Myoungsoo Shin

High-performance silicon-based multicomponent battery anodes produced via synergistic coupling of multifunctional coating layers

Nanostructured Si-based materials are key building blocks for next-generation energy storage devices. To meet the requirements of practical energy storage devices, Si-based materials should exhibit high-power, low volume change, and high tap density. So far, there have been no reliable materials reported satisfying all of these requirements. Here, we report a novel Si-based multicomponent design, in which the Si core is covered with multifunctional shell layers. The synergistic coupling of Si with the multifunctional shell provides vital clues for satisfying all Si anode requirements for practical batteries. The Si-based multicomponent anode delivers a high capacity of ∼1000 mA h g−1, a highly stable cycling retention (∼65% after 1000 cycles at 1 C), an excellent rate capability (∼800 mA h g−1 at 10 C), and a remarkably suppressed volume expansion (12% after 100 cycles). Our synthetic process is simple, low-cost, and safe, facilitating new methods for developing electrode materials for practical energy storage.

Large‐Scale Synthesis of Interconnected Si/SiOx Nanowire Anodes for Rechargeable Lithium‐Ion Batteries

Down to the wire: Three-dimensional interconnected Si-based nanowires are produced through the combination of thermal decomposition of SiO and a metal-catalyzed nanowire growth process. This low-cost and scalable approach provides a promising candidate for high-capacity anodes in lithium-ion batteries.

Control of Interfacial Layers for High-Performance Porous Si Lithium-Ion Battery Anode

We demonstrate a facile synthesis of micrometer-sized porous Si particles via copper-assisted chemical etching process. Subsequently, metal and/or metal silicide layers are introduced on the surface of porous Si particles using a simple chemical reduction process. Macroporous Si and metal/metal silicide-coated Si electrodes exhibit a high initial Coulombic efficiency of ∼90%. Reversible capacity of carbon-coated porous Si gradually decays after 80 cycles, while metal/metal silicide-coated porous Si electrodes show significantly improved cycling performance even after 100 cycles with a reversible capacity of >1500 mAh g(-1). We confirm that a stable solid-electrolyte interface layer is formed on metal/metal silicide-coated porous Si electrodes during cycling, leading to a highly stable cycling performance.

Amphiphilic Graft Copolymers as a Versatile Binder for Various Electrodes of High‐Performance Lithium‐Ion Batteries

It is known that grafting one polymer onto another polymer backbone is a powerful strategy capable of combining dual benefits from each parent polymer. Thus amphiphilic graft copolymer precursors (poly(vinylidene difluoride)-graft-poly(tert-butylacrylate) (PVDF-g-PtBA)) have been developed via atom transfer radical polymerization, and demonstrated its outstanding properties as a promising binder for high-performance lithium-ion battery (LIB) by using in situ pyrolytic transformation of PtBA to poly(acrylic acid) segments. In addition to its superior mechanical properties and accommodation capability of volume expansion, the Si anode with PVDF-g-PtBA exhibits the excellent charge and discharge capacities of 2672 and 2958 mAh g(-1) with the capacity retention of 84% after 50 cycles. More meaningfully, the graft copolymer binder shows good operating characteristics in both LiN0.5 M1.5 O4 cathode and neural graphite anode, respectively. By containing such diverse features, a graft copolymer-loaded LiN0.5 M1.5 O4 /Si-NG full cell has been successfully achieved, which delivers energy density as high as 546 Wh kg(-1) with cycle retention of ≈70% after 50 cycles (1 C). For the first time, this work sheds new light on the unique nature of the graft copolymer binders in LIB application, which will provide a practical solution for volume expansion and low efficiency problems, leading to a high-energy-density lithium-ion chemistry.

Revisiting Surface Modification of Graphite: Dual‐Layer Coating for High‐Performance Lithium Battery Anode Materials

Surface modification of electrode active materials has garnered considerable attention as a facile way to meet stringent requirements of advanced lithium-ion batteries. Here, we demonstrated a new coating strategy based on dual layers comprising antimony-doped tin oxide (ATO) nanoparticles and carbon. The ATO nanoparticles are synthesized via a hydrothermal method and act as electronically conductive/electrochemically active materials. The as-synthesized ATO nanoparticles are introduced on natural graphite along with citric acid used as a carbon precursor. After carbonization, the carbon/ATO-decorated natural graphite (c/ATO-NG) is produced. In the (carbon/ATO) dual-layer coating, the ATO nanoparticles coupled with the carbon layer exhibit unprecedented synergistic effects. The resultant c/ATO-NG anode materials display significant improvements in capacity (530 mA h g(-1) ), cycling retention (capacity retention of 98.1 % after 50 cycles at a rate of C/5), and low electrode swelling (volume expansion of 38 % after 100 cycles) which outperform that of typical graphite materials. Furthermore, a full-cell consisting of a c/ATO-NG anode and an LiNi0.5 Mn1.5 O4 cathode presents excellent cycle retention (capacity retention of >80 % after 100 cycles). We envision that the dual-layer coating concept proposed herein opens a new route toward high-performance anode materials for lithium-ion batteries.

Hierarchical multiscale hyperporous block copolymer membranes via tunable dual-phase separation

A new class of amphiphilic block copolymer–based porous membranes is fabricated via tunable dual-phase separation. The rational design and realization of revolutionary porous structures have been long-standing challenges in membrane science. We demonstrate a new class of amphiphilic polystyrene-block-poly(4-vinylpyridine) block copolymer (BCP)–based porous membranes featuring hierarchical multiscale hyperporous structures. The introduction of surface energy–modifying agents and the control of major phase separation parameters (such as nonsolvent polarity and solvent drying time) enable tunable dual-phase separation of BCPs, eventually leading to macro/nanoscale porous structures and chemical functionalities far beyond those accessible with conventional approaches. Application of this BCP membrane to a lithium-ion battery separator affords exceptional improvement in electrochemical performance. The dual-phase separation–driven macro/nanopore construction strategy, owing to its simplicity and tunability, is expected to be readily applicable to a rich variety of membrane fields including molecular separation, water purification, and energy-related devices.

pH-tunable plasmonic properties of Ag nanoparticle cores in block copolymer micelle arrays on Ag films

Particle-on-film plasmonic systems provide interesting plasmonic properties, which can be easily tuned by controlling the particle–film gaps. However, there has been no study on the active control of gap distances and the resulting plasmonic properties in response to the external stimuli. In this study, we introduce a particle–film plasmonic system with the ability of active control of particle–film gap distances and thus the plasmonic properties based on pH-responsive block copolymer micelle–metal monolayer arrays on metal films. We synthesize pH-sensitive polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) spherical micelles that contain Ag nanoparticles in the micellar core. Then, we demonstrate that the pH-sensitive micelle monolayer films on Ag films modulate gap distances between the Ag nanoparticles (Ag NPs) within micelle cores and Ag films, leading to great changes in particle–film plasmon couplings (gap plasmons) that strongly influence the surface-enhanced Raman scattering (SERS) signal. The suggested plasmonic system with dynamic plasmonic properties will play a critical role in diverse applications such as chemical and biosensors, diagnostics, and smart optical devices.

Zinc‐Reduced Mesoporous TiOx Li‐Ion Battery Anodes with Exceptional Rate Capability and Cycling Stability

We demonstrate a unique synthetic route for oxygen-deficient mesoporous TiOx by a redox-transmetalation process by using Zn metal as the reducing agent. The as-obtained materials have significantly enhanced electronic conductivity; 20 times higher than that of as-synthesized TiO2 material. Moreover, electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT) measurements are performed to validate the low charge carrier resistance of the oxygen-deficient TiOx . The resulting oxygen-deficient TiOx battery anode exhibits a high reversible capacity (∼180 mA h g-1 at a discharge/charge rate of 1 C/1 C after 400 cycles) and an excellent rate capability (∼90 mA h g-1 even at a rate of 10 C). Also, the full cell, which is coupled with a LiCoO2 cathode material, exhibits an outstanding rate capability (>75 mA h g-1 at a rate of 3.0 C) and maintains a reversible capacity of over 100 mA h g-1 at a discharge/charge of 1 C/1 C for 300 cycles.