Nitrogen salts of substituted trifluoroborate-containing anions and use thereof in an electrolyte composition in an energy storage device

Abstract

The present disclosure relates to highly conductive nitrogen salts of trifluoroborates preferably substituted with electron-withdrawing groups (EWG), and to the use thereof in an electrolyte composition. The present disclosure relates in particular to the use thereof in an electrolyte composition in electrochemical energy storage devices, such as supercapacitors.

Description

[0001] Nitrogen salts of substituted trifluoroborate-containing anions and their use in an electrolyte composition in an energy storage device

[0002] This disclosure relates to highly conductive nitrogen salts of trifluoroborates preferably substituted with electron-withdrawing groups (EWGs) and their use in an electrolyte composition. In particular, this disclosure relates to their use in an electrolyte composition in electrochemical energy storage devices, such as supercapacitors.

[0003] Technical background

[0004] Electromobility requires high-performance energy storage systems. Rapid load changes in electromobility systems lead to a drop in performance and a reduction in the lifespan of electrochemical energy storage devices. Therefore, high-performance electrical storage buffers are needed to relieve the strain on electrochemical energy storage devices in electromobility systems, as well as energy storage devices with higher energy density. New materials for more efficient energy storage are required for vehicles with electric motors. The desired novel materials should guarantee a rapid and continuous availability of drive energy. In particular, novel electrolyte compositions in capacitors with increased storage capacity and power would be desirable. This would buffer the load, especially during rapid load changes caused by charging or discharging the electrochemical batteries, and thus extend the battery lifespan.

[0005] Efficient energy storage and conversion in electric motors is possible using electrochemical supercapacitors and ultracapacitors. In electromobility, electrochemical double-layer capacitors (EDLCs) are particularly common. The charge capacity and performance of supercapacitors and ultracapacitors are significantly influenced by the electrolyte composition. 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 undesirably high hygroscopicity.

[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. The viscosity of the salt solutions depends on the concentration, the molecular weight of the salts, and also on the presence of weakly polarizable substituents on the anionic ions.

[0007] March 24, 2026 1 / 17. This eliminates the generally attractive use of ionic liquids, as they have far too high a viscosity. Another important factor influencing performance is the possible electrochemical window, which means that a compromise must be made between these properties when selecting the solvent.

[0008] Furthermore, currently available electrolyte compositions for supercapacitors and ultracapacitors are characterized by a relatively high solvent content. Many electrolyte salts for double-layer capacitors are also limited to the use of acetonitrile. Consequently, the operating temperature of these double-layer capacitors is limited to the boiling point of acetonitrile. Additionally, commercial electrolyte salts such as tetraethylammonium tetrafluoroborate (TE-ABF4) decompose rapidly due to a small amount of water. This reduces the performance and lifespan of the energy storage device. To date, no alternative to TEABF4 is known that offers comparable performance and greater stability. The development of a new electrolyte composition to overcome these drawbacks would be highly desirable.

[0009] It is therefore an objective of the present disclosure to overcome the disadvantages of the prior art. In particular, it is an objective to provide further improved electrolyte salts and a process for their preparation for use in electrolyte compositions in energy storage devices, especially in supercapacitors and ultracapacitors.

[0010] Summary of Revelation

[0011] In a first aspect, the disclosure relates to a nitrogen salt of substituted trifluoroborates with the structural formula

[0012] (R 2 N) + R 1 BF3-

[0013] with

[0014] R 1= partially fluorinated or perfluorinated alkyl group, partially fluorinated or perfluorinated aryl group, partially chlorinated or perchlorinated alkyl group, partially chlorinated or perchlorinated aryl group, mixed fluorinated and chlorinated alkyl group, mixed fluorinated and chlorinated aryl group, CN, partially cyanated alkyl group, partially cyanated aryl group, methyl group, ethyl group, propyl group; and (R 2 N) + = dimethylpyrrolidinium ion, bis-spiropyrrolidinium ion.

[0015] It should be noted that mixed fluorinated and chlorinated alkyl groups and aryl groups include those that have fluorine and chlorine attached to a single carbon atom.

[0016] March 24, 2026 2 / 17, for example -CF2CI, as well as those that carry fluorine and chlorine separately on different C atoms, for example -CCI2CF3.

[0017] In the bis-spiropyrrolidinium ion, the positive charge is localized on the nitrogen atom, which also forms the spiro atom that connects the two pyrrolidine rings. Its structure is therefore similar to that of the dimethylpyrrolidinium ion, differing from it only by the bond between the two methyl groups, which is closed with two additional carbon atoms to form a five-membered ring.

[0018] In various formulations, the anion is selected from the group comprising methyl trifluoroborate, ethyl trifluoroborate, propyl trifluoroborate, trifluoromethyl trifluoroborate, pentafluoroethyl trifluoroborate, heptafluoropropyl trifluoroborate, nonafluorobutyl trifluoroborate, undecafluoropentyl trifluoroborate, trichloromethyl trifluoroborate, pentachloroethyl trifluoroborate, heptachloropropyl trifluoroborate, nonachlorobutyl trifluoroborate, undecachloropentyl trifluoroborate, pentafluorophenyl trifluoroborate, heptafluoronaphtyl trifluoroborate, pentachlorophenyl trifluoroborate, heptachloronaphtyl trifluoroborate and cyanotrifluoroborate.

[0019] Surprisingly, the alkyltrifluoroborate anions of the type R-BF3- with R = HC also prove to be effective. n H 2n and n = 1-3 as weakly coordinating and hydrolytically stable anions with a wide electrochemical window and potential profile analogous to the CF3BF3 anion.

[0020] In a second aspect, the disclosure relates to a process for the preparation of a nitrogen salt of substituted trifluoroborates, wherein according to the general reaction equation

[0021] (R 2 N) + X- (aq) + M + R 1 BF 3-(aq) — > (R 2 N) + R 1 BF 3-(s) + M + X' (aq)

[0022] with R 2 N = (dimethylpyrrolidinium, bis-spiropyrrolidinium, tetraethylammonium), X = (F, CI, Br, I, OH), M = (Na, K, Rb, Cs) and R 1 = electron-withdrawing group

[0023] (R 2 N) + X' and M + R 1 BF3 is dissolved in water, alcohol, or a mixture thereof, and the solutions are mixed together, thereby creating the (R 2 N) + R 1BF3- precipitates and is separated. This applies in particular to the tetraalkylammonium cations in combination with the alkyltrifluoroborates.

[0024] In a third aspect, the disclosure relates to the use of a nitrogen salt of substituted trifluoroborates according to aspect 1 in an electrolyte composition in an energy storage device, in particular a capacitor.

[0025] This applies in particular to the use of a nitrogen salt of hydrolysis-stable compounds, such as-

[0026] March 24, 2026 3 / 17 of recoverable substituted trifluoroborates. These are particularly distinguished by the fact that their hydrolysis stability allows for simple production and, due to the associated recoverability, enables particularly good recycling.

[0027] In a fourth aspect, the disclosure relates to an electrolyte composition for an energy storage device, in particular a capacitor, comprising a 0 < x < 5 molar solution of a nitrogen salt of substituted trifluoroborates according to aspect 1 in a solvent selected from the group comprising acetonitrile, propylene carbonate, diethyl ether, carbonic acid esters and γ-butyrolactone, as well as mixtures of two or more of these.

[0028] Detailed description of the revelation

[0029] As the inventors have recognized, the nitrogen salts of substituted trifluoroborates according to the invention enable a combined improvement of commercial electrolyte salts such as tetraethylammonium tetrafluoroborate (TEABF4). Firstly, by modifying the anion in the common solvents (acetonitrile and propylene carbonate), consistently superior conductivities compared to the tetrafluoroborate anion can be achieved. Furthermore, the tetrafluoroborate anion in TEABF4, due to its susceptibility to hydrolysis, also contributes to the performance degradation when a small amount of water is present in the electrolyte solution.

[0030] Compared to TEABF4, the disclosed substituted nitrogen trifluoroborate salts offer significantly better conductivity and solubility. Furthermore, the salts are readily soluble in solvents other than acetonitrile, which, in addition to maintaining equally good conductivity, also allows for the use of other solvents with higher boiling points and thus a wider operating temperature range. The use of the R is essential for achieving these advantages. 1 BF3--Anions. This allows for better tolerance of temperature spikes during rapid load changes and in large-volume EDLC supercapacitors.

[0031] By using trifluoroborates, particularly those substituted with electron-withdrawing substituents, a significantly superior ionic conductivity can be achieved compared to the prior art using the dimethylpyrrolidinium and bis-spiropyrrolidinium ions. This is not possible with BF4 as the anion, as the charge distribution in trifluoroborates substituted with electron-withdrawing substituents is significantly improved, which simultaneously enhances the properties of the anions in solution. Dimethylpyrrolidinium and bis-spiropyrrolidinium trifluoromethyltrifluoroborate are at least 1.5 molar soluble in common acetonitrile.

[0032] Furthermore, trifluoromethyltrifluoroborate is significantly more hydrolysis-stable than tetrafluoroborate. Therefore

[0033] March 24, 2026 4 / 17, a degradation mechanism on the anion side is simultaneously minimized compared to the state of the art.

[0034] The same advantages as for the trifluoromethyl substituent as an electron-withdrawing substituent on the trifluoroborate anion are also achieved by other electron-withdrawing substituents, thus enabling optimization with regard to the desired solvent, for example. In various embodiments, the electron-withdrawing substituent can therefore be a partially fluorinated or perfluorinated alkyl group.

[0035] In addition to their advantageous solvent properties in common solvents used in energy storage applications (acetonitrile, propylene carbonate, etc.), these compounds exhibit very low solubility in water and alcohols (ethanol, isopropanol). This allows them to be readily precipitated from aqueous solutions, greatly simplifying the necessary purification and drying processes and thus opening up particularly simple and cost-effective avenues for electrolyte recycling.

[0036] In other embodiments, the electron-withdrawing substituent can be a partially fluorinated or perfluorinated aryl group.

[0037] In other embodiments, the electron-withdrawing substituent can be a partially chlorinated or perchlorinated alkyl group.

[0038] In other embodiments, the electron-withdrawing substituent can be a partially chlorinated or perchlorinated aryl group.

[0039] In other embodiments, the electron-withdrawing substituent can be a mixed fluorinated and chlorinated alkyl group.

[0040] In other embodiments, the electron-withdrawing substituent can be a mixed fluorinated and chlorinated aryl group.

[0041] In various embodiments, the electron-withdrawing substituents can be a perfluorinated alkyl group with a length of C1-C5 or a perfluorinated aryl group.

[0042] In various embodiments, the electron-withdrawing substituents can be a partially fluorinated alkyl group with a length of CCs or a partially fluorinated aryl group.

[0043] In various embodiments, the electron-withdrawing substituents can be a mixed fluorinated and chlorinated alkyl group with a length of C C5 or a mixed fluorinated and chlorinated aryl group.

[0044] March 24, 2026 5 / 17 In other embodiments, the electron-withdrawing substituent can be a CN group.

[0045] In other embodiments, the electron-withdrawing substituent can be a partially cyanated alkyl group.

[0046] In other embodiments, the electron-withdrawing substituent can be a partially cyanated aryl group.

[0047] These and the other substituted trifluoroborates are characterized by resistance to aqueous hydrolysis and thus also offer advantages in the cell manufacturing process as well as in recovery in the recycling loop.

[0048] The disclosed nitrogen salts with substituted trifluoroborates can be used in an electrolyte composition for an energy storage device. In particular, the energy storage device can be a capacitor. In various embodiments, the capacitor is an electrochemical supercapacitor or ultracapacitor, especially an electrochemical double-layer capacitor (EDLC).

[0049] An electrolyte composition as disclosed may comprise a 0 < x < 5 molar solution of a nitrogen salt of substituted trifluoroborates as disclosed. In embodiments, the solution may be a 0 < x < 5 molar solution, a 0 < x < 4 molar solution, a 0 < x < 3 molar solution, a 0 < x < 2 molar solution, or a 0 < x < 1 molar solution. In embodiments, the solution may be a 0.5 < x < 5 molar solution, a 1.0 < x < 5 molar solution, a 1.5 < x < 5 molar solution, a 2.0 < x < 5 molar solution, a 2.5 < x < 5 molar solution, or a 3.0 < x < 5 molar solution. In various configurations, the solution can be a 0.5 < x < 4 molar solution, a 0.5 < x < 3 molar solution, a 0.5 < x < 2 molar solution, or a 0.5 < x < 1.5 molar solution.

[0050] In various embodiments, the solvent can be selected from the group comprising acetonitrile, propylene carbonate, diethyl ether, carbonic acid esters and γ-butyrolactone, as well as mixtures of two or more of these.

[0051] In various embodiments, the electrolyte composition can be a nitrogen salt of substituted trifluoroborates dissolved in acetonitrile, as disclosed, in a concentration of 0 < x < 5 molar solution, 0 < x < 4 molar solution, 0 < x < 3 molar solution, 0 < x < 2 molar solution, 0 < x < 1 molar solution, 0.5 < x < 5 molar solution, 1.0 < x < 5 molar solution, 1.5 < x < 5 molar solution, 2.0 < x < 5 molar solution, 2.5 < x < 5 molar solution or 3.0 < x < 5 molar solution.

[0052] March 24, 2026 6 / 17 In embodiment variants, the electrolyte composition can be a nitrogen salt of substituted trifluoroborates dissolved in acetonitrile in a concentration of a 0.5 < x < 5 molar solution, a 0.5 < x < 4 molar solution, a 0.5 < x < 3 molar solution, a 0.5 < x < 2 molar solution or a 0.5 < x < 1.5 molar solution.

[0053] In various embodiments, the electrolyte composition can be a nitrogen salt of substituted trifluoroborates dissolved in propylene carbonate in a concentration of a 0 < x < 5 molar solution, a 0 < x < 4 molar solution, a 0 < x < 3 molar solution, a 0 < x < 2 molar solution, a 0 < x < 1 molar solution, a 0.5 < x < 5 molar solution, a 1.0 < x < 5 molar solution, a 1.5 < x < 5 molar solution, a 2.0 < x < 5 molar solution, a 2.5 < x < 5 molar solution or a 3.0 < x < 5 molar solution.

[0054] In various embodiments, the electrolyte composition can be a nitrogen salt of substituted trifluoroborates dissolved in propylene carbonate in a concentration of a 0.5 < x < 5 molar solution, a 0.5 < x < 4 molar solution, a 0.5 < x < 3 molar solution, a 0.5 < x < 2 molar solution or a 0.5 < x < 1.5 molar solution.

[0055] In various embodiments, the electrolyte composition can be a nitrogen salt of substituted trifluoroborates dissolved in diethyl ether, carbonic acid ester or γ-butyrolactone in a concentration of a 0 < x < 5 molar solution, a 0 < x < 4 molar solution, a 0 < x < 3 molar solution, a 0 < x < 2 molar solution, a 0 < x < 1 molar solution, a 0.5 < x < 5 molar solution, a 1.0 < x < 5 molar solution, a 1.5 < x < 5 molar solution, a 2.0 < x < 5 molar solution, a 2.5 < x < 5 molar solution or a 3.0 < x < 5 molar solution.

[0056] In embodiment variants, the electrolyte composition can be a dimethylpyrrolidinium ion salt of substituted trifluoroborates dissolved in diethyl ether, carbonic acid ester or γ-butyrolactone, as disclosed, in a concentration of a 0.5 < x < 5 molar solution, a 0.5 < x < 4 molar solution, a 0.5 < x < 3 molar solution, a 0.5 < x < 2 molar solution or a 0.5 < x < 1.5 molar solution.

[0057] In embodiment variants, the electrolyte composition can be a bis-spiropyrrolidinium ion salt of substituted trifluoroborates dissolved in diethyl ether, carbonic acid ester or γ-butyrolactone, as disclosed, in a concentration of a 0.5 < x < 5 molar solution, a 0.5 < x < 4 molar solution, a 0.5 < x < 3 molar solution, a 0.5 < x < 2 molar solution or a 0.5 < x < 1.5 molar solution.

[0058] March 24, 2026 7 / 17 Synthesis of nitrogen salts with substituted trifluoroborates (R2 N) + R 1 BF3 _

[0059] The manifested (R 2 N) + R 1 BF3s can be manufactured according to the following general rule:

[0060] (R 2 N) + X- (aq) + M + R 1 BF3' (aq) — > (R 2 N) + R 1 BF 3-(s) + M + X' (aq)

[0061] (R 2 N) + X - (with R 2 N = (Dimethylpyrrolidinium (DMP), Bis-Spiropyrrolidinium (BSP)), and X = F, CI, Br, I, OH) and M + R 1 BF3- (with M = (Na, K, Rb, Cs) and R 1 = EEC) each dissolved in water, alcohol, or a mixture thereof, and the solutions mixed together. The desired (R) then precipitates. 2 N) + R 1BF3- precipitates out and is subsequently separated. Mixing can be achieved, for example, by stirring. Separation can be accomplished, for example, by filtration, filtering, or centrifugation.

[0062] In various embodiments, the reaction can be carried out at a temperature in the range of 0 °C to 80 °C, preferably in the range of 0 °C to 40 °C, particularly preferably in the range of 0 °C to 25 °C.

[0063] The manufacturing process also shows that the electrolytes can be recovered from the capacitor cells in a good and clean manner.

[0064] Brief description of the characters

[0065] Figure 1 shows the conductivity of the disclosed trifluoromethyltrifluoroborate salts of dimethylpyrrolidinium (DMP) and bis-spiropyrrolidinium (BSP) in 1 and 1.5 M solutions, respectively (for DMP). +CF3BF3- also 2 M), in acetonitrile depending on the temperature compared to the tetraethylammonium (TEA) salts TEA + BF4- (1 M in acetonitrile) and TEA + CF3BF3- (1 M and 1.5 M in acetonitrile).

[0066] Figure 2 shows the comparison of cyclic voltagrams (50 mV / s) between TEA + BF4 _ and the disclosed DMP + F3CBF3- (each 1 molar in propylene carbonate).

[0067] Figure 3 shows the conductivity of the disclosed methyl methyl trifluoroborate salt of tetraethylammonium (TEA) in 1 M solution in acetonitrile compared to the tetraethylammonium (TEA) salt TEA + BF4- (also 1 M in acetonitrile) as a function of temperature.

[0068] March 24, 2026 8 / 17

[0069]

[0070] The present invention is illustrated by the following examples, although the invention is not limited to these. For the sake of simplicity, dimethylpyrrolidinium cations (DMP) and tetraethylammonium cations have been consistently chosen for the examples. These apply analogously to bis-spiropyrrolidinium cations (BSP).

[0071] Unless otherwise stated, for the purposes of this disclosure, "room temperature" shall be understood to mean a temperature in the range of 20 °C - 25 °C, in particular 22 °C.

[0072] 1. Synthesis of dimethylpyrrolidinium salts with substituted trifluoroborates

[0073] 1.1 Example 1 -

[0074]

[0075] F3CBF3i

[0076] It was K + F3CBF3 and DMP + Ck was dissolved in water and the solutions were combined. The solution was then filtered and the residue dried.

[0077] DMP + Ck (aq) + K + F3CBF3' (aq) DMP + F3CBF3' (s) + K + Ck (aq)

[0078] 1.2 Example 2 -

[0079]

[0080] It was K + F5C2BF3 and DPM + Ck was dissolved in water and the solutions were combined. The solution was then filtered and the residue dried.

[0081] DMP + Ck (aq) + K + F5C2BF 3-(aq) DMP + F5C2BF 3-(s) + K + Ck (aq)

[0082] 1.3 Example 3 -

[0083]

[0084] CI3CBF3-)

[0085] It was K + CI3CBF3 and DMP + Ck was dissolved in water and the solutions were combined. The solution was then filtered and the residue dried.

[0086] DMP + Ck (aq) + K +CI3CBF 3-(aq) — > DMP + CI3CBF 3-(s) + K + Ck (aq)

[0087] 1.4 Example 4 - Dimethylpyrrolidinium pentafluorophenyltrifluoroborate (DMP) + F5C fi BF3

[0088] It was K + F5C6BF3 and DMP + Ck was dissolved in water and the solutions were combined. The solution was then filtered and the residue dried.

[0089] DMP + Ck (aq) + K + F5C6BF 3-(aq) DMP + F5C6BF 3-(s) + K + Ck (aq)

[0090] March 24, 2026 9 / 17TU0070P-WC

[0091] 1.5 Example 5 - Dimethylpyrrolidinium heptachloronaphtyl trifluoroborate (DMP) + CI7C10BF3')

[0092] It was K + CI7C 10 BF3 and DMP + Ck was dissolved in water and the solutions were combined. The solution was then filtered and the residue dried.

[0093] DMP + Cl'(aq) + K + ClyCioBF3'( aq ) DMP + ClyCioBF3'( s ) + K + Cl'(aq)

[0094] 1.6 Example 6 - Dimethylpyrrolidinium cyanotrifluoroborate (DMP) + CNBF<)

[0095]

[0096] It was K + CNBF3 and DMP + Ck was dissolved in water and the solutions were combined. The solution was then filtered and the residue dried.

[0097]

[0098] DMP + Ck (aq) + K + CNBF 3-(aq) DMP + CNBF 3-(s) + K + Ck (aq)

[0099] 1.7 Example 7 - Dimethylpyrrolidinium methyltrifluoroborate (DMP) + CH3BF3~)

[0100] It was K + CH3BF3 and DMP +Ck was dissolved in water and the solutions were combined. The solution was then filtered and the residue dried.

[0101] DMP + Ck (aq) + K + CH3BF 3-(aq) —> DMP + CH3BF3-+ K + Ck (aq)

[0102] 1.8 Example 8 - Tetraethylammonium methyltrifluoroborate (TEA + CH3BF<)

[0103]

[0104] It was K + CH3BF3 and TEA + Ck was dissolved in water and the solutions were combined. The solution was then filtered and the residue dried.

[0105] TEA + Ck (aq) + K + CH3BF 3-(aq) — > TEA + CH3BF3-+ K + Ck (aq)

[0106] 2. Electrolyte composition for a capacitor

[0107] As an example of a suitable electrolyte composition, 1 M and 1.5 M solutions of DMPCF3BF3 and BSPCF3BF3 were prepared in acetonitrile (Sigma Aldrich; 99.99%), and a 2 M solution of DMPCF3BF3 was also prepared. These were then electrochemically characterized with 1 M and 1.5 M solutions of tetraethylammonium trifluoromethyl trifluoroborate (TEA), prepared according to the same general procedure described above. + F3CBF3j and a 1 M solution of the commercially used TEABF4 in acetonitrile were compared.

[0108] March 24, 2026 10 / 17 A comparative measurement of the conductivity as a function of temperature was carried out. This was performed in a closed measuring cell "TSC 1600 Closed" from rhd Instruments with a 1 ml sample volume.

[0109] The result of this comparative measurement is shown in Figure 1. As can be seen, all characteristic curves lie above that of the prior art reference salt TEABF4, which proves that the conductivity is better than that of TEABF4 in the relevant temperature range (10–60 °C). The DMP and BSP salts according to the disclosure also exceed the conductivity of TEA at the respective concentrations. + F3CBF3 _ .

[0110] Figure 2 shows the comparison of cyclic voltagrams (50 mV / s) between TEA + BF4 and the disclosed DMP + F3CBF3- (each 1 molar in propylene carbonate) is shown, demonstrating an improved capacity of DMPCF3BF3.

[0111] Furthermore, the DMP can be used + F3CBF3 - higher capacity-enhancing concentrations were achieved. For this purpose, solutions in acetonitrile were prepared in a test series with concentrations of 0.5 M, 1 M, 1.5 M, 2 M and 5 M.

[0112] Furthermore, alternative solvents were tested. For this purpose, 1 M solutions of the DMP were used. + F3CBF3n is produced by propylene carbonate, diethyl ether, carbonic acid ester and y-butyrolactone.

[0113] Figure 3 shows the conductivity measurement of TEA. + CH3CBF3- was plotted. Here, comparable measured values ​​to TEABF4 from the state of the art were achieved.

[0114] As weakly coordinating cations, the 4-substituted ammonium cations exhibit a low Coulomb interaction with the similarly weakly coordinating substituted trifluoroborate anions. This weak polar interaction also applies to polar solvents and solvent mixtures, which is advantageous for achieving the desired low equivalent series resistance (ESR).

[0115] March 24, 2026 11 / 17

Claims

Claims 1. Nitrogen salt of substituted trifluoroborates with the structural formula (R 2 N) + R 1 BF3- with R 1 = partially fluorinated or perfluorinated alkyl group, partially fluorinated or perfluorinated aryl group, partially chlorinated or perchlorinated alkyl group, partially chlorinated or perchlorinated aryl group, mixed fluorinated and chlorinated alkyl group, mixed fluorinated and chlorinated aryl group, CN, partially cyanated alkyl group, partially cyanated aryl group, methyl group, ethyl group, propyl group; and (R 2 N) + = dimethylpyrrolidinium ion, bis-spiropyrrolidinium ion.

2. Nitrogen salt of substituted trifluoroborates according to claim 1, wherein R 1BF3- is selected from the group comprising methyl trifluoroborate, ethyl trifluoroborate, propyl trifluoroborate, trifluoromethyl trifluoroborate, pentafluoroethyl trifluoroborate, heptafluoropropyl trifluoroborate, nonafluorobutyl trifluoroborate, undecafluoropentyl trifluoroborate, trichloromethyl trifluoroborate, pentachloroethyl trifluoroborate, heptachloropropyl trifluoroborate, nonachlorobutyl trifluoroborate, undecafluoropentyl trifluoroborate, pentafluorophenyl trifluoroborate, heptafluoronaphtyl trifluoroborate, pentachlorophenyl trifluoroborate, heptachloronaphtyl trifluoroborate and cyanotrifluoroborate.

3. Process for the preparation of a nitrogen salt of substituted trifluoroborates, wherein according to the general reaction equation (R 2 N) + X- (aq) + M + R 1 BF 3-(aq) — > (R 2 N) + R 1 BF 3-(s) + M + X' (aq) with R 2N = (dimethylpyrrolidinium, bis-spiropyrrolidinium, tetraethylammonium), X = (F, CI, Br, I, OH), M = (Na, K, Rb, Cs) and R 1 = electron-withdrawing group (R 2 N) + X' and M + R 1 BF3 is dissolved in water, alcohol, or a mixture thereof, and the solutions are mixed together, thereby creating the (R 2 N) + R 1 BF3 falls as precipitation and is separated.

4. The method according to claim 3, wherein the reaction is carried out at a temperature in the range of 0 °C to 80 °C, preferably in the range of 0 °C to 40 °C, particularly preferably in the range of 0 °C to 25 °C. March 24, 2026 12 / 17TU0070P-WG 5. Use of a nitrogen salt of hydrolysis-stable, recoverable substituted trifluoroborates according to one of claims 1 or 2 in an electrolyte composition in an energy storage device, in particular a capacitor.

6. Electrolyte composition for an energy storage device, in particular a capacitor, comprising a 0 < x < 5 molar solution of a nitrogen salt of substituted trifluoroborates according to one of claims 1 or 2 in a solvent selected from the group comprising acetonitrile, propylene carbonate, diethyl ether, carbonic acid esters and γ-butyrolactone, as well as mixtures of two or more of these. March 24, 2026 13 / 17

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