Synthesis and electrochemical studies of nanostructured metal oxides for lithium ion batteries
Date of Issue2016
School of Materials Science and Engineering
The key to optimize lithium ion batteries (LIBs) for future advanced application is to develop novel electrode materials with outstanding electrochemical properties. Nanomaterials with precisely designed configurations provide one of the most desirable ways. As one of the most studied candidates, metal oxides, especially Sn-based and Co-based oxides, are currently extensively exploited as anode for LIBs. Nevertheless, several issues need to be addressed that handicap the commercial application of these metal oxides. So, scientific research and breakthroughs are imperative to meet the requirements for real use. With this in view, a series of one-dimensional (1D) Sn-based (ASnO3) and Co-based (ACo2O4) ternary oxides with various nanoarchitectures has been prepared by simple and versatile electrospinning techniques. In this thesis, one major aim is to investigate the effect of different nanostructures on the electrochemical performance of LIBs. Meanwhile, the possible formation mechanism for the unique structure will be studied to shed some light on the controllable fabrication of other metal oxides with similar morphology. Benefiting from their unique structural features, eggroll-like CaSnO3 nanotubes (CSO-NT), hierarchical CaCo2O4 nanofibes (CCO-NF), and porous NiCo2O4 nanotubes (NCO-NT) demonstrate superior electrochemical performance compared to their corresponding counter-parts, respectively. To gain deep understanding on the enhanced batteries performance, by comparing the lithium storage capability of as-prepared different nanostructures, the effect of counter ions substitution, especially A-site substitution, in ASnO3 and ACo2O4 systems has been systematically discussed. By virtue of excellent properties of the active matrix elements Ni, porous NCO-NT with large capacity and remarkable cycling stability is identified as the most potential anode materials for LIBs. As the electrochemical reaction mechanisms and capacity degradation is critical for the rational design of advanced LIBs, this thesis performed fundamental investigation for the structure evolution of eggroll-like CSO-NT, hierarchical CCO-NF, and porous NCO-NT. The origin of the capacity degradation and lithium storage mechanisms have been proposed and discussed. Moreover, the reaction kinetics and lithium diffusion coefficients were also analyzed in depth. Lastly, it is hoped that all of studies could shed more light on the fundamental science.