Search for: All records

Abstract High-entropy oxides (HEOs) offer vast compositional design space for discovering emergent functionalities, yet their controlled nanoscale synthesis remains challenging. Here, we develop a generalizable colloidal strategy that enables precision synthesis of HEO nanocrystals with compositions spanning quinary to septenary systems. Mechanistic studies reveal that differences in precursor reactivity drive a multistage growth pathway and that cooperative multimetal chemistry─where one metal initiates single-phase nucleation and a vacancy-forming metal promotes cation redistribution during growth─enables homogeneous multication incorporation. The resulting rocksalt HEO nanocrystals can be transformed into spinel phases and exhibit excellent oxygen-evolution reaction activity. Machine-learning-accelerated theoretical analysis and operando characterization identify Co–Co bridge sites on spinel {111} facets as the dominant oxygen-evolution active motifs operating through a lattice oxygen-mediated mechanism. These findings establish guiding principles for controlling nucleation, cation mixing, and active-site formation in compositionally complex oxides, enabling the rational design and data-driven optimization of high-entropy materials. 

A major challenge for lithium-containing electrochemical systems is the formation of lithium carbonates. Solid-state electrolytes circumvent the use of organic liquids that can generate these species, but they are still susceptible to Li2CO3 formation from exposure to water vapor and carbon dioxide. It is reported here that trace quantities of Li2CO3, which are re-formed following standard mitigation and handling procedures, can decompose at high charging potentials and degrade the electrolyte–cathode interface. Operando electrochemical mass spectrometry (EC–MS) is employed to monitor the outgassing of solid-state batteries containing the garnet electrolyte Li7La3Zr2O12 (LLZO) and using appropriate controls CO2 and O2 are identified to emanate from the electrolyte–cathode interface at charging potentials > 3.8 V (vs Li/Li+). The gas evolution is correlated with a large increase in cathode interfacial resistance observed by potential-resolved impedance spectroscopy. This is the first evidence of electrochemical decomposition of interfacial Li2CO3 in garnet cells and suggests a need to report “time-to-assembly” for cell preparation methods