Liquid low-temperature molten salt electrolyte and battery using the same

Abstract

The application relates to the field of electricity storage, in particular to a liquid low-temperature molten salt electrolyte which comprises anhydrous aluminum chloride, an organic ammonium halide and an inorganic salt additive, the organic ammonium halide is one of alkane ammonium halide, olefin halide or aromatic hydrocarbon halide, the inorganic salt additive is a chlorine salt, and the liquid low-temperature molten salt electrolyte is a transparent liquid at room temperature. The liquid low-temperature molten salt electrolyte has high conductivity, so that chloroaluminate complex ions and other chloroaluminate complexes can flow more smoothly in the liquid electrolyte, the energy conversion efficiency is improved, a battery using the electrolyte does not need a diaphragm and has no explosion risk, the battery structure is simplified, and the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and in particular to a liquid low-temperature molten salt electrolyte and a battery using the liquid low-temperature molten salt electrolyte. Background Technology

[0002] With the current focus on new energy sources, molten salt electrolytes, as crucial electrolytes, have attracted considerable attention and extensive research from scholars both domestically and internationally. Traditional molten salt electrolytes typically utilize high-temperature cryolite molten salts, containing chloride salts such as sodium chloride and potassium chloride as their main components. However, traditional molten salt electrolytes suffer from several drawbacks, such as high melting points and high costs, which limit their application in certain fields.

[0003] The high melting point of traditional cryolite molten salt electrolytes not only increases energy costs but also poses a corrosion problem to production materials due to the high temperature of the molten salt, and high-temperature production also presents significant safety hazards. Furthermore, the high cost of using 1-butyl-3-methylimidazolium chloride (EMIC) and other similar electrolyte raw materials also presents challenges to the industrial production of electrolytes.

[0004] Therefore, in order to solve the problems of traditional molten salt electrolytes, it is urgent to develop a new type of liquid low-temperature molten salt electrolyte. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a liquid low-temperature molten salt electrolyte, comprising anhydrous aluminum chloride, an organic ammonium halide, and an inorganic salt additive. The organic ammonium halide is one of alkane ammonium halide, olefin halide, or aromatic hydrocarbon halide. The inorganic salt additive is a chloride salt. The liquid low-temperature molten salt electrolyte is a transparent liquid at room temperature.

[0006] Furthermore, the aromatic hydrocarbon halide is one of benzyl ammonium chloride, triethylbenzyl ammonium chloride, and dibenzyldimethyl ammonium chloride.

[0007] Furthermore, the olefin halide is one of tetraallyl ammonium chloride and allyltrimethylammonium chloride.

[0008] Furthermore, the alkane ammonium halide compound is one of alkane ammonium chloride, alkane ammonium fluoride, or alkane ammonium bromide.

[0009] Furthermore, the alkane ammonium chloride compound is selected from one of tetraalkylammonium salts, trialkylammonium salts, and dialkylammonium salts.

[0010] Furthermore, the alkane ammonium chloride is selected from alkyl groups having 1 to 3 carbon atoms.

[0011] Furthermore, the ammonium alkane fluoride is selected from alkyl groups having 1 to 3 carbon atoms.

[0012] Furthermore, based on the total weight of the electrolyte, the weight percentage of the organic ammonium halide is X, the weight percentage of the anhydrous aluminum chloride is Y, and the weight percentage of the inorganic salt additive is Z, where X and Y simultaneously satisfy the conditions expressed in equations (1) and (2): 90% ≤ (X+Y) ≤ 95wt%…(1); and 0.45≤(X / Y)≤2.1…(2).

[0013] Furthermore, the chloride salt is a mixture of NaCl, KCl, and LiCl, wherein the mass percentage of NaCl in the total electrolyte is 0.5% to 1.5%, the mass percentage of KCl in the total electrolyte is 0.5% to 1.5%, and the mass percentage of LiCl in the total electrolyte is 4% to 8%.

[0014] The present invention also provides a battery comprising a liquid low-temperature molten salt electrolyte, a negative electrode containing aluminum, and a positive electrode containing sulfur.

[0015] The beneficial effects of this invention are: (1) The liquid low-temperature molten salt electrolyte of the present invention has high conductivity, which allows chloroaluminate complex ions and other chloroaluminate complexes to flow more smoothly in the liquid electrolyte, improving energy conversion efficiency. Batteries using this electrolyte do not require a separator and have no risk of explosion, simplifying the battery structure and reducing production costs.

[0016] (2) The aluminum-sulfur battery using the liquid low-temperature molten salt electrolyte of this invention maintains a capacity retention rate of 90% after 800 cycles, demonstrating excellent cycle stability and high capacity retention, making it very suitable for long-term and high-load applications. Simultaneously, the liquid low-temperature molten salt electrolyte of this invention exhibits good ionic conductivity at different temperatures, indicating excellent ion conduction performance and high stability over a wide temperature range, adapting to various working environments. The battery operates stably at around 30°C during normal operation, avoiding damage to the positive and negative electrodes caused by high-temperature operation, thereby extending battery life and reducing safety hazards such as explosions and leaks caused by high temperatures, thus improving battery safety. The battery using this liquid low-temperature molten salt electrolyte has an aluminum negative electrode, resulting in a significantly increased energy density of 750Wh / kg. Furthermore, the materials used in this invention—the positive electrode, negative electrode, and low-temperature molten salt electrolyte—are abundant and inexpensive on Earth, greatly reducing the manufacturing cost of the battery. Attached Figure Description

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

[0018] Figure 1 This is a schematic diagram of the conductivity test curve of the low-temperature molten salt electrolyte at 25°C in this invention.

[0019] Figure 2 This is a schematic diagram of the 1C cycle capacity retention rate of a battery using the liquid low-temperature molten salt electrolyte of the present invention.

[0020] Figure 3 This is a schematic diagram of the battery's first and 80th charge-discharge curves in Embodiment 1 of the present invention. Detailed Implementation

[0021] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0024] This invention provides a liquid low-temperature molten salt electrolyte, comprising anhydrous aluminum chloride, an organic ammonium halide, and an inorganic salt additive. The organic ammonium halide is one of alkane ammonium halide, olefin halide, or aromatic hydrocarbon halide. The inorganic salt additive is a chloride salt. The liquid low-temperature molten salt electrolyte is a transparent liquid at room temperature. The aromatic hydrocarbon halide is one of benzylammonium chloride, triethylbenzylammonium chloride, or dibenzyldimethylammonium chloride. The olefin halide is one of tetraallylammonium chloride or allyltrimethylammonium chloride. The alkane ammonium halide is one of alkane ammonium chloride, alkane ammonium fluoride, or alkane ammonium bromide. The alkane ammonium fluoride is selected from alkyl groups having 1 to 3 carbon atoms. The alkane ammonium chloride is selected from alkyl groups having 1 to 3 carbon atoms. The alkane ammonium chloride is selected from tetraalkylammonium salts, trialkylammonium salts, or dialkylammonium salts. The alkane ammonium chloride compound is one of tetramethylammonium chloride, diethylammonium chloride hydrochloride, trimethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, and tetrabutylammonium chloride. The molar ratio of the alkane ammonium chloride to anhydrous aluminum chloride is 0.5 to 0.91.

[0025] Based on the total weight of the liquid low-temperature molten salt electrolyte of the present invention, the weight percentage of the organic ammonium halide is X, the weight percentage of the anhydrous aluminum chloride is Y, and the weight percentage of the inorganic salt additive is Z. X and Y simultaneously satisfy the conditions expressed by equations (1) and (2): 90% ≤ (X + Y) ≤ 95 wt%…(1); and 0.45 ≤ (X / Y) ≤ 2.1…(2). Preferably, the molar ratio of the anhydrous aluminum chloride to the organic ammonium compound is 1 to 2. When the molar ratio is 1, aluminum chloride combines with a chloride ion to form a monovalent aluminum tetrachloride anion AlCl4. - However, when the molar ratio is 2, chloride ions and aluminum tetrachloride anions (AlCl4)... - Further coordination forms aluminum heptachloride anion Al2Cl7 - At this point, the solution will contain mainly alkylammonium cations and aluminum heptachloride anions (Al₂Cl₇). - When the molar ratio is between 1 and 2, aluminum tetrachloride anion and aluminum heptachloride anion Al2Cl7 coexist. -This liquid molten salt electrolyte has a low melting point because the organic substituents in the ammonium ions shield the positive charge, weakening the interaction between positive and negative charges. It is liquid at room temperature, containing only anions and cations, resulting in low viscosity and good conductivity, thus possessing the basic elements of an electrolyte. Preferably, the NaCl content in the electrolyte is 0.5%–1.5% by mass, the KCl content is 0.5%–1.5% by mass, and the LiCl content is 4%–8% by mass. Example 1

[0026] I. Preparation of Liquid Low-Temperature Molten Salt Electrolytes The method for preparing liquid low-temperature molten salt electrolyte of the present invention includes the following steps: S1. At room temperature, weigh out 191.81g of trimethylamine hydrochloride, 5.9g of NaCl, 5.9g of KCl, and 29.6g of LiCl in advance, seal them well, and dry them in an oven at 105℃ for 12 hours to fully remove the moisture from the sample. S2. Weigh 400g of reagent-pure anhydrous aluminum chloride in a glove box, mix the anhydrous aluminum chloride with the mixture in S1, and stir to form a low-temperature ionic liquid; S3. After stirring the ionic liquid in S2 for 8 hours, a liquid low-temperature molten salt electrolyte is obtained.

[0027] It should be noted that the above preparation process was carried out entirely in a glove box. In the glove box, 2 mol of trimethylamine hydrochloride, 3 mol of anhydrous aluminum chloride, 0.1 mol of NaCl, 0.08 mol of KCl, and 0.7 mol of LiCl were mixed. This process was conducted under an inert gas atmosphere (such as nitrogen or argon) to prevent interference from moisture and oxygen. During the thorough stirring of the mixture with solid anhydrous aluminum chloride, the mixture gradually turned into a pale yellow-green liquid, simultaneously releasing hydrogen chloride gas and forming a characteristic white gas. In this process, the anhydrous aluminum chloride reacted completely with tetrabutylammonium chloride to generate a liquid low-temperature molten salt electrolyte.

[0028] II. Battery Manufacturing The battery made using the low-temperature molten salt electrolyte prepared in this embodiment does not require a separator. It includes a low-temperature molten salt electrolyte and positive and negative electrodes partially immersed in the low-temperature molten salt electrolyte. The materials of the positive and negative electrodes can be the same or different, and the materials can be metals or conductive non-metals. The positive electrode material can be a porous foam nickel-based composite material, and the negative electrode material can be aluminum foil.

[0029] Preparation of negative electrode The negative electrode comprises metallic aluminum and / or an aluminum alloy. Preferably, the aluminum alloy is an aluminum alloy containing one or more metallic elements with a reduction potential higher than that of metallic aluminum.

[0030] Preparation of positive electrode The preparation method of the positive electrode includes the following steps: mixing conductive material C, PVC particles and sulfur in proportion; measuring the required conductive material C, PVC particles and sulfur, mixing them in a certain proportion and ball milling them in a ball mill; taking out the mixed SC positive electrode material and baking it in a low temperature oven to remove moisture and organic residues from the material; adding the mixed SC positive electrode material to NNMP and stirring to form a mixed solution; coating the mixed solution onto the substrate; and then placing the substrate coated with the mixture into a drying room or oven to dry it, removing NMP and allowing the positive electrode to dry and solidify.

[0031] The preparation of an aluminum-sulfur battery involves fixing the prepared positive electrode sheet to one side of the battery casing, ensuring it is firmly secured and not easily moved. The negative electrode sheet is then fixed to the other side of the battery casing, ensuring sufficient spacing between the positive and negative electrodes to avoid direct contact. Electrolyte is then injected into the battery casing until it is evenly distributed and completely covers both the positive and negative electrodes. The battery casing is then sealed to prevent electrolyte leakage. Finally, the positive and negative electrodes are connected to the external terminals of the battery, thus completing the aluminum-sulfur battery.

[0032] The battery described in this application achieves the charging and discharging of an aluminum-sulfur secondary battery through the movement of chloride ions between the positive and negative electrodes. During charging, elemental sulfur at the positive electrode loses electrons to become sulfur (S). + Subsequently, it reacts with free aluminum heptachloride anions or aluminum tetrachloride anions in the liquid low-temperature molten salt electrolyte to form the compound disulfide dichloride. The negative electrode can be regarded as Al 3+ Electron-gaining reduction yields elemental aluminum. The reaction equation is: Anode reaction: 6S + 6AlCl4 - / 6Al2Cl6 - -6e====3S2Cl2+6AlCl3 Cathode reaction: 2Al 3+ +6e====2Al; During discharge, the elemental aluminum at the negative electrode oxidizes and loses charge to become Al. 3 +, at the positive electrode, disulfur dichloride gains electrons and is reduced to elemental sulfur. The reaction equation is: Negative electrode reaction: 2Al – 6e ==== 2Al 3 + Positive electrode reaction: 3S₂Cl₂ + 6e⁻ + 6AlCl₃ === 6S + 6AlCl₄ - / 6Al2Cl6 - .

[0033] The ionic conductivity of the prepared liquid molten salt electrolyte was tested: In this application, electrochemical impedance spectroscopy (EIS) was used to measure the conductivity of the electrolyte molten salt, with test temperatures ranging from 25°C to 70°C. The tested ionic conductivity of this liquid low-temperature molten salt electrolyte at 0°C, 25°C, 40°C, 50°C, and 70°C was 1.1 × 10⁻⁶. -1 S / m, 1.7×10 -1 S / m, 2.2×10 -1 S / m, 3.4×10 -1 S / m and 5.2×10 -1 S / m.

[0034] The following battery data was obtained based on a 75Ah battery, with battery dimensions of 80×80×67mm.

[0035] The aluminum-sulfur battery prepared from the liquid low-temperature molten salt electrolyte was tested using a Xinwei battery testing device (CT-4008) at 10 mA·cm⁻¹. -2 The battery's cycle performance was tested using high charge / discharge current density. At 25°C, the prepared battery was charged to 2.5V with a constant current of 1C, then charged to 0.05C with a constant voltage of 2.5V. After resting for 10 minutes, it was discharged to 1.5V with a constant current of 1C. This was the battery's first charge / discharge cycle, and the discharge capacity of this cycle was recorded as the battery's first cycle discharge capacity (C0). The above steps were repeated for the same battery. After 800 cycles, the battery's discharge capacity (C1) was measured. The capacity retention rate after 800 cycles was C1 / C0 × 100% = 68%.

[0036] Comparative Example 1 Based on Example 1, only the separator configuration was changed. A cation separator was added to the aluminum-sulfur battery of Comparative Example 1: an electric field was formed around the cation separator, and the negative terminal of a DC power supply was electrically connected to the composite separator, while the positive terminal of the DC power supply was grounded. This configuration enables the formation of an electric field at the composite separator, which is negatively charged. The negative charge attached to the composite separator attracts free cations in the electrolyte to move towards the composite separator and then pass through the micropores of the composite separator.

[0037] The positive electrode, separator, and negative electrode are stacked sequentially, with the separator placed between the positive and negative electrodes for isolation. This creates a bare cell, which is then welded with tabs. The bare cell is placed in an outer package and filled with liquid cryogenic molten salt electrolyte. Following this, encapsulation, settling, formation, shaping, and capacity testing are performed to fabricate an aluminum-sulfur battery.

[0038] The prepared aluminum-sulfur battery was tested using a Xinwei battery testing device (CT-4008) at 10 mA·cm⁻¹. -2The battery's cycle performance was tested using high charge-discharge current density. At 25°C, the prepared battery was charged to 2.5V with a constant current of 1C, then charged at a constant voltage of 2.5V until the current dropped to 0.05C. After resting for 10 minutes, it was discharged to 1.5V with a constant current of 1C. This charge-discharge cycle was repeated. Each charge-discharge cycle constituted one full cycle. The battery life was considered to have ended when the discharge capacity of the aluminum-sulfur battery decreased to 80% of the capacity of the first discharge cycle. The number of charge-discharge cycles was recorded. The number of cycles was 233.

[0039] This is the battery's first charge / discharge cycle. The discharge capacity of this cycle is recorded as the battery's first cycle discharge capacity (C0). Repeat the above steps for the same battery. After 200 cycles, the battery's discharge capacity (C1) is recorded. The battery capacity retention rate is 22%. Example 2

[0040] I. Preparation of Liquid Low-Temperature Molten Salt Electrolytes The method for preparing the liquid low-temperature molten salt electrolyte includes the following steps: S1. At room temperature, weigh out 557.96g of tetrabutylammonium chloride, 400g of anhydrous aluminum chloride, 9.6g of NaCl, 9.6g of KCl, and 47.9g of LiCl in advance, seal them well, and dry them in an oven at 105℃ for 12 hours to fully remove the moisture from the sample. S2. Weigh 400g of reagent-pure anhydrous aluminum chloride in the glove box, mix it with the mixture in S1, and stir to form a low-temperature ionic liquid; S3. After stirring the ionic liquid in S2 for 8 hours, a liquid low-temperature molten salt electrolyte is obtained.

[0041] It should be noted that the above preparation process was all completed in a glove box. In the glove box, 2 mol of tetrabutylammonium chloride, 3 mol of anhydrous aluminum chloride, 0.1 mol of NaCl, 0.1 mol of KCl, and 1 mol of LiCl were mixed. This process was carried out under an inert gas (such as nitrogen or argon) to prevent interference from moisture and oxygen. During the thorough stirring of the mixture with solid anhydrous aluminum chloride, the mixture gradually turned into a pale yellow-green liquid, simultaneously releasing hydrogen chloride gas and forming a characteristic white gas. In this process, the anhydrous aluminum chloride and tetrabutylammonium chloride reacted completely to generate a liquid low-temperature molten salt electrolyte.

[0042] The battery is fabricated using the low-temperature molten salt electrolyte prepared in this embodiment. It includes the low-temperature molten salt electrolyte and positive and negative electrodes partially immersed in it. The negative electrode is metallic aluminum and / or an aluminum alloy. The preparation methods for the positive and negative electrodes are consistent with those in Example 1.

[0043] The ionic conductivity of the prepared liquid molten salt electrolyte was tested: In this application, electrochemical impedance spectroscopy (EIS) was used to measure the conductivity of the electrolyte molten salt, with test temperatures ranging from 25°C to 70°C. The tested ionic conductivity of this liquid low-temperature molten salt electrolyte at 0°C, 25°C, 40°C, 50°C, and 70°C was 1.7 × 10⁻⁶. -1 S / m, 2.2×10 -1 S / m, 3.3×10 -1 S / m, 4.5×10 -1 S / m and 5.9×10 -1 S / m.

[0044] The following battery data was obtained based on a 117Ah battery, with dimensions of 42×177×108mm. 3 .

[0045] The aluminum-sulfur battery prepared from the liquid low-temperature molten salt electrolyte was tested using a Xinwei battery testing device (CT-4008) at 10 mA·cm⁻¹. -2 The battery's cycle performance was tested using high charge / discharge current density. At 25°C, the prepared battery was charged to 4.0V with a constant current of 1C, then charged to 0.05C with a constant voltage of 4.0V. After resting for 10 minutes, it was discharged to 1.5V with a constant current of 1C. This was the battery's first charge / discharge cycle, and the discharge capacity of this cycle was recorded as the battery's first cycle discharge capacity (C0). The above steps were repeated for the same battery. After 800 cycles, the battery's discharge capacity (C1) was measured. The capacity retention rate after 800 cycles was calculated as C1 / C0 × 100% = 73%.

[0046] Comparative Example 2 Based on Example 2, only the membrane configuration was changed. A cation separator was added to the aluminum-sulfur battery of Comparative Example 2: an electric field was formed around the cation separator, and the negative terminal of a DC power supply was electrically connected to the composite separator, while the positive terminal of the DC power supply was grounded. This configuration enables the formation of an electric field at the composite separator, which is negatively charged. The negative charge attached to the composite separator attracts free cations in the electrolyte to move towards the composite separator and then pass through the micropores of the composite separator.

[0047] The positive electrode, separator, and negative electrode are stacked sequentially, with the separator placed between the positive and negative electrodes for isolation. This creates a bare cell, which is then welded with tabs. The bare cell is placed in an outer package and filled with liquid cryogenic molten salt electrolyte. Following this, encapsulation, settling, formation, shaping, and capacity testing are performed to fabricate an aluminum-sulfur battery.

[0048] The prepared aluminum-sulfur battery was tested using a Xinwei battery testing device (CT-4008) at 10 mA·cm⁻¹. -2The battery's cycle performance was tested using high charge-discharge current density. At 25°C, the prepared battery was charged to 2.5V with a constant current of 1C, then charged at a constant voltage of 2.5V until the current dropped to 0.05C. After resting for 10 minutes, it was discharged to 1.5V with a constant current of 1C. This charge-discharge cycle was repeated. Each charge-discharge cycle constituted one full cycle. The battery life was considered to have ended when the discharge capacity of the aluminum-sulfur battery decreased to 80% of the discharge capacity of the first cycle. The number of charge-discharge cycles was recorded. The total number of cycles was 268.

[0049] This is the battery's first charge / discharge cycle. The discharge capacity of this cycle is recorded as the battery's first cycle discharge capacity (C0). Repeat the above steps for the same battery. After 200 cycles, the battery's discharge capacity (C1) is recorded. The battery capacity retention rate is 28%. Example 3

[0050] I. Preparation of Liquid Low-Temperature Molten Salt Electrolytes The method for preparing the liquid low-temperature molten salt electrolyte includes the following steps: S1. At room temperature, weigh out 275.36g of triethylamine hydrochloride, 400g of anhydrous aluminum chloride, 6.7g of NaCl, 6.7g of KCl, and 33.7g of LiCl in advance, seal them well, and dry them in an oven at 105℃ for 12 hours to fully remove the moisture from the sample. S2. Weigh 400g of reagent-pure anhydrous aluminum chloride in the glove box, mix it with the mixture in S1, and stir to form a low-temperature ionic liquid; S3. After stirring the ionic liquid in S2 for 8 hours, a liquid low-temperature molten salt electrolyte is obtained.

[0051] It should be noted that the above preparation process was all completed in a glove box. In the glove box, 2 mol of triethylamine hydrochloride, 3 mol of anhydrous aluminum chloride, 0.1 mol of NaCl, 0.1 mol of KCl, and 0.8 mol of LiCl were mixed. This process was carried out under an inert gas (such as nitrogen or argon) to prevent interference from moisture and oxygen. During the thorough stirring of the mixture with solid anhydrous aluminum chloride, the mixture gradually turned into a pale yellow-green liquid, simultaneously releasing hydrogen chloride gas and forming a characteristic white gas. In this process, the anhydrous aluminum chloride reacted completely with tetrabutylammonium chloride to generate a liquid low-temperature molten salt electrolyte.

[0052] II. Battery Manufacturing The battery made using the low-temperature molten salt electrolyte prepared in this embodiment includes the low-temperature molten salt electrolyte and positive and negative electrodes partially immersed in the low-temperature molten salt electrolyte. The negative electrode is metallic aluminum and / or an aluminum alloy. The preparation methods of the positive and negative electrodes are consistent with those in Example 1.

[0053] The ionic conductivity of the prepared liquid molten salt electrolyte was tested: In this application, electrochemical impedance spectroscopy (EIS) was used to measure the conductivity of the electrolyte molten salt, with test temperatures ranging from 25°C to 70°C. The tested ionic conductivity of this liquid low-temperature molten salt electrolyte at 0°C, 25°C, 40°C, 50°C, and 70°C was 1.7 × 10⁻⁶. -1 S / m, 2.9×10 -1 S / m, 3.8×10 -1 S / m, 4.6×10 -1 S / m and 6.5×10 -1 S / m.

[0054] The liquid low-temperature molten salt electrolyte was used to prepare an aluminum-sulfur battery, and the battery was tested using a Xinwei battery testing device (CT-4008) at 10 mA·cm⁻¹. -2 The battery's cycle performance was tested using high charge / discharge current density. At 25°C, the prepared battery was charged to 4.0V with a constant current of 1C, then charged to 0.05C with a constant voltage of 4.0V. After resting for 10 minutes, it was discharged to 1.5V with a constant current of 1C. This was the battery's first charge / discharge cycle, and the discharge capacity of this cycle was recorded as the battery's first cycle discharge capacity (C0). The above steps were repeated for the same battery. After 800 cycles, the battery's discharge capacity (C1) was recorded. The capacity retention rate after 800 cycles was C1 / C0 × 100% = 75%.

[0055] Comparative Example 3 Based on Example 3, only the separator configuration was changed. A cation separator was added to the aluminum-sulfur battery of Comparative Example 3: an electric field was formed around the cation separator, and the negative terminal of a DC power supply was electrically connected to the composite separator, while the positive terminal of the DC power supply was grounded. This configuration can create an electric field at the composite separator, which is negatively charged. The negative charge attached to the composite separator attracts free cations in the electrolyte to move towards the composite separator and then pass through the micropores of the composite separator.

[0056] The positive electrode, separator, and negative electrode are stacked sequentially, with the separator placed between the positive and negative electrodes for isolation. This creates a bare cell, which is then welded with tabs. The bare cell is placed in an outer package and filled with liquid cryogenic molten salt electrolyte. Following this, encapsulation, settling, formation, shaping, and capacity testing are performed to fabricate an aluminum-sulfur battery.

[0057] The prepared aluminum-sulfur battery was tested using a Xinwei battery testing device (CT-4008) at 10 mA·cm⁻¹. -2The battery's cycle performance was tested using high charge-discharge current density. At 25°C, the prepared battery was charged to 2.5V with a constant current of 1C, then charged at a constant voltage of 2.5V until the current dropped to 0.05C. After resting for 10 minutes, it was discharged to 1.5V with a constant current of 1C. This charge-discharge cycle was repeated. Each charge-discharge cycle constituted one full cycle. The battery life was considered to have ended when the discharge capacity of the aluminum-sulfur battery decreased to 80% of the capacity of the first discharge cycle. The number of charge-discharge cycles was recorded. The number of cycles was 301.

[0058] This is the battery's first charge / discharge cycle. The discharge capacity of this cycle is recorded as the battery's first cycle discharge capacity (C0). Repeat the above steps for the same battery. After 250 cycles, the battery's discharge capacity (C1) is recorded. The battery capacity retention rate is 30%. Example 4

[0059] I. Preparation of Liquid Low-Temperature Molten Salt Electrolytes The method for preparing the liquid low-temperature molten salt electrolyte includes the following steps: S1. At room temperature, weigh out 654.55g of dibenzyldimethylammonium chloride, 333.32g of anhydrous aluminum chloride, 9.9g of NaCl, 9.9g of KCl, and 49.4g of LiCl in advance, seal them well, and dry them in an oven at 105℃ for 12 hours to fully remove the moisture from the sample. S2. Weigh 400g of reagent-pure anhydrous aluminum chloride in the glove box, mix it with the mixture in S1, and stir to form a low-temperature ionic liquid; S3. After stirring the ionic liquid in S2 for 8 hours, a liquid low-temperature molten salt electrolyte is obtained.

[0060] It should be noted that the above preparation process was carried out entirely in a glove box. In the glove box, 2.5 mol of dibenzyldimethylammonium chloride, 2.5 mol of anhydrous aluminum chloride, 0.2 mol of NaCl, 0.1 mol of KCl, and 1.2 mol of LiCl were mixed. This process was conducted under an inert gas atmosphere (such as nitrogen or argon) to prevent interference from moisture and oxygen. During the thorough stirring of the mixture with solid anhydrous aluminum chloride, the mixture gradually turned into a pale yellow-green liquid, simultaneously releasing hydrogen chloride gas and forming a characteristic white gas. In this process, the anhydrous aluminum chloride reacted completely with tetrabutylammonium chloride to generate a liquid low-temperature molten salt electrolyte.

[0061] II. Battery Manufacturing The battery made using the low-temperature molten salt electrolyte prepared in this embodiment includes the low-temperature molten salt electrolyte and positive and negative electrodes partially immersed in the low-temperature molten salt electrolyte. The negative electrode is metallic aluminum and / or an aluminum alloy. The preparation methods of the positive and negative electrodes are consistent with those in Example 1.

[0062] The ionic conductivity of the prepared liquid molten salt electrolyte was tested: In this application, electrochemical impedance spectroscopy (EIS) was used to measure the conductivity of the electrolyte molten salt at temperatures ranging from 25°C to 70°C. The tested ionic conductivity of this liquid low-temperature molten salt electrolyte at 0°C, 25°C, 40°C, 50°C, and 70°C was 1.2 × 10⁻⁶. -1 S / m, 4.5×10 -1 S / m, 4.7×10 -1 S / m, 5.3×10 -1 S / m and 7.2×10 -1 S / m.

[0063] The liquid low-temperature molten salt electrolyte was used to prepare an aluminum-sulfur battery, and the battery was tested using a Xinwei battery testing device (CT-4008) at 10 mA·cm⁻¹. -2 The battery's cycle performance was tested using high charge / discharge current density. At 25°C, the prepared battery was charged to 4.0V with a constant current of 1C, then charged to 0.05C with a constant voltage of 4.0V. After resting for 10 minutes, it was discharged to 1.5V with a constant current of 1C. This was the battery's first charge / discharge cycle, and the discharge capacity of this cycle was recorded as the battery's first cycle discharge capacity (C0). The above steps were repeated for the same battery. The discharge capacity (C1) of the battery after 800 cycles was recorded. The capacity retention rate after 800 cycles = C1 / C0 × 100% = 79%.

[0064] Comparative Example 4 Based on Example 4, only the membrane configuration was changed. A cation separator was added to the aluminum-sulfur battery of Comparative Example 4: an electric field was formed around the cation separator, and the negative terminal of a DC power supply was electrically connected to the composite separator, while the positive terminal of the DC power supply was grounded. This configuration enables the formation of an electric field at the composite separator, which is negatively charged. The negative charge attached to the composite separator attracts free cations in the electrolyte to move towards the composite separator and then pass through the micropores of the composite separator.

[0065] The positive electrode, separator, and negative electrode are stacked sequentially, with the separator placed between the positive and negative electrodes for isolation. This creates a bare cell, which is then welded with tabs. The bare cell is placed in an outer package and filled with liquid cryogenic molten salt electrolyte. Following this, encapsulation, settling, formation, shaping, and capacity testing are performed to fabricate an aluminum-sulfur battery.

[0066] The prepared aluminum-sulfur battery was tested using a Xinwei battery testing device (CT-4008) at 10 mA·cm⁻¹. -2The battery's cycle performance was tested using high charge-discharge current densities. At 25°C, the prepared battery was charged to 2.5V with a constant current of 1C, then charged at a constant voltage of 2.5V until the current dropped to 0.05C. After resting for 10 minutes, it was discharged to 1.5V with a constant current of 1C. This charge-discharge cycle was repeated. Each charge-discharge cycle constituted one complete cycle. The battery life was considered to have ended when the discharge capacity of the aluminum-sulfur battery decreased to 80% of the capacity of the first cycle. The number of charge-discharge cycles was recorded. The number of cycles was 277.

[0067] This is the battery's first charge / discharge cycle. The discharge capacity of this cycle is recorded as the battery's first cycle discharge capacity (C0). Repeat the above steps for the same battery. After 250 cycles, the battery's discharge capacity (C1) is recorded. The battery capacity retention rate is 26%. Example 5

[0068] I. Preparation of Liquid Low-Temperature Molten Salt Electrolytes The method for preparing the liquid low-temperature molten salt electrolyte includes the following steps: S1. At room temperature, weigh out 534.45g of tetraallyl ammonium chloride, 333.32g of anhydrous aluminum chloride, 8.68g of NaCl, 8.68g of KCl, and 43.39g of LiCl in advance, seal them well, and dry them in an oven at 105℃ for 12 hours to fully remove the moisture from the sample. S2. Weigh 400g of reagent-pure anhydrous aluminum chloride in the glove box, mix it with the mixture in S1, and stir to form a low-temperature ionic liquid; S3. After stirring the ionic liquid in S2 for 8 hours, a liquid low-temperature molten salt electrolyte is obtained.

[0069] It should be noted that the above preparation process was carried out entirely in a glove box. In the glove box, 2.5 mol of tetraallyl ammonium chloride, 2.5 mol of anhydrous aluminum chloride, 0.2 mol of NaCl, 0.1 mol of KCl, and 1 mol of LiCl were mixed. This process was conducted under an inert gas atmosphere (such as nitrogen or argon) to prevent interference from moisture and oxygen. During the thorough stirring of the mixture with solid anhydrous aluminum chloride, the mixture gradually turned into a pale yellow-green liquid, simultaneously releasing hydrogen chloride gas and forming a characteristic white gas. In this process, the anhydrous aluminum chloride and tetrabutylammonium chloride reacted completely to generate a liquid low-temperature molten salt electrolyte.

[0070] II. Battery Manufacturing The battery made using the low-temperature molten salt electrolyte prepared in this embodiment includes the low-temperature molten salt electrolyte and positive and negative electrodes partially immersed in the low-temperature molten salt electrolyte. The negative electrode is metallic aluminum and / or an aluminum alloy. The preparation methods of the positive and negative electrodes are consistent with those in Example 1.

[0071] The ionic conductivity of the prepared liquid molten salt electrolyte was tested: In this application, electrochemical impedance spectroscopy (EIS) was used to measure the conductivity of the electrolyte molten salt, with test temperatures ranging from 25°C to 70°C. The tested ionic conductivity of this liquid low-temperature molten salt electrolyte at 0°C, 25°C, 40°C, 50°C, and 70°C was 1.1 × 10⁻⁶. -1 S / m, 3.5×10 -1 S / m, 3.8×10 -1 S / m, 4.1×10 -1 S / m and 6.4×10 -1 S / m.

[0072] The liquid low-temperature molten salt electrolyte was used to prepare an aluminum-sulfur battery, and the battery was tested using a Xinwei battery testing device (CT-4008) at 10 mA·cm⁻¹. -2 The battery's cycle performance was tested using high charge / discharge current density. At 25°C, the prepared battery was charged to 4.0V with a constant current of 1C, then charged to 0.05C with a constant voltage of 4.0V. After resting for 10 minutes, it was discharged to 1.5V with a constant current of 1C. This was the battery's first charge / discharge cycle, and the discharge capacity of this cycle was recorded as the battery's first cycle discharge capacity (C0). The above steps were repeated for the same battery. The discharge capacity (C1) of the battery after 800 cycles was recorded. The capacity retention rate after 800 cycles = C1 / C0 × 100% = 79%.

[0073] Comparative Example 5 Based on Example 5, only the membrane configuration was changed. A cation separator was added to the aluminum-sulfur battery of Comparative Example 5: an electric field was formed around the cation separator, and the negative terminal of a DC power supply was electrically connected to the composite separator, while the positive terminal of the DC power supply was grounded. This configuration enables the formation of an electric field at the composite separator, which is negatively charged. The negative charge attached to the composite separator attracts free cations in the electrolyte to move towards the composite separator and then pass through the micropores of the composite separator.

[0074] The positive electrode, separator, and negative electrode are stacked sequentially, with the separator placed between the positive and negative electrodes for isolation. This creates a bare cell, which is then welded with tabs. The bare cell is placed in an outer package and filled with liquid cryogenic molten salt electrolyte. Following this, encapsulation, settling, formation, shaping, and capacity testing are performed to fabricate an aluminum-sulfur battery.

[0075] The prepared aluminum-sulfur battery was tested using a Xinwei battery testing device (CT-4008) at 10 mA·cm⁻¹. -2The battery's cycle performance was tested using high charge-discharge current densities. At 25°C, the prepared battery was charged to 2.5V with a constant current of 1C, then charged at a constant voltage of 2.5V until the current dropped to 0.05C. After resting for 10 minutes, it was discharged to 1.5V with a constant current of 1C. This charge-discharge cycle was repeated, with each cycle constituting one full cycle. The battery life was considered to have ended when the discharge capacity of the aluminum-sulfur battery decreased to 80% of the capacity of the first discharge cycle. The number of charge-discharge cycles was recorded. The number of cycles was 183.

[0076] This is the battery's first charge / discharge cycle. The discharge capacity of this cycle is recorded as the battery's first cycle discharge capacity (C0). Repeat the above steps for the same battery. After 150 cycles, the battery's discharge capacity (C1) is recorded. The battery capacity retention rate is 24%.

[0077] III. Analysis of Test Results for Each Embodiment and Comparative Example The low-temperature molten salt electrolytes for each embodiment and comparative example, and the batteries using the electrolytes, were prepared according to the aforementioned method, and various performance parameters were measured. The results are shown in Tables 1 and 2 below:

[0078] Table 1 Preparation Parameters

[0079] Table 2 Performance Table Experimental results show that the aluminum-sulfur battery of the present invention exhibits high performance in terms of cycle life and capacity retention. This is because the aluminum-sulfur battery of the present invention does not have a separator, and the liquid molten salt electrolyte contains Al2Cl7. - and AlCl4 - The anions exhibit excellent insertion and extraction properties in the SC cathode. In contrast, the battery using a cation exchange membrane in the comparative example had fewer cycle times and less than ideal secondary charge-discharge performance. Further experiments revealed that this was due to the presence of Al in the electrolyte. 3+ After the ions intercalate at the intercalation site, an irreversible reaction occurs, leading to the intercalated Al... 3+ The inability to completely detach the separator prevents the cation exchange membrane battery from effectively recharging and discharging. Under the same test conditions, the battery of this invention can achieve more charge-discharge cycles, and the battery capacity retention is significantly higher.

[0080] The aluminum-sulfur battery using the liquid cryogenic molten salt electrolyte of this invention maintains a capacity retention of 79% after 800 cycles, demonstrating excellent cycle stability and high capacity retention, making it ideal for long-duration and high-load applications. Simultaneously, the liquid cryogenic molten salt electrolyte of this invention exhibits good ionic conductivity at different temperatures, indicating excellent ion conduction performance and high stability over a wide temperature range, adapting to various working environments. The battery operates stably at around 30°C during normal operation, avoiding damage to the positive and negative electrodes caused by high-temperature operation, thereby extending battery life and reducing safety hazards such as explosions and leaks caused by high temperatures, thus improving battery safety. The battery using this liquid cryogenic molten salt electrolyte has an aluminum negative electrode, resulting in a significantly increased energy density of 750 Wh / kg. Furthermore, the materials used in this invention—the positive electrode, negative electrode, and cryogenic molten salt electrolyte—are abundant and inexpensive on Earth, greatly reducing battery manufacturing costs.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A liquid low-temperature molten salt electrolyte, characterized in that, It includes anhydrous aluminum chloride, organic ammonium halides, and inorganic salt additives. The organic ammonium halides are one of alkane ammonium halides, olefin halides, or aromatic hydrocarbon halides. The inorganic salt additives are chloride salts. The liquid low-temperature molten salt electrolyte is a transparent liquid at room temperature.

2. The liquid low-temperature molten salt electrolyte according to claim 1, characterized in that, The aromatic hydrocarbon halide is one of benzyl ammonium chloride, triethylbenzyl ammonium chloride, and dibenzyldimethyl ammonium chloride.

3. The liquid low-temperature molten salt electrolyte according to claim 1, characterized in that, The olefin halide is one of tetraallyl ammonium chloride and allyltrimethylammonium chloride.

4. The liquid low-temperature molten salt electrolyte according to claim 1, characterized in that, The alkane ammonium halide compound is one of the following: alkane ammonium chloride compound, alkane ammonium fluoride compound, or alkane ammonium bromide compound.

5. The liquid cryogenic molten salt electrolyte according to claim 2, characterized in that, The alkane ammonium chloride compound is selected from one of tetraalkylammonium salts, trialkylammonium salts, and dialkylammonium salts.

6. The liquid low-temperature molten salt electrolyte according to claim 2, characterized in that, The alkane ammonium chloride is selected from alkyl groups having 1 to 3 carbon atoms.

7. The liquid low-temperature molten salt electrolyte according to claim 2, characterized in that, The ammonium fluoride alkane is selected from alkyl groups having 1 to 3 carbon atoms.

8. The liquid cryogenic molten salt electrolyte according to claim 1, characterized in that, Based on the total weight of the electrolyte, the weight percentage of the organic ammonium halide is X, the weight percentage of the anhydrous aluminum chloride is Y, and the weight percentage of the inorganic salt additive is Z, where X and Y simultaneously satisfy the conditions expressed in equations (1) and (2): 90% ≤ (X+Y) ≤ 95wt%…(1); and 0.45≤(X / Y)≤2.1…(2).

9. The liquid cryogenic molten salt electrolyte according to claim 8, characterized in that, The chloride salt is a mixture of NaCl, KCl and LiCl, wherein the mass percentage of NaCl in the total electrolyte is 0.5% to 1.5%, the mass percentage of KCl in the total electrolyte is 0.5% to 1.5%, and the mass percentage of LiCl in the total electrolyte is 4% to 8%.

10. A battery, characterized in that, The battery includes a liquid low-temperature molten salt electrolyte as described in any one of claims 1 to 9, a negative electrode containing aluminum, and a positive electrode containing sulfur.

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