Speaker
Description
Lithium-excess disordered rocksalt (DRX) materials are a promising class of Co- and Ni-free lithium-ion battery cathodes that offer high specific energy density (up to 1000 Wh kg$^{-1}$) and reversible capacity (up to 300 mAh g$^{-1}$). Compared to traditional Li-ion cathodes (e.g., LiNi$_x$Mn$_y$Co$_{1-x-y}$O$_2$), DRX oxides/oxyfluorides are compatible with a wider range of earth abundant transition metals, such as Ti and Mn. DRX cathodes are traditionally synthesized via solid-state or mechanochemical reactions, which are difficult to scale and provide little control over particle morphology. Furthermore, recent development of DRX compositions show Mn-rich concentrations substantially improve performance by increasing Mn-redox and inhibiting irreversible O-redox. To address this issue, the present study reports a scalable, two-step reaction route to prepare Mn/Ti-based DRX oxyfluoride cathodes with the nominal composition Li$_{1.1}$Mn$_{0.8}$Ti$_{0.1}$O$_{1.9}$F$_{0.1}$ (LMTF1811). The first step utilizes a glycine-nitrate combustion reaction to produce an orthorhombic Mn$_{0.8}$Ti$_{0.1}$O$_{1.4}$ (MTO814) precursor, which is subsequently lithiated and fluorinated by reacting with Li$_2$CO$_3$ and LiF. The effects of annealing temperature (900°C-1100°C) and cooling rate (5-120°C min$^{-1}$) on the product’s structure and DRX phase conversion are explored. Interestingly, heating at 1000°C and quenching between 5 and 120°C min$^{-1}$ shows varying phase purities between 80 and 95%, respectively. However, heating to 1100°C produces Mn-rich phase-pure DRX regardless of quench rate. Phase-pure DRX prepared through this novel synthesis platform exhibit promising electrochemical performance, attaining reversible capacities ~200 mAh g$^{-1}$ with 86% capacity retention after 100 cycles in Li metal half-cells.
Acknowledgements
SEM imaging was performed at the Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility. Research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the US Department of Energy (DOE) and was sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) in the Vehicle Technologies Office (VTO) through the DRX+ consortium.
| Topical Area | Hard matter: energy materials |
|---|
