A surface layer doped with rare earth elements lead-acid battery grid and its preparation method

Abstract

The application provides a surface layer rare earth element doped lead acid battery grid and a preparation method thereof. The grid forms a doped rare earth element alloy layer-organic / inorganic composite intermediate layer-polymer conductive layer composite structure by introducing an organic / inorganic intermediate layer, can significantly improve the interface bonding force, prevents the conductive polymer layer from peeling off, the conductive particles in the intermediate layer provide additional conductive paths, ensure that the overall conductivity of the grid is not affected, make the doped rare earth element layer and the conductive polymer layer synergistically act, inhibit the attenuation of the conductivity, improve the corrosion resistance of the grid coating, and improve the cycle life.

Description

Technical Field

[0001] This invention belongs to the field of lead-acid batteries, specifically relating to a lead-acid battery grid with surface doped with rare earth elements and its preparation method. Background Technology

[0002] Lead-acid batteries, with their advantages of readily available raw materials, high reliability, good safety, and mature recycling technology, still hold an irreplaceable market share in fields such as automotive starting, communication backup power, energy storage systems, and electric vehicles. The grid, as a key component of lead-acid batteries, plays a crucial role in supporting the active materials, conducting current, and uniformly distributing the electric field. The performance of the grid material directly determines the battery's capacity, rate discharge performance, cycle life, and reliability. However, with emerging fields such as new energy storage and electric vehicles placing higher demands on battery energy density, deep cycle life, and fast charging capabilities, traditional grid materials are gradually revealing their performance bottlenecks, becoming one of the key shortcomings restricting the technological upgrade of lead-acid batteries.

[0003] Currently, lead-acid battery grid alloys widely used in industry are mainly divided into two systems: lead-antimony (Pb-Sb) alloys and lead-calcium (Pb-Ca) alloys. Lead-antimony alloys possess excellent deep-cycle performance and casting properties, but suffer from low hydrogen evolution overpotential and severe water loss, making them unsuitable for maintenance-free batteries. Lead-calcium alloys, due to their good hydrogen evolution suppression characteristics and low self-discharge rate, have become the mainstream grid material for valve-regulated sealed lead-acid batteries (VRLA). However, this system exhibits a significant "antimony-free effect"—the presence of calcium in the alloy leads to the formation of a high-resistance anodic corrosion layer on the grid surface, severely weakening the battery's deep-cycle life. Furthermore, during charge-discharge cycles, selective corrosion easily occurs at grain boundaries in lead-calcium alloys, leading to grain shedding and early grid failure. Studies show that the corrosion rate of the positive electrode grid should be controlled at ≤0.15 mm / year, and the amount of active material shed should be <3%, requirements that traditional lead-calcium alloys struggle to meet long-term.

[0004] To improve the overall performance of grid alloys, researchers have explored various alloying modification strategies. The addition of elements such as tin, silver, and bismuth can refine the grain size and improve the mechanical properties and corrosion resistance of the alloy to some extent. However, the improvement effect of adding a single element is limited, and some elements (such as cadmium) are highly toxic and their use has been gradually restricted. In recent years, rare earth elements have attracted widespread attention from battery material researchers due to their unique physicochemical properties. Rare earth elements (such as lanthanum (La), cerium (Ce), and ytterbium (Yb) have atomic radii close to calcium and similar electronegativity, but their hardness and mechanical properties are superior to calcium, and theoretically, they can form good solid solutions with lead. Studies have shown that the appropriate addition of rare earth elements can significantly refine the grain size of grid alloys, increase the grain boundary area, and effectively reduce the corrosion per unit area at the same current density, thereby improving the corrosion resistance of the alloy. Simultaneously, the addition of rare earth elements can also inhibit the growth of a high-resistivity PbO layer in the anolyte film, reduce interfacial resistance, and improve the deep-cycle performance of the battery. However, existing rare earth modification technologies mainly adopt the overall alloying method of directly melting and adding rare earth elements into lead alloys. This method has problems such as low rare earth utilization, difficulty in accurately controlling the amount added, and poor uniformity of alloy composition. Moreover, different rare earth elements have significant differences in their effects on alloy performance. Some rare earth elements (such as La and Ce) may worsen corrosion resistance due to the increase in grain boundary area while refining grains.

[0005] To address the aforementioned issues, Chinese invention patent CN104409783B discloses a method for rare-earth modified lead-acid battery electrode plates. This method involves adding rare-earth sulfates or oxides to the battery formation solution and then using an electrochemical method to modify the electrode surface with rare earth elements. While this method improves rare-earth utilization, the modification process is coupled with the formation process, resulting in complex process control, and the bonding strength between the modified layer and the substrate needs further verification. Other studies have employed rapid solidification technology to prepare rare-earth lead alloys to improve the supersaturated solid solubility and compositional uniformity of rare-earth elements. However, rapid solidification requires sophisticated equipment, making large-scale continuous production difficult. Therefore, developing a novel grid modification technology that leverages the advantages of rare-earth element modification while achieving precise rare-earth distribution, improving rare-earth utilization, and simplifying the preparation process has significant research value and engineering application prospects. Summary of the Invention

[0006] To overcome the problems existing in the prior art, the present invention aims to provide a lead-acid battery grid with a surface doped with rare earth elements. This grid introduces a rare earth element-doped alloy layer, an organic / inorganic composite intermediate layer, and a polymer conductive layer. The coordination bonding between the carboxyl groups of the organic / inorganic composite intermediate layer and the rare earth elements enhances the interfacial bonding force. At the same time, the interaction between the carboxyl groups and sulfonic acid groups of the organic / inorganic composite intermediate layer and the polar groups of the conductive polymer enhances the interfacial bonding force. Conductive pathways are formed through the conductive particles of the intermediate layer. Meanwhile, the surface doping of rare earth elements and the dense protection of the polymer conductive layer improve the corrosion resistance of the coating. The synergistic effect of the multiple layers effectively suppresses the decay of conductivity and achieves a synergistic improvement in high interfacial bonding strength and long cycle life of the grid.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A lead-acid battery grid with surface doped with rare earth elements, characterized in that the grid comprises: Matrix material; The first metal layer covers the surface of the substrate material; The second metal layer is coated on the surface of the first metal layer. The second metal layer is a lead or lead alloy coating doped with rare earth elements. An organic / inorganic composite intermediate layer is formed on the surface of the second metal layer; A conductive polymer layer is formed on the surface of an organic / inorganic composite intermediate layer.

[0008] The organic / inorganic composite intermediate layer contains a composite material of polyacrylic acid, polystyrene sulfonic acid, and conductive particles.

[0009] Preferably, the conductive particles in the organic / inorganic composite intermediate layer are selected from one or more of PbO2, graphene, and carbon nanotubes, and the mass percentage of the conductive particles is 30-50%.

[0010] Preferably, the organic / inorganic composite intermediate layer contains 10-50% polyacrylic acid and 10-50% polystyrene sulfonic acid by mass.

[0011] Preferably, the mass percentage of polyacrylic acid and polystyrene sulfonic acid in the organic / inorganic composite intermediate layer is 1:5-5:1.

[0012] Preferably, the mass percentage of polyacrylic acid and polystyrene sulfonic acid in the organic / inorganic composite intermediate layer is 1:1.

[0013] Preferably, the rare earth elements doped in the second metal layer are selected from one or more of cerium (Ce), yttrium (Y), and neodymium (Nd), and the total rare earth content is 0.01-0.05 wt%.

[0014] Preferably, the thickness of the organic / inorganic composite intermediate layer is 0.5-5 μm.

[0015] Preferably, the conductive polymer layer is selected from one or more of polyaniline (PANI), poly(3,4-ethylenedioxythiophene-polystyrene sulfonate) (PEDOT:PSS), and polypyrrole (PPy).

[0016] Preferably, the matrix material is selected from one of copper, aluminum, titanium, conductive plastic or carbon foam.

[0017] This invention also provides a method for preparing the lead-acid battery grid, comprising the following steps: (1) Matrix pretreatment: The matrix material is degreased, pickled and activated; (2) Plating the first metal layer: Plating a copper or nickel layer on the pretreated substrate surface; (3) Plating a rare earth-doped second metal layer: Rare earth elements are doped into the second metal layer by electroplating, and the electroplating solution contains lead salts and rare earth compounds. (4) Coating an organic / inorganic composite intermediate layer: A mixed solution of polyacrylic acid, polystyrene sulfonic acid and conductive particles is coated on the surface of the second metal layer and dried and cured to form an intermediate layer; (5) Coating a conductive polymer layer: The conductive polymer solution is coated on the surface of the organic / inorganic composite intermediate layer and dried and cured to form a conductive polymer layer.

[0018] The electroplating solution in step (3) contains: lead acetate 32-40 g / L, potassium antimony tartrate 2.2-4.5 g / L, stannous chloride 0.5-0.7 g / L, citric acid 100-200 g / L, boric acid 35 g / L, and cerium oxide 100-200 ppm, yttrium oxide 100-200 ppm, and neodymium oxide 50-100 ppm.

[0019] The formulation of the mixed solution in step (4) is: 10-50 wt% polyacrylic acid, 10-50 wt% polystyrene sulfonic acid, 30-50 wt% PbO2 particles, and the remainder is solvent.

[0020] Preferably, the conductive particles in the organic / inorganic composite intermediate layer are selected from one or more of PbO2, graphene, and carbon nanotubes, and the mass percentage of the conductive particles is 30-50%.

[0021] Preferably, the organic / inorganic composite intermediate layer contains 10-50% polyacrylic acid and 10-50% polystyrene sulfonic acid by mass.

[0022] Preferably, the mass percentage of polyacrylic acid and polystyrene sulfonic acid in the organic / inorganic composite intermediate layer is 1:5-5:1.

[0023] Preferably, the mass percentage of polyacrylic acid and polystyrene sulfonic acid in the organic / inorganic composite intermediate layer is 1:1.

[0024] Preferably, the rare earth elements doped in the second metal layer are selected from one or more of cerium (Ce), yttrium (Y), and neodymium (Nd), and the total rare earth content is 0.01-0.05 wt%.

[0025] Preferably, the thickness of the organic / inorganic composite intermediate layer is 0.5-5 μm.

[0026] Preferably, the conductive polymer layer is selected from one or more of polyaniline (PANI), poly(3,4-ethylenedioxythiophene-polystyrene sulfonate) (PEDOT:PSS), and polypyrrole (PPy).

[0027] Preferably, the matrix material is selected from one of copper, aluminum, titanium, conductive plastic or carbon foam.

[0028] The beneficial effects of this invention are as follows: 1) By introducing an organic / inorganic interlayer, a composite structure of a rare earth element alloy layer, an organic / inorganic composite interlayer, and a polymer conductive layer is formed. This significantly improves the interfacial bonding force and prevents the conductive polymer layer from peeling off. At the same time, the conductive particles in the interlayer provide additional conductive pathways, ensuring that the overall conductivity of the grid is not affected. This allows the rare earth element layer and the conductive polymer layer to work synergistically to suppress conductivity decay, while also improving the corrosion resistance of the grid coating and increasing cycle life.

[0029] 2) The organic / inorganic interlayer works synergistically with the polyacrylic acid and polystyrene sulfonic acid compound, resulting in better interfacial bonding. This allows the rare earth doped coating, organic / inorganic interlayer, and conductive polymer layer to be tightly bonded together and work synergistically to provide protection. This results in the lead-acid battery grid exhibiting higher peel strength, lower surface resistivity, lower capacity decay rate, higher acid resistance, lower corrosion current density, and lower annual corrosion rate. It can effectively inhibit the decay of conductivity and effectively prevent electrolyte penetration into the grid through the dense protection of the conductive polymer layer, significantly improving the corrosion resistance of the composite grid and increasing cycle life. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The present invention will be further explained and described below with reference to specific embodiments.

[0031] Example 1 A lead-acid battery grid with rare earth element doping on its surface is prepared by the following steps: Step 1, Matrix Pretreatment Using pure aluminum foil (0.5mm thick) as the base material, the pretreatment steps are as follows: Degreasing: Immerse the aluminum foil in acetone and ultrasonically clean for 10 minutes to remove surface oil. Alkaline washing: Immerse in NaOH solution (50g / L, 60℃) for 8 minutes; Pickling: Immerse in 10% HNO3 solution for 30 seconds to remove the natural oxide film; One-time zinc immersion: Immersion in a zinc immersion solution of 20g / L ZnO and 120g / L NaOH at room temperature for 45 seconds; Zinc removal: Immerse in 50% HNO3 solution for 12 seconds; Double zinc immersion: In the same zinc immersion solution, a uniform and dense zinc layer is formed on the aluminum surface in 25 seconds.

[0032] Step 2, deposit the first metal layer A copper layer is plated onto the pretreated aluminum substrate using electroplating: Electroplating solution composition: CuSO4·5H2O 200g / L, H2SO4 60g / L 60ppm; Electroplating was performed at room temperature for 15 minutes at a current density of 3 A / dm² to obtain a copper layer with a thickness of approximately 8 μm.

[0033] Step 3: Deposit a second rare-earth-doped metal layer. A second metal layer is deposited on the surface of the copper layer using electroplating: Electroplating solution formula: Lead acetate: 36g / L Potassium antimony tartrate: 3.5 g / L Stannous chloride: 0.6 g / L Citric acid: 120g / L Boric acid: 35g / L Cerium oxide (CeO2): 150 ppm Yttrium oxide (Y2O3): 100 ppm Neodymium oxide (Nd₂O₃): 80 ppm Butynyl propoxy compound (BMP): 15 ppm At room temperature, the pH value was adjusted to 5.0 with ammonia water, and electroplating was carried out for 8 minutes at a current density of 2.5 A / dm² to obtain a lead-antimony-tin-rare earth alloy layer with a thickness of about 6 μm.

[0034] Step 4, apply organic / inorganic intermediate layer Intermediate layer slurry formulation: Polyacrylic acid (PAA, Mw=150,000): 30wt% Polystyrene sulfonic acid: 30wt% PbO2 particles (1μm in diameter): 40wt% Isopropanol: Adjust viscosity as needed Weigh the materials according to the slurry formula, mix PbO2 particles with polyacrylic acid and polystyrene sulfonic acid solution, and ball mill and disperse for 2 hours to obtain slurry; use spraying method to uniformly coat the slurry onto the surface of the second metal layer; dry at 80℃ for 15 minutes to form an intermediate layer with a thickness of about 2μm.

[0035] Step 5, Apply conductive polymer layer Conductive polymer solution formulation: 1.3 wt% poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) aqueous dispersion, followed by the addition of 5 wt% dimethyl sulfoxide to obtain PEDOT:PSS solution.

[0036] The grid from step 4 was immersed in PEDOT:PSS solution for 30 seconds using an impregnation method; after removal, it was dried at 60°C for 30 minutes; the impregnation-drying step was repeated twice to form a conductive polymer layer with a thickness of about 5 μm.

[0037] Example 2 A lead-acid battery grid with rare earth elements doped on the surface was prepared according to the method of Example 1, except that polyacrylic acid was replaced with polystyrene sulfonic acid in step 4.

[0038] Example 3 A lead-acid battery grid with rare earth elements doped on the surface was prepared according to the method of Example 1, except that polystyrene sulfonic acid in step 4 was replaced with polyacrylic acid.

[0039] Example 4 A lead-acid battery grid with rare earth elements doped on the surface was prepared according to the method of Example 1, the only difference being that the polyacrylic acid content in step 4 was adjusted to 10 wt% and the polystyrene sulfonic acid content was adjusted to 50 wt%.

[0040] Example 5 A lead-acid battery grid with rare earth elements doped on the surface was prepared according to the method of Example 1, the only difference being that the polyacrylic acid content in step 4 was adjusted to 50wt% and the polystyrene sulfonic acid content was adjusted to 10wt%.

[0041] Example 6 A lead-acid battery grid with rare earth elements doped on the surface was prepared according to the method of Example 1, the only difference being that polyacrylic acid was replaced with polyvinylpyrrolidone.

[0042] Example 7 A lead-acid battery grid with rare earth elements doped on the surface was prepared according to the method of Example 1, except that polyacrylic acid was replaced with polyethylene oxide.

[0043] Comparative Example 1 A lead-acid battery grid with surface doped with rare earth elements was prepared according to the method of Example 1, except that step 4 was omitted.

[0044] Comparative Example 2 A lead-acid battery grid with surface doped with rare earth elements was prepared according to the method of Example 1, except that step 5 was omitted.

[0045] The performance of the lead-acid battery grids with rare earth element doping on the surface obtained in Examples 1-7 and Comparative Examples 1-2 was characterized: Interface bonding strength: The bonding strength between the coatings of the grid is determined according to GB / T 9286-1998 and the coating adhesion test standard.

[0046] Conductivity: The surface resistivity of the grid was measured using a four-probe resistivity meter, and the bulk resistance of the grid was also measured.

[0047] Cycle life: The grids of the examples and comparative examples were assembled into 2V single cells (the positive grid was the test sample, and the negative electrode used a conventional lead plate). The cells were charged and discharged using the Arbin BT2000 charge-discharge test system. The cells were charged at a constant current of 0.2C to 2.45V, then charged at a constant voltage until the current dropped to 0.05C, and discharged at a constant current of 0.2C to 1.75V. The cells were continuously charged and discharged for 500 cycles.

[0048] Acid resistance: According to GB / T 10125, the grid sample was immersed in 4.5 mol / L H2SO4 solution at 60℃ for 30 days, and the blistering, cracking and peeling of the coating were observed.

[0049] Electrochemical corrosion performance: Potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) were performed using a three-electrode system on an electrochemical workstation. Electrolyte: 4.5 mol / L H2SO4 solution; Reference electrode: Hg / Hg2SO4 electrode; Auxiliary electrode: platinum sheet electrode; Scan range: -1.0 V to 1.6 V (vs. Hg / Hg2SO4); Scan rate: 0.5 mV / s.

[0050] Table 1 Performance of lead-acid battery grids with rare earth element doping on the surface

[0051] As can be seen from the comparison of Example 1, Comparative Example 1, and Comparative Example 2, the present invention can significantly improve the interfacial bonding force by introducing an organic / inorganic intermediate layer, prevent the conductive polymer layer from peeling off, and at the same time, the conductive particles in the intermediate layer provide additional conductive pathways, ensuring that the overall conductivity of the grid is not affected. This allows the rare earth element doping layer and the conductive polymer layer to work synergistically to suppress the decay of conductivity, while improving the corrosion resistance of the grid coating and increasing the cycle life.

[0052] A comparison of Examples 1, 2, and 3 shows that the combination of polyacrylic acid and polystyrene sulfonic acid exhibits a synergistic effect. The lead-acid battery grid of Example 1 demonstrates higher peel strength, lower surface resistivity, lower capacity decay rate, higher acid resistance, lower corrosion current density, and lower annual corrosion rate. This is likely because, compared to using polyacrylic acid or polystyrene sulfonic acid alone, on the one hand, the carboxyl groups of polyacrylic acid can chelate with rare earth elements in the rare earth element-doped coating to form coordination compounds, and can also chelate with lead elements in the organic / inorganic intermediate layer to form coordination compounds. Furthermore, it has good compatibility and polar group interaction with polystyrene sulfonic acid. On the other hand... In this study, polystyrene sulfonic acid and poly(styrene sulfonate) in the polymer conductive layer have similar structures. The sulfonic acid groups of polystyrene sulfonic acid can act as dopants to combine with PEDOT (poly(3,4-ethylenedioxythiophene)) in the polymer conductive layer, helping the water-insoluble PEDOT to be stably dispersed in water and regulating its conductivity. This allows the intermediate layer to exert better interfacial bonding force, enabling the rare earth doped coating, organic / inorganic intermediate layer and conductive polymer layer composite structure to be tightly combined and work synergistically to protect the structure. This effectively inhibits the decay of conductivity and effectively prevents electrolyte from penetrating into the grid through the dense protection of the conductive polymer layer, significantly improving the corrosion resistance of the composite grid and increasing cycle life.

[0053] A comparison of Examples 1-5, 6, and 7 shows that, compared to polyvinylpyrrolidone and polyethylene oxide, the combination of polyacrylic acid and polystyrene sulfonic acid results in higher peel strength, lower surface resistivity, lower capacity decay rate, higher acid resistance, lower corrosion current density, and lower annual corrosion rate for lead-acid battery grids. This is likely because, compared to polyvinylpyrrolidone and polyethylene oxide, both polyacrylic acid and polystyrene sulfonic acid have excellent polar solvent dispersibility and can improve compatibility through the interaction of polar groups. Furthermore, the carboxyl groups of polyacrylic acid can chelate with rare earth elements in the rare earth element-doped coating to form coordination compounds, and can also chelate with lead elements in the organic / inorganic interlayer to form coordination compounds. This allows the organic / inorganic interlayer to exert better interfacial bonding, enabling the composite structure of rare earth doped coating, organic / inorganic interlayer, and conductive polymer layer to work synergistically to protect the grid, suppress conductivity decay, effectively prevent electrolyte penetration into the grid, significantly improve the corrosion resistance of the composite grid, and increase cycle life.

[0054] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A lead-acid battery grid with a surface layer doped with rare earth elements, characterized in that, The grid includes: Matrix material; The first metal layer covers the surface of the substrate material; The second metal layer is coated on the surface of the first metal layer. The second metal layer is a lead or lead alloy coating doped with rare earth elements. An organic / inorganic composite intermediate layer is formed on the surface of the second metal layer; A conductive polymer layer is formed on the surface of an organic / inorganic composite intermediate layer; The organic / inorganic composite intermediate layer contains a composite material of polyacrylic acid, polystyrene sulfonic acid, and conductive particles.

2. The lead-acid battery grid with surface doped rare earth elements according to claim 1, characterized in that: The conductive particles in the organic / inorganic composite intermediate layer are selected from one or more of PbO2, graphene, and carbon nanotubes, and the mass percentage of the conductive particles is 30-50%.

3. The lead-acid battery grid with surface doped rare earth elements according to claim 1, characterized in that: The organic / inorganic composite intermediate layer contains 10-50% polyacrylic acid and 10-50% polystyrene sulfonic acid by mass.

4. The lead-acid battery grid with surface doped rare earth elements according to claim 1, characterized in that: The mass percentage of polyacrylic acid and polystyrene sulfonic acid in the organic / inorganic composite intermediate layer is 1:5-5:

1.

5. The lead-acid battery grid with surface doped rare earth elements according to claim 1, characterized in that: The thickness of the organic / inorganic composite intermediate layer is 0.5-5 μm.

6. The lead-acid battery grid with surface doped rare earth elements according to claim 1, characterized in that: The rare earth elements doped in the second metal layer are selected from one or more of cerium, yttrium, and neodymium, and the total rare earth content is 0.01-0.05 wt%.

7. The lead-acid battery grid with surface doped rare earth elements according to claim 1, characterized in that: The conductive polymer layer is selected from one or more of polyaniline, poly(3,4-ethylenedioxythiophene-polystyrene sulfonate), and polypyrrole.

8. The method for preparing a lead-acid battery grid with surface doped rare earth elements according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Matrix pretreatment: The matrix material is degreased, pickled and activated; (2) Plating the first metal layer: Plating a copper or nickel layer on the pretreated substrate surface; (3) Plating a rare earth-doped second metal layer: Rare earth elements are doped into the second metal layer by electroplating, and the electroplating solution contains lead salts and rare earth compounds. (4) Coating an organic / inorganic composite intermediate layer: A mixed solution of polyacrylic acid, polystyrene sulfonic acid and conductive particles is coated on the surface of the second metal layer and dried and cured to form an intermediate layer; (5) Coating a conductive polymer layer: The conductive polymer solution is coated on the surface of the organic / inorganic composite intermediate layer and dried and cured to form a conductive polymer layer.

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