Method for modifying negative electrode interface in solid-state lithium battery by using composite two-dimensional material

Abstract

The application discloses a method for modifying the negative electrode interface in a solid-state lithium battery by using a composite two-dimensional material, and belongs to the field of lithium battery energy sources. The method forms an interface intermediate layer between a solid-state electrolyte and a lithium negative electrode, thereby improving interface contact, inhibiting dendrite growth, and improving battery cycle stability. The method mainly comprises the following steps: grinding a mixture of pyridine-modified g-C3N4 and BN powders to prepare a composite two-dimensional material; dispersing the ground composite two-dimensional material in a solvent to prepare a precursor solution; uniformly coating the precursor solution on the surface of the solid-state electrolyte and performing drying to obtain a solid-state electrolyte with a composite two-dimensional material layer on the surface; and tightly pressing a lithium sheet on the surface of the modified solid-state electrolyte and performing heat treatment to form an interface intermediate layer between the solid-state electrolyte and the lithium negative electrode through in-situ chemical reaction. The application is mainly used for improving battery interface contact, inhibiting dendrite growth, and improving battery cycle stability.

Description

Technical Field

[0001] This invention relates to the field of lithium battery energy, and more specifically, to a method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials. Background Technology

[0002] With the depletion of non-renewable resources such as fossil fuels and the increasing severity of environmental pollution, the research and utilization of green and renewable energy, as well as environmental protection, have become common issues in a globalized context. Secondary batteries, capable of efficient energy storage and conversion, are not only crucial for national economic development and strategic security but also closely related to daily life, making them a key focus and hot topic in scientific research. Lithium-ion secondary batteries offer advantages such as long cycle life, low self-discharge, and low cost, and have been widely used in large-scale energy storage and electronic products. Traditional liquid lithium batteries based on carbonate electrolytes, however, pose risks such as electrolyte leakage, combustion, and explosion, thus facing serious safety issues.

[0003] In recent years, solid-state lithium batteries based on various types of solid electrolytes have gradually emerged. These solid electrolytes are non-flammable and highly stable, effectively mitigating problems such as electrolyte leakage, combustion, and explosion. However, at the negative electrode interface of solid-state lithium batteries, due to the non-flowability of the electrolyte, the contact between it and the lithium metal negative electrode is solid-solid, with a limited and uneven contact area. This easily leads to local current concentration at the interface, increased interface impedance and polarization, and the induction of dendrite growth. For example, the multilayer lithium metal electrode and its manufacturing method disclosed in CN106716690B prevents battery performance degradation and internal short circuits by generating buffer and protective layers. Furthermore, the residual electronic conductivity of the solid electrolyte causes electrons from the lithium metal negative electrode to diffuse into the electrolyte. These electrons combine with lithium ions in the electrolyte, forming dendrites within the solid electrolyte. The formation and continuous growth of lithium dendrites eventually lead to dendrite penetration and battery short circuits, severely hindering the safety and cycle life of solid-state lithium batteries. Summary of the Invention

[0004] The purpose of this invention is to provide a method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials. This method improves interface contact, inhibits dendrite growth, and enhances battery cycle stability by forming an interfacial intermediate layer between the solid electrolyte and the lithium negative electrode.

[0005] This invention is achieved through the following technical solution:

[0006] A method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials includes the following steps:

[0007] S1: Thoroughly grind the mixed powder of pyridine-modified g-C3N4 and BN to prepare composite two-dimensional materials;

[0008] S2: Disperse the ground composite two-dimensional material in a solvent to prepare a precursor solution;

[0009] S3: The above precursor solution is uniformly coated onto the surface of the solid electrolyte and dried to obtain a solid electrolyte with a composite two-dimensional material layer modified on the surface.

[0010] S4: Press the lithium sheet tightly onto the surface of the modified solid electrolyte and perform heat treatment to form an interfacial intermediate layer between the solid electrolyte and the lithium anode through in-situ chemical reaction.

[0011] Furthermore, the pyridine-modified g-C3N4 is copolymerized from g-C3N4 matrix and pyridine, with a mass ratio of pyridine to g-C3N4 matrix of 0-50%.

[0012] Furthermore, the pyridine-modified g-C3N4 and BN are uniformly dispersed in a solvent by ultrasonic and magnetic stirring, and the mass ratio of pyridine-modified g-C3N4 to BN is 0-80%.

[0013] Furthermore, the solvent is any one of anhydrous ethanol, methanol, isopropanol, acetone, acetonitrile, N-methylpyrrolidone, and dimethylformamide.

[0014] Furthermore, the amount of the precursor solution used is 0.5 to 50 μL, and the coating method is any one of spin coating, dip coating, drop coating, or blade coating; drying is carried out in an oven at a temperature of 60 to 150°C.

[0015] Furthermore, the solid electrolyte is any one of oxide solid electrolyte, sulfide solid electrolyte, and halide solid electrolyte, wherein the oxide solid electrolyte includes Li7La3Zr2O. 12 (LLZO), Li 1+x Al x Ti 2-x (PO4)3(LATP), Li 3x La 2 / 3-x TiO3 (LLTO) and its derivatives; sulfide solid electrolytes including Li 10 (Ge 1-x M x P2S 12 (LGPS), Li6PS5X and its derivatives; halide solid electrolytes including Li a MX b M represents a metallic element, and X represents a halogen element.

[0016] Furthermore, the thickness of the composite two-dimensional material layer is 50 nm to 10 μm.

[0017] Furthermore, the lithium sheet has a diameter of 5–20 mm and a thickness of 50 μm–2 mm.

[0018] Furthermore, the heating rate of the heat treatment is 1-20℃ / min, the heat treatment temperature is 200-500℃, and the heat treatment time is 0.5-12h.

[0019] Furthermore, the interface intermediate layer is composed of pyridine-modified g-C3N4, BN, Li3N generated during the heat treatment of lithium metal, lithium-containing alloy, and the pyridine portion of pyridine-modified g-C3N4 that is stable but unreacted during the heat treatment process; the thickness of the intermediate layer is 5nm to 20μm; the lithium-containing alloy is composed of lithium-carbon alloy and lithium-boron alloy.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. Both g-C3N4 and BN contain abundant nitrogen sites, which have a strong adsorption effect on lithium ions, thus facilitating lithium ion transport. Pyridine doping further enhances the conductivity of g-C3N4. Under high-temperature conditions, the C3N4 matrix in pyridine-modified g-C3N4 reacts chemically with lithium metal, generating an interfacial intermediate phase containing Li3N and a lithium-carbon alloy in situ. The pyridine portion in pyridine-modified g-C3N4 remains stable with lithium at high temperatures, enhancing the adsorption and migration of lithium ions at the interface. Similarly, BN also reacts chemically with lithium metal at high temperatures, generating an interfacial intermediate phase containing Li3N and a lithium-boron alloy in situ. Li3N is a solid-state ionic conductor, promoting ion transport at the interface and inhibiting electron migration from the lithium metal anode to the electrolyte. The alloy exhibits strong wettability with lithium metal, forming a dense solid-solid contact, thereby improving the anode interface, inhibiting dendrite growth, and enhancing battery cycle stability.

[0022] 2. This method is simple and easy to implement. It can enhance the wettability of solid electrolyte to lithium metal anode, obtain dense interfacial contact, reduce interfacial impedance and polarization, and at the same time suppress the migration and diffusion of electrons into the electrolyte, thereby improving the safety and cycle performance of the battery. It has good prospects for industrial application. Attached Figure Description

[0023] Figure 1 This is the impedance spectrum of a lithium symmetric battery based on composite two-dimensional material modification according to Embodiment 1 of the present invention;

[0024] Figure 2 This is the impedance spectrum of a lithium symmetric battery based on composite two-dimensional material modification according to Embodiment 2 of the present invention;

[0025] Figure 3This is the constant current cycling curve of the lithium symmetric battery based on composite two-dimensional material modification in Embodiment 1 of the present invention;

[0026] Figure 4 This is the constant current cycling curve of the lithium symmetric battery based on composite two-dimensional material modification in Embodiment 2 of the present invention. Detailed Implementation

[0027] The present invention will now be further described in conjunction with the accompanying drawings.

[0028] Example 1: A method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials, comprising the following steps:

[0029] 1) Grind 5% pyridine-doped g-C3N4(CN-5) powder and BN powder thoroughly at a mass ratio of 20:80. Disperse the ground composite two-dimensional material powder in anhydrous ethanol by ultrasonication for 0.5 h and magnetic stirring for 12 h to prepare a uniform precursor solution.

[0030] 2) Take 2 μL of the precursor solution from step 1) and drop it onto Ta-doped LLZO (Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The LLZTO solid electrolyte surface is then dried in an oven at 60°C. After drying, 2 μL of the precursor solution from step 1) is also dropped onto the other side of the LLZTO solid electrolyte, and then dried again in an oven at 60°C (the thickness of the composite two-dimensional material layer is 2 μm). Finally, it is taken out for use.

[0031] 3) Cut the 450μm thick lithium sheet into a 10mm diameter circular piece, then press the two lithium sheets tightly against the solid electrolyte in step 2), place them on the flat heating table in the glove box, set the heating rate to 10℃ / min, the temperature to 350℃, the heat treatment time to 2h, and let them cool naturally before use.

[0032] 4) The LLZTO solid electrolyte with lithium sheets on both sides (the solid electrolyte and the lithium anode have formed an interfacial intermediate layer through in-situ chemical reaction, and the thickness of the intermediate layer is 5μm) is encapsulated into a button cell to obtain a lithium symmetric battery with a modified anode interface.

[0033] Figure 1 The impedance spectrum of the lithium symmetric battery modified with CN-5 and BN composite two-dimensional material in Example 1 shows that the total impedance of the symmetric battery is less than 290Ω, which is beneficial to the uniform transport of lithium ions. Figure 3 The lithium-symmetric battery modified with CN-5 and BN composite two-dimensional materials in Example 1 operates at a current density of 0.1 mA / cm². 2The constant current cycling curves show that the overall polarization of the symmetrical cell is very small, about 40mV, which demonstrates the excellent cycling performance of the modified symmetrical cell.

[0034] Example 2: A method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials, comprising the following steps:

[0035] 1) Grind 20% pyridine-doped g-C3N4(CN-20) powder and BN powder thoroughly at a mass ratio of 50:50. Disperse the ground composite two-dimensional material powder in anhydrous ethanol by ultrasonication for 0.5 h and magnetic stirring for 12 h to prepare a uniform precursor solution.

[0036] 2) Take 2 μL of the precursor solution from step 1) and drop it onto Ta-doped LLZO (Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The LLZTO solid electrolyte surface is then dried in an oven at 60°C. After drying, 2 μL of the precursor solution from step 1) is also dropped onto the other side of the LLZTO solid electrolyte, and then dried again in an oven at 60°C (the thickness of the composite two-dimensional material layer is 2 μm). Finally, it is taken out for use.

[0037] 3) Cut the 450μm thick lithium sheet into a 10mm diameter circular piece, then press the two lithium sheets tightly against the solid electrolyte in step 2), place them on the flat heating table in the glove box, set the heating rate to 10℃ / min, the temperature to 350℃, the heat treatment time to 2h, and let them cool naturally before use.

[0038] 4) The LLZTO solid electrolyte with lithium sheets on both sides (the solid electrolyte and the lithium anode have formed an interfacial intermediate layer through in-situ chemical reaction, and the thickness of the intermediate layer is 5μm) is encapsulated into a button cell to obtain a lithium symmetric battery with a modified anode interface.

[0039] Figure 2 The impedance spectrum of the lithium symmetric battery modified with CN-20 and BN composite two-dimensional material in Example 2 shows that the total impedance of the symmetric battery is less than 220Ω, which is beneficial to the uniform transport of lithium ions. Figure 4 The lithium-symmetric battery modified with CN-20 and BN composite two-dimensional materials in Example 2 operates at a current density of 0.1 mA / cm². 2 The constant current cycling curves show that the overall polarization of the symmetrical cell is very small, about 25mV, which demonstrates the excellent cycling performance of the modified symmetrical cell.

[0040] Both g-C3N4 and BN contain abundant nitrogen sites, which strongly adsorb lithium ions, thus facilitating lithium ion transport. Pyridine doping further enhances the conductivity of g-C3N4. At high temperatures, the C3N4 matrix in pyridine-modified g-C3N4 reacts chemically with lithium metal, forming an interfacial intermediate phase containing Li3N and a lithium-carbon alloy. The pyridine moiety in the pyridine-modified g-C3N4 remains stable with lithium at high temperatures, enhancing lithium ion adsorption and migration at the interface. Similarly, BN reacts chemically with lithium metal at high temperatures, forming an interfacial intermediate phase containing Li3N and a lithium-boron alloy. Li3N is a solid-state ionic conductor, promoting ion transport at the interface and inhibiting electron migration from the lithium metal anode to the electrolyte. The alloy exhibits strong wettability with lithium metal, forming a dense solid-solid contact, thereby improving the anode interface, inhibiting dendrite growth, and enhancing battery cycle stability.

Claims

1. A method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials, characterized in that: Includes the following steps: S1: Thoroughly grind the mixed powder of pyridine-modified g-C3N4 and BN to prepare composite two-dimensional materials; S2: Disperse the ground composite two-dimensional material in a solvent to prepare a precursor solution; S3: The above precursor solution is uniformly coated onto the surface of the solid electrolyte and dried to obtain a solid electrolyte with a composite two-dimensional material layer modified on the surface. S4: Press the lithium sheet tightly onto the surface of the modified solid electrolyte and perform heat treatment to form an interfacial intermediate layer between the solid electrolyte and the lithium anode through in-situ chemical reaction. The interface intermediate layer is composed of pyridine-modified g-C3N4, BN, Li3N generated during lithium metal heat treatment, lithium-containing alloy, and unreacted pyridine; the thickness of the intermediate layer is 5 nm to 20 μm; the lithium-containing alloy is composed of lithium-carbon alloy and lithium-boron alloy.

2. The method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials according to claim 1, characterized in that: The pyridine-modified g-C3N4 is a copolymer of g-C3N4 matrix and pyridine, with a mass ratio of pyridine to g-C3N4 matrix of 5% to 20%.

3. The method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials according to claim 1, characterized in that: The pyridine-modified g-C3N4 and BN are uniformly dispersed in a solvent by ultrasonic and magnetic stirring, and the mass ratio of pyridine-modified g-C3N4 to BN is 25%~50%.

4. The method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials according to claim 1, characterized in that: The solvent is any one of anhydrous ethanol, methanol, isopropanol, acetone, acetonitrile, N-methylpyrrolidone, and dimethylformamide.

5. The method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials according to claim 1, characterized in that: The amount of precursor solution used is 0.5~50 μL, and the coating method is any one of spin coating, dip coating, drop coating, or blade coating; drying is carried out in an oven at a temperature of 60~150 ℃.

6. The method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials according to claim 1, characterized in that: The solid electrolyte is any one of oxide solid electrolyte, sulfide solid electrolyte, and halide solid electrolyte, wherein the oxide solid electrolyte includes Li7La3Zr2O. 12 Li 1+x Al x Ti 2-x (PO4)3, Li 3x La 2 / 3-x TiO3 and its derivatives; sulfide solid electrolytes including Li 10 (Ge 1-x M x P2S 12 Li6PS5X and its derivatives; halide solid electrolytes including Li a MX b M represents a metallic element, and X represents a halogen element.

7. The method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials according to claim 1, characterized in that: The thickness of the composite two-dimensional material layer is 50 nm to 10 μm.

8. The method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials according to claim 1, characterized in that: The lithium sheet has a diameter of 5-20 mm and a thickness of 50 μm-2 mm.

9. The method for modifying the negative electrode interface in a solid-state lithium battery using composite two-dimensional materials according to claim 1, characterized in that: The heating rate of the heat treatment is 1~20 ℃ / min, the heat treatment temperature is 200~500 ℃, and the heat treatment time is 0.5~12 h.

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