ELECTROLYTE COMPOSITION FOR HIGH ENERGY DENSITY BATTERIES

Abstract

Electrolyte composition for batteries, the electrolyte composition comprising: ethylene carbonate; Diethyl carbonate; Ethyl methyl carbonate; vinylethylene carbonate; vinyl carbonate; Propane-1,3-sultone; ethylene sulfate; and lithium difluorophosphate; and wherein the ethylene carbonate, the diethyl carbonate and the ethyl methyl carbonate are each present in the electrolyte composition in an amount of 10 parts by weight to 50 parts by weight based on 100 parts by weight of the electrolyte composition; wherein the ethylene carbonate, the diethyl carbonate and the ethyl methyl carbonate are present in a ratio of 1:1:1; wherein the vinylethylene carbonate is present in the electrolyte composition at 0.5 parts by weight based on 100 parts by weight of the electrolyte composition; wherein the vinyl carbonate is present in the electrolyte composition at 1.0 part by weight based on 100 parts by weight of the electrolyte composition; and wherein the propane-1,3-sultone is present in the electrolyte composition at 1.5 parts by weight based on 100 parts by weight of the electrolyte composition.

Description

INTRODUCTION

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

[0002] Battery cells may contain an anode, a cathode, an electrolyte composition, and a separator. A battery cell can operate in charge mode, absorbing electrical energy. A battery cell can operate in discharge mode, delivering electrical energy. A battery cell can operate through charge and discharge cycles, with the battery first absorbing and storing electrical energy and then releasing electrical energy to an attached system. In vehicles that use electrical energy to generate motive power, the vehicle's battery cells can be charged, and the vehicle can then drive for a period of time, using the stored electrical energy to generate motive power.

[0003] A battery cell contains an electrolyte composition that provides lithium-ion conduction pathways between the anode and the cathode. The electrolyte is an ionic conductor. The electrolyte is also an electronically insulating material.

[0004] Such and comparable electrolyte compositions as well as batteries are described, for example, in CN 1 12 563 570 A and the following Liu article. (Liu, J; Chen, Z.; Busking, S.; Belharouak, I.; Amine Kh.: Effect of electrolyte additives in improving the cycle and calendar life of graphite /

[0005] Li1.1[Ni1 / 3Co1 / 3Mn1 / 3]0.902 Li-Ion cells. In: Journal of Power Sources, 174; Vol. 2, 2007, pp. 852-855) SUMMARY

[0006] An electrolyte composition for batteries is provided. The electrolyte composition comprises ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, vinyl ethylene carbonate, vinyl carbonate, propane-1,3-sultone, ethylene sulfate, and lithium difluorophosphate. The ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate are each present in the electrolyte composition in an amount of 10 parts by weight to 50 parts by weight, based on 100 parts by weight of the electrolyte composition, with the ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate being present in a ratio of 1:1:1. The vinyl ethylene carbonate is present in the electrolyte composition at 0.5 parts by weight, based on 100 parts by weight of the electrolyte composition. The vinyl carbonate is present in the electrolyte composition at 1.0 parts by weight, based on 100 parts by weight of the electrolyte composition.The propane-1,3-sultone is present in the electrolyte composition at 1.5 parts by weight, based on 100 parts by weight of the electrolyte composition.

[0007] In some embodiments, the ethylene sulfate is present in the electrolyte composition at least 0.95 parts by weight based on 100 parts by weight of the electrolyte composition.

[0008] In some embodiments, the ethylene sulfate is present in the electrolyte composition in an amount of up to 1.05 parts by weight based on 100 parts by weight of the electrolyte composition.

[0009] In some embodiments, the ethylene sulfate is present in the electrolyte composition in an amount of 0.95 parts by weight to 1.05 parts by weight, based on 100 parts by weight of the electrolyte composition.

[0010] In some embodiments, the lithium difluorophosphate is present in the electrolyte composition at least 0.5 parts by weight based on 100 parts by weight of the electrolyte composition.

[0011] In some embodiments, the lithium difluorophosphate is present in the electrolyte composition at least 0.1 parts by weight based on 100 parts by weight of the electrolyte composition.

[0012] In some embodiments, the lithium difluorophosphate is present in the electrolyte composition in an amount of 0.5 parts by weight to 1.5 parts by weight, based on 100 parts by weight of the electrolyte composition.

[0013] In some embodiments, the lithium difluorophosphate is present in the electrolyte composition in an amount of 0.1 parts by weight to 1.5 parts by weight, based on 100 parts by weight of the electrolyte composition.

[0014] In some embodiments, the ethylene sulfate is present in the electrolyte composition in an amount of 0.95 parts by weight to 1.05 parts by weight, based on 100 parts by weight of the electrolyte composition. The lithium difluorophosphate is present in the electrolyte composition in an amount of 0.1 parts by weight to 1.5 parts by weight, based on 100 parts by weight of the electrolyte composition.

[0015] According to an alternative embodiment, a battery with an electrolyte composition is provided. The battery includes a graphite anode, a nickel-based cathode, and the electrolyte composition. The electrolyte composition comprises ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, vinyl ethylene carbonate, vinyl carbonate, propane-1,3-sultone, ethylene sulfate, and lithium difluorophosphate. The ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate are each present in the electrolyte composition in an amount of 10 parts by weight to 50 parts by weight, based on 100 parts by weight of the electrolyte composition, with the ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate being present in a ratio of 1:1:1. The vinyl ethylene carbonate is present in the electrolyte composition at 0.5 parts by weight, based on 100 parts by weight of the electrolyte composition.The vinyl carbonate is present in the electrolyte composition at 1.0 part by weight, based on 100 parts by weight of the electrolyte composition. The propane-1,3-sultone is present in the electrolyte composition at 1.5 parts by weight, based on 100 parts by weight of the electrolyte composition.

[0016] In some embodiments, the ethylene sulfate is present in the electrolyte composition at least 0.95 parts by weight based on 100 parts by weight of the electrolyte composition.

[0017] In some embodiments, the lithium difluorophosphate is present in the electrolyte composition at least 0.1 parts by weight based on 100 parts by weight of the electrolyte composition.

[0018] In some embodiments, the ethylene sulfate is present in the electrolyte composition in an amount of 0.95 parts by weight to 1.05 parts by weight, based on 100 parts by weight of the electrolyte composition. The lithium difluorophosphate is present in the electrolyte composition in an amount of 0.1 parts by weight to 1.5 parts by weight, based on 100 parts by weight of the electrolyte composition.

[0019] A device is not described according to the invention. The device comprises a starting component and a battery configured to supply electrical energy to the starting component. The battery contains a graphite anode, a nickel-based cathode, and an electrolyte composition. The electrolyte composition comprises ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, vinyl ethylene carbonate, vinyl carbonate, propane-1,3-sultone, ethylene sulfate, and lithium difluorophosphate. The ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate are each present in the electrolyte composition in an amount of 10 parts by weight to 50 parts by weight, based on 100 parts by weight of the electrolyte composition. The vinyl ethylene carbonate is present in the electrolyte composition in an amount of up to 0.5 parts by weight, based on 100 parts by weight of the electrolyte composition.The vinyl carbonate is present in the electrolyte composition in an amount of up to 1.0 part by weight, based on 100 parts by weight of the electrolyte composition. The propane-1,3-sultone is present in the electrolyte composition in an amount of up to 1.5 parts by weight, based on 100 parts by weight of the electrolyte composition.

[0020] In some embodiments, the ethylene sulfate is present in the electrolyte composition at least 0.95 parts by weight based on 100 parts by weight of the electrolyte composition.

[0021] In some embodiments, the lithium difluorophosphate is present in the electrolyte composition at least 0.1 parts by weight based on 100 parts by weight of the electrolyte composition.

[0022] In some embodiments, the ethylene sulfate is present in the electrolyte composition in an amount of 0.95 parts by weight to 1.05 parts by weight, based on 100 parts by weight of the electrolyte composition. The lithium difluorophosphate is present in the electrolyte composition in an amount of 0.1 parts by weight to 1.5 parts by weight, based on 100 parts by weight of the electrolyte composition.

[0023] 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 modes for carrying out the disclosure when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 schematically shows an exemplary battery cell having an anode, a cathode, a separator, and an electrolyte composition according to the present disclosure; Fig. 2 schematically illustrates an exemplary device having a battery pack including a plurality of battery cells according to the present disclosure; Fig. 3 is a graph illustrating exemplary test results of a relationship between the capacity retention of a battery cell and a number of charge / discharge cycles through which the battery cell is operated, according to the present disclosure; Fig. 4 is a graph illustrating exemplary test results comparing the normalized capacity of a battery cell in one charge cycle with the number of charge / discharge cycles the battery cell is operated in, in accordance with the present disclosure; Fig. 5 is a graph showing exemplary test results comparing the normalized capacity of a battery cell in one discharge cycle with the number of charge / discharge cycles the battery cell is operated in accordance with the present disclosure; and Fig. 6 is a graph illustrating exemplary test results comparing the capacity retention of a plurality of battery cells with the number of charge / discharge cycles the battery cells are operated with, wherein the plurality of battery cells contain different concentrations of LiPO2F2 added to the electrolyte, in accordance with the present disclosure. DETAILED DESCRIPTION

[0024] High-capacity, high-performance nickel-based cathode materials are useful for a lithium-ion energy storage system that powers a battery-powered electric vehicle. Such an energy storage system can be referred to as a high-energy-density battery. The battery cells can contain a graphite anode and a nickel-based cathode.

[0025] The capacity and cycle tolerance of the battery cells may vary depending on operating conditions. The performance of the battery cells may vary depending on the selection of the cathode and anode materials. An electrolyte composition disclosed herein provides excellent cycle life for the battery cells. According to the invention, the electrolyte contains ethylene carbonate (EC) / diethyl carbonate (DEC) / ethyl methyl carbonate (EMC) in a ratio of 1:1:1. The electrolyte further contains vinyl ethylene carbonate (VEC) at 0.5 weight percent, vinyl carbonate (VC) at 1 weight percent, and propane-1,3-sultone (PS) at 1.5 weight percent. The electrolyte exhibits excellent cycle performance by further containing ethylene sulfate (DTD) in an amount between 0.1 and 1.0 weight percent and lithium difluorophosphate (LiPO2F2) in an amount between 0.1 and 1.5 weight percent. In some embodiments, DTD may be added in an amount between 0.5 wt% and 1.0 wt%.In some embodiments, LiPO2F2 may be added in an amount between 0.5 wt% and 1.5 wt%.

[0026] Tests have shown that the addition of DTD and LiPO2F2 in the described weight proportions improves the formation of the solid electrolyte interface (SEI) on the anode and forms an excellent preservative layer on both the cathode and the anode. An SEI can form on the surface of an anode. An SEI is formed by a chemical reaction between the anode and a liquid or gel-like electrolyte that interacts with the anode. The SEI forms as a film on the anode.

[0027] Referring now to the drawings, in which like reference numerals refer to like features in the several views, Fig. 1 schematically illustrates an exemplary battery cell 100 including 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 serves to separate the anode 110 from the cathode 120 and to enable ion transfer through the separator 130. The electrolyte composition 140 is a liquid or gel that forms a lithium ion conduction pathway between the anode 110 and the cathode 120.

[0028] The anode 110 may be made of graphite. The cathode 120 may be made of a nickel-based substance. In one embodiment, the cathode 120 may be made of a nickel-manganese-cobalt (NMC) substance.

[0029] The electrolyte composition 140 contains EC / DEC / EMC in a 1:1:1 composition. The electrolyte composition 140 may contain variations of the 1:1:1 composition, with each of the components EC, DEV, and EMC being present in a range between 10 and 50 weight percent. The electrolyte composition 140 also contains VEC at 0.5 weight percent, VC at 1 weight percent, and PS at 1.5 weight percent. Not according to the invention, the electrolyte composition 140 may contain variations in the presence of VEC, VC, and PS, with VEC being present at up to 0.5 weight percent, VC at up to 1 weight percent, and PS at up to 1.5 weight percent. The electrolyte provides excellent cycling performance by continuing to contain DTD in an amount between 0.1 and 1.0 wt% and LiPO2F2 in an amount between 0.1 and 1.5 wt%.In some embodiments, DTD may be added in an amount between 0.5 wt.% and 1.0 wt.%. In some embodiments, LiPO2F2 may be added in an amount between 0.5 wt.% and 1.5 wt.%.

[0030] The battery cell 100 can be used in a wide range of applications and drive systems. Fig. 2 schematically shows an exemplary device 200, e.g., a battery electric vehicle (BEV), with a battery pack 210 containing a plurality of battery cells 100. The plurality of battery cells 100 can be connected together in various combinations, e.g., by connecting some in parallel and some in series, to achieve the delivery of electrical energy at the desired voltage. The battery pack 210 is electrically connected to a motor-generator unit 220, which supplies motive power to the vehicle 200. The motor-generator unit 220 can include an output component, e.g., an output shaft, that provides mechanical energy to generate the motive power for the vehicle 200. Numerous variations of the vehicle 200 are conceivable, and the disclosure is not intended to be limited to the examples shown.

[0031] Fig. 3 is a graph 300 showing exemplary test results of a relationship between the capacity retention of a battery cell and the number of charge / discharge cycles with which the battery cell is operated. A vertical axis 304 describes the capacity retention of the tested battery cell as a percentage of the original battery capacity. A horizontal axis 302 describes the number of charge / discharge cycles. The graph 310 shows the electrolyte composition 140 of Fig. 1 without any DTD or LiPO2F2 additive. Diagram 320 shows the electrolyte composition 140 of Fig. 1 with added DTD. Diagram 330 shows the electrolyte composition 140 of Fig. 1 with LiPO2F2 additive. It is shown that both DTD and LiPO2F2 significantly improve the cycling stability of the battery cells, with the tested battery cells maintaining excellent capacity over an increasing number of charge / discharge cycles.

[0032] Fig. 4 is a graph 400 showing exemplary test results comparing the normalized capacity of a battery cell in a charge cycle with the number of charge / discharge cycles the battery cell is operated with. The vertical axis 404 indicates the normalized capacity of the tested battery cell in percent. The normalized capacity is defined as the ratio between the capacity of the current cycle and the capacity of the original cycle. A horizontal axis 402 describes the number of charge / discharge cycles. The graph 410 shows the electrolyte composition 140 of Fig. 1 without any DTD or LiPO2F2 additive. Diagram 420 shows the electrolyte composition 140 of Fig. 1 with added DTD. Diagram 430 shows the electrolyte composition 140 of Fig. 1 with LiPO2F2 additive. Fig. 5 is a graph 500 with exemplary test results comparing the normalized capacity of a battery cell in one discharge cycle with the number of charge / discharge cycles with which the battery cell is operated. The vertical axis 504 indicates the normalized capacity of the tested battery cell in percent. A horizontal axis 502 describes the number of charge / discharge cycles. The graph 510 shows the electrolyte composition 140 of Fig. 1 without a DTD or LiPO2F2 additive. Diagram 520 shows the electrolyte composition 140 of Fig. 1 with DTD additive. Diagram 530 shows the electrolyte composition 140 of Fig. 1 with LiPO2F2 additive. One can Fig. 4 and Fig. 5 shows that both the DTD and the LiPO2F2 significantly improve the cycling performance of the battery cells, with the tested battery cells maintaining excellent normalized capacity over an increasing number of charge / discharge cycles.

[0033] Fig. 6 is a graph 600 illustrating exemplary test results comparing the capacity retention of a plurality of battery cells with the number of charge / discharge cycles at which the battery cells are operated, wherein the plurality of battery cells contain different concentrations of LiPO2F2 added to the electrolyte for comparison purposes. A vertical axis 604 describes the capacity retention of the tested battery cell as a percentage of the original battery capacity. A horizontal axis 602 describes the number of charge / discharge cycles. The graph 610 shows the electrolyte composition 140 of Fig. 1 without any DTD or LiPO2F2 additive. Diagram 620 shows the electrolyte composition 140 of Fig. 1 with a LiPO2F2 addition of 0.5 weight percent. Diagram 630 shows the electrolyte composition 140 of Fig. 1 with a LiPO2F2 addition of 1.0 weight percent. Diagram 640 shows the electrolyte composition 140 of Fig. 1 with a LiPO2F2 addition of 1.5 weight percent. The addition of LiPO2F2 can be made in a selected amount based on the desired properties of the electrolyte composition 140.

Claims

[1] Electrolyte composition for batteries, the electrolyte composition comprising: Ethylene carbonate; Diethyl carbonate; Ethyl methyl carbonate; Vinylethylene carbonate; Vinyl carbonate; Propane-1,3-sulton; Ethylene sulfate; and Lithium difluorophosphate; and wherein the ethylene carbonate, the diethyl carbonate and the ethyl methyl carbonate are each present in the electrolyte composition in an amount of 10 parts by weight to 50 parts by weight, based on 100 parts by weight of the electrolyte composition; wherein the ethylene carbonate, the diethyl carbonate and the ethyl methyl carbonate are present in a ratio of 1:1:1; wherein the vinylethylene carbonate is present in the electrolyte composition at 0.5 parts by weight, based on 100 parts by weight of the electrolyte composition; wherein the vinyl carbonate is present in the electrolyte composition at 1.0 part by weight, based on 100 parts by weight of the electrolyte composition; and where the propane-1,3-sulton is present in the electrolyte composition at 1.5 parts by weight, based on 100 parts by weight of the electrolyte composition. [2] Electrolyte composition according to claim 1, wherein the ethylene sulfate is present in the electrolyte composition to at least 0.95 parts by weight, based on 100 parts by weight of the electrolyte composition. [3] Electrolyte composition according to claim 2, wherein the ethylene sulfate is present in the electrolyte composition in an amount of up to 1.05 parts by weight, based on 100 parts by weight of the electrolyte composition. [4] Electrolyte composition according to claim 1, wherein the ethylene sulfate is present in the electrolyte composition in an amount of 0.95 parts by weight to 1.05 parts by weight, based on 100 parts by weight of the electrolyte composition. [5] Electrolyte composition according to claim 1, wherein the lithium difluorophosphate is present in the electrolyte composition to at least 0.5 parts by weight, based on 100 parts by weight of the electrolyte composition. [6] Electrolyte composition according to claim 1, wherein the lithium difluorophosphate is present in the electrolyte composition to at least 0.1 parts by weight, based on 100 parts by weight of the electrolyte composition. [7] Electrolyte composition according to claim 1, wherein the lithium difluorophosphate is present in the electrolyte composition in an amount of 0.1 parts by weight to 1.5 parts by weight, based on 100 parts by weight of the electrolyte composition. [8] Electrolyte composition according to claim 1, wherein the ethylene sulfate is present in the electrolyte composition in an amount of 0.95 parts by weight to 1.05 parts by weight, based on 100 parts by weight of the electrolyte composition; and wherein the lithium difluorophosphate is present in the electrolyte composition in an amount of 0.1 parts by weight to 1.5 parts by weight, based on 100 parts by weight of the electrolyte composition. [9] Battery with an electrolyte composition, the battery comprising: a graphite anode; a nickel-based cathode; and the electrolyte composition, including: Ethylene carbonate; Diethyl carbonate; Ethyl methyl carbonate; Vinylethylene carbonate; Vinyl carbonate; Propane-1,3-sulton; Ethylene sulfate; and Lithium difluorophosphate; and wherein the ethylene carbonate, the diethyl carbonate and the ethyl methyl carbonate are each present in the electrolyte composition in an amount of 10 parts by weight to 50 parts by weight, based on 100 parts by weight of the electrolyte composition; wherein the ethylene carbonate, the diethyl carbonate and the ethyl methyl carbonate are present in a ratio of 1:1:1; wherein the vinylethylene carbonate is present in the electrolyte composition at 0.5 parts by weight, based on 100 parts by weight of the electrolyte composition; wherein the vinyl carbonate is present in the electrolyte composition at 1.0 part by weight, based on 100 parts by weight of the electrolyte composition; and where the propane-1,3-sulton is present in the electrolyte composition at 1.5 parts by weight, based on 100 parts by weight of the electrolyte composition.

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