Solid electrolyte for anode-free metal battery cells

Abstract

To provide a solid electrolyte for an anode-free metal battery cell.SOLUTION: The present invention relates to a solid-state electrolyte (SSE) for an anode-free metal battery cell, wherein the metal is an alkali metal, an alkaline earth metal or a metal of group Ib, IIb or IIIa of the periodic table, the SSE comprising a non-aqueous solvent, a metal salt of an alkali metal, an alkaline earth metal or a metal of group Ib, IIb or IIIa of the periodic table, an aluminum-based halogenated compound AlXn, and a bis (fluorosulfonyl) imide anion, wherein X is a halogen atom and n is from 1 to 6. The invention further relates to a method of making such an SSE, the method comprising preparing a liquid precursor and exposing the liquid precursor to a temperature between 20 °C and 80 °C to solidify the liquid precursor, thereby obtaining a solid electrolyte.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a solid electrolyte for an anode-free metal battery cell.The present invention relates to a method for producing a solid electrolyte for an anode-free metal battery cell. [Background technology]

[0002] Recently, the development and improvement of batteries for various devices requiring batteries, such as mobile phones, wireless household appliances, and electric cars and motorcycles, has become an important area of ​​research and interest. In particular, the field of secondary batteries continues to advance with the development of smaller, thinner batteries with improved life spans.

[0003] In response to these recent developments, lithium secondary batteries, which have lithium metal as the active material, have attracted attention. Lithium metal is known to have a low redox potential (-3.045 V vs. the standard hydrogen electrode) and a high gravimetric energy density (3860 mAh / g), making it an attractive material for the cathode (negative electrode).

[0004] It is known to use lithium metal as the cathode by adhering lithium foil to the negative electrode current collector. However, since lithium is an alkali metal, it reacts with water and oxygen due to its high reactivity. This has the drawback that such batteries are considered dangerous, for example, due to the risk of explosion in the event of leakage into the environment. Handling lithium foil is also dangerous.

[0005] Additionally, when lithium metal is exposed to air, oxidation typically results in the formation of an oxide layer, which acts as an insulator, thereby increasing electrical resistance and therefore reducing battery performance.

[0006] To solve this problem, anode-free battery cells have been developed. These battery cells typically contain only a negative current collector, and a metal (e.g., lithium) layer as the negative electrode is formed (deposited) in situ on the negative current collector during battery charging and consumed during battery discharge.

[0007] U.S. Patent Application Publication No. 2016 / 0261000 (Patent Document 1) discloses an anode-free rechargeable battery including a negative electrode current collector, a separator, and a positive electrode. The battery further includes a liquid electrolyte including a salt or salt mixture containing an active metal cation (e.g., lithium ion) dissolved in a non-aqueous solvent, solvent mixture, or polymer. The separator can be injected with the electrolyte. During charging of the battery, a negative electrode is formed in situ on the surface of the negative electrode current collector.

[0008] A drawback of the above electrolytes is that they are liquids, which can lead to leakage of the electrolyte from the battery, resulting in loss of functionality. Another drawback is that the metal (e.g., lithium) ions interact with the solvent, thereby reducing the amount of ions available for in situ deposition as the negative electrode layer.

[0009] U.S. Patent Application Publication No. 2020 / 0203757 (Patent Document 2) discloses a lithium secondary battery including an anode, a cathode current collector, a separator, and an electrolyte inserted between the electrodes. The electrolyte is a gel polymer electrolyte that can be crosslinked. The gel polymer electrolyte includes a polymer matrix and a lithium salt dissolved in an organic solvent mixture. A lithium metal layer is formed in situ on the cathode current collector during charging.

[0010] A drawback of gel polymer electrolytes is that their lithium ion conductivity is known to be low, typically less than 1 mS / cm. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] US Patent Application Publication No. 2016 / 0261000 [Patent Document 2] U.S. Patent Application Publication No. 2020 / 0203757 Summary of the Invention

[0012] It is an object of the present invention to overcome one or more of the aforementioned drawbacks. It is an object of the present invention to provide an improved solid electrolyte for anode-free metal battery cells. In particular, it is an object of the present invention to provide a solid electrolyte that is more stable chemically, physically, and electrochemically.

[0013] It is an objective to provide a solid electrolyte that allows for reducing or minimizing interactions between the electrolyte and metal ions in a battery cell during use.

[0014] It is a further object to provide a solid electrolyte for an anode-free battery cell that improves the performance of the battery cell and / or extends the life of the battery cell compared to electrolytes for anode-free battery cells in the art.

[0015] It is also an object of the present invention to provide a method for producing an improved solid electrolyte for anode-free metal battery cells that involves a limited number of processing steps.

[0016] In a first aspect of the present invention, there is provided a solid state electrolyte (SSE) for an anode-free metal battery cell, as set out in the accompanying claims.

[0017] The metal of the anode-free metal battery cell is an alkali metal, alkaline earth metal, or metal from Group Ib, IIb, or IIIa of the periodic table. The metal is preferably lithium, sodium, magnesium, aluminum, zinc, or silver.

[0018] The solid electrolyte comprises a non-aqueous solvent, in other words, the SSE comprises at least one, for example, two or more, non-aqueous solvents.

[0019] The solid electrolyte further comprises a metal salt. In other words, the SSE comprises at least one, e.g., two or more, metal salts. The metal salt is an alkali metal, an alkaline earth metal, or a metal salt of Group Ib, IIb, or IIIa of the periodic table.

[0020] The metal of the metal salt is preferably lithium, sodium, magnesium, aluminum, zinc or silver, in other words, the metal salt is preferably a lithium salt, a sodium salt, a magnesium salt, an aluminum salt, a zinc salt or a silver salt.

[0021] When the SSE includes two or more metal salts, the metals can be the same or different. For example, but not limited to, the SSE can include a combination of two lithium salts or a lithium salt and a magnesium salt.

[0022] As is well known, metal salts advantageously contain anions. As is well known, metal salts advantageously also contain cations. Advantageously, the cation is the cation of the metal of the metal salt. For example, if the metal salt is a lithium salt, the cation is the lithium cation (Li + )

[0023] The solid electrolyte is an aluminum-based halide compound, AlX n and / or polymeric versions thereof, wherein X is a halogen atom. Advantageously, n is 1 to 6, for example 1 to 3. Advantageously, X is chloride, bromide, or iodide, preferably chloride. Advantageously, AlX n The polymer type of (AlX n ) m where m is 2 or greater.

[0024] Advantageously, X is chloride, n is 3, and the aluminum-based halide compound is AlCl. Advantageously, X is chloride, n is 3, m is 2 or more, and the polymeric aluminum-based halide compound is (AlCl). m is.

[0025] The inventors have surprisingly found that the aluminum-based halide compounds AlX in solid electrolytes n and / or the presence of these polymeric forms can protect non-aqueous solvents. In particular, aluminum-based halide compounds AlX and AlX+ during use in anode-free metal battery cells. n The polymeric form of either of these, when present, reduces or even minimizes any interaction between the non-aqueous solvent of the SSE and the metal ions that migrate through the SSE during charging and discharging of the battery cell. Thus, the aluminum-based halide compounds AlX in the SSE n The presence of these polymeric forms advantageously allows the functionality of the SSE to be maintained, and their presence also advantageously reduces metal ion depletion in the anode-free battery cell, thereby enhancing the performance and lifespan of the anode-free battery cell.

[0026] The solid electrolyte further comprises a bis(fluorosulfonyl)imide (FSI) anion. The inventors have surprisingly found that the presence of the FSI anion in the SSE is related to the presence of an aluminum-based halide compound, AlX n and / or have found that the solid-state properties of electrolytes containing these polymeric forms can be maintained.

[0027] In other words, the inventors have realized that without the presence of the FSI anion, the essentially solid-state nature of the electrolyte cannot be realized, i.e., the electrolyte remains a liquid electrolyte. Without wishing to be bound by any theory, the inventors believe that the presence of the FSI anion is due to the interaction of the fluoride atom of the FSI anion with the aluminum-based halide compound AlX. n It is believed that the present invention allows for the establishment of strong interactions between AlX and any of these polymer types, regardless of which is present in the SSE. This strong interaction is advantageously n and / or provide a network of one or more FSI anions in these polymeric solid-state matrices. The presence of one or more FSI anions in the network may be AlX nThe inventors believe that immobilizing the FSI anions and / or in these polymeric solid-state matrices imparts higher transference numbers to the electrolyte, thereby contributing to the increased overall efficiency of battery cells in which the solid electrolytes of the present invention are used, compared to conventional SSEs.

[0028] Advantageously, the molar ratio of metal salt to aluminum-based halide compound and / or their polymeric form in the solid electrolyte is from 1:2 to 50:1, preferably from 1:1 to 30:1, for example from 2:1 to 20:1, more preferably from 3:1 to 10:1.

[0029] Advantageously, the molar ratio of FSI anions to aluminum-based halogenated compounds and / or their polymeric forms in the solid electrolyte is from 1:2 to 50:1, preferably from 1:1 to 30:1, for example from 2:1 to 20:1, more preferably from 3:1 to 10:1.

[0030] In the first embodiment of the solid electrolyte of the present disclosure, the anion of the metal salt is FSI, for example, the metal of the metal salt is lithium (Li), and the metal salt is advantageously LiFSI.

[0031] Optionally, in the first embodiment, the SSE may contain at least one additional metal salt, for example, a second, third, or fourth metal salt. Any additional metal salt also contains a cation and an anion, as is well known. Advantageously, the anion of the at least one additional metal salt is FSI, bis(trifluoromethane)sulfonimide (TFSI), dicyanamide (DCA), perchloric acid (ClO), sodium tetrachloroaluminate (AlCl), difluorobis(oxalato)borate (DFOB), or hexafluorophosphate (PF).

[0032] For example, the SSE may contain two metal salts, such as LiFSI and NaFSI, both of which have different cations and both have FSI as the anion. For example, the SSE may contain three metal salts, at least one of which has FSI as the anion. Advantageously, when the SSE contains three metal salts, one of the salts contains FSI as the anion and the other two metal salts have the same or different cations and / or the same or different anions, such as LiFSI as the first FSI-containing metal salt and LiTFSI and LiPF6 as the second and third metal salts, respectively.

[0033] Advantageously, when the metal salt or at least one anion of the two or more metal salts is FSI, the non-aqueous solvent is selected from the group consisting of nitriles, ethers, esters, carbonates, sulfones, amides, and ionic liquids. Preferred examples of non-aqueous solvents include, but are not limited to, acetonitrile, dimethoxyethane, and ionic liquids.

[0034] Ionic liquids are known in the art as salts that are in liquid form at moderate temperatures without the need for the salt to be dissolved in another solvent. Ionic liquids are typically composed of ions—cations and anions. Advantageously, when the non-aqueous solvent is an ionic liquid, it contains an organic cation and an inorganic or organic anion.

[0035] In a second embodiment of the solid electrolyte of the present disclosure, the non-aqueous solvent is an ionic liquid in which the anion of the ionic liquid is FSI.

[0036] Optionally, in the first embodiment, the SSE may comprise at least one further non-aqueous solvent. Advantageously, the at least one further non-aqueous solvent is selected from the group consisting of nitriles, ethers, esters, carbonates, sulfones, amides, and ionic liquids. Preferred examples of the at least one further non-aqueous solvent include acetonitrile, dimethoxyethane, and ionic liquids.

[0037] When one of the second or further non-aqueous solvents is an ionic liquid, the anion thereof is preferably FSI, TFSI, DCA, AlCl4, ClO4, DFOB, or PF6. For example, an SSE may include two ionic liquids as non-aqueous solvents, each having FSI as the anion and a different cation. Alternatively, each ionic liquid may have different anions, one of which is FSI, and the same cation. In other words, the anion of the second or further ionic liquid as a non-aqueous solvent may be other than FSI.

[0038] Advantageously, when the non-aqueous solvent or at least one of the two or more non-aqueous solvents is an ionic liquid having an FSI anion, the anion of the metal salt of the SSE is TFSI, DCA, DFOB, ClO4, AlCl4, or PF6.

[0039] A third embodiment of the solid electrolyte of the present disclosure includes a combination of the first and second embodiments. In other words, in the third embodiment, the anion of at least one of the metal salt or two or more metal salts is FSI, and the non-aqueous solvent or at least one of the two or more non-aqueous solvents is an ionic liquid, and the anion thereof is FSI.

[0040] In a second aspect of the present invention, there is provided a method for producing a solid electrolyte (SSE) for an anode-free metal battery cell, as set out in the accompanying claims.

[0041] The metal in the anode-free metal battery cell is an alkali metal, alkaline earth metal, or metal from Group Ib, IIb, or IIIa of the periodic table. Advantageously, the metal is lithium, sodium, magnesium, aluminum, zinc, or silver.

[0042] The method includes preparing a liquid precursor and solidifying the liquid precursor. The liquid precursor is an aluminum-based halide compound, AlX n and a metal salt in a non-aqueous solvent.

[0043] Aluminum-based halide compounds AlX n is advantageously as defined hereinbefore. Advantageously, n is 1 to 6, for example 1 to 3. Advantageously, X is chloride, bromide or iodide, preferably chloride.

[0044] Advantageously, X is chloride, n is 3 and the aluminium-based halide compound is AlCl3. Alternatively or additionally, the aluminium-based halide compound is M y AlX n where X is a halogen atom, n is 1 to 6, M is a metal cation, and y is at least 1. Advantageously, the metal cation is an alkali metal, an alkaline earth metal, or a metal from Group Ib, IIb, or IIIa of the periodic table. In particular, the metal cation is a lithium cation, a sodium cation, or a magnesium cation. For example, when the metal cation is sodium, y is 3, X is F, n is 6, and the aluminum-based halide compound is NaAlF.

[0045] The metal salt is advantageously as described hereinbefore. Advantageously, the metal salt is a metal salt of an alkali metal, an alkaline earth metal or a metal of group Ib, IIb or IIIa of the periodic table.

[0046] The non-aqueous solvent is advantageously as described hereinbefore. For example, the non-aqueous solvent may be an ionic liquid. Advantageously, suitable ionic liquids are as described hereinbefore.

[0047] The liquid precursor further comprises bis(fluorosulfonyl)imide (FSI) anions. Advantageously, the FSI anions in the liquid precursor are provided by or present via a metal salt (or at least one of two or more metal salts) and / or a non-aqueous solvent (or at least one of two or more non-aqueous solvents) that is an ionic liquid having FSI anions as their anions.

[0048] Advantageously, aluminum-based halide compounds AlXn and / or the metal salt is at least partially soluble in the non-aqueous solvent.

[0049] Advantageously, the concentration of the metal salt in the liquid precursor is between 0.5 and 6M.

[0050] The liquid precursor is solidified by exposure to an elevated temperature. Advantageously, the temperature is between 20°C and 120°C, preferably between 20°C and 100°C, more preferably between 20°C and 80°C. Upon exposure of the liquid precursor to such a temperature, a solid electrolyte is obtained. Advantageously, the liquid precursor is exposed to a temperature between 20°C and 120°C for a period (i.e., duration) sufficient to solidify the liquid precursor.

[0051] Advantageously, upon exposure of the liquid precursor to temperatures between 20°C and 120°C, aluminum-based halide compounds AlX n solidifies, whereby the resulting SSE is converted into an aluminum-based halide compound, AlX n and / or polymeric versions thereof. Aluminum-based halide compounds AlX n The polymeric form of is advantageously as described hereinbefore.

[0052] In a third aspect of the present invention, there is provided the use of a solid electrolyte (SSE) according to the first aspect for the deposition of a metal layer in an anode-free metal battery cell.

[0053] Advantages of the present invention include, but are not limited to, that the solid electrolyte enables deposition of a metal layer in an anode-free metal battery cell, thereby reducing metal ion loss due to interaction with the electrolyte solvent. In other words, the SSE is advantageously substantially chemically and electrochemically stable, thereby extending the life of the battery cell in which the SSE is used.

[0054] An advantage of the method for producing SSEs of the present invention is that the method has a limited number of processing steps. A further advantage is that the method can be carried out at moderate or light processing conditions without requiring extremely high temperatures or high pressures or vacuums. Aspects of the present invention will now be described in more detail with reference to the accompanying drawings, in which like reference numerals refer to like features, and in which: [Brief explanation of the drawings]

[0055] [Figure 1] 1 shows a Raman spectrum of a solid electrolyte according to the present invention. [Figure 2] 1 shows a Raman spectrum of another solid electrolyte according to the present invention. [Figure 3] 1 shows a Raman spectrum of a further solid electrolyte according to the present invention. [Figure 4] 1 shows the voltage (V) of an electrochemical cell having copper and Li foils as individual electrodes and an SSE of the present invention, and the subsequent dissolution of deposited lithium as a function of cell capacity on the copper foil. [Figure 5] 1 shows the voltage (V) of electrochemical cells with copper foil and Li foil as individual electrodes, and an SSE of the present invention, and with a reference liquid electrolyte, as a function of cell capacity during lithium dissolution after the first lithium deposition. [Figure 6] 1 shows the voltage of a battery cell having an SSE of the present invention as a function of specific charge per gram of active material. DETAILED DESCRIPTION OF THE INVENTION

[0056] As explained above, the solid electrolyte (SSE) of the present disclosure comprises at least one metal salt and at least one non-aqueous solvent.

[0057] SSE also contains aluminum-based halide compounds, AlX n and / or polymeric versions thereof, wherein X is a halogen atom and n is 1-6.

[0058] Alternatively or additionally, the aluminum-based halide compound may be M y AlX nwhere X is a halogen atom, n is 1 to 6, M is a metal cation, and y is at least 1. Advantageously, the metal cation is an alkali metal, an alkaline earth metal, or a metal from Group Ib, IIb, or IIIa of the periodic table. In particular, the metal cation is a lithium cation, a sodium cation, or a magnesium cation. For example, when the metal cation is sodium, y is 3, X is F, n is 6, and the aluminum-based halide compound is NaAlF.

[0059] The solid electrolyte further comprises at least one bis(fluorosulfonyl)imide (FSI) anion.

[0060] Advantageously, and according to a first embodiment, the source of FSI anions in the solid electrolyte is a metal salt.

[0061] Advantageously, when the SSE comprises one metal salt, the metal salt has as anion the FSI anion. The metal salt having the FSI anion is advantageously as described herein above in the first embodiment.

[0062] Advantageously, when the SSE comprises two or more metal salts, at least one of the metal salts has FSI as the anion. Advantageously, the anions of the other metal salts, i.e., the metal salts without the FSI anion, can be any anion known in the art. Non-limiting examples include bis(trifluoromethane)sulfonimide (TFSI or (SOCF)N), dicyanamide (DCA), perchloric acid (ClO), hexafluorophosphate (PF), difluorobis(oxalato)phosphate (DFBOP), difluorobis(oxalato)borate (DFOB), tetrafluoroborate (BF), hexafluoroarsenic acid (AsF), sodium tetrachloroaluminate (AlCl), (fluoromethylsulfonyl)(trifluoromethylsulfonyl)imide (FTFSI), and trifluoromethanesulfonate (CFSO).

[0063] Advantageously, the cation of the metal salt is an ion of an alkali metal, an alkaline earth metal, or a metal from group Ib, IIb, or IIIa of the periodic table. Advantageously, the alkali metal is lithium (Li), sodium (Na), or potassium (K). Advantageously, the alkaline earth metal is beryllium (Be), magnesium (Mg), or calcium (Ca). Advantageously, the group Ib metal is silver (Ag) or gold (Au). Advantageously, the group IIb metal is zinc (Zn) or cadmium (Cd). Advantageously, the group IIIa metal is aluminum (Al).

[0064] Preferred examples of metal salts with FSI as the anion are LiFSI, NaFSI, KFSI, Mg(FSI)2 and Al(FSI)3, especially LiFSI.

[0065] In a further first embodiment, when the SSE contains two or more metal salts, they may have the same or different cations and / or the same or different anions, and at least one metal salt has FSI as the anion. For example, when the SSE contains two metal salts, they may have different cations and the same anion, such as LiFSI and NaFSI. For example, when the SSE contains two metal salts, they may have the same cation and different anion, and one of them is FSI, such as LiFSI and LiTFSI.

[0066] The SSE comprises one or more non-aqueous solvents. The non-aqueous solvents are preferably as described herein above. Non-limiting examples of suitable solvents include acetonitrile, dimethoxyethane (also known as 1,2-dimethoxyethane), propylene carbonate, ethylene carbonate, tetrahydrofuran, diethyl carbonate, γ-butyrolactone, 2-methyltetrahydrofuran, 1-3 dioxolane, tetramethylsulfone (sulfolane), dimethylsulfone (DMSO), and ionic liquids. Advantageously, ionic liquids suitable as non-aqueous solvents are as described herein above.

[0067] Non-limiting examples of cations of ionic liquids suitable as non-aqueous solvents according to the first embodiment are 1-butyl-1-methylpyrrolidinium, N-butyl-N-methylpyrrolidinium, 1-propyl-1-methylpyrrolidinium, N-propyl-NN-methylpyrrolidinium, and 1-ethyl-1-methylpyrrolidinium.

[0068] Advantageously, according to the first embodiment, the ionic liquid does not have FSI as an anion. Non-limiting examples of suitable anions include TFSI, DCA, ClO4, PF6, DFBOP, DFOB, BF4, FTFSI, AlCl4, AsF6, and CF3SO3.

[0069] According to a second embodiment, the source of the FSI anions in the solid electrolyte is a non-aqueous solvent. Advantageously, the non-aqueous solvent containing the FSI anions is an ionic liquid.

[0070] Advantageously, when the SSE comprises one non-aqueous solvent, the non-aqueous solvent is an ionic liquid having as an anion the FSI anion. The ionic liquid having the FSI anion is advantageously as described above in the Summary of the Invention section as the second embodiment.

[0071] Advantageously, when the SSE comprises two or more non-aqueous solvents, at least one of the plurality of non-aqueous solvents is an ionic liquid having an FSI anion.

[0072] Advantageously, when the SSE comprises two or more non-aqueous solvents, at least one of the plurality of non-aqueous solvents is an ionic liquid having FSI as the anion. Advantageously, the other solvents, i.e., solvents that are not ionic liquids having the FSI anion, are as described hereinabove. Non-limiting examples include acetonitrile, dimethoxyethane (also known as 1,2-dimethoxyethane), propylene carbonate, ethylene carbonate, tetrahydrofuran, diethyl carbonate, γ-butyrolactone, 2-methyltetrahydrofuran, 1,3 dioxolane, tetramethyl sulfone, dimethyl sulfone, and ionic liquids having anions other than FSI.

[0073] Non-limiting examples of anions of ionic liquids having anions other than FSI include TFSI, DCA, ClO4, PF6, DFBOP, DFOB, BF4, FTFSI, AlCl4, AsF6, and CF3SO3.

[0074] Non-limiting examples of cations of ionic liquids suitable as non-aqueous solvents, i.e., having as anion FSI or another anion as described herein above according to the second embodiment, include 1-butyl-1-methylpyrrolidinium, N-butyl-N-methylpyrrolidinium, 1-propyl-1-methylpyrrolidinium, N-propyl-NN-methylpyrrolidinium, and 1-ethyl-1-methylpyrrolidinium.

[0075] Non-limiting examples of ionic liquids having an FSI anion are 1-butyl-1-methylpyrrolidinium FSI, N-butyl-N-methylpyrrolidinium FSI, 1-propyl-1-methylpyrrolidinium FSI, N-propyl-NN-methylpyrrolidinium FSI, and 1-ethyl-1-methylpyrrolidinium FSI.

[0076] The SSE further comprises one or more metal salts. Advantageously, the cations of the metal salts are as described hereinabove. Non-limiting examples of suitable anions of the metal salts include TFSI, DCA, ClO, PF, DFBOP, DFOB, BF, FTFSI, AlCl, AsF, and CFSO.

[0077] According to a third embodiment, the source of the FSI anions in the solid electrolyte is a metal salt and a non-aqueous solvent. Advantageously, the non-aqueous solvent containing the FSI anions is an ionic liquid.

[0078] Advantageously, the metal salt as the source of the FSI anion is as described herein above in the first embodiment. The SSE may comprise one or more further metal salts, for example, a second, third, or fourth metal salt. When the SSE comprises multiple metal salts, for example, at least two metal salts, they are advantageously as described herein above in the first embodiment.

[0079] Advantageously, the non-aqueous solvent as a source of FSI anions is as described herein above in the second embodiment. The SSE may comprise one or more further non-aqueous solvents. When the SSE comprises multiple non-aqueous solvents, for example at least two non-aqueous solvents, they are advantageously as described herein above in the second embodiment.

[0080] Example Example 1 A first liquid precursor was prepared by adding 11.22 g of LiFSI as a metal salt and 2.66 g of AlCl to 8.00 g of acetonitrile (ACN). The liquid precursor was then kept at a temperature of 20 °C for 24 hours to obtain a solid electrolyte (SSE).

[0081] The SSE contained 51.28 wt% LiFSI, 12.16 wt% AlCl3, and 36.56 wt% ACN, based on the total weight of the SSE.

[0082] The presence of AlCl and / or one or more of these polymeric forms in the compositions was analyzed by Raman spectroscopy. To minimize moisture absorption by the SSE samples, the SSEs were deposited in silicon wafers and placed in sealed plastic pouches.

[0083] The Raman spectrum was acquired using a green laser with a wavelength of 532 nm. Figure 1 shows the acquired spectrum. -1 The peak at 385 cm originates from the silicon wafer. -1 This peak 2 is a broad peak at the position of (AlCl3) mThis is attributed to the polymeric form of AlCl3, denoted as , and also called "higher-order AlCl3 polymers." It is the only prominent feature in the spectrum of the solid electrolyte. However, this does not exclude the possibility of the presence of (limited amounts of) AlCl3 in the SSE.

[0084] Example 2 A second liquid precursor was prepared by adding 5.62 g of LiFSI as a metal salt and 2.00 g of AlCl to 4.00 g of acetonitrile (ACN). The liquid precursor was then kept at a temperature of 20 °C for 24 hours to obtain a (second) solid electrolyte (SSE).

[0085] The SSE contained 48.38 wt% LiFSI, 17.21 wt% AlCl3, and 34.41 wt% ACN, based on the total weight of the SSE.

[0086] The presence of AlCl and / or one or more of these polymeric forms in the compositions was analyzed by Raman spectroscopy. To minimize moisture absorption by the SSE samples, the SSEs were deposited in silicon wafers and placed in sealed plastic pouches.

[0087] The Raman spectrum was acquired using a green laser with a wavelength of 532 nm. Figure 2 shows the acquired spectrum. -1 Peak 3 in the spectrum originates from the silicon wafer. The average feature value of the spectrum is 385 cm -1 This peak 4 is a broad peak at the position of (AlCl3) m This is attributed to the polymeric form of AlCl3, denoted as α, and is the only prominent feature in the spectrum of the solid electrolyte. However, this does not exclude the possibility of the presence of (limited amounts of) AlCl3 in the SSE.

[0088] Compared to the liquid precursor used to obtain the SSE of Example 1, the liquid precursor used to obtain the SSE of Example 2 has a higher amount (in wt%) of AlCl, which results in peak 4 having a higher intensity than peak 2.

[0089] Example 3 A third liquid precursor was prepared by adding 9.35 g of LiFSI as a metal salt and 2.22 g of AlCl to 9.00 g of dimethoxyethane (DME). The resulting suspension was then heated to 60°C for 10 minutes to obtain a homogeneous mixture of the components, thereby obtaining a liquid precursor. The liquid precursor was then maintained at a temperature of 20°C for 24 hours to obtain a (third) solid electrolyte (SSE).

[0090] The SSE contained 45.46 wt % LiFSI, 10.78 wt % AlCl 3 and 43.76 wt % DME, based on the total weight of the SSE.

[0091] The presence of AlCl and / or one or more of these polymeric forms in the compositions was analyzed by Raman spectroscopy. To minimize moisture absorption by the SSE samples, the SSEs were deposited in silicon wafers and placed in sealed plastic pouches.

[0092] The Raman spectrum was acquired using a green laser with a wavelength of 532 nm. Figure 3 shows the acquired spectrum. -1 Peak 5 originates from the silicon wafer. The average feature value of the spectrum is 385 cm -1 The broad peak 6 at position 0.05 is assigned to the polymeric form of AlCl3 and is the only prominent feature in the spectrum of the solid electrolyte. However, this does not exclude the possibility of the presence of (limited amounts of) AlCl3 in the SSE.

[0093] Example 3 shows that the presence of AlCl3 and / or one or more polymeric forms thereof in the SSE is not related to the use of ACN as the solvent (which was used in Examples 1 and 2).

[0094] Example 4 Two anode-free lithium metal battery cells were prepared. The first battery cell was prepared using a liquid precursor that had not yet solidified into an electrolyte. The second battery cell was prepared using the same electrolyte composition, but after solidification at 20°C for 24 hours. The second battery cell was therefore prepared using an SSE according to the present invention.

[0095] A liquid precursor was prepared by adding 12.00 g of LiFSI as a metal salt, 5.00 g of AlCl, and 0.40 g of LiCl to 11.00 g of ACN and 1.00 g of toluene (non-aqueous solvent). In other words, both the liquid precursor and the SSE precursor (i.e., the solidified liquid precursor) contained 40.82 wt% LiFSI, 17.01 wt% AlCl, 1.36 wt% LiCl, 37.41 wt% ACN, and 3.40 wt% toluene, based on the total weight of the electrolyte.

[0096] A 25 μm-thick lithium foil laminated on copper foil was used as the positive electrode and positive current collector. Copper foil was used as the negative current collector. A three-layer ceramic separator, consisting of one layer of polyethylene sandwiched between two layers of polyvinylidene fluoride, was placed between the positive and negative current collectors.

[0097] The anode-free lithium metal battery cell was then discharged for 1 hour at 1 mA, or 0.15 mA / cm2 of the lithium surface. 2 The battery cells were then charged to 0.5 V. The battery cells were then cycled up to 50 times (i.e., 50 charge / discharge cycles). The coulombic efficiency was measured for both battery cells after 1, 2, 3, 4, 5, and 50 cycles. The results are shown in Table 1.

[0098] Table 1: Coulombic efficiency of anode-free Li metal battery cells TIFF2026003070000002.tif102170

[0099] From Table 1, it is clear that the battery cells with the SSE of the present disclosure exhibit good deposition of lithium on the copper foil negative current collector, resulting in a coulombic efficiency after one cycle that is already more than double the highest coulombic efficiency measured in a battery cell with the same electrolyte composition, but in solid form (38.2% vs. 17.2%).

[0100] Furthermore, the coulombic efficiency for the battery cell with the SSE of the present invention increases with each charge / discharge cycle, reaching 92.7% after 50 cycles. However, the coulombic efficiency of the battery cell with the liquid electrolyte undergoes an initial decrease in coulombic efficiency after 2 cycles, after which it increases slightly, but the value remains extremely low, much lower than that obtained for the anode-free lithium metal battery cell with a solid electrolyte.

[0101] Example 5 To evaluate the performance of an anode-free lithium metal battery cell including an SSE of the present invention in conjunction with an anode-free lithium metal battery cell including a reference electrolyte, two anode-free electrochemical cells were prepared: the first electrochemical cell was prepared using an SSE of the present invention, and the second electrochemical cell was prepared using a reference liquid electrolyte.

[0102] A liquid precursor was prepared by adding 12.65 g of LiFSI as a first metal salt, 19.42 g of LiTFSI as a second metal salt, 3.00 g of AlCl, and 2.02 g of HFE as a surfactant to 20.25 g of DME as a non-aqueous solvent.

[0103] The reference liquid electrolyte contained 40.00 wt. % LiFSI, 30.00 wt. % HFE as a surfactant, and 30.00 wt. % DME, based on the total weight of the liquid electrolyte, and therefore did not contain AlCl.

[0104] The electrochemical cell was prepared as a bi-stack pouch cell containing a copper foil sandwiched between two lithium foils as individual electrodes. A three-layer ceramic separator, consisting of one layer of polyethylene sandwiched between two layers of polyvinylidene fluoride, was placed between the positive and negative current collectors.

[0105] The liquid precursor was provided in a battery cell in a liquid state and then maintained at a temperature of 60°C for 24 hours, thereby obtaining a solid electrolyte (SSE) containing 22.07 wt% LiFSI, 33.87 wt% LiTFSI, 5.23 wt% AlCl, 3.53 wt% HFE, and 35.31 wt% DME based on the total weight of the SSE.

[0106] In situ lithium deposition on the Cu negative electrode current collector was carried out using a galvanostatic method at 1 mA for 1 h (0.066 mA / cm for the Cu surface). 2 ).

[0107] Next, the voltage of the battery cell (or Li / Li) due to the cell capacity during charging and discharging of the battery cell + The potential (potential with respect to the potential) was measured at room temperature.

[0108] 4 shows the results of lithium deposition and dissolution for an electrochemical cell having copper foil and Li foil as separate electrodes and an SSE of the present invention. The measured voltage is shown as a function of cell capacity for the first dissolution of the deposited lithium (8a), the second lithium deposition on the copper foil (7), and the second dissolution of the deposited lithium (8b).

[0109] FIG. 5 shows the first lithium dissolution of deposited lithium for a reference electrochemical cell (liquid electrolyte; line 10) and for an electrochemical cell with an SSE of the present invention (line 9). The electrochemical cells had copper foil and Li foil as separate electrodes. The capacity ratio of curves 9 and 10 represents the coulombic efficiency of the first cycle. A capacity of 1 mAh corresponds to a coulombic efficiency of 100%. It is clear from FIG. 5 that the reference battery cell had a coulombic efficiency of only 48%, while the battery cell with an SSE of the present invention had a coulombic efficiency of 90%.

[0110] Example 6 Another anode-free battery cell was prepared using the SSE of Example 5. Again, the liquid precursor was placed in the battery cell and kept at 60° C. for 24 hours to obtain the SSE.

[0111] The anode-free battery cells were prepared as bi-stack pouch cells containing two copper foils as negative current collectors sandwiching a positive electrode containing NCA as the active material. A three-layer ceramic separator, consisting of one layer of polyethylene sandwiched between two layers of polyvinylidene fluoride, was placed between the positive and negative current collectors.

[0112] Next, the battery cell was charged and discharged at 5 mA using a galvanostatic method (0.39 mA / cm on the positive electrode surface). 2 ), the cell potential was measured at room temperature as a function of the specific charge per gram of active material. The results are shown in Figure 6, where line 11 represents the charge curve and line 12 represents the discharge curve. It is clear from Figure 6 that 158 ​​mAh / g of the predicted 170 mAh / g is usable. In other words, only 12 mAh / g is lost during the initial in situ lithium deposition. [Explanation of symbols]

[0113] 1. Silicon wafer peaks in the Raman spectrum 2. Polymeric AlCl3 peaks in the Raman spectrum 3 Silicon wafer peaks in the Raman spectrum 4. Polymeric AlCl3 peaks in Raman spectra 5. Silicon wafer peaks in Raman spectra 6. Polymeric AlCl3 peaks in Raman spectra 7 First Lithium Deposition Curve 8a First lithium dissolution curve 8b Lithium dissolution curve 9 Lithium dissolution curve 10 Lithium dissolution curve 11 Charging curve 12 Discharge curve

Claims

1. A solid electrolyte for an anode-free metal battery cell, wherein the metal is an alkali metal, an alkaline earth metal, or a metal from Group Ib, Group IIb, or Group IIIa of the periodic table, the solid electrolyte comprising a non-aqueous solvent and a metal salt of the alkali metal, alkaline earth metal, or a metal from Group Ib, Group IIb, or Group IIIa of the periodic table, the solid electrolyte comprising an aluminum-based halide compound AlX ｎ and / or a polymeric form thereof, and further comprising a bis(fluorosulfonyl)imide (FSI) anion, wherein X is a halogen atom and n is 1 to 6.

2. X is chloride, n is 3, and the aluminum-based halide compound is AlCl ３ The solid electrolyte according to claim 1 ,

3. 2. The solid electrolyte of claim 1, wherein the metal is lithium, sodium, magnesium, aluminum, zinc, or silver.

4. 2. The solid electrolyte of claim 1, wherein the molar ratio of said metal salt to said aluminum-based halide compound and / or polymeric form thereof is from 1:2 to 50:

1.

5. 10. The solid electrolyte of claim 1, wherein the metal salt comprises an anion, and the anion of the metal salt is FSI.

6. The method further comprises at least one additional metal salt comprising an anion, wherein the anion of the at least one additional metal salt is selected from the group consisting of FSI, bis(trifluoromethane)sulfonimide (TFSI), dicyanamide (DCA), perchloric acid (ClO ４ ), difluorobis(oxalato)borate (DFOB), or hexafluorophosphate (PF ６ 6. The solid electrolyte according to claim 5, wherein

7. 6. The solid electrolyte of claim 5, wherein the non-aqueous solvent is selected from the group consisting of nitriles, ethers, esters, carbonates, sulfones, amides, and ionic liquids.

8. 8. The solid electrolyte of claim 7, wherein the non-aqueous solvent is acetonitrile, dimethoxyethane, or an ionic liquid.

9. 2. The solid electrolyte of claim 1, wherein the non-aqueous solvent is an ionic liquid containing an anion, and the anion of the ionic liquid is FSI.

10. 1. A method for producing a solid electrolyte for an anode-free metal battery cell, wherein the metal is an alkali metal, an alkaline earth metal, or a metal from Group Ib, IIb, or IIIa of the periodic table, comprising: - aluminum-based halide compounds AlX ｎ and a metal salt in a non-aqueous solvent, thereby obtaining a liquid precursor; - exposing said liquid precursor to a temperature of between 20°C and 80°C for a period of time sufficient to solidify said liquid precursor, thereby obtaining said solid electrolyte; wherein X is a halogen atom, n is 1 to 6, the metal salt is a metal salt of the alkali metal, the alkaline earth metal, or the metal in Group Ib, IIb, or IIIa of the periodic table, and the liquid precursor comprises bis(fluorosulfonyl)imide (FSI) anions.

11. The method for producing a solid electrolyte according to claim 10, wherein the concentration of the metal salt in the liquid precursor is 0.5 to 6M.

12. The aluminum-based halide compound AlX ｎ and / or the metal salt is at least partially dissolved in the non-aqueous solvent.

13. X is chloride, n is 3, and the aluminum-based halide compound is AlCl ３ The method for producing a solid electrolyte according to claim 10,

14. 11. The method for producing a solid electrolyte according to claim 10, wherein the metal salt contains an anion, and the anion of the metal salt is FSI, and / or the non-aqueous solvent is an ionic liquid containing an anion, and the anion of the ionic liquid is FSI.

15. 10. Use of the solid electrolyte of claim 1 for in-situ deposition of said metal layer in an anode-free metal battery cell.

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