(Invited) Multiscale Chemical Complexities in Layered Oxides for Sodium Ion Batteries

Abstract

Applications such as large-scale stationary energy storage call for significantly reduced cost of batteries. Sodium ion batteries offer one of the most feasible alternatives to meet these particular demands. Layered oxide materials are regarded as a technologically important class of cathode materials due to their excellent reversibility in cycling sodium ions and relatively smaller degree of lattice volume change. Various transition metal ions can be incorporated in the transition metal layer of sodium layered oxides giving considerable flexibility to the choice of the transition metals. The different choices of transition metals make it challenging to obtain the perfectly homogeneous distribution in multielemental sodium layered oxide materials because of their differences in the ionic size and electronic properties. However, how much does the homogeneous elemental distribution matter in the battery performance? What are the chemical and structural transformations of heterogeneous layered oxides during charging and discharging? In this presentation, we will discuss our recent progress in understanding the multiscale heterogeneity in sodium layered oxide materials. First, we will establish the relationship between the cathode surface chemistry and the sodium full-cell electrochemistry through a range of complementary advanced spectroscopic and imaging diagnostic techniques. Second, we will highlight our effort in decoupling the multiscale electrochemistry in sodium layered oxide materials. We will illustrate that engineering the three-dimensional distribution of metal cations in electrode particles can take advantage of the depth-dependent charging mechanisms thus empowering superior battery performance.