Electrolyte system for lithium-selenium-chalcogen batteries

Abstract

Electrochemical cell in which lithium ions move back and forth, comprising: Electrode comprising a chalcogen-containing electroactive material, wherein the chalcogen-containing electroactive material comprises elemental selenium or a selenium-containing active material; and Electrolyte system, including: one or more lithium salts selected from the group consisting of: lithium bis(fluorosulfonyl)imide (LiN(FSO2)2), bis(trifluoromethane)sulfonimide lithium salt (LiN(CF3SO2)2), lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium difluoro(oxalato)borate (LiBF2(C2O4)), LiPF3(C2F5)3, LiPF4(CF3)2, lithium tetrafluoro(oxalato)phosphate (LiPF4(C2O4)), LiPF3(CF3)3, LiSO3CF3 and combinations thereof, and one or more solvents selected from the group consisting of: cyclic carbonates, linear carbonates, aliphatic carboxylic esters, γ-lactones, chain structure ethers, cyclic ethers and combinations thereof, wherein the electrolyte system is essentially free of lithium nitrate (LiNO3) and the electrochemical cell has a minimum charge potential of more than or equal to about 0.8 V to less than or equal to about 1.8 V.

Description

INTRODUCTION

[0001] This section provides background information relating to the present disclosure, which is not necessarily the prior art.

[0002] The present disclosure relates to electrolyte systems for electrochemical cells with electrodes, including a chalcogen-containing electroactive material and methods for producing the electrolyte systems.

[0003] Against this background, high-energy-density electrochemical cells, such as lithium-ion and lithium-sulfur batteries, can be used in a wide variety of consumer products and vehicles, including hybrid electric vehicles (HEVs) and electric vehicles (EVs). Typical lithium-ion and lithium-sulfur chalcogen batteries comprise a first electrode, a second electrode, an electrolyte material, and a separator. One electrode serves as the positive electrode or cathode, and the other serves as the negative electrode or anode. Often, a stack of lithium-ion battery cells is electrically interconnected to increase overall performance. Conventional rechargeable lithium-ion and lithium-sulfur chalcogen batteries operate by reversibly transferring lithium ions back and forth between the negative and positive electrodes.An electrically insulating separator and an electrolyte are positioned between the negative and positive electrodes. The electrolyte is suitable for conducting lithium ions and can be in solid (e.g., solid-state diffusion) or liquid form. During charging, lithium ions move from a cathode (positive electrode) to an anode (negative electrode), and during discharging, they move in the opposite direction.

[0004] Many different materials can be used to manufacture components for lithium-ion batteries and lithium-chalcogen batteries (e.g., lithium-sulfur-chalcogen batteries, lithium-selenium-chalcogen batteries). As a non-restrictive example, cathode materials for lithium-ion batteries typically include an electroactive material into which lithium ions can be inserted or alloyed. The electrolyte typically contains one or more lithium salts that can be dissolved and ionized in a non-aqueous solvent, such as a carbonate-based or ether-based solvent system. Common negative electrode materials include lithium insertion materials or alloy host materials, such as carbon-based materials like lithium-graphite intercalation compounds or lithium-silicon compounds, lithium-tin alloys, and lithium titanate (Li₄³⁺Ti₅O₆). 12, where 0 ≤ x ≤ 3, such as Li4Ti5O 12 (LTO). The negative electrode can also be made of a lithium-containing material such as metallic lithium, so the electrochemical cell is considered a lithium-metal battery or cell.

[0005] Electrochemical cells, particularly lithium chalcogen batteries, with an electrolyte containing lithium nitrate (LiNO3), generally exhibit a minimum voltage of approximately 1.8 V, as the lithium nitrate (LiNO3) decomposes below this voltage and subsequently becomes gaseous. This minimum voltage can result in an energy loss of about 15%. Nevertheless, lithium nitrate (LiNO3) is generally included in the electrolyte for rechargeable lithium chalcogen batteries to induce successful cyclic charging of the electrochemical cell. Furthermore, the electrolyte system is generally limited to ether-based solvents, as opposed to, for example, carbonate-based electrolytes, due to the negative effects of active radical chalcogens, particularly in sulfur-based batteries, which can form in the presence of carbonate-based electrolytes.Accordingly, it would be desirable to develop materials for use in rechargeable lithium chalcogen batteries, especially lithium sulfur and lithium selenium chalcogen batteries, which exhibit both increased energy densities and desirable levels of redox reactions.

[0006] Well-known lithium chalcogen batteries are described, for example, in DE 10 2015 119 522 A1. SUMMARY

[0007] This section provides a general summary of the disclosure and is not a comprehensive disclosure of the full scope of protection or all features.

[0008] According to the invention, the present disclosure presents an electrochemical cell in which lithium ions move back and forth. The electrochemical cell can comprise an electrode comprising a chalcogen-containing electroactive material, wherein the chalcogen-containing electroactive material comprises elemental selenium or a selenium-containing active material, and an electrolyte system comprising one or more lithium salts selected from the group consisting of: lithium bis(fluorosulfonyl)imide (LiN(FSO2)2), bis(trifluoromethane)sulfonimide lithium salt (Li(CF3SO2)2), lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiC lO4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium difluoro(oxalato) borate (LiBF2(C2O4)), LiPF3(C2F5)3, LiPF4(CF3)2, lithium tetrafluoro(oxalato) phosphate (LiPF4(C2O4)), LiPF3(CF3)3, LiSO3CF3 and combinations thereof, as well as one or more solvents selected from the group consisting of: cyclic carbonates, linear carbonates, aliphatic carboxylic esters, γ-lactones, chain ethers, cyclic ethers and combinations thereof. The electrolyte system may be substantially free of lithium nitrate (LiNO3); and the electrochemical cell may have a minimum charge potential of more than or equal to about 0.8 V to less than or equal to about 1.8 V.

[0009] According to one aspect, the electrochemical cell can have a maximum charge potential of more than or equal to about 2.5 V down to less than or equal to about 3 V.

[0010] According to one aspect, the one or more lithium salts in the electrolyte system can have a concentration of more than or equal to about 2 M up to less than or equal to about 5 M.

[0011] According to one aspect, the cyclic carbonates can be selected from the group consisting of: ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, fluoroethylene carbonate (FEC) and combinations thereof; the linear carbonates can be selected from the group consisting of: dimethyl carbonate (DMC), dimethyl dicarbonate (DMDC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and combinations thereof; the aliphatic carboxylic acid esters can be selected from the group consisting of: methyl formate, methyl acetate, methyl propionate and combinations thereof; the γ-lactones can be selected from the group consisting of: γ-butyrolactone, γ-valerolactone and combinations thereof; the chain structure ethers can be selected from the following group: 1,2-dimethoxyethane (DME), 1,2-diethoxyethane, ethoxymethoxyethane and combinations thereof;and the cyclic ethers can be selected from the group consisting of: 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran and combinations thereof.;

[0012] According to one aspect, after 25 cycles of lithium ions moving back and forth in the electrode of the electrochemical cell, the electrochemical cell may exhibit a Coulomb capacitance loss of less than or equal to approximately 10%.

[0013] Not according to the invention, the present disclosure presents another exemplary electrochemical cell in which lithium ions move back and forth. The electrochemical cell can comprise a positive electrode comprising a chalcogen-containing electroactive material, a separator, a negative electrode comprising a negative electroactive material, and an electrolyte system with one or more lithium salts selected from the group consisting of: lithium bis(fluorosulfonyl)imide (LiN(FSO2)2), bis(trifluoromethane)sulfonimide lithium salt (LiN(CF3SO2)2), lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiC lO4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium difluoro(oxalato) borate (LiBF2(C2O4)), LiPF3(C2F5)3, LiPF4(CF3)2, lithium tetrafluoro(oxalato) phosphate (LiPF4(C2O4)), LiPF3(CF3)3, LiSO3CF3 and combinations thereof; and one or more solvents selected from the group consisting of: ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), dimethyl dicarbonate (DMDC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, methyl propionate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran and combinations thereof.The electrolyte system can be essentially free of lithium nitrate (LiNO3), and the electrochemical cell can have a minimum charge potential of more than or equal to about 0.8 V to less than or equal to about 1.8 V and a maximum charge potential of more than or equal to about 2.5 V to less than or equal to about 3 V.

[0014] According to one aspect, the one or more lithium salts in the electrolyte system have a concentration of more than or equal to about 2 M to less than or equal to about 5 M.

[0015] According to one aspect, the chalcogen-containing electroactive material can include elemental sulfur or a sulfur-containing active material.

[0016] According to one aspect, the chalcogen-containing electroactive material can include elemental selenium or a selenium-containing active material.

[0017] According to one aspect, after 25 cycles of lithium ions moving back and forth in the electrode of the electrochemical cell, the electrochemical cell may exhibit a Coulomb capacitance loss of less than or equal to approximately 10%.

[0018] Not according to the invention, the present disclosure provides a method for producing an electrolyte system that improves or increases the energy density and promotes stable cycling behavior of an electrochemical cell with an electrode comprising a chalcogen-containing electroactive material. The electrochemical cell can have a minimum charge potential of more than or equal to about 0.8 V to less than or equal to about 1.8 V and a maximum charge potential of more than or equal to about 2.5 V to less than or equal to about 3 V. The method can include mixing one or more lithium salts selected from the group consisting of: lithium bis(fluorosulfonyl)imide (LiN(FSO2)2), bis(trifluoromethane)sulfonimide lithium salt (Li(CF3SO2)2), lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiC6). lO4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium difluoro(oxalato) borate (LiBF2(C2O4)), LiPF3(C2F5)3, LiPF4(CF3)2, lithium tetrafluoro(oxalato) phosphate (LiPF4(C2O4)), LiPF3(CF3)3, LiSO3CF3 and combinations thereof, as well as one or more solvents selected from the group consisting of: cyclic carbonates, linear carbonates, aliphatic carboxylic esters, γ-lactones, chain ethers, cyclic ethers and combinations thereof. The electrolyte system may be essentially free of lithium nitrate (LiNO3).

[0019] According to one aspect, the one or more lithium salts in the electrolyte system can have a concentration of more than or equal to about 2 M up to less than or equal to about 5 M.

[0020] According to one aspect, the cyclic carbonates can be selected from the group consisting of: ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, fluoroethylene carbonate (FEC) and combinations thereof; the linear carbonates can be selected from the group consisting of: dimethyl carbonate (DMC), dimethyl dicarbonate (DMDC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and combinations thereof; the aliphatic carboxylic acid esters can be selected from the group consisting of: methyl formate, methyl acetate, methyl propionate and combinations thereof; the γ-lactones can be selected from the group consisting of: γ-butyrolactone, γ-valerolactone and combinations thereof; the chain structure ethers can be selected from the following group: 1,2-dimethoxyethane (DME), 1,2-diethoxyethane, ethoxymethoxyethane and combinations thereof;and the cyclic ethers can be selected from the group consisting of: 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran and combinations thereof.;

[0021] According to one aspect, the chalcogen-containing electroactive material can include elemental sulfur or a sulfur-containing active material.

[0022] According to one aspect, the chalcogen-containing electroactive material can include elemental selenium or a selenium-containing active material.

[0023] According to one aspect, the electrochemical cell may exhibit a capacity loss of less than or equal to approximately 10% over 100 cycles.

[0024] Further areas of application will become apparent from the description presented here. The description and specific examples in this summary serve solely for illustration and are in no way intended to limit the scope of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described here serve solely to illustrate selected embodiments and do not represent the entirety of possible realizations and are not intended to limit the scope of the present disclosure. Fig. Figure 1 is a schematic representation of an exemplary electrochemical battery cell with a separator. Fig. Figures 2A - 2B are graphical representations of a lithium-sulfur-chalcogen battery with an electrolyte system containing an ether-based solvent and lithium nitrate (LiNO3); Fig. 2A is a graphical representation of voltages (V) and capacities (mAh), and Fig. 2B is a graphical representation of differential capacitance analyses (dQ / dV) and voltages (V). Fig. 3A-3C are graphical representations of a lithium selenium chalcogen battery; Fig. 3A is a graphical representation of the voltages (V) and capacities (mAh) for a lithium selenium chalcogen battery with an electrolyte system containing a carbonate-based solvent; Fig. Figure 3B is a graphical representation of the voltages (V) and capacities (mAh) for a lithium selenium chalcogen battery with an electrolyte system containing a carbonate-based solvent and lithium nitrate (LiNO3); and Fig. 3C is a graphical representation of voltage (V) and capacity (mAh) for a lithium selenium chalcogen battery with an electrolyte system manufactured according to certain aspects of the present disclosure. Fig. Figure 4 is a graphical representation of the capacity conservation per cycle of an example of an electrochemical cell comprising an electrolyte system manufactured according to certain aspects of the present disclosure.

[0026] Similar reference symbols in the different views of the drawings denote similar parts. DETAILED DESCRIPTION

[0027] Exemplary embodiments are provided to ensure that this disclosure is thorough and fully conveys its scope to those skilled in the art. Numerous specific details are presented, such as examples of specific compositions, components, devices, and methods, to facilitate a thorough understanding of embodiments of the present disclosure. Those skilled in the art will recognize that specific details may not be necessary, that exemplary embodiments can take many different forms, and that none of the embodiments is intended to limit the scope of the disclosure. In some exemplary embodiments, well-known methods, well-known device structures, and well-known techniques are not described in detail.

[0028] The terminology used herein serves solely to describe certain exemplary embodiments and is not intended to be restrictive in any way. As used herein, the singular forms "a" and "the" include the plural forms where appropriate, unless the context clearly excludes this. The terms "comprises," "comprehensive," "included," and "exhibit" are inclusive and therefore indicate the presence of the specified features, elements, combinations, steps, integers, processes, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, processes, elements, components, and / or groups thereof.Although the term “comprises” is to be understood as a non-restrictive term used to describe and claim various embodiments set forth herein, the term may, under certain considerations, be understood alternatively, for example, as a more limiting and restrictive term, such as “consisting of” or “consisting substantially of”. Thus, any embodiment that lists compositions, materials, components, elements, functions, integers, operations, and / or process steps expressly includes, in the present disclosure, embodiments consisting of, or consisting substantially of, such compositions, materials, components, elements, functions, numbers, operations, and / or process steps.In the case of "consisting of", the alternative embodiment excludes any additional compositions, materials, components, elements, functions, numbers, operations, and / or process steps, whereas in the case of "consisting essentially of", any additional compositions, materials, components, elements, functions, numbers, operations, and / or process steps that materially impair the basic and new properties are excluded from such an embodiment, however, any compositions, materials, components, elements, functions, integers, operations, and / or process steps that materially do not impair the basic and new properties may be included in the embodiment.

[0029] All procedures, processes, and operations described herein are not to be interpreted as meaning that the described or depicted sequence is absolutely necessary, unless specifically stated as the order of execution. It should also be noted that additional or alternative steps may be applied unless otherwise specified.

[0030] When a component, element, or layer is described as "on / at," "interacting with," "connected with," or "coupled with" another component, element, or layer, it may be directly on / at, interacting with, connected to, or coupled with that other component, element, or layer, or there may be intervening elements or layers. Conversely, when an element is described as "directly on / at," "directly interacting with," "directly connected with," or "directly coupled with" another element or layer, there may be no intervening elements or layers. Other words used to describe the relationship between elements are to be understood in the same way (e.g., "between" and "directly between," "adjacent" and "directly adjacent," etc.).As used here, the term “and / or” includes all combinations of one or more of the related listed elements.

[0031] Although the terms first, second, third, etc., may be used here to describe different steps, elements, components, areas, layers, and / or sections, these steps, elements, components, areas, layers, and / or sections are not intended to be restricted by these expressions. These terms are used only to distinguish one step, element, component, area, layer, or section from another. Terms such as "first," "second," and other numerical terms, when used herein, do not imply any sequence or order unless clearly indicated by the context.Thus, a first step, first element, component, area, layer or section discussed below could be referred to as a second step, second element, second component, second area, second layer or second section without deviating from the teaching of the exemplary embodiments.

[0032] Spatial or temporal terms, such as "before," "after," "inner," "outer," "below," "under," "lower," "above," "upper," and the like, can be used here to better describe the relationship of one element or property to other element(s) or property(ies), as illustrated in the figures. Spatial or temporal terms may also be intended to describe various arrangements of the device or system in use or operation, in addition to the orientation shown in the figures.

[0033] In this disclosure, the numerical values ​​generally represent approximate measured values ​​or limits of ranges, including minor deviations from the specified values ​​and embodiments that exhibit approximately the stated value, as well as those with exactly the stated value. In contrast to the application examples provided at the end of the detailed description, all numerical values ​​of the parameters (e.g., quantities or conditions) in this specification, including the appended claims, are to be understood in all cases by the term "approximately," regardless of whether or not "approximately" actually precedes the numerical value. "Approximately" indicates that the disclosed numerical value permits a certain degree of inaccuracy (with a certain approximation to exactness in the value; approximately or realistically close to the value; close to).If the imprecision provided by "approximately" is not otherwise understood in technical circles by this ordinary meaning, then "approximately," as used herein, indicates at least variations resulting from ordinary methods of measurement and the use of such parameters. For example, "about" may include a variation of less than or equal to 5%, possibly less than or equal to 4%, possibly less than or equal to 3%, possibly less than or equal to 2%, possibly less than or equal to 1%, possibly less than or equal to 0.5%, and, under certain considerations, possibly less than or equal to 0.1%.

[0034] Furthermore, specifying ranges includes specifying all values ​​and further subdivided ranges within the entire range, including the endpoints and sub-ranges specified for the ranges.

[0035] Exemplary embodiments will now be described in more detail with reference to the accompanying drawings.

[0036] The present technology relates to improved electrochemical cells, including batteries, in particular lithium-selenium batteries, which can be used in vehicle applications. However, the current technology can also be used in other electrochemical devices, especially those containing lithium, such as other lithium chalcogen batteries.

[0037] An exemplary and schematic representation of a battery 20 in which lithium ions move back and forth is shown in Fig. Figure 1 shows the battery 20 as follows: The battery 20 can be an electrochemical lithium-ion cell, an electrochemical lithium-sulfur cell (not according to the invention), or a lithium-selenium battery (according to the invention), each comprising a negative electrode 22, a positive electrode 24, and a porous separator 26 arranged between the two electrodes 22 and 24. The separator 26 comprises an electrolyte system 30, which may also be contained in the negative electrode 22 and the positive electrode 24. A negative electrode current collector 32 can be arranged on or near the negative electrode 22, and a positive electrode current collector 34 can be positioned on or near the positive electrode 24. The negative electrode current collector 32 and the positive electrode current collector 34 each accept the electrons and transport the free electrons to and from an external circuit 40.An interruptible external circuit 40 and consumer device 42 connects the negative electrode 22 (via its current collector 32) and the positive electrode 24 (via its current collector 34).

[0038] The porous separator 26, which serves both as an electrical insulator and for mechanical support, is inserted between the negative electrode 22 and the positive electrode 24 to prevent physical contact and thus avoid the occurrence of a short circuit. In addition to providing a physical barrier between the two electrodes 22 and 24, the porous separator 26 can provide a minimal resistance path for the internal passage of lithium ions (and their associated anions) during the lithium-ion cycle, thus supporting the function of the battery 20. While in lithium-ion batteries lithium is incorporated into or alloyed with the active materials of the electrode, in a lithium-sulfur battery, instead of being incorporated into or alloyed with it, the lithium detaches from the negative electrode and migrates to the positive electrode, where it reacts during discharge.This is plated, while during charging it plates the negative electrode.

[0039] The battery 20 can be recharged and made usable at any time by connecting an external voltage source to it, thus reversing the electroactive reactions of battery discharge. Connecting an external voltage source to the battery 20 forces the generation of electrons and the release of lithium ions from the positive electrode 24. The electrons, which flow back to the negative electrode 22 through the external circuit 40, and the lithium ions, which are transported back to the negative electrode 22 through the electrolyte 30 and the separator 26, recombine at the negative electrode 22 and replenish it with stored lithium for use in the next battery discharge cycle. Thus, each discharge and charge event is considered a cycle in which lithium ions move back and forth between the positive electrode 24 and the negative electrode 22.

[0040] The external voltage source used to charge the battery 20 can vary in size, construction, and the specific end application of the battery 20. Some notable and exemplary external sources include, but are not limited to, an AC wall outlet and a motor vehicle alternator. In many lithium-ion, lithium-sulfur, and lithium-selenium battery configurations, the negative current collector 32, the negative electrode 22, the separator 26, the positive electrode 24, and the positive current collector 34 are each fabricated as relatively thin layers (for example, from a few micrometers to one millimeter or less in thickness) and assembled in layers that are connected in electrical parallel to provide a suitable energy package.

[0041] Furthermore, the battery 20 may include a variety of other components which, although not shown here, are well known to experts. For example, the battery 20 may include a casing, seals, terminal caps, tabs, battery terminals, and any other conventional components or materials that may be located within the battery 20, including, as a non-limiting example, between or around the negative electrode 22, the positive electrode 24, and / or the separator 26. As mentioned above, the size and shape of the battery 20 may vary depending on the specific application for which it is designed. Battery-powered vehicles and portable consumer electronics are two examples where the battery 20 would likely have a different size, capacity, and power output.The battery 20 can also be connected in series or parallel with other, similar lithium-ion cells or batteries to produce a greater voltage output, energy and power when required by the consumer 42.

[0042] Accordingly, the battery 20 can generate electrical current at a load 42, which may be operationally connected to the external circuit 40. While the load 42 can be any number of electrically powered devices, some specific examples of current-consuming load devices include an electric motor for a hybrid or fully electric vehicle, a laptop computer, a tablet computer, a mobile phone, and a cordless power tool or household appliances as non-limiting examples. The load device 42 can also be a power-generating device that charges the battery 20 to store energy. In some other variations, the electrochemical cell can be a supercapacitor, such as a lithium-ion-based supercapacitor.

[0043] With renewed reference to Fig. 1. In certain cases, the porous separator 26 may include a microporous polymeric separator, including a polyolefin as a non-restrictive example. The polyolefin may be a homopolymer (derived from a single monomer component) or a heteropolymer (derived from more than one monomer component), which may be either linear or branched. If a heteropolymer is derived from two monomer components, the polyolefin may adopt any copolymer chain arrangement, including that of a block copolymer or a statistical copolymer. Likewise, a polyolefin that is a heteropolymer derived from more than two monomer components may also be a block copolymer or a statistical copolymer. In certain aspects, the polyolefin may be polyethylene (PE), polypropylene (PP), or a mixture of PE and PP, or a multilayered structured porous film of PE and / or PP.Commercially available porous polyolefin membranes 26 include CELGARD® 2500 (a single-layer polypropylene separator) and CELGARD® 2320 (a three-layer polypropylene / polyethylene / polypropylene separator) from Celgard LLC.

[0044] If the porous separator 26 is a microporous polymeric separator, it can be a single layer or a multilayer laminate produced by either a dry or wet process. For example, in one embodiment, a single layer of the polyolefin can constitute the entire microporous polymeric separator 26. Regarding other aspects, the separator 26 can be a fibrous membrane with numerous pores extending between opposing surfaces and can, for example, have a thickness of less than one millimeter. As another example, the microporous polymeric separator 26 can also be composed of several separate layers of the same or dissimilar polyolefin. Furthermore, the porous separator 26 can be blended with a ceramic material or its surface can be coated with a ceramic material.A ceramic coating can, for example, contain aluminum oxide (Al₂O₃), silicon dioxide (SiO₂), or combinations thereof. Various conventional polymers and commercial products for the formation of separator 26 are considered, as well as the many manufacturing processes that can be used to produce such a microporous polymeric separator 26.

[0045] In a lithium-ion battery, the positive electrode 24 can be formed from a lithium-based active material capable of undergoing sufficient lithium insertion and removal, alloying and delegating, or plating and stripping while serving as the positive terminal of the battery 20. For example, in a lithium-sulfur-chalcogen battery, the positive electrode 24 can comprise sulfur-based compounds as a positive active material. A sulfur-based compound can consist of at least one of: elemental sulfur, Li₂Sn (where n is greater than or equal to 1), Li₂Sn (where n is greater than or equal to 1) dissolved in a catholyte, an organic sulfur compound, or a carbon-sulfur polymer (e.g., (C₂S₂)₂). x ) n(where x = 2.5, and n is 2 or greater) or any combination thereof. In a lithium-selenium-chalcogen battery, the positive electrode can comprise 24 selenium-based compounds as the positive active material. A selenium-based compound can be selected from the following: elemental selenium, selenium sulfide alloys, and combinations thereof.

[0046] In certain variations, these positive active materials can be mixed with an optional electrically conductive material and at least one polymeric binder to structurally reinforce the positive active material along with optionally dispersed electrically conductive particles. For example, the active materials and optional conductive materials can be cast with binders such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), ethylene propylene diene monomer (EPDM) rubber, carboxymethylcellulose (CMC), nitrile butadiene rubber (NBR), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, or lithium alginate. Electrically conductive materials can include graphite, carbon-containing materials, nickel powder, metal particles, or a conductive polymer. Carbon-containing materials can be represented by a non-restrictive example, KETCHEN. TM -, THINK TMThese include acetylene, carbon black particles, and the like. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole, and the like. In certain aspects, mixtures of conductive materials may be used. The positive current collector 34 may be made of aluminum (Al) or any other suitable electrically conductive material.

[0047] According to various aspects, the negative electrode 22 contains an electroactive material in the form of a lithium host material, which can serve as the negative terminal of a lithium-ion battery. The electroactive material comprises lithium in various aspects and can be lithium metal. The negative electrode 22 can thus include the electroactive lithium host material and, optionally, another electrically conductive material as well as one or more polymeric binding materials for structurally holding the lithium host material together.For example, in certain cases, the negative electrode 22 may contain an active material comprising graphite, silicon (Si), tin (Sn), or other negative electrode particles mixed with a binder material selected from the group consisting of: polyvinylidene fluoride (PVDF), ethylene propylene diene monomer (EPDM) rubber or carboxymethylcellulose (CMC), nitrile butadiene rubber (NBR), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate, polyimides, and combinations thereof, as a non-limiting example. Suitable additional electrically conductive materials may include carbon-containing materials or a conductive polymer. Carbon-containing materials may include, as a non-limiting example, KETCHEN. TM -, THINK TMThese include acetylene, carbon black particles, and the like. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole, and the like. In certain applications, mixtures of conductive materials can be used.

[0048] Graphite is frequently used to form the negative electrode 22 because it exhibits desirable properties for lithium insertion and removal, is relatively non-reactive in the environment of electrochemical cells, and can store lithium in quantities that result in a relatively high energy density. Commercial graphite forms and other graphene materials that can be used to fabricate the negative electrode 22 are available, as a non-limiting example, from Timcal Graphite and Carbon by Bodio, Switzerland; Lonza Group, Basel, Switzerland; or Superior Graphite, Chicago, USA. Other materials can also be used to form the negative electrode 22, including, for example, lithium-silicon and silicon-containing binary and ternary alloys and / or tin-containing alloys such as Si-Sn, SiSnFe, SiSnAl, SiFeCo, SnO2, and the like. In certain cases, lithium-titanium anode materials such as Li4+xTi5O are conceivable. 12, where 0 ≤ x ≤ 3, including lithium titanate (Li4Ti5O) 12 ) (LTO). The negative electrode current collector 32 can be made of copper (Cu) or any other suitable electrically conductive material, as is known to those skilled in the art.

[0049] In various aspects, the positive electrode 24, the negative electrode 22, and the separator 26 can each comprise an electrolyte solution or system 30 capable of conducting lithium ions between the negative electrode 22 and the positive electrode 24. The electrolyte system 30 can be a non-aqueous liquid electrolyte solution comprising one or more salts dissolved in a solvent or a mixture of solvents. Depending on certain aspects, the one or more salts can have a concentration in the electrolyte of more than or equal to approximately 2 M up to less than or equal to approximately 5 M, and optionally, depending on certain aspects, more than or equal to approximately 2.5 M up to less than or equal to approximately 4.5 M.

[0050] In certain variations, the one or more salts may comprise one or more lithium salts selected from the group consisting of: lithium bis(fluorosulfonyl)imide (LiN(FSO2)2) (“LIFSI”), bis(trifluoromethane)sulfonimide lithium salt (Li(CF3SO2)2) (“LITFSI”), lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiC l O4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium difluoro(oxalato) borate (LiBF2(C2O4)) (“LiODFB”), LiPF3(C2F5)3 (“LiFAP”), LiPF4(CF3)2, lithium tetrafluoro(oxalato) phosphate (LiPF4(C2O4))) (“LiFOP”), LiPF3(CF3)3, LiSO3CF3, and combinations thereof. Optionally, depending on certain aspects, one or more lithium salts from the group consisting of: lithium bis(fluorosulfonyl)imide (LiN(FSO2)2) (“LIFSI”), bis(trifluoromethane)sulfonimide lithium salt (Li(CF3SO2)2) (“LITFSI”), and combinations thereof may be selected.

[0051] In certain variations, the solvent or solvent mixture may comprise one or more organic solvents selected from the group consisting of: cyclic carbonates, linear carbonates, aliphatic carboxylic esters, γ-lactones, chain ethers, cyclic ethers, and combinations thereof. Depending on various aspects, the cyclic carbonates may be selected from the group consisting of: ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, fluoroethylene carbonate (FEC), and combinations thereof; the linear carbonates may be selected from the group consisting of: dimethyl carbonate (DMC), dimethyl dicarbonate (DMDC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and combinations thereof; the aliphatic carboxylic esters may be selected from the group consisting of: methyl formate, methyl acetate, methyl propionate, and combinations thereof.The γ-lactones can be selected from the group consisting of: γ-butyrolactone, γ-valerolactone, and combinations thereof; the chain structure ethers can be selected from the group consisting of: 1,2-dimethoxyethane (DME), 1,2-diethoxyethane, ethoxymethoxyethane, and combinations thereof; and the cyclic ethers can be selected from the group consisting of: 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, and combinations thereof. Optionally, one or more solvents can be selected from the group consisting of: 1,2-dimethoxyethane (DME), dimethyl dicarbonate (DMDC), fluoroethylene carbonate (FEC), and combinations thereof, depending on specific criteria.

[0052] According to various aspects, the electrolyte system 30 improves the energy density and promotes stable long-term cycle performance of the battery 20, particularly without lithium nitrate (LiNO3) and without a general restriction on the solvent class (e.g., carbonate-based solvent versus ether-based solvent). The electrochemical cell containing the electrolyte system 30 can have a minimum potential of more than or equal to approximately 0.8 V to less than or equal to approximately 1.8 V and a maximum charge potential of more than or equal to approximately 2.5 V to less than or equal to approximately 3 V, and optionally, depending on specific considerations, a maximum charge potential of more than or equal to approximately 2.7 V to less than or equal to approximately 3 V.

[0053] As a non-restrictive background, lithium chalcogen batteries, in which the chalcogen-containing electroactive material includes elemental sulfur or a sulfur-containing active material, generally require the use of an ether-based electrolyte system because internal redox reactions form active radicals that attack one or more of the solvents, particularly carbonate-based solvents. However, such electrolyte systems often require the use or inclusion of lithium nitrate (LiNO3), without which the lithium sulfur chalcogen battery may not successfully charge or complete its cycles. Such batteries, as in the Fig. Figures 2A-2B show a minimum or cutoff voltage of approximately 1.8 V because lithium nitrate (LiNO3) decomposes and becomes gaseous, which can lead to energy loss, for example, an energy loss of approximately 15%. As shown, the lithium-sulfur-chalcogen battery has a capacity of less than approximately 0.5 mAh. The y-axis or vertical axis 60 of Fig. Line 2A shows the voltage (V), while the x-axis, or horizontal axis 62, represents the capacity in milliampere-hours (mAh). Line 64 of Fig. 2A is the charge-voltage curve, while line 66 illustrates the decomposition of lithium nitrate (LiNO3) within a lithium-sulfur-chalcogen battery, including an ether-based solvent. The y-axis, or vertical axis 70, of Fig. Figure 2B shows the differential capacitance analysis (dQ / dV), while the x-axis or horizontal axis 72 represents the voltage (V). Line 74 of Fig. Figure 2B shows the lithium nitrate (LiNO3) decomposition voltage, which starts at about 1.85 V.

[0054] In contrast, rechargeable lithium-chalcogen batteries, where the chalcogen-containing electroactive material includes elemental selenium or a selenium-containing active material, are not generally limited to ether-based electrolyte systems, as the elemental selenium or the selenium-containing active material does not form the same active radicals as, for example, sulfur. Although the use of a wider variety of solvents is possible, the electrolyte systems of many lithium-selenium-chalcogen batteries also require the use or inclusion of lithium nitrate (LiNO3), without which the lithium-selenium-chalcogen battery may not successfully charge or complete its cycles, due to, for example, the internal redox reaction occurring within it.

[0055] As can be seen in FIG. 3A, the lithium-selenium-chalcogen battery stabilizes at approximately 2.2 V when no use or inclusion of lithium nitrate (LiNO3) is intended. The y-axis or vertical axis 80 of Fig. Line 3A shows the voltage (V), while the x-axis or horizontal axis 82 represents the capacity in milliampere-hours (mAh). Line 84 of Fig. Line 3A shows the charging voltage, while line 86 represents the discharge voltage curve. Line 84 clearly shows an internal redox reaction. As in Fig. As can be seen in Figure 3B, the charge potential of the lithium-selenium-chalcogen battery (see line 94) increases when the system contains lithium nitrate (LiNO3). As shown in Fig. As can be seen in Figure 2A, the lithium selenium chalcogen battery has a minimum or cutoff voltage of approximately 1.8 V (see line 96) because lithium nitrate (LiNO3) decomposes and then becomes gaseous, which can lead to an energy loss of about 15%. As shown, the lithium selenium chalcogen battery has a capacity of less than approximately 0.5 mAh. The y-axis, or vertical axis 90, of Fig. Line 3B shows the voltage (V), while the x-axis or horizontal axis 92 represents the capacity in milliampere-hours (mAh). Line 94 of Fig. Figure 3B shows the successful suppression of an internal redox reaction, while line 96 illustrates the discharge voltage.

[0056] Fig. Figure 3C illustrates a lithium-selenium-chalcogen battery with an electrolyte system prepared according to certain aspects of the present disclosure. The electrolyte system comprises a concentration of about 4.0 M lithium bis(fluorosulfonyl)imide (LiN(FSO₂)₂) (“LIFSI”) in 1,2-dimethoxyethane. As shown, the lithium-selenium-chalcogen battery containing the electrolyte system prepared according to certain aspects of the present disclosure exhibits a minimum potential of more than or equal to about 0.8 V to less than or equal to about 1.8 V, a maximum charge potential of more than or equal to about 2.5 V to less than or equal to about 3 V, and a capacity of about 0.7 mAh. The lithium-chalcogen battery with an electrolyte system (e.g., Figure 30) prepared according to certain aspects of the present disclosure thus provides sufficient redox potential while also possessing an improved energy density.The y-axis or vertical axis 100 of . Fig. Line 3C shows the voltage (V), while the x-axis, or horizontal axis 102, represents the capacity in milliampere-hours (mAh). Line 104 of Fig. 3C shows the successful charging of the lithium selenium chalcogen battery, including the prepared electrolyte system, to approximately 2.7 V with no lithium nitrate (LiNO3) present, while line 106 illustrates the discharge voltage.

[0057] From certain perspectives, the electrochemical cell, which contains a chalcogen-containing electrodeactive material and an electrolyte system as described above, exhibits good capacity conservation, for example with a Coulomb capacitance loss of less than or equal to about 10% after 25 cycles of reciprocating lithium ions in the electrode of the electrochemical cell.

[0058] The embodiments of the present technology are further illustrated by the following non-limiting example. Example 1

[0059] Fig.Figure 4 shows the charge and discharge profiles (e.g., cycle life) of the electrochemical reference cells 110, 120, and 130, which comprise an electrode containing a chalcogen-containing electroactive material and various electrolyte systems containing one or more lithium salts along with one or more solvents. The y-axis, or vertical axis 140, represents the capacity maintenance in milliampere-hours (mAh), while the cycle number is shown on the x-axis 150. Electrochemical cell 110 comprises a conventional basic electrolyte system comprising the lithium salts bis(trifluoromethane)sulfonimide lithium salt (Li(CF3SO2)2) (“LITFSI”) and lithium nitrate (LiNO3) in 1,2-dimethoxyethane (DME). Electrochemical cells 120 and 130 comprise electrolyte systems prepared according to certain aspects of the present disclosure.In particular, the electrolyte system of electrochemical cell 120 comprises lithium bis(fluorosulfonyl)imide (LiN(FSO2)2) ("LIFSI") in 1,2-dimethoxyethane (DME), an ether-based solvent. The electrolyte system of electrochemical cell 130 comprises lithium bis(fluorosulfonyl)imide (LiN(FSO2)2) ("LIFSI") in dimethyl dicarbonate (DMDC), a carbonate-based solvent. The electrolyte systems of electrochemical cells 120 and 130 have a lithium bis(fluorosulfonyl)imide (LiN(FSO2)2) ("LIFSI") salt concentration of approximately 4 M.

[0060] As can be seen, electrochemical cells 120 and 130 have improved over electrochemical cell 110 in the long term. In particular, electrochemical cell 110, which contains lithium nitrate (LiNO3), experiences an immediate and continuous capacity loss, while electrochemical cells 120 and 130 experience little to no capacity loss. Accordingly, electrochemical cells 120 and 130, manufactured according to certain aspects of the present disclosure, exhibit significantly improved cycle performance and reduced capacity decay.

Claims

[1] Electrochemical cell in which lithium ions move back and forth, comprising: Electrode comprising a chalcogen-containing electroactive material, wherein the chalcogen-containing electroactive material comprises elemental selenium or a selenium-containing active material; and Electrolyte system, including: one or more lithium salts selected from the group consisting of: lithium bis(fluorosulfonyl)imide (LiN(FSO2)2), bis(trifluoromethane)sulfonimide lithium salt (LiN(CF3SO2)2), lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium difluoro(oxalato)borate (LiBF2(C2O4)), LiPF3(C2F5)3, LiPF4(CF3)2, lithium tetrafluoro(oxalato)phosphate (LiPF4(C2O4)), LiPF3(CF3)3, LiSO3CF3 and combinations thereof, and one or more solvents selected from the group consisting of: cyclic carbonates, linear carbonates, aliphatic carboxylic esters, γ-lactones, chain structure ethers, cyclic ethers and combinations thereof, wherein the electrolyte system is essentially free of lithium nitrate (LiNO3) and the electrochemical cell has a minimum charge potential of more than or equal to about 0.8 V to less than or equal to about 1.8 V. [2] Electrochemical cell according to claim 1, wherein the electrochemical cell has a maximum charge potential of more than or equal to about 2.5 V to less than or equal to about 3 V. [3] Electrochemical cell according to claim 1, wherein the one or more lithium salts in the electrolyte system have a concentration of more than or equal to about 2 M to less than or equal to about 5 M. [4] Electrochemical cell according to claim 1, wherein the cyclic carbonates are selected from the group consisting of: ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, fluoroethylene carbonate (FEC) and combinations thereof; wherein linear carbonates are selected from the group consisting of: dimethyl carbonate (DMC), dimethyl dicarbonate (DMDC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and combinations thereof; wherein the aliphatic carboxylic acid esters are selected from the group consisting of: methyl formate, methyl acetate, methyl propionate and combinations thereof; wherein γ-lactones are selected from the group consisting of: γ-butyrolactone, γ-valerolactone and combinations thereof; wherein chain structure ethers are selected from the group consisting of: 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane and combinations thereof; and where cyclic ethers are selected from the group consisting of: 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran and combinations thereof. [5] Electrochemical cell according to claim 1, wherein the electrochemical cell has a Coulomb capacitance loss of less than or equal to about 10% after 25 cycles of reciprocating lithium ions in the electrode of the electrochemical cell.

Images