55 Search Results

Lithium-ion batteries are indispensable power sources for a wide range of modern electronic devices. However, battery lifespan remains a critical limitation, directly affecting the sustainability and user experience. Conventional battery failure analysis in controlled lab settings may not capture the complex interactions and environmental factors encountered in real-world, in-device operating conditions. Here, this study analyzes the failure of commercial wireless earbud batteries as a model system within their intended usage context. Through multiscale and multimodal characterizations, the degradations from the material level to the device level are correlated, elucidating a failure pattern that is closely tied to the specific devicemore » configuration and operating conditions. The findings indicate that the ultimate failure mode is determined by the interplay of battery materials, cell structural design, and the in-device microenvironment, such as temperature gradients and their fluctuations. This holistic, in-device perspective on environmental influences provides critical insights for battery integration design, enhancing the reliability of modern electronics.« less

High-valent Fe^IV=O species are common intermediates in biological and artificial catalysts. Heme and nonheme S=1 Fe^IV=O sites have been synthesized and studied for decades but little quantitative experimental comparison of their electronic structures has been available, due to the lack of direct methods focused on the iron. This study allows a rigorous determination of the electronic structure of a nonheme Fe^IV=O center and its comparison to an Fe^IV=O heme site using 1s2p resonant inelastic X-ray scattering (RIXS) and Fe L-edge X-ray absorption spectroscopy (XAS). Further, variable temperature magnetic circular dichroism (VT-MCD) of the ligand field transitions, combined with nuclear resonancemore » vibrational spectroscopy of the two S=1 Fe^IV=O systems show that the equatorial ligand field decreases from a nonheme to a heme Fe^IV=O site. Alternatively, RIXS and Fe L-edge XAS combined with MCD show that the Fe dπ orbitals are unperturbed in the Fe^IV=O heme relative to the nonheme site because the strong axial Fe-O bond uncouples the Fe dπ orbitals from the porphyrin π-system. As a consequence, the thermodynamics and kinetics of the H-atom abstraction reactions are actually very similar for heme compound II and nonheme Fe^IV=O active sites.« less

Diamond as a templating substrate is largely unexplored, and the unique properties of diamond, including its large bandgap, thermal conductance, and lack of cytotoxicity, makes it versatile in emergent technologies in medicine and quantum sensing. Surface termination of an inert diamond substrate and its chemical reactivity are key in generating new bonds for nucleation and growth of an overlayer material. Oxidized high-pressure high temperature (HPHT) nanodiamonds (NDs) are largely terminated by alcohols that act as nucleophiles to initiate covalent bond formation when an electrophilic reactant is available. In this work, we demonstrate a templated synthesis of ultrathin boron on NDmore » surfaces using trigonal boron compounds. Boron trichloride (BCl₃), boron tribromide (BBr₃), and borane (BH₃) were found to react with ND substrates at room temperature in inert conditions. BBr₃ and BCl₃ were highly reactive with the diamond surface, and sheet-like structures were produced and verified with electron microscopy. Surface-sensitive spectroscopies were used to probe the molecular and atomic structure of the ND constructs’ surface, and quantification showed the boron shell was less than 1 nm thick after 1–24 h reactions. Observation of the reaction supports a self-terminating mechanism, similar to atomic layer deposition growth, and is likely due to the quenching of alcohols on the diamond surface. X-ray absorption spectroscopy revealed that boron-termination generated midgap electronic states that were originally predicted by density functional theory (DFT) several years ago. DFT also predicted a negative electron surface, which has yet to be confirmed experimentally here. The boron-diamond nanostructures were found to aggregate in dichloromethane and were dispersed in various solvents and characterized with dynamic light scattering for future cell imaging or cancer therapy applications using boron neutron capture therapy (BNCT). The unique templating mechanism based on nucleophilic alcohols and electrophilic trigonal precursors allows for covalent bond formation and will be of interest to researchers using diamond for quantum sensing, additive manufacturing, BNCT, and potentially as an electron emitter.« less

Ti₃C₂T_x MXene is an emerging family of two-dimensional materials, and because of its large specific surface area, it has potential for many applications. Herein, a new application using Cu-doped MILD (minimally intensive layer delamination) synthesized Ti₃C₂T_x MXene for urea removal is demonstrated. The doping of Cu on MXene results in an increase in its affinity for urea adsorption as compared to the pristine MILD synthesized MXene due to the formation of the Cu–urea complex. Previous computational studies have shown that the adsorption energies of urea on the MXene surface can be improved in the presence of Cu. The valence statemore » of Cu in the doped MILD synthesized MXene, which binds on to the surface via Ti–O–Cu linkage, is between 0 and +1 as verified by XAS and XPS. As the optimal urea adsorption occurs on Cu as a single atom site, an increase in Cu doping on MXene does not increase urea removal due to Cu agglomeration. Furthermore, looking at the adsorption behaviour, it seems that Cu-doped MXene follows the monolayer adsorption on homogenous surface model.« less

Deep sodium extraction/insertion of sodium cathodes usually causes undesired Jahn–Teller distortion and phase transition, both of which will reduce structural stability and lead to poor long-cycle reliability. Here we report a zero-strain P2- Na_2/3Li1/6Co_1/6Mn_2/3O₂ cathode, in which the lithium/cobalt substitution contributes to reinforcing the host structure by reducing the Mn³⁺/Mn⁴⁺ redox, mitigating the Jahn–Teller distortion, and minimizing the lattice change. 94.5 % of Na⁺ in the unit structure can be reversibly cycled with a charge cut-off voltage of 4.5 V (vs. Na⁺/Na). Impressively, a solid-solution reaction without phase transitions is realized upon deep sodium (de)intercalation, which poses a minimal volumemore » deviation of 0.53 %. Finally, it attains a high discharge capacity of 178 mAh g^–1, a high energy density of 534 Wh kg^–1, and excellent capacity retention of 95.8 % at 1 C after 250 cycles.« less

Recently, Mg doped Na metal oxide layered cathode compounds have attracted strong interest for Na-ion battery applications. We report a new type of asymmetric phase evolution between charge and discharge is found to show much-enhanced discharge voltage in P2-Na_2/3Mg_0.205Ni_0.1Fe_0.05Mn_0.645O₂ over the parent cathode compound. P2 solid solution is found to show an abnormal coexistence with O2-P2 two-phase reaction during discharge with simultaneous reduction of O, Ni, and Fe redoxes, distinct from the conventional P2-O2 two-phase reaction in the charge. Our analysis suggests that the P2 and O2 two-phase boundary forms a novel unidirectional Schottky barrier to impede electron and Namore » diffusions in discharge only, thus making the kinetically preferred P2 solid solution phase abnormally coexist with the two-phase region for high discharge voltage and low polarization. Our work demonstrates tuning dynamic evolution of electronic Schottky barrier as a new dimension for advanced kinetic design of high-performance battery cathode materials.« less

P2-Na_0.67Ni_0.33Mn_0.67O₂ represents a promising cathode for Na-ion batteries, but it suffers from severe structural degradation upon storing in a humid atmosphere and cycling at a high cutoff voltage. Here we propose an in situ construction to achieve simultaneous material synthesis and Mg/Sn cosubstitution of Na_0.67Ni_0.33Mn_0.67O₂ via one-pot solid-state sintering. Here, the materials exhibit superior structural reversibility and moisture insensitivity. In-operando XRD reveals an essential correlation between cycling stability and phase reversibility, whereas Mg substitution suppressed the P2–O2 phase transition by forming a new Z phase, and Mg/Sn cosubstitution enhanced the P2–Z transition reversibility benefiting from strong Sn–O bonds. DFT calculationsmore » disclosed high chemical tolerance to moisture, as the adsorption energy to H₂O was lower than that of the pure Na_0.67Ni_0.33Mn_0.67O₂. A representative Na_0.67Ni_0.23Mg_0.1Mn_0.65Sn_0.02O₂ cathode exhibits high reversible capacities of 123 mAh g^–1 (10 mA g^–1), 110 mAh g^–1 (200 mA g^–1), and 100 mAh g^–1 (500 mA g^–1) and a high capacity retention of 80% (500 mA g^–1, 500 cycles).« less

Superconducting detectors have become an important tool in experimental astroparticle physics, which seeks to provide a fundamental understanding of the Universe. In particular, such detectors have demonstrated excellent potential in two challenging research areas involving rare event search experiments, namely, the direct detection of dark matter (DM) and the search for neutrinoless double beta decay. Here, we review the superconducting detectors that have been and are planned to be used in these two categories of experiments. We first provide brief histories of the two research areas and outline their significance and challenges in astroparticle physics. Then, we present an extensivemore » overview of various types of superconducting detectors with a focus on sensor technologies and detector physics, which are based on calorimetric measurements and heat flow in the detector components. Finally, we introduce leading experiments and discuss their future prospects for the detection of DM and the search for neutrinoless double beta decay employing superconducting detectors.« less