Conversion-type positive electrode material for aluminum battery, aluminum battery positive electrode, secondary aluminum battery, and preparation method and application thereof

Abstract

The present application relates to the technical field of secondary aluminum battery, in particular to a conversion-type positive electrode material for aluminum battery, a positive electrode of aluminum battery, a secondary aluminum battery and a preparation method and application thereof. The conversion-type positive electrode material for aluminum battery comprises at least one of an indium-containing compound, a chromium-containing compound and a vanadium-containing compound. The conversion-type positive electrode material has fast kinetics and structure self-repairing characteristics.

Description

Technical Field

[0001] This invention relates to the field of secondary aluminum battery technology, and more specifically, to conversion cathode materials for aluminum batteries, aluminum battery cathodes, secondary aluminum batteries, their preparation methods, and applications. Background Technology

[0002] Faced with the threats of climate change and the energy crisis, grid-scale energy storage systems are considered fundamental to increasing the market penetration of sustainable energy. With the increasing demand for low-cost and high-energy-density electrochemical energy storage technologies, novel electrochemical battery technologies have developed rapidly in recent years. Lithium-ion batteries currently dominate the commercial electrochemical field, but the high cost of lithium limits its penetration. Therefore, rechargeable aluminum batteries, which are low-cost, air-stable, safe, and abundant (8.1 wt% in the Earth's crust), have attracted widespread attention, and the aluminum metal anode has a relatively high capacity (8040 mAh / cm³). -3 ).

[0003] Current solutions for rechargeable aluminum metal batteries face several problems, including limited charge storage capacity, poor reaction kinetics, and short cycle life. Research reports indicate the use of graphite-based cathodes and room-temperature aluminochloride ionic liquid electrolytes to construct aluminum metal batteries, with aluminochloride anions (AlCl4) in the electrolyte. - Energy storage is achieved through rapid insertion and extraction between graphite layers; however, the capacity ranges from 60 to 200 mAh / g. -1 The low capacity and severe electrolyte consumption of Al hinder the practical application of this type of battery. Some other metal compounds are based on Al... 3+ The intercalation-extraction reaction exhibits higher capacity (100-300 mAh g). -1 Examples of suitable materials include TiO2, Mo6S8, and vanadium-based MXenes, but these exhibit large overpotentials (0.4–0.8 V) and poor rate-delay capabilities due to the slow intercalation reaction kinetics based on solid-state materials and the limited Al content. 3+ Charge carriers have strong electrostatic repulsion.

[0004] In contrast, conversion chemistry ensures greater battery capacity through phase transitions involving complete structural reconstruction. In lithium-ion battery chemistry, phase transitions are typically based on solid-to-solid conversion chemistry, but these suffer from poor diffusion / reaction kinetics, large volume changes, and electrode structure disintegration. Most reports on aluminum batteries focus on transition metals and their sulfides, achieving capacities up to 400 mAh g based on solid-to-solid conversion reactions. -1 Despite this positive electrode conversion mechanism, the low diffusion rate and low reactivity of solid materials lead to extremely high polarization, low rate capability, and severe capacity decay in the battery.

[0005] Therefore, it is of great significance to develop a new system of conversion cathode with fast charging characteristics and high capacity and its secondary aluminum battery.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The primary objective of this invention is to provide a conversion cathode material for aluminum batteries, which possesses unique rapid kinetics and structural self-healing properties. This solves the problems faced by traditional aluminum batteries based on solid-solid conversion cathodes, such as low actual capacity, slow reaction kinetics, and rapid capacity decay.

[0008] The second objective of this invention is to provide an aluminum battery cathode with unique rapid kinetics and structural self-healing properties.

[0009] A third objective of this invention is to provide a secondary aluminum battery. Compared to traditional liquid metal batteries, this secondary aluminum battery based on a conversion-type positive electrode operates at a lower temperature, and significantly reduces both the battery's packaging and thermal management costs.

[0010] A fourth objective of this invention is to provide a method for preparing a secondary aluminum battery. This method can yield a secondary aluminum battery with unique rapid kinetics and structural self-healing characteristics based on a liquid-solid conversion reaction cathode.

[0011] The fifth objective of this invention is to provide an electrical device in which the aforementioned secondary aluminum battery can be used in large-scale independent energy storage power stations, distributed renewable energy grid connection, park and home energy storage systems, electric vehicles and other fields.

[0012] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0013] The present invention provides a conversion cathode material for aluminum batteries, the conversion cathode material comprising at least one of indium-containing compounds, chromium-containing compounds, and vanadium-containing compounds.

[0014] The present invention also provides an aluminum battery cathode, comprising the aforementioned conversion cathode material for aluminum batteries.

[0015] The present invention also provides a secondary aluminum battery, comprising a negative electrode, an electrolyte, a separator, and the positive electrode of the aluminum battery.

[0016] The present invention also provides a method for preparing the aforementioned secondary aluminum battery, comprising the following steps:

[0017] A conversion-type positive electrode material, a positive electrode current collector, a negative electrode, and a separator are obtained, and the conversion-type positive electrode material is dispersed in an electrolyte to form a positive electrode, which is then assembled.

[0018] And / or, obtain an active material containing a conversion-type positive electrode material, and mix the active material, conductive agent and binder and coat it on the surface of the current collector to obtain a positive electrode, and then assemble it.

[0019] The present invention also provides an electrical device, including the aforementioned secondary aluminum battery.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) The conversion cathode material for aluminum batteries provided by the present invention has fast charging characteristics and structural self-healing characteristics.

[0022] (2) The aluminum battery cathode provided by the present invention has fast charging characteristics and excellent cycle stability.

[0023] (3) The aluminum battery based on the liquid-solid conversion cathode provided by this invention has excellent fast-charging characteristics and long cycle performance. Taking the InCl cathode as an example, a highly reversible conversion occurs between the liquid InCl and solid InCl3 during the reaction process, exhibiting excellent fast-charging characteristics (approximately 100 mAh g / kg at a 50C current density). -1 It has reversible capacity and very stable cycle performance, with no capacity decay after 500 cycles at a high charging current density of 20C.

[0024] (4) The secondary aluminum battery provided by this invention has an operating temperature that is much lower than that of current liquid metal batteries based on molten salt (>450°C) and also lower than that of conventional Zebra batteries based on molten salt (>270°C). At the lower operating temperature, the sealing corrosion problem and the problem of excessive energy consumption during heating start-up of molten salt aluminum batteries are solved, and the battery packaging cost and thermal management cost are also significantly reduced.

[0025] (5) The secondary aluminum battery provided by the present invention also has the advantages of non-flammability, high safety and low cost.

[0026] (6) The molten salt electrolyte in the secondary aluminum battery provided by the present invention can not only meet the solubility requirements of the liquid-solid conversion reaction, enabling the aluminum battery based on the liquid-solid conversion cathode to exhibit higher reversible capacity and higher coulombic efficiency; but also provides low dissociation energy and high diffusion kinetics, which can effectively support the fast reaction kinetics of the aluminum battery, and has the advantages of low temperature, fast reaction kinetics and high safety. Attached Figure Description

[0027] 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.

[0028] Figure 1 This is a rate test cycle diagram of the secondary molten salt aluminum battery provided in Embodiment 1 of the present invention;

[0029] Figure 2 This is a voltage curve of a secondary molten salt aluminum battery under different current densities provided in Embodiment 1 of the present invention;

[0030] Figure 3 This is a rate test cycle diagram of the secondary molten salt aluminum battery provided in Embodiment 2 of the present invention;

[0031] Figure 4 This is a voltage curve diagram of a secondary molten salt aluminum battery under different current densities provided in Embodiment 2 of the present invention;

[0032] Figure 5 The constant current charge-discharge test voltage curve of the secondary molten salt aluminum battery prepared in Example 3 is shown in Figure 3.

[0033] Figure 6 The rate test cycle diagram is shown for the secondary molten salt aluminum battery prepared in Example 4.

[0034] Figure 7 The voltage curves of the secondary molten salt aluminum battery prepared in Example 4 at different current densities are shown.

[0035] Figure 8 The constant current charge-discharge test voltage curve of the secondary molten salt aluminum battery prepared in Example 6 is shown.

[0036] Figure 9 The constant current charge-discharge test cycle diagram is shown for the secondary aluminum battery prepared in Comparative Example 1. Detailed Implementation

[0037] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0038] In a first aspect, the present invention provides a conversion cathode material for aluminum batteries, the conversion cathode material comprising at least one of indium-containing compounds, chromium-containing compounds, and vanadium-containing compounds.

[0039] This conversion-type cathode material for aluminum batteries undergoes a liquid-to-solid phase transition reaction during charging and discharging. Specifically, during discharge, the conversion-type cathode material is a dissolved low-valence metal ion, i.e., in the liquid phase; during charging, it is a slightly soluble high-valence metal halide, i.e., in the solid phase. In other words, the conversion-type cathode material undergoes a liquid-solid conversion reaction during charging and discharging.

[0040] Based on the stability of the redox couple in the liquid-solid conversion reaction, the following two requirements apply: (1) The material in the reduced state (denoted as M) red+ It should be highly soluble in electrolytes, and M red+ / M(0) corresponds to a more negative redox potential than Al(III) / Al(0); (2) Materials in the oxidized state (denoted as M) ox+ It should be slightly soluble or insoluble in electrolytes, M ox+ / M red+ Redox couples possess high potentials to generate high battery voltages. This invention, based on the liquid-solid conversion reaction mechanism, screens suitable redox couples, expanding the range of cathode materials and obtaining a series of cathode materials that combine high performance and low cost.

[0041] Specific types of metal compounds are used as conversion-type cathode materials. In their reduced state, they exhibit a certain solubility in the electrolyte and do not undergo spontaneous chemical reactions with the aluminum anode. In their oxidized state, they are only slightly soluble in the electrolyte, avoiding the shuttle effect during charging. During charging, based on surface precipitation reactions, low-valence metal ions in the solution phase are oxidized into slightly soluble high-valence metal halide solids. During discharging, the slightly soluble high-valence metal halides are converted into soluble low-valence metal ions, exhibiting structural self-repair properties.

[0042] The conversion-type cathode material for aluminum batteries provided by this invention broadens the range of cathode material systems for secondary aluminum batteries, possesses rapid conversion reaction kinetics, and has broad application prospects. This conversion-type cathode material avoids the rapid capacity decay caused by the large volume change during cycling in traditional solid-solid conversion cathodes, and achieves excellent cycle stability by realizing the self-healing characteristics of the cathode structure.

[0043] On the one hand, the liquid-solid conversion reaction exhibits fast-charging characteristics. During charging, low-valence metal ions in the solution phase exhibit rapid ion diffusion and reaction kinetics in the molten salt electrolyte, leading to deposition reactions on the highly conductive current collector surface. On the other hand, the liquid-solid conversion reaction possesses structural self-healing properties. During battery charging and discharging, a reversible transformation occurs between low-valence metal ions in the solution phase and slightly soluble high-valence metal halides, resulting in deposition and stripping reactions on the current collector surface, thus achieving self-repair of the current collector structure.

[0044] Specifically, compared to traditional solid-solid conversion cathode systems, this invention, based on innovative electrode reaction mechanisms, designs a series of novel liquid-solid conversion cathode systems by screening redox couples and optimizing the composition of the molten salt. In aluminate molten salt electrolytes, reduced low-valence metal ions have high solubility and do not spontaneously react with the aluminum metal anode, enabling high capacity aluminum batteries. During charging, low-valence metal ions in the solution phase exhibit rapid ion diffusion and reaction kinetics in the molten salt electrolyte, undergoing deposition reactions on the highly conductive current collector surface to form slightly soluble high-valence metal halides. From the perspective of chemical reaction mechanisms, liquid-solid conversion reactions can support ultra-fast charging processes. Therefore, the novel cathode with liquid-solid conversion reactions provided by this invention possesses both high diffusion kinetics and ultra-fast charging kinetics.

[0045] In publicly available conversion-type aluminum battery systems, the solid-solid conversion reaction at the positive electrode involves significant volume changes, leading to electrode structure degradation and limited mass transfer / conductivity, resulting in severe capacity decay. This invention, however, is based on a liquid-solid conversion reaction. During charging, low-valence metal ions in the solution phase deposit on the surface of a highly conductive current collector, forming a slightly soluble high-valence metal halide coating without altering the original main structure. During discharge, the slightly soluble high-valence metal halide transforms into soluble low-valence metal ions, exhibiting structural self-healing properties. Therefore, the entire liquid-solid conversion reaction fundamentally avoids the volume changes caused by the conversion reaction at the electrode, while also possessing unique structural self-healing characteristics, enabling long-term cycle stability of the aluminum battery.

[0046] In a preferred embodiment, the conversion cathode material has a certain solubility in the electrolyte during charging and discharging, wherein the solubility is 0.05 to 10 g / mL.

[0047] To further improve the fast-charging performance and cycle stability of the conversion cathode material, the types of metal compounds were optimized. In a preferred embodiment, the indium-containing compound includes at least one of indium chloride, indium bromide, indium iodide, indium oxide, indium sulfide, and indium selenide.

[0048] In a preferred embodiment, the chromium-containing compound includes at least one of chromium chloride, chromium bromide, chromium iodide, chromium sulfide, and chromium oxide.

[0049] In a preferred embodiment, the vanadium-containing compound includes at least one selected from vanadium chloride, vanadium bromide, vanadium iodide, vanadium sulfide, and vanadium oxide.

[0050] In a preferred embodiment, the indium-containing compound includes at least one of InCl, InBr, InCl3, InBr3, InI, InI3, In2O3, In2S3, and In2Se3.

[0051] In a preferred embodiment, the chromium-containing compound includes at least one of CrCl2, CrCl3, CrCl4, CrBr2, CrBr3, CrBr4, CrI2, CrI3, CrI4, CrI2, Cr2O3, and Cr2S3.

[0052] In a preferred embodiment, the vanadium-containing compound includes at least one of VCl2, VCl3, VCl4, VBr2, VBr3, VBr4, VI2, VI3, VI4, VI2, V2O3, and V2S3.

[0053] To improve the electrochemical performance of aluminum batteries made from the aforementioned conversion cathode material, the electrolyte in the aluminum batteries made from the aforementioned conversion cathode material was optimized. In a preferred embodiment, the electrolyte includes a molten salt electrolyte; the molten salt electrolyte includes electrolytes with the general formula A. a AlX b The molten salt, wherein A includes at least one of Li, Na, K, Rb, Cs, Ca and Mg; X includes at least one of F, Cl, Br and I; 0.25≤a≤0.8, 3.25≤b≤3.8.

[0054] Secondly, the present invention provides an aluminum battery cathode, comprising the aforementioned conversion cathode material for aluminum batteries.

[0055] The positive electrode of this aluminum battery exhibits excellent electrochemical performance, especially fast charging characteristics and excellent cycle stability.

[0056] Thirdly, the present invention provides a secondary aluminum battery, which includes a negative electrode, an electrolyte, a separator, and the aforementioned aluminum battery positive electrode.

[0057] Based on the above-mentioned liquid-solid conversion reaction mechanism, this invention constructs a secondary aluminum battery with fast charging characteristics and excellent cycle stability.

[0058] In a preferred embodiment, the electrolyte of the secondary aluminum battery comprises a molten salt electrolyte.

[0059] Existing aluminum batteries based on chloride ionic liquids face high dissociation barriers and relatively slow diffusion kinetics, limiting their reaction kinetics. The inorganic molten salt electrolyte provided by this invention not only meets the solubility requirements of the liquid-solid conversion reaction (high solubility for low-valence metal ions and extremely low solubility for high-valence metal halides), enabling aluminum batteries based on liquid-solid conversion cathodes to exhibit higher reversible capacity and higher coulombic efficiency, but also provides low dissociation energy and high diffusion kinetics, effectively supporting the rapid reaction kinetics of aluminum batteries, combining low temperature, rapid reaction kinetics, and high safety. During the electrochemical reaction of the liquid-solid conversion cathode, the solubility of the liquid phase in the electrolyte determines the overall capacity and fast-charging characteristics of the battery. Even if low-valence metal compounds have poor solubility in the electrolyte, their active components simultaneously promote dissolution in the molten salt electrolyte as the liquid-solid conversion reaction occurs during charging, achieving high battery capacity. Compared to traditional ionic liquid electrolytes, inorganic molten salt electrolytes have higher solubility for low-valence metal ions and extremely low solubility for high-valence metal halides, enabling aluminum batteries based on liquid-solid conversion cathodes to exhibit higher reversible capacity and higher coulombic efficiency.

[0060] In a preferred embodiment, the molten salt electrolyte comprises a general formula A a AlX b A molten salt, wherein A includes at least one of Li, Na, K, Rb, Cs, Ca, and Mg; X includes at least one of F, Cl, Br, and I; 0.25 ≤ a ≤ 0.8, 3.25 ≤ b ≤ 3.8. The molten salt electrolyte is acidic.

[0061] The above general formula A a AlX b In this context, a includes, but is not limited to, point values ​​of any one of 0.3, 0.4, 0.5, 0.6, and 0.7, or a range of values ​​between any two; b includes, but is not limited to, point values ​​of any one of 3.3, 3.4, 3.5, 3.6, and 3.7, or a range of values ​​between any two.

[0062] This invention controls the chemical composition of a molten salt electrolyte, resulting in advantages such as high solubility, non-flammability, high safety, low cost, and high reaction kinetics. On one hand, this inorganic acidic molten salt electrolyte meets the solubility requirements of liquid-solid conversion reactions, meaning low-valence metal ions exhibit high solubility, while high-valence metal halides exhibit slight solubility. On the other hand, compared to traditional organic ionic liquids, the inorganic molten salt lowers the bond-breaking energy barrier of the aluminum-halogen covalent bond, improves desolvation capability, and achieves rapid reaction kinetics.

[0063] Specifically, in the above-mentioned molten salt electrolyte, ions can move freely at lower temperatures, the bond-breaking energy barrier of aluminum-halogen covalent bonds is low, and it has a high desolvation capability, thus enabling the molten salt to still have rapid reaction kinetics at lower operating temperatures.

[0064] In a preferred embodiment, the method for preparing the molten salt electrolyte includes: mixing aluminum halide and a halide containing element A and heating to obtain the molten salt electrolyte. The heating temperature is 80–200°C, including but not limited to any one of 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, and 190°C, or a range between any two.

[0065] The raw materials for preparing the above-mentioned molten salt electrolyte are low-cost alkali metal halides and aluminum halides. Therefore, the material cost of the molten salt aluminum battery made from them is relatively low.

[0066] In a preferred embodiment, the negative electrode comprises metallic aluminum and / or an aluminum alloy. Aluminum is abundant and inexpensive, further reducing the cost of molten salt aluminum batteries.

[0067] In a preferred embodiment, the operating temperature of the secondary aluminum battery is ≤300℃; including but not limited to any one of 280℃, 260℃, 250℃, 230℃, 210℃, 200℃, 180℃, 160℃, 150℃, 130℃, 110℃, 100℃, 90℃, 80℃, and 60℃, or a range between any two.

[0068] In a preferred embodiment, the operating temperature of the secondary aluminum battery is 90 to 200°C, including but not limited to any one of 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, and 190°C, or a range between any two.

[0069] Fourthly, the present invention provides a method for preparing the aforementioned secondary aluminum battery, comprising the following steps:

[0070] A conversion-type positive electrode material, a positive electrode current collector, a negative electrode, and a separator are obtained, and the conversion-type positive electrode material is dispersed in an electrolyte to form a positive electrode, which is then assembled.

[0071] And / or, obtain an active material containing a conversion-type positive electrode material, and mix the active material, conductive agent and binder and coat it on the surface of the current collector to obtain a positive electrode, which is then assembled with a negative electrode, a separator and an electrolyte.

[0072] This method can produce secondary aluminum batteries with unique rapid kinetics and structural self-healing properties based on a liquid-solid conversion reaction cathode. Furthermore, this method offers advantages such as simple operation, mild conditions, short process flow, and suitability for mass production.

[0073] Fifthly, the present invention provides an electrical device including the aforementioned secondary aluminum battery.

[0074] Among them, electrical equipment includes large-scale independent energy storage power stations, distributed renewable energy grid connection, park and home energy storage systems, electric vehicles, etc., but is not limited to these.

[0075] The aforementioned secondary aluminum battery system has advantages such as non-flammability, high safety, excellent electrical performance, and low cost, and therefore has broad application prospects in fields such as smart grid peak shaving, solar power plants, wind power plants, distributed power plants, backup power, smart microgrids, and communication base stations.

[0076] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0077] The electrical performance of the secondary aluminum batteries prepared in the following embodiments and comparative examples of the present invention is tested at a temperature of 150°C.

[0078] Example 1

[0079] The preparation method of the molten salt electrolyte provided in this embodiment includes the following steps: Under inert gas protection, AlCl3, NaCl, and KCl are weighed according to a molar ratio of 61:26:13, added to a container and sealed. The container is then transferred to an oven and kept at 150°C for 24 hours to allow the components to mix evenly and liquefy completely. After cooling, the mixture is ground into powder to obtain the molten salt electrolyte. The molecular formula of this molten salt electrolyte is Na... 0.43 K 0.21 AlCl 3.64 (Approximately obtained by taking two significant figures; the same applies to the following examples). The melting point of this molten salt electrolyte is 95°C.

[0080] The conversion cathode material provided in this embodiment is InCl. At 95°C, the solubility of InCl in the electrolyte is 0.05 g / mL; at 125°C, the solubility of InCl in the electrolyte is 1.0 g / mL.

[0081] The secondary molten salt aluminum battery provided in this embodiment has a Swagelok-type sealed structure. Designed according to the battery model, the separator, positive electrode, and negative electrode are cut and prepared. The preparation method includes the following steps: In an argon-protected glove box, activated carbon cloth is used as the positive electrode current collector, aluminum sheet as the negative electrode, the aforementioned molten salt electrolyte is used as the electrolyte, glass fiber is used as the separator, and InCl powder is weighed and directly added to the molten salt electrolyte. The resulting InCl areal loading is 3 mg / cm³. 2 Here, the surface load refers to the ratio of the total mass of InCl to the geometric area of ​​the activated carbon cloth.

[0082] like Figure 1 The figure shows the rate test cycle diagram of the secondary molten salt aluminum battery prepared in this embodiment. From... Figure 1 As can be seen, the secondary molten aluminum salt battery prepared in Example 1 exhibits excellent capacities of 327 mAh / g, 319 mAh / g, 244 mAh / g, and 179 mAh / g at 1C, 2C, 5C, and 10C, respectively. Notably, it achieves capacities of 134 mAh / g and 100 mAh / g at ultra-fast charging rates of 20C and 50C, respectively. After 75 cycles, it still retains 251 mAh / g at a 5C charging rate, demonstrating excellent cycle stability. At a high charging current density of 20C, the molten aluminum salt battery retains 98% of its capacity after 500 cycles.

[0083] like Figure 2 The figure shows the voltage curves of the secondary molten salt aluminum battery prepared in this embodiment under different current densities. From... Figure 2 As can be seen, the charge-discharge curves show a clear voltage plateau and low overpotential (the overpotential is half the difference between the average charging and discharging voltages), which is beneficial for the high energy efficiency (EE) of energy storage device applications (e.g., 0.11V overpotential and 83% EE at 10C).

[0084] Example 2

[0085] The conversion-type cathode material provided in this embodiment is InCl. InCl is prepared using indium foil as a raw material.

[0086] The secondary molten salt aluminum battery provided in this embodiment has a Swagelok-type sealed structure. The separator, positive electrode, and negative electrode are cut according to the battery model design. The preparation method includes the following steps: In an argon-protected glove box, activated carbon cloth is used as the positive electrode current collector, aluminum sheet as the negative electrode, the molten salt electrolyte obtained in Example 1 is used as the electrolyte, and glass fiber is used as the separator. Considering that metallic In reacts chemically with the molten salt electrolyte to form metallic Al and InCl, during battery assembly, In foil is placed between the separator and the aluminum negative electrode to provide sufficient InCl active components.

[0087] like Figure 3 The figure shows the rate test cycle diagram of the secondary molten salt aluminum battery prepared in this embodiment. From... Figure 3 It can be seen that when at 2mA / cm 2 At a current density of 5 mA / cm², the battery exhibits a small overpotential (0.11 V) and a coulombic efficiency (CE) of approximately 98.6%. 2 10mA / cm 2 and 20mA / cm 2 At higher charging rates, the average discharge specific capacity of the battery is 1.25 mAh / cm³. 2 0.92mAh / cm 2 and 0.76mAh / cm 2 At 10mA / cm 2 At high charging current density, molten salt aluminum batteries retain 98% of their capacity after 500 cycles.

[0088] like Figure 4 The figure shows the voltage curves of the secondary molten salt aluminum battery prepared in this embodiment under different current densities. From... Figure 4 It can be seen that at each charging rate (up to 20mA / cm) 2 They maintained good platform behavior throughout.

[0089] Furthermore, the electrical performance test results of Examples 1 and 2 show that the molten salt aluminum battery based on the liquid-solid conversion cathode provided by this invention exhibits excellent cycle stability, high specific capacity, good fast-charge rate performance, and low overpotential. This demonstrates that, compared to the traditional solid-solid conversion reaction, the novel liquid-solid conversion reaction mechanism provided by this invention has significant advantages, possessing the following characteristics: First, the liquid-solid conversion reaction exhibits fast-charging characteristics. During charging, low-valence metal ions in the solution phase exhibit rapid ion diffusion and reaction kinetics in the molten salt electrolyte, undergoing deposition reactions on the highly conductive current collector surface, thus achieving the battery's fast-charge rate characteristics and low overpotential. Second, the liquid-solid conversion reaction possesses structural self-healing characteristics. During battery charging and discharging, a reversible transformation occurs between low-valence metal ions in the solution phase and slightly soluble high-valence metal halides, resulting in reversible deposition and stripping reactions on the current collector surface, while maintaining the stability and self-healing characteristics of the main structure, achieving long-term cycle stability of the battery. Therefore, the results of the above examples demonstrate the enormous application potential of the liquid-solid conversion reaction mechanism in aluminum batteries.

[0090] Example 3

[0091] The secondary molten salt aluminum battery provided in this embodiment is basically the same as that in Embodiment 1, except that a carbon nanotube film is used as the positive electrode current collector.

[0092] like Figure 5 The figure shown is a constant current charge-discharge test voltage curve of the secondary molten salt aluminum battery prepared in this embodiment. From... Figure 5 It can be seen that using carbon nanotube films with high surface area as current collectors can achieve a current collector density of approximately 9.2 mAh / cm². 2 The high areal capacity and high CE (energy efficiency) of over 96% further demonstrate the practicality of the conversion cathode material provided by this invention. Furthermore, the resulting secondary molten salt aluminum battery exhibits ultra-low overpotential and good single-plateau reaction, resulting in a relatively high energy efficiency (greater than 90%). At 5 mA / cm²... 2 At high charging current density, molten salt aluminum batteries retain 98% of their capacity after 500 cycles.

[0093] Comparing the electrical performance test results of Example 2 and Example 3, it can be seen that Example 3 has approximately 9.2 mAh / cm³. 2 It exhibits a high areal specific capacity and a high coulombic efficiency of over 96%, exceeding the areal specific capacity of Example 2 (approximately 2 mAh / cm²). 2The high areal specific capacity in Example 3 is attributed to the high specific surface area of ​​the carbon nanotube film used as the positive electrode current collector. From the perspective of chemical reaction mechanism, during battery charging and discharging, a reversible transition occurs between low-valence metal ions in the solution phase and slightly soluble high-valence metal halides, resulting in reversible deposition and stripping reactions on the current collector surface. The high specific surface area of ​​the current collector provides more deposition sites, allowing more active components to participate in the reaction, thereby achieving a high specific capacity. This example provides insights into the application of liquid-solid conversion positive electrodes.

[0094] Example 4

[0095] The secondary molten salt aluminum battery provided in this embodiment has a Swagelok-type sealed structure. Based on the battery model, the separator, positive electrode, and negative electrode are cut and prepared. The preparation method includes the following steps:

[0096] (1) Preparation of carbon-supported In2O3 nanorods (i.e., obtaining active materials containing conversion-type cathode materials): Indium nitrate pentahydrate and 2-aminoterephthalic acid were added to N,N-dimethylformamide solvent at a molar ratio of 1:2 and stirred thoroughly to dissolve. The solution was then transferred to a reaction vessel and kept at 125°C for 5 hours to obtain a yellow powder, which is an indium-based MOF nanorod. The indium-based MOF nanorod was then kept at 480°C under an inert atmosphere for 3 hours to obtain carbon-supported In2O3 nanorods.

[0097] (2) Preparation of the positive electrode: The carbon-supported In2O3 nanorods obtained in step (1), Super P carbon black conductive agent, and polytetrafluoroethylene binder were mixed at a mass ratio of 8:1:1 using a slurry coating method. Isopropanol was used as a solvent to prepare the slurry, which was then coated onto the surface of a molybdenum foil current collector and dried in an oven at 90°C to obtain the positive electrode. The surface loading of In2O3 in the obtained positive electrode was 3 mg / cm³. 2 .

[0098] (3) Assembly: The positive electrode obtained in step (2) is used, with aluminum sheet as negative electrode, molten salt obtained in Example 1 as electrolyte, and glass fiber as diaphragm for assembly.

[0099] At 95℃, the solubility of In2O3 in this electrolyte is 0.1 g / mL; at 125℃, the solubility of In2O3 in this electrolyte is 1.5 g / mL.

[0100] like Figure 6 The figure shows the rate test cycle diagram of the secondary molten salt aluminum battery prepared in this embodiment. From... Figure 6As can be seen, the battery exhibits excellent capacities of 341 mAh / g, 301 mAh / g, 255 mAh / g, 189 mAh / g, 139 mAh / g, 115 mAh / g, and 89 mAh / g at 0.2 A / g, 0.3 A / g, 0.5 A / g, 1 A / g, 2 A / g, 5 A / g, and 10 A / g, respectively. At a charging current density of 6 A / g, the molten salt aluminum battery retains a capacity of 101 mAh / g and a capacity retention rate as high as 99% after 500 cycles. Notably, when the current density returns to 0.5 A / g, the battery still maintains high capacity retention, demonstrating excellent cycle stability.

[0101] like Figure 7 The figure shows the voltage curves of the secondary molten salt aluminum battery prepared in this embodiment under different current densities. From... Figure 7 As can be seen, the charge-discharge curves show a clear single voltage plateau and low overpotential, which is beneficial for the high energy efficiency of energy storage device applications.

[0102] The superior electrochemistry of Example 4 is attributed to its carbon-supported In₂O₃ nanorods, whose carbon framework structure provides excellent electronic conductivity, abundant deposition sites, and a stable host structure. Therefore, this example further demonstrates the universality of the liquid-solid conversion reaction proposed in this invention, and its applicability to a variety of material systems.

[0103] Example 5

[0104] The preparation method of the molten salt electrolyte provided in this embodiment includes the following steps: Under inert gas protection, AlCl3, NaCl, KCl, and KBr are weighed according to a molar ratio of 61:26:8:5, added to a container and sealed. The container is then transferred to an oven and kept at 150°C for 24 hours to allow the components to mix evenly and liquefy completely. After cooling, the mixture is ground into powder to obtain the molten salt electrolyte. The molecular formula of this molten salt electrolyte is Na... 0.43 K 0.21 AlCl 3.56 Br 0.08 The melting point of this molten salt electrolyte is 90°C.

[0105] The secondary molten salt aluminum battery provided in this embodiment uses the molten salt electrolyte prepared above, and the positive electrode material and battery preparation method used are exactly the same as those in Example 1.

[0106] The liquid-solid conversion cathode material provided in this embodiment is InCl. At 95°C, the solubility of InCl in the electrolyte is 0.08 g / mL; at 125°C, the solubility of InCl in the electrolyte is 2.1 g / mL.

[0107] The molten aluminum salt battery prepared in this embodiment was subjected to rate testing. The battery exhibited high capacities of 339 mAh / g, 311 mAh / g, 267 mAh / g, 192 mAh / g, 147 mAh / g, 134 mAh / g, and 112 mAh / g at 0.2 A / g, 0.3 A / g, 0.5 A / g, 1 A / g, 2 A / g, 5 A / g, and 10 A / g, respectively. Furthermore, it maintained a high capacity retention rate at the high rate of 10 A / g (approximately 33% capacity retention compared to the capacity at the low current density of 0.2 A / g), demonstrating excellent rate performance. At a high charging current density of 2 A / g, the molten aluminum salt battery retained 98% of its capacity after 500 cycles.

[0108] Compared to Example 4, the molten salt aluminum battery prepared in Example 5 exhibits higher specific capacity and superior rate performance under similar loading and current density conditions. This demonstrates that introducing other halide ions (such as Br₂) into the low-temperature molten salt electrolyte system... - On the one hand, by participating in the conversion reaction process of the positive electrode, it enhances the conversion reaction kinetics of the positive electrode, reduces the battery overpotential, and improves rate performance. On the other hand, by adjusting the cluster structure of the molten salt electrolyte, it reduces the symmetry of the cluster structure, which in turn facilitates the desolvation process of aluminum and achieves a rapid mass transfer process. This also proves that the composition of the molten salt electrolyte plays a key role in battery performance.

[0109] Example 6

[0110] The conversion cathode material provided in this embodiment is CrCl2.

[0111] The preparation method of the secondary molten salt aluminum battery provided in this embodiment is basically the same as that in Example 1, except that InCl powder is replaced with CrCl2 powder, and the resulting CrCl2 areal loading is 2 mg / cm³. 2 At 95℃, the solubility of CrCl2 in this electrolyte is 0.25 g / mL; at 125℃, the solubility of InCl in this electrolyte is 3.4 g / mL.

[0112] like Figure 8 The figure shown is a constant current charge-discharge test voltage curve of the secondary molten salt aluminum battery prepared in this embodiment. From... Figure 8It can be seen that using CrCl2 powder as the positive electrode active component, the secondary molten salt aluminum battery can achieve a reversible capacity of approximately 58 mAh / g, a defined voltage plateau of approximately 0.9 V, and a CE of up to 92%. The reaction process of the molten salt battery in Example 6 involves the reversible conversion of CrCl2 and CrCl3. At a high charging current density of 1 A / g, the molten salt aluminum battery exhibits a 95% capacity retention after 500 cycles. This further demonstrates the universality of the conversion-type positive electrode material proposed in this invention.

[0113] Example 7

[0114] The liquid-solid conversion cathode material provided in this embodiment is VCl3.

[0115] The electrolyte and battery preparation method used in this embodiment of the secondary molten salt aluminum battery are basically the same as those in Example 1, except that InCl powder is replaced with VCl3 powder, and the resulting VCl3 areal loading is 3.0 mg / cm³. 2 At 95℃, the solubility of VCl3 in this electrolyte is 0.35 g / mL; at 125℃, the solubility of InCl in this electrolyte is 2.4 g / mL.

[0116] Constant current charge-discharge tests were conducted on the secondary molten aluminum salt battery prepared in this embodiment. Using VCl3 powder as the positive electrode active component, the secondary molten aluminum salt battery exhibited a reversible capacity of 210 mAh / g, and maintained 96% capacity retention after 500 cycles at a high charging current density of 5C.

[0117] Example 8

[0118] The liquid-solid conversion cathode materials provided in this embodiment are InCl and CrCl2.

[0119] The preparation method of the secondary molten salt aluminum battery provided in this embodiment is basically the same as that in Example 1, except that the InCl powder is replaced with InCl powder and CrCl2 powder in a mass ratio of 1:1, and the total areal loading of InCl powder and CrCl2 powder is 3.0 mg / cm³. 2 .

[0120] The rechargeable molten aluminum salt battery prepared in this embodiment underwent constant current charge-discharge testing. Using InCl and CrCl2 powders as the positive electrode active components, the rechargeable molten aluminum salt battery exhibited a reversible capacity of 245 mAh / g. At a high charging current density of 10C, the molten aluminum salt battery retained 95% of its capacity after 500 cycles. In this embodiment, the specific capacity was calculated by the sum of the weights of the InCl and CrCl2 powders.

[0121] Comparative Example 1

[0122] The preparation method of the ionic liquid electrolyte provided in this comparative example includes the following steps: In an argon glove box, AlCl3 and 1-methyl-3-ethylimidazole chloride are weighed in a molar ratio of 1.3:1. AlCl3 is slowly added to 1-methyl-3-ethylimidazole chloride at room temperature, and the mixture is stirred to completely mix and liquefy the components to obtain the ionic liquid electrolyte.

[0123] The preparation method of the secondary aluminum battery for ionic liquid provided in this comparative example is basically the same as that in Example 2, except that the ionic liquid electrolyte prepared above is used as the electrolyte. The test temperature of this secondary aluminum battery is 150°C.

[0124] like Figure 9 The figure shows the constant current charge-discharge test cycle diagram of the secondary aluminum battery prepared in this comparative example. From Figure 9 It can be seen that the ion liquid aluminum battery in Comparative Example 1 operates at 1 mA / cm². 2 At a current density of only about 0.09 mAh / cm³ and an operating temperature of 150°C, it showed a current density of only about 0.09 mAh / cm³. 2 Extremely low capacity and less than 50% CE. At 5 mA / cm 2 At high charging current density, the ionic liquid aluminum battery retains 78% of its capacity after 500 cycles.

[0125] By comparing the electrical performance results of Comparative Example 1 and Example 2, it can be found that, compared with Comparative Example 1, the molten salt aluminum battery prepared in Example 2 has a higher areal specific capacity (approximately 2 mAh / cm²) under similar load and test conditions. 2 The area specific capacity of Comparative Example 1 is approximately 0.09 mAh / cm². 2 The aluminum battery exhibits higher capacity and coulombic efficiency (approximately 98% coulombic efficiency in Example 2, compared to approximately 49% in Comparative Example 1). For the ionic liquid aluminum battery (Comparative Example 1), the extremely low capacity is attributed to the formation of negligible soluble InCl in the electrolyte, with an indium concentration of only 0.17%. The low coulombic efficiency can be attributed to the solubility of the generated InCl3 in the ionic liquid, leading to a severe shuttle effect during charging. This significant difference confirms the unique physicochemical properties of indium chemistry in inorganic molten salt electrolytes. On one hand, compared to ionic liquids, inorganic molten salt electrolytes possess low dissociation energies and high diffusion kinetics, effectively supporting the rapid reaction kinetics of aluminum batteries. On the other hand, molten salt electrolytes have higher solubility for low-valence metal ions and extremely low solubility for high-valence metal halides, resulting in higher reversible capacity and higher coulombic efficiency for aluminum batteries based on liquid-solid conversion cathodes. Therefore, these results demonstrate that both liquid-solid conversion cathodes and molten salt electrolytes are crucial for achieving high-performance aluminum batteries.

[0126] Comparative Example 2

[0127] The preparation method of the secondary molten salt aluminum battery provided in this comparative example is basically the same as that in Example 1, except that the InCl powder is replaced with SnCl2 powder, and the areal loading of SnCl2 powder is 3.0 mg / cm³. 2 .

[0128] Constant current charge-discharge tests were performed on the secondary molten salt aluminum battery prepared in this comparative example. SnCl2 powder was used as the positive electrode active component, and the secondary battery achieved a constant current charge-discharge rate of 1 mA / cm². 2 At a current density of only about 0.129 mAh / cm³ and an operating temperature of 150°C, it showed a current density of only about 0.129 mAh / cm³. 2 Extremely low capacity. At 5mA / cm 2 At high charging current densities, the aluminum battery retained only 2% of its capacity after 500 cycles. This is attributed to the fact that SnCl2 does not dissolve in the electrolyte and is easily reduced by Al metal to rapidly form solid Sn, which punctures the separator and leads to battery instability. Compared to Examples 1-8, the SnCl2 selected in this comparative example cannot achieve the liquid-solid conversion reaction of the battery because it has no solubility and undergoes a spontaneous reduction reaction with Al metal. Therefore, the chemical stability between the selected metal ions and Al metal is also crucial for constructing a new liquid-solid conversion system.

[0129] Experimental Example 1

[0130] The capacity retention rate of the secondary aluminum batteries prepared in the above embodiments and comparative examples was tested after 500 cycles at high charging current density. The test results are shown in Table 1.

[0131] Table 1. Test results of capacity retention of secondary aluminum batteries in the examples and comparative examples.

[0132] Example 1 <![CDATA[InCl、Na 0.43 K 0.21 AlCl 3.64 ]]> 20C、98％ Example 2 <![CDATA[InCl、Na 0.43 K 0.21 AlCl 3.64 ]]> <![CDATA[10mA / cm 2 、97%]]> Example 3 <![CDATA[InCl、Na 0.43 K 0.21 AlCl 3.64 ]]> <![CDATA[5mA / cm 2 、98%]]> Example 4 <![CDATA[In2O3、Na 0.43 K 0.21 AlCl 3.64 ]]> 6A / g, 99% Example 5 <![CDATA[InCl、Na 0.43 K 0.21 AlCl 3.56 Br 0.08 ]]> 2A / g, 98% Example 6 <![CDATA[CrCl2、Na 0.43 K 0.21 AlCl 3.64 ]]> 1A / g, 95% Example 7 <![CDATA[VCl3、Na 0.43 K 0.21 AlCl 3.64 ]]> 5C、96％ Example 8 <![CDATA[InCl and CrCl2, Na 0.43 K 0.21 AlCl 3.64 > 10C、95％ Comparative Example 1 InCl, ionic liquids <![CDATA[5mA / cm 2 、78%]]> Comparative Example 2 <![CDATA[SnCl2、Na 0.43 K 0.21 AlCl 3.64 ]]> <![CDATA[5mA / cm 2 、2%]]>

[0133] As can be seen from Table 1, the secondary aluminum batteries prepared in each embodiment showed almost no capacity decay after 500 cycles at a high charging current density of 20C, indicating that the secondary aluminum batteries prepared in each embodiment have very stable cycle performance.

[0134] In contrast, Comparative Example 1 suffers from low capacity, low coulombic efficiency, and poor cycle stability of the ionic liquid secondary battery due to the low solubility of InCl in the ionic liquid, severe shuttle effect, and poor high-temperature stability of the ionic liquid.

[0135] Comparative Example 2: Due to the extremely low solubility of the dissolved active SnCl2, it exists in a solid state, and Sn... 2+ It undergoes a spontaneous reduction reaction with the aluminum anode, leading to battery instability and extremely poor cycle stability.

[0136] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can 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 therein, without departing from the spirit and scope of the present invention; 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; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A conversion-type cathode material for aluminum batteries, characterized in that, The conversion-type cathode material includes at least one of indium-containing compounds, chromium-containing compounds, and vanadium-containing compounds; The conversion cathode material undergoes a liquid-to-solid phase transformation reaction during charging and discharging: during discharge, the conversion cathode material is a dissolved low-valence metal ion, present as a liquid phase; during charging, the conversion cathode material is a slightly soluble high-valence metal halide, present as a solid phase. The indium-containing compound includes at least one of InCl, InBr, InCl3, InBr3, InI, InI3, In2O3, In2S3, and In2Se3; The chromium-containing compound includes at least one of CrCl2, CrCl3, CrCl4, CrBr2, CrBr3, CrBr4, CrI2, CrI3, CrI4, CrI2, Cr2O3, and Cr2S3; The vanadium-containing compound includes at least one of VCl2, VCl3, VCl4, VBr2, VBr3, VBr4, VI2, VI3, VI4, VI2, V2O3, and V2S3.

2. The positive electrode of an aluminum battery, characterized in that, Includes the conversion cathode material for aluminum batteries as described in claim 1.

3. A secondary aluminum battery, characterized in that, It includes a negative electrode, an electrolyte, a separator, and an aluminum battery positive electrode as described in claim 2.

4. The secondary aluminum battery according to claim 3, characterized in that, The electrolyte in the secondary aluminum battery includes a molten salt electrolyte.

5. The secondary aluminum battery according to claim 4, characterized in that, The molten salt electrolyte includes those with the general formula A. a AlX b The molten salt, wherein A includes at least one of Li, Na, K, Rb, Cs, Ca and Mg; X includes at least one of F, Cl, Br and I; 0.25≤a≤0.8, 3.25≤b≤3.

8.

6. The secondary aluminum battery according to claim 3, characterized in that, The operating temperature of the secondary aluminum battery is ≤300℃.

7. The secondary aluminum battery according to claim 3, characterized in that, The operating temperature of the secondary aluminum battery is 90~200℃.

8. The method for preparing a secondary aluminum battery according to any one of claims 3 to 7, characterized in that, Includes the following steps: A conversion-type positive electrode material, a positive electrode current collector, a negative electrode, and a separator are obtained, and the conversion-type positive electrode material is dispersed in an electrolyte to form a positive electrode, which is then assembled. And / or, obtain an active material containing a conversion-type positive electrode material, and mix the active material, conductive agent and binder and coat it on the surface of the current collector to obtain a positive electrode, and then assemble it.

9. Electrical equipment, characterized in that, Including the secondary aluminum battery as described in any one of claims 3 to 7.

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