Alkaline anti-freezing electrolyte and preparation method of low-temperature nickel-zinc battery

Abstract

The invention relates to the technical field of chemical power sources, and discloses an alkaline anti-freezing electrolyte and a preparation method of a low-temperature nickel-zinc battery. The alkaline anti-freezing electrolyte comprises solvent water and solute dissolved in the solvent water; the solute comprises a main electrolyte KOH, an anti-freezing conductive agent potassium formate, a positive stabilizer LiOH, a basic zinc source ZnO, a deposition regulator zinc acetate dihydrate and a corrosion inhibitor KF; wherein the concentration of the potassium formate is 35wt%-55wt%. The preparation method of the alkaline anti-freezing electrolyte adopts a segmented temperature control dissolution process aiming at high-concentration potassium formate. A water molecule hydrogen bond network is destroyed through potassium formate, the freezing point is reduced, the low-temperature conductivity is improved, and zinc is induced to be laid and deposited and hydrogen evolution is inhibited in cooperation with a functional additive. The working temperature range of the battery is from-60 DEG C to 25 DEG C, the problem of electrolyte freezing at low temperature is effectively solved, and the battery has excellent low-temperature discharge capacity and cycle life.

Description

Technical Field

[0001] This invention relates to the field of data processing technology, specifically to a method for preparing an alkaline antifreeze electrolyte and a low-temperature nickel-zinc battery. Background Technology

[0002] Currently, the demand for chemical power sources in high-altitude and frigid regions, aerospace, and special equipment is growing. Nickel-zinc batteries, with their advantages of high energy density, high power output, low cost, and environmental friendliness, have become highly competitive energy storage devices. Compared to lead-acid and lithium-ion batteries, nickel-zinc batteries exhibit superior safety, eliminating the risk of thermal runaway and fire. The industry is working to explore their operational potential under extreme climatic conditions to meet energy supply demands in harsh environments.

[0003] For the aforementioned application scenarios, existing nickel-zinc batteries primarily rely on alkaline aqueous solutions for charge transport. In conventional technologies, high-concentration potassium hydroxide or sodium hydroxide solutions are often used as the main solvent. These electrolytes utilize hydroxides to provide abundant hydroxide ion carriers, combined with zinc oxide as the basic zinc source, to construct an ion conduction network. During charging and discharging, hydroxide ions shuttle between the positive and negative electrodes, maintaining the redox reaction of the nickel electrode and the dissolution and deposition reaction of the zinc electrode, thereby achieving the storage and release of electrical energy.

[0004] However, conventional alkaline electrolyte systems have shortcomings in low-temperature adaptability and interfacial stability. Firstly, traditional potassium hydroxide aqueous solutions have a high eutectic point; when the ambient temperature drops below -20°C, free water molecules easily associate to form ice crystals, physically blocking ion migration channels, causing a sharp increase in internal resistance, and rapid battery failure. Secondly, some technologies attempt to introduce organic alcohols such as ethylene glycol as antifreeze agents, but this often leads to increased electrolyte viscosity and decreased ionic conductivity, making it unable to support high-current discharge. Thirdly, the zinc anode has inherent thermodynamic instability in the liquid phase environment; uneven zinc ion deposition kinetics during charge and discharge easily induce dendrite vertical growth that pierces the separator, accompanied by continuous hydrogen evolution corrosion and electrode passivation. These problems are intertwined, making it difficult to simultaneously achieve low-temperature performance and long cycle life.

[0005] Therefore, the present invention provides an alkaline antifreeze electrolyte and a method for preparing a low-temperature nickel-zinc battery to overcome the shortcomings of the prior art. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an alkaline antifreeze electrolyte and a method for preparing a low-temperature nickel-zinc battery. This solves the problems of existing nickel-zinc batteries failing to function properly in extremely low-temperature environments due to electrolyte freezing or a sharp increase in internal resistance, as well as the tendency of the zinc anode to generate dendrites and corrosion, thus affecting the battery's cycle life.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides an alkaline antifreeze electrolyte, comprising solvent water and solute dissolved in the solvent water, wherein the solute comprises: a main electrolyte, an antifreeze conductive agent, a positive electrode stabilizer, a basic zinc source, a deposition regulator and a corrosion inhibitor; The antifreeze conductive agent is potassium formate, and its mass percentage concentration in the electrolyte is 35wt% to 55wt%.

[0008] By employing the above technical solution, potassium formate is used as the core antifreeze conductive component to construct a stable solid-liquid coexistence system with water molecules. Formate ions, with their asymmetric structure and high charge density, effectively disrupt the original tetrahedral hydrogen bond network between water molecules through strong solvation in solution, hindering the formation and growth of ice crystal nuclei, thereby lowering the freezing point of the electrolyte. Within a concentration range of 35wt% to 55wt%, potassium formate not only ensures that the electrolyte does not completely freeze at extremely low temperatures of -60℃, maintaining liquid or slurry-like ion transport channels, but also, compared to organic alcohol antifreeze agents such as ethylene glycol, potassium formate aqueous solutions have lower viscosity and higher ionic conductivity, ensuring the migration rate of potassium and hydroxide ions at low temperatures. This solves the problem of traditional alkaline electrolytes freezing or experiencing a sharp increase in internal resistance at low temperatures, leading to battery failure to discharge.

[0009] Preferably, the main electrolyte is potassium hydroxide, and its molar concentration in the electrolyte is 3.5M to 4.5M; the positive electrode stabilizer is lithium hydroxide, and its molar concentration in the electrolyte is 0.5M to 1.5M; the basic zinc source is zinc oxide, and its mass percentage concentration in the electrolyte is 1.5wt% to 2.5wt%.

[0010] By employing the above technical solution, a high-concentration strongly alkaline environment was constructed. 3.5M–4.5M potassium hydroxide provided sufficient OH-. - Charge carriers maintain the conductivity required for high-rate discharge; an appropriate amount of lithium hydroxide (0.5M~1.5M) is embedded in the positive electrode lattice to suppress the structural collapse and phase transition of the nickel electrode during charging and discharging, thereby improving the cycle stability of the positive electrode material; 1.5wt%~2.5wt% of zinc oxide maintains the saturation of zincate ions in the electrolyte through the common ion effect, thereby suppressing the self-corrosion and dissolution of the zinc active material in the negative electrode during standing.

[0011] Preferably, the deposition regulator is zinc acetate dihydrate, and its molar concentration in the electrolyte is 0.01M to 0.1M; the corrosion inhibitor is potassium fluoride, and its mass percentage concentration in the electrolyte is 0.1wt% to 1.0wt%.

[0012] By adopting the above technical solution, zinc acetate dihydrate and potassium fluoride work synergistically to regulate the deposition morphology of zinc anode.

[0013] Acetate ions preferentially adsorb on specific crystal faces of zinc crystals, changing the crystal growth energy barrier and inducing zinc deposition to change from vertically growing dendrites to layered or moss-like structures that spread along the surface, thereby physically blocking the risk of dendrites piercing the diaphragm. Fluoride ions in potassium fluoride react with the zinc surface to form a dense and ion-conducting zinc fluoride / zinc oxide composite protective film. This interfacial film reduces the direct contact area between the electrode and the water interface, lowers the exchange current density of the hydrogen evolution side reaction, and thus improves the coulombic efficiency and long-term cycle life of the battery.

[0014] Preferably, the solvent water is deionized water; the positive electrode stabilizer is anhydrous lithium hydroxide.

[0015] By adopting the above technical solution, deionized water eliminates the corrosive interference of impurities such as chloride ions and iron ions in tap water on the electrodes; using anhydrous lithium hydroxide as a raw material enables more precise control of the total water volume in the electrolyte system, avoids concentration deviations caused by the introduction of crystal water, and ensures the reproducibility and stability of high-concentration electrolyte formulations.

[0016] Secondly, the present invention provides a method for preparing an alkaline antifreeze electrolyte, comprising the following steps: S1. Add the weighed potassium formate to deionized water, stir to dissolve, and obtain potassium formate solution; S2. Add the positive electrode stabilizer, main electrolyte, corrosion inhibitor, basic zinc source and deposition regulator to the potassium formate solution in sequence, and stir until completely dissolved to obtain the alkaline antifreeze electrolyte. In step S1, the dissolution temperature is controlled according to the concentration of potassium formate: when the mass percentage concentration of potassium formate is ≤45wt%, it is dissolved by stirring at room temperature; when the mass percentage concentration of potassium formate is >45wt%, deionized water is preheated to 35℃~40℃, potassium formate is added and stirred to dissolve, and after the solution is clear, it is cooled to room temperature before proceeding to step S2.

[0017] By adopting the above technical solution, a segmented temperature-controlled dissolution strategy is used for potassium formate of different concentrations, which solves the contradiction between the difficulty of dissolving high-concentration salts and the stability of heat-sensitive additives.

[0018] When the potassium formate concentration exceeds 45 wt%, the solution approaches saturation, exhibiting an endothermic dissolution effect and increased solution viscosity, making complete dissolution difficult at room temperature. Preheating to 35℃~40℃ provides the activation energy required to overcome the lattice energy, accelerating solute diffusion and ensuring the formation of a homogeneous, clear, high-concentration base solution, thus avoiding compositional inhomogeneity caused by crystal precipitation. Before proceeding to step S2, the solution is forcibly cooled to room temperature. The potassium hydroxide added subsequently releases a significant heat of dissolution upon dissolution. If the base solution itself is too hot, the combined exothermic effect may lead to localized temperature runaway, causing thermal decomposition or volatilization of organic additives, or even side reactions and precipitation of components such as potassium fluoride. By preheating and dissolving the main salt, followed by cooling, and then adding the strong alkali and additives at a low temperature, the process ensures the stable coexistence of all components under mild conditions.

[0019] Preferably, in step S2, the system temperature is controlled to be ≤25℃.

[0020] By adopting the above technical solution, the system temperature during the dissolution and mixing process of strong alkali is strictly limited to prevent excessive evaporation of solvent water and oxidative degradation of organic additives caused by high temperature, thus ensuring that the component ratio of the final electrolyte product is consistent with the design value.

[0021] Thirdly, the present invention provides a low-temperature nickel-zinc battery, which adopts the following technical solution: A low-temperature nickel-zinc battery includes a positive electrode, a negative electrode, a separator, and the alkaline antifreeze electrolyte.

[0022] By adopting the above technical solution, the aforementioned alkaline antifreeze electrolyte is applied to the nickel-zinc battery system. Utilizing the electrolyte's high ionic conductivity and antifreeze properties at low temperatures, combined with the interface protection mechanism of the positive and negative electrodes, the operating temperature window of the nickel-zinc battery is broadened. This allows the battery to maintain normal electrochemical reactions and a high discharge capacity retention rate even in extreme low-temperature environments of -60℃. Simultaneously, it exhibits excellent cycle life in both room temperature and low-temperature cycling, solving the industry pain point of conventional nickel-zinc batteries failing in extremely cold climates.

[0023] This invention provides an alkaline antifreeze electrolyte and a method for preparing a low-temperature nickel-zinc battery. It has the following beneficial effects: 1. This invention introduces potassium formate at a mass percentage of 35wt%–55wt% as an antifreeze conductive agent to construct a high-conductivity low-temperature electrolyte system. The solvation effect of formate ions disrupts the original hydrogen bond network of water molecules, lowering the freezing point of the electrolyte and ensuring that the electrolyte remains liquid and maintains efficient ion migration channels even in extremely cold environments. Compared to traditional organic antifreeze agents such as ethylene glycol, this system exhibits lower low-temperature viscosity and higher conductivity, effectively solving the problem of nickel-zinc batteries failing to discharge at low temperatures due to electrolyte freezing or a sharp increase in internal resistance.

[0024] 2. This invention improves the deposition morphology and interfacial stability of the zinc anode through the synergistic combination of zinc acetate dihydrate and potassium fluoride. Acetate ions alter the crystal growth energy barrier through adsorption, inducing the zinc deposition layer to transform from a vertically growing dendritic structure to a layered structure that spreads along the surface, physically reducing the risk of puncturing the separator. Simultaneously, fluoride ions participate in the formation of a dense interfacial protective film on the electrode surface, reducing direct contact between zinc and water, lowering the hydrogen evolution side reaction and self-corrosion rate, thereby improving the coulombic efficiency and cycle life of the battery while ensuring low-temperature performance.

[0025] 3. This invention employs a segmented temperature-controlled dissolution process for high-concentration systems, resolving the contradiction between the difficulty in dissolving high-concentration salts and the easy decomposition of heat-sensitive components. By preheating the high-concentration potassium formate to overcome the dissolution energy barrier, and by forcibly cooling the base solution to room temperature before adding strong alkalis and functional additives, localized high temperatures in the system caused by the exothermic reaction of potassium hydroxide dissolution are effectively avoided. This process prevents the thermal decomposition of organic additives such as acetate and the unexpected volatilization of the solvent water, ensuring the precision of the high-concentration antifreeze electrolyte components and the chemical stability of the finished product. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In embodiments of the present invention, the alkaline antifreeze electrolyte for nickel-zinc batteries includes water as a solvent and solutes dissolved therein. To adapt to different application scenarios (such as different low-temperature requirements or discharge rate requirements), the content of each component can be adjusted within a certain range, with the following preferred ranges: Antifreeze conductive agent (HCOOK): 35wt%~55wt% by mass; Main electrolyte (KOH): molar concentration of 3.5M to 4.5M (e.g., 3.5M, 3.8M, 4.0M, 4.2M, 4.5M); Positive electrode stabilizer (LiOH): molar concentration of 0.5M to 1.5M (e.g., 0.5M, 0.8M, 1.0M, 1.2M, 1.5M); Basic zinc source (ZnO): 1.5wt% to 2.5wt% by mass (e.g., 1.5wt%, 1.8wt%, 2.0wt%, 2.2wt%, 2.5wt%). Deposition regulator (Zn(CH3COO)2·2H2O): molar concentration of 0.01M~0.1M; Corrosion inhibitor (KF): 0.1wt% to 1.0wt% by mass.

[0028] When the above components fluctuate within the above range, the antifreeze performance and electrochemical stability of the electrolyte can be maintained by combining the specific concentration of potassium formate of the present invention. In order to more intuitively compare the specific effects of the concentration change of the core antifreeze agent potassium formate (HCOOK) on the performance of the electrolyte, the following Examples 1-3 will fix the amount of other components and only change the concentration of HCOOK for comparative experiments.

[0029] Examples 1-3: Example 1: This example provides a method for preparing an alkaline antifreeze electrolyte and a low-temperature nickel-zinc battery (HCOOK concentration is 35wt%), including the following steps: Weigh the raw materials: 350.0g of potassium formate (HCOOK), 224.0g of main electrolyte KOH (corresponding to 4.0M), 23.9g of anhydrous positive electrode stabilizer LiOH (corresponding to 1.0M), 20.0g of basic zinc source ZnO (corresponding to 2.0wt%), 9.2g of deposition regulator Zn(CH3COO)2·2H2O (corresponding to 0.05M), and 5.0g of corrosion inhibitor KF (corresponding to 0.5wt%).

[0030] Preparation by dissolution: Take an appropriate amount of deionized water (about 367.9g), and at room temperature of 25℃, first add potassium formate to the deionized water and stir for about 30 minutes until completely dissolved.

[0031] Add in sequence: Add LiOH, KOH, KF, ZnO and Zn(CH3COO)2·2H2O to the above solution in sequence, stir continuously, and control the system temperature ≤25℃ until all solids are completely dissolved to obtain a clear and transparent alkaline antifreeze electrolyte with a total mass of 1000g.

[0032] Example 2: This example provides a method for preparing an alkaline antifreeze electrolyte and a low-temperature nickel-zinc battery (HCOOK concentration is 45wt%), including the following steps: Raw materials: Weigh 450.0g of potassium formate (HCOOK), and weigh the remaining components (KOH, LiOH, ZnO, Zn(CH3COO)2·2H2O, KF) in the same amounts as in Example 1.

[0033] Preparation by dissolution: Measure an appropriate amount of deionized water (approximately 267.9 g), and add potassium formate to the deionized water at room temperature (25°C). Stir to dissolve. Due to the increased concentration, ensure thorough stirring until the solution becomes clear.

[0034] Add in sequence: Add the remaining components to the above solution in sequence, following the same process steps as in Example 1, controlling the dissolution temperature to ≤25℃, and dilute with deionized water to a total mass of 1000g.

[0035] Example 3: This example provides a method for preparing an alkaline antifreeze electrolyte and a low-temperature nickel-zinc battery (HCOOK concentration is 55wt%). A preheating dissolution process is used for the high-concentration antifreeze agent, including the following steps: Raw materials: Weigh 550.0g of potassium formate (HCOOK), and weigh the remaining components (KOH, LiOH, ZnO, Zn(CH3COO)2·2H2O, KF) in the same amounts as in Example 1.

[0036] Preheating and dissolving: Measure out approximately 217.9g of deionized water (adjust according to the volume requirement) and preheat to 35-40℃. Add 550.0g of potassium formate to the warm water and stir at a constant temperature for 60 minutes until the potassium formate is completely dissolved, obtaining a high-concentration base solution.

[0037] Cooling and maturation: Allow the base liquid to cool naturally to 25°C (room temperature). After observing that no crystals precipitate, proceed with subsequent operations.

[0038] Add the following ingredients in sequence: LiOH, KOH, KF, ZnO, and Zn(CH3COO)2·2H2O to the cooled base solution. During this process, strictly control the temperature of the reaction system to ≤25℃ (especially when adding KOH, which is exothermic, a water bath is required for cooling). Stir until completely dissolved to obtain a clear, high-concentration antifreeze electrolyte with a total mass of 1000g.

[0039] Comparative Examples 1-3: Comparative Example 1: This comparative example provides a conventional nickel-zinc battery electrolyte without antifreeze.

[0040] The difference compared to Example 1 is as follows: Potassium formate (HCOOK) was not added, and the amount of deionized water was increased accordingly (approximately 717.9g) to maintain the total electrolyte mass at 1000g.

[0041] In terms of preparation process, the potassium formate dissolution operation was eliminated. Deionized water was directly mixed and dissolved with the remaining components (KOH, LiOH, ZnO, etc.). The types, amounts (molar concentration / mass percentage) of the remaining components and preparation conditions were the same as in Example 1.

[0042] Comparative Example 2: This comparative example provides an electrolyte using a conventional nonionic antifreeze agent (ethylene glycol).

[0043] The difference compared to Example 1 is as follows: Replace 350.0g of potassium formate (HCOOK) with an equal mass of ethylene glycol (HOCH2, 35wt%).

[0044] The preparation process was adjusted as follows: 350.0g of ethylene glycol was added to 200g of deionized water and stirred for 20min until the mixture was uniform. The dosage of other components and subsequent addition steps (adding KOH, LiOH, ZnO, etc.) were the same as in Example 1.

[0045] Comparative Example 3: This comparative example provides an electrolyte using a different type of antifreeze (calcium chloride).

[0046] The difference compared to Example 1 is as follows: Replace 350.0g of potassium formate (HCOOK) with an equal mass of calcium chloride (CaCl2, 35wt%).

[0047] The preparation process was adjusted as follows: 350.0g of calcium chloride was added to 200g of deionized water and stirred for 30min until completely dissolved. The dosage of other components and subsequent addition steps were the same as in Example 1.

[0048] Test example: Performance testing: To verify the performance of the alkaline antifreeze electrolyte for nickel-zinc batteries of the present invention, the following tests were conducted on the electrolytes prepared in Examples 1-3 and Comparative Examples 1-3 above.

[0049] 1. Ionic conductivity test: The ionic conductivity of the electrolyte was tested using an electrochemical workstation.

[0050] Test Procedure: The electrolyte to be tested was injected into a standard conductivity cell and placed in constant temperature baths at -60℃, -25℃, and 25℃ respectively, and allowed to stand for 2 hours to ensure temperature equilibrium. An AC impedance scan was performed in the frequency range of 100kHz to 10mHz. The volume resistance was calculated based on the high-frequency intercept of the Nyquist plot, and the ionic conductivity (S / cm) was obtained by converting this value with the cell constant.

[0051] 2. Freeze-freeze stability test: The phase stability of the electrolyte was tested using the static refrigeration observation method.

[0052] Test procedure: Take 50 mL of each electrolyte sample and seal it in a transparent glass bottle. Place them in low-temperature test chambers at -60℃ and -25℃ respectively, and let them stand at the constant temperature for 72 hours. Immediately after removal, observe and record the state of the electrolyte (clear, turbid, partially frozen or completely frozen).

[0053] 3. Discharge performance testing: Electrochemical performance testing was conducted on nickel-zinc pouch cells. The specific battery fabrication process is as follows: Negative electrode preparation: Nano zinc oxide (70 parts), zinc powder (20 parts), bismuth oxide (6.1 parts), titanium suboxide (1 part), aluminum oxide (0.2 parts), indium oxide (0.1 parts), polypropylene fiber (0.1 parts), carboxymethyl cellulose (0.4 parts), sodium polyacrylate (0.1 parts) and styrene-butadiene rubber (2 parts) are mixed evenly, and an appropriate amount of water is added to stir into a slurry. The slurry is coated on a copper mesh current collector, dried and rolled to form a negative electrode sheet.

[0054] Positive electrode preparation: Cobalt-coated nickel suboxide (94 parts), cobalt suboxide (0.5 parts), ruthenium dioxide (0.5 parts), titanium suboxide (1 part) and styrene-butadiene rubber (4 parts) are mixed evenly, slurry is prepared and coated on nickel foam current collector, dried and rolled to form positive electrode sheet.

[0055] Battery assembly: The positive electrode, separator, and negative electrode are stacked and assembled, 2.4g of electrolyte to be tested is injected, and the battery is sealed and left to stand for aging for 24 hours.

[0056] Test conditions: The assembled batteries were placed in -60℃ and -25℃ temperature chambers for 4 hours respectively. The batteries were then discharged at a constant current rate of 0.2C using a battery testing system, and the first discharge capacity was recorded.

[0057] 4. Cycle life test: The nickel-zinc batteries prepared in step 3 were subjected to charge-discharge cycle tests at 25℃, -25℃ and -60℃ respectively.

[0058] Test procedure: Charge at a constant current of 0.2C to the cutoff voltage (1.9V), let stand for 10 minutes, then discharge at a constant current of 0.2C to the cutoff voltage (1.2V). Continue cycling until the battery discharge capacity decays to 80% of the initial capacity, and record the number of cycles at this point.

[0059] Test results: Table 1. Summary of test results of physical properties of electrolyte and electrochemical performance of battery for each group. Test Project Experimental Example 1 Experiment Example 2 Experimental Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Ionic conductivity at -60℃ (S / cm) <![CDATA[1.2×10 -3 ]]> <![CDATA[2.5×10 -3 ]]> <![CDATA[3.1×10 -3 ]]> <![CDATA[3.0×10 -6 (Completely frozen) <![CDATA[8.0×10 -4 ]]> <![CDATA[4.5×10 -6 ]]> Ionic conductivity at -25℃ (S / cm) <![CDATA[8.5×10 -3 ]]> <![CDATA[1.5×10 -2 ]]> <![CDATA[1.8×10 -2 ]]> <![CDATA[1.2×10 -4 (Partial freeze) <![CDATA[5.2×10 -3 ]]> <![CDATA[2.8×10 -3 ]]> Ionic conductivity at 25℃ (S / cm) 0.20 0.22 0.15 0.12 0.09 0.16 -60℃ frozen state No freezing, slightly cloudy No freezing, clear and transparent No freezing, clear and transparent Completely frozen, solid. No freezing, cloudy Completely frozen, solid. -25℃ frozen state No freezing, clear and transparent No freezing, clear and transparent No freezing, clear and transparent Partially frozen, with a paste-like consistency. No freezing, clear and transparent No freezing, cloudy -60℃ discharge capacity (relative to room temperature) 480 676 682 0% (Unable to discharge) 300 0 (Cannot discharge) Cycle life (cycles) with 80% capacity retention at -60℃ 203 215 206 0 17 0 -25℃ discharge capacity (mAh / g) 1020 1332 1232 225 824 450 Cycle life (cycles) with 80% capacity retention at -25℃ 175 182 186 16 172 90 Discharge capacity at 25℃ (mAh / g) 1500 1502 1503 1500 1498 1500 Cycle life (times) with 80% capacity retention at 25℃ 241 242 207 294 156 206 Conclusion: Based on the test data in Table 1, the effectiveness of the technical solution of this invention is analyzed as follows: Comparing the data from the examples and comparative examples, it can be seen that potassium formate exhibits superior overall performance compared to ethylene glycol and calcium chloride in this system.

[0060] At an extreme low temperature of -60°C, Examples 1-3 with added potassium formate remained liquid, and the ionic conductivity was maintained at 10. -3 The conductivity is on the order of S / cm. In contrast, Comparative Example 2 used the nonionic antifreeze ethylene glycol, which, although not completely frozen at -60°C, had a conductivity of only 8.0 × 10⁻⁶. -4 S / cm, lower than 2.5 × 10 in Example 2. -3S / cm. This indicates that potassium formate, as an ionic compound, dissociates K+ while lowering the freezing point. + and HCOO - It directly participates in charge transport, establishing an effective ion migration channel; while ethylene glycol, although inhibiting crystallization, hinders ion migration due to its nonionic properties and increased viscosity.

[0061] Comparative Example 3 used calcium chloride as a salt-based antifreeze agent, which completely froze at -60°C, causing the battery to fail to discharge. This demonstrates that not all salts are suitable for alkaline zinc-nickel systems. Potassium formate achieves a specific antifreeze effect by disrupting the hydrogen bond network of water molecules and forming a stable eutectic structure with the alkaline electrolyte system.

[0062] The effect of concentration on electrochemical performance: Data from Examples 1 to 3 revealed a nonlinear relationship between potassium formate concentration and battery performance.

[0063] Low-temperature performance increases with concentration: As the potassium formate concentration increases from 35 wt% to 55 wt%, the ionic conductivity and discharge capacity at -60 °C show an increasing trend. Example 3 (55 wt%) exhibits the highest conductivity (3.1 × 10⁻⁶) at -60 °C. -3 The high concentration of solute (S / cm) and discharge capacity (682mAh / g) demonstrate that the high concentration of solute has a stronger destructive effect on the hydrogen bond network and is more conducive to maintaining the liquid environment at deep cryogenic temperatures.

[0064] Room temperature performance and viscosity limitations: At room temperature (25°C), the cycle life of Example 3 (207 cycles) was lower than that of Example 2 (242 cycles), and the room temperature conductivity (0.15 S / cm) was lower than that of Example 2 (0.22 S / cm). This is because when the potassium formate concentration approaches saturation (55 wt%), the solution viscosity increases, leading to increased resistance to ion migration at room temperature. Additionally, the high concentration of formate ions may slightly inhibit the reaction kinetics on the zinc electrode surface.

[0065] The comprehensive performance evaluation of Example 2 (45wt% HCOOK) achieved the best balance between low-temperature performance and room-temperature cycle life. Its discharge capacity at -60°C reached 676 mAh / g, close to the level of Example 3; simultaneously, its cycle life at 25°C reached 242 cycles, superior to Comparative Example 2 (156 cycles). Combined with the preheating and dissolution process for high-concentration systems proposed in this invention, this formulation ensures deep-temperature operation capability without sacrificing the battery's room-temperature lifespan, demonstrating high industrial application value.

Claims

1. An alkaline antifreeze electrolyte, characterized in that, It includes water as a solvent and solutes dissolved in the water as a solvent, wherein the solutes include: main electrolyte, antifreeze conductive agent, positive electrode stabilizer, basic zinc source, deposition regulator and corrosion inhibitor; The antifreeze conductive agent is potassium formate, and its mass percentage concentration in the electrolyte is 35wt% to 55wt%.

2. The alkaline antifreeze electrolyte according to claim 1, characterized in that, The main electrolyte is potassium hydroxide, and its molar concentration in the electrolyte is 3.5M to 4.5M.

3. The alkaline antifreeze electrolyte according to claim 1, characterized in that, The positive electrode stabilizer is lithium hydroxide, and its molar concentration in the electrolyte is 0.5M to 1.5M.

4. The alkaline antifreeze electrolyte according to claim 1, characterized in that, The basic zinc source is zinc oxide, and its mass percentage concentration in the electrolyte is 1.5wt% to 2.5wt%.

5. The alkaline antifreeze electrolyte according to claim 1, characterized in that, The deposition regulator is zinc acetate dihydrate, with a molar concentration of 0.01M to 0.1M in the electrolyte; the corrosion inhibitor is potassium fluoride, with a mass percentage concentration of 0.1wt% to 1.0wt% in the electrolyte.

6. The alkaline antifreeze electrolyte according to claim 1, characterized in that, The solvent water is deionized water; the positive electrode stabilizer is anhydrous lithium hydroxide.

7. A method for preparing an alkaline antifreeze electrolyte, characterized in that, Includes the following steps: S1. Add the weighed potassium formate to deionized water, stir to dissolve, and obtain potassium formate solution; S2. Add the positive electrode stabilizer, main electrolyte, corrosion inhibitor, basic zinc source and deposition regulator to the potassium formate solution in sequence, and stir until completely dissolved to obtain the alkaline antifreeze electrolyte. In step S1, the dissolution temperature is controlled according to the concentration of potassium formate: when the mass percentage concentration of potassium formate is ≤45wt%, it is dissolved by stirring at room temperature; when the mass percentage concentration of potassium formate is >45wt%, deionized water is preheated to 35℃~40℃, potassium formate is added and stirred to dissolve, and after the solution is clear, it is cooled to room temperature before proceeding to step S2.

8. The method for preparing an alkaline antifreeze electrolyte according to claim 7, characterized in that, In step S2, the system temperature is controlled to be ≤25℃.

9. A low-temperature nickel-zinc battery, comprising a positive electrode, a negative electrode, a separator, and the alkaline antifreeze electrolyte as described in any one of claims 1-6.

10. A low-temperature nickel-zinc battery according to claim 9, characterized in that, The operating temperature range of the low-temperature nickel-zinc battery is -60℃ to 25℃.