Electrolyte composition, battery and device with this composition

Abstract

An electrolyte composition for batteries is provided. The electrolyte composition comprises a solvent containing one or more fluorinated carbonates. The electrolyte composition also comprises a lithium-based salt and a lithium (oxalato)borate salt. A battery comprising the electrolyte composition is also provided. The battery comprises an anode, a nickel-based cathode, and the electrolyte composition positioned between the anode and the nickel-based cathode.

Description

[0001] The disclosure relates generally to an electrolyte composition for batteries.

[0002] Battery cells can contain an anode, a cathode, an electrolyte mixture, and a separator. A battery cell can operate in charging mode, absorbing electrical energy. A battery cell can also operate in discharging mode, releasing electrical energy. A battery cell can undergo charge and discharge cycles, in which the battery first absorbs and stores electrical energy and then releases electrical energy to a connected system. In vehicles that use electrical energy to generate propulsion, the vehicle's battery cells can be charged, and then the vehicle can drive for a period of time, using the stored electrical energy to generate propulsion.

[0003] A battery cell contains an electrolyte that provides pathways for lithium ions to conduct between the anode and the cathode. The electrolyte is an ionic conductor and also an electrically insulating material.

[0004] One of the factors that determines the economic viability of a battery cell is its capacity and cycle life. A battery cell for an electric vehicle may need to last for at least 30,000 operating hours. Such demanding requirements can pose a challenge for the vehicle's battery cell(s).

[0005] An electrolyte composition for batteries according to one or more embodiments is provided. The electrolyte composition comprises a solvent, a lithium-based salt, and a lithium (oxalato)borate salt. The solvent comprises one or more fluorinated carbonates.

[0006] In some embodiments, the lithium (oxalato)borate salt is selected from LiDFOB, LiBOB or a combination thereof.

[0007] In some embodiments, the lithium (oxalato)borate salt is LiDFOB.

[0008] In some embodiments, one or more fluorinated carbonates are selected from FEC, FEMC, bis(2,2,2-trifluoroethyl)carbonate, FDEC, 3,3,3-trifluoropropylene carbonate, TFPC, dichloroethylene carbonate or a combination thereof.

[0009] In some embodiments, one or more fluorinated carbonates comprise FEC and a second fluorinated carbonate selected from FEMC, bis(2,2,2-trifluoroethyl)carbonate, FDEC, 3,3,3-trifluoropropylene carbonate, TFPC, dichloroethylene carbonate or a combination thereof.

[0010] In some embodiments, the second fluorinated carbonate is FEMC.

[0011] In some embodiments, the lithium-based salt is selected from lithium hexafluorophosphate, LiPF6, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide or a combination thereof.

[0012] In some embodiments, the lithium-based salt comprises LiPF6.

[0013] In some embodiments, the lithium-based salt is present in the electrolyte composition at a molar concentration of about 0.5 to about 1.5 molarity, M.

[0014] In some embodiments, the solvent comprises FEC and FEMC, which are present in a weight ratio of FEC:FEMC of approximately 1:9.

[0015] In some embodiments, the lithium (oxalato)borate salt is present in an amount of about 0.5 to about 1.0 wt.% based on the electrolyte composition.

[0016] A battery according to one or more embodiments is provided. The battery comprises an anode, a nickel-based cathode, and an electrolyte composition arranged between the anode and the nickel-based cathode. The electrolyte composition comprises a solvent, a lithium-based salt, and a lithium (oxalato)borate salt. The solvent comprises one or more fluorinated carbonates.

[0017] In some embodiments, the nickel-based cathode comprises Li, Ni, Co, Mn and O.

[0018] In some embodiments, the nickel-based cathode comprises a nickel-based active cathode material comprising Ni in an amount of about 60 wt.% or more of the nickel-based active cathode material.

[0019] In some embodiments, the nickel-based cathode comprises an active nickel-based cathode material with the formula LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0020] In some embodiments, the anode comprises SiO₂. x Graphite, Si, SiO x , lithium metal or a combination thereof, where x is a value greater than 0.

[0021] In some embodiments, the lithium (oxalato)borate salt is selected from LiDFOB, LiBOB or a combination thereof.

[0022] In some embodiments, one or more fluorinated carbonates comprise FEC and a second fluorinated carbonate selected from FEMC, bis(2,2,2-trifluoroethyl)carbonate, FDEC, 3,3,3-trifluoropropylene carbonate, TFPC, dichloroethylene carbonate or a combination thereof.

[0023] In some embodiments, the lithium-based salt comprises LiPF6.

[0024] A device according to one or more embodiments is provided. The device comprises an output component and a battery configured to supply electrical energy to the output component. The battery comprises an anode, a nickel-based cathode, and an electrolyte composition arranged between the anode and the nickel-based cathode. The electrolyte composition comprises a solvent comprising one or more fluorinated carbonates selected from FEC, FEMC, bis(2,2,2-trifluoroethyl)carbonate, FDEC, 3,3,3-trifluoropropylene carbonate, TFPC, dichloroethylene carbonate, or a combination thereof. The electrolyte composition further comprises a lithium-based salt selected from lithium hexafluorophosphate, LiPF6, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or a combination thereof.The lithium-based salt is present in the electrolyte composition at a molar concentration of approximately 0.5 to approximately 1.5 M. The electrolyte composition further comprises a lithium (oxalato)borate salt selected from LiDFOB, LiBOB, or a combination thereof. The lithium (oxalato)borate salt is present at an amount of approximately 0.5 to approximately 1.0 wt% based on the electrolyte composition.

[0025] The above features and advantages, as well as other features and advantages of the present disclosure, are readily apparent from the following detailed description of the best ways of carrying out the disclosure when considered in conjunction with the accompanying drawings. Brief description of the drawings Fig. Figure 1 schematically shows an exemplary battery cell with an anode, a cathode, a separator and an electrolyte composition according to the present disclosure; Fig. Figure 2 schematically shows an exemplary device with a battery pack comprising a plurality of battery cells, according to the present disclosure; Fig. Figures 3A-3C schematically show an enlarged area of ​​the cathode, which is connected to the in Fig. 1. The electrolytes shown are in contact at various stages of the formation of a solid electrolyte interface (SEI) in accordance with the present disclosure; and Fig. Figure 4 is a diagram showing the results of DSC (Differential Scanning Calorimetry) tests for the thermal release of the cathode in the presence of various electrolytes according to the present disclosure. Detailed description

[0026] As required, detailed embodiments of the present disclosure are disclosed here; however, it should be understood that the disclosed embodiments are merely exemplary of the disclosure, which can be embodied in various and alternative forms. The illustrations are not necessarily to scale; some features may be exaggerated or reduced in size to show details of certain components. Therefore, specific structural and functional details disclosed here are not to be understood as limiting, but merely as a representative basis to show the person skilled in the art how to apply the present disclosure in various ways.

[0027] Unless explicitly stated in the context, the term "approximately" here means within a normal tolerance range, for example, within two standard deviations of the mean. "Approximately" can be understood as within 10%, 5%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. "Approximately" can also be understood as stating the exact value. Unless otherwise indicated in the context, the numerical values ​​given here are modified by the term "approximately."

[0028] High-capacity, high-performance nickel-based cathode materials are useful for lithium-ion energy storage systems that power battery-electric vehicles. Such an energy storage system can be described as a high-energy-density battery. The battery cells may contain a graphite- and / or silicon-containing anode and a nickel-based cathode.

[0029] The capacity and cycle life of the battery cells can vary depending on operating conditions. The performance of the battery cells can also vary depending on the choice of cathode and anode materials. An electrolyte composition disclosed herein offers excellent cycle life for the battery cells. In one embodiment, the electrolyte composition comprises a solvent containing one or more fluorinated carbonates, a lithium-based salt, and a lithium (oxalato)borate salt. In one or more embodiments of the disclosure, the lithium (oxalato)borate salt is present in an amount of approximately 0.5 to approximately 1 wt%, based on the total weight of the electrolyte composition.

[0030] Tests have shown that the addition of lithium (oxalato)borate salt in the described weight percentages improves the formation of a solid electrolyte interface (SEI) on the electrode(s), or more precisely, the formation of a cathode-electrolyte interface (CEI) on the nickel-based cathode. A CEI is formed by a chemical reaction between the nickel-based cathode and a liquid or gel-like electrolyte interacting with the cathode. The CEI forms as a film on the nickel-based cathode and can extend the lifespan of the battery cell.

[0031] Fig. Figure 1 schematically shows an exemplary battery cell 100 with an anode 110, a cathode 120, a separator 130, and an electrolyte composition 140. The battery cell 100 enables the conversion of electrical energy into stored chemical energy in a charge cycle, and the battery cell 100 enables the conversion of stored chemical energy into electrical energy in a discharge cycle. A negative current collector 112 is connected to the anode 110, and a positive current collector 122 is connected to the cathode 120. The separator 130 is configured to separate the anode 110 from the cathode 120 and to allow ion transfer through the separator 130. The electrolyte composition 140 is a liquid or gel that provides a lithium-ion conduction path between the anode 110 and the cathode 120.

[0032] The anode 110 can be made of silicon, a silicon alloy or another silicon-containing material (for example SiO₂). x where x is a value greater than 0) and / or be composed of a graphite- or graphite-containing material and / or lithium metal. In an exemplary embodiment, the cathode 120 is a nickel-based cathode comprising a nickel-based active cathode material. The nickel-based active cathode material comprises Ni in an amount of about 60 wt.% or more of the nickel-based active cathode material. In an exemplary embodiment, the nickel-based cathode comprises Li, Ni, Co, Mn, and O. In one embodiment, the active material of the nickel-based cathode has the formula LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0033] In one or more embodiments of the disclosure, the electrolyte composition 140 comprises a solvent, a lithium-based salt, and a lithium (oxalato)borate salt. The solvent comprises one or more fluorinated carbonates, such as fluoroethylene carbonate (FEC), 2,2,2-trifluoroethylmethyl carbonate (FEMC), bis(2,2,2-trifluoroethyl) carbonate (FDEC), 3,3,3-trifluoropropylene carbonate (TFPC), and / or dichloroethylene carbonate. In an exemplary embodiment, the solvent comprises FEC as a first fluorinated carbonate and a second fluorinated carbonate such as FEMC, bis(2,2,2-trifluoroethyl) carbonate (FDEC), 3,3,3-trifluoropropylene carbonate (TFPC), and / or dichloroethylene carbonate. In one embodiment, the second fluorinated carbonate is FEMC. In an exemplary embodiment, the solvent comprises FEC and FEMC present in a weight ratio of FEC:FEMC of approximately 1:9. Optionally, the FEC:FEMC ratio can be between 1:19 and 1:4.Alternatively, the FEC:FEMC ratio can be between 1:19 and 1:2.

[0034] In one exemplary embodiment, the lithium (oxalato)borate salt is selected from lithium difluoro(oxalato)borate (LiDFOB) and / or lithium bix(oxalato)borate (LiBOB). In one embodiment, the lithium (oxalato)borate salt is LiDFOB. In one exemplary embodiment, the lithium (oxalato)borate salt is present in an amount of about 0.5 to about 1.0 wt.%, based on the total weight of electrolyte composition 140. Optionally, the lithium (oxalate)borate salt is present in an amount of about 0.2 to about 2.0 wt.%.

[0035] In an exemplary embodiment, the lithium-based salt is selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or a combination thereof. In another embodiment, the lithium-based salt comprises or is LiPF6. In another exemplary embodiment, the lithium-based salt is present in electrolyte composition 140 at a molar concentration of about 0.5 to about 1.5 M.

[0036] The electrolyte composition 140 may also contain other additives. For example, the electrolyte composition 140 may also contain one or more phosphorus- and silicon-based additives. Non-limiting examples of phosphorus- and silicon-based additives are tris(trimethylsilyl)phosphite and / or tris(trimethylsilyl)phosphate. In an exemplary embodiment, the one or more phosphorus- and silicon-based additives are present in an amount of about 0.1 to about 2 wt.%, based on the total weight of the electrolyte composition 140. Other possible electrolyte additives include polymerizable additives such as: vinylene carbonate (VC), vinylethylene carbonate (VEC), allyl ethyl carbonate, vinyl acetate, maleic anhydride, 2-vinylpyridine, lithium difluorophosphate (LiPO₂F₂), 1,3,2-dioxathiolane 2,2-dioxide (DTD), dimethylacrylamide, tris(trimethylsilyl)phosphite, and the like.

[0037] With reference to the Fig. 3A-3C The lithium (oxalato)borate salt 150 in the described weight proportions improves the formation of the solid electrolyte interface (SEI), in particular the formation of the cathode-electrolyte interface (CEI) 156 at the cathode 120. In particular, the lithium (oxalato)borate salt 150 interacts with the metal oxides 151 on the cathode 120 (shown in Fig. 3A), to produce an intermediate product 154 (shown in Fig. 3B) to form, which further reacts to form the CEI 156 as a protective layer to create a more stable interface along the cathode 120, protecting the metal oxide bonds 151 to prevent or minimize the release of oxygen (O) to mitigate thermal runaway.

[0038] The battery cell 100 can be used in a wide range of applications and powertrains. Fig. Figure 2 schematically shows an exemplary device 200, for example, a battery-powered electric vehicle (BEV), with a battery pack 210 comprising a plurality of battery cells 100. The plurality of battery cells 100 can be connected in various combinations, for example, by connecting some in parallel and some in series, to achieve the goal of providing electrical energy at a desired voltage. The battery pack 210 is shown electrically connected to a motor-generator unit 220, which serves to supply the vehicle 200 with motive power. The motor-generator unit 220 can include an output component, for example, an output shaft, which is supplied with mechanical energy to provide the motive power for the vehicle 200. A number of variants of the vehicle 200 are conceivable, and the disclosure is not intended to be limited to the examples given.

[0039] Fig. Figure 4 is a diagram 300 showing the results of differential scanning calorimetry (DSC) tests on the thermal release from the cathode in the presence of various electrolytes according to the present disclosure. A vertical axis 302 describes the heat flux in units of mW / mg. A horizontal axis 304 describes the temperature in units of Celsius (°C).

[0040] As shown, line 306 represents an electrolyte composition that includes LiPF6 in EC:EMC 3:7 + 2% VC as the first control electrolyte composition, line 308 represents an electrolyte composition that includes LiPF6 in FEC:FEMC 1:9 + 1% LiDFOB as the second electrolyte composition, and line 310 represents an electrolyte composition that includes LiPF6 in FEC:FEMC 1:9 as the third electrolyte composition. Comparing electrolyte compositions 308 and 310 with the control electrolyte composition 306, it can be seen that FEC and FEMC significantly improve the thermal stability of the electrolyte compositions. For example, the peak temperatures of the electrolyte compositions are delayed by 10°C and 17°C respectively, and the total heat dissipation is reduced by 21% and 24% respectively, based on the total heat dissipation for electrolyte composition 306 of 721 J / g, electrolyte composition 308 of 566 J / g and electrolyte composition 310 of 545 J / g.

[0041] While the best modes for carrying out the disclosure have been described in detail, those who are familiar with the prior art to which this disclosure relates will recognize various alternative designs and embodiments for carrying out the disclosure within the scope of the attached claims.

Claims

[1] Electrolyte composition for batteries, comprising the electrolyte composition: a solvent comprising one or more fluorinated carbonates; a lithium-based salt; and a lithium (oxalato)borate salt. [2] Electrolyte composition according to claim 1, wherein the lithium (oxalato)borate salt is selected from LiDFOB, LiBOB or a combination thereof. [3] Electrolyte composition according to claim 1, wherein the lithium (oxalato)borate salt is LiDFOB. [4] Electrolyte composition according to claim 1, wherein one or more fluorinated carbonates are selected from FEC, FEMC, bis(2,2,2-trifluoroethyl)carbonate, FDEC, 3,3,3-trifluoropropylene carbonate, TFPC, dichloroethylene carbonate or a combination thereof. [5] Electrolyte composition according to claim 1, wherein one or more fluorinated carbonates comprise FEC and a second fluorinated carbonate selected from FEMC, bis(2,2,2-trifluoroethyl)carbonate, FDEC, 3,3,3-trifluoropropylene carbonate, TFPC, dichloroethylene carbonate or a combination thereof. [6] Electrolyte composition according to claim 5, wherein the second fluorinated carbonate is FEMC. [7] Electrolyte composition according to claim 1, wherein the solvent comprises FEC and FEMC in a weight ratio of FEC:FEMC of about 1:

9. [8] Battery, comprising: an anode; a nickel-based cathode; and an electrolyte composition arranged between the anode and the cathode, based on nickel, comprising the electrolyte composition: a solvent comprising one or more fluorinated carbonates; a lithium-based salt; and a lithium (oxalato)borate salt. [9] Battery according to claim 8, wherein the lithium (oxalato)borate salt is selected from LiDFOB, LiBOB or a combination thereof. [10] Battery according to claim 8, wherein one or more fluorinated carbonates comprise FEC and a second fluorinated carbonate selected from FEMC, bis(2,2,2-trifluoroethyl)carbonate, FDEC, 3,3,3-trifluoropropylene carbonate, TFPC, dichloroethylene carbonate or a combination thereof.

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