A method for applying a PDMS protective layer to the zinc metal anode of an aqueous zinc-ion battery

Abstract

This invention discloses a method for applying a PDMS protective layer to the zinc metal anode of an aqueous zinc-ion battery. The deposition layer on the zinc metal surface uses polydimethylsiloxane (PDMS), which is vaporized by heating at a certain temperature and then deposited onto the zinc metal surface after cooling. Firstly, the deposited PDMS layer has a desolvation effect, effectively regulating the deposition kinetics of zinc ions. Secondly, the interstitial structure of the surface PDMS deposition layer restricts the zinc ion flow rate and regulates the zinc ion deposition behavior, allowing zinc ions to be uniformly deposited along the (002) crystal plane of the zinc metal. Finally, the construction of the hydrophobic PDMS layer reduces parasitic side reactions at the zinc metal interface, improving battery safety and enhancing the performance of the zinc-ion battery.

Description

Technical Field

[0001] This invention belongs to the field of aqueous zinc-ion batteries, specifically addressing the preparation of the negative electrode protective layer for aqueous zinc-ion batteries. Background Technology

[0002] While the extensive use of fossil fuels has brought some economic growth to the world, it has also led to rising CO2 concentrations and the harmful effects of global warming. Therefore, to address this change, the development of renewable energy sources, such as wind and solar power, is strongly encouraged. However, wind and solar energy are not readily available; they are subject to strict limitations such as geographical location and time constraints. Therefore, large-scale energy storage is necessary to better utilize these resources. Furthermore, modern society has entered the information age, with a surge in electronic and electrical devices, all of which require energy storage. Currently, energy storage batteries are developing rapidly and are well-suited for both storage and power supply. Lithium-ion batteries, in particular, have been commercialized and widely used in devices such as electric vehicles and mobile phones, facilitating daily life. However, the scarcity of lithium resources on Earth keeps their price high, severely limiting their further large-scale use. There have also been reports of electric vehicles catching fire and exploding due to problems with the organic electrolytes used in lithium batteries, posing a serious threat to personal safety. Therefore, researchers have begun to focus their research on safer aqueous lithium-ion batteries. Furthermore, compared to organic electrolytes, aqueous electrolytes exhibit superior ionic conductivity. Zinc metal, due to its relatively abundant reserves on Earth, low and relatively stable price, possesses a high electrode potential (-0.76V vs. standard hydrogen electrode) and a high volumetric energy density (5855 mAh cm⁻¹). -3 Aqueous zinc-ion batteries can achieve three times the efficiency of lithium metal and are environmentally friendly. Therefore, they have a very promising future market. The electrolytes in aqueous zinc-ion batteries typically use weakly acidic or neutral zinc salt electrolytes such as zinc sulfate, zinc trifluoromethanesulfonate, zinc acetate, and zinc chloride. Many positive electrode materials (manganese-based materials, vanadium-based materials, Prussian blue analogs, organic electrode materials, etc.) have been studied for aqueous zinc-ion batteries, and battery performance has improved to some extent. However, short battery life and low coulombic efficiency still exist. This is mainly attributed to the fact that the negative electrode of aqueous zinc-ion batteries uses zinc metal, which is prone to dendrite formation, hydrogen evolution, corrosion, and passivation, severely limiting the commercialization of these batteries. Therefore, we urgently need to develop effective protection for the negative electrode of aqueous zinc-ion batteries.

[0003] To address the problems at the zinc-metal interface, preparing a protective layer on its surface is the most direct and effective strategy. Current strategies for preparing organic coatings mostly involve blade coating or spin coating. For example, Zhang Naiqing's research team (Adv. Mater. 2022, 34, 2105133) publicly utilized PDMS and TiO2. 2-X A mixture of these materials can be spin-coated onto a zinc metal surface to construct an adaptive protective layer, providing some protection. However, this method results in a thick and dense zinc coating, severely limiting zinc ion transport and necessitating improvements in battery cycle life. Furthermore, some coatings use adhesives, which can block active sites on the zinc metal surface, significantly impacting battery capacity. Therefore, we need to improve the strategy for preparing the protective layer to achieve better protection. Summary of the Invention

[0004] The purpose of this invention is to address the problems of zinc dendrites and parasitic side reactions in zinc metal by preparing a deposition layer on the zinc metal surface through a one-step vaporization deposition method. This invention utilizes direct heating of PDMS to vaporize and deposit it onto the zinc metal surface to form a protective layer, thereby suppressing dendrite growth and parasitic side reactions in zinc metal. The thickness of the deposited PDMS layer can be controlled by adjusting the heating temperature and time. Simultaneously, the desolvation effect of the PDMS layer can regulate the deposition kinetics of zinc ions, and the interstitial structure can limit the zinc ion flow rate and regulate the deposition behavior. The hydrophobicity exhibited by the alkyl functional groups abundant in the PDMS layer can block active water molecules, protect the zinc anode, and improve overall battery performance.

[0005] To solve the technical problem of this invention, the proposed technical solution is as follows: a method for forming a PDMS protective layer on the zinc metal anode of an aqueous zinc-ion battery. The method involves preparing the protective layer using polydimethylsiloxane PDMS vapor deposition, wherein the deposited layer on the zinc metal surface is polydimethylsiloxane PDMS with a molecular weight of 15,000-25,000. The PDMS is vaporized by heating at a certain temperature, and after cooling, it is deposited onto the zinc metal surface. The thickness of the deposited layer is adjusted by controlling the heating temperature and heating time to achieve the effect of protecting the zinc anode. The heating temperature is 240-400℃, and the heating time is 1-6 hours.

[0006] Preferably, the deposited PDMS layer has a desolvation effect, which can effectively regulate the deposition kinetics of zinc ions. Secondly, the gap structure of the surface PDMS deposited layer can limit the flow of zinc ions and regulate the deposition behavior of zinc ions, so that zinc ions can be uniformly deposited along the (002) crystal plane of zinc metal. Finally, the construction of the PDMS hydrophobic layer reduces parasitic side reactions at the zinc metal interface, improves the safety of the battery and enhances the performance of zinc-ion batteries.

[0007] Preferably, the aqueous zinc-ion battery electrolyte uses a weakly acidic or neutral zinc salt electrolyte.

[0008] Preferably, the aqueous zinc-ion battery electrolyte uses zinc sulfate, zinc trifluoromethanesulfonate, zinc acetate, or zinc chloride.

[0009] Preferably, the concentration of the electrolyte is 1-3 mol / L. -1 .

[0010] Preferably, PDMS with a molecular weight of 20,000 and zinc metal electrodes cut to a diameter of 12 mm are heated together at 350°C for 2 hours. During the subsequent cooling process, the vaporized PDMS deposits onto the surface of the zinc metal, forming a uniformly distributed PDMS layer. The zinc metal protected by the prepared PDMS layer serves as the two electrodes of an aqueous zinc-ion symmetric battery, with glass fiber used as the battery separator, and 1 mol / L electrolyte. -1 Zinc sulfate solution was used to assemble 2025 button batteries.

[0011] Preferably, PDMS with a molecular weight of 20,000 and zinc metal electrodes cut to a diameter of 12 mm are heated together at 350°C for 2 hours. During the subsequent cooling process, the vaporized PDMS deposits onto the surface of the zinc metal, forming a uniformly distributed PDMS layer. The zinc metal protected by the prepared PDMS layer is used as the negative electrode of an aqueous zinc-ion full cell, with glass fiber used as the separator and 1 mol / L electrolyte. -1 Zinc sulfate solution, the positive electrode of the battery utilizes NH4V4O 10 With a loading capacity of 1mg, assemble 2025 button batteries.

[0012] To address the technical problem of this invention, another technical solution is proposed: a PDMS protective layer for the zinc anode of an aqueous zinc-ion battery, prepared according to any of the above methods.

[0013] The positive electrode material is one of the following: manganese-based material, vanadium-based material, Prussian blue analogue, or organic electrode material.

[0014] Beneficial effects:

[0015] 1. The one-step gasification deposition method of the present invention has simple operation steps, easy control of the thickness of the deposited layer, readily available materials and equipment, and low cost.

[0016] 2. The PDMS layer prepared by this invention has a desolvation effect, which can remove active water molecules around zinc ions and regulate the deposition kinetics of zinc ions.

[0017] 3. The alkyl groups on the PMDS layer prepared by this invention make it hydrophobic, which can form an isolation layer to reduce excessive contact of active water molecules and reduce parasitic side reactions.

[0018] 4. The PDMS layer prepared by the present invention has a gap structure that can limit the flow rate of zinc ions and regulate the deposition behavior of zinc ions to make them deposit uniformly.

[0019] 5. This can be extended to the point that as long as zinc metal is used for the negative electrode, other positive electrode materials can be selected, and the deposited PDMS layer can play a role in protecting the zinc negative electrode.

[0020] 6. Preferred Example 1 is the best embodiment. The symmetric battery assembled using a zinc metal anode protected by a PDMS layer has a cycle life of up to 1000 hours, which is 8.3 times that of a symmetric battery assembled with bare zinc. Due to the desolvation effect of the PDMS layer, the zinc deposition kinetics are modulated and side reactions such as water decomposition are reduced. The aqueous zinc-ion symmetric battery assembled with zinc metal with a PDMS layer has less voltage hysteresis, less significant voltage fluctuation, and good cycle stability and reversibility.

[0021] The full cell assembled with a zinc anode protected by deposited PDMS still exhibited a superior capacity retention of 76.3% after 1000 cycles, while the full cell assembled with bare zinc only retained 23.8% of its capacity. This indicates that the protection of PDMS effectively suppressed side reactions such as dendrite growth and water splitting, improved the overall electrochemical performance of the aqueous zinc-ion full cell, and demonstrated excellent cycle stability and reversibility, making the battery possible for practical long-cycle applications.

[0022] 7. This invention first provides a method for constructing a protective layer on the surface of zinc metal using a one-step vapor deposition method. Compared with commonly used methods such as blade coating and spin coating, the preparation process is simpler and does not require the addition of binders, thus avoiding obstruction of active sites on the zinc metal surface. The thickness of the prepared deposited layer is also easily controlled by deposition time and temperature. The deposited PDDS layer has a desolvation effect, which can regulate the deposition kinetics of zinc ions. Its interstitial structure can also limit the zinc ion flow rate and regulate the deposition behavior of zinc ions to ensure uniform deposition. The alkyl functional groups in the PMDS layer can endow it with hydrophobic properties, reducing parasitic side reactions on the zinc anode surface. This invention provides a simple method for preparing a protective layer, protects the zinc metal anode, and optimizes the electrochemical performance of the battery. Attached Figure Description

[0023] Figure 1 This is a cross-sectional SEM image of the PDMS layer deposited on the zinc metal surface after heating at 350°C for 2 hours in Example 1.

[0024] Figure 2This is a cross-sectional SEM image of the PDMS layer deposited on the zinc metal surface after heating at 240°C for 2 hours in Example 2.

[0025] Figure 3 This is a cross-sectional SEM image of the PDMS layer deposited on the zinc metal surface after heating at 350°C for 6 hours in Example 3.

[0026] Figure 4 This is a graph showing the long-cycle performance test of the aqueous zinc-ion symmetric battery assembled in the embodiment.

[0027] Figure 5 This is a graph showing the long-cycle performance test of the aqueous zinc-ion full cell assembled in the embodiment. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments shown below are merely for clearer illustration of the preparation technology and the performance of the protective layer, and are not limited to the embodiments shown.

[0029] Example 1:

[0030] Preparation of a PDMS vaporization deposition layer:

[0031] PDMS with a molecular weight of 20,000 and zinc metal electrodes with a diameter of 12 mm were heated together at 350°C for 2 hours. Then, as the temperature dropped, the vaporized PDMS was deposited on the surface of the zinc metal to form a uniformly distributed PDMS layer.

[0032] Figure 1 This is a cross-sectional SEM image of the PDMS layer deposited on the zinc metal surface after heating at 350°C for 2 hours in Example 1. The uniform gap structure on the surface can be clearly seen, and the thickness is about 6 μm.

[0033] Assembly and performance testing of symmetrical cells:

[0034] The prepared PDMS-protected zinc metal was used as the two electrodes of an aqueous zinc-ion symmetric battery, with glass fiber as the separator and 1 mol L⁻¹ electrolyte. -1 Zinc sulfate solution was used to assemble 2025 button cells. The PDMS-protected zinc metal was replaced with bare zinc, while other conditions remained unchanged. Testing was conducted using a Newway testing system. Cyclic test conditions were: current density 1 mA cm⁻¹. -2 The surface capacity is 0.5mAh cm. -2 .

[0035] Figure 4 This is a long-cycle performance test of the aqueous zinc-ion symmetric battery assembled in the example. The two electrodes are zinc metal electrodes protected by a deposited PDMS layer, and the electrolyte is 1 mol L⁻¹.-1 The zinc sulfate electrolyte was used. A control test was conducted with the zinc metal electrode protected by the deposited PDMS layer replaced with bare zinc, all other conditions remaining the same.

[0036] Results Analysis: The symmetric cell assembled with a zinc metal anode protected by a PDMS layer exhibits a cycle life of up to 1000 hours, which is 8.3 times that of the symmetric cell assembled with bare zinc. Due to the desolvation effect of the PDMS layer, which modulates the zinc deposition kinetics and reduces side reactions such as water decomposition, the aqueous zinc-ion symmetric cell assembled with the PDMS-deposited zinc metal layer exhibits lower voltage hysteresis, less significant voltage fluctuations, and good cycle stability and reversibility.

[0037] Assembly and performance testing of the full battery:

[0038] The prepared PDMS-protected zinc metal was used as the negative electrode in an aqueous zinc-ion full cell, with glass fiber as the separator and 1 mol / L electrolyte. -1 Zinc sulfate solution, the positive electrode of the battery utilizes NH4V4O 10 A 2025 button cell was assembled with a loading capacity of approximately 1 mg. The PDMS-protected zinc metal was replaced with bare zinc, while other conditions remained unchanged. Testing was conducted using a Newway testing system. Cyclic test conditions were: current density 1 A g. -1 .

[0039] Figure 5 This is a long-cycle performance test of the aqueous zinc-ion full cell assembled in the example. The negative electrode of the full cell is zinc metal protected by a deposited PDMS layer, and the electrolyte is 1 mol / L. -1 The zinc sulfate electrolyte, with NH4V4O as the positive electrode preferred. 10 The material was loaded with approximately 1 mg of zinc. A control test was conducted with the zinc metal anode protected by the deposited PDMS layer replaced with bare zinc, while maintaining the same other conditions.

[0040] Results analysis: The full cell assembled with a zinc anode protected by deposited PDMS still exhibited a superior capacity retention of 76.3% after 1000 cycles, while the full cell assembled with bare zinc only retained 23.8% of its capacity. This indicates that the protection of PDMS effectively suppressed side reactions such as dendrite growth and water decomposition, improved the overall electrochemical performance of the aqueous zinc-ion full cell, and demonstrated excellent cycle stability and reversibility, making the battery possible for practical long-cycle applications.

[0041] Example 2:

[0042] Preparation of a PDMS vaporization deposition layer:

[0043] PDMS with a molecular weight of 20,000 and zinc metal electrodes with a diameter of 12 mm were heated together at 240°C for 2 hours. Then, as the temperature dropped, the vaporized PDMS was deposited on the surface of the zinc metal to form a sparsely distributed PDMS layer.

[0044] Figure 2 This is a cross-sectional SEM image of the PDMS layer deposited on the zinc metal surface after heating at 240°C for 2 hours in Example 2. It can be clearly seen that the surface has a relatively sparse interstitial structure with a thickness of about 4 μm.

[0045] Assembly and performance testing of symmetrical cells:

[0046] The prepared PDMS-protected zinc metal was used as the two electrodes of an aqueous zinc-ion symmetric battery, with glass fiber as the separator and 1 mol L⁻¹ electrolyte. -1 Zinc sulfate solution was used to assemble 2025 button cells. The PDMS-protected zinc metal was replaced with bare zinc, while other conditions remained unchanged. Testing was conducted using a Newway testing system. Cyclic test conditions were: current density 1 mA cm⁻¹. -2 The surface capacity is 0.5mAh cm. -2 .

[0047] Results Analysis: The symmetric cell assembled with a zinc metal anode protected by a PDMS layer exhibits a cycle life of 310 hours, which is 2.6 times that of the symmetric cell assembled with bare zinc. Although the deposited layer is relatively sparse, the PDMS layer still has a desolvation effect and a large gap, which modulates the kinetics and deposition behavior of zinc deposition. The aqueous zinc-ion symmetric cell assembled with the deposited PDMS layer has smaller voltage hysteresis and better cycle stability and reversibility.

[0048] Assembly and performance testing of the full battery:

[0049] The prepared PDMS-protected zinc metal was used as the negative electrode in an aqueous zinc-ion full cell, with glass fiber as the separator and 1 mol / L electrolyte. -1 Zinc sulfate solution, the positive electrode of the battery utilizes NH4V4O 10 A 2025 button cell was assembled with a load of approximately 1 mg. The PDMS-protected zinc metal was replaced with bare zinc, while other conditions remained unchanged. Testing was conducted using a Newway testing system. Cyclic test conditions were: current density 1 Ag. -1 .

[0050] Results analysis: The full cell assembled with zinc anode protected by deposited PDMS retained 58.8% capacity after 1000 cycles, while the full cell assembled with bare zinc retained only 23.8% capacity. This indicates that the protection of PDMS can suppress side reactions such as dendrite formation and water decomposition to a certain extent, thereby improving the capacity retention and cycle stability of aqueous zinc-ion full cells.

[0051] Example 3:

[0052] Preparation of a PDMS vaporization deposition layer:

[0053] PDMS with a molecular weight of 20,000 and zinc metal electrodes with a diameter of 12 mm were heated together at 350°C for 6 hours. Then, as the temperature dropped, the vaporized PDMS was deposited on the surface of the zinc metal to form a relatively thick and dense PDMS layer.

[0054] Figure 3 This is a cross-sectional SEM image of the PDMS layer deposited on the zinc metal surface after heating at 350°C for 6 hours in Example 3. The thick and dense interstitial structure on the surface can be clearly seen, with a thickness of about 30 μm.

[0055] Assembly and performance testing of symmetrical cells:

[0056] The prepared PDMS-protected zinc metal was used as the two electrodes of an aqueous zinc-ion symmetric battery, with glass fiber as the separator and 1 mol L⁻¹ electrolyte. -1 Zinc sulfate solution was used to assemble 2025 button cells. The PDMS-protected zinc metal was replaced with bare zinc, while other conditions remained unchanged. Testing was conducted using a Newway testing system. Cyclic test conditions were: current density 1 mA cm⁻¹. -2 The surface capacity is 0.5mAh cm. -2 .

[0057] Results Analysis: The symmetrical battery assembled with a zinc metal anode protected by a PDMS layer exhibits a cycle life of 720 hours, which is 6.0 times that of the symmetrical battery assembled with bare zinc. Because the PDMS deposition layer is thicker and lacks obvious gap structures, the battery exhibits significant voltage hysteresis during the early cycling stages. However, its hydrophobic effect is more pronounced, effectively suppressing side reactions such as water decomposition. Overall, the symmetrical battery shows minimal voltage fluctuations and demonstrates good cycle stability and reversibility.

[0058] Assembly and performance testing of the full battery:

[0059] The prepared PDMS-protected zinc metal was used as the negative electrode in an aqueous zinc-ion full cell, with glass fiber as the separator and 1 mol / L electrolyte. -1Zinc sulfate solution, the positive electrode of the battery utilizes NH4V4O 10 A 2025 button cell was assembled with a load of approximately 1 mg. The PDMS-protected zinc metal was replaced with bare zinc, while other conditions remained unchanged. Testing was conducted using a Newway testing system. Cyclic test conditions were: current density 1 Ag. -1 .

[0060] Results analysis: The full cell assembled with a zinc anode protected by deposited PDMS retained 52.7% of its capacity after 1000 cycles, while the full cell assembled with bare zinc retained only 23.8% of its capacity. This indicates that the presence of the PDMS layer can protect the anode, reduce side reactions such as hydrogen desorption from water, and improve the capacity retention and cycle stability of the aqueous zinc-ion full cell.

[0061] The above description is merely a preferred embodiment of the present invention, which is readily understood by those skilled in the art. It should be specifically pointed out that any modifications or similar substitutions made on the basis of the principles of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for applying a PDMS protective layer to the zinc metal anode of an aqueous zinc-ion battery, characterized in that: PDMS with a molecular weight of 20,000 and zinc metal electrodes with a diameter of 12 mm were heated together at 350 °C for 2 h. Then, as the temperature dropped, the vaporized PDMS was deposited on the surface of the zinc metal to form a uniformly distributed PDMS layer. The PDMS layer deposited on the zinc metal surface after heating at 350 ℃ for 2 h clearly shows a uniform interstitial structure and a thickness of 6 μm. The prepared PDMS-protected zinc metal was used as the negative electrode in an aqueous zinc-ion full cell, with glass fiber as the separator and 1 mol L⁻¹ electrolyte. -1 Zinc sulfate solution, the positive electrode of the battery utilizes NH4V4O 10 A 2025 button cell was assembled with a loading capacity of 1 mg. The PDMS-protected zinc metal was replaced with bare zinc, and other conditions remained unchanged. The cell was tested using the Xinwei testing system. The cycle test conditions were: current density 1 A g. -1 ; The full cell assembled with a zinc anode protected by deposited PDMS still exhibited a superior capacity retention of 76.3% after 1000 cycles, while the full cell assembled with bare zinc only retained 23.8% of its capacity. This indicates that the protection of PDMS effectively suppressed dendrite growth and water splitting side reactions, improved the overall electrochemical performance of the aqueous zinc-ion full cell, and demonstrated excellent cycle stability and reversibility.

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