The effect of metal-cluster redox identity on the thermal decarboxylation of a series of isostructural metal-organic frameworks (MOFs) with tetracarboxylate-based ligands and trinuclear μ3-oxo clusters was investigated. The PCN-250 series...

The high specific capacity of lithium metal is ideal to meet the current demand in rechargeable batteries but lithium dendrites and irreversible volume expansions are major hurdles. 3D lithium host materials can alleviate these problems by lowering the current density with large surface areas and accommodating lithium metal in their pores. However, lithium dendrites are persistently observed because of sluggish lithium‐ion diffusion through tortuous pores, resulting in clogging and thereby dendrite growth. Herein, layered metal–organic frameworks (MOFs) are deposited on carboxylated carbon nanotube (CNT) scaffolds via coordination bonding. The MOF layer on the outside of the CNT scaffold has augmented lithium insertion into the porous scaffolds (24 mAh cm−2 at 8 mA cm−2) and lithium plating/stripping lifetime (over 1700 h with 20 mAh cm−2 cycle−1). MOF has pores large enough for lithium ions to permeate through, and its electronically insulating property creates capacitive effects, distributing lithium ions over the surface of the MOF layer to avoid dendrite growth and clogging during lithium plating. Outstanding volumetric and gravimetric capacities (≈940 mAh cm−3 and ≈980 mAh g−1) along with exceptional cumulative capacity (≈4.9 Ah cm−2) are obtained. This promising approach can store lithium without dendrites to deliver high energy densities required for the current rechargeable batteries.

An efficient method has been developed to analyze metal species by using laser‐induced breakdown spectroscopy (LIBS). A least squares support vector machine (LSSVM) was applied to quantitative analysis of multimetal samples with different matrix content, as LSSVM can select the input variables and convert the mapping to the feature space to obtain the linear performance. In this work, three kinds of metal species (alloy steel, ferrochromium alloy, and ferromanganese alloy) were used to construct the LSSVM model. The correlation coefficients (R2), the root‐mean‐square error of prediction (RMSEP), and the average relative error (ARE) were calculated according to the estimated concentrations of chromium (Cr), manganese (Mn), titanium (Ti), and molubdenum (Mo) using the LSSVM model. The results showed that RMSEP decreased from 1.7047%, 1.3453%, 1.9253%, and 2.9431% to 0.0747%, 0.0942%, 0.0192%, and 0.0809%. The ARE of Cr, Mn, Ti, and Mo decreased from 10.2370, 9.8276%, 13.2460%, and 16.2386% to 1.0179%, 1.3937%, 2.1228%, and 1.6257%, respectively. This study demonstrated that LSSVM is an effective algorithm to improve both the accuracy and stability for metal analysis using LIBS.

We present a high-repetition-rate, high-pulse-energy, high-beam-quality, and high-average-power laser system using an ultraclean closed-type stimulated-Brillouin-scattering phase-conjugate mirror (SBS-PCM). By controlling microparticles of SBS-PCM down to 40 nm, thermal load capacity of such closed-type SBS-PCM was greatly improved, which presented the best reported cleanliness. The closed-type SBS-PCM, lacking scanning wedge plates, achieved reflectivity as high as 92% and showed no optical breakdown phenomena or obvious thermal effects at a 500 Hz pulse-repetition frequency (PRF). Operation at 550 W output power, approximately 1.1 J pulse energy, and beam quality M of approximately 2 represents, to our knowledge, the best reported performance. Thermal phase distortion was compensated, and the maximum-output-power pulse-width compression improved from 30 ns to approximately 10 ns.