Abstract
Although it is widely accepted that the long-range (average) crystal structure plays a critical role in determining the electrochemical performance of battery materials, the relationship between local structural features and electrochemical performance is rarely studied. Disordered rock salt oxides (DRX), which have become serious contenders for next generation Li-ion electrode materials, provide an ideal platform for exploring correlations between local structure and electrochemical performance as they exhibit a simple face-centered cubic structure and combine long-range disorder and short-range order on the cation sublattice. This work examines the Li1.1Mn0.7Zr0.2−xTixO2 series of DRX cathodes and investigates the links between local structure rearrangements and capacity activation. The end-member Li1.1Mn0.7Zr0.2O2 compound exhibits a low capacity in the as-synthesized state, attributed to unfavorable short-range order that hinders Li-ion transport, yet its capacity increases seven-fold, from 20 to 140 mAh g−1, after chemical delithiation followed by a 400 °C heat treatment. Capacity activation is associated with the appearance of local spinel-like structural features that depart from the short-range order originally present in the material, without significant change to the bulk composition and average crystal structure. Investigation of a series of Li1.1Mn0.7Zr0.2−xTixO2 (x ≤ 0.2) DRX compounds reveals that the correlation length of the spinel-like ordering that emerges during the heat treatment strongly depends on the Zr : Ti ratio. Yet, dramatic capacity activation and electrochemical (pseudo-)plateaus reminiscent of Mn-based spinel cathodes are observed for all compounds irrespective of the size of the ordered domains. To explain this phenomenon, we propose that the DRX phase undergoes a complete transformation to a spinel-like domain structure, which improves bulk Li-ion transport regardless of domain size.
| Original language | English |
|---|---|
| Pages (from-to) | 634-651 |
| Number of pages | 18 |
| Journal | Chemical Science |
| Volume | 17 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 7 2026 |
Funding
This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technologies Office under the Applied Battery Materials Program of the US Department of Energy (DOE) under contract number DE-AC02-05CH11231 (DRX+). This work made use of the Spectroscopy, and Microscopy and Microanalysis shared facilities of the UC Santa Barbara MRSEC (DMR–2308708), a member of the Materials Research Facilities Network. The calorimetric work at ASU was supported by DOE Office of Science grant DE-SC0021987. Use of the Stanford Synchrotron Radiation Light source, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract no. DE-AC02-76SF00515. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The beam time was allocated to NOMAD on proposal number IPTS-32507.1. Synchrotron diffraction data were collected at beamline I-11 at Diamond Light Source under Proposal No. CY36397. The authors would like to thank Dr Lucy Sanders and Dr Sarah Day for their assistance with sample preparation and data collection.