Fluorinated electrolytes for battery cells including cathode electrodes with lithium and manganese rich (LMR) active materials

Abstract

The present invention relates to a fluorinated electrolyte for a battery cell comprising a cathode electrode having lithium-rich and manganese-rich (LMR) active materials. A battery cell includes a battery cell stack comprising C cathode electrodes comprising a lithium-rich and manganese-rich cathode active (LMR) material, A anode electrodes comprising an anode active material, and S separators, where C, A and S are integers greater than 1. An enclosure encloses the battery stack and the electrolyte. The electrolyte includes a mixture of a fluorinated carbonate and a fluorinated ester and a lithium salt.

Description

Technical Field

[0001] The present disclosure relates to battery pack cells, and more particularly to battery pack cells including a cathode electrode comprising a lithium- and manganese-rich cathode active material and a fluorinated electrolyte. Background Art

[0002] The information provided in this section is for a general introduction to the background of the present disclosure. The work of the currently named inventors described in this section, as well as aspects of the specification that may not be otherwise determined to be prior art at the time of filing, are not expressly or implicitly admitted to be prior art of the present disclosure.

[0003] Electric vehicles (EVs), such as battery electric vehicles (BEVs), hybrid vehicles, and / or fuel cell vehicles include one or more electric motors and a battery pack system including one or more battery pack cells, modules, and / or packs. A power control system is used to control charging and / or discharging of the battery pack system during charging and / or driving.

[0004] A battery pack cell includes a cathode electrode, an anode electrode, and a separator. The cathode electrode includes a cathode active material layer (including a cathode active material) disposed on a cathode current collector. The anode electrode includes an anode active material layer (including an anode active material) disposed on an anode current collector. Summary of the Invention

[0005] A battery pack cell includes a battery pack cell stack including C cathode electrodes, A anode electrodes, and S separators, the cathode electrodes comprising a lithium- and manganese-rich cathode active (LMR) material, the anode electrodes comprising an anode active material, where C, A, and S are integers greater than 1. A housing encapsulates the battery pack cell stack and an electrolyte. The electrolyte includes a mixture of fluorinated carbonates and fluorinated esters and a lithium salt.

[0006] In other features, the ratio of the fluorinated carbonate to the fluorinated ester is from 60:40 to 20:80 volume %. The lithium salt is from 0.5 M to 5 M. The lithium salt is from 1 M to 2 M. The lithium salt is selected from LiPF 6 、LiClO 4 、LiBF 4 、LiAsF 6 、LiTFSI, LiFSI, LiDFOB, LiBOB, LiPO 2 F 2 and combinations thereof. The fluorinated carbonate is selected from fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) carbonate, methyl 2,2,2-trifluoroethyl carbonate (FEMC), difluoroethylene carbonate (FDEC), and combinations thereof.

[0007] Among other features, the fluorinated ester is selected from ethyl 2,2,2-trifluoroacetate (TFEA), methyl pentafluoropropionate (MTFP), methyl 3,3,3-trifluoropropionate (MPFP), 2,2,2-trifluoroethyl butyrate (TFEB), and combinations thereof. The electrolyte further comprises a non-fluorinated carbonate. The ratio of the fluorinated carbonate and the fluorinated ester to the non-fluorinated carbonate is from 20:80 to 80:20% by volume. The fluorinated carbonate is selected from ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and combinations thereof.

[0008] Among other features, the anode active material is selected from silicon oxide / graphite, graphite, silicon, silicon oxide, lithium metal, and combinations thereof. The battery cell of the battery pack operates in a voltage window of 2.0 V to 5.0 V, and the charging rate of the battery cell of the battery pack is from C / 100 to 6C.

[0009] The electrolyte for a battery cell of a battery pack comprises 0.5 M to 5 M of a lithium salt; and a mixture of a fluorinated carbonate and a fluorinated ester. The ratio of the fluorinated carbonate to the fluorinated ester is from 60:40 to 20:80% by volume.

[0010] Among other features, the lithium salt is from 1 M to 2 M. The lithium salt is selected from LiPF 6 , LiClO 4 , LiBF 4 , LiAsF 6 , LiTFSI, LiFSI, LiDFOB, LiBOB, LiPO 2 F 2 and combinations thereof. The fluorinated carbonate is selected from fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) carbonate, methyl 2,2,2-trifluoroethyl carbonate (FEMC), difluoroethylene carbonate (FDEC), and combinations thereof. The fluorinated ester is selected from ethyl 2,2,2-trifluoroacetate (TFEA), methyl pentafluoropropionate (MTFP), methyl 3,3,3-trifluoropropionate (MPFP), 2,2,2-trifluoroethyl butyrate (TFEB), and combinations thereof.

[0011] The electrolyte further comprises a non-fluorinated carbonate. The ratio of the fluorinated carbonate and the fluorinated ester to the non-fluorinated carbonate is from 20:80 to 80:20% by volume. The fluorinated carbonate is selected from ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and combinations thereof.

[0012] The present invention discloses the following solutions:

[0013] Solution 1. A battery pack battery, comprising:

[0014] A battery pack battery stack, comprising:

[0015] C cathode electrodes, comprising a lithium-rich and manganese-rich cathode active (LMR) material;

[0016] A anode electrodes, comprising an anode active material; and

[0017] S separators, where C, A, and S are integers greater than 1; and

[0018] A casing, comprising the battery pack battery stack and an electrolyte,

[0019] where the electrolyte comprises a mixture of a fluorinated carbonate and a fluorinated ester and a lithium salt.

[0020] Solution 2. The battery pack battery according to Solution 1, where the ratio of the fluorinated carbonate to the fluorinated ester is 60:40 to 20:80 vol%.

[0021] Solution 3. The battery pack battery according to Solution 1, where the lithium salt is 0.5 M to 5 M.

[0022] Solution 4. The battery pack battery according to Solution 1, where the lithium salt is 1 M to 2 M.

[0023] Solution 5. The battery pack battery according to Solution 1, where the lithium salt is selected from LiPF 6 , LiClO 4 , LiBF 4 , LiAsF 6 , LiTFSI, LiFSI, LiDFOB, LiBOB, LiPO 2 F 2 and combinations thereof.

[0024] Solution 6. The battery pack battery according to Solution 1, where the fluorinated carbonate is selected from fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) carbonate, methyl 2,2,2-trifluoroethyl carbonate (FEMC), difluoroethylene carbonate (FDEC), and combinations thereof.

[0025] Solution 7. The battery pack battery according to Solution 1, where the fluorinated ester is selected from ethyl 2,2,2-trifluoroacetate (TFEA), methyl pentafluoropropionate (MTFP), methyl 3,3,3-trifluoropropionate (MPFP), ethyl 2,2,2-trifluorobutyrate (TFEB), and combinations thereof.

[0026] Solution 8. The battery pack battery according to Solution 1, where the electrolyte further comprises a non-fluorinated carbonate.

[0027] Embodiment 9. The battery cell according to Embodiment 8, wherein the ratio of the fluorinated carbonate and the fluorinated ester to the non-fluorinated carbonate is 20:80 to 80:20% by volume.

[0028] Embodiment 10. The battery cell according to Embodiment 1, wherein the fluorinated carbonate is selected from ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and combinations thereof.

[0029] Embodiment 11. The battery cell according to Embodiment 1, wherein the anode active material is selected from silicon oxide / graphite, graphite, silicon, silicon oxide, lithium metal, and combinations thereof.

[0030] Embodiment 12. The battery cell according to Embodiment 1, wherein the battery cell operates in a voltage window of 2.0 V to 5.0 V, and the charging rate of the battery cell is C / 100 to 6C.

[0031] Embodiment 13. An electrolyte for a battery cell, comprising

[0032] 0.5 M to 5 M of a lithium salt; and

[0033] a mixture of a fluorinated carbonate and a fluorinated ester,

[0034] wherein the ratio of the fluorinated carbonate to the fluorinated ester is 60:40 to 20:80% by volume.

[0035] Embodiment 14. The electrolyte according to Embodiment 13, wherein the lithium salt is 1 M to 2 M.

[0036] Embodiment 15. The electrolyte according to Embodiment 13, wherein the lithium salt is selected from LiPF 6 , LiClO 4 , LiBF 4 , LiAsF 6 , LiTFSI, LiFSI, LiDFOB, LiBOB, LiPO 2 F 2 and combinations thereof.

[0037] Embodiment 16. The electrolyte according to Embodiment 13, wherein the fluorinated carbonate is selected from fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) carbonate, methyl 2,2,2-trifluoroethyl carbonate (FEMC), difluoroethylene carbonate (FDEC), and combinations thereof.

[0038] Aspect 17. The electrolyte according to Aspect 13, wherein the fluorinated ester is selected from ethyl 2,2,2-trifluoroacetate (TFEA), methyl pentafluoropropionate (MTFP), methyl 3,3,3-trifluoropropionate (MPFP), 2,2,2-trifluoroethyl butyrate (TFEB), and combinations thereof.

[0039] Aspect 18. The electrolyte according to Aspect 13, wherein the electrolyte further comprises a non-fluorinated carbonate.

[0040] Aspect 19. The electrolyte according to Aspect 18, wherein the ratio of the fluorinated carbonate and the fluorinated ester to the non-fluorinated carbonate is 20:80 to 80:20% by volume.

[0041] Aspect 20. The electrolyte according to Aspect 18, wherein the fluorinated carbonate is selected from ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and combinations thereof.

[0042] Further applicable fields of the present disclosure will be apparent from the detailed description, the claims, and the drawings. The detailed description and the specific examples are only intended to illustrate and are not intended to limit the scope of the present disclosure. Description of the Drawings

[0043] The present disclosure will be more fully understood from the detailed description and the accompanying drawings, wherein:

[0044] Figure 1 is a side cross-sectional view of a battery cell of a battery pack stack including an anode electrode, an LMR cathode electrode, a separator, and a fluorinated electrolyte in a battery pack housing according to the present disclosure.

[0045] Figure 2 is a side cross-sectional view of an LMR cathode electrode according to the present disclosure.

[0046] Figure 3 is a side cross-sectional view of an anode electrode according to the present disclosure.

[0047] Figure 4A is a graph showing the capacity of a battery cell of a battery pack including an LMR cathode electrode using different fluorinated electrolyte mixtures as a function of cycles according to the present disclosure;

[0048] Figure 4B is a graph showing the percentage of discharge capacity retention of a battery cell of a battery pack including an LMR cathode electrode using different fluorinated electrolyte mixtures as a function of cycles according to the present disclosure;

[0049] Figure 4C is a graph showing the ionic conductivity of various fluorinated electrolyte mixtures according to the present disclosure;

[0050] Figure 5A is a graph showing the capacity of a battery cell of a battery pack including an LMR cathode electrode using different fluorinated electrolyte mixtures as a function of cycles;

[0051] Figure 5B is a graph showing the percentage of discharge capacity retention of a battery cell of a battery pack including an LMR cathode electrode using different fluorinated electrolyte mixtures as a function of cycles; and

[0052] Figure 5C is a graph showing the ionic conductivity of various fluorinated electrolyte mixtures according to the present disclosure.

[0053] In the drawings, reference numerals may be reused to designate similar and / or identical elements. Detailed Description

[0054] Although the battery cell of a battery pack according to the present disclosure is shown in the context of an electric vehicle, the battery cell of the battery pack can be used in stationary applications and / or other applications.

[0055] Compared to conventional cathode active materials such as lithium iron phosphate (LFP) and lithium nickel manganese cobalt oxide (NMC), lithium-rich and manganese-rich (LMR) cathode active materials have a higher specific capacity. However, non-fluorinated carbonate-based electrolyte solvents commonly used with LMR chemistries undergo severe decomposition at high voltages (e.g., 4.3 V or higher), resulting in poor discharge capacity retention, gas generation during cycling, and / or low Coulombic efficiency.

[0056] To improve the cycling performance of the LMR cathode when operating at higher voltages (e.g., 4.3 V or higher), the battery cell of a battery pack according to the present disclosure uses an electrolyte comprising a fluorinated solvent as a stabilizing electrolyte solvent. The fluorinated solvent includes a combination of fluorinated esters and fluorinated carbonates. A fluorinated carbonate such as fluoroethylene carbonate (FEC) can form a stable cathode electrolyte interface (CEI), while a fluorinated ester (e.g., trifluoroacetate (TFEA)) has weak coordinating ability and low viscosity, which is beneficial for good ionic conductivity.

[0057] The battery cell of a battery pack according to the present disclosure uses a combination of fluorinated esters and fluorinated carbonates to improve the capacity retention when the battery cell of the battery pack is cycled at high voltages. The concentration of the fluorinated ester in the electrolyte mixture is optimized to increase the ionic conductivity of the electrolyte without including capacity retention. The fluorinated esters and carbonates described below are compatible with the LMR cathode active material.

[0058] Now referring to Figure 1, the battery cell 10 of the battery pack includes C cathode electrodes 20, A anode electrodes 40, and S separators 32 arranged in a battery cell stack 12 of the battery pack in a predetermined order, where C, S, and A are integers greater than zero. The battery cell stack 12 is arranged in a housing 50. An electrolyte 52 containing a lithium salt and a solvent is added to the housing 50, and the solvent includes a fluorinated ester, a fluorinated carbonate, and optionally a non-chlorinated carbonate, as will be further described below. The C cathode electrodes 20-1, 20-2,..., and 20-C include a cathode active material layer 24 arranged on one or both sides of a cathode current collector 26.

[0059] During charging / discharging, the A anode electrodes 40 and the C cathode electrodes 20 exchange lithium ions. The A anode electrodes 40-1, 40-2,..., and 40-A include an anode active material layer 42 arranged on one or both sides of an anode current collector 46. In some examples, the cathode active material layer 24 and / or the anode active material layer includes a coating applied to the current collector, and the coating includes one or more active materials, one or more conductive additives, and / or one or more binder materials.

[0060] In some examples, the cathode current collector 26 and / or the anode current collector 46 includes a metal foil, a metal mesh, a perforated metal, a three-dimensional (3D) metal foam, and / or an expanded metal. In some examples, the current collector is made of one or more materials selected from copper, stainless steel, brass, bronze, zinc, aluminum, and / or their alloys. The external tabs 28 and 48 are respectively connected to the current collectors of the cathode electrode and the anode electrode, and can be arranged on the same side or different sides of the battery cell stack 12. The external tabs 28 and 48 are connected to the terminals of the battery cell stack 12.

[0061] In some examples, the electrolyte 52 includes a lithium salt and a mixture of one or more fluorinated carbonates and one or more fluorinated esters. In some examples, the lithium salt is selected from LiPF 6 , LiClO 4 , LiBF 4 , LiAsF 6 , LiTFSI, LiFSI, LiDFOB, LiBOB, LiPO 2 F 2 and combinations thereof. In some examples, the electrolyte mixture further includes one or more non-fluorinated carbonates.

[0062] Examples of fluorinated carbonates include fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) carbonate, methyl 2,2,2-trifluoroethyl carbonate (FEMC), difluoroethylene carbonate (FDEC), and combinations thereof. Examples of fluorinated esters include ethyl 2,2,2-trifluoroacetate (TFEA), methyl pentafluoropropionate (MTFP), methyl 3,3,3-trifluoropropionate (MPFP), ethyl 2,2,2-trifluorobutyrate (TFEB), and combinations thereof. Examples of non-fluorinated carbonates include ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and combinations thereof.

[0063] In some examples, the ratio of fluorinated carbonate to fluorinated ester is from 60:40 to 20:80 volume %. The lithium salt is from 0.5 M to 5 M. The lithium salt is from 1 M to 2 M. In some examples, a non-fluorinated carbonate is added to the mixture of fluorinated carbonate and fluorinated ester. If used, the ratio of fluorinated carbonate and fluorinated ester to non-fluorinated carbonate is from 20:80 to 80:20 volume %.

[0064] Now referring to Figure 2 , C cathode electrodes 20 are shown in further detail. The cathode active material layer 24 of the C cathode electrodes 20 includes a cathode active material 62, an optional conductive additive 64, and an optional binder 66. In some examples, the cathode active material 62 comprises a lithium-rich and manganese-rich cathode active material.

[0065] Now referring to Figure 3 , A anode electrodes 40 are shown in further detail. The anode active material layer 42 of the anode electrode 40 includes an anode active material 72, an optional conductive additive 74, and an optional binder 76. In some examples, the anode active material 72 includes SiO x / graphite, graphite, silicon, SiO x , lithium metal, and combinations thereof.

[0066] In some examples, the LMR battery pack cells operate at a voltage of from 2.0 V to 5.0 V. In some examples, the charge rate of the battery pack cells is from C / 100 to 6C. In some examples, the N / P ratio of the battery pack cells is from 1 to 3.

[0067] Now referring to Figure 1 to FIG. 4. As Figures 4A to 4C shown, the fluorinated solvent is more stable at higher oxidation potentials. In some examples, the battery pack cells include LMR as the cathode active material and 5.5% SiO x -graphite as the anode active material. In Figure 4A and 4BTherein, the capacity and discharge capacity retention % of electrolytes including a mixture of FEC:DEC (ratio 20:80 vol%), a mixture of FED:FDEC (ratio 20:80 vol%), and a mixture of FEC:FDEC:DEC (ratio 20:40:40 vol%) are shown as a function of cycles. The battery pack cells are operated at a C / 3 charge rate at a voltage of 2 V to 4.6 V. At Figure 4C , the ionic conductivity of the electrolyte is shown. As Figures 4A to 4C shown, partial replacement of non-fluorinated carbonates (e.g., DEC) with fluorinated carbonates (e.g., FDEC) is more stable than non-fluorinated carbonates alone, but has significantly lower ionic conductivity.

[0068] Now referring to Figures 5A to 5C , the capacity and discharge capacity retention % are shown as a function of cycles for various electrolytes. At Figure 5A , the electrolyte includes a mixture of FEC:DEC:FDEC (ratio 20:40:40 vol%), a mixture of FED:FDEC (ratio 20:80 vol%), a mixture of FEC:FDEC:TFEA (ratio 20:40:40 vol%), a mixture of FEC:FDEC:TFEA (ratio 20:20:60 vol%), and a mixture of FEC:TFEA (ratio 20:80 vol%). At Figure 5C , the ionic conductivity of the electrolyte mixture is shown. The ionic conductivity increases with increasing fluorinated ester concentration (as shown by the arrows in Figure 5A and 5C ) up to about 80 vol%, and the ionic conductivity decreases at higher fluorinated ester concentrations. It can be seen that adding a fluorinated ester (e.g., TFEA) to the electrolyte mixture improves cycle stability without compromising ionic conductivity.

[0069] The foregoing description is merely exemplary and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure may be implemented in a variety of forms. Thus, although the disclosure includes specific examples, the true scope of the disclosure should not be so limited since other modifications will become apparent after study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be performed in a different order (or simultaneously) without altering the principles of the disclosure. Additionally, although the embodiments are described above as having certain features, any one or more of the features described with respect to any one embodiment of the disclosure may be implemented in any other embodiment and / or combined with the features of any other embodiment, even if not explicitly described in combination. In other words, the embodiments are not mutually exclusive, and permutations of one or more embodiments are still within the scope of the disclosure.

[0070] Various terms are used to describe spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.), including "connected", "joined", "coupled", "adjacent", "next to", "on top of", "on", "under", and "disposed". Unless explicitly described as "direct", when describing the relationship between a first element and a second element in the foregoing disclosure, the relationship can be a direct relationship in which no other intervening elements exist between the first element and the second element, or an indirect relationship in which one or more intervening elements exist between the first element and the second element (spatially or functionally). The phrase "at least one of A, B, and C" as used herein should be construed to mean a logical (A or B or C) using non-exclusive logical OR and should not be construed to mean "at least one of A, at least one of B, and at least one of C".

[0071] In the drawings, the direction of an arrow as indicated by the arrowhead generally shows the information flow (such as data or instructions) of interest in the illustration. For example, when element A and element B exchange various information and the information sent from element A to element B is relevant to the illustration, the arrow can point from element A to element B. Such a unidirectional arrow does not mean that no other information is sent from element B to element A. In addition, for the information transmitted from element A to element B, element B can send a request for the information or receive an acknowledgment to element A.

Claims

1. A battery cell comprising: A battery cell stack comprising: C cathode electrodes comprising lithium-rich and manganese-rich cathode active (LMR) materials; A anode electrode comprising an anode active material; and S spacers, wherein C, A, and S are integers greater than 1; and a housing comprising the battery cell stack and an electrolyte, The electrolyte comprises a mixture of fluorinated carbonate and fluorinated ester and a lithium salt. 2 . The battery cell according to claim 1 , wherein the ratio of the fluorinated carbonate to the fluorinated ester is 60:40 to 20:80 volume %.

3. The battery cell of claim 1, wherein the lithium salt is 0.5M to 5M.

4. The battery cell according to claim 1, wherein the lithium salt is 1M to 2M.

5. The battery cell of claim 1, wherein the lithium salt is selected from the group consisting of LiPF6, LiClO4, LiBF4, LiAsF6, LiTFSI, LiFSI, LiDFOB, LiBOB, LiPO2F2, and combinations thereof.

6. The battery cell of claim 1, wherein the fluorinated carbonate is selected from the group consisting of fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) carbonate, methyl 2,2,2-trifluoroethyl carbonate (FEMC), difluoroethylene carbonate (FDEC), and combinations thereof.

7. The battery cell of claim 1, wherein the fluorinated ester is selected from the group consisting of ethyl 2,2,2-trifluoroacetate (TFEA), methyl pentafluoropropionate (MTFP), methyl 3,3,3-trifluoropropionate (MPFP), 2,2,2-trifluoroethylbutyrate (TFEB), and combinations thereof.

8. The battery cell of claim 1, wherein the electrolyte further comprises a non-fluorinated carbonate.

9. The battery cell according to claim 8, wherein the ratio of the fluorinated carbonate and the fluorinated ester to the non-fluorinated carbonate is 20:80 to 80:20 volume %.

10. The battery cell of claim 1, wherein the fluorinated carbonate is selected from the group consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and combinations thereof.

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