Negative plate for nickel-carbon battery as well as preparation method and application of negative plate

Abstract

The invention relates to the technical field of nickel-carbon batteries, in particular to a negative plate for a nickel-carbon battery and a preparation method and application thereof.The preparation method comprises the following steps that A, a porous current collector is prepared, carbon nanotubes are sputtered to the surface of the porous current collector through the magnetron sputtering technology, the carbon nanotubes are made to permeate into the porous current collector, and the porous current collector is prepared; the porous current collector permeated with the carbon nanotubes is obtained; and B, infiltrating negative electrode slurry into the porous current collector infiltrated with the carbon nanotubes by using a spraying process, compounding the negative electrode slurry with the pre-infiltrated carbon nanotubes, and drying to form a composite electrode coating, thereby obtaining the negative plate for the nickel-carbon battery. The preparation method of the negative plate for the nickel-carbon battery, provided by the invention, is simple and high in operability, and is beneficial to improving the energy density, the conductivity and the rate capability on the premise of ensuring the structural stability and the cycle life.

Description

Technical Field

[0001] This invention relates to the field of nickel-carbon battery technology, and in particular to a negative electrode sheet for nickel-carbon batteries, its preparation method, and its application. Background Technology

[0002] With the global energy structure transformation and the deepening of the "dual carbon" strategy, higher performance requirements are being placed on batteries. Among many energy storage devices, nickel-carbon batteries, as a typical hybrid supercapacitor, are widely used in smart grids, rail transportation, and industrial energy conservation due to their excellent temperature adaptability, extremely high safety, and environmental friendliness.

[0003] As a crucial component of nickel-carbon batteries, the negative electrode provides power density and cycle life through the double-layer capacitance effect. Specifically, the conventional method for preparing a negative electrode involves coating a negative electrode slurry onto the surface of a porous current collector (such as nickel foam), drying it to form an electrode coating, and thus obtaining the negative electrode. Existing negative electrode slurries commonly use activated carbon with a high specific surface area as the main active material. In this system, activated carbon achieves energy storage and release through the reversible physical adsorption / desorption of ions in the electrolyte. This process is characterized by fast kinetics and low intrinsic decay, providing high power density and potentially long cycle life for nickel-carbon batteries. However, with increasingly demanding application scenarios, the inherent defects of this traditional technology system are becoming increasingly apparent, limiting the full realization of its performance potential, as follows: First, the energy density bottleneck is significant. In this traditional system, the energy storage of activated carbon only occurs at the two-dimensional interface between the activated carbon particles and the electrolyte (i.e., the surface physical adsorption mechanism relied upon by activated carbon). Regardless of the specific surface area of ​​the activated carbon, the charge can only be statically adsorbed in a thin layer at the atomic level, and energy storage cannot be carried out using the internal space of the three-dimensional bulk phase of the activated carbon; only a limited double layer can be formed. In contrast, traditional batteries (such as graphite anode sheets) are based on intercalation reactions, where lithium ions can be intercalated and stored within the lattice of the entire bulk phase of the active material, thus fully utilizing the three-dimensional volume of the material for energy storage, making its energy storage sites and effective area far exceed surface physical adsorption. These differences result in the volumetric and gravimetric energy densities of anode sheets prepared using activated carbon being significantly lower than those of anode sheets in traditional batteries, thus limiting the improvement of the energy density of nickel-carbon batteries.

[0004] Secondly, insufficient electrode structural stability restricts the achievement of cycle potential and high-rate performance. Traditional coating processes result in a significant physical interface between the dried electrode coating and the porous current collector. Although the industry has made improvements by optimizing binders or increasing compaction density, the problem of weak interfacial adhesion has not been fundamentally solved. This leads to the active material in the electrode coating and the porous current collector being primarily physically attached, lacking strong chemical bonds or a three-dimensional interpenetrating structure, resulting in poor structural stability of the negative electrode. During long-term high-current cycling, repeated volume changes of the active material easily lead to interfacial failure, causing active material detachment and irreversible capacity decay, severely affecting the cycle life of the negative electrode structure. Furthermore, while weak adhesion itself does not directly affect conductivity, under high-current cycling (rate charging and discharging itself also exacerbates volume changes), the formation of interfacial microcracks drastically increases interfacial contact resistance, and may even cause some active material to completely fail, leading to the destruction of the effective conductive network and thus a decrease in rate performance.

[0005] Third, insufficient intrinsic conductivity limits rate performance. Activated carbon itself has poor conductivity, and even with the addition of conventional conductive agents, the constructed conductive network is still insufficient during high-rate charge and discharge, leading to increased electrode internal resistance, intensified polarization, and significant thermal effects, ultimately limiting the battery's rate performance.

[0006] In summary, existing nickel-carbon battery anode sheets suffer from low energy density, poor electrode structure stability, and insufficient intrinsic conductivity, making it difficult to simultaneously and fully leverage the combined advantages of high energy density, high power density, and ultra-long cycle life. Therefore, there is an urgent need to develop a nickel-carbon battery anode sheet that can improve energy density, conductivity, and rate performance while ensuring structural stability and cycle life. Summary of the Invention

[0007] One of the objectives of this invention is to provide a method for preparing a negative electrode sheet for nickel-carbon batteries. This method is simple, easy to operate, and helps to improve energy density, conductivity, and rate performance while ensuring structural stability and cycle life, thereby overcoming the shortcomings of the prior art.

[0008] The second objective of this invention is to provide a negative electrode sheet for nickel-carbon batteries prepared by the above method, which is beneficial to improve energy density, conductivity and rate performance while ensuring structural stability and cycle life.

[0009] The third objective of this invention is to propose an application of a negative electrode sheet for nickel-carbon batteries in the preparation of nickel-carbon batteries, so that the nickel-carbon batteries prepared using the above-mentioned negative electrode sheet for nickel-carbon batteries have high energy density, conductivity and rate performance while ensuring structural stability and cycle life.

[0010] To achieve this objective, the present invention adopts the following technical solution: A method for preparing a negative electrode sheet for a nickel-carbon battery includes the following steps: A. Prepare a porous current collector, and use magnetron sputtering technology to sputter carbon nanotubes onto the surface of the porous current collector, allowing the carbon nanotubes to penetrate into the interior of the porous current collector, thereby obtaining a porous current collector permeated with carbon nanotubes; wherein, the penetration depth of the carbon nanotubes is 1 / 3 to 1 / 2 of the thickness of the porous current collector; B. Using a spraying process, the negative electrode slurry is penetrated into the interior of the porous current collector permeated with carbon nanotubes, and combined with the pre-permeated carbon nanotubes. After drying, a composite electrode coating is formed to obtain a negative electrode sheet for nickel-carbon batteries. Wherein, the penetration depth of the negative electrode slurry is the same as the thickness of the porous current collector; The negative electrode slurry comprises the following raw materials: hydrogen storage alloy, activated carbon powder, sodium carboxymethyl cellulose, yttrium oxide, styrene-butadiene rubber latex, and water.

[0011] Further, in step A, the method of the magnetron sputtering technology is as follows: inert gas is filled into the vacuum cavity of the magnetron sputtering equipment, and an electric field is applied to ionize the inert gas to generate plasma; The plasma bombards the carbon target under the acceleration of the electric field, causing carbon atoms in the carbon target to be sputtered onto the surface of the porous current collector and carbon nanotubes to penetrate into the interior of the porous current collector.

[0012] Furthermore, in step A, the areal density of the porous current collector is 400–450 g / m³. 2 The pore density is 100–150 pores / m³. 2 .

[0013] Further, in step B, the negative electrode slurry comprises the following raw materials by mass percentage: 10-15% hydrogen storage alloy, 0.2-0.3% activated carbon powder, 0.1-0.2% sodium carboxymethyl cellulose, 0.8-1% yttrium oxide, 1-1.5% styrene-butadiene rubber latex, and 82-87% water.

[0014] Furthermore, in step B, the hydrogen storage alloy is an AB5 type nickel-based alloy; The hydrogen storage alloy comprises the following components by mass percentage: Mn 31.06–31.86%, La 24.63–25.63%, and Ce 3.98–4.98%, with the remainder being Ni.

[0015] Further, in step B, the styrene-butadiene rubber content in the styrene-butadiene rubber emulsion is 40-70% by mass percentage.

[0016] Further, in step B, the method for preparing the negative electrode slurry is as follows: The alloy nickel powder, activated carbon powder, sodium carboxymethyl cellulose, yttrium oxide, and 30% of the formula amount of water are mixed evenly to obtain a mixture; Add the formulated amount of styrene-butadiene rubber latex and the remaining formulated amount of water to the mixture, and mix evenly to obtain the negative electrode slurry.

[0017] Furthermore, in step B, the drying temperature is 90–115°C.

[0018] A negative electrode sheet for nickel-carbon batteries is prepared using the above-described method for preparing a negative electrode sheet for nickel-carbon batteries.

[0019] An application of a negative electrode sheet for nickel-carbon batteries in the preparation of nickel-carbon batteries, wherein the above-mentioned negative electrode sheet for nickel-carbon batteries is used, and the application method is as follows: Using a nickel-carbon battery negative electrode sheet as the negative electrode and a nickel oxide electrode as the positive electrode, the negative electrode, separator and positive electrode are assembled sequentially in an argon-filled glove box, and electrolyte is injected. After sealing, the battery is left to stand at room temperature for 10-12 hours to obtain a nickel-carbon battery.

[0020] The technical solution provided by this invention may include the following beneficial effects: 1. This technical solution utilizes magnetron sputtering technology to infiltrate carbon nanotube precursor particles into a porous current collector in a high-energy form, thereby increasing the penetration depth (e.g., ... Figure 1 (m in the figure represents 1 / 3 to 1 / 2 of the thickness of the porous current collector.) During this process, carbon nanotube precursor particles are "pinned" and grow in situ within the micropores and uneven structure of the porous current collector, forming a strong three-dimensional mechanically interlocked network between the carbon nanotubes and the porous current collector. Simultaneously, high-energy impacts induce close interactions between the carbon nanotube precursor particles and the atoms on the surface of the porous current collector at the interface, leading to metal-carbon chemical bonds. This superimposed chemical bonding force on top of the mechanical anchoring. This interface bonding method, combining mechanical anchoring and chemical bonding, effectively resists repeated physical stress and chemical impacts during cycling, effectively preventing carbon nanotubes from detaching from the porous current collector under the physical and chemical stresses of cyclic charging and discharging. This ensures the structural stability of the negative electrode structure and thus extends its cycle life.

[0021] 2. Traditional negative electrode structures rely on the surface physical adsorption mechanism of activated carbon, resulting in limited energy density. This technical solution, however, constructs a composite active material system composed of carbon nanotubes, activated carbon, and a hydrogen storage alloy by first infiltrating carbon nanotubes and then infiltrating the negative electrode slurry. Furthermore, this system not only limits the infiltration depth of the carbon nanotubes to 1 / 3 to 1 / 2 of the thickness of the porous current collector, but also limits the infiltration depth of the negative electrode slurry (e.g., ...). Figure 1The thickness of the alloy (as shown in n) is the same as that of the porous current collector, effectively increasing the total content of active material, which is beneficial for increasing the content of active material and thus improving energy density. More importantly, it introduces the bulk electrochemical energy storage mechanism of the hydrogen storage alloy. The hydrogen storage alloy achieves energy storage through the insertion / extraction of hydrogen atoms (forming / decomposing metal hydrides). Its theoretical mass specific capacity and volume specific capacity far exceed those of activated carbon that relies solely on surface double-layer adsorption, which is beneficial for breaking through the energy density limit of traditional negative electrode sheets, thereby further improving energy density.

[0022] 3. This technical solution pre-constructs a highly conductive, seamlessly connected three-dimensional network structure composed of one-dimensional carbon nanotubes extending from the surface to 1 / 3 to 1 / 2 of the internal position within the porous current collector using magnetron sputtering technology. This network structure not only significantly improves the conductive surface area and efficiency of the porous current collector, but also provides an extremely short electron transport path for the filled hydrogen storage alloy particles. This allows electrons to directly and quickly reach each hydrogen storage alloy particle from the porous current collector through the three-dimensional network structure, significantly reducing the ohmic resistance of the entire negative electrode and thus improving conductivity. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the permeation of carbon nanotubes and negative electrode slurry according to the present invention.

[0024] Among them, porous current collector 1, carbon nanotubes 2, and negative electrode slurry 3. Detailed Implementation

[0025] This technical solution provides a method for preparing a negative electrode sheet for nickel-carbon batteries, including the following steps: A. Prepare a porous current collector, and use magnetron sputtering technology to sputter carbon nanotubes onto the surface of the porous current collector, allowing the carbon nanotubes to penetrate into the interior of the porous current collector, thereby obtaining a porous current collector permeated with carbon nanotubes; wherein, the penetration depth of the carbon nanotubes is 1 / 3 to 1 / 2 of the thickness of the porous current collector; B. Using a spraying process, the negative electrode slurry is penetrated into the interior of the porous current collector permeated with carbon nanotubes, and combined with the pre-permeated carbon nanotubes. After drying, a composite electrode coating is formed to obtain a negative electrode sheet for nickel-carbon batteries. Wherein, the penetration depth of the negative electrode slurry is the same as the thickness of the porous current collector; The negative electrode slurry comprises the following raw materials: hydrogen storage alloy, activated carbon powder, sodium carboxymethyl cellulose, yttrium oxide, styrene-butadiene rubber latex, and water.

[0026] To address the common technical problems of poor stability, short cycle life, and insufficient energy density, conductivity, and rate performance in existing nickel-carbon battery anode sheets, this technical solution proposes a method for preparing anode sheets for nickel-carbon batteries, including A (permeated carbon nanotubes) and B (permeated anode slurry). By optimizing the preparation method and raw materials, it is beneficial to improve energy density, conductivity, and rate performance while ensuring stability and cycle life, so as to meet practical application requirements.

[0027] Specifically, this technical solution utilizes magnetron sputtering technology to infiltrate carbon nanotube precursor particles into a porous current collector in a high-energy form, thereby increasing the penetration depth (e.g., Figure 1 (m in the figure represents 1 / 3 to 1 / 2 of the thickness of the porous current collector.) During this process, carbon nanotube precursor particles are "pinned" and grow in situ within the micropores and uneven structure of the porous current collector, forming a strong three-dimensional mechanically interlocked network between the carbon nanotubes and the porous current collector. Simultaneously, high-energy impacts induce close interactions between the carbon nanotube precursor particles and the atoms on the surface of the porous current collector at the interface, leading to metal-carbon chemical bonds. This superimposed chemical bonding force on top of the mechanical anchoring. This interface bonding method, combining mechanical anchoring and chemical bonding, effectively resists repeated physical stress and chemical impacts during cycling, effectively preventing carbon nanotubes from detaching from the porous current collector under the physical and chemical stresses of cyclic charging and discharging. This ensures the structural stability of the negative electrode structure and thus extends its cycle life.

[0028] Furthermore, the spraying process utilizes high-pressure gas to atomize the negative electrode slurry into tiny droplets, which penetrate and fill the interior of the porous current collector. This means the slurry droplets not only fill the remaining spaces in the porous current collector where carbon nanotubes haven't penetrated, but also fill the voids in the three-dimensional network structure formed by the carbon nanotubes, forming an integral whole with the network. Based on the strong bond between the carbon nanotubes and the porous current collector, the negative electrode slurry, after drying, also forms a stable interfacial connection with the porous current collector through the three-dimensional network structure. Simultaneously, the sodium carboxymethyl cellulose and styrene-butadiene rubber contained in the slurry act as binders after curing, further enhancing the interfacial bonding strength and ensuring the structural stability of the negative electrode sheet, thereby extending its cycle life.

[0029] Furthermore, the composite electrode coating in this technical solution essentially comprises carbon nanotubes and a solid matrix formed after the negative electrode slurry is dried. Because carbon nanotubes possess excellent flexibility and mechanical strength, they can effectively buffer and absorb the volume expansion and contraction of the hydrogen storage alloy in the solid matrix during hydrogen absorption / desorption during charging and discharging. This significantly inhibits the micronization and shedding of active materials (such as the hydrogen storage alloy), maintains the integrity of the negative electrode structure, and thus extends the battery's cycle life.

[0030] Secondly, traditional negative electrode structures rely on the surface physical adsorption mechanism of activated carbon, resulting in limited energy density. In contrast, this technical solution constructs a composite active material system composed of carbon nanotubes, activated carbon, and a hydrogen storage alloy by first infiltrating carbon nanotubes and then infiltrating the negative electrode slurry. Furthermore, this system not only limits the infiltration depth of the carbon nanotubes to 1 / 3 to 1 / 2 of the thickness of the porous current collector, but also limits the infiltration depth of the negative electrode slurry (e.g., ...). Figure 1 The thickness of the alloy (as shown in n) is the same as that of the porous current collector, effectively increasing the total content of active material, which is beneficial for increasing the content of active material and thus improving energy density. More importantly, it introduces the bulk electrochemical energy storage mechanism of the hydrogen storage alloy. The hydrogen storage alloy achieves energy storage through the insertion / extraction of hydrogen atoms (forming / decomposing metal hydrides). Its theoretical mass specific capacity and volume specific capacity far exceed those of activated carbon that relies solely on surface double-layer adsorption, which is beneficial for breaking through the energy density limit of traditional negative electrode sheets, thereby further improving energy density.

[0031] Furthermore, this technical solution pre-constructs a highly conductive, seamlessly connected three-dimensional network structure composed of one-dimensional carbon nanotubes extending from the surface to 1 / 3 to 1 / 2 of the internal position within the porous current collector using magnetron sputtering technology. This network structure not only significantly improves the conductive surface area and efficiency of the porous current collector, but also provides an extremely short electron transport path for the filled hydrogen storage alloy particles. This allows electrons to directly and rapidly reach each hydrogen storage alloy particle from the porous current collector through the three-dimensional network structure, significantly reducing the ohmic resistance of the entire negative electrode and thus improving conductivity.

[0032] Finally, rate performance depends on the transport rates of ions and electrons within the electrode. As mentioned earlier, carbon nanotubes, with their superior one-dimensional nanostructure and intrinsic conductivity, construct an efficient, stable, and multi-dimensional conductive network within the negative electrode, greatly promoting the rapid transport of electrons and ions. Simultaneously, the porous structure of the porous current collector and the inherent porous structure of the carbon nanotube network ensure that, after the negative electrode slurry is filled, abundant and interconnected electrolyte wetting channels remain within the negative electrode, guaranteeing rapid ion migration. Furthermore, yttrium trioxide (Y₂O₃) in the negative electrode slurry, as a functional additive, effectively improves the surface properties of the hydrogen storage alloy and promotes hydrogen atom diffusion, thereby further enhancing reaction kinetics. Additionally, the strong bond between the composite electrode coating and the porous current collector prevents the formation of interfacial microcracks during high-current cycling, which would drastically increase interfacial contact resistance and even cause some active materials to completely lose connectivity, leading to the destruction of the effective conductive network and a decrease in rate performance. This helps ensure optimal rate performance.

[0033] In summary, this technical solution improves rate performance by constructing channels that facilitate ion and electron transport.

[0034] It should be noted that the porous current collector can be nickel foam, and the specific type is not limited here.

[0035] To further explain, in step A, the method of the magnetron sputtering technology is as follows: inert gas is filled into the vacuum cavity of the magnetron sputtering equipment, and an electric field is applied to ionize the inert gas to generate plasma; The plasma bombards the carbon target under the acceleration of the electric field, causing carbon atoms in the carbon target to be sputtered onto the surface of the porous current collector and carbon nanotubes to penetrate into the interior of the porous current collector.

[0036] This technical solution optimizes magnetron sputtering technology by bombarding a carbon target with plasma, causing carbon atoms in the target to be sputtered in gaseous form and deeply penetrate into the pores of the porous current collector. This achieves uniform penetration from the surface to the interior, avoiding pore blockage that may occur with liquid coating processes. Furthermore, the resulting carbon nanotubes exhibit high bonding strength with the porous current collector substrate, thus ensuring the performance of the obtained negative electrode. It should be noted that the inert gas can be nitrogen, and the specific type is not limited here.

[0037] Preferably, the carbon target is either a graphite target or a glass carbon target.

[0038] To further clarify, in step A, the areal density of the porous current collector is 400–450 g / m³. 2 The pore density is 100–150 pores / m³. 2 .

[0039] If the surface density of a porous current collector is high, its conductivity, mechanical properties and load-bearing capacity are all high, but it is easy to increase the cost of raw materials; if the surface density of a porous current collector is low, it has the advantages of low cost, high porosity and large specific surface area, but it will also reduce conductivity and poor mechanical properties.

[0040] Furthermore, if the pore density of a porous current collector is high, it will be beneficial to improve the loading capacity and ion transport performance, but it has defects such as low mechanical strength and low conductivity; if the pore density of a weakly porous current collector is low, it will be beneficial to improve the mechanical strength and conductivity, but it has defects such as limited loading of active material and hindered ion transport.

[0041] Therefore, by limiting the areal density and pore density of the porous current collector, this technical solution can improve the load capacity and conductivity while reducing raw material costs, thereby ensuring the performance of the obtained negative electrode sheet.

[0042] To further explain, in step B, the negative electrode slurry comprises the following raw materials by mass percentage: 10-15% hydrogen storage alloy, 0.2-0.3% activated carbon powder, 0.1-0.2% sodium carboxymethyl cellulose, 0.8-1% yttrium oxide, 1-1.5% styrene-butadiene rubber latex, and 82-87% water.

[0043] This technical solution limits the amount of each raw material added to the negative electrode slurry formulation, which helps each raw material to exert its performance advantages as much as possible, thereby ensuring the performance of the obtained negative electrode sheet.

[0044] To further clarify, in step B, the hydrogen storage alloy is an AB5 type nickel-based alloy; The hydrogen storage alloy comprises the following components by mass percentage: Mn 31.06–31.86%, La 24.63–25.63%, and Ce 3.98–4.98%, with the remainder being Ni.

[0045] AB5-type nickel-based alloys are intermetallic compounds with a specific CaCu5-type crystal structure. As active materials, they achieve energy storage and release through the reversible formation / decomposition of metal hydrides, thus facilitating the achievement of high energy density. It should be noted that in AB5-type nickel-based alloys, A represents a mixture of one or more rare earth elements (such as La, Ce, Nd, and Pr); B represents an elemental combination dominated by nickel and mixed with other transition metals (such as Co, Mn, and Al); and 5 represents the atomic ratio of A to B elements as 1:5, meaning one rare earth atom corresponds to five (nickel-based) transition metal atoms. This fixed atomic ratio constitutes its specific CaCu5-type hexagonal crystal structure.

[0046] Furthermore, calculated by mass percentage, the hydrogen storage alloy comprises the following components: Mn 31.06–31.86%, La 24.63–25.63%, and Ce 3.98–4.98%, with the remainder being Ni. The high Mn content effectively expands the cell volume of the hydrogen storage alloy, reduces the formation enthalpy of metal hydrides and the equilibrium hydrogen pressure, thereby significantly improving the specific capacity of the hydrogen storage alloy. La, as the main A-site element, with a content of 24.63–25.63%, not only ensures a good thermodynamic basis and high initial activation ability for the hydrogen storage alloy, but also helps to maintain high mechanical strength while ensuring capacity, avoiding excessive lattice distortion that leads to rapid cycle life decay. The introduction of Ce significantly improves the electrocatalytic activity of the alloy surface, promotes the adsorption and recombination of hydrogen atoms, and thus greatly enhances the rate performance of the electrode. Furthermore, the specific ratio of cerium to lanthanum helps enhance the oxidation and corrosion resistance of hydrogen storage alloys under high-temperature conditions (e.g., 45-60℃), effectively suppressing high-temperature self-discharge and capacity decay. Additionally, limiting the amount of Ce and lanthanum (La) added also enhances the oxidation and corrosion resistance of hydrogen storage alloys under high-temperature conditions (e.g., 45-60℃), effectively suppressing high-temperature self-discharge and capacity decay.

[0047] In summary, this technical solution optimizes the composition and content of the hydrogen storage alloy, enabling it to achieve a comprehensive balance of capacity, power, and high-temperature performance without relying on the amount of expensive Co. This breaks the traditional bias that AB5 alloys must add a large amount of Co to obtain good performance, fundamentally reducing raw material costs and avoiding the adverse effects of Co content fluctuations on performance.

[0048] To further explain, in step B, the styrene-butadiene rubber content in the styrene-butadiene rubber emulsion is 40-70% by mass percentage.

[0049] This technical solution, by limiting the content of styrene-butadiene rubber in the styrene-butadiene rubber emulsion, helps to ensure the performance of the obtained negative electrode sheet.

[0050] To further explain, in step B, the method for preparing the negative electrode slurry is as follows: The alloy nickel powder, activated carbon powder, sodium carboxymethyl cellulose, yttrium oxide, and 30% of the formula amount of water are mixed evenly to obtain a mixture; Add the formulated amount of styrene-butadiene rubber latex and the remaining formulated amount of water to the mixture, and mix evenly to obtain the negative electrode slurry.

[0051] This technical solution optimizes the preparation method of the negative electrode slurry, which helps to ensure the uniform mixing of the components in the negative electrode slurry, thereby ensuring the performance of the obtained negative electrode slurry.

[0052] To further explain, in step B, the drying temperature is 90–115°C.

[0053] This technology, by limiting the drying temperature, prevents the highly active hydrogen storage alloy from spontaneously combusting, thus allowing the hydrogen storage alloy to exert its active material function.

[0054] A negative electrode sheet for nickel-carbon batteries is prepared using the above-described method for preparing a negative electrode sheet for nickel-carbon batteries.

[0055] This solution also proposes a method for preparing a nickel-carbon battery negative electrode sheet, which is beneficial to improve energy density, conductivity and rate performance while ensuring structural stability and cycle life.

[0056] An application of a negative electrode sheet for nickel-carbon batteries in the preparation of nickel-carbon batteries, wherein the above-mentioned negative electrode sheet for nickel-carbon batteries is used, and the application method is as follows: Using a nickel-carbon battery negative electrode sheet as the negative electrode and a nickel oxide electrode as the positive electrode, the negative electrode, separator and positive electrode are assembled sequentially in an argon-filled glove box, and electrolyte is injected. After sealing, the battery is left to stand at room temperature for 10-12 hours to obtain a nickel-carbon battery.

[0057] This technical solution also proposes the application of a negative electrode sheet for nickel-carbon batteries in the preparation of nickel-carbon batteries, so that the nickel-carbon batteries prepared using the above-mentioned negative electrode sheet for nickel-carbon batteries have high energy density, conductivity and rate performance while ensuring structural stability and cycle life.

[0058] It should be noted that the diaphragm can be a polyacrylamide membrane or a cellulose membrane; the specific type is not limited here. The electrolyte can be a potassium hydroxide solution; the specific type is not limited here.

[0059] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0060] Example 1 A. Prepare a porous current collector. Nitrogen gas is introduced into the vacuum chamber of a magnetron sputtering device, and an electric field is applied to ionize the nitrogen gas and generate plasma. The plasma, accelerated by the electric field, bombards a graphite target, causing carbon atoms from the graphite target to sputter onto the surface of the porous current collector and allowing carbon nanotubes to penetrate into the interior of the porous current collector, resulting in a porous current collector permeated with carbon nanotubes. The penetration height of the carbon nanotubes is half the internal height of the porous current collector. The porous current collector is nickel foam, and its surface density is 420 g / m³. 2 The pore density is 130 pores / m³. 2 ; B. A negative electrode slurry is penetrated into a porous current collector permeated with carbon nanotubes using a spray coating process, and then combined with the pre-permeated carbon nanotubes. After drying at 100°C, a composite electrode coating is formed, resulting in a negative electrode sheet for nickel-carbon batteries. The penetration depth of the negative electrode slurry is the same as the thickness of the porous current collector. The negative electrode slurry comprises the following raw materials: 12% hydrogen storage alloy, 0.2% activated carbon powder, 0.1% sodium carboxymethyl cellulose, 1% yttrium oxide, 1.2% styrene-butadiene rubber emulsion, and 85.5% water. The hydrogen storage alloy is an AB5 type nickel-based alloy. Calculated by mass percentage, the hydrogen storage alloy comprises the following components: 31.06% Mn, 24.73% La, 4.02% Ce, and Ni. 40.19%; Calculated by mass percentage, the content of styrene-butadiene rubber in the styrene-butadiene rubber latex is 60%; The preparation method of the negative electrode slurry is as follows: Mix the alloy nickel powder, activated carbon powder, sodium carboxymethyl cellulose, yttrium oxide and 30% of the formula amount of water evenly to obtain a mixture; add the styrene-butadiene rubber latex and the remaining formula amount of water to the mixture, mix evenly to obtain the negative electrode slurry.

[0061] Example 2 A. Prepare a porous current collector. Nitrogen gas is introduced into the vacuum chamber of a magnetron sputtering device, and an electric field is applied to ionize the nitrogen gas and generate plasma. The plasma, accelerated by the electric field, bombards a graphite target, causing carbon atoms from the graphite target to sputter onto the surface of the porous current collector and allowing carbon nanotubes to penetrate into the interior of the porous current collector, resulting in a porous current collector permeated with carbon nanotubes. The penetration height of the carbon nanotubes is 1 / 3 of the internal height of the porous current collector. The porous current collector is nickel foam, and its areal density is 400 g / m³. 2 The pore density is 100 pores / m³ 2 ; B. A negative electrode slurry is penetrated into a porous current collector permeated with carbon nanotubes using a spray coating process, and then combined with the pre-permeated carbon nanotubes. After drying at 90°C, a composite electrode coating is formed, resulting in a negative electrode sheet for nickel-carbon batteries. The penetration depth of the negative electrode slurry is the same as the thickness of the porous current collector. The negative electrode slurry comprises the following raw materials: 15% hydrogen storage alloy, 0.3% activated carbon powder, 0.2% sodium carboxymethyl cellulose, 0.8% yttrium oxide, 1% styrene-butadiene rubber emulsion, and 82.7% water. The hydrogen storage alloy is an AB5 type nickel-based alloy. Calculated by mass percentage, the hydrogen storage alloy comprises the following components: 31.7% Mn, 25.32% La, 4.53% Ce, and Ni. 38.45%; calculated by mass percentage, the content of styrene-butadiene rubber in the styrene-butadiene rubber latex is 50%; the preparation method of the negative electrode slurry is as follows: the alloy nickel powder, activated carbon powder, sodium carboxymethyl cellulose, yttrium oxide and 30% of the formula amount of water are mixed evenly to obtain a mixture; the styrene-butadiene rubber latex and the remaining formula amount of water are added to the mixture, and after mixing evenly, the negative electrode slurry is obtained.

[0062] Example 3 A. Prepare a porous current collector. Nitrogen gas is introduced into the vacuum chamber of a magnetron sputtering device, and an electric field is applied to ionize the nitrogen gas and generate plasma. The plasma, accelerated by the electric field, bombards a graphite target, causing carbon atoms from the graphite target to sputter onto the surface of the porous current collector and allowing carbon nanotubes to penetrate into the interior of the porous current collector, resulting in a porous current collector permeated with carbon nanotubes. The penetration height of the carbon nanotubes is half the internal height of the porous current collector. The porous current collector is nickel foam, and its areal density is 450 g / m³. 2 The pore density is 140 pores / m³. 2 ; B. A negative electrode slurry is penetrated into a porous current collector permeated with carbon nanotubes using a spray coating process, and then combined with the pre-permeated carbon nanotubes. After drying at 115°C, a composite electrode coating is formed, resulting in a negative electrode sheet for nickel-carbon batteries. The penetration depth of the negative electrode slurry is the same as the thickness of the porous current collector. The negative electrode slurry comprises the following raw materials: 11% hydrogen storage alloy, 0.2% activated carbon powder, 0.2% sodium carboxymethyl cellulose, 0.8% yttrium oxide, 1.5% styrene-butadiene rubber emulsion, and 86.3% water. The hydrogen storage alloy is an AB5 type nickel-based alloy. Calculated by mass percentage, the hydrogen storage alloy comprises the following components: 31.8% Mn, 25.1% La, and 1% Ce. 4.67% and Ni 38.43%; calculated by mass percentage, the content of styrene-butadiene rubber in the styrene-butadiene rubber emulsion is 40%; the preparation method of the negative electrode slurry is as follows: the alloy nickel powder, activated carbon powder, sodium carboxymethyl cellulose, yttrium oxide and 30% of the formula amount of water are mixed evenly to obtain a mixture; the styrene-butadiene rubber emulsion and the remaining formula amount of water are added to the mixture, and after mixing evenly, the negative electrode slurry is obtained.

[0063] Comparative Example 1 The preparation method and raw materials of this comparative example are the same as those of Example 1, except that step A is missing in this comparative example.

[0064] The electrochemical performance of the nickel-carbon battery anode sheets prepared in the examples and comparative examples was tested, and the testing methods are as follows: Using the negative electrode sheet prepared in the examples and comparative examples as the negative electrode and the nickel oxide electrode as the positive electrode, the negative electrode, separator, and positive electrode were assembled sequentially in an argon-filled glove box. A 6 mol / L potassium hydroxide solution was injected as the electrolyte, and after encapsulation, the battery was allowed to stand at room temperature for 12 hours to obtain the nickel-carbon battery. The performance of the nickel-carbon battery was tested using a LAND CT2001A battery testing system. The test items are as follows: 1. Ratio Performance Test: The battery is activated by performing charge-discharge cycles 3 times at a rate of 0.5C; subsequently, constant current charge-discharge tests are carried out at rates of 1C, 2C, 5C, and 10C respectively, with 5 cycles for each rate; the discharge specific capacity at different rates is recorded, and based on the discharge specific capacity at a rate of 1C, the rate capacity retention is calculated. If the capacity retention at a rate of 5C ≥ 75%, the rate performance is qualified.

[0065] 2. Cycle life test: The battery undergoes constant current charge-discharge cycles at a rate of 2C, with a voltage window of 0.8 - 1.6V (relative to the Ni(OH)2 / NiOOH counter electrode). The change in the capacity retention of the battery with the number of cycles is recorded. When the capacity retention drops to 80% of the initial capacity, the number of cycles experienced is recorded as the cycle life of the battery. If the number of cycles experienced ≥ 14000 times, the cycle life is qualified.

[0066] 3. Structural stability characterization: After the cycle life test, the battery is disassembled, the negative electrode sheet is taken out, rinsed with deionized water and dried in vacuum; a scanning electron microscope is used to observe the surface morphology, structural integrity of the negative electrode sheet after cycling, and the bonding situation between the coating and the porous current collector. If there is no large-area peeling of the composite electrode coating and it is tightly bonded to the porous current collector, the performance is qualified.

[0067] 4. Electrode conductivity test: The sheet resistance of the negative electrode sheet is directly measured using a four-probe resistivity tester, and its volume resistivity is calculated. Among them, the calculation formula for the volume resistivity (ρ) is ρ = R × t (R is the sheet resistance, t is the thickness of the electrode sheet). If the volume resistivity ≤ 0.5Ω·cm, the performance is qualified.

[0068] 5. Energy density test: Through half-cell charge-discharge tests, the weight specific capacity and voltage window of the negative electrode sheet material are measured. Based on the average discharge voltage and weight specific capacity of the negative electrode sheet material, its energy density is calculated. If the energy density ≥ 65Wh / kg, the performance is qualified. Among them, the calculation formula is: Energy density = average discharge voltage × weight specific capacity.

[0069] The performance test results of the negative electrode sheets of the nickel-carbon batteries prepared in the examples and comparative examples are shown in Table 1 below: Table 1 Relevant performance test results of the negative electrode sheets of nickel-carbon batteries

[0070] As can be seen from the test data in Table 1, the nickel-carbon battery negative electrode obtained by this technical solution has a capacity retention rate of ≥75% at 5C rate; when the capacity retention rate drops to 80% of the initial capacity, the number of cycles experienced is ≥14,000; after the cycle life test, the composite electrode coating does not peel off over a large area and is tightly bonded to the porous current collector; the volume resistivity is ≤0.5Ω·cm; and the energy density is ≥65Wh / kg. This is beneficial to improve energy density, conductivity, and rate performance while ensuring structural stability and cycle life, so as to meet the actual application requirements.

[0071] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a negative electrode sheet for a nickel-carbon battery, characterized in that, Includes the following steps: A. Prepare a porous current collector, and use magnetron sputtering technology to sputter carbon nanotubes onto the surface of the porous current collector, allowing the carbon nanotubes to penetrate into the interior of the porous current collector, thereby obtaining a porous current collector permeated with carbon nanotubes; wherein, the penetration depth of the carbon nanotubes is 1 / 3 to 1 / 2 of the thickness of the porous current collector; B. Using a spraying process, the negative electrode slurry is penetrated into the interior of the porous current collector permeated with carbon nanotubes, and combined with the pre-permeated carbon nanotubes. After drying, a composite electrode coating is formed to obtain a negative electrode sheet for nickel-carbon batteries. Wherein, the penetration depth of the negative electrode slurry is the same as the thickness of the porous current collector; The negative electrode slurry comprises the following raw materials: hydrogen storage alloy, activated carbon powder, sodium carboxymethyl cellulose, yttrium oxide, styrene-butadiene rubber latex, and water.

2. The method for preparing a negative electrode sheet for a nickel-carbon battery according to claim 1, characterized in that, In step A, the method of the magnetron sputtering technology is as follows: inert gas is filled into the vacuum cavity of the magnetron sputtering equipment, and an electric field is applied to ionize the inert gas to generate plasma; The plasma bombards the carbon target under the acceleration of the electric field, causing carbon atoms in the carbon target to be sputtered onto the surface of the porous current collector and carbon nanotubes to penetrate into the interior of the porous current collector.

3. The method for preparing a negative electrode sheet for a nickel-carbon battery according to claim 1, characterized in that, In step A, the areal density of the porous current collector is 400–450 g / m³. 2 The pore density is 100–150 pores / m³. 2 .

4. The method for preparing a negative electrode sheet for a nickel-carbon battery according to claim 1, characterized in that, In step B, the negative electrode slurry comprises the following raw materials by mass percentage: 10-15% hydrogen storage alloy, 0.2-0.3% activated carbon powder, 0.1-0.2% sodium carboxymethyl cellulose, 0.8-1% yttrium oxide, 1-1.5% styrene-butadiene rubber latex, and 82-87% water.

5. The method for preparing a negative electrode sheet for a nickel-carbon battery according to claim 1, characterized in that, In step B, the hydrogen storage alloy is an AB5 type nickel-based alloy; The hydrogen storage alloy comprises the following components by mass percentage: Mn 31.06–31.86%, La 24.63–25.63%, and Ce 3.98–4.98%, with the remainder being Ni.

6. The method for preparing a negative electrode sheet for a nickel-carbon battery according to claim 1, characterized in that, In step B, the styrene-butadiene rubber content in the styrene-butadiene rubber emulsion is calculated as 40-70% by mass percentage.

7. The method for preparing a negative electrode sheet for a nickel-carbon battery according to claim 4, characterized in that, In step B, the method for preparing the negative electrode slurry is as follows: The alloy nickel powder, activated carbon powder, sodium carboxymethyl cellulose, yttrium oxide, and 30% of the formula amount of water are mixed evenly to obtain a mixture; Add the formulated amount of styrene-butadiene rubber latex and the remaining formulated amount of water to the mixture, and mix evenly to obtain the negative electrode slurry.

8. The method for preparing a negative electrode sheet for a nickel-carbon battery according to claim 1, characterized in that, In step B, the drying temperature is 90–115°C.

9. A negative electrode sheet for a nickel-carbon battery, characterized in that... It is prepared using the method for preparing a negative electrode sheet for a nickel-carbon battery according to any one of claims 1 to 8.

10. The application of a negative electrode sheet for nickel-carbon batteries in the preparation of nickel-carbon batteries, characterized in that, The application method using the negative electrode sheet for nickel-carbon batteries as described in claim 9 is as follows: Using a nickel-carbon battery negative electrode sheet as the negative electrode and a nickel oxide electrode as the positive electrode, the negative electrode, separator and positive electrode are assembled sequentially in an argon-filled glove box, and electrolyte is injected. After sealing, the battery is left to stand at room temperature for 10-12 hours to obtain a nickel-carbon battery.

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