Jing Peng

Bio: Jing Peng is an academic researcher from Beihang University. The author has contributed to research in topics: Electrolyte & Membrane. The author has an hindex of 15, co-authored 39 publications receiving 1161 citations. Previous affiliations of Jing Peng include City University of New York & Hunter College.

Liquid Structure with Nano-Heterogeneity Promotes Cationic Transport in Concentrated Electrolytes

Abstract: Using molecular dynamics simulations, small-angle neutron scattering, and a variety of spectroscopic techniques, we evaluated the ion solvation and transport behaviors in aqueous electrolytes containing bis(trifluoromethanesulfonyl)imide. We discovered that, at high salt concentrations (from 10 to 21 mol/kg), a disproportion of cation solvation occurs, leading to a liquid structure of heterogeneous domains with a characteristic length scale of 1 to 2 nm. This unusual nano-heterogeneity effectively decouples cations from the Coulombic traps of anions and provides a 3D percolating lithium–water network, via which 40% of the lithium cations are liberated for fast ion transport even in concentration ranges traditionally considered too viscous. Due to such percolation networks, superconcentrated aqueous electrolytes are characterized by a high lithium-transference number (0.73), which is key to supporting an assortment of battery chemistries at high rate. The in-depth understanding of this transport mechanism ...

Solvation behavior of carbonate-based electrolytes in sodium ion batteries

Abstract: Sodium ion batteries are on the cusp of being a commercially available technology. Compared to lithium ion batteries, sodium ion batteries can potentially offer an attractive dollar-per-kilowatt-hour value, though at the penalty of reduced energy density. As a materials system, sodium ion batteries present a unique opportunity to apply lessons learned in the study of electrolytes for lithium ion batteries; specifically, the behavior of the sodium ion in an organic carbonate solution and the relationship of ion solvation with electrode surface passivation. In this work the Li+ and Na+-based solvates were characterized using electrospray mass spectrometry, infrared and Raman spectroscopy, 17O, 23Na and pulse field gradient double-stimulated-echo pulse sequence nuclear magnetic resonance (NMR), and conductivity measurements. Spectroscopic evidence demonstrate that the Li+ and Na+ cations share a number of similar ion–solvent interaction trends, such as a preference in the gas and liquid phase for a solvation shell rich in cyclic carbonates over linear carbonates and fluorinated carbonates. However, quite different IR spectra due to the PF6− anion interactions with the Na+ and Li+ cations were observed and were rationalized with the help of density functional theory (DFT) calculations that were also used to examine the relative free energies of solvates using cluster – continuum models. Ion–solvent distances for Na+ were longer than Li+, and Na+ had a greater tendency towards forming contact pairs compared to Li+ in linear carbonate solvents. In tests of hard carbon Na-ion batteries, performance was not well correlated to Na+ solvent preference, leading to the possibility that Na+ solvent preference may play a reduced role in the passivation of anode surfaces and overall Na-ion battery performance.

Anion Solvation in Carbonate-Based Electrolytes

Abstract: With the correlation between Li+ solvation and interphasial chemistry on anodes firmly established in Li-ion batteries, the effect of cation–solvent interaction has gone beyond bulk thermodynamic and transport properties and become an essential element that determines the reversibility of electrochemistry and kinetics of Li-ion intercalation chemistries. As of now, most studies are dedicated to the solvation of Li+, and the solvation of anions in carbonate-based electrolytes and its possible effect on the electrochemical stability of such electrolytes remains little understood. As a mirror effort to prior Li+ solvation studies, this work focuses on the interactions between carbonate-based solvents and two anions (hexafluorophosphate, PF6–, and tetrafluoroborate, BF4–) that are most frequently used in Li-ion batteries. The possible correlation between such interaction and the interphasial chemistry on cathode surface is also explored.

Comparative Study of Ether-Based Electrolytes for Application in Lithium–Sulfur Battery

Abstract: Herein, we report the characteristics of electrolytes using various ether-solvents with molecular composition CH3O[CH2CH2O]nCH3, differing by chain length, and LiCF3SO3 as the lithium salt. The electrolytes, considered as suitable media for lithium–sulfur batteries, are characterized in terms of thermal properties (TGA, DSC), lithium ion conductivity, lithium interface stability, cyclic voltammetry, self-diffusion properties of the various components, and lithium transference number measured by NMR. Furthermore, the electrolytes are characterized in lithium cells using a sulfur–carbon composite cathode by galvanostatic charge–discharge tests. The results clearly evidence the influence of the solvent chain length on the species mobility within the electrolytes that directly affects the behavior in lithium sulfur cell. The results may effectively contribute to the progress of an efficient, high-energy lithium–sulfur battery.

Reviving the lithium metal anode for high-energy batteries

Abstract: Lithium-ion batteries have had a profound impact on our daily life, but inherent limitations make it difficult for Li-ion chemistries to meet the growing demands for portable electronics, electric vehicles and grid-scale energy storage. Therefore, chemistries beyond Li-ion are currently being investigated and need to be made viable for commercial applications. The use of metallic Li is one of the most favoured choices for next-generation Li batteries, especially Li-S and Li-air systems. After falling into oblivion for several decades because of safety concerns, metallic Li is now ready for a revival, thanks to the development of investigative tools and nanotechnology-based solutions. In this Review, we first summarize the current understanding on Li anodes, then highlight the recent key progress in materials design and advanced characterization techniques, and finally discuss the opportunities and possible directions for future development of Li anodes in applications.

Highly reversible zinc metal anode for aqueous batteries.

Abstract: Metallic zinc (Zn) has been regarded as an ideal anode material for aqueous batteries because of its high theoretical capacity (820 mA h g–1), low potential (−0.762 V versus the standard hydrogen electrode), high abundance, low toxicity and intrinsic safety. However, aqueous Zn chemistry persistently suffers from irreversibility issues, as exemplified by its low coulombic efficiency (CE) and dendrite growth during plating/ stripping, and sustained water consumption. In this work, we demonstrate that an aqueous electrolyte based on Zn and lithium salts at high concentrations is a very effective way to address these issues. This unique electrolyte not only enables dendrite-free Zn plating/stripping at nearly 100% CE, but also retains water in the open atmosphere, which makes hermetic cell configurations optional. These merits bring unprecedented flexibility and reversibility to Zn batteries using either LiMn2O4 or O2 cathodes—the former deliver 180 W h kg–1 while retaining 80% capacity for >4,000 cycles, and the latter deliver 300 W h kg–1 (1,000 W h kg–1 based on the cathode) for >200 cycles.

Achieving high energy density and high power density with pseudocapacitive materials

Abstract: Batteries and supercapacitors serve as the basis for electrochemical energy-storage devices. Although both rely on electrochemical processes, their charge-storage mechanisms are dissimilar, giving rise to different energy and power densities. Pseudocapacitive materials store charge through battery-like redox reactions but at fast rates comparable to those of electrochemical double-layer capacitors; these materials, therefore, offer a pathway for achieving both high energy and high power densities. Materials that combine these properties are in demand for the realization of fast-charging electrochemical energy-storage devices capable of delivering high power for long periods of time. In this Review, we describe the fundamental electrochemical properties of pseudocapacitive materials, with emphasis on kinetic processes and distinctions between battery and pseudocapacitive materials. In addition, we discuss the various types of pseudocapacitive materials, highlighting the differences between intrinsic and extrinsic materials; assess device applications; and consider the future prospects for the field. Pseudocapacitive materials can bridge the gap between high-energy-density battery materials and high-power-density electrochemical capacitor materials. In this Review, we examine the electrochemistry and physical signatures of pseudocapacitive charge-storage processes and discuss existing pseudocapacitive materials.

Advances and issues in developing salt-concentrated battery electrolytes

Abstract: With a worldwide trend towards the efficient use of renewable energies and the rapid expansion of the electric vehicle market, the importance of rechargeable battery technologies, particularly lithium-ion batteries, has steadily increased. In the past few years, a major breakthrough in electrolyte materials was achieved by simply increasing the salt concentration in suitable salt–solvent combinations, offering technical superiority in numerous figures of merit over alternative materials. This long-awaited, extremely simple yet effective strategy can overcome most of the remaining hurdles limiting the present lithium-ion batteries without sacrificing manufacturing efficiency, and hence its impact is now widely felt in the scientific community, with serious potential for industrial development. This Review aims to provide timely and objective information that will be valuable for designing better realistic batteries, including a multi-angle analysis of their advantages and disadvantages together with future perspectives. Emphasis is placed on the pathways to address the remaining technical and scientific issues rather than re-highlighting the many technical advantages. New electrolyte materials can offer breakthroughs in the development of next-generation batteries. Here Atsuo Yamada and colleagues review the progress made and the road ahead for salt-concentrated electrolytes, an emerging and promising electrolyte candidate.