Prelithiation of electrode materials in semi-solid electrodes

Abstract

Embodiments described herein generally relate to electrochemical cells having prelithiated semi-solid electrodes, and particularly to semi-solid electrodes that are prelithiated during mixing of the semi-solid electrode slurry, thereby forming a solid electrolyte interface (SEI) layer within the semi-solid electrode prior to formation of the electrochemical cell. In some embodiments, the semi-solid electrode comprises about 20% to about 90% by volume of an active material, about 0% to about 25% by volume of a conductive material, about 10% to about 70% by volume of a liquid electrolyte, and a sufficient amount of lithium (as lithium metal, a lithium-containing material, and / or a lithium metal equivalent) to substantially prelithiate the active material. The lithium metal is configured to form a solid electrolyte interface (SEI) layer on the surface of the active material prior to the first charge cycle of an electrochemical cell containing the semi-solid electrode.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62 / 074,372, entitled "Pre-Lithiation of Electrode Materials in a Semi-Solid Electrode," filed November 3, 2014, the disclosure of which is incorporated herein by reference in its entirety. [Background technology]

[0002] background With the increasing demand for batteries with higher electronic performance, such as higher charge capacity, energy density, conductivity, and rate capacity, new electrode designs that meet these criteria are needed. Lithium-ion electrodes, and especially negative electrodes, experience irreversible capacity loss during the battery formation stage (i.e., the first cycle process involving charging and discharging the electrochemical cell). Irreversible capacity loss can occur due to the migration of lithium ions from the positive electrode active material to the negative electrode, where they are used to form a solid electrode interface (SEI) layer. Summary of the Invention [Means for solving the problem]

[0003] overview Embodiments described herein generally relate to electrochemical cells having prelithiated semi-solid electrodes (e.g., negative electrodes), particularly semi-solid electrodes that are prelithiated during mixing of a semi-solid electrode slurry, thereby forming a solid electrolyte interface (SEI) layer within the semi-solid electrode prior to electrochemical electrode formation and / or first cycling. In some embodiments, the semi-solid electrode comprises about 20% to about 90% by volume of an active material, about 0% to about 25% by volume of a conductive material, about 10% to about 70% by volume of a liquid electrolyte, and a sufficient amount of lithium (as lithium metal, lithium-containing material, and / or lithium metal equivalent) to substantially prelithiate the active material. The lithium metal is configured to form a solid electrolyte interface (SEI) layer on the surface of the active material prior to the first charge cycle of an electrochemical cell containing the semi-solid electrode, and optionally lithiate and charge the electrode material. [Brief explanation of the drawings]

[0004] [Figure 1] FIG. 1 is a schematic diagram of an electrochemical cell according to an embodiment. [Figure 2] FIG. 1 is a schematic flow diagram of a method for preparing a prelithiated negative electrode, according to an embodiment. [Figure 3] 1 shows an optical image of the lithium-coated copper foil used to prelithiate the semi-solid negative electrode, which is shown peeled from the copper foil after prelithiation. [Figure 4A] 1 is a voltage versus capacity profile of a standard electrochemical cell containing a standard semi-solid negative electrode and a pre-lithiated electrochemical cell containing a pre-lithiated semi-solid negative electrode. [Figure 4B] 1 is a graph of the capacity difference (dQ / dV) versus charge capacity between a standard electrochemical cell and a prelithiated electrochemical cell. [Figure 5A] FIG. 4 is a graph of the coulombic efficiency after eight charge-discharge cycles of a second electrochemical cell including the prelithiated semi-solid negative electrode shown in FIG. 3. [Figure 5B]4 is a graph of the capacity retained after eight charge-discharge cycles by a second electrochemical cell including the prelithiated semi-solid negative electrode shown in FIG. 3. [Figure 6A] 1 shows an optical image of a semi-solid negative electrode suspension onto which lithium metal powder is deposited prior to mixing. [Figure 6B] 1 shows a semi-solid negative electrode suspension that was mixed and then stored for one day. DETAILED DESCRIPTION OF THE INVENTION

[0005] Detailed Description The embodiments described herein generally relate to electrochemical cells having prelithiated semi-solid electrodes, and particularly to semi-solid electrodes that are prelithiated during mixing of the semi-solid electrode slurry, thereby forming a solid electrolyte interface (SEI) layer in the semi-solid electrode prior to formation of the electrochemical cell. Consumer electronic batteries have been steadily increasing in energy density with advances in lithium-ion battery technology. The stored energy, or charge capacity, of a fabricated battery is a function of (1) the specific charge capacity (mAh / g) of the active material, (2) the volume (cm) of the electrode, and (3) the volume (cm) of the electrode. 3 ) (i.e., the product of the electrode thickness, the electrode area, and the number of layers (stacks)), and (3) the filling of the active material into the electrode medium (e.g., the filling of the active material into 1 cm of the electrode medium). 3 Therefore, to increase commercial attractiveness (e.g., increased energy density and lower cost), it is common to increase the areal charge capacity (mAh / cm 2 ) and also to reduce irreversible capacity loss that can occur, especially in lithium-ion batteries.

[0006] The semi-solid electrodes described herein (i) can be made thicker (e.g., greater than about 250 μm, up to about 2,000 μm or more) due to the reduced flexibility and increased electronic conductivity of the semi-solid electrodes, (ii) can have increased active material loadings, and (iii) can have simplified manufacturing processes that utilize less equipment. Such semi-solid electrodes can be formed in either a fixed or fluid configuration, reducing the volume, mass, and cost impact of inactive components on the active materials, thereby enhancing the commercial appeal of batteries fabricated with the semi-solid electrodes. The reduced flexibility and increased electronic conductivity of the semi-solid electrodes described herein can result in excellent rate and charge capacities for electrochemical cells formed from the semi-solid electrodes.

[0007] Because the semi-solid electrodes described herein can be substantially thicker than conventional electrodes, the ratio of active material (i.e., semi-solid positive and / or negative electrodes) to inactive material (i.e., current collectors and separators) can be much higher in batteries formed from electrochemical cell stacks with semi-solid electrodes than in similar batteries formed from electrochemical cell stacks including conventional electrodes, thereby substantially increasing the overall charge capacity and energy density of batteries including the semi-solid electrodes described herein. Examples of electrochemical cells utilizing thick semi-solid electrodes and various formulations thereof are described in U.S. patent application Ser. No. 13 / 872,613, entitled "Semi-Solid Electrodes Having High Rate Capability," filed April 29, 2013 (also referred to as the "'613 application"), and U.S. patent application Ser. No. 14 / 202,606, entitled "Asymmetric Battery Having a Semi-Solid Cathode and High Energy Density Anode," filed March 10, 2014 (also referred to as the "'606 application"), the disclosures of which are incorporated herein by reference in their entireties.

[0008] Lithium-ion electrodes, and particularly their negative electrodes, can experience irreversible capacity loss during the battery formation stage (i.e., the initial cycling step involving charging and discharging an electrochemical cell containing the electrode). Irreversible capacity loss can result from the consumption of lithium ions from the positive electrode active material by the negative electrode, which uses these lithium ions to form the SEI layer. The amount of lithium consumed is unavailable for subsequent charge storage applications and therefore represents an undesirable irreversible capacity loss. Furthermore, this irreversible capacity loss can be accompanied by volume expansion of the negative electrode due to the irreversible incorporation of lithium ions into the negative electrode material. This volume expansion problem is more pronounced in the case of semi-solid negative electrodes that include high-capacity negative electrode materials (e.g., silicon or tin) in their formulation, because these materials can incorporate larger amounts of lithium (enabling higher-energy cell designs) compared to conventional materials such as graphite. For example, graphite can incorporate approximately one lithium atom for every six carbon atoms, while silicon can theoretically incorporate approximately 4.4 lithium atoms per silicon atom. While this higher capacity may enable the creation of electrochemical cells with much higher charge capacity per unit area relative to conventional electrochemical cells, the greater number of incorporated lithium ions also means that semi-solid anodes containing high-capacity materials will consume more lithium from the cathode to form the SEI layer, resulting in a much higher degree of irreversible capacity. Furthermore, silicon undergoes substantial volume expansion due to the incorporation of lithium ions into the silicon atoms. Repeated volume changes (i.e., expansion and / or contraction) can adversely affect charge capacity and cause irreversible mechanical damage, which can shorten the life of the electrochemical cell.The effect of lithiation on the stress and morphology of silicon electrodes is described in more detail in V. Sethuraman et al., "In situ Measurements of Stress Evolution in Silicon Thin Films During Electrochemical Lithiation and Delithiation," Journal of Power Sources 195 (2010) 5061-5066, the entire contents of which are incorporated herein by reference.

[0009] The semi-solid electrode embodiments described herein are prelithiated with lithium during the preparation of the semi-solid electrode suspension and prior to the formation of an electrochemical cell, at least partially overcoming the aforementioned problems of irreversible capacity loss and volume expansion. Unlike conventional electrodes, the semi-solid electrodes described herein allow for the incorporation of lithium metal during the electrode slurry mixing process. This is possible because the semi-solid electrodes described herein include an electrolyte that is mixed into the semi-solid electrode composition. The electrolyte provides a medium for the lithium ions provided by the lithium metal to interact with the active material (e.g., graphite) or high-capacity material (e.g., silicon or tin) contained in the semi-solid electrode, particularly the semi-solid negative electrode. This allows for the formation of an SEI layer during the mixing step, and when such a prelithiated semi-solid negative electrode is paired with a positive electrode in an electrochemical cell, lithium ions from the positive electrode are not used to form the SEI layer. In other words, due to the prelithiation, lithium ions from the positive electrode do not contribute to irreversible capacity loss in the negative electrode, allowing the positive electrode to retain its original capacity after the formation of the electrochemical cell. Furthermore, the electrolyte contained in the semi-solid electrode composition can also protect the lithium metal from the surrounding environment (e.g., moisture or humidity in the surrounding environment) and keep the lithium metal stable during the mixing process.

[0010] Another advantage provided by the prelithiation of the semi-solid electrode described herein is that the negative electrode can be prelithiated so that it is fully charged before being paired with a positive electrode. This allows the use of a positive electrode that does not contain any lithium available for the formation of an SEI layer in the negative electrode. Therefore, carbon-based negative electrode materials can be used instead of lithium metal, leading to better cycling stability and safety. Furthermore, lithium ion intercalation into the high-capacity material contained in the negative electrode can also occur during the mixing step, thereby allowing some expansion of the high-capacity material during the mixing step. In other words, because the prelithiation allows the semi-solid negative electrode to expand in advance, the semi-solid negative electrode does not expand significantly during electrochemical cell formation and subsequent charge / discharge cycles. In this way, physical damage to the electrochemical cell due to the expansion of the semi-solid negative electrode can be substantially reduced or, in some cases, eliminated. Therefore, electrochemical cells including such prelithiated semi-solid negative electrodes can have substantially higher mechanical stability and longer lifespans compared to non-prelithiated negative electrodes (e.g., semi-solid negative electrodes).

[0011] Embodiments of the prelithiated semi-solid electrodes described herein offer several advantages over conventional electrodes, including: (1) the formation of an SEI layer on the active material of the semi-solid electrode (e.g., anode) before the formation of an electrochemical cell; (2) the limited or otherwise substantial elimination of the formation of an SEI layer with lithium ions extracted from the other electrode (e.g., cathode); (3) the retention of substantially all of the initial capacity of the other electrode (e.g., cathode) after the formation of the electrochemical cell; (4) the pre-expansion of the semi-solid negative electrode comprising a high capacity material by prelithiation before the formation of the electrochemical cell limits and / or reduces any volumetric expansion of the semi-solid negative electrode during the formation of the electrochemical cell and during normal use; and (5) the increased charge capacity and extended operating life of the electrochemical cell.

[0012] In some embodiments, the semi-solid electrode comprises about 20% to about 90% by volume of an active material, about 0% to about 25% by volume of a conductive material, about 10% to about 70% by volume of a liquid electrolyte, and a sufficient amount of lithium (as lithium metal, a lithium-containing material, and / or a lithium metal equivalent) to substantially prelithiate the active material. The lithium is configured to form a solid electrolyte interface (SEI) on the surface of the active material prior to the first charge cycle of an electrochemical cell including the semi-solid electrode. In some embodiments, the lithium metal can comprise at least one of lithium metal powder, a lithium salt, a lithium foil, and lithium metal deposited on a semi-solid electrode current collector.

[0013] In some embodiments, the semi-solid electrode, excluding the electrolyte component, comprises about 75% to about 100% by weight of active material, about 0% to about 50% by weight of conductive material, and about 1% to about 50% by weight of lithium metal or lithium ion equivalent. The entire solid component of the electrode consists of the active material, conductive material, and lithium ion equivalent. The solid component consists of 35% to about 90% by volume of the semi-solid electrode, and the electrolyte consists of 10% to about 90% by volume of the semi-solid electrode. Lithium metal is added to this electrode to consume the irreversible capacity of the negative electrode material, which can range from 1% to 50% of the theoretical first charge capacity of the negative electrode material. In other applications, lithium metal may be mixed with an unlithiated positive electrode material, such as FeS2, to produce a positive electrode material that is lithiated for use in a second battery. In this case, the amount of lithium metal or lithium ion equivalent used would equal the entire available capacity of the positive electrode. Another application of prelithiation is to not only lithiate the negative electrode to consume all of its irreversible capacity, but also to further lithiate the negative electrode to provide a buffer for active lithium ions, which would be stored as a reserve for later cycling. In such embodiments, the amount of lithium metal used would be in the range of 10% to 50% of the theoretical capacity of the negative electrode. In another example, the prelithiation process can be used to lithiate a positive electrode material to provide it with an excess amount of lithium ions (i.e., to "overlithiate" the positive electrode), thus making the material more stable during electrochemical cycling.

[0014] In some embodiments, a method for preparing a prelithiated negative electrode includes combining an active material with lithium metal to form a prelithiated negative electrode. An electrolyte is combined with the prelithiated material to form a semi-solid negative electrode material. The semi-solid negative electrode material is then formed into a semi-solid negative electrode. In some embodiments, an optional conductive material can be combined with the prelithiated negative electrode material. In some embodiments, an optional high capacity material can be combined with the prelithiated negative electrode material.

[0015] As used herein, the terms "about" and "approximately" generally mean plus or minus 10% of the stated numerical value, for example, about 250 μm includes 225 μm to 275 μm, and about 1,000 μm includes 900 μm to 1,100 μm.

[0016] As used herein, the term "semi-solid" refers to a material that is a mixture of a liquid and a solid phase, such as a particle suspension, a colloidal suspension, an emulsion, a gel, or a micelle.

[0017] As used herein, the terms "conductive carbon network" and "network carbon" refer to the general qualitative state of an electrode. For example, an electrode having a carbon network (or network carbon) is one in which the carbon particles within the electrode have individual particle morphologies and arrangements relative to one another that facilitate electrical contact and conduction between the particles and through the thickness and length of the electrode. In contrast, the term "non-network carbon" refers to an electrode in which the carbon particles exist as islands of individual particles or clusters of multiple particles that may not be connected enough to provide sufficient electrical conductivity through the electrode.

[0018] As used herein, the term "electrochemical cell formation" refers to the first charge and / or discharge cycle performed on an electrochemical cell after the electrochemical cell components (e.g., positive electrode, negative electrode, spacer, current collector, etc.) are initially assembled to form the electrochemical cell.

[0019] As used herein, the term "capacity" may be synonymous with "battery capacity," "volumetric energy density," and / or "specific energy."

[0020] FIG. 1 shows a schematic diagram of an electrochemical cell 100. The electrochemical cell 100 includes a positive electrode current collector 110, a negative electrode current collector 120, and a separator 130 disposed between the positive electrode current collector 110 and the negative electrode current collector 120. The positive electrode current collector 110 is spaced a first distance t1 from the separator 130, at least partially defining a positive electroactive area. The negative electrode current collector 120 is spaced a second distance t2 from the separator 130, at least partially defining a negative electroactive area. A semi-solid positive electrode 140 is disposed within the positive electroactive area, and a semi-solid negative electrode 150 is disposed within the negative electroactive area. In some embodiments, the thickness of the positive electroactive area defined by distance t1 and / or the thickness of the negative electroactive area defined by distance t2 can be in the range of about 250 μm to about 2,000 μm.

[0021] The semi-solid positive electrode 140 and / or semi-solid negative electrode 150 can be disposed on a current collector, and can be deposited using, for example, coating, casting, drop coating, pressing, roll pressing, or any other suitable method. The semi-solid positive electrode 140 can be disposed on the positive current collector 110, and the semi-solid negative electrode 150 can be disposed on the negative current collector 120. For example, the semi-solid positive electrode 140 and / or semi-solid negative electrode 150 can be coated, cast, calendared, and / or pressed onto the positive current collector 110 and the negative current collector 120, respectively. The positive current collector 110 and the negative current collector 120 can be any current collector that is electronically conductive and electrochemically inert under the operating conditions of the cell. Typical current collectors for lithium cells include copper, aluminum, or titanium sheet or mesh for the negative current collector 120, and aluminum sheet or mesh for the positive current collector 110, or a combination thereof.

[0022] The current collector material can be selected to be stable at the operating potential of the semi-solid positive electrode 140 and semi-solid negative electrode 150 of the electrochemical cell 100. For example, in a non-aqueous lithium system, the positive electrode current collector 110 can comprise aluminum or a Li / Li +The negative electrode current collector 120 may comprise aluminum coated with a conductive material that is not electrochemically dissolved at an operating potential of 2.5 to 5.0 V relative to the negative electrode. Materials for coating aluminum current collectors may include platinum, gold, nickel, conductive metal oxides such as vanadium oxide, and carbon. The negative electrode current collector 120 may comprise copper or other metals that do not form alloys or intermetallic compounds with lithium, carbon, and / or coatings containing such materials deposited on other conductors.

[0023] The semi-solid positive electrode 140 and semi-solid negative electrode 150 contained within the electrochemical cell can be separated by a separator 130. For example, the separator 130 can be any conventional membrane that allows ion transport. In some embodiments, the separator 130 is a liquid-permeable membrane, i.e., a solid or gel-like ion conductor, that allows ion transport therethrough. In some embodiments, the separator 130 is a porous polymer membrane impregnated with a liquid electrolyte that allows ion transport between the electroactive materials of the semi-solid positive electrode 140 and semi-solid negative electrode 150 while preventing electron transport. In some embodiments, the separator 130 is a microporous membrane that prevents particles forming the positive and negative electrode compositions from passing through the membrane. In some embodiments, the separator 130 is a single-layer or multi-layer microporous separator of the type used in the lithium-ion battery industry and familiar to those skilled in the art, optionally with the ability to melt or "close" above a certain temperature to prevent ion transport during operation. In some embodiments, the separator 130 can include a polyethylene oxide (PEO) polymer complexed with a lithium salt to provide lithium conductivity, or a Nafion™ membrane, which is a proton conductor. For example, a PEO-based electrolyte can be used as the separator 130, which is a solid ion conductor without pinhole defects, optionally stabilized with another membrane, such as a glass fiber separator, as a support layer. PEO can also be used as a slurry stabilizer, dispersant, or other additive in positive or negative redox compositions. PEO is stable in contact with typical alkyl carbonate-based electrolytes. This can be particularly beneficial in phosphoric acid-based cell chemistries, where the cell potential at the positive electrode is less than about 3.6 V relative to Li metal. The operating temperature of the redox cell can be increased, if necessary, to improve the ionic conductivity of the membrane.

[0024] The semi-solid cathode 140 can be a semi-solid stationary cathode. The semi-solid cathode 140 can include an ion-storing solid phase material, which can include, for example, an active material and / or a conductive material. The amount of the ion-storing solid phase can be in the range of about 0% to about 90% by volume. The semi-solid cathode 140 can include an active material, which can include, for example, a lithium carrier composition (e.g., lithium iron phosphate (LFP), LiCoO, Mg-doped LiCoO, LiNiO, Li(Ni,Co,Al)O (referred to as NCA), Li(Ni,Mn,Co)O (referred to as NMC), LiMnO and its derivatives, etc.). The semi-solid cathode 140 can also include a conductive material, such as graphite, carbon powder, pyrolytic carbon, carbon black, carbon fiber, carbon microfiber, carbon nanotubes (CNTs), single-walled CNTs, multi-walled CNTs, fullerene carbon including "buckyballs," graphite sheets, aggregates of graphite sheets, and / or any other conductive material, alloy, or combination thereof. The semi-solid cathode 140 can also include a non-aqueous liquid electrolyte, such as ethylene carbonate, dimethyl carbonate, diethyl carbonate, propylene carbonate, gamma butyrolactone, or any other electrolyte described herein or combination thereof.In some embodiments, the electrolyte comprises one or more of the following salts: lithium hexafluorophosphate (LiPF), LiPF(CF), LiPF(C), LiPF(C), LiPF(CF), LiPF(CF), LiPF(CF), LiPF(CF), LiPF(CF), LiPF(CF), LiPF(C), LiBF, LiBF(C), LiBOB, lithium bis(oxalato)borate (LiBOP), lithium oxalyldifluoroborane (LiO), Lithium difluoro(oxalato)borate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide (LiFSI), LiN(SO2F3)2, lithium bis(fluorosulfonyl)imide (LiFSI), LiN(SO2F)2, LiN(SO2C2F5)2, LiCF3SO3, LiAsF6, LiSbF6, LiClO4, LiTFSI, LiFSI, and / or other organic or inorganic anions and / or compounds, for example, belonging to the families listed herein.

[0025] In some embodiments, the semi-solid anode 150 includes an ion-storing solid phase material, which can include, for example, an active material and / or a conductive material. The amount of ion-storing solid phase material can range from about 0% to about 90% by volume. The anode 150 can include anode active materials such as lithium metal, carbon, lithium-intercalated carbon, graphite, lithium nitride, lithium alloys, and lithium alloys that form compounds with silicon, bismuth, boron, gallium, indium, zinc, tin, tin oxide, antimony, aluminum, titanium oxide, molybdenum, germanium, manganese, niobium, vanadium, tantalum, gold, platinum, iron, copper, chromium, nickel, cobalt, zirconium, yttrium, molybdenum oxide, germanium oxide, silicon oxide, silicon carbide, any other material or alloy thereof, and any other combination thereof.

[0026] Semi-solid anode 150 (e.g., semi-solid anode) can also include a conductive material, which can be a carbonaceous material such as graphite, carbon powder, pyrolytic carbon, carbon black, carbon fiber, carbon microfiber, carbon nanotubes (CNTs), single-walled CNTs, multi-walled CNTs, fullerene carbon including "buckyballs," graphite sheets, aggregates of graphite sheets, and / or any other conductive material, alloy, or combination thereof. In some embodiments, semi-solid anode 150 can also include a non-aqueous liquid electrolyte such as ethylene carbonate, dimethyl carbonate, diethyl carbonate, propylene carbonate, gamma butyrolactone, or any other electrolyte described herein or combinations thereof.

[0027] In some embodiments, semi-solid positive electrode 140 and / or semi-solid negative electrode 150 can include an active material and, optionally, a conductive material in the form of particulates suspended in a non-aqueous liquid electrolyte. In some embodiments, the particles of semi-solid positive electrode 140 and / or semi-solid negative electrode 150 (e.g., positive or negative electrode particles, which in some embodiments are secondary particles formed by agglomeration of primary particles) can have an effective particle size of at least about 1 μm. In some embodiments, the effective particle size of the positive or negative electrode particles is between about 1 μm and about 10 μm. In other embodiments, the effective particle size of the positive or negative electrode particles is at least about 10 μm or greater. In some embodiments, the effective particle size of the positive or negative electrode particles is less than about 1 μm. In other embodiments, the effective particle size of the positive or negative electrode particles is less than about 0.5 μm. In other embodiments, the effective particle size of the positive or negative electrode particles is less than about 0.25 μm. In other embodiments, the effective particle size of the positive or negative electrode particles is less than about 0.1 μm. In other embodiments, the effective particle size of the positive or negative electrode particles is less than about 0.05 μm, hi other embodiments, the effective particle size of the positive or negative electrode particles is less than about 0.01 μm.

[0028] In some embodiments, semi-solid positive electrode 140 includes about 20% to about 90% by volume of active material. In some embodiments, semi-solid positive electrode 140 includes about 40% to about 75% by volume, about 50% to about 75% by volume, about 60% to about 75% by volume, or about 60% to about 90% by volume of active material.

[0029] In some embodiments, the semi-solid cathode 140 can include between about 0% and about 25% by volume of the conductive material. In some embodiments, the semi-solid cathode 140 can include between about 0.5% and about 25% by volume, between about 1% and about 6% by volume, between about 6% and about 12% by volume, or between about 2% and about 15% by volume of the conductive material.

[0030] In some embodiments, the semi-solid cathode 140 can include about 10% to about 70% by volume of electrolyte. In some embodiments, the semi-solid cathode 140 can include about 30% to about 60% by volume, about 40% to about 50% by volume, or about 10% to about 40% by volume of electrolyte.

[0031] In some embodiments, semi-solid negative electrode 150 includes about 20% to about 90% by volume of active material. In some embodiments, semi-solid negative electrode 150 includes about 40% to about 75% by volume, about 50% to about 75% by volume, about 60% to about 75% by volume, or about 60% to about 90% by volume of active material.

[0032] In some embodiments, semi-solid negative electrode 150 can include about 0% to about 20% by volume of conductive material. In some embodiments, semi-solid negative electrode 150 can include about 1% to about 10% by volume, 1% to about 6% by volume, about 0.5% to about 2% by volume, about 2% to about 6% by volume, or about 2% to about 4% by volume of conductive material.

[0033] In some embodiments, semi-solid negative electrode 150 can include about 10% to about 70% by volume of electrolyte. In some embodiments, semi-solid negative electrode 150 can include about 30% to about 60% by volume, about 40% to about 50% by volume, or about 10% to about 40% by volume of electrolyte.

[0034] Examples of semi-solid positive electrode 140 and / or semi-solid negative electrode 150 compositions, their various formulations, and active materials, conductive materials, and / or electrolytes usable in electrochemical cells formed therefrom are described in the '613 and '606 applications.

[0035] In some embodiments, the semi-solid negative electrode 150 can also include about 1% to about 30% by volume of a high-capacity material. Such high-capacity materials can include, for example, silicon, bismuth, boron, gallium, indium, zinc, tin, antimony, aluminum, titanium oxide, molybdenum, germanium, manganese, niobium, vanadium, tantalum, iron, copper, gold, platinum, chromium, nickel, cobalt, zirconium, yttrium, molybdenum oxide, germanium oxide, silicon oxide, silicon carbide, or any other high-capacity material or alloy thereof, and any combination thereof. In some embodiments, the semi-solid negative electrode can include about 1% to about 5%, about 1% to about 10%, or about 1% to about 20% by volume of the high-capacity material. In some embodiments, the high-capacity material can comprise up to 50% of the volume of the semi-solid negative electrode. In other embodiments, the high-capacity material can comprise up to 100% or substantially all of the volume of the semi-solid negative electrode. Examples of semi-solid negative electrodes 150, their various formulations, and high capacity materials that can be included in electrochemical cells formed therefrom are described in the '606 application.

[0036] The semi-solid anode 150 and / or the semi-solid cathode 140 may also be made of lithium metal, lithium-containing materials (e.g., LiFePO, Li(Mn 1 / 3 Ni 1 / 3 Co 1 / 3)O2, and LiMn2O4, and / or LiCoO2), and / or lithium metal equivalents (e.g., lithium ions, whether intercalated into and / or associated with the electrode material) can also be included in the semi-solid electrode composition. In some embodiments, lithium metal can be included / introduced into the semi-solid negative electrode 150 and / or the semi-solid positive electrode 140 during mixing of the semi-solid electrode suspension. Lithium metal, lithium-containing materials, and / or lithium metal equivalents can be present in the semi-solid negative electrode and / or semi-solid positive electrode in an amount sufficient to at least partially (or in some embodiments, substantially completely) "prelithiate" the semi-solid negative electrode and / or semi-solid positive electrode. For example, lithium metal, lithium-containing materials, and / or lithium metal equivalents can be included in the semi-solid negative electrode 150 and / or semi-solid positive electrode 140 before the electrochemical cell 100 is assembled and formed. The lithium metal, lithium-containing material, and / or lithium metal equivalent can be configured to form an SEI layer on the surface of the active material contained in the semi-solid electrode (e.g., semi-solid anode (150)) prior to the first charge cycle of the electrochemical cell 100 (i.e., prior to electrochemical cell formation). As such, during the formation stage of the electrochemical cell 100, little or no lithium from the semi-solid cathode 140 is consumed to form the SEI layer on the surface of the semi-solid anode. Thus, the potential for capacity loss of the semi-solid cathode 140 due to consumption of cathode lithium ions during anode SEI layer formation is reduced or eliminated.

[0037] In some embodiments, the amount of lithium metal, lithium-containing material, and / or lithium metal equivalent may be sufficient to fully compensate for (i.e., prevent) conventional lithium consumption (e.g., lithium ions “stolen” from the positive electrode) that occurs during initial cell cycling to form an SEI layer. In other embodiments, the amount of lithium metal, lithium-containing material, and / or lithium metal equivalent may exceed the amount necessary to fully compensate for conventional SEI layer formation. In such embodiments, the excess lithium contained within the negative electrode can help offset capacity loss due to side reactions occurring in the negative electrode and / or allow the negative electrode itself to be “pre-charged.” The amount of pre-charge of the negative electrode depends on the amount of lithium metal, lithium-containing material, and / or lithium metal equivalent added by the excess intercalated lithium (e.g., metallic Li or its compounds or ions). As a result, it is theoretically possible to achieve or exceed a “fully charged” negative electrode state through prelithiation alone. As shown in Tables 1-6 (discussed below), the required amount of lithium (e.g., provided in the form of lithium metal, lithium-containing material, and / or lithium metal equivalent) may be calculated by considering several factors, which, depending on the embodiment, may include the capacity (e.g., charge capacity) of one or more active materials, the weight of one or more active materials, the percentage of the capacity of one or more active materials that is irreversible capacity, the weight and type of one or more additives, the irreversible capacity of one or more additives, the capacity of lithium (e.g., lithium metal, lithium-containing material, and / or lithium metal equivalent), the overall capacity of the electrode, and the amount of additional (i.e., "buffer") capacity desired.

[0038] The amount of lithium metal included in the semi-solid negative electrode 150 can depend on the active material included in the semi-solid negative electrode 150. For example, in a semi-solid negative electrode 150 including graphite as the active material, loss due to SEI layer formation primarily manifests as irreversible capacity loss during the first cycle of the electrochemical cell 100 (i.e., electrochemical cell formation). The added lithium metal itself forms contact between the SEI and the electrolyte, which results in further irreversible loss. Therefore, the amount of lithium metal added to the semi-solid negative electrode 150 can be directly related to the irreversible capacity loss during the first cycle of the electrochemical cell 100. Generally, for graphite negative electrodes, the irreversible capacity loss can be about 5% to about 30% of the initial capacity of the negative electrode. The amount of lithium metal that can be included in a negative electrode including graphite as the active material (e.g., a graphite semi-solid negative electrode or any other graphite containing graphite) can be calculated as described below. When Faraday's constant is 96,500 C / mol, the graphite formula weight is 12 grams per mole (i.e., the molar weight of the "6-C" ring is about 72 g / mol), and its density is 1 cm 3 per 2.2 grams, the theoretical capacity of prelithiated graphite (with respect to LiC6) is 372 mAh / g, and the theoretical volumetric capacity is 818 mAh / cm 3 The theoretical capacity of graphite (for LiC6) is calculated as follows:

number

[0039] In some embodiments in which the semi-solid anode 150 comprises a high-capacity material (e.g., silicon, tin, or any other high-capacity material described herein), the degree of lithiation should keep the material within an operating range that minimizes volume change. For silicon, this may be anywhere between 10% and 80% lithiation. This can extend the life of the semi-solid anode 150 during charge / discharge cycling by limiting the expansion or contraction of the semi-solid anode 150. This is because prelithiation of the semi-solid anode 150 allows lithium to be inserted into the high-capacity material (e.g., silicon) prior to electrochemical cell formation. See V. Sethuraman et al., "In Situ Measurements of Stress Evolution in Silicon Thin Films During Electrochemical Lithiation and Delithiation," Journal of Power Source 195 (2010) 5062-5066, cited above. The lithium in the pre-lithiated semi-solid anode 150 permanently shifts the lithium concentration range over which the anode is cycled, increasing the minimum lithium concentration in the semi-solid anode 150 at the end of discharge (i.e., the semi-solid anode remains substantially lithiated before, during, and after formation of the electrochemical cell 100 during charge and discharge of the cell). Thus, for semi-solid anodes comprising high capacity materials, the amount of lithium metal added for effective pre-lithiation can be determined by the optimal cycling range for the semi-solid anode 150, and can be calculated in a manner similar to that described herein for graphite. For example, silicon has a formula weight of 29 grams per mole and a density of 1 cm3. 3 2.33 g per 1000 kJ / kg, and Li 4.4 At this composition, the theoretical capacity of prelithiated silicon is 4,212 mAh / g, and the corresponding theoretical volumetric capacity is 9,814 mAh / cm 3where t is the mass and volume of the silicon starting material. Thus, semi-solid negative electrodes of the present disclosure that include a high capacity material (e.g., silicon) may be formulated to include sufficient lithium (i.e., in a "prelithiation stage") to minimize volume change during cycling.

[0040] Because the lithium metal added to a semi-solid negative electrode 150 containing a high-capacity material can be used not only to form an SEI layer but also to partially lithiate the negative electrode, the amount of prelithiation can be determined based on the amount of active material present in the semi-solid negative electrode 150. For example, in a semi-solid negative electrode 150 containing a high-capacity material and an inactive material but no active material, the amount of lithium added during prelithiation is used only to prelithiate the high-capacity material (e.g., intercalated into the high-capacity material). In contrast, in a semi-solid negative electrode 150 containing an active material, silicon as a high-capacity material, and an inactive material, the amount of lithium added during prelithiation is used not only by the active material (e.g., in forming an SEI layer) but also by the high-capacity material (e.g., intercalated into the high-capacity material). Additionally, for semi-solid negative electrodes that experience large volume changes during cycling, particle fracture and / or particle aggregation during cycling can expose new surface areas to the electrolyte, further loss of working lithium can occur, and new SEI layers can form on such surfaces.

[0041] Any suitable form of lithium metal can be included in the semi-solid anode 150 and / or the semi-solid cathode 140 for prelithiation. For example, the lithium metal can include lithium metal powder, lithium salts, and / or lithium foil. Furthermore, the lithium metal can have any shape or size, such as a powder, microparticles, nanoparticles, flakes, foil, etc. In some embodiments, the lithium metal can first be deposited on a foil (e.g., copper foil or aluminum foil) or electrode. The semi-solid anode 150 and / or the semi-solid cathode 140 can be deposited on a metal foil or other electrode material and prelithiated from the metal foil or other electrode by diffusion or electroplating prior to assembly of the electrochemical cell 100.

[0042] The lithium metal used for prelithiation can be mixed with the semi-solid anode 150 and / or semi-solid cathode 140 suspension during the preparation of the suspension. The lithium metal can have one or more coatings or treatments to protect it from the ambient environment, so that the lithium metal does not react with ambient moisture during the mixing process. For example, the lithium metal can be treated with CO or coated with Al-Li to protect it from reacting with the environment. Once mixed, the electrolyte included in the semi-solid anode 150 and semi-solid cathode 140 formulation can protect the lithium metal from reacting with the environment. In some embodiments, a coating on the lithium metal can be formulated to dissolve in the electrolyte and allow the lithium metal to interact with components of the semi-solid anode 150 and / or semi-solid cathode (e.g., form an SEI layer on the active material of the semi-solid anode 150).

[0043] In some embodiments, the aforementioned semi-solid anode 150 and semi-solid cathode 140 suspension can be mixed in a batch process, e.g., using a batch mixer, which can include, for example, high shear mixing, planetary mixing, centrifugal planetary mixing, sigma mixing, CAM mixing, and / or roller mixing, with the components added in a specific spatial and / or temporal order. In some embodiments, the semi-solid anode 150 and / or semi-solid cathode 140 suspension can be mixed in a continuous process (e.g., in an extruder) with the components added in a specific spatial and / or temporal order. Once the components of the slurry are properly mixed, solid particles, e.g., ionically conductive polymers, can be further mixed into the semi-solid electrode slurry. In some embodiments, mixing of the slurry can be performed at low temperatures, e.g., below about 25 degrees Celsius (e.g., about 5 degrees Celsius). Once the semi-solid anode 150 and / or semi-solid cathode 140 suspension is cast into a semi-solid electrode, the temperature can be increased, e.g., above about 37 degrees Celsius. In some embodiments, the mixing can be carried out under vacuum, in a moisture-free environment, and / or in an inert gas atmosphere (e.g., N2 or argon).

[0044] Mixing and forming the components of the semi-solid positive electrode 140 and semi-solid negative electrode 150 suspensions generally includes (i) conveying and / or feeding raw materials, (ii) mixing, (iii) conveying the mixed slurry, (iv) spreading and / or extruding, and (v) forming. In some embodiments, multiple steps in the process can be performed simultaneously and / or in the same equipment. For example, mixing and conveying the slurry can be performed simultaneously with an extruder. Each step in the process can include one or more embodiments of that step. For example, each step in the process can be performed manually or with various process equipment. Each step can also include one or more sub-processes and, optionally, inspection steps to monitor process quality.

[0045] In some embodiments, a negative electrode according to the present disclosure is mixed and dispensed via standard methods. The stabilized lithium metal powder is weighted so that the total mass of lithium (excluding the inert stabilizing coating) has a capacity equivalent to the target prelithiation capacity. The lithium powder is selected so that the average particle size is at least one order of magnitude smaller than the target height of the negative electrode. The powder is then spread so that it evenly covers the top surface of the negative electrode. A separator is then lightly pressed onto the top surface of the electrode, and the positive electrode is placed on top of the separator to create a unit cell.

[0046] In some embodiments, the process conditions can be selected to produce a prepared semi-solid positive electrode 140 and / or semi-solid negative electrode 150 whose mixing index is at least about 0.80, at least about 0.90, at least about 0.95, or at least about 0.975. In some embodiments, the process conditions can be selected to produce a semi-solid negative electrode 150 whose electronic conductivity is at least about 10 -6 S / cm, at least about 10 -5 S / cm, at least about 10 -4 S / cm, at least about 10 -3 S / cm, at least about 10 -2 S / cm, at least about 10 -1In some embodiments, the process conditions can be selected to produce a semi-solid positive electrode 140 and / or semi-solid negative electrode 150 suspension whose apparent viscosity at room temperature is greater than or equal to 100 S / cm, at least about 1 S / cm, or at least about 10 S / cm. -1 The process conditions can be selected to produce semi-solid positive electrode 140 and / or semi-solid negative electrode 150 suspensions with a viscosity of less than about 100,000 Pa-s, less than about 10,000 Pa-s, or less than about 1,000 Pa-s. In some embodiments, the process conditions can be selected to produce semi-solid positive electrode 140 and / or semi-solid negative electrode 150 suspensions having two or more properties described herein. Examples of systems and methods that can be used to prepare the semi-solid electrodes described herein are described in U.S. patent application Ser. No. 13 / 832,861, entitled "Electrochemical Slurry Compositions and Methods for Preparing the Same," filed March 15, 2013 (also referred to as the "'861 Application"), the disclosure of which is incorporated herein by reference in its entirety.

[0047] FIG. 2 is a schematic diagram of a method 200 for preparing a prelithiated semi-solid anode, such as semi-solid anode 150 or any other semi-solid anode described herein. Method 200 includes, at 202, combining an active material with lithium metal to form a prelithiated anode material. The active material can include any of the active materials described with respect to semi-solid anode 150, such as graphite. The lithium metal can be in any form, such as lithium metal powder, lithium salt, or lithium foil. Furthermore, the lithium metal can be in any shape or size, such as powder, microparticles, nanoparticles, flakes, foil, etc. In some embodiments, the lithium metal can be deposited on the surface of the active material. For example, lithium metal microparticles or nanoparticles can be deposited on the surface of the active material (e.g., graphite). In some embodiments, the lithium metal mixed with the active material can be in a liquid form. For example, the lithium metal can be in a molten state or dissolved in a suitable solvent to form a solution that can be mixed with the active material. In some embodiments, the lithium metal can have one or more coatings or treatments to protect it from the surrounding environment, so that it does not react with ambient moisture during the mixing process. For example, the lithium metal can be treated with CO or coated with Al-Li to protect it from reaction with the environment. The thickness of the coating can be controlled to reduce the reactivity of the lithium metal. Furthermore, in some embodiments, the coating on the lithium metal can be formulated to dissolve in the electrolyte included in the semi-solid negative electrode formulation, as described herein, thereby allowing the lithium metal to interact with the components of the semi-solid negative electrode, i.e., the active material. By combining the lithium metal with the active material, the lithium metal can form an SEI layer on the surface of the active material, as described herein.

[0048] In some embodiments, a conductive material can be combined with the prelithiated cathode material at 204. The conductive material can include carbon powder, CNTs, or any other conductive material described with respect to the semi-solid anode 150.

[0049] In some embodiments, a high-capacity material can also be combined with the prelithiated negative electrode material at 206. The high-capacity material can be silicon, tin, or any other high-capacity material described with respect to the semi-solid negative electrode 150. The lithium metal contained within the prelithiated negative electrode can also form an SEI layer on the high-capacity material (e.g., silicon). Additionally, ions of the lithium metal can intercalate into the high-capacity material, resulting in expansion of the high-capacity material. In some embodiments, the lithium metal can be combined with a small portion of the total amount of active material and / or high-capacity material contained within the semi-solid negative electrode, such that an SEI layer is formed on a portion of the active material and high-capacity material. Once the SEI layer is formed, the remaining active material and / or high-capacity material can be combined with the prelithiated portion of the active material and / or high-capacity material.

[0050] At 208, an electrolyte is combined with the prelithiated anode material to form a semi-solid anode material. The electrolyte can include any suitable electrolyte, such as any of the electrolytes described with respect to the semi-solid anode 150. The electrolyte can, for example, not only form a semi-solid anode suspension but also short-circuit the active material, conductive material, and / or high-capacity material contained in the semi-solid anode, thereby reducing bends and impedance in the semi-solid anode. Additionally, the electrolyte can dissolve any protective coatings on the lithium metal, shorting the lithium metal to the active material and / or high-capacity material, thereby promoting the formation of an SEI layer.

[0051] Thereafter, at 210, the semi-solid negative electrode material is formed into a semi-solid negative electrode. For example, the semi-solid negative electrode material can be cast, drop-coated, or formed into a semi-solid negative electrode using any suitable method described with respect to the semi-solid negative electrode 150. The formed semi-solid negative electrode can be paired with a positive electrode, such as a semi-solid positive electrode (e.g., the semi-solid positive electrode 140), and included in an electrochemical cell, such as the electrochemical cell 100. Because the pre-lithiated semi-solid negative electrode formed using method 200 already has an SEI layer formed on the active material, little or no lithium is consumed from the positive electrode to form the SEI layer during electrochemical cell formation. As a result, the positive electrode can retain substantially all of its initial capacity (i.e., the capacity before electrochemical cell formation) after the electrochemical cell formation process. Furthermore, if the pre-lithiated semi-solid negative electrode formed using method 200 includes a high-capacity material, lithium metal is already intercalated into the high-capacity material, and the high-capacity material, and thus the pre-lithiated semi-solid negative electrode, are pre-expanded. As such, the prelithiated negative electrode swells only negligibly during the electrochemical cell formation process, which substantially reduces mechanical damage to the semi-solid negative electrode due to swelling, prevents reduction in cell voltage and / or capacity (e.g., electrode breakage and / or "capacity fade"), and can improve the performance and extend the operating life of the prelithiated semi-solid negative electrode and, therefore, the electrochemical cell.

[0052] The following examples demonstrate the electronic performance of prelithiated negative electrodes prepared using the methods described herein and prelithiated negative electrodes. These examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. [Example]

[0053] Example 1: Prelithiation of a semi-solid negative electrode using lithium-coated copper foil In this example, a semi-solid negative electrode was prelithiated with lithium-coated copper foil. The semi-solid negative electrode was prepared by mixing approximately 50% by volume of mesophase graphite powder (MGP-A, available from China Steel Chemical Corporation) as the active material with approximately 2% by volume of carbon black (C45, available from Timcal) as the conductive material and approximately 48% by volume of electrolyte. The electrode contained a 30:70 ratio of ethylene carbonate (EC) and gamma-butyl lactone (GBL), approximately 1.1 mol of LiBF4, approximately 2% by weight of vinylene carbonate (VC), approximately 1.5% by weight of LiBOB, and approximately 0.5% by weight of tris(2-ethylhexyl)phosphate (TOP). The components of the semi-solid negative electrode were mixed in a RESODYN® mixer for approximately 12 minutes. The semi-solid negative electrode was deposited on both sides of lithium-coated copper foil, which also served as the negative electrode current collector. The semi-solid negative electrode was paired with a semi-solid positive electrode. The semi-solid positive electrode contained approximately 50% by volume of LFP as the active material, approximately 0.8% by volume of Ketjen black as the conductive material, and approximately 49.2% by volume of electrolyte, the same electrolyte used to prepare the semi-solid negative electrode suspension. The components of the semi-solid positive electrode were mixed for approximately 90 seconds in a speed mixer at approximately 1,250 rpm. A pre-lithiated electrochemical cell was prepared by placing the semi-solid positive electrode on one side of a current collector and pairing it with a semi-solid negative electrode, with a spacer placed between them. Since the negative electrodes were placed on both sides of the lithium-coated copper foil, two positive electrodes were prepared and paired with a semi-solid negative electrode placed on each side of the lithium-coated copper foil. The pre-lithiated electrochemical cell was placed in a vacuum-sealed pouch and stored under dry conditions for 3 days to allow the negative electrode to pre-lithiate with lithium metal placed on the lithium-coated copper foil.

[0054] Figure 3 shows a test semi-solid anode, prepared using the same process as the semi-solid anode described herein, peeled from the lithium metal-coated copper foil after three days of storage in a vacuum-sealed pouch. The portion of the lithium metal-coated copper foil on which the test semi-solid anode was placed was completely devoid of lithium after the anode was peeled off, revealing the copper underneath. This indicates that the lithium metal placed on the portion of the copper foil in contact with the test semi-solid anode diffused into the test semi-solid anode and / or reacted with the graphite contained therein, presumably forming an SEI layer on the graphite, thus prelithiating the semi-solid anode.

[0055] The standard electrochemical cell was fabricated in exactly the same manner as the prelithiated electrochemical cell, except that the negative electrode current collector comprised bare copper foil that was not coated with lithium metal, and therefore the semi-solid negative electrode of the standard electrochemical cell was not prelithiated.

[0056] Electrochemical testing was performed on the prelithiated electrochemical cell containing the prelithiated semi-solid negative electrode to determine the electronic performance of the electrochemical cell. The electrochemical cell was subjected to two cycles at a C-rate of C / 10 and ten cycles at a C-rate of C / 4. The testing was performed using a MACCOR® Battery Tester.

[0057] FIG. 4A shows a graph of voltage versus capacity for a prelithiated electrochemical cell and a standard electrochemical cell after one charge / discharge cycle, and FIG. 4B shows a graph of different capacities (dQ / dV) versus capacity for the prelithiated and standard electrochemical cells obtained from FIG. 4A. The coulombic efficiency of the prelithiated electrochemical cell was about 96.6%, and the coulombic efficiency of the standard electrochemical cell was about 88.2%. As can be seen from FIGS. 4A and 4B, the prelithiated electrochemical cell charges substantially faster than the standard electrochemical cell. The final capacity retained by the prelithiated electrochemical cell is slightly lower than that of the standard electrochemical cell, but this is due to poor cell quality and data variation. One explanation is that the semi-solid anode is placed on a lithium-coated copper foil current collector, and the portion of the lithium that contacts the semi-solid anode is inserted into the semi-solid anode material, pre-lithiating the semi-solid anode, so that the copper foil placed underneath the lithium metal comes into contact with the pre-lithiated semi-solid anode. However, this contact can be of poor quality, which can reduce the overall charge capacity of pre-lithiated electrochemical cells fabricated using the lithium-coated copper foil approach.

[0058] Figure 5A shows a graph of the coulombic efficiency of the prelithiated electrochemical cell after eight cycles, and Figure 5B shows a graph of the capacity retained by the prelithiated electrochemical cell after eight cycles. The prelithiated electrochemical cell retained about 96% of its initial coulombic efficiency and about 72% of its initial capacity after eight cycles. This is again due to the poor quality of the prelithiated electrochemical cell, which is caused by poor electrical contact between the prelithiated semi-solid negative electrode and the copper foil negative electrode current collector after the lithium metal coating reacts with the semi-solid negative electrode active material and is incorporated into the semi-solid negative electrode.

[0059] Example 2: Prelithiation by mixing lithium powder in a semi-solid negative electrode suspension In this example, lithium powder was introduced into the semi-solid anode during the preparation of the semi-solid anode suspension to prelithiate the anode. The semi-solid anode suspension was prepared in the same manner as the semi-solid anode described in Example 1. The semi-solid anode was mixed with lithium powder and stored for one day. The amount of lithium powder mixed with the semi-solid anode suspension was such that the lithium powder capacity accounted for approximately 15% of the total charge capacity (including that of the graphite) contained in the semi-solid anode. Figure 6A shows an optical image of a semi-solid anode to which lithium powder was added but not mixed into the semi-solid anode suspension. The semi-solid anode suspension appears wet, indicating that lithium metal has not reacted with the active material of the semi-solid anode, i.e., graphite. Figure 6B shows the semi-solid anode suspension after mixing and storage for one day. The semi-solid anode suspension appears dry after one day, indicating that lithium has reacted with the graphite, possibly forming an SEI layer on the graphite.

[0060] Tables 1-6 below provide exemplary electrode component parameters according to some embodiments of the present disclosure, along with calculations of the theoretical percentage of lithium present in a prelithiated semi-solid negative electrode before application of current under various conditions. Table 1 provides exemplary parameters and calculations for a negative electrode formulation in which one active material (mesofase-based graphite powder (MGP-A)) is used and the lithium content is sufficient to fully "prelithiate" (i.e., compensate for conventional SEI formation) without additional "buffer" or excess capacity from excess intercalated lithium. Table 2 provides exemplary parameters and calculations in which one active material (MGP-A) is used and the percentage of lithium is calculated to include a 5% buffer (i.e., the graphite is charged approximately 5% before cell assembly and / or cycling). Tables 3 and 4 include similar parameters and calculations to those in Table 2, but for buffer percentages of 50% and 100%, respectively. Table 5 shows exemplary parameters and calculations for an anode formulation where two active materials (MGP-A and soft carbon) are used and calculated to include a buffer with a lithium percentage of 5%. Table 6 shows exemplary parameters and calculations for an anode formulation where two active materials (MGP-A and silicon, a high capacity material) are used and calculated to include a buffer with a lithium percentage of 5%.

[0061] [Table 1]

[0062] [Table 2]

[0063] [Table 3]

[0064] [Table 4]

[0065] [Table 5]

[0066] [Table 6]

[0067] While various embodiments of systems, methods, and apparatus have been described above, it should be understood that they are presented by way of example only, and not by way of limitation. While the methods and steps described above depict certain events occurring in a particular order, those skilled in the art will recognize, with the benefit of this disclosure, that the order of certain steps may be changed and that such changes would also be in accordance with variations of the invention. In addition, some of the steps may be performed sequentially as well as simultaneously in parallel processing processes where possible, as described above. While embodiments have been specifically shown and described, it will be understood that various changes in form and detail may be made.

Claims

1. 1. A method for preparing a prelithiated semi-solid negative electrode, comprising: mixing an active material, lithium metal or a lithium-containing material, and a liquid electrolyte comprising an electrolyte salt to form a prelithiated semi-solid negative electrode material such that a solid electrolyte interface (SEI) layer at least partially forms during the mixing, the lithium metal or the lithium-containing material being in an amount sufficient to provide a buffer for active lithium ions during cycling; storing the prelithiated semi-solid negative electrode material in a dry environment for a period of time sufficient to form the SEI layer on substantially all of the surface of the active material; forming a prelithiated semi-solid negative electrode from the prelithiated semi-solid negative electrode material; A method comprising:

2. 10. The method of claim 1, further comprising combining a conductive material with the prelithiated semi-solid negative electrode material.

3. 10. The method of claim 1, further comprising combining a high capacity material with the prelithiated semi-solid negative electrode material, wherein the high capacity material comprises at least one of tin, silicon, antimony, aluminum, titanium oxide, and / or an oxide or alloy of tin, silicon, or antimony.

4. The method of claim 1 , wherein the active material is graphite.

5. the prelithiated semi-solid negative electrode comprises 1% to 50% by volume of a high capacity material; The method of claim 1 , wherein the high capacitance material comprises at least one of tin, silicon, antimony, aluminum, titanium oxide, and / or an oxide or alloy of tin, silicon, antimony, or aluminum.

6. 10. The method of claim 1, wherein the liquid electrolyte comprises at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, propylene carbonate, gamma butyrolactone, or combinations thereof.

7. A method for producing a negative electrode, comprising: preparing an anode mix by mixing an active material, a conductive material, a liquid electrolyte including an electrolyte salt, and lithium metal and / or a lithium-containing material such that a solid electrolyte interface (SEI) layer is at least partially formed during the mixing; storing the negative electrode mixture in a dry environment for a period of time sufficient to substantially prelithiate the negative electrode mixture before it is incorporated into an electrochemical cell and to form the SEI layer on substantially all of the surfaces of the active material; A method comprising:

8. The method of claim 7 , wherein the active material comprises 20% to 90% by volume of the negative electrode mixture.

9. 8. The method of claim 7, wherein the liquid electrolyte comprises 10% to 70% by volume of the negative electrode mixture.

10. The method of claim 7, wherein the conductive material comprises between 0% and 25% by volume of the conductive material.

11. 8. The method of claim 7, wherein the liquid electrolyte comprises at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, propylene carbonate, gamma butyrolactone, or combinations thereof.

12. 8. The method of claim 7, wherein the anode mix further comprises a high capacity material comprising at least one of tin, silicon, antimony, aluminum, titanium oxide, and / or an oxide or alloy of tin, silicon, antimony, or aluminum.

13. 1. A method of manufacturing an electrochemical cell, comprising: A process for assembling a cell stack, mixing an anode mixture including an active material, a conductive material, a liquid electrolyte including an electrolyte salt, and a lithium carrier material so as to at least partially form a solid electrolyte interface (SEI) layer; placing a separator membrane over the negative electrode mixture; placing a positive electrode on the separator film; and storing the cell stack in a dry environment for a period of time sufficient to substantially prelithiate the negative electrode mixture prior to cycling and to form the SEI layer on substantially all of the surfaces of the active material; A method comprising:

14. 14. The method of claim 13, wherein the storage period is sufficient to form a solid electrolyte interface (SEI) on substantially all of the surface of the active material.

15. The method of claim 13, wherein the active material comprises 20% to 90% by volume of the negative electrode mixture.

16. 14. The method of claim 13, wherein the anode mix further comprises a high capacity material comprising at least one of tin, silicon, antimony, aluminum, titanium oxide, and / or an oxide or alloy of tin, silicon, antimony, or aluminum.

17. The assembling step includes: Further active materials and a further conductive material; and More electrolytes and Lithium in an amount sufficient to improve the stability of the positive electrode; preparing a positive electrode mix comprising: forming a positive electrode from the positive electrode mixture; 14. The method of claim 13, further comprising:

18. 14. The method of claim 13, wherein the liquid electrolyte comprises at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, propylene carbonate, gamma butyrolactone, or combinations thereof.

19. 14. The method of claim 13, wherein the liquid electrolyte comprises 10% to 70% by volume of the negative electrode mixture.

Images