Hi all,
Tomorrow Zhenpeng will speak at group meeting. See below for his title and
abstract.
All the best,
Ian
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Title: Towards Understanding and Designing of Advanced Li-ion Batteries
from First-principles
Abstract:
Lithium ion batteries (LIBs) have been the most prominent electrochemical
energy storage technology over the past decades and enabled the wireless
evolution of portable electronic devices. Yet the expanded use of renewable
but intermittent energy sources coupled with increasing demand for electric
transportation vehicles put forward requirements to electrochemical energy
storage techniques for higher capacity, lower cost, and fast rate capacity.
State-of-the-art LIB electrodes are typically lithium transition metal
oxides and phosphates, which store (release) the electrical energy via the
Li extraction and re-accommodation, accompanied by redox reactions of TM
cations. The specific capacity of the electrode is therefore limited by the
safe amount of Li can be removed from the system without causing structure
collapse and the number of electrons per TM cation that can participate in
the redox reaction. To boost the capacity and energy density, conversion
reaction electrode materials which can overcome the inherent structural
limitation and anionic redox active electrodes with oxygen ions
complementarily providing the charge- compensating electrons were
introduced to the rechargeable battery chemistry. Here we use the density
functional theory (DFT) based first-principles calculations to understand
the electrochemical charge and discharge of the conversion reaction
electrodes via exploring the equilibrium and non-equilibrium thermodynamics
with a mechanistic method as designed. We provide detailed information for
the origin of large voltage hysteresis and volume expansion which have been
hindering the practical application of conversion reaction materials and
offer tips on alleviating them through reasonably operation range
restrictions. For the anionic redox active electrodes, we demonstrate how
the coordination structure and bonding environment enable the reversible
oxygen redox in the 3d metal oxides. The specific redox active Li6-O local
Li-excess configuration as identified for the iron oxide electrode enriches
the anionic redox battery chemistry with a low-cost high energy density
battery designed. For the manganese oxide anionic redox active electrodes,
we predict novel materials with improved properties compared to the
original system through high-throughput DFT screening. On the other hand,
using kinetics calculations we discover a novel 2-dimensional material with
superior electric and ionic conductivity compared to traditional
2-dimensional nanosheet-like graphene which can be used to boost the
rate capacity
of state-of-the-art LIBs. We accurately reveal the mechanism of the
kinetics-dominated electrochemical sodiation and lithiation reactions of
selenium. We clarify the relationship between the stability and ionic
conductivity of the complex borohydride based lithium ion conductors and
giving guidance on their further investigations. Our findings will shed
light on the development of the next generation, high energy density, and
fast rate advanced lithium ion batteries.
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