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Confining molecules in the nanoscale environment can lead to dramatic changes of their physical and chemical properties, which opens possibilities for new applications. There is a growing interest in liquefied gas electrolytes for electrochemical devices operating at low temperatures due to their low melting point. However, their high vapor pressure still poses potential safety concerns for practical usages. Herein, we report facile capillary condensation of gas electrolyte by strong confinement in sub-nanometer pores of metal-organic framework (MOF). By designing MOF-polymer membranes (MPMs) that present dense and continuous micropore (~0.8 nm) networks, we show significant uptake of hydrofluorocarbon molecules in MOF pores at pressure lower than the bulk counterpart. This unique property enables lithium/fluorinated graphite batteries with MPM-based electrolytes to deliver a significantly higher capacity than those with commercial separator membranes (~500 mAh g−1 vs., Liquefied gas electrolytes (LGE) can enable the operation of electrochemical devices in cold conditions but their high vapour pressure poses safety concerns. Here, the authors show that the nano-confinement effect of metal-organic framework allows battery with LGE to work at low temperature and reduced pressure.

Haptic devices are in general more adept at mimicking the bulk properties of materials than they are at mimicking the surface properties. This paper describes a haptic glove capable of producing sensations reminiscent of three types of near-surface properties: hardness, temperature, and roughness. To accomplish this mixed mode of stimulation, three types of haptic actuators were combined: vibrotactile motors, thermoelectric devices, and electrotactile electrodes made from a stretchable conductive polymer synthesized in our laboratory. This polymer consisted of a stretchable polyanion which served as a scaffold for the polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT). The scaffold was synthesized using controlled radical polymerization to afford material of low dispersity, relatively high conductivity (0.1 S cm(−1)), and low impedance relative to metals. The glove was equipped with flex sensors to make it possible to control a robotic hand and a hand in virtual reality (VR). In psychophysical experiments, human participants were able to discern combinations of electrotactile, vibrotactile, and thermal stimulation in VR. Participants trained to associate these sensations with roughness, hardness, and temperature had an overall accuracy of 98%, while untrained participants had an accuracy of 85%. Sensations could similarly be conveyed using a robotic hand equipped with sensors for pressure and temperature.

The momentum in developing next-generation high energy batteries calls for an electrolyte that is compatible with both lithium (Li) metal anodes and high-voltage cathodes, and is also capable of providing high power in a wide temperature range. Here, we present a fluoromethane-based liquefied gas electrolyte with acetonitrile cosolvent and a higher, yet practical, salt concentration. The unique solvation structure observed in molecular dynamics simulations and confirmed experimentally shows not only an improved ionic conductivity of 9.0 mS cm−1 at +20 °C but a high Li transference number (tLi+ = 0.72). Excellent conductivity (>4 mS cm−1) was observed from −78 to +75 °C, demonstrating operation above fluoromethane's critical point for the first time. The liquefied gas electrolyte also enables excellent Li metal stability with a high average coulombic efficiency of 99.4% over 200 cycles at the aggressive condition of 3 mA cm−2 and 3 mA h cm−2. Also, dense Li deposition with an ideal Li–substrate contact is seen in the liquefied gas electrolyte, even at −60 °C. Attributed to superior electrolyte properties and the stable interfaces on both cathode and anode, the performances of both Li metal anode and Li/NMC full cell (up to 4.5 V) are well maintained in a wide-temperature range from −60 to +55 °C. This study provides a pathway for wide-temperature electrolyte design to enable high energy density Li–metal battery operation between −60 to +55 °C.

Among the several challenges to enable next-generation batteries is the development of an electrolyte which compatible with both lithium (Li) metal anode and high-voltage cathode at wide temperature range. Liquefied gas electrolytes with a new cosolvent and higher salt concentration show improved ionic conductivity of > 4 mS/cm at wide temperature range from -80 to +70 °C. With a new solvation structure, the liquefied gas electrolytes demonstrated high-temperature operation of Li-metal batteries at 55°C, which is the operation above the electrolytes’ critical point for the first time. The electrolytes enable improved Li metal stability and coulombic efficiency at aggressive current and capacity of 3 mA·cm-2 and 3 mAh·cm-2 with average coulombic efficiency of 99%. The use of liquefied gas electrolytes presents stable cycling of Li/NMC (4.4 V) cell at all-temperature range between -60 and 55°C. This study opens up a promising avenue toward the applications of all-temperature high energy density Li-metal batteries.

We report the application of a nonvolatile ionic gel as a soft, conductive interface for electrotactile stimulation. Materials characterization reveals that, compared to a conventional ionic hydrogel, a glycerol-containing ionic gel does not dry out in air, has better adhesion to skin, and exhibits a similar impedance spectrum in the range of physiological frequencies. Moreover, psychophysical experiments reveal that the nonvolatile gel also exhibits a wider window of comfortable electrotactile stimulation. Finally, a simple pixelated device is fabricated to demonstrate spatial resolution of the haptic signal.

Development of safe electrolytes that are compatible with both lithium metal anodes and high-voltage cathodes that can operate in a wide-temperature range is a formidable, yet important challenge. Recently, a new class of electrolytes based on liquefied gas solvents has shown promise in addressing this issue. Concerns, however, have been raised on the pressure, flammability and low maximum operating temperature of these systems. Here, we endeavor to mitigate safety and practicality concerns by demonstrating an enhanced safety feature inherent in liquefied gas electrolytes and by showing the viability of using difluoromethane as a liquefied gas solvent which has lower pressure, lower flammability, and improved maximum operation temperature characteristics compared with fluoromethane. We create a custom-built setup to enable liquefied gas electrolyte characterization through Raman spectroscopy and supplement this with molecular dynamics (MD) simulations. The electrolyte shows good conductivity through a wide temperature range and compatibility with both the lithium metal anode and 4 V class cathodes. The demonstrated use of such alternative liquefied gas solvents opens a path towards the further development of high-energy and safe batteries that can operate in a wide-temperature range.

Summary Among the several challenges to enable next-generation batteries is the development of an electrolyte that maintains a dendrite-free and high Coulombic efficiency lithium-metal anode over extended cell cycling. A new electrolyte solvation structure and transport mechanism is demonstrated in fluoromethane-based liquefied gas electrolytes with the introduction of additive amounts of tetrahydrofuran, which is shown to fully coordinate with the lithium cations and greatly enhance salt dissociation and transport. The resulting electrolyte shows a high conductivity and transference number (t+ > 0.79), which leads to a dramatic improvement of the cycling performance of the lithium-metal anode. Systems using the enhanced liquefied gas electrolytes demonstrate a long-term high average Coulombic efficiency of 99.6%, 99.4%, and 98.1% (± 0.3%) at capacities of 0.5, 1, and 3 mAh·cm−2, respectively, with dendrite-free morphology and remarkable rate capability. Both the rate and cycling performance are well maintained from +20°C to −60°C.

Batteries will play critical roles in modernizing energy grids, as they will allow a greater penetration of renewable energy and perform applications that better match supply with demand. Applying storage technology is a business decision that requires potential revenues to be accurately estimated to determine the economic viability, which requires models that consider market rules and prices, along with battery and application-specific constraints. Here we use models of storage connected to the California energy grid and show how the application-governed duty cycles (power profiles) of different applications affect different battery chemistries. We reveal critical trade-offs between battery chemistries and the applicability of energy content in the battery and show that accurate revenue measurement can only be achieved if a realistic battery operation in each application is considered. The findings in this work could call for a paradigm shift in how the true economic values of energy storage devices could be assessed. Large variations exist in the revenue prediction of grid-scale storage due to uncertainties in operations of storage technologies. Here the authors integrate the economic evaluation of energy storage with key battery parameters for a realistic measure of revenues.

When substituting excess lithium in the transition metal layer, oxygen extends its role as a framework in classical layered oxide cathodes, exhibiting electrochemical activity and enhancing the reversible capacities of layered oxides through anionic redox mechanisms. However, oxygen activity comes with instability in the form of oxygen loss, which is associated with irreversible voltage decay and capacity fade. To understand this irreversible loss and to increase the stability of lattice oxygen, density functional theory is applied to calculate oxygen vacancy formation energies in lithium rich transition metal layered oxides for a variety of dopants, noting increased stability upon doping with 4d elements Mo and Ru. Driven by these findings, Mo is co-doped with Co into Li[Li0.2Ni0.2Mn0.6]O2, showing notably reduced voltage decay and capacity fade without sacrificing energy density and cycle life, and the evidence of Mo incorporation is presented. Calculations suggest that this is due to a modified charge density distribution around anions upon incorporation of Mo, altering the local band structure and impeding oxygen vacancy formation, while maintaining the anionic activity available for redox.

Batteries will undoubtedly play critical roles in modernizing energy grids, allowing greater penetration of renewable generation and providing services that help grids function. Applying storage technology to grid applications is a business decision that requires potential revenues to be accurately measured to determine economic viability. Using models of storage connected to the California energy grid, we simulate grid-scale applications to estimate such revenues under current market conditions. All calculations are undertaken over two full years of operation of the storage device where a simulation of the grid-connected battery is undertaken so that control and decision are made in real time. Control and decision are made with data available at the time and mimics actual use as it might have happened. The use of a long period of data provides precise estimates as to the values of different applications of the battery. Each simulation results in duty cycles (power profiles) on which the cell-level batteries are tested. We examine the effects of these differing duty cycles on the efficiencies of batteries with various chemsitries. For the first time, we reveal critical tradeoffs between the battery chemistries and the applicability of their energy content, and show that accurate revenue measurement can only be achieved if realistic battery operation in each application is taken into account. The findings in this work could call for a paradigm shift on how the true economic values of energy storage devices could be assessed.

Lithium-rich layered cathode materials, where excess lithium occupies transition metal (TM) sites in the TM layer, have shown capacities well beyond commercially available traditional layered cathodes. This is largely attributed to redox behavior of oxygen within the cathode, and has recently been examined computationally1. However this increased capacity is accompanied by a high degree of irreversible capacity loss in first cycling, voltage decay, and low rate capability. This is partially attributed to an oxygen release mechanism, where oxygen vacancy formation accompanies delithiation, rather than the redox of TM ions2. Numerous methods have been attempted to prevent the release of oxygen from the lattice, including TM substitution, morphology control, and surface coating. In this work, we employ density functional theory to calculate the oxygen vacancy formation energy in layered lithium-rich nickel manganese oxide with a variety of cation dopants. Computational results elucidate the impact of doping on the system, and provide rationale for these behaviors. These calculations further describe the impact of local TM bonding environment on specific oxygen sites, rationalizing their relative vacancy formation energies. Driven by these computational results, we experimentally introduce relevant dopants into our cathode materials and observe electrochemical cycling changes commensurate with the predicted changes. Characterization methods verify the predicted oxidation states and incorporation of the relevant dopants. 1. Seo, D. et al. "The structural and chemical origin of the oxygen redox activity in layered and cation-disordered Li-excess cathode materials." Nat. Chem.8, 1–6 (2016). 2. Hy, S. et al. "Performance and Design Considerations For The lithium Excess Layered Oxide Positive Electrode Materials For Lithium Ion Batteries." Energy Environ. Sci. 9, 1931–1954 (2016).

Henry Gerhard Appenzeller (1858–1902)—along with Horace N. Allen, Horace G. Underwood, William B. Scranton, and Marion F. Scranton— pioneered Protestantism in Korea at the turn of the nineteenth century from about 1885 to 1902. Appenzeller intended to convert Koreans to Methodism, to establish Methodist societies, to reform Korean society in agreement with American Protestant evangelical teachings, and, finally, to help Korea become independent, democratic, and modernized, using the United States as a model. Appenzeller's commitment to “convert the heathen” and to reform Korean society along American Protestant Evangelical lines is easy to understand. But why the commitment to Korean independence, democratic reform, and modernization? Why did a pietistic, evangelical Protestant missionary place political concerns on a par with evangelical concerns in Korea? Appenzeller, and the rest of the small American community in Korea during the late nineteenth century, brought along the partially articulated, partially unconscious agenda to build the late nineteenth-century American evangelical Protestant vision of the City on a Hill. Appenzeller attempted to create a Christian Korea in a manner similar to late nineteenthcentury Protestant efforts to create a Christian America. Appenzeller's concept of a City on a Hill provides the key to understanding his commitment to independence, democracy, and modernization in Korea. Citizens had to hold the evangelical Protestant faith. They had to have Anglo-Saxon manners and customs. They had to live morally. The nation had to maintain independence from foreign powers, maintain a democratic form of government, and enjoy the benefits of modernization. We will consider the development of that vision in American history below.