BATTERY ELECTROLYTE

Abstract

In one aspect of the disclosure, an electrode assembly is presented. The electrode assembly includes a positive electrode, a negative electrode, a separator positioned between the positive and negative electrodes, and an electrolyte. The electrolyte comprises lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, fluoroethylene carbonate, vinylene carbonate, and an additive, dissolved in a solvent of ethylene carbonate and ethyl methyl carbonate. This electrolyte saturates the negative electrode, the positive electrode, and the separator. The additive is (S)-N-(1-(2-((4-(3-(Trifluoromethyl)phenyl)piperzin-1-yl)methyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)-3-methyl-2-(2-oxo-1,3-diazaspier[4.5]decan-1-yl)butanamide, which contributes to improved performance and stability of the electrode assembly.

Description

AREA OF TECHNOLOGY

[0001] This disclosure concerns electrolytes for lithium-ion batteries. GENERAL STATE OF THE ART

[0002] Electrode materials, such as lithium and silicon, can be used to achieve high energy density and capacity. With its high specific capacity, silicon can form lithium silicide during charge and discharge cycles. Lithium silicide can irreversibly precipitate onto the electrode surface, increasing cell resistance. Furthermore, the expansion and contraction of silicon can cause cell swelling. SUMMARY

[0003] In one aspect of the disclosure, an electrode assembly is presented. The electrode assembly includes a positive electrode, a negative electrode, a separator positioned between the positive and negative electrodes, and an electrolyte comprising lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, fluoroethylene carbonate, vinylene carbonate, and an additive, dissolved in a solvent of ethylene carbonate and ethyl methyl carbonate, and saturating the negative electrode, the positive electrode, and the separator, wherein the additive is (s)-n-(1-(2-((4-(3-(Trifluoromethyl)phenyl)piperazin-1-yl)methyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)-3-methyl-2-(2-oxo-1,3-diazaspiso[4,5]decan-1-yl)butanamide. The electrolyte may contain 0.7 M lithium hexafluorophosphate and 0.3 M lithium bis(fluorosulfonyl)imide. The solvent may contain ethylene carbonate and ethyl methyl carbonate in a volume ratio of 25 / 75.The electrolyte may contain 1 wt% fluoroethylene carbonate. The electrolyte may also contain 1 wt% vinylene carbonate. In some configurations, the electrolyte may contain 0.3 wt% of the additive. The multifunctional additive may contain a sulton group and a fluorinated phosphorus group within its chemical structure. The additive may form a lithium polymer structure through ring closure. In other configurations, a combination of lithium bis(fluorosulfonyl)imide, fluoroethylene carbonate, vinylene carbonate, and the additive may result in reduced resistance and swelling compared to a battery cell without the combination. The positive and negative electrodes may exhibit increased swelling suppression under storage at 60 °C compared to a battery cell without the electrolyte.In other configurations, the positive electrode and the negative electrode can exhibit increased cycle life performance at 45 °C for up to 500 cycles compared to a battery cell without the electrolyte.

[0004] Another aspect of the revelation presents a method for manufacturing a battery cell. The process involves positioning a separator between a negative electrode and a positive electrode, dissolving 0.7 M lithium hexafluorophosphate, 0.3 M lithium bis(fluorosulfonyl)imide, 1 wt% fluoroethylene carbonate, 1 wt% vinylene carbonate, and 0.3 wt% of a multifunctional additive in a solvent mixture of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 25 / 75 to form an electrolyte, wherein the multifunctional additive is (s)-n-(1-(2-((4-(3-(trifluoromethyl)phenyl)piperazin-1-yl)methyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)-3-methyl-2-(2-oxo-1,3-diazaspiso[4,5]decan-1-yl)butanamide, and saturating the negative electrode, the positive electrode, and the separator with the Electrolytes.The multifunctional additive can contain a sultan group and a fluorinated phosphorus group within its chemical structure. The multifunctional additive can form a lithium polymer structure through ring closure.

[0005] In yet another aspect of the disclosure, an electrolyte for a battery cell is presented. The electrolyte comprises 0.7 M lithium hexafluorophosphate, 0.3 M lithium bis(fluorosulfonyl)imide, 1 wt% fluoroethylene carbonate, 1 wt% vinylene carbonate, 0.3 wt% a multifunctional additive, and a solvent mixture of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 25 / 75, wherein the multifunctional additive is (s)-n-(1-(2-((4-(3-(trifluoromethyl)phenyl)piperazin-1-yl)methyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)-3-methyl-2-(2-oxo-1,3-diazaspiso[4,5]decan-1-yl)butanamide. The multifunctional additive may contain a sultan group and a fluorinated phosphorus group within its chemical structure. The multifunctional additive can form a lithium polymer structure through ring closure.In some configurations, lithium bis(fluorosulfonyl)imide, fluoroethylene carbonate, vinylene carbonate, and the multifunctional additive can lead to reduced resistance and swelling in a battery cell containing the electrolyte compared to a battery cell without the electrolyte. A battery cell containing the electrolyte may exhibit increased swelling suppression during storage at 60°C compared to a battery cell without the electrolyte. A battery cell containing the electrolyte may exhibit increased cycle life performance at 45°C for up to 500 cycles compared to a battery cell without the electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic representation of an additive according to one or more aspects of the revelation; Fig. 2 is a schematic representation of an additive according to one or more aspects of the revelation; Fig. Figure 3 is a diagram of a differential potential versus a differential voltage of a battery with an electrolyte in which the additive from Fig. 2 is introduced; Fig. Figure 4 is a diagram of a linear sweep voltammetry of a battery with an electrolyte containing the additive from Fig. 2 is introduced; Fig. 5 is a table of electrolyte properties according to one or more aspects of the disclosure; Fig. 6 is a table of electrolyte compositions and their properties according to one or more aspects of the disclosure; Fig. Figure 7 is a diagram of the percentage conservation of batteries into which electrolytes are introduced according to one or more aspects of the disclosure; Fig. Figure 8 is a diagram of the internal DC resistance of batteries into which electrolytes are introduced according to one or more aspects of the disclosure; Fig. Figure 9 is a diagram of the percentage swelling rate of batteries into which electrolytes are introduced according to one or more aspects of the disclosure; and Fig. Figure 10 is a schematic representation of a battery with an electrolyte according to one or more aspects of the disclosure. DETAILED DESCRIPTION

[0006] Depending on the requirements, detailed embodiments of the claimed subject matter are disclosed in this document; however, it is understood that the disclosed embodiments are merely representative and can be implemented in various and alternative forms. The figures are not necessarily to scale; some features may be greatly enlarged or reduced to show details of certain components. Therefore, the specific structural and functional details disclosed in this document are not to be interpreted as limiting, but merely as a representative basis to teach the person skilled in the art the diverse applications of the embodiments of the claimed subject matter.

[0007] Unless expressly stated otherwise, all numerical values ​​and ranges relating to quantities, measurements, percentages, weights, and similar numerical references within this document are to be understood as being preceded by the phrase "approximately." This applies even where the phrase "approximately" is not explicitly used. All values ​​and ranges are intended to encompass variations that may arise from standard measurement, manufacturing processes, material properties, and the intended functionality of aspects of the disclosure. For example, if the liquid electrolyte is described as having "5 wt% of a component," this is to be understood as "approximately 5 wt% of a component." Furthermore, when numerical values ​​are presented as a range, such as "100 to 200 units," this range should be interpreted as effectively meaning "approximately 100 to approximately 200 units."Such variations are implicitly included in the scope of the present disclosure.

[0008] The present disclosure relates to an electrolyte composition for lithium (Li)-ion batteries designed to increase performance and longevity under various conditions. A specific multifunctional additive (MFA) ((s)-n-(1-(2-((4-(3-(Trifluoromethyl)phenyl)piperzin-1-yl)methyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)-3-methyl-2-(2-oxo-1,3-diazaspier[4.5]decan-1-yl)butanamide) for inclusion in electrolyte compositions is disclosed. This MFA carries both a sultan group and a fluorinated phosphorus group and exhibits the potential to form a Li-polymer structure by ring closure. The presented electrolyte comprises a combination of 0.7 mol (M) lithium hexafluorophosphate (LiPF6) as a primary salt, 0.3 M lithium bis(fluorosulfonyl)imide (LiFSI) as a secondary salt, a solvent mixture of ethylene carbonate / ethyl methyl carbonate (EC / EMC) with 25 / 75 vol% and additives, including 1 wt% fluoroethylene carbonate (FEC), 1 wt%Contains -% vinylene carbonate (VC) and 0.3 wt% MFA. This formulation exhibits swelling suppression under high-temperature storage conditions (60 °C) and maintains cycle life performance at elevated temperatures (45 °C) for up to 500 cycles.

[0009] Fig. Figure 1 is a schematic representation of the chemical structure of the additive 1,3-propanediol cyclosulfate (PA355). The structure features a six-membered ring that forms the core of the molecule. At the top of the ring is a CH₂ group, represented by a single line forming a point. This group is bonded to two oxygen atoms, one on each side, with "O" symbols. At the bottom of the ring structure is a sulfur atom, represented by an "S". This sulfur atom is connected to the rest of the ring by four lines, indicating that it forms a sulfhydryl group with double bonds to two oxygen atoms. Cyclic sulfates give the molecule its properties as a sulfate-based additive, which can be advantageous for use in battery electrolytes or other chemical processes.

[0010] Fig. Figure 2 is a schematic representation of the chemical structure of the additive (s)-n-(1-(2-((4-(3-(Trifluoromethyl)phenyl)piperazin-1-yl)methyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)-3-methyl-2-(2-oxo-1,3-diazaspiro[4.5]decan-1-yl)butanamide (PA800). The structure is shown as an ionic compound with two distinct parts. On the left is a complex anion, enclosed in square brackets with a negative charge. This anion contains two phosphorus atoms, each bonded to two fluorine atoms and two oxygen atoms. It also includes a sulfur atom bonded to two oxygen atoms and two lithium ions associated with the oxygen atoms. On the right is a cation, specifically an ethylammonium ion.This cation features a central nitrogen atom with a positive charge, three ethyl groups (CH2CH3) bonded to the nitrogen, and a hydrogen atom also bonded to the nitrogen. This ionic structure gives PA800 its properties, making it useful as an electrolyte additive in battery applications where its complex chemical composition can improve performance or stability.

[0011] Fig. Figure 3 is a diagram of the differential capacitance (dQ / dV) versus a voltage in electron volts per volt (Ewb / V) of a battery with and without the in Fig. 2 PA800 additives shown. Fig. Figure 3 illustrates the properties of high reducibility and solid electrolyte membrane formation of PA800. The x-axis represents the voltage in the range of 1.8 to 3.2 volts (V), while the y-axis represents the differential capacitance in the range of 0 to 300 microampere-hours per volt (µAh / V). The diagram compares a base electrolyte without additives, labeled "Without Add.", with the same base electrolyte containing 1 wt% PA800 additive. The base electrolyte composition is 1 M EC / EMC in a volume ratio (v / v) of 3 / 7. The battery electrodes are nickel-cobalt-manganese (NCM) 811 paired with graphite, where NCM is a cathode material with a ratio of 80% nickel, 10% cobalt, and 10% manganese.A dashed box highlights the range labeled "PA800 Reduction" between approximately 2.2 and 2.4 volts, where the PA800 additive undergoes a reduction that contributes to the formation of a solid electrolyte interface (SEI) layer. The curves show distinct differences in behavior: the "No Add." curve has a peak at about 3 V followed by a decline, while the PA800 curve shows a more gradual rise with several smaller peaks between 2.8 V and 3.2 V. This comparison suggests that the addition of PA800 alters the electrochemical behavior of the battery, potentially improving the formation of a stable SEI layer and increasing the overall battery performance.

[0012] Fig. Figure 4 is a linear sweep voltammetry (LSV) diagram showing the high oxidation stability of a battery electrolyte with and without the in Fig. The diagram shows two PA800 additives. The x-axis represents the potential (V) in a range of 3 V to 7 V, while the y-axis represents the current in milliamperes (mA) from 0 to 1.60. The diagram compares two electrolyte compositions: a base electrolyte without additives, labeled "Without Add.", and the same base electrolyte with 1 wt% PA800 additive, labeled "PA800 1%". The working electrode is platinum (Pt) versus Li / Li. + The sampling rate is 1 millivolt per second (mV / s) and the sampling range is 3 V to 7 V. An inserted table provides additional data showing that at a current density of 0.1 mA / cm² 2The electrolyte "without additive" reaches this threshold at 5.42 V, while the electrolyte PA800 1 wt% reaches it at 5.66 V. Both curves remain relatively flat up to approximately 5.5 V, after which they show a current increase. The curve for the PA800 additive shows a higher initial potential for oxidation and a less steep current rise compared to the base electrolyte, indicating improved oxidation stability of the electrolyte with the PA800 additive.

[0013] Fig. Figure 5 is a table of electrolyte compositions, illustrating their various formulations and their effects on battery performance. The reference sample (Ref. No. 1) contains 1.0 M LiPF6, 25% EC, 75% EMC, 1.0 wt% FEC, and 1.0 wt% VC. The first set of compositions (Nos. 2–5) investigates the effect of salt-like additives and PA800. These compositions retain the base electrolyte while incorporating various additives: 1.0 wt% lithium difluorophosphate (LiPO2F2 or PA77) in composition No. 2, 0.3 wt% PA800 in composition No. 3, 0.5 wt% PA800 in composition No. 4, and 0.3 wt% PA355 in composition No. 5. This series aims to evaluate the effect of these additives on the electrolyte's performance. The next set of compositions (Nos. 6-7) determines the effect of 1,3-propanesultone (PS). These compositions contain 0.5 wt. % or 1.0 wt. % respectively.-% PS was introduced, while other components were kept constant. Experiments Nos. 8-10 focused on the effect of PA355 at 0.3 wt%, 0.5 wt%, and 1.0 wt%, respectively. Experiment No. 11 introduced a dual-salt system. This composition included 0.7 M LiPF6 and 0.3 M LiFSI, while the other components were maintained. The final set of compositions (Nos. 12-14) built upon this dual-salt system, combining 0.7 M LiPF6 and 0.3 M LiFSI with 0.3 wt% and 0.5 wt% PA800, respectively, while in No. 14, 0.5 wt% PS was added to the dual-salt base.

[0014] The statistical design of experiments (SDO) indicates that certain compositions showed particularly promising results. In particular, the formulations with 0.5 wt% PS (No. 6), 0.5 wt% PA355 (No. 9), and 0.3 wt% PA800 (No. 3) demonstrated swelling suppression and reduced DC internal resistance (DC-IR) under 60 °C storage test conditions. These compositions also exhibited acceptable cycle life performance at 45 °C. Based on these results, additional experiments (Nos. 11–14) were conducted to investigate the potential of combining the dual-salt system with the most effective additives.

[0015] Fig. Figure 6 is a table of electrolyte compositions and their corresponding properties. The reference composition (Ref. No. 1) contains 1.0 M LiPF6 as the salt with a solvent mixture of 25 vol% EC and 75 vol% EMC. This reference also includes 1.0 wt% FEC and 1.0 wt% VC as additives. The properties of this reference electrolyte are as follows: viscosity of 3.12 centipoise (cP), conductivity of 9.241 microsiemens per centimeter (µS / cm), and density of 1.1978 grams per cubic centimeter (g / cm³). 3The reference formulation lists a hydrofluoric acid (HF) content of 11.495 parts per million (ppm) and a color number of 4 according to the American Public Health Association (APHA) Hazen scale. The following sections examine the effects of modifying this base formulation. Formulation No. 11 incorporates a dual-salt system in which a portion of the LiPF6 is replaced by LiFSI. This formulation uses 0.7 M LiPF6 and 0.3 M LiFSI, maintaining the same solvent and additive ratios as the reference formulation. This modification results in a decrease in viscosity to 3.00 cP, a slight increase in conductivity to 9.526 µS / cm, and a slight decrease in density to 1.1968 g / cm³. 3 and an increase in HF content to 31,944 ppm. The color number also increases to 7 APHA.

[0016] In composition no. 12, 0.3 wt% PA800 is added to the dual salt composition, resulting in a slight increase in viscosity to 3.05 cP, a decrease in conductivity to 9.311 µS / cm, and a slight increase in density to 1.1972 g / cm³. 3 and a significant decrease in HF content to 30.649 ppm. The color number increased to 8 APHA. Composition No. 13 investigates the effect of 0.5% PA355, which resulted in a significant decrease in viscosity to 2.43 cP, a slight decrease in conductivity to 9.233 µS / cm, and a slight increase in density to 1.1977 g / cm³. 3 and a decrease in HF content to 28.132 ppm. The color number further increases to 12 APHA. Composition No. 14 investigates the effect of 0.5% PS, which results in similar properties to the PA355 composition with a viscosity of 2.42 cP, a conductivity of 9.214 µS / cm, and a density of 1.1979 g / cm³. 3and results in an HF content of 28,083 ppm. The color number for this composition is the highest at 13 APHA.

[0017] Fig. Figure 7 is a graph of the capacity retention performance of various electrolyte compositions over 500 charge-discharge cycles. The graph represents the percentage retention on the y-axis in a range of 75% to 100%, plotted against the number of cycles on the x-axis from 0 to 500. A nickel / graphite pouch cell was used as the test condition, charging at a rate of 1 charge / discharge rate (C) ampere-hour (Ah) to a limit of 4.2 V (0.02 C) and discharging at a rate of 1 C (Ah) to 2.7 V. The graph compares five different electrolyte compositions, designated No. 1, No. 11, No. 12, No. 13, and No. 14, which are described in Figure 7. Fig. correspond to the 6 specified compositions.

[0018] The reference composition, No. 1, exhibits a moderate capacity loss rate, maintaining approximately 85% capacity after 500 cycles. Composition No. 11, which replicates the dual-salt system, performs slightly worse than the reference, ultimately maintaining around 84% capacity. Composition No. 12, which incorporates the dual-salt system and PA800, demonstrates the best performance. It maintains the highest capacity retention throughout the test, ultimately reaching approximately 90% after 500 cycles. In contrast, composition No. 13, with the dual-salt system and PA355, exhibits a rapid initial capacity loss for up to approximately 150 cycles before stabilizing, ultimately maintaining around 82% capacity. Composition No. 14, which incorporates the dual-salt system and PS, performs the worst, with the steepest initial decline and the lowest final capacity retention of approximately 79%.This illustrates that adding PA800 to the dual-salt system (No. 12) increases capacity retention over many cycles. Conversely, the other additives (PA355 and PS) do not increase performance compared to the reference or dual-salt system alone.

[0019] Fig. Figure 8 is a DC-IR graph at 50% state of charge (SOC) for the electrolyte compositions over a 4-week storage period at 60°C. The graph represents the percentage change in DC-IR on the y-axis from -40% to 80%, plotted against the storage time in weeks on the x-axis from 0 to 4 weeks. The test conditions include a nickel / graphite pouch cell. The DC-IR test was performed at a 50% SOC with varying C-rates (0.5°C / 1.0°C / 2.0°C / 2.5°C) for 10 seconds. The diagram compares the five different electrolyte compositions: No. 1, No. 11, No. 12, No. 13, and No. 14. All compositions start with a DC-IR change of 0% in week 0 but exhibit different behavior over the 4-week storage period. The reference composition, No. 1, shows relatively stable performance with minor fluctuations, reaching a slightly negative DC-IR change after 4 weeks.Composition No. 11, which represents the dual salt system, shows the most volatile behavior with large positive peaks in the DC-IR in weeks 2 and 4, indicating an increase in internal resistance.

[0020] Composition No. 12, which includes the dual-salt system and PA800, shows more stable performance compared to No. 11, with less fluctuation and a moderate increase in DC-IR up to week 4. Compositions No. 13 and No. 14, which form the dual-salt system with PA355 and PS respectively, show similar trends. They both exhibit an initial decrease in DC-IR followed by an increase, with No. 13 having a slightly higher DC-IR than No. 14 after 4 weeks. Composition No. 12 appears to offer good balance and shows less fluctuation in DC-IR compared to the other dual-salt compositions. This suggests that the addition of PA800 to the dual-salt system may help stabilize the battery's internal resistance during prolonged high-temperature storage.

[0021] Fig. Figure 9 is a graph of the swelling rate of nickel / graphite pouch battery cells with different electrolyte compositions over a storage period of 4 weeks at 60 °C. The graph plots the percentage swelling rate on the y-axis (0% to 90%) against the storage time in weeks on the x-axis (0 to 4 weeks). The graph compares the five different electrolyte compositions, labeled No. 1, No. 11, No. 12, No. 13, and No. 14. All compositions start with 0% swelling in week 0 but exhibit different behavior over the 4-week storage period. The reference composition, No. 1, shows the highest swelling rate, reaching approximately 78% by the end of week 4.

[0022] This indicates that the reference electrolyte provides the least protection against cell swelling under high-temperature storage conditions. Composition No. 11, which replicates the dual-salt system, shows improved swelling resistance compared to the reference, with a final swelling rate of approximately 62% after 4 weeks. This suggests that the dual-salt system alone offers some benefit in reducing cell swelling. Composition No. 12, which includes the dual-salt system and PA800, exhibits the best performance in terms of swelling resistance. It shows the lowest swelling rate throughout the entire test period, reaching only about 45% swelling after week 4.

[0023] This improvement over both the reference and the dual-salt system alone indicates that the addition of PA800 plays a role in mitigating cell swelling under high-temperature conditions. Compositions No. 13 and No. 14, using the dual-salt system with PA355 and PS respectively, show moderate performance. They both exhibit lower swelling rates than the reference and the dual-salt system alone, but higher rates than the PA800 composition. No. 13 ultimately achieves a swelling rate of approximately 53%, while No. 14 shows slightly better performance with a final swelling rate of about 50%.

[0024] Fig.Figure 10 represents a battery cell 10 comprising a positive electrode 12, a negative electrode 14, and a separator 16 positioned between the positive electrode 12 and the negative electrode 14. The positive electrode 12 contains a positive active material 18 forming a layer of the positive electrode 12. The battery cell 10 contains a liquid electrolyte 20. The liquid electrolyte 20 permeates the surface of the positive active material layer and comprises 0.7 M LiPF6, 0.3 M LiFSI, 1 wt% FEC, 1 wt% VC, and 0.3 wt% MFA, dissolved in a solvent of EC and EMC in a volume ratio of 25 / 75. This specific composition of the liquid electrolyte 20 is configured to suppress electrochemical oxidation of the positive active material layer 18 during electrochemical cycles.The MFA in the liquid electrolyte 20 is (s)-n-(1-(2-((4-(3-(Trifluoromethyl)phenyl)piperzin-1-yl)methyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)-3-methyl-2-(2-oxo-1,3-diazaspier[4.5]decan-1-yl)butanamide. This additive contains a sultan group and a fluorinated phosphorus group within its chemical structure and is capable of forming a Li-polymer structure by ring closure. The liquid electrolyte 20 saturates the positive electrode 12, the negative electrode 14, and the separator 16 such that the combination of LiFSI, FEC, VC, and the MFA results in reduced resistance and reduced swelling compared to an otherwise identical battery cell without this combination.Furthermore, the battery cell 10 with this electrolyte composition exhibits increased swelling suppression under storage at 60 °C and increased cycle life performance at 45 °C for up to 500 cycles compared to an otherwise identical battery cell without this electrolyte.

[0025] In another embodiment, the liquid electrolyte 20 comprises the same composition as described above, which saturates the positive electrode 12 and the negative electrode 14. The MFA can interact with the other components to form stable interfaces on the electrode surfaces, thereby reducing impedance and improving cycle life. The solvent mixture of EC and EMC in a volume ratio of 25 / 75 provides a balance between high ionic conductivity and stability, thereby increasing the performance of the battery cell 10 and its cycle life. The positive active material layer 18 can be composed of a suitable Li-containing compound that offers high capacity and thermal stability, contributing to the overall performance and stability of the battery cell 10.The battery cell 10 is configured to maintain its capacity over a longer period with improved performance characteristics due to the electrolyte composition, which includes the MFA that forms a Li-polymer structure through ring closure.

[0026] Although representative embodiments have been described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the terms used in the patent specification are descriptive rather than limiting, and it is understood that various modifications can be made without departing from the claimed subject matter.

[0027] Furthermore, the features of different implemented embodiments can be combined to form further embodiments within the scope of the claimed subject matter that are not expressly described or illustrated.

[0028] According to the present invention, an electrode assembly is provided comprising: a positive electrode; a negative electrode; a separator positioned between the positive electrode and the negative electrode; and an electrolyte comprising lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, fluoroethylene carbonate, vinylene carbonate, and an additive, dissolved in a solvent of ethylene carbonate and ethyl methyl carbonate, and saturating the negative electrode, the positive electrode, and the separator, wherein the additive is (s)-n-(1-(2-((4-(3-(Trifluoromethyl)phenyl)piperazin-1-yl)methyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)-3-methyl-2-(2-oxo-1,3-diazaspiso[4,5]decan-1-yl)butanamide.

[0029] According to one embodiment, the electrolyte comprises 0.7 M lithium hexafluorophosphate and 0.3 M lithium bis(fluorosulfonyl)imide.

[0030] According to one embodiment, the solvent comprises ethylene carbonate and ethyl methyl carbonate in a volume ratio of 25 / 75.

[0031] According to one embodiment, the electrolyte contains 1 wt% fluoroethylene carbonate.

[0032] According to one embodiment, the electrolyte contains 1 wt% vinylene carbonate.

[0033] According to one embodiment, the electrolyte contains 0.3 wt% of the additive.

[0034] According to one embodiment, the additive contains a sultan group and a fluorinated phosphorus group within its chemical structure.

[0035] According to one embodiment, the additive forms a lithium polymer structure by ring closure.

[0036] According to one embodiment, a combination of lithium bis(fluorosulfonyl)imide, fluoroethylene carbonate, vinylene carbonate and the additive leads to reduced resistance and reduced swelling compared to an otherwise identical battery cell without the combination.

[0037] According to one embodiment, the positive electrode and the negative electrode exhibit increased swelling suppression when stored at 60 °C compared to an otherwise identical battery cell without the electrolyte.

[0038] According to one embodiment, the positive electrode and the negative electrode exhibit increased cycle life performance at 45 °C for up to 500 cycles compared to an otherwise identical battery cell without the electrolyte.

[0039] According to the present invention, a method for manufacturing a battery cell comprises: positioning a separator between a negative electrode and a positive electrode; dissolving 0.7 M lithium hexafluorophosphate, 0.3 M lithium bis(fluorosulfonyl)imide, 1 wt% fluoroethylene carbonate, 1 wt% vinylene carbonate, and 0.3 wt% of a multifunctional additive in a solvent mixture of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 25 / 75 to form an electrolyte, wherein the multifunctional additive is (s)-n-(1-(2-((4-(3-(Trifluoromethyl)phenyl)piperazin-1-yl)methyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)-3-methyl-2-(2-oxo-1,3-diazaspiso[4,5]decan-1-yl)butanamide; and saturating the negative electrode, the positive electrode and the separator with the electrolyte.

[0040] In one aspect of the invention, the multifunctional additive contains a sultan group and a fluorinated phosphorus group within its chemical structure.

[0041] In one aspect of the invention, the multifunctional additive forms a lithium polymer structure by ring closure.

[0042] According to the present invention, an electrolyte for a battery cell is provided comprising: 0.7 M lithium hexafluorophosphate; 0.3 M lithium bis(fluorosulfonyl)imide; 1 wt% fluoroethylene carbonate; 1 wt% vinylene carbonate; 0.3 wt% of a multifunctional additive, wherein the multifunctional additive is (s)-n-(1-(2-((4-(3-(Trifluoromethyl)phenyl)piperazin-1-yl)methyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)-3-methyl-2-(2-oxo-1,3-diazaspiso[4,5]decan-1-yl)butanamide; and a solvent mixture of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 25 / 75.

[0043] According to one embodiment, the multifunctional additive contains a sultan group and a fluorinated phosphorus group within its chemical structure.

[0044] According to one embodiment, the multifunctional additive is configured to form a lithium polymer structure by ring closure.

[0045] According to one embodiment, lithium bis(fluorosulfonyl)imide, fluoroethylene carbonate, vinylene carbonate and the multifunctional additive lead to reduced resistance and reduced swelling in a battery cell with the electrolyte compared to an otherwise identical battery cell without the electrolyte.

[0046] According to one embodiment, a battery cell with the electrolyte exhibits increased swelling suppression when stored at 60 °C compared to an otherwise identical battery cell without the electrolyte.

[0047] According to one embodiment, a battery cell with the electrolyte exhibits an increased cycle life performance at 45 °C for up to 500 cycles compared to an otherwise identical battery cell without the electrolyte.

Claims

[1] Electrode assembly comprising: a positive electrode; a negative electrode; a separator positioned between the positive electrode and the negative electrode; and an electrolyte comprising lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, fluoroethylene carbonate, vinylene carbonate and an additive dissolved in a solvent of ethylene carbonate and ethyl methyl carbonate, and saturating the negative electrode, the positive electrode and the separator, wherein the additive is (s)-n-(1-(2-((4-(3-(Trifluoromethyl)phenyl)piperazin-1-yl)methyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)-3-methyl-2-(2-oxo-1,3-diazaspiso[4,5]decan-1-yl)butanamide. [2] Electrode assembly according to claim 1, wherein the electrolyte comprises 0.7 M lithium hexafluorophosphate and 0.3 M lithium bis(fluorosulfonyl)imide. [3] Electrode assembly according to claim 1, wherein the solvent comprises ethylene carbonate and ethyl methyl carbonate in a volume ratio of 25 / 75. [4] Electrode assembly according to claim 1, wherein the electrolyte contains 1 wt% fluoroethylene carbonate. [5] Electrode assembly according to claim 1, wherein the electrolyte contains 1 wt% vinylene carbonate. [6] Electrode assembly according to claim 1, wherein the electrolyte contains 0.3 wt% of the additive. [7] Electrode assembly according to claim 1, wherein the additive contains a sultan group and a fluorinated phosphorus group within its chemical structure. [8] Electrode assembly according to claim 1, wherein the additive forms a lithium polymer structure by ring closure. [9] Electrode assembly according to claim 1, wherein a combination of the lithium bis(fluorosulfonyl)imide, fluoroethylene carbonate, vinylene carbonate and the additive results in reduced resistance and reduced swelling compared to an otherwise identical battery cell without the combination. [10] Electrode assembly according to claim 1, wherein the positive electrode and the negative electrode exhibit increased swelling suppression when stored at 60 °C compared to an otherwise identical battery cell without the electrolyte. [11] Electrode assembly according to claim 1, wherein the positive electrode and the negative electrode exhibit increased cycle life performance at 45 °C for up to 500 cycles compared to an otherwise identical battery cell without the electrolyte. [12] Method for manufacturing a battery cell, comprising: Positioning a separator between a negative electrode and a positive electrode; Dissolving 0.7 M lithium hexafluorophosphate, 0.3 M lithium bis(fluorosulfonyl)imide, 1 wt% fluoroethylene carbonate, 1 wt% vinylene carbonate, and 0.3 wt% of a multifunctional additive in a solvent mixture of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 25 / 75 to form an electrolyte, wherein the multifunctional additive is (s)-n-(1-(2-((4-(3-(trifluoromethyl)phenyl)piperazin-1-yl)methyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)-3-methyl-2-(2-oxo-1,3-diazaspiso[4,5]decan-1-yl)butanamide; and Saturate the negative electrode, the positive electrode and the separator with the electrolyte. [13] Method according to claim 12, wherein the multifunctional additive contains a sultan group and a fluorinated phosphorus group within its chemical structure. [14] Method according to claim 12, wherein the multifunctional additive forms a lithium polymer structure by ring closure. [15] Electrolyte for a battery cell, comprising: 0.7M lithium hexafluorophosphate; 0.3M lithium bis(fluorosulfonyl)imide; 1 wt% fluoroethylene carbonate; 1 wt.% vinyl carbonate; 0.3 wt% of a multifunctional additive, wherein the multifunctional additive is (s)-n-(1-(2-((4-(3-(Trifluoromethyl)phenyl)piperazin-1-yl)methyl)pyrrolidin-1-yl)-3,3-dimethyl-1-oxobutan-2-yl)-3-methyl-2-(2-oxo-1,3-diazaspiro[4.5]decan-1-yl)butanamide; and a solvent mixture of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 25 / 75.

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