Novel battery system based on lithium difluorophosphate

Abstract

A non-aqueous electrolyte for a lithium ion battery: an additive mixture comprising a lithium salt, a first non-aqueous solvent, and a first effective additive comprising lithium difluorophosphate and a second effective additive comprising fluoroethylene carbonate or vinylene carbonate. A lithium ion battery includes a negative electrode, a positive electrode comprising an NMC having micron-sized grains, and a non-aqueous electrolyte having lithium ions dissolved in a first non-aqueous solvent, and a first effective additive having fluoroethylene carbonate or vinylene carbonate and 1, 3, 2-dioxathiane-2, 2, 3, 4-tetramethyl-1, 3, 4-triazole-2, 3, 4-tetramethyl-1, 3, 4-tetramethyl-1, 3, 4-tetramethyl-1, 3, 4-tetramethyl-1, 3, 4-tetramethyl-1, 3, 4-tetramethyl-1, 3, 4-tetramethyl-1, 3, 4-tetramethyl-1, 3-tetramethyl-1 and a second effective additive selected from lithium difluorophosphate, 1, 2-dioxide, another sulfur-containing additive, or lithium difluorophosphate.

Description

[0001] This application is a divisional application of the patent application for invention with international application number PCT / IB2018 / 055745, international filing date July 31, 2018, date of entry into the Chinese national phase March 30, 2020, national application number 201880063848.5, and invention title "Novel Battery System Based on Lithium Difluorophosphate". Technical Field

[0002] The present disclosure relates to rechargeable battery systems, and more particularly to the chemical composition of such systems, including effective electrolyte additives and electrodes, for improving the performance of rechargeable lithium-ion battery systems. Background Art

[0003] Rechargeable batteries are an integral component of energy storage systems for electric vehicles and grid storage (e.g., for backup power during power outages, as part of a microgrid, etc.). Lithium-ion-based batteries are a common type of rechargeable battery.

[0004] Electrolyte additives have been shown to be effective and increase the lifespan and performance of lithium-ion-based batteries. For example, in J.C. Burns et al., Journal of the Electrochemical Society, 160, A1451 (2013), five proprietary, undisclosed electrolyte additives were shown to increase cycle life compared to electrolyte systems without or with only one additive. Other studies have focused on performance improvements of electrolyte systems containing three or four additives as described in U.S. 2017 / 0025706. However, researchers generally do not understand the interactions between different additives that allow them to work in concert with the electrolyte and specific positive and negative electrodes. Thus, the composition of additive blends for certain systems is often based on trial and error and cannot be predicted in advance.

[0005] Existing studies have not identified such a dual-additive electrolyte system that can be incorporated into a lithium-ion battery system to produce a stable system with sufficient performance for grid or automotive applications. As discussed in US2017 / 0025706, the dual-additive systems studied (e.g., 2% VC + 1% allyl methanesulfonate and 2% PES + 1% TTSPi) generally perform worse than tri-additive electrolyte systems and tetra-additive electrolyte systems. (See, e.g., Tables 1 and 2 of U.S.2017 / 0025706). US20170025706 discloses a third compound, generally tris(trimethylsilyl) phosphate (TTSP) or tris(trimethylsilyl) phosphite (TTSPi), the concentration of which must be between 0.25 - 3 wt% to produce a stable lithium-ion battery system. (See, e.g., paragraph 72 of US 2017 / 0025706.) However, since the additives can be expensive and difficult to incorporate into lithium-ion batteries on a manufacturing scale, there is a need for simpler but effective battery systems, including those with fewer additives. Summary of the Invention

[0006] The present disclosure encompasses novel battery systems with fewer effective electrolyte additives that can be used in different energy storage applications, e.g., in vehicle and grid storage. More specifically, the present disclosure includes dual-additive electrolyte systems that increase the performance and lifespan of lithium-ion batteries while reducing the cost of other systems that rely on more additives. The present disclosure also discloses effective positive and negative electrodes that work with the disclosed dual-additive electrolyte systems to provide further system enhancements.

[0007] The disclosed effective dual-additive electrolyte systems include: 1) a combination of vinylene carbonate (VC) with 1,3,2-dioxathiolane-2,2-dioxide (DTD, also known as ethylene sulfite), or another sulfur-containing additive (such as methylene methane disulfonate, trimethylene sulfate, 3-hydroxypropylsulfonic acid γ-lactone, ethylene sulfite or other sulfur-containing additives); 2) a combination of fluoroethylene carbonate (FEC) with DTD or another sulfur-containing additive; and 3) a combination of propenyl-1,3-sultone (PES) with DTD or another sulfur-containing additive. Additionally, since VC and FEC provide similar improvements (and are believed to act in a similar manner), a mixture of VC and FEC can be considered a single effective electrolyte. That is, another disclosed effective dual-additive electrolyte system includes a mixture of VC and FEC combined with DTD or another sulfur-containing additive. When used as part of a larger battery system that includes an electrolyte, an electrolyte solvent, a positive electrode, and a negative electrode, these dual-effective additive electrolyte systems can produce the desired properties for energy storage applications, including vehicle and grid applications.

[0008] More specifically, a positive electrode of lithium nickel manganese cobalt oxide (NMC), a graphite negative electrode, a lithium salt dissolved in an organic or non-aqueous solvent, and two additives are used to form a battery system with desired properties for different applications. The solvent can include methyl acetate (MA). The electrolyte solvent can be the following solvents or a combination thereof: ethylene carbonate (EC), ethyl methyl carbonate (EMC), methyl acetate, propylene carbonate, dimethyl carbonate, diethyl carbonate, another carbonate solvent (cyclic or acyclic), another organic solvent, and / or other non-aqueous solvents. The concentration of the solvent is greater than the concentration of the additives, typically greater than 6% by weight. The solvent can be combined with the disclosed dual-additive pairs (such as VC with DTD, FEC with DTD, a mixture of VC and FEC with DTD, or another combination) to form a battery system with desired properties for different applications. The positive electrode can be coated with materials such as alumina (Al2O3), titanium dioxide (TiO2), or another coating. Additionally, to save costs, the negative electrode can be formed of natural graphite. However, depending on the pricing structure, in some cases, artificial graphite is cheaper than natural graphite.

[0009] The disclosure herein is supported by experimental data that shows the symbiotic characteristics of a dual-additive electrolyte system and the selected electrodes. Exemplary battery systems include two additives (e.g., FEC, VC or PES and DTD or another sulfur-based additive), a graphite negative electrode (naturally occurring graphite or synthetic graphite), an NMC positive electrode, a lithium electrolyte (e.g., formed from a lithium salt such as lithium hexafluorophosphate having a chemical composition of LiPF6), and an organic or non-aqueous solvent. A lithium-ion battery can include a negative electrode, a positive electrode, and a non-aqueous electrolyte, the positive electrode includes NMC having micron-sized grains, the non-aqueous electrolyte contains lithium ions dissolved in a first non-aqueous solvent, and an additive mixture that has a first effective additive of fluoroethylene carbonate or vinylene carbonate, and a second effective additive of 1,3,2-dioxathiolane-2,2-dioxide, another sulfur-containing additive or lithium difluorophosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic diagram of a vehicle including a battery storage system.

[0011] Figure 2 is a schematic diagram of an exemplary battery storage system.

[0012] Figure 3 is a schematic diagram of a lithium-ion battery cell system.

[0013] Figure 4A -J shows typical experimental data collected during ultra-high-precision charging experiments of battery systems with different electrolyte compositions.

[0014] Figure 4A shows the relationship between the time-normalized Coulombic inverse efficiency per hour (CIE / h) and the number of cycles for electrolyte systems that include: 1% DTD, 2% VC, and 2% VC + 1% DTD, respectively.

[0015] Figure 4B shows the relationship between the Coulombic efficiency (CE) and the number of cycles for electrolyte systems that include: 1% DTD, 2% VC, and 2% VC + 1% DTD, respectively.

[0016] Figure 4C shows the relationship between the charging end point capacity and the number of cycles for electrolyte systems that include: 1% DTD, 2% VC, and 2% VC + 1% DTD, respectively.

[0017] Figure 4D shows the relationship between the discharge capacity and the number of cycles for electrolyte systems that include: 1% DTD, 2% VC, and 2% VC + 1% DTD, respectively.

[0018] Figure 4E Shows the relationship between the change in open circuit voltage and the number of cycles for the following electrolyte systems, which respectively include: 1% DTD, 2% VC, and 2% VC + 1% DTD.

[0019] Figure 4F Shows the relationship between the time-normalized coulombic inverse efficiency per hour (CIE / h) and the number of cycles for the following electrolyte systems, which respectively include: 1% DTD, 2% FEC, and 2% FEC + 1% DTD.

[0020] Figure 4G Shows the relationship between the coulombic efficiency (CE) and the number of cycles for the following electrolyte systems, which respectively include: 1% DTD, 2% FEC, and 2% FEC + 1% DTD.

[0021] Figure 4H Shows the relationship between the charge end point capacity and the number of cycles for the following electrolyte systems, which respectively include: 1% DTD, 2% FEC, and 2% FEC + 1% DTD.

[0022] Fig. 4I Shows the relationship between the discharge capacity and the number of cycles for the following electrolyte systems, which respectively include: 1% DTD, 2% FEC, and 2% FEC + 1% DTD.

[0023] Figure 4J Shows the relationship between the difference (ΔV) between the average charge voltage and the average charge voltage for the following electrolyte systems, which respectively include: 1% DTD, 2% FEC, and 2% FEC + 1% DTD.

[0024] Figure 5A -C shows Figure 4A The average value of the data for the last three cycles shown in -J, and shows a lower coulombic inverse efficiency per hour and a lower fractional slip per hour for the combinations of FEC + DTD and VC + DTD compared to any single additive of FEC, VC, or DTD.

[0025] Figure 5A Shows during Figure 4A The average coulombic inverse efficiency per hour of the data for the last three cycles generated during the experiment shown in -J.

[0026] Figure 5B Shows during Figure 4A The average fractional slip of the data for the last three cycles generated during the experiment shown in -J.

[0027] Figure 5C Shows during Figure 4A -The average fractional decay of the data for the last three cycles generated during the experiment shown in -J.

[0028] Fig. 6A -F shows typical experimental data for the long-term cycling at 40 °C, C / 3 CCCV, which shows the advantages of including DTD as an additive in electrolyte systems of VC or FEC.

[0029] Fig. 6A Shows the relationship between the capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.2 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD.

[0030] Figure 6B Shows the relationship between the normalized capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.2 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD.

[0031] Figure 6C Shows the relationship between the voltage hysteresis (the difference between the average charging voltage and the average discharging voltage) and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.2 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD.

[0032] Fig.6D Shows the relationship between the capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.2 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD.

[0033] Fig. 6E Shows the relationship between the normalized capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.2 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD.

[0034] Fig. 6F Shows the relationship between the voltage hysteresis (the difference between the average charging voltage and the average discharging voltage) and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.2 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD.

[0035] Fig. 7A-F shows typical experimental data of the study on long-term cycling at 20 °C and C / 3 CCCV, which shows the advantages of including DTD as an additive in the electrolyte systems of VC or FEC.

[0036] Fig. 7A Shows the relationship between the capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD.

[0037] Figure 7B Shows the relationship between the normalized capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD.

[0038] Figure 7C Shows the relationship between the voltage hysteresis (the difference between the average charging voltage and the average discharging voltage) and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD.

[0039] Fig.7D Shows the relationship between the capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD.

[0040] Fig. 7E Shows the relationship between the normalized capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD.

[0041] Figure 7F Shows the relationship between the voltage hysteresis (the difference between the average charging voltage and the average discharging voltage) and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD.

[0042] Fig. 8A -I shows typical empirical data collected for each electrolyte component during the cycling experiment according to certain embodiments of the present disclosure.

[0043] Fig. 8A Shows the relationship between the peak capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate at 40 °C. These electrolyte systems include, respectively: 2% FEC, 1% FEC + 1% DTD, 2% FEC + 1% DTD, 1% FEC + 1% MMDS, and 2% FEC + 1% MMDS.

[0044] Figure 8B Shows the relationship between the normalized capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate at 40 °C. These electrolyte systems include, respectively: 2% FEC, 1% FEC + 1% DTD, 2% FEC + 1% DTD, 1% FEC + 1% MMDS, and 2% FEC + 1% MMDS.

[0045] Figure 8C Shows the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) of the following electrolyte systems cycled between 3.0 V and 4.3 V in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate at 40 °C. These electrolyte systems include, respectively: 2% FEC, 1% FEC + 1% DTD, 2% FEC + 1% DTD, 1% FEC + 1% MMDS, and 2% FEC + 1% MMDS.

[0046] Fig.8D Shows the relationship between the peak capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate at 40 °C. These electrolyte systems include, respectively: 2% VC, 1% VC + 1% DTD, 2% VC + 1% DTD, 1% VC + 1% MMDS, and 2% VC + 1% MMDS.

[0047] Fig. 8E Shows the relationship between the normalized capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate at 40 °C. These electrolyte systems include, respectively: 2% VC, 1% VC + 1% DTD, 2% VC + 1% DTD, 1% VC + 1% MMDS, and 2% VC + 1% MMDS.

[0048] Figure 8F Shows the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) of the following electrolyte systems cycled between 3.0 V and 4.3 V in a base electrolyte of 1.2 M LiPF6 in 30 wt% ethylene carbonate and 70 wt% ethyl methyl carbonate at 40 °C. These electrolyte systems include, respectively: 2% VC, 1% VC + 1% DTD, 2% VC + 1% DTD, 1% VC + 1% MMDS, and 2% VC + 1% MMDS.

[0049] Figure 8G Shows the relationship between the peak capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate at 40 °C. These electrolyte systems include, respectively: 2% PES, 1% PES + 1% DTD, 2% PES + 1% DTD, 1% PES + 1% MMDS, and 2% PES + 1% MMDS.

[0050] Figure 8H Shows the relationship between the normalized capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate at 40 °C. These electrolyte systems include, respectively: 2% PES, 1% PES + 1% DTD, 2% PES + 1% DTD, 1% PES + 1% MMDS, and 2% PES + 1% MMDS.

[0051] Figure 8I Shows the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) of the following electrolyte systems cycled between 3.0 V and 4.3 V in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate at 40 °C. These electrolyte systems include, respectively: 2% PES, 1% PES + 1% DTD, 2% PES + 1% DTD, 1% PES + 1% MMDS, and 2% PES + 1% MMDS.

[0052] Figures 9A-9H Shows typical experimental data collected during some ultra-high-precision charging experiments, which shows that methyl acetate can be added to electrolyte systems containing DTD and VC or FEC to increase electrolyte conductivity and reduce viscosity without sacrificing too much lifespan. For certain applications that require faster charging speeds, increasing conductivity and reducing viscosity are important.

[0053] Fig.9AShows typical experimental data according to certain embodiments of the present disclosure, which shows the relationship between the Coulombic efficiency (CE) of an electrolyte system and the number of cycles.

[0054] Fig. 9B Shows typical experimental data according to certain embodiments of the present disclosure, which shows the relationship between the charge end point capacity of an electrolyte system and the number of cycles.

[0055] Fig. 9C Shows typical experimental data according to certain embodiments of the present disclosure, which shows the relationship between the discharge capacity of an electrolyte system and the number of cycles.

[0056] Fig.9D Shows typical experimental data according to certain embodiments of the present disclosure, which shows the relationship between the difference between the average charge voltage and the average charge voltage (ΔV) in the open circuit voltage of an electrolyte system and the number of cycles.

[0057] Fig.9E Shows typical experimental data of the Coulombic efficiency (CE) of an electrolyte system according to certain embodiments of the present disclosure versus the number of cycles.

[0058] Fig.9F Shows typical experimental data of the relationship between the charge end point capacity of an electrolyte system and the number of cycles according to certain embodiments of the present disclosure.

[0059] Figure 9G Shows typical experimental data of the relationship between the discharge capacity of an electrolyte system and the number of cycles according to certain embodiments of the present disclosure.

[0060] Figure 9H Shows typical experimental data of the relationship between the difference (ΔV) between the average charge voltage and the average charge voltage of an electrolyte system and the number of cycles according to certain embodiments of the present disclosure.

[0061] Fig. 10A -C is a graph that summarizes the experimental data and illustrates that as the MA content increases, the electrolyte additives VC and FEC alone, and the electrolyte additives VC and FEC in the presence of DTD still provide acceptable performance.

[0062] Fig. 10A Is a graph that summarizes the experimental data of the time-normalized CIE as a function of the MA content.

[0063] Fig. 10B Is a graph that summarizes the experimental data of the time-normalized fractional decay as a function of the MA content.

[0064] Fig. 10C Is a graph that summarizes the experimental data of the time-normalized fractional charge end point capacity slip as a function of the MA content.

[0065] Fig.11 is a graph summarizing experimental data of parasitic heat flow as a function of voltage for different electrolyte compositions containing FEC in the voltage range of 4.0 V to 4.2 V, and the difference between this parasitic heat flow and the parasitic heat flow of a cell containing 2% FEC + 0% MA as a function of voltage.

[0066] Fig. 12A -B is a graph summarizing experimental data of parasitic heat flow as a function of voltage for different electrolyte compositions containing FEC in the voltage range of 4.0 V to 4.3 V, and the difference between this parasitic heat flow and the parasitic heat flow of a cell containing 2% FEC + 0% MA as a function of voltage. Fig. 12A Shows the results of the first cycle up to 4.3 V. Fig. 12B Shows the results of the second cycle.

[0067] Fig.13A -B is a graph summarizing experimental data of parasitic heat flow as a function of voltage for different electrolyte compositions containing FEC in the voltage range of 4.0 V to 4.4 V, and the difference between this parasitic heat flow and the parasitic heat flow of a cell containing 2% FEC + 0% MA as a function of voltage. Fig.13A Shows the results of the first cycle up to 4.4 V. Fig. 13B Shows the results of the second cycle.

[0068] Fig.14 is a graph summarizing experimental parasitic heat flow data, which includes Figure 11-1 the data shown in FIG. 3.

[0069] Fig.15A -F is a graph of experimental data of the capacity, normalized capacity, and voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) versus the number of cycles for an electrolyte system containing FEC at 20°C.

[0070] Fig.15A is a graph of experimental data of the capacity versus the number of cycles of an electrolyte system containing FEC at 20°C using cycles up to 4.2 V.

[0071] Fig. 15B is a graph of experimental data of the normalized capacity versus the number of cycles of an electrolyte system containing FEC at 20°C using cycles up to 4.2 V at 20°C.

[0072] Fig. 15CIt is a graph of the experimental data on the relationship between the voltage hysteresis (the difference between the average charging voltage and the average discharging voltage) and the number of cycles of an electrolyte system containing FEC, which is cycled up to 4.2V and conducted at 20°C.

[0073] Fig.15D It is a graph of the experimental data on the relationship between the capacity and the number of cycles of an electrolyte system containing FEC, which is cycled up to 4.3V and conducted at 20°C.

[0074] Fig.15E It is a graph of the experimental data on the relationship between the normalized capacity and the number of cycles of an electrolyte system containing FEC, which is cycled up to 4.3V and conducted at 20°C.

[0075] Fig.15F It is a graph of the experimental data on the relationship between the voltage hysteresis (the difference between the average charging voltage and the average discharging voltage) and the number of cycles of an electrolyte system containing FEC, which is cycled up to 4.3V and conducted at 20°C.

[0076] Fig.16A -F is a graph of the experimental data on the capacity, normalized capacity, and voltage hysteresis of an electrolyte system containing FEC at 40°C.

[0077] Fig.16A It is a graph of the experimental data on the relationship between the capacity and the number of cycles of an electrolyte system containing FEC, which is cycled up to 4.2V and conducted at 40°C.

[0078] Fig. 16B It is a graph of the experimental data on the relationship between the normalized capacity and the number of cycles of an electrolyte system containing FEC, which is cycled up to 4.2V and conducted at 40°C.

[0079] Fig. 16C It is a graph of the experimental data on the relationship between the voltage hysteresis (the difference between the average charging voltage and the average discharging voltage) and the number of cycles of an electrolyte system containing FEC at 40°C, which is cycled up to 4.2V.

[0080] Fig.16D It is a graph of the experimental data on the relationship between the capacity and the number of cycles of an electrolyte system containing FEC, which is cycled up to 4.3V and conducted at 40°C.

[0081] Fig.16E It is a graph of the experimental data on the relationship between the normalized capacity and the number of cycles of an electrolyte system containing FEC, which is cycled up to 4.3V and conducted at 40°C.

[0082] Fig.16FIt is a graph of the experimental data on the relationship between the voltage hysteresis (the difference between the average charging voltage and the average discharging voltage) and the number of cycles of an electrolyte system containing FEC, which is cycled up to 4.3V at 40°C.

[0083] Fig.17A -F is a graph of the experimental data on the capacity, normalized capacity, and voltage hysteresis of an electrolyte system containing FEC, VC, and / or DTD.

[0084] Fig.17A It is a graph of the experimental data on the relationship between the capacity and the number of cycles of an electrolyte system containing FEC and / or DTD, which is cycled up to 4.3V.

[0085] Fig. 17B It is a graph of the experimental data on the relationship between the normalized capacity and the number of cycles of an electrolyte system containing FEC and / or DTD, which is cycled up to 4.3V.

[0086] Fig. 17C It is a graph of the experimental data on the relationship between the voltage hysteresis (the difference between the average charging voltage and the average discharging voltage) and the number of cycles of an electrolyte system containing FEC and / or DTD, which is cycled up to 4.3V.

[0087] Fig.17D It is a graph of the experimental data on the relationship between the capacity and the number of cycles of an electrolyte system containing VC and / or DTD, which is cycled up to 4.3V.

[0088] Fig.17E It is a graph of the experimental data on the relationship between the normalized capacity and the number of cycles of an electrolyte system containing VC and / or DTD, which is cycled up to 4.3V.

[0089] Fig.17F It is a graph of the experimental data on the relationship between the voltage hysteresis (the difference between the average charging voltage and the average discharging voltage) and the number of cycles of an electrolyte system containing VC and / or DTD, which is cycled up to 4.3V.

[0090] Fig.18A It is a graph of the experimental data on the relationship between the capacity and the number of cycles of an electrolyte system containing FEC, which is cycled up to 4.3V.

[0091] Fig.18B It is a graph of the experimental data on the relationship between the normalized capacity and the number of cycles of an electrolyte system containing FEC, which is cycled up to 4.3V.

[0092] Fig.19It is a graph of experimental data on the relationship between the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) of an electrolyte system with FEC included and the number of cycles up to 4.3V.

[0093] Fig. 20 It is a graph of experimental data summarizing the volume of formation gas generated by different electrolyte systems during battery formation.

[0094] Fig.21 It is a graph of experimental data summarizing the charge transfer impedance of different electrolyte systems.

[0095] Fig. 22 It is a graph of experimental data summarizing the low-rate capacity loss of different electrolyte systems measured after charging the battery 30 cycles at three different charging rates at 20°C.

[0096] Fig.23 It is a graph of experimental data that summarizes the relationship between the peak capacity and the number of cycles of different electrolyte systems used in batteries charged at different charging rates at 20°C.

[0097] Fig.24 It is a graph of experimental data that summarizes the relationship between the peak capacity and the number of cycles of different electrolyte systems used in batteries charged at different charging rates at 20°C.

[0098] Fig.25 It is a graph of experimental data summarizing the volume of formation gas for different additives in MA solvent with varying concentrations.

[0099] Fig.26 It is a graph of experimental data summarizing the charge transfer impedance of different additives in electrolytes containing MA solvent with varying concentrations.

[0100] Fig. 27 It is a graph of experimental data summarizing the low-rate capacity loss of different electrolyte compositions after charging at 1, 1.5, and 2C for 30 times at 20°C.

[0101] Fig.28 is Fig. 27 a partial enlarged view of certain experimental data shown.

[0102] Fig.29 It summarizes the experimental data of ΔV (the difference between the average charge voltage and the average discharge voltage) of an electrolyte system containing FEC as a function of the number of cycles.

[0103] Fig.30 It summarizes the experimental data of the peak capacity of an electrolyte system containing FEC as a function of the number of cycles.

[0104] Fig.31 Outlined are the experimental data of the energy hysteresis of an electrolyte system containing FEC as a function of the number of cycles.

[0105] Fig.32 Outlined are the experimental data of ΔV (the difference between the average charge voltage and the average discharge voltage) of an electrolyte system containing VC as a function of the number of cycles.

[0106] Fig.33 Outlined are the experimental data of the peak capacity of an electrolyte system containing VC as a function of the number of cycles.

[0107] Fig.34 Outlined are the experimental data of the energy hysteresis of an electrolyte system containing VC as a function of the number of cycles.

[0108] Fig.35A -D Outlined are the experimental data for an electrolyte system having a NMC532 positive electrode and an artificial graphite negative electrode.

[0109] Fig.35A Outlined are the experimental impedance data that plot the negative of the imaginary part of the impedance versus the real part of the impedance for different electrolyte systems, including systems containing LFO.

[0110] Fig.35B Outlined are the experimental impedance data that plot the negative of the imaginary part of the impedance versus the real part of the impedance for different electrolyte systems, including systems containing VC, PES, or LFO.

[0111] Fig.35C Outlined are the experimental impedance data that plot the negative of the imaginary part of the impedance versus the real part of the impedance for different electrolyte systems, including systems containing FEC, DTD, or LFO.

[0112] Fig.35D Outlined are the experimental impedance data for different electrolyte systems that contain VC, FEC, DTD, PES, or LFO; a NMC532 positive electrode and an artificial graphite negative electrode.

[0113] Fig.36 Outlined are the experimental data for different electrolyte systems containing VC, FEC, DTD, PES, or LFO.

[0114] Fig.37A -F Outlined are the experimental storage data for different electrolyte systems containing LFO compared to a control without LFO.

[0115] Fig.37AOutlined are the voltage drop data of different electrolyte systems containing LFO after the system was stored at 60 °C at 4.4 V for 500 hours, compared to a control without LFO.

[0116] Fig.37B Outlined are the voltage drop data of different electrolyte systems containing LFO after the system was stored at 60 °C at 2.5 V for 500 hours, compared to a control without LFO.

[0117] Fig.37C Outlined are the volume change data of different electrolyte systems containing LFO after the system was stored at 60 °C at 4.4 V for 500 hours, compared to a control without LFO.

[0118] Fig.37D Outlined are the volume change data of different electrolyte systems containing LFO after the system was stored at 60 °C at 2.5 V for 500 hours, compared to a control without LFO.

[0119] Fig.37E Outlined are the impedance data of different electrolyte systems containing LFO before and after the system was stored at 60 °C at 4.4 V for 500 hours, compared to a control without LFO.

[0120] Fig.37F Outlined are the impedance data of different electrolyte systems containing LFO before and after the system was stored at 60 °C at 2.5 V for 500 hours, compared to a control without LFO.

[0121] Fig.38A -F Outlined are the experimental storage data of different electrolyte systems containing LFO compared to a control without LFO.

[0122] Fig.38A Outlined are the voltage drop data of different electrolyte systems containing LFO after the system was stored at 60 °C at 4.4 V for 500 hours, compared to a control without LFO.

[0123] Fig.38B Outlined are the voltage drop data of different electrolyte systems containing LFO after the system was stored at 60 °C at 2.5 V for 500 hours, compared to a control without LFO.

[0124] Fig.38C Outlined are the volume change data of different electrolyte systems containing LFO after the system was stored at 60 °C at 4.4 V for 500 hours, compared to a control without LFO.

[0125] Fig.38DOutlined are the volume change data of different electrolyte systems containing LFO compared to a control without LFO after the system was stored at 60 °C at 2.5 V for 500 hours.

[0126] Fig.38E Outlined are the impedance data of different electrolyte systems containing LFO compared to a control without LFO before and after the system was stored at 60 °C at 4.4 V for 500 hours.

[0127] Fig.38F Outlined are the impedance data of different electrolyte systems containing LFO compared to a control without LFO before and after the system was stored at 60 °C at 2.5 V for 500 hours.

[0128] Fig.39A -H Outlined are the experimental data of different electrolyte systems containing LFO compared to a control without LFO.

[0129] Fig.39A Outlined are the data of the relationship between the Coulombic efficiency (CE) and the number of cycles of electrolyte systems cycled to 4.1 V, including systems containing LFO.

[0130] Fig.39B Outlined are the data of the relationship between the voltage change and the number of cycles of different electrolyte systems cycled to 4.1 V, including systems containing LFO.

[0131] Fig.39C Outlined are the data of the relationship between the charge end point capacity and the number of cycles of different electrolyte systems cycled to 4.1 V, including systems containing LFO.

[0132] Fig.39D Outlined are the data of the relationship between the normalized discharge capacity and the number of cycles of different electrolyte systems cycled to 4.1 V, including systems containing LFO.

[0133] Fig.39E Outlined are the data of the relationship between the Coulombic efficiency (CE) and the number of cycles of electrolyte systems cycled to 4.2 V, including systems containing LFO.

[0134] Fig.39F Outlined are the data of the relationship between the voltage change and the number of cycles of different electrolyte systems cycled to 4.2 V, including systems containing LFO.

[0135] Figure 39GData showing the relationship between the end-of-charge capacity and the number of cycles for different electrolyte systems cycled up to 4.2V are presented, including systems containing LFO.

[0136] Fig.39H Data showing the relationship between the normalized discharge capacity and the number of cycles for different electrolyte systems cycled up to 4.2V are presented, including systems containing LFO.

[0137] Fig.40A -H Experimental data for different electrolyte systems containing LFO compared to a control without LFO are presented.

[0138] Fig.40A Data showing the relationship between the Coulombic efficiency (CE) and the number of cycles for electrolyte systems cycled up to 4.3V are presented, including systems containing LFO.

[0139] Fig.40B Data showing the relationship between the open-circuit voltage change and the number of cycles for different electrolyte systems cycled up to 4.3V are presented, including systems containing LFO.

[0140] Fig.40C Data showing the relationship between the end-of-charge capacity and the number of cycles for different electrolyte systems cycled up to 4.3V are presented, including systems containing LFO.

[0141] Fig.40D Data showing the relationship between the normalized discharge capacity and the number of cycles for different electrolyte systems cycled up to 4.3V are presented, including systems containing LFO.

[0142] Fig.40E Data showing the relationship between the Coulombic efficiency (CE) and the number of cycles for electrolyte systems cycled up to 4.4V are presented, including systems containing LFO.

[0143] Fig.40F Data showing the relationship between the open-circuit voltage change and the number of cycles for different electrolyte systems cycled up to 4.4V are presented, including systems containing LFO.

[0144] Figure 40G Data showing the relationship between the end-of-charge capacity and the number of cycles for different electrolyte systems cycled up to 4.4V are presented, including systems containing LFO.

[0145] Figure 40HData is outlined showing the relationship between the normalized discharge capacity and the number of cycles for different electrolyte systems using cycles up to 4.4 V, including systems containing LFO.

[0146] Fig.41A Data is outlined showing the relationship between the coulombic inverse efficiency and the upper cut-off voltage for different electrolyte systems, including systems containing LFO.

[0147] Fig.41B Data is outlined showing the relationship between the fractional decay and the upper cut-off voltage for different electrolyte systems, including systems containing LFO.

[0148] Fig.41C Data is outlined showing the relationship between the charge end point capacity slip and the upper cut-off voltage for different electrolyte systems, including systems containing LFO.

[0149] Fig.42A Shows Fig.41A an enlarged view of, and data is outlined showing the relationship between the coulombic inverse efficiency and the upper cut-off voltage for different electrolyte systems, including systems containing LFO.

[0150] Fig.42B Shows Fig.41B an enlarged view of, and data is outlined showing the relationship between the fractional decay and the upper cut-off voltage for different electrolyte systems, including systems containing LFO.

[0151] Fig.42C Shows Fig.41C an enlarged view of, and data is outlined showing the relationship between the charge end point capacity slip and the upper cut-off voltage for different electrolyte systems, including systems containing LFO.

[0152] Fig.43A -D Outlines long-term cycling data for different electrolyte systems, including systems containing LFO.

[0153] Fig.43A Data is outlined showing the normalized discharge capacity data for different electrolyte systems using cycles occurring at 40 °C, including systems containing LFO.

[0154] Fig.43B Data is outlined showing the average charge voltage data for different electrolyte systems using cycles occurring at 40 °C, including systems containing LFO.

[0155] Fig.43C Data is outlined showing the normalized discharge capacity data for different electrolyte systems using cycles occurring at 20 °C, including systems containing LFO.

[0156] Fig.43D Outlines the average charge voltage data of different electrolyte systems that cycle at 20 °C, including systems containing LFO.

[0157] Fig.44A -D Outlines the long-term cycling data of different electrolyte systems at high-rate charging, including systems containing LFO.

[0158] Fig.44A Outlines the normalized discharge capacity data of different electrolyte systems that cycle during the first experiment at 20 °C, including systems containing LFO.

[0159] Fig.44B Outlines the average charge voltage data of different electrolyte systems that cycle during the first experiment at 20 °C, including systems containing LFO.

[0160] Fig.44C Outlines the normalized discharge capacity data of different electrolyte systems that cycle during the second experiment at 20 °C, including systems containing LFO.

[0161] Fig.44D Outlines the average charge voltage data of different electrolyte systems that cycle during the second experiment at 20 °C, including systems containing LFO.

[0162] Fig.45A Outlines the voltage data of different electrolyte systems when the battery is held at 40 °C, including systems containing LFO.

[0163] Fig.45B Outlines the volume change data of different electrolyte systems when the battery is held at 40 °C, including systems containing LFO.

[0164] Fig.46A -D Outlines the voltage drop and impedance data generated during the storage experiment.

[0165] Fig.46A Outlines the voltage drop data of different electrolyte systems after the battery is held at 60 °C at 4.4 V for 500 hours, including systems containing LFO.

[0166] Fig.46B Outlines the impedance data of different electrolyte systems before and after the battery is held at 60 °C at 4.4 V for 500 hours, including systems containing LFO.

[0167] Fig.46C Outlines the voltage drop data of different electrolyte systems after the battery is maintained at 2.5 V at 60 °C for 500 hours, and these electrolyte systems include the systems containing LFO.

[0168] Fig.46D Outlines the impedance data of different electrolyte systems before and after the battery is maintained at 2.5 V at 60 °C for 500 hours, and these electrolyte systems include the systems containing LFO.

[0169] Fig.47 Shows the exemplary data during certain charge and discharge scenarios.

[0170] Fig.48A -F Outlines the relationship between experimental heat flow data and voltage. Fig.48A 、C and E show the results of the first cycle up to 4.4 V. Fig.48B 、D and F show the results of the second cycle up to 4.4 V.

[0171] Fig.48A Outlines the experimental parasitic heat flow data as a function of voltage for different electrolyte systems in the voltage range of 4.0 V to 4.4 V during the first cycle, and the difference between this parasitic heat flow and the parasitic heat flow of the battery containing 2% VC + 1% DTD as a function of voltage. These electrolyte systems include the systems containing DTD.

[0172] Fig.48B Outlines the experimental parasitic heat flow data as a function of voltage for different electrolyte systems in the voltage range of 4.0 V to 4.4 V during the second cycle, and the difference between this parasitic heat flow and the parasitic heat flow of the battery containing 2% VC + 1% DTD as a function of voltage. These electrolyte systems include the systems containing DTD.

[0173] Fig.48C Outlines the experimental parasitic heat flow data as a function of voltage for different electrolyte systems in the voltage range of 4.0 V to 4.4 V during the first cycle, and the difference between this parasitic heat flow and the parasitic heat flow of the battery containing 2% VC + 1% DTD as a function of voltage. These electrolyte systems include the systems containing LFO.

[0174] Fig.48D Outlines the experimental parasitic heat flow data as a function of voltage for different electrolyte systems in the voltage range of 4.0 V to 4.4 V during the second cycle, and the difference between this parasitic heat flow and the parasitic heat flow of the battery containing 2% VC + 1% DTD as a function of voltage. These electrolyte systems include the systems containing LFO.

[0175] Fig.48E Outlined are the experimental parasitic heat flow data as a function of voltage for different electrolyte systems in the voltage range of 4.0 V to 4.4 V during the first cycle, and the difference between this parasitic heat flow and the parasitic heat flow of a battery containing 2% VC + 1% DTD as a function of voltage, where these electrolyte systems include the system containing LFO.

[0176] Fig.48F Outlined are the experimental parasitic heat flow data as a function of voltage for different electrolyte systems in the voltage range of 4.0 V to 4.4 V during the second cycle, and the difference between this parasitic heat flow and the parasitic heat flow of a battery containing 2% VC + 1% DTD as a function of voltage, where these electrolyte systems include the system containing LFO.

[0177] Fig.49A -C Outlined are the experimental average parasitic heat flow data for different electrolyte systems as a function of the number of cycles.

[0178] Fig.49A Outlined are the experimental average parasitic heat flow data as a function of the number of cycles for electrolyte systems containing 2% VC + 1% DTD and 2% FEC + 1% DTD, respectively.

[0179] Fig.49B Outlined are the experimental average parasitic heat flow data as a function of the number of cycles for electrolyte systems containing 0.5% LFO, 1% LFO, 1.5% LFO, 0.5% LFO + 1% VC + 1% FEC, 1.0% LFO + 1% VC + 1% FEC, and 1.5% LFO + 1% VC + 1% FEC, respectively.

[0180] Fig.49C Outlined are the experimental average parasitic heat flow data as a function of the number of cycles for electrolyte systems containing 1% LFO, 1% LFO + 1% VC, 1% LFO + 1% FEC, and 1% LFO + 1% VC + 1% FEC, respectively.

[0181] Fig.50 Outlined are the experimental data from Fig.49A -C that show the best-performing battery according to the parasitic heat flow experiment.

[0182] Fig.51A -D Outlined are the experimental data for different electrolyte systems containing LFO compared to a control without LFO using cycles up to 4.2 V.

[0183] Fig.51A Outlined are the data on the relationship between the Coulombic efficiency and the number of cycles for electrolyte systems using cycles up to 4.2 V, where these electrolyte systems include the system containing LFO.

[0184] Fig.51B Data outlining the relationship between the charge end-point capacity and the number of cycles for different electrolyte systems cycled to 4.2 V, including systems containing LFO.

[0185] Fig.51C Data outlining the relationship between the voltage change and the number of cycles for different electrolyte systems cycled to 4.2 V, including systems containing LFO.

[0186] Fig.51D Data outlining the relationship between the normalized discharge capacity and the number of cycles for different electrolyte systems cycled to 4.2 V, including systems containing LFO.

[0187] Fig.52A -D Experimental data for different electrolyte systems containing LFO compared to a control without LFO, cycled to 4.3 V, including systems containing LFO.

[0188] Fig.52A Data outlining the relationship between the coulombic efficiency and the number of cycles for electrolyte systems cycled to 4.3 V, including systems containing LFO.

[0189] Fig.52B Data outlining the relationship between the charge end-point capacity and the number of cycles for different electrolyte systems cycled to 4.3 V, including systems containing LFO.

[0190] Fig.52C Data outlining the relationship between the voltage change and the number of cycles for different electrolyte systems cycled to 4.3 V, including systems containing LFO.

[0191] Fig.52D Data outlining the relationship between the normalized discharge capacity and the number of cycles for different electrolyte systems cycled to 4.3 V, including systems containing LFO.

[0192] Fig.53A -D Experimental data for different electrolyte systems containing LFO compared to a control without LFO, cycled to 4.4 V.

[0193] Fig.53A Experimental data outlining the relationship between the coulombic efficiency and the number of cycles for electrolyte systems cycled to 4.4 V, including systems containing LFO.

[0194] Fig.53BExperimental data showing the relationship between the end-of-charge capacity and the number of cycles for different electrolyte systems cycled to 4.4V are summarized, including systems containing LFO.

[0195] Fig.53C Experimental data showing the relationship between the voltage change and the number of cycles for different electrolyte systems cycled to 4.4V are summarized, including systems containing LFO.

[0196] Fig.53D Experimental data showing the relationship between the normalized discharge capacity and the number of cycles for different electrolyte systems cycled to 4.4V are summarized, including systems containing LFO.

[0197] Fig.54A Data showing the relationship between the Coulombic efficiency and the upper cut-off voltage for different electrolyte systems, including systems containing LFO, are summarized.

[0198] Fig.54B Data showing the relationship between the fractional decay and the upper cut-off voltage for different electrolyte systems, including systems containing LFO, are summarized.

[0199] Fig.54C Data showing the relationship between the end-of-charge capacity shift and the upper cut-off voltage for different electrolyte systems, including systems containing LFO, are summarized.

[0200] Fig.55A Shows Fig.54A An enlarged view of, and data showing the relationship between the Coulombic efficiency and the upper cut-off voltage for different electrolyte systems, including systems containing LFO, are summarized.

[0201] Fig.55B Shows Fig.54B An enlarged view of, and data showing the relationship between the fractional decay and the upper cut-off voltage for different electrolyte systems, including systems containing LFO, are summarized.

[0202] Fig.55C Shows Fig.54C An enlarged view of, and data showing the relationship between the end-of-charge capacity shift and the upper cut-off voltage for different electrolyte systems, including systems containing LFO, are summarized.

[0203] Fig.56 Impedance data generated during and after ultra-high-precision cycling experiments are summarized.

[0204] Fig.57A-D summarizes the experimental data of an electrolyte system containing LFO with a positive electrode made of NMC 622 with two different coatings.

[0205] Fig.57A Summarizes the experimental data of the voltage drop of various electrolyte systems at 4.4 V after storage at 60 °C for 500 hours.

[0206] Fig.57B Summarizes the experimental data of the impedance of various electrolyte systems before and after storage at 60 °C for 500 hours at 4.4 V.

[0207] Fig.57C Summarizes the experimental data of the voltage drop of various electrolyte systems at 2.5 V after storage at 60 °C for 500 hours.

[0208] Fig.57D Summarizes the experimental data of the impedance of various electrolyte systems before and after storage at 60 °C for 500 hours at 2.5 V.

[0209] Fig.58 Summarizes the experimental data of the mass change of LFO over time due to air exposure from Guangzhou Tinci Materials Technology Co., Ltd. and Shenzhen Capchem Technology Co., Ltd.

[0210] Fig.59 Summarizes the experimental data of the thermogravimetric analysis of LFO from Guangzhou Tinci Materials Technology Co., Ltd. and Shenzhen Capchem Technology Co., Ltd. Detailed Description

[0211] Figure 1 Illustrates the basic components of an electric vehicle (EV) 100 powered by a battery. The electric vehicle 100 includes at least one drive motor (traction motor) 102A and / or 102B, at least one transmission 104A and / or 104B coupled to the corresponding drive motor 102A and / or 102B, a battery unit 106, and electronics 108. Generally, the battery unit 106 supplies power to the power electronics of the electric vehicle 100 and uses the drive motor 102A and / or 102B to propel the electric vehicle 100. The electric vehicle 100 includes a large number of other components not described herein but known to those of ordinary skill in the art. Although Figure 1The configuration of the electric vehicle 100 is shown as having four wheels, but different electric vehicles can have fewer or more than four wheels. Additionally, different types of electric vehicles 100 can incorporate the inventive concepts described herein, which include motorcycles, airplanes, trucks, boats, and train engines among other types of vehicles. Certain components resulting from the use of the embodiments of the present disclosure can be used in the vehicle 100.

[0212] Figure 2 A schematic illustration of an exemplary energy storage system 200 is shown, which shows various components. The energy storage system 200 generally includes a modular housing that has at least a base 202 and four sidewalls 204 (only two sidewalls are shown in the figure). The modular housing is generally electrically isolated from the battery cells 206 housed therein. This can be achieved by physical separation, an electrical insulation layer, selecting an insulating material as the modular housing, any combination thereof, or another method. The base 202 can be an electrical insulation layer on top of a metal sheet or a non-conductive / electrically insulating material such as polypropylene, polyurethane, polyvinyl chloride, another plastic, a non-conductive composite material, or insulating carbon fiber. The sidewalls 204 can also include an insulation layer or be formed of a non-conductive or electrically insulating material such as polypropylene, polyurethane, polyvinyl chloride, another plastic, a non-conductive composite material, or insulating carbon fiber. One or more interconnect layers 230 can be positioned above the battery cells 206, with a top plate 210 located above the interconnect layers 230. The top plate 210 can be a single plate or can be formed of multiple plates.

[0213] Individual battery cells 106 and 206 are typically lithium-ion battery cells that have an electrolyte containing lithium ions as well as a positive electrode and a negative electrode. Figure 3 A schematic illustration of a lithium-ion battery 300 is shown. Lithium ions 350 are dispersed throughout an electrolyte 320 within a container 360. The container 360 can be part of the battery cell. Lithium ions 350 migrate between a positive electrode 330 and a negative electrode 340. A separator 370 separates the negative electrode and the positive electrode. A circuitry 310 connects the negative electrode and the positive electrode.

[0214] The inventors' new research has identified novel electrolytes and battery systems for use in grid and electric vehicle applications. These systems are based on combinations of dual additives with electrolyte systems, which include 1) vinylene carbonate (VC) combined with 1,3,2-dioxathiolane-2,2-dioxide (DTD, also known as ethylene sulfite), or another sulfur-containing additive combination, 2) fluoroethylene carbonate (FEC) combined with DTD or another sulfur-containing additive combination, and 3) prop-1-ene-1,3-sultone (PES) combined with DTD or another sulfur-containing additive combination. These dual-additive electrolyte systems are paired with a positive electrode made of a lithium nickel manganese cobalt oxide having a composition of LNi x Mn y Co z O2 (commonly abbreviated as NMC or NMCxyz, where x, y, and z are the molar ratios of nickel, manganese, and cobalt, respectively). In certain embodiments, the positive electrode is formed from NMC111, NMC532, NMC811, or NMC622. In certain embodiments, the NMC532 positive electrode is formed from single-crystalline, micron-sized particles, which results in a micron-sized region of the electrode having a continuous lattice (or grain). The NMC532 positive electrode exhibits particular stability, in part because these materials and processing conditions result in a larger grain size compared to using conventional materials and processing conditions.

[0215] Typical processing conditions result in NMC electrodes having larger micron-sized agglomerates formed from nano-sized particles, creating grain boundaries at the nanoscale. Grain boundaries are defects that tend to reduce desirable properties (e.g., electrical properties), so it is generally desirable to reduce the number of grains and increase the grain size. Processing can produce larger domains at the micron-sized level, reducing the number of grain boundaries in the NMC electrode and thus improving electrical properties. The improvement in properties leads to a more stable battery system. In certain embodiments, other NMC electrodes (e.g., NMC111, NMC811, NMC622, or another NMC compound) can be processed to produce a larger domain size (at the micron-sized level or larger) to produce a more stable system.

[0216] The positive electrode can be coated with a material such as aluminum oxide (Al2O3), titanium dioxide (TiO2), or another coating. Coating the positive electrode is advantageous because it can help reduce interfacial phenomena at the positive electrode, such as parasitic reactions, thermal abuse, or another phenomenon that may degrade the system. The negative electrode can be made of natural graphite, artificial graphite, or other materials.

[0217] The electrolyte can be a lithium salt (such as LiPF6) dissolved in a combination of organic or non-aqueous solvents, and the organic or non-aqueous solvents include ethylene carbonate, ethyl methyl carbonate, methyl acetate, propylene carbonate, dimethyl carbonate, diethyl carbonate, another carbonate solvent (cyclic or acyclic), another organic solvent, and / or another non-aqueous solvent. The concentration of the solvent is greater than the concentration of the additive, typically greater than 6% by weight. Although experimental data was generated using electrolyte solvents including EC and EMC (with or without MA), these solvents are merely examples of other carbonate solvents, and in particular, examples of other non-aqueous solvents. EC and EMC solvents were used in the experiments as control experiments for the system under test to understand the effects of additives, electrodes, and adding MA as a solvent. Thus, the electrolyte system can use other carbonate solvents and / or other non-carbonate solvents, including propylene carbonate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, another carbonate solvent (cyclic or acyclic), another organic solvent, and / or other non-aqueous solvents. The concentration of the solvent is greater than the concentration of the additive, typically greater than 6% by weight.

[0218] In the dual additive mixture of FEC and DTD, the concentration of FEC is preferably between 0.5% and 6% by weight, while the concentration of DTD is preferably between 0.25% and 5% by weight. In the dual additive mixture of VC and DTD, the concentration of VC is preferably between 0.5% and 6% by weight, and the concentration of DTD is preferably between 0.25% and 5% by weight.

[0219] Some of these new battery systems can be used for energy storage applications as well as automotive applications (including energy storage within electric vehicles), where the charge and discharge rates and the lifespan when charging and discharging rapidly are important. Specifically, MA can be used as an electrolyte solvent to provide a longer lifespan when charging and discharging at a higher current rate.

[0220] Settings before the experiment

[0221] According to the present disclosure, although the battery systems themselves can be packaged differently, the experimental setup generally uses machine-made "pouch cells" to systematically evaluate the battery systems using a common setup that includes a dual additive electrolyte system and specific materials for the positive and negative electrodes. Unless otherwise stated, all percentages mentioned in the present disclosure are weight percentages. Those skilled in the art will understand that the type of additive to be used and the concentration to be employed will depend on the properties for which improvement is most desired, as well as the other components and design used in the lithium-ion battery to be manufactured, and will be apparent from the present disclosure.

[0222] Pouch cell

[0223] The pouch cells used in the experimental setup contain 1M LiPF6 in a solvent, and additives will be added thereto. Depending on the concentration of methyl acetate (0%, 20%, or 40%), the electrolyte consists of 1M LiPF6 in the following: (1) 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate, (2) 1.2M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; or (3) 1.2M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate. The additive components are added to the electrolyte at the specified weight percentages.

[0224] Unless otherwise stated, the pouch cells use a positive electrode made of NMC532 (sometimes referred to as single crystal NMC532) with micron-sized grains, and a negative electrode made of artificial graphite. For testing certain battery systems, other positive and negative electrodes are used. The positive electrodes include standard NMC532 (with smaller grains compared to NMC with micron-sized grains) and NMC622, and the negative electrodes include natural graphite.

[0225] Before filling the electrolyte, the pouch cells are cut under heat seal and dried at 100 °C for 12 hours under vacuum to remove any residual water. Then, the cells are immediately transferred to an argon-filled glove box for filling and vacuum sealing, and then the electrolyte is filled. After filling, the cells are vacuum sealed.

[0226] After sealing, the pouch cells are placed in a temperature chamber at 40.0 + / - 0.1 °C and held at 1.5V for 24 hours to complete wetting. Then, the pouch cells undergo a formation process. Unless otherwise stated, the formation process includes charging the pouch cells to 4.2V at 11 mA (C / 20), and then discharging to 3.8V. C / x indicates that when the cell has an initial capacity, the time taken to charge or discharge the cell at the selected current is x hours. For example, C / 20 indicates that the charge or discharge will take 20 hours. After formation, the cells are transferred and moved to the glove box, cut to release any generated gas, and then vacuum sealed again, and appropriate experiments are conducted.

[0227] Electrochemical impedance spectroscopy

[0228] After storage and formation, Electrochemical Impedance Spectroscopy (EIS) measurements were performed on pouch cells. The cells were charged or discharged to 3.8 V and then transferred to a temperature chamber set to 10.0 ± 0.1 °C. AC impedance spectra were collected at 10.0 ± 0.1 °C, with ten points per decade from a frequency of 100 kHz to 10 mHz, where the signal amplitude was 10 mV.

[0229] Effect of LFO on impedance: In some embodiments, LFO is included in a dual electrolyte additive system or a triple electrolyte additive system, in part to reduce the impedance of the system. Fig.35A -D shows that in most cases, LiPO2F2 (LFO or lithium difluorophosphate) reduces the impedance of the cell after formation. However, when LFO was included with 2% PES + 1% DTD + 1% TTSPi (collectively referred to as PES211), an increase in impedance was observed. The positive electrode was single crystal NMC 532 and the negative electrode was artificial graphite.

[0230] Fig.35A -D summarizes the experimental data for an electrolyte system with a positive electrode of NMC 111 and a negative electrode of artificial graphite. After formation, pouch cells were measured at 10 °C and 3.8 V. Fig.35A The control electrolyte in -D was 1.0 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate. Fig.35A Summarizes the experimental impedance data, which plots the negative of the imaginary part of the impedance versus the real part of the impedance for: 1.0 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate (control electrolyte); 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; control electrolyte + 1% LiPO2F2; control electrolyte + 2% LiPO2F2; and 20% methyl acetate + 1% LiPO2F2. Fig.35B Summarizes the experimental impedance data, which plots the negative of the imaginary part of the impedance versus the real part of the impedance for the following: control electrolyte (same control as Fig.35A above); 2% VC; 2% VC + 1% LiPO2F2; 20% MA + 1% LiPO2F2 + 2% VC; PES211; and PES211 + 1% LiPO2F2. Fig.35C Summarizes the experimental impedance data, which plots the negative of the imaginary part of the impedance versus the real part of the impedance for the following: control electrolyte (same control as Fig.35A above); 2% FEC; 2% FEC + 1% LiPO2F2; 1% DTD; and 1% DTD + 1% LiPO2F2. Fig.35DThe experimental impedance data is outlined, which plots the negative of the imaginary part of the impedance against the real part of the impedance for the following: the control electrolyte (the same control as Fig.35A ); 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 1% LiPO2F2; 2% LiPO2F2; 20% MA + 1% LiPO2F2; 2% VC; 2% VC + 1% LiPO2F2; 20% MA + 1% LiPO2F2 + 2% VC; PES211; PES211 + 1% LiPO2F2; 2% FEC, 2% FEC + 1% LiPO2F2; 1% DTD; and 1% DTD + 1% LiPO2F2.

[0231] As can be seen from Fig.35A -D, adding LFO can reduce the impedance for most systems. However, in the presence of PES211, adding LFO increases the impedance.

[0232] Fig.36 The experimental EIS data of electrolyte systems containing the following additives in an electrolyte solution of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate is outlined: 2% VC; 1% LiPO2F2 + 2% VC; 1% LiPO2F2 + 2% FEC; and 1% LiPO2F2 + 1% VC + 1% FEC. The EIS measurements were carried out at 10 °C at 3.8 V after formation. The positive electrode is single-crystal NMC532, and the negative electrode is artificial graphite.

[0233] In the test system with an NMC532 positive electrode and an artificial graphite negative electrode, LFO did not reduce the impedance. The failure to reduce the impedance may be due to a large cathode or anode surface. However, LFO also did not increase the impedance. Therefore, adding LFO either reduces the impedance or has a neutral effect.

[0234] Ultra-high-precision cycling and storage experiments

[0235] To study the effectiveness of the battery system of the present disclosure, which includes an active electrolyte additive and electrodes, an Ultra-High Precision Cycle (UHPC) is performed. The standard UHPC procedure involves cycling the battery 15 cycles between 2.8 and 4.3 V at 40 °C using a current corresponding to C / 20 to generate data. UPHC is employed to measure the coulombic efficiency, charge end-point capacity slippage, and other parameters, with an accuracy of up to 30 ppm in the case of the coulombic efficiency. Details of the UHPC process are described in “Journal of the Electrochemical Society”, 160, A521 (2013), T.M. Bond, J.C. Burns, D.A. Stevens, H.M. Dahn, and J.R. Dahn, which is hereby incorporated by reference in its entirety.

[0236] Metrics measured and / or determined from the UHPC measurements that are of particular interest include: coulombic efficiency, normalized coulombic inefficiency, normalized charge end-point capacity slippage, normalized discharge capacity (or decay rate), and ΔV (delta V). The coulombic efficiency is the discharge capacity (Q d ) divided by the charge capacity (Q c ) of the previous cycle. It tracks parasitic reactions occurring in the lithium-ion battery and includes contributions from both the positive and negative electrodes. A higher CE value indicates less electrolyte degradation in the battery. The coulombic inefficiency per hour (CIE / h) is the normalized (per hour) coulombic inefficiency, where the coulombic inefficiency is defined as 1 - CE. The coulombic inefficiency per hour is calculated by taking 1 - CE and dividing it by the cycle time at which the CE is measured. The charge end-point capacitance shift (or slippage) tracks parasitic reactions occurring at the positive electrode and mass loss (if any) of the positive electrode material. Less shift is preferred and is associated with less electrolyte oxidation. The normalized discharge capacity or decay rate is another important metric, where a lower decay rate is desired and generally it indicates a battery system with a longer life. ΔV is calculated as the difference between the average charge voltage and the average discharge voltage. The change in ΔV is closely related to polarization growth, where a smaller change in ΔV as cycling occurs is preferred. UHPC measurements are particularly suitable for comparing electrolyte compositions because UHPC measurements allow tracking of metrics with high accuracy and precision and allow evaluation of various degradation mechanisms in a relatively rapid manner.

[0237] Dual - electrolyte systems with FEC or VC as additives: In certain embodiments, the dual - additive electrolyte system forms part of a battery system, with the concentration of each additive being about 0.25 - 6%. The battery system can also include a positive electrode made of NMC111, NMC532, NMC811, NMC622, or other NMC compositions (NMCxyz). In certain embodiments, a positive electrode made of NMC532 with micron - sized grains has shown to be particularly stable, partly because the grain size produced by the processing conditions is larger than that produced by typical processing conditions.

[0238] Typical processing conditions result in NMC electrodes where nanosized particles are packed into larger micron - sized agglomerates, creating grain boundaries at the nanoscale. Grain boundaries are defects that tend to reduce desirable properties (e.g., electrical properties), so it is generally desirable to reduce the number of grains and increase the grain size. Current processing can produce larger domains at the micron - size level, reducing the number of grain boundaries in the NMC electrode and thus improving electrical properties. The improvement in properties leads to a more stable battery system. In certain embodiments, other NMC electrodes (e.g., NMC11, NMC811, NMC622, or another NMC compound) can be processed to produce a larger domain size (micron - size level or larger) to create a more stable system.

[0239] The positive electrode can be coated with a material such as alumina (Al2O3), titanium dioxide (TiO2), or another coating. Figure 4A -J shows typical experimental data of two additive systems of the present disclosure collected during UHPC experiments compared to a single - additive electrolyte system, where the novel dual - additive electrolyte systems (VC + DTD and FEC + DTD) in a base electrolyte system use a positive electrode composed of single - crystal NMC532 and a negative electrode composed of artificial graphite. The base electrolyte system contains 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate. Figure 4A -J shows the benefits of the dual - additive systems of the present disclosure, specifically, adding DTD to an electrolyte system containing VC or FEC.

[0240] Figure 4A Shows the relationship between the time - normalized Coulombic inverse efficiency per hour (CIE / h) and the number of cycles for electrolyte systems containing 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 4B Shows the relationship between the Coulombic efficiency (CE) and the number of cycles for electrolyte systems containing 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 4CShows the relationship between the charge end point capacity and the number of cycles for electrolyte systems containing 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 4D Shows the relationship between the discharge capacity and the number of cycles for electrolyte systems containing 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 4E Shows the relationship between the difference between the average charge voltage and the average discharge voltage and the number of cycles for electrolyte systems containing 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 4F Shows the relationship between the time-normalized Coulombic inverse efficiency per hour (CIE / h) and the number of cycles for electrolyte systems containing 1% DTD, 2% FEC, and 2% FEC + 1% DTD. Figure 4G Shows the relationship between the Coulombic efficiency (CE) and the number of cycles for electrolyte systems containing 1% DTD, 2% FEC, and 2% FEC + 1% DTD. Figure 4H Shows the relationship between the charge end point capacity and the number of cycles for electrolyte systems containing 1% DTD, 2% FEC, and 2% FEC + 1% DTD. Fig. 4I Shows the relationship between the discharge capacity and the number of cycles for electrolyte systems containing 1% DTD, 2% FEC, and 2% FEC + 1% DTD. Figure 4J Shows the relationship between the difference between the average charge voltage and the average discharge voltage and the number of cycles for electrolyte systems containing 1% DTD, 2% FEC, and 2% FEC + 1% DTD.

[0241] Figure 4A -J shows the benefits of electrolytes with two additives - specifically VC + DTD and FEC + DTD. Experimental data show that adding DTD to electrolyte systems containing VC or FEC in a base electrolyte system can improve the performance of electrolyte systems containing only VC or FEC as additives, where the base electrolyte system contains 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate by weight. Specifically, Figure 4A -J shows that the dual additive system containing (VC + DTD and FEC + DTD) has a higher CE (lower electrolyte degradation in the battery) and a lower charge end point shift (lower electrolyte degradation at the positive electrode) compared to systems without these additives or with only one additive. Further, Figure 4A -J also shows the desired lower decay rate (Q d ). Thus, electrolyte systems with two additives (VC + DTD and / or FEC + DTD) have better performance (in terms of CIE / h, CE, charge end point slip) compared to electrolyte systems containing only a single additive DTD, VC, or FEC.

[0242] Figure 5A -C outlines the data of the last three cycles generated during the experiment shown in Figure 4A -J. Figure 5A An overview of the time-normalized coulombic inverse efficiency per hour (CIE / h) for the last three cycles of electrolyte systems containing 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD is shown. Figure 5B An overview of the fractional slip per hour for the last three cycles of electrolyte systems containing 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD is shown. Figure 5C An overview of the fractional decay per hour for the last three cycles of 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD is shown.

[0243] Figure 5A -C shows that electrolyte systems containing VC + DTD and FEC + DTD exhibit lower time-normalized coulombic inverse efficiency (CIE / h) and lower fractional slip per hour (which means these electrolyte systems have longer lifetimes) compared to systems containing only one additional additive - 2% FEC, 2% VC, or 1% DTD. Figure 5A And 5B shows that 1% DTD without other additives shows the highest CIE / h and fractional slip. However, when DTD is combined with VC or FEC, the two additives form a previously unanticipated synergistic effect, resulting in less CIE / h and fractional slip in the dual-additive electrolyte systems compared to single additives. Figure 5C shows that the presence of 1% DTD, whether as a single additive or as part of a dual-additive electrolyte system with VC or FEC, reduces the fractional decay per hour. This indicates that DTD is an important additive for increasing the lifetime of the battery system of the present invention. In addition to DTD, other sulfur-containing compounds can act in a similar manner and increase battery life.

[0244] Methyl acetate as an electrolyte solvent: In certain embodiments, when higher charge and discharge rates and other properties are desired, methyl acetate is used as a solvent (at a concentration of up to 60%) to improve the battery system lifetime. This is particularly important for vehicles and other applications. Fig.9A -H shows typical data collected during some ultra-high-precision charging experiments, which shows that methyl acetate can be added to electrolyte systems containing DTD and VC or FEC to increase the conductivity of the electrolyte and reduce the viscosity without sacrificing much lifetime. For certain applications that require faster charging rates, increasing conductivity and reducing viscosity are important.

[0245] Fig.9A Shows the relationship between the Coulombic efficiency (CE) and the number of cycles for the following electrolyte systems, which respectively include: 2% FEC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate; and 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate.

[0246] Fig. 9B Shows the relationship between the end charge capacity and the number of cycles for the following electrolyte systems, which respectively include: 2% FEC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate; and 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate.

[0247] Fig. 9CShows the relationship between the discharge capacity and the number of cycles for the following electrolyte systems, which respectively include: 2% FEC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate; and 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate.

[0248] Fig.9D Shows the relationship between the difference between the average charge voltage and the average discharge voltage and the number of cycles for the following electrolyte systems, which respectively include: 2% FEC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate; and 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate.

[0249] Fig.9EShows the relationship between the Coulombic efficiency (CE) and the number of cycles for the following electrolyte systems, which respectively include: 2% VC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% VC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% VC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% VC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% VC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate; and 2% VC + 1% DTD in a solution of 1.2 M LiPF6 in a base electrolyte of 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate.

[0250] Fig.9F Shows the relationship between the end charge capacity and the number of cycles for the following electrolyte systems, which respectively include: 2% VC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% VC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% VC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% VC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% VC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate; and 2% VC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate.

[0251] Figure 9GShows the relationship between the discharge capacity and the number of cycles of the following electrolyte systems, which respectively include: 2% VC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% VC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% VC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% VC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% VC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate; and 2% VC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in a solution of 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate.

[0252] Figure 9H Shows the relationship between the difference between the average charge voltage and the average discharge voltage and the number of cycles of the following electrolyte systems, which respectively include: 2% VC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% VC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% VC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% VC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% VC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate; and 2% VC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate.

[0253] Fig.9A -H indicates that in a system including both VC and FEC, adding MA as an electrolyte solvent does not significantly sacrifice the overall performance of the battery system, and as will be shown by the long-term cycling and precipitation experiments described later, it can increase the life at higher charging rates. In particular, in the case of adding MA as a solvent, the performance of the dual-additive electrolyte system of the present disclosure is not sacrificed. Fig. 10A -C shows the average value of the data of the last three cycles generated during the experiment shown in Fig.9A -H. Fig. 10A-C confirmed that adding MA as an electrolyte solvent does not significantly sacrifice the overall performance of the battery systems of the present disclosure, including the dual-additive electrolyte system.

[0254] LFO as an additive: Fig.39A -H and 40A-H outlined the results of the UHPC experiments, which showed that LFO generally performs well in the electrolyte system, making the system perform well compared to the control electrolyte.

[0255] Fig.37A -F and Fig.38A -F outlined the experimental storage data of different electrolyte systems containing LFO compared to the control without LFO.

[0256] Fig.37A -F showed that, in the absence of other additives, LFO significantly improved storage. When LFO was added, after storage, the voltage drop was significantly reduced, the gas evolution was significantly reduced, and the impedance was significantly reduced. LMA was also effective in the presence of MA. Fig.38A -F showed similar results when LFO was added to the EC / DMC-based electrolyte. When using a good additive package (e.g., 1% FEC + 1% DTD), the additional benefits brought by LFO were small. However, the DTD-based electrolyte system may be removed in the future because they change color over time when mixed and stored in the glove box.

[0257] Fig.46A -D showed the results of the storage experiments of the batteries with more complex electrolytes, which showed the ability to match 2% FEC + 1% DTD in storage performance.

[0258] Fig.51A -D, Fig.52A -D, Figure 53A -D and Figure 54A -C showed the results of additional electrolyte systems containing LFO, as well as the results of 2% VC + 1% DTD for comparison purposes. It was observed that some electrolyte systems with LFO performed the same or slightly better compared to the 2% VC + 1% DTD system. Figure 55A -C showed the results of additional experiments for CIE, fractional decay, and fractional slip. The electrolyte system of 2% VC + 1% DTD performed very well. The electrolyte systems of 1% LFO + 2% VC and 1% LFO + 1% VC + 1% FEC also performed well (although not as well as the 2% VC + 1% DTD system). This experimental data was consistent with the TAM experimental data.

[0259] Figure 56 Showed the effect of UHPC cycling on impedance. The LFO system generally performed well. Figure 57A-D summarizes the experimental data of electrolyte systems containing LFO, where the positive electrode is made of NMC 622 with two different coatings, which are designated as A and B. For the different electrolyte systems studied, LFO has the effect of reducing the voltage drop and the system impedance.

[0260] LFO can be obtained from multiple suppliers, including Guangzhou Tinci Materials Technology Co., Ltd. and Shenzhen Capchem Technology Co., Ltd. Figure 58 It is shown that, independent of the supplier, in the presence of air, the reaction rates are similar for at least 50 minutes or a shorter time period. Figure 59 It is shown that through thermogravimetric analysis ("TGA") experiments performed with a temperature ramp of 5 °C / min in an argon environment, the mass losses are also similar.

[0261] Long-term cycling

[0262] The lifespan of a battery system is an important property of the battery system. The charge and discharge rates can affect the lifespan. Long-term cycling experiments help to determine the resilience of the battery system over a period of time under expected operating conditions. It is important to select a battery system with sufficient lifespan for the desired application.

[0263] Embodiments of the present disclosure exhibit desirable long-term cycling for different applications including grid and vehicle storage. Specifically, dual-additive electrolyte systems of VC+DTD and FEC+DTD, where up to 60% concentration of MA is used as a solvent, are particularly suitable for automotive applications (especially energy storage within electric vehicles), where the charge and discharge rates are typically higher than grid storage applications.

[0264] In long-term cycling experiments, single-crystal NMC532 is typically used as the positive electrode (unless otherwise specified) and artificial graphite is used as the negative electrode (unless otherwise specified). Before long-term cycling experiments, pouch cells undergo a formation process. The cells are first charged to 4.2 V at 11 mA (C / 20) and then discharged to 3.8 V. The cells are transferred and moved into a glove box, cut open to release the generated gas, and then vacuum-sealed again. After formation, the cells are cycled on a Neware charging system. The cells are housed in a temperature-controlled chamber at 40 °C + / - 0.2 °C or 20 °C + / - 0.2 °C. The cells are cycled between 3.0 V and the maximum charge voltage (4.2 V or 4.3 V), using a current of C / 3 (a half-cycle of 3 h), and a constant voltage step at the maximum charge, until the current drops below C / 20. Every 50 cycles, the cells undergo a full cycle at C / 20.

[0265] Dual - electrolyte systems with FEC or VC as additives: In certain embodiments, the dual - additive electrolyte system forms part of a battery system, and the concentration of each additive is about 0.25 - 6%. Figure 6A -F shows typical experimental data for the study at 40 °C and a C / 3 constant charge, constant voltage (CCCV) charge rate. Figure 6A -F shows the advantages of the dual - additive electrolyte systems of the present disclosure, specifically, electrolytes containing DTD with VC or FEC. Figure 6A Shows experimental data of the relationship between the capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.2 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 6B Shows experimental data of the relationship between the normalized capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.2 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 6C Shows experimental data of the relationship between the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.2 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 6D Shows experimental data of the relationship between the capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.2 V, which respectively include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 6E Shows experimental data of the relationship between the normalized capacity and the number of cycles of electrolyte systems cycled between 3.0 V and 4.2 V, which include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 6F Shows experimental data of the relationship between the voltage hysteresis and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.2 V, which include: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD. The experimental data shows that compared with single - additive electrolyte systems of VC or FEC, when cycled to 4.2 or 4.3 V, the dual - additive electrolyte systems (DTD + FEC and DTD + VC) experience less capacity loss and lower polarization growth.

[0266] Figure 7A-F shows typical experimental data for the long-term cycling at 20 °C at a C / 3 CCCV charge rate. Similar to Figure 6A -F, Figure 7A -F shows the advantages of including DTD as an additive in an electrolyte system containing VC or FEC as an additive. Figure 7A -F confirms that the advantages seen at 40 °C still exist at lower temperatures, in this case 20 °C. Figure 7A Shows experimental data of the relationship between the capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V, which electrolyte systems include respectively: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 7B Shows experimental data of the relationship between the normalized capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V, which electrolyte systems include respectively: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 7C Shows experimental data of the relationship between the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V, which electrolyte systems include respectively: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 7D Shows experimental data of the relationship between the capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V, which electrolyte systems include respectively: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 7E Shows experimental data of the relationship between the normalized capacity and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V, which electrolyte systems include respectively: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 7F Shows experimental data of the relationship between the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) and the number of cycles of the following electrolyte systems cycled between 3.0 V and 4.3 V, which electrolyte systems include respectively: 1% DTD, 2% FEC, 2% FEC + 1% DTD, 2% VC, and 2% VC + 1% DTD. Figure 7A -F confirms the advantages of including DTD in an electrolyte with VC or FEC, especially when cycling occurs up to 4.3 V.

[0267] Figure 6A -F shows the benefits of a dual-additive electrolyte system composed of DTD + VC or DTD + FEC. Figure 6A-F shows that including DTD as part of a dual-additive electrolyte system together with VC or FEC and cycling at 40 °C results in less capacity loss at 4.2 and 4.3 V and reduced polarization growth. Similarly, Figure 7A -F shows the benefits of DTD when cycling long-term at 20 °C. Figure 7A -F shows that including DTD as part of a dual-additive electrolyte system together with VC or FEC and cycling at 20 °C results in less capacity loss at 4.2 V (slightly) and 4.3 V (more significantly) and reduced polarization growth. Thus, at 20 °C or 40 °C, the dual-additive system including DTD with VC or FEC improves the battery system by reducing capacity loss and reducing polarization growth.

[0268] In certain embodiments, the positive electrode is formed of NMC111, NMC532, NMC822, NMC622, and / or NMCxyz. In particular, a positive electrode made of single-crystalline NMC532 has been shown to be particularly stable, in part because the grain size of NMC532 is larger than that of other standard NMC materials, which are more polycrystalline and have smaller grain sizes. Figure 8A -I shows typical empirical data collected during cycling experiments for electrolyte compositions according to certain embodiments of the present disclosure, which include a positive electrode formed of single-crystalline NMC532. Figure 8A Experimental data showing the relationship between peak capacity and number of cycles for the following electrolyte systems in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate, cycled at 40 °C between 3.0 V and 4.3 V, which electrolyte systems include 2% FEC, 1% FEC + 1% DTD, 2% FEC + 1% DTD, 1% FEC + 1% MMDS, and 2% FEC + 1% MMDS, respectively. Figure 8B Experimental data showing the relationship between normalized capacity and number of cycles for the following electrolyte systems in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate, cycled at 40 °C between 3.0 V and 4.3 V, which electrolyte systems include 2% FEC, 1% FEC + 1% DTD, 2% FEC + 1% DTD, 1% FEC + 1% MMDS, and 2% FEC + 1% MMDS, respectively. Figure 8CExperimental data showing the relationship between the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) and the number of cycles of the following electrolyte systems in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate cycled at 40 °C between 3.0 V and 4.3 V, where the electrolyte systems include 2% FEC, 1% FEC + 1% DTD, 2% FEC + 1% DTD, 1% FEC + 1% MMDS, and 2% FEC + 1% MMDS, respectively. Figure 8D Experimental data showing the relationship between the peak capacity and the number of cycles of the following electrolyte systems in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate cycled at 40 °C between 3.0 V and 4.3 V, where the electrolyte systems include 2% VC, 1% VC + 1% DTD, 2% VC + 1% DTD, 1% VC + 1% MMDS, and 2% VC + 1% MMDS, respectively. Figure 8E Experimental data showing the relationship between the normalized capacity and the number of cycles of the following electrolyte systems in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate cycled at 40 °C between 3.0 V and 4.3 V, where the electrolyte systems include 2% VC, 1% VC + 1% DTD, 2% VC + 1% DTD, 1% VC + 1% MMDS, and 2% VC + 1% MMDS, respectively. Figure 8F Experimental data showing the relationship between the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) and the number of cycles of the following electrolyte systems in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate (by weight) cycled at 40 °C between 3.0 V and 4.3 V, where the electrolyte systems include 2% FEC, 1% VC + 1% DTD, 2% VC + 1% DTD, 1% VC + 1% MMDS, and 2% VC + 1% MMDS, respectively. Figure 8G Experimental data showing the relationship between the peak capacity and the number of cycles of the following electrolyte systems in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate cycled at 40 °C between 3.0 V and 4.3 V, where the electrolyte systems include 2% PES, 1% PES + 1% DTD, 2% PES + 1% DTD, 1% PES + 1% MMDS, and 2% PES + 1% MMDS, respectively. Figure 8HExperimental data showing the relationship between the normalized capacity and the number of cycles of the following electrolyte systems in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate, cycled at 40 °C between 3.0 V and 4.3 V, which electrolyte systems include: 2% PES, 1% PES + 1% DTD, 2% PES + 1% DTD, 1% PES + 1% MMDS, and 2% PES + 1% MMDS. Figure 8I Experimental data showing the relationship between the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) and the number of cycles of the following electrolyte systems in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl carbonate, cycled at 40 °C between 3.0 V and 4.3 V, which electrolyte systems include: 2% FEC, 1% PES + 1% DTD, 2% PES + 1% DTD, 1% PES + 1% MMDS, and 2% PES + 1% MMDS. Figure 8A -Figure I shows that NMC532 performs well in a dual - additive electrolyte system of 1% DTD with 1% VC, 2% VC, 1% FEC, or 2% FEC. In the case of VC or FEC, DTD performs better as an additive than MMDS.

[0269] Methyl acetate as an electrolyte solvent: In certain embodiments, methyl acetate is used as an electrolyte solvent at a concentration of up to 60% (by weight) and is typically combined with ethylene carbonate and / or ethyl methyl carbonate. Figure 15A -Figures 16A - F show the experimental results conducted at 20 °C and 40 °C respectively. In the cells containing MA as a solvent, the cells with DTD perform better than the cells without DTD.

[0270] Figure 15AIt is a graph of experimental data on the relationship between the capacity and the number of cycles of the following electrolyte systems, which are cycled up to 4.2 V at 20°C. These electrolyte systems respectively include: 2% FEC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 1% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate; and 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate.

[0271] Figure 15B It is a graph of experimental data on the relationship between the normalized capacity and the number of cycles of the following electrolyte systems, which are cycled up to 4.2 V at 20°C. These electrolyte systems respectively include: 2% FEC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 1% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate; and 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate.

[0272] Figure 15CIt is a graph of experimental data on the relationship between the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) and the number of cycles of the following electrolyte systems at 20°C with cycles up to 4.2V. These electrolyte systems respectively include: 2% FEC in a base electrolyte of 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 1% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate; and 2% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate.

[0273] Figure 15D It is a graph of experimental data on the relationship between the capacity and the number of cycles of the following electrolyte systems at 20°C with cycles up to 4.3V. These electrolyte systems respectively include: 2% FEC in a base electrolyte of 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 1% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate; and 2% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate.

[0274] Figure 15EIt is a graph of experimental data on the relationship between the normalized capacity and the number of cycles of the following electrolyte systems at 20 °C with cycles up to 4.3 V. These electrolyte systems include, respectively: 2% FEC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 1% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate; and 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate.

[0275] Figure 15F It is experimental data at 20 °C on the relationship between the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) and the number of cycles of the following electrolyte systems with cycles up to 4.3 V. These electrolyte systems include, respectively: 2% FEC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 1% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate; and 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate.

[0276] Figure 15A -F shows the importance of DTD in systems containing FEC and in systems using MA as a solvent at 20 °C. Cells with DTD perform better than cells without DTD, especially in cells containing MA. Specifically, 2% FEC + 1% DTD with a 20% MA solvent shows very stable capacity retention at 4.3 V.

[0277] Figure 16A -F shows the experimental results conducted at 40°C. Among the cells containing MA, the cells with DTD perform better than those without DTD. Figure 16A It is a graph of the experimental data of the relationship between the capacity and the number of cycles of the following electrolyte systems conducted at 40°C using cycles up to 4.2V. These electrolyte systems include respectively: 2% FEC in a base electrolyte of 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 1% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate.

[0278] Figure 16B It is a graph of the experimental data of the relationship between the normalized capacity and the number of cycles of the following electrolyte systems conducted at 40°C using cycles up to 4.2V. These electrolyte systems include respectively: 2% FEC in a base electrolyte of 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 1% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate and 40% methyl acetate.

[0279] Figure 16CIt is a graph using experimental data on the relationship between the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) and the number of cycles at 40 °C for electrolyte systems with cycles up to 4.2 V. These electrolyte systems respectively include: 2% FEC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 1% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate; and 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate.

[0280] Figure 16D It is a graph using experimental data on the relationship between the capacity and the number of cycles at 40 °C for electrolyte systems with cycles up to 4.3 V. These electrolyte systems respectively include: 2% FEC in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 1% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate; and 2% FEC + 1% DTD in a base electrolyte of 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate.

[0281] Figure 16EIt is a graph of experimental data on the relationship between the normalized capacity and the number of cycles of the following electrolyte systems that are cycled up to 4.3V at 40°C. These electrolyte systems include, respectively: 2% FEC in a base electrolyte of 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 1% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate.

[0282] Figure 16F It is a graph of experimental data on the relationship between the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) and the number of cycles of the following electrolyte systems that are cycled up to 4.3V at 40°C. These electrolyte systems include, respectively: 2% FEC in a base electrolyte of 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 1% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; 2% FEC in a base electrolyte of 1.2M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; 2% FEC in a base electrolyte of 1.2M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate; 2% FEC + 1% DTD in a base electrolyte of 1.2M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate.

[0283] Figure 16A-F shows the importance of DTD at 40 °C, in systems containing FEC, and using MA as a solvent. Generally, cells with DTD perform better than cells without DTD, especially in cells containing MA. In a dual-additive electrolyte system with 2% FEC + 1% DTD and 20% MA solvent, the effect of DTD is slightly diminished compared to the same dual-additive electrolyte system but without MA as a solvent. Additionally, at 4.3 V, adding up to 40% MA reduces the cycle life. That is, DTD and MA can have a symbiotic increase in the performance of the dual-additive electrolyte system, but this increase is diminished when operating in cycles up to 4.3 V. Thus, in certain embodiments of the present disclosure, the electrolyte system is only operated up to 4.2 V. In other embodiments of the present disclosure, the electrolyte system is operated up to 4.3 V, but the system has an MA concentration of less than 40%.

[0284] NMC622 as the positive electrode: In certain embodiments, the battery system has a positive electrode made of NMC622. In certain embodiments, the positive electrode is coated with a material such as alumina (Al2O3), titanium dioxide (TiO2), or another coating. Figure 17A -F shows experimental data for the long-term cycling of a single-additive electrolyte system and a dual-additive electrolyte system with a coated NMC622 as the positive electrode at 40 °C, C / 3 CCCV. The dashed line is extrapolated from the experimental data.

[0285] More specifically, Figure 17A is a graph of experimental data showing the relationship between the capacity and the number of cycles for an electrolyte system containing FEC and / or DTD using cycles up to 4.3 V. Figure 17B is a graph of experimental data showing the relationship between the normalized capacity and the number of cycles for an electrolyte system containing FEC and / or DTD using cycles up to 4.3 V. Figure 17C is a graph of experimental data showing the relationship between the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) and the number of cycles for an electrolyte system containing FEC and / or DTD using cycles up to 4.3 V. Figure 17D is a graph of experimental data showing the relationship between the capacity and the number of cycles for an electrolyte system containing VC and / or DTD using cycles up to 4.3 V. Figure 17E is a graph of experimental data showing the relationship between the normalized capacity and the number of cycles for an electrolyte system containing VC and / or DTD using cycles up to 4.3 V. Figure 17F is a graph of experimental data showing the relationship between the voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) and the number of cycles for an electrolyte system containing VC and / or DTD using cycles up to 4.3 V.

[0286] Figure 17A -F indicates that even when different positive electrodes are selected, experimental data show that electrolyte systems with two additives - VC+DTD and FEC+DTD - perform better than any single additive VC, FEC, or DTD.

[0287] Natural graphite as the negative electrode: In certain embodiments, the battery system has a negative electrode made of natural graphite. Figure 18A -B and 19 show data of additional long-term cycling experiments performed at 40 °C, C / 3 CCCV, using single-crystal NMC532 as the positive electrode and natural graphite as the negative electrode. Figure 18A Shows the relationship between capacity and number of cycles. Figure 18B Shows the relationship between normalized capacity and number of cycles. Figure 19 Shows the relationship between voltage hysteresis (the difference between the average charge voltage and the average discharge voltage) and number of cycles. Figure 18A -B and 19 show that the dual electrolyte additive system containing DTD+FEC has improved performance compared to the electrolyte system containing only FEC as an additive. However, a comparison with Figure 6-F in which an artificial graphite negative electrode is used shows that in the dual additive electrolyte system of the present disclosure, the performance of this specific artificial graphite negative electrode is better than that of this specific natural graphite negative electrode.

[0288] In certain embodiments, the battery system has a natural graphite negative electrode. Compared with artificial graphite, using natural graphite as the negative electrode is an important cost-saving measure, as artificial graphite is generally more expensive. Therefore, when cost is the main driving factor and some performance compromises may be required, natural graphite can be a good choice.

[0289] LFO as an additive: In certain embodiments, LFO is added as an electrolyte system. Figure 41A Data outlining the relationship between the coulombic inverse efficiency and the upper cut-off voltage of different electrolyte systems (including systems containing LFO). Figure 41B Data outlining the relationship between the fractional decay and the upper cut-off voltage of different electrolyte systems (including systems containing LFO). Figure 41C Data outlining the relationship between the charge end point capacity slip and the upper cut-off voltage of different electrolyte systems (including systems containing LFO). Figure 42A Shows Figure 41A An enlarged view of, and data outlining the relationship between the coulombic inverse efficiency and the upper cut-off voltage of different electrolyte systems (including systems containing LFO). Figure 42B Shows Figure 41BAn enlarged view, and data outlining the fractional decay versus upper cut-off voltage for different electrolyte systems, including those containing LFO. Figure 42C Shows Figure 41C An enlarged view, and data outlining the charge end-point capacity slip versus upper cut-off voltage for different electrolyte systems, including those containing LFO. Adding LFO to the control electrolyte can greatly improve the UHPC results. In the presence of MA, 1% LFO can greatly improve the situation compared to 0.5% LFO. For 1% LFO in the control, CIE / h is approximately 4×10 -5 h -1 . In contrast, the best electrolyte system without LFO (e.g., 2% VC + 1% DTD in the control) is close to 3×10 -5 h -1 .

[0290] Figure 43A -D outlines the long-term cycling data for different electrolyte systems, including those containing LFO. The long-term cycling results show that adding LFO can significantly improve impedance growth in the tested systems and confirm the UHPC data. In particular, adding 1% LFO to the control electrolyte and to the electrolyte system containing 20% MA can improve long-term cycling and impedance.

[0291] Microcalorimetry measurements

[0292] Microcalorimetry measurements the heat flow to the battery during operation. The heat flow to the battery is a combination of three different effects: (1) ohmic heating; (2) entropy change due to lithium insertion into the electrodes; and (3) parasitic reactions (degradation of the electrolyte, including additives, at either electrode). Since the test batteries have the same physical design, differing only in the electrolyte, the differences in heat flow are mainly attributed to differences in parasitic heat flow. However, the parasitic heat flow can be extracted from the total heat flow using the procedures developed by Downie et al. (Journal of the Electrochemical Society, 161, A1782 - A1787 (2014)) and Glazier et al. (Journal of the Electrochemical Society, 164(4), A567 - A573 (2017)). Both of these references are incorporated herein by their entirety. Batteries with lower parasitic heat flow during cycling have better lifetimes. The voltage dependence of the parasitic reaction rate can be observed by plotting the measured parasitic heat flow as a function of the battery voltage.

[0293] Microcalorimetry measurement procedure: Two cells for each electrolyte were connected to a Maccor charger at 40.0 °C and inserted into a TAMIII microcalorimeter (TA Instruments, stability ±0.0001 °C, accuracy ±1 μC, precision ±1 nW). The baseline drift during the experiment was no more than ±0.5 μL. All specifications and information regarding microcalorimetry calibration, cell connection, and operation procedures can be found in previous literature (e.g., Downie et al., ECS Electrochemical Letters 2, A106 - A109 (2013)). The cells were cycled four times at a C / 20 rate between 3.0 V and 4.2 V to ensure a well - formed and stable SEI, and then charged at 1 mA between 4.0 V and different upper cut - off limits to study the performance and parasitic heat flow in different voltage ranges. The performance of each pair of cells was almost the same, so only one set of heat flow data is shown for each electrolyte.

[0294] The cycling scheme at 1 mA was as follows:

[0295] 1. Charge to 4.2 V and discharge to 4.0 V

[0296] 2. Charge to 4.3 V and discharge to 4.0 V (repeated)

[0297] 3. Charge to 4.4 V and discharge to 4.0 V (repeated)

[0298] 6. Charge to 4.2 V and discharge to 4.0 V

[0299] Other experimental details are described in Journal of the Electrochemical Society, 164(4) A567 - A573 (2017), which is incorporated herein by reference in its entirety.

[0300] In Figures 11 - 14 the experimental data shown, pouch cells with a positive electrode made of single - crystal NMC532 and a negative electrode of artificial graphite were used. Except for the additive, depending on the concentration of methyl acetate (0%, 20%, or 40%), the electrolyte was (1) 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate; or (2) 1.2 M LiPF6 in 24% ethylene carbonate, 56% ethyl methyl carbonate, and 20% methyl acetate; or (3) 1.2 M LiPF6 in 18% ethylene carbonate, 42% ethyl methyl carbonate, and 40% methyl acetate.

[0301] Figure 11 The experimental data (relationship between parasitic heat flow and voltage) of the calorimetry experiment when charging to 4.2 V are shown. Figure 12A and12B Shows the experimental data (relationship between parasitic heat flow and voltage) of a calorimetry experiment when charged to 4.3 V. Since charging to 4.3 V was repeated, each graph shows the result of one charge. Figure 13A and 13B Shows the experimental data (relationship between parasitic heat flow and voltage) when charged to 4.4 V. Since charging to 4.4 V was repeated, each graph shows the result of one charge. The difference graphs ( Figure 11 , 12A , the lower graphs in 12B, 13A, and 13B) were calculated by obtaining the heat flow of each electrolyte mixture and subtracting the heat flow generated by the control (2% FEC). Figure 14 Shows an overview of the experimental data conveyed in Figure 11 - 1 3. Table 1 summarizes the data shown in Figure 14 .

[0302] Table 1: Average parasitic heat flow per cycle (μW) (40 °C, 4.0 V to UCV, 1 mA)

[0303]

[0304] Figures 11 - 14 And Table 1 show that the addition of DTD to FEC results in a reduction in parasitic heat flow (reduction in parasitic reaction rate). Figures 11 - 14 And Table 1 also show that the addition of MA results in a higher parasitic heat flow (higher parasitic reaction rate), but this increase can be mitigated by DTD, which helps to reduce the parasitic reaction rate increased due to the addition of MA.

[0305] LFO as an additive : Figure 47 Shows the relationship between charge heat flow, parasitic heat flow, charge overpotential, and discharge overpotential. Figure 48A -F shows the results of the TAM experiment. The difference graph compares the system with 2% VC + 1% DTD . Figure 48A -F shows that 2% VC + 1 DTD is superior to 2% FEC + 1 DTD. These graphs also show that when optimized for LFO within the system, above 4.3 V, 1% LFO + 1% VC + 1% FEC is superior to 2% VC + 1% DTD. Compared with the system with 1% LFO, above 4.3 V, 1% LFO + 1% VC performs equivalently to 1% LFO + 1% VC + 1% FEC and is superior to 2% VC + 1% DTD. In Figure 49A -C, it was observed that the optimal LFO composition is approximately 1.0%. Figure 50Shows the relationship between the average parasitic heat flow of the best-performing battery and the number of cycles. After cycling at 4.4 V, 0.5% LFO with 1% VC + 1% FEC is the best-performing system. 2% VC + 1% LFO is equivalent to 2% VC + 1% DTD. Thus, systems with VC, with or without DTD, are possible.

[0306] Plating experiment

[0307] The plating experiment tests the ability to charge at a rapid rate. When energy storage is part of a vehicle, rapid charging is very important in energy storage, while lower charging rates are acceptable in grid storage applications. High-rate charging is mainly limited by lithium plating on the negative electrode, which causes safety issues and shortens cycle and calendar life. Thus, an electrolyte system that allows a higher charging rate without plating is advantageous. To study plating on the negative electrode, the plating experiment is performed. A larger capacity loss indicates greater lithium plating.

[0308] The plating experiment is performed to test the charging ability of the battery. After EIS measurement, the battery is charged and discharged using a Maccor charger system at a constant current (C-rate) of 1C, 1.5C, and 2.0C between 2.8 and 4.1 V at 20.0 ± 0.1 °C. For each charging rate, paired cells are tested to ensure reproducibility. To determine the loss of active lithium during cycling, the battery is cycled once at C / 20 before and after the high charging rate segment. The upper cut-off voltage is set to 4.1 V to minimize electrolyte oxidation at the positive electrode and to ensure away from the negative electrode with full load, which occurs at 4.4 V for these batteries. All pouch cells are cycled using an external fixture to eliminate the effect of a small amount of gas that may be generated during cycling. The battery is stopped after approximately 350 hours of cycling or when the capacity loss reaches 20%.

[0309] Dual electrolyte systems using FEC or VC as additives: In some embodiments, a dual additive electrolyte system forms part of the battery system, with the concentration of each additive being about 0.25 - 6%. Figure 22 Shows the experimental data of the plating experiment for different battery systems at different current charging rates. Figure 22 Indicates that adding DTD does not significantly increase the maximum current at which plating occurs. For example, at 1C, 1.5C, and 2C, compared to the electrolyte system composed of a single additive 2% FEC, the low-rate capacity loss of the electrolyte system composed of two additives - 2% FEC + 1% DTD - is reduced. Similarly, Figure 22It is shown that at 1C and 1.5C, compared with the electrolyte system composed of a single additive 2% FEC, the low-rate capacity loss of the electrolyte system composed of two additives - 1% FEC + 1% DTD - is reduced. At 2C, the low-rate capacity loss of this electrolyte system is also only slightly higher.

[0310] Figure 23 Experimental data from the precipitation test are shown, where the charging current increases after every 30 cycles. A large capacity loss rate indicates lithium precipitation. At the charging current of 2C, lithium begins to precipitate in each cell. However, the cells with DTD lose less capacity during precipitation. This indicates that the amount of precipitation in the cells with DTD is less than that in the cells without DTD. In addition to DTD, other sulfur-containing compounds can also act in a similar way to reduce precipitation.

[0311] Figure 24 The results of experimental data showing the relationship between the peak capacity and the number of cycles of different electrolyte systems are shown. When DTD or MMDS is combined with VC, DTD performs better than MMDS in maintaining the peak capacity of the dual-additive electrolyte system.

[0312] Methyl acetate as an electrolyte solvent: According to certain embodiments, up to 60% by weight of methyl acetate is used as a solvent to reduce precipitation. Figures 27 - 34 The effects of using MA as a solvent in different electrolyte systems are shown. Figure 27 The results of the precipitation experiment are shown to determine the effects of the presence of MA as a solvent and DTD as an additive on the battery impedance. The electrolyte systems tested contain 2% additives (VC, FEC, and PES) in electrolytes with 0%, 20%, and 40% MA. The remaining electrolyte for 0% MA is 1.2M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate. The remaining electrolyte for 20% MA is 1.2M LiPF6 in 24% ethylene carbonate and 56% ethyl methyl carbonate. The remaining electrolyte for 40% MA is 1.2M LiPF6 in 18% ethylene carbonate and 42% ethyl methyl carbonate. Figure 28 is Figure 27 An enlarged view of some data with smaller low-rate capacity loss as shown.

[0313] In Figure 27 and 28 a larger capacity loss indicates a larger amount of lithium precipitation. Figure 27 and 28It is shown that even at a charging rate of 2C, the presence of MA reduces the low-rate capacity loss. Therefore, electrolyte systems containing 20% or 40% MA are good candidates for use in fast-charging applications, such as energy storage in vehicles that may be subjected to high charging current rates.

[0314] Figure 29 、 30 And 31 show the results of experimental data for electrolyte systems containing FEC as an additive. As shown in the legend in the figure, the different data sets include DTD and / or MA. Figure 29 、 30 And 31 show that adding MA in a single-additive system and a dual-electrolyte system with FEC can achieve higher charging rates without significant precipitation, and the higher charging rates include charging up to 2C.

[0315] Similarly, Figure 32 、 33 And 34 show the results of experimental data for electrolyte systems containing VC as an additive. As shown in the legend in the figure, the different data sets include DTD and / or MA. Figure 32 、 33 And 34 show that adding MA in a single-additive system and a dual-additive electrolyte system with VC can achieve higher charging rates without significant precipitation, and the higher charging rates include charging up to 2C.

[0316] LFO as an electrolyte additive: Figure 44A -D outlines the long-term cycling data of different electrolyte systems (including systems containing LFO) under high-rate charging. It can be seen from the experimental data that the presence of MA reduces the amount of precipitation. In addition, LFO reduces the possibility of lithium precipitation during high-rate charging. For example, in Figure 44A , compared with other systems without MA or LFO, the electrolyte system with 20% MA + 1% LFO shows significantly less loss of the normalized discharge capacity. The loss of the normalized discharge capacity indicates precipitation.

[0317] Gas volume measurement

[0318] Before a battery is used in its intended application, such as grid storage or energy storage in an automotive vehicle such as an electric vehicle, a formation process is performed. In the formation process, the battery is subjected to precisely controlled charge and discharge cycles that are designed to activate the electrodes and electrolyte for its intended application. During the start of the formation process, gas is generated. If a sufficient amount of gas (depending on the specific tolerances allowed by the battery and the battery packaging) is generated, the gas may need to be released after the formation process and before application use. This typically requires additional steps as follows: breaking the seal and then resealing. Although these steps are common for many battery systems, it is desirable to eliminate these steps by selecting a system that generates less gas, if possible.

[0319] The gas volume experiment was conducted as follows: Ex-situ (static) gas measurements were used to measure gas evolution during formation and cycling. The measurements were performed using Archimedes' principle, where the battery was suspended from a balance while being immersed in a liquid. The change in the weight of the battery suspended in the fluid before and after the test is directly related to the change in buoyancy and the change in volume. The change in the mass Δm of the battery suspended in a fluid with density ρ is related to the change in the battery volume Δv by the following equation: Δv = Δm / ρ.

[0320] Dual electrolyte systems using FEC or VC as additives: In certain embodiments, the dual additive electrolyte system forms part of the battery system, and the concentration of each additive is about 0.25 - 6%. Figure 20 The results of the gas generation experiment are shown, where the amount of gas generated was measured according to the above process. Figure 20 It is shown that systems without DTD generally perform better. For example, a system containing only 2% FEC as an additive performs better than 1% FEC + 1% DTD and 2% FEC + 1% DTD. That is, DTD results in a higher gas volume generation during the formation process. If DTD is used as an additive due to its desired properties when combined with other additives (e.g., VC and FEC), the system must include a mechanism to safely handle the gas generated by DTD, such as gas release after formation as discussed above. Figure 20 It is shown that a dual additive electrolyte system containing MMDS and PES or FEC does not generate much (if any) additional gas compared to the case of adding only 2% PES or FEC.

[0321] Methyl acetate as an electrolyte solvent: According to certain embodiments, methyl acetate with a concentration of up to 60% by weight is used as a solvent to reduce precipitation. Figure 25The results of gas generation experiments are shown to determine the effect of the presence of MA as a solvent and DTD as an additive on the generated formation gas. The electrolyte systems tested included 2% additives (VC, FEC, and PES) in electrolytes with 0%, 20%, and 40% MA. The remaining electrolyte for 0% MA was 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate. The remaining electrolyte for 20% MA was 1.2 M LiPF6 in 24% ethylene carbonate and 56% ethyl methyl carbonate. The remaining electrolyte for 40% MA was 1.2 M LiPF6 in 18% ethylene carbonate and 42% ethyl methyl carbonate.

[0322] Figure 25 It is shown that in the dual-additive electrolyte systems containing DTD and VC or FEC, as the amount of MA increases, the change in the amount of gas with added MA is less. That is, the marginal amount of gas generated is less when DTD is part of the dual-additive electrolyte system compared to a single-additive electrolyte system having only VC or FEC.

[0323] In-situ gas volume measurement

[0324] Figure 45A and 45B summarizes the results of in-situ gas experiments at 40 °C. Cells with LFO but without MA showed less gas evolution during the hold segments of these tests.

[0325] Cell impedance

[0326] The dual-additive electrolyte systems and novel battery systems disclosed herein have low cell impedance. Since cell impedance reduces the energy efficiency of the battery, it is desirable to minimize the cell impedance. On the contrary, low impedance results in higher charging rates and higher energy efficiency.

[0327] Cell impedance was measured using electrochemical impedance spectroscopy (EIS). Unless otherwise stated, pouch cells used single-crystal NMC532 positive electrodes and artificial negative electrodes, where EIS measurements were performed after formation. The cells were charged or discharged to 3.80 V before being moved to a 10.0 + / - 0.1 °C temperature chamber. AC impedance spectra were collected at 10.0 + / - 0.1 °C with ten points per decade from 100 kHz to 10 mHz, with a signal amplitude of 10 mV. Based on the measured AC impedance, the charge transfer resistance (R ct ) was calculated and plotted.

[0328] Dual electrolyte systems using FEC or VC as additives: In certain embodiments, the dual-additive electrolyte system forms part of a battery system, and the concentration of each additive is about 0.25 - 6%.Figure 21 Experimental data of the cell charge transfer impedance experiment of a dual-additive electrolyte system composed of 1% DTD with 1% or 2% PES, FEC, or VC are shown. Figure 21 It is shown that such a dual-additive electrolyte system with 1% or 2% PES, FEC, or VC and 1% DTD does not significantly increase the cell charge transfer impedance. In particular, the systems of 1% VC with 1% DTD, 2% VC with 1% DTD, 1% FEC with 1% DTD, and 2% FEC with 1% DTD exhibit cell impedance values similar to those of the single-additive system without DTD: the observed cell charge transfer impedance of the single-additive system without DTD. Thus, these novel dual-additive electrolyte systems do not sacrifice significant charge transfer impedance performance by including DTD.

[0329] Methyl acetate as an electrolyte solvent: According to certain embodiments, up to 60% by weight of methyl acetate is used as a solvent to reduce precipitation. Figure 26 Results of the cell charge transfer impedance experiment on electrolyte systems composed of a single-additive system and a dual-additive system are shown, where MA is one of the solvents in the solvent. The tested additive electrolyte systems contain 2% VC, FEC, and PES as additives and with and without 1% DTD to show the effects of DTD and MA on the electrolyte systems in electrolyte solvents with 0%, 20%, and 40% MA. The electrolyte for 0% MA is 1.2 M LiPF6 in 30% ethylene carbonate and 70% ethyl methyl carbonate. The remaining electrolyte for 20% MA is 1.2 M LiPF6 in 24% ethylene carbonate and 56% ethyl methyl carbonate. The remaining electrolyte for 40% MA is 1.2 M LiPF6 in 18% ethylene carbonate and 42% ethyl methyl carbonate. Figure 26 It is shown that DTD only produces a slight increase in the charge transfer impedance. In addition, in the dual-additive electrolyte systems containing DTD and VC or FEC, the addition of MA reduces the cell charge transfer impedance. In the 40% MA solvent, the VC+DTD and FEC+DTD systems show a reduced charge transfer impedance compared to the corresponding systems without DTD and without MA as a solvent. In the PES+DTD dual-additive electrolyte system, MA also reduces the charge transfer impedance of the system.

[0330] The foregoing disclosure is not intended to limit the present disclosure to the exact forms or particular fields of use disclosed. Accordingly, it is contemplated that various embodiments and / or modifications of the present disclosure are possible, whether or not explicitly described or implied herein. Having described embodiments of the present disclosure, those of ordinary skill in the art will recognize that changes may be made in form and detail without departing from the scope of the present disclosure. Accordingly, the present disclosure is limited only by the claims. Unless otherwise indicated in the specification, references to additives in the specification generally refer to operative additives.

[0331] In the foregoing specification, the present disclosure has been described with reference to specific embodiments. However, as will be understood by those skilled in the art, the various embodiments disclosed herein may be modified or otherwise implemented in a variety of other ways without departing from the spirit and scope of the present disclosure. Accordingly, this specification should be regarded as illustrative and is for the purpose of teaching those skilled in the art the manner of making and using the various embodiments of the disclosed battery systems. It should be understood that the forms of the disclosure shown and described herein are to be regarded as representative embodiments. Equivalent elements or materials may be substituted for those representatively shown and described herein. Additionally, certain features of the present disclosure may be utilized independently of the use of other features, all of which will be apparent to those skilled in the art who have benefited from the description of the present disclosure. Recitations such as "including," "comprising," "incorporating," "consisting of," "having," "is," used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, i.e., to allow the presence of items, components, or elements not expressly described. References to the singular should also be construed as relating to the plural, and references to "about" or "approximately" should be construed as meaning plus or minus 10%. References to percentages of any additive should be construed as meaning plus or minus 10%.

[0332] Furthermore, the various embodiments disclosed herein are to be understood in an illustrative and explanatory sense and should in no way be construed as a limitation on the present disclosure. All references to couplings (e.g., attachment, fixation, coupling, connection, etc.) are used only to assist the reader in understanding the present disclosure and may not impose limitations, particularly as to the location, orientation, or use of the systems and / or methods disclosed herein. Accordingly, references to couplings (if any) should be construed broadly. Moreover, such coupling references do not necessarily infer that two elements are directly connected to each other.

[0333] Additionally, all numerical terms (such as but not limited to "first", "second", "third", "primary", "secondary", "main", or any other ordinary and / or numerical terms) should also be regarded as mere identifiers to assist the reader in understanding the various elements, embodiments, variations, and / or modifications of the present disclosure and may not impose any limitations, particularly with respect to the order of any element, embodiment, variation, and / or modification relative to another element, embodiment, variation, and / or modification or the preference between them.

[0334] It should also be understood that one or more of the elements depicted in the drawings / figures may also be implemented in a more separated or integrated manner, or even removed or rendered ineffective in some cases, as long as it is beneficial according to a particular application.

Claims

1. A non-aqueous electrolyte, comprising: a lithium salt; a first non-aqueous solvent of a carbonate solvent; a second non-aqueous solvent of methyl acetate; and an additive mixture, consisting of: a first effective additive of vinylene carbonate fluoride; and a second effective additive of 1,3,2-dioxathiolane-2,2-dioxide or another sulfur-containing additive, said another sulfur-containing additive selected from the group consisting of: methylene methane disulfonate, trimethylene sulfate, 3-hydroxypropane sulfonic acid γ-lactone; wherein the concentrations of the first effective additive and the second effective additive are both 0.25% - 6% by weight.

2. The non-aqueous electrolyte according to claim 1, wherein the non-aqueous electrolyte does not include additional effective additives.

3. A lithium-ion battery, comprising: a negative electrode; a positive electrode, comprising NMC having micron-sized grains; and the non-aqueous electrolyte according to claim 1, wherein the battery has an initial capacity retention rate of 95% after cycling 200 times between 3.0V and 4.3V at a charging rate of C / 3CCCV at 40°C.

4. The lithium-ion battery according to claim 3, wherein the lithium-ion battery does not include effective additives of tris(trimethylsilyl) phosphate and tris(trimethylsilyl) phosphite at 0.25% or more by weight.

5. The lithium-ion battery according to claim 3, wherein the NMC is selected from the group consisting of: NMC111, NMC532, NMC811, and NMC622.

6. The lithium-ion battery according to claim 5, wherein the positive electrode is NCM532 or NMC622.

7. The lithium-ion battery according to claim 3, wherein the grain size of the positive electrode including NMC is greater than 0.5 microns.

8. The lithium-ion battery according to claim 3, wherein the battery has an initial capacity retention rate of 95% after cycling 400 times between 3.0V and 4.3V at a charging rate of C / 3CCCV at 40°C.

9. The lithium-ion battery according to claim 3, wherein the non-aqueous electrolyte does not include additional additives.

10. The lithium-ion battery according to claim 3, wherein the carbonate solvent is selected from the group consisting of: ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and combinations thereof.

11. The lithium-ion battery according to claim 3, wherein the positive electrode is coated with alumina or titanium dioxide.

12. An electric vehicle having a rechargeable battery, comprising: a drive motor; a transmission; electronics; and the lithium-ion battery according to claim 3.

13. The electric vehicle according to claim 12, wherein the lithium-ion battery includes methyl acetate at a concentration in the range of 20% to 60% by weight.

14. The electric vehicle according to claim 13, wherein the lithium-ion battery includes methyl acetate at a concentration of about 40% by weight.

15. The electric vehicle according to claim 13, wherein the lithium-ion battery includes methyl acetate at a concentration of about 20% by weight.

16. The electric vehicle according to claim 15, wherein the lithium-ion battery exhibits a stable capacity retention rate at 4.3 V.

17. The electric vehicle according to claim 12, wherein the lithium-ion battery includes a positive electrode, and the positive electrode includes NMC532 or NMC622.

18. The electric vehicle according to claim 17, wherein the positive electrode is coated with alumina or titanium dioxide.

19. A non-aqueous electrolyte, comprising: A lithium salt, which mainly consists of lithium hexafluorophosphate; dissolved in a first non-aqueous solvent, the first non-aqueous solvent includes methyl acetate and a carbonate solvent, and the carbonate solvent is selected from ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate, and combinations thereof; and an additive mixture, the additive mixture includes: A first effective additive of vinylene carbonate, wherein the concentration of the first effective additive ranges from 0.25% to 6% by weight; A second effective additive of 1,3,2-dioxathiolane-2,2-dioxide, wherein the concentration of the second effective additive ranges from 0.25% to 6% by weight; wherein the concentration of methyl acetate ranges from 20% to 60% by weight, and wherein the concentration of the carbonate solvent ranges from 30% to 80% by weight.

20. The non-aqueous electrolyte according to claim 19, wherein the non-aqueous electrolyte does not include additional additives.

21. The non-aqueous electrolyte according to claim 19, wherein the non-aqueous solvent includes at least two carbonate solvents.

22. The non-aqueous electrolyte according to claim 21, wherein the at least two carbonate solvents include ethylene carbonate (EC) and ethyl methyl carbonate (EMC).

23. The non-aqueous electrolyte according to claim 19, wherein the non-aqueous electrolyte includes less than 0.25% by weight of tris(trimethylsilyl) phosphate.

24. The non-aqueous electrolyte according to claim 19, wherein the non-aqueous electrolyte includes less than 0.25% by weight of tris(trimethylsilyl) phosphite.

25. A lithium-ion battery, comprising: A negative electrode; A positive electrode; And The non-aqueous electrolyte according to claim 19.

26. The lithium-ion battery according to claim 25, wherein the non-aqueous electrolyte does not include additional additives.

27. The lithium-ion battery according to claim 25, wherein the first non-aqueous solvent includes at least two carbonate solvents.

28. The lithium-ion battery according to claim 27, wherein the at least two carbonate solvents include ethylene carbonate (EC) and ethyl methyl carbonate (EMC).

29. The lithium-ion battery according to claim 20, wherein the positive electrode includes NMC532 or NMC622, and its grain size is greater than 0.5 microns.

30. The lithium-ion battery according to claim 29, wherein the positive electrode is coated with alumina or titanium dioxide.

31. The lithium-ion battery according to claim 25, wherein the battery system has an initial capacity retention rate of 95% after 200 cycles at a charging rate of C / 3 CCCV between 3.0 V and 4.3 V at 40 °C.

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