Preparation method of LiF-CFx film and LiF-CFx film

Abstract

The invention discloses a preparation method of a LiF-CFx film and the LiF-CFx film, and relates to the technical field of semiconductor material growth, and the preparation method comprises the following steps: placing a lithium ion battery positive electrode material in a reaction cavity of ALD equipment meeting preset conditions; sequentially introducing the first precursor and the second precursor into the reaction cavity in which the lithium ion battery positive electrode material is placed in a pulse form to obtain a LiF-CFx thin film; the first precursor and the second precursor are both gas-phase precursors; and introducing preset inert gas into the reaction cavity to purge the reaction cavity, and carrying out ALD circulation to obtain the LiF-CFx films with different thicknesses. According to the technical scheme provided by the invention, the grown film has better element control, the reaction has self-limitation, and the LiF-CFx film with better protection performance can be prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor material growth, and in particular to a preparation method of a LiF-CFx thin film and the LiF-CFx thin film. BACKGROUND

[0002] Lithium ion batteries (LIB) have mature stability and long cycle life, and are widely used in notebook computers, mobile phones and electric tools. With the rise of electric vehicles in recent years, the next generation of lithium ion batteries will have higher energy density and need to withstand higher operating temperatures. The key to providing high voltage, low cost and high safety is to use LiMn1.5Ni0.5O4 (LMNO), which is a high-energy cathode material. However, as the operating temperature of the lithium ion battery increases, the number of charge and discharge cycles increases, and the material structure changes, thereby affecting the overall performance of the battery. In order to prevent the structure of the LMNO material from changing, a protective layer needs to be coated on its surface. Currently, MgF2 and AlF3 coatings are used on LMNO materials as protective coatings, and compared with LMNO materials without coatings, they exhibit higher stability in 100 charge and discharge cycles. LiF-CFx coatings have higher chemical stability and long-term cycle stability compared to MgF2 and AlF3 coatings.

[0003] ALD (Atomic Layer Deposition) technology has obvious advantages in three-dimensional shape retention, two-dimensional flatness, and atomic layer level thickness control performance. There is currently existing technology for preparing LiF thin films on lithium ion battery anode materials by ALD technology, but there is no LiF-CFx material prepared in the existing technology.

[0004] Therefore, there is an urgent need to provide a more reliable thermal atomic layer deposition technology for growing LiF-CFx. SUMMARY

[0005] The present application aims to provide a preparation method of a LiF-CFx thin film and the LiF-CFx thin film, so that the grown thin film has better element control, the reaction has self-limiting property, and a LiF-CFx thin film with better protection performance can be prepared.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] In a first aspect, the present application provides a preparation method of a LiF-CFx thin film, the method comprising:

[0008] placing a lithium ion battery cathode material in a reaction cavity of an ALD device that meets a predetermined condition;

[0009] The first precursor and the second precursor are introduced into the reaction cavity in the form of pulses to obtain a LiF-CFx film.

[0010] The reaction cavity is purged by filling the preset inert gas into the reaction cavity, and ALD cycles are performed to obtain LiF-CFx films with different thicknesses.

[0011] Optionally, the first precursor and the second precursor are introduced into the reaction cavity in the form of pulses to obtain a LiF-CFx film, which comprises:

[0012] The first precursor is introduced into the reaction cavity in the form of pulses to obtain a substrate with a surface containing the first precursor.

[0013] The reaction cavity is purged by filling the preset inert gas into the reaction cavity.

[0014] The second precursor is introduced into the reaction cavity in the form of pulses in the presence of the preset inert gas to react with the first precursor on the surface of the substrate to obtain a LiF-CFx film; the first precursor is a Li-containing precursor; and the second precursor is an F-containing precursor.

[0015] Optionally, the lithium ion battery cathode material is placed in the reaction cavity of the ALD device that meets the preset conditions, which comprises:

[0016] The lithium ion battery cathode material is placed in the reaction cavity of the ALD device, the reaction cavity is kept in a vacuum state, and the reaction cavity is kept at a preset temperature; the preset temperature is 100-300°C.

[0017] Optionally, the reaction cavity is purged by filling the preset inert gas into the reaction cavity, and ALD cycles are performed to obtain LiF-CFx films with different thicknesses, which comprises:

[0018] After the first precursor and the second precursor are introduced into the reaction cavity in the form of pulses to obtain a LiF-CFx film, the reaction cavity is purged by filling the preset inert gas into the reaction cavity for a second purging operation to complete one ALD cycle.

[0019] The ALD cycle is repeated for 10-1200 times to obtain LiF-CFx films with different thicknesses.

[0020] Optionally, the first precursor is introduced into the reaction cavity in the form of pulses to obtain a substrate with a surface containing the first precursor, which further comprises:

[0021] The preset amount of preset inert gas is introduced into the reaction cavity, and after the pressure of the reaction cavity is kept stable, the first precursor is introduced into the reaction cavity in a pulse form to obtain a substrate containing the first precursor on the surface.

[0022] Optionally, the first precursor is lithium tert-butoxide with a purity of 80% to 99.99%, and the second precursor is hexafluoroacetylacetone with a purity of 85% to 99.99%.

[0023] Optionally, the positive electrode material of the lithium ion battery includes one or more of LiMn2O4 (LMO), LiCoO2 (LCO) and LiMn1.5Ni0.5O4 (LMNO).

[0024] Optionally, the duration of a single pulse for introducing the first precursor into the reaction cavity in a pulse form for deposition is 0.5 to 5 s.

[0025] During the first purging operation, the preset inert gas flow is 30 to 200 sccm, the purging time of the first purging operation is 5 to 100 s, and the pressure of the reaction cavity is kept at 0.05 to 2 Torr.

[0026] Optionally, the duration of a single pulse for introducing the second precursor into the reaction cavity in a pulse form for deposition is 0.1 to 5 s, the purging time of the second purging operation is 10 to 120 s, the preset inert gas flow is kept at 10 to 200 ml / min, and the pressure of the reaction cavity is kept at 0.1 to 3 Torr.

[0027] Compared with the prior art, the preparation method of the LiF-CFx thin film provided by the application places the positive electrode material of the lithium ion battery in the reaction cavity of the ALD equipment meeting the preset conditions, introduces the first precursor and the second precursor into the reaction cavity in which the positive electrode material of the lithium ion battery is placed in a pulse form in sequence to obtain the LiF-CFx thin film, the first precursor and the second precursor are both gas-phase precursors, the reaction cavity is purged by filling the preset inert gas into the reaction cavity, the ALD cycle is performed, and the LiF-CFx thin film with different thicknesses is obtained. The application is dedicated to preparing the thin film material by theoretical simulation and using the thermal atomic layer deposition technology, selecting the appropriate F-containing precursor, doping the CFx into the LiF material, forming the LiF-CFx thin film, and having better positive electrode material protection characteristics compared with the LiF material. The application selects the gas-phase precursor to prepare the LiF-CFx thin film, the precursor has high volatility, thermal stability and reactivity, is non-corrosive, has low manufacturing cost, and has low energy consumption required for the reaction. In addition, by calculating the Gibbs energy, the grown thin film has better element control, the reaction has self-limiting property, and the LiF-CFx thin film with better protection performance can be prepared.

[0028] In a second aspect, the present application provides a LiF-CFx thin film prepared by the method for preparing a LiF-CFx thin film according to the first aspect. BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the present application and together with the description serve to explain the principles of the present application. In the drawings:

[0030] Figure 1 A flowchart of a method for preparing a LiF-CFx thin film according to the present application;

[0031] Figure 2 A complete flowchart of a method for preparing a LiF-CFx thin film according to the present application;

[0032] Figure 3 A reaction mechanism diagram of a LiF-CFx thin film according to the present application;

[0033] Figure 4 An XPS image of a LiF-CFx thin film according to the present application. DETAILED DESCRIPTION

[0034] In order to clearly describe the technical solutions of the embodiments of the present application, in the embodiments of the present application, the terms of "first", "second", etc. are used to distinguish the same or similar items with basically the same function and effect. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and do not limit the order. Those skilled in the art can understand that the terms of "first", "second", etc. do not limit the number and execution order, and the terms of "first", "second", etc. also do not necessarily mean different.

[0035] It should be noted that in the present application, the words "exemplary" or "for example" are used to mean serving as an example, instance, or illustration. Any embodiment or design described as "exemplary" or "for example" in the present application should not be construed as being preferred or superior over other embodiments or design solutions. Rather, the use of the words "exemplary" or "for example" is intended to present concepts in a particular manner.

[0036] In the present application, "at least one" means one or more, and "multiple" means two or more. The "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the following three cases: A exists alone, A and B exist together, and B exists alone, wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it. "At least one of the following" or similar expressions means any combination of these items, including any combination of single or multiple items. For example, at least one of a, b or c can represent a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b and c, wherein a, b and c can be single or multiple.

[0037] The ALD reaction process is a series of chemical reaction processes. A suitable precursor combination can not only reduce the reaction temperature and control the element ratio of the thin film, but also affect the roughness, shape retention, uniformity, conductivity and other physical and chemical properties of the thin film.

[0038] The present application provides a method for preparing LiF-CFx by using lithium tert-butoxide and hexafluoroacetylacetone as precursors through thermal atomic layer deposition technology. The present application is committed to preparing thin film materials through theoretical simulation and thermal atomic layer deposition technology, selecting suitable F-containing precursors, incorporating CFx into LiF materials to form LiF-CFx thin films, which have better positive material protection properties than LiF materials.

[0039] The present application selects lithium tert-butoxide and hexafluoroacetylacetone as precursors to prepare LiF-CFx thin films, which has not been applied in the prior art. Compared with other F-containing precursors, hexafluoroacetylacetone forms LiF-CFx thin films after reaction, which has higher stability than LiF thin films. The precursor has high volatility, thermal stability and reactivity, is non-corrosive, has low production cost and low energy consumption. In addition, by calculating the Gibbs energy, the present application performs theoretical thermodynamic analysis on different precursor combinations of LiF-CFx. The selected lithium tert-butoxide and hexafluoroacetylacetone precursor combination has better element control of the grown thin film, the reaction has self-limiting property, and can prepare LiF-CFx thin films with better protection performance. Next, the scheme provided by the embodiments of the present application will be described in combination with the drawings:

[0040] As shown in the flowchart of FIG. 1, Figure 1 the flowchart can include the following steps:

[0041] Step 110: Place the lithium ion battery positive electrode material in the reaction cavity of the ALD device that meets the preset conditions.

[0042] Before starting the surface treatment of the lithium ion battery cathode material, the cathode material needs to be placed in the reaction cavity of the ALD (atomic layer deposition) equipment. At this time, specific temperature, pressure and preset inert gas atmosphere need to be set to ensure that the subsequent thin film deposition process can be carried out in a stable and controllable environment, avoid external factors such as oxygen and water vapor in the air from interfering with the reaction, and thus create a good foundation for the formation of high-quality thin films.

[0043] Step 120: sequentially introduce the first precursor and the second precursor into the reaction cavity in which the lithium ion battery cathode material is placed in the form of pulses to obtain a LiF-CFx thin film; the first precursor and the second precursor are both gas-phase precursors.

[0044] In step 120, the first precursor and the second precursor are sequentially introduced into the reaction cavity in which the lithium ion battery cathode material is placed in the form of pulses. The first precursor and the second precursor are both gas-phase precursors, and the temperature is maintained at 0-200℃.

[0045] The precursors are substances that can undergo chemical reactions and ultimately form the composition of the target thin film, and exist in a gaseous state so that they can uniformly contact the surface of the cathode material in the reaction cavity. The first precursor and the second precursor respectively contain the elemental components required to form the LiF-CFx thin film, and under certain reaction conditions, will chemically react with the surface of the cathode material, gradually deposit and grow a layer of LiF-CFx thin film.

[0046] Step 130: fill the reaction cavity with a preset inert gas to purge the reaction cavity and perform ALD cycles to obtain LiF-CFx thin films of different thicknesses.

[0047] After introducing the precursors, the reaction cavity is filled with a preset inert gas for purging to clean up the impurities such as unreacted precursors and reaction byproducts remaining in the reaction cavity, ensuring that the environment in the reaction cavity is pure and preparing for the next round of reaction cycles. By performing ALD cycles, the thickness of the LiF-CFx thin film can be controlled. The thickness of the thin film deposited each time is very thin, usually on the order of atomic or molecular, so by increasing the number of cycles, LiF-CFx thin films of different thicknesses can be accumulated to meet the requirements of different application scenarios for the thickness of the thin film.

[0048] Figure 1The method described involves placing lithium-ion battery cathode material in the reaction chamber of an ALD (Atomic Layer Deposition) device that meets preset conditions; sequentially introducing a first precursor and a second precursor into the reaction chamber in a pulsed manner to obtain LiF-CFx films; both the first and second precursors are gas-phase precursors; and the reaction chamber is purged with a preset inert gas to perform ALD cycling, resulting in LiF-CFx films of different thicknesses. This invention focuses on preparing thin film materials using thermal atomic layer deposition (TLD) technology through theoretical simulation. A suitable F-containing precursor is selected to dope LiF material with CFx, forming LiF-CFx films, which exhibit better cathode material protection characteristics compared to LiF material. This invention uses gas-phase precursors to prepare LiF-CFx films, which have high volatility, thermal stability, and reactivity, are non-corrosive, have low production costs, and require low energy consumption for the reaction. Furthermore, by calculating the Gibbs energy, the grown film exhibits better elemental control and self-limiting reaction, enabling the preparation of LiF-CFx films with better protective properties.

[0049] based on Figure 1 In addition to the method described herein, this specification also provides some specific implementation methods of this method, which will be described below.

[0050] Step 120 may include:

[0051] The first precursor is introduced into the reaction chamber in the form of a pulse to obtain a substrate with the first precursor on its surface.

[0052] A first purging operation is performed by filling the reaction chamber with a preset inert gas;

[0053] In the presence of a pre-set inert gas, the second precursor is introduced into the reaction chamber in a pulsed manner to react with the first precursor on the substrate surface to obtain a LiF-CFx thin film; the first precursor is a Li-containing precursor; the second precursor is an F-containing precursor.

[0054] Step 110 may include:

[0055] The positive electrode material of the lithium-ion battery is placed in the reaction chamber of the ALD device. The reaction chamber is kept under vacuum and at a preset temperature, which is 100 to 300°C.

[0056] Step 130 may include:

[0057] After the first precursor and the second precursor are sequentially introduced into the reaction chamber containing the positive electrode material of the lithium-ion battery in the form of pulses to obtain the LiF-CFx film, the reaction chamber is filled with a preset inert gas to perform a second purging operation, thus completing one ALD cycle.

[0058] The ALD cycle is repeated 10-1200 times to obtain LiF-CFx films with different thicknesses.

[0059] In summary, in combination with Figure 2 The application provides a preparation method of a LiF-CFx film, and the specific implementation process can include the following steps.

[0060] Step 1: Place clean lithium ion battery positive electrode material in a reaction cavity of an ALD device kept in a vacuum state and at a certain temperature.

[0061] Step 2: Introduce a certain amount of preset inert gas into the reaction cavity, and after the pressure of the reaction cavity is kept stable, introduce a first precursor into the reaction cavity in a pulse form to obtain a substrate containing the first precursor on the surface; the first precursor is a gas phase source.

[0062] Step 3: Introduce a certain amount of preset inert gas into the reaction cavity to purge the reaction cavity.

[0063] Step 4: Introduce a second precursor into the reaction cavity in a pulse form in the presence of the preset inert gas to react with the first precursor on the surface of the substrate to obtain a LiF-CFx film.

[0064] Step 5: Introduce a certain amount of preset inert gas into the reaction cavity to purge the reaction cavity to complete one ALD cycle.

[0065] Step 6: Repeat steps 2-5 for 10-1200 times to obtain LiF-CFx films with different thicknesses.

[0066] It should be noted that in the above steps, the first precursor is a Li-containing precursor, for example, lithium salts (such as Li2CO3, LiOH, LiF, etc.), lithium oxides (such as Li2O, Li2O2), and lithium phosphates (such as LiH2PO4, Li3PO4), etc. In one of the embodiments of the application, preferably, the first precursor can be lithium tert-butoxide with a purity of 80%-99.99%.

[0067] The second precursor is an F-containing and carbon-containing precursor, for example, fluoroketone compounds with special substituents, fluorinated ester compounds, etc. In the application, the second precursor is preferably hexafluoroacetylacetone with a purity of 85%-99.99%. Through the combination of experimental testing and theoretical calculation, new F-containing compounds more suitable as thermal atomic layer deposition precursors are screened out, further enriching the types of available precursors and providing more possibilities for preparing LiF-CFx films with better performance.

[0068] Next, the application will be described in detail in combination with the following examples. Figure 2The preparation process parameters in each step in the method are further defined as follows:

[0069] Preferably, the positive electrode material of the lithium ion battery comprises one or more of LiMn2O4(LMO), LiCoO2(LCO), and LiMn1.5Ni0.5O4(LMNO).

[0070] Preferably, Figure 2 The reaction cavity deposition temperature of step 1 in the method is 100-300℃.

[0071] The duration of a single pulse of the first precursor in step 2 is 0.5-5s.

[0072] The preset inert gas flow in step 2 is 30-200sccm.

[0073] The purging time of the reaction cavity in step 3 is 5-100s, wherein the preset inert gas flow is maintained at 20-100ml / min, and the pressure of the reaction cavity is maintained at 0.05-2Torr.

[0074] The duration of a single pulse of the second precursor in step 4 is 0.1-5s.

[0075] The preset inert gas flow in step 4 is 10-100sccm.

[0076] The purging time of the reaction cavity in step 5 is 10-120s, wherein the preset inert gas flow is maintained at 10-200ml / min, and the pressure of the reaction cavity is maintained at 0.1-3Torr.

[0077] The preset inert gas is one or more of high-purity nitrogen or high-purity argon.

[0078] Next, the scheme of the present application is described in detail with specific embodiments as follows:

[0079] Step 1: Before placing the substrate, the substrate needs to be cleaned and dried to ensure that the surface of the substrate is clean, so as to ensure that the surface of the lithium ion battery positive electrode material is not contaminated. Before placing the substrate, the atomic layer deposition equipment is vacuumed and heated, and the clean lithium ion battery positive electrode material is placed in the reaction cavity of the ALD equipment. The reaction cavity is kept in a vacuum state, and a certain temperature is maintained for the reaction cavity, so as to ensure that the reaction cavity and pipeline in the atomic layer deposition equipment are dry and have no water vapor residue.

[0080] Step two: a certain amount of preset inert gas is introduced into the reaction cavity, and after the pressure of the reaction cavity is kept stable, the first precursor is introduced into the reaction cavity in the form of pulse, the first precursor is a gas source, and a substrate containing the first precursor on the surface is obtained;

[0081] Step three: a certain amount of preset inert gas is introduced into the reaction cavity to purge the reaction cavity;

[0082] Step four: in the presence of the preset inert gas, the second precursor is introduced into the reaction cavity in the form of pulse to react with the first precursor on the surface of the substrate, and a LiF-CFx thin film is obtained;

[0083] Step five: a certain amount of preset inert gas is introduced into the reaction cavity to purge the reaction cavity, and one ALD cycle is completed;

[0084] Step six: the operations of steps two to five are repeated 100-500 times, and a LiF-CFx thin film with different thicknesses is obtained.

[0085] Specifically, the first precursor is a Li-containing precursor, which is lithium tert-butoxide with a purity of 99%-99.99%, and the second precursor is an F-containing precursor, which is hexafluoroacetylacetone with a purity of 98%-99.99%.

[0086] Specifically, the first precursor and the second precursor are both gas-phase precursors, and the temperature is kept at 20-200°C, the temperature of the first precursor can be one of 150°C, 175°C and 200°C, and the temperature of the second precursor can be one of 20°C, 25°C and 30°C.

[0087] Specifically, the lithium ion positive electrode material is LiMn1.5Ni0.5O4(LMNO).

[0088] Specifically, the deposition temperature of the reaction cavity in step one is 100-300°C, more preferably 120°C-250°C, and most preferably 150°C-250°C, and the temperature can be one of 175°C, 200°C and 225°C.

[0089] Specifically, the duration of a single pulse for depositing the first precursor into the reaction cavity in the form of pulse in step two is 0.5-5s, more preferably 1-4s, and most preferably 1.5-3s, and can be one of 2s, 2.5s and 3s.

[0090] Specifically, the flow rate of the preset inert gas in step two is 30-200sccm, more preferably 50-100sccm, and most preferably 60-80sccm, and can be one of 65sccm, 70sccm and 70sccm.

[0091] Specifically, the purging time of the reaction cavity in the step three is 5-100s, more optionally 10-90s, and most preferably 20-80s, wherein the preset inert gas flow is kept at 20-100ml / min, and the pressure of the reaction cavity is kept at 0.05-2Torr.

[0092] Specifically, the duration of a single pulse of the second precursor in the step four is 0.1-5s, more optionally 0.3-4s, and most preferably 0.5-3s, which can be one of 0.8s, 1.0s or 2.0s.

[0093] Specifically, the preset inert gas flow in the step four is 10-100sccm, more optionally 15-80sccm, and most preferably 25-70sccm, which can be one of 30sccm, 50sccm or 60sccm.

[0094] Specifically, the purging time of the reaction cavity in the step five is 10-120s, more optionally 20-100s, and most preferably 30-80s, wherein the preset inert gas flow is kept at 10-200ml / min, and the pressure of the reaction cavity is kept at 0.1-3Torr.

[0095] Specifically, the preset inert gas is one or more of high-purity nitrogen or high-purity argon.

[0096] Specifically, the repeating of the steps two to five is optionally 100-1000 times, more optionally 200-800 times, and most preferably 300-500 times.

[0097] On the basis of the embodiments of the present application, the step one further comprises the steps of:

[0098] The substrate is ultrasonically cleaned with anhydrous ethanol solution for 3-30min, then ultrasonically cleaned with deionized water for 3-30min, and finally dried with high-purity nitrogen. By pretreating the substrate, the adsorbed impurities on the surface of the substrate can be removed, and the adsorption of the precursor on the surface of the substrate can be improved.

[0099] On the basis of the embodiments of the present application, the substrate is ultrasonically cleaned with anhydrous ethanol solution for 3-30min, then ultrasonically cleaned with deionized water for 3-30min, and finally dried with high-purity nitrogen.

[0100] In some embodiments, the elemental content of the LiF-CFx thin film includes 20.2% to 50.5% of Li element, 25.2% to 47.5% of F element, and 30.4% to 52.3% of C element in terms of mass fraction, the thickness of the LiF-CFx thin film is 10 nm to 50 nm, and the growth rate of the LiF-CFx thin film is 0.2 A to 1.2 A / cycle.

[0101] Based on the same idea, the application also provides a LiF-CFx thin film prepared by the preparation method of the LiF-CFx thin film.

[0102] More specifically, the reaction mechanism of the LiF-CFx thin film mentioned in the application is as shown in Figure 3 Figure 3 is an ALD reaction equation, and the ALD is composed of two half reactions, the first half reaction is the reaction equation after the surface bonding functional group LMNO is introduced into lithium tert-butyl alcohol, and the second half reaction is the reaction equation after Hfac is introduced after the first half reaction.

[0103] The XPS image of the LiF-CFx thin film is as shown in Figure 4 Figure 4 is the XPS for testing after the film is completed, which can qualitatively observe the elements in the thin film. Further, Figure 4 The abscissa in the above formula represents the binding energy (Binding Energy), which refers to the energy required to remove an electron from its atomic orbital, expressed in electron volts (eV). In the XPS image, different atomic orbitals (such as Li 1s, F 1s, C 1s, etc.) have specific binding energies. Through the abscissa, the elements present in the sample and their chemical states can be determined. By comparing the binding energy values in the standard database, the elemental composition of the material surface can be identified. The ordinate is the count (Counts), which is the number of detected photoelectrons, and can be used to estimate the relative content of different elements in the sample. The entire XPS image shows the elemental composition and relative content information of the LiF-CFx thin film in the surface region. By identifying different binding energy peaks (abscissa characteristic position), the existing elements such as Li, F, and C can be determined. At the same time, according to the intensity of the peak (ordinate count), the relative content of these elements can be estimated, so as to understand the chemical composition of the thin film. The distribution and bonding of fluorine elements in the thin film can also be analyzed.

[0104] The technical scheme provided by the application at least has the following technical effects:

[0105] (1) The F-containing precursor used in the application can grow a LiF-CFx thin film, and the LiF-CFx thin film has better protection effect than the LiF thin film. ​​

[0106] (2) The F-containing precursor used in the application has no corrosivity, and the material requirement for the pipeline and cavity is low, thereby reducing the equipment cost.

[0107] (3) The precursor reaction used in the application has self-limiting property, and the film thickness is accurately controllable.

[0108] Although the application has been described in connection with the embodiments thereof, it will be understood that many modifications will be suggested to those skilled in the art, and that the application is entitled to broad coverage in scope or equivalent elements. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. A single processor or other unit can fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to an advantage. The reference signs in the claims should not be construed as limiting the scope of the application.

[0109] Although the application has been described in connection with specific embodiments thereof, it will be understood that it is capable of modifications and alternative constructions and combinations of parts herein described, drawings and examples without departing from the spirit and scope of the application. Accordingly, the description and drawings are to be regarded simply as illustrative in nature and are not to be taken in a limiting sense, as is intended that only the scope of the appended claims should be regarded to define the scope of the application. Obviously, many modifications and variations of the present application are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A method for producing a LiF-CFx thin film, characterized by, The method comprises: placing a lithium ion battery positive electrode material in a reaction cavity of an ALD device meeting preset conditions; pulsatingly inputting a first precursor and a second precursor into the reaction cavity in which the lithium ion battery positive electrode material is placed to obtain a LiF-CFx thin film; the first precursor and the second precursor are both gas-phase precursors; inflating the reaction cavity with a preset inert gas to purge the reaction cavity, performing ALD circulation, and obtaining a LiF-CFx thin film with different thicknesses.

2. The method of claim 1, wherein the LiF-CFx thin film is prepared by a method comprising: The pulsating inputting of the first precursor and the second precursor into the reaction cavity in which the lithium ion battery positive electrode material is placed to obtain the LiF-CFx thin film comprises: pulsatingly inputting the first precursor into the reaction cavity to obtain a substrate with the first precursor on the surface; inflating the reaction cavity with a preset inert gas to perform a first purging operation on the reaction cavity; in the presence of the preset inert gas, pulsatingly inputting the second precursor into the reaction cavity to react with the first precursor on the surface of the substrate to obtain the LiF-CFx thin film; the first precursor is a Li-containing precursor; and the second precursor is an F-containing precursor.

3. The method of claim 1, wherein the LiF-CFx thin film is prepared by a method comprising: The placing of the lithium ion battery positive electrode material in the reaction cavity of the ALD device meeting the preset conditions comprises: placing the lithium ion battery positive electrode material in the reaction cavity of the ALD device, wherein the reaction cavity is kept in a vacuum state, and the reaction cavity is kept at a preset temperature; the preset temperature is 100-300 DEG C.

4. The method of claim 1, wherein the LiF-CFx thin film is prepared by a method comprising: The inflating of the reaction cavity with the preset inert gas to purge the reaction cavity, the performance of the ALD circulation, and the obtaining of the LiF-CFx thin film with different thicknesses comprise: after the pulsating inputting of the first precursor and the second precursor into the reaction cavity in which the lithium ion battery positive electrode material is placed to obtain the LiF-CFx thin film, inflating the reaction cavity with a preset inert gas to perform a second purging operation on the reaction cavity to complete one ALD circulation; repeating the ALD circulation for 10-1200 times to obtain the LiF-CFx thin film with different thicknesses.

5. The method of claim 2, wherein the LiF-CFx thin film is prepared by a method comprising: The pulsating inputting of the first precursor into the reaction cavity to obtain the substrate with the first precursor on the surface further comprises: after inflating the reaction cavity with a preset amount of a preset inert gas and keeping the pressure of the reaction cavity stable, pulsatingly inputting the first precursor into the reaction cavity to obtain the substrate with the first precursor on the surface.

6. The method of claim 2, wherein the LiF-CFx thin film is prepared by a method comprising: The first precursor is lithium tert-butoxide with a purity of 80%-99.99%; and the second precursor is hexafluoroacetylacetone with a purity of 85%-99.99%.

7. The method for preparing LiF-CFx thin films according to claim 1, characterized in that, The positive electrode material of the lithium ion battery comprises one or more of LiMn2O4 (LMO), LiCoO2 (LCO), and LiMn1.5Ni0.5O4 (LMNO).

8. The method for preparing LiF-CFx thin films according to claim 2, characterized in that, The duration of a single pulse of the pulsating inputting of the first precursor into the reaction cavity for deposition is 0.5-5 s; when performing the first purging operation, the flow rate of the preset inert gas is 30-200 sccm; the purging time of the first purging operation is 5-100 s, and the pressure of the reaction cavity is kept at 0.05-2 Torr.

9. The method of claim 4, wherein the LiF-CFx thin film is prepared by a method comprising: The duration of a single pulse of the second precursor introduced into the reaction cavity in the form of pulses is 0.1-5 s; the purge time of the second purge operation is 10-120 s, the preset inert gas flow is maintained at 10-200 ml / min, and the pressure in the reaction cavity is maintained at 0.1-3 Torr.

10. A LiF-CFx thin film, characterized by, The LiF-CFx thin film is prepared by the method of any one of claims 1-9.

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