Electro-chemo-mechanics of anode-free solid-state batteries.

Anode-free solid-state batteries contain no active material at the negative electrode in the as-manufactured state, yielding high energy densities for use in long-range electric vehicles. The mechanisms governing charge-discharge cycling of anode-free batteries are largely controlled by electro-chemo-mechanical phenomena at solid-solid interfaces, and there are important mechanistic differences when compared with conventional lithium-excess batteries. This Perspective provides an overview of the factors governing lithium nucleation, growth, stripping and cycling in anode-free solid-state batteries, including mechanical deformation of lithium, the chemical and mechanical properties of the current collector, microstructural effects, and stripping dynamics.

Impact of Asymmetric Microstructure on Ion Transport in TiCT Membranes.

Consolidation or densification of low-dimensional MXene materials into membranes can result in the formation of asymmetric membrane structures. Nanostructural (short-range) and microstructural (long-range) heterogeneity can influence mass transport and separation mechanisms. Short-range structural dynamics include the presence of water confined between the 2D layers, while long-range structural properties include the formation of defects, micropores, and mesopores.

Silicon Composite Anode Degradation during Freeze-Thaw Temperature-Swings.

Batteries used in space applications can be exposed to large temperature-swings. During these large temperature-swings, the battery electrolyte can undergo a phase transformation from a liquid to a solid and back to a liquid. The nature of the solvent and the type of salt influence the crystallization processes.

Temperature and Pressure Effects on Unrecoverable Voids in Li Metal Solid-State Batteries.

All-solid-state batteries (ASSB) can potentially achieve high gravimetric and volumetric energy densities (900 Wh/L) if paired with a lithium metal anode and solid electrolyte. However, there is a lack in critical understanding about how to operate lithium metal cells at high capacities and minimize unwanted degradation mechanisms such as dendrites and voids. Herein, we investigate how pressure and temperature influence the formation and annihilation of unrecoverable voids in lithium metal upon stripping.

Ultrasparse View X-ray Computed Tomography for 4D Imaging.

X-ray computed tomography (CT) is a noninvasive, nondestructive approach to imaging materials, material systems, and engineered components in two and three dimensions. Acquisition of three-dimensional (3D) images requires the collection of hundreds or thousands of through-thickness X-ray radiographic images from different angles. Such 3D data acquisition strategies commonly involve suboptimal temporal sampling for and studies (4D imaging).

Polymorphism of garnet solid electrolytes and its implications for grain-level chemo-mechanics.

Understanding and mitigating filament formation, short-circuit and solid electrolyte fracture is necessary for advanced all-solid-state batteries. Here, we employ a coupled far-field high-energy diffraction microscopy and tomography approach for assessing the chemo-mechanical behaviour for dense, polycrystalline garnet (LiLaZrO) solid electrolytes with grain-level resolution. In situ monitoring of grain-level stress responses reveals that the failure mechanism is stochastic and affected by local microstructural heterogeneity.

In situ investigation of water on MXene interfaces.

A continuum of water populations can exist in nanoscale layered materials, which impacts transport phenomena relevant for separation, adsorption, and charge storage processes. Quantification and direct interrogation of water structure and organization are important in order to design materials with molecular-level control for emerging energy and water applications. Through combining molecular simulations with ambient-pressure X-ray photoelectron spectroscopy, X-ray diffraction, and diffuse reflectance infrared Fourier transform spectroscopy, we directly probe hydration mechanisms at confined and nonconfined regions in nanolayered transition-metal carbide materials.

Scalable Manufacturing of Hybrid Solid Electrolytes with Interface Control.

Hybrid solid electrolytes are promising alternatives for high energy density metallic lithium batteries. Scalable manufacturing of multi-material electrolytes with tailored transport pathways can provide an avenue toward controlling Li stripping and deposition mechanisms in all-solid-state devices. A novel roll-to-roll compatible coextrusion device is demonstrated to investigate mesostructural control during manufacturing.

Tortuosity Effects in Garnet-Type LiLaZrO Solid Electrolytes.

Intrinsic material microstructure features, such as pores or void spaces, grains, and defects can affect local lithium-ion concentration profiles and transport properties in solid ion conductors. The formation of lithium-deficient or -excess regions can accelerate degradation phenomena, such as dendrite formation, lithium plating, and electrode/electrolyte delamination. This paper evaluates the effects pores or void spaces have on the tortuosity of a garnet-type LiLaZrO solid electrolyte.

The Role of Adventitious Carbon in Photo-catalytic Nitrogen Fixation by Titania.

Photo-catalytic fixation of nitrogen by titania catalysts at ambient conditions has been reported for decades, yet the active site capable of adsorbing an inert N molecule at ambient pressure and the mechanism of dissociating the strong dinitrogen triple bond at room temperature remain unknown. In this work in situ near-ambient-pressure X-ray photo-electron spectroscopy and density functional theory calculations are used to probe the active state of the rutile (110) surface. The experimental results indicate that photon-driven interaction of N and TiO is observed only if adventitious surface carbon is present, and computational results show a remarkably strong interaction between N and carbon substitution (C*) sites that act as surface-bound carbon radicals.

Stack the Bowls: Tailoring the Electronic Structure of Corannulene-Integrated Crystalline Materials.

We report the first examples of purely organic donor-acceptor materials with integrated π-bowls (πBs) that combine not only crystallinity and high surface areas but also exhibit tunable electronic properties, resulting in a four-orders-of-magnitude conductivity enhancement in comparison with the parent framework. In addition to the first report of alkyne-azide cycloaddition utilized for corannulene immobilization in the solid state, we also probed the charge transfer rate within the Marcus theory as a function of mutual πB orientation for the first time, as well as shed light on the density of states near the Fermi edge. These studies could foreshadow new avenues for πB utilization for the development of optoelectronic devices or a route for highly efficient porous electrodes.

Direct observation of active material interactions in flowable electrodes using X-ray tomography.

Understanding electrical percolation and charging mechanisms in electrochemically active biphasic flowable electrodes is critical for enabling scalable deionization (desalination) and energy storage. Flowable electrodes are dynamic material systems which store charge (remove ions) and have the ability to flow. This flow process can induce structural changes in the underlying material arrangement and result in transient and non-uniform material properties.

Charge- and Size-Selective Ion Sieving Through Ti3C2Tx MXene Membranes.

Nanometer-thin sheets of 2D Ti3C2Tx (MXene) have been assembled into freestanding or supported membranes for the charge- and size-selective rejection of ions and molecules. MXene membranes with controllable thicknesses ranging from hundreds of nanometers to several micrometers exhibited flexibility, high mechanical strength, hydrophilic surfaces, and electrical conductivity that render them promising for separation applications. Micrometer-thick MXene membranes demonstrated ultrafast water flux of 37.

Materials for suspension (semi-solid) electrodes for energy and water technologies.

Suspension or semi-solid electrodes have recently gained increased attention for large-scale applications such as grid energy storage, capacitive water deionization, and wastewater treatment. A suspension electrode is a multiphase material system comprised of an active (charge storing) material suspended in ionic solution (electrolyte). Gravimetrically, the electrolyte is the majority component and aids in physical transport of the active material.

Effect of oxidation of carbon material on suspension electrodes for flow electrode capacitive deionization.

Flow electrode deionization (FCDI) is an emerging area for continuous and scalable deionization, but the electrochemical and flow properties of the flow electrode need to be improved to minimize energy consumption. Chemical oxidation of granular activated carbon (AC) was examined here to study the role of surface heteroatoms on rheology and electrochemical performance of a flow electrode (carbon slurry) for deionization processes. Moreover, it was demonstrated that higher mass densities could be used without increasing energy for pumping when using oxidized active material.

Composite manganese oxide percolating networks as a suspension electrode for an asymmetric flow capacitor.

In this study, we examine the use of a percolating network of metal oxide (MnO2) as the active material in a suspension electrode as a way to increase the capacitance and energy density of an electrochemical flow capacitor. Amorphous manganese oxide was synthesized via a low-temperature hydrothermal approach and combined with carbon black to form composite flowable electrodes of different compositions. All suspension electrodes were tested in static configurations and consisted of an active solid material (MnO2 or activated carbon) immersed in aqueous neutral electrolyte (1 M Na2SO4).