Method for efficiently preparing solid electrolyte and alkali metal interface by room temperature laser welding engineering

Abstract

The application belongs to the field of solid electrolyte, and discloses a method for efficiently preparing a solid electrolyte and an alkali metal interface by room-temperature laser welding engineering. The method does not introduce any alloy compound or polymer modification layer. When a high-power focused laser beam generated by laser welding is irradiated to the surface of an alkali metal foil, part of the light energy will be absorbed by the material and converted into heat energy, so that the alkali metal foil is closely attached to the surface of the solid electrolyte. The corresponding different material surface points are in sufficient contact. In this process, the heat energy makes the alkali metal ions in the interface rapidly diffuse, promotes atomic-level tight welding, reduces the gap generated between the interfaces, and maximizes the interface contact between the alkali metal foil and the solid electrolyte. The application can make the interface between the solid electrolyte and the alkali metal negative electrode closely contact in a very short time, reduce the interface impedance, and effectively improve the charge and discharge capacity of the solid-state battery.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolytes, and specifically relates to a method for efficiently preparing solid electrolyte-alkali metal interfaces in room temperature laser welding engineering. Background Technology

[0002] Lithium-ion batteries are widely used in portable electronic products and electric vehicles. However, due to the use of flammable liquid electrolytes, safety concerns remain regarding commercially available lithium-ion batteries. Furthermore, regardless of improvements to the cathode / anode and liquid electrolyte interface or the use of different anode and cathode materials, their energy density will likely reach its limit in the near future. Therefore, finding energy storage systems with higher energy density is of paramount importance. Lithium metal possesses high theoretical specific capacity and low electrochemical potential, making it suitable as anode material in lithium batteries. However, lithium metal is unstable in liquid electrolytes, leading to severe side reactions such as electrolyte decomposition and the generation of toxic volatile gases. Additionally, liquid lithium-ion batteries are prone to lithium dendrite formation during charge and discharge, resulting in internal short circuits and thermal runaway. To address these issues, solid-state electrolytes have been introduced into lithium batteries. All-solid-state lithium batteries offer good safety and potentially high energy density, promising to meet the demands of large-scale energy storage applications and widely considered the next-generation battery technology to replace traditional lithium-ion batteries. Solid-state electrolytes are a crucial component of all-solid-state lithium batteries and are key to their commercialization. An ideal solid-state lithium battery should have high ionic conductivity and charge-discharge cycle performance, enabling it to operate safely and stably for extended periods at high rates.

[0003] In recent years, solid-state electrolytes have developed rapidly, including LISICON oxides, NASICON oxides, perovskite oxides, garnet oxides, and sulfide glass / glass-ceramic / crystalline electrolytes. Each system has its own advantages and disadvantages. Among them, phosphate solid-state electrolytes with a NASICON structure (such as those made from Li...) 1+x Al x Ti 2-x The NASICON-type lithium aluminum titanium phosphate (LATP) composed of (PO4)3 has attracted attention, mainly due to its stability to air, wide electrochemical window, and high theoretical ionic conductivity. However, the solid electrolyte and the metal anode are in a solid-solid contact, which easily generates a large interfacial impedance during charge and discharge, leading to a decrease in electrochemical stability. Currently, there are many methods for modifying the solid electrolyte interface, such as magnetron sputtering, chemical vapor deposition, and atomic layer deposition, but these methods are expensive, complex, and time-consuming, making them unsuitable for mass production.

[0004] Therefore, it is necessary to study a method to achieve close contact between the solid electrolyte and the metal anode in a short time, reduce interfacial impedance, and improve the charge and discharge capacity of solid-state batteries. Summary of the Invention

[0005] To overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a method for efficiently preparing a solid electrolyte-alkali metal interface using room-temperature laser welding. This method enables close contact between the solid electrolyte and the alkali metal anode interface in a very short time, reducing interfacial impedance and effectively improving the charge and discharge capacity of the solid-state battery. Furthermore, the preparation method employed in this invention is simple, efficient, and has good repeatability, which is beneficial for large-scale industrial applications.

[0006] Another objective of this invention is to provide a solid electrolyte-alkali metal interface prepared by the above method.

[0007] Another objective of this invention is to provide the application of the solid electrolyte-alkali metal interface prepared by the above method in solid-state batteries.

[0008] The objective of this invention is achieved through the following solution:

[0009] A method for efficiently preparing solid electrolyte-alkali metal interfaces using room temperature laser welding includes the following steps:

[0010] In an inert atmosphere, alkali metal foil and solid electrolyte are welded together using laser welding to obtain the solid electrolyte-alkali metal interface.

[0011] The method for efficiently preparing solid electrolyte-alkali metal interfaces in room temperature laser welding specifically includes the following steps:

[0012] The alkali metal foil and solid electrolyte are placed in a glove box filled with inert gas. The alkali metal foil is pressed onto the surface of the solid electrolyte. The metal probe of a laser welding machine is placed above the alkali metal foil, and power is applied to obtain the interface between the solid electrolyte and the alkali metal.

[0013] As a preferred method, the alkali metal foil may be lithium, sodium, or potassium metal foil; as a further preferred method, the alkali metal foil may be lithium metal foil.

[0014] As a preferred method, the thickness of the alkali metal foil ranges from 30 to 50 μm; as a further preferred method, the thickness of the alkali metal foil is 40 μm.

[0015] As a preferred method, the solid electrolyte can be synthesized by solid-phase method, sol-gel method or co-precipitation method, and more preferably by solid-phase method;

[0016] As a preferred method, the solid electrolyte is an inorganic solid electrolyte, which is at least one of NASICON electrolyte, LISICON electrolyte, garnet-type electrolyte or sulfide-type electrolyte, and more preferably NASICON electrolyte.

[0017] As a preferred method, the thickness of the solid electrolyte ranges from 0.5 to 1.5 mm; as a further preferred method, the thickness of the solid electrolyte is 1 mm.

[0018] As a preferred method, the inert atmosphere is at least one of Ar, He, or Ne; as a further preferred method, the inert gas is Ar.

[0019] As a preferred method, the laser welding power is 40-120W and the welding time is 5-40s;

[0020] As a further preferred method, the laser welding power is 50-100W and the welding time is 10-20s;

[0021] As a further preferred method, the laser welding power is 70W and the welding time is 15s.

[0022] As a preferred method, the solid electrolyte-alkali metal interface is Li alkali metal foil / Li 1+x Al x Ti 2-x A (PO4)3(LATP) solid electrolyte layer, wherein 0.1 ≤ x ≤ 0.5; as a preferred method, x = 0.3 is selected;

[0023] More preferably, the Li 1+x Al x Ti 2-x (PO4)3 solid electrolyte is synthesized via a solid-phase method, including the following steps:

[0024] (1) To synthesize Li 1+x Al x Ti 2-x The raw materials of (PO4)3 are put into a ball mill jar, organic solvent is added for ball milling, calcination, and LATP powder after one ball milling is obtained. The LATP powder obtained after one ball milling is ball milled a second time to obtain a slurry, which is then dried and sieved to obtain LATP powder.

[0025] (2) Take LATP powder and binder and mix them. Put the mixed powder into a mold and press it into a tablet. Place the obtained ceramic tablet in a muffle furnace for sintering to obtain LATP solid electrolyte.

[0026] As a preferred method, the Li described in step (1) 1+x Alx Ti 2-x (PO4)3 is Li 1.3 Al 0.3 Ti 1.7 (PO4)3 solid electrolyte;

[0027] As a preferred method, the Li described in step (1) 1+x Al x Ti 2-x The raw materials for (PO4)3 are Li source, Al source, TiO2, and H6NO4P, and each raw material is weighed according to the stoichiometric ratio. The excess mass fraction of Li source is 5% to 15%. As a further optimization method, the excess mass fraction of Li source is 10%.

[0028] As a preferred method, the organic solvent in step (1) is at least one of alcohol, acetone, or methanol; as a further preferred method, the organic solvent is alcohol; in the ball milling in step (1), the organic solvent and Li 1+ x Al x Ti 2-x The mass ratio of all raw materials in (PO4)3 is 1.5–2:1–1.5, the ball milling time is 6–10 h, and the ball milling speed is 250–350 r / min; as a further preferred method, the organic solvent and Li 1+x Al x Ti 2-x The mass ratio of each raw material in (PO4)3 is 1.5:1; the ball milling time is 8 hours and the ball milling speed is 300 r / min;

[0029] As a preferred method, the calcination mentioned in step (1) refers to calcination in a muffle furnace, in an atmosphere such as air, N2, Ar or H2, by raising the temperature from room temperature to 800-1000℃ at a rate of 5-10℃ / min and holding it for 4-8 hours; as a further preferred method, an air atmosphere is selected, and the temperature is raised to 900℃ at a rate of 5℃ / min and held for 6 hours.

[0030] As a preferred method, the drying in step (1) refers to drying in a drying oven at 60-100°C for 4-6 hours until the powder is completely dry; as a further preferred method, drying in a drying oven at 80°C for 5 hours;

[0031] As a preferred method, the adhesive mentioned in step (2) is at least one of polyvinyl butyral resin (PVB) or polyvinyl alcohol (PVA); as a further preferred method, the adhesive is PVB; the LATP powder and the adhesive mentioned in step (2) are mixed and stirred, wherein the mass ratio of LATP to adhesive is 8-10:1-1.5; as a further preferred method, the mass ratio of LATP to adhesive is 10:1.

[0032] As a preferred method, the mold described in step (2) is used for pressing the tablet, and the diameter of the selected mold is 10-18 mm; as a further preferred method, the diameter of the mold is 12.7 mm.

[0033] As a preferred method, the sintering atmosphere in step (2) is one of N2, Ar or air; the sintering temperature is 800-1000℃ and the sintering time is 4-8h; as a further preferred method, the sintering time is 6h.

[0034] As a preferred method, the thickness of the LATP solid electrolyte in step (1) is 0.5 to 1.5 mm, and as a further preferred method, the thickness of the solid electrolyte is 1 mm.

[0035] The solid electrolyte and alkali metal interface prepared by the above method.

[0036] Application of the solid electrolyte-alkali metal interface prepared by the above method in solid-state batteries.

[0037] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0038] This invention utilizes room-temperature laser welding to modify the interface of a solid electrolyte. When a high-power focused laser beam generated by laser welding is applied to the surface of an alkali metal foil within a short time, some of the light energy is absorbed by the material and converted into heat energy. This causes the alkali metal foil to adhere tightly to the surface of the solid electrolyte, ensuring full contact between different material surfaces. During this process, the heat energy causes the alkali metal ions at the interface to diffuse rapidly, promoting atomic-level tight welding, reducing the gaps between interfaces, maximizing the contact between the alkali metal foil and the solid electrolyte. This tight interface contact reduces interface impedance and effectively improves the charge and discharge capacity of the solid-state battery. Attached Figure Description

[0039] Figure 1 Impedance spectrum of LATP solid electrolyte provided in Example 1 at room temperature;

[0040] Figure 2 Impedance spectrum of Li / LATP / Li-70W laser-welded symmetrical cell provided in Example 1 at room temperature;

[0041] Figure 3 Impedance spectrum of Li / LATP / Li-100W laser-welded symmetrical cell provided in Example 2 at room temperature;

[0042] Figure 4 Impedance spectrum of Li / LATP / Li-50W laser-welded symmetrical cell provided in Example 3 at room temperature;

[0043] Figure 5 Impedance spectrum of Na / LLZO / Na-70W laser-welded symmetrical cell provided in Example 4 at room temperature;

[0044] Figure 6 Impedance spectra of the Li / LATP / Li-unwelded symmetric cell provided for Comparative Example 1 at room temperature;

[0045] Figure 7 Impedance spectra of Li / LATP / Li-ultrasonic welded symmetrical cells provided for Comparative Example 2 at room temperature;

[0046] Figure 8 Impedance spectra of the Na / LLZO / Na- weld-free symmetric cell provided for Comparative Example 3 at room temperature;

[0047] Figure 9 The Li / LATP / Li-70W laser-welded symmetric cell provided in Example 1 was tested at 0.1 mA / cm². 2 Cyclic spectrum at current density;

[0048] Figure 10 The Li / LATP / Li-100W laser-welded symmetric cell provided in Example 2 was tested at 0.1 mA / cm². 2 Cyclic spectrum at current density

[0049] Figure 11 The Li / LATP / Li-50W laser-welded symmetric cell provided in Example 3 was tested at 0.1 mA / cm². 2 Cyclic spectrum at current density

[0050] Figure 12 This is a charge-discharge curve of the LFP / LATP / Li solid-state battery provided in Example 1 at 0.1C.

[0051] Figure 13 The graph shows the charge / discharge specific capacity and charge / discharge efficiency of the LFP / LATP / Li solid-state battery provided in Example 1 at a rate of 0.1C.

[0052] Figure 14 The graph shows the specific capacity and charge / discharge efficiency of the LFP / LATP / Li solid-state battery provided in Example 1 at different rates. Detailed Implementation

[0053] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0054] Example 1

[0055] Synthesis of Li using traditional solid-state method 1.3 Al 0.3 Ti 1.7 (PO4)3 solid electrolyte: The required amounts of substances were calculated based on stoichiometry, and the compounds were nano-Al2O3, excess 10wt% Li2CO3 (Li is volatile), TiO2, and H6NO4P. All raw materials were placed in a ball mill jar for ball milling, with the mass ratio of alcohol to the total raw materials being 1.5:1. The ball milling time was 8 hours, and the milling speed was 300 r / min. The powder was then calcined at room temperature by increasing the temperature to 800℃ at a rate of 5℃ / min and holding for 6 hours. The obtained powder was then ball milled a second time, with the mass ratio of alcohol to LATP powder being 1.5:1. The ball milling time was 8 hours, and the milling speed was 300 r / min. The slurry was then dried and sieved to obtain LATP powder. The LATP powder and PVB were mixed and stirred. 0.25 g of the mixed powder was placed in a mold with a diameter of 12.7 mm for tableting (the electrolyte area is S = 120 mm²). 2 The obtained ceramic sheets were heated to 380℃ at room temperature at 1℃ / min and held for 6h, then heated to 600℃ at 3℃ / min and held for 6h, and finally heated to 950℃ at 5℃ / min and held for 6h for sintering to obtain LATP solid electrolyte.

[0056] Li metal foil and LATP solid electrolyte were placed in a glove box filled with Ar gas. The Li metal foil was pressed onto the surface of the LATP solid electrolyte. A 70W laser welding machine probe was placed above the Li metal foil, and power was applied. The laser welding operation was completed in 15 seconds, ultimately producing an ultra-tightly bonded Li metal foil / LATP solid electrolyte layer. These were then assembled into coin cells: Li / LATP / SS, Li / LATP / Li, and LFP / LATP / Li.

[0057] In the process of preparing the Li metal foil / LATP solid electrolyte layer using laser welding, the thickness of the Li metal foil can be a conventional thickness, generally 30–50 μm, for example, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm; in this embodiment, the thickness of the Li metal foil is 40 μm. The thickness of the LATP solid electrolyte layer is also a conventional thickness, generally 0.5–1.5 mm; in this embodiment, the thickness of the LATP solid electrolyte layer is 1 mm.

[0058] The aforementioned solid-state battery, Li / LATP / SS, comprises a negative electrode shell, nickel foam (1 mm thick, 10 mm in diameter), a Li metal negative electrode, a solid electrolyte, a stainless steel sheet, and a positive electrode shell. The Li metal foil is laser-welded to one side of the solid electrolyte. The nickel foam is placed between the negative electrode shell / negative electrode and the positive electrode shell / positive electrode. The positive electrode is a stainless steel sheet, and the battery is encapsulated using a 2032 battery case. This battery is used to test the resistance of the solid electrolyte LATP and calculate its ionic conductivity. The battery was tested at 25°C with a test voltage of 0.5V.

[0059] The aforementioned solid-state battery, Li / LATP / Li, comprises a negative electrode shell, nickel foam (1 mm thick, 10 mm in diameter), a Li metal negative electrode, a solid electrolyte, and a positive electrode shell, and is labeled as a Li / LATP / Li-70W laser-welded symmetrical battery. Specifically, Li metal foil is laser-welded to both sides of the solid electrolyte, and nickel foam is placed between the negative electrode shell / negative electrode and the positive electrode shell / positive electrode, respectively. It is encapsulated using a 2032 battery case. This battery is used to test the interfacial resistance of the solid electrolyte LATP. The battery was tested at 25°C with a test voltage of 0.5V.

[0060] The aforementioned solid-state battery LFP / LATP / Li (LFP being lithium iron phosphate) comprises a negative electrode shell, nickel foam (1 mm thick, 10 mm in diameter), a Li metal negative electrode, a solid electrolyte, an LFP positive electrode sheet, and a positive electrode shell. The Li metal foil is laser-welded to one side of the solid electrolyte. The nickel foam is placed between the negative electrode shell / negative electrode and the positive electrode shell / positive electrode. The positive electrode is the LFP, and the battery is encapsulated using a 2032 battery case. This battery was used to test the charge-discharge performance of solid-state batteries. The battery was tested at 25°C, with a cutoff voltage of 2.8–3.8 V and a current density of 0.1 C.

[0061] The preparation method of the above-mentioned LiFePO4 positive electrode sheet is as follows: LFP, conductive carbon black, and PVDF are uniformly mixed in a mass ratio of 8:1:1, and then NMP is added and mixed uniformly. The solid content is 30%, with 0.8g of LFP, 0.1g of conductive carbon black, 0.1g of PVDF, and 2.33g of NMP. The mixed slurry is coated onto aluminum foil and dried in an oven at 100℃ for 12 hours. The dried positive electrode sheet is then cut into small electrode discs with a diameter of 12mm for later use. The areal density of these small positive electrode discs is 1.8mg / cm³. 2 .

[0062] Figure 1 The impedance spectrum of Li / LATP / SS provided in Example 1 at room temperature is shown in the figure. It can be seen from the figure that the impedance value of the LATP solid electrolyte at room temperature is 100Ω. Calculations show that (where d = 1 mm, S = 120 mm) 2 The ionic conductivity of this solid electrolyte is 8.3 x 10⁻⁶. -4 With a conductivity of S / cm, it exhibits extremely high ionic conductivity.

[0063] Figure 2 The impedance spectrum of the Li / LATP / Li-70W laser-welded symmetrical cell provided in Example 1 at 25°C and 0.5V test voltage shows an interface resistance of 450Ω. This indicates that after 70W laser welding, the LATP solid electrolyte interface exhibits very low impedance, suggesting that the LATP solid electrolyte and Li anode have an excellent contact interface, which is beneficial to the Li... + Free transport and effective suppression of lithium dendrite formation ensure the normal operation of solid-state batteries.

[0064] Figure 9 The Li / LATP / Li-70W laser-welded symmetric cell provided in Example 1 was tested at 0.1 mA / cm². 2 The cycling spectrum at current density shows that after laser welding with a power of 70W, the polarization voltage of LATP is around 0.1V. It does not fluctuate or fail over a long period of time (100h), demonstrating a good ability to suppress lithium dendrite growth.

[0065] Figure 12 The charge-discharge curve of the LFP / LATP / Li solid-state battery provided in Example 1 at 0.1C shows that the specific capacity of the first charge can reach 159mAh / g, the specific capacity of the first discharge can reach 154mAh / g, and the first efficiency is 96.9%, which shows that it has extremely high charge-discharge energy storage capacity and coulombic efficiency.

[0066] Figure 13The graphs showing the charge / discharge specific capacity and charge / discharge efficiency of the LFP / LATP / Li solid-state battery provided in Example 1 at 25°C and 0.1C rate demonstrate that the electrolyte exhibits excellent charge / discharge performance. After 85 cycles, the charge specific capacity reaches 133 mAh / g, the discharge capacity reaches 131 mAh / g, and the coulombic efficiency is 98%. This is attributed to the high ionic conductivity and low interfacial impedance, indicating that using a 70W laser welding process at the solid electrolyte / Li anode interface is beneficial to improving the overall performance of the solid-state battery.

[0067] Figure 14 The graphs for the LFP / LATP / Li solid-state battery provided in Example 1 show the charge / discharge specific capacity and charge / discharge efficiency at 25°C and different rates (0.1C, 0.2C, 0.5C, 0.2C, and 0.1C). The graphs indicate that the solid electrolyte, after being charged and discharged at different rates, achieves a charging specific capacity of 149.3 mAh / g and a discharging specific capacity of 128 mAh / g with an efficiency of 86% at 0.1C. At 0.5C, the charging specific capacity reaches 126.0 mAh / g, the discharging specific capacity reaches 124.7 mAh / g, and the efficiency is 98.9%. Upon returning to 0.1C, the charging specific capacity reaches 121.9 mAh / g, the discharging specific capacity reaches 121.4 mAh / g, and the efficiency is 99.5%. These results demonstrate that the battery exhibits excellent cycle stability and high specific capacity.

[0068] Example 2

[0069] Synthesis of Li using traditional solid-state method 1.3 Al 0.3 Ti 1.7 (PO4)3 solid electrolyte, the required amounts of which were calculated based on stoichiometry, consisted of nano-Al2O3, excess 10wt% Li2CO3 (Li is volatile), TiO2, and H6NO4P. All raw materials were placed in a ball mill jar for ball milling, with an alcohol-to-total-raw-materials mass ratio of 1.5:1, a milling time of 8 hours, and a milling speed of 300 r / min. The mixture was then calcined at room temperature by increasing the temperature to 800℃ at a rate of 5℃ / min and holding for 6 hours. The resulting powder was then subjected to a second ball milling, with an alcohol-to-LATP powder mass ratio of 1.5:1, a milling time of 8 hours, and a milling speed of 300 r / min. The slurry was then dried and sieved to obtain LATP powder. LATP powder and PVB were mixed and stirred. 0.25g of the mixed powder was pressed into a mold with a diameter of 12.7mm and then pressed into a ceramic sheet. The resulting ceramic sheet was heated to 380℃ at room temperature at 1℃ / min and held for 6h, then heated to 600℃ at 3℃ / min and held for 6h, and finally sintered at 950℃ at 5℃ / min and held for 6h to obtain LATP solid electrolyte.

[0070] The Li metal foil and LATP solid electrolyte were placed in a glove box filled with Ar gas. The Li metal foil was pressed onto the surface of the LATP solid electrolyte. The metal probe of a 100W laser welding machine was placed above the Li metal foil, and the power was applied. The laser welding operation was completed in 15 seconds, and finally an ultra-tightly bonded Li metal foil / LATP solid electrolyte layer was prepared.

[0071] In the process of preparing the Li metal foil / LATP solid electrolyte layer using laser welding, the thickness of the Li metal foil can be a conventional thickness; in this embodiment, the thickness of the Li metal foil is 40 μm. The thickness of the LATP solid electrolyte layer is 1 mm.

[0072] The preparation steps and testing conditions of the Li / LATP / Li-100W laser-welded symmetric cell provided in this embodiment are basically the same as those in Example 1. The difference is that the power of the laser welding machine used in the preparation process of this embodiment is 100W. Figure 3 The impedance spectrum of the Li / LATP / Li-100W laser-welded symmetrical cell provided in Example 2 at room temperature shows an interface resistance of 512Ω, which also exhibits a relatively small interface impedance.

[0073] Figure 10 The Li / LATP / Li-100W laser-welded symmetric cell provided in Example 2 was tested at 0.1 mA / cm². 2 The cyclic spectrum at current density, after a 100W laser welding process, showed a polarization voltage of approximately 0.15V, indicating a slight increase in interfacial impedance (compared to Example 1). Figure 3 The experimental results are consistent, indicating that when the laser welding power is further increased from 70W to 100W, the interface performance is slightly reduced, resulting in a decrease in the Li ion insertion / extraction ability during charging and discharging.

[0074] Example 3

[0075] Synthesis of Li using traditional solid-state method 1.3 Al 0.3 Ti 1.7(PO4)3 solid electrolyte, the required amounts of which were calculated based on stoichiometry, consisted of nano-Al2O3, excess 10wt% Li2CO3 (Li is volatile), TiO2, and H6NO4P. All raw materials were placed in a ball mill jar for ball milling, with an alcohol-to-total-raw-materials mass ratio of 1.5:1, a milling time of 8 hours, and a milling speed of 300 r / min. The mixture was then calcined at room temperature by increasing the temperature to 800℃ at a rate of 5℃ / min and holding for 6 hours. The resulting powder was then subjected to a second ball milling, with an alcohol-to-LATP powder mass ratio of 1.5:1, a milling time of 8 hours, and a milling speed of 300 r / min. The slurry was then dried and sieved to obtain LATP powder. LATP powder and PVB were mixed and stirred. 0.25g of the mixed powder was pressed into a mold with a diameter of 12.7mm and then pressed into a ceramic sheet. The resulting ceramic sheet was heated to 380℃ at room temperature at 1℃ / min and held for 6h, then heated to 600℃ at 3℃ / min and held for 6h, and finally sintered at 950℃ at 5℃ / min and held for 6h to obtain LATP solid electrolyte.

[0076] The Li metal foil and LATP solid electrolyte were placed in a glove box filled with Ar gas. The Li metal foil was pressed onto the surface of the LATP solid electrolyte. The metal probe of a 50W laser welding machine was placed above the Li metal foil, and the power was applied. The laser welding operation was completed in 15 seconds, and finally an ultra-tightly bonded Li metal foil / LATP solid electrolyte layer was prepared.

[0077] In the process of preparing the Li metal foil / LATP solid electrolyte layer using laser welding, the thickness of the Li metal foil can be a conventional thickness; in this embodiment, the thickness of the Li metal foil is 40 μm. The thickness of the LATP solid electrolyte layer is 1 mm.

[0078] The preparation steps and testing conditions of the Li / LATP / Li-50W laser-welded symmetric cell provided in this embodiment are basically the same as those of the Li / LATP / Li-70W laser-welded symmetric cell in Example 1. The difference is that the laser welding machine used in this embodiment has a power of 50W. Figure 4 The impedance spectrum of the Li / LATP / Li-50 W laser-welded symmetrical cell provided in Example 3 is shown at room temperature, with an interface resistance of 608Ω.

[0079] Figure 11 The Li / LATP / Li-50W laser-welded symmetric cell provided in Example 3 was tested at 0.1 mA / cm². 2The cyclic spectrum at current density, after a 50W laser welding process, showed a polarization voltage of approximately 0.2V, indicating an increase in interfacial impedance (compared to Example 1). This suggests that using low-power laser welding may slightly worsen interfacial contact, leading to Li... + Their migration ability has decreased.

[0080] Example 4

[0081] Synthesis of Li7La3Zr using a traditional solid-state method 1.7 Ti 0.3 O 12 (LLZO) solid electrolyte, the required amounts of substances were calculated based on stoichiometry, including Li₂CO₃ (10% excess Li source by mass), La₂O₃, ZrO₂, and TiO₂. All raw materials were placed in a ball mill jar for ball milling, with the mass ratio of alcohol to the total raw materials being 1.5:1. The ball milling time was 8 hours at a speed of 300 r / min. The powder was then calcined at room temperature by increasing the temperature to 800℃ at a rate of 5℃ / min and holding for 6 hours. The obtained powder was then subjected to a second ball milling, with the mass ratio of alcohol to LLZO powder being 1.5:1. The ball milling time was 8 hours at a speed of 300 r / min. The slurry was then dried and sieved to obtain LLZO powder. LLZO powder and PVB were mixed and stirred. 0.25g of the mixed powder was pressed into a mold with a diameter of 12.7mm. The resulting ceramic sheets were heated to 380℃ at room temperature at 1℃ / min and held for 6h, then heated to 600℃ at 3℃ / min and held for 6h, and finally heated to 900℃ at 5℃ / min and held for 6h for sintering to obtain LLZO solid electrolyte.

[0082] Na metal foil and LLZO solid electrolyte were placed in a glove box filled with Ar gas. The Na metal foil was pressed onto the surface of the LLZO solid electrolyte. A metal probe of a 70W laser welding machine was placed above the Na metal foil, and power was applied. The laser welding operation was completed in 15 seconds, and finally an ultra-tightly bonded Na metal foil / LLZO solid electrolyte layer was prepared.

[0083] In the process of preparing the Na metal foil / LLZO solid electrolyte layer using laser welding, the thickness of the Na metal foil can be a conventional thickness, generally 30–50 μm, for example, 30 μm, 35 μm, 40 μm, 45 μm, and 50 μm; in this embodiment, the thickness of the Na metal foil is 40 μm. The thickness of the LATP solid electrolyte layer is 1 mm.

[0084] The preparation steps and testing conditions of the Na / LLZO / Na-70 W laser-welded symmetric cell provided in this embodiment are basically the same as those of the Li / LATP / Li-100 W laser-welded symmetric cell in Example 1. The difference is that this embodiment uses Na metal foil and LLZO solid electrolyte. Figure 5 The impedance spectrum of the Na / LLZO / Na-70 W laser-welded symmetrical cell provided in Example 4 is shown at room temperature, with an interface resistance of 735Ω.

[0085] Comparative Example 1

[0086] The preparation method of LATP solid electrolyte is the same as that in Example 1.

[0087] The Li metal foil and LATP solid electrolyte were placed in a glove box filled with Ar gas. The Li metal foil was pressed onto the surface of the LATP solid electrolyte to assemble the Li / LATP / Li button cell, and then EIS testing was performed on it.

[0088] Figure 6 Impedance spectra of the Li / LATP / Li- weldless symmetric cell provided for Comparative Example 1 at room temperature, with an interface resistance of 1.5 x 10⁻⁶. 5 The interfacial impedance (Ω) is significantly higher than that of the Li / LATP / Li-70W laser-welded symmetrical cells, Li / LATP / Li-100W laser-welded symmetrical cells, and Li / LATP / Li-50W laser-welded symmetrical cells provided in Examples 1-3. This indicates that the untreated LATP / Li has a very high interfacial impedance, which may cause extreme concentration polarization in the solid-state battery during charging and discharging, affecting the Li... + The free transport capability leads to the formation of a large number of lithium dendrites, ultimately preventing normal charging and discharging.

[0089] Comparative Example 2

[0090] The preparation method of LATP solid electrolyte is the same as that in Example 1.

[0091] The Li metal foil and LATP solid electrolyte were placed in a glove box filled with Ar gas. The Li metal foil was pressed onto the surface of the LATP solid electrolyte. Ultrasonic welding was performed using a power of 70W. The metal probe of the welding machine was placed above the Li metal foil. Power was applied and the ultrasonic welding operation was completed in 1 minute. The Li / LATP / Li button cell was assembled and subjected to EIS testing.

[0092] Figure 7The EI impedance spectrum of the Li / LATP / Li-ultrasonically welded symmetric cell provided for Comparative Example 2 at room temperature shows an interface resistance of 2400 Ω, indicating a reduction in interface resistance after ultrasonic welding. This reduction is an order of magnitude smaller than the untreated LATP / Li interface resistance in Comparative Example 1, suggesting that ultrasonic welding has a certain effect on interface modification. However, compared to laser welding, the effect is not as significant. This may be because ultrasonic welding utilizes vibration to force particles to adhere tightly together under pressure, but repeated vibrations may also cause some deformation of the bulk material surface, resulting in a less noticeable reduction in interface resistance. However, the interface resistance of the laser-welded LATP / Li is as follows... Figure 2 As shown, the interface impedance is significantly reduced. This is due to the heat generated by laser welding, which allows the particles on the material surface to fully contact each other (point-to-point). The heat source is transferred evenly, and the deformation is small, which enables the LATP / Li interface to quickly and tightly bond together, reducing the interface contact gap and greatly reducing the interface resistance.

[0093] Comparative Example 3

[0094] The preparation method of LLZO solid electrolyte is the same as that in Example 4.

[0095] Na metal foil and LLZO solid electrolyte were placed in a glove box filled with Ar gas. The Na metal foil was pressed onto the surface of the LLZO solid electrolyte to assemble a Na / LLZO / Na button cell, which was then subjected to EIS testing.

[0096] Figure 8 Impedance spectrum of the Na / LLZO / Na- weldless symmetric cell provided in Comparative Example 3 at room temperature, with an interface resistance of 2.1 x 10⁻⁶. 5 The high interfacial impedance (Ω) indicates that untreated LLZO / Na has a large interfacial impedance, which affects Na. + Insertion / de-insertion performance.

[0097] Analyzing the above embodiments and comparative examples, it can be seen from Examples 1-3 and Comparative Examples 1 and 2 that, compared with Comparative Example 1 which directly pressed Li metal foil onto the surface of LATP solid electrolyte to obtain the LATP / Li metal interface layer, and Comparative Example 2 which used ultrasonic welding to obtain the LATP / Li metal interface layer, the use of laser welding in Examples 1-3 to prepare the LATP / Li metal interface layer can effectively reduce the interface contact gap and greatly reduce the interface resistance. The energy of laser welding has a certain influence on the welding effect. As the laser welding power increases (from 50W to 100W), the interface impedance between LATP and Li metal first decreases and then increases, reaching its minimum when the laser welding power is 70W. This may be because when the laser welding energy is low (50W), the interface contact is relatively insufficient; as the laser welding energy increases (70W), the interface achieves further contact, and the impedance value decreases; when the laser welding energy is high (100W), the interface resistance of the LATP solid electrolyte increases, indicating that high-power lasers may generate high-energy heat that damages the interface structure, leading to a slight increase in resistance, which is not conducive to suppressing lithium dendrite formation. As can be seen from Example 4 and Comparative Example 3, Comparative Example 3 directly pressed Na metal foil onto the surface of LLZO solid electrolyte to obtain the LLZO / Na metal interface layer. The tested Na / LLZO / Na interface impedance was very high, indicating poor contact performance, which is not conducive to Na… + Transmission; and in Example 4, laser welding was used to prepare the LLZO / Na metal interface layer, which effectively reduced the interface contact gap and greatly reduced the interface resistance. As can be seen from Examples 1 and 4, laser welding is not only suitable for the rapid and tight bonding between LATP and Li metals, but also for the interface contact between LLZO and Na metals, indicating that this laser welding has excellent effects on the efficient preparation of various inorganic solid electrolytes and alkali metal interfaces.

[0098] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for efficiently preparing a solid electrolyte-alkali metal interface using room temperature laser welding, characterized in that, Includes the following steps: Alkali metal foil and solid electrolyte are placed in a glove box filled with inert gas. The alkali metal foil is pressed onto the surface of the solid electrolyte. The metal probe of a laser welding machine is placed above the alkali metal foil, and power is applied to obtain the interface between the solid electrolyte and the alkali metal. The laser welding power is 40~120 W, and the welding time is 5~40 s.

2. The method for efficiently preparing a solid electrolyte-alkali metal interface using room temperature laser welding as described in claim 1, characterized in that: The alkali metal foil is lithium, sodium, or potassium metal foil; The thickness of the alkali metal foil is in the range of 30~50 μm; The inert gas is at least one of Ar, He, or Nr.

3. The method for efficiently preparing a solid electrolyte-alkali metal interface using room temperature laser welding as described in claim 2, characterized in that: The alkali metal foil is lithium metal foil.

4. The method for efficiently preparing a solid electrolyte-alkali metal interface using room temperature laser welding as described in claim 1, characterized in that: The solid electrolyte is an inorganic solid electrolyte; The thickness of the solid electrolyte ranges from 0.5 to 1.5 mm.

5. The method for efficiently preparing a solid electrolyte-alkali metal interface using room temperature laser welding as described in claim 4, characterized in that: The solid electrolyte is at least one of NASICON electrolyte, LISICON electrolyte, garnet-type electrolyte or sulfide-type electrolyte.

6. The method for efficiently preparing a solid electrolyte-alkali metal interface using room temperature laser welding as described in claim 4, characterized in that: The solid electrolyte is a NASICON electrolyte.

7. The method for efficiently preparing a solid electrolyte-alkali metal interface using room temperature laser welding as described in claim 1, characterized in that: The laser welding power is 50~100 W, and the welding time is 10~20 s.

8. The method for efficiently preparing a solid electrolyte-alkali metal interface using room temperature laser welding as described in claim 1, characterized in that: The solid electrolyte-alkali metal interface is Li alkali metal foil / Li 1+x Al x Ti 2-x (PO4)3 solid electrolyte layer, where 0.1 ≤ x ≤ 0.5; The Li 1+x Al x Ti 2-x (PO4)3 solid electrolyte is synthesized via a solid-phase method, including the following steps: (1) Synthesize Li 1+x Al x Ti 2-x The raw materials of (PO4)3 are placed in a ball mill jar, organic solvent is added for ball milling, calcination, and LATP primary ball milling powder is obtained. The obtained LATP primary ball milling powder is then ball milled a second time to obtain a slurry, which is then dried and sieved to obtain LATP powder. (2) Take LATP powder and binder and mix them. Put the mixed powder into a mold and press it into a tablet. Place the obtained ceramic tablet in a muffle furnace for sintering to obtain LATP solid electrolyte.

9. The method for efficiently preparing a solid electrolyte-alkali metal interface using room temperature laser welding as described in claim 8, characterized in that: The Li mentioned in step (1) 1+x Al x Ti 2-x The raw materials for (PO4)3 are Li source, Al source, TiO2 and H6NO4P, and each raw material is weighed according to the stoichiometric ratio, wherein the Li source is in excess by a mass fraction of 5% to 15%; The organic solvent mentioned in step (1) is at least one of alcohol, acetone or methanol; The ball milling described in step (1), wherein the organic solvent and Li 1+x Al x Ti 2-x The total mass ratio of all raw materials in (PO4)3 is 1.5~2:1~1.5, the ball milling time is 6~10 h, and the ball milling speed is 250~350 r / min; The calcination mentioned in step (1) refers to calcination in a muffle furnace, under an atmosphere of air, N2, Ar or H2, by raising the temperature from room temperature to 800-1000 ℃ at a rate of 5-10℃ / min and holding it at that temperature for 4-8 h. The secondary ball milling in step (1) involves a mass ratio of organic solvent to powder of 1.5~2:1~1.5, a ball milling time of 6~10 h, and a ball milling speed of 250~350 r / min.

10. The method for efficiently preparing a solid electrolyte-alkali metal interface in room temperature laser welding engineering according to claim 9, characterized in that: The Li 1+x Al x Ti 2-x (PO4)3 solid electrolyte is Li 1.3 Al 0.3 Ti 1.7 (PO4)3 solid electrolyte.

11. The method for efficiently preparing a solid electrolyte-alkali metal interface using room temperature laser welding as described in claim 8, characterized in that: The adhesive mentioned in step (2) is at least one of polyvinyl butyral resin or polyvinyl alcohol; the LATP powder and adhesive mentioned in step (2) are mixed and stirred, wherein the mass ratio of LATP powder to adhesive is 8~10:1~1.5; The mold described in step (2) is used for pressing, and the diameter of the selected mold is 10~18 mm; The sintering atmosphere in step (2) is at least one of N2, Ar or air; the sintering temperature is 800~1000℃ and the sintering time is 4~8 h; The thickness of the LATP solid electrolyte mentioned in step (2) is 0.5 mm to 1.5 mm.

12. The solid electrolyte-alkali metal interface prepared by the method according to claim 1.

13. The application of the solid electrolyte-alkali metal interface according to claim 12 in solid-state batteries.

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