A hybrid ion battery based on sodium salt-controlled ion liquid and its preparation method

Abstract

This invention relates to a hybrid ion battery based on sodium salt-regulated ionic liquid and its preparation method, belonging to the field of electrochemical energy storage technology. By introducing sodium salt into the ionic liquid to construct a stable hybrid ion synergistic energy storage mechanism, the ion migration behavior at the electrode-electrolyte interface can be effectively regulated and the interfacial charge transfer impedance reduced, thereby improving the insertion / extraction kinetics of aluminum tetrachloride ions and sodium ions. Compared with the traditional single aluminum ion system, it can achieve higher capacity output and better cycle stability. The use of a self-supporting polyanionic cathode material is beneficial to improving electrode structural stability and electrolyte tolerance. The hybrid ion battery has comprehensive advantages in terms of capacity performance, cycle stability, and structural reliability.

Description

Technical Field

[0001] This invention relates to a hybrid ion battery based on sodium salt-regulated ion liquid and its preparation method, belonging to the field of electrochemical energy storage technology. Background Technology

[0002] The continuous advancement of electrochemical energy storage technology has driven an urgent demand for energy storage systems with high safety, low cost, and long cycle life. Aluminum-ion batteries, using aluminum metal as the negative electrode and aluminochloride ionic liquid as the electrolyte, possess significant advantages such as abundant resources, environmental friendliness, and high theoretical capacity. Ionic liquids, as commonly used electrolytes, exhibit characteristics such as low toxicity and non-flammability, low vapor pressure, and a wide electrochemical window. In this type of system, the energy storage process typically involves aluminate ions (AlCl4). - Or Al2Cl7 - The insertion and extraction of anions in the cathode material enables reversible charge storage. However, traditional aluminum-ion battery systems typically use a single anion as the primary energy carrier, which limits their capacity output and energy density to some extent. Especially during high-rate or long-term cycling, the battery is prone to problems such as increased polarization and capacity decay due to limited ion diffusion and slow interfacial reaction kinetics.

[0003] Currently, the main technical solutions for improving the capacity and electrochemical performance of traditional aluminum-ion batteries focus on electrode material structure design, composition control, and electrolyte optimization. While these approaches have improved battery performance to some extent, limitations remain. For example, while high specific surface area or nanostructured materials can increase active sites, their complex manufacturing processes may affect structural stability. Elemental doping methods are costly and not conducive to large-scale applications. Furthermore, optimizing single-anion electrolyte energy storage systems also offers limited potential for capacity improvement.

[0004] In recent years, hybrid-ion batteries have gradually attracted attention due to their ability to simultaneously utilize cations and anions in energy storage reactions, thereby improving battery capacity and capacity retention to some extent. Existing research largely focuses on traditional organic electrolyte systems. Furthermore, the structural stability and interfacial compatibility of the cathode material are important factors affecting the performance of hybrid-ion batteries. Polyanionic cathode materials are composed of tetrahedral (XO4) cathodes. n- (X = S, P, Si, B, Mo, W) or its derivatives (X m O 3m+1 ) n- With transition metal-oxygen polyhedra [MO] x[M is a transition metal element] A framework compound constructed through specific covalent bonds. As a mature cathode material for sodium-ion batteries, polyanionic cathode materials possess high operating voltage, excellent structural stability, and good ion diffusion performance, and have been widely used in sodium-ion battery systems. However, in conventional sodium-ion battery systems, polyanionic cathode materials generally suffer from low intrinsic electronic conductivity. Therefore, it is usually necessary to introduce conductive agents (such as Ketjenblack) and adopt a coated electrode structure composed of active material, conductive agent, and binder, while relying on a metal current collector to construct electron transport paths and provide mechanical support for the electrode. In highly corrosive electrolyte environments such as aluminochloride ionic liquids, electrode structures relying on traditional solvents, binders, and metal current collectors are prone to problems such as decreased structural stability and interfacial contact failure during cycling, thus affecting the cycle stability of the battery. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a hybrid ion battery based on sodium salt-regulated ionic liquid and its preparation method. By introducing sodium salt into the ionic liquid to construct a stable hybrid ion synergistic energy storage mechanism, the ion migration behavior at the electrode-electrolyte interface can be effectively regulated and the interfacial charge transfer impedance reduced, thereby improving the insertion-extraction kinetics of aluminum tetrachloride ions and sodium ions. Compared with the traditional single aluminum ion system, it can achieve higher capacity output and better cycle stability. The use of a self-supporting polyanionic cathode material is beneficial to improving electrode structural stability and electrolyte tolerance. The hybrid ion battery has comprehensive advantages in terms of capacity performance, cycle stability, and structural reliability, and is of great significance for improving the practical application value of energy storage systems.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] A hybrid ion battery based on sodium salt-regulated ionic liquid includes an AlCl3 / imidazolium salt ionic liquid containing inorganic sodium salt, a self-supporting polyanionic positive electrode, and an aluminum sheet negative electrode; wherein the inorganic sodium salt is soluble in the AlCl3 / imidazolium salt ionic liquid and does not chemically react with the ionic liquid.

[0008] Preferably, in the AlCl3 / imidazolium salt ionic liquid containing inorganic sodium salt, the molar ratio of AlCl3 to imidazolium salt ionic liquid is 1.1~1.5:1, and the concentration of inorganic sodium salt in the AlCl3 / imidazolium salt ionic liquid is 0.05~1 M. More preferably, the molar ratio of AlCl3 to imidazolium salt ionic liquid is 1.3:1, and the concentration of inorganic sodium salt in the AlCl3 / imidazolium salt ionic liquid is 0.1~0.5 M.

[0009] Preferably, the imidazolium salt comprises one or more of 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl), 1-butyl-3-methylimidazolium chloride ([BMIm]Cl), and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIm]TFSI). More preferably, the imidazolium salt is 1-ethyl-3-methylimidazolium chloride.

[0010] Preferably, the inorganic sodium salt is sodium chloride and / or sodium sulfate.

[0011] Preferably, the active material of the positive electrode includes phosphates, pyrophosphates, sulfates, and fluorophosphates; phosphates include sodium titanium phosphate, sodium vanadium phosphate, sodium iron phosphate, sodium manganese titanium phosphate, sodium manganese vanadium phosphate, sodium chromium phosphate, and sodium indium phosphate; pyrophosphates include sodium iron pyrophosphate; sulfates include sodium iron sulfate, sodium ferric sulfate dihydrate, and sodium cobalt sulfate dihydrate; and fluorophosphates include sodium vanadium fluorophosphate. More preferably, the active material of the positive electrode is sodium vanadium fluorophosphate (NVPF).

[0012] Preferably, the loading of active material in the positive electrode sheet is 5-6 mg / cm³. -2 .

[0013] A method for preparing a hybrid ion battery based on sodium salt-regulated ion liquid according to the present invention includes the following steps:

[0014] (1) Under inert gas protection, anhydrous AlCl3 is added to imidazolium salt to form AlCl3 / imidazolium salt ionic liquid; then inorganic sodium salt is added and dissolved to obtain AlCl3 / imidazolium salt ionic liquid containing inorganic sodium salt; (2) Mix the positive electrode active material, conductive agent and binder, grind and mix them, transfer them evenly to a metal plate, compact them, cut them and dry them to obtain a self-supporting polyanionic positive electrode sheet; (3) Under the protection of inert gas, AlCl3 / imidazolium salt ionic liquid containing inorganic sodium salt, self-supporting polyanionic positive electrode and aluminum negative electrode are assembled to obtain a hybrid ion battery based on sodium salt-regulated ionic liquid.

[0015] Preferably, in step (2), the conductive agent is Ketjen Black and the binder is polytetrafluoroethylene; the mass ratio of the positive electrode active material, the conductive agent and the binder is 7:2:1.

[0016] Preferably, in step (2), the positive electrode active material and the conductive agent are first mixed and ground evenly, and then the binder is added and ground.

[0017] Beneficial effects (1) This invention introduces inorganic sodium salt into the ionic liquid electrolyte system for aluminum-ion batteries, which together with the self-supporting polyanionic positive electrode and the aluminum negative electrode, constructs a stable hybrid ion battery system, realizing the synergistic storage and transport of cations and anions. This strategy effectively regulates the ion composition and ion transport behavior in the electrolyte, reduces the polarization voltage of the battery during charging and discharging, and improves the reversibility of the electrochemical reaction.

[0018] (2) The present invention regulates the ionic liquid system by sodium salt, which can effectively improve the ionic conductivity and interfacial stability of the electrolyte and enhance the structural stability of the battery during long cycle; it helps to improve the cycle life and capacity retention of the hybrid ion battery, while improving the rate performance and coulombic efficiency, thereby significantly improving the overall electrochemical performance of the battery.

[0019] (3) The method for preparing the self-supporting polyanionic cathode material of the present invention utilizes the fibrillation properties of PTFE, which transforms it into a network fiber structure under high shear force, thereby effectively bonding the electrode active material and conductive agent, and realizing the formation of a self-supporting electrode sheet under solvent-free conditions. Compared with the traditional wet process, this method not only avoids the use of solvents, but also has significant advantages in terms of the uniformity of the electrode microstructure and the compaction density. The self-supporting electrode has good mechanical stability and interfacial stability, which helps to maintain the integrity of the electrode structure during repeated charge and discharge, and can still maintain good cycle stability under the synergistic effect of multiple ion insertion / extraction.

[0020] (4) The hybrid ion battery system based on sodium salt-regulated ionic liquid constructed in this invention can realize the reversible insertion / extraction behavior of sodium ions and aluminochlorochloride ions during charging and discharging, which helps to improve the specific capacity and energy density of the electrode material. At the same time, by controlling the type and concentration of ions, this system can effectively broaden the working voltage window of the battery and improve the energy output capability of the battery, and has good application potential.

[0021] (5) The battery preparation process of the present invention is simple and feasible. The sodium salt used is widely available and inexpensive, and no complex synthesis steps or special equipment are required. It has good operability and repeatability. This technical solution has the advantages of high economy and large-scale preparation, and is suitable for the development and engineering application of new energy storage systems. It has good industrial application prospects. Attached Figure Description

[0022] Figure 1 The diagram shows the cycle performance of Example 3 (Cycle number is the number of battery cycles, Capacity is the battery capacity, and Coulombic Efficiency is the battery coulombic efficiency).

[0023] Figure 2 This is the charge / discharge curve diagram for Example 3 (Capacity is the battery capacity, and Voltage is the battery voltage).

[0024] Figure 3 The CV performance graph for Example 4 is shown (Current is the battery current, and Voltage is the battery voltage).

[0025] Figure 4 The graph shows the cyclic performance of Comparative Example 1.

[0026] Figure 5 This is a charge-discharge curve for Comparative Example 1. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments.

[0028] A hybrid ion battery based on sodium salt-regulated ion liquid and its preparation method are disclosed. The battery comprises an AlCl3 imidazolium salt ion liquid containing dissolved sodium salt and a self-supporting polyanionic cathode material. The method includes the following steps: Step 1: Preparation of ionic liquid: Under inert gas protection, anhydrous AlCl3 is slowly added to imidazolium salt. Through mechanical vibration, the mixture is allowed to fully react and form a homogeneous and transparent ionic liquid.

[0029] Step 2: Preparation of Sodium Salt-Regulated Ionic Liquid: Weigh a certain amount of sodium salt and slowly add it to the ionic liquid prepared in Step 1. Continuously agitate to allow the sodium salt to fully dissolve in the ionic liquid, forming a sodium-containing composite ionic liquid electrolyte. Maintain system stability during stirring to avoid introducing impurities or moisture.

[0030] Step 3: Preparation of self-supporting polyanionic positive electrode: After thoroughly mixing and grinding the active material and conductive agent, a binder is added. Through continuous grinding, the binder undergoes fibrillation, forming a uniform fibrous network between the electrode material particles, thereby obtaining a self-supporting electrode material with certain mechanical strength. The electrode material is compacted by rolling or sheet forming to control the electrode thickness and surface uniformity. The self-supporting positive electrode sheet is then cut to an appropriate size.

[0031] Step 4: Drying: Place the prepared electrode in a vacuum drying device and dry it under the set temperature conditions. Store the dried electrode in a dry environment for later use.

[0032] Step 5, Battery Assembly: In an argon-filled glove box, using an aluminum sheet as the negative electrode and the aforementioned self-supporting electrode as the positive electrode, a glass fiber membrane as the separator, and a sodium-containing composite ionic liquid electrolyte, a hybrid ion battery based on sodium salt-regulated ionic liquid is assembled.

[0033] Step Six: Sample Collection and Testing: Store the prepared positive electrode in a glove box for later use to prevent reaction with air. The positive electrode prepared in the above steps is used to prepare a hybrid ion battery. Batteries are assembled separately in ionic liquid and ionic liquid systems containing dissolved sodium salts for electrochemical performance testing.

[0034] In step one, the molar ratio of anhydrous aluminum chloride to imidazolium salt is preferably 1.1 to 1.5, and more preferably 1.3.

[0035] In step two, the sodium salt is an inorganic sodium salt, preferably sodium chloride or sodium sulfate. The sodium salt should meet the following conditions: it should be able to dissolve or disperse stably in the ionic liquid and not react significantly with the AlCl3 / imidazolium salt ionic liquid; it should have good chemical and electrochemical stability under battery charging / discharging and high-voltage conditions, and be less prone to decomposition, gas evolution, or side reactions; its addition should not significantly reduce the ionic conductivity and electrochemical stability window of the ionic liquid; and it should reduce side reactions at the electrode / electrolyte interface, improving battery cycle stability and safety. Preferably, the anion in the sodium salt has good compatibility with the aluminochlorochlorohydrate ionic liquid system and is less likely to cause structural instability of the ionic liquid or corrosion of the aluminum anode.

[0036] In step two, the concentration of the sodium salt in the ionic liquid is preferably 0.1~1 M.

[0037] In step three, the active substance includes phosphates, pyrophosphates, sulfates, and fluorophosphates; phosphates include sodium titanium phosphate, sodium vanadium phosphate, sodium iron phosphate, sodium manganese titanium phosphate, sodium manganese vanadium phosphate, sodium chromium phosphate, and sodium indium phosphate; pyrophosphates include sodium iron pyrophosphate; sulfates include sodium iron sulfate, sodium ferric sulfate dihydrate, and sodium cobalt sulfate dihydrate; and fluorophosphates include sodium vanadium fluorophosphate. More preferably, the active substance is sodium vanadium fluorophosphate (NVPF).

[0038] In step three, the conductive agent is preferably Ketjen Black.

[0039] In step three, the adhesive is preferably polytetrafluoroethylene.

[0040] In step three, the preferred mass ratio of NVPF, Ketjen Black, and PTFE is 7:2:1.

[0041] In step four, the preferred NVPF loading in the electrode is 5~6 mg cm⁻¹. -2 .

[0042] In step five, the drying temperature is 60~120 °C, more preferably 80 °C.

[0043] In step five, the drying time is preferably 12 hours.

[0044] Example 1 A method for preparing a hybrid ion battery based on sodium salt-controlled ion liquid, the specific steps of which are as follows: Step 1: Preparation of the ionic liquid: In an argon-filled glove box, weigh 10 g of anhydrous aluminum chloride (AlCl3, 99.99%) and slowly add it to an isotope bottle containing 8.46 g of 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl). Then, mechanically shake at room temperature for 2 min until a homogeneous and transparent ionic liquid is formed.

[0045] Step 2, Addition of sodium salt: Weigh 0.0414 g of sodium chloride (NaCl) to a concentration of 0.5 M in the ionic liquid and add it to the ionic liquid prepared above. Continue mechanical shaking for 5 min until the sodium salt is completely dissolved to obtain the ionic liquid electrolyte based on sodium salt regulation.

[0046] Step 3: Preparation of the self-supporting NVPF positive electrode: Weigh out 0.7 g Na3V2(PO4)2F3 (NVPF), 0.2 g Ketjen black, and 0.1 g polytetrafluoroethylene (PTFE) for later use. First, grind the NVPF and Ketjen black thoroughly in an agate mortar for 15 min to ensure that the conductive agent is uniformly dispersed in the active material. Then add PTFE powder and continue grinding until the mixture gradually forms a sheet material with a certain viscosity. Place the above sheet material on a smooth stainless steel plate and roll it out using a stainless steel roller to make the electrode thickness uniform, controlling the NVPF loading of the electrode sheet to be 5.0-6.0 mg cm⁻¹. -2 The electrodes were then cut into squares with sides of 0.9 cm.

[0047] Step 4: Drying: Place the prepared electrode in a vacuum drying oven and dry it at 80°C for 12 hours to obtain a self-supporting NVPF electrode. After the electrode cools to room temperature, immediately transfer it to a glove box filled with high-purity argon gas to avoid adverse effects of moisture and oxygen in the air on the electrode material and to prepare for subsequent battery assembly.

[0048] Step 5, Battery Assembly: In an argon-filled glove box, using an aluminum sheet (0.05 mm thick) as the negative electrode, the above-mentioned self-supporting NVPF electrode as the positive electrode, and a glass fiber membrane as the separator, 50 μL of the ionic liquid electrolyte prepared above is added to assemble a hybrid ion battery based on sodium salt-regulated ionic liquid.

[0049] Example 2 A method for preparing a hybrid ion battery based on sodium salt-controlled ion liquid, the specific steps of which are as follows: Step 1: Preparation of the ionic liquid: In an argon-filled glove box, weigh 10 g of anhydrous aluminum chloride (AlCl3, 99.99%) and slowly add it to an isotope bottle containing 8.46 g of 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl). Then, mechanically shake at room temperature for 2 min until a homogeneous and transparent ionic liquid is formed.

[0050] Step 2, Addition of sodium salt: Weigh 0.201 g of sodium sulfate (Na2SO4) to make its concentration in the ionic liquid 1M, add it to the ionic liquid prepared above, and continue mechanical shaking for 2 min until the sodium salt is completely dissolved to obtain the ionic liquid electrolyte based on sodium salt regulation.

[0051] Step 3: Preparation of the self-supporting NVPF positive electrode: Weigh out 0.7 g Na3V2(PO4)2F3 (NVPF), 0.2 g Ketjen black, and 0.1 g polytetrafluoroethylene (PTFE) for later use. First, grind the NVPF and Ketjen black thoroughly in an agate mortar for 15 min to ensure that the conductive agent is uniformly dispersed in the active material. Then add PTFE powder and continue grinding until the mixture gradually forms a sheet material with a certain viscosity. Place the above sheet material on a smooth stainless steel plate and roll it out using a stainless steel roller to make the electrode thickness uniform, controlling the NVPF loading of the electrode sheet to be 5.0-6.0 mg cm⁻¹. -2 Then, using a ruler and scalpel, the electrodes were cut into squares with sides of 0.9 cm.

[0052] Step 4: Drying: Place the prepared electrode in a vacuum drying oven and dry it at 80 °C for 12 h to obtain a self-supporting NVPF electrode. After the electrode cools to room temperature, immediately transfer it to a glove box filled with high-purity argon gas to avoid adverse effects of moisture and oxygen in the air on the electrode material and to prepare for subsequent battery assembly.

[0053] Step 5, Battery Assembly: In an argon-filled glove box, using an aluminum sheet (0.05 mm thick) as the negative electrode, the above-mentioned self-supporting NVPF electrode as the positive electrode, and a glass fiber membrane as the separator, 50 μL of the ionic liquid electrolyte prepared above is added to assemble a hybrid ion battery based on sodium salt-regulated ionic liquid.

[0054] Example 3 A method for preparing a hybrid ion battery based on sodium salt-controlled ion liquid, the specific steps of which are as follows: Step 1: Preparation of the ionic liquid: In an argon-filled glove box, weigh 20 g of anhydrous aluminum chloride (AlCl3, 99.99%) and slowly add it to an isotope bottle containing 16.92 g of 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl). Then, mechanically shake at room temperature for 2 min until a homogeneous and transparent ionic liquid is formed.

[0055] Step 2, Addition of sodium salt: Weigh 0.0166 g of sodium chloride (NaCl) to make its concentration in the ionic liquid 0.1 M, add it to the ionic liquid prepared above, and continue mechanical shaking for 2 min until the sodium salt is completely dissolved to obtain the ionic liquid electrolyte based on sodium salt regulation.

[0056] Step 3: Preparation of the self-supporting NVPF positive electrode: Weigh out 0.7 g Na3V2(PO4)2F3 (NVPF), 0.2 g Ketjen black, and 0.1 g polytetrafluoroethylene (PTFE) for later use. First, grind the NVPF and Ketjen black thoroughly in an agate mortar for 15 min to ensure that the conductive agent is uniformly dispersed in the active material. Then add PTFE powder and continue grinding until the mixture gradually forms a sheet material with a certain viscosity. Place the above sheet material on the surface of a smooth stainless steel plate and roll it out using a stainless steel roller to make the electrode thickness uniform, controlling the NVPF loading of the electrode sheet to be 5.0-6.0 mg cm⁻¹. -2 Then, using a ruler and scalpel, the electrodes were cut into squares with sides of 0.9 cm.

[0057] Step 4: Drying: Place the prepared electrode in a vacuum drying oven and dry it at 80°C for 12 h.

[0058] Step 5, Battery Assembly: In an argon-filled glove box, using an aluminum sheet (0.05 mm thick) as the negative electrode, the above-mentioned self-supporting NVPF electrode as the positive electrode, and a glass fiber membrane as the separator, 50 μL of the ionic liquid electrolyte prepared above is added to assemble a hybrid ion battery based on sodium salt-regulated ionic liquid.

[0059] Step 6: Collect samples and test them. The cathode materials prepared in the above steps were used to assemble a hybrid ion battery and their electrochemical performance was tested.

[0060] Electrochemical tests were performed on the assembled hybrid ion battery based on sodium salt-regulated ion liquid. The test results are as follows: Figure 1 and Figure 2 As shown, by Figure 1 It can be seen that, thanks to the hybrid ion insertion and extraction mechanism, the Al / NVPF battery can achieve a coulombic efficiency of up to 97.46%, and maintain a stable efficiency of 115.7 mAh g⁻¹ after stable operation.-1 The specific capacity has a capacity retention rate of ≥91.3%. Figure 2 It can be seen that the hybrid ion battery exhibits two distinct voltage plateaus during both charging and discharging, corresponding to the two ion insertions and extractions. After the battery stabilizes, the voltage plateaus show relatively small changes.

[0061] Example 4 The method described in Example 2 is the same as in Example 2, except that the amount of sodium sulfate (Na2SO4) added in step two is adjusted to 0.0201 g, so that its concentration in the ionic liquid is 0.1 M. The remaining steps are the same as in Example 2. The test results are as follows: Figure 3 As shown in the CV curve, at a scan rate of 1 mV, there are two oxidation peaks and one reduction peak, corresponding to two ion insertions and extractions.

[0062] Example 5 The method described in Example 4 differs from that in step two, the amount of sodium sulfate (Na2SO4) added is adjusted to 0.1005 g, so that its concentration in the ionic liquid is 0.5 M. The remaining steps are the same as in Example 4.

[0063] Example 6 The method described in Example 3 differs from that in step two, the amount of sodium chloride (NaCl) added is adjusted to 0.0498 g, so that its concentration in the ionic liquid is 0.3 M. The remaining steps are the same as in Example 3.

[0064] Comparative Example 1 The method described in Example 3 differs from that in step two, no sodium salt was added, and AlCl3 / [EMIm]Cl ionic liquid was used directly as the electrolyte. The remaining steps are the same as in Example 3.

[0065] Electrochemical tests were performed on the assembled battery containing sodium-containing ionic liquids, and the results are as follows: Figure 4 and Figure 5 As shown, by Figure 4 It can be seen that the coulombic efficiency of the Al / NVPF battery using blank ionic liquid after stable operation is only 93.61%, and its specific capacity never exceeds 100 mAg. -1 . Figure 5 In the 1.5 V-1.8 V range, only a stable voltage plateau appeared. The capacity was significantly lower than that of the electrochemical performance of Example 3. Furthermore, the capacity decreased with increasing cycle number, the charge-discharge curve shifted downward as a whole, and the plateau characteristics weakened.

[0066] Comparative Example 2 The method described in Example 3 differs in that, in step two, the type of sodium salt added is changed to sodium perchlorate, and the amount added is 0.0347 g, making its concentration in the ionic liquid 0.1 M. In step two, a reaction occurs during the mixing of sodium perchlorate and the ionic liquid, causing the sodium perchlorate to decompose and release gas. Therefore, it cannot be used as an electrolyte in a hybrid ion battery.

[0067] Comparative Example 3 The method described in Example 3 is the same as in Example 3, except that in step two, the type of sodium salt added is changed to sodium hexafluorophosphate, and the amount added is 0.0476 g, so that its concentration in the ionic liquid is 0.1 M. The remaining steps are the same as in Example 3. In step two, sodium hexafluorophosphate has poor solubility in the ionic liquid and cannot form a stable and homogeneous electrolyte.

[0068] Comparative Example 4 The method described in Example 3 differs from that in step two, the concentration of sodium chloride in the ionic liquid is 1.5 M; the remaining steps are the same as in Example 3. In step two, the 1 M sodium chloride is not completely dissolved in the ionic liquid, and some white granular solid remains.

[0069] The specific capacity and coulombic efficiency results of the batteries after stabilization in the examples and comparative examples are shown in Table 1.

[0070] Table 1

[0071] The results from Examples 1-6 and Comparative Example 1 show that the hybrid ion batteries constructed by adding soluble inorganic sodium salts to ion liquids in all examples have higher specific capacities than the single-ion batteries in the comparative example, and their coulombic efficiencies are no lower than those of the single-ion batteries. This demonstrates that polyanionic cathodes have high compatibility with sodium salt-controlled ion liquid systems. Figure 2 The two distinct voltage plateaus in the charge-discharge curves indicate that the addition of sodium chloride or sodium sulfate leads to a two-step ion insertion / extraction reaction in the battery system, thereby increasing the battery's energy storage capacity. When sodium chloride is used as the sodium salt, the electrochemical performance of Examples 1 (0.5 M NaCl) and 3 (0.1 M NaCl) is significantly better than that of Comparative Example 1, demonstrating that the addition of an appropriate amount of sodium chloride is beneficial for constructing a stable mixed-ion energy storage system and improving battery capacity and cycle stability. Example 3 exhibits the highest specific capacity and high coulombic efficiency, indicating that at a concentration of 0.1 M, the ionic liquid system can maintain good ion transport capability and interfacial stability.

[0072] The results from Examples 1, 3, and Comparative Example 4 show that when the NaCl concentration is increased to 1.5 M, the battery specific capacity decreases significantly, essentially losing its reversible energy storage capability. This is because excess Cl... It will destroy AlCl4 in ionic liquids With Al2Cl7 The coordination balance between them leads to a reduction in reversible active ion pairs in the system, which prevents the aluminum anode side from undergoing normal aluminum deposition / dissolution reactions, resulting in a significant decrease in battery performance.

[0073] The results from Examples 2, 4, 5, and Comparative Example 1 show that Examples 4 (0.1 M Na₂SO₄) and 5 (0.5 M Na₂SO₄) both exhibited high specific capacity and good coulombic efficiency, indicating that an appropriate amount of sodium sulfate can also promote mixed-ion reactions and improve battery energy storage performance. The specific capacity of the 0.5 M Na₂SO₄ system was slightly higher than that of the 0.1 M system, while the coulombic efficiency decreased slightly. This indicates that as the sodium sulfate concentration increases, the number of ions that can participate in the reaction increases, which is beneficial for capacity improvement, but may also lead to increased interfacial side reactions and intensified polarization. When the sodium sulfate concentration was further increased to 1 M (Example 2), the battery specific capacity decreased, indicating that excessively high concentrations of sulfate ions can adversely affect ion transport and interfacial stability in ionic liquid systems, thereby reducing battery electrochemical performance. In conclusion, the type and concentration of sodium salt have a significant impact on the electrochemical performance of mixed-ion batteries. The addition of appropriate amounts of sodium salts can help improve battery capacity, coulombic efficiency, and cycle stability, while excessively high concentrations can disrupt the stable coordination environment of the ionic liquid system, thereby reducing battery performance.

[0074] The results from Examples 1-6 and Comparative Examples 2-3 show that the choice of sodium salt has a significant impact on hybrid ion battery systems. Simply introducing commonly used sodium salts from sodium-ion batteries directly into the ionic liquid system does not guarantee stable operation. The type of sodium salt not only affects its solubility and dispersion stability in the ionic liquid but also further influences the chemical stability of the electrolyte system, the electrochemical stability window, and the safety and cycle stability of the battery under high voltage conditions. Specifically, sodium perchlorate (NaClO4), upon addition to the AlCl3 / [EMIm]Cl ionic liquid, reacts with the strongly Lewis acidic components in the system, leading to the decomposition of the perchlorate anion and the release of gas, causing instability in the electrolyte system and rendering it unsuitable for hybrid ion battery systems. While sodium hexafluorophosphate is widely used in sodium-ion batteries with traditional organic electrolyte systems, its solubility in chloroaluminate ionic liquid systems is poor, and PF6... Under conditions of high Lewis acidity and high voltage, decomposition reactions are likely to occur, which may generate fluorine-containing byproducts, thereby affecting the stability of the electrolyte and the cycle performance of the battery. Therefore, it is also not suitable for the system of this invention.

[0075] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. A hybrid ion battery based on sodium salt-controlled ion liquid, characterized in that: It includes an AlCl3 / imidazolium salt ionic liquid containing inorganic sodium salt, a self-supporting polyanionic positive electrode, and an aluminum sheet negative electrode; wherein the inorganic sodium salt is soluble in the AlCl3 / imidazolium salt ionic liquid and does not chemically react with the ionic liquid.

2. The hybrid ion battery based on sodium salt-controlled ionic liquid as described in claim 1, characterized in that: In the AlCl3 / imidazolium salt ionic liquid containing inorganic sodium salt, the molar ratio of AlCl3 to imidazolium salt ionic liquid is 1.1~1.5:1, and the concentration of inorganic sodium salt in AlCl3 / imidazolium salt ionic liquid is 0.05~1 M.

3. A hybrid ion battery based on sodium salt-regulated ionic liquid as described in claim 1 or 2, characterized in that: The molar ratio of AlCl3 to imidazolium salt ionic liquid is 1.3:1, and the concentration of inorganic sodium salt in AlCl3 / imidazolium salt ionic liquid is 0.1~0.5 M.

4. A hybrid ion battery based on sodium salt-regulated ionic liquid as described in claim 1 or 2, characterized in that: The imidazolium salt includes one or more of 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt.

5. A hybrid ion battery based on sodium salt-regulated ionic liquid as described in claim 1 or 2, characterized in that: The inorganic sodium salt is sodium chloride and / or sodium sulfate.

6. A hybrid ion battery based on sodium salt-controlled ionic liquid as described in claim 1, characterized in that: The active materials of the positive electrode include phosphates, pyrophosphates, sulfates, and fluorophosphates; phosphates include sodium titanium phosphate, sodium vanadium phosphate, sodium iron phosphate, sodium manganese titanium phosphate, sodium manganese vanadium phosphate, sodium chromium phosphate, and sodium indium phosphate; pyrophosphates include sodium iron pyrophosphate; sulfates include sodium iron sulfate, sodium iron disulfate dihydrate, and sodium cobalt disulfate dihydrate; and fluorophosphates include sodium vanadium fluorophosphate.

7. A hybrid ion battery based on sodium salt-controlled ionic liquid as described in claim 1, characterized in that: The loading of active material in the positive electrode is 5-6 mg / cm³. -2 .

8. A method for preparing a hybrid ion battery based on sodium salt-controlled ion liquid as described in any one of claims 1 to 7, characterized in that: The method steps include: (1) Under inert gas protection, anhydrous AlCl3 is added to imidazolium salt to form AlCl3 / imidazolium salt ionic liquid; then inorganic sodium salt is added and dissolved to obtain AlCl3 / imidazolium salt ionic liquid containing inorganic sodium salt; (2) Mix the positive electrode active material, conductive agent and binder, grind and mix them, transfer them evenly to a metal plate, compact them, cut them and dry them to obtain a self-supporting polyanionic positive electrode sheet; (3) Under the protection of inert gas, AlCl3 / imidazolium salt ionic liquid containing inorganic sodium salt, self-supporting polyanionic positive electrode and aluminum negative electrode are assembled to obtain a hybrid ion battery based on sodium salt-regulated ionic liquid.

9. The method for preparing a hybrid ion battery based on sodium salt-regulated ion liquid as described in claim 8, characterized in that: In step (2), the conductive agent is Ketjen Black and the binder is polytetrafluoroethylene; the mass ratio of the positive electrode active material, the conductive agent and the binder is 7:2:

1.

10. The method for preparing a hybrid ion battery based on sodium salt-regulated ion liquid as described in claim 8, characterized in that: In step (2), the positive electrode active material and the conductive agent are first mixed and ground evenly, and then the binder is added and ground.

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