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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Fluorinated cation-disordered rocksalt materials and methods of making thereof

This disclosure provides systems, methods, and apparatus related to lithium metal oxyfluorides. In one aspect, a method for manufacturing a lithium metal oxyfluoride having a general formula Li 1+x (MM′) z O 2-y F y , with 0.6 ≤ z ≤ 0.95, 0 < y ≤ 0.67, and 0.0 5 ≤ x ≤ 0.4, the lithium metal oxyfluoride having a cation-disordered rocksalt structure, includes: providing at least one lithium-based precursor; providing at least one redox-active transition metal-based precursor; providing at least one redox-inactive transition metal-based precursor; providing at least one fluorine-based precursor comprising a fluoropolymer; and mixing the at least one lithium-based precursor, the at least one redox-active transition metal-based precursor, the at least redox-inactive transition metal-based precursor, and the at least one fluorine-based precursor comprising a fluoropolymer to form a mixture.

Ahn, Juhyeon↗
DOE OSTI2026

Visualizing Crystallization Dynamics and Transformation Pathways of Disordered Rocksalt Oxides During Thermally Activated Sol–Gel Synthesis

Sol–gel synthesis is a wet-chemical processing route for fabricating functional materials with control over composition and microstructure at relatively low temperatures compared to conventional solid-state synthesis. While sol–gel process initiates with intermixed molecular precursors, the early-stage nucleation pathways are insufficiently understood. Here, in this study, the chemical and structural transformation of ion disordered rocksalt (DRX) Li 1.2 Mn 0.4 Ti 0.4 O 2 (LMTO), a promising cathode material for lithium batteries, is studied by multiscale characterizations. In situ heating transmission electron microscopy (TEM) using a liquid cell visualizes and identifies crystallization pathways at the nanoscale. While some regions follow a classical multi-step transition through thermodynamically stable intermediates, others exhibit a kinetic shortcut via a localized amorphous matrix to directly form the DRX structure. Macroscale Fourier transform infrared spectroscopy corroborates the findings and reveals that transition metal ions are more strongly incorporated into the acetate-coordinated network than lithium. Although in situ heating TEM captures diverse local transformation pathways, in situ synchrotron X-ray diffraction indicates that the macroscopic transformation proceeds predominantly through spinel LMTO and lithium titanates toward DRX-LMTO. The findings uncover the spatiotemporal chemical and structural transformations in sol–gel derived DRX-LMTO materials, and call for fine-tuning of such sol–gel chemistries to manipulate the crystallization pathways and achieve target material homogeneity more efficiently.

cathode material↗
DOE OSTI2021

Role of Fluorine in Chemomechanics of Cation-Disordered Rocksalt Cathodes

The role of nanoscale chemomechanical behavior in the macroscopic performance of functional materials is well recognized. For lithium-ion battery cathodes, tremendous effort has been devoted to the development of new chemistry and structure, yet fundamental understanding of the correlation between redox processes and mechanical properties of the novel materials lags behind. In the present study, we prepare large discrete single grains of Li-excess cation-disordered rocksalts (DRX) and investigate their chemomechanical behavior at the particle level, using nanoresolution X-ray and electron-based spectro-imaging and chemical mapping techniques. While irregular cracking upon lithium extraction leads to the eventual breakdown of the baseline DRX oxide (Li 1.2 Ti 0.4 Mn 0.4 O 2 ) particles at a high delithiation state, the fluorinated-DRX (Li 1.3 Ti 0.3 Mn 0.4 O 1.7 F 0.3 ) clearly displays aligned cracking along the <001> direction. The resulting periodicity in the cracking pattern enables the particles to retain their integrity and, consequently, improved electrochemical stability. Density functional theory (DFT) calculations showed that fluorination leads to increased concentration of Li+ on the (001) planes and preferential Li movements along the <001>-family directions, revealing the underlying mechanism for directional cracking. Overall, our study demonstrates the unique role of fluorine in modulating nanoscale chemomechanics, which in turn influences the evolution of charge and strain heterogeneity at the particle level. These insights provide important design guidelines in further improving DRX cathode materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Toward Stable Cycling of a Cost-Effective Cation-Disordered Rocksalt Cathode via Fluorination

The recently developed Li-excess cation-disordered rock salts (DRXs) exhibit an excellent chemical diversity for the development of alternative Co/Ni-free high-energy cathodes. Herein, the synthesis of a highly fluorinated DRX cathode, Li 1.2 Mn 0.6 Ti 0.2 O 1.8 F 0.2 , based on cost-effective and earth-abundant transition metals, via a solid-state reaction, is reported. The fluorinated DRX cathode using ammonium fluoride precursor exhibits more uniform particle size and delivers a specific discharge capacity of 233 mAh g -1 and specific energy of 754 Wh kg -1 , with 206 mAh g -1 retained after 200 cycles. Further, the combined synchrotron X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy analysis reveals that the remarkable cycling performance is attributed to the high fluorination and thus enhanced Mn content, enabling the utilization of more Mn redox than the oxide analog. This study demonstrates a great promise to develop next-generation cost-effective DRX cathodes with enhanced capacity retention for high-energy Li-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2025

Designing Advanced Electrolytes for High-Voltage High-Capacity Disordered Rocksalt Cathodes

Lithium (Li)-excess transition metal oxide materials which crystallize in the cation-disordered rock salt (DRX) structure are promising cathodes for realizing low-cost, high-energy-density Li batteries. However, the state-of-the-art electrolytes for Li-ion batteries cannot meet the high-voltage stability requirement for high-voltage DRX cathodes, thus new electrolytes are urgently demanded. It has been reported that the solvation structures and properties of the electrolytes critically influence the performance and stability of the batteries. In this study, the structure–property relationships of various electrolytes with different solvent-to-diluent ratios are systematically investigated through a combination of theoretical calculations and experimental tests and analyses. This approach guides the development of electrolytes with unique solvation structures and characteristics, exhibiting high voltage stability, and enhancing the formation of stable electrode/electrolyte interphases. These electrolytes enable the realization of Li||Li 1.094 Mn 0.676 Ti 0.228 O 2 (LMTO) DRX cells with improved performance compared to the conventional electrolyte. Specifically, Li||LMTO cells with the optimized advanced controlled-solvation electrolyte deliver higher specific capacity and longer cycle life compared to cells with the conventional electrolyte. Additionally, the investigation into the structure–property relationship provides a foundational basis for designing advanced electrolytes, which are crucial for the stable cycling of emerging high-voltage cathodes.

25 ENERGY STORAGE↗
DOE OSTI2021

Understanding cation-disordered rocksalt oxyfluoride cathodes

Partial fluorine (F) substitution into the oxygen (O) sublattice has been shown to improve cycling stability of cation-disordered Li-excess rocksalt oxide (DRX) cathodes. Detailed understanding on failure mechanisms and key optimization knowledge of fluorinated-DRX (F-DRX), however, are lacking. In the present study, we incorporate different amounts of F into a baseline DRX system, Li 1.2 Ti 0.4 Mn 0.4 O 2 (LTMO3.0, 3.0 denotes nominal Li/Mn ratio), and synthesize two oxyfluoride compounds, Li-rich Li 1.3 Ti 0.3 Mn 0.4 O 1.7 F 0.3 (LTMOF3.25) and Mn-rich Li 1.2 Ti 0.2 Mn 0.6 O 1.8 F 0.2 (LTMOF2.0) with an increased and reduced Li/Mn ratio of 3.25 and 2.0, respectively. Through careful monitoring of chemical and structural evolution, we show that cycling-induced changes are manifested not only by Mn reduction and degradation of its local coordination environment, but also by F enrichment and formation of LiF-type of domains on the surface. A “concerted-densification” based failure mechanism, involving atomic-level changes in both transition-metal cationic sublattice and oxygen/fluorine anionic sublattice, is proposed for the degradation in F-DRX cathode materials. The study reveals that increasing F content accompanied by reduced Li/Mn ratio mitigates the degradation process, offering key design strategies in achieving balanced cathode capacity and stability.

25 ENERGY STORAGE↗
DOE OSTI2024

Enhanced Electrochemical Performance of Disordered Rocksalt Cathodes in a Localized High‐Concentration Electrolyte

Abstract Lithium (Li)‐rich transition metal oxide cathodes with a cation disordered rock salt structure (DRX) are increasingly gaining popularity for advanced Li batteries as they offer high capacity and cost benefits over the commonly used layered Li transition metal oxide cathodes. However, the performance of DRX cathodes and their applications are limited by severe side reactions between the cathode and the state‐of‐the‐art carbonate‐based electrolytes at high voltage of 4.8 V, transition metal dissolution, and structural instability of the cathode particles. In this work, an advanced localized high‐concentration electrolyte (LHCE) is developed to form a stable cathode‐electrolyte interphase and mitigate structural instability of the Li 1.13 Mn 0.66 Ti 0.21 O 2 (LMTO) DRX during electrochemical cycling. Li||LMTO half cells with the LHCE demonstrate increased capacity, cycling stability, and superior rate capability compared with cells containing a conventional carbonate electrolyte. For instance, the Li||LMTO cells cycled in LHCE show a higher initial capacity of 205.2 mAh g −1 and a better capacity retention of 72.5% after 200 cycles at a current density of 20 mA g −1 than those with the conventional electrolyte (initial capacity of 187.7 mAh g −1 and capacity retention of 19.9%). This work paves the way to the development of practical DRX cathode‐based high‐energy Li batteries.

25 ENERGY STORAGE↗
DOE OSTI2024

Accelerating the Electrochemical Formation of the δ Phase in Manganese-Rich Rocksalt Cathodes

Mn-rich disordered rocksalt materials with Li-excess (DRX) materials have emerged as a promising class of earth-abundant and energy-dense next-generation cathode materials for lithium-ion batteries. Recently, an electrochemical transformation to a spinel-like “δ” phase has been reported in Mn-rich DRX materials, with improved capacity, rate capability, and cycling stability compared with previous DRX compositions. However, this transformation unfolds slowly over the course of cycling, complicating the development and understanding of these materials. In this work, it is reported that the transformation of Mn-rich DRX materials to the promising δ phase can be promoted to occur much more rapidly by electrochemical pulsing at elevated temperature, rate, and voltage. To extend this concept, micron-sized single-crystal DRX particles are also transformed to the δ phase by the same method, possessing greatly improved cycling stability in the first demonstration of cycling for large, single-crystal DRX particles. To shed light on the formation and specific structure of the δ phase, X-ray diffraction, scanning electron nanodiffraction (SEND) and atomic resolution STEM-HAADF are used to reveal a nanodomain spinel structure with minimal remnant disorder.

25 ENERGY STORAGE↗
DOE OSTI2024

Integrated rocksalt–polyanion cathodes with excess lithium and stabilized cycling

Co- and Ni-free disordered rocksalt cathodes utilize oxygen redox to increase the energy density of lithium-ion batteries, but it is challenging to achieve good cycle life at high voltages >4.5 V (versus Li/Li + ). Here, in this study, we report a family of Li-excess Mn-rich cathodes that integrates rocksalt- and polyanion-type structures. Following design rules for cation filling and ordering, we demonstrate the bulk incorporation of polyanion groups into the rocksalt lattice. This integration bridges the two primary families of lithium-ion battery cathodes—layered/spinel and phosphate oxides—dramatically enhancing the cycling stability of disordered rocksalt cathodes with 4.8 V upper cut-off voltage. The cathode exhibits high gravimetric energy densities above 1,100 Wh kg -1 and >70% retention over 100 cycles. This study opens up a broad compositional space for developing battery cathodes using earth-abundant elements such as Mn and Fe.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Activated Internetwork Pathways in Partially‐Disordered Spinel Cathode Materials with Ultrahigh Rate Performance

Abstract In this study, a class of earth‐abundant, cation‐excess partially disordered spinel materials which demonstrate superior rate performance as Li‐ion cathodes compared to disordered rocksalt materials is computationally investigated. These results show that the partial disorder creates solid solution lithiation with spinel‐like features at the atomic level. A low‐voltage capacity gain is possible with lithiation past the rock salt stoichiometry. It is argued that high rate in partially disordered spinel materials comes from newly activated 16c/16d internetwork pathways which are not possible in normal spinel where only 16c intranetwork diffusion occurs. The assessment and understandings motivate the incorporation of some degree of partial spinel ordering in future disordered rocksalt electrodes to enable superior rate performance.

Yang, Julia H.↗
DOE OSTI2021

Non-topotactic reactions enable high rate capability in Li-rich cathode materials

High-rate cathode materials for Li-ion batteries require fast Li transport kinetics, which typically rely on topotactic Li intercalation/de-intercalation because it minimally disrupts Li transport pathways. In contrast to this conventional view, here we demonstrate that the rate capability in a Li-rich cation-disordered rocksalt cathode can be significantly improved when the topotactic reaction is replaced by a non-topotactic reaction. The fast non-topotactic lithiation reaction is enabled by facile and reversible transition metal octahedral-to-tetrahedral migration, which improves rather than impedes Li transport. Using this concept, we show that high-rate performance can be achieved in Mn- and Ni-based cation-disordered rocksalt materials when some of the transition metal content can reversibly switch between octahedral and tetrahedral sites. Overall, this study provides a new perspective on the design of high-performance cathode materials by demonstrating how the interplay between Li and transition metal migration in materials can be conducive to fast non-topotactic Li intercalation/de-intercalations.

25 ENERGY STORAGE↗