Graphene Oxide Induced Surface Modification for Functional Separators in Lithium Secondary Batteries

Abstract

Functional separators, which have additional functions apart from the ionic conduction and electronic insulation of conventional separators, are highly in demand to realize the development of advanced lithium ion secondary batteries with high safety, high power density, and so on. Their fabrication is simply performed by additional deposition of diverse functional materials on conventional separators. However, the hydrophobic wetting nature of conventional separators induces the polarity-dependent wetting feature of slurries. Thus, an eco-friendly coating process of water-based slurry that is highly polar is hard to realize, which restricts the use of various functional materials dispersible in the polar solvent. This paper presents a surface modification of conventional separators that uses a solution-based coating of graphene oxide with a hydrophilic group. The simple method enables the large-scale tuning of surface wetting properties by altering the morphology and the surface polarity of conventional separators, without significant degradation of lithium ion transport. On the surface modified separator, superior wetting properties are realized and a functional separator, applicable to lithium metal secondary batteries, is demonstrated as an example. We believe that this simple surface modification using graphene oxide contributes to successful fabrication of various functional separators that are suitable for advanced secondary batteries.

A Review of Functional Separators for Lithium Metal Battery Applications

“…Kim et al have developed an eco-friendly coating process of GO to fabricate modified functional separators [ 125 ]. Through this method, surface of the separator can be fully covered by GO flakes, which provided the hydrophilic wetting nature owing to many hydrophilic functional groups existing on the GO, enabling eco-friendly water-based slurry method.…”

Synthetic polymer-based membranes for lithium-ion batteries

“…A surface modification of PE separators has been developed via a simple solution-based coating of graphene oxide (GO) with hydrophilic groups as shown in Figure 5.9 [130]. This separator demonstrates that the ceramic and adhesive layers, composed of uniform micron-sized spherical particles, prevent the suppression of Li + diffusion between the NMC532 cathode and graphite anode while performing its intrinsic function and imparting thermal and mechanical stability [138].…”

Applications of two-dimensional material-functional separator in lithium battery

“…(a) Scheme of 2D BN nanosheet modified separator to inhibit dendrite growth; (b) scheme of cycle stability of Li-metal battery at 0.5 mA/cm 2 [96] . 湿性照片 [104] . Copyright © 2019 Nature.…”

“…(a) Scheme of solid-liquid-gas interface and wettability picture of common separator. (b) Photograph of wetting characteristics of GO membranes [104] . Copyright © 2019 Nature.…”