Improved electrochemical cells suitable for high energy battery use

Abstract

A rechargeable electrochemical cell and components and structures of an electrochemical cell having a SO2 solvent-based electrolyte comprising any of the components and structures are provided. The cathode can include one or more elemental transition metals and / or one or more partially oxidized transition metals. The SO2 solvent-based electrolyte can include a halide-containing salt additive as an SEI film-forming additive. The anode current collector can include a carbon-coated metal, an alloy of two or more metals, or a carbon-coated alloy of two or more metals. The electrochemical cell can include additional non-dissolved / solid alkali halides. The components, structures, and cells can be used in devices.

Description

[0001] Invention Field

[0002] This invention relates to a rechargeable electrochemical cell. In particular, this invention relates to the cell described above that uses a novel salt cathode and supports a high-energy-density salt metal cathode, the cell of which can use an SO2-based electrolyte.

[0003] background

[0004] High-performance, low-cost electrochemical cells, such as batteries, have broad application prospects in mobile electronics, energy production, distribution, and transportation. Inventions that can further improve cell performance will benefit both industry and commerce.

[0005] Invention Summary

[0006] This invention improves the technical level of rechargeable (secondary) electrochemical cells. The foundation of battery cells utilizing sodium metal anodes has been established in FI 20150270. This invention discloses significant improvements in battery cells, basic electrochemical cell structure, operating principles, and performance, such as higher cell voltage and higher coulombic efficiency. This invention is also applicable to improving the performance of other battery chemistry families. The object of this invention is to disclose high-performance electrochemical cells for, for example, secondary high-energy batteries. Devices according to the invention have the features described in the claims.

[0007] The first aspect of the present invention describes a cathode for a rechargeable electrochemical cell. The cathode can be used in rechargeable electrochemical cells assembled in a charged state, a discharged state, and / or a half-charged (half-discharged) state. Cells using the cathode can use SO2 solvent-based electrolytes. The cathode may include one or more alkali metal halides. The alkali metal in the one or more alkali metal halides may be lithium, sodium, potassium, rubidium, cesium, and / or francium. The alkali metal halide in the one or more alkali metal halides may be fluorine, chlorine, bromine, iodine, and / or astatine, and the alkali metal halide of the cathode may be NaF, NaCl, NaBr, NaI, LiF, LiCl, LiBr, LiI, or any mixture thereof. According to the present invention, other alkali metal halides may also be used. The cathode may include one or more transition metal compounds. The one or more transition metals may be partially oxidized transition metals. The one or more partially oxidized transition metals may be in the form of one or more partially oxidized transition metal compounds. The one or more partially oxidized transition metal compounds may be one or more partially oxidized transition metal halides. The one or more partially oxidized transition metal halides may adopt M y X is in the form of M, where M is a partially oxidized transition metal, X is a halide, and y is the M / X ratio that causes the transition metal to be in a partially oxidized state. The one or more partially oxidized transition metal halides may be Cu. y Br, Cuy I, Cu y Cl, Cu y F (where y is greater than 0.5) or any mixture thereof. The transition metal compound may be a fully oxidized transition metal compound. The one or more fully oxidized transition metal compounds may be transition metal halides. The transition metal halide may be a fully oxidized transition metal halide. The fully oxidized transition metal halide may be CuBr2, CuI2, CuCl2, CuF2 or combinations thereof. According to the invention, other transition metal halides (fully oxidized and partially oxidized) may also be used. The transition metal halide may be used alone, or as a supplement to or in combination with alkali metal halides. The alkali metal halide may be used alone, or as a supplement to or in combination with transition metal halides. The cathode may further comprise one or more elemental and / or partially oxidized transition metals or mixtures of several elemental and / or partially oxidized transition metals. The one or more elemental and / or partially oxidized transition metals may be used as a supplement to alkali metals and / or transition metal halides. The elemental transition metal may be elemental copper. According to the invention, other elemental transition metals may also be used. Examples of elemental transition metals include, but are not limited to, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, lutetium, lanthanum, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, actinium, and uranium. Lanthanum, bismuth, lead, indium, tin, gallium, and / or germanium. According to the present invention, lanthanum, bismuth, lead, indium, tin, gallium, and germanium can also be considered as elemental transition metals. The one or more partially oxidized transition metals can be one or more partially oxidized transition metal compounds M. y A is one or more components, M is a partially oxidized transition metal, A is an oxidizing agent, and y is the M / A ratio that allows the transition metal to be in a partially oxidized state. For example, A can be oxygen, nitrogen, sulfur, antimony, or cyanide, or any combination thereof. Partially oxidized transition metal compounds include, but are not limited to, Sc. x A, Ti y A, Mn y A, Fe y A, Co y A. Ni y A, Cu y A, Zn y A, where A can be oxygen (thus forming an oxide), nitrogen (thus forming a nitride), sulfur (thus forming a sulfide), antimony (thus forming an antimony compound), or cyano (thus forming a cyanide), or any combination thereof. The transition metal compound M y The M in A can be Cu. (M is a transition metal compound.) yThe A in A can be O, or M in a transition metal compound. y The y-value of A can be greater than 1. In this case, the transition metal compound is a partially oxidized transition metal compound. Transition metal compound M y A can be Cu y O, where y is greater than 1, in which case the transition metal compound is a partially oxidized transition metal compound. According to the invention, other fully or partially oxidized transition metals and fully or partially oxidized transition metal compounds can also be used. The cathode may include a variety of fully or partially oxidized transition metals and / or fully or partially oxidized transition metal compounds and any combination thereof. During assembly, the cathode is in the same state as previously prepared, and the molar ratio of alkali metal halide to transition metal can be any ratio greater than 1:0. Preferably, the ratio is at least 1:1. More preferably, the ratio is between 1:1 and 5:1.

[0008] A second aspect of the invention describes an SO2 solvent-based electrolyte comprising a halide salt additive. The halide salt additive may be a fluoride salt additive. The fluoride salt additive may be Na-DFOB (sodium difluoro-oxalate-borate), Li-DFOB (lithium difluoro-oxalate-borate), Na-Triflate (sodium trifluoromethane-sulfonate), Li-Triflate (lithium trifluoromethane-sulfonate), or combinations thereof. According to the invention, other halide salt additives may also be used.

[0009] A third aspect of the invention describes an SO2 solvent-based electrolyte composed of a mixture of alkali metal electrolyte salts. The alkali metal salts may be lithium and / or sodium electrolyte salts. The electrolyte salts may include a mixture of LiAlCl4 and NaAlCl4. According to the invention, other alkali metal electrolyte salts may also be used.

[0010] A fourth aspect of the invention describes an anode current collector for a rechargeable electrochemical cell, comprising a carbon-coated metal, an alloy of two or more metals, or a carbon-coated alloy of two or more metals. The carbon-coated metal anode current collector may be carbon-coated aluminum. The current collector composed of an alloy of two or more metals may be a copper-nickel alloy. Other carbon-coated metals may also be used according to the invention. Other alloys may also be used according to the invention.

[0011] A fifth aspect of the present invention discloses an electrochemical cell comprising any of the cathodes described in the first aspect of the present invention, wherein the electrolyte is at least partially of the SO2 solvent type.

[0012] The sixth aspect of the present invention discloses an electrochemical cell comprising any electrolyte described in the second and / or third aspects of the present invention and / or any cathode described in the first aspect of the present invention and / or any anode current collector described in the fourth aspect of the present invention.

[0013] According to a seventh aspect of the invention, one or more insoluble / solid alkali metal halides can be added to the battery cell. For example, in a battery cell composed of a cathode containing NaCl, additional solid NaCl that is insoluble in the electrolyte can be added to the battery cell. For example, the insoluble / solid alkali halide can be NaF, NaCl, NaBr, NaI, LiF, LiCl, LiBr, or LiI; other insoluble / solid alkali halides can also be used according to the invention.

[0014] The eighth aspect of the invention describes the use of any electrolyte described in the second and / or third aspects of the invention and / or any cathode described in the first aspect of the invention and / or any anode current collector described in the fourth aspect of the invention in a device. For example, the device may be an electronic device, an electrical device, a mobile device, a power transmission device, or an energy storage device. Examples of electronic devices include computing devices and communication devices. Examples of electrical devices include power tools, motors, and robots. Examples of mobile devices include electric vehicles. Examples of energy storage devices include batteries, battery packs, backup power supplies, and energy storage units for local, regional, or district power grids and uninterruptible power supplies. Examples of power transmission devices include engine starter batteries. The device may be a combination of an electrochemical cell according to the invention and one or more components utilizing the power and / or energy provided by the electrochemical cell. The device may be a charging device for providing power and / or energy to the electrochemical cell.

[0015] Any of the electrochemical cells can be assembled in a charged, half-charged, or discharged state. When assembled in a discharged state, the anode current collector is substantially free of alkali metals during cell assembly. In a discharged or half-charged state, one or more alkali metals may be deposited in metallic form on the current collector during charging. This deposition may occur during the first charge of the cell. The first charge may occur after cell assembly. When assembled in a charged or half-charged state, the anode current collector may include a layer of alkali metal during cell assembly.

[0016] The term "SO2 solvent-based electrolyte" here is understood to refer to any electrolyte in an electrochemical cell that includes SO2 as a significant component, wherein the molar fraction of the solvent material used is preferably at least 10%, more preferably at least 25%, and even more preferably at least 50%. According to the invention, other molar fractions of SO2 may also be used.

[0017] In one embodiment, the battery cell has a cathode with an alkali halide base, wherein the cathode is selected from NaF, LiF, NaCl, LiCl, NaBr, LiBr, NaI, LiI, or mixtures thereof. According to the invention, other alkali halides may also be used. An alkali halide is a compound containing at least one alkali metal and one halogen. Examples of alkali metals include lithium, sodium, potassium, rubidium, cesium, and francium. Examples of halides include fluorine, chlorine, bromine, iodine, and astatine.

[0018] The term "alkali halide salt cathode" here is understood to refer to any cathode of an electrochemical cell containing one or more alkali halide salts as an important component, wherein the molar fraction of the cathode material used is preferably at least 1%, more preferably at least 5%, more preferably at least 10%, and even more preferably at least 20%. According to the invention, other molar fractions of alkali halide salts may also be used.

[0019] The alkaline halide-based cathode can be used as the active component in discharge-state assembly, meaning the cell can be in a discharged state during assembly. Such a cell is referred to as a "discharge-state assembled" cell. The cathode can also be used as the active component in charge-state assembly, meaning the cell can be in a charged state during assembly. The cathode can also be used as the active component in a half-charge (half-discharge) state assembly, meaning the cell can be in a half-charge or half-discharge state during assembly. Here, half-charge and half-discharge are equivalent. Such a cell is referred to as a "half-discharge assembled" or "half-charge assembled" cell. The cell may include the use of further additives disclosed in this invention for improving cell efficiency, voltage, and energy density.

[0020] In one embodiment of the invention, the anode current collector comprises an alloy. The alloy may be a copper-nickel alloy. Other alloys may also be used according to the invention. For example, the current collector may also serve as a mechanical support for the anode. When there is no obvious anode material on the anode current collector, such as when the battery is discharging, the current collector can act as a mechanical support. When the anode material itself does not have sufficient mechanical integrity within the cell, the current collector can serve as a mechanical support.

[0021] Surprisingly, the copper-nickel alloy anode current collector remains stable in SO2-based electrolytes throughout the entire charging cycle, even when the cell is in a prolonged charging state, thus serving as an effective and robust current collector / mechanical support. Importantly, sodium-on-substrate deposition produces a smoother surface compared to pure nickel substrates, thereby improving the cell's coulombic efficiency and lifespan. Research has found that the copper-nickel alloy substrate material is even suitable for reversible lithium-on-substrate deposition, opening up possibilities for the use of lithium-based salts in conventional rechargeable batteries. The Cu:Ni ratio can be between 10:90 and 90:10, more preferably between 20:80 and 80:20, even more preferably between 40:60 and 60:40, and most preferably approximately 55:45, the so-called constantan. According to the invention, additional alloying components can also be added or used to replace copper and nickel.

[0022] In one embodiment of the invention, the anode current collector comprises a carbon-coated metal. The carbon-coated metal may be aluminum. Surprisingly, the carbon-coated aluminum anode current collector is stable in SO2-based electrolytes and facilitates reversible deposition of Na and Li on the substrate during the charging cycle.

[0023] In one embodiment of the invention, the cathode active material may comprise a lithium-based salt. Correspondingly, the electrolyte salt may comprise LiAlCl4. The electrolyte may be SO2-based. When the electrolyte is SO2-based, the corresponding electrochemical cell may be SO2 electrolyte-based. The formulation may be LiAlCl4·xSO2, wherein x is preferably between 1 and 5, more preferably between 1.5 and 3, even more preferably between 1.8 and 2.2, and most preferably approximately 2. In one embodiment of the invention, the electrolyte salt may also comprise NaAlCl4. Studies have found that the presence of NaAlCl4 in the electrolyte improves the stability and reversibility of lithium deposition. The preferred molar ratio of LiAlCl4 to NaAlCl4 is between 10:90 and 99.999:0.001, more preferably between 90:10 and 95:5. According to the invention, other transition metal-based electrolyte salts may also be used. According to the invention, other electrolyte salt ratios may also be used. According to the present invention, other combinations can be made for the upper and lower limits of the electrolyte salt ratio.

[0024] In one embodiment of the invention, the electrolyte may further include a fluorinated salt as an additive. The fluorinated salt additive can serve as an SEI film-forming additive. The additive can alter the SEI between the anode and the electrolyte. We have found that the presence of the fluorinated salt additive improves the coulombic efficiency and lifespan of the battery cell disclosed in this invention. Na-DFOB (sodium difluoro-oxalate-borate), Li-DFOB (lithium difluoro-oxalate-borate), Na-Triflate (sodium trifluoromethane-sulfonate), or Li-Triflate (lithium trifluoromethane-sulfonate) are particularly desirable fluorinated additives. Without being bound by theory, fluorinated salt additives are considered to improve the anode SEI during initial charging of alkaline halide cathodes. The concentration of the fluorinated salt additive is preferably between 0.0001% and 5% of the electrolyte mass, more preferably between 0.1% and 3% of the electrolyte mass, and most preferably between 0.5% and 2% of the electrolyte mass. According to the invention, other concentrations of fluorinated salt additives may also be added. According to the present invention, other combinations can be made for the concentration limits of fluoride-containing salt additives.

[0025] In one embodiment of the present invention, a cathode for a rechargeable electrochemical cell is disclosed, the cathode comprising one or more alkali metal halides and one or more transition metals. These may be active components assembled in a discharged state. The alkali metal halide may be selected from LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, or any mixture thereof. The one or more transition metals may be a mixture or alloy of transition metals. In one embodiment, the transition metal is elemental copper. According to the present invention, other alkali metal halides may also be used. According to the present invention, other transition metals and their alloys may also be used.

[0026] The SEI (solid electrolyte interface membrane) can be an anodic SEI or a cathode SEI. SEI is defined herein as a membrane or layer that allows target ions to pass through but not one or more other materials / molecules. Such blocking / filtering materials may include those that react with the electrodes (anode and cathode) or other battery materials / components (such as current collectors) or have an adverse effect on the electrodes or electrode materials or other battery materials / components (such as current collectors or current collector materials).

[0027] For the avoidance of doubt, SEI forming and / or reinforcing materials, films or layers refer to materials, films or layers that themselves form SEI, serve as precursors to SEI, combine with existing SEI, or otherwise enhance the function of SEI.

[0028] For the avoidance of doubt, cationic conductive materials, films or layers refer to materials, films or layers that allow cations (such as basic cations) to migrate between materials, films or layers.

[0029] To avoid ambiguity, the anode or cathode current collector can also serve as a supporting structure / mechanical support.

[0030] According to one embodiment of the present invention, the electrochemical cell may include the above-described auxiliary cathode structure, SO2-based electrolyte, electrolyte additives containing fluoride salts and / or NaAlCl4, and a copper-nickel alloy current collector on the anode side.

[0031] Attached Figures

[0032] Figure 1 The cross-section of an electrochemical cell in a charged or half-charged state according to the present invention is shown, having an anode (1), a cathode (2), an electrolyte (3), and may also include one or more SEI layers (4), an anode current collector (5), and / or a cathode current collector (6).

[0033] Figure 2 The cross-section of an electrochemical cell in a discharged state according to the present invention is shown, having a cathode (2), an electrolyte (3), and may also include one or more SEI layers (4), an anode current collector (5) and / or a cathode current collector (6).

[0034] Figure 3 The average discharge voltage evolution of a battery cell using a NaCl-based cathode and a common constantan foil anode substrate is shown. The horizontal axis represents the cycle number. The electrolyte used was NaAlCl4·2SO2. The working electrode has a geometric area of ​​2.5 cm². 2 .

[0035] Figure 4 The average discharge voltage evolution of the cell using a 2NaCl:Cu cathode and Na metal anode is shown. The horizontal axis represents the cycle number. The electrolyte used was NaAlCl4·2SO2. The working electrode has a geometric area of ​​2.5 cm². 2 .

[0036] Figure 5 The voltage evolution over one cycle is shown for a cell using a 2NaCl:Cu cathode and a Na metal anode. The electrolyte used is NaAlCl4·2SO2. The working electrode has a geometric area of ​​2.5 cm². 2 .

[0037] Figure 6 The voltage evolution over one cycle is shown for a battery cell using a 2LiF:Cu cathode and a Li metal anode formulation. The electrolyte used was LiAlCl4·2SO2 with 1 wt% LiDFOB additive. The working electrode had a geometric area of ​​2.5 cm². 2 .

[0038] Detailed description of the embodiments

[0039] Specific embodiments of the present invention are disclosed herein with reference to the accompanying drawings. The following paragraphs describe improvements related to high-energy-density battery cells using SO2 solvent-based electrolytes.

[0040] The cathode of a rechargeable electrochemical cell assembled in a discharged state or a half-charged state is described, the cell having an SO2 solvent-based electrolyte comprising one or more basic transition metals and / or one or more partially oxidized transition metals. At least one of the one or more partially oxidized transition metals may be a component of a partially oxidized transition metal compound. At least one of the one or more partially oxidized transition metal compounds may be M... y The form A, where M is a partially oxidized transition metal, A is an oxidizing agent, and y is the M / A ratio that causes the transition metal to be in a partially oxidized state. At least one of the one or more oxidizing agents A can be oxygen, nitrogen, sulfur, antimony, or a cyanide, or any combination thereof. At least one of the one or more partially oxidized transition metal compounds can be an oxide, sulfide, halide, cyanide, nitride, or any combination thereof. At least one of the one or more transition metal halides can include Cu. y Br, Cu y I, Cu y Cl, Cu y F (where y is greater than 0.5) or any combination thereof. At least one of the one or more partially oxidized transition metal oxides may include Cu. y O, where y is greater than 1. At least one of the one or more elemental transition metals may include copper. The cathode may further comprise one or more alkali metal halides. The one or more alkali metal halides may include NaF, NaCl, NaBr, NaI, LiF, LiCl, LiBr, LiI, or any combination thereof. During assembly, the molar ratio of alkali metal halide to transition metal compound may be greater than 1:0.

[0041] A SO2 solvent-based electrolyte is described using a halide salt additive as an SEI film-forming additive. The halide salt additive may include a fluoride salt additive. The fluoride salt additive may include Na-DFOB (sodium difluoro-oxalate-borate), Li-DFOB (lithium difluoro-oxalate-borate), Na-Triflate (sodium trifluoromethane-sulfonate), or Li-Triflate (lithium trifluoromethane-sulfonate), or combinations thereof.

[0042] An SO2 solvent-based electrolyte comprising a mixture of alkali metal electrolyte salts is described. The alkali metal electrolyte salts may be lithium electrolyte salts and sodium electrolyte salts. The electrolyte salts may include a mixture of LiAlCl4 and NaAlCl4.

[0043] An anode current collector for a rechargeable electrochemical battery cell is described, the cell having an SO2 solvent-based electrolyte comprising a carbon-coated metal, an alloy of two or more metals, or a carbon-coated alloy of two or more metals. The carbon-coated metal may include carbon-coated aluminum and / or alloys thereof including copper-nickel alloys.

[0044] An electrochemical cell having at least a cathode, an anode, and an electrolyte is described, wherein the electrolyte is composed of any of the described electrolytes and / or any of the described cathodes and / or any of the described anode current collectors.

[0045] An electrochemical cell comprising at least the anode, electrolyte, and cathode is described. The cathode may comprise one or more elemental transition metals and / or one or more partially oxidized transition metals. At least one of the one or more partially oxidized transition metals may be a component of a partially oxidized transition metal compound. At least one of the one or more partially oxidized transition metal compounds may be M... y The form A, where M is a partially oxidized transition metal, A is an oxidizing agent, and y is the M / A ratio that causes the transition metal to be in a partially oxidized state. At least one of the one or more oxidizing agents A can be oxygen, nitrogen, sulfur, antimony, or a cyanide, or any combination thereof. At least one of the one or more partially oxidized transition metal compounds can be an oxide, sulfide, halide, cyanide, nitride, or any combination thereof. At least one of the one or more transition metal halides can include Cu. y Br, Cu y I, Cu y Cl, Cu y F (where y is greater than 0.5) or any combination thereof. At least one of the one or more partially oxidized transition metal oxides may include Cu. yO, where y is greater than 1. At least one of the one or more elemental transition metals may include copper. The cathode may further include one or more alkali metal halides. The one or more alkali metal halides may include NaF, NaCl, NaBr, NaI, LiF, LiCl, LiBr, LiI, or any combination thereof. During assembly, the molar ratio of alkali metal halide to transition metal compound may be greater than 1:0. The SO2 solvent-based electrolyte may include halide salt additives as SEI film-forming additives. The halide salt additives may include fluorine salt additives. The fluorine salt additives may include Na-DFOB (sodium-difluoro-oxalate-borate), Li-DFOB (lithium-difluoro-oxalate-borate), Na-Triflate (sodium-trifluoromethane-sulfonate), or Li-Triflate (lithium-trifluoromethane-sulfonate), or combinations thereof. The SO2 solvent-based electrolyte may include a mixture of alkali metal electrolyte salts. The alkali metal electrolyte salts may be lithium electrolyte salts and sodium electrolyte salts. The electrolyte salt may include a mixture of LiAlCl4 and NaAlCl4. One or more additional insoluble / solid alkali metal halides may be added to the cell. These additional insoluble / solid alkali halides may include NaF, NaCl, NaBr, NaI, LiF, LiCl, LiBr, LiI, or any mixture thereof. The cell may further include a spacer / separator between the anode current collector and the cathode.

[0046] An electrochemical cell having at least a cathode, an anode, and an electrolyte is described, wherein the electrolyte is composed of an SO2 solvent-based electrolyte and / or any of the cathode and / or any of the anode current collectors described.

[0047] The description refers to any electrochemical cell with one or more additional non-soluble / solid alkali metal halides. The additional non-soluble / solid alkali halides may include NaF, NaCl, NaBr, NaI, LiF, LiCl, LiBr, LiI, or any mixture thereof. The cell may further include a spacer / separator between the anode current collector and the cathode.

[0048] The use of any of the electrolytes, cathodes, anode current collectors, and / or electrochemical cells in the device is described. The use of the anode current collectors and / or electrochemical cells in the device is also described.

[0049] Figure 1The cross-section of an electrochemical cell embodiment according to the present invention in a charged or half-charged state is shown, having an anode (1), a cathode (2), an electrolyte (3), and may also include one or more SEI layers (4), an anode current collector (5), and / or a cathode current collector (6).

[0050] The cell may also include a spacer / splitter (7, not shown) at the anode (1), anode current collector (5), SEI layer 4a or SEI layer 4b, and any cathode (2), cathode current collector (6), SEI layer 4b, SEI layer 4c, or SEI layer 4d. According to the invention, 0, 1, 2, 3, or 4 SEI layers may be present.

[0051] Figure 2 A cross-section of an electrochemical cell embodiment in a discharged state according to the present invention is shown, comprising a cathode (2), an electrolyte (3), and may further include one or more SEI layers (4), an anode current collector (5), and / or a cathode current collector (6). As shown, the cell may further include a spacer / separator (7) between SEI layers 4a and 4b, but may also include any anode current collector (5), SEI layer 4a or SEI layer 4b with any cathode (2), cathode current collector (6), SEI layer 4b, SEI layer 4c or SEI layer 4d. According to the present invention, 0, 1, 2, 3 or 4 SEI layers may be present. The spacer / separator can provide space for the anode during charging. The spacer / separator can be used to physically separate the anode and cathode and / or their associated SEI layers. The spacer / separator can leave space for the electrolyte to exist within the cell. According to one embodiment of the present invention, the spacer / separator may be composed of a porous material or otherwise contain a large number of void spaces. Preferably, the porosity is greater than 10%, more preferably greater than 20%, even more preferably greater than 40%, even more preferably greater than 60%, even more preferably greater than 70%, and most preferably greater than 80%. The spacer / separator can comprise any material compatible with the electrolyte. The spacer / separator can comprise cellulose and / or SiO2. According to the invention, other materials can also be used for the spacer / separator.

[0052] According to the present invention, Figure 1 and Figure 2 Any combination of the cell structures shown is possible. According to the present invention, Figure 1 and Figure 2 Any part of 1-7 can overlap or be mixed with another part.

[0053] Surprisingly, LiCl can be reversibly used as an active cathode material in battery cells using LiAlCl4·xSO2 type electrolytes. A LiCl-based cathode was constructed by injecting LiCl into a carbon-based framework. Cycling this battery cell based on the LiCl active cathode material yielded approximately 90% of the theoretical 600 mAh / g discharge capacity compared to the mass of LiCl.

[0054] In LiCl-type cathodes with LiAlCl4·xSO2 electrolytes, the required charging voltage may be in the range of 4.4–4.6 V compared to the Li / Li+ reference. The combined use of NaCl cathode materials with anode substrates has been described in FI 20150270 to promote the deposition of metallic Na on the anode side. Equivalent methods for metallic lithium deposition are problematic due to the tendency for dendritic lithium deposition. Surprisingly, we have discovered several complementary methods to achieve highly reversible, dendrite-free metallic lithium deposition, even in LiAlCl4·xSO2 electrolytes. First, we were surprised to find that copper-nickel alloys are stable in SO2-based electrolytes throughout the entire charge cycle, and the surfaces produced by Na and Li deposition on the substrate are smoother than those on nickel substrates. This improves the coulombic efficiency and lifespan of the cell. The Cu:Ni ratio can be between 10:90 and 90:10, more preferably between 20:80 and 80:20, even more preferably between 40:60 and 60:40, and most preferably around 55:45, i.e., the so-called constantan. According to the invention, additional alloying components can also be added or used to replace Cu and Ni. As alternatives to copper-nickel alloys, we found that carbon-coated metals and alloys remain stable throughout the entire charge cycle in SO2-based electrolytes, and the on-substrate Na and on-substrate Li depositions on carbon-coated metal and alloy substrates are sufficiently smooth to achieve stable cell cycling. In particular, aluminum and aluminum alloys remain stable throughout the entire charge cycle in SO2-based electrolytes, and the on-substrate sodium and on-substrate lithium depositions on carbon-coated metal and alloy substrates are sufficiently smooth to achieve stable cell cycling. Aluminum-based substrates have the advantages of low cost and light weight, which are more advantageous than copper-nickel alloys. Secondly, surprisingly, the presence of sodium salts in the electrolyte, such as NaAlCl4, improves the stability and reversibility of lithium deposition. Without theoretical constraints, the NaAlCl4 content in the electrolyte induces initial sodium deposition in the early stages of charging, thereby improving the stability and reversibility of subsequent lithium deposition. The LiAlCl4:NaAlCl4 ratio can be between 10:90 and 99.999:0.001, more preferably between 90:10 and 95:5. Third, we found that the presence of fluorinated salt additives improves the coulombic efficiency and lifespan of the battery cell disclosed in this invention. Without theoretical constraints, fluorinated salt additives are considered to improve the anodic SEI during the initial charging process of the alkaline halide cathode. Na-DFOB (sodium-difluoro-oxalate-borate), Li-DFOB (lithium-difluoro-oxalate-borate), Na-Triflate (sodium-trifluoromethane-sulfonate), or Li-Triflate (lithium-trifluoromethane-sulfonate) are particularly desirable fluorinated additives.The concentration of the fluorinated salt additive is preferably between 0.0001% and 5% of the electrolyte mass, more preferably between 0.1% and 3% of the electrolyte mass, and most preferably between 0.5% and 2% of the electrolyte mass. According to the present invention, other concentrations of the fluorinated salt additive can also be added. According to the present invention, other combinations of the concentration limits of the fluorinated salt additive can also be made.

[0055] Other alkaline salt type cathodes can be constructed by injecting NaF, LiF, NaBr, LiBr, NaI, LiI, or mixtures thereof into a carbon-based framework to form a structure similar to NaCl or LiCl. In the case of NaCl or LiCl type cathodes, a mixture of dissolved Cl2 and SO2Cl2 is generated in the electrolyte during charging. In the case of NaBr or LiBr type cathodes, dissolved Br2 is mainly generated in the electrolyte during charging, resulting in a lower coulombic efficiency during cell cycling compared to NaCl or LiCl type cathodes. In the case of NaI or LiI type cathodes, dissolved I2 is mainly generated in the electrolyte during charging, resulting in a lower coulombic efficiency during cell cycling compared to NaCl or LiCl type cathodes. In the case of NaF or LiF type cathodes, a mixture of dissolved Cl2 and SO2Cl2 is generated in the electrolyte during charging, while AlCl4- electrolyte salt anions are converted to AlCl3F- by absorbing F- from the cathode salt. Therefore, the rechargeability of NaF or LiF is limited by the available AlCl4- electrolyte salt. Preferred alkali metal halide cathode materials are NaCl / LiCl, or a mixture of NaCl / LiCl and NaF / LiF.

[0056] We further discovered that when certain transition metals are added to the alkali salt containing the cathode, these metals facilitate the absorption of chlorine and / or fluorides, and / or bromine, and / or iodine during charging cycles, enabling highly reversible subsequent battery cycles. Without theoretical constraints, these metal additives can be understood as eliminating or reducing the necessity for electrolyte absorption of oxidized halides, thus opening up the possibility of using alkali fluoride-type cathode compositions. Among the transition metals, elemental copper was found to be a particularly preferred cathode component. Without theoretical constraints, the beneficial effect of copper is thought to be because it can reversibly convert between elemental +1 copper oxide ore halides (CuF, CuCl, CuBr, or CuI) and elemental +2 copper oxide ore halides (such as CuF2, CuCl2, CuBr2, or CuI2) without reducing the anode side to elemental copper in SO2-type electrolytes. Figure 3 and Figure 4The study shows the difference in cell voltage with the presence of copper, highlighting the different chemical operations of the cell in the presence of copper. Surprisingly, the SO2-type electrolyte promotes this reversible conversion reaction starting from elemental copper, allowing the cell to be assembled in a discharged state. The resulting battery cells have high energy round-trip efficiency in the 90-95% range, and what is particularly surprising is their very high cycle stability, as previously known conversion-cathode battery cells have poor energy efficiency and rapid capacity decay. Figure 5 The voltage evolution of the battery cell consisting of a 2NaCl:Cu cathode and a metallic Na anode is shown. Figure 6 The cell voltage evolution of a 2LiF:Cu battery consisting of a 2LiF:Cu cathode and a metallic Li anode is shown. Figure 6 The cell discharge data shown demonstrates that it is feasible to fully utilize the theoretical capacity of the 2LiF:Cu cathode. According to the invention, the SO2-type electrolyte may comprise NaAlCl4·xSO2 or LiAlCl4·xSO2 or any mixture thereof. The cathode active material may consist of an alkali halide:copper molar ratio, preferably between 1:1 and 10:1, more preferably between 1.5:1 and 3:1, and most preferably between 1.9:1 and 2.1:1. For other transition metals and other alkali halides, the alkali halide:metal molar ratio is preferably the same as that of copper.

[0057] Another construction method for assembly in the discharged state is to build the cell in the charged state. For example, it has been surprisingly discovered that lithium batteries can also be assembled in the charged state using an anode already containing metallic lithium and a cathode containing a transition metal halide. For example, the transition metal can be copper. According to the invention, other transition metals can also be used. For example, copper fluoride (CuF2) can be injected into a conductive carbon framework to form CuF2 containing a cathode. According to the invention, other transition metal halides can also be used. During assembly, the metallic lithium anode can be an anode current collector that already has a layer or deposit of metallic aluminum. The charged-state cell can operate in the same electrolyte as used for the discharged-state battery structure. According to the invention, any of the aforementioned anode current collectors can be used.

[0058] Example

[0059] Preparation of electrolyte

[0060] Example 1

[0061] NaAlCl4·2SO2 electrolyte was synthesized according to [1]. LiAlCl4·2SO2 electrolyte was prepared using the same process, but with LiCl precursor instead of NaCl.

[0062] Example 2

[0063] An ideal NaAlCl4:LiAlCl4 electrolyte ratio was prepared by mixing NaAlCl4·2SO2 and LiAlCl4·2SO2 electrolytes in a specific ratio. Specifically, the NaAlCl4:LiAlCl4 ratio in the Li-based battery cell was 1:10.

[0064] Example 3

[0065] Electrolytes containing LiDFOB additive were prepared by incorporating 1 wt% LiDFOB additive into the electrolytes of Examples 1 and 2. Similarly, electrolytes containing NaDFOB, LiTriflate, or NaTriflate additives can be prepared.

[0066] Preparation of active materials

[0067] Example 4

[0068] A porous carbon cathode is prepared by adding NaCl, LiCl, NaBr, LiBr, NaI, or LiI to methanol to create a saturated solution, dispersing the porous carbon in the solution, and then evaporating the solution. In the case of using NaF and LiF, propylene carbonate is used instead of methanol.

[0069] Example 5

[0070] Following the steps described in [2], copper nitrate was dissolved in ethanol, and copper was injected into the material of Example 4 to obtain a cathode material based on an alkali metal halide:copper formulation. The amount of copper precursor was adjusted so that the molar ratio of alkali metal halide to copper was 2:1.

[0071] Preparation of positive electrode

[0072] Example 6

[0073] The electrode was prepared from a mixture of 94 wt% of the active materials from Examples 4 and 5 and 6 wt% of PTFE. The mixture was dry-pressed onto a carbon-coated aluminum current collector according to the dry-pressing procedure of [3].

[0074] Preparation of rechargeable batteries

[0075] Example 7

[0076] A rechargeable NaCl active material battery was prepared, comprising a constantan anode current collector, a 200-micrometer-thick glass microfiber separator immersed in a NaAlCl4·2SO2 electrolyte, and a NaCl cathode obtained by the steps described in Examples 4 and 6. The average discharge voltage evolution of the battery prepared for this example is as follows: Figure 3 As shown.

[0077] Example 8

[0078] A rechargeable 2NaCl:Cu active material formulation battery was prepared. The battery has a metallic sodium anode, a 200-micrometer-thick glass microfiber separator immersed in a NaAlCl4·2SO2 electrolyte, and a 2NaCl:Cu formulation cathode obtained through the steps described in Examples 4, 5, and 6. The average discharge voltage evolution of the battery prepared for this example is as follows: Figure 4 As shown, the voltage evolution of a single charge-discharge cycle is as follows: Figure 5 As shown.

[0079] Example 9

[0080] A rechargeable 2LiF:Cu active material formulation battery was prepared. The battery has a lithium metal anode, a 200-micrometer-thick glass microfiber separator immersed in a LiAlCl4·2SO2 electrolyte containing 1 wt% LiDFOB additive, and a 2LiF:Cu formulation cathode was obtained through the steps described in Examples 4, 5, and 6. The charge-discharge voltage evolution of the battery prepared for this example over one cycle is as follows: Figure 6 As shown.

[0081] References:

[0082] 1. DOI: 10.1038 / srep12827

[0083] 2. DOI: 10.1002 / adfm.201304156

[0084] 3. Patent No. DE 10 2012 203 019 A1.

Claims

1. An electrochemical cell comprising at least an anode current collector, an SO2 solvent-based electrolyte, and a cathode, wherein the SO2 constitutes at least 25% of the solvent material used, and wherein when the cell is assembled in a discharged state, the anode current collector is substantially free of alkali metals during cell assembly, and one or more alkali metals are deposited in metallic form on the anode current collector during charging; wherein the cathode comprises one or more alkali metal halides containing fluorides and one or more elemental transition metals containing Cu, wherein the one or more alkali metal halides containing fluorides are selected from LiF and NaF.

2. The electrochemical cell of claim 1, wherein the anode current collector comprises a carbon-coated metal, an alloy of two or more metals, or a carbon-coated alloy of two or more metals.

3. The electrochemical cell of claim 2, wherein the carbon-coated metal comprises carbon-coated aluminum and / or wherein the alloy comprises a copper-nickel alloy.

4. The electrochemical cell of claim 1, wherein the cathode comprises one or more additional elemental transition metals and / or one or more partially oxidized transition metals.

5. The electrochemical cell of claim 4, wherein at least one of the one or more partially oxidized transition metals is a component of a partially oxidized transition metal compound.

6. The electrochemical cell of claim 5, wherein at least one of the one or more partially oxidized transition metal compounds is M. y The form A is where M is a partially oxidized transition metal, A is an oxidizing agent, and y is the M / A ratio that causes the transition metal to be in a partially oxidized state.

7. The electrochemical cell of claim 6, wherein at least one of the one or more oxidants A is oxygen, nitrogen, sulfur, antimony, or cyanide, or any combination thereof.

8. The electrochemical cell according to any one of claims 5-7, wherein at least one of the one or more partially oxidized transition metal compounds is an oxide, sulfide, halide, cyanide, nitride, or any combination thereof.

9. The electrochemical cell of claim 8, wherein at least one of the one or more transition metal halides comprises Cu. y Br, Cu y I, Cu y Cl, Cu y F or any combination thereof, where y is greater than 0.

5.

10. The electrochemical cell of claim 8, wherein at least one of the one or more partially oxidized transition metal oxides includes Cu. y O, where y is greater than 1.

11. The electrochemical cell of any one of claims 4, wherein at least one of the one or more elemental transition metals includes copper.

12. The electrochemical cell of claim 1, wherein the cathode further comprises one or more additional alkali metal halides.

13. The electrochemical cell of claim 12, wherein the one or more additional alkali metal halides include NaCl, NaBr, NaI, LiCl, LiBr, LiI, or any combination thereof.

14. The electrochemical cell according to any one of claims 12-13, wherein, During assembly, the molar ratio of alkali metal halide to transition metal compound is greater than 1:

0.

15. The electrochemical cell of claim 1, wherein the SO2 solvent-based electrolyte includes a halide salt additive as an SEI film-forming additive.

16. The electrochemical cell of claim 15, wherein the halide salt additive includes a fluorine salt additive.

17. The electrochemical cell of claim 16, wherein the fluorinated salt additive comprises sodium Na-DFOB difluoro-oxalate-borate, lithium Li-DFOB lithium difluoro-oxalate-borate, sodium Na-Triflate trifluoromethane-sulfonate, lithium Li-Triflate trifluoromethane-sulfonate, or combinations thereof.

18. The electrochemical cell of claim 1, wherein the SO2 solvent-based electrolyte comprises a mixture of alkali metal electrolyte salts.

19. The electrochemical cell of claim 18, wherein the alkali metal electrolyte salt is a lithium and sodium electrolyte salt.

20. The electrochemical cell of claim 19, wherein the electrolyte salt comprises a mixture of LiAlCl4 and NaAlCl4.

21. The electrochemical cell of claim 1, wherein one or more additional non-soluble solid alkali metal halides are added to the cell.

22. The electrochemical cell of claim 21, wherein the additional non-soluble solid alkali metal halide comprises NaF, NaCl, NaBr, NaI, LiF, LiCl, LiBr, LiI, or any mixture thereof.

23. The electrochemical cell of claim 1, wherein the cell further comprises a spacer between the anode current collector and the cathode.

24. Use of the electrochemical cell according to any one of claims 1-23 in a device.

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