CN111416155A - Oxide solid electrolyte material and preparation method and application thereof - Google Patents

Abstract

The invention relates to an oxide solid electrolyte material and a preparation method and application thereof. The preparation method of the oxide solid electrolyte material is as follows: 1) dissolving lithium carbonate, lanthanum oxide and gallium oxide in an organic solvent, centrifuging and drying after ball milling; 2) carry out an air-fired at 870-930 ℃, then collect the powder and grind and press it into tablets; 3) carry out a second air-firing at 950-1050 ℃ to obtain Li ₁₉ La ₃₆ Ga ₇ O ₇₄ oxide solid electrolyte material. Compared with the prior art, the present invention uses lithium, lanthanum, gallium and oxygen as constituent elements to prepare an oxide solid-state electrolyte material through solid-phase synthesis reaction at low temperature, and its morphology and characteristics are uniform and regular. Ga and O elements are effectively dispersed in the electrolyte material and have high ionic conductivity. Applying them to polymer solid electrolytes and assembling them into batteries can effectively improve the electrochemical performance of batteries, and the preparation process temperature is low, and the synthesis process Simple.

Description

A kind of oxide solid electrolyte material and preparation method and application thereof

technical field

The invention belongs to the technical field of solid electrolyte materials, and relates to an oxide solid electrolyte material and a preparation method and application thereof.

Background technique

At present, commercial lithium-ion batteries mainly use organic electrolytes, which have potential safety hazards such as liquid leakage, combustion, and explosion in unconventional environments. Solid-state batteries based on inorganic solid ceramic electrolytes are of great significance to solve the safety problems of traditional liquid batteries. In general, solid-state electrolytes should possess high Li-ion conductivity, wide chemical window, and good chemical stability against electrode materials.

The garnet-structured lithium ion solid electrolyte (Li ₇ La ₃ Zr ₂ O ₁₂ , LLZO), which has been widely studied, has high electrical conductivity (nearly 10 ^-4 S cm ^-1 ), is stable to metallic lithium, and has a wide electrochemical window (0- 4V) and other advantages, it is one of the candidate electrolyte materials for the next generation of high-safety solid-state lithium batteries. However, its sintering temperature is relatively high, usually above 1100 °C, and the current research work on solid-state batteries based on LLZO ceramics is less, and the battery performance is not good, and still needs a lot of exploration and improvement.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an oxide solid state electrolyte material and its preparation method and application in order to overcome the above-mentioned defects in the prior art. The oxide solid state electrolyte material of the present invention has high ionic conductivity and low sintering temperature. The active filler is added to the polymer solid electrolyte, and finally assembled into a battery, which can effectively improve the electrochemical performance of the battery.

The object of the present invention can be realized through the following technical solutions:

A preparation method of an oxide solid state electrolyte material, the method comprises the following steps:

1) Dissolving lithium carbonate, lanthanum oxide and gallium oxide in an organic solvent, centrifuging and drying after ball milling;

2) Carry out an air-fire at 870-930 ° C, then collect the powder and grind it into tablets;

3) Perform secondary air firing at 950-1050° C. to obtain Li ₁₉ La ₃₆ Ga ₇ O ₇₄ oxide solid electrolyte material.

Further, in step 1), the organic solvent is isopropanol.

Further, in step 1), the ball milling is wet ball milling, and in the ball milling process, the ball milling speed is 500-800 r/min, and the ball milling time is 24-48 h.

Further, in step 1), in the centrifugation process, the centrifugation speed is 7000-9000 r/min.

Further, in step 1), in the drying process, the drying temperature is 50-70° C., and the drying time is 8-16 h.

Further, in step 2), the time of the first empty burning is 4-6h; in step 3), the time of the second empty burning is 4-6h.

An oxide solid state electrolyte material prepared by the method.

An application of an oxide solid electrolyte material, the material is used as an active filler to prepare a polymer solid electrolyte.

A preparation method of PEO-based polymer solid electrolyte, the method comprises: grinding the oxide solid electrolyte material into powder, and mixing PEO (polyethylene oxide), LiTFSI (bis(trifluoromethylsulfonyl) Lithium imide) was added to acetonitrile together, and then the solution was used to cast a Faradic membrane to obtain the PEO-based polymer solid electrolyte. The weight ratio of PEO, LiTFSI and oxide solid electrolyte material is 8:1:1-5.

A PEO-based polymer solid electrolyte is prepared by the method.

In the present invention, the one-time air firing is sintering at a slightly lower temperature to form a cubic phase solid electrolyte with high lithium ion conductivity, and then sintering at a higher temperature after pressing, so that the electrolyte sheet has a higher density, thereby better transport lithium ions.

Compared with the prior art, the present invention uses lithium, lanthanum, gallium and oxygen as constituent elements, and the solid electrolyte formed by these four elements can have more oxygen vacancies and lithium ion transport channels. Compared with the current LLZO electrolyte, In the preparation process, an oxide solid-state electrolyte material can be prepared by a solid-phase synthesis reaction at a lower temperature, so that it is easier to scale, its morphology is uniform and regular, and La, Ga and O elements are effectively dispersed in the electrolyte material. It has high ionic conductivity (10 ^-4 S/cm) and is applied to polymer solid electrolytes and assembled into batteries, which can effectively improve the electrochemical performance of batteries, and the preparation process temperature is low, and the synthesis process is simple.

Description of drawings

1 is a TEM image of the oxide solid electrolyte material prepared in Example 1;

2 is an EDS diagram of the oxide solid state electrolyte material prepared in Example 1;

Fig. 3 is the XRD pattern of the oxide solid state electrolyte material obtained in Example 1;

4 is a cross-section and a cross-sectional SEM image of the PEO-based polymer solid electrolyte prepared in Example 1;

5 is an impedance diagram of the oxide solid electrolyte material prepared in Example 1;

6 is an impedance diagram of the PEO-based polymer solid electrolyte prepared in Example 1 at 60°C;

7 is a rate cycling diagram at 70°C of a Li/PEO-LiTFSI-Li19/LiFePO ₄ polymer solid-state battery assembled with the PEO-based polymer solid-state electrolyte prepared in Example 1.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and provides a detailed implementation manner and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

Example 1:

A preparation method of an oxide solid electrolyte material is as follows: dissolving lithium carbonate, lanthanum oxide and gallium oxide in isopropanol, wet ball milling with isopropanol for 24-48 hours, the ball milling speed is 500-800r/min, After high-speed centrifugation at 8000 r/min, drying at 60 °C for 12 hours, then air-fired at 900 °C for 5 h, the powder was collected and ground into tablets; then air-fired at 950 °C-1050 °C for 5 h to obtain Li ₁₉ La ₃₆ Ga ₇ O ₇₄ oxide solid electrolyte material .

A preparation method of a PEO-based polymer solid electrolyte doped with Li ₁₉ La ₃₆ Ga ₇ O ₇₄ is as follows: PEO, LiTFSI and Li ₁₉ La ₃₆ Ga ₇ O ₇₄ oxide solid electrolyte material powder are dissolved in acetonitrile, and the weight ratio of the The ratio is 8:1:1 to 5, and then the Farad membrane is cast with a solution to obtain a PEO-based polymer solid electrolyte.

The obtained film-like PEO-based polymer solid-state electrolyte is sliced and assembled with lithium iron phosphate material and lithium slices to form a full battery. Among them, the preparation method of the lithium iron phosphate material is: grinding lithium iron phosphate, acetylene black and a binder (polyvinylidene fluoride or polytetrafluoroethylene, etc.) into a slurry in a mass ratio of 8:1:1, and then grinding the slurry Pull mill on aluminum foil and vacuum dry overnight at 80 °C. The dried lithium iron phosphate material was cut into pieces, and a 2032 battery case was selected for full battery assembly in a glove box. After the assembled battery was left to dry overnight, the electrochemical performance was tested with blue dots.

FIG. 1 is a TEM image of the prepared oxide solid electrolyte material. It can be seen from Figure 1 that the particle size of the solid electrolyte powder is 800 × 400 nm, which is very small and is more conducive to the transport of ions in the solid phase after tableting.

FIG. 2 is the EDS diagram of the prepared oxide solid electrolyte material. It can be seen that the distribution of lanthanum, gallium and oxygen is relatively uniform.

FIG. 3 is an XRD pattern of the prepared oxide solid electrolyte material. It can be seen from Figure 3 that the XRD peaks of the measured substances are basically consistent with the main peaks of the standard comparison card, indicating that the Li ₁₉ La ₃₆ Ga ₇ O ₇₄ substance was successfully synthesized.

FIG. 4 is a cross-section and a cross-sectional SEM image of the prepared PEO-based polymer solid electrolyte. It can be seen from Figure 4 that the cross section is flat, and the Li ₁₉ La ₃₆ Ga ₇ O ₇₄ powder is uniformly distributed in the polymer electrolyte membrane. From the cross section, it can be concluded that the thickness of the polymer membrane is about 120 μm.

FIG. 5 is an impedance diagram of the prepared oxide solid electrolyte material. It can be seen from Figure 5 that the impedance value of the electrolyte sheet measured by the blocking electrode method after pressing Li ₁₉ La ₃₆ Ga ₇ O ₇₄ into a sheet is 830Ω, and then the impedance value of the electrolyte sheet can be calculated to be 8×10 ^{− 4} S/cm, which is larger than the currently widely used LLZO-type solid electrolyte.

Figure 6 is an impedance diagram of the prepared PEO-based polymer solid electrolyte at 60°C. It can be seen from Figure 6 that the impedance value on the left side of the spectrum is measured by adding Li ₁₉ La ₃₆ Ga ₇ O ₇₄ powder, which is smaller than the impedance value on the right side without adding powder. It shows that after adding Li ₁₉ La ₃₆ Ga ₇ O ₇₄ powder, the impedance value of the system becomes smaller, which is more conducive to the conduction of lithium ions.

Figure 7 is a rate cycling diagram of the Li/PEO-LiTFSI-Li9/LiFePO ₄ polymer solid-state battery assembled with the prepared PEO-based polymer solid-state electrolyte at 70°C. It can be seen from Figure 7 that the assembled polymer solid-state battery has good cycle stability, can maintain a high specific capacity at 0.5C, and has a low capacity loss per cycle, and has good rate performance.

Example 2:

A kind of oxide solid state electrolyte material, its preparation method comprises the following steps:

1) Dissolve lithium carbonate, lanthanum oxide and gallium oxide in isopropanol, centrifuge and dry after wet ball milling. In the ball milling process, the ball milling speed is 500r/min, and the ball milling time is 48h; in the centrifugation process, the centrifugal speed is 7000r/min; in the drying process, the drying temperature is 70 ℃, and the drying time is 8h.

2) Carry out an air sintering at 930°C for 4 hours, then collect the powder and grind it into tablets;

3) Carry out secondary air firing at 1050° C. for 4 hours to obtain Li ₁₉ La ₃₆ Ga ₇ O ₇₄ oxide solid electrolyte material.

The material is used as an active filler for the preparation of polymer solid electrolytes. The preparation method of the PEO-based polymer solid electrolyte is as follows: the oxide solid electrolyte material is ground into powder, and added to acetonitrile together with PEO and LiTFSI, and the weight ratio of PEO, LiTFSI and the oxide solid electrolyte material is 8:1: 5. After that, the Farad membrane is cast with the solution to obtain the PEO-based polymer solid electrolyte.

Example 3:

A kind of oxide solid state electrolyte material, its preparation method comprises the following steps:

1) Dissolve lithium carbonate, lanthanum oxide and gallium oxide in isopropanol, centrifuge and dry after wet ball milling. In the ball milling process, the ball milling speed is 800r/min, and the ball milling time is 24h; in the centrifugation process, the centrifugal speed is 9000r/min; in the drying process, the drying temperature is 50 ℃, and the drying time is 16h.

2) Carry out an air calcination at 870°C for 6h, then collect the powder and grind it into tablets;

3) Perform secondary air firing at 950° C. for 6 hours to obtain Li ₁₉ La ₃₆ Ga ₇ O ₇₄ oxide solid electrolyte material.

The material is used as an active filler for the preparation of polymer solid electrolytes. The preparation method of PEO-based polymer solid electrolyte is as follows: the oxide solid electrolyte material is ground into powder, and added to acetonitrile together with PEO and LiTFSI, and the weight ratio of PEO, LiTFSI and oxide solid electrolyte material is 8:1: 1. After that, the Farad membrane is cast with a solution to obtain a PEO-based polymer solid electrolyte.

Example 4:

A kind of oxide solid state electrolyte material, its preparation method comprises the following steps:

1) Dissolve lithium carbonate, lanthanum oxide and gallium oxide in isopropanol, centrifuge and dry after wet ball milling. In the ball milling process, the ball milling speed is 600r/min, and the ball milling time is 36h; in the centrifugation process, the centrifugal speed is 8000r/min; in the drying process, the drying temperature is 60 ℃, and the drying time is 12h.

2) Carry out an air sintering at 900°C for 5h, then collect the powder and grind it into tablets;

3) Carry out secondary air firing at 1000° C. for 5 hours to obtain Li ₁₉ La ₃₆ Ga ₇ O ₇₄ oxide solid electrolyte material.

The material is used as an active filler for the preparation of polymer solid electrolytes. The preparation method of the PEO-based polymer solid electrolyte is as follows: the oxide solid electrolyte material is ground into powder, and added to acetonitrile together with PEO and LiTFSI, and the weight ratio of PEO, LiTFSI and the oxide solid electrolyte material is 8:1: 3. After that, the Farad membrane is cast with a solution to obtain a PEO-based polymer solid electrolyte.

The foregoing description of the embodiments is provided to facilitate understanding and use of the invention by those of ordinary skill in the art. It will be apparent to those skilled in the art that various modifications to these embodiments can be readily made, and the generic principles described herein can be applied to other embodiments without inventive step. Therefore, the present invention is not limited to the above-mentioned embodiments, and improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should all fall within the protection scope of the present invention.

Claims (10)

1. a preparation method of oxide solid state electrolyte material, is characterized in that, this method comprises the following steps: 1) Dissolving lithium carbonate, lanthanum oxide and gallium oxide in an organic solvent, centrifuging and drying after ball milling; 2) Carry out an air-fire at 870-930 ° C, then collect the powder and grind it into tablets; 3) Perform secondary air firing at 950-1050° C. to obtain Li ₁₉ La ₃₆ Ga ₇ O ₇₄ oxide solid electrolyte material. 2 . The preparation method of an oxide solid electrolyte material according to claim 1 , wherein, in step 1), the organic solvent is isopropanol. 3 . 3. the preparation method of a kind of oxide solid electrolyte material according to claim 1, is characterized in that, in step 1), described ball milling is wet ball milling, in ball milling process, ball milling rotational speed is 500-800r/min , the ball milling time is 24-48h. 4 . The preparation method of an oxide solid electrolyte material according to claim 1 , wherein in step 1), during the centrifugation process, the centrifugation speed is 7000-9000 r/min. 5 . 5 . The method for preparing an oxide solid electrolyte material according to claim 1 , wherein in step 1), in the drying process, the drying temperature is 50-70° C. and the drying time is 8-16 h. 6 . 6 . The preparation method of an oxide solid electrolyte material according to claim 1 , wherein, in step 2), the time of the primary empty firing is 4-6h; in step 3), the The time of the second air burning is 4-6h. 7 . An oxide solid state electrolyte material, characterized in that, the material is prepared by the method according to any one of claims 1 to 6 . 8. An application of the oxide solid state electrolyte material according to claim 7, wherein the material is used as an active filler to prepare a polymer solid state electrolyte. 9. a preparation method of PEO-based polymer solid electrolyte, characterized in that, the method is: grinding the oxide solid electrolyte material described in claim 7 into powder, and adding PEO, LiTFSI into acetonitrile , and then the Farad membrane is cast with a solution to obtain the PEO-based polymer solid electrolyte. 10 . A PEO-based polymer solid electrolyte, characterized in that, the electrolyte is prepared by the method as claimed in claim 9 .

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