Method for analyzing alkali ion composition in lipon thin film, method for analyzing alkali ion composition in all-solid-state battery, and apparatus for analyzing alkali ion composition in lipon thin film

Abstract

The present invention provides a method for analyzing an alkali ion composition in a LiPON thin film and a method for analyzing an alkali ion composition in an all-solid-state battery. The method for analyzing an alkali ion composition in a LiPON thin film comprises: a step of preparing a substrate and a sample including a lithium phosphorus oxynitride (LiPON) thin film disposed on one surface of the substrate; and a step of irradiating monatomic ion beams to the surface of the lithium phosphorus oxynitride thin film, wherein in the step of irradiating ion beams, a positive voltage is applied to the other surface of the substrate.

Description

Method for analyzing alkaline ion composition in LIPON thin film, method for analyzing alkaline ion composition in all-solid-state battery, and device for analyzing alkaline ion composition in LIPON thin film

[0001] The present invention relates to a method for analyzing the composition of alkaline ions in a LiPON thin film, a method for analyzing the composition of alkaline ions in an all-solid-state battery, and a device for analyzing the composition of alkaline ions in a LiPON thin film, and more particularly, to a method and device for analyzing the composition distribution of alkaline ions in a LiPON thin film or an all-solid-state battery using ion beam sputtering.

[0002] Lithium-ion batteries consist of a cathode, anode, a separator, and an electrolyte. Batteries whose electrolytes are solid rather than liquid are called all-solid-state batteries. Solid electrolytes can be categorized into sulfide, oxide, and polymer types. Meanwhile, alkali metal ions move between the cathode and anode through the solid electrolyte. Accurate analysis and accurate interpretation of the behavior and quantitative distribution of alkali metal ions under varying charge and discharge conditions within the all-solid-state battery are essential.

[0003] In order to understand the chemical state and depth distribution information of alkali metals, accurate information can be obtained through ToF-SIMS (time-of-flight secondary ion mass spectrometry), X-ray photoelectron spectroscopy (XPS, X-ray photoelectron spectroscopy), etc. For example, depth distribution analysis (depth profiling) using X-ray photoelectron spectroscopy involves Ar + , C 60 + , Ar n +The process of sputtering the surface layer to a desired depth through ion bombardment that accelerates ions such as ions to the sample surface, and then analyzing the photoelectrons by irradiating X-rays again is repeated. However, during ion bombardment, the positive ions colliding with the sample form an electric field on the sample surface, which pushes or attracts the conductive ions in the sample, causing a problem in that the composition distribution of the sample changes significantly compared to the original state during the depth distribution analysis. A representative example is Ar + Li upon cation bombardment of the back + , Na + It is widely known that alkaline cations, such as ions, are pushed out from the surface and accumulate (pile-up) in large quantities at the bottom of the sample. This phenomenon not only obscures the original compositional distribution of the sample, but also causes chemical reactions within the sample during the movement of ions, resulting in the loss of the original physical and chemical properties of the material that were originally intended to be studied.

[0004] Therefore, various countermeasures have been proposed to prevent this ion accumulation phenomenon during depth distribution analysis using ion bombardment. Examples include changing the type of element used for ion bombardment, providing additional negative charges on the surface to prevent electric field formation, drastically lowering the sample temperature to reduce ion migration, and performing ion bombardment with ion clusters instead of single atomic ions. However, these methods have many limitations in practical application, such as difficulty in universal application in various environments, potential negative effects on observed signal strength, and significant time and cost required for implementation.

[0005] The present invention is to solve the above conventional problems, and when analyzing the composition of lithium phosphorus oxynitride (LiPON), which is a type of inorganic solid electrolyte, the cations (particularly, Li) in the solid electrolyte +) and to present a technique that enables more accurate depth distribution analysis. However, these tasks are exemplary and the scope of the present invention is not limited thereby.

[0006] According to one aspect of the present invention, a method for analyzing the composition of alkali ions in a LiPON thin film is provided.

[0007] The method for analyzing the composition of alkali ions in the LiPON thin film includes the steps of preparing a sample including a substrate and a lithium phosphate nitride (LiPON) thin film arranged on one surface of the substrate; and the step of irradiating a monatomic ion beam onto the surface of the lithium phosphate nitride (LiPON) thin film; and may be characterized in that a positive voltage is applied to the other surface of the substrate in the ion beam irradiation step.

[0008] According to one embodiment, the ion beam irradiation step may include a step of supplying any one gas selected from the group consisting of hydrogen (H2), nitrogen (N2), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe) as a gas for generating the monoatomic ion beam.

[0009] In one embodiment, the ion beam irradiation step may include a step of accelerating the monoatomic ion beam with an acceleration voltage of 0.5 keV to 4 keV.

[0010] According to another aspect of the present invention, a method for analyzing the composition of alkaline ions in an all-solid-state battery is provided.

[0011] The method for analyzing the composition of alkaline ions in the above-mentioned all-solid-state battery comprises the steps of: preparing an all-solid-state battery including an electrode layer; and a solid electrolyte layer including a lithium phosphate oxynitride (LiPON) thin film disposed on one surface of the electrode layer; and irradiating a monatomic ion beam onto the surface of the solid electrolyte layer; and may be characterized in that a positive voltage is applied to the other surface of the electrode layer in the ion beam irradiation step.

[0012] In one embodiment, the applied positive voltage may be greater than or equal to the operating voltage of the all-solid-state battery.

[0013] In one embodiment, the all-solid-state battery is a lithium secondary battery, and the applied positive voltage may be 3.7 V or higher.

[0014] In one embodiment, the all-solid-state battery is a sodium secondary battery, and the applied positive voltage may be 2.3 V or higher.

[0015] In one embodiment, the applied positive voltage is lithium It may be above the critical potential at which ion accumulation occurs.

[0016] In one embodiment, when the ion gun energy is 2000 eV in the ion beam irradiation step, the applied positive voltage may be 7 V or more.

[0017] According to another aspect of the present invention, a device for analyzing the composition of alkaline ions in a LiPON thin film is provided.

[0018] The above-described device for analyzing alkaline ion composition in a LiPON thin film is a device for analyzing a sample including a substrate and a lithium phosphate oxynitride (LiPON) thin film disposed on one surface of the substrate, and may include: an ion beam generation unit provided to supply gas for generating a single-atomic ion beam; and a power control unit for controlling a positive voltage to be applied to the other surface of the substrate when the single-atomic ion beam generated in the ion beam generation unit is irradiated on the surface of the thin film.

[0019] In one embodiment, the device may be an X-ray photoelectron spectrometer (XPS).

[0020] In one embodiment, the device may further include a flood gun for supplying electrons to the sample surface.

[0021] According to the embodiments of the present invention, as described above, accurate spatial distribution and quantitative distribution analysis of alkali metal ions are possible, thereby preventing errors in characteristic analysis of lithium all-solid-state batteries and contributing to improved performance. Furthermore, the present invention has the advantage of being less dependent on experimental environments and easier to apply compared to existing ion accumulation prevention techniques.

[0022] Of course, the scope of the present invention is not limited by these effects.

[0023] Figure 1 is a schematic diagram of (a) general ion beam sputtering and (b) ion beam sputtering according to an embodiment of the present invention.

[0024] Figure 2 is a depth distribution analysis spectrum of alkali metal (Li) in an all-solid-state battery according to an embodiment of the present invention.

[0025] Figure 3 is a graph showing the depth distribution analysis of alkali metal (Li) in an all-solid-state battery according to an embodiment of the present invention.

[0026] Fig. 4 is a schematic diagram showing an alkaline ion composition analysis device in a LiPON thin film according to an embodiment of the present invention.

[0027] Figures 5 and 6 are graphs showing the movement of alkali ions (Li) in a LiPON thin film according to conventional ion beam sputtering.

[0028] Figure 7 is a graph showing the movement of alkali ions in a LiPON thin film according to an embodiment of the present invention.

[0029] FIG. 8 is a result of XPS spectrum analysis inside a LiPO sample according to bias voltage in an embodiment of the present invention.

[0030] FIG. 9 is a result of XPS spectrum analysis at the LiPO / Si interface according to the bias voltage in an embodiment of the present invention.

[0031] FIG. 10 is a graph showing the Si atom concentration according to the magnitude of the bias voltage applied during ion beam sputtering according to an embodiment of the present invention.

[0032] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings. These embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. The following embodiments may be modified in various different forms, and the scope of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to more faithfully and completely explain the present disclosure and to fully convey the spirit of the present invention to those skilled in the art. In addition, the thickness and size of each layer in the drawings are exaggerated for convenience and clarity of explanation.

[0033] Hereinafter, a method for analyzing the composition of alkaline ions in a LiPON thin film, a method for analyzing the composition of alkaline ions in an all-solid-state battery, and a device for analyzing the composition of alkaline ions in a LiPON thin film according to an embodiment of the present invention will be described.

[0034] Lithium phosphorus oxynitride (LiPON), a type of inorganic solid electrolyte, has stable contact with lithium metal and a wide potential difference (0~5.5 V vs. Li / Li). + ) and has the advantage of negligibly low electrical conductivity. Therefore, LiPON has been widely used as a reference electrolyte in the research and development of thin-film all-solid-state lithium batteries, but has low ionic conductivity (~10 at 25°C). -6 Scm -1) can only be used in the form of a thin film electrolyte.

[0035] In the case of all-solid-state batteries containing lithium phosphate oxynitride (LiPON) thin films as electrolytes, alkali metals migrate within the all-solid-state material during charge and discharge. However, these alkali metals must not migrate during measurements and analysis to analyze the depth-wise composition of the all-solid-state battery. If alkali metals migrate, the composition changes at the interface between the positive electrode and the solid electrolyte, the interface between the negative electrode and the solid electrolyte, and within the all-solid-state material, which may result in deterioration of battery performance.

[0036] Accordingly, the present invention aims to provide an analytical method for accurate composition analysis and correct interpretation of alkali metals in all-solid-state batteries.

[0037] A method for analyzing an alkaline ion composition in a LiPON thin film according to one embodiment of the present invention comprises the steps of preparing a sample including a substrate and a lithium phosphate nitride (LiPON) thin film disposed on one surface of the substrate; and the step of irradiating a monatomic ion beam onto the surface of the lithium phosphate nitride (LiPON) thin film; wherein, in the ion beam irradiation step, a positive voltage is applied to the other surface of the substrate.

[0038] First, a sample including a substrate and a lithium phosphate nitride (LiPON) thin film disposed on one surface of the substrate is prepared.

[0039] The substrate may be glass, silicon, plastic, or other dielectric substrate. The method for depositing a lithium phosphate nitride thin film on the substrate is not particularly limited, and for example, a LiPON thin film may be deposited on the substrate by high-frequency sputtering a Li3PO4 target in a nitrogen atmosphere. It is also possible to use a lithium phosphate (LiPO) sample in a form in which nitrogen (N) has been removed by exposing the sample manufactured in this way to air at room temperature.

[0040] Next, a monatomic ion beam is irradiated onto the surface of the lithium phosphate nitride (LiPON) thin film.

[0041] As a gas for generating the above single-atom ion beam, hydrogen (H2), nitrogen (N2), oxygen (O2), argon (Ar), neon (Ne), krypton (Kr) or xenon (Xe) gas can be supplied. The supplied gas is H + , N2 + , O + , Ar + , Kr + , Xe + It can be ionized into monoatomic ions such as, etc. The ionized monoatomic ions are accelerated and collided with the surface of the LiPON thin film of the sample, and at this time, they are preferably accelerated at an acceleration voltage of 0.5 keV to 4 keV.

[0042] When a single-atom ion beam is irradiated on a sample, energy is transferred to atoms within the LiPON thin film, which can increase the mobility of alkali ions such as lithium.

[0043] Figure 1 is a schematic diagram of (a) general ion beam sputtering and (b) ion beam sputtering according to an embodiment of the present invention.

[0044] Figure 1(a) shows Ar in a solid electrolyte sample. + Electric field generation at the surface during single-atom ion beam sputtering and resulting Li + This is a schematic diagram showing the movement of cations and the resulting ion accumulation phenomenon.

[0045] Ar + As the ions collide with the sample surface, the lithium (Li) on the sample surface and in the corresponding area becomes positively charged. Lithium cations (Li + ) is a positive charge (δ +) try to move away from the surface charged with lithium and migrate (migrate & drift) to the lower part of the sample with relatively less positive charge through ion conduction. Then, when it encounters an area where ion conduction is not smooth (here, the Si substrate), the lithium cations can no longer move and pile up in that area. In other words, during ion bombardment, the upper part (surface) of the sample is gradually depleted of lithium, while the lower part (inside, near the substrate) becomes over-distributed with lithium compared to the original composition.

[0046] Fig. 1(b) is an example of a method for resolving this ion accumulation phenomenon, in which a positive bias having a magnitude greater than the surface potential converged at the bottom of the sample can be applied to prevent the movement of lithium cations. Here, the potential was applied to the bottom of the sample by applying a positive bias to the Si substrate. The positive potential applied to the bottom of the sample also repels lithium cations similarly to the surface potential. As a result, the movement of lithium cations downwards in the sample is suppressed as the bottom potential increases, and when the magnitude of the bottom potential is greater than the surface potential, lithium cations do not move downward any further and remain on the surface. This prevents the abnormal behavior of lithium cations and enables accurate composition analysis.

[0047] According to another embodiment of the present invention, a method for analyzing the composition of alkaline ions in an all-solid-state battery is provided.

[0048] The method for analyzing the composition of alkaline ions in the above-mentioned all-solid-state battery comprises the steps of: preparing an all-solid-state battery including an electrode layer; and a solid electrolyte layer including a lithium phosphate oxynitride (LiPON) thin film disposed on one surface of the electrode layer; and irradiating a monatomic ion beam onto the surface of the solid electrolyte layer; characterized in that a positive voltage is applied to the other surface of the electrode layer in the ion beam irradiation step.

[0049] First, an all-solid-state battery including a solid electrolyte layer comprising a lithium phosphate nitride (LiPON) thin film is prepared. The solid electrolyte layer is interposed between the positive and negative electrode layers and serves as a conductor responsible for the movement of alkaline ions during charging and discharging of the all-solid-state battery.

[0050] The above electrode layer includes a positive electrode, and the positive electrode is configured to generate lithium ions through a chemical reaction when charging an all-solid-state battery, and may include a positive electrode active material that is a metal oxide, and preferably may further include a conductive material, a binder, and a solid electrolyte.

[0051] The above electrode layer includes a cathode, and the cathode may include a metal-based cathode active material, and may be manufactured by press-molding onto a current collector.

[0052] Next, a monatomic ion beam is irradiated onto the surface of the solid electrolyte layer.

[0053] In the above ion beam irradiation step, a positive voltage is applied to the other surface of the electrode layer on which the solid electrolyte layer is not formed.

[0054] Here, the applied positive voltage may be higher than the operating voltage of the all-solid-state battery. If the applied positive voltage falls short of the battery's operating voltage, the external electric field cannot be expected to offset the movement of lithium cations during measurement.

[0055] For example, the all-solid-state battery may be a lithium secondary battery, and in this case, the applied positive voltage is preferably 3.7 V or higher. As another example, the all-solid-state battery may be a sodium secondary battery, and in this case, the applied positive voltage is preferably 2.3 V or higher. However, this is an exemplary case, and the present invention is not limited thereto, and any voltage higher than the operating voltage of the all-solid-state battery may be used.

[0056] In an embodiment of the present invention, since the lithium ion pile-up phenomenon requires the loss of chemical bonds (mobilization) of Li by ion bombardment, it is preferable to apply a positive voltage equal to or greater than the breakdown potential, which is a critical potential that induces the accumulation of lithium ions. As long as the positive voltage applied to the substrate is higher than the breakdown potential, the degree of lithium ion accumulation in the all-solid-state battery may decrease, so it is preferable to apply a positive voltage near the breakdown potential.

[0057] However, since the critical substrate potential for solving the ion accumulation phenomenon may vary depending on the sample properties and experimental conditions related to ion bombardment, it is desirable to confirm the degree of ion accumulation under each experimental condition and apply a positive voltage corresponding to the breakdown potential.

[0058] Figure 2 is a depth distribution analysis spectrum of alkali metal (Li) in an all-solid-state battery depending on the presence or absence of bias.

[0059] Figure 2 (a) shows the Li 1s core-level spectrum when no bias is applied (ground), and (b) shows the Li 1s core-level spectrum when a positive voltage is applied (positive bias). Referring to this, in the case of ion beam sputtering according to (a), it can be confirmed that Li takes on a metallic form as it moves from the surface toward the substrate as sputtering progresses. That is, when a positive voltage is not applied, alkali ions can move toward the interface between the electrode layer and the solid electrolyte layer and accumulate (pile-up). When a positive voltage is applied to the same specimen according to (b), it can be seen that the cation form is distributed more than the metal form in the depth direction.

[0060] Figure 3 is a graph showing the depth distribution analysis of alkali metal (Li) in an all-solid-state battery according to an embodiment of the present invention.

[0061] Referring to Fig. 3, a graph is shown that converts the Li quantification into a depth distribution profile based on the Li 1s spectrum obtained through an X-ray spectrometer. When no bias is applied (ground bias), it shows a form in which alkali metals accumulate at the interface (black arrow). However, when a positive voltage (positive bias) is applied, it can be seen that the phenomenon at the interface disappears. In this case, the relative sensitivity factors used were A (1.0) and B (Xx), respectively.

[0062] Meanwhile, LiPON can have an interface reaction with the electrode layer by X-ray photoemission, but this reaction is limited and can be neglected.

[0063] According to another embodiment of the present invention, an alkaline ion composition analysis device in a LiPON thin film is provided.

[0064] The alkaline ion composition analysis device in the above LiPON thin film may be an X-ray photoelectron spectrometer (XPS) that analyzes a sample including a substrate and a lithium phosphorus oxynitride (LiPON) thin film disposed on one surface of the substrate.

[0065] The device may include an ion beam generating unit equipped to supply gas for generating a monoatomic ion beam; and a power control unit that controls a positive voltage to be applied to the other surface of the substrate when the monoatomic ion beam generated in the ion beam generating unit is irradiated onto the surface of the thin film. In addition, the device may further include a flood gun that supplies electrons to the surface of the sample.

[0066] FIG. 4 is a schematic diagram of an X-ray photoelectron spectroscopy (XPS) device as an alkaline ion composition analysis device in a LiPON thin film according to one embodiment of the present invention.

[0067] Referring to FIG. 4, a sample (S) is placed on a sample holder (H), and an X-ray source (A) that irradiates X-rays to the sample (S), an ion beam generation unit (B) that irradiates an ion beam, a flood gun (C) that supplies electrons, and a power control unit (40) that controls a positive voltage to be applied to the other side of the sample when a single-atom ion beam generated from the ion beam generation unit (B) is irradiated to one side of the sample (S).

[0068] The ion beam generation unit (B) is equipped with a monoatomic ion beam injection unit (11) and a gas cluster ion beam injection unit (12), and has a structure capable of injecting monoatomic ions and gas cluster ions, respectively. The flood gun (C) is a device that functions to neutralize the surface of a sample, and has a first mode (21) that controls the energy and area of ​​the applied electrons, but this is set to the condition in a general ground state. Therefore, a separate mode suitable for the condition in which a positive bias is applied is required, and it is used by setting it to the second mode (22) that is optimized for a specific amount of power.

[0069] In addition, for quantitative analysis of all-solid-state battery components, a relative sensitivity factor (RSF) is used. In addition to the fixed first RSF (31), a second RSF (32) optimized for the condition in which the surface potential changes when a positive power other than ground power is applied to the sample surface, thereby changing the ionization rate of electrons by X-rays, can be provided.

[0070] Hereinafter, the present invention will be described in more detail with examples. However, these examples are provided for illustrative purposes only and are not intended to limit the scope of the present invention.

[0071] <Example>

[0072] As a comparative example, Ar was measured on the surface of a lithium phosphate oxynitride (LiPON) thin film placed on top of a substrate using X-ray photoelectron spectroscopy. + , Ne +Monoatomic ion beam was investigated.

[0073] Figures 5 and 6 are graphs showing the movement of alkali ions (Li) in a LiPON thin film when various ion gun energies are irradiated using Ar and Ne gases according to conventional single-atom ion beam sputtering.

[0074] In Fig. 5(a), Ar + Experiments were conducted by varying the single-atom ion gun energy to (a-1) 500 eV, (a-2) 1000 eV, (a-3) 2000 eV, and (a-4) 4000 eV, and the Li pile-up phenomenon occurred in all energy bands. Although the Li pile-up phenomenon increased with increasing ion gun energy, it was not linearly proportional.

[0075] Figure 5(b) is a diagram illustrating the amount of Li accumulation (pile-up) at the interface according to the variation of ion gun energy. The X-axis represents the ion gun energy, and the Y-axis represents the result of subtracting the average Li composition in the LiPON thin film from the Li content at the interface. As a result, it can be confirmed that the accumulation (pile-up) phenomenon is observed at all ion gun energies.

[0076] Figure 6 is a graph showing the movement of alkali ions (Li) in a LiPON thin film when various ion gun energies are applied using Ne gas.

[0077] Referring to Figure 6, the results of an experiment to improve the Li pile-up phenomenon using Ne, which has a smaller atomic number than Ar, are shown.

[0078] In Fig. 6(a), Ne + As a result of experiments in which the single-atom ion gun energy was varied to (a-1) 500 eV, (a-2) 1000 eV, (a-3) 2000 eV, and (a-4) 4000 eV, it was confirmed that the Li pile-up phenomenon occurred in all methods using Ne gas.

[0079] Figure 6(b) shows the relative degree of Li accumulation according to the change in Ne ion gun energy, and through this, it can be confirmed that in the case of conventional single-atom ion beam sputtering, lithium mobility is induced, leading to Li accumulation at the boundary.

[0080] As an example, Ar was measured on the surface of a lithium phosphate oxynitride (LiPON) thin film disposed on a substrate using an X-ray photoelectron spectroscopy. + A monoatomic ion beam was applied at an ion gun energy of 2000 eV. At this time, a positive voltage was applied to the lower part of the substrate.

[0081] Figure 7 is a graph showing the movement of alkali ions in a LiPON thin film according to the applied bias voltage.

[0082] Referring to Figure 7, it can be confirmed that the Li accumulation phenomenon generally decreases as the bias voltage increases. In particular, it was confirmed that the lithium accumulation phenomenon hardly occurs at voltages above +7 V. This is presumed to be due to the reduced mobility of lithium cations within the LiPON thin film due to the bias application.

[0083] Figure 8 shows the results of analyzing the Li 1s, O 1s, and P 2p core level spectra inside a LiPO sample (etching time 150 s) according to the bias voltage applied.

[0084] What can be seen in Fig. 8 is that as the substrate potential increases in the positive direction, the portion corresponding to Li2O, which is the lower binding energy side of the Li 1s and O 1s peaks, increases. This change is particularly noticeable when a potential higher than the critical potential for ion accumulation resolution is applied. Another fact is that as the substrate potential increases, the portion corresponding to the higher binding energy shoulder of the O 1s peak and the portion corresponding to POP, which is the bonding of the P-centered atom of lithium phosphate, tends to decrease. In addition, when a potential higher than the critical potential is applied, it can be seen from the change in the lower binding energy side of the P 2p peak that some reduced P compounds and lithium phosphide (LixP) are formed from LiPO.

[0085] In summary, first, when the substrate potential is small or in the negative direction (when Li accumulation occurs smoothly), the surface Li that has lost its chemical bond due to ion etching quickly moves down the sample and leaves the surface. However, as the substrate potential increases, the accumulation phenomenon weakens, and the Li that cannot move downward remains on the surface and easily forms new reactants. This situation can be understood as the formation of an interface between mobile Li and LiPO generated by ion etching. At the same time, the result also suggests that when Li accumulation occurs, the Li generated by ion etching quickly moves downward without much reaction from the surface, and that the application of a positive substrate potential inhibits the movement of Li, promoting the retention and reaction of Li on the surface.

[0086] Next, we examined the chemical changes in the region where actual Li accumulation occurs, that is, the interface between LiPO and the Si substrate.

[0087] Figure 9 shows the Li 1s, O 1s, P 2p, and Si 2p XPS spectra in the LiPO / Si interface (etching time 300 s) region, arranged according to the applied substrate potential.

[0088] The first thing that can be seen in Figure 9 is that when a potential lower than the critical potential is applied, a component that is considerably thin (small FWHM) and clearly distinct from other chemical states is captured at the lowest binding energy side of the Li 1s peak. This appears to correspond to lithium silicide (LixSi), which is close to a metallic state. The presence of this peak is direct evidence for the presence, movement, and accumulation of mobile Li in the depth distribution analysis accompanied by ion etching. In addition, the proportion of this silicide peak decreases as the substrate potential increases, and when the substrate potential exceeds the critical value, the silicide peak does not appear prominently.

[0089] Secondly, what can be inferred from the Li 1s and O 1s peaks is that Li2O and lithium silicate (Li) are present at the interface. x Si y O z ) is formed. In addition, in the O 1s peak, a lithium-rich oxide (Li-rich oxide) with a significantly low binding energy is formed. x O)) or a component presumed to be a specific lithium silicate (Li silicate(phyllo / ino-silicate)) is also identified.

[0090] Next, what can be inferred from the P 2p peak is that lithium phosphide and reduced P compounds are also generated at the LiPO / Si interface. Relatively strong lithium phosphide formation (not shown here) is observed at the point above the interface (etch time 200–250 s) compared to bulk LiPO. Therefore, it is presumed that the stronger the Li accumulation overall, the more lithium phosphide is formed. In addition, when the substrate potential is large, especially when it is applied above the critical potential, lithium phosphide formation is reduced, but instead, the formation of reduced P compounds increases. Therefore, applying a substrate potential above the critical potential also serves the additional function of suppressing the reaction with Li at the bottom of the sample, thereby keeping the chemical state of the sample closer to the native LiPO.

[0091] Finally, what can be seen from the Si 2p peak is that the higher the substrate potential, the less Si is exposed for the same etching time. This fact is also revealed in Fig. 10. Fig. 10 shows the Ar 2p peak at 2 keV kinetic energy. + This is the result of listing the Si atomic concentrations at an etching time of 300 s during ion etching according to the lower voltage level. It is clear that the Si composition ratio decreases as the substrate potential increases. This means that the etching rate of the LiPO sample decreases as the substrate potential increases. This is thought to be because the stronger the Li accumulation, the more LiPO is decomposed at the interface, weakening the structure and thus accelerating the sample.

[0092] These results suggest that the following conclusions can be drawn: Mobile Li, which migrates downward due to Li accumulation, also reacts with LiPO at the LiPO / Si interface. The reaction between Li and LiPO decomposes LiPO to form lithium oxide, lithium phosphide, and reduced lithium phosphate. Furthermore, if there is sufficient mobile Li, in addition to the decomposition of LiPO, it reacts with the Si substrate to form interphases such as lithium silicide and lithium silicate. This decomposition reaction is more active as more Li accumulates at the bottom, that is, as the degree of Li accumulation increases. Since the reactions within the sample discussed above occur in the absence of Li accumulation, the reactions at the LiPO / Si interface with a large amount of Li accumulation are typically more intense than those within the sample. Furthermore, Li accumulation not only induces the decomposition of LiPO, changing its chemical composition, but also reduces the robustness of the LiPO sample during the decomposition process, thereby increasing the ion etching rate. Therefore, it is clear that the Li accumulation phenomenon causes multi-faceted degradation of solid electrolyte samples such as LiPO and LiPON, and it was confirmed that overcoming Li accumulation through application of the substrate potential application method according to the embodiment of the present invention is absolutely necessary in order to obtain more accurate and original physical / chemical information on solid electrolytes through depth distribution analysis accompanied by ion etching.

[0093] According to the embodiments of the present invention, as described above, by simultaneously applying a positive voltage to the bottom of an all-solid-state battery while using a single-atom ion beam, ion movement and non-ideal behavior can be prevented. This can drastically shorten the time required for depth-wise compositional analysis of an all-solid-state battery, and can contribute to improved performance of the all-solid-state battery through accurate depth-wise quantitative analysis.

[0094] Furthermore, the analysis method according to the embodiment of the present invention is not limited to the case of solid electrolytes containing Li such as LiPON and LiPO, but can be universally applied to resolve the ion accumulation phenomenon that may occur when analyzing the depth distribution of various solid electrolytes (especially containing alkali ions) and ion conductive materials, and is therefore expected to greatly contribute to more accurate composition analysis of energy / battery-related materials.

[0095] While the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will appreciate that various modifications and equivalent alternative embodiments are possible. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the appended claims.

Claims

1. A step of preparing a sample including a substrate and a lithium phosphate nitride (LiPON) thin film disposed on one surface of the substrate; and A step of irradiating a monatomic ion beam onto the surface of the lithium phosphorus nitride (LiPON) thin film; Characterized in that a positive voltage is applied to the other surface of the substrate in the above ion beam irradiation step. Method for analyzing alkaline ion composition in LiPON thin films.

2. In paragraph 1, The above ion beam irradiation step is, A step of supplying any one gas selected from the group consisting of hydrogen (H2), nitrogen (N2), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe) as a gas for generating the above single-atom ion beam, Method for analyzing alkaline ion composition in LiPON thin films.

3. In paragraph 1, The above ion beam irradiation step is, A step of accelerating the above single-atom ion beam with an acceleration voltage of 0.5 keV to 4 keV, Method for analyzing alkaline ion composition in LiPON thin films.

4. A step of preparing an all-solid-state battery including an electrode layer; and a solid electrolyte layer including a lithium phosphorus oxynitride (LiPON) thin film disposed on one surface of the electrode layer; and A step of irradiating a monatomic ion beam onto the surface of the solid electrolyte layer; Characterized in that a positive voltage is applied to the other surface of the electrode layer in the above ion beam irradiation step. Method for analyzing alkaline ion composition in all-solid-state batteries.

5. In paragraph 4, The above-mentioned applied positive voltage is higher than the operating voltage of the above-mentioned all-solid-state battery. Method for analyzing alkaline ion composition in all-solid-state batteries.

6. In paragraph 4, The above all-solid-state battery is a lithium secondary battery, The positive voltage applied above is 3.7 V or higher, Method for analyzing alkaline ion composition in all-solid-state batteries.

7. In paragraph 4, The above all-solid-state battery is a sodium secondary battery, The positive voltage applied above is 2.3 V or higher, Method for analyzing alkaline ion composition in all-solid-state batteries.

8. In paragraph 4, The positive voltage applied above is lithium Above the critical potential where ion accumulation (Li Pile-up) occurs, Method for analyzing alkaline ion composition in all-solid-state batteries.

9. In paragraph 8, When the ion gun energy is 2000 eV in the above ion beam irradiation step, The above applied positive voltage is 7 V or more, Method for analyzing alkaline ion composition in all-solid-state batteries.

10. In a device for analyzing a sample including a substrate and a lithium phosphate nitride (LiPON) thin film disposed on one surface of the substrate, An ion beam generation unit equipped to supply gas for generating a single-atom ion beam; and A power control unit that controls a positive voltage to be applied to the other surface of the substrate when a single-atom ion beam generated from the ion beam generating unit is irradiated onto the surface of the thin film; Device for analyzing alkaline ion composition in LiPON thin films.

11. In paragraph 10, The above device is an X-ray photoelectron spectrometer (XPS), Device for analyzing alkaline ion composition in LiPON thin films.

12. In paragraph 11, further comprising a flood gun for supplying electrons to the surface of the sample; Device for analyzing alkaline ion composition in LiPON thin films.

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