | 南京工业大学 | A kind of high intensity beta-Al2o3method for preparing solid electrolyte |
-
2017
- 2017-06-09 CN CN201710433799.7A patent/CN109037759B/en active Active
Non-Patent Citations (1)
| Title |
|---|
| 高电导率F掺杂Li7La3Zr2O12石榴石结构固体电解质;刘才 等;《无机材料学报》;20150610;第30卷(第9期);全文 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109037759A (en) | 2018-12-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109037759B (en) | Sintering method for preparing compact garnet-type lithium ion solid electrolyte | |
| Huang et al. | Two-step sintering strategy to prepare dense Li-Garnet electrolyte ceramics with high Li+ conductivity | |
| Cheng et al. | Effect of microstructure and surface impurity segregation on the electrical and electrochemical properties of dense Al-substituted Li 7 La 3 Zr 2 O 12 | |
| JP7294371B2 (en) | Spinel material powder, interconnector protective film, and manufacturing method of spinel material powder | |
| KR101592752B1 (en) | Garnet powder, manufacturing method thereof, solid electrolyte sheet using hot-press and manufacturing method thereof | |
| CN112088409B (en) | Ion conductor and power storage device | |
| CN111116198A (en) | LLZO inorganic oxide solid electrolyte doped with solid solution and preparation method thereof | |
| CN112467198B (en) | Oxide solid electrolyte for lithium ion battery and preparation method thereof | |
| CN108793987B (en) | Lithium ion conductive oxide solid electrolyte and preparation method thereof | |
| CN109626996A (en) | A kind of ferro-aluminum codope carbuncle type Li7La3Zr2O12Lithium Ionic Conducting Materials and preparation method thereof | |
| Duran et al. | Processing and characterisation of a fine nickel oxide/zirconia/composite prepared by polymeric complex solution synthesis | |
| US6709628B2 (en) | Process for the production of sintered ceramic oxide | |
| CN108794001B (en) | Modified ZrO2Preparation method of base solid composite electrolyte ceramic material | |
| INAGUMA et al. | Lithium ion conductivity in a perovskite lanthanum lithium titanate single crystal | |
| CN114249593A (en) | High-entropy perovskite structure cathode material and preparation method and application thereof | |
| CN110128140A (en) | A kind of ytterbium aluminium codope carbuncle type Li7La3Zr2O12Lithium Ionic Conducting Materials and preparation method thereof | |
| Wu et al. | Fabrication and characterization of Ca2+, Sr2+, Ba2+, Sm3+, and La3+ co-doped ceria-based electrolyte powders for low-temperature anode-supported solid oxide fuel cells | |
| Zhang et al. | Improvement of ionic conductivity and densification of Na3Zr2Si2PO12 solid electrolyte rapidly prepared by microwave sintering | |
| KR101537067B1 (en) | Solid electrolyte for all solid state rechargeable lithium battery, method for preparing the same, and all solid state rechargeable lithium battery including the same | |
| Gao et al. | Electrical properties of garnet-like lithium ionic conductors Li 5+ x Sr x La 3− x Bi 2 O 12 fabricated by spark plasma sintering method | |
| CN114315345B (en) | High-temperature piezoelectric energy collection ceramic material with wide-temperature stable transduction coefficient and preparation method thereof | |
| US20190165414A1 (en) | Methods for lowering the hot-pressing temperatures of garnet structured ionic conductors | |
| CN103011803A (en) | Leadless ceramic with high thermoelectric effect and preparation method thereof | |
| Butee et al. | Electrical properties of sodium beta-alumina ceramics synthesized by citrate sol-gel route using glycerine | |
| KR102206961B1 (en) | Solid electrolyte, method for manufacturing the same, and all solid state rechargeable lithium battery including the same |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |