Positive electrode slurry for nickel-metal hydride battery as well as preparation method and application of positive electrode slurry

Abstract

The invention relates to the technical field of nickel-metal hydride batteries, in particular to positive electrode slurry for a nickel-metal hydride battery and a preparation method and application thereof.The positive electrode slurry is prepared from, by mass, 180-220 parts of spherical nickel hydroxide, 2-3 parts of ytterbium trioxide, 5-9 parts of composite binder, 1.5-2.5 parts of zinc oxide, 1-2 parts of calcium hydroxide, 1.5-2 parts of cerium dioxide, 1-2 parts of polyaniline and 180-200 parts of water; the composite binder comprises diquat, sodium carboxymethyl cellulose and a polytetrafluoroethylene solution. According to the positive electrode slurry for the nickel-metal hydride battery as well as the preparation method and the application of the positive electrode slurry, the high-temperature cycle life is prolonged, the rate capability is improved, and the defects in the prior art are overcome.

Description

Technical Field

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

[0002] With the deepening of the global energy structure transformation and the "dual-carbon" strategy, higher requirements are being placed on the comprehensive performance of energy storage batteries. Among the many energy storage technologies, nickel-metal hydride batteries, as a mature and safe battery, are widely used in backup power, energy storage power stations, rail transportation, and special equipment fields due to their advantages such as excellent wide temperature range adaptability, long cycle life, environmental friendliness, and no heavy metal pollution.

[0003] As the core energy storage component of nickel-metal hydride (NiMH) batteries, the performance of the cathode slurry directly determines the battery's energy output, power characteristics, and cycle life. Existing cathode slurries mainly consist of spherical nickel hydroxide (active material), conductive agents, and binders. In this slurry system, nickel hydroxide achieves the conversion of chemical energy into electrical energy through a reversible redox reaction [Ni(OH)2 / NiOOH], which is the fundamental source of energy storage and release in the battery.

[0004] However, as application scenarios become increasingly demanding, the inherent shortcomings of this traditional technology system are becoming more and more apparent, limiting the full realization of its performance potential, as follows: First, the electrode coating formed by the positive electrode slurry is prone to detachment, which restricts the achievement of high-temperature cycle life and high-rate performance. During battery manufacturing, the positive electrode slurry is typically loaded onto a porous current collector through coating or filling processes, and then dried to form an electrode coating, resulting in the positive electrode sheet. However, during long-term deep charge-discharge cycles, the active material particles undergo repeated volume expansion and contraction. Traditional binder systems struggle to provide durable and robust mechanical constraints and adhesion, leading to gradual deterioration of the interface between the active material particles within the electrode coating and between the electrode coating and the porous current collector. This causes the electrode coating to detach from the porous current collector. The detachment of the electrode coating directly results in the loss of active material and damage to the conductive network, causing irreversible capacity decay and a continuous increase in internal resistance. At high temperatures, this degradation process is drastically accelerated, creating a vicious cycle of "structural failure → active material loss" and "increased internal resistance → accelerated performance degradation," thus severely shortening the cycle life of nickel-metal hydride batteries at high temperatures. In addition, although the weak bonding force between the electrode coating and the porous current collector does not directly affect the conductivity, once it is cycled under high current (the rate charge and discharge itself will also aggravate the volume change), the generation of interfacial microcracks will drastically increase the interfacial contact resistance, resulting in a decrease in the electron transport efficiency between the electrode coating and the porous current collector, thus causing a decrease in rate performance.

[0005] Second, intrinsic side reactions limit cycle life at high temperatures. During the charging process, especially towards the end of charging or at high rate charging, in addition to the main conversion of nickel hydroxide [Ni(OH)2] to nickel hydroxyl oxide (NiOOH) in the electrode coating, an oxygen evolution side reaction (4OH) also occurs. - →O2↑+2H2O+4e - The generated oxygen oxidizes organic components in the positive electrode slurry (such as binders like sodium carboxymethyl cellulose), producing carbon dioxide and other byproducts. High temperatures not only accelerate electrochemical side reactions but also exacerbate carbon dioxide generation and its reaction with potassium hydroxide in the electrolyte to form potassium carbonate crystals. These potassium carbonate crystals clog the pores of the porous current collector, leading to a decrease in ionic conductivity and a sharp increase in internal resistance, increased polarization, and a decrease in usable capacity.

[0006] Third, insufficient intrinsic conductivity limits rate performance. High-rate charge and discharge require the positive electrode to have rapid ion and electron transport capabilities. In traditional positive electrode slurry formulations, the electron transport efficiency in the network formed by the active material and conductive agent needs to be improved, resulting in huge concentration polarization under high current, causing the battery voltage to drop sharply during discharge and resulting in poor rate performance.

[0007] In summary, existing cathode slurries for nickel-metal hydride batteries generally suffer from poor high-temperature cycle life and insufficient rate performance. Summary of the Invention

[0008] The purpose of this invention is to provide a positive electrode slurry for nickel-metal hydride batteries, its preparation method and application, which is beneficial to improving high-temperature cycle life and rate performance, and overcoming the shortcomings of the prior art.

[0009] To achieve this objective, the present invention adopts the following technical solution: A positive electrode slurry for nickel-metal hydride batteries, comprising, by weight parts: 180-220 parts spherical nickel hydroxide, 2-3 parts ytterbium trioxide, 5-9 parts composite binder, 1.5-2.5 parts zinc oxide, 1-2 parts calcium hydroxide, 1.5-2 parts cerium dioxide, 1-2 parts polyaniline, and 180-200 parts water; The composite adhesive comprises a precipitant, sodium carboxymethyl cellulose, and a polytetrafluoroethylene solution.

[0010] Further, calculated by mass parts, it includes 180-220 parts of spherical nickel hydroxide, 2-3 parts of ytterbium trioxide, 2-4 parts of precipitate, 1-2 parts of sodium carboxymethyl cellulose, 2-3 parts of polytetrafluoroethylene solution, 1.5-2.5 parts of zinc oxide, 1-2 parts of calcium hydroxide, 1.5-2 parts of cerium dioxide, 1-2 parts of polyaniline, and 180-200 parts of water.

[0011] Furthermore, calculated by mass parts, it includes 210 parts of spherical nickel hydroxide, 3 parts of ytterbium trioxide, 4 parts of precipitate, 1 part of sodium carboxymethyl cellulose, 3 parts of polytetrafluoroethylene solution, 2 parts of zinc oxide, 2 parts of calcium hydroxide, 2 parts of cerium dioxide, 2 parts of polyaniline, and 200 parts of water.

[0012] Further, calculated by mass parts, the polytetrafluoroethylene solution comprises 0.2 to 0.5 parts polytetrafluoroethylene, 0.2 to 0.5 parts surfactant, 0.1 to 0.2 parts thickener, and 2 to 4 parts water.

[0013] Furthermore, the thickener is xanthan gum.

[0014] Furthermore, the surfactant includes either hexadecyl carboxylate betaine or hexadecyl hydroxypropyl ammonium chloride.

[0015] A method for preparing a positive electrode slurry for nickel-metal hydride batteries, comprising the following steps: A. Mix the prescribed amount of calcium hydroxide with 15% of the prescribed amount of water until homogeneous to obtain a calcium hydroxide solution; mix the prescribed amount of sodium carboxymethyl cellulose with 25% of the prescribed amount of water until homogeneous to obtain a sodium carboxymethyl cellulose solution; add the calcium hydroxide solution to the continuously stirred sodium carboxymethyl cellulose solution to obtain a sodium carboxymethyl cellulose-calcium hydroxide composite solution. B. Mix the amount of the formulated adhesive with 10% of the amount of water to obtain the adhesive solution; C. After mixing the spherical nickel hydroxide, ytterbium trioxide, zinc oxide, cerium dioxide and polyaniline in the prescribed amounts evenly, a mixed powder is obtained; the remaining amount of water is added to the mixed powder, and after mixing evenly, a first mixed liquid is obtained; D. Add sodium carboxymethyl cellulose-calcium hydroxide composite solution and osmotic adhesive solution to the first mixture, stir evenly, and then perform vacuum degassing to obtain the second mixture; E. Add the formulated amount of polytetrafluoroethylene solution to the second mixture, stir evenly, and obtain the positive electrode slurry for nickel-metal hydride batteries.

[0016] The application of a positive electrode slurry for nickel-metal hydride batteries in the preparation of nickel-metal hydride batteries, using the above-mentioned positive electrode slurry for nickel-metal hydride batteries, and the application method is as follows: The positive electrode slurry is sprayed onto a porous current collector and allowed to penetrate into the interior of the porous current collector. After drying, a positive electrode coating is formed, resulting in a positive electrode sheet. Using the prepared positive electrode sheet as the positive electrode and the hydrogen storage alloy as the negative electrode, the negative electrode, separator and positive electrode were assembled in sequence in an argon-filled glove box, and electrolyte was injected. After encapsulation, the battery was left to stand at room temperature for 10-12 hours to obtain a nickel-metal hydride battery.

[0017] Furthermore, the porous current collector is nickel foam.

[0018] Furthermore, the areal density of the porous current collector is 150–180 g / m³. 2 The pore density is 80–100 pores / m³. 2 .

[0019] The technical solution provided by this invention may include the following beneficial effects: 1. Calcium hydroxide exhibits slight soluble properties in alkaline electrolytes, forming and maintaining a locally high concentration of hydroxide ions (OH-) within the porous current collector of the positive electrode. - The environment. When CO2 generated by the side reactions of the nickel-metal hydride battery dissolves and diffuses into the pores of the porous current collector of the positive electrode, CO2 preferentially undergoes an efficient neutralization reaction with the aforementioned localized calcium hydroxide, generating insoluble calcium carbonate (CaCO3) solid precipitate, which is then fixed at the original reaction site of calcium hydroxide. This reaction captures and fixes CO2 before it reacts with KOH in the main electrolyte to form potassium carbonate crystals, blocking the formation and precipitation pathway of high-resistivity potassium carbonate crystals at the source. This mechanism effectively maintains the long-term unobstructed electrolyte ion channels inside the porous current collector and in the membrane, ensuring the OH- necessary for the charge-discharge reaction. - The stable supply and rapid transport of ions suppress the rapid increase in battery internal resistance caused by electrolyte carbonation under harsh conditions such as high temperature, maintain the long-term stability of the battery's internal chemical environment and electrochemical performance, and enable it to have a high cycle life at high temperature (i.e., better high-temperature cycle life).

[0020] 2. The working principle of ytterbium trioxide is as follows: Ytterbium trioxide can increase the overpotential of the oxygen evolution side reaction and increase the energy barrier for the occurrence of the oxygen evolution side reaction, so that even under high temperature environment, the oxygen evolution side reaction is effectively suppressed. This not only greatly improves the charging efficiency, but also fundamentally reduces the large amount of carbon dioxide generated due to the violent oxygen evolution side reaction, further blocking the formation of high-resistivity potassium carbonate crystals, which is also conducive to improving the high temperature cycle life. Detailed Implementation

[0021] This technical solution provides a positive electrode slurry for nickel-metal hydride batteries, which, by weight, comprises 180-220 parts of spherical nickel hydroxide, 2-3 parts of ytterbium trioxide, 5-9 parts of composite binder, 1.5-2.5 parts of zinc oxide, 1-2 parts of calcium hydroxide, 1.5-2 parts of cerium dioxide, 1-2 parts of polyaniline, and 180-200 parts of water. The composite adhesive comprises a precipitant, sodium carboxymethyl cellulose, and a polytetrafluoroethylene solution.

[0022] To address the common technical problems of poor high-temperature cycle life and insufficient rate performance in existing nickel-metal hydride battery cathode slurries, this technical solution proposes a new cathode slurry for nickel-metal hydride batteries. By optimizing the formulation of the cathode slurry, it is beneficial to improve high-temperature cycle life and rate performance to meet practical application requirements.

[0023] Specifically, the raw materials for the positive electrode slurry of nickel-metal hydride batteries include spherical nickel hydroxide, ytterbium trioxide, a composite binder, zinc oxide, calcium hydroxide, cerium dioxide, polyaniline, and water. The composite binder's raw materials include a sizing agent, sodium carboxymethyl cellulose, and a polytetrafluoroethylene (PTFE) solution. Among these, the PTFE solution, cerium dioxide, polyaniline, and ytterbium trioxide all enable the electrode coating formed after the positive electrode slurry solidifies to adhere firmly to the porous current collector even at high temperatures.

[0024] The working principle of the polytetrafluoroethylene (PTFE) solution is as follows: (1) PTFE in the PTFE solution has extremely high chemical inertness, which allows it to completely resist the corrosion of strong alkaline electrolytes even at high temperatures and not degrade throughout the entire battery life cycle, thus providing durable and stable adhesion; (2) During the charging and discharging process of the battery, the active material (such as spherical nickel hydroxide) undergoes repeated volume changes. PTFE has good elasticity and ductility, and can effectively buffer the above-mentioned periodic stress and strain even at high temperatures, preventing the internal stress generated by volume changes from being directly transmitted and destroying the bonding interface between the active material particles and between the electrode coating and the porous current collector, thereby reducing the risk of the electrode coating falling off the current collector.

[0025] Meanwhile, the working principle of cerium dioxide is as follows: nano-sized cerium dioxide particles can fill the spaces between the positive electrode active material nickel hydroxide particles, playing a pinning effect and providing skeletal support. Even at high temperatures, it can effectively constrain the active material particles during charging and discharging (H2O). + The expansion and contraction during the embedding / extraction process can also prevent the electrode coating from falling off the porous current collector.

[0026] Furthermore, the working principle of polyaniline is as follows: the molecular chains of polyaniline can form a conductive coating layer on the surface of the spherical nickel hydroxide particles, and construct a continuous, flexible three-dimensional hybrid conductive network structure between the spherical nickel hydroxide particles. The high molecular weight properties of polyaniline endow the conductive network structure with good mechanical toughness, which can buffer the stress caused by repeated volume changes of the active material during high-rate charging and discharging even at high temperatures, maintaining the structural integrity of the conductive network and preventing the electrode coating from structurally detaching from the porous current collector due to brittle fracture of the conductive network.

[0027] Furthermore, the working principle of ytterbium trioxide is as follows: (1) As a structural dopant, ytterbium trioxide exerts a lattice anchoring effect by entering the lattice of nickel hydroxide or occupying grain boundaries. It can pin the lattice, increase the stability of the crystal structure, and effectively suppress the repeated insertion and extraction of hydrogen ions and changes in the valence state of nickel (Ni) during charging and discharging. 2+ / Ni 3+ (1) The lattice parameters caused by the severe fluctuations; (2) It can preferentially occupy the grain boundary, hindering the generation and growth of highly active and easily expandable harmful crystal phases (such as γ-NiOOH). The above-mentioned dual stabilizing effect from the inside of the crystal to the interface effectively buffers the volume stress of the active material particles in the cycle even at high temperature, thereby preventing the phenomenon of electrode coating falling off the porous current collector caused by the shedding of active material particles.

[0028] Secondly, both calcium hydroxide and ytterbium trioxide can utilize their intrinsic properties to improve high-temperature cycle life. The working principle of calcium hydroxide is as follows: Calcium hydroxide exhibits slight solubility in alkaline electrolytes, forming and maintaining a locally high concentration of hydroxide ions (OH-) within the porous current collector of the positive electrode. - The environment. When CO2 generated by the side reactions of the nickel-metal hydride battery dissolves and diffuses into the pores of the porous current collector of the positive electrode, CO2 preferentially undergoes an efficient neutralization reaction with the aforementioned localized calcium hydroxide, generating insoluble calcium carbonate (CaCO3) solid precipitate, which is then fixed at the original reaction site of calcium hydroxide. This reaction captures and fixes CO2 before it reacts with KOH in the main electrolyte to form potassium carbonate crystals, blocking the formation and precipitation pathway of high-resistivity potassium carbonate crystals at the source. This mechanism effectively maintains the long-term unobstructed electrolyte ion channels inside the porous current collector and in the membrane, ensuring the OH- necessary for the charge-discharge reaction. - The stable supply and rapid transport of ions suppress the rapid increase in battery internal resistance caused by electrolyte carbonation under harsh conditions such as high temperature, maintain the long-term stability of the battery's internal chemical environment and electrochemical performance, and enable it to have a high cycle life at high temperature (i.e., better high-temperature cycle life).

[0029] The working principle of ytterbium trioxide is as follows: Ytterbium trioxide can increase the overpotential of the oxygen evolution side reaction and increase the energy barrier for the occurrence of the oxygen evolution side reaction, so that even under high temperature environment, the oxygen evolution side reaction is effectively suppressed. This not only greatly improves the charging efficiency, but also fundamentally reduces the large amount of carbon dioxide generated due to the violent oxygen evolution side reaction, further blocking the formation of high-resistivity potassium carbonate crystals, and is also conducive to improving the high temperature cycle life.

[0030] Furthermore, as mentioned above, the electrode coating formed after the positive electrode slurry is cured in this technical solution adheres firmly to the porous current collector. This electrode coating system is particularly effective in resisting repeated physical stress and chemical shocks under high-temperature cycling, effectively avoiding the risk of active material nickel hydroxide falling off the porous current collector under the physical and chemical stress of cyclic charging and discharging, causing loss of active material and damage to the conductive network. It also suppresses the continuous increase of internal resistance and irreversible capacity decay of nickel-metal hydride batteries, thereby extending their high-temperature cycle life.

[0031] Furthermore, the raw materials for the positive electrode slurry also include ytterbium trioxide, cerium dioxide, and polyaniline, all of which can utilize their intrinsic properties to improve rate performance. The working principle of ytterbium trioxide is as follows: as a functional p-type dopant, ytterbium trioxide directly acts on the bulk nickel hydroxide active material of the positive electrode and optimizes the bulk electronic structure of nickel hydroxide through the doping effect, thereby improving the conductivity of the positive electrode and reducing polarization.

[0032] The working principle of cerium dioxide is as follows: Cerium dioxide (CeO2) has excellent oxygen ion storage and release capabilities (derived from Ce). 3+ / Ce 4+ (Variable valence state). When it is doped into the positive electrode slurry, it can improve the microenvironment at the interface between the positive electrode and the electrolyte, and promote the proliferation of protons (H+) at the interface. + The transfer of ) effectively reduces the activation energy of the positive electrode reaction and improves the rate performance.

[0033] The principle behind polyaniline's improved rate performance is as follows: As shown earlier, polyaniline can construct a continuous, flexible, three-dimensional hybrid conductive network structure between spherical nickel hydroxide particles. This conductive network structure not only greatly improves the electron transport efficiency within the positive electrode and reduces interfacial contact resistance, but its own redox activity also acts as a charge transfer station, promoting rapid exchange between electrons and active materials, thereby accelerating electrochemical reaction kinetics and improving the battery's rate performance.

[0034] In addition, as mentioned above, the electrode coating formed after the positive electrode slurry is cured in this technical solution is firmly adhered to the porous current collector. This avoids the situation where the generation of interfacial microcracks during high-current cycling will drastically increase the interfacial contact resistance, leading to a decrease in the electron transfer efficiency between the electrode coating and the porous current collector, thereby reducing the rate performance. This helps to ensure the rate performance.

[0035] To further explain, the composition, calculated by mass parts, includes 180–220 parts of spherical nickel hydroxide, 2–3 parts of ytterbium trioxide, 2–4 parts of precipitate, 1–2 parts of sodium carboxymethyl cellulose, 2–3 parts of polytetrafluoroethylene solution, 1.5–2.5 parts of zinc oxide, 1–2 parts of calcium hydroxide, 1.5–2 parts of cerium dioxide, 1–2 parts of polyaniline, and 180–200 parts of water.

[0036] This technical solution, by limiting the ratio of raw materials in the positive electrode slurry for nickel-metal hydride batteries, helps to ensure the performance of the positive electrode slurry, thereby further ensuring the structural stability, high-temperature cycle life, and rate performance of the positive electrode sheet prepared using the positive electrode slurry.

[0037] To further explain, the composition, calculated by mass, includes 210 parts of spherical nickel hydroxide, 3 parts of ytterbium trioxide, 4 parts of precipitate, 1 part of sodium carboxymethyl cellulose, 3 parts of polytetrafluoroethylene solution, 2 parts of zinc oxide, 2 parts of calcium hydroxide, 2 parts of cerium dioxide, 2 parts of polyaniline, and 200 parts of water.

[0038] This technical solution optimizes the addition amount of each raw material in the positive electrode slurry for nickel-metal hydride batteries, so that each raw material in the formula can give full play to its own performance advantages, which is conducive to improving the performance of the positive electrode slurry for nickel-metal hydride batteries, thereby further ensuring the high-temperature cycle life and rate performance of nickel-metal hydride batteries.

[0039] To further explain, the polytetrafluoroethylene solution comprises, by mass, 0.2 to 0.5 parts polytetrafluoroethylene, 0.2 to 0.5 parts surfactant, 0.1 to 0.2 parts thickener, and 2 to 4 parts water.

[0040] This technical solution optimizes the polytetrafluoroethylene (PTFE) solution, which helps ensure the performance of the PTFE solution and thus improves the performance of the positive electrode slurry for nickel-metal hydride batteries.

[0041] To further clarify, the thickener is xanthan gum.

[0042] This technical solution uses xanthan gum as the thickener and leverages its pseudoplasticity or thixotropic properties to optimize the storage stability and processing performance of the polytetrafluoroethylene (PTFE) solution. When stationary, xanthan gum provides sufficiently high viscosity to effectively prevent PTFE particles from settling or separating from the surfactant, ensuring a uniform and stable system. Under high-speed shear (such as during spraying or stirring), the viscosity of the PTFE solution decreases sharply (i.e., shear thinning), giving the PTFE solution excellent fluidity, facilitating the spraying of the positive electrode slurry containing the PTFE solution.

[0043] To further clarify, the surfactant includes either hexadecyl carboxylate betaine or hexadecyl hydroxypropyl ammonium chloride.

[0044] This technical solution preferentially uses hexadecyl carboxylate betaine or hexadecyl hydroxypropyl ammonium chloride as the surfactant, utilizing the long-chain hydrophobic structure and cationic / zwitterionic properties of hexadecyl carboxylate betaine or hexadecyl hydroxypropyl ammonium chloride to achieve efficient and stable dispersion of polytetrafluoroethylene. Simultaneously, both hexadecyl carboxylate betaine and hexadecyl hydroxypropyl ammonium chloride exhibit excellent electrolyte (salt and alkali resistance) stability, capable of resisting high-valence metal ions (such as Ca) in the positive electrode slurry. 2+ This ensures that the polytetrafluoroethylene emulsion does not break down or flocculate in the positive electrode slurry formulation, thereby maintaining its uniform distribution and functional integrity as a binder for a long time.

[0045] A method for preparing a positive electrode slurry for nickel-metal hydride batteries, comprising the following steps: A. Mix the prescribed amount of calcium hydroxide with 15% of the prescribed amount of water until homogeneous to obtain a calcium hydroxide solution; mix the prescribed amount of sodium carboxymethyl cellulose with 25% of the prescribed amount of water until homogeneous to obtain a sodium carboxymethyl cellulose solution; add the calcium hydroxide solution to the continuously stirred sodium carboxymethyl cellulose solution to obtain a sodium carboxymethyl cellulose-calcium hydroxide composite solution. B. Mix the amount of the formulated adhesive with 10% of the amount of water to obtain the adhesive solution; C. After mixing the spherical nickel hydroxide, ytterbium trioxide, zinc oxide, cerium dioxide and polyaniline in the prescribed amounts evenly, a mixed powder is obtained; the remaining amount of water is added to the mixed powder, and after mixing evenly, a first mixed liquid is obtained; D. Add sodium carboxymethyl cellulose-calcium hydroxide composite solution and osmotic adhesive solution to the first mixture, stir evenly, and then perform vacuum degassing to obtain the second mixture; E. Add the formulated amount of polytetrafluoroethylene solution to the second mixture, stir evenly, and obtain the positive electrode slurry for nickel-metal hydride batteries.

[0046] This technical solution optimizes the preparation method of the positive electrode slurry for nickel-metal hydride batteries, following the principle of step-by-step preparation and gradual mixing. This effectively avoids excessively high local concentrations and ensures the uniformity and stability of the positive electrode slurry for nickel-metal hydride batteries.

[0047] The application of a positive electrode slurry for nickel-metal hydride batteries in the preparation of nickel-metal hydride batteries, using the above-mentioned positive electrode slurry for nickel-metal hydride batteries, and the application method is as follows: The positive electrode slurry is sprayed onto a porous current collector and allowed to penetrate into the interior of the porous current collector. After drying, a positive electrode coating is formed, resulting in a positive electrode sheet. Using the prepared positive electrode sheet as the positive electrode and the hydrogen storage alloy as the negative electrode, the negative electrode, separator and positive electrode were assembled in sequence in an argon-filled glove box, and electrolyte was injected. After encapsulation, the battery was left to stand at room temperature for 10-12 hours to obtain a nickel-metal hydride battery.

[0048] This technical solution also proposes the application of a positive electrode slurry for nickel-metal hydride batteries in the preparation of nickel-metal hydride batteries, which is beneficial to improving high-temperature cycle life and rate performance.

[0049] It should be noted that the diaphragm can be a polyacrylamide membrane or a cellulose membrane, and the specific type is not limited here. The electrolyte can be a potassium hydroxide solution, and the specific type is not limited here. The hydrogen storage alloy can be LaNi5, and the specific type is not limited here. Furthermore, the diaphragm, electrolyte, and hydrogen storage alloy are not the focus of this technical solution.

[0050] To further clarify, the porous current collector is nickel foam.

[0051] The unique three-dimensional network structure of nickel foam provides a mechanical anchoring and highly conductive integrated framework for active materials (such as spherical nickel hydroxide), enabling the nickel foam to firmly lock the sprayed positive electrode slurry and alleviate the problem of active material detachment from the positive electrode slurry due to volume changes during charge-discharge cycles. Simultaneously, the high porosity and large specific surface area of ​​nickel foam ensure a high loading capacity of active materials and facilitate electrolyte wetting and ion (OH) ion exchange. - Rapid diffusion provides ample channels, greatly reducing concentration polarization. In addition, the excellent metallic conductivity of nickel foam itself constructs a low-resistance, three-dimensional electron transport network from the porous current collector to the active material particles, thereby synergistically improving ion conductivity and electronic conductivity, ultimately achieving high-rate performance and long high-temperature cycle life of the battery.

[0052] To further clarify, the areal density of the porous current collector is 150–180 g / m³. 2 The pore density is 80–100 pores / m³. 2 .

[0053] 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.

[0054] Furthermore, if the porous current collector has a high pore density, 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 porous current collector has a low pore density, it will be beneficial to improve the mechanical strength and conductivity, but it has defects such as limited loading of active material and obstructed ion transport.

[0055] 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 nickel-metal hydride battery.

[0056] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0057] Example 1 In this embodiment, the positive electrode slurry for nickel-metal hydride batteries, calculated by mass parts, includes 210 parts of spherical nickel hydroxide, 3 parts of ytterbium trioxide, 4 parts of precipitate, 1 part of sodium carboxymethyl cellulose, 3 parts of polytetrafluoroethylene solution, 2 parts of zinc oxide, 2 parts of calcium hydroxide, 2 parts of cerium dioxide, 2 parts of polyaniline, and 200 parts of water. The polytetrafluoroethylene solution comprises, by weight, 0.5 parts polytetrafluoroethylene, 0.3 parts hexadecyl carboxylate betaine, 0.2 parts xanthan gum, and 3 parts water; The preparation method of the positive electrode slurry includes the following steps: A. Mix the prescribed amount of calcium hydroxide with 15% of the prescribed amount of water until homogeneous to obtain a calcium hydroxide solution; mix the prescribed amount of sodium carboxymethyl cellulose with 25% of the prescribed amount of water until homogeneous to obtain a sodium carboxymethyl cellulose solution; add the calcium hydroxide solution to the continuously stirred sodium carboxymethyl cellulose solution to obtain a sodium carboxymethyl cellulose-calcium hydroxide composite solution. B. Mix the amount of the formulated adhesive with 10% of the amount of water to obtain the adhesive solution; C. After mixing the spherical nickel hydroxide, ytterbium trioxide, zinc oxide, cerium dioxide and polyaniline in the prescribed amounts evenly, a mixed powder is obtained; the remaining amount of water is added to the mixed powder, and after mixing evenly, a first mixed liquid is obtained; D. Add sodium carboxymethyl cellulose-calcium hydroxide composite solution and osmotic adhesive solution to the first mixture, stir evenly, and then perform vacuum degassing to obtain the second mixture; E. Add the formulated amount of polytetrafluoroethylene solution to the second mixture, stir evenly, and obtain the positive electrode slurry for nickel-metal hydride batteries.

[0058] Example 2 In this embodiment, the positive electrode slurry for nickel-metal hydride batteries, calculated by mass, includes 180 parts of spherical nickel hydroxide, 2 parts of ytterbium trioxide, 4 parts of precipitate, 2 parts of sodium carboxymethyl cellulose, 2 parts of polytetrafluoroethylene solution, 1.5 parts of zinc oxide, 1 part of calcium hydroxide, 1.5 parts of cerium dioxide, 1 part of polyaniline, and 180 parts of water. The polytetrafluoroethylene solution comprises, by weight, 0.5 parts polytetrafluoroethylene, 0.5 parts hexadecyl hydroxypropyl ammonium chloride, 0.1 parts xanthan gum, and 2 parts water; The preparation method of the positive electrode slurry includes the following steps: A. Mix the prescribed amount of calcium hydroxide with 15% of the prescribed amount of water until homogeneous to obtain a calcium hydroxide solution; mix the prescribed amount of sodium carboxymethyl cellulose with 25% of the prescribed amount of water until homogeneous to obtain a sodium carboxymethyl cellulose solution; add the calcium hydroxide solution to the continuously stirred sodium carboxymethyl cellulose solution to obtain a sodium carboxymethyl cellulose-calcium hydroxide composite solution. B. Mix the amount of the formulated adhesive with 10% of the amount of water to obtain the adhesive solution; C. After mixing the spherical nickel hydroxide, ytterbium trioxide, zinc oxide, cerium dioxide and polyaniline in the prescribed amounts evenly, a mixed powder is obtained; the remaining amount of water is added to the mixed powder, and after mixing evenly, a first mixed liquid is obtained; D. Add sodium carboxymethyl cellulose-calcium hydroxide composite solution and osmotic adhesive solution to the first mixture, stir evenly, and then perform vacuum degassing to obtain the second mixture; E. Add the formulated amount of polytetrafluoroethylene solution to the second mixture, stir evenly, and obtain the positive electrode slurry for nickel-metal hydride batteries.

[0059] Example 3 In this embodiment, the positive electrode slurry for nickel-metal hydride batteries, calculated by mass parts, includes 220 parts of spherical nickel hydroxide, 3 parts of ytterbium trioxide, 4 parts of precipitate, 2 parts of sodium carboxymethyl cellulose, 2 parts of polytetrafluoroethylene solution, 2.5 parts of zinc oxide, 1 part of calcium hydroxide, 2 parts of cerium dioxide, 2 parts of polyaniline, and 200 parts of water. The polytetrafluoroethylene solution comprises 0.2 parts polytetrafluoroethylene, 0.3 parts hexadecyl carboxylate betaine, 0.2 parts xanthan gum, and 4 parts water, calculated by mass. The preparation method of the positive electrode slurry includes the following steps: A. Mix the prescribed amount of calcium hydroxide with 15% of the prescribed amount of water until homogeneous to obtain a calcium hydroxide solution; mix the prescribed amount of sodium carboxymethyl cellulose with 25% of the prescribed amount of water until homogeneous to obtain a sodium carboxymethyl cellulose solution; add the calcium hydroxide solution to the continuously stirred sodium carboxymethyl cellulose solution to obtain a sodium carboxymethyl cellulose-calcium hydroxide composite solution. B. Mix the amount of the formulated adhesive with 10% of the amount of water to obtain the adhesive solution; C. After mixing the spherical nickel hydroxide, ytterbium trioxide, zinc oxide, cerium dioxide and polyaniline in the prescribed amounts evenly, a mixed powder is obtained; the remaining amount of water is added to the mixed powder, and after mixing evenly, a first mixed liquid is obtained; D. Add sodium carboxymethyl cellulose-calcium hydroxide composite solution and osmotic adhesive solution to the first mixture, stir evenly, and then perform vacuum degassing to obtain the second mixture; E. Add the formulated amount of polytetrafluoroethylene solution to the second mixture, stir evenly, and obtain the positive electrode slurry for nickel-metal hydride batteries.

[0060] Comparative Example 1 This comparative example has the same preparation method and raw materials as Example 1, except that calcium hydroxide is not added to the positive electrode slurry formula for the nickel-hydrogen battery. That is, calculated by mass fraction, the positive electrode slurry for the nickel-hydrogen battery includes 212 parts of spherical nickel hydroxide, 3 parts of ytterbium sesquioxide, 4 parts of Dingyou glue, 1 part of sodium carboxymethyl cellulose, 3 parts of polytetrafluoroethylene solution, 2 parts of zinc oxide, 2 parts of cerium dioxide, 2 parts of polyaniline, and 200 parts of water.

[0061] Comparative Example 2 This comparative example has the same preparation method and raw materials as Example 1, except that ytterbium sesquioxide is not added to the positive electrode slurry formula for the nickel-hydrogen battery. That is, calculated by mass fraction, the positive electrode slurry for the nickel-hydrogen battery includes 212.8 parts of spherical nickel hydroxide, 4.2 parts of Dingyou glue, 1 part of sodium carboxymethyl cellulose, 3 parts of polytetrafluoroethylene solution, 2 parts of zinc oxide, 2 parts of calcium hydroxide, 2 parts of cerium dioxide, 2 parts of polyaniline, and 200 parts of water.

[0062] The electrochemical properties of the positive electrode slurries prepared in the examples and comparative examples were detected respectively, and the detection method is as follows: The positive electrode slurries prepared in the examples and comparative examples were sprayed on nickel foam (surface density: 180 g / m 2 , pore density: 90 pores / m 2 ), and the positive electrode slurry was infiltrated into the interior of the porous current collector. After drying at a temperature of 100 °C, a positive electrode coating was formed to obtain a positive electrode sheet; using the prepared positive electrode sheet as the positive electrode and a hydrogen storage alloy as the negative electrode, in a glove box filled with argon, the negative electrode, separator, and positive electrode were assembled in sequence, and a potassium hydroxide solution with a concentration of 6 mol / L was injected as the electrolyte. After encapsulation, it was left standing at room temperature for 12 h to obtain a nickel-hydrogen battery. The performance of the nickel-hydrogen battery was detected using a LAND CT2001A battery test system. The detection items are as follows: 1. Rate performance test: The battery was subjected to charge and discharge cycling 3 times at a rate of 0.5C for activation; then constant current charge and discharge tests were carried out at rates of 1C, 2C, 5C, and 10C respectively, with 5 cycles for each rate; the discharge specific capacity at different rates was recorded, and based on the discharge specific capacity at a rate of 1C, the rate capacity retention rate was calculated. If the capacity retention rate at a rate of 5C ≥ 80%, and the capacity retention rate at a rate of 10C ≥ 60%, the rate performance is qualified.

[0063] 2. High-temperature cycle life test: The nickel-metal hydride battery is placed in an environment of 60 °C and undergoes constant current charge and discharge cycles at a rate of 2C, with a voltage window of 0.8 - 1.6V. Record the change in the capacity retention rate of the nickel-metal hydride battery with the number of cycles. When the capacity retention rate 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 ≥ 5000 times, the high-temperature cycle life is qualified.

[0064] The performance test results of the positive electrode slurry of the nickel-metal hydride battery prepared in the examples and comparative examples are shown in Table 1 below: Table 1 Related performance test results of the positive electrode slurry for nickel-metal hydride batteries

[0065] From the test data in Table 1, it can be seen that the positive electrode slurry for nickel-metal hydride batteries obtained by this technical solution has a capacity retention rate ≥ 80% at a rate of 5C and a capacity retention rate ≥ 60% at a rate of 10C; when the capacity retention rate drops to 80% of the initial capacity, the number of cycles experienced ≥ 5000 times, which is beneficial to improving the high-temperature cycle life and rate performance.

[0066] The technical principle of the present invention has been described above in combination with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be construed in any way as a limitation on the protection scope of the present invention. Based on the explanations herein, those skilled in the art can联想到 other specific embodiments of the present invention without creative efforts, and these embodiments will fall within the protection scope of the present invention.

Claims

1. A positive electrode slurry for nickel-metal hydride batteries, characterized in that, The composition, calculated by weight, includes 180–220 parts of spherical nickel hydroxide, 2–3 parts of ytterbium trioxide, 5–9 parts of composite binder, 1.5–2.5 parts of zinc oxide, 1–2 parts of calcium hydroxide, 1.5–2 parts of cerium dioxide, 1–2 parts of polyaniline, and 180–200 parts of water. The composite adhesive comprises a precipitant, sodium carboxymethyl cellulose, and a polytetrafluoroethylene solution.

2. The positive electrode slurry for nickel-metal hydride batteries according to claim 1, characterized in that, The composition, calculated by mass parts, includes 180–220 parts of spherical nickel hydroxide, 2–3 parts of ytterbium trioxide, 2–4 parts of precipitate, 1–2 parts of sodium carboxymethyl cellulose, 2–3 parts of polytetrafluoroethylene solution, 1.5–2.5 parts of zinc oxide, 1–2 parts of calcium hydroxide, 1.5–2 parts of cerium dioxide, 1–2 parts of polyaniline, and 180–200 parts of water.

3. The positive electrode slurry for nickel-metal hydride batteries according to claim 2, characterized in that, The composition, calculated by mass, includes 210 parts of spherical nickel hydroxide, 3 parts of ytterbium trioxide, 4 parts of precipitate, 1 part of sodium carboxymethyl cellulose, 3 parts of polytetrafluoroethylene solution, 2 parts of zinc oxide, 2 parts of calcium hydroxide, 2 parts of cerium dioxide, 2 parts of polyaniline, and 200 parts of water.

4. The positive electrode slurry for nickel-metal hydride batteries according to claim 1, characterized in that, The polytetrafluoroethylene solution comprises, by weight, 0.2 to 0.5 parts polytetrafluoroethylene, 0.2 to 0.5 parts surfactant, 0.1 to 0.2 parts thickener, and 2 to 4 parts water.

5. The positive electrode slurry for nickel-metal hydride batteries according to claim 4, characterized in that, The thickener is xanthan gum.

6. The positive electrode slurry for nickel-metal hydride batteries according to claim 4, characterized in that, The surfactant includes either hexadecyl carboxylate betaine or hexadecyl hydroxypropyl ammonium chloride.

7. A method for preparing a positive electrode slurry for nickel-metal hydride batteries, characterized in that, The preparation of the positive electrode slurry for nickel-metal hydride batteries as described in any one of claims 2 to 6 includes the following steps: A. Mix the prescribed amount of calcium hydroxide with 15% of the prescribed amount of water to obtain a calcium hydroxide solution; mix the prescribed amount of sodium carboxymethyl cellulose with 25% of the prescribed amount of water to obtain a sodium carboxymethyl cellulose solution; add the calcium hydroxide solution to the continuously stirred sodium carboxymethyl cellulose solution to obtain a sodium carboxymethyl cellulose-calcium hydroxide composite solution. B. Mix the amount of the formulated adhesive with 10% of the amount of water to obtain the adhesive solution; C. After mixing the spherical nickel hydroxide, ytterbium trioxide, zinc oxide, cerium dioxide and polyaniline in the prescribed amounts evenly, a mixed powder is obtained; the remaining amount of water is added to the mixed powder, and after mixing evenly, a first mixed liquid is obtained; D. Add sodium carboxymethyl cellulose-calcium hydroxide composite solution and osmotic adhesive solution to the first mixture, stir evenly, and then perform vacuum degassing to obtain the second mixture; E. Add the formulated amount of polytetrafluoroethylene solution to the second mixture, stir evenly, and obtain the positive electrode slurry for nickel-metal hydride batteries.

8. The application of a positive electrode slurry for nickel-metal hydride batteries in the preparation of nickel-metal hydride batteries, characterized in that, The application method using the positive electrode slurry for nickel-metal hydride batteries as described in any one of claims 1 to 6 is as follows: The positive electrode slurry is sprayed onto a porous current collector and allowed to penetrate into the interior of the porous current collector. After drying, a positive electrode coating is formed, resulting in a positive electrode sheet. Using the prepared positive electrode sheet as the positive electrode and the hydrogen storage alloy as the negative electrode, the negative electrode, separator and positive electrode were assembled in sequence in an argon-filled glove box, and electrolyte was injected. After encapsulation, the battery was left to stand at room temperature for 10-12 hours to obtain a nickel-metal hydride battery.

9. The application of the positive electrode slurry for nickel-metal hydride batteries according to claim 8 in the preparation of nickel-metal hydride batteries, characterized in that, The porous current collector is nickel foam.

10. The application of the positive electrode slurry for nickel-metal hydride batteries according to claim 8 in the preparation of nickel-metal hydride batteries, characterized in that, The areal density of the porous current collector is 150–180 g / m³. 2 The pore density is 80–100 pores / m³. 2 .

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