Inhwa Lee

Mussel‐Inspired Adhesive Binders for High‐Performance Silicon Nanoparticle Anodes in Lithium‐Ion Batteries

Conjugation of mussel-inspired catechol groups to various polymer backbones results in materials suitable as silicon anode binders. The unique wetness-resistant adhesion provided by the catechol groups allows the silicon nanoparticle electrodes to maintain their structure throughout the repeated volume expansion and shrinkage during lithiation cycling, thus facilitating substantially improved specific capacities and cycle lives of lithium-ion batteries.

Wearable Textile Battery Rechargeable by Solar Energy

Wearable electronics represent a significant paradigm shift in consumer electronics since they eliminate the necessity for separate carriage of devices. In particular, integration of flexible electronic devices with clothes, glasses, watches, and skin will bring new opportunities beyond what can be imagined by current inflexible counterparts. Although considerable progresses have been seen for wearable electronics, lithium rechargeable batteries, the power sources of the devices, do not keep pace with such progresses due to tenuous mechanical stabilities, causing them to remain as the limiting elements in the entire technology. Herein, we revisit the key components of the battery (current collector, binder, and separator) and replace them with the materials that support robust mechanical endurance of the battery. The final full-cells in the forms of clothes and watchstraps exhibited comparable electrochemical performance to those of conventional metal foil-based cells even under severe folding-unfolding motions simulating actual wearing conditions. Furthermore, the wearable textile battery was integrated with flexible and lightweight solar cells on the battery pouch to enable convenient solar-charging capabilities.

Efficient Welding of Silver Nanowire Networks without Post-Processing

Silver nanowire (AgNW) random meshes have attracted considerable attention as flexible and high-performance transparent electrodes. Notably, post-treatment of the AgNW random meshes, such as thermal annealing, is usually required to guarantee comparable optical transparency and electrical conductivity to commercial indium tin oxide (ITO). Here, the integral elements of preparing a high-performance, large-area AgNW random mesh network are discussed. High-performance nanostructured transparent electrodes can be obtained without any post-treatment, thereby relieving the restrictions related to the substrate. Solvent washing and a large-area spray-coating method effectively reduce the wire-wire contact resistances, thus reducing or eliminating the requirement for post-treatment.

Hyperbranched β-Cyclodextrin Polymer as an Effective Multidimensional Binder for Silicon Anodes in Lithium Rechargeable Batteries

Polymeric binders play an important role in electrochemical performance of high-capacity silicon (Si) anodes that usually suffer from severe capacity fading due to unparalleled volume change of Si during cycling. In an effort to find efficient polymeric binders that could mitigate such capacity fading, herein, we introduce polymerized β-cyclodextrin (β-CDp) binder for Si nanoparticle anodes. Unlike one-dimensional binders, hyperbranched network structure of β-CDp presents multidimensional hydrogen-bonding interactions with Si particles and therefore offers robust contacts between both components. Even the Si nanoparticles that lost the original contacts with the binder during cycling recover within the multidimensional binder network, thus creating a self-healing effect. Utilizing these advantageous features, β-CDp-based Si electrode shows markedly improved cycling performance compared to those of other well-known binder cases, especially when combined with linear polymers at an appropriate ratio to form hybrid binders.

Millipede-inspired structural design principle for high performance polysaccharide binders in silicon anodes

We systematically investigate polysaccharide binders for high-capacity silicon anodes in lithium ion batteries to find critical factors for the binder function. Analogous to the millipedes strong adhesion based on adhesive pads located on each leg, xanthan gum exhibits the best performance by utilizing its double helical superstructure with side chains and ion–dipole interactions, revealing the great importance of the superstructure and charge interactions in the Si binder design.

Systematic Molecular-Level Design of Binders Incorporating Meldrum's Acid for Silicon Anodes in Lithium Rechargeable Batteries

Covalent or Noncovalent? Systematic investigation of polymeric binders incorporating Meldrums acid reveals most critical binder properties for silicon -anodes in lithium ion batteries, that is self-healing effect facilitated by a series of noncovalent interactions.

Synergistic enhancement and mechanism study of mechanical and moisture stability of perovskite solar cells introducing polyethylene-imine into the CH3NH3PbI3/HTM interface

High performance perovskite solar cells with high stability in moist air are required for their practical applications. We have developed a simple approach to enhance device stability via the introduction of a polyethyleneimine (PEI) compatibilizer between the perovskite (CH3NH3PbI3) and upper hole transporting material layers (HTMs). The PEI effectively reduces moisture intrusion into the CH3NH3PbI3 layer under a high humidity condition. Moreover, the incorporation of PEI increases the adhesion at the CH3NH3PbI3/HTM interface, which allows the protective HTMs to strongly adhere onto the CH3NH3PbI3 layer during degradation and significantly decreases the direct exposure of CH3NH3PbI3 to moist air. As a result, the solar cell device was found to exhibit remarkably improved moisture stability, maintaining a performance of 85% for 14 days of exposure to 85% relative humidity without any encapsulation. We investigated the effects of the PEI introduction on the perovskite solar cell properties and demonstrated for the first time that the strong adhesion of the CH3NH3PbI3/HTM layer results in a perovskite solar cell device that is not only mechanically stable but also exhibits high long-term stability.

Simultaneously Enhancing the Cohesion and Electrical Conductivity of PEDOT:PSS Conductive Polymer Films using DMSO Additives

UNLABELLED Conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PEDOT PSS) has attracted significant attention as a hole transport and electrode layer that substitutes metal electrodes in flexible organic devices. However, its weak cohesion critically limits the reliable integration of PEDOT PSS in flexible electronics, which highlights the importance of further investigation of the cohesion of PEDOT PSS. Furthermore, the electrical conductivity of PEDOT PSS is insufficient for high current-carrying devices such as organic photovoltaics (OPVs) and organic light emitting diodes (OLEDs). In this study, we improve the cohesion and electrical conductivity through adding dimethyl sulfoxide (DMSO), and we demonstrate the significant changes in the properties that are dependent on the wt % of DMSO. In particular, with the addition of 3 wt % DMSO, the maximum enhancements for cohesion and electrical conductivity are observed where the values increase by 470% and 6050%, respectively, due to the inter-PEDOT bridging mechanism. Furthermore, when OLED devices using the PEDOT PSS films are fabricated using the 3 wt % DMSO, the display exhibits 18% increased current efficiency.

Role of a paramagnetic amorphous CoZr seed layer in CoCrPt/Ti perpendicular recording media

A fresh CoZr45 paramagnetic amorphous layer of 20 nm thickness is introduced as a seed layer prior to the Ti underlayer deposition on glass substrate in CoCrPt/Ti perpendicular recording media. By the fresh layer introduction, the thickness of Ti underlayer could be reduced to 100 A to obtain good perpendicular magnetic properties. The cause of this reduction of the critical Ti underlayer thickness is the formation of a more smooth and absorbed impurity free surface by the CoZr layer deposition. This ensures better aligned and finer Ti grain formation at an early stage. Details of the improvements of magnetic properties are discussed. In the second half, we are reporting high Ku behaviors of the CoCrPt/Ti films when the magnetic layers are thinner than 200 A. The high Ku behavior was associated with the (10.0) lattice expansion of the Co alloy to maintain coherency with (10.0) lattice of the Ti film at the interfaces. These will be discussed.

Large area multi-stacked lithium-ion batteries for flexible and rollable applications

The demand for lithium ion batteries (LIBs) in various flexible mobile electronic devices is continuously increasing. With this in mind, a vast number of smart approaches, such as implementation of conductive nanomaterials onto paper and textiles, have been recently demonstrated. Most of them were, however, limited to the single-cell level. In the present study, large area flexible battery modules were developed in an attempt to expand the knowledge and design accumulated from the single-cell level approaches to larger-scale applications. A multi-stacked configuration was adopted to produce a high areal energy density in each single-cell. Meanwhile textile-based electrodes on both sides grant mechanical stability, even on the module level, by efficiently releasing the stress generated during aggressive folding and rolling motions. Moreover, the connection between and stacking of the single-cells allow the wide tuning of the overall voltage and capacity of the module. This battery design should be immediately applicable to a broad range of outdoor, building, and military items.