Organometallic compounds for metal ion batteries

Abstract

A compound of formula (I): # imgabs0 # wherein X is Al or B; r1 is, independently at each occurrence, a monovalent substituent; r2 is a divalent organic group; and M + is a cation. The compounds of formula (I) are useful as electrolytes in metal or metal ion batteries.

Description

Background Art

[0001] WO 00 / 53611 discloses a compound containing a monoanion of formula (II):

[0002]

[0003] WO 99 / 12938 discloses a polyfluorinated alkoxide coordinated with a transition metal or an element of Group III, IV, or V. The use of the compound in batteries is disclosed.

[0004] Nolan et al., "Nonaqueous Lithium Battery Electrolytes Based on Bis(polyfluorodiolato)borates" 2003 J. Electrochem. Soc. 150 A1726 discloses lithium salts used as battery electrolytes.

[0005] JP2002 / 260734 discloses an electrolyte of formula (1):

[0006]

[0007] US6783896 discloses a compound of formula (I):

[0008]

[0009] EP1075036 discloses a compound of formula (1):

[0010]

[0011] WO2022 / 243470 discloses an electrolyte containing solvated lithium ions. Summary of the Invention

[0012] The present disclosure provides a compound of formula (I):

[0013]

[0014] wherein X is Al or B; R 1 is independently a monovalent substituent at each occurrence; R 2 is a divalent organic group; and M + is a cation.

[0015] Optionally, R 2 is a group of formula (II):

[0016]

[0017] wherein R 3 is independently H or a substituent each time it appears, and Ar 1 is a C 6-20 arylene group or a heteroarylene group.

[0018] Optionally, Ar 1 is an unsubstituted or substituted 1,2-phenylene.

[0019] Optionally, each R 1 is independently selected from C 1-20 alkyl, wherein one or more C atoms other than the C atom or the terminal C atom bonded to the O of OR 1 may be replaced by O, and one or more H atoms may be replaced by F.

[0020] Optionally, X is B.

[0021] Optionally, M + is a lithium ion.

[0022] The present disclosure provides an electrolyte comprising a compound of formula (I) and at least one of a solvent and a polymer.

[0023] Optionally, the electrolyte comprises a solvent selected from C 2-10 alkylene carbonate; di(C 1-10 alkyl) carbonate; a straight-chain, branched-chain or cyclic compound containing two or more ether groups; and mixtures thereof.

[0024] The present disclosure provides a metal battery or a metal ion battery comprising an anode, a cathode, and the electrolyte described herein disposed between the anode and the cathode. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of a battery comprising the compound described herein;

[0026] Figure 2 shows an explanatory Nyquist plot of the initial and steady states of an electrode assembly containing Comparative Compound 1; and

[0027] Figure 3 shows linear sweep voltammograms of Compound Example 1 and Comparative Compounds 1 and 2. DETAILED DESCRIPTION

[0028] Unless the context clearly requires otherwise, throughout the specification and claims, the words “comprise,” “comprising,” and the like shall be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, the meaning of “including but not limited to.” Additionally, as used in this application, the words “herein,” “above,” “below,” and words of similar import refer to the application as a whole and not to any particular portion of the application. Where the context permits, words in the singular or plural of particular embodiments may also include the plural or singular, respectively. The word “or” in reference to a list of two or more items covers all of the following interpretations of that word: any of the items in the list, all of the items in the list, and any combination of the items in the list. As used in this application, a layer referred to as “above” another layer means that the layers may be in direct contact or that one or more intervening layers may be present. As used in this application, a layer referred to as “on” another layer means that the layers are in direct contact. References to elements of the periodic table include any isotopes of that element.

[0029] The teachings of the technology provided herein can be applied to other systems without necessarily being applied to the systems described below. The elements and acts of the various examples described below can be combined to provide further implementations of the technology. Some alternative implementations of the technology can include not only additional elements of those implementations mentioned below, but also fewer elements.

[0030] These and other changes can be made to the technology in light of the following detailed description. Although this specification describes certain examples of the technology and describes the best mode contemplated, no matter how detailed the specification may appear, the technology can be practiced in many ways. As noted above, the specific terms used in describing certain features or aspects of the technology should not be taken to imply that the term is redefined herein to be limited to any specific property, feature, or aspect of the technology associated with that term. In general, the terms used in the following claims should not be construed to limit the technology to the specific examples disclosed in the specification unless the detailed description section explicitly defines these terms. Thus, the actual scope of the technology not only covers the disclosed examples, but also covers all equivalent ways of practicing or implementing the technology under the claims.

[0031] To reduce the number of claims, certain aspects of the technology are presented below in the form of certain claims, but the applicant contemplates various aspects of the technology in any number of claim forms.

[0032] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the implementation of the disclosed technology. However, it will be apparent to one of ordinary skill in the art that embodiments of the disclosed technology may be practiced without some of these specific details.

[0033] Compound of formula (I)

[0034] The present inventors have unexpectedly found that the compounds of formula (I) can have both high electrochemical stability and high ionic conductivity and / or high lithium transference number.

[0035]

[0036] X is Al or B.

[0037] R 1 is independently a monovalent substituent at each occurrence, and wherein R 1 is bonded to the O of OR 1 through a C atom of R 1 to the O of OR.

[0038] Preferably, each R 1 is independently selected from linear, branched or cyclic C 1-40 alkyl groups, wherein one or more C atoms of the C 1-40 alkyl group other than the C atom bonded to the O of OR 1 or the terminal C atom of the C 1-40 alkyl group can be replaced by O, and one or more H atoms can be replaced by F.

[0039] As used herein, the "terminal C atom" of an alkyl group refers to the methyl C atom of a normal alkyl chain or the methyl C atom of a branched alkyl chain.

[0040] Preferred R 1 groups are:

[0041] –(CH2CH2O)n-R 5 wherein R 5 is C 1-4 alkyl, and n is from 1 to 15, and wherein one or more H atoms can be replaced by F; and

[0042] C 1-12 alkyl, wherein one or more H atoms can be replaced by F.

[0043] In some embodiments, the R 1 groups are the same.

[0044] In some embodiments, the R 1 groups are different.

[0045] R 2 is a divalent organic group, where each O of O-R 2 -O is bonded to a carbon atom of R 2 . Preferably, R 2 is a group of formula (II):

[0046]

[0047] wherein R 3 is independently H or a substituent each time it appears, and Ar 1 is an arylene group or heteroarylene group. 6-20

[0048] Preferably, Ar 1 is an unsubstituted or substituted 1,2-phenylene, or an unsubstituted or substituted 5- or 6-membered heteroaromatic ring. Particularly preferred heteroaromatic group Ar 1 is a 6-membered heteroaromatic ring in which the ring atoms are composed only of C and N atoms, such as pyridine or pyrimidine.

[0049] If present, the substituents of Ar 1 are preferably and independently selected from F and C 1-12 alkyl, where one or more non-adjacent, non-terminal C atoms of the C 1-12 alkyl may be replaced by O, S, NR 4 , CO, COO or CONR 4 , where R 4 is independently a C 1-12 hydrocarbyl group each time it appears, and one or more H atoms of the C 1-12 alkyl group may be replaced by F.

[0050] Any C 1-12 hydrocarbyl group described anywhere herein is preferably selected from C 1-12 alkyl; phenyl; and phenyl substituted by one or more C 1-6 alkyl groups.

[0051] Preferably, R 3 is independently H, F or a C 1-12 alkyl group each time it appears, where one or more H atoms may be replaced by F, and one or more non-terminal C atoms may be replaced by O. In a preferred embodiment, at least one R 3 (optionally each R 3 ) is a C 1-6 perfluoroalkyl group.

[0052] M + is a cation. M + is preferably an alkali metal cation, more preferably Li + ​。

[0053] The compounds of formula (I) can be formed by reacting a compound of formula (III) with a compound selected from the compounds of formula (IVa) and formula (IVb) and a compound selected from the compounds of formula (Va), (Vb) and (Vc):

[0054] XH4 - M +

[0055] (III)

[0056]

[0057] The compound of formula (IVa) can be a primary alcohol, a secondary alcohol or a tertiary alcohol.

[0058] The compound of formula (IVb) can be an aldehyde or a ketone.

[0059] Exemplary compounds of formula (III) include, but are not limited to, lithium aluminum hydride (LiAlH4) and lithium borohydride (LiBH4).

[0060] Exemplary compounds of formula (I) include, but are not limited to:

[0061]

[0062] Electrolyte

[0063] The electrolyte containing the compound of formula (I) preferably further comprises at least one of a polymer and a solvent. If both the polymer and the solvent are present, the electrolyte can be a gel.

[0064] The polymer can be selected from any known ion-conductive polymers, including but not limited to: poly(alkylene oxide), such as poly(ethylene oxide) and poly(propylene oxide); and fluorinated polymers, such as PVDF, PVDF-HFP; PMMA; polyacrylonitrile; polycarbonate; polyethylene; polypropylene; poly(vinyl methyl ketone); polyvinylpyrrolidone; polyetheretherketone; polyisoprene; polybutadiene; polystyrene-block-polyisoprene-block-polystyrene; poly(1-vinylpyrrolidone-co-vinyl acetate); polystyrene-block-polybutadiene-block-polystyrene; polystyrene-block-poly(ethylene oxide)-block-polystyrene; copolymers and mixtures thereof.

[0065] The polymer is preferably a neutral polymer, that is, a polymer not substituted by ionic groups, and in particular, preferably not a single-ion conductive polymer containing anionic groups.

[0066] The electrolyte can contain one or more solvents. The solvent is preferably selected from C 2-10 alkylene carbonate, di(C 1-10alkyl) esters, such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate; straight-chain, branched-chain or cyclic compounds containing two or more ether groups, such as 1,3-dioxolane, 2,5-dimethyltetrahydrofuran, glycol dimethyl ether (dimethoxyethane), diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether; cyclic lactones and mixtures thereof.

[0067] The compound of formula (I) may contain solvated M + cation.

[0068] Optionally, the electrolyte present in the battery contains no more than 10 moles of solvent molecules per mole of M+ cations. The solvent / M+ ratio can be determined by 1 1H NMR spectroscopy of the electrolyte before its addition to the battery.

[0069] Battery

[0070] Figure 1 A battery containing the compound of formula (I) is shown. The battery can be a metal battery or a metal ion battery, preferably a lithium battery or a lithium ion battery.

[0071] The battery includes an anode current collector 101 on the surface of which an anode 103 is carried; a cathode current collector 109 on the surface of which a cathode 107 is provided; and a layer 105 which contains an electrolyte comprising the compound described herein disposed between the anode and the cathode.

[0072] The layer 105 may contain a porous separator in which the electrolyte (such as a liquid electrolyte or a gel electrolyte) is absorbed. If the electrolyte contains a solid, such as a gel containing a polymer and the compound of formula (I), the porous separator may or may not be present.

[0073] In the case of a metal battery, the anode is a layer of metal (such as lithium) which is formed above the anode current collector during charging of the battery and stripped during discharging of the battery.

[0074] In the case of a metal ion battery (such as a lithium ion battery), the anode contains an active material (such as graphite) for absorbing metal ions.

[0075] The cathode can be selected from any cathode known to those skilled in the art.

[0076] The anode and cathode current collectors can be any suitable conductive materials known to those skilled in the art, such as one or more layers of metal or metal alloy, such as aluminum or copper.

[0077] The battery can be formed by providing the electrolyte described herein on the surface of one of the anode and the cathode and providing the other of the anode and the cathode and the associated current collector above the electrolyte.

[0078] A metal battery precursor can be formed by disposing an electrolyte as described herein on the surface of an anode current collector; and disposing a cathode and a cathode current collector above the electrolyte. After applying a charging bias, a metal anode can form between the electrolyte and the anode current collector.

[0079] Figure 1 A battery is shown in which the anode and cathode are separated only by a single layer comprising or consisting of an electrolyte, such as a separator comprising an electrolyte. In other embodiments, one or more additional layers can be disposed between the anode and cathode.

[0080] For simplicity, Figure 1 A battery is shown in which the anode and cathode are separated only by a single layer 105, but it is understood that during use, a solid electrolyte interface typically forms on the anode surface.

[0081] Examples

[0082] Compound Example 1

[0083] Compound Example 1 was prepared according to the following reaction scheme:

[0084]

[0085] At -70 °C, a solution of lithium borohydride (9.2 ml, 4.6 mmol, 0.5 M in THF) was added dropwise to a solution of hexafluoro-2-(2-hydroxyphenyl)propan-2-ol (1 g in 8 ml THF, 3.84 mmol). The mixture was stirred between -70 °C and -60 °C for 3 hours and then warmed to 0 °C. A solution of 2,2,3,3,4,4,5,5-octafluoropentanol (1 ml in 8 m THF, 7.68 mmol) was added dropwise to the mixture, and the solution was stirred at room temperature for 1.75 hours. The temperature was raised to 60 °C, and the mixture was stirred overnight. The reaction mixture was cooled to room temperature, and a solution of lithium borohydride (0.4 ml, 0.8 mmol, 2 M in THF) was added dropwise. The mixture was stirred at 60 °C for 4 hours and then cooled to room temperature. Propylene carbonate (0.65 ml, 7.66 mmol) was added. The excess solvent was removed under vacuum (3.1x10 -2 mbar) at 25 °C for 1 hour and then at 40 °C for 2 hours, yielding a white thick oil. Additional propylene carbonate (0.6 ml, 7.1 mmol) was added, yielding 3.8 g of a white oil (86% yield).

[0086] Calculated from the integration of the NMR peaks, in one mole of hexafluoro-2-(2-hydroxyphenyl)propan-2-ol corresponding to one mole of lithium cations, there are 0.1 mole of THF and 4.0 moles of propylene carbonate (PC).

[0087] 1 H NMR (600 MHz) in deuterated THF: δ (ppm), 1.39 (12H, d, J = 6.2 Hz, CH3 from PC), 1.78 (0.5H, m, CH2 from THF), 3.62 (0.5H, m, CH2 from THF), 3.90 (4H, m), 4.00 (4H, t, J = 8.0 Hz, CH from PC, 4H), 4.50 (4H, t, J = 8.1 Hz, CH from PC), 4.80 (m, CH from PC, 4H), 6.6 - 6.86 (4H, m), 7.15 (1H, td, J = 7.6 Hz, J = 1.4 Hz), 7.32 (1H, d, J = 7.6 Hz).

[0088] Compound Example 2

[0089] Compound Example 2 was prepared according to the following reaction scheme:

[0090]

[0091] The number of repeating units was determined by 1 H NMR measurement.

[0092] Between -90 °C and -80 °C, a solution of lithium borohydride (9.2 ml, 4.6 mmol, 0.5 M in THF) was added dropwise to a solution of hexafluoro-2-(2-hydroxyphenyl)propan-2-ol (1 g dissolved in 8 ml THF, 3.84 mmol). The mixture was stirred between -85 °C and -70 °C for 3 hours and then warmed to 0 °C. A solution of MPEG350 (2.87 g, dissolved in 8 m THF, 7.68 mmol) was added dropwise to the mixture, and the solution was stirred at room temperature for 1 hour. The temperature was raised to 60 °C and maintained for 30 minutes, then the mixture was cooled to room temperature overnight. Propylene carbonate (0.62 ml, 7.31 mmol) was added. Under vacuum (3.2 x 10 -2 mbar) at 25 °C for 2 hours, and then the excess solvent was removed at 40 °C for 4 hours to give 4.0 g of Compound Example 2 as a colorless oil (yield 85%).

[0093] Calculated from the integration of the NMR peaks, in one mole of hexafluoro-2-(2-hydroxyphenyl)propan-2-ol corresponding to one mole of lithium cations, there are 1.88 moles of propylene carbonate (PC).

[0094] Compound Example 3

[0095] Compound Example 3 was prepared according to the following reaction scheme:

[0096]

[0097] At -70 °C, a 7 mL anhydrous tetrahydrofuran solution of 1,1,1,3,3,3-hexafluoropropan-2-ol (0.8 mL, 7.68 mmol) was added dropwise to a tetrahydrofuran solution of lithium borohydride (7.9 mL, 3.84 mmol, 0.5 M). The mixture was then stirred between -70 °C and -60 °C for 1 hour and then warmed to 0 °C. At room temperature, a 7 mL anhydrous THF solution of hexafluoro-2-(2-hydroxyphenyl)propan-2-ol (1 g, 3.84 mmol) was added dropwise to the reaction mixture. The mixture was stirred at 65 °C for 4 hours and stirred overnight at room temperature. Additional lithium borohydride (0.23 mL, 0.46 mmol) and hexafluoro-2-(2-hydroxyphenyl)propan-2-ol (0.1 g, 0.38 mmol) were added, and the reaction mixture was stirred at 65 °C for 2 hours. The mixture was cooled to room temperature and propylene carbonate (0.96 mL, 11.5 mmol) was added. Further propylene carbonate was added to obtain a clear liquid.

[0098] 1 H NMR (600 MHz) in deuterated THF: δ (ppm), 1.38 (d, CH3 from propylene carbonate 15.6H), 3.97 (m, CH from propylene carbonate, 5.1H), 4.52 (t, CH from propylene carbonate and CH from HFP, 6.8H), 4.81 (m, CH from propylene carbonate 4.7H), 6.67 (m, 2H), 7.12 (td, J = 7.7 Hz, J = 1.6 Hz, 1H), 7.29 (d, J = 7.9 Hz, 1H).

[0099] Calculated from the integration of the NMR peaks, there are 5.1 moles of propylene carbonate per mole of hexafluoro-2-(2-hydroxyphenyl)propan-2-ol corresponding to one mole of lithium cation.

[0100] Compound Example 4

[0101] Compound Example 4 was prepared according to the following reaction scheme:

[0102]

[0103] At -70 °C, a 7 mL anhydrous tetrahydrofuran solution of 2,2,3,3-tetrafluoropropan-1-ol (0.68 mL, 7.68 mmol) was added dropwise to a tetrahydrofuran solution of lithium borohydride (7.9 mL, 3.84 mmol, 0.5 M). The mixture was then stirred between -70 °C and -60 °C for 1 hour and then warmed to 0 °C. At room temperature, a 7 mL anhydrous THF solution of hexafluoro-2-(2-hydroxyphenyl)propan-2-ol (1 g, 3.84 mmol) was added dropwise to the reaction mixture. The mixture was stirred at 65 °C for 4 hours and stirred overnight at room temperature. Additional lithium borohydride (0.1 mL, 0.2 mmol) and hexafluoro-2-(2-hydroxyphenyl)propan-2-ol (0.06 g, 0.23 mmol) were added in sequence, and the reaction mixture was stirred at 65 °C for 1 hour. The mixture was cooled to room temperature and propylene carbonate (0.96 mL, 11.5 mmol) was added. Further propylene carbonate was added to obtain a clear liquid.

[0104] 1 H NMR (600 MHz) in deuterated THF: δ (ppm), 1.38 (d, CH3, from propylene carbonate 11.6H), 3.77 (m, 4.2H), 3.97 (m, CH, from propylene carbonate 3.7H), 4.52 (t, CH, from propylene carbonate 3.7H), 4.80 (m, CH, from propylene carbonate 3.3H), 6.10 (t, J = 53.51 Hz, J = 5.97 Hz, 2H), 6.70 (m, 2H), 7.14 (td, J = 7.7 Hz, J = 1.6 Hz, 1H), 7.31 (d, J = 8.0 Hz, 1H).

[0105] Calculated from the integration of the NMR peaks, there are 3.70 moles of propylene per mole of hexafluoro-2-(2-hydroxyphenyl)propan-2-ol corresponding to one mole of lithium cation.

[0106] Compound Example 5

[0107] Compound Example 5 was prepared according to the following reaction scheme:

[0108]

[0109] At -70 °C, a 7 mL anhydrous tetrahydrofuran solution of 1,1,1,3,3,3-hexafluoro-2-methylpropan-2-ol (0.94 mL, 7.68 mmol) was added dropwise to a tetrahydrofuran solution of lithium borohydride (7.9 mL, 3.84 mmol, 0.5 M). The mixture was then stirred between -70 °C and -60 °C for 1 hour and then warmed to 0 °C. At room temperature, a 7 mL anhydrous THF solution of hexafluoro-2-(2-hydroxyphenyl)propan-2-ol (1 g, 3.84 mmol) was added dropwise to the reaction mixture. The mixture was stirred at 65 °C for 4 hours and stirred overnight at room temperature. Additional lithium borohydride (0.04 mL, 0.08 mmol) was added, and the reaction mixture was stirred at 65 °C for 5 hours and stirred overnight at room temperature. Propylene carbonate (0.96 mL, 11.5 mmol) was added. Further propylene carbonate was added to obtain a stable clear liquid.

[0110] 1 H NMR (600 MHz) in deuterated THF: δ (ppm), 1.38 (d, CH3, from propylene carbonate 15.4H), 1.61 (s, 5.3H), 3.97 (m, CH, from propylene carbonate 5.3H), 4.52 (t, CH, from propylene carbonate, 5.3H), 4.80 (m, CH, from propylene carbonate 5.1H), 6.62 (m, 2H), 7.10 (td, J = 7.7 Hz, J = 1.6 Hz, 1H), 7.27 (d, J = 7.7 Hz, 1H).

[0111] Calculated from the integration of the NMR peaks, there are 5.2 moles of propylene carbonate per mole of hexafluoro-2-(2-hydroxyphenyl)propan-2-ol corresponding to one mole of lithium cations.

[0112] Cell Example 1

[0113] Type 2032 button cells were fabricated in a strictly dry, oxygen-free and argon-filled MBraun glove box using a casing purchased from Cambridge Energy Solutions.

[0114] A stainless steel spacer was inserted at the bottom of the button cell, and then a lithium disc and a fluoro-silicone template (purchased from Silex Silicones) were inserted. The template was in the shape of a disc with a diameter of 15.5 mm and had a circular hole with a diameter of 5 mm cut in the middle (the thickness of the template in the cell after crimping was 360 μm). 30 μl of an electrolyte solution containing Compound Example 1 was added to the hole. The solvents are listed in Table 1 below.

[0115] Place a lithium disk on top of the template, then place a stainless steel spacer, a wave spring, and a button cell cover. Finally, crimp the button cell.

[0116] Cell Example 2

[0117] The preparation method of the cell is the same as that of Cell Example 1, but Compound Example 3 is used instead of Compound Example 1.

[0118] Cell Example 3

[0119] The preparation method of the cell is the same as that of Cell Example 1, but Compound Example 4 is used instead of Compound Example 1.

[0120] Comparative Cell 1

[0121] For comparison, the preparation method of the cell is the same as that of Cell Example 1, but Comparative Compound 1 is used instead of Compound Example 1.

[0122]

[0123] Comparative Cell 2

[0124] For comparison, the preparation method of the cell is the same as that of Cell Example 1, but Comparative Compound 2 is used instead of Compound Example 1.

[0125]

[0126] Measurement

[0127] Electrochemical impedance spectroscopy (EIS) measurements were carried out at room temperature. The measurement frequency range of the electrolyte impedance was 1 Hz to 1 MHz, and the amplitude was 5 mV.

[0128] The ionic conductivity was calculated from these data using the following formula:

[0129]

[0130] Where:

[0131] 1. l is the thickness of the material between the two lithium disks, which corresponds to the thickness of the template in the crimped cell.

[0132] 2. A is the film area, which corresponds to the round hole cut out in the middle of the template.

[0133] 3. R is the electrolyte impedance.

[0134] The impedance of the electrolyte was determined by estimating the intercept of the first semicircle of the Nyquist plot with the x-axis. This is Figure 2At the lower left corner of the explanatory Nyquist plot of Comparative Compound 1.

[0135] The lithium transference number (LTN) was measured using the above-mentioned coin cell type 2032 according to the method of Evans (J. Evans et al., Polymer, 1987, Vol. 28).

[0136] Before the LTN measurement, the device was left standing overnight for about 19 hours to ensure the stability of the interface between the electrolyte and the lithium disk.

[0137] After standing:

[0138] 1. The first EIS spectrum was measured.

[0139] 2. Next, a DC current measurement was carried out (the applied constant voltage was adjusted individually for each cell to achieve an initial current of about 0.5 μA. Once the current dropped to a steady state, the measurement was terminated).

[0140] 3. Then the sequence was completed with a second EIS measurement.

[0141] The EIS measurements were carried out at room temperature. The EIS measurements were carried out in the frequency range from 1 Hz to 1 MHz with an amplitude of 5 mV.

[0142] The LTN value was calculated based on the model developed by Evans et al. according to the following formula.

[0143]

[0144] Where (refer to Figure 2 the explanatory Nyquist plot of Comparative Compound 1 shown):

[0145] 1. R 0 is the initial impedance obtained from the first EIS spectrum (determined by estimating the intercept of the Nyquist plot of the second semicircle (right hand side) on the x-axis).

[0146] 2. R s is the steady-state impedance obtained from the second EIS after applying a DC bias (determined by estimating the intercept of the Nyquist plot of the second semicircle (right hand side) on the x-axis).

[0147] 3. I 0 is the initial current obtained when the voltage step is applied to the set value.

[0148] 4. I s is the steady-state current obtained at the end of the DC measurement.

[0149] The ionic conductivities and LTNs of different solvated ionic liquids were calculated and representative values are reported in Table 1, where "PC" is propylene carbonate and "DME" is dimethoxyethane.

[0150] Table 1

[0151]

[0152] Linear sweep voltammetry

[0153] The oxidation stabilities of Compound Example 1 and Comparative Compounds 1 and 2 were measured using linear sweep voltammetry with an asymmetric coin cell. The cells were assembled as described in Cell Example 1 and Comparative Cells 1 and 2, respectively, but without the top lithium disk.

[0154] For the measurements, Compound Example 1 contained 0.1 mol of THF and 4.0 mol of propylene carbonate per mol of lithium; Comparative Compound 1 contained 0.05 mol of THF and 1.9 mol of propylene carbonate per mol of lithium; and Comparative Compound 2 contained 6.0 mol of propylene carbonate per mol of lithium.

[0155] Linear sweep voltammograms of each cell were obtained using a Gamry potentiostat. The scan rate was 1 mV per second, and the cells were scanned from the open circuit potential to 5 V versus Li / Li + except for the cell containing Comparative Compound 1, which was scanned to 6 V due to its high electrochemical stability.

[0156] The oxidation stability was calculated by fitting a line in the region below 4 V and above 5 μA and calculating the voltage value at the intersection of the two lines.

[0157]

[0158] Where:

[0159] 1) E ox is the oxidation stability value, unit: volt

[0160] 2) C A is the y-axis intercept of the straight line fitted between two points (one point at a current of 12 μA and the other point at a current of 6 μA)

[0161] between.

[0162] 3) S A is the slope of the line.

[0163] 4) C B is the y-axis intercept of the straight line fitted between two points (one point at a voltage of 4 V and the other point at a voltage of 3.3 V)

[0164] The y-intercept of the fitted straight line.

[0165] 5)S B is the slope of the straight line.

[0166] Figure 3 Figure 1 shows the linear sweep voltammograms of an asymmetric cell containing Compound Example 1, Comparative Compound 1, and Comparative Compound 2. The calculated oxidation stabilities are listed in Table 2.

[0167] Table 2

[0168] Material Oxidation stability / V Compound Example 1 4.6 Comparative Compound 1 4.8 Comparative Compound 2 4.3

[0169] As listed in Table 1 and Table 2, the ionic conductivity and LTN of Compound Example 1 are higher than those of Comparative Compound 1, and the oxidation stability is higher than that of Comparative Compound 2. Therefore, it has good stability, ionic conductivity, and LTN.

Claims

1. A compound of formula (I): wherein X is Al or B; R 1 is, independently at each occurrence, a monovalent substituent; R 2 is a divalent organic group; And M + is a cation.

2. The compound according to claim 1, wherein R 2 is a group of formula (II): wherein R 3 is independently H or a substituent each time it appears, and Ar 1 is a C 6-20 arylene group or a heteroarylene group.

3. The compound according to claim 2, wherein Ar 1 is unsubstituted or substituted 1,2-phenylene.

4. A compound according to any one of the preceding claims, wherein each R 1 is independently selected from C 1-20 alkyl, wherein one or more C atoms other than the C atom bonded to the O of OR 1 or the terminal C atom may be replaced by O, and one or more H atoms may be replaced by F.

5. The compound according to any one of the preceding claims, wherein X is B.

6. The compound according to any one of the preceding claims, wherein M + is a lithium ion.

7. An electrolyte comprising the compound according to any one of the preceding claims and at least one of a solvent and a polymer.

8. The electrolyte according to claim 7, wherein the electrolyte comprises a solvent selected from the following: C 2-10 alkylene carbonate; di(C 1-10 alkyl) carbonate; a straight-chain, branched-chain or cyclic compound containing two or more ether groups; and mixtures thereof.

9. A metal battery or metal ion battery comprising an anode, a cathode, and the electrolyte according to claim 7 or 8 disposed between the anode and the cathode.

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