Applications for Nanoscale X-ray Imaging at High Pressure

Coupling nanoscale transmission X-ray microscopy (nanoTXM) with a diamond anvil cell (DAC) has exciting potential as a powerful three-dimensional probe for non-destructive imaging at high spatial resolution of materials under extreme conditions. In this article, we discuss current developments in high-resolution X-ray imaging and its application in high-pressure nanoTXM experiments in a DAC with third-generation synchrotron X-ray sources, including technical considerations for preparing successful measurements. We then present results from a number of recent in situ high-pressure measurements investigating equations of state (EOS) in amorphous or poorly crystalline materials and in pressureinduced phase transitions and electronic changes. These results illustrate the potential this technique holds for addressing a wide range of research areas, ranging from condensed matter physics and solidstate chemistry to materials science and planetary interiors. Future directions for this exciting technique and opportunities to improve its capabilities for broader application in high-pressure science are discussed.

Revisiting the capacity-fading mechanism of P2-type sodium layered oxide cathode materials during high-voltage cycling

P2-type sodium layered oxide cathode (Na_(2/3)Ni_(1/3)Mn_(2/3)O_(2)P2-NNMO) has attracted great attention as a promising cathode material for sodium ion batteries because of its high specific capacity. However, this material suffers from a rapid capacity fade during high-voltage cycling. Several mechanisms have been proposed to explain the capacity fade, including intragranular fracture caused by the P2-O2 phase transion, surface structural change, and irreversible lattice oxygen release. Here we systematically investigated the morphological, structural, and chemical changes of P2-NNMO during high-voltage cycling using a variety of characterization techniques. It was found that the lattice distortion and crystal-plane buckling induced by the P2-O2 phase transition slowed down the Na-ion transport in the bulk and hindered the extraction of the Na ions. The sluggish kinetics was the main reason in reducing the accessible capacity while other interfacial degradation mechanisms played minor roles. Our results not only enabled a more complete understanding of the capacity-fading mechanism of P2-NNMO but also revealed the underlying correlations between lattice doping and the moderately improved cycle performance.

Ribozymes and the mechanisms that underlie RNA catalysis

Ribozymes 是普遍的，并且在房间催化一些极其重要的反应。最机械学地掉进二个班之一，用任何一个金属离子或一般酸硷的催化作用。nucleolytic ribozymes 掉进后者班，主要用 nucleobases。这些的一个子集使用加腺嘌酸基础的 guanine 的联合催化劈开反应。新 ribozymes 仍然在常规间隔正在被发现，我们能在 ribozymes 的潜在的存在上推测在 phosphoryl 转移反应以外催化化学，也许使用小分子的辅酶。

Data-Driven Lithium-Ion Battery Cathode Research with State-of-the-Art Synchrotron X-ray Techniques

CONSPECTUS:The lithium-ion battery(LIB)is a tremendously successful technology for energy storage thanks to its favorable characteristics including high energy density,long lifespan,affordability,and safety.It has been widely adopted in sectors including consumer electronics and electric vehicles,which are featured by an enormous market value.To meet the ever-increasing demands for energy density and cycle life,industry and academia are continuously devoting efforts to improve the current LIB technology.This requires an in-depth understanding of the electrochemical reaction processes and degradation/failure mech-anisms,to which advanced characterization is pivotal.Combining advanced synchrotron X-ray techniques with machine learning(ML)methods has been demonstrated as a powerful tool for uncovering the fundamental reaction and aging mechanisms in LIB and is emerging as an important research frontier.Our group’s research has been focusing on the battery cathode,which is a major limiting factor in today’s LIB technology.The degradation and failure of cathode materials in LIB are multiscale.The chemo mechanical processes at these different length scales are intertwined and mutually modulated.Therefore,it is crucial to understand the underlying mechanisms of charge−lattice−morphology−kinetics interactions in battery cathodes as a function of the electrochemical states.Synchrotron X-ray technology has unique advantages.It can detect lattice structure,electronic structure,chemical valence state,and multiscale morphology in different experimental modes,with high resolution and high efficiency.However,the large-scale experimental data bring great challenges in terms of reduction,analysis,and interpretation.Data-driven methods based on ML can greatly assist researchers to understand,control,and predict the electrochemical behavior of the complex battery cathode systems.In this Account,we focus on showcasing the integration of synchrotron and ML techniques for LIB cathode research.We review our recent findings on charge−lattice−morphology−kinetics in LIB cathode materials via this approach.First,the ML-based morphological study of cathode materials is discussed,highlighting a ML-assisted automatic feature recognition,particle identification,and statistical analysis of the prolonged cycling-induced particle damage and detachment from the carbon matrix.Second,we discuss the chemical heterogeneity and lattice deformation in cathode materials revealed by ML-assisted multimodal synchrotron characterizations.The role of ML tools in identifying and understanding chemical outliers and lattice defects in NCM cathodes is highlighted.Third,we provide our perspective on a future“dream”experiment for investigating the spatial distribution of cation−anion redox coupling effects in the battery cathode by means of resonant inelastic X-ray scattering(RIXS)imaging with ML.We anticipate that this new approach will provide new horizons for the development of novel high-energy and high-power-density LIB cathode materials.With an emphasis on the data-driven approaches for researching battery materials with synchrotron X-ray techniques,we hope that this Account will lead to more endeavors in this research field.