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.
View Article and Find Full Text PDFNonflammable 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.
View Article and Find Full Text PDFRational 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.
View Article and Find Full Text PDFRedox 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.
View Article and Find Full Text PDFChemical 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.
View Article and Find Full Text PDFJ Phys Chem C Nanomater Interfaces
February 2018
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.
View Article and Find Full Text PDFLayered 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.
View Article and Find Full Text PDFRechargeable 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.
View Article and Find Full Text PDFA 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.
View Article and Find Full Text PDFSolar-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.
View Article and Find Full Text PDFThe 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.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
November 2016
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.
View Article and Find Full Text PDFSeveral "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.
View Article and Find Full Text PDFPhase 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.
View Article and Find Full Text PDFCubic 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+).
View Article and Find Full Text PDFThe 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.
View Article and Find Full Text PDFAliovalent 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.
View Article and Find Full Text PDFThe present study aims to provide insights into the behavior of LiNi0.4Mn0.4Co0.
View Article and Find Full Text PDFDiverse 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.
View Article and Find Full Text PDFNanoparticle electrodes in lithium-ion batteries have both near-surface and interior contributions to their redox capacity, each with distinct rate capabilities. Using combined electron microscopy, synchrotron X-ray methods and ab initio calculations, we have investigated the lithiation pathways that occur in NiO electrodes. We find that the near-surface electroactive (Ni(2+) → Ni(0)) sites saturated very quickly, and then encounter unexpected difficulty in propagating the phase transition into the electrode (referred to as a "shrinking-core" mode).
View Article and Find Full Text PDFThe investigation of chemical and structural dynamics in battery materials is essential to elucidation of structure-property relationships for rational design of advanced battery materials. Spatially resolved techniques, such as scanning/transmission electron microscopy (S/TEM), are widely applied to address this challenge. However, battery materials are susceptible to electron beam damage, complicating the data interpretation.
View Article and Find Full Text PDFThe present study sheds light on the long-standing challenges associated with high-voltage operation of LiNi(x)Mn(x)Co(1-2x)O2 cathode materials for lithium-ion batteries. Using correlated ensemble-averaged high-throughput X-ray absorption spectroscopy and spatially resolved electron microscopy and spectroscopy, here we report structural reconstruction (formation of a surface reduced layer, to transition) and chemical evolution (formation of a surface reaction layer) at the surface of LiNi(x)Mn(x)Co(1-2x)O2 particles. These are primarily responsible for the prevailing capacity fading and impedance buildup under high-voltage cycling conditions, as well as the first-cycle coulombic inefficiency.
View Article and Find Full Text PDFIntercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. During insertion or removal of alkali metal ions, the redox states of transition metals in the compounds change and structural transformations such as phase transitions and/or lattice parameter increases or decreases occur. These behaviors in turn determine important characteristics of the batteries such as the potential profiles, rate capabilities, and cycle lives.
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