Demand for fast-charging lithium-ion batteries (LIBs) has escalated incredibly in the past few years. A conventional method to improve the performance is to chemically partly substitute the transition metal with another to increase its conductivity. In this study, we have chosen to investigate the lithium diffusion in doped anatase (TiO<inf>2</inf>) anodes for high-rate LIBs. Substitutional doping of TiO<inf>2</inf> with the pentavalent Nb has previously been shown to increase the high-rate performances of this anode material dramatically. Despite the conventional belief, we explicitly show that Nb is mobile and diffusing at room temperature, and different diffusion mechanisms are discussed. Diffusing Nb in TiO<inf>2</inf> has staggering implications concerning most chemically substituted LIBs and their performance. While the only mobile ion is typically asserted to be Li, this study clearly shows that the transition metals are also diffusing, together with the Li. This implies that a method that can hinder the diffusion of transition metals will increase the performance of our current LIBs even further.

Layered transition metal dichalcogenides (TMDs) are model systems to investigate the interplay between superconductivity and the charge density wave (CDW) order. Here, we use muon spin rotation and relaxation (mu+SR) to probe the superconducting ground state of polycrystalline 2H-TaS2, which hosts a CDW transition at 76 K and superconductivity below 1 K. The mu+SR measurements, conducted down to 0.27 K, are consistent with a nodeless, BCS-like single-gap s-wave state. Fits to the temperature dependence of the depolarization rate and Knight shift measurements support spin-singlet pairing. Crucially, no evidence of time-reversal symmetry breaking (TRSB) is observed, distinguishing 2H-TaS2 from polymorphs like 4Hb-TaS2, where TRSB and unconventional superconductivity have been reported. These findings establish 2H-TaS2 as a canonical BCS superconductor and provide a reference point for understanding the diverse electronic ground states that emerge in structurally distinct TMD polymorphs.

This study explores the magnetic properties of YbCo₂ through specific heat measurements, muon spin rotation spectroscopy, and neutron diffraction under external magnetic fields. A magnetic transition anomaly at 0.3 K in specific heat marks the onset of magnetic order, further corroborated by muon spin resonance data. A second anomaly in specific heat observed in an applied magnetic field indicates a field-induced change of magnetic ordering, confirmed by neutron diffraction experiment in magnetic fields. Yb magnetic moments exhibit a collinear ferromagnetic ordering, while Co moments align antiparallel to Yb moments at low magnetic fields. Increasing the external magnetic field, Co moments develop an additional antiferromagnetic component, modifying the overall magnetic structure. The observed magnetic order in low and high magnetic fields is consistently described by the single magnetic space group Imm'a’ and aligns well with theoretical predictions.

Understanding ion diffusion mechanisms in layered materials is critical for advancing next-generation battery technologies. Using the well-characterized NaxCoO2 (NCO) system as a model platform, we investigated the temperature-dependent diffusion properties across a broad compositional range (x=0.33−0.89) using muon spin relaxation (μ+SR). Unexpected low-temperature internal magnetic field fluctuations were observed, systematically varying with Na content and appearing well before the onset of long-range diffusion. These fluctuations are attributed to phonon-assisted local Na motion, as suggested by a systematic increase in A with x, concurrent with a decreasing activation energy. The diffusion coefficient was calculated based on the crystal structure using a tailored diffusion model accounting for two inequivalent Na sites, yielding values consistent with those found in other layered battery materials. This work highlights the crucial role of phonon-coupled diffusion mechanisms in enabling ion transport at the microscopic scale, providing new insights into ion dynamics in layered solid-state conductors and their relevance to sodium-ion battery technology.

The assertion of intrinsic material properties based on measured experimental data is being challenged by emerging sample synthesis protocols, which opens new avenues for discovering novel functionalities. In this study, we revisit one of the most widely studied strongly correlated materials of the early 2000s, NaxCoO2 (NCO). Leveraging the sensitivity of muon spin rotation and relaxation (μ+SR) measurements, we discern significant differences between NCO samples synthesized via conventional solid-state reaction (SSR) and our electrochemical reaction (ECR) approach. Contrary to SSR-synthesized Na0.7CoO2, which exhibits a nonmagnetic ground state, our ECR-derived sample showcases an antiferromagnetic (AF) order from x≥0.7, challenging established phase boundaries. We attribute the observed magnetic phenomena in ECR-NCO to long-range order of Na-ions and/or vacancies, as well as the inherent flexibility of the crystal framework. Our study holds implications for tailoring and optimization of next-generation devices based on layered materials.

Layered oxides (AMO2, where A = Li or Na and M = transition metal) are essential positive electrode materials for lithium- and sodium-ion batteries. A fundamental question in ion transport is whether Li+ or Na+ diffuses faster in these materials; however, distinguishing intrinsic diffusion properties from the effects of particle size and electrode composition is challenging. Using operando muon spin spectroscopy and molecular dynamics simulations, we determined the Li+ and Na+ self-diffusion coefficients in O3-LixCoO2, O3-NaxCoO2, and P2-NaxCoO2. Our findings revealed that Na+ diffusion is higher in the P2-type structure than in the O3-type structure primarily due to weaker electrostatic interactions. In the O3-type structure, Li+ diffuses faster than Na+, whose larger ionic size hinders mobility. These insights clarify the ion transport mechanisms and advance the design of next-generation battery materials. 

Low-dimensional quantum magnets are a versatile materials platform for studying the emergent many-body physics and collective excitations that can arise even in systems with only short-range interactions. Understanding their low-temperature structure and spin Hamiltonian is key to explaining their magnetic properties, including unconventional quantum phases, phase transitions, and excited states. We study the metal-organic coordination compound (C5H9NH3)2CuBr4 and its deuterated counterpart, which upon its discovery was identified as a candidate two-leg quantum (S=12) spin ladder in the strong-leg coupling regime. By growing large single crystals and probing them with both bulk and microscopic techniques, we deduce that two previously unknown structural phase transitions take place between 136 and 113 K. The low-temperature structure has a monoclinic unit cell that gives rise to two inequivalent spin ladders. We further confirm the absence of long-range magnetic order down to 30 mK and investigate the implications of this two-ladder structure for the magnetic properties of (C5H9NH3)2CuBr4 by analyzing our own specific-heat and susceptibility data.

In this study, we investigate the influence of Cr-Cr distances on the magnetic properties of triangular lattice antiferromagnets through the lens of the recently synthesized Cr compounds LiCrSe2, 2 , LiCrTe2, 2 , and NaCrTe2. 2 . Our comprehensive analysis integrates existing magnetic structure data and new insights from muon spin rotation measurements, revealing a striking mutual influence between strongly correlated electrons and structural degrees of freedom in systems possessing very different magnetic properties despite having the same crystal symmetry. In particular, we delineate how Cr-Cr distances specifically dictate the magnetic behaviors of the triangular lattice antiferromagnets LiCrSe2, 2 , LiCrTe2, 2 , and NaCrTe2. 2 . By crafting phase diagrams based on these distances, we establish a clear correlation between the structural parameters and the magnetic ground states of these materials together with a wide variety of trivalent Cr triangular lattice layered magnets. Our analysis uncovers a transition range for in-plane and out-of-plane Cr-Cr distances that demarcates distinct magnetic behaviors, highlighting the nuanced role of lattice geometry in the spin-lattice interaction and electron correlation dynamics.

Understanding the processes guiding the confinement of adsorbed H2 in different porous structures is vital for the development of adsorbents for effective cryo-adsorptive H2 storage systems. Quasi-elastic neutron scattering (QENS) is applied over a wide range of timescales (0.2 ps – 150 ps) to determine different self-diffusion mechanisms of H2 adsorbed in a carbide (synthesized from TiC via the sol-gel method) derived carbon (sol-gel TiC-CDC) adsorbent with hierarchical porous structure. The bulk and porous structure is characterized by gas adsorption, Raman spectroscopy, and wide-angle X-ray scattering methods. Sol-gel TiC-CDC belongs to a series of CDCs that have been previously characterized and where the self-diffusion of adsorbed H2 has been investigated with QENS. Sol-gel TiC-CDC is very mesoporous, has relatively high stacking (2.76 graphenic layers per stack), and small interlayer spacing of graphenic sheets (3.43 Å) in comparison to other CDCs in the series, thus, being a well-ordered highly porous CDC. Restricted rotational self-diffusion of adsorbed H2 is determined in ultramicropores (pore width, w, < 7 Å) and translationally self-diffusing H2 adsorbed in multilayers across multiple timescales are determined in micro- and mesopores (7 Å < w < 500 Å). The microporous and graphenic structure of the CDC does not remarkably affect the self-diffusion of H2 at high surface coverages. The simultaneous determination of adsorbed H2 motions across different timescales allows to analyze the influence of micro- and mesopores under H2 loading conditions, which are close to the ones used in technical applications and are vital for adsorbent optimization.

Virucidal filter materials were prepared by electrospinning a solution of 28 wt % poly(vinylidene difluoride) in N,N-dimethylacetamide without and with the addition of 0.25 wt %, 0.75 wt %, 2.0 wt %, or 3.5 wt % Cu(NO3)2 · 2.5H2O as virucidal agent. The fabricated materials had a uniform and defect free fibrous structure and even distribution of copper nanoclusters. X-ray diffraction analysis showed that during the electrospinning process, Cu(NO3)2 · 2.5H2O changed into Cu2(NO3)(OH)3. Electrospun filter materials obtained by electrospinning were essentially macroporous. Smaller pores of copper nanoclusters containing materials resulted in higher particle filtration than those without copper nanoclusters. Electrospun filter material fabricated with the addition of 2.0 wt % and 3.5 wt % of Cu(NO3)2 · 2.5H2O in a spinning solution showed significant virucidal activity, and there was 2.5 ± 0.35 and 3.2 ± 0.30 logarithmic reduction in the concentration of infectious SARS-CoV-2 within 12 h, respectively. The electrospun filter materials were stable as they retained virucidal activity for three months.