Analytical ultracentrifugation (AUC) is applied to the characterization of as-dispersed graphene nanoplatelet dispersions and differential sedimentation separated daughter dispersions. The liquid-phase characterization of AUC is demonstrated to resolve both the broad sedimentation coefficient distributions of as-dispersed samples and changes in daughter dispersions determined by a protocol of applied differential sedimentation process steps. Comparison is made to measurements on deposited samples by scanning electron microscopy and atomic force microscopy. The value of AUC to rapidly monitor changes in the sedimentation distribution of each particle population is demonstrated to allow tailoring of the differential sedimentation protocol to produce significantly narrower population distributions. This rapid characterization is particularly important for technologies in which dispersed nanoparticles cannot be removed from a solvent solution for microscopy analysis.

Printed electronics is a disruptive technology in multiple applications including environmental and biological sensors, flexible displays, and wearable diagnostic devices. With superlative electronic, optical, mechanical, and chemical properties, two-dimensional (2D) materials are promising candidates for printable electronic inks. While liquid-phase exfoliation (LPE) methods can produce electronic-grade 2D materials, conventional batch separation processes typically rely on centrifugation, which requires significant time and effort to remove incompletely exfoliated bulk powders, hindering the scale-up of 2D ink manufacturing. While cross-flow filtration (CFF) has emerged as a promising continuous flow separation method for solution-processed 2D nanosheets, previously demonstrated polymer CFF membranes necessitate low 2D nanosheet concentrations to avoid fouling, which ultimately limits mass throughput. Here, we demonstrate a fully flow-based, exfoliation-to-ink system for electronic-grade 2D materials using an integrated cross-flow separation and concentration system. To overcome the relatively low-throughput processing concentrations of incumbent polymer CFF membranes, we employ porous ceramic CFF membranes that are tolerant to 10-fold higher nanosheet concentrations and flow rates without compromising separation efficiency. Furthermore, we demonstrate a concentration method via cross-flow ultrafiltration, where the retentate can be directly formulated into printable inks with electronic-grade performance that meets or exceeds centrifugally produced inks. Life cycle assessment and technoeconomic analysis quantitatively confirm the advantages of ceramic versus polymer CFF membranes including reductions of 97%, 96%, 94%, and 93% for greenhouse gas emissions, water consumption, fossil fuel consumption, and specific production costs, respectively. Overall, this work presents an environmentally sustainable and cost-effective solution for the fabrication, separation, and printing of electronic-grade 2D materials.

The absence of scalable and environmentally sustainable methods for producing electronic-grade graphene nanoplatelets remains a barrier to the industrial-scale application of graphene in printed electronics and conductive composites. To address this unmet need, here we report the utilization of carboxylated cellulose nanocrystals (CNCs) extracted from the perennial tall grass Miscanthus × giganteus as a biorenewable dispersant for the aqueous liquid-phase exfoliation of few-layer graphene nanoplatelets. This CNC-based exfoliation procedure was optimized using a Bayesian machine learning model, resulting in a significant graphite-to-graphene conversion yield of 13.4% and a percolating graphene thin-film electrical conductivity of 3.4 × 104 S m-1. The as-exfoliated graphene dispersions were directly formulated into an aerosol jet printing ink using cellulose-based additives to achieve high-resolution printing (∼20 μm line width). Life cycle assessment of this CNC-based exfoliation method showed substantial improvements for fossil fuel consumption, greenhouse gas emissions, and water consumption compared to incumbent liquid-phase exfoliation methods for electronic-grade graphene nanoplatelets. Mechanistically, potential mean force calculations from molecular dynamics simulations reveal that the high exfoliation yield can be traced back to the favorable surface interactions between CNCs and graphene. Ultimately, the use of biorenewable CNCs for liquid-phase exfoliation will accelerate the scalable and eco-friendly manufacturing of graphene for electronically conductive applications.

Liquid phase exfoliation (LPE) of graphene is a potentially scalable method to produce conductive graphene inks for printed electronic applications. Among LPE methods, wet jet milling (WJM) is an emerging approach that uses high-speed, turbulent flow to exfoliate graphene nanoplatelets from graphite in a continuous flow manner. Unlike prior WJM work based on toxic, high-boiling-point solvents such as n-methyl-2-pyrollidone (NMP), this study uses the environmentally friendly solvent ethanol and the polymer stabilizer ethyl cellulose (EC). Bayesian optimization and iterative batch sampling are employed to guide the exploration of the experimental phase space (namely, concentrations of graphite and EC in ethanol) in order to identify the Pareto frontier that simultaneously optimizes three performance criteria (graphene yield, conversion rate, and film conductivity). This data-driven strategy identifies vastly different optimal WJM conditions compared to literature precedent, including an optimal loading of 15 wt% graphite in ethanol compared to 1 wt% graphite in NMP. These WJM conditions provide superlative graphene production rates of 3.2 g hr-1 with the resulting graphene nanoplatelets being suitable for screen-printed micro-supercapacitors. Finally, life cycle assessment reveals that ethanol-based WJM graphene exfoliation presents distinct environmental sustainability advantages for greenhouse gas emissions, fossil fuel consumption, and toxicity.

Solution-processed graphene is a promising material for numerous high-volume applications including structural composites, batteries, sensors, and printed electronics. However, the polydisperse nature of graphene dispersions following liquid-phase exfoliation poses major manufacturing challenges, as incompletely exfoliated graphite flakes must be removed to achieve optimal properties and downstream performance. Incumbent separation schemes rely on centrifugation, which is highly energy-intensive and limits scalable manufacturing. Here, cross-flow filtration (CFF) is introduced as a centrifuge-free processing method that improves the throughput of graphene separation by two orders of magnitude. By tuning membrane pore sizes between microfiltration and ultrafiltration length scales, CFF can also be used for efficient recovery of solvents and stabilizing polymers. In this manner, life cycle assessment and techno-economic analysis reveal that CFF reduces greenhouse gas emissions, fossil energy usage, water consumption, and specific production costs of graphene manufacturing by 57%, 56%, 63%, and 72%, respectively. To confirm that CFF produces electronic-grade graphene, CFF-processed graphene nanosheets are formulated into printable inks, leading to state-of-the-art thin-film conductivities exceeding 104 S m-1 . This CFF methodology can likely be generalized to other van der Waals layered solids, thus enabling sustainable manufacturing of the diverse set of applications currently being pursued for 2D materials.

Nickel-rich layered oxides are widely used as cathodematerialsfor energy-dense lithium-ion batteries. These chemistries, based onthe parent compound LiNiO2 (LNO), are highly sensitiveto ambient environments and are known to readily react with moistureand carbon dioxide. As a result, impurities such as lithium hydroxidesand lithium carbonates are formed at the LNO surface, compromisingelectrochemical behavior. Here, we address this issue by coating LNOcathode particles with a hydrophobic barrier layer composed of grapheneand ethyl cellulose (GrEC). This coating limits contact between atmosphericmoisture and the LNO surface, which minimizes the generation of lithiumimpurities. This scheme is evaluated by exposing coated LNO to humidifiedCO(2) for 24 h as an accelerated ambient degradation test.Subsequent spectroscopy, microscopy, and electrochemical characterizationshow no detectable signatures of carbonates on the LNO surface, thusverifying that the GrEC coating prevents ambient degradation. By demonstratingthis methodology for the ultimate nickel-rich chemistry, this approachcan likely be generalized to a wide range of ambient-sensitive batterymaterials.

Advanced Materials TechnologiesVolume 8, Issue 22 2370125 Back CoverFree Access Fully Inkjet-Printed, 2D Materials-Based Field-Effect Transistor for Water Sensing (Adv. Mater. Technol. 22/2023) Xiaoyu Sui, Xiaoyu Sui Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, 60637 USA Chemical Sciences and Engineering Division, Physical Sciences and Engineering Directorate, Argonne National Laboratory, Lemont, IL, 60439 USA Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorSonal V. Rangnekar, Sonal V. Rangnekar Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorJaesung Lee, Jaesung Lee Department of Industrial and Systems Engineering, University of Wisconsin–Madison, Madison, WI, 53706 USA Wm Michael Barnes '64 Department of Industrial and Systems Engineering, Texas A&M University, College Station, TX, 77843 USASearch for more papers by this authorStephanie E. Liu, Stephanie E. Liu Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorJulia R. Downing, Julia R. Downing Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorLindsay E. Chaney, Lindsay E. Chaney Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorXiaodong Yan, Xiaodong Yan Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorHyun-June Jang, Hyun-June Jang Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, 60637 USA Chemical Sciences and Engineering Division, Physical Sciences and Engineering Directorate, Argonne National Laboratory, Lemont, IL, 60439 USASearch for more papers by this authorHaihui Pu, Haihui Pu Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, 60637 USA Chemical Sciences and Engineering Division, Physical Sciences and Engineering Directorate, Argonne National Laboratory, Lemont, IL, 60439 USASearch for more papers by this authorXiaoao Shi, Xiaoao Shi Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, 60637 USASearch for more papers by this authorShiyu Zhou, Shiyu Zhou Department of Industrial and Systems Engineering, University of Wisconsin–Madison, Madison, WI, 53706 USASearch for more papers by this authorMark C. Hersam, Mark C. Hersam Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USA Department of Chemistry, Northwestern University, Evanston, IL, 60208 USA Department of Electrical and Computer Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorJunhong Chen, Junhong Chen Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, 60637 USA Chemical Sciences and Engineering Division, Physical Sciences and Engineering Directorate, Argonne National Laboratory, Lemont, IL, 60439 USASearch for more papers by this author Xiaoyu Sui, Xiaoyu Sui Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, 60637 USA Chemical Sciences and Engineering Division, Physical Sciences and Engineering Directorate, Argonne National Laboratory, Lemont, IL, 60439 USA Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorSonal V. Rangnekar, Sonal V. Rangnekar Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorJaesung Lee, Jaesung Lee Department of Industrial and Systems Engineering, University of Wisconsin–Madison, Madison, WI, 53706 USA Wm Michael Barnes '64 Department of Industrial and Systems Engineering, Texas A&M University, College Station, TX, 77843 USASearch for more papers by this authorStephanie E. Liu, Stephanie E. Liu Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorJulia R. Downing, Julia R. Downing Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorLindsay E. Chaney, Lindsay E. Chaney Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorXiaodong Yan, Xiaodong Yan Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorHyun-June Jang, Hyun-June Jang Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, 60637 USA Chemical Sciences and Engineering Division, Physical Sciences and Engineering Directorate, Argonne National Laboratory, Lemont, IL, 60439 USASearch for more papers by this authorHaihui Pu, Haihui Pu Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, 60637 USA Chemical Sciences and Engineering Division, Physical Sciences and Engineering Directorate, Argonne National Laboratory, Lemont, IL, 60439 USASearch for more papers by this authorXiaoao Shi, Xiaoao Shi Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, 60637 USASearch for more papers by this authorShiyu Zhou, Shiyu Zhou Department of Industrial and Systems Engineering, University of Wisconsin–Madison, Madison, WI, 53706 USASearch for more papers by this authorMark C. Hersam, Mark C. Hersam Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208 USA Department of Chemistry, Northwestern University, Evanston, IL, 60208 USA Department of Electrical and Computer Engineering, Northwestern University, Evanston, IL, 60208 USASearch for more papers by this authorJunhong Chen, Junhong Chen Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, 60637 USA Chemical Sciences and Engineering Division, Physical Sciences and Engineering Directorate, Argonne National Laboratory, Lemont, IL, 60439 USASearch for more papers by this author First published: 24 November 2023 https://doi.org/10.1002/admt.202370125AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Graphical Abstract 2D Materials-Based Sensors 2D nanomaterials of graphene and molybdenum disulfide are inkjet-printed onto a flexible substrate to produce a fully-printed field-effect transistor (FET) sensor, as demonstrated by Junhong Chen and co-workers in article 2301288. The sensor can be used to detect lead ions in water down to 10 nM. This work paves the way for additive nanomanufacturing of FET-based sensors and related devices using 2D nanomaterials. Volume8, Issue22November 24, 20232370125 RelatedInformation

Aerosol jet printing is a noncontact, digital, additive manufacturing technique compatible with a wide variety of functional materials. Although promising, development of new materials and devices using this technique remains hindered by limited rational ink formulation, with most recent studies focused on device demonstration rather than foundational process science. In the present work, a systematic approach to formulating a polymer-stabilized graphene ink is reported, which considers the effect of solvent composition on dispersion, rheology, wetting, drying, and phase separation characteristics that drive process outcomes. It was found that a four-component solvent mixture composed of isobutyl acetate, diglyme, dihydrolevoglucosenone, and glycerol supported efficient ink atomization and controlled in-line drying to reduce overspray and wetting instabilities while maintaining high resolution and electrical conductivity, thus overcoming a trade-off in deposition rate and resolution common to aerosol jet printing. Biochemical sensors were printed for amperometric detection of the pesticide parathion, exhibiting a detection limit of 732 nM and a sensitivity of 34 nA μM-1, demonstrating the viability of this graphene ink for fabricating functional electronic devices.

Despite significant progress in solution-processing of 2D materials, it remains challenging to reliably print high-performance semiconducting channels that can be efficiently modulated in a field-effect transistor (FET). Herein, electrochemically exfoliated MoS2 nanosheets are inkjet-printed into ultrathin semiconducting channels, resulting in high on/off current ratios up to 10(3). The reported printing strategy is reliable and general for thin film channel fabrication even in the presence of the ubiquitous coffee-ring effect. Statistical modeling analysis on the printed pattern profiles suggests that a spaced parallel printing approach can overcome the coffee-ring effect during inkjet printing, resulting in uniform 2D flake percolation networks. The uniformity of the printed features allows the MoS2 channel to be hundreds of micrometers long, which easily accommodates the typical inkjet printing resolution of tens of micrometers, thereby enabling fully printed FETs. As a proof of concept, FET water sensors are demonstrated using printed MoS2 as the FET channel, and printed graphene as the electrodes and the sensing area. After functionalization of the sensing area, the printed water sensor shows a selective response to Pb2+ in water down to 2 ppb. This work paves the way for additive nanomanufacturing of FET-based sensors and related devices using 2D nanomaterials.

Ultrasensitive Molecular Sensors In article number 2106830, Nicholas R. Glavin and co-workers describe a real-time impedance spectroscopy approach, which enables ultrasensitive molecular sensors in solution processed 2D nanomaterials. Through bypassing traditionally dominant interflake interactions and selectively extracting intraflake doping effects, detection of NO2 vapor down to 1 ppb is readily achievable with an ultimate limit of detection approaching 63 ppt. Image by Dr. Jo Richers (www.jorichers.com).

Shortages of personal protective equipment (PPE) at the start of the COVID-19 pandemic caused medical workers to reuse medical supplies such as N95 masks. While ultraviolet germicidal irradiation (UVGI) is commonly used for sterilization, UVGI can also damage the elastomeric components of N95 masks, preventing effective fit and thus weakening filtration efficacy. Although PPE shortage is no longer an acute issue, the development of sterilizable and reusable UV-resistant elastomers remains of high interest from a long-term sustainability and health perspective. Here, graphene nanosheets, produced by scalable and sustainable exfoliation of graphite in ethanol using the polymer ethyl cellulose (EC), are utilized as UV-resistant additives in polyurethane (PU) elastomer composites. By increasing the graphene/EC loading up to 1 wt %, substantial UV protection is imparted by the graphene nanosheets, which strongly absorb UV light and hence suppress photoinduced degradation of the PU matrix. Additionally, graphene/EC provides mechanical reinforcement, such as increasing Young's modulus, elongation at break, and toughness, with negligible changes following UV exposure. These graphene/EC-PU composites remain mechanically robust over at least 150 sterilization cycles, enabling safe reuse following UVGI. Beyond N95 masks, these UVGI-compatible graphene/EC-PU composites have potential utility in other PPE applications to address the broader issue of single-use waste.

Printed 2D materials, derived from solution‐processed inks, offer scalable and cost‐effective routes to mechanically flexible optoelectronics. With micrometer‐scale control and broad processing latitude, aerosol‐jet printing (AJP) is of particular interest for all‐printed circuits and systems. Here, AJP is utilized to achieve ultrahigh‐responsivity photodetectors consisting of well‐aligned, percolating networks of semiconducting MoS2 nanosheets and graphene electrodes on flexible polyimide substrates. Ultrathin (≈1.2 nm thick) and high‐aspect‐ratio (≈1 μm lateral size) MoS2 nanosheets are obtained by electrochemical intercalation followed by megasonic atomization during AJP, which not only aerosolizes the inks but also further exfoliates the nanosheets. The incorporation of the high‐boiling‐point solvent terpineol into the MoS2 ink is critical for achieving a highly aligned and flat thin‐film morphology following AJP as confirmed by grazing‐incidence wide‐angle X‐ray scattering and atomic force microscopy. Following AJP, curing is achieved with photonic annealing, which yields quasi‐ohmic contacts and photoactive channels with responsivities exceeding 103 A W−1 that outperform previously reported all‐printed visible‐light photodetectors by over three orders of magnitude. Megasonic exfoliation coupled with properly designed AJP ink formulations enables the superlative optoelectronic properties of ultrathin MoS2 nanosheets to be preserved and exploited for the scalable additive manufacturing of mechanically flexible optoelectronics.

Lithium-Ion Batteries In article number 2106402, Mark C. Hersam and co-workers show that lattice oxygen loss plays a critical role in the O3–O1 stacking transition in cobalt-free LiNiO2 lithium-ion battery cathodes, which subsequently induces Ni-ion migration and irreversible stacking faults, microscale electrochemical creep, cracking, and even bending of layers after high-voltage cycling. By suppressing oxygen evolution, hermetic graphene coatings arrest this degradation cascade, resulting in substantially improved high-voltage capacity retention.

Printed graphene electrodes have been demonstrated as a versatile platform for electrochemical sensing, with numerous examples of rapid sensor prototyping using laboratory-scale printing techniques such as inkjet and aerosol jet printing. To leverage these materials in a scalable production framework, higher-throughput printing methods are required with complementary advances in ink formulation. Flexography printing couples the attractive benefits of liquid-phase graphene printing with large-scale manufacturing. Here, we investigate graphene flexography for the fabrication of electrodes by analyzing the impacts of ink and process parameters on print quality and electrical properties. Characterization of the printed patterns reveals anisotropic structure due to striations along the print direction, which is related to viscous fingering of the ink. However, high-resolution imaging reveals a dense graphene network even in regions of sparse coverage, contributing to robust electrical properties even for the thinnest films (< 100 nm). Moreover, the mechanical and environmental sensitivity of the printed electrodes is characterized, with particular focus on atmospheric response and thermal hysteresis. Overall, this work reveals the conditions under which graphene inks can be employed for high-speed flexographic printing, which will facilitate the development of graphene-based sensors and related devices.

Carbon-supported Pt nanoparticles are the leading catalysts for the cathode oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells. However, these ORR catalysts suffer from poor electrochemical durability, particularly the loss of electrochemical surface area (ECSA) due to Pt nanoparticle dissolution and agglomeration. Here, Pt loss is mitigated through a Pickering emulsion-processing strategy that employs graphene nanoplatelet dispersions stabilized by the polymer ethyl cellulose. The resulting graphene-Pt/Vulcan carbon (Pt/C) catalysts exhibit superior durability and ECSA retention throughout an accelerated stress test compared with a commercial Pt/C standard catalyst, both in a diagnostic-rotating disc electrode setup and in a membrane electrode assembly full cell. These graphene-Pt/C catalysts also improve durability at high-voltage conditions, providing further evidence of their exceptional electrochemical stability. Consistent with density functional theory calculations, postelectrochemical characterization reveals that Pt nanoparticles localize at graphene defects both on the basal plane and especially at the edges of the graphene nanoplatelets. Since this Pt nanoparticle localization suppresses Pt nanoparticle dissolution and agglomeration without hindering accessibility of the reactant species to the catalyst surface, the ORR performance under both idealized and practical experimental conditions shows significantly improved durability while maintaining high electrochemical activity.

Chemical sensors based on solution‐processed 2D nanomaterials represent an extremely attractive approach toward scalable and low‐cost devices. Through the implementation of real‐time impedance spectroscopy and development of a three‐element circuit model, redox exfoliated MoS 2 nanoflakes demonstrate an ultrasensitive empirical detection limit of NO 2 gas at 1 ppb, with an extrapolated ultimate detection limit approaching 63 ppt. This sensor construct reveals a more than three orders of magnitude improvement from conventional direct current sensing approaches as the traditionally dominant interflake interactions are bypassed in favor of selectively extracting intraflake doping effects. This same approach allows for an all solution‐processed, flexible 2D sensor to be fabricated on a polyimide substrate using a combination of graphene contacts and drop‐casted MoS 2 nanoflakes, exhibiting similar sensitivity limits. Finally, a thermal annealing strategy is used to explore the tunability of the nanoflake interactions and subsequent circuit model fit, with a demonstrated sensitivity improvement of 2× with thermal annealing at 200 °C.

Rapid, inexpensive, and easy-to-use coronavirus disease 2019 (COVID-19) home tests are key tools in addition to vaccines in the world-wide fight to eliminate national and local shutdowns. However, currently available tests for SARS-CoV-2, the virus that causes COVID-19, are too expensive, painful, and irritating, or not sufficiently sensitive for routine, accurate home testing. Herein, we employ custom-formulated graphene inks and aerosol jet printing (AJP) to create a rapid electrochemical immunosensor for direct detection of SARS-CoV-2 Spike Receptor-Binding Domain (RBD) in saliva samples acquired non-invasively. This sensor demonstrated limits of detection that are considerably lower than most commercial SARS-CoV-2 antigen tests (22.91 ± 4.72 pg/mL for Spike RBD and 110.38 ± 9.00 pg/mL for Spike S1) as well as fast response time (~30 mins), which was facilitated by the functionalization of printed graphene electrodes in a single-step with SARS-CoV-2 polyclonal antibody through the carbodiimide reaction without the need for nanoparticle functionalization or secondary antibody or metallic nanoparticle labels. This immunosensor presents a wide linear sensing range from 1 to 1000 ng/mL and does not react with other coexisting influenza viruses such as H1N1 hemagglutinin. By combining high-yield graphene ink synthesis, automated printing, high antigen selectivity, and rapid testing capability, this work offers a promising alternative to current SARS-CoV-2 antigen tests.

Nanoscale materials possess distinct physical and chemical attributes including size-dependent properties, quantum confinement, high surface-to-volume ratio, and superior catalytic activity. These unique qualities enable sensors with high sensitivity, robustness, and fast time response. As the emergence of the Internet of Things (IoT) demands increased production of sensors, it also provides an impetus for concentrated nanomaterial-based sensor research. Meanwhile, additive manufacturing (AM) of nanomaterial-based sensors is critical to bridge the gap between one-off, lab-scale fabrication and cost-effective, industrial-scale production with high reproducibility. By applying the design flexibility and cost savings of AM techniques, a new generation of nanomaterial-based sensing platforms can be integrated with IoT devices in the consumer space. Furthermore, emergent research in human–machine interfaces, food safety, and point-of-care diagnostics will be expedited by the development of sensors that can be printed with irregular form factors. In this Review, the relative strengths and weaknesses of printed sensor systems based on zero-, one-, and two-dimensional nanomaterials are discussed. In addition, sensors enabled by printable soft nanomaterials, heterostructures, and nanocomposites are surveyed due to their synergistic advantages for wearable healthcare monitoring and soft robotics. Finally, a roadmap for the next decade of research on this topic is provided.

Layered-type, nickel-rich lithium nickel manganese cobalt oxides (NMCs) are well-established cathode materials for high-performance lithium-ion batteries. These materials exhibit stable cycling within mild voltage windows (up to 4.3 V vs. Li/Li + ) but can be charged to higher potentials (4.8 V vs. Li/Li + ) to access additional capacity. However, high-voltage operation is generally avoided due to severe interfacial and chemomechanical degradation, such as electrolyte decomposition reactions and non-uniform buildup of chemomechanical strains that can result in particle fracture and compromised cyclability. In this work, we find that a conformal graphene coating enables significant enhancements in the cycle life and coulombic efficiency of NMC cathodes during high voltage electrochemical cycling. Postmortem surface chemical analysis reveals that graphene-coated NMC electrodes exhibit reduced spectral intensities corresponding to electrolyte decomposition products, suggesting that the interfacial graphene layer limits parasitic electrode-electrolyte interactions. Furthermore, global and local structural analysis shows that the graphene coating mitigates mechanical degradation, which was evidenced by reduced microstrain, particle fracture, and electrochemical creep. Based on these observations, we propose a mechanistic relationship between the spatial uniformity of lithium flux and primary particle-level mechanical degradation, and show that a conformal graphene coating is well-suited to address these issues associated with high voltage chemomechanical degradation. Overall, these results delineate a pathway for rationally mitigating high-voltage chemomechanical degradation of nickel-rich cathodes that can be applied to existing and emerging classes of battery materials. https://doi.org/10.1021/acsaem.1c01995

LiNiO2 (LNO) is a promising cathode material for next-generation Li-ion batteries due to its exceptionally high capacity and cobalt-free composition that enables more sustainable and ethical large-scale manufacturing. However, its poor cycle life at high operating voltages over 4.1 V impedes its practical use, thus motivating efforts to elucidate and mitigate LiNiO2 degradation mechanisms at high states of charge. Here, a multiscale exploration of high-voltage degradation cascades associated with oxygen stacking chemistry in cobalt-free LiNiO2, is presented. Lattice oxygen loss is found to play a critical role in the local O3-O1 stacking transition at high states of charge, which subsequently leads to Ni-ion migration and irreversible stacking faults during cycling. This undesirable atomic-scale structural evolution accelerates microscale electrochemical creep, cracking, and even bending of layers, ultimately resulting in macroscopic mechanical degradation of LNO particles. By employing a graphene-based hermetic surface coating, oxygen loss is attenuated in LNO at high states of charge, which suppresses the initiation of the degradation cascade and thus substantially improves the high-voltage capacity retention of LNO. Overall, this study provides mechanistic insight into the high-voltage degradation of LNO, which will inform ongoing efforts to employ cobalt-free cathodes in Li-ion battery technology.