Lithium alloy anodes in the form of dense foils offer significant potential advantages over lithium metal and particulate alloy anodes for solid-state batteries (SSBs). However, the reaction and degradation mechanisms of dense alloy anodes remain largely unexplored. Here, we investigate the electrochemical lithiation/delithiation behavior of 12 elemental alloy anodes in SSBs with Li6PS5Cl solid-state electrolyte (SSE), enabling direct behavioral comparisons. The materials show highly divergent first-cycle Coulombic efficiency, ranging from 99.3% for indium to â¼20% for antimony. Through microstructural imaging and electrochemical testing, we identify lithium trapping within the foil during delithiation as the principal reason for low Coulombic efficiency in most materials. The exceptional Coulombic efficiency of indium is found to be due to unique delithiation reaction front morphology evolution in which the high-diffusivity LiIn phase remains at the SSE interface. This study links composition to reaction behavior for alloy anodes and thus provides guidance toward better SSBs.
Control over material structure and morphology during electrodeposition is necessary for material synthesis and energy applications. One approach to guide crystallite formation is to take advantage of epitaxy on a current collector to facilitate crystallographic control. Single-layer graphene on metal foils can promote "remote epitaxy" during Cu and Zn electrodeposition, resulting in growth of metal that is crystallographically aligned to the substrate beneath graphene. However, the substrate-graphene-deposit interactions that allow for epitaxial electrodeposition are not well understood. Here, we investigate how different graphene layer thicknesses (monolayer, bilayer, trilayer, and graphite) influence the electrodeposition of Zn and Cu. Scanning transmission electron microscopy and electron backscatter diffraction are leveraged to understand metal morphology and structure, demonstrating that remote epitaxy occurs on mono- and bilayer graphene but not trilayer or thicker. Density functional theory (DFT) simulations reveal the spatial electronic interactions through thin graphene that promote remote epitaxy. This work advances our understanding of electrochemical remote epitaxy and provides strategies for improving control over electrodeposition.
Metal negative electrodes that alloy with lithium have high theoretical charge storage capacity and are ideal candidates for developing high-energy rechargeable batteries. However, such electrode materials show limited reversibility in Li-ion batteries with standard non-aqueous liquid electrolyte solutions. To circumvent this issue, here we report the use of non-pre-lithiated aluminum-foil-based negative electrodes with engineered microstructures in an all-solid-state Li-ion cell configuration. When a 30-µm-thick Al94.5In5.5 negative electrode is combined with a Li6PS5Cl solid-state electrolyte and a LiNi0.6Mn0.2Co0.2O2-based positive electrode, lab-scale cells deliver hundreds of stable cycles with practically relevant areal capacities at high current densities (6.5 mA cm-2). We also demonstrate that the multiphase Al-In microstructure enables improved rate behavior and enhanced reversibility due to the distributed LiIn network within the aluminum matrix. These results demonstrate the possibility of improved all-solid-state batteries via metallurgical design of negative electrodes while simplifying manufacturing processes.
Ion-solid surface interactions are one of the fundamental principles in liquid-interfacing devices ranging from various electrochemical systems to electrolyte-driven energy conversion devices. The interplays between these two phases, especially containing charge carriers in the solid layer, work as a pivotal role in the operation of these devices, but corresponding details of those effects remain as unrevealed issues in academic fields. Herein, an ion-charge carrier interaction at an electrolyte-semiconductor interface is interrogated with an ion-dynamics-induced (ionovoltaic) energy transducer, controlled by interfacial self-assembled molecules. An electricity generating mechanism from interfacial ionic diffusion is elucidated in terms of the ion-charge carrier interaction, originated from a dipole potential effect of the self-assembled molecular layer (SAM). In addition, this effect is found to be modulated via chemical functionalization of the interfacial molecular layer and transition metal ion complexation therein. With the aiding of surface analytic techniques and a liquid-interfacing Hall measurement, electrical behaviors of the device depending on the magnitude of the ion-ligand complexation are interrogated, thereby demonstrating the ion-charge carrier interplays spanning at electrolyte-SAM-semiconductor interface. Hence, this system can be applied to study molecular interactions, including chemical and physical influences, occurring at the solid-liquid interfacial region.
A surficial molecular dipole effect depending on ion-molecular interactions has been crucial issues regarding to an interfacial potential, which can modulate solid electronic and electrochemical systems. Their properties near the interfacial region can be dictated by specific interactions between surface and adsorbates, but understandings of the corresponding details remain at interesting issues. Here, intuitive observations of an ionic pair formation-induced interfacial potential shifts are presented with an ionovoltaic system, and corresponding output signal variations are analyzed in terms of the surficial dipole changes on self-assembled monolayer. With aiding of photoelectron spectroscopies and density function theory simulation, the ionic pair formation-induced potential shifts are revealed to strongly rely on a paired molecular structure and a binding affinity of the paired ionic moieties. Chemical contributions to the binding event are interrogated in terms of polarizability in each ionic group and consistent with chaotropic/kosmotropic character of the ionic groups. Based on these findings, the ionovoltaic output changes are theoretically correlated with an adsorption isotherm reflecting the molecular dipole effect, thereby demonstrating as an efficient interfacial molecular probing method under electrolyte interfacing conditions.
Water-infiltration-induced power generation has the renewable characteristic of generating electrical energy from ambient water. Importantly, it is found that the carrier concentration in semiconductor constituting the energy generator seriously affect the electricity generation. Nevertheless, few studies are conducted on the influence of semiconductor carrier concentration, a crucial factor on electricity generation. Due to this, understanding of the energy harvesting mechanism is still insufficient. Herein, the semiconductor carrier concentration-dependent behavior in water-infiltration-induced electricity generation and the energy harvesting mechanism by ionovoltaic effect are comprehensively verified. A clue to enhance the electric power generation efficiency is also proposed. When 20 µL of water (NaCl, 0.1 m) infiltrates into a porous CuO nanowires film (PCNF), electric power of ≈0.5 V and ≈1 µA are produced for 25 min. Moreover, the PCNF shows good practicability by generating electricity using various ambient water, turning on LEDs, and being fabricated as a curved one.
Electricity , Water , Semiconductors
The change in electrical properties of electrodes by adsorption or desorption at interfaces is a well-known phenomenon required for signal production in electrically transduced sensing technologies. Furthermore, in terms of electrolyte-insulator-semiconductor (EIS) structure, several studies of energy conversion techniques focused on ion-adsorption at the solid-liquid interface have suggested that the electric signal is generated by ionovoltaic phenomena. However, finding substantial clues for the ion-adsorption phenomena in the EIS structure is still a difficult task because direct evidence for carrier accumulation in semiconductors by Coulomb interactions is insufficient. Here, a sophisticated Hall measurement system is demonstrated to quantitatively analyze accumulated electron density-change inside the semiconductor depending on the ion-adsorption at the solid-liquid interface. Also, an enhanced EIS-structured device is designed in an aqueous-soaked system that works with the ionovoltaic principle to monitor the ion-dynamics in liquid electrolyte media, interestingly confirming ion-concentration dependence and ion-specificity by generated peak voltages. This newly introduced peculiar method contributes to an in-depth understanding of the ionovoltaic phenomena in terms of carrier actions in the semiconductors and ionic behaviors in the aqueous-bulk phases, providing informative analysis about interfacial adsorptions that can expand the scope of ion-sensing platforms.
Aqueous ion-solid interfacial interactions at an electric double layer (EDL) are studied in various research fields. However, details of the interactions at the EDL are still not fully understood due to complexity induced from the specific conditions of the solid and liquid parts. Several technical tools for ion-solid interfacial probing are experimentally and practically proposed, but they still show limitations in applicability due to the complicated measurements. Recently, an energy conversion device based on ion dynamics (called ionovoltaic device) was also introduced as another monitoring tool for the EDL, showing applicability as a novel probing method for interfacial interactions. Herein, a monitoring technique for specific ion adsorption (Cu2+ and Pb2+ in the range of 5 × 10-6 -1000 × 10-6 m) in the solid-liquid interface based on the ionovoltaic device is newly demonstrated. The specific ion adsorption and the corresponding interfacial potentials profiles are also investigated to elucidate a working mechanism of the device. The results give the insight of molecular-level ion adsorption through macroscopic water-motion-induced electricity generation. The simple and cost-effective detection of the device provides an innovative route for monitoring specific adsorption and expandability as a monitoring tool for various solid-liquid interfacial phenomena that are unrevealed.
A new class of simple and highly sensitive piezocapacitive sensors that are capable of detecting static and dynamic pressure changes is reported. The pressure sensor structure is formed by vertically sandwiching a sandpaper-molded carbon nanotube/poly(dimethylsiloxane) composite (CPC) dielectric layer between two ion-gel thin film electrodes. Such a capacitive sensor system enables the distinguishable detection of directional movement of applied pressure as well as static pressure variation by modulating ion distribution in the ion-gel thin films. The resulting capacitive pressure sensors exhibit high sensitivity (9.55 kPa-1), high durability, and low operating voltage (0.1 V). Our proposed pressure sensors are successfully applied as potential platforms for monitoring human physiological signals and finger sliding motions in order to demonstrate their capability for practical usage. The outstanding sensor performance of the pressure sensors can permit applications in wearable electronic devices for human-machine connecting platforms, health care monitoring systems, and artificial skin.
We report a new class of simple microfluidic strain sensors with high stretchability, transparency, sensitivity, and long-term stability with no considerable hysteresis and a fast response to various deformations by combining the merits of microfluidic techniques and ionic liquids. The high optical transparency of the strain sensors was achieved by introducing refractive-index matched ionic liquids into microfluidic networks or channels embedded in an elastomeric matrix. The microfluidic strain sensors offer the outstanding sensor performance under a variety of deformations induced by stretching, bending, pressing, and twisting of the microfluidic strain sensors. The principle of our microfluidic strain sensor is explained by a theoretical model based on the elastic channel deformation. In order to demonstrate its capability of practical usage, the simple-structured microfluidic strain sensors were performed onto a finger, wrist, and arm. The highly stretchable and transparent microfluidic strain sensors were successfully applied as potential platforms for distinctively monitoring a wide range of human body motions in real time. Our novel microfluidic strain sensors show great promise for making future stretchable electronic devices.
Biosensing Techniques/methods , Microfluidics/methods , Motion , Nanotechnology/methods , Human Body , Humans
