Speaker：Prof.Xiangfeng Duan
Department of Chemistry and Biochemistry
University of California, Los Angeles,US
Speech：Optimizing Charge Transport in 3D Holey Graphene Composite for Ultrahigh
Rate Energy Storage
Time：2017年7月10日，上午9:00
Abstract:
Supercapacitors and batteries represent two distinct electrochemical energy storage devices of increasing importance for applications in mobile electronics, electric vehicles, and renewable energy industry. A common feature of these devices involves coupled ion transport (and storage) and electron transport in active electrode materials. Tremendous progress has been made in new electrode materials (e.g., silicon and niobia) that may promise far higher energy or power density than those of today’s batteries. However, these new materials have thus far failed to deliver their promise in practical devices because the exceptional performance is typically only achieved in ultrathin electrodes with very low mass loadings (< 1 mg cm-2) and cannot be easily scaled into devices with practical levels of mass loading (>10 mg cm-2). To sustain the same electrochemical performance in practical electrodes with higher mass loading requires the delivery of proportionally more charge (both electrons and ions) across a proportionally longer distance, which represents a formidable challenge, particularly for new electrode materials with intrinsically higher capacity or rate capability that require the correspondingly higher charge delivery rate. In this talk, I will discuss the critical role of charge transport in electrochemical devices how their performance can be dramatically affected by tailoring the charge transport process. In particular, I will describe the design of a three-dimensional holey graphene framework (3D-HGF) as an ideal conductive scaffold for electrochemical materials. The 3D-HGF features a highly interconnected graphene network for excellent electron transport, a hierarchical porous structure for rapid ion transport, and an ultrahigh high surface area for the efficient loading of electrochemical active nanostructures without sacrificing reaction efficiency. By systematically tailoring the porosity in the holey graphene backbone, we show charge transport in the composite architecture can be optimized to enable a HGF/niobia or HGF/Si composite anode with an unprecedented combination of high areal capacity and high areal current density at practical levels of mass loadings (>10 mg cm-2), marking critical step towards applying high performance electrode materials in practical devices.
