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Definitions

• the present invention relates to the design and synthesis of high entropy cation-disordered rocksalt (DRX) cathodes with a strategic increase in the number of transition metal (TM) species directed at providing a reduced short-range order (SRO) cathode.
• TM transition metal
• SRO short-range order
• the increased number of TM species mitigates SRO and yields improvements in the capacity and rate capability of the DRX cathodes.
• the invention confirms, via testing, high-entropy as a novel avenue for the design of high capacity and high rate performance Li-ion cathodes.
• Li transport in the DRX materials has been shown to rely mainly on the 0-TM networks (percolation network), where the tetrahedral sites in the Li migration path are coordinated by zero transition metal.
• the Li connected to the percolation network is referred to as “percolating Li”.
• the amount of percolating Li is an important indicator of the overall Li transport properties in DRX materials.
• LRO long-range order
• SRO local cation short-range order
• TEM transmission electron microscope
• SRO is viewed in most cases as reducing the amount of percolating Li in the DRX materials, as shown by a previous Monte Carlo study [6]. It follows that a challenge exists to reduce the cation SRO so that capacity and rate performance of DRX cathodes can be improved.
• SUMMARY OF THE INVENTION The invention establishes that improvements in capacity and rate performance of DRX materials are possible when SRO is reduced.
• the approach in achieving this involves the use of “high entropy” mixtures to synthesize the DRX materials – a high entropy DRX design strategy.
• the strategy involves the use of a relatively large number of components, which limits the ability of the cations to form a specific short-range order.
• DRX cation-disordered rocksalt
• the compound of illustrative point 1, wherein [n] is from four to ten of said transition metal species. 5.
• the compound of illustrative point 1, wherein the at least four of said transition metal species are selected from the group of Mn 3+ , Ti 4+ , Mn 2+ , Nb 5+ , Co 2+ , and Cr 3+ .
• the compound of illustrative point 1, wherein 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 illustrative point 1, wherein 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 . 8.
• the compound of illustrative point 5 which delivers a high capacity of 307 mAh/g at a cycling rate of 20 mA/g. 9.
• the compound of illustrative point 1 wherein the cation ion order reflects a mitigated short range order (SRO) characterized by the fact that, in TEM electron diffraction patterns, the SRO diffuse scattering pattern intensity is equal to or less than around 0.31 a.u. larger than the background intensity, and preferably equal to or less than around 0.19 a.u. larger than the background intensity. 11.
• SRO mitigated short range order
• An electrode material comprising: a. a compound according to any one of illustrative points 1-11.
• a lithium-ion battery comprising: a. an electrolyte; and b. the electrode material of illustrative point 12.
• a portable electronic device, an automobile, or an energy storage system comprising: a. the lithium-ion battery of illustrative point 14. 16.
• TM[n] species are selected from Mn 3+ , Ti 4+ , Mn 2+ , Nb 5+ , Co 2+ , and Cr 3+ . 18.
• a. the precursor powder is subjected to mechanical mixing by dispensing the precursor powder into a planetary ball mill. 19.
• the method of illustrative point 16, wherein the compound is inclusive of Mn 3+ and Ti 4+ .
• TM[n] further includes at least two of Mn 2+ , Nb 5+ , Co 2+ , and Cr 3+ . 21.
• the compound of illustrative point 26 wherein the cation ion order reflects a mitigated short range order (SRO) characterized by the fact that, in TEM electron diffraction patterns, the SRO diffuse scattering pattern intensity is equal to or less than around 1.07 a.u. larger than the background intensity, preferably equal to or less than around 0.31 a.u. larger than the background intensity, and more preferably equal to or less than around 0.19 a.u. larger than the background intensity. 31.
• SRO mitigated short range order
• the Li 1+x TM[n] 1-x O 2-y F y compositions featured under the present invention include the following: an excess of lithium, a redox center, a d 0 charge compensator and, optionally, a fluorination agent.
• the particular transmission metal (TM) species, as well as the number thereof, are strategically chosen for use either as the redox center TM or the d 0 charge compensator TM, with the number of TM species being sufficient to implement a high entropy DRX design strategy that reduces SRO.
• the present invention is thus inclusive of lithium metal oxides having a general formula: Li 1+x TM[n] 1-x O 2-y F y, said lithium metal oxide having a cation-disordered rocksalt structure, wherein 0.05 ⁇ x ⁇ 0.3 and 0 ⁇ y ⁇ 0.5, and with TM[n] designating a number of transition metal species (inclusive of those differentiated by redox-active species or d 0 redox-inactive charge compensators).
• the general formula may include 0.09 ⁇ x ⁇ 0.3 and 0.10 ⁇ y ⁇ 0.35.
• [n] is four or more TMs, with the four or more TMs preferably selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Sn, and Sb.
• TM may be selected from the more preferable group consisting of Mn, Nb, Ti, Cr, and Co.
• the value of [n] is 6 or more, with higher values representing higher entropy characteristics, and with the upper limit being potentially capped by processing and added complexity synthesis limitations.
• species distribution is provided. That is, a random mixture is one where the species distributed over a set of sites is randomly assigned to a given site without any consideration of the occupation of the neighboring sites.
• SRO correlations are not limited to the nearest neighbor bonds but can extend to a longer distance. These deviations from randomness are called short-range order or “SRO” and can be measured by a variety of techniques, including single-crystal X-ray scattering and electron diffraction in TEM. [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 is directed at mitigating SRO formation, with the resultant mitigation being verifiable by testing under the present invention, to yield improvements in capacity and rate performance, which may also be verified by testing carried out under the present invention.
• To illustrate advantages of the present invention’s high entropy DRX design strategy there was formed three prototype compositions TM2, TM4, and TM6. These compositions differ in the transitional metal species present. Li, O, and F are kept constant in these three compositions, with Li present in excess in each. Six additional compounds with the same prototype composition were also designed to confirm it is the overall entropic effect that leads to the improvement in capacity.
• All of the prototype compositions (TM2, TM4, and TM6) designed for testing featured 30% Li-excess (i.e., Li 1.3 per formula unit) as an amount sufficient to enable good Li transport, while on the other hand, avoiding too much limitation on TM redox capacity.
• Li-excess i.e., Li 1.3 per formula unit
• fluorine substitution was 15% to further increase the TM redox reservoir.
• the combination of Mn 3+ and Ti 4+ was designed as a baseline composition (e.g., in addition to being a high functioning baseline combination under the present invention, it is also helpful in showing higher entropy improvements under the present invention testing).
• TM6 TMs Mn 2+ , Nb 5+ , Co 2+ , and Cr 3+ to form 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 , which contains six TM species, referred to hereafter as TM6. All three prototype compositions were successfully synthesized using traditional solid- state methods. Scanning electron microscopy (SEM) shows that the particle size of the as- synthesized material reaches around 5-10 ⁇ m and can be reduced to 200-500 nm after shakermill with carbon during electrode fabrication.
• SEM scanning electron microscopy
• Synchrotron X-ray diffraction (XRD) patterns and time- of-flight (TOF) neutron diffraction patterns confirm the formation of pure DRX structures with no observable impurity peaks.
• Rietveld refinement yield lattice constants of 4.1918 ⁇ , 4.2286 ⁇ and 4.2544 ⁇ for TM2, TM4, and TM6, respectively.
• Energy-dispersive spectroscopy (EDS) mapping using a transmission electron microscope (TEM) was applied to confirm the uniform distribution of multi-elements in the materials.
• the compounds of the invention are suited for use in the preparation of electrodes, especially, cathodes.
• the compounds have an increased number of TM species (e.g., TM[n], where [n] is four or more (e.g., 4-10) and, more preferably in some environments, six or more (e.g., 6- 10)).
• TM[n] is four or more (e.g., 4-10) and, more preferably in some environments, six or more (e.g., 6- 10)).
• the increased number of TMs mitigates SRO, which is shown under the present invention to improve the capacity and rate capability of resultant DRX cathodes.
• the species can differ in terms of charge and/or d-shell conformation.
• the DRX cathodes are characterized by improved performance as can be seen in that, when cycled between 1.5 and 4.7 V at a rate of 20 mA g -1 , the TM2 prototype delivers a relatively high capacity (specific energy) of 220 mAh g -1 (704 Wh kg -1 ), whereas the TM4 prototype, with a greater number of TM species demonstrates an even a higher capacity of 269 mAh g -1 (849 Wh kg -1 ), while the TM6 prototype, with a yet greater number of TM species, further increases to 307 mAh g -1 (955 Wh kg -1 ).
• the high entropy TM6 compound can continue to deliver a relatively high discharge capcacity of 246 mAh g -1 (803 Wh kg -1 ), even when cycled at a smaller voltage window of 2.0 – 4.5V at a rate of 20 mA g -1 .
• Six additional compounds with the same prototype composition are also presented to demonstrate the role of the overall entropic effect (rather than any specific transition metal ion), which leads to the enhancement in capacity. The performance of these compounds confirms high-entropy as a novel avenue of design for high capacity and high rate performance Li-ion cathodes.
• Lithium-ion batteries that employ these cathodes also evidence improved performance, and thus portable electronic devices, vehicles (such as spacecraft and automobiles), and energy storage systems that employ such a battery will likewise evidence improved performance.
• compounds under the present invention may be readily synthesized using conventional techniques by combining a strategic number (and combination) (“collection”) of stoichiometric compounds composed of, for example, Li, Mn, Ti, Nb, O, and F to yield a precursor powder which is then preferably mechanically mixed to obtain the phase pure powder through mechanochemical alloying. Li is advantageously present in excess. Further improvements are introduced by including in the precursor powder a combination of Mn, Ti, Nb, Co, and Cr.
• the ball mill used is preferably a planetary ball mill.
• FIG. 1 shows a face-center cubic (FCC) unit cell cation sublattice. The relationship between cation octahedron and tetrahedron structures is also shown.
• FIGS. 1 shows a face-center cubic (FCC) unit cell cation sublattice. The relationship between cation octahedron and tetrahedron structures is also shown.
• FIG.2a-f show the design and structural characterization of the synthesized prototype materials TM2, TM4, and TM6.
• FIG.2a shows a prototype composition design of DRX cathodes with the different numbers of TMs in the respective compositions.
• FIG.2c shows neutron diffraction patterns of the synthesized prototype compositions.
• FIG.2d shows SEM images of TM6 as-synthesized (upper panel) and as shaker-milled with carbon black (lower panel).
• FIG.2e shows TEM/EDS mapping of the elemental distribution in a particle cluster of the as-synthesized TM6.
• FIG. 2f shows 19 F frequency-stepping NMR spectra obtained by summing over multiple spin echo sub-spectra acquired at different excitation frequencies, with the spectra scaled according to the amount of sample in the rotor, and with 19 F spin echo spectra collected on LiF powder overlaid for comparison.
• FIGS.3a-e show the electrochemical performance of the TM2, TM4, and TM6 prototype compositions.
• FIGS.3a-3c show voltage profiles and capacity retention (1.5-4.7V, at 20 mA g -1 ; RT) for the TM2, TM4, TM6 compositions, respectively.
• FIG.3d shows the voltage profile and capacity retention of TM6 (2.0-4.5V, at 20 mA g -1 ; RT).
• FIG. 3e shows the first cycle voltage profiles of the TM2, TM4, and TM6 compositions from galvanostatic intermittent titration tests (GITT).
• FIGS.4a-f show short range order and Li transport analyses of the TM2, TM4, and TM6 compositions.
• FIGS.4a-4c show TEM electron diffraction (ED) patterns for the TM2, TM4, TM6 compositions, respectively, along the zone axis [100].
• FIGS.4d-4f show the rate capacity of the TM2, TM4, and TM6 compositions, respectively, as cycled between 1.5-4.7 V at various rates.
• FIGS.5a-5b show SRO intensity patterns, with FIG.5a showing SRO intensities based on normalization of the TEM diffraction pattern of FIGS. 4a-4c, and FIG. 5b showing comparative SRO maximum intensities of the separate prototype materials from FIGS.4a-4c.
• FIGS.6a-6c show details of comparative DRX materials TM2-Mn 2+ Nb and TM2-Mn 3+ Nb, with FIG.6a showing XRD patterns of the two comparative DRX materials, FIG.6b showing the voltage profile and capacity retention of TM2-Mn 2+ Nb, and FIG. 6c showing the voltage profile and capacity retention of TM2-Mn 3+ Nb.
• FIGS.7a-7c show details of comparative DRX materials TM4-Co and TM5, with FIG.7a showing XRD patterns of the two comparative DRX materials, FIG.7b showing the voltage profile and capacity retention of TM4-Co, and FIG.7c showing the voltage profile and capacity retention of TM5.
• FIGS. 8a-8c show details of comparative DRX materials MCN and MCT, with FIG.
• FIG. 8a showing XRD patterns of the two comparative DRX materials
• FIG.8b showing the voltage profile and capacity retention of MCN
• FIG.8c showing the voltage profile and capacity retention of MCT DETAILED DESCRIPTION OF THE INVENTION
• a random mixture with short-range order In a random mixture with short-range order (SRO), the probability that a site (such as those depicted in FIG.1) is occupied by a certain species is determined in part by the occupancy of the neighboring site.
• a random mixture is one where the species distributed over a set of sites is randomly assigned without any consideration of the occupation of the neighboring sites.
• SRO short-range order
• SRO can be measured by a variety of techniques, including single-crystal X-ray scattering and electron diffraction in TEM. [7-8]. SRO can also be inferred from a variety of other techniques including pair distribution functions obtained from neutron diffraction [6].
• High entropy DRX design strategies are directed at mitigating SRO formation so as to yield improvements in capacity and rate performance, as shown by testing carried out under the present invention.
• TM2, TM4, and TM6 are formed three prototype compositions TM2, TM4, and TM6. As shown in FIG. 2a, these illustrative compositions differ in the transitional metal species present, while Li, O, and F (if present) are kept constant, with Li present in excess.
• Each of the prototype compositions (TM2, TM4, and TM6) featured 30% Li-excess (i.e., Li 1.3 per formula unit) as an amount sufficient to enable good Li transport, while avoiding undesirable limitations on TM redox capacity.
• TM2 Li 1.3 Mn 3+ 0.4 Ti 0.3 O 1.7 F 0.3
• TM4 Mn 2+ and Nb 5+ were further incorporated into the baseline composition TMs to form Li 1.3 Mn 2+ 0.2 Mn 3+ 0.2 Ti 0.1 Nb 0.2 O 1.7 F 0.3 , thereby resulting in a composition with four TM species (referred to hereafter as TM4).
• TM6 Mn 2+ , Nb 5+ , Co 2+ , and Cr 3+ were added to the baseline composition to form 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 , thereby resulting in a composition with six TM species (referred to hereafter as TM6).
• TM6 TM6 species
• the present invention addresses three prototype compositions having two, four and six TM species respectively, it will be understood that the present invention is inclusive of compositions having other numbers of TM species.
• the present invention may include compositions with five TM species, such as: 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 Ti 0.1 Nb 0.2 O 1.7 F 0.3 ; and may also include compositions with seven TM species, such as: 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 .
• TM species such as: 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 .
• TM[5] and TM[7] are non-limiting, and the present invention may likewise comprise compositions of any number of TM species that meet the further criteria set forth herein.
• Synthesis Compounds according to the present invention can be synthesized using conventional techniques by combining a collection of stoichiometric compounds composed of Li, TMs, O, and optionally F to yield a precursor powder which is then mechanically mixed to obtain the phase pure powder through mechanochemical alloying.
• the prototype compositions TM2, TM4, and TM6, as well as the additional six DRX compounds as comparatives were each synthesized with Li 2 CO 3 (Alfa Aesar, ACS, 99% min), MnO (Alfa Aesar, 99%), CoCO 3 (Alfa Aesar, 99.5%), Mn 2 O 3 (Alfa Aesar, 99.9%), Cr2O3 (Sigma- Aldrich, 98%), TiO 2 (Alfa Aesar, 99.9%), Nb 2 O 5 (Sigma-Aldrich, 99.99%) and LiF (Alfa Aesar, 99.99%) used as precursors.
• All the precursors were stoichiometrically mixed (except for adding 10% more Li 2 CO 3 and 5% more CoCO 3 in order to compensate possible loss during synthesis) with a Retsch PM 400 planetary ball mill at a rate of 180 rpm for 12 hours.
• the precursors were then dried in 70°C oven overnight and pelletized.
• the precursor pellets were pre-heated at 600°C for 3 hours, followed by sintered at 1,000°C under argon atmosphere, except for all TM2 compounds, MCN and MCT , which were sintered at 1,050°C. The duration of sintering was 6 hours.
• the pellets were then fast cooled in an argon atmosphere, transferred to a glovebox, and ground into powders.
• cathode films comprising the noted synthesized compounds. All cathode films thus produced were composed of active materials, SUPER C65 (Timcal), and polytetrafluoroethylene (PTFE, DuPont, Teflon 8A) at a weight ratio of 70:20:10. To make the cathode films, 280 mg as-synthesized active materials and 80 mg SUPER C65 were mixed and shaker-milled for 90 minutes in argon atmosphere with SPEX 800M Mixer/Mill, and PTFE was later added and manually mixed with the shaker-milled mixture for 40 minutes.
• active materials SUPER C65 (Timcal)
• PTFE polytetrafluoroethylene
• FIG.3e shows cycle voltage profiles for the TM2, TM4, and TM6 prototype compositions from galvanostatic intermittent titration tests (GITT).
• GITT galvanostatic intermittent titration tests
• Rietveld refinement was done with PANalytical X’pert HighScore Plus software.
• Scanning electron microscopy (SEM) images were collected using a Zeiss Gemini Ultra-55 Analytical Field Emission SEM in the Molecular Foundry at Lawrence Berkeley National Lab (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 in the Molecular Foundry at LBNL.
• Neutron powder diffraction was measured at Nanoscale Ordered Materials Diffractometer (NOMAD) at the Spallation Neutron Source in Oak Ridge National Laboratory.
• NOMAD Nanoscale Ordered Materials Diffractometer
• Samples for neutron diffraction experiment were prepared using 7 Li enriched precursors ( 7 LiF and 7 Li 2 CO 3 ). The refinement was performed using TOPAS software.
• Solid-state nuclear magnetic resonance (NMR) spectroscopy ssNMR data were collected on TM2, TM4, and TM6 pristine powders 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.
• the data were obtained at 60 kHz magic- angle spinning (MAS) using a 1.3 mm double-resonance HX probe.
• MAS magic- angle spinning
• Lineshape analysis was carried out within the Bruker Topspin software using the SOLA lineshape simulation package.
• the resonant frequency range of 19 F nuclei in TM2, TM4, and TM6 was larger than the excitation bandwidth of the RF pulse used in the NMR experiment.
• eleven spin echo spectra were collected for TM2 and nine spin echo spectra were collected for TM4 and TM6.
• Scanning electron microscopy shows that the particle size of the as-synthesized material reaches around 5-10 ⁇ m (FIG.2d, upper panel) and can be reduced to 200-500 nm (FIG. 2d, lower panel) after shakermill with carbon during electrode fabrication.
• Synchrotron X-ray diffraction (XRD) patterns and time-of-flight (TOF) neutron diffraction patterns confirm the formation of pure DRX structures with no observable impurity peaks, as shown in FIGS.2b and 2c, respectively.
• FIG.2e shows the TEM/EDS mapping on a representative particle of as-synthesized TM6, it being evident from the images that the different TMs, as well as F, were distributed uniformly in the whole particle.
• 19 F nuclear magnetic resonance (NMR) measurement was further conducted to confirm the bulk incorporation of F into the DRX lattice, as shown in FIG.2f.
• TM2 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 FIG.3a.
• TM4 With an increased number of TM species in the DRX structure, TM4 demonstrates a higher capacity of 269 mAh/g (849 Wh/kg), as shown in FIG.3b; and with a yet higher number of TM species, the capacity of TM6 further increases to 307 mAh/g (955 Wh /kg), as shown in FIG.3c.
• the binary DRXs include the prior discussed TM2 (Li 1.3 Mn 3+ 0.4 Ti 0.3 O 1.7 F 0.3 ), as shown in FIG. 3a, as well as two additional binaries of Li 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+ Nb), as shown in FIGS.6a-6c. These four compounds each share the same prototype composition “Li 1.3 TM 0.7 O 1.7 F 0.3 ”, and were synthesized using the same solid state method.
• each of the binary compounds exhibits a smaller capacity than that of the quaternary compound – with TM2 exhibiting a capacity of 220 mAh g –1 (FIG.3a), TM2-Mn 2+ Nb providing a capacity of 236 mAh g –1 (FIG.6b), and TM2-Mn 3+ Nb having a capacity of 247 mAh g –1 (FIG.6c), which are each smaller than the capacity of TM4 at 269 mAh g –1 (FIG.3b).
• the effects of the Cr 3+ species were studied by comparing two Cr-containing ternary compounds, Li 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), as shown in FIGS. 8a-8c, relative to the 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 ) compound, as shown in FIG. 3c.
• the Cr 3+ concentration (0.1 per f.u.) in the two ternaries is the same as that in the TM6 compound.
• Binary compounds were not used for this comparison as the low solubility of Cr 3+ in DRXs precludes phase-pure Cr-based binary DRX compounds using the same synthesis method by which the aforementioned compounds are produced. Comparison of these compounds again revealed that a higher entropic composition provided a superior capacity – with TM6 having a much larger capacity pf 307 mAh g –1 (FIG.3c), as compared to the lower capacities of MCN at 244 mAh g –1 (FIG.8b) and MCT at 243 mAh g –1 (FIG.8c).
• Galvanostatic intermittent titration tests were also conducted to investigate the polarization in the three prototype materials, as shown in FIG.3e. Overpotential at each GITT step between 100 mAh/g charged states and the top of charge states were also calculated. It can be observed that the polarization is greatly reduced when more TM species are incorporated into the DRX lattice, as evidenced by the reduced voltage relaxation.
• the local SRO of the three prototype materials were evaluated using TEM electron diffraction (ED), as shown in FIGS.4a-4c. The round spots, which originate from the long-range order in the materials, are indexed to be Fm-3m space group. The square-like diffuse scattering patterns are attributed to the SRO.
• Quantifications of SRO pattern intensity are displayed to the right of the corresponding ED patterns.
• the TEM diffraction patterns for each material was normalized by integrating the Bragg diffraction intensity of the Bragg diffraction patterns in the first column left-of-center.
• the normalized SRO intensities are shown in FIG.5a, with distance (1/nm) along the horizontal axis and intensity (atomic unit – a.u.) along the vertical axis.
• the relative SRO intensities of the individual materials were then compared by assessing the maximum intensity values in the second column left-of-center (as noted by rectangular sections in FIGS.
• FIG. 5b Comparative SRO intensities of the prototype materials may be seen in FIG. 5b, which provides an overlay of the SRO intensities from FIGS. 4a-4c with approximated maximum intensities identified by long-dash broken lines and approximated baseline intensities identified by short-dash broken lines.
• the TM2 sample was observed to yield a maximum intensity of approximately 2.20 a.u. relative to a base intensity of approximately 1.13 a.u. (an SRO intensity that is around 1.07 a.u. larger than the background intensity); the TM4 sample was observed to yield a maximum intensity of approximately 1.56 a.u. relative to a base intensity of approximately 1.25 a.u.
• TM4 An 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 FIG.4e.
• TM6 A further improvement is achieved with TM6, with a yet 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 FIG.4f.

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