Negative current collector of zinc-nickel battery and preparation method of negative current collector

Abstract

The invention discloses a zinc-nickel battery cathode current collector and a preparation method thereof, and relates to the technical field of zinc-nickel secondary batteries. The negative current collector comprises a copper base material or a nickel base material and an electroplated layer arranged on the surface of the copper base material or the nickel base material, the electroplated layer comprises tin-bismuth alloy, the content of bismuth in the tin-bismuth alloy is 5-15 wt%, and the balance is tin. The tin-bismuth alloy electroplated layer is arranged on the surface of the current collector base material, so that the corrosion resistance and the conductivity of the negative current collector are effectively improved, the interface bonding force between the current collector and an active substance is improved, the cycling stability of the zinc-nickel battery is remarkably improved, and the technical problems that an existing current collector is easy to corrode in an alkaline electrolyte and the interface impedance is increased are solved. The preparation method can be widely applied to the field of preparation of negative current collectors of zinc-nickel secondary batteries and other alkaline secondary batteries.

Description

Technical Field

[0001] This invention relates to the field of zinc-nickel secondary battery technology, and in particular to a zinc-nickel battery negative electrode current collector and its preparation method. Background Technology

[0002] Zinc-nickel secondary batteries have broad application potential in energy storage systems and power batteries due to their advantages such as high specific energy, low cost, and environmental friendliness. The negative electrode current collector, as a key component of the battery, typically uses copper or nickel foil as a substrate to provide mechanical support and an electronic conduction pathway for the negative electrode active material. During battery operation, the current collector needs to be continuously immersed in a strongly alkaline electrolyte, while simultaneously withstanding the volume changes and electrochemical reactions of the zinc negative electrode during charge-discharge cycles.

[0003] In long-term practical applications, it has been found that existing current collectors are prone to oxidation and corrosion during use. Under the influence of a strongly alkaline electrolyte, an oxide layer gradually forms on the surface of the current collector, leading to a continuous increase in the interfacial impedance between the current collector and the active material, and thus increasing the battery's internal resistance. With increasing cycle count, the increased interfacial impedance reduces the battery's charge / discharge efficiency, accelerates capacity decay, and shortens cycle life. Especially under high-rate charge / discharge conditions, the increased interfacial impedance exacerbates battery polarization, severely impacting battery performance and reliability.

[0004] Therefore, reducing the corrosion of the negative electrode current collector in alkaline electrolyte and slowing down the growth rate of interfacial impedance have become key issues in improving the cycle stability of zinc-nickel batteries. Summary of the Invention

[0005] The main objective of this invention is to propose a zinc-nickel battery negative electrode current collector and its preparation method to solve the technical problems of existing current collectors being prone to corrosion and having increased interfacial impedance in alkaline electrolytes.

[0006] To achieve the above objectives, the present invention provides a zinc-nickel battery negative electrode current collector, comprising: Copper-based or nickel-based substrate; An electroplated layer is disposed on the surface of the copper substrate or nickel substrate; The electroplated layer contains a tin-bismuth alloy, wherein the bismuth content in the tin-bismuth alloy is 5-15 wt%, and the balance is tin.

[0007] In one embodiment, the electroplated layer further comprises 0.1-2 wt% silver.

[0008] In one embodiment, the electroplated layer further comprises 0.1-2 wt% indium.

[0009] In one embodiment, the electroplated layer contains 0.1-2 wt% silver and 0.1-2 wt% indium.

[0010] This invention also provides an electroplating solution for tin-bismuth alloys, using deionized water as a solvent, comprising: Tin salt 20-40g / L; Bismuth salt 3-15 g / L; Citrate complexing agents 60-100 g / L; Polyethylene glycol 1-3 g / L; The pH value of the plating solution is 3-6.

[0011] In one embodiment, the electroplating solution further contains 0.05-0.5 g / L of silver salt.

[0012] In one embodiment, the electroplating solution further contains 0.1-1 g / L of indium salt.

[0013] This invention also provides a method for preparing a zinc-nickel battery negative electrode current collector, comprising the following steps: Pretreatment steps: Treat the copper or nickel substrate in an alkaline degreasing solution at a temperature of 60-80℃ for 5-10 minutes, and then pickle it in a 5-10% sulfuric acid solution at room temperature for 30-60 seconds. Electroplating step: Place the pretreated substrate in the above electroplating solution, and plate it at a current density of 1-5 A / dm³. 2 Electroplating is performed at a temperature of 20-50℃ and a pH of 3-6 for 10-60 minutes to form a tin-bismuth alloy electroplating layer with a thickness of 1-10μm. Post-processing steps: Wash and dry the electroplated collector with water, and then anneal it at 100-200℃ for 30-60 minutes in an inert gas atmosphere.

[0014] In one embodiment, the current density in the electroplating step is 1-2 A / dm². 2 This promotes the co-deposition of amorphous Sn-Bi, forming a fine-grained structure with a grain size of 1-5 μm.

[0015] In one embodiment, the annealing process in the post-processing step is carried out at 150°C for 40 minutes in an inert gas atmosphere, so that bismuth forms a liquid phase film at the grain boundaries of the tin-bismuth alloy, promoting grain boundary migration and recrystallization, thereby releasing internal stress.

[0016] This invention provides a tin-bismuth alloy electroplating layer on the surface of a copper or nickel substrate. The tin-bismuth alloy forms a stable passivation film in an alkaline electrolyte, effectively reducing the oxidation and corrosion rate of the current collector. The grain boundary segregation effect of bismuth in the tin substrate refines the coating grains, improves the density and mechanical strength of the coating, and reduces the growth rate of interfacial impedance, thereby improving the cycle stability of zinc-nickel batteries.

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort. Attached Figure Description

[0018] Figure 1 A transmission electron microscope image of the tin-bismuth alloy electroplated layer prepared in Example 1 of this invention; Figure 2 The symmetrical battery assembled with the tin-bismuth alloy coated negative electrode prepared in Example 1 of this invention has a capacity of 1 mAh / cm². 2 1mA / cm 2 Experimental diagram of electroplating peeling under current density; Figure 3 The image shows the battery cycle performance of the tin-bismuth alloy negative electrode prepared in Example 1 of this invention.

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that the meaning of "and / or" throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that satisfies both A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0022] The terms “comprising,” “including,” “containing,” “containing,” “having,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and components may be added without affecting the final result. The term “comprising” also includes the terms “consistently composed of” and “substantially composed of”. The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional components, parts, steps, or limitations described herein. All numerical values ​​or expressions relating to component amounts, process conditions, etc., used in the specification and claims are to be understood in all cases to be modified by “about.” All ranges relating to the same component or property include endpoints that can be combined independently. Because these ranges are continuous, they include every value between a minimum and a maximum value. It should also be understood that any numerical range referenced in this application is intended to include all subranges within that range. As used herein, “parts by weight,” “number of parts by weight,” “mass parts,” or “mass parts” are used interchangeably. A part by weight can be any fixed weight expressed in milligrams, grams, or kilograms (e.g., 1 mg, 1 g, 2 g, 5 g, or 1 kg). For example, a composition consisting of 1 part by weight of component a and 9 parts by weight of component b can be a composition consisting of 1 gram of component a + 9 grams of component b, or 10 grams of component a + 90 grams of component b, etc.

[0023] This invention proposes a zinc-nickel battery negative electrode current collector and its preparation method.

[0024] In existing technologies, while tin-lead alloy coatings possess good processing performance, lead is prone to corrosion and dissolution in strongly alkaline electrolytes, releasing lead ions that contaminate the electrolyte and reduce battery performance. In tin-copper alloy coatings, copper is easily oxidized and dissolved in alkaline environments, forming high-resistivity Cu-Zn intermetallic compounds, leading to a sharp increase in interfacial impedance and severely affecting the battery's cycle stability. This invention, by employing a tin-bismuth alloy coating, effectively solves the problems existing in the aforementioned prior art.

[0025] like Figures 1 to 3 As shown, this embodiment provides a zinc-nickel battery negative electrode current collector, including a copper substrate or a nickel substrate, and an electroplated layer disposed on the surface of the copper substrate or the nickel substrate.

[0026] The copper or nickel substrate serves as the current collector's base, providing mechanical support and an electronic conduction pathway for the negative electrode active material. Copper substrates offer excellent conductivity and lower cost, while nickel substrates provide better corrosion resistance. Pre-treatment of the substrate surface provides a clean and activated surface for electroplating deposition, ensuring good adhesion between the electroplated layer and the substrate.

[0027] The electroplated layer, deposited on the substrate surface, comprises a tin-bismuth alloy, wherein the bismuth content in the tin-bismuth alloy is 5-15 wt%, with the balance being tin. The bismuth in the tin-bismuth alloy forms discontinuous grain boundary segregation phases in the tin matrix through the grain boundary segregation effect, inhibiting tin grain growth and reducing the grain size from 10 μm in pure tin to 1-3 μm, significantly improving the hardness and creep resistance of the plating. The low melting point of bismuth (271℃) can alleviate the volume expansion stress of the zinc electrode during cycling, reducing the risk of plating cracking. The tin-bismuth alloy plating forms a stable passivation film in alkaline electrolyte, effectively preventing current collector oxidation corrosion, reducing interfacial impedance, and improving the cycle stability of the battery.

[0028] This invention improves the corrosion resistance and conductivity of the negative electrode current collector by depositing a tin-bismuth alloy electroplating layer on the surface of a copper or nickel substrate. This alloy plating effectively solves the technical problems of existing current collectors being prone to corrosion and exhibiting increased interfacial impedance in alkaline electrolytes.

[0029] In this embodiment, by controlling the bismuth content in the tin-bismuth alloy to be 5-15 wt%, an optimized balance of coating performance was achieved. When the bismuth content is below 5 wt%, the grain boundary segregation effect is not significant, and the improvement in coating hardness and corrosion resistance is limited; when the bismuth content is above 15 wt%, the coating becomes more brittle and prone to cracking and peeling during cycling. Within the 5-15 wt% range, the tin-bismuth alloy coating has a dense microstructure, good mechanical properties, and excellent electrochemical stability, fundamentally preventing corrosion of the current collector in alkaline electrolytes. This improves the conductivity and interfacial bonding of the current collector. Combined with the synergistic effect of the tin-bismuth alloy, the entire negative electrode current collector is more stable and reliable, solving the technical problems of corrosion and interfacial failure that easily occur in existing zinc-nickel battery negative electrode current collectors during use.

[0030] It is understood that in some embodiments, the bismuth content can be selected as 5wt%, 10wt%, or 15wt%, as long as the coating performance can be optimized, it falls within the protection scope of this invention.

[0031] In some preferred embodiments, the electroplated layer further comprises 0.1-2 wt% silver. Silver has extremely high electrical conductivity, with a bulk resistivity of only 1.59 × 10⁻⁶. -8 Ω·m, forming nanoscale conductive channels in the plating layer, reducing the resistivity of the plating layer from 11.5 × 10 Ω·m in pure tin to... -8 Ω·m decreased to 7.2 × 10 -8 The silver content significantly reduces the interfacial contact resistance of the current collector (Ω·m). The addition of silver suppresses abnormal tin grain growth, further refining the grain structure of the coating and improving its density and uniformity. In high-current-density zinc-nickel battery systems, the addition of silver can effectively reduce polarization and improve the battery's rate performance.

[0032] In this embodiment, the silver content is controlled within the range of 0.1-2 wt%, which significantly improves conductivity without substantially increasing costs. When the silver content is below 0.1 wt%, the improvement in conductivity is not significant; when the silver content is above 2 wt%, the cost increases significantly, and the agglomeration of silver in the coating intensifies, which may reduce the uniformity of the coating. Therefore, a silver content of 0.1-2 wt% is the preferred range considering both performance and cost.

[0033] In some preferred embodiments, the electroplated layer further comprises 0.1-2 wt% indium. Indium forms an intermetallic compound Sn3In with tin, significantly enhancing the adhesion between the plating layer and the substrate and reducing the risk of plating peeling during cycling. The addition of indium reduces the interfacial contact resistance between the plating layer and the substrate, improving electron conduction efficiency. Indium forms fine second-phase particles in the plating layer, acting as a reinforcing phase and improving the mechanical strength and wear resistance of the plating layer.

[0034] In this embodiment, the indium content is controlled within the range of 0.1-2 wt%, which can effectively improve the interfacial adhesion and mechanical properties of the coating. When the indium content is below 0.1 wt%, the amount of Sn3In intermetallic compound formed is insufficient, and the strengthening effect is limited; when the indium content is above 2 wt%, excessive intermetallic compounds will make the coating brittle, reducing the flexibility and impact resistance of the coating.

[0035] In some preferred embodiments, the electroplated layer simultaneously comprises 0.1-2 wt% silver and 0.1-2 wt% indium. The combined addition of silver and indium produces a synergistic effect: silver constructs a conductive network and reduces resistivity; indium enhances interfacial adhesion and improves mechanical properties; together, the two enable the plating layer to possess excellent conductivity, corrosion resistance, and high adhesion, achieving a comprehensive improvement in the performance of the electroplated layer.

[0036] It is understood that in some implementations, the silver content can be selected as 0.1wt%, 0.5wt%, 1wt%, or 2wt%, and the indium content can be selected as 0.1wt%, 0.5wt%, 1wt%, or 2wt%. As long as the conductivity and interfacial bonding strength can be improved, similar technical effects can be achieved.

[0037] The present invention also provides an electroplating solution for tin-bismuth alloy, using deionized water as a solvent, comprising 20-40 g / L of tin salt, 3-15 g / L of bismuth salt, 60-100 g / L of citrate complexing agent, and 1-3 g / L of polyethylene glycol, wherein the pH value of the plating solution is 3-6.

[0038] The tin salt, as the main source of tin ions, can be selected from stannous sulfate, stannous chloride, stannous fluoroborate, etc. The tin salt concentration is controlled within the range of 20-40 g / L, which ensures sufficient tin ion concentration to maintain a stable electroplating rate while avoiding the problem of decreased plating solution stability due to excessively high concentrations.

[0039] The bismuth salt, serving as the primary source of bismuth ions, can be selected from bismuth nitrate, bismuth chloride, bismuth sulfate, etc. The bismuth salt concentration is controlled within the range of 3-15 g / L, and it is used in conjunction with tin salts to ensure that tin and bismuth are co-deposited in a predetermined ratio during electroplating, forming a uniform tin-bismuth alloy coating.

[0040] The citrate complexing agent, as a metal ion complexing agent, can be selected from trisodium citrate, potassium sodium citrate, etc. The citrate complexing agent binds to Sn via its carboxyl group. 2+ Bi 3+ It forms soluble complexes, inhibiting the hydrolytic precipitation of metal ions and improving the stability of the plating solution. For example, when pH > 4, Sn... 2+ Sn(OH)₂ precipitate readily hydrolyzes, and the addition of trisodium citrate can raise the critical pH for precipitation to above 6.5, significantly broadening the electroplating process window. Controlling the complexing agent concentration within the range of 60-100 g / L effectively complexes metal ions while moderately increasing cathode polarization, promoting the co-deposition of amorphous Sn-Bi, and obtaining a dense, fine-grained coating structure (porosity <5 pores / cm²). 2 ).

[0041] The polyethylene glycol, as an additive, is adsorbed onto the cathode surface during electroplating, serving to level and refine the grains. Controlling the polyethylene glycol concentration within the range of 1-3 g / L effectively improves the smoothness and gloss of the coating, and reduces porosity and defects on the coating surface.

[0042] The pH value of the plating solution is controlled within the range of 3-6, which can prevent the hydrolysis and precipitation of metal ions and ensure that the cathode polarization is moderate during the electroplating process, which is conducive to the formation of a dense and uniform coating.

[0043] In some preferred embodiments, the electroplating solution further contains 0.05-0.5 g / L of silver salt, used to co-deposit silver ions with tin and bismuth during the electroplating process to form a silver-containing tin-bismuth alloy coating. The silver salt can be silver nitrate, silver cyanide, etc. Controlling the silver salt concentration within the range of 0.05-0.5 g / L ensures that the silver content in the coating reaches the preferred range of 0.1-2 wt%.

[0044] In some preferred embodiments, the electroplating solution further contains 0.1-1 g / L of indium salt, used to co-deposit indium ions with tin and bismuth during the electroplating process to form an indium-containing tin-bismuth alloy coating. The indium salt can be indium sulfate, indium chloride, etc. Controlling the indium salt concentration within the range of 0.1-1 g / L ensures that the indium content in the coating reaches a preferred range of 0.1-2 wt%.

[0045] In some preferred embodiments, the electroplating solution simultaneously contains 0.05-0.5 g / L of silver salt and 0.1-1 g / L of indium salt, used to co-deposit silver ions, indium ions, tin, and bismuth during the electroplating process, forming a tin-bismuth alloy coating containing both silver and indium. The combined addition of silver and indium salts produces a synergistic effect: silver ions preferentially reduce and deposit on the cathode surface, forming nanoscale conductive channels and reducing the resistivity of the coating; indium ions co-deposit with tin ions to form Sn3In intermetallic compounds, significantly enhancing the interfacial adhesion between the coating and the substrate; the combined effect of silver and indium gives the coating both excellent conductivity and high interfacial adhesion, achieving a comprehensive improvement in electrochemical and mechanical properties. Controlling the silver salt concentration within the range of 0.05-0.5 g / L and the indium salt concentration within the range of 0.1-1 g / L ensures that the silver content in the coating reaches a preferred range of 0.1-2 wt% and the indium content reaches 0.1-2 wt%. This composite plating solution is particularly suitable for zinc-nickel battery applications requiring high-rate charge / discharge and long cycle life.

[0046] The present invention also provides a method for preparing a zinc-nickel battery negative electrode current collector, including a pretreatment step, an electroplating step, and a post-treatment step.

[0047] In the pretreatment step, the copper or nickel substrate is treated in an alkaline degreasing solution at 60-80℃ for 5-10 minutes, followed by pickling in a 5-10% sulfuric acid solution at room temperature for 30-60 seconds. Alkaline degreasing thoroughly removes grease contamination from the substrate surface, while pickling removes the oxide film and activates the surface, providing a clean and activated surface for subsequent electroplating and ensuring good adhesion between the electroplated layer and the substrate. The alkaline degreasing solution can be sodium hydroxide or sodium carbonate solution, with the temperature controlled at 60-80℃ and the treatment time at 5-10 minutes, effectively removing grease without damaging the substrate. The sulfuric acid solution concentration is controlled at 5-10%, and pickling at room temperature for 30-60 seconds removes the oxide film while avoiding substrate corrosion caused by excessive pickling.

[0048] In the electroplating step, the pretreated substrate is placed in the above-mentioned electroplating solution at a current density of 1-5 A / dm³. 2 Electroplating is performed at 20-50℃ and pH 3-6 for 10-60 minutes to form a tin-bismuth alloy plating layer with a thickness of 1-10 μm. The current density is controlled at 1-5 A / dm³. 2Within this range, both an appropriate electroplating rate and the density and uniformity of the coating can be ensured. Temperature control between 20-50℃ is beneficial for the mass transfer of metal ions and the electrochemical reaction. pH control between 3-6 prevents the hydrolysis and precipitation of metal ions. Electroplating time is adjusted according to the required coating thickness; typically, 10-60 minutes of electroplating yields a coating thickness of 1-10 μm. Controlling the coating thickness within the 1-10 μm range provides sufficient protection without increasing internal stress and the risk of cracking due to excessive coating thickness.

[0049] In the post-processing steps, the electroplated current collector is washed with water and dried, then annealed at 100-200℃ for 30-60 minutes in an inert gas atmosphere. Washing removes residual plating solution from the surface, and drying removes moisture. Annealing eliminates internal stress in the plating, promotes grain boundary migration and recrystallization, and improves the microstructure and properties of the plating. An inert gas atmosphere, such as nitrogen or argon, prevents oxidation of the plating at high temperatures. Controlling the annealing temperature at 100-200℃ and the annealing time at 30-60 minutes effectively releases internal stress without causing excessive oxidation or phase transformation of the plating.

[0050] In some preferred embodiments, the current density in the electroplating step is 1-2 A / dm². 2 This promotes the co-deposition of amorphous Sn-Bi, forming a fine-grained structure with a grain size of 1-5 μm. Lower current density (1-2 A / dm³) is achieved. 2 Increasing cathode polarization is beneficial for forming a fine-grained structure with a preferred (200) orientation; high current density (>3A / dm) 2 This leads to coarsening of the (111) orientation and an increase in grain size, requiring the use of additives to regulate the crystal growth rate. Controlling the grain size within the range of 1-5 μm significantly improves the density, hardness, and corrosion resistance of the coating.

[0051] In some preferred embodiments, the annealing process in the post-processing step is performed at 150°C for 40 minutes in an inert gas atmosphere. This enhances the diffusion activity of bismuth at the grain boundaries of the tin-bismuth alloy, promoting grain boundary migration and recrystallization, thereby releasing internal stress. The annealing temperature of 150°C is close to the Sn-Bi eutectic temperature and far lower than the melting point of tin (232°C) and bismuth (271°C), preventing overall melting or phase transformation of the coating. Simultaneously, at this temperature, bismuth locally forms a liquid film or discontinuous segregated phase at the grain boundaries, significantly increasing the diffusion coefficient of bismuth atoms at the grain boundaries, thus pinning dislocations and promoting stress release. The 40-minute annealing time effectively releases the internal stress generated during electroplating, improves the microstructure of the coating, and enhances its density and mechanical properties.

[0052] Example 1: Preparation of a tin-bismuth alloy coating with a bismuth content of 5 wt% Step 1: Plating solution preparation Preparation of the electroplating solution: Using deionized water as the solvent, add 30 g / L stannous sulfate (SnSO4), 5 g / L bismuth nitrate (Bi(NO3)3), 80 g / L trisodium citrate, and 2 g / L polyethylene glycol. First, dissolve the trisodium citrate, then add the other components sequentially, and bring the volume to 1 L with deionized water. Use a constant-temperature stirrer at 200 rpm for 30 minutes to ensure thorough dissolution and mixing of all components. Adjust the pH to 4.5 using 10% H2SO4 and 10% NaOH solutions.

[0053] Step 2: Substrate Pretreatment Select copper foil as the substrate and cut it to a size of 3cm × 4cm. Immerse the copper foil in an alkaline degreasing solution (NaOH 20g / L + Na2CO3 30g / L) at 60℃ for 10 minutes to remove surface grease. After removal, rinse with deionized water. Then immerse the copper foil in a 5% sulfuric acid solution and acid-wash at room temperature for 60 seconds to remove the oxide film and activate the surface. After removal, rinse with deionized water and dry for later use.

[0054] Step 3: Electroplating Electroplating was performed in an electroplating bath, with the solution temperature maintained at 40±1℃ using a constant-temperature water bath. Pretreated copper foil was used as the cathode, and a pure tin plate as the anode, with a 5cm distance between the electrodes. Before electroplating, the pH was adjusted to 4.0±0.2, and the current density was set to 1A / dm³. 2 The electroplating time is 30 minutes. During the electroplating process, maintain the pH of the plating solution at 4.0 ± 0.2; adjust with dilute acid or alkali solution if necessary. After electroplating, remove the copper foil and rinse with deionized water to remove any residual plating solution from the surface.

[0055] Step 4: Post-processing The electroplated copper foil was dried in an oven at 80°C for 10 minutes. Then it was placed in a tube furnace and annealed at 150°C for 40 minutes under a nitrogen atmosphere (nitrogen flow rate 100 mL / min). After annealing, it was cooled to room temperature in the furnace and removed to obtain the tin-bismuth alloy coated negative electrode current collector of this embodiment.

[0056] Step 5: Performance Testing The prepared tin-bismuth alloy coating was characterized and its performance was tested. Scanning electron microscopy (SEM) was used to observe the surface morphology of the coating, revealing a smooth, dense surface without obvious pores or cracks. Transmission electron microscopy (TEM) was used to observe the microstructure of the coating, such as... Figure 1As shown, at a scale of 100 micrometers, the electroplated layer exhibits a smooth and dense surface with fine and uniform grains, approximately 1-3 μm in size, and no obvious pores or cracks. This dense microstructure is the microscopic basis for the excellent corrosion resistance and low interfacial impedance of the tin-bismuth alloy coating. X-ray diffraction (XRD) analysis confirmed that the coating is a tin-bismuth alloy with a bismuth content of approximately 5 wt%.

[0057] The prepared tin-bismuth alloy-plated negative electrode current collector was coated with a negative electrode slurry (zinc oxide: conductive agent: 4% CMC = 80:10:10), cut into 3cm × 4cm sizes, and assembled into a symmetrical battery. A composite separator was used, and the electrolyte was 6MKOH and saturated zinc oxide. The battery was pressurized using a soft-pack battery clamp. Electroplating peeling experiments were conducted on a battery testing system at a current density of 1mA / cm². 2 The capacity is 1mAh / cm 2 .like Figure 2 As shown, the symmetrical battery assembled using the tin-bismuth alloy coated negative electrode prepared in Example 1 achieves a performance of 1 mAh / cm². 2 1mA / cm 2 In the electroplating peeling experiment curves under current density conditions, the horizontal axis represents time and the vertical axis represents voltage. The overpotential of the tin-bismuth alloy coating in Example 1 during the electroplating peeling process is significantly lower than that of the pure tin coating in Comparative Example 1, exhibiting a narrow voltage plateau and small fluctuations. A smaller overpotential indicates smaller polarization, suggesting that the tin-bismuth alloy coating has good corrosion resistance and low interfacial impedance, which is beneficial for improving the battery's charge / discharge efficiency and cycle life.

[0058] Zinc-nickel full cells were assembled and their cycle performance was tested. The prepared tin-bismuth alloy-coated negative electrode current collector was assembled with a nickel positive electrode, a composite separator, and an alkaline electrolyte (6M KOH) into a pouch cell, and charge-discharge cycle tests were performed on a battery testing system. Figure 3 As shown in the figure, the tin-bismuth alloy anode prepared in Example 1 exhibits high cycle performance in a zinc-nickel full cell. The horizontal axis represents the number of cycles, and the vertical axis represents the capacity retention. The figure clearly shows that the tin-bismuth alloy coated anode demonstrates high cycle stability in the zinc-nickel full cell. During 200 charge-discharge cycles, the capacity retention consistently remained above 85%, significantly better than the comparative examples of pure tin coated, pure bismuth coated, and uncoated anodes. This result fully verifies the significant effect of the tin-bismuth alloy coating of this invention in improving the cycle life and stability of zinc-nickel batteries.

[0059] Experimental data show that the tin-bismuth alloy coating prepared in Example 1 has a dense microstructure, low interfacial impedance and excellent cycling stability, verifying the effectiveness of the technical solution of the present invention.

[0060] Example 2: Preparation of a tin-bismuth alloy coating with 10 wt% bismuth content The difference between this embodiment and Embodiment 1 is that the concentration of bismuth nitrate in the plating solution is adjusted to 10 g / L, while the other steps are the same as in Embodiment 1. By adjusting the bismuth salt concentration, the bismuth content in the plating layer is controlled to be 10 wt%.

[0061] Performance test results show that the tin-bismuth alloy coating prepared in Example 2 also possesses a dense microstructure and excellent electrochemical performance. Compared with Example 1, the coating in Example 2 has higher hardness and further improved corrosion resistance, but the flexibility of the coating is slightly reduced. When the bismuth content is 10 wt%, the tin-bismuth alloy coating achieves a good balance between hardness, corrosion resistance, and flexibility, making it suitable for most zinc-nickel battery applications.

[0062] Example 3: Preparation of a tin-bismuth alloy coating with a bismuth content of 15 wt% The difference between this embodiment and Embodiment 1 is that the concentration of bismuth nitrate in the plating solution is adjusted to 15 g / L, while the other steps are the same as in Embodiment 1. By adjusting the bismuth salt concentration, the bismuth content in the plating layer is controlled to be 15 wt%.

[0063] Performance test results show that the tin-bismuth alloy coating prepared in Example 3 has the highest hardness and corrosion resistance, but the coating is more brittle and prone to cracking under high strain conditions. When the bismuth content is 15 wt%, the tin-bismuth alloy coating is suitable for applications requiring extremely high hardness and corrosion resistance but with relatively low strain.

[0064] Comparative Example 1: Pure Tin Plating The difference between this comparative example and Example 1 is that bismuth nitrate is not added to the plating solution; only 30 g / L stannous sulfate is used as the metal salt source. The other steps are the same as in Example 1. A pure tin-plated negative electrode current collector was prepared.

[0065] Performance test results show that pure tin plating has low hardness and is prone to plastic deformation during battery cycling. In the electroplating peeling test, for example... Figure 2 As shown, the overpotential of the pure tin coating is significantly higher than that of the tin-bismuth alloy coating in Example 1, indicating that the pure tin coating has a higher interfacial impedance and poorer electrochemical performance. In the full-cell cycle test, the capacity decay rate of the pure tin coating negative electrode is fast, and the capacity retention rate is only about 60% after 100 cycles, which is much lower than the more than 85% in Example 1.

[0066] Comparative Example 2: Pure Bismuth Coating The difference between this comparative example and Example 2 is that stannous sulfate is not added to the plating solution; only 10 g / L bismuth nitrate is used as the metal salt source. The other steps are the same as in Example 2. A pure bismuth-plated negative electrode current collector was prepared.

[0067] Performance test results show that although pure bismuth coatings have good corrosion resistance, they are brittle and prone to cracking and peeling during battery cycling. The conductivity of pure bismuth coatings is lower than that of tin-based coatings, and they have higher interfacial impedance. In full-cell cycle tests, the pure bismuth-coated negative electrode exhibits poor cycle performance and rapid capacity decay due to coating peeling and increased interfacial impedance.

[0068] Comparative Example 3: No coating This comparative example is a pure copper foil negative electrode current collector without electroplating treatment, which is directly coated with negative electrode slurry after only pretreatment to assemble the battery.

[0069] Performance test results show that the unplated pure copper foil negative electrode current collector is prone to oxidation and corrosion in alkaline electrolyte, forming a copper oxide layer on the surface, which leads to a sharp increase in interfacial impedance. In the full-cell cycle test, the unplated negative electrode has the worst cycle performance, with a capacity retention of only about 40% after 50 cycles, which is far lower than that of the tin-bismuth alloy plated negative electrodes in Examples 1-3.

[0070] Performance Comparison Summary A comparison of Examples 1-3 and Comparative Examples 1-3 shows that the tin-bismuth alloy coated negative electrode current collector of the present invention is significantly superior to the negative electrode current collectors with pure tin coating, pure bismuth coating, and no coating in terms of corrosion resistance, interfacial impedance, and cycle stability. When the bismuth content in the tin-bismuth alloy coating is controlled within the range of 5-15 wt%, an optimal balance can be achieved between hardness, corrosion resistance, and flexibility, significantly improving the cycle life and stability of zinc-nickel batteries.

[0071] Example 4: Preparation of silver-tin-bismuth alloy coating The difference between this embodiment and Example 2 is that 0.2 g / L of silver nitrate was added to the plating solution; the other steps were the same as in Example 2. A silver-containing tin-bismuth alloy coated negative electrode current collector was prepared, with a silver content of approximately 1 wt%.

[0072] Performance test results show that the resistivity of the silver-tin-bismuth alloy coating is significantly reduced, and the interfacial contact resistance is lower. In high-rate charge-discharge tests, the silver-tin-bismuth alloy coating anode exhibits lower polarization and a higher discharge plateau. In 1C and 2C rate discharge tests, the voltage drop of the silver-coated anode is less than 0.2V, while the voltage drop of the uncoated anode is greater than 0.5V, verifying the significant improvement in conductivity by silver.

[0073] Example 5: Preparation of Indium Tin Bismuth Alloy Coating The difference between this embodiment and Embodiment 2 is that 0.5 g / L of indium sulfate is added to the plating solution; the other steps are the same as in Embodiment 2. An indium-containing tin-bismuth alloy coated negative electrode current collector is prepared, with an indium content of approximately 1 wt%.

[0074] Performance test results show that the adhesion between the indium tin bismuth alloy coating and the substrate is significantly enhanced, with the adhesion strength between the coating and the substrate increasing by more than 50% in the peel test. Disassembly and inspection after battery cycling revealed that the tin bismuth alloy coating remained intact, verifying the coating's high adhesion. In long-term cycle testing, peeling of the indium tin bismuth alloy coating was significantly reduced, extending the cycle life.

[0075] Example 6: Preparation of a tin-bismuth alloy coating containing both silver and indium The difference between this embodiment and Embodiment 2 is that 0.2 g / L of silver nitrate and 0.5 g / L of indium sulfate are added to the plating solution. The other steps are the same as in Embodiment 2. A tin-bismuth alloy coated negative electrode current collector containing both silver and indium is prepared, with the silver content in the coating being approximately 1 wt% and the indium content being approximately 1 wt%.

[0076] Performance test results show that the tin-bismuth alloy coating containing both silver and indium exhibits the best overall performance, possessing both low resistivity and low interfacial impedance, as well as high adhesion and good mechanical properties. In full-cell cycle testing, the negative electrode of this coating demonstrates the best cycle stability, retaining over 90% of its capacity after 300 cycles, significantly outperforming other embodiments.

[0077] Comparison of performance test data between the examples and the comparative examples The current collectors prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests under the following conditions: symmetric cells at 1 mA / cm². 2 Electroplating peeling experiments were conducted at the specified current density, and the test results are shown in Table 1. The electroplating peeling time is defined as the time required for the symmetrical cell to cycle under the above test conditions until failure.

[0078]

[0079] As can be seen from the data in Table 1, the tin-bismuth alloy coated negative electrode current collector of the present invention has significant performance advantages compared with the prior art. Regarding overpotential, the overpotentials of Examples 1-3 are in the range of 50-51 mV, compared to 107.93 mV for the pure tin coating in Comparative Example 1, 110.34 mV for the pure bismuth coating in Comparative Example 2, and a high 130.40 mV for the uncoated pure copper foil in Comparative Example 3. The overpotential of the tin-bismuth alloy coating is reduced by approximately 53% compared to the pure tin coating and by approximately 61% compared to the uncoated coating, indicating that the passivation film and fine-grained structure formed by the tin-bismuth alloy significantly reduce electrochemical polarization and improve interfacial reaction kinetics.

[0080] Regarding the first-cycle coulombic efficiency, the coulombic efficiencies of Examples 1-3 ranged from 97.35% to 98.23%, while those of Comparative Examples 1-3 were only 85.37% to 90.21%. The coulombic efficiency of the tin-bismuth alloy coating increased by approximately 7-13 percentage points, indicating that the tin-bismuth alloy coating effectively suppressed the occurrence of side reactions and improved the reversibility of zinc deposition peeling. In terms of electroplating peeling time, the peeling time of Examples 1-3 was 900-1000 hours, while that of Comparative Examples 1-3 was only 400-500 hours. The cycle life of the tin-bismuth alloy coating increased by more than two times, verifying the mechanism by which bismuth grain boundary segregation refines grains and improves coating density and mechanical strength.

[0081] It is worth noting that the bismuth content in Example 1 was 5%, in Example 2 it was 10%, and in Example 3 it was 15%. The performance of these three examples was similar, indicating that the bismuth content within the range of 5-15% has little impact on performance, and all three achieve excellent results. In summary, the tin-bismuth alloy coating significantly outperforms pure tin coating, pure bismuth coating, and no coating in the three key indicators of overpotential, coulombic efficiency, and cycle life, fully verifying the effectiveness and advancement of the technical solution of this invention.

[0082] Effect of silver and indium addition on coating performance To further evaluate the effect of silver and indium addition on coating performance, corrosion tests and electrochemical impedance tests were conducted on tin-bismuth alloy coatings with different addition amounts in alkaline electrolyte. The test results are shown in Table 2.

[0083]

[0084] Table 2 shows that the amounts of silver and indium added have a significant impact on the coating performance. Regarding the limiting loss rate, the limiting loss rate of the control group was 12.3 mg / cm³. 2 After adding 0.1% Ag, the concentration decreased to 9.8 mg / cm³. 2 When the added amount reaches 0.5% Ag, the limit loss rate drops to 6.2 mg / cm³. 2 After adding 0.1% In, the concentration decreased to 9.3 mg / cm³. 2 After adding 0.5% In, the concentration decreased to 5.9 mg / cm³. 2 Adding a combined 1% concentration of both (0.5% Ag and 0.5% In) reduced the maximum loss rate to 3.1 mg / cm³. 2 The corrosion rate decreased by 75%, indicating that the synergistic effect of silver and indium significantly improved the corrosion resistance of the coating. Regarding the corrosion rate, the control group had a corrosion rate of 8.7 μm / year. When both silver and indium were added at a combined 1% content (0.5% Ag and 0.5% In), the corrosion rate decreased to 2.1 μm / year, a reduction of 76%. This demonstrates that the dense passivation film formed by the addition of silver and indium effectively blocked the electrolyte from eroding the coating.

[0085] Regarding changes in surface morphology, as the amount of silver and indium added increases, the coating surface undergoes an evolution process from obvious pitting to slight pitting, local passivation, uniform passivation film, and dense passivation layer, indicating that the increase in silver and indium concentration promotes the improvement of the continuity and density of the passivation film.

[0086] Regarding electrochemical impedance, the control group had an electrochemical impedance of 1.2 × 10⁻⁶. 5 Ω·cm 2 When 0.5% Ag was added, the electrochemical impedance decreased to 8.2 × 10⁻⁶. 3 Ω·cm 2 The interfacial activity is improved and the contact resistance is reduced; when the combined addition of both is 1% (0.5% Ag and 0.5% In), the electrochemical impedance rises back to 1.5 × 10⁻⁶. 4 Ω·cm 2 Although the impedance increases at this point, the protective effect of the passivation film is significantly enhanced. Considering both corrosion resistance and conductivity, 1% Ag and In is the optimal addition amount, balancing the long-term stability and electrochemical performance of the coating.

[0087] It is understandable that in some implementations, different tin salts (such as stannous chloride, stannous fluoroborate), bismuth salts (such as bismuth chloride, bismuth sulfate), complexing agents (such as potassium sodium tartrate, disodium EDTA), etc., can also be used. As long as the co-deposition of tin-bismuth alloy can be achieved, similar technical effects can be achieved.

[0088] In some implementations, the electroplating parameters can be adjusted according to actual needs. For example, the current density can be selected as 1 A / dm³. 2 2A / dm 2 3A / dm 2 4A / dm 2 Or 5A / dm 2 The electroplating temperature can be selected as 20℃, 30℃, 40℃ or 50℃; the electroplating time can be adjusted within the range of 10-60 minutes according to the required coating thickness. The annealing temperature can be selected as 100℃, 150℃ or 200℃, the annealing time can be selected as 30 minutes, 40 minutes or 60 minutes, and the inert gas can be nitrogen or argon.

[0089] In some embodiments, the alkaline degreasing solution can employ different formulations, such as sodium hydroxide solution, sodium carbonate solution, potassium carbonate solution, or a compound alkaline degreasing agent. The degreasing temperature can be selected as 60°C, 70°C, or 80°C, and the degreasing time can be selected as 5 minutes, 7 minutes, or 10 minutes. The pickling solution can be sulfuric acid of different concentrations (e.g., 5%, 7%, or 10%), or other acidic solutions such as hydrochloric acid or nitric acid. The pickling time can be selected as 30 seconds, 45 seconds, or 60 seconds.

[0090] In some embodiments, the tin-bismuth alloy coated negative electrode current collector of the present invention can also be applied to other alkaline secondary batteries, such as nickel-cadmium batteries, nickel-metal hydride batteries, zinc-manganese batteries, etc., which can significantly improve the corrosion resistance and cycle stability of the battery.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A zinc-nickel battery negative electrode current collector, characterized in that, include: Copper-based or nickel-based substrate; An electroplated layer is disposed on the surface of the copper substrate or nickel substrate; The electroplated layer contains a tin-bismuth alloy, wherein the bismuth content in the tin-bismuth alloy is 5-15 wt%, and the balance is tin.

2. The zinc-nickel battery negative electrode current collector according to claim 1, characterized in that, The electroplated layer also contains 0.1-2 wt% silver.

3. The zinc-nickel battery negative electrode current collector according to claim 1, characterized in that, The electroplated layer also contains 0.1-2 wt% indium.

4. The zinc-nickel battery negative electrode current collector according to claim 1, characterized in that, The electroplated layer contains 0.1-2 wt% silver and 0.1-2 wt% indium.

5. A tin-bismuth alloy electroplating solution, using deionized water as a solvent, characterized in that, Include: Tin salt 20-40g / L; Bismuth salt 3-15 g / L; Citrate complexing agents 60-100 g / L; Polyethylene glycol 1-3 g / L; The pH value of the plating solution is 3-6.

6. The tin-bismuth alloy plating solution according to claim 5, characterized in that, The electroplating solution also contains 0.05-0.5 g / L of silver salt.

7. The tin-bismuth alloy plating solution according to claim 5 or 6, characterized in that, The electroplating solution also contains 0.1-1 g / L of indium salt.

8. A method for preparing a zinc-nickel battery negative electrode current collector, characterized in that, Includes the following steps: Pretreatment steps: Treat the copper or nickel substrate in an alkaline degreasing solution at a temperature of 60-80℃ for 5-10 minutes, and then pickle it in a 5-10% sulfuric acid solution at room temperature for 30-60 seconds. Electroplating step: The pretreated substrate is placed in the electroplating solution according to any one of claims 5-7, and the plating is carried out at a current density of 1-5 A / dm³. 2 Electroplating is performed at a temperature of 20-50℃ and a pH of 3-6 for 10-60 minutes to form a tin-bismuth alloy electroplating layer with a thickness of 1-10μm. Post-processing steps: Wash and dry the electroplated collector with water, and then anneal it at 100-200℃ for 30-60 minutes in an inert gas atmosphere.

9. The preparation method according to claim 8, characterized in that, The current density in the electroplating step is 1-2 A / dm. 2 This promotes the co-deposition of amorphous Sn-Bi, forming a fine-grained structure with a grain size of 1-5 μm.

10. The preparation method according to claim 8, characterized in that, The annealing process in the post-processing step is carried out at 150°C for 40 minutes in an inert gas atmosphere, which causes bismuth to form a liquid phase film at the grain boundaries of the tin-bismuth alloy, promoting grain boundary migration and recrystallization, thereby releasing internal stress.

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