3 research outputs found
Magnesium Anode Pretreatment Using a Titanium Complex for Magnesium Battery
Although
magnesium batteries have received a great deal of attention
as a promising power source, the native oxide layer on the Mg surface
significantly impedes practical applications, because of the sluggish
kinetic behavior of Mg-ion deposition and dissolution. Here, a new
approach to improve electrochemical reactivity of Mg anode is proposed,
based on chemical pretreatment of the Mg anode using a titanium complex,
TiÂ(TFSI)<sub>2</sub>Cl<sub>2</sub>, that effectively removes the native
oxide layer on the Mg anode surface. The pretreatment of the Mg anode
by TiÂ(TFSI)<sub>2</sub>Cl<sub>2</sub> remarkably decreases the binding
affinity between Mg and O via the formation of a multicoordinate complex
(Mg–O–Ti). Thereafter, a series of chemical reactions
cleave the Mg–O bonds, resulting in a fresh Mg surface. This
creates a cell comprised of the TiÂ(TFSI)<sub>2</sub>Cl<sub>2</sub>-pretreated Mg anode, glyme-based electrolytes, and cathode material
that exhibits reversible electrochemical behavior at the electrode/electrolyte
interface, resulting in practical applicability and good electrochemical
performance
Anion Engineering for Stabilizing Li Interstitial Sites in Halide Solid Electrolytes for All-Solid-State Li Batteries
Halide solid electrolytes (SEs) have been highlighted
for their
high-voltage stability. Among the halide SEs, the ionic conductivity
has been improved by aliovalent metal substitutions or choosing a
ccp-like anion-arranged monoclinic structure (C2/m) over hcp- or bcc-like anion-arranged structures. Here,
we present a new approach, hard-base substitution, and its underlying
mechanism to increase the ionic conductivity of halide SEs. The oxygen
substitution to Li2ZrCl6 (trigonal, hcp) increased
the ionic conductivity from 0.33 to 1.3 mS cm–1 at
Li3.1ZrCl4.9O1.1 (monoclinic, ccp),
while the sulfur and fluorine substitutions were not effective. A
systematic comparison study revealed that the energetic stabilization
of interstitial sites for Li migration plays a key role in improving
the ionic conductivity, and the ccp-like anion sublattice is not sufficient
to achieve high ionic conductivity. We further examined the feasibility
of the oxyhalide SE for practical and all-solid-state battery applications
Bi-Morphological Form of SiO<sub>2</sub> on a Separator for Modulating Li-Ion Solvation and Self-Scavenging of Li Dendrites in Li Metal Batteries
The
lithium (Li) metal anode is highly desirable for high-energy
density batteries. During prolonged Li plating–stripping, however,
dendritic Li formation and growth are probabilistically high, allowing
physical contact between the two electrodes, which results in a cell
short-circuit. Engineering the separator is a promising and facile
way to suppress dendritic growth. When a conventional coating approach
is applied, it usually sacrifices the bare separator structure and
severely increases the thickness, ultimately decreasing the volumetric
density. Herein, we introduce dielectric silicon oxide with the feature
of bi-morphological form, i.e., backbone-covered and backbone-anchored,
onto the conventional polyethylene separator without any volumetric
change. These functionally vary the Li+ transference number
and the ionic conductivity so as to modulate Li-ion solvation and
self-scavenging of Li dendrites. The proposed separator paves the
way to maximizing the full cell performance of Li/NCM622 toward practical
application