(Invited) Graphene-Based Scaffolds for Electrochemical Energy Storage

Abstract

The efficient transport of charge species within energy storage devices is critical to realizing both large power and energy densities, especially when operating under extreme conditions (e.g. ultralow temperatures, high charge/discharge rates, etc.). A number of resistances can contribute to sluggish ion/electron transport in a cell such as charge transfer at interfaces, electrolyte resistance, electrode resistance, and diffusive transport within porous electrodes. Several strategies have been pursued to address these transport limitations. Electrolyte engineering is an effective approach as it can influence both electrolyte resistance and charge transfer resistances. Electrode materials discovery and development is another popular strategy as the charge storage mechanism and electrode resistance play a key role in kinetics of the device. Within electrode materials development, engineering of the electrode pore architecture is an extremely effective strategy to decrease the diffusive transport lengths and electrode resistances. This pore engineering can be achieved through synthetic chemistry for small pores (e.g. <10 um) and via additive manufacturing for larger pores (> 10 um). Here we show how electrolyte engineering and electrode materials development can be used to overcome sluggish transport in graphene-based electrodes. Particular focus will be given to the use of synthetic means to tune to the properties of a graphene aerogel scaffold (e.g. surface area, pore size, mechanical properties) and additive manufacturing to define the larger pore structure to facilitate uniform deposition of active materials (e.g. MnO2) and improve energy density and rate capability of the energy storage device. We explore a number of additive manufacturing techniques (e.g. direct ink write, projection microstereolithography, etc.) to print a variety of lattice structures and computer-guided designs to determine the optimal electrode architecture.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.