Systems and methods for prelithiated electrodes for electrochemical cells

Abstract

Aspects of the present disclosure relate to prelithiating electrodes of electrochemical cells to counteract lithium loss when the electrochemical cells are formed and cycled. One embodiment includes a method including the steps of: a) providing an electrode composite having lithium ion conductivity and diffusivity, the electrode composite including a silicon-containing material, a carbon-based conductive additive, a solid electrolyte, and a binder; b) disposing a thin continuous layer of lithium in proximity to the electrode composite; and c) pressure laminating the thin continuous layer of lithium to the electrode composite. This process transfers lithium to the solid electrode composite by contacting a lithium metal film with the electrode composite without the use of a liquid medium traditionally used to aid in lithium ion transfer.

Description

[Technical field]

[0001] Various aspects described herein relate to the field of solid state primary and secondary electrochemical cells, electrodes and electrode materials, electrolytes, and electrolyte compositions, and corresponding methods of making and using the same.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS This Patent Cooperation Treaty (PCT) application is related to and claims priority to U.S. Provisional Application No. 63 / 265,669, "Prelithiated Negative Electrodes for Electrochemical Cells and Method for Making Same," filed on December 17, 2021, the entire contents of which are hereby incorporated by reference in their entirety for all purposes. [Background technology]

[0003] The ever-increasing number and diversity of mobile devices, the evolution of hybrid / electric vehicles, and the development of Internet of Things devices (IoT) are driving a greater need for battery technologies with improved reliability, capacity (Ah), thermal properties, life span, and rechargeability. Summary of the Invention

[0004] Currently, lithium solid-state battery technology offers potential increases in safety, packaging efficiency, and enables new high-energy chemistries compared to other types of batteries, but improvements in lithium battery technology and other solid-state battery technologies are needed.

[0005] Aspects of the present disclosure have been conceived with these observations in mind, among others. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 illustrates the fabrication of a prelithiated electrode using a calendar press, according to an embodiment of the present disclosure. [Figure 2A]FIG. 2A is a simplified cross-section of a pre-lithiated electrode for an electrochemical cell according to an embodiment of the present disclosure. [Figure 2B] FIG. 2B is a simplified cross-section of a pre-lithiated electrode for an electrochemical cell according to an embodiment of the present disclosure. [Diagram 3] FIG. 3 is a flow chart of a method for prelithiation of an electrode composite for an electrochemical cell according to an embodiment of the present disclosure. [Figure 4] FIG. 4 illustrates the fabrication of a pre-lithiated electrode using a calendar press and peeler apparatus according to an embodiment of the present disclosure. [Diagram 5] FIG. 5 shows a graph of discharge capacity versus cycle number for an electrochemical cell including both a first prelithiated anode and a first non-prelithiated anode. [Figure 6] FIG. 6 shows a graph of discharge capacity versus cycle number for an electrochemical cell containing both a second prelithiated anode and a second non-prelithiated anode. [Figure 7] FIG. 7 shows a graph of discharge capacity versus cycle number for electrochemical cells including a first prelithiated anode, a second prelithiated anode, and a non-prelithiated anode. [Figure 8] FIG. 8 shows a representative cross-section of an electrode stack through a process for forming a pre-lithiated electrode for an electrochemical cell including a carrier foil adjacent to a lithium layer according to an embodiment of the disclosure. [Figure 9] FIG. 9 shows a representative cross-section of an electrode stack through a process for forming a pre-lithiated electrode for an electrochemical cell that includes a passivation layer, according to an embodiment of the present disclosure. [Figure 10] FIG. 10 illustrates a cross-section of an electrochemical cell according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Aspects of the disclosure relate to electrochemical electrode materials, assemblies, and processes for improving the energy density and cycle life of an electrochemical cell by providing a reservoir of lithium ions within an electrode (such as an anode of an electrochemical cell) to mitigate lithium loss as the electrochemical cell is cycled (also referred to herein as "prelithiation" of the electrode). Thus, in some implementations, the disclosure relates to a method of synthesizing a prelithiated electrode composite for an electrochemical cell. The method includes: (a) providing an electrode composite having lithium ion conductivity and diffusivity, the electrode composite including a silicon-containing material, a carbon-based conductive additive, a solid electrolyte, and a binder; (b) disposing a thin continuous layer of lithium in proximity to the electrode composite; and (c) press laminating the thin continuous layer of lithium to the electrode composite.

[0008] Another aspect of the disclosure relates to a method of making a battery electrode that can include placing a successive layer of lithium adjacent to an electrode composite of an electrode stack and pressing the successive layer of lithium against the electrode composite to prelithiate the electrode composite with at least a portion of the successive layer of lithium.

[0009] Another aspect of the present disclosure relates to a solid-state electrochemical cell that can include a first electrode, a solid-state electrolyte adjacent to the first electrode, and a second electrode adjacent to the solid-state electrolyte, where the second electrode is prelithiated by dry lamination of successive layers of lithium to the second electrode composite.

[0010] Yet another aspect of the present disclosure relates to a method of making a battery electrode, which may include compressing an electrode stack including an electrode composite, a current collector, and a continuous layer of lithium adjacent the electrode composite, where at least a portion of the continuous layer of lithium is absorbed by the electrode composite during compression to prelithiate the electrode composite.

[0011] In some embodiments, the electrodes can be prelithiated using a pressure lamination process with a pressure ranging from 1,500 to 100,000 psi. In another embodiment, the lamination pressure is maintained for a duration of 0.01 to 600 minutes. In yet another embodiment, following a pressure lamination process with a duration of 0.01 to 600 minutes, the lamination pressure is removed for a duration ranging from 1 to 60 minutes.

[0012] In one embodiment, the laminated layer of lithium has a thickness in the range of 0.1 to 20 microns.

[0013] In one embodiment, the laminated layers of lithium include a lithium alloy.

[0014] In one embodiment, stacked layers of lithium are deposited on a support (carrier), which may include copper foil.

[0015] In yet another embodiment, the method further comprises removing the carrier foil from the pre-lithiated electrode composite.

[0016] In one embodiment, the pressure lamination is carried out at a temperature in the range of 0-180°C.

[0017] In one embodiment, the method further comprises monitoring the state of lithiation during the pressure lamination process.

[0018] In one embodiment, the pressure lamination is carried out via a roll-to-roll calendar apparatus. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present disclosure can be understood by reference to the following detailed description in conjunction with the drawings, which are briefly described below: It should be noted that for clarity of illustration, certain elements in the drawings may not be drawn to scale.

[0020] Detailed Description Aspects of the present disclosure relate to prelithiating an electrode of an electrochemical cell (such as the anode of the cell) to mitigate lithium loss that may occur when the electrochemical cell is cycled. Conventional electrode lithiation techniques in conventional liquid electrolyte electrochemical cells include performing a formation step during an initial cycle or cycles of an assembled cell. During formation, lithium migrates from the cathode of the cell through the electrolyte to the anode during one or more formation cycles involving charging and discharging. However, due to the chemical composition of the components of the electrochemical cell, some of the lithium ions deposited in the anode are lost, which is often referred to as the first cycle efficiency of the electrochemical cell. The lithium loss that occurs during the formation step reduces the overall efficiency of the electrochemical cell; because the number of lithium ions that migrate through the electrolyte during discharge has a direct impact on the efficiency of the cell.

[0021] The present disclosure describes a method and system for prelithiation of an electrode composite for a solid-state lithium-ion electrochemical cell. In general, the method can include transferring lithium to an electrode of an electrochemical device to prelithiate the electrode with lithium. In some cases, a thin (typically <10 microns) film of lithium metal can be used as the lithium source. The lithium is transferred to the solid electrode composite by contacting the lithium metal film with the electrode composite. This process is performed on the electrode prior to assembly into a solid cell. Furthermore, this process does not require a liquid electrolyte or, more generally, the use of a liquid medium that is traditionally used to aid in the migration of lithium ions in liquid electrolyte cells. The film may be pressed against the electrode. In one example, the system includes a calendering process in which the film is pressed against the electrode, which promotes the migration of lithium from the metal film to the electrode. Advantageously, the solid electrode composite can contain a solid electrolyte, which can be a good conductor of lithium ions without the liquid. This property of the solid electrode composite enables a unique, rapid, dry process for prelithiation that supports the scalability of uniform prelithiation over large areas.

[0022] In one embodiment, the method can include: (a) providing an electrode composite (e.g., an anode) having lithium ion conductivity and diffusivity; (b) disposing a thin continuous layer of lithium adjacent to the electrode composite; and (c) pressure laminating the thin continuous layer of lithium to the electrode composite.

[0023] 1 is a diagram 100 illustrating a system for manufacturing a pre-lithiated electrode 102 using a calendar press apparatus 104 according to an aspect of the disclosure. While an embodiment including a calendar press is described, other mechanisms for forcing lithium into the electrode are possible, such as hydraulic presses, mechanical presses, pneumatic presses, electromechanical presses, or other types of presses. In one implementation, the pre-lithiated electrode 102 can include an electrode composite 106, a metal current collector 108, and a lithium-containing layer 110. It should be noted that the electrode used in the cell includes an electrode composite pre-lithiated with lithium from the lithium-containing layer and a current collector, with it being recognized that the lithium-containing layer is eventually removed.

[0024] In some embodiments, the electrode composite 106 may include, for example, a composite material that includes an active material made of silicon metal, a solid electrolyte material, a carbon-based conductive additive, and one or more polymers as a binder. The current collector layer 108 may include a thin metal foil, such as copper or stainless steel. The lithium-containing layer 110 may be a source of lithium metal or lithium metal alloy and includes a thin sheet or foil. In some cases, the lithium-containing layer 110 may be lithium metal or an alloy deposited on a support material, such as copper foil or other material, where the lithium does not alloy with the support material. The electrode composite 106 may also be coated on a thin support film, such as copper foil or other material, in some cases. More or fewer layers, including other combinations and compositions of layers, may be used for other types of electrodes. Additionally, the electrodes described herein may be the negative (or anode) or positive (or cathode) electrodes of an electrochemical device.

[0025] To produce the prelithiated electrode 102, the layers described above may be fed through a calendar press apparatus 104 in a lithium-electrode-current collector layer stack. In some implementations, the prelithiated electrode 102 may have an electrode-lithium-current collector layer stack. Various prelithiated electrode stacks are described in more detail below with reference to FIGS. 2A-2B. The calendar press 104 may include a first roller 114 and a second roller 116 between which the prelithiated electrode 102 may pass. The opposing cylindrical surfaces of each roller 114, 116 apply a compressive clamping force to the prelithiated electrode 102 to press the layers together. In one implementation, pressure applied to the stack 102 may cause at least a portion of the lithium layer to be absorbed into the electrode layer 106, thereby prelithiating the electrode layer. Prelithiation of the electrode layer via pressure applied to the stack may modify or eliminate the conventional formation steps described above. In other words, the electrode 106 can be prelithiated with lithium ions such that the conservation of said lithium ions within the electrochemical device is maintained during charging and discharging of the electrochemical device.

[0026] The pressure applied to the stack 102 may be correlated to the spacing 118 between the first roller 114 and the second roller 116, among other factors such as the temperature of the stack. The spacing may be fixed or adjustable, as the case may be, and may be adjustable by the controller. For example, the controller may increase or decrease the distance between the rollers 114, 116 to ensure prelithiation of the electrode layer 106 with the lithium-containing layer 110. For example, a thicker lithium-containing layer 110 and / or electrode layer 106 may correspond to an increase in the spacing between the calendar press rolls 114, 116. A thinner electrode stack 102 layer may correspond to a decrease in the spacing between the calendar press rolls. In some cases, the spacing of the calendar press 104 may be adjustable based on feedback information received from the rollers 114, 116 or other sensor elements related to the production of the prelithiated electrode 102 (force measurements, layer thickness measurements, layer temperatures, etc.).

[0027] 2A and 2B are simplified cross-sections of an exemplary electrode stack 102 for an electrochemical cell before pressing. After pressing, at least a portion of the lithium from the lithium-containing layer may be absorbed into the electrode composite layer, thereby prelithiating the electrode composite layer. The exemplary electrode 200 of FIG. 2A includes a current collector 210, an electrode composite 220, and a lithium-containing layer 230 stacked in a current collector-electrode-lithium configuration. The exemplary electrode 250 of FIG. 2B includes a current collector 260, an electrode composite 280, and a lithium-containing layer 270 in a current collector-lithium-electrode configuration. Electrodes 200 and 250 are similar but differ in the arrangement of layers, specifically the relative arrangement of the lithium-containing layers. However, in either case, the lithium-containing layer may be adjacent to an electrode layer such that lithium ions from the lithium-containing layer may be absorbed into the electrode composite layer either before, during, or after calendaring of the stack. In particular, while a portion of the lithium ions of the lithium-containing layer may be absorbed into the electrode composite layer upon contact, calendaring may aid in further dispersing the lithium ions throughout the electrode composite layer.

[0028] In some implementations, the current collectors 210 and 260 can be thin metal foils such as copper or stainless steel. The electrode composites 220 and 280 can be composites including, for example, an active material made of silicon metal, a solid electrolyte material, a carbon-based conductive additive, and one or more polymers as binders. The composition of the electrode composites 220, 280 generally provides the composites with sufficiently high ionic and electronic conductivity to support rapid lithiation of the composites, particularly silicon-based materials. Since silicon materials can expand up to 300% of their original unlithiated volume as they are lithiated, one or more polymers and / or one or more binders can be used to support continued cohesion of the composites during prelithiation. The electrode composites 220, 280 can be formulated to support the desired ionic and electronic conductivity, structural integrity to withstand stacking process pressures of up to 100,000 psi, as well as the expansion and contraction that the electrode composites will experience during cycling during use of an electrochemical cell in which the electrode composites are included.

[0029] The electrode composite 220, 280 may generally include silicon or its compounds, a carbon-based conductive additive, a solid electrolyte, and / or a binder material. Proportionately and in one example, the electrode composite 220, 280 may include at least 30% by weight of silicon or its compounds; 0% to 15% by weight of a carbon-based conductive additive; 0% to 70% by weight of a solid electrolyte; and 0% to 20% by weight of a binder. In the exemplary electrode composite 220, 280, the solid electrolyte may be completely absent apart from the active material (Si), the conductive additive (carbon), and the binder (polymer / binder).

[0030] More specifically, the silicon or silicon compounds contained in the electrode composite 220, 280 can include elemental silicon, silicon dioxide, coated silicon, and coated silicon dioxide. Coatings for silicon or silicon compounds include carbon-based shells, oxides of Al. 2 O 3 , ZrO 2 The oxide-based shell is Li, and the sulfide-based shell is Li. 2S, a sulfide-based shell, or Li 3 P.S. 4 , Li 7 P 3 S 11 , or Li 6 P.S. 5 The electrolyte may include a sulfide electrolyte such as Cl. As described herein, the occurrence and persistence of the morphological changes in the composite depends on the volume expansion of the silicon-based material and the cohesive retention of the binder. To support the volume expansion and similar chemical compatibility, other materials that exhibit similar volume expansion to silicon can be substituted for silicon. Germanium (Ge) and tin (Sn) undergo similar volume expansion by the lithiation process, with Ge expanding by about 280% and Sn expanding by about 257%. These materials or other intercalation-based materials may be substituted, fully or partially, for silicon-based materials.

[0031] Binders or polymers useful for inclusion in the electrode composite 220, 280 may be one or more fluorine-containing binders, such as polyvinylene difluoride (PVdF). In another embodiment, the binder may contain fluororesins as structural units, such as vinylidene fluoride (VdF), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), and derivatives thereof. Specific examples include homopolymers, such as poly(vinylene difluoride-hexafluoropropylene) copolymers (PVdF-HFP), polyhexafluoropropylene (PHFP), and binary copolymers, such as copolymers of VdF and HFP. In yet another embodiment, the binder may be one or more selected from thermoplastics, such as, but not limited to, polystyrene, polyethylene, polypropylene, polycarbonate, and polyvinyl chloride. In further embodiments, the binder may be one or more selected from a thermoplastic elastomer, such as, but not limited to, styrene-butadiene rubber (SBR), styrene butadiene styrene copolymer (SBS), poly(styrene-isoprene-styrene) copolymer (SIS), poly(styrene-ethylene-butylene-styrene) copolymer (SEBS), polyacrylonitrile (PAN), nitrile-butylene rubber (NBR), polybutadiene, polyisoprene, poly(methacrylate) nitrile-butadiene rubber (PMMA-NBR), etc. In yet another embodiment, the binder may be an acrylic resin, such as, but not limited to, one or more selected from polymethyl methacrylate (meth)acrylate, polyethyl (meth)acrylate, polyisopropyl (meth)acrylate, polyisobutyl (meth)acrylate, polybutyl (meth)acrylate, and combinations thereof. Any particular binder or combination and its concentration within the composite can be adjusted to support overall uniform segmentation and fracture generation, as well as long term cohesion of the composite under cycling to ensure electron / ion mobility. Binder selection also supports adhesion of the composite to the current collector and in part determines the rheological properties of the slurry.

[0032] The carbon-based conductive additive of the electrode composite 220, 280 may be one or more of vapor grown carbon fiber (VGCF), carbon black, acetylene black, activated carbon, furnace black, carbon nanotubes, Ketjen black, graphite such as natural or synthetic graphite, and graphene. The carbon-based conductive additive cooperates with the solid electrolyte material to regulate the distribution of electrons throughout the volume of the composite, thereby uniformly distributing the charge density throughout the composite.

[0033] The solid electrolyte is Li 2 SP 2 S 5 , Li 2 SP 2 S 5 - LiI, Li 2 SP 2 S 5 -LiBr, Li 2 SP 2 S 5 -LiCl, Li 2 SP 2 S 5 -GeS 2 , Li 2 SP 2 S 5 -Li 2 O, Li 2 SP 2 S 5 -Li 2 O-LiI, Li 2 -P 2 S 5 -LiI-LiBr, Li 2 S-SiS 2 , Li 2 S-SiS 2 - LiI, Li 2 S-SiS 2 -LiBr, Li 2 SS-SiS 2 - LiI, Li 2 SS-SiS 2 -B 2 S 3 - LiI, Li 2 SS-SiS 2 -P 2 S 5-LiI, Li 2 S-B 2 S 3 、Li 2 S-P 2 S 5 -ZnSn (where m and n are positive numbers, and Z is Ge, Zn, or Ga), Li 2 S-GeS 2 、Li 2 S-S-SiS 2 -Li 3 PO 4 、及びLi 2 S-S-SiS 2 -Li x MO y (where x and y are positive numbers, and M is P, Si, Ge, B, Al, Ga, or In). Specific exemplary electrolyte materials are Li 3 PS 4 、Li 4 P 2 S 6 、Li 6 PS 7 、Li 7 P 3 S 11 、Li 10 GeP 2 S 12 、Li 10 SnP 2 S 12 may be one or more of these. In another embodiment, the electrolyte material is Li 6 PS 5 Cl, Li 6 PS 5 Br, Li 6 PS 5 I, or Li 7-y PS 6-y X y may be one or more of these, where "X" represents at least one halogen element and / or pseudohalogen, 0 < y ≤ 2.0, the halogen may be one or more of F, Cl, Br, I, and the pseudohalogen is N, NH, NH 2 、NO、NO 2 、BF 4 、BH 4 、AlH 4In yet another embodiment, the electrolyte material may be one or more of Li 8-y-z P 2 S 9-y-z X y W z where "X" and "W" represent at least one halogen element and / or pseudohalogen, with 0≦y≦1 and 0≦z≦1, the halogen may be one or more of F, Cl, Br, I, and the pseudohalogen may be one or more of N, NH, NH 2 , NO, NO 2 , B.F. 4 , B.H. 4 , AlH 4 In a further embodiment, the electrolyte material may be one or more of Li 4 P.S. 4 X, Li 4 GeS 4 X, Li 4 SbS 4 X, and Li 4 SiS 4 X, where "X" represents at least one halogen element and / or pseudohalogen, where halogen can be one or more of F, Cl, Br, I, and pseudohalogen can be one or more of N, NH, NH 2 , NO, NO 2 , B.F. 4 , B.H. 4 , AlH 4 The solid electrolyte material may be one or more of: CN, CN, and SCN. When mixed with a binder, the solid electrolyte material can form a flexible matrix. The carbon additive and silicon-containing material can then be suspended in this matrix. The flexible matrix provides the composite with the ability to maintain interparticle contact while the silicon-containing material expands and contracts under cycling.

[0034] The lithium-containing layer 230, 270 may be a source of lithium metal or lithium metal alloy in the form of a thin sheet or foil. The layer 230, 270 may also be lithium metal or alloy deposited on a support material, such as copper foil or other material, where the lithium does not alloy with the support material. In one example, the lithium-containing layer 230, 270 may be a layer of lithium ranging from 0.1 to 35 μm (microns) thick on a layer of copper foil as a support. In some specific implementations, the lithium-containing layer 230, 270 may be a layer of lithium ranging from 0.1 to 20 microns thick. In some examples, the lithium may be laminated to the electrode composite 220, 280 by applying pressure ranging from 4000 to 8000 psi, such as via the calendar press 140 described above. Additionally, this configuration limits the extrusion of lithium outside the original boundaries of the interface between the electrode composite 220, 280 and the lithium layer 230, 270 during the pressure lamination process. An additional advantage of using a carrier for the lithium is that the attachment or reaction of the lithium to the device applying the lamination force can be limited. For example, a carrier foil for the lithium-containing layer 230, 270 can prevent the upper roller 114 or the lower roller 116 of the calendar press 104 during the lamination process of the stack 102. After lithiation of the electrode composite layer 220, 280, the carrier foil may be free of lithium metal, and the carrier foil can be removed from the surface of the lithiated electrode composite without damaging the electrode. In some embodiments, the lithiation of the electrode composite layer 220, 280 can remove substantially all of the lithium from the carrier. For example, after prelithiation, 99% or more of the lithium from the carrier migrates to the electrode, so that 1% or less of the total lithium remains on the carrier. In another embodiment, the carrier foil may contain more than 1% and less than 5% lithium after lithiation of the silicon-containing layer. Thus, in some examples, 95% to 99% of the lithium on the carrier migrates to the electrode. In FIG. 2B, where lithium-containing layer 270 is located between current collector 260 and electrode composite layer 280, the electrode composite can be formed into a slurry and cast / coated onto the film of lithium on copper.The cast layers can then be dried to remove any solvent that was in the slurry and laminated / densified to ensure proper compression of the layers and to initiate the lithiation process.

[0035] FIG. 3 is a flow chart of a method 300 for prelithiation of an electrode composite for an electrochemical cell according to an embodiment of the disclosure. Beginning with operation 302, any necessary or desired preparation of the various layers of the electrode stack 102 described above can be performed, such as, but not limited to, electrode preparation and electrode densification. In one particular example, the electrode composite can be coated onto a carrier foil to form an electrode composite layer 220, 280. In other implementations, the electrode composite layer 220, 280 can be free of a carrier foil. The composition of the electrode composite layer 220, 280 and / or the carrier foil are discussed in more detail above. Additionally, in some examples, the lithium-containing layer 230, 270 can also be coated onto a carrier foil.

[0036] In operation 304, the lithium-containing layers 230, 270 and the electrode composite layers 220, 280 may be contacted. Specifically, the lithium-retaining surfaces of the lithium-containing layers 230, 270 may be contacted with the silicon-containing surfaces of the electrode composite layers 220, 280 to facilitate the lithiation process of the electrode composite layers. After the contact is made, pressure may be applied to the contacted layers to facilitate the lithiation process of the electrode composite layers 220, 280. In one particular embodiment, the contacted layers may be fed through a calendar press apparatus 104 to apply pressure to the electrode stack 102. In some examples, the pressure applied from the calendar 104 may establish a compressive force in the range of 1,000 psi to 150,000 psi such that the lithium of the lithium-containing layers 230, 270 is laminated to and pressed into the surfaces of the electrode composite layers 220, 280. In another example, the pressure may be in the range of 2,000 to 125,000 psi. In a further example, the pressure may range from 3,000 psi to 100,000 psi. In yet another example, the pressure may range from 4,000 psi to 75,000 psi. In yet another example, the pressure may range from 4,500 psi to 50,000 psi. In a further example, the pressure may range from 5,000 to 25,000 psi. Pressure may be applied to the electrode stack 102 unidirectionally to either of the contacted layers or bidirectionally to both contacted layers or intermediate surfaces. In many cases, pressure may be applied mechanically, hydraulically, or pneumatically via any pressing device, which may be uniform or spatially varied, with the calendar device 104 being one example of such a pressing device. Generally, pressures in excess of 1500 psi can enhance the rate of diffusion of lithium into the electrode composite layers 220, 280. This effect is due to increased ionic and electronic conductivity of the electrode composite resulting from greater particle-particle contact between the silicon material, the conductive additive, and the solid electrolyte within the electrode composite layers 220, 280.

[0037] Generally, a higher pressure can be used to ensure uniform contact between the lithium-containing layers 230, 270 and the electrode composite layers 220, 280 to aid in more uniform initial lithiation. Additionally, as the silicon material lithiates, it becomes more ionically conductive. This can increase the ability of lithium to diffuse through the already lithiated silicon near the contacted surfaces between the layers and to begin alloying with the silicon further inside the electrode composite. In this way, lithium can propagate through the electrode composite, allowing for faster lithiation.

[0038] When sufficient compressive force is applied, the silicon in the electrode composite 220, 280 can begin to lithiate to form a silicon-lithium alloy. In some examples, a waiting period may be established to allow lithiation of the electrode composite layer 220, 280 to occur. The waiting period or other parameters of the lithiation process may be predetermined or actively controlled based on monitoring the properties of the electrode composite being lithiated. For example, if the lithium-containing layer 230, 270 is deposited on a transparent substrate, the progress of the reaction may be monitored optically by transmission or reflectance measurements. Lithiation may also be monitored by electrical methods, including but not limited to eddy current sensing and resistivity measurements, to help determine proper lithiation of the electrode composite layer 220, 280.

[0039] Depending on the degree of lithiation, the thickness of the layers, and the pressure, lithiation can occur in the range of 1 to 600 minutes. In some embodiments, the electrode stack 102 may be under pressure for 0.01 to 1 minute to ensure contact between the lithium-containing layers 230, 270 and the electrode composite layers 220, 280, at which point the pressure may be removed. The electrode stack 102 may be left undisturbed for 0.01 to 600 minutes, or until the desired degree of lithiation is reached. In another embodiment, the electrode stack 102 may be under pressure for 0.01 to 600 minutes to ensure contact between the lithium-containing layers 230, 270 and the electrode composite layers 220, 280 and to allow lithiation of the electrodes to occur.

[0040] In one example, the contacted layers may be pressure loaded for a sufficient time such that all of the lithium present in the lithium-containing layer 230, 270 is transferred into the electrode composite layer 220, 280. The thickness of the lithium-containing layer 230, 270 may be selected such that all of the lithium metal in the lithium-containing layer is consumed in the electrode composite layer 220, 280 when a desired level of prelithiation is reached. The electrode composite layer 220, 280 may include both lithiated silicon (silicon-lithium alloy) and non-lithiated silicon (silicon metal), and the ratio of lithiated silicon to non-lithiated silicon may be controlled by how much lithium is introduced to the surface of the electrode composite. Increased reaction times may, in some cases, be substituted with higher pressures, thereby ensuring complete reaction of the lithium metal with the electrode composite layer 220, 280. For example, a similar consumption of lithium may be achieved using approximately 12,000 psi for a duration of 60 seconds, or 8,000 psi for a duration of 180 seconds. Relatedly, using 12,000 psi, lithium consumption can be about 3 microns / minute. Additionally, the above operations of method 300 may occur within an ambient or bed temperature range of about 0-180° C. Although lithiation generally can occur at higher rates at higher temperatures, the above operations may be configured to balance reaction kinetics for lithiation based on reduced processing time and resulting mechanical properties of the prelithiated electrode composite. For example, excessive temperatures may result in very rapid lithiation with reduced mechanical stability (cracking) of the prelithiated electrode composite. Alternatively, temperature ranges of 25-100° C., or 25-75° C. may be used.

[0041] As an alternative to the use of a separate lithium-containing layer 230, 270, a thin film of lithium-containing material may be deposited directly onto the surface of the electrode composite layer 220, 280 using techniques such as vapor deposition (PVD, CVD, ALD). Alternatively, lithium metal may be deposited first onto the solid electrolyte separator layer. The lithium may be transferred from the solid electrolyte separator to the electrode composite layer 220, 280 as the separator is laminated to the electrode composite using applied pressure from a calendar or linear press (discussed in more detail below). Alternatively, the lithium may be in the form of particles such as SLMP (stabilized lithium metal powder). This SLMP may be mixed into the electrode composite or coated onto the electrode composite layer.

[0042] If a carrier material, such as copper, was used with the lithium-containing layer 230, 270, the carrier may then be removed from the surface of the electrode stack in operation 308. In some instances, some of the lithium of the lithium-containing layer may remain attached to the carrier material without being absorbed by the electrode composite layer. In such circumstances, removal of the carrier from the surface of the electrode stack may further remove some or all of the remaining lithium-containing layer 230, 270 that was not absorbed during the calendaring process. In operation 310, the exposed pre-lithiated electrode composite layer 220, 280 may be contacted with a separator layer. For example, FIG. 4 is a diagram 400 illustrating the fabrication of a pre-lithiated electrode using a calendar press and a peeler device. Some elements of diagram 400 are similar to those described above with reference to FIG. 1. For example, an electrode stack 102 is shown comprising an electrode composite 106, a metal current collector 108, and a lithium-containing layer 110. The electrode stack 102 may be provided in a lithium-electrode-current collector configuration 200 (as shown in FIG. 2A ) or an electrode-lithium-current collector configuration 250 (as shown in FIG. 2B ). Also, as described above, the electrode stack 102 may be fed through a calendar press apparatus 104, which may prelithiate the electrode layer 106 with the lithium-containing layer 110. The calendar press apparatus 104 may include an upper roller 114 and a lower roller 116, which may press at least a portion of the lithium of the lithium-containing layer 110 into the electrode layer 106, thus transferring a portion of the lithium ions into the electrode layer. As described above in connection with operation 308 of FIG. 3 , any remaining lithium-containing layer 110 may be removed from the stack, although such an operation is not shown in FIG. 4 .

[0043] In any case, the prelithiated stack 406 may be in contact with a separator layer 402, also referred to as a solid electrolyte layer. Generally, the separator layer 402 may be in contact with the exposed surface 410 of the prelithiated electrode composite layer. The separator layer 402 may optionally include a sulfide-based solid electrolyte material and a binder. Additionally, in some implementations, the separator layer 402 may be coated as a thin layer on a carrier film, such as an aluminum foil, although other materials may be used. The separator layer 402 may conduct ions but not electrons during use in a battery cell, such that the separator layer provides electrical insulation for the prelithiated electrode composite layer 410.

[0044] In operation 312, the prelithiated stack 406 having the separator layer 402 in contact with the prelithiated electrode layer 410 may be fed through a second calendar press 404 for further pressing. The pressure applied by the second calendar press 404 may laminate the separator layer 402 to the prelithiated electrode layer 410, at least partially adhering the separator layer to the prelithiated electrode layer. In some implementations, the prelithiated stack 406 may be fed through the first calendar press 104 such that the second press 404 is not required. Nevertheless, the laminated electrode stack 414 including the separator layer 402 may be used in an electrochemical cell as the anode or cathode of the cell. Prelithiating the electrode layer 410 may eliminate the need for the forming steps described above while increasing the efficiency of lithium transfer between the electrodes of an electrochemical cell compared to non-prelithiated electrodes.

[0045] For illustrative purposes and to describe certain embodiments of the present disclosure, examples are described below.However, the scope of claims is in no way limited by the examples described herein.Various changes and modifications to the disclosed embodiments are obvious to those skilled in the art, and such changes and modifications can be made without departing from the spirit of the present disclosure and the technical scope of the appended claims, including but not limited to those related to the chemical structure, substituents, derivatives, preparations, or techniques of the present disclosure.The definitions of variables in the structures in the schemes herein are equivalent to those of the corresponding positions in the formulas presented herein.

[0046] In a first example, an anode was prelithiated according to the systems and methods described herein and then formed into an electrochemical cell containing the prelithiated anode. A comparative non-prelithiated anode was also produced and then formed into an electrochemical cell. The performance of the cell and associated prelithiated anode as well as the cell with the non-prelithiated anode were measured. Table 1 provides comparative information. FIG. 5 shows a graph 500 of discharge capacity 502 versus cycle number 504 of an electrochemical cell containing a prelithiated anode (line 506) and a non-prelithiated anode 508 (line 508). The performance data in Table 1 shows various characteristics of the prelithiated anode (and associated cell) and the non-prelithiated anode (and associated cell) used to generate the results shown in the graph 500 of FIG. 5. In particular, Table 1 shows the weight percent of silicon, the degree of prelithiation, the discharge capacity, the ratio of the area measurement of the anode to the area measurement of the cathode (A:C ratio), the first cycle efficiency (FCE), and the weight percent of solid electrolyte in the anode for each of the prelithiated and non-prelithiated anodes shown in Figure 5. A stack pressure of 1500 PSI was applied during cell cycling for each of the samples.

[0047] [Table 1]

[0048] As can be seen from the cycling data shown in graph 500 and Table 1, the anodes prelithiated using the methods described herein had consistently higher discharge capacities 506 compared to the discharge capacity 508 of anodes that were not prelithiated, all else being equal. Furthermore, the prelithiated anodes also demonstrated better stability at 1500 psi stack pressure and greater than 90% first cycle efficiency compared to similar anodes that were not prelithiated - a more than 5% higher first cycle efficiency.

[0049] FIG. 6 shows a second graph and example of discharge capacity 602 versus cycle number 604 for an electrochemical cell including a prelithiated anode 606 versus a cell including a non-prelithiated anode 608. Table 2, as above, shows various properties of the cell and prelithiated anode and the cell and non-prelithiated anode used to generate the results shown in graph 600 of FIG. 6. A stack pressure of 1500 PSI was applied during the first cell cycle for each of the samples in Table 2. The A:C ratio of the cell in the first example is greater than 1.5, and the A:C ratio of the cell in the second example is less than 1.5 (and greater than 1).

[0050] [Table 2]

[0051] As with the first example, as shown in the cycling data depicted in graph 600, cells including anodes prelithiated using the methods described herein consistently had higher discharge capacities 606 compared to cells having anodes that were not prelithiated. Furthermore, the prelithiated anodes also exhibited better stability at 1500 psi stack pressure and higher first cycle efficiencies (>93%) compared to similar anodes that were not prelithiated (90.7%).

[0052] A third set of examples is shown in graph 700 of FIG. 7. Here, the graph shows the discharge capacity 702 versus cycle number 704 of electrochemical cells including a first prelithiated anode 706, a second prelithiated anode 708, and a non-prelithiated anode 710, respectively. As shown in Table 3 below, the first prelithiated anode 706 includes 30% prelithiation, the second prelithiated anode 708 includes 15% prelithiation, and the non-prelithiated anode includes 0% prelithiation. Other properties of the prelithiated and non-prelithiated anodes are also shown in Table 3. As above, the stack pressure during the first cell cycle for each of the samples in Table 2 was applied at 1500 psi. In the example of FIG. 7 and Table 3, the A:C ratios are 1.21, 1.13, and 1.24, respectively, for the cells having the first, second, and non-prelithiated anodes.

[0053] [Table 3]

[0054] Graph 700 shows that the cells having the first prelithiated anode 706 and the second prelithiated anode 708 had consistently higher discharge capacity compared to the cell having the non-prelithiated anode 710. Additionally, although the second prelithiated anode 708 had a higher discharge capacity than the first prelithiated anode (136.4 mAh / g compared to 135.3 mAh / g as shown in Table 3), the first prelithiated anode 706 had a more consistent discharge capacity than the second prelithiated anode 708 over the course of cycle 704, ultimately achieving a higher discharge capacity. Thus, a reasonably relatively low initial prelithiation percentage may correspond to a more consistent (or more desirable) electrochemical performance of the anode over the life of the electrochemistry.

[0055] FIG. 8 shows a representative cross-section 800 of an electrode stack from a process for forming a cell using a prelithiated electrode for an electrochemical cell including a carrier foil adjacent to a lithium layer. As explained above, the electrode stack can include a current collector layer 808 adjacent to an electrode composite layer 806, and a lithium-containing layer 804, as shown in step A (810) of the prelithiation process 800. The current collector layer 808, the electrode composite layer 806, and the lithium-containing layer 804 can include materials as described above for each layer. In addition, a carrier layer 802, such as a metal foil, can be adjacent to the lithium-containing layer 804 and can be on the opposite side of the surface of the lithium-containing layer that contacts the electrode composite layer 806. In step B 812, the lithium-containing layer 804 can be placed in contact with the electrode composite layer 806 to initiate prelithiation of the electrode composite layer. As described above, at least a portion of the lithium-containing layer 804 can be absorbed into the electrode composite layer 806, and in some cases, the entire lithium-containing layer can be absorbed by the electrode composite layer, as shown in step 814. In some implementations, prelithiation of the electrode composite layer 806 may include compressing the electrode stack with the lithium-containing layer 804 in contact with the electrode composite 806. During this compression, lithium from the lithium-containing layer 804 alloys with the material of the electrode composite 806, prelithiating the electrode.

[0056] Generally, the carrier layer 802 can protect the freshly lithiated electrode layer 806 from air and moisture, which can degrade the bare electrode surface during and after the lithiation process. Prior to inclusion in an electrochemical cell, the protective carrier layer 802 can be removed from the electrode composite layer 806 by a peeling process, and the remaining layers of the stack can be included as electrodes in an electrochemical cell, as shown in step D816.

[0057] 9 illustrates a representative cross-section 900 of an electrode stack through a process for forming a pre-lithiated electrode for an electrochemical cell that includes a passivation layer. Many of the layers of the electrode stack illustrated in cross-section 900 are the same as those described above with respect to FIG. 8. In particular, the electrode stack can include a current collector layer 908 adjacent to an electrode composite layer 906 and a lithium-containing layer 904 adjacent to a support layer 902. However, in this implementation, the lithium-containing layer 904 can be adjacent to the support layer 902 on one surface and adjacent to a passivation layer 920 on the opposite surface. In some implementations, the passivation layer 920 can be adjacent to the Li 2 CO 3 , Li 2 O, Li 3 In step B912 of the illustrated process, the lithium-containing layer 904 (sandwiched or otherwise disposed between the carrier layer 902 and the passivation layer 920) is contacted with the electrode composite layer 906, with the passivation layer disposed between the lithium-containing layer and the electrode composite layer. In step C, the lithium-containing layer 904 may be absorbed into the electrode composite layer 906 through the passivation layer, as shown in step C914. In particular, during compression of the stack, lithium from the lithium-containing layer 904 diffuses through the passivation layer 920 and alloys with the electrode composite material, resulting in a pre-lithiated electrode layer 906 with the lithium-rich passivation layer 920 positioned above the electrode composite layer. The carrier layer 902 may also remain after lithiation of the electrode composite layer 906 and may be removed from the stack, as shown in step C914. Once the carrier layer 906 is removed, the pre-lithiated electrode remains with a passivation layer 920 covering the outer surface of the electrode 906 opposite the current collector layer 908. This passivation layer 920 may further protect the newly lithiated electrode layer 906 from air and moisture, which can degrade the bare electrode surface during and after the lithiation process.

[0058] The electrode stack including the passivation layer 920 can be used in an electrochemical cell. In particular, FIG. 10 shows a representative cross-section of an electrochemical cell 1000 including a pre-lithiated anode with a passivation layer produced by the process described above. The cell 1000 includes several layers: a cathode current collector 1002, a cathode electrode 1004, a separator layer 1006 (e.g., a solid-state electrolyte (SSE) layer), a passivation layer 1008, a pre-lithiated anode layer 1010, and an anode current collector layer 1012. In this configuration, when assembled into an electrochemical cell, the passivation layer 1008 is between the pre-lithiated anode layer 1010 and the separator layer 1006. In some circumstances, the passivation layer 1020 can prevent the lithiated anode layer 1010 from reacting with the solid electrolyte layer 1006; because the passivation layer remains stable between the anode and the separator layer. In this manner, the protective passivation layer 1020 may be incorporated into an electrochemical cell stack as an additional protective barrier for one or both of the cell's electrodes.

[0059] Referring again to FIG. 9, in some embodiments, a lithium alloy can be used for the lithium-containing layer 904. In this case, the lithium alloying components (sodium, potassium, aluminum, magnesium, calcium, etc.) do not need to be alloyed with the electrode composite material. Instead, only the lithium can be extracted from the lithium alloy to prelithiate the electrode composite layer 904. When all of the lithium is consumed through the lithiation process, what remains is a layer of the other components of the alloy. This layer 920 can remain on the surface of the electrode composite layer 906, similar to a passivation layer. When this anode is assembled into an electrochemical cell, the passivation layer 1008 of FIG. 10 can include a metal alloy layer containing one or more of the metals from the lithium-containing layer 904, e.g., sodium, potassium, aluminum, magnesium, calcium, etc. The metal alloy layer can be located between the anode 1010 and the separator layer 1006. Generally, this metal layer does not alloy with the material of the anode 1010 and can act as a "soft" interface layer between the anode and separator layer 1006 to improve ionic contact between the layers.

[0060] The embodiments of the present disclosure include various steps described herein. The steps may be performed by hardware components or may be embodied in machine-executable instructions that can be used to cause a general-purpose or special-purpose processor programmed with the instructions to perform the steps. Alternatively, the steps may be performed by a combination of hardware, software, and / or firmware.

[0061] Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the above-described embodiments refer to particular features, the scope of the present invention also includes embodiments having different combinations of features and embodiments that do not include all of the features described. Accordingly, the scope of the present invention is intended to embrace all such alternatives, modifications, and variations, together with all equivalents thereof.

[0062] Although specific implementations are described, it should be understood that this is done for illustrative purposes only. Those skilled in the art will recognize that other components and configurations may be used without departing from the spirit and scope of the present disclosure. Thus, the following description and drawings are illustrative and should not be construed as limiting. Numerous specific details are described to provide a thorough understanding of the present disclosure. However, in some cases, well-known or conventional details are not described to avoid obscuring the description. A reference to one or an embodiment in this disclosure may be a reference to the same embodiment or any embodiment, and such a reference means at least one of the embodiments.

[0063] Reference to "one embodiment" or "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the invention. The appearance of the phrase "in one embodiment" in various places in the description is not necessarily referring to the same embodiment, nor are the embodiments mutually exclusive of each other, independent or alternative. Furthermore, various features are described that are exhibited by some embodiments and not by other embodiments.

[0064] The terms used herein generally have their ordinary meaning in the art, within the context of this disclosure and in the specific context in which each term is used. Alternative language and synonyms may be used for any one or more of the terms discussed herein, and no special significance should be placed on whether a term is detailed or discussed herein. In some cases, synonyms of a particular term are provided. The listing of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification, including examples of any term discussed herein, is merely illustrative and is not intended to further limit the scope and meaning of the disclosure or any example term. Similarly, this disclosure is not limited to the various aspects provided herein.

[0065] Although not intended to limit the scope of the present disclosure, examples of instruments, devices, methods, and their related results according to the embodiments of the present disclosure are presented below.Please note that for the convenience of the reader, titles or subtitles may be used in the examples, and this should not limit the scope of the present disclosure in any way.Unless otherwise defined, technical and scientific terms used herein have the meanings that are commonly understood by those skilled in the art to which the present disclosure belongs.In case of conflict, the present specification, including definitions, shall prevail.

[0066] Additional features and advantages of the present disclosure will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the principles disclosed herein. The features and advantages of the present invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the present disclosure will become more fully apparent from the following description and the appended claims, or may be learned by the practice of the principles as described herein.

Claims

1. disposing a continuous layer of lithium adjacent the electrode composite of the electrode stack; and pressing said continuous layer of lithium against said electrode composite to prelithiate said electrode composite with at least a portion of said continuous layer of lithium; A method for producing a battery electrode, comprising:

2. and disposing a separator layer in the electrode stack adjacent to the prelithiated electrode composite, the separator layer comprising a solid electrolyte. The method of claim 1.

3. pressing the continuous layer of lithium against the electrode composite; feeding the electrode stack through a calender press comprising a first roller and a second roller; the first roller is positioned above the second roller and separated by a press gap, the press gap being based on a thickness of at least one layer of the electrode stack; The method of claim 1.

4. The method of claim 1 , wherein the electrode composite comprises a silicon-containing material, a carbon-based conductive additive, a solid electrolyte, and a binder.

5. The method of claim 1 , wherein the successive layers of lithium are pressed onto the electrode composite at a pressure of about 1,500 to 100,000 psi.

6. The method of claim 1, wherein the successive layer of lithium is pressed onto the electrode composite for a duration of 0.01 to 60 minutes.

7. The method of claim 1, wherein the continuous layer of lithium has a thickness in the range of 0.1 to 20 microns.

8. the continuous layer of lithium comprises a lithium alloy; 10. The method of claim 1, wherein at least a portion of the lithium ions of the lithium alloy are transferred to the electrode composite by pressing the continuous layer of lithium against the electrode composite.

9. casting a continuous layer of said lithium onto a carrier foil; and removing the carrier foil from the continuous layer of lithium after pressing the continuous layer of lithium onto the electrode composite; The method of claim 1 further comprising:

10. The method of claim 9 , wherein the carrier foil comprises a copper foil.

11. 10. The method of claim 1, wherein the continuous layer of lithium includes a passivation layer adjacent to the electrode composite, the passivation layer remaining after pressing the continuous layer of lithium against the electrode composite.

12. monitoring a state of lithiation of the electrode composite during the pressing of successive layers of the lithium onto the electrode composite; and adjusting parameters of the impressing of the successive layers of lithium onto the electrode composite based on the monitoring of the state of lithiation of the electrode composite. The method of claim 1 further comprising:

13. A first electrode; a solid electrolyte adjacent to the first electrode; a second electrode adjacent to the solid electrolyte; A solid-state electrochemical cell comprising: the second electrode is prelithiated by dry lamination of a successive layer of lithium onto a second electrode composite; Solid-state electrochemical cells.

14. 14. The solid-state electrochemical cell of claim 13, wherein the second electrode is dry laminated through a calendar press including a first roller and a second roller, the first roller positioned above the second roller and separated by a press gap.

15. 13. The solid-state electrochemical cell of claim 12, wherein at least a portion of the continuous layer of lithium is absorbed into the second electrode composite, thereby prelithiating the second electrode.

16. 13. The solid state electrochemical cell of claim 12, wherein the continuous layer of lithium has a thickness in the range of 0.1 to 20 microns prior to dry lamination processing.

17. 14. The solid-state electrochemical cell of claim 13, wherein the continuous layer of lithium comprises a lithium alloy.

18. 14. The solid-state electrochemical cell of claim 13, wherein the continuous layer of lithium is disposed adjacent a surface of the second electrode composite opposite a current collector.

19. 1. A method for manufacturing a battery electrode, comprising: compressing an electrode stack including the electrode composite, a current collector, and a continuous layer of lithium adjacent to the electrode composite; Including, at least a portion of the successive layers of lithium are absorbed by the electrode composite during said compression, thereby prelithiating the electrode composite; method.

20. 20. The method of claim 19, wherein the continuous layer of lithium of the electrode stack is disposed between the electrode composite and the current collector.

21. 20. The method of claim 19, wherein the electrode composite of the electrode stack is disposed between the successive layer of lithium and the current collector.

22. The method of making a battery electrode as recited in claim 19, wherein the electrode composite comprises prelithiation in the range of 1% to 15%.

23. The method of claim 19, wherein the electrode composite comprises a plelium content in the range of 15% to 30%.

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