Phase change materials (PCMs) are in high demand for applications such as thermal energy storage in buildings, electronics cooling, and thermal management of electric vehicle batteries and data centers. Among these materials, salt hydrate PCMs are particularly attractive due to their high thermal energy storage capacity and low cost. However, they suffer from two major issues: leakage in the melted phase and phase segregation during phase transitions. Microencapsulation is the primary process capable of addressing both of these challenges. However, there is no reliable or scalable method available for microencapsulating salt hydrate PCMs. As a result, the full potential of salt hydrates for building and data center applications has yet to be realized. In this work, we present an innovative method for the microencapsulation of salt hydrate PCMs using a co-axial pushing technique. This process creates core-shell fibers, with the salt hydrate as the core and a polymer as the shell. Our approach demonstrates strong potential for scalable microencapsulation of salt hydrate PCMs. Achieving scalability could enable their widespread use in applications such as data center cooling, battery thermal management, and building climate control.

The transition to electric vehicles (EVs) is pivotal for achieving energy security and integrating grid stability, with lithium-ion batteries (LIBs) playing a central role in this transformation. However, the conventional wet electrode manufacturing relying on N-methyl-2-pyrrolidone (NMP) solvent is energy intensive and costly. Dry processing (DP) has emerged as a promising alternative, eliminating solvents and using polytetrafluoroethylene (PTFE) binder for electrode fabrications. Despite its advantages, DP faces a critical challenge: poor interfacial adhesion between the hydrophobic PTFE binder and the hydrophilic cathode active material (CAM), particularly LiNi0.8Mn0.1Co0.1O2 (NMC811), which undermines electrode performance. To address this, we introduced a novel vapor-phase trimethoxymethylsilane (TMMS) coating to hydrophobize the CAM surface, enhancing compatibility with PTFE. This surface modification significantly enhances binder-CAM interactions, enabling uniform mixing and robust electrode integrity without damaging the CAM particles. Our findings advance the feasibility of environmentally sustainable and cost-effective dry processing, representing a significant step toward sustainable battery manufacturing.

The next generation of batteries requires electrolytes with high conductivity, mechanical stability, good adhesion with electrodes, wide electrochemical windows, and scalability. The present study introduces a concept of doped quasi single-ion conducting copolymers based on methacrylate-(trifluoromethanesulfonyl)imide (TFSI) and vinyl ethylene carbonate which at room temperature are mechanically robust and display ionic conductivities of similar to 0.1 mS/cm. These electrolytes can be polymerized/crosslinked in-situ, making them easily implementable in current battery manufacturing technologies. They also allow for switching between Li+ and Na+ transport using simple chemistry procedures. To demonstrate their potential for battery applications, the newly developed Li conductors have been tested in symmetric cells, exhibiting overall impedance below 350 Ohm and plating/stripping stability up to 1 mA/cm(2). Moreover, lithium metal batteries incorporating this electrolyte and high-voltage Lithium Nickel Manganese Cobalt Oxide (NMC) cathodes show good capacity retention (similar to 79%) during charging and discharging for 80 cycles at C/10 rate and a Coulombic efficiency close to 100% in the entire measurement range. The compositional, mechanical and electrochemical versatility of these electrolytes opens new venues for the design of polymer-based batteries capable of fast charging and extended cycle life, aligning with the current global green energy storage strategies.

Electric vehicles are pivotal in the global shift toward decarbonizing road transport, with lithium-ion batteries at the heart of this technological evolution. However, the pursuit of batteries capable of extremely fast charging that also satisfy high energy and safety criteria, poses a significant challenge to current lithium-ion batteries technologies. Additionally, the increasing demand for aluminum (Al) and copper (Cu) in electrification, solar energy technologies, and vehicle light-eighting is driving these metals toward near-critical status in the medium term. This study introduces metalized polythylene terephthalate (mPET) polymer films by depositing an Al or Cu thin layer onto two sides of a polyethylene terephthalate film-named mPET/Al and mPET/Cu, as lightweight, cost-effective alternatives to traditional metal current collectors in lithium-ion batteries. We have fabricated current collectors that significantly reduce weight (by 73%), thickness (by 33%), and cost (by 85%) compared with traditional metal foil counterparts. These advancements have the potential to enhance energy density to 280 Wh kg-1 at the electrode level under 10-min charging at 6 C. Through testing, including a novel extremely fast charging protocol across various C-rates and long-term cycling (up to 1000 cycles) in different cell configurations, the superior performance of these metalized polymer films has been demonstrated. Notably, mPET/Cu and mPET/Al films exhibited comparable capacities to conventional cells under extremely fast charging, with the mPET cells showing a 27% improvement in energy density at 6 C and maintaining significant energy density after 1000 cycles. This study underscores the potential of mPET films to revolutionize the roll-to-roll battery manufacturing process and significantly advance the performance metrics of lithium-ion batteries in electric vehicles applications.

Contact resistance between the cathode active material (CAM) and the Al current collector can be reduced by applying carbon coatings to the Al current collector surface. However, this process requires an additional step of carbon layer coating on the current collector, which increases both manufacturing costs and processing time. In the present work, an interlayer of continuous unsized carbon fibers aligned in one direction (CF interlayer), is introduced between the Al current collector and the NMC811 cathode during cathode deposition on the Al current collector. This single-step approach eliminates the need for the additional carbon layer coating on the current collector. Additionally, this approach removes the use of toxic solvents and insulative polymers used for making the carbon coating. The CF interlayer improves the rate capability at higher C-rates. The CF interlayer lowers the contact resistance between the cathode particles and the current collector while improving the activation energy of charge transfer. The peel test showed that the CF interlayer does not affect the adhesion strength of the cathode layer with the current collector.

Energy storage technologies, particularly those utilizing phase change materials (PCMs), have gained attention for their high energy density and efficient thermal management. PCMs, which store energy through solid-liquid phase transitions, can efficiently capture and release thermal energy, but face the challenge of leakage during the phase change process. Inorganic PCMs, such as salt hydrates, offer high energy storage capacity, but are difficult to encapsulate due to their corrosive nature. Conventional encapsulation techniques for inorganic PCMs are limited, particularly for scalable applications. In this work, we present an innovative method for the encapsulation of salt hydrate-based inorganic PCMs (CaCl2·6H2O) using co-axial electrospinning. The process involves the creation of co-axial fibers, with salt hydrate as the core and polymer (e.g., PVP) as the outer shell, effectively preventing leakage and improving the stability of the PCM. This approach demonstrates the potential for scalable microencapsulation of inorganic PCMs, marking the first report of using co-axial electrospinning for this purpose. This novel technique could contribute to enhancing the performance and applicability of PCMs in thermal energy storage systems and other energy efficiency applications.

Roll-to-roll powder-to-film dry processing (DP) and single-crystal (SC) active materials (AMs) with many advantages are two hot topics of lithium-ion batteries (LIBs). However, DP of SC AMs for LIBs is rarely reported. Consequently, the impact of SC AMs on DPed LIBs is not well understood. Herein, via a set of experimental and theoretical studies of the conventional polycrystalline-AM- and SC-AM-based LIB electrodes, our work not only reports a high-performance dry SC-AM cathode for LIB manufacturing, but also establishes some fundamental understanding of SC-based DPed electrodes, including their morphology, structure, mechanical strength, electronic conductivity and LIB electrochemical behavior. The results suggest that DP of SC AMs is promising, which can dramatically improve the electrochemical kinetics at electrode level and particle level. Therefore, this comprehensive study marks a significant milestone for DP strategy and SC AMs, enlightening future research and development of LIB manufacturing.

Dry processing (DP) is an advanced manufacturing technique for lithium-ion battery (LIB) electrodes. Unlike conventional wet-process-based manufacturing that involves dissolving polyvinylidene fluoride (PVDF) binder in n-methyl-2-pyrrolidone (NMP) solvent for slurry-casting, DP involves fibrillation of polymer binders. This method offers environmental and cost benefits by eliminating the need for expensive and environmentally hazardous organic solvents. However, DP-produced electrode films often lack mechanical stability due to the absence of a current collector substrate during electrode material layer fabrication. This reduced mechanical instability results in difficulty during fabricating of thin electrodes (approximate to 5 mAh/cm(2)). To address this issue, long (>8 mm) carbon fiber (CF) has been incorporated to reinforce the mechanical strength of the electrode films. The study demonstrates that the inclusion of long carbon fiber boosts the mechanical, electrical, thermal, and electrochemical performance of DP electrodes.

While the potential use of copolymerized electrolytes in Li metal batteries is subject to intense investigation, the fundamental understanding of the nanoscale domain formation and its effect on Li+ transport is still lacking. In this study, we investigated the correlation between the Li+ transport mechanism and the miscibility of monomers in polymer blend electrolytes derived from the in situ copolymerization of methyl methacrylate (MMA) and vinylene carbonate (VC) in the presence of polyethylene glycol dimethyl ether (PEGDME) plasticizer and bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. The addition of a polar short chain plasticizer reduced the dynamic and structural heterogeneities of the electrolyte. Small-angle X-ray scattering (SAXS) measurements and coarse-grained molecular dynamics (MD) simulations were used to investigate the nanoscale structure of the electrolytes. The distribution of relaxation times corresponding to the three distinct diffusion mechanisms of the free and interfacial Li+ ions at the copolymer/plasticizer and electrolyte/SEI boundaries was analyzed in a broad temperature range to elucidate the Li+ transport mechanism. The chemical composition of the SEI and the contribution of a ceramic lithium lanthanum zirconium oxide (LLZO, Li7La3Zr2O12) phase on the interfacial resistance, salt degradation, and SEI stability were studied by X-ray photoelectron spectroscopy (XPS) depth profile analysis and electrochemical testing.

The predictive design of flexible and solvent-free polymer electrolytes for solid-state batteries requires an understanding of the fundamental principles governing the ion transport. In this work, we establish a correlation among the composite structures, polymer segmental dynamics, and lithium ion (Li+) transport in a ceramic-polymer composite. Elucidating this structure-property relationship will allow tailoring of the Li+ conductivity by optimizing the macroscopic electrochemical stability of the electrolyte. The ion dissociation from the slow polymer segmental dynamics was found to be enhanced by controlling the morphology and functionality of the polymer/ceramic interface. The chemical structure of the Li+ salt in the composite electrolyte was correlated with the size of the ionic cluster domains, the conductivity mechanism, and the electrochemical stability of the electrolyte. Polyethylene oxide (PEO) filled with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium bis(fluorosulfonyl) imide (LiFSI) salts was used as a matrix. A garnet electrolyte, aluminum substituted lithium lanthanum zirconium oxide (Al-LLZO) with a planar geometry, was used for the ceramic nanoparticle moieties. The dynamics of the strongly bound and highly mobile Li+ were investigated using dielectric relaxation spectroscopy. The incorporation of the Al-LLZO platelets increased the number density of more mobile Li+. The structure of the nanoscale ion-agglomeration was investigated by small-angle X-ray scattering, while molecular dynamics (MD) simulation studies were conducted to obtain the fundamental mechanism of the decorrelation of the Li+ in the LiTFSI and LiFSI salts from the long PEO chain.

Solid-state batteries (SSBs) are promising candidates for next-generation energy storage, although their performance can be compromised by interfacial heterogeneity within the electrolyte. Furthermore, ensuring the quality of large form-factors electrolyte film is crucial for establishing a robust manufacturing platform for solid-state batteries. Herein, we report on the use of ARJUNA, an electrochemical interface mapping system, to characterize heterogeneities at solid electrolyte interfaces and to serve as a quality control system for SSB manufacturing. In addition to spatial mapping, the proposed system can also probe the interface behavior as a function of pressure and temperature. We present the operating principle, design, instrumentation, and evaluation of the system alongside a typical hybrid solid electrolyte produced using two common manufacturing processes. This report showcases the capability of ARJUNA to probe the heterogeneity and quality of processed solid electrolyte films.

Roll-to-roll powder-to-film dry processing (DP) and single-crystal (SC) active materials (AMs) with many advantages are two hot topics of lithium-ion batteries (LIBs). However, DP of SC AMs for LIBs is rarely reported. Consequently, the impact of SC AMs on dry-processed LIBs is not well understood. Herein, for the first time, via a set of experimental and theoretical studies of the conventional polycrystalline-AM- and SC-AM-based DPed electrodes (DPEs), this work not only reports a high-performance dry SC-AM cathode for LIB manufacturing, but also establishes some fundamental understanding of SC-based dry-processed electrodes, including their morphology, structure, mechanical strength, electronic conductivity and LIB electrochemical behavior. The results suggest that DP of SC AMs is promising, which can dramatically improve the electrochemical kinetics at electrode level and particle level. Specifically, for the rate capability and long-term cyclability in full cells, SC DPEs exhibit a discharge specific capacity of 152.1 mAh g- 1 at 1C and a capacity retention rate of 79.9 % at C/3 over 500 cycles, which are superior to those of PC DPEs (135.6 mAh g- 1 and 68.3 %) at the same conditions and are further confirmed by the simulation data from the theoretical modelling study. Therefore, this comprehensive work marks a significant milestone for DP strategy and SC AMs, enlightening future research and development of LIB manufacturing.

Atomic Layer Deposition (ALD) has emerged as a strategic enhancement method for lithium-ion battery (LIB) materials offering potential benefits and durability benefits for industrial battery production. However, the translation from laboratory achievements to commercial-scale applications has been limited. This study aims to bridge this gap by comprehensively evaluating the effects of commercially scalable Al2O3 ALD coatings using full pouch cell performance as a means to assess the ALD impact. We utilized large-scale slot-die coating techniques to ensure consistent electrode quality and tested four configurations of pouch cells to analyze the individual effects of ALD coating on anode and cathode electroactive materials. Our extensive testing matrix included long-term cycling, fast discharge, fast charge, leakage current, and high voltage tests. While at lower C-rates (<similar to 1C), the influence of Al2O3 coatings on cell performance is not significant. Fast charging conditions reveal that the anode ALD coating significantly enhances performance via a passivating effect, while on the cathode, it is detrimental, potentially due to increased resistance of the thin interfacial layer formed during the ALD processing. Leakage current and high-voltage tests show that the application of ALD coatings on either anode or cathode effectively minimizes side reactions at the electrode-electrolyte interface. Additionally, ALD coatings significantly mitigate concentrated and localized lithium plating on the anodes. These insights provide a valuable understanding of the potential of ALD technologies in LIB manufacturing to tailor cell performance, paving the way for safer, more efficient, and cost-effective battery solutions.

Lithium-ion battery (LIB) electrodes are typically produced with n-methyl-2-pyrrolidone, a toxic solvent that is a known carcinogen and reproductive hazard. Accordingly, aqueous processing has been an expanding area of research interest in the field of LIB manufacturing. Although aqueous processing has been widely successful in anode processing, serious challenges remain in processing the cathode. In this work, the drying mechanics of cathode processed with both solvents is investigated though implementation of a chemical-engineering-based model to better understand the utilization of heat provided by experimentally determining the heat and mass transfer coefficients. Electrochemical performance is also evaluated to determine the impact of drying temperature on cycling performance. Binder distribution is determined via various methods to confirm differences in binder homogeneity as a function of both solvent and drying temperature. Identified is the large difference in the efficiency in which the heat is used as well as an ideal drying temperature for both aqueous and non-aqueous processed cathodes. Also identified is the increased sensitivity to processing temperature for aqueous processed electrodes compared to non-aqueous processed counterparts, pointing to the possibility of tuned drying regimes which would capitalize on the potential cost savings of aqueous processing for cathodes. The drying mechanics of lithium-ion battery cathodes processed with aqueous and NMP solvents is investigated though implementation of a chemical-engineering-based model. Binder distribution is determined via various methods to confirm differences in binder homogeneity as a function of both solvent, coating thickness and drying temperature. image

A facile freeze tape casting (FTC) strategy is utilized to prepare bi-layered cathodes with a high LiNi0.6Co0.2Mn0.2O2 active material loading of 4 mAh cm-2. The bottom layer is a conventional non-aqueous electrode, which has dense structure for high-energy purpose. The top layer is prepared by the proposed FTC, exhibiting porous feature for high-power requirement. With the assistance of FTC, the bi-layered electrodes successfully deliver enhanced rate and cyclic performance due to the improved lithium-ion diffusion kinetics and pathways. Therefore, the proposed FTC strategy and its delivered electrodes are promising for energy- and power-density lithium-ion batteries, potentially enlightening the research and development of lithium-ion battery manufacturing.

The requirement for high energy density batteries is driving the development of high-capacity electrode materials while reducing the amount of inactive battery components such as separators, binders, and current collectors. Though current collectors are an inactive component, they are still required for successful working of a battery cell. Conventional current collectors include aluminum foil for cathode and copper foil for anode. Copper foil is quite heavy (8.7 mg/cm2) for 10 mu m thickness. Therefore, there is a need for a lightweight current collector for anode applications. In this work, a metal-free current collector comprised of aligned carbon fiber (CFs) layer filled with carbon nanotubes (CNTs) mixed in polymer (P) is developed to be used as a current collector for anodes. Anodes coated on the CF-CNT-P showed lower charge transfer resistance and improved rate capability compared with the anodes fabricated on conventional copper foil-based current collectors. The CF-CNT-P are lighter (approximate to 1.5 mg/cm2) than the commonly used copper foil (8.7 mg/cm2), which will increase the gravimetric energy density.

Solid state batteries with high-energy density and high-power density require the development of thick and energy dense cathodes. Structured cathode electrodes with a double-layer configuration were enabled using a freeze tape casting technique. A bottom dense layer was utilized to enhance the energy density whereas a top porous layer with vertically aligned walls was utilized to enhance the power density. The porous structure of the power layer was achieved by ice templating this layer on top of the densified energy layer of the cathode. This configuration was found to better utilize the active material of the cathodes and was optimized using numerical simulation and computer modeling. Cells with Li metal anode and LiNi0.6Mn0.2Co0.2O2 (NMC622) at approximately 5 and 20 mg/cm2 were cycled at 70 degrees C at different C-rates. Poly(ethylene oxide) (PEO) with lithium bistrifluoromethanesulfonimide (LiTFSI) was used for the catholyte and the solid-state electrolyte. The structured cathodes exhibited more than double capacity values as well as better Coulombic efficiency compared to nonstructured (single-layer) thick cathodes. Synchrotron X-ray tomography and scanning electron microscopy were used to characterize the microstructure of the cathodes.

High energy density demand is pushing the development of high-voltage cathode materials, which necessitates improved electrochemical stability of other battery components such as binders, electrolytes, and current collectors. Current collectors are considered to be an inactive component but still play an essential role. In this study, a metal-free composite film containing directionally aligned carbon fiber (CF), carbon nanotube (CNT), and polymer (P) was developed to replace aluminum foil as a cathode current collector, which relies on forming an Al2O3 layer to ensure electrochemical stability at high voltage. Each component in the new cathode current collector played a functional role. The CNTs provided uniform current densities, and CFs improved the electronic conductivity and mechanical strength of the composite material. The polymer enhanced the adhesion of the cathode coating with the current collector and provided an impervious support to the cathode materials. The CF-CNT-P composite demonstrated excellent electrochemical and thermal stability. Cathodes coated on the CF-CNTP composite exhibited lower charge transfer resistance, improved rate capability, and improved cyclic stability compared with the cathodes deposited on conventional aluminum foil. Additionally, the composite current collector was lighter (1.81 mg/cm(2) and 15 mu m thick) than the commonly used aluminum foil (4.35 mg/cm(2) and 15 mu m thick), which can increase the cell energy density. Additionally, the CF-CNT-P did not need to be separated from the cathode coating during recycling and can be burnt out with binder, simplifying the recycling process.

Lithium-ion battery cathode materials suffer from bulk and interfacial degradation issues, which negatively affect their electrochemical performance. Oxide coatings can mitigate some of these problems and improve electrochemical performance. However, current coating strategies have low throughput, are expensive, and have limited applicability. In this article, we describe a low-cost and scalable strategy for applying oxide coatings on cathode materials. We report synergistic effects of these oxide coatings on the performance of aqueously processed cathodes in cells. The SiO2 coating strategy developed herein improved mechanical, chemical, and electrochemical performance of aqueously processed Ni-, Mn- and Co-based cathodes. This strategy can be used on a variety of cathodes to improve the performance of aqueously processed Li-ion cells.

Designing a robust cathode is one of the major objectives in R&D of lithium-ion batteries. The challenges only get amplified in case of solid state battery cells as the methods for introduction of electrolyte into the cathode structure need to be developed. Ideally, a cathode should support high energy density of a cell which implies necessity for high thickness. This requirement is not trivial to fulfil, both from the standpoint of manufacturing and from the standpoint of overcoming transport limitations in thick cathodes. In this work, inspired by the previous effort on graded porosity cathode design [1], we present a two-layer cathode based on LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622). The cathode is built using a densified “energy layer” as a support for the “power layer” in which high porosity and low tortuosity is achieved by the freeze tape casting technique. The distribution of the material in the two layers is guided by numerical simulations based on actual cathode microstructure. The performance of the structured cathodes containing Poly(ethylene oxide) (PEO) with lithium bis-trifluoromethanesulfonimide (LiTFSI) was experimentally investigated in cells containing metallic lithium counter electrode. The structured cathodes showed more than double capacity values and improved Coulombic efficiency compared to uniform cathodes of the same material loading. [1] Kalnaus, S., Livingston, K., Hawley, W.B., Wang, H., Li, J., 2021, “Design and processing for high performance Li ion battery electrodes with double-layer structure J Energy Storage 44 (2021) 103582. Acknowledgments: This research at Oak Ridge National Laboratory (ORNL), managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725, was sponsored by Laboratory Directed Research and Development Program at ORNL.