Cross-Reference To Related Application

[1001] This application claims the priority benefit, under 35 U.S.C. 119(e), of U.S. Application No. 62/567,378, entitled "SYSTEMS AND METHODS FOR PREPARING STABILIZED LITHIATED ELECTRODES FOR ELECTROCHEMICAL ENERGY STORAGE DEVICES" and filed on October 3, 2017, the disclosure of which is hereby incorporated by reference in its entirety.

Background

[1002] Lithium-ion capacitor technology is an emerging energy storage technology that can simultaneously provide a high energy density and a high power density. In order to achieve a concurrent high energy density and power density, some lithium-ion capacitor technologies utilize pre-lithiated electrodes to incorporate lithium ions into the electrodes. The pre-lithiated electrodes are then combined with other lithium-ion capacitor components, such as a cathode, an electrolyte, and a separator to form a lithium-ion capacitor.

Summary

[1003] Embodiments described herein relate generally to a system and methods for preparing stabilized pre-lithiated electrodes for electrochemical energy storage devices. The electrodes are pre-lithiated by transferring lithium ions into the electrodes using an electrolyte that includes a lithium salt prior to the electrochemical cell formation stage. The pre-lithiation process is fast and uniform, and the pre-lithiated electrodes are stabilized by a barrier. In some embodiments, the barrier can include one or more materials commonly used as electrolyte solvents. The stabilized pre-lithiated electrodes are stable in ambient conditions and can be handled without specialized equipment during manufacturing of electrochemical energy storage devices.

[1004] In one aspect, a method of pre-lithiating an electrode for an electrochemical energy storage device is described. The method includes providing a current collector including an electrode material disposed thereon, disposing a source of lithium metal onto the electrode material, immersing the source of lithium metal and the electrode material in an electrolyte to form a pre-lithiated electrode material, and removing the source of lithium metal from the pre-lithiated electrode material.

[1005] The current collector can include at least one of aluminum, copper, carbon, graphite, nickel, stainless steel, tantalum, titanium, tungsten, and vanadium, and any combinations thereof and alloys or composites thereof. The current collector can be a foil of a metal or a metal mesh.

[1006] The electrode material can include at least one of graphene, graphene sheets or aggregates of graphene sheets, graphite/graphitic or non-graphitic carbon, amorphous carbon, mesocarbon microbeads, boron-carbon alloys, hard or disordered carbon, carbon nanotubes, mixtures thereof and composites thereof. The electrode material comprises at least one of silicon, bismuth, boron, gallium, indium, zinc, tin, antimony, aluminum, molybdenum, germanium, manganese, niobium, vanadium, tantalum, iron, copper, gold, silver, platinum, chromium, nickel, cobalt, zirconium, yttrium, silicon carbide, alloys thereof, and combinations thereof. The electrode material comprises at least one of tin oxide, iron oxide, cobalt oxides, copper oxides, titanium oxide, molybdenum oxide, germanium oxide, silicon oxide and any oxides in the lithium titanium oxide (lithium titanate), and combinations thereof. The electrode material can include at least one of sulfur, lead sulfide, tantalum sulfide, molybdenum sulfide and tungsten sulfide.

[1007] The source of lithium metal can be a source that is not a lithium metal powder. The source of lithium metal can be a source that is not dispersed within the electrode material. The source of lithium metal can be a lithium alloy. The source of lithium metal can be a lithium foil. The source of lithium metal can be directly applied onto a single electrode.

[1008] The electrolyte can include at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), ethylene methyl carbonate (EMC), diethyl carbonate (DEC), propylene carbonate (PC), γ-butyrolactone (GBL), methyl formate, ethyl formate, ethylmethyl sulfone, butyl sulfone, and l-fluoro-2-(m ethyl sulfonyl) benzene, ethyl acetate, ethyl butyrate, and methyl propionate, and combinations thereof.

[1009] In one aspect, the method can further include applying a voltage or a current between the electrode material in the electrolyte and the source of lithium metal. In one aspect, the method can further include forming a barrier coating on the electrode material in the electrolyte. The barrier coating can include a lithium salt. The lithium salt can include at least one of lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluorob orate (L1BF4), lithium perchlorate (L1CIO4), lithium bis(oxalato) borate (LiBOB), difluoro(oxalate)borate (LiDFOB), lithium hexafluoroarsenate (LiAsF ₆ ), Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), Lithium Bis(fluorosulfonyl) Imide (LiFSI), and lithium monocarbon trifluorosulfite (L1CF3SO3) and combinations thereof. The barrier coating can include a non-aqueous solvent or an electrolyte. The non-aqueous solvent or electrolyte includes at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), ethylene methyl carbonate (EMC), diethyl carbonate (DEC), propylene carbonate (PC), γ-butyrolactone (GBL), methyl formate, ethyl formate, ethylmethyl sulfone, butyl sulfone, and l-fluoro-2-(methylsulfonyl) benzene, ethyl acetate, ethyl butyrate, and methyl propionate, and combinations thereof. The barrier coating can dissolve under during one or more charging and discharging cycles. When the barrier coating dissolves under during the charging and discharging cycle is does so without increasing the ESR of the electrochemical energy storage device. The barrier coating can be configured to protect the electrode material in an oxygen containing environment.

[1010] In one aspect, the method can further include drying the pre-lithiated electrode material. The electrode can be an anode. The electrochemical energy storage device can be a lithium-ion capacitor or a lithium-ion battery.

[1011] In one aspect, a method of forming a pre-lithiated anode for an electrochemical energy storage device is described. The method includes mixing electrode material, a binder, and a liquid to form a slurry, degassing the slurry, coating the slurry on a current collector, drying the slurry to form a solid electrode material, disposing a source of lithium metal on the solid electrode material, immersing the source of lithium metal and the solid electrode material in an electrolyte, removing the source of lithium metal from a pre-lithiated electrode material, and drying the pre-lithiated electrode material to form a pre-lithiated anode.

[1012] The electrode material can include at least one of graphene, graphene sheets or aggregates of graphene sheets, graphite/graphitic or non-graphitic carbon, amorphous carbon, mesocarbon microbeads, boron-carbon alloys, hard or disordered carbon, carbon nanotubes, mixtures thereof and composites thereof. The electrode material can include at least one of silicon, bismuth, boron, gallium, indium, zinc, tin, antimony, aluminum, molybdenum, germanium, manganese, niobium, vanadium, tantalum, iron, copper, gold, silver, platinum, chromium, nickel, cobalt, zirconium, yttrium, silicon carbide, alloys thereof, and combinations thereof. The electrode material can include at least one of tin oxide, iron oxide, cobalt oxides, copper oxides, titanium oxide, molybdenum oxide, germanium oxide, silicon oxide and any oxides in the lithium titanium oxide (lithium titanate), and combinations thereof. The electrode material can include at least one of sulfur, lead sulfide, tantalum sulfide, molybdenum sulfide and tungsten sulfide.

[1013] The binder is a styrene-butadiene rubber (SBR). The liquid used to make the slurry can be water.

[1014] The current collector can include at least one of aluminum, copper, carbon, graphite, nickel, stainless steel, tantalum, titanium, tungsten, and vanadium, and any combinations thereof and alloys or composites thereof. The current collector can be a foil of a metal or a metal mesh.

[1015] The source of lithium metal can be a source that is not a lithium metal powder. The source of lithium metal can be a source that is not dispersed within the electrode material. The source of lithium metal can be a lithium alloy. The source of lithium metal can be a lithium foil. The source of lithium metal can be directly applied onto a single electrode.

[1016] The electrolyte can include at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), ethylene methyl carbonate (EMC), diethyl carbonate (DEC), propylene carbonate (PC), γ-butyrolactone (GBL), methyl formate, ethyl formate, ethylmethyl sulfone, butyl sulfone, and l-fluoro-2-(m ethyl sulfonyl) benzene, ethyl acetate, ethyl butyrate, and methyl propionate, and combinations thereof.

[1017] In one aspect, the method can further include applying a voltage or a current between the electrode material in the electrolyte and the source of lithium metal. In one aspect, the method can further include forming a barrier coating on the electrode material in the electrolyte. The barrier coating can include a lithium salt. The lithium salt can include at least one of lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluorob orate (LiBF ₄ ), lithium perchlorate (LiC10 ₄ ), lithium bis(oxalato) borate (LiBOB), difluoro(oxalate)borate (LiDFOB), lithium hexafluoroarsenate (LiAsF ₆ ), Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), Lithium Bis(fluorosulfonyl) Imide (LiFSI), and lithium monocarbon trifluorosulfite (L1CF3SO3) and combinations thereof. The barrier coating can include a non-aqueous solvent or an electrolyte. The non-aqueous solvent or electrolyte includes at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), ethylene methyl carbonate (EMC), diethyl carbonate (DEC), propylene carbonate (PC), γ-butyrolactone (GBL), methyl formate, ethyl formate, ethylmethyl sulfone, butyl sulfone, and l-fluoro-2-(methyl sulfonyl) benzene, ethyl acetate, ethyl butyrate, and methyl propionate, and combinations thereof. The barrier coating can dissolve under during one or more charging and discharging cycles. When the barrier coating dissolves under during the charging and discharging cycle is does so without increasing the ESR of the electrochemical energy storage device. The barrier coating can be configured to protect the electrode material in an oxygen containing environment.

[1018] In one aspect, the method can further include drying the pre-lithiated electrode material. The electrode can be an anode. The electrochemical energy storage device can be a lithium-ion capacitor or a lithium-ion battery. In one aspect, the method can further include applying a voltage or a current between the electrode material in the electrolyte and the source of lithium metal.

[1019] In one aspect, the method can further include forming a barrier coating on the electrode material in the electrolyte. The barrier coating can include a lithium salt. The lithium salt includes at least one of lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluorob orate (LiBF ₄ ), lithium perchlorate (L1CIO4), lithium bis(oxalato) borate (LiBOB), lithium hexafluoroarsenate (LiAsF ₆ ), Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), Lithium Bis(fluorosulfonyl) Imide (LiFSI), and lithium monocarbon trifluorosulfite (L1CF3SO3) and combinations thereof. The barrier coating can include a non-aqueous solvent or an electrolyte. The non-aqueous solvent or electrolyte can include at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), ethylene methyl carbonate (EMC), diethyl carbonate (DEC), propylene carbonate (PC), γ-butyrolactone (GBL), methyl formate, ethyl formate, ethylmethyl sulfone, butyl sulfone, and l-fluoro-2-(methylsulfonyl) benzene, ethyl acetate, ethyl butyrate, and methyl propionate, and combinations thereof. The barrier coating can dissolves under during one or more charging and discharging cycles. The barrier coating can dissolve under during the one or more charging and discharging cycles without increasing the ESR of the electrochemical energy storage device. The barrier coating is configured to protect the electrode material in an oxygen containing environment.

[1020] In one aspect, the method can further include drying the pre-lithiated electrode material under an inert atmosphere. The electrochemical energy storage device is a lithium- ion capacitor. The electrochemical energy storage device is a lithium-ion battery. In one aspect, the method can further include drying the slurry in a vacuum oven. In one aspect, the method can further pressing the solid electrode material to a uniform thickness. In one aspect, the method can further disposing the source of lithium metal and the solid electrode material in a pouch. The electrolyte can include LiPF ₆ in a solvent having a molar ratio of 3 mols EC : 3 mols DMC : 4 mols EMC. [1021] In one aspect, the electrochemical energy storage device is described. The electrochemical energy storage device includes a first current collector, a cathode disposed on the first current collector, a second current collector, a pre-lithiated anode disposed on a second current collector, the pre-lithiated anode including a barrier coating configured to protect the pre-lithiated anode from an oxygen containing environment. The electrochemical energy storage device also includes a separator disposed between the cathode and the pre- lithiated anode, and an electrolyte.

[1022] The barrier coating can be stable in a dry, non-condensing atmosphere. The barrier coating can be impervious to air. The barrier coating may not require any special handling equipment due to atmospheric conditions. The barrier coating can comprise a lithium salt. The lithium salt can include at least one of lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluorob orate (LiBF ₄ ), lithium perchlorate (L1CIO4), lithium bis(oxalato) borate (LiBOB), lithium hexafluoroarsenate (LiAsF ₆ ), Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), Lithium Bis(fluorosulfonyl) Imide (LiFSI), and lithium monocarbon trifluorosulfite (L1CF3SO3) and combinations thereof. The barrier coating can include a non-aqueous solvent or an electrolyte. The non-aqueous solvent or electrolyte can include at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), ethylene methyl carbonate (EMC), diethyl carbonate (DEC), propylene carbonate (PC), γ-butyrolactone (GBL), methyl formate, ethyl formate, ethylmethyl sulfone, butyl sulfone, and l-fluoro-2-(methylsulfonyl) benzene, ethyl acetate, ethyl butyrate, and methyl propionate, and combinations thereof. The barrier coating can dissolve under during one or more charging and discharging cycles. The barrier coating can dissolve under during the one or more charging and discharging cycle without increasing the ESR of the electrochemical energy storage device.

Brief Description of the Drawings

[1023] FIG. 1 shows a schematic block diagram of a stabilized pre-lithiated electrode for electrochemical energy storage devices, according to an embodiment.

[1024] FIG. 2 illustrates an exemplary process flow diagram for preparing a barrier to stabilize a pre-lithiated electrode for electrochemical energy storage devices, according to an embodiment.

[1025] FIGS. 3A-3D show scanning electron microscope (SEM) micrographs of blank hard carbon electrode materials and pre-lithiated hard carbon electrode materials. [1026] FIGS. 4A-4D show SEM micrographs of blank hard carbon electrode materials and pre-lithiated hard carbon electrode materials after 50 days.

[1027] FIGS. 5A-5D show SEM micrographs of blank graphite electrode materials and pre-lithiated graphite electrode materials.

[1028] FIG. 6 shows a plot of cycling stability of a lithium ion capacitor prepared using stabilized pre-lithiated electrodes at room temperature, according to an embodiment.

[1029] FIG. 7 shows a plot of cycling stability of a lithium ion capacitor prepared using stabilized pre-lithiated electrodes at 60° C, according to an embodiment.

Detailed Description

[1030] Embodiments described herein generally relate to systems and methods for preparing stabilized pre-lithiated electrodes for electrochemical energy storage devices. As the demand increases for electrochemical energy storage devices having better electronic performance, for example, higher storage capacity, energy density, conductivity, and rate capabilities, new electrode designs are needed to meet these criteria. Typical lithium-ion battery electrodes consist of carbon anodes (hard carbon, graphene or graphite anodes) and lithium metal oxide cathodes. There are unavoidable irreversible reactions during initial charging/discharging if primary carbon electrodes were used, resulting in electrolyte consuming. Lithium-ion battery electrodes, and particularly anodes, suffer from irreversible capacity loss at the battery formation stage, i.e., the initial cycling step which includes charging and discharging of the electrochemical cell. The irreversible capacity loss can happen during the first charging cycle when lithium ions are transferred from the cathode to the anode in the formation of the solid electrolyte interphase (SEI) layer. During this process, decomposition of electrolyte components occurs, and lithium ions are also consumed through the formation of lithium compounds, such as L12CO3, lithium alkyl carbonate, lithium alkyloxide, and other salt moieties such as LiF for LiPF ₆ -based electrolytes.

[1031] For lithium-ion capacitors, there are electrochemical reactions that occur on anodes (e.g., lithium ion insertion into and de-insertion). On the cathode side, lithium ions or PF ₆ ^" ions can be absorbed on internal surfaces of activated carbon electrodes, depending upon the cell's operating voltage. For example, at high operating voltages (e.g., 3.0V to 3.8V), PF ₆ ^" ions can be absorbed on internal surfaces of activated carbon electrodes, whereas at lower operating voltages (e.g., 2.2V to 3.0V), lithium ions can be absorbed on the internal surfaces of the activated carbon electrodes. The energy storage mechanisms of LiC anodes mirror those of the anodes of lithium ion batteries, and the cathode energy storage mechanisms mirror those of electric double-layer capacitors (EDLC).

[1032] One way to compensate the loss of lithium ions in the formation stage is the use of pre-lithiated electrodes. For example, pre-lithiated carbon electrodes can minimize irreversible loss of lithium ions in parasitic reactions by having excess lithium ions in the carbon anodes. As such, electrochemical storage devices with pre-lithiated carbon electrodes can have high capacity, charge/discharge efficiency and long-term cycling stability. Some of the devices that can benefit from the use of pre-lithiated electrodes are lithium-ion batteries and lithium-ion capacitors. However, there are several challenges that have prevented wide adoption of pre-lithiated electrodes including, for example, lithium being a very active material (i.e., particularly sensitive to air and moisture), which creates problems with mass manufacturing.

[1033] One of the proposed methods to overcome the challenges has been to use stabilized lithium metal powder (SLMP) in electrode compositions and/or during processing. The SLMP can be prepared by disposing a layer of LiF coating on lithium metal powders to prevent reactions between the lithium metal and air or moisture in the atmosphere. The SLMP can be then dispersed onto the surface of carbon electrodes. Although SLMP can be handled in a dry atmosphere, incorporating SLMP into electrodes can be a complicated process due, in part, to health and safety issues concerning handling of very light and very fine SLMP particles. Since the SLMP particle size ranges from 10-500 μπι and lithium being the lightest metal known, these particles can float in air and can be considered hazardous materials. Furthermore, when the LiF-coated SLMP are used in electrodes, the coating layers can usually remain in the electrodes even after lithium powders have been dissolved by electrochemical reactions. Compared to other components in the electrodes, the LiF coatings from the SLMP have very low electronic conductivity, i.e., high electrical resistance. Therefore, using LiF-coated SLMP in pre-lithiated electrodes for lithium-ion batteries or lithium-ion capacitors can result in the batteries or capacitors having very high equivalent series resistances (ESR). In other words, the side effect of using LiF-coated SLMP is the undissolved LiF coating materials remaining in these electrochemical systems, and increasing the ESR of these electrochemical systems.

[1034] Another proposed method of pre-lithiating electrodes has been attempted in the development of lithium-ion capacitors. As an emerging energy storage technology, the lithium-ion capacitor technology can simultaneously provide high energy density and high power density, which is a highly attractive technological exploit to many industries, including customer electronics, transportation, and manufacturing industries. In order to achieve high energy density and high power density, a lithium-ion capacitor can be typically configured to use a pre-lithiated carbon-based anode, along with an activated carbon cathode, electrolyte, and a separator all packaged into a lithium-ion based capacitor. The pre-lithiated anodes for lithium-ion capacitors can be constructed as follows: A piece of lithium metal foil is attached on the surface of an electrode stack with porous or perforated foils. The terminal of the electrode stack is then connected to the lithium metal foil. The pre-lithiation (also called pre- doping) process is then initiated and maintained after an electrolyte is added to the cell assembly comprising the electrode stack. This pre-doping/pre-lithiation process is very time- consuming because only one piece of lithium foil is applied to the entire stack of electrodes, and the dissolved lithium ions have to penetrate through the entire electrode stack in order to reach the other end of the stack. Therefore, the entire pre-lithiation process can take up to several weeks. And since the pre-lithiation/pre-doping technique is not a uniform process due to the use of a single lithium foil on one end of the electrode stack, it results in a non-uniform gradient of lithium concentration across the electrode stack. The non-uniformity in the pre- lithiated electrodes may cause rapid capacity degradation along with an accelerated ESR gain during normal electrochemical charging/discharging cycles.

[1035] As described herein, the pre-lithiation process can be improved upon earlier attempts (as presented above) by creating a better physical contact between the electrode material and the lithium source during pre-lithiation. In other words, the diffusion pathway from the source of lithium ions to the electrode material is reduced. In some embodiments described herein, the pre-lithiation process can be designed to trigger accelerated electrochemical reactions by applying a current or voltage across the electrodes. In some embodiments, the electrodes are pre-lithiated by a solution or a solvent blend that can readily form a barrier coating that is stable enough that the pre-lithiated electrodes can be handled in any dry condition. The "coated" pre-lithiated electrodes can then be used in lithium-ion batteries, lithium-ion capacitors, and other energy storage devices.

[1036] Systems and methods according to the present disclosure offer several distinct advantages in the production of pre-lithiated electrodes, including: (1) the disclosed methods can significantly reduce the pre-lithiation or pre-doping time to hours or even minutes instead of days (e.g., 20 days or more), (2) the lithium ions are more evenly distributed volumetrically (i.e., better uniformity) in the finished electrodes (e.g., pre-lithiated electrodes), (3) the process is safer because fine particles of SLMP are not used, (4) the finished, pre-lithiated, electrodes are safer because of the barrier (i.e., the stabilized electrodes do not require any special handling equipment or atmospheric conditions), (5) the finished, pre-lithiated, electrodes can be used in standard battery and/or capacitor manufacturing processes, and (6) the barrier (i.e., passivation or coating) can dissolve under normal electrochemical reactions during charging and discharging cycles, without increasing the ESR of the electrochemical system. Therefore, the disclosed systems and methods can provide a significant improvement over prior pre-lithiation methods, and can overcome the obstacles that have impeded the adoption of pre-lithiated electrodes.

[1037] As used in this herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, the term "a member" is intended to mean a single member or a combination of members, "a material" is intended to mean one or more materials, or a combination thereof.

[1038] As used herein, the term "set" and "plurality" can refer to multiple features or a singular feature with multiple parts. For example, when referring to a set of electrodes, the set of electrodes can be considered as one electrode with multiple portions, or the set of electrodes can be considered as multiple, distinct electrodes. Additionally, for example, when referring to a plurality of electrochemical cells, the plurality of electrochemical cells can be considered as multiple, distinct electrochemical cells or as one electrochemical cell with multiple portions. Thus, a set of portions or a plurality of portions may include multiple portions that are either continuous or discontinuous from each other. A plurality of particles or a plurality of materials can also be fabricated from multiple items that are produced separately and are later joined together (e.g., via mixing, an adhesive, or any suitable method).

[1039] As used herein, the term "about" and "approximately" generally mean plus or minus 10% of the value stated, e.g., about 250 μπι would include 225 μπι to 275 μπι, about 1,000 μιη would include 900 μιη to 1,100 μιη.

[1040] As used herein, the term "electrochemical cell formation" refers to the initial charge and/or discharge cycle performed on an electrochemical cell after the components of the electrochemical cell (e.g., cathode, anode, spacer, current collectors, etc.) are assembled for the first time to form the electrochemical cell. [1041] As used herein, the term "capacity" may be synonymous with "battery capacity," "volumetric energy density," and/or "specific energy."

[1042] FIG. 1 shows a schematic block diagram of a stabilized pre-lithiated electrode that can be used in electrochemical energy storage devices, according to an embodiment. The system includes an electrode 120 that includes a current collector 140 and an electrode material 160, and a barrier 180 configured to protect (i.e., shield) the electrode 120 from an environment 190. In some embodiments, the electrode 120 can be pre-lithiated. In some embodiments, the barrier 180 can be configured to protect the pre-lithiated electrode 120 from the environment 190. In some embodiments, the environment 190 can be any oxygen containing environment.

[1043] In some embodiments, the electrode 120 can be any conventional electrode. In some embodiments, the electrode 120 can be an anode. In some embodiments, the electrode 120 can be any carbon containing electrode. In some embodiments, the electrode 120 can be a pre-lithiated electrode. The electrode can be initially formed by any of the conventional and aforementioned electrode manufacturing methods and can comprise any electrode materials described herein. For example, U.S. Patent Publication No. 2009-0080141, U.S. Patent Publication No. 2009-0279230, U.S. Patent Publication No. 2010-0053844, U.S. Patent Publication No. 2010-0079109, U.S. Patent Publication No. 2011- 0032661, U.S. Patent Publication No. 2011-0149473, U.S. Patent Publication No. 2011-0271855, U.S. Patent Publication No. 2012-0033347, U.S. Patent Publication No. 2012-0187347, U.S. Patent Publication No. 2014-0002958, U.S. Patent Publication No. 2015-0016021, U.S. Patent Publication No. 2016-0217937, U.S. Patent Publication No. 2016-0254104, and U.S. Patent Publication No. 2017-0301486 disclose electrodes and methods of forming electrodes, the disclosure of all of which are hereby incorporated by reference in their entireties.

[1044] In some embodiments, the current collector 140 can be any electronically conductive material that is electrochemically inactive under the operating conditions of electrochemical cell. Said another way, the current collector 140 does not form alloys or intermetallic compounds with lithium during operation of the cell. In some embodiments, the current collector 140 can any conductive material, including aluminum, copper, carbon, graphite, nickel, stainless steel, tantalum, titanium, tungsten, and vanadium, and any combination of the materials and/or alloys or composites thereof. [1045] In some embodiments, the current collector 140 can be a foil of metal or metal mesh. In some embodiments, the current collector 140 can be aluminum foil or copper foil. In some embodiments, the current collector 140 can have corrosion resistant properties. In some embodiments, the current collector 140 can have a thickness ranging from about 100 nm to about 1 mm, including about 100 nm, about 200 nm, about 300 nm, about 400 nm, about 500 nm, about 600 nm, about 700 nm, about 800 nm, about 900 nm, about 1 μιτι, about 1.1 μιτι, about 1.2 μιη, about 1.3 μιτι, about 1.4 μηι, about 1.5 μηι, about 1.6 μηι, about 1.7 μηι, about 1.8 μηι, about 1.9 μηι, about 2.0 μηι, about 2.1 μηι, about 2.2 μηι, about 2.3 μηι, about 2.4 μηι, about 2.5 μηι, about 2.6 μηι, about 2.7 μηι, about 2.8 μηι, about 2.9 μηι, about 3.0 μηι, about 3.5 μηι, about 4.0 μηι, about 4.5 μηι, about 5.0 μηι, about 5.5 μηι, about 6.0 μηι, about 6.5 μηι, about 7.0 μηι, about 7.5 μηι, about 8.0 μηι, about 8.5 μηι, about 9.0 μηι, about 10 μηι, about 11 μηι, about 12 μηι, about 13 μηι, about 14 μηι, about 15 μηι, about 16 μηι, about 17 μηι, about 18 μηι, about 19 μηι, about 20 μηι, about 22 μηι, about 24 μηι, about 26 μηι, about 28 μηι, about 30 μηι, about 35 μηι, about 40 μηι, about 45 μηι, about 50 μηι, about 55 μηι, about 60 μηι, about 65 μηι, about 70 μηι, about 75 μηι, about 80 μηι, about 85 μηι, about 90 μηι, about 95 μηι, about 100 μηι, about 110 μηι, about 120 μηι, about 130 μηι, about 140 μηι, about 150 μηι, about 160 μηι, about 170 μηι, about 180 μm, about 190 μηι, about 200 μηι, about 250 μηι, about 300 μηι, about 350 μηι, about 400 μηι, about 450 μηι, about 500 μηι, about 550 μηι, about 600 μηι, about 650 μηι, about 700 μηι, about 750 μηι, about 800 μηι, about 850 μηι, about 900 μηι, about 950 μηι, and about 1 mm, inclusive of all thicknesses therebetween.

[1046] In some embodiments, the electrode materials 160 can comprise any carbon based electrode materials, including graphene, graphene sheets or aggregates of graphene sheets, graphite/graphitic or non-graphitic carbon, amorphous carbon, mesocarbon microbeads, boron-carbon alloys, hard or disordered carbon, carbon nanotubes, or mixture of these materials and composites thereof. In some embodiments, the electrode materials 160 can include at least one high capacity anode materials selected from silicon, bismuth, boron, gallium, indium, zinc, tin, antimony, aluminum, titanium oxide, molybdenum, germanium, manganese, niobium, vanadium, tantalum, iron, copper, gold, silver, platinum, chromium, nickel, cobalt, zirconium, yttrium, molybdenum oxide, germanium oxide, silicon oxide, silicon carbide, any other high capacity materials or alloys thereof, and any combination thereof. In some embodiments, the electrode material 160 can include silicon, silicon/carbon composites, and/or alloys thereof. In some embodiments, the electrode material 160 can include tin and/or alloys thereof. In some embodiments, the electrode materials 160 can include one or more from the following metal oxides, including tin oxide, iron oxides, cobalt oxides, copper oxides, titanium oxide, molybdenum oxide, germanium oxide, silicon oxide and any oxides in the lithium titanium oxide (lithium titanate), and any combinations of metal oxides thereof. In some embodiments, the electrode materials 160 can include one or more from the following transition metal chalcogenides, such as lead sulfide, tantalum sulfide, molybdenum sulfide and tungsten sulfide. In some embodiments, the electrode materials 160 can include sulfur. In some embodiments, the electrode materials 160 can include any combination, composites or alloys of the electrode materials 160 described herein.

[1047] As described herein, the barrier 180 can be configured and/or formulated to protect the electrode 120 from the environment 190. In some embodiments, the barrier 180 can be an inert coating. In some embodiments, the barrier 180 can comprise a stable lithium salt coating. In some embodiments, the barrier 180 can be a coating stable in a dry atmosphere. In some embodiments, the barrier 180 can comprise a coating of electrolyte containing one or more lithium salts and one or more organic solvents. In some embodiments, the barrier 180 can comprise a solvent with a high melting point, or an electrolyte. In some embodiments, the barrier 180 can comprise a non-aqueous solvent or electrolyte.

[1048] In some embodiments, the non-limiting list of lithium salts that can be included in the electrolyte and in the barrier 180 includes lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluorob orate (LiBF ₄ ), lithium perchlorate (L1CIO4), lithium bis(oxalato) borate (LiBOB), difluoro(oxalate)borate (LiDFOB), lithium hexafluoroarsenate (LiAsF ₆ ), Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), Lithium Bis(fluorosulfonyl) Imide (LiFSI), and lithium monocarbon trifluorosulfite (L1CF3SO3) or any mixture of these salts. In some embodiments, the non-limiting list of organic solvents that can be included in electrolyte and in the barrier 180 includes ethylene carbonate (EC), dimethyl carbonate (DMC), ethylene methyl carbonate (EMC), diethyl carbonate (DEC), propylene carbonate (PC), γ- butyrolactone (GBL), methyl formate, ethyl formate, ethylmethyl sulfone, ethyl acetate, ethyl butyrate, and methyl propionate or a solvent blend including any mixture of these solvents. Some of the high melting solvents that can be used in the barrier 180 can include, but are not limited to EC, ethylmethyl sulfone, butyl sulfone, and l-fluoro-2-(methylsulfonyl) benzene.

[1049] In some embodiments, the environment 190 that the barrier 180 is configured to protect the electrode 120 can include any oxygen containing environment, such as ambient air, dry or moist environments, or environments under vacuum. [1050] FIG. 2 illustrates an exemplary process flow diagram describing a method 200 for preparing a barrier to stabilize a pre-lithiated electrode for electrochemical energy storage devices, according to an embodiment. The preparation method 200 includes forming an electrode, at step 202. The electrode can be formed by any conventional electrode manufacturing process using any of the current collectors and electrode materials described herein.

[1051] After the electrode is formed, the electrode can be pre-lithiated, at step 204. The electrode can be pre-lithiated by placing the electrode in direct contact with a source of lithium metal materials/lithium alloy materials or by generally inducing an electrochemical reaction between the electrode and the source of lithium. In some embodiments, the pre- lithiation of the electrode can be initiated by disposing a source of lithium metal or lithium alloy onto the electrode. In some embodiments, the source of lithium material is placed in direct physical contact with the electrode to improve the diffusion of lithium ions (i.e., lithiation) from the lithium source to the electrode. In some embodiments, the source of lithium metal can be a foil of lithium metal or alloys thereof, a sheet of lithium metal or alloys thereof, or lithium metal particles or particles that include lithium alloys.

[1052] In some embodiments, the pre-lithiation process can be initiated after the electrode and the lithium source are placed inside a container (e.g., a pouch, canister, etc.) and an electrolyte is introduced into the container. In some embodiments, the pre-lithiation process may be continuous. In some embodiments, the pre-lithiation process may be discontinuous. In some embodiments, the pre-lithiation process can include transferring an electrode (e.g., from a roll) to a container that includes an electrolyte and a lithium source. As the electrode moves through the container, lithium is transferred from the lithium source to the electrode thereby pre-lithiating the electrode. After the electrode has spent a sufficient time in the electrolyte, the electrode can be removed and wound onto a roll. This process can be preformed in a substantially continuous manner by unwinding the electrode from one roll, feeding the electrode through the electrolyte, and then winding the pre-lithiated electrode onto a second roll simultaneously. The speed of the unwinding and winding can be controlled such that the electrode is in the electrolyte and therefore in communication with the lithium source for a sufficient time to allow adequate pre-lithiation of the electrode. As the lithium source is consumed (i.e., transferred to the electrode material as it passes through the electrolyte, the lithium source can be resupplied. In some embodiments, the pre-lithiation can be performed by applying a voltage or current between the electrode and the lithium source. [1053] In some embodiments, the pre-lithiation process can take less than 24 hours, and in some embodiments the process can take less than one hour. In some embodiments, the pre- lithiation process can take about 5 minutes, about 10 minutes, about 20 minutes, about 30 minutes, about 40 minutes, about 50 minutes, about 1 hour, about 1.5 hour, about 2 hours, about 2.5 hours, about 3 hours, about 3.5 hours, about 4 hours, about 4.5 hours, about 5 hours, about 5.5 hours, about 6 hours, about 6.5 hours, about 7 hours, about 7.5 hours, about 8 hours, about 8.5 hours, about 9 hours, about 9.5 hours, about 10 hours, about 10.5 hours, about 11 hours, about 11.5 hours, about 12 hours, about 13 hours, about 14 hours, about 15 hours, about 16 hours, about 17 hours, about 18 hours, about 19 hours, about 20 hours, about 21 hours, about 22 hours, about 23 hours, and about 24 hours, inclusive of all time durations therebetween.

[1054] In some embodiments, the electrolyte used in the pre-lithiation process can include one or more lithium salts and one or more organic solvents as described above with reference to FIG. 1. In some embodiments, the electrolyte can include a high melting temperature solvent or solvent blend.

[1055] In some embodiments, the remaining lithium material and/or electrolyte can be removed and/or reused after the pre-lithiation of electrodes has completed.

[1056] In some embodiments, the pre-lithiated electrode can include a barrier (e.g., a layer of protective material or coating), at step 206. In some embodiments, the pre-lithiated electrode can include a barrier that acts as a passivation layer to protect the pre-lithiated electrode from an environment, such as an oxygen containing environment. In some embodiments, the barrier on the surface of the pre-lithiated electrode can include a layer of dried (e.g., solid at room temperature) electrolyte. In some embodiments, the pre-lithiated electrode can include a layer of dried electrolyte that contains lithium salts and little to no solvent. In some embodiments, the barrier on the pre-lithiated electrode can be substantially free of low melting temperature solvent.

[1057] After pre-lithiation, the pre-lithiated electrode can be further stabilized with a second barrier coating, at step 208. In some embodiments, the second barrier coating can be formed using a solution of one or more solvents and high concentrations of one or more lithium salts. In some embodiments, the lithium salts can be one or more of LiPF ₆ , LiAsF ₆ , and L1CF3SO3. In some embodiments, the lithium salt for the second barrier coating can be the same or a substantially similar lithium salt used in the pre-lithiation process at step 204. In some embodiments, the lithium salt can be a lithium salt that is normally used in conventional electrochemical energy storage devices.

[1058] In some embodiments, the solvent can have high vapor pressure, and thus, can be easily removed by applying a vacuum to the pre-lithiated electrode. In some embodiments, the high vapor-pressure solvents utilized in the barrier coating forming process can include, for example, EMC, ethyl acetate, ethylmethyl formate, methyl formate, ethyl butyrate, and methyl propionate.

[1059] In some embodiments, the second barrier coating can include a high melting temperature solvent or solvents. In some embodiments, the high melting temperature solvent or solvents can include lithium salts as described herein. The high melting temperature solvent can be formulated to remain solid at room temperature. In some embodiments, the high melting temperature solvent can include, for example, EC, ethylmethyl sulfone, butyl sulfone, l-fluoro-2-(m ethyl sulfonyl) benzene, and combinations thereof.

[1060] The stabilized pre-lithiated electrode is produced after the solvent has been evaporated from the barrier coating, at step 210. In some embodiments, the barrier coating of the stabilized pre-lithiated electrode can be a relatively thin barrier coating. In other words, when compared to the total thickness of the electrode itself, the barrier coating does not substantially increase the thickness of the electrode. In some embodiments, the barrier coating can stabilize or substantially stabilize the pre-lithiated electrode so that the barrier- coated pre-lithiated electrode can be safely stored or handled in a dry or normal atmosphere.

[1061] Once the limitation of air-sensitivity or incompatibility with ambient working conditions have been eliminated by the stabilized coating in pre-lithiated electrodes, the challenges that have long prevented earlier technologies from mass producing lithium-ion capacitors can now be overcome. For example, being impervious to air in a normal atmosphere can enable a direct integration of a production line for producing stabilized pre- lithiated electrodes into a conventional electrode manufacturing system. Much like ordinary electrodes, the pre-lithiated electrodes can now be handled the same way and therefore, can be worked with in the same way. Similarly, being inert to an ambient atmosphere can allow the stabilized pre-lithiated electrodes to be used in lithium-ion batteries and lithium-ion capacitors without the limitations that prevented the use of other pre-lithiated electrodes produced by earlier technologies. In other words, the stabilized pre-lithiated electrodes can now be used in any electrochemical device that utilizes an electrode. [1062] The following examples illustrate some of the specific preparation processes for producing stabilized pre-lithiated electrodes, according to some embodiments.

Example 1

[1063] The starting materials are the following: 69.4 g of hard carbon A, 0.7g of cellulose, and 3.2g of carbon black are mixed for 10 minutes in a planetary mixer at a mixing speed of 20 rpm. Then, 102 g suspension solution of styrene-butadiene rubber (SBR) binder and water are added to the mixture. The mixture is stirred 10 min at 40 rpm, and further mixed for 20 min at 100 rpm to obtain an electrode slurry. The slurry is degassed for 5 minutes under vacuum, and the resulting slurry is then coated on the surface of a 10 μπι copper foil using a film applicator. After the electrode coating is dried in a vacuum oven, it is passed through a jeweler roller for pressing.

[1064] The pressed electrode (80 μπι) is cut into a 100 mm by 70 mm rectangular electrode. A piece of lithium metal foil with larger dimensions than that of the electrode is disposed onto the electrode. The electrode with the lithium foil is then put into a laminated aluminum pouch with a 1 molar LiPF ₆ in EC/DMC/EMC (with the ratio 3/3/4) electrolyte. Gas bubbles are generated near the electrode surface due to the electrolyte decomposition. After 3 hours (pre-lithiation) of immersion in the electrolyte, the lithium foil is peeled off the electrode. The pre-lithiated electrode is dried under vacuum.

[1065] FIGS. 3A-3D show scanning electron microscope (SEM) micrographs of pre- lithiated hard carbon and blank hard carbon. FIGS. 3A and 3B show the surface of the blank electrode without pre-lithiation. FIGS. 3C and 3D show the surfaces of the pre-lithiated electrode after 3 hours of pre-lithiation and after 24 hours of pre-lithiation, respectively. These surfaces clearly show coating with a layer of materials. The coated pre-lithiated electrode is very stable, and no temperature rise is observed. The electrochemical potential of the pre-lithiated electrode was measured at different periods of time, and no significant changes were observed 24 hours after pre-lithiation. Pre-lithiated electrodes have substantially no self-heating under ambient atmosphere. Even pre-lithiated electrodes that were heated up to 140°C under ambient atmosphere with high humidity, emitted no smoke, did not ignite, and exhibited no appearance change. These properties demonstrate that the barrier coating can stabilize pre-lithiated electrodes. Example 2

[1066] The example is similar to that of example 1 except that a different electrode formula is applied. 2,000 g of hard carbon B, 90g of carbon black, 20 g of cellulose, and 2,001 g suspension solution of SBR binder are used for preparing electrodes. The electrode is pre-lithiated for 22 hours in a 1 molar LiPFe in EC/DMC/EMC (3/3/4) electrolyte.

[1067] As shown in the SEM micrographs of FIGS. 4A-4D, the pre-lithiated electrode has a barrier coating, which shows a good stable coating. FIG. 4A shows the surface of the blank electrode without pre-lithiation. FIGS. 4B-4C show SEM micrographs of the specimens after 50 days in a dry room. The pre-lithiated electrode includes a compact barrier coating, which consists of EC and LiPF ₆ . After vacuum drying, the surface of the stabilized pre-lithiated electrode can be seen with some holes that are created by evaporated solvent. The evaporated solvent includes EC and a mixture of high melting point solvents. FIG. 4D shows that the stabilized pre-lithiated electrode still has some coating remaining after soaking for 24 hours in an EMC solvent. This remaining coating is a passivation layer formed by decomposition of electrolyte during pre-lithiation of the electrode.

Example 3

[1068] 5,000 g of graphite, 225 g of carbon black, 50 g of cellulose, and 5,000 g of suspension solution are used for electrode preparation. Electrodes are pre-lithiated for 24 hours in a 1 molar LiPFe in EC/DMC/EMC (3/3/4) electrolyte and stabilized in an EC/EMC (1 : 1 by weight) solvent for 1 minute. After the stabilized pre-lithiated electrode is dried in a glove box filled with argon gas. The surfaces of the electrode are observed by SEM as shown in FIGS. 5A-5D. The SEM micrographs clearly show that the stabilized pre-lithiated electrodes have good protective coating layers.

Example 4

[1069] 100 g of hard carbon B, 4.5 g of carbon black, 1 g of cellulose, and 99 g of suspension solution are used for electrode slurry preparation. The electrode slurry is then coated on 9.5 μπι copper foil, and the final thickness of a double-sided electrode is 208 μπι after drying and pressing. [1070] Cathode preparation: 25 g of activated carbon, 0.45 g cellulose, 3.4 g binder solution, and 63g deionized water are used for slurry preparation. The resulting slurry is coated on 20 μιη aluminum foil.

[1071] Hard carbon electrodes (2 pieces of 103 mm by 60 mm electrodes) are pre- lithiated by attaching a lithium metal foil on the electrode surfaces for 23 hours in a 1 molar LiPFe in EC/DMC/EMC (3/3/4) electrolyte. The pre-lithiated electrodes are then dried in a glove box filled with argon gas.

[1072] The thickness of double-sided activated carbon cathodes is 220 μπι. One piece of electrode with a dimension of 100 mm by 58 mm is cut and dried in a 140 ^° C vacuum oven for 17 hours.

[1073] Once the electrodes are ready, an electrochemical cell is assembled by stacking the electrodes and polyethylene separators in a dry room. A 1 molar LiPF6 in EC/DMC/PC/EA (ethyl acetate) electrolyte is then filled to complete formation of the electrochemical cell.

[1074] The electrochemical cell's cycling stability is determined by applying a 5 A charge/discharge current. After each 5000 cycles, the cell is cooled down, and available energy is measured at a 0.25 A. The measured available energy is plotted as a function of cycle numbers, as shown in FIG. 6. It can be seen that the cell has very good cycling stability. The available energy loss is measured to be around 4% after approximately 800,000 cycles.

Example 5

[1075] The preparation method of slurry is the same as that of Example 4. The thickness of anodes (single-sided coating) is 85 μπι. Anodes (2 pieces of 105 mm by 60 mm) are pre- lithiated for 15 hours in a 1 molar LiPFe in EC/DMC/PC/EA (ethyl acetate) electrolyte. After anodes are dried in argon atmosphere, cells are assembled in a dry room and filled with an electrolyte which is the same as that of the electrolyte used in the pre-lithiation.

[1076] The cell's performance is evaluated at 60 ^° C at a 150 mA/F of current density. FIG. 7 shows cycling stability at 60 ^° C as a function of cycle number. It can be seen that the cell has a good high temperature performance. The available energy loss is 8% after approximately 945,000 cycles.