10 research outputs found
Scalable Fracture-free SiOC Glass Coating for Robust Silicon Nanoparticle Anodes in Lithium Secondary Batteries
A variety of silicon (Si) nanostructures
and their complex composites
have been lately introduced in the lithium ion battery community to
address the large volume changes of Si anodes during their repeated
chargeādischarge cycles. Nevertheless, for large-scale manufacturing
it is more desirable to use commercial Si nanoparticles with simple
surface coating. Most conductive coating materials, however, do not
accommodate the volume expansion of the inner Si active phases and
resultantly fracture during cycling. To overcome this chronic limitation,
herein, we report silicon oxycarbide (SiOC) glass as a new coating
material for Si nanoparticle anodes. The SiOC glass phase can expand
to some extent due to its active nature in reacting with Li ions and
can therefore accommodate the volume changes of the inner Si nanoparticles
without disintegration or fracture. The SiOC glass also grows in the
form of nanocluster to bridge Si nanoparticles, thereby contributing
to the structural integrity of secondary particles during cycling.
On the basis of these combined effects, the SiOC-coated Si nanoparticles
reach a high reversible capacity of 2093 mAh g<sup>ā1</sup> with 92% capacity retention after 200 cycles. Furthermore, the coating
and subsequent secondary particle formation were produced by high-speed
spray pyrolysis based on a single precursor solution
Spray Drying Method for Large-Scale and High-Performance Silicon Negative Electrodes in Li-Ion Batteries
Nanostructured
silicon electrodes have shown great potential as
lithium ion battery anodes because they can address capacity fading
mechanisms originating from large volume changes of silicon alloys
while delivering extraordinarily large gravimetric capacities. Nonetheless,
synthesis of well-defined silicon nanostructures in an industrially
adaptable scale still remains as a challenge. Herein, we adopt an
industrially established spray drying process to enable scalable synthesis
of siliconācarbon composite particles in which silicon nanoparticles
are embedded in porous carbon particles. The void space existing in
the porous carbon accommodates the volume expansion of silicon and
thus addresses the chronic fading mechanisms of silicon anodes. The
composite electrodes exhibit excellent electrochemical performance,
such as 1956 mAh/g at 0.05C rate and 91% capacity retention after
150 cycles. Moreover, the spray drying method requires only 2 s for
the formation of each particle and allows a production capability
of ā¼10 g/h even with an ultrasonic-based lab-scale equipment.
This investigation suggests that established industrial processes
could be adaptable to the production of battery active materials that
require sophisticated nanostructures as well as large quantity syntheses
One-Dimensional CarbonāSulfur Composite Fibers for NaāS Rechargeable Batteries Operating at Room Temperature
NaāS batteries are one type
of molten salt battery and have
been used to support stationary energy storage systems for several
decades. Despite their successful applications based on long cycle
lives and low cost of raw materials, NaāS cells require high
temperatures above 300 Ā°C for their operations, limiting their
propagation into a wide range of applications. Herein, we demonstrate
that NaāS cells with solid state active materials can perform
well even at room temperature when sulfur-containing carbon composites
generated from a simple thermal reaction were used as sulfur positive
electrodes. Furthermore, this structure turned out to be robust during
repeated (de)Āsodiation for ā¼500 cycles and enabled extraordinarily
high rate performance when one-dimensional morphology is adopted using
scalable electrospinning processes. The current study suggests that
solid-state NaāS cells with appropriate atomic configurations
of sulfur active materials could cover diverse battery applications
where cost of raw materials is critical
Solution Processed Aluminum Paper for Flexible Electronics
As an alternative to vacuum deposition, preparation of
highly conductive
papers with aluminum (Al) features is successfully achieved by the
solution process consisting of Al precursor ink (AlH<sub>3</sub>{OĀ(C<sub>4</sub>H<sub>9</sub>)<sub>2</sub>}) and low temperature stamping
process performed at 110 Ā°C without any serious hydroxylation
and oxidation problems. Al features formed on several kinds of paper
substrates (calendar, magazine, and inkjet printing paper substrates)
are less than ā¼60 nm thick, and their electrical conductivities
were found to be as good as thermally evaporated Al film or even better
(ā¤2 Ī©/ā”). Strong adhesion of Al features to paper
substrates and their excellent flexibility are also experimentally
confirmed by TEM observation and mechanical tests, such as tape and
bending tests. The solution processed Al features on paper substrates
show different electrical and mechanical performance depending on
the paper type, and inkjet printing paper is found to be the best
substrate with high and stable electrical and mechanical properties.
The Al conductive papers produced by the solution process may be applicable
in disposal paper electronics
Restacking-Inhibited 3D Reduced Graphene Oxide for High Performance Supercapacitor Electrodes
Graphene has received considerable attention in both scientific and technological areas due to its extraordinary material properties originating from the atomically single- or small number-layered structure. Nevertheless, in most scalable solution-based syntheses, graphene suffers from severe restacking between individual sheets and thus loses its material identity and advantages. In the present study, we have noticed the intercalated water molecules in the dried graphene oxide (GO) as a critical mediator to such restacking and thus eliminated the hydrogen bonding involving the intercalated water by treating GO with melamine resin (MR) monomers. Upon addition of MR monomers, porous restacking-inhibited GO sheets precipitated, leading to the carbonaceous composite with an exceptionally large surface area of 1040 m<sup>2</sup>/g after a thermal treatment. Utilizing such high surface area, the final graphene composite exhibited excellent electrochemical performance as a supercapacitor electrode material: specific capacitance of 210 F/g, almost no capacitance loss for 20ā000 cycles, and ā¼7 s rate capability. The current study delivers a message that various condensation reactions engaging GO sheets can be a general synthetic approach for restacking-inhibited graphene in scalable solution processes
Lattice Water for the Enhanced Performance of Amorphous Iron Phosphate in Sodium-Ion Batteries
We report amorphous iron phosphate
with lattice water, namely FePO<sub>4</sub>Ā·<i>x</i>H<sub>2</sub>O (<i>x</i> ā¼ 2.39), as a promising
sodium-ion battery (SIB) cathode.
After carbon coating, micrometer-sized FePO<sub>4</sub>Ā·<i>x</i>H<sub>2</sub>O exhibits a reversible capacity that is higher
than that of its counterpart without lattice water (130.0 vs 50.6
mAhāÆg<sup>ā1</sup> at 0.15<i>C</i> rate) along
with clearly enhanced rate capability and cyclability. The superior
electrochemical performance of FePO<sub>4</sub>Ā·<i>x</i>H<sub>2</sub>O is attributed to the lattice water that facilitates
sodium-ion diffusion via enlarged channel dimensions and the screening
of the electrostatic interactions between sodium ions and host anions.
The amorphous phase is also advantageous in accommodating the stress
created in the host framework during sodium-ion (de)Āintercalation.
The presence of lattice water also protects the oxidation state of
Fe from reductive surface carbon coating and slightly lowers the operation
voltage via reduced inductive effect. The current study provides a
useful insight into how to design SIB electrode materials particularly
focusing on facile sodium-ion diffusion
LithiumāSulfur Capacitors
Although many existing hybrid energy
storage systems demonstrate promising electrochemical performances,
imbalances between the energies and kinetics of the two electrodes
must be resolved to allow their widespread commercialization. As such,
the development of a new class of energy storage systems is a particular
challenge, since future systems will require a single device to provide
both a high gravimetric energy and a high power density. In this context,
we herein report the design of novel lithiumāsulfur capacitors.
The resulting asymmetric systems exhibited energy densities of 23.9ā236.4
Wh kg<sup>ā1</sup> and power densities of 72.2ā4097.3
W kg<sup>ā1</sup>, which are the highest reported values for
an asymmetric system to date. This approach involved the use of a
prelithiated anode and a hybrid cathode material exhibiting anion
adsorptionādesorption in addition to the electrochemical reduction
and oxidation of sulfur at almost identical rates. This novel strategy
yielded both high energy and power densities, and therefore establishes
a new benchmark for hybrid systems
A Half Millimeter Thick Coplanar Flexible Battery with Wireless Recharging Capability
Most of the existing flexible lithium
ion batteries (LIBs) adopt the conventional cofacial cell configuration
where anode, separator, and cathode are sequentially stacked and so
have difficulty in the integration with emerging thin LIB applications,
such as smart cards and medical patches. In order to overcome this
shortcoming, herein, we report a coplanar cell structure in which
anodes and cathodes are interdigitatedly positioned on the same plane.
The coplanar electrode design brings advantages of enhanced bending
tolerance and capability of increasing the cell voltage by in series-connection
of multiple single-cells in addition to its suitability for the thickness
reduction. On the basis of these structural benefits, we develop a
coplanar flexible LIB that delivers 7.4 V with an entire cell thickness
below 0.5 mm while preserving stable electrochemical performance throughout
5000 (un)Ābending cycles (bending radius = 5 mm). Also, even the pouch
case serves as barriers between anodes and cathodes to prevent Li
dendrite growth and short-circuit formation while saving the thickness.
Furthermore, for convenient practical use wireless charging via inductive
electromagnetic energy transfer and solar cell integration is demonstrated
A Half Millimeter Thick Coplanar Flexible Battery with Wireless Recharging Capability
Most of the existing flexible lithium
ion batteries (LIBs) adopt the conventional cofacial cell configuration
where anode, separator, and cathode are sequentially stacked and so
have difficulty in the integration with emerging thin LIB applications,
such as smart cards and medical patches. In order to overcome this
shortcoming, herein, we report a coplanar cell structure in which
anodes and cathodes are interdigitatedly positioned on the same plane.
The coplanar electrode design brings advantages of enhanced bending
tolerance and capability of increasing the cell voltage by in series-connection
of multiple single-cells in addition to its suitability for the thickness
reduction. On the basis of these structural benefits, we develop a
coplanar flexible LIB that delivers 7.4 V with an entire cell thickness
below 0.5 mm while preserving stable electrochemical performance throughout
5000 (un)Ābending cycles (bending radius = 5 mm). Also, even the pouch
case serves as barriers between anodes and cathodes to prevent Li
dendrite growth and short-circuit formation while saving the thickness.
Furthermore, for convenient practical use wireless charging via inductive
electromagnetic energy transfer and solar cell integration is demonstrated
Hierarchical Porous Carbon by Ultrasonic Spray Pyrolysis Yields Stable Cycling in LithiumāSulfur Battery
Utilizing the unparalleled theoretical
capacity of sulfur reaching
1675 mAh/g, lithiumāsulfur (LiāS) batteries have been
counted as promising enablers of future lithium ion battery (LIB)
applications requiring high energy densities. Nevertheless, most sulfur
electrodes suffer from insufficient cycle lives originating from dissolution
of lithium polysulfides. As a fundamental solution to this chronic
shortcoming, herein, we introduce a hierarchical porous carbon structure
in which meso- and macropores are surrounded by outer micropores.
Sulfur was infiltrated mainly into the inner meso- and macropores,
while the outer micropores remained empty, thus serving as a ābarricadeā
against outward dissolution of long-chain lithium polysulfides. On
the basis of this systematic design, the sulfur electrode delivered
1412 mAh/g<sub>sulfur</sub> with excellent capacity retention of 77%
after 500 cycles. Also, a control study suggests that even when sulfur
is loaded into the outer micropores, the robust cycling performance
is preserved by engaging small sulfur crystal structures (S<sub>2ā4</sub>). Furthermore, the hierarchical porous carbon was produced in ultrahigh
speed by scalable spray pyrolysis. Each porous carbon particle was
synthesized through 5 s of carrier gas flow in a reaction tube