CN115763957A - Heterovalent difunctional co-doped garnet type solid electrolyte and preparation method thereof - Google Patents
Heterovalent difunctional co-doped garnet type solid electrolyte and preparation method thereof Download PDFInfo
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Abstract
The invention provides an aliovalent difunctional co-doped garnet type solid electrolyte and a preparation method thereof, wherein the electrolyte material has a chemical general formula of Li 7‑x La 3 Zr 2‑x‑y M x N y O 12 ，0<x≤0.5，0<y is less than or equal to 0.5, the electrolyte material has a cubic phase structure, and M is one of Ta, nb, as, sb and VAll of these elements are represented by M 5+ Formally Zr-position substitution; n is one of Hf, W, sn and Pb, and the elements are N 4+ Formally Zr-position substitution; the ion content of M and N in the solid electrolyte is controlled by regulating and controlling the values of x and y, the synergistic effect of doping of the M element and the N element is promoted, the high compactness of the micro appearance of the prepared solid electrolyte material, no air holes and no microcracks are ensured, the reaction of the prepared garnet solid electrolyte with water and carbon dioxide in the air can be effectively prevented, and the air stability of the solid electrolyte is improved.
Description
Technical Field
The invention relates to the technical field of preparation of all-solid-state electrolyte materials, in particular to an allovalence bifunctional co-doped garnet type solid electrolyte and a preparation method thereof.
Background
Lithium ion batteries play an important role in the storage of renewable energy sources, but the current lithium ion batteries have difficulty in meeting the requirements of large-scale energy storage on energy density, safety and cost. In addition, the narrow electrochemical window of liquid electrolytes in conventional lithium ion batteries limits the application of high voltage cathodes and lithium metal anodes. Compared to conventional lithium ion batteries, all solid-state lithium batteries (ASSLBs) exhibit many outstanding advantages, such as no electrolyte leakage, no thermal runaway, strong resistance to lithium dendrites, and higher energy density, and thus, ASSLBs are considered to be one of the most promising next-generation lithium batteries. The properties of the solid-state electrolyte and its interface with the electrodes are critical to the performance of the all-solid-state battery. High lithium ion conductivity and good stability are fundamental characteristics of a solid electrolyte for an all solid-state lithium ion battery. To date, various room temperature conductivities of greater than 10 have been developed -4 S/cm inorganic solid electrolyte comprising cubic garnet-type Li 7 La 3 Zr 2 O 12 (LLZO), NASICON type LiM 2 (PO 4 ) 3 (M = Ti, ge, zr, hf) and sulfide series. Among these solid electrolytes, cubic phase LLZO is widely studied for its excellent stability to a cathode and a metallic lithium anode.
The LLZO solid electrolyte mainly faces the problems of unstable cubic phase structure, low ionic conductivity and poor stability in air. These problems severely restrict the capacity, rate capability and cycle life of all solid-state lithium batteries, hindering the application of LLZO solid electrolytes. Therefore, how to solve the above problems is a focus of the research on the LLZO solid electrolyte.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, the present invention is directed to solving the problems and providing a heterovalent bifunctional co-doped garnet-type solid electrolyte and a method for preparing the same, wherein the problems of the solid electrolyte include unstable cubic phase structure, low ionic conductivity and poor stability in air. The co-doped solid electrolyte prepared by the method has a more stable cubic phase structure, higher conductivity and more excellent air stability.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a heterovalent difunctional co-doped garnet solid electrolyte is disclosed, wherein the chemical general formula of the electrolyte material is Li 7- x La 3 Zr 2-x-y M x N y O 12 Wherein 0 is<x≤0.5，0<y is less than or equal to 0.5, the electrolyte material has a cubic phase structure, M is one of Ta, nb, as, sb and V, and M is used As the element 5+ Formally Zr-position substitution; n is one of Hf, W, sn and Pb, and the elements are N 4+ Formally Zr-site substitution occurs.
Preferably, by selecting different M 5+ Doping to generate more lithium ion vacancies so as to achieve the aim of stabilizing the cubic phase structure of the garnet solid electrolyte; selecting different N 4+ Doping and widening a lithium ion transmission channel so as to achieve the purpose of improving the ionic conductivity of the garnet solid electrolyte; the ion contents of M and N in the solid electrolyte are controlled by regulating and controlling the values of x and y, the synergistic effect of doping of M element and N element is promoted, the micro-morphology of the prepared solid electrolyte material is ensured to be free of pores and microcracks, the reaction of the prepared garnet type solid electrolyte with water and carbon dioxide in the air is prevented, and the air stability of the solid electrolyte is improved.
Preferably, the crystal structure of the material is a pure cubic phase structure, and the conductivity is 8.1 multiplied by 10 -4 S/cm-1.05×10 -3 And S/cm, the prepared solid electrolyte does not react with water and carbon dioxide in the air to generate lithium carbonate harmful to the electrochemical performance of the solid electrolyte after being exposed in the air for 10-20 days.
The invention also provides a preparation method of the heterovalent bifunctional co-doped garnet type solid electrolyte, which comprises the following raw materials:
a lithium source: one of lithium hydroxide, lithium oxide, lithium carbonate and lithium nitrate;
a lanthanum source: one of lanthanum hydroxide, lanthanum oxide and lanthanum nitrate;
a zirconium source: one of zirconium hydroxide, zirconium oxide and zirconium nitrate;
m source: one of tantalum pentoxide, niobium pentoxide, arsenic pentoxide, antimony pentoxide, and vanadium pentoxide;
n source: one of hafnium oxide, tungsten oxide, tin oxide and lead oxide;
the components of the solid electrolyte material are mixed according to the chemical general formula, and are subjected to first ball milling and mixing, presintering is carried out for 1-6 hours at the temperature of 750-1000 ℃ to obtain presintering powder, and then the presintering powder is subjected to second ball milling and mixing, and is sintered for 1-12 hours at the temperature of 1050-1250 ℃ to obtain the final heterovalent bifunctional co-doped garnet type solid electrolyte material.
Preferably, the preparation method comprises the following steps:
step 1: according to the formula Li 7-x La 3 Zr 2-x-y M x N y O 12 Respectively weighing a lithium source, a lanthanum source, a zirconium source, an M source and an N source according to the metering ratio of the Li, the La, the Zr, the M and the N;
step 2: adopting a wet ball milling process, taking yttrium-stabilized zirconia balls as a ball milling medium, adding a ball milling solvent, and grinding according to a fixed mixture ratio to obtain a uniformly mixed ball milling material A;
and step 3: placing the ball grinding material A obtained in the step 2 in a muffle furnace for presintering to obtain presintering powder B;
and 4, step 4: performing secondary ball milling on the pre-sintered powder B obtained in the step 3 to obtain a secondary ball grinding material C which is uniformly mixed;
and 5: putting the secondary ball grinding material C obtained in the step 4 into a forming die for dry pressing forming to obtain a green body D;
step 6: and (4) placing the green body D obtained in the step (5) in a muffle furnace for sintering to obtain the final heterovalent bifunctional co-doped garnet type solid electrolyte material.
Preferably, in step 2 and step 4, the ball milling solvent is one of alcohol and isopropanol; the ball mill is a high-energy ball mill, the ball milling rotating speed is 200-500r/min, and the ball milling time is 1-10 hours; the fixed mixing ratio is material: ball milling medium: solvent =1: (4-8): (1.5-3.5).
In a preferable mode, in the step 3 and the step 5, the pre-sintering temperature is 750-1000 ℃, the heating rate is 1-5 ℃/min, and the heat preservation time is 1-6 hours; the sintering temperature is 1050-1250 ℃, the heating rate is 5-20 ℃/min, and the heat preservation time is 1-12 hours.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention adopts a heterovalent difunctional co-doping method and selects different M with smaller ionic radius 5+ Doping generates more lithium ion vacancies so as to achieve the aim of stabilizing the cubic phase structure of the garnet-type solid electrolyte.
(2) According to the invention, different N with larger ionic radius is selected by a heterovalent bifunctional co-doping method 4+ Doping widens the lithium ion transmission channel to achieve the purpose of improving the ion conductivity of the garnet solid electrolyte.
(3) In the formula, the ion contents of M and N in the solid electrolyte can be controlled by regulating and controlling the values of x and y, the synergistic effect of doping of the M element and the N element is promoted, the high compactness of the micro-morphology of the prepared solid electrolyte material, no air holes and no microcracks are ensured, the reaction of the prepared garnet solid electrolyte with water and carbon dioxide in the air can be effectively prevented, and the air stability of the solid electrolyte is improved.
Drawings
FIG. 1 shows example 1 (Li) 6.5 La 3 Zr 1.3 Nb 0.5 Pb 0.2 O 12 ) Comparison with comparative example 1 (Li) 7 La 3 Zr 2 O 12 ) X-ray diffraction pattern of solid electrolyte prepared, li prepared in example 1 from the top 6.5 La 3 Zr 1.3 Nb 0.5 Pb 0.2 O 12 Li prepared in comparative example 1 7 La 3 Zr 2 O 12 And the cubic phase standard PDF card #45-0109.
FIG. 2 shows example 2 (Li) 6.5 La 3 Zr 1.4 Ta 0.3 W 0.3 O 12 ) Comparison with comparative example 1 (Li) 7 La 3 Zr 2 O 12 ) And the prepared solid electrolyte has an alternating-current impedance map, wherein the left figure is the alternating-current impedance map of the electrolyte in example 2, and the right figure is the alternating-current impedance map of the electrolyte in comparative example 1.
FIG. 3 shows example 3 (Li) 6.5 La 3 ZrSb 0.5 Sn 0.5 O 12 ) Comparison with comparative example 1 (Li) 7 La 3 Zr 2 O 12 ) The prepared solid electrolyte has a field emission scanning electron microscope image, wherein the left image is the scanning electron microscope image of the electrolyte crystal grains of the example 3, and the right image is the scanning electron microscope image of the electrolyte crystal grains of the comparative example 1.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
The chemical general formula of the allovalence bifunctional co-doped garnet type solid electrolyte provided by the embodiment is Li 7-x La 3 Zr 2-x-y M x N y O 12 Wherein, 0<x≤0.5，0<y is less than or equal to 0.5, the electrolyte material has a cubic phase structure, M is one of Ta, nb, as, sb and V, and M is used As the element 5+ Form generation of ZrA substitution at a position; n is one of Hf, W, sn and Pb, and the elements are N 4+ Formally Zr-site substitution occurs.
By selecting different M 5+ Doping to generate more lithium ion vacancies so as to achieve the aim of stabilizing the cubic phase structure of the garnet solid electrolyte; selecting different N 4+ Doping and widening a lithium ion transmission channel so as to achieve the purpose of improving the ionic conductivity of the garnet solid electrolyte; the ion contents of M and N in the solid electrolyte are controlled by regulating and controlling the values of x and y, the synergistic effect of doping of M element and N element is promoted, the micro-morphology of the prepared solid electrolyte material is ensured to be free of pores and microcracks, the reaction of the prepared garnet type solid electrolyte with water and carbon dioxide in the air is prevented, and the air stability of the solid electrolyte is improved.
The crystal structure of the material is a pure cubic phase structure, and the conductivity is 8.1 multiplied by 10 -4 S/cm-1.05×10 -3 And the prepared solid electrolyte does not react with water and carbon dioxide in the air to generate lithium carbonate harmful to the electrochemical performance of the solid electrolyte after being exposed in the air for 10-20 days.
The preparation method of the heterovalent bifunctional co-doped garnet type solid electrolyte provided by the embodiment comprises the following raw materials:
a lithium source: one of lithium hydroxide, lithium oxide, lithium carbonate and lithium nitrate;
a lanthanum source: one of lanthanum hydroxide, lanthanum oxide and lanthanum nitrate;
a zirconium source: one of zirconium hydroxide, zirconium oxide and zirconium nitrate;
m source: one of tantalum pentoxide, niobium pentoxide, arsenic pentoxide, antimony pentoxide, and vanadium pentoxide;
and N source: one of hafnium dioxide, tungsten dioxide, tin dioxide and lead dioxide;
the components of the solid electrolyte material are mixed according to the chemical general formula, and are subjected to first ball milling and mixing, presintering is carried out for 1-6 hours at the temperature of 750-1000 ℃ to obtain presintering powder, and then the presintering powder is subjected to second ball milling and mixing, and is sintered for 1-12 hours at the temperature of 1050-1250 ℃ to obtain the final heterovalent bifunctional co-doped garnet type solid electrolyte material.
The preparation method comprises the following steps:
step 1: according to the formula Li 7-x La 3 Zr 2-x-y M x N y O 12 Respectively weighing a lithium source, a lanthanum source, a zirconium source, an M source and an N source according to the metering ratio of the Li, the La, the Zr, the M and the N;
step 2: adopting a wet ball milling process, taking yttrium-stabilized zirconia balls as a ball milling medium, adding a ball milling solvent, and grinding according to a fixed mixture ratio to obtain a uniformly mixed ball milling material A;
and step 3: placing the ball grinding material A obtained in the step 2 in a muffle furnace for presintering to obtain presintering powder B;
and 4, step 4: performing secondary ball milling on the pre-sintered powder B obtained in the step 3 to obtain a secondary ball grinding material C which is uniformly mixed;
and 5: putting the secondary ball grinding material C obtained in the step 4 into a forming die for dry pressing forming to obtain a green body D;
step 6: and (5) placing the green body D obtained in the step (5) in a muffle furnace for sintering to obtain the final heterovalent difunctional co-doped garnet type solid electrolyte material.
In the step 2 and the step 4, the ball milling solvent is one of alcohol and isopropanol; the ball mill is a high-energy ball mill, the ball milling rotating speed is 200-500r/min, and the ball milling time is 1-10 hours; the fixed mixing ratio is material: ball milling medium: solvent =1: (4-8): (1.5-3.5).
In the step 3 and the step 5, the presintering temperature is 750-1000 ℃, the heating rate is 1-5 ℃/min, and the heat preservation time is 1-6 hours; the sintering temperature is 1050-1250 ℃, the heating rate is 5-20 ℃/min, and the heat preservation time is 1-12 hours.
Example 1 (M is Nb, N is Pb, x =0.5, y = 0.2):
step 1: according to the formula Li 6.5 La 3 Zr 1.3 Nb 0.5 Pb 0.2 O 12 In the proportion of Li, la, zr, nb and Pb, respectively weighing Li according to the metering ratio 2 CO 3 、La 2 O 3 、ZrO 2 、Nb 2 O 5 And PbO 2 ；
Step 2: adopting a wet ball milling process, taking yttrium-stabilized zirconia balls as a ball milling medium, taking isopropanol as a ball milling solvent, and mixing the materials according to the following ratio: grinding balls: the mass ratio of the isopropanol is 1;
and step 3: placing the ball grinding material obtained in the step 2 in a muffle furnace for presintering, heating to 750 ℃ at the speed of 2 ℃/min, and presintering at 750 ℃ for 3 hours to obtain presintering powder;
and 4, step 4: and (4) performing secondary ball milling on the pre-sintered powder obtained in the step (3), taking yttrium-stabilized zirconia balls as a ball milling medium, taking alcohol as a ball milling solvent, and mixing the materials: grinding balls: the mass ratio of the alcohol is 1;
and 5: putting the secondary ball grinding material obtained in the step 4 into a forming die for dry pressing and forming to obtain a green body;
step 6: placing the green body obtained in the step 5 into a muffle furnace for sintering, heating to 1250 ℃ at the speed of 10 ℃/min, and then sintering for 3 hours at 1250 ℃ to obtain the final heterovalent difunctional co-doped garnet type solid electrolyte material Li 6.5 La 3 Zr 1.3 Nb 0.5 Pb 0.2 O 12 。
X-ray diffractometer is adopted to carry out pairing on prepared Li 6.5 La 3 Zr 1.3 Nb 0.5 Pb 0.2 O 12 The characterization is carried out, and the comparison of garnet type solid electrolyte standard PDF card #45-0109 shows that the prepared heterovalent bifunctional co-doped garnet type solid electrolyte material Li 6.5 La 3 Zr 1.3 Nb 0.5 Pb 0.2 O 12 Spraying gold on the surface of electrolyte to prepare a blocking electrode with a pure cubic phase structure, measuring the impedance of the solid electrolyte by an alternating current impedance spectroscopy method, wherein the measurement range is 10Hz-10MHz, and calculating Li at 25 ℃ according to data obtained from the measurement result 6.5 La 3 Zr 1.3 Nb 0.5 Pb 0.2 O 12 The ionic conductivity of the solid electrolyte is 8.1 × 10 -4 S/cm. Will be prepared intoAfter the prepared solid electrolyte is exposed in the air and placed for 10 days, through the analysis of a field emission scanning electron microscope and an X-ray energy spectrum, lithium carbonate and lithium hydroxide generated after the reaction with water and carbon dioxide in the air do not appear on the surface of the electrolyte, which shows the excellent air stability of the solid electrolyte.
Example 2 (M is Ta, N is W, x =0.3, y = 0.3):
step 1: according to the formula Li 6.5 La 3 Zr 1.4 Ta 0.3 W 0.3 O 12 In the proportion of Li, la, zr, ta and W, liOH and La (OH) are respectively weighed according to the metering ratio 3 、ZrO 2 、Ta 2 O 5 And WO 2 ；
Step 2: adopting a wet ball milling process, taking yttrium-stabilized zirconia balls as a ball milling medium, taking alcohol as a ball milling solvent, and mixing the materials according to the following ratio: grinding balls: the mass ratio of the alcohol is 1;
and step 3: placing the ball grinding material obtained in the step 2 in a muffle furnace for presintering, heating to 900 ℃ at the speed of 5 ℃/min, and presintering at 900 ℃ for 6 hours to obtain presintering powder;
and 4, step 4: and (3) performing secondary ball milling on the pre-sintered powder obtained in the step (3), taking yttrium-stabilized zirconia balls as ball milling media, taking alcohol as ball milling solvent, and mixing the materials: grinding balls: the mass ratio of the alcohol is 1;
and 5: putting the secondary ball grinding material obtained in the step 4 into a forming die for dry pressing and forming to obtain a green body;
step 6: placing the green body obtained in the step 5 into a muffle furnace for sintering, heating to 1150 ℃ at the speed of 20 ℃/min, and then sintering for 3 hours at 1150 ℃ to obtain the final heterovalent bifunctional co-doped garnet type solid electrolyte material Li 6.5 La 3 Zr 1.4 Ta 0.3 W 0.3 O 12 。
X-ray diffractometer for prepared Li 6.5 La 3 Zr 1.4 Ta 0.3 W 0.3 O 12 The characterization is carried out, and the comparison of garnet type solid electrolyte standard PDF card #45-0109 shows that the prepared heterovalent bifunctional co-doped garnet type solid electrolyte material Li 6.5 La 3 Zr 1.4 Ta 0.3 W 0.3 O 12 Spraying gold on the surface of electrolyte to prepare a blocking electrode with a pure cubic phase structure, measuring the impedance of the solid electrolyte by an alternating current impedance spectroscopy method, wherein the measurement range is 10Hz-10MHz, and calculating Li at 25 ℃ according to data obtained from the measurement result 6.5 La 3 Zr 1.4 Ta 0.3 W 0.3 O 12 The ionic conductivity of the solid electrolyte is 9.32 x 10 -4 S/cm. After the prepared solid electrolyte is exposed in the air and placed for 15 days, through field emission scanning electron microscope and X-ray energy spectrum analysis, lithium carbonate and lithium hydroxide generated after the reaction between the electrolyte surface and water and carbon dioxide in the air do not appear, which shows the excellent air stability of the solid electrolyte.
Example 3 (M is Sb, N is Sn, x =0.5, y = 0.5):
step 1: according to the formula Li 6.5 La 3 ZrSb 0.5 Sn 0.5 O 12 In the proportion of Li, la, zr, sb and Sn, liNO is respectively weighed according to the metering ratio 3 、La(NO 3 ) 3 、Zr(NO 3 ) 4 、Sb 2 O 5 And SnO 2 ；
Step 2: adopting a wet ball milling process, taking yttrium-stabilized zirconia balls as a ball milling medium, taking isopropanol as a ball milling solvent, and mixing the materials according to the following ratio: grinding balls: the mass ratio of the isopropanol is 1;
and step 3: placing the ball grinding material obtained in the step 2 in a muffle furnace for presintering, heating to 950 ℃ at the speed of 3 ℃/min, and presintering at 950 ℃ for 1 hour to obtain presintering powder;
and 4, step 4: and (3) performing secondary ball milling on the pre-sintered powder obtained in the step (3), taking yttrium-stabilized zirconia balls as a ball milling medium, taking isopropanol as a ball milling solvent, and mixing the materials according to the following ratio: grinding balls: the mass ratio of the isopropanol is 1;
and 5: putting the secondary ball grinding material obtained in the step 4 into a forming die for dry pressing and forming to obtain a green body;
step 6: placing the green body obtained in the step 5 into a muffle furnace for sintering, heating to 1050 ℃ at the speed of 10 ℃/min, and then sintering at 1050 ℃ for 12 hours to obtain the final heterovalent bifunctional co-doped garnet type solid electrolyte material Li 6.5 La 3 ZrSb 0.5 Sn 0.5 O 12 。
X-ray diffractometer for prepared Li 6.5 La 3 ZrSb 0.5 Sn 0.5 O 12 The characterization is carried out, and the comparison of garnet type solid electrolyte standard PDF card #45-0109 shows that the prepared heterovalent bifunctional co-doped garnet type solid electrolyte material Li 6.5 La 3 ZrSb 0.5 Sn 0.5 O 12 Spraying gold on the surface of electrolyte to prepare a blocking electrode with a pure cubic phase structure, measuring the impedance of the solid electrolyte by an alternating current impedance spectroscopy method, wherein the measurement range is 10Hz-10MHz, and calculating Li at 25 ℃ according to data obtained from the measurement result 6.5 La 3 ZrSb 0.5 Sn 0.5 O 12 The ionic conductivity of the solid electrolyte is 1.05X 10 -3 S/cm. After the prepared solid electrolyte is exposed in the air and placed for 20 days, through the field emission scanning electron microscope and X-ray energy spectrum analysis, lithium carbonate and lithium hydroxide generated after the reaction with water and carbon dioxide in the air do not appear on the surface of the electrolyte, which shows the excellent air stability of the solid electrolyte.
Comparative example 1 (x =0, y = 0):
step 1: according to the formula Li 7 La 3 Zr 2 O 12 In the proportion of Li, la and Zr, respectively weighing LiOH and La according to the metering ratio 2 O 3 And ZrO 2 ；
Step 2: adopting a wet ball milling process, taking yttrium-stabilized zirconia balls as a ball milling medium, taking isopropanol as a ball milling solvent, and mixing the materials according to the following ratio: grinding balls: the mass ratio of isopropanol is 1;
and step 3: placing the ball grinding material obtained in the step 2 in a muffle furnace for presintering, heating to 1000 ℃ at the speed of 5 ℃/min, and presintering at 1000 ℃ for 3 hours to obtain presintering powder;
and 4, step 4: and (3) performing secondary ball milling on the pre-sintered powder obtained in the step (3), taking yttrium-stabilized zirconia balls as a ball milling medium, taking isopropanol as a ball milling solvent, and mixing the materials according to the following ratio: grinding balls: the mass ratio of the isopropanol is 1;
and 5: putting the secondary ball grinding material obtained in the step (4) into a forming die for dry pressing forming to obtain a green body;
step 6: placing the green body obtained in the step 5 into a muffle furnace for sintering, heating to 1150 ℃ at the speed of 2 ℃/min, and then sintering at 1150 ℃ for 6 hours to obtain the final undoped garnet type solid electrolyte material Li 7 La 3 Zr 2 O 12 。
X-ray diffractometer for prepared Li 7 La 3 Zr 2 O 12 Performing characterization, comparing garnet type solid electrolyte standard PDF card #45-0109, and preparing undoped garnet type solid electrolyte material Li 7 La 3 Zr 2 O 12 Distinct tetragonal phase-specific splitting peaks appear at 2 θ =25.6 ° and 30.5 °, indicating that Li was produced 7 La 3 Zr 2 O 12 The electrolyte material has a tetragonal hetero-phase, which greatly affects the ionic conductivity of the solid electrolyte. Spraying gold on the surface of the electrolyte to prepare a blocking electrode, measuring the impedance of the solid electrolyte by adopting an alternating current impedance spectroscopy method, wherein the measurement range is 10Hz-10MHz, and calculating Li at 25 ℃ according to data obtained by the measurement result 7 La 3 Zr 2 O 12 The ionic conductivity of the solid electrolyte is 1.17 x 10 -7 S/cm. After the prepared solid electrolyte is exposed in the air and placed for 1 day, the observation of a field emission scanning electron microscope shows that the solid electrolyte reacts with water and carbon dioxide in the air to generate lithium carbonate which is unevenly distributed on the surfaces of crystal grains,this indicates that the undoped garnet-type solid electrolyte material Li 7 La 3 Zr 2 O 12 Very poor air stability.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (7)
1. An aliovalent difunctional co-doped garnet type solid electrolyte is characterized in that: the chemical general formula of the electrolyte material is Li 7-x La 3 Zr 2-x-y M x N y O 12 Wherein, 0<x≤0.5，0<y is less than or equal to 0.5, the electrolyte material has a cubic phase structure, M is one of Ta, nb, as, sb and V, and M is used As the element 5+ Formally Zr-position substitution; n is one of Hf, W, sn and Pb, and the elements are N 4+ Formally Zr-site substitution occurs.
2. The heterovalent bifunctional co-doped garnet-type solid electrolyte according to claim 1, wherein: by selecting different M 5+ Doping to generate more lithium ion vacancies so as to achieve the aim of stabilizing the cubic phase structure of the garnet solid electrolyte; selecting different N 4+ Doping and widening lithium ion transmission channel to improve garnet qualityThe purpose of ionic conductivity of the type solid electrolyte; the ion contents of M and N in the solid electrolyte are controlled by regulating and controlling the values of x and y, the synergistic effect of doping of M element and N element is promoted, the micro-morphology of the prepared solid electrolyte material is ensured to be free of pores and microcracks, the reaction of the prepared garnet type solid electrolyte with water and carbon dioxide in the air is prevented, and the air stability of the solid electrolyte is improved.
3. The heterovalent, bifunctional, co-doped garnet-type solid electrolyte of claim 1, wherein: the crystal structure of the material is a pure cubic phase structure, and the conductivity is 8.1 multiplied by 10 -4 S/cm-1.05×10 -3 And the prepared solid electrolyte does not react with water and carbon dioxide in the air to generate lithium carbonate harmful to the electrochemical performance of the solid electrolyte after being exposed in the air for 10-20 days.
4. The method of any one of claims 1 to 3, wherein the method comprises the following steps: the raw materials comprise:
a lithium source: one of lithium hydroxide, lithium oxide, lithium carbonate and lithium nitrate;
a lanthanum source: one of lanthanum hydroxide, lanthanum oxide and lanthanum nitrate;
a zirconium source: one of zirconium hydroxide, zirconium oxide and zirconium nitrate;
m source: one of tantalum pentoxide, niobium pentoxide, arsenic pentoxide, antimony pentoxide, and vanadium pentoxide;
n source: one of hafnium oxide, tungsten oxide, tin oxide and lead oxide;
the components of the solid electrolyte material are mixed according to the chemical general formula, and are subjected to first ball milling and mixing, presintering is carried out for 1-6 hours at the temperature of 750-1000 ℃ to obtain presintering powder, and then the presintering powder is subjected to second ball milling and mixing, and is sintered for 1-12 hours at the temperature of 1050-1250 ℃ to obtain the final heterovalent bifunctional co-doped garnet type solid electrolyte material.
5. The method for preparing an isovalent bifunctional co-doped garnet-type solid electrolyte according to claim 4, comprising the following steps:
step 1: according to the formula Li 7-x La 3 Zr 2-x-y M x N y O 12 Respectively weighing a lithium source, a lanthanum source, a zirconium source, an M source and an N source according to the metering ratio of the Li, the La, the Zr, the M and the N;
step 2: adopting a wet ball milling process, taking yttrium-stabilized zirconia balls as a ball milling medium, adding a ball milling solvent, and grinding according to a fixed mixture ratio to obtain a uniformly mixed ball milling material A;
and step 3: placing the ball grinding material A obtained in the step 2 in a muffle furnace for presintering to obtain presintering powder B;
and 4, step 4: performing secondary ball milling on the pre-sintered powder B obtained in the step 3 to obtain a secondary ball grinding material C which is uniformly mixed;
and 5: putting the secondary ball grinding material C obtained in the step 4 into a forming die for dry pressing forming to obtain a green body D;
step 6: and (4) placing the green body D obtained in the step (5) in a muffle furnace for sintering to obtain the final heterovalent bifunctional co-doped garnet type solid electrolyte material.
6. The method for preparing an aliovalent bifunctional co-doped garnet-type solid electrolyte as claimed in claim 5, wherein the method comprises the following steps: in the step 2 and the step 4, the ball milling solvent is one of alcohol and isopropanol; the ball mill is a high-energy ball mill, the ball milling rotating speed is 200-500r/min, and the ball milling time is 1-10 hours; the fixed mixing ratio is material: ball milling medium: solvent =1: (4-8): (1.5-3.5).
7. The method for preparing an aliovalent bifunctional co-doped garnet-type solid electrolyte as claimed in claim 5, wherein the method comprises the following steps: in the step 3 and the step 5, the presintering temperature is 750-1000 ℃, the heating rate is 1-5 ℃/min, and the heat preservation time is 1-6 hours; the sintering temperature is 1050-1250 ℃, the heating rate is 5-20 ℃/min, and the heat preservation time is 1-12 hours.
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