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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Understanding the Nature of Capacity Decay and Interface Properties in Li//LiNi 0.5 Mn 1.5 O 4 Cells by Cycling Aging and Titration Techniques

The spinel structure LiNi 0.5 Mn 1.5 O 4 (LNMO) is a propitious cathode material for next-generation lithium-ion batteries for fast charge–discharge applications, but its capacity decay mechanism and rate-limiting process are not yet well understood. In this work, electrochemical impedance spectroscopy (EIS) with galvanostatic intermittent titration (GITT) and cycling aging techniques were employed to investigate the nature of capacity decay in disordered-phase LNMO. Different resistive components were separated after every 10 cycles. Cell overvoltages (ΔVs) due to ohmic conduction, charge transfer (CT), and concentration polarization (CP) were individually determined. Results revealed that the cell exhibited a higher ΔV at a higher discharged state. However, the ΔV value for CP was higher at a higher state of charge (SOC), and the overall LNMO/electrolyte interface played a major role in the rate-determining step. Battery life was estimated based on the results. Battery calendar life was found to be more vulnerable than cycle life. Furthermore, results also indicated that the working SOC range could be optimized based on the resistance analysis by avoiding those SOCs that have the most detrimental impact (e.g., heat generation and fire hazard).

25 ENERGY STORAGE↗
DOE OSTI2025

CACTUS: CO 2 Aerogel Capture Towards Utilization and Sequestration

The CACTUS project aimed to develop a novel solid sorbent and sorption module prototype for direct air capture (DAC) of carbon dioxide, by a moisture-swing adsorption (MSA) mechanism. Because MSA uses changes in humidity, not temperature to switch the sorbent from capturing CO 2 to releasing concentrated CO 2 it is > 4X more energy-efficient than the thermal swing process. The goal was to develop a sorbent with a CO 2 capture capacity of 1 mmol CO 2 /g sorbent (or 0.75 mmol CO 2 /g structured sorbent), at a projected scaled cost of < $\$$15/kg sorbent and demonstration of a path to < $\$$100/ton CO 2 . At the end of the project, we achieved 0.8 mmol CO 2 /g sorbent powders, 0.37 mmol CO 2 /g structured sorbent (50% of target), at a projected cost of $\$$29/kg sorbent and an estimated cost of $\$$160/ton CO 2 . The key innovation was SRI’s patented polymer aerogel synthesis platform, which was adapted to produce a nanoporous aerogel with a high density of CO 2 -adsorbing quaternary ammonium groups. This research discovered a new ammonium polymer sorbent and identified a chemical path for its fabrication. The new process solved the monomer immiscibility challenge encountered with the initial method (ammonium is hydrophilic and the crosslinker is hydrophobic). The team fabricated structured sorbent sheets consisting of a non-woven porous substrate impregnated with ammonium polymer and demonstrated its operation in custom made breakthrough test setup MSA DAC built at SRI, and which operates similarly to the envisioned large-scale CO 2 capture plant, to provide data for techno-economic analysis (TEA). TEA sensitivity analysis indicated that ∼$\$$100/ton CO 2 can be achieved if the target capacity of 0.75 mmol CO 2 /g structured sorbent is met. Also identified routes to decrease sorbent manufacturing cost to ∼$\$$19/kg by reducing amounts and recycling the organic solvents. More work is needed on transitioning process manufacturing from powders (which showed a capacity of up to 0.8 mmol/g sorbent) to structured sheets which showed a capacity of 0.37 mmol CO 2 /g structured sorbent (or 0.44 mmol/g sorbent if one excludes the inert porous substrate). This is likely due to different micro/nano-structure of the sorbent and material processing constraints at the laboratory scale. Sorbent cycling studies (> 100 cycles) are needed to investigate its performance stability over time.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2021

MX Anti-MXenes from Non-van der Waals Bulks for Electrochemical Applications: The Merit of Metallicity and Active Basal Plane

Two-dimensional transition-metal compounds (2DTMCs) are promising materials for electrochemical applications, but 2DTMCs with metallicity and active basal planes are rare. In this work, we proposed a simple and effective strategy to extract 2DTMCs from non-van der Waals bulk materials and established a material library of 79 2DTMCs, which we named as anti-MXenes since they are composed of one M atomic layer sandwiched by two X atomic layers. By means of density functional theory computations, 24 anti-MXenes were confirmed to be thermodynamically, dynamically, mechanically, and thermally stable. The metallicity and active basal plane endow these anti-MXenes with potential as excellent electrode materials, for example, as electrocatalysts for hydrogen evolution reactions (HER). Among the noble-metal free anti-MXenes with favorable H-binding, CuS can boost HER at the whole range of H coverages, while CoSi, FeB, CoB, and CoP show promise for HER at some specific H coverages. The active sites are the tetra-coordinating nonmetal atoms at the basal planes, thus rendering a very high density of active sites for these materials. CoB is also a promising anode material for lithium-ion batteries, showing low Li diffusion energy barriers, a very high capacity, and a suitable open circuit voltage. Overall, this work promotes the “computational exfoliation” of 2D materials from non-van der Waals bulks and exemplifies the applications of anti-MXenes in various electrochemical processes.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Modulating Surface Anionic Redox Chemistry toward Highly Stable Li-Rich Cathodes with Negligible Oxygen Loss

Low initial Coulombic efficiency and severe capacity/voltage fading during cycling caused by serious irreversible oxygen release, especially in the initial cycle, and resultantly induced unstable electrode/electrolyte interfacial chemistry, largely prohibit the commercial application of high-capacity Li-rich layered oxide cathodes (LLOs). Here, in this work, a dual reductive gas interface cotreatment strategy is applied to regulate the lattice oxygen redox activity and reversibility with a multiple defective structure design including Li/O/TM (TM = transition metal) vacancies and the intrinsic TM doping as well as a full-surface protective layer, which can suppress the irreversible TM migration and then undesirable phase transformation, resisting the corrosion of electrolyte during cycling effectively. Importantly, the introduced reversible SO 3 2- /SO 4 2- redox couple that provides extra capacity compensation could alleviate the distortion of oxygen-central octahedral structure and structural collapse caused by immoderate oxygen oxidation. Thus, the lattice oxygen redox chemistry is optimized, with negligible oxygen loss during the initial cycle. And the designed AS-LLO cathode with greatly enhanced structure stability shows high-capacity retentions of 99.2% at 0.3C after 100 cycles and 82.4% even after 1000 cycles at 5C. This work provides a guideline for manipulating the oxygen redox chemistry to achieve long-lifespan Li-rich layered oxide cathodes for high-energy-density lithium batteries.

25 ENERGY STORAGE↗
DOE OSTI2026

All-organic self-separating three-dimensionally nanoarchitected electrochemical energy storage devices

This work realizes a three-dimensionally (3D) nanoarchitected, all organic, "self-separating" lithium-ion electrochemical energy storage (EES) device that is cycled as a solid-state full cell. The device is enabled by a monolithic carbon anode with a co-continuous pore network, derived from the structure direction of resols by an ultra-large molar mass block copolymer (BCP), poly(styrene-block-2-dimethylaminoethyl methacrylate) (SA). Electropolymerization of a single-phase conductive and redox-active material, poly((2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methyl 9,10-dioxo-9,10-dihydroanthracene-2-carboxylate) (PAQEDOT), into the pore space provides the cathode of the cell. The device is electronically contacted to the relevant electrode network enabled by the co-continuous nature of each electrode. Electrochemical processing via cycling against external lithium in an electrolyte generates a solid electrolyte interphase (SEI) as a separator and lithiates the cell electrodes, after which the EES device is cycled in the solid state. While the full cell does not demonstrate high cyclability, the best full cell demonstrates a discharge capacity of 267 milliamp hours per gram (mAh/g). This work marks, to the best of knowledge of the authors, the first example of an all-organic materials derived 3D nanoarchitected EES device, as well as the first design of "self-separating" cell fabrication. Furthermore, generalization of the design to another co-continuous carbon form factor is demonstrated.

FOS: Physical sciences↗
DOE OSTI2024

Cost-Benefit Analysis For Indonesia Building Sector: Whole-Building Cooling Solutions

The Net Zero World (NZW) Initiative Collaborative Work Program with the Government of Indonesia (GoI) includes technical assistance and investment mobilization facilitation to accelerate deployment of energy efficiency technologies and solutions for the building sector. A February 2023 U.S.–Indonesia Joint Workshop on Decarbonizing the Building Sector yielded a NZW Indonesia Building Decarbonization Working Group (NZW IBDWG) with four sub-working groups (SWG): SWG-A National Center, SWG-B Capacity Building, SWG-C Investment and Financing, and SWG-D Pilot Projects. Technical analysis of whole-building cooling solutions for tropical climates of Indonesia was conducted by SWG-A to quantify energy savings, carbon dioxide reductions, and comfort improvements offered by 12 passive or low-energy cooling strategies: ceiling fans with and without thermostat setbacks; cool roofs; cool walls; exterior awnings; exterior shades; interior shades; insulated roofs; insulated walls; low-e windows; solar window films; and natural ventilation. Leveraging the results from SWG-A, cost-benefit analysis (CBA) was conducted by SWG-C to assess the consumer and national costs and impacts associated with these 12 cooling solutions. The evaluation involved estimating life-cycle costs (LCC), payback period (PBP), net present values (NPV), annual electricity burden change for low-income households, and reduced national annual power-sector generation demand by 2030, 2040, 2050, and 2060. This evaluation can help guide Indonesia’s Just Energy Transition Partnership (JETP) investments in policies and programs to advance research, development, deployment, and commercial adoption (RDDCA) of efficient residential building sector cooling technologies and solutions in Indonesia. Four key energy conservation measures (ECM) have been identified to reduce air-conditioning (AC) energy demand in single-family housing in Indonesia: ceiling fan with temperature setback (to 28.1 °Celcius from 25 °C); insulated walls; insulated roof; and cool roof. This study found that low-income households with AC installations in Indonesia currently face a high energy cost burden of approximately 10%. However, by implementing a ceiling fan with temperature setback, this burden could decrease to 2.5% today and further reduce to 1.3% by the year 2060. The PBP for a ceiling fan with temperature setback is one year, indicating one of the lowest LCC and best NPV. In the planned upcoming phase of CBA, a series of building cooling improvement scenarios can be further defined, incorporating more than one ECM in combination with socio-economic factors evaluated in the initial CBA phase. Additionally, the analysis of ECM effects in multifamily housing can be expanded. This broader national analysis aims to encompass a holistic and comprehensive system-level perspective, including factors such as avoided power sector infrastructure investments, domestic job creation, domestic manufacturing job creation, and gross domestic product (GDP) growth.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2024

Influence of Linker Group on Bipolar Redox-Active Molecule Performance in Non-Aqueous Redox Flow Batteries

Redox flow batteries (RFBs) are an attractive choice for stationary energy storage of renewables such as solar and wind. Non-aqueous redox flow batteries (NARFBs) have garnered broad interest due to their high voltage operation compared to their aqueous counterparts. Further, the utilization of bipolar redox-active molecules (BRMs) is a practical way to alleviate crossover faced by asymmetric RFBs. In this work, ferrocene (Fc) and phthalimide (PI) are covalently linked with various tethering groups which vary in structure and length. The compiled results suggest that the length and steric shielding ability of the linker group can greatly influence the stability and overall performance of Fc-n-PI BRM-based NARFBs. Primary sources of capacity loss are found to be BRM degradation for straight chain spacers <6 carbons and membrane (Nafion) fouling. Fc-hexyl-PI provided the most stable battery cycling and coulombic efficiencies of >98 % over 100 cycles (~13 days). NARFB using Fc-hexyl-PI as an active material exhibited high working voltage (1.93 V) and maximum capacity (1.28 Ah L -1 ). Additionally, this work highlights rational strategies to improve cycling stability and optimize NARFB performance.

25 ENERGY STORAGE↗
NASA NTRS2015

Uncertainties in Isoprene Photochemistry and Emissions: Implications for the Oxidative Capacity of Past and Present Atmospheres and for Climate Forcing Agents

Current understanding of the factors controlling biogenic isoprene emissions and of the fate of isoprene oxidation products in the atmosphere has been evolving rapidly. We use a climate-biosphere-chemistry modeling framework to evaluate the sensitivity of estimates of the tropospheric oxidative capacity to uncertainties in isoprene emissions and photochemistry. Our work focuses on trends across two time horizons: from the Last Glacial Maximum (LGM, 21 000 years BP) to the preindustrial (1770s); and from the preindustrial to the present day (1990s). We find that different oxidants have different sensitivities to the uncertainties tested in this study, with OH being the most sensitive: changes in the global mean OH levels for the LGM-to-preindustrial transition range between -29 and +7, and those for the preindustrial-to-present day transition range between -8 and +17, across our simulations. Our results suggest that the observed glacial-interglacial variability in atmospheric methane concentrations is predominantly driven by changes in methane sources as opposed to changes in OH, the primary methane sink. However, the magnitudes of change are subject to uncertainties in the past isoprene global burdens, as are estimates of the change in the global burden of secondary organic aerosol (SOA) relative to the preindustrial. We show that the linear relationship between tropospheric mean OH and tropospheric mean ozone photolysis rates, water vapor, and total emissions of NOx and reactive carbon first reported in Murray et al. (2014) does not hold across all periods with the new isoprene photochemistry mechanism. Our results demonstrate that inadequacies in our understanding of present-day OH and its controlling factors must be addressed in order to improve model estimates of the oxidative capacity of past and present atmospheres.

methane↗
NASA NTRS1981

Enzymatic capacities of skeletal muscle - Effects of different types of training

Long-term adaptation mechanisms to maintain homeostasis at increased levels of exertion such as those caused by regular exercise are described. Mitochondrial changes have been found to be a result of endurance exercises, while mitochondrial responses to other types of exercise are small. Further discussion is devoted to long-term changes in glucose transport, hexokinase, phosphofructokinase, pyruvate kinase, and the increased sensitivity of an endurance trained muscle to insulin. Less lactate has been found to be produced by the skeletal muscles at the same work rate after adaptation to endurance exercise training, and the capacity for the flux of the two-carbon acetyl chain through the citric acid cycle increases in skeletal muscles in response to endurance training. Finally, endurance training is noted to result in glycogen sparing and an increase in the capacity to utilize fatty acids.

Booth, F. W.↗
DOE OSTI2021

Saturation Carrying Capacity for Group A Particles in a Circulating Fluidized Bed

Empirical models continue to play a significant role in the design process of multiphase chemical reactors, particularly riser reactors in circulating fluidized bed (CFB) processes. It is imperative that accurate, industrial relevant correlations are developed to aid these design efforts. Using poor correlations could result in startup issues and significant redesign work. In this work, a new correlation is proposed to predict the saturation carrying capacity of Geldart Group A particles. This new correlation improves upon the currently available correlations for these materials and covers a broad range of Geldart Group A particles (particle diameters from 52 to 70 µm, and Archimedes numbers ranging from 5 to 20), superficial gas velocities (1 to 4 m/s), and riser diameters (0.066 to 0.3048 m). The new correlation has an Absolute Average Percent Deviation of only 17.6%, making it the most accurate correlation for Geldart Group A particles in the current literature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Performance Modeling of a Thermoelectric Heat Pump Clothes Dryer with Very High Air Flow

Previous research has shown that a clothes dryer heated by thermoelectric (Peltier) heat pumps can be up to 85% more efficient than a conventional electric-resistance dryer. A previous thermoelectric prototype used a conventional dryer’s air flow of 120 ft3/min (0.06 m3/s) and provided about 1,300 W of thermoelectric heating capacity at a heating coefficient of performance (COP) of approximately 1.2. In this work, the performance of a clothes dryer with a very high air flow rate, up to 300 ft3/min (1.14 m3/s), and only 400 W of thermoelectric heating capacity was investigated using a thermohydraulic model. Key aspects of the model were validated experimentally. Results for dry time and efficiency are presented for various air flow and heating rates.

Boudreaux, Philip↗
DOE OSTI2022

Dimensionality effect of conductive carbon fillers in LiNi 1/3 Mn 1/3 Co 1/3 O 2 cathode

Developing advanced electrode architectures through modifying active materials, conductive fillers, binders, and electrolytes as well as processing methods has drawn significant research interest. Due to the insufficient electrical conductivity of many active materials, adding conductive carbon fillers to composite electrodes provides the necessary electrical conductivity. The dimensionality effect among different conductive fillers has a significant impact on electrochemistry, which can be associated with morphological and chemical heterogeneities of electrodes. In this study, synchrotron X-ray mosaic nanotomography and X-ray spectroscopy nanoimaging provided direct three-dimensional (3D) visualization and quantification capabilities to investigate the dimensionality effects of Super P (SP) and single-walled carbon nanotube (SWCNT) fillers on the capacity retention of LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC111). The results indicate that NMC/SWCNT electrodes, with a wrapping effect from the SWCNTs, exhibited more homogeneous particle size distributions, morphological changes, and chemical states than NMC/SP electrodes, without the wrapping effect. This work developed a framework of 3D quantification methods to study the capacity fading behavior associated with morphological and chemical heterogeneities and paved the way toward designing electrodes for high rate energy storage applications.

25 ENERGY STORAGE↗
DOE OSTI2025

Porous and Amorphous Mn x Mo 3 S 13 Chalcogel Electrode for High-Capacity Conversion-Based Lithium-Ion Batteries

While Li-ion batteries (LIBs) are a leading energy storage technology, their energy densities are limited by the low capacity of conventional intercalation cathodes, driving interest in high energy-density Li–S batteries that make use of conversion chemistry. Achieving high capacity, reversibility, and cycle stability, and controlling volume changes in conversion batteries during the charge–discharge process, however, remains challenging. Here, in this study, we present a porous, amorphous, sulfide-based Mn x Mo 3 S 13 chalcogel, which concurrently offers high capacity and cycle stability. The solution-processable room temperature synthesized Mn x Mo 3 S 13 (x = 0.25) chalcogel exhibits a local structure that resembles the Mo 3 S 13 cluster with Mn 2+ distributed across the Mo 3 S 13 matrix, as determined by synchrotron X-ray pair distribution function (PDF) and extended X-ray absorption fine structure (EXAFS). Ab initio molecular dynamics (AIMD) simulations reveal that Mn 2+ incorporation shortens the polysulfide chain in the gel matrix compared to the Mo 3 S 13 chalcogel, while forming a coordination environment with disulfide groups, analogous to the experimental findings. A Li/Mn 0.25 Mo 3 S 13 half-cell delivers 897 mAh g –1 capacity during the first discharge and retains 571 mAh g –1 capacity after 100 cycles at a C/3 rate. Distribution of relaxation time (DRT) unveils a stable solid–electrolyte interphase (SEI) formation upon cycling that enables charge–discharge reversibility. Here, the enhanced capacity retention and cycle stability compared to those of the Li/Mo 3 S 13 cell are attributed to the reduced dissolution of active mass into the electrolyte, facilitated by the formation of shorter polysulfide chains within the Mn 0.25 Mo 3 S 13 structure and the strong affinity of Lewis-acidic Mn 2+ for polysulfide anions generated during the charge–discharge process of the Li/Mn 0.25 Mo 3 S 13 cell. Thus, this work illustrates a design principle of material for high-capacity and cycle-stable Li-metal sulfide batteries.

25 ENERGY STORAGE↗
DOE OSTI2025

A hybrid numerical and machine learning framework for evaluating the performance of a 780 cm 2 aqueous organic redox flow battery

Aqueous organic redox flow battery (AORFB) is a promising cost-competitive technology for large-scale energy storage. Among existing work, the dihydroxyphenazine (DHP)-based AORFB has demonstrated high energy density and low capacity degradation in 10 cm2 cells during lab tests. However, its commercial-scale performance in more complex environments remains unknown, posing a barrier for commercialization. To address this gap, this work presents a comprehensive performance evaluation of a 780 cm 2 DHP-based AORFB by combining physics-based numerical model, machine learning (ML)-based surrogate models, and ML-derived sensitivity quantification. Specifically, we first select 12 key battery parameters that include 10 physicochemical quantities and 2 operation quantities, then select 6 performance metrics that include energy efficiency (EE), discharging capacity, charging energy, and power losses due to concentration, activation, and ohmic over-potentials. With such selection, 12800 combinations of the 12 parameters are subsequently generated using the Latin Hypercube Sampling method. These combinations, together with 38 pre-defined State of Charge, are then integrated to a validated AORFB model developed in COMSOL to compute the performance metrics. With both input parameters and performance metrics, 60 deep neural network (DNN) surrogate models are then trained to approximate the relationship between the 10 physicochemical quantities and 6 performance metrics at each flow rate and current density. Sensitivity scores are then calculated based on the DNN models. Two additional sensitivity analysis tools, i.e., MARS, and SHAP, are also used to cross-validate the sensitivity scores from the DNN. The results demonstrate that 1) the standard potential ranks the first in controlling EE and charging energy, 2) the membrane conductivity is most critical for power loss and EE, and 3) specific area and reaction rate control activation power loss.

25 ENERGY STORAGE↗
NASA NTRS1989

Statistical prediction with Kanerva's sparse distributed memory

A new viewpoint of the processing performed by Kanerva's sparse distributed memory (SDM) is presented. In conditions of near- or over-capacity, where the associative-memory behavior of the model breaks down, the processing performed by the model can be interpreted as that of a statistical predictor. Mathematical results are presented which serve as the framework for a new statistical viewpoint of sparse distributed memory and for which the standard formulation of SDM is a special case. This viewpoint suggests possible enhancements to the SDM model, including a procedure for improving the predictiveness of the system based on Holland's work with genetic algorithms, and a method for improving the capacity of SDM even when used as an associative memory.

Rogers, David↗
DOE OSTI2021

Stable bismuth-antimony alloy cathode with a conversion-dissolution/deposition mechanism for high-performance zinc batteries

Although a large number of intercalation cathode materials for aqueous Zn batteries have been reported, limited intercalation capacity precludes achieving a higher energy density. Here, for this work, we develop a high-performance aqueous Zn battery based on BiSb alloy (Bi 0.5 Sb 0.5 ) using a high-concentrated strong-basic polyelectrolyte. We demonstrate that a conversion-dissolution/deposition electrochemical mechanism (BiSb ↔ Bi + SbO 2 – ↔ Bi + SbO 3 – ↔ Bi 2 O 3 ) through in situ X-ray diffraction (XRD), Raman, and ex-situ X-ray photoelectron spectrometry (XPS) characterizations with the help of density functional theory calculations. The BiSb cathode delivers large capacity of 512 mAh g –1 at 0.3 Ag –1 and superior rate capability of 90 mAh g –1 even at 20 Ag –1 , and long-term cyclability with capacity retentions of 184 mAh g –1 after 600 cycles at 0.5 Ag –1 and 130 mAh g –1 after 1300 cycles at 1 Ag –1 . Remarkably, even at temperatures as low as –10 and –20 °C, capacities of 210 and 197 mAh g –1 are reserved at 1 Ag –1 , respectively. Moreover, the prepared pouch Zn//BiSb battery delivers a high energy density of 303 Wh kg –1 BiSb at 0.3 Ag –1 . When coupled with a high concentration polyelectrolyte, the Zn/BiSb battery exhibits an excellent performance over a wide temperature range (–40 to 40 °C). Our research reveals the metal cathode is promising for Zn batteries to achieve a high performance with the unique mechanism and alloys can be an effective approach to stabilize metal electrodes for cycling.

25 ENERGY STORAGE↗
DOE OSTI2023

Heat capacity of microgram oxide samples by fast scanning calorimetry

Quantitative scanning calorimetry on microgram-sized samples opens a broad, new range of opportunities for studying the thermodynamic properties of quantity-limited materials, including those produced under extreme conditions or found as rare accessory minerals in nature. We calibrated the Mettler Toledo Flash DSC 2+ calorimeter to obtain quantitative heat capacities in the range 200–350 °C, using samples weighing between 2 and 11.5 μg. Our technique is applied to a new set of oxide materials to which it has never been used before, without the need for melting, glass transitions, or phase transformations. Heat capacity data were obtained for silica in the high pressure stishovite (rutile) structure, dense post-stishovite glass, standard fused quartz, and for TiO2 rutile. These heat capacities agree within 5%–15% with the literature values reported for rutile, stishovite, and fused SiO2 glass. The heat capacity of post-stishovite glass, made by heating stishovite to 1000 °C, is a newly reported value. After accurate calibrations, measured heat capacities were then used to calculate masses for samples in the microgram range, a substantial improvement over measurement in conventional microbalances, which have uncertainties approaching 50%–100% for such small samples. Since the typical uncertainty of heat capacities measured on 10–100 mg samples in conventional differential scanning calorimetry is typically 7% (1%–5% with careful work), flash differential scanning calorimetry, using samples a factor of 1000 smaller, increases the uncertainty of heat capacity measurements by a factor of <3, opening the door for meaningful measurements on ultra-small, high-pressure samples and other quantity-limited materials.

Instruments & Instrumentation↗
DOE OSTI2020

Additive‐Free Aqueous MXene Inks for Thermal Inkjet Printing on Textiles

Abstract Direct printing of functional inks onto flexible substrates allows for scalable fabrication of wearable electronics. However, existing ink formulations for inkjet printing require toxic solvents and additives, which make device fabrication more complex, limit substrate compatibility, and hinder device performance. Even water‐based carbon or metal nanoparticle inks require supplemental surfactants, binders, and cosolvents to produce jettable colloidal suspensions. Here, a general approach is demonstrated for formulating conductive inkjet printable, additive‐free aqueous Ti 3 C 2 T x MXene inks for direct printing on various substrates. The rheological properties of the MXene inks are tuned by controlling the Ti 3 C 2 T x flake size and concentration. Ti 3 C 2 T x ‐based electrical conduits and microsupercapacitors (MSCs) are printed on textile and paper substrates by optimizing the nozzle geometry for high‐resolution inkjet printing. The chemical stability and electrical properties of the printed devices are also studied after storing the devices for six months under ambient conditions. Current collector‐free, textile‐based MSCs show areal capacitance values up to 294 mF cm −2 (2 mV s −1 ) in poly(vinyl alcohol)/sulfuric acid gel electrolyte, surpassing reported printed MXene‐based MSCs and inkjet‐printed MSCs using other 2D nanomaterials. This work is an important step toward increasing the functional capacity of conductive inks and simplifying the fabrication of wearable textile‐based electronics.

Uzun, Simge↗