Impact of Structural Flexibility of Amine Moieties as Bridges for Redox-Active Sites on Secondary Battery Performance.

Although environmentally benign organic cathode materials for secondary batteries are in demand, their high solubility in electrolyte solvents hinders broad applicability. In this study, a bridging fragment to link redox-active sites is incorporated into organic complexes with the aim of preventing dissolution in electrolyte systems with no significant performance loss. Evaluation of these complexes using an advanced computational approach reveals that the type of redox-active site (i. e., dicyanide, quinone, or dithione) is a key parameter for determining the intrinsic redox activity of the complexes, with the redox activity decreasing in the order of dithione>quinone>dicyanide. In contrast, the structural integrity is strongly reliant on the bridging style (i. e., amine-based single linkage or diamine-based double linkage). In particular, owing to their rigid anchoring effect, diamine-based double linkages incorporated at dithione sites allow structural integrity to be maintained with no significant decrease in the high thermodynamic performance of dithione sites. These findings provide insights into design directions for insoluble organic cathode materials that can sustain high performance and structural durability during repeated cycling.

Microwave-assisted design of nanoporous graphene membrane for ultrafast and switchable organic solvent nanofiltration.

Layered two-dimensional materials can potentially be utilized for organic solvent nanofiltration (OSN) membrane fabrication owing to their precise molecular sieving by the interlayer structure and excellent stability in harsh conditions. Nevertheless, the extensive tortuosity of nanochannels and bulky solvent molecules impede rapid permeability. Herein, nanoporous graphene (NG) with a high density of sp2 carbon domain was synthesized via sequential thermal pore activation of graphene oxide (GO) and microwave-assisted reduction. Due to the smooth sp2 carbon domain surfaces and dense nanopores, the microwave-treated nanoporous graphene membrane exhibited ultrafast organic solvent permeance (e.g., IPA: 2278 LMH/bar) with excellent stability under practical cross-flow conditions. Furthermore, the membrane molecular weight cut-off (MWCO) is switchable from 500 Da size of molecule to sub-nanometer-size molecules depending on the solvent type, and this switching occurs spontaneously with solvent change. These properties indicate feasibility of multiple (both binary and ternary) organic mixture separation using a single membrane. The nanochannel structure effect on solvent transport is also investigated using computation calculations.