Electrolyte formulation for nickel-rich cathode and silicon-rich anode battery cells

Abstract

This disclosure provides an electrolyte, a battery cell, and a vehicle having a vehicle battery. The electrolyte comprises a ternary salt, a bicyclic solvent, a linear carbonate solvent, and a quaternary additive. The ternary salt comprises lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium difluoro(oxalate)borate (LiDFOB). The bicyclic solvent comprises 0-30 vol% ethylene carbonate (EC) and 0-30 vol% fluoroethylene carbonate (FEC). The linear carbonate solvent comprises at least one selected from ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or diethyl carbonate (DEC). The linear carbonate solvent comprises 60-80 vol%. The quaternary additive comprises 0.5-2% by weight vinylene carbonate (VC), 0.25-1% by weight trimethylsilyl (TMSi), 0.5-2% by weight bis(2,2,2-trifluoroethyl) carbonate (DFDEC), and 0.25-1% by weight succinic anhydride (SA).

Description

Technical Field

[0001] This disclosure relates to vehicle battery packs and battery cells, and more specifically, to electrolytes for lithium-ion battery cells within battery packs. Background Technology

[0002] Electric vehicle and hybrid electric vehicle technologies are realized through the development and deployment of rechargeable secondary batteries that power the vehicle's powertrain. Secondary batteries, including lithium-ion batteries, typically consist of a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode provides the lithium-ion source and determines the battery's capacity and average voltage. The negative electrode stores the lithium-ions received from the positive electrode and releases them when energy is needed. The separator prevents the positive and negative electrodes from contacting and prevents short circuits, while the electrolyte provides the medium through which lithium-ions pass between the two electrodes. The energy density, or areal capacity, of a secondary battery can be increased by adding more active materials to the positive and negative electrodes and by increasing their density. At high temperatures, the negative electrode may expand during cycling, while the positive electrode may undergo structural collapse. Degradation of the positive, negative, and electrolyte components leads to a rapid decrease in capacity, reduced efficiency, and shortened battery life.

[0003] Therefore, while existing lithium-ion battery cell chemistry has achieved its intended purpose, new and improved chemistry is still needed to provide improved electrochemical performance and cycle life while maintaining ultra-fast charging capacity. Summary of the Invention

[0004] According to several aspects of this disclosure, an electrolyte for a battery cell having a nickel-rich positive electrode and a silicon-rich negative electrode is provided. The electrolyte comprises a ternary salt, a bicyclic solvent, a linear carbonate solvent, and a quaternary additive. The ternary salt comprises 0.5-1.2 mol (M) of lithium hexafluorophosphate (LiPF6) to provide lithium conductivity, 0.1-0.3 mol (M) of lithium bis(fluorosulfonyl)imide (LiFSI) to provide lithium conductivity, and 0.1-0.3 mol (M) of lithium difluoro(oxalate)borate (LiDFOB) to form a positive electrode electrolyte interphase (CEI) on the nickel-rich positive electrode. The bicyclic solvent comprises 0-30 vol% of ethylene carbonate (EC) to form a solid electrolyte interphase (SEI) on the silicon-rich negative electrode, and 0-30 vol% of fluoroethylene carbonate (FEC) to form a solid electrolyte interphase (SEI) on the silicon-rich negative electrode. The linear carbonate solvent includes at least one of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or diethyl carbonate (DEC). The linear carbonate solvent accounts for 60-80% by volume to enhance the solubility of the ternary salt. The quaternary additive includes 0.5-2% by weight of vinylene carbonate (VC) to form a solid electrolyte interphase (SEI) on the silicon-rich anode, 0.25-1% by weight of trimethylsilyl (TMSi) to form a positive electrolyte interphase (CEI) on the nickel-rich cathode, 0.5-2% by weight of bis(2,2,2-trifluoroethyl) carbonate (DFDEC) to form a solid electrolyte interphase (SEI) on the silicon-rich anode, and 0.25-1% by weight of succinic anhydride (SA) to form a positive electrolyte interphase (CEI) on the nickel-rich cathode.

[0005] According to another aspect of this disclosure, the concentration of lithium hexafluorophosphate (LiPF6) is about 0.8 M.

[0006] According to another aspect of this disclosure, the concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is about 0.2 M.

[0007] According to another aspect of this disclosure, the concentration of lithium difluoro(oxalate)borate (LiDFOB) is about 0.2 M.

[0008] According to another aspect of this disclosure, ethylene carbonate (EC) accounts for approximately 20% by volume.

[0009] According to another aspect of this disclosure, fluoroethylene carbonate (FEC) comprises about 10% by volume.

[0010] According to another aspect of this disclosure, ethyl methyl carbonate (EMC) accounts for approximately 70% by volume.

[0011] According to another aspect of this disclosure, vinylene carbonate (VC) accounts for about 0.5% by weight.

[0012] According to another aspect of this disclosure, trimethylsilyl (TMSi) comprises about 0.5% by weight.

[0013] According to another aspect of this disclosure, bis(2,2,2-trifluoroethyl) carbonate (DFDEC) accounts for about 1% by weight.

[0014] According to another aspect of this disclosure, succinic anhydride (SA) accounts for about 0.5% by weight.

[0015] According to another aspect of this disclosure, the nickel-rich cathode is formed of nickel-cobalt-manganese-aluminum (NCMA) with a capacity of 3.7 ampere-hours (Ah).

[0016] According to another aspect of this disclosure, the nickel-rich cathode includes at least one of LiNiO2 (LNO), nickel cobalt manganese (NCM), nickel cobalt aluminum (NCA), or lithium manganese iron phosphate (LMFP) / nickel cobalt manganese aluminum (NCMA).

[0017] According to another aspect of this disclosure, the nickel-rich cathode has a nickel content of 60% or more by weight.

[0018] According to another aspect of this disclosure, the silicon-rich anode comprises 10-60% by weight of silicon.

[0019] According to another aspect of this disclosure, the silicon content of the silicon-rich anode is greater than or equal to 40% by weight.

[0020] According to another aspect of this disclosure, the silicon-rich anode has a capacity of 3-8 mA / cm². 2 Electrode load.

[0021] According to several aspects of this disclosure, a battery cell for a vehicle battery pack is provided. The battery cell includes a nickel-rich positive electrode, a silicon-rich negative electrode, and an electrolyte, the electrolyte providing a medium for lithium ion passage between the nickel-rich positive electrode and the silicon-rich negative electrode. The electrolyte includes a ternary salt, a bicyclic solvent, a linear carbonate solvent, and a quaternary additive. The ternary salt includes lithium hexafluorophosphate (LiPF6) at a concentration of 0.5-1.2 mol (M) to provide lithium conductivity, lithium bis(fluorosulfonyl)imide (LiFSI) at a concentration of 0.1-0.3 mol (M) to provide lithium conductivity, and lithium difluoro(oxalate)borate (LiDFOB) at a concentration of 0.1-0.3 mol (M) to form a positive electrode electrolyte interface phase (CEI) on the nickel-rich positive electrode. The bicyclic solvent comprises 0-30 vol% ethylene carbonate (EC) to form a solid electrolyte interphase (SEI) on the silicon-rich anode, and 0-30 vol% fluoroethylene carbonate (FEC) to form a solid electrolyte interphase (SEI) on the silicon-rich anode. The linear carbonate solvent comprises at least one of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or diethyl carbonate (DEC). The linear carbonate solvent comprises 60-80 vol% to enhance the solubility of the ternary salt. The quaternary additive comprises 0.5-2 wt% vinylene carbonate (VC) to form a solid electrolyte interphase (SEI) on the silicon-rich anode, 0.25-1 wt% trimethylsilyl (TMSi) to form a positive electrode electrolyte interphase (CEI) on the nickel-rich cathode, 0.5-2 wt% bis(2,2,2-trifluoroethyl) carbonate (DFDEC) to form a solid electrolyte interphase (SEI) on the silicon-rich anode, and 0.25-1 wt% succinic anhydride (SA) to form a positive electrode electrolyte interphase (CEI) on the nickel-rich cathode.

[0022] According to another aspect of this disclosure, the battery cell is at least one of a prismatic battery, a pouch battery, or a cylindrical battery.

[0023] According to several aspects of this disclosure, a vehicle having a vehicle battery is provided. The vehicle includes a vehicle battery pack comprising multiple battery cells. Each battery cell includes a nickel-rich positive electrode, a silicon-rich negative electrode, and an electrolyte that provides a medium for lithium ions to pass through between the nickel-rich positive electrode and the silicon-rich negative electrode. The electrolyte comprises a ternary salt, a bicyclic solvent, a linear carbonate solvent, and a quaternary additive. The ternary salt comprises lithium hexafluorophosphate (LiPF6) at a concentration of 0.5-1.2 mol (M) to provide lithium conductivity, lithium bis(fluorosulfonyl)imide (LiFSI) at a concentration of 0.1-0.3 mol (M) to provide lithium conductivity, and lithium difluoro(oxalate)borate (LiDFOB) at a concentration of 0.1-0.3 mol (M) to form a positive electrode electrolyte interface phase (CEI) on the nickel-rich positive electrode. The bicyclic solvent comprises 0-30 vol% ethylene carbonate (EC) to form a solid electrolyte interphase (SEI) on the silicon-rich anode, and 0-30 vol% fluoroethylene carbonate (FEC) to form a solid electrolyte interphase (SEI) on the silicon-rich anode. The linear carbonate solvent comprises at least one of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or diethyl carbonate (DEC). The linear carbonate solvent comprises 60-80 vol% to enhance the solubility of the ternary salt. The quaternary additive comprises 0.5-2 wt% vinylene carbonate (VC) to form a solid electrolyte interphase (SEI) on the silicon-rich anode, 0.25-1 wt% trimethylsilyl (TMSi) to form a positive electrode electrolyte interphase (CEI) on the nickel-rich cathode, 0.5-2 wt% bis(2,2,2-trifluoroethyl) carbonate (DFDEC) to form a solid electrolyte interphase (SEI) on the silicon-rich anode, and 0.25-1 wt% succinic anhydride (SA) to form a positive electrode electrolyte interphase (CEI) on the nickel-rich cathode.

[0024] The above-described features and advantages, as well as other features and advantages, of the currently disclosed systems and methods will become apparent when considered in conjunction with the accompanying drawings and the specific implementation including the claims and embodiments. Attached Figure Description

[0025] This disclosure will be more fully understood through detailed description and accompanying drawings.

[0026] Figure 1 This is a perspective view illustrating an embodiment of a vehicle with an electric motor according to the present disclosure, the electric motor being powered by a battery pack having a nickel-rich positive electrode, a silicon-rich negative electrode, and an electrolyte.

[0027] Figure 2 Based on this disclosure Figure 1 The diagram shows a cross-sectional view of a battery cell in the battery pack of a vehicle, wherein the battery cell includes a nickel-rich positive electrode, a silicon-rich negative electrode, and an electrolyte. Detailed Implementation

[0028] The following description is merely exemplary in nature and is not intended to limit this disclosure, its application, or its uses. Furthermore, it is not intended to be bound by any express or implied theory presented in the foregoing technical field, background art, summary of the invention, or the following detailed description. It should be understood that throughout the drawings, corresponding reference numerals denote similar or corresponding parts and features.

[0029] Reference will now be made in detail to several embodiments of the present disclosure illustrated in the accompanying drawings. Wherever possible, the same or similar reference numerals are used in the drawings and description to refer to the same or similar parts or steps. The drawings are simplified and not drawn to exact scale. The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or its uses.

[0030] Nickel-rich silicon-based battery cells boast high energy density and hold great promise in the electric vehicle battery market. However, several challenges remain, including negative electrode expansion during cycling and positive electrode structural collapse at high temperatures. These issues typically lead to rapid capacity decay, especially when silicon content is high (e.g., silicon content greater than 30% on the negative electrode side). The electrolyte and battery cell disclosed herein improve cycle life and calendar life while maintaining the ultra-fast charging capability of nickel-rich positive and silicon-rich negative electrode battery cells. The electrolyte and battery cell disclosed herein are also used to construct a uniform and robust positive electrolyte interface (CEI) on the nickel-rich positive electrode and a flexible, robust, and adaptive solid electrolyte interface (SEI) on the silicon-rich negative electrode.

[0031] Reference Figure 1 This illustration shows a perspective view of a vehicle 10 having a vehicle battery pack 12 according to the present disclosure. The battery pack 12 is shown together with the exemplary vehicle 10. The vehicle 10 is an electric vehicle or a hybrid vehicle having wheels 14 driven by at least one electric motor / inverter 16. The electric motor / inverter 16 receives power from the battery pack 12. Although the vehicle 10 is shown as a passenger road vehicle, it should be understood that the battery pack 12 can be used with a variety of other types of vehicles. For example, the battery pack 12 can be used in marine vehicles (e.g., boats) or air vehicles (e.g., drones or passenger aircraft). Furthermore, the battery pack 12 can be used as a stationary power source separate from and independent of the vehicle. The battery pack 12 includes a housing 18 for carrying and supporting a plurality of battery cells 20. In embodiments, the battery pack 12 may have fifty or more battery cells 20.

[0032] As used herein, “vehicle” is not limited to automobiles. While this document primarily describes the technology in conjunction with electric vehicles and hybrid electric vehicles, the technology is not limited to electric vehicles and hybrid electric vehicles. These concepts can be used in a variety of applications, such as those relating to components used in motorcycles, mopeds, locomotives, aircraft, ships and other vehicles, as well as other applications using batteries, such as portable power stations (e.g., portable power stations for remote work sites), emergency backup power, and permanent power stations associated with buildings and equipment, all of which can be powered by, for example, solar or wind power systems, power lines and fuel-based generators (e.g., gasoline generators, propane generators, kerosene generators or diesel generators) and Stirling engines.

[0033] Figure 2 It shows Figure 1 A battery cell 20 is shown within the battery pack 12. The battery pack 12 and battery cell 20 are to be understood as rechargeable batteries that can discharge when a load is applied and recharge when an external power source is applied. Although battery cell 20 is shown as a prismatic battery cell, battery cell 20 may also include, for example, pouch battery cells and / or cylindrical battery cells.

[0034] Settings Figure 1 Each battery cell 20 within the battery pack 12 shown has a housing 18 (or casing or container) and at least one electrode stack 22, the at least one electrode stack 22 further comprising a positive electrode 24, a negative electrode 26, an electrolyte 28, and / or a separator 30. Each battery cell 20 may have tens or hundreds of electrode stacks 22. Each electrode stack 22 is connected to current collectors 32, 34. The electrode stacks are placed within the housing 18, which is filled with the electrolyte 28. The electrolyte 28 transports ions between the positive electrode 24 and the negative electrode 26. The current collectors 32, 34 are thin metal plates or foils disposed on the sides of the electrode stacks 22 and / or the housing 18, and are typically 0.001 mm to 1 mm thick. The current collectors 32, 34 may be made of copper (e.g., 6 μm foil) or aluminum (e.g., 12 μm foil) and are attached to the electrode stacks 22 to transmit current to an external circuit (not shown).

[0035] During discharge, when a load is applied to battery cell 20, Li + Ions move from the negative electrode 26 to the positive electrode 24 through the electrolyte 28 and membrane 30. Equivalent electrons e - Energy is supplied to the battery load by moving energy from the positive terminal 24 to the negative terminal 26 through the battery circuit. When charging and when an external voltage is applied, Li... + Ions move from the positive electrode 24 to the negative electrode 26 through the electrolyte 28 and the membrane 30, and can be embedded in the negative electrode 26.

[0036] Each battery cell has 20 cells, for example Figure 2 The battery cell shown typically includes a positive electrode 24 disposed on a positive current collector 32, a negative electrode 26 disposed on a negative current collector 34, a separator 30 disposed between the positive electrode 24 and the negative electrode 26, and an electrolyte 28. Although the battery cell 20 shown contains one negative electrode 26 (with a negative current collector 34) and one positive electrode 24 (with a positive current collector 32), the battery cell 20 may alternatively include two or more positive electrodes 24 (with positive current collectors 32) and one or more negative electrodes 26 (with negative current collectors 34). In any of the above designs, one or more separators 30 are interleaved between the positive electrode 24 and the negative electrode 26 to prevent contact between the positive electrode 24 and the negative electrode 26.

[0037] In the battery cell 20 of the type described above, the positive current collector 32 and the negative current collector 34 are formed of conductive materials. In an embodiment, the positive current collector 32 comprises aluminum. Alternatively or additionally, the positive current collector 32 may comprise copper-clad aluminum and / or stainless steel. The negative current collector 34 may comprise one or more of copper, nickel, stainless steel, or titanium. Current collectors 32 and 34 are shown in the form of foil; however, it should be understood that other forms may be presented, such as mesh, wire, or composite materials. In an embodiment, the foil positive current collector 32 and the foil negative current collector 34 are impermeable. The positive current collector 32 may have a thickness in the range of 5 micrometers to 50 micrometers (inclusive of all values ​​and ranges therein, e.g., in the range of 5 micrometers to 25 micrometers). The negative current collector 34 may have a thickness in the range of 5 micrometers to 50 micrometers (inclusive of all values ​​and ranges therein, e.g., in the range of 5 micrometers to 25 micrometers).

[0038] Positive electrode 24 includes a positive electrode active material that provides lithium ions (Li... +The cathode 24 can be a source and can undergo reversible insertion or intercalation of lithium ions, thereby determining, for example, the battery capacity and average voltage. Generally, the cathode 24 can be nickel-rich (e.g., greater than or equal to 60% by weight of nickel). In embodiments, the cathode active material includes lithium manganese iron phosphate (LMFP) and / or lithium nickel cobalt manganese aluminum oxide (NCMA). The cathode active material can include lithium manganese iron phosphate (LMFP) because LMFP batteries are known for their thermal stability and safety, because iron and manganese are more abundant and less expensive than other materials (e.g., nickel and cobalt), which can reduce the overall cost of the battery, and because LMFP batteries have good energy density and long lifespan. The cathode active material can include lithium nickel cobalt manganese aluminum oxide (NCMA) because NCMA batteries have a high nickel content, which increases energy density, because NCMA reduces dependence on cobalt, which can be expensive, and because the addition of aluminum enhances thermal stability and overall battery safety. The cathode active material can also include LiNiO2 (LNO), nickel cobalt manganese (NCM), and / or nickel cobalt aluminum (NCA). In one embodiment, the nickel-rich cathode is formed of nickel-cobalt-manganese-aluminum (NCMA) with a capacity of 3.7 ampere-hours (Ah).

[0039] The negative electrode 26 comprises a material capable of undergoing reversible insertion or intercalation of lithium ions at a lower electrochemical potential than that of the positive electrode 24, such that an electrochemical potential difference exists between the negative electrode 26 and the positive electrode 24. In embodiments, the negative electrode 26 comprises 10-60% by weight of silicon, more preferably, the negative electrode 26 comprises greater than or equal to 40% by weight of silicon. The negative electrode 26 may comprise one or more of lithium metal, lithium alloys (e.g., lithium-silicon alloys, lithium-aluminum alloys, lithium-indium alloys, lithium titanate, and lithium-tin alloys), carbon-based materials (e.g., graphite, activated carbon, carbon black, and graphene), silicon, silicon-based alloys, silicon oxide, silicon-based composites, tin oxide, aluminum, indium, zinc, germanium, and titanium oxide, as well as any combination thereof. In embodiments, the thickness of the negative electrode 26 may range from 50 micrometers to 150 micrometers, including all values ​​and ranges therein. In specific embodiments, the negative electrode 26 is silicon-rich and has a capacity of 3-8 mAh / cm². 2 The electrode load is provided by the combined negative electrode 26 and negative current collector 34.

[0040] The negative electrode 26 includes a negative electrode active material. The negative electrode active material may include man-made graphite (AG graphite) and / or naturally occurring graphite (NG graphite), at least one binder, and / or at least one carbon additive. AG graphite, also known as synthetic graphite, includes artificial carbon produced by high-temperature processing of carbon materials such as petroleum coke and coal tar pitch. NG graphite may include crystalline carbon in naturally occurring forms found in metamorphic and igneous rocks.

[0041] The separator 30 comprises a porous material formed of an electrically insulating material that prevents contact between the positive electrode 24 and the negative electrode 26 and potentially prevents short circuits in the battery circuitry. The separator 30 is sandwiched or at least partially enclosed between the positive electrode 24 and the negative electrode 26, allowing lithium ions and electrolyte 28 to pass through the pores of the separator 30. The separator 30 may comprise one or more of composite materials, polymeric materials, or nonwoven materials. In embodiments, the separator 30 comprises at least one of polyethylene, polypropylene, polyamide, polytetrafluoroethylene, polyvinylidene fluoride, and polyvinyl chloride. Additionally, the separator 30 may be filled, i.e., include a filler dispersed therein, wherein the filler comprises a material such as glass fiber. In additional or alternative embodiments, the separator 30 may comprise at least one of a thermally stable porous polymer coating and a ceramic coating (e.g., an alumina coating). The coating may be disposed on one or more surfaces of the porous polymer membrane, wherein the polymer membrane may be selected from at least one of polyethylene and polypropylene. The separator 30 may comprise one or more layers, wherein each layer is formed of one or more of the aforementioned materials. The diaphragm 30 may be in the form of a membrane or a mesh, such as a woven mesh or a slit film. It should be understood that the diaphragm 30 may include layers and / or coatings of various other constructions.

[0042] Electrolyte 28 provides a medium for lithium ions to pass through between the positive electrode 24 and the negative electrode 26. This medium can be liquid, gel, or solid and is capable of conducting lithium ions between the positive electrode 24 and the negative electrode 26. Electrolyte 28 permeates the pores of the porous membrane 30 and wets or otherwise contacts the positive electrode 24, the negative electrode 26, and the surface of the membrane 30.

[0043] In an embodiment, the electrolyte 28 comprises one or more lithium salts dissolved in a non-aqueous organic solvent. The lithium salts may include one or more of the following: lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF4), lithium tetraphenylborate (LiB(C6H5)4), lithium bis(oxalate)borate (LiBOB or "LSO") (LiB(C2O4)2), lithium difluorooxalate borate (LiBF2(C2O4)), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethane)sulfonylimide (lithium... Lithium bis(trifluoromethane)sulfonylimide (LiN(CF3SO2)2), lithium bis(fluorosulfonyl)imide (LiN(FSO2)2)(LiSFI), lithium bis(trifluoromethanesulfonyl)imide (Li(G3)(TFSI)), and / or lithium bis(trifluoromethanesulfonyl)azanide (LiTFSA). The lithium salts can be present in electrolyte 28 at concentrations ranging from 0.5 M to 2.16 M (moles of salt per liter of solvent (M)) (inclusive of all values ​​and ranges, e.g., 1 M or 2 M). The electrolyte may include a solvent (e.g., carbonate) and may include one or more additives (e.g., fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3,2-dioxazolthiophene 2,2-dioxide (DTD), tris(trimethylsilyl)phosphite (TMSPi), lithium difluoro(oxalate)borate (LiDFOB), tris(trimethylsilyl)borate (TMSPB), etc.).

[0044] The electrolyte 28 may also include one or more of various alkyl carbonates, such as cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), fluoroethylene carbonate (FEC)), linear carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC)), aliphatic carboxylic acid esters (e.g., methyl formate, methyl acetate, methyl propionate), γ-lactones (e.g., γ-butyrolactone, γ-valerolactone), chain ethers (e.g., 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane), and / or cyclic ethers (e.g., tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane).

[0045] In addition, the electrolyte 28 may include a variety of additives, such as, but not limited to, vinyl ethylene carbonate (VEC), propane sulfonate, lithium difluorophosphate (LiPF2O2), and / or combinations thereof. Other additives may include diluents that do not coordinate with lithium ions but can reduce the viscosity of the electrolyte 28, such as bis(2,2,2-trifluoroethyl) ether (BTFE) and / or flame retardants, such as triethyl phosphate.

[0046] In an embodiment, when used with a nickel-rich positive electrode 24 and a silicon-rich negative electrode 26, the electrolyte 28 comprises a ternary salt. In this embodiment, the ternary salt comprises lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium difluoro(oxalate)borate (LiDFOB). The concentration of lithium hexafluorophosphate (LiPF6) is about 0.5-1.2 mol (M), preferably about 0.8 M, and serves to provide lithium conductivity. The concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is about 0.1-0.3 mol (M), preferably about 0.2 M, and serves to provide lithium conductivity. The concentration of lithium difluoro(oxalate)borate (LiDFOB) is about 0.1-0.3 mol (M), preferably about 0.2 M, and serves to form a positive electrode electrolyte interphase (CEI) on the nickel-rich positive electrode. Those skilled in the art will understand the term "about". Alternatively, the term "about" will be understood to mean ±0.1M.

[0047] Continuing with this embodiment, the electrolyte 28 comprises a bicyclic solvent. The bicyclic solvent comprises ethylene carbonate (EC) and fluoroethylene carbonate (FEC). Ethylene carbonate (EC) may be 0-30% by volume, preferably about 20% by volume. Fluoroethylene carbonate (FEC) may be 0-30% by volume, preferably about 10% by volume. Those skilled in the art will understand the term "about." Alternatively, the term "about" will be understood to mean ±1% by volume. Ethylene carbonate (EC) and fluoroethylene carbonate (FEC) serve to form a solid electrolyte interphase (SEI) on the silicon-rich anode 26.

[0048] Continuing with this embodiment, the electrolyte 28 includes a linear carbonate solvent, which includes at least one of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or diethyl carbonate (DEC). The linear carbonate solvent may comprise 60-80% by volume of the electrolyte 28, preferably about 70% by volume. Those skilled in the art will understand the term "about". Alternatively, the term "about" will be understood to mean ±1% by volume. The linear carbonate solvent is used to enhance the solubility of the ternary salt.

[0049] Continuing with this embodiment, the electrolyte 28 includes a quaternary additive. The quaternary additive may include vinylene carbonate (VC), trimethylsilyl (TMSi), bis(2,2,2-trifluoroethyl) carbonate (DFDEC), and succinic anhydride (SA). Vinylene carbonate (VC) may comprise 0.5-2% by weight of the electrolyte 28, preferably about 0.5% by weight (if LiBOB is greater than 30% by weight). Vinylene carbonate (VC) is used to form a solid electrolyte interphase (SEI) on the silicon-rich anode. Trimethylsilyl (TMSi) may comprise 0.25-1% by weight, more preferably about 0.5% by weight. Trimethylsilyl (TMSi) is used to form a positive electrode electrolyte interphase (CEI) on the nickel-rich cathode. Bis(2,2,2-trifluoroethyl) carbonate (DFDEC) may comprise 0.5-2% by weight, more preferably about 1% by weight. Bis(2,2,2-trifluoroethyl) carbonate (DFDEC) is used to form a solid electrolyte interphase (SEI) on a silicon-rich anode. Succinic anhydride (SA) may be 0.25-1% by weight, more preferably about 0.5% by weight. Succinic anhydride (SA) is used to form a positive electrode electrolyte interphase (CEI) on a nickel-rich cathode. Those skilled in the art will understand the term "about". Alternatively, the term "about" will be understood to mean ±0.1% by weight.

[0050] In a specific embodiment, the electrolyte 28 comprises a ternary salt including 0.8 M LiPF6, 0.2 M LiFSi, and 0.1 M LiDFOB, a solvent comprising EC / FEC / EMC in a solvent ratio of 2:1:7, and additives including 0.5 wt% VC, 0.5 wt% TMSi, 1 wt% DFDEC, and 0.5 wt% SA. It should be understood that the electrolyte 28 may include various other components and their amounts / concentrations.

[0051] Compared to existing technologies, the electrolyte 28 and battery cell 20 of this disclosure are advantageous and beneficial. The electrolyte 28 and battery cell 20 improve cycle life and calendar life while maintaining the ultra-fast charging capability of the nickel-rich cathode and silicon-rich anode battery cells. The electrolyte and battery cell can also construct a uniform and robust cathode electrolyte interface (CEI) on the nickel-rich cathode and a flexible, robust, and adaptive solid electrolyte interface (SEI) on the silicon-rich anode.

[0052] This description is merely illustrative in nature and is in no way intended to limit this disclosure, its application, or its use. The broad teachings of this disclosure can be implemented in many forms. Therefore, while this disclosure includes specific embodiments, its true scope should not be so limited, as other modifications will become apparent upon examination of the drawings, description, and appended claims.

Claims

1. An electrolyte for a battery cell having a nickel-rich positive electrode and a silicon-rich negative electrode, comprising: Ternary salt, wherein the ternary salt comprises: Lithium hexafluorophosphate (LiPF6) at a concentration of 0.5-1.2 mol (M) is used to provide lithium conductivity; Lithium bis(fluorosulfonyl)imide (LiFSI) at a concentration of 0.1–0.3 mol (M) is used to provide lithium conductivity; and Lithium difluoro(oxalate)borate (LiDFOB) with a concentration of 0.1-0.3 mol (M) is used to form a positive electrode electrolyte interface phase (CEI) on the nickel-rich positive electrode; Bicyclic solvents, wherein the bicyclic solvents include: 0-30 vol% ethylene carbonate (EC) to form a solid electrolyte interphase (SEI) on the silicon-rich anode; and 0-30% by volume of fluoroethylene carbonate (FEC) is used to form the solid electrolyte interphase (SEI) on the silicon-rich anode. A linear carbonate solvent, wherein the linear carbonate solvent comprises at least one of the following: Ethyl methyl carbonate (EMC); Dimethyl carbonate (DMC); or Diethyl carbonate (DEC), wherein the linear carbonate solvent comprises 60-80% by volume to enhance the solubility of the ternary salt; and A quaternary additive, wherein the quaternary additive comprises: 0.5-2% by weight of vinylene carbonate (VC) to form the solid electrolyte interfacial phase (SEI) on the silicon-rich anode; 0.25-1% by weight of trimethylsilyl (TMSi) is used to form the cathode electrolyte interface phase (CEI) on the nickel-rich cathode. 0.5-2 wt% bis(2,2,2-trifluoroethyl) carbonate (DFDEC) to form the solid electrolyte interphase (SEI) on the silicon-rich anode; and 0.25-1% by weight of succinic anhydride (SA) is used to form the cathode electrolyte interphase (CEI) on the nickel-rich cathode.

2. The electrolyte of claim 1, wherein, The concentration of the lithium hexafluorophosphate (LiPF6) is approximately 0.8 M.

3. The electrolyte of claim 1, wherein, The concentration of the lithium bis(fluorosulfonyl)imide (LiFSI) is approximately 0.2 M.

4. The electrolyte of claim 1, wherein, The concentration of the lithium difluoro(oxalate)borate (LiDFOB) is approximately 0.2 M.

5. The electrolyte of claim 1, wherein, The ethylene carbonate (EC) comprises approximately 20% by volume.

6. The electrolyte of claim 1, wherein, The fluoroethylene carbonate (FEC) comprises approximately 10% by volume.

7. The electrolyte according to claim 1, wherein, The ethyl methyl carbonate (EMC) comprises approximately 70% by volume.

8. The electrolyte according to claim 1, wherein, The vinylene carbonate (VC) comprises approximately 0.5% by weight.

9. The electrolyte according to claim 1, wherein, The trimethylsilyl (TMSi) comprises approximately 0.5% by weight.

10. The electrolyte according to claim 1, wherein, The bis(2,2,2-trifluoroethyl) carbonate (DFDEC) comprises about 1% by weight.

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