Negative electrode comprising tin and aluminum

Abstract

The present invention relates to an electrochemical cell comprising a negative electrode comprising tin (Sn) and aluminum (Al), a positive electrode, and an electrolyte. The invention also relates to a method for producing a negative electrode comprising tin and aluminum for an electrochemical cell.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to an anode comprising tin and aluminum, and more particularly to an electrochemical cell comprising such an anode. The present disclosure also relates to a method of manufacturing such an anode. BACKGROUND

[0002] Lithium-ion batteries have been widely used in various applications due to their high energy density and cycling stability. However, the limited availability of lithium resources and safety concerns have prompted researchers to seek alternative energy storage devices. Among them, aqueous aluminum metal batteries (AAMBs) have attracted much attention due to the excellent properties of aluminum (Al). First, Al is the most abundant metal element in the earth's crust, making it more sustainable than other metals. Second, Al is less chemically reactive than lithium or sodium, thereby enhancing the safety of AAMBs, especially when using aqueous electrolytes. Third, since Al ions can transfer three electrons in a redox reaction, AAMBs offer one of the highest theoretical energy densities. In addition, Al benefits from a well-established manufacturing industry, making it possible to reduce costs, which is essential for practical applications.

[0003] However, AAMBs face challenges due to the relatively negative reduction potential of Al (-1.66 V). This property leads to the hydrogen evolution reaction (HER) on the negative side of the battery during charging, significantly hindering the reversibility of the Al anode. In addition, the spontaneous formation of an oxidation / passivation layer on the Al surface hinders charge transfer kinetics and increases the internal resistance of the battery. These factors collectively reduce the coulombic efficiency and lifetime of AAMBs, making their overall performance far from satisfactory.

[0004] Anode engineering is an effective strategy to improve the performance of AAMBs. In this regard, various practices have been reported. One approach involves applying an artificial solid electrolyte interface (SEI) on the surface of the Al electrode. However, the SEI layer can dissolve during cycling, leading to its failure. Another technique is to combine Al with other metals. Aluminum-zinc (Zn) alloy anodes can be prepared by depositing Al on a Zn foil in an Al(OTF)3 electrolyte or depositing Zn on an Al foil in an Al(OTF)3+HOTF+Zn(OTF)2 mixed electrolyte. However, it must be noted that Zn 2+Also having energy storage activity are multivalent metal ions, thus making such batteries more accurately described as hybrid batteries. Copper (Cu) and cerium (Ce) were also chosen to make Al-Cu and Al-Ce eutectic alloys, which consist of alternating a-Al and intermetallic lamellar structures. These lamellar structures can act as electron transfer pathways and guide Al deposition. The use of such eutectic alloys can enhance the reversibility of Al deposition. However, the fabrication process involves energy-consuming arc melting. Another approach includes the use of a negative electrode comprising amorphous Al. Amorphous Al has a lower Al deposition nucleation barrier, enabling fast interfacial ion transfer kinetics, thus suppressing HER and promoting Al deposition. However, the fabrication process of this approach involves alloying and dealloying with lithium, which is against the concept of "beyond lithium" batteries. Furthermore, the fabrication process is relatively complex and time-consuming, hindering the scalability of practical applications.

[0005] Therefore, it is necessary to provide an electrochemical battery that overcomes or at least ameliorates one or more of the above-mentioned disadvantages. SUMMARY In an aspect of the present disclosure, an electrochemical battery is provided, comprising: a negative electrode comprising tin (Sn) and aluminum (Al); a positive electrode; and an electrolyte.

[0007] In another aspect of the present disclosure, a method for preparing a negative electrode comprising tin and aluminum for an electrochemical battery is provided, the method comprising: (a) layering Sn foil and Al foil; (b) folding the layered foils; and (c) applying pressure to compress the folded layered foils, wherein the thickness of the compressed folded layered foils in step (c) is less than the thickness of the folded layered foils in step (b).

[0008] Advantageously, the electrochemical battery disclosed herein can exhibit high voltage plateau, high coulombic efficiency, and high capacity while maintaining high capacity retention and stable cycling.

[0009] More advantageously, the negative electrode comprising Sn and Al exhibits excellent Al stripping and plating performance. The inventors surprisingly found that, during the stripping process, the Al matrix can serve as an abundant source of Al ions; while during the plating process, the Sn backbone can provide a large number of active sites for the underpotential deposition (UPD) of Al.

[0010] In embodiments, the negative electrode comprises a Sn-Al composite material, which is a laminated metal composite material. The spaces and gaps between the layers of the laminated metal composite material can advantageously increase the specific surface area of the electrode and enhance ion transport.

[0011] In another embodiment, the negative electrode comprises a polymer disposed on at least a portion of the negative electrode surface. The polymer can advantageously enhance the corrosion resistance of the negative electrode. The inventors also unexpectedly discovered that placing the polymer on the negative electrode can inhibit Al passivation while still promoting Al stripping and electroplating.

[0012] Even more advantageously, the disclosed method provides a low-cost and simple way to manufacture such anodes, while the manufactured anodes have high capacity and high stability.

[0013] definition Unless otherwise defined in this application, the scientific and technical terms used herein should have meanings generally understood by those skilled in the art. Generally, the chemical-related terms and techniques described herein are those well-known and commonly used in the field.

[0014] Unless the context otherwise requires or explicitly states the contrary, the inventive integers, steps, or elements listed herein as single integers, steps, or elements obviously cover both the singular and plural forms of said integers, steps, or elements.

[0015] As used in this article, "composite material" refers to a material made of two or more components with different physical or chemical properties, the resulting material having properties different from those of the individual components when these components are mixed. At both the macroscopic and microscopic scales, the components remain separate and distinct in the final structure of the composite material.

[0016] As used herein, the term "laminated metal composite" refers to a material consisting of layers of metal or metal alloy. Laminated metal composites are obtained by bonding multiple layers of different metals or metal alloys together. The layers can be bonded together by rolling, pressing, or adhesive bonding.

[0017] The word “substantially” does not exclude “completely”; for example, a composition that is “substantially free” of Y may be completely free of Y. The word “substantially” may be omitted from the definition of an invention if necessary.

[0018] The phrase "at least" as used in the specification and claims, when referring to a list of one or more elements, should be understood to mean at least one element selected from any one or more elements in the list, but not necessarily including at least one of each element specifically listed in the list, and does not exclude any combination of elements in the list. This definition also allows for the optional presence of elements referred to by the word "at least" in addition to those explicitly identified in the list, regardless of their relation to those explicitly identified elements. Thus, as a non-limiting example, "at least one of A and B" (or equivalently, "at least one of A or B", or equivalently, "at least one of A and / or B"), in one embodiment, may refer to at least one (optionally including more than one) A, but not B (optionally including elements other than B); in another embodiment, it may refer to at least one (optionally including more than one) B, but not A (optionally including elements other than A); in yet another embodiment, it may refer to at least one (optionally including more than one) A and at least one (optionally including more than one) B (optionally including other elements); and so on.

[0019] Unless otherwise stated, the terms “including” and “contains” and their grammatical variations are intended to indicate “open-ended” or “inclusive” wording, thus covering both the listed elements and allowing for the inclusion of additional unlisted elements.

[0020] The term “about” as used in this article, in the context of formulation component concentration, usually means ±5% of the nominal value, more usually means ±4% of the nominal value, more usually means ±3% of the nominal value, more usually means ±2% of the nominal value, even more usually means ±1% of the nominal value, and even more usually means ±0.5% of the nominal value.

[0021] Throughout this specification, certain embodiments may be disclosed in the form of scope. It should be understood that scope descriptions are for convenience and brevity only and should not be construed as rigid limitations on the disclosed scope. Therefore, a description of a scope should be considered as specifically disclosing all possible sub-scopes and individual values ​​within that scope. For example, a description of a scope such as 1-6 should be considered as specifically disclosing sub-scopes such as 1-3, 1-4, 1-5, 2-4, 2-6, 3-6, and individual values ​​within that scope, such as 1, 2, 3, 4, 5, 6. This applies regardless of the scope width.

[0022] This document may also describe certain embodiments in a broader and higher sense. Each of the narrower categories and subgroups falling within the scope of this higher-level disclosure constitutes a part of this disclosure. This includes higher-level descriptions of embodiments with attached conditions or negative limitations that remove any subject matter from the higher-level concept, regardless of whether such removed material is specifically described herein.

[0023] Brief description of the attached figures The accompanying drawings illustrate the disclosed embodiments and explain the principles of the disclosed embodiments. However, it should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0024] Figure 1 Figure 1 A series of figures are provided, in which: (a) shows a diagram of inefficient Al deposition on a bulk Al surface in aqueous solution; (b) depicts underpotential deposition (UPD) of Al on Sn / Cu; (c) and (d) show energy-dispersive X-ray spectra (EDS) of Sn and Cu foils after cyclic voltammetry (CV) testing in a three-electrode system, respectively; and (e) shows a comparative embodiment (Sn|0.5 M Al2(SO4)3|Al x Cyclic performance of MnO2 full cells.

[0025] Figure 2 Figure 2 This is a spectrum showing the EDS analysis of carbon paper after CV testing in a three-electrode system.

[0026] Figure 3 Figure 3 A series of figures illustrate the preparation and characterization of the embodiments of the present invention (Sn@Al foil), wherein: (a) the process for preparing the embodiments is shown; (b) X-ray diffraction (XRD) patterns of the embodiments and their precursors (Sn foil and Al foil) are shown; (c) X-ray photoelectron spectroscopy (XPS) Al 2p spectrum of the embodiments is shown; and (d) XPS Sn 3d spectrum of the embodiments is shown. 5 / 2 (e) shows a top-view scanning electron microscope (SEM) secondary electron image and EDS plot of the embodiment, and (f) shows a cross-sectional SEM backscattered electron image of a local structure of the embodiment.

[0027] Figure 4 Figure 4The figures are a series of images, in which (a) is a photograph showing an embodiment of the present invention (Sn@Al foil) and its precursors (Sn foil and Al foil), and (b) shows Sn@Al anodes and Al foils prepared with different folding / rolling times. x A full cell with MnO2 cathode at 100 mA g -1 Typical voltage curve under specific current.

[0028] Figure 5 Figure 5 This is an XPS spectrum showing the full spectrum of the embodiment of the present invention (Sn@Al foil).

[0029] Figure 6 Figure 6 Here are a series of spectra, where (a) shows the XPS Al 2p spectrum of an Al foil, and (b) shows the XPS Sn 3d spectrum of a Sn foil. 5 / 2 Spectrum.

[0030] Figure 7 Figure 7 A series of figures show the electrochemical performance of the embodiments of the present invention (Sn@Al foil) and comparative embodiments (bare Al), wherein: (a) shows the symmetrical cells using different negative electrodes at 10 mV s -1 (a) shows the CV curves at the scan rate; (b) shows the plate model used for theoretical calculations and the corresponding adsorption energies of Al atoms on Al and Sn substrates; (c) shows the Nyquist plots of symmetric cells with different negative electrodes; (d) shows the CV curves of symmetric cells with different negative electrodes in 0.5 M Al2(SO4)3 electrolyte at 0.05 mA cm⁻¹. -2 Current density and 0.1 mAh cm⁻¹ -2 Voltage curves during cycling under area capacity.

[0031] Figure 8 Figure 8 The figures show the Nyquist plots and equivalent circuit fits of (a) the embodiment of the present invention (Sn@Al), (b) the comparative embodiment (bare Al), and the second embodiment of the present invention (p-Sn@Al).

[0032] Figure 9 Figure 9 The graph shows the voltage curves of a symmetrical cell with the embodiment of the present invention (Sn@Al electrode) and a comparative embodiment (bare Al electrode) in 0.5 M Al2(SO4)3 electrolyte, with the symmetrical cell maintaining a voltage of 0.1 mAh cm⁻¹. -2While maintaining the area capacity, at 0.05, 0.1, and 0.2 mA cm⁻¹ -2 Cycling at current density.

[0033] Figure 10 Figure 10 The figures are a series of images, in which: (a) a schematic diagram of the stripping / electroplating process of the embodiment of the present invention (Sn@Al electrode) and the comparative embodiment (Al electrode); (b) a cross-sectional SEM image and EDS plot of the embodiment of the present invention after 500 stripping / electroplating cycles; (c) a top-view SEM image of the comparative embodiment after 300 stripping / electroplating cycles; and (d) the XPS Al 2p spectrum of the embodiment after stripping / electroplating cycles.

[0034] Figure 11 Figure 11 The spectrum is shown in (a) for the full XPS spectrum of the embodiment of the present invention (Sn@Al electrode) after a stripping / electroplating cycle, and (b) for its Sn 3d 5 / 2 Spectrum.

[0035] Figure 12 Figure 12 The figures are a series, where (a) shows the XRD pattern of MnO powder and (b) shows its SEM image.

[0036] Figure 13 Figure 13 It is a series of figures, in which: (a) shows an embodiment of the invention (Sn@Al||Al) x MnO2 battery) and comparative implementation scheme (Al||Al) x (a) shows the CV curve of MnO2; (b) shows the Nyquist plot of the embodiment; (c) shows the embodiment at 100 mA g -1 Typical voltage curves at specific currents, (d) shows the embodiment at 100 mAg. -1 Cycling performance at specific current, (e) shows the rate performance of the described embodiment, and (f) shows the second embodiment of the present invention (Sn@Al||KNHCF battery) and the second comparative embodiment (Al||KNHCF battery) at 100 mA g. -1 Typical voltage curves at specific currents, (g) shows the second embodiment at 100 mA g. -1The cycle performance under the conditions is shown in (h), and the OCV comparison of full cells with the third embodiment of the present invention (Sn@Al anode) paired with MnO and KNHCF cathodes and the third and fourth comparative embodiments (Sn and Al anodes) is shown.

[0037] Figure 14 Figure 14 It is a series of figures showing (a) an embodiment of the invention (Sn@Al||Al) x (a) MnO2 battery and (b) comparative implementation scheme (Al||Al) x Nyquist plot and equivalent circuit fitting of MnO2 battery.

[0038] Figure 15 Figure 15 The figures are a series of images, where (a) shows the XRD pattern of KNHCF powder and (b) shows its SEM image.

[0039] Figure 16 Figure 16 The graphs show the rate performance of the embodiment of the present invention (Sn@Al||KNHCF battery) and the comparative embodiment (Al||KNHCF battery).

[0040] Figure 17 Figure 17 This is a series of figures showing the characterization and electrochemical performance of the embodiments of the present invention (p-Sn@Al electrode), wherein: (a) a cross-sectional SEM image of the embodiment is shown; (b) attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) of the embodiment and the second embodiment of the present invention (Sn@Al electrode) is shown; (c) contact angle measurement results of the embodiment with 0.5 M Al2(SO4)3 aqueous solution are shown; (d) linear polarization curves of the embodiment in a symmetric cell using 0.5 M Al2(SO4)3 electrolyte are shown; and (e) the third embodiment of the present invention (p-Sn@Al||KNHCF cell) at 100 mA g -1 Cyclic performance under specific current.

[0041] Figure 18 Figure 18 The figures are a series of graphs showing the Nyquist plots and equivalent circuit fits of (a) the comparative embodiment (Al||KNHCF battery), (b) the embodiment of the present invention (Sn@Al||KNHCF battery), and (c) the second embodiment of the present invention (p-Sn@Al||KNHCF battery).

[0042] Figure 19 Figure 19 This is a schematic diagram illustrating the coating function of the hydrophobic polymer in the embodiment of the present invention (p-Sn@Al anode).

[0043] Figure 20 Figure 20 The images are a series of top-view SEM images of embodiments of the present invention after cycling, wherein (a) shows the p-Sn@Al anode and (b) shows the Sn@Al anode.

[0044] Figure 21 Figure 21 These are a series of spectra showing the EDS analysis of the following: (a) Sn foil after CV testing in a three-electrode system, (b) Sn foil after immersion in electrolyte, (c) Cu foil after CV testing in a three-electrode system, (d) Cu foil after immersion in electrolyte, (e) Ni foil after CV testing in a three-electrode system, and (f) Ni foil after immersion in electrolyte.

[0045] Figure 22 Figure 22 These are photographs showing the incompatibility between Cu foil and Al foil during the rolling process. Invention Details Due to Al's large negative reduction potential, aqueous aluminum metal batteries (AAMBs) typically face issues related to the promoted hydrogen evolution reaction (HER) during charging. Furthermore, the use of aqueous electrolytes can lead to the spontaneous formation of an oxide / passivation layer on the Al surface, which hinders charge transfer kinetics and increases the battery's internal resistance. These factors therefore negatively impact the coulombic efficiency and lifetime of AAMBs.

[0047] Furthermore, the challenge of achieving sufficient Al deposition in aqueous solutions poses a significant obstacle to aqueous Al batteries, such as... Figure 1 As shown in figure a, this figure depicts the inefficient deposition of Al on a bulk Al surface in aqueous solution. In the preliminary study, Al deposition on carbon paper was evaluated using cyclic voltammetry (CV) in a three-electrode system. Figure 2 As shown, energy-dispersive X-ray spectroscopy (EDS) analysis did not produce a detectable Al signal, highlighting the challenge of Al deposition in aqueous solutions. To overcome this problem, a promising approach is to incorporate foreign metals to achieve up-dispersion (UPD) of Al.

[0048] However, it was found that planar substrates for metal foils resulted in lower capacity. For example, in the assembly of button cells, Sn foil was used as the current collector in the negative electrode, and its electrochemical performance was evaluated.Figure 1 As shown in e, the specific capacity exhibited by this full cell is limited, <42 mAh g. -1 This is because the surface area of ​​the foil is limited. Once Al covers the surface, the UPD effect disappears, such as... Figure 1 As shown in b. Given the limitations of planar foils in providing surface area and capacity, the inventors unexpectedly discovered that combining Sn foil and Al foil in a hierarchical structure increases the interface between Sn and Al.

[0049] Hereinafter, the present invention provides an electrochemical battery including a negative electrode comprising Sn-Al, as a solution to overcome the hydrogen evolution reaction (HER) at the negative electrode during charging of the electrochemical battery and the spontaneous formation of an oxide / passivation layer on the surface of the Al negative electrode. The inventors unexpectedly discovered that the electrochemical battery disclosed herein exhibits a high voltage plateau, high coulombic efficiency, and high capacity while maintaining high capacity retention and stable cycling.

[0050] This invention provides an electrochemical cell comprising: The positive electrode contains tin (Sn) and aluminum (Al); Negative electrode; and Electrolytes.

[0051] In some embodiments, the negative electrode may comprise a Sn-Al composite material. In some embodiments, the negative electrode may consist substantially of a Sn-Al composite material. In some embodiments, the negative electrode may be composed of a Sn-Al composite material.

[0052] The inventors unexpectedly discovered that selecting Sn could endow the composite material with properties suitable for use as a negative electrode. For example, Sn exhibits good interfacial adhesion with Al, which advantageously allows them to bond tightly with the same elongation under pressure. Sn also has a higher working function than Al, which allows Al to produce underpotential deposition (UPD) on the Sn surface. The UPD of Al ions on the Sn surface can improve Al exfoliation. Furthermore, Sn can form local galvanic couples with Al, thereby promoting Al exfoliation, reducing internal resistance, and improving charge transfer kinetics. Sn can also have a higher overpotential required for hydrogen evolution, thereby suppressing the hydrogen evolution reaction (HER) at the negative electrode. Sn has good ductility, which prevents it from breaking during preparation. In addition, Sn can be stable in weakly acidic electrolytes, which allows it to be recycled extensively in electrochemical cells without replacement. Sn is inexpensive, which makes it possible to manufacture electrochemical cells at a lower cost.

[0053] It was found that planar foils offer limited surface area and capacity for the up-displacement (UPD) of Al ions on Sn. Furthermore, it was discovered that when Al is completely deposited on the Sn foil, the UPD effect is lost. The inventors unexpectedly discovered that Al can be advantageously activated when the metals (e.g., Sn and Al) are in a multilayer structure (e.g., laminated metal composites).

[0054] In some embodiments, the composite material may be a laminated metal composite material. A laminated metal composite material may comprise multiple layers of different metals or metal alloys. The layers may be arranged in an alternating manner. In some embodiments, the metals may include Sn and Al.

[0055] In some embodiments, the laminated metal composite material may comprise at least 3 to 8193 layers, for example, about 3 to about 8193 layers, about 3 to about 8000 layers, about 3 to about 7500 layers, about 3 to about 7000 layers, about 3 to about 6500 layers, about 3 to about 6000 layers, about 3 to about 5500 layers, about 3 to about 5000 layers, about 3 to about 4500 layers, about 3 to about 4097 layers, about 3 to about 4000 layers, about 3 to about 3500 layers, about 3 to about 3000 layers, about 3 to about 2500 layers, about 3 to about 2049 layers, about 3 to about 2000 layers, about 3 to about 1500 layers. Floor 0, approximately 3 floors to approximately 1025 floors, approximately 3 floors to approximately 1000 floors, approximately 3 floors to approximately 900 floors, approximately 3 floors to approximately 800 floors, approximately 3 floors to approximately 700 floors, approximately 3 floors to approximately 600 floors, approximately 3 floors to approximately 513 floors, approximately 3 floors to approximately 500 floors, approximately 3 floors to approximately 400 floors, approximately 3 floors to approximately 300 floors, approximately 3 floors to approximately 257 floors, approximately 3 floors to approximately 200 floors, approximately 3 floors to approximately 129 floors, approximately 3 floors to approximately 100 floors, approximately 3 floors to approximately 65 floors, approximately 3 floors to approximately 33 floors, approximately 3 floors to approximately 17 floors, approximately 3 floors to approximately 9 floors, approximately 3 floors to approximately 5 floors, or approximately 5 floors to approximately 8193 floors, approximately 9 floors to approximately 8193 floors, approximately 17 floors to approximately 8 193 floors, approximately 33 floors to approximately 8193 floors, approximately 65 floors to approximately 8193 floors, approximately 100 floors to approximately 8193 floors, approximately 129 floors to approximately 8193 floors, approximately 200 floors to approximately 8193 floors, approximately 257 floors to approximately 8193 floors, approximately 300 floors to approximately 8193 floors, approximately 400 floors to approximately 8193 floors, approximately 500 floors to approximately 8193 floors, approximately 513 floors to approximately 8193 floors, approximately 600 floors to approximately 8193 floors, approximately 700 floors to approximately 8193 floors, approximately 800 floors to approximately 8193 floors, approximately 900 floors to approximately 8193 floors, approximately 1000 floors to approximately 8193 floors, approximately 1025 floors to approximately 8193 floors, approximately 1500 floors Floors to approximately 8193, approximately 2000 floors to approximately 8193, approximately 2049 floors to approximately 8193, approximately 2500 floors to approximately 8193, approximately 3000 floors to approximately 8193, approximately 3500 floors to approximately 8193, approximately 4000 floors to approximately 8193, approximately 4097 floors to approximately 8193, approximately 4500 floors to approximately 8193, approximately 5000 floors to approximately 8193, approximately 5500 floors to approximately 8193, approximately 6000 floors to approximately 8193, approximately 6500 floors to approximately 8193, approximately 7000 floors to approximately 8193, approximately 7500 floors to approximately 8193, approximately 8000 floors to approximately 8193.Or at least approximately 3 floors, at least approximately 5 floors, at least approximately 9 floors, at least approximately 17 floors, at least approximately 33 floors, at least approximately 65 floors, at least approximately 100 floors, at least approximately 129 floors, at least approximately 200 floors, at least approximately 257 floors, at least approximately 300 floors, at least approximately 400 floors, at least approximately 500 floors, at least approximately 513 floors, at least approximately 600 floors, at least approximately 700 floors, at least approximately 800 floors, at least approximately 900 floors, at least approximately 1000 floors, at least approximately 1025 floors, at least approximately 1 500 layers, at least approximately 2000 layers, at least approximately 2049 layers, at least approximately 2500 layers, at least approximately 3000 layers, at least approximately 3500 layers, at least approximately 4000 layers, at least approximately 4097 layers, at least approximately 4500 layers, at least approximately 5000 layers, at least approximately 5500 layers, at least approximately 6000 layers, at least approximately 6500 layers, at least approximately 7000 layers, at least approximately 7500 layers, at least approximately 8000 layers, at least approximately 8193 layers, or any value or range thereof. It should be understood that the above ranges should be understood to include and support any subranges or discrete values ​​(discrete values ​​may be integers or not) falling within the stated ranges.

[0056] Advantageously, the laminated metal composite material can contain structures that enable the negative electrode to exhibit excellent Al exfoliation and electroplating capabilities. The inventors unexpectedly discovered that during exfoliation, the Al matrix can serve as a rich source of Al ions; while during electroplating, the Sn framework can provide numerous active sites for the Al UPD. The inventors also unexpectedly discovered that the spaces and gaps between the layers can increase the specific surface area of ​​the electrode and enhance ion transport.

[0057] In some implementations, the composite material may have formula (I): Sn y Al z --Formula (I) In some implementations, the y:z ratio in formula (I) can be from about 0.10:1 to about 0.80:1, from about 0.10:1 to about 0.75:1, from about 0.10:1 to about 0.70:1, from about 0.10:1 to about 0.65:1, from about 0.10:1 to about 0.60:1, from about 0.10:1 to about 0.55:1, from about 0.10:1 to about 0.50:1, or from about 0.10:1 to about 0.45. :1. Approximately 0.10:1 to approximately 0.40:1, approximately 0.10:1 to approximately 0.35:1, approximately 0.10:1 to approximately 0.30:1, approximately 0.10:1 to approximately 0.25:1, approximately 0.10:1 to approximately 0.20:1, approximately 0.10:1 to approximately 0.15:1, or approximately 0.15:1 to approximately 0.80:1, approximately 0.20:1 to approximately 0.80:1, approximately 0.25:1 to approximately 0.80:1, Approximately 0.30:1 to approximately 0.80:1, approximately 0.35:1 to approximately 0.80:1, approximately 0.40:1 to approximately 0.80:1, approximately 0.45:1 to approximately 0.80:1, approximately 0.50:1 to approximately 0.80:1, approximately 0.55:1 to approximately 0.80:1, approximately 0.60:1 to approximately 0.80:1, approximately 0.65:1 to approximately 0.80:1, approximately 0.70:1 to approximately 0.80:1, approximately 0.7 The ratio is within the range of 5:1 to approximately 0.80:1, or approximately 0.10:1, approximately 0.15:1, approximately 0.20:1, approximately 0.25:1, approximately 0.30:1, approximately 0.35:1, approximately 0.40:1, approximately 0.45:1, approximately 0.50:1, approximately 0.55:1, approximately 0.60:1, approximately 0.65:1, approximately 0.70:1, approximately 0.75:1, approximately 0.80:1, or any value or range thereof. It should be understood that the above ranges should be understood to include and support any subranges or discrete values ​​(discrete values ​​may be integers or not) falling within the stated ranges. The inventors unexpectedly discovered that when the y:z ratio is within the range of the above values, HER can be substantially suppressed during the charging process of the electrochemical cell.

[0058] In some embodiments, the electrochemical cell may be an aluminum-ion cell. In some embodiments, the electrochemical cell may be an aqueous aluminum-ion cell.

[0059] In some implementations, the thickness of the negative electrode or composite material can be approximately 20 μm to 200 μm, approximately 20 μm to 190 μm, approximately 20 μm to 180 μm, approximately 20 μm to 170 μm, approximately 20 μm to 160 μm, approximately 20 μm to 150 μm, approximately 20 μm to 140 μm, approximately 20 μm to 130 μm, approximately 20 μm to 120 μm, approximately 20 μm to 110 μm, approximately 20 μm to 100 μm, approximately 20 μm to 90 μm, approximately 20 μm to 80 μm, approximately 20 μm to 70 μm, approximately 20 μm to 60 μm, approximately 20 μm to 50 μm, approximately 20 μm to 40 μm, approximately 20 μm to 30 μm, or approximately 30 μm to 200 μm, approximately 40 μm to 200 μm. The range is approximately 50 μm to 200 μm, approximately 60 μm to 200 μm, approximately 70 μm to 200 μm, approximately 80 μm to 200 μm, approximately 90 μm to 200 μm, approximately 100 μm to 200 μm, approximately 110 μm to 200 μm, approximately 120 μm to 200 μm, approximately 130 μm to 200 μm, approximately 140 μm to 200 μm, approximately 150 μm to 200 μm, approximately 160 μm to 200 μm, approximately 170 μm to 200 μm, approximately 180 μm to 200 μm, approximately 190 μm to 200 μm, or approximately 20 μm, approximately 30 μm, approximately 40 μm, approximately 50 μm, approximately 60 μm, approximately 70 μm, approximately 80 μm, approximately 90 μm. μm, approximately 100 μm, approximately 110 μm, approximately 120 μm, approximately 130 μm, approximately 140 μm, approximately 150 μm, approximately 160 μm, approximately 170 μm, approximately 180 μm, approximately 190 μm, approximately 200 μm, or any value or range thereof. It should be understood that the above ranges should be understood to include and support any subranges or discrete values ​​(discrete values ​​may or may not be integers) falling within the stated ranges.

[0060] In some implementations, the positive electrode can be selected from Al. x MnO2, KNHCF, V2O5, and sulfur. The positive electrode may contain Al. x MnO2, KNHCF, V2O5 and sulfur.

[0061] In some embodiments, the electrolyte may be an aqueous aluminum salt. In some embodiments, the electrolyte may be selected from Al2(SO4)3 and Al(OTf)3. In some embodiments, the electrolyte may be non-corrosive. Non-corrosive electrolytes can advantageously result in less dissolution of Al at the negative electrode in the laminated metal composite.

[0062] The inventors also unexpectedly discovered that placing the polymer on the negative electrode could suppress Al passivation while simultaneously promoting Al stripping and electroplating.

[0063] In some implementations, the polymer can be disposed on at least a portion of the negative electrode surface.

[0064] In some embodiments, the polymer may be selected from PVDF, sulfonated tetrafluoroethylene vinyl fluoropolymer copolymers, and polyethylene glycol.

[0065] Advantageously, the polymer disposed on the negative electrode can enhance its corrosion resistance. Electrochemical cells containing such negative electrodes can still exhibit a high capacity retention of about 80% even after a large number of cycles.

[0066] In some implementations, the electrochemical cell may include: The negative electrode contains Al1Sn 0.6 ; The positive electrode contains Al x MnO2 or KNHCF; and Electrolytes, which contain Al2(SO4)3.

[0067] This invention provides a method for preparing a tin-aluminum-containing negative electrode for use in electrochemical cells, the method comprising: (a) Place Sn foil and Al foil in layers; (b) Folding the layered foil; and (c) Apply pressure to compress the folded layered foil. In step (c), the thickness of the compressed folded layered foil is less than the thickness of the folded layered foil in step (b).

[0068] Advantageously, the disclosed method provides a low-cost and simple way to manufacture such anodes, while producing anodes with high capacity and high stability.

[0069] In some implementations, steps (b) and (c) may be repeated at least once. In some implementations, steps (b) and (c) may be repeated about 1 to about 12 times, about 1 to about 11 times, about 1 to about 10 times, about 1 to about 9 times, about 1 to about 8 times, about 1 to about 7 times, about 1 to about 6 times, about 1 to about 5 times, about 1 to about 4 times, about 1 to about 3 times, about 1 to about 2 times, or about 2 to about 12 times, about 3 to about 12 times, about 4 to about 12 times, about 5 to about 12 times, about 6 to about 12 times, about 7 to about 12 times, about 8 to about 12 times, about 9 to about 12 times, about 10 to about 12 times, about 11 to about 12 times, or about 1 time, about 2 times, about 3 times, about 4 times, about 5 times, about 6 times, about 7 times, about 8 times, about 9 times, about 10 times, about 11 times, about 12 times, or any value or range thereof. It should be understood that the above range should be understood to include and support any subranges or discrete values ​​(discrete values ​​may or may not be integers) within the range.

[0070] Advantageously, after undergoing the number of folding / rolling cycles disclosed herein, the negative electrode can be activated, thereby achieving high battery capacity while maintaining corrosion resistance and exhibiting a low failure rate during the initial discharge process.

[0071] In some implementations, the method may further include: (d) Apply the polymer solution to the folded layered foil compressed in step (c).

[0072] In some implementations, the method may further include: (e) Apply an additional polymer solution to the product of step (d).

[0073] In some embodiments, the polymer in the polymer solution may be selected from polyvinylidene fluoride (PVDF) and sulfonated tetrafluoroethylene vinyl fluoropolymer copolymers.

[0074] Example Non-limiting embodiments and comparative examples of the invention will be described in more detail by way of specific examples, which should not be construed as limiting the scope of the invention in any way.

[0075] Materials and methods General characterization procedures Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed using a field emission SEM (JEOL JSM-7600F). X-ray diffraction (XRD) patterns were acquired using an X-ray diffractometer (Bruker D8 Advance) equipped with a Cu Kα radiation source (λ=1.5406 Å). X-ray photoelectron spectroscopy (XPS) spectra were collected using an XPS spectrometer (Kratos Axis Supra) equipped with an Al Kα X-ray source. Contact angles were measured using a DataPhysics OCA 15Pro instrument. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was performed on a PerkinElmer Frontier FTIR spectrometer with an ATR accessory.

[0076] General procedures for electrochemical measurements A 2032-type button cell was assembled using Whatman GF / A glass microfiber filter paper as the separator. The bare Al electrode was polished before use. Galvanostatic charge-discharge (GCD) measurements were performed using a Neware BTS4000 battery testing system. Cyclic voltammetry (CV) tests were performed on an Autolab PGSTAT204 electrochemical workstation. In the three-electrode system tests, a graphite rod was used as the counter electrode, Ag / AgCl as the reference electrode, and 0.5 M Al2(SO4)3 aqueous solution as the electrolyte. Electrochemical impedance spectroscopy (EIS) measurements were performed in the frequency range of 100,000 Hz to 0.01 Hz with an amplitude of 10 mV. Equivalent circuit fitting of the Nyquist plot was performed using NOVA software. All electrochemical tests were performed at room temperature (25°C).

[0077] Adsorption energy calculations Adsorption energy calculations were performed using density functional theory (DFT) and the Vienna Ab initio Simulation Package. For the exchange-correlation potential, the Perdew-Burke-Ernzerhof generalized gradient approximation was used. The plane wave cutoff energy was set at 520 eV, and the energy criterion for iterative solving the Kohn-Sham equations was set at 10 eV. -5 eV. The atomic structure was relaxed until the residual forces on the atoms decreased to below 0.01 eV / Å. A plate model was used to simulate the surface of Al or Sn metals to ensure that the vacuum layer thickness was greater than 25 Å to avoid any interactions between the layers. The plate thickness was set to be greater than 15 Å to minimize the surface energy. The adsorption energies of Al atoms on the (111) plane of Al metal and the (001) plane of Sn metal were studied using DFT calculations.

[0078] Example 1: Preparation and characterization of Sn@Al electrode Sn-Al composite materials (Sn@Al) were prepared using repeated folding and rolling methods, such as... Figure 3 As shown in figure a. Typically, Sn foil is laminated onto Al foil, and the foil is roughly folded in half. The foil is then compressed with rollers to reduce its thickness. This process is repeated to form a multilayer laminated Sn-Al composite material.

[0079] More specifically, rectangular aluminum and tin foils of the same size and 100 µm thickness were cleaned with ethanol and stacked together. They were then folded lengthwise with the tin layer on the outside. The foils were then rolled using a rolling mill until the Sn-Al foil thickness was reduced to 100 µm. This folding and rolling process was repeated nine times to obtain Sn@Al with a final thickness of 100 µm. This iterative process gradually increased the number of metal layers while gradually decreasing the thickness (Table 1). Finally, the Sn@Al foil was cut into square pieces of the appropriate size for electrochemical measurements.

[0080] Sn and Al foils undergo flattening and reorganization during rolling to form an interlaced layered structure. Due to Sn's excellent ductility and affinity for Al, the resulting Sn@Al is a dense and complete sheet, such as... Figure 4 As shown, Figure 4 This shows that Sn and Al are bonded together, allowing direct interaction between the Sn framework and the Al framework.

[0081] Table 1. Theoretical thickness calculation for each layer, assuming that the thinning coefficients of Al and Sn are equal. X-ray diffraction (XRD) patterns confirmed that Sn@Al is a mixture of Sn and Al, and no new peaks were observed. Figure 3 b). X-ray photoelectron spectroscopy (XPS) was performed on Sn@Al, Al foil, and Sn foil to capture surface information. Full XPS spectra showed the presence of Al, Sn, and O elements in the prepared Sn@Al. Figure 5 The Al 2p spectrum of Sn@Al ( Figure 3 c) Analysis revealed the presence of a metal corresponding to Al. 0 and Al oxidation 3+ The peak. Based on peak area fitting, the proportion of oxidized states is much lower than that of the original Al foil ( Figure 6 a). In Sn@Al's Sn 3d 5 / 2 Spectrum ( Figure 3 In d), the metal Sn was observed to be... 0 And the peak of Sn oxide. Similarly, the proportion of Sn oxide is lower than that of the original Sn foil ( Figure 6b). These observations indicate a reduction in the surface oxide layer of Sn@Al compared to the original Al and Sn foils. This can be explained by the fact that the metal undergoes plastic deformation and elongation during rolling, while the brittle oxide layer can only withstand fracture stress. Commercial Al and Sn foils have an oxide film on their surfaces. After repeated rolling, the oxide layer breaks down and is uniformly distributed throughout the overall structure, thus reducing the surface oxide layer. Scanning electron microscopy (SEM) images and energy-dispersive X-ray spectroscopy (EDS) plots of the top view of Sn@Al demonstrate the coexistence and patterned distribution of Sn and Al on the surface. Figure 3 e). SEM cross-sectional images reveal that the 100 μm thick Sn@Al layer is uniform and intact. Figure 3 f). In backscattered electron imaging mode, local areas exhibit a layered structure of Sn and Al hybrids (f). Figure 3 g).

[0082] Example 2: Electrochemical performance of Sn@Al electrode in symmetrical electrolytic cell CV tests were performed on Sn@Al and Al symmetric cells to compare the behavior of Sn@Al and Al electrodes. Figure 7 The results show that the Al electrode exhibits an asymmetric curve, with a typical HER-shaped peak on the plating side (negative voltage), indicating that Al plating is not possible and severe HER is present. On the stripping side (positive voltage), suppressed current density is observed, which may be due to the surface passivation layer. In contrast, the Sn@Al electrode exhibits a more symmetrical curve and enhanced current density, which can be attributed to improved Al stripping / plating. The enhanced Al plating can be explained by the UPD of Al ions on the Sn surface. Simultaneously, HER is suppressed due to the higher overpotential required for hydrogen evolution on Sn. The enhanced Al stripping can be explained by the galvanocoupler principle. This principle states that when two metals with different electrode potentials come into contact in an electrolyte, the more reactive metal accelerates dissolution / stripping. The noble metal Sn with different electrode potentials and the non-noble metal Al will form a local Al / Sn galvanocoupler, thereby effectively promoting Al stripping.

[0083] To explore the feasibility of aluminum being more readily deposited on Sn@Al electrodes compared to bare Al electrodes, density functional theory (DFT) was used to calculate the adsorption energies of Al atoms on Sn and Al substrates. Figure 7 As shown in b, the adsorption energies of a single Al atom on the Al(111) and Sn(001) surfaces were compared. The calculated adsorption energy of Al on the Sn surface was -5.02 eV, which is more negative than the adsorption energy of Al atoms on the Al surface (-2.28 eV). This result indicates that Al deposition is more favorable on Sn. This confirms that the nucleation energy barrier for Al deposition on the Sn surface can be lowered.

[0084] Electrochemical impedance spectroscopy (EIS) measurements were performed on symmetrical cells, namely Sn@Al||Sn@Al and Al||Al. Figure 7 As shown in Figure c, the Nyquist plots obtained from these measurements show significant differences, with the Al electrode exhibiting a significantly higher internal resistance compared to the Sn@Al electrode. The charge transfer resistance (Rc) was determined by equivalent circuit fitting. ct ),like Figure 8 As shown in a and 8b and calculated, the energy barrier is 6.28 kΩ for the Al||Al cell and 187 kΩ for the Sn@Al||Sn@Al cell. This difference can be attributed to the difference in passivation layer coverage between the two electrodes. When the insulating passivation layer covers the surface of the Al electrode, a significant energy barrier prevents Al ions from entering the electrolyte from below the passivation layer. Therefore, the transfer kinetics of Al ions are severely limited. Conversely, in the case of the Sn@Al electrode, the passivation layer is either thinner or discontinuously distributed, resulting in a smaller energy barrier to overcome.

[0085] Long-term Al stripping / electroplating of Sn@Al and bare Al electrodes was investigated in a symmetrical electrolytic cell. The electroplating process was carried out at 0.05 mA cm⁻¹. -2 The current density and 0.1 mAh cm⁻¹ -2 During capacity cycling, the Al||Al battery exhibited fluctuating overpotentials around 0.6 V and ultimately failed after 320 hours. Figure 7 d). This large overpotential can be attributed to the accumulation of the passivation layer. Despite pre-polishing of the bare Al foil, alumina formation could not be prevented in the aqueous electrolyte environment. Failure after 320 h can be attributed to irreversible Al consumption. As the Al plating amount was less than the Al stripping amount in each cycle (due to HER dominance), the Al electrode gradually thinned until it lost sufficient contact with the coin cell casing. Consequently, the internal resistance increased significantly, even leading to an open circuit. In contrast, the Sn@Al||Sn@Al battery could cycle for over 900 h with a consistently smooth overpotential below 0.5 V. Figure 7 d). At 0.1 mA cm -2 and 0.2 mA cm -2 At higher current densities, the overpotential of the Sn@Al||Sn@Al cell is still lower than that of the Al||Al cell. Figure 9 These results demonstrate that the Sn@Al electrode exhibits excellent Al stripping / deposition capabilities within a certain current density range.

[0086] Figure 10The provided diagrams demonstrate the superior performance of the Sn@Al electrode. The Sn@Al structure is specifically designed to optimize battery performance. In this design, the aluminum substrate acts as a rich source of Al ions during stripping, while the Sn framework provides numerous active sites for underpotential Al deposition during electroplating. The spaces and gaps between layers increase the electrode's specific surface area and enhance ion transport. The interconnected Sn framework within the electrode helps maintain structural stability. Furthermore, the noble metal Sn with its different electrode potentials forms localized Al / Sn couples with the non-noble metal Al, effectively promoting Al stripping. The high HER overpotential of Sn is crucial for minimizing hydrogen generation. Conversely, the bare Al electrode faces a significant energy barrier to penetrate the passivation layer during stripping. During electroplating, Al's high negative reduction potential makes Al deposition difficult. Therefore, HER is severe, significantly impairing battery reversibility.

[0087] Post-hoc SEM images of the Sn@Al electrode revealed that the layered Sn and Al distribution did not change significantly. Figure 10 b). However, after cycling, numerous pits were observed on the Al electrode, which can be attributed to corrosion and irreversible Al consumption ( Figure 10 c). After cycling, the XPS full spectrum of the Sn@Al electrode showed a newly generated S 2p peak originating from the Al2(SO4)3 electrolyte. Figure 11 a). Sn 3d 5 / 2 The spectrum showed a higher proportion of oxidized states than observed after preparation, indicating an increase in tin oxide on the surface during cycling. Figure 11 b). Given that SnO2 is considered a semiconductor, the additional surface oxide layer formed during Al stripping / electroplating may introduce higher overpotentials in electron conduction and ion diffusion. Figure 7 The increase in overpotential within the initial 300 hours in d reflects this. The Al 2p spectra of the Sn@Al electrode and the bare Al electrode after cycling further reveal the differences. Figure 10 d). In the case of a bare Al electrode, a symmetrical peak was observed at 74.8 eV, corresponding to the Al 2p peak of Al₂O₃ / Al(OH)₃ / AlO(OH). This indicates the presence of a passivation layer, suggesting inefficient Al deposition or severe side reactions. The Sn@Al electrode exhibited an asymmetric peak with a lower binding energy, indicating that it was decomposed into metallic Al. 0 and Al oxidation 3+ Al 0 The obvious presence of the peak indicates that Al was effectively deposited on the Sn@Al electrode.

[0088] Example 3: Electrochemical characteristics of Sn@Al electrode in full cell Example 3a: Preparation of MnO positive electrode 4 g of potassium permanganate was dissolved in 200 mL of 2.5 M sulfuric acid solution and stirred at 75 °C for 2 h. The resulting precipitate was collected by centrifugation, thoroughly washed with deionized water and ethanol, and dried overnight in a vacuum oven at 60 °C. The precursor was then reduced in a tube furnace under a hydrogen atmosphere at 400 °C for 10 h to obtain brown MnO powder.

[0089] To prepare the manganese oxide cathode slurry, MnO powder, carbon black (Super-P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 6:2:2. N-methyl-2-pyrrolidone (NMP) was added appropriately, and the mixture was stirred overnight. The resulting slurry was coated onto hydrophobic carbon fiber paper and dried in a vacuum oven at 80°C for 12 hours. The loading mass of the active material was maintained at approximately 1 mg / cm³. -2 .

[0090] Example 3b: Preparation of KNHCF positive electrode 0.3 g of polyvinylpyrrolidone was added to 10 mL of 0.07 M nickel(II) tetrahydrate aqueous solution and stirred. Then, while stirring continuously for 2 hours, 10 mL of 0.05 M potassium(III) hexacyanoferrate aqueous solution was added dropwise to the mixture. The precipitate was collected by centrifugation, washed with deionized water, and dried at 60 °C for 12 hours to obtain KNHCF powder.

[0091] To prepare the KNHCF positive electrode, deionized KNHCF powder, Super-P, and carboxymethyl cellulose (CMC) were mixed in a weight ratio of 6:2:2. The mixture was then coated onto hydrophilic carbon fiber paper. The loading mass of the active material was approximately 1 mg cm⁻¹. -2 .

[0092] Example 3c: Al 2 (SO 4 ) 3 Preparation of electrolyte To prepare the 0.5 M Al2(SO4)3 electrolyte, 0.05 mol of aluminum sulfate octadecylhydrate was dissolved in 100 mL of deionized water. For the constant current charge-discharge stability test, 0.15 M manganese(II) sulfate was included to inhibit manganese dissolution.

[0093] Example 3d: Electrochemical testing of Sn@Al electrode in full cell After confirming the excellent performance of the Sn@Al electrode in symmetric cells, the Sn@Al anode was further tested in full cells. A low-cost, fluorine-free aqueous Al2(SO4)3 electrolyte was utilized. Due to the presence of manganese oxide (Al... x Due to the high capacity and redox potential of MnO2, it was initially chosen as the cathode material. MnO powder was prepared using the procedure described in our previous report. XRD patterns and SEM images verified its phase and confirmed it to be a cubic structure with a size of 100 nm.Figure 12 ). at 0.1 mV s -1 The scan rate was measured by CV to evaluate Al||Al x MnO2 and Sn@Al||Al x Redox activity of MnO2 batteries ( Figure 13 a) Both bare Al and Sn@Al cells exhibit a pair of redox peaks. However, the peak positions differ significantly. Al||Al x The reduction peak of the MnO2 cell appears at 0.99 V. In contrast, for Sn@Al||Al x The MnO2 battery exhibited a reduction peak at 1.40 V. This 0.41 V increase can be attributed to improved charge transfer kinetics on the negative electrode side and a decrease in internal resistance during discharge. Furthermore, a Sn@Al||Al peak was observed at 1.71 V. x The oxidation peak of the MnO2 battery is higher than that of Al||Al. x The MnO2 battery is 1.58 V.

[0094] EIS testing was performed to study the resistance of the full cell. Figure 13 b shows a clear difference in the Nyquist plot. This is achieved through equivalent circuit fitting ( Figure 14 Sn@Al||Al x R of MnO2 battery ct The measured Ω was 684 Ω, significantly lower than Al||Al. x The MnO2 battery showed a value of 2.19 kΩ. This result indicates an improvement in charge transfer kinetics at the electrode-electrolyte interface. Given that the positive electrode remains constant, this improvement can be attributed to enhanced charge transfer kinetics at the Sn@Al negative electrode interface. Furthermore, due to the use of the same electrolyte, the solution resistance (R0) was reduced. s ) and Warburg resistor (Z w The values ​​are quite similar.

[0095] Subsequently, Al||Al x MnO2 and Sn@Al||Al x The MnO2 battery was subjected to constant current charge-discharge (GCD) testing, and 0.15 M MnSO4 was added as an inhibitor to suppress the dissolution of manganese oxide cathode. Figure 13 c shows at 100 mA g -1 Typical voltage curve under specific current. (Compared to Al||Al) x Compared to MnO2, the charge / discharge voltage plateau of Sn@Al||AlxMnO2 cells is higher, which is consistent with the trend observed in the CV curves. Figure 13 a). In addition, such as Figure 13 As shown in d, in terms of capacity retention and coulombic efficiency, Sn@Al||Alx MnO2 batteries exhibit significantly better cycle performance than Al||Al x MnO2 battery. After 75 cycles, Sn@Al||Al x The MnO2 battery still maintains a capacity of 177 mAh g. -1 The specific capacity of Al||Al is approximately 95%. In comparison, Al||Al x The specific capacity of the MnO2 battery after 60 cycles is only 46 mAh g. -1 The Coulomb efficiency is less than 55%. Al||Al x The rapid capacity decay and below-standard coulombic efficiency of MnO2 cells can be attributed to the accumulation of the passivation layer and severe side reactions, primarily HER. Furthermore, we investigated Sn||Al x The cycle performance of MnO2 batteries. However, as... Figure 1 As shown in e, Sn||Al x MnO2 batteries exhibit limited electrochemical activity. This observation highlights the limited energy storage capacity of tin in this system when using a weakly acidic aluminum sulfate electrolyte. Therefore, for batteries with a Sn@Al anode, the capacity contribution of the Sn component is negligible. Sn@Al||Al x The capacity decay of MnO2 batteries may be caused by structural collapse of the positive electrode due to the strong electrostatic interaction of Al ions. For example... Figure 13 As shown in Figure e, the rate performance was evaluated by cycling at different specific currents. Sn@Al||Al x MnO2 batteries at 0.5 A g -1 The following shows approximately 50 mAh g -1 The specific capacitance when the current drops to 0.1 A g -1 At that time, its capacity recovered to approximately 170 mAh g. -1 In contrast, Al||Al x MnO2 batteries at 0.2 A g -1 The inability to maintain capacity can be attributed to the slow kinetics of Al ions.

[0096] To evaluate the compatibility of Sn@Al anode with different types of cathodes, its performance was assessed when paired with potassium nickel hexacyanoferrate (KNHCF) cathode. XRD patterns and SEM images of KNHCF powder are shown below. Figure 15 As shown. The KNHCF cathode, a Prussian blue analogue (PBA), is characterized by limited capacity but enhanced stability. This unique characteristic complements the properties of manganese oxide. At 100 mA g in the voltage range of 0.5–1.6 V. -1During charge and discharge, the voltage curve of the Sn@Al||KNHCF battery exhibits a higher voltage plateau than that of the Al||KNHCF battery. Figure 13 f). Furthermore, the Sn@Al||KNHCF battery exhibited an initial specific capacity of 50 mAh g. -1 After 90 cycles, the capacity retention rate was 72%. Figure 13 g). Moreover, it exhibits a high coulombic efficiency of approximately 95%, outperforming Al||KNHCF cells. When the specific current is increased to 1 A g -1 At that time, the Sn@Al||KNHCF battery still maintained about 50% capacity retention, while the Al||KNHCF battery even maintained a capacity retention of 0.5 A g. -1 It is difficult to maintain capacity (under) Figure 16 These results indicate that the Sn@Al anode has the potential to be compatible with the PBA cathode, thus expanding its application as an AAMB anode.

[0097] Then the open-circuit voltages (OCVs) of six full cells were compared, such as Figure 13 As shown in h, the full cell with a Sn anode consistently exhibits the lowest OCV when paired with a MnO or KNHCF cathode. This observation is easily understood because OCV is related to the electrochemical potential difference between the cathode and anode, and Sn has a relatively positive potential. On the other hand, theoretically, a cell with an Al anode should have a high OCV due to the negative potential of Al metal. However, in reality, it provides only slightly higher OCV values ​​than the cell with a Sn anode, mainly due to the presence of a surface passivation layer. In contrast, the cell using a Sn@Al anode exhibits an OCV approximately 0.3 V higher than its Al anode counterpart. This improvement is attributed to the activation of Al metal in the Sn@Al anode.

[0098] Example 4: Polymer-coated electrode Example 4a: Preparation of polymer-coated Sn@Al (p-Sn@Al) Through N A 5 wt% PVDF solution was prepared by thoroughly stirring a certain amount of polyvinylidene fluoride (PVDF) powder in methyl-2-pyrrolidone (NMP). Simultaneously, Nafion™ 117 solution was added to dimethylformamide (DMF) and mixed thoroughly. The PVDF solution was then first coated onto Sn@Al, followed by coating with the Nafion solution. The solvent was then slowly dried on a hot plate at 60 °C for 1 h.

[0099] Example 4b: Evaluation of p-Sn@Al Al activation significantly benefits the electrochemical performance of the Sn@Al electrode. However, it also presents a new challenge: enhanced chemical reactivity between Al and the weakly acidic electrolyte (pH 2.5 of 0.5 M Al2(SO4)3). Therefore, a balance needs to be struck between the synergistic effects of passivation and Al activation. A hybrid polymer film made of Nafion and polyvinylidene fluoride (PVDF) was drop-coated onto Sn@Al. The resulting electrode is denoted as p-Sn@Al. Figure 17 a demonstrates the uniformity of a coating with a thickness of approximately 45 µm. EIS test ( Figure 8 c) indicates that the R of the p-Sn@Al||p-Sn@Al battery ct The Ω value is 279 Ω. Although this represents a 49% increase compared to Sn@Al||Sn@Al cells, it is still quite small compared to Al||Al cells. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of the polymer film were obtained. Figure 17 b). Analysis revealed characteristic bands associated with PVDF and Nafion. Notably, PVDF was significantly observed at 1180 and 875 cm⁻¹. -1 CF2 vibration at 1405 cm -1 The CH2 vibration occurs at 1055 cm⁻¹. Furthermore, at 1055 cm⁻¹... -1 The band at that location corresponds to SO 3- Stretching vibration, and 1150 cm -1 The band at this point indicates the CH2 stretching vibration of Nafion. Contact angle (CA) measurements were performed to assess the change in wettability between p-Sn@Al and Sn@Al. Notably, p-Sn@Al exhibited a significantly larger CA (90.5°) compared to Sn@Al's CA of 50.6°. Figure 17 c). This difference indicates the hydrophobicity of the coating, which may limit the interaction between water molecules and Sn@Al, thereby inhibiting corrosion. This observation is consistent with reported PVDF coatings in aqueous batteries. Furthermore, the linear polarization curve ( Figure 17 d) Prove that the corrosion current of the p-Sn@Al electrode ( i corr The corrosion resistance was lower than that of the Sn@Al electrode, thus confirming that the coating imparts enhanced corrosion resistance. Thanks to the advantages of the coating, the p-Sn@Al||KNHCF battery exhibited a stable charge-discharge process over 700 cycles, while also demonstrating a high coulombic efficiency of >97%. Figure 17 e). Using the capacity after 10 cycles of stabilization as a reference, the p-Sn@Al||KNHCF cell retains 82% of its capacity after 700 cycles. EIS testing and equivalent circuit fitting reveal that the introduction of a 269 Ω parallel resistance in the p-Sn@Al||KNHCF cell is attributed to the coating (Figure 18 However, the overall resistivity is still much lower than that of Al||KNHCF. Although the polymer coating may increase the resistivity and affect the kinetic properties, it can hinder proton transfer, thus protecting the surface from HER and corrosion, such as... Figure 19 As shown. Figure 20 As shown in the SEM images, the surface of the p-Sn@Al electrode remained intact after cycling, without the cracks and debris observed in the Sn@Al electrode.

[0100] Comparative example Comparative Example 1: Preparation of Cu@Al The experiment was conducted using a three-electrode system to test Al deposition on other metals such as Sn, Cu, and Ni. Metal foils (Sn, Cu, Ni) were used as working electrodes for CV (conductive chromatography) measurements. Figure 1 As shown in c, 1d, 21a, and 21c, EDS analysis revealed significant Al signals on the Sn and Cu substrates. In contrast, the Sn and Cu foils did not exhibit Al signals after immersion in the electrolyte. Figure 21 b and 21d), thus removing the Al source from electrolyte adsorption. As for Ni, the Al signal is weaker than that of Sn and Cu ( Figure 21 e and 21f).

[0101] Therefore, the same rolling and folding process described in Example 1 was performed on Cu foil and Al foil. Experimental results show that Cu is incompatible with Al during the rolling process ( Figure 22 Specifically, Figure 22 This indicates that Cu and Al foils cannot adhere together under pressure, and due to their difference in ductility, they cannot elongate uniformly and form a well-contacting interface. In contrast, Sn and Al exhibit excellent interfacial adhesion, allowing them to bond tightly under pressure at the same elongation. Therefore, they can withstand repeated rolling processes.

[0102] Comparative Example 2: Sn@Al and p-Sn@Al vs. Zn-Al By Al 3+ Zn-Al anodes were synthesized by deposition onto a Zn foil substrate. An assembly including the Zn-Al anode and Al... x An electrochemical battery with MnO2 cathode and Al(OTf)3 electrolyte was constructed and compared with the electrochemical battery of the present invention.

[0103] Table 3. Comparison of electrochemical properties of Al composite material AAMB Based on the above results, when the accompanying metal in the negative electrode is changed from zinc (Zn) to tin (Sn), the capacity and retention rate of the electrochemical cell are improved, while the discharge plateau period remains largely unchanged. Simultaneously, a lower concentration and non-corrosive Al2(SO4)3 electrolyte is used instead of Al(OTf)3.

[0104] Furthermore, when a polymer coating is added to the negative electrode (p-Sn@Al), the retention rate of the electrochemical cell is significantly increased compared to that of the Zn-Al negative electrode. Even at nearly 10 times the cycle count, the retention rate of the electrochemical cell of this invention remains at 82%, which is more than twice the retention rate of the cell with the Zn-Al negative electrode.

[0105] Comparative Example 3: Prussian blue analogue-based aqueous aluminum-ion batteries The voltage plateau and capacity retention of the p-Sn@Al||KNHCF cell were compared with those of other known PBA-based AAMB cells in the prior art, and the results are shown in Table 4.

[0106] Table 4. Comparison of known electrochemical performance of PBA-based AAMB Compared to other known AAMB batteries, the p-Sn@Al||KNHCF battery exhibits a stable charge / discharge process over 700 cycles, while also demonstrating a high coulombic efficiency of >97%. Figure 19 e). Using the capacity of the 10th cycle after stabilization as a reference, the p-Sn@Al||KNHCF battery still retains 82% of its capacity after 700 cycles. This demonstrates that the electrochemical battery of this invention maintains a high capacity retention rate while also possessing a high discharge plateau.

[0107] Industrial applicability This invention relates to electrochemical batteries, particularly aqueous aluminum batteries. The electrochemical battery of this invention maintains stability during long-term cycling while exhibiting high charging capacity. The production cost of this electrochemical battery is also low. Therefore, this invention has industrial applicability.

[0108] Obviously, after reading the above disclosure, various other modifications and adaptations of the invention will be apparent to those skilled in the art without departing from the spirit and scope of the invention, and all such modifications and adaptations are intended to fall within the scope of the appended claims.

Claims

1. Electrochemical cells, including: The negative electrode contains tin (Sn) and aluminum (Al); positive electrode; as well as Electrolytes.

2. The electrochemical battery of claim 1, wherein the negative electrode comprises a Sn-Al composite material.

3. The electrochemical cell of claim 1 or 2, wherein the negative electrode is composed of Sn-Al composite material or substantially composed of Sn-Al composite material.

4. The electrochemical battery according to claim 2 or 3, wherein the composite material is a laminated metal composite material.

5. The electrochemical battery according to any one of claims 2-4, wherein the composite material is a laminated metal composite material comprising at least 100 layers.

6. The electrochemical cell according to any one of claims 2-5, wherein the composite material has formula (I): Sn y Al z -- Formula (I); The ratio of y:z is approximately 0.1:1 to approximately 0.8:

1.

7. The electrochemical cell of claim 6, wherein the y:z ratio is from 0.4:1 to 0.8:

1.

8. The electrochemical battery according to any one of claims 1-7, wherein the electrochemical battery is an aluminum-ion battery.

9. The electrochemical cell according to any one of claims 1-8, wherein the thickness of the negative electrode or composite material is from about 20 μm to 200 μm.

10. The electrochemical cell according to any one of claims 1-9, wherein the positive electrode is selected from Al. x MnO2, KNHCF, V2O5, iodine, and sulfur.

11. The electrochemical battery according to any one of claims 1-10, wherein the electrolyte is an aqueous aluminum salt.

12. The electrochemical battery according to any one of claims 1-11, wherein the electrolyte is selected from Al2(SO4)3 and Al(OTf)3.

13. The electrochemical cell according to any one of claims 1-12, wherein the polymer is disposed on at least a portion of the surface of the negative electrode.

14. The electrochemical battery of claim 13, wherein the polymer is selected from PVDF, sulfonated tetrafluoroethylene vinyl fluoropolymer copolymer, and polyethylene glycol.

15. The electrochemical cell according to any one of claims 1-14, comprising: The negative electrode contains Al1Sn 0.6 ; The positive electrode contains Al x MnO2 or KNHCF; as well as Electrolytes, which contain Al2(SO4)3.

16. A method for preparing a tin-aluminum-containing negative electrode for use in an electrochemical cell, the method comprising: (a) Place Sn foil and Al foil in layers; (b) Fold the layered foil; as well as (c) Apply pressure to compress the folded layered foil. In step (c), the thickness of the compressed folded layered foil is less than the thickness of the folded layered foil in step (b).

17. The method of claim 16, wherein steps (b) and (c) are repeated at least once.

18. The method of claim 16 or 17, wherein steps (b) and (c) are repeated about 5-12 times.

19. The method of any one of claims 16-18, wherein the method further comprises: (d) Apply the polymer solution to the folded layered foil compressed in step (c).

20. The method of claim 19, wherein the method further comprises: (e) Apply an additional polymer solution to the product of step (d).

21. The method of claim 19 or 20, wherein the polymer in the polymer solution is selected from polyvinylidene fluoride (PVDF) and sulfonated tetrafluoroethylene vinyl fluoropolymer copolymers.

22. The method of any one of claims 16-21, wherein the negative electrode comprises the composite material of any one of claims 2-9.

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