Electrolyte comprising alkyl alkanoates, ketones and / or nitriles as main organic solvents for batteries for recycling lithium ions

Abstract

The invention relates to an electrolyte comprising alkyl alkanoates, ketones and / or nitriles as main organic solvents for batteries for recycling lithium ions. A lithium ion circulating battery includes an electrolyte including an organic solvent and a lithium salt in the organic solvent. The organic solvent comprises greater than or equal to 70% by weight of a primary solvent comprising alkyl alkanoates, ketones, nitriles, or a combination thereof. The electrolyte is advantageously useful in a battery comprising a positive electrode comprising an electroactive material comprising a layered nickel-rich lithium transition metal oxide.

Description

Technical Field

[0001] This disclosure relates to electrolytes for cyclic lithium-ion battery packs, and more particularly to organic solvents for electrolytes used in battery packs comprising layered nickel-rich lithium transition metal oxides as electroactive positive electrode materials. Background Technology

[0002] The information provided in this section is for the purpose of generally presenting the background of this disclosure. The work of the currently named inventors (to the extent described in this section) and aspects of the description that may not constitute prior art at the time of filing are neither expressly nor implied to be considered prior art to this disclosure.

[0003] Cyclic lithium-ion battery packs typically include a positive electrode, a negative electrode separated from the positive electrode, and an ion-conducting electrolyte that provides the medium for lithium ions to conduct between the positive and negative electrodes during the discharge and charge processes of the battery pack. This electrolyte can be formulated to exhibit certain desirable properties, including high ionic conductivity, high dielectric constant (related to high salt solubility), good thermal stability, a wide electrochemical stability window, the ability to form a stable ion-conducting solid electrolyte interphase on the surfaces of the positive and / or negative electrodes, and chemical compatibility with other components of the battery pack. Summary of the Invention

[0004] According to one or more embodiments of this disclosure, a cyclic lithium-ion battery pack includes a positive electrode and an electrolyte permeating the positive electrode. The positive electrode comprises an electroactive material comprising a layered nickel-rich lithium transition metal oxide. The electrolyte comprises an organic solvent and a lithium salt in the organic solvent. The organic solvent comprises greater than or equal to 70% by weight of a main solvent, said main solvent comprising an alkyl ester of an alkanolide, a ketone, a nitrile, or a combination thereof.

[0005] The primary solvent may contain a solvent having the formula R 1 -COO-R 2 Alkyl esters of alkyl alkyl acids, wherein R 1 It is H, C1-C3 alkyl, or C1-C3 fluoroalkyl, and wherein R is... 2 It is a C1-C4 alkyl or a C1-C4 fluoroalkyl.

[0006] The primary solvent may contain at least one alkyl alkyl ester of an alkanonic acid, selected from 2,2,2-trifluoroethyl acetate (FEA), ethyl acetate (EA), n-propyl acetate (nPA), isopropyl acetate (iPA), n-butyl acetate (nBA), isobutyl acetate (iBA), methyl propionate (MP), methyl butyrate (MB), methyl formate (MF), ethyl formate (EF), n-propyl formate (nPF), isopropyl formate (iPF), n-butyl formate (nBF), and isobutyl formate (iBF).

[0007] The primary solvent may contain a solvent having the formula R 3 -C(=O)-R 4 ketones, of which R 3 and R 4 Each is independently a C1-C2 alkyl or C1-C2 fluoroalkyl.

[0008] The primary solvent may contain at least one ketone selected from acetone and 2-butanone.

[0009] The primary solvent may contain a solvent having the formula R 5 -C≡N nitriles, where R 5 It is a C1-C3 alkyl or a C1-C3 fluoroalkyl.

[0010] The primary solvent may contain at least one nitrile selected from acetonitrile (ACN), propionitrile (PN), n-butyronitrile (nBN), and isobutyronitrile (iBN).

[0011] The organic solvent may contain more than 0% by weight and less than 30% by weight of at least one linear organic carbonate selected from dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC).

[0012] The organic solvent may contain more than 0% by weight and less than 15% by weight of at least one cyclic organic carbonate selected from ethylene carbonate (EC), propylene carbonate (PC) and fluoroethylene carbonate (FEC).

[0013] This electrolyte may be essentially free of cyclic organic carbonates.

[0014] The electrolyte may contain at least one lithium salt of greater than or equal to 0.5 moles and less than or equal to 4 moles, wherein the lithium salt is selected from lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium tetrafluoroborate (LiBF4), lithium bis(oxalate)borate (LiBOB), and lithium difluoro(oxalate)borate (LiDFOB).

[0015] The electrolyte may contain a primary lithium salt consisting of LiPF6 in an amount greater than or equal to 0.6 mol and less than or equal to 1 mol. The electrolyte may contain at least one secondary lithium salt selected from LiFSI and LiTFSI in an amount greater than or equal to 0.2 mol and less than or equal to 0.6 mol.

[0016] The electrolyte may further contain more than 0% by weight and less than or equal to 10% by weight of at least one additive selected from succinic anhydride (SA), trimethoxymethylsilane (TMSi) and tri(trimethylsilyl) phosphite (TMSPi).

[0017] The electroactive material of the positive electrode can include LiNi. 1-x Me x O2 represents a layered nickel-rich lithium transition metal oxide, where 0 ≤ x < 0.4, and Me contains manganese (Mn), cobalt (Co), aluminum (Al), or combinations thereof.

[0018] According to one or more embodiments of this disclosure, a cyclic lithium-ion battery pack includes a negative electrode, a positive electrode spaced apart from the negative electrode, and an electrolyte permeating the negative and positive electrodes. The negative electrode comprises an electroactive negative electrode material comprising silicon, silicon oxide, lithium-modified silicon oxide, and / or graphite. The positive electrode comprises an electroactive positive electrode material comprising the formula LiNi. 1-x Me x O2 represents a layered nickel-rich lithium transition metal oxide, wherein 0 ≤ x < 0.4, and wherein Me comprises manganese (Mn), cobalt (Co), aluminum (Al), or a combination thereof. This electrolyte provides a medium for the conduction of lithium ions between the negative and positive electrodes. The electrolyte contains greater than or equal to 60% by weight and less than or equal to 93% by weight of an organic solvent and a lithium salt in the organic solvent. The organic solvent contains greater than or equal to 70% by weight of a main solvent, which comprises at least one of the following: having the formula R 1 -COO-R 2 Alkyl esters of alkyl alkyl acids, wherein R 1 It is H, C1-C3 alkyl, or C1-C3 fluoroalkyl, and wherein R is... 2 It is a C1-C4 alkyl or C1-C4 fluoroalkyl; having the formula R 3 -C(=O)-R 4 ketones, of which R 3 and R 4 Each is independently a C1-C2 alkyl or C1-C2 fluoroalkyl; or has the formula R 5 -C≡N nitriles, where R 5 It is a C1-C3 alkyl or a C1-C3 fluoroalkyl.

[0019] The primary solvent may contain at least one alkyl alkyl ester of a alkyl alkyl ester selected from 2,2,2-trifluoroethyl acetate (FEA), ethyl acetate (EA), n-propyl acetate (nPA), isopropyl acetate (iPA), n-butyl acetate (nBA), isobutyl acetate (iBA), methyl propionate (MP), methyl butyrate (MB), methyl formate (MF), ethyl formate (EF), n-propyl formate (nPF), isopropyl formate (iPF), n-butyl formate (nBF), and isobutyl formate (iBF).

[0020] The main solvent can be composed of 2,2,2-trifluoroethyl acetate (FEA).

[0021] The primary solvent may contain at least one ketone selected from acetone and 2-butanone.

[0022] The primary solvent may contain at least one nitrile selected from acetonitrile (ACN), propionitrile (PN), n-butyronitrile (nBN), and isobutyronitrile (iBN).

[0023] The organic solvent may contain more than 0% by weight and less than 30% by weight of at least one linear organic carbonate selected from dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). The organic solvent may contain more than 0% by weight and less than 15% by weight of at least one cyclic organic carbonate selected from ethylene carbonate (EC), propylene carbonate (PC), and fluoroethylene carbonate (FEC).

[0024] The present invention discloses the following solutions:

[0025] Option 1. A cyclic lithium-ion battery pack, the battery pack comprising:

[0026] A positive electrode comprising an electroactive material, said electroactive material comprising a layered nickel-rich lithium transition metal oxide; and

[0027] The electrolyte permeating the positive electrode, the electrolyte comprising:

[0028] Organic solvents comprising 70% by weight or more of a main solvent comprising alkyl esters of alkanes, ketones, nitriles or combinations thereof, and

[0029] Lithium salt in the organic solvent.

[0030] Option 2. The battery pack according to Option 1, wherein the main solvent comprises having formula R 1 -COO-R 2 Alkyl esters of alkanonic acids,

[0031] Where R 1 It is H, C1-C3 alkyl, or C1-C3 fluoroalkyl, and

[0032] Where R 2 It is a C1-C4 alkyl or a C1-C4 fluoroalkyl.

[0033] Option 3. The battery pack according to Option 2, wherein the main solvent comprises at least one alkyl alkyl ester of alkyl alkanoate selected from 2,2,2-trifluoroethyl acetate (FEA), ethyl acetate (EA), n-propyl acetate (nPA), isopropyl acetate (iPA), n-butyl acetate (nBA), isobutyl acetate (iBA), methyl propionate (MP), methyl butyrate (MB), methyl formate (MF), ethyl formate (EF), n-propyl formate (nPF), isopropyl formate (iPF), n-butyl formate (nBF), and isobutyl formate (iBF).

[0034] Option 4. The battery pack according to Option 1, wherein the main solvent comprises having formula R 3 -C(=O)-R 4 ketones,

[0035] Where R 3 and R 4 Each is independently a C1-C2 alkyl or C1-C2 fluoroalkyl.

[0036] Option 5. The battery pack according to Option 4, wherein the primary solvent comprises at least one ketone selected from acetone and 2-butanone.

[0037] Option 6. The battery pack according to Option 1, wherein the main solvent comprises having formula R 5 Nitriles with -C≡N

[0038] Where R 5 It is a C1-C3 alkyl or a C1-C3 fluoroalkyl.

[0039] Option 7. The battery pack according to Option 6, wherein the primary solvent comprises at least one nitrile selected from acetonitrile (ACN), propionitrile (PN), n-butyronitrile (nBN), and isobutyronitrile (iBN).

[0040] Option 8. The battery pack according to Option 1, wherein the organic solvent comprises more than 0% by weight and less than 30% by weight of at least one linear organic carbonate selected from dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC).

[0041] Option 9. The battery pack according to Option 1, wherein the organic solvent comprises more than 0% by weight and less than 15% by weight of at least one cyclic organic carbonate selected from ethylene carbonate (EC), propylene carbonate (PC) and fluoroethylene carbonate (FEC).

[0042] Option 10. The battery pack according to Option 1, wherein the electrolyte is substantially free of cyclic organic carbonates.

[0043] Option 11. The battery pack according to Option 1, wherein the electrolyte comprises at least one lithium salt in an amount greater than or equal to 0.5 moles and less than or equal to 4 moles, wherein the lithium salt is selected from lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium tetrafluoroborate (LiBF4), lithium bis(oxalate)borate (LiBOB), and lithium difluoro(oxalate)borate (LiDFOB).

[0044] Option 12. The battery pack according to Option 1, wherein the electrolyte comprises a primary lithium salt consisting of LiPF6 in an amount greater than or equal to 0.6 mol and less than or equal to 1 mol, and wherein the electrolyte comprises at least one secondary lithium salt selected from LiFSI and LiTFSI in an amount greater than or equal to 0.2 mol and less than or equal to 0.6 mol.

[0045] Option 13. The battery pack according to Option 1, wherein the electrolyte further comprises more than 0% by weight and less than or equal to 10% by weight of at least one additive selected from succinic anhydride (SA), trimethoxymethylsilane (TMSi) and tris(trimethylsilyl)phosphite (TMSPi).

[0046] Option 14. The battery pack according to Option 1, wherein the electroactive material of the positive electrode comprises LiNi 1- x Me x O2 represents a layered nickel-rich lithium transition metal oxide, where 0 ≤ x < 0.4, and where Me comprises manganese (Mn), cobalt (Co), aluminum (Al), or a combination thereof.

[0047] Option 15. A cyclic lithium-ion battery pack, the battery pack comprising:

[0048] A negative electrode comprising an electroactive negative electrode material, wherein the electroactive negative electrode material comprises silicon, silicon oxide, lithium-modified silicon oxide, and / or graphite;

[0049] A positive electrode separated from the negative electrode and comprising an electroactive positive electrode material, the electroactive positive electrode material comprising the formula LiNi 1-x Me x O2 represents a layered nickel-rich lithium transition metal oxide, where 0 ≤ x < 0.4, and where Me comprises manganese (Mn), cobalt (Co), aluminum (Al), or a combination thereof; and

[0050] An electrolyte permeating the negative electrode and the positive electrode, the electrolyte providing a medium for lithium ion conduction between the negative electrode and the positive electrode, the electrolyte comprising:

[0051] 60% or more and 93% or less by weight of an organic solvent, wherein the organic solvent comprises 70% or more of a main solvent, which comprises at least one of the following:

[0052] Having the formula R 1 -COO-R 2 Alkyl esters of alkyl alkyl acids, wherein R 1 It is H, C1-C3 alkyl, or C1-C3 fluoroalkyl, and wherein R is... 2 It is a C1-C4 alkyl or C1-C4 fluoroalkyl.

[0053] Having the formula R 3 -C(=O)-R 4 ketones, of which R 3 and R 4 Each is independently a C1-C2 alkyl or a C1-C2 fluoroalkyl, or

[0054] Having the formula R 5 -C≡N nitriles, where R 5 It is a C1-C3 alkyl or C1-C3 fluoroalkyl, and

[0055] Lithium salt in the organic solvent.

[0056] Option 16. The battery pack according to Option 15, wherein the primary solvent comprises at least one alkyl alkyl ester of a alkyl alkanoate selected from 2,2,2-trifluoroethyl acetate (FEA), ethyl acetate (EA), n-propyl acetate (nPA), isopropyl acetate (iPA), n-butyl acetate (nBA), isobutyl acetate (iBA), methyl propionate (MP), methyl butyrate (MB), methyl formate (MF), ethyl formate (EF), n-propyl formate (nPF), isopropyl formate (iPF), n-butyl formate (nBF), and isobutyl formate (iBF).

[0057] Option 17. The battery pack according to Option 15, wherein the main solvent is composed of 2,2,2-trifluoroethyl acetate (FEA).

[0058] Option 18. The battery pack according to Option 15, wherein the primary solvent comprises at least one ketone selected from acetone and 2-butanone.

[0059] Option 19. The battery pack according to Option 15, wherein the primary solvent comprises at least one nitrile selected from acetonitrile (ACN), propionitrile (PN), n-butyronitrile (nBN), and isobutyronitrile (iBN).

[0060] Option 20. The battery pack according to Option 15, wherein the organic solvent comprises more than 0% by weight and less than 30% by weight of at least one linear organic carbonate selected from dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), and wherein the organic solvent comprises more than 0% by weight and less than 15% by weight of at least one cyclic organic carbonate selected from ethylene carbonate (EC), propylene carbonate (PC) and fluoroethylene carbonate (FEC).

[0061] Other applications of this disclosure will become apparent from the detailed description, claims, and drawings. These detailed descriptions and specific examples are for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0062] This disclosure will be more fully understood from the detailed embodiments and accompanying drawings, in which:

[0063] Figure 1 This is a schematic perspective view of a motor vehicle powered by a battery pack comprising multiple battery modules.

[0064] Figure 2 yes Figure 1 A schematic cross-sectional view of a portion of a battery pack module, which includes multiple electrochemical cells or battery packs for cycling lithium ions.

[0065] Figure 3 This is a schematic cross-sectional view of a cyclic lithium-ion battery pack, which includes a positive electrode, a negative electrode, a porous separator, and an electrolyte that permeates the positive and negative electrodes and the porous separator.

[0066] Figure 4 The graph is an intensity (in any unit) vs. 2θ (degrees) curve, depicting the XRD spectrum of layered nickel-rich transition metal oxides as heated from ambient temperature to approximately 430°C.

[0067] Figure 5 The graph is a voltage (V) vs. specific capacity (mAh / g) curve, which depicts the charging and discharging curves during the formation process of a battery pack containing an electrolyte according to one or more embodiments of the present disclosure.

[0068] Figure 6 It is a voltage (V) vs. specific capacity (mAh / g) graph, depicting the charge and discharge curves of a battery pack containing an electrolyte according to one or more embodiments of the present disclosure, charged and discharged at a C / 3 rate.

[0069] Figure 7It is a graph showing the discharge capacity retention (%) vs. cycle number of a battery pack comprising one or more embodiments according to this disclosure at different discharge rates.

[0070] Figure 8 It is a graph showing the capacity retention (%) vs. number of cycles of a battery pack charged at different rates and comprising one or more embodiments according to this disclosure.

[0071] Figure 9 This is a graph showing the heat flow (W / g) vs. temperature (°C) of a positive electrode containing layered nickel-rich transition metal oxides as electroactive materials, both in the absence and with different electrolyte formulations.

[0072] In the accompanying drawings, reference numerals may be used repeatedly to identify similar and / or identical elements. Detailed Implementation

[0073] The electrolyte of this disclosure is formulated for use in cyclic lithium-ion battery packs and comprises alkyl esters of alkanes, ketones, and / or nitriles as the primary organic solvents therein. The primary organic solvents in the electrolyte of this disclosure are formulated to eliminate or reduce the need for the inclusion of cyclic organic carbonates (e.g., ethylene carbonate EC) and / or linear organic carbonates in the electrolyte, which are often included in the electrolytes of cyclic lithium-ion battery packs to give the electrolyte high ionic conductivity (i.e., high dielectric constant and low viscosity).

[0074] Using the electrolyte of this disclosure can be particularly advantageous in battery packs that include layered nickel-rich lithium transition metal oxides (Ni-rich oxides) as electroactive positive electrode materials. Without being theoretically constrained, it is believed that when Ni-rich oxides are used as electroactive positive electrode materials in cyclic lithium-ion battery packs, they can decompose at high temperatures (e.g., at temperatures greater than or equal to about 210 °C) and generate oxygen (O) radicals within the battery pack. If such battery packs include electrolytes containing cyclic organic carbonates, the oxygen radicals generated by the thermal decomposition of Ni-rich oxides can react exothermically with these cyclic organic carbonates, leading to undesirable heat generation. The electrolyte of this disclosure has high ionic conductivity without containing cyclic organic carbonates and / or linear organic carbonates, and can thus be used in cyclic lithium-ion battery packs to help reduce or eliminate the need for containing cyclic organic carbonates in the electrolyte, thereby improving its thermal stability.

[0075] Figure 1A motor vehicle 2 is depicted, powered by an electric motor 4 that draws power from a battery pack 6 comprising one or more battery modules 8. The battery modules 8 may be electrically connected together in series and / or parallel to meet the desired capacity and power requirements of the electric motor 4. The vehicle 2 may be an all-electric vehicle and may be powered solely by the electric motor 4, or the vehicle 2 may be a hybrid electric vehicle and may be powered by both the electric motor 4 and an internal combustion engine (not shown).

[0076] like Figure 2 As shown, each battery module 8 includes one or more electrochemical cells or battery packs 10 for cycling lithium ions. In practice, the battery packs 10 in the battery module 8 are often assembled as a stack of layers, including a negative electrode layer 12, a negative electrode current collector 13, a positive electrode layer 14, a positive electrode current collector 15, and a separator layer 16. Each battery pack 10 is defined by the negative electrode layer 12 and the positive electrode layer 14, which are separated from each other by the separator layer 16. In practice, the separator layer 16 may be permeated with an electrolyte that provides a medium for the conduction of lithium ions between the negative electrode layer 12 and the positive electrode layer 14, or the separator layer 16 itself may act as an electrolyte. The negative electrode layer 12 is disposed on and electrically connected to the negative electrode current collector 13, and the positive electrode layer 14 is disposed on and electrically connected to the positive electrode current collector 15. Figure 2 As shown, for efficiency, these layers can be stacked such that some negative electrode current collectors 13 and some positive electrode current collectors 15 are double-sided, and each side includes a negative electrode layer 12 or a positive electrode layer 14. In this configuration, adjacent negative electrode layers 12 and positive electrode layers 14 share a single negative electrode current collector 13 or positive electrode current collector 15.

[0077] Figure 3 An electrochemical battery or battery pack 20 for cycling lithium-ion batteries is depicted. The battery pack 20 can generate current during discharge, which can be used to power a load device (e.g., an electric motor 4), and can be charged by connecting to a power source. Figure 1 and 2 Similar to the battery pack 10 shown, the battery pack 20 can be used in several ways to power the electric motor 4 of the motor vehicle 2. Additionally or alternatively, the battery pack 20 can be used in other transportation applications (e.g., motorcycles, boats, tractors, buses, motorbikes, mobile homes, campers, tanks, and aircraft) and can be used to power stationary and / or portable electronic devices, components, and devices used in a variety of other industries and applications, which, as a non-limiting example, include industrial, residential and commercial buildings, consumer products, industrial equipment and machinery, agricultural or farm equipment, and heavy machinery.

[0078] Battery pack 20 includes a negative electrode 22, a positive electrode 24, a separator 26, and an electrolyte 28 that provides a medium for the conduction of lithium ions between the negative electrode 22 and the positive electrode 24. The negative electrode 22 is disposed on the main surface of the negative electrode current collector 30, and the positive electrode 24 is disposed on the main surface of the positive electrode current collector 32. In practice, the negative electrode current collector 30 and the positive electrode current collector 32 are electrically connected to a power source or load 34 (e.g., a motor 4) via an external circuit 36. The negative electrode 22 and the positive electrode 24 are configured such that an electrochemical potential difference is established between the negative electrode 22 and the positive electrode 24 when the battery pack 20 is at least partially charged. During the discharge of the battery pack 20, the electrochemical potential established between the negative electrode 22 and the positive electrode 24 drives spontaneous reduction and oxidation (redox) reactions within the battery pack 20 and the release of lithium ions and electrons from the negative electrode 22. The released lithium ions move from the negative electrode 22 through the separator 26 and the electrolyte 28 to the positive electrode 24, while electrons travel from the negative electrode 22 to the positive electrode 24 via the external circuit 36, which generates an electric current. After the negative electrode 22 has been partially or completely depleted of lithium, the battery pack 20 can be charged by connecting the negative electrode 22 and the positive electrode 24 to a power source 34. This drives a non-spontaneous redox reaction within the battery pack 20 and the release of lithium ions and electrons from the positive electrode 24. The repeated discharge and charge of the battery pack 20 is referred to herein as a "cycle," where a full charge event and a subsequent full discharge event are considered a complete cycle.

[0079] The positive electrode 24 is configured to store and release lithium ions during the discharge and charging processes of the battery pack 20. The positive electrode 24 may be in the form of a continuous porous layer disposed on the main surface of the positive electrode current collector 32. The positive electrode 24 comprises an electrochemically active (electroactive) material (electroactive positive electrode material), a polymer binder, and optionally a conductive material. In several respects, the electroactive material of the positive electrode 24 may be a particulate material, and the particles of the electroactive material of the positive electrode 24 may be mixed with the polymer binder and optionally the conductive material.

[0080] The electroactive material of the positive electrode 24 can store and release lithium ions by undergoing a reversible redox reaction with lithium at a higher electrochemical potential than that of the electrochemically active material of the negative electrode 22, thereby creating an electrochemical potential difference between the negative electrode 22 and the positive electrode 24. The electroactive material of the positive electrode 24 may comprise an intercalation host material capable of reversible lithium ion insertion and extraction. In such cases, the electroactive material of the positive electrode 24 may comprise a lithium transition metal oxide. For example, the electroactive material of the positive electrode 24 may comprise layered lithium transition metal oxides represented by formula LiMeO2 and / or Li2MeO3, or Li... 1+x Me 1-xA layered lithium-rich transition metal oxide represented by O2 (where 0 < x ≤ 0.33), an olivine-type lithium transition metal oxide represented by the formula LiMePO4, a monoclinic-type lithium transition metal oxide represented by the formula Li3Me2(PO4)3, a spinel-type lithium transition metal oxide represented by the formula LiMe2O4, a lithiophilite represented by one or both of the following formulas LiMeSO4F or LiMePO4F, or a combination thereof, where Me is a transition metal (such as Co, Ni, Mn, Fe, Al, V, or a combination thereof). The electroactive material of the positive electrode 24 can constitute, by weight, greater than or equal to 70%, optionally greater than or equal to 80%, or optionally greater than or equal to 90% and less than or equal to 98%, or optionally less than or equal to 95% of the positive electrode 24.

[0081] In various aspects, the electroactive material of the positive electrode 24 can include a layered nickel-rich lithium transition metal oxide represented by the formula LiNi 1-x Me x O2, where x is greater than or equal to 0, or optionally greater than or equal to 0.1 and less than 0.4, optionally less than or equal to 0.3, optionally less than or equal to 0.2, or optionally less than or equal to 0.1, and where Me includes a transition metal. In various aspects, Me can include manganese (Mn), cobalt (Co), aluminum (Al), or a combination thereof.

[0082] In various aspects, the electroactive material of the positive electrode 24 can include a layered lithium-rich manganese-based oxide (LMR) represented by the formula Li 1+x Me 1-x O2, where x is greater than 0 and less than or equal to 0.33, Me includes a transition metal, and Me includes greater than or equal to 50 atomic% of Mn.

[0083] The polymeric binder is electrochemically inert and can be included in the positive electrode 24 to provide structural integrity to the positive electrode 24 and / or assist the positive electrode 24 in adhering to the main surface of the positive electrode current collector 32. Examples of polymeric binders include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), ethylene propylene diene monomer (EPDM) rubber, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), nitrile rubber (NBR), styrene butadiene rubber (SBR), styrene ethylene butene styrene copolymer (SEBS), polyacrylate, alginate, polyacrylic acid, and combinations thereof. The polymeric binder can constitute, by weight, greater than or equal to 1%, or optionally greater than or equal to 5% and less than or equal to 10% of the positive electrode 24.

[0084] The optional conductive material is electrochemically inert and may be included in the positive electrode 24 to provide sufficient conductivity to support the permeation of electrons through it. Examples of conductive materials include carbon-based materials, metals (e.g., nickel), and / or conductive polymers. Examples of conductive carbon-based materials include carbon black (CB) (e.g., acetylene black), graphite, graphene (e.g., graphene nanosheets GNP), graphene oxide, carbon nanotubes (CNTs), and / or carbon fibers (e.g., carbon nanofibers). Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, and / or polypyrrole. When included in the positive electrode 24, the optional conductive material may constitute greater than 0%, optionally greater than or equal to 1%, or optionally greater than or equal to 5% and less than or equal to 10% of the positive electrode 24 by weight.

[0085] The negative electrode 22 is configured to store and release lithium ions to facilitate the charging and discharging of the battery pack 20, respectively. The negative electrode 22 may be in the form of a continuous layer of material disposed on the main surface of the negative electrode current collector 30. The negative electrode 22 comprises an electrochemically active (electroactive) material (electroactive negative electrode material) capable of storing and releasing lithium ions through a reversible redox reaction with lithium during the charging and discharging of the battery pack 20. Examples of electroactive negative electrode materials include lithium, lithium-based materials (e.g., alloys of lithium with silicon, aluminum, indium, and / or tin), carbon-based materials (e.g., graphite, activated carbon, carbon black, hard carbon, soft carbon, and / or graphene), silicon, silicon-based materials (e.g., alloys of silicon with lithium, tin, iron, aluminum, and / or cobalt), silicon oxide, silicon oxide-based materials (e.g., lithium silicon oxide), tin oxide, aluminum, indium, zinc, germanium, titanium oxide, lithium titanate, and combinations thereof. The electroactive material of the negative electrode 22 may constitute greater than or equal to 70%, optionally greater than or equal to 80%, or optionally greater than or equal to 90% and less than or equal to 98%, or optionally less than or equal to 95% by weight. The same polymer binder and / or conductive material disclosed above with respect to the positive electrode 24 may be used in substantially the same amount for the negative electrode 22.

[0086] The electrolyte 28 is ionicly conductive and provides a medium for lithium ions to conduct between the negative electrode 22 and the positive electrode 24. The electrolyte 28 is formulated to help improve the thermal stability of the battery pack 20, particularly in embodiments where the electroactive material of the positive electrode 24 comprises a layered nickel-rich lithium transition metal oxide. The electrolyte 28 comprises an organic solvent, a lithium salt in the organic solvent, and optional additives.

[0087] The organic solvent comprises a primary solvent and an optional secondary solvent. The organic solvent may, by weight, constitute 60% or more, optionally 70% or more, optionally 80% or more, or optionally 90% or more and less than or equal to 95%, optionally less than or equal to 93%, or optionally less than or equal to 90% of the electrolyte 28.

[0088] The primary solvent is formulated to give the electrolyte 28 chemical stability, good ionic conductivity, and the ability to facilitate the formation of a cathode electrolyte interface (CEI) on the electroactive material surface of the positive electrode 24 during battery pack 20 cycling. The primary solvent comprises fluorinated or non-fluorinated, saturated, acyclic alkyl alkyl esters, ketones, nitriles, or combinations thereof. The primary solvent may constitute 70% or more, optionally 80% or more, optionally 90% or more, optionally 95% or more, optionally 97% or more, optionally 99% or more, or optionally 99.9% or more and less than or equal to 100% of the organic solvent by weight.

[0089] In aspects where the primary solvent comprises an alkyl alkanoate, the alkyl alkanoate may have the formula R 1 -COO-R 2 , where R 1 It is H or an alkyl or fluoroalkyl group having 1 to 3 carbon atoms (i.e., C1-C3 alkyl or C1-C3 fluoroalkyl), and R 2 It is an alkyl or fluoroalkyl group having 1 to 4 carbon atoms (i.e., C1-C4 alkyl or C1-C4 fluoroalkyl). The term "alkyl" refers to an alkyl group that does not contain an unsaturated straight-chain or branched hydrocarbon group. The term "fluoroalkyl" refers to an alkyl group in which at least one hydrogen atom is replaced by fluorine. It has the formula R 1 -COO-R 2 Examples of alkyl alkyl esters of alkyl alkylates include 2,2,2-trifluoroethyl acetate (FEA), ethyl acetate (EA), n-propyl acetate (nPA), isopropyl acetate (iPA), n-butyl acetate (nBA), isobutyl acetate (iBA), methyl propionate (MP), methyl butyrate (MB), methyl formate (MF), ethyl formate (EF), n-propyl formate (nPF), isopropyl formate (iPF), n-butyl formate (nBF), and isobutyl formate (iBF). In several respects, the primary solvent may include FEA.

[0090] In aspects where the primary solvent comprises a ketone, the ketone may have the formula R 3 -C(=O)-R 4 , where R 3 and R 4 Each is independently an alkyl or fluoroalkyl group having one or two carbon atoms (i.e., C1-C2 alkyl or C1-C2 fluoroalkyl). Having the formula R 3 -C(=O)-R 4 Examples of ketones include acetone and 2-butanone.

[0091] In the aspect where the primary solvent comprises a nitrile, the nitrile may have the formula R 5 -C≡N, where R 5It is a C1-C3 alkyl or C1-C3 fluoroalkyl. It has the formula R 5 Examples of -C≡N nitriles include acetonitrile (ACN), propionitrile (PN), n-butyronitrile (nBN), and isobutyronitrile (iBN).

[0092] An optional secondary solvent can be formulated to give the electrolyte 28 good ionic conductivity, for example, by giving the electrolyte 28 a relatively high dielectric constant and / or a relatively low viscosity compared to the primary solvent. When present in the organic solvent, the secondary solvent may account for more than 0% and less than or equal to 30% of the organic solvent by weight.

[0093] The optional secondary solvent may comprise linear organic carbonates, cyclic organic carbonates, or combinations thereof. Examples of linear organic carbonates include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). When present in electrolyte 28, the linear organic carbonate may constitute greater than 0% and less than or equal to 30%, optionally less than or equal to 20%, optionally less than or equal to 10%, optionally less than or equal to 5%, optionally less than or equal to 3%, optionally less than or equal to 1%, or optionally less than or equal to 0.1% by weight of the organic solvent. Examples of cyclic organic carbonates include ethylene carbonate (EC), propylene carbonate (PC), and fluoroethylene carbonate (FEC). When present in electrolyte 28, the cyclic organic carbonate may constitute greater than 0% and less than or equal to 15%, optionally less than or equal to 10%, optionally less than or equal to 5%, optionally less than or equal to 3%, optionally less than or equal to 1%, or optionally less than or equal to 0.1% by weight of the organic solvent. In several respects, the electrolyte 28 may be substantially free of organic carbonates. In several respects, the electrolyte 28 may be substantially free of cyclic organic carbonates. In several respects, the electrolyte 28 may be substantially free of ethylene carbonate (EC).

[0094] Optional additives may be formulated to participate in the formation of a solid electrolyte interface (SEI and / or CEI) on the electroactive material surfaces of the negative electrode 22 and / or the positive electrode 24. When present in the electrolyte 28, the additive may constitute greater than 0% and less than or equal to 10% by weight of the electrolyte 28. In several aspects, the additive may comprise a first chemical compound formulated to participate in the formation of a CEI on the electroactive material surface of the positive electrode 24 and / or a second chemical compound formulated to participate in the formation of a SEI on the electroactive material surface of the negative electrode 24.

[0095] Examples of chemical compounds that may be included in the electrolyte 28 as additives to aid in the formation of CEI on the electroactive material surface of the positive electrode 24 include succinic anhydride (SA), trimethoxymethylsilane (TMSi), and tris(trimethylsilyl) phosphite (TMSPi). When present in the electrolyte 28, the first chemical compound may constitute greater than or equal to 0.1% by weight, or optionally greater than or equal to 0.5% and less than or equal to 5%, optionally less than or equal to 3%, or optionally less than or equal to 1% by weight of the electrolyte 28. In several respects, the electrolyte 28 may contain approximately 1% TMSi and approximately 0.5% SA by weight.

[0096] Examples of chemical compounds that can be included in the electrolyte 28 as additives to aid in the formation of an SEI on the surface of the electroactive material of the negative electrode 22 include ethylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3,2-dioxane-2,2-dioxide (DTD). In embodiments where the electroactive material of the negative electrode 22 comprises silicon, FEC can be particularly beneficial for the formation of an SEI on the surface of the electroactive material of the negative electrode 22. When present in the electrolyte 28, the second chemical compound may constitute greater than or equal to 0.1%, optionally greater than or equal to 0.5%, optionally greater than or equal to 2%, or optionally greater than or equal to 5% and less than or equal to 15%, optionally less than or equal to 10%, or optionally less than or equal to 5% by weight of the electrolyte 28. In several aspects, the electrolyte 28 may contain greater than or equal to 0.5% and less than or equal to 2% VC by weight. In several aspects, the electrolyte 28 may contain greater than or equal to 5% and less than or equal to 15% FEC by weight.

[0097] The lithium salt is soluble in an organic solvent and provides a channel for lithium ions to pass through the electrolyte 28. Examples of lithium salts include lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiN(FSO2)2) (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2) (LiTFSI), lithium tetrafluoroborate (LiBF4), lithium bis(oxalate-containing)borate (LiB(C2O4)2) (LiBOB), and lithium difluoro(oxalate-containing)borate (LiBF2(C2O4)) (LiDFOB). In several aspects, the lithium salt may contain LiPF6. The lithium salt may be dissolved in an organic solvent and present in the electrolyte 28 at a concentration greater than or equal to 0.5 mol, or optionally greater than or equal to 0.8 mol and less than or equal to 4 mol, optionally less than or equal to 1.6 mol, or optionally less than or equal to 1.2 mol. This means that the lithium salt accounts for more than or equal to 8%, optionally more than or equal to 10%, optionally more than or equal to 15% and less than or equal to 30%, or optionally less than or equal to 20% of the electrolyte 28 by weight.

[0098] In several respects, the lithium salt may comprise a primary lithium salt and a secondary lithium salt. In such cases, the primary lithium salt may comprise LiPF6 and may be present in the electrolyte 28 at a concentration greater than or equal to 0.6 mol and less than or equal to 1 mol. The secondary lithium salt may comprise LiFSI and / or LiTFSI and may be present in the electrolyte 28 at a concentration greater than or equal to 0.2 mol and less than or equal to 0.6 mol.

[0099] The separator 26 physically separates and electrically isolates the negative electrode 22 and the positive electrode 24 from each other while allowing lithium ions to pass through. The separator 26 has an open microporous structure and may contain organic and / or inorganic materials. For example, the separator 26 may contain a polymer. Examples of polymers used for the separator 26 include polyolefins (e.g., polyethylene PE and / or polypropylene PP), polyamides (PA), poly(tetrafluoroethylene) (PTFE), polyvinylidene fluoride (PVDF), poly(vinyl chloride) (PVC), and combinations thereof. In one form, the separator 26 may contain a laminate of polymers, such as a laminate of PE and PP. In several aspects, the separator 26 may include a ceramic coating (not shown) disposed on one or both sides thereof. In such cases, the ceramic coating may contain particles of alumina (Al2O3) and / or silica (SiO2).

[0100] Negative electrode current collector 30 and positive electrode current collector 32 are electrochemically active and conductive. Negative electrode current collector 30 and positive electrode current collector 32 are formulated to provide electrical connections between external circuit 36 ​​and negative electrode 22 and positive electrode 24, respectively. In several aspects, negative electrode current collector 30 and positive electrode current collector 32 may be in the form of non-porous metal foil, perforated metal foil, porous metal mesh, or combinations thereof. Negative electrode current collector 30 and positive electrode current collector 32 may be made of metal or other suitable conductive materials (e.g., carbon). In aspects where negative electrode current collector 30 and / or positive electrode current collector 32 are made of metal, the metal may be a substantially pure elemental metal or an alloy of an elemental metal with one or more other metallic or non-metallic elements (referred to as an "alloying" element). In some instances, negative electrode current collector 30 may be made of copper, nickel, or stainless steel, and positive electrode current collector 32 may be made of aluminum.

[0101] experiment

[0102] The LiNi alloy was evaluated using in-operation X-ray diffraction (XRD) analysis. 1-x-y-z Co x Mn y Al zThe thermal stability of layered nickel-rich oxides of O2(NCMA), where 0 < (x + y + z) ≤ 0.4, is used to determine the change in the crystal structure of nickel-rich oxides when heated from approximately ambient temperature (e.g., 25 °C) to approximately 430 °C. Figure 4 This is a graph showing the XRD spectra of nickel-rich oxides at various temperatures, plotted as intensity (arbitrary units) 100 vs. 2θ (degrees) 110. Figure 4 As shown, Ni-rich oxides undergo a change in crystal structure when heated at a temperature greater than or equal to 210°C.

[0103] All coin cells comprising an electrolyte according to an embodiment of this disclosure were assembled and evaluated using a constant current charge-discharge scheme. All battery packs included a positive electrode comprising an electroactive material having the formula LiNi. 1-x-y-z Co x Mn y Al z The positive electrode is composed of layered nickel-rich oxide O2 (NCMA), where 0 < (x + y + z) ≤ 0.4. It has a diameter of approximately 3 mm and a capacitance of approximately 4 mA-h / cm². 2 The battery pack includes a negative electrode containing electroactive material composed of a mixture of 30 wt% lithium-ionized silicon oxide and 70 wt% graphite. This negative electrode has a load of approximately 4.4 mAh / cm³. 2 The load. All battery packs include 120 microliters (μL) of an exemplary electrolyte containing 1 mole of LiPF6 dissolved in 1 liter of 2,2,2-trifluoroethyl acetate (FEA), having 2 wt% FEC and 1 wt% VC. The LiPF6 accounts for approximately 9.1% by weight of the exemplary electrolyte, and the FEA accounts for approximately 87.9% by weight of the exemplary electrolyte.

[0104] The battery was subjected to constant current charging and discharging at 25°C. During formation, the battery was charged to 4.2V at a C / 20 rate and then discharged to 2.5V. Figure 5 The graph shows the charge and discharge curves of one of the batteries during the formation process, with a voltage (V) of 200 vs. a specific capacity (mAh / g) of 210. After formation, the battery has an average charge specific capacity of 231 mAh / g, an average discharge specific capacity of 202.5 mAh / g, and an average coulombic efficiency of 87.6%.

[0105] After formation, the battery is charged and discharged at different rates using a constant current and constant voltage (CCCV) scheme. Figure 6This is a graph showing the voltage (V) 300 vs. specific capacity (mAh / g) 310, depicting the charge and discharge curves of one of the batteries charged and discharged at a C / 3 rate. After 100 cycles, the battery retains approximately 95% of its capacity when charged and discharged at a C / 3 rate.

[0106] Figure 7 This is a graph showing the discharge capacity (%) of one of the batteries discharged at different rates versus the number of cycles at 410. Figure 7 The discharge capacity retention value shown is calculated as a percentage of the battery's discharge capacity at a specific discharge rate relative to its discharge capacity at a C / 3 discharge rate.

[0107] Figure 8 This is a graph showing the capacity retention (%) of one of the batteries charged at different rates (500 vs. 510 cycles). Figure 8 The capacity retention value shown is calculated as a percentage of the battery capacity at a specific discharge rate relative to the battery capacity at a C / 3 discharge rate.

[0108] After subjecting a number of batteries to full charge and discharge cycles, the positive electrodes were removed and analyzed using differential scanning calorimetry (DSC) to evaluate their thermal stability upon heating in the absence and presence of different electrolyte formulations. After removal from the batteries, the positive electrodes were washed with dimethyl carbonate (DMC) to remove residual salts, dried at 80°C to remove DMC, placed in an aluminum boat, sealed, and heated to 300°C at a heating rate of 5°C / min in a DSC machine. For comparison, 40 wt% of a baseline electrolyte or an exemplary electrolyte formulated according to embodiments of this disclosure was added to a number of positive electrodes in an aluminum boat. The baseline electrolyte comprised 1 mole of LiPF6 in 1 liter of an organic solvent containing a mixture of EC and EMC (EC:EMC volume ratio = 30:70), with 2 wt% FEC and 1 wt% VC added. The exemplary electrolyte comprises 1 mole of LiPF6 dissolved in 1 liter of 2,2,2-trifluoroethyl acetate (FEA), with 2% by weight of FEC and 1% by weight of VC added.

[0109] Figure 9This is a graph showing the heat flux (watts / gram, W / g) 600 vs. temperature (°C) 610 for a dry positive electrode (without electrolyte) 620, a positive electrode 630 with 40 wt% baseline electrolyte, and a positive electrode 640 with 40 wt% exemplary electrolyte. As shown, when the dry positive electrode 620 and the positive electrode 640 with 40 wt% exemplary electrolyte are heated, a small exothermic peak is observed at approximately 220°C, indicating that the Ni-rich oxide in the positive electrode undergoes a phase temperature with oxygen release upon heating at such a temperature. However, unlike the positive electrode 630 with 40 wt% baseline electrolyte, the dry positive electrode 620 and the positive electrode 640 with 40 wt% exemplary electrolyte do not undergo an acute exothermic reaction.

[0110] The foregoing description is merely illustrative and is by no means intended to limit this disclosure, its application, or its use. The broad teachings of this disclosure can be implemented in various forms. Therefore, while this disclosure includes specific examples, its true scope should not be so limited, as other modifications will become apparent upon examination of the drawings, description, and appended claims. It should be understood that one or more steps within the method can be performed in different orders (or simultaneously) without altering the principles of this disclosure. Furthermore, although each embodiment is described above as having certain features, any one or more of those features described with respect to any embodiment of the invention may be implemented in any of other embodiments and / or combined with features of any of other embodiments, even if such combinations are not explicitly described. In other words, the described embodiments are not mutually exclusive, and substitution of one or more embodiments for each other remains within the scope of this disclosure.

[0111] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a” and “the” used herein are intended to include the plural forms as well. The terms “comprising,” “including,” and “having” are congruent and thus specify the presence of said features, elements, compositions, steps, integers, operations, and / or components thereof, but do not exclude the presence or inclusion of one or more other features, integers, steps, operations, elements, components, and / or sets thereof. Although the open-ended terms “comprising,” “including,” and “having” should be understood as non-limiting terms used to describe and claim the various embodiments described herein, in some respects, these terms may alternatively be understood as more restrictive and limiting terms such as “consisting of” or “substantially consisting of.” Thus, for any given embodiment recounting a composition, material, component, element, feature, integer, operation, and / or process step, this disclosure also specifically includes embodiments consisting of or substantially consisting of such said compositions, materials, components, elements, features, integers, operations, and / or process steps. In the case of “consisting of…”, the alternative embodiments exclude any additional compositions, materials, components, elements, features, integers, operations and / or process steps. In the case of “essentially composed of…”, any additional compositions, materials, components, elements, features, integers, operations and / or process steps that substantially affect the essential and novel characteristics are excluded from such embodiments. However, any compositions, materials, components, elements, features, integers, operations and / or process steps that do not substantially affect the essential and novel characteristics may be included in the embodiments.

[0112] The phrases A, B, and C used in this document should be interpreted as referring to logic (A or B or C) using non-exclusive logic OR, and should not be interpreted as meaning "at least one of A, at least one of B, and at least one of C".

[0113] The terms “composition” and “material” as used herein are used interchangeably to refer to a substance that contains at least preferred chemical components, elements, or compounds, but may also contain additional elements, compounds, or substances, including trace impurities, unless otherwise stated. A “X-based” composition or material generally refers to a composition or material in which “X” is a single largest component based on a weight percentage (%). This may include compositions or materials having more than 50% X by weight, and those having less than 50% X by weight, provided that X is the single largest component of the composition or material based on its total weight. When a composition or material is referred to as “substantially free” of a substance, the composition or material may contain less than 5%, optionally less than 3%, optionally less than 1%, or optionally less than 0.1% of that substance by weight.

Claims

1. A cyclic lithium-ion battery pack, the battery pack comprising: A positive electrode comprising an electroactive material, said electroactive material comprising a layered nickel-rich lithium transition metal oxide; and The electrolyte permeating the positive electrode, the electrolyte comprising: An organic solvent comprising at least 70% by weight of a main solvent comprising an alkyl ester of an alkanolide, a ketone, a nitrile, or a combination thereof, wherein the organic solvent comprises less than 15% by weight of a cyclic organic carbonate, and Lithium salt in the organic solvent.

2. The battery pack according to claim 1, wherein the primary solvent comprises having formula R 1 -COO-R 2 Alkyl esters of alkanonic acids, Where R 1 It is H, C1-C3 alkyl, or C1-C3 fluoroalkyl, and Where R 2 It is a C1-C4 alkyl or a C1-C4 fluoroalkyl.

3. The battery pack according to claim 2, wherein the primary solvent comprises at least one alkyl alkyl ester of alkyl alkanoate selected from 2,2,2-trifluoroethyl acetate (FEA), ethyl acetate (EA), n-propyl acetate (nPA), isopropyl acetate (iPA), n-butyl acetate (nBA), isobutyl acetate (iBA), methyl propionate (MP), methyl butyrate (MB), methyl formate (MF), ethyl formate (EF), n-propyl formate (nPF), isopropyl formate (iPF), n-butyl formate (nBF), and isobutyl formate (iBF).

4. The battery pack of claim 1, wherein the primary solvent comprises having formula R 3 -C(=O)-R 4 ketones, Where R 3 and R 4 Each is independently a C1-C2 alkyl or C1-C2 fluoroalkyl.

5. The battery pack according to claim 4, wherein the primary solvent comprises at least one ketone selected from acetone and 2-butanone.

6. The battery pack of claim 1, wherein the primary solvent comprises having formula R 5 Nitriles with -C≡N Where R 5 It is a C1-C3 alkyl or a C1-C3 fluoroalkyl.

7. The battery pack according to claim 6, wherein the primary solvent comprises at least one nitrile selected from acetonitrile (ACN), propionitrile (PN), n-butyronitrile (nBN), and isobutyronitrile (iBN).

8. The battery pack of claim 1, wherein the electrolyte is substantially free of cyclic organic carbonates.

9. The battery pack according to claim 1, wherein the electrolyte comprises at least one lithium salt of greater than or equal to 0.5 moles and less than or equal to 4 moles, wherein the lithium salt is selected from lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium tetrafluoroborate (LiBF4), lithium bis(oxalate-based)borate (LiBOB), and lithium difluoro(oxalate-based)borate (LiDFOB).

10. The battery pack according to claim 1, wherein the electroactive material of the positive electrode comprises LiNi 1-x Me x O2 represents a layered nickel-rich lithium transition metal oxide, where 0 ≤ x < 0.4, and where Me comprises manganese (Mn), cobalt (Co), aluminum (Al), or a combination thereof.

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