Solid Electrolyte Bimodal Grain Structures for Improved Cycling Performance.

The application of solid-state electrolytes in Li batteries is hampered by the occurrence of Li-dendrite-caused short circuits. To avoid cell failure, the electrolytes can only be stressed with rather low current densities, severely restricting their performance. As grain size and pore distributions significantly affect dendrite growth in ceramic electrolytes such as LiLaZrO and its variants; here, a "detour and buffer" strategy to bring the superiority of both coarse and fine grains into play, is proposed.

Effect of Liquid Electrolyte Soaking on the Interfacial Resistance of LiLaZrO for All-Solid-State Lithium Batteries.

The impact of liquid electrolyte soaking on the interfacial resistance between the garnet-structured LiLaZrO (LLZO) solid electrolyte and metallic lithium has been studied. Lithium carbonate (LiCO) formed by inadvertent exposure of LLZO to ambient conditions is generally known to increase interfacial impedance and decrease lithium wettability. Soaking LLZO powders and pellets in the electrolyte containing lithium tetrafluoroborate (LiBF) shows a significantly reduced interfacial resistance and improved contact between lithium and LLZO.

Distinct Surface and Bulk Thermal Behaviors of LiNiMnCoO Cathode Materials as a Function of State of Charge.

Understanding how structural and chemical transformations take place in particles under thermal conditions can inform designing thermally robust electrode materials. Such a study necessitates the use of diagnostic techniques that are capable of probing the transformations at multiple length scales and at different states of charge (SOC). In this study, the thermal behavior of LiNiMnCoO (NMC-622) was examined as a function of SOC, using an array of bulk and surface-sensitive techniques.

Scalable Freeze-Tape-Casting Fabrication and Pore Structure Analysis of 3D LLZO Solid-State Electrolytes.

Nonflammable solid-state electrolytes can potentially address the reliability and energy density limitations of lithium-ion batteries. Garnet-structured oxides such as LiLaZrO (LLZO) are some of the most promising candidates for solid-state devices. Here, three-dimensional (3D) solid-state LLZO frameworks with low tortuosity pore channels are proposed as scaffolds, into which active materials and other components can be infiltrated to make composite electrodes for solid-state batteries.

Three-Dimensionally Aligned Sulfur Electrodes by Directional Freeze Tape Casting.

Rational design of sulfur electrodes is exceptionally important in enabling a high-performance lithium/sulfur cell. Constructing a continuous pore structure of the sulfur electrode that enables facile lithium ion transport into the electrode and mitigates the reconstruction of sulfur is a key factor for enhancing the electrochemical performance. Here, we report a three-dimensionally (3D) aligned sulfur electrode cast onto conventional aluminum foil by directional freeze tape casting.

Propagation topography of redox phase transformations in heterogeneous layered oxide cathode materials.

Redox phase transformations are relevant to a number of metrics pertaining to the electrochemical performance of batteries. These phase transformations deviate from and are more complicated than the conventional theory of phase nucleation and propagation, owing to simultaneous changes of cationic and anionic valence states as well as the polycrystalline nature of battery materials. Herein, we propose an integrative approach of mapping valence states and constructing chemical topographies to investigate the redox phase transformation in polycrystalline layered oxide cathode materials under thermal abuse conditions.

Oxygen Release Induced Chemomechanical Breakdown of Layered Cathode Materials.

Chemical and mechanical properties interplay on the nanometric scale and collectively govern the functionalities of battery materials. Understanding the relationship between the two can inform the design of battery materials with optimal chemomechanical properties for long-life lithium batteries. Herein, we report a mechanism of nanoscale mechanical breakdown in layered oxide cathode materials, originating from oxygen release at high states of charge under thermal abuse conditions.

Interface Instability of Fe-Stabilized LiLaZrO versus Li Metal.

The interface stability versus Li represents a major challenge in the development of next-generation all-solid-state batteries (ASSB), which take advantage of the inherently safe ceramic electrolytes. Cubic LiLaZrO garnets represent the most promising electrolytes for this technology. The high interfacial impedance versus Li is, however, still a bottleneck toward future devices.

Electrochemical Characteristics of Layered Transition Metal Oxide Cathode Materials for Lithium Ion Batteries: Surface, Bulk Behavior, and Thermal Properties.

Layered lithium transition metal oxides, in particular, NMCs (LiNiCoMnO) represent a family of prominent lithium ion battery cathode materials with the potential to increase energy densities and lifetime, reduce costs, and improve safety for electric vehicles and grid storage. Our work has focused on various strategies to improve performance and to understand the limitations to these strategies, which include altering compositions, utilizing cation substitutions, and charging to higher than usual potentials in cells. Understanding the effects of these strategies on surface and bulk behavior and correlating structure-performance relationships advance our understanding of NMC materials.

Synchrotron X-ray Analytical Techniques for Studying Materials Electrochemistry in Rechargeable Batteries.

Rechargeable battery technologies have ignited major breakthroughs in contemporary society, including but not limited to revolutions in transportation, electronics, and grid energy storage. The remarkable development of rechargeable batteries is largely attributed to in-depth efforts to improve battery electrode and electrolyte materials. There are, however, still intimidating challenges of lower cost, longer cycle and calendar life, higher energy density, and better safety for large scale energy storage and vehicular applications.

CoLi[(OH)O][(POOH)(PO)], a Lithium-Stabilized, Mixed-Valent Cobalt(II,III) Hydroxide Phosphate Framework.

A new metastable phase, featuring a lithium-stabilized mixed-valence cobalt(II,III) hydroxide phosphate framework, CoLi[(OH)O][(POOH)(PO)], corresponding to the simplified composition CoLi(OH)PO, is prepared by hydrothermal synthesis. Because the pH-dependent formation of other phases such as Co(OH)(POOH) and olivine-type LiCoPO competes in the process, a pH value of 5.0 is crucial for obtaining a single-phase material.

A spongy nickel-organic CO reduction photocatalyst for nearly 100% selective CO production.

Solar-driven photocatalytic conversion of CO into fuels has attracted a lot of interest; however, developing active catalysts that can selectively convert CO to fuels with desirable reaction products remains a grand challenge. For instance, complete suppression of the competing H evolution during photocatalytic CO-to-CO conversion has not been achieved before. We design and synthesize a spongy nickel-organic heterogeneous photocatalyst via a photochemical route.

In Situ Engineering of the Electrode-Electrolyte Interface for Stabilized Overlithiated Cathodes.

The first-ever demonstration of stabilized Si/lithium-manganese-rich full cells, capable of retaining >90% energy over early cycling and >90% capacity over more than 750 cycles at the 1C rate (100% depth-of-discharge), is made through the utilization of a modified ionic-liquid electrolyte capable of forming a favorable cathode-electrolyte interface.

Tailoring Transition-Metal Hydroxides and Oxides by Photon-Induced Reactions.

Controlled synthesis of transition-metal hydroxides and oxides with earth-abundant elements have attracted significant interest because of their wide applications, for example as battery electrode materials or electrocatalysts for fuel generation. Here, we report the tuning of the structure of transition-metal hydroxides and oxides by controlling chemical reactions using an unfocused laser to irradiate the precursor solution. A Nd:YAG laser with wavelengths of 532 nm or 1064 nm was used.

Structural and Electrochemical Consequences of Al and Ga Cosubstitution in LiLaZrO Solid Electrolytes.

Several "Beyond Li-Ion Battery" concepts such as all solid-state batteries and hybrid liquid/solid systems envision the use of a solid electrolyte to protect Li-metal anodes. These configurations are very attractive due to the possibility of exceptionally high energy densities and high (dis)charge rates, but they are far from being realized practically due to a number of issues including high interfacial resistance and difficulties associated with fabrication. One of the most promising solid electrolyte systems for these applications is Al or Ga stabilized LiLaZrO (LLZO) based on high ionic conductivities and apparent stability against reduction by Li metal.

Elucidation of the surface characteristics and electrochemistry of high-performance LiNiO2.

Phase pure LiNiO2 was prepared using a solid-state method and the optimal synthesis conditions led to a remarkably high capacity of 200 mA h g(-1) with excellent retention. The combination of bulk and surface characterization elucidated an essential role of the excess Li in phase formation during synthesis and the subsequent electrochemical performance.

Synthesis, Crystal Chemistry, and Electrochemical Properties of Li(7-2x)La3Zr(2-x)Mo(x)O12 (x = 0.1-0.4): Stabilization of the Cubic Garnet Polymorph via Substitution of Zr(4+) by Mo(6+).

Cubic Li7La3Zr2O12 (LLZO) garnets are exceptionally well suited to be used as solid electrolytes or protecting layers in "Beyond Li-ion Battery" concepts. Unfortunately, cubic LLZO is not stable at room temperature (RT) and has to be stabilized by supervalent dopants. In this study we demonstrate a new possibility to stabilize the cubic phase at RT via substitution of Zr(4+) by Mo(6+).

Sodiation Kinetics of Metal Oxide Conversion Electrodes: A Comparative Study with Lithiation.

The development of sodium ion batteries (NIBs) can provide an alternative to lithium ion batteries (LIBs) for sustainable, low-cost energy storage. However, due to the larger size and higher m/e ratio of the sodium ion compared to lithium, sodiation reactions of candidate electrodes are expected to differ in significant ways from the corresponding lithium ones. In this work, we investigated the sodiation mechanism of a typical transition metal-oxide, NiO, through a set of correlated techniques, including electrochemical and synchrotron studies, real-time electron microscopy observation, and ab initio molecular dynamics (MD) simulations.

Computational and Experimental Investigation of Ti Substitution in Li1(NixMnxCo1-2x-yTiy)O2 for Lithium Ion Batteries.

Aliovalent substitutions in layered transition-metal cathode materials has been demonstrated to improve the energy densities of lithium ion batteries, with the mechanisms underlying such effects incompletely understood. Performance enhancement associated with Ti substitution of Co in the cathode material Li1(NixMnxCo1-2x)O2 were investigated using density functional theory calculations, including Hubbard-U corrections. An examination of the structural and electronic modifications revealed that Ti substitution reduces the structural distortions occurring during delithiation due to the larger cation radius of Ti(4+) relative to Co(3+) and the presence of an electron polaron on Mn cations induced by aliovalent Ti substitution.

Tailoring the surface properties of LiNi(0.4)Mn(0.4)Co(0.2)O2 by titanium substitution for improved high voltage cycling performance.

The present study aims to provide insights into the behavior of LiNi0.4Mn0.4Co0.

Interrelationships among Grain Size, Surface Composition, Air Stability, and Interfacial Resistance of Al-Substituted Li7La3Zr2O12 Solid Electrolytes.

The interfacial resistances of symmetrical lithium cells containing Al-substituted Li7La3Zr2O12 (LLZO) solid electrolytes are sensitive to their microstructures and histories of exposure to air. Air exposure of LLZO samples with large grain sizes (∼150 μm) results in dramatically increased interfacial impedances in cells containing them, compared to those with pristine large-grained samples. In contrast, a much smaller difference is seen between cells with small-grained (∼20 μm) pristine and air-exposed LLZO samples.

Tuning complex transition metal hydroxide nanostructures as active catalysts for water oxidation by a laser-chemical route.

Diverse transition metal hydroxide nanostructures were synthesized by laser-induced hydrolysis in a liquid precursor solution for alkaline oxygen evolution reaction (OER). Several active OER catalysts with fine control of composition, structure, and valence state were obtained including (Lix)[Ni0.66Mn0.

High-voltage cathode materials for lithium-ion batteries: freeze-dried LiMn0.8Fe0.1M0.1PO4/C (M = Fe, Co, Ni, Cu) nanocomposites.

Four LiMn0.8Fe0.1M0.