Considered as an imperative alternative to the commercial LiFePO4 battery, the potassium metal battery possesses great potential in grid-scale energy storage systems due to the low cost, low standard redox potential, and high abundance of potassium. The potassium dendrite growth, large volume change, and unstable solid electrolyte interphase (SEI) on the potassium metal anode have, however, hindered its applications. Although conductive scaffolds coupling with potassium metal have been widely proposed to address the above issues, it remains challenging to fabricate a uniform composite with uncompromised capacity. Herein, we propose a facile and efficient strategy to construct dendrite-free and practical carbon-based potassium composite anodes via amine functionalization of the carbon scaffolds that enables fast molten potassium infusion within several seconds. On the basis of experiments and theoretical calculations, we show that highly potassiophilic amine groups immediately transform carbon scaffolds from nonwetting to wetting to postassium. Our carbon-cloth-based potassium composite anode (K@CC) can accommodate volume fluctuation, provide abundant nucleation sites, and lower the local current density, achieving nondendritic morphology with a stable SEI. The fabricated K0.7Mn0.7Ni0.3O2|K@CC full cell displays excellent rate capability and an ultralong lifespan over 8000 cycles (68.5% retention) at a high current of 1 A g–1.

Multistation observations of Schumann resonance (SR) intensity document common behavior in the evolution of continental‐scale lightning activity in two super El Niño events, occurring in 1997/98 and 2015/16. The vertical electric field component of SR at Nagycenk, Hungary and the two horizontal magnetic field components in Rhode Island, USA in 1997, and in 2014–2015, the two horizontal magnetic field components at Hornsund, Svalbard and Eskdalemuir, United Kingdom as well as in Boulder Creek, California and Alberta, Canada exhibit considerable increases in SR intensity from some tens of percent up to a few hundred percents in the transition months preceding the two super El Niño events. The UT time distribution of anomalies in SR intensity indicates that in 1997 the lightning activity increases mainly in Southeast Asia, the Maritime Continent and India, i.e. the Asian chimney region. On the other hand, a global response in lightning is indicated by the anomalies in SR intensity in 2014 and 2015. SR‐based results are strengthened by comparison to independent lightning observations from the Optical Transient Detector and the World Wide Lightning Location Network, which also exhibit increased lightning activity in the transition months. The increased lightning is attributable to increased instability due to thermodynamic disequilibrium between the surface and the midtroposphere during the transition. The main conclusion is that variations in SR intensity may act as a precursor for the occurrence and magnitude of these extreme climate events, and in keeping with earlier findings, as a precursor to maxima in global surface air temperature.

Cavity optomechanical systems are being widely developed for precision force and displacement measurements. For nanomechanical transducers, there is usually a trade-off between the frequency (f M ) and quality factor (Q M ), which limits temporal resolution and sensitivity. Here, we present a monolithic cavity optomechanical transducer supporting both high f M and high Q M . By replacing the common doubly-clamped, Si 3 N 4 nanobeam with a tuning fork geometry, we demonstrate devices with the fundamental f M ≈ 29 MHz and Q M ≈ 2.2×105 , corresponding to an f M Q M product of 6.35×10 12 Hz, comparable to the highest values previously demonstrated for room temperature operation. This high f M Q M product is partly achieved by engineering the stress of the tuning fork to be 3 times the residual film stress through clamp design, which results in an increase of f M up to 1.5 times. Simulations reveal that the tuning fork design simultaneously reduces the clamping, thermoelastic dissipation, and intrinsic material damping contributions to mechanical loss. This work may find application when both high temporal and force resolution are important, such as in compact sensors for atomic force microscopy.Cavity optomechanical systems are being developed for many applications in precision force and displacement measurements 1,2 . Monolithic systems in which nanomechanical transducers are combined with integrated optical readout have been developed in geometries where optical resonances and mechanical modes are co-located within the same physical structure 3-7 , and in systems for which optical and mechanical modes are supported by different physical structures and are near-fieldcoupled 8,9 . Such near-field coupling enables the mechanical resonator size to be scaled down to the nanoscale while maintaining high displacement sensitivity 8,9 in contrast to far-field optical readout, where diffraction effects limit the mechanical resonator size that can be sensitively detected 10 . For a given desired mechanical stiffness (determined by the force sensing application), a nanoscale cantilever can have much higher resonant frequency f M (and therefore transduction bandwidth/temporal resolution) than a microscale counterpart, due to its smaller effective motional mass (m). Such a high frequency mechanical resonator would ideally exhibit a high mechanical quality factor (Q M ), as the force sensitivity scales as 1/(fHowever, there is usually a tradeoff between f M and Q M because shrinking down the resonator size comes at the expense of a reduction in Q M , due to increased clamping losses 11,12 . Here, we demonstrate an integrated silicon nitride cavity optomechanical system where high f M and Q M are simultaneously achieved. Using microdisk optical resonators with intrinsic optical quality factor Q o > 6×10 5 for readout, we develop a doubly-clamped tuning fork geometry as a) Electronic mail: yliu11@wpi.edu the mechanical resonator, where we take advantage of elastic wave interference to limit the mechanical loss, while retaining th...