Self-supporting composite air electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of electrode materials, in particular to a self-supporting composite air electrode material and a preparation method and application thereof. The preparation method of the self-supporting composite air electrode material comprises the following steps: clamping a conductive porous material between two porous nickel metal sheets, and pressing to form an integrated blank; taking the integrated green body as a working electrode, forming a three-electrode system, performing electric activation in an alkaline electrolyte solution, driving the surface of the porous nickel metal to generate an oxidation-reduction reaction, and enabling an active layer containing the metal element to grow on the surface of the porous nickel metal in situ; or assembling the integrated green body and a zinc sheet into a zinc air battery, and carrying out charge-discharge activation. The electrode material has high structural stability, excellent catalytic activity and efficient charge transfer capability, has lower overpotential than pressed three-layer foamed nickel, and improves the performance of the metal-air battery.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and in particular to a self-supporting composite air electrode material, its preparation method, and its application. Background Technology

[0002] Metal-air batteries have shown broad application prospects in energy storage systems and electric vehicles due to their advantages such as good safety and low cost. Their core performance lies in the air electrode, which typically consists of a conductive porous current collector, a catalytic active layer, and a gas diffusion layer.

[0003] Nickel foam, due to its three-dimensional porous structure and good conductivity, is often used as the air electrode substrate material in metal-air batteries such as zinc-air batteries. However, when using nickel foam as an air electrode, its inherent defects severely restrict the overall performance and cycle life of the battery: low catalytic activity, with weak catalytic ability for oxygen reduction (ORR), resulting in low discharge voltage, high polarization, and poor power performance; poor structural stability, with a soft framework that is prone to collapse and damage during long-term cycling, leading to conductive network destruction, increased internal resistance, and rapid capacity decay; weak interfacial bonding and high impedance, making it easy for the supported catalyst to detach, and the high interfacial contact resistance within the electrode hinders efficient charge transport. In summary, the existing technology of using monolayer nickel foam as an air electrode has inherent defects such as low intrinsic catalytic activity, poor structural stability, and weak interfacial bonding, which severely restrict the overall electrochemical performance and cycle life of metal-air batteries. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned shortcomings of the prior art by proposing a self-supporting composite air electrode material, its preparation method, and its application.

[0005] The first objective of this invention is to provide a method for preparing a self-supporting composite air electrode material, comprising the following steps: Conductive porous material is sandwiched between two porous nickel metal sheets and pressed to form an integral blank; Using the integrated preform as the working electrode, a three-electrode system is formed and electro-activated in an alkaline electrolyte solution to drive the oxidation-reduction reaction on the porous nickel metal surface, thereby causing an active layer containing the metal element to grow in situ on the surface of the porous nickel metal sheet. Alternatively, an integrated blank can be assembled with zinc sheets to form a zinc-air battery, which can then be activated by charging and discharging.

[0006] Furthermore, the porous nickel metal sheet is one of nickel foam, nickel microfiber felt, or nickel-copper nanowire felt.

[0007] Furthermore, the conductive porous material is one of stainless steel mesh or porous stainless steel sheet.

[0008] Furthermore, the conductive porous material is washed using acetone, hydrochloric acid, and anhydrous ethanol.

[0009] Furthermore, the pressing process involves placing the rollers in a double-roll mill and applying a pressure of 15-30 MPa, maintaining the pressure for 10-60 seconds.

[0010] Furthermore, the alkaline electrolyte solution includes one of potassium hydroxide, sodium hydroxide, and lithium hydroxide electrolyte solutions; the concentration of the electrolyte in the electrolyte solution is 2-10 mol / L.

[0011] Furthermore, electroactivation involves applying an activation potential range of 0.2-1.8V, a scan rate of 40-50 mV / s, and activation for at least 2 hours.

[0012] Furthermore, at 50 mA / cm 2 Activation is completed by charging and discharging.

[0013] A second objective of this invention is to provide a self-supporting composite air electrode material, which is obtained using the preparation method described above.

[0014] A third objective of this invention is to provide an application of the self-supporting composite air electrode material as described above for use as an air electrode in a metal-air battery.

[0015] The electrode material of this invention consists of two layers of porous nickel metal with a rigid conductive network sandwiched in between. The porous nickel metal serves as both a three-dimensional porous conductive substrate and a nickel precursor in the activation process. The intermediate layer provides mechanical support and suppresses the rise in charging voltage. Simultaneously, this composite framework generates highly active catalytic substances on its surface through in-situ electrochemical activation. These substances are composed of nanoparticles and short rod-shaped primary units, possessing a richer pore and interconnected pore network, effectively increasing the number and utilization of active sites. This results in an integrated self-supporting sandwich electrode with high structural stability, excellent catalytic activity, and efficient charge transport capabilities. Compared to pressed three-layer foamed nickel, it has a lower overpotential, thus improving the performance of metal-air batteries.

[0016] The electrode material prepared according to this invention was tested as an air electrode in a zinc-air battery at 50 mA / cm. 2 It can operate stably for 280 hours at a current density with an energy efficiency of 47.38%; in contrast, the performance of the pressed three-layer foamed nickel begins to decline rapidly after only 80 hours of operation, with the energy efficiency decreasing from 30.03% to 21.99%. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the self-supporting composite air electrode and the zinc-air battery assembled therefrom in Example 1; Figure 2TEM image of dehydrogenated nickel hydroxyl oxide generated after activation of the nickel foam prepared in Example 1; Figure 3 LSV curve of NF / SS of the self-supporting composite air electrode prepared in Example 1; Figure 4 LSV curve of NF / SS for the self-supporting composite air electrode prepared in Example 2; Figure 5 The LSV curve of the self-supporting composite air electrode NF / SS prepared in Example 3; Figure 6 The LSV curve of the self-supporting composite air electrode NF / SS prepared in Example 4; Figure 7 The zinc-air battery assembled from the self-supporting composite air electrode NF / SS prepared in Example 5 and the monolayer foamed nickel air electrode NF prepared in Comparative Example 1 achieved a speed of 50 mA / cm². 2 The long-cycle stability plot below.

[0018] Figure 8 The zinc-air battery assembled from the self-supporting composite air electrode NF / SS prepared in Example 5 and the monolayer foamed nickel air electrode NF prepared in Comparative Example 1 achieved a speed of 20 mA / cm². 2 The long-cycle stability plot below. Detailed Implementation

[0019] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0020] A method for preparing a self-supporting composite air electrode material includes the following steps: Pretreatment: Commercially available nickel foam was used as the current collector for pretreatment, which involved degreasing, water washing, acid washing, and then cleaning with ethanol and water. Specifically, the nickel foam was immersed in acetone solution at 25°C for 20 minutes, rinsed three times with deionized water, ultrasonically acid-washed with 20%-30% hydrochloric acid for 20 minutes, and finally ultrasonically washed with anhydrous ethanol for 20 minutes. It was then dried in a vacuum oven at 40°C-60°C or by blowing with nitrogen. Two pieces (1.5×5cm) were then cut. 2 The same sheet material is used as the upper and lower electrode layers, and a piece of stainless steel mesh of the same size is cut as the middle layer.

[0021] Pressing: Lay the stainless steel mesh flat between two pieces of nickel foam, place it in a roller press and apply a pressure of 15-30 MPa, maintain the pressure for 10-60 seconds, and roll to form an integral blank; Electrochemical activation: The obtained integrated preform is used as the working electrode and activated for 2 hours in a 2-10 mol / L KOH electrolyte solution at an activation potential range of 0.2-1.8 V (vs. RHE); or the integrated preform is assembled with a zinc sheet into a zinc-air battery, and activated at 50 mA / cm². 2 The electrode was obtained by completing the activation process through charge and discharge. The electrode was named NF / SS.

[0022] Example 1 A method for preparing a self-supporting composite air electrode material includes the following steps: (1) Cleaning of nickel foam: Cut the nickel foam into pieces of 1.5×5cm. 2 Soak in acetone and sonicate for 20 minutes; remove and rinse several times with water, then soak in 20% HCl and sonicate for 20 minutes; rinse several times with water; finally soak in anhydrous ethanol and sonicate for 20 minutes, then dry in a vacuum oven at 40°C.

[0023] (2) Pressing: Stack the nickel foam, stainless steel mesh and nickel foam in the order of “foam nickel-stainless steel mesh-foam nickel”, place them in a roller press and apply 25 MPa pressure for 30 seconds; continue to apply 20 MPa pressure for 30 seconds; apply 15 MPa pressure for 30 seconds. These three roller presses will eventually form a dense and integrated blank. (3) Electrochemical activation: The integrated preform was used as the working electrode, the carbon rod as the counter electrode, and the Hg / HgO (1 M KOH) electrode as the reference electrode, forming a three-electrode system. The NF / SS electrode was prepared by applying a potential range of 0.2-1.8 V (vs. RHE) in a 2 mol / L potassium hydroxide (KOH) electrolyte solution at a scan rate of 50 mV / s for 2 h.

[0024] Example 2 A method for preparing a self-supporting composite air electrode material includes the following steps: (1) Cleaning of nickel foam: Cut the nickel foam into pieces of 1.5×5cm. 2 Soak in acetone and sonicate for 20 minutes; remove and rinse several times with water, then soak in 20% HCl and sonicate for 20 minutes; rinse several times with water; finally soak in anhydrous ethanol and sonicate for 20 minutes, then dry in a vacuum oven at 40°C.

[0025] (2) Pressing: Stack the nickel foam, stainless steel mesh and nickel foam in the order of “foam nickel-stainless steel mesh-foam nickel”, place them in a roller press and apply 25 MPa pressure for 30 seconds; continue to apply 20 MPa pressure for 30 seconds; apply 15 MPa pressure for 30 seconds. These three roller presses will eventually form a dense and integrated blank. (3) Electrochemical activation: The integrated preform was used as the working electrode, the carbon rod as the counter electrode, and the Hg / HgO (1 M KOH) electrode as the reference electrode, forming a three-electrode system. The NF / SS electrode was prepared by applying a potential range of 0.2-1.8 V (vs. RHE) in a 6 mol / L potassium hydroxide (KOH) electrolyte solution at a scan rate of 50 mV / s for 2 h of activation.

[0026] Example 3 A method for preparing a self-supporting composite air electrode material includes the following steps: (1) Cleaning of nickel foam: Cut the nickel foam into pieces of 1.5×5cm. 2 Soak in acetone and sonicate for 20 minutes; remove and rinse several times with water, then soak in 20% HCl and sonicate for 20 minutes; rinse several times with water; finally soak in anhydrous ethanol and sonicate for 20 minutes, then dry in a vacuum oven at 40°C.

[0027] (2) Pressing: Stack the nickel foam, stainless steel mesh and nickel foam in the order of “foam nickel-stainless steel mesh-foam nickel”, place them in a roller press and apply 25 MPa pressure for 30 seconds; continue to apply 20 MPa pressure for 30 seconds; apply 15 MPa pressure for 30 seconds. These three roller presses will eventually form a dense and integrated blank. (3) Electrochemical activation: The integrated preform was used as the working electrode, the carbon rod as the counter electrode, and the Hg / HgO (1 M KOH) electrode as the reference electrode, forming a three-electrode system. The NF / SS electrode was prepared by applying a potential range of 0.2-1.8 V (vs. RHE) in a 6 mol / L sodium hydroxide (NaOH) electrolyte solution at a scan rate of 50 mV / s for 2 h of activation.

[0028] Example 4 A method for preparing a self-supporting composite air electrode material includes the following steps: (1) Cleaning of nickel microfiber felt: Cut the nickel microfiber felt into 1.5×5cm pieces. 2 Soak in acetone and sonicate for 20 minutes; remove and rinse several times with water, then soak in 20% HCl and sonicate for 20 minutes; rinse several times with water; finally soak in anhydrous ethanol and sonicate for 20 minutes, then dry in a vacuum oven at 40°C.

[0029] (2) Pressing: Stack the nickel microfiber felt, stainless steel mesh and nickel microfiber felt in the order of “nickel microfiber felt”, place them in a roller press and apply 25 MPa pressure for 30 seconds; continue to apply 20 MPa pressure for 30 seconds; apply 15 MPa pressure for 30 seconds. These three pressing processes will eventually form a dense and integrated blank. (3) Electrochemical activation: The integrated preform was used as the working electrode, the carbon rod as the counter electrode, and the Hg / HgO (1 M KOH) electrode as the reference electrode, forming a three-electrode system. The NF / SS electrode was prepared by applying a potential range of 0.2-1.8 V (vs. RHE) in a 6 mol / L potassium hydroxide (KOH) electrolyte solution at a scan rate of 50 mV / s for 2 h.

[0030] Example 5 A method for preparing a self-supporting composite air electrode material includes the following steps: (1) Cleaning of nickel foam: Cut the nickel foam into pieces of 1.5×5cm. 2 Soak in acetone and sonicate for 20 minutes; remove and rinse several times with water, then soak in 20% HCl and sonicate for 20 minutes; rinse several times with water; finally soak in anhydrous ethanol and sonicate for 20 minutes, then dry in a vacuum oven at 40°C.

[0031] (2) Pressing: Stack the nickel foam, stainless steel mesh and nickel foam in the order of “foam nickel-stainless steel mesh-foam nickel”, place them in a roller press and apply 25 MPa pressure for 30 seconds; continue to apply 20 MPa pressure for 30 seconds; apply 15 MPa pressure for 30 seconds. These three roller presses will eventually form a dense and integrated blank. (3) Electrochemical activation: The integrated preform and zinc sheet are assembled into a liquid zinc-air battery using potassium hydroxide (6 mol / L concentration) containing 0.2 mol / L zinc acetate additive as the electrolyte, at 50 mA / cm². 2 The electrode NF / SS was obtained by completing the activation process through charge and discharge.

[0032] Comparative Example 1 A method for preparing a pressed three-layer nickel foam air electrode includes the following steps: (1) Cleaning of nickel foam: Cut the nickel foam into pieces of 1.5×5cm. 2 Soak in acetone and sonicate for 20 minutes; remove and rinse several times with water, then soak in 20% HCl and sonicate for 20 minutes; rinse several times with water; finally soak in anhydrous ethanol and sonicate for 20 minutes, then dry in a vacuum oven at 40°C.

[0033] (2) Pressing: Three layers of foamed nickel are stacked and placed in a roller mill. A pressure of 25 MPa is applied and the pressure is maintained for 30 seconds. Then, a pressure of 20 MPa is applied and the pressure is maintained for 30 seconds. Then, a pressure of 15 MPa is applied and the pressure is maintained for 30 seconds. These three pressing processes eventually form a dense and integrated blank. (3) Electrochemical activation: The integrated preform and zinc sheet are assembled into a liquid zinc-air battery using potassium hydroxide (6 mol / L concentration) containing 0.2 mol / L zinc acetate additive as the electrolyte, at 50 mA / cm². 2 The electrode NF was obtained by completing the activation process through charge and discharge.

[0034] Figure 1 This is a schematic diagram of the self-supporting composite air electrode and the assembled zinc-air battery of Example 1. The diagram clearly shows a flow zinc-air battery using a composite air electrode as the positive electrode and a zinc sheet as the negative electrode, employing potassium hydroxide (6 mol / L concentration) containing 0.2 mol / L zinc acetate additive as the electrolyte solution.

[0035] Figure 2 This is a TEM image of dehydrogenated nickel hydroxyl oxide generated after activation of the nickel foam prepared in Example 1. Figure 2 As shown, the dehydrogenated nickel oxide produced after activation treatment of nickel foam exhibits a typical nanostructure morphology. The material is mainly composed of nanoparticles and short rod-shaped primary units. These primary units further aggregate through surface interactions to form multi-level assemblies, resembling fluffy flower clusters or sea urchin-like secondary aggregates. Abundant mesopores or gaps are visible inside the aggregates, with a loose and open structure, exhibiting high porosity and specific surface area characteristics. This morphological feature is conducive to exposing abundant active surfaces and providing channels for mass transfer processes, consistent with the typical structural characteristics of highly active nanomaterials.

[0036] Figure 3 The LSV curves for the self-supported composite air electrode NF / SS prepared in Example 1 are shown. The results demonstrate that the self-supported composite air electrode, after activation under 2 mol KOH conditions, exhibits a lower overpotential at the same current density. This improvement can be attributed to the surface reconstruction of the material during activation, which forms highly active (oxy)hydroxide species and increases the electrochemically active area. Specifically, before activation (red line), approximately 1.52 V is required to reach 10 mA / cm². After activation (black line), approximately 1.45 V - 1.46 V is required to reach 10 mA / cm². The overpotential decreases by approximately 60-70 mV, representing a very significant performance improvement and fully demonstrating the effectiveness of this activation strategy.

[0037] Figure 4The LSV curve for the NF / SS of the self-supporting composite air electrode prepared in Example 2; specifically, the curve is for a driving current of 10 mA cm⁻¹. -2 The current density required before activation was approximately 1.50 V, while after activation it was only approximately 1.43 V, a reduction of approximately 70 mV in overpotential. This means that to achieve the same catalytic yield, energy consumption is significantly reduced, resulting in higher efficiency. At the same applied potential, activated nickel foam can generate a much higher current density than before activation. For example, at a potential of 1.60 V (vs. RHE), the current density before activation is approximately 75 mA cm⁻¹. -2 Upon activation, it jumps to approximately 180 mA cm⁻¹ -2 The performance was improved by approximately 1.4 times. This indicates that the reaction rate (i.e., catalytic activity) was significantly accelerated under the same voltage drive. This is attributed to the fact that the nickel foam acts as both a three-dimensional porous conductive substrate and a nickel precursor in the activation process; the activation process induces electrochemical reconstruction on the surface of the nickel foam, generating more highly active nickel (oxy) hydroxide species and increasing the electrochemically active surface area, thereby significantly improving its intrinsic electrocatalytic activity. The intermediate stainless steel layer provides mechanical support and suppresses the rise of charging voltage; at the same time, this composite framework can generate highly active catalytic substances on its surface through in-situ electrochemical activation, effectively increasing the number and utilization of active sites.

[0038] Figure 5 The LSV curve of the NF / SS of the self-supporting composite air electrode prepared in Example 3 is shown; the results demonstrate the effect of electrochemical activation treatment of the self-supporting composite air electrode under 6 mol NaOH conditions. Figure 5 As shown, the LSV curve shifted upwards after activation, indicating a significantly higher current density at the same potential compared to before activation. Specifically, at a potential of 1.60 V (vs. RHE), the current density increased dramatically from approximately 5 mA / cm² before activation to approximately 25 mA / cm², an increase of about 5 times. Simultaneously, the required overpotential decreased by approximately 70 mV to achieve a current density of 10 mA / cm². This demonstrates that the activation treatment effectively enhanced the intrinsic activity and reaction kinetics of the material.

[0039] Figure 6 The LSV curve of the self-supporting composite air electrode NF / SS prepared in Example 4 is shown. The results show that the overpotential required to reach the same current density (e.g., 10 mA / cm²) is significantly reduced (e.g., reduced by about 20 mV) after cyclic activation treatment of the self-supporting composite air electrode made of nickel microfiber felt as metal matrix.

[0040] Figure 7 The zinc-air battery assembled from the self-supporting composite air electrode NF / SS prepared in Example 5 and the monolayer foamed nickel air electrode NF prepared in Comparative Example 1 achieved a speed of 50 mA / cm². 2Long-cycle stability plot at 50 mA / cm 2 The zinc-air battery assembled from the self-supporting composite air electrode NF / SS prepared in Example 5 operated stably for 280 hours at the specified current density, maintaining a stable charge / discharge voltage plateau without significant degradation, and achieving an energy efficiency of 47.38%. The average charging voltage was approximately 1.90 V, significantly lower than the ~2.15 V of NF; simultaneously, its average discharging voltage was approximately 0.92 V, higher than the ~0.52 V of NF. In contrast, the performance of the pressed three-layer nickel foam began to degrade rapidly after 80 hours of operation, with the energy efficiency decreasing from 30.03% to 21.99%. This indicates that the NF / SS material exhibits lower voltage polarization and higher energy efficiency.

[0041] Using the self-supporting composite air electrode NF / SS prepared in Example 5 of this application as a self-supporting air cathode, a zinc sheet as the anode, and potassium hydroxide (6 mol / L concentration) containing 0.2 mol / L zinc acetate additive as the electrolyte, a liquid zinc-air battery was assembled. The test was conducted at 20 mA / cm². 2 Long-term stability at current density.

[0042] And by Figure 8 It can be known that 20mA / cm 2 The zinc-air battery assembled with the self-supporting composite air electrode NF / SS prepared in Example 5 can operate stably for 90 hours under high current density. This proves that the zinc-air battery assembled with NF / SS material can operate stably not only under high current (50 mA / cm²) but also under high current density. 2 It exhibits superior performance at relatively low current densities (20 mA / cm²). 2 It can also maintain durability, further highlighting its application potential as a high-performance, long-life electrode material.

[0043] For any points not covered above, existing technologies shall apply.

[0044] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a self-supporting composite air electrode material, characterized in that, Includes the following steps: Conductive porous material is sandwiched between two porous nickel metal sheets and pressed to form an integral blank; Using the integrated preform as the working electrode, a three-electrode system is formed and electro-activated in an alkaline electrolyte solution to drive the oxidation-reduction reaction on the surface of the porous nickel metal sheet, thereby causing an active layer containing the metal element to grow in situ on the surface of the porous nickel metal sheet. Alternatively, an integrated blank can be assembled with zinc sheets to form a zinc-air battery, which can then be activated by charging and discharging.

2. The preparation method according to claim 1, characterized in that, The porous nickel metal sheet is one of nickel foam, nickel microfiber felt, or nickel-copper nanowire felt.

3. The preparation method according to claim 1, characterized in that, The conductive porous material is one of stainless steel mesh or porous stainless steel sheet.

4. The preparation method according to claim 1, characterized in that, The conductive porous material is washed with acetone, hydrochloric acid and anhydrous ethanol.

5. The preparation method according to claim 1, characterized in that, The pressing process involves placing the rollers in a double roller press and applying a pressure of 15-30 MPa, maintaining the pressure for 10-60 seconds.

6. The preparation method according to claim 1, characterized in that, The alkaline electrolyte solution includes one of potassium hydroxide, sodium hydroxide, and lithium hydroxide electrolyte solutions; In the electrolyte solution, the concentration of the electrolyte is 2-10 mol / L.

7. The preparation method according to claim 1, characterized in that, Electroactivation involves applying an activation potential range of 0.2-1.8V, with a scan rate of 40-50 mV / s, and activation time of not less than 2 hours.

8. The preparation method according to claim 1, characterized in that, At 50mA / cm 2 Activation is completed by charging and discharging.

9. A self-supporting composite air electrode material, characterized in that, It is obtained by the preparation method according to any one of claims 1-7.

10. An application of the self-supporting composite air electrode material as described in claim 9, characterized in that, Air electrode for metal-air batteries.

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