Electrolyte composition and method for its preparation, lithium-ion battery

Abstract

Systems and methods are provided for using electrolyte compositions in lithium ion batteries. In one example, an electrolyte composition can include vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, vinyl sulfite, and a conductive salt including no less than 80 mole percent of a lithium salt of bis(fluorosulfonyl)imide. In this way, the capacity retention of the lithium ion battery such as during high temperature storage at 100% state of charge can be maintained.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Application No. 62 / 959,774, filed January 10, 2020, entitled "Electrolyte Composition for Lithium-ion Batteries". The entire contents of the foregoing application are incorporated herein by reference for all purposes. Technical Field

[0003] This disclosure generally relates to electrolyte compositions for use in lithium-ion batteries.

[0004] Background Technology and Summary of the Invention

[0005] Lithium-ion batteries, or lithium-ion rechargeable batteries, have become more commonly used as power sources for electric and hybrid electric vehicles. In a lithium-ion battery, lithium ions move back and forth between the negative and positive electrodes via an electrolyte medium (usually a liquid electrolyte). Such electrolytes typically include one or more conductive salts, such as lithium hexafluorophosphate (LiPF6). However, using LiPF6 alone can be problematic due to its instability at high temperatures in the presence of moisture, which can lead to the formation of hydrogen fluoride (HF) and capacity degradation in lithium-ion batteries.

[0006] The inventors have identified the above-mentioned problems and have determined a solution to at least partially address them. In one example, a non-aqueous electrolyte is provided, comprising, for example, a lithium bis(fluorosulfonyl)imide salt (LiFSI, LiN(FSO2)2) as the primary conductive salt and at least four additives. In some examples, the non-aqueous electrolyte may also include LiPF6 as a secondary conductive salt. Compared to using LiPF6 as the primary conductive salt, the non-aqueous electrolyte may be able to reduce capacity decay and impedance growth of lithium-ion batteries during high-temperature storage.

[0007] In one example, an electrolyte composition may include vinylene carbonate (VC), fluoroethylene carbonate (FEC), 1,3-propanesulfonyl lactone (PS), vinyl sulfite (ES), and a conductive salt comprising not less than 80 mol% LiFSI. In this way, a lithium-ion battery including said electrolyte composition can maintain high capacity during high-temperature storage applications.

[0008] It should be understood that the above overview is provided to present the selection of concepts further described in the detailed embodiments in a simplified form. Identification of key or essential features of the claimed subject matter is not intentional, and the scope of the subject matter is defined only by the claims following the detailed embodiments. Furthermore, the claimed subject matter is not limited to implementations that address any shortcomings mentioned above or in any part of this disclosure. Attached Figure Description

[0009] Figure 1A A lithium ion battery including an exemplary electrolyte composition is shown.

[0010] Figure 1B A graph depicting exemplary electrolyte compositions by weight is shown.

[0011] Figure 2A A graph depicting relative capacity of exemplary lithium ion batteries during high temperature storage at 100% state of charge is shown.

[0012] Figure 2B A graph depicting relative impedance of exemplary lithium ion batteries during high temperature storage at 100% state of charge is shown.

[0013] Figure 3 A flowchart of a method for forming an exemplary electrolyte composition for use in a lithium ion battery is shown. DETAILED DESCRIPTION

[0014] The following description relates to systems and methods for using electrolyte compositions in lithium ion batteries, the electrolyte compositions including lithium bis(fluorosulfonyl)imide salt (LiFSI, LiN(FS02)2) as a primary conductive salt and at least four additional additive components. One exemplary lithium ion battery including an electrolyte composition is depicted in Figure 1A and the relative component weights of various exemplary electrolyte compositions are graphically depicted in Figure 1B . Graphs depicting relative capacity and relative impedance of exemplary lithium ion batteries are depicted in Figure 2A and Figure 2B , respectively, indicating that the use of LiFSI as a primary conductive salt in the presence of vinylene carbonate (VC), fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), and vinyl ethylene sulfite (ES) can better preserve capacity and impedance at 100% state of charge (SOC) under high temperature (e.g., 60°C) storage conditions. A method for forming an electrolyte composition for subsequent use in a lithium ion battery is provided in Figure 3 .

[0015] Reference is now made to Figure 1ALi-ion battery 100 includes a housing 102 comprising a negative electrode 104 and a positive electrode 106 enclosed in an electrolyte 110. Further, a separator 108 (e.g., a porous membrane separator) can be disposed between the negative electrode 104 and the positive electrode 106 within the housing 102 such that physical contact between the negative electrode 104 and the positive electrode 106 can be avoided. During charging of the Li-ion battery 100, lithium ions can flow from the negative electrode 104 to the positive electrode 106. The electrolyte 110 can fill any empty volume within the housing 102 of the Li-ion battery 100 such that the electrolyte 110 can facilitate lithium ion transport between the negative electrode 104 and the positive electrode 106, i.e., across the separator 108.

[0016] The housing 102 can be a hermetic pouch or can. In some examples, the hermetic pouch can be composed of a pouch material that can be formed into a rectangular cross-sectional shape, where the sides of the pouch can be heat sealed. In additional or alternative examples, one or more of the sides of the housing 102 can be folded or rolled up. Other materials can be used for the housing 102 as would be known to at least one of ordinary skill in the art.

[0017] The negative electrode 104 can include a negative electrode active material, such as a lithium intercalation compound (e.g., a lithium addition compound or a lithium acceptance compound). In some examples, the negative electrode active material can be a lithium iron phosphate, a lithium metal phosphate, a lithium double metal phosphate, a lithium multi-metal phosphate, or another material that includes lithium and phosphate. It will be appreciated that other negative electrode active materials can be contemplated within the scope of the present disclosure.

[0018] The negative electrode 104 can also include a conductive additive and a binder. In some examples, the conductive additive can be carbonaceous. For example, the conductive additive can be carbon (e.g., carbon black) and the source of the conductive additive can include polyvinyl alcohol, polyvinyl butyral, a sugar, another source, or a combination of sources. In some examples, the binder can be a polymeric binder (e.g., polyvinylidene fluoride, polyvinylpyrrolidone, etc.). In some examples, the conductive additive and / or the binder can be a single material or a plurality of materials. The conductive additive and the binder are not particularly limited in composition and can be known to one of ordinary skill in the art. Each of the negative electrode active material, the conductive additive, and the binder can be included in a negative electrode slurry that can be cast, dried, and calendered on a negative electrode current collector (e.g., an aluminum-based conductive substrate).

[0019] The positive electrode 106 can include a positive electrode active material, such as one or more of lithium metal, sapphire, graphene, silicon, silicon oxide, tin, tin oxide lithium, or another tin oxide. It will be appreciated that other positive electrode active materials can be contemplated within the scope of the present disclosure. The positive electrode active material can be included in a positive electrode slurry, which can be cast, dried, and calendered onto a positive electrode current collector (e.g., a copper-based conductive substrate). The positive electrode 106 can also include a conductive additive and a binder. As an example, the conductive additive can be carbon black, and the binder can be polyvinylidene fluoride. In some examples, the conductive additive and / or the binder can be a single material or multiple materials, which are similar to the materials mentioned above with respect to the negative electrode active material. The conductive additive and the binder are not particularly limited in composition and can be known to those of ordinary skill in the art.

[0020] The separator 108 can have high porosity, excellent stability in the electrolyte 110, and excellent absorption properties. Exemplary materials for the separator 108 can be selected from non-woven fabrics or porous membranes made of polyolefins, such as polyethylene and / or polypropylene, or ceramic-coated polymeric materials. Other materials can be used for the separator 108, as known to at least those of ordinary skill in the art.

[0021] The electrolyte 110 can be formed from an electrolyte composition that includes a conductive salt and at least four additives. As Figure 1A As exemplified in the foregoing, each electrolyte composition provided herein can include at least LiFSI (e.g., as a conductive salt), VC, FEC, PS, and ES (e.g., as the at least four additives). Such particular electrolyte compositions can impart corresponding particular technical benefits to the lithium-ion battery 100. For example, the inventors recognize herein that an electrolyte (e.g., 110) that includes LiFSI in combination with particular amounts of VC, FEC, PS, and ES additives dispersed in a lithium-ion battery (e.g., 100) can slow capacity fade at high SOC (e.g., 100%) during high-temperature (e.g., 60°C) storage without corroding the negative electrode current collector. In other words, using LiFSI as the primary conductive salt and the particular amounts of additives mentioned above, in combination, exhibits unexpected advantages in terms of moisture resistance and improving battery performance, as compared to other approaches that, for example, rely on lithium hexafluorophosphate (LiPF6) as the primary conductive salt.

[0022] In additional or alternative examples, the electrolyte composition can also include LiPF6 as a secondary conductive salt. In further or alternative examples, the at least four additives can also include 1,3,2-dioxazolothiophene 2,2-dioxide (DTD). LiPF6 and / or DTD can be combined with LiFSI, VC, FEC, PS, and ES in particular ratios to balance various battery performance benefits in the lithium-ion battery 100.

[0023] The conductive salt can include one or both of a primary conductive salt and a secondary conductive salt. In some examples, the primary (majority) conductive salt can be LiFSI, and the secondary (e.g., minority) conductive salt can be LiPF6.

[0024] In other examples, however, the electrolyte composition can not include or substantially not include a secondary conductive salt. In such examples, LiFSI can be the only conductive salt included in the electrolyte composition.

[0025] The use of LiFSI as the primary conductive salt can improve the capacity retention of the lithium-ion battery 100 because LiFSI can not produce hydrogen fluoride (HF) in side reactions with moisture, which can be detrimental to battery performance. In this way, the electrolyte 110 can have a higher resistance to moisture and can better maintain battery performance compared to electrolytes with LiPF6 as the primary conductive salt, because excess LiPF6 can produce hydrogen fluoride that is detrimental to battery performance. LiFSI and LiPF6 can be included in the electrolyte 110 at a ratio selected to preserve the battery performance benefits attributed mostly to LiFSI. For example, the primary conductive salt (e.g., LiFSI) can make up 80 mole percent or more of all conductive salts (e.g., primary and secondary conductive salts) in the electrolyte composition, such that sufficient LiFSI can be present to provide capacity retention benefits for the lithium-ion battery 100. As such, the secondary conductive salt (e.g., LiPF6) can make up 20 mole percent or less of all conductive salts in the electrolyte composition.

[0026] In some examples, the primary conductive salt can be greater than 80 mole percent of all conductive salts in the electrolyte composition. In other examples, the primary conductive salt can be greater than 85 mole percent of all conductive salts in the electrolyte composition. In other examples, the primary conductive salt can be greater than 90 mole percent of all conductive salts in the electrolyte composition. In other examples, the primary conductive salt can be greater than 95 mole percent of all conductive salts in the electrolyte composition. In other examples, the primary conductive salt can make up 100 mole percent of all conductive salts in the electrolyte composition (e.g., the secondary conductive salt can not be present). In one example, the primary conductive salt can make up about 80 mole percent of all conductive salts in the electrolyte composition (as used herein, “about” can refer to a numerical value having a tolerance or deviation of up to 5 percent). In another example, the primary conductive salt can make up substantially exactly 80 mole percent of all conductive salts in the electrolyte composition.

[0027] In some examples, the secondary conductive salt can be less than 20 mole % of all conductive salts in the electrolyte composition. In other examples, the secondary conductive salt can be less than 15 mole % of all conductive salts in the electrolyte composition. In other examples, the secondary conductive salt can be less than 10 mole % of all conductive salts in the electrolyte composition. In other examples, the secondary conductive salt can be less than 5 mole % of all conductive salts in the electrolyte composition. In one example, the secondary conductive salt can be about 20 mole % of all conductive salts in the electrolyte composition. In another example, the secondary conductive salt can be substantially exactly 20 mole % of all conductive salts in the electrolyte composition.

[0028] The at least four additives can include a first additive, for example, VC. In some examples, the first additive can be present in the electrolyte composition from 0.1 wt% to 10 wt%. In other examples, the first additive can be present in the electrolyte composition from 0.2 wt% to 5 wt%. In other examples, the first additive can be present in the electrolyte composition from 0.5 wt% to 2 wt%. In one example, the first additive can be VC and present in the electrolyte composition from 0.5 wt% to 1.5 wt%.

[0029] The at least four additives can also include a second additive, for example, FEC. In some examples, the second additive can be present in the electrolyte composition from 0.1 wt% to 10 wt%. In other examples, the second additive can be present in the electrolyte composition from 0.2 wt% to 5 wt%. In other examples, the second additive can be present in the electrolyte composition from 0.5 wt% to 2 wt%. In one example, the second additive can be FEC and present in the electrolyte composition from 0.5 wt% to 1.5 wt%.

[0030] The at least four additives can also include a third additive, for example, PS. In some examples, the third additive can be present in the electrolyte composition from 0.1 wt% to 10 wt%. In other examples, the third additive can be present in the electrolyte composition from 0.2 wt% to 5 wt%. In other examples, the third additive can be present in the electrolyte composition from 0.5 wt% to 2 wt%. In one example, the third additive can be PS and present in the electrolyte composition from 0.5 wt% to 1.5 wt%.

[0031] The at least four additives can also include a fourth additive, e.g., ES. In some examples, the fourth additive can be present in the electrolyte composition from 0.1 wt% to 10 wt%. In other examples, the fourth additive can be present in the electrolyte composition from 0.2 wt% to 5 wt%. In other examples, the fourth additive can be present in the electrolyte composition from 0.5 wt% to 2 wt%. In one example, the fourth additive can be ES and present in the electrolyte composition from 0.5 wt% to 1.5 wt%.

[0032] In some examples, the at least four additives can include one or more additional additives other than VC, FEC, PC, and ES. For example, the at least four additives can also include a fifth additive, e.g., DTD. In some examples, the fifth additive can be present in the electrolyte composition from 0.1 wt% to 10 wt%. In other examples, the fifth additive can be present in the electrolyte composition from 0.2 wt% to 5 wt%. In other examples, the fifth additive can be present in the electrolyte composition from 0.2 wt% to 2 wt%. In some examples, the fifth additive can be DTD and present in the electrolyte composition from 0.5 wt% to 1.5 wt%.

[0033] The electrolyte 110 can be non-aqueous in that each of the conductive salt and the additives can be dissolved in a non-aqueous solvent. In particular, the non-aqueous solvent can include one or more cyclic carbonate solvents and one or more linear carbonate solvents. The one or more cyclic carbonate solvents can include diethyl carbonate (EC) and propylene carbonate (PC). The one or more linear carbonate solvents can include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). In some examples, the non-aqueous solvent can also include one or more propionate derivative solvents, e.g., ethyl propionate (EP) and / or methyl propionate (MP). The one or more propionate derivative solvents can increase the overall wettability of the electrolyte 110 and decrease the viscosity of the electrolyte 110 such that the electrolyte 110 can be suitable for low temperature power applications. Other solvents can be included in the electrolyte 110 as known to at least those of ordinary skill in the art.

[0034] Reference is now made to Figure 1BGraphs 120 and 140 depict exemplary electrolyte compositions for use in lithium-ion batteries (e.g., 100). Each electrolyte composition can include LiFSI as a first conductive salt 150, VC as a first additive 151, FEC as a second additive 152, PS as a third additive 153, ES as a fourth additive 154, and a non-aqueous solvent 160; optionally, DTD as a fifth additive 156 and / or LiPF6 as a second conductive salt 158 can also be included in the exemplary electrolyte compositions. Graphs 120 and 140 also indicate the relative amounts of the various components by weight, indicating that the conductive salt can be included in the exemplary electrolyte compositions in substantially greater amounts than the additives, and that the first, second, third, fourth, and fifth additives (e.g., 151, 152, 153, 154, and 156) can be included in substantially equal amounts.

[0035] For example, as shown in graph 120, a first electrolyte composition can include 10-15 wt% of a first conductive salt 150 (e.g., LiFSI), 1-5 wt% of a second conductive salt 158 (e.g., LiPF6), 0.5-1.5 wt% of a first additive 151 (e.g., VC), 0.5-1.5 wt% of a second additive 152 (e.g., FEC), 0.5-1.5 wt% of a third additive 153 (e.g., PS), 0.5-1.5 wt% of a fourth additive 154 (e.g., ES), and a non-aqueous solvent 160, specifically including 30-50 wt% EMC, 20-30 wt% EC, 0-10 wt% PC, and 0-10 wt% DEC.

[0036] The exemplary electrolyte compositions can also include a fifth additive 156. For example, as shown in graph 140, a second electrolyte composition can include 12-16 wt% of a first conductive salt 150 (e.g., LiFSI), 0.5-1.5 wt% of a first additive 151 (e.g., VC), 0.5-1.5 wt% of a second additive 152 (e.g., FEC), 0.5-1.5 wt% of a third additive 153 (e.g., PS), 0.5-1.5 wt% of a fourth additive 154 (e.g., ES), 0.5-1.5 wt% of a fifth additive 156 (e.g., DTD), and a non-aqueous solvent 160, specifically including 30-50 wt% EMC, 20-30 wt% EC, 5-20 wt% DMC, 5-20 wt% EP, 0-10 wt% PC, and 0-10 wt% DEC.

[0037] The electrolyte compositions provided herein can impart unique electrochemical benefits to lithium ion batteries (e.g., 100) by virtue of the specific amounts of each component included therein and the specific ratios between the components. For example, the inclusion of small amounts (e.g., 0.5 wt% to 1.5 wt%) of substantially equal amounts of each of VC, FEC, PS, and ES (e.g., additives 151, 152, 153, and 154) in the electrolyte composition can provide the capacity retention and impedance benefits discussed in detail below with respect to Figure 2A and Figure 2B The capacity retention and impedance benefits discussed in detail below. Such electrolyte compositions are not anticipated in the art because only the complex combination of specific amounts of specific components can yield the claimed technical advantages.

[0038] The preparation of a given electrolyte composition for use in a lithium ion battery (e.g., 100) is discussed in more detail below with respect to Figure 3 Briefly, the electrolyte composition can be prepared in one or more mixing steps that include mixing each of LiFSI, VC, FEC, PS, and ES (each in particulate form) and, optionally, LiPF6and / or DTD (each in particulate form) in a nonaqueous solvent until each of the conductive salts and additives is substantially dissolved. As such, in some examples, no filtration, sieving (e.g., for particle size control), or purification steps can be used in the preparation of the electrolyte composition. The electrolyte composition can then be used to fill the empty volume of a lithium ion battery.

[0039] Referring now to Figure 2A Graph 200 depicts the relative capacity of exemplary lithium ion batteries in high temperature (about 60 °C) storage at substantially 100% SOC. In particular, the dashed curve 202 shows the relative capacity of a first lithium ion battery that includes an electrolyte with LiPF6as the primary (e.g., majority) conductive salt, while the solid curve 204 shows the relative capacity of a second lithium ion battery that includes an electrolyte with the first electrolyte composition (e.g., with LiFSI as the primary conductive salt, with LiPF6as the secondary conductive salt, and with VC, FEC, PS, and ES as additives) as described above with respect to Figure 1B

[0040] Referring now to Figure 2B Graph 206 depicts the relative impedance of exemplary lithium ion batteries in high temperature (about 60 °C) storage at substantially 100% SOC. In particular, the dashed curve 208 shows the relative impedance of a first lithium ion battery that includes an electrolyte with LiPF6as the primary (e.g., majority) conductive salt, while the solid curve 210 shows the relative impedance of a second lithium ion battery that includes an electrolyte with the first electrolyte composition (e.g., with LiFSI as the primary conductive salt, with LiPF6as the secondary conductive salt, and with VC, FEC, PS, and ES as additives) as described above with respect to Figure 1B ​The relative impedance of a second lithium-ion battery of the described first electrolyte composition (e.g., with LiFSI as the primary conductive salt, with LiPF6 as the secondary conductive salt, and with VC, FEC, PS, and ES as the additives) electrolyte.

[0041] As shown by comparing the solid curve 204 to the dashed curve 202 in the plot 200 of Figure 2A As further shown by comparing the solid curve 210 to the dashed curve 208 in the plot 206 of Figure 2B As further shown by comparing the solid curve 210 to the dashed curve 208 in the plot 206 of - hydrolysis of PF6 anions attributed to LiPF6, such as occurs when LiPF6 is included as the primary conductive salt, as in the first lithium-ion battery. In some examples, the deleterious effects can include corrosion of the negative current collector in the lithium-ion battery, which arises from the HF production from the hydrolysis of PF6 anions during high-temperature storage. In some examples, the deleterious effects can include corrosion of the negative current collector in the lithium-ion battery, which arises from the HF production from the hydrolysis of PF6 anions during high-temperature storage. - In this way, improved lithium-ion battery capacity retention can be imparted via the use of the particular electrolyte compositions provided herein, as compared to similar batteries that rely on the use of LiPF6 as the primary conductive salt in combination with suboptimal additive ratios.

[0042] Referring now to Figure 3 , a flowchart of a method 300 for forming an electrolyte composition for use in a lithium-ion battery is depicted. In particular, the electrolyte composition can be formed by dissolving at least one primary conductive salt and four additives in a nonaqueous solvent, from which the electrolyte composition can then fill the empty volume of a lithium-ion battery. It will be appreciated that the method 300 can be described with respect to the components described above with reference to Figure 1A and Figure 1B For example, the lithium-ion battery can be the lithium-ion battery 100, while the electrolyte composition can characterize the electrolyte 110.

[0043] At 302, the method 300 can include forming an electrolyte composition. In particular, at 304, a first conductive salt can be mixed in a non-aqueous solvent until the first conductive salt is substantially dissolved in the non-aqueous solvent. The first conductive salt can be a primary conductive salt. That is, the first conductive salt can be a majority component (by molar concentration) of all conductive salts included in the electrolyte composition. In some examples, the first conductive salt can be LiFSI.

[0044] At 306, a second conductive salt can be optionally mixed in the non-aqueous solvent until the second conductive salt is substantially dissolved in the non-aqueous solvent. The second conductive salt can be a secondary conductive salt. That is, the second conductive salt can be a minority component (by molar concentration) of all conductive salts included in the electrolyte composition. For example, the molar ratio of the first conductive salt to the second conductive salt can be no less than 4: 1 (but can be higher than 4: 1). In some examples, the second conductive salt can be LiPF6.

[0045] At 308, a first additive can be mixed in the non-aqueous solvent until the first additive is substantially dissolved in the non-aqueous solvent. In some examples, the first additive can be added in an amount sufficient to form 0.5% to 1.5% by weight of the electrolyte composition ultimately formed.

[0046] At 310, a second additive can be mixed in the non-aqueous solvent until the second additive is substantially dissolved in the non-aqueous solvent. In some examples, the second additive can be added in an amount sufficient to form 0.5% to 1.5% by weight of the electrolyte composition ultimately formed.

[0047] At 312, a third additive can be mixed in the non-aqueous solvent until the third additive is substantially dissolved in the non-aqueous solvent. In some examples, the third additive can be added in an amount sufficient to form 0.5% to 1.5% by weight of the electrolyte composition ultimately formed.

[0048] At 314, a fourth additive can be mixed in the non-aqueous solvent until the fourth additive is substantially dissolved in the non-aqueous solvent. In some examples, the fourth additive can be added in an amount sufficient to form 0.5% to 1.5% by weight of the electrolyte composition ultimately formed.

[0049] The first through fourth additives can be selected from VC, FEC, PS, and ES. However, once an additive is selected, the additive cannot be selected again. As a non-limiting example, in the case where the first additive is selected to be VC, the second, third, and fourth additives then cannot be VC (but can be selected from FEC, PS, and ES). In this case, if the second additive is then selected to be FEC, the third and fourth additives cannot be VC or FEC (but can be selected from PS and ES), and so on.

[0050] At 316, the fifth additive can optionally be mixed in the non-aqueous solvent until the fifth additive is substantially dissolved in the non-aqueous solvent. In some examples, the fifth additive can be DTD. In some examples, the fifth additive can be added in an amount sufficient to form 0.5 wt% to 1.5 wt% of the finally formed electrolyte composition.

[0051] The mixing steps described above can be performed in a container of any format sufficient for mixing the desired volume. In some examples, the mixing can be performed by hand shaking or via mechanical shaking for 5 minutes or another duration (e.g., 1 minute, 10 minutes, 30 minutes, or 60 minutes). In some examples, the mixing can be performed at a predetermined speed (e.g., 2000 RPM) or at another mixing speed (e.g., 1000 RPM, 1500 RPM, or 2500 RPM). The type of mixing container and process used is not particularly limited and can be known to one of ordinary skill in the art. It will be appreciated that the mixing parameters can vary depending on the desired electrolyte composition. Further, it can be appreciated that in some examples, the formation of the electrolyte composition can include a filtration step (e.g., after step 316 of method 300). However, in other examples, it can be appreciated that filtration can not be used without departing from the scope of the present disclosure.

[0052] Accordingly, an electrolyte composition can be formed. As a first example, the electrolyte composition can include 1 wt% to 5 wt% LiPF6, 10 wt% to 15 wt% LiFSI, 0.5 wt% to 1.5 wt% VC, 0.5 wt% to 1.5 wt% FEC, 0.5 wt% to 1.5 wt% PS, 0.5 wt% to 1.5 wt% ES, 30 wt% to 50 wt% EMC, 20 wt% to 30 wt% EC, 0 wt% to 10 wt% PC, and 0 wt% to 10 wt% DEC. As a second example, the electrolyte composition can include 12 wt% to 16 wt% LiFSI, 0.5 wt% to 1.5 wt% VC, 0.5 wt% to 1.5 wt% FEC, 0.5 wt% to 1.5 wt% PS, 0.5 wt% to 1.5 wt% ES, 0.5 wt% to 1.5 wt% DTD, 30 wt% to 50 wt% EMC, 20 wt% to 30 wt% EC, 5 wt% to 20 wt% DMC, 5 wt% to 20 wt% EP, 0 wt% to 10 wt% PC, and 0 wt% to 10 wt% DEC. It will be appreciated that numerous electrolyte compositions can be contemplated by one of ordinary skill in the art within the scope of the present disclosure. That is, the electrolyte compositions described above are merely exemplary and should not be construed as limiting the scope within the present disclosure.

[0053] At 318, the method 300 can include filling the empty volume of the lithium-ion battery with the electrolyte composition. For example, the anode, the cathode, and the separator can be placed within the housing. The empty volume within the housing that is not occupied by the anode, the cathode, or the separator, as well as the pores of the anode, the cathode, and the separator can be filled with the electrolyte composition such that each of the anode, the cathode, and the separator is immersed in the electrolyte composition. The housing can be air-tight such that the anode, the cathode, the separator, and the electrolyte composition are enclosed within the housing. The method 300 can then end.

[0054] In this way, an electrolyte composition for a lithium-ion battery is provided. The electrolyte composition can include LiFSI as the primary conductive salt, thereby partially or completely replacing LiPF6 as the primary conductive salt. The technical effect of selecting LiFSI as the primary conductive salt is that detrimental side reactions involving LiPF6 can be avoided. The electrolyte composition can also include specific amounts of VC, FEC, PS, and ES by weight ratio to maximize the electrochemical benefits attributed to the use of LiFSI. In some examples, DTD can also be included as an additive in the electrolyte composition. The technical effect of such specific electrolyte composition is that capacity fade in the lithium-ion battery can be mitigated, especially during high-temperature storage at high SOC.

[0055] In one example, an electrolyte composition includes VC, FEC, PS, ES, and a conductive salt including not less than 80 mole % of LiFSI. A first example of the electrolyte composition further includes where the conductive salt includes LiPF6. A second example of the electrolyte composition, optionally including the first example of the electrolyte composition, further includes where LiPF6 comprises 20 mole % or less of the conductive salt. A third example of the electrolyte composition, optionally including one or more of the first and second examples of the electrolyte composition, further includes where LiFSI comprises 100 mole % of the conductive salt. A fourth example of the electrolyte composition, optionally including one or more of the first through third examples of the electrolyte composition, further includes DTD. A fifth example of the electrolyte composition, optionally including one or more of the first through fourth examples of the electrolyte composition, further includes where DTD comprises 0.5 wt % to 1.5 wt % of the electrolyte composition. A sixth example of the electrolyte composition, optionally including one or more of the first through fifth examples of the electrolyte composition, further includes where LiFSI comprises 10 wt % to 15 wt % of the electrolyte composition and LiPF6 comprises 1 wt % to 5 wt % of the electrolyte composition. A seventh example of the electrolyte composition, optionally including one or more of the first through sixth examples of the electrolyte composition, further includes where LiFSI comprises 12 wt % to 16 wt % of the electrolyte composition. An eighth example of the electrolyte composition, optionally including one or more of the first through seventh examples of the electrolyte composition, further includes where VC comprises 0.5 wt % to 1.5 wt % of the electrolyte composition, FEC comprises 0.5 wt % to 1.5 wt % of the electrolyte composition, PS comprises 0.5 wt % to 1.5 wt % of the electrolyte composition, and ES comprises 0.5 wt % to 1.5 wt % of the electrolyte composition. A ninth example of the electrolyte composition, optionally including one or more of the first through eighth examples of the electrolyte composition, further includes a nonaqueous solvent selected from the group including EC, PC, DEC, EMC, DMC, EP, MP, and combinations thereof.

[0056] In another example, a lithium ion battery, the lithium ion battery comprising: a negative electrode; a positive electrode; a separator disposed between the negative electrode and the positive electrode; and a non-aqueous electrolyte comprising one or more cyclic carbonate solvents, one or more linear carbonate solvents, VC, FEC, PS, ES, and a conductive salt comprising not less than 80 mole % of LiFSI, wherein each of the negative electrode, the positive electrode, and the separator is immersed in the non-aqueous electrolyte. A first example of the lithium ion battery further comprises wherein the conductive salt further comprises LiPF6. A second example of the lithium ion battery, optionally comprising the first example of the lithium ion battery, further comprises wherein the non-aqueous electrolyte further comprises DTD. A third example of the lithium ion battery, optionally comprising one or more of the first example of the lithium ion battery and the second example of the lithium ion battery, further comprises wherein the non-aqueous electrolyte further comprises one or more propionic acid derivative solvents.

[0057] In yet another example, a method, the method comprising: forming an electrolyte composition, comprising: mixing a first conductive salt in a non-aqueous solvent until the first conductive salt is substantially dissolved, wherein the first conductive salt is LiFSI and the first conductive salt comprises no less than 80 mole percent of all conductive salts of the electrolyte composition; mixing a first additive in the non-aqueous solvent until the first additive is substantially dissolved; mixing a second additive in the non-aqueous solvent until the second additive is substantially dissolved; mixing a third additive in the non-aqueous solvent until the third additive is substantially dissolved; and mixing a fourth additive in the non-aqueous solvent until the fourth additive is substantially dissolved, wherein the first additive through the fourth additive each comprise one of VC, FEC, PS, and ES, and the first additive through the fourth additive are not the same; and filling a void volume of a lithium-ion battery with the electrolyte composition. A first example of the method further comprises wherein the non-aqueous solvent is selected from the group comprising: EC, PC, DEC, EMC, DMC, EP, MP, and combinations thereof. A second example of the method, optionally comprising the first example of the method, further comprises wherein forming the electrolyte composition further comprises mixing a second conductive salt in a non-aqueous solvent until the second conductive salt is substantially dissolved, wherein the second conductive salt is LiPF6. A third example of the method, optionally comprising one or more of the first example and the second example of the method, further comprises wherein forming the electrolyte composition further comprises mixing a fifth additive in the non-aqueous solvent until the fifth additive is substantially dissolved, wherein the fifth additive is DTD. A fourth example of the method, optionally comprising one or more of the first example through the third example of the method, further comprises wherein the electrolyte composition comprises: 10 weight percent to 15 weight percent of the first conductive salt; 1 weight percent to 5 weight percent of the second conductive salt; 0.5 weight percent to 1.5 weight percent of the first additive; 0.5 weight percent to 1.5 weight percent of the second additive; 0.5 weight percent to 1.5 weight percent of the third additive; 0.5 weight percent to 1.5 weight percent of the fourth additive; 30 weight percent to 50 weight percent of a first component of the non-aqueous solvent, the first component being EMC; 20 weight percent to 30 weight percent of a second component of the non-aqueous solvent, the second component being EC; 0 weight percent to 10 weight percent of a third component of the non-aqueous solvent, the third component being PC; and 0 weight percent to 10 weight percent of a fourth component of the non-aqueous solvent, the fourth component being DEC.A fifth example of the method, optionally including one or more of the first through fourth examples of the method, further includes wherein the electrolyte composition includes: 12 to 16 percent by weight of the first conductive salt; 0.5 to 1.5 percent by weight of the first additive; 0.5 to 1.5 percent by weight of the second additive; 0.5 to 1.5 percent by weight of the third additive; 0.5 to 1.5 percent by weight of the fourth additive; 0.5 to 1.5 percent by weight of the fifth additive; 30 to 50 percent by weight of a first component of the nonaqueous solvent, the first component being EMC; 20 to 30 percent by weight of a second component of the nonaqueous solvent, the second component being EC; 0 to 10 percent by weight of a third component of the nonaqueous solvent, the third component being PC; 0 to 10 percent by weight of a fourth component of the nonaqueous solvent, the fourth component being DEC; 5 to 20 percent by weight of a fifth component of the nonaqueous solvent, the fifth component being DMC; and 5 to 20 percent by weight of a sixth component of the nonaqueous solvent, the sixth component being EP.

[0058] The foregoing claims are considered particularly pointed out as being novel and non-obvious. These claims can refer to "a" or "a first" element or the equivalent thereof. Such claims should be understood as including one or more of such elements, without requiring or excluding two or more of such elements. Other combinations and subcombinations of disclosed features, functions, elements, and / or properties can be claimed by amendment of the present claims or by presentation of additional claims in the application or in related applications. Such amended claims, whether they broaden or narrow the claims, are to be considered within the scope of the disclosure.

Claims

1. An electrolyte composition, the electrolyte composition comprising: vinylene carbonate (VC); fluoroethylene carbonate (FEC); 1,3-propane sultone (PS), wherein the PS comprises 5 wt% to 10 wt% of the electrolyte composition; vinyl sulfite (ES); a conductive salt comprising greater than 90 mole% of lithium bis(fluorosulfonyl)imide (LiFSI); and 1,3,2-dioxazolothiophene 2,2-dioxide (DTD), wherein the DTD comprises 0.5 wt% to 1.5 wt% of the electrolyte composition.

2. The electrolyte composition of claim 1, wherein, the conductive salt comprises LiPF6.

3. The electrolyte composition of claim 2, wherein, the LiPF6comprises 20 mole% or less of the conductive salt, or the LiFSI comprises 100 mole% of the conductive salt.

4. The electrolyte composition of claim 2, wherein the LiFSI comprises 10 wt% to 15 wt% of the electrolyte composition; and the LiPF6comprises 1 wt% to 5 wt% of the electrolyte composition.

5. The electrolyte composition of claim 1, wherein, the LiFSI comprises 12 wt% to 16 wt% of the electrolyte composition.

6. The electrolyte composition of claim 1, wherein the vinylene carbonate comprises 0.5 wt% to 1.5 wt% of the electrolyte composition; the fluoroethylene carbonate comprises 0.5 wt% to 1.5 wt% of the electrolyte composition; and the vinyl sulfite comprises 0.5 wt% to 1.5 wt% of the electrolyte composition.

7. The electrolyte composition of any one of the preceding claims, further comprising a non-aqueous solvent selected from the group comprising: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), ethyl propionate (EP), methyl propionate (MP), and combinations thereof.

8. A lithium ion battery, the lithium ion battery comprising: a negative electrode; a positive electrode; a separator disposed between the negative electrode and the positive electrode; and the electrolyte composition of claim 1.

9. A method of making an electrolyte composition, the method comprising: forming an electrolyte composition, comprising: mixing a first conductive salt in a non-aqueous solvent until the first conductive salt dissolves, wherein the first conductive salt is lithium bis(fluorosulfonyl)imide (LiFSI) and the first conductive salt comprises greater than 90 mole% of all conductive salts in the electrolyte composition; mixing a first additive in the non-aqueous solvent until the first additive dissolves; mixing a second additive in the non-aqueous solvent until the second additive dissolves; mixing a third additive in the non-aqueous solvent until the third additive dissolves; mixing a fourth additive in the non-aqueous solvent until the fourth additive dissolves, and mixing a fifth additive in the non-aqueous solvent until the fifth additive dissolves, ​ wherein the first additive through the fifth additive each include one of vinylene carbonate VC, fluoroethylene carbonate FEC, 1,3-propane sultone PS, ethylene sulfite ES, and 1,3,2-dioxathiolane 2,2-dioxide DTD, and none of the first additive through the fifth additive are the same, wherein the PS is 0.5 wt% to 1.5 wt% of the electrolyte composition, and the DTD is 0.5 wt% to 1.5 wt% of the electrolyte composition; and filling a void volume of a lithium ion battery with the electrolyte composition.

10. The method of claim 9, wherein, The non-aqueous solvent is selected from the group including: ethylene carbonate EC, propylene carbonate PC, diethyl carbonate DEC, ethyl methyl carbonate EMC, dimethyl carbonate DMC, ethyl propionate EP, methyl propionate MP, and combinations thereof; wherein forming the electrolyte composition further comprises: mixing a second conductive salt in a non-aqueous solvent until the second conductive salt is dissolved, wherein the second conductive salt is lithium hexafluorophosphate LiPF6.

11. The method of claim 10, wherein, The electrolyte composition includes: 10 wt% to 15 wt% of the first conductive salt; 1 wt% to 5 wt% of the second conductive salt; 0.5 wt% to 1.5 wt% of the first additive; 0.5 wt% to 1.5 wt% of the second additive; 0.5 wt% to 1.5 wt% of the fourth additive; 30 wt% to 50 wt% of a first component of the non-aqueous solvent, the first component being ethyl methyl carbonate; 20 wt% to 30 wt% of a second component of the non-aqueous solvent, the second component being vinylene carbonate; 0 wt% to 10 wt% of a third component of the non-aqueous solvent, the third component being propylene carbonate; and 0 wt% to 10 wt% of a fourth component of the non-aqueous solvent, the fourth component being diethyl carbonate.

12. The method of claim 9, wherein, The electrolyte composition includes: 12 wt% to 16 wt% of the first conductive salt; 0.5 wt% to 1.5 wt% of the first additive; 0.5 wt% to 1.5 wt% of the second additive; 0.5 wt% to 1.5 wt% of the fourth additive; 30 wt% to 50 wt% of a first component of the non-aqueous solvent, the first component being ethyl methyl carbonate; 20 wt% to 30 wt% of a second component of the non-aqueous solvent, the second component being vinylene carbonate; 0 wt% to 10 wt% of a third component of the non-aqueous solvent, the third component being propylene carbonate; 0 wt% to 10 wt% of a fourth component of the non-aqueous solvent, the fourth component being diethyl carbonate; 5 wt% to 20 wt% of a fifth component of the non-aqueous solvent, the fifth component being dimethyl carbonate; and 5 wt% to 20 wt% of a sixth component of the non-aqueous solvent, the sixth component being ethyl propionate.

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