Superionic conductor electrolyte and preparation method thereof, hybrid superionic conductor electrolyte, quasi-solid flexible superionic conductor electrolyte, alkaline battery superionic conductor electrolyte and energy storage device

Abstract

The present application relates to the technical field of ionic liquid and new energy battery electrolyte composite, in particular to superionic conductor electrolyte and its preparation method, hybrid superionic conductor electrolyte, quasi-solid flexible superionic conductor electrolyte, alkaline battery superionic conductor electrolyte and energy storage equipment. The superionic conductor electrolyte includes ionic liquid [A]X, wherein [A] is derived from choline or its halide, and X is derived from pyrimidine carboxylic acid derivative. The superionic conductor electrolyte has super-high ionic conductivity, thermal stability, electrochemical stability, non-volatility and non-flammability; has the dual nature of super-high ionic conductor and green solvent, and can completely replace volatile organic solvent as green solvent, thereby improving the safety, stability and green environmental protection of battery electrolyte. It has the characteristics of wide temperature range ionic liquid electrolyte, meets and exceeds the ideal low-temperature electrolyte standard, and is suitable for the application of battery electrolyte, supercapacitor electrolyte and electrochemical sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of composites of ionic liquids and new energy battery electrolyte materials, and in particular to superionic conductor electrolytes and preparation methods thereof, hybrid superionic conductor electrolytes, quasi-solid-state flexible superionic conductor electrolytes, alkaline battery superionic conductor electrolytes and energy storage devices. Background Art

[0002] Electrolyte is one of the important components of electrochemical energy storage devices. The stability and ionic conductivity of electrolyte are the key to determining battery performance (Chen Renjie, Zhao Taolin, "Ionic Liquid Electrolytes", Science Press, first edition 2023). The high conductivity of electrolyte is the key to reducing Li + Migration resistance is an important guarantee for improving battery rate performance and determines the rapid charge and discharge performance of ion batteries. Improving the conductivity of the electrolyte, especially the ionic conductivity under low temperature conditions, is of particular significance for broadening the practical application range of lithium-ion batteries and enabling their use under extreme conditions (Li Fujun, ed., "Secondary Battery Science and Technology", Science Press, first edition 2021).

[0003] Battery safety is considered to be a more important issue than performance, and the extensive use of volatile organic solvents poses a major threat to battery safety. Organic solvents are flammable and can easily cause temperature increases under conditions such as battery heating, overcharging or over-discharging, short circuit, and high temperature, accelerating heat generation inside the battery. Excessive heat accumulates inside the battery, causing thermal decomposition of the electrode active material or oxidation of the electrolyte, generating a large amount of gas, causing a sharp increase in the internal pressure of the battery, and triggering safety hazards such as combustion or explosion. Existing ionic electrolytes are ionic conductors in which lithium / sodium salts are dissolved in organic solvents. At present, the representative solvent with a high dielectric constant is a carbonate solvent such as ethylene carbonate (EC), which is almost an indispensable component in all lithium-ion battery electrolytes (Chen Renjie, "Advanced Battery Functional Electrolyte Materials", Science Press, first edition 2020).

[0004] Ionic liquids are organic salts composed entirely of positively charged cations and negatively charged anions, and have excellent electrochemical properties, such as a wide electrochemical window, high ionic conductivity, and interfacial compatibility with electrode materials. Ionic liquids are also a type of green design solvent with good thermal stability, non-volatility, and non-flammability. They can replace volatile organic solvents, reduce the adverse effects of electrolyte organic solvents on ionic conductivity, and further improve battery safety, reduce environmental and health damage, and achieve truly green and clean battery resources. In short, the flexibility of ionic liquid design and ionic properties play an important role in electrochemical fields such as electrolytes, electrocatalysis, supercapacitors, and electrochemical sensors (Xie Ze'an, Zhao Fangxuan, Wang Yiyi, et al. Application of ionic liquids in electrochemistry [J]. Journal of Shenyang Normal University (Natural Science Edition), 2024, 42(01): 19-23.).

[0005] However, the performance of ionic liquids as electrolytes for energy storage devices still needs further optimization. Ionic liquids have low conductivity and high viscosity (their viscosity is 1-2 orders of magnitude higher than that of typical organic solvents), which can lead to suboptimal rate performance. For sodium-ion batteries, there is currently no ideal ionic liquid electrolyte formulation that combines a suitable potential window, fast ion conduction, and the ability to withstand extreme temperatures (Chen Renjie and Zhao Taolin, "Ionic Liquid Electrolytes," Science Press, first edition 2023).

[0006] Wide temperature range refers to a wide operating temperature range. With the continuous expansion of lithium battery application scenarios, the development of high and low temperature lithium battery technology is imminent, and liquid electrolytes with a wide operating temperature range are key (Qi Shihan, Wang Zhongsheng, Guo Kanglong, et al. Research progress of wide temperature range lithium battery electrolytes [J]. Science Bulletin, 2022, 67(24): 2937-2949.). The standards for ideal low-temperature electrolytes are: (1) ionic conductivity higher than 1mS / cm at -40°C, (2) able to operate in the temperature range of -40°C to 60°C (Chen Renjie, Advanced Battery Functional Electrolyte Materials, Science Press, first edition 2020). Existing electrolyte materials solidify at low temperatures, causing a significant decrease in ionic conductivity, and are prone to thermal decomposition at high temperatures, leading to safety issues, and cannot meet the requirements for a wide operating temperature range.

[0007] Chinese patent CN 118530183 A discloses a pyrimidine ionic liquid, its preparation method, and its application. This pyrimidine ionic liquid has advantages such as low viscosity, stability to air and water, good solute compatibility, and excellent solubility. It is suitable for use as a functionalized ionic liquid solvent in the biopharmaceutical field.

[0008] Chinese patent CN 106058312 B discloses a solid-state ionic liquid electrolyte, its preparation method, and application. It is an imidazolium ionic liquid hybrid solid-state ionic liquid electrolyte synthesized under nearly anhydrous conditions and under nitrogen and argon protection. Its ionic conductivity at 0°C, 30°C, and 60°C is 0.79, 1.91, and 4.79 mS / cm, respectively. The low ionic conductivity and narrow operating temperature range make it unable to meet the ideal low-temperature electrolyte standards and higher electrochemical performance requirements.

[0009] Therefore, the purpose of the present invention is to design an ionic liquid electrolyte that can completely replace volatile organic solvents and further improve the ionic conductivity and operating temperature range of the electrolyte material.

[0010] In view of this, the present invention is proposed. Summary of the Invention

[0011] The present invention aims to provide a superionic conductor electrolyte that can completely replace volatile organic solvents, further improving the electrolyte material's ionic conductivity and operating temperature range. This superionic conductor electrolyte exhibits ultrahigh ionic conductivity, thermal stability, electrochemical stability, non-volatility, and non-flammability. Possessing the dual properties of a superionic conductor and a green solvent, it can replace volatile organic solvents, further enhancing the stability, safety, and environmental friendliness of battery electrolyte materials. It meets ideal low-temperature electrolyte standards and can operate within a temperature range of -46°C to +270°C.

[0012] The present invention is achieved in that:

[0013] In a first aspect, the present invention provides a superionic conductor electrolyte comprising an ionic liquid [A]X, wherein [A] represents a cationic portion, X represents an anionic portion, [A] is derived from choline or a halide thereof, and X is derived from a pyrimidinecarboxylic acid derivative.

[0014] In an optional embodiment, [A] is derived from any one of the compounds represented by the following structural formulas:

[0015]

[0016] In an optional embodiment, X is derived from a compound represented by the following structural formula:

[0017] wherein R1 is selected from H or hydroxyl, and R2 is selected from C1-C4 alkyl;

[0018] Preferably, X is derived from any one of the compounds represented by the following structural formulas:

[0019]

[0020] In an optional embodiment, the molar ratio of [A] to X is (1:1) to (14:1), preferably (2:1) to (10:1).

[0021] In an optional embodiment, the superionic conductor electrolyte is a pure aqueous superionic conductor electrolyte; the pure aqueous superionic conductor electrolyte does not contain any organic solvent;

[0022] Preferably, the superionic conductor electrolyte consists of water and ionic liquid [A]X;

[0023] Preferably, the concentration of the ionic liquid [A]X in the superionic conductor electrolyte is 10-70 wt%.

[0024] In a second aspect, the present invention provides a method for preparing the superionic conductor electrolyte described in the aforementioned embodiment, comprising: mixing and dissolving a raw material for forming a cation [A] and a raw material for forming an anion X;

[0025] Preferably, the preparation is carried out under non-vacuum conditions;

[0026] Preferably, the temperature of the mixed dissolution is 30-50°C and the time is 10-30 minutes;

[0027] Preferably, water is used to dissolve the raw materials for forming the cation [A] and the raw materials for forming the anion X;

[0028] Preferably, the process comprises: adding a raw material for forming the cation [A] and a raw material for forming the anion X into a small amount of water, stirring them conventionally at room temperature and pressure until they are completely dissolved, and synthesizing the required amount of ionic liquid [A]X in situ; and adding water to make the total liquid volume 100%.

[0029] In a third aspect, the present invention provides a hybrid superionic conductor electrolyte, which comprises the superionic conductor electrolyte described in the aforementioned embodiment and an electrolyte additive; the electrolyte additive is an electrolyte salt;

[0030] Preferably, the electrolyte salt is selected from any one of lithium salt, sodium salt, aluminum salt, magnesium salt, zinc salt, copper salt and metal oxide;

[0031] Preferably, the concentration of the electrolyte salt in the hybrid superionic conductor electrolyte is 5-30 wt%.

[0032] In a fourth aspect, the present invention provides a quasi-solid-state flexible superionic conductor electrolyte, comprising the superionic conductor electrolyte described in the aforementioned embodiment and an electrolyte additive; the electrolyte additive is an electrolyte salt and a polymer; or the electrolyte additive is a polymer;

[0033] Preferably, the electrolyte salt is selected from any one of lithium salt, sodium salt, aluminum salt, magnesium salt, zinc salt, copper salt and metal oxide;

[0034] Preferably, the polymer is selected from any one of polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol, polyvinylidene fluoride, polyacrylamide, agar, carrageenan, xanthan gum, sodium alginate and cellulose;

[0035] Preferably, the concentration of the electrolyte salt in the quasi-solid flexible superionic conductor electrolyte is 5-30 wt%;

[0036] The concentration of the polymer in the quasi-solid flexible superionic conductor electrolyte is 5-20 wt %.

[0037] In a fifth aspect, the present invention provides an alkaline battery superionic conductor electrolyte, comprising the superionic conductor electrolyte described in the aforementioned embodiment and an electrolyte additive; the electrolyte additive is selected from any one of sodium hydroxide and potassium hydroxide;

[0038] Preferably, the concentration of the electrolyte additive in the alkaline battery superionic conductor electrolyte is 5-15 wt%.

[0039] In a sixth aspect, the present invention provides an energy storage device and an electrochemical sensor, comprising at least one of the superionic conductor electrolyte described in the aforementioned embodiment, the hybrid superionic conductor electrolyte described in the aforementioned embodiment, the quasi-solid-state flexible superionic conductor electrolyte described in the aforementioned embodiment, and the alkaline battery superionic conductor electrolyte described in the aforementioned embodiment.

[0040] Preferably, the energy storage device includes a battery and a supercapacitor;

[0041] Preferably, the battery comprises any one of a wide temperature range lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, a zinc-ion battery, a copper-ion battery and a fuel cell.

[0042] The present invention has the following beneficial effects: The embodiment of the present invention provides a superionic conductor electrolyte with ultra-high ionic conductivity, thermal stability, electrochemical stability, non-volatility and non-flammability. In particular, it has the duality of a superionic conductor and a green solvent, and then it can be used as an electrolyte itself. It can also replace the volatile organic solvents in existing electrolytes, further improving the safety, stability and green environmental protection of the electrolyte. At the same time, it meets and exceeds the ideal low-temperature electrolyte standards, and can operate in the range of -46°C to +270°C, and can then be used to prepare wide-temperature lithium-ion batteries, sodium-ion batteries, magnesium-ion batteries, zinc-ion fuel cells, copper-ion batteries, supercapacitors and other energy storage devices and electrochemical sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 A correlation diagram between the molar ratio of the composition of the ionic liquid [A]X and the ionic conductivity provided in an embodiment of the present invention;

[0045] Figure 2 A correlation diagram between the mass concentration of the ionic liquid [A]X and the ionic conductivity provided in an embodiment of the present invention;

[0046] Figure 3 A differential scanning calorimetry (DSC) curve of the superionic conductor electrolyte provided in Example 1 of the present invention;

[0047] Figure 4 This is a thermogravimetric analysis (TGA) curve of the superionic conductor electrolyte provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0048] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0049] The challenge in the electrochemical application of ionic liquids lies in designing ionic liquids with a wide electrochemical window and high conductivity. The main obstacle to the application of ionic liquid electrolytes in existing technologies is their low conductivity, which decreases with decreasing temperature. Obviously, the conductivity of an ionic liquid depends on its composition, which also determines its thermodynamic and electrochemical stability. Therefore, the key to preparing ionic liquid electrolytes that meet practical needs lies in the correct selection and design of ion pairs.

[0050] The embodiments of the present invention adopt a de novo design strategy for hydrated ionic liquids to obtain a series of ionic liquids [A]X. It was unexpectedly discovered that ionic liquid [A]X has ultra-high ionic conductivity characteristics. In preliminary tests, its room temperature ionic conductivity can reach over 100 mS / cm, and its stable temperature range is between -46°C and +270°C. This meets and exceeds the standards of an ideal low-temperature electrolyte. Therefore, the superionic conductor electrolyte provided by the embodiments of the present invention has both superionic conductor properties and wide temperature range properties, and is suitable for wide temperature range lithium-ion batteries, as well as non-lithium-ion battery electrolytes such as sodium ions, magnesium ions, zinc ions, and copper ions, supercapacitor electrolytes, and electrochemical sensors.

[0051] Specifically, in a first aspect, the present invention provides a superionic conductor electrolyte, which includes an ionic liquid [A]X, wherein [A] represents a cationic portion, X represents an anionic portion, [A] is derived from choline or its halide, and X is derived from a pyrimidinecarboxylic acid derivative.

[0052] Specifically, [A] is derived from any one of the compounds represented by the following structural formulas:

[0053]

[0054] That is, [A] is derived from any one of choline, choline chloride, choline bromide, choline iodide, choline fluoride, choline chlorofluoride and β-methylcholine chloride.

[0055] X is derived from the compound represented by the following structural formula:

[0056] wherein R1 is selected from H or hydroxyl, and R2 is selected from C1-C4 alkyl;

[0057] Preferably, X is derived from any one of the compounds represented by the following structural formulas:

[0058]

[0059] The superionic conductor electrolyte provided by the embodiments of the present invention has ultra-high ionic conductivity and wide temperature range. Its room-temperature ionic conductivity is as high as 100 mS / cm or higher, and its operating temperature range is between -46°C and +270°C. Therefore, it can be used as an electrolyte in energy storage devices such as wide-temperature batteries and supercapacitors, providing a reliable power supply for these devices in extreme environments.

[0060] The stability and ionic conductivity of electrolyte materials are key factors in determining battery performance. Since the cation portion [A] of the ionic liquid [A]X in the embodiments of the present invention is choline and its halide, the strong electronegativity of the halogen atoms facilitates the dissociation of metal ions and anions, thereby affecting the electrochemical performance of the ionic liquid electrolyte, exhibiting low migration energy barriers and ultrahigh ionic conductivity, thus possessing superionic conductor properties.

[0061] On the other hand, since the anion portion X of the ionic liquid [A]X constituting the embodiment of the present invention is a pyrimidinecarboxylic acid derivative, it has a significant water structuring effect, which can make more water molecules in a bound water state, thereby weakening the influence of the solvent effect of water, which helps to reduce the battery capacity attenuation and safety problems caused by salting out on the negative electrode surface during low temperature and high rate charging of the power battery.

[0062] Furthermore, the relationship between the molar ratio and concentration of the ionic liquid [A]X and the ionic conductivity was tested in the examples. The results showed that: (1) the ionic conductivity increased with the increase of the ratio of [A]:X in the ionic liquid [A]X. When the molar ratio of [A]:X was 8:1, the ionic conductivity approached the peak value and then slowly increased (see Table 1, Figure 1 ); (2) The ionic conductivity increases with the concentration of ionic liquid [A]X. When the concentration reaches 30-40 wt%, the ionic conductivity approaches the peak value and then begins to decrease (see Table 2, Figure 2 ).

[0063] Furthermore, the molar ratio of [A] to X is (1:1) to (14:1), for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, and 14:1, and is preferably any value between (1:1) and (14:1), for example, (2:1) to (10:1);

[0064] Furthermore, the superionic conductor electrolyte is a pure aqueous superionic conductor electrolyte; the pure aqueous superionic conductor electrolyte does not contain any organic solvent and comprises only water and an ionic liquid [A]X. The concentration of the ionic liquid [A]X in the superionic conductor electrolyte is 10-70 wt %, for example, 10%, 20%, 30%, 40%, 50%, 60%, 70%, or any other value between 10-70%.

[0065] Aqueous liquid electrolyte is a green electrolyte that does not cause environmental pollution. Compared with conventional non-aqueous electrolytes, it has advantages in cost, safety and battery power density. In contrast, existing lithium-ion batteries use anhydrous organic solvents containing lithium ions as electrolytes, and the organic solvents used are not only toxic but also flammable. In addition, the production cost is also significantly increased due to the anhydrous operating environment, which limits its application in large-scale energy storage and other fields. Therefore, using aqueous electrolytes instead of organic solvent electrolytes is considered to be one of the effective methods (Chen Renjie, "Advanced Battery Functional Electrolyte Materials", Science Press, first edition in 2020).

[0066] Furthermore, since the raw materials for forming the ionic liquid [A]X are all non-toxic, harmless and biodegradable substances of natural origin, they are completely green and biocompatible.

[0067] In a second aspect, the present invention provides a method for preparing the superionic conductor electrolyte described in the aforementioned embodiment, comprising: mixing and dissolving a raw material for forming a cation [A] and a raw material for forming an anion X.

[0068] Specifically, the raw materials for forming the cation [A] and the raw materials for forming the anion X are sequentially added to a small amount of water, mixed and dissolved at room temperature and pressure, first synthesizing the required amount of ionic liquid [A]X in situ, and then adding water to the total liquid volume to 100%; preferably, the mixed dissolution temperature is 30-50°C and the time is 10-30 minutes.

[0069] Thirdly, the present invention provides a hybrid superionic conductor electrolyte. Because the superionic conductor electrolyte provided by the embodiments of the present invention possesses the dual properties of a superionic conductor and a green solvent, it can completely replace the volatile organic solvents in existing electrolytes, further improving the safety, stability, and environmental friendliness of the electrolyte material.

[0070] The metal cations doped in the electrolyte rotate with the surrounding anions through the interaction of orientation forces and induction forces, and always rotate in the direction of reducing the energy barrier of the metal ions, allowing metal ions such as lithium ions to migrate rapidly along the minimum energy path, further improving the ionic conductivity of the electrolyte.

[0071] Specifically, ionic liquid [A]X can replace volatile organic solvents commonly used in existing electrolyte technologies, such as carbonates, nitriles, and ethers. This optimizes carbonate-centered electrolyte formulations, avoids metal reactions and interfacial instability caused by excessive carbonates, strengthens the electrode-electrolyte interface structure, and reduces interfacial impedance. It provides a superior lithium-ion conduction pathway compared to existing electrolytes and optimizes the compatibility between the electrolyte and electrode materials.

[0072] Furthermore, different electrolyte salts, such as lithium, sodium, aluminum, magnesium, zinc, copper, and metal oxides, can be added to the electrolyte in the absence of organic solvents to construct hybrid superionic conductor electrolytes, further optimizing battery electrolyte performance for applications under different conditions. For example, simply adding a small amount of lithium trifluoromethanesulfonyl imide (LiTFSi, 5 wt%) can significantly increase the ionic conductivity of the superionic conductor electrolyte (~120 mS / cm).

[0073] The concentration of the electrolyte salt in the hybrid superionic conductor electrolyte is 5-30 wt%, for example, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or any other value between 5-30 wt%.

[0074] Furthermore, because the superionic conductive electrolytes provided by the embodiments of the present invention can be easily and conveniently dissolved into various electrolyte salts without organic solvents, they can be used to prepare strategically important, low-cost hybrid electrolytes for non-lithium ion batteries, such as sodium ion, magnesium ion, and zinc ion. Unlike lithium-ion batteries, sodium-ion batteries are widely considered to possess excellent fast-charging and low-temperature performance, making them the preferred choice for the next generation of resource-independent, high-efficiency energy storage systems.

[0075] Furthermore, since there is no need to add a large amount of organic solvent, the hybrid superionic conductor electrolyte can be prepared by conventional stirring at room temperature and pressure, thereby further simplifying the electrolyte composition and preparation process, and preparing the hybrid superionic conductor electrolyte by a simple, low-cost, low-energy, and pollution-free process, further optimizing the production process, electrochemical properties, and extreme environmental applicability of the ionic liquid electrolyte.

[0076] Fourthly, the present invention provides a quasi-solid-state flexible superionic conductor electrolyte that further optimizes the performance and environmental compatibility of battery electrolytes, thereby improving battery performance. For example, it can be used as a battery electrolyte in fields such as wearable devices and biomedical engineering, which require higher safety and convenience, as well as in supercapacitors and electrochemical sensors.

[0077] Since the superionic conductor electrolyte provided by the embodiment of the present invention has the dual properties of a superionic conductor and a green solvent, a quasi-solid-state flexible superionic conductor electrolyte can be simply and conveniently prepared by directly combining a polymer with an electrolyte salt or simply dissolving the polymer in the superionic conductor electrolyte without the need for an organic solvent, while maintaining its superionic conductor properties.

[0078] The polymer is selected from any one of polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, polyvinylidene fluoride, polyacrylamide, agar, carrageenan, xanthan gum, sodium alginate and cellulose. The mass concentration of the polymer in the quasi-solid flexible superionic conductor electrolyte is 5-20%, for example, 5%, 10%, 15%, 20% or any value between 5-20%.

[0079] The electrolyte salt is selected from any one of lithium salt, sodium salt, aluminum salt, magnesium salt, zinc salt, copper salt and metal oxide. The mass concentration of the electrolyte salt in the quasi-solid flexible superionic conductor electrolyte is 5-30%, for example, 5%, 10%, 15%, 20%, 25% and 30% or any value between 5-30%.

[0080] In the fifth aspect, the embodiments of the present application provide a superionic conductor electrolyte for alkaline batteries, which comprises the superionic conductor electrolyte and the electrolyte additive in the foregoing embodiments. The electrolyte additive is selected from any one of sodium hydroxide and potassium hydroxide. For example, the concentration of the electrolyte additive in the superionic conductor electrolyte for alkaline batteries is 5-15wt%. For example, 5wt%, 10wt% and 15wt% or any value between 5-15wt%.

[0081] In the sixth aspect, the present application provides a superionic conductor electrolyte, a hybrid superionic conductor electrolyte, a quasi-solid flexible superionic conductor electrolyte and a superionic conductor electrolyte for alkaline batteries in the foregoing embodiments. The energy storage device comprises a battery and a supercapacitor. For example, the battery comprises any one of wide temperature range lithium ion battery, sodium ion battery, magnesium ion battery, zinc ion battery, copper ion battery and fuel cell.

[0082] Further, since the conductive layer is the core component of the electrochemical sensor for converting and transmitting signals, and the vapor pressure of the ionic liquid is almost negligible, the electrochemical sensor based on the superionic conductor electrolyte can work stably for a long time without performance loss in an open environment or even in a vacuum condition, and further improves the conductivity, responsiveness and stability of the electrochemical sensor.

[0083] In summary, the superionic conductor electrolyte provided by the embodiments of the present application has the following characteristics:

[0084] (1) Duality of Superionic Conductor and Green Solvent: Due to the naturally low viscosity of the ionic liquid [A]X (~95-285 mPa·s), the superionic conductor electrolyte provided by the embodiments of the present invention has the duality of being a superionic conductor and a green solvent. Polymers and electrolyte salts can be directly dissolved in the superionic conductor electrolyte without the need for organic solvents, thereby simply and conveniently preparing an aqueous, hybrid, quasi-solid-state flexible superionic conductor electrolyte without compromising its superionic conductor properties. Even when a high polymer content is present and a nearly immobile quasi-solid gel is formed, its ionic conductivity remains as high as 13 mS / cm.

[0085] In contrast, the electrical conductivity of metal halide solid electrolytes is basically between 0.01 and 0.1 mS / cm, and rarely reaches 10 mS / cm (Wang Weizong, Zhao Hongshun, Zhao Qian, et al. Computational simulation-assisted research on chloride solid electrolytes for lithium-ion batteries [J]. Chinese Science: Chemistry, 2024, 54(07): 991-1011.).

[0086] (2) Characteristics of wide temperature range ionic liquids: Wide temperature range refers to a wide operating temperature range. In application scenarios such as electric vehicles and portable electronic devices, lithium batteries only need to meet an operating temperature of 15 to 35°C. However, in some special application scenarios, lithium batteries need to exceed this temperature range. For example, the oil industry requires lithium batteries to adapt to an operating environment of about 80°C, and lithium batteries used in robots working in extreme environments even need to operate stably in an environment of ~150°C. In terms of low temperatures, application scenarios such as polar exploration and the aerospace industry require lithium batteries to operate in an environment of -40°C or even -80°C. Too low an operating temperature will slow down the kinetic process of the electrochemical reaction in the lithium battery, and even make it difficult to work (Qi Shihan, Wang Zhongsheng, Guo Kanglong, et al. Research progress of wide temperature range lithium battery electrolytes [J]. Science Bulletin, 2022, 67(24): 2937-2949.).

[0087] Thermodynamic stability tests of the superionic conductor electrolyte provided by the embodiments of the present invention showed a low glass transition temperature of -46.2°C and a thermal decomposition temperature of +272.4°C. This indicates that the superionic conductor electrolyte provided by the embodiments of the present invention remains stable in the temperature range of -46°C to +270°C, exhibiting the characteristics of a wide-temperature ionic liquid electrolyte, meeting and exceeding the standards of an ideal low-temperature electrolyte, and further expanding the applicability of battery electrolytes in extreme environmental conditions.

[0088] (3) Non-volatility and non-flammability: Battery safety is considered to be more important than performance. In fact, under existing technologies, traditional lithium-ion batteries all use organic solvents (EC+DMC, EC+DEC, EC+DMC+EMC, EC+DMC+DEC, etc.) as electrolytes, and their safety has become the biggest problem. In order to improve its safety performance, researchers have explored the use of polymer electrolytes, but the low ion conductivity and high ohmic drop of polymers hinder its application (National Natural Science Foundation of China, Chinese Academy of Sciences, "China's Discipline Development Strategy: Chemical Process Intensification", Science Press, first edition 2018).

[0089] In contrast, ionic liquids are non-volatile and non-flammable, and therefore can greatly improve the safety of existing battery electrolytes without compromising battery electrolyte performance.

[0090] (4) Unique double-layer structure: Compared with lithium-ion batteries, capacitors can have higher energy density without sacrificing power density. Among them, double-layer capacitors can withstand tens of thousands of ultra-long cycle life due to their fast charging and discharging speed and the absence of electrochemical reactions during the process. In principle, there are two ways to increase the energy density of double-layer capacitors: one is to maximize the double-layer capacitance per unit area, and the other is to maximize the interface area per unit volume. Obviously, method one is the key, and the unique double-layer structure of ionic liquids at the interface provides conditions for the application of double-layer capacitors (National Natural Science Foundation of China, Chinese Academy of Sciences, "China's Discipline Development Strategy: Chemical Process Intensification", Science Press, first edition 2018).

[0091] At the microscopic level, the short-range ion-ion interactions present in ionic liquids have a significant impact on the properties of the ionic liquid and its interface, giving it unique electrochemical properties, manifested in a special charge transfer mode and double-layer structure. Specifically, the double layer at the interface of an ionic liquid is a multiple ion layer formed by alternating anion and cation layers, rather than the diffuse double layer found in conventional aqueous solutions. Therefore, the superionic conductor electrolyte provided by the embodiments of the present invention is used in supercapacitors, improving the energy density, operating temperature range, and safety performance of existing supercapacitors.

[0092] (5) Properties of proton ionic liquids: According to the acid-base proton theory, the compounds choline and its halides, and pyrimidine carboxylic acid derivatives that form the ionic liquid [A]X can accept and donate protons, respectively, and thus exhibit the properties of proton ionic liquids. The exchangeable and reactive active protons in their structure are rapidly transported between electrodes, making them suitable for use as electrolytes in fuel cells. Furthermore, ionic liquids are also highly promising catalyst layer additives that can promote redox reactions in fuel cells (Chen Renjie and Zhao Taolin, Ionic Liquid Electrolytes, Science Press, first edition, 2023).

[0093] Therefore, compared with existing technologies, the superionic electrolytes provided by the embodiments of the present invention possess the dual properties of a superionic conductor and a green solvent, a wide temperature range, and excellent safety. Therefore, they are suitable for wide-temperature-range lithium-ion batteries, as well as electrolytes for non-lithium-ion batteries such as sodium ions, magnesium ions, zinc ions, and copper ions, alkaline battery electrolytes, fuel cell electrolytes, supercapacitors, and electrochemical sensors. Furthermore, the microscopic double-layer structure of ionic liquids can further improve the energy density, operating temperature range, and safety of existing supercapacitors.

[0094] Materials: 2-methyl-1,4,5,6-tetrahydropyrimidinecarboxylic acid, 5-hydroxy-2-methyl-1,4,5,6-tetrahydropyrimidinecarboxylic acid (100%, Merck), choline, choline chloride (90%, Macklin), choline bromide, choline iodide, β-methylcholine chloride, lithium bromide, lithium trifluoromethanesulfonyl imide, lithium hexafluorophosphate, sodium alginate (98-99%, AR, Aladdin), polyvinyl pyrrolidone K-90 (Ashland), polyvinyl alcohol 1799 (analytical grade, Zhonglian), PEG-1450NF (Dow), sodium chloride, sodium hydroxide, potassium hydroxide, magnesium sulfate (analytical grade, Xiyu), cerium oxide (Guangli).

[0095] Detection method:

[0096] Ionic conductivity (Λ) test: Direct measurement using a conductivity meter (DDS-307A). The actual test temperature for room temperature ionic conductivity is 20-25 degrees Celsius, and the actual test temperature for low temperature ionic conductivity is stable at -19.1 degrees Celsius. Unit: mS / cm;

[0097] Thermal stability window (ΔT) test: glass transition temperature, using differential scanning calorimetry (DSC, NETZSCH DSC204F1) thermal analysis method; thermal decomposition temperature, using thermogravimetric analysis (TGA, NETZSCH STA 2500) thermal analysis method.

[0098] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0099] Example 1

[0100] Example 1 of the present invention provides a method for preparing a superionic conductor electrolyte, comprising: adding choline chloride (CHC) and 2-methyl-1,4,5,6-tetrahydropyrimidinecarboxylic acid, raw materials for forming [A]X, in sequence according to the molar ratio (mol) and mass concentration (wt%) in Table 1, and stirring at room temperature for 10 to 30 minutes until completely dissolved; then adding water to a total liquid volume of 100%, thereby obtaining the superionic conductor electrolyte of Example 1.

[0101] The composition and physicochemical properties of Example 1 are summarized in Table 1.

[0102] The ionic conductivity (Λ, unit: mS / cm) and pH value of a set of superionic conductor electrolyte solutions with different composition molar ratios and the same concentration provided in Example 1 were tested at room temperature (~25°C) to obtain a correlation index between the [A]:X molar ratio in the ionic liquid [A]X and the ionic conductivity.

[0103] The results show that the ionic conductivity of the superionic conductor electrolyte provided in Example 1 increases with the increase of the molar ratio of [A]:X in the ionic liquid [A]X. When the molar ratio of [A]:X is 8:1, the ionic conductivity approaches the peak value and then slowly increases (see Table 1, Figure 1 ).

[0104] Table 1 Composition and physicochemical properties of Example 1

[0105]

[0106] Herein, the molar ratio is rounded to an integer.

[0107] Example 2

[0108] Example 2 of the present invention provides a method for preparing a superionic conductor electrolyte, comprising: adding choline chloride (CHC) and 2-methyl-1,4,5,6-tetrahydropyrimidinecarboxylic acid, raw materials for forming [A]X, in sequence according to the molar ratio (mol) and mass concentration (wt%) in Table 2, and stirring at room temperature for 10 to 30 minutes until completely dissolved; then adding water to a total liquid volume of 100%, thereby obtaining the superionic conductor electrolyte of Example 2.

[0109] The composition and physicochemical properties of Example 2 are summarized in Table 2.

[0110] The ionic conductivity (Λ, unit: mS / cm) and pH value of a set of superionic conductor electrolyte solutions with the same composition molar ratio and different concentrations provided in Example 2 were tested at room temperature (~25°C) to obtain a correlation index between the mass concentration of the ionic liquid [A]X and the ionic conductivity.

[0111] The results show that the ionic conductivity of the superionic conductor electrolyte provided in Example 2 increases with the increase in the mass concentration of the ionic liquid [A]X. When the concentration of [A]X reaches 30-40 wt%, the ionic conductivity approaches the peak value and then begins to decrease (see Table 2, Figure 2 ).

[0112] Table 2 Composition and physicochemical properties of Example 2

[0113]

[0114] Herein, the molar ratio is rounded to an integer.

[0115] Examples 3-8

[0116] Examples 3 to 8 of the present invention provide a method for preparing a superionic conductor electrolyte, comprising: adding choline chloride (CHC), choline bromide (CHB), choline iodide (CHI), β-methylcholine chloride (CHM), choline (CHO), and a pyrimidinecarboxylic acid derivative, the raw materials for forming [A]X, to a small amount of water in sequence according to the molar ratio (mol) and mass concentration (wt%) shown in Table 3; stirring at room temperature for 10 to 30 minutes until completely dissolved, thereby synthesizing the required amount of ionic liquid [A]X in situ; and then adding water to a total liquid volume of 100%, thereby obtaining the superionic conductor electrolytes of Examples 3 to 8. The anion portion X of the ionic liquid [A]X of Examples 3 to 7 is 2-methyl-1,4,5,6-tetrahydropyrimidinecarboxylic acid, and the anion portion X of Example 8 is 5-hydroxy-2-methyl-1,4,5,6-tetrahydropyrimidinecarboxylic acid.

[0117] The compositions and physicochemical properties of Examples 3 to 8 are summarized in Table 3.

[0118] The experimental results show that the room temperature ionic conductivity of the superionic conductor electrolytes provided by Examples 3 to 8 is between 81 and 105 mS / cm, and has typical superionic conductor characteristics.

[0119] Furthermore, a low-temperature ionic conductivity test was performed on the superionic conductor electrolyte provided in Example 3. The results showed that the ionic conductivity at a low temperature of -19.1°C was 82.5 mS / cm (not shown in Table 3).

[0120] Furthermore, the thermodynamic stability test of the superionic conductor electrolyte provided in Example 3 was conducted. The results showed that its glass transition temperature was as low as -46.2°C and its thermal decomposition temperature was +272.4°C (see Figure 3 、 Figure 4 ). It is suggested that the superionic conductor electrolyte provided by Example 3 of the present invention remains stable in the temperature range of -46°C to +270°C, has the characteristics of a wide temperature range ionic liquid electrolyte, and its operating temperature range is much higher than the ideal low-temperature electrolyte standard.

[0121] Table 3 Composition and physicochemical properties of Examples 3 to 8

[0122]

[0123] Herein, the molar ratio is rounded to an integer.

[0124] Examples 9-16

[0125] Examples 9 to 16 of the present invention provide a method for preparing a hybrid superionic conductor electrolyte, comprising: sequentially adding choline chloride (CHC) and 2-methyl-1,4,5,6-tetrahydropyrimidinecarboxylic acid, raw materials for forming [A]X, to a small amount of water according to the composition molar ratio (mol) and mass concentration (wt%) in Table 4, stirring at room temperature for 10-30 minutes until completely dissolved, first synthesizing the required amount of ionic liquid [A]X in situ; then, doping different electrolyte salts until completely dissolved, and replenishing water to a total liquid volume of 100%, thereby obtaining the hybrid superionic conductor electrolytes of Examples 9 to 16.

[0126] The compositions and physicochemical properties of Examples 9 to 16 are summarized in Table 4.

[0127] Experimental results show that metal ion doping can lead to increased ionic conductivity. Compared with Example 3, the ionic conductivity of lithium bromide (LiBr), lithium carbonate (Li2CO3), lithium bis(trifluoromethanesulfonyl imide) (LiTFSI), and lithium hexafluorophosphate (LiPF6) increased by ~20%, with the ionic conductivity increasing accordingly with increasing lithium salt concentration. The ionic conductivity of sodium chloride (NaCl) increased by ~42%, the ionic conductivity of magnesium sulfate (MgSO4) increased by approximately ~10%, and the ionic conductivity of metal oxide (CeO2) increased by ~10%.

[0128] Among them, lithium carbonate and lithium hexafluorophosphate have low solubility in the ionic liquid [chc]X composed of choline chloride and 2-methyl-1,4,5,6-tetrahydropyrimidinecarboxylic acid, and lithium salts precipitate in the solution, but this does not affect the change in ionic conductivity.

[0129] Table 4 Composition and physicochemical properties of Examples 9 to 16

[0130]

[0131] Herein, the molar ratio is rounded to an integer.

[0132] Examples 17-20

[0133] Embodiments 17 to 20 of the present invention provide a method for preparing a quasi-solid-state flexible superionic conductor electrolyte, comprising: adding choline chloride (CHC) and 2-methyl-1,4,5,6-tetrahydropyrimidinecarboxylic acid, the raw materials for forming [A]X, to a small amount of water in sequence according to the composition molar ratio (mol) and mass concentration (wt%) in Table 5, stirring conventionally for 10-30 minutes at room temperature until completely dissolved, first in situ synthesizing the required amount of ionic liquid [A]X; then adding additives (lithium salt and polymer) in sequence and stirring until completely dissolved, and supplementing water to a total liquid volume of 100%, thereby obtaining the quasi-solid-state flexible superionic conductor electrolytes of Embodiments 17 to 20.

[0134] The compositions and physicochemical properties of Examples 17 to 20 are summarized in Table 5.

[0135] Experimental results show that the addition of polymers produces a quasi-solid-state superionic conductor electrolyte, but this results in a ~30% decrease in ionic conductivity. This decreases further with increasing polymer content and gel viscosity. However, even when the PVA addition reaches 20 wt% and the gel is virtually immobile, its room-temperature ionic conductivity remains as high as 13 mS / cm. Polyvinyl pyrrolidone has a weaker adverse effect on ionic conductivity than polyvinyl alcohol. Doping lithium salts into the quasi-solid-state gel electrolyte increases ionic conductivity, and this increases with increasing lithium salt concentration.

[0136] Among them, Example 17 is a flowable gel formed by adding PVP (K-90, 10 wt%) to Example 3. Compared with Example 3, the ionic conductivity decreased by ∼30% (101 mS / cm to 73 mS / cm);

[0137] Among them, Example 18 is a flowable gel obtained by adding lithium salt (LiBr, 10 wt%) to Example 17. Compared with Example 17, the ionic conductivity increased by 7% (73 mS / cm to 78 mS / cm);

[0138] In Example 19, PVP was replaced with an equal amount of PVA (PVA1799, 10 wt %) to form a flowable gel based on Example 18. Compared with Example 18, the ionic conductivity decreased by ∼18% (78 mS / cm to 64 mS / cm).

[0139] In Example 20, based on Example 19, the amount of polymer PVP was further increased to 20 wt % to obtain a nearly non-flowing viscous gel, and the ionic conductivity decreased by 80% (64 mS / cm to 13 mS / cm).

[0140] Table 5 Composition and physicochemical properties of Examples 17 to 20

[0141]

[0142] Herein, the molar ratio is rounded to an integer.

[0143] Examples 21-22

[0144] Embodiments 21 and 22 of the present invention provide a method for preparing a superionic conductor electrolyte for an alkaline battery, comprising: sequentially adding choline chloride (CHC) and 2-methyl-1,4,5,6-tetrahydropyrimidinecarboxylic acid, the raw materials for forming [A]X, to a small amount of water according to the composition molar ratio (mol) and mass concentration (wt%) in Table 6, stirring at room temperature for 10-30 minutes until completely dissolved, first synthesizing the required amount of ionic liquid [A]X in situ; dissolving sodium hydroxide and potassium hydroxide in the remaining amount of water to prepare sodium hydroxide solution and potassium hydroxide solution, respectively, and slowly dripping these into the in situ synthesized ionic liquid [A] under continuous stirring, thereby obtaining the superionic conductor electrolyte for alkaline batteries of embodiments 21 and 22.

[0145] The compositions and physicochemical properties of Examples 21 and 22 are summarized in Table 6.

[0146] Examples 21 and 22 demonstrate the compatibility of the superionic conductor electrolytes provided in the examples of this application with sodium hydroxide and potassium hydroxide. The results show that sodium hydroxide and potassium hydroxide, at concentrations below 15 wt%, are compatible with the superionic conductor electrolytes and significantly enhance ionic conductivity (>199 mS / cm), demonstrating superionic conductor properties. Application of superionic conductor electrolytes in wide-temperature alkaline batteries can optimize the electrochemical performance, safety, and stability of existing alkaline batteries.

[0147] Table 6 Composition and physicochemical properties of Examples 21 to 18

[0148]

[0149] Herein, the molar ratio is rounded to an integer.

[0150] Molecular simulation experiments

[0151] Ion pairs were screened through molecular simulation experiments, and the experimental results are summarized in Table 7.

[0152] Table 7 Molecular simulation experimental results

[0153]

[0154]

[0155] Molecular simulation experimental data show that at 298.15K and 1.00Atm, in the reactions of 2-methyl-1,4,5,6-tetrahydropyrimidinecarboxylic acid and 5-hydroxy-2-methyl-1,4,5,6-tetrahydropyrimidinecarboxylic acid with choline, choline chloride, choline bromide, choline iodide, choline fluoride, choline chlorofluoride, and β-methylcholine chloride, respectively, the Gibbs free energy changes (ΔG < 0) for the reaction of 5-hydroxy-2-methyl-1,4,5,6-tetrahydropyrimidinecarboxylic acid with choline fluoride and choline chlorofluoride predict that the reactions will not proceed spontaneously, suggesting that stable ionic liquids can be formed.

[0156] In the ionic liquids that can be formed, strong hydrogen bonding is formed between molecules (bond energy BE ~23-98 kcal / mol), resulting in strong solubility properties; and they have different polarities (dipole moments μ ~1.11-9.20 Debye). The experimental data are consistent with the results of the examples, and in the examples, they can completely replace the electrolyte organic solvent.

[0157] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A superionic conductor electrolyte, characterized in that The superionic conductor electrolyte comprises an ionic liquid [A]X, wherein [A] represents a cationic portion, X represents a carboxylate-containing anionic portion, [A] is derived from choline or its halide, and X is derived from a pyrimidinecarboxylic acid derivative; The superionic conductor electrolyte is a pure water-based superionic conductor electrolyte; and the pure water-based superionic conductor electrolyte does not contain any organic solvent; the superionic conductor electrolyte is composed of water and ionic liquid [A]X.

2. The superionic conductor electrolyte according to claim 1, characterized in that [A] is derived from any one of the compounds represented by the following structural formulas: ， ， ， ， ， ， 。 3. The superionic conductor electrolyte according to claim 1, characterized in that X is derived from the compound represented by the following structural formula: , wherein R1 is selected from H or hydroxyl, and R2 is selected from C1-C4 alkyl.

4. The superionic conductor electrolyte according to claim 1, characterized in that X is derived from any one of the compounds represented by the following structural formulas: and .

5. The superionic conductor electrolyte according to any one of claims 1 to 4, characterized in that The molar ratio of [A] to X is (1:1) to (14:1).

6. The superionic conductor electrolyte according to any one of claims 1 to 4, characterized in that The molar ratio of [A] to X is (2:1) to (10:1).

7. The superionic conductor electrolyte according to any one of claims 1 to 4, characterized in that The concentration of the ionic liquid [A]X in the superionic conductor electrolyte is 10-70 wt%.

8. A method for preparing the superionic conductor electrolyte according to claim 1, characterized in that: include: The raw material for forming the cation [A] and the raw material for forming the anion X are mixed and dissolved.

9. The preparation method according to claim 8, characterized in that Preparation was performed under non-vacuum conditions; The temperature for mixed dissolution is 30-50°C and the time is 10-30 minutes.

10. The preparation method according to claim 8, characterized in that The raw materials for forming the cation [A] and the raw materials for forming the anion X are dissolved in water.

11. The preparation method according to claim 8, characterized in that include: The raw materials for forming the cation [A] and the raw materials for forming the anion X are added to a small amount of water and stirred conventionally at room temperature and pressure until completely dissolved to synthesize the required amount of ionic liquid [A]X in situ; water is added to the total liquid volume to 100%.

12. A hybrid superionic conductor electrolyte, characterized in that: The invention comprises the superionic conductor electrolyte according to claim 1 and an electrolyte additive; the electrolyte additive is an electrolyte salt.

13. The hybrid superionic conductor electrolyte according to claim 12, characterized in that The electrolyte salt is selected from any one of lithium salts, sodium salts, aluminum salts, magnesium salts, zinc salts, copper salts and metal oxides.

14. The hybrid superionic conductor electrolyte according to claim 12, characterized in that The concentration of the electrolyte salt in the hybrid superionic conductor electrolyte is 5-30 wt %.

15. A quasi-solid-state flexible superionic conductor electrolyte, characterized in that: The invention comprises the superionic conductor electrolyte and an electrolyte additive according to claim 1; the electrolyte additive is an electrolyte salt and a polymer; or the electrolyte additive is a polymer.

16. The quasi-solid-state flexible superionic conductor electrolyte according to claim 15, characterized in that: The electrolyte salt is selected from any one of lithium salt, sodium salt, aluminum salt, magnesium salt, zinc salt, copper salt and metal oxide; The polymer is selected from any one of polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol, polyvinylidene fluoride, polyacrylamide, agar, carrageenan, xanthan gum, sodium alginate and cellulose.

17. The quasi-solid-state flexible superionic conductor electrolyte according to claim 15, characterized in that: The concentration of the electrolyte salt in the quasi-solid flexible superionic conductor electrolyte is 5-30 wt %; The concentration of the polymer in the quasi-solid flexible superionic conductor electrolyte is 5-20 wt %.

18. A superionic conductor electrolyte for alkaline batteries, characterized in that: The invention comprises the superionic conductor electrolyte according to claim 1 and an electrolyte additive; the electrolyte additive is selected from any one of sodium hydroxide and potassium hydroxide.

19. The alkaline battery superionic conductor electrolyte according to claim 18, characterized in that The concentration of the electrolyte additive in the alkaline battery superionic conductor electrolyte is 5-15 wt %.

20. An energy storage device, characterized in that: It comprises at least one of the superionic conductor electrolyte according to claim 1, the hybrid superionic conductor electrolyte according to claim 12, the quasi-solid-state flexible superionic conductor electrolyte according to claim 15, or the alkaline battery superionic conductor electrolyte according to claim 18.

21. The energy storage device according to claim 20, characterized in that The energy storage device includes a battery and a supercapacitor.

22. The energy storage device according to claim 21, characterized in that The battery includes any one of a wide temperature range lithium ion battery, a sodium ion battery, a magnesium ion battery, a zinc ion battery, a copper ion battery and a fuel cell.

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