Electrolyte comprising oxalate-based additive and battery comprising same

Abstract

A battery circulating lithium ions includes a positive electrode including an electroactive material including an oxide containing lithium and manganese, and an electrolyte permeating the positive electrode. The electrolyte includes an organic solvent, a lithium salt in the organic solvent, and an oxalate-based additive in the organic solvent. The oxalate-based additive includes at least one oxalate compound selected from the group consisting of bis (2, 2, 2-trifluoroethyl) oxalate, tert-butyl 2, 2, 2-trifluoroethyl oxalate, methyl 2, 2, 2-trifluoroethyl oxalate, ethyl 2, 2, 2-trifluoroethyl oxalate, bis (2-chloroethyl) oxalate, and diethyl oxalate.

Description

Technical Field

[0001] The present disclosure relates to electrolytes for batteries that recycle lithium ions, and more particularly to additives for battery electrolytes, the battery including an oxide containing lithium and manganese as an electroactive positive electrode material. Background Art

[0002] The information provided in this section is for the purpose of presenting the background of the present disclosure generally. To the extent described in this section, the work of the presently named inventors, as well as aspects that may not qualify as prior art at the time of filing, are neither expressly nor implicitly admitted as prior art with respect to the present disclosure.

[0003] Batteries that recycle lithium ions typically include a positive electrode, a negative electrode spaced apart from the positive electrode, and an ion-conductive electrolyte that provides a medium for the conduction of lithium ions between the positive and negative electrodes during discharge and charge of the battery. Layered lithium- and manganese-based oxides (LMR) have become attractive candidates for positive electrode electroactive materials due to their relatively high capacity (e.g., >250 mAh / g), thermal stability, and relatively low cost. However, it has been found that LMR exhibits voltage decay, low Coulombic efficiency, and irreversible capacity loss after repeated charge and discharge cycles. Summary of the Invention

[0004] According to one or more embodiments of the present disclosure, a battery that recycles lithium ions includes a positive electrode and an electrolyte permeating the positive electrode. The positive electrode includes an electroactive material containing an oxide containing lithium and manganese. The electrolyte includes an organic solvent, a lithium salt in the organic solvent, and an oxalate-based additive in the organic solvent. The oxalate-based additive includes at least one oxalate compound selected from bis(2,2,2-trifluoroethyl) oxalate, tert-butyl 2,2,2-trifluoroethyl oxalate, methyl 2,2,2-trifluoroethyl oxalate, ethyl 2,2,2-trifluoroethyl oxalate, bis(2-chloroethyl) oxalate, and diethyl oxalate.

[0005] The oxalate-based additive may include at least one fluorinated oxalate compound selected from bis(2,2,2-trifluoroethyl) oxalate, tert-butyl 2,2,2-trifluoroethyl oxalate, methyl 2,2,2-trifluoroethyl oxalate, and ethyl 2,2,2-trifluoroethyl oxalate.

[0006] The oxalate-based additive may constitute from greater than or equal to 0.001% to less than or equal to 10% by weight of the electrolyte.

[0007] The oxalate-based additive may include bis(2,2,2-trifluoroethyl) oxalate. In this case, bis(2,2,2-trifluoroethyl) oxalate may constitute from greater than or equal to 0.1% to less than or equal to 2% by weight of the electrolyte.

[0008] The oxalate-based additive may further comprise at least one other compound selected from lithium oxalate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, magnesium bis(trifluoromethanesulfonyl)imide, calcium bis(trifluoromethanesulfonyl)imide, lithium 4,5-dicyano-2-(trifluoromethyl)imidazole, 2-methoxy-2-oxoethyl 2,2,2-trifluoroacetate, 2,2,2-trifluoroethyl acetate, ethyl 2-(2,2,2-trifluoroethoxy)acetate, ethyl 2-ethylperoxy-2-oxoacetate, 1,6-bis(thioalkyl)hexane-3,4-dione, trifluoroacetic anhydride, pentafluoropropionic anhydride, 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) carbonate, tris(2,2,2-trifluoroethyl) borate, and tris(2,2,2-trifluoroethyl) orthoformate.

[0009] The electroactive material of the positive electrode may include lithium manganese-based oxides represented by the formulae LiMeO2, Li2MeO3, LiMe2O4, and / or Li 1+x Me 1-x O2, where Me includes transition metals selected from Co, Ni, Mn, Fe, Al, and V, where Me includes at least 50% by weight of manganese (Mn), and where 0 < x ≤ 0.33.

[0010] The lithium salt may include lithium hexafluorophosphate (LiPF6).

[0011] The organic solvent may include linear carbonates and cyclic carbonates.

[0012] The organic solvent may contain fluoroethylene carbonate (FEC) and diethyl carbonate (DEC).

[0013] According to one or more embodiments of the present disclosure, a battery for cycling lithium ions includes a negative electrode, a positive electrode, and an electrolyte permeating the positive electrode. The negative electrode includes an electroactive negative electrode material. The positive electrode includes an electroactive positive electrode material, which includes lithium manganese-based oxides represented by the formulae LiMeO2, Li2MeO3, LiMe2O4, and / or Li 1+x Me 1-xA lithium manganese-based oxide represented by O2, where Me includes transition metals selected from Co, Ni, Mn, Fe, Al, and V, where Me includes manganese (Mn) at greater than or equal to 50% by weight, and where 0 < x ≤ 0.33. The electrolyte contains an organic solvent, a lithium salt in the organic solvent, and an oxalate-based additive in the organic solvent. The oxalate-based additive contains at least one oxalate compound selected from bis(2,2,2-trifluoroethyl) oxalate, tert-butyl 2,2,2-trifluoroethyl oxalate, methyl 2,2,2-trifluoroethyl oxalate, ethyl 2,2,2-trifluoroethyl oxalate, bis(2-chloroethyl) oxalate, and diethyl oxalate.

[0014] The oxalate-based additive may contain at least one fluorinated oxalate compound selected from bis(2,2,2-trifluoroethyl) oxalate, tert-butyl 2,2,2-trifluoroethyl oxalate, methyl 2,2,2-trifluoroethyl oxalate, and ethyl 2,2,2-trifluoroethyl oxalate.

[0015] The oxalate-based additive may constitute from 0.001% to 10% by weight of the electrolyte.

[0016] In some aspects, the oxalate-based additive may include bis(2,2,2-trifluoroethyl) oxalate. In this case, bis(2,2,2-trifluoroethyl) oxalate may constitute from 0.1% to 2% by weight of the electrolyte.

[0017] The oxalate-based additive may further contain at least one other compound selected from lithium oxalate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, magnesium bis(trifluoromethanesulfonyl)imide, calcium bis(trifluoromethanesulfonyl)imide, 4,5-dicyano-2-(trifluoromethyl)imidazole lithium, 2-methoxy-2-oxoethyl 2,2,2-trifluoroacetate, 2,2,2-trifluoroethyl acetate, ethyl 2-(2,2,2-trifluoroethoxy)acetate, ethyl 2-ethylperoxy-2-oxoacetate, 1,6-bis(thioalkyl)hexane-3,4-dione, trifluoroacetic anhydride, pentafluoropropionic anhydride, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) carbonate, tris(2,2,2-trifluoroethyl) borate, and tris(2,2,2-trifluoroethyl) orthoformate.

[0018] The lithium salt may include lithium hexafluorophosphate (LiPF6).

[0019] The organic solvent may contain fluoroethylene carbonate (FEC) and diethyl carbonate (DEC).

[0020] In some aspects, the electroactive negative electrode material may include at least one of a silicon oxide-based material and a carbon-based material.

[0021] In other aspects, the electroactive negative electrode material may contain more than 97% lithium by weight.

[0022] Further application areas of the present disclosure will become apparent from the detailed description, claims, and drawings. The detailed description and specific examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present disclosure will be more fully understood from the detailed description and the drawings, in which:

[0024] Figure 1 is a schematic perspective view of a motor vehicle powered by a battery pack including a plurality of battery modules.

[0025] Figure 2 is Figure 1 a schematic cross-sectional view of a part of one of the battery modules, the battery module including a plurality of electrochemical battery cells or batteries that cycle lithium ions.

[0026] Figure 3 is a schematic cross-sectional view of a battery that cycles lithium ions, the battery including a positive electrode, a negative electrode, a porous separator, and an electrolyte that permeates the positive electrode, the porous separator, and an optional negative electrode.

[0027] In the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION

[0028] The presently disclosed electrolyte is formulated for a battery that cycles lithium ions and includes a positive electrode containing an oxide containing lithium and manganese as an electroactive material. The presently disclosed electrolyte contains an oxalate-based additive formulated to improve the cycle life of the battery, for example by helping to improve the cycle stability and capacity retention of the positive electrode.

[0029] Figure 1 Depicts a motor vehicle 2 powered by an electric motor 4, the electric motor 4 drawing power from a battery pack 6 including one or more battery modules 8. The battery modules 8 may be arranged in series and / or in parallel and electrically coupled together to meet the desired capacity and power requirements of the electric motor 4. The vehicle 2 may be a pure electric vehicle and may be powered only by the electric motor 4, or the vehicle 2 may be a hybrid electric vehicle and may be powered by the electric motor 4 and an internal combustion engine (not shown).

[0030] As Figure 2As shown, each battery module 8 includes one or more electrochemical battery cells or batteries 10 that cycle lithium ions. In practice, the batteries 10 in the battery module 8 are often assembled into stacked 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 10 is defined by the negative electrode layer 12 and the positive electrode layer 14, and the negative electrode layer 12 and the positive electrode layer 14 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 serve as the electrolyte. The negative electrode layer 12 is disposed on and in electrical communication with the negative electrode current collector 13, and the positive electrode layer 14 is disposed on and in electrical communication with the positive electrode current collector 15. As Figure 2 shown, for efficiency, these layers can be stacked such that some of the negative electrode current collectors 13 and some of the positive electrode current collectors 15 are double-sided and include the negative electrode layer 12 or the positive electrode layer 14, respectively, on both of their sides. In such an arrangement, adjacent negative electrode layers 12 and positive electrode layers 14 share a single negative electrode current collector 13 or positive electrode current collector 15, respectively.

[0031] Figure 3 An electrochemical battery cell or battery 20 that cycles lithium ions is depicted. The battery 20 can generate a current during discharge that can be used to power a load device (such as an electric motor 4), and can be charged by connection to a power source. Similar to Figure 1 and Figure 2 the battery 10 shown in

[0032] The battery 20 includes a negative electrode 22, a positive electrode 24, a separator 26, and an electrolyte 28. The electrolyte 28 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 a negative electrode current collector 30, and the positive electrode 24 is disposed on the main surface of a positive electrode current collector 32. In practice, the negative electrode current collector 30 and the positive electrode current collector 32 are electrically coupled to a power source or a load 34 (such as an electric 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 20 is at least partially charged. During discharge of the battery 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 20 and the release of lithium ions and electrons from the negative electrode 22. The released lithium ions move from the negative electrode 22 to the positive electrode 24 through the separator 26 and the electrolyte 28, while the electrons move from the negative electrode 22 to the positive electrode 24 through the external circuit 36, thereby generating an electric current. After the negative electrode 22 has been partially or completely depleted of lithium, the battery 20 can be charged by connecting the negative electrode 22 and the positive electrode 24 to a power source 34, which drives non-spontaneous redox reactions within the battery 20 and the release of lithium ions and electrons from the positive electrode 24. The repeated discharge and charge of the battery 20 may be referred to herein as a "cycle", and a full discharge event following a full charge event is considered a complete cycle.

[0033] The positive electrode 24 is configured to store and release lithium ions during discharge and charge of the battery 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 includes an electrochemically active (electroactive) material (electroactive positive electrode material), a polymer binder, and an optional conductive material. In some aspects, the electroactive material of the positive electrode 24 may be particulate material, and the particles of the electroactive material of the positive electrode 24 may be mixed with the polymer binder and the optional conductive material.

[0034] The electroactive material of the positive electrode 24 can store and release lithium ions by undergoing a reversible redox reaction with lithium at an electrochemical potential higher than that of the electrochemically active material of the negative electrode 22, such that an electrochemical potential difference exists between the negative electrode 22 and the positive electrode 24. The electroactive material of the positive electrode 24 may include materials capable of undergoing lithium insertion and extraction or materials capable of undergoing a conversion reaction with lithium. In aspects where the electroactive material of the positive electrode 24 includes an insertion host material capable of reversibly inserting or embedding lithium ions, the electroactive material of the positive electrode 24 may include lithium transition metal oxides. For example, the electroactive material of the positive electrode 24 may comprise layered lithium transition metal oxides represented by the formula LiMeO2 and / or L i2 MeO3, spinel lithium transition metal oxides represented by the formula 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 lithium transition metal oxide represented by the formula Li3Me2(PO4)3, a spinel-type lithium transition metal oxide represented by the formula LiMe2O4, a titanate or a combination thereof represented by one or both of the following formulas LiMeSO4F or LiMePO4F, 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 the positive electrode 24 that is greater than or equal to about 50% by weight, optionally greater than or equal to about 60%, or optionally greater than or equal to about 70% and less than or equal to about 97%, optionally less than or equal to about 90%, or optionally less than or equal to about 80%.

[0035] In an embodiment, the electroactive material of the positive electrode 24 can include an oxide containing lithium and manganese. For example, in an embodiment, the electroactive material of the positive electrode 24 can include a lithium-manganese-based oxide represented by the formula LiMeO2, Li2MeO3 (such as Li2MnO3) and / or LiMe2O4, where Me is a transition metal, and where Me includes manganese (Mn) that is greater than or equal to about 50% by weight. As another example, in an embodiment, the electroactive material of the positive electrode 24 can include a layered lithium-rich manganese-based transition metal oxide represented by the formula Li 1+x Me 1-x O2 (where 0 < x ≤ 0.33), where Me includes manganese (Mn) that is greater than or equal to about 50% by weight (LMR). Other examples of oxides containing lithium and manganese include spinel-phase lithium manganese oxide (LiMn2O4, LMO), high-voltage spinel-phase lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4, LNMO), lithium nickel cobalt manganese aluminum oxide (NCMA), lithium nickel manganese cobalt oxide (NMC), lithium nickel manganese oxide (LNMO), such as LiNi 0.5 Mn 1.5 O4 and / or Li 1.2 Ni 0.2 Mn 0.6 O2. Additionally or alternatively, the electroactive material of the positive electrode 24 can include lithium iron manganese phosphate (LMFP), lithium iron phosphate (LFP), lithium nickel cobalt aluminum oxide (NCA) or a combination thereof. In an embodiment, the electroactive material of the positive electrode 24 can include a high-voltage electroactive material that is formulated to operate at a voltage greater than or equal to 4.4 volts (V), optionally greater than or equal to 4.6 volts, or optionally greater than or equal to 4.8 volts and less than or equal to 5 volts relative to Li + / Li.

[0036] The polymeric binder is electrochemically inert and can be included in the positive electrode 24 to provide the positive electrode 24 with structural integrity and / or assist the positive electrode 24 in adhering to the major surface of the positive electrode current collector 32. Examples of polymeric binders include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), ethylene propylene diene monomer (EPDM), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), nitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), styrene ethylene butylene styrene copolymer (SEBS), polyacrylate, alginate, polyacrylic acid, and combinations thereof. The polymeric binder can constitute greater than or equal to about 1% by weight, or alternatively greater than or equal to about 5% and less than or equal to about 10% of the positive electrode 24.

[0037] The optional conductive material is electrochemically inactive and can be included in the positive electrode 24 to provide the positive electrode 24 with sufficient electrical conductivity to support electron percolation therethrough. Examples of conductive materials include carbon-based materials, metals (such as nickel), and / or conductive polymers. Examples of conductive carbon-based materials include carbon black (CB) (such as acetylene black), graphite, graphene (such as graphene nanosheets, GNP), graphene oxide, carbon nanotubes (CNT), and / or carbon fibers (such as carbon nanofibers). Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, and / or polypyrrole. When included in the positive electrode 24, the optional conductive material can constitute greater than 0% by weight, optionally greater than or equal to about 1%, or optionally greater than or equal to about 5% and less than or equal to about 10% of the positive electrode 24.

[0038] The negative electrode 22 is configured to store and release lithium ions to facilitate charging and discharging of the battery 20, respectively. The negative electrode 22 can be in the form of a continuous material layer disposed on the major surface of the negative electrode current collector 30. The negative electrode 22 includes an electroactive material (electroactive negative electrode material) that can store and release lithium ions by undergoing reversible redox reactions with lithium during charging and discharging of the battery 20. Examples of electroactive negative electrode materials include lithium, lithium-based materials (such as alloys of lithium and silicon, aluminum, indium, and / or tin), carbon-based materials (such as graphite, activated carbon, carbon black, hard carbon, soft carbon, and / or graphene), silicon, silicon-based materials (such as alloys of silicon and lithium, tin, iron, aluminum, and / or cobalt), silicon oxide, silicon oxide-based materials (such as lithium silicon oxide), tin oxide, aluminum, indium, zinc, germanium, titanium oxide, lithium titanate, and combinations thereof. The electroactive material of the negative electrode 22 can constitute greater than or equal to about 50% by weight, optionally greater than or equal to about 60%, or optionally greater than or equal to about 70% and less than or equal to about 97%, optionally less than or equal to about 90%, or optionally less than or equal to about 80% of the negative electrode 22.

[0039] In an embodiment, the electroactive material of the negative electrode 22 can include a silicon oxide-based material (such as Si, SiO xand / or Li y SiO x ) and a carbon-based material (such as graphite). In this case, the silicon oxide-based material may constitute an electroactive material of the negative electrode 22 that is greater than or equal to about 10% to less than or equal to about 70% by weight, or alternatively less than or equal to about 30%, and the carbon-based material (such as graphite) may constitute an electroactive material of the negative electrode 22 that is greater than or equal to about 30% by weight, or alternatively about 70% to less than or equal to about 90%.

[0040] In an embodiment, the negative electrode 22 may be porous, and the electroactive material of the negative electrode 22 may be particulate material. In embodiments where the electroactive material of the negative electrode 22 is particulate material, the particles of the electroactive material of the negative electrode 22 may be mixed with a polymeric binder and an optional conductive material. The same polymeric binder and / or conductive material disclosed above with respect to the positive electrode 24 may be used in substantially the same amounts in the negative electrode 22. In other embodiments, the electroactive material of the negative electrode 22 may be composed of lithium, and the negative electrode 22 may be in the form of a non-porous metal film or foil, such as a lithium metal film or a lithium metal foil. In this case, the negative electrode 22 may contain greater than 97% by weight of lithium, or alternatively greater than 99% of lithium. In embodiments where the electroactive material of the negative electrode 22 is composed of lithium, the negative electrode 22 may be substantially free of elements or compounds that undergo reversible redox reactions with lithium during operation of the battery 20. Additionally, in such embodiments, the negative electrode 22 may be substantially free of a polymeric binder.

[0041] The separator 26 physically separates and electrically insulates 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 include organic and / or inorganic materials. For example, the separator 26 may include a polymer. Examples of polymers for the separator 26 include polyolefins (such as polyethylene PE and / or polypropylene PP), polyamides (PA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), and combinations thereof. In one form, the separator 26 may include a polymer laminate, such as a PE and PP laminate. In some aspects, the separator 26 may include a ceramic coating (not shown) disposed on one or both of its sides. In this case, the ceramic coating may include alumina (Al2O3) and / or silica (SiO2) particles.

[0042] The electrolyte 28 is ion-conductive and provides a medium for the conduction of lithium ions between the negative electrode 22 and the positive electrode 24. The electrolyte 28 includes an organic solvent, a lithium salt in the organic solvent, and an oxalate-based additive.

[0043] The organic solvent may include a non-aqueous aprotic organic solvent. Non-limiting examples of the non-aqueous aprotic organic solvent include cyclic carbonates (such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC)); linear carbonates (such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC)); aliphatic carboxylates (such as methyl formate, methyl acetate, and methyl propionate); lactones (such as γ-butyrolactone, γ-valerolactone, and / or δ-valerolactone); nitriles (such as succinonitrile, glutaronitrile, and / or adiponitrile); sulfones (such as tetramethylene sulfone, ethyl methyl sulfone, vinyl sulfone, phenyl sulfone, 4-fluorophenyl sulfone, benzyl sulfone, and / or sulfolane); aliphatic ethers (such as triglyme, tetraglyme, 1,3-dimethoxypropane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and / or ethoxymethoxyethane); cyclic ethers (such as 1,4-dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane); phosphates (such as triethyl phosphate and / or trimethyl phosphate); and combinations thereof. In some aspects, the organic solvent may include a mixture of a cyclic carbonate (such as FEC) and a linear carbonate (such as DEC). The organic solvent may constitute greater than or equal to about 80% by weight, or alternatively greater than or equal to about 85% by weight, and less than or equal to about 95% by weight, or alternatively less than or equal to about 90% by weight of the electrolyte 28.

[0044] The lithium salt is soluble in the organic solvent and provides a channel for lithium ions to pass through the electrolyte 28. The lithium salt may include an inorganic lithium salt, an organic lithium salt, or a combination thereof. Examples of the lithium salt include lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(fluorosulfonyl)imide (LiN(FSO2)2) (LiFSI), lithium tetraphenylborate (LiB(C6H5)4), and combinations thereof. In some aspects, the lithium salt may include LiPF6. The lithium salt may be dissolved in the organic solvent at a concentration greater than or equal to about 0.5 mole and less than or equal to about 2 moles. In some aspects, the lithium salt may be dissolved in the organic solvent at a concentration of about 1.2 moles. The lithium salt may constitute greater than or equal to about 5% by weight, alternatively greater than or equal to about 10% by weight, and less than or equal to about 20% by weight, or alternatively less than or equal to about 15% by weight of the electrolyte 28.

[0045] A oxalate-based additive is formulated to increase the cycle life of the battery 20, for example, by helping to improve the cycle stability and capacity retention of the positive electrode 24. The oxalate-based additive comprises at least one oxalate compound selected from bis(2,2,2-trifluoroethyl) oxalate, tert-butyl 2,2,2-trifluoroethyl oxalate, methyl 2,2,2-trifluoroethyl oxalate, ethyl 2,2,2-trifluoroethyl oxalate, bis(2-chloroethyl) oxalate, and diethyl oxalate. In an embodiment, the oxalate-based additive may comprise at least one fluorinated oxalate compound selected from bis(2,2,2-trifluoroethyl) oxalate, tert-butyl 2,2,2-trifluoroethyl oxalate, methyl 2,2,2-trifluoroethyl oxalate, and ethyl 2,2,2-trifluoroethyl oxalate. The oxalate-based additive may constitute from greater than or equal to 0.001% by weight, optionally greater than or equal to 0.01%, optionally greater than or equal to 0.1%, optionally greater than or equal to 0.5%, or optionally greater than or equal to 1%, and less than or equal to 10%, optionally less than or equal to 5%, or optionally less than or equal to 2% of the electrolyte 28. In an embodiment, bis(2,2,2-trifluoroethyl) oxalate may constitute from greater than or equal to 50% by weight, optionally greater than or equal to 60%, optionally 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 100% of the oxalate-based additive.

[0046] In addition, the oxalate-based additive may optionally comprise at least one other compound selected from the following: lithium oxalate, lithium difluorophosphate (LiPO2F2), lithium bis(oxalate) borate (LiB(C2O4)2) (LiBOB), lithium difluoro(oxalate) borate (LiBF2(C2O4)) (LiDFOB), lithium bis(trifluoromethanesulfonyl) imide (LiN(CF3SO2)2) (LiTFSI), magnesium bis(trifluoromethanesulfonyl) imide, calcium bis(trifluoromethanesulfonyl) imide, 4,5-dicyano-2-(trifluoromethyl) imidazole lithium, 2-methoxy-2-oxoethyl 2,2,2-trifluoroacetate, 2,2,2-trifluoroethyl acetate, ethyl 2-(2,2,2-trifluoroethoxy) acetate, ethyl 2-ethylperoxy-2-oxoacetate, 1,6-bis(thioalkyl) hexane-3,4-dione, trifluoroacetic anhydride, pentafluoropropionic anhydride, 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) carbonate, tris(2,2,2-trifluoroethyl) borate, and tris(2,2,2-trifluoroethyl) orthoformate. When present, the at least one other compound may constitute from greater than 0% by weight, optionally greater than or equal to 1%, optionally greater than or equal to 10%, optionally greater than or equal to 20%, or optionally greater than or equal to 30%, and less than 50% of the oxalate-based additive.

[0047] The negative electrode current collector 30 and the positive electrode current collector 32 are conductive and provide electrical connections between the external circuit 36 and the negative electrode 22 and the positive electrode 24, respectively. In some aspects, the negative electrode current collector 30 and the positive electrode current collector 32 can be made of metal and can be in the form of a non-porous metal foil, a perforated metal foil, a porous metal mesh, or a combination thereof. The negative electrode current collector 30 can be made of copper, nickel, or an alloy thereof, stainless steel, or other suitable conductive materials. The positive electrode current collector 32 can be made of aluminum (Al) or another suitable conductive material.

[0048] Test

[0049] Full coin cell units including different electrolyte formulations were assembled and evaluated using a constant current charge and discharge protocol. All cell units included a negative electrode composed of an electroactive material consisting of a mixture of 5.5 wt% silicon oxide, graphite, conductive particles, and a polymer binder. All cell units included a positive electrode that included an electroactive material consisting of Li2MnO3, conductive particles, and a polymer binder. A control electrolyte was prepared, which consisted of 1.2 mol LiPF6 in a mixture of FEC and DEC (FEC:DEC = 1:4 volume / volume). Electrolytes according to embodiments of the present disclosure were prepared by adding 0.5 wt% bis(2,2,2-trifluoroethyl) oxalate (BEFEO) or 1 wt% BEFEO to the control electrolyte.

[0050] Cell units including the control electrolyte, the 0.5 wt% BEFEO electrolyte, or the 1 wt% BEFEO electrolyte were charged and discharged at a constant current at 25°C. During formation, the cell units were charged to 4.5 V at a C / 20 rate. Then, the battery was charged to a potential of about 4.4 V at a constant current using a C / 3 charge rate using a constant current and constant voltage (CCCV) protocol, and then charged at a constant voltage at 4.4 V until the current reached C / 20. Subsequently, the cell units were discharged to 2.0 V at a constant current using a C / 3 discharge rate.

[0051] Cells containing 0.5 wt% BEFEO electrolyte have a higher capacity retention rate than cells containing a control electrolyte. After about 100 cycles, cells containing 0.5 wt% BEFEO electrolyte have a capacity retention rate greater than about 97.5%, while cells containing the control electrolyte have a capacity retention rate less than about 87.5%. After about 80 cycles, cells containing the control electrolyte and cells containing 1 wt% BEFEO electrolyte have substantially similar capacity retention levels (i.e., less than about 88%). Between cycles 1 - 60, the discharge capacity of cells containing 0.5 wt% BEFEO electrolyte and cells containing 1 wt% BEFEO electrolyte is less than the discharge capacity of cells containing the control electrolyte. After about 100 cycles, the discharge capacity of cells containing 0.5 wt% BEFEO electrolyte is greater than the discharge capacity of cells containing the control electrolyte.

[0052] The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Thus, while the disclosure includes specific examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon study of the drawings, the specification, and the appended claims. It should be understood that one or more steps in a method can be performed in a different order (or simultaneously) without changing the principles of the disclosure. Further, although each embodiment above is described as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more of the embodiments are still within the scope of the disclosure.

[0053] The terms used herein are for the purpose of describing example embodiments only and are not intended to be limiting. As used herein, the singular forms "a", "an" and "the" may also be intended to include the plural forms, unless the context clearly indicates otherwise. The terms "comprising", "including", "containing" and "having" are inclusive and thus specify the presence of the stated features, elements, components, steps, integers, operations and / or parts, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or combinations thereof. Although the open-ended terms "comprising", "including", "containing" and "having" should be understood as non-limiting terms for describing and claiming the various embodiments set forth herein, in some aspects, these terms may alternatively be understood as more restrictive and limiting terms, such as "consisting of" or "consisting essentially of". Thus, for any given embodiment that recites a composition, material, component, element, ingredient, feature, integer, operation and / or process step, the present disclosure also specifically includes embodiments consisting of or consisting essentially of these recited compositions, materials, components, elements, ingredients, features, integers, operations and / or process steps. In the case of "consisting of", alternative embodiments do not include any additional compositions, materials, components, elements, ingredients, features, integers, operations and / or process steps, while in the case of "consisting essentially of", any additional compositions, materials, components, elements, features, integers, operations and / or process steps that materially affect the basic and novel features are not included in such embodiments, but any compositions, materials, components, elements, ingredients, features, integers, operations and / or process steps that do not materially affect the basic and novel features may be included in the embodiment.

[0054] As used herein, the phrase "at least one of A, B, and C" should be construed to represent the logic (A or B or C) using a non-exclusive logical OR and should not be construed to mean "at least one A, at least one B, and at least one C".

[0055] As used herein, the terms "composition" and "material" are used interchangeably and generally refer to a substance that includes at least a preferred chemical component, element or compound, but may also include additional elements, compounds or substances, including trace impurities, unless otherwise specified. A "composition or material based on X" broadly refers to a composition or material in which "X" is the weight percentage (%) of the single largest component of the composition or material. This can include compositions or materials having more than 50% by weight of X, as well as compositions or materials having less than 50% by weight of X, provided that X is the single largest component of the composition or material based on its total weight. When a composition or material is said to be "substantially free of" a substance, the composition or material may contain less than 5% by weight, optionally less than 3% by weight, optionally less than 1% by weight, or optionally less than 0.1% by weight of the substance.

Claims

1. A circulating lithium ion battery, the battery comprising: a negative electrode comprising an electroactive negative electrode material; A positive electrode comprising an electroactive positive electrode material, the electroactive positive electrode material comprising a lithium manganese-based oxide represented by the formula LiMeO2, Li2MeO3, LiMe2O4 and / or Li 1+x Me 1-x O2, where Me comprises a transition metal selected from Co, Ni, Mn, Fe, Al, and V, where Me comprises manganese (Mn) in an amount greater than or equal to 50% by weight, and where 0 < x ≤ 0.33; and An electrolyte permeates the positive electrode, the electrolyte comprising: Organic solvents; Lithium salts in organic solvents; and An oxalate-based additive in an organic solvent, the oxalate-based additive comprising at least one oxalate compound selected from the group consisting of bis(2,2,2-trifluoroethyl)oxalate, tert-butyl 2,2,2-trifluoroethyl oxalate, methyl 2,2,2-trifluoroethyl oxalate, ethyl 2,2,2-trifluoroethyl oxalate, bis(2-chloroethyl)oxalate and diethyl oxalate.

2. The battery according to claim 1, wherein The oxalate-based additive comprises at least one fluorinated oxalate compound selected from the group consisting of bis(2,2,2-trifluoroethyl)oxalate, 2,2,2-trifluoroethyl tert-butyl oxalate, 2,2,2-trifluoroethyl methyl oxalate and 2,2,2-trifluoroethyl ethyl oxalate.

3. The battery according to claim 1, wherein The oxalate-based additive constitutes greater than or equal to 0.001% and less than or equal to 10% by weight of the electrolyte.

4. The battery according to claim 1, wherein The oxalate-based additive includes bis(2,2,2-trifluoroethyl)oxalate.

5. The battery according to claim 4, wherein The bis(2,2,2-trifluoroethyl)oxalate constitutes greater than or equal to 0.1% and less than or equal to 2% by weight of the electrolyte.

6. The battery according to claim 1, wherein The oxalate-based additive further comprises at least one other compound selected from the group consisting of lithium oxalate, lithium difluorophosphate, lithium bis(oxalate)borate, lithium difluoro(oxalate)borate, lithium bis(trifluoromethanesulfonyl)imide, magnesium bis(trifluoromethanesulfonyl)imide, calcium bis(trifluoromethanesulfonyl)imide, lithium 4,5-dicyano-2-(trifluoromethyl)imidazolium, 2-methoxy-2-oxoethyl 2,2,2-trifluoroacetate, 2,2,2-trifluoroethyl trifluoroethyl) borate, tris(2,2,2-trifluoroethyl)orthoformate.

7. The battery according to claim 1, wherein The lithium salt includes lithium hexafluorophosphate (LiPF6).

8. The battery according to claim 1, wherein The organic solvent includes fluoroethylene carbonate (FEC) and diethyl carbonate (DEC).

9. The battery according to claim 1, wherein The electroactive negative electrode material includes at least one of a silicon oxide-based material and a carbon-based material.

10. The battery according to claim 1, wherein The electroactive negative electrode material comprises greater than 97% by weight lithium.

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