Garnet-type composite solid electrolyte, preparation method therefor and use thereof

Abstract

A garnet-type composite solid electrolyte, a preparation method therefor, and a use thereof. The garnet-type composite solid electrolyte comprises a garnet-type solid electrolyte film and a negative electrode interface layer; the negative electrode interface layer is a rare-earth nickelate coating deposited on a surface of the garnet-type solid electrolyte film; the chemical formula of the garnet-type solid electrolyte is LixA2(LaO4)3 (A comprising one or more of the metals Al, Fe, Ga, Zr, Ta and Sc), and the chemical formula of the rare-earth nickelate is RNiO3 (R being a rare-earth metal other than La). Coating the garnet-type solid electrolyte film with a perovskite-structured rare-earth nickelate using pulsed laser deposition technology effectively inhibits the occurrence of reduction reactions at the negative electrode interface, preventing the formation and growth of lithium dendrites, and providing a material basis for the commercial development of all-solid-state lithium batteries.

Description

Garnet composite solid electrolyte and preparation method and application thereof TECHNICAL FIELD

[0001] The application belongs to the field of solid electrolytes, and particularly relates to a garnet composite solid electrolyte and a preparation method and application thereof. BACKGROUND

[0002] Solid electrolytes have great prospects and are the inevitable development direction of the energy storage field due to high safety and high energy density by replacing liquid electrolytes. Garnet solid electrolytes have high room-temperature ionic conductivity, a wide electrochemical window and high mechanical strength, and have great development prospects. However, the garnet solid electrolyte still faces many practical problems to be solved, such as easy generation of impurities such as lithium carbonate, poor physical contact caused by rigid contact with the positive and negative electrodes, which hinders the conduction of ions and electrons, and side reactions at the interface, and easy generation of lithium dendrites to cause battery short circuit.

[0003] Lithium metal has a high theoretical specific capacity and is the holy grail of lithium-ion batteries, but direct use of lithium metal as a negative electrode is in contact with the solid electrolyte and is easy to form lithium dendrites to cause battery short circuit.

[0004] SUMMARY

[0005] The purpose of the application is to provide a garnet composite solid electrolyte and a preparation method and application thereof to solve the problems in the prior art.

[0006] The application adopts a pulsed laser deposition technology to deposit a rare earth nickelate with a perovskite structure on the interface between the garnet solid electrolyte and Li, effectively inhibits the occurrence of negative electrode interface reduction reaction, avoids the formation and growth of lithium dendrites, and provides a material basis for the commercial development of all-solid-state lithium batteries.

[0007] The purpose of the application can be achieved by the following scheme:

[0008] The application provides a garnet composite solid electrolyte, which comprises a garnet solid electrolyte film and a negative electrode interface layer; the negative electrode interface layer is a rare earth nickelate coating deposited on the surface of the garnet solid electrolyte film.

[0009] The rare earth nickelate coating is deposited on one side of the surface of the garnet solid electrolyte film. When a solid-state battery is prepared, the rare earth nickelate coating is in contact with the negative electrode. The solid-state battery is an all-solid-state lithium-ion battery, and the negative electrode is a lithium negative electrode.

[0010] As an embodiment of the application, the chemical general formula of the garnet solid electrolyte is Li xA2(LaO4)3; wherein A comprises one or more of Al, Fe, Ga, Zr, Ta, Sc, and the like, x>0, preferably 7>x>6.

[0011] As an embodiment of the present application, the chemical formula of the rare earth nickelate is RNiO3; R is one of the rare earth metals other than La, including one of Nd, Sm, and Sr. The rare earth nickelate of the present application is a perovskite structure rare earth nickelate. The rare earth nickelate is preferably SmNiO3.

[0012] LaNiO3 cannot undergo phase transition under the action of an electric field, and cannot inhibit the occurrence of the reduction reaction of the interface in the lithium ion transmission process, so La is not suitable for the present application. Other rare earth acid salts (rare earth silicates, rare earth niobates, rare earth tantalates, rare earth zirconates, etc.) cannot undergo phase transition under the action of an electric field, and cannot be used in the present application.

[0013] As an embodiment of the present application, the thickness of the garnet-type solid electrolyte thin film is 50-500 μm.

[0014] As an embodiment of the present application, the thickness of the rare earth nickelate coating layer is 5-150 nm.

[0015] The present application provides a preparation method of a garnet-type composite solid electrolyte, comprising the following steps:

[0016] S1, tabletting the garnet-type solid electrolyte, and sintering to obtain a garnet-type solid electrolyte thin film;

[0017] S2, using a pulsed laser deposition technology to deposit a rare earth nickelate coating layer on the surface of the obtained garnet-type solid electrolyte thin film, to obtain the garnet-type solid electrolyte.

[0018] As an embodiment of the present application, in step S1, the sintering temperature is 350-500°C, and the time is 4h-24h.

[0019] As an embodiment of the present application, in step S2, the target material used in the pulsed laser deposition technology is RNiO3; R is one of the rare earth metals other than La, including one of Nd, Sm, and Sr.

[0020] As an implementation method of the present application, in step S1, in the pulsed laser deposition technology, the oxygen partial pressure is in the range of 1-40 Pa; the deposition temperature is in the range of 300-600 DEG C. Sol-gel and other technologies can also be used to synthesize rare earth nickelate, but such methods use solvents, and solvents can reduce the ionic conductivity of electrolytes (solvents can react with electrolytes to generate impurities that reduce ionic conductivity), inhibit lithium ion transmission.

[0021] The present application provides a negative electrode interface modification method based on a garnet solid-state electrolyte, comprising the following steps:

[0022] A1, tabletting the garnet solid-state electrolyte, and sintering to obtain a garnet solid-state electrolyte film;

[0023] A2, using a pulsed laser deposition technology to deposit a rare earth nickelate coating on the surface of the obtained garnet solid-state electrolyte film, and when preparing a full solid-state battery, the side of the rare earth nickelate coating can be assembled with the negative electrode.

[0024] The present application also provides a full solid-state battery comprising the garnet composite solid-state electrolyte negative electrode. When preparing a full solid-state battery, the side of the rare earth nickelate coating can be assembled with the negative electrode.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] (1) The garnet solid-state electrolyte is prone to generate impurities such as lithium carbonate, and the rigid contact with the positive and negative electrodes leads to poor physical contact, thereby hindering the conduction of ions and electrons; there are also side reactions at the positive and negative electrode interfaces, and lithium metal cannot be used as the negative electrode to directly contact the solid-state electrolyte. The present application coats the garnet solid-state electrolyte film with a perovskite structure rare earth nickelate, effectively inhibits the occurrence of negative electrode interface reduction reactions, and avoids the formation and growth of lithium dendrites.

[0027] (2) The electronic conductivity of the perovskite structure rare earth nickelate material decreases at low voltage, and reversibly reduces to the original conductivity at high voltage, so during the discharge process, the electronic conductivity of the electrolyte and the negative electrode interface decreases, the electrolyte does not undergo reduction reaction, and the side reaction at the negative electrode interface does not occur, so the lithium metal can be directly contacted, and the stability of the negative electrode interface is improved.

[0028] (3) The rare earth nickelate coating can inhibit the occurrence of side reactions caused by the reduction of the electrolyte at low voltage; improve the stability of the negative electrode / electrolyte interface; and allow the direct use of lithium metal, avoiding the formation and growth of lithium dendrites. BRIEF DESCRIPTION OF DRAWINGS

[0029] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0030] Figure 1 shows the first charge-discharge curves of the sulfide all-solid-state batteries prepared in Example 1 and Comparative Examples 1 and 2.

[0031] Figure 2 shows the cycle stability curves of the sulfide all-solid-state batteries prepared in Example 2 and Comparative Example 3 at 2C rate.

[0032] Figure 3 shows the first charge-discharge curves of the sulfide all-solid-state batteries prepared in Example 2, Comparative Example 4, and Comparative Example 5 at a 0.1C rate. Detailed Implementation

[0033] The present invention will now be described in detail with reference to specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0034] Example 1

[0035] 1) Weigh out 20 mg of Li7La3Zr2O 12 Solid electrolyte powder was pressed into sheets using a 10mm tableting mold at 400MPa and then calcined in a muffle furnace at 500℃ for 4h to obtain a solid electrolyte film with a thickness of 100μm.

[0036] 2) A pulsed laser deposition device was used. The target material was SmNiO3 powder, and the substrate was the solid electrolyte film prepared in step 1). The target material was deposited onto the substrate to a thickness of 100 nm using a pulsed laser at an oxygen partial pressure of 30 Pa and a temperature of 400 °C. The film was then cooled to room temperature and removed.

[0037] 3) In a glove box filled with argon gas, weigh out 75 mg NCM811 and 22 mg Li7La3Zr2O. 12 Electrolyte powder and 3 mg VGCF powder are placed in a mortar and ground for 30 minutes until the powders are uniformly mixed to obtain a composite cathode material for later use.

[0038] 4) Assemble the pressure cell: in the glove box filled with argon, weigh 40 mg of the composite positive electrode material prepared in step 3) into a 10 mm diameter pressure cell mold, rotate the composite positive electrode material flat by rotating the stainless steel column, and press it into a tablet on a tablet press with a pressure of 120 MPa and a pressure holding time of 2 min; place the deposited electrolyte film prepared in step 2) (the direction without deposition coating facing the positive electrode) into 9 mm diameter lithium metal on the electrolyte surface with deposition coating, and the current collector is Cu foil. After assembly, apply a pressure of 50 MPa to obtain a full solid-state lithium ion battery.

[0039] Example 2

[0040] 1) Weigh 20 mg of Li 6.3 La3Zr 1.4 Ta 0.6 O 12 Solid-state electrolyte powder, use a 10 mm tablet mold to press the electrolyte into a tablet at 400 MPa, and calcine in a muffle furnace at 500°C for 4 h to obtain a solid-state electrolyte film with a thickness of 100 μm;

[0041] 2) Use a pulsed laser deposition device, the target material uses NdNiO3 powder, and the substrate is the solid-state electrolyte film prepared in step 1). At an oxygen partial pressure of 25 Pa and a temperature of 550°C, the above-mentioned target material is deposited on the substrate to a thickness of 100 nm by pulsed laser, and then cooled to room temperature and removed.

[0042] 3) In the glove box filled with argon, weigh 70 mg of NCM811, 28 mg of Li 6.3 La3Zr 1.4 Ta 0.6 O 12 Electrolyte powder, 2 mg of VGCF powder are placed in a mortar and ground for 30 min to uniformly mix the above-mentioned powders to obtain a composite positive electrode material for standby use.

[0043] 4) Assemble the pressure cell: in the glove box filled with argon, weigh 40 mg of the composite positive electrode material prepared in step 3) into a 10 mm diameter pressure cell mold, rotate the composite positive electrode material flat by rotating the stainless steel column, and press it into a tablet on a tablet press with a pressure of 120 MPa and a pressure holding time of 2 min; place the deposited electrolyte film prepared in step 2) (the direction without deposition coating facing the positive electrode) into 9 mm diameter lithium metal on the electrolyte surface with deposition coating, and the current collector is Cu foil. After assembly, apply a pressure of 50 MPa to obtain a full solid-state lithium ion battery.

[0044] Comparative Example 1

[0045] The difference from Example 1 is that the electrolyte is not subjected to the pulsed laser deposition coating process, and the pressure battery solid electrolyte directly uses the electrolyte film of step 1) in Example 1.

[0046] Comparative Example 2

[0047] The difference from Example 1 is that the negative electrode interface layer obtained by pulsed laser deposition is a lithium nickelate coating.

[0048] Comparative Example 3

[0049] The difference from Example 2 is that the negative electrode interface layer obtained by pulsed laser deposition is a lanthanum nickelate coating.

[0050] Comparative Example 4

[0051] The difference from Example 2 is that the negative electrode interface layer obtained by pulsed laser deposition is a lithium silicate coating.

[0052] Comparative Example 5

[0053] The difference from Example 2 is that the negative electrode interface layer obtained by pulsed laser deposition is a Nd(NO3)3 coating.

[0054] Performance test

[0055] The all-solid-state battery was tested using a new battery test system, equipment model: CT-4000, using 0.1C / 0.1C charge-discharge steps, to test the first charge-discharge capacity of the solid-state lithium battery, and the first efficiency % = first discharge capacity / first charge capacity x 100%. Figure 1 is the first charge-discharge curve of the sulfide all-solid-state battery prepared by Example 1 and Comparative Examples 1 and 2. The first charge-discharge efficiency of Example 1 is 84.22%, and the charge-discharge specific capacity is 218.87 mAh / g and 195.08 mAh / g, respectively; the first charge-discharge efficiency of Comparative Example 1 is 80.80%, and the charge-discharge specific capacity is 218.87 mAh / g and 176.85 mAh / g, respectively. The first charge-discharge efficiency of Comparative Example 2 is 59.03%, and the charge-discharge specific capacity is 88.12 mAh / g and 52.01 mAh / g, respectively.

[0056] Similarly, the all-solid-state battery was tested using a new battery test system, equipment model: CT-4000, using 2C / 2C charge-discharge steps to test the capacity retention rate at the 50th cycle. Figure 2 is the cycle stability curve of the sulfide all-solid-state battery prepared by Example 2 and Comparative Example 3 at a 2C rate. After 50 cycles of charge-discharge, the capacity retention rate of Example 1 is 93.7%, and the capacity retention rate of Comparative Example 1 is 82.66%.

[0057] Figure 3 is the first cycle charge-discharge curve of the sulfide all-solid-state battery prepared in Example 2 and Comparative Examples 4 and 5 at 0.1C rate. The first charge-discharge efficiency of Example 2 is 80.28%, and the specific charge-discharge capacity is 256.70 mAh / g and 206.08 mAh / g, respectively. The first charge-discharge efficiency of Comparative Example 3 is 63.76%, and the specific charge-discharge capacity is 252.68 mAh / g and 161.10 mAh / g, respectively. The first charge-discharge efficiency of Comparative Example 4 is 57.31%, and the specific charge-discharge capacity is 251.32 mAh / g and 144.02 mAh / g, respectively.

[0058] The specific embodiments of the present application have been described. It is to be understood that the application is not limited to the specific embodiments described above and various modifications and changes can be made by those skilled in the art without departing from the spirit and scope of the application as defined in the appended claims.

Claims

1. A garnet-type composite solid electrolyte, characterized by, The garnet-type composite solid electrolyte comprises a garnet-type solid electrolyte film and a negative electrode interface layer. The negative electrode interface layer is a rare earth nickelate coating deposited on the surface of the garnet-type solid electrolyte film.

2. The garnet-type composite solid-state electrolyte according to claim 1, characterized by, In the garnet-type solid electrolyte thin film, the chemical general formula of the garnet-type solid electrolyte is Li x A2(LaO4)3; wherein A includes one or more of Al, Fe, Ga, Zr, Ta, Sc metals, and x>0.

3. The garnet-type composite solid-state electrolyte according to claim 1, characterized by, The rare earth nickelate has a general chemical formula of RNiO3, wherein R is one of rare earth metals other than La.

4. The garnet-type composite solid-state electrolyte according to claim 1, characterized by, The thickness of the garnet-type solid electrolyte film is 50-500 μm. The thickness of the rare earth nickelate coating is 5-150 nm.

5. A method of producing the garnet-type composite solid-state electrolyte according to claim 1, characterized by, The preparation method comprises the following steps: S1, tabletting the garnet-type solid electrolyte, and sintering to obtain a garnet-type solid electrolyte film; S2, depositing a rare earth nickelate coating on the surface of the obtained garnet-type solid electrolyte film by using a pulsed laser deposition technique, to obtain the garnet-type composite solid electrolyte.

6. The preparation method according to claim 5, characterized in that, In step S1, the sintering temperature is 350-500 ℃, and the sintering time is 4-24 h.

7. The preparation method according to claim 5, characterized in that, In step S2, the target material used in the pulsed laser deposition technique is RNiO3, wherein R is one of rare earth metals other than La, including one of Nd, Sm, and Sr.

8. The preparation method according to claim 5, characterized in that, In step S2, in the pulsed laser deposition technique, the oxygen partial pressure is 1-40 Pa, and the deposition temperature is 300-600 ℃.

9. An all-solid battery, characterized by, The garnet-type composite solid electrolyte according to claim 1.

10. The all-solid battery according to claim 9, characterized by, When preparing a full solid-state battery, the rare earth nickelate coating side is assembled with a negative electrode.

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