Amorphous iron nitride-sulfide thin film positive electrode material and preparation method thereof, and thin film lithium battery

Abstract

The application provides an amorphous iron nitride sulfide thin film positive electrode material, a preparation method thereof and a thin film lithium battery containing the same. The positive electrode material uses nitrogen atoms to replace part of sulfur atoms in amorphous ferrous sulfide to form amorphous iron nitride sulfide, and the atomic ratio of iron, sulfur and nitrogen in the iron nitride sulfide is 1:(0.3-0.6):(0.3-0.6). The amorphous structure of the iron nitride sulfide can avoid the volume expansion of the crystalline material caused by lattice distortion; and the presence of nitrogen atoms can effectively inhibit the shuttle effect of polysulfides generated in the cycle process, so that the positive electrode thin film can be more firm, the diffusion of the active material into the electrolyte can be avoided, and the capacity and cycle life of the battery can be improved. The preparation method is simple, and the obtained iron nitride sulfide positive electrode material has the advantages of good conductivity, fast growth speed, high specific capacity, long cycle life, low preparation temperature and the like.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to an amorphous iron nitrogen sulfide thin film cathode material and its preparation method, and a thin film lithium battery. Background Technology

[0002] Currently, the new generation of high-energy-density lithium-ion batteries mainly utilize intercalation reaction cathode materials (such as lithium cobalt oxide and lithium iron phosphate), which usually only undergo single-electron transfer reactions, so the specific capacity is severely limited, generally within 200 mAh / g.

[0003] To overcome this limitation, many researchers have pursued cathode materials with higher capacity, using compounds that store lithium ions through so-called conversion reactions. These include fluorides, sulfides, and oxides, because they can fully utilize all oxidation states of transition metals, each of which can store more than one lithium ion, thus providing higher capacity compared to intercalated cathodes.

[0004] Since the pioneering work of Poizot et al., conversion reaction-based materials have been extensively studied. In recent years, pyrite, as a conversion reaction-based material, has regained attention due to its high theoretical energy density, low cost, abundant clay content, and non-toxicity.

[0005] Lithium-free ferrous sulfide cathodes exhibit high specific capacity (theoretical specific capacity up to 600 mAh g). -1 ) and energy density (900Wh Kg) -1 Ferrous sulfide, as a cathode material in lithium-ion batteries, undergoes the reaction FeS + 2Li during battery cycling. + +2e - The conversion reaction →Fe+Li2S gives the battery advantages such as good conductivity and fast charge / discharge rate.

[0006] However, the ion insertion in ferrous sulfide cathode materials inevitably leads to lattice distortion, generating large strain energy and causing significant volume expansion, resulting in irreversible and severe damage to the substrate. For ferrous sulfide thin films, this substantial volume expansion causes pulverization of the film material and shedding of active material and current collector, severely impacting the battery's cycle life. Simultaneously, the polysulfides generated during cycling also exhibit a shuttle effect in the electrolyte, further affecting battery capacity and cycle life. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing an amorphous iron sulfide thin-film cathode material and a thin-film lithium battery. The iron sulfide cathode material of this invention is amorphous, which avoids the volume expansion caused by lattice distortion in crystalline materials. Furthermore, the presence of nitrogen atoms can effectively suppress the shuttle effect of polysulfides generated during cycling, thereby making the cathode film more robust and preventing the diffusion of active materials into the electrolyte. This can achieve the beneficial effects of improving battery capacity and cycle life.

[0008] According to a first aspect of the present invention, an amorphous iron sulfide thin film cathode material is provided, the cathode material comprising iron sulfide, wherein the iron sulfide is amorphous and the atomic ratio of iron, sulfur and nitrogen in the iron sulfide is 1:(0.3-0.6):(0.3-0.6).

[0009] According to a second aspect of the present invention, a method for preparing an amorphous iron nitrogen sulfide thin film cathode material is provided, comprising the following steps:

[0010] With FeS x The target, used as the target material for magnetron sputtering, is equipped with FeS. x After the target material and positive electrode current collector are prepared, the sputtering chamber is closed, the sputtering chamber is evacuated, and a nitrogen source is introduced. After setting the sputtering power, substrate temperature, and sputtering time, sputtering is started, and amorphous iron nitride thin film positive electrode material can be obtained on the positive electrode current collector.

[0011] Among them, FeS x In this context, x represents the atomic ratio, with a value of 0.7 ≤ x ≤ 1.4; the substrate temperature is 15℃-300℃.

[0012] Preferably, the nitrogen source is nitrogen gas or a nitrogen-argon mixture.

[0013] Preferably, when the nitrogen source is a nitrogen-argon mixture, the flow rate ratio of nitrogen to argon is (1-10):1.

[0014] Preferably, the sputtering chamber is evacuated to a pressure ≤1.0×10⁻⁶. -4 Pa, magnetron sputtering power is 50-120W, sputtering time is 0.5-24h.

[0015] Preferably, the positive electrode current collector film is one of the following: glass sheet, polyimide, alumina sheet, paper, stainless steel, silicon wafer, and metal foil coated with a conductive current collector layer.

[0016] According to a third aspect of the present invention, a thin-film lithium battery is provided, wherein the positive electrode material of the thin-film lithium battery is the aforementioned amorphous iron nitride thin-film positive electrode material.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. The amorphous iron sulfide nitrogen thin film cathode material of the present invention has an amorphous state, in which lithium ions can directly enter the vacancies without causing lattice distortion or generating very large strain energy. Moreover, the amorphous iron sulfide nitrogen does not have a preferred ion diffusion channel, but has an isotropic lithium diffusion channel and a higher diffusion coefficient, thereby effectively alleviating the volume expansion problem of ferrous sulfide, making the thin film material less prone to pulverization, improving the cycle performance of the battery, and having better rate performance.

[0019] Amorphous iron nitride (Fe-SN) has a network structure formed by the Fe-N bonds and Fe-S bonds due to the addition of N atoms. This network structure is more stable than the network structure formed by Fe-S bonds alone. Therefore, it can adapt to the stress and strain caused by ion intercalation to a greater extent. Moreover, due to the addition of N atoms, the amorphousness of the amorphous iron nitride film is further improved, thereby further optimizing and improving the ability to alleviate the volume expansion of ferrous sulfide.

[0020] Furthermore, the addition of nitrogen atoms gradually forms a stable SEI film on the electrode surface during cycling. This film can effectively suppress the shuttle effect of polysulfides generated during cycling in the electrolyte, preventing the continuous loss of active materials into the electrolyte and further improving the battery capacity and cycle life.

[0021] 2. This invention uses FeS x Using magnetron sputtering as the target material, the ions ionized by the working gas can sputter a certain proportion of iron and sulfur atoms from the target material. Nitrogen gas or a nitrogen-argon mixture itself provides the nitrogen source. Under specific conditions, Fe, S, and N atoms then bond and aggregate in a certain proportion to form a film, resulting in an amorphous iron sulfide cathode thin film material.

[0022] The amorphous iron sulfide obtained by this method has advantages such as uniform distribution of Fe, S and N atoms, dense and smooth film surface, and strong adhesion to the substrate. It further suppresses the problem of cathode film detachment, improves the performance of film material, and the preparation method of this invention makes it easier to control the film growth rate and has good repeatability.

[0023] 3. The amorphous iron nitrogen sulfide thin film cathode material of the present invention has a cost that is much lower than that of lithium-containing cathode materials. It also has the advantages of good conductivity, fast growth rate, high specific capacity, long cycle life and low preparation temperature, which can significantly reduce production costs and expand its application range. Attached Figure Description

[0024] Figure 1 This is a TEM selected area diffraction pattern of the sample obtained in Example 1 of the present invention.

[0025] Figure 2a ,2b 2c and 2d are respectively Figure 1 The corresponding elemental distribution diagrams for Fe, S, N, and O.

[0026] Figure 3 This is a TEM selected area diffraction pattern of the sample obtained in Comparative Example 1 of this invention.

[0027] Figure 4 These are Raman comparison images of the samples obtained in Example 1 and Comparative Example 1 of this invention.

[0028] Figure 5 These are XRD comparison images of the samples obtained in Example 1 and Comparative Example 2 of this invention.

[0029] Figure 6 This is a graph showing the electrochemical performance of the amorphous iron sulfide film obtained in Example 1 of this invention.

[0030] Figure 7 This is a comparison chart of the electrochemical performance of the samples obtained in Example 1 and Comparative Example 1 of this invention.

[0031] Figure 8 This is a graph showing the electrochemical performance of the sample obtained in Comparative Example 2 of this invention. Detailed Implementation

[0032] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0033] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, in which numerous illustrative embodiments are shown. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described below in more detail, can be implemented in any of a number of ways.

[0034] This invention proposes an amorphous iron sulfide nitrogen thin film cathode material. The cathode material of this invention uses amorphous ferrous sulfide as the matrix material. By replacing some sulfur atoms in the amorphous ferrous sulfide with nitrogen atoms, amorphous iron sulfide nitrogen is formed. This avoids the volume expansion caused by lattice distortion in crystalline materials. Furthermore, the presence of nitrogen atoms can effectively suppress the shuttle effect of polysulfides generated during cycling, thereby making the cathode film more robust and preventing the diffusion of active materials into the electrolyte. This can achieve the beneficial effects of improving battery capacity and cycle life.

[0035] In an exemplary embodiment of the present invention, an amorphous iron sulfide nitrogen thin film cathode material is provided, the cathode material comprising iron sulfide nitrogen, wherein the iron sulfide nitrogen is amorphous and the atomic ratio of iron, sulfur and nitrogen in the iron sulfide nitrogen is 1:(0.3-0.6):(0.3-0.6).

[0036] It should be understood that the proportions of iron atoms, sulfur atoms, and nitrogen atoms in the obtained amorphous iron sulfide include, but are not limited to, the proportions mentioned above, and are mainly determined based on the proportions of iron atoms and sulfur atoms in the raw materials.

[0037] In one embodiment, the amorphous iron nitride sulfide thin film cathode material is composed only of Fe-SN; in other embodiments, the amorphous iron nitride sulfide thin film cathode material may also include other impurities or substances that help improve the performance of the target material in addition to Fe-SN.

[0038] Ferrous sulfide is usually prepared into crystalline thin films using synthesis methods such as sol-gel method, electrochemical deposition method and hydrothermal method. However, the growth rate of the film is difficult to control, the repeatability is poor, the surface of the grown film is rough, and ferric sulfide films are difficult to prepare using other methods.

[0039] Therefore, in another exemplary embodiment of the present invention, a method for preparing an amorphous iron nitrogen sulfide thin film cathode material is also provided, using FeS x Using a nitrogen source as the target material, and under certain substrate temperature conditions, amorphous iron sulfide nitrogen thin film cathode material is obtained by magnetron sputtering on the cathode current collector film.

[0040] In a specific embodiment, the preparation method of the amorphous iron sulfide nitrogen thin film cathode material specifically includes the following steps:

[0041] With FeS x The target, used as the target material for magnetron sputtering, is equipped with FeS. x After the target material and positive electrode current collector are prepared, the sputtering chamber is closed, the sputtering chamber is evacuated, and a nitrogen source is introduced. After setting the sputtering power, substrate temperature, and sputtering time, sputtering is started, and amorphous iron nitride thin film positive electrode material can be obtained on the positive electrode current collector.

[0042] Among them, FeS x In this context, x represents the atomic ratio, with a value of 0.7 ≤ x ≤ 1.4; the substrate temperature is 15℃-300℃, particularly preferably 25℃-80℃.

[0043] The main component of the target material is FeS x This should be understood as meaning that it may include only FeS. x It can also include, in addition to FeS x Other than impurities or substances that help improve the performance of the target material.

[0044] In a preferred embodiment, the nitrogen source is nitrogen gas or a nitrogen-argon mixture. Nitrogen gas or the nitrogen-argon mixture also serves as the working gas, and has the following functions:

[0045] Firstly, it can act as a protective gas to prevent the sputtered atoms from being oxidized and changing their composition.

[0046] Secondly, the ions emitted from the ionization of the gas can sputter out a certain proportion of Fe and S atoms;

[0047] Third, nitrogen gas is used as a nitrogen source to provide nitrogen atoms. Under specific temperature, sputtering power and working gas pressure, Fe, S and N atoms are then linked together and aggregated into a film in a certain proportion to obtain a nitrided modified amorphous ferrous sulfide cathode thin film material.

[0048] In a preferred embodiment, when the nitrogen source is a nitrogen-argon mixture, the flow rate ratio of nitrogen to argon is (1-10):1. This provides sufficient nitrogen atoms to replace sulfur atoms.

[0049] It should be understood that when the nitrogen source is nitrogen gas, its flow rate is not limited because there is only nitrogen gas in the entire chamber, which can provide a sufficient number of nitrogen atoms.

[0050] In a preferred embodiment, the sputtering chamber is evacuated to a pressure ≤1.0×10⁻⁶. -4 Pa, magnetron sputtering power is 50-120W, sputtering time is 0.5-24h.

[0051] In a preferred embodiment, the positive current collector film is one of the following: a glass sheet coated with a conductive current collector layer, polyimide, alumina sheet, paper, stainless steel, silicon wafer, and metal foil.

[0052] In another exemplary embodiment of the present invention, a thin-film lithium battery is also provided, wherein the positive electrode material of the thin-film lithium battery is the aforementioned amorphous iron nitride thin-film positive electrode material.

[0053] It should be understood that the cathode material of the present invention is more suitable for thin-film batteries or micro batteries, and can provide better electrochemical performance.

[0054] The following specific embodiments illustrate the preparation process of the aforementioned amorphous iron nitrogen sulfide cathode thin film material.

[0055]

Example 1

[0056] Ferrous sulfide (Fe / S = 1:1) was used as the target material for magnetron sputtering, and carbon-coated aluminum foil was selected as the positive electrode current collector. After installing the target material and the positive electrode current collector, the sputtering chamber was closed and evacuated to a vacuum of 1.0 × 10⁻⁶. -4 When the pressure is below Pa, nitrogen gas is introduced as both the nitrogen source and the working gas. With a sputtering power of 120W, a substrate temperature of 25℃, and a sputtering time of 1h, an amorphous iron sulfide film with a thickness of 300nm can be directly obtained on the positive electrode current collector.

[0057]

Example 2

[0058] Ferrous sulfide (Fe / S = 1:1.2) was used as the target material for magnetron sputtering, and carbon-coated aluminum foil was selected as the positive electrode current collector. After installing the target material and the positive electrode current collector, the sputtering chamber was evacuated to 1.0 × 10⁻⁶. -4 Below Pa, a nitrogen-argon mixture (N2:Ar = 20 sccm: 20 sccm) is introduced as the nitrogen source and working gas; with the sputtering power set to 100 W, the substrate temperature to 80 °C, and the sputtering time to 10 h, an amorphous iron sulfide film with a thickness of 3.1 μm can be directly obtained on the positive electrode current collector.

[0059]

Example 3

[0060] Ferrous sulfide (Fe / S = 1:1.4) was used as the target material for magnetron sputtering, and carbon-coated aluminum foil was selected as the positive electrode current collector. After installing the target material and the positive electrode current collector, the sputtering chamber was evacuated to 1.0 × 10⁻⁶. -4 Below Pa, a nitrogen-argon mixed gas (N2:Ar = 40 sccm: 20 sccm) is introduced as the nitrogen source and working gas; with the sputtering power set to 100 W, the substrate temperature to 150 °C, and the sputtering time to 15 h, an amorphous iron sulfide film with a thickness of 1.6 μm can be directly obtained on the positive electrode current collector.

[0061]

Example 4

[0062] Ferrous sulfide (Fe / S = 1:0.7) was used as the target material for magnetron sputtering, and carbon-coated aluminum foil was selected as the positive electrode current collector. After installing the target and positive electrode current collector, the sputtering chamber was evacuated to 1.0 × 10⁻⁶. -4 Below Pa, a nitrogen-argon mixture (N2:Ar = 50 sccm: 10 sccm) is introduced as the nitrogen source and working gas; with the sputtering power set to 100 W, the substrate temperature to 25 °C, and the sputtering time to 10 h, an amorphous iron sulfide film with a thickness of 2.1 μm can be directly obtained on the positive electrode current collector.

[0063]

Example 5

[0064] Ferrous sulfide (Fe / S = 1:1) was used as the target material for magnetron sputtering, and carbon-coated aluminum foil was selected as the positive electrode current collector. After installing the target material and the positive electrode current collector, the sputtering chamber was closed and evacuated to a vacuum of 1.0 × 10⁻⁶. -4 Below Pa, a nitrogen-argon mixture (N2:Ar = 100 sccm: 10 sccm) is introduced as the nitrogen source and working gas; with the sputtering power set to 120 W, the substrate temperature to 200 °C, and the sputtering time to 10 h, an amorphous iron sulfide film with a thickness of 1.9 μm can be directly obtained on the positive electrode current collector.

[0065]

Example 6

[0066] Ferrous sulfide (Fe / S = 1:1) was used as the target material for magnetron sputtering, and carbon-coated aluminum foil was selected as the positive electrode current collector. After installing the target material and the positive electrode current collector, the sputtering chamber was closed and evacuated to a vacuum of 1.0 × 10⁻⁶. -4 When the pressure is below Pa, nitrogen gas is introduced as both the nitrogen source and the working gas. With a sputtering power of 120W, a substrate temperature of 300℃, and a sputtering time of 1h, an amorphous iron sulfide film with a thickness of 200nm can be directly obtained on the positive electrode current collector.

[0067] Comparative Example 1

[0068] A ferrous sulfide target (Fe / S = 1:1) was used as the magnetron sputtering target, and a stainless steel sheet was selected as the positive current collector. After installing the target and positive current collector, the sputtering chamber was closed and evacuated to a vacuum of 1.0 × 10⁻⁶. -4 When the pressure is below Pa, argon is introduced as the working gas; with the sputtering power set to 120W, the substrate temperature to 25℃, and the sputtering time to 1h, an amorphous ferrous sulfide film with a thickness of 600nm can be directly obtained on the positive electrode current collector.

[0069] Comparative Example 2

[0070] A ferrous sulfide target (Fe / S = 1:1) was used as the magnetron sputtering target, and a stainless steel sheet was selected as the positive current collector. After installing the target and positive current collector, the sputtering chamber was closed and evacuated to a vacuum of 1.0 × 10⁻⁶. -4 When the pressure is below Pa, argon is introduced as the working gas; with the sputtering power set to 120W, the substrate temperature to 350℃, and the sputtering time to 1h, a crystalline ferrous sulfide film with a thickness of 460nm can be directly obtained on the positive electrode current collector.

[0071] Comparative Example 3

[0072] A LiCoO2 target was used as the magnetron sputtering target, and a platinum sheet was selected as the positive current collector. After installing the target and positive current collector, the sputtering chamber was closed and evacuated to a vacuum of 1.0 × 10⁻⁶. -4 When the pressure is below Pa, argon is introduced as the working gas; with the sputtering power set to 100W, the substrate temperature to 300℃, and the sputtering time to 6h, an amorphous LiCoO2 film with a thickness of 1μm can be directly obtained on the positive electrode current collector.

[0073]

test

[0074] TEM, Raman and XRD

[0075] Figure 1 This is a TEM image of the amorphous iron nitride thin film cathode material obtained in Example 1. As can be seen from the image, no diffraction spots appear on the diffraction ring, but rather a halo of diffuse reflection appears, indicating that the sample is amorphous.

[0076] From Mapping data ( Figures 2a-2d It can be seen that the four elements Fe, O, S and N are uniformly distributed in the thin film of Example 1. The presence of O is because a certain amount of O will inevitably be mixed in during the preparation of the sample. O is a conventional element. Therefore, it can be seen that the present invention has successfully prepared an amorphous iron nitride thin film cathode material.

[0077] Figure 3 This is a TEM image of the amorphous ferrous sulfide film obtained in Comparative Example 1. As can be seen from the image, the sample still exhibits an amorphous phase, but... Figure 3 The diffraction halo is more blurred and the diffuse reflection halo is more obvious, indicating that the crystallinity of the sample in Comparative Example 1 is higher than that of the amorphous iron nitride film in Example 1.

[0078] Figure 4 These are Raman images of the amorphous ferrous sulfide films in Example 1 and Comparative Example 1. As can be seen from the images, the main component of the amorphous ferrous sulfide films is still ferrous sulfide.

[0079] Figure 5 The images show the XRD patterns of the ferrous sulfide films in Example 1 and Comparative Example 2. It can be seen that the FeS film in Comparative Example 2 is crystalline, while the amorphous ferrous sulfide film obtained in Example 1 is amorphous.

[0080] Electrochemical testing

[0081] The testing method is as follows: the material is cut into electrode sheets of a certain size, and the electrode sheets are used as working electrodes, lithium sheets as counter electrodes, and 1M LiPF6 dissolved in ethyl carbonate (EC) and diethyl carbonate (DEC) (volume ratio of 1:1) as electrolyte to prepare a button battery to test the electrochemical performance of the material.

[0082] The test voltage range is 1-3V, and the current density at 1C is 1000mAg. -1 .

[0083] The samples obtained in Examples 1-3 and Comparative Examples 1-3 were subjected to electrochemical testing

[0084] from Figure 6 It can be seen that the nitrided modified amorphous ferrous sulfide thin film cathode in Example 1 exhibits good performance at room temperature and 1C (1C = 1000 mAg). -1 Under the charge and discharge current of ), the test voltage range is 1-3V, the cycle stable capacity is as high as 415mAh / g, and it can still maintain 80% of the initial capacity after 1000 cycles, showing good cycle life.

[0085] Figure 7The graph shows a comparison of the cycling performance of the samples in Example 1 and Comparative Example 1. It can be observed that after 300 cycles, Example 1 still maintains a capacity of 300 mAh g / L. -1 The specific capacity of the amorphous iron nitride thin film cathode material of the present invention is significantly superior to that of the sample in Comparative Example 1, while the capacity of Comparative Example 1 begins to decay sharply after 50 cycles. Therefore, the performance of the amorphous iron nitride thin film cathode material of the present invention has a huge advantage over that of the sample in Comparative Example 1.

[0086] Pure amorphous ferrous sulfide cathode materials, due to their inherent vacancy defects, can to some extent suppress the massive volume expansion caused by ion intercalation, including limiting the coarsening of elemental iron during the conversion reaction. However, this effect is limited, and in liquid lithium-ion battery cycling, pure ferrous sulfide materials, including amorphous ferrous sulfide materials, cannot avoid the shuttle effect of polysulfides in the liquid electrolyte. This shuttle effect causes continuous loss of active material into the electrolyte, thus affecting the battery's capacity and cycle life.

[0087] Based on the above results, amorphous iron sulfide nitrogen film, as a lithium-ion cathode material, can not only work normally, but also has a maximum capacity of 415 mAh / g and excellent electrochemical performance, with a significantly improved cycle life. This is because amorphous iron sulfide nitrogen film overcomes the shuttle effect of polysulfides.

[0088] The crystalline ferrous sulfide positive electrode in Comparative Example 2 was tested

[0089] from Figure 8 It can be seen that the cycle performance of this material is drastically reduced compared with that of Example 1. This is because the substrate temperature is increased to 350°C. Combined with XRD, it can be seen that the crystallinity of this material is increased, which will lead to problems such as volume expansion and thin film pulverization caused by the large strain energy of the crystalline cathode material, thus affecting the cycle performance of the battery.

[0090] The amorphous LiCoO2 thin film positive electrode in Comparative Example 3 was tested

[0091] The material obtained in Comparative Example 3 was used as the working electrode to prepare a button cell to test the electrochemical performance of the material. The test voltage range was 3-4.2V, and the current density at 1C was 140mA / g.

[0092] The results are as follows: The low-crystallinity LiCoO2 film can only cycle for 15 times at a current density of 1C, exhibiting very poor cycling performance. Moreover, the specific capacity of the low-crystallinity LiCoO2 film is lower than that of the amorphous iron nitride film.

[0093] Therefore, compared with the traditional cathode thin film material LiCoO2, amorphous iron sulfide films have more outstanding specific capacity, better cycle performance and lower preparation temperature.

[0094] As can be seen from the above, the present invention has successfully prepared an amorphous iron nitrogen sulfide thin film cathode material, which can be used in thin film lithium batteries or micro lithium batteries. It can avoid the volume expansion caused by lattice distortion of crystalline materials, and effectively suppress the shuttle effect of polysulfides generated by ferrous sulfide materials during cycling, thereby improving the battery capacity and cycle life.

[0095] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. An amorphous iron nitrogen sulfide thin film cathode material, characterized in that: The cathode material includes iron sulfide nitrogen, which is amorphous, and the atomic ratio of iron, sulfur and nitrogen in the iron sulfide nitrogen is 1:(0.3-0.6):(0.3-0.6). The amorphous iron nitrogen sulfide has a network structure formed by Fe-N bonds and Fe-S bonds, which enhances its ability to alleviate the volume expansion of ferrous sulfide. In addition, a stable SEI film is gradually formed on the electrode surface during cycling, which effectively suppresses the shuttle effect of polysulfides generated during cycling in the electrolyte and avoids the continuous loss of active materials into the electrolyte.

2. A method for preparing the amorphous iron nitrogen sulfide thin film cathode material as described in claim 1, characterized in that, Includes the following steps: With FeS x The target, used as the target material for magnetron sputtering, is equipped with FeS. x After the target material and positive electrode current collector are prepared, the sputtering chamber is closed, the sputtering chamber is evacuated, and a nitrogen source is introduced. After setting the sputtering power, substrate temperature, and sputtering time, sputtering is started, and amorphous iron nitride thin film positive electrode material can be obtained on the positive electrode current collector. Among them, FeS x In this context, x represents the atomic ratio, with a value of 0.7 ≤ x ≤ 1.4; the substrate temperature is 15 ℃-300 ℃.

3. The method for preparing the amorphous iron nitride thin film cathode material according to claim 2, characterized in that, The nitrogen source is nitrogen gas or a nitrogen-argon mixture.

4. The method for preparing the amorphous iron nitride thin film cathode material according to claim 3, characterized in that, When the nitrogen source is a nitrogen-argon mixture, the flow rate ratio of nitrogen to argon is (1-10):

1.

5. The method for preparing the amorphous iron nitride thin film cathode material according to claim 2, characterized in that, The sputtering chamber was evacuated to a pressure ≤1.0×10⁻⁶. -4 Pa, magnetron sputtering power of 50-120 W, sputtering temperature of room temperature to 300℃, sputtering time of 0.5-24 h.

6. The method for preparing the amorphous iron nitride thin film cathode material according to claim 2, characterized in that, The positive electrode current collector film is one of the following: glass sheet, polyimide, alumina sheet, paper, stainless steel, silicon wafer, and metal foil coated with a conductive current collector layer.

7. A thin-film lithium battery, characterized in that, The positive electrode material of the thin-film lithium battery is the amorphous iron nitride thin-film positive electrode material as described in claim 1.

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