WO2024178062A1 - Deagglomeration by transient salt liquids for the synthesis or recycling of battery cathodes - Google Patents

Abstract

A mechanochemical process to synthesize single-crystalline cathode powders for the formation of cathodes in a lithium-ion battery includes mixing a transient metal oxide precursor with a lithium salt mixture. Thereafter, a mechanical agitation process may be applied to selectively melt the lithium salt mixture to form a molten salt liquid that wets, corrodes, and separates the grain boundaries of secondary particles in the transient metal oxide precursor. As a result, the secondary particles are deagglomerated resulting in a colloidal dispersion of primary particles. The mixture is then calcined to facilitate growth of single-crystalline particles from the primary particles, thus forming a single-crystalline cathode powder. The single-crystalline particles exhibit large particle size and little to no phase separation, thus improving electrochemical performance. This highly scalable process can be used to synthesize single-crystalline cathode powders from chemical-grade precursors or black mass.

Description

DEAGGLOMERATION BY TRANSIENT SALT LIQUIDS FOR THE SYNTHESIS OR RECYCLING OF BATTERY CATHODES

CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001 ] This application claims the priority benefit, under 35 U.S.C. 119(e), of U.S. Application No. 63/486,131, filed February 21, 2023 and entitled, “PLANETARY CENTRIFUGAL DEAGGLOMERATION BY TRANSIENT SALT LIQUIDS FOR THE SYNTHESIS OR RECYCLING OF BATTERY CATHODES,” which is incorporated herein by reference in its entirety.

GOVERNMENT SUPPORT

[0002] This invention was made with government support under HR0011-1-72-0029 awarded by the Defense Advanced Research Projects Agency. The government has certain rights in the invention.

BACKGROUND

[0003] The ever-increasing demand for energy storage in various industry sectors, such as the automative industry and electric utilities, has created a desire for more advanced lithium-ion batteries (LIBs) with a higher energy density, a longer cycle life, and superior safety. Additionally, cost reduction is an important factor in achieving scalable synthesis of advanced LIBs.

[0004] Several state-of-the-art LIB cathode materials have recently emerged that exhibit at least some of the foregoing properties desired for advanced LIBs. These materials include Ni- rich layered oxides or Li-/Mn-rich layered oxides. Both of these materials typically have poly crystalline morphologies with fine-grained primary particles (-100-200 nm grain size) that cluster together to form larger secondary particles (-10 pm diameter). This microstructure is designed to increase cycle life and volumetric energy density. Moreover, the microstructure is readily formed using industrialized co-precipitation techniques that ensure uniform transition metal (ternary or more) distributions, high reaction activity, and low lithiation temperature with the hydroxide/carbonate lithium salts. However, these polycrystalline cathodes are prone to intergranular cracking during electrode calendering and battery cycling. The intergranular cracking electronically isolates active materials, thus exposing unprotected fresh surfaces of the material to the liquid electrolyte leading to more side reactions and degradation in electrochemical performance. SUMMARY

[0005] The Inventors have recognized and appreciated single-crystalline cathodes (i.e., micron-sized free-standing particles free of grain boundaries) have the potential to achieve greater stability and reliability compared to current state-of-the-art polycrystalline cathodes. At present, the production of high-performance Ni-rich single-crystalline cathodes typically requires a multi-step high-temperature calcination process, processes using excess lithium salt, and/or processes using molten salt (e.g., NaCl, KC1, and Li2SO4) followed by additional washing and/or calcination. These molten salts do not react with the cathodes or the precursors. As a result, additional processing steps after calcination are often performed. Additionally, the agglomeration of cathode primary particles remains a significant barrier to the formation of high-quality single-crystalline cathodes. Lastly, a general cost-effective methodology to synthesize Ni-rich and Li-/Mn-rich cathodes remains elusive.

[0006] In view of the foregoing limitations of conventional single-crystalline cathode materials, the Inventors have recognized mechanochemistry can provide a way to synthesize high-quality single-crystalline cathode materials. Mechanochemistry is a branch of material chemistry and mechanochemical synthesis provides unique capabilities for mechanical activation and production of metastable phases under far-from-equilibrium conditions. For LIBs, mechanochemical synthesis has been used previously to synthesize Li-excess cation- disordered rocksalt cathodes where raw chemicals (i.e., precursors) are planetary ball-milled at high rates using stainless steel jars and grinding media to obtain a non-equilibrium phase.

[0007] Conventional mechanochemical synthesis techniques (e.g., ball-milling), however, often require significant capital and energy costs, thus limiting scalability and thus the use of mechanochemical synthesis in practical applications. This is especially limiting for the mass production of LIB cathodes at low cost and high reproducibility. In addition, the synthesized powders are often agglomerated with a large size distribution and contaminated by impurities from the grinding media. Lastly, the underlying mechanisms remain poorly understood as the state variables (e.g., temperature) are difficult to quantify and real-time observations are often not available.

[0008] Therefore, the present disclosure is directed to various inventive implementations of mechanochemical processes to synthesize high-quality single crystalline cathode powders, which, in turn, may be used to form a cathode for a LIB. The mechanochemical processes disclosed herein may involve mixing a polycrystalline precursor with a lithium salt mixture. The lithium salt mixture may be a eutectic composition (e.g., a mixture of LiOH and LiNCh at a molar ratio of 40:60). The mixture of the precursor and the lithium salt mixture may then be mechanically agitated by a mechanical agitator (e.g., a planetary centrifugal mixer), which causes the lithium salt mixture to melt and form a molten salt. The molten salt, in turn, may reactively wet, corrode, and separate the grain boundaries of the polycrystalline precursor. As a result, the precursor may become deagglomerated, i.e., the primary particles of the precursor may become separated and isolated one another. Once the primary particles are deagglomerated, the resulting mixture may be calcined to facilitate single-crystal growth from the primary particles.

[0009] The mechanochemical processes described above may produce a single-crystalline cathode powder, which may be subsequently used to form a cathode for a LIB. Compared to conventional single-crystalline cathode materials, the single-crystalline cathode powders formed using the processed disclosed herein may achieve comparable, if not larger singlecrystalline particles (e.g., greater than or equal to 1 pm). Further, the single-crystalline cathode powders may exhibit appreciably less phase separation. Said another way, the constituent elements of the single-crystalline cathode powder may be more uniformly distributed spatially across each single-crystalline particle. The uniform distribution of the constituent elements may also correspond to the distribution of different crystal phases across each single-crystalline particle. For example, respective single-crystalline particles may include a thin layer (e.g., less than or equal to 1 nm) of a rocksalt-like phase at the surface with the bulk having a spinel phase. These foregoing properties of the single-crystalline cathode powders may facilitate improved electrochemical performance compared to conventional single-crystalline cathodes. [0010] In one example implementation, a method for forming a single-crystalline cathode powder including a plurality of single-crystalline particles comprises: A) providing, to a mechanical agitator, a mixture including: a precursor including a plurality of secondary particles, each secondary particle of the plurality of secondary particles including a plurality of primary particles directly coupled together; and a lithium salt having a eutectic composition; B) mixing, by the mechanical agitator, the mixture such that the lithium salt melts and forms a molten lithium salt, the molten lithium salt deagglomerating the plurality of secondary particles such that respective primary particles of the pluralities of primary particles are substantially separate from each other; and C) calcinating the mixture to form the plurality of singlecrystalline particles of the single-crystalline cathode powder from the pluralities of primary particles.

[00111 The precursor may not include lithium. The precursor may not include fluorine and carbon black. The precursor may include black mass. The precursor may include lithium in an amount less than or equal to about 0.9 mol. The precursor may include at least one of fluorine or carbon black. The plurality of primary particles may include at least one of spinel -type M3O4, Mno.6Nio.2Coo.2(OH)2, Nio.8Mno.iCoo.i(OH)2, Li1-xNio.8Coo.1Mno.1O2, Li1-xNio.eCoo.2Mno.2O2, or Li1-xNio.5Coo.2Mno.3O2. The lithium salt may include LiOH and LiNOi and a molar ratio of LiOH and LiNOi may range between about 40:60 to about 45:55. The lithium salt may have a melting point ranging from about 180°C to about 200°C. The precursor may further include at least one of a cobalt (Co) salt, a manganese (Mn) salt, or an aluminum (Al) salt. The plurality of single-crystalline particles may include at least one of Li1.2Mno.48Nio.i6Coo.i6O2, or LiNio.8Coo.1Mno.1O2. The mechanical agitator may be a planetary centrifugal mixer. The method may further include: forming a cathode from the single-crystalline cathode powder, wherein the cathode is formed without: grinding the single-crystalline cathode powder; washing the single-crystalline cathode powder; annealing the single-crystalline cathode powder; or sieving the single-crystalline cathode powder.

[0012] In another example implementation, a method for forming a single-crystalline cathode powder including a plurality of single-crystalline particles comprises: A) providing, to a mechanical agitator, a mixture including: a precursor including black mass; and a lithium salt having a eutectic composition; B) mixing, by the mechanical agitator, the mixture such that the lithium salt melts and forms a molten lithium salt, the molten lithium salt deagglomerating the precursor; and C) calcinating the mixture to form the plurality of single-crystalline particles of the single-crystalline cathode powder from the pluralities of primary particles.

[00.13] The black mass may include at least one of Li1-xNio.8Coo.1Mno.1O2, Lii- xNio.6Coo.2Mno.2O2, or Li1-xNio.5Coo.2Mno.3O2. The lithium salt may include LiOH and LiNOi and a molar ratio of LiOH and LiNOi ranges between about 40:60 to about 45:55. The plurality of single-crystalline particles may have an average diameter greater than or equal to 1 pm.

[0014] In yet another example implementation, a single-crystalline cathode powder comprises: a plurality of single-crystalline particles including a transition metal oxide, wherein: the plurality of single-crystalline particles has an average diameter greater than or equal to 1 pm; and at least a transition metal in the transition metal oxide is uniformly distributed within each single-crystalline particle of the plurality of single-crystalline particles.

[0015] The transition metal oxide may be one of A) a lithium-rich and a manganese-rich layered transition metal oxide or B) a nickel-rich layered transition metal oxide. The transition metal oxide may include at least one of Li1.2Mno.48Nio.i6Coo.i6O2 or LiNio.8Coo.1Mno.1O2.

[0016] In yet another example implementation, a method includes the following steps: (a) providing a mixture including lithium salts having concentrations at or near the eutectic composition (b) transferring the mixture to a planetary centrifugal mixer; (c) centrifuging the mixture; and (d) collecting the mixture after centrifugation, wherein a matrix of Li0H-LiN03 eutectic liquid including nano-sized primary particles is produced.

[0017] The mixture including lithium salts may further include Mn-rich precursor compounds (Mn>0.4, e.g., Mno.6Nio.2Coo.2(OH)2) or Ni-rich precursor (Ni>0.4, e.g., Nio.8Mno.iCoo.i(OH)2). The lithium salts may include LiNCh and LiOH. The mixture may include a LiOH-LiNCh having a 40:60 molar ratio at the eutectic composition. The step of centrifuging may be performed at 600, 800, 1000, 1250, 1500, 1750, 2000, 2500, or 3000 rpm. The step of centrifuging may be performed for at least 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 minutes. The step of centrifuging may be performed for less than 60 minutes. The method may produce primary particles of A/3O4 precursors that are well dispersed in a matrix of a LiOH-LiNCh eutectic. The method may produce secondary particles that are completely separated and deagglomerated. The method may produce an oxide/lithium salt that is uniformly distributed at a fine scale. The method may be performed in the absence of any grinding media. The method may provide for the synthesis of high- performance single-crystalline cathodes. The method may produce a Li-/Mn-rich layered cathode Li1.2Mno.48Nio.i6 C00.16O2 with singlecrystalline morphology after thermal treatment. The method may produce Ni-rich layered cathode Li1.oNio.8Mno.1Coo.1O2 with single-crystalline morphology after thermal treatment.

[0018] The method may be used to recycle cathodes of lithium batteries. The method may be used to upcycle cathodes of lithium batteries, by adding additional low-melting-point lithium salts containing one or more of LiOH-Li NO3 lithium hydroxide, lithium nitrate, lithium acetate, lithium formate, or a mixture thereof to relithiate the used cathode. The method may be used to upcycle cathodes of lithium batteries, by adding additional low-melting-point lithium salts containing one or more of lithium hydroxide, lithium nitrate, lithium acetate, and their mixtures, and/or transition metal salts containing one or more of Ni, Co, Mn, Fe, Ti, V, Cr, Cu, Y, Zr, Nb, Mo, Hf, Ta, and W, and/or salts containing one or more of Mg and/or Al to relithiate the used cathode and change the non-lithium metal ratios in the upcycled product. The method may be performed for upcycling process of cathode powders, wherein the mixture including by low-melting-point lithium salts containing one or more of lithium hydroxide, lithium nitrate, lithium acetate, and their mixtures, and/or transition metal salts containing one or more of Ni, Co, Mn, Fe, Ti, V, Cr, Cu, Y, Zr, Nb, Mo, Hf, Ta, and W, and/or salts containing one or more of Mg and/or Al a and further including a lithium transition metal oxide presented by the following formula: LixNiaCobMncXdCh, wherein 0.5<x<0.99, 0.33<a<0.96, 0.01<b<0.33, 0.010. l<c<0.33, 0.01<d<0.33, and X = one or more of Fe, Ti, V, Cr, Cu, Y, Zr, Nb, Mo, Hf, Ta, W, Mg and Al. [0019) The thermal treatment may include a first thermal treatment step and a second thermal treatment step, the first treatment step is followed by the second thermal treatment step, and a thermal treatment in the first thermal treatment step is higher than a thermal treatment step in the second thermal treatment step. The first thermal treatment may include thermal treatment at a temperature of about 800°C to about 1000°C under atmospheric or oxidizing condition for about 2 hours to about 5 hours. The second thermal treatment includes thermal treatment at a temperature of about 700°C to about 800°C under atmospheric or oxidizing condition for about 5 hours to about 12 hours.

[0020] It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It should also be appreciated that terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The skilled artisan will understand that the drawings primarily are for illustrative purposes and are not intended to limit the scope of the inventive subject matter described herein. The drawings are not necessarily to scale; in some instances, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and/or structurally similar elements).

[0022] FIG. 1 shows an example process for deagglomeration to facilitate synthesis of singlecrystalline cathodes.

[0023] FIG. 2A shows an image of a mixture comprising /W3O4 precursors and lithium salts before mixing using a planetary centrifugal mixer.

[0024J FIG. 2B shows an image of the mixture of FIG. 2A after 3 minutes of mixing using a planetary centrifugal mixer.

[0025] FIG. 2C shows an image of the mixture of FIG. 2A after 6 minutes of mixing using a planetary centrifugal mixer. [0026] FIG. 2D shows an image of the mixture of FIG. 2A after 12 minutes of mixing using a planetary centrifugal mixer.

[0027] FIG. 2E shows a scanning electron microscopy (SEM) image of the mixture of FIG. 2 A after 3 minutes of mixing.

[0028] FIG. 2F shows an SEM image of the mixture of FIG. 2A after 12 minutes of mixing.

[0029] FIG. 2G shows a secondary electron (SE) image of the mixture of FIG. 2A after 12 minutes of mixing and corresponding energy dispersive X-ray (EDX) maps of oxygen (O), nitrogen (N), and manganese (Mn).

[0030] FIG. 2H shows a phase diagram of LiOH-LiNCh system (adapted from the FACT salt database). The 6 tested compositions of LiOH-LiNCh mixture are marked by a green triangle if the mixed salt melts and the A/3O4 precursors are deagglomerated and by a red cross if not.

[0031] FIG. 3 A shows a cross-sectional high resolution transmission electron microscope (HR- TEM) image of a A/3O4 precursor with a spinel phase.

[0032] FIG. 3B shows a high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of the A/3O4 precursor of FIG. 3A.

[0033] FIG. 3C shows a cross-sectional HR-TEM image of a A/3O4 precursor that was planetary-centrifugally mixed with eutectic lithium salt. As shown, the precursor has a spinel phase in the bulk and a disordered rocksalt phase at its surface.

[0034] FIG. 3D shows a HAADF-STEM image of the A/3O4 precursor of FIG. 3C.

[0035] FIG. 3E shows an HR-TEM image and corresponding FFT patterns (selected region site A for the surface and site B for the bulk) of a A/3O4 precursor planetary-centrifugally mixed with eutectic lithium salt.

[0036] FIG. 3F shows an atomic-resolution scanning electron transmission microscopy (STEM) image of the A/3O4 precursor planetary-centrifugally mixed with eutectic lithium salt. The yellow-dashed line indicates the boundary between disordered rocksalt and spinel phases. The filled circles in the schematics are as follows: Li at 4a site in yellow, transition metals at 4a site in blue, transition metals at 16d site in green, and transition metals in 8a site in purple.

[0037] FIG. 4A shows an SEM image of a polycrystalline lithium-rich manganese based layered oxide (PC-LMR) with the composition Li1.2Mno.48Nio.i6Coo.i6O2.

[0038] FIG. 4B shows a cross-sectional SE image and corresponding transmission energy dispersive X-ray spectroscopy (TEM-EDS) maps of Mn, Ni, and cobalt (Co) on a PC-LMR particle of FIG. 4 A.

[0039] FIG. 4C shows an SEM image of a single-crystalline lithium-rich manganese based layered oxide (SC-LMR) with the composition Li1.2Mno.48Nio.i6Coo.i6O2. [0040] FIG. 4D shows a cross-sectional SE image and corresponding TEM-EDS maps of Mn, Ni, and cobalt (Co) on a SC-LMR particle of FIG. 4C.

[0041] FIG. 4E shows a comparison of X-ray diffraction (XRD) patterns of PC-LMR and SC- LMR. Superlattice peaks for LiMne ordering at 20-25° are highlighted in the inset.

[0042] FIG. 4F shows an atomic-resolution STEM image measured along the [100] monoclinic direction of PC-LMR.

[0043] FIG. 4G shows an atomic-resolution STEM image measured along the [100] monoclinic direction of SC-LMR.

[0044] FIG. 5 A shows voltage-capacity curves of PC-LMR and SC-LMR for 100 cycles at 0.3C in the voltage range of 2.0-4.8 V vs. Li/Li⁺ at 25 °C (1C defined as 250mAh g ').

[0045] FIG. 5B shows the cycling performance of PC-LMR and SC-LMR corresponding to the voltage-capacity curves of FIG. 5 A.

[0046] FIG. 5C shows discharge curves of galvanic intermittent titration technique (GITT) measurements conducted at the 5^th and 100^th cycles of a 0.3C cycling test.

[0047] FIG. 5D shows differential electrochemical mass spectrometry (DEMS) results of PC- LMR and SC-LMR during the 1^st cycle at 0.1C. The mass spectra of mass to charge ratio mlz = 32 for O2 and mlz = 44 for CO2 were collected.

[0048] FIG. 5E shows dissolved Ni, Co and Mn in the electrolytes measured by inductively coupled plasma - optical emission spectroscopy (ICP-OES) after 1 week and 2 weeks of storage at 60°C. The cathode electrodes were at a fully charged state and the electrolytes from three different containers were measured to obtain the averages and standard deviations for each data point.

[0049] FIG. 6A shows an SEM image of single-crystalline nickel cobalt manganese oxide (SC- NCM).

[0050] FIG. 6B shows an SEM image of polycrystalline nickel cobalt manganese oxide (PC- NCM).

[0051] FIG. 6C shows cross-sectional STEM images of PC-NCM (top) and SC-NCM (bottom) before cycling. The inset shows PC-NCM with residue porosities.

[0052] FIG. 6D shows cross-sectional SEM images of PC-NCM (top) and SC-NCM (bottom) after cycling.

[0053] FIG. 6E shows cross-sectional STEM images of PC-NCM (top) and SC-NCM (bottom) after cycling.

[0054] FIG. 6F shows atomic-resolution STEM images of PC-NCM (top) and SC-NCM (bottom) after cycling. [0055] FIG. 6G shows the cycling performance of PC-NCM and SC-NCM for 200 cycles at 0.5 C/0.5 C charge/discharge rate in the voltage range of 2.8-4.3 V vs. Li/Li⁺ at 25 °C (1 C defined as 200 mAh g ¹ ).

[0056] FIG. 7A shows an SEM image of a powder mixture comprising a Mn-rich precursor and a solid-state Li-based salt (LiOH and LiNCh) after 3 minutes of planetary centrifugal mixing.

[0057] FIG. 7B shows a magnified SEM image of the powder mixture of FIG. 7A.

[0058] FIG. 7C shows an SE image and corresponding energy dispersive spectroscopy (EDS) maps of N, O, and Mn for the powder mixture of FIG. 7 A.

[0059] FIG. 8A shows an SEM image of a powder mixture Mn-rich precursor and Li-based solid/molten-salts (at a eutectic composition of LiOH and LiNCh) after 3 minutes of planetary centrifugal mixing.

[0060] FIG. 8B shows an SEM image of the powder mixture of FIG. 8 A after 6 minutes of planetary centrifugal mixing.

[0061] FIG. 8C shows an SEM image of the powder mixture of FIG. 8A after 12 minutes of planetary centrifugal mixing.

[0062] FIG. 9 shows XRD patterns of a powder mixture of Mn-rich precursor and Li-based solid/molten-salt (at a eutectic composition of LiOH and LiNCh) in its initial form, after 3 minutes of planetary centrifugal mixing, 6 minutes of planetary centrifugal mixing, and 12 minutes of planetary centrifugal mixing.

[0063] FIG. 10 shows a comparison of the effect of particle deagglomeration for different compositions of the LiOH-LiNOs salt mixture.

[0064] FIG. 11 A shows a STEM image of a cross-sectioned Mn-rich precursor after 12 min of planetary centrifugal deagglomeration.

[0065] FIG. 1 IB shows a higher magnification STEM image of the precursor of FIG. 11 A.

[0066] FIG. 11C shows a higher magnification STEM image of the precursor of FIG. 1 IB.

[0067] FIG. 12A shows a STEM image of a Mn-rich precursor.

[0068] FIG. 12B shows electron energy loss spectroscopy (EELS) line-scans along the designated line of the Mn-rich precursor in FIG. 12 A.

[0069] FIG. 13 A shows an SE image and corresponding TEM-EDS maps of Mn, O, Ni, and Co on a cross-section of PC-LMR particles.

[0070] FIG. 13B shows a lower magnification SE image and corresponding TEM-EDS maps of Mn, O, Ni, and Co for the PC-LMR particles of FIG. 13 A. [00711 FIG. 13C shows a higher magnification SE image and corresponding TEM-EDS maps of Mn, O, Ni, and Co for the PC-LMR particles of FIG. 13 A.

[0072] FIG. 13D shows a SE image and corresponding TEM-EDS maps of Mn, O, Ni, and Co on a cross-section of a SC-LMR particle.

[0073] FIG. 14A shows an atomic-resolution STEM image of PC-LMR.

[0074] FIG. 14B shows a higher magnification atomic-resolution STEM image of the PC-LMR of FIG. 14 A.

[0075] FIG. 14C shows an atomic-resolution STEM image of SC-LMR.

[0076] FIG. 14D shows a higher magnification atomic-resolution STEM image of the SC- LMR of FIG. 14C.

[0077] FIG. 15A shows a Rietveld refinement of an XRD pattern for PC-LMR. The fitting details are available in FIG. 37.

[0078] FIG. 15B shows a Rietveld refinement of an XRD pattern for SC-LMR. The fitting details are available in FIG. 37.

[0079] FIG. 16A shows an atomic-resolution STEM image and a corresponding fast-Fourier transform (FFT) pattern measured along the [100] monoclinic direction showing long-range honeycomb ordering in PC-LMR.

[0080] FIG. 16B shows an atomic-resolution STEM image and a corresponding fast-Fourier transform (FFT) pattern measured along the [100] monoclinic direction showing short-range honeycomb ordering in SC-LMR.

[0081] FIG. 17 shows the first-cycle charge-discharge profile (i.e., formation cycle) at 0.1C in between 2.0 and 4.8V (vs. Li/Li⁺) at 25°C (1C=25O mA g ') for PC-LMR and SC-LMR.

[0082] FIG. 18A shows the discharge energy density of PC-LMR and SC-LMR for 100 cycles at 0.3C in the voltage range of 2.0-4.8 V vs. Li/Li⁺ at 25 °C (1 C defined as 250 mAh g '). Solid curve indicates the average value for 3 cells. Shaded region indicates standard deviations at each data point for 3 cells.

[0083] FIG. 18B shows the discharge capacity of PC-LMR and SC-LMR for 100 cycles at 0.3C in the voltage range of 2.0-4.8 V vs. Li/Li⁺ at 25 °C (1 C defined as 250 mAh g '). Solid curve indicates the average value for 3 cells. Shaded region indicates standard deviations at each data point for 3 cells.

[0084] FIG. 18C shows the discharge average voltage of PC-LMR and SC-LMR for 100 cycles at 0.3C in the voltage range of 2.0-4.8 V vs. Li/Li⁺ at 25 °C (1 C defined as 250 mAh g '). Solid curve indicates the average value for 3 cells. Shaded region indicates standard deviations at each data point for 3 cells.

[0085] FIG. 19A shows TEM and STEM images of cross-sectioned PC-LMR after 100 cycles during 0.3C cycling (between 2.0 and 4.8V at 25°C).

[0086] FIG. 19B shows TEM and STEM images of cross-sectioned SC-LMR after 100 cycles during 0.3C cycling (between 2.0 and 4.8V at 25°C).

[0087] FIG. 20 shows an example measurement of ohmic loss and non-ohmic loss in a galvanostatic intermittent titration technique (GITT) curve of PC-LMR after the 5^th cycle (between 2.0 and 4.8 V at 25°C).

[0088] FIG. 21 A shows the voltage profiles after 5^th and 100^th cycles for PC-LMR.

[0089] FIG. 2 IB shows the voltage profiles after 5^th and 100^th cycles for SC-LMR.

[0090] FIG. 21C shows ohmic and non-ohmic voltage losses separately plotted as a function of depth of discharge in PC-LMR.

[0091] FIG. 21D shows ohmic and non-ohmic voltage losses separately plotted as a function of depth of discharge in SC-LMR.

[0092] FIG. 22A shows digital images of Ni-rich precursor and Li-based salt mixture at different times of planetary centrifugal mixing (0, 6 and 12 minutes).

[0093] FIG. 22B shows an SEM image of the powder mixture of FIG. 22 A after 3 minutes of mixing.

[0094] FIG. 22C shows an SEM image of the powder mixture of FIG. 22A after 12 minutes of mixing.

[0095] FIG. 23 A shows an SEM image of a Ni-rich precursor (Nio.8Coo.iMno.i(OH)2)

[0096] FIG. 23B shows an SEM image of poly-crystalline NCM (PC-NCM) particles.

[0097] FIG. 24A shows an SEM image of NCM synthesized using a eutectic LiOH-LiNCh mixture, which was hand-mixed and calcined at 940 °C for 2 hours and then at 760 °C for 10 hours in flowing oxygen.

[0098] FIG. 24B shows a magnified SEM image of the NCM of FIG. 24 A.

[0099] FIG. 24C shows an SEM image of a Ni-rich cathode synthesized using a eutectic LiOH- LiNCh mixture, which was planetary centrifugally mixed and calcined at 920 °C for 2 hours and then at 760 °C for 10 hours in flowing oxygen.

[0100] FIG. 24D shows a magnified SEM image of the Ni-rich cathode of FIG. 24C.

[0101] FIG. 24E shows an SEM image of a Ni-rich cathode synthesized using a eutectic LiOH- LiNCh mixture, which was planetary centrifugally mixed and calcined at 960 °C for 2 hours and then at 760 °C for 10 hours in flowing oxygen. [0102] FIG. 24F shows a magnified SEM image of the Ni-rich cathode of FIG. 24F.

[0103] FIG. 25 A shows an SEM image of a cross-sectioned PC-NCM electrode before cycling. [0104] FIG. 25B shows an SEM image of a cross-sectioned single-crystalline NCM (SC- NCM) electrode before cycling.

[0105] FIG. 26 shows the first-cycle charge-discharge profile (i.e., formation cycle) at 0.1 C in between 2.8 and 4.3 V (vs. Li/Li⁺) at 25°C (1 C=200 mA g ') for PC-NCM and SC-NCM.

[0106] FIG. 27A shows voltage profiles of PC-NCM during 1.0 C/1.0 C cycling test in FIG. 6E between 2.8 and 4.3 V (vs. Li/Li⁺) at 25°C (1 C=200 mA g ').

[0107] FIG. 27B shows voltage profiles of SC-NCM during 1.0 C/1.0 C cycling test in FIG. 6E between 2.8 and 4.3 V (vs. Li/Li⁺) at 25°C (1 C=200 mA g ')

[0108] FIG. 28 shows the cycling performance of PC-NCM and SC-NCM for 200 cycles at 0.5 C/0.5 C charge/discharge rate in the voltage range of 2.8-4.3 V vs. Li/Li⁺ at 25 °C (1 C defined as 200 mAh g '). The solid curve indicates the average value for 3 cells. The shaded region indicates standard deviations at each data point for 3 cells.

[0109] FIG. 29A shows an SEM image of a cross-sectioned PC-NCM electrode after 200 cycles at 0.5 C/0.5 C within voltage of 2.8-4.3 V (vs. Li/Li⁺).

[01.10] FIG. 29B shows a higher magnification SEM image of the PC-NCM electrode of FIG. 29A.

[0111| FIG. 29C shows an SEM image of a cross-sectioned SC-NCM electrode after 200 cycles at 0.5 C/0.5 C within voltage of 2.8-4.3 V (vs. Li/Li⁺).

[0112] FIG. 29D shows a higher magnification SEM image of the SC-NCM electrode of FIG. 29A.

[0113] FIG. 30A shows electrochemical impedance spectroscopy (EIS) measurements on PC- NCM after 5 and 200 cycles of 0.5 C/0.5 C cycling between 2.8 V and 4.3 V (vs. Li/Li⁺) at 25°C.

[0114] FIG. 30B shows EIS measurements on SC-NCM after 5 and 200 cycles of 0.5 C/0.5 C cycling between 2.8 V and 4.3 V (vs. Li/Li⁺) at 25°C.

[0115] FIG. 31A shows in-situ differential electrochemical mass spectrometry data of PC- NCM during the first charge at 0.05 C in the voltage range of 2.8-4.3 V (vs. Li/Li⁺) at 25°C.

[0116] FIG. 3 IB shows in-situ differential electrochemical mass spectrometry data of SC- NCM during the first charge at 0.05 C in the voltage range of 2.8-4.3 V (vs. Li/Li⁺) at 25°C.

[0117] FIG. 32 shows the concentration of dissolved Ni, Co and Mn in electrolytes measured by inductively coupled plasma - optical emission spectroscopy (ICP-OES), for charged PC- NCM and SC-NCM electrodes during high-temperature storage at 60°C. For each measurement, electrolytes from three batches were measured to calculate the average and standard deviation.

|0118] FIG. 33 A shows an SE image and corresponding EDX maps of N, O, Ni, Co, and Mn for a sample of deagglomerated secondary particles of NCM523(Lii-_x Nio.5Coo.2Mno.3O2) waste powder obtained after 15min of planetary centrifugal mixing.

[0119] FIG. 33B shows an EDX spectrum corresponding to the EDX maps of FIG. 33 A.

[0120] FIG. 34A shows an SEM image of waste secondary particles made of NCM523.

[0121] FIG. 34B shows a higher magnification SEM image of the secondary particles of FIG. 34A.

[0122] FIG. 34C shows an SEM image of upcycled Ni80-NCM synthesized by eutectic LiOH- LiNCb mixture with planetary centrifugal mixing and calcined at 900 °C for 2 hours and then at 760 °C for 10 hours.

[0123] FIG. 34D shows a higher magnification SEM image of the upcycled Ni80-NCM of FIG. 34C.

[01 4] FIG. 35 shows a table of the chemical composition for PC-LMR and SC-LMR measured by ICP-OES

[0125] FIG. 36 shows a table of the particle size distributions of SC-LMR and PC-LMR.

]0126 J FIG. 37 shows a table of refined XRD data for PC-LMR and SC-LMR assuming Ni and Mn can cation-mixed with Li.

[0127] FIG. 38 shows a table comparing different Li-/Mn-rich cathode materials based on the synthesis method, cost, test specification and electrochemical performances.

[0128] FIG. 39 shows a table of the concentration of dissolved Ni, Co and Mn in electrolytes measured by ICP-OES, for charged PC-LMR and SC-LMR electrodes during high-temperature storage at 6O0C. For each measurement, electrolytes from three batches were measured to calculate the average and standard deviation.

[0129] FIG. 40 shows a table of the chemical composition of PC-NCM and SC-NCM measured by ICP-OES.

[0130] FIG. 41 shows a table of the particle size distributions of PC-NCM and SC-NCM.

[0131] FIG. 42 shows a table of refined XRD data for PC-NCM and SC-NCM assuming only Ni can cation -mix with Li.

[0132] FIG. 43 A shows a first portion of a table comparing single-crystalline Ni-rich cathode materials based on the synthesis method, particle size, and electrochemical performances.

[0133] FIG. 43B shows a second portion of the table of FIG. 43 A. DETAILED DESCRIPTION

[0134] Following below are more detailed descriptions of various concepts related to, and implementations of, processes for synthesizing single-crystalline cathode materials using a combination of eutectic lithium salts and mechanical agitation. The present disclosure is also directed to various inventive implementations of single-crystalline cathode materials having appreciably improved electrochemical performance facilitated, in part, by a morphology comprising relatively large single-crystalline grains and constituent materials that are uniformly distributed throughout each grain. It should be appreciated that various concepts introduced above and discussed in greater detail below may be implemented in multiple ways. Examples of specific implementations and applications are provided primarily for illustrative purposes so as to enable those skilled in the art to practice the implementations and alternatives apparent to those skilled in the art.

[0135] The figures and example implementations described below are not meant to limit the scope of the present implementations to a single embodiment. Other implementations are possible by way of interchange of some or all of the described or illustrated elements. Moreover, where certain elements of the disclosed example implementations may be partially or fully implemented using known components, in some instances only those portions of such known components that are necessary for an understanding of the present implementations are described, and detailed descriptions of other portions of such known components are omitted so as not to obscure the present implementations.

[0.136] In the discussion below, various examples of inventive processes for synthesizing single-crystalline cathode materials and the single-crystalline cathode materials themselves are provided, wherein a given example or set of examples showcases a precursor (e.g., a fresh precursor, black mass), a lithium salt, a mechanical agitator, and an apparatus to facilitate calcination.

[0137] It should be appreciated that one or more features discussed in connection with a given example process or single-crystalline cathode material may be employed in other respective examples of processes or single-crystalline cathode materials according to the present disclosure, such that the various features disclosed herein may be readily combined in a given process or single-crystalline cathode material, respectively, according to the present disclosure (provided that respective features are not mutually inconsistent).

[0138] Certain parameters and dimensions of the processes and the single-crystalline cathode materials formed by the processes are described herein using the terms “approximately,” “about,” “substantially,” and/or “similar.” As used herein, the terms “approximately,” “about,” “substantially,” and/or “similar” indicates that each of the described dimensions or features is not a strict boundary or parameter and does not exclude functionally similar variations therefrom. Unless context or the description indicates otherwise, the use of the terms “approximately,” “about,” “substantially,” and/or “similar” in connection with a numerical parameter indicates that the numerical parameter includes variations that, using mathematical and industrial principles accepted in the art (e.g., rounding, measurement or other systematic errors, manufacturing tolerances, etc.), would not vary the least significant digit.

1. An Example Mechanochemical Process for Synthesizing Single-Crystalline Cathode Powders

[0139| FIG. 1 shows an example mechanochemical process 100 for synthesizing a singlecrystalline cathode powder. As shown, the process 100 may begin at step 102 by mixing one or more precursors 210 with a lithium salt mixture 240. The precursor(s) 210 comprise at least a transition metal oxide precursor. The precursor(s) 210 may include a plurality of primary particles 212 that are agglomerated to form a secondary particle 214. At step 104, the mixture of the precursor(s) 210 and the lithium salt mixture 240 is mechanically agitated by a mechanical agitator 110. During the agitation process, the lithium salt mixture 240 melts to form a transient molten salt liquid 242, The molten salt liquid 242 may reactively wet the secondary particles 212 and corrode the grain boundaries of the secondary particles 212. This, in turn, causes the primary particles 212 to separate and disperse within the molten salt liquid 242. Once step 104 is complete, the molten salt liquid 242 may solidify and the primary particles 212 may remain dispersed and separated within the solidified lithium salt. The mixture of the precursor 210 and the lithium salt are uniformly distributed at a fine scale, e.g., at a submicron scale. In some implementations, the primary particles 212 of the precursor 210 may be separated, on average, by a distance less than about 1 pm, less than about 900 nm, less than about 800 nm, less than about 700 nm, less than about 600 nm, less than about 500 nm, less than about 400 nm, less than about 300 nm, less than about 200 nm, or less than about 100 nm. In some implementations, the primary particles 212 of the precursor 210 may physically contact one another. In some implementations, the solidified portions of lithium salt may be separated, on average, by a distance less than about 1 pm, less than about 900 nm, less than about 800 nm, less than about 700 nm, less than about 600 nm, less than about 500 nm, less than about 400 nm, less than about 300 nm, less than about 200 nm, or less than about 100 nm. In some implementations, the solidified portions of lithium salt may physically contact one another. Thereafter, at step 106, the mixture may be calcined to facilitate growth of single- crystalline particles 222 from the primary particles 212. During the calcination process, the lithium salt mixture may provide a source of lithium during synthesis of the particles 222.

[0140] The process 100 is general and may be implemented to synthesize single-crystalline cathode powders with various compositions from a variety of precursor materials. In one example, the process 100 may synthesize single-crystalline cathode powders from chemical grade precursor(s) (also sometimes referred to as “fresh precursor(s)”). A chemical grade precursor may be a precursor that includes little to no impurities, such as fluorine or carbon (e.g., carbon black). For example, the concentration of impurities may be less than about 1 wt%, about 0.5 wt%, or about 0.1 wt%. The term “about,” when used to describe the concentration of impurities in the precursors, is intended to cover any variations in composition that may arise during manufacture. For example, “about 1 wt%” may correspond to the following ranges: 0.95 wt% to 1.05 wt% (+/- 5% variation), 0.98 wt% to 1.02 wt% (+/- 2% variation), 0.99 wt% to 1.01 wt% (+/- 1% variation), 0.992 wt% to 1.008 wt% (+/- 0.8% variation), 0.994 wt% to 1.006 wt% (+/- 0.6% variation), 0.996 wt% to 1.004 wt% (+/- 0.4% variation), or 0.998 wt% to 1.002 wt% (+/- 0.2% variation), including all values and sub-ranges in between. In some implementations, a chemical grade precursor may not include any lithium. In some implementations, the chemical grade precursor may comprise a spinel-type transition metal oxide of the form M3O4, such as a metal oxide or a metal hydroxide. For example, the chemical grade precursor may include, but is not limited to, Mno.6Nio.2Coo.2(OH)2 and Nio.8Mno.iCoo.i(OH)2.

In another example, the process 100 may be used to synthesize single-crystalline cathode powders by recycling, or even upcycling, waste precursor materials. A waste precursor material (also referred to as “black mass”) may be cathode materials originating from used LIBs. Black mass typically includes impurities, such as fluorine and/or carbon (e.g., carbon black). Despite the presence of these impurities, the process 100 may nevertheless form singlecrystalline cathode powders that exhibit a capacity and/or energy density as good as or, in some instances, better than the original cathodes from the LIBs. In some implementations, a black mass precursor may comprise lithium in an amount less than or equal to about 0.9 mol, about 0.8 mol, about 0.7 mol, about 0.6 mol, or about 0.5 mol. In some implementations, the black mass precursor may include, but is not limited to, Li1-xNio.8Coo.1Mno.1O2, Lii- xNio.6Coo.2Mno.2O2, or Li1-xNio.5Coo.2Mno.3O2.

[0142] More generally, the precursor(s) 210 may include a lithium transition metal oxide of the form, Li_xNi_aCobMn_cXdO2. The parameter x may range from about 0.5 to about 0.99, including any values or sub-ranges in between. The parameter a may range from about 0.33 to about 0.96, including any values or sub-ranges in between. The parameter b may range from about 0.01 to about 0.33, including any values or sub-ranges in between. The parameter c may range from about 0.01 to about 0.33, including any values or sub-ranges in between. The parameter d may range from about 0.01 to about 0.33, including any values or sub-ranges in between. Further, X may include one or more of Fe, Ti, V, Cr, Cu, Y, Zr, Nb, Mo, Hf, Ta, W, Mg, or Al.

|0143] The term “about,” when used to describe the amount of lithium, is intended to cover any variations in composition that may arise during manufacture. For example, “about 1 mol” may correspond to the following ranges: 0.95 mol to 1.05 mol (+/- 5% variation), 0.98 mol to 1.02 mol (+/- 2% variation), 0.99 mol to 1.01 mol (+/- 1% variation), 0.992 mol to 1.008 mol (+/- 0.8% variation), 0.994 mol to 1.006 mol (+/- 0.6% variation), 0.996 mol to 1.004 mol (+/- 0.4% variation), or 0.998 mol to 1.002 mol (+/- 0.2% variation), including all values and subranges in between.

[0144] It should also be appreciated that the process 100 is agnostic to the shape and/or size of the primary particles 212 and the secondary particles 214. For example, the primary particles 212 and the secondary particles 214 may respectively have various shapes including, but not limited to, a sphere, a spheroid, an ellipsoid, a polyhedron, and any combination of the foregoing. In some implementations, the primary particles 212 may have a diameter that ranges from about 100 nm to about 500 nm, including all values and sub-ranges in between. In some implementations, the primary particles 212 may have a diameter that ranges from about 100 nm to about 200 nm, including all values and sub-ranges in between. In some implementations, the secondary particles 214 may have a diameter that ranges from about 1 pm to about 20 pm, including all values and sub-ranges in between. In some implementations, the primary particles 212 may have a diameter that ranges from about 4 pm to about 6 pm, including all values and sub-ranges in between.

10145] The term “about,” when used to describe the dimensions of the primary particles 212 and the secondary particles 214, is intended to cover any variations in particle geometry that may arise during synthesis. For example, “about 1 pm” may correspond to the following ranges: 0.95 pm to 1.05 pm (+/- 5% variation), 0.98 pm to 1.02 pm (+/- 2% variation), 0.99 pm to 1.01 pm (+/- 1% variation), 0.992 pm to 1.008 pm (+/- 0.8% variation), 0.994 pm to 1.006 pm (+/- 0.6% variation), 0.996 pm to 1.004 pm (+/- 0.4% variation), or 0.998 pm to 1.002 pm (+/- 0.2% variation), including all values and sub-ranges in between.

[0146] In some implementations, the stoichiometry and/or the composition of the transition metal oxide precursor may be adjusted by adding additional salts to the mixture during step 102. These salts may include, but are not limited to, nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), titanium (Ti), vanadium (V), chromium (Cr), copper (Cu), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), and tungsten (W). For example, the stoichiometry of black mass precursors may vary based on the type of waste batteries used. That composition, however, may be adjusted to obtain a single-crystalline cathode powder with a different, more desirable stoichiometry. See Section 2.6 for additional examples of tailoring the stoichiometry and/or composition of a cathode powder by adding one or more salts.

[0147] As described above, the lithium salt mixture 240 may serve two functions in the process 100. The first function is the formation of the molten salt liquid 242 to facilitate deagglomeration of the precursor(s) 210. The second function is to provide a source of lithium during calcination of the primary particles 212. In some implementations, these functions may be facilitated, in part, by the lithium salt mixture 240 having a eutectic mixture of two or more compounds. For example, the lithium salt mixture 240 may be a binary compound, a ternary compound, a quaternary compound, and the like. The compounds include, but are not limited to, lithium hydroxide (LiOH), lithium nitrate (LiNCh), lithium acetate, and the like.

[0148] The eutectic mixture may have a melting point suitable to ensure the lithium salt mixture 240 melts during the mechanical agitation process during step 104 of the process 100 while still remaining higher than room temperature. For example, the melting point may range from about 180°C to about 200°C, including all values and sub-ranges in between. The term “about,” when used to describe the melting point of the lithium salt mixture 240, is intended to cover any variations in the composition (e.g., molar ratio) of the mixture. For example, “about 200°C” may correspond to the following ranges: 190°C to 210°C (+/- 5% variation), 196°C to 204°C (+/- 2% variation), 198°C to 202°C (+/- 1% variation), including all values and subranges in between.

10149] The melting point may be adjusted, in part, by altering the molar ratios of the constituent compounds in the lithium salt mixture 240. For example, if the lithium salt mixture 240 includes LiOH and LiNOs, the molar ratio may range from about 40:60 to about 45:55. The molar ratio may be constrained to ensure the mixture remains eutectic. It should be appreciated that the range of suitable melting points may depend on the nature of the mechanical agitation. For example, mechanical agitators that provide relatively more vigorous agitation of the mixture may achieve higher local temperatures within the mixture during step 104. Accordingly, lithium salt mixtures with a higher melting point may be used given the higher local temperatures attainable. The term “about,” when used to describe the molar ratio of the lithium salt mixture 240, is intended to cover variations in amount of compounds used in the mixture during synthesis. For example, “about 40:60” may correspond to the following: 42:58, 41.5:58.5, 41 :59, 40.5:59.5, 40:60, 39.5:60.5, 39:61, 38.5:61.5, 38:62, including all values and sub-ranges in between.

[0150] At step 104, the mechanical agitator 110 is used to melt the lithium salt mixture 240 to form a molten salt liquid 242. In some implementations, the mechanical agitator 110 may be a planetary centrifugal mixer. More generally, the mechanical agitator 110 may be any mechanical device used for mixing, dispersing, deaerating, and/or making slurry. In some implementations, the mechanical agitator 110 may be a device that consumes appreciably less power compared to a ball-milling system. For example, the mechanical agitator 110 mechanically agitate the mixture for tens of minutes as opposed to conventional ball milling systems, which are used for hours in conventional mechanochemical processes for the synthesis of LIB cathodes.

[01511 At step 106, the deagglomerated mixture is calcined to facilitate growth of the singlecrystalline particles 222. The calcination process may involve heating the mixture to an elevated temperature for a prolonged period of time. In some implementations, the calcination process may include multiple heating processes where the mixture is heated to different temperatures for different periods of time.

[0152] For example, the mixture may be heated to a first temperature for a first period of time and then a second temperature for a second period of time where the second temperature is less than the first temperature and the second period of time is greater than the first period of time. In some implementations, the first temperature may range from about 900°C to about 1000°C, including all values and sub-ranges in between. In some implementations, the second temperature may range from about 600°C to about 800°C, including all values and sub-ranges in between. In some implementations, the first period of time may range from about 1.5 hours to about 2.5 hours, including all values and sub-ranges in between. In some implementations, the second period of time may range from about 9 hours to about 13 hours, including all values and sub-ranges in between.

[0153] The term “about,” when used to describe the first temperature and the second temperature, is intended to cover any fluctuations in temperature during calcination. For example, “about 1000°C” may correspond to the following ranges: 990°C to 1010°C (+/- 1% variation), 992°C to 1008°C (+/- 0.8% variation), 994°C to 1006°C (+/- 0.6% variation), 996°C to 1004°C (+/- 0.4% variation), or 998°C to 1002°C (+/- 0.2% variation), including all values and sub-ranges in between. The term “about,” when used to describe the first and second periods of time, is intended to cover any variations in timing that may arise when loading or unloading the mixture. For example, “about 2 hours” may correspond to the following ranges: 1.9 hours to 2.1 hours (+/- 5% variation), 1.96 hours to 2.04 hours (+/- 2% variation), 1.98 hours to 2.02 hours (+/- 1% variation), including all values and sub-ranges in between.

[0154] Compared to conventional processes for synthesizing single-crystalline cathode materials, the period of time during which the mixture is exposed to a high temperature (e.g., the first period of time for the first temperature above) is appreciably reduced, thus reducing the loss of oxygen and/or a transition metal from the mixture. This, in turn, may reduce any undesirable segregation of transition metals and/or undesirable formation of certain crystal phases within the single-crystalline particles 222, as discussed further below. Said another way, reducing or, in some instances, mitigating the loss of oxygen and/or a transition metal may facilitate the synthesis of single-crystalline particles 222 where its constituent elements are more uniformly distributed, as discussed further below.

[0155] The process 100 may be used to synthesize single-crystalline powders of various compositions and/or stoichiometries. For example, the single-crystalline powders formed by the process 100 may include, but is not limited to, a Li-/Mn-rich layered oxide (Li1.2Mno.48Nio.i6Coo.i6O2) and a Ni-rich layered oxide (LiNio.8Coo.1Mno.1O2).

[0156] Additionally, the single-crystalline powders formed herein may exhibit several desirable morphological properties. These morphological properties may generally lead to improvements in electrochemical performance, such as capacity retention, energy density, and the like.

101571 For example, the single-crystalline particles 222 formed by the process 100 may generally have dimensions on the order of microns. In some implementations, the singlecrystalline particles 222 may have a diameter that ranges from about 1 pm to about 10 pm, including all values and sub-ranges in between. The term “about,” when used to describe the dimensions of the single-crystalline particles 222, is intended to cover any variations in particle geometry that may arise during synthesis. For example, “about 1 pm” may correspond to the following ranges: 0.95 pm to 1.05 pm (+/- 5% variation), 0.98 pm to 1.02 pm (+/- 2% variation), 0.99 pm to 1.01 pm (+/- 1% variation), 0.992 pm to 1.008 pm (+/- 0.8% variation), 0.994 pm to 1.006 pm (+/- 0.6% variation), 0.996 pm to 1.004 pm (+/- 0.4% variation), or 0.998 pm to 1.002 pm (+/- 0.2% variation), including all values and sub-ranges in between.

[0158] In another example, the single-crystalline particles 222 may exhibit appreciably less phase separation. Said another way, the constituent elements of the single-crystalline particles 222, especially the transition metal in the transition metal oxide, may be uniformly distributed within respective particles. Herein, uniformity may be defined based on the relative difference in the concentration of any one constituent element across the volume of a particle 222. For example, the concentration of a particular element, such as the transition metal, at any two locations within the particle 222 may differ by less than about 20%, about 10%, about 5%, about 2%, or about 1%.

[0159] In yet another example, the single-crystalline particles 222 may exhibit a desirable distribution of different crystal phases. In particular, the single-crystalline particles 222 may include a surface layer having a rocksalt-like phase and the bulk of the particle 222 may have a layered phase (see, for example, FIGS. 14C and 14D). In some implementations, the layer of the rocksalt-like phase may have a thickness less than or equal to about 1 nm. The term “about,” when used to describe the dimensions of the rocksalt-like phase, is intended to cover any variations thickness that may arise during synthesis. For example, “about 1 nm” may correspond to the following ranges: 0.5 nm to 1.5 nm, 0.8 nm to 1.2 nm, or 0.9 nm to 1.1 nm including all values and sub-ranges in between. These different crystalline phases may initially form during step 104, i.e., when mechanically agitating the lithium salt and the precursors. For example, the melted lithium salt and the precursors may partially react during mixing and form a layered-spinel phase.

[0160] The quality of the mixture formed after mechanical agitation (e.g., after step 104, but before step 106) and/or the single-crystalline cathode powders may also be ascertained by various measurements used to characterize the morphological properties of cathode materials. For example, X-ray diffraction (XRD) may be used to characterize the crystal structure of the mixture formed after mechanical agitation or the single-crystalline particles 222. For example, FIG. 4E shows example XRD spectra of a polycrystalline Li-/Mn-rich mixture and a singlecrystalline Li-/Mn-rich mixture after step 104, but before step 106. As shown, both the polycrystalline and single-crystalline mixtures exhibit a LiMn6 honeycomb structure, as indicated by the peak corresponding to (020)M. However, the single-crystalline mixture exhibits a weaker peak as evidenced by a larger full width at half maximum (FWHM) (e.g., FWHM equal to 0.53). Accordingly, for Li-Mn-rich mixtures having a LiMn6 honeycomb structure, the FWHM corresponding to (020)M may range from about 0.5 to about 0.6, including all values and sub-ranges in between.

|0161| The single-crystalline powder may thus comprise the single-crystalline particles 222 formed by the process 100 above. Thereafter, the single-crystalline powder may be used to form a cathode. For example, the single-crystalline powder, which acts as the active material, may be mixed with a binder and a conductive agent to form a slurry. The slurry may then be used to coat an electrode (e.g., an aluminum foil) and dried at an elevated temperature for a predetermined period of time (e.g., at 120°C for 10 hours). The binder may include, but is not limited to, poly(vinylidene fluoride) (PVDF). The conductive agent may include, but is not limited to, carbon black (e.g., Super-P). In some implementations, a cathode may include the active material (i.e., the single-crystalline powder) at a concentration greater than or equal to about 80 wt%, about 90 wt%, about 95 wt%, or about 99 wt%. The concentration of the binder may be less than or equal to about 10 wt%, about 5 wt%, or about 1 wt%. The concentration of the conductive agent may be less than or equal to about 10 wt%, about 5 wt%, or about 1 wt%. See Section 2.8 for additional examples of cathodes formed using the single-crystalline powders herein.

[0162] The term “about,” when used to describe the concentration of the active material, the binder, and/or the conductive agent, is intended to cover any variations in composition that may arise during mixing and assembly of a cathode. For example, “about 1 wt%” may correspond to the following ranges: 0.95 wt% to 1.05 wt% (+/- 5% variation), 0.98 wt% to 1.02 wt% (+/- 2% variation), 0.99 wt% to 1.01 wt% (+/- 1% variation), 0.992 wt% to 1.008 wt% (+/- 0.8% variation), 0.994 wt% to 1.006 wt% (+/- 0.6% variation), 0.996 wt% to 1.004 wt% (+/- 0.4% variation), or 0.998 wt% to 1.002 wt% (+/- 0.2% variation), including all values and sub-ranges in between.

2. Example Processes for Synthesizing Single-Crystalline Li-/Mn-rich and Ni-Rich Cathode Powders

[0163] Following below is an example demonstration of a mechanochemical process for synthesizing single-crystalline cathode powders using a planetary centrifugal mixer. This process may be used to produce single-crystalline cathodes at scale for various compositions including Li-/Mn-rich and Ni-rich compositions synthesized from home-made or commercially available co-precipitation precursors. The precursors are dry -mixed with a lithium salt mixture (e.g., LiOH-LiNCh salts near the eutectic-point composition) in a planetary centrifugal mixer. During this mixing process, the lithium salt mixture melts in-situ due to inter-particle frictional forces and thereafter reactively wet, corrode, and separate the grain boundaries of the polycrystalline precursors. This, in turn, deagglomerates the secondary particles into dispersed nanoparticles, which assists single-crystal growth in a subsequent calcination step. The well- deagglomerated nano-oxides readily react with the surrounding salts at the calcination stage and coarsen into micron-sized free-standing single-crystalline powders that flow well and exhibit superior electrochemical performance and stability by eliminating intergranular cracking during electrode calendering and battery cycling.

[0164] The example demonstration below shows facile mechanochemical activation using a planetary centrifugal mixer for tens of minutes, instead of high-energy ball milling for hours, may cause remarkable reactive wetting of precursor oxides by a lithium eutectic salt mixture. Moreover, the processes used do not require excess chemicals because LiOH-LiNCh may be fully utilized in the high-temperature lithiation process, thus serving as a transient molten salt for efficient deagglomeration. High-performance single-crystalline cathodes with flexible compositions may further be synthesized without any extra steps of washing, annealing, or sieving, thus decreasing the resource input, energy consumption, and environmental burden of the cathode production for sustainable energy infrastructure. The suppressed oxygen evolution (even up to 4.8 V charging vs. Li/Li⁺), transition-metal dissolution and voltage decay of the Li- /Mn-rich single crystals and the NCM single crystals, and the simple scalable processing, bode well for the industrialization of single-crystalline layered cathodes.

2.1 Phenomenological Deagglomeration

](I165| In this example, a planetary centrifugal mixer (THINKY AR-100, maximum capacity: 140 g) is used in accordance with the process 100 shown in FIG. 1. This mixer is widely used for mixing, dispersing, deaerating, and slurry making. Targeting Li-/Mn-rich layered cathode Li1.2Mno.48Nio.i6Coo.i6O2 (LMR) as the final product, the hydroxide precursor Mno.6Nio.2Coo.2(OH)2 is first treated at 600°C to obtain a spinel-phase oxide Mi O4 ( =Mn, Ni, and Co) and then mixed with LiOH-LiNOs (40:60 molar ratio at the eutectic composition) in the planetary centrifugal mixer at 2,000 rpm. Polypropylene containers were used without adding any grinding media.

[0166] FIGS. 2A-2D show that, during planetary centrifugal mixing, the molten lithium salts deagglomerate the secondary particles of the precursors. In particular, as the time of mixing increased, dramatic changes in the mixture morphology were observed that are easily identified visually and are well correlated with the microstructure under a scanning electron microscope (SEM). Compared with the raw chemical mixture before mixing (see FIG. 2A), the powders after 3 minutes of planetary centrifugal mixing look uniform in color and maintain a drypowder morphology (see FIG. 2B). SEM imagery shows that the oxide precursors and the lithium salts remain in their original microstructure (see FIG. 2E) and are non-uniformly distributed at a scale of a few microns (see FIGS. 7A-7C). After 6 minutes of mixing, however, the powders assembled into seed-like large particles (see FIG. 2C). Meanwhile, the secondary particle microstructure of the oxide particles is partially destroyed (see FIGS. 8A-8C) and the lithium salts are uniformly distributed in the fine oxide-particle matrix at a sub-micron scale. Upon further mixing up to 12 minutes, the powders have the appearance of a solidified liquid (see FIG. 2D) and under SEM, the primary particles of the /W3O4 precursors were found to be well dispersed in the matrix of the LiOH-LiNCh eutectic (see FIGS. 2F and 8A-8C). In other words, the secondary particles of the Mn-rich precursor were completely separated and deagglomerated. Energy dispersive X-ray (EDX) mapping shows uniform elemental distributions (O, N, and Mn) as shown in FIG. 2G. Thus, the oxide/lithium salt are uniformly distributed at a fine scale.

[0167] Along with the drastic microstructure changes, an interesting phase evolution in the composite mixture was observed using X-ray diffraction (XRD). As shown in FIG. 9, the oxide precursors remain in the same spinel phase before and after the planetary centrifugal mixing. However, the intensities of the peaks for lithium nitrate become much weaker after 12 minutes of mixing. It should be appreciated that the XRD results are not in situ but collected ex situ and at room temperature.

[0168] Together with the microstructural features, these results indicate the LiOH-LiNCh eutectic melts during the planetary centrifugal mixing process after a certain time and does not fully crystalize after cooling down naturally to room temperature. This is surprising given that the planetary centrifugal mixing reaches an “effective” temperature higher than the melting point of LiOH-LiNCh eutectic (Z_m=183⁰C) simply from the frictional forces between the mixed particles. Meanwhile, there was no visible damage to any of the polypropylene containers where the dry powders were mixed. Therefore, the “effective” high temperature is more likely to hold locally and dynamically, while the global temperature of the container remains lower. These eutectic liquids (i.e., molten salts) that are formed in situ appear to facilitate efficient and spontaneous deagglomeration.

[0169] To better understand the deagglomeration mechanism, several experiments were performed to quantify the “effective” temperature during the planetary centrifugal mixing at 2,000 rpm. By varying the salt compositions across the equilibrium LiOH-LiNCh phase diagram (see FIG. 2H), it was confirmed by the visual morphology and SEM (see FIG. 10) that LiOH-LiNCh mixtures with mole ratios of 0: 100 (Zm=255°C), 35:65 (Zm=202°C), 50:50 (Zm=210°C), and 100:0 (Z_m=462⁰C) did not melt or deagglomerate the oxide precursors after 12 minutes of mixing at 2,000 rpm. However, the mixtures with mole ratios of 40:60 (Zm=183°C) and 45:55 (Z_m=191⁰C) were observed to melt and deagglomerate the oxide precursors after 12 minutes of mixing at 2,000 rpm. [0170| These control experiments narrow down the “effective” temperature to a range of 191- 202°C, which offers insight to design and utilize similar processes for a variety of applications. For example, other low-melting-point salt systems may be chosen, and the “effective” temperature may be raised by adding some zirconia balls as the inertial energy media. Lastly, as the raw chemical LiOH contains crystalline water and LiNCh is sensitive to moisture, water may also contribute to the melting and deagglomeration event, which in effect shifts the solid/liquid equilibrium for a fixed lithium salt composition.

2.2 Mechanochemistry at the Nanoscale

[0171] For an atomistic understanding of the facile deagglomeration process, a transmission electron microscopy (TEM) study was conducted on the /W3O4 precursors before and after planetary centrifugal mixing. The cross-sectional image shown in FIG. 3A shows a polycrystalline morphology of the secondary particles with densely packed/bonded primary particles before the mixing treatment. FIG. 3B shows high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) imagery of the surface and lattice of the A/3O4 precursors, which have the same spinel structure. The interlayer distance between neighboring lattice planes is measured to be 0.485 nm corresponding to the (101) lattice fringe of AACk-type spinel oxide. In comparison, the cross-sectional image of FIG. 3C shows that, after 12 minutes of mixing, the primary particles are nicely separated with the original grain boundaries corroded by and filled with the molten lithium salts, which have weak TEM contrasts yet still bond the oxide particles together in the lifted-out TEM sample. Additional examples are shown in FIGS. 11A-11C, which show each primary particle of Mn-rich precursor is distinctly separated by molten Li-salts. The HAADF-STEM image of FIG. 3D shows a disordered rocksalt phase Lii-ALO with the lattice fringe changed to 0.241 nm. The disordered rocksalt phase occurs at the surface of the thus-treated oxide particles. The bulk spinel phase is also confirmed. Using a density of 1.7 g cm ³ for the eutectic lithium salt and 4.59 g cm ³ for the spinel oxide, it is estimated the volume ratio of the eutectic to the oxide is about 3: 1, which is sufficient for wetting and complete separation of the primary particles of the oxide.

[0172] It is further confirmed that the surface phase transformation is general by multiple measurements at different particles. For example, FIG. 3E shows a high-resolution TEM image of the surface disordered rocksalt phase with Fm-3m symmetry after fast-Fourier transform (FFT) and the bulk spinel phase with Fd-3m symmetry after FFT. FIG. 3F shows an atomic- resolution STEM image where different atomic packing of the transition metal elements are observed, which are assigned to disordered rocksalt phase at the surface and spinel phase in the bulk. FIGS. 12A and 12B show an electron energy loss spectroscopy (EELS) line scan with varying Li content and chemical signals of Mn and O from the bulk to the surface. Therefore, the molten lithium salts not only wet the surface and separate the grain boundaries of the oxide precursor, but they also react with the oxide precursor along its atomically thin surface as well as up to a few nanometers of the bulk lattice. It should be appreciated that at greater lattice depths, the bulk lattice is not lithiated as shown by TEM and XRD. Such a remarkable mechanochemical reactive wetting at the nanoscale provides a unique driving force for deagglomeration and phase transformation. On the kinetic side, the lithiation of the layered cathode precursors and the phase transformation to the disordered rocksalt phase have previously been shown to start at 200-250°C. So, the ~200°C “effective” temperature estimated above should be enough to enable the nanoscale phase transformation.

2.3 Structure of Single-Crystalline LMR

[0173] Planetary centrifugal mixing facilitates the synthesis of high-performance singlecrystalline cathodes. To qualify the performance of the single-crystalline cathodes formed herein, a reference sample is first created. The reference sample is created by calcinating AAO4 precursors hand-mixed with the lithium salts (LiOH-LiNCh at the eutectic composition, without the planetary centrifugal mixing treatment) at 950°C for 12 hours. Despite the extended calcination time, only polycrystalline LMR (PC-LMR) was formed with fine primary particles (-100-200 nm) as shown in FIG. 4A. FIG. 4B provides TEM-EDS mapping under high magnification, which shows Ni segregation and Mn and Co depletion at the surface of PC- LMR. FIGS. 13A-13C show more examples of Ni segregation in PC-LMR. The segregation behavior correlates with a rocksalt-like phase (-2-4 nm) formed at the surface of PC-LMR. FIGS. 14A and 14B further show PC-LMR has much thicker rock-salt structure along the surface than that of SC-LMR.

[0174] In comparison, the deagglomerated A/3O4 precursors with uniformly infiltrated lithium salts allow the production of single-crystalline LMR (SC-LMR) cathode powders. The planetary centrifugal mixed powders formed using LiOH-LiNCh eutectic were calcined at 950°C for 2 hours and 760°C for 10 hours to obtain SC-LMR with a larger particle size (-1 pm) and without any secondary particle morphology as shown in FIG. 4C. Detailed comparisons of the chemical compositions, Brunauer-Emmett-Teller surface areas, and particle size distributions measured by the particle-size analyzer are also provided in FIGS. 35 and 36. The SC-LMR powders flow well and may be readily used in slurry preparation without grinding or sieving. FIGS. 4D and 13D further show TEM-EDS mapping results where Ni, Co, and Mn are shown to have uniform distributions without surface enrichment/depletion in SC- LMR. The rocksalt-like surface phase is also much thinner in SC-LMR (~1 nm) as shown in FIGS. 14C and 14D, indicating a high quality of the final lithiation reaction step.

[0175] The faster particle growth kinetics after the planetary centrifugal mixing highlights the role of the lithium salt distribution and the packing of the A/3O4 oxide precursor particles. The shorter calcination time at 950°C appreciably reduces oxygen loss and Ni reduction, thus reducing or, in some instances, mitigating the transition-metal segregation and surface phase transformation. Surface migration during Ostwald ripening process also refreshes the lattice compositions and homogenizes the transition-metal distributions, further reducing or, in some instances, eliminating undesirable segregation and phase transformation at the surface. This behavior also profoundly affects the phase structure and cation ordering in the lattice. FIG. 4E, which compares the XRD spectra of PC-LMR and SC-LMR, shows SC-LMR has a wider full- width-at-half-maximum (FWHM) of the superlattice peaks at 20°-25° compared to PC-LMR. This indicates less Li/Mn ordering in the lithium layer, e.g., less LiMne honeycomb ordering in Li2MnOs as shown in the Rietveld analysis of FIGS. 15A, 15B, and 37. This is further supported by atomic-resolution STEM images measured along the [100] monoclinic direction. As shown in FIGS. 4F and 4G, PC-LMR shows clearer Li/Mn ordering than SC-LMR, which may be inferred from the clear dumbbell-like bright spots in FIG. 4F. FIGS. 16A and 16B show the same trend is observed in atomic-resolution STEM images collected over a large area. These surface and lattice structural features affect the electrochemical performance, especially the cycling stability.

2.4 Electrochemistry of Single-Crystalline LMR

[0176] In this demonstration, the electrochemical performance of PC-LMR and SC-LMR were then evaluated as a lithium-ion battery (LIB) cathode. During the first cycle (also referred to as the “formation cycle”), the cathode is charged and discharged at 0.1 C (1 C defined as 250 mA g ¹ ) between 2.0 V and 4.8 V (vs. Li/Li⁺). A cathode formed of PC-LMR was measured to have a discharge capacity of 254 mAh g ¹ and a first-cycle Coulombic efficiency (CE) of 76.2%. In comparison, a cathode formed from SC-LMR had a slightly higher discharge capacity of 259 mAh g ¹ and a higher first-cycle CE of 82.4% (see FIG. 17). After cycling at 0.3 C for 100 cycles, FIGS. 18A-18C show SC-LMR has more stable charge-discharge curves than PC-LMR (see FIGS. 5 A and 5B), better capacity retention (90.6% for SC-LMR vs. 82.1% for PC-LMR), slower voltage decay (2.32 mV per cycle for SC-LMR vs. 5.36 mV per cycle for PC-LMR), and better retention of the discharge energy density (84.9% for SC-LMR vs. 69.9% for PC- LMR at the 100^th cycle). FIGS. 18A-18C show the average values and standard deviations of the cycling data for 3 cells.

[0177] Compared with previous studies on SC-LMR, the samples synthesized according to the methods disclosed herein show a larger grain size, more uniform size distribution, compelling electrochemical performance (see FIG. 38), and less degradation in terms of gassing and transition metal dissolution, as discussed further below. To gain a better understanding of the improved cycling stability, galvanostatic intermittent titration technique (GITT) measurements were performed with a titration current of 0.3 C after the 5^th and 100^th cycle, the results of which are shown in FIG. 5C.

[0178] For these measurements, the data in the voltage curves obtained after each relaxation step (see solid curves in FIG. 5C) were of particular interest because this portion of the voltage curve represents quasi-equilibrium conditions and thus reflects the bulk redox chemistry. As shown, the shape of the voltage curves was better maintained in SC-LMR compared to PC- LMR, indicating less structural changes in the bulk. Indeed, the TEM images of FIGS. 19A and 19B show extensive cavities formed in the lattice of cycled PC-LMR, accompanied by bulk phase transformations from layered to spinel/rocksalt phases. These structural changes may be due to enhanced oxygen ion mobility in the lattice and bulk oxygen loss. In comparison, SC-LMR shows less structural changes in the lattice. Additional GITT analysis (see FIGS. 20 and 21A-21D) further shows the capacity decay in PC-LMR cathodes is mostly caused by changes in the bulk redox chemistry rather than impedance growth. In FIGS. 21A-12D, the GITT measurements on PC-LMR and SC-LMR were obtained after certain cycles during 0.3C cycling (between 2.0 and 4.8V at 25°C) as shown in FIG. 5C.

[0179] Without intergranular cracking that exposes extensive unprotected surfaces to the organic liquid electrolyte, the single-crystalline morphology should offer superior stability and less cathode-electrolyte side reactions. To show this, the gas evolution during the first charge to 4.8 V (vs. Li/Li⁺) was first measured by in situ differential electrochemical mass spectrometry (DEMS). As shown in FIG. 5D, O2 and CO2, which are present due to electrolyte decomposition when freed oxygen from the cathode is encountered, start to evolve in PC-LMR when charged to ~4.4 V (vs. Li/Li⁺). In contrast, the evolution of O2 and CCh is suppressed up to 4.8 V (vs. Li/Li⁺) in SC-LMR. The mitigated gassing issue is a synergistic effect of the low specific surface area, lower-misfit-strain single-crystal lattice that does not crack, and reductions in bulk oxygen loss. FIGS. 5E and 39 show less transition metal (Mn, Ni, and Co) dissolution was found in the electrolytes of the charged SC-LMR cells than PC-LMR cells stored at elevated temperature (60°C) for 2 weeks, which corroborates the DEMS data. Therefore, the coupled side reactions of gassing (oxygen loss), and transition metal reduction and dissolution into electrolyte are indeed suppressed in SC-LMR, thus greatly improving the electrochemical cycling stability.

2.5 Generalization to a Single-Crystalline Ni-Rich Cathode

[01801 Inspired by the single crystalline morphology of the Li-/Mn-rich cathode, the generality of the methods disclosed herein are examined for their suitability in synthesizing other singlecrystalline cathodes formed from other material systems. As another example demonstration, the method is used to synthesize a Ni-rich layered cathode composition, LiNio.8Coo.1Mno.1O2 (NCM), which is of great industrial importance.

| (11811 FIGS. 22A-22C show that starting from the co-precipitation precursors (see FIG. 23 A), a similar visual morphology, eutectic salt melting, microstructural change, and deagglomeration outcome is observed. FIG. 6A shows single-crystalline NCM (SC-NCM) with ~4 pm size is successfully synthesized by calcinating the planetary centrifugal mixed powders (e.g., hydroxide precursors plus LiOH-LiNOs eutectic) using a two-step heat treatment process where the powders were heated to a temperature of 920 °C for 2 hours and then at 760 °C for 10 hours in flowing oxygen. In contrast, FIGS. 6B and 23B show when an identical lithium salt mixture is mixed by hand instead of planetary centrifugal mixing, the primary particles of the Ni-rich cathode only coarsened marginally to form polycrystalline NCM (PC-NCM) with a spherical secondary particle morphology. The hand-mixed powders were heated to a temperature of 800°C for 12 hours in flowing oxygen. Further details about the chemical and physical properties are provided in FIGS. 40-42.

[0182] FIGS. 24A and 24B show the size of the primary particles for PC-NCM may be increased slightly by heating the powders to higher temperatures (e.g., 940°C). However, the secondary particle morphology is still present in these samples. This is in stark contrast to the single-crystalline morphology of planetary centrifugal mixed samples treated at similar temperatures (see FIGS. 24C-24F). Residual porosities were also observed in some PC-NCM particles (see inset of FIG. 6C (top)).

[0183] For SC-NCM, the intergranular cracking modes are appreciably or, in some instances, entirely eliminated as shown in FIG. 6C (bottom). This allows SC-NCM to be subjected to harsher calendering conditions leading to a higher electrode density of ~3.5 g cm ³. In contrast, the home-synthesized PC-NCM samples could only attain an electrode density of ~3.1 g cm ³ without suffering performance degradation (see FIGS. 25 A and 25B). Despite being subjected to more severe calendering, FIGS. 6G, 26, 27, and 28 show SC-NCM is still capable of delivering better capacity retention (89.7% after 200 cycles at 0.5 C/0.5 C) with less voltage loss than PC-NCM (81.0%). It should be appreciated that in FIG. 28, the average values and standard deviations of the cycling data for 3 cells are shown. Furthermore, FIGS. 43 A and 43B show the SC-NCM samples synthesized in this example demonstration provide compelling electrochemical performance compared to previous demonstrations of Ni-rich cathodes with a single-crystalline morphology.

10184] For PC-NCM, FIGS. 6D (top), 6E (top), 29 A, and 29B show extensive intergranular cracking was observed in the electrode after cycling. The formation of these cracks leads to electronic insulation of the active cathode particles and exposes unprotected surfaces prone to various forms of side reactions (e.g., a thick cation-densified rocksalt-like surface phase, as shown in FIG. 6F (top)). Substantial lattice mismatch with a surface reconstruction layer may induce bulk fatigue of the Ni-rich layered cathode. Thus, the combination of a thicker surface reconstruction layer and a larger surface area in PC-NCM is likely to induce rapid capacity decay, as evidenced by a faster impedance growth (see electrochemical impedance spectra, EIS, in FIGS. 30A and 30B). In comparison, FIGS. 6D-6F (bottom), 29C, and 29D show the microstructure of SC-NCM remains stable, thus preserving the integrity of the original structure even after cycling and suppressing side reactions. This is due, in part, to the thinner rocksalt-like surface phase (see FIG. 6F (bottom)), a decrease in O2 and CO2 evolution (see FIGS. 31A and 3 IB), and a decrease in transition metal dissolution (see FIG. 32). Therefore, the facile deagglomeration method disclosed herein is equally applicable to the synthesis of high-performance Ni-rich single crystals.

2.6 Generalization to Recycling and Upcycling of Used Battery Cathodes

(0185] The technique of planetary centrifugal mixing and deagglomeration may be used to recycle poor-performance waste cathodes from degraded lithium-ion batteries to create high- performance cathodes that have comparable or higher capacity/energy density than commercially available cathodes with similar chemical compositions. The cathode material obtained from waste cathodes is also referred to as “black mass.”

(0186] For example, polycrystalline Ni-rich cathode LiNio.8Coo.1Mno.1O2 used in commercial lithium-ion batteries typically experience capacity decay, loss of lithium, and irreversible phase transformations from a layered phase to rocksalt/spinel-like phases. By applying planetary centrifugal mixing and deagglomeration, the capacity of waste LiNio.8Coo.1Mno.1O2 in a degraded state was recovered, thus exhibiting a high capacity in the as-synthesis state, which demonstrates direct recycling is possible with the methods disclosed herein. The amount of lithium salts used in this recycling process depends on the chemical state of the waste cathodes. Generally, the amount of lithium salts is less than the amount used to synthesize new cathodes from Li-free transition metal oxide/hydroxide/carbonate precursors. Depending on the application, the morphology of the recycled LiNio.8Coo.1Mno.1O2 may be turned into a single crystalline morphology with grains having a diameter on the order of a few microns or into the original polycrystalline morphology. Waste single-crystalline cathodes may similarly be recycled to recover their original electrochemical performance.

[0187] In another example, waste Ni-rich cathode LiNio.6Coo.2Mno.2O2 in degraded lithium-ion batteries was treated using planetary centrifugal mixing and deagglomeration techniques disclosed herein followed by a heat treatment process similar to the methodology described above. In addition to lithium salts, Ni salts, such as nickel nitrate, may be added before or during the planetary centrifugal mixing and deagglomeration process. Depending on the ratio of the lithium salts to the Ni salts, the end product may have a chemical composition of LiNio.6+xCoo.2-x/2Mno.2-x/202, a high capacity and energy density, and good cycling stability. Because Ni-richer LiNio.6+xCoo.2-x/2Mno.2-x/202 has higher capacity and energy density than LiNio.6Coo.2Mno.2O2 at the same voltage range, this process is called upcycling. The planetary centrifugal mixing and deagglomeration techniques disclosed herein may upcycle waste cathodes into higher-energy-density cathodes with a tunable chemistry. In particular, the amounts of Co, Mn, and Al may be similarly adjusted by adding corresponding salts (e.g., a Co salt, a Mn salt, an Al salt) before or during the planetary centrifugal mixing process.

[0188] In yet another example, FIGS. 34A and 34B show SEM images of waste LiNio.5Coo.2Mno.3O2 (NCM523) powder. By applying the deagglomeration and calcination processes disclosed above, the NCM523 powder may be converted to upcycled Ni80-NCM powder with a single-crystalline morphology, as shown in FIGS. 34C and 34D. FIGS. 33 A and 33B further show the degraded NCM523 secondary particles were completely separated and deagglomerated by the melted precursors (see further details in Section 2.7).

2.7 Material Synthesis

[0189] Hydroxide Nio.8Mno.iCoo.2(OH)2 was synthesized by a co-precipitation method using a continuous stirred-tank reactor (CSTR). 2 M of metal solution (molar ratio Mn:Ni:Co=3: l : l) and 4 M of NaOH solution were prepared with the stoichiometric amounts of MnSCh 5H2O (99.0%, JUNSEI), NiSCU 6H2O (99.0%, SAMCHUN), CoSO₄ 7H₂O (98.0%, SAMCHUN) and NaOH H2O (99.0%, SAMCHUN). The reagent solutions were pumped and stirred in the CSTR at 50°C for 10 hours. The precipitates (Mno.6Nio.2Coo.2(OH)2) were collected, washed, dried at 120°C overnight and calcined at 600°C for 5 hours to obtain spinel -type A/3O4 precursors.

[0190] For SC-LMR synthesis, a mixture of the A/3O4 precursors and lithium salt mixture with a molar ratio of 1 : 1.52 (transition metal :Li), were mixed using a planetary centrifugal mixer (AR- 100, THINKY). The lithium salt mixture comprised LiOH H2O (99.0%, Sigma Aldrich) and LiNCh (99.0%, Sigma Aldrich). The planetary-centrifugally mixed powders were calcined at 950°C for 2 hours and then at 760°C for 10 hours in air to obtain SC-LMR. For PC-LMR synthesis, the A/3O4 precursors were hand-mixed with a lithium salt mixture (LiOH H2O and LiNCh) at the eutectic composition with a molar ratio of 1 : 1.52 (transition metal :Li) and annealed at 950°C for 12 hours in air.

[0191] Hydroxide Mno.8Nio.iCoo.i(OH)2 was synthesized by a co-precipitation method. An aqueous solution containing 3.2 M Ni²⁺, 0.4 M Co²⁺, and 0.4 M Mn²⁺ was prepared by dissolving NiSO₄ 6H2O (99.0%, SAMCHUN), CoSO₄ 7H₂O (98.0%, SAMCHUN) and MnSO4 AH2O (99.0%, JUNSEI), with a molar ratio of 8: 1 : 1. The solution was continuously fed into a stirred tank reactor (4 L capacity) with 4.0 M sodium hydroxide (NaOH) and 0.4 M ammonia (NH4OH) solutions under feeding rates of 300, 300, and 40 mL h respectively. A reaction temperature of 50°C was stably maintained by an external water circulator for 20 hours, after which the precipitates were collected, washed, and dried at 110°C for overnight.

[01 2] SC-NCM was synthesized by planetary centrifugally mixing the hydroxide precursors (composition treated as Nio.8Coo.iMno.i(OH)2) with a lithium salt mixture (LiOH H2O and LiNCh) at the eutectic composition with a molar ratio of 1 : 1.025 (transition metal:Li), followed by calcination at 920 °C for 2 hours and then at 760 °C for 10 hours in flowing oxygen. For PC-NCM synthesis, the hydroxide precursors were hand mixed with a lithium salt mixture (LiOH H2O and LiNCh) at the eutectic composition with a molar ratio of 1 : 1.025 (transition metal :Li) followed by calcination at 800°C for 12 hours in flowing oxygen. The venting line was tightly connected outside at the opposite side of the tube furnace to exhaust the gas naturally. Using this venting line, the gas pressure of the furnace was maintained, and gas products (e.g., toxic NO2) were properly removed.

[0193] To upcycle degraded NCM523 (Li1-xNio.5Coo.2Mno.3O2) into Ni80-NCM (Li1.0Ni0.807Co0.077Mn0.n6O2), O.lmol of the degraded NCM523 cathode powder (~10 g, a mixture of NCM523, conductive agent, and polymer binder) was mixed with 0.07 mol of LiOH, 0.10 mol of LiNOi and 0.16 mol of Ni(NOs)2 6H2O using planetary centrifugal mixing for 15 minutes. The lithium salt mixture, which included both LiOH and LiNOs, was in 2-10% excess to facilitate complete re-lithiation. During the planetary centrifugal mixing process, Li- salts and nickel nitrate precursors were melted, and the degraded NCM523 secondary particles were completely separated and deagglomerated by melted precursors (see FIGS. 33 A and 33B). The mixture was transferred into a crucible. The material mixture was heated to 900 °C for 2 hours and then at 760 °C for 10 hours under blowing high purity oxygen. The obtained powders were recovered from the crucible and ground in an agate mortar. The Ni80-NCM powder was passed through a 400-mesh sieve and then stored in a humidity-controlled storage container. The Ni80-NCM exhibits a single-crystalline morphology with ~3pm particle size (see FIGS. 34C and 34D).

2.8 Electrochemical Measurements

{0I94| For LMR cathodes, the composite cathodes were prepared by mixing 80 wt% active material, 10 wt% Super-P (as the conductive agent), and 10 wt% poly(vinylidene fluoride) (PVDF, as the binder) in N-methyl-2-pyrrolidone (NMP). The NCM electrodes were prepared by mixing 90 wt% active material, 5 wt% Super-P, and 5 wt% PVDF in NMP. The slurry obtained was coated onto aluminum foil and dried at 120°C for 10 hours. All cathodes were controlled with a loading level of 10.0±0.5 mg cm’². The prepared electrodes were assembled using a 2032R coin type cell in an Ar-filled glove box, with cathodes (diameter 12 mm), lithium metal foils (diameter 14 mm) as the counter and reference electrode, respectively, and 1.15 M LiPFe in ethylene carbonate/ethyl methyl carb onate/di ethyl carbonate with 5wt% fluoroethylene carbonate additive (EC:EMC:DEC = 3/6/1 vol% with 5% FEC; Enchem) as the electrolyte.

|0195] For LMR electrodes, the cells were evaluated with constant current-constant voltage mode between 2.0 and 4.8 V (vs. Li/Li⁺) at 25°C. The first charge-discharge cycle was conducted at 0.1 C (for LMR 1.0 C is defined as 250 mA g '). After 3 times of pre-cycling at 0.2 C, the cells were charged/ discharged at 0.3 C for 100 cycles to evaluate the cycling stability. GITT measurements were conducted after 5^th and 100^th cycles of the 0.3 C cycling, between 2.0 and 4.8 V (vs. Li/Li⁺) with a titration step at 0.3 C of 10 min and a relaxation step of 2 h. The ohmic loss (voltage drop during the transition from the titration step to the relaxation step) and non-ohmic loss (voltage drop during the long-time relaxation step) were collected and plotted at each depth-of-discharge.

|0196] For NCM electrodes, the cells were evaluated with constant current-constant voltage mode between 2.8 and 4.3 V (vs. Li/Li⁺) at 25°C. The first charge-discharge cycle (as the formation step) was conducted at 0.1 C (for NCM, 1.0 C is defined as 200 mA g '). After the first cycle, the cells were charged and discharged at 0.5 C/0.5 C for 200 cycles. After specific cycles, EIS measurements were conducted on cells charged to 4.3 V (vs. Li/Li⁺) from 1 MHz to 10 MHz and with AC voltage amplitude of 10 mV using VMP-300 potentiostat (Bio-logic). 101971 All electrochemical tests (except for EIS) were carried out using a CT2001A battery cycler (Landt Instrument).

2.9 Characterization

(01 8 J The chemical compositions of the cathode material and the electrolyte were determined by an inductively coupled plasma optical emission spectrometer (ICP-OES, Varian 700-ES, Varian, Inc.). The specific surface area was measured by a BET analyzer (Macsorb model- 1208, Mountech). Phases were characterized by XRD using a parallel beam XRD instrument (Smartlab, Rigaku, with Cu Ka with a wavelength of 1.542 A). The crystallographic analysis was conducted by using PDXL analysis software (Rigaku). Phase identification was performed using PDXL software package, including crystallography open database (COD). Crosssections of the cathodes were cut by ion milling (IM -40000, Hitachi) and characterized under scanning electron microscopy (SEM, Merlin, Zeiss) equipped with energy dispersive X-ray spectroscopy detector (EDS, XFlash® 6130, Bruker). Morphologies and chemical compositions of the prepared cathode powders and electrodes were also characterized by SEM and EDS.

[0199| For TEM analysis, samples were prepared by a dual-beam focused ion beam (FIB, Helios 450HP, FEI) and thinned by an Ar-ion milling system (Model 1040 Nanomill, Fischione). High-resolution TEM (HR- TEM, ARM300, JEOL) was conducted under 150 and 300 keV to collect scanning transmission electron microscopy (STEM) images for atomic and structural analysis. Electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDX) were conducted by HR- TEM (Aztec, Oxford). For transition-metal dissolution analysis, coin cells with as-prepared cathode and Li metal foil (anode) were first constructed and charged to cut-off voltage (4.8 V for LMR and 4.3 V for NCM). The charged electrodes were disassembled and soaked in a clean electrolyte (3:7 by volume of EC:EMC) in Ar-filled glove box and transferred to an oven at 60°C. The organic solution was stored at 60°C, collected after 1 and 2 weeks and then under HNO3 acid digestion following an established method. The digested solution was diluted to 20 ml for the ICP measurement. The real-time gas evolution was monitored by in situ DEMS analysis under galvanostatic charge-discharge of the cell. For LMR electrodes, in situ DEMS was conducted on hole-perforated 2032-type coin cells between 2.0 and 4.8 V (vs. Li/Li⁺; 2.8-4.3 V for NCM electrodes). 3. Conclusion

[02G0| All parameters, dimensions, materials, and configurations described herein are meant to be exemplary and the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. It is to be understood that the foregoing embodiments are presented primarily by way of example and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein.

[0201] In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of respective elements of the exemplary implementations without departing from the scope of the present disclosure. The use of a numerical range does not preclude equivalents that fall outside the range that fulfill the same function, in the same way, to produce the same result.

[0202] Also, various inventive concepts may be embodied as one or more methods, of which at least one example has been provided. The acts performed as part of the method may in some instances be ordered in different ways. Accordingly, in some inventive implementations, respective acts of a given method may be performed in an order different than specifically illustrated, which may include performing some acts simultaneously (even if such acts are shown as sequential acts in illustrative embodiments).

[0203 J All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.

[0204] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.

[0205J The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

[0206] The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, z.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e. , “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0207| As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0208] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc. [0209} In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, z.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

1. A method for forming a single-crystalline cathode powder comprising a plurality of single-crystalline particles, the method comprising:

A) providing, to a mechanical agitator, a mixture comprising: a precursor comprising a plurality of secondary particles, each secondary particle of the plurality of secondary particles comprising a plurality of primary particles directly coupled together; and a lithium salt having a eutectic composition;

B) mixing, by the mechanical agitator, the mixture such that the lithium salt melts and forms a molten lithium salt, the molten lithium salt deagglomerating the plurality of secondary particles such that respective primary particles of the pluralities of primary particles are substantially separate from each other; and

C) calcinating the mixture to form the plurality of single-crystalline particles of the single-crystalline cathode powder from the pluralities of primary particles.

2. The method of claim 1, wherein the precursor does not comprise lithium.

3. The method of claim 1, wherein the precursor does not comprise fluorine and carbon black.

4. The method of claim 1, wherein the precursor comprises black mass.

5. The method of claim 1, wherein the precursor comprises lithium in an amount less than or equal to about 0.9 mol.

6. The method of claim 1, wherein the precursor further comprises at least one of fluorine or carbon black.

7. The method of claim 1, wherein the plurality of primary particles comprises at least one of spinel-type M3O4, Mno.6Nio.2Coo.2(OH)2, Nio.8Mno.iCoo.i(OH)2, Li1-xNio.8Coo.1Mno.1O2, Li1-xNio.6Coo.2Mno.2O2, or Li1-xNio.5Coo.2Mno.3O2.

8. The method of claim 1, wherein: the lithium salt comprises LiOH and LiNOs; and a molar ratio of LiOH and LiNOi ranges between about 40:60 to about 45:55.

9. The method of claim 1, wherein the lithium salt has a melting point ranging from about 180°C to about 200°C.

10. The method of claim 1, wherein the precursor further comprises at least one of a cobalt (Co) salt, a manganese (Mn) salt, or an aluminum (Al) salt.

11. The method of claim 1, wherein the plurality of single-crystalline particles comprises at least one of Li1.2Mno.48Nio.i6Coo.i6O2, or LiNio.8Coo.1Mno.1O2.

12. The method of claim 1, wherein the mechanical agitator is a planetary centrifugal mixer.

13. The method of claim 1, further comprising: forming a cathode from the single-crystalline cathode powder, wherein the cathode is formed without: grinding the single-crystalline cathode powder; washing the single-crystalline cathode powder; annealing the single-crystalline cathode powder; or sieving the single-crystalline cathode powder.

14. A method for forming a single-crystalline cathode powder comprising a plurality of single-crystalline particles, the method comprising:

A) providing, to a mechanical agitator, a mixture comprising: a precursor comprising black mass; and a lithium salt having a eutectic composition;

B) mixing, by the mechanical agitator, the mixture such that the lithium salt melts and forms a molten lithium salt, the molten lithium salt deagglomerating the precursor; and

C) calcinating the mixture to form the plurality of single-crystalline particles of the single-crystalline cathode powder from the pluralities of primary particles.

15. The method of claim 14, wherein the black mass comprises at least one of Lii- xNio.8Coo.1Mno.1O2, Li1-xNio.6Coo.2Mno.2O2, or Li1-xNio.5Coo.2Mno.3O2.

16. The method of claim 14, wherein: the lithium salt comprises LiOH and LiNCh; and a molar ratio of LiOH and LiNOi ranges between about 40:60 to about 45:55.

17. The method of claim 14, wherein the plurality of single-crystalline particles has an average diameter greater than or equal to 1 pm.

18. A single-crystalline cathode powder, comprising: a plurality of single-crystalline particles comprising a transition metal oxide, wherein: the plurality of single-crystalline particles has an average diameter greater than or equal to 1 pm; and at least a transition metal in the transition metal oxide is uniformly distributed within each single-crystalline particle of the plurality of single-crystalline particles.

19. The powder of claim 18, wherein the transition metal oxide is one of A) a lithium -rich and a manganese-rich layered transition metal oxide or B) a nickel-rich layered transition metal oxide.

20. The powder of claim 18, wherein the transition metal oxide comprises at least one of Li1.2Mno.48Nio.i6Coo.i6O2 or LiNio.8Coo.1Mno.1O2.