5 research outputs found
Spin dynamics of FeGaGe studied by Electron Spin Resonance
The intermetallic semiconductor FeGa acquires itinerant ferromagnetism
upon electron doping by a partial replacement of Ga with Ge. We studied the
electron spin resonance (ESR) of high-quality single crystals of
FeGaGe for from 0 up to 0.162 where ferromagnetic order is
observed. For we observed a well-defined ESR signal, indicating the
presence of pre-formed magnetic moments in the semiconducting phase. Upon Ge
doping the occurrence of itinerant magnetism clearly affects the ESR properties
below ~K whereas at higher temperatures an ESR signal as seen in
FeGa prevails independent on the Ge-content. The present results show
that the ESR of FeGaGe is an appropriate and direct tool to
investigate the evolution of 3d-based itinerant magnetism.Comment: 12 pages, 7 figure
Suppressing High-Current-Induced Phase Separation in Ni-Rich Layered Oxides by Electrochemically Manipulating Dynamic Lithium Distribution
Understanding the cycling rate-dependent kinetics is crucial for managing the performance of batteries in high-power applications. Although high cycling rates may induce reaction heterogeneity and affect battery lifetime and capacity utilization, such phase transformation dynamics are poorly understood and uncontrollable. In this study, synchrotron-based operando X-ray diffraction is performed to monitor the high-current-induced phase transformation kinetics of LiNi0.6Co0.2Mn0.2O2. The sluggish Li diffusion at high Li content induces different phase transformations during charging and discharging, with strong phase separation and homogeneous phase transformation during charging and discharging, respectively. Moreover, by exploiting the dependence of Li diffusivity on the Li content and electrochemically tuning the initial Li content and distribution, phase separation pathway can be redirected to solid solution kinetics at a high charging rate of 7 C. Finite element analysis further elucidates the effect of the Li-content-dependent diffusion kinetics on the phase transformation pathway. The findings suggest a new direction for optimizing fast-cycling protocols based on the intrinsic properties of the materials
A Kinetic Indicator of Ultrafast Nickel-Rich Layered Oxide Cathodes
Elucidating high-rate cycling-induced nonequilibriumelectrodereactions is crucial for developing extreme fast charging (XFC) batteries.Herein, we unveiled the distinct rate capabilities of a series ofNi-rich layered oxide (NRLO) cathodes by quantitatively establishingtheir dynamic structure-kinetics relationships. Contrary toconventional views, we discovered electrode kinetic properties obtained ex-situ near equilibrium states failed to assess the effectiverate capability of NRLOs at ultrafast C rates. Further, the kineticphase heterogeneity, characterized by the dynamic separations in in-situ X-ray diffraction patterns and deviations in NRLO c-axis lattice parameters, exclusively correlated with thecapacity reduction under XFC and became an effective indicator ofthe NRLO rate capability. Enhancing the cycling temperature boostedthe rate capability of studied NRLOs by similar to 10%, which was furtherverified to mitigate the kinetic phase heterogeneity during XFC. Overall,this study lays the groundwork for tuning the kinetic phase heterogeneityof electrodes to develop ultrafast batteries.N
A Kinetic Indicator of Ultrafast Nickel-Rich Layered Oxide Cathodes
Elucidating high-rate cycling-induced nonequilibrium
electrode
reactions is crucial for developing extreme fast charging (XFC) batteries.
Herein, we unveiled the distinct rate capabilities of a series of
Ni-rich layered oxide (NRLO) cathodes by quantitatively establishing
their dynamic structure–kinetics relationships. Contrary to
conventional views, we discovered electrode kinetic properties obtained ex-situ near equilibrium states failed to assess the effective
rate capability of NRLOs at ultrafast C rates. Further, the kinetic
phase heterogeneity, characterized by the dynamic separations in in-situ X-ray diffraction patterns and deviations in NRLO c-axis lattice parameters, exclusively correlated with the
capacity reduction under XFC and became an effective indicator of
the NRLO rate capability. Enhancing the cycling temperature boosted
the rate capability of studied NRLOs by ∼10%, which was further
verified to mitigate the kinetic phase heterogeneity during XFC. Overall,
this study lays the groundwork for tuning the kinetic phase heterogeneity
of electrodes to develop ultrafast batteries