Positive aluminum foil current collector of lithium-sulfur battery, lithium-sulfur battery and preparation method

Abstract

The invention discloses a lithium-sulfur battery positive electrode aluminum foil current collector, and a positive electrode is composed of an aluminum foil current collector modified by a physical vapor deposition (PVD) technology, a CrN layer deposited on the surface of the aluminum foil current collector, and an active material layer coated on the aluminum foil current collector. A CrN layer is deposited on the surface of an aluminum foil through a physical vapor deposition (PVD) technology, the CrN layer has conductivity and adsorption and catalysis performance on lithium polysulfide (LiPSs), diffusion of the LiPSs is effectively inhibited, and reaction kinetics between sulfur and Li2S is improved. Compared with a traditional current collector, the CrN modified aluminum foil current collector prepared by the method has the advantages that interface electron transport and reaction kinetics are optimized, the electrochemical performance of a battery can be remarkably improved, the process is simple, the cost is low, and an effective solution is provided for development of a high-energy-density lithium-sulfur battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-sulfur batteries, and in particular to a positive electrode aluminum foil current collector for a lithium-sulfur battery and a preparation method thereof, which is particularly suitable for inhibiting the diffusion of polysulfides and improving the cycle performance of lithium-sulfur batteries. Background Art

[0002] With the increasing demand for energy storage devices in electronic devices, lithium-sulfur batteries (LiS) are considered the first choice for the next generation of high-energy-density energy storage systems to replace traditional lithium-ion batteries, with their theoretical energy density of 2600Wh / kg. However, due to the formation of soluble lithium polysulfides (LiPSs) during charge and discharge and the large concentration gradient of LiPSs between the cathode and electrolyte, severe diffusion loss of LiPSs is inevitable, inhibiting long-term cycling stability. In addition, the sluggish reaction kinetics also limit the improvement of the electrochemical performance of the sulfur cathode and hinder the practical application of LiS batteries in modern society.

[0003] Prior art attempts to inhibit the diffusion of LiPSs have involved introducing porous host materials, functional additives, or optimizing the electrolyte interface into the sulfur cathode, as exemplified by the Chinese invention patent application CN119812217A. However, these approaches have failed to effectively address the issues of electron conduction and reaction kinetics at the interface between the current collector and the active material layer.

[0004] Existing aluminum current collectors are susceptible to surface oxidation, forming Al₂O₃, which results in insufficient conductivity and LiPSs adsorption capacity. While studies have attempted to improve performance by modifying aluminum current collectors with graphene or carbon nanotubes, the process is complex and costly. Therefore, a simple and efficient current collector modification technology is urgently needed to improve interfacial properties and enhance the overall performance of lithium-sulfur batteries. Summary of the Invention

[0005] The present invention aims to provide a method for modifying the surface of a current collector by physical vapor deposition (PVD) technology, so as to effectively suppress the shuttle effect of polysulfides and improve the cycle stability, energy density and safety of lithium-sulfur batteries. Traditional modification strategies are mostly focused on optimizing the interface between the active material layer or the cathode-electrolyte, while the present invention focuses on the interface between the current collector and the active material layer, and deposits a CrN film onto an aluminum-silicon current collector by PVD technology to form a CrN-Al composite current collector. This method has the advantages of simple equipment, a wide deposition range, a fast deposition rate, a controllable coating and a strong bonding with the substrate. The good electronic conductivity of the CrN film can ensure the electron transfer between the current collector and the active material, and its adsorption and catalytic properties for lithium polysulfide can effectively suppress the diffusion and loss of polysulfides, thereby improving the electrochemical performance of the battery.

[0006] The technical solution adopted by the present invention is: a positive electrode aluminum foil current collector for a lithium-sulfur battery, comprising an aluminum base layer, a CrN layer and a sulfur-containing active material layer, wherein the CrN layer is modified and prepared by a magnetron sputtering method.

[0007] As a further improvement of the present invention, the sulfur-containing active material layer is composed of a sulfur-carbon composite material, conductive carbon black and polyvinylidene fluoride.

[0008] As a further improvement of the present invention, the sulfur-carbon composite material has a sulfur content of 65 to 75 wt% and is prepared by a dissolution-recrystallization method; the sulfur-carbon composite material, conductive carbon black and polyvinylidene fluoride are mixed in N-methylpyrrolidone in a mass ratio of 8:1:1 to form a uniform suspension.

[0009] As a further improvement of the present invention, the thickness of the CrN layer is nanometer-scale, and CrN nanoparticles are distributed on the surface of the CrN layer. The particle size of the nanoparticles is 50 to 200 nm.

[0010] As a further improvement of the present invention, a method for preparing a positive electrode aluminum foil current collector for a lithium-sulfur battery includes the following steps: S1, performing surface pretreatment on the aluminum current collector: ion bombarding the aluminum foil by argon glow discharge, the bias voltage is -800V, and the treatment time is 4 to 6 minutes; S2, depositing a CrN layer on the surface of the aluminum foil by magnetron sputtering technology: placing the aluminum foil in a vacuum chamber, using a pure Cr target as a sputtering source, and depositing in a mixed atmosphere of argon and nitrogen; the argon to nitrogen flow ratio is 2:1, the working pressure is 0.7-1.0Pa, and the deposition time is 4 to 6 minutes; S3, coating the sulfur-containing active material layer on the surface of the CrN-modified aluminum current collector to obtain a composite positive electrode.

[0011] As a further improvement of the present invention, in step S1, the pressure of the argon gas for ion bombardment is 0.7-1.0 Pa.

[0012] As a further improvement of the present invention, in step S2, the substrate rotation speed in the vacuum chamber is 2.5 to 3.5 rpm, and no external heating is applied during the deposition process. This prevents aluminum from reacting with residual oxygen to form aluminum oxide, which is non-conductive and would hinder electron transport.

[0013] As a further improvement of the present invention, a lithium-sulfur battery includes a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode uses a modified CrN layer aluminum foil current collector as a composite positive electrode.

[0014] As a further improvement of the present invention, the electrolyte comprises 1.0 M lithium bis(trifluoromethylsulfonyl)imide and 2 wt % LiNO 3 , and the solvent is a mixture of 1,3-dioxolane and / or 1,2-dimethoxyethane (DOL / DME).

[0015] As a further improvement of the present invention, a method for preparing a lithium-sulfur battery comprises the following steps: S1, depositing a CrN film on an aluminum foil current collector according to the methods of S1 and S2 in claim 5; S2, applying the sulfur-containing active material suspension in claim 3 on the modified CrN film; S3, drying the modified aluminum foil current collector prepared in S2 in an oven at a temperature of 45 to 60° C. for 12 hours to obtain a composite positive electrode; S4, combining the composite positive electrode, negative electrode, separator and electrolyte to form a battery.

[0016] The present invention has the following beneficial effects: 1) The CrN layer can effectively inhibit the polysulfide shuttle effect, ensuring that more active sulfur participates in the electrochemical reaction, thereby improving the energy density and capacity retention of the battery. CrN has a strong adsorption capacity for polysulfides, which can inhibit their diffusion, while catalyzing the redox reaction of polysulfides and improving the reaction kinetics. 2) The introduction of the CrN layer forms a stable electrode / electrolyte interface, effectively preventing side reactions between the electrode material and the electrolyte, reducing the increase in interfacial impedance, and thus improving the electrochemical performance of the battery. 3) The provision of the CrN layer can also prevent the loss of sulfur positive electrode active materials, reduce the impact of the volume expansion of the electrode material on the battery structure, and further extend the service life of the battery.

[0017] Meanwhile, physical vapor deposition (PVD) technology is a well-established method for preparing functional coatings. Magnetron sputtering offers the advantages of fast deposition rates, uniform film formation, and strong adhesion. Magnetron sputtering requires no complex post-processing, and the deposition time is short (≤10 minutes), making it suitable for large-scale production. By manipulating sputtering parameters (gas ratio, target power, and deposition time), a highly conductive CrN layer rich in active sites is formed on the surface of the aluminum current collector. Compared to traditional aluminum current collectors, the introduction of the CrN layer effectively improves the electron transfer process between the current collector and the sulfur-containing active material layer. It also adsorbs LiPSs generated during charge and discharge, improving the reaction kinetics of the LiPSs and enhancing the electrochemical performance of the sulfur cathode. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the present invention.

[0019] Figure 2 (a) CrN-Al foil; (b) SEM images of Al foil.

[0020] Figure 3 Element distribution diagram of CrN-Al foil.

[0021] Figure 4 This is a comparison chart of the cycle performance of the lithium-sulfur battery of the present invention and conventional lithium-sulfur batteries. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Embodiment, a lithium sulfur battery, the preparation method is as follows:

[0024] (1) Substrate selection: Commercial pure aluminum foil was used as the substrate. The surface was first bombarded with argon plasma at a bias voltage of -800 V for 5 minutes to clean the surface of the aluminum foil and enhance the adhesion of the aluminum foil surface so that a uniform CrN modified layer could be subsequently sputtered.

[0025] (2) Preparation of CrN modified layer: A Cr target with a purity of 99.9% and a target size of 300 mm × 75 mm × 6 mm was used. A DC pulse power supply was used to connect the target. The deposition process was carried out in a mixed atmosphere of argon and nitrogen. The gas flow ratio of argon (Ar) to nitrogen (N2) was 2:1. The bias voltage was -80 V, the working pressure was 0.8 Pa, the deposition time was 5 minutes, and the substrate rotation speed was 3 r / min.

[0026] (3) Preparation of the sulfur-containing active material layer: A sulfur-carbon composite material (YP80 / S, 70 wt% sulfur content), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to form a suspension. The suspension was applied to the modified CrN aluminum foil current collector and dried in an oven at 50°C for 12 h to serve as the positive electrode.

[0027] (4) A lithium-sulfur battery was composed of a composite positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode was a purchased commercial lithium sheet, the electrolyte included 1.0 M lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and 2 wt% LiNO3, the solvent was a mixture of 1,3-dioxolane and 1,2-dimethoxyethane (DOL / DME) in a volume ratio of 1:1, and the separator was a Celgard 2400 polypropylene film.

[0028] Lithium-sulfur batteries using the composite cathode of the present invention were tested. Using a CrN-coated aluminum foil as the current collector, the sulfur cathode achieved discharge capacities of 896.6 mAh / g, 688.9 mAh / g, 583.2 mAh / g, 482.3 mAh / g, and 377.4 mAh / g at current densities of 0.2C, 0.5C, 1.0C, 2.0C, and 3.0C, respectively. After 500 cycles, the capacity retention of the CrN-coated aluminum foil-based sulfur cathode was 72.9%.

[0029] Comparative Example

[0030] A lithium-sulfur battery is prepared as in Example 1, except that untreated commercial pure aluminum foil is directly used as the positive electrode to assemble the battery. The lithium-sulfur battery using commercial aluminum foil as the positive electrode is tested.

[0031] The discharge capacities at current densities of 0.2C, 0.5C, 1.0C, 2.0C, and 3.0C were 785.2 mAh / g, 586.3 mAh / g, 482.7 mAh / g, 385.6 mAh / g, and 298.4 mAh / g, respectively. After 500 cycles, the capacity retention rate was 44.3%.

[0032] The test results of the above examples and comparative examples demonstrate that depositing a CrN coating on the aluminum foil using PVD significantly improves the electrochemical performance of the sulfur cathode. The introduction of the modified CrN coating effectively inhibits the diffusion of lithium polysulfides and enhances the reaction kinetics of the sulfur cathode, thereby increasing the battery's discharge capacity and cycling stability.

[0033] Those skilled in the art should know that the protection scheme of the present invention is not limited to the above-mentioned embodiments, and various arrangements, combinations and transformations can be made on the basis of the above-mentioned embodiments. Without violating the spirit of the present invention, various transformations of the present invention fall within the protection scope of the present invention.

Claims

1. A positive electrode aluminum foil current collector for a lithium-sulfur battery, characterized in that The invention comprises an aluminum base layer, a CrN layer and a sulfur-containing active material layer, wherein the CrN layer is prepared by modifying a magnetron sputtering method.

2. The positive electrode aluminum foil current collector of a lithium-sulfur battery according to claim 1, characterized in that The sulfur-containing active material layer consists of a sulfur-carbon composite material, conductive carbon black and polyvinylidene fluoride.

3. The positive electrode aluminum foil current collector of a lithium-sulfur battery according to claim 2, characterized in that The sulfur-carbon composite material has a sulfur content of 65-75% by weight and is prepared by a dissolution-recrystallization method; the sulfur-carbon composite material, conductive carbon black and polyvinylidene fluoride are mixed in N-methylpyrrolidone at a mass ratio of 8:1:1 to form a uniform suspension.

4. The positive electrode aluminum foil current collector of a lithium-sulfur battery according to claim 1, characterized in that The thickness of the CrN layer is nanometer-scale, and CrN nanoparticles are distributed on the surface of the CrN layer. The particle size of the nanoparticles is 50-200 nm.

5. A method for preparing a positive electrode aluminum foil current collector for a lithium-sulfur battery, comprising the following steps: S1, surface pretreatment of the aluminum current collector: ion bombardment of the aluminum foil by argon glow discharge with a bias voltage of -800 V for 4 to 6 minutes; S2, using magnetron sputtering technology to deposit a CrN layer on the surface of the aluminum foil: the aluminum foil is placed in a vacuum chamber, and a pure Cr target is used as the sputtering source. The deposition is carried out in an argon and nitrogen mixed atmosphere; the argon and nitrogen flow ratio is 2:1, the working pressure is 0.7-1.0 Pa, and the deposition time is 4-6 minutes; S3, coating a sulfur-containing active material layer on the surface of the CrN-modified aluminum current collector to prepare a composite positive electrode.

6. The preparation method according to claim 5, wherein In the step S1, the pressure of the argon gas for ion bombardment is 0.7-1.0 Pa.

7. The preparation method according to claim 5, wherein In step S2, the substrate rotation speed in the vacuum chamber is 2.5-3.5 r / min, and no external heating is applied during the deposition process.

8. A lithium-sulfur battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, characterized in that: The positive electrode uses the aluminum foil current collector according to any one of claims 1 to 4 as a composite positive electrode.

9. A lithium-sulfur battery according to claim 8, characterized in that The electrolyte includes 1.0M lithium bis(trifluoromethylsulfonyl)imide and 2 wt% LiNO3, and the solvent is a mixed solution of 1,3-dioxolane and / or 1,2-dimethoxyethane (DOL / DME); the separator is a Celgard 2400 polypropylene film.

10. A method for preparing a lithium-sulfur battery, comprising the following steps: S1, depositing a CrN film on an aluminum foil current collector according to the method of S1 and S2 in claim 5; S2, coating the modified CrN film with the sulfur-containing active material suspension according to claim 3; S3, drying the modified aluminum foil current collector prepared in S2 in an oven at a temperature of 45-60° C. for 12 hours to obtain a composite positive electrode; S4, a battery is formed by combining a composite positive electrode, a negative electrode, a separator and an electrolyte.

Images