Lithium-ion battery electrolyte mobility at nano-confined graphene interfaces

Abstract

Interfaces are essential in electrochemical processes, providing a critical nanoscopic design feature for composite electrodes used in Li-ion batteries. Understanding the structure, wetting and mobility at nano-confined interfaces is important for improving the efficiency and lifetime of electrochemical devices. Here we use a Surface Forces Apparatus to quantify the initial wetting of nanometre-confined graphene, gold and mica surfaces by Li-ion battery electrolytes. Our results indicate preferential wetting of confined graphene in comparison with gold or mica surfaces because of specific interactions of the electrolyte with the graphene surface. In addition, wetting of a confined pore proceeds via a profoundly different mechanism compared with wetting of a macroscopic surface. We further reveal the existence of molecularly layered structures of the confined electrolyte. Nanoscopic confinement of less than 4–5 nm and the presence of water decrease the mobility of the electrolyte. These results suggest a lower limit for the pore diameter in nanostructured electrodes.

Wettability and Applications of Nanochannels

“…Understanding the water wettability and mobility in 2D nanochannels is important for design of nanoscopic composite electrodes used in Li‐ion batteries to improve their efficiency and lifetime. Moeremans et al quantified the initial wetting of nanochannels of mica–mica, mica–gold and mica–graphene by electrolytes with a Surface Forces Apparatus . For mica–gold and mica–mica experiments, the system remained stable after the initial drop, demonstrating no wetting of the dried nanochannels by the electrolytes ( Figure a).…”

“…b) Population analysis for opposing materials: mica–gold, mica–mica, and mica–graphene. a,b) Reproduced with permission . Copyright 2016, Nature Publishing Group.…”

“…The explorations of 1D nanochannels wettability include CNTs, boron nitride nanotubes (BNNTs), polymeric nanochannels, alumina nanochannels, and silicon nitride nanochannels . 2D nanochannels comprised of graphene, mica, gold, reduced graphene oxide (rGO), and graphene oxide are studied to understand the confined 2D nanochannels wettability. The utilization of 3D nanochannels for wettability research contains porous carbon, porous metal, mesoporous silica, porous titanium dioxide, shale nanopores, and metal‐organic frameworks (MOFs) .…”

Role of hydration energy and co-ions association on monovalent and divalent cations adsorption at mica-aqueous interface

“…The Gouy-Chapman theory assumes ions to be point charges and describe their distribution in the diffuse layer successfully, however, fails to predict their adsorption in the Stern layer 16 , 17 . Thus, a molecular level understanding of the ions distribution, role of hydration energy and co-ions association in the Stern layer is essential for enhancing the above processes, especially for improving charge densities in electrochemical devices 18 , 19 to meet the growing energy demand, and for exploiting the metal ion exchange capability of naturally available clay minerals for remediation of nuclear waste 1 , 20 , 21 .…”

A 3-mirror surface force balance for the investigation of fluids confined to nanoscale films between two ultra-smooth polarizable electrodes

“…15 Other asymmetric setups have been proposed using mica and a Hg droplet 16 or mica and graphene. 17 However, the asymmetry and inability to directly measure or control the electrical potential of the mica surface limit the type of experiments that can be performed and pose challenges to the interpretation of the experimental results.…”