(622h) Thermally Cross-Linked Poly(acrylic acid) / Reduced-Graphene Oxide Aerogels As a Replacement for Metal-Foil Current Collectors in Lithium Ion Batteries

Lithium-ion batteries (LIBs) are widely used as the energy storage device in portable electronics, and they have demonstrated great promise for use in electric transportation. While the specific capacities of active materials in LIB electrodes are relatively high, the electrodes’ specific capacities (energy per unit mass of the electrode) are partially restricted by the high weight fraction of so-called inactive materials, such as metal current-collectors, separators, polymer binders, etc. One solution to address this practical limitation is to increase the electrode’s thickness, such that active materials have a higher loading per unit area of the electrode, thereby increasing the cell energy density. Unfortunately, current electrode architectures are limited by kinetic limitations and poor mechanical integrity of the electrode. To overcome these limitations, the development of intelligently designed electrode materials and architectures is highly attractive.

To decrease the weight fraction of inactive components, the use of 3-D conductive electrode architectures and substrates has been proposed. Our focus has been on demonstrating the use of a thermally cross-linked poly(acrylic acid) (PAA)/ reduced graphene oxide (rGO) (further referred as rGO-PAA) porous foam structure called an aerogel as a substitute for the metal current collector in a LIB architecture. rGO has been studied extensively by many other groups and has shown excellent electronic conductivity; rGO aerogels share the same merits as rGO, and the void volume can be fully loaded with active-materials without fracture. Moreover, the thermally cross-linked structure of PAA on the rGO sheets make the aerogel elastic and mechanically robust. As a result, the low density (5 mg/cm³), conductive (5.3 × 10^-2 ± 3 × 10^-2 S/m) and porous (99.6% void space) rGO-PAA aerogel can be used as an electrode in LIBs in a way that allows removal of conventional metal current collectors. The synthesis and assembly of these electrodes and their resulting electrochemical performance will also be shown in detail. From these data, the rGO-PAA aerogel shows great promise as an alternative current collector in LIBs.