Edward Mu

All Publications

• Electrochemical and Thermal Control of Continuous Phase Transitions in P2-NaxNi1/3Mn2/3O2. Journal of the American Chemical Society Edelman, D. A., Cattermull, J., Liu, J., Jiang, Z., Ramachandran, H., Mu, E., Li, C., Van der Ven, A., Harmon, K. J., Chueh, W. C. 2026; 148 (34): 36610-36619

  Abstract

  Sodium layered oxides often undergo phase transformations involving ordering or disordering of Na+ upon desodiation, i.e., when cycled as a battery electrode. Accurately characterizing these phases is crucial for understanding functional properties, such as chemical diffusivity. In this work, we reveal that Na+-vacancy (dis)ordering in a layered oxide is intrinsically coupled to symmetry-changing phase transformations of the host structure. We examine the low-symmetry orthorhombic unit cell of P2-NaxNi1/3Mn2/3O2 (NNM) using both neutron and X-ray diffraction. Specifically, special sodium stoichiometries (x = 2/3 and 1/2) exhibit concomitant Na+-vacancy ordering and an orthorhombic distortion from the parent hexagonal unit cell. We then demonstrate that electrochemical desodiation drives symmetry-changing transformations in NNM that are linked to Na+-vacancy (dis)ordering, with evidence of second-order behavior observed near x = 2/3. Variable-temperature synchrotron X-ray diffraction further clarifies the coupling between Na+-vacancy disordering and orthorhombic-to-hexagonal phase transitions in NNM. Surprisingly, the temperature-driven phase transitions at x = 2/3 and 1/2 differ in character, appearing second-order and first-order, respectively. Our analysis of the phase transitions in NNM has fundamental consequences for sodium chemical diffusivity in the vicinity of the ordered phases and leads to design principles for modifying phase transition behavior in the broader class of intercalation electrodes.

  View details for DOI 10.1021/jacs.6c06069

  View details for PubMedID 42701265

• A formal FeIII/V redox couple in an intercalation electrode. Nature materials Ramachandran, H., Mu, E. W., Lomeli, E. G., Braun, A., Goto, M., Hsu, K. H., Liu, J., Jiang, Z., Lim, K., Busse, G. M., Moritz, B., Kas, J. J., Vinson, J., Rehr, J. J., Park, J., Abate, I. I., Shimakawa, Y., Solomon, E. I., Yang, W., Gent, W. E., Devereaux, T. P., Chueh, W. C. 2025

  Abstract

  Iron redox cycling between low-valent oxidation states of FeII and FeIII drives crucial processes in nature. The FeII/III redox couple charge compensates the cycling of lithium iron phosphate, a positive electrode (cathode) for lithium-ion batteries. High-valent iron redox couples, involving formal oxidation higher than FeIII, could deliver higher electrochemical potentials and energy densities. However, because of the instability of high-valent Fe electrodes, they have proven difficult to probe and exploit in intercalation systems. Here we report and characterize a formal FeIII/V redox couple by revisiting the charge compensation mechanism of (de)lithiation in Li4FeSbO6. Valence-sensitive experimental and computational core-level spectroscopy reveal a direct transition from FeIII (3d5) to a negative-charge-transfer FeV (3d5L2) ground state on delithiation, without forming FeIV, or oxygen dimers. We identify that the cation ordering in Li4FeSbO6 drives a templated phase transition to stabilize the unique FeV species and demonstrate that disrupting cation ordering suppresses the FeIII/V redox couple. Exhibiting resistance to calendar aging, high operating potential and low voltage hysteresis, the FeIII/V redox couple in Li4FeSbO6 provides a framework for developing sustainable, Fe-based intercalation cathodes for high-voltage applications.

  View details for DOI 10.1038/s41563-025-02356-x

  View details for PubMedID 41094071

  View details for PubMedCentralID 4002152

• Substituent Effects on Exchange Coupling and Magnetic Relaxation in 2,2′-Bipyrimidine Radical-Bridged Dilanthanide Complexes JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Gould, C. A., Mu, E., Vieru, V., Darago, L. E., Chakarawet, K., Gonzalez, M., Demir, S., Long, J. R. 2020; 142 (50): 21197-21209

  Abstract

  Systematic analysis of related compounds is crucial to the design of single-molecule magnets with improved properties, yet such studies on multinuclear lanthanide complexes with strong magnetic coupling remain rare. Herein, we present the synthesis and magnetic characterization of the series of radical-bridged dilanthanide complex salts [(Cp*2Ln)2(μ-5,5'-R2bpym)](BPh4) (Ln = Gd, Dy; R = NMe2 (1), OEt (2), Me (3), F (4); bpym = 2,2'-bipyrimidine). Modification of the substituent on the bridging 5,5'-R2bpym radical anion allows the magnetic exchange coupling constant, JGd-rad, for the gadolinium compounds in this series to be tuned over a range from -2.7 cm-1 (1) to -11.1 cm-1 (4), with electron-withdrawing or -donating substituents increasing or decreasing the strength of exchange coupling, respectively. Modulation of the exchange coupling interaction has a significant impact on the magnetic relaxation dynamics of the single-molecule magnets 1-Dy through 4-Dy, where stronger JGd-rad for the corresponding Gd3+ compounds is associated with larger thermal barriers to magnetic relaxation (Ueff), open magnetic hysteresis at higher temperatures, and slower magnetic relaxation rates for through-barrier processes. Further, we derive an empirical linear correlation between the experimental Ueff values for 1-Dy through 4-Dy and the magnitude of JGd-rad for the corresponding gadolinium derivatives that provides insight into the electronic structure of these complexes. This simple model applies to other organic radical-bridged dysprosium complexes in the literature, and it establishes clear design criteria for increasing magnetic operating temperatures in radical-bridged molecules.

  View details for DOI 10.1021/jacs.0c10612

  View details for Web of Science ID 000600204900034

  View details for PubMedID 33322909

• Functional degradation: A mechanism of NLRP1 inflammasome activation by diverse pathogen enzymes SCIENCE Sandstrom, A., Mitchell, P. S., Goers, L., Mu, E. W., Lesser, C. F., Vance, R. E. 2019; 364 (6435): 42-+

  Abstract

  Inflammasomes are multiprotein platforms that initiate innate immunity by recruitment and activation of caspase-1. The NLRP1B inflammasome is activated upon direct cleavage by the anthrax lethal toxin protease. However, the mechanism by which cleavage results in NLRP1B activation is unknown. In this study, we find that cleavage results in proteasome-mediated degradation of the amino-terminal domains of NLRP1B, liberating a carboxyl-terminal fragment that is a potent caspase-1 activator. Proteasome-mediated degradation of NLRP1B is both necessary and sufficient for NLRP1B activation. Consistent with our functional degradation model, we identify IpaH7.8, a Shigella flexneri ubiquitin ligase secreted effector, as an enzyme that induces NLRP1B degradation and activation. Our results provide a unified mechanism for NLRP1B activation by diverse pathogen-encoded enzymatic activities.

  View details for DOI 10.1126/science.aau1330

  View details for Web of Science ID 000463585700027

  View details for PubMedID 30872533

  View details for PubMedCentralID PMC6532986