Electrochemical-Structural Correlations of Complex Metal-Carbon Nanostructures with Energy Storage Performance

Supervisors: Maria Gimenez Lopez, Royal Society DH Research Fellow, School of Chemistry, Faculty of Sciences; George Chen, Prof. of Electrochemical Technologies, Faculty of Engineering.

To meet the increasingly higher requirements of future systems, from portable consumer electronics, hybrid and electric vehicles, to large-scale industrial power systems, the performance of electrochemical energy storage devices has to be substantially improved by developing new materials and better understanding of the fundamental electrochemical processes at the interface. Much effort has been placed on the development of nanohybrid electrodes combining carbon nanomaterials such as graphene and carbon nanotubes that exhibit electrical double-layer capacitance with pseudocapacitor nanocomponents typically
metal oxides materials exhibiting complex redox and/or intercalation processes. However, the development of high-performance nanohybrids with controllable porosity, size, density, composition and morphology with enhanced cycling stability has just begun (Fig. 1(A-D)).

The central aim of this PhD studentship is to develop nanoscale hybrid electrode materials for both batteries and supercapacitors in which pseudocapacitors with well-determined size and surface chemistry are stabilised on graphene or confined within highly-conductive one-dimensional hollow porous carbon structures (concentric nanotubes and stack-cup graphitised nanofibers), thus improving performance in terms of cyclability (Fig. 1E), electrochemical contact and phase-controlled transformations. To achieve
this we propose to use structural and electrostatic effects from the carbon support (i.e., electron transfer from the graphene stack and step-edges in nanocone structures) for controlling and stabilising the size of small nanoparticles of the designated pseudocapacitors (including coordination polymers, polioxometalates and transition metal complexes among others) via the application of supramolecular chemistry concepts at the nanoscale. We will study the effect of confinement on the cycling performance and the concept of microelectrochemical cell will be tested as starting point.

An important challenge in this project is to establish electrochemical-structural correlations of the obtained complex hybrid heterostructures and to engineer supercapacitors and batteries with them. High-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), energy X-ray (EDX) analysis and X-ray diffraction techniques will be used in combination to structurally characterise the hybrid heterostructures, while chronopotentiometry (CP) (galvanostatic charge-discharge
studies), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) will be used for their advanced electrochemical characterisation. Both the School of Chemistry and the Engineering department can provide access to this instrumentation and a world-class training environment in support of this PhD project.

The overall objectives of this project are:
• Rational design and synthesis of hybrid complex heterostructures for the next-generation of hybrid supercapacitor-battery electrode materials combining high-energy and power densities with an excellent cycling stability.
• Precise control of the electrostatic and structural interactions between the nanocarbon and the pseudocapacitor nanocomponent leading to new understanding of electrochemical properties for energy storage applications.
• Construction and testing of supercapacitor and battery devices.