Preparation method of h-BN doped LiPON solid electrolyte film
By employing segmented magnetron sputtering and h-BN doping, the problems of low ionic conductivity and stress accumulation in LiPON electrolyte films were solved, resulting in the fabrication of high-performance h-BN-doped LiPON solid electrolyte films suitable for flexible electronic devices.
Patent Information
- Application Number
- CN202511099054.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-06
- Publication Date
- 2025-12-12
AI Technical Summary
The existing LiPON electrolyte films have low ionic conductivity, which makes it difficult to meet the requirements of high sputtering, and the stress accumulation problem caused by inconsistent thermal expansion coefficients during sputtering has not been effectively solved.
A segmented magnetron sputtering method was adopted, using Li3PO4 and h-BN targets. By controlling the sputtering parameters and segmented process, h-BN-doped LiPON solid electrolyte films were prepared, which reduced the thermal expansion coefficient mismatch caused by temperature changes and improved the film density and uniformity.
The ionic conductivity and mechanical properties of LiPON thin films were improved, and a dense, defect-free film was prepared, which is suitable for flexible electronic devices, with an ionic conductivity of 6.3×10-6 S/cm.
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Figure CN121109969A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of solid-state lithium ion thin film batteries, and particularly relates to a preparation method of h-BN doped LiPON solid thin film. BACKGROUND
[0002] Lithium ion batteries are widely concerned in today's global economic development due to their advantages of high working voltage, high energy density, excellent cycle stability, no memory effect and environmental friendliness. Among them, all-solid-state thin film lithium ion batteries are widely used in wearable electronic devices, micro-electromechanical systems, flexible foldable electronic devices, implantable medical devices and other fields due to their unique advantages of ultra-thin, flexible, high safety, long service life, wide working temperature range, miniaturization and no risk of liquid leakage, becoming an important branch of lithium ion battery development. Unlike the preparation method of conventional lithium ion batteries, all-solid-state thin film batteries usually use physical or chemical vapor deposition technologies such as magnetron sputtering, pulsed laser deposition and electron beam evaporation to directly prepare current collector film, positive electrode film, solid electrolyte film and negative electrode film on the substrate in sequence, realizing the thin film and all-solid-state of the battery structure.
[0003] In 1992, the Oak Ridge National Laboratory successfully synthesized lithium phosphorus oxynitride (LiPON) thin film electrolyte for the first time. It used a radio frequency magnetron sputtering method, used Li3PO4 as the target material, and carried out reactive sputtering in a high-purity nitrogen environment to obtain a solid electrolyte thin film with an amorphous structure. Undoped N Li3PO4 has a tetrahedral structure, and during the N2 atmosphere deposition process, N elements destroy the -O- and =O bonds in the Li3PO4 structure, forming Nt (three-coordinated N) and Nd (two-coordinated N). The incorporation of N elements increases the cross-linking structure in the thin film, promoting the migration of Li ions. Although LiPON has excellent comprehensive performance, its low ion conductivity is difficult to meet the high rate demand; at the same time, continuous sputtering causes the internal temperature of the sputtering chamber to rise, causing stress accumulation in the thin film, and the deformation of the substrate and the thin film caused by temperature is inconsistent, resulting in cracks.
[0004] Current research directions mainly focus on single element doping, such as Chen et al. (Chen H, Tao H, Zhao X, et al. Fabrication and ionic conductivity of amorphous Li-Al-Ti-P-O thin film [J]. Journal of Non-Crystalline Solids, 2011, 357 (16-17): 3267-3271) by sputtering Li 1.3 Al 0.3 Ti 1.7LiAlTiPO solid electrolytes were prepared using (PO4)3 target material. During deposition, the increased substrate temperature made the electrolyte film smoother and denser, thus inducing higher ionic conductivity. Fanprikis T et al. (Fanprikis T, Galipaud J, Clemens O, et al. Composition Dependence of Ionic Conductivity in LiSiPO(N)Thin-Film Electrolytes for Solid-State Batteries[J].ACS Applied Energy Materials, 2019, 2(7):4782–4791.) studied the deposition of LiAlTiPO solid electrolytes using sputtered LiAlTiPO(N)3 target material. 3+x Si x P 1-x LiSiPO(N) electrolytes were prepared using O4((1–x)Li3PO4–xLi4SiO4) single-phase crystal targets, and their amorphization, nitriding, and mixed precursor effects were studied. However, the above two methods have limited effect on improving the performance of LiPON electrolytes, and there is still no solution to the stress accumulation problem. Summary of the Invention
[0005] To address the problems existing in the background technology, the present invention aims to provide a method for preparing h-BN-doped LiPON solid electrolyte thin films. This method employs segmented magnetron sputtering, using Li3PO4 and h-BN as sputtering targets. By adjusting the deposition process parameters, the density of the solid electrolyte thin film is improved, and its ionic conductivity is enhanced. At the same time, it solves the stress problem caused by the uneven deformation of the thin film electrolyte and substrate due to the coefficient of thermal expansion during the sputtering process.
[0006] To achieve the above objectives, the technical solution of the present invention is as follows:
[0007] A method for preparing h-BN-doped LiPON solid electrolyte thin films includes the following steps:
[0008] Step 1. Clean the substrate;
[0009] Step 2. Place the substrate on the sample holder inside the magnetron sputtering chamber, and then fix the Li3PO4 target and h-BN target on the two target holders respectively;
[0010] Step 3. Perform segmented sputtering, the specific process is as follows:
[0011] Step 3.1. Close the chamber cover of the magnetron sputtering instrument and evacuate the chamber to the background vacuum level;
[0012] Step 3.2. N2 is filled, the internal pressure of the chamber is adjusted to keep at 1-2 Pa, and then pre-sputtering is performed;
[0013] Step 3.3. After pre-sputtering is completed, the gas inlet is adjusted to keep the pressure at 0.5-1 Pa, the shutter and the rotating device are opened, the rotating speed is set to 0.2-0.8 RPM, the sputtering is formally started, and the sputtering time is 50-90 min;
[0014] Step 3.4. After the sputtering is completed, the alternating current power supply and the bias voltage are turned off, the gas inlet valve is closed, the sputtering chamber is kept in a vacuum state, and the substrate is cooled to room temperature for 2-4 h;
[0015] Step 3.5. Steps 3.2-3.4 are repeated several times until the h-BN doped LiPON solid electrolyte thin film with a desired thickness is obtained.
[0016] Further, the substrate is preferably an electrically conductive glass, a stainless steel sheet or the like.
[0017] Further, the purity of the Li3PO4 target is not less than 99.99%, and the purity of the h-BN target is not less than 99.9%.
[0018] Further, the sputtering power of the Li3PO4 target is 140-180 W, and the sputtering power of the h-BN target is 15-25 W.
[0019] Further, the gas flow of N2 is 20-40 sccm.
[0020] Further, the thickness of the h-BN doped LiPON solid electrolyte thin film is 500 nm-1200 nm.
[0021] Further, the doping amount of h-BN in the LiPON solid electrolyte thin film is 0.5-5 Wt%.
[0022] Further, in step 3.5, the number of repetitions is more than 2.
[0023] The mechanism of the present application is as follows:
[0024] h-BN has a layered structure, and the interlayer spacing thereof is about 0.333 nm, which is greater than the intrinsic ion channel of LiPON (0.2-0.3 nm), so that a low-energy-barrier ion transmission path is formed in the amorphous network of LiPON. Li+ can migrate rapidly along the surface of the h-BN layer by the "adsorption-desorption" mechanism, and h-BN reacts with Li to form Li3N / Li-B ion conducting layers, thereby improving the interface stability. h-BN is doped to change the amorphous structure thereof and improve the Li ion transmission efficiency, so that a LiPON thin film electrolyte with a dense surface, no defects and uniform thickness is prepared, and the ionic conductivity thereof is further improved.
[0025] In the sputtering stage, the plasma heat load causes the local temperature of the substrate to rise (ΔT>100℃), which triggers the mismatch of the thermal expansion coefficients of the film and the substrate, forms compressive thermal stress, and the film is prone to fall off or produce holes; at the same time, the high-energy particle bombardment accumulates intrinsic tensile stress. The segmented sputtering of the application reduces the substrate temperature by standing, reduces the change of the substrate temperature, and realizes double relaxation.
[0026] In summary, due to the adoption of the above technical solutions, the application has the following advantages:
[0027] 1. Compared with the conventional one-time sputtering of the electrolyte film, the segmented sputtering method adopted by the application can reduce the influence of the temperature change on the mismatch of the thermal expansion coefficients, thereby making the prepared electrolyte film have higher quality, improving the overall density and uniformity of the film, and thus giving the electrolyte higher ionic conductivity.
[0028] 2. The application adopts h-BN doping to improve the performance of the LiPON thin film electrolyte, the interlayer slip of h-BN layer buffers the stress and enhances the mechanical properties of the LiPON thin film electrolyte, improves the bending resistance of the film, and the prepared thin film battery can be designed and manufactured for the use scene of flexible electronic devices. The ionic conductivity of the prepared LiPON solid electrolyte thin film can reach 6.3×10 - 6 S / cm. BRIEF DESCRIPTION OF DRAWINGS
[0029] Figure 1 It is a physical map of h-BN doped LiPON solid electrolyte film.
[0030] Figure 2 It is a temperature-time change graph of segmented sputtering in Example 1 of the application.
[0031] Figure 3 It is a temperature-time change graph of continuous sputtering in Comparative Example 1.
[0032] Figure 4 It is a surface SEM graph of the LiPON solid electrolyte thin film prepared in Example 1 and Comparative Example 1 of the application.
[0033] Figure 5 It is an impedance comparison graph of the LiPON solid electrolyte thin film prepared in Example 1 and Example 3 of the application.
[0034] Figure 6 It is an impedance comparison graph of the LiPON solid electrolyte thin film prepared in Example 1, Comparative Example 2 and Comparative Example 2 of the application. DETAILED DESCRIPTION
[0035] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments and drawings.
[0036] Example 1
[0037] A preparation method of an h-BN-doped LiPON solid electrolyte thin film, comprising the following steps:
[0038] Step 1. Cleaning the conductive glass substrate:
[0039] The 5*5 cm conductive glass is sequentially cleaned with acetone, ethanol and deionized water (10 minutes for each process) to remove oil stains and impurity particles on the surface of the substrate; the cleaned substrate is placed in a forced air drying oven and dried at 100 DEG C for 10 minutes to remove residual moisture on the surface; the mask plate and the substrate are fixed on the substrate with high-temperature glue, and then placed in a plasma cleaning machine and cleaned for 20 minutes using a power of 120 W; the mask plate is used to cover the area that does not want to be sputtered;
[0040] Step 2. The cleaned conductive glass substrate is placed on a sample holder in the chamber of a magnetron sputtering instrument, a Li3PO4 target is installed at target 1 position, and an h-BN target is installed at target 2 position, the distance between the two targets is adjusted to 10 cm, the substrate is placed in the sputtering chamber so that the target is opposite to the substrate, the chamber cover is closed, and the chamber is sealed;
[0041] Step 3. Subsection sputtering, the specific process is as follows:
[0042] Step 3.1. Close the chamber cover of the magnetron sputtering instrument, open the mechanical pump and the pre-pumping valve, when the vacuum degree reaches 6 Pa, open the molecular pump, and the vacuum degree of the chamber is pumped to 4*10 -4 Pa;
[0043] Step 3.2. Control the cleaning gas path by the gas path valve and introduce nitrogen gas, the gas flow is 100 sccm, when the gas pressure reaches 1 Pa, open the AC power connected to target 1, adjust the ignition power to 180 W, open the AC power connected to target 2, adjust the ignition power to 45 W, and perform pre-sputtering for 20 minutes;
[0044] Step 3.3. After pre-sputtering, adjust the pressure to 0.5 Pa, adjust the Li3PO4 power to 150 W, and adjust the h-BN target power to 20 W, open the baffle and the rotating device, and set the rotating speed to 0.3 RPM, then perform formal sputtering for 1 hour;
[0045] Step 3.4. After sputtering, record the substrate temperature at this time, close the AC power and the bias, close the gas inlet valve, keep the sputtering chamber in a vacuum state, and wait for 3 hours until the substrate cools to room temperature;
[0046] Step 3.5. Repeat steps 3.2-step 3.4 for 3 times until the desired thickness of the h-BN doped LiPON solid-state electrolyte thin film is obtained.
[0047] After sputtering, sputter a top electrode on the surface of the h-BN doped LiPON solid-state electrolyte thin film for subsequent electrical performance testing of the thin film, and the preparation process of the top electrode is as follows:
[0048] Using a magnetron sputtering method, a gold target is used, the gold target is fixed on the target seat, high-purity Ar cleaning gas is filled for 10 minutes, the gas flow is 30 sccm, the internal pressure of the chamber is adjusted to maintain at 1 Pa, the target is ignited using an alternating current power supply, the sputtering power is 20 W, after the glow is stable, the gas flow is adjusted to maintain the pressure at 0.5 Pa; Before formal sputtering, 20 minutes of pre-sputtering is performed; After pre-sputtering is completed, the shutter and the rotating device are opened, the rotating speed is set to 0.5 RPM, and formal sputtering is started; After sputtering for 10 minutes, the top electrode preparation is completed.
[0049] The actual picture of the h-BN doped LiPON solid-state electrolyte thin film with a gold electrode is as shown in Figure 1 .
[0050] Example 2
[0051] The h-BN doped LiPON solid-state electrolyte thin film is prepared according to the steps of Example 1, and the formal sputtering time of step 3.3 is adjusted to 1.5 h; In step 3.5, steps 3.2-step 3.4 are repeated for 2 times, and other steps remain unchanged.
[0052] Example 3
[0053] The h-BN doped LiPON solid-state electrolyte thin film is prepared according to the steps of Example 1, and only the sputtering power of the h-BN target in step 3.3 is adjusted to 15 W and 25 W, and other steps remain unchanged.
[0054] Comparative Example 1
[0055] The h-BN doped LiPON solid-state electrolyte thin film is prepared according to the steps of Example 1, and only the sputtering time of step 3.3 is adjusted to 3 h, steps 3.4 and 3.5 are removed, and other steps remain unchanged.
[0056] Comparative Example 2
[0057] A method for preparing a LiPON solid-state electrolyte thin film, comprising the following steps:
[0058] Step 1. Clean the conductive glass substrate:
[0059] The 5*5 cm conductive glass was sequentially cleaned with acetone, ethanol and deionized water (10 minutes for each process) to remove oil stains and impurities on the surface of the substrate; the cleaned substrate was placed in a blast drying oven and dried at 100℃ for 10 minutes to remove residual moisture on the surface; the mask plate and substrate were fixed on the substrate with high-temperature glue, and then placed in a plasma cleaning machine and cleaned for 20 minutes at a power of 120W;
[0060] Step 2. The cleaned conductive glass substrate was placed on a sample holder in the chamber of a magnetron sputtering instrument, a Li3PO4 target was installed at position 1, the target-substrate distance was adjusted to 10 cm, the substrate was placed in the sputtering chamber with the target facing the substrate, the chamber cover was closed to seal the chamber;
[0061] Step 3. The process was as follows:
[0062] Step 3.1. The chamber cover of the magnetron sputtering instrument was closed, the mechanical pump and the pre-pumping valve were opened, and when the vacuum degree reached 6 Pa, the molecular pump was opened to reduce the vacuum degree of the chamber to 4*10 -4 Pa;
[0063] Step 3.2. The cleaning gas path was controlled by the gas path valve and nitrogen was introduced at a flow rate of 100 sccm. When the gas pressure reached 1 Pa, the AC power connected to the target 1 was turned on and the ignition power was adjusted to 180 W for pre-sputtering for 20 minutes to remove the oxides on the surface of the target;
[0064] Step 3.3. After pre-sputtering, the pressure was adjusted to 0.5 Pa and the Li3PO4 power was adjusted to 150 W. The baffle and the rotating device were opened and the rotating speed was set to 0.3 RPM. The formal sputtering was carried out for 1 hour;
[0065] Step 3.4. After sputtering, the substrate temperature was recorded, the AC power and the bias were turned off, the gas inlet valve was closed, and the sputtering chamber was kept in a vacuum state for 3 hours until the substrate cooled to room temperature;
[0066] Step 3.5. Steps 3.2-3.4 were repeated three times to obtain the desired thickness of the LiPON solid electrolyte film.
[0067] Figure 2 It is a temperature-time variation graph of the step-by-step sputtering in Example 1 of the present application. As can be seen from the graph, through the step-by-step sputtering process, the substrate temperature is controlled and the substrate temperature is maintained below 105℃ throughout the preparation process.
[0068] Figure 3 It is a temperature-time variation graph of the continuous sputtering in Comparative Example 1. As can be seen from the graph, during the one-time step-by-step sputtering process, the substrate temperature continuously rises and the highest temperature can reach about 130℃. Figure 2 andFigure 3 It can be seen that the segmented sputtering method can reduce the temperature of the substrate, thereby reducing the possibility of mismatching of the thermal expansion coefficients of the thin film and the substrate.
[0069] Figure 4 The surface SEM images of the LiPON solid electrolyte thin films prepared in Example 1 and Comparative Example 1 of the present application are shown in the figure. As can be seen from the figure, the temperature of the substrate is controlled to be below 105 DEG C by using the segmented sputtering method of the present application in Example 1, so that the surface of the prepared electrolyte thin film is smooth and dense; while the temperature is not controlled in Comparative Example 1, and the highest temperature can reach 125 DEG C, so that the surface of the prepared thin film has large pores. The main function of the electrolyte is to conduct ions; the pores, cracks or open grain boundaries will become obstacles or interruption points of the ion transmission path, and the ions cannot effectively pass through these non-conductive areas, resulting in a significant decrease in the overall ionic conductivity.
[0070] Figure 5 The impedance comparison graphs of the LiPON solid electrolyte thin films prepared in Example 1 and Example 3 of the present application are shown in the figure. The difference between Example 1 and Example 3 is that the sputtering time is the same, the power is different, and the doping amount is different. As can be seen from the figure, the conductivity of the LiPON solid electrolyte thin films obtained by the present application with different doping amounts is high.
[0071] Figure 6 The impedance comparison graphs of the LiPON solid electrolyte thin films prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present application are shown in the figure. As can be seen from the figure, the segmented sputtering and h-BN doping methods used in the present application can effectively improve the impedance performance of the prepared LiPON solid electrolyte thin film.
[0072] The electrochemical impedance spectroscopy test of each example and comparative example was performed using a program test clamp, and the frequency range was 300 Hz-600 kHz. The specific test results are shown in Table 1.
[0073] Table 1
[0074]
[0075] The above is only a specific embodiment of the present application, and any feature disclosed in the specification can be replaced by other equivalent or similar purpose alternative features, unless specifically described; all features disclosed, or steps in all methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.
Claims
1. A method for preparing a h-BN doped LiPON solid-state electrolyte thin film, the method comprising: providing a substrate; depositing a LiPON layer on the substrate; and exposing the LiPON layer to a h-BN source. The method comprises the following steps: Step 1. Cleaning the substrate; Step 2. Placing the substrate on a sample holder in the chamber of a magnetron sputtering instrument, and then fixing a Li3PO4 target and an h-BN target on two target seats respectively; Step 3. Carrying out segmented sputtering, specifically as follows: Step 3.
1. Closing the chamber cover of the magnetron sputtering instrument, and vacuumizing the chamber to a background vacuum degree; Step 3.
2. Filling N2, adjusting the pressure in the chamber to 1-2 Pa, and then carrying out pre-sputtering; Step 3.
3. After pre-sputtering, adjusting the gas flow to keep the pressure at 0.5-1 Pa, opening the shutter and the rotating device, setting the rotating speed at 0.2-0.8 RPM, and starting formal sputtering, with a sputtering time of 50-90 min; Step 3.
4. After sputtering, closing the alternating current power supply and the bias voltage, closing the gas valve, keeping the sputtering chamber in a vacuum state, and waiting for 2-4 h, until the substrate is cooled to room temperature; Step 3.
5. Repeating steps 3.2-3.4 for several times until the h-BN doped LiPON solid-state electrolyte film with a desired thickness is obtained.
2. The method of claim 1, wherein the h-BN doped LiPON solid-state electrolyte thin film is prepared by a method comprising: The substrate is conductive glass or a stainless steel sheet.
3. The method of claim 1, wherein the h-BN doped LiPON solid-state electrolyte thin film is prepared by a method comprising: The purity of the Li3PO4 target is not less than 99.99%, and the purity of the h-BN target is not less than 99.9%.
4. The method of claim 1, wherein the h-BN doped LiPON solid-state electrolyte thin film is prepared by a method comprising: The sputtering power of the Li3PO4 target is 140-180 W, and the sputtering power of the h-BN target is 15-25 W.
5. The method of claim 1, wherein the h-BN doped LiPON solid-state electrolyte thin film is prepared by a method comprising: The gas flow of N2 is 20-40 sccm.
6. The method of claim 1, wherein the h-BN doped LiPON solid-state electrolyte thin film is prepared by a method comprising: The thickness of the h-BN doped LiPON solid-state electrolyte film is 500 nm-1200 nm.
7. The method of claim 1, wherein the h-BN doped LiPON solid-state electrolyte thin film is prepared by a method comprising: The doping amount of h-BN in the LiPON solid-state electrolyte film is 0.5-5 Wt%.
8. The method of claim 1, wherein the h-BN doped LiPON solid-state electrolyte thin film is prepared by a method comprising: In step 3.5, the number of repetitions is more than 2.