WO2025111383A1 - D0-less disordered rocksalt oxides and oxyfluoride cathode materials - Google Patents

Abstract

A cathode active material useful in an electrode and including a compound comprising a lithium transition metal oxide, a sodium transition metal oxide, a lithium transition metal oxyfluoride, or a sodium transition metal oxyfluoride. The compound has a cation disordered rocksalt (DRX) structure, and all of the cation sites of the DRX structure are occupied by a transition metal ion (M) that has one or more electrons in its d-shell. Further, the compound is comprised of large (micron-sized) particles.

Description

D⁰-LESS DISORDERED ROCKSALT OXIDES AND OXYFLUORIDE CATHODE MATERIALS CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit under 35 U.S.C. Section 119(e) of the following co-pending and commonly-assigned application: U.S. Provisional Application Serial No.63/601,146, filed on November 20, 2023, by Vincent Wu and Raphaële Clément, entitled “D⁰- LESS DISORDERED ROCKSALT OXIDES AND OXYFLUORIDE CATHODE MATERIALS,” attorneys’ docket number G&C 30794.0852USP2 (UC-2024-869-1); which application is incorporated by reference herein. BACKGROUND OF THE INVENTION 1. Field of the Invention. The present disclosure relates to cathode active materials and methods of making the same. 2. Description of the Related Art. The increasing demand for energy dense, portable power has motivated the development of Li-ion batteries. The cathode component is typically the most expensive and limiting in terms of charge storage capacity. Disordered rocksalt oxides and oxyfluorides are promising high energy density cathodes with a flexible choice of redox-active metal (Mn, Fe, V, Ni, Cr). However, the preparation of micron-sized DRX compounds has so far required the presence of a d⁰ transition metal ion, that is, a transition metal with no electrons in its d electronic shell (e.g., Ti⁴⁺, Zr⁴⁺, Nb⁵⁺, V⁵⁺, Mo⁶⁺) and therefore no redox activity, reducing overall capacity. In contrast, mechanochemical synthesis has enabled the preparation of “d⁰-less” DRX compounds (6-7), but at the cost of drastic particle size reduction, which has been associated with reduced cycle life. What is needed are improved cathode active materials, specifically, d⁰- less compounds comprising large (micron-sized) particles for enhanced capacity and capacity retention during cycling. The present disclosure satisfies this need. SUMMARY OF THE INVENTION The present disclosure reports on new, high energy density battery cathode materials, specifically, “d⁰-less” disordered rocksalts (DRX), which comprise large (micron-sized) particles. Characterization of representative systems demonstrates that utilization of 1) rapid high- temperature microwave heating, and/or 2) d⁵ metal ions such as Fe³⁺, can produce phase pure micron-sized DRX materials that do not rely on d⁰ transition metal ions and exhibit both high capacity and excellent capacity retention during electrochemical cycling. The compositional flexibility of d⁰-less DRX is demonstrated by the synthesis of 8 new compositions, including Mn, Mn-Fe, Mn-Ni, Mn- Cu, and Mn-Cr DRX that do not contain any d⁰ transition metal ion. A ^{particular composition, Li} _{1.1Mn(III)0.8Mn(IV)0.1O1.9F0.1 (referred to as} LM9) is highlighted, and its electrochemical performance is compared to the current state-of-the-art DRX (comprising d⁰ species), Li_1.1Mn_0.8Ti_0.1O_1.9F_0.1 (referred to as LMT81). LM9 demonstrates superior cycling performance to LMT81 with higher energy densities and improved voltage retention. Both LMT81 and LM9 undergo a phase transformation during cycling, which leads to capacity activation and increases the energy density of the cathode. The phase transition in LM9 is kinetically facile and occurs over fewer charge-discharge cycles than LMT81, enabling high performance cycling of large (micron-sized) LM9 particles, with remarkable cycling stability. Overall, a large and unexplored compositional space for DRX cathodes has been opened, and the LM9 composition represents a significant leap towards the practical commercialization of next- generation, high energy density, Ni- and Co-free Li-ion cathode materials. BRIEF DESCRIPTION OF THE DRAWINGS The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. Referring now to the drawings in which like reference numbers represent corresponding parts throughout: Figure 1: Lab powder XRD of (a) successful microwave s^{ynthesis of all Mn, Mn-Ni, Mn-Cu, Mn-Cr, and Mn-Fe d0} _{-less DRX} compositions, (b) unsuccessful solid-state synthesis of LM9 at various sintering temperatures, and (c) successful solid-state synthesis of Mn- Fe d⁰-less DRX compositions at 1100°C. Figure 2: Neutron diffraction patterns along with Rietveld refinement fits of as-synthesized LMT81 and LM9, plotted with linear (a,b) and logarithmic (c, d) intensity axes. Figure 3: a) Overlaid neutron PDF data of LMT81 and LM9, along with fits to LM9 PDF data at short correlation lengths (2-10Å) using b) a cubic rocksalt model (space group Fm-3m, #255) and c) a spinel tetragonal model (space group I41/amd, #141). Figure 4: a,b) Scanning Electron Microscope (SEM) images of as-synthesized LMT81 and LM9. c) ⁷Li and d) ¹⁹F spin echo solid-state NMR spectra of LM9. All spectra were acquired at 2.35 T with a magic angle spinning (MAS) speed of 60 kHz, and spinning side bands are indicated by asterisks. Figure 5: Galvanostatic cycling voltage profiles and differential capacity (dQ/dV) plots for large particle, post-formation a,b) LMT81 and c,d) LM9 composite cathodes. Plots of the discharge capacity e), and of the average discharge voltage f), against the cycle index for large particle, post-formation LMT81 and LM9 composite cathodes. Figure 6: Electrochemical performance of LM9 with three different cathode processing parameters: large particle, post formation (LM9-PF), small particle, no formation (LM9-SP), and large particle, no formation (LM9-NF). Capacity (a), capacity retention (b), average discharge voltage (c), and gravimetric energy density (d), are plotted against cycle index. Figure 7: Flowchart illustrating a method of making a composition of matter. Figure 8: Schematic of a crucible used for holding the precursors during microwave synthesis. Figure 9: Schematic of a rocksalt structure 900 according to one or more embodiments, Green polyhedrals 904 indicate Li+, purple polyhedrals 906 indicate transition metal ions, and the red balls 908 indicate anions (O2- or F-). Figures 10a-10c. XANES on as-synthesized LM9 and LMT81, wherein LM9 is Li1.1Mn(III)0.8Mn(IV)0.1O1.9F0.1 and LMT81is Li1.1Mn(III)0.8Ti(IV)0.1O1.9F0.1 and average Mn oxidation slightly > 3 for LM9, and slightly <3 for LMT81, wherein Figure 10a shows normalized absorbance, Figure 10b shows zoomed in view of Figure 10a, and Figure 10c shows zoomed in view of Figure 10b. Figure 11a-11e. Electrochemical tests on other d0 less cathodes comprising LMN711 (Figure 11a): LiMn(III)_0.75Mn(IV)_0.125Ni_0.125O₂, LMC531 (Figure 11b): Li_1.1Mn(III)_0.5Mn(IV)_0.3Cu_0.1O₂, LM9: Li_1.1Mn(III)_0.8Mn(IV)_0.1O₂, M62: Li_1.2Mn(III)_0.6Mn(IV)_0.2O₂ ; LMOF-C3 (Figure 11c), LMOF-C01 (Figure 11d) and LMN531 (Figure 11e): Li_1.1Mn(III)_0.5Mn(IV)_0.3Ni_0.1O₂ (20 mA/g, 3-4.5V, 25°C small particles, no formation) Figure 12. Specific capacity measurements. Figure 13a. Schematic of a battery comprising the cathode active material. Figure 13b. Schematic of an anode-less battery comprising the cathode active material. DETAILED DESCRIPTION OF THE INVENTION In the following description of the preferred embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. Technical Description As noted above, d⁰ transition metal ions are not redox active, thus it would be desirable to remove them from the DRX cathode structure. Furthermore, large (micron-sized) cathode particles are desirable for capacity retention. The present disclosure reports on the demonstration of micron-sized “d⁰-less” DRX compositions which, as the name suggests, can be stabilized without d⁰ transition metal ions through rapid and high temperature heating (e.g., microwave synthesis), and/or by including a d⁵ ion such as Fe³⁺. In one or more embodiments, a cathode active material useful as an electrode comprises a lithium transition metal oxide, a sodium transition metal oxide, a lithium transition metal oxyfluoride, or a sodium transition metal oxyfluoride having a cation disordered rocksalt (DRX) structure, wherein all of the cation sites of the DRX structure are occupied by a transition metal ion that has one or more electrons in its d-shell. In typical embodiments, the cathode active material has the general formula: A_1+xM_1-xO_2-yF_y, wherein A is Li or Na, M comprises one or more transition metal ion species, and x ≤ 0.4 and y ≤ 0.2, e.g., as measured by ICP-OES. As a demonstration, 8 new d⁰-less DRX compositions have been successfully synthesized: Li_1.1Mn(III)_0.8Mn(IV)_0.1O_1.9F_0.1, Li_1.2Mn(III)_0.6Mn(IV)_0.2O_1.8F_0.2, Li_1.1Mn(III)_0.5Mn(IV)_0.3Ni_0.1O_1.9F_0.1, LiMn(III)_0.75Mn(IV)_0.125Ni_0.125O_1.9F_0.1, Li_1.1Mn(III)_0.5Mn(IV)_0.3Cu_0.1O- _1.9F_0.1, Li_1.2Mn(III)_0.7Mn(IV)_0.1Cr_0.1O_1.9F_0.1, Li_1.05Mn(III)_0.65Fe_0.3O_1.9F_0.1, Li_1.1Mn(III)_0.65Mn(IV)_0.1Fe_0.2O_1.9F_0.1,e .g., as measured by ICP-OES. In the following examples, the performance of Li_1.1Mn(III)_0.8Mn(IV)_0.1O_1.9F_0.1, hereafter referred to as LM9, is highlighted and compared against the current state-of-the-art d⁰ transition metal-containing DRX composition, Li_1.1Mn(III)_0.8Ti_0.1O_1.9F_0.1, hereafter referred to as LMT81, where LM9 has significantly higher energy density than LMT81 (600 Wh/kg vs.500 Wh/kg). In particular, we have demonstrated that high-Mn content DRX, such as LMT81, can be cycled as large particles due to an electrochemically-induced phase transformation to a partially spinel- ordered structure with improved Li-ion transport. To accelerate this phase transformation, an electrochemical processing or conditioning can be performed, wherein the electrochemical cell is subjected to one or more charge/discharge cycles. The slow phase transformation for LMT81 results in either reduced capacity due to incomplete transformation, or an unreasonably long formation protocol to increase the specific capacity of the cathode. The d⁰-less LM9 cathode, on the other hand, shows a much faster phase transformation, enabling a reasonably short formation protocol and a high activated capacity. More specifically, electrochemical testing of composite cathodes comprising large (micron-sized) LM9 particles in a Li half-cell results in a remarkable 220 mAh/g of capacity, with an impressive 96.5% capacity retention after 50 cycles, corresponding to a cycle life of 227 cycles given end-of-life defined as 20% capacity fade. For context, there are two major competing cathode chemistries currently on the market: lithium iron phosphate (LFP), and layered nickel-manganese-cobalt oxides (NMC811). LFP has a capacity of ~140 mAh/g, while NMC811 has a capacity of ~200 mAh/g. We further emphasize electrochemical testing of LMT81 and LM9 is performed on cathode composites made from large particle DRX, whereas most reports on DRX performance are on post-processed DRX where particles are downsized via a milling step. First Example: Microwave (MW) synthesis of d⁰-less DRX and of LMT81 1. Selection of precursor compounds Li₂CO₃ and LiF were chosen as Li and F sources. However, most Li- and F- containing compounds can also be used, such as Li₂O, LiNO₃, PTFE, etc. In general, an oxide of the transition metal with the proper ^{oxidation state of interest is selected. For LM9, Mn} _{2O3 and MnO2 are} used to provide Mn³⁺ and Mn⁴⁺. However, salts containing proper metal ion species can also be used. 2. Preparation of precursor pellets for LMT81 and LM9 LMT81: Li₂CO₃, LiF, Mn₂O₃, and TiO₂ powders were measured out such that Mn, Ti and F stoichiometries matched the chemical formula Li_1.1Mn_0.8Ti_0.1O_1.9F_0.1. LM9: Li₂CO₃, LiF, Mn₂O₃, and MnO₂ powders were measured out such that Li, Mn³⁺, Mn⁴⁺, and F stoichiometries matched the chemical formula Li_1.1Mn(III)_0.8Mn(IV)_0.1O_1.9F_0.1. Precursor powders were mixed by ball milling with ethanol at 300 rpm, dried, and then pressed into 200 mg pellets. 3. Microwave heating and quenching of precursor pellets A double crucible setup 800was arranged, whereby a small alumina crucible 804 is placed in the center of a larger crucible 808 as illustrated in Fig.8, and activated carbon 806 was added to the larger crucible to surround the smaller inner crucible. A layer of sacrificial precursor powder was added to the small crucible, and the precursor pellet 802 was carefully placed on top of the powder in the small crucible. The setup was placed into a 1200 W conventional microwave in an ambient atmosphere and irradiated with microwaves 810 at a set power level (5) and time (5 min). The activated carbon serves to resonate with the microwaves and heat up, and the pellet is initially heated via a conductive process. Past a critical temperature however, the pellet material becomes susceptible to microwave irradiation, whereby heating occurs via direct interaction with the microwaves, leading to high reaction temperatures. Immediately after the microwave heating terminated, the pellet was rapidly quenched in distilled water. The pellet was dried on a hotplate and ground to obtain a fine powder of the final DRX product. Second Example: Solid-state synthesis of d⁰-less LM9 and Mn-Fe compositions An identical precursor pellet fabrication protocol was used as described for microwave synthesized LM9. Standard solid-state reaction was performed at 900°C and/or at 1100°C for 2h under Ar flow. After calcination, the pellet was allowed to cool quickly by opening the furnace. The solid-state synthesis method comprises to mix precursor powders, pelletizing the mixture to form a pellet, and then sintering the pellet at a high temperature (with or without additional grinding, pelletizing, or one or more sintering steps). The method used here used one single sintering step. Third Example: Comparison of Microwave and solid state synthesized compositions and impact on stabilization of d⁰-less DRX compositions Large differences in ionic radii between Li and transition metals destabilize (increase the enthalpy of formation) of DRX oxides as compared to their ordered (layered or spinel) transition metal oxide counterparts. Traditionally, some amount of d⁰ transition metals, i.e. Ti⁴⁺, Nb⁵⁺, V⁵⁺, is required in order to stabilize the DRX structure and allow its high temperature synthesis. Microwave synthesis provides a very different thermodynamic and kinetic pathway towards DRX formation when compared to traditional solid-state (furnace) synthesis. In particular, higher temperatures and rapid quenching can be achieved. Without being bound to a particular scientific theory, we postulate that microwave synthesis enables the preparation of d⁰-less DRX compositions by providing entropic stabilization at high temperatures, followed by a fast quench to room temperature to prevent the formation transformation of more stable ordered (layered or spinel) phases on cooling. The first d⁰-less compositions were obtained by replacing Ti⁴⁺ by Mn⁴⁺ in Li_1.2Mn_0.6Ti_0.2O_1.8F_0.2 (LMT62) and LMT81, resulting in Li_1.2Mn(III)_0.6Mn(IV)_0.2O_1.8F_0.2 and Li_1.1Mn(III)_0.8Mn(IV)_0.1O_1.9F_0.1. Figure 1a shows the successful (phase pure) preparation of these compounds through microwave synthesis. However, all attempts to synthesize those two compositions via standard solid-state sintering were unsuccessful (Figure 1b), indicating the need for rapid microwave heating, followed by quenching. We extended our compositional space to other d⁰-less compositions based on Mn-Cr, Mn-Ni, and Mn-Cu. Mn⁴⁺ was utilized in all of these compositions to maintain a high transition metal valence to enable the presence of Li excess, but other metals may also be possible (Figure 1a). Mn-Fe d⁰-less compositions were also stabilized. Interestingly, those compositions could be prepared by both microwave synthesis (Figure 1a) and solid-state synthesis (Figure 1c), suggesting that the redox-active, half-filled d⁵ (Fe³⁺) ions impart some stability to the DRX structure. The successful synthesis of d⁰-less DRX via microwave synthesis opens new avenues for the design and compositional optimization of DRX cathodes. In addition, d⁰-less DRX compounds containing a d⁵ ion can also be stabilized with solid-state synthesis (Figure 1c). Third Example: Structural and composition characterization of LM9 and LMT81 a. X-ray diffraction measurements In this example, the d⁰-containing LMT81 and d⁰-less LM9 compounds prepared by microwave synthesis were compared. Neutron diffraction patterns for LMT81 and LM9 are shown in Figure 2, where sharp DRX peaks can be observed for both samples indicating largely phase pure products with a high crystallinity. In addition to intense Bragg reflections, broad peaks are also observed, and correspond to short-range cation ordering in the DRX materials. The broad peaks are better observed when the signal intensity is plotted on a log scale (Figure 2c-d). The similar broad peaks observed for LMT81 and LM9 indicate similar cation short-range orderings. These broad reflections are well fit with a tetragonal spinel-like I41/amd model, where Li preferentially occupies the octahedral 4a site, while transition metals (Mn and Ti) largely occupy the 4b site and is in line with prior studies of short-range order in Mn-based DRX. In addition to diffraction, pair density function (PDF) data was also analyzed to provide more direct insight into cation short-range ordering (Figure 3). Almost identical PDF patterns are obtained for LMT81 and LM9 (Figure 3a), corroborating the neutron diffraction results and indicating similar cation short-range ordering in the two samples. Fits to short correlation length are better for an ordered I41/amd model than for the disordered Fm-3m model, also a sign of cation short- range ordering in the material. b. Composition and particle morphology of microwave synthesized LMT81 and LM9 powder samples by NMR and ICP-EOS

Table 1: DRX stoichiometries of LMT81 and LM9, obtained from ICP, F-ISE, and solid-state NMR results.

In most as-synthesized DRX samples, low crystallinity Li and/or F- containing impurity phases are present but difficult to detect through diffraction. Here, ⁷Li and ¹⁹F solid-state nuclear magnetic resonance (NMR) was used to quantify impurity phases. Solid-state NMR, combined with inductively coupled plasma optical emission spectroscopy (ICP-OES) and fluoride ion selective electrode (F-ISE) measurements, allows to determine the impurity content and the true stoichiometry of the DRX cathode phase. The ⁷Li ssNMR spectrum for LM9 is shown in Figure 4c, where the broad lineshape correspond to Li species in the DRX phase, while the sharp peak near 0 ppm corresponds to Li species in diamagnetic impurities such as Li₂CO₃, LiF, and Li₂O. These components can be fit and integrated to provide the Li content in the DRX phase. A similar analysis can be carried out for F species using ¹⁹F solid- state NMR (Figure 4d). However, ¹⁹F solid-state NMR is only semiquantitative as F species directly bonded to Mn in the DRX are NMR-invisible due to paramagnetic interactions. Thus, only an upper and a lower bound for the F content in the DRX phase can be determined. The final DRX stoichiometries for LMT81 and LMT9 can be determined by combining ICP, F-ISE, ⁷Li and ¹⁹F solid-state NMR results, as shown in Table 1, where close to expected Li, Mn and Ti contents are obtained. In line with prior studies, a low F solubility limit is observed for those high-Mn DRX compositions. Scanning electron microscopy (SEM) images show similar particle morphologies and sizes between LMT81 and LM9, where single crystals ranging from 0.5-3 µm are observed. Overall, microwave synthesis results in the preparation of LMT81 and LM9 DRX cathode samples with a similar cation short-range ordering in the DRX phase, similar particle morphology and size, and similar impurity contents. Those similarities allow a fair comparison of their electrochemical properties in the next section. Fourth Example: Electrochemical performance of micron-sized LMT81 and LM9 a. Electrochemical conditioning In order to obtain significant capacity from DRX cathode samples comprised of large (micron-sized) particles, further electrochemical processing is required (e.g., performing one or more charging and discharging cycles in a battery), which is referred to as the formation protocol hereafter. b. Comparing the performance of micron-sized LMT81 and LM9 composite cathodes Figure 5 compares the electrochemical performance of post- formation, large particle (micron-sized) LMT81 and LM9 composite cathodes, where Li half-cells were cycled galvanostatically at 25°C with a 20 mA/g rate. LMT81 has an initial capacity of 171 mAh/g, which increases slowly to a maximum capacity of 183 mAh/g corresponding to an energy density of 500 Wh/kg at 40 cycles. LM9 has a starting capacity of 213 mAh/g which more rapidly rises to a maximum value of 220 mAh/g with a corresponding energy density of 600 Wh/kg by the 9^th cycle, ~40 mAh/g (100 Wh/kg) greater than the peak capacity for LMT81. Both DRX compositions display pseudo voltage plateaus on discharge at 4 V and 3 V vs. Li/Li⁺, however LM9 exhibits greater capacity in the high voltage regime than LMT81 (54 vs.36 mAh/g), indicative of more extensive growth of spinel-like domains (Figure 5a-d). While the capacity increase for LMT81 occurs slowly over 40 cycles, the much quicker rise in capacity for LM9 indicates a faster transformation process for the d⁰-less composition. The 3 V pseudo-plateau in LMT81 initially reduces in size, shifting the ~3 V redox peak on discharge to lower potentials (Figures 5a-b) and resulting in a decrease in the average discharge voltage. In contrast, only a very small decrease in the 3 V pseudo-plateau occurs in LM9 (Figures 5c-d). A flatter and more extended 3V pseudo-plateau on charge for LM9 results in a sharper dQ/dV peak at lower voltages, as seen in Figures 5a-d. Overall, the larger capacity at high voltage, reduced voltage fade at the ~3 V pseudo-plateau on discharge, and the lower redox peak on charge for LM9 results in not only a higher operating voltage but also a significantly reduced voltage hysteresis at 50 cycles (1.0 and 0.7 V difference between charge and discharge potential, for LMT81 and LM9 respectively). c. Impact of particle size on LM9 electrochemical performance Two additional LM9 cathodes subjected to different post-synthesis processing protocols were galvanostatically cycled under similar conditions: • large particle LM9 prepared in the same manner as described prior, albeit without a formation step (LM9-NF), • small particle LM9 downsized via ball milling with conductive carbon, also cycled without preliminary formation (LM9-SP). Comparison of the capacity curves for LM9-SP and LM9-NF in Figure 6a highlights the impact of particle size on the DRX to partially spinel-ordered phase transformation and the ensuing capacity activation observed during the first few charge-discharge cycles. Though neither cathode has been subjected to a formation protocol, LM9-SP still shows a high initial capacity of 211 mAh/g, in contrast to LM9-NF where the initial capacity is of only 58 mAh/g. The capacity retention of LM9-PF is 92.3 % (relative to peak capacity) after 100 cycles, while LM9-SP exhibits peak capacity at cycle 11, with just 76.1 % capacity retention after 100 cycles. The stable cycling performance of LM9-PF is achieved without particle coating or electrolyte optimization, and further improvements in long-term cycling stability are expected after some optimization. LM9-NF takes 25 cycles to reach a relatively low maximum capacity of 145 mAh/g while LM9-LP only takes 10 cycles to reach a much higher maximum capacity of 268 mAh/g. While the peak capacity of LM9-SP is higher than that of LM9-PF (268 mAh/g vs.220 mAh/g), the capacity retention of LM9-PF is much improved (96.5% vs.89.7% retention at 50 cycles). When extrapolated to obtain cell lifetime defined as 80% of peak capacity, the operable cycle life of LM9-PF is 227 cycles, compared to just 66 cycles for LM9-SP, a more than three-fold increase. As we expected, the presence of large (micron-sized) primary particles imparts significant cycling stability to DRX cathodes, as detrimental reactions at the cathode-electrolyte interface are reduced due to the smaller relative surface areas and lack of high-energy surface defects that would be generated during the milling step that is typically used for particle downsizing. While downsizing particles is required for most DRX compositions to enable any significant electrochemical activity, practical commercialization of DRX requires that larger (micron-sized) particles be cycled without further downsizing through mechanochemical milling, due to several key issues: The milling step is difficult to scale and will contribute unacceptable material loss during production due to imperfect powder recovery. Moreover: • The high surface area to volume ratio of nanosized powders exacerbates interfacial cathode-electrolyte decomposition reactions, resulting in rapid capacity fading and a short cell cycle lifetime. • Nanosized powders cannot be packed as densely, resulting in reduced volumetric energy densities. Experimental methods and protocols used to obtain the data in the examples Powder X-ray diffraction patterns were collected using a laboratory-source Panalytical Empyrean diffractometer with Cu Kα radiation in reflection geometry. Neutron total scattering data (including neutron diffraction and neutron PDF) was collected at the NOMAD beamline at Oak Ridge National Laboratory. Rietveld refinements for neutron diffraction data were carried out using GSASII, and neutron PDF data was analyzed with PDFGui. Scanning Electron Microscope (SEM) images were obtained using a Thermo Fisher Apreo C LoVac SEM instrument with an accelerating voltage of 5 keV and current of 0.4 nA. Bulk chemical compositions were determined via Inductively Coupled Plasma Optical Emission Analysis/Spectroscopy (ICP-OES), using an Agilent 5800 ICP-OES, and fluoride selective ion electrode (F- ISE) measurements using a Cole-Parmer system. DRX samples were digested in a mixture of nitric acid and hydrochloric acid. For ICP-OES, the digested solutions were diluted with distilled water. For F-ISE measurements, the solutions were diluted using a 23 sodium acetate buffer and a fluoride ionic strength adjuster solution (TISAB, Cole- Parmer). The amount of Li and M in the active material powders was measured with an Inductively Coupled Plasma (ICP) method by using an Agilent 5800 ICP-OES instrument.10 mg of the powder sample was dissolved into a mixture of 4 mL concentrated nitric acid and 1 mL concentrated hydrochloric acid. Afterwards, a 1 mL aliquot of the dissolved sample solution was pipetted into a falcon tube, followed by 13 mL of distilled water, resulting in a 14x dilution by volume. The diluted solution was used for ICP-OES measurement. The Li, Mn, Ti, measured are expressed as mol% of the total of these contents. The amount of F in the active material powder was measured with the fluoride ion selective electrode (F-ISE ) measurements. A ~0.5 g aliquot of the dissolved sample solution prepared above was measured and added to a plastic HDPE bottle. ~2 g of distilled water was added to the bottle. Finally, ~25 mL of a mixture of 15% aqueous sodium acetate: Tisab buffer (obtained from Cole-Parmer) in a 10:1 wt ratio was added, to adjust the final solution pH to be between 5 and 8, and to provide an ionic strength adjuster for fluoride. This final solution was used for the F-ISE measurement. Since the mass of every component of the final solution was measured, the amount of F in the original dissolved sample solution could be back calculated and the mol% of F in relation to Li, Mn, and Ti from ICP results could be obtained. The Li, Mn, Ti, F measured are expressed as mol% of the total of these contents. Materials Processing Steps Figure 7 is a flowchart illustrating a method of synthesizing a d⁰- less DRX composition of matter. Block 700 represents mixing precursor powders to form a precursor mixture, wherein the precursor powders comprise a lithium or sodium precursor and one or more transition metal precursors comprising one or more transition metals having one or more electrons in their d- shells. In one or more examples, the precursors comprise PTFE or a sol- gel precursor. In one or more embodiments, the precursors comprise LiF. Without being bound by a particular scientific theory, the LiF may act as a sintering agent to help the diffusion of the elements in the rocksalt structure during the heating to form the calcined powder in Block 702. Block 702 represents heating the precursor mixture to a temperature high enough (e.g., at least 1100°C, e.g., 1500°C) and at a heating rate above a threshold so as to form a calcined powder comprising a d⁰-less rocksalt-type crystalline structure comprising a disordered arrangement of cations. In one or more embodiments, the heating comprises microwave ^{heating using microwave radiation having a frequency in a range 0.1 to} 10 GHz, e.g., in an air environment for at least 10 minutes. Fig.8 illustrates an example crucible for holding the precursors during the microwave synthesis. In one or more embodiments, the one or more of the transition metals comprise a d⁵ ion (e.g., Fe³⁺) and the heating comprises solid state synthesis in a furnace, e.g., for at least 2 hours at a temperature of 900-1100°C under Ar gas flow. Block 704 represents cooling (e.g., stopping the heating and quenching) at a rate sufficiently fast so that the calcined powder cools into a cathode active material retaining the rocksalt-type crystalline structure at room temperature. In one or more examples, the quenching is in a liquid such as water or liquid nitrogen. In an embodiment using microwave synthesis, the cooling comprises stopping the radiation and quenching in a liquid medium for a duration of less than 2 minutes. Block 706 represents the end result, a composition of matter useful as a cathode active material for a battery. Fig.9 illustrates an embodiment comprising a rocksalt structure, comprising a lithium transition metal oxide, a sodium transition metal oxide, a lithium transition metal oxyfluoride, or a sodium transition metal oxyfluoride, wherein the compound has a cation disordered rocksalt (DRX) structure, and all of the cation sites of the DRX structure are occupied by lithium and/or sodium and a transition metal ion that has one or more electrons in its d- shell. Example compositions and cathode active materials manufactured using the method are described in the following section. In one or more embodiments, the method can further comprise assembling the cathode active material in a cathode composite to be used in a battery, and conditioning the cathode active material by e.g., charging and discharging the battery to transform the rocksalt-type crystalline structure into a partially spinel-ordered structure. While we induced the formation of a partially spinel ordered rocksalt structure through electrochemical cycling (repeated charge/discharge), one can also induce this transformation by chemical delithiation (extraction of Li using an oxidizing agent) followed by a heat treatment (e.g., somewhere between ca.100°C and 400°C or more). Further preparation details The following samples described herein:

Li_1.1Mn(III)_0.5Mn(IV)_0.3Ni_0.1O_1.9F_0.1, LiMn(III)_0.75Mn(IV)_0.125Ni_0.125O_1.9F_0.1, Li_1.1Mn(III)_0.5Mn(IV)_0.3Cu_0.1O_1.9F_0.1, Li_1.2Mn(III)_0.7Mn(IV)_0.1Cr_0.1O_1.9F_0.1, Li_1.05Mn(III)_0.65Fe_0.3O_{- 1}.9F_0.1, Li_1.1Mn(III)_0.65Mn(IV)_0.1Fe_0.2O_1.9F_0.1. were prepared using the following method. Stoichiometric amounts of Li₂CO₃, LiF, Mn(III)₂O₃, Mn(IV)O₂ and TiO₂ precursors targeting corresponding to Li_1.1Mn(III)_0.8Ti_0.1O_1.9F_0.1 for LMT81 and Li1.1Mn(III)0.8Mn(IV)0.1O1.9F0.1 for LM9 were used. Precursors were ^{mixed by ball-milling with ethanol at 300 rpm, dried, and then pressed} into 200 mg pellets. A double crucible setup was used for microwave synthesis, where a small alumina crucible was placed inside a larger crucible filled with 5 g of activated charcoal. The precursor pellet was placed in the small alumina crucible on top of a layer of sacrificial precursor powder to prevent reaction between the alumina surface and the pellet. The entire setup was placed in a conventional 1200W microwave, and heated at appropriate 600W for 5 min in an ambient air atmosphere. Upon termination of microwaves, the pellet was immediately quenched into a beaker of distilled water to stabilize the DRX phase. The DRX pellet was then dried on a hot plate and ground into powder. For additional d0 DRX compositions, an identical procedure was used, albeit with different precursors. Li2CO3, LiF, Mn(III)2O3, Mn(IV)O2, NiO, CuO, Fe₂O₃, Cr₂O₃ were used as sources for Li, F, Mn(III), Mn(IV), Ni, Cu, Fe, and Cr, respectively, and for each compositions, stoichiometric amounts of the corresponding precursors were measured out. After a mixing and pelletizing step, all compositions could be synthesized at 600W for 5 min under an ambient air environment. Distilled water was used as a quenching media for all compositions, with the exception of Cr- based DRX, where ethanol was used to prevent dissolution of Cr ions into water. XANES characterization technique to identify the oxidation state of Mn. The Mn oxidation state for the Li1.1Mn(III)0.8Mn(IV)0.1O1.9F0.1 (LM9) and Li1.1Mn(III)0.8Ti(IV)0.1O1.9F0.1 (LMT81) compounds was obtained from XANES. The data is shown in Figure 10.. Methods: X-ray absorption spectroscopy was performed at beamline TPS 44A at the Taiwanese National Synchrotron and Radiation Research Center (NSRRC). The ATHENA suite was used for all XAS analysis. Additional electrochemical data is presented in Figure 11 and Figure 12. Device, composition of matter, and method embodiments (e.g., manufacturable using the method described in relation to Fig.7). Illustrative embodiments include, but are not limited to, the following (referring also to Figs.1-13). 1. A cathode active material (or composition of matter) 400 useful as a battery electrode, comprising particles 402 comprising a lithium transition metal oxide, a sodium transition metal oxide, a lithium transition metal oxyfluoride, and/or a sodium transition metal oxyfluoride, wherein the cathode active material has a disordered rocksalt (DRX) structure 900, wherein the cation sites 902 of the DRX structure are occupied by lithium 904, sodium, and/or a transition metal 906 having at least one electron in its d-shell, wherein the particles have a particle size D of at least 0.5 micron, e.g., as used during operation of a battery comprising a cathode comprising the cathode active material. 2. A cathode active material according to embodiment 1, wherein the disordered rocksalt structure is according to the formula A_1+xM_1-xO_2-yF_y, wherein: A is Li or Na, M comprises Mn and at least a transition metal having at least one electron in its d-shell, x ≤ 0.4 and y ≤ 0.2. In one or more embodiments, the content of Li, M and F is measured by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), Fluoride ion selective electrode (F-ISE), and ⁷Li and ¹⁹F solid-state nuclear magnetic resonance spectroscopy (ss- NMR). 3. A cathode active material according to embodiment 2, wherein M comprises Mn and a transition metal selected from Fe, Ni, Cu, and Cr. In one or more embodiments, the content of Li, Mn, Fe, Ni, Cu, Cr and F is measured by ICP-OES. 4. A cathode active material according to embodiment 2 or 3, wherein A is Li. 5. A cathode active material according to any of the embodiments 2 to 4, wherein x ≤ 0.2, optionally x ≤ 0.1, or optionally x is 0.1, 0.05 or 0. 6. A cathode active material according to any of the embodiments 2 to 5, wherein y ≤ 0.1 or optionally y is 0.1. 7. A cathode active material according to any of the embodiments 1 to 5, wherein the DRX structure is selected from Li_1.1Mn(III)_0.8Mn(IV)_0.1O_1.9F_0.1, Li_1.2Mn(III)_0.6Mn(IV)_0.2O_1.8F_0.2, Li_1.1Mn(III)_0.5Mn(IV)_0.3Ni_0.1O_1.9F_0.1, Li_1.0Mn(III)_0.75Mn(IV)_0.125Ni_0.125O- _1.9F_0.1, Li_1.1Mn(III)_0.5Mn(IV)_0.3Cu_0.1O_1.9F_0.1, Li_1.2Mn(III)_0.7Mn(IV)_0.1Cr_0.1O_1.9F_0.1, Li_1.05Mn(III)_0.65Fe_0.3O_1.9F_0.1, and Li_1.1Mn(III)_0.65Mn(IV)_0.1Fe_0.2O_1.9F_0.1, In one or more embodiments, the content of Li, Mn, Fe, Ni, Cu, Cr and F is measured by ICP-OES. 8. A cathode active material according to any of the embodiments 1 to 7, further comprising a partially spinel-ordered rocksalt structure. 9. The cathode active material according to any of the embodiments 1-8, wherein the transition metal has 5 electrons in its d- shell. 10. The cathode active material according to any of the embodiments 1-9, wherein the particles have the particle size comprising a diameter D (e.g., largest diameter or width) in a range of 0.5-10 micrometers. 11. The cathode active material of any of the embodiments 1, 4- 6, or 8-10, wherein the transition metal ion species (M) comprise at least one of Mn, Fe, Ni, Cu, or Cr. 12. .The cathode active material of any of the embodiments 1- 11, wherein the compound is phase pure without any segregated ordered oxide phases as characterized by X-ray diffraction. The cathode active material of any of the embodiments 1-12, wherein the structure further comprises a partially spinel-ordered rocksalt structure after further electrochemical processing (e.g., charging/discharging cycles in a battery configuration) or after further chemical and thermal processing (e.g., chemical delithiation followed by a heat treatment). 14. The cathode active material of any of the embodiments 1 or 3-13, wherein: the compound has the general formula: A_1+xM_1-xO_2-yF_y, wherein: A is Li or Na, M comprises one or more transition metal ion species, and x ≤ 0.4 and y ≤ 0.2. 15. A cathode active material 400, comprising: a compound having a cation disordered rocksalt (DRX) structure 900 and the general formula: A_1+xM_1-xO_2-yF_y, wherein: A is Li or Na, M comprises at least two different transition metal ion species and/or the same transition metal species in at least two different oxidation states, the transition metal species have at least one electron in their d- shells, and x ≤ 0.4 and y ≤ 0.2 16. The cathode active material of embodiment 15, wherein the M is Mn or comprises Mn in two different oxidation states (e.g., Mn(III) and Mn(IV)), or the cathode active material of embodiment 15 comprising the cathode active material of any of the embodiments 3-14. 17. The cathode active material of any of the embodiments 1-17, wherein the one or more transition metal ion species comprise a d⁵ ion. 18. A method for manufacturing a cathode active material (e.g., preferably/optionally according to any of the embodiments 1 to 17), comprising the following steps: Step 1) mixing ionic compound precursors together to form a precursor mixture, Step 2) heating the precursor mixture to a temperature of at least 1100°C or at least 1600°C to form a calcined powder comprising an ionic compound having a rocksalt-type crystalline structure with a disordered arrangement of cations, Step 3) cooling the calcined powder to form the active material retaining the rocksalt-type crystalline structure at room temperature. 19. The method according to embodiment 18, wherein Step 2) comprises exposing the precursor mixture to microwave radiation with a power and duration sufficient to form a microwaved powder comprising an ionic compound having a rocksalt-type crystalline structure with a disordered arrangement of cations. 20. The method according to embodiment 19, wherein the microwave radiation has a frequency in a range 0.1 to 10 GHz. 21. The method according to embodiment 19 or 20, wherein Step 3) comprises quenching the microwaved powder to form the active material retaining the rocksalt-type crystalline structure at room temperature. 22. The method according to any of the embodiments 18-21 wherein the cooling comprises quenching that is provided in a liquid (e.g., water or liquid nitrogen). 23. The method of any of the embodiments 19-22, wherein the microwave heating is an air environment for at least 10 minutes and the cooling comprises stopping the radiation and quenching in a liquid medium for a duration of less than 2 minutes. 24. The method of any of the embodiments 18 or 22, wherein one or more of the transition metals comprise a d⁵ ion (e.g., Fe³⁺) and the heating comprises solid state synthesis in a furnace. 25. The method of embodiment 24, wherein the heating is for at least 2 hours at a temperature of 900°C-1100°C, 900°C-1600°C ,1600°C or more ,or 1100°C under Ar gas flow. 26. The method of any of the embodiments 18-25, further comprising assembling the cathode active material in a cathode composite to be used in a battery, and conditioning the cathode active material by charging and discharging the battery to transform the rocksalt-type crystalline structure into a partially spinel-ordered structure. 27. The method of embodiment 26, wherein the conditioning uses less charging and discharging cycles as compared to the conditioning of the cathode active material comprising one or more d⁰ transition metal ions occupying the cation sites or the conditioning comprising a chemical ^{and thermal processing (e.g., chemical delithiation followed by a heat} treatment) uses a lower temperature as compared to the conditioning of the cathode active material comprising one or more d⁰ transition metal ions occupying the cation sites. 28. The method of any of the embodiments 18-27, wherein the cathode active material comprises particles having a diameter D (e.g., largest diameter) in the range of 0.5-10 microns that are not downsized by further mechanochemical milling. 29. The method of any of the embodiments 18-28, wherein one or more of the transition metals comprises a d⁵ ion and the temperature and the rate of cooling are lower than the temperature and rate of cooling used to form the ionic compound without the d⁵ ion. 30. The method of any of the embodiments 18-29, wherein the precursors comprise LiF. 31. The method of embodiment 30, further comprising using the LiF acting as a sintering agent to help the diffusion of the elements in the rocksalt structure during the heating to form the calcined powder. 32. The method of embodiment 30 or 31, wherein the precursors are selected to form the cathode active material comprising Li_1.1Mn(III)_0.8Mn(IV)_0.1O_1.9F_0.1. 33. The cathode active material of any of the embodiments 1-17 manufactured using the method of any of the embodiments 18-32. 34. A cathode active material 400 useful in an electrode, comprising: particles 402 comprising a compound comprising a lithium transition metal oxide, a sodium transition metal oxide, a lithium transition metal oxyfluoride, or a sodium transition metal oxyfluoride, wherein: the compound has a cation disordered rocksalt (DRX) structure 900, all of the cation sites 902 of the DRX structure are occupied by lithium 904 or a transition metal ion (M) 906 that has one or more electrons in its d-shell, and wherein the particles 402 are formed by quenching microwaved precursors or a process comprising mixing precursors, microwaving the precursors to form a microwaved powder, and quenching the microwaved powder. 35. The cathode active material of embodiment 34 comprising further comprising the cathode active material of any of the embodiments 1-17. 36. A battery 1300 comprising the cathode active material of any of the embodiments 1-35. 37. The battery of embodiment 36 comprising a cathode 1302 comprising the cathode active material 400; optionally an anode 1306 or current collector 1310; and an electrolyte 1304 between the cathode and the anode or current collector. 38. The battery of embodiment 37, wherein the electrolyte comprises an organic (carbonate)-based Li-ion electrolyte, a locally high concentration electrolyte (LHCEs), or an ionic liquid. 39. The battery of embodiment 37 or 38, wherein the anode comprises graphite, Li metal, Si, an Si-C composite, an alloy, a transition metal-containing compound (e.g. oxide), or the battery is anodeless. 40. The battery of any of the embodiments 38-39 wherein the cathode further comprises a binder and a carbon conductive additive. 41. An anode-less battery 1308 comprising the cathode-active material of any of the embodiments 1-35, 38, or 39, comprising the electrolyte between the cathode 1302 and a current collector 1310 such that lithium or sodium extracted from the composite cathode upon initial charging of the battery is plated directly onto the current collector 1310 to form an anode. 42. The cathode active material of any of the embodiments 1-41, comprising the particles 402 as formed by quenching microwaved precursors. 43. The cathode active material 400 of any of the embodiments 1-42, wherein the particles 402 have the particles D size greater than 0.5 micron resulting in a capacity retention greater than 92% of the peak capacity after 100 cycles, as measured in an electrochemical cell 1300 comprising an electrolyte 1304 between an anode 1306 and the cathode active material without coating of the particles, without electrolyte optimization, and wherein each cycle comprises a charge and discharge of the cell. 44. The cathode active material of clause 42 or 43, wherein the particles are not further processed after the quenching of the microwave precursors. 45. The cathode active material in any of the embodiments 34-44 manufactured using the method of any of the embodiments 18-32. Commercial advantages and improvements DRX alkali (lithium or sodium) transition metal oxide or oxyfluoride are promising candidates for next-generation cathodes as they do not rely on expensive Ni and Co transition metals. However, to date, DRX compounds have either been successfully prepared following the incorporation of a redox-inactive transition metal ions (Ti⁴⁺, Nb⁵⁺, Zr⁴⁺, V⁵⁺) with no electrons in their d electronic shell (d⁰ electronic configuration) to stabilize the structure, reducing the active cation (Li⁺ and redox-active transition metals) reservoir and thus the capacity, and/or through mechanochemical milling and therefore drastic particle downsizing, reducing their capacity retention during electrochemical cycling. The ability to prepare d⁰-less disordered rocksalt (DRX) compounds comprising large (micron-sized) particles opens up a large and unexplored compositional space for sustainable and high energy density transition metal oxide and oxyfluoride cathodes. d⁰-less DRXs are prepared through rapid microwave heating and no longer require the presence of redox-inactive transition metal ions (Ti⁴⁺, Nb⁵⁺, Zr⁴⁺, V⁵⁺) to stabilize the DRX structure, increasing their energy density. For example, the Li_1.1Mn(III)_0.8Mn(IV)_0.1O_1.9F_0.1 (referred to as LM9) d⁰-less DRX cathode exhibits a remarkable energy density of 600 Wh/kg, significantly higher than the 500 Wh/kg for the best performing Li_1.1Mn_0.8Ti_0.1O_1.9F_0.1 (referred to as LMT81) DRX cathode to date. Notably, micron-sized particles of LM9 show high capacities without particle downsizing ^{through mechanochemical milling, removing a major obstacle towards} DRX commercialization. To date, almost all DRX materials require post- processing of as-synthesized materials particles where powders are milled to downsize into a nanosized morphology. While this step significantly improves cathode performance, such a process is difficult to scale and often contributes unacceptable material loss during production due to imperfect powder recovery. Additionally, while initial capacities for downsized DRX are high, the large surface area to volume ratio exacerbates electrolyte decomposition during electrochemical cycling, leading to poor capacity retention. Thus, the ability to cycle large DRX particles is a critical step towards commercialization. While large particle LMT81 cycling has been demonstrated through a pre-formation process, the presence of the d⁰ ion Ti⁴⁺ slows this transformation, resulting in prohibitively long formation steps and reduced capacities. In contrast, LM9 consists of mobile Mn ions resulting in fast transformation, enabling high capacities with a reasonable formation time. The performance of large (micron-sized) particle LM9 is particularly impressive, where a high capacity of 220 mAh/g is observed with 96.5% capacity retention at 50 cycles (corresponding to a cell lifetime of 227 cycles). References The following references are incorporated by reference herein (1) Lee, J.; Kitchaev, D. A.; Kwon, D. H.; Lee, C. W.; Papp, J. K.; Liu, Y. S.; Lun, Z.; Clément, R. J.; Shi, T.; McCloskey, B. D.; Guo, J.; Balasubramanian, M.; Ceder, G. Reversible Mn2+/Mn4+ Double Redox in Lithium-Excess Cathode Materials. Nature 2018, 556 (7700), 185–190. (2) Ji, H.; Urban, A.; Kitchaev, D. A.; Kwon, D.-H.; Artrith, N.; Ophus, C.; Huang, W.; Cai, Z.; Shi, T.; Kim, J. C.; Kim, H.; Ceder, G. Hidden Structural and Chemical Order Controls Lithium Transport in Cation-Disordered Oxides for Rechargeable Batteries. Nat. Commun. 2019, 10 (1), 592. (3) Hyeseung Chung; Zachary Lebens-Higgins; Baharak Sayahpour; Carlos Mejia; Antonin Grenier; E. Kamm, G.; Yixuan Li; Ricky Huang; J. Piper, L. F.; W. Chapman, K.; Jean- Marie Doux; Shirley Meng, Y. Experimental Considerations to Study Li- Excess Disordered Rock Salt Cathode Materials. J. Mater. Chem. A 2021, 9 (3), 1720–1732. (4) Baur, C.; Källquist, I.; Chable, J.; Chang, J. H.; Johnsen, R. E.; Ruiz-Zepeda, F.; Ateba Mba, J. M.; Naylor, A. J.; Garcia-Lastra, J. M.; Vegge, T.; Klein, F.; Schür, A. R.; Norby, P.; Edström, K.; Hahlin, M.; Fichtner, M. Improved Cycling Stability in High-Capacity Li-Rich Vanadium Containing Disordered Rock Salt Oxyfluoride Cathodes. J. Mater. Chem. A 2019, 7 (37), 21244–21253. (5) Crafton, M. J.; Yue, Y.; Huang, T.-Y.; Tong, W.; McCloskey, B. D.; Crafton, M. J.; Huang, T.; McCloskey, B. D.; Yue, Y.; Tong, W. Anion Reactivity in Cation-Disordered Rocksalt Cathode Materials: The Influence of Fluorine Substitution. Adv. Energy Mater. 2020, 10 (35), 2001500. (6) https://doi.org/10.1149/2.1071707jes , Structure Evolution and Thermal Stability of High-Energy- Density Li-Ion Battery Cathode Li₂VO₂F Xiaoya Wang¹, Yiqing Huang¹, Dongsheng Ji², Fredrick Omenya², Khim Karki^1,3, Shawn Sallis^1,4, Louis F. J. Piper^1,4, Kamila M. Wiaderek⁵, Karena W. Chapman⁵, Natasha A. Chernova¹ and M. Stanley Whittingham^6,7,1,2 Published 24 May 2017 • © 2017 The Electrochemical Society Journal of The Electrochemical Society, Volume 164, Number 7 (7) https://doi.org/10.1039/C7TA07476J , Nanostructured Li₂MnO₃: a disordered rock salt type structure for high energy density Li ion batteriesM. Freire,^a O. I. Lebedev,^a A. Maignan,^a C. Jordy^b and V. Pralong, Journal of Materials Chemistry A, Issue 41, 2017. (8) ACS Energy Letters, Vol 9/Issue 6, Letter May 30, 2024, The Limited Incorporation and Role of Fluorine in Mn-rich Disordered Rocksalt Cathodes By Vincent C. Wu et/ al. (9) Rapid and Energy-Efficient Synthesis of Disordered Rocksalt Cathodes Vincent C. Wu, Hayden A. Evans, Raynald Giovine, Molleigh B. Preefer, Julia Ong, Eric Yoshida, Pierre-Etienne Cabelguen, Raphaële J. Clément https://doi.org/10.1002/aenm.202203860, Adv. Energy Mater.2023, 13, 2203860. (10) Solid-state microwave route to cation-disordered rocksalt oxide and oxyfluoride cathodes, PCT application publication No. WO2024092218A1 (application No. PCT/US2023/078060 filed 10/27/2023). 5 Conclusion This concludes the description of the preferred embodiment of the present invention. The foregoing description of one or more embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to 10 the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.

Claims

WHAT IS CLAIMED IS: 1. A cathode active material comprising particles comprising a lithium transition metal oxide, a sodium transition metal oxide, a lithium ^{transition metal oxyfluoride, and/or a sodium transition metal oxyfluoride,} wherein the cathode active material has a disordered rocksalt (DRX) structure, wherein the cation sites of the DRX structure are occupied by lithium, sodium, and/or a transition metal having at least one electron in its d-shell, and wherein the particles have a particle size of at least 0.5 micron. 2. A cathode active material according to claim 1, wherein the disordered rocksalt structure is according to the formula A_1+xM_1-xO_2-yF_y, wherein: A is lithium (Li) or sodium (Na), M comprises manganese (Mn) and at least a transition metal having at least one electron in its d-shell, x ≤ 0.4 and y ≤ 0.2, and wherein the content of Li, M and fluorine (F) is measured by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP- OES), Fluoride ion selective electrode (F-ISE), and ⁷Li and ¹⁹F solid- state nuclear magnetic resonance spectroscopy (ss-NMR). 3. A cathode active material according to claim 2, wherein M comprises Mn and a transition metal selected from iron (Fe), nickel (Ni), copper (Cu), or chromium (Cr), wherein the content of Li, Mn, Fe, Ni, Cu, Cr and F is measured by ICP-OES. 4. A cathode active material according to claim 2, wherein A is Li. 5. A cathode active material according to claim 2, wherein x ≤ 0.2.. 6. A cathode active material according to claim 2, wherein y ≤ 0.1, . 7. A cathode active material according to claim 1, wherein the DRX structure is selected from Li_1.1Mn(III)_0.8Mn(IV)_0.1O_1.9F_0.1, Li_1.2Mn(III)_0.6Mn(IV)_0.2O_1.8F_0.2, Li_1.1Mn(III)_0.5Mn(IV)_0.3Ni_0.1O_1.9F_0.1,Li_1.0Mn(III)_0.75Mn(IV)_0.125Ni_0.125O_1.9F _0.1, Li_1.1Mn(III)_0.5Mn(IV)_0.3Cu_0.1O_1.9F_0.1,Li_1.2Mn(III)_0.7Mn(IV)_0.1Cr_0.1O_1.9F_0.1, Li_1.05Mn(III)_0.65Fe_0.3O_1.9F_0.1, and Li_1.1Mn(III)_0.65Mn(IV)_0.1Fe_0.2O_1.9F_0.1, wherein the content of Li, Mn, Fe, Ni, Cu, Cr and F is measured by ICP-OES. 8. A cathode active material according to claim 1, further comprising a partially spinel-ordered rocksalt structure.

9. The cathode active material according to claim 1, wherein the transition metal has 5 electrons in its d-shell. 10. The cathode active material according to claim 1, wherein the particles have a particle size comprising a diameter in the range of 0.5-10 micrometers. 11. The cathode active material of claim 1 wherein the transition metal ion species (M) comprise at least one of Mn, Fe, Ni, Cu, or Cr. 12. The cathode active material of claim 1, wherein the compound is phase pure without any segregated ordered oxide phases as characterized by X-ray diffraction. 13. The cathode active material of claim 8 comprising the partially spinel ordered rocksalt structure after: further electrochemical processing, or further chemical and thermal processing. 14. The cathode active material of claim 1, wherein: the compound has the general formula: A_1+xM_1-xO_2-yF_y, wherein: A is Li or Na, M comprises one or more transition metal ion species, and x ≤ 0.4 and y ≤ 0.2.

15. A cathode active material, comprising: a compound having a cation disordered rocksalt (DRX) structure and the general formula: A_1+xM_1-xO_2-yF_y, wherein: A is Li or Na, M comprises at least two different transition metal ion species and/or the same transition metal species in at least two different oxidation states, the transition metal species have at least one electron in their d- shells, and x ≤ 0.4 and y ≤ 0.2 16. The cathode active material of claim 15, wherein the M is Mn or comprises Mn in two different oxidation states. 17. The cathode active material of claim 15, wherein the one or more transition metal ion species comprise a d⁵ ion. 18. A method for manufacturing a cathode active material, comprising the following steps: mixing ionic compound precursors together to form a precursor mixture; heating the precursor mixture to a temperature of at least 1100°C or at least 1600°C to form a calcined powder comprising an ionic compound having a rocksalt-type crystalline structure with a disordered arrangement of cations; and cooling the calcined powder to form the cathode active material retaining the DRX rocksalt-type crystalline structure at room temperature; and so that the cation sites of the DRX structure are occupied by lithium, sodium, and/or a transition metal having at least one electron in its d-shell. 19. The method according to claim 18, wherein the heating comprises exposing the precursor mixture to microwave radiation with a power and duration sufficient to form a microwaved powder comprising an ionic compound having a rocksalt-type crystalline structure with a disordered arrangement of cations. 20. The method according to claim 18, wherein the microwave radiation has a frequency in a range 0.1 to 10 GHz. 21. The method according to claim 18, wherein the cooling comprises quenching the calcined powder or the microwaved powder to form the active material retaining the rocksalt-type crystalline structure at room temperature. 22. The method according to claim 21 wherein the quenching is provided in a liquid. 23. The method of claim 19, wherein the microwave heating is an air environment for at least 10 minutes and the cooling comprises stopping the radiation and quenching in a liquid medium for a duration of less than 2 minutes. 24. The method of claim 18, wherein one or more of the transition metals comprise a d⁵ ion and the heating comprises solid state synthesis in a furnace. 25. The method of claim 24, wherein the heating is for at least 2 hours at a temperature of 900-1600°C under Ar gas flow. 26. The method of claim 18, further comprising assembling the cathode active material in a cathode composite to be used in a battery, and conditioning the cathode active material to transform the rocksalt- type crystalline structure into a partially spinel-ordered structure. 27. The method of claim 26, wherein: the conditioning comprising electrochemical conditioning uses less charging and discharging cycles as compared to the conditioning of the cathode active material comprising one or more d⁰ transition metal ions occupying the cation sites, or the conditioning comprising a chemical and thermal processing uses a lower temperature as compared to the conditioning of the cathode active material comprising one or more d⁰ transition metal ions occupying the cation sites.

28. The method of claim 18, wherein the cathode active material comprises particles having a diameter in the range of 0.5-10 microns that are not downsized by further mechanochemical milling. 29. The method of claim 18, wherein one or more of the transition metals comprises a d⁵ ion and the temperature and the rate of cooling are lower than the temperature and rate of cooling used to form the ionic compound without the d⁵ ion. 30. The method of claim 18, wherein the precursors comprise LiF. 31. The method of claim 30, further comprising using the LiF acting as a sintering agent to help the diffusion of the elements in the rocksalt stucture during the heating to form the calcined powder. 32. The method of claim 30 or 31, wherein the precursors are selected to form the cathode active material comprising Li_1.1Mn(III)_0.8- Mn(IV)_0.1O_1.9F_0.1. 33. A battery comprising a cathode comprising the cathode active material of claim 1; and an electrolyte between an anode and the cathode or between a current collector and the cathode.

34. The cathode active material of claim 1, wherein a majority (more than 50%) of the particles have the particle size of at least 0.5 microns. 5 35. The cathode active material of claim 1, comprising the particles as formed by quenching microwaved precursors. 36. The cathode active material of claim 1, wherein the particles have the particles size greater than 0.5 micron resulting in a capacity 10 retention greater than 92% of the peak capacity after 100 cycles, as measured in an electrochemical cell comprising an electrolyte between an anode and the cathode active material without coating of the particles, without electrolyte optimization, and wherein each cycle comprises a charge and discharge of the cell. 15