Zn-doped molybdenum nitride film and preparation method and application thereof

Abstract

The invention belongs to the technical field of supercapacitor electrode materials, and particularly relates to a Zn-doped molybdenum nitride film and a preparation method and application thereof. A molybdenum target and zinc palladium are used as target materials, nitrogen is used as reaction gas for magnetron sputtering, an initial Zn-doped molybdenum nitride film is obtained on the surface of a substrate, and the doping amount of the Zn element in the initial Zn-doped molybdenum nitride film is 0.5-11%; and the initial Zn-doped molybdenum nitride thin film is subjected to annealing treatment, the Zn-doped molybdenum nitride thin film is obtained, and the annealing treatment temperature ranges from 100 DEG C to 300 DEG C. The binder-free (Zn-Mo-N) thin film materials with different Zn doping concentrations are prepared through a magnetron sputtering method, and the binder-free (Zn-Mo-N) thin film materials prepared through the method have excellent energy storage performance when serving as a negative electrode material and have wide application prospects in supercapacitors.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor electrode material technology, specifically relating to a Zn-doped molybdenum nitride thin film, its preparation method, and its application. Background Technology

[0002] Supercapacitors, as a novel energy storage device with high power density, rapid charge / discharge capability, and long cycle life, have shown broad application prospects in wearable devices, portable electronic products, and electric vehicles. However, traditional carbon-based electrode materials such as activated carbon and graphene, while possessing good conductivity and cycle stability, are limited by their relatively low energy density. Transition metal oxides, although exhibiting high capacitance, suffer from low conductivity and poor cycle stability, which also restricts their further applications. Therefore, exploring advanced electrode materials that combine high specific capacitance with good structural stability is crucial for realizing high-performance supercapacitors.

[0003] In recent years, transition metal nitrides (TMNs) have gradually become a research hotspot for high-performance supercapacitor electrode materials due to their excellent electrochemical properties, such as CrN, VN, RuN, W₂N, and TiN. TMNs possess metallicity, conductivity, chemical stability, and abundant oxidation state characteristics, enabling rapid and reversible pseudocapacitive reactions at or near the electrode surface. Therefore, they can improve energy density while maintaining excellent power density and cycle stability. Molybdenum nitride (Mo₂N) is particularly noteworthy for its multiple oxidation states (Mo... 2+ ~Mo 6+ Its redox behavior and good electron / ion transport properties give it excellent electrochemical performance in the field of supercapacitors.

[0004] At that time, when molybdenum nitride (Mo2N) was used as the negative electrode material for supercapacitors, its energy storage performance was still relatively poor. Summary of the Invention

[0005] The purpose of this invention is to provide a Zn-doped molybdenum nitride thin film, its preparation method, and its application. The Zn-doped molybdenum nitride thin film provided by this invention, as a binder-free (Zn-Mo-N) thin film electrode, exhibits excellent energy storage performance in supercapacitors and has broad application prospects in supercapacitors.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing Zn-doped molybdenum nitride thin films, comprising the following steps: Using molybdenum and zinc-palladium targets as targets and nitrogen as the reactive gas, magnetron sputtering was performed to obtain an initial Zn-doped molybdenum nitride film on the substrate surface. The Zn doping content in the initial Zn-doped molybdenum nitride film was 0.5-11%. The initial Zn-doped molybdenum nitride film is annealed to obtain the Zn-doped molybdenum nitride film. The annealing temperature is 100~300℃.

[0007] Preferably, the power of the zinc palladium is 10~40W.

[0008] Preferably, the power of the zinc palladium is 30±2W; the doping amount of Zn element in the Zn-doped molybdenum nitride film is 8~8.5%.

[0009] Preferably, the purity of the molybdenum palladium is ≥99.95%; the size of the molybdenum palladium is Φ60×3mm; and the power of the molybdenum palladium is 220±10W.

[0010] Preferably, the purity of the zinc-palladium is ≥99.95%; the size of the zinc-palladium is Φ60×3mm; the substrate includes a stainless steel substrate or a silicon substrate; the temperature of the substrate is 300±50℃; and the sputtering pressure of the magnetron sputtering is 0.4±0.1Pa.

[0011] Preferably, the purity of the nitrogen gas is ≥99.999%; the flow rate of the nitrogen gas is 10~30 sccm; the magnetron sputtering also uses a sputtering gas, the sputtering gas is argon gas, the purity of the argon gas is ≥99.999%, and the flow rate of the argon gas is 20~40 sccm.

[0012] Preferably, the annealing temperature is 200~300℃; the annealing holding time is 2~4h.

[0013] The present invention provides a Zn-doped molybdenum nitride thin film prepared by the preparation method described in the above technical solution.

[0014] This invention provides the application of the Zn-doped molybdenum nitride thin film described above as an electrode material in supercapacitors.

[0015] This invention provides an asymmetric supercapacitor device, wherein the negative electrode material includes the Zn-doped molybdenum nitride thin film described in the above technical solution.

[0016] This invention provides a method for preparing Zn-doped molybdenum nitride thin films (i.e., (Zn-Mo-N) thin films), comprising the following steps: using a molybdenum target and a zinc-palladium target as the target material, and nitrogen as the reactant gas for magnetron sputtering to obtain an initial Zn-doped molybdenum nitride thin film on the substrate surface, wherein the Zn doping amount in the initial Zn-doped molybdenum nitride thin film is 0.5~11%; annealing the initial Zn-doped molybdenum nitride thin film to obtain the Zn-doped molybdenum nitride thin film, wherein the annealing temperature is 100~300℃. This invention is the first to use magnetron sputtering to dope Zn into Mo2N thin films, preparing Zn-Mo2N thin films with different Zn doping concentrations. Based on this, the obtained films are subjected to low-temperature annealing at 100℃ to 300℃. This invention systematically studies the influence of the synergistic effect of low-temperature annealing and Zn doping on the microstructure and electrochemical energy storage performance of the thin film. The Zn-doped molybdenum nitride thin film prepared by this invention does not use a binder during the preparation process, and the resulting film product is a binder-free (Zn-Mo-N) thin film. The results of the examples show that an appropriate amount of Zn... 2+ Doping can induce lattice expansion and distortion in Mo2N, broaden ion diffusion channels, and provide more active sites. Annealing further modulates the film density and defect state distribution, effectively suppressing electrolyte corrosion of the substrate and improving cycle stability. Electrochemical test results show that the Zn-Mo-N thin film electrode with 8.23% Zn doping and annealed at 200℃ in the embodiments of this invention exhibits the best energy storage performance at 1 mA·cm⁻¹. -2 The specific capacitance reaches 442.18 F·g at current density. -1 This capacitance is significantly higher than that of currently reported transition metal nitrides, and the capacitance retention remains at 90.24% after 2000 cycles. In summary, this invention prepared binder-free (Zn-Mo-N) thin film materials with different Zn doping concentrations via magnetron sputtering, and systematically investigated the synergistic effect of low-temperature annealing and Zn doping concentration on the crystal structure, microstructure, and electrochemical performance of the Zn-Mo-N thin films. The binder-free (Zn-Mo-N) thin film materials prepared in this invention show broad application prospects as anode materials in supercapacitors. Attached Figure Description

[0017] Figure 1 XRD patterns of Zn-Mo-N thin films prepared under different Zn target sputtering powers; Figure 2 The images show the surface morphology of Zn-Mo-N films obtained with different Zn doping concentrations. Figure 2 The zinc content in (a) is 0, (b) is 0.59%, (c) is 5.54%, (d) is 8.23%, and (e) is 10.88%. Figure 3 Electrochemical properties of thin films obtained with different zinc doping concentrations; Figure 3 In the figure, (a) is the CV curve, (b) is the GCD curve, (c) is the specific capacitance, and (d) is the cycle stability of the film when the zinc content is 8.23%. Figure 4 The electrochemical properties of Zn-Mo-N thin films with a zinc content of 8.23% after annealing at different temperatures are shown. Figure 4 In the diagram, (a) is the CV curve, (b) is the GCD curve, (c) is the cycle stability curve, and (d) is the EIS impedance diagram. Figure 5 This is a Ragone diagram of an asymmetric supercapacitor device. Figure 5 The illustration shows the device successfully lighting up the LED after being charged. Detailed Implementation

[0018] This invention provides a method for preparing Zn-doped molybdenum nitride thin films, comprising the following steps: Using molybdenum and zinc-palladium targets as targets and nitrogen as the reactive gas, magnetron sputtering was performed to obtain an initial Zn-doped molybdenum nitride film on the substrate surface. The Zn doping content in the initial Zn-doped molybdenum nitride film was 0.5-11%. The initial Zn-doped molybdenum nitride film is annealed to obtain the Zn-doped molybdenum nitride film. The annealing temperature is 100~300℃.

[0019] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0020] This invention uses a molybdenum target and a zinc-palladium target as the target material, and nitrogen as the reactant gas for magnetron sputtering to obtain an initial Zn-doped molybdenum nitride thin film on the substrate surface. The Zn doping content in the initial Zn-doped molybdenum nitride thin film is 0.5% to 11%. In this invention, the magnetron sputtering is magnetron co-sputtering, specifically radio frequency reactive magnetron co-sputtering. The magnetron sputtering method used in this invention is a green, high-purity, and highly controllable physical vapor deposition method, suitable for the preparation of the Zn-doped molybdenum nitride thin film provided by this invention. Compared with traditional chemical synthesis methods, this invention uses magnetron sputtering, which eliminates the need for binders or high-temperature heat treatment, and can directly form a dense and uniform thin film on the substrate at a lower temperature, possessing good industrial compatibility and potential for large-scale application.

[0021] In this invention, the purity of the molybdenum-palladium is preferably ≥99.95%. The size of the molybdenum-palladium can be Φ60×3mm. The purity of the zinc-palladium is preferably ≥99.95%. The size of the zinc-palladium can be Φ60×3mm. The purity of the nitrogen gas is preferably ≥99.999%. The magnetron sputtering preferably also uses a sputtering gas, which is preferably argon. The purity of the argon gas is preferably ≥99.999%. In this invention, the substrate preferably includes a stainless steel substrate or a silicon substrate, wherein the stainless steel substrate can be a 304 stainless steel substrate. The silicon substrate can be a Si (100) wafer.

[0022] The present invention preferably pre-treats the substrate, which preferably includes washing and drying the substrate sequentially. The washing preferably includes ultrasonic cleaning with acetone, anhydrous ethanol, and deionized water sequentially; the ultrasonic cleaning time with acetone is preferably 5-10 minutes. The ultrasonic cleaning time with anhydrous ethanol is preferably 5-10 minutes. The ultrasonic cleaning time with deionized water is preferably 5-10 minutes. The present invention preferably removes contaminants from the substrate surface through washing, and the specific implementation of the drying method is not particularly important.

[0023] In this invention, the preferred conditions for magnetron sputtering include: a sputtering pressure of 0.4 ± 0.1 Pa; a nitrogen flow rate of 10–30 sccm, which can be 20 sccm in the embodiment; an argon flow rate of 20–40 sccm, which can be 30 sccm in the embodiment; a substrate temperature of 300 ± 50 °C, which can be 300 °C in the embodiment; a molybdenum-palladium power of 220 ± 10 W, which can be 220 W in the embodiment; and a zinc-palladium power of 10–40 W, more preferably 30 ± 2 W, which can be 5, 10, 15, 20, 25, 30, 35, or 40 W in the embodiment.

[0024] In this invention, the Zn doping amount in the initial Zn-doped molybdenum nitride film is 0.5-11%, preferably 5-11%, more preferably 6-10%, and most preferably 8-8.5%. In the embodiments, it can be 0.59%, 5.54%, 8.23%, or 10.88%. In this invention, the doping amount is the percentage of the mass of Zn element to the total mass of the initial Zn-doped molybdenum nitride film. In this invention, the Zn doping amount is the percentage of the number of Zn atoms in the total number of atoms in the initial Zn-doped molybdenum nitride film. The Zn doping amount in this invention is quantitatively determined based on EDS testing.

[0025] After obtaining the initial Zn-doped molybdenum nitride thin film, the present invention anneals the initial Zn-doped molybdenum nitride thin film to obtain the Zn-doped molybdenum nitride thin film. In the present invention, the annealing temperature is 100~300℃, preferably 200~300℃, and in the embodiments it can be 100, 150, 200, 250 or 300℃. The holding time of the annealing treatment is preferably 2~4h, and in the embodiments it can be 3h.

[0026] The present invention provides a Zn-doped molybdenum nitride thin film prepared by the preparation method described in the above technical solution.

[0027] The Zn doping amount in the Zn-doped molybdenum nitride thin film provided by the present invention is 0.5-11%, preferably 5-11%, more preferably 6-10%, and most preferably 8-8.5%. In the embodiments, it can be 0.59%, 5.54%, 8.23%, or 10.88%.

[0028] This invention employs zinc doping to introduce defect structures into Mo2N, which can significantly improve the electrochemical reaction and structural stability of Mo2N.

[0029] This invention utilizes zinc doping to form a solid solution of zinc in Mo₂N crystals. Simultaneously, because zinc exhibits a +2 valence state, Zn in the crystal... 2+ The radius of OH is greater than that of Mo, therefore, replacing Mo with Zn in the crystal structure can increase the unit cell volume, thereby increasing the OH- ion's ionic radius. - Ions diffuse more easily. This invention adjusts the intrinsic electronic structure of Mo2N by using zinc to dope Zn. 2+ The intrinsic conductivity of Mo2N is improved, and the electrochemical performance of Mo2N is significantly improved.

[0030] This invention provides the application of the Zn-doped molybdenum nitride thin film described above as an electrode material in supercapacitors. In this invention, the Zn-doped molybdenum nitride thin film serves as the negative electrode material of the supercapacitor.

[0031] This invention provides an asymmetric supercapacitor device, wherein the negative electrode material comprises the Zn-doped molybdenum nitride thin film described in the above-mentioned technical solution. In this invention, the positive electrode material of the asymmetric supercapacitor device can be LaSmTMO3 material with a perovskite structure.

[0032] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0033] Example 1 This embodiment uses a JGP-560b magnetron sputtering apparatus manufactured by the Shenyang Scientific Instrument Research Center of the Chinese Academy of Sciences. 304 stainless steel was used as the substrate, and the substrate was ultrasonically cleaned for 10 minutes each with acetone, anhydrous ethanol, and deionized water in an ultrasonic cleaner to remove surface contaminants. High-purity Mo and Zn targets (target purity ≥99.95%, target size Φ60×3mm) were used as sputtering targets. High-purity argon (99.999% purity) and high-purity nitrogen (99.999% purity) were used as sputtering and reactant gases, respectively, with the high-purity argon flow rate set to 30 sccm and the high-purity nitrogen flow rate set to 20 sccm. The substrate temperature was maintained at 300 °C, and the Mo target power was fixed at 220 W under a sputtering pressure of 0.4 Pa. A series of Zn-Mo2N thin films were obtained by varying the sputtering power of the Zn target, with the Zn target sputtering power set to 0 W, 10 W, 20 W, 30 W, and 40 W, respectively. Thin film samples with different Zn contents obtained under different Zn target sputtering power conditions were named "Undoped Mo2N", Z1, Z2, Z3, and Z4, respectively. Subsequently, the Z3 thin film sample was annealed in a nitrogen atmosphere at 100, 200, and 300 °C for 3 hours, and then naturally cooled to room temperature. The effects of Zn doping concentration and annealing temperature on the comparative capacitance and cycle stability were investigated.

[0034] Figure 1 The images show the XRD patterns of Zn-Mo-N thin films prepared under different power conditions in Example 1. Figure 1 No diffraction peaks of the Zn phase were observed, indicating that zinc entered the Mo2N lattice and formed a solid solution. Since zinc is in the +2 valence state, its radius is larger than that of molybdenum ions in the Mo2N lattice. The incorporation of zinc into the Mo2N lattice causes its lattice to expand, thus shifting the diffraction peaks of the Zn-Mo-N film after Zn doping to smaller angles.

[0035] EDS tests showed that when the sputtering power of the Zn target was 10W, 20W, 30W and 40W, the Zn content in the Zn-Mo-N film was 0.59%, 5.54%, 8.23% and 10.88%, respectively.

[0036] Figure 2 The images show the surface morphology of Zn-Mo-N films obtained with different Zn doping amounts prepared in Example 1. Figure 2 (a) in the sample is a sample with a zinc content (i.e., zinc doping) of 0 (“Undoped Mo2N”). Figure 2 (b) in the sample is the one with a zinc content of 0.59% (Z1). Figure 2 (c) Sample (Z2) with a zinc content of 5.54%; Figure 2(d) in the sample is (Z3) with a zinc content of 8.23%; Figure 2 (e) in the sample is Z4, which has a zinc content of 10.88%. From... Figure 2 As can be seen, when the zinc doping content is 8.23%, the surface exhibits spherical particles that are unlinked and independent of each other. This structure has a large specific surface area, and if used as an electrode material for supercapacitors, it may have more active reaction sites and thus greater capacitance performance.

[0037] In this invention, the electrochemical performance of the above-mentioned thin-film electrode was characterized using a three-electrode system in a 1 M KOH electrolyte system, and the results are as follows: Figure 3 As shown. Figure 3 The electrochemical performance of the films obtained with different zinc doping amounts prepared in Example 1 is shown. Figure 3 (a) in the figure is the CV curve. Figure 3 (b) in the figure is the GCD curve. Figure 3 In this context, (c) represents the specific capacitance. Figure 3 In the figure, (d) represents the cycling stability of the film (Z3) when the zinc content is 8.23%.

[0038] from Figure 3 As can be seen, the film with a zinc content of 8.23% exhibits the largest specific capacitance, reaching 534.27 F·g. -1 This value is higher than the 247.36 F·g of undoped Mo2N films. -1 302.28 F·g when zinc content is 0.59% -1 443.76 F·g when zinc content is 5.54% -1 371.70 F·g when zinc content is 10.88% -1 This capacitance value is much higher than that of existing transition metal nitride films.

[0039] But from Figure 3 As can be seen in (d), although the Zn-Mo-N film with a zinc content of 8.23% exhibits excellent electrochemical performance, its performance at a current density of 5 mA·cm⁻¹ is limited. -2 During long-cycle stability testing, the capacitance retention dropped to 86.13% of its original value after 1000 cycles, and then decreased sharply, reaching only 11.38% of its original value after 2000 cycles. This indicates poor cycle stability of the film. The reason for this poor cycle stability is that the film is relatively porous. This structure allows corrosive electrolytes to quickly penetrate the porous film and reach the substrate interface, thereby corroding the interface and leading to film failure.

[0040] This invention involves annealing a Zn-Mo-N thin film with a zinc content of 8.23% at temperatures ranging from 100°C to 300°C. This invention utilizes annealing to make the porous film more compact and to adjust its surface morphology, thereby increasing the cycle stability of the film during electrochemical testing. The electrochemical performance of the annealed film in this invention is as follows: Figure 4 As shown. Figure 4 Electrochemical properties of Zn-Mo-N thin films with a zinc content of 8.23% after annealing at different temperatures. Figure 4 (a) in the figure represents the CV curve; Figure 4 (b) in the figure represents the GCD curve; Figure 4 (c) in the figure represents the cyclic stability curve; Figure 4 (d) in the diagram is the EIS impedance diagram. From Figure 4 The CV and GCD curves show that the capacitance performance of the annealed film is reduced to varying degrees compared to the unannealed film. However, the film with the lowest capacitance performance reduction is observed at an annealing temperature of 200℃, still maintaining 442.18 F·g. -1 The capacitance. However, from Figure 4 As shown in (c), the cycling stability of the film was greatly improved under annealing temperatures of 200℃ and 300℃. At an annealing temperature of 200℃, the film's capacitance remained at 90.42% of its original value after 2000 cycles. This indicates that the cycling stability of the film was significantly improved at an annealing temperature of 200℃. Figure 4 The impedance diagram in (d) also shows that the impedance of the film after annealing at 200℃ is significantly reduced compared to before annealing.

[0041] The above-mentioned thin film and LaSmTMO3 material with perovskite structure were used to assemble an asymmetric supercapacitor device. Figure 5 This is a Ragone diagram of an asymmetric supercapacitor device. (See diagram below.) Figure 5 As shown, at a power density of 462.96 W·Kg -1 At that time, the device had a maximum energy density of 31.37 Wh·Kg. -1 Even at a maximum power density of 2314.81 W·Kg -1 At that time, it was still able to provide 26.04 Wh·Kg. -1 The energy density. This invention uses two all-solid-state LaSmTMO3 / / Zn-Mo2N capacitors connected in series as a power source to light up the LED. Figure 5 The illustration shows the device successfully lighting up a light-emitting diode after charging. The device successfully lit a red LED after charging, with the LED remaining lit for up to 220 seconds. This demonstrates the significant potential of this ASCII device for high-energy storage.

[0042] As can be seen from the above embodiments, the Zn-Mo-N thin film electrode with a Zn doping amount of 8.23% and annealed at 200°C provided by the present invention exhibits the best energy storage performance at 1 mA cm⁻¹. -2 The specific capacitance reaches 442.18 F·g at current density. -1 This capacitance is significantly higher than that of currently reported transition metal nitrides, and the capacitance retention remains at 90.24% after 2000 cycles. In summary, this invention prepared binder-free (Zn-Mo-N) thin film materials with different Zn doping concentrations via magnetron sputtering, and systematically investigated the synergistic effect of low-temperature annealing and Zn doping concentration on the crystal structure, microstructure, and electrochemical performance of the Zn-Mo-N thin films. The binder-free (Zn-Mo-N) thin film materials prepared in this invention show broad application prospects as anode materials in supercapacitors.

[0043] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a Zn-doped molybdenum nitride thin film, characterized in that, Includes the following steps: A molybdenum target and a zinc-palladium target were used as the target materials, and nitrogen was used as the reactive gas for magnetron sputtering to obtain an initial Zn-doped molybdenum nitride film on the substrate surface. The Zn doping content in the initial Zn-doped molybdenum nitride film was 0.5% to 11%. The initial Zn-doped molybdenum nitride film is annealed to obtain the Zn-doped molybdenum nitride film. The annealing temperature is 100~300℃.

2. The preparation method according to claim 1, characterized in that, The power of the zinc palladium is 10~40W.

3. The preparation method according to claim 1 or 2, characterized in that, The power of the zinc-palladium is 30±2W; the doping amount of Zn element in the Zn-doped molybdenum nitride film is 8~8.5%.

4. The preparation method according to claim 1, characterized in that, The purity of the molybdenum palladium is ≥99.95%; the size of the molybdenum palladium is Φ60×3mm; and the power of the molybdenum palladium is 220±10W.

5. The preparation method according to claim 1, characterized in that, The zinc-palladium has a purity of ≥99.95%; the zinc-palladium has a size of Φ60×3mm; the substrate includes a stainless steel substrate or a silicon substrate; the substrate temperature is 300±50℃; and the magnetron sputtering sputtering pressure is 0.4±0.1Pa.

6. The preparation method according to claim 1 or 5, characterized in that, The purity of the nitrogen gas is ≥99.999%; the flow rate of the nitrogen gas is 10~30 sccm; the magnetron sputtering also uses a sputtering gas, the sputtering gas is argon, the purity of the argon gas is ≥99.999%, and the flow rate of the argon gas is 20~40 sccm.

7. The preparation method according to claim 1, characterized in that, The annealing temperature is 200~300℃; the annealing holding time is 2~4h.

8. The Zn-doped molybdenum nitride thin film prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the Zn-doped molybdenum nitride thin film as an electrode material in supercapacitors according to claim 8.

10. An asymmetric supercapacitor device, characterized in that, The negative electrode material includes the Zn-doped molybdenum nitride thin film as described in claim 8.

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