Hui (Claire) Xiong

• Ph.D.
• Professor (Assistant) at Boise State University

All-solid-state batteries (ASSBs) have drawn significant attention as future energy storage technologies. Sulfide-based solid electrolytes are promising due to their high ionic conductivity and favorable mechanical properties. However, their reactivity with moisture, leading to decomposition and release of toxic gases such as H2S, poses health and...

Intercalation-type layered oxides are the most promising positive electrodes for next-generation sodium-ion batteries due to their high energy density, low cost, and tunable chemistry. However, these materials are often subjected to substantial phase transitions and lattice changes when cycled at high voltage, leading to fast capacity decay. In thi...

P2-layered Na0.67Ni0.33Mn0.67O2 (NNMO) has emerged as a promising positive electrode material for sodium ion batteries due to its appealing electrochemical properties. Synthesis of polycrystalline NNMO (PC-NNMO) materials through conventional calcination of solid precursors remains the prevailing method, where heating occurs in a dry environment wi...

Polymer electrolytes hold great promise for safe and high-energy batteries comprising solid or semi-solid electrolytes. Multiphase polymer electrolytes, consisting of mobile and rigid phases, exhibit fast ion conduction and desired mechanical properties. However, fundamental challenges exist in understanding and regulating interactions at the elect...

Designing the solid–electrolyte interphase (SEI) is critical for stable, fast-charging, low-temperature Li-ion batteries. Fostering a “fluorinated interphase,” SEI enriched with LiF, has become a popular design strategy. Although LiF possesses low Li-ion conductivity, many studies have reported favorable battery performance with fluorinated SEIs. S...

High‐manganese content sodium‐ion positive electrodes have received heightened interest as an alternative to contemporary Li‐ion chemistries due to their high abundance, low toxicity, and even geographical distribution. However, these materials typically suffer from poor capacity, unstable cycling performance, and sluggish Na⁺ kinetics. Herein, we...

All-solid-state batteries offer high-energy-density and eco-friendly energy storage but face commercial hurdles due to dendrite formation, especially with lithium metal anodes. Here we report that dendrite formation in Li/Li7La3Zr2O12/Li batteries occurs via two distinct mechanisms, using non-invasive solid-state nuclear magnetic resonance and magn...

Solid electrolytes (SEs) are crucial for advancing next-generation rechargeable battery technologies, but their commercial viability is partially limited by expensive precursors, unscalable synthesis, or low ionic conductivity. Lithium tetrahaloaluminates offer an economical option but exhibit low Li⁺ conductivities with high activation energy barr...

Localized atomistic disorder in halide‐based solid electrolytes (SEs) can be leveraged to boost Li⁺ mobility. In this study, Li⁺ transport in structurally modified Li3HoCl6, via Br⁻ introduction and Li⁺ deficiency, is explored. The optimized Li3‐3yHo1+yCl6‐xBrx achieves an ionic conductivity of 3.8 mS cm⁻¹ at 25 °C, the highest reported for holmium...

Ether solvents are suitable for formulating solid-electrolyte interphase (SEI)-less ion-solvent cointercalation electrolytes in graphite for Na-ion and K-ion batteries. However, ether-based electrolytes have been historically perceived to cause exfoliation of graphite and cell failure in Li-ion batteries. In this study, we develop strategies to ach...

Niobium pentoxide (Nb2O5) is a promising negative electrode for sodium ion batteries (SIBs). By engineering the morphology and crystallinity of nanochanneled niobium oxides (NCNOs), the kinetic behavior and charge storage mechanism of Nb2O5 electrodes were investigated. Amorphous and crystalline NCNO samples were made by modulating anodization cond...

Developing stable cathode materials that are resistant to storage degradation is essential for practical development and industrial processing of Na-ion batteries as many sodium layered oxide materials are susceptible to hygroscopicity and instability upon exposure to ambient air. Among the various layered compounds, Fe-substituted O3-type Na(Ni1/2...

Solid-electrolyte interphases (SEIs) in advanced rechargeable batteries ensure reversible electrode reactions at extreme potentials beyond the thermodynamic stability limits of electrolytes by insulating electrons while allowing the transport of working ions. Such selective ion transport occurs naturally in biological cell membranes as a ubiquitous...

Group IV elements and their oxides, such as Si, Ge, Sn and SiO have much higher theoretical capacity than commercial graphite anode. However, these materials undergo large volume change during cycling, resulting in severe structural degradation and capacity fading. Al2O3coating is considered an approach to improve the mechanical stability of high-c...

Interface engineering in electrode materials is an attractive strategy for enhancing charge storage, enabling fast kinetics, and improving cycling stability for energy storage systems. Nevertheless, the performance improvement is usually ambiguously ascribed to the “synergetic effect”, the fundamental understanding toward the effect of the interfac...

Amorphous ceramics are a unique class of materials with unusual properties and functionalities. While these materials are known to crystallize when subjected to thermal annealing, they have sometimes been observed to crystallize athermally when exposed to extreme irradiation environments. Because irradiation is almost universally understood to intr...

Intercalation-type metal oxides are promising negative electrode materials for safe rechargeable lithium-ion batteries due to the reduced risk of Li plating at low voltages. Nevertheless, their lower energy and power density along with cycling instability remain bottlenecks for their implementation, especially for fast-charging applications. Here,...

Multiphase layered transition metal oxides (LTMOs) for sodium ion battery (SIB) positive electrodes with phase interfaces across multiple length scales are a promising avenue toward practical, high‐performance SIBs. Combinations of phases can complement each other's strengths and mitigate their weaknesses if their interfaces are carefully controlle...

Layered Na0.67Ni0.33Mn0.67O2 is an attractive cathode material for sodium ion batteries. The thermal stability of cathode materials is crucial to their practical applications. In this work, we investigate structural and morphological evolution in layered P2-type Na0.67Ni0.33Mn0.67O2 cathode materials during annealing via in situ synchrotron X-ray d...

Understanding of structural and morphological evolution in nanomaterials is critical in tailoring their functionality for applications such as energy conversion and storage. Here, we examine irradiation effects on the morphology and structure of amorphous TiO2 nanotubes in comparison with their crystalline counterpart, anatase TiO2 nanotubes, using...

As a promising alternative to the market-leading lithium-ion batteries, low-cost sodium-ion batteries (SIBs) are attractive for applications such as large-scale electrical energy storage systems. The energy density, cycling life, and rate performance of SIBs are fundamentally dependent on dynamic physiochemical reactions, structural change, and mor...

P2-structured Na0.67Ni0.33Mn0.67O2 (PNNMO) is a promising Na-ion battery cathode material, but its rapid capacity decay during cycling remains a hurdle. Li doping in layered transition-metal oxide (TMO) cathode materials is known to enhance their electrochemical properties. Nevertheless, the influence of Li at different locations in the structure h...

Layered NaNi x Fe y Mn z O2 cathode (NFM) is of great interest in sodium ion batteries because of its high theoretical capacity and utilization of abundant, low-cost, environmentally friendly raw materials. Nevertheless, there remains insufficient understanding on the concurrent local environment evolution in each transition metal (TM) that largely...

Constructing heterostructures are capable of offering fascinating performance for electronics owing to the built-in charge transfer driving force. However, exploring a universal methodology to rationally design and controllable synthesis of heterostructure with high stability of interface is a big challenge. Also the synergistic effect of the heter...

The role of defects in the charge transfer and transport properties of electrode materials for lithium-ion batteries has recently garnered increased interest. It is widely recognized that ion irradiation promotes the formation of defects within a crystalline solid. Among all ion species used for irradiation, protons are expected to create primarily...

The sluggish kinetic in electrode materials is one of the critical challenges in achieving high-power sodium ion storage. We report a coaxial core-shell nanostructure composed of carbon nanotube (CNT) as the core and TiO2@MoO2@C as shells for a hierarchically nanoarchitectured anode for improved electrode kinetics. The 1D tubular nanostructure can...

Transition metal phosphides (TMPs) have gained extensive attention as an attractive candidate for anode materials used in lithium-ion batteries owing to their relatively low potentials and high theoretical capacities. Nevertheless, TMPs suffer from severe volume changes during cycling and low electrical conductivity, which limits their further appl...

The O3-type layered Na(NixFeyMnz)O2 (0 < x, y, z < 1) cathode materials have attracted great interest in sodium-ion batteries due to the abundance and cost of raw materials and their high specific capacities. However, the cycling stability and rate capability at high voltages (> 4.0V) of these materials remains an issue. In this work, we successful...

We report an amorphous boron nanorod anode material for lithium-ion batteries prepared through smelting non-toxic boron oxide in liquid lithium. Boron in theory can provide capacity as high as 3099 mAh g⁻¹ by alloying with Li to form B4Li5. However, experimental studies of boron anode were rarely reported for room temperature lithium-ion batteries....

The effects of proton irradiation on nanostructured metal oxides have been investigated. Recent studies suggest that the presence of structural defects (e.g. vacancies and interstitials) in metal oxides may enhance the material’s electrochemical charge storage capacity. A new approach to introduce defects in electrode materials is to use ion irradi...

We report the application of disordered 3 D multi-layer graphene, synthesized directly from CO2 gas through a reaction with Li at 550 °C, as an anode for Na-ion batteries (SIBs) toward a sustainable and greener future. The material exhibited a reversible capacity of ∼190 mA h g(-1) with a Coulombic efficiency of 98.5 % at a current density of 15 mA...

Classical molecular dynamics (MD) simulations and M06-2X hybrid density functional theory calculations have been performed to investigate the interaction of various nonaqueous organic electrolytes with Na + ion in rechargeable Na-ion batteries. We evaluate trends in solvation behavior of seven common electrolytes namely pure carbonate solvents (eth...

Three families of ZnTe magic sized nanoclusters (MSNCs) were obtained exclusively using poly-tellurides as a tellurium pre-cursor in one-pot reaction by simply varying the reaction temperature and time only. Different ZnTe MSNCs exhibit different self-assembling or aggregation behavior, owing to their different structure, cluster size, and dipole-d...

Electrolytes are an important component of electrochemical energy storage systems and their optimization is critical for emerging beyond lithium ion technologies. Here, an integrated computational-experimental approach is used to rank-order and aid the selection of suitable electrolytes for a Na-ion battery. We present an in silico strategy based o...

Experimental and theoretical studies on the compositional dependence of stability and compressibility in lithiated cubic titania are presented. The crystalline-to-amorphous phase transition pressure increases monotonically with Li concentration (from ∼17.5 GPa for delithiated to no phase transition for fully lithiated cubic titania up to 60 GPa). T...

Directed colloidal synthesis of conductive organic-inorganic hybrid mesoscale structures is reported. The technique is simple but allows hierarchical assembly and 2D patterning of materials. A focused laser spot is used to direct the colloidal assembly of nanoparticles into electrically conductive organic-inorganic hybrid mesoscale filaments with a...

Material design in terms of their morphologies other than solid nanoparticles can lead to more advanced properties. At the example of iron oxide, we explored the electrochemical properties of hollow nanoparticles with an application as a cathode and anode. Such nanoparticles contain very high concentration of cation vacancies that can be efficientl...

Microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes were evaluated for their ability to achieve the world's most stringent Hg discharge criterion (<1.3ng/L) in an oil refinery's wastewater. The membrane processes were operated at three different pressures to demonstrate the potential for each membrane...

We report an electrochemically driven transformation of amorphous TiO2 nanotubes for Li-ion battery anodes into a face-centered-cubic crystalline phase that self-improves as the cycling proceeds. The intercalation/deintercalation processes of Li ions in the electrochemically grown TiO2 nanotubes were studied by synchrotron X-ray diffraction and abs...

Tailoring nanoarchitecture of materials offers unprecedented opportunities in utilization of their functional properties. Nanostructures of vanadium oxide, synthesized by electrochemical deposition, are studied as a cathode material for rechargeable Na-ion batteries. Ex situ and in situ synchrotron characterizations revealed the presence of an elec...

Sodium ion batteries are an attractive alternative to lithium ion batteries that alleviate problems with lithium availability and cost. Despite several studies of cathode materials for sodium ion batteries involving layered oxide materials, there are few low-voltage metal oxide anodes capable of operating sodium ion reversibly at room temperature....

In the past decade, development of thin-film solid oxide fuel cells (TFSOFCs) has evolved from microfabrication of thermomechanically stable yttria-stabilized zirconia (YSZ) electrolyte membranes, to implementation of platinum (Pt) and Pt-based composite cathodes, to the replacement of Pt or Pt-based cathodes with oxide cathodes, as well as perform...

Here we report on the novel application of scanning electrochemical microscopy (SECM) to enable spatially resolved electrochemical characterization of individual single-walled carbon nanotubes (SWNTs). The feedback imaging mode of SECM was employed to detect a pristine SWNT (approximately 1.6 nm in diameter and approximately 2 mm in length) grown h...

La0.6Sr0.4Co0.8Fe0.2O3 – δ (LSCF) has been sputtered on bare Si and Si3N4 and yttria-stabilised zirconia (YSZ) thin films to investigate annealing temperature- and thickness-dependent microstructure and functional properties, as well as their implications for designing failure-resistant micro-solid oxide fuel cell (μSOFC) membranes. The LSCF thin f...

Low-temperature electrochemical characterization of dense ultra-thin lanthanum strontium cobalt ferrite (La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3) cathodes synthesized by RF-sputtering on nanoporous alumina-supported Y-doped zirconia membranes: Lanthanum stronium cobalt ferrite Solid oxide fuel cell Cathode Ultra-thin films Nanocrystalline Area-specific res...

Scanning electrochemical microscopy (SECM) is developed as a powerful approach to electrochemical characterization of individual one-dimensional (1D) nanostructures under unbiased conditions. 1D nanostructures comprise high-aspect-ratio materials with both nanoscale and macroscale dimensions such as nanowires, nanotubes, nanobelts, and nanobands. F...

Thin-film solid oxide fuel cells (SOFCs) were fabricated with both Pt and mixed conducting oxide cathodes using sputtering, lithography, and etching. Each device consists of a 75–150nm thick yttria-stabilized zirconia (YSZ) electrolyte, a 40–80nm porous Pt anode, and a cathode of either 15–150nm dense La0.6Sr0.4Co0.8Fe0.2O3−δ (LSCF) or 130nm porous...

Nanocrystalline lanthanum strontium cobalt ferrite (LSCF) ultra-thin films with high in-plane electrical conductivity have been deposited by RF sputtering from composite targets. The films, with nominal thickness of 54nm, are crystalline when annealed or deposited at temperatures above 450°C. Effects of annealing temperature, annealing time, and su...

We report on a simple, quantitative relationship between structure and permeability of a novel ultrathin nanoporous membrane based on nanocrystalline silicon. Large permeability of the free-standing nanomembrane to Ru(NH3)63+, O2, or 1,1'-ferrocenedimethanol, which was able to be measured for the first time by employing scanning electrochemical mic...

The theory of the feedback mode of scanning electrochemical microscopy is extended for probing heterogeneous electron transfer at an unbiased conductor. A steady-state SECM diffusion problem with a pair of disk ultramicroelectrodes as a tip and a substrate is solved numerically. The potential of the unbiased substrate is such that the net current f...

Recent applications of scanning electrochemical microscopy (SECM) to studies of single biological cells are reviewed. This scanning probe microscopic technique allows the imaging of an individual cell on the basis of not only its surface topography but also such cellular activities as photosynthesis, respiration, electron transfer, single vesicular...

Local feedback mode is introduced as a novel operation mode of scanning electrochemical microscopy (SECM) for electrochemical characterization of a single one-dimensional (1D) nanostructure, for example, a wire, rod, band, and tube with 1-100-nm width and micrometer to centimeter length. To demonstrate the principle, SECM feedback effects under dif...

Selectively etched optical fibers were used as a new template material of conical ultramicroelectrodes, which are suitable for use as a probe in scanning electrochemical microscopy (SECM). Multistep index optical fibers with high-GeO2-doped core surrounded by two cladding layers were etched in a NH4F/HF solution for reproducible construction of tap...