Malachi Noked

Next-Generation Lithium Metal Anode Engineering via Atomic Layer Deposition

Lithium metal is considered to be the most promising anode for next-generation batteries due to its high energy density of 3840 mAh g(-1). However, the extreme reactivity of the Li surface can induce parasitic reactions with solvents, contamination, and shuttled active species in the electrolyte, reducing the performance of batteries employing Li metal anodes. One promising solution to this issue is application of thin chemical protection layers to the Li metal surface. Using a custom-made ultrahigh vacuum integrated deposition and characterization system, we demonstrate atomic layer deposition (ALD) of protection layers directly on Li metal with exquisite thickness control. We demonstrate as a proof-of-concept that a 14 nm thick ALD Al2O3 layer can protect the Li surface from corrosion due to atmosphere, sulfur, and electrolyte exposure. Using Li-S battery cells as a test system, we demonstrate an improved capacity retention using ALD-protected anodes over cells assembled with bare Li metal anodes for up to 100 cycles.

Enhancing the Reversibility of Mg/S Battery Chemistry through Li+ Mediation

Mg metal is a promising anode material for next generation rechargeable battery due to its dendrite-free deposition and high capacity. However, the best cathode for rechargeable Mg battery was based on high molecular weight MgxMo3S4, thus rendering full cell energetically uncompetitive. To increase energy density, high capacity cathode material like sulfur is proposed. However, to date, only limited work has been reported on Mg/S system, all plagued by poor reversibility attributed to the formation of electrochemically inactive MgSx species. Here, we report a new strategy, based on the effect of Li(+) in activating MgSx species, to conjugate a dendrite-free Mg anode with a reversible polysulfide cathode and present a truly reversible Mg/S battery with capacity up to 1000 mAh/gs for more than 30 cycles. Mechanistic insights supported by spectroscopic and microscopic characterization strongly suggest that the reversibility arises from chemical reactivation of MgSx by Li(+).

Limitations of Charge Efficiency in Capacitive Deionization II. On the Behavior of CDI Cells Comprising Two Activated Carbon Electrodes

The charge efficiency of electrochemical capacitive deionization (CDI) of salty-brackish water in symmetric cells comprising activated highly porous carbon electrodes was investigated as a function of the applied potential during charging (deionization) and discharging. The charge efficiency of water CDI in such cells is highly affected by the fact that the potential applied drives always simultaneously adsorption of counterions and desorption of co-ions. A previous stage of this work concentrated in the study of single activated carbon electrodes in processes. In this study, we demonstrated that it is possible to estimate the charge efficiency of symmetric CDI cells from measurements of single electrodes. Guidelines for improving the charge efficiency in water desalination by CDI processes are outlined herein. For instance, it was demonstrated based on experimental findings that it is possible to maximize the charge efficiency by applying discharge potentials (upon regeneration) higher than zero.

Mechanistic Role of Li+ Dissociation Level in Aprotic Li–O2 Battery

The kinetics and thermodynamics of oxygen reduction reactions (ORR) in aprotic Li electrolyte were shown to be highly dependent on the surrounding chemical environment and electrochemical conditions. Numerous reports have demonstrated the importance of high donor number (DN) solvents for enhanced ORR, and attributed this phenomenon to the stabilizing interactions between the reduced oxygen species and the solvent molecules. We focus herein on the often overlooked effect of the Li salt used in the electrolyte solution. We show that the level of dissociation of the salt used plays a significant role in the ORR, even as important as the effect of the solvent DN. We clearly show that the salt used dictates the kinetics and thermodynamic of the ORR, and also enables control of the reduced Li2O2 morphology. By optimizing the salt composition, we have managed to demonstrate a superior ORR behavior in diglyme solutions, even when compared to the high DN DMSO solutions. Our work paves the way for optimization of various solvents with reasonable anodic and cathodic stabilities, which have so far been overlooked due to their relatively low DN.

Mapping the Challenges of Magnesium Battery.

Rechargeable Mg battery has been considered a major candidate as a beyond lithium ion battery technology, which is apparent through the tremendous works done in the field over the past decades. The challenges for realization of Mg battery are complicated, multidisciplinary, and the tremendous work done to overcome these challenges is very hard to organize in a regular review paper. Additionally, we claim that organization of the huge amount of information accumulated by the great scientific progress achieved by various groups in the field will shed the light on the unexplored research domains and give clear perspectives and guidelines for next breakthrough to take place. In this Perspective, we provide a convenient map of Mg battery research in a form of radar chart of Mg electrolytes, which evaluates the electrolyte under the important components of Mg batteries. The presented radar charts visualize the accumulated knowledge on Mg battery and allow for navigation of not only the current research state but also future perspective of Mg battery at a glance.

A Rechargeable Al/S Battery with an Ionic‐Liquid Electrolyte

Aluminum metal is a promising anode material for next generation rechargeable batteries owing to its abundance, potentially dendrite-free deposition, and high capacity. The rechargeable aluminum/sulfur (Al/S) battery is of great interest owing to its high energy density (1340 Wh kg(-1) ) and low cost. However, Al/S chemistry suffers poor reversibility owing to the difficulty of oxidizing AlSx . Herein, we demonstrate the first reversible Al/S battery in ionic-liquid electrolyte with an activated carbon cloth/sulfur composite cathode. Electrochemical, spectroscopic, and microscopic results suggest that sulfur undergoes a solid-state conversion reaction in the electrolyte. Kinetics analysis identifies that the slow solid-state sulfur conversion reaction causes large voltage hysteresis and limits the energy efficiency of the system.

Fabrication of 3D core-shell multiwalled carbon nanotube@RuO2 lithium-ion battery electrodes through a RuO2 atomic layer deposition process.

Pushing lithium-ion battery (LIB) technology forward to its fundamental scaling limits requires the ability to create designer heterostructured materials and architectures. Atomic layer deposition (ALD) has recently been applied to advanced nanostructured energy storage devices due to the wide range of available materials, angstrom thickness control, and extreme conformality over high aspect ratio nanostructures. A class of materials referred to as conversion electrodes has recently been proposed as high capacity electrodes. RuO2 is considered an ideal conversion material due to its high combined electronic and ionic conductivity and high gravimetric capacity, and as such is an excellent material to explore the behavior of conversion electrodes at nanoscale thicknesses. We report here a fully characterized atomic layer deposition process for RuO2, electrochemical cycling data for ALD RuO2, and the application of the RuO2 to a composite carbon nanotube electrode scaffold with nucleation-controlled RuO2 growth. A growth rate of 0.4 Å/cycle is found between ∼ 210-240 °C. In a planar configuration, the resulting RuO2 films show high first cycle electrochemical capacities of ∼ 1400 mAh/g, but the capacity rapidly degrades with charge/discharge cycling. We also fabricated core/shell MWCNT/RuO2 heterostructured 3D electrodes, which show a 50× increase in the areal capacity over their planar counterparts, with an areal lithium capacity of 1.6 mAh/cm(2).

DMSO–Li2O2 Interface in the Rechargeable Li–O2 Battery Cathode: Theoretical and Experimental Perspectives on Stability

One of the greatest obstacles for the realization of the nonaqueous Li-O2 battery is finding a solvent that is chemically and electrochemically stable under cell operating conditions. Dimethyl sulfoxide (DMSO) is an attractive candidate for rechargeable Li-O2 battery studies; however, there is still significant controversy regarding its stability on the Li-O2 cathode surface. We performed multiple experiments (in situ XPS, FTIR, Raman, and XRD) which assess the stability of the DMSO-Li2O2 interface and report perspectives on previously published studies. Our electrochemical experiments show long-term stable cycling of a DMSO-based operating Li-O2 cell with a platinum@carbon nanotube core-shell cathode fabricated via atomic layer deposition, specifically with >45 cycles of 40 h of discharge per cycle. This work is complemented by density functional theory calculations of DMSO degradation pathways on Li2O2. Both experimental and theoretical evidence strongly suggests that DMSO is chemically and electrochemically stable on the surface of Li2O2 under the reported operating conditions.

Solid Electrolyte Lithium Phosphous Oxynitride as a Protective Nanocladding Layer for 3D High-Capacity Conversion Electrodes

Materials that undergo conversion reactions to form different materials upon lithiation typically offer high specific capacity for energy storage applications such as Li ion batteries. However, since the reaction products often involve complex mixtures of electrically insulating and conducting particles and significant changes in volume and phase, the reversibility of conversion reactions is poor, preventing their use in rechargeable (secondary) batteries. In this paper, we fabricate and protect 3D conversion electrodes by first coating multiwalled carbon nanotubes (MWCNT) with a model conversion material, RuO2, and subsequently protecting them with conformal thin-film lithium phosphous oxynitride (LiPON), a well-known solid-state electrolyte. Atomic layer deposition is used to deposit the RuO2 and the LiPON, thus forming core double-shell MWCNT@RuO2@LiPON electrodes as a model system. We find that the LiPON protection layer enhances cyclability of the conversion electrode, which we attribute to two factors. (1) The LiPON layer provides high Li ion conductivity at the interface between the electrolyte and the electrode. (2) By constraining the electrode materials mechanically, the LiPON protection layer ensures electronic connectivity and thus conductivity during lithiation/delithiation cycles. These two mechanisms are striking in their ability to preserve capacity despite the profound changes in structure and composition intrinsic to conversion electrode materials. This LiPON-protected structure exhibits superior cycling stability and reversibility as well as decreased overpotentials compared to the unprotected core-shell structure. Furthermore, even at very low lithiation potential (0.05 V), the LiPON-protected electrode largely reduces the formation of a solid electrolyte interphase.

Dual-template synthesis of ordered mesoporous carbon/Fe2O3 nanowires: high porosity and structural stability for supercapacitors

Carbon/metal oxide composites are considered promising materials for high energy density supercapacitors. So far, impregnation of the oxide into ordered mesoporous carbon materials has been demonstrated either in hard-templated carbon synthesized by using ordered mesoporous silica or alumina scaffolds, or soft-templated carbon derived from surfactant micelles. The hard-template method can provide a high pore volume but the instability of these mesostructures hinders total electrode performances upon oxide impregnation. While the soft-template methods can provide a stable mesostructure, these methods produce scaffolds with a much smaller pore volume and surface area, leading to limited metal oxide loading and electrode capacitance. Herein, anodized aluminum oxide (AAO) and triblock copolymer F127 are used together as hard and soft-templates to fabricate ordered mesoporous carbon nanowires (OMCNWs) as a host material for Fe2O3 nanoparticles. This dual-template strategy provides a high pore volume and surface area OMCNW that retains its stable structure even for high metal oxide loading amounts. Additionally, the unique nanowire morphology and mesoporous structure of the OMCNW/Fe2O3 facilitate high ionic mobility in the composite, leading to >260 F g−1 specific capacitance with good rate capability and cycling stability. This work highlights the dual-template approach as a promising strategy for the fabrication of next generation heterogeneous composites for electrochemical energy storage and conversion.