EP4695847A2

EP4695847A2 - High-capacity mn-based rock salt cathodes with structural changes

Info

Publication number: EP4695847A2
Application number: EP24928655.0A
Authority: EP
Inventors: Zijian CAI; Han-Ming HAU; Shashwat ANAND; Tara Prasad MISHRA; Juhyeon Ahn; Guoying Chen; Gerbrand Ceder
Original assignee: University of California; University of California Berkeley; University of California San Diego UCSD
Current assignee: University of California; University of California Berkeley; University of California San Diego UCSD
Priority date: 2023-04-13
Filing date: 2024-04-12
Publication date: 2026-02-18
Also published as: WO2025188327A8; WO2025188327A2; CN121241027A; WO2025188327A3

Abstract

A material includes a phase-transformed disordered rocksalt having partially disordered spinel cation ordering to provide suitable galvanostatic cycling behavior. The phase-transformed disordered rocksalt has a chemical formula of Li_xMn_yTM_zO_2-uF_u, where 0.9≤x≤1.3, 0≤y≤1, 0≤z≤0.5,and 0≤u≤0.5, and with TM being Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Sn, W, or mixtures thereof. Additionally, the phase-transformed disordered rocksalt includes a first set of domains and a second set of domains interspersed with the first set of domains. The second set of domains is separated from the first set of domains by one or more antiphase boundaries. Methods and systems are described in this disclosure.

Description

PATENT Attorney Docket No.077429-1434173-024110WO Client Reference No.: 2023-055-02 HIGH-CAPACITY MN-BASED ROCK SALT CATHODES WITH STRUCTURAL CHANGES CROSS-REFERENCES TO RELATED APPLICATIONS [0001] This application claims the benefit of and the priority to U.S. Provisional Application No.63/495,826 filed April 13, 2023 and U.S. Provisional Application No.63/571,580 filed March 29, 2024, which are hereby incorporated by reference in their entirety for all purposes. STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT [0002] This invention was made with government support under Contract No. DE-AC02- 05CH11231 awarded by the U.S. Department of Energy. The government has certain rights in this invention. BACKGROUND [0003] With an increasing energy demand arising from electric vehicles with extended range and personal electronics that can operate for extended periods of time, developing high energy density cathode materials with earth-abundant elements is needed to meet the energy demands. Mn-based materials have been proposed for lithium-ion batteries to replace conventional cathodes, such as LiFePO₄, due to being earth abundant, relatively low cost, and stable. Additionally, manganese-based materials can provide safety benefits due to the relatively low toxicity of Mn minerals and the high stability of the charged Mn⁴⁺ state, which improves safety when integrating cells at the pack level. [0004] Although high capacities can be obtained in typical Mn-rich layered and spinel-type oxides, local structure changes and structural distortions can lead to voltage fade, capacity decay and impedance rise, thereby resulting in poor electrochemical performance upon cycling. For instance, a typical spinel can undergo a detrimental two-phase lithiation reaction present near 3 V that can hinder high energy density and rate capability in the Mn-based materials. [0005] Embodiments described herein allow for suitable rate performance and discharge capacity using synthesis strategies that cause structural transformations of Mn-based rocksalt materials. Embodiments include these and other improvements. BRIEF SUMMARY [0006] In accordance with embodiments of this disclosure, a phase-transformed disordered rocksalt (DRX) material includes nanosized partially disordered spinel domains that enable suitable cycling performance. The phase-transformed DRX material can also be referred to as a delta-phase material. The partially disordered spinel domains can be separated by one or more antiphase boundaries. The relatively small length of the partially disordered spinel domains can modify a two-phase reaction of a typical spinel structure into solid solution such that the phase- transformed DRX material can provide high energy density and rate capability when implemented as a cathode material. Preparing the phase-transformed DRX material can involve chemically delithiating a Mn-based DRX material and applying a subsequent heat treatment. Manganese is a low-toxicity, earth abundant transition metal with a highly stable charged Mn⁴⁺ state, facilitating improvements to battery safety and stability as well as sustainability. Chemical delithiation can initiate a transformation of the Mn-based DRX material into the phase- transformed DRX material. The heat treatment can ensure that the Mn-based DRX material uniformly transforms into the phase-transformed DRX material. [0007] In embodiments, methods of preparing a delta-phase material may include providing a material including LixMnyTMzO2-uFu, where 0.9≤x≤1.3, 0<y≤1, 0<z≤0.5, and 0≤u≤0.5, with TM being Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Sn, W, or mixtures thereof. Immobile transition metals, including Ti, can prevent the formation of complete and long-range order. Methods may in addition include delithiating the material to initiate a phase transformation of the material into the delta-phase material including partially disordered spinel cation ordering. Methods may also include heat treating the delithiated material such that the delithiated material continues to undergo the phase transformation to form the delta-phase material. The delta-phase material includes a first set of domains and a second set of domains interspersed with the first set of domains, where the second set of domains is separated from the first set of domains by one or more antiphase boundaries. [0008] In embodiments, a battery may include a cathode that includes a phase-transformed disordered rocksalt including LixMnyTMzO2-uFu, where 0.9≤x≤1.3, 0<y≤1, 0<z≤0.5, and 0≤u≤0.5, with TM being Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Sn, W, or mixtures thereof. The cathode may additionally include a first set of domains and a second set of domains interspersed with the first set of domains. The second set of domains may be separated from the first set of domains by one or more antiphase boundaries. The battery may further include an anode. The battery may additionally include an electrolyte between the cathode and the anode. [0009] A better understanding of the nature and advantages of embodiments of the present invention may be gained with reference to the following detailed description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0010] FIG.1 shows a schematic of structural changes of an example Mn-based disordered rocksalt material through synthesis steps to form a delta-phase material according to embodiments of the present invention. [0011] FIG.2 shows a plot of a synchrotron x-ray diffraction (XRD) pattern for an example Mn-based rocksalt material having a chemical composition of Li_1.2Mn_0.65Ti_0.15O_1.9F_0.1 according to embodiments of the present invention. [0012] FIG.3 shows a plot of a synchrotron XRD pattern for the example Mn-based rocksalt material of FIG.2 after chemical delithiation according to embodiments of the present invention. [0013] FIG.4 shows a plot of a synchrotron XRD pattern for the example Mn-based rocksalt material of FIG.2 after chemical delithiation and heat treatment at 200 °C for 2 hours according to embodiments of the present invention. [0014] FIG.5 shows a temperature-time profile and an intensity map when heating an example Mn-based rocksalt material to 240 °C in increments of 30 °C after being partially delithiated using chemical delithiation according to embodiments of the present invention. [0015] FIG.6 shows XRD patterns of an example Mn-based rocksalt material when heating the example Mn-based rocksalt material from 100 °C to 600 °C, wherein the example Mn-based rocksalt material is partially delithiated using chemical delithiation according to embodiments of the present invention. [0016] FIG.7 shows a zoomed-in view between 4.5 degrees and 7.5 degrees of the XRD patterns shown in FIG.6 according to embodiments of the present invention. [0017] FIG.8 shows a high-angle annular dark-field (HAADF) image of an example Mn- based rocksalt (DRX) material having a chemical composition of Li1.2Mn0.65Ti0.15O1.9F0.1 according to embodiments of the present invention. [0018] FIG.9 shows a mean scanning electron nano diffraction (SEND) pattern of an example Mn-based DRX material having a chemical composition of Li1.2Mn0.65Ti0.15O1.9F0.1 according to embodiments of the present invention. [0019] FIG.10 shows an intensity associated with the SEND pattern of FIG.9 overlaid with calculated disordered rocksalt peaks according to embodiments of the present invention. [0020] FIG.11 shows a HAADF image of an example delithiated Mn-based DRX material according to embodiments of the present invention. [0021] FIG.12 shows a SEND pattern of an example delithiated Mn-based DRX material according to embodiments of the present invention. [0022] FIG.13 shows a spatial distribution of an example delta-phase material in disordered rocksalt material according to embodiments of the present invention. [0023] FIG.14 shows a HAADF image of an example Mn-based DRX material that has undergone delithiation and heat treatment according to embodiments of the present invention. [0024] FIG.15 shows a SEND pattern of an example particle of a Mn-based DRX material that has undergone delithiation and heat treatment according to embodiments of the present invention. [0025] FIG.16 shows a spatial distribution of an example delta-phase material according to embodiments of the present invention. [0026] FIG.17 shows a mean SEND pattern of an example Mn-based DRX material that has undergone delithiation and heat treatment according to embodiments of the present invention. [0027] FIG.18 shows an integrated spatial distribution of an example delta-phase material from one or more SEND patterns collected from the example Mn-based DRX material of FIG. 17 according to embodiments of the present invention. [0028] FIG.19 shows an atomic resolution HAADF-STEM image corresponding to a portion of FIG.18 with an amplitude of a Fourier transform shown in the inset and having a scale bar of 5 nm according to embodiments of the present invention. [0029] FIG.20 shows cation ordering from Bragg filtering applied to frequency components of the Fourier transform shown in FIG.19 according to embodiments of the present invention. [0030] FIG.21 shows a first-cycle voltage profile of an example electrochemical cell when cycled between 2 V and 4.8 V at 20 mAh/g, where the example electrochemical cell includes a Mn-based DRX material as cathode active material according to embodiments of the present invention. [0031] FIG.22 shows a first-cycle voltage profile of an example electrochemical cell when cycled between 2 V and 4.6 V at 20 mAh/g, where the example electrochemical cell includes a Mn-based DRX material that has undergone delithiation and heat treatment as cathode active material according to embodiments of the present invention. [0032] FIG.23 shows specific capacity retention of an example Mn-based DRX material and an example Mn-based delithiated and heat treated DRX material when cycled in different voltage windows at 20 mA/g according to embodiments of the present invention. [0033] FIG.24 shows specific energy retention of an example Mn-based DRX material and an example Mn-based delithiated and heat treated DRX material when cycled in different voltage windows at 20 mA/g, where the example Mn-based DRX has a chemical composition of Li1.2Mn0.65Ti0.15O1.9F0.1 and the example delithiated and heat treated Mn-based DRX material has a chemical composition of Li_0.7Mn_0.65Ti_0.1O_1.9F_0.1 according to embodiments of the present invention. [0034] FIG.25 shows rate performance of an example electrochemical cell including Mn- based DRX as cathode active material at a first cycle discharge when measured between 2 V and 4.8 V at 50 mA/g, 100 mA/g, 200 mA/g, and 500 mA/g according to embodiments of the present invention. [0035] FIG.26 shows rate performance of an example electrochemical cell including delithiated and heat-treated Mn-based DRX as cathode active material at a first cycle discharge when measured between 2 V and 4.8 V at 50 mA/g, 100 mA/g, 200 mA/g, and 500 mA/g according to embodiments of the present invention. [0036] FIG.27 shows a voltage profile and in-situ XRD patterns of an example delithiated and heat treated Mn-based DRX material at a current rate of 20 mA/g with an X-ray scan performed every 30 minutes according to embodiments of the present invention. [0037] FIG.28 shows a voltage profile and in-situ XRD patterns of LiMn₂O₄ at a current rate of 20 mA/g with an X-ray scan performed every 30 minutes according to embodiments of the present invention. [0038] FIG.29 shows a flowchart of a process for preparing a delta-phase material using a Mn-based disordered rocksalt material according to embodiments of the present invention. [0039] FIG.30 shows a flowchart of a process for preparing a delta-phase material using charge/discharge cycling according to embodiments of the present invention. [0040] FIG.31 shows an example battery including delta-phase material as cathode active material according to embodiments of the present invention. DETAILED DESCRIPTION [0041] Current Li-ion cathodes (e.g., lithium nickel manganese cobalt oxides) may rely on a stability of nickel (Ni) and cobalt (Co) in octahedral sites to achieve stable cycling performance. Though other transition metals, such as Cr, Mn, Fe, and Cu, may be more earth-abundant compared to Ni and Co, these other transition metals lack the intrinsic site stability of Ni and Co. As a result, these transition metals require further processing and engineering to be incorporated as Li-ion energy storage materials. Mn-based disordered rocksalt materials can be a suitable alternative due to high stability of the charged Mn⁴⁺ state. But the Mn-based disordered rocksalt materials often undergo a two-phase reaction upon cycling that can create inhomogeneity and stress in the materials, thereby limiting energy density and rate capability of these disordered rocksalt materials. [0042] Embodiments described herein include a delta-phase material prepared by delithiating and heat treating a Mn-based disordered rocksalt material. The delta-phase material can be a nanostructured material having nanosized partially disordered spinel domains with a coherence length of from 1 nm to 10 nm. The partially disordered spinel domains can be separated by one or more antiphase boundaries. The delta-phase material may be characterized by a peak intensity ratio of a first x-ray diffraction (XRD) peak intensity and a second XRD peak intensity that ranges from 0.15 to 1. The first XRD peak intensity and the second XRD peak intensity can respectively correspond to a firs peak angle of 2 degrees and a second peak angle of 5 degrees with respect to a measured wavelength of 0.1818 Å. Additionally or alternatively, the delta-phase material can be characterized by a continuous increase in specific capacity within a voltage range of 2.6 V to 3.2 V, indicating a lack of the two-phase lithiation reaction that limits cycling performance of typical disordered rocksalt materials. Delithiating the Mn-based disordered rocksalt material can initiate a phase transformation of the Mn-based disordered rocksalt material into the delta-phase material. Chemical delithiation can be applied to partially delithiate the Mn- based disordered rocksalt material. Heating the delithiated Mn-based disordered rocksalt material can cause the delithiated Mn-based disordered rocksalt material to undergo further phase transformation to form the delta-phase material. The intrinsic stability of this ordering creates highly stable cycling retention performance. [0043] Embodiments described herein may correspond to a Mn-based cathode material prepared using a Mn-based disordered rocksalt material to provide improved capacity and rate performance compared to conventional rocksalt materials. The Mn-based cathode material can provide beneficial performance for a variety of electrochemical cells, such as batteries, when incorporated therein. Heating a partially delithiated Mn-based disordered rocksalt material can cause the Mn-based disordered rocksalt material to form one or more partially ordered spinel domains that impinge on each other at antiphase boundaries. The partially ordered spinel domains can form a nano-mosaic structure. The partially ordered spinel domains can be of 3 nm to 7 nm in size such that a two-phase lithiation reaction that typically occurs near 3 V in a regular spinel is avoided. Additionally, in contrast to other transition metals, such as Ni, Mn is thermally stable, even when fully charged. Accordingly, incorporating the delta-phase materials as battery electrodes can be beneficial with respect to minimizing a risk of battery-related hazards. [0044] Batteries including the Mn-based cathode material and methods for preparing the Mn- based cathode material are described in further detail in this disclosure. I. STRUCTURAL CHARACTERIZATION OF DRX AND DELTA-PHASE MATERIALS [0045] Li1.2Mn0.65Ti0.15O1.9F0.1 (referred to herein as L12M65) is a disordered rocksalt (DRX) that was chosen as a starting material to prepare the delta-phase material described herein due to its chemical composition. For instance, its high Mn content and low Ti content has been shown to lead to a transformation that improves performance upon electrochemical cycling. Additionally, 20 % Li-excess can allow for suitable Li-ion percolation for battery applications or other electrochemical applications. [0046] FIG.1 shows structural changes of each synthesis step used to transform L12M65110 into the delta-phase material 120. L12M65110 was synthesized through a solid-state method. As shown in FIG.1, after undergoing chemical delithiation, L12M65110 begins to form a partially disordered spinel (e.g., delta-phase material 120). Applying a heat treatment can finish transforming L12M65110 into the delta-phase material 120. The delta-phase material 120 can include at least one first domain 122a separated from at least one second domain 122b by an antiphase boundary 130. A synchrotron x-ray diffraction (XRD) pattern shown in FIG.2 indicated that the as-synthesized L12M65 includes DRX without any detectable impurities. Rietveld refinement based on the rocksalt structure (Fm-3m) resulted in a lattice parameter of 4.133 Å. Particle morphology measured by scanning electron microscopy (SEM) for the as- synthesized L12M65 indicated a primary particle size of 20 µm for L12M65. Delithiation to Li_0.7Mn_0.65Ti_0.15O_1.9F_0.1 (referred to herein as L07M65-D) was achieved by applying a solution of 0.1 M NO2BF4 at 45 °C for 2 days. XRD was performed to analyze the resulting L07M65-D. FIG.3 shows peak shifts toward higher angles, consistent with delithiation. Rietveld refinement based on the rocksalt structure (Fm-3m) for L07M65-D resulted in a refined lattice parameter of 4.067 Å. The emergence of some delta-phase can also be observed by the increase in (111) peak intensity at 2.13 °. [0047] After heat treatment at 200 °C for 2 hours, L07M65-D formed L07M65-DH that shows a further increase in (111) peak intensity, as shown in FIG.4. SEM was performed to determine an average particle size of 12 µm. Broadening of (111), (311) and (333) peaks, which are consistent with spinel-type ordering, indicated a short coherence length of cation ordering. Rietveld refinement modeled on a spinel structure (Fd-3m) with selective peak broadening applied to Bragg peaks with an odd l index resulted in a good fit with Rwp= 9.59 % and a refined lattice parameter of 8.211 Å. [0048] FIG.5 shows in-situ XRD data when heating the sample from 100 to 600 °C. As depicted, changes can be induced in the partially delithiated L07M65-D by this heat treatment. For instance, a phase sequence of DRX to delta-phase to spinel structure can be observed. FIG.6 shows a selection of XRD patterns corresponding to L07M65-D after heating from 100 °C to 600 °C at each temperature shown in FIG.6 for 20 minutes. Rocksalt peaks are indicated with a subscript R, and spinel peaks are indicated with a subscript S. At 100 °C, L07M65-D showed dominant (002) and (022) peaks that result from DRX structure. Between 150 and 200 °C, broad features emerged for diffraction peaks with odd l index (e.g., (111) peak at 2.13° and (311) peak at 4.21°). In contrast, enlarged views of (002) and (022) rocksalt peaks in FIG.7 show that these rocksalt peaks have not broadened, indicating that a grain size over which an anion lattice extends remained unchanged. Upon heating from 250 to 500 °C, the diffraction peaks with odd l index sharpened and increased in intensity, as shown in FIG.5 and FIG.6. In addition, as shown in FIG.7, the (002) and (022) peaks from the delta-phase at about 5.11° and about 7.23° split, indicating a formation of a new phase with new peaks at 5.04° and 7.14°. In fact, the peaks splitting can be observed for all diffraction peaks with even l index. Above 500 °C, all peaks become sharper with increased peak intensity, as shown in FIG.6. Given the spinel-type cation ordering in the delta-phase, the new phase may likely be a spinel with a larger lattice parameter possibly due to reduction induced by heating. [0049] In some embodiments, the delta-phase material can be characterized with respect to its XRD peaks, such as those shown in FIGS.6 and 7. As one example, the delta-phase material can have a width-to-height ratio of a first XRD peak at a peak angle of 2 degrees that ranges from 0.01 to 0.2 (e.g., from 0.01 to 0.1, from 0.1 to 0.2, or anywhere in between). As another example, the delta-phase material can have another width-to-height ratio of a second XRD peak at a different peak angle of 5 degrees that ranges from 0.001 to 0.03 (e.g., from 0.001 to 0.01, from 0.01 to 0.03, or anywhere in between). Although the first XRD peak and the second XRD peak are described herein with reference to a particular peak angle, it will be appreciated that the particular peak angle may vary based on a measured wavelength. In other words, the first peak angle and the second peak angle may vary depending on the wavelength used for the XRD measurement of the delta-phase material. A relationship between the peak angle and the measured wavelength is provided below as Equation 1. [0050] In some embodiments, the delta-phase material can be defined with respect to a peak intensity ratio of two XRD peaks, such as selected from XRD peaks shown in FIGS.6 and 7. The peak intensity ratio can range from 0.15 to 1 (e.g., from 0.15 to 0.55, from 0.55 to 1, or anywhere in between). As a non-limiting example, the peak intensity ratio can correspond to a ratio between a first XRD peak intensity at the first peak angle around 2 degrees and a second XRD peak intensity at the second peak angle around 5 degrees. The peak angle (e.g., the first peak angle and/or the second peak angle) can relate to a measured wavelength according to Equation 1 below: n_{λ ൌ 2dsinθ ^1^} where n is an integer, λ is the measured wavelength, d corresponds to a crystal lattice spacing between atomic planes of the phase-transformed disordered rocksalt, and θ is the peak angle. II. ATOMIC-SCALE CHARACTERIZATION OF DELTA-PHASE MATERIALS [0051] To obtain a more detailed understanding of the structural evolution of the sample upon chemical delithiation and heating, four-dimensional scanning electron nano diffraction (SEND) was conducted on L12M65 (pristine), L07M65-D (after delithiation), and L07M65-DH (after delithiation and heat treatment at 200° C). FIG.8 shows a high-angle annular dark-field (HAADF) image of L12M65 on which SEND patterns were collected. The mean of the diffraction patterns from this particle is shown in FIG 9. Sharp diffraction spots suggest a high degree of crystallinity of the pristine DRX particle. Selected diffraction patterns from the SEND dataset, all of which can be indexed to a rocksalt structure, suggest an absence of any other phase. The mean diffraction pattern shows arcs in the diffraction spots indicating a small in- plane rotational variation in this largely single-crystal particle. The intensity from the diffraction peaks across the particle is radially integrated and overlaid with the powder pattern for Fm-3m space group in FIG.10. Crystal planes that are normal to the electron beam will not be represented in TEM diffraction data, which can explain the absence of some of the simulated peaks in the experimental radially integrated diffraction pattern. Additionally, the kinematical diffraction approximation with which the DRX peaks are simulated does not capture the dynamic electron scattering occurring due to a thickness of the sample, thereby leading to mismatch in the intensity between the simulated and experimentally observed diffraction patterns. [0052] FIG.11 shows a HAADF image of L07M65-D. FIG.12 shows mean SEND patterns of the chemically delithiated L07M65-D particle that is shown in FIG.11. By integrating the intensity of the diffraction reflections unique to the delta-phase material from each SEND pattern and normalizing the intensity with a full acquired scattering range (from 0.175 A^-1 to 1.2 A^-1) to account for thickness, the spatial extent of the delta-phase material can be mapped. The effect of thickness normalization was investigated using a control sample made using a focused ion beam with a uniform thickness. FIG.13 shows a spatial distribution of the delta-phase material. The delta-phase intensity is higher in the surface layer (50 nm) than in the bulk. The results indicate that much of the DRX-to-delta transformation initiates from the surface during the delithiation process. However, even in the bulk region there exist pockets of significant DRX-to-delta transformation. [0053] A similar procedure was undertaken to map the delta-phase extent in a L07M65-DH sample that was chemically delithiated and subsequently heated at 200 °C for 2 hours. FIG.14 shows the STEM-HAADF image of the particle with the mean SEND diffraction pattern in FIG. 15. FIG.16 shows that the entire particle has uniformly transformed into the delta-phase after heating. The delta-phase signal has much higher intensity after heating (FIG.16) suggesting that the heat treatment contributes to the complete formation of the delta-phase. [0054] To investigate the cation ordering in the delta-phase in detail, SEND was augmented with atomic-resolution HAADF imaging on a particle from the L07M65-DH sample. To study the Li distribution post chemical delithiation, electron energy loss spectroscopy (EELS) of L07M65-DH was also measured on the same particle. The homogeneous intensity of the Li k- edge signal was seen throughout the particle, confirming that there is no preferential delithiation during the synthesis or subsequent delithiation and heating. FIG.17 shows the mean SEND pattern from this particle. FIG.18 shows an integration of the diffraction peaks unique to the delta-phase and normalized with the full acquired scattering range (from 0.175 A^-1 to 1.2 A^-1) from the SEND patterns from the particle, confirming that the entire particle transforms into the delta-phase. Region 1810 corresponds to an atomic resolution image collected from FIG.18 marked with a rectangular region and is shown in further detail in FIG.19. The fast Fourier transform of the HAADF-STEM micrograph is shown as an inset in FIG.19. An inverse Fourier transform of the spinel-like peaks marked with a first circle 1910 and a second circle 1920 in the inset of FIG.19 is shown in FIG.20. The fringes of the filtered image in FIG.20 are color- coded based on an isolated frequency component used to obtain them, as marked in the inset of FIG.19. A prevalence of antiphase boundaries, where one variant of the spinel ordering meets another, can be observed. An example antiphase boundary is shown in a dashed box 2010 in the top right of FIG.20. In some examples, the domain size of the delta-phase material is estimated to range from 3 nm to 7 nm by counting an average number of lattice fringes between antiphase boundaries of the delta-phase material. The domain size agrees well with the calculated coherence length obtained by applying the Scherrer equation to the (111) XRD peak in FIG.4. III. ELECTROCHEMICAL PERFORMANCE OF DELTA-PHASE MATERIALS [0055] The electrochemical performance of L07M65-DH and L12M65 was evaluated using galvanostatic cycling between 2 V and 4.8 V at 20 mAh/g. Both samples retained a large average particle size near 5 μm after being fabricated into a cathode film. As shown in FIG.21, L07M65-DH delivered 201 mAh/g in a first discharge, substantially higher than the 159 mAh/g for L12M65. Voltage curves 2110a and 2110b correspond to L12M65, while voltage curves 2120a and 2120b correspond to L07M65-DH. This improvement in cycling behavior is maintained in a narrower voltage window of 2 V to 4.6 V, as shown in FIG 22. The voltage profile of L12M65 corresponding to voltage curves 2210a and 2210b is characterized by a mostly linear relationship for the range of specific capacities tested. In contrast, voltage curves 2220a and 2220b of L07M65-DH show plateau-like 4 V and 3 V regions, with the 3 V region longer than the 4 V region. [0056] FIG.23 and FIG.24 respectively show specific capacity retention and specific energy retention of L12M65 and L07M65-DH when cycled in different voltage windows at 20 mA/g. As shown in FIG.24, L07M65-DH exhibited a maximum specific energy of 645 Wh/kg between 2 V and 4.8 V and 532 Wh/kg between 2 V to 4.6 V, which is higher than what L12M65 delivered in the same voltage region. In particular, L12M65 exhibited a maximum specific energy of 555 Wh/kg between 2 V to 4.8 V and 506 Wh/kg between 2 V to 4.6 V. Hard X-ray spectroscopy and soft X-ray mapping of the resonant inelastic X-ray scattering (mRIXS) revealed that both Mn and oxygen redox contribute to the high capacity of L07M65-DH. [0057] FIGS.25 and 26 show rate performance of L12M65 and L07M65-DH at a first cycle discharge when measured between 2 V and 4.8 V at various current densities. The capacity increase from L12M65 to L07M65-DH was determined to be accompanied by improvements in rate capability. The performance of L12M65 and L07M65-DH was tested at current densities ranging from 50 mA/g to 500 mA/g, such as 50 mA/g, 100 mA/g, 200 mA/g, and 500 mA/g. As shown in FIG.25, while the pristine L12M65 only delivers 68 mAh/g at 500 mA/g (42.7 % of that at 20 mA/g), L07M65-DH shows significantly improved rate performance with 110 mAh/g at 500 mA/g (54.6 % of that at 20 mA/g), as shown in FIG.26. Such high specific energy and rate capability have previously only been obtained in nano-sized DRX materials, rather than in micron-sized particles of the delta-phase material described herein. [0058] Further testing was performed to understand the structural processes upon electrochemical cycling. FIG.27 shows in-operando diffraction data obtained during the cycling of L07M65-DH between 1.5 V to 4.8 V at 20 mA/g. For comparison, data for the cycling of well-ordered LiMn2O4 spinel under the same conditions is shown in FIG.28. For L07M65-DH the (222), (400), and (440) peaks continuously shift to a lower angle upon Li insertion, consistent with a continuous increase in lattice parameter. When discharged to below 2.7 V, the (400) and (440) peaks split, indicating the formation of the tetragonal phase. However, the lattice parameter for the cubic and tetragonal phases continuously changed during discharge, indicating that the system of L07M65-DH remains a solid solution at all times. In contrast, the data for LiMn₂O₄ in FIG.28 show that the (311), (400), and (440) peaks remained at the same angle when discharging across the 3 V plateau region while their intensity gradually decreased. [0059] As shown in FIG.27, the diffraction peaks of L07M65-DH continuously shift at a voltage range from 2.6 V to 3.2 V, indicating an absence of a two-phase reaction. The continuous shifting behavior of L07M65-DH contrasts with behavior exhibited by the diffraction peaks of the LiMn₂O₄ spinel shown in FIG.28. Additionally, as shown in in FIG.27, L07M65-DH exhibits a continuous increase in specific capacity within the voltage range from 2.6 V to 3.2 V, further supporting the absence of the two-phase reaction that detrimentally affects cycling performance of typical spinel materials. In particular, the L07M65-DH can exhibit a specific capacity of from about 50 mAh-g^-1 to about 130 mAh-g^-1 within the voltage range. In contrast to the continuous increase in specific capacity of L07M65-DH, the LiMn2O4 spinel exhibits at least one plateau, contributing to a stepwise trend shown in FIG.28. A. Correlation between nanoscale structural effects and electrochemical performance [0060] Material properties of manganese make it a suitable transition metal to enable the scaling of Li-ion battery production. DRX cathodes can incorporate Mn as active redox couple but often have limited rate capability unless nanosized. The present disclosure describes a unique nanostructured, but large particle-sized, Mn-based cathode material with high specific energy, capacity, and suitable rate capability. While the voltage curves of this delta-phase material are reminiscent of well-ordered LiMn₂O₄ spinel, significant differences exist between the two materials. For example, unlike regular spinel, the delta-phase material shows no two-phase reaction near 3 V and lithiates as a solid solution in this voltage range. In addition, the capacity of the delta-phase material in the 3 V region is larger than in the 4 V region. The two-phase reaction of the regular spinel near 3 V can result in inhomogeneity, leading to particle cracking and degradation of the cathode material. Though the two-phase reaction can be removed by creating cation disorder through mechanochemical synthesis that involves a milling process, the milling process is not practical for scale-up. The delta-phase material also has better capacity and rate capability than untransformed DRX with similar particle size, similar to the delta-like transformation observed when high-Mn content DRX materials were transformed slowly into a new structure by electrochemical cycling. [0061] As disclosed herein, the unique nanoscale microstructure in the delta-phase material is determined to be responsible for its distinct electrochemical behavior. We also show that the delta-phase material can be formed through an ex-situ process of chemical delithiation and low- temperature heat treatment, which significantly decreases the time required for DRX-to-delta transformation from 3 weeks of electrochemical cycling to 2 days at an average particle size of about 10 μm. [0062] The XRD and SEND analyses described herein present a detailed characterization of an example L12M65 sample as it transforms towards the delta-phase material. Delithiation and heating reveal cell doubling peaks characteristic of spinel-type cation ordering in L07M65-DH, with a (111) peak at 2.13° and a (311) peak at 4.21° as shown in FIG.4. In parallel, SEND analysis shown in FIG.10 indicates that the delta-phase evolution is initiated on the surface of the L07M65-DH particle after chemical delithiation of L12M65 (FIG.13) and proceeds to a uniform transformation throughout the L07M65-DH particle after mild heating (FIG.16). These SEND findings are consistent with the XRD data. L07M65-D, prepared after chemical delithiation of L12M65, displays a weak (111) XRD peak (FIG.3), signaling an incomplete transformation to the delta-phase material. Upon heat treatment, however, the delta-phase's characteristic XRD peaks intensified significantly (FIG.4) yet retain their broad profile. Even after a complete transformation, the broadness of the XRD peaks with odd l index persists, consistent with the small domain size indicated by the STEM-HAADF data. This multi-modal characterization clearly shows that the delta-phase differs from an ordered spinel and is characterized by cation ordering with a short coherence length, which in turn is critical for the solid solution behavior in the 3 V region to avoid a detrimental two-phase reaction. [0063] The atomic structure of the delta-phase material depicted in the STEM-HAADF image shown in FIG.20 shows partially disordered spinel domains with a coherence length ranging from 3 nm to 7 nm, separated by antiphase boundaries. The presence of antiphase boundaries reflects the high symmetry of the parent DRX phase allowing for the formation of eight distinct spinel variants (e.g., two translational and four rotational). The process that occurs during delithiation and heating or other synthesis steps, such as cycling, therefore seems to be one where spinel ordering starts in DRX in a randomly selected domain variant, which then grows until it meets another variant, separated by an antiphase boundary. This understanding highlights the unique relationship between the delta-phase material and DRX. Only when spinel forms from a DRX rocksalt structure does it create a large number of spinel variants which can remain nanosized by impinging on each other at antiphase boundaries. The size of these domains appears remarkably consistent and stable around 3 nm to 7 nm, indicating that their further growth is limited, potentially by a lack of driving force or by the presence of the immobile Ti ions which cannot easily move between octahedral sites. [0064] The nanoscale domain structure and small coherence length (e.g., from 3 nm to 7 nm) of partially disordered spinel-like domains contributes to the electrochemical performance of the delta-phase material. These attributes of the delta-phase material effectively suppress the two- phase reaction, similar to what has been observed in nanomaterials. Reducing coherence length in a material can transform first-order transformations into second-order transformation or completely remove the first-order transformations. In the delta-phase material, the small coherence length has remarkable effects on the electrochemical performance, removing the 3 V plateau and turning the associate phase transition into a solid solution region, as shown in FIG. 27. This key feature of the delta-phase material eliminates any phase transformation strain as a potential degradation mechanism of the cathode material and enables cycling of a Mn-based spinel over its full theoretical capacity range. B. Comparison to other materials [0065] The delta-phase material may be a suitable intermediate between the fully disordered DRX compounds and well-ordered spinels. In DRX materials, randomly distributed cations create a wide Li site energy distribution, which leads to a sloping voltage profile and reduced Li diffusivity, necessitating a small particle size in the cathode. By transforming the DRX material into a more ordered partial spinel-type structure with small coherence length, the energy density increases due to the increase in capacity delivered in the 4 V and 3 V regions. The formation of delta-phase material also improves rate performance consistent with prior theoretical work showing that spinel-like configurations possess a more extended low-barrier 0-TM percolation network that is favorable for Li transport. In the delta-phase material^ more of the capacity is delivered at a higher voltage, which is beneficial for power delivery in practical batteries. The delta-phase material approaches these spinel-like properties in voltage profile and rate while retaining small enough coherence length to remain a solid solution and preventing the two-phase reaction that occurs in an ordered spinel. See FIG.27 and FIG.28 and related description. [0066] Due to the unusual nano-scale features of its microstructure, the delta-phase L07M65- DH delivered a capacity of 201 mAh/g and high rate capability with an average particle size of 4.7 μm. See FIGS.21-26 and related description. In contrast, typical DRX materials can only deliver high capacity and energy density with a particle size smaller than 500 nm. For example, DRX Li_1.3Mn_0.4Nb_0.3O₂ typically delivers only 101 mAh/g discharge capacity when the average particle size is at the micron level. By creating the delta-phase material in which the particle size is decoupled from the spinel domain size, a maximum specific energy of 645 Wh/kg could be achieved in L07M65-DH, which is higher than commercial cathode materials such as LiMn₂O₄ and LiFePO4, and approaching similar values to LiNi1/3Co1/3Mn1/3O2 (NMC111). The crystal density of delta-phase material is around 4 g/cc, placing it between LiFePO4 and NMC cathode materials. The present disclosure described herein shows the benefits of engineering local order and microstructure at the nanoscale and show applications of earth-abundant Mn-based cathode materials. IV. EXAMPLE MATERIALS [0067] In some embodiments, the material may include a phase-transformed disordered rocksalt comprising LixMnyTMzO2-uFu, wherein 0.9≤x≤1.3, 0<y≤1, 0<z≤0.5, and 0≤u≤0.5, with TM being Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Sn, W, or mixtures thereof. In some embodiments, TM can correspond to one or more redox-inactive transition metals that function as a structural stabilizer of the disordered rocksalt. Non-limiting examples of the redox-inactive transition metals include Zr, Nb, Mo, Sn, W, or mixtures thereof. The phase transformation of the disordered rocksalt can be driven by an amount of Mn in the disordered rocksalt. In other words, the phase transformation of the disordered rocksalt can occur based on the amount of Mn in the disordered rocksalt being above a predefined threshold regardless of the transition metal or mixture of transition metals selected to prepare the disordered rocksalt. [0068] In some embodiments, the delta-phase material includes a first plurality of domains and a second plurality of domains interspersed with the first plurality of domains. The second plurality of domains may be separated from the first plurality of domains by one or more antiphase boundaries. The antiphase boundaries can form when the first plurality of domains and the second plurality of domains contact to display opposite compositional bonds or opposite order across an interface. In some embodiments, the first plurality of domains includes partially disordered spinel cation ordering. The second plurality of domains may include a disordered arrangement of metal atoms (e.g., transition metal atoms) on a cation lattice. The first plurality of domains may be more ordered than the disordered arrangement associated with the second plurality of domains. In other words, the first plurality of domains may correspond to the delta- phase material that can exhibit partially disordered spinel cation ordering after delithiation and heat treatment. The second plurality of domains can correspond to the Mn-based disordered rock salt material used to prepare the delta-phase material. [0069] The rocksalt may include Li1.05Mn0.85Ti0.1O2, Li1.1Mn0.7Ti0.2O2, Li1.15Mn0.55Ti0.3O2, Li1.2Mn0.4Ti0.4O2, Li1.2Mn0.5Ti0.3O1.9F0.1, Li1.2Mn0.7Ti0.1O1.9F0.1, Li1.1Mn0.75Ti0.15O1.95F0.05, Li_1.1Mn_0.8Ti_0.1O_1.9F_0.1, Li_1.15Mn_0.7Ti_0.15O_1.85F_0.15, or Li_1.1Mn_0.8Ti_0.1O_1.9F_0.1. [0070] In some embodiments, the partially disordered spinel cation ordering can suppress a two-phase reaction of the delta-phase material at a voltage range, such as from 2.6 V to 3.2 V (e.g., from 2.6 V to 2.7 V, from 2.7 V to 2.8 V, from 2.8 V to 2.9 V, from 2.9 V to 3.0 V, from 3.0 V to 3.1 V, from 3.1 V to 3.2 V, or anywhere in between). In some embodiments, the delta- phase material exhibits continuous shifting of diffraction peaks at the voltage range. In some embodiments, the delta-phase material exhibits a continuous increase in specific capacity within the voltage range. As a non-limiting example, the delta-phase material may exhibit a specific capacity of from about 50 mAh-g^-1 to about 130 mAh-g^-1 within the voltage range. [0071] In some embodiments, the delta-phase material can be characterized based on XRD characteristics. As a non-limiting example, an XRD peak of the delta-phase material can have a width-to-height ratio ranging from 0.001 to 0.2. For example, the width-to-height ratio of a particular XRD peak at a peak angle of 2 degrees with respect to a measured wavelength of 0.1818 Å can range from 0.01 to 0.2 (e.g., from 0.01 to 0.02, from 0.02 to 0.03, from 0.03 to 0.04, from 0.04 to 0.05, from 0.05 to 0.06, from 0.06 to 0.07, from 0.07 to 0.08, from 0.08 to 0.09, from 0.09 to 0.10, from 0.10 to 0.11, from 0.11 to 0.12, from 0.12 to 0.13, from 0.13 to 0.14, from 0.14 to 0.15, from 0.15 to 0.16, from 0.16 to 0.17, from 0.17 to 0.18, from 0.18 to 0.19, from 0.19 to 0.20, or anywhere in between). As another example, the width-to-height ratio of another XRD peak at a peak angle of 5 degrees with respect to the measured wavelength can range from 0.001 to 0.03 (e.g., from 0.001 to 0.002, from 0.002 to 0.003, from 0.003 to 0.004, from 0.004 to 0.005, from 0.005 to 0.006, from 0.006 to 0.007, from 0.007 to 0.008, from 0.008 to 0.009, from 0.009 to 0.01, from 0.01 to 0.011, from 0.011 to 0.012, from 0.012 to 0.013, from 0.013 to 0.014, from 0.014 to 0.015, from 0.015 to 0.016, from 0.016 to 0.017, from 0.017 to 0.018, from 0.018 to 0.019, from 0.019 to 0.02, from 0.02 to 0.021, from 0.021 to 0.022, from 0.022 to 0.023, from 0.023 to 0.024, from 0.024 to 0.025, from 0.025 to 0.026, from 0.026 to 0.027, from 0.027 to 0.028, from 0.028 to 0.029, from 0.029 to 0.03, or anywhere in between). It will be appreciated that the peak angle described herein may vary depending on the measured wavelength that can change depending on individual equipment or testing conditions used to perform XRD. Equation 1 described herein can be used to determine a corresponding peak angle for a measured wavelength that differs from the measured wavelength of 0.1818 Å. [0072] In some embodiments, the delta-phase material can be characterized based on a peak intensity ratio of a first XRD peak intensity and a second XRD peak intensity that ranges from 0.15 to 1 (e.g., from 0.15 to 0.20, from 0.20 to 0.25, from 0.25 to 0.30, from 0.30 to 0.35, from 0.35 to 0.40, from 0.40 to 0.45, from 0.45 to 0.50, from 0.50 to 0.55, from 0.55 to 0.60, from 0.60 to 0.65, from 0.65 to 0.70, from 0.70 to 0.75, from 0.75 to 0.80, from 0.80 to 0.85, from 0.85 to 0.90, from 0.90 to 0.95, from 0.95 to 1, or anywhere in between). The first XRD peak intensity can be at a first peak angle of 2 degrees with respect to the measured wavelength. The second XRD peak intensity can be at a second peak angle of 5 degrees with respect to the measured wavelength. As noted above, the first peak angle and second peak angle described herein may vary depending on the measured wavelength. [0073] As described herein, the partially disordered spinel cation ordering of the delta-phase material can suppress a two-phase lithiation reaction typically exhibited in spinel structures during galvanostatic cycling. The two-phase reaction may typically occur within a voltage range from 2.6 V to 3.2 V. In some embodiments, the delta-phase material may have a coherence length from 1.0 nm to 10.0 nm (e.g., from 1.0 nm to 2.0 nm, from 2.0 nm to 3.0 nm, from 3.0 nm to 4.0 nm, from 4.0 nm to 5.0 nm, from 5.0 nm to 6.0 nm, from 6.0 nm to 7.0 nm, from 7.0 nm to 8.0 nm, from 8.0 nm to 9.0 nm, from 9.0 nm to 10.0 nm, or anywhere in between). The coherence length can correspond to a size of the first plurality of domains forming the delta- phase material. The coherence length being relatively short can modify the two-phase lithiation reaction into a solid solution, thereby enabling high energy density and rate capability at large particle scale. The delta-phase material may have materials and structural characteristics the same or similar to any delta-phase materials described herein, including, but not limited to, with reference to FIG.1, FIGS.4-6, FIGS.13-24, and FIGS.26-27. V. EXAMPLE METHODS [0074] FIG.29 is a flowchart of an example process 2900 for preparing a delta-phase material according to embodiments of the present invention. In some implementations, one or more process blocks of FIG.29 may be performed to prepare a delta-phase material that can be incorporated into an electrochemical cell, such as battery 3100 described below with respect to FIG.31. The delta-phase material may be any delta-phase material described herein. [0075] At block 2910, a material including lithium (Li), one or more transition metals, oxygen, and fluorine is prepared. In some embodiments, a material having a chemical composition of LixMnyTMzO2-uFu is prepared, where x ranges from 0.9 to 1.3, y ranges from 0 to 1, z ranges from 0 to 0.5, and u ranges from 0 to 0.5, and where TM is aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zirconium (Zr), niobium (Nb), molybdenum (Mo), tin (Sn), tungsten (W), or mixtures thereof. In some embodiments, the material can be a Mn-based disordered rock salt (DRX) material. The Mn- based disordered rock salt material can include transition metal oxide material with a crystalline rocksalt structure and a disordered arrangement of transition metal on a cation lattice. In some embodiments, the material can be prepared using a solid-state synthesis method. The solid-state synthesis method can involve milling a mixture of one or more precursors, pelletizing the mixture to form a pellet, and sintering the pellet to form the material. [0076] At block 2920, the material is delithiated to initiate a phase transformation of the material into the delta-phase material including partially disordered spinel cation ordering. In some embodiments, the delithiation step can be chemical delithiation where a chemical oxidant solution is applied to the material for up to 1 week (e.g., from 0 to 1 hour, from 1 to 5 hours, from 5 to 10 hours, from 10 to 20 hours, from 20 to 30 hours, from 30 to 40 hours, from 40 to 50 hours, from 50 to 100 hours, from 100 to 150 hours, from 150 to 168 hours, from 10 hours to 48 hours, from 30 hours to 50 hours, or anywhere in between). The chemical oxidant solution can include NO2BF4, (NH4)2SO4, other suitable chemical compounds with oxidizing properties, or a mixture thereof. In some embodiments, a delithiation amount of the material delithiated can range from 0.1 Li/formula unit (f.u.) to 1 Li/f.u. For example, the delithiation amount can be from 0.1 Li/f.u. to 0.2 Li/f.u., from 0.2 to 0.3 Li/f.u., from 0.3 Li/f.u. to 0.4 Li/f.u., from 0.4 Li/f.u. to 0.5 Li/f.u., from 0.5 Li/f.u. to 0.6 Li/f.u., from 0.6 Li/f.u. to 0.7 Li/f.u., from 0.7 Li/f.u. to 0.8 Li/f.u., from 0.8 Li/f.u. to 0.9 Li/f.u., from 0.9 Li/f.u. to 1.0 Li/f.u., or anywhere in between. [0077] At block 2930, the delithiated material is heat treated such that the delithiated material continues to undergo the phase transformation to form the delta-phase material. The heat treatment of the delithiated material can involve heating the delithiated material at a temperature ranging from 100 °C to 500 °C (e.g., from 100 °C to 200 °C, from 200 °C to 300 °C, from 300 °C to 400 °C, from 400 °C to 500 °C, or anywhere in between). The heat treatment may be performed for up to 5 hours (e.g., from 10 minutes to 30 minutes, from 30 minutes to 1 hour, from 1 hour to 2 hours, from 2 hours to 3 hours, from 3 hours to 4 hours, from 4 hours to 5 hours, or anywhere in between). For example, the delithiated material may be heated at 200 °C for 2 hours under vacuum. After the heat treatment step, the delithiated material may optionally be quenched to room temperature. [0078] Process 2900 may further include steps to prepare a cathode using the delta-phase material. The cathode can be prepared in an inert atmosphere, such as argon, nitrogen, etc. In some embodiments, the delta-phase material can be combined with a carbon-based material (e.g., carbon black, graphitic carbon, graphene, conductive carbon, etc.) to form a composite powder that can be mixed with a polymer (e.g., polytetrafluoroethylene) to form a mixed composite. The mixed composite can be rolled into thin films and cut to prepare a cathode that can be incorporated into an electrochemical cell. The cathode including the delta-phase material as cathode active material can used in battery applications (e.g., liquid cells, solid-state cells, coin cells, prismatic cells, pouch cells, cylindrical cells, etc.). [0079] Process 2900 or certain steps of process 2900 may be repeated or performed more than once. Process 2900 may include additional implementations, such as any single implementation or any combination of implementations described herein and/or in connection with one or more other processes described elsewhere herein. [0080] Although FIG.29 shows example blocks of process 2900, in some implementations, process 2900 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in FIG.29. Additionally or alternatively, two or more of the blocks of process 2900 may be performed in parallel. [0081] FIG.30 is a flowchart of an example process 3000 for preparing a delta-phase material using charge/discharge cycling according to embodiments of the present invention. In some embodiments, the delta-phase material may be prepared by cycling a disordered rocksalt material as a cathode in a lithium-ion battery. The delta-phase material may be any delta-phase material described herein. [0082] At block 3010, a material including lithium (Li), one or more transition metals, oxygen, and fluorine, is provided in a disordered rocksalt phase. In some embodiments, providing the material involves a solid-state synthesis method to prepare the material in powder form. In some embodiments, the material is provided as a cathode in a lithium-ion battery. Providing the material as the cathode can involve mixing the material in powder form with a carbon-based material, such as carbon black, using mechanochemical mixing (e.g., high-energy ball milling) to reduce a particle size of a resulting cathode material. In some embodiments, an average particle size of the cathode material after ball milling can range from 2 μm to 10 μm (e.g., from 2 μm to 3 μm, from 3 μm to 4 μm, from 4 μm to 5 μm, from 5 μm to 6 μm, from 6 μm to 7 μm, from 7 μm to 8 μm, from 8 μm to 9 μm, from 9 μm to 10 μm, or anywhere in between). In some embodiments, the average particle size of the cathode material may be nanosized, such as within a range of several hundred nanometers. [0083] At block 3020, the lithium-ion battery undergoes charge/discharge cycling that transforms the disordered rocksalt phase of the material to the delta-phase material. In some embodiments, the delta-phase material includes a first plurality of domains and a second plurality of domains interspersed with the first plurality of domains. The second plurality of domains can be separated from the first plurality of domains by one or more antiphase boundaries. The first plurality of domains and the second plurality of domains can be formed at least in part by the charge/discharge (e.g., galvanostatic) cycling of the lithium-ion battery, such as battery 3100 described below with respect to FIG.31. For example, the charge/discharge cycling is at about 2 volts to 4.8 volts at about 15 mAHg^-1 to 25 mAHg^-1, including at about 15 to 20 mAHg^-1 and at about 20 to 25 mAHg^-1. The charge/discharge cycling voltage range may have a lower voltage from 1.5 V to 2.0 V, 2.0 V to 2.5 V, or 2.5 V to 3.0 V. The charge/discharge cycling voltage range may have a higher voltage from 4.0 V to 4.5 V, 4.5 V to 5.0 V, or 5.0 V to 5.5 V. The charge/discharge cycling can be performed for 15 to 25 charge/discharge cycles (e.g., 15 charge/discharge cycles, 16 charge/discharge cycles, 17 charge/discharge cycles, 18 charge/discharge cycles, 19 charge/discharge cycles, 20 charge/discharge cycles, 21 charge/discharge cycles, 22 charge/discharge cycles, 23 charge/discharge cycles, 24 charge/discharge cycles, or 25 charge/discharge cycles. [0084] In embodiments in which the one or more transition metals includes manganese, at high voltage, Mn⁴⁺ and Li⁺ vacancies being present in the material can promote local cation ordering, leading to a formation of the first plurality of domains and the second plurality of domains. In some embodiments, prior to charging the lithium-ion battery, an average Mn oxidation state can be close to 3+. After charging the lithium-ion battery to 4.8 volts, Mn content in the cathode can be oxidized to 4+. The average Mn oxidation state can return to 3+ upon subsequent discharge, such as to 1.5 volts. During discharge, Mn⁴⁺ reduction and Li insertion can transform a disordered framework of the disordered rocksalt phase into a partially disordered rocksalt phase with a β’-LiFeO₂-type arrangement. The first plurality of domains and the second plurality of domains can be randomly oriented, allowing reversible structural changes and stable electrochemical cycling. [0085] Process 3000 or certain steps of process 3000 may be repeated or performed more than once. Process 3000 may include additional implementations, such as any single implementation or any combination of implementations described herein and/or in connection with one or more other processes described elsewhere herein. [0086] Although FIG.30 shows example blocks of process 3000, in some implementations, process 3000 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in FIG.30. Additionally or alternatively, two or more of the blocks of process 3000 may be performed in parallel. VI. EXAMPLE BATTERIES [0087] FIG.31 shows a schematic illustration of an example battery 3100 incorporating the delta-phase material described herein according to embodiments of the present invention. Cathode active material of battery 3100 may be prepared by performing all or part of process 2900. Although battery 3100 is described herein as a lithium-ion battery, it will be appreciated that other alkali metal systems, alkaline earth metal systems, or other metal systems can be used in place of lithium. In embodiments, battery 3100 may be formed using multilayer stacks of anodes and cathodes, e.g., as in a pouch cell, a coin cell, or some prismatic cells. For simplicity, FIG.31 shows a single cathode 3120 and a single anode 3150. [0088] Battery 3100 includes a cathode current collector 3110, a cathode 3120, an electrolyte 3130, a separator 3140, an anode 3150, and an anode current collector 3160. In some embodiments, additional components or fewer components beyond those depicted in FIG.31 may be included in battery 3100. Cathode current collector 3110 can be any suitable material that conducts electricity (e.g., a metallic element or a metallic compound). In a non-limiting example, cathode current collector 3110 includes aluminum. [0089] As described herein, cathode 3120 can include the delta-phase material as cathode active material. In addition to the delta-phase material, cathode 3120 may include other components, such as a conductive additive or a binder. In some embodiments, the cathode can include a first plurality of domains and a second plurality of domains interspersed with the first plurality of domains with one or more antiphase boundaries separating the first plurality of domains and second plurality of domains. In some embodiments, the first plurality of domains and the second plurality of domains can be formed using chemical delithiation and heating. [0090] Electrolyte 3130 can be a liquid electrolyte or a solid-state electrolyte. As a liquid electrolyte, electrolyte 3130 can include a solvent and one or more salts dissolved in the solvent. Non-limiting examples of the solvent include one or more carbonate solvents, such as ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), or any combination of these. A non-limiting example of the salts in electrolyte 3130 includes LiPF6. In some embodiments, electrolyte 3130 may include additives, such as to stabilize battery 3100 or to function as safety protection agents to prevent overcharge or provide fire retardation. [0091] Separator 3140 can include any suitable ion conducting and electrically insulating material. In a non-limiting example, separator 3140 is a porous polymeric layer. In some cases, separator may be single layer or multilayer polymer sheets. Additionally or alternatively, separator 3140 may include glass materials, ceramic materials, composite materials, coated materials, etc. In some embodiments, separator 3140 may not be present, such as if cathode 3120 and anode 3150 are separated by some other means. As another example, if electrolyte 3130 is a solid-state electrolyte, separator 3140 may be omitted. [0092] Anode 3150 can include any suitable material to provide a lithium alloying anode or lithium uptake anode. In some non-limiting examples, anode 3150 includes lithium metal or a lithium metal alloy, graphite, etc. Anode current collector 3160 can include any suitable material that conducts electricity. In a non-limiting example, anode current collector 3160 includes copper. [0093] As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present disclosure. [0094] The above description of example embodiments of the present disclosure has been presented for the purposes of illustration and description and are set forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use embodiments of the present disclosure. It is not intended to be exhaustive or to limit the disclosure to the precise form described nor are they intended to represent that the experiments are all or the only experiments performed. Although the disclosure has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is readily apparent to those of ordinary skill in the art in light of the teachings of this disclosure that certain changes and modifications may be made thereto without departing from the spirit or scope of the appended claims. [0095] Accordingly, the preceding merely illustrates the principles of the invention. It will be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the disclosure being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. The scope of the present invention, therefore, is not intended to be limited to the exemplary embodiments shown and described herein. Rather, the scope and spirit of present invention is embodied by the appended claims. [0096] A recitation of “a”, “an” or “the” is intended to mean “one or more” unless specifically indicated to the contrary. The use of “or” is intended to mean an “inclusive or,” and not an “exclusive or” unless specifically indicated to the contrary. Reference to a “first” component does not necessarily require that a second component be provided. Moreover, reference to a “first” or a “second” component does not limit the referenced component to a particular location unless expressly stated. The term “based on” is intended to mean “based at least in part on.” [0097] The claims may be drafted to exclude any element which may be optional. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely”, “only”, and the like in connection with the recitation of claim elements, or the use of a “negative” limitation. [0098] Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed within embodiments of the present disclosure. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the present disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the present disclosure. [0099] The terms “about” or “approximate” and the like are synonymous and are used to indicate that the value modified by the term has an understood range associated with it, where the range can be ± 20%, ± 15%, ± 10%, ± 5%, or ± 1%. The terms “substantially” and the like are used to indicate that a value is close to a targeted value, where close can mean, for example, the value is within 80% of the targeted value, within 85% of the targeted value, within 90% of the targeted value, within 95% of the targeted value, or within 99% of the targeted value. [0100] All patents, patent applications, publications, and descriptions mentioned herein are hereby incorporated by reference in their entirety for all purposes as if each individual publication or patent were specifically and individually indicated to be incorporated by reference and are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. None is admitted to be prior art.

Claims

WHAT IS CLAIMED IS: 1. A material comprising: a phase-transformed disordered rocksalt comprising Li_xMn_yTM_zO_2-uF_u, wherein 0.9≤x≤1.3, 0<y≤1, 0<z≤0.5, and 0≤u≤0.5, with TM being Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Sn, W, or mixtures thereof, and including: a first plurality of domains; and a second plurality of domains interspersed with the first plurality of domains, the second plurality of domains being separated from the first plurality of domains by one or more antiphase boundaries. 2. The material of claim 1, wherein a width-to-height ratio of an XRD peak of the phase-transformed disordered rocksalt at a peak angle of 2 degrees ranges from 0.01 to 0.

2.

3. The material of claim 1, wherein a width-to-height ratio of an XRD peak of the phase-transformed disordered rocksalt at a peak angle of 5 degrees ranges from 0.001 to 0.03.

4. The material of claim 1, wherein a peak intensity ratio of a first XRD peak intensity and a second XRD peak intensity of the phase-transformed disordered rocksalt ranges from 0.15 to 1, wherein the first XRD peak intensity is at a first peak angle of 2 degrees and the second XRD peak intensity is at a second peak angle of 5 degrees.

5. The material of any of claims 2-4, wherein the peak angle relates to a measured wavelength according to the formula: nλ=2dsinθ, wherein n is an integer, λ is the measured wavelength, d corresponds to a crystal lattice spacing between atomic planes of the phase-transformed disordered rocksalt, and θ is the peak angle.

6. The material of claim 1, wherein the first plurality of domains comprises partially disordered spinel cation ordering.

7. The material of claim 6, wherein the second plurality of domains comprises a disordered arrangement of metal atoms on a cation lattice, and wherein the first plurality of domains is more ordered than a disordered arrangement associated with the second plurality of domains.

8. The material of claim 6, wherein the partially disordered spinel cation ordering of the phase-transformed disordered rocksalt suppresses a two-phase reaction of the phase-transformed disordered rocksalt at a voltage range.

9. The material of claim 8, wherein the material exhibits continuous shifting of diffraction peaks at the voltage range, wherein the voltage range is from 2.6 V to 3.2 V.

10. The material of claim 8, wherein the material exhibits a continuous increase in specific capacity within the voltage range.

11. The material of claim 10, wherein the material exhibits a specific capacity of from about 50 mAh-g^-1 to about 130 mAh-g^-1 within the voltage range, wherein the voltage range is from 2.6 V to about 3.2 V.

12. The material of claim 1, wherein the rocksalt comprises Li1.05Mn0.85Ti0.1O2, Li1.1Mn0.7Ti0.2O2, Li1.15Mn0.55Ti0.3O2, Li1.2Mn0.4Ti0.4O2, Li1.2Mn0.5Ti0.3O1.9F0.1, Li1.2Mn0.7Ti0.1O1.9F0.1, Li1.1Mn0.75Ti0.15O1.95F0.05, Li1.1Mn0.8Ti0.1O1.9F0.1, Li_1.15Mn_0.7Ti_0.15O_1.85F_0.15, or Li_1.1Mn_0.8Ti_0.1O_1.9F_0.1.

13. A method of preparing a delta-phase material, the method comprising: providing a material comprising LixMnyTMzO2-uFu, wherein 0.9≤x≤1.3, 0<y≤1, 0<z≤0.5, and 0≤u≤0.5, with TM being Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Sn, W, or mixtures thereof; delithiating the material to initiate a phase transformation of the material into the delta-phase material comprising partially disordered spinel cation ordering; and heat treating the delithiated material such that the delithiated material continues to undergo the phase transformation to form the delta-phase material, the delta-phase material comprising a first plurality of domains and a second plurality of domains interspersed with the first plurality of domains, wherein the second plurality of domains is separated from the first plurality of domains by one or more antiphase boundaries.

14. The method of claim 13, wherein the delta-phase material has a coherence length from 1.0 nm to 10.0 nm.

15. The method of claim 13, wherein the delithiation step comprises chemical delithiation.

16. The method of claim 14, wherein the delithiation step comprises applying a chemical oxidant solution to the material for up to 1 week, wherein the chemical oxidant solution is selected from the group consisting of NO₂BF₄ and (NH₄)₂SO₄.

17. The method of claim 13, wherein a delithiation amount of the delithiation step ranges from 0.1 Li/formula unit to 1 Li/formula unit.

18. The method of claim 13, wherein the heat treating step is at a temperature ranging from 100 °C to 500 °C.

19. The method of claim 13, wherein the heat treating step is performed at a temperature for up to 5 hours.

20. A battery, comprising: a cathode, the cathode comprising a phase-transformed disordered rocksalt comprising Li_xMn_yTM_zO_2-uF_u, wherein 0.9≤x≤1.3, 0<y≤1, 0<z≤0.5, and 0≤u≤0.5, with TM being Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Sn, W, or mixtures thereof, and including: a first plurality of domains; and a second plurality of domains interspersed with the first plurality of domains, the second plurality of domains being separated from the first plurality of domains by one or more antiphase boundaries; an anode; and an electrolyte between the cathode and the anode.

21. The battery of claim 20, wherein the first plurality of domains and the second plurality of domains of the cathode are formed at least in part by charge/discharge cycling the battery.

22. The battery of claim 21, wherein the charge/discharge cycling is at about 2 volts to 4.8 volts at about 15 mAHg^-1 to 25 mAHg^-1.

23. The battery of claim 21, wherein the charge/discharge cycling consists of 15 to 25 charge/discharge cycles.

24. A cathode comprising the delta-phase material produced by the method of any of claims 13-19.

25. A method comprising: providing a material comprising LixMnyTMzO2-uFu, with 0.9≤x≤1.3, 0<y≤1, 0<z≤0.5, and 0≤u≤0.5, with TM being Al, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Sn, W, and mixtures thereof, the material being in a disordered rocksalt phase, and the material being a cathode in a lithium-ion battery; and charge/discharge cycling the lithium-ion battery, the cycling transforming the disordered rocksalt phase to a delta-phase material comprising a first plurality of domains and a second plurality of domains interspersed with the first plurality of domains, wherein the second plurality of domains is separated from the first plurality of domains by one or more antiphase boundaries.

26. The method of claim 25, wherein the charge/discharge cycling is at about 2 volts to 4.8 volts at about 15 mAHg^-1 to 25 mAHg^-1.

27. The method of claim 25, wherein charge/discharge cycling comprises 15 to 25 charge/discharge cycles.