No abstract

Artificial skins reproducing properties of human skin are emerging and significant for study in various areas, such as robotics, medicine, and textiles. Perspiration, as one of the most imperative thermoregulation functions of human skin, is gaining increasing attention, but how to realize ideal artificial skin for perspiration simulation remains challenging. Here, an integrated 3D hydrophilicity/hydrophobicity design is proposed for artificial sweating skin (i‐TRANS). Based on normal fibrous wicking materials, the selective surface modification with gradient of poly(dimethylsiloxane) (PDMS) creates hydrophilicity/hydrophobicity contrast in both lateral and vertical directions. With the additional help of bottom hydrophilic Nylon 6 nanofibers, the constructed i‐TRANS is able to transport “sweat” directionally without trapping undesired excess water and attain uniform “secretion” of sweat droplets on the top surface, decently mimicking human skin perspiration situation. This fairly comparable simulation not only presents new insights for replicating skin properties, but also provides proper in vitro testing platforms for perspiration‐relevant research, greatly avoiding unwanted interference from the “skin” layer. In addition, the facile, fast, and cost‐effective fabrication approach and versatile usage of i‐TRANS can further facilitate its application.

Electrolyte engineering is a critical approach to improve battery performance, particularly for lithium metal batteries. In this work, we introduce the concept of high entropy electrolytes (HEEs) that achieve improved ionic conductivity while maintaining excellent electrochemical stability. We find that increasing the molecular diversity and concomitantly the mixing entropy of weakly solvating electrolytes can reduce ion clustering while retaining anion-rich solvation structure, confirmed through synchrotron-based X-ray scattering and molecular dynamics simulations. Less clustered electrolytes exhibit higher diffusivity and ionic conductivity, enabling high current density cycling up to 2C (> 6 mA cm-2) for up to ~80 cycles in anode-free NMC-Cu pouch cells. We substantiate the generality of the concept by verifying performance improvement in three disparate electrolyte systems. This work highlights a large unexplored design space of HEEs that can improve electrolyte properties for lithium metal batteries.

Electrolyte engineering is crucial for improving battery performance, particularly for lithium metal batteries. Recent advances in electrolytes have greatly improved cyclability by enhancing electrochemical stability at the electrode interfaces, but concurrently achieving high ionic conductivity has remained challenging. Here we report an electrolyte design strategy for enhanced lithium metal batteries by increasing the molecular diversity in electrolytes, which essentially leads to high entropy electrolytes (HEEs). We find that in weakly solvating electrolytes, the entropy effect reduces ion clustering while preserving the characteristic anion-rich solvation structures, which is characterized by synchrotron-based X-ray scattering and molecular dynamics simulations. Electrolytes with smaller-sized clusters exhibit a 2-fold improvement in ionic conductivity compared to conventional weakly-solvating electrolytes, enabling stable cycling at high current densities up to 2C (6.2 mA cm-2) in anode-free LiNi0.6Mn0.2Co0.2 (NMC622) || Cu pouch cells. The efficacy of the design strategy is verified by performance improvements in three disparate weakly solvating electrolyte systems.