Boise State University,
Keywords: interface, intergrowth phase, sodium ion battery, degradation
Summary:Sodium ion batteries (SIBs) are attractive alternative energy storage technology to lithium-ion batteries due to low cost, high abundance, and large worldwide availability of raw materials. There has been growing attention in developing new electrode materials for sodium ion batteries. Compared to lithium ion batteries, SIBs suffer from more issues in power performance and long-term stability, resulted from the sluggish kinetics and large volume change upon cycling due to the much larger Na+ ion (~ two times the size of Li+). Several approaches to enhance the electrode performance have been explored such as doping, nanostructuring, and carbon coating. In this talk, we will discuss our recent work on developing advanced electrode materials for SIBs through interfacial engineering. We have developed a coaxial core-shell nanostructured negative composite electrode composed of carbon nanotube (CNT) as the core and TiO2@MoO2@C as shells. The 1D tubular nanostructure can effectively reduce ion diffusion path, increase electrical conductivity, accommodate the stress due to volume change upon cycling, and provide additional interfacial active sites for enhanced charge storage and transport properties. Significantly, a synergistic effect between TiO2 and MoO2 nanostructures is investigated through ex-situ solid state nuclear magnetic resonance. We also developed a Li-substituted layered-tunneled (O3-spinel) intergrowth positive electrode (LS-NFM), which exhibits enhanced capacity and cycling stability. The remarkable structural compatibility and connectivity of the two phases were confirmed by X-ray diffraction (XRD), selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). At the end of the talk we will also discuss how stabilizing the Na electrolyte and mitigating the degradation of the electrolyte could promote the shelf life and performance sodium ion batteries through our recent work.