Electrolyte additives for batteries including lithium manganese rich positive electrodes

Abstract

The invention relates to an electrolyte additive for a battery comprising a lithium manganese rich positive electrode. A battery circulating lithium ions includes a positive electrode and an electrolyte infiltrating the positive electrode. The positive electrode comprises an electroactive material comprising a lithium-rich manganese oxide. The electrolyte comprises an organic solvent, an inorganic lithium salt, and a functional additive comprising lithium fluoride (LiF), lithium phosphate (Li3PO4), or a combination thereof.

Description

Technical Field

[0001] The present disclosure relates to electrolytes for batteries that cycle lithium ions, and more particularly to additives for electrolytes for batteries that contain layered lithium-rich manganese oxides as positive electrode materials to promote the formation of a protective interfacial layer on the surface of the positive electrode material. Background Art

[0002] The information provided in this section is intended to generally introduce the background of the present disclosure. To the extent that work currently named as inventors is described in this section, and aspects of the specification that may not have been otherwise identified as prior art at the time of filing, are not admitted, either explicitly or implicitly, as prior art to the present disclosure.

[0003] Batteries that cycle 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 lithium ion conduction between the positive electrode and the negative electrode during discharge and charge of the battery. The electrolyte can be formulated to exhibit certain desirable properties, including high ionic conductivity, high dielectric constant (related to a high ability to dissolve salts), good thermal stability, a wide electrochemical stability window, the ability to form a stable ion-conductive solid electrolyte interface on the surface of the positive electrode and / or the negative electrode, and chemical compatibility with the other components of the battery. Summary of the invention

[0004] According to one or more embodiments of the present disclosure, a battery pack for circulating lithium ions includes a positive electrode and an electrolyte immersed in the positive electrode. The positive electrode includes an electroactive material containing a lithium-rich manganese oxide. The electrolyte includes an organic solvent, an inorganic lithium salt in the organic solvent, and a functional additive in the organic solvent. The functional additive includes lithium fluoride (LiF), lithium phosphate (Li3PO4), or a combination thereof.

[0005] The functional additive may account for greater than or equal to about 0.001 wt % to less than or equal to about 10 wt % of the electrolyte.

[0006] LiF may comprise greater than or equal to about 0.001 wt % to less than or equal to about 3 wt % of the electrolyte.

[0007] Li3PO4 may comprise greater than or equal to about 0.001 wt% to less than or equal to about 3 wt% of the electrolyte.

[0008] The functional additive may not be generated in the electrolyte as a result of electrochemical decomposition of lithium difluorophosphate (LiPO 2 F 2 ).

[0009] When the battery is assembled, the functional additive may be deposited on the surface of the electroactive material of the positive electrode and form an interfacial layer thereon, which separates the physical contact between the electroactive material of the positive electrode and the electrolyte.

[0010] The battery may further include an interfacial layer formed in situ on the electroactive material of the positive electrode after initial assembly of the battery. The interfacial layer may contain the functional additive and may physically separate the electroactive material of the positive electrode from contact with the electrolyte.

[0011] The electrolyte may further include a co-additive selected from lithium carbonate (Li2CO3), lithium carboxylate (LiCO2CH3), lithium oxide (Li2O), lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (LiTDi), and combinations thereof.

[0012] The organic solvent may include linear carbonates and cyclic carbonates.

[0013] The inorganic lithium salt may be selected from 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(trifluoromethane)sulfonyl imide (LiN(CF3SO2)2), lithium bis(fluorosulfonyl) imide (LiN(FSO2)2)(LiSFI), and combinations thereof. Examples of inorganic lithium salts include lithium tetraphenylborate (LiB(C6H5)4), lithium bis(oxalato)borate (LiB(C2O4)2)(LiBOB), lithium difluorooxalatoborate (LiBF2(C2O4)), and combinations thereof.

[0014] According to one or more embodiments of the present disclosure, a battery pack for circulating lithium ions includes a positive electrode, a negative electrode, and an electrolyte immersed in the positive electrode and the negative electrode. The positive electrode includes an electroactive material containing a lithium-rich manganese oxide. The negative electrode includes an electroactive material containing silicon oxide and graphite. The electrolyte includes an organic solvent, an inorganic lithium salt in the organic solvent, and a functional additive in the organic solvent. The organic solvent includes a cyclic carbonate and a linear carbonate. The functional agent includes lithium fluoride (LiF) and lithium phosphate (Li3PO4).

[0015] Lithium fluoride may comprise greater than or equal to about 0.01 wt % to less than or equal to about 10 wt % of the electrolyte.

[0016] LiF may account for greater than or equal to about 0.001 wt % to less than or equal to about 3 wt % of the electrolyte. Li3PO4 may account for greater than or equal to about 0.001 wt % to less than or equal to about 3 wt % of the electrolyte.

[0017] LiF and Li3PO4 may not be generated in the electrolyte as products of the electrochemical decomposition of lithium difluorophosphate (LiPO2F2).

[0018] When assembling the battery pack, the functional additive may be deposited on the surface of the electroactive material of the positive electrode and form a first interface layer thereon, the first interface layer separating the physical contact between the electroactive material of the positive electrode and the electrolyte. In addition, when assembling the battery pack, the functional additive may be deposited on the surface of the electroactive material of the negative electrode and form a second interface layer thereon, the second interface layer separating the physical contact between the electroactive material of the negative electrode and the electrolyte.

[0019] The battery pack may further include a first interface layer disposed on the electroactive material of the positive electrode and a second interface layer disposed on the electroactive material of the negative electrode. The first interface layer may physically separate the contact between the electroactive material of the positive electrode and the electrolyte. The second interface layer may physically separate the contact between the electroactive material of the negative electrode and the electrolyte. The first interface layer and the second interface layer may be formed in situ after the battery pack is assembled. The first interface layer and the second interface layer may not contain decomposition products of lithium difluorophosphate (LiPO2F2).

[0020] The electrolyte may further include a co-additive selected from lithium carbonate (Li2CO3), lithium carboxylate (LiCO2CH3), lithium oxide (Li2O), lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (LiTDi), and combinations thereof.

[0021] The organic solvent may include fluoroethylene carbonate (FEC) and diethyl carbonate (DEC).

[0022] The inorganic lithium salt may include lithium hexafluorophosphate (LiPF6).

[0023] The electroactive material of the positive electrode may include Li2MnO3.

[0024] The present invention discloses the following scheme:

[0025] Solution 1. A circulating lithium ion battery pack, the battery pack comprising:

[0026] a positive electrode comprising an electroactive material comprising a lithium-rich manganese oxide; and

[0027] An electrolyte infiltrated into the positive electrode, the electrolyte comprising:

[0028] Organic solvents;

[0029] an inorganic lithium salt in the organic solvent; and

[0030] The functional additive in the organic solvent comprises lithium fluoride (LiF), lithium phosphate (Li3PO4) or a combination thereof.

[0031] Option 2. The battery pack according to Option 1, wherein the functional additive accounts for greater than or equal to about 0.001 wt % to less than or equal to about 10 wt % of the electrolyte.

[0032] Option 3. The battery pack according to Option 1, wherein LiF accounts for greater than or equal to about 0.001 wt % to less than or equal to about 3 wt % of the electrolyte.

[0033] Option 4. A battery pack according to Option 1, wherein Li3PO4 accounts for greater than or equal to about 0.001 wt% to less than or equal to about 3 wt% of the electrolyte.

[0034] Option 5. The battery pack according to Option 1, wherein the functional additive is not generated in the electrolyte as a product of electrochemical decomposition of lithium difluorophosphate (LiPO2F2).

[0035] Option 6. A battery pack according to Option 1, wherein when the battery pack is assembled, the functional additive is deposited on the surface of the electroactive material of the positive electrode and forms an interface layer thereon, wherein the interface layer separates the physical contact between the electroactive material of the positive electrode and the electrolyte.

[0036] Solution 7. The battery pack according to Solution 1, further comprising:

[0037] an interfacial layer formed in situ on the electroactive material of the positive electrode after initial assembly of the battery,

[0038] The interfacial layer contains the functional additive and physically separates the contact between the electroactive material of the positive electrode and the electrolyte.

[0039] Option 8. A battery pack according to Option 1, wherein the electrolyte further comprises a co-additive, and the co-additive is selected from lithium carbonate (Li2CO3), lithium carboxylate (LiCO2CH3), lithium oxide (Li2O), lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (LiTDi), and combinations thereof.

[0040] Embodiment 9. The battery pack according to embodiment 1, wherein the organic solvent comprises a linear carbonate and a cyclic carbonate.

[0041] Embodiment 10. The battery pack according to Embodiment 1, wherein the inorganic lithium salt is selected from 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(trifluoromethane)sulfonyl imide (LiN(CF3SO2)2), lithium bis(fluorosulfonyl)imide (LiN(FSO2)2)(LiSFI), and combinations thereof. Examples of inorganic lithium salts include lithium tetraphenylborate (LiB(C6H5)4), lithium bis(oxalato)borate (LiB(C2O4)2)(LiBOB), lithium difluorooxalatoborate (LiBF2(C2O4)), and combinations thereof.

[0042] Solution 11. A circulating lithium ion battery pack, the battery pack comprising:

[0043] a positive electrode comprising an electroactive material comprising a lithium-rich manganese oxide;

[0044] a negative electrode comprising an electroactive material comprising silicon oxide and graphite;

[0045] An electrolyte infiltrated into the positive electrode and the negative electrode, the electrolyte comprising:

[0046] Organic solvents containing cyclic carbonates and linear carbonates;

[0047] an inorganic lithium salt in the organic solvent; and

[0048] The functional additive in the organic solvent comprises lithium fluoride (LiF) and lithium phosphate (Li3PO4).

[0049] Embodiment 12. The battery pack according to Embodiment 11, wherein lithium fluoride accounts for greater than or equal to about 0.01 weight % and less than or equal to about 10 weight % of the electrolyte.

[0050] Option 13. A battery pack according to Option 11, wherein LiF accounts for greater than or equal to about 0.001 wt. % to less than or equal to about 3 wt. % of the electrolyte, and wherein Li3PO4 accounts for greater than or equal to about 0.001 wt. % to less than or equal to about 3 wt. % of the electrolyte.

[0051] Option 14. A battery pack according to Option 13, wherein LiF and Li3PO4 are not generated in the electrolyte as products of the electrochemical decomposition of lithium difluorophosphate (LiPO2F2).

[0052] Option 15. A battery pack according to Option 11, wherein, when assembling the battery pack, the functional additive can be deposited on the surface of the electroactive material of the positive electrode and form a first interface layer thereon, and the first interface layer separates the physical contact between the electroactive material of the positive electrode and the electrolyte, and wherein, when assembling the battery pack, the functional additive is deposited on the surface of the electroactive material of the negative electrode and forms a second interface layer thereon, and the second interface layer separates the physical contact between the electroactive material of the negative electrode and the electrolyte.

[0053] Solution 16. The battery pack according to solution 11, further comprising:

[0054] a first interface layer disposed on the electroactive material of the positive electrode, the first interface layer physically separating the electroactive material of the positive electrode from contact with the electrolyte; and

[0055] a second interface layer disposed on the electroactive material of the negative electrode, the second interface layer physically separating the electroactive material of the negative electrode from contact with the electrolyte,

[0056] wherein the first interface layer and the second interface layer are formed in situ after the battery pack is assembled, and

[0057] The first interface layer and the second interface layer do not contain decomposition products of lithium difluorophosphate (LiPO2F2).

[0058] Option 17. A battery pack according to Option 11, wherein the electrolyte further comprises a co-additive, and the co-additive is selected from lithium carbonate (Li2CO3), lithium carboxylate (LiCO2CH3), lithium oxide (Li2O), lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (LiTDi), and combinations thereof.

[0059] Embodiment 18. The battery pack according to embodiment 11, wherein the organic solvent comprises fluoroethylene carbonate (FEC) and diethyl carbonate (DEC).

[0060] Embodiment 19. A battery pack according to Embodiment 11, wherein the inorganic lithium salt comprises lithium hexafluorophosphate (LiPF6).

[0061] Option 20. A battery pack according to Option 11, wherein the electroactive material of the positive electrode comprises Li2MnO3.

[0062] Further areas of applicability of the present disclosure will become apparent from the detailed description, claims and drawings.The detailed description and specific examples are intended to be illustrative only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The present disclosure will be more fully understood through the detailed description and accompanying drawings, in which:

[0064] Figure 1 is a schematic perspective view of a motor vehicle powered by a battery pack including a plurality of battery modules.

[0065] Figure 2 yes Figure 1 Schematic cross-sectional view of a portion of one of a battery module comprising a plurality of electrochemical cells or batteries that circulate lithium ions.

[0066] Figure 3 is a schematic cross-sectional view of a battery stack for cycling lithium ions, the battery stack including a positive electrode, a negative electrode, a porous separator, and an electrolyte that permeates the pores of the positive and negative electrodes and the porous separator.

[0067] Figure 4 is a graph of capacity retention (%) versus cycle number for coin cells including a control electrolyte (dashed line), a 0.05 wt % LiF electrolyte (dashed line), a 0.2 wt % LiF electrolyte (dotted line), and a 1 wt % LiF electrolyte (solid line).

[0068] Among the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION

[0069] The electrolyte disclosed herein is formulated for use in cycling lithium-ion batteries and comprises a layered lithium-rich manganese oxide (LMR) as a positive electrode material that can operate at ultra-high voltages (e.g., relative to Li + / Li>4.5V). The electrolyte disclosed in the present invention comprises functional additives of lithium fluoride (LiF) and lithium phosphate (Li3PO4), which are formulated to be deposited on the surface of the positive electrode and the negative electrode material and form a protective interface layer thereon. The protective interface layer formed by the functional additive helps to separate the physical contact between the positive electrode and the negative electrode material and the electrolyte, which can help improve the cycle stability and capacity retention of the battery pack, for example, by preventing undesirable chemical reactions between the positive electrode and the negative electrode material and the electrolyte during the cycle of the battery pack.

[0070] Figure 1 A motor vehicle 2 is depicted that is powered by an electric motor 4 that draws power from a battery pack 6 that includes one or more battery modules 8. The battery modules 8 may be electrically connected together in a series and / or parallel arrangement 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).

[0071] like Figure 2 As shown in , each battery module 8 includes one or more electrochemical cells or batteries 10 that circulate lithium ions. In practice, the batteries 10 in the battery module 8 are often assembled as stacked layers, and the battery 10 includes 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 a negative electrode layer 12 and a positive electrode layer 14, which are separated from each other by a separator layer 16. The negative electrode layer 12 is disposed on and electrically connected to the negative electrode current collector 13, while the positive electrode layer 14 is disposed on and electrically connected to the positive electrode current collector 15. As shown in Figure 2 As shown in , for efficiency, the layers may be stacked so that some of the negative electrode current collectors 13 and the positive electrode current collectors 15 are double-sided and contain negative electrode layers 12 or positive electrode layers 14 on both sides thereof. 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.

[0072] Figure 3 An electrochemical cell or battery 20 of circulating lithium ions is depicted. The battery 20 can generate an electric current during discharge that can be used to power a load device (e.g., an electric motor 4), and can be recharged by connection to a power source. Figure 1 and Figure 2Similar to the battery pack 10 depicted in FIG. 2 , in some aspects, the battery pack 20 may be used to power the electric motor 4 of the motor vehicle 2. Additionally or alternatively, the battery pack 20 may be used in other transportation applications (e.g., motorcycles, boats, tractors, buses, motorbikes, mobile homes, campers, tanks, and aircraft), and may be used to power stationary and / or mobile electronic devices, components, and devices used in various other industries and applications, including, by way of non-limiting example, industrial, residential and commercial construction, consumer products, industrial equipment and machinery, agricultural or farm equipment, and heavy machinery.

[0073] The battery 20 includes a negative electrode 22, a positive electrode 24, a separator 26, and an electrolyte 28 that wets the surfaces of the negative electrode 22, the positive electrode 24, and the separator 26. The negative electrode 22 is disposed on a negative electrode current collector 30, and the positive electrode 24 is disposed on a 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 12) via an external circuit 36. The negative electrode 22 and the positive electrode 24 are configured so 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 a spontaneous redox reaction within the battery 20 and the release of lithium ions and electrons at 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, and the electrons move 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 20 can be charged by connecting the negative electrode 22 and the positive electrode 24 to the power source 34, which drives the non-transient redox reaction 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," where a full charge event followed by a full discharge event is considered a full cycle.

[0074] The negative electrode 22 is configured to store and release lithium ions during charging and discharging of the battery 20. The negative electrode 22 can be in the form of a continuous layer of material disposed on a major surface of the negative electrode current collector 30. The negative electrode 22 is configured to store and release lithium ions to facilitate charging and discharging of the battery 20, respectively. To achieve this, the negative electrode 22 includes one or more electrochemically active (electroactive) materials that can facilitate the storage and release of lithium ions by undergoing a reversible redox reaction with lithium during charging and discharging of the battery 20. Examples of electroactive materials for the negative electrode 22 include lithium, lithium-based materials, lithium alloys (e.g., alloys of lithium and silicon, aluminum, indium, tin, or combinations thereof), carbon-based materials (e.g., graphite, activated carbon, carbon black, hard carbon, soft carbon, and / or graphene), silicon, silicon-based materials (e.g., silicon oxide, alloys of silicon and tin, iron, aluminum, cobalt, or combinations thereof, and / or composites of silicon and / or silicon oxide and carbon), tin oxide, aluminum, indium, zinc, germanium, silicon oxide, lithium silicon oxide, lithium silicide, titanium oxide, lithium titanate, and combinations thereof.

[0075] In some aspects, the negative electrode 22 can be in the form of a non-porous metal film or foil, such as a lithium metal film or lithium metal foil. In other aspects, the negative electrode 22 can be porous, and the electroactive material of the negative electrode 22 can be a granular material. In such cases, the particles of the electroactive material of the negative electrode 22 can be mixed with a polymer binder and / or a conductive material. The polymer binder can provide structural integrity for the negative electrode 22. Examples of polymer 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 butylene styrene copolymer (SEBS), polyacrylates, alginate, polyacrylic acid and combinations thereof. Conductive materials can provide good conductivity for the negative electrode 22. 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), graphene (e.g., graphene nanosheets GNP), graphene oxide, carbon nanotubes (CNT), and / or carbon fibers (e.g., carbon nanofibers). Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, and / or polypyrrole. In some aspects, the negative electrode 22 may include a conductive material that includes carbon black.

[0076] The positive electrode 24 is configured to store and release lithium ions during discharge and charge of the battery pack 20. The positive electrode 24 may be in the form of a continuous porous layer disposed on a major surface of the positive electrode current collector 20. The positive electrode 24 includes one or more electrochemically active (electroactive) materials that can undergo a reversible redox reaction with lithium at an electrochemical potential higher than that of the electroactive material of the negative electrode 22, such that an electrochemical potential difference exists between the positive electrode 12 and the negative electrode 14. For example, the electroactive material of the positive electrode 24 may include an intercalation host material capable of reversible insertion or embedding of lithium ions. In such cases, the electroactive material of the positive electrode 24 may include a layered oxide represented by the formula LiMeO2 and / or Li2MeO3, a layered oxide represented by the formula Li 1+x Me 1-x O2 (where 0 < x ≤ 0.33), a layered lithium-rich oxide represented by the formula LiMePO4, an olivine-type oxide represented by the formula Li3Me2(PO4)3, a spinel-type oxide represented by the formula LiMe2O4, a hydroxyapatite represented by one or both of the following formulas LiMeSO4F or LiMePO4F, or a combination thereof, wherein Me is a transition metal (e.g., Co, Ni, Mn, Fe, Al, V, or a combination thereof). The electroactive material of the positive electrode 24 may account for greater than or equal to about 80% by weight, optionally about 90% by weight, optionally about 95% by weight to less than or equal to about 99% by weight, or optionally about 98% by weight of the positive electrode 24.

[0077] In some aspects, the electroactive material of positive electrode 24 may include a material having the formula Li 1+x Me 1-x O2 (where 0 < x ≤ 0.33) based on a layered lithium-rich manganese transition metal oxide, wherein Me contains greater than or equal to about 50 wt % manganese (Mn). In some aspects, the electroactive material of the positive electrode 24 may include a layered lithium-rich manganese oxide represented by the formula Li2MnO3 (LMR). In some aspects, the electroactive material of the positive electrode 24 may include a layered lithium-rich manganese oxide represented by the formula Li 1+x Me 1-x O2 (where 0 < x ≤ 0.33) represented by a layered lithium-rich nickel-based transition metal oxide, wherein Me contains greater than or equal to about 50 wt % nickel (Ni). In some aspects, the electroactive material of the positive electrode 24 may include lithium manganese iron phosphate (LMFP), lithium iron phosphate (LFP), spinel lithium manganese oxide (LiMn2O4, LMO), high voltage spinel (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 Mn1.5 O4 and / or Li 1.2 Ni 0.2 Mn 0.6 O2), lithium nickel cobalt aluminum oxide (NCA), or a combination thereof.

[0078] Similar to the electroactive material of the negative electrode 22, the electroactive material of the positive electrode 24 may be a granular material, and the particles of the electroactive material of the positive electrode 24 may be mixed with particles of a polymer binder and / or a conductive material. The same polymer binder and / or conductive material disclosed above with respect to the negative electrode 22 may be used in the positive electrode 24. In some aspects, the positive electrode 24 may include a polymer binder comprising polyvinylidene fluoride.

[0079] The separator 26 physically separates and electrically separates the negative electrode 22 and the positive electrode 24 from each other, while allowing lithium ions to pass therethrough. The separator 26 has an open microporous structure and may include organic and / or inorganic materials. For example, the separator 26 may include a combination of one polymer or multiple polymers. For example, the separator 26 may include one or more polyolefins, such as polyethylene (PE), polypropylene (PP), polyamide (PA), poly(tetrafluoroethylene) (PTFE), polyvinylidene fluoride (PVdF) and / or poly(vinyl chloride) (PVC). In one form, the separator 26 may include a laminate of polymers, such as a laminate of PE and PP. In some 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 include particles of aluminum oxide (Al2O3) and / or silicon dioxide (SiO2).

[0080] The electrolyte 28 is ionically conductive, provides a medium for the conduction of lithium ions between the negative electrode 22 and the positive electrode 24, and is formulated to provide enhanced cycling stability to the battery 20. The electrolyte 28 includes an organic solvent, an inorganic lithium salt, a functional additive, and optional co-additives. Figure 3 As shown in , the functional additives and optional co-additives are formulated to assist in forming a first interfacial layer 38 on a surface 40 of the negative electrode 22 and a second interfacial layer 42 on a surface 44 of the positive electrode 24 .

[0081] The organic solvent may include a non-aqueous aprotic organic solvent or a mixture of a plurality of non-aqueous aprotic organic solvents. Non-limiting examples of non-aqueous aprotic organic solvents include cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC)), linear carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC)), aliphatic carboxylates (e.g., methyl formate, methyl acetate, methyl propionate), γ-lactones (e.g., γ-butyrolactone, γ-valerolactone), chain structure ethers (e.g., 1,2-dimethoxyethane, 1-2-diethoxyethane, ethoxymethoxyethane), cyclic ethers (e.g., tetrahydrofuran, 2-methyltetrahydrofuran), 1,3-dioxolane) and combinations thereof. The organic solvent may account for greater than or equal to about 70 wt % to less than or equal to about 90 wt % of the electrolyte 28. In some aspects, the organic solvent may include a mixture of cyclic carbonates and linear carbonates. For example, the organic solvent may include a mixture of FEC and DEC. In such cases, the volume ratio of FEC to DEC in the organic solvent may be about 1:4.

[0082] Inorganic lithium salts are soluble in organic solvents and provide pathways for lithium ions to pass through electrolyte 28. Examples of inorganic lithium salts 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(trifluoromethane)sulfonyl imide (LiN(CF3SO2)2), lithium bis(fluorosulfonyl)imide (LiN(FSO2)2)(LiSFI), and combinations thereof. The lithium salt may be dissolved in the organic solvent at a concentration of greater than or equal to about 0.5 molar to less than or equal to about 1.5 molar. In some aspects, the lithium salt may be dissolved in the organic solvent at a concentration of about 1 molar. The lithium salt may account for greater than or equal to about 5 wt% to less than or equal to about 20 wt% of the electrolyte 28. In some aspects, the lithium salt can comprise LiPF6.

[0083] The functional additive is formulated to be deposited on the surface 40 of the negative electrode 22 and the surface 44 of the positive electrode 24 to assist in forming the first interface layer 38 and the second interface layer 42. After assembly of the battery pack 20, the first interface layer 38 and the second interface layer 42 may be inherently formed in situ on the surface 40 of the negative electrode 22 and the surface 44 of the positive electrode 24, respectively.

[0084] The functional additive comprises lithium fluoride (LiF), lithium phosphate (Li3PO4) or a combination thereof. The functional additive may account for greater than or equal to about 0.001 wt%, optionally about 0.01 wt%, optionally about 0.1 wt% to less than or equal to about 10 wt%, optionally about 5 wt%, or optionally about 3 wt% of the electrolyte 28. In some aspects, the functional additive may account for about 1 wt% of the electrolyte 28. LiF may account for greater than or equal to about 0.001 wt%, optionally about 0.01 wt%, optionally about 0.1 wt% to less than or equal to about 10 wt%, optionally about 5 wt%, or optionally about 3 wt% of the electrolyte 28. In some aspects, LiF may account for about 1 wt% of the electrolyte 28. Li3PO4 may account for greater than or equal to about 0.001 wt%, optionally about 0.01 wt%, optionally about 0.1 wt% to less than or equal to about 10 wt%, optionally about 5 wt%, or optionally about 3 wt% of the electrolyte 28. In some aspects, Li 3 PO 4 can comprise about 1 wt % of electrolyte 28 .

[0085] LiF and Li3PO4 may be substantially insoluble in organic solvents and may be deposited on the surface 40 of the negative electrode 22 and the surface 44 of the positive electrode 24 without undergoing an electrochemical decomposition reaction within the battery 20. In addition, LiF and Li3PO4 may be present within the electrolyte 28 after initial assembly of the battery 20 and prior to initial charging of the battery 20. In particular, LiF and Li3PO4 are not generated in the electrolyte 28 as a product of the electrochemical decomposition of lithium difluorophosphate (LiPO2F2).

[0086] When LiPO2F2 is used as an electrolyte additive in a battery (e.g., battery 20) that cycles lithium ions, it is believed that the LiPO2F2 electrochemically decomposes within the battery 20 and generates LiF and Li3PO4, as well as undesirable hydrogen fluoride (HF). It has been found that the generation of HF in a battery (e.g., battery 20) that cycles lithium ions degrades the electrochemical performance of the positive electrode 24 by, for example, decomposing the electroactive materials thereof, which can lead to a cascade of deleterious effects. In addition, although LiPO2F2 can advantageously lead to the generation of LiF and / or Li3PO4 in the electrolyte 28 and thereby assist in the formation of the first interface layer 38 and the second interface layer 42, LiPO2F2 has a relatively low solubility in organic carbonate solvents, which limits the amount of LiPO2F2 that can be effectively added to the electrolyte 28, and thus limits the amount of LiF and / or Li3PO4 that can be generated therefrom.

[0087] Unlike LiPO2F2, LiF and / or Li3PO4 can be directly deposited on the surface 40 of the negative electrode 22 and the surface 44 of the positive electrode 24 without first undergoing an electrochemical decomposition reaction within the battery 20. In addition, LiF and / or Li3PO4 can participate in the formation of the first interface layer 38 and the second interface layer 42 without generating HF. In addition, without wishing to be bound by theory, it is believed that the inclusion of LiF in the electrolyte 28 can inhibit the hydrolysis of the lithium salt LiPF6, which can further inhibit the generation of HF within the battery 20. In addition to or as an alternative to LiPO2F2, LiF and / or Li3PO4 can be included in the electrolyte 28.

[0088] The first interface layer 38 and the second interface layer 42 include LiF and / or Li3PO4. The first interface layer 38 and the second interface layer 42 are electrically insulating and ionically conductive and are configured to help prevent undesirable chemical reactions from occurring between the electrolyte 28 and the respective negative electrode 22 and positive electrode 24 during cycling of the battery 20. For example, after the first interface layer 38 and the second interface layer 42 are formed on the surface 40 of the negative electrode 22 and the surface 44 of the positive electrode 24, respectively, the first interface layer 38 and the second interface layer 42 can help prevent chemical reactions from occurring between components of the electrolyte 28 and the negative electrode 22 and the positive electrode 24 during charging and / or discharging of the battery 20. Without wishing to be bound by theory, it is believed that the formation of the first interface layer 38 and the second interface layer 42 can help prevent undesirable chemical reactions from occurring between the electrolyte 28 and the respective negative electrode 22 and positive electrode 24 without hindering the flow of lithium ions between the electrolyte 28 and the negative electrode 22 and the positive electrode 24.

[0089] exist Figure 3 , the first interface layer 38 is depicted as being disposed along the interface between the negative electrode 22 and the separator 26, and the second interface layer 42 is depicted as being disposed along the interface between the positive electrode 24 and the separator 26; however, other arrangements are possible. For example, in some aspects, the electroactive materials of the negative electrode 22 and the positive electrode 24 are in the form of granular materials, and the first interface layer 38 can extend at least partially into the negative electrode 22 (toward the negative electrode current collector 30) and can be disposed on the surface of one or more electroactive material particles of the negative electrode 22. Similarly, in some aspects, the second interface layer 42 can extend at least partially into the positive electrode 24 (toward the positive electrode current collector 32) and can be disposed on the surface of one or more electroactive material particles of the positive electrode 24.

[0090] The optional co-additive is formulated to assist in forming the first interface layer 38 and / or the second interface layer 42. The optional co-additive may include lithium carbonate (Li2CO3), lithium carboxylate (LiCO2R) (e.g., lithium acetate, LiCO2CH3), lithium oxide (Li2O), lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)borate (C2BF2LiO4, LiDFOB), lithium bis(oxalato)borate (C4BLiO8, LiBOB), 4,5-dicyano-2-(trifluoromethyl)imidazolium lithium (C6F3LiN4, LiTDi), or a combination thereof. The optional co-additive may comprise greater than or equal to about 0.01 wt % to less than or equal to about 3 wt % of the electrolyte 28.

[0091] The positive electrode current collector 30 and the negative electrode current collector 32 are conductive and provide electrical connections between the external circuit 36 ​​and their respective positive electrode 22 and negative electrode 24. In some aspects, the positive electrode current collector 30 and the negative electrode current collector 32 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 material. The positive electrode current collector 32 can be made of aluminum (Al) or another suitable conductive material.

[0092] experiment

[0093] Entire button cells containing different electrolyte formulations were assembled and evaluated using a constant current charge and discharge scheme. All batteries included a negative electrode consisting of the following materials: an electroactive material consisting of a mixture of graphite and silicon oxide, conductive particles, and a polymer binder. All batteries included a negative electrode consisting of the following materials: an electroactive material consisting of Li2MnO3, conductive particles, and a polymer binder. A comparative electrolyte consisting of the following items was prepared: 1.2 moles of 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 0.05 wt% LiF, 0.2 wt% LiF, or 1 wt% LiF to the comparative electrolyte.

[0094] Cells including a comparative electrolyte, a 0.05 wt% LiF electrolyte, a 0.2 wt% LiF electrolyte, or a 1 wt% LiF electrolyte were charged and discharged at 25°C constant current. During formation, the cell was charged to 4.5V at a C / 20 rate. Then, a constant current and constant voltage (CCCV) protocol was used to charge the cell to a potential of about 4.4V at a constant current using a C / 3 charge rate, and then charged at a constant voltage at 4.4V until the current reached C / 20. The cell was subsequently discharged to 2.0V at a constant current using a C / 3 discharge rate.

[0095] Figure 4 is a graph of capacity retention (%) 100 vs. cycle number 200 of batteries including a comparative electrolyte (dashed line), a 0.05 wt % LiF electrolyte (dashed line), a 0.2 wt % LiF electrolyte (dotted line), and a 1 wt % LiF electrolyte (solid line). Figure 4 As shown in , the battery including the LiF-containing electrolyte exhibits a higher capacity retention rate than the battery including the comparative electrolyte.

[0096] The foregoing description is essentially only exemplary and is absolutely not intended to limit the present disclosure, its application or use. The broad teachings of the present disclosure can be implemented in various forms. Therefore, although the present disclosure includes specific examples, the true scope of the present disclosure should not be limited thereto, because after studying the drawings, the specification and the following claims, other modifications will become apparent. It should be understood that one or more steps in the method may be implemented in different orders (or simultaneously) without changing the principles of the present disclosure. In addition, although each embodiment is described above as having certain features, any one or more features described with respect to any embodiment of the present disclosure may be implemented in any other embodiment and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the embodiments are not mutually exclusive, and the mutual replacement of one or more embodiments is still within the scope of the present disclosure.

[0097] The terms used herein are intended to be limited only for the purpose of describing exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms "one" and "the" used herein are intended to also include plural forms. The terms "comprising", "including" and "having" are inclusive, and therefore specify the presence of specified features, elements, compositions, steps, integers, operations and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their combinations. Although the open terms "comprising", "including" and "having" should be understood as non-limiting terms for describing and requesting the various embodiments described herein, in some aspects, these terms are understood as more restrictive and constraining terms, such as "consisting of..." or "consisting essentially of..." Therefore, for any given embodiment of a composition, material, component, element, ingredient, feature, integer, operation and / or method step, the present disclosure also clearly includes an embodiment consisting of or essentially consisting of these enumerated compositions, materials, components, elements, ingredients, features, integers, operations and / or method steps. In the case of “consisting of,” the alternative embodiment does not include any additional compositions, materials, components, elements, ingredients, features, integers, operations and / or method steps, while in the case of “consisting essentially of,” such an embodiment does not include any additional compositions, materials, components, elements, ingredients, features, integers, operations and / or method steps that substantially affect the basic and novel characteristics, but may include any compositions, materials, components, elements, ingredients, features, integers, operations and / or method steps that do not substantially affect the basic and novel characteristics in the embodiment.

[0098] Any method steps, methods, and operations described herein are not to be construed as necessarily requiring their performance in the order discussed or illustrated, unless expressly specified as an order of performance. It is also to be understood that additional or alternative steps may be used unless otherwise specified.

[0099] When a component, element, or layer is referred to as being "on," "engaged," "connected," or "coupled" to another element or layer, it may be directly on, directly engaged, connected, or coupled to, or there may be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly engaged," "directly connected," or "directly coupled" to another element or layer, there may be no intervening elements or layers. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" vs. "directly between," "adjacent" vs. "directly adjacent," etc.). The term "and / or" as used herein includes a combination of one or more related enumerated items.

[0100] Unless otherwise indicated, although the term first, second, third etc. can be used to describe various steps, elements, components, regions, layers and / or parts in this article, these steps, elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish a step, element, component, region, layer or part from another step, element, component, region, layer or part. Unless the context clearly indicates, when using terms such as "first", "second" and other numerical terms in this article, order or sequence are not implied. Therefore, without departing from the teaching of the exemplary embodiment, the first step, element, component, region, layer or part discussed below can be referred to as the second step, element, component, region, layer or part.

[0101] For ease of description, spatially relative terms such as "before", "after", "inside", "outside", "below", "below", "lower", "above", "upper", etc. may be used herein to describe the relationship of one element or feature to another element or feature, as shown in the figures. The spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures.

[0102] Throughout this disclosure, numerical values ​​represent approximate measurements or limits to ranges, and encompass minor deviations from given values ​​and embodiments, with approximately the values ​​mentioned and with the exact values ​​mentioned. In addition to the working examples provided at the end of the specific embodiments, the numerical values ​​of the parameters (e.g., quantities or conditions) in this specification should be understood in all cases as being modified by the term "about" in each corresponding instance, regardless of whether "about" actually appears before the numerical value. "About" means that the specified numerical value allows some slight imprecision (making the value accurate by some method; approximately or quite close to the value; almost). If the imprecision provided by "about" is not understood in the art with this common meaning, the "about" used herein at least indicates the changes that may be produced by the common methods of measuring and using such parameters. For example, "about" can include changes that are less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some aspects, optionally less than or equal to 0.1%. Additionally, the disclosure of ranges includes disclosure of individual values ​​and further subdivided ranges within the entire range, including the endpoints and sub-ranges given for the ranges.

[0103] As used herein, the terms "composition" and "material" are used interchangeably to refer broadly to a substance containing at least a preferred chemical composition, element or compound, but unless otherwise indicated, it may also contain additional elements, compounds or substances, including trace amounts of impurities. An "X-based" composition or material broadly refers to a composition or material in which "X" is the single largest constituent of the composition or material based on a weight percentage (%). This can include compositions or materials having greater than 50 wt % X, as well as those having less than 50 wt % X, as long as X is the single largest constituent of the composition or material based on its total weight. When a composition or material is referred to as being "substantially free" of a substance, the composition or material may contain less than 5 wt %, optionally less than 3 wt %, optionally less than 1 wt %, or optionally less than 0.1 wt % of the substance.

[0104] As used herein, the term "metal" may refer to a pure elemental metal or an alloy of an elemental metal with one or more other metals or nonmetallic elements, referred to as "alloying" elements. Alloying elements may be selected to impart certain desirable properties to the alloy that are not exhibited by the base metal element.

Claims

1. A battery pack for circulating lithium ions, the battery pack comprising: a positive electrode comprising an electroactive material comprising a lithium-rich manganese oxide; a negative electrode comprising an electroactive material comprising silicon oxide and graphite; An electrolyte infiltrated into the positive electrode and the negative electrode, the electrolyte comprising: Organic solvents containing cyclic carbonates and linear carbonates; an inorganic lithium salt in the organic solvent; and The functional additive in the organic solvent comprises lithium fluoride (LiF) and lithium phosphate (Li3PO4).

2. The battery of claim 1, wherein lithium fluoride comprises greater than or equal to about 0.01 wt % to less than or equal to about 10 wt % of the electrolyte.

3. The battery of claim 1, wherein LiF comprises greater than or equal to about 0.001 wt % to less than or equal to about 3 wt % of the electrolyte, and wherein Li3PO4 comprises greater than or equal to about 0.001 wt % to less than or equal to about 3 wt % of the electrolyte.

4. The battery according to claim 3, wherein LiF and Li3PO4 are not generated in the electrolyte as products of the electrochemical decomposition of lithium difluorophosphate (LiPO2F2).

5. The battery pack according to claim 1, wherein: When assembling the battery pack, the functional additive can be deposited on the surface of the electroactive material of the positive electrode and form a first interface layer thereon, wherein the first interface layer separates the physical contact between the electroactive material of the positive electrode and the electrolyte, and wherein, when assembling the battery pack, the functional additive is deposited on the surface of the electroactive material of the negative electrode and forms a second interface layer thereon, wherein the second interface layer separates the physical contact between the electroactive material of the negative electrode and the electrolyte.

6. The battery pack according to claim 1, further comprising: a first interface layer disposed on the electroactive material of the positive electrode, the first interface layer physically separating the electroactive material of the positive electrode from contact with the electrolyte; and a second interface layer disposed on the electroactive material of the negative electrode, the second interface layer physically separating the electroactive material of the negative electrode from contact with the electrolyte, wherein the first interface layer and the second interface layer are formed in situ after the battery pack is assembled, and The first interface layer and the second interface layer do not contain decomposition products of lithium difluorophosphate (LiPO2F2).

7. The battery of claim 1, wherein the electrolyte further comprises a co-additive selected from the group consisting of lithium carbonate (Li2CO3), lithium carboxylate (LiCO2CH3), lithium oxide (Li2O), lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium 4,5-dicyano-2-(trifluoromethyl)imidazolium (LiTDi), and combinations thereof. 8 . The battery according to claim 1 , wherein the organic solvent comprises fluoroethylene carbonate (FEC) and diethyl carbonate (DEC).

9. The battery of claim 1, wherein the inorganic lithium salt comprises lithium hexafluorophosphate (LiPF6).

10. The battery of claim 1, wherein the electroactive material of the positive electrode comprises Li2MnO3.

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