Kyu Hwan Oh

Because human-computer interactions are increasingly important, touch panels may require stretchability and biocompatibility in order to allow integration with the human body. However, most touch panels have been developed based on stiff and brittle electrodes. We demonstrate an ionic touch panel based on a polyacrylamide hydrogel containing lithium chloride salts. The panel is soft and stretchable, so it can sustain a large deformation. The panel can freely transmit light information because the hydrogel is transparent, with 98% transmittance for visible light. A surface-capacitive touch system was adopted to sense a touched position. The panel can be operated under more than 1000% areal strain without sacrificing its functionalities. Epidermal touch panel use on skin was demonstrated by writing words, playing a piano, and playing games.

Microscale C-Li4Ti5O12 particles with high tap density were synthesized by a simple solid-state reaction using TiO2, Li2CO3, and pitch. The effect of the carbon content on the physicochemical and electrochemical properties of this material was extensively studied. On calcination of the particles at high temperature in an inert atmosphere, the uniformly coated carbon layer from pitch inhibited the growth of primary particles, maintaining the spherical morphology, similar to the TiO2 precursor in size and shape, and also enabling partial reduction of the starting Ti4+ to Ti3+. Excellent electronic conductivity of the C-coated Li4Ti5O12 resulted from the presence of the highly conducting carbon coating layer and the mixed valence state of Ti3+ and Ti4+. Both the nanoporous morphology and highly conducting carbon coating layer in Li4Ti5O12 particles gave rise to ultra high rate capability.

Micrometer-size LiFePO4 spheres with homogeneous double carbon coating layers have been prepared as potential electrode materials for battery applications. The double carbon-coated LiFePO4 electrodes in a lithium-ion cell exhibited discharge capacities of the order of 160 mAh g−1 and 115 mAh g−1 at 25 °C under 0.1 C-rate and 10 C-rate, respectively. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

We are currently in the midst of a race to discover and develop new battery materials capable of providing high energy-density at low cost. By combining a high-performance Si electrode architecture with a room temperature ionic liquid electrolyte, here we demonstrate a highly energy-dense lithium-ion cell with an impressively long cycling life, maintaining over 75% capacity after 500 cycles. Such high performance is enabled by a stable half-cell coulombic efficiency of 99.97%, averaged over the first 200 cycles. Equally as significant, our detailed characterization elucidates the previously convoluted mechanisms of the solid-electrolyte interphase on Si electrodes. We provide a theoretical simulation to model the interface and microstructural-compositional analyses that confirm our theoretical predictions and allow us to visualize the precise location and constitution of various interfacial components. This work provides new science related to the interfacial stability of Si-based materials while granting positive exposure to ionic liquid electrochemistry. Silicon is a promising anode material for lithium ion batteries, but suffers from structural degradation during operations. Here, the authors combine silicon with a room temperature ionic liquid to stabilize the electrode-electrolyte interface and achieve long-term cyclability.