Flexible, Self-Supported Anode for Organic Batteries with a Matched Hierarchical Current Collector System for Boosted Current Density

Abstract

The inherent flexibility of redox-active organic polymers and carbon-based fillers, combined with flexible current collectors (CCs) is ideal for the fabrication of flexible batteries. Herein, a one-step electrophoretic deposition of polyviologen (PV)/graphene-oxide (GO) aqueous composites onto a flexible mesh of 60 mu m thick wires, 100 mu m apart, is described. Notably, during electrodeposition, GO is transformed into conductive reduced GO (rGO), and nanoscopic pores are formed by self-assembly allowing charge/discharge of the redox sites over dozens of micrometers. Typically, electrodeposition of PV alone on a flat CC (FCC) is limited by its electrically insulating structure to approximate to 0.15 mAh cm(-2), but the presence of rGO allows thicker active layers without loss in (dis-)charging kinetics and reaching areal capacities of approximate to 2 mAh cm(-2). Remarkably, when the FCC is replaced by a mesh, the deposition of significantly more anode materials (approximate to 5 mAh cm(-2)) is possible, while the (dis-)charging kinetics is considerably improved. It exhibits high capacity retention at an ultrafast rate of 100 C (<3%) and excellent bending stabilities. This represents the first combination of a microscopic-CC (mesh wires) with a molecular-electronic and -ionic conductor (rGO with its pores), i.e., a hierarchical-CC system with maximized polymer thickness and minimized wire thickness. The stacking of such modified grids paves the road to further increase the areal capacity.