Engineering Papers⌕ Search

Engineering topics

Cui, Yi

Publications and source records attributed to Cui, Yi.

At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Characterization of dynamic morphological changes of tin anode electrode during (de)lithiation processes using in operando synchrotron transmission X-ray microscopy

The morphological evolution of tin particles with different sizes during the first lithiation and delithiation processes has been visualized by an in operando synchrotron transmission X-ray microscope (TXM). Here, the in operando lithium ion battery cell was operated at constant current condition during TXM imaging. Two-dimensional projection images with 40 nm resolution showing morphological evolution were obtained and analyzed. The analysis of relative area change shows that the morphology of tin particles with different sizes changed simultaneously. This phenomenon is mainly because of a negative feedback mechanism among tin particles in the battery electrode at a constant current operating condition. For irregular-shaped tin particles, the contour analysis demonstrates that the regions with higher curvature started volume expansion first, and then the entire particle expanded almost homogeneously. This study provides insights for understanding the dynamic morphological change and the particle-particle interactions in high capacity lithium ion battery electrodes.

25 ENERGY STORAGE↗
DOE OSTI2019

Fast lithium growth and short circuit induced by localized-temperature hotspots in lithium batteries

Fast-charging and high-energy-density batteries pose significant safety concerns due to high rates of heat generation. Understanding how localized high temperatures affect the battery is critical but remains challenging, mainly due to the difficulty of probing battery internal temperature with high spatial resolution. Here we introduce a method to induce and sense localized high temperature inside a lithium battery using micro-Raman spectroscopy. We discover that temperature hotspots can induce significant lithium metal growth as compared to the surrounding lower temperature area due to the locally enhanced surface exchange current density. More importantly, localized high temperature can be one of the factors to cause battery internal shorting, which further elevates the temperature and increases the risk of thermal runaway. This work provides important insights on the effects of heterogeneous temperatures within batteries and aids the development of safer batteries, thermal management schemes, and diagnostic tools.

25 ENERGY STORAGE↗
DOE OSTI2019

Uniform High Ionic Conducting Lithium Sulfide Protection Layer for Stable Lithium Metal Anode

Artificial solid-electrolyte interphase (SEI) is one of the key approaches in addressing the low reversibility and dendritic growth problems of lithium metal anode, yet its current effect is still insufficient due to insufficient stability. Here, a new principle of “simultaneous high ionic conductivity and homogeneity” is proposed for stabilizing SEI and lithium metal anodes. Fabricated by a facile, environmentally friendly, and low-cost lithium solid-sulfur vapor reaction at elevated temperature, a designed lithium sulfide protective layer successfully maintains its protection function during cycling, which is confirmed by both simulations and experiments. Stable dendrite-free cycling of lithium metal anode is realized even at a high areal capacity of 5 mAh cm -2 , and prototype Li–Li 4 Ti 5 O 12 cell with limited lithium also achieves 900 stable cycles. These findings give new insight into the ideal SEI composition and structure and provide new design strategies for stable lithium metal batteries.

25 ENERGY STORAGE↗
DOE OSTI2019

Surface-engineered mesoporous silicon microparticles as high-Coulombic-efficiency anodes for lithium-ion batteries

High-capacity silicon anodes suffer from rapid capacity decay due to large volume expansion, which causes mechanical fracture, electrical contact loss and unstable solid electrolyte interphase (SEI). Nanostructuring has proved to be effective in addressing these problems over the past decade; however, new issues such as poor initial Coulombic efficiencies due to increased surface area remain unsolved. Here we develop a surface-engineering strategy by depositing a dense silicon skin onto each mesoporous silicon microparticle and further encapsulating it with a conformal graphene cage, which improves both the initial and later-cycle Coulombic efficiencies. The silicon skin lowers the unfavorable electrolyte/electrode contact area and minimizes SEI formation, resulting in an initial Coulombic efficiency over twice as high as that without silicon skin coating. Furthermore, the graphene cage combined with the inner void space of mesoporous silicon allow for silicon expansion, which guarantees structural integrity and SEI stability, resulting in high later-cycle Coulombic efficiencies (99.8–100% for later cycles) and impressive cycling stability.

25 ENERGY STORAGE↗
DOE OSTI2019

Selenium Nanocomposite Cathode with Long Cycle Life for Rechargeable Lithium‐Selenium Batteries

Abstract Selenium (Se) is a potential cathode material for high energy density rechargeable lithium batteries. In this study, a binder‐free Se‐carbon nanotube (CNT) composite electrode has been prepared by a facile chemical method. At initial state, Se is present in the form of branched nanowires with a diameter of <150 nm and a length of 1–2 μm, interwoven with CNTs. After discharge and re‐charge, the Se nanowires are converted to nanoparticles embedded in the CNT network. This synthesis method provides a path for fabricating the Se cathodes with controllable mass loading and thickness. By studying the composite electrodes with different Se loading and thickness, we found that the electrode thickness has a critical impact on the distribution of Se during repeated cycling. Promising cycling performance was achieved in thin electrodes with high Se loading. The composite electrode with 23 μm thickness and 60 % Se loading shows a high initial capacity of 537 mAh g −1 and stable cycling performance with a capacity of 401 mAh g −1 after 500 cycles at 1 C rate. This study reports a synthesis strategy to obtain Se/CNT composite cathode with long cycle life for rechargeable Li−Se batteries.

Cui, Yi↗
DOE OSTI2019

Designing polymers for advanced battery chemistries

Electrochemical energy storage devices are becoming increasingly important to our global society, and polymer materials are key components of these devices. As the demand for high-energy density devices increases, innovative new materials that build on the fundamental understanding of physical phenomena and structure–property relationships will be required to enable high-capacity next-generation battery chemistries. In this Review, we discuss core polymer science principles that are used to facilitate progress in battery materials development. Specifically, we discuss the design of polymeric materials for desired mechanical properties, increased ionic and electronic conductivity and specific chemical interactions. We also discuss how polymer materials have been designed to create stable artificial interfaces and improve battery safety. Furthermore, the focus is on these design principles applied to advanced silicon, lithium-metal and sulfur battery chemistries.

25 ENERGY STORAGE↗
DOE OSTI2019

Amidoxime-Functionalized Macroporous Carbon Self-Refreshed Electrode Materials for Rapid and High-Capacity Removal of Heavy Metal from Water

Heavy metal pollution continues to be one of the most serious environmental problems which has attracted major global concern. Here, a rapid, high-capacity, yet economical strategy for deep cleaning of heavy metals ions in water is reported based on amidoxime-functionalized macroporous carbon electrode materials. The active sites of our material can be self-refreshed during the electrochemical removal process, which is different from traditional methods. The novel filter device in this work can purify contaminated water very rapidly (3000 L h –1 m –2 ), and can decrease heavy metal ion concentrations to below 5 ppb with a very short contact time (only 3 s). The original treatment efficiency of the device can be retained even after 1 week of continuous device operation. An extremely high removal capacity of over 2300 mg g –1 can be achieved with 2–3 orders of magnitude higher efficiency than that of surface adsorption-based commercial filters without any decay. Additionally, the cost of energy consumed in our method is lower than $6.67 × 10 –3 per ton of wastewater. We envision that this approach can be routinely applied for the rapid, efficient, and thorough removal of heavy metals from both point-of-use water and industrial wastewater.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Composite lithium electrode with mesoscale skeleton via simple mechanical deformation

Lithium metal–based batteries are attractive energy storage devices because of high energy density. However, uncontrolled dendrite growth and virtually infinite volume change, which cause performance fading and safety concerns, have limited their applications. In this work, we demonstrate that a composite lithium metal electrode with an ion-conducting mesoscale skeleton can improve electrochemical performance by locally reducing the current density. In addition, the potential for short-circuiting is largely alleviated due to side deposition of mossy lithium on the three-dimensional electroactive surface of the composite electrode. Moreover, the electrode volume only slightly changes with the support of a rigid and stable scaffold. Therefore, this mesoscale composite electrode can cycle stably for 200 cycles with low polarization under a high areal current density up to 5 mA/cm 2 . Most attractively, the proposed fabrication process, which only involves simple mechanical deformation, is scalable and cost effective, providing a new strategy for developing high performance and long lifespan lithium anodes.

25 ENERGY STORAGE↗
DOE OSTI2019

Bright sub-20-nm cathodoluminescent nanoprobes for electron microscopy

Electron microscopy has been integral in our understanding of complex biological systems. Although electron microscopy reveals cellular morphology with nanoscale resolution, it does not provide information on the location of different types of proteins. An electron-microscopy-based bioimaging technology capable of localizing individual proteins and resolving protein-protein interactions with respect to cellular ultrastructure would provide important insights into the molecular biology of a cell. In this report, we synthesize small lanthanide-doped nanoparticles and measure the absolute photon emission rate of individual nanoparticles resulting from a given electron excitation flux (cathodoluminescence). Our results indicate that the optimization of nanoparticle composition, synthesis protocols and electron imaging conditions can lead to sub-20-nm nanolabels that would enable high signal-to-noise localization of individual biomolecules within a cellular context. In ensemble measurements, these labels exhibit narrow spectra of nine distinct colours, so the imaging of biomolecules in a multicolour electron microscopy modality may be possible.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

High-Rate and Large-Capacity Lithium Metal Anode Enabled by Volume Conformal and Self-Healable Composite Polymer Electrolyte

The widespread implementation of lithium–metal batteries (LMBs) with Li metal anodes of high energy density has long been prevented due to the safety concern of dendrite–related failure. Here a solid–liquid hybrid electrolyte consisting of composite polymer electrolyte (CPE) soaked with liquid electrolyte is reported. The CPE membrane composes of self–healing polymer and Li + –conducting nanoparticles. The electrodeposited lithium metal in a uniform, smooth, and dense behavior is achieved using a hybrid electrolyte, rather than dendritic and pulverized structure for a conventional separator. The Li foil symmetric cells can deliver remarkable cycling performance at ultrahigh current density up to 20 mA cm –2 with an extremely low voltage hysteresis over 1500 cycles. A large areal capacity of 10 mAh cm –2 at 10 mA cm –2 could also be obtained. Furthermore, the Li|Li 4 Ti 5 O 12 cells based on the hybrid electrolyte achieve a higher specific capacity and longer cycling life than those using conventional separators. The superior performances are mainly attributed to strong adhesion, volume conformity, and self–healing functionality of CPE, providing a novel approach and a significant step toward cost–effective and large–scalable LMBs.

25 ENERGY STORAGE↗
DOE OSTI2019

Quasi-Ballistic Thermal Transport Across MoS 2 Thin Films

Layered two-dimensional (2D) materials have highly anisotropic thermal properties between the in-plane and cross-plane directions. Conventionally, it is thought that cross-plane thermal conductivities (κ z ) are low, and therefore c -axis phonon mean free paths (MFPs) are small. Here, we measure κ z across MoS 2 films of varying thickness (20–240 nm) and uncover evidence of very long c -axis phonon MFPs at room temperature in these layered semiconductors. Experimental data obtained using time-domain thermoreflectance (TDTR) are in good agreement with first-principles density functional theory (DFT). These calculations suggest that ~50% of the heat is carried by phonons with MFP > 200 nm, exceeding kinetic theory estimates by nearly 2 orders of magnitude. Because of quasi-ballistic effects, the κ z of nanometer-thin films of MoS 2 scales with their thickness and the volumetric thermal resistance asymptotes to a nonzero value, ~10 m 2 K GW –1 . This contributes as much as 30% to the total thermal resistance of a 20 nm thick film, the rest being limited by thermal interface resistance with the SiO 2 substrate and top-side aluminum transducer. Furthermore, these findings are essential for understanding heat flow across nanometer-thin films of MoS 2 for optoelectronic and thermoelectric applications.

42 ENGINEERING↗
DOE OSTI2019

Pathways for practical high-energy long-cycling lithium metal batteries

Lithium (Li)-ion batteries play a critical role in modern day technologies, but their specific energy (Wh kg-1) and energy density (Wh L-1) are approaching the maximum practically achievable values based on existing manufacturing processes with the conventional cathode and anode materials. Developing the next generation rechargeable batteries with a specific energy higher than 300 Wh kg-1, up to 500 Wh kg-1, is a significant challenge. This paper discusses the pathways to build the next generation 500 Wh kg-1 rechargeable Li battery based on Li metal anode and a high nickel-content lithium nickel-manganese-cobalt oxide (high-Ni NMC) cathode. The fundamental requirements and practical technical approaches will be explored to hopefully address this grand challenge. In particular, we discuss the detailed cell level requirements and parameters to achieve high energy density, as well as the significant scientific challenges and potential solutions, including but not limited to enable the direct utilization of Li metal anode with high efficiency and long-term cycling stability, dendrite-free Li metal deposition, high utilization of the cathode materials with high mass loading and reasonable electrode thickness along with minimum parasitic weight in the cathode side. The cell level understanding and validation of the materials properties for high performance and control of interfacial reactions across the whole cell will be explored. New concepts in emerging multifunctional materials and electrolytes/additives and their implications will also be discussed.

lithium metal anode, lithium nickel manganese coba↗
DOE OSTI2019

Epigenetic biomarker screening by FLIM-FRET for combination therapy in ER+ breast cancer

Hormone-dependent gene expression involves dynamic and orchestrated regulation of epigenome leading to a cancerous state. Estrogen receptor (ER)-positive breast cancer rely on chromatin remodeling and association with epigenetic factors in inducing ER-dependent oncogenesis and thus cell over-proliferation. The mechanistic differences between epigenetic regulation and hormone signaling provide an avenue for combination therapy of ER-positive breast cancer. We hypothesized that epigenetic biomarkers within single nucleosome proximity of ER-dependent genes could serve as potential therapeutic targets. We described here a Fluorescence lifetime imaging-based Förster resonance energy transfer (FLIM-FRET) methodology for biomarker screening that could facilitate combination therapy based on our study. We screened 11 epigenetic-related markers which include oxidative forms of DNA methylation, histone modifications, and methyl-binding domain proteins. Among them, we identified H4K12acetylation (H4K12ac) and H3K27 acetylation (H3K27ac) as potential epigenetic therapeutic targets. When histone acetyltransferase inhibitor targeting H4K12ac and H3K27ac was combined with tamoxifen, an enhanced therapeutic outcome was observed against ER-positive breast cancer both in vitro and in vivo. Together, we demonstrate a single molecule approach as an effective screening tool for devising targeted epigenetic therapy.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Wrinkled Graphene Cages as Hosts for High-Capacity Li Metal Anodes Shown by Cryogenic Electron Microscopy

Lithium (Li) metal has long been considered the “holy grail” of battery anode chemistry but is plagued by low efficiency and poor safety due to its high chemical reactivity and large volume fluctuation, respectively. Here we introduce a new host of wrinkled graphene cage (WGC) for Li metal. Different from recently reported amorphous carbon spheres, WGC show highly improved mechanical stability, better Li ion conductivity, and excellent solid electrolyte interphase (SEI) for continuous robust Li metal protection. At low areal capacities, Li metal is preferentially deposited inside the graphene cage. Cryogenic electron microscopy characterization shows that a uniform and stable SEI forms on the WGC surface that can shield the Li metal from direct exposure to electrolyte. With increased areal capacities, Li metal is plated densely and homogeneously into the outer pore spaces between graphene cages with no dendrite growth or volume change. As a result, a high Coulombic efficiency (CE) of ~98.0% was achieved under 0.5 mA/cm 2 and 1–10 mAh/cm 2 in commercial carbonate electrolytes, and a CE of 99.1% was realized with high-concentration electrolytes under 0.5 mA/cm 2 and 3 mAh/cm 2 . Full cells using WGC electrodes with prestored Li paired with Li iron phosphate showed greatly improved cycle lifetime. With 10 mAh/cm 2 Li metal deposition, the WGC/Li composite anode was able to provide a high specific capacity of ~2785 mAh/g. Furthermore, with its roll-to-roll compatible fabrication procedure, WGC serves as a highly promising material for the practical realization of Li metal anodes in next-generation high energy density secondary batteries.

36 MATERIALS SCIENCE↗