Fast-charging, high-energy and high-power density Lithium-ion batteries (LIBs) are critical to advancing next generation portable electronic, electric vehicle, and grid-scale applications. Conventional LIBs are made of flat, uniform anode and cathode electrode stacks that can be optimized for energy or power, but typically not both simultaneously. This is due to transport limitations that occur with increases in electrode thickness. The performance of thick battery electrodes can be significantly enhanced by patterning their active material particles, ideally enabling faster charging rates and higher power densities without the need for new materials. Structured Electrodes (SEs) have been proposed as a solution to address these challenges. 1 SEs engineer battery electrodes into three-dimensional (3D) spatial arrangements of material on a scale ranging from tens to hundreds of microns to reduce electrode tortuosity and enable rapid ionic transport in thick electrodes. While a promising concept, scalable manufacturing methods for depositing SEs over large areas and understanding the limits of these electrode designs remain a challenge. This talk will discuss a new manufacturing approach to enable rapid, large-area fabrication of LIB SEs based on field-assisted patterning. Specifically, principles of acoustophoresis are used to enable rapid particle assembly in conventional battery slurries. With this processing method, acoustic patterning forces operate independent of material chemistry and instead rely on differences in particle morphology, density, and fluid medium properties. Models of acoustic particle focusing 2 have been developed to guide process development with the goal of assembling thick SEs (> 100µm). Standing acoustic waves are used to deposit line-patterned and grid-patterned battery electrodes. Using conventional battery slurries based on carbon black, polyvinylidene fluoride, and N-methyl-2-pyrrolidone, initial experimental results with graphite and LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC-622) electrodes in 2032 coin cells show SEs can have a 10-140% improvement in specific discharge capacity at C/2 – 2C rates. To understand the limits of SEs, 3D computational models were developed to guide process development and investigate the impact of different SE geometries on thick graphite|NMC-622 battery cells based on the footprint of an electric vehicle pouch cell. Modeling results show that gravimetric and volumetric energy density improvements of 18%–24% at 4C–6C rates can be achieved over conventional pouch cells made with the same materials. 3 This talk will conclude by highlighting opportunities for acoustic processing of functional materials in other application spaces. References C. L. Cobb and S. E. Solberg, J. Electrochem. Soc., 164 (7), A1339-A1341 (2017). E.N. Armstrong, K.E. Johnson, K.A. Herbruger, A.K. Sanchez, M.R. Begley, C.L. Cobb, Additive Manufacturing , 104778 (2025). C.-H. Hung, S. Allu, C.L. Cobb, J. Electrochem. Soc. , 172, 010513 (2025). Acknowledgements This material is based upon work supported in part by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Advanced Materials and Manufacturing Technologies Office (AMMTO) Award Number DE-EE0010226. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government. This material is based upon work supported in part by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Advanced Materials and Manufacturing Technologies Office (AMMTO) Award Number DE-EE0009112. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government. This work was partially carried out at the Materials Engineering Research Facility (MERF) at Argonne National Laboratory, which is supported by the DOE, Office of Energy Efficiency and Renewable Energy, and the Vehicle Technologies Office, under the Contract No. DE-AC02-06CH11357. The MERF synthesized size-specific NMC-622 for the project. The authors are thankful for the support and resources from Compute and Data Environment for Science (CADES) used for conducting the simulations at Oak Ridge National Laboratory.

Long-range electric vehicles (EVs) require high-energy-density batteries that also meet the power demands of high current charge and discharge. Ultra-thick (>100 mu m) Lithium-ion battery electrodes are critical to enable this need, but slow ion transport in conventional uniform electrodes (UEs) reduces battery capacity at increasing charge/discharge rates. We present a 3D computational analysis on the impact of structured electrode (SE) and graded electrode (GE) geometries on the discharge rate capability of ultra-thick graphite|LiNi0.6Mn0.2Co0.2O2 (NMC-622) battery cells based on the footprint of a commercial EV pouch cell. SE cathodes with either a "grid" or "line" geometry and GEs with two layers of porosity were modeled. Based on the results of 230 models, we found that the electrolyte volume fraction is a key parameter that impacts capacity improvements in UEs, GEs, and SEs at 2 C-6 C discharge rates. SEs have the greatest discharge rate capability, outperforming GEs and UEs due to reduced Lithium-ion concentration gradients across the electrode thickness, which mitigates electrolyte depletion at high rates. The best SE model has a "grid" geometry with gravimetric and volumetric energy density improvements of 0.9%-4% at C/2-2 C and 18%-24% at 4 C-6 C relative to UEs.

Patterned functional materials offer improved properties (electrical, thermal, etc.) over their bulk counterparts in many applications, including energy storage, flexible electronics, and sensors. However, manufacturing approaches for patterning materials over large areas with features on the order of hundreds of microns or less are limited. Acoustophoresis, which uses acoustic forces to control particle arrangement in a fluid medium, is a pathway to address this challenge. This process is dependent on particle and fluid properties and enables patterning of a broad range of materials. Herein, a model with experimental validation is presented to demonstrate that acoustophoresis can be combined with direct-ink writing (DIW) to fabricate line patterns over large cm-scale areas. An in-nozzle particle interaction model was developed to investigate the impact of processing conditions on multi-nodal acoustophoretic DIW. The model predicts patterned line widths within a factor of two relative to experimental results for a high-viscosity case study. The model was used to investigate the impact of frequency, particle loading, particle radius, and acoustic pressure on line width and patterning time, providing critical feedback regarding the processing conditions suitable for a target application. Model results illustrate that frequency had the greatest impact on line patterns: increasing from 1 to 3 MHz resulted in a greater than 65% reduction in line width and a greater than 85% reduction in patterning time. Additionally, experiments were conducted with an alumina-epoxy ink, and a similar to 21 cm(2) area pattern was rastered in similar to 5.5 minutes, demonstrating a path towards large-area line-patterned composite fabrication.

Hybrid digital fabrication combines 3D printing with additional fabrication functionality such as pick-and-place (PnP) to enable customizable, printed electronic (PE) devices with an expansive array of form factors. Researchers have investigated a wide range of new materials, methods, and processes to advance PE devices. However, existing platforms cannot be easily modified or customized, severely limiting one’s ability to adapt hybrid digital fabrication platforms to ever evolving research and prototype needs. This paper introduces Jitterbug, a hybrid digital fabrication platform that supports rapid prototyping of PEs. Jitterbug consists of a toolpath generation workflow and an automatic tool-changing hardware system that builds upon existing open-source 3-axis motion frameworks. The toolpath generation workflow allows users to design PEs and generate toolpath programs directly in its computer-aided design (CAD) environment, provides granular control of the fabrication workflow, and enables printing of conductive traces on substrates with curved features at low-incline angles (< 50°). For demonstration purposes, Jitterbug’s initial tool-changing system is designed with the core fused filament fabrication (FFF), direct ink writing (DIW), and PnP tools necessary for hybrid digital fabrication; the system can support up to ten tools for different PE workflows. Jitterbug’s capabilities are demonstrated through fabrication of two functional light-emitting diode (LED) prototype devices, and its implications on designing specialized workflows for PEs are discussed.

Separators play a critical role in lithium-ion batteries (LIBs) by facilitating lithium-ion (Li-ion) transport while enabling safe battery operation. However, commercial separators made from polypropylene (PP) or polyethylene (PE) impose a discrete processing step in current LIB manufacturing as they cannot be manufactured with the same slot-die coating process used to fabricate the electrodes. Moreover, commercial separators cannot accommodate newer manufacturing processes used to produce leading-edge microbatteries and flexible batteries with customized form factors. As a path toward rethinking LIB fabrication, we have developed a high-viscosity polymer composite separator slurry that enables the fabrication of both freestanding and direct-on-electrode films. A streamlined phase inversion process is used to impart porosity in cast separator films upon drying. To understand the impacts of material composition and rheology on phase inversion processing and separator performance, we investigated four different separator formulations. We used either diethylene glycol (DEG) or triethyl phosphate (TEP) as a nonsolvent, and either silica (SiO2) or alumina (Al2O3) as an inorganic additive in a polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) matrix. Through a down-selection process, we developed a TEP-SiO2 separator formulation that matched or outperformed a commercial Celgard 2325 (PP/PE/PP) separator and a Beyond Battery ceramic-coated PE (CC/PE/CC) separator under rate and cycle life tests in LiFePO4|Li4Ti5O12 (LFP|LTO) and LiNi0.5Mn0.3Co0.2O2|graphite (NMC-532|graphite) coin cells at C/10-1C rates. Our TEP-SiO2 slurry had a viscosity of 298 Pa s at a 1 s(-1) shear rate and shear-thinning behavior. When deposited directly onto an LTO anode and cycled against an LFP cathode, the direct-on-electrode TEP-SiO2 separator increased the specific capacity by 58% and 304% at 2C rates relative to the PP/PE/PP and CC/PE/CC separators, respectively. Additionally, the freestanding TEP-SiO2 separator maintained dimensional stability when heated to 200 degrees C for 1 h and demonstrated a higher elastic modulus and hardness than the PP/PE/PP and CC/PE/CC separators when measured with nanoindentation.

The cathode–electrolyte interphase plays a pivotal role in determining the usable capacity and cycling stability of electrochemical cells, yet it is overshadowed by its counterpart, the solid–electrolyte interphase. This is primarily due to the prevalence of side reactions, particularly at low potentials on the negative electrode, especially in state-of-the-art Li-ion batteries where the charge cutoff voltage is limited. However, as the quest for high-energy battery technologies intensifies, there is a pressing need to advance the study of cathode–electrolyte interphase properties. Here, we present a comprehensive approach to analyse the cathode–electrolyte interphase in battery systems. We underscore the importance of employing model cathode materials and coin cell protocols to establish baseline performance. Additionally, we delve into the factors behind the inconsistent and occasionally controversial findings related to the cathode–electrolyte interphase. We also address the challenges and opportunities in characterizing and simulating the cathode–electrolyte interphase, offering potential solutions to enhance its relevance to real-world applications. The cathode–electrolyte interphase (CEI) is vital for battery cell capacity and stability but receives less attention than the solid–electrolyte interphase. The authors review CEI properties, emphasize using model cathode materials and coin cell protocols, and address challenges and opportunities in characterizing and simulating CEI for real-world applications.

Two-dimensional patterning of microparticles enables a wide range of functional materials, including patterned energy storage electrodes, flexible electronics, and sensor arrays. Particle patterning via acoustics offers an attractive path to generate a wide variety of 2D periodic patterns that introduce tailorable hierarchical porosity, useful for controlling surface area, transport distances, and other properties. This method is most effective with micron scale particles and patterns of tens to hundreds of microns. To enable systematic exploration of the broad design space for such patterns, this work develops a model of 2D and 3D assembly of particles at high loadings and validates the obtained patterns against both experiments and more computationally intensive modeling techniques. Using this simple model, connections are mapped between input parameters (like actuation conditions, particle volume fraction, material properties) and output geometrical features (like void size and shape, pattern connectivity, and surface area) so that they can be tailored to given applications. The utility of this simple model is illustrated by predicting and then experimentally demonstrating new hierarchical patterns resulting from multiple waves of different frequencies interacting. These multiscale patterns offer the potential to lift the limits on surface area, diffusion distances, and other features.

Additive manufacturing (AM) enables the fabrication of complex shapes and formfactors that are inefficient or impossible to produce with traditional subtractive machining tools. AM emerged in the 1980s to enable the rapid creation of functional prototypes (also known as rapid prototyping). The first commercial implementation of AM was a stereolithography (SLA) system developed by 3D Systems in 1987, wherein a laser solidified thin layers of a photoactive polymer solution. In the early 1990s, fused deposition modeling (FDM), selective laser sintering, and other AM modalities began to emerge and have continued to grow in the decades since. Within the last ten years, AM has gained traction as an approach to fabricate Lithium-ion batteries (LIBs) because it enables (1) novel three-dimensional (3D) electrodes that optimize energy and power performance and (2) customizable battery shapes for integrated and mechanically robust batteries for portable device applications. As energy storage demands grow, so does the need for LIBs to come in a multitude of sizes, shapes, and materials that meet the needs of a given application. In this chapter, we review the main AM approaches that have been used to produce LIBs with a focus on FDM, direct-ink write (DIW), inkjet printing (IJP), aerosol jet printing (AJP), electrostatic spray deposition (ESD), stereolithography (SLA), and newer field-assisted (FA) methods.

Digital fabrication machines are controlled through code. Software that generates this code, such as slicers, often rely on abstractions that restrict practitioners from exploring the full design space. We contribute Vespidae, a programming framework for developing custom toolpaths and visualizations. Vespidae module types include Toolpaths, Actions, Solvers, and Export. These generate geometry, specify machine tasks, sort and visualize action sequences, and generate and stream machine code. We show example workflows that demonstrate Vespidae’s strengths in supporting iteration and unconventional practice. These include non-planar 3D printing, varying a print’s tactile qualities with under-extrusion, and exploring the design space of milling marks. Furthermore, we used Vespidae over the course of six months to explore multi-material 3D printing for energy storage devices on a custom machine. Finally, we discuss how Vespidae contributes to a movement in HCI arguing for human-machine collaboration.

The performance of functional composites can rely critically on the arrangement of secondary phases; for example, patterned networks of conductive particles can impart anisotropic thermal, electric or ionic conductivity while preserving flexibility in the matrix. We demonstrate the use of standing acoustic waves to generate periodic patterns of short fibers. We extend the range of possible patterns with the first demonstration of both rectangular grids and arrays of octagons interspersed with rectangles. These newly demonstrated patterns are rationalized using theoretical models of acoustic forces and torques on fibers that account for two-dimensional spatial variations arising from applied acoustic fields. The models enable simulations of fiber motion, which are used to (i) map out final fiber positions as a function of initial position and orientation, and (ii) corroborate experiments visualizing fiber motion and final patterns. This approach provides a fast and accurate way to predict emergent fiber patterns as a function of excitation modality and fiber length. The theory and experiments clearly indicate strong coupling between the length of the fibers and the spacing of the acoustic nodes. This coupling is used to estimate reductions in percolation thresholds associated with the ratio of fiber length and acoustic wavelength.

Conventional lithium-ion batteries (LIBs) are composed of planar stacks of anodes, cathodes, and separators, all immersed in electrolyte and sandwiched between current collectors. However, planar LIBs have a performance trade-off where increasing electrode thickness leads to higher capacity but lower rate capability. Three-dimensional (3D) batteries circumvent this issue with 3D electrode architecture. Herein, we systematically analyze 3D LIBs from experimental publications over the past 20 years. Using a previously developed empirical model, we obtain parameters to quantify the rate capability and rate-limiting mechanisms of 3D LIBs. Compared to conventional LIBs, 3D LIBs exhibit better rate capability-confirming their expected performance benefit. To provide further insight, we investigate the impact of liquid-phase and solid-phase diffusion mechanisms on this performance benefit. Lastly, we discuss the design landscape of 3D LIBs across multiple electrode designs and material sets and highlight our perspective on the applicability of 3D LIBs at different application scales.

Opportunities to improve thermal management in electronic devices are currently hindered by processing constraints that limit thermal conductivity in polymer‐matrix composites. Active patterning of filler particles is a promising route to improve conductivity while retaining processability by improving particle contact density and directing heat along optimized pathways. This study employs acoustic patterning to align and compact filler particles into stripes during stereolithographic 3D printing. This approach produces polymer‐based composite materials with highly efficient embedded heat transport pathways which reach 95 vol% particle utilization (relative to the parallel conduction upper limit). These composites exhibit anisotropic thermal conductivity up to 300% higher than unpatterned composites, with in‐plane anisotropy ratios of up to 350%. Combining this high conductivity with 3D printing enables materials with engineered heat networks that optimize transport from hot spots to heatsinks while maintaining low viscosity for fast particle patterning and for infiltration around electronic components. Finally, numerical simulations of acoustic assembly of particles with varied geometry, when compared to experimentally characterized particle packing, illuminate pathways for further improving conductivity by optimizing particle geometry for alignment and stacking of particles with maximum contact surface area.

Achieving high-energy and high-power density Lithium-ion batteries (LIBs) with fast charge behavior is critical for the future of electric vehicle applications. Conventional LIBs have planar anode and cathode electrode stacks that can be optimized for energy or power, but not both simultaneously due to fundamental ion transport limitations with increasing electrode thickness. Three-dimensional (3D) electrode architectures1,2 can remove these performance trade-offs through engineered ion-transport in thick electrodes. However, scalable manufacturing methods for patterning these architectures over large areas at meaningful time scales is still limited. As a path to solving this challenge, we leverage both modeling and experiments to investigate the feasibility of deploying acoustophoresis to assemble and pattern 3D battery electrodes. Acoustophoresis employs acoustic standing waves to focus particles and enables near micron-scale control over particle placement in a fluid medium at time scales < 1 second. Prior research has shown the potential for rapid assembly of particles with this approach,3,4 making acoustic-based processing a promising methodology for manufacturing 3D electrodes over large areas. In this talk, we expand a previously developed model4 that solves differential equations of acoustic forces to track particle trajectories and define how the acoustic forces are influenced by slurry viscosity, particle loading, and particle morphology. Our initial experiments with different material systems, including LiNi0.6Mn0.2Co0.2O2 (NMC-622), help validate our model and process conditions to as a path towards acoustophoretic fabrication of 3D electrode architectures. References C. L. Cobb and S. E. Solberg, J. Electrochem. Soc., 164, A1339–A1341 (2017). C. L. Cobb and M. Blanco, Journal of Power Sources, 249, 357–366 (2014). D. S. Melchert et al., Materials & Design, 109512 (2021). R. R. Collino et al., Materials Research Letters, 6, 191–198 (2018). Acknowledgements This material is based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Advanced Manufacturing Office (AMO) Award Number DE-EE0009112. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

We conduct numerical simulations of acoustic focusing in dense suspensions to map the design space of acoustically patterned materials and understand the relationships between input parameters, structural features, and functional properties. We develop closed-form expressions for acoustic forces on particles, enabling rapid simulation of thousands of particles, and find excellent agreement with experimentally focused patterns over a range of conditions. We map the geometrical and microstructural features of focused particle patterns and their dependence on processing parameters. We find that mesostructural geometrical features (focused line height, width, and profile shape) can be controlled reliably over a broad range by modulating input parameters, and that while microstructural features are less readily modulated via input parameters, they are well-suited for various transport properties in functional materials. Notably, packing density nears the random close packing limit at 0.64, and particle contact density shows anisotropy favoring particle contacts along the focused lines. These results guide process design for controlling the properties of patterned materials, and outline the property ranges accessible via acoustic focusing. Additionally, we discuss the dependence of material functionalities, particularly electrical, thermal, and ionic transport properties, on the meso- and micro-structural features of patterned composite materials in the context of acoustic focusing.

Separators isolate the anode and cathode electrodes in Lithium-ion (Li-ion) batteries and play a critical role in facilitating ion transport while enabling safe battery operation. Commercial polyolefin separators made of polypropylene (PP) and polyethylene (PE) are used widely in traditional liquid electrolyte Li-ion batteries. However, these materials have limited thermal stability and are not compatible with additive manufacturing approaches for fabrication of new battery electrode architectures [1]. Researchers have investigated phase-inversion composite separators as a means to solve these problems, but there is limited data available on the relative effects of material composition and processing conditions on final separator morphology and performance. In our work, we analyze the effects of solvents, inorganic additives and phase inversion processing conditions on the separator’s ionic conductivity, rate capability, and mechanical integrity. Silica (SiO2), alumina (Al2O3), and glass particles are used as inorganic additives in varying combinations and ratios in a polyvinylidene fluoride (PVDF) polymer matrix. The PVDF concentration in our solvent solution is varied to understand the impact of solution viscosity on the phase inversion process and resultant mechanical performance of our separators. Through this study we begin to elucidate relationships between processing conditions, material composition and electrochemical and mechanical performance to facilitate further development of alternative Li-ion battery separators that are compatible with additive manufacturing. [1] Cobb, C. L.; Ho, C. C. Electrochem. Soc. Interface 2016, 25 (1), 75–78. Acknowledgement This work was funded in part by a Defense Advanced Research Projects Agency (DARPA) Young Faculty Award under grant number D19AP00038. The views, opinions, and/or findings expressed are those of the authors and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government.

This roadmap includes the perspectives and visions of leading researchers in the key areas of flexible and printable electronics. The covered topics are broadly organized by the device technologies (sections 1–9), fabrication techniques (sections 10–12), and design and modeling approaches (sections 13 and 14) essential to the future development of new applications leveraging flexible electronics (FE). The interdisciplinary nature of this field involves everything from fundamental scientific discoveries to engineering challenges; from design and synthesis of new materials via novel device design to modelling and digital manufacturing of integrated systems. As such, this roadmap aims to serve as a resource on the current status and future challenges in the areas covered by the roadmap and to highlight the breadth and wide-ranging opportunities made available by FE technologies.

Conventional Lithium-ion intercalation batteries that are composed of planar cathode, separator, and anode layers have an intrinsic trade-off between energy density and power density. While thick electrodes allow for more active material loading and higher energy densities, thick electrodes lengthen ion transport pathways and limit power performance. Conversely, thin electrodes have fast ion transport at the cost of reduced material loading which leads to lower energy densities. Three-dimensional (3D) batteries can potentially mitigate this power and energy trade-off through electrode architecture. Unlike planar electrodes, 3D batteries have unique and integrated electrode architectures that can modify ion transport pathways in three-dimensions on a micron to millimeter scale. These architectures may be locally imbalanced in material loading, leading to nonuniform current density and local depletion of the electrode or electrolyte material. These nonuniformities can terminate a discharge or charge cycle prematurely. Although many 3D battery architectures have been proposed to date, few comparative modeling studies have been conducted for these architectures to understand their relative performance gains. In this presentation, we will investigate the impact of 3D electrode architecture on current density uniformity and material lithiation at different discharge rates in several 3D batteries. Our batteries are simulated using the software CAEBAT: AMPERES 1 , which provides a 3D electrochemical model on the continuum level using volume-averaging techniques. 3D batteries with different parameterizations and geometries of interdigitated anode and cathode electrodes are studied. In addition, the effects of current collector placement, material loading, and electrode feature shapes are also presented. 1. Allu, S., Kalnaus, S., Simunovic, S., Nanda, J., Turner, J. A., and Pannala, S., J. Power Sources, 325, 42 (2016)

Technology progressions in wearable devices, portable electronics, and electric vehicles have motivated a shift in Lithium-ion batteries to accommodate rapid charge, long cycle life, high power and high energy performance in more compact packaging. An emerging trend to address this technology shift is employing three-dimensional (3D) electrode architectures and Additive Manufacturing (AM) methods to rapidly fabricate batteries with customized geometries on a micron to millimeter scale, changing the way we fundamentally design and manufacture energy storage devices. 3D electrode architectures enhance ion transport in existing intercalation materials, thereby increasing gravimetric and volumetric energy and power densities relative to conventional batteries. Typically, increases in power density are only possible through sacrifices in energy density. Our research has shown that 3D electrode architectures can mitigate these trade-offs. This talk will focus on promising design and AM fabrication methods developed in our research group for high-performance 3D Lithium-ion batteries to enable customizable and scalable electrode architectures for a wide range of applications.