141 research outputs found
Nanoscale Voltage Enhancement at Cathode Interfaces in Li-ion Batteries
Interfaces are ubiquitous in Li-ion battery electrodes, occurring across
compositional gradients, regions of multiphase intergrowths, and between
electrodes and solid electrolyte interphases or protective coatings. However,
the impact of these interfaces on Li energetics remains largely unknown. In
this work, we calculated Li intercalation-site energetics across cathode
interfaces and demonstrated the physics governing these energetics on both
sides of the interface. We studied the olivine/olivine-structured
LixFePO4/LixMPO4 (x=0 and 1, M=Co, Ti, Mn) and layered/layered-structured
LiNiO2/TiO2 interfaces to explore different material structures and transition
metal elements. We found that across an interface from a high- to low-voltage
material the Li voltage remains constant in the high-voltage material and
decays approximately linearly in the low-voltage region, approaching the Li
voltage of the low-voltage material. This effect ranges from 0.5-9nm depending
on the interfacial dipole screening. This effect provides a mechanism for a
high-voltage material at an interface to significantly enhance the Li
intercalation voltage in a low-voltage material over nanometer scale. We showed
that this voltage enhancement is governed by a combination of electron transfer
(from low- to high-voltage regions), strain and interfacial dipole screening.
We explored the implications of this voltage enhancement for a novel
heterostructured-cathode design and redox pseudocapacitors
Exploring the high-pressure materials genome
A thorough in situ characterization of materials at extreme conditions is
challenging, and computational tools such as crystal structural search methods
in combination with ab initio calculations are widely used to guide experiments
by predicting the composition, structure, and properties of high-pressure
compounds. However, such techniques are usually computationally expensive and
not suitable for large-scale combinatorial exploration. On the other hand,
data-driven computational approaches using large materials databases are useful
for the analysis of energetics and stability of hundreds of thousands of
compounds, but their utility for materials discovery is largely limited to
idealized conditions of zero temperature and pressure. Here, we present a novel
framework combining the two computational approaches, using a simple linear
approximation to the enthalpy of a compound in conjunction with
ambient-conditions data currently available in high-throughput databases of
calculated materials properties. We demonstrate its utility by explaining the
occurrence of phases in nature that are not ground states at ambient conditions
and estimating the pressures at which such ambient-metastable phases become
thermodynamically accessible, as well as guiding the exploration of
ambient-immiscible binary systems via sophisticated structural search methods
to discover new stable high-pressure phases.Comment: 14 pages, 6 figure
A materials informatics approach to the identification of one-band correlated materials analogous to the cuprates
One important yet exceedingly rare property of the cuprate high-temperature
superconductors is the presence of a single correlated band in the
low-energy spectrum, leading to the one-band Hubbard model as the minimal
description. In order to search for materials with interesting strong
correlation physics as well as possible benchmark systems for the one-band
Hubbard model, here we present a new approach to find one-band correlated
materials analogous to the cuprates by leveraging the emerging area of
materials informatics. Using the composition, structure, and formation energy
of more than half a million real and hypothetical inorganic crystalline
materials in the Open Quantum Materials Database, we search for synthesizable
materials whose nominal transition metal electron count and crystal field
are compatible with achieving an isolated half-filled band. Five Cu
compounds, including bromide, oxide, selenate, and pyrophosphate chemistries,
are shown to successfully achieve the one-band electronic structure based on
density functional theory band structure calculations. Further calculations
including magnetism and explicit on-site Coulomb interaction reveal significant
evidence for strong correlation physics in the five candidates, including Mott
insulating behavior and antiferromagnetism. The success of our data-driven
approach to discovering new correlated materials opens up new avenues to design
and discover materials with rare electronic properties
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