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Li, Matthew

Publications and source records attributed to Li, Matthew.

63 records · Page 4

The Absence and Importance of Operando Techniques for Metal-Free Catalysts

Operando characterization techniques have played an important role in modern technological developments. In contrast to the experimental uncertainties introduced by ex situ techniques, the simultaneous measurement of desired sample characteristics and near-realistic electrochemical testing provides a representative picture of the underlying physics. From Li-ion batteries to metal-based electrocatalysts, the insights offered by real-time characterization data have enabled more efficient research programs. As an emerging class of catalyst, much of the mechanistic understanding of metal-free electrocatalysts continues to be elusive in comparison to their metal-based counterparts. Yet, there is a clear absence of operando characterization performed on metal-free catalysts. Through the proper execution of operando techniques, it can be expected that metal-free catalysts can achieve exceptional technological progress. Here, the motivation of using operando characterization techniques for metal-free carbon-based catalyst system is considered, followed by a discussion of the possibilities, difficulties and benefits of their applications.

36 MATERIALS SCIENCE↗

Construction of Hierarchically Porous Nanoparticles@Metal-Organic Frameworks Composites by Inherent Defects for the Enhancement of Catalytic Efficiency

Nanoparticles@metal-organic frameworks (MOFs) composites have attracted considerable attention in recent years due to the prominent selective catalytic activity. However, it is highly desirable to develop a simple and universal way to settle the trade-off between the catalytic efficiency and selectivity. Herein, by employing the thermal instability of inherent defects, hierarchically porous Pt@UiO-66-NH 2 , Pt@UiO-66, Pt@ZIF-8, and Au@ZIF-8 are successfully constructed after annealing at an appropriate temperature, respectively. The generated mesopores in the MOFs can be located around the external nanoparticle to retain the MOF shell for catalytic selectivity. Lastly, when tested in olefin hydrogenation, Pt@UiO-66-NH 2 shows significantly improved catalytic rate and enhanced dynamic selectivity.

36 MATERIALS SCIENCE↗

A Lithium-Sulfur Battery using a 2D Current Collector Architecture with a Large-Sized Sulfur Host Operated under High Areal Loading and Low E/S Ratio

While backless freestanding 3-D electrode architectures for high loading sulfur batteries have flourished in the recent years, the more traditional and industrially turnkey 2-D architecture have not received the same amount of attention. In this paper, we report a spray dried sulfur composite with large intrinsic internal pores, ensuring adequate local electrolyte availability. This material offered good performance with a electrolyte content of 7 µL mg -1 at high areal loadings (5-8 mg cm -2 ), while also offering the first reported 2.8 µL mg -1 (8 mg cm -2 ) to enter into the 2nd plateau of discharge and continue to operate for 20 cycles. Furthermore, we provide evidence that the high frequency semi-circle (i.e. interfacial resistance) is mainly responsible for the often observed bypassing of the 2nd plateau in lean electrolyte discharges.

25 ENERGY STORAGE↗

Li 2 S- or S-Based Lithium-Ion Batteries

While members of the Li-S battery research community are becoming more consciences of the practical testing parameters, the widespread commercialization of a S based battery is still far from realization. Particularly the metallic Li used as the anode poses potential safety and cycle stability concerns. Alternatively, other S battery configurations without a Li-anode, i.e. lithium-ion Li 2 S or S battery, do not suffer from the same safety concerns and can possibly serve as a better method to bring room temperature S-based battery technologies to the industry. However, whether Li 2 S or S will be used as the initiating cathode material remains unclear as each offers their own unique advantages and disadvantages. In conclusion, this research news will discuss briefly both S and Li 2 S as cathodes and bring forward the key benefits of Li 2 S.

25 ENERGY STORAGE↗

30 Years of Lithium-Ion Batteries

Over the past 30 years, significant commercial and academic progress has been made on Li-based battery technologies. From the early Li-metal anode iterations to the current commercial Li-ion batteries (LIBs), the story of the Li-based battery is full of breakthroughs and back tracing steps. This review will discuss the main roles of material science in the development of LIBs. As LIB research progressed and the materials of interest changed, different emphasis on the different sub-disciplines of material science were placed. Early works on LIBs focused more on solid state physics whereas near the end of the 20th century with nanotechnology on the rise, researchers began to focus more on the morphological aspects (surface coating, porosity, size and shape) of electrode materials. While it is easy to point out which specific cathode and anode materials are currently good candidates for the next-generation of batteries, it is difficult to explain exactly why those were chosen. We hope to clearly draw for the reader a complete developmental story of LIB along with an explanation of the reasons responsible for the various technological shifts. In conclusion, this review will end with a statement of caution for the current modern battery research along with a brief discussion on beyond lithium-ion battery chemistries.

25 ENERGY STORAGE↗

Revisiting the Role of Polysulfides in Lithium–Sulfur Batteries

Intermediate polysulfides (S n , where n = 2–8) play a critical role in both mechanistic understanding and performance improvement of lithium–sulfur batteries. The rational management of polysulfides is of profound significance for high-efficiency sulfur electrochemistry. In this paper, the key roles of polysulfides are discussed, with regard to their status, behavior, and their correspondingimpact on the lithium–sulfur system. Finally, two schools of thoughts for polysulfide management are proposed, their advantages and disadvantages are compared, and future developments are discussed.

25 ENERGY STORAGE↗

Chemisorption of polysulfides through redox reactions with organic molecules for lithium–sulfur batteries

Lithium-sulfur battery possesses high energy density but suffers from severe capacity fading due to the dissolution of lithium polysulfides. Novel design and mechanisms to encapsulate lithium polysulfides are greatly desired by high-performance lithium-sulfur batteries towards practical applications. Herein, we report a strategy of utilizing anthraquinone, a natural abundant organic molecule, to suppress dissolution and diffusion of polysulfides species through redox reactions during cycling. The keto groups of anthraquinone play a critical role in forming strong Lewis acid-based chemical bonding. This mechanism leads to a long cycling stability of sulfur-based electrodes. With a high sulfur content of ~73%, a low capacity decay of 0.019% per cycle for 300 cycles and retention of 81.7% over 500 cycles at 0.5 C rate can be achieved. Here, this finding and understanding paves an alternative avenue for the future design of sulfur-based cathodes toward the practical application of lithium-sulfur batteries.

25 ENERGY STORAGE↗

Silicon‐Based Anodes for Lithium‐Ion Batteries: From Fundamentals to Practical Applications

Abstract Silicon has been intensively studied as an anode material for lithium‐ion batteries (LIB) because of its exceptionally high specific capacity. However, silicon‐based anode materials usually suffer from large volume change during the charge and discharge process, leading to subsequent pulverization of silicon, loss of electric contact, and continuous side reactions. These transformations cause poor cycle life and hinder the wide commercialization of silicon for LIBs. The lithiation and delithiation behaviors, and the interphase reaction mechanisms, are progressively studied and understood. Various nanostructured silicon anodes are reported to exhibit both superior specific capacity and cycle life compared to commercial carbon‐based anodes. However, some practical issues with nanostructured silicon cannot be ignored, and must be addressed if it is to be widely used in commercial LIBs. This Review outlines major impactful work on silicon‐based anodes, and the most recent research directions in this field, specifically, the engineering of silicon architectures, the construction of silicon‐based composites, and other performance‐enhancement studies including electrolytes and binders. The burgeoning research efforts in the development of practical silicon electrodes, and full‐cell silicon‐based LIBs are specially stressed, which are key to the successful commercialization of silicon anodes, and large‐scale deployment of next‐generation high energy density LIBs.

Feng, Kun↗

Orthogonal potency analysis of mesenchymal stromal cell function during ex vivo expansion

Highlights: • MSC potencies for their different functions are not identically affected by age. • In vitro age can strongly predict MSC adipogenic and hematopoietic-supporting potencies. • MSC shape can also strongly predict for hematopoietic-supporting potency. Adult bone marrow mesenchymal stromal cells (MSCs) have cross-functional, intrinsic potency that is of therapeutic interest. Their ability to regenerate bone, fat, and cartilage, modulate the immune system, and nurture the growth and function of other bone marrow hematopoietic stem/progenitor cells have all been evaluated by transplant applications of MSCs. These applications require the isolation and expansion scaled cell production. To investigate biophysical properties of MSCs that can be feasibly utilized as predictors of bioactivity during biomanufacturing, we used a low-density seeding model to drive MSCs into proliferative stress and exhibit the hallmark characteristics of in vitro aging. A low-density seeding method was used to generate MSCs from passages 1–7 to simulate serial expansion of these cells to maximize yield from a single donor. MSCs were subjected to three bioactivity assays in parallel to ascertain whether patterns in MSC age, size, and shape were associated with the outcomes of the potency assays. MSC age was found to be a predictor of adipogenesis, while cell and nuclear shape was strongly associated to hematopoietic-supportive potency. Together, these data evaluate morphological changes associated with cell potency and highlight new strategies for purification or alternatives to assessing MSC quality.

60 APPLIED LIFE SCIENCES↗