CN115036564A - Surface-coated modified lithium lanthanum zirconium-based solid electrolyte material and preparation method and application thereof - Google Patents

Surface-coated modified lithium lanthanum zirconium-based solid electrolyte material and preparation method and application thereof Download PDF

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CN115036564A
CN115036564A CN202210724608.3A CN202210724608A CN115036564A CN 115036564 A CN115036564 A CN 115036564A CN 202210724608 A CN202210724608 A CN 202210724608A CN 115036564 A CN115036564 A CN 115036564A
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solid electrolyte
based solid
llzo
lanthanum zirconium
coating
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殷裕鑫
冯道言
刘继康
蒋苗
孔霞
李慧皓
王超
肖旋
叶超
张攀
周达
严旭丰
刘瑞
李琮熙
孙辉
刘相烈
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Ningbo Ronbay Lithium Battery Material Co Ltd
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Ningbo Ronbay Lithium Battery Material Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M2300/0085—Immobilising or gelification of electrolyte
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Abstract

The invention provides a surface-coated modified lithium lanthanum zirconium-based solid electrolyte material, which comprises the following components in percentage by weight: an inner core comprising an LLZO-based solid state electrolyte; a coating layer coated on the surface of the core, the coating layer comprising: a non-oxide containing lithium; in addition, the residual alkali content of the surface-coated modified lithium lanthanum zirconium-based solid electrolyte material is 100-10000 ppm. The surface-coated and modified LLZO-based solid electrolyte provided by the invention can avoid the side reaction of the lithium carbonate inert layer. The invention fully utilizes the original residual lithium hydroxide on the surface of the LLZO-based solid electrolyte particles to carry out the coating reaction of acid-base neutralization, can effectively consume the residual alkali on the surface, and avoids the problems of polymer gelation and discoloration, difficult homogenization and the like caused by high residual alkali on the surface when the LLZO material is used in a solid battery. The invention also provides a preparation method and application of the surface coating modified lithium lanthanum zirconium-based solid electrolyte material.

Description

Surface-coated modified lithium lanthanum zirconium-based solid electrolyte material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of electrolyte materials, and particularly relates to a surface-coated modified lithium lanthanum zirconium-based solid electrolyte material, and a preparation method and application thereof.
Background
The use of solid electrolytes instead of conventional flammable organic liquid electrolytes is considered to be a necessary solution to the safety problem of lithium batteries. The oxide electrolyte, especially the garnet-type lithium lanthanum zirconium-based oxide electrolyte (LLZO), has the advantages of high conductivity, simple preparation process, relatively low price and the like, is a solid electrolyte which is researched more at present, however, the problems of high residual alkali and instability to air interface exist on the surface of the lithium lanthanum zirconium-based solid electrolyte, and the practical application of the material is influenced.
At present, the improvement technical means aiming at the surface instability of the lithium lanthanum zirconium-based solid electrolyte mainly adopts a coating method: coating the LLZO surface with an inert substance that is non-reactive with carbon dioxide, such as Al 2 O 3 、TiO 2 And the coating of these materials having no lithium ion conductivity lowers the conductivity. In addition, the coating method is to synthesize some fast ion conductors in situ on the surface of the LLZO electrolyte, which can not only achieve the coating effect, but also promote the interface lithium ion conduction. However, the coating method mostly adopts a chemical vapor deposition method, a sol-gel method, and the like, and large-scale industrial application is difficult to realize.
Therefore, how to modify the surface of the LLZO by coating can not only improve the stability of the particle interface to air without affecting the conduction of the lithium ion interface, but also can be easily enlarged for industrial application, and is a problem to be solved in the field.
Disclosure of Invention
In view of the above, the present invention provides a surface-coated modified lithium lanthanum zirconium based solid electrolyte material, and a preparation method and an application thereof, and the present invention provides a dry-process high-temperature solid phase coating technique which is simple and easy to industrially amplify to modify the surface of Lithium Lanthanum Zirconium Oxygen (LLZO) based solid electrolyte particles, so as to solve the problems of high residual alkali on the surface of the existing LLZO based solid electrolyte and unstable and easy generation of lithium carbonate in the air, and significantly improve the interfacial lithium ion conductivity.
The invention provides a surface-coated modified lithium lanthanum zirconium-based solid electrolyte material, which comprises the following components in percentage by weight:
an inner core comprising an LLZO-based solid state electrolyte;
a coating layer coated on the surface of the core, the coating layer comprising: a non-oxide containing lithium;
the residual alkali content of the surface-coated modified lithium lanthanum zirconium-based solid electrolyte material is 100-10000 ppm.
Preferably, the particle size of the LLZO-based solid electrolyte is 50 nm to 200 μm.
Preferably, the LLZO-based solid electrolyte is selected from one or more of undoped LLZO electrolyte and doped LLZO electrolyte;
the undoped LLZO electrolyte has a chemical formula of: li 7 La 3 Zr 2 O 12 ；
The doped LLZO electrolyte comprises a doping element selected from one or more of Ta, Ca, Al, Ba, W, Mo, Nb, Sr, Ce, Mg, Ga, Ti, Y, V and Si.
Preferably, the particle size of the lithium-containing non-oxide is 1 nm to 50 μm.
Preferably, the lithium-containing non-oxide is selected from LiBO 2 、Li 2 B 4 O 7 、Li 2 MoO 4 、Li 3 PO 4 〃12MoO 3 、Li 3 [P(W 3 O 10 )] 4 And Li 2 WO 4 One or more of them.
The invention provides a preparation method of a surface-coated modified lithium lanthanum zirconium-based solid electrolyte material, which comprises the following steps:
mixing the LLZO-based solid electrolyte and a solid acid to obtain a mixture;
and carrying out heat treatment on the mixture to obtain the surface-coated modified lithium lanthanum zirconium-based solid electrolyte material.
Preferably, the solid acid is one or more selected from boric acid, molybdic acid, phosphomolybdic acid, phosphotungstic acid and tungstic acid.
Preferably, the number of moles of hydrogen ions in the solid acid is 30 to 300% of the number of moles of hydroxyl groups in the LLZO-based solid state electrolyte.
Preferably, the temperature of the heat treatment is 80-650 ℃, and the time is 1-20 h.
The present invention provides a lithium battery including: the surface-coated modified lithium lanthanum zirconium-based solid electrolyte material described in the above technical scheme, or the surface-coated modified lithium lanthanum zirconium-based solid electrolyte material prepared by the method described in the above technical scheme.
The surface-coated and modified LLZO-based solid electrolyte provided by the invention has stable property to air, and can avoid the side reaction that the surface of the original LLZO-based solid electrolyte particles is in contact reaction with carbon dioxide and water in the air to generate a lithium carbonate inert layer. According to the coating modified LLZO solid electrolyte provided by the invention, the coating layer is some lithium-containing fast ion conductor compounds, such as lithium metaborate, lithium pyroborate, lithium molybdate and the like, so that the lithium ion conduction capability among particle interfaces can be improved, and the overall lithium ion conductivity of the LLZO-based electrolyte can be further effectively improved. The invention fully utilizes the original residual lithium hydroxide on the surface of the LLZO-based solid electrolyte particle to carry out the coating reaction of acid-base neutralization, can effectively consume the residual alkali on the surface, and avoids the problems of polymer (binder) gelation and discoloration, difficult homogenization and the like caused by high residual alkali on the surface when the LLZO material is used in a solid battery. Particularly, compared with the prior art, the method adopts the common materials and mature process in the ternary cathode material coating modification technology, is very simple and feasible in technology, is convenient for industrial amplification, and has very high practical value.
Drawings
FIG. 1 is a scanning electron microscope image of a surface-coated modified solid electrolyte prepared in example 1 of the present invention;
FIG. 2 is a scanning electron microscope image of a surface-coated modified solid electrolyte prepared in example 2 of the present invention;
FIG. 3 is a graph showing an X-ray energy spectrum analysis of a surface-coating-modified solid electrolyte prepared in example 2 of the present invention;
fig. 4 is an XRD pattern of the surface-coating-modified solid electrolyte prepared in example 2 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a surface-coated modified lithium lanthanum zirconium-based solid electrolyte material, which comprises the following components in percentage by weight:
an inner core comprising an LLZO-based solid state electrolyte;
a coating layer coated on the surface of the core, the coating layer comprising: a non-oxide containing lithium;
the residual alkali content of the surface-coated modified lithium lanthanum zirconium-based solid electrolyte material is 100-10000 ppm.
In humid air for 10 days, the conductivity of the lithium lanthanum zirconium-based solid electrolyte material with the modified surface coating is improved by more than 30 percent compared with the conductivity of the lithium lanthanum zirconium-based solid electrolyte material without the surface coating; in humid air for 20 days, the conductivity of the lithium lanthanum zirconium-based solid electrolyte material with the surface coated and modified provided by the invention is improved by more than 50 percent compared with the conductivity of the lithium lanthanum zirconium-based solid electrolyte material without the surface coated; in humid air for 30 days, the conductivity of the lithium lanthanum zirconium-based solid electrolyte material with the surface coated and modified provided by the invention is improved by more than 80 percent compared with the conductivity of the lithium lanthanum zirconium-based solid electrolyte material without the surface coated.
In the present invention, the surface-coating-modified lithium lanthanum zirconium-based solid electrolyte material may be an LLZO-based solid electrolyte powder or an electrolyte sheet.
In the present invention, the particle size of the LLZO-based solid electrolyte is preferably 50 nm to 200 μm, more preferably 50 nm to 150 μm, more preferably 50 nm to 100 μm, more preferably 50 nm to 50 μm, more preferably 50 nm to 10 μm, and most preferably 50 nm to 2 μm.
In the present invention, the LLZO-based solid electrolyte may be one or more of an undoped LLZO electrolyte and a doped LLZO electrolyte.
In the present invention, the chemical formula of the undoped LLZO electrolyte is preferably: li 7 La 3 Zr 2 O 12 。
In the present invention, the doping element in the doped LLZO electrolyte is preferably selected from one or more of Ta, Ca, Al, Ba, W, Mo, Nb, Sr, Ce, Mg, Ga, Ti, Y, V and Si, and more preferably from one or more of Ta, Al, Nb and Mg.
In the present invention, the LLZO-based solid electrolyte is more preferably composed of: li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 。
The source of the LLZO-based solid electrolyte is not particularly limited in the present invention, and the LLZO-based solid electrolyte can be prepared by a method well known in the art, such as a high temperature solid phase synthesis method, and preferably comprises:
mixing a lithium-containing compound, a lanthanum-containing compound, a zirconium-containing compound and a tantalum-containing compound to obtain a mixture;
and sequentially carrying out primary sintering and secondary sintering on the mixture to obtain the coated and modified lithium lanthanum zirconium-based LLZTO solid electrolyte.
In the present invention, the lithium-containing compound is preferably lithium hydroxide monohydrate; the lanthanum containing compound is preferably selected from lanthanum hydroxide or lanthanum oxide; the zirconium-containing compound is preferably zirconium dioxide; the tantalum-containing compound is preferably tantalum pentoxide.
In the present invention, the lithium-containing compound, the lanthanum-containing compound, the zirconium-containing compound, and the tantalum-containing compound are preferably used in an amount corresponding to a stoichiometric ratio of the components to be obtained, wherein the lithium-containing compound is preferably used in an excess amount of 10 to 15%, more preferably 12 to 13%.
In the present invention, the method of mixing preferably includes ball milling and tumbling.
In the present invention, the sintering is preferably carried out in a saggar of corundum.
In the invention, the temperature of the primary sintering is preferably 850-950 ℃, more preferably 880-920 ℃, and most preferably 900 ℃; the time for the primary sintering is preferably 10 to 12 hours, and more preferably 11 hours. In the invention, the temperature of the secondary sintering is preferably 1050-1200 ℃, more preferably 1100-1150 ℃, and most preferably 1120-1130 ℃; the time for the secondary sintering is preferably 3 to 5 hours, and more preferably 4 hours. In the invention, the independent heating rate of the primary sintering and the secondary sintering is preferably 2-4 ℃/min, and more preferably 3 ℃/min.
In the present invention, the particle size of the lithium-containing non-oxide is preferably 1 nm to 50 μm, more preferably 1 nm to 10 μm, more preferably 1 nm to 3 μm, and most preferably 1 nm to 1 μm.
In the present invention, the lithium-containing non-oxide is preferably selected from LiBO 2 、Li 2 B4O 7 、Li 2 MoO 4 、Li 3 PO 4 〃12MoO 3 、Li 3 [P(W 3 O 10 )] 4 And Li 2 WO 4 One or more of them.
In the present invention, the coating layer may be one or more of a continuous coating layer, a discontinuous coating layer, a particle coating layer, and an island coating layer.
The surface-coated and modified LLZO-based solid electrolyte provided by the invention has the property of being relatively stable to air; meanwhile, the LLZO particle interfaces are covered by a layer of lithium-containing fast ion conductor, so that the conduction capability of interface lithium ions is improved; meanwhile, residual alkali on the surface of the LLZO particles is reduced, so that the application of the LLZO particles in a solid-state battery is facilitated; meanwhile, the process method based on the ternary anode coating technology is very simple and is easy to realize large-scale application.
The invention provides a preparation method of a surface-coated modified lithium lanthanum zirconium-based solid electrolyte material, which comprises the following steps:
mixing the LLZO-based solid electrolyte and a solid acid to obtain a mixture;
and carrying out heat treatment on the mixture to obtain the surface-coated modified lithium lanthanum zirconium-based solid electrolyte material.
In the invention, the coating layer is coated by utilizing the in-situ neutralization reaction of residual alkali LiOH on the surface of the LLZO particles and corresponding solid acid.
In the present invention, the LLZO-based solid electrolyte is preferably an LLZO-based solid electrolyte powder; preferably, the LiOH content of the surface of the LLZO-based solid electrolyte is detected, and the residual alkali OH on the surface of the LLZO-based solid electrolyte is preferably tested by an automatic potentiometric titrator - 。
In the present invention, the solid acid is preferably solid acid particles; the solid acid is preferably one or more selected from boric acid, molybdic acid, phosphomolybdic acid, phosphotungstic acid and tungstic acid.
In the invention, the mole number of the hydrogen ions capable of being ionized in the solid acid is preferably 30-300%, more preferably 70-150%, and most preferably 80-100% of the mole number of the hydroxyl in the LLZO-based solid electrolyte; according to the invention, according to the measured LiOH content of the surface of the LLZO-based solid electrolyte, the corresponding solid acid substances are mixed according to the proportion according to the principle of acid-base neutralization.
In the present invention, the mixing is preferably one or more of mechanical ball milling, high-speed mixer mixing and coulter mixing.
In the invention, the mechanical ball milling is preferably dry milling, no liquid solvent is added, the ball milling beads are preferably zirconia, the ball-to-material ratio is preferably (6-1): 1, and more preferably (2-4): 1, most preferably 2: 1; the ball milling temperature is preferably lower than 80 ℃; the ball milling speed is preferably 200-2000 r/min, more preferably 500-1500 r/min, more preferably 500-1000 r/min, and most preferably 500-600 r/min; the ball milling time is preferably 3 to 18 hours, more preferably 5 to 15 hours, more preferably 8 to 12 hours, and most preferably 10 to 12 hours.
In the invention, the rotating speed of the main shaft mixed by the high-speed mixer is preferably 600-1500 revolutions per minute, more preferably 800-1200 revolutions per minute, more preferably 900-1000 revolutions per minute, and most preferably 950 revolutions per minute; the mixing time is preferably 10 to 60 minutes, more preferably 20 to 50 minutes, and most preferably 40 to 50 minutes.
In the present invention, it is preferable that the mixture is charged into a sagger and placed in a kiln for heat treatment; the temperature of the heat treatment is preferably 80-650 ℃, more preferably 100-600 ℃, more preferably 250-600 ℃, and most preferably 300-400 ℃; the time of the heat treatment is preferably 1-20 h, more preferably 2-15 h, more preferably 2-12 h, and most preferably 2-5 h.
In the present invention, a gas is preferably introduced during the heat treatment to carry away gases such as water vapor generated by the reaction, and the introduced gas is preferably air.
In the present invention, the coating agent formed in the coating layer obtained after the heat treatment is a coating agent of a common ternary positive electrode material, and the coating agent may be lithium metaborate, lithium pyroborate, lithium molybdate, or the like, depending on the component of the solid acid used.
The present invention provides a lithium battery including: the surface-coated modified lithium lanthanum zirconium-based solid electrolyte material described in the above technical scheme, or the surface-coated modified lithium lanthanum zirconium-based solid electrolyte material prepared by the method described in the above technical scheme.
The surface-coated and modified LLZO-based solid electrolyte provided by the invention has stable property to air, and can avoid the side reaction that the surface of the original LLZO-based solid electrolyte particles is in contact reaction with carbon dioxide and water in the air to generate a lithium carbonate inert layer. According to the coated and modified LLZO solid electrolyte provided by the invention, the coating layer is some lithium-containing fast ion conductor compounds, such as lithium metaborate, lithium pyroborate, lithium molybdate and the like, so that the lithium ion conductivity between particle interfaces can be improved, and further the overall lithium ion conductivity of the LLZO-based electrolyte is effectively improved. The invention fully utilizes the original residual lithium hydroxide on the surface of the LLZO-based solid electrolyte particle to carry out the coating reaction of acid-base neutralization, can effectively consume the residual alkali on the surface, and avoids the problems of polymer (binder) gelation and discoloration, difficult homogenization and the like caused by high residual alkali on the surface when the LLZO material is used in a solid battery. Particularly, compared with the prior art, the method adopts the common materials and mature process in the ternary cathode material coating modification technology, is very simple and feasible in technology, is convenient for industrial amplification, and has very high practical value.
The LLZTO solid electrolyte used in the following embodiment of the invention is synthesized and prepared by an autonomous high temperature solid phase method, and the specific method comprises the following steps:
weighing lithium hydroxide monohydrate, lanthanum hydroxide, zirconium dioxide and tantalum pentoxide according to a stoichiometric ratio, performing ball milling and rolling to uniformly mix the materials, wherein the lithium hydroxide monohydrate is excessive by 12%;
sintering the obtained mixture twice in a sagger made of corundum materials, wherein the temperature of the first sintering is 900 ℃, and the time is 11 hours; the secondary sintering temperature is 1150 ℃ and the time is 4 hours; the heating rate of the primary sintering and the secondary sintering is 3 ℃/min, and the base material coated with the modified lithium lanthanum zirconium base LLZTO solid electrolyte is obtained.
Example 1
50g of LLZTO (Li) are weighed 6.5 La 3 Zr 1.5 Ta 0.5 O 12 ) Electrolyte powder, measuring residual alkali OH on the surface of the electrolyte powder by using an automatic potentiometric titrator - About 25000ppm, 4.56g of boric acid was added, calculated on a 100% acid-base neutralized stoichiometric basis.
Mixing 50g of LLZTO powder with 4.56g of boric acid powder, adding ball milling beads according to the ball milling ratio of 2:1, wherein the ball milling speed is 500 r/min, and the ball milling time is 10 hours to obtain a mixture.
And (3) annealing the mixture at the temperature of 300 ℃ for 5 hours in the atmosphere of air to obtain the coated solid electrolyte.
The LLZTO solid electrolyte after coating modification is characterized by methods such as XRD, EDS, SEM, potentiometric titration residual alkali and the like, an electron microscope (SEM) result shows an obvious island-shaped uniform coating effect, and the modified LLZTO solid electrolyte can be considered to obtain a uniform island-shaped core-shell coating layer structure by combining a residual alkali test result. The results of XRD tests showed that the solid electrolyte prepared in example 1 of the present invention has a lithium lanthanum zirconium based LLZTO solid electrolyte as the core component, and the LiBO having an amorphous phase as the main component of the coating layer coated on the surface of the core 2 。
LLZTO @ LiBO prepared in example 1 of the invention 2 The morphology of the solid electrolyte is shown in FIG. 1, and it can be seen that compared with the original bare sample, LLZTO @ LiBO 2 The surface becomes rougher with a distinct island-like coating structure.
Comparative example 1
Weighing 54.56g of LLZTO electrolyte, and performing ball milling and mixing: adding ball milling beads in a ball-material ratio of 2:1, wherein the ball milling speed is 500 r/min, and the ball milling time is 10 hours.
And annealing the obtained mixed material at the temperature of 300 ℃ for 5 hours in the atmosphere of air to obtain an electrolyte product.
The electrolyte products prepared in example 1 and comparative example 1 were simultaneously placed in a humid atmosphere for 1 month; then preparing an electrolyte sheet by adopting a hot-pressing sintering method, filling the electrolyte into a die, compacting the electrolyte into a sheet by using a tablet machine, and then sintering the sheet in an air atmosphere at 1050 ℃ for 3 hours; after sintering, cutting and polishing the obtained electrolyte sheet into a wafer with the diameter of 10mm and the thickness of 1 mm; plating silver electrodes on two sides of the LLZTO electrolyte sheet by using a magnetron sputtering technology, testing the residual alkali content and the conductivity of the LLZTO electrolyte sheet, and measuring the residual alkali content by using an automatic potentiometric titrator. The detection method of the conductivity comprises the following steps: and (3) accessing the LLZTO ceramic wafer obtained above to an electrochemical workstation for impedance test to obtain an impedance value R, and substituting the impedance value R into a formula: and rho is RS/L, wherein S is the area of the wafer, and L is the thickness of the wafer.
The detection results are as follows:
sample (I) Residual alkali OH -1 (ppm) 10 days (S cm) -1 ) 20 days (S cm) -1 ) 30 days (S cm) -1 )
Example 1 834 7.98×10 -4 7.73×10 -4 7.45×10 -4
Comparative example 1 24532 4.38×10 -4 2.18×10 -4 0.994×10 -4
LLZTO@LiBO 2 The electrolytes prepared in example 1 had conductivities of 7.98 × 10, respectively -4 Scm -1 、7.73×10 - 4 Scm -1 、7.45×10 -4 Scm -1 (ii) a The advantage of the electrolyte is obviously better than that of comparative example 1, which shows that the LLZTO electrolyte with the modified surface coating has better stability to air; meanwhile, the test result of the coated residual alkali also shows a smaller numerical value; LLZTO @ LiBO 2 Has lower residual alkali, higher air stability and ionic conductivity.
Example 2
50g of LLZTO (Li) are weighed 6.5 La 3 Zr 1.5 Ta 0.5 O 12 ) The electrolyte powder had a residual alkali OH-content of about 25000ppm on the surface thereof as measured by an automatic potentiometric titrator, and the amount of molybdic acid to be added was calculated to be 5.95g in terms of the stoichiometric amount for 100% acid-base neutralization.
50g of LLZTO powder was mixed with 5.95g of molybdic acid powder in a ball mill ratio of 2:1 adding ball milling beads, wherein the ball milling rotating speed is 500 r/min, and the ball milling time is 10 hours to obtain a mixture.
And annealing the mixture at 300 ℃ for 5 hours in the atmosphere of air to obtain the coated solid electrolyte.
The solid electrolyte prepared in example 2 of the present invention was tested according to the method of example 1, and as a result, the solid electrolyte prepared in example 2 of the present invention had a lithium lanthanum zirconium based LLZTO solid electrolyte as a core component and lithium molybdate (Li) as a coating component coated on the surface of the core 2 MoO 4 )。
LLZTO @ Li prepared in example 2 of the invention 2 MoO 4 The morphology of the solid electrolyte is shown in FIG. 2. from FIG. 2, it can be seen that LLZTO @ Li is compared with the original bare sample 2 MoO 4 The surface becomes rougher with a distinct island-like coating structure. X-ray energy spectrum analysis (EDS) and XRD detection As shown in FIGS. 3 and 4, it was confirmed that the material surface had a molybdenum coating layer, molybdenum was detected in EDS, and Li was directly detected in XRD 2 MoO 4 。
Comparative example 2
Weighing 55.95g of LLZTO electrolyte, ball-milling and mixing, adding ball-milling beads according to the ball-material ratio of 2:1, wherein the ball-milling speed is 500 r/min, and the ball-milling time is 10 hours.
And annealing the obtained mixed material at the temperature of 300 ℃ for 5 hours in the atmosphere of air to obtain an electrolyte product.
The products prepared in example 2 and comparative example 2 of the present invention were tested for alkali residue and conductivity according to the methods of example 1 and comparative example 1, and the results were as follows:
sample(s) Residual alkali OH -1 (ppm) 10 days (S cm) -1 ) 20 days (S cm) -1 ) 30 days (S cm) -1 )
Example 2 918 6.28×10 -4 6.23×10 -4 6.19×10 -4
Comparative example 2 23217 3.31×10 -4 1.81×10 -4 0.771×10 -4
LLZTO @ Li prepared in example 2 2 MoO 4 The electrolyte has a conductivity of 6.28 × 10 -4 Scm -1 、6.23×10 - 4 Scm -1 、6.19×10 -4 Scm -1 (ii) a The surface-coated modified LLZTO electrolyte has better stability to air; meanwhile, the coated residual alkali test result also shows a smaller value; LLZTO @ Li 2 MoO 4 Has lower residual alkali, higher air stability and ionic conductivity.
Example 3
250kg of LLZTO electrolyte powder was weighed out, and the amount of molybdic acid to be added was calculated to be 29.75kg of molybdic acid in a 100% acid-base neutralization stoichiometric ratio.
250kg of LLZTO electrolyte powder and 29.75kg of molybdic acid were mixed in a high mixer at a set rotation speed of 950 rpm for 50 minutes to obtain a mixture.
And (3) annealing the mixture at the temperature of 300 ℃ for 5 hours in a flowing air atmosphere to obtain the coated solid electrolyte.
The solid electrolyte prepared in example 3 of the present invention was tested according to the method of example 1, and as a result, the solid electrolyte prepared in example 3 of the present invention had a lithium lanthanum zirconium based LLZTO solid electrolyte as a core component and lithium molybdate (Li) as a coating component coated on the surface of the core 2 MoO 4 )。
Comparative example 3
279.75kgLLZTO electrolyte powder is weighed and mixed by a high-speed mixer, the set rotating speed is 950 r/min, and the mixing time is 50 min.
And (3) annealing the obtained mixture at the temperature of 300 ℃ for 5 hours in flowing air atmosphere to obtain an electrolyte product.
The products prepared in example 3 and comparative example 3 were subjected to residual alkali and conductivity tests according to the conductivity test methods of example 1 and comparative example 1, and the test results were:
sample (I) Residual alkali OH -1 (ppm) 10 days (S cm) -1 ) 20 days (S cm) -1 ) 30 days (S cm) -1 )
Example 3 1023 7.62×10 -4 7.28×10 -4 7.12×10 -4
Comparative example 3 22981 4.06×10 -4 2.47×10 -4 0.762×10 -4
LLZTO @ Li prepared in example 3 2 MoO 4 The electrolyte has a conductivity of 7.62X 10 -4 Scm -1 、7.28×10 - 4 Scm -1 、7.12×10 -4 Scm -1 (ii) a The advantage of the electrolyte is obviously better than that of comparative example 3, which shows that the LLZTO electrolyte with the modified surface coating has better stability to air; LLZTO @ Li 2 MoO 4 Has lower residual alkali, higher air stability and ionic conductivity.
The surface-coated and modified LLZO-based solid electrolyte provided by the invention has stable property to air, and can avoid the side reaction that the surface of the original LLZO-based solid electrolyte particles is in contact reaction with carbon dioxide and water in the air to generate a lithium carbonate inert layer. According to the coated and modified LLZO solid electrolyte provided by the invention, the coating layer is some lithium-containing fast ion conductor compounds, such as lithium metaborate, lithium pyroborate, lithium molybdate and the like, so that the lithium ion conductivity between particle interfaces can be improved, and further the overall lithium ion conductivity of the LLZO-based electrolyte is effectively improved. The invention fully utilizes the original residual lithium hydroxide on the surface of the LLZO-based solid electrolyte particle to carry out the coating reaction of acid-base neutralization, can effectively consume the residual alkali on the surface, and avoids the problems of polymer (binder) gelation and discoloration, difficult homogenization and the like caused by high residual alkali on the surface when the LLZO material is used in a solid battery. Especially, compared with the prior art, the invention adopts the materials and mature processes commonly used in the ternary cathode material coating modification technology, is very simple and feasible in technology, is convenient for industrial amplification, and has very strong practical value.
While the invention has been described and illustrated with reference to specific embodiments thereof, such description and illustration are not intended to limit the invention. It will be clearly understood by those skilled in the art that various changes in form and details may be made therein without departing from the true spirit and scope of the invention as defined by the appended claims, to adapt a particular situation, material, composition of matter, substance, method or process to the objective, spirit and scope of this application. All such modifications are intended to be within the scope of the claims appended hereto. Although the methods disclosed herein have been described with reference to particular operations performed in a particular order, it should be understood that these operations may be combined, sub-divided, or reordered to form equivalent methods without departing from the teachings of the present disclosure. Accordingly, unless specifically indicated herein, the order and grouping of the operations is not a limitation of the present application.

Claims (10)

1. A surface-coating modified lithium lanthanum zirconium-based solid electrolyte material comprises:
an inner core comprising an LLZO-based solid state electrolyte;
a coating layer coated on the surface of the core, the coating layer comprising: a non-oxide containing lithium;
the residual alkali content of the surface-coated modified lithium lanthanum zirconium-based solid electrolyte material is 100-10000 ppm.
2. The surface coating modified lithium lanthanum zirconium based solid electrolyte material of claim 1, wherein the particle size of the LLZO based solid electrolyte is 50 nanometers to 200 micrometers.
3. The surface coating modified lithium lanthanum zirconium based solid electrolyte material of claim 1, wherein the LLZO based solid electrolyte is selected from one or more of undoped LLZO electrolyte and doped LLZO electrolyte;
the undoped LLZO electrolyte has a chemical formula of: li 7 La 3 Zr 2 O 12 ；
The doped LLZO electrolyte comprises a doping element selected from one or more of Ta, Ca, Al, Ba, W, Mo, Nb, Sr, Ce, Mg, Ga, Ti, Y, V and Si.
4. The surface-coating-modified lithium lanthanum zirconium-based solid electrolyte material according to claim 1, characterized in that the particle size of the lithium-containing non-oxide is 1 nanometer to 50 micrometers.
5. The surface-coating-modified lithium lanthanum zirconium-based solid electrolyte material of claim 1, characterized in that the lithium-containing non-oxide is selected from LiBO 2 、Li 2 B 4 O 7 、Li 2 MoO 4 、Li 3 PO 4 〃12MoO 3 、Li 3 [P(W 3 O 10 )] 4 And Li 2 WO 4 One or more of them.
6. A preparation method of a surface-coated modified lithium lanthanum zirconium-based solid electrolyte material comprises the following steps:
mixing the LLZO-based solid electrolyte and a solid acid to obtain a mixture;
and carrying out heat treatment on the mixture to obtain the lithium lanthanum zirconium-based solid electrolyte material with the surface coated and modified.
7. The method according to claim 6, wherein the solid acid is selected from one or more of boric acid, molybdic acid, phosphomolybdic acid, phosphotungstic acid and tungstic acid.
8. The method according to claim 6, wherein the number of moles of hydrogen ions in the solid acid is 30 to 300% of the number of moles of hydroxyl groups in the LLZO-based solid state electrolyte.
9. The method according to claim 6, wherein the temperature of the heat treatment is 80 to 650 ℃ and the time is 1 to 20 hours.
10. A lithium battery, comprising: the surface-coating-modified lithium lanthanum zirconium-based solid electrolyte material according to any one of claims 1 to 5 or the surface-coating-modified lithium lanthanum zirconium-based solid electrolyte material prepared by the method according to any one of claims 6 to 9.
CN202210724608.3A 2022-06-24 2022-06-24 Surface-coated modified lithium lanthanum zirconium-based solid electrolyte material and preparation method and application thereof Pending CN115036564A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115548428A (en) * 2022-11-30 2022-12-30 中自环保科技股份有限公司 Preparation method of solid electrolyte with lithium carbonate on surface removed by reduced pressure roasting, battery solid electrolyte and solid battery
CN116023134A (en) * 2022-12-27 2023-04-28 合肥国轩高科动力能源有限公司 Lithium lanthanum zirconium oxide material, preparation method thereof, solid electrolyte and solid lithium ion battery

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115548428A (en) * 2022-11-30 2022-12-30 中自环保科技股份有限公司 Preparation method of solid electrolyte with lithium carbonate on surface removed by reduced pressure roasting, battery solid electrolyte and solid battery
CN116023134A (en) * 2022-12-27 2023-04-28 合肥国轩高科动力能源有限公司 Lithium lanthanum zirconium oxide material, preparation method thereof, solid electrolyte and solid lithium ion battery
CN116023134B (en) * 2022-12-27 2024-01-19 合肥国轩高科动力能源有限公司 Lithium lanthanum zirconium oxide material, preparation method thereof, solid electrolyte and solid lithium ion battery

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