1. Layered sodium transition metal oxides of NaTMO₂ (TM = 3d transition metal) show unique capability to mix different compositions of Fe to the TM layer for further reduced cost, a phenomenon that does not exist in LiTMO₂. In our recent paper on Adv. Funct. Mater. DOI: 10.1002/adfm.201803896, a novel spontaneous TM layer rippling in the sodium ion battery cathode materials is reported, revealed by in situ X-ray diffraction, Cs-corrected scanning transmission electron microscopy, and density functional theory simulation, where the softening and distortion of FeO₆ octahedra collectively drives the flat TM planes into rippled ones with inhomogeneous interlayer distance at high voltage. In such a rippling phase, charge and discharge of Na ions take different evolution pathways, resulting in an unusual hysteresis voltage loop. Importantly, upon discharge beyond a certain Na composition, the rippling TM layer will go back to flat, giving the reversibility of such structural evolution in the following cycles. We expect that fully exploration and utilization of the rippling phase may lead to sodium cathode materials with further improved performance.

2. Na_xMnO₂ shows Mn³⁺ and Mn⁴⁺ charge separation with the charge stripe ordering upon Na de-intercalation at x = 5/8. We show in a paper published on Adv. Funct. Mater. that, surprisingly, at lower Na compositions of 5/8 > x ≥ 1/18 the phase evolution pathway of Na_xMnO₂ upon Na de-intercalation shows a unique phenomenon of super charge separation, where the Mn³⁺ and Mn⁴⁺ ions fully charge-separate into charge super-planes formed by succession of charge stripes in the third dimension. The Mn³⁺ super-planes attract Na ions electronically, and dominate the antiferromagnetic interactions in NaMnO₂.  Na ions in Mn³⁺ super-planes also naturally pillar the MnO­₂ layers to form the unusual O1 phases with large interlayer distances at x < 1/3, which dominates the unique electrochemical behavior of NaMnO₂ with asymmetric charge discharge evolution and increased cycling performance at voltage cutoff higher than 3.6V.

3. Coating is an effective strategy to stabilize the interface chemically and electrochemically in solid state batteries. In our work on Advanced Energy Materials (https://doi.org/10.1002/aenm.201900807), high‐throughput analysis of density functional theory phase data is used to understand the interface decomposition in solid‐state batteries based on ceramic sulfides. Elemental analysis reveals key trends in the relation between composition and susceptibility for decay. Large‐scale electrochemical analysis provides over 3000 materials that are predicted to form stable interfaces with Li₁₀SiP₂S₁₂.

4. Dynamic charge fluxes were found to strongly couple with anharmonic phonons to help stabilize a special phase with abnormal Jahn-Teller distortion in Na_1/2MnO₂ (Matter https://www.sciencedirect.com/science/article/abs/pii/S2590238521006378). The study untilizes neutron diffractions, (in situ) (synchrotron) XRD, Raman spectroscopy, and DFT simulations.

5. Machine learning voltage curve as images is shown as an effective way to predict battery performance and failure ( Advanced Intelligent Systems, https://doi.org/10.1002/aisy.201900102)