In-situ control of solid electrolyte interface for improving the cycle performance of lithium metal cells.

Abstract

This invention provides an electrochemical cell for increasing the cycle life of lithium metal batteries. [Solution] An electrochemical cell is provided comprising an anode containing lithium metal, a lithium alloy, or a combination thereof as an anode active material, an electrolyte containing a fluorinated organic solvent, a cathode, and a solid electrolyte interface layer disposed between the anode and the electrolyte, wherein the solid electrolyte interface layer contains LiF and has (1) a hardness of 0.001 GPa or more and 5 GPa or less, and / or (2) a porosity of 1% or more and 90% or less, and the electrochemical cell exhibits a decrease in discharge capacity of 10% or less after 100 charge-discharge cycles relative to the discharge capacity at the 5th charge-discharge cycle after formation.

Description

[Technical Field]

[0001] This invention relates in general to lithium batteries, and more specifically to in-situ control of a solid electrolyte interface for improving the cycle performance of lithium metal batteries. [Background technology]

[0002] In recent years, there has been considerable interest in the development of high-energy-density rechargeable batteries with lithium-containing anodes. In such cells, current electrolytes, particularly those used in low-temperature applications, are typically based on solutions of lithium salts and carbonate electrolytes. In particular, lithium metal anodes are highly reactive with typical electrolytes and consequently degrade rapidly in the presence of these electrolytes during charging and discharging. As a result, lithium metal rechargeable batteries using such electrolytes generally exhibit a limited cycle life. Therefore, articles and methods for increasing cycle life, as well as other improvements, are desirable. [Overview of the project]

[0003] This invention relates in general to lithium batteries, and more specifically to in-situ control of solid electrolyte interfaces for improving the performance of lithium metal batteries. The subject matter disclosed herein includes, in some cases, interrelated products, alternative solutions to specific problems, and / or multiple different applications of one or more systems and / or articles.

[0004] In some embodiments, an electrochemical cell is provided.

[0005] In some embodiments, the electrochemical cell comprises an anode containing lithium metal, a lithium alloy, or a combination thereof as an anode active material, an electrolyte containing a fluorinated organic solvent, a cathode, and a solid electrolyte interphase layer disposed between the anode and the electrolyte, wherein the solid electrolyte interphase layer contains an inorganic material containing LiF and Li2CO3, and a first ratio of fluorine atoms to oxygen atoms adjacent to the electrolyte is higher than a second ratio of fluorine atoms to oxygen atoms adjacent to the anode in the solid electrolyte interphase layer.

[0006] In some embodiments, the electrochemical cell comprises an anode containing lithium metal, a lithium alloy, or a combination thereof as an anode active material; an electrolyte containing a fluorinated organic solvent; a cathode; and a solid electrolyte interface layer disposed between the cathode and the electrolyte, wherein the solid electrolyte interface layer contains LiF and has (1) a hardness of 0.001 GPa to 5 GPa; and / or (2) a porosity of 1% to 90%, and the electrochemical cell exhibits a decrease in discharge capacity of 10% or less after 100 charge-discharge cycles relative to the discharge capacity at the 5th charge-discharge cycle after formation.

[0007] In some embodiments, the electrochemical cell comprises an anode containing lithium metal, a lithium alloy, or a combination thereof as an anode active material; an electrolyte containing a fluorinated organic solvent; a cathode; and a solid electrolyte interface layer disposed between the cathode and the electrolyte, wherein the solid electrolyte interface layer contains LiF and has (1) a hardness of 0.001 GPa to 5 GPa; and / or (2) a porosity of 1% to 90%, and the electrochemical cell exhibits an increase in discharge resistance of 10% or less after 100 charge-discharge cycles compared to the discharge resistance after the 5th charge-discharge cycle after formation.

[0008] In some embodiments, methods for storing and using electrical energy are provided.

[0009] In some embodiments, the method comprises an electrochemical cell having an anode having a surface, the anode having a lithium metal, lithium alloy, or a combination thereof as an anode active material; a cathode; and an electrolyte having a fluorinated organic solvent disposed between the cathode and the anode, the method comprising the steps of applying an anisotropic force to the surface of the anode; applying a formation voltage during at least one period of charging and / or discharging the cell; and forming a solid electrolyte interface layer adjacent to the surface of the anode, wherein the formation voltage is greater than 4.35 V; and the solid electrolyte interface layer comprises an inorganic material having LiF and Li2CO3. [Brief explanation of the drawing]

[0010] Non-limiting embodiments of the present invention will be described by reference to the accompanying drawings, which are schematic and not intended to be shown to a specific scale. In the drawings, each identical or substantially identical component shown is usually represented by a single number. For clarity, not all components are necessarily labeled in all drawings, and the drawings are all components of each embodiment of the present invention shown where it is not necessary for those skilled in the art to understand the invention. [Figure 1] These are schematic cross-sectional views of electrochemical cells including a solid electrolyte interface (SEI) layer according to various embodiments. [Figure 2] This is a schematic cross-sectional view of a solid electrolyte interface layer containing LiF, according to several embodiments. [Figure 3A] This is a schematic cross-sectional view of a solid electrolyte interface (SEI) layer containing a substantially non-uniform distribution of inorganic materials (e.g., LiF and / or Li2CO3) according to various embodiments. [Figure 3B] This is a schematic cross-sectional view of a solid electrolyte interface (SEI) layer containing a substantially homogeneous distribution of inorganic material (e.g., LiF and / or Li2CO3) according to various embodiments. [Figure 4]This graph shows a comparison of the cell cycle lifetime of an electrochemical cell containing a LiF-rich SEI layer, cycled under pressure according to several embodiments, and the cell cycle lifetime of an electrochemical cell cycled without pressure. [Figure 5] This graph shows a comparison of the cell cycle lifetime of an electrochemical cell containing a LiF-rich SEI layer, cycled under pressure according to several embodiments, and the cell cycle lifetime of an electrochemical cell cycled without pressure. [Figure 6] This graph shows a comparison of the cell cycle lifetime of an electrochemical cell containing a LiF-rich SEI layer, cycled under pressure according to several embodiments, and the cell cycle lifetime of an electrochemical cell cycled without pressure. [Figure 7] This graph shows a comparison of the cell cycle lifetime of an electrochemical cell containing a LiF-rich SEI layer, cycled under pressure according to several embodiments, and the cell cycle lifetime of an electrochemical cell cycled without pressure. [Figure 8A] This graph shows a comparison of the cell cycle lifetime of an electrochemical cell containing a LiF-rich SEI layer, cycled under pressure according to several embodiments, and the cell cycle lifetime of an electrochemical cell cycled without pressure. [Figure 8B] This is a graph showing the 5-minute discharge resistance of electrochemical cells according to several embodiments, from Figure 8A. [Figure 9] This graph shows a comparison of the cell cycle life of an electrochemical cell having a LiF-rich SEI layer according to several embodiments, and the cell cycle life of an electrochemical cell without a LiF-containing SEI layer. [Figure 10] This graph shows a comparison of the cell cycle lifetime of an electrochemical cell with a LiF-rich SEI layer and no pressure applied, according to several embodiments, and the cell cycle lifetime of an electrochemical cell without a LiF-rich SEI layer and no pressure applied. [Figure 11]This graph shows a comparison of the cell cycle life of an electrochemical cell with pressure applied and a LiF-rich SEI layer, according to several embodiments, with the cell cycle life of an electrochemical cell with pressure applied but without a LiF-rich SEI layer. [Figure 12A] This graph shows the cell cycle lifetime of electrochemical cells containing inorganic-rich SEI layers formed at different conversion voltages according to several embodiments. [Figure 12B] This graph shows the 5-minute discharge resistance of the electrochemical cell in Figure 12A according to several embodiments. [Figure 13] This graph shows the cell cycle lifetime of electrochemical cells cycled at various conversion voltages in the presence of LiBOB, according to several embodiments. [Figure 14] This graph shows the cell cycle lifetime of electrochemical cells containing relatively high fluoroethylene carbonate (FEC) content and cyclically subjected to various conversion voltages, according to several embodiments. [Figure 15] This graph shows the cell cycle life of electrochemical cells containing high fluoroethylene carbonate (FEC) and LiBOB, cycled at various conversion voltages, according to several embodiments. [Figure 16] This graph shows the cell cycle lifetime of an electrochemical cell containing an acetate-based solvent, cycled at various conversion voltages at room temperature according to several embodiments. [Figure 17] This graph shows the cell cycle lifetime of an electrochemical cell containing an acetate-based solvent, cycled at 0°C with various conversion voltages according to several embodiments. [Figure 18] This graph shows a comparison of the cell cycle lifetime of an electrochemical cell containing LiFSI and cycled under pressure, according to several embodiments, and the cell cycle lifetime of an electrochemical cell cycled without pressure. [Figure 19]This graph compares the cell cycle lifetime of an electrochemical cell cycled under pressure in the presence of LiFSI and a higher content of fluoroethylene carbonate (FEC), according to several embodiments, with that of an electrochemical cell cycled without pressure. [Figure 20A] These are SEM images of a 50 μm scale bar of the SEI layer formed between the anode and the separator, according to several embodiments. [Figure 20B] This is an EDS mapping of the SEI layer from Figure 20A, according to several embodiments. [Figure 20C] High-magnification SEM images of the 500nm scale bar of the SEI layer adjacent to the separator, from Figure 20A, according to several embodiments. [Figure 21] These are SEM / EDS line scan images of a 5 μm scale bar in the SEI layer, according to several embodiments. [Figure 22A] This is an X-ray photoelectron spectroscopy (XPS) graph of the fluorine content (F 1s) in the SEI layer according to several embodiments. [Figure 22B] XPS graphs of lithium content (Li 1s) in the SEI layer according to several embodiments. [Figure 22C] XPS graphs of carbon content (C1s) in the SEI layer according to several embodiments. [Figure 23] These are X-ray diffraction (XRD) spectra characterizing the crystallinity of the SEI layer according to several embodiments. [Figure 24] This figure shows a comparison of the cycle performance of an electrochemical cell cycled under pressure and a cell cycled without pressure, according to several embodiments. [Figure 25] This is an SEM / EDS line scan of an electrochemical cell cycled without a fluorinating solvent and without pressure, according to several embodiments. [Figure 26]This is an SEM / EDS line scan of an electrochemical cell that is cyclically subjected to pressure and does not contain a fluorinating solvent, according to several embodiments. [Figure 27] This is an SEM / EDS line scan of an electrochemical cell containing a fluorinated solvent and cyclically performed without pressure, according to several embodiments. [Figure 28] This is an SEM / EDS line scan of an electrochemical cell containing a fluorinated solvent and cyclically subjected to pressure, according to several embodiments. [Figure 29] This graph shows the percentage (%) of residual Li in cells that have been cycled under pressure, with or without a fluorinating solvent, according to several embodiments. [Figure 30] This graph shows the discharge capacity as a function of cycles for cells that are cycled under pressure, with or without a fluorinated solvent, according to several embodiments. [Modes for carrying out the invention]

[0011] Some aspects of the present invention relate to electrochemical cells for lithium batteries. In some embodiments, the electrochemical cell comprises a stable solid electrolyte interface (SEI) layer formed at the interface between the anode and the electrolyte as a result of, for example, an interaction (e.g., a reaction) between the anode and the electrolyte. The solid electrolyte interface layer may advantageously contain a substantial amount of certain inorganic material that improves the performance of the electrochemical cell, such as LiF and / or Li2CO3. For example, the solid electrolyte interface layer can help improve the stability of the anode during cycling (or reduce anode degradation), improve the compatibility between a typical electrolyte and a lithium metal anode, and / or improve the cycle life of the cell.

[0012] Some aspects of the present invention relate to methods for forming and using electrochemical cells comprising a stable SEI layer rich in a specific inorganic material. For example, the application of anisotropic forces to the electrochemical cell and / or the application of a high conversion voltage during charging and discharging may lead to the in-situ formation of a controlled SEI layer rich in inorganic material that improves the overall performance of the cell. For example, the cell may exhibit improved performance, such as slower growth of discharge resistance, controlled SEI growth, suppression of cell polarization during charging and discharging, longer cycle life, and / or improved low-temperature performance.

[0013] In some embodiments, electrochemical cells are provided herein. In some such embodiments, the electrochemical cell comprises a first electrode (e.g., an anode), an electrolyte comprising a fluorinated organic solvent, a second electrode (e.g., a cathode), and a solid electrolyte interface layer disposed between the first electrode (e.g., anode) and the electrolyte. For example, Figure 1 shows such an embodiment. As shown, the electrochemical cell 10 comprises an anode 12, an electrolyte 14, a cathode 16, and a solid electrolyte interface layer 18 disposed between the anode 12 and the electrolyte 14. In some embodiments, the electrochemical cell comprises a porous separator material which may contain a non-solid electrolyte. For example, the electrolyte 14 may be impregnated in the porous separator. As used herein, a non-solid electrolyte may refer to a material which cannot withstand static shear stress and, when shear stress is applied, the non-solid material experiences continuous and permanent strain. Examples of non-solid materials include, for example, liquids and deformable gels.

[0014] In some embodiments where a separator is present, the separator may be located between a first electrode (e.g., an anode) and a second electrode (e.g., a cathode) and may contain pores in which an electrolyte can be present. In some such embodiments, a solid electrolyte interface layer is located between the first electrode (e.g., an anode) and the separator containing pores filled with electrolyte. In some embodiments, the anode includes a lithium metal, a lithium alloy, or a combination thereof as the anode active material. The anode active material refers to any electrochemically active species associated with the anode.

[0015] In some embodiments, the solid electrolyte interface layer includes one or more inorganic materials that can advantageously increase anode stability and thereby increase the cycle life of the electrochemical cell. Non-limiting examples of such inorganic materials include, but are not limited to, LiF, Li2CO3, Li2O, etc. In some such embodiments, the formation of one or more inorganic materials in the solid electrolyte interface layer may be due to the decomposition of the electrolyte and / or the interaction between the electrolyte and the anode active material, as will be described in more detail later.

[0016] In some embodiments, the solid electrolyte interface layer includes LiF. Figure 2 is a schematic cross-sectional view of a portion 100 of an electrochemical cell (e.g., electrochemical cell 10 in Figure 1) having a solid electrolyte interface layer containing LiF, according to some embodiments. As shown, the solid electrolyte interface layer 18 containing LiF, having a thickness of 19, is positioned between a portion of the anode 12 and a portion of the electrolyte 14. In some embodiments, the solid electrolyte interface layer is LiF-rich, for example, LiF is present in a relatively high concentration in the solid electrolyte interface layer and / or in a relatively high concentration compared to other inorganic materials in the solid electrolyte interface layer. Although only LiF is shown in Figure 2, it should be noted that other inorganic materials (e.g., Li2O) may also be present in the solid electrolyte interface layer, as will be described in more detail later.

[0017] In some embodiments, the electrochemical cell may be a lithium-based electrochemical cell, such as a lithium-sulfur electrochemical cell, a lithium-ion electrochemical cell, a lithium metal lithium-ion electrochemical cell, an intercalated lithium metal oxide electrochemical cell, or an intercalated lithium metal phosphate electrochemical cell.

[0018] In some embodiments, the solid electrolyte interface layer comprises an inorganic material including LiF and Li2CO3. Figure 3A is a schematic cross-sectional view of a portion 200 of an electrochemical cell (e.g., electrochemical cell 10 in Figure 1) comprising a solid electrolyte interface layer containing LiF and Li2CO3, according to some embodiments. As shown in Figure 3A, the solid electrolyte interface layer 118 containing the mixed LiF and Li2CO3 is positioned between a portion of the anode 12 and a portion of the electrolyte 14. In some embodiments, the solid electrolyte interface layer may be both LiF-rich and Li2CO3-rich, for example, with LiF and Li2CO3 present in relatively high concentrations in the solid electrolyte interface layer and / or in relatively high concentrations compared to the presence of certain other inorganic materials in the solid electrolyte interface layer. The inorganic material (e.g., LiF, Li2CO3) may be present in any of the various amounts described herein. In some embodiments, the solid electrolyte interface layer may further contain one or more inorganic materials, including but not limited to lithium alkoxides, lithium oxides, lithium salts, and other decomposition products of the electrolyte.

[0019] In some embodiments, the solid electrolyte interface layer contains a substantially non-uniform distribution of various inorganic materials and / or atomic species. For example, in one set of embodiments, in the solid electrolyte interface layer, a first ratio of fluorine atoms to oxygen atoms adjacent to the electrolyte (or on the side facing an electrode such as an anode) is higher than a second ratio of fluorine atoms to oxygen atoms adjacent to an electrode (e.g., an anode). Referring again to Figure 3A, the Li2CO3 and LiF species in the solid electrolyte interface layer 118 are not substantially uniformly distributed within the solid electrolyte interface layer 118 across its thickness 119. Rather, in Figure 3A, substantially higher concentrations of LiF species are localized on or near the surface of the solid electrolyte interface layer adjacent to the electrolyte 14. Thus, across the thickness 119 of the solid electrolyte interface layer, in the solid electrolyte interface layer 118, a first ratio of fluorine atoms to oxygen atoms adjacent to the electrolyte 14 is higher than a second ratio of fluorine atoms to oxygen atoms adjacent to the anode 12. In addition to LiF and Li2CO3, additional inorganic materials (e.g., Li2O, lithium alkoxide, etc.) may also be present, and may contribute to the ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer. For example, in some embodiments, the solid electrolyte interface layer may contain relatively small amounts of fluorine-containing inorganic material associated with the presence of fluorine-containing salts and / or additives (e.g., LixPFy, LixPOyFz, etc.).

[0020] In some embodiments where fluorine and oxygen atoms are not substantially uniformly distributed across the thickness of the solid electrolyte interface layer, the ratio of fluorine atoms to oxygen atoms (fluorine / oxygen) at any given point in the cross-section of the thickness of the solid electrolyte interface layer varies by at least 25% (e.g., at least 30%, at least 50%, at least 70%, or at least 90%) compared to the average ratio of fluorine atoms to oxygen atoms over the entire solid electrolyte interface layer. For example, referring again to Figure 3A, the first ratio of fluorine atoms to oxygen atoms at any point A (e.g., a point adjacent to the electrolyte) in the cross-section 121 of the solid electrolyte interface layer 118, or the second ratio of fluorine atoms to oxygen atoms at any point B (e.g., a point adjacent to the anode), varies by at least 25% compared to the average ratio of fluorine atoms to oxygen atoms over the entire solid electrolyte interface layer 118. As an illustrative calculation, if the average ratio of fluorine atoms to oxygen atoms in a solid electrolyte interface layer is 1, and any point in the cross-section across the thickness of the solid electrolyte layer (e.g., point A or B in Figure 3B) has a ratio of 0.75 or less or 1.25 or greater, then the solid electrolyte interface layer is considered to be substantially inert. If point A or B in Figure 3B has a ratio of 0.75 or less or 1.25 or greater, then the solid electrolyte interface layer is considered to have a substantially non-uniform distribution of fluorine and oxygen atoms across the thickness of the solid electrolyte interface layer, based on the average ratio of fluorine and oxygen atoms in the solid electrolyte interface layer.

[0021] In some embodiments, a first ratio of fluorine atoms to oxygen atoms on one side of the solid electrolyte interface layer (e.g., adjacent to the electrolyte), measured over the thickness of the solid electrolyte layer, is higher than a second ratio of fluorine atoms to oxygen atoms on the other side of the solid electrolyte interface layer (e.g., adjacent to the anode). In some such embodiments, the first ratio of fluorine atoms to oxygen atoms at a point on one side of the solid electrolyte interface layer (e.g., adjacent to the electrolyte, point A in Figure 3A) in a cross-section of the thickness of the solid electrolyte interface layer is substantially higher than the second ratio of fluorine atoms to oxygen atoms on the other side of the solid electrolyte interface layer (e.g., adjacent to the anode, point B in Figure 3A). For example, the first ratio (e.g., point A in Figure 3A) may be at least 25%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 100%, at least 200%, or at least 300% higher than the second ratio (e.g., point B in Figure 3A). In some embodiments, the first ratio (e.g., point A in Figure 3A) is 400%, 300%, 200%, 100%, 90%, 80%, 70%, 60%, or 50% higher than the second ratio (e.g., point B in Figure 3A). Combinations of the above ranges are also possible (e.g., at least 25%, 400%). Other ranges are also possible.

[0022] In some embodiments, a first ratio of fluorine atoms to oxygen atoms on one side of the solid electrolyte interface layer (e.g., a point adjacent to the electrolyte, such as point A in Figure 3A), measured over the thickness of the solid electrolyte interface layer, is higher than the average ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer. For example, the first ratio (e.g., point A in Figure 3A) may be at least 25%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 100%, at least 200%, or at least 300% higher than the average ratio. In some embodiments, the first ratio (e.g., point A in Figure 3A) may be 400%, 300%, 200%, 100%, 90%, 80%, 70%, or 60% higher than the average ratio. Combinations of the above ranges are also possible (e.g., at least 25%, 400%). Other ranges are also possible.

[0023] Additionally or alternatively, in some embodiments, the second ratio of fluorine atoms to oxygen atoms at a point adjacent to the anode in the cross-section of the thickness of the solid electrolyte interface layer (e.g., point B in Figure 3A) is substantially smaller than the average ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer. For example, the second ratio of fluorine atoms to oxygen atoms at a point adjacent to the anode is at least 25%, at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% smaller than the average ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer. In some embodiments, the second ratio of fluorine atoms to oxygen atoms at a point adjacent to the anode in the cross-section of the thickness of the solid electrolyte interface layer (e.g., point B in Figure 3A) is 100%, 90%, 80%, 70%, or 60% smaller than the average ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer. Combinations of the above ranges are also possible (e.g., 25% to 100%). Other ranges are also possible.

[0024] The amounts of fluorine and oxygen atoms within the solid electrolyte interface layer and in any cross-section of the solid electrolyte interface layer may be measured using a combination of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX or EDS) techniques. For example, the following procedure can be performed: To measure the amounts of fluorine and oxygen atoms, a stack of anode / SEI layer / separator, or anode / SEI and SEI / separator, may be recovered from cells at various stages of cycle lifetime. The recovered anode / SEI layer / separator stack may be ion-milled to produce a smooth cross-section, and then analyzed by SEM / EDS.

[0025] In some embodiments, the first ratio of fluorine atoms to oxygen atoms relates to a position relatively close to the surface of the electrolyte (e.g., point A in Figure 3A). For example, in some embodiments, the first ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer is located at a position of 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, or 1% or less of the thickness of the solid electrolyte interface layer (e.g., thickness 119 of SEI layer 118 in Figure 3A) away from the surface of the electrolyte (e.g., surface 123 in Figure 3A). In some embodiments, the first ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer relates to a position of 0% or more, 1% or more, 5% or more, 10% or more, 20% or more, 30% or more, or 40% or more of the thickness of the solid electrolyte interface layer away from the surface of the electrolyte. Combinations of the above ranges are also possible (e.g., 0% or more, 50% or less). Other ranges are also possible. In one set of embodiments, the first ratio of fluorine atoms to oxygen atoms is located directly adjacent to (e.g., in contact with) the surface of the electrolyte.

[0026] In some embodiments, the second ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer is related to a position relatively further away from the electrolyte surface (or relatively close to the anode surface) (e.g., point B in Figure 3A). For example, in some embodiments, the second ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer is located at a position where the thickness of the solid electrolyte interface layer (e.g., thickness 119 of the SEI layer 118 in Figure 3A) is 100%, 90%, 80%, 70%, or 60% or less, away from the electrolyte surface (e.g., surface 123 in Figure 3A). In some embodiments, the second ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer is related to a position where the thickness of the solid electrolyte interface layer is 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more, away from the electrolyte surface. Combinations of the above ranges are also possible (e.g., 50% to 100%). Other ranges are also possible.

[0027] As an illustrative calculation, if the SEI layer has a thickness of 500 nm, and the first ratio of fluorine atoms to oxygen atoms is related to a location within the SEI layer that is less than 10% of the thickness away from the electrolyte surface (e.g., point A in Figure 3A), and the second ratio of fluorine atoms to oxygen atoms is related to a location within the SEI layer that is more than 60% of the thickness away from the electrolyte surface (e.g., point B in Figure 3B), then the first ratio of fluorine atoms to oxygen atoms is related to a location less than 50 nm away from the electrolyte surface, and the second ratio of fluorine atoms to oxygen atoms is related to a location more than 300 nm away from the electrolyte surface. Furthermore, if the SEI layer has an average ratio of fluorine atoms to oxygen atoms of 1, and the first ratio of fluorine atoms to oxygen atoms is at least 50 wt% higher than the average ratio, and the second ratio of fluorine atoms to oxygen atoms is at least 50 wt% lower than the average ratio, then the first ratio of fluorine atoms to oxygen atoms is at least 1.5, and the second ratio of fluorine atoms to oxygen atoms is 0.5 or less.

[0028] In some embodiments where fluorine and oxygen atoms are not substantially uniformly distributed across the thickness of the solid electrolyte interface layer, the ratio of fluorine atoms to oxygen atoms at any given point in the cross-section of the thickness of the solid electrolyte interface layer varies by 50% or more (e.g., 60% or more, 70% or more, 80% or more, or 90% or more) at any given point in the cross-section of the thickness of the solid electrolyte interface layer from the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer. For example, referring again to Figure 3A, the ratio of fluorine atoms to oxygen atoms at any point A (e.g., a point adjacent to the electrolyte) or at any point B (e.g., a point adjacent to the anode) in the cross-section 121 of the solid electrolyte interface layer 118 varies by 50% or more compared to the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer 118. As an exemplary calculation, if a solid electrolyte interface layer has a maximum ratio of fluorine atoms to oxygen atoms of 1, and any point in a cross-section (e.g., cross-section 121) over the thickness of the solid electrolyte interface layer (e.g., point A or point B in Figure 3A) has a ratio of 0.5 or less, then the solid electrolyte interface layer is considered to have a substantially non-uniform distribution of fluorine atoms and oxygen atoms over the thickness of the solid electrolyte interface layer, based on the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer.

[0029] In some embodiments, the first ratio of fluorine atoms to oxygen atoms at a specific point relatively close to the electrolyte surface and within the cross-section of the thickness of the solid electrolyte interface layer varies substantially less than the maximum ratio of fluorine atoms to oxygen atoms at a point relatively far from the electrolyte surface, compared to the second ratio of fluorine atoms to oxygen atoms at a point relatively far from the electrolyte surface. For example, referring again to Figure 3A, the first ratio of fluorine atoms to oxygen atoms at a specific point (e.g., point A) relatively close to the surface of the electrolyte 14 and within the cross-section of the thickness 119 of the solid electrolyte interface layer 118 varies substantially less than the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer 118, compared to the second ratio of fluorine atoms to oxygen atoms at a specific point (e.g., point B) relatively far from the electrolyte surface. For example, in some embodiments, the first ratio of fluorine atoms to oxygen atoms at a specific point relatively close to the electrolyte surface (e.g., point A) is less varied than the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer by at least 10%, at least 20%, at least 30%, at least 50%, at least 70%, or at least 90%, compared to the second ratio of fluorine atoms to oxygen atoms at a specific point further relatively far from the electrolyte surface (e.g., point B). In some embodiments, the first ratio of fluorine atoms to oxygen atoms at a specific point relatively close to the electrolyte surface (e.g., point A) is less varied than the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer by at least 99%, at least 90%, at least 70%, at least 50%, at least 30%, or at least 20%, compared to the second ratio of fluorine atoms to oxygen atoms at a specific point relatively far from the electrolyte surface (e.g., point B). Combinations of the above ranges are possible (e.g., at least 10%, at least 99%). Other ranges are also possible.

[0030] In some embodiments, the first ratio of fluorine atoms to oxygen atoms at a specific point (e.g., point A in Figure 3A) relatively close to the surface of the electrolyte and within the cross-section of the thickness of the solid electrolyte interface layer may have a value of 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, or 99% or more of the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer. In some embodiments, the specific point (e.g., point A in Figure 3A) relatively close to the surface of the electrolyte and within the cross-section of the thickness of the solid electrolyte interface layer may have a value of 100% or less, 99% or less, 95% or less, 90% or less, 80% or less, 70% or less, or 60% or less of the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer. Combinations of the above values ​​are also possible (e.g., 50% or more, 100% or less). Other values ​​are also possible. In one embodiment, the first ratio of fluorine atoms to oxygen atoms located adjacent to (e.g., directly adjacent to) the electrolyte (e.g., point A in Figure 3A) is the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer.

[0031] In some embodiments, the second ratio of fluorine atoms to oxygen atoms at a specific point (e.g., point B in Figure 3A) relatively far from the electrolyte surface (or relatively close to the anode surface) and within the cross-section of the thickness of the solid electrolyte interface layer may have a value of 1% or more, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, or 45% or more of the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer. In some embodiments, the second ratio of fluorine atoms to oxygen atoms at a specific point (e.g., relatively far from the electrolyte surface (or relatively close to the anode surface) and within the cross-section of the thickness of the solid electrolyte interface layer (e.g., point B in Figure 3A) may have a value of 50% or less, 45% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer. Combinations of the above values ​​are also possible (e.g., 1% to 50%). Other values ​​are also possible.

[0032] The amounts and ratios (e.g., maximum ratio, average ratio, ratio at any point) of fluorine atoms and oxygen atoms and / or LiF and Li2CO3 (and other oxygen-containing inorganic materials, e.g., Li2O) within a cross-section of the solid electrolyte interface layer may be measured using a combination of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX or EDS) techniques. The distance between the location containing a specific ratio of fluorine atoms to oxygen atoms and / or LiF to Li2CO3 (and other oxygen-containing inorganic materials, e.g., Li2O) (e.g., first ratio, second ratio, etc.) and the electrolyte surface and / or anode surface can, in some examples, be determined by performing SEM / EDS on an ion-milled SEI cross-section recovered from an electrochemical cell.

[0033] Figure 3A shows an embodiment in which fluorine and oxygen atoms are not substantially uniformly distributed over the thickness of the solid electrolyte interface layer, although embodiments in which fluorine and oxygen atoms are substantially uniformly distributed over the thickness of the solid electrolyte interface layer are also possible. Figure 3B is a schematic cross-sectional view of an embodiment in which fluorine and oxygen atoms are substantially uniformly distributed over the thickness of the solid electrolyte interface layer. In Figure 3B, the solid electrolyte interface layer 128 contains Li2CO3 and LiF species substantially uniformly distributed within the solid electrolyte interface layer 128 over a thickness of 129. Thus, the ratio of fluorine atoms to oxygen atoms adjacent to the electrolyte 14 does not substantially change over a thickness of 129 from the second ratio of fluorine atoms to oxygen atoms adjacent to the anode 12 within the solid electrolyte interface layer 128. In addition to LiF and Li2CO3, it should be understood that, optionally, further inorganic materials (e.g., Li2O) may also be present and contribute to the overall ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer.

[0034] In some embodiments where fluorine and oxygen atoms are substantially uniformly distributed over the thickness of the solid electrolyte interface layer, the ratio of fluorine atoms to oxygen atoms at any given point in the cross-section of the thickness of the solid electrolyte interface layer varies by 25% or less (e.g., from the average ratio of fluorine atoms to oxygen atoms measured over the thickness, to 20%, 15%, 10%, 5%, 2%, etc., at any point in the cross-section of the thickness of the solid electrolyte interface layer). For example, referring again to Figure 3B, at any point C or any point D in the cross-section 122 of the solid electrolyte interface layer 128, the oxygen atoms... The ratio of fluorine atoms to elementary atoms varies by no more than 25% compared to the average ratio of fluorine atoms to oxygen atoms in the solid electrolyte layer 128. As an illustrative calculation, if the solid electrolyte interface layer has an average ratio of fluorine atoms to oxygen atoms of 1, and any point in the cross-section across the thickness of the solid electrolyte interface layer (e.g., point C or D in Figure 3B) has a ratio of 0.75 or greater or 1.25 or less, then the solid electrolyte interface layer is considered to have a substantially homogeneous distribution of fluorine and oxygen atoms across its thickness, based on the average ratio of fluorine and oxygen atoms in the solid electrolyte interface layer.

[0035] In some embodiments in which fluorine and oxygen atoms are substantially uniformly distributed across the thickness of the solid electrolyte interface layer, the ratio of fluorine atoms to oxygen atoms at any given point in the cross-section of the thickness of the solid electrolyte interface layer varies by 50% or less (e.g., 40%, 30%, 20%, 10%, 5%, etc.) from the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer at any point in the cross-section of the thickness of the solid electrolyte interface layer. For example, referring again to Figure 3B, the ratio of fluorine atoms to oxygen atoms at any point C in the cross-section 122 of the solid electrolyte interface layer 128, or the ratio of fluorine atoms to oxygen atoms at any point D, varies by only 50% or less compared to the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer 128. As an illustrative calculation, if a solid electrolyte interface layer has a maximum ratio of fluorine atoms to oxygen atoms of 1, and all points (e.g., point D in Figure 3B) in at least several cross-sections (e.g., cross-section 122) across the thickness of the solid electrolyte interface layer have a ratio of 0.5 or greater, then the solid electrolyte interface layer is considered to have a substantially homogeneous distribution of fluorine atoms and oxygen atoms across the thickness of the solid electrolyte interface layer, based on the maximum ratio of fluorine atoms to oxygen atoms in the solid electrolyte interface layer.

[0036] In some embodiments, methods for storing and using electrical energy in an electrochemical cell are disclosed herein. In some embodiments, the method includes applying an anisotropic force to the cell, applying a conversion voltage to the cell, and forming an SEI layer as described herein within the cell, as described in more detail below.

[0037] In some embodiments, the method for storing and using electrical energy in an electrochemical cell involves applying an anisotropic force to the surface of the anode (e.g., the active surface). In some such embodiments, the electrochemical cell comprises an anode containing lithium metal, a lithium alloy, or a combination thereof as the anode active material, a cathode, and an electrolyte containing a fluorinated organic solvent placed between the anode and the cathode. In some embodiments, the anode has a surface adjacent to the electrolyte, such as the active surface of an electrode where an electrochemical reaction may occur. For example, as shown in Figure 1, the electrochemical cell 10 comprises an anode 12 having a surface 24, a cathode 16, and an electrolyte 14 containing a fluorinated organic solvent placed between the anode 12 and the cathode 16. In some such embodiments, the application of an anisotropic force to the surface of the anode (e.g., the active surface) can enhance the performance of the electrochemical cell (e.g., discharge resistance, cycle life, etc.), as described elsewhere in this specification.

[0038] In some embodiments, applying an anisotropic force to the surface of the anode (e.g., the active surface) includes applying the anisotropic force during at least one period in a charge cycle and a discharge cycle. In some embodiments, the force may be applied continuously, over a single period, or over multiple periods with varying durations and / or periods. The anisotropic force may optionally be applied at one or more predetermined locations and may optionally be distributed across the surface of the anode. In some embodiments, the anisotropic force is applied uniformly across the surface of the anode (e.g., the active surface).

[0039] For example, at least one period may include an initial formation cycle (e.g., a charge-discharge cycle while a stable solid electrolyte interface layer is formed on the cell) and / or subsequent charge-discharge cycles. In one embodiment, the application of anisotropic forces to the anode surface persists throughout the entire cycle (e.g., all formation cycles and subsequent charge-discharge cycles).

[0040] In some embodiments, the force includes an anisotropic force having a component perpendicular to the surface of the anode (e.g., the active surface). In the case of a plane, the force may include an anisotropic force having a component perpendicular to the surface at the point where the force is applied. For example, referring to Figure 1, the force may be applied in the direction of arrow 26. Arrow 28 indicates the component of the force perpendicular to the surface 24 of the anode 12. As shown, the surface 24 of the anode 12 is a surface configured to face the anode current collector 22 and the cathode 16. In the case of a curved surface, such as a concave or convex surface, the force may include an anisotropic force having a component perpendicular to a plane tangent to the curved surface at the point where the force is applied.

[0041] In some cases, one or more forces applied to a cell have components that are not perpendicular to the anode surface (e.g., the active surface). For example, in Figure 1, force 26 is not perpendicular to the anode surface 24, and force 26 includes a component 30 that is substantially parallel to the anode surface 24. Furthermore, in some cases, a force 25 substantially parallel to the anode surface 24 may be applied to the cell. In one set of embodiments, the sum of the components of all anisotropic forces applied perpendicular to the anode surface is greater than the sum of any components that are not perpendicular to the anode surface. In some embodiments, the sum of the components of all applied anisotropic forces perpendicular to the anode surface is at least about 5%, at least about 10%, at least about 20%, at least about 35%, at least about 50%, at least about 75%, at least about 90%, at least about 95%, at least about 99%, or at least about 99.9% greater than any sum of the components parallel to the anode surface.

[0042] In some embodiments, the application of an anisotropic force during at least one period of charging and / or discharging of the cell is related to the formation of a solid electrolyte interface layer (e.g., including one or more of LiF, Li2CO3, Li2O, etc.) having a specific set of advantageous properties at the anode and electrolyte interface. For example, in a set of embodiments, the application of an anisotropic pressure results in the formation of a stable and controlled solid electrolyte interface layer (e.g., SEI layer 18 in FIG. 1) having a relatively high compatibility with the anode surface, such that the solid electrolyte interface layer can efficiently protect the anode from harmful reactions and / or degradation. Further, the application of an anisotropic force during cycling can assist in regulating the growth of resistive SEI accumulation during cycling, thereby reducing the rate of increase of discharge resistance and suppressing the polarization of the cell during cycling. As a result, the cell can exhibit an enhanced cycle life.

[0043] In some embodiments, an anisotropic force having a component perpendicular to the surface of the anode (e.g., the active surface) is applied to an extent effective to suppress an increase in the surface area of the anode surface (e.g., the active surface) during at least one period of charging and / or discharging of the electrochemical device relative to an increase in surface area in the absence of an anisotropic force.

[0044] In some embodiments, the component of the anisotropic force perpendicular to the surface of the electrode (e.g., the active surface) is at least about 1 kg / cm 2 , at least about 2 kg / cm 2 , at least about 4 kg / cm 2 , at least about 6 kg / cm 2 , at least about 6 kg / cm 2 , at least about 7 kg / cm 2 , at least about 8 kg / cm 2 , at least about 10. kg / cm 2 , at least about 12 kg / cm 2 , at least about 14 kg / cm 2 , at least about 16 kg / cm 2 , at least about 18 kg / cm 2 , at least about 20. kg / cm2 , at least about 22 kg / cm³ 2 , at least about 24 kg / cm³ 2 , at least about 26 kg / cm³ 2 , at least about 28 kg / cm³ 2 , at least about 30 kg / cm³ 2 , at least about 32 kg / cm³ 2 , at least about 34 kg / cm³ 2 , at least about 36 kg / cm³ 2 , at least about 38 kg / cm³ 2 , at least about 40 kg / cm 2 , at least about 42 kg / cm³ 2 , at least about 44 kg / cm³ 2 , at least about 46 kg / cm³ 2 , or at least about 48 kg / cm³ 2 This defines the pressure. In some embodiments, the component of the anisotropic force perpendicular to the surface is, for example, about 50 kg / cm². 2 Less than approximately 48 kg / cm³ 2 Less than approximately 46 kg / cm³ 2 Less than approximately 44 kg / cm³ 2 Less than approximately 42 kg / cm³ 2 Less than approximately 40 kg / cm³ 2 Less than approximately 38 kg / cm³ 2 Less than approximately 36 kg / cm³ 2 Less than approximately 34 kg / cm³ 2 Less than approximately 32 kg / cm³ 2 Less than approximately 30 kg / cm³ 2 Less than approximately 28 kg / cm³ 2 Less than approximately 26 kg / cm³ 2 Less than approximately 24 kg / cm³ 2 Less than approximately 22 kg / cm³ 2 Less than approximately 20 kg / cm³ 2 Less than approximately 18 kg / cm³ 2 Less than approximately 16 kg / cm³ 2 Less than approximately 14 kg / cm³ 2 Less than approximately 12 kg / cm³ 2 Less than approximately 10 kg / cm³ 2 Less than approximately 8 kg / cm³ 2 Less than approximately 7 kg / cm³ 2 Less than approximately 6 kg / cm³2 Less than approximately 4 kg / cm³ 2 Less than, or approximately 2 kg / cm³ 2 Pressures below a certain level may also be specified. Combinations of the above ranges are also possible (for example, at least about 7 kg / cm²). 2 About 50kg / cm or more 2 Less than approximately 8 kg / cm³ 2 Approximately 30kg / cm 2 Less than approximately 10 kg / cm³ 2 Approximately 25kg / cm 2 (Less than). Other ranges are also possible.

[0045] Force and pressure are generally expressed in units of Newtons and Newtons per unit area, respectively, but force and pressure can also be expressed in units of kilogram-force and kilogram-force (i.e., kgf / cm²) per unit area, respectively. 2 or kg / cm 2 It can also be expressed in units of ). A person skilled in the art will be familiar with kilogram-force-based units and will understand that 1 kilogram-force is equivalent to approximately 9.8 Newtons.

[0046] In some embodiments, a method for storing and using electrical energy in an electrochemical cell includes applying a formation voltage during at least one period of charging and / or discharging the cell. In some such embodiments, at least one period of charging and / or discharging relates to a formation cycle, i.e., an initial charging and / or discharging cycle associated with the formation of a stable solid electrolyte interface layer. For example, in some embodiments, the formation cycle occurs for at least the first 1, at least the first 2, at least the first 3, at least the first 4, or at least the first 5 charging and discharging cycles of the cell. In some embodiments, the formation cycle occurs for no more than the first 6, no more than the first 5, no more than the first 4, no more than the first 3, or no more than the first 2 charging and discharging cycles of the cell. Combinations of the above ranges are also possible (e.g., 1 to 5 cycles, 1 to 4 cycles, 1 to 3 cycles). Other ranges are also possible.

[0047] According to several embodiments, the formation voltage is the voltage applied during the formation cycle. For example, in one set of embodiments, the formation voltage is applied for one or more, two or more, three or more, four or more, or five or more charge and discharge cycles of the cell. In some embodiments, the formation voltage is applied for six or fewer, five or fewer, four or fewer, three or fewer, or two or fewer charge and discharge cycles of the cell. Combinations of the above ranges are also possible (e.g., one to five cycles, one to four cycles, one to three cycles). Other ranges are also possible.

[0048] In some embodiments, the formation of Li2CO3 in the solid electrolyte interface layer (for example, as shown in Figure 3A) is associated with a relatively high conversion voltage applied during at least one period of charging and / or discharging the cell. In some such embodiments, a relatively high conversion voltage may favorably initiate the reaction that forms Li2CO3 in the SEI layer and / or increase the rate of Li2CO3 formation, resulting in the presence of a substantial amount of Li2CO3 in the solid electrolyte interface layer. The presence of a relatively high concentration of Li2CO3 in the solid electrolyte interface layer may result in improved performance of the electrochemical cell (e.g., anode stability, cycle life, etc.).

[0049] In some embodiments, relatively high conversion voltages are 4.35V or higher, 4.4V or higher, 4.45V or higher, 4.5V or higher, 4.55V or higher, 4.6V or higher, 4.65V or higher, 4.7V or higher, 4.75V or higher, 4.8V or higher, 4.85V or higher, 4.9V or higher, or 4.95V. In some embodiments, relatively high conversion voltages are 5V or lower, 4.95V or lower, 4.9V or lower, 4.85V or lower, 4.8V or lower, 4.75V or lower, 4.7V or lower, 4.65V or lower, 4.6V or lower, 4.55V or lower, 4.5V or lower, or 4.45V or lower. Combinations of the above ranges are also possible (e.g., 4.4V to 5V, 4.5V to 4.9V, or 4.55V to 4.75V). Other ranges are also possible.

[0050] In some embodiments, a relatively high conversion voltage may be applied for any of a variety of durations. For example, in one set of embodiments, the conversion voltage may be a total of 1 minute or more, 5 minutes or more, 10 minutes or more, 20 minutes or more, 30 minutes or more, 60 minutes or more, 120 minutes or more, 180 minutes or more, 360 minutes or more, 540 minutes or more, 720 minutes or more, 900 minutes or more, 1080 minutes or more, or 1260 minutes or more. In some embodiments, the conversion voltage may be applied for a total of 1440 minutes or less, 1260 minutes or less, 1080 minutes or less, 900 minutes or less, 720 minutes or less, 540 minutes or less, 360 minutes or less, 180 minutes or less, 120 minutes or less, 60 minutes or less, 30 minutes or less, 20 minutes or less, 15 minutes or less, 10 minutes or less, or 5 minutes or less. Combinations of the above ranges are also possible (for example, 1 minute to 1440 minutes, 5 minutes to 720 minutes, or 10 minutes to 360 minutes). Other ranges are also possible.

[0051] In some embodiments, the application of anisotropic forces and a high conversion voltage during at least one period of charging and / or discharging the cell is associated with the formation of a solid electrolyte interface layer containing LiF and Li2CO3 having advantageous properties (e.g., as shown in Figure 3A). These properties include, but are not limited to, high compatibility with the anode, high stability, and high ionic conductivity. The application of anisotropic forces during and / or subsequent discharge and / or charging cycles can further improve the performance of the electrochemical cell (e.g., the accumulation of resistive SEI and the rate of growth of discharge resistance, improved cycle life, etc.).

[0052] In some embodiments, the method for storing and using electrical energy in an electrochemical cell involves forming a solid electrolyte interface layer adjacent to the surface of the anode (e.g., the active surface). In some such embodiments, the solid electrolyte interface layer, comprising one or more inorganic materials (e.g., LiF, Li2CO3, Li2O, etc.), is formed in situ during charging and / or discharging of the electrochemical cell. For example, referring again to Figure 1, when the electrochemical cell 100 undergoes charging and / or discharging, it results in the in situ formation of a solid electrolyte interface layer 18 adjacent to the surface 24 of the anode 12. In some such embodiments, the controlled formation of the solid electrolyte interface layer is at least in part related to the application of anisotropic forces and / or the application of a conversion voltage during the charging and / or discharging cycle.

[0053] In some embodiments, the solid electrolyte interface layer comprises an inorganic material containing LiF and / or Li2CO3 (for example, as shown in Figures 2-3). Depending on the type of inorganic material, the pathways by which these inorganic materials are formed may differ. For example, in one set of embodiments, LiF is formed in situ as a result of the decomposition of one or more fluorinated electrolyte solvents during charging and / or discharging (for example, as shown in Figures 2-3).

[0054] In one embodiment, Li2CO3 is formed in situ by the reaction of CO2 with lithium metal on the anode surface (e.g., as shown in Figure 3). For example, CO2 may be generated during charging and / or discharging from various components of the cell, e.g., from the decomposition of the electrolyte solvent (e.g., ester-based, carbonate-based solvents) and / or from gas generation from the cathode during the cycle (e.g., impurities in the NCM cathode). As described above and with respect to Figure 3, the in-situ formation of a solid electrolyte interface layer containing a relatively high proportion of Li2CO3 may be caused at least in part by a high conversion voltage applied during at least one period (e.g., the formation cycle) during the charging and / or discharging of the cell. The solid electrolyte interface layer may further contain one or more inorganic materials (e.g., lithium alkoxides, lithium oxides, lithium salts, and other decomposition products of the electrolyte) as a result of the charging and / or discharging of the cell.

[0055] This disclosure generally describes the in-situ formation of a solid electrolyte interface layer during charging and / or discharging, although in some cases at least a portion of the solid electrolyte interface layer may be formed ex situ. In some such embodiments, a portion of the solid electrolyte interface layer containing Li2CO3 is formed by pre-passivation of the anode (e.g., the electroactive layer of the anode) using CO2 before assembly of the electrochemical cell. In some such embodiments, after the pre-passivated anode is assembled into the electrochemical cell, an additional solid electrolyte interface layer containing LiF and / or Li2CO3 may be formed in situ in the manner described above.

[0056] In some embodiments, the solid electrolyte interface layer contains a relatively high amount of inorganic material. In some such embodiments, the solid electrolyte interface layer contains a total amount of inorganic material of 10% or more by weight, 20% or more by weight, 30% or more by weight, 40% or more by weight, 50% or more by weight, 60% or more by weight, 70% or more by weight, 80% or more by weight, 90% or more by weight, or 95% or more by weight. In some embodiments, the solid electrolyte interface layer contains a total amount of inorganic material of 100% or less by weight, 90% or less by weight, 80% or less by weight, 70% or less by weight, 60% or less by weight, 50% or less by weight, 40% or less by weight, 30% or less by weight, or 20% or less by weight. Combinations of the above ranges are also possible (e.g., 10% to 100% by weight). Other ranges are also possible.

[0057] In some embodiments, the solid electrolyte interface layer contains a relatively high amount of fluorine-containing inorganic material (e.g., LiF). In some such embodiments, the solid electrolyte interface layer contains fluorine-containing inorganic material (e.g., LiF) in amounts of 10% or more by weight, 20% or more by weight, 30% or more by weight, 40% or more by weight, 50% or more by weight, 60% or more by weight, 70% or more by weight, 80% or more by weight, 90% or more by weight, or 95% or more by weight. In some embodiments, the solid electrolyte interface layer may contain fluorine-containing inorganic material (e.g., LiF) in amounts of 100% or less by weight, 90% or less by weight, 80% or less by weight, 70% or less by weight, 60% or less by weight, 50% or less by weight, 40% or less by weight, 30% or less by weight, or 20% or less by weight. Combinations of the above ranges are also possible (e.g., 10% to 100% by weight). Other ranges are also possible. In some embodiments, the SEI layer may include additional fluorine-containing inorganic materials associated with the presence of fluorine-containing salts and / or fluorine-containing additives (e.g., LixPFy, LixPOyFz, etc.).

[0058] In some embodiments, the solid electrolyte interface layer contains a relatively high amount of Li2CO3. In some such embodiments, the solid electrolyte interface layer contains 10% or more by weight, 20% or more by weight, 30% or more by weight, 40% or more by weight, 50% or more by weight, 60% or more by weight, 70% or more by weight, 80% or more by weight, 90% or more by weight, or 95% or more by weight of Li2CO3. In some embodiments, the solid electrolyte interface layer contains 100% or less by weight, 90% or less by weight, 80% or less by weight, 70% or less by weight, 60% or less by weight, 50% or less by weight, 40% or less by weight, 30% or less by weight, or 20% or less by weight of Li2CO3. Combinations of the above ranges are also possible (e.g., 10% to 100% by weight). Other ranges are also possible.

[0059] In some embodiments, the solid electrolyte interface layer contains relatively high amounts of both LiF and Li2CO3. In some such embodiments, LiF and Li2CO3 may be present independently, in any of the aforementioned amounts, or in combination.

[0060] The solid electrolyte interface layer may contain LiF and Li2CO3 in any of a variety of suitable weight ratios. In some embodiments, the weight ratio of LiF to Li2CO3 may be 1:100 or more, 1:50 or more, 1:10 or more, 1:5 or more, 1:2 or more, 1:1 or more, 2:1 or more, 3:1 or more, 5:1 or more, 10:1 or more, 25:1 or more, 50:1 or more, or 75:1 or more. In some embodiments, the weight ratio of LiF to Li2CO3 may be 100:1 or less, 75:1 or less, 50:1 or less, 25:1 or less, 10:1 or less, 5:1 or less, 3:1 or less, 2:1 or less, 1:1 or less, 1:2 or less, 1:5 or less, 1:10 or less, or 1:50 or less. Combinations of the above ranges are also possible (e.g., 1:100 or more, 100:1 or less). Other ranges are also possible.

[0061] In some embodiments, other inorganic materials, such as Li2O, may be formed in the SEI layer in any of a variety of suitable amounts. For example, the formation of Li2O may be related to the presence of a fluorinating solvent (e.g., fluoroethylene carbonate) and / or a passivating agent (e.g., LiBOB). In some such embodiments, Li2O may be formed in any of a variety of suitable amounts. For example, in some embodiments, the solid electrolyte interface layer contains Li2O in amounts of 5% or more by weight, 10% or more by weight, 20% or more by weight, 30% or more by weight, 40% or more by weight, or 50% or more by weight. In some embodiments, the solid electrolyte interface layer contains Li2O in amounts of 60% or less by weight, 50% or less by weight, 40% or less by weight, 30% or less by weight, 20% or less by weight, or 10% or less by weight. Combinations of the above ranges are also possible (e.g., 10% to 50% or 5% to 50% or 5% to 50% or 5% or more by weight). Other ranges are also possible.

[0062] In some embodiments, the solid electrolyte interface layer may contain LiF and Li2O in any of a variety of suitable weight ratios. In some embodiments, the weight ratio of LiF to Li2O may be 1:5 or greater, 1:4 or greater, 1:3 or greater, 1:2 or greater, 1:1 or greater, 2:1 or greater, 3:1 or greater, 5:1 or greater, 10.1 or greater, 25:1 or greater, 50.1 or greater, or 75:1 or greater. In some embodiments, the weight ratio of LiF to Li2O may be 10.01 or less, 75:1 or less, 50.1 or less, 25:1 or less, 10.1 or less, 5:1 or less, 3:1 or less, 2:1 or less, 1:1 or less, 1:2 or less, 1:3 or less, or 1:4 or less. Combinations of the above ranges are also possible (e.g., 1:5 or greater and 100:1 or less, or 1:5 or greater and 2:1 or less). Other ranges are also possible.

[0063] In some embodiments, at least a portion of the inorganic material (e.g., LiF, Li2O, Li2CO3, etc.) in the solid electrolyte interface layer may be in crystalline form.

[0064] In some embodiments, at least a portion of the inorganic material may be in nanocrystalline form. In some embodiments, the solid electrolyte interface layer may include a nanocrystalline inorganic material having a size (e.g., diameter, width, length, etc.) of 5 nm or more, 7.5 nm or more, 10 nm or more, 12.5 nm or more, 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, or 35 nm or more. In some embodiments, the solid electrolyte interface layer may include a nanocrystalline inorganic material having a size (e.g., diameter, width, length, etc.) of 40 nm or less, 35 nm or less, 30 nm or less, 25 nm or less, 20 nm or less, 15 nm or less, 12.5 nm or less, or 10 nm or less, or 7.5 nm or less. Combinations of the above ranges are also possible (e.g., 5 nm to 40 nm, or 10 nm to 25 nm). Other ranges are also possible.

[0065] For example, in one embodiment, at least 5%, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 70%, at least 80%, or at least 90% of the LiF in the solid electrolyte interface layer is in crystalline form. For example, in some embodiments, 100% or less, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the LiF in the solid electrolyte interface layer is in crystalline form. Combinations of the above ranges are also possible (e.g., 5% or more, 100% or less). Other ranges are also possible.

[0066] In one embodiment, at least 5%, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 70%, at least 80%, or at least 90% of the Li2O in the solid electrolyte interface layer is in crystalline form. For example, in some embodiments, 100% or less, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the Li2O in the solid electrolyte interface layer is in crystalline form. Combinations of the above ranges are also possible (e.g., 5% or more, 100% or less). Other ranges are also possible.

[0067] The solid electrolyte interface layer may have any of a variety of suitable porosity. In some embodiments, the SEI layer may have relatively high porosity so that the SEI layer can facilitate efficient ion transport across the SEI layer. In some such embodiments, the solid electrolyte interface layer containing LiF has a porosity of 1% or more, 5% or more, 10% or more, 15% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, or 80% or more. In some embodiments, the solid electrolyte interface layer has a porosity of 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less. Combinations of the above ranges are also possible (e.g., 10% or more, 90% or less). Other ranges are also possible.

[0068] The solid electrolyte interface layer may have any of a variety of suitable hardness values. In some embodiments, the solid electrolyte interface layer has a hardness of 0.001 GPa or higher, 0.005 GPa or higher, 0.01 GPa or higher, 0.05 GPa or higher, 0.1 GPa or higher, 0.5 GPa or higher, 1 GPa or higher, 1.5 GPa or higher, 2 GPa or higher, 2.5 GPa or higher, 3 GPa or higher, 3.5 GPa or higher, 4 GPa or higher, or 5 GPa or higher. In some embodiments, the solid electrolyte interface layer has a hardness of 10 GPa or less, 5 GPa or less, 4.5 GPa or less, 4 GPa or less, 3.5 GPa or less, 3 GPa or less, 2.5 GPa or less, 2 GPa or less, 1.5 GPa or less, 1 GPa or less, 0.5 GPa or less, 0.1 GPa or less, 0.05 GPa or less, 0.01 GPa or less, or 0.005 GPa or less. Combinations of the above ranges are also possible (for example, 0.001 GPa or higher, and 5 GPa or lower). Other ranges are also possible.

[0069] Hardness values ​​can be measured using a nanohardness tester with a Berkovitch tip. Loads of 0.5N to 2.5N may be used to maintain penetration depth into the SEI layer. Hardness values ​​may also be measured according to the methods disclosed in ASTM E2546 and ISO 14577-4. Examples of hardness measurement methods include, but are not limited to, Rockwell, Vickers, and Martens.

[0070] For example, the solid electrolyte interface layer may have any of several preferred Vickers Pyramid Number (HV) values. For instance, the solid electrolyte interface layer may have a Vickers Pyramid Number of 0.1 or higher, 1 or higher, 5 or higher, 10 or higher, 20 or higher, 30 or higher, 50 or higher, or 70 or higher. In some embodiments, the solid electrolyte interface layer may have a Vickers Pyramid Number (HV) of 90 or lower, 70 or lower, 50 or lower, 30 or lower, 10 or lower, 5 or lower, or 1 or lower. Combinations of the above ranges are also possible (e.g., 1 or higher, 90 or lower). Other ranges are also possible.

[0071] For example, the solid electrolyte interface layer may have any of several suitable Martens hardness numbers. For instance, the solid electrolyte interface layer can have a Martens hardness number of 0.0003 or higher, 0.0005 or higher, 0.001 or higher, 0.005 or higher, 0.01 or higher, 0.05 or higher, 0.1 or higher, or 0.3 or higher. In some embodiments, the solid electrolyte interface layer has a Martens hardness number of 0.5 or lower, 0.3 or lower, 0.1 or lower, 0.05 or lower, 0.01 or lower, 0.005 or lower, or 0.0005 or lower. Combinations of the above ranges are also possible (e.g., 0.0003 to 0.5). Other ranges are also possible.

[0072] The solid electrolyte interface layer may have any of a variety of suitable thicknesses. For example, the solid electrolyte interface layer may have a thickness of 10 nm or more, 20 nm or more, 50 nm or more, 100 nm or more, 200 nm or more, 500 nm or more, 1 μm or more, 2 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, 50 μm or more, 75 μm or more, or 100 μm or more (for example, as shown by thicknesses 19, 119 and 129 in Figures 1 to 3). In some embodiments, the solid electrolyte interface layer may have a thickness of 200 μm or less, 100 μm or less, 75 μm or less, 50 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 20 μm or less, 10 μm or less, 5 μm or less, 2 μm or less, 1 μm or less, 500 nm or less, 200 nm or less, 100 nm or less, 50 nm or less, or 20 nm or less. Combinations of the above ranges are also possible (for example, 10 nm to 200 μm, 10 nm to 75 μm, or 10 nm to 50 μm). Other ranges are also possible.

[0073] The solid electrolyte interface layer may have any of a variety of suitable bulk densities. In some embodiments, the solid electrolyte interface layer may have a relatively high bulk density. In some embodiments, the solid electrolyte interface layer has a bulk density of 0.5 g / cm³. 3 More than 1.0g / cm 3 More than 1.5g / cm 3 More than 2.0g / cm 3 More than 2.5g / cm 3 More than 3.0g / cm 3 More than 4.0g / cm 3 More than 5.0g / cm 3 It may have a bulk density greater than or equal to the above. In some embodiments, the solid electrolyte interface layer has a bulk density of 7.5 g / cm³. 3 Below, 5.0g / cm 3 Below, 4.0g / cm 3 Below 3.0g / cm 3 Below 2.5g / cm 3 Below 2.0g / cm 3 Below 1.5g / cm 3 The following, or 1 g / cm³ 3The following bulk densities may be present. Combinations of the above ranges are also possible (for example, 0.5 g / cm³). 3 More than 7.5g / cm 3 The following, or 1 g / cm³ 3 More than 3g / cm 3 (See below). Other ranges are also possible.

[0074] The solid electrolyte interface layer may have any of several suitable modulus values. For example, the solid electrolyte interface layer may have a modulus of elasticity of 0.003 GPa or higher, 0.005 GPa or higher, 0.01 GPa or higher, 0.05 GPa or higher, 0.1 GPa or higher, 0.5 GPa or higher, 1 GPa or higher, 1.5 GPa or higher, 2 GPa or higher, 2.5 GPa or higher, 3 GPa or higher, 3.5 GPa or higher, or 4 GPa or higher. In some embodiments, the solid electrolyte interface layer has a modulus of elasticity of 5 GPa or less, 4.5 GPa or less, 4 GPa or less, 3.5 GPa or less, 3 GPa or less, 2.5 GPa or less, 2 GPa or less, 1.5 GPa or less, 1 GPa or less, 0.5 GPa or less, 0.1 GPa or less, 0.05 GPa or less, 0.01 GPa or less, or 0.005 GPa or less. Combinations of the above ranges are also possible (e.g., 0.003 GPa or higher, 5 GPa or less). Other ranges are also possible.

[0075] In some embodiments, the solid electrolyte interface layer (e.g., adjacent to the electrolyte and / or electrolyte-impregnated separator) comprises particles (e.g., crystalline particles) having any of a variety of suitable sizes. In some embodiments, the solid electrolyte interface layer adjacent to the electrolyte comprises particles having sizes of 10 nm or more, 20 nm or more, 40 nm or more, 60 nm or more, 80 nm or more, 100 nm or more, 125 nm or more, 150 nm or more, 175 nm or more, or 200 nm or more. In some embodiments, the solid electrolyte interface layer adjacent to the electrolyte comprises particles having sizes of 250 nm or less, 200 nm or less, 175 nm or less, 150 nm or less, 125 nm or less, 100 nm or less, 80 nm or less, 60 nm or less, 40 nm or less, or 20 nm or less. Combinations of the above ranges are also possible (e.g., 10 nm to 200 nm). Other ranges are also possible.

[0076] In some embodiments, electrochemical cells containing a solid electrolyte interface layer as described herein exhibit a slower rate of decrease in discharge capacity compared to electrochemical cells that do not contain such a solid electrolyte interface layer but are otherwise equivalent. The discharge capacity C is given by the following equation (1): C=I dch ·t (1) According to this, current I dch This can be calculated by multiplying by the time t until the discharge voltage cutoff is reached after the cycle. As the cycle continues, the discharge capacity can be determined for each subsequent cycle.

[0077] In some embodiments, the electrochemical cell exhibits a decrease in discharge capacity of 0% or more, 0.01% or more, 0.05% or more, 0.1% or more, 0.5% or more, 1% or more, 1.5% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, or 15% or more after 100 charge-discharge cycles, relative to the discharge capacity at the 5th charge-discharge cycle (e.g., the formation cycle). In some embodiments, the electrochemical cell exhibits a decrease in discharge capacity of 20% or less, 15% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, 1% or less, 0.5% or less, 0.1% or less, 0.05% or less, or 0.01% or less, relative to the discharge capacity at the 5th charge-discharge cycle. Combinations of the above ranges are also possible (e.g., 0% to 20%). Other ranges are also possible.

[0078] In some embodiments, electrochemical cells including a solid electrolyte interface layer as described herein exhibit a slower rate of increase in discharge resistance compared to electrochemical cells that do not include such a solid electrolyte interface layer but are otherwise equivalent. The discharge resistance of an electrochemical cell during cycling may be measured by the following general procedure (or protocol). First, the electrochemical cell can be connected to a battery cycler channel capable of supplying the electrochemical cell with manufacturer-specified current and voltage. The cell is first discharged to the manufacturer-specified voltage with the manufacturer-specified current and then left idle for a certain period (e.g., at least 2 minutes). Next, the cell is charged to the manufacturer-specified voltage with the manufacturer-specified current, the voltage is maintained at the specified voltage until the current decays to a specific value, and the cell is left idle again for a certain period (e.g., at least 2 minutes). The voltage during idle (V1) was measured at the end of this idle period. Then, the cell is discharged again to the specified voltage with the manufacturer-specified current. It is possible to measure the voltage (V2) 5 minutes after this discharge. The discharge resistance, also known as the 5-minute discharge resistance R, is given by the following equation (2): R=(V2-V1) / I dch (2) (In the formula, V1 is the voltage at the end of the pause before discharge, V2 is the voltage measured 5 minutes after the start of discharge, I dch This is the discharge current (A). It is possible to calculate this using [this method]. As the cycle continues, the discharge resistance can be determined for each subsequent cycle.

[0079] In some such embodiments, the electrochemical cell exhibits an increase in discharge resistance of 0%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or 15% or more after 100 charge-discharge cycles, relative to the discharge resistance at the fifth charge-discharge cycle after formation. In some embodiments, the electrochemical cell exhibits an increase in discharge resistance of 20% or less, 15% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, 1% or less, 0.5% or less, 0.1% or less, 0.05% or less, or 0.01% or less after 100 charge-discharge cycles, relative to the discharge resistance at the fifth charge-discharge cycle after formation. Combinations of the above ranges are also possible (e.g., 0% to 20%). Other ranges are also possible.

[0080] In some embodiments, electrochemical cells comprising a solid electrolyte interface layer described herein (e.g., one or more of LiF, Li2CO3, Li2O, etc.) exhibit improved cycle life. In some embodiments, electrochemical cells comprising a solid electrolyte interface layer described herein exhibit cycle lives of 100 cycles or more, 150 cycles or more, 200 cycles or more, 250 cycles or more, 300 cycles or more, 350 cycles or more, 400 cycles or more, 450 cycles or more, 500 cycles or more, 1000 cycles or more, or 1500 cycles or more. In some embodiments, electrochemical cells comprising a solid electrolyte interface layer described herein exhibit cycle lives of 2000 cycles or less, 1500 cycles or less, 1000 cycles or less, 500 cycles or less, 450 cycles or less, 400 cycles or less, 350 cycles or less, 300 cycles or less, 250 cycles or less, 200 cycles or less, or 150 cycles or less. Combinations of the above ranges are also possible (e.g., 100 cycles or more, 2000 cycles or less). Other ranges are also possible.

[0081] In some embodiments, electrochemical cells comprising a solid electrolyte interface layer as described herein (e.g., one or more of LiF, Li2CO3, Li2O, etc.) exhibit improved cycle life compared to electrochemical cells that do not contain such a solid electrolyte interface layer but are otherwise equivalent. In some embodiments, electrochemical cells comprising a solid electrolyte interface layer as described herein exhibit a cycle life of 2 or more, 3 or more, 5 or more, 10 or more, 15 or more, 20 or more, 25 or more, 30 or more, 40 or more, 50 or more, 100 or more, 200 or more, 300 or more, or 400 or more than that of electrochemical cells that do not contain such a solid electrolyte interface layer but are otherwise equivalent. In some embodiments, an electrochemical cell comprising a solid electrolyte interface layer as described herein exhibits a cycle life of 500 times or less, 400 times or less, 300 times or less, 200 times or less, 100 times or less, 50 times or less, 40 times or less, 30 times or less, 20 times or less, 10 times or less, or 3 times or less than that of an electrochemical cell that does not contain a solid electrolyte interface layer but is otherwise equivalent. Combinations of the above ranges are also possible (e.g., 2 times or more, 500 times or less). Other ranges are also possible.

[0082] In some embodiments, electrochemical cells comprising a solid electrolyte interface layer with anisotropic force application during at least the duration of a charge-discharge cycle (e.g., one or more of LiF, Li2CO3, Li2O, etc.) exhibit improved physical properties compared to cells comprising a solid electrolyte interface layer without anisotropic force application. In some embodiments, electrochemical cells comprising a solid electrolyte interface layer as described herein, with anisotropic force application during at least the duration of a charge-discharge cycle (e.g., one or more of LiF, Li2CO3, Li2O, etc.), exhibit a cycle life of 2, 3, 5, 10, 15, 20, 25 times, 30, 40, 50, 100, 200, 300, or 400 times longer than an otherwise equivalent electrochemical cell comprising a solid electrolyte interface layer but formed without pressure. In some embodiments, an electrochemical cell comprising a solid electrolyte interface layer as described herein, with the application of an anisotropic force during at least the duration of a charge-discharge cycle, exhibits a cycle life of 500 times or less, 400 times or less, 300 times or less, 200 times or less, 100 times or less, 50 times or less, 40 times or less, 30 times or less, 20 times or less, 10 times or less, or 3 times or less of a cycle life of an otherwise equivalent electrochemical cell comprising a solid electrolyte interface layer but formed without pressure. Combinations of the above ranges are also possible (e.g., 2 times or more, 500 times or less). Other ranges are also possible. The magnitude of the applied anisotropic force may be one or more of the ranges described herein.

[0083] In some embodiments, an electrochemical cell comprising a solid electrolyte interface layer formed in the presence of a fluorinated electrolyte solvent (e.g., one or more such as LiF, Li2CO3, Li2O, etc.) and subjected to an anisotropic force applied at least for the duration of a charge-discharge cycle exhibits improved physical properties compared to a otherwise equivalent cell comprising a solid electrolyte interface layer formed in the presence of a non-fluorinated electrolyte solvent and subjected to the same applied anisotropic force. For example, compared to the solid electrolyte interface layer of a cell comprising a non-fluorinated electrolyte and subjected to anisotropic force, the solid electrolyte interface layer of an electrochemical cell comprising a fluorinated electrolyte solvent and subjected to the same anisotropic force may exhibit a more gradual increase in thickness and / or a more gradual decrease in bulk density over charge-discharge cycles. These differences in physical properties may contribute, at least in part, to an improved cycle life.

[0084] In some embodiments, electrochemical cells comprising a solid electrolyte interface layer formed under a high conversion voltage (e.g., one or more of LiF, Li2CO3, Li2O, etc.) exhibit improved physical properties compared to otherwise equivalent electrochemical cells comprising a solid electrolyte interface layer but formed without using a high conversion voltage. In some embodiments, electrochemical cells comprising a solid electrolyte interface layer as described herein, formed under a high conversion voltage (e.g., one or more of LiF, Li2CO3, Li2O, etc.), exhibit cycle lives of 2, 3, 5, 10, 15, 20, 25, 30, 40, 50, 100, 200, 300, or 400 times or more than those of otherwise equivalent electrochemical cells comprising a solid electrolyte interface layer but formed without using a high conversion voltage. In some embodiments, an electrochemical cell including a solid electrolyte interface layer formed under a high conversion voltage exhibits a cycle life of 500 times or less, 400 times or less, 300 times or less, 200 times or less, 100 times or less, 50 times or less, 40 times or less, 30 times or less, 20 times or less, 10 times or less, or 3 times or less than that of an otherwise equivalent electrochemical cell including a solid electrolyte interface layer but formed without using a high conversion voltage. Combinations of the above ranges are also possible (e.g., 2 times or more, 500 times or less). Other ranges are also possible.

[0085] In some embodiments, an electrochemical cell containing a solid electrolyte interface layer (e.g., one or more rich in LiF, Li2CO3, Li2O, etc.) helps maintain the charge-discharge capacity within the electrochemical cell at relatively low temperatures (e.g., below 0°C, below -25°C, below -40°C, etc.). In some such embodiments, when charging and discharging at relatively low temperatures, an electrochemical cell containing the solid electrolyte interface layer described herein exhibits an improved cycle life of 60 cycles or more, 80 cycles or more, 90 cycles or more, 100 cycles or more, 125 cycles or more, 150 cycles or more, 250 cycles or more, 500 cycles or more, or 750 cycles or more. In some embodiments, when charging and discharging at relatively low temperatures, an electrochemical cell containing the solid electrolyte interface layer described herein exhibits a cycle life of 1000 cycles or less, 750 cycles or less, 500 cycles or less, 250 cycles or less, 175 cycles or less, 150 cycles or less, 125 cycles or less, 100 cycles or less, 90 cycles or less, 80 cycles or less, or 70 cycles or less. Combinations of the above ranges are also possible (for example, 60 cycles or more, and 1000 cycles or less). Other ranges are also possible.

[0086] In some embodiments, the electrolyte includes a solvent. In one set of embodiments, the solvent includes at least one fluorinated organic solvent. In some embodiments, a fluorinated organic solvent and / or a mixture of fluorinated organic solvents is used as the sole solvent in the electrolyte. In some embodiments, when the fluorinated organic solvent and / or mixture of fluorinated organic solvents is exposed for a certain period during charge and discharge cycles, it results in the formation of a solid electrolyte interface layer containing relatively high concentrations of inorganic material (e.g., LiF, Li2CO3, Li2O, etc.). In some embodiments, a non-fluorinated solvent may be present.

[0087] In some embodiments, at least one fluorinated organic solvent is selected from the group consisting of cyclic and linear fluorinated carbonates, fluorinated ethers, and fluorinated esters (e.g., fluorinated alkyl esters). For example, in one embodiment, the solvent comprises at least one fluorinated organic solvent selected from fluoroethylene carbonate and / or difluoroethylene carbonate. Further non-limiting examples of fluorinated organic solvents, but not limited to these, include methyl, 2,2,2-trifluoroethyl carbonate, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl difluoroacetate, ethyl difluoroacetate, methyl trifluoroacetate, and ethyl trifluoroacetate.

[0088] The fluorinated organic solvent may be present in the electrolyte in any of several suitable amounts. In some embodiments, the fluorinated organic solvent (e.g., fluoroethylene carbonate (FEC)) may be present in amounts of 10% or more by weight, 11% or more by weight, 12% or more by weight, 13% or more by weight, 14% or more by weight, 15% or more by weight, 17% or more by weight, 20% or more by weight, 30% or more by weight, 35% or more by weight, 40% or more by weight, 50% or more by weight, 60% or more by weight, 70% or more by weight, 80% or more by weight, or 88% or more by weight, based on the total weight of the electrolyte. In some embodiments, the fluorinated organic solvent may be present in amounts of 90% or less by weight, 88% or less by weight, 80% or less by weight, 70% or less by weight, 60% or less by weight, 50% or less by weight, 40% or less by weight, 30% or less by weight, 20% or less by weight, 17% or less by weight, 15% or less by weight, 13% or less by weight, 12% or less by weight, or 11% or less by weight, based on the total weight of the electrolyte. Combinations of the above ranges are also possible (for example, 10% to 90% by weight, 14% to 88% by weight, or 17% to 44% by weight). Other ranges are also possible.

[0089] In some embodiments, the solvent further comprises at least one non-fluorinated organic solvent. In some embodiments, when the non-fluorinated solvent (or its decomposition products) is exposed for a certain period of time during charging and discharging cycles, it results in the formation of one or more inorganic materials (e.g., Li2CO3, Li2O) in the solid electrolyte interface layer. In some embodiments, the at least one non-fluorinated organic solvent comprises an ester solvent. In some embodiments, the organic solvent may comprise one or more of carboxylic acid esters, phosphoric acid esters, linear and cyclic ethers and acetals, sulfuric acid esters, sulfonic acid esters, esters formed from carboxylic acids and halogenated alcohols, and alkyl esters.

[0090] In some embodiments, at least one non-fluorinated organic solvent comprises a cyclic and / or linear carbonate. In some such embodiments, the non-fluorinated solvent may comprise one or more carbonate-based solvents selected from the group consisting of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, and ethylene carbonate. Additionally or alternatively, at least one non-fluorinated organic solvent may comprise acetates (e.g., methyl acetate, ethyl acetate), alkyl esters (e.g., ethyl butyrate), lactones (e.g., γ-butyrolactone), and the like.

[0091] Non-fluorinated organic solvents may be present in the electrolyte in any of a variety of suitable amounts. In some embodiments, the non-fluorinated organic solvent may be present in amounts of 0% or more by weight, 5% or more by weight, 10% or more by weight, 15% or more by weight, 20% or more by weight, 30% or more by weight, 35% or more by weight, 40% or more by weight, 50% or more by weight, 60% or more by weight, or 70% or more by weight of the total weight of the electrolyte. In some embodiments, the non-fluorinated organic solvent may be present in amounts of 75% or less by weight, 70% or less by weight, 60% or less by weight, 50% or less by weight, 40% or less by weight, 30% or less by weight, 20% or less by weight, 15% or less by weight, 10% or less by weight, or 5% or less by weight of the total weight of the electrolyte. Combinations of the above ranges are also possible (e.g., 0% to 75% by weight). Other ranges are also possible.

[0092] The electrolyte solvent may contain a fluorinated organic solvent and a non-fluorinated organic solvent in any of a variety of suitable weight ratios. In some embodiments, the weight ratio of the fluorinated organic solvent (e.g., fluoroethylene carbonate) to the non-fluorinated organic solvent may be, in some cases, 1:10 or more, 1:8 or more, 1:5 or more, 1:4 or more, 1:3 or more, 1:2 or more, 1:1 or more, 2:1 or more, 3:1 or more, 5:1 or more, 10:1 or more, 30:1 or more, 50:1 or more, 70:1 or more, or 90:1 or more. In some embodiments, the weight ratio of fluorinated organic solvent to non-fluorinated organic solvent is 100:1 (e.g., 99:1) or less, 90:1 or less, 70:1 or less, 50:1 or less, 30:1 or less, 10:1 or less, 5:1 or less, 3:1 or less, 2:1 or less, 1:1 or less, 1:2 or less, 1:3 or less, 1:4 or less, 1:5 or less, 1:8 or less, 1:10 or less, or 1:15 or less. Combinations of the above ranges are also possible (e.g., 1:10 to 100:1, 1:10 to 2:1, 1:4 to 1:1, or 1:3 to 1:1). Other ranges are also possible.

[0093] Further non-limiting examples of useful electrolytes, but not limited to these, include, for example, N-methylacetamide, acetonitrile, acetals, ketals, esters (e.g., esters of carbonates), carbonates (e.g., dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate), sulfones, sulfites, sulfolanes, sulfonimides (e.g., lithium bis(trifluoromethane)sulfonimides), aliphatic ethers, acyclic ethers, cyclic ethers, glimes, polyethers, phosphate esters (e.g., hexafluorophosphates), siloxanes, dioxolanes, N-alkylpyrrolidones, nitrate-containing compounds, the aforementioned substitution forms, and blends thereof. Examples of usable acyclic ethers, but not limited to these, include diethyl ether, dipropyl ether, dibutyl ether, dimethoxymethane, trimethoxymethane, 1,2-dimethoxyethane, diethoxyethane, 1,2-dimethoxypropane, and 1,3-dimethoxypropane. Examples of usable cyclic ethers, but not limited to these, include tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, and trioxane. Examples of usable polyethers, but not limited to these, include diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglime), tetraethylene glycol dimethyl ether (tetraglime), higher grime, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, dipropylene glycol dimethyl ether, and butylene glycol ether. Examples of usable sulfones, but not limited to these, include sulfolane, 3-methylsulfolane, and 3-sulfolene. The aforementioned fluorinated derivatives are also useful as liquid electrolyte solvents.

[0094] In one embodiment, the solvent comprises a mixture of fluoroethylene carbonate (FEC) and a non-fluorinated carbonate solvent (e.g., dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or a combination thereof). In some such embodiments, the weight ratio of fluoroethylene carbonate in the organic solvent to the non-fluorinated carbonate solvent may be, in some cases, 1:10 or more (e.g., 1:9), 1:8 or more, 1:5 or more, 1:4 or more, 1:3 or more, 1:2 or more, or 1:1 or more. In some embodiments, the weight ratio of fluoroethylene carbonate to the non-fluorinated carbonate solvent may be 2:1 or less, 1:1 or less, 1:2 or less, 1:3 or less, 1:4 or less, 1:5 or less, or 1:8 or less. Combinations of the above ranges are also possible (1:10 or more and 2:1 or less, or 1:4 or more and 1:1 or less, or 1:3 or more and 1:1 or less). Other ranges are also possible. In some embodiments, the weight ratio of the fluorinated solvent (e.g., FEC) to the non-fluorinated solvent (e.g., DMC) is between 1:4 and 1:1.

[0095] In some embodiments, the electrolyte comprises at least one passivating agent. In some embodiments, the passivating agent can form a passivation layer on the electrodes (e.g., an anode such as a lithium metal electrode, and / or a cathode such as a lithium intercalation electrode). In some such embodiments, the resulting passivation layer is part of the solid electrolyte interface layer described herein. In some embodiments, an electrochemical cell comprising a solid electrolyte interface layer formed in the presence of a passivating agent may exhibit improved physical properties (e.g., anode stability, cycle life, discharge resistance, and discharge capacity) compared to a cell comprising a solid electrolyte interface layer formed in the absence of a passivating agent, where all other factors are equal.

[0096] For example, in some embodiments, electrochemical cells comprising a solid electrolyte interface layer formed in the presence of a passivator (e.g., one or more of LiF, Li2CO3, Li2O, etc.) exhibit improved physical properties compared to otherwise equivalent cells comprising a solid electrolyte interface layer in the absence of a passivator. In some embodiments, electrochemical cells comprising a solid electrolyte interface layer as described herein, formed in the presence of a passivator (e.g., one or more of LiF, Li2CO3, Li2O, etc.), exhibit cycle lives of 2, 3, 5, 10, 15, 20, 25, 30, 40, 50, 100, 200, 300, or 400 times longer than those of otherwise equivalent electrochemical cells comprising a solid electrolyte interface layer but without a passivator. In some embodiments, an electrochemical cell comprising a solid electrolyte interface layer formed in the presence of a passivator exhibits a cycle life of 500 times or less, 400 times or less, 300 times or less, 200 times or less, 100 times or less, 50 times or less, 40 times or less, 30 times or less, 20 times or less, 10 times or less, or 3 times or less than that of an otherwise equivalent electrochemical cell comprising a solid electrolyte interface layer but formed in the absence of a passivator. Combinations of the above ranges are also possible (e.g., 2 times to 500 times). Other ranges are also possible.

[0097] Suitable passivators include, but are not limited to, boron-containing compounds, such as compounds containing an (oxalato)borate group. The (oxalato)borate group may include, for example, a bis(oxalato)borate anion and / or a difluoro(oxalato)borate anion. In some embodiments, the passivator may contain a salt (e.g., an oxalate). In some embodiments, the passivator containing a salt may contain a lithium cation. For example, the lithium salt may contain bis(oxalato)lithium borate (LiBOB) and / or difluoro(oxalato)lithium borate (LiDFOB). In some embodiments, the lithium salt may contain lithium tetrafluoroborate (LiBF4).

[0098] In some embodiments, the total weight of the passivating agent (e.g., (oxalato)borate groups such as lithium bis(oxalato)borate (LiBOB) and / or lithium difluoro(oxalato)borate) in the electrochemical cell may be about 30% by weight or less, about 28% by weight or less, about 25% by weight or less, about 22% by weight or less, about 20% by weight or less, about 18% by weight or less, about 15% by weight or less, about 12% by weight or less, about 10% by weight or less, about 8% by weight or less, about 6% by weight or less, about 5% by weight or less, about 4% by weight or less, about 3% by weight or less, about 2% by weight or less, or about 1% by weight or less, relative to the total weight of the electrolyte. In some embodiments, the total weight of the passivator in the electrochemical cell is greater than about 0.2% by weight, greater than about 0.5% by weight, greater than about 1% by weight, greater than about 2% by weight, greater than about 3% by weight, greater than about 4% by weight, greater than about 6% by weight, greater than about 8% by weight, greater than about 10% by weight, greater than about 15% by weight, greater than about 18% by weight, greater than about 20% by weight, greater than about 22% by weight, greater than about 25% by weight, or greater than about 28% by weight. Combinations of the above ranges are also possible (e.g., between about 0.2% by weight and about 30% by weight, between about 0.2% by weight and about 20% by weight, between about 0.5% by weight and about 20% by weight, between about 1% by weight and about 8% by weight, between about 1% by weight and about 6% by weight, between about 4% by weight and about 10% by weight, between about 6% by weight and about 15% by weight, or between about 8% by weight and about 20% by weight). Other ranges are also possible.

[0099] In some embodiments, the electrochemical cell may contain two or more passivators. The two or more passivators may interact synergistically to enhance one or more properties of the electrochemical cell beyond the extent that would be expected from the effect of any one of the passivators on the electrochemical cell individually.

[0100] Further examples of passivators include, but are not limited to, sultones (e.g., 1,3-propanesultone (PS), prop-1-ene-1,3-sultone (PES)), sulfonates (e.g., methylene methanesulfonate (MMDS)), vinylene carbonates, phosphites, lithium salts (e.g., LiBF4)), xanthate groups (e.g., lithium xanthate, potassium xanthate, lithium ethyl xanthate, potassium ethyl xanthate, lithium isobutyl xanthate, potassium isobutyl xanthate, lithium tert-butyl xanthate, potassium tert-butyl xanthate), polyxanthate groups, carbamate groups (e.g., lithium dithiocarbamate, potassium dithiocarbamate, lithium diethyldithiocarbamate, and potassium diethyldithiocarbamate), polycarbamate groups, N-O groups (e.g., lithium nitrate, magnesium nitrate), and silanes. Further examples of passivating agents and methods of using them are described in detail, for example, in U.S. Patent Application Publication No. 2018-0351158, which is incorporated herein by reference in its entirety.

[0101] In some embodiments, the electrolyte comprises at least one lithium salt. In one set of embodiments, the lithium salt may comprise one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Further examples of lithium salts include LiSCN, LiBr, LiI, LiSO3CH3, LiNO3, LiPF6, LiBF4, LiB(Ph)4, LiClO4, LiAsF6, Li2SiF6, LiSbF6, LiAlCl4, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, salts containing the tris(oxalato)phosphate anion (e.g., lithium tris(oxalato)phosphate, without limitation), LiC(SO2CF3)3, LiCF3SO3, LiN(SO2F)2, LiN(SO2CF3)2, LiC(C n F 2n+1 SO2)3 (where n is an integer in the range of 1 to 20), and (C n F 2n+1 SO2) m XLi (where n is an integer in the range of 1 to 20, m is 1 when X is selected from oxygen or sulfur, m is 2 when X is selected from nitrogen or phosphorus, and m is 3 when X is selected from carbon or silicon. Other electrolyte salts that may be useful include lithium polysulfide (Li2Sx) and lithium salts of organic polysulfides (LiSxR) n where x is an integer from 1 to 20, n is an integer from 1 to 3, R is an organic group, and those disclosed in U.S. Patent No. 5,538,812 to Lee et al., which is hereby incorporated by reference in its entirety for all purposes.

[0102] If present, lithium salts may be present in the electrolyte at various preferred concentrations. In some embodiments, lithium salts are present in the electrolyte at concentrations of 0.01 M or higher, 0.02 M or higher, 0.05 M or higher, 0.1 M or higher, 0.2 M or higher, 0.5 M or higher, 1 M or higher, 2 M or higher, or 5 M or higher. Lithium salts may be present in the electrolyte at concentrations of 10 M or lower, 5 M or lower, 2 M or lower, 1 M or lower, 0.5 M or lower, 0.2 M or lower, 0.1 M or lower, 0.05 M or lower, or 0.02 M or lower. Combinations of the above ranges are also possible (e.g., 0.01 M to 10 M, or 0.01 M to 5 M). Other ranges are also possible.

[0103] In some embodiments, the electrolyte comprises one or more room-temperature ionic liquids. If present, the room-temperature ionic liquids typically comprise one or more cations and one or more anions. Non-limiting examples of suitable cations include one or more quaternary ammonium cations such as lithium cation and / or imidazolium cation, pyrrolidinium cation, pyridinium cation, tetraalkylammonium cation, pyrazolium cation, piperidinium cation, pyridazinium cation, pyrimidinium cation, pyrazinium cation, oxazolium cation, and trizolium cation. Non-limiting examples of suitable anions include trifluoromethylsulfonate (CF3SO3). - ), bis(fluorosulfonyl)imide(N(FSO2)2 - ), bis(trifluoromethylsulfonyl)imide((CF3SO2)2N - ), bis(perfluoroethylsulfonyl)imide ((CF3CF2SO2)2N - ) and tris(trifluoromethylsulfonyl)methide((CF3SO2)3C -Examples of suitable ionic liquids include N-methyl-N-propylpyrrolidinium / bis(fluorosulfonyl)imide and 1,2-dimethyl-3-propylimidazolium / bis(trifluoromethanesulfonyl)imide. In some embodiments, the electrolyte comprises both a room-temperature ionic liquid and a lithium salt. In some other embodiments, the electrolyte comprises a room-temperature ionic liquid and does not contain a lithium salt.

[0104] Suitable active electrode materials for use as the first electrode (for example, as the anode active electrode species in the anode of the electrochemical cell described herein) include, but are not limited to, lithium metals such as lithium foil or lithium deposited on a substrate, and lithium alloys (e.g., lithium-aluminum alloy or lithium-tin alloy). The lithium may be contained as one or more films, optionally separated by a protective material such as a ceramic material or an ion-conducting material described herein. Suitable ceramic materials include silica, alumina, and / or lithium-containing glassy materials, such as lithium phosphate, lithium aluminate, lithium silicate, lithium carbonate, lithium oxide, lithium oxynitride phosphate, lithium tantalum oxide, lithium aluminosulfide, lithium titanium oxide, lithium silcosulfide, lithium germanosulfide, lithium aluminosulfide, lithium borosulfide, lithium phosphosulfide, and combinations of two or more of the above. Suitable lithium alloys for use in the embodiments described herein include alloys of lithium with aluminum, magnesium, silicon, indium, silver, and / or tin. In some embodiments, these materials are preferred, but other cell compounds are also intended. In some embodiments, the first electrode may include one or more binder materials (e.g., polymers).

[0105] In some embodiments, the thickness of the first electrode (e.g., anode) may vary, for example, from about 1 to about 200 μm. For example, the first electrode (e.g., anode) may have a thickness of less than about 200 μm, less than about 100 μm, less than about 50 μm, less than about 25 μm, less than about 10 μm, or less than about 5 μm. In some embodiments, the first electrode (e.g., anode) may have a thickness of about 1 μm or more, about 5 μm or more, about 10 μm or more, about 25 μm or more, about 50 μm or more, about 100 μm or more, or about 150 μm or more. Combinations of the above ranges are also possible (e.g., between about 1 μm and about 200 μm, between about 1 μm and about 100 μm, between about 5 μm and about 50 μm, between about 5 μm and about 25 μm, or between about 10 μm and about 25 μm). Other ranges are also possible. The choice of thickness may depend on cell design parameters such as the desired lithium excess, cycle life, and the thickness of the second electrode.

[0106] Methods for depositing a negative electrode material (e.g., an alkali metal anode such as lithium) onto a substrate include thermal deposition, sputtering, jet deposition, and laser ablation. Alternatively, if the anode includes a lithium foil, or a lithium foil and a substrate, these may be laminated together by lamination methods known in the art to form the anode.

[0107] In some embodiments, the electroactive material within the second electrode (e.g., the cathode active electrode species in the cathode of the electrochemical cell described herein) may include a metal oxide. In some embodiments, an intercalation electrode (e.g., a lithium intercalation cathode, also referred to herein as a lithium-ion intercalation cathode) may be used (e.g., as the second electrode). Non-limiting examples of suitable materials capable of intercalating ions of electroactive materials (e.g., alkali metal ions) include oxides, titanium sulfide, and iron sulfide. In some embodiments, the second electrode (e.g., the cathode) may include an intercalation electrode comprising a lithium transition metal oxide or a lithium transition metal phosphate. As a further example, Li x CoO2 (also referred to herein as lithium cobalt oxide; e.g., Li 1.1 CoO2), Li x NiO2, Li x MnO2, Li x Mn2O4 (e.g., Li 1.05 Mn2O4), Li x CoPO4, Li x MnPO4, LiCo x Ni (1-x) O2, and LiCo x Ni y Mn (1-x-y) O2 are included, Li 1.05 Mn2O4), Li x CoPO4, Li x MnPO4, LiCo x Ni (1-x) O2, and LiCo x Ni y Mn (1-x-y) O2 (also referred to herein as lithium-nickel-manganese-cobalt oxide; e.g., LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiNi 3 / 5 Mn 1.5 Co 1.5 O2, LiNi 4 / 5 Mn 1 / 10 Co 1 / 10 O2, LiNi1 / 2 Mn3 / 10 Co 1.5 Examples include O2). X (for example, Li (a chemical composition as described elsewhere in this specification) x M y O z In the case of an intercalation cathode having (where M is a metal or a combination of metals), X may be 0 or greater and 2 or less. Typically, X is 1 or greater and 2 or less when the electrochemical cell is fully discharged, and less than 1 when the electrochemical cell is fully charged. In some embodiments, a fully charged electrochemical cell may have a value of x of 1 or greater and 1.05 or less, 1 or greater and 1.1 or less, or 1 or greater and 1.2 or less. Further examples include (0 <x≦1)であるLi x NiPO4, LiMn (x+y=2) x Ni y O4 (for example, LiMn 1.5 Ni 0.5 LiNi (O4), (x+y+z=1) x Co y Al z Examples include O2, LiFePO4, and combinations thereof. In some embodiments, the electroactive material in the cathode comprises a lithium transition metal phosphate (e.g., LiFePO4), which in some embodiments can be substituted with a borate and / or silicate.

[0108] In some embodiments, the electroactive material in the second electrode (e.g., the cathode-active electrode species in the cathode of an electrochemical cell described herein) may include electroactive transition metal chalcogenides (or chalcogenides), electroactive conductive polymers, and / or electroactive sulfur-containing materials, as well as combinations thereof. As used herein, the term “chalcogenide” refers to compounds containing one or more elements of oxygen, sulfur, and selenium. Examples of suitable transition metal chalcogenides include, but are not limited to, electroactive oxides, sulfides, and selenides of transition metals selected from the group consisting of Mn, V, Cr, Ti, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, and Ir. In one embodiment, the transition metal chalcogenide is selected from the group consisting of electroactive oxides of nickel, manganese, cobalt, and vanadium, and electroactive sulfides of iron. In one embodiment, the cathode comprises one or more materials from manganese dioxide, iodine, silver chromate, silver oxide and vanadium pentoxide, copper oxide, copper oxyphosphate, lead sulfide, iron sulfide, lead bismuthate, bismuth trioxide, cobalt dioxide, copper chloride, manganese dioxide, and carbon. In another embodiment, the cathode active layer comprises an electroactive conductive polymer. Examples of suitable electroactive conductive polymers include, but are not limited to, electroactive and electronically conductive polymers selected from the group consisting of polypyrroles, polyanilines, polyphenylenes, polythiophenes, and polyacetylenes. In some embodiments, it is desirable to use polypyrroles, polyanilines, and polyacetylenes as conductive polymers.

[0109] In some embodiments, various cathode active materials are suitable for use in the cathode of the electrochemical cell described herein. In some embodiments, the cathode active material comprises a lithium intercalation compound (e.g., a compound that can reversibly insert lithium ions into lattice sites and / or interstitial sites). In some cases, the cathode active material comprises a layered oxide. A layered oxide generally refers to an oxide having a lamellar structure (e.g., multiple sheets or layers stacked on top of each other). Non-limiting examples of suitable layered oxides include lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), and lithium manganeseate (LiMnO2). In some embodiments, the layered oxide is lithium nickel manganese cobalt oxide (LiNi x Mn y Co z O2 (also called "NMC" or "NCM") is a suitable NMC compound, for example, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), and Li 1+X (Ni 0.85 Co 0.10 Mn 0.05 ) 1-X O2(NCM851005), where x is approximately 0.01. In some embodiments, the layered oxide is given by the formula (Li2MnO3)x(LiMO2) (1-X) It may have, where M is one or more of Ni, Mn, and Co. For example, a layered oxide is (Li2MnO3) 0.25 (LiNi 0.3 Co 0.15 Mn 0.55 O2) 0.75 That's fine.

[0110] In some embodiments, the layered oxide is lithium nickel cobalt aluminum oxide (LiNi X Co y Al z O2 (also called "NCA") is one example of a suitable NCA compound, a non-limiting example being LiNi 0.8 Co 0.15 Al 0.05 It is O2.

[0111] In some embodiments, the cathode active material comprises a transition metal polyanion oxide (e.g., a compound containing a transition metal, oxygen, and / or an anion having a charge greater than 1). A non-limiting example of a suitable transition metal polyanion oxide is lithium iron phosphate (LiFePO4, also known as "LFP"). Another non-limiting example of a suitable transition metal polyanion oxide is lithium manganese iron phosphate (LiMn x Fe 1-x PO4 (also known as "LMFP"). A non-limiting example of a suitable LMFP compound is LiMn 0.8 Fe 0.2 It is PO4. In some embodiments, the cathode active material includes spinel (for example, a compound having the structure AB2O4 where A may be Li, Mg, Fe, Mn, Zn, Cu, Ni, Ti, or Si, and B may be Al, Fe, Cr, Mn, or V). A non-limiting example of a preferred spinel is lithium manganese oxide (LiMn2O4, also called "LMO"). Another non-limiting example is lithium manganese nickel oxide (LiNi x M 2-x O4 (also known as "LMNO") is a suitable LMNO compound. Non-limiting examples of suitable LMNO compounds include LiNi 0.5 Mn 1.5 It is O4. In some cases, the electroactive material is Li 1.14 Mn 0.42 Ni 0.25 Co 0.29O2 ("HC-MNC"), lithium carbonate (Li2CO3), lithium carbide (e.g., Li2C2, Li4C, Li6C2, Li8C3, Li6C3, Li4C3, Li4C5), vanadium oxide (e.g., V2O5, V2O3, V6O 13 ), and / or vanadium phosphate (e.g., lithium vanadium phosphate such as Li3V2(PO4)3), or any combination thereof.

[0112] In some embodiments, the cathode active material comprises a conversion compound. For example, the cathode may be a lithium conversion cathode. It is recognized that cathodes containing a conversion compound can have a relatively large specific capacity. While we do not wish to be bound by any particular theory, a relatively large specific capacity can be achieved by utilizing all possible oxidation states of the compound through conversion reactions that result in multiple electron transfers for each transition metal (e.g., compared to 0.1 to 1 electron transfer in intercalation compounds). Suitable conversion compounds include, but are not limited to, transition metal oxides (e.g., Co3O4), transition metal hydrides, transition metal sulfides, transition metal nitrides, and transition metal fluorides (e.g., CuF2, FeF2, FeF3). Transition metals generally refer to elements that have a partially filled d-shell (e.g., Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Rf, Db, Sg, Bh, Hs).

[0113] The electrodes described herein may be part of an electrochemical cell incorporated into a battery (e.g., a rechargeable battery). In some embodiments, an electrochemical cell (including one or more electrodes described herein) may be used to power an electric vehicle or otherwise incorporated into an electric vehicle. As a non-limiting example, an electrochemical cell described herein may, in some cases, be used to power the drivetrain of an electric vehicle. The vehicle may be any suitable vehicle adapted for travel on land, at sea, and / or in the air. For example, the vehicle may be an automobile, a truck, a motorcycle, a boat, a helicopter, an airplane, and / or any other suitable type of vehicle.

[0114] In some embodiments, the electrochemical cells described herein include at least one current collector. For example, referring again to Figure 1, the electrochemical cell 10 includes a cathode current collector 20 and an anode current collector 22. The material of the current collector may in some cases be selected from metals (e.g., copper, nickel, aluminum, passivated metals, and other suitable metals), metallized polymers, conductive polymers, polymers containing conductive particles dispersed therein, and other suitable materials. In some embodiments, the current collector is deposited on the electrode layer using physical vapor deposition, chemical vapor deposition, electrochemical vapor deposition, sputtering, doctor blade method, flash deposition, or any other suitable deposition technique for the selected material. In some cases, the current collector is formed separately and bonded to the electrode structure. However, it should be understood that in some embodiments, a current collector separate from the electroactive layer may not be required.

[0115] A set of embodiments described herein relates to the formation of electrode slurries, such as electrode slurries, that maintain fluid-like properties over the period between slurry formation and application (or coating) of the slurry to a current collector. These slurries may be easier to process (e.g., easier to mix, easier to coat, easier to coat uniformly) than slurries that do not maintain fluid-like properties (e.g., slurries having at least a gelled and / or solidified portion). The slurry may comprise particulate electroactive material and a solvent. In some embodiments, the slurry may further comprise a binder and / or one or more additives. The particulate electroactive material in the slurry may have one or more characteristics that promote gelation (e.g., may have a small average particle size and may contain a certain amount of nickel), but may still be components of a slurry that maintains fluid-like properties. In some embodiments, one or more reactive groups (e.g., -OH groups, -COOH groups) present on the surface of the particulate electroactive material may be passivated before slurry formation (e.g., by exposure to a second passivating agent as described herein, by exposure to a silane compound).

[0116] As used herein, a slurry is typically, but not always, a material comprising at least one liquid component and at least one solid component. The solid component may be at least partially suspended in the liquid and / or at least partially dissolved in the liquid.

[0117] As described herein, in some embodiments, the electrochemical cell includes a separator. The separator generally comprises a polymer material (e.g., a polymer material that swells when exposed to an electrolyte, or a polymer material that does not swell). In some embodiments, the separator is located between the electrolyte and the electrodes (e.g., between the electrolyte and a first electrode, between the electrolyte and a second electrode, between the electrolyte and an anode, or between the electrolyte and a cathode).

[0118] In some embodiments, the electrochemical cell may further include a separator interposed between the cathode and the anode. The separator may be a solid non-conductive or insulating material that separates or insulates the anode and cathode from each other to prevent short circuits and allows ion transport between the anode and the cathode. In some embodiments, the porous separator may be permeable to the electrolyte.

[0119] The pores of the separator may be partially or substantially filled with electrolyte. The separator may be supplied as a porous, self-supporting membrane sandwiched between the anode and cathode during cell manufacturing. Alternatively, the porous separator layer may be coated directly onto one of the electrodes, for example, as described in International Publication No. 99 / 33125 by Carlson et al. and U.S. Patent No. 5,194,341 by Bagley et al.

[0120] Separators can be made from a variety of materials. Separators may be made of polymers in some cases, or they may be formed from inorganic materials (e.g., glass fiber filter paper). Examples of suitable separator materials, but not limited to these, include: polyolefins (e.g., polyethylene, poly(butene-1), poly(n-pentene-2), polypropylene, polytetrafluoroethylene), polyamines (e.g., poly(ethyleneimine) and polypropyleneimine (PPI)); polyamides (e.g., polyamide(nylon), poly(ε-caprolactam)(nylon 6), poly(hexamethyleneadipamide)(nylon 66)); and polyimides (e.g., polyimide, polynitrile). Poly(pyromelliimide-1,4-diphenyl ether) ("Kapton®") ("NOMEX®") ("KEVLAR®")); polyether ether ketone (PEEK); vinyl polymer (e.g., polyacrylamide, poly(2-vinylpyridine), poly(N-vinylpyrrolidone), poly(methylcyanoacrylate), poly(ethylcyanoacrylate), poly(butylcyanoacrylate), poly(isobutylcyanoacrylate), poly(vinyl acetate) Poly(vinyl), poly(vinyl alcohol), poly(vinyl chloride), poly(vinyl fluoride), poly(2-vinylpyridine), vinyl polymer, polychlorotrifluoroethylene, and poly(isohexyl cyanoacrylate)); polyacetal; polyester (e.g., polycarbonate, polybutylene terephthalate, polyhydroxybutyrate); polyether (poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), poly(tetramethylene oxide) (PTMO)); vinyl Redene polymers (e.g., polyisobutylene, poly(methylstyrene), poly(methyl methacrylate) (PMMA), poly(vinylidene chloride), and poly(vinylidene fluoride)); polyaramids (e.g., poly(imino-1,3-phenyleneiminoisophthaloyl) and poly(imino-1,4-phenyleneiminoterephthaloyl)); polyheteroaromatic compounds (e.g., polybenzimidazole (PBI), polybenzobisoxazole (PBO), and polybenzobisthiazole (PBT));Examples include polyheterocyclic compounds (e.g., polypyrrole); polyurethanes; phenolic polymers (e.g., phenol-formaldehyde); polyalkynes (e.g., polyacetylene); polydienes (e.g., 1,2-polybutadiene, cis- or trans-1,4-polybutadiene); polysiloxanes (e.g., poly(dimethylsiloxane) (PDMS), poly(diethylsiloxane) (PDES), polydiphenylsiloxane (PDPS), and polymethylphenylsiloxane (PMPS)); and inorganic polymers (e.g., polyphosphazenes, polyphosphonates, polysilanes, and polysilazanes). In some embodiments, the polymer may be selected from poly(n-pentene-2), polypropylene, polytetrafluoroethylene, polyamide (e.g., polyamide(nylon), poly(ε-caprolactam)(nylon 6), poly(hexamethyleneadipamide)(nylon 66), polyamide (e.g., polynitrile, and poly(pyromelliimide-1,4-diphenyl ether) ("Kapton®") ("NOMEX®") ("KEVLAR®")), polyetheretherketone (PEEK), and combinations thereof.

[0121] The separator may be coated with various materials (e.g., ceramics). In some embodiments, the separator is a ceramic-coated separator. Non-limiting examples of ceramics include alumina, boehmite, and / or silica. In some embodiments, the separator comprising the aforementioned polymer material (e.g., polyolefin) may be coated with the ceramics described herein.

[0122] Liquid electrolyte solvents are also useful as plasticizers for gel polymer electrolytes, i.e., electrolytes comprising one or more polymers that form a semi-solid network. Examples of useful gel polymer electrolytes, but not limited to them, include polyethylene oxide, polypropylene oxide, polyacrylonitrile, polysiloxane, polyimide, polyphosphazene, polyether, sulfonated polyimide, perfluoroelastomer (NAFION resin), polydivinyl polyethylene glycol, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polysulfone, polyethersulfone, their derivatives, their copolymers, their crosslinked structures and network structures, and their blends, and optionally one or more polymers selected from the group consisting of one or more plasticizers. In some embodiments, the gel polymer electrolyte comprises 10-20% by volume, 20-40% by volume, 60-70% by volume, 70-80% by volume, 80-90% by volume, or 90-95% by volume of heterogeneous electrolyte.

[0123] In some embodiments, one or more solid polymers may be used to form an electrolyte. Examples of useful solid polymer electrolytes, but not limited to these, include one or more polymers selected from the group consisting of polyethers, polyethylene oxides, polypropylene oxides, polyimides, polyphosphazenes, polyacrylonitriles, polysiloxanes, their derivatives, their copolymers, their crosslinked structures and network structures, and blends thereof.

[0124] In addition to electrolyte solvents, gelling agents, and polymers known in the art for forming the electrolyte, the electrolyte may further contain one or more ionic electrolyte salts also known in the art to enhance ionic conductivity.

[0125] According to some embodiments, it may be advantageous to apply an anisotropic force to the electrochemical cell described herein during charging and / or discharging. In some embodiments, the electrochemical cell and / or electrodes described herein may be configured to withstand the applied anisotropic force (e.g., a force applied to reinforce the morphology of the electrodes within the cell) while maintaining their structural integrity.

[0126] In some embodiments, any of the electrodes described herein may be part of an electrochemical cell constructed and positioned such that an anisotropic force having a component perpendicular to the surface (e.g., active surface) of the electrode (e.g., an anode including lithium metal and / or lithium alloy) within the electrochemical cell is applied to the cell during at least one period of charging and / or discharging the cell. In one set of embodiments, the applied anisotropic force may be selected to enhance the morphology of the electrode (e.g., an anode such as a lithium metal and / or lithium alloy anode).

[0127] Anisotropic force, in its usual sense in the art, refers to a force that is not equal in all directions. An example of a force equal in all directions is an internal pressure within a fluid or substance, such as the internal gas pressure of an object. An example of a force that is not equal in all directions is a force directed in a particular direction, such as the force exerted by an object on a table through gravity. Another example of an anisotropic force is the force exerted by a band placed around an object. For example, a rubber band or turnbuckle can exert a force around the object it is wrapped around. However, the band should not directly exert a force on any part of the outer surface of the object that is not in contact with the band. Furthermore, if the band is stretched more along a first axis than along a second axis, the band can exert a greater force in the direction parallel to the first axis than a force applied parallel to the second axis.

[0128] In such cases, the anisotropic force includes a component perpendicular to the surface of the electrode in the electrochemical cell (e.g., the active surface). In this specification, the term “active surface” is used to refer to the surface of the electrode where an electrochemical reaction may occur. A force having a “normal component” to the surface is given the usual meaning that will be understood by those skilled in the art, and includes, for example, forces that act at least partially substantially perpendicular to the surface. For example, if an object rests on a horizontal table and is only affected by gravity, the object exerts a force substantially entirely perpendicular to the surface of the table. If the object is also biased laterally across the surface of the horizontal table, the object exerts a force on the table, and this force is not entirely perpendicular to the horizontal surface, but includes a component perpendicular to the surface of the table. Those skilled in the art will understand other examples of these terms, particularly those applied in the descriptions herein. In the case of curved surfaces (e.g., concave or convex), the component of the anisotropic force perpendicular to the surface of the electrode (e.g., the active surface) can correspond to a component perpendicular to the plane tangent to the curved surface at the point where the anisotropic force is applied. The anisotropic force may, in some cases, be applied at one or more predetermined locations arbitrarily distributed on the surface of the anode (e.g., the active surface). In some embodiments, the anisotropic force is applied uniformly on the surface (e.g., the active surface) of the first electrode (e.g., the anode).

[0129] Any of the characteristics and / or performance metrics of an electrochemical cell described herein may be achieved alone or in combination with each other while an anisotropic force is applied to the electrochemical cell during charging and / or discharging (e.g., during charging and / or discharging of the cell). In some embodiments, the anisotropic force applied to the electrode or electrochemical cell (e.g., during at least one period of charging and / or discharging of the cell) may include a component perpendicular to the surface (e.g., the active surface) of the electrode (e.g., the anode such as a lithium metal and / or lithium alloy anode in an electrochemical cell).

[0130] As described herein, in some embodiments, the surface of the anode may be strengthened during the cycle by applying an externally applied (uniaxial, in some embodiments) pressure (for example, in the case of lithium, the occurrence of lithium moss or rough surface may be reduced or eliminated). In some embodiments, the externally applied pressure may be selected to be greater than the yield stress of the material forming the anode. For example, in the case of anodes containing lithium, the cell may be subjected to at least about 8 kgf / cm². 2 , at least about 9 kgf / cm² 2 , at least about 10 kgf / cm² 2 , at least about 20 kgf / cm² 2 , at least about 30 kgf / cm² 2 , at least about 40 kgf / cm² 2 , or at least about 50 kgf / cm² 2 This may also be under an externally applied anisotropic force having a component that defines the pressure. This is because the yield stress of lithium is approximately 7-8 kgf / cm². 2 Therefore, at pressures greater than this value (e.g., uniaxial pressure), the mossy Li or surface roughness may be reduced or suppressed to some extent. The surface roughness of lithium may mimic the surface it is pressed against. Therefore, at least about 8 kgf / cm 2 , at least about 9 kgf / cm² 2 , at least about 10 kgf / cm² 2 , at least about 20 kgf / cm² 2 , at least about 30 kgf / cm² 2 , at least about 40 kgf / cm² 2 , or at least about 50 kgf / cm² 2 When cycling under externally applied pressure, if the pressing surface is smooth, the lithium surface may become smoother through cycling. The pressing surface can be modified by selecting an appropriate material to be placed between the cathode and anode, as described herein.

[0131] As described herein, anisotropic forces applied during charging and / or discharging may be applied using any method known in the art. In some embodiments, the force may be applied using a compression spring. The force may also be applied using other elements (either inside or outside the containment structure), including, but not limited to, Belleville washers, mechanical screws, pneumatic devices, and / or weights. In some cases, the cell is pre-compressed before being inserted into the containment structure and expands upon insertion to generate a net force in the cell. Preferred methods for applying such forces are described in detail, for example, in U.S. Patent No. 9,105,938, which is incorporated herein by reference in its entirety.

[0132] In some embodiments, the electrochemical cells described herein are designed to include a second electrode having an electroactive material (e.g., a cathode-active electrode species in the cathode of the electrochemical cell described herein) having a suitable voltage relative to lithium metal. The voltage of the electroactive material relative to lithium metal can be measured by first cycling the electrochemical cell containing the electroactive material and lithium metal at a rate of C / 5 at least four times (e.g., five, six, eight, or ten times), then discharging the electrochemical cell at a rate of C / 5, and measuring the voltage as the cell discharge. The average voltage measured over the discharge process is then determined, and this value is considered the voltage relative to lithium metal. In some embodiments, the electroactive material in the second electrode has a voltage relative to lithium metal of 2.8V or higher, 3V or higher, 3.2V or higher, 3.4V or higher, 3.6V or higher, 3.8V or higher, 4.0V or higher, 4.2V or higher, or 4.4V or higher. In some embodiments, the electroactive material in the second electrode has a voltage relative to lithium metal of 4.5V or less, 4.2V or less, 4.0V or less, 3.8V or less, 3.6V or less, 3.4V or less, 3.2V or less, or 3V or less. Combinations of the above ranges are also possible (e.g., 2.8V to 4.5V). Other ranges are also possible.

[0133] In some embodiments, the electrochemical cell described herein is designed to include a second electrode having an electroactive material (e.g., a cathode-active electrode species in the cathode of the electrochemical cell described herein) having a suitable open-circuit voltage with respect to lithium metal. The open-circuit voltage of the electroactive material with respect to lithium metal may be measured by determining the open-circuit voltage when a battery containing the electroactive material and lithium metal is charged to half its capacity. This may be achieved by first determining the battery capacity by cycling the battery. The battery may then be charged to half its measured capacity and left to rest for 2 minutes. After these steps, the open-circuit voltage may be measured. In some embodiments, the electroactive material in the second electrode has an open-circuit voltage with respect to lithium metal of 2.8V or higher, 3V or higher, 3.2V or higher, 3.4V or higher, 3.6V or higher, 3.8V or higher, 4.0V or higher, 4.2V or higher, or 4.4V or higher. In some embodiments, the electroactive material in the second electrode has an open-circuit voltage for lithium metal of 4.5V or less, 4.2V or less, 4.0V or less, 3.8V or less, 3.6V or less, 3.4V or less, 3.2V or less, or 3V or less. Combinations of the above ranges are also possible (e.g., 2.8V to 4.5V). Other ranges are also possible.

[0134] Other properties of the electroactive material (e.g., for the second electrode) besides their voltages to lithium and open-circuit voltages may also be relevant in some embodiments. For example, in some embodiments, the electrochemical cell may include a second electrode containing an electroactive material (e.g., a cathode-active electrode species in the cathode of the electrochemical cell described herein) that exhibits one or more plateaus (or flat regions) in the voltage value with respect to lithium as a function of the cycle life during charging and / or discharging, and the plateau value may be one or more of the aforementioned values ​​related to the voltage of the material with respect to lithium metal. As used herein, the electroactive material exhibits a plateau (i.e., plateau voltage) if it exhibits a constant or substantially constant voltage (e.g., varying by 10% or less, or 5% or less) with respect to lithium for at least a portion of the charging and / or discharging procedure. The voltage at which a plateau occurs with respect to the electroactive material (i.e., plateau voltage) may be determined by employing the same procedure used to determine the voltage of the electroactive material with respect to lithium metal, evaluating whether a region coinciding with a plateau is observed, and if so, determining the average voltage of that region. In some embodiments, the electroactive material in the second electrode has plateau voltages for lithium metal of 2.8V or higher, 3V or higher, 3.2V or higher, 3.4V or higher, 3.6V or higher, 3.8V or higher, 4.0V or higher, 4.2V or higher, and 4.4V or higher. In some embodiments, the electroactive material in the second electrode has plateau voltages for lithium metal of 4.5V or lower, 4.2V or lower, 4.0V or lower, 3.8V or lower, 3.6V or lower, 3.4V or lower, 3.2V or lower, or 3V or lower. Combinations of the above ranges are also possible (e.g., 2.8V to 4.5V). Other ranges are also possible.

[0135] As another example, an electrochemical cell may include a second electrode containing an electroactive material suitable for charging to less than 5V, less than 4.5V, less than 4V, or less than 3.5V under normal operating conditions (for example, charging the second electrode to, for example, 5V, 4.5V, 4V, or 3.5V or higher, respectively, is typically considered an abusive test, is not recommended by the manufacturer, and / or raises safety concerns).

[0136] In some embodiments, one or more voltages (e.g., maximum voltage, minimum voltage, median voltage, mode voltage) measured during the charging and / or discharging process in a cell containing lithium metal electrodes may have one or more of the aforementioned values ​​relative to the average voltage. In some embodiments, the electroactive material in the second electrode has a maximum voltage to lithium metal of 2.8V or higher, 3V or higher, 3.2V or higher, 3.4V or higher, 3.6V or higher, 3.8V or higher, 4.0V or higher, 4.2V or higher, or 4.4V or higher. In some embodiments, the electroactive material in the second electrode has a maximum voltage to lithium metal of 4.5V or lower, 4.2V or lower, 4.0V or lower, 3.8V or lower, 3.6V or lower, 3.4V or lower, 3.2V or lower, or 3V or lower. Combinations of the above ranges are also possible (e.g., 2.8V to 4.5V). Other ranges are also possible.

[0137] In some embodiments, the electroactive material in the second electrode has a minimum voltage to lithium metal of 2.8V or higher, 3V or higher, 3.2V or higher, 3.4V or higher, 3.6V or higher, 3.8V or higher, 4.0V or higher, 4.2V or higher, or 4.4V or higher. In some embodiments, the electroactive material in the second electrode has a minimum voltage to lithium metal of 4.5V or lower, 4.2V or lower, 4.0V or lower, 3.8V or lower, 3.6V or lower, 3.4V or lower, 3.2V or lower, or 3V or lower. Combinations of the above ranges are also possible (e.g., 2.8V to 4.5V). Other ranges are also possible.

[0138] In some embodiments, the electroactive material in the second electrode has a median voltage to lithium metal of 2.8V or higher, 3V or higher, 3.2V or higher, 3.4V or higher, 3.6V or higher, 3.8V or higher, 4.0V or higher, 4.2V or higher, or 4.4V or higher. In some embodiments, the electroactive material in the second electrode has a median voltage to lithium metal of 4.5V or lower, 4.2V or lower, 4.0V or lower, 3.8V or lower, 3.6V or lower, 3.4V or lower, 3.2V or lower, or 3V or lower. Combinations of the above ranges are also possible (e.g., 2.8V to 4.5V). Other ranges are also possible.

[0139] In some embodiments, the electroactive material in the second electrode has a modal voltage for lithium metal of 2.8V or higher, 3V or higher, 3.2V or higher, 3.4V or higher, 3.6V or higher, 3.8V or higher, 4.0V or higher, 4.2V or higher, or 4.4V or higher. In some embodiments, the electroactive material in the second electrode has a modal voltage for lithium metal of 4.5V or lower, 4.2V or lower, 4.0V or lower, 3.8V or lower, 3.6V or lower, 3.4V or lower, 3.2V or lower, or 3V or lower. Combinations of the above ranges are also possible (e.g., 2.8V to 4.5V). Other ranges are also possible.

[0140] In some embodiments, the electrochemical cell described herein may have additional layers. In some embodiments, one or more intervening layers (e.g., ion-conducting layers) may be present between the anode 12 and the electrolyte 14 in Figure 1. In one set of embodiments, the ion-conducting layer (e.g., a single ion-conducting layer) may have a shape or structure that protects the anode electroactive material layer from one or more undesirable components (in the electrolyte) within the electrochemical cell. In some such embodiments, the anode electroactive material layer may be at least partially sealed by the ion-conducting layer.

[0141] In some embodiments, the ion-conducting layer may be formed by any of a variety of suitable methods and may comprise any of a variety of suitable materials. Some methods relate to forming the ion-conducting layer by aerosol deposition. Aerosol deposition is known in the art and generally involves depositing (e.g., spraying) particles (e.g., inorganic particles, polymer particles) onto a surface at a relatively high speed. Aerosol deposition as described herein generally results in collision and / or elastic deformation of at least some of the particles. In some embodiments, aerosol deposition may be carried out under conditions (e.g., using velocity) sufficient to cause fusion between at least some of the particles and at least other parts of the particles. For example, in some embodiments, the particles are deposited onto an electroactive material (and / or any sublayer placed thereon) at a relatively high speed such that at least some of the particles fuse together (e.g., form part of a protective layer and / or a sublayer of the protective layer). The rate required for particle fusion may depend on factors such as the material composition of the particles, the size of the particles, the Young's modulus of the particles, and / or the yield strength of the particles or the material forming the particles.

[0142] In some embodiments, the ion-conducting layer described herein comprises an inorganic material. The inorganic material may include a ceramic material (e.g., glass, glass-ceramic material). The inorganic material may be crystalline, amorphous, or partially crystalline and partially amorphous. In some embodiments, the ion-conducting layer comprises LixMPySz. In the case of such an inorganic material, x, y, and z may be integers (e.g., integers less than 32), and / or M may include Sn, Ge, and / or Si. As an example, the inorganic material may be Li 22 SiP2S 18 Li 24 MP2S 19 (For example, Li 24 SiP2S 19 ), LiMP2S 12(For example, M = Sn, Ge, Si), and / or LiSiPS may be included. Further examples of suitable inorganic materials include garnet, sulfides, phosphates, perovskites, anti-perovskites, other ion-conducting inorganic materials and / or mixtures thereof. When LixMPySz particles are employed in their ion-conducting layer, they may be formed using, for example, the raw material components Li2S, SiS2 and P2S5 (or alternatively Li2S, Si, S and P2S5).

[0143] In some embodiments, the ion-conducting layers described herein include oxides, nitrides, and / or oxynitrides of lithium, aluminum, silicon, zinc, tin, vanadium, zirconium, magnesium, and / or indium, and / or alloys thereof. Non-limiting examples of preferred oxides include Li2O, LiO, LiO2, LiRO2 (e.g., lithium lanthanum oxide) where R is a rare earth metal, lithium titanium oxide, Al2O3, ZrO2, SiO2, CeO2, and Al2TiO5. Further examples of suitable materials that may be employed include lithium nitrate (e.g., LiNO3), lithium silicate, lithium borate (e.g., lithium bis(oxalate)borate, lithium difluoro(oxalate)borate), lithium aluminate, lithium oxalate, lithium phosphate (e.g., LiPO3, Li3PO4), lithium phosphate oxynitride, lithium silicosulfide, lithium germanosulfide, lithium fluoride (e.g., LiF, LiBF4, LiAlF4, LiPF6, LiAsF6, LiSbF6, Li2SiF6, LiSO3F, LiN(SO2F)2, LiN(SO2CF3)2), lithium borosulfide, lithium aluminosulfide, lithium phosphosulfide, oxysulfide (e.g., lithium oxysulfide), and / or combinations thereof. In some embodiments, the plurality of particles include Li-Al-Ti-PO4 (LATP).

[0144] In some embodiments, the ion-conducting layer described herein comprises an inorganic material having a structure in which at least a plurality of partially fused particles and / or particles attached by aerosol deposition. For example, the plurality of particles having a structure in which at least a plurality of partially fused particles and / or particles attached by aerosol deposition may be formed from an inorganic material. In some embodiments, the plurality of particles having a structure in which at least a plurality of partially fused particles and / or particles attached by aerosol deposition comprises two or more inorganic materials. The plurality of particles may include any suitable material as described above. [Examples]

[0145] In the following examples and comparative examples, cells were fabricated using the following methods. The anode consisted of either vacuum-deposited Li (VDLi) (approximately 15-25 μm thick) placed on a 200 nm Cu current collector on a polyethylene terephthalate (PET) substrate, or commercially available Li foil (2 mil) (1 mil / cathode thickness) from Rockwood Lithium. VDLi differed in the degree of passivation by CO2 and were denoted as HP VDLi or LP VDLi. The degree of passivation was indicated by the brightness of the lithium appearance measured using a Konica Minolta Color Reader CR-10 Plus 10.01575 in the L color space. Generally, Li was considered heavily passivated and denoted as HP VDLi when L was less than 40, while Li was considered less passivated and denoted as LP VDLi when L was greater than 60. If the color space value of L is within the range of 40 to 60, it is considered normal passivated Li and is denoted as VDLi.

[0146] The porous separator used was either 25 μm polyolefin (Celgard 2325) or 9 μm polyethylene (Entek EP). The cathode used contained NCM622, NCM721, or NCM811 coated on a 12-20 μm aluminum substrate, with an ACM load of approximately 19.3-22 mg / cm³. 2 The surface area was 100 cm². The above components were assembled in a three-layer stacked structure of anode / separator / cathode / separator / anode. 2 The cell components were sealed in foil pouches, and then 0.5 mL to 0.55 mL of the appropriate electrolyte was added. The cell packages were then vacuum-sealed. These cells were immersed in the electrolyte for 24 to 72 hours without restraint, and then subjected to a load of 10 to 12 kg / cm³. 2 The following pressure was applied. Unless otherwise specified, all cells were cycled under this pressure. Unless otherwise specified, all cells were cycled for the first three cycles at a charging voltage of 4.35V, cut off at C / 12 (30mA), gradually reduced to 3mA, and discharged at C / 3 (120mA). Subsequent charge-discharge cycles were performed under the following conditions unless otherwise specified: charged to 4.35V at 0.2C (75mA), then gradually reduced to 3mA at 4.35V, and discharged to 3.2V at 0.8C (300mA).

[0147] In the following examples and comparative examples, the specific procedure used to measure the discharge capacity of the electrochemical cell during the cycle was as follows: First, the cell was connected to a battery cycler channel (such as Maccor, Arbin, or Bitrode) capable of supplying the manufacturer-specified current and voltage. The cell was first discharged to the recommended voltage (e.g., 3.2V) at the recommended current (e.g., C rate), and then left to rest for 5 minutes. Next, it was charged to the recommended voltage (e.g., 4.35V) at the recommended current (e.g., C / 4), maintaining the recommended voltage (e.g., 4.35V) until the current decayed to a specific value (e.g., C / 20), and then left to rest again for 5 minutes. The voltage during rest (V1) was measured at the end of this 5-minute rest. Next, the cell was discharged again to the recommended voltage (e.g., 3.2V) at the recommended current (e.g., C rate). The voltage (V2) was measured 5 minutes after the start of this discharge.

[0148] The discharge capacity C is given by the following formula (1): C=I dch ·t (1) According to this, current I dch This can be calculated by multiplying it by the time t required to reach the discharge voltage cutoff after each cycle. The discharge resistance R (for example, the discharge resistance for 5 minutes) is given by the following equation (2): R=(V2-V1) / I dch (2) (In the formula, V1 is the voltage at the end of the pause before discharge, V2 is the voltage measured 5 minutes after the start of discharge, I dch This is the discharge current (A). It is possible to calculate using [this method]. Following the procedure described above, the discharge capacity and discharge resistance were calculated for each subsequent cycle. Unless otherwise noted, all cells were cycled at room temperature.

[0149] (Examples 1-5 and Comparative Examples 1-5) These examples and comparative examples compare the cycle lifetime of cells containing a LiF-rich SEI layer formed under pressure application with that of otherwise equivalent cells without pressure application.

[0150] In the following examples and comparative examples, cells were fabricated, assembled, and cycled using the method described above. Specifically, the anode was a vacuum-deposited lithium (HP VDLi) (approximately 15-25 μm thick) placed on a 200 nm thick copper current collector on a polyethylene terephthalate (PET) substrate. The cathode used had an ACM loading of approximately 19.3-22 mg / cm³. 2 The NCM811 was coated on an aluminum substrate with a thickness of 12-20 μm. The specific components and characteristics of the cell are shown in Table 1.

[0151] (Comparative Example 1) The cell described above was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC):ethyl methyl carbonate (EMC) in a weight ratio of 1:1.5:1.5. The electrolyte solvent mixture also contained 1 wt% LiBOB. This cell was not cyclic under pressure.

[0152] (Comparative Example 2) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC):methyl acetate (MA) in a weight ratio of 1:2:1. The electrolyte solvent mixture further contained 1 wt% LiBOB. This cell was not cyclic under pressure.

[0153] (Comparative Example 3) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):ethyl methyl carbonate (EMC):methyl acetate (MA) in a weight ratio of 1:2:1. This electrolyte solvent mixture also contained 1 wt% LiBOB. This cell was not cyclic under pressure.

[0154] (Comparative Example 4) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC):ethyl acetate (EA) in a weight ratio of 1:2:1. This electrolyte solvent mixture also contained 1 wt% LiBOB. This cell was not cyclic under pressure.

[0155] (Comparative Example 5) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC) and dimethyl carbonate (DMC) in a weight ratio of 1:3. The electrolyte solvent mixture also contained 1 wt% LiBOB. This cell was not cyclic under pressure.

[0156] (Example 1) The electrochemical cell was identical to the cell in Comparative Example 1, except that the cell in Example 1 was cycled under pressure.

[0157] (Example 2) The electrochemical cell was identical to the cell in Comparative Example 2, except that the cell in Example 2 was cycled under pressure.

[0158] (Example 3) The electrochemical cell was identical to the cell in Comparative Example 3, except that the cell in Example 3 was cycled under pressure.

[0159] (Example 4) The electrochemical cell was identical to the cell in Comparative Example 4, except that the cell in Example 4 was cycled under pressure.

[0160] (Example 5) The electrochemical cell was identical to the cell in Comparative Example 5, except that the cell in Example 5 was cycled under pressure.

[0161] TIFF2026136223000001.tif107159

[0162] The effect of pressure application on cycle life The effect of pressure application on the cycle life of electrochemical cells containing a LiF-rich SEI layer (an SEI layer containing a relatively high amount of LiF) was investigated. Figures 4 to 8A show the discharge capacity as a function of cycle number for various electrolyte systems, comparing cells with pressure applied (Examples 1 to 5) and cells without pressure applied (Comparative Examples 1 to 5). As shown in Table 1, a LiF-rich SEI layer was formed as a result of FEC degradation during the cycle in both types of cells, regardless of whether pressure was applied or not. As illustrated, cells containing a LiF-rich SEI layer formed under pressure showed a longer cycle life (as shown in Figures 4 to 8A) compared to cells containing a LiF-rich SEI layer formed without pressure. Additional inorganic materials (e.g., Li2O) related to the degradation of the electrolyte (e.g., FEC) were also observed in the SEI layers of Examples 1 to 5.

[0163] As shown in Figures 4 to 8A, in the presence of a passivator (e.g., LiBOB), the cycle life of cells without pressure (Comparative Examples 1 to 5) was approximately 20 to 50 cycles, but at 12 kg / cm² 2 Cells cycled under pressure exceeded 250 cycles. Thus, cells containing LiF-rich SEI layers formed without pressure had a significantly lower cycle life than cells containing LiF-rich SEI layers formed under pressure. This result suggests that applying pressure allowed for in-situ control of SEI growth during cycling, thereby extending the cell cycle life.

[0164] The formation of resistive SEI, which continues to grow during the cycle, was one of the main causes of cell failure due to polarization accumulation. To investigate the effect of pressure application on the in-situ formation of resistive SEI during the cycle, the discharge resistance (i.e., 5-minute discharge resistance) for Example 5 was calculated according to equation (2) and compared with the discharge resistance of Comparative Example 5. Figure 8B shows the 5-minute discharge resistance of cells with and without pressure applied, normalized to the 5-minute discharge resistance at the 5th charge-discharge cycle of each cell. As shown in Figure 8B, the increase in 5-minute discharge resistance was slower in the cells with pressure applied (Example 5) compared to the cells without pressure applied (Comparative Example 5). This result suggests that pressure application during the cycle suppressed the growth of SEI resistance, thus delaying the accumulation of polarization in the cells and significantly increasing the cycle performance from approximately 20 cycles (Comparative Example 5) to approximately 250 cycles (Example 5).

[0165] (Example 6 and Comparative Examples 6-10) These examples and comparative examples compare the cycle lifetime of cells containing a LiF-rich SEI layer with that of cells without a LiF-rich SEI layer but otherwise equivalent.

[0166] In the following examples and comparative examples, cells were fabricated, assembled, and cycled using the method described above. Specifically, the anode was a vacuum-deposited lithium (HP VDLi) (thickness approximately 15-25 μm) placed on a 200 nm copper layer acting as a current collector on a polyethylene terephthalate (PET) substrate. The cathode used had an ACM loading of approximately 19.3-22 mg / cm³. 2 The NCM811 was coated on an aluminum substrate with a thickness of 12-20 μm. The specific components and characteristics of the cell are shown in Table 2.

[0167] (Comparative Example 6) The cell described above was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of ethylene carbonate (EC):ethyl methyl carbonate (EMC) (BASF LP57) in a weight ratio of 3:7.

[0168] (Comparative Example 7) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of ethylene carbonate (EC):diethyl carbonate (DEC) (BASF LP47) in a weight ratio of 3:7.

[0169] (Comparative Example 8) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture (BASF LP50) with a weight ratio of ethylene carbonate (EC) to ethyl methyl carbonate (EMC).

[0170] (Comparative Example 9) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (BASF LP40) in a weight ratio of 1:1.

[0171] (Comparative Example 10) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture (BASF LP30) of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a 1:1 weight ratio.

[0172] (Example 6) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC) in a weight ratio of 1:4.

[0173] TIFF2026136223000002.tif73152

[0174] As shown in Figure 9, cells containing EC-based electrolytes (Comparative Examples 6-10) exhibited a lifespan of approximately 30-110 cycles (80% of rated capacity) even under pressure application during cycling, significantly lower than the cell using FEC as a cosolvent (Example 6). As illustrated, cells containing FEC as a cosolvent in the electrolyte mixture exhibited a cycle life of approximately 190 cycles and showed the formation of a LiF-rich SEI layer (an SEI layer containing a relatively high amount of LiF) that was not formed in the cells of Comparative Examples 6-10 (Table 1). This result indicates that the formation of an inorganic-rich SEI layer (e.g., LiF) is important for improving the cycle life of Li metal cells. It should be noted that LP30, LP40, LP50, LP47, and LP57 are standard electrolytes commonly used in Li-ion batteries.

[0175] (Example 7 and Comparative Examples 11-15) These examples and comparative examples compare the individual effects of pressure application, additives, cathode type, and fluorinated electrolyte solvents (e.g., FEC) on the cycle life of electrochemical cells.

[0176] In the following examples and comparative examples, cells were fabricated, assembled, and cycled using the method described above. Specifically, the anode was a vacuum-deposited lithium (HP VDLi or LP VDLi) (thickness approximately 15-25 μm) placed on a 200 nm copper current collector placed on a polyethylene terephthalate (PET) substrate. The cathode used was an aluminum substrate with an ACM load of approximately 19.3-22 mg / cm³. 2 The NCM622 was coated on the surface. The specific components and characteristics of the cell are shown in Table 3.

[0177] (Comparative Example 11) The cell described above was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of ethylene carbonate (EC):dimethyl carbonate (DMC) (BASF LP30) in a weight ratio of 1:1. This cell was not cyclic under pressure.

[0178] (Comparative Example 12) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC) and dimethyl carbonate (DMC) in a weight ratio of 1:4. This cell was not cyclic under pressure.

[0179] (Comparative Example 13) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC) in a weight ratio of 1:4. This electrolyte solvent mixture also contained 1 wt% LiBOB. This cell was not cyclic under pressure.

[0180] (Comparative Example 14) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) (BASF LP30) in a weight ratio of 1:1. This cell was cycled under pressure.

[0181] (Comparative Example 15) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):ethylene carbonate (EC):dimethyl carbonate (DMC) in a weight ratio of 1:10:10 (BASF LP30 containing 4 wt% FEC). This cell was cycled under pressure.

[0182] (Example 7) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC) and dimethyl carbonate (DMC) in a weight ratio of 1:4. This cell was cycled under pressure.

[0183] TIFF2026136223000003.tif74160

[0184] As shown in Figure 10, cells cycled without pressure (Comparative Examples 11-13) exhibited limited cycle life, even in the presence of LiF-rich SEI and LiBOB additives. This poor cycle performance, attributed to the lack of pressure application in the Li metal cells, was observed regardless of the cell cathode type, e.g., NCM622 in Comparative Examples 11-13 or NCM811 in Comparative Examples 1-5.

[0185] Furthermore, as shown in Figure 11, the cell containing 4% FEC in the electrolyte (Comparative Example 15) showed slightly improved cycle performance compared to the cell without FEC in the electrolyte (Comparative Example 14), but still considerably lower than the cell containing a higher concentration of FEC that resulted in the formation of a LiF-rich SEI layer (Example 7), according to Table 3. Moreover, Figure 11 shows that for cells with cathode NCM622 and Li metal (LP VDLI), the combination of a LiF-rich SEI layer and pressure application resulted in improved cycle life of the electrochemical cell because it slowed down the polarization that accumulated during the cell cycle.

[0186] (Examples 8-16) These examples compare the cycle lifetime of cells containing LiF and Li2CO3-rich SEI layers with that of cells containing only LiF-rich SEI layers but otherwise equivalent.

[0187] In the following examples and comparative examples, cells were fabricated, assembled, and cycled using the method described above. Specifically, the anode used was a commercially available Li foil (2 mil) from Rockwood Lithium (thickness 1 mil / cathode). The cathode used had an ACM load of approximately 19.3-22 mg / cm³. 2 The NCM811 was coated on an aluminum substrate with a thickness of 12-20 μm. The specific components and characteristics of the cell are shown in Table 4.

[0188] (Example 8) The above cell was fabricated using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture with a weight ratio of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC) of 1:4. The formation voltage of this cell was 4.35 V.

[0189] (Example 9) The above cell was fabricated using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture with a weight ratio of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC) of 1:4. The formation voltage of this cell was 4.6 V.

[0190] (Example 10) The above cell was fabricated using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture with a weight ratio of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC) of 1:4. The formation voltage of this cell was 4.7 V.

[0191] (Example 11) The above cell was fabricated using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture with a weight ratio of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC) of 1:4. The formation voltage of the cell was 4.4 V. The electrolyte solvent mixture further contained 1 wt% LiBOB.

[0192] (Example 12) The above cell was fabricated using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture with a weight ratio of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC) of 1:4. The formation voltage of the cell was 4.6 V. The electrolyte solvent mixture further contained 1 wt% LiBOB.

[0193] (Example 13) The above cell was fabricated using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture with a weight ratio of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC) of 1:3. The formation voltage of this cell was 4.35 V.

[0194] (Example 14) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC) and dimethyl carbonate (DMC) in a weight ratio of 1:3. The conversion voltage of this cell was 4.6 V.

[0195] (Example 15) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC) in a weight ratio of 1:3. The conversion voltage of the cell was 4.4 V. The electrolyte solvent mixture further contained 1 wt% LiBOB.

[0196] (Example 16) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC) in a weight ratio of 1:3. The conversion voltage of the cell was 4.7 V. The electrolyte solvent mixture also contained 1 wt% LiBOB.

[0197] TIFF2026136223000004.tif99155

[0198] Examples 8-10 investigated the effects of increasing the conversion voltage. As shown in Table 4, increasing the conversion voltage resulted in the formation of a Li2CO3-rich inorganic SEI layer in addition to LiF (Examples 9-10). The LiF and Li2CO3-rich SEI layers contained relatively high concentrations of LiF and Li2CO3. Furthermore, as shown in Figure 12A, higher conversion voltages resulted in an increase in cell cycle performance beyond 350 cycles (Example 10). A similar increase in cell cycle performance at higher conversion voltages was observed in cells with electrolytes having higher FEC content (Examples 13-14, as shown in Figure 14).

[0199] The effect of a high conversion voltage on the in-situ formation of resistive SEI during cycling was investigated and is shown in Figure 12B. Discharge resistance (i.e., 5-minute discharge resistance) was calculated for Examples 8-10. Figure 12B plots the 5-minute discharge resistance of each cell normalized to the 5-minute discharge resistance at the 5th cycle of each cell. As shown, the cell with a high conversion voltage (Example 10) showed a slower increase in 5-minute discharge resistance during cycling compared to the cell with a low conversion voltage (Example 8). This suggests that the application of a high conversion voltage affected the in-situ formation of the SEI layer and suppressed the growth of SEI resistance. As a result, as shown in Figure 12A, the cycling performance of the cell formed at 4.7V (Example 10) improved by more than 100 cycles compared to the cell formed at the normal 4.35V (Example 8).

[0200] The effects of additives (LiBOB) in addition to high conversion voltage were investigated and are shown in Figure 13. As shown, the cycle performance at high voltage (4.6V) using LiBOB further improved the cycle life to 350 cycles (Example 12). A similar increase in cell cycle performance using LiBOB at higher conversion voltages was observed in cells using electrolytes with higher FEC content (Examples 15-16, as shown in Figure 15).

[0201] These examples demonstrate that in-situ Li passivation by CO2 generated at higher conversion voltages (e.g., 4.4, 4.6, and 4.7 V) increased the inorganic content of the SEI layer. Such high inorganic compound content (LiF and Li2CO3) in the SEI layer, along with in-situ control of SEI growth by pressure application, resulted from FEC and higher conversion voltages, significantly suppressing cell impedance buildup and greatly improving cycle performance.

[0202] (Examples 17-20) These examples demonstrate the cycle life of cells containing acetate-based electrolyte cosolvents at various temperatures (e.g., 0°C, room temperature (RT)) and various conversion voltages.

[0203] In the following examples and comparative examples, the cells were fabricated, assembled, and cycled according to the method described above. Specifically, the cathode was a vacuum-deposited lithium (HP VDLi) (approximately 15-25 μm thick) placed on a 200 nm thick Cu current collector on a polyethylene terephthalate (PET) substrate. For the anode, NCM811 coated on a 12-20 μm aluminum substrate was used, with an ACM load of approximately 19.3-22 mg / cm³. 2 It was a plane. The specific components and characteristics of the cell are shown in Table 5.

[0204] (Example 17) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC):methyl acetate (MA) in a weight ratio of 1:2:1. The conversion voltage of this cell was 4.35 V, and it was cycled at room temperature.

[0205] (Example 18) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC):methyl acetate (MA) in a weight ratio of 1:2:1. The conversion voltage of this cell was 4.6 V, and it was cycled at room temperature.

[0206] (Example 19) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC):methyl acetate (MA) in a weight ratio of 1:2:1. The conversion voltage of this cell was 4.35 V, and it was cycled at 0°C.

[0207] (Example 20) The above cell was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC):methyl acetate (MA) in a weight ratio of 1:2:1. The cell was cyclic at 0°C with a conversion voltage of 4.6 V.

[0208] TIFF2026136223000005.tif56162

[0209] The effect of high conversion voltage on cycle life was investigated in Examples 17-18 and is shown in Figure 16. As shown, a high conversion voltage of 4.6V (Example 18) resulted in an increased cycle life for cells cyclic at room temperature containing LiF and Li2CO3-rich SEI layers and methyl acetate (MA) as a cosolvent. Similar positive effects (e.g., increased cycle life) were observed for cells cyclic at 0°C containing LiF and Li2CO3-rich SEI layers and MA as a cosolvent for higher conversion voltages of 4.6V (Examples 19-20 in Figure 17).

[0210] (Examples 21-22 and Comparative Examples 16-17) These examples compare the cycle lifetime of cells containing LiFSI and LiF-rich SEI layers under conditions of cycling with and without pressure, while all other factors remain the same.

[0211] In the following examples and comparative examples, cells were fabricated, assembled, and cycled using the method described above. Specifically, the anode was a vacuum-deposited lithium (HP VDLi) (thickness approximately 15-25 μm) placed on a 200 nm copper layer acting as a current collector on a polyethylene terephthalate (PET) substrate. The cathode used had an ACM loading of approximately 19.3-22 mg / cm³. 2 The NCM811 was coated on an aluminum substrate with a thickness of 12-20 μm. The specific components and characteristics of the cell are shown in Table 6.

[0212] (Comparative Example 16) The cell described above was prepared using an electrolyte containing 0.8 M LiFSI in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC) in a weight ratio of 1:4. The cell was not cycled under pressure. The electrolyte solvent mixture further contained 1% by weight of LiBOB.

[0213] (Comparative Example 17) The above cell was fabricated using an electrolyte containing 0.8 M LiFSI in an electrolyte solvent mixture with a weight ratio of fluoroethylene carbonate (FEC):ethyl methyl carbonate (EMC) of 1:3. The cell did not cycle under pressure. The electrolyte solvent mixture further contained 1 wt% LiBOB.

[0214] (Example 21) The electrochemical cell was identical to the cell of Comparative Example 16, except that the cell of Example 21 was cycled under pressure.

[0215] (Example 22) The electrochemical cell was identical to the cell of Comparative Example 17, except that the cell of Example 22 was cycled under pressure.

[0216] TIFF2026136223000006.tif56150

[0217] These examples demonstrated that in a lithium bis(fluorosulfonyl)imide (LiFSI)-based electrolyte, an inorganic (e.g., LiF)-rich SEI layer formed by the FEC solvent, and the application of pressure resulted in improved cycling performance (e.g., Examples 21 and 22 shown in FIGS. 18 - 19). This trend was consistent with the previous examples (Examples 1 - 20) using LiPF6 as the salt.

[0218] As shown in FIGS. 18 - 19, the SEI layers in each example and comparative example showed the formation of inorganic compounds (e.g., LiF-rich) due to the presence of FEC. However, cells without pressure applied generally had less than 20 cycles, significantly lower than the cells (Examples 21 - 22) cycled under a pressure of 12 kg / cm 2 exceeding 250 cycles. This result suggested that in-situ control of SEI growth by pressure is important in LiFSI-based electrolytes.

[0219] Furthermore, promising results were observed when these LiFSIs were used in cells. LiFSI, a salt known to cause Al corrosion, is typically used as a co-salt with LiPF6, an Al corrosion inhibitor, to prevent Al corrosion. However, as shown in the results of Examples 21-22, Al corrosion was suppressed even when LiFSI was used as a monosalt. Using LiFSI as a monosalt in electrochemical cells may be advantageous for high-temperature applications due to its high thermal stability.

[0220] (Example 23) This embodiment shows the physical properties of the SEI layer formed within the electrochemical cell.

[0221] The cells were fabricated, assembled, and cycled using the method described above. Specifically, the anode used was commercially available Li foil (2 mil) from Rockwood Lithium (thickness 1 mil / cathode). The porous separator used was 25 μm polyolefin (Celgard 2325), and the cathode used had an ACM load of approximately 19.3-22 mg / cm³. 2 NCM622 coated on an aluminum substrate with a thickness of 12-20 μm on each side The above components were assembled into a three-layer structure of anode / separator / cathode / separator / anode. The cells were prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC) in a weight ratio of 1:4. The electrolyte solvent mixture further contained 1 wt% LiBOB.

[0222] In the first three formation cycles, the cell was charged to 4.35V at 30mA, gradually reduced to 10mA, and discharged at 120mA. Subsequent charge and discharge cycles were performed under the following conditions: charged to 4.35V at 200mA, gradually reduced to 10mA, and then pulsed discharged at 800mA for 1 second, with a 3-second pause between each pulse, until the voltage reached 3.2V. The cutoff was 60% of the rated capacity. The cell was cycled while applying pressure.

[0223] The SEI was characterized by SEM / EDS (Figures 20A-20B). The cycled anode was recovered from a cell that had reached the end of its lifespan (after 123 charge and discharge cycles), rinsed with dimethyl carbonate, and analyzed by SEM / EDS. As shown in the figures, Figures 20A-20B show the presence of an SEI layer containing two regions with different atomic content: a first region of the SEI layer adjacent to the separator and a second region of the SEI layer adjacent to the anode. The first region of the SEI layer adjacent to the separator is fluorine atom rich. Furthermore, Figure 20C shows that the portion of the SEI layer adjacent to the separator contains nano-sized particles.

[0224] (Example 24) This embodiment shows the chemical composition of the SEI layer formed within the electrochemical cell.

[0225] The cells were fabricated, assembled, and cycled using the method described above. Specifically, the anode was a vacuum-deposited lithium (HP VDLi) (approximately 20 μm thick) placed on a 200 nm copper layer acting as a current collector on a polyethylene terephthalate (PET) substrate. The porous separator used was 9 μm polyethylene (Entek EP), and the cathode used had an ACM load of approximately 19.3-22 mg / cm³. 2 The NCM721 was coated on an aluminum substrate with a thickness of 12-20 μm on each side. The above components were assembled into a three-layer stacked structure of anode / separator / cathode / separator / anode. The cells were prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC):dimethyl carbonate (DMC) in a weight ratio of 1:4. The electrolyte solvent mixture further contained 1 wt% LiBOB.

[0226] In the first three formation cycles, the cell was charged to 4.4V at 30mA, gradually reduced to 10mA, and discharged at 120mA. Subsequent charge and discharge cycles were performed under the following conditions: charged to 4.4V at 75mA, gradually charged to 10mA, and then charged to 3.2V at 300mA. The cell was cycled under pressure.

[0227] SEM / EDS was performed on the cross-section of the SEI layer / separator interface (Figure 21). The sample was prepared by sputter-coating an ultrathin conductive palladium layer onto the cross-section. The composition of the SEI layer was shown by EDS line scanning of the ion-milled cross-section (line width 0.1 μm at 5 KV). As shown by the EDS line scanning, the region of the SEI layer adjacent to the separator was fluorine-rich.

[0228] The chemical composition of fluorine in the SEI layer is shown in Figure 22A. As shown, at least 70% of the total fluorine content in the SEI layer comes from LiF.

[0229] Figure 22B shows the chemical composition of lithium in the SEI layer. As shown in the figure, in addition to LiF, other inorganic materials (e.g., Li2O) were also present in the SEI layer.

[0230] Figure 22C shows the chemical composition of carbon in the SEI layer. Other carbon-containing species such as alkyl carbonates (ROCO2Li), possibly alkoxides (ROLi), and polyethers (-CH2O-) were also present in the SEI layer.

[0231] The crystallinity of the SEI layer was measured and is shown in Figure 23. As shown in the figure, the XRD results indicated the presence of crystalline LiF and Li2O in the SEI layer.

[0232] (Examples 25-26 and Comparative Examples 18-19) In this embodiment, the cycle life of a cell containing an SEI layer formed by applying pressure is compared with that of a cell containing an SEI layer formed without applying pressure, while all other factors are the same.

[0233] In the following examples and comparative examples, the cells were fabricated and assembled by the method described above. Specifically, the anode was vacuum-deposited Li(HP VDLi) (thickness approximately 15-25 μm). The cathode used was NCM811. The porous separator used was a 9 μm polyethylene (Entek EP) separator. The above components were assembled into a three-layer laminated structure of anode / separator / cathode / separator / anode. After sealing the cell components in a foil pouch, the electrolyte was added. The cell package was then vacuum-sealed. These cells were immersed in the electrolyte for 24-72 hours without restraint, and then subjected to a pressure of 12 kg / cm³. 2 The following pressure was applied. Unless otherwise specified, all cells were cycled under this pressure. The cell capacity of each cell was 370mAh. Unless otherwise specified, all cells were cycled for the first three formation cycles at a charging voltage of 4.35V, cut off at C / 12 (30mA), gradually reduced to 10mA, and discharged at a rate of C / 3 (120mA). Subsequent charge and discharge cycles were performed under the following conditions unless otherwise specified: charged to 4.35V at 0.2C (75mA), gradually reduced to 10mA, and discharged to 3.2V at 0.8C (300mA).

[0234] (Comparative Example 18) The cell described above was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a weight ratio of 1:1. The cell was not cycled under pressure. The conversion voltage of the cell was 4.35 V.

[0235] (Comparative Example 19) The cell described above was prepared using an electrolyte containing 1 M LiPF6 in an electrolyte solvent mixture of fluoroethylene carbonate (FEC) and dimethyl carbonate (DMC) in a weight ratio of 1:1. The cell was not cycled under pressure. The conversion voltage of the cell was 4.35 V.

[0236] (Example 25) The electrochemical cell was prepared by applying 12 kg / cm³ to the cell in Example 25.2 The cell was identical to that of Comparative Example 18, except that the cycle was performed under a different pressure. The conversion voltage of the cell was 4.35V.

[0237] (Example 26) The electrochemical cell was prepared by applying 12 kg / cm³ to the cell in Example 26. 2 The cell was identical to that of Comparative Example 19, except that the cycle was performed under a different pressure. The conversion voltage of the cell was 4.35V.

[0238] Figure 24 shows the cycle performance of electrochemical cells cycled under pressure (Examples 25 and 26) and cells cycled without pressure (Comparative Examples 18 and 19). In each example and comparative example shown in Figure 24, two identical cells were tested (n=2). As shown in Figure 24, the cells cycled under pressure (Examples 25 and 26) showed a considerably longer cycle life than the cells cycled without pressure (Comparative Examples 18 and 19). The cell without a fluorinated solvent (Comparative Example 18) had a lower cycle life when cycled without pressure. Furthermore, even when pressure was applied during the cycle, the cell without a fluorinated solvent (Example 25) performed worse than the cell containing a fluorinated solvent and all other factors being the same (Example 26) (i.e., had a shorter cycle life). The longest cycle life was observed in the cell containing a fluorinated solvent and cycled under pressure (Example 26).

[0239] XRD, SEM, and EDS measurements were performed on the cross-sections of the separator interface / SEI layer / anode interface. After 25 discharges, each sample was opened and the section containing the Li anode with SEI was recovered. Ion-milled cross-sections were obtained for each example. The composition of the SEI layer was shown by EDS line scanning of the ion-milled cross-sections. Figures 25-28 show SEM / EDS line scans of the electrochemical cells from Comparative Example 18, Example 25, Comparative Example 19, and Example 26, respectively.

[0240] As shown by the EDS line scan in Figure 25, in the electrochemical cell containing a non-fluorinated solvent and cyclic without pressure (Comparative Example 18), the SEI layer within the cell was oxygen-rich throughout its entire thickness. Similarly, as shown by the EDS line scan in Figure 26, in the electrochemical cell containing a non-fluorinated solvent and cyclic with pressure (Example 25), the SEI layer within the cell was still oxygen-rich throughout its entire thickness. Furthermore, as shown in Figure 27, in the electrochemical cell containing a fluorinated solvent and cyclic without pressure (Comparative Example 19), the SEI layer within the cell was oxygen-rich throughout its entire thickness. However, as shown in Figure 28, in the electrochemical cell containing a fluorinated solvent and cyclic with pressure (Example 26), the region of the SEI layer adjacent to the separator was fluorine-rich.

[0241] XDR was performed to measure the crystallinity and composition of various SEI layers in the samples of Examples 25-26 and Comparative Examples 18-19. As shown in Table 7, nanocrystalline LiF was observed in samples containing FEC-containing electrolytes (Comparative Example 19 and Example 26), regardless of whether the samples were cycled under pressure. Furthermore, the electrolytes in the samples from Comparative Example 19 and Example 26 induced the formation of inorganic-rich SEI containing both nanocrystalline LiF and Li2O. In addition, the cell cycled under pressure (Example 26) showed a LiF / Li2O ratio of 0.2, which was lower than the LiF / Li2O ratio of 2.1 in the cell cycled without pressure (Comparative Example 19). As shown in Table 7 and Figure 24, the cycling performance could be improved by controlling the presence of various SEI components, for example, by applying pressure to achieve a favorable LiF / Li2O ratio. The presence of other non-elemental components detected in the SEI layer is shown in Table 7.

[0242] TIFF2026136223000007.tif77144

[0243] The increase in SEI resistivity (or polarization) and Li protection capability were measured for various cells in Examples 25–56 and Comparative Examples 18–19 using C-rate Li stripping techniques (e.g., as shown in Figure 29). The Li stripping technique was performed as follows: cells at 25th discharge (Q25), 100th discharge (Q100), and 75% cutoff capacity (EOL) were discharged to 0V at 300mA, 50mA, 25mA, 10mA, 5mA, and 2mA, respectively. The realized capacity was converted to lithium thickness based on theoretical capacity (3862mAh / g) and density (0.534g / cc). As shown in Tables 8 and 9, the SEI thickness and density were measured at Q25 and Q100 to evaluate the physical properties and growth of the SEI layer. In particular, cells without pressure (Comparative Examples 18 and 19) reached EOL before 25 cycles. The weight of the SEI layer was calculated based on the cycle anode weight and the difference in residual metallic Li between sister cells, as measured by Li stripping.

[0244] Figure 29 shows the percentage of residual Li (%) in a cell (Example 25) that was cycled under pressure without a fluorinated solvent, compared to a cell (Example 26) that was cycled under pressure with a fluorinated solvent. The percentage of residual Li (%) at the C rate is equal to (Li removed at the C rate) / (total Li removed at all rates). The percentage of Li removed at the C rate (%) could be used to indicate the resistivity of the SEI. A higher percentage of removed Li (corresponding to a lower percentage of residual Li (%)) correlated with a cell with less polarization and showed a lower resistive SEI. As shown in Figure 29, the SEI resistivity of the cell (Example 26) with a fluorinated solvent increased at a slower rate over the course of the cycle life compared to the SEI resistivity of the cell (Example 25) without a fluorinated solvent. The cell (Example 26) with a fluorine-rich SEI showed a decrease in polarization.

[0245] As shown in Tables 8 and 9, the effect of pressure application on the thickness and density of the resulting SEI layer was observed to differ between cells containing a fluorinated electrolyte solvent (Example 26) and cells without a fluorinated electrolyte solvent (Example 25). Under pressure application, a significant decrease in the increase in thickness and bulk density was observed in cells without a fluorinated electrolyte solvent (Example 25), while no substantial change in thickness and bulk density was observed in cells using a fluorinated electrolyte solvent (Example 26). This result indicates that the combination of a fluorinated solvent and pressure application during cycling can be used to adjust the SEI chemical composition and improve cycling performance, which is consistent with the XRD results shown in Table 7. Furthermore, compared to cells without a fluorinated electrolyte solvent (Example 25), the combination of a fluorinated electrolyte solvent and pressure application was observed to slow down the increase in SEI thickness and the decrease in SEI bulk density.

[0246] TIFF2026136223000008.tif58136

[0247] TIFF2026136223000009.tif57138

[0248] Figure 30 shows the discharge capacity as a function of the number of cycles for cells (Examples 25 and 26) that were cycled under pressure, with and without the presence of a fluorinated solvent. Table 10 shows the effect of lithium stripping on the cells in Figure 30. For each of Examples 25 and 26, two identical cells were tested (n=2). As shown by the considerably larger amount of lithium stripped at the C rate shown in Table 10, the cell containing the fluorine-rich SEI layer (Example 26) had higher conductivity compared to the cell without the fluorine-rich SEI layer (Example 25). Furthermore, the cell containing the fluorine-rich SEI layer (Example 26) had better protective capabilities and therefore lower lithium loss per cycle and lithium loss per storage capacity.

[0249] TIFF2026136223000010.tif58155

[0250] While several embodiments of the present invention are described and illustrated herein, those skilled in the art will readily anticipate a variety of other means and / or structures for performing the function and / or obtaining the results and / or one or more of the aforementioned advantages, and such variations and / or improvements will each be considered within the scope of the present invention. More generally, those skilled in the art will readily understand that all parameters, dimensions, materials and configurations described herein are illustrative, and that actual parameters, dimensions, materials and / or configurations will depend on the specific application for which the teachings of the present invention are used. Those skilled in the art can recognize or confirm many equivalents to some aspects of the present invention described herein by means of routine experimentation alone. Thus, it should be understood that the aforementioned embodiments are shown for illustrative purposes only and, within the scope of the appended claims and their equivalents, the present invention can be carried out in ways other than those specifically described and described in the claims. The present invention relates to individual features, systems, articles, materials, kits and / or methods described herein. Furthermore, combinations of two or more such features, systems, articles, materials, kits, and / or methods are included within the scope of the present invention, provided that such features, systems, articles, materials, kits, and / or methods do not conflict with each other.

[0251] All definitions should be understood to govern dictionary definitions, definitions in references incorporated by reference, and / or the ordinary meanings of the terms defined herein, as defined and used herein.

[0252] As used in the specification and claims, the indefinite articles "a" and "an" should be understood to mean "at least one" unless explicitly stated otherwise.

[0253] As used in the specification and claims, the phrase “and / or” should be understood to mean “either or both” of the combined elements, i.e., elements that exist together in some cases and separately in the other. Unless explicitly stated, other elements may optionally exist in addition to those specifically identified by the “and / or” phrase, whether related or not to those specifically identified elements. Thus, as a non-restrictive example, when used in conjunction with an open-ended phrase such as “including ~”, it means, in one embodiment, A without B (optionally including elements other than B); in another embodiment, B without A (optionally including elements other than A); in yet another embodiment, both A and B (optionally including other elements); and so on.

[0254] As used in the specification and claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” is inclusive, i.e., It should be interpreted that a number of elements or a list of elements includes at least one, including more than one, and optionally any further items not listed. Only clearly indicated items, such as "only one of" or "exactly one of," or "including" as used in claims, mean to include exactly one of a number of elements or a list of elements. In general, the term "or" as used herein should be interpreted only as indicating an exclusive choice (i.e., "one or both, but the other") when preceded by an exclusive term such as "either," "one of," "only one of," or "exactly one of." "Essentially including" as used in claims has its usual meaning as it is used in the field of patent law.

[0255] As used in the specification and claims, the phrase “at least one” relating to a single list of one or more elements should be understood to mean at least one element selected from one or more elements in the list of elements, but not necessarily including at least one of each element specifically listed in the list of elements, nor necessarily excluding combinations of elements in the list of elements. This definition also allows for the possibility that there may be elements other than those specifically identified in the list of elements, meaning whether or not they are related to those specifically identified elements. Therefore, as a non-restrictive example, “at least one of A and B” (equivalently, “at least one of A or B,” or equivalently, “at least one of A and / or B”) can mean, in one embodiment, at least one A (including any element other than B) in which there is no B, which includes any more than one; in another embodiment, at least one B (including any element other than A) in which there is no A, which includes any more than one; and in yet another embodiment, at least one A and at least one B (including any other element) which includes any more than one; and so on.

[0256] Furthermore, unless otherwise explicitly stated, the order of steps or actions in a method described herein, which includes multiple steps or actions, should be understood to be not necessarily limited to a specific order of steps or actions.

[0257] In the claims as well as in the specification, all such transitional clauses as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” and “holding” are understood to be open-ended, meaning they include but are not limited to them. Only the transitional clauses “including” and “essentially including” are closed or semi-closed transitional clauses, as described in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03. [Explanation of Symbols]

[0258] 10, 100 ... Electrochemical cells 12 … Anode 14 … electrolyte 16 ... Cathode 18, 118 … solid electrolyte interfacial layer 20 ... Cathode current collector 22 ... Anode current collector 24 … Anode surface

Claims

1. Anodes containing lithium metal, lithium alloy, or combinations thereof as anode active material, Electrolytes containing fluorinated organic solvents, Cathode, and A solid electrolyte interface layer is placed between the anode and the electrolyte. Equipped with, The solid electrolyte interface layer comprises LiF and Li ２ CO ３ It contains inorganic materials, An electrochemical cell in which, in the solid electrolyte interface layer, a first ratio of fluorine atoms to oxygen atoms adjacent to the electrolyte is higher than a second ratio of fluorine atoms to oxygen atoms adjacent to the anode.

2. Anodes containing lithium metal, lithium alloy, or combinations thereof as anode active material, Electrolytes containing fluorinated organic solvents, Cathode, and A solid electrolyte interface layer is placed between the anode and the electrolyte. Equipped with, The solid electrolyte interface layer contains LiF, and (1) Hardness of 0.001 GPa or more and 5 GPa or less, and / or (2) Porosity of 1% to 90% It has, An electrochemical cell in which the discharge capacity decreases by 10% or less after 100 charge-discharge cycles compared to the discharge capacity after the 5th charge-discharge cycle following its formation.

3. Anodes containing lithium metal, lithium alloy, or combinations thereof as anode active material, Electrolytes containing fluorinated organic solvents, Cathode, and A solid electrolyte interface layer is placed between the anode and the electrolyte. Equipped with, The solid electrolyte interface layer contains LiF, and (1) Hardness of 0.001 GPa or more and 5 GPa or less, and / or (2) Porosity of 1% to 90% It has, An electrochemical cell that exhibits an increase in discharge resistance of less than 10% after 100 charge-discharge cycles compared to the discharge resistance after the 5th charge-discharge cycle following its formation.

4. The anode active material includes lithium metal, lithium alloy, or a combination thereof, and has a surface. Cathode, and Electrolyte containing a fluorinated organic solvent placed between the anode and cathode Equipped with, A step of applying an anisotropic force to the surface of the anode, A step of applying a conversion voltage during at least one period of charging and / or discharging the cell, and A step of forming a solid electrolyte interface layer adjacent to the surface of the anode. This includes performing the following: The aforementioned chemical conversion voltage is greater than 4.35V, The solid electrolyte interface layer comprises LiF and Li ２ CO ３ A method for storing and using electrical energy, including inorganic materials containing [the specified substance].

5. The electrochemical cell or method according to any one of claims 1 to 4, wherein the solid electrolyte interface layer containing LiF is formed in situ during charging and / or discharging of the electrochemical cell.

6. The electrochemical cell or method according to any one of claims 1 to 5, wherein the formation of the solid electrolyte interface layer containing LiF is related to the application of an anisotropic force applied to the surface of the anode during at least one period of charging and / or discharging of the electrochemical cell.

7. The electrochemical cell or method according to any one of claims 1 to 6, wherein the LiF is present in the solid electrolyte interface layer in an amount of at least 10% by weight.

8. The solid electrolyte interface layer contains at least 10% by weight of Li ２ An electrochemical cell or method according to any one of claims 1 to 7, further comprising O.

9. The electrochemical cell or method according to any one of claims 1 to 8, wherein at least 5% of the LiF in the solid electrolyte interface layer is in crystalline form.

10. The Li ２ An electrochemical cell or method according to any one of claims 1 to 9, wherein at least 5% of the oxygen is in crystalline form.

11. The electrochemical cell or method according to any one of claims 1 to 10, further comprising a separator disposed between the anode and the cathode, wherein the separator includes pores in which an electrolyte can be present.

12. The electrochemical cell or method according to any one of claims 1 to 11, wherein the solid electrolyte interface layer adjacent to the separator contains particles having a size of 10 nm to 200 nm.

13. LiF and Li ２ CO ３ The electrochemical cell or method according to any one of claims 1 to 12, wherein the solid electrolyte interface layer containing is formed in situ during charging and / or discharging of the electrochemical cell.

14. LiF and Li ２ CO ３ The in-situ formation of the solid electrolyte interface layer containing the same is related to the combination of a formation voltage applied during at least one period during charging and / or discharging of the electrochemical cell and the application of an anisotropic force applied to the surface of the anode during at least one period during charging and / or discharging of the electrochemical cell. The electrochemical cell or method according to any one of claims 1 to 13.

15. LiF and Li ２ CO ３ Li in the solid electrolyte interface layer including ２ CO ３ The electrochemical cell or method according to any one of claims 1 to 14, wherein the formation is related to a conversion voltage applied during at least one period of charging and / or discharging of the electrochemical cell.

16. The electrochemical cell or method according to any one of claims 1 to 15, wherein the conversion voltage is greater than 4.35V and 4.7V or less, or greater than 4.4V and 4.9V or less.

17. The electrochemical cell or method according to any one of claims 1 to 16, wherein the conversion voltage is applied over at least one cycle, at least two cycles, or at least three cycles of charging and discharging the electrochemical cell, and the conversion voltage is applied for a total of at least 10 minutes.

18. The electrochemical cell or method according to any one of claims 1 to 17, wherein the conversion voltage is applied for three or fewer charge-discharge cycles of the electrochemical cell.

19. LiF and Li ２ CO ３ The solid electrolyte interface layer containing Li ２ CO ３ A portion of the solid electrolyte interface layer containing is formed with ex situ, Li ２ CO ３ An electrochemical cell or method according to any one of claims 1 to 18, wherein a portion of the solid electrolyte interface layer containing is formed by pre-passivating the anode before assembly of the electrochemical cell.

20. The Li ２ CO ３ However, CO at the surface of the anode ２ An electrochemical cell or method according to any one of claims 1 to 19, formed by a reaction with a lithium metal.

21. The solid electrolyte interface layer is a mixture of LiF and Li ２ CO ３ An electrochemical cell or method according to any one of claims 1 to 20, comprising:

22. The electrochemical cell or method according to any one of claims 1 to 21, wherein the LiF is present in the solid electrolyte interface layer in an amount of at least 10% by weight.

23. The Li ２ CO ３ The electrochemical cell or method according to any one of claims 1 to 22, wherein the solid electrolyte interface layer contains at least 10% by weight.

24. The electrochemical cell or method according to any one of claims 1 to 23, wherein the solid electrolyte interface layer has a hardness of 0.001 GPa or more and 5 GPa or less.

25. The electrochemical cell or method according to any one of claims 1 to 24, wherein the solid electrolyte interface layer has a porosity of 1% or more and 90% or less.

26. The electrochemical cell or method according to any one of claims 1 to 25, wherein the solid electrolyte interface layer further comprises one or more lithium alkoxides, lithium oxides, lithium salts, and electrolyte decomposition products.

27. The electrochemical cell or method according to any one of claims 1 to 26, wherein the electrolyte comprises a solvent.

28. The electrochemical cell or method according to any one of claims 1 to 27, wherein the solvent comprises at least one fluorinated organic solvent selected from cyclic and linear fluorinated carbonates, fluorinated ethers, and fluorinated esters.

29. The electrochemical cell or method according to any one of claims 1 to 28, wherein the solvent comprises at least one fluorinated organic solvent selected from fluoroethylene carbonate and / or difluoroethylene carbonate.

30. The electrochemical cell or method according to any one of claims 1 to 29, wherein the solvent is a fluorinated organic solvent or a mixture of fluorinated organic solvents.

31. The electrochemical cell or method according to any one of claims 1 to 30, wherein the organic solvent comprises at least one non-fluorinated organic solvent, and the at least one non-fluorinated organic solvent comprises an ester-based solvent.

32. The electrochemical cell or method according to any one of claims 1 to 31, wherein the electrolyte containing a fluorinated organic solvent further comprises at least one non-fluorinated organic solvent containing cyclic and linear carbonates, and the cyclic and linear carbonates include one or more of diethyl carbonate, ethylmethyl carbonate, and dimethyl carbonate.

33. The electrochemical cell or method according to any one of claims 1 to 32, wherein the fluorinated organic solvent is present in an amount of 14% by weight or more and 88% by weight or less of the total electrolyte weight.

34. The electrochemical cell or method according to any one of claims 1 to 33, wherein the electrolyte containing a fluorinated organic solvent further comprises at least one passivating agent, the passivating agent comprising an oxalate.

35. The electrochemical cell or method according to any one of claims 1 to 34, wherein the passivating agent comprises an oxalate containing (oxalato)borate and / or difluoro(oxalato)borate.

36. The electrochemical cell or method according to any one of claims 1 to 35, wherein the electrolyte comprises a lithium salt.

37. The electrochemical cell or method according to any one of claims 1 to 36, wherein the cathode comprises an electroactive transition metal oxide and a chalcogenide, an electroactive conductive polymer, and / or an electroactive sulfur-containing material, and a combination thereof.

38. The electrochemical cell or method according to any one of claims 1 to 37, wherein the cathode is a lithium-intercalation cathode.

39. The electrochemical cell or method according to any one of claims 1 to 38, wherein the cathode containing an electroactive transition metal chalcogenide comprises a material selected from the group consisting of electroactive oxides of nickel, manganese, cobalt, and vanadium, and electroactive sulfides of iron.

40. An electrochemical cell or method according to any one of claims 1 to 39, wherein, based on the average ratio of fluorine atoms to oxygen atoms over the thickness of the solid electrolyte interface layer, a first ratio of fluorine atoms adjacent to the electrolyte to oxygen atoms in the solid electrolyte interface layer is higher than a second ratio of fluorine atoms adjacent to the anode to oxygen atoms.

41. An electrochemical cell or method according to any one of claims 1 to 40, wherein, based on the maximum ratio of fluorine atoms to oxygen atoms over the thickness of the solid electrolyte interface layer, a first ratio of fluorine atoms adjacent to the electrolyte to oxygen atoms in the solid electrolyte interface layer is higher than a second ratio of fluorine atoms adjacent to the anode to oxygen atoms.

42. The electrochemical cell or method according to any one of claims 1 to 41, wherein the solid electrolyte interface layer comprises nanocrystalline LiF.

43. The solid electrolyte interface layer is made of nanocrystalline Li ２ An electrochemical cell or method according to any one of claims 1 to 42, comprising O.

44. The solid electrolyte interface layer contains LiF and Li in a weight ratio of 1:5 to 2:

1. ２ An electrochemical cell or method according to any one of claims 1 to 43, comprising O.

45. The electrochemical cell or method according to any one of claims 1 to 44, wherein the solid electrolyte interface layer has a thickness of 10 nm or more and 75 μm or less.

46. The solid electrolyte interface layer is 1 g / cm³ ３ 3g / cm or more ３ An electrochemical cell or method according to any one of claims 1 to 45, having the following bulk density.

47. The solid electrolyte interface layer is made of nanocrystalline LiF and / or nanocrystalline Li having a size of 5 nm to 40 nm. ２ An electrochemical cell or method according to any one of claims 1 to 46, comprising O.

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