A Method for Modifying the Interface between a Dual-Filler Doped Interfacial Buffer Layer Solid-State Electrolyte and a High-Voltage Cathode

Abstract

The present invention provides a method for modifying the interface between a dual-filler-doped interfacial buffer layer solid electrolyte and a high-voltage cathode. The polymer matrix of the interfacial buffer layer is PEO, and the two fillers are LiPO2F2 and fullerene C 60 , and the selected solid electrolyte is Li 1.4 Al 0.4 Ti 1.6 (PO4)3 (LATP), the cathode material is NCM811, and the preparation method includes the following steps: S1. Prepare a precursor solution by dissolving PEO and LiTFSI in a certain amount of acetonitrile, and then successively add LiPO2F2 and fullerene C 60 thereto, and heat and stir evenly; S2. Take an appropriate amount of the precursor solution obtained in step S1 and drop-coat it on the surface of the LATP sheet, and place it in an oven for vacuum drying to form a film; S3. Attach the NCM811 electrode sheet to the other side of the interfacial buffer layer. Through the synergistic effect of LiPO2F2 and fullerene C 60 in the interfacial buffer layer, the present invention realizes the spontaneous formation of a thin and uniform CEI film rich in Li x PO y F z , LiP x F y and C 60 F n on the surface of the NCM811 particles, effectively improving the structural stability of the NCM811 cathode and the electrolyte during cycling, and enhancing the long cycling life of the LATP-based high-voltage solid-state battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation and application, and more specifically, relates to a method for modifying the solid electrolyte-high voltage cathode interface with a double filler (LiPO2F2 and fullerene C 60 60)) doped interfacial buffer layer. Background Art

[0002] Since the 1990s, lithium-ion batteries have been widely used in portable electronic devices and new energy vehicles due to their high energy density, long cycle life, and no memory effect. However, there are still problems such as poor cycle performance and insufficient safety, which cannot meet the commercial requirements. Solid-state batteries based on high-voltage layered oxide cathodes have high energy density and high safety, and have broad application prospects. However, problems such as poor compatibility between the solid electrolyte and the high-voltage cathode interface, high interfacial impedance caused by poor contact, and the existence of the space charge layer effect limit the electrochemical performance of the battery. Therefore, improving the solid electrolyte-high voltage cathode interface is of great significance for promoting the development and application of high-voltage solid-state batteries.

[0003] Adding a buffer layer at the high-voltage cathode-solid electrolyte interface is an effective solution, which can alleviate the rigid "point-to-point" contact at the interface. CN117747957A discloses a nitrile-containing curing solution for modifying the solid electrolyte-cathode interface, enhancing the interfacial contact, improving the ion transport at the interface, and simultaneously improving the cycle stability and rate performance of the battery.

[0004] Although the above modification methods have improved the interfacial contact problem between the solid electrolyte and the cathode to a certain extent, it is difficult to improve the structural stability of the cathode and the electrolyte at high voltage. Summary of the Invention

[0005] Based on the deficiencies of the existing technology, the present invention discloses a method for modifying the solid electrolyte-high voltage cathode interface with a double filler doped interfacial buffer layer. Through the synergistic effect of LiPO2F2 and fullerene C 60 60 in the interfacial buffer layer, a thin and uniform CEI film rich in Li x PO y F z , LiP x F y and C 60 F n is spontaneously formed on the surface of NCM811 particles, effectively improving the structural stability of the NCM811 cathode and the electrolyte during cycling, and enhancing the long cycle life of the LATP-based high-voltage solid-state battery.

[0006] The present invention includes the following technical solutions:

[0007] A method for modifying the interface between a solid electrolyte and a high-voltage cathode with a double-filler-doped interfacial buffer layer, characterized in that the polymer matrix of the interfacial buffer layer is PEO, and the two fillers are LiPO2F2 and fullerene C 60 , the solid electrolyte is Li 1.4 Al 0.4 Ti 1.6 (PO4)3 (LATP), the cathode material is NCM811, and the preparation method includes the following steps:

[0008] S1. Prepare a precursor solution by dissolving PEO and LiTFSI in acetonitrile, and then sequentially add LiPO2F2 and fullerene C 60 thereto, and heat and stir evenly;

[0009] S2. Use a pipette to transfer and evenly drop the precursor solution obtained in step S1 onto the surface of the LATP wafer, and place it in an oven for vacuum drying to form a film to obtain an interfacial buffer layer;

[0010] S3. Attach the NCM811 electrode sheet to the other side of the interfacial buffer layer.

[0011] Further, in the above method for modifying the interface between a solid electrolyte and a high-voltage cathode with a double-filler-doped interfacial buffer layer, the molar ratio of PEO monomer to LiTFSI in step S1 is 20:1.

[0012] Further, in the above method for modifying the interface between a solid electrolyte and a high-voltage cathode with a double-filler-doped interfacial buffer layer, the heating and stirring temperature in step S1 is 60 °C, and the stirring speed is 800 - 1000 rpm.

[0013] Further, in the above method for modifying the interface between a solid electrolyte and a high-voltage cathode with a double-filler-doped interfacial buffer layer, the vacuum drying temperature in step S2 is 60 °C, and the time is 12 h.

[0014] Further, in the above method for modifying the interface between a solid electrolyte and a high-voltage cathode with a double-filler-doped interfacial buffer layer, the LATP wafer in step S2 is synthesized by a solid-phase method.

[0015] Further, in the above method for modifying the interface between a solid electrolyte and a high-voltage cathode with a double-filler-doped interfacial buffer layer, the LATP wafer in step S2 is synthesized by the following method:

[0016] Weigh Li2CO3, NH4H2(PO4)3, TiO2 and Al2O3 according to the stoichiometric ratio; preferably, (Li2CO3 is in excess by 5% to compensate for lithium loss); and use anhydrous ethanol as the ball-milling medium to ball-mill for 2 h for mixing to obtain a uniform slurry. After drying the slurry, place it in an oven at 180 °C and bake for 7 days, then calcine at 700 °C for 4 h to form a phase to obtain the initial powder. The initial powder is ball-milled for 8 h for the second time to obtain a uniform slurry. After drying the uniform slurry, granulate and press it into a tablet with a diameter of 12 mm and sinter at 900 °C for 6 h to obtain an LATP tablet with a diameter of about 10 mm.

[0017] Further, in the method for modifying the solid electrolyte-high voltage cathode interface with a double filler-doped interface buffer layer, the NCM811 cathode sheet in step S3 is prepared by the following steps:

[0018] Mix the cathode material NCM811, the active material acetylene black and PVDF in a mass ratio of 8:1:1 in an NMP solution, stir overnight, then coat it on an aluminum foil and place it in a vacuum drying oven at 80 °C for drying for 12 h to obtain it.

[0019] Further, in the method for modifying the solid electrolyte-high voltage cathode interface with a double filler-doped interface buffer layer, the loading of NCM811 in the NCM811 cathode sheet is 2 mg cm -2 .

[0020] The present invention also discloses a solid electrolyte-high voltage cathode interface prepared by the method described in any one of the above.

[0021] The present invention also discloses the use of the above preparation method in the preparation of LATP-based high voltage solid-state batteries with long cycle life.

[0022] Compared with the prior art, the present invention has the following outstanding beneficial effects:

[0023] The present invention discloses a method for modifying the solid electrolyte-high voltage cathode interface with a double filler-doped interface buffer layer. By introducing a thin double filler-doped interface buffer layer between the LATP-NCM811 interface, a CEI film rich in Li x PO y F z , LiP x F y and C 60 F n is spontaneously formed on the surface of the NCM811 particles, effectively improving the structural stability of the NCM811 cathode and the electrolyte during the cycling process, and enhancing the long cycle life of the LATP-based high voltage solid-state battery. The preparation method of the present invention is simple, can be prepared on a large scale, and has a wide application scenario in the field of high voltage solid-state batteries. Description of the Drawings

[0024] Figure 1 TEM images of the NCM811 cathode after 150 cycles of the batteries in Comparative Example 1, Comparative Example 2, and Example 1;

[0025] Figure 2 XPS spectra of the NCM811 cathode after 150 cycles of the battery in Example 1;

[0026] Figure 3 Comparison chart of the 150-cycle performance of the batteries in Comparative Example 1 and Example 1 at a current density of 0.5C in the voltage range of 2.7 - 4.3V;

[0027] Figure 4 Comparison chart of the rate performance of the batteries in Comparative Example 1 and Example 1. Detailed implementation manners

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] Example 1

[0030] 1. Prepare a precursor solution by dissolving 0.25 g of PEO and 0.09 g of LiTFSI in 5 mL of acetonitrile, and then sequentially add 0.017 g of LiPO2F2 and 0.017 g of C thereto 60 , heat and stir evenly, the temperature during heating and stirring is 60°C, and the stirring speed is 800 - 1000 r / min -1 ;

[0031] 2. Use a pipette to transfer 30 μL of the precursor slurry obtained in step 1 and evenly drop it on the surface of the LATP sheet, and place it in a 60°C oven for vacuum drying for 12 h to form a film;

[0032] 3. Attach the NCM811 electrode sheet to the other side of the interface buffer layer.

[0033] Example 2

[0034] 1. Prepare a precursor solution by dissolving 0.25 g of PEO and 0.09 g of LiTFSI in 5 mL of acetonitrile, and then sequentially add 0.017 g of LiPO2F2 and 0.003 g of C thereto 60 , heat and stir evenly; the temperature during heating and stirring is 60°C, and the stirring speed is 800 - 1000 r / min -1 ;

[0035] 2. Pipette 30 μL of the precursor slurry obtained in 1 and evenly drop-coat it on the surface of the LATP sheet, and place it in an oven at 60 °C for vacuum drying for 12 h to form a film;

[0036] 3. Attach the NCM811 electrode sheet to the other side of the interfacial buffer layer.

[0037] Example 3

[0038] 1. Prepare a precursor solution by dissolving 0.25 g of PEO and 0.09 g of LiTFSI in 5 mL of acetonitrile, and then sequentially add 0.017 g of LiPO2F2 and 0.010 g of C 60 , heat and stir evenly; the temperature during heating and stirring is 60 °C, and the stirring speed is 800 - 1000 r min -1 ;

[0039] 2. Pipette 30 μL of the precursor slurry obtained in 1 and evenly drop-coat it on the surface of the LATP sheet, and place it in an oven at 60 °C for vacuum drying for 12 h to form a film;

[0040] 3. Attach the NCM811 electrode sheet to the other side of the interfacial buffer layer.

[0041] Example 4

[0042] 1. Prepare a precursor solution by dissolving 0.25 g of PEO and 0.09 g of LiTFSI in 5 mL of acetonitrile, and then sequentially add 0.017 g of LiPO2F2 and 0.031 g of C 60 , heat and stir evenly; the temperature during heating and stirring is 60 °C, and the stirring speed is 800 - 1000 r min -1 ;

[0043] 2. Pipette 30 μL of the precursor slurry obtained in 1 and evenly drop-coat it on the surface of the LATP sheet, and place it in an oven at 60 °C for vacuum drying for 12 h to form a film;

[0044] 3. Attach the NCM811 electrode sheet to the other side of the interfacial buffer layer.

[0045] Comparative Example 1

[0046] 1. Prepare a precursor solution by dissolving 0.25 g of PEO and 0.09 g of LiTFSI in 5 mL of acetonitrile, heat and stir evenly; the temperature during heating and stirring is 60 °C, and the stirring speed is 800 - 1000 r min -1 ;

[0047] 2. Pipette 30 μL of the precursor slurry obtained in 1 and evenly drop-coat it on the surface of the LATP sheet, and place it in an oven at 60 °C for vacuum drying for 12 h to form a film;

[0048] 3. Attach the NCM811 electrode to the other side of the interface buffer layer.

[0049] Comparative Example 2

[0050] 1. Prepare a precursor solution by dissolving 0.25 g of PEO and 0.09 g of LiTFSI in 5 mL of acetonitrile, and then sequentially add 0.017 g of LiPO2F2 thereto, and heat and stir evenly; the temperature during heating and stirring is 60 °C, and the stirring speed is 800 - 1000 r min -1 ;

[0051] 2. Use a pipette to transfer 30 μL of the precursor slurry obtained in 1 and evenly drop it on the surface of the LATP wafer, and place it in an oven at 60 °C for vacuum drying for 12 h to form a film;

[0052] 3. Attach the NCM811 electrode to the other side of the interface buffer layer.

[0053] Comparative Example 3

[0054] 1. Prepare a precursor solution by dissolving 0.25 g of PEO and 0.09 g of LiTFSI in 5 mL of acetonitrile, and then sequentially add 0.017 g of C 60 , heat and stir evenly; the temperature during heating and stirring is 60 °C, and the stirring speed is 800 - 1000 r min -1 ;

[0055] 2. Use a pipette to transfer 30 μL of the precursor slurry obtained in 1 and evenly drop it on the surface of the LATP wafer, and place it in an oven at 60 °C for vacuum drying for 12 h to form a film;

[0056] 3. Attach the NCM811 electrode to the other side of the interface buffer layer.

[0057] Test Example

[0058] Perform performance tests on the above-mentioned examples and comparative examples as solid electrolyte-high voltage cathode interface buffer layers applied in high voltage solid state batteries.

[0059] Figure 1 It is the TEM image of the NCM811 positive electrode after 150 cycles of the batteries in Comparative Example 1, Comparative Example 2 and Example 1. From Figure 1 it can be seen that due to the synergistic effect of LiPO2F2 and C 60 , a uniform and thin CEI film is formed on the surface of the NCM811 positive electrode particles. Figure 2 It is the XPS image of the NCM811 positive electrode after 150 cycles of the battery in Example 1. It can be seen that the CEI film component on the surface of the NCM811 particles in Example 1 is Li x PO y Fz , LiP x F y and C 60 F n . Figure 3 The cycling performance and Figure 4 rate performance indicate that the electrochemical performance of the battery modified by the double-doped buffer layer of LiPO2F2 and C 60 has been improved.

[0060] The long cycling performance of the batteries in the examples and comparative examples of the present invention was tested, and the results are shown in Table 1.

[0061] Table 1 Long cycling performance of the batteries in the examples and comparative examples at a voltage range of 2.7 - 4.3 V and a current density of 0.5C

[0062]

[0063]

[0064] Note: The capacity retention rate is the ratio of the discharge specific capacity at 150 cycles to the discharge specific capacity at the first cycle.

[0065] From the above examples and test examples, it can be seen that through the synergistic effect of LiPO2F2 and fullerene C in the interfacial buffer layer of the present invention, 60 a thin and uniform CEI film rich in Li x PO y F z , LiP x F y and C 60 F n is spontaneously formed on the surface of the NCM811 particles, effectively improving the structural stability of the NCM811 cathode and the electrolyte during cycling, and enhancing the long cycling life of the LATP-based high-voltage solid-state battery. The preparation method of the present invention is simple and can be prepared on a large scale, and has a wide range of application scenarios in the field of high-voltage solid-state batteries.

[0066] The above are only a limited number of preferred embodiments of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for modifying the interface between a dual-filler doped interfacial buffer layer solid electrolyte and a high-voltage cathode, characterized in that, The polymer matrix of the interface buffer layer is PEO, and the two fillers are LiPO2F2 and fullerene C respectively. 60 , the solid electrolyte is LATP, and LATP is specifically Li 1.4 Al 0.4 Ti 1.6 (PO4)3; the cathode material is NCM811, and the preparation method includes the following steps: S1. Prepare a precursor solution by dissolving PEO and LiTFSI in acetonitrile, and then sequentially adding LiPO2F2 and fullerene C thereto, and heating to 60 °C and stirring evenly; 60 and heating to a temperature of 60 °C and stirring evenly; S2. Use a pipette to uniformly pipette and drop the precursor solution obtained in step S1 onto the surface of the LATP sheet, and place it in an oven for vacuum drying to form a film, obtaining an interfacial buffer layer; S3. Attach the NCM811 electrode sheet to the other side of the interfacial buffer layer.

2. The method for modifying the interface between a dual-filler doped interfacial buffer layer solid electrolyte and a high-voltage cathode according to claim 1, characterized in that In step S1, the mass of PEO is 0.25 g, and the mass of LiTFSI is 0.09 g.

3. A method for modifying a solid electrolyte-high voltage cathode interface with a double-filler doped interfacial buffer layer according to claim 1, characterized in that, The stirring speed in step S1 is 800 - 1000 rpm.

4. A method for modifying the interface between a dual-filler doped interfacial buffer layer solid electrolyte and a high-voltage cathode, according to claim 1, characterized in that, The vacuum drying temperature in step S2 is 60 °C, and the time is 12 h.

5. A method for modifying the interface between a dual-filler doped interfacial buffer layer solid electrolyte and a high-voltage cathode, according to claim 1, wherein The LATP sheet in step S2 is synthesized by the solid-phase method.

6. A method for modifying a solid electrolyte-high voltage cathode interface with a double filler doped interfacial buffer layer according to claim 1, characterized in that, The NCM811 electrode sheet in step S3 is prepared by the following steps: Mix the cathode material NCM811, acetylene black, and PVDF in a mass ratio of 8:1:1 in an NMP solution, stir overnight, then coat it on an aluminum foil, and place it in a vacuum drying oven at 80 °C for 12 h to obtain.

7. A method for modifying a solid electrolyte-high voltage cathode interface with a double filler doped interfacial buffer layer according to claim 6, characterized in that, The loading of NCM811 in the NCM811 electrode is 2 mg cm -2 .

8. A solid electrolyte-high voltage cathode interface, characterized in that, Prepared by the method according to any one of claims 1 - 7.

9. Use of the method according to any one of claims 1 - 7 in the preparation of an LATP-based high-voltage solid-state battery with a long cycle life.

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