There
is a keen interest in the use of electrochromic materials
because they can regulate light and heat, thereby reducing the cooling
and heating energy. However, the long response time, short cycle life,
and high power consumption of an electrochromic film hinder its development.
Here, we report an electrochromic material of complex niobium tungsten
oxides. The Nb18W16O93 thin films
in the voltage range of 0 to −1.5 V show good redox kinetics
with the coloration time of 4.7 s and bleaching time of 4.0 s, respectively.
The electrochromic device based on the Nb18W16O93 thin film has an optical modulation of 53.1% at a
wavelength of 633 nm, with the coloration efficiency of ∼46.57
cm2 C–1. An excellent electrochemical
stability of 78.1% retention after 8000 cycles is also achieved. These
good performances are due to the fast and stable Li-ion intercalation/extraction
in the open framework of Nb18W16O93 with multiple ion positions. Our work provides a strategy for electrochromic
materials with fast response time and good cycle stability.
The
uncontrolled deposition/dissolution process of lithium dendrites
during electrochemical cycling in batteries limits the large-scale
application of Li metal anodes. Investigating the microstructure of
Li dendrites is a focal point. Currently, the only way to protect
and observe sensitive Li dendrites is through low-temperature transmission
electron microscopy (LT-TEM), whereas room-temperature characterization
is still lacking. In this work, the room-temperature microstructure
of Li dendrites was obtained by TEM using both vacuum- and inert-gas-transfer
methods. Detailed comparison between LT- and room-temperature (RT-)TEM
characterizations was provided to show the pros and cons of each method.
Especially, RT-TEM shows the advantage of flexible incorporation with
multifunctional characterizations, such as 3D tomography. By using
RT-TEM, microstructural evolution of Li dendrites during the electrodeposition/dissolution
process, including increase of the quantity of inorganic Li2O compounds in the solid electrolyte interphase, lateral growth behavior,
and two types of inactive Li, has been revealed, enriching the understanding
of the structure–property relationship of Li dendrites.
Solid-state
batteries using ceramic solid electrolytes promise
to deliver enhanced energy density and intrinsic safety. However,
the challenge of integrating solid electrolytes with electrode materials
limits the electrochemical performance. Herein, we report a solvent-free
ceramic-based lithium-metal battery with good cycling stability at
a wide temperature range from 45 to 100 °C, enabled by an inorganic
ternary salt of low eutectic point. By using a garnet electrolyte
with molten salts at the electrolyte|cathode interface, the Li||LiFePO4 cells perform a long cycling with capacity retention of 81.4%
after 1000 cycles at 1 C. High-voltage LiFe0.4Mn0.6PO4 cathodes also deliver good electrochemical performance.
Specifically, commercial electrode pieces with high area capacities
can be adopted directly in the quasi-solid-state lithium-metal batteries.
These stable performances are ascribable to the low melting point,
high ionic conductivity and good thermal/electrochemical stability
of the ternary salt system. Our findings provide an effective method
on fabrication of solid-state batteries for practical applications.
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