Engineering topics
Cui, Yi
Publications and source records attributed to Cui, Yi.
Correlating Structure and Function of Battery Interphases at Atomic Resolution Using Cryoelectron Microscopy
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Design of Hollow Nanostructures for Energy Storage, Conversion and Production
Abstract Hollow nanostructures have shown great promise for energy storage, conversion, and production technologies. Significant efforts have been devoted to the design and synthesis of hollow nanostructures with diverse compositional and geometric characteristics in the past decade. However, the correlation between their structure and energy‐related performance has not been reviewed thoroughly in the literature. Here, some representative examples of designing hollow nanostructure to effectively solve the problems of energy‐related technologies are highlighted, such as lithium‐ion batteries, lithium‐metal anodes, lithium–sulfur batteries, supercapacitors, dye‐sensitized solar cells, electrocatalysis, and photoelectrochemical cells. The great effect of structure engineering on the performance is discussed in depth, which will benefit the better design of hollow nanostructures to fulfill the requirements of specific applications and simultaneously enrich the diversity of the hollow nanostructure family. Finally, future directions of hollow nanostructure design to solve emerging challenges and further improve the performance of energy‐related technologies are also provided.
Lithium Electrochemical Tuning for Electrocatalysis
Abstract Electrocatalysis is of great importance to a variety of energy conversion processes, where developing highly efficient catalysts is critical. While common strategies involve screening a wide range of materials with new chemical compositions or structures, a different approach to continuously, controllably, and effectively tune the electronic properties of existing catalytic materials for optimized activities has been demonstrated recently. Inspired by studies in lithium‐ion batteries, systematical lithium electrochemical tuning (LiET) methods such as Li intercalation, extraction, cycling, and strain engineering, are employed to effectively tune the electronic structures of different existing catalysts and thus improve their catalytic activities dramatically. Herein, the advantages of the LiET method in electrocatalysis are introduced, and then some recent representative examples in improving the performances of important electrochemical reactions are reviewed briefly. Lastly, a few promising directions on extending the applications of the LiET method in electrocatalysis are proposed.
A Dual‐Crosslinking Design for Resilient Lithium‐Ion Conductors
Abstract Solid‐state electrolyte materials are attractive options for meeting the safety and performance needs of advanced lithium‐based rechargeable battery technologies because of their improved mechanical and thermal stability compared to liquid electrolytes. However, there is typically a tradeoff between mechanical and electrochemical performance. Here an elastic Li‐ion conductor with dual covalent and dynamic hydrogen bonding crosslinks is described to provide high mechanical resilience without sacrificing the room‐temperature ionic conductivity. A solid‐state lithium‐metal/LiFePO 4 cell with this resilient electrolyte can operate at room temperature with a high cathode capacity of 152 mAh g −1 for 300 cycles and can maintain operation even after being subjected to intense mechanical impact testing. This new dual crosslinking design provides robust mechanical properties while maintaining ionic conductivity similar to state‐of‐the‐art polymer‐based electrolytes. This approach opens a route toward stable, high‐performance operation of solid‐state batteries even under extreme abuse.
Solubility-mediated sustained release enabling nitrate additive in carbonate electrolytes for stable lithium metal anode
Here, the physiochemical properties of the solid-electrolyte interphase, primarily governed by electrolyte composition, have a profound impact on the electrochemical cycling of metallic lithium. Herein, we discover that the effect of nitrate anions on regulating lithium deposition previously known in ether-based electrolytes can be extended to carbonate-based systems, which dramatically alters the nuclei from dendritic to spherical, albeit extremely limited solubility. This is attributed to the preferential reduction of nitrate during solid-electrolyte interphase formation, and the mechanisms behind which are investigated based on the structure, ion-transport properties, and charge transfer kinetics of the modified interfacial environment. To overcome the solubility barrier, a solubility-mediated sustained-release methodology is introduced, in which nitrate nanoparticles are encapsulated in porous polymer gel and can be steadily dissolved during battery operation to maintain a high concentration at the electroplating front. As such, effective dendrite suppression and remarkably enhanced cycling stability are achieved in corrosive carbonate electrolytes.
Encapsulated sulfur cathodes for rechargeable lithium batteries
A method of forming a sulfur-based cathode material includes: 1) providing a sulfur-based nanostructure; 2) coating the nanostructure with an encapsulating material to form a shell surrounding the nanostructure; and 3) removing a portion of the nanostructure through the shell to form a void within the shell, with a remaining portion of the nanostructure disposed within the shell.
Lithium metal stripping beneath the solid electrolyte interphase
Lithium stripping is a crucial process coupled with lithium deposition during the cycling of Li metal batteries. Lithium deposition has been widely studied, whereas stripping as a subsurface process has rarely been investigated. Here we reveal the fundamental mechanism of stripping on lithium by visualizing the interface between stripped lithium and the solid electrolyte interphase (SEI). We observed nanovoids formed between lithium and the SEI layer after stripping, which are attributed to the accumulation of lithium metal vacancies. High-rate dissolution of lithium causes vigorous growth and subsequent aggregation of voids, followed by the collapse of the SEI layer, i.e., pitting. We systematically measured the lithium polarization behavior during stripping and find that the lithium cation diffusion through the SEI layer is the rate-determining step. Nonuniform sites on typical lithium surfaces, such as grain boundaries and slip lines, greatly accelerated the local dissolution of lithium. As a result, the deeper understanding of this buried interface stripping process provides beneficial clues for future lithium anode and electrolyte design.
An Ultrastrong Double-Layer Nanodiamond Interface for Stable Lithium Metal Anodes
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Engineering stable interfaces for three-dimensional lithium metal anodes
Lithium metal has long been considered one of the most promising anode materials for advanced lithium batteries (for example, Li-S and Li-O 2 ), which could offer significantly improved energy density compared to state-of-the-art lithium ion batteries. Despite decades of intense research efforts, its commercialization remains limited by poor cyclability and safety concerns of lithium metal anodes. One root cause is the parasitic reaction between metallic lithium and the organic liquid electrolyte, resulting in continuous formation of an unstable solid electrolyte interphase, which consumes both active lithium and electrolyte. Until now, it has been challenging to completely shut down the parasitic reaction. We find that a thin-layer coating applied through atomic layer deposition on a hollow carbon host guides lithium deposition inside the hollow carbon sphere and simultaneously prevents electrolyte infiltration by sealing pinholes on the shell of the hollow carbon sphere. By encapsulating lithium inside the stable host, parasitic reactions are prevented, resulting in impressive cycling behavior. In conclusion, we report more than 500 cycles at a high coulombic efficiency of 99% in an ether-based electrolyte at a cycling rate of 0.5 mA/cm 2 and a cycling capacity of 1 mAh/cm 2 , which is among the most stable Li anodes reported so far.
Stable cycling of lithium sulfide cathodes through strong affinity with multifunctional binders
A manufacturing method of a battery electrode includes: (1) mixing Li.sub.2S particles with a binder to form a slurry, the binder including at least one of: (a) an ester moiety, (b) an amide moiety, (c) a ketone moiety, (d) an imine moiety, (e) an ether moiety, and (f) a nitrile moiety; and (2) disposing the slurry on a current collector.
Resonance-Enhanced Absorption in Hollow Nanoshell Spheres with Omnidirectional Detection and High Responsivity and Speed
Optical resonance formed inside a nanocavity resonator can trap light within the active region and hence enhance light absorption, effectively boosting device or material performance in applications of solar cells, photodetectors (PDs), and photocatalysts. Complementing conventional circular and spherical structures, a new type of multishelled spherical resonant strategy is presented. Due to the resonance–enhanced absorption by multiple convex shells, ZnO nanoshell PDs show improved optoelectronic performance and omnidirectional detection of light at different incidence angles and polarization. In addition, the response and recovery speeds of these devices are improved (0.8 and 0.7 ms, respectively) up to three orders of magnitude faster than in previous reports because of the existence of junction barriers between the nanoshells. As a result, the general design principles behind these hollow ZnO nanoshells pave a new way to improve the performance of sophisticated nanophotonic devices.
Spectrally Selective Nanocomposite Textile for Outdoor Personal Cooling
Outdoor heat stress poses a serious public health threat and curtails industrial labor supply and productivity, thus adversely impacting the wellness and economy of the entire society. With climate change, there will be more intense and frequent heat waves that further present a grand challenge for sustainability. However, an efficient and economical method that can provide localized outdoor cooling of the human body without intensive energy input is lacking. Here, a novel spectrally selective nanocomposite textile for radiative outdoor cooling using zinc oxide nanoparticle–embedded polyethylene is demonstrated. By reflecting more than 90% solar irradiance and selectively transmitting out human body thermal radiation, this textile can enable simulated skin to avoid overheating by 5–13 °C compared to normal textile like cotton under peak daylight condition. In conclusion, owing to its superior passive cooling capability and compatibility with large–scale production, this radiative outdoor cooling textile is promising to widely benefit the sustainability of society in many aspects spanning from health to economy.
Crosslinked Poly(tetrahydrofuran) as a Loosely Coordinating Polymer Electrolyte
Abstract Solid polymer electrolytes (SPEs) promise to improve the safety and performance of lithium ion batteries (LIBs). However, the low ionic conductivity and transference number of conventional poly(ethylene oxide) (PEO)‐based SPEs preclude their widespread implementation. Herein, crosslinked poly(tetrahydrofuran) (xPTHF) is introduced as a promising polymer matrix for “beyond PEO” SPEs. The crosslinking procedure creates thermally stable, mechanically robust membranes for use in LIBs. Molecular dynamics and density functional theory (DFT) simulations accompanied by 7 Li NMR measurements show that the lower spatial concentration of oxygen atoms in the xPTHF backbone leads to loosened O–Li + coordination. This weakened interaction enhances ion transport; xPTHF has a high lithium transference number of 0.53 and higher lithium conductivity than a xPEO SPE of the same length at room temperature. It is demonstrated that organic additives further weaken the O–Li + interaction, enabling room temperature ionic conductivity of 1.2 × 10 −4 S cm −1 with 18 wt% N,N ‐dimethylformamide in xPTHF. In a solid‐state LIB application, neat xPTHF SPEs cycle with near theoretical capacity for 100 cycles at 70 °C, with rate capability up to 1 C. The plasticized xPTHF SPEs operate at room temperature while maintaining respectable rate capability and capacity. The novel PTHF system demonstrated here represents an exciting platform for future studies involving SPEs.
Core–Shell Nanofibrous Materials with High Particulate Matter Removal Efficiencies and Thermally Triggered Flame Retardant Properties
Dust filtration is a crucial process for industrial waste gas treatment. Great efforts have been devoted to improve the performance of dust filtration filters both in industrial and fundamental research. Conventional air-filtering materials are limited by three key issues: (1) Low filtration efficiency, especially for particulate matter (PM) below 1 μm; (2) large air pressure drops across the filter, which require a high energy input to overcome; and (3) safety hazards such as dust explosions and fires. Here, we have developed a “smart” multifunctional material which can capture PM with high efficiency and an extremely low pressure drop, while possessing a flame retardant design. This multifunctionality is achieved through a core–shell nanofiber design with the polar polymer Nylon-6 as the shell and the flame retardant triphenyl phosphate (TPP) as the core. At 80% optical transmittance, the multifunctional materials showed capture efficiency of 99.00% for PM 2.5 and >99.50% for PM 10–2.5 , with a pressure drop of only 0.25 kPa (0.2% of atmospheric pressure) at a flow rate of 0.5 m s –1 . Furthermore, during direct ignition tests, the multifunctional materials showed extraordinary flame retardation; the self-extinguishing time of the filtrate-contaminated filter is nearly instantaneous (0 s/g) compared to 150 s/g for unmodified Nylon-6.
An intermediate temperature garnet-type solid electrolyte-based molten lithium battery for grid energy storage
Batteries are an attractive grid energy storage technology, but a reliable battery system with the functionalities required for a grid such as high power capability, high safety and low cost remains elusive. Here, we report a solid electrolyte-based molten lithium battery constructed with a molten lithium anode, a molten Sn–Pb or Bi–Pb alloy cathode and a garnet-type Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) solid electrolyte tube. We show that the assembled Li||LLZTO||Sn–Pb and Li||LLZTO||Bi–Pb cells can stably cycle at an intermediate temperature of 240 °C for about one month at current densities of 50 mA cm –2 and 100 mA cm –2 respectively, with almost no capacity decay and an average Coulombic efficiency of 99.98%. Furthermore, the cells demonstrate high power capability with current densities up to 300 mA cm –2 (90 mW cm –2 ) for Li||LLZTO||Sn–Pb and 500 mA cm –2 (175 mW cm –2 ) for Li||LLZTO||Bi–Pb. Lastly, our design offers prospects for grid energy storage with intermediate temperature operations, high safety margin and low capital and maintenance costs.
Malic Acid Carbon Dots: From Super-resolution Live-Cell Imaging to Highly Efficient Separation
As-synthesized malic acid carbon dots are found to possess photoblinking properties that are outstanding and superior compared to those of conventional dyes. Considering their excellent biocompatibility, malic acid carbon dots are suitable for super-resolution fluorescence localization microscopy under a variety of conditions, as we demonstrate in fixed and live trout gill epithelial cells. In addition, during imaging experiments, the so-called "excitation wavelength-dependent" emission was not observed for individual as-made malic acid carbon dots, which motivated us to develop a time-saving and high throughput separation technique to isolate malic acid carbon dots into fractions of different particle size distributions using C-18 reversed-phase silica gel column chromatography. This post-treatment allowed us to determine how particle size distribution influences the optical properties of malic acid carbon dot fractions, that is, optical band gap energies and photoluminescence behaviors.