Densified vertically lamellar thick battery electrodes via bidirectional freeze-casting method

Abstract

Described are electrodes for use in lithium-ion and lithium metal electrochemical cells, lithium-ion and lithium metal electrochemical cells, and methods of making the electrodes using a bidirectional freeze-casting process. The electrodes described herein include vertical lamellar structures that provide beneficial performance characteristics to the electrochemical cells incorporating the electrodes. The electrodes can be prepared using a slurry that includes a conductive additive, particles of active material, a binder, and a solvent, such as water. The bidirectional freeze-casting process can freeze the slurry to form the vertical lamellar structures as an active material layer on a surface of a current collector. The vertical lamellar structures can define interlamellar channels that facilitate decoupling of lithium-ion transport in interlamellar and intralamellar regions of the electrodes, thereby providing beneficial areal capacity and rate capability performance.

Description

Attorney Docket No.: 093331-14498348180 YU-WO DENSIFIED VERTICALLY LAMELLAR THICK BATTERY ELECTRODES VIA BIDIRECTIONAL FREEZE-CASTING METHOD CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Provisional Application No. 63 / 513,752, filed on July 14, 2023, and U.S. Provisional Application No.63 / 590,263, filed on October 23, 2023, both titled “DENSIFIED VERTICALLY LAMELLAR THICK BATTERY ELECTRODES VIA BIDIRECTIONAL FREEZE-CASTING METHOD,” the contents of which are herein incorporated by reference in their entirety for all purposes. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under Grant no. DE-SC0012673 awarded by the Department of Energy. The government has certain rights in the invention. FIELD

[0003] This application relates to electrode materials, such as in the field of lithium-ion and lithium metal batteries. This application relates generally to an improvement to lithium-ion battery electrodes created using a bidirectional freeze-casting method that forms thick electrodes characterized by lamellar segments defining interlamellar channels that improve charge transport kinetics of the thick electrodes. More specifically, and without limitation, this application relates to electrodes including a series of active material layers in the form of lamellae or thin two- dimensional structures, methods for making such electrodes, and devices or systems incorporating such electrodes. BACKGROUND

[0004] Developing rechargeable batteries with high energy density, long cycle life, and reliable safety is becoming important for facilitating vehicle electrification and sustainable mobility. Among the various types of rechargeable batteries, lithium-ion batteries (LIBs) have dominated the battery markets in portable devices and are regarded as the primary practical candidate for electric vehicles (EVs). Current LIBs are facing challenges associated with physiochemical limits in gravimetric and volumetric capacities falling short of meeting energy and power demands in EVs. Making battery electrodes thicker has been investigated to improve the energy density of LIBs, which is an important consideration for applications with weight or volume constraints, such as electric-powered transportation. However, thicker battery electrodes are often limited by because of kinetics, such as where elongated or tortuous charge traveling distances restrict use of the battery electrodes within a short charging or discharging time. Additionally, electrodesprepared using conventional tape-casting methods typically exhibit a low critical cracking thickness that hinders increasing the thickness of these conventional electrodes. Further, an overpotential of the electrodes can increase with an increase in electrode thickness of charging rate, resulting in degradation of active particles and battery failure after extended cycling. SUMMARY

[0005] The present disclosure provides electrodes for use in electrochemical cells, electrochemical cells incorporating such electrodes, and methods of making and using the electrodes and electrochemical cells. The electrodes described herein include thick electrodes with vertical lamellae created using a bidirectional freeze-casting process that provide beneficial performance characteristics to the electrochemical cells incorporating the electrodes.

[0006] In examples, an electrode comprises a current collector and an active material layer in contact with the current collector, with the active material layer including a plurality of lamellar segments extending from a surface of the current collector. Each lamellar segment may correspond to a planar electrode structure aligned along a lamellar axis, the planar electrode structure comprising a conductive additive, a binder, and particles of an active material. In some examples, the active material of the active material layer comprises a lithium host material, a lithium transition metal oxide cathode, lithium nickel manganese cobalt oxide, lithium iron phosphate, or lithium cobalt oxide. In some examples, the conductive additive comprises carbon black, graphite, or conductive carbon. In some examples, the binder comprises a carbon-based material. Examples of the carbon-based material of the binder include, but are not limited to, sodium carboxymethyl cellulose, lignin, or chitin. Other carbon-based materials may be used. In some examples, the current collector comprises a metallic element or metallic compound. Examples of the metallic element or metallic compound include, but are not limited to, aluminum or copper. For example, aluminum metal or an aluminum alloy may be used as the current collector for a cathode.

[0007] In some examples, the active material layer is characterized by a porosity of from about 30% to about 80%, such as from 30% to 35%, from 35% to 40%, from 40% to 45%, from 45% to 50%, from 50% to 55%, from 55% to 60%, from 60% to 65%, from 65% to 70%, from 70% to 75%, or from 75% to 80%. In some examples, the active material layer is characterized by an areal mass loading of from about 50 mg cm-2to about 300 mg cm-2, such as from 50 mg cm-2to 75 mg cm-2, from 75 mg cm-2to 100 mg cm-2, from 100 mg cm-2to 125 mg cm-2, from 125 mg cm-2to 150 mg cm-2, 150 mg cm-2to 175 mg cm-2, from 175 mg cm-2to 200 mg cm-2, from 200 mg cm-2to 225 mg cm-2, from 225 mg cm-2to 250 mg cm-2, 250 mg cm-2to 275 mg cm-2, or from 275 mg cm-2to 300 mg cm-2. In some examples, the plurality of lamellar segments may have a thickness of about 1.0 mm to about 1.5 mm, such as from 1.0 mm to 1.05 mm, from 1.05 mm to 1.1 mm, from 1.1 mm to 1.15 mm, from 1.15 mm to 1.2 mm, from 1.2 mm to 1.25 mm, from 1.25 mm to 1.3 mm, from 1.3 mm to 1.35 mm, from 1.35 mm to 1.4 mm, from 1.4 mm to 1.45 mm, or from 1.45 mm to 1.5 mm. The plurality of lamellar segments can define a plurality of interlamellar channels configured to facilitate charge transport kinetics of the electrode. In some examples, the electrode exhibits or is configured to exhibit a discharge capacity of from about 60 mAh g-1to about 90 mAh g-1at a C-rate of about 1C, such as a discharge capacity of from 60 mAh g-1to 65 mAh g-1at 1C, from 65 mAh g-1to 70 mAh g-1at 1C, from 70 mAh g-1to 75 mAh g-1at 1C, from 75 mAh g-1to 80 mAh g-1at 1C, from 80 mAh g-1to 85 mAh g-1at 1C, or from 85 mAh g-1to 90 mAh g-1at 1C. In some examples, the electrode exhibits or is configured to exhibit an areal capacity of from about 20 mAh cm-2to about 50 mAh cm-2, such as from 20 mAh cm-2to 25 mAh cm-2, from 25 mAh cm-2to 30 mAh cm-2, from 30 mAh cm-2to 35 mAh cm-2, from 35 mAh cm-2to 40 mAh cm-2, from 40 mAh cm-2to 45 mAh cm-2, or from 45 mAh cm-2to 50 mAh cm-2. In some examples, the electrode exhibits or is configured to exhibit a volumetric capacity of from about 200 mAh cm-3to about 400 mAh cm-3, such as from 200 mAh cm-3to 225 mAh cm-3, from 225 mAh cm-3to 250 mAh cm-3, from 250 mAh cm-3to 275 mAh cm-3, from 275 mAh cm-3to 300 mAh cm-3, from 300 mAh cm-3to 325 mAh cm-3, from 325 mAh cm-3to 350 mAh cm-3, from 350 mAh cm-3to 375 mAh cm-3, or from 375 mAh cm-3to 400 mAh cm-3.

[0008] The plurality of lamellar segments can be grown on a surface of the current collector using a bidirectional freeze casting process. In some examples, the bidirectional freeze casting process comprises freezing a slurry in contact with the current collector by subjecting the slurry to a first temperature gradient along the lamellar axis and a second temperature gradient along an axis perpendicular to the lamellar axis to form a frozen slurry. In some examples, the slurry comprises the conductive additive, particles of the active material, the binder, and a solvent. In some examples, the bidirectional freeze casting process further comprises freeze-drying the frozen slurry to remove the solvent from the frozen slurry through sublimation. In some examples, the plurality of lamellar segments corresponds to a plurality of compressed electrodes. Optionally, a compressed electrode is formed by applying a compressive force to the plurality of lamellar segments to reduce an interlamellar spacing between the plurality of lamellar segments. In some examples, the compressed electrode is characterized by a decrease in volume of from about 20% to about 80% by application of the compressive force.

[0009] Methods of making the electrode are also disclosed. In some examples, such a method comprises growing a plurality of lamellar segments on a surface of a current collector using abidirectional freeze casting process to collectively form an active material layer of an electrode, such as where a lamellar segment corresponds to a planar electrode structure aligned along a lamellar axis, the planar electrode structure comprising a conductive additive, a binder, and particles of an active material, such as where the bidirectional freeze casting process comprises freezing a slurry in contact with the current collector by subjecting the slurry to a first temperature gradient along the lamellar axis and a second temperature gradient along an axis perpendicular to the lamellar axis to form a frozen slurry, the slurry comprising the conductive additive, particles of the active material, the binder, and a solvent. In some examples, the bidirectional freeze casting process further comprises freeze-drying the frozen slurry to remove the solvent from the frozen slurry through sublimation, and applying a compressive force to the plurality of lamellar segments to reduce an interlamellar spacing between the plurality of lamellar segments. In some examples, the first temperature gradient is generated based on a distance from the current collector along the lamellar axis. In some examples, the second temperature gradient is generated based on at least in part on relative thicknesses of a first layer comprising the current collector having a first thermal conductivity and a second layer comprising a material having a second thermal conductivity different from the first thermal conductivity. In some examples, the first thermal conductivity is lower than the second thermal conductivity. In some examples the first temperature gradient and the second temperature gradient are generated at least in part by a heat sink. In some examples, the heat sink comprises nitrogen.

[0010] Any suitable solvent of the slurry may be used. The solvent may be prepared using any suitable technique. In some examples, the solvent of the slurry comprises water. In some examples, the freezing step is configured to exhibit ice propagation within the slurry that is aligned with the first temperature gradient. In some examples, the freeze-drying step is performed at a freeze-drying temperature of from 0 to -100 °C. In some examples, compressing the plurality of lamellar segments reduces a volume of the electrode by about 20% to about 80%. In some examples, compressing the plurality of lamellar segments is performed in a compression direction that is orthogonal the plurality of lamellar segments. In some examples, compressing the plurality of lamellar segments is performed by calendering the plurality of lamellar segments. In some examples, calendering the plurality of lamellar segments is performed using a calendering direction that is orthogonal to the plurality of lamellar segments. In some examples, calendering the plurality of lamellar segments causes the plurality of lamellar segments to tilt at an angle of between 15° to 60° relative to the current collector.

[0011] A battery including the electrode described herein is also disclosed. In some examples, such a battery comprises a freeze-casted cathode, the freeze-casted cathode comprising a currentcollector and an active material layer in contact with the current collector, such as where the active material layer includes a plurality of lamellar segments extending from a surface of the current collector, such as where each lamellar segment corresponds to a planar electrode structure aligned along a lamellar axis, the planar electrode structure comprising a conductive additive, a binder, and particles of an active material; an anode; and an electrolyte between the freeze-casted cathode and the anode. In some examples, the anode comprises a lithium alloying anode. In some examples, the electrolyte comprises a liquid electrolyte. The liquid electrolyte can include an electrolyte solvent and one or more salts. Examples of the electrolyte solvent include, but are not limited to, one or more of ethylene carbonate (EC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or propylene carbonate (PC). Examples of the one or more salts include, but are not limited to, LiPF6, LiTFSI, LiFSI, LiBF4, LiCIO4, LiNO3, LiAlCl4, LiAlF4, LiAsF6, LiCF3SO3, LiC(CF3SO2)3, or LiC4F3SO3. Other suitable electrolytes may be used. For example, the electrolyte may be a solid-state electrolyte or a gel electrolyte. Other suitable types of electrochemical cells may be made or prepared using the electrode described herein. For example, a capacitor or a supercapacitor can be made using the electrode described herein.

[0012] The battery or other suitable electrochemical cells may optionally include other components. For example, an electrochemical cell may comprise a separator between the freeze- casted cathode and the anode, a cathode electrolyte interphase in contact with the freeze-casted cathode, a solid–electrolyte interphase in contact with the anode, an anode current collector in contact with active material of the anode, or a cathode current collector in contact with active material of the freeze-casted cathode.

[0013] Without wishing to be bound by any particular theory, there can be discussion herein of beliefs or understandings of underlying principles relating to the invention. It is recognized that regardless of the ultimate correctness of any mechanistic explanation or hypothesis, an embodiment of the invention can nonetheless be operative and useful. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG.1 provides a schematic illustration of an example electrochemical cell.

[0015] FIG.2 provides an overview and data relating to charge transport kinetics in vertically lamellar-architected thick battery electrodes. (Panel A) Schematic illustration of the lithium-ion flux in a vertically lamellar thick electrode. (Panel B) Relationship between tortuosity and porosity in electrodes with random and vertically lamellar pores. (Panel C) Dependences of normalized diffusion coefficient and mass proportion on channel width with a constant wallthickness of 10 μm. (Panel D) Simulated electrochemical properties of thick electrodes with vertically lamellar pores and random pores and with the porosity of 70% (hollow) and 40% (solid). The decrease of the porosity in vertically lamellar electrodes is solely due to the decrease of the channel width. (Panel E) Simulation of the lithium-ion concentration along the electrode thickness. (Panel F) Simulation of the state-of-charge (SOC) of active material particles across the electrode depth.

[0016] FIG.3 provides data relating to electrochemical properties of random and vertically lamellar electrodes determined using a modeling simulation. (Panel A) Simulated rate performance (capacity retention versus C-rate) of the random and vertically lamellar electrodes with the porosity of 40% and 70%, respectively. (Panel B) Simulation of the Li-ion concentration versus normalized electrode depth in electrodes with a porosity of 40% at an overall state of charge of 70%. Normalized distance of 0% represents the current collector side while normalized distance of 100% represents the separator side. (Panel C) Simulation of the state of charge versus normalized electrode depth.

[0017] FIG.4 provides schematics and data for bidirectional freeze-casting and densification methodology for high-density vertically lamellar-architected thick electrodes. (Panel A) Schematic illustration of the vertically lamellar thick electrodes preparation process via a combination of bidirectional freeze-casting and compression-induced densification. (Panels B-D) Top-view SEM images (Panel B and Panel C) and side-view SEM image (Panel D) of the thick vertically lamellar lithium cobalt oxide (LCO) electrode with a high porosity of 76%. (Panels E- G) Top-view SEM images (Panel E and Panel F) and side-view SEM image (Panel G) of the densified vertically lamellar LCO electrodes with a low porosity of 40%.

[0018] FIG.5 provides images of an example bidirectional freeze-casting setup. (Panel A and Panel B) Front view (Panel A) and top view (Panel B) of the bidirectional freeze casting setup. (Panel C) Zoom-in digital image of the bidirectional freeze casting setup. The setup includes a PTFE mold (inner size: 1.6 cm × 1.6 cm; height: 1.0 cm) to accommodate the electrode slurry, a PDMS wedge (size: 2.0 cm × 2.0 cm; height: 0.73 cm; angle: 20°) to create a temperature gradient orthogonal to the z-direction, a copper wedge (size: 2.0 cm × 2.0 cm; height: 0.73 cm; angle: 20°) for fast heat transfer, a copper column for rapid heat conduction in the z-direction, and a foam container with liquid nitrogen (b.p. = −196 °C) as a cooling reservoir. (Panel D) Top-view digital images showing the ice propagation direction (from left to right) that aligned with the temperature gradient created by the PDMS wedge.

[0019] FIG.6 provides images of an example bidirectional freeze-casted (BFC) LCO electrode before and after compression. (Panel A) Top-view digital image of the example BFC LCO electrode with the area of 1.6 cm × 1.6 cm. (Panel B) Electrode thickness measured by a digital micrometer. The electrode thickness of the fabricated example BFC LCO electrode is about 1.2 mm. (Panel C) Electrode images before and after compression. A subset of LCO electrodes was cut from the example BFC LCO electrode with a size of 5 mm × 5 mm. In the compression process, the force was applied orthogonally to the lamellae structure. The right one is a 5 mm × 2 mm electrode after compression, with an electrode volume decrease of 60%.

[0020] FIG.7 provides data characterizing an example LCO electrode region with non-uniform ice dendrite growth. (Panel A) Top-view SEM image of the electrode morphology shows the randomly distributed pores in the region where ice starts to grow (left 1 / 4 region in FIG.5, Panel D). (Panel B) Zoomed-in SEM image shows the random active material particle, conductive carbon, binder, and pore distribution.

[0021] FIG.8 provides data characterizing architectures of an example LCO electrode region with uniform dendrite growth. (Panels A-C) Top-view SEM images of the example LCO BFC electrode show the lamellar architecture at various magnifications (the right 2 / 3 region in FIG.5, Panel D). (Panels D-F) Side-view SEM images show the vertically aligned channels and walls. LCO particles are not fully buried inside the walls due to their larger particle size (diameter: 10 μm to 20 μm) compared to the wall thickness (about 10 μm). The bottom layer (about 160 μm thick), which can be seen in Panel D, is due to volume expansion (about 10%) during the freezing process that lifts the PTFE mold at the side that freezing ends.

[0022] FIG.9 provides data showing elemental mapping on an example BFC LCO electrode. (Panel A) Side-view SEM image of the bottom layer and corresponding element maps of carbon, oxygen, and cobalt. (Panel B) Side-view SEM image of the top layer and corresponding element maps. (Panel C) EDS spectra of the bottom (left) and top (right) regions.

[0023] FIG.10 provides data characterizing architectures of an example BFC LCO electrode fabricated with a high solid content of 32 vol%. (Panels A-D) Top-view (Panel A and Panel B) and side-view (Panel C and Panel D) SEM images of the electrode at different magnifications. A 10 wt% CMCNa binder solution was used to replace the 5 wt% one to fabricate the example BFC LCO electrode with a low porosity. No lamellar architecture was observed in the example LCO BFC electrode because the high viscosity of the slurry can affect the ice crystal growth.

[0024] FIG.11 provides data characterizing an example BFC LCO electrode after densification. (Panels A-D) Top-view (Panel A and Panel B) and side-view (Panel C and Panel D) SEM images of the LCO-60% electrode at different magnifications.

[0025] FIG.12 provides data determining channel width and wall thickness in example LCO electrodes before and after densification. (Panel A and Panel B) Channel width (Panel A) and wall thickness (Panel B) in LCO-0% and LCO-60% electrodes. The channel width and wall thickness are collected from the top-view SEM images in FIG.8 and FIG.11.

[0026] FIG.13 provides data showing electrochemical properties of example vertically lamellar LCO electrodes. (Panel A and Panel B) Galvanostatic charge-discharge voltage profiles of the example vertically lamellar electrodes before (Panel A) and after densification (Panel B). The example electrodes before and after densification are with the sizes of 5 mm × 5 mm × 1.1 mm and 5 mm × 2 mm × 1.1 mm, respectively. (Panel C) Rate performance of the example vertically lamellar electrodes and conventional thick electrodes. (Panel D) Cycling stability of the example densified electrodes and conventional electrodes discharged at a practical current density of ~3.5 mA cm-2. The applied current on the LCO-60% electrode is ~0.35 mA. (Panel F) Comparison among high-areal-capacity thick battery electrodes (CA>10 mAh cm-2) in terms of areal and volumetric capacities. (Panel F) Nyquist plots of the vertically lamellar electrodes via the EIS- symmetric cell test. (Panel G) Depolarization curves of the example vertically lamellar electrodes in the DC polarization-depolarization test. (Panel H) Measured tortuosity and porosity in the example vertically lamellar electrodes fitted by the modified Bruggeman equation.

[0027] FIG.14 provides data showing dependence of electrode size on rate capabilities. (Panel A) Rate performance of an example BFC LCO electrode with a size of 1.0 cm × 1.0 cm and an area of 1.0 cm2. (Panel B) Rate performance of an example densified BFC LCO electrode with a size of 1.0 cm × 0.4 cm and an area of 0.4 cm2. (Panel C) Rate performance comparison among example BFC LCO electrodes with different sample sizes. The small sample sizes are 0.4 cm2and 0.1 cm2for the example electrodes before and after densification, respectively, while the large sample sizes are 1.0 and 0.4 cm2for the example electrodes before and after densification, respectively.

[0028] FIG.15 provides data determined using a modeling simulation revealing a dependence of electrode size on Li-ion concentration distributions and electrochemical properties. (Panel A) Three example electrodes with different ratios of the top area versus the combination of top and side areas, which are 37.3%, 53.2%, and 58.1%, respectively. (Panel B and Panel C) Simulated 2D electrolyte concentration distribution in electrodes with random pores (Panel B) and verticallylamellar pores (Panel C) discharged at a current density of 5 mA cm-2. (Panel D) Simulated discharged capacities in the example electrodes with different sizes.

[0029] FIG.16 provides data characterizing example LCO electrodes that are tape-cast. (Panel A) Top-view SEM image of the example LCO electrode with a total areal loading of about 60 mg cm-2. Inset: the digital image showing the example LCO electrode with little cracks on its top surface. (Panel B) Side-view SEM image of the example LCO electrode. (Panel C) Nyquist plot of the example LCO electrode. (Panel D) Charge-discharge voltage profiles of the example LCO electrode at various C-rates.

[0030] FIG.17 provides data showing first charge-discharge voltage profiles of example tape- cast and BFC LCO electrodes. The example tape-cast and BFC LCO electrodes show specific capacities of 145 and 140 mAh g-1, areal capacities of 8.2 and 33 mAh cm-2, and ICE of 96.4% and 95.8%, respectively.

[0031] FIG.18 provides an image of Li metal after cycling in an example BFC LCO electrode under a current density of about 3.5 mA cm-2.

[0032] FIG.19 provides data showing charge-discharge voltage profiles of example LCO thick electrodes. (Panel A and Panel B) Charge-discharge voltage profiles of an example conventional tape-cast LCO electrode (Panel A) and an example BFC LCO-60% electrode (Panel B) at cycle numbers of 1, 10, 20 and 50.

[0033] FIG.20 provides data characterizing ionic transport in example BFC LCO electrodes. (Panel A and Panel B) Nyquist plots of the LCO-0% (Panel A) and LCO-60% (Panel B) electrodes with symmetric cell configuration.

[0034] FIG.21 provides data showing Li-ion diffusion coefficient measurement in bulk electrolyte with a DC depolarization curve of a symmetric cell with a PTFE O-ring.

[0035] FIG.22 provides data characterizing a morphology of various active material particles. (Panels A-C) SEM images of LCO particles (Panel A), NMC111 particles (Panel B), and LFP particles (Panel C).

[0036] FIG.23 provides data showing exploration of universality of bidirectional freeze-casting methodology in multiple thick cathode systems. (Panel A and Panel B) Top-view SEM images of the BFC NMC electrodes before (Panel A) and after (Panel B) densification. (Panel C) Rate performance of the vertically lamellar NMC electrode with the maximum areal capacity of about 32 mAh cm-2. (Panel D and Panel E) Top-view SEM images of the BFC LFP electrodes before (Panel D) and after (Panel E) densification. (Panel F) Rate capability of the LFP electrode withthe maximum areal capacity of about 19 mAh cm-2. (Panel G and H) Cycling stability measurements on the densified NMC (Panel G) and LFP (Panel H) electrodes at a C-rate of 0.1C.

[0037] FIG.24 provides data characterizing architecture of an example BFC NMC electrode. (Panels A-C) Top-view SEM images show the lamellar structure in the example BFC NMC electrode at various magnifications. (Panel D) Side-view SEM image of the example BFC LCO electrode exhibits the same vertically aligned architecture as the example BFC LCO electrode.

[0038] FIG.25 provides data characterizing architecture of an example BFC LFP electrode. (Panels A-C) Top-view SEM images show the lamellar structures in the example BFC LFP electrode. (Panel D) Side-view SEM image of the example BFC LFP electrode.

[0039] FIG.26 provides data characterizing example tape-cast thick NMC and LFP electrodes. (Panel A) Top-view SEM image of the tape-cast NMC electrodes with a total areal loading of ~50 mg cm-2. Inset: image showing the example NMC thick electrode. (B) Side-view SEM image of the conventional NMC electrode. (Panel C) Galvanostatic charge-discharge voltage profiles of the conventional NMC electrode at various C-rates. (Panel D and Panel E) Top-view (Panel D) and side-view (Panel E) SEM image of the conventional LFP electrodes with a total areal loading of about 30 mg cm-2. (Panel F) Charge-discharge voltage profiles of the conventional LFP electrode.

[0040] FIG.27 provides data showing charge-discharge voltage profiles of example densified electrodes. Charge-discharge voltage profiles of an example densified NMC electrode (Panel A) and an example LFP electrode (Panel B) cycled at a C-rate of 0.1C.

[0041] FIG.28 provides a schematic and images of a scalable lamellar electrode fabrication methodology via bidirectional freeze-casting and calendering-induced densification. (Panel A) Schematic of the setup for the scalable lamellar electrode fabrication. Here, bidirectional freeze- casting is achieved by placing the liquid nitrogen as the cold reservoir at one side, by which means another lateral temperature gradient can be created compared to the typical longitudinal temperature gradient using the conventional freeze-casting method. After freeze-drying, the electrode can be calendered, with the calendering direction orthogonal to the lamellae, resulting in tilted yet aligned channels in the electrode. (Panel B) Digital images showing the ice propagation in the bidirectional freeze-casting process (Panels i to iii), the frozen electrode (Panel iv), the electrode under freeze-drying (Panel v), the freeze-dried electrode (Panel vi), the electrode after roll-to-roll calendering (cut to fit the calendering machine) (Panel vii), and the calendered lamellar electrode with a size of 5 cm × 5 cm (Panel viii).

[0042] FIG.29 provides data characterizing architectures of example tape-cast BFC electrodes before calendering. (Panels A-C) Top-view SEM images of the example BFC electrodes with the solid volume contents of 42% (Panel A), 40% (Panel B), and 38% (Panel C), respectively. In the example BFC electrodes, the weight ratio of LCO, Super P, and CMCNa is 94:3:3.

[0043] FIG.30 provides data characterizing side-view example electrode architectures before and after roll-to-roll calendering. (Panel A and Panel B) Side-view SEM images of an example BFC LCO electrode with a thickness of about 280 μm (Panel A) and an example calendered BFC LCO electrode with a thickness of about 230 μm.

[0044] FIG.31 provides data showing electrochemical properties of example BFC electrodes after calendering. (Panel A and Panel B) Rate performance of an example calendered BFC LCO electrode (Panel A) and an example LCO electrode (Panel B). (Panel C) Plot of discharged capacity versus C-rate of the example electrodes. DETAILED DESCRIPTION

[0045] Described herein are electrodes for use in alkali metal, alkali metal ion, alkaline-earth metal, and other metal electrochemical cells, and methods of making such electrodes. The electrodes described herein include vertical lamellar segments that provide beneficial performance characteristics to the electrochemical cells incorporating the electrodes. The vertical lamellar electrode architecture can facilitate compact energy storage by overcoming a thickness limit affecting conventional electrodes. Additionally, the vertical lamellar electrode architecture can facilitate or redistribute lithium-ion flux, enabling high rate capability and stable cycling performance of electrochemical cells incorporating the electrodes. Advantageously, the electrodes can be prepared via a bidirectional freeze-casting process using a water-based slurry (e.g., using water as a solvent of the slurry) including a carbon-based binder, like sodium carboxymethyl cellulose. The bidirectional freeze-casting process to produce the electrodes described herein can avoid using hazardous chemical compounds, such as N-methyl-2-pyrrolidone, that are conventionally used to prepare electrodes for lithium-ion batteries. Additionally, various types of cathode active material (e.g., LCO, LFP, NMC, etc.) can be used in the bidirectional freeze-casting process, indicating a universality of the bidirectional freeze-casting process for a variety of applications.

[0046] The electrodes provide beneficial performance for a variety of electrochemical cells, such as batteries or supercapacitors. In some examples, batteries or other suitable electrochemical cells can achieve beneficial performance by incorporating the electrodes disclosed herein. For example, the electrodes can have an engineered architecture of vertically lamellar segments that definechannels for improving Li ion or electron transport. Due to the vertically lamellar segments, the electrodes can exhibit relatively low-tortuosity, thereby improving charge transport distance to enable improved utilization of active material under short charge or discharge conditions. The bidirectional freeze-casting process can enable controlled formation of the vertically lamellar segments (e.g., with respect to channel width or wall thickness) by tuning a cooling rate of the slurry or introducing additives. Additionally, the electrodes can undergo a densification process that can preserve the lamellar architecture of the electrodes while decreasing channel width and electrode volume to improve the energy density of the electrodes. In some aspects, the electrodes can be characterized by a greater thickness than conventional electrodes, contributing to the improved energy density of the electrodes. Additionally, the bidirectional freeze-casting process can overcome problems (e.g., cracking, delamination, accumulated strain and stress, etc.) experienced in conventional tape-casting methods to produce thick electrodes. For example, the electrodes formed using the bidirectional freeze-casting process can exhibit suitable mechanical strength to undergo calendering or other compression methods for the densification process.

[0047] FIG.1 provides a schematic illustration of an example electrochemical cell 100. Electrochemical cell 100 is described as a lithium-ion electrochemical cell, but it will be appreciated that other alkali metal systems, alkaline earth metal systems, or other metal systems, can be used in place of lithium, such as sodium ion systems, potassium ion systems, magnesium ion systems, aluminum ion systems, zinc ion systems, etc. Electrochemical cell 100 includes a cathode current collector 105 (e.g., aluminum foil), a cathode active material layer 110, an electrolyte 120, a separator 125, an anode active material 135, and an anode current collector 140 (e.g., copper foil). In some cases, additional components beyond those illustrated may be included in electrochemical cell 100. In some cases, additional or fewer components beyond those illustrated may be included in electrochemical cell 100. For example, electrochemical cell 100 can form a solid-electrolyte interface (SEI) during operation (e.g., cycling of electrochemical cell 100). Separator 125 can comprise any suitable ion conducting and electrically insulating material (e.g., a porous polymeric layer). As an example, separator 125 may include three layers of polymer material. In some cases, separator 125 may not be present, such as if cathode active material layer 110 and anode active material 135 are separated from one another by some other means.

[0048] Electrolyte 120 can be a liquid electrolyte that can comprise an electrolyte solvent and one or more salts. Non-limiting examples of the electrolyte solvent include one or more carbonate solvents, such as ethylene carbonate (EC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), propylene carbonate (PC), or any combination of these and including optional additives or the like. Non-limiting examples ofthe salts in electrolyte 120 include LiPF6, LiTFSI, LiFSI, LiBF4, LiCIO4, LiNO3, LiAlCl4, LiAlF4, LiAsF6, LiCF3SO3, LiC(CF3SO2)3, or LiC4F3SO3.

[0049] Cathode current collector 105 can be any suitable material (e.g., a metallic element or metallic compound). In a non-limiting example, cathode current collector 105 comprises aluminum. Cathode active material layer 110 may comprise a conductive additive, a binder, and particles of any suitable cathode active material. For example, cathode active material layer 110 may comprise a lithium host material, a lithium transition metal oxide cathode, lithium nickel manganese cobalt oxide, lithium iron phosphate, or lithium cobalt oxide. Non-limiting examples of the conductive additive include carbon black, graphite, or conductive carbon. Cathode active material layer 110 can comprise a carbon-based binder or a conductive polymer-based binder. As a non-limiting example, cathode active material layer 110 comprises sodium carboxymethyl cellulose as the binder. Cathode active material layer 110 can exhibit a discharge capacity of from about 60 mAh g-1to about 90 mAh g-1at a C-rate of about 1C. Additionally, the cathode active material layer 110 can exhibit an areal capacity of from about 20 mAh cm-2to about 50 mAh cm-2and a volumetric capacity of from about 200 mAh cm-3to about 400 mAh cm-3.

[0050] In some aspects, cathode active material layer 110 can be a planar electrode structure formed from one or more lamellar segments extending from a surface of cathode current collector 105. Growing the lamellar segments on the surface of cathode current collector 105 can involve the bidirectional freeze casting process. The bidirectional freeze-casting process can involve depositing a water-based slurry that contains the components of cathode active material layer 110 onto a surface of cathode current collector 105. Once the water-based slurry is deposited on the surface of cathode current collector 105, the slurry can be frozen to form a frozen slurry by or while subjecting the slurry to a first temperature gradient and a second temperature gradient. The first temperature gradient can correspond to a lamellar axis along which the lamellar segments are aligned and can be generated based on a distance from cathode current collector 105 along the lamellar axis. In some embodiments, ice propagation within the water-based slurry can be aligned with the first temperature gradient.

[0051] The second temperature gradient can correspond to an axis perpendicular to the lamellar axis. When growing the lamellar segments, cathode current collector 105 can be considered a first layer and may be positioned on a second layer comprising a material (e.g., metal, polymer, etc.) having a different thermal conductivity than cathode current collector 105. For example, cathode current collector 105 can comprise aluminum or an aluminum alloy, while the second layer may comprise copper. Accordingly, a first thermal conductivity of the first layer can be lower than asecond thermal conductivity of the second layer. The second temperature gradient can be generated based on at least in part on relative thicknesses of the first layer and the second layer. In some cases, the first temperature gradient and the second temperature gradient may be generated at least in part by a heat sink, cold finger, or the like (e.g., comprising or in contact with a low- temperature material like liquid nitrogen). After the frozen slurry is formed, the frozen slurry can be freeze-dried to remove the solvent (e.g., water) from the frozen slurry through sublimation, for example causing ice to become water vapor. In some cases, the frozen slurry can be freeze-dried at or below 0 °C (e.g., at a freeze-drying temperature of from 0 to -100 °C or less). Additionally, the freeze-drying step can be performed under vacuum (e.g., at a freeze-drying pressure of less than 5 Pa).

[0052] The lamellar segments can define one or more interlamellar channels to facilitate charge transport kinetics of cathode active material layer 110. Additionally, the lamellar segments can have a thickness of about 1.0 mm to about 1.5 mm (e.g., about 1.1 mm, about 1.2 mm, about 1.3 mm, about 1.4 mm, or about 1.5 mm). In some cases, cathode active material layer 110 can be characterized by a porosity of from about 30% to about 80% (e.g., from 30% to 50%, from 40% to 60%, or from 50% to 80%). An areal mass loading of cathode active material layer 110 can be from about 50 mg cm-2to about 300 mg cm-2(e.g., 50 mg cm-2to 100 mg cm-2, 80 mg cm-2to 150 mg cm-2, 100 mg cm-2to 200 mg cm-2, 150 mg cm-2to 220 mg cm-2, or from 200 mg cm-2to 300 mg cm-2). In some examples, cathode active material layer 110 can be compressed to form a compressed electrode by applying a compressive force to the lamellar segments, thereby reducing an interlamellar spacing between the lamellar segments. Accordingly, the compressed electrode can be characterized by a decrease in volume of from about 20% to about 80% (e.g., from 20% to 40%, from 35% to 50%, or from 40% to 80%) by application of the compressive force. As an example, the compressive force may be applied in a compression direction that is orthogonal to the lamellar segments. In some cases, compressing the lamellar segments may involve calendering the lamellar segments, for example using a calendering direction that is orthogonal to the lamellar segments. In such cases, calendering the lamellar segments can cause the lamellar segments to tilt at an angle of between 15° to 60° relative to cathode current collector 105.

[0053] Anode active material 135 can comprise any suitable material to provide a lithium alloying anode or lithium uptake anode. In some non-limiting examples, anode active material 135 comprises lithium metal or a lithium metal alloy, graphite, or the like. Anode current collector 140 can comprise any suitable material. In a non-limiting example, anode current collector 140 comprises copper.

[0054] The invention may be further understood by the following non-limiting examples. EXAMPLE 1: DENSIFIED VERTICALLY LAMELLAR ELECTRODE ARCHITECTURES FOR COMPACT ENERGY STORAGE

[0055] Decreasing electrode tortuosity is considered as a promising approach to facilitate charge transport kinetics in thick electrodes by improving lithium-ion transport kinetics via controlling spatial pore distribution of the electrode while maintaining a pore volume in the electrode. However, typical low-tortuosity architecture in battery electrodes often have a high porosity due to an intrinsic limitation of conventional electrode preparation methods. Additionally, a practical volumetric energy or power density of the typical low-tortuosity battery electrodes is often much lower than conventional LIB electrodes. Furthermore, precisely tailoring parameters of the low- tortuosity electrodes can be challenging. This Example presents a low-tortuosity electrode including vertical lamellar segments fabricated using a bidirectional freeze-casting process that enables control over channel width and wall thickness with respect to the vertical lamellar segments by tuning a cooling rate or introducing sacrificial additives. As depicted in FIG.2, Panel A, lithium-ion transport in electrolyte-filled pores of the electrode can be divided into two parts: lithium-ion diffusion in an interlamellar region corresponding to channels formed from the vertical lamellar segments and an intralamellar region corresponding to walls of the vertical lamellar segments.

[0056] Preparing the low-tortuosity electrode can furth involve compression-induced densification to produce thick electrodes with a thickness over one millimeter and exhibiting high density and low tortuosity. Using LiCoO2(LCO) as active material, the thick electrodes can deliver an areal capacity of approximately 33 mAh cm-2at a practical current density of approximately 3.5 mA cm-2, providing electrochemical properties beyond conventional LIB electrodes. The improved electrochemical properties of the thick electrodes can be attributed to facilitated lithium-ion transport in the vertically oriented channels and walls that are defined by the vertical lamellar segments of the thick electrodes. Through tailoring channel width, lithium-ion transport in the channels and walls can be decoupled, providing insights into architecture designs in the thick electrodes for efficient yet compact energy storage. This Example highlights the utility of high-density low-tortuosity thick electrodes and provides a method to use bidirectional freeze-casting to produce these electrodes for use in electrochemical cells.

[0057] In conventional battery electrodes with spherical active material particles, a relationship between porosity (ε) and tortuosity (τ) can be described by the Bruggeman equation, as shown below in Equation 1:τ = ε-α(1) in which α is the Bruggeman exponent. In ideal conditions, α equals 0.5 in random porous media, as shown in the top curve of FIG.2, Panel B. When considering the thick electrodes with the vertically lamellar pores, it can be assumed that the walls (e.g., lamellae) and channels (e.g., pores) are resistance in series, leading to Equation 2 below:where Deff, Deff,w, and Deff,trepresent the effective diffusion coefficients of Li ions in the electrode, in the channels and in the walls, respectively, and t and w are the wall thickness and channel width, respectively. Meanwhile, the effective diffusion coefficients in the channels and walls are related to the electrode architecture, which can be expressed as Equations 3 and 4 below:in which D0represents the intrinsic diffusion coefficient of Li ions in the bulk electrolyte, εwand εtrepresent the porosity of the channels and walls, respectively, and τwand τtrepresent the tortuosity of the channels and walls, respectively. It can be assumed the channels are totally empty such that εw= 0 and τw= 1. εtcan be estimated as 0.2 for electrolyte penetration into the walls, and τtcan be calculated to be 2.236 according to the Bruggeman relationship in Equation 1. Therefore, Equation 2 can be rearranged into Equation 5 below:The wall thickness (t) can be set as 10 μm as a fixed parameter, and the channel width (w) can be a variable parameter ranging from 500 to 0.01 μm. The total porosity of the electrode (ε) can be expressed as Equation 6 below:(6)In this way, both tortuosity and porosity in the vertically lamellar electrodes can be obtained from Equations 5 and 6.

[0058] Thus, a correlation of tortuosity and porosity can be drawn as the bottom curve of FIG.2, Panel B. As depicted in FIG.2, Panel B, electrodes with vertically lamellar pores typically possess lower tortuosity compared to those with random pores. When the width of the channels isinfinite or zero (e.g., corresponding to the porosity of 1.0 or 0.2, respectively), the two electrodes with different pore distributions can possess the same tortuosity. Varying the width while fixing the thickness of the walls to be 10 μm, dependencies of effective diffusion coefficient (Deff) and solid content on the width of the channels can be determined, as depicted in FIG.2, Panel C. For example, 10 μm can be chosen due to being similar to diameters of conventional active material particles, and electrolyte can easily access the surface of these particles in the walls. For an electrode with a relatively large width, lithium-ion diffusion kinetics can be improved, whereas electrode energy density may be relatively low. In contrast, a relatively small width can result in a high electrode density although ion transport may be sluggish. Accordingly, an electrode architecture of low-tortuosity channels with a moderate width can simultaneously achieve high energy and high power densities.

[0059] Simulations were conducted to forecast electrochemical properties in the thick electrodes with random and vertically lamellar pores. Table 1 below provides simulation parameters. Table 1. General modeling parameters Parameters Nomenclature Value Vmax(V) Upper limit voltage in charging 4.25 Vmin (V) Lower limit voltage in discharging 3.3 d (cm) Out-of-plane thickness for the 2D model 2 Dint(m2s-1) Ionic diffusion coefficient in the electrolyte 2×10-10cElsalt(mol m-3) Electrolyte salt concentration 1000 ρLCO(kg m-3) Density of lithium cobalt oxide 5000 SOCminMinimum state of charge 0.43 SOCmaxMaximum state of charge 1 Cs, max(mol m-3) Maximum lithium-ion concentration in LCO 56250 rp(m) Average distance from particle center to surface 4×10-6σ (S m-1) Electronic conductivity of the cathode 1×106i0, ref, c(A m-2) Reference exchange current density for cathode 1 i0, ref, a(A m-2) Reference exchange current density for anode 100 ds(μm) Thickness of the separator 25 εsPorosity of the separator 0.4 αaAnodic transfer coefficient 0.5 αcCathodic transfer coefficient 0.5 F (C mol-1) Faraday constant 96485R (J mol-1K-1) Gas constant 8.314 T (K) Temperature 298

[0060] In examples in which the porosity is high (e.g., 70%), the vertically lamellar electrode can show a slightly higher rate capability compared to the random orientation sample, as shown in FIG.2, Panel D. However, when the porosity is decreased to 40%, significant differences can be observed. Under a practical current density of 5 mA cm-2, approximately 80% of the maximum capacity may be retained in the vertically lamellar electrode while the random electrode can maintain approximately 40% of its maximum capacity. The drastically different electrochemical properties can be attributed to accumulated polarization in both electrolyte and active material particles in the random electrode, as depicted in FIG.3, Panels A-C. The large lithium-ion concentration gradient in the electrolyte can result in an increased concentration polarization, while the vertically lamellar electrode can demonstrate a more uniform concentration along the electrode thickness, as depicted in FIG.2, Panel E. Furthermore, in the random electrode, most active material particles can be utilized at a separator side while a large number of particles at a current collector side may remain unreacted, as depicted in FIG.2, Panel F. The poor active material utilization across the random electrode leads to unstable cyclability due to the potential overcharge of the active material at the top of the random electrode.

[0061] Based on the simulations, the bidirectional freeze-casting and densification method can be used to prepare densified vertically lamellar electrode architectures, as depicted in FIG.4, Panel A. To realize the bidirectional freeze-casting, a polydimethylsiloxane (PDMS) wedge can be positioned adjacent to a copper wedge to create biaxial temperature gradients. Due to different thermal conductivities of PDMS and copper, an additional temperature gradient in the x axis can be introduced compared to unidirectional freeze-casting with a single temperature gradient in the z axis. After the freeze-drying process, a vertically lamellar electrode with a large interlamellar spacing can be obtained. Due to weak interconnectivity between the lamellae of the electrode, the as-fabricated electrode can be easily compressed in the y axis (e.g., orthogonal to the lamellae) to densify the electrode. The vertically aligned channels can be maintained after densification, while the porosity of the compressed electrode may be as low as conventional electrodes. With a setup as depicted in FIG.5, Panels A-C, an ice propagation direction was observed to be aligned with the temperature gradient created by the PDMS wedge, as depicted in FIG.5, Panel D. The bidirectional freeze-cast (BFC) LCO electrode showed a size of 1.6 cm × 1.6 cm and a thickness of about 1.1 to 1.2 mm, as depicted in FIG.6, Panel A and Panel B. The electrode architectures were characterized through scanning electron microscopy (SEM). As depicted in FIG.7, in the regionwhere ice starts to grow, the electrode exhibited random architecture due to rapid ice nucleation in the beginning of the freeze-casting process. As depicted in FIG.8, Panels A-C, uniform lamellar architectures can be observed in the region of steady ice growth. Top-view SEM images exhibited long-range lamellar architectures across several millimeters in the BFC electrode, as shown in FIG.4, Panel B and Panel C. As depicted in FIG.4, Panel D and FIG.8 Panels D-F, the vertically oriented channels can also be observed from side-view SEM images across the electrode thickness. Elemental mapping results probed by energy-dispersive x-ray spectroscopy (EDS) can indicate a homogeneous material distribution in both top and bottom regions, as shown in FIG.9.

[0062] It is noted that sufficient water is included in the LCO slurry to form the lamellar architecture, as depicted in FIG.10. As shown in FIG.6, Panel C, the densification process can effectively decrease the electrode volume by approximately 60%. The long-range lamellar architectures can be preserved after compressing the electrode, as confirmed by both top-view and side-view SEM images provided in FIG.4, Panels E-G. Additionally, the porosity of the BFC electrode can be decreased to 40% from 76% after compressing the electrode. The decrease of the width of the electrode can be clearly viewed after electrode densification, as shown in FIG.4, Panel E and Panel F, and FIG.11. As shown in FIG.12, through the quantitative analysis on the lamellar architectures, changes in width and thickness can be determined before and after compression. The electrode after compression can exhibit an average width of 9.0 μm, corresponding to a decrease of 61% compared to the width of 22.8 μm before compression. Meanwhile, similar average thicknesses of 8.7 and 9.5 μm can be determined before and after compression, respectively. The average thicknesses being similar can indicate that the decrease of the electrode porosity is due to the decrease of the width. With the vertically lamellar architectures with controllable interlamellar spacing, the electrochemical properties of these architected electrodes can be further investigated.

[0063] Rate capabilities can be determined to reveal a channel size effect on electrochemical properties of the vertically lamellar electrodes. Electrodes before and after densification are referred to herein as LCO-0% and LCO-60%, respectively, according to their compression ratio. For example, a first size of the LCO-0% electrode can be 5 mm × 5 mm × 1.1 mm, and a second size of the LCO-60% electrode can be 5 mm × 2 mm × 1.1 mm. Galvanostatic charge-discharge voltage profiles of LCO-0% and LCO-60% electrodes are shown in FIG.13, Panel A and Panel B, respectively. With a capacity retention of 49%, the LCO-0% electrode can exhibit a specific capacity of 144 mAh g-1at a C-rate of 0.1C and a specific capacity of 71 mAh g-1at a C-rate of 1C. For the LCO-60% electrode, a similar specific capacity of 140 mAh g-1can be delivered at a C-rate of 0.1C, which indicates suitable material utilization and electrolyte accessibility associated withthe low C-rate. However, a lower capacity of 40 mAh g-1is achieved in the LCO-60% electrode at 1C compared to that of the LCO-0% electrode, implying a decrease of the channel size still affects lithium-ion diffusion kinetics even with the vertically aligned architecture of the electrode. Sluggish charge kinetics can potentially be attributed to the lower pore volume in the densified electrode. Thus, lithium ions in local electrolyte can be fully consumed as the electrochemical reaction proceeds, resulting in less active material utilization. The slower charge transport kinetics of the LCO-60% electrode can also be revealed by a longer constant-voltage (CV) process in the LCO-60% electrode compared to the LCO-0% electrode. To exclude a side area effect considering the high electrode thickness and small electrode lateral size, electrode size-dependent electrochemical properties were investigated in both experimental aspects and modeling aspects. As shown in FIG.14, similar rate capabilities were observed in electrodes with larger lateral sizes, suggesting the side electrode area plays little role in electrochemical reactions. From numerical simulations, the vertically aligned lamellae were determined to block Li-ion diffusion in an in- plane direction.

[0064] Therefore, as depicted in FIG.15, the side walls may lack an ability to function as an electrochemical active surface as an electrode top surface. To exclude an effect of the electrolyte outside of the side walls of the thick vertically lamellar electrodes, a set of different electrodes with different size ratios were considered. The size ratios can be associated with the top area versus a combination of the top area and side areas. The side ratios considered were 37.3%, 53.2%, and 58.1%. For electrodes with random pores, a difference in discharged capacities was observed when increasing the sample size from 0.1 cm2to 0.5 cm2, indicating that the side walls of the random thick electrodes can also be considered as a surface since Li ions can diffuse inside to compensate for a local ion depletion in the electrochemical reaction. However, for the vertically lamellar thick electrode, due to high in-plane tortuosity (e.g., greater than 10) of the lamellae, it can be difficult for outside Li ions to diffuse inside and function similarly as Li ions in electrodes with random pores. To simplify the model, five layers of lamella were added on each side to illustrate the effect. The porosity and tortuosity in these lamellae were 0.4 and 10, respectively. Accordingly, with an increase in lateral size (or top area ratio) of the lamellar electrodes, surrounding electrolyte may have little to no effect on the Li-ion concentration distribution in these electrodes, as shown in (FIG.15, Panel C). Theoretically, the electrochemical results from the small-sized samples can be linearly extended to the large-sized samples. As shown in FIG 15, Panel D, all three electrodes with vertically lamellar pores can exhibit very similar discharged capacities. These simulation results can strongly support experimental data as shown in FIG.14.Therefore, with respect to the electrode, only the top electrode area may be considered when calculating the areal capacity.

[0065] As shown in FIG.16, for tape-cast LCO electrodes, a maximum areal loading that can be reached can be approximately 60 mg cm-2, with a thickness of about 270 μm. It is noted this thickness is close to its critical cracking thickness by tape-casting method. The LCO-60% electrode can have a similar porosity as the conventional electrode, as indicated in Table 2 and Table 3 below. Electrode porosity can be calculated using Equation 7 shown below:in which mArepresents the areal mass loading, l represents the electrode thickness, ωAM, ωB, and ωCArepresent mass proportions of the active material, binder, and conductive additive, respectively, and ρAM, ρB, and ρCArepresent true densities of active material, binder, and conductive additive, respectively. In the LCO case, the true densities used for LCO, PVDF, CMCNa, and Super P are 5.0, 1.8, 1.6, and 1.6 g cm-3, respectively. Table 2. Porosity calculation of the tape-cast conventional LCO electrode Total Super P PVDF AM areal Electrode mass areal areal Thickness Density loading Porosity type loading loading loading (mm) (g cm-3) (mg-2g cm-2cm ) (m ) (mg cm-2) (mg cm-2) Tape- 60 53 3.6 3.6 0.27 0.45 2.2 cast Table 3. Porosity calculation of BFC LCO electrode before and after densification CMCNa Total Super P AM areal areal Electrode mass areal Thickness Density loading loading Porosity type loading loading (mm) (g cm-3) (mg-2 --2cm ) (mg cm (mg cm ) (mg cm-2)2) LCO-0% 108 95 6.5 6.5 1.12 0.76 0.9 LCO- 273 240 15.4 15.4 1.12 0.40 2.4 60%

[0066] With the similar porosity, the LCO-60% electrode can exhibit a similar initial Coulombic efficiency and a smaller activation overpotential in a first charge-discharge cycle (FIG.17). For the BFC LCO-60% electrode, the areal capacity can be calculated using Equation 8 provided below: CA, LCO-60%= Cs× MA, LCO= 139.53 mAh g-1× 240 mg cm-2= 33.49 mAh cm-2(8) in which CA, LCO-60%represents the areal capacity of the LCO-60% electrode, Csrepresents the specific capacity of LCO, and MA, LCOrepresents the areal mass loading of LCO.

[0067] As shown in FIG.17, the tape-cast electrode and BFC electrode can exhibit specific capacities of 145 mAh g-1and 140 mAh g-1, areal capacities of 8.2 mAh cm-2and 33 mAh cm-2, and an initial Coulombic efficiency (ICE) of 96.4% and 95.8%, respectively. Compared to the tape-cast electrode, the LCO-60% electrode may exhibit smaller activation overpotential in the initial charging process, indicating better electrolyte penetration due to the vertically lamellar architecture. Although the areal loading of the BFC LCO electrode is over four times that of the tape-cast electrode, the BFC LCO electrode can still show similar specific capacity and ICE at a C- rate of 0.1C.

[0068] In addition, the conventional electrode can show dramatic capacity decay when increasing the C-rate to 1C, suggesting poor ionic transport kinetics with random and tortuous pores. Comparing the areal capacities of the vertically lamellar electrode and conventional electrodes at various C-rates, the LCO-60% electrode can reach a maximum areal capacity of about 33 mAh cm-2, corresponding to a volumetric capacity of about 300 mAh cm-3. Additionally, the LCO-60% electrode can attain a retained areal capacity of about 10 mAh cm-2at a C-rate of 1C (FIG.13, Panel C), while the conventional electrode may only deliver an areal capacity of <3.5 mAh cm-2at a C-rate of 1C. In addition to the high rate capability, the LCO-60% electrode also can show stable cycling discharged at about 3.5 mA cm-2, with a retained capacity of about 21 mAh cm-2after 45 cycles (FIG.13, Panel D). After replacing the cycled Li metal covered by mossy Li dendrites, the areal capacity can be recovered back to about 27 mAh cm-2. As depicted in FIG.18, a large amount of mossy lithium dendrite can be observed on a surface of the Li metal. Cycled under a practical current density and a high areal capacity, the dead lithium can contribute to a capacity decrease in the cycling of the LCO electrode. After replacing the Li metal with fresh Li metal and adding additional electrolyte, the capacity of the LCO electrode can partially be recovered. Charge-discharge voltage profiles can reveal smaller polarization and a more obvious charge / discharge plateau with the fresh Li metal (FIG.19). The unrecovered part of LCO capacity can be ascribed to a crystal structure change under repeated cycling at the high voltage. For theconventional electrode, rapid capacity decay can be observed after about 30 cycles such that only about 3 mAh cm-2may be retained after 50 cycles. Compared to conventional high-areal-capacity thick cathodes (CA >10 mAh cm-2), the LCO-60% electrode can show superior areal capacity, volumetric capacity, and rate capability due to the densified vertically lamellar architecture (FIG. 13, Panel E).

[0069] Ionic diffusion kinetics were comprehensively studied in the vertically lamellar electrodes via various electrochemical characterization methods. Ionic resistances (Rion) of the vertically lamellar electrodes were probed by electrochemical impedance spectroscopy (EIS) in a symmetric cell configuration (FIG.20). The EIS symmetric cell characterization to determine the ionic resistance of the vertically lamellar electrodes can be based on a transmission line model (TLM) for ideal cylindrical pores. The EIS-SC measurements can be conducted in electrodes with a SOC of 0% to avoid any Faradaic process. In some cases, pristine LCO electrodes can be used in the symmetric cell assembly. Theoretically, in a high frequency region, the plot is linear with a 45-degree slope from the real axis and can transition to a constant Zω value at a low frequency region. Limiting values of the real (Z’ω) and imaginary (Z”ω) parts in the condition of ω→0 can be expressed by Equation 9 and Equation 10 provided below:where Rionrepresents a characteristic parameter to describe the lithium-ion diffusion in electrode pores. The real part in the 45-degree region equals Rion / 3. Rsolcan represent the resistance of Li-ion transport in the bulk electrolyte, and Rhighcan represent the interfacial ionic resistance and contact resistance. The measured Rioncan be correlated with τ using Equation 11:in which kintrepresents the intrinsic diffusivity of Li ions in the electrolyte (6 × 10-3cm2s-1).

[0070] The LCO-0% and LCO-60% electrodes can exhibit a Rionof 66 and 159 Ohm cm2, corresponding to the calculated τ of 1.25 and 1.59 via the blocking-electrolyte method, respectively, as shown in FIG.13, Panel F and Table 4 below.Table 4. Tortuosity measured by electrolyte-blocking method Electrode type Rion(Ohm cm2) Tortuosity τ LCO-0% 66 1.25 LCO-60% 159 1.59 A direct current (DC) polarization-depolarization method was also employed to determine the effective lithium-ion diffusion coefficients. The depolarization plots in the relaxation process are shown in FIG.13, Panel G. The intrinsic diffusion coefficient (Dint) of the electrolyte was measured in a cell with an O-ring spacer (FIG.21). In DC polarization-depolarization measurements, the concentration gradient relaxation of the cell voltage can be correlated with the electrode tortuosity. The relaxation voltage can be expressed as Equation 12 below:in which iprepresents the polarization current, σ, σel, σionrepresent the total, electronic, and ionic conductivities, respectively, and tδrepresents the characteristic time. Plotting ln |U (t) - U (t = ∞)| versus t, the characteristic time tδcan be obtained from the fitting slope (tδ= 1 / slope). The effective diffusion coefficient (Deff) can be determined according to Equation 13 as follows:

[0071] For example, the Dintcan be measured to be 1.83 × 10-6cm2s-1, while the Defffor the LCO-0% and LCO-60% electrodes can be 9.93 × 10-7and 4.31 × 10-7cm2s-1, respectively. As shown in Table 5 below, the Deffvalues can correspond to the τ of 1.38 and 1.67, respectively. Table 5. Tortuosity measured by DC polarization-depolarization method Diffusion Electrode type Thickness (mm) Fitted slope coefficient Tortuosity τ (cm2s-1) PTFE O-ring 1.0 -1.8×10-31.83×10-61 LCO-0% 1.2 -6.8×10-49.93×10-71.38 LCO-60% 1.2 -3.0×10-44.31×10-71.67

[0072] With the measured τ and ε in the vertically lamellar electrodes, the tortuosity-porosity correlation can be established with the modified Bruggeman equation according to Equation 14 below: τ = γε-α(14) in which γ represents a Bruggeman factor that can adjust a deviation of the ideal case from the practical case. As an example, for the conventional LCO electrode, γ and α can be determined to be 1.8 and 0.53, respectively, indicating that the actual tortuosity of the LCO electrode can be much higher than the theoretical value. The difference between the actual tortuosity and the theoretical value may be due to the particle arrangement and the carbon binder region (FIG.13, Panel H). As an example, in the vertically lamellar electrodes, the fitted γ and α can be 1.2 and 0.34, respectively. The smaller α of the vertically lamellar electrodes can indicate that the ion transport pathway is less tortuous than the conventional LCO electrode, deviating from that in the spherical particle-based electrodes. This tortuosity-porosity relationship can suggest the merit of the vertically lamellar pores that can promote the lithium-ion transport even in a low-porosity electrode.

[0073] The method for fabricating low-tortuosity high-density thick electrodes was expanded to active material systems beyond LCO. Vertically laminar architectures can be successfully created in other commercially available cathodes, such as LiNi1 / 3Mn1 / 3Co1 / 3O2(NMC) and LiFePO4(LFP) (FIG.22). The BFC NMC electrodes can exhibit smaller width (e.g., 20.7 μm) with larger thickness (e.g., 15.8 μm) compared to dimensions of the LCO electrodes with active material particles penetrating the lamellae (FIG.23, Panel A and FIG.24). It is noted that the channel width (20.7 μm) is smaller while the wall thickness (15.8 μm) is larger than that of the BFC LCO electrode. NMC particles can be observed penetrating the walls from FIG.24, Panel C. After densification, a significant decrease of the width (e.g., to 7.5 μm) can be observed, forming a densely packed lamellar structure (FIG.23, Panel B). The thick NMC electrode can deliver high areal capacities of 32 mAh cm-2and 10 mAh cm-2at a C-rate of 0.1C and 1C, respectively. The areal capacities can correspond to specific capacities of 137 mAh g-1NMCand 43 mAh g-1NMC, respectively (FIG.23, Panel C). In the LFP electrode, a width (e.g., 23.3 μm) and thickness (e.g., 10.8 μm) can be similar to the LCO electrodes, while LFP particles are all buried inside the lamellae due to their smaller particle size (FIG.23, Panel D and FIG.25). After densification, lamellar structure can also be maintained in the LFP electrode, for example resulting in a shortened width of 6.2 μm, as shown in FIG.23, Panel E. Due to a low electrical conductivity as well as a large specific surface area of LFP particles, more conductive filler and binder comparedto the LCO electrodes may be used to ensure high electrical conductivity and mechanical strength, resulting in a lower areal capacity compared to the LCO and NMC ones even with a similar electrode thickness. The LFP electrode can reach a maximum areal capacity of 19 mAh cm-2, with a capacity retention of 48% when increasing the C-rate to 1C. For the conventional tape-cast electrodes, the maximum electrode thicknesses can be about 250 μm and about 150 μm for NMC and LFP, respectively, making the maximum areal capacities less than 8 and 4 mAh cm-2for these conventional electrodes (FIG.26). It is noted that more binder and conductive carbon can be required to prepare suitable BFC and conventional LFP electrodes due to a lower electrical conductivity, lower true density, and larger particle surface area of LFP compared to LCO and NMC. The areal capacities and rate capabilities of these densified vertically lamellar electrodes can be superior to conventional thick electrodes, which presents merits of architecting the interlamellar spacing in low-tortuosity electrodes for efficient ion transport in both channels and walls. Additionally, cell-level specific energy and energy density can be significantly enhanced via reducing an inactive component ratio by pairing the thick electrode with a Li metal anode.

[0074] Cell-level specific energy calculations can be calculated using the weight of cathode, anode, electrolyte, and separator according to Equation 15 below:where U represents the operating cell voltage during discharge, Ccellrepresents the areal cell capacity, and mcell, mcathode, manode, mseparator, and melectrolyterepresent areal mass of the cell, cathode, anode, separator, and electrolyte, respectively. Current collector may not be used in this cell configuration. It can be assumed that the electrolyte accumulates in the pores inside the cathode and the separator and that no extra volume may be required in the cells. As an example, manodecan be 25.3 mg cm-2(e.g., for a lithium metal chip with a thickness of 0.25 mm), mseparator can be 1.2 mg cm-2(e.g., for a 20-μm thick trilayer PP / PE / PP polymer separator with a porosity of 0.4), and melectrolytecan be calculated as 1.1 × (Vp, cathode+ 1.0) mg cm-2. Vp, cathodecan be the pore volume of the cathode electrode (mm3). Cell-level energy density calculations can follow Equation 16 as follows:where Vcell, Vcathode, Vanode, Vseparator, and Velectrolyterepresent a volume of the cell, cathode, anode, separator, and electrolyte, respectively. As an example, for simplicity, thicknesses of cathode,anode and separator used in the cell-level energy density calculation can be determined while estimating the cell area as 1.0 cm2.

[0075] The densified BFC electrodes can exhibit specific energies of 373 Wh kg-1, 354 Wh kg-1, and 252 Wh kg-1for LCO, NMC, and LFP, respectively, as shown below in Table 6. Table 6. Calculations of specific energy and energy density for LCO, NMC, LFP Electrode Method Specific Energy Energy Density LCO 373 Wh kg-1940 Wh L-1NMC Bidirectional freeze casting 354 Wh kg-1839 Wh L-1and densification LFP 252 Wh kg-1474 Wh L-1Meanwhile, these thick electrode-based cells can exhibit high energy densities of 940 Wh L-1, 839 Wh L-1, and 474 Wh L-1for LCO electrodes, NMC electrodes, and LFP electrodes, respectively. For cycling stability, high areal capacity retentions can be achieved in both NMC and LFP cells at a C-rate of 0.1C for over 70 cycles (FIG.23, Panel G and Panel H). Charge-discharge voltage profiles can reveal a gradual increase of polarization in the NMC cell with extended cycles, while the LFP cell with a lower areal capacity can exhibit little difference in charge-discharge curves under different cycle numbers (FIG.27).

[0076] Additionally, integrating the bidirectional freeze-casting process and densification concept with commercial roll-to-roll electrode manufacturing was considered. For example, a large-sized densified BFC LCO electrode with a current collector can be provided using a modified bidirectional freeze-casting setup shown in FIG.28. Densification can be realized by calendering the BFC electrode, with the calendering direction orthogonal to the lamellae, which can result in tilted yet aligned channels in densified electrodes. Long-range lamellar structure can be formed with a solid content of 38 vol% in the slurry (FIG.29). As an example, the weight ratio of LCO, Super P, and CMCNa can 94:3:3. It is noted that water content may contribute to the formation of lamellar structure. For example, 38 vol% of the solid content can be a maximum for LCO active material. Although, the solid content for the long-range lamellar structure is higher than the one used in FIG.10 (e.g., 32 vol%), a less amount of Super P and binder (6 wt%) can decrease slurry viscosity. Accordingly, the vertically lamellar architectures can still be formed.

[0077] After being calendered, the vertically aligned channels can become tilted with an angle of about 35° relative to the current collector plane, as shown in side-view SEM images of FIG.30. Porosity of the BFC electrode decreases from 0.52 to 0.41 after calendering. The electrodedensification is mainly contributed by making the lamellae tilted with an angle of ~35° relative to the current collector plane. The fabricated electrode can show suitable integrity on the current collector with a high areal mass loading of 60 mg cm-2to 70 mg cm-2. For rate performance, the densified BFC electrode can deliver a discharged capacity of 76 mAh g-1at a C-rate of 1C, which is about 1.7 times of the tape-cast electrode (e.g., 45 mAh g-1), suggesting that the aligned channels are beneficial to efficient charge transport inside the thick electrode (FIG.31). The areal loadings of LCO electrodes used are about 60 mg cm-2to 65 mg cm-2, corresponding to areal capacities of about 8 mAh cm-2to 9 mAh cm-2. Porosity of these electrodes was controlled to be about 40% by calendering. Utilizing the modified setup, it can also be possible to scale up the BFC electrode fabrication with other cathode materials.

[0078] In summary, an effective methodology can combine bidirectional freeze-casting and densification to prepare versatile high-density vertically lamellar electrode architectures for the next generation of scalable high-energy storage systems. With tunable interlamellar spacing via controlling the compression ratio, simultaneous high energy density and power density can be achieved due to decoupled ion transport in channels and walls of the electrodes. The densified electrode can exhibit both a high areal capacity of about 33 mAh cm-2, which is about 8 times that of conventional electrodes, and a high volumetric capacity of about 300 mAh cm-3even with a thickness over one millimeter. Furthermore, an areal capacity over 10 mAh cm-2can be retained when operated at a large current density of about 34 mA cm-2. The tortuosity-porosity correlation was probed via various electrochemical characterization approaches, revealing facilitated charge transport kinetics in the vertically lamellar architectures. Combined with numerical simulations, the simultaneous thin wall thickness and channel width was shown to contribute to the superior electrochemical properties compared to the electrodes with random pore distribution, alleviating concentration polarization in the electrolyte and homogenizing the active material (de)lithiation states across the electrode depth. The electrode architecture design rationale in low-tortuosity electrodes was presented and can bring additional insights into tailoring spatial pore distribution to overcome the trade-off of energy and power in thick battery electrodes for practical energy storage systems.

[0079] Preparation of Versatile BFC Electrodes. For preparing BFC LCO electrodes, 220 mg LCO powder, 15 mg Super P conductive carbon, and 300 mg 5 wt% sodium carboxymethyl cellulose binder (CMCNa; Mw~250,000) dissolved in de-ionized (DI) water were mixed with a mass ratio of 88:6:6 in a mixer for 10 min. For bidirectional freeze-casting, the LCO slurry was transferred into a polytetrafluoroethylene (PTFE) mold with a size of 1.6 cm × 1.6 cm. The PTFEmold was placed on PDMS and copper wedges with the same angle of inclination of 20°. The wedges were used to control thermal conduction in both longitudinal and lateral directions due to the different thermal conductivities of PDMS (0.16 W mK-1) and copper (398 W mK-1). Liquid nitrogen was used as the cold reservoir. After the LCO slurry was completely frozen, the slurry was transferred into a lyophilizer and freeze-dried at -50 °C and <5 Pa for 12 h. The freeze-dried LCO electrodes were stored in a vacuum oven at 90 °C overnight before use. To densify the LCO electrodes, the as-fabricated LCO electrodes were first cut into small pieces with a size of 5 mm × 5 mm. Then, these electrodes were compressed by 60 vol% in the direction orthogonal to the lamellae and the densified electrodes were with a size of 5 mm × 2 mm. The thicknesses of these electrodes were about 1.1 to 1.2 mm. For NMC electrodes, 220 mg NMC111 powder, 15 mg Super P, and 300 mg 5 wt% CMCNa solution were mixed with a ratio of 88:6:6 for 10 min. For LFP electrodes, 190 mg LFP, 22.5 mg Super P, 375 mg 10 wt% CMCNa solution, and 50 μl extra DI water with a ratio of 76:9:15 was used. The bidirectional freeze-casting and densification processes in preparing the NMC and LFP electrodes were the same as the LCO ones. For the conventional thick electrodes, LCO, NMC, and LFP electrodes were fabricated with the same component ratio as those of the BFC electrodes. Polyvinylidene difluoride and N-Methyl-2- pyrrolidone were used as the binder and solvent, respectively. For the scaling up demonstration, LCO, Super P, and CMCNa (7.5 wt% in water) were mixed with a weight ratio of 94:3:3 and a solid content of 38 vol%. The slurry was tape-cast on an Al foil as the current collector and bidirectional freeze-casting was enabled by a modified setup. The freeze-dried electrode was calendered in the direction orthogonal to the lamellae to achieve the densified lamellar electrodes.

[0080] Electrode Architecture and Electrochemical Characterization. The morphology of the commercial LCO, NMC, and LFP powders were characterized by a scanning electron microscope. The architecture of the BFC electrodes were imaged by an environmental scanning electron microscope. EDS spectra were characterized by a low-vacuum scanning electron microscope.2320-type coin cells were used to investigate the electrochemical properties of the BFC electrodes. The coin cells were assembled in an Ar-filled glove box with water and oxygen contents both lower than 0.1 ppm. In the half-cell assembly, trilayer microporous membranes were used as the separator, lithium metal discs with a diameter of 16 mm and a thickness of 0.45 mm were used as the anode, and 200 μl 1.0 M lithium hexafluorophosphate (LiPF6) dissolved in the mixture of ethylene carbonate and diethyl carbonate with the volume ratio of 1:1 was used as the electrolyte. Electrochemical performance of the cells was tested on a battery tester. For LCO, NMC and LFP cathodes, constant current-constant voltage (CC-CV) charge and CC discharge were applied in the electrochemical window of 2.8-4.20 or 4.25 V vs. Li+ / Li. For the ratecapability tests, the electrodes were first charged at 0.1C (1C = 140, 150 and 170 mA g-1for LCO, NMC, and LFP, respectively) and the voltage was held at 4.25 V (for LCO and NMC) and 4.20 V (for LFP) until the current reaches the current limit (0.01C). Then, the electrodes were discharged at various C-rates from 0.1 to 1C. For cycling tests, the cells were operated at 0.1C following the CC-CV charge and CC discharge protocol. EIS and DC polarization / depolarization measurements were conducted on a potentiostat. Half-cell and symmetric-cell EIS were carried out with a frequency range from 1 MHz to 0.1 Hz and an amplitude of 10 mV. In symmetric-cell EIS measurements, two identical battery electrodes were paired with a separator between them. In DC polarization-depolarization tests, the test electrode was sandwiched by lithium chips, and separators were placed between the electrode and lithium chips to block electron conduction. To determine the intrinsic diffusion coefficient, a PTFE O-ring was used to replace the battery electrode. After being stimulated by a current of 0.1 mA for 2 h, the cells were placed for 2 h for relaxation.

[0081] Modeling Simulation.2D models were constructed, and simulations were conducted. LCO served as the active material in the cathode, and lithium metal was the anode. 1 mol L-1LiPF6in EC / DEC (1:1 in volume) was selected as the electrolyte in these models. The galvanostatic charging rate was set to 0.01 C for all cells, followed by being charged at a constant voltage until the current density reached one-tenth of the charging current density. After the charging process, galvanostatic discharging at various current densities was performed.

[0082] For electrodes with parallelly aligned 2D channels, the porosity of the electrode can be controlled by changing the channel width, with the porosity in walls (0.2) being unchanged. Because of the low-tortuosity architecture, the tortuosity of these vertically lamellar-architected electrodes can be set to 1. The tortuosity of the electrodes with random pores can be set as 3 and 1.3 in the low-porosity and the high-porosity cases, respectively. The wall thickness of electrodes with vertically lamellar architectures can be set as 10 μm. The thickness of the electrodes can be 1.2 mm. REFERENCES

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[0136] All references throughout this application, for example patent documents, including issued or granted patents or equivalents and patent application publications, and non-patent literature documents or other source material are hereby incorporated by reference herein in their entireties, as though individually incorporated by reference.

[0137] All patents and publications mentioned in the specification are indicative of the levels of skill of those skilled in the art to which the invention pertains. References cited herein are incorporated by reference herein in their entirety to indicate the state of the art, in some cases as of their filing date, and it is intended that this information can be employed herein, if needed, to exclude (for example, to disclaim) specific embodiments that are in the prior art.

[0138] When a group of substituents is disclosed herein, it is understood that all individual members of those groups and all subgroups and classes that can be formed using the substituents are disclosed separately. When a Markush group or other grouping is used herein, all individual members of the group and all combinations and subcombinations possible of the group are intended to be individually included in the disclosure. As used herein, “and / or” means that one, all, or any combination of items in a list separated by “and / or” are included in the list; for example “1, 2 and / or 3” is equivalent to “1, 2, 3, 1 and 2, 1 and 3, 2 and 3, or 1, 2, and 3”.

[0139] Every formulation or combination of components described or exemplified can be used to practice the invention, unless otherwise stated. Specific names of materials are intended to be exemplary, as it is known that one of ordinary skill in the art can name the same material differently. It will be appreciated that methods, device elements, starting materials, and synthetic methods other than those specifically exemplified can be employed in the practice of the invention without resort to undue experimentation. All art-known functional equivalents, of any such methods, device elements, starting materials, and synthetic methods are intended to be included in this invention. Whenever a range is given in the specification, for example, a temperature range, a time range, or a composition range, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure.

[0140] As used herein, “comprising” is synonymous with “including,” “containing,” or “characterized by,” and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, “consisting of” excludes any element, step, or ingredient not specified in the claim element. As used herein, “consisting essentially of” does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. Any recitation herein of the term “comprising”, particularly in a description of components of a composition, in a description of a method, or in a description of elements of a device, is understood to encompass those compositions, methods, or devices consisting essentially of and consisting of the recited components or elements, optionally in addition to other components or elements. The invention illustratively described herein suitably may be practiced in the absence of any element, elements, limitation, or limitations which is not specifically disclosed herein.

[0141] The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosedby preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.

Claims

Attorney Docket No.: 093331-14498348180 YU-WO WHAT IS CLAIMED IS:

1. An electrode, comprising: a current collector; and an active material layer in contact with the current collector and including a plurality of lamellar segments extending from a surface of the current collector, wherein each lamellar segment corresponds to a planar electrode structure aligned along a lamellar axis, the planar electrode structure comprising a conductive additive, a binder, and particles of an active material.

2. The electrode of claim 1, wherein the active material of the active material layer comprises a lithium host material, a lithium transition metal oxide cathode, lithium nickel manganese cobalt oxide, lithium iron phosphate, or lithium cobalt oxide.

3. The electrode of claim 1, wherein the conductive additive comprises carbon black, graphite, or conductive carbon.

4. The electrode of claim 1, wherein the binder comprises a carbon-based material.

5. The electrode of claim 4, wherein the binder comprises sodium carboxymethyl cellulose, lignin, or chitin.

6. The electrode of claim 1, wherein the current collector comprises a metallic element or metallic compound.

7. The electrode of claim 6, wherein the current collector comprises aluminum or copper.

8. The electrode of claim 1, wherein the active material layer is characterized by a porosity of from about 30% to about 80%.

9. The electrode of claim 1, wherein the active material layer is characterized by an areal mass loading of from about 50 mg cm-2to about 300 mg cm-2.

10. The electrode of claim 1, wherein the plurality of lamellar segments are characterized by a thickness of about 1.0 mm to about 1.5 mm.

11. The electrode of claim 1, wherein the plurality of lamellar segments defines a plurality of interlamellar channels configured to facilitate charge transport kinetics of the electrode.

12. The electrode of claim 1, wherein the electrode exhibits or is configured to exhibit a discharge capacity of from about 60 mAh g-1to about 90 mAh g-1at a C-rate of about 1C.

13. The electrode of claim 1, wherein the electrode exhibits or is configured to exhibit an areal capacity of from about 20 mAh cm-2to about 50 mAh cm-2.

14. The electrode of claim 1, wherein the electrode exhibits or is configured to exhibit a volumetric capacity of from about 200 mAh cm-3to about 400 mAh cm-3.

15. The electrode of claim 1, wherein the plurality of lamellar segments are grown on a surface of the current collector using a bidirectional freeze casting process, wherein the bidirectional freeze casting process comprises freezing a slurry in contact with the current collector by subjecting the slurry to a first temperature gradient along the lamellar axis and a second temperature gradient along an axis perpendicular to the lamellar axis to form a frozen slurry, the slurry comprising the conductive additive, particles of the active material, the binder, and a solvent, and wherein the bidirectional freeze casting process further comprises freeze-drying the frozen slurry to remove the solvent from the frozen slurry through sublimation.

16. The electrode of claim 1, wherein the plurality of lamellar segments correspond to a plurality of compressed electrodes, wherein a compressed electrode is formed by applying a compressive force to the plurality of lamellar segments to reduce an interlamellar spacing between the plurality of lamellar segments.

17. The electrode of claim 16, wherein the compressed electrode is characterized by a decrease in volume of from about 20% to about 80% by application of the compressive force.

18. A method, comprising: growing a plurality of lamellar segments on a surface of a current collector using a bidirectional freeze casting process to collectively form an active material layer of an electrode,wherein a lamellar segment corresponds to a planar electrode structure aligned along a lamellar axis, the planar electrode structure comprising a conductive additive, a binder, and particles of an active material, wherein the bidirectional freeze casting process comprises freezing a slurry in contact with the current collector by subjecting the slurry to a first temperature gradient along the lamellar axis and a second temperature gradient along an axis perpendicular to the lamellar axis to form a frozen slurry, the slurry comprising the conductive additive, particles of the active material, the binder, and a solvent, and wherein the bidirectional freeze casting process further comprises freeze- drying the frozen slurry to remove the solvent from the frozen slurry through sublimation; and applying a compressive force to the plurality of lamellar segments to reduce an interlamellar spacing between the plurality of lamellar segments.

19. The method of claim 18, wherein the first temperature gradient is generated based on a distance from the current collector along the lamellar axis.

20. The method of claim 18, wherein the second temperature gradient is generated based on at least in part on relative thicknesses of a first layer comprising the current collector having a first thermal conductivity and a second layer comprising a material having a second thermal conductivity different from the first thermal conductivity.

21. The method of claim 20, wherein the first thermal conductivity is lower than the second thermal conductivity.

22. The method of claim 18, wherein the first temperature gradient and the second temperature gradient are generated at least in part by a heat sink.

23. The method of claim 22, wherein the heat sink comprises liquid nitrogen.

24. The method of claim 18, wherein the solvent of the slurry comprises water.

25. The method of claim 18, wherein the freezing step is configured to exhibit ice propagation within the slurry that is aligned with the first temperature gradient.

26. The method of claim 18, wherein the freeze-drying step is performed at a freeze-drying temperature of from 0 to -100 °C.

27. The method of claim 18, wherein the freeze-drying step is performed at a freeze-drying pressure of less than 5 Pa.

28. The method of claim 18, wherein compressing the plurality of lamellar segments reduces a volume of the electrode by about 20% to about 80%.

29. The method of claim 18, wherein compressing the plurality of lamellar segments is performed in a compression direction that is orthogonal the plurality of lamellar segments.

30. The method of claim 18, wherein compressing the plurality of lamellar segments is performed by calendering the plurality of lamellar segments.

31. The method of claim 30, wherein calendering the plurality of lamellar segments is performed using a calendering direction that is orthogonal to the plurality of lamellar segments.

32. The method of claim 30, wherein calendering the plurality of lamellar segments causes the plurality of lamellar segments to tilt at an angle of between 15° to 60° relative to the current collector.

33. The method of any of claims 18-32, wherein the electrode comprises the electrode of any of claims 1-17.

34. A battery, comprising: a freeze-casted cathode, the freeze-casted cathode comprising a current collector and an active material layer in contact with the current collector, wherein the active material layer includes a plurality of lamellar segments extending from a surface of the current collector, wherein each lamellar segment corresponds to a planar electrode structure aligned along a lamellar axis, the planar electrode structure comprising a conductive additive, a binder, and particles of an active material; an anode; and an electrolyte between the freeze-casted cathode and the anode.

35. The battery of claim 34, wherein the plurality of lamellar segments are grown on a surface of the current collector using a bidirectional freeze casting process,wherein the bidirectional freeze casting process comprises freezing a slurry in contact with the current collector by subjecting the slurry to a first temperature gradient along the lamellar axis and a second temperature gradient along an axis perpendicular to the lamellar axis to form a frozen slurry, the slurry comprising the conductive additive, particles of the active material, the binder, and a solvent, wherein the bidirectional freeze casting process further comprises freeze-drying the frozen slurry to remove the solvent from the frozen slurry through sublimation, and wherein a compressive force is applied to the plurality of lamellar segments to reduce an interlamellar spacing between the plurality of lamellar segments.

36. The battery of claim 34, wherein the anode comprises a lithium alloying anode.

37. The battery of claim 34, wherein the electrolyte comprises a liquid electrolyte.

38. The battery of claim 37, wherein the liquid electrolyte comprises an electrolyte solvent including one or more of ethylene carbonate (EC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or propylene carbonate (PC) and one or more salts including LiPF6, LiTFSI, LiFSI, LiBF4, LiCIO4, LiNO3, LiAlCl4, LiAlF4, LiAsF6, LiCF3SO3, LiC(CF3SO2)3, or LiC4F3SO3.

39. The battery of any of claims 34-38, wherein the freeze-casted cathode comprises the electrode of any of claims 1-17.

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