Bicyclic triol borates and production and use thereof in an electrolyte composition in an energy store

Abstract

The present disclosure relates to bicyclic triol borates and the production and use thereof in an electrolyte composition. The present disclosure relates in particular to the use of zwitterionic bicyclic triol borates in an electrolyte composition in electrochemical supercapacitors and ultracapacitors, for example in double-layer capacitors in electric motors.

Description

[0001] Bicyclic triolborates and their preparation and use in an electrolyte composition in an energy storage device

[0002] The present disclosure relates to bicyclic triol borates and their preparation and use in an electrolyte composition. In particular, the present disclosure relates to the use of zwitterionic bicyclic triol borates in an electrolyte composition in electrochemical super- and ultracapacitors, for example, in double-layer capacitors in electric motors.

[0003] Technical background

[0004] Electromobility requires high-performance energy storage systems. Rapid load changes in electromobile systems lead to a drop in performance and a shortened service life of electrochemical energy storage devices. Therefore, high-performance electrical storage buffers are needed to relieve the load on electrochemical energy storage devices in electromobile systems. For vehicles with electric motors, new materials for more powerful energy storage devices are required. The desired novel materials should guarantee the rapid and continuous availability of drive energy. In particular, novel electrolyte compositions in capacitors with increased storage capacity and performance would be desirable.

[0005] Efficient energy storage and conversion in electric motors is possible with electrochemical supercapacitors and ultracapacitors. Electrochemical double-layer capacitors (EDLCs) are particularly used in electromobility. The charge capacity and performance of supercapacitors and ultracapacitors are significantly influenced by the electrolyte composition. The electrolyte compositions available to date in supercapacitors and ultracapacitors are predominantly based on strongly acidic or basic aqueous salt solutions. Typically, 1 M solutions of tetraethylammonium BF4 are used. However, the electrolyte compositions available to date exhibit limited charge capacity, a restricted electrochemical window, and undesirable thermal expansion upon heating.

[0006] Furthermore, when using salts as electrolytes, the viscosity of the solution has the dominant influence on the capacitor's resistance, as the ions migrate through the solution to the electrode. This rules out the inherently attractive use of ionic liquids, as their viscosity is far too high. Another important factor influencing performance is the potential electrochemical window, which means that a compromise between these properties must always be made when selecting the solvent.

[0007] Furthermore, previously available electrolyte compositions in supercapacitors and ultracapacitors are characterized by the use of a relatively high proportion of solvent. This reduces the proportion of conductive ions, which negatively impacts the conductivity of the energy storage device. Furthermore, the ions previously available in electrolyte compositions exhibit an undesirably high reactivity. This leads to undesirable reactions of the ions with the solvent of the electrolyte composition or with the surface of the electrode. This reduces the performance and service life of the energy storage device. The provision of a new electrolyte composition to overcome these disadvantages would be desirable.

[0008] The bicyclic triol borates described in DE 10 2019 108 288 A represent progress in this direction. A multi-step process was proposed for the preparation of the bicyclic triol borates, in which the bicyclic triol borates are synthesized by ion exchange reactions from the corresponding lithium triol borate salt, for example, lithium 1,4-dimethyl-2,6,7-trioxa-1-boratobicyclo-[2.2.2]-octane or lithium 1-butyl-4-methyl-2,6,7-trioxa-1-boratobicyclo-[2.2.2]-octane. The lithium triol borate salts were prepared from triisopropyl borate and the respective alkyllithium compounds. A multi-step process was used to prepare the alkyl borate cage anions with tetraalkylammonium cations. There is still room for improvement in the yield of the reactions and the necessary reactive effort, especially in the latter multi-step process.

[0009] It is therefore an object of the present disclosure to overcome the disadvantages of the prior art. In particular, it is an object to provide further improved electrolyte salts and a method for their production for use in electrolyte compositions in energy storage devices, in particular in supercapacitors and ultracapacitors. The electrolyte composition should be characterized in particular by low viscosity and increased charge capacity. The production process should be further simplified and improved.

[0010] In a first aspect, the disclosure relates to a zwitterionic bicyclic triolborate having the following structural formula where Ri is selected from the group comprising

[0011] - substituted or unsubstituted linear or branched alkyl group,

[0012] - substituted aryl group,

[0013] - substituted or unsubstituted heteroaryl group,

[0014] - substituted or unsubstituted cycloalkyl group,

[0015] - substituted or unsubstituted naphthyl group,

[0016] - an electron-withdrawing group, in particular -CN, -N3, -OH, -F, (R)sC-, (R3C-, (Rf)O2S- and (R)2N-, where R is selected from the group comprising substituted alkyl group, substituted aryl group, substituted or unsubstituted heteroalkyl group, -F and -CN and Rf is a partially fluorinated or perforated substituent from the group comprising substituted alkyl group, substituted aryl group and substituted or unsubstituted heteroalkyl group; and where R2, R3 and R4 are independently selected from the group comprising substituted or unsubstituted alkyl group, substituted or unsubstituted aryl group.

[0017] In embodiment variants, for Ri in the substituted linear or branched alkyl groups the substituents can be selected from ether radicals -OR, halogens, in particular fluorine and chlorine, and cyanide, and / or in the substituted aryl groups the substituents can be selected from ether radicals -OR, amino groups, halogens, in particular fluorine and chlorine, and cyanide, and / or in the substituted heteroaryl groups the substituents can be selected from ether radicals -OR, amino groups, halogens, in particular fluorine and chlorine, and cyanide.

[0018] In embodiment variants, Ri can be selected from the group comprising an alkyl radical having 1-8 carbon atoms, 1-7 carbon atoms, 1-6 carbon atoms, 1-5 carbon atoms, 1-4 carbon atoms, 1-3 carbon atoms, 1-2 carbon atoms or one carbon atom; a haloalkyl radical having 1-8 carbon atoms, 1-7 carbon atoms, 1-6 carbon atoms, 1-5 carbon atoms, 1-4 carbon atoms, 1-3 carbon atoms, 1-2 carbon atoms or one carbon atom; and a substituted or unsubstituted heteroaryl group based on a furan structure, a thiophene structure, a pyrrole structure, a pyridine structure, a pyrazine structure, a thiazole structure, an oxazole structure or a quinoline structure.

[0019] In a second aspect, the disclosure relates to a process for preparing a bicyclic triolborate, wherein a tetraalkylammonium hydroxide Alk4N +OH' with an organoboric acid RI-B(OH)2 and a 1,1,1-tris(hydroxymethyl)alkane according to the reaction scheme wherein Ri is selected from the group comprising substituted or unsubstituted alkyl group, substituted or unsubstituted isoalkyl group, and substituted aryl group; Alk4 is selected from the group comprising tetramethyl group, tetraethyl group, triethylmethyl group, tetrapropyl group and tetrabutyl group; and Rs is selected from the group comprising methyl group and ethyl group.

[0020] In a third aspect, the disclosure relates to a process for preparing a bicyclic triolborate, wherein a boric acid ester B(OR')3 is reacted with a 1,1,1-tris(hydroxymethyl)alkane and a salt MX according to the reaction scheme wherein R' is selected from the group comprising methyl group, ethyl group, propyl group, isopropyl group and butyl group; M is selected from the group comprising alkali metal cation, alkaline earth metal cation and tetraalkylammonium ion; X is selected from the group comprising (R)3C (RfhC (Rf)SO2', (R^N NC N3 and F with R = substituted alkyl, aryl, heteroalkyl or cyano group and Rf = perforated or partially fluorinated substituent; and Re is selected from the group comprising substituted or unsubstituted alkyl group, substituted or unsubstituted aryl group.

[0021] In a fourth aspect, the disclosure relates to a process for preparing a bicyclic triolborate, wherein in a first step a tetraalkylammonium hydroxide Alk4N +OH' with a boric acid ester B(OR')3 and a trimethylsilyl perfluoroalkyl compound (HsC^Si-Rf) and then with a 2,2-bis(hydroxymethyl)-alkan-1-ol according to the reaction scheme wherein R' is selected from the group comprising methyl group, ethyl group, propyl group, isopropyl group and butyl group; Alk4 is selected from the group comprising tetramethyl group, tetraethyl group, triethylmethyl group, tetrapropyl group and tetrabutyl group; Rf = perforated or partially fluorinated substituent; and Rs is selected from the group comprising methyl group and ethyl group.

[0022] In a fifth aspect, the disclosure relates to a process for preparing a zwitterionic bicyclic triolborate according to the first aspect, wherein in a first step a 2-(dialkylamino)-2-(hydroxymethyl)-1,3-propanediol hydrochloride is silylated with trimethylchlorosilane and pyridine, in a second step the silylated 2-(dialkylamino)-2-(hydroxymethyl)-1,3-propanediol is alkylated with an alkylating agent and in a third step the silylated and alkylated 2-(dialkylamino)-2-(hydroxymethyl)-1,3-propanediol is reacted with an organoboric acid Ri-B(OH)2 and an alkali metal hydroxide MOH according to the reaction scheme is implemented.

[0023] In a sixth aspect, the disclosure relates to the use of a zwitterionic bicyclic triolborate according to aspect 1 in an electrolyte composition in an energy storage device, in particular a capacitor.

[0024] Detailed description of the revelation

[0025] The new process, using new precursors and intermediates for the synthesis of bicyclic triol borates, is not only characterized by improved yields and a shorter synthesis route, but also allows the preparation of zwitterionic bicyclic triol borates starting from tetraalkylammonium hydroxides. These novel cage borates are dipolar zwitterions in which the bicyclic cage structure rigidly connects cationic and anionic groups at opposite, tetrahedral positions of the triangular, elongated bipyramid (also called triakis triangular prism or Johnson body J14). Until now, there have been no attempts to use zwitterions in general, let alone zwitterionic bicyclic triol borates, in electrical double-layer capacitors.These represent a completely new class of electrolyte salts for use in electrolyte compositions of supercapacitors and ultracapacitors. They are characterized by extraordinary dipole moments, which gives them superior properties in the electrolyte.

[0026] As already mentioned, dissolved salts such as 1 M tetraethylammonium BF4 are commonly used in electrolyte compositions. These ions then stabilize the excess charge in the electrode at the oppositely charged electrode. The localized arrangement of the respective counterions within the zwitterionic bicyclic triol borates results in a viscosity-reducing, low molecular weight, improved solubility in polar solvents, and fast response times in an electric field. These zwitterions are therefore particularly suitable for electrolyte use as strong dielectrics in supercapacitors and ultracapacitors. Their dipole moments, calculated using density functional theory in the commonly used B3LYP hybrid method, are approximately 18 Debye, higher than previously known values ​​for molecular compounds.

[0027] Since zwitterions simply align in an electric field and no longer migrate, the resistance of the electrolyte decreases and the importance of viscosity diminishes. This allows the use of solvents with better electrochemical properties and the adaptation of the substituent pattern of the zwitterions, allowing them to exist as ionic liquids.

[0028] The direct, one-step cage borate synthesis using quaternary ammonium hydroxide and the activating protecting group chemistry on both different pointed trigonal caps of the target compounds enables a multitude of new, previously inaccessible borate cages. The silylated and alkylated 2-(dialkylamino)-2-(hydroxymethyl)-1,3-propanediols and their desilylated counterparts, which were discovered as precursors or intermediates for the improved synthesis, are previously unknown and not only simplify the preparation of the alkyl borate cage anions with tetraalkylammonium cations into a single-step process, but also, surprisingly, enable the first preparation of zwitterionic bicyclic triolborates. The incorporation of the two opposing charge carriers into a rigid, linear, zwitterionic molecule with highly variable substituents of widely varying electronegativity and thus dielectric properties becomes possible.Due to the variability of the different substituents at both opposite positions, a formulation of the electrolyte specialized for the application can be adjusted by targeted selection from the various cage molecules.

[0029] Simplified synthesis of bicyclic triolborates

[0030] In cage formation, the multi-step process using alkali metal hydroxides and subsequent cation exchange to form the desired ammonium salts Al l was replaced by a simplified and more cost-effective synthesis method with high yields of pure substances for the bicyclic triol borates. In the new process, commercially available tetraalkylammonium hydroxides Alk4N are used for basic cage borate formation. + OH _, also known as quats, and also commercially available, inexpensive organoboric acids RB(OH)2 in a so-called "one-pot process".

[0031] In the reaction scheme, Ri = alkyl, aryl; Alk4 = tetramethyl, tetraethyl, triethyl-methyl, tetrapropyl, tetrabutyl; and Rs = methyl, ethyl.

[0032] In embodiments, the reaction can be carried out at a temperature in the range of 20 °C to 125 °C, preferably in the range of 45 °C to 100 °C, particularly preferably in the range of 70 °C to 85 °C.

[0033] The disclosed reaction procedure improves yield and purity. Furthermore, it eliminates complex and therefore expensive additional process steps. The radicals Ri can be, in particular, alkyl or aryl substituents or weakly coordinating anions of corresponding strong Lewis acids of the substituted aromatic or heteroaromatic type.

[0034] Further borate cages can be synthesized using boric acid esters and salts of the type MX with M = alkali metal cation, alkaline earth metal cation or tetraalkylammonium ion and X = (R)3C (R 3C (R^SCh (R^N NC N3 or F; with R = substituted alkyl, aryl, heteroalkyl or cyano group and Rf = perforated or partially fluorinated substituent). The direct reaction takes place in suitable solvents such as methanol according to the following reaction scheme.

[0035] In embodiments, the reaction can be carried out at a temperature in the range of 20 °C to 125 °C, preferably in the range of 45 °C to 100 °C, particularly preferably in the range of 70 °C to 85 °C.

[0036] The direct syntheses of the tetraalkylammonium cage borates shown above could be extended to compounds with fluorinated alkyl substituents on the boron, as shown in the following reaction scheme.

[0037]

[0038] In embodiment variants, the reaction in the first step can be carried out at a temperature in the range of 20 °C to 125 °C, preferably in the range of 45 °C to 100 °C, particularly preferably in the range of 75 °C to 90 °C. In embodiment variants, the reaction in the second step can be carried out at a temperature in the range of 20 °C to 125 °C, preferably in the range of 45 °C to 100 °C, particularly preferably in the range of 70 °C to 85 °C.

[0039] Synthesis of zwitterions of bicyclic triolborates

[0040] The disclosed zwitterions of bicyclic triolborates of the general formula can in principle be prepared using the corresponding aminotriols as starting materials. However, depending on the substitution pattern, these compounds tend to form intra- and intermolecular hydrogen bonds, making them unreactive. Furthermore, their low solubility in suitable solvents prevents conversion to the target products (MJ Taylor, JA Grigg, IANH Laban, Polyhedron 1996, 15, 3261-3270).

[0041] However, the inventors were able to find that by means of a silylation of OH groups, which is known from the literature, readily soluble and reactive intermediates can be prepared, which then, as disclosed, can be directly and easily isolated to give the cage borates, with the resulting by-products being easily separable.

[0042] Surprisingly, the concept of protecting group chemistry for activating aminotriols for cage borate formation could then be applied not only to the OH group, but also to the amino group on the tertiary carbon atom. This then allowed the corresponding cage borates to be formed. Derivatization at the nitrogen of the amino group can be achieved, for example, according to Darabantu, Mircea, et al. "Synthesis and stereochemistry of some 1,3-oxazolidine systems based on TRIS (α, α, α-trimethylolaminomethane) and related aminopolyols skeleton. Part 2: 1-aza-3, 7-dioxabicyclo[3.3.0]octanes." (Tetrahedron 56.23 (2000): 3799-3816) and Wawzonek S., "REDUCTION OF 5-HYDROXYMETHYL-1-AZA-3, 7-DIOXABICYCLO[3.3.0]OC-TANE AND OF 2-PHENYL-4,4-DIMETHYLOXAZOLIDINE WITH FORMIC ACID" (Organic Preparations and Procedures International, 13:2, 126-129) as hydrochloride.The following reaction scheme shows as an example the N-methylation of tris(hydroxymethyl)aminomethane (R2 = alkyl; R3 = alkyl):.

[0043] In embodiments, the reaction can be carried out at a temperature in the range of 20 °C to 125 °C, preferably in the range of 45 °C to 100 °C, particularly preferably in the range of 70 °C to 85 °C.

[0044] In variants, 2-(dialkylamino)-2-(hydroxymethyl)-1,3-propanediol hydrochloride can be prepared from tris(hydroxymethyl)aminomethane, formaldehyde and p-toluenesulfonic acid followed by reaction with formic acid and acidification with HCl.

[0045] This hydrochloride was protected by a silyl group for the first time. The following reaction scheme shows the silylation of 2-(dialkylamino)-2-(hydroxymethyl)-1,3-propanediol (R2 =alkyl; R3 =alkyl).

[0046] Further alkylation and subsequent desilylation (with R2 = alkyl; R3 = alkyl; R4 = alkyl) can then be carried out, for example, using the corresponding alkyl iodide as alkylating agent and fluoride ions to remove the silyl groups:

[0047] In embodiments, the reaction can be carried out at a temperature in the range of -50 °C to 25 °C, preferably in the range of -25 °C to 10 °C, particularly preferably in the range of -10 °C to 5 °C.

[0048] This procedure, in the presence of an alkylating agent, allows the preparation of the novel trialkylammonium salt. It has also been found that quaternization at the nitrogen atom is also successful with the aforementioned silylated dialkylaminotriols disclosed. This can be cleaved in a further step with fluorine compounds, thereby producing the novel trialkylammonium trialcohols.

[0049] With the silylated quaternary ammonium trioies, the synthesis of zwitterionic triolborate cages was achieved for the first time, with the cationic ammonium group providing intramolecular charge balance to the borate. The following reaction scheme (R1 = alkyl; R2 = alkyl; R3 = alkyl; R4 = alkyl) illustrates this reaction using the example of silylated and alkylated 2-(dialkylamino)-2-(hydroxymethyl)-1,3-propanediol with a boronic acid:

[0050] In embodiments, the reaction can be carried out at a temperature in the range of 20 °C to 125 °C, preferably in the range of 45 °C to 100 °C, particularly preferably in the range of 70 °C to 85 °C.

[0051] Short description of the characters

[0052] Figure 1 shows the specific conductivity of compounds (I), (J) and (K) in H2O for different temperatures.

[0053] Figure 2 shows the Arrhenius plot of the experimentally determined conductivities of compounds (I), (J) and (K).

[0054] Figure 3 shows the cyclic voltammogram of compounds (I), (J) and (K) in H2O at 10 mV s- 1 .

[0055] Figure 4 shows the discharge capacities of compounds (I), (J) and (K) in H2O over 120 cycles at a constant current of 1 mA.

[0056] Figure 5 shows the Nyquist plot of compounds (I), (J) and (K) in H2O.

[0057] Examples

[0058] The present invention is illustrated by the following examples, but the invention is not limited thereto. Unless otherwise stated, "room temperature" in this disclosure refers to a temperature in the range of 20°C - 25°C, in particular 22°C.

[0059] 1. Synthesis of precursors and intermediates, bicyclic triolborates and zwitterionic bicyclic triolborates

[0060] Table 1 below lists the names and structural formulas of the precursors and intermediates, bicyclic triol borates and zwitterionic bicyclic triol borates prepared as examples.

[0061]

[0062] 1.1 Example 1

[0063] In Example 1, the substance tetraethylammonium 1,4-dimethyl-2,6,7-trioxa-1-boratobicyclo-[2.2.2]-octane with structural formula (A) was synthesized as follows. 3 mmol of methylboronic acid, 4.5 mmol of tetraethylammonium hydroxide, and 4.5 mmol of 1,1,1-tris(hydroxymethyl)ethane were heated to boiling in a rotary evaporator for one hour. After the reaction, the solution was evaporated to dryness, yielding 3 mmol of product (A).

[0064] 1.2 Example 2

[0065] In Example 2, the substance potassium 1-cyano-4-ethyl-2,6,7-trioxa-1-boratobicyclo-[2.2.2]-octane with the structural formula (B) was synthesized as follows. 24.69 mmol of potassium cyanide and 37.04 mmol of triisopropyl borate were stirred in 30 ml of anhydrous acetonitrile under protective gas for 12 hours at room temperature. The reaction mixture was then evaporated to dryness. In the next step, 24.69 mmol of 1,1,1-tris(hydroxymethyl)propane were added. and 20 ml anhydrous trimethylorthoformate 0GH3 was added under protective gas, and the reaction mixture was heated at 100 °C for one hour. The reaction mixture was then evaporated to dryness, yielding 24.69 mmol of product (B).

[0066] 1.3 Example s

[0067] In Example 3, the substance potassium 1-trifluoromethyl-4-ethyl-2,6,7-trioxa-1-boratobicyclo[2.2.2]octane with structural formula (C) was synthesized as follows. 22 mmol of Ruppert-Prakash reagent (CFsSiMes), 20 mmol of potassium fluoride, 30 mmol of trimethyl borate, and 20 mmol of 1,1,1-tris(hydroxymethyl)propane were stirred under protective gas in 20 ml of anhydrous tetrahydrofuran for 36 hours. The reaction mixture was then evaporated to dryness to yield 20 mmol of product (C).

[0068] 1.4 Example 4a

[0069] In Example 4a, the substance 5-hydroxymethyl-1-aza-3,7-dioxabicyclo-[3.3.0]-octane with structural formula (D) was synthesized as follows. 0.3 mol of tris(hydroxymethyl)aminomethane, 3.12 mol of a 35% formaldehyde solution, 3.94 mmol of p-toluenesulfonic acid, and 120 ml of toluene were refluxed for 24 hours in a water separator with continuous removal of the resulting water. After the reaction was complete, the reaction mixture was neutralized with NaHCO3, and the excess toluene was removed on a rotary evaporator. The solution was then dried on a Schlenk line until a white solid precipitated. 0.24 mol of the substance with structural formula (D) was obtained.

[0070] 1.5 Example 4b

[0071] In Example 4b, the substance 2-(dimethylamino)-2-(hydroxymethyl)-1,3-propanediol hydrochloride with structural formula (E) was synthesized as follows. 0.17 mol of the substance 5-hydroxymethyl-1-aza-3,7-dioxabicyclo-[3.3.0]-octane with structural formula (D) was heated to reflux with 1.72 mol of formic acid for 24 hours. After the reaction was complete, the excess formic acid was removed on a rotary evaporator. The solution was then acidified with 30 ml of 6N HCl, stirred for 30 minutes, and evaporated to dryness on a rotary evaporator until a white solid precipitated. The resulting solid was filtered off and washed with 100 ml of MeOH. 0.14 mol of the substance with structural formula (E) was obtained. 1.6 Example 5

[0072] In Example 5, the substance 2-(dimethylamino)-2-(trimethylsilyloxymethyl)-1,3-propanediol bis(trimethylsilyl) ether with the structural formula (F) was synthesized as follows. 13.67 mmol of the substance 2-(dimethylamino)-2-(hydroxymethyl)-1,3-propanediol hydrochloride with

[0073] Structural formula (E) were dissolved in 109 mmol of anhydrous pyridine.

[0074] 49 mmol of trichloromethylsilane in 20 ml of anhydrous toluene were added at room temperature and heated for 24 hours at 85 °C with stirring. After the reaction, the reaction solution was extracted three times with 20 ml of water each time. Excess water from the extract was removed with calcium chloride. The extract was then evaporated to dryness.

[0075] 5.47 mmol of the substance with the structural formula (F) were obtained.

[0076] 1.7 Example 6a

[0077] In Example 6a, the substance 2-(trimethylammonium)-2-(trimethylsilyloxymethyl)-1,3-propanediol bis(trimethylsilyl) ether iodide with structural formula (G) was synthesized as follows. 87 mmol of the substance 2-(dimethylamino)-2-(trimethylsilyloxymethyl)-1,3-propanediol bis(trimethylsilyl) ether with structural formula (F) were stirred with 176 mmol of methyl iodide in an ice bath until a white / yellow solid was obtained. The resulting reaction mixture was then evaporated to dryness along the Schlenk line. This yielded 87 mmol of the substance with structural formula (G).

[0078] 1.8 Example 6b

[0079] In Example 6b, the substance 2-((butyldimethyl)ammonium)-2-(trimethylsilyloxymethyl)-1,3-propanediol bis(trimethylsilyl) ether bromide with structural formula (H) was synthesized as follows. 87 mmol of the substance 2-(dimethylamino)-2-(trimethylsilyloxymethyl)-1,3-propanediol bis(trimethylsilyl) ether with structural formula (F) were stirred with 435 mmol of 1-bromobutane and 30 ml of acetonitrile for 4 days at room temperature. After the reaction was complete, the solvent was removed using a rotary evaporator, yielding a yellow oil. This was taken up in 30 ml of chloroform and extracted five times with 30 ml of water each time. Excess water in the extract was removed with magnesium sulfate. The extract was then concentrated to dryness. 87 mmol of the substance with the structural formula (H) were obtained.

[0080] 1.9 Example 7a

[0081] In Example 7a, the substance 4-trimethylamino,1-methyl-2,6,7-trioxa-1-boratobicyclo[2.2.2]octane with structural formula (I) was synthesized as follows. 10.69 mmol of the substance 2-(trimethylammonium)-2-(trimethylsilyloxymethyl)-1,3-propanediol bis(trimethylsilyl) ether iodide with structural formula (G), 10.69 mmol of methylboronic acid MeB(OH)2, and 12.83 mmol of potassium hydroxide in 5 ml of MeOH were heated to boiling for one hour. The resulting solid was filtered off, and the filtrate was concentrated on a rotary evaporator and further dried on the Schlenk line. 10 mmol of the substance with structural formula (I) were obtained.

[0082] 1.10 Example 7b

[0083] In Example 7b, the substance 1-isobutyl-4-trimethylamino-2,6,7-trioxa-1-boratobicyclo[2.2.2]octane with structural formula (J) was synthesized as follows. 10.69 mmol of the substance 2-(trimethylammonium)-2-(trimethylsilyloxymethyl)-1,3-propanediol bis(trimethylsilyl) ether iodide with structural formula (G), 10.69 mmol of isobutylboronic acid, and 12.83 mmol of potassium hydroxide in 5 ml of MeOH were heated to boiling for one hour. The resulting solid was filtered off, and the filtrate was concentrated on a rotary evaporator and further dried on the Schlenk line. 10 mmol of the substance with structural formula (J) were obtained.

[0084] 1.11 Example 7c

[0085] In Example 7c, the substance 4-((butyldimethyl)amino),1-methyl-2,6,7-trioxa-1-boratobicyclo-[2.2.2]-octane with the structural formula (K) was synthesized as described below. 10.69 mmol of the substance 2-((butyldimethyl)ammonium)-2-(trimethylsilyloxymethyl)-1,3-propanediol bis(trimethylsilyl) ether bromide with the structural formula (H), 10.69 mmol of methylboronic acid, and 12.83 mmol of potassium hydroxide in 5 ml of MeOH were heated to boiling for one hour. The resulting solid was filtered off, and the filtrate was concentrated on a rotary evaporator and further dried on the Schlenk line. 9.5 mmol of the substance with the structural formula (K) were obtained.

[0086] 2. Nuclear magnetic resonance spectroscopy

[0087] The substances of Examples 1 to 7 were characterized by nuclear magnetic resonance spectroscopy (NMR). 1 H-NMR, 13 C-NMR, and 11 B-NMR measurements at 300 K and

[0088] The NMR spectra were measured at 500 MHz on an Ascend 500 MHz spectrometer equipped with an Avance Neo console and a BBFO broadband probe head with Z-gradient, as well as a SampleXpress sample changer from Bruker Biospin GmbH using deuterated dimethyl sulfoxide. Table 2 shows the peaks measured in the obtained NMR spectra for substances (A), (B), (C), (D), (E), (F), (G), (H), (I), (J), and (K).

[0089] Table 2

[0090] 3. Electrochemical characterization

[0091] A comparative measurement of the conductivity of examples (I), (J), and (K) was performed as a function of temperature. This was carried out in a closed measuring cell "TSC 1600 Closed" from rhd Instruments with a sample volume of 1 ml. For this purpose, 1 molar solutions of the substances in H2O were prepared and measured.

[0092] The results of this comparative measurement are plotted in Figure 1. As can be seen, the prepared substances (I), (J), and (K) exhibit a change in conductivity with temperature. Figure 1 also demonstrates that substituent variation has a direct influence on the electrochemical behavior. This makes it possible to control the conductivity of the zwitterionic bicyclic triolborates.

[0093] Regarding conductivity, more sterically demanding substituents increase the conductivity of the zwitterionic bicyclic triolborates. An Arrhenius plot of the specific conductivity as a function of the reciprocal temperature for compounds (I), (J), and (K) is shown in Figure 2. It shows that compound (K) has the lowest activation energy with 15.5 J mol -1 The other two compounds have a similar activation energy value of 19.4 J mol' 1for (J) and 20.1 J mol' 1 for (I). In ionic liquids, the activation energy can be considered a measure of the potential energy landscape during diffusion of the particle (Truhlar, Donald G. "Interpretation of the activation energy." Journal of Chemical Education 55.5 (1978): 309.).

[0094] In addition to the conductivity measurements, the performance of examples (I), (J), and (K) in a supercapacitor was investigated. This measurement was carried out in a "TSC battery measuring cell" from rhd Instruments with a sample volume of 100 μl. The compounds were measured as 1 molar aqueous solutions. Figure 3 shows the cyclic voltammogram of compounds (I), (J), and (K).

[0095] As can be seen in Figure 3, all examples shown exhibit the rectangular curve typical of supercapacitors. This demonstrates that the prepared compounds can be used as electrolytes in a supercapacitor. Furthermore, the influence of different substituents on the electrochemical behavior is also evident here. The area under the curve (the "size" of the rectangle) is a measure of the capacitance of the electrolyte solution. As can be seen in Figure 3, compound (K) exhibits the highest capacitive behavior.

[0096] This is supported by an examination of the discharge capacities over 120 cycles (Figure 4). This plot shows that compound (K) exhibits the highest capacity over 120 cycles. Compound (J) has the second-highest capacity over 120 cycles, followed by compound (I), which exhibits the lowest capacity. One reason for this could be the lower energy required for diffusion of compound (K) (see Figure 2).

[0097] This assumption can be supported by the Nyquist diagram in Figure 5. This plot shows the resistance in the supercapacitor, which also affects the electrolyte. This plot shows that compound (K) produces the lowest resistance among the compounds shown.

[0098] Furthermore, the disclosure may concern the following subjects:

[0099] Item 1 : Process for the preparation of a bicyclic triolborate, wherein a tetraalkylammonium hydroxide Alk4N + OH _ with an organoboric acid RI-B(OH)2 and a 1,1,1-tris(hydroxymethyl)alkane according to the reaction scheme wherein Ri is selected from the group comprising substituted or unsubstituted alkyl group, substituted or unsubstituted isoalkyl group, and substituted aryl group; Alk4 is selected from the group comprising tetramethyl group, tetraethyl group, triethylmethyl group, tetrapropyl group and tetrabutyl group; and Rs is selected from the group comprising methyl group and ethyl group. : Process according to item 1, wherein the reaction is carried out at a temperature in

[0100] Range from 20 °C to 125 °C, preferably in the range from 45 °C to 100 °C, particularly preferably in the range from 70 °C to 85 °C.

[0101] Process for the preparation of a bicyclic triolborate, wherein a boric acid ester B(OR')3 is reacted with a 1,1,1-tris(hydroxymethyl)alkane and a salt MX according to the reaction scheme wherein R' is selected from the group comprising methyl group, ethyl group, propyl group, isopropyl group and butyl group; M is selected from the group comprising alkali metal cation, alkaline earth metal cation and tetraalkylammonium ion; X is selected from the group comprising (R)3C (RfhC (Rf)SO2', (R^N NC N3 and F; with R = substituted alkyl, aryl, heteroalkyl or cyano group and Rf = perforated or partially fluorinated substituent; and Re is selected from the group comprising substituted or unsubstituted alkyl group, substituted or unsubstituted aryl group.

[0102] Process according to item 3, wherein the reaction is carried out at a temperature in

[0103] Range from 20 °C to 125 °C, preferably in the range from 45 °C to 100 °C, particularly preferably in the range from 70 °C to 85 °C.

[0104] Process for the preparation of a bicyclic triolborate, wherein in a first

[0105] Step one Tetraalkylammonium hydroxide Alk4N + OH _ with a boric acid ester

[0106] B(OR')3 and a trimethylsilyl-perfluoroalkyl compound (HsQsSi-Rf and then with a 1,1,1-tris(hydroxymethyl)alkane according to the reaction scheme

[0107] wherein R' is selected from the group comprising methyl group, ethyl group, propyl group, isopropyl group and butyl group; Alk4 is selected from the group comprising tetramethyl group, tetraethyl group, triethylmethyl group, tetrapropyl group and tetrabutyl group; Rf = perforated or partially fluorinated substituent; and Rs is selected from the group comprising methyl group and ethyl group.

[0108] Item 6: Process according to item 5, wherein the reaction in the first step is carried out at a temperature in the range from 20 °C to 125 °C, preferably in the range from 45 °C to 100 °C, particularly preferably in the range from 75 °C to 90 °C and / or the reaction in the second step is carried out at a temperature in the range from 20 °C to 125 °C, preferably in the range from 45 °C to 100 °C, particularly preferably in the range from 70 °C to 85 °C.

Claims

Claims 1. Zwitterionic bicyclic triolborate with the following structural formula where R 1 is selected from the group comprising substituted or unsubstituted linear or branched alkyl group, substituted aryl group, substituted or unsubstituted heteroaryl group, substituted or unsubstituted cycloalkyl group, substituted or unsubstituted naphthyl group, an electron-withdrawing group, in particular -CN, -N 3 , -OH, -F, (R ) s C-, (R 3 C-, (R 0 2 S- and (R ) 2 N-, where R is selected from the group comprising substituted alkyl group, substituted aryl group, substituted or unsubstituted heteroalkyl group, -F and -CN and R f is a partially fluorinated or perforated substituent from the group comprising substituted alkyl group, substituted aryl group and substituted or unsubstituted heteroalkyl group; and where R 2 , R 3 and R 4 are independently selected from the group comprising substituted or unsubstituted alkyl group, substituted or unsubstituted aryl group.

2. Zwitterionic bicyclic triolborate according to claim 1, wherein Ri is selected from the group comprising - an alkyl radical having 1-8 carbon atoms, 1-7 carbon atoms, 1-6 carbon atoms, 1-5 carbon atoms, 1-4 carbon atoms, 1-3 carbon atoms, 1-2 carbon atoms or one carbon atom; - a haloalkyl radical having 1-8 carbon atoms, 1-7 carbon atoms, 1-6 carbon atoms, 1-5 carbon atoms, 1-4 carbon atoms, 1-3 carbon atoms, 1-2 carbon atoms or one carbon atom; and - a substituted or unsubstituted heteroaryl group based on a furan structure, a thiophene structure, a pyrrole structure, a pyridine structure, a pyrazine structure, a thiazole structure, an oxazole structure or a quinoline structure.

3. A process for the preparation of a zwitterionic bicyclic triolborate according to one of claims 1 or 2, wherein in a first step a 2-(dialkylamino)-2-(hydroxymethyl)-1,3-propanediol hydrochloride is silylated with trimethylchlorosilane and pyridine, in a second step the silylated 2-(dialkylamino)-2-(hydroxymethyl)-1,3-propanediol is alkylated with an alkylating agent and in a third step the silylated and alkylated 2-(dialkylamino)-2-(hydroxymethyl)-1,3-propanediol is reacted with an organoboric acid RI-B(OH)2 and an alkali hydroxide MOH according to the reaction scheme is implemented.

4. The process according to claim 3, wherein the reaction in the second step is carried out at a temperature in the range of -50 °C to 25 °C, preferably in the range of -25 °C to 10 °C, particularly preferably in the range of -10 °C to 5 °C and / or the reaction in the third step is carried out at a temperature in the range of 20 °C to 125 °C, preferably in the range of 45 °C to 100 °C, particularly preferably in the range from 70 °C to 85 °C.

5. A process according to any one of claims 3 or 4, wherein the 2-(dialkylamino)-2-(hydroxymethyl)-1,3-propanediol hydrochloride is prepared from tris(hydroxymethyl)aminomethane, formaldehyde and p-toluenesulfonic acid, followed by reaction with formic acid and acidification with HCl.

6. Use of a zwitterionic bicyclic triolborate according to claim 1 or 2 in an electrolyte composition in an energy storage device, in particular a capacitor.

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