Synergy of Epoxy Chemical Tethers and Defect-Free Graphene in Enabling Stable Lithium Cycling of Silicon Nanoparticles.

We report a new approach for nanosilicon-graphene hybrids with uniquely stable solid electrolyte interphase. Expanded graphite is gently exfoliated creating "defect-free" graphene that is non-catalytic towards electrolyte decomposition, simultaneously introducing high mass loading (48 wt. %) Si nanoparticles.

Direct Structure-Performance Comparison of All-Carbon Potassium and Sodium Ion Capacitors.

A hybrid ion capacitor (HIC) based on potassium ions (K) is a new high-power intermediate energy device that may occupy a unique position on the Ragone chart space. Here, a direct performance comparison of a potassium ion capacitor (KIC) versus the better-known sodium ion capacitor is provided. Tests are performed with an asymmetric architecture based on bulk ion insertion, partially ordered, dense carbon anode (hard carbon, HC) opposing N- and O-rich ion adsorption, high surface area, cathode (activated carbon, AC).

Sulfur-Grafted Hollow Carbon Spheres for Potassium-Ion Battery Anodes.

Sulfur-rich carbons are minimally explored for potassium-ion batteries (KIBs). Here, a large amount of S (38 wt%) is chemically incorporated into a carbon host, creating sulfur-grafted hollow carbon spheres (SHCS) for KIB anodes. The SHCS architecture provides a combination of nanoscale (≈40 nm) diffusion distances and CS chemical bonding to minimize cycling capacity decay and Coulombic efficiency (CE) loss.

Sodium Metal Anodes: Emerging Solutions to Dendrite Growth.

This comprehensive Review focuses on the key challenges and recent progress regarding sodium-metal anodes employed in sodium-metal batteries (SMBs). The metal anode is the essential component of emerging energy storage systems such as sodium sulfur and sodium selenium, which are discussed as example full-cell applications. We begin with a description of the differences in the chemical and physical properties of Na metal versus the oft-studied Li metal, and a corresponding discussion regarding the number of ways in which Na does not follow Li-inherited paradigms in its electrochemical behavior.

Directional Flow-Aided Sonochemistry Yields Graphene with Tunable Defects to Provide Fundamental Insight on Sodium Metal Plating Behavior.

We report a directional flow-aided sonochemistry exfoliation technique that allows for unparalleled control of graphene structural order and chemical uniformity. Depending on the orientation of the shockwave relative to the flow-aligned graphite flakes, the resultant bilayer and trilayer graphene is nearly defect free (at-edge sonication graphene "AES-G") or is highly defective (in-plane sonication graphene "IPS-G"). AES-G has a Raman G/D band intensity ratio of 14.

Li-Rich Li[Li Fe Ni Mn ]O (LFNMO) Cathodes: Atomic Scale Insight on the Mechanisms of Cycling Decay and of the Improvement due to Cobalt Phosphate Surface Modification.

Lithium-rich Li[Li Fe Ni Mn ]O (0.4Li MnO -0.6LiFe Ni Mn O , LFNMO) is a new member of the xLi MnO ·(1 - x)LiMO family of high capacity-high voltage lithium-ion battery (LIB) cathodes.

Review of Hybrid Ion Capacitors: From Aqueous to Lithium to Sodium.

In this critical Review we focus on the evolution of the hybrid ion capacitor (HIC) from its early embodiments to its modern form, focusing on the key outstanding scientific and technological questions that necessitate further in-depth study. It may be argued that HICs began as aqueous systems, based on a Faradaic oxide positive electrode (e.g.

Understanding CO capture mechanisms in aqueous hydrazine via combined NMR and first-principles studies.

Aqueous amines are currently the most promising solution for large-scale CO capture from industrial sources. However, molecular design and optimization of amine-based solvents have proceeded slowly due to a lack of understanding of the underlying reaction mechanisms. Unique and unexpected reaction mechanisms involved in CO absorption into aqueous hydrazine are identified using H, C, and N NMR spectroscopy combined with first-principles quantum-mechanical simulations.

The Bright Future for Electrode Materials of Energy Devices: Highly Conductive Porous Na-Embedded Carbon.

High electrical conductivity and large accessible surface area, which are required for ideal electrode materials of energy conversion and storage devices, are opposed to each other in current materials. It is a long-term goal to solve this issue. Herein, we report highly conductive porous Na-embedded carbon (Na@C) nanowalls with large surface areas, which have been synthesized by an invented reaction of CO with liquid Na.

First-principles assessment of CO capture mechanisms in aqueous piperazine solution.

Piperazine (PZ) and its blends have emerged as attractive solvents for CO capture, but the underlying reaction mechanisms still remain uncertain. Our study particularly focuses on assessing the relative roles of PZCOO and PZH produced from the PZ + CO reaction. PZCOO is found to directly react with CO forming COOPZCOO, whereas PZH will not.

On the origin of preferred bicarbonate production from carbon dioxide (CO₂) capture in aqueous 2-amino-2-methyl-1-propanol (AMP).

AMP and its blends are an attractive solvent for CO2 capture, but the underlying reaction mechanisms still remain uncertain. We attempt to elucidate the factors enhancing bicarbonate production in aqueous AMP as compared to MEA which, like most other primary amines, preferentially forms carbamate. According to our predicted reaction energies, AMP and MEA exhibit similar thermodynamic favorability for bicarbonate versus carbamate formation; moreover, the conversion of carbamate to bicarbonate also does not appear more favorable kinetically in aqueous AMP compared to MEA.

Anomalous Stagewise Lithiation of Gold-Coated Silicon Nanowires: A Combined In Situ Characterization and First-Principles Study.

Through a combined density functional theory and in situ scanning electron microscopy study, the effects of presence of gold (Au) spreading on the lithiation process of silicon nanowire (SiNW) were systematically examined. Different from a pristine SiNW, an Au-coated SiNW (Au-SiNW) is lithiated in three distinct stages; Li atoms are found to be incorporated preferentially in the Au shell, whereas the thin AuSi interface layer may serve as a facile diffusion path along the nanowire axial direction, followed by the prompt lithiation of the Si core in the radial direction. The underlying mechanism of the intriguing stagewise lithiation behavior is explained through our theoretical analysis, which appears well-aligned with the experimental evidence.

Long-life Li/polysulphide batteries with high sulphur loading enabled by lightweight three-dimensional nitrogen/sulphur-codoped graphene sponge.

Lithium-sulphur batteries with a high theoretical energy density are regarded as promising energy storage devices for electric vehicles and large-scale electricity storage. However, the low active material utilization, low sulphur loading and poor cycling stability restrict their practical applications. Herein, we present an effective strategy to obtain Li/polysulphide batteries with high-energy density and long-cyclic life using three-dimensional nitrogen/sulphur codoped graphene sponge electrodes.

On the influence of polarization effects in predicting the interfacial structure and capacitance of graphene-like electrodes in ionic liquids.

The electric double layer (CD) and electrode quantum (CQ) capacitances of graphene-based supercapacitors are investigated using a combined molecular dynamics and density functional theory approach. In particular, we compare an approach that includes electronic polarization to one that is polarization-free by evaluating both CD and CQ using [EMIM][BF4] ionic liquid as a model electrolyte. Our results indicate that the inclusion of polarization effects can yield higher CD values-in this study by up to 40% around ±2 V-which we attribute primarily to the presence of charge smearing at the electrode-electrolyte interface.

Reaction mechanisms of aqueous monoethanolamine with carbon dioxide: a combined quantum chemical and molecular dynamics study.

Aqueous monoethanolamine (MEA) has been extensively studied as a solvent for CO2 capture, yet the underlying reaction mechanisms are still not fully understood. Combined ab initio and classical molecular dynamics simulations were performed to revisit and identify key elementary reactions and intermediates in 25-30 wt% aqueous MEA with CO2, by explicitly taking into account the structural and dynamic effects. Using static quantum chemical calculations, we also analyzed in more detail the fundamental interactions involved in the MEA-CO2 reaction.

Large capacitance enhancement induced by metal-doping in graphene-based supercapacitors: a first-principles-based assessment.

Chemically doped graphene-based materials have recently been explored as a means to improve the performance of supercapacitors. In this work, we investigate the effects of 3d transition metals bound to vacancy sites in graphene with [BMIM][PF6] ionic liquid on the interfacial capacitance; these results are compared to the pristine graphene case with particular attention to the relative contributions of the quantum and electric double layer capacitances. Our study highlights that the presence of metal-vacancy complexes significantly increases the availability of electronic states near the charge neutrality point, thereby enhancing the quantum capacitance drastically.

Relative contributions of quantum and double layer capacitance to the supercapacitor performance of carbon nanotubes in an ionic liquid.

Motivated by promising demonstrations of carbon nanotube (CNT) electrodes in supercapacitors, we evaluate the capacitive performance of a (6,6) CNT in [BMIM][PF6] ionic liquid (IL), with particular attention to the relative contributions of the electric double layer (EDL) capacitance (CD) at the CNT/IL interface and the quantum capacitance (CQ) of the CNT. Our classical molecular dynamics simulations reveal that the use of the CNT improves CD when compared to planar graphene, which we discuss in terms of how the electrode curvature affects both the electric field strength and IL packing density. In addition, according to density functional theory calculations, the CQ of the CNT is constant and significantly larger than that of graphene near the Fermi level, which is a consequence of the larger number of available electron states in the CNT.