Cation-disordered rocksalt-type high-entropy cathode with reduced short-range order for Li-ion batteries

Abstract

A class of compositions comprising lithium metal oxide or oxyfluoride compounds having the general formula LiTM[n]OF, where TM[n] is a charge or d 0 [n] represents the number of transition metal species, including transition metal species distinguished by electronic shell structure, where [n] is at least four of the transition metal species, and the lithium metal oxide or oxyfluoride has a cation-disordered rock salt (DRX) structure and a relaxed SRO via a high-entropy DRX design strategy. Also featured are methods for synthesizing the high-entropy DRX lithium metal oxide or oxyfluoride compounds and their use in Li-ion batteries, particularly in the cathodes of such Li-ion batteries.

Description

[Technical Field]

[0001] This invention relates to the design and synthesis of high-entropy cation-disordered rock salt (DRX) cathodes with strategically increased numbers of transition metal (TM) species, aiming to provide reduced short-range-order (SRO) cathodes. Increasing the number of TM species alleviates SRO, leading to improved capacity and rate capability of DRX cathodes. Through testing, this invention validates high entropy as a novel approach for the design of high-capacity and high-rate-performance Li-ion cathodes. [Background technology]

[0002] The increasing demand for cheap, portable, high-density energy storage for personal devices, transportation, and on the power grid has driven the development of advanced Li-ion battery systems [1-3]. Modern high-energy density battery systems are currently based on layered oxides targeting high voltage redox activity for Co, Mn, and Ni.

[0003] Recent studies have identified disordered rock salt (DRX) systems as potential high-capacity cathodes. This is because DRX systems offer flexibility in composition and redox behavior while avoiding rate capability degradation when at least 55% of the cation sublattice is occupied by Li. [4-5] Li transport in DRX materials has been shown to rely primarily on the 0-TM network (percolating network), in which tetrahedral sites in the Li migration pathway are coordinated by zero-valent transition metals. Li connected to the percolating network is called "percolating Li." The amount of percolating Li is an important indicator of the overall Li transport properties in DRX materials. Although these DRX cathode materials lack long-range order (LRO), the presence of local cation short-range order (SRO) has been demonstrated using transmission electron microscopy (TEM) electron diffraction techniques, and its presence can significantly affect the capacity and rate capability of DRX materials. [6] To date, SRO appears to reduce the amount of permeated Li in DRXed materials in many cases, as shown by previous Monte Carlo studies [6].

[0004] Therefore, there is a problem of reducing the cation SRO so that the capacity and rate performance of DRX cathodes can be improved. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention establishes that reducing SRO enables improved capacity and rate performance of DRX materials. Approaches to achieve this include the use of "high-entropy" mixtures to synthesize DRX materials, i.e., a high-entropy DRX design strategy. This strategy involves using a relatively large number of building blocks, which limits the ability of cations to form specific short-range order. This has the effect of reducing short-range order, so that the system more closely resembles a random mixture of ions in the cation sublattice. This results in improved Li permeation, in contrast to DRX cathodes with unrelaxed SRO. [Means for solving the problem]

[0006] Aspects of the present invention are illustrated by the following points 1-31. 1. General formula Li 1+x TM[n] 1-x O 2-y F y where TM[n] is a redox active species or d 0 A compound comprising transition metal species, including those distinguished by redox-inactive charge compensators, wherein [n] is at least four of said transition metal species, and wherein said lithium metal oxide or oxyfluoride has a cation-disordered rock salt (DRX) structure. 2. TM[n] is at least Mn 3+ and Ti 4+ The compound of example point 1, comprising 3. The compound of example point 1, wherein [n] is at least six of said transition metal species. 4. The compound of example point 1, wherein [n] is 4 to 10 of the transition metal species. 5. The at least four of the transition metal species are Mn 3- , Ti 4+ , Mn 2+ , Nb 5+ , Co 2+ and Cr 3+ The compound of example point 1, selected from the group 6. The compound is Li 1.3 Mn 2+ 0.2 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7 F 0.3 The compound shown in Example Point 1 is 7. The compound is Li 1.3 Mn 2+ 0.1 Co 2+ 0.1 Cr 3+ 0.1 Mn 3+ 0.1 Ti 0.1 Nb 0.2 O 1.7 F 0.3 The compound shown in Example Point 1 is 8. Compound of example point 5, giving a capacity of 307 mAh / g at a repetition rate of 20 mA / g. 9. The compound of example point 5, which retains a high capacity of 170 mAh / g at a repetition rate of 2 A / g. 10. The compound of example point 1, wherein the cation-ionic order reflects a relaxed short-range order (SRO), characterized by the fact that in a TEM electron diffraction pattern, the SRO diffuse scattering pattern intensity is equal to the background intensity or less than about 0.31 au above the background intensity, and preferably equal to the background intensity or less than about 0.19 au above the background intensity. 11. General formula Li 1+x TM[1] a TM[2] b TM[3] c TM[4] d = (1-x-a-b-c) O 2-y F yThe compound of example point 1 has the formula: wherein 0.05≦x≦0.35, 0.1≦a≦0.4, 0.1≦b≦0.4, 0.1≦c≦0.4, 0.1≦d≦0.4 and 0≦y≦0.7, or more preferably 0.1≦x≦0.3, 0.1≦a≦0.3, 0.1≦b≦0.3, 0.1≦c≦0.3, 0.1≦d≦0.3 and 0≦y≦0.5. 12. a. An electrode material comprising a compound according to any one of the example points 1 to 11. 13. a. Electrolytes and b. A lithium-ion battery comprising the electrode material of example point 12. 14. The lithium-ion battery of example point 13, wherein the electrode material forms a cathode. 15. a. A portable electronic device, automobile, or energy storage system comprising the lithium-ion battery of example point 14. 16. General formula Li 1+x TM[n] 1-x O 2-y F y wherein TM[n] is a redox active species or d 0 and optionally including transition metal species differentiated by redox-inactive charge compensators, wherein [n] is at least four of said transition metal species; a. combining a collection of stoichiometric or essentially stoichiometric compounds formed by Li, TM[n], O, and optionally F, in the presence of excess Li, to produce a precursor powder; b. mixing said precursor powders to obtain a phase-pure powder, wherein the mixing is preferably by mechano-chemical alloying. 17. The TM[n] species is Mn 3+ , Ti 4+ , Mn 2+ , Nb 5+ , Co 2+ and Cr 3+17. The method according to example point 16, wherein the 18. The method according to example point 16, wherein the precursor powder is subjected to mechanical mixing by feeding the precursor powder into a planetary ball mill. 19. The compound is Mn 3+ and Ti 4+ The method of example point 16, including 20. TM[n] is Mn 2+ , Nb 5+ , Co 2+ and Cr 3+ 19. The method of example point 19, further comprising at least two of: 21. The compound is Li 1.3 Mn 2+ 0.2 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7 F 0.3 The method shown in example point 16 is as follows. 22. The compound is Li 1.3 Mn 2+ 0.1 Co 2+ 0.1 Cr 3+ 0.1 Mn 3+ 0.1 Ti 0.1 Nb 0.2 O 1.7 F 0.3 The method shown in example point 16 is as follows. 23. The compound has the general formula Li 1+x TM[1] a TM[2] b TM[3] c TM[4] d= (1-x-a-b-c) O 2-y F y 17. The method of example point 16, wherein 0.05≦x≦0.3, 0.1≦a≦0.3, 0.1≦b≦0.3, 0.1≦c≦0.3, 0.1≦d≦0.3, and 0≦y≦0.5. 24. The compound is Li 1.3 Mn 2+0.2 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7 F 0.3 The method shown in example point 23 is as follows. 25. The compound is Li 1.3 Mn 2+ 0.1 Co 2+ 0.1 Cr 3+ 0.1 Mn 3+ 0.1 Ti 0.1 Nb 0.2 O 1.7 F 0.3 The method shown in example point 23 is as follows. 26. General formula Li 1+x TM[n] 1-x O 2-y F y a lithium metal oxide or oxyfluoride compound having a cation-disordered rock salt (DRX) structure, wherein TM[n] is at least Mn 3+ and Ti 4+ Compounds showing a number of different transition metal species comprising: 27. Redox active species or d 0 Distinguished by redox-inactive charge compensators and Mn 2+ , Co 2+ , Cr 3+ 27. The compound according to example point 26, further comprising at least two additional transition metal species selected from the group consisting of: Nb and Nb. 28. The compound is Li 1.3 Mn 2+ 0.2 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7 F 0.3 The compound according to example point 26, 29. The compound is Li 1.3 Mn 2+ 0.1 Co 2+ 0.1 Cr 3+0.1 Mn 3+ 0.1 Ti 0.1 Nb 0.2 O 1.7 F 0.3 The compound according to example point 26, 30. The compound of exemplary point 26, wherein the cation-ion ordering reflects relaxed short-range order (SRO), characterized by the fact that in a TEM electron diffraction pattern, the SRO diffuse scattering pattern intensity is equal to the background intensity or less than about 1.07 au above the background intensity, preferably equal to the background intensity or less than about 0.31 au above the background intensity, and more preferably equal to the background intensity or less than about 0.19 au above the background intensity. 31. The compound according to any one of example points 1 to 11 and 26 to 30, wherein the compound exhibits an enhanced charge capacity based on the overall entropy corresponding to the number of transition metal species TM[n] contained therein, independently of any particular transition metal species contained therein.

[0007] All possible exemplary combinations of points 1-31 listed above (as exemplified by point 12, which references points 1-11 respectively, and point 31, which references points 1-11 and 26-30) are intended to be encompassed by the present invention. [Effects of the Invention]

[0008] Thus, a subembodiment of the present invention is a compound of the general formula Li 1+x TM[n] 1-x O 2-y F y where TM[n] is a variable charge or d 0 The present invention includes various transition metal species having electron shell structures. 1+x TM[n] 1-x O 2-y F y The composition contains the following: excess lithium, redox centers, d 0The specific transition metal (TM) species and their number are determined by the number of redox centers TM or d, with the number of TM species being sufficient to implement a high-entropy DRX design strategy that reduces SRO. 0 Strategically selected for use as a charge compensator™.

[0009] Therefore, the present invention provides compounds of the general formula Li 1+x TM[n] 1-x O 2-y F y wherein 0.05≦x≦0.3 and 0<y≦0.5, and TM[n] is a redox active species or d 0 Redox inactive charge compensator (d 0 The formula represents multiple transition metal species (including those distinguished by a redox-inactive charge compensator). In one embodiment, the general formula may include 0.09≦x≦0.3 and 0.10≦y≦0.35. In another embodiment, [n] is four or more TM, with the four or more TM preferably selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Sn, and Sb. For example, the TM may be selected from the more preferred group consisting of Mn, Nb, Ti, Cr, and Co. In yet another embodiment, the value of [n] is six or more, with higher values ​​representing higher entropy characteristics, with the upper limit potentially limited by processing and additional complexity synthesis limitations. Thus, some non-limiting examples of suitable compositions designed for higher entropy include Li, with SRO formation mitigated. 1.3 Mn 2+ 0.2 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7 F 0.3 and Li 1.3 Mn2+ 0.1 Co 2+ 0.1 Cr 3+ 0.1 Mn 3+ 0.1 Ti 0.1 Nb 0.2 O 1.7 F 0.3 Contains:

[0010] To further our understanding of how high-entropy DRX design strategies reduce SRO, we provide some insight into species distribution. That is, a random mixture is one in which species distributed across a set of sites are randomly assigned to a given site without consideration of the occupancy of neighboring sites. As an example, let us consider the mole fraction χ A and χ B In a random mixture of A and B cations with , the probability that a site is occupied by A is PA = χ A Similarly, the probability that a site is occupied by B is P B =χ B Since the occupancies of each site are uncorrelated, the probability that a particular nearest neighbor is type AA is P AA =P A *P A =χ 2 A A similar formula is P BB and P AB There are also cases where

[0011] In a mixture with SRO, the probability that a site will be occupied by a particular species is determined in part by the occupancy of neighboring sites. AB ≠P A *P B, because the presence of A at the first site influences the likelihood that B will be present at a neighboring site. Such SRO correlations are not limited to nearest-neighbor bonds but can extend over longer distances. This deviation from randomness is called short-range order, or "SRO," and can be measured by various techniques, including single-crystal X-ray scattering in a TEM and electron diffraction [7-8]. SRO can also be inferred from a variety of other techniques, including pair distribution functions obtained from neutron diffraction [6]. The high-entropy DRX design strategy of the present invention aims to mitigate SRO formation and result in improved capacity and rate performance, with the resulting relaxation demonstrable by testing under the present invention.

[0012] To illustrate the benefits of the high-entropy DRX design strategy of the present invention, three prototype compositions, TM2, TM4, and TM6, were formed. These compositions differ from existing transition metal species. Li, O, and F were held constant in these three compositions, with Li present in excess in each. Six additional compounds with the same prototype compositions were also designed to demonstrate the overall entropy effect that leads to capacity enhancement.

[0013] All prototype compositions (TM2, TM4, and TM6) contained a 30% Li excess (i.e., Li per formula unit) sufficient to allow good Li transport. 1.3 The prototype formulation designed for testing features Mn while avoiding excessive limitations on the TM redox capacity. A 15% fluorine substitution was made to further increase the TM redox reservoir. 3+ and Ti 4+ was designed as a baseline composition (e.g., in addition to being a high-performance baseline combination in the present invention, it is also useful in demonstrating higher entropy enhancement under the test of the present invention). Thus, the baseline combination alone can be used to determine the compound formula Li 1.3Mn 3+ 0.4 Ti 0.3 O 1.7 F 0.3 (hereinafter referred to as TM2) is provided. In the present invention, Mn 2+ and Nb 5+ is further incorporated into the baseline composition 1.3 Mn 2+ 0.2 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7 F 0.3 This contains four TM species, hereafter referred to as TM4. 2+ , Nb 5+ , Co 2+ and Cr 3+ In addition, Li 1.3 Mn 2+ 0.1 Co 2+ 0.1 Cr 3+ 0.1 Mn 3+ 0.1 Ti 0.1 Nb 0.2 O 1.7 F 0.3 This contains six TM species, hereafter referred to as TM6.

[0014] All three prototype compositions were successfully synthesized using conventional solid-state methods. Scanning electron microscopy (SEM) shows that the particle size of the as-synthesized materials reaches approximately 5–10 μm and can be reduced to 200–500 nm after carbon shaker milling during electrode fabrication. Synchrotron X-ray diffraction (XRD) and time-of-flight (TOF) neutron diffraction patterns confirm the formation of pure DRX structures with no observable impurity peaks. Rietveld refinement yields lattice constants of 4.1918 Å, 4.2286 Å, and 4.2544 Å for TM2, TM4, and TM6, respectively. Energy dispersive spectroscopy (EDS) mapping using a transmission electron microscope (TEM) was applied to verify the homogeneous distribution of multi-elements in the materials.

[0015] The compounds of the present invention are suitable for use in the fabrication of electrodes, particularly cathodes. The compounds have an increased number of TM species (e.g., TM[n] where [n] is 4 or more (e.g., 4-10), and in some circumstances more preferably 6 or more (e.g., 6-10)). Increasing the number of TM species mitigates SRO. This is shown in the present invention by improving the capacity and rate capability of the resulting DRX cathode. The species may differ with respect to charge and / or d-shell conformation. DRX cathodes have been shown to have a 20 mA g -1 The TM2 prototype delivered 220mAh g when cycled between 1.5 and 4.7V at a rate of -1 (704Wh kg -1 ), while the TM4 prototype, which has a larger number of TM species, outputs a relatively high capacity (specific energy) of 269 mAh g -1 (849Wh kg -1 ), but the TM6 prototype, which has a higher number of TM species, has a capacity of 307 mAh g -1 (955Wh kg -1The high-entropy TM6 compound is characterized by improved performance as seen in a further increase in the current to 20 mA g -1 Even when cycled over a smaller voltage window of 2.0 to 4.5 V at a rate of 246 mAh g -1 (803Wh kg -1 ) can continue to exhibit relatively high discharge capacities. Six additional compounds with the same prototype composition are also presented to demonstrate the role of overall entropy effects (rather than specific transition metal ions), which leads to improved capacity. The performance of these compounds validates high entropy as a novel design approach for high-capacity and high-rate capable Li-ion cathodes. Lithium-ion batteries employing these cathodes will also exhibit improved performance, and therefore, portable electronics, vehicles (such as spacecraft and automobiles), and energy storage systems employing such batteries will similarly exhibit improved performance.

[0016] Furthermore, the compounds of the present invention can be readily synthesized using conventional techniques by combining strategic numbers (and combinations) of stoichiometric compounds ("ensembles") formed, for example, with Li, Mn, Ti, Nb, O, and F to produce precursor powders, which are then preferably mechanically mixed to obtain phase pure powders by mechanochemical alloying.

[0017] Both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the invention as claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description, serve to explain the principles of the invention.

[0018] Further features and advantages of the present invention can be seen from the following detailed description taken in conjunction with the drawings described below. [Brief explanation of the drawings]

[0019] [Figure 1] The face-centered cubic (FCC) unit cell cation sublattice is shown. The relationship between the cation octahedral and tetrahedral structures is also shown. [Figure 2a] Figure 1 shows the design and structural characteristics of synthesized prototype materials TM2, TM4, and TM6. Figure 2 shows the prototype composition designs of DRX cathodes with different numbers of TMs in each composition. [Figure 2b] Figure 1 shows the design and structural characterization of the synthesized prototype materials TM2, TM4, and TM6. Figure 2 shows the synchrotron XRD patterns and refined lattice parameters of the synthesized prototype compositions at λ = 0.18208 Å. [Figure 2c] Figure 1 shows the design and structural characterization of the synthesized prototype materials TM2, TM4, and TM6. Figure 2 shows the neutron diffraction patterns of the synthesized prototype compositions. [Figure 2d] The design and structural characteristics of the synthesized prototype materials TM2, TM4, and TM6 are shown. SEM images of as-synthesized TM6 (top) and as-shaker-milled TM6 with carbon black (bottom) are shown. [Figure 2e] Figure 1 shows the design and structural characterization of the synthesized prototype materials TM2, TM4, and TM6. Figure 2 shows TEM / EDS mapping of elemental distribution in particle clusters of as-synthesized TM6. [Figure 2f] The 19F frequency-stepped NMR spectrum, obtained by summing over multiple spin echo sub-spectra acquired at different excitation frequencies, is shown, along with the spectrum scaled according to the amount of sample in the rotor and, for comparison, an overlaid 19F spin echo spectrum collected on LiF powder. [Figure 3a] Figure 1 shows the electrochemical performance of the TM2 prototype composition. The voltage profile and capacity retention (1.5-4.7 V, at 20 mA g-1, RT) for the TM2 composition are shown. [Figure 3b]Figure 1 shows the electrochemical performance of the TM4 prototype composition. The voltage profile and capacity retention (1.5-4.7 V, at 20 mA g-1, RT) for the TM4 composition are shown. [Figure 3c] Figure 1 shows the electrochemical performance of the TM6 prototype composition. The voltage profile and capacity retention (1.5-4.7 V, at 20 mA g-1, RT) for the TM6 composition are shown. [Figure 3d] Figure 1 shows the electrochemical performance of the TM6 prototype composition. The voltage profile and capacity retention (2.0-4.5 V, at 20 mA g-1, RT) for the TM6 composition are shown. [Figure 3e] 1 shows the electrochemical performance of TM2, TM4, and TM6 prototype compositions. 1st cycle voltage profiles of TM2, TM4, and TM6 compositions from galvanostatic intermittent titration test (GITT) are shown. [Figure 4a] Short-range order and Li transport analysis of the TM2 composition are shown. TEM electron diffraction (ED) patterns of the TM2 composition are shown along the zone axis

[0100] . [Figure 4b] Short-range order and Li transport analysis of the TM4 composition are shown. TEM electron diffraction (ED) patterns of the TM4 composition are shown along the zone axis

[0100] . [Figure 4c] Short-range order and Li transport analysis of the TM6 composition are shown. TEM electron diffraction (ED) patterns of the TM6 composition are shown along the zone axis

[0100] . [Figure 4d] Short-range order and Li transport analysis of the TM2 composition are shown. The rate capacity of the TM2 composition when cycled between 1.5 and 4.7 V at various rates is shown. [Figure 4e] Short-range order and Li transport analysis of the TM4 composition are shown. The rate capacity of the TM4 composition when cycled between 1.5 and 4.7 V at various rates is shown. [Figure 4f] Short-range order and Li transport analysis of the TM6 composition are shown. The rate capacity of the TM6 composition when cycled between 1.5 and 4.7 V at various rates is shown. [Figure 5a] The SRO intensity patterns are shown, which show the SRO intensities based on the normalization of the TEM diffraction patterns in Figures 4a to 4c. [Figure 5b] 4a-4c show SRO strength patterns and comparative maximum SRO strengths for different prototype materials. [Figure 6a] 1 shows details of comparative DRXed materials TM2-Mn2+Nb and TM2-Mn3+Nb, and shows the XRD patterns of the two comparative DRXed materials. [Figure 6b] Figure 1 shows a detail of the comparative DRX material TM2-Mn2+Nb, showing the voltage profile and capacity retention of TM2-Mn2+Nb. [Figure 6c] Figure 1 shows a detail of the comparative DRX material TM2-Mn3+Nb, showing the voltage profile and capacity retention of TM2-Mn3+Nb. [Figure 7a] 1 shows details of comparative DRXed materials TM4-Co and TM5, and shows the XRD patterns of the two comparative DRXed materials. [Figure 7b] 1 shows a detail of the comparative DRX material TM4-Co, showing the voltage profile and capacity retention of TM4-Co. [Figure 7c] 1 shows a detail of the comparative DRX material TM5, showing the voltage profile and capacity retention of TM5. [Figure 8a] 1 shows details of comparative DRXed materials MCN and MCT, and shows the XRD patterns of the two comparative DRXed materials. [Figure 8b] 1 shows a detail of a comparative DRX material, MCN, showing the voltage profile and capacity retention of the MCN. [Figure 8c] 1 shows a detail of a comparative DRX material, MCT, showing the voltage profile and capacity retention of the MCT. DETAILED DESCRIPTION OF THE INVENTION

[0020] In the following disclosure, the invention will be discussed with reference to examples illustrated in the accompanying drawings, without however limiting the invention to these examples.

[0021] To facilitate a better understanding of the tests performed and the structural origins of the improvements possible under the high-entropy DRX design strategy of the present invention, reference is made to Figure 1, which shows the face-centered cubic (FCC) unit cell cation sublattice, along with the relationship between the cation octahedral and tetrahedral structures.

[0022] In a random mixture with short-range order (SRO), the probability that a site (as depicted in Figure 1) is occupied by a particular species is determined in part by the occupancy of neighboring sites. Typically, a random mixture is one in which species are randomly assigned to be distributed across a set of sites without regard to the occupancy of neighboring sites. As an example, the mole fraction χ A and χ B In a normal random mixture of A and B cations with , the probability that a site is occupied by A is PA = χ A x A and the probability that a site is occupied by B is PB=χ B Since site occupancies are uncorrelated, the probability that a particular pair of nearest-neighbor sites is type AA is P AA =P A *P A =χ 2 A A similar formula is given for type BB(P BB =P B *P B =χ 2 B ) and Type AB(P AB =P A *P B =χ A χ B ) for the nearest pair of sites.

[0023] However, in a random mixture with SRO, the probability that a site is occupied by a species is influenced in part by the occupancy of neighboring sites, and the probability that a particular pair of nearest-neighbor sites is of type AB is not the same as in a normal random mixture. That is, the fact that A is present at a first site will affect the probability that B is present at a neighboring site, so P AB ≠P A *P B Such SRO correlations are not limited to nearest-neighbor bonds but can extend over longer distances to more separated sites. This deviation from randomness is called short-range order or "SRO" and can be measured by various techniques, including single-crystal X-ray scattering in TEM and electron diffraction. [7-8] SRO can also be inferred from various other techniques, including pair distribution functions obtained from neutron diffraction. [6] The high-entropy DRX design strategy of the present invention aims to mitigate SRO formation, resulting in improved capacity and rate performance, as shown by tests performed under this invention.

[0024] To illustrate the benefits of the high-entropy DRX design strategy, three prototype compositions, TM2, TM4, and TM6, were formed. As shown in Figure 2a, these exemplary compositions differ from existing transition metal species, but retain Li, O, and F (if present), with Li in excess.

[0025] The prototype compositions (TM2, TM4, and TM6) each contained a 30% Li excess (i.e., Li per formula unit) sufficient to allow good Li transport. 1.3 ), but avoids the undesirable limitation on the TM redox capacity. In the prototype composition, there is 15% fluorine substitution to further increase the TM redox reservoir. In the first prototype composition, Mn 3+ and Ti 4+ was designed as the baseline TM composition for exemplary testing purposes, and Li 1.3 Mn 3+ 0.4Ti 0.3 O 1.7 F 0.3 (hereafter referred to as TM2). In another prototype composition, Mn 2+ and Nb 5+ is further incorporated into the baseline composition TM 1.3 Mn 2+ 0.2 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7 F 0.3 This resulted in a composition with four TM species (hereafter referred to as TM4). 2+ , Nb 5+ , Co 2+ and Cr 3+ in addition to the baseline composition, Li 1.3 Mn 2+ 0.1 Co 2+ 0.1 Cr 3+ 0.1 Mn 3+ 0.1 Ti 0.1 Nb 0.2 O 1.7 F 0.3 , resulting in a composition with six TM species (hereafter referred to as TM6).

[0026] Although the present invention addresses three prototype compositions having two, four, and six TM species, respectively, it will be understood that the present findings encompass compositions having other numbers of TM species. For example, the present findings address the problem of Li 1.3 Mn 2+ 0.1 Co 2+ 0.1 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7 F 0.3 or Li 1.3 Mn 2+ 0.2 Cr 3+ 0.1 Mn 3+ 0.1 Ti0.1 Nb 0.2 O 1.7 F 0.3 and Li 1.3 Mn 2+ 0.1 Co 2+ 0.1 Cr 3+ 0.1 Mn 3+ 0.1 Ti 0.1 Nb 0.1 Ta 0.1 O 1.7 F 0.3 These five and seven TM species examples (i.e., TM[5] and TM[7]) are non-limiting, and the invention may similarly comprise compositions with any number of TM species that meet the additional criteria described herein.

[0027] synthesis The compounds of the present invention can be synthesized using conventional techniques by combining a collection of stoichiometric compounds containing Li, TM, O, and optionally F to produce a precursor powder, which is then preferably mechanically mixed to obtain a phase pure powder by mechanochemical alloying. The example DRX oxyfluoride compounds described herein were synthesized by conventional solid-state methodology as described above, with guidance provided by the inventive prototype compositional design of DRX cathodes with different numbers of TM (TM[n]) in Figure 2a.

[0028] Prototype compositions TM2, TM4, and TM6, as well as six additional DRX compounds as comparative examples, were synthesized using Li2CO3 (Alfa Aesar, ACS, 99% min), MnO (Alfa Aesar, 99%), CoCO3 (Alfa Aesar, 99.5%), Mn2O3 (Alfa Aesar, 99.9%), Cr2O3 (Sigma-Aldrich, 98%), TiO2 (Alfa Aesar, 99.9%), Nb2O5 (Sigma-Aldrich, 99.99%), and LiF (Alfa Aesar, 99.99%) as precursors. All precursors were stoichiometrically mixed (except for adding 10% more Li2CO3 and 5% more CoCO3 to compensate for potential losses during synthesis) in a Retsch PM 400 planetary ball mill at a rate of 180 rpm for 12 hours. The precursors were then mixed for 70 min. o These precursor pellets were dried overnight in an oven at 600°C to form pellets. o Preheat at 1,000°C for 3 hours and then place in an argon atmosphere. o C, but for all TM2 compounds, MCN and MCT, 1,050 o The pellets were sintered at C. The duration of sintering was 6 h. The pellets were then quenched in an argon atmosphere, transferred to a glove box, and ground into powder. All DRX compositions were successfully synthesized using conventional solid-state methods.

[0029] electrochemistry To illustrate the examples used as cathodes, cathode membranes were fabricated using the compounds synthesized above. All cathode membranes thus fabricated were formed from the active material, SUPER C65 (Timcal), and polytetrafluoroethylene (PTFE, DuPont, Teflon 8A) in a weight ratio of 70:20:10. To fabricate the cathode membranes, 280 mg of the as-synthesized active material and 80 mg of SUPER C65 were mixed and shaker-milled in a SPEX 800M Mixer / Mill for 90 minutes under an argon atmosphere. PTFE was then added and manually mixed with the shaker-milled mixture for 40 minutes. The components were then rolled into a thin film in a glove box. Commercially available 1 M LiPF6 in an ethylene carbonate (EC) and dimethyl carbonate (DMC) solution (volume ratio 1:1) was used as the electrolyte. Glass microfiber (Whatman) was used as the separator. FMC Li metal foil was used as the anode. Coin cells were assembled in a glove box and tested in an Arbin battery test instrument at room temperature. The film loading density was approximately 3-4 mg / cm based on active material. 2 The rate capability test was about 2.5 mg / cm based on the active material. 2 A smaller loading density of 100 mAh g was used. Specific capacity was then calculated based on the weight (70%) of the active material in the cathode film. Figure 3e shows the cycling voltage profiles for the TM2, TM4, and TM6 prototype compositions from the galvanostatic intermittent titration test (GITT). For these GITT measurements, each step in the voltage profile corresponds to a 10 mAh / g constant current charge / discharge at a rate of 20 mA / g, followed by a 6-hour relaxation step. -1 The overpotential at each step between the first state of charge and the highest state of charge is calculated and plotted as dots in the diagram.

[0030] Characterization Synchrotron X-ray diffraction (XRD) patterns for the as-synthesized compounds were collected at beamline 28-ID-2 at Brookhaven National Laboratory. Rietveld refinement was performed using PANalytical X'pert HighScore Plus software. Scanning electron microscope (SEM) images were collected using a Zeiss Gemini Ultra-55 Analytical Field Emission SEM at the Molecular Foundry at Lawrence Berkeley National Laboratory (LBNL). Scanning transmission electron microscopy (STEM), energy dispersive spectroscopy (EDS), and electron diffraction (ED) measurements were performed on a JEM-2010F microscope equipped with an X-mas EDS detector at the Molecular Foundry at LBNL. Neutron powder diffraction was measured on a Nanoscale Ordered Materials Diffractometer (NOMAD) at the Spallation Neutron Source at Oak Ridge National Laboratory. The sample for the neutron diffraction experiment was 7 Li enriched precursor ( 7 Li enriched precursor)( 7 LiF and 7 The analysis was performed using TOPAS software.

[0031] Solid state nuclear magnetic resonance (NMR) spectroscopy ssNMR data for the TM2, TM4, and TM6 initial powders were collected using a Bruker Avance 300 MHz (7.05 T) wide-bore NMR spectrometer with Larmor frequencies of 282.40 MHz and 116.64 MHz, respectively, at room temperature. Data were acquired using a 1.3 mm double-resonance HX probe with magic-angle spinning at 60 kHz. 19 F and 7 Li NMR data was analyzed using lithium fluoride (LiF, δ( 19 F) = -204 ppm and δ( 7Li = -1 ppm. Lineshape analysis was performed within Bruker Topspin software using the SOLA lineshape simulation package. 19 The resonant frequency range of the F nuclei was larger than the excitation bandwidth of the RF pulse used in the NMR experiments. To obtain a full spectrum, 11 spin-echo spectra were collected for TM2 and 9 for TM4 and TM6. These were performed from -759 to 361 ppm with a frequency step of 140 ppm (739.5 kHz), with a step size slightly below the excitation bandwidth of the RF pulse. The individual subspectra were processed using zero-order phase correction and then summed to give an overall sum spectrum in the absorption regime, which does not require further phase correction. This method, "frequency stepping," "spin-echo mapping," or "VOCS" (variable offset cumulative spectrum), provides a wide excitation bandwidth, thereby enabling the generation of a wide range of spin-echo spectra. 19 The F signal was uniformly excited using a 5.2 μs 90° RF pulse and a 10.4 μs 180° RF pulse at 100 W with a recycle delay of 30 ms. 19 F spin echo spectra were collected. For reference, spin echo spectra were collected for LiF using similar RF pulses but with a recycle delay of 30 s. 19 Similar acquisition parameters for the F spectrum were used to obtain it on an empty probe. 19 The F spectrum showed no significant background signal.

[0032] Results and Discussion The high-entropy DRX design strategy was demonstrated using three prototype compositions, TM2, TM4, and TM6. Each of TM2, TM4, and TM6 contains excess lithium, redox centers, and d 0 Compensator (d 0 and a fluorinating agent according to the general formula LiTMOF, wherein the TM species is a redox center and a d 0 It is included as a charge compensation material.

[0033] Scanning electron microscopy (SEM) shows that the particle size of the as-synthesized material reaches approximately 5–10 μm (Figure 2d, top), which can be reduced to 200–500 nm (Figure 2d, bottom) after shaker milling with carbon during electrode fabrication. Synchrotron X-ray diffraction (XRD) and time-of-flight (TOF) neutron diffraction patterns confirm the formation of a pure DRX structure with no observable impurity peaks, as shown in Figures 2b and 2c, respectively. Rietveld refinement of the composition yielded lattice parameters of 4.1918 Å, 4.2286 Å, and 4.2544 Å for TM2, TM4, and TM6, respectively.

[0034] Energy dispersive spectroscopy (EDS) mapping using transmission electron microscopy (TEM) was applied to verify the uniform distribution of multiple elements in the material. Figure 2e shows the TEM / EDS mapping for a representative particle of as-synthesized TM6, and the image reveals that the different TMs and F are uniformly distributed throughout the particle. 19 F nuclear magnetic resonance (NMR) measurements were further performed to verify the bulk incorporation of F into the DRXed lattice, as shown in Figure 2f. 19It can be seen that the F NMR spectrum is significantly different from that of the LiF reference. The former spectrum consists of multiple broad overlapping signals arising from the strong paramagnetic interaction between the unpaired d electrons on the TM ions and the F nuclei, and shifted from the resonance frequency of LiF at -204 ppm. This confirms that a large proportion of the F ions are incorporated into the DRX phase.

[0035] The electrochemical performance of the three prototype materials was first evaluated using a galvanostatic cycling test. When cycled between 1.5 and 4.7 V at a rate of 20 mA / g, TM2 delivers a high capacity (specific energy) of 220 mAh / g (704 Wh / kg), as shown in Figure 3a. TM4, which has a higher number of TM species in the DRX structure, exhibits a higher capacity of 269 mAh / g (849 Wh / kg), as shown in Figure 3b. TM6, which has an even higher number of TM species, further increases its capacity to 307 mAh / g (955 Wh / kg), as shown in Figure 3c. The higher-entropy TM6 compound still delivers a high discharge capacity of 246 mAh / g (803 Wh / kg), as shown in Figure 3d, when cycled over a smaller voltage window of 2.0 to 4.5 V.

[0036] That the superior performance results from overall entropy effects rather than the incorporation of a specific transition metal ion is further supported by testing several comparative compounds synthesized to resemble that of TM6, but with a lower entropy design. By evaluating similar compounds as TM6, but with fewer building blocks and therefore a design that reduces the benefit of the high-entropy design, the effects of high entropy may be better distinguished from those that are a product of the different transition metals used in the high-entropy design.

[0037] In the first test, TM4(Li 1.3Mn 2+ 0.2 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7 F 0.3 The performance of the TM2 (Li) was compared with that of the binary DRX, which includes a subset of four TMs used in TM4, as shown in Figure 3b. The binary DRX is implemented using the TM2 (Li) as shown in Figure 3a. 1.3 Mn 3+ 0.4 Ti 0.3 O 1.7 F 0.3 ) and Li as shown in Figures 6a to 6c. 1.3 Mn 2+ 0.367 Nb 0.333 O 1.7 F 0.3 (TM2-Mn 2+ Nb) and Li 1.3 Mn 3- 0.55 Nb 0.15 O 1.7 F 0.3 (TM2-Mn 3+ Each of these four compounds has the same prototype composition, Li 1.3 TM 0.7 O 1.7 F 0.3 Another binary compound, Li, shares the same structure and was synthesized using the same solid-state method. 1.3 Mn 2+ 0.2 Ti 0.5 O 1.7 F 0.3 It should be noted that TM2, TM2-Mn are not obtained as pure phases because the product contains a second phase of LiF. Of these four compounds, three binary (TM2, TM2-Mn 2+ Nb and TM2-Mn 3+ Nb), which includes all elements present in the fourth (TM4).

[0038] Each binary compound was found to have a lower capacity than the fourth compound: TM2 had a capacity of 220 mAh g -1 (Fig. 3a) shows the capacity of TM2-Mn 2+ Nb is 236mAh g -1 (Fig. 6b) and TM2-Mn 3+ Nb is 247mAh g -1 (Fig. 6c), which are 269mAh g -1 (Figure 3b) These results demonstrate that, apart from interactions resulting from simply mixing TM mixtures alone, better electrochemical performance can be achieved by mixing TM species with high-entropy coordination.

[0039] Further testing revealed that the metal species Co, which is not present in TM4 but is present in TM6, 2+ and Cr 3+ The results achieved by the inclusion of

[0040] Co 2+ The effect of the seed is shown in Figures 7a to 7c. 1.3 Co 2+ 0.2 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7 F 0.3 (TM4-Co) and Li 1.3 Co 2+ 0.1 Mn 2+ 0.1 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7 F 0.3 Based on the comparison of the two compositions, TM4 (Li 1.3 Mn 2+ 0.2 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7F 0.3 ) were studied. Here too, it was observed that the higher entropy composition had a superior capacity, i.e., 269 mAh g -1 (Fig. 3b) TM4 and 250mAh g -1 TM5 has a capacity of 288 mAh g compared to the lower capacity of TM4-Co (Figure 7b). -1 (Fig. 7c) These results show that Co 2+ Apart from the interactions resulting from the inclusion of TM itself, it is demonstrated that mixing multiple TM species with high entropy coordination results in better electrochemical performance.

[0041] Cr 3- The effect of the species was investigated using two Cr-containing ternary compounds, Li, shown in Figures 8a-8c. 1.3 Mn 2+ 0.3 Cr 3+ 0.1 Nb 0.3 O 1.7 F 0.3 (MCN) and Li 1.3 Mn 3+ 0.3 Cr 3+ 0.1 Ti 0.3 O 1.7 F 0.3 (MCT) was used as TM6 (Li 1.3 Mn 2+ 0.1 Co 2+ 0.1 Mn 3+ 0.1 Cr 3+ 0.1 Ti 0.1 Nb 0.2 O 1.7 F 0.3 ) compounds. 3+ The concentration (0.1 per fu) is the same as that in the TM6 compound. The phase-pure Cr-based binary DRX compounds using the same synthetic method as the above compounds were prepared. 3+Binary compounds were not used for this comparison because they were precluded by the low solubility of 244 mAh g. Comparison of these compounds again revealed that the higher entropy composition resulted in a superior capacity: 244 mAh g. -1 (Fig. 8b) MCN and 243 mAh g -1 Compared with MCT in (Fig. 8c), TM6 has a pf of 307 mAh g -1 (Fig. 3c) shows that Cr 3+ Apart from the interactions resulting from the inclusion of TM itself, it is demonstrated that mixing multiple TM species with high entropy coordination results in better electrochemical performance.

[0042] Without being bound by theory, we believe that this series of experiments demonstrates that the increasing improvements realized when going from TM2 to TM4 to TM6 are not attributable to the direct or indirect effects of specific TMs (e.g., electronic structure or size), or even to specific combinations of TMs, but rather are the result of synergistic effects in bringing together increasingly larger numbers of TMs in a high-entropy design.

[0043] Galvanostatic intermittent titration tests (GITT) were also performed to investigate the polarization in the three prototype materials, as shown in Figure 3e. The overpotential at each GITT step between the 100 mAh g state of charge and the highest state of charge was also calculated. It can be observed that incorporating more TM species into the DRX lattice significantly reduces the polarization, as evidenced by the decrease in voltage relaxation.

[0044] The local SRO of the three prototype materials was evaluated using TEM electron diffraction (ED), as shown in Figures 4a-c. Round dots resulting from long-range order in the materials are indexed as Fm-3m space group. The square-shaped diffuse scattering pattern is ascribed to SRO. Quantification of the SRO pattern intensity, obtained by grouping counts within the dashed rectangular area, is shown to the right of the corresponding ED pattern.

[0045] To demonstrate the comparative differences in SRO intensity for each of the prototype materials, the TEM diffraction patterns for each material were normalized by incorporating the Bragg diffraction intensity of the Bragg diffraction pattern into the first row to the left of the center. The normalized SRO intensity is shown in Figure 5a, with distance (1 / nm) on the horizontal axis and intensity (atomic units, or au) on the vertical axis. The relative SRO intensity of each material was then compared to the overall intensity summarized for each image by assessing the maximum intensity value in the second row to the left of the center (indicated by the rectangular sections in Figures 4a-c).

[0046] Comparative SRO intensities for the prototype materials can be seen in Figure 5b, which shows an overlay of the SRO intensities from Figures 4a-4c, with the approximate maximum intensity identified by the long-dashed line and the approximate baseline intensity identified by the short-dashed line. As shown in Figure 5b, the TM2 sample was observed to produce a maximum intensity of approximately 2.20 au with a base intensity of approximately 1.13 au (SRO intensity approximately 1.07 au above background). The TM4 sample was observed to produce a maximum intensity of approximately 1.56 au with a base intensity of approximately 1.25 au (SRO intensity approximately 0.31 au above background). The TM6 sample was observed to produce a maximum intensity of approximately 1.38 au with a base intensity of approximately 1.19 au (SRO intensity approximately 0.19 au above background). Thus, as shown by example in Figure 5b, we observe an inverse correlation between entropy and SRO in prototype materials TM2, TM4, and TM6, with increasing entropy correlating with decreasing SRO intensity. Thus, with increasing numbers of TM species from TM2 to TM4 to TM6, SRO in the DRX structure is largely annihilated, as evidenced by the decreased SRO signal intensity in electron diffraction.

[0047] Without being bound by theory, we believe that the reduction in SRO leads to improved Li transport properties and, therefore, higher capacity and improved rate capability. This is supported by the differences in the measured rate performance of the three materials, as can be seen by comparing Figures 4d-4f. As seen in Figure 4d, for TM2, discharge capacities of 220 mAh / g and 58 mAh / g are observed when cycled at 20 mA / g and 2000 mA / g, respectively, corresponding to a 74% capacity loss from lower to higher rates. Improved capacity retention is achieved with TM4, as evidenced by a 58% loss between discharge capacities of 269 mAh / g and 114 mAh / g when cycled at 20 mA / g and 2000 mA / g, respectively, as seen in Figure 4e. Further improvement is realized by TM6 with an even lower capacity loss of 45% between discharge capacities of 307 mAh / g and 170 mAh / g when cycled at 20 mA / g and 2000 mA / g, respectively, as seen in Figure 4f.

[0048] While the present invention has been described with reference to particular embodiments, those skilled in the art will understand that the foregoing disclosure deals only with exemplary embodiments, that the scope of the present invention is not limited to the disclosed embodiments, and that the scope of the present invention may encompass additional embodiments that include various changes and modifications to the examples disclosed herein without departing from the scope of the present invention as defined in the appended claims and their equivalents. For example, while the foregoing description describes the present invention in the context of cathodes, it will be understood that the compositions of the present invention are not limited to only cathodes, but may encompass other structures in which the present high-entropy design can be applied to provide the described benefits.

[0049] Although the disclosed methods may be performed by performing all of the disclosed steps in the exact order disclosed, without any intervening steps, one of ordinary skill in the art will understand that the methods may be performed with additional intervening steps between the disclosed steps, with the disclosed steps performed in an order other than the exact order disclosed, with one or more disclosed steps performed simultaneously, and with the omission of one or more disclosed steps.

[0050] To the extent necessary to understand or complete the disclosure of the present invention, all publications, patents, and patent applications mentioned herein are expressly incorporated herein by reference to the same extent as if each were individually incorporated (such incorporation does not imply any license with respect to the commonly owned references). The ranges set forth in this disclosure include the endpoints of each range, all values ​​between the endpoints, and all intermediate ranges encompassed by the endpoints. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the disclosure. As used herein, the singular form "a," "an," and the invention are characterized by the appended claims.

[0051] Reference materials [1] B. Kang, G. Ceder, Nature 458, 190-193 (2009). [2] P. Barpanda et al. Nature materials 10, 772-779 (2011). [3] K. Kang, YS Meng, J. Breger, CP Grey, G. Ceder, Science 311, 977-980 (2006). [4] J. Lee, A. Urban, X. Li, D. Su, G. Hautier, G. Ceder, Science 343, 519-522 (2014). [5] A. Urban, J. Lee, G. Ceder, Advanced Energy Materials 4, 1400478 (2014). [6] Ji, H., Urban, A., Kitchaev, D.A., Kwon, D.-H., Artrith, N., Ophus, C., Huang, W., Cai, Z., Shi, banerT., Kim, J.C. et al. Nature Communications 10, 592. (2019). [7] R. De Ridder, G. van Tendeloo and S. Amelinckx, Acta Crystallogr, A 32, 216 - 224. (1976). [8] Banerjee, S., K. Urban and M. Wilkens. Acta Metallurgica 32.3, 299 - 311 (1984).

Claims

1. As-synthesized, general formula Li 1+x TM[n] 1-x O 2-y F y Lithium metal oxide or oxide having Fluoride compounds, where TM[n] is a redox active species or d 0 Distinguished by redox-inactive charge compensators represents the number of transition metal species, including TM[n] is at least four of the transition metal species; The lithium metal oxide or oxyfluoride has a cation-disordered rock salt (DRX) structure. 、 TM[n] is at least Mn 3+ and Ti 4+ wherein 0.05≦x≦0.35, and 0≦y≦0.

5.

2. As-synthesized, general formula Li 1+x TM[n] 1-x O 2-y F y Lithium metal oxide or oxide having Fluoride compounds, where TM[n] is a redox active species or d 0 Distinguished by redox-inactive charge compensators represents the number of transition metal species, including TM[n] is at least six of said transition metal species; The lithium metal oxide or oxyfluoride has a cation-disordered rock salt (DRX) structure and has the general formula 0.05≦x≦0.35, and 0≦y≦0.

5.

3. As-synthesized, general formula Li 1+x TM[n] 1-x O 2-y F y Lithium metal oxide or oxide having Fluoride compounds, where TM[n] is a redox active species or d 0 Distinguished by redox-inactive charge compensators represents the number of transition metal species, including TM[n] is TM[1] a, TM[2] b, TM[3] c and TM[4] d At least four of the transition metal species are represented by TM[1] a, TM[2] b, TM[3] c and TM[4] d wherein 0.05≦x≦0.35, 0.1≦a≦0.3, 0.1≦b≦0.3, 0.1≦c≦0.3, 0.1≦d≦0.3, and 0≦y≦0.5; The lithium metal oxide or oxyfluoride has a cation-disordered rock salt (DRX) structure. ru, compound.

4. 4. The compound of claim 1, wherein TM[n] represents four or more TM species selected from the group Mn, Nb, Ti, Cr and Co.

5. TM[n] is Mn 3+ , Ti 4+ , Mn 2+ , Nb 5+ , Co 2+ and Cr 3+ 4. The compound of any one of claims 1 to 3, which exhibits four or more TM species selected from the group:

6. The compound is Li 1.3 Mn 2+ 0.2 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7 F 0.3 The compound of claim 1.

7. The compound is Li 1.3 Mn 2- 0.1 Co 2+ 0.1 Cr 3+ 0.1 Mn 3+ 0.1 Ti 0.1 Nb 0.2 O 1.7 F 0.3 It is said that, 2. The compound of claim 1.

8. An electrode material comprising the compound according to any one of claims 1 to 7.

9. Electrolytes, A lithium ion battery comprising the electrode material of claim 8.

10. A method of forming a compound according to any one of claims 1 to 7, comprising: A cluster of compounds formed by Li, TM[n], O, and optionally F in the presence of excess Li. producing a precursor powder of said compound by combining and mixing the precursor powders to obtain a phase-pure powder by mechanochemical alloying.

11. The four or more transition metal species TM[n] are Mn 3+ , Ti 4+ , Mn 2+ , Nb 5+ , Co 2+ and Cr 3+ 11. The method of claim 10, wherein the compound is selected from the group consisting of:

12. 11. The method of claim 10, wherein the precursor powder is subjected to mechanical mixing by feeding the precursor powder into a planetary ball mill.

13. TM[n] is Mn 3+ and Ti 4+ 11. The method of claim 10, comprising:

14. the compound contains lithium in the amount of Li1.3; 11. The method of claim 10, wherein TM[n] comprises Mn, Ti and two additional transition metal species.

15. The compounds have the general formula Li 1+x TM[1] a TM[2] b TM[3] c TM[4] d = (1-x-a-b-c) O 2-y F y and has the formula 11. The method of claim 10, wherein 0.05≦x≦0.35, 0.1≦a≦0.3, 0.1≦b≦0.3, 0.1≦c≦0.3, 0.1≦d≦0.3, and 0≦y≦0.5.

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