Cost-effective synthesis of oxide materials for lithium-ion batteries

Abstract

A method for synthesizing a single-crystalline Ni-rich cathode material is disclosed. The Ni-rich cathode material has the formula LiNixMn y M z Co 1-x-y-z O2, where M represents one or more dopant metals, and x≧0.6, 0.01≦y<0.2, 0≦z≦0.05, and x+y+z≦1.0. These methods are cost-effective and include methods for solid-state synthesis, molten salt synthesis, and flash sintering synthesis.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of back-to-filing dates of U.S. Provisional Application No. 63 / 028,146, filed May 21, 2020, and U.S. Provisional Application No. 63 / 020,621, filed May 6, 2020, each of which is incorporated herein by reference in its entirety.

[0002] Government support approval This invention was made with government support under Contract DE-AC05-76RL01830 awarded by the U.S. Department of Energy. The government has certain rights in this invention. [Background technology]

[0003] Field Methods for synthesizing crystalline oxide materials are disclosed, as well as cathodes including these crystalline oxide materials and lithium ion batteries including these cathodes. Summary of the Invention [Means for solving the problem]

[0004] overview Embodiments of methods for synthesizing crystalline oxide materials are disclosed. Cathodes including these crystalline oxide materials, and lithium ion batteries including these cathodes are also disclosed.

[0005] In some embodiments, the solid-state method comprises: S1 By NixMn y M z Co 1-x-y-zheating a solid hydroxide precursor comprising (OH)2 to convert the solid hydroxide precursor to a solid oxide precursor, wherein M represents one or more dopant metals, and x≧0.6, 0.01≦y<0.2, 0≦z≦0.05, and x+y+z≦1.0; combining the solid oxide precursor with a molar excess of a lithium compound; heating the solid oxide precursor and the lithium compound to a temperature T S2 for an effective period of time t2 to produce a first product; cooling the first product to ambient temperature; reducing an average particle size of the first product to between 0.1 μm and 10 μm; and heating the first product having the reduced average particle size to a temperature T S3 for an effective period of time t3 to produce a second product; cooling the second product to ambient temperature; reducing the average particle size of the second product to between 0.1 μm and 10 μm; and cooling the second product having the reduced average particle size to a temperature T S4 for a period of time t4 to form a compound of formula LiNixMn y M z Co 1-x-y-z forming a monocrystalline lithium nickel manganese cobalt oxide with O2;

[0006] In some embodiments, the molten state process comprises: M1 By NixMn y M z Co 1-x-y-z heating a solid hydroxide precursor comprising (OH)2 to convert the solid hydroxide precursor to a solid oxide precursor, wherein M represents one or more dopant metals, and x≧0.6, 0.01≦y<0.2, 0≦z≦0.05, and x+y+z≦1.0; combining the solid oxide precursor with a molar excess of a lithium compound and a sintering agent to form a mixture; combining the solid oxide precursor with a molar excess of a lithium compound and a sintering agent to form a mixture; heating the mixture in an oxygen-containing atmosphere at a temperature T M2 for a period t2; M3 >Temperature T M2At temperature T M3 The mixture is heated to a temperature T M3 for a period of time t3 to form a first product and a sintering agent; separating the sintering agent from the first product; drying the first product; and heating the first product in an oxygen-containing atmosphere at a temperature T M4 for a period of time t4 to form a compound of formula LiNixMn y M z Co 1-x-y-z forming a monocrystalline lithium nickel manganese cobalt oxide with O2 to form a monocrystalline lithium nickel manganese cobalt oxide.

[0007] In some embodiments, the flash sintering process comprises: NixMn y M z Co 1-x-y-z combining a solid hydroxide precursor comprising (OH) with a molar excess of a lithium compound to form a hydroxide mixture, wherein M represents one or more dopant metals, and x≧0.6, 0.01≦y<0.2, 0≦z≦0.05, and x+y+z≦1.0; heating the hydroxide mixture in an oxygen-containing atmosphere at a temperature T F1 for a period of time t1 to form an oxide mixture comprising oxides of nickel, manganese, cobalt, lithium, and, if present, one or more dopant metals, or combinations thereof; increasing the temperature at a rate of ≥ 10°C / min to a temperature T F2 and subjecting the oxide mixture to an oxygen-containing atmosphere at a temperature T F2 for a period of time t2 to form a compound of formula LiNixMn y M z Co 1-x-y-z forming a monocrystalline lithium nickel manganese cobalt oxide with O2 to form a monocrystalline lithium nickel manganese cobalt oxide.

[0008] In any of the foregoing embodiments, the solid hydroxide precursor is prepared by: preparing a 1.5-2.5 M solution of metal salts in water, the metal salts including a nickel(II) salt, a manganese(II) salt, a cobalt(II) salt, and optionally one or more dopant metal salts, wherein the mole fraction x of the nickel(II) salt in the solution is ≧0.6, the mole fraction y of the manganese(II) salt is 0.01≦y<0.2, the mole fraction z of the one or more dopant metal salts is 0≦z≦0.05, and the mole fraction of the cobalt(II) salt is 1−xyz, where x+y+z≦1.0. The solid hydroxide precursor may be prepared by combining a solution containing metal salts in water with aqueous NH3 and aqueous NaOH or KOH to provide a combined solution having a pH of 10.5-12 and a combined metal salt concentration of 0.1 M to 3 M; aging the combined solution for 5 to 48 hours at a temperature of 25° C. to 80° C. to co-precipitate nickel, manganese, and cobalt hydroxides to provide a solid hydroxide precursor; and drying the solid hydroxide precursor, wherein the solid hydroxide precursor comprises particles having an average particle size of 0.5 μm to 2.5 μm.

[0009] In some embodiments, the cathode is monocrystalline LiNixMn y M z Co 1-x-y-z O2, where M represents one or more dopant metals; x≧0.6, 0.01≦y<0.2, z≦0.05, and x+y+z≦1.0; and monocrystalline LiNixMn y M z Co 1-x-y-z The O2 has an average particle size of 0.5 μm to 5 μm. In some embodiments, a battery system includes a cathode, an anode, an electrolyte, and a separator positioned between the anode and the cathode.

[0010] The above and other objects, features, and advantages of the present invention will become more apparent from the following detailed description which proceeds with reference to the accompanying drawings.

[0011] The patent or application file contains at least one colored drawing. Copies of this patent or patent application publication with colored drawing(s) will be provided by the Office upon request and payment of the necessary fee. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of one embodiment of a method for making a nickel manganese cobalt hydroxide precursor.

[0013] [Figure 2] FIG. 2 is a schematic diagram of one embodiment of a solid state method for making single crystalline lithium nickel manganese cobalt oxide.

[0014] [Figure 3] FIG. 3 is a schematic diagram of one embodiment of the molten salt method for making single crystalline lithium nickel manganese cobalt oxide.

[0015] [Figure 4] FIG. 4 is a schematic diagram of one embodiment of a flash sintering method for making single crystalline lithium nickel manganese cobalt oxide.

[0016] [Figure 5] FIG. 5 is a schematic diagram of an exemplary lithium-ion battery.

[0017] [Figure 6] FIG. 6 is a schematic side elevation view of a simplified pouch cell.

[0018] [Figure 7]Figures 7A-7H show the characterization of single-crystalline LiNi0.76M0.14C0.1O2 (NMC76). Figure 7A is a scanning electron microscope (SEM) image of single-crystalline NMC76. Figure 7B is a cross-sectional image of single-crystalline NMC76. Figure 7C is a selected-area electron diffraction (SAED) pattern of single-crystalline NMC76. Figure 7D shows synchrotron X-ray diffraction and Rietveld refinement patterns. Figure 7E is a high-resolution HAADF-STEM (high-angle dark-field scanning transmission electron microscopy) image of single-crystalline NMC76 (corresponding to the square in Figure 7B). Figure 7F is a higher magnification image of the corresponding boxed area in Figure 7E. Figure 7G shows EDS (energy dispersive x-ray spectroscopy) elemental mapping of Ni, Mn, Co, and O. Figure 7H is a line-scan EDS overlay image showing elemental distribution intensity.

[0019] [Figure 8] Figures 8A-8F show the characterization of NMC76 secondary (polycrystalline) particles. Figure 8A is a cross-sectional image. Figure 8B shows the SAED results. Figure 8C is an HRTEM image of a primary particle. Figures 8D and 8E are HRTEM images of the surface structure. Figure 8F is an HRTEM image of the grain boundary.

[0020] [Figure 9] FIG. 9 shows the cyclic voltammetry curves of single crystalline NMC76 in different voltage windows using Li metal as the anode; a scan rate of 0.1 mV / sec.

[0021] [Figure 10] Figure 10 shows the cycling stability of monocrystalline NMC76 at various areal densities between 2.7 and 4.5 V in half cells using Li metal as the anode, charged at 0.1 C and discharged at 0.33 C.

[0022] [Figure 11]Figure 11 shows the initial charge-discharge curves between various cutoff voltages at 0.1 C using Li metal as the anode. The discharge capacities at 4.3, 4.4, and 4.5 V cutoff voltages are 184.9, 194.1, and 203.1 mAh / g, respectively.

[0023] [Figure 12-1] 12A-12C show the electrochemical performance of monocrystalline NMC76 at 4.2 V cutoff (12A), 4.3 V cutoff (12B), and 4.4 V cutoff (12C) tested in full cells using graphite as the anode. [Figure 12-2] 12A-12C show the electrochemical performance of monocrystalline NMC76 at 4.2 V cutoff (12A), 4.3 V cutoff (12B), and 4.4 V cutoff (12C) tested in full cells using graphite as the anode.

[0024] [Figure 13] 13A-13C show the corresponding charge-discharge curves for the cells of FIGS. 12A-12C, along with SEM images of the monocrystalline NMC76 after cycling.

[0025] [Figure 14] 14A-14B show the initial charge-discharge curves of single crystal NMC76 between 2.7 and 4.2 V (vs. graphite) (14A) and the midpoint voltage and voltage difference of the charge-discharge curves over 200 cycles (14B).

[0026] [Figure 15] 15A-15B show the initial charge-discharge curves of single crystal NMC76 between 2.7 and 4.3 V (vs. graphite) (15A) and the midpoint voltage and voltage difference of the charge-discharge curves over 200 cycles (15B).

[0027] [Figure 16] 16A-16B show the initial charge-discharge curves of single crystal NMC76 between 2.7 and 4.4 V (vs. graphite) (16A) and the intermediate voltages and voltage difference of the charge-discharge curves over 200 cycles (16B).

[0028] [Figure 17] 17A-17F are SEM images of single crystal NMC76 after cycling tests: 2.7-4.2 V vs. graphite (17A-B); 2.7-4.3 V vs. graphite (17C-D); 2.7-4.4 V vs. graphite (17E-F).

[0029] [Figure 18] Figures 18A-18L show morphology and structural studies of single crystalline NMC76. (18A) SEM image of single crystalline NMC76 after 200 cycles. (18B) Cross-sectional STEM bright-field image of single crystalline NMC76 after 200 cycles. (18C) STEM bright-field image of internal slicing. (18D) STEM-HAADF image near the slicing area. The top inset is a magnified image of the slipped area. (18E) SAED of the slipped area. (18F) EELS mapping of the selected area in (18B). (18G) SEM image of single crystalline NMC76 initially charged to 4.8 V (vs. Li+ / Li). (18H) SEM image of single crystalline NMC76 discharged to 2.7 V (after being charged to 4.8 V vs. Li+ / Li). (18I-J) STEM images of monocrystalline NMC76 in a 4.4 V charged state (full cell cycled between 2.7 and 4.4 V for 120 cycles). (18K-L) STEM images of monocrystalline NMC76 in a discharged state (full cell cycled between 2.7 and 4.4 V for 120 cycles).

[0030] [Figure 19] Figure 19 shows SEM images of the single crystal in the same electrode before cycling. Eight different areas were randomly selected and analyzed in SEM images 1-8. No pre-existing "slip" lines are present in the untreated single-crystalline NMC76.

[0031] [Figure 20]Figure 20 shows SEM images of single-crystalline NMC76 positioned at eight different locations on the same electrode after 120 cycles (2.7 to 4.4 V vs. graphite). Sliding steps are clearly observed in the cycled single crystal.

[0032] [Figure 21] FIG. 21 shows SEM images of monocrystalline NMC76 positioned at eight different locations on the same electrode after 200 cycles (between 2.7 and 4.4 V vs. graphite).

[0033] [Figure 22] FIG. 22 shows the EELS electron energy loss spectra of the O K-edge, Ni L-edge, Mn L-edge, and Co L-edge corresponding to test points 1 to 6 in FIG. 18B.

[0034] [Figure 23] 23A and 23B are SEM images of monocrystalline NMC76 charged to 4.8 V (vs. Li / Li) (23A) and discharged to 2.7 V after charging to 4.8 V (vs. Li / Li) (23B).

[0035] [Figure 24] Figures 24A-24D are STEM images of single crystalline NMC76 after 120 cycles in the charged state (cycled between 2.2 and 4.4 V vs. graphite). Figure 24A is a cross-sectional image of the cycled single crystal. Figure 24B is a STEM image of the boxed area in Figure 24A. Figures 24C-24D are STEM images of the lower (24C) and upper (24D) tip regions near an internal microcrack in the charged state.

[0036] [Figure 25]Figures 25A-25E are STEM images of single crystalline NMC76 after 120 cycles in a discharged state (cycled between 2.2 and 4.4 V vs. graphite). Figure 25A is a cross-sectional image of cycled single crystalline NMC76. Figure 25B is a STEM image of cycled single crystalline NMC76. Figure 25C is a STEM bright-field image of the boxed area in Figure 25B. Figure 25D is a STEM-HAADF image of the boxed area. Figure 25E is a comparison of two selected areas from Figure 25D.

[0037] [Figure 26] Figures 26A-26F show the evolution of surface structure and morphology by in situ AFM and mechanical analysis for single-crystalline NMC76. Figure 26A is an AFM image under OCV conditions. Figures 26B-26C are a comparison of the evolution of selected surfaces during in situ AFM testing. Figure 26D shows COMSOL-simulated shear stress along the yz direction during charging (delithiation) at a time scale of 0.1 T. Figure 26E shows COMSOL-simulated shear stress along the yz direction during discharging (lithiation) at a time scale of 0.1 T. Figure 26F is a schematic diagram of the structural evolution of single-crystalline NMC76 during cycling.

[0038] [Figure 27] 27A and 27B are graphs showing sliding step width versus test time (FIG. 27A) and sliding step width versus voltage (FIG. 27B).

[0039] [Figure 28] Figures 28A-28D show the time evolution of Li concentration and stress during the delithiation process. Figure 28A shows the Li concentration gradient during the delithiation process. Figures 28B-28D show the distribution of radial stress (28B), tangential stress (28C), and axial stress (28D) at various times.

[0040] [Figure 29]Figures 29A-29D show the time evolution of Li concentration and stress during the lithiation process. Figure 29A shows the Li concentration gradient during the lithiation process. Figures 29B-29D show the distribution of radial stress (29B), tangential stress (29C), and axial stress (29D) at various times.

[0041] [Figure 30] 30A-30C are SEM and STEM images of single crystalline NMC76 showing microcracks propagating from the center to the surface to form fractures.

[0042] [Figure 31] Figures 31A-31D show the elastic stress tensor in the local Cartesian coordinate system on the yz plane at a time scale of 0.1 T, as numerically solved by the COMSOL model. Figure 31A shows the normal stress along the zz direction, which is responsible for crack opening along the (003) direction during delithiation (charging). Figure 31B shows the shear stress along the yz direction, which is responsible for slippage during delithiation (charging). Figure 31C shows the shear stress along the yz direction during lithiation (discharging). Figure 31D shows the shear stress along the yz direction during lithiation (discharging) due to anisotropic strain.

[0043] [Figure 32] FIG. 32 shows SEM images and images obtained by in situ AFM of 20 μm single crystal NMC76.

[0044] [Figure 33] Figures 33A-33D are SEM images of untreated Ni0.76Mn0.14Co0.1(OH)2 (33A) and oxides prepared by heating Ni0.76Mn0.14Co0.1(OH)2 for 15 hours at 800°C (33B), 900°C (33C), or 1000°C (33D).

[0045] [Figure 34]FIG. 34 is a schematic diagram illustrating one embodiment of the molten salt process disclosed herein, as well as SEM images of the hydroxide precursor, oxide precursor, and single crystal LiNiMnCoO.

[0046] [Figure 35] Figures 35A and 35B are SEM images of Ni0.76Mn0.14Co0.1O2 prepared without (35A) and with (35B) NaCl.

[0047] [Figure 36] Figures 36A-36C show the initial charge-discharge curves of LiNi0.76Mn0.14Co0.1O2 prepared with and without NaCl (36A), the cycling stability of a single-crystal NMC76 electrode (20 mg / cm2) in a full cell using graphite as the anode between 2.7 and 4.2 V, charging at 0.1 C and discharging at 0.33 C (36B), and the cycling stability of a single-crystal NMC76 electrode (21.5 mg / cm2) in a full cell using graphite as the anode between 2.7 and 4.3 V. 1 C = 200 mA / g (36C).

[0048] [Figure 37] 37A-37C are SEM images of LiNi0.7Mn0.22Co0.08O2 washed with water (37A) and formamide (FM) (37B), as well as the initial charge-discharge curve of the sample (37C).

[0049] [Figure 38] FIG. 38 is a schematic diagram comparing the synthesis processes for polycrystalline and single crystalline LiNixMnyCo1-x-yO2.

[0050] [Figure 39] 39A-39C are SEM images of LiNi0.76Mn0.14Co0.1O2 prepared by flash sintering at ramp rates of 2°C / min (39A), 10°C / min (39B), and 20°C / min (39C).

[0051] [Figure 40] 40A-40B are SEM images of LiNi0.76Mn0.14Co0.1O2 prepared without (40A) or with (40B) preheating before flash sintering.

[0052] [Figure 41] FIG. 41 shows the charge-discharge curves of the flash-sintered LiNi0.76Mn0.14Co0.1O2 of FIGS. 40A and 40B.

[0053] [Figure 42] 42A-42C are SEM images of NiMnCo(OH) (42A), oxide precursor (42B), and single crystal LiNiMnCoO (42C) prepared by the solid-state method disclosed herein.

[0054] [Figure 43] FIG. 43 shows the charge-discharge curves of LiNi0.76Mn0.14Co0.1O2 in FIG. 42C.

[0055] [Figure 44] 44A and 44B show the charge-discharge curves of a LiNi0.76Mn0.14Co0.1O2 cathode prepared by the molten salt synthesis disclosed herein (44A) and an SEM image of LiNi0.76Mn0.14Co0.1O2 (44B).

[0056] [Figure 45] 45A and 45B show the charge-discharge curves of a LiNi0.76Mn0.14Co0.1O2 cathode prepared by the molten salt synthesis disclosed herein (45A) and an SEM image of LiNi0.76Mn0.14Co0.1O2 (45B).

[0057] [Figure 46] Figure 46 shows SEM, HRTEM, and SAED images of single crystal LiNi0.76Mn0.12Co0.1Mg0.01Ti0.01O2.

[0058] [Figure 47] Figures 47A and 47B are x-ray diffraction patterns comparing LiNi0.76Mn0.14Co0.1O2 and LiNi0.76Mn0.12Co0.1Mg0.01Ti0.01O2.

[0059] [Figure 48] Figures 48A and 48B compare the charge-discharge curves (48A) and cycling stability (48B) of LiNi0.76Mn0.14Co0.1O2 and LiNi0.76Mn0.12Co0.1Mg0.01Ti0.01O2.

[0060] [Figure 49] Figure 49 shows an SEM image of LiNi0.76Mn0.12Co0.1Mg0.01Ti0.01O2 after cycling. DETAILED DESCRIPTION OF THE INVENTION

[0061] Detailed Description

[0062] Nickel-rich lithium manganese cobalt oxide (NMC) cathode (LiNi x Mn y Co 1-x-y O2) is a promising cathode for next-generation lithium-ion batteries. Such batteries may be used, for example, in long-range electric vehicles. In particular, NMC cathodes with x≧0.6, capacities of ≧200 mAh / g, and cathodes capable of operating at high voltages (>3.8 V) are desirable.

[0063] Traditionally, NMC cathodes are prepared by coprecipitation, where nanosized primary particles aggregate into microsized secondary polycrystalline particles. This aggregated particle structure shortens the diffusion length of the primary particles and increases the number of pores and grain boundaries within the secondary particles, accelerating the electrochemical reaction and improving the rate capacity of NMCs. Secondary micron-sized particles formed from aggregated nanosized primary particles are the most common morphology for conventional NMC cathodes. However, challenges arise as the Ni content increases above 0.6. For example, such Ni-rich NMC cathodes are susceptible to moisture sensitivity, aggressive side reactions, and / or gas evolution during cycling, raising safety concerns. These challenges stem from the large surface area of ​​the secondary particles. Furthermore, although the creation of spherical secondary polycrystalline NMC particles reduces the surface-to-volume ratio, fracture of weak internal grain boundaries is commonly observed after cycling. These cracks are induced by the nonuniform volume change of the primary particles during cycling and are exacerbated by the anisotropy of individual grains and between grains in polycrystalline NMCs. Intergranular cracks expose new surfaces to the electrolyte, allowing side reactions to occur and accelerating cell degradation. As the Ni content increases to ≥ 0.8 in NMC, the main challenges for Ni-rich NMC cathodes become quite different from those for conventional NMCs. For example, NMC811 is highly sensitive to moisture, creating challenges for the manufacturing, storage, and transportation of Ni-rich NMCs. After extensive cycling, gas evolution from side reactions raises safety concerns.

[0064] The present disclosure relates to embodiments of methods for synthesizing monocrystalline Ni-rich cathode materials. Some embodiments of the disclosed methods may be used to synthesize large batches, e.g., 1 kg or larger, of monocrystalline lithium nickel manganese cobalt oxide. In some embodiments, the monocrystalline Ni-rich cathode comprises monocrystalline lithium nickel manganese cobalt oxide. In certain embodiments, the monocrystalline cathode comprises reduced surface area, phase boundaries, and / or a more integrated crystal structure compared to polycrystalline cathodes. Advantageously, some embodiments of the monocrystalline Ni-rich cathode demonstrate reduced gas evolution during cycling and / or grain cracking along grain boundaries. In some embodiments, the monocrystalline lithium nickel manganese cobalt oxide has the formula LiNixMn y M z Co 1-x-y-z O2, where M represents one or more dopant metals, and x≧0.6, 0.02≦y<0.2, 0≦z≦0.05, and x+y+z≦1.0. In certain embodiments, the formula is Ni x Mn y Co 1-x-y O2, where x≧0.6, 0.02≦y<0.2, and x+y≦1.0.

[0065] I. Definitions and Abbreviations

[0066] The following explanations of terms and abbreviations are provided for a better description of the present disclosure and to guide those skilled in the art in practicing the present disclosure. As used herein, unless the context clearly dictates otherwise, "comprising" means "including," and the singular forms "a" or "an" or "the" include plural referents. The term "or" refers to a single element or a combination of two or more of the alternative elements referenced, unless the context clearly dictates otherwise.

[0067] Unless otherwise explained, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in practicing or testing this disclosure, suitable methods and materials are described below. The materials, methods, and examples are merely illustrative and not limiting. Other features of the present disclosure will be apparent from the following detailed description and claims.

[0068] The disclosure of numerical ranges should be understood to refer to each individual point within the range, including the endpoints, unless otherwise noted. Unless otherwise indicated, all numerical values ​​expressing component amounts, molecular weights, percentages, temperatures, times, and the like used in the specification or claims are understood to be modified by the term "about." Thus, unless otherwise implicitly or explicitly indicated, or unless the context is appreciated by those skilled in the art to have a more determinative configuration, the numerical parameters described are approximations that may depend on the desired properties and / or detection limits sought under standard test conditions / methods known to those skilled in the art. When directly and explicitly distinguishing an embodiment from the prior art being discussed, the numerical values ​​of the embodiments are not approximations unless the word "about" is recited.

[0069] Although there may be alternatives for the various ingredients, parameters, operating conditions, etc. described herein, this does not mean that such alternatives are necessarily equivalent and / or function substantially equivalently. Unless otherwise stated, the alternatives are not meant to be listed in order of preference.

[0070] Definitions of common terms in chemistry can be found in Richard J. Lewis, Sr. (ed.), Hawley's Condensed Chemical Dictionary, published by John Wiley & Sons, Inc., 2016 (ISBN 978-1-118-13515-0). In order to facilitate review of the various embodiments of this disclosure, the following explanations of specific terms are provided:

[0071] Active Salt: As used herein, the term "active salt" refers to a salt that significantly participates in the electrochemical process of an electrochemical device. In the case of a battery, it refers to the charge / discharge process involved in the energy conversion that ultimately enables the battery to deliver / store energy. As used herein, the term "active salt" refers to a salt that constitutes at least 5% of the redox active material that participates in the redox reactions during the battery cycles after the first charge.

[0072] Annealing: The process of heating a material to a specified temperature for a specified period of time and then gradually cooling it. The annealing process can remove internal strains from previous operations, eliminating distortions and defects to produce a stronger and more uniform material.

[0073] Anode: An electrode through which electric charge flows into a polarized electronic device. From an electrochemical standpoint, negatively charged anions migrate toward the anode and / or positively charged cations move away from it to balance the electrons that leave through an external circuit.

[0074] Areal capacitance or specific areal capacitance is the capacity per unit area of ​​the electrode (or active material) surface, typically in mAh cm -2 It is expressed in units of

[0075] Capacity: The capacity of a battery is the amount of charge it can deliver. Capacity is typically expressed in mAh or Ah and indicates the maximum constant current the battery can produce over one hour. For example, a battery with a capacity of 100 mAh can deliver 100 mA of current for one hour, or 5 mA of current for 20 hours.

[0076] Cathode: The electrode through which charge flows and exits a polarized electronic device. From an electrochemical point of view, positively charged cations always move toward the cathode and / or negatively charged anions move away from it to balance the electrons arriving from the external circuit.

[0077] Cell: As used herein, a cell refers to an electrochemical device used to generate voltage or current from a chemical reaction, or vice versa, where a chemical reaction is induced by an electric current. Examples include voltaic cells, electrolytic cells, and fuel cells, among others. A battery contains one or more cells. The terms "cell" and "battery" are used interchangeably when referring to a battery containing only one cell.

[0078] Coulombic efficiency (CE): The efficiency with which charge is transferred within a system to facilitate an electrochemical reaction. CE can be defined as the amount of charge leaving a battery during a discharge cycle divided by the amount of charge entering the battery during a charge cycle.

[0079] Current density: A term referring to the amount of current per unit area. Current density is typically expressed in mA / cm 2 It is expressed in units of

[0080] Electrolyte: A substance containing free ions that acts as an electrically conductive medium. Electrolytes generally contain ions in solution, although molten and solid electrolytes are also known.

[0081] Microparticle: As used herein, the term "microparticle" refers to a particle having a size measured in microns, such as a particle having a diameter between 1 and 100 μm.

[0082] Nanoparticle: As used herein, the term "nanoparticle" refers to a particle having a size measured in nanometers, such as a particle having a diameter between 1 and 100 nm.

[0083] Pouch Cell: A pouch cell is a battery completely or substantially completely enclosed in a flexible outer cover, such as a heat-sealable foil, fabric, or polymer film. The term "flexible" means that the outer cover can be easily bent without breaking; thus, the outer cover can be wrapped around the battery components. Because pouch cells lack an outer rigid shell, they are flexible and lighter than conventional batteries.

[0084] Precursor: A precursor participates in a chemical reaction to form another compound. As used herein, the term "precursor" refers to a metal-containing compound used to prepare lithium nickel manganese cobalt oxide and metal-doped lithium nickel manganese cobalt oxide.

[0085] Separator: A battery separator is a porous sheet or film placed between the anode and cathode. The separator prevents physical contact between the anode and cathode while facilitating ion transport.

[0086] Solid-Phase: Consisting of solid components. As defined herein, solid-state synthesis proceeds directly with the solid components without the use of a sintering agent.

[0087] Specific Capacity: A term referring to capacity per unit of mass. Specific capacity may be expressed in units of mAh / g, often expressed as mAh / g carbon when referring to carbon-based electrodes in Li / air batteries.

[0088] Specific energy: A term referring to the energy per unit of mass. Specific energy is typically expressed in units of Wh / kg or J / kg.

[0089] II. Synthesis of crystalline oxide materials

[0090] Disclosed are embodiments of methods for making single crystalline lithium nickel manganese cobalt oxide (NMC) and metal-doped lithium nickel manganese cobalt oxide. In some embodiments, the single crystalline lithium nickel manganese cobalt oxide has the formula LiNixMn y M z Co 1-x-y-z O2, where M represents one or more dopant metals, and x≧0.6, 0.02≦y<0.2, 0≦z≦0.05, and x+y+z≦1.0. More particularly, 0.62≦x+y+z≦1.0. In certain embodiments, z is 0, and the single crystalline lithium nickel manganese cobalt oxide has the formula LiNixMn y Co 1-x-y O2, where x≧0.6, 0.02≦y<0.2, and x+y≦1.0. More particularly, 0.62≦x+y≦1.0. In some embodiments, x=0.65-0.99, y=0.01-0.2, z=0-0.02, and x+y+z=0.66-1.0. In certain embodiments, x=0.65-0.9, y=0.05-0.2, z=0-0.02, and x+y+z=0.7-0.95. In some embodiments, x is between 0.7 and 0.9, such as between 0.75 and 0.9 or between 0.8 and 0.9; y is between 0.05 and 0.15, such as between 0.05 and 0.14 or between 0.05 and 0.1; z is between 0 and 0.02; and x+y+z is between 0.8 and 0.98, such as between 0.8 and 0.95.

[0091] When single crystalline lithium nickel manganese cobalt oxide is doped, the general formula is LiNixMn y M z Co 1-x-y-z O2, where M represents one or more dopant metals. In some embodiments, M represents two or more dopant metals. Thus, M z are collectively referred to as M1 z1 +M2 z2 +M3 z3 ...+Mp zpwhere M1, M2, M3, etc. represent dopant metals, and z1 + z2 + z3 ... + zp = z. Suitable dopant metals include, but are not limited to, Mg, Ti, Al, Zn, Fe (e.g., Fe 3+ ), Zr, Sn (e.g., Sn 4+ ), Sc, V, Cr, Fe, Cu, Zu, Ga, Y, Zr, Nb, Mo, Ru, Ta, W, Ir, and combinations thereof.

[0092] The lithium nickel manganese cobalt oxide crystals prepared by embodiments of the disclosed methods are microparticles. In some embodiments, the single crystals have an average particle size of 1-5 μm, such as 1-4 μm or 1-3 μm. This characteristic contrasts significantly with traditional NMCs, which comprise particles of primary nanoparticles aggregated into secondary polycrystalline microparticles.

[0093] A. Synthesis of hydroxide precursor

[0094] In any of the foregoing or following embodiments, the synthesis may begin with a solid precursor comprising hydroxides of nickel, manganese, and cobalt. In some embodiments, the synthesis may further include a solid hydroxide precursor of one or more dopant metals, such as hydroxides of Mg, Ti, Al, Zn, Fe, Zr, Sn, or any combination thereof. In some embodiments, the hydroxide precursor is NiMn y M z Co 1-x-y-z(OH)2, where M represents one or more dopant metals, and x≧0.6, 0.01≦y<0.2, z≦0.05, and x+y+z≦1.0. More particularly, 0.62≦x+y+z≦1.0. In some embodiments, x=0.65-0.99, y=0.01-0.2, z=0-0.02, and x+y+z=0.66-1.0. In an independent embodiment, x=0.65-0.95, y=0.01-0.2, z=0-0.02, and x+y+z=0.66-0.98. In another independent embodiment, x=0.65-0.9, y=0.05-0.2, z=0-0.02, and x+y+z=0.7-0.95. In some embodiments, x is between 0.7 and 0.9, such as between 0.75 and 0.9 or between 0.8 and 0.9; y is between 0.05 and 0.15, such as between 0.05 and 0.14 or between 0.05 and 0.1; z is between 0 and 0.02; and x+y+z is between 0.8 and 0.98, such as between 0.8 and 0.95.

[0095] In any of the above or following embodiments, a method for synthesizing single-crystalline lithium nickel manganese cobalt oxide (including doped variants) includes synthesizing a hydroxide precursor. In some embodiments (FIG. 1), the hydroxide precursor is synthesized by preparing a 1.5 M to 2.5 M solution of metal salts in water (101), including nickel, manganese, cobalt, and, optionally, one or more dopant metal salts; combining the solution of metal salts in water with aqueous NH3 and aqueous NaOH or KOH to provide a combined solution having a pH of 10.5 to 12 (102); aging the solution for 5 to 48 hours to co-precipitate nickel, manganese, and cobalt hydroxides to provide a solid hydroxide precursor (103); and drying the solid hydroxide precursor (104). In any of the foregoing or following embodiments, the metal salts may include nickel(II) salts, manganese(II) salts, and cobalt(II) salts (where x+y+z<1).

[0096] The solution containing metal salts in water has a concentration of 1.5 to 2.5M, where 1.5M to 2.5M is the total concentration of all salts in the water. In some embodiments, the concentration is 1.7M to 2.3M, 1.8M to 2.2M, or 1.9M to 2.1M. In any of the above or below embodiments, the salt may be sulfate, nitrate, chloride, acetate, or a combination thereof. In one embodiment, the salt is sulfate. In another embodiment, the salt is nitrate. The concentration of each metal salt is selected based on the desired amount of metal in the final product. For example, Ni 0.76 Mn 0.14 Co 0.1 When the hydroxide precursor containing (OH)2 is prepared, nickel, manganese, and cobalt salts are combined in a molar ratio of Ni:Mn:Co of 0.76:0.14:0.1. 0.76 Mn 0.12 Co 0.1 Mg 0.01 Ti 0.01 When the hydroxide precursor containing (OH)2 is prepared, nickel, manganese, cobalt, magnesium, and titanium salts are combined in a molar ratio of Ni:Mn:Co:Mg:Ti of 0.76:0.12:0.01:0.01.

[0097] In any of the foregoing or following embodiments, combining a solution comprising a metal salt in water with aqueous NH3 and aqueous NaOH or KOH to provide a pH of 10.5-12 may include preparing an aqueous NH3 solution comprising 0.5 wt% to 1 wt% or 0.2-0.5 M NH3 in water; preheating the aqueous NH3 solution to 25°C to 80°C; and adding the metal salt solution, more concentrated aqueous ammonia (e.g., 25 wt% to 35 wt% or 13 M to 18 M NH3·HO), and aqueous NaOH or KOH to provide a pH of 10.5-12 and a final metal salt concentration of 0.1 M to 3 M. In some embodiments, the aqueous NH3 solution is preheated to 30°C to 75°C, e.g., 35°C to 70°C, 40°C to 60°C, or 45°C to 55°C. In some embodiments, the final metal salt concentration is 0.1 M to 2 M, 0.1 M to 1 M, or 0.2 M to 0.8 M. In some embodiments, the metal salt solution and more concentrated ammonia are added simultaneously in a volume ratio of 2-4 parts metal salt solution to 1 part concentrated ammonia solution. The aqueous NH3 solution may be continuously stirred as the metal salt solution and concentrated ammonia solution are added. In certain examples, the metal salt solution is added at a rate of 3 mL / min, and the concentrated ammonia is added at a rate of 1 mL / min. Sufficient aqueous NaOH or KOH is added to provide a combined solution having a pH of 10.5-12, e.g., a pH of 11-11.5. In some embodiments, the aqueous NaOH or KOH has a concentration of 6 M to 10 M. In any of the above or following embodiments, the combined solution may be aged for 5-48 hours at a temperature of 25° C. to 80° C. to co-precipitate hydroxides of the metals (Ni, Mn, Co, and any dopant metals), thereby producing hydroxide precursors. In some embodiments, the combined solution is continuously stirred while aging. In certain embodiments, the combined solution is aged for 10 to 48 hours, 15 to 45 hours, 20 to 40 hours, or 25 to 35 hours. In some embodiments, the temperature is 30° C. to 75° C., e.g., 35° C. to 70° C., 40° C. to 60° C., or 45° C. to 55° C.In some examples, the combined solution was aged at 50° C. for 30 hours with continuous stirring.

[0098] In any of the foregoing or following embodiments, the hydroxide precursor may be collected by any suitable method. In some embodiments, the aged combined solution is filtered to collect the coprecipitated hydroxide. The collected hydroxide precursor may be washed, for example with deionized water, to remove impurities such as ammonia, residual NaOH or KOH, and / or soluble sulfates and / or nitrates. The hydroxide precursor is then dried. In some embodiments, the hydroxide precursor is dried at a temperature of 80° C. to 120° C., for example, 90° C. to 110° C., for a period of 5 hours to 20 hours, for example, 10 hours to 15 hours.

[0099] Advantageously, low concentrations of metal salt solutions, i.e., 1.5M to 2.5M, facilitate the formation of small hydroxide precursor particles. In any of the foregoing embodiments, the hydroxide precursor particles may have an average size of 0.5 μm to 10 μm. In some embodiments, the hydroxide precursor particles have an average size of 0.5 μm to 7.5 μm, 0.5 μm to 5 μm, or 0.5 μm to 2.5 μm.

[0100] B. Solid phase method

[0101] In some embodiments, single crystalline lithium nickel manganese cobalt oxide (or doped variants thereof) is synthesized by a solid-state method. Referring to FIG. 2, in some embodiments, the solid-state method is y M z Co 1-x-y-z A solid hydroxide precursor containing (OH)2 is heated in an oxygen-containing atmosphere at a temperature T S1 for a period of time t1 to convert the solid hydroxide precursor to a solid oxide precursor (201); combining the solid oxide precursor with a molar excess of a lithium compound (202); heating the solid oxide precursor and the lithium compound at a temperature T S2for an effective period of time t2 to produce a first product (203); cooling the first product to ambient temperature (204); reducing the average particle size of the first product to 0.1 μm to 10 μm (205); and heating the first product having the reduced average particle size to a temperature T S3 for an effective period of time t3 to produce a second product (206); cooling the second product to ambient temperature (207); reducing the average particle size of the second product to 0.1 μm to 10 μm (208); and heating the second product having the reduced average particle size to a temperature T S4 for a period of time t4 to form a compound of formula LiNixMn y M z Co 1-x-y-z and forming (209) a monocrystalline lithium nickel manganese cobalt oxide having O2. In the formula above, M represents one or more dopant metals, and x≧0.6, 0.01≦y<0.2, z≦0.05, and x+y+z≦1.0. More particularly, 0.62≦x+y+z≦1.0. In some embodiments, x=0.65-0.99, y=0.01-0.2, z=0-0.02, and x+y+z=0.7-1.0. In an independent embodiment, x=0.65-0.95, y=0.01-0.2, z=0-0.02, and x+y+z=0.7-0.98. In another independent embodiment, x = 0.65 to 0.9, y = 0.05 to 0.2, z = 0 to 0.02, and x + y + z = 0.7 to 0.95. In some examples, x = 0.7 to 0.9, y = 0.05 to 0.15, z = 0 to 0.02, and x + y + z = 0.7 to 0.95. In one embodiment, x is 0.76, y is 0.14, and z is 0. In an independent embodiment, x is 0.76, y is 0.12, and z is 0.02. In another independent embodiment, x is 0.8, y is 0.1, and z is 0. In yet another independent embodiment, x is 0.9, y is 0.05, and z is 0.

[0102] In any of the foregoing or following embodiments, the temperature T S1may be between 400°C and 1000°C, and / or the effective period t1 may be between 1 hour and 30 hours. S1 is between 500°C and 1000°C, between 600°C and 1000°C, between 800°C and 1000°C, or between 850°C and 950°C. S1 Advantageously, the temperature T S1 In any of the above or below embodiments, the temperature is increased at a rate of 1° C. / min to 300° C. / min, e.g., 1° C. / min to 200° C. / min, 1° C. / min to 100° C. / min, 1° C. / min to 50° C. / min, 5° C. / min to 25° C. / min, or 5° C. / min to 15° C. / min, to a temperature T S1 In one example, the ramp rate was 10°C / min. Then the temperature T S1 is maintained for an effective period t1. In some embodiments, the effective period t1 is 5 to 25 hours, 10 to 20 hours, or 12 to 18 hours. In one particular example, the effective period t1 was 15 hours. In any of the above or following embodiments, the oxygen-containing atmosphere may be pure oxygen or air. As used herein, "pure oxygen" means at least 95 mol% oxygen. In any of the above or following embodiments, most or all of the solid hydroxide precursor may be converted to the solid oxide precursor. In some embodiments, 90 to 100 wt% of the solid hydroxide precursor is converted to the solid oxide precursor, e.g., 95 to 100 wt%, 97 to 100 wt%, 98 to 100 wt%, or 99 to 100 wt%. In one particular embodiment, all of the solid hydroxide precursor is converted to the solid oxide precursor.

[0103] The solid oxide precursor is combined with a molar excess of a Li compound. In any of the above or below embodiments, the Li compound may include lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium peroxide, lithium acetate, lithium oxalate, or any combination thereof. In some embodiments, the Li compound includes lithium hydroxide. The LiOH may be an anhydrous or hydrated salt, such as LiOH·H2O. In any of the above or below embodiments, the Li compound may have an average particle size of 10 μm to 100 μm. In any of the above or below embodiments, the solid oxide precursor and the lithium compound may be combined in a Li:solid oxide precursor molar ratio of 0.8:1 to 3:1, e.g., 0.9:1 to 3:1, 1:05:1 to 2:1, 1:05:1 to 1.5:1, 1.1:1 to 1.4:1, or 1.1:1 to 1.2:1. The mixture of solid oxide precursor and Li compound was subjected to a series of three annealing processes to produce the first product, the second product, and LiNixMn y M z Co 1-x-y-z Forms O2.

[0104] The mixture of the solid oxide precursor and the Li compound is heated to a temperature T S2 In any of the above or following embodiments, the temperature T S2 may be between 400°C and 1000°C, and / or the effective period t2 may be between 1 hour and 30 hours. S2 is between 400°C and 800°C, between 400°C and 600°C, or between 450°C and 550°C. S2 is below the melting or vaporization temperature of the oxide precursor and the lithium compound. S2 was 500° C. In some embodiments, the valid period t2 is 1 hour to 5 hours, 1 hour to 20 hours, 1 hour to 10 hours, or 2 hours to 6 hours. In one particular example, the valid period t2 was 5 hours.

[0105] The first product is cooled to ambient temperature, reducing the average particle size of the first product to 0.1 μm to 10 μm. In some embodiments, the average particle size is reduced to 0.2 μm to 10 μm, 0.5 μm to 10 μm, or 1 μm to 10 μm. In any of the above or below embodiments, cooling the first product to ambient temperature may include cooling the first product to 20°C to 30°C, for example, 20°C to 25°C. In any of the above or below embodiments, reducing the average particle size of the first product to 0.1 μm to 10 μm may include grinding or milling the first product to achieve the desired particle size.

[0106] The first product having a reduced average particle size is heated to a temperature T S3 In any of the above or following embodiments, the temperature T S3 In some embodiments, the temperature T S3 is between 700°C and 1000°C, between 700°C and 900°C, or between 750°C and 850°C. S3 The temperature was 800° C. In some embodiments, the effective period t3 is 1 to 25 hours, 1 to 20 hours, 1 to 10 hours, or 2 to 6 hours. In one particular example, the effective period t3 was 5 hours.

[0107] The second product is cooled to ambient temperature, reducing the average particle size of the second product to 0.1 μm to 10 μm. In some embodiments, the average particle size is reduced to 0.2 μm to 10 μm, 0.5 μm to 10 μm, or 1 μm to 10 μm. In any of the above or below embodiments, cooling the second product to ambient temperature may include cooling the second product to 20°C to 30°C, e.g., 20°C to 25°C. In any of the above or below embodiments, reducing the average particle size of the second product to 0.1 μm to 10 μm may include grinding or milling the second product to achieve the desired particle size.

[0108] The second product having a reduced average particle size is heated to a temperature T S4 for a period of time t4 to form a compound of formula LiNixMn y M z Co 1-x-y- In any of the above or following embodiments, a single crystalline lithium nickel manganese cobalt oxide having a temperature T S4 In some embodiments, the temperature T S4 is between 600°C and 1000°C, between 700°C and 1000°C, between 700°C and 900°C, or between 750°C and 850°C. S4 was 800° C. In some embodiments, the valid period t4 is between 1 hour and 25 hours, between 1 hour and 20 hours, between 1 hour and 10 hours, or between 2 hours and 6 hours. In one particular example, the valid period t4 was 5 hours.

[0109] In any of the preceding or following embodiments, the solid hydroxide precursor may be prepared as discussed above. In any of the preceding or following embodiments, the solid hydroxide precursor may have an average particle size of 0.5 to 10 μm. In some embodiments, the hydroxide precursor particles have an average size of 0.5 μm to 7.5 μm, 0.5 μm to 5 μm, or 0.5 μm to 2.5 μm. In any of the preceding or following embodiments, the single-crystalline lithium nickel manganese cobalt oxide may have an average particle size of 0.5 μm to 5 μm. In some embodiments, the solid hydroxide precursor has an average particle size of 1 μm to 2 μm. In certain embodiments, the single-crystalline lithium nickel manganese cobalt oxide has an average particle size of 1 μm to 5 μm or 1 μm to 3 μm. In any of the foregoing or following embodiments, the dopant metal(s) M may include Mg, Ti, Al, Zn, Fe, Zr, Sn, Sc, V, Cr, Fe, Cu, Zu, Ga, Y, Zr, Nb, Mo, Ru, Ta, W, Ir, or any combination thereof.

[0110] C. Molten salt method

[0111] In some embodiments, the monocrystalline lithium nickel manganese cobalt oxide (or doped variants thereof) is synthesized by a molten salt method. Referring to FIG. 3, in some embodiments, the molten salt method is y M z Co 1-x-y-z A solid hydroxide precursor containing (OH)2 is heated in an oxygen-containing atmosphere at a temperature of T M1 for an effective period of time t1 to convert the solid hydroxide precursor to a solid oxide precursor (301); combining the solid oxide precursor with a molar excess of a lithium compound and a sintering agent to form a mixture (302); heating the mixture in an oxygen-containing atmosphere at a temperature T M2 heating (303) at a temperature of T M3 >T M2 At temperature T M3 The mixture is heated to a temperature T M3 for a period of time t3 to form a first product and a sintering agent (304); cooling the first product and the sintering agent to ambient temperature (305); separating the sintering agent from the first product (306); drying the first product (307); and heating the first product in an oxygen-containing atmosphere at a temperature T M4 for a period of time t4 to restore any lost oxygen in the lattice and form a compound of the formula LiNixMn y M z Co 1-x-y-zand forming (308) a monocrystalline lithium nickel manganese cobalt oxide having O2. In the foregoing formula, M represents one or more dopant metals, and x≧0.6, 0.01≦y<0.2, z≦0.05, and x+y+z≦1.0. More particularly, 0.62≦x+y+z≦1.0. In some embodiments, x=0.65-0.99, y=0.01-0.2, z=0-0.02, and x+y+z=0.66-1.0. In an independent embodiment, x=0.65-0.95, y=0.01-0.2, z=0-0.02, and x+y+z=0.7-0.98. In another independent embodiment, x = 0.65 to 0.9, y = 0.05 to 0.2, z = 0 to 0.02, and x + y + z = 0.7 to 0.95. In some examples, x is 0.7 to 0.9, e.g., 0.75 to 0.9 or 0.8 to 0.9; y is 0.05 to 0.15, e.g., 0.05 to 0.14 or 0.05 to 0.1; z is 0 to 0.02; and x + y + z is 0.8 to 0.98, e.g., 0.8 to 0.95.

[0112] In any of the foregoing or following embodiments, the temperature T M1 may be between 400°C and 1000°C, and / or the effective period t1 may be between 1 hour and 30 hours. M1 is between 500°C and 1000°C, between 600°C and 1000°C, between 800°C and 1000°C, or between 850°C and 950°C. M1 was 800°C, 900°C or 1000°C. Advantageously, the temperature T M1 is below the melting point of the hydroxide precursor. In any of the preceding or following embodiments, the temperature is M1 The temperature may be increased at a rate of 1°C / min to 300°C / min, e.g., 1°C / min to 200°C / min, 1°C / min to 100°C / min, 1°C / min to 50°C / min, 1°C / min to 25°C / min, or 1°C / min to 15°C / min. In one example, the rate was 5°C / min. The temperature T M1is maintained for an effective period t1. In some embodiments, the effective period t1 is 5 to 25 hours, 10 to 20 hours, or 12 to 18 hours. In one particular example, the effective period t1 was 15 hours. In any of the above or below embodiments, the oxygen-containing atmosphere may be air or pure oxygen. In some embodiments, the oxygen-containing atmosphere is air. In any of the above or below embodiments, most or all of the solid hydroxide precursor may be converted to the solid oxide precursor. In some embodiments, 90 to 100 wt. % of the solid hydroxide precursor is converted to the solid oxide precursor, e.g., 95 to 100 wt. %, 97 to 100 wt. %, 98 to 100 wt. %, or 99 to 100 wt. %. In one particular embodiment, all of the solid hydroxide precursor is converted to the solid oxide precursor.

[0113] The solid oxide precursor is combined with a molar excess of a Li compound and a sintering agent to form a mixture. In any of the above or below embodiments, the Li compound may include lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium peroxide, or any combination thereof. In any of the above or below embodiments, the Li compound may have an average particle size of 10 μm to 100 μm. In some embodiments, the Li compound includes lithium oxide (LiO). In any of the above or below embodiments, the solid oxide precursor and the lithium compound may be combined in a Li:solid oxide precursor molar ratio of 1:1 to 5:1, e.g., 1:1 to 4:1, 1:1 to 3:1, 1:1 to 2:1, 1:1 to 1.5:1, 1.1:1 to 1.4:1, or 1.1:1 to 1.2:1. In any of the above or below embodiments, the sintering agent may be NaCl or KCl. In some embodiments, the sintering agent is NaCl. NaCl may reduce the sintering temperature and / or time. In any of the foregoing or following embodiments, the weight ratio of the sintering agent to the combined solid oxide precursor and lithium compound can be from 0.2:1 to 1:0.2, e.g., from 0.3:1 to 1:0.3, from 0.4:1 to 1:0.4, from 0.5:1 to 1:0.5, from 0.6:1 to 1:0.6, from 0.7:1 to 1:0.7, from 0.8:1 to 1:0.8, from 0.85:1 to 1:0.85, or from 0.9:1 to 1:0.9. In one particular example, the weight ratio was 1:1.

[0114] The mixture is heated in an oxygen-containing atmosphere at a temperature T M2 In any of the above or following embodiments, the temperature is heated at a temperature T M2 The temperature may be increased at a rate of 1°C / min to 300°C / min, e.g., 1°C / min to 200°C / min, 1°C / min to 100°C / min, 1°C / min to 50°C / min, 5°C / min to 25°C / min, or 5°C / min to 15°C / min. In one example, the rate was 10°C / min. The temperature T M2 In any of the above or following embodiments, the temperature TM2 In some embodiments, the temperature T M2 is between 500°C and 1000°C, between 600°C and 1000°C, between 700°C and 900°C, or between 750°C and 850°C. M2 was 800°C. In some embodiments, the effective period t2 is 1 hour to 25 hours, 5 hours to 20 hours, or 5 hours to 15 hours. In one particular example, the effective period t2 was 10 hours. In any of the above or following embodiments, the oxygen-containing atmosphere may be air or pure oxygen. In some embodiments, the oxygen-containing atmosphere is pure oxygen.

[0115] The mixture is then heated to a temperature T M3 for a period of time t3 to produce the first product and the sintering agent. M3 is the temperature T M2 In any of the preceding or following embodiments, the temperature T M3 In some embodiments, the temperature T M3 is between 700°C and 1000°C, between 800°C and 1000°C, or between 850°C and 950°C. In certain embodiments, the temperature T M3 was 900° C. In some embodiments, the valid period t3 is 1 hour to 25 hours, 1 hour to 20 hours, 1 hour to 10 hours, or 2 hours to 6 hours. In one particular example, the valid period t3 was 5 hours.

[0116] The first product and sintering agent are cooled to ambient temperature. In any of the above or below embodiments, cooling the first product to ambient temperature may include cooling the first product to 20°C to 30°C, for example, 20°C to 25°C. In some embodiments, the average particle size of the first product is reduced to 0.1 μm to 10 μm. In any of the above or below embodiments, reducing the average particle size of the first product to 0.1 μm to 10 μm may include grinding the first product to achieve the desired particle size.

[0117] The sintering agent is separated from the first product. In any of the above or following embodiments, separating the sintering agent may include washing the sintering agent and the first product with a solvent in which the sintering agent is soluble and the first product is insoluble or substantially insoluble (e.g., less than 5% by weight of the first product is soluble in the solvent). In some embodiments, the solvent is water. In certain embodiments, washing the sintering agent and the first product includes stirring the ground sintering agent and the first product in water and / or sonicating the ground sintering agent and the first product in water. The resulting solution may be filtered to collect the first product. The first product is then dried to remove the water. In any of the above or following embodiments, drying the first product may include heating the first product at a temperature effective to evaporate the solvent and for a time effective to remove the solvent, for example, at least 80%, at least 90%, at least 95%, at least 97%, or at least 99% by weight of the solvent. In some embodiments, the solvent is water and the temperature is 60°C to 95°C, e.g., 70°C to 90°C. In certain embodiments, the first product may be heated under reduced pressure to facilitate solvent removal. In any of the above or following embodiments, the time may be 1 to 10 hours, e.g., 1 to 5 hours or 1 to 3 hours. In some examples, the first product is heated under vacuum at 80°C for 2 hours.

[0118] The first product is heated in an oxygen-containing atmosphere at a temperature T M4 for a useful period t4 and has the formula LiNixMn y M z Co 1-x-y-z In any of the preceding or following embodiments, a single crystalline lithium nickel manganese cobalt oxide having O2 is produced at a temperature T M4 may be between 500°C and 1000°C, and / or the effective time t4 may be between 1 hour and 30 hours. M4 is between 500°C and 800°C, between 500°C and 700°C, or between 550°C and 650°C. In certain embodiments, the temperature T M4 was 580°C. In some embodiments, the effective period t4 is 1 hour to 25 hours, 1 hour to 20 hours, 1 hour to 10 hours, or 2 hours to 6 hours. In one particular example, the effective period t4 was 4 hours. In any of the above or below embodiments, the oxygen-containing atmosphere may be air or pure oxygen. In some embodiments, the oxygen-containing atmosphere is pure oxygen.

[0119] In any of the preceding or following embodiments, the hydroxide precursor may be prepared as discussed above. In any of the preceding or following embodiments, the solid hydroxide precursor may have an average particle size of 0.5 μm to 10 μm. In some embodiments, the hydroxide precursor particles have an average size of 0.5 μm to 7.5 μm, 0.5 μm to 5 μm, or 0.5 μm to 2.5 μm. In any of the preceding or following embodiments, the single-crystalline lithium nickel manganese cobalt oxide may have an average particle size of 0.5 μm to 5 μm. In some embodiments, the solid hydroxide precursor has an average particle size of 1 μm to 2 μm. In certain embodiments, the single-crystalline lithium nickel manganese cobalt oxide has an average particle size of 1 μm to 5 μm, or 1 μm to 3 μm. In any of the foregoing or following embodiments, the dopant metal(s) M may include Mg, Ti, Al, Zn, Fe, Zr, Sn, Sc, V, Cr, Fe, Cu, Zu, Ga, Y, Zr, Nb, Mo, Ru, Ta, W, Ir, or any combination thereof.

[0120] D. Flash sintering

[0121] In some embodiments, single crystalline lithium nickel manganese cobalt oxide (or doped variants thereof) is synthesized by flash sintering. Referring to FIG. 4, in some embodiments, flash sintering is performed to synthesize NixMn y M z Co 1-x-y-z combining a solid hydroxide precursor comprising (OH) with a molar excess of a lithium compound to form a hydroxide mixture (401); heating the hydroxide mixture in an oxygen-containing atmosphere at a temperature T F1 for a period of time t1 to form an oxide mixture (402) comprising oxides of nickel, manganese, cobalt, lithium, and, if present, one or more dopant metals, or combinations thereof; F2 and heating the oxide mixture in an oxygen-containing atmosphere at a temperature T F2for a period of time t2 to form a compound of formula LiNixMn y M z Co 1-x-y-z and forming (404) a monocrystalline lithium nickel manganese cobalt oxide with O. In the foregoing formula, M represents one or more dopant metals, and x≧0.6, 0.01≦y<0.2, z≦0.05, and x+y+z≦1.0. More particularly, 0.62≦x+y+z≦1.0. In some embodiments, x=0.65-0.99, y=0.01-0.2, z=0-0.02, and x+y+z=0.7-1.0. In an independent embodiment, x=0.65-0.95, y=0.01-0.2, z=0-0.02, and x+y+z=0.7-0.98. In another independent embodiment, x = 0.65 to 0.9, y = 0.05 to 0.2, z = 0 to 0.02, and x + y + z = 0.7 to 0.95. In some examples, x is 0.7 to 0.9, e.g., 0.75 to 0.9 or 0.8 to 0.9; y is 0.05 to 0.15, e.g., 0.05 to 0.14 or 0.05 to 0.1; z is 0 to 0.02; and x + y + z is 0.8 to 0.98, e.g., 0.8 to 0.95.

[0122] The solid hydroxide precursor is combined with a molar excess of a Li compound to form a hydroxide mixture. In any of the above or below embodiments, the Li compound may include lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium peroxide, or any combination thereof. In any of the above or below embodiments, the Li compound may have an average particle size of 10 μm to 100 μm. In some embodiments, the Li compound includes lithium hydroxide. The LiOH may be an anhydrous or hydrated salt, such as LiOH·H2O. In any of the above or below embodiments, the solid hydroxide precursor and the lithium compound may be combined in a Li:solid hydroxide precursor molar ratio of 0.8:1 to 3:1, e.g., 0.9:1 to 3:1, 0.9:1 to 2:1, 0.9:1 to 1.5:1, 1:1 to 1.5:1, 1.1:1 to 1.4:1, or 1.1:1 to 1.2:1.

[0123] The hydroxide mixture is heated in an oxygen-containing atmosphere at a temperature T F1 for an effective period of time t1 to form an oxide mixture comprising oxides of nickel, manganese, cobalt, lithium, and, if present, one or more dopant metals, or combinations thereof. In some embodiments, the hydroxide mixture is heated to a temperature T F1 In any of the preceding or following embodiments, the temperature T F1 may be between 400°C and 1000°C, and / or the effective period t1 may be between 1 hour and 30 hours. F1 is between 400°C and 900°C, between 400°C and 800°C, between 400°C and 600°C, or between 450°C and 550°C. F1 The temperature was 480°C. In any of the above or below embodiments, the effective period t1 is 1 hour to 30 hours. In some embodiments, the effective period t1 is 1 hour to 25 hours, 1 hour to 20 hours, 1 hour to 15 hours, or 1 hour to 10 hours. In certain examples, the period t1 was 5 hours. In any of the above or below embodiments, the oxygen-containing atmosphere may be air or pure oxygen. In some embodiments, the oxygen-containing atmosphere is pure oxygen. In any of the above or below embodiments, some or all of the hydroxide mixture is converted to an oxide mixture. In some embodiments, at least 25 wt%, at least 50 wt%, at least 75 wt%, or at least 90 wt% of the hydroxide mixture is converted to an oxide mixture. In certain embodiments, 25-100 wt%, 50-100 wt%, 75-100 wt%, 90-100 wt%, or 95-100 wt% of the hydroxide mixture is converted to an oxide mixture.

[0124] The temperature is then increased at a rate of ≥ 10°C / min to a temperature T F2In any of the above or following embodiments, the ramp rate may be 10°C / min to 3000°C / min (50°C / sec). In some embodiments, the ramp rate is 10°C / min to 2000°C / min, e.g., 10°C / min to 1000°C / min, 10°C / min to 500°C / min, 10°C / min to 250°C / min, or 10°C / min to 100°C / min. In certain examples, the ramp rate was 10-20°C / min. In any of the above or following embodiments, the temperature T F2 In some embodiments, the temperature T F2 In some embodiments, the temperature T F2 was 800°C.

[0125] The oxide mixture is heated in an oxygen-containing atmosphere at a temperature T F2 for a period of time t2 to form a compound of formula LiNixMn y M z Co 1-x-y-z A monocrystalline lithium nickel manganese cobalt oxide is formed with O. In any of the above or below embodiments, the effective period t2 may be 1 hour to 30 hours. In some embodiments, the effective period t2 is 1 hour to 25 hours, 1 hour to 20 hours, 5 hours to 20 hours, or 5 hours to 15 hours. In one particular example, the period t2 was 10 hours. In any of the above or below embodiments, the oxygen-containing atmosphere comprises pure oxygen or air. In some embodiments, the oxygen-containing atmosphere is pure oxygen.

[0126] In any of the preceding or following embodiments, the hydroxide precursor may be prepared as discussed above. In any of the preceding or following embodiments, the solid hydroxide precursor may have an average particle size of 0.5 μm to 10 μm. In some embodiments, the hydroxide precursor particles have an average size of 0.5 μm to 7.5 μm, 0.5 μm to 5 μm, or 0.5 μm to 2.5 μm. In any of the preceding or following embodiments, the single-crystalline lithium nickel manganese cobalt oxide may have an average particle size of 0.5 μm to 5 μm. In some embodiments, the solid hydroxide precursor has an average particle size of 1 μm to 2 μm. In certain embodiments, the single-crystalline lithium nickel manganese cobalt oxide has an average particle size of 1 μm to 5 μm or 1 μm to 3 μm. In any of the foregoing or following embodiments, the dopant metal(s) M may include Mg, Ti, Al, Zn, Fe, Zr, Sn, Sc, V, Cr, Fe, Cu, Zu, Ga, Y, Zr, Nb, Mo, Ru, Ta, W, Ir, or any combination thereof.

[0127] III. Cathode and Lithium-ion Batteries

[0128] The monocrystalline lithium nickel manganese cobalt oxide (NMC) and doped variants thereof made by embodiments of the disclosed methods may be used in cathodes, such as cathodes for lithium ion batteries. In some embodiments, the cathode is monocrystalline LiNixMn y M z Co 1-x-y-zO2, where M represents one or more dopant metals, and x≧0.6, 0.01≦y<0.2, z≦0.05, and x+y+z≦1.0. In some embodiments, x=0.65-0.99, y=0.01-0.2, z=0-0.02, and x+y+z=0.66-1.0. In an independent embodiment, x=0.65-0.95, y=0.01-0.2, z=0-0.02, and x+y+z=0.66-0.98. In another independent embodiment, x=0.65-0.9, y=0.05-0.2, z=0-0.02, and x+y+z=0.7-0.95. In some embodiments, x is between 0.7 and 0.9, such as between 0.75 and 0.9 or between 0.8 and 0.9; y is between 0.05 and 0.15, such as between 0.05 and 0.14 or between 0.05 and 0.1; z is between 0 and 0.02; and x+y+z is between 0.8 and 0.98, such as between 0.8 and 0.95.

[0129] In any of the preceding or following embodiments, the single crystalline LiNixMn y M z Co 1-x-y-z The average particle size of O may be 0.5 μm to 5 μm, for example 1 μm to 5 μm, or 1 μm to 3 μm. In one embodiment, the NMC is LiNi 0.76 Mn 0.14 Co 0.1 In an independent embodiment, the NMC is LiNi 0.8 Mn 0.1 Co 0.1 In another independent embodiment, the NMC is LiNi 0.9 Mn 0.05 Co 0.05 In yet another independent embodiment, the NMC is LiNi 0.76 Mn 0.12 Co 0.1 Mg 0.01 Ti 0.01 It is O2.

[0130] In any of the above or following embodiments, the cathode may have a capacity >180 mAh / g. In some embodiments, the cathode has a capacity >185 mAh / g, >190 mAh / g, or even >200 mAh / g. In any of the above or following embodiments, the cathode may be capable of operating at a high voltage, for example, at a voltage >3.8 V. In some embodiments, the cathode is capable of operating at a voltage between 2 and 4.6 V, for example, between 2 and 4.5 V or between 2 and 4.4 V. In any of the above or following embodiments, the cathode may have a capacity between 15 and 25 mg / cm. 2 , e.g., 18-24 mg / cm 2 (about 3.5~4.5mAh / cm 2 In some embodiments, the coating weight on each side of the cathode may be such that the areal capacity on each side is 3.5 to 4.5 mAh / cm. 2 Assuming that 2 , e.g., 9 to 12 mg / cm 2 may be.

[0131] In any of the above or following embodiments, the cathode may further include one or more inert materials, such as binders and / or additives (e.g., carbon). In some embodiments, the cathode may include 0 to 10 wt. % of the inert material, e.g., 2 to 5 wt. %. Suitable binders include, but are not limited to, polyvinyl alcohol, polyvinyl fluoride, ethylene oxide polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, epoxy resins, nylon, polyimide, and the like. Suitable conductive additives include, but are not limited to, carbon black, acetylene black, Ketjen black, carbon fibers (e.g., vapor-grown carbon fibers), metal powders or fibers (e.g., Cu, Ni, Al), and conductive polymers (e.g., polyphenylene derivatives). In some embodiments, a slurry containing NMC and optional inert materials is coated onto a substrate such as aluminum foil. In certain embodiments, the coating may have a thickness of 50 to 80 μm on each side, for example, a thickness of 60 to 70 μm. In any of the above or following embodiments, the cathode may have a coating thickness of 2.5 to 3.5 g / cm 3 , e.g., 3 g / cm 3 The electrode may have an electrode press density of

[0132] In some embodiments, a lithium-ion battery includes a cathode comprising the monocrystalline NMC disclosed herein, an anode, an electrolyte, and optionally a separator. Figure 5 is a schematic diagram of one exemplary embodiment of a rechargeable battery 500 including a cathode 520 disclosed herein, a separator 530 infused with electrolyte, and an anode 540. In some embodiments, the battery 500 also includes a cathode current collector 510 and / or an anode current collector 550. The electrolyte may be any electrolyte compatible with the anode and suitable for use in lithium-ion batteries.

[0133] In any of the foregoing or following embodiments, the lithium-ion battery may be a pouch cell. Figure 6 is a schematic side elevation view of one embodiment of a simplified pouch cell 600. The pouch cell 600 includes an anode 610 including a graphite material, an anode current collector 630, a cathode 640 including an NMC cathode material 650 disclosed herein and a cathode current collector 660, a separator 670, and packaging material defining a pouch 680 that encloses the anode 610, the cathode 640, and the separator 670. The pouch 680 further encloses an electrolyte (not shown). The anode current collector 630 has a protruding tab 631 extending outside the pouch 680, and the cathode current collector 660 has a protruding tab 661 extending outside the pouch 680. The weight of a pouch cell includes all components of the cell, i.e., anode, cathode, separator, electrolyte, and pouch material. In some embodiments, the pouch cell has a ratio of anode (negative electrode) areal capacity to cathode (positive electrode) areal capacity—N / P ratio—of 0.02 to 5, 0.1 to 5, 0.5 to 5, or 1 to 5. In certain embodiments, the pouch cell has a ratio of electrolyte mass to cell capacity—E / C ratio—of 1 to 6 g / Ah, e.g., 2 to 6 g / Ah or 2 to 4 g / Ah.

[0134] In any of the above or following embodiments, the current collector can be a metal or another conductive material, such as, but not limited to, nickel (Ni), copper (Cu), aluminum (Al), iron (Fe), stainless steel, or a conductive carbon material. The current collector may also be a foil, foam, or polymer substrate coated with a conductive material. Advantageously, the current collector is stable (i.e., does not corrode or react) when in contact with the anode or cathode and electrolyte within the operating voltage window of the battery. The anode and cathode current collectors may be omitted when the anode or cathode, respectively, is free-standing, e.g., when the anode is a free-standing film and / or when the cathode is a free-standing film. "Free-standing" means that the film itself has sufficient structural integrity to allow the film to be positioned within the battery without a supporting material.

[0135] In any of the foregoing or following embodiments, the anode may be any anode suitable for lithium-ion batteries. In some embodiments, the anode is lithium metal, graphite, an intercalation material, or a conversion compound. The intercalation material or conversion compound may be deposited on a substrate (e.g., a current collector) or provided as a free-standing film, typically containing one or more binders and / or conductive additives. Suitable binders include, but are not limited to, polyvinyl alcohol, polyvinyl chloride, polyvinyl fluoride, ethylene oxide polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, epoxy resins, nylon, polyimide, and the like. Suitable conductive additives include, but are not limited to, carbon black, acetylene black, Ketjen black, carbon fibers (e.g., vapor-grown carbon fibers), metal powders or fibers (e.g., Cu, Ni, Al), and conductive polymers (e.g., polyphenylene derivatives). Exemplary anodes for lithium batteries include, but are not limited to, lithium metal, carbon-based anodes (e.g., graphite), silicon-based anodes (e.g., porous silicon, porous silicon with a carbon coating, porous silicon with a carbon / silicon carbide coating), Mo6S8, TiO2, VO5, Li4Mn5O 12 , Li4Ti5O 12 , C / S composites, and polyacrylonitrile (PAN)-sulfur composites. In some embodiments, the anode is lithium metal. In certain embodiments, the anode has an areal capacity of 2 to 5.1 mAh / cm on each side. 2 On the assumption that 2 The current collector may have a lithium coating weight of 10000 on each side thereof.

[0136] In any of the foregoing or following embodiments, the separator may be glass fiber, a porous polymer film (e.g., a polyethylene or polypropylene-based material) with or without a ceramic coating, or a composite (e.g., a porous film of inorganic particles and a binder). One exemplary polymer separator is Celgard® K1640 polyethylene (PE) membrane. Another exemplary polymer separator is Celgard® 2500 polypropylene membrane. Another exemplary polymer separator is Celgard® 3501 surfactant-coated polypropylene membrane. The separator may be infused with an electrolyte.

[0137] In any of the foregoing or following embodiments, the electrolyte may include a lithium active salt and a solvent. In some embodiments, the lithium active salt is selected from the group consisting of LiPF, LiAsF, LiBF, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalato)borate (LiB(C2O4), LiBOB), lithium difluoro(oxalato)borate (LiBF2(C2O4), LiDFOB), lithium bis(pentafluoroethanesulfonyl)imide (LiN(SO2CF2CF3), LiBETI), lithium (fluorosulfonyltrifluoromethanesulfonyl)imide (LiN(SO2CF2CF3), LiBETI), and lithium bis(fluorosulfonyltrifluoromethanesulfonyl)imide (LiN(SO2CF2CF3), LiBETI). Lithium cyclohexafluoropropane-1,3-bis(sulfonyl)imide (LiN(SO2CF3)(SO2CF3), LiFTFSI), lithium (fluorosulfonylpentafluoroethanesulfonyl)imide (LiN(SO2F)N(SO2CF2CF3), LiFBETI), lithium cyclo(tetrafluoroethylenedisulfonyl)imide (LiN(SO2CF2CF2SO2), LiCTFSI), lithium (trifluoromethanesulfonyl)(n-nonafluorobutanesulfonyl)imide (LiN(SO2CF3)(SO2-n-CF9), LiTNFSI), lithium cyclohexafluoropropane-1,3-bis(sulfonyl)imide, or combinations thereof. The solvent may be any non-aqueous solvent suitable for use with the lithium active salt, lithium metal anode, and packaging materials.Exemplary solvents include, but are not limited to, triethyl phosphate, trimethyl phosphate, tributyl phosphate, triphenyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, bis(2,2,2-trifluoroethyl)methyl phosphate; trimethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphite; dimethyl methylphosphonate, diethyl ethylphosphonate, diethyl phenylphosphonate, bis(2,2,2-trifluoroethyl)methylphosphonate; hexamethoxazole, methylphosphoramide; hexamethoxyphosphazene, hexafluorophosphazene, 1,2-dimethoxyethane (DME), 1,3-dioxolane (DOL), tetrahydrofuran (THF), allyl ether, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), 4-vinyl-1,3-dioxola 4-Methylene-1,3-dioxolan-2-one (vinyl ethylene carbonate, VEC), 4-methylene-1,3-dioxolan-2-one (methylene ethylene carbonate, MEC), 4,5-dimethylene-1,3-dioxolan-2-one, dimethyl sulfoxide (DMSO), dimethyl sulfone (DMS), ethyl methyl sulfone (EMS), ethyl vinyl sulfone (EVS), tetramethylene sulfone (i.e., sulfolane, TMS), trifluoromethyl ethyl sulfone (FMES), trifluoromethyl isopropyl sulfone Examples of suitable solvents include fluoromethane (FMIS), trifluoropropyl methyl sulfone (FPMS), diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), tetraethylene glycol dimethyl ether (tetraglyme), methyl butyrate, ethyl propionate, gamma-butyrolactone, acetonitrile (AN), succinonitrile (SN), adiponitrile, triallylamine, triallyl cyanurate, triallyl isocyanurate, or any combination thereof. In some embodiments, the solvent comprises a flame retardant compound. The flame retardant compound may constitute the entire solvent.Alternatively, the solvent may contain at least 5 wt. % of a flame retardant compound in combination with one or more additional solvents and / or diluents. Exemplary flame retardant compounds include, but are not limited to, triethyl phosphate, trimethyl phosphate, tributyl phosphate, triphenyl phosphate, tris(2,2,2-trifluoroethyl)phosphate, bis(2,2,2-trifluoroethyl)methyl phosphate; trimethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl)phosphite; dimethyl methylphosphonate, diethyl ethylphosphonate, diethyl phenylphosphonate, bis(2,2,2-trifluoroethyl)methyl phosphonate; hexamethylphosphoramide; hexamethoxyphosphazene, hexafluorophosphazene, and combinations thereof. In some embodiments, the electrolyte has a lithium active salt concentration of 0.5 to 8 M, e.g., 1 to 8 M, 1 to 6 M, or 1 to 5 M. In some embodiments, the electrolyte comprises LiPF6 in a carbonate solvent, for example, 1.0 M LiPF6 in EC / EMC.

[0138] In some embodiments, the electrolyte is a localized ultra-concentrated electrolyte (LSE), also known as a localized high-concentration electrolyte. An LSE comprises an active salt, a solvent in which the active salt is soluble, and a diluent, with the active salt having a solubility in the diluent that is at least one-tenth of the solubility of the active salt in the solvent. In an LSE, lithium ions remain associated with solvent molecules after the addition of the diluent. Anions are also in the vicinity of or associated with the lithium ions, thus forming localized regions of solvent-cation-anion aggregates. In contrast, the lithium ions and anions are not associated with diluent molecules and remain free in solution. In an LSE, the electrolyte is not concentrated overall; instead, there are localized regions of high concentration where lithium cations are associated with solvent molecules. Diluted electrolytes have few or no free solvent molecules, thereby providing the benefits of ultra-concentrated electrolytes without the associated disadvantages. The solubility of the active salt in the solvent (absent diluent) can be greater than 3 M, e.g., at least 4 M or at least 5 M. In some embodiments, the solubility and / or concentration of the active salt in the solvent is between 3 M and 10 M, e.g., between 3 M and 8 M, between 4 M and 8 M, or between 5 M and 8 M. However, in some embodiments, the molarity of the active salt in the LSE as a whole is between 0.5 M and 3 M, between 0.5 M and 2 M, between 0.75 M and 2 M, or between 0.75 M and 1.5 M.

[0139] Exemplary salts and solvents for LSE are disclosed above. In some embodiments, the diluent comprises a fluoroalkyl ether (also called a hydrofluoroether (HFE)), a fluorinated orthoformate, or a combination thereof. Exemplary diluents include, but are not limited to, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), bis(2,2,2-trifluoroethyl)ether (BTFE), 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TFTFE), methoxynonafluorobutane (MOFB), ethoxynonafluorobutane (EOFB), tris(2,2,2-trifluoroethyl)orthoformate (TFEO), tris(hexafluoroisopropyl)orthoformate (THFiPO), tris(2,2-difluoroethyl)orthoformate (TDFEO), bis(2,2,2-trifluoroethyl)methylorthoformate (BTFEMO), tris(2,2,3,3,3-pentafluoropropyl)orthoformate (TPFPO), tris(2,2,3,3-tetrafluoropropyl)orthoformate (TTPO), or any combination thereof. In certain embodiments where the diluent and solvent are immiscible, the electrolyte may further include a bridging solvent having a different composition from the solvent and a different composition from the diluent, where the bridging solvent is miscible with the solvent and the diluent. Exemplary cross-linking solvents include acetonitrile, dimethyl carbonate, diethyl carbonate, propylene carbonate, dimethyl sulfoxide, 1,3-dioxolane, dimethoxyethane, diglyme (bis(2-methoxyethyl) ether), triglyme (triethylene glycol dimethyl ether), tetraglyme (tetraethylene glycol dimethyl ether), or combinations thereof. Additional information regarding LSEs can be found in US 2018 / 0254524 A1, US 2018 / 0251681 A1, and US 2019 / 148775 A1, each of which is incorporated by reference in its entirety.

[0140] In any of the above-mentioned or following embodiments, the lithium-ion battery may have a cell energy density of 200 Wh / kg to 400 Wh / kg, e.g., 200 Wh / kg to 350 Wh / kg, 250 Wh / kg to 300 Wh / kg, or 250 Wh / kg to 275 Wh / kg. In any of the above-mentioned or following embodiments, the lithium-ion battery may have a first cycle capacity of 2 Ah to 5 Ah. In any of the above-mentioned or following embodiments, the lithium-ion battery may be capable of operation at a rate up to 3 C, e.g., 0.1 C to 3 C. In any of the above-mentioned or following embodiments, the lithium-ion battery may demonstrate an average coulombic efficiency of at least 80%, e.g., 80-100%, 85-100%, 90-100%, 95-100%, or 95-99%, over at least 100 cycles, at least 150 cycles, or at least 200 cycles. In any of the foregoing or following embodiments, the lithium-ion battery may have a capacity retention of at least 70%, at least 75%, or at least 80% after at least 100 cycles, at least 150 cycles, or at least 200 cycles. In some embodiments, the capacity retention after 200 cycles is 70-90%, e.g., 70-85%. Advantageously, the cathode may be more stable (e.g., resistant to cracking) over extensive cycling, undergo fewer side reactions, be less sensitive to moisture, and / or generate less gas during cycling compared to conventional Ni-rich cathodes (e.g., Ni≧0.6) prepared with polycrystalline and / or monocrystalline NMC. [Example]

[0141] IV. Working Examples Example 1 Single crystal LiNi 0.76 M 0.14 C 0.1 Molten salt synthesis and characterization of O2(NMC76) synthesis

[0142] Ni 0.76 Mn 0.14 Co 0.1 The (OH)2 precursor was synthesized by the coprecipitation method using a 5 L reactor at 55 °C. Prior to the coprecipitation reaction, 1.5 L of deionized (DI) HO and 65 mL of concentrated NH3·HO (approximately 28 wt%) were added to the reactor and heated to 55 °C as the starting solution. A 2 mol / L transition metal (TM) sulfate solution (molar ratio of Ni:Mn:Co = 0.76:0.14:0.10) was prepared using Ni(SO4)2·6HO, MnSO4·HO, and Co(SO4)2·7HO, and then pumped into the reactor together with 8 M NaOH and 10 mol / L NH3·HO buffer solution. The pumping rates of the TM sulfate and NH3·HO solutions were set at 3 and 1 mL / min, respectively. The pH was controlled at 11.2 during the reaction by adjusting the NaOH addition rate. The synthesized precursor was filtered and washed with DI H2O to remove impurities. After drying at 100 °C for 12 h, Ni 0.76 Mn 0.14 Co 0.1 (OH)2 precursor was obtained. 0.76 Mn 0.14 Co 0.1 The oxide precursor was prepared by heating (OH)2 at 900°C for 15 hours in air. The stoichiometry of the oxide precursor was analyzed by ICP-OES. The oxide precursor and lithium oxide were mixed in a molar ratio of 1:0.6 (TM:Li = 1:1.2), and then NaCl (1:1.1 weight ratio) was added to the precursor and mixed uniformly. The mixture was sintered at 800°C for 10 hours, followed by sintering at 900°C for 5 hours using a ramp rate of 10°C / min in an oxygen atmosphere. The sintered product was washed and dried at 80°C in vacuum for 2 hours. Post-annealing at 580°C (10°C / min ramp) in an oxygen atmosphere was then performed, after which the final product was collected. Pure NaCl was used as the molten salt medium to reduce the sintering time / temperature of the single crystal, thereby reducing the cost of synthesizing the single crystal.

[0143] Characterization

[0144] Scanning electron images (SEM) were collected on a Helios NanoLab scanning electron microscope (FEI, Hillsboro, Oregon). Powder X-ray diffraction (XRD) data were collected at the 28-ID-2 (XPD) beamline at the National Synchrotron Light Source II (NSLS II), Brookhaven National Laboratory (BNL). A Perkin Elmer amorphous-Si flat panel detector was used. The wavelength was 0.1821 Å. The raw powder was placed in a Kapton® polyimide capillary tube (1.0 mm diameter) in an Ar-filled glovebox and attached to the base at the beamline. Rietveld refinement of the XRD data was performed with TOPAS6 (Coelho, J. Appl. Crystallogr. 2018, 51:210-218). Transmission electron microscopy (TEM) specimen preparation was performed on an FEI Helios Dual Beam FIB operating at 2-30 kV. TEM imaging, selected area electron diffraction (SAED), high-resolution TEM (HRTEM) imaging, and scanning TEM energy-dispersive X-ray spectroscopy (STEM-EDS) were performed on an FEI Titan 80-300 S / TEM microscope equipped with a probe spherical aberration corrector at 300 kV. HR STEM high-angle annular dark-field (HRSTEM-HAADF) imaging and STEM-electron energy-loss spectroscopy (STEM-EELS) were performed on a probe aberration-corrected JEOL JEM-ARM200CF microscope (JEOL USA, Peabody, Massachusetts) at 200 kV.

[0145] Because the TEM samples were very thin and self-absorption in the TEM samples was negligible, EDS quantification was performed by using a simple ratio technique (Cliff-Lorimer quantification), in which peak intensities are proportional to concentration and specimen thickness, and the effect of various specimen thicknesses is removed by taking the ratio of intensities for elemental peaks, and introducing a "k-factor" to relate intensity ratios to concentration ratios: C A / C B =k AB I A / IB (1)

[0146] In the formula, I A is the peak intensity for element A, and C A is the concentration in weight percent. Each element pair requires a different k-factor, which depends on the detector efficiency, ionization cross section, and fluorescence yield of the two elements in question. The k-factor, k, is calculated as follows: k ab =(A a ω b Q b ) / (A b ω a Q a ) (2)

[0147] In the formula, A a and A b are the atomic masses of the elements causing the analytical lines a and b, respectively, and Q a and Q b is the ionization cross section of the shell that, when ionized, gives rise to analytical lines at the specified accelerating voltage. Fluorescence yield ω a and ω b gives the probability of emission of that line when the appropriate shell is ionized. Knowing the k-factor, the element concentration in weight percent can be calculated.

[0148] The as-prepared single crystalline NMC76 has a tap density of 2.12 mg / cm 3 while polycrystalline NMC76 has 2.08 mg / cm 3 The increased tap density will provide cell level energy benefits due to reduced porosity and improved electrode press density.

[0149] Electrochemical Testing

[0150] To understand the electrochemical properties of single-crystalline NMC76 on an industrially relevant scale, cathodes with reasonably high loadings are required. However, half-cells are not the preferred test medium for evaluating high mass loadings of cathode materials due to accelerated Li metal decomposition when coupled with thick cathodes. Electrochemical performance was evaluated in 2032-type coin cells. Single-crystalline NMC76 was mixed with carbon additive (C65 carbon black) and PVDF in a 96:2:2 weight ratio in NMP (N-methyl-2-pyriolidone) solvent and loaded onto carbon-coated Al foils. 5–26 mg / cm 2 The area loading of the electrode was adjusted by adjusting the height of the doctor blade. After drying at 80 °C under vacuum, thick electrodes (approximately 20 mg / cm) were prepared. 2 The graphite powder was calendered (approximately 32% porosity) and cut into 1 / 2-inch disks to assemble the cells. Before calendering, the porosity was 62%. Graphite powder was mixed with carbon additive (C65), CMC, and SBR in a weight ratio of 94.5:1:2.25:2.25 and loaded onto copper foil. The dried graphite electrode was calendered and cut into 15-mm disks. 1.0 M LiPF6 in EC / EMC (3:7 weight ratio) containing 2 wt% VC was used as the electrolyte for both half-cell and full-cell tests. Half-cells were assembled using 450 μm-thick Li metal as the anode. The cation / cation (N / P) ratio for full-cell assembly was controlled between 1.15 and 1.2 (approximately 0.1 mg of Li metal in the graphite anode). In all cell tests, 1C is referred to as 200mA / g.

[0151] In situ electrochemical AFM measurement (EC-AFM)

[0152] Fabrication of the working electrode for in situ EC-AFM: Aluminum (Al) foil was selected as the substrate due to its electronic conductivity and stability during electrochemical cycling. Synthesized Ni-rich NMC single crystals were dropped onto the Al foil. The Al foil with Ni-rich NMC was then placed under a 5-ton press and held for 100 seconds. Weakly bonded and unfixed Ni-rich NMC crystals were removed by flowing N2 gas. The Al foil was then attached to an AFM sample holder with epoxy, and electrical contact was made to the bottom of the Al foil with a flattened nickel wire. Silicone grease was used to cover the outer rim of the O-ring to enhance the solution seal. The nickel wire was insulated from the solution due to the larger diameter of the Al foil than the O-ring. The cell was ready for in situ AFM testing after assembly with an O-ring, a sealing cap with Li wires for the counter and reference electrodes, and another free-standing sealing cap.

[0153] All in situ EC-AFM images were acquired at room temperature (23 °C) in peak force or tapping mode using a Nanoscope 8 atomic force microscope (J scanner, Bruker, Santa Barbara, CA) (Habraken et al., Nat Commun 2013, 4:1507; Tao et al., PNAS USA 2019, 116:13867-13872). The AFM probe consisted of a silicon tip on a silicon nitride cantilever (HA_C series, ETALON probe, k = 0.26 N / m, tip radius <10 nm; K-TEK Nanotechnology, https: / / kteknano.com / product-category / etalon / ). A 1.0 M LiPF6 electrolyte solution in EC / EMC (3:7 weight ratio) was used as the test solution. The working cathode electrode (described above) was connected to a Solartron 1287 electrochemical workstation (Solartron, Farnborough, Hampshire, UK) via a nickel wire. Thin Li wires (counter and reference electrodes) with sealing caps were inserted into the test solution through separate channels in the liquid cell (Lvet et al., Nano Lett 2017, 17:1602-1609). The Solartron 1287 electrochemical workstation inputted electrical signals into the AFM liquid cell with a two-electrode configuration. The applied voltage was started from OCV, increased to 4.50 V, and decreased to 2.70 V at a uniform scan rate of 0.3 mV / s. In typical imaging conditions, images were collected at a scan rate of 1 Hz.

[0154] Several protocols were followed to ensure that the AFM images were representative of the surface topography evolution. First, the imaging force was reduced to the smallest possible value (approximately 100 pN) at which the tip was still able to track the surface and there was no measurable effect of the scan on surface cracks. We verified this by zooming out to a larger scan box and comparing the crack number density with a smaller scan area. Imaging the same area results in fewer bound particles being displaced on the surface. This procedure ensures that the crack growth dynamics are minimally affected. Images were also collected at various scan angles, and images were regularly tracked and retracted to compare them to eliminate the possibility of imaging artifacts from tip contamination. Images were analyzed using the image processing software package Nanoscope Analysis 2.0 (Bruker).

[0155] The average width of these steps increases approximately linearly at higher voltages (vs. Li+ / Li) during the charging process, then decreases linearly at lower voltages during the discharging process, with values ​​of 30.3 ± 0.7 nm at the open circuit voltage (OCV), a maximum of 52.5 ± 2.5 nm at 4.50 V in the charged state, and a drop to 38.4 ± 1.3 nm at 4.19 V during discharging. The average step width is calculated by dividing the total lateral width by the total number of steps (between 21 and 43 steps) at each voltage during in situ AFM monitoring. The error bars on the step width are estimated by averaging three measurements of the lateral width at each time point.

[0156] simulation

[0157] A cylindrical electrode particle diffusion-induced stress model was used herein, with material properties predicted by density functional theory (DFT) (28, 33). The particles are considered isotropic solids with a Young's modulus (E) that increases linearly with Li concentration. In layered Ni-rich electrodes, lithium ion diffusion is confined to two-dimensional channels, i.e., between layers; therefore, lithium diffusion along the radial direction is assumed in the model. The dimensionless particle size, time, Li concentration, and stress are used according to the definitions in Deshpande et al., J Electrochem Soc 2010, 157:A967-A971. The parameters in the simulation are: α = 0.0067; E = 59.8 GPa; E = E + 204.2 C; ν = 0.3 (Qiet al. J Electrochem Soc 2014, 161:F3010-F3018); and γ = 2.1 J / m. 2 Li 16 (Ni 14 CoMn)O 32 (Steinet et al., Acter Mater 2018, 159:225-240). Analytical solutions are provided in Figures 29A-29D and 30A-30D. Numerical solutions from the COMSOL 5.5 model are provided in Figures 31A-31D. For the anisotropic chemical strain solved in Figure 31D, α = (0, 0, 0.02).

[0158] Results and Discussion

[0159] The synthesized NMC76 has an average grain size of 3 μm (Figure 7A). The cross-sectional view (Figure 7B) shows that NMC76 has a dense structure without cavities or grain boundaries. The pure phase of the α-NaFeO2-type layered structure is confirmed by both selected-area electron diffraction (SAED, Figure 7C) and X-ray diffraction (XRD, Figure 7D). The lattice parameters a and c are 2.8756(1) Å and 14.2221(1) Å, respectively, from the Rietveld refinement (Table 1). For comparison, polycrystalline NMC76 is found to contain many internal pores and intergranular boundaries along the surface coating, formed from the reaction between NMC and air (Figures 8A-8F) (Jung et al., J Electrochem Soc 2018, 165:A132-A141). In contrast, the surface of monocrystalline NMC76 is highly uniform (Figures 7E and 7F). Elemental mapping (Figures 7G and 7H) shows a homogeneous distribution of Ni, Mn, and Co with the designed stoichiometry (Table 2). Sequential phase transitions occur as the potential is changed, similar to polycrystalline NMC76 (Figure 9) (Zhenget et al., Nano Energy 2018, 49:538-548). During charging, the phase transitions occur in the order H1 to M (H and M are the hexagonal and monoclinic phases, respectively), M to H2, and H2 to H3, similar to polycrystalline NMC76.

[0160] [Table 1]

[0161] [Table 2]

[0162] Monocrystalline NMC76 was further tested in graphite / NMC full cells under realistic conditions. Typical loadings of NMC76 cathodes were approximately 20 mg / cm. 2 (=4mAh / cm 2), which is required to construct a 250 Wh / kg Li-ion cell (Table 3). At such high cathode loadings, Li metal degrades cycling stability due to the enhanced Li exfoliation / deposition process (Figures 10 and 11). Between 2.7 V and 4.2 V (vs. graphite), monocrystalline NMC76 delivered 182.3 mAh / g discharge capacity at 0.1 C and retained 86.5% of its initial capacity after 200 cycles (Figure 12A). At a cutoff of 4.3 V, monocrystalline NMC76 delivered 193.4 mAh / g capacity with 81.6% capacity retention after 200 cycles (Figure 12B). Further increasing the voltage to 4.4 V, a discharge capacity of 196.8 mAh / g was observed with 72.0% capacity retention after 200 cycles (Figure 12C). Note that 200 cycles at a C / 10 charge rate and a C / 3 discharge rate represent 2600 hours of cycling. The total test time was equivalent to a cell undergoing 1300 cycles at 1C. Increased polarization (Figures 13A-13C) was observed as the cutoff voltage increased, likely due to enhanced electrolyte decomposition at high voltages (Figures 14A-B, 15A-B, 16A-B) and therefore higher impedance resulting from cathode passivation film and single-crystal lattice changes. Crystalline slippage and cracking were observed when the cutoff voltage was below 4.3 V (Figures 13A-13C). Table 4 summarizes the electrochemical performance and test conditions of all previously published single-crystalline Ni-rich NMC (Ni>0.6) cathode materials.

[0163] [Table 3]

[0164] [Table 4]

[0165] Lattice slip was clearly observed in the single-crystalline NMC76 at high voltages. Between 2.7 and 4.2 V (vs. graphite), the entire single crystal was well maintained after 200 cycles (Figure 13A). When the cutoff voltage was increased to 4.3 V, some slip lines were visible on the crystal surface after 200 cycles (Figure 13B). Upon cycling to 4.4 V, the single crystal appeared to "slice" (Figures 13C, 17A-17F) parallel to the (003) plane and perpendicular to the c-axis of the layered structure (Figure 18C), indicating model II cracking (in-plane shear) in fracture mechanics. Furthermore, small cracks indicative of model I fracture (opening) were also found at 4.4 V (Figure 13C). All characterizations were performed by selecting different regions of the NMC76 electrode, and the same phenomenon was repeatedly observed (Figures 19-21). Although the entire grain of single-crystalline NMC76 remained intact (Figure 12A), slippage was the primary mechanical degradation mode, especially at cutoff voltages above 4.3 V. The notable "slip steps" formed in cycled crystals are distinct from the cracks along the intergranular boundaries of polycrystalline NMC particles. Scanning transmission electron microscopy (STEM) images (Figures 18B–18D) of single-crystalline NMC76 confirmed that the d-spacing (0.48 nm) of the (003) plane remained unchanged on both sides of the slip plane (yellow line in Figure 18D), and the layered structure was well maintained after the "slip" mark occurred, thereby ensuring that the long-range lattice symmetry of the bulk material remained unchanged. Ni, Mn, Co, and O remained uniformly distributed near the slip plane based on electron energy loss spectroscopy (EELS) analysis (Figures 18F and 22). The uniform elemental distribution and tightly attached lattice across the slip plane strongly demonstrated that planar slip occurs but does not generate new boundaries, and the "sliced" regions maintain the same lattice structure and chemistry as in the bulk phase. It should be noted that slip lines (or slice marks) cannot be observed in the cross-section of bulk particles by SEM and are only visible by STEM bright-field (BF) on thinly sliced ​​TEM samples. While the internal lattice symmetry was well maintained after slip, repeated slip near the surface eventually evolved into microcracks, exposing new surfaces to the electrolyte (Figures 13A-13C).

[0166] To further induce lattice slippage, the cutoff voltage of the NMC76 single crystals was increased to 4.8 V (vs. Li+ / Li). "Slice marks" and microcracks were present in almost all charged single crystals (Figure 23A). Slight deformation of individual single crystals was clearly observed (Figure 18G), likely because the slippage of each layer appears to move equally in the same symmetrical direction. Surprisingly, after discharging back to 2.7 V, most of the single crystals returned to their original morphology, and the previously observed steps and microcracks disappeared (Figure 23B). The "slid" layers within the single crystals almost completely "slid" back to their original locations (Figure 18H) and fully recovered from the deformation (Figure 18G), although some "traces" were visible (labeled in Figure 18H). After extensive cycling within the "regular" electrochemical window of 2.7–4.4 V (vs. graphite), lattice slippage and microcracks were also observed within the crystal lattice in the charged state (Figure 18I). STEM analysis of NMC76 crystals (Figure 18J) shows that microcracks initiate from the inside of the crystal. In the discharged state of these cycled crystals (cutoff at 4.4 V), few ridges or cracks are visible on the crystals. Although not as visible as in the charged crystals, STEM still uncovered some "slice marks" on the discharged NMC76 single crystals (Figure 18K), which likely underwent a reversible back-and-forth "slip" process during 120 cycles. No microcracks were identified in these "self-healed" single crystals (Figure 18L), suggesting that lattice slip and cracking in parts of the crystals were still reversible after 120 cycles. With continued cycling, grain deformation became dominant. Dislocations were also observed near the tip region of the microcrack in the single crystals charged at 4.4 V (Figures 24A-24D). The accumulation of dislocations accompanied the propagation of the microcrack. Trace amounts of nanosized NiO-like rocksalt phase (Figures 25A-25E) were observed in the slip-exposed step regions of single-crystal NMC76 after cycling.

[0167] In situ AFM has been used to image crystal surfaces in real time in electrochemical cells. NMC76 single crystals of approximately 3 μm size were studied by in situ AFM during charging and discharging (Figures 26A-26F). Regions B and C in Figure 26A are enlarged in Figures 26B and 26C, respectively, to investigate the origin and evolution of "sliding steps" and microcracks under an electric field. The formation of nano-sized crack domains was observed during charging at an open circuit voltage (OCV) of 4.50 V (Li +Up to 4.20 V (vs. Li), planar slip was observed on the lateral side, whereas these domains disappeared during the discharge process (Figure 26B). Furthermore, planar slip was characterized by the appearance of wide crystalline steps on the lateral side due to the uneven movement between adjacent layers during polarization. Wider slip steps were observed on the lateral side, starting from the charging process at 4.20 V, leading to even wider (approximately 85 nm) slip steps at 4.50 V (Figure 26C). When the cell potential was reduced to 4.19 V, several wide slip steps decreased in width (Figures 27A-27B), indicating that the atomic layers returned to their original positions (Figure 26C). The average step width increased approximately linearly with increasing voltage (vs. Li+ / Li) during the charging process and then decreased linearly with decreasing voltage during the discharging process, with values ​​of 30.3 ± 0.7 nm at the open-circuit voltage (OCV), a maximum of 52.5 ± 2.5 nm at 4.50 V in the charged state, and a minimum of 38.4 ± 1.3 nm at 4.19 V during discharging. The average step width was calculated by dividing the total lateral width by the total number of steps (between 21 and 43 steps) at each voltage during in situ AFM monitoring. The error bars for the step width were estimated by averaging three measurements of the lateral width at each time point. This "first increase, then decrease" behavior of the average step width versus voltage indicates a reversible sliding process of these NMC crystals with each cycle. The reversible sliding process is further illustrated in Figure 26F. The observed lattice slip is a direct observation of "lattice-invariant shear (LIS)" (Radin et al., Nano Lett 2017, 17:7789-7795). LIS should be present in many layered electrode materials that undergo stacking-ordering-change phase transitions due to lithium concentration changes. LIS was also predicted to result in particle deformation and ridges on the particle surface, but these signals appear to be embedded in internal boundaries in spherical secondary polycrystalline materials. Micron-sized single crystals provide a clear platform for observing slip or LIS-induced mechanical degradation.

[0168] The electrochemical potential difference is the driving force for lithium ion diffusion and the formation of a lithium concentration gradient (Xiao, Sci 2019, 366:426-427). The stress is the Li ion diffusion gradient after the establishment of the lithium concentration gradient in the lattice. + This would occur during diffusion. An analytical cylindrical isotropic diffusion-induced stress model was applied to understand the stress evolution as lithium ions diffused radially within the particle. Analytical solutions for the dimensionless principal stresses along the axial, tangential, and radial directions within this cylindrical particle showed that it experienced compressive or tensile forces during cycling, reaching maximum stress when the Li+ concentration gradient was highest. Peak tensile stresses along the tangential and axial directions occurred near the surface at the onset of delithiation (or 0.01 T) (Figures 28A-28D). Conversely, peak tensile stresses in all three directions occurred at the center of the particle during lithiation (Figures 29A-29D). During charging (delithiation), tensile stresses along the axial and tangential directions localized at the surface of the single crystal, leading to microcracks that opened perpendicular to the (003) plane. Figures 30A-30C are SEM images showing microcracks propagating from the center to the surface, forming fractures.

[0169] The local stress also has shear components along other directions, which are numerically solved via COMSOL. The shear stress components along the yz direction, which can induce slip along the (003) plane, are shown in Figures 20D and 20E. Although the signs of the shear stress during lithiation and delithiation are opposite, this explains reversible slip, and their absolute values ​​are not the same because the elastic modulus is a function of Li concentration (Figures 31A–31D). Therefore, the slip motion should be largely, but not completely, reversible. The peak stresses in Figures 31C and 31D are not exactly the same, providing an explanation for the largely, but not completely, reversible slip in the single-crystalline NMC76 particles. Comparing the stress difference between Figures 31C and 31D suggests that anisotropic volume expansion (chemical strain) leads to increased shear stress. The peak shear stress is located inside the particle during lithiation and delithiation, suggesting that slip appears to be initiated within the particle. Irreversible slip can generate small damages that accumulate within the crack opening over long periods of cycling, analogous to fatigue crack nucleation, leading to the ridges and microcracks seen on the surface of single crystals after cycling.

[0170] A simple isotropic diffusion-induced stress model can be used to predict whether cracks can be stabilized within a single crystal. The strain energy within the grain increases during delithiation, T p Since it reaches a maximum value near the time scale of = 0.1 T (Figures 22A-22D), comparison with its fracture energy (2γ) is used as a criterion to evaluate the critical size of single crystal NMC76. If the accumulated strain energy is not large enough to cut the entire crystal, the crack will stabilize inside the grain.

number

[0171] where h is the height of the cylindrical particle, α is the concentration expansion coefficient, E is the Young's modulus of the unlithiated particle, E is the Young's modulus at a given lithium ion concentration, and C Ris the lithium ion concentration at the surface, C0 is the lithium ion concentration at the center, ν is Poisson's ratio, ξ represents the dimensionless stress (Figures 22A-D, 23A-D), and γ is the surface energy. A lower bound estimate of the critical size of the single crystal is predicted to be approximately 3.5 μm, below which cracks can be considered stable within the grain. Simulation results suggest that fractures along the (003) direction appear in the single crystal during cycling, but once formed, the cracks are stable and do not initiate the catastrophic reaction that produces a fracture zone that ultimately shatters the entire single crystal. Increasing the applied current density will result in a higher concentration gradient and higher stress generation. Increasing the cutoff voltage reduces the (C R This is equivalent to an increase in the charge density (C0). This implies higher stress generation and larger strain energy at high voltages, leading to greater slippage and cracking (Figures 7A-7C). The findings offer several strategies to stabilize single-crystalline Ni-rich NMCs, either by reducing the crystal size below 3.5 μm and absorbing the stored strain energy through structural symmetry modifications, or by simply optimizing the depth of charge without sacrificing the highly reversible capacity.

[0172] Figure 32 shows SEM images and in situ AFM images of a 20 μm single crystal NMC76. Selective formation of a passivation film on certain planes of NMC76 was found. Dissolution and recrystallization were observed on the surface of the single crystal. Parallel cracks along the

[0001] plane were directly acquired.

[0173] Example 2 Single crystal LiNi 0.76 M 0.14 C 0.1 Molten salt synthesis and characterization of O2(NMC76)

[0174] synthesis

[0175] The hydroxide precursor was prepared as follows: A 2M solution of transition metal (TM) sulfate salts (Ni:Mn:Co = 0.76:0.14:0.10 molar ratio) was prepared in 805 g of deionized water: Ni(SO4)2·6H2O, MnSO4·H2O, and Co(SO4)2·7H2O. Separately, 160 g of NaOH was dissolved in 500 g of H2O. Concentrated NH3·H2O (28%) was diluted with DI H2O in a 1:1 volume ratio. 1.5 L of DI H2O and 50 mL of concentrated NH3·H2O (28%) were added to the reactor as the starting solution. The reactor was heated to 50 °C. The TMSO4 solution, NaOH, and NH3·H2O were simultaneously pumped into the reactor. The pumping speeds were 3 mL / min and 1 mL / min for TMSO4 and NH3·H2O, respectively. The pH was controlled at 11.0–11.5. When all the TMSO4 solution was added to the reactor, the coprecipitated hydroxide was aged in the reactor for 30 h. The precipitate was filtered and washed with DI H2O. 200 g of DI H2O was used for washing 3–5 times for every 100 g of precipitate. After drying at 100 °C for 12 h, the hydroxide precursor Ni 0.76 Mn 0.14 Co 0.1 (OH)2 was obtained. Each batch produced approximately 150 g of hydroxide precursor.

[0176] The mixed hydroxide precursor was heated in air for 15 hours to decompose into the mixed oxides. Three different temperatures, 800, 900, and 1000 °C, were used to study the effect of temperature on the oxide particle size. The ramp rate was 5 °C / min. The morphologies of the untreated hydroxide precursor and the oxides obtained at 800, 900, and 1000 °C are shown in Figures 33A-33D, respectively. The optimal calcination temperature was found to be 800 °C, 900 °C, and 1000 °C. 0.76 Mn 0.14 Co 0.1 For (OH)2, it was found to be 900°C. Suitable temperatures range from 400 to 1000°C.

[0177] The oxide precursor was mixed with LiO in a molar ratio of 1:0.6 (TM:Li = 1:1.2), and the TM-Li mixture was then mixed with the sintering agent NaCl using a 1:1 weight ratio. The TM-Li-NaCl mixture was heated in a tubular furnace filled with flowing pure oxygen gas. The temperature was increased at a rate of 10°C / min. The mixture was maintained at 800°C for 10 hours, then at 900°C for an additional 5 hours. The product was cooled to room temperature. The sintered product (brick) was crushed in an agate mortar and then transferred to a beaker to wash off the NaCl. 30 g of water was added to each 15 g sample. The crushed sample was stirred in water for 2 minutes. After 2 minutes of sonication, the mixture was stirred for an additional 10 minutes to dissolve all residual NaCl. After filtration, the washed powder was heated in a vacuum at 80°C for 2 hours to remove the water. The dried samples were further sintered in pure oxygen at 580°C for 4 hours to restore some of the lost oxygen in the lattice.

[0178] A schematic of the process is shown in Figure 34, which also shows SEM images of the hydroxide precursor, oxide precursor, and single crystal product.

[0179] Agglomerated LiNi in the absence of NaCl as a sintering agent 0.76 Mn 0.14 Co 0.1 O2 (NMC76) particles form instead of single crystals. NaCl is an inexpensive sintering agent, lowering the cost of scaling up the synthesis. Figures 35A-35B are SEM images of NMC76 prepared without (Figure 35A) and with (Figure 35B) NaCl sintering agent. Without NaCl, the sample was polycrystalline (Figure 35A). With NaCl, the sample was single crystalline (Figure 35B).

[0180] Figure 36A shows the initial charge-discharge curves of NMC76 prepared with and without NaCl. Figure 36B shows the charge-discharge curves of a thick single-crystal NMC76 electrode (20 mg / cm) in a full cell using graphite as the anode, with a charge of 0.1 C and a discharge of 0.33 C between 2.7 and 4.2 V. 2) in a full cell using graphite as the anode between 2.7 and 4.3 V. 2 ) shows the cycle operation stability.

[0181] Additional samples were prepared to compare washing with water and other solvents. Samples washed with deionized water exhibited the best structural integrity and electrochemical properties. Figures 37A and 37B show the results of single-crystal LiNi after washing with water (37A) or formamide (FM) (37B). 0.7 Mn 0.22 Co 0.08 Figure 37C shows the initial charge-discharge curves of these two samples.

[0182] Figure 38 shows the structure of polycrystalline and single crystalline LiNi x Mn y Co 1-x-y 1 is a schematic diagram comparing the synthesis processes for O. When synthesis proceeds directly from hydroxide precursors, a polycrystalline product is formed. However, when synthesis proceeds via oxide precursors as described herein, single crystals are obtained.

[0183] Example 3 Single crystal LiNi 0.76 M 0.14 C 0.1 Flash sintering synthesis and characterization of O2(NMC76)

[0184] synthesis

[0185] The hydroxide precursor was prepared as described in Example 2. The hydroxide precursor and LiOH were mixed in a molar ratio of 1:1.2 and ground in an agate mortar. The mixture was transferred to a flash sintering furnace and heated to 800°C in a pure oxygen atmosphere at a ramp rate ranging from 2°C / min to 20°C / min. The temperature was maintained at 800°C for 10 hours. No sintering agent was used. Ramp rates of up to 50°C / sec or faster may be used.

[0186] 39A-39C show LiNi SiO2 films prepared at ramp rates of 2°C / min (39A), 10°C / min (39B), and 20°C / min (39C). 0.76 Mn 0.14 Co 0.1 Figure 39C shows SEM images of O2. As the heating rate increased, the particle size increased. Particle agglomeration also significantly decreased when the heating rate increased at 20°C, resulting in the formation of large single crystals (Figure 39C). However, at a heating rate of 2°C, the particles mostly agglomerated together to form secondary particles instead of individual single crystals.

[0187] The preheating process was found to facilitate flash sintering. Without being bound to a particular theory of operation, preheating reduces the mismatch in reaction rates. The hydroxide precursor and lithium hydroxide mixture were preheated at 480°C for 5 hours and then flash sintered. During this preheating process, mixed oxides (including Li oxide) were formed. NMC single crystals derived from the preheated precursor exhibited smaller grain sizes, which were also found to improve the electrochemical kinetics of the single crystal NMC. Figures 40A and 40B show LiNiNMC prepared without (40A) or with (40B) preheating prior to flash sintering at a ramp rate of 50°C / min. 0.76 Mn 0.14 Co 0.1 Figure 41 shows the charge-discharge curves of the single-crystal NMC samples prepared with and without the preheating process, demonstrating the obvious improvement in reversible capacity due to preheating.

[0188] Example 4 Single crystal LiNi 0.76 M 0.14 C 0.1 Solid-phase synthesis and characterization of O2(NMC76)

[0189] synthesis

[0190] The hydroxide precursor was prepared as follows: A 2M solution of transition metal (TM) sulfate salts (Ni:Mn:Co = 0.76:0.14:0.10 molar ratio) was prepared in 805 g of deionized water using Ni(SO4)2·6H2O, MnSO4·H2O, and Co(SO4)2·7H2O. Separately, 160 g of NaOH was dissolved in 500 g of H2O. Concentrated NH3·H2O (28%) was diluted with DI H2O in a 1:1 volume ratio. 3 L of DI H2O and 50 mL of concentrated NH3·H2O (28%) were added to the reactor as the starting solution. The reactor was heated to 50 °C. The TMSO4 solution, NaOH, and NH3·H2O were simultaneously pumped into the reactor. The pumping speeds were 3 mL / min and 1 mL / min for TMSO4 and NH3·H2O, respectively. The pH was controlled at 10.8. When all the TMSO4 solution was added to the reactor, the coprecipitated hydroxide was aged in the reactor for 30 hours. The precipitate was filtered and washed with DI H2O. 200 g of DI H2O was used for washing 3 to 5 times for every 100 g of precipitate. After drying at 100 °C for 12 hours, the hydroxide precursor Ni 0.76 Mn 0.14 Co 0.1 (OH)2 was obtained. Each batch produced approximately 150 g of hydroxide precursor.

[0191] Ni 0.76 Mn 0.14 Co 0.1 (OH)2 was heated to 900 °C for 15 h in an oxygen atmosphere at a ramp rate of 10 °C / min. The hydroxide precursor was converted to the oxide precursor in this step.

[0192] The oxide precursor was mixed with LiOH in a 1:1.07 Li:TM molar ratio and annealed at 500°C for 5 hours. The product was cooled at room temperature and crushed. A second anneal was performed at 800°C for 5 hours. After crushing again at room temperature, a third anneal was performed at 800°C for another 5 hours. The final product was passed through a 400 mesh sieve and collected.

[0193] Figures 42A and 42B show Ni 0.76 Mn 0.14 Co0.1 (OH)2 and Ni 0.76 Mn 0.14 Co 0.1 Figure 42C is an SEM image of a small particle of the O precursor. 0.76 Mn 0.14 Co 0.1 The use of small hydroxide precursor particles allows for the desired monocrystalline LiNiO2. 0.76 Mn 0.14 Co 0.1 Figure 43 shows the results of LiNi at 0.1 C between 2.7 and 4.4 V. 0.76 Mn 0.14 Co 0.1 1 shows a first charge / discharge curve of O2.

[0194] Single crystalline LiNi prepared by the molten salt method of Example 2 0.76 Mn 0.14 Co 0.1 O2-containing cathodes and single-crystalline LiNi prepared by solid-state method 0.76 Mn 0.14 Co 0.1 The cathodes containing O2 were compared. Figures 44A and 45A show the charge-discharge curves of these two cathodes. Single-crystalline LiNi prepared by the solid-state method 0.76 Mn 0.14 Co 0.1 O2 delivered approximately 184 mAh / g. Further development is expected to provide a reversible capacity of >200 mAh / g for NMC811 single crystals, which is competitive with commercially available polycrystalline NMC, but with significantly enhanced stability and safety. Figures 44B and 45B show the monocrystalline LiNi used in each cathode. 0.76 Mn 0.14 Co 0.1 44B are SEM images of O2. The individual crystal size in Figure 44B is approximately 3 μm. The individual crystal size in Figure 45B is approximately 1 μm.

[0195] Example 5 Single crystal LiNi 0.76 M 0.12 C 0.1 Mg 0.01 Ti 0.01Synthesis and characterization of O2

[0196] synthesis

[0197] The hydroxide precursor was prepared as follows: A 2M solution of transition metal (TM) sulfate salts (Ni:Mn:Co:Mg:Ti = 0.76:0.12:0.10:0.01:0.01 molar ratio) was prepared in 805 g of deionized water using Ni(SO4)2·6H2O, MnSO4·H2O, Co(SO4)2·7H2O, MgSO4, and TiOSO4. Separately, 160 g of NaOH was dissolved in 400 g of H2O. Concentrated NH3·H2O (28%) was diluted with DI H2O in a 1:1 volume ratio. 1.5 L of DI H2O and 50 mL of concentrated NH3·H2O (28%) were added to a reactor as a starting solution and preheated to 50 °C. The TMSO4 solution, NaOH, and NH3·H2O were simultaneously pumped into the reactor. The pumping rates were 3 mL / min and 1 mL / min for TMSO4 and NH3·H2O, respectively. The pH was controlled at 11.5. When all the TMSO4 solution was added to the reactor, the coprecipitated hydroxide was aged in the reactor for 30 hours at 50 °C. The precipitate was filtered and washed with DI H2O. 200 g of DI H2O was used for washing 3 to 5 times for every 100 g of precipitate. After drying at 100 °C for 12 hours, the Mg-Ti doped hydroxide precursor was obtained.

[0198] The doped hydroxide precursor was heated at 900°C for 15 hours in an oxygen atmosphere at a ramp rate of 10°C / min. The hydroxide precursor was converted to the oxide precursor in this step.

[0199] The oxide precursor was mixed with LiO (1:1.4 molar ratio). NaCl was then added to the NaCl:TM-Li mixture in a 1:1.1 weight ratio. The resulting mixture was then annealed at 800°C for 10 hours and then at 900°C for 5 hours. The product was cooled to room temperature. The sintered product was crushed in an agate mortar and then transferred to a beaker to wash off the NaCl. 30 g of water was added to each 15 g of sample. The crushed sample was stirred in water for 2 minutes. After 2 minutes of sonication, the mixture was stirred for an additional 10 minutes to dissolve all residual NaCl. After filtration, the washed powder was heated in vacuum at 80°C for 2 hours to remove the water. The dried sample was further sintered at 580°C in pure oxygen for 4 hours to restore some of the lost oxygen in the lattice and produce LiNi with 1 at% Mg and 1 at% Ti. 0.76 Mn 0.12 Co 0.1 Mg 0.01 Ti 0.01 O2 was provided.

[0200] The modified single crystals have a slightly reduced grain size of approximately 2 μm with a very dense structure (Figure 46). The modified single crystals have a reduced peak ratio of (003) / (104), suggesting increased cation disorder (Figure 47A). The peak shift to lower angles in the modified single crystals indicates an expansion of the crystal lattice compared to untreated single crystal NMC76 (47B).

[0201] Figures 48A and 48B show LiNi 0.76 Mn 0.14 Co 0.1 O2 and LiNi 0.76 Mn 0.12 Co 0.1 Mg 0.01 Ti 0.01The O2 charge-discharge curves (48A) and cycling stability (48B) are compared. The modified single-crystal NMC76 delivered slightly slower capacity, approximately 191 mAh / g, compared to untreated single-crystal NMC76 in full cells tested under relevant conditions—high mass loading and thick electrodes. The modified NMC76 exhibited improved cycling stability, with 81.8% capacity retention after 200 cycles compared to untreated NMC76, which had 72.0% capacity retention. As shown in Figure 49, no obvious cracks were observed in the modified NMC76 after cycling.

[0202] Example 6 Pouch cell design

[0203] Table 5 provides parameters for 2.2-2.3 Ah pouch cells using graphite / NMC811 and graphite / NMC955 chemistries. Coin cells with similar cathode loading, areal capacity, porosity, press density, N / P ratio, and the like will be used for initial testing. By replacing graphite with Si or Li metal, cell-level energy can be increased to 300-350 Wh / kg with a single crystal NMC cathode.

[0204] [Table 5]

[0205] In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be understood that the illustrated embodiments are merely preferred examples of the invention and should not be construed as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope and spirit of these claims. The present invention provides, for example, the following items. (Item 1) Validity period t 1 in an oxygen-containing atmosphere at temperature T S1 By NixMn yM z Co 1-x-y-z (OH) 2 wherein M represents one or more dopant metals, and x≧0.6, 0.01≦y<0.2, 0≦z≦0.05, and x+y+z≦1.0; combining said solid oxide precursor with a molar excess of a lithium compound; The solid oxide precursor and the lithium compound are heated to a temperature T S2 Validity period t 2 to form a first product; cooling the first product to ambient temperature; reducing the average particle size of the first product to between 0.1 μm and 10 μm; The first product having the reduced average particle size is heated to a temperature T S3 Validity period t 3 to form a second product; cooling the second product to ambient temperature; reducing the average particle size of the second product to between 0.1 μm and 10 μm; and The second product having the reduced average particle size is heated to a temperature T S4 Validity period t 4 to form a compound of formula LiNixMn y M z Co 1-x-y-z O 2 forming a single crystalline lithium nickel manganese cobalt oxide having By this, single crystalline lithium nickel manganese cobalt oxide can be prepared. A solid phase method comprising: (Item 2) (i) the solid hydroxide precursor has an average particle size of 0.5 μm to 2.5 μm, or (ii) the monocrystalline lithium nickel manganese cobalt oxide has an average particle size of 0.5 μm to 5 μm; or (iii) the dopant metal M comprises Mg, Ti, Al, Zn, Fe, Zr, Sn, Sc, V, Cr, Fe, Cu, Zu, Ga, Y, Zr, Nb, Mo, Ru, Ta, W, Ir, or any combination thereof; or (iv) Any combination of (i) to (iii) 2. The solid phase method according to Item 1, (Item 3) (i) The temperature T S1 is between 400°C and 1000°C, or (ii) the validity period t 1 is between 1 hour and 30 hours, or (iii) the temperature T S2 is between 400°C and 1000°C, or (iv) the validity period t 2 is between 1 hour and 30 hours, or (v) Said temperature T S3 is between 600°C and 1000°C, or (vi) the validity period t 3 is between 1 hour and 30 hours, or (vii) said temperature T S4 is between 600°C and 1000°C, or (viii) the validity period t 4 is between 1 hour and 30 hours, or (ix) Any combination of (i) to (viii) 2. The solid phase method according to Item 1, (Item 4) The solid hydroxide precursor is heated in the oxygen-containing atmosphere at the temperature T S1 In the validity period t 1 Further, heating over a period of (i) increasing the temperature to the temperature T S1 and heating the solid hydroxide precursor to the temperature T S1 In the validity period t 1 or (ii) heating the solid hydroxide precursor in pure oxygen or air, or (iii) both (i) and (ii). Item 2. The solid phase method according to item 1, comprising: (Item 5) (i) x = 0.65 to 0.9, y = 0.05 to 0.2, z = 0 to 0.02, and x + y + z = 0.7 to 0.95, or (ii) the lithium compound comprises lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium peroxide, or any combination thereof; or (iii) the solid oxide precursor and the lithium compound are combined in a molar ratio of Li:solid oxide precursor of 0.9:1 to 3:1; or (iv) any combination of (i), (ii), and (iii). 2. The solid phase method according to Item 1, (Item 6) preparing a 1.5-2.5M solution of metal salts in water, the metal salts comprising a nickel(II) salt, a manganese(II) salt, a cobalt(II) salt, and optionally one or more dopant metal salts, wherein the molar fraction x of the nickel(II) salt in the solution is ≧0.6, the molar fraction y of the manganese(II) salt is 0.01≦y<0.2, the molar fraction z of the one or more dopant metal salts is 0≦z≦0.05, and the molar fraction of the cobalt(II) salt is 1−xyz, where x+y+z≦1.0; The solution containing metal salts in water is treated with aqueous NH 3 and with aqueous NaOH or KOH to provide a combination solution having a pH of 10.5-12 and a combined metal salt concentration of 0.1M to 3M; aging the combined solution for 5 to 48 hours at a temperature of 25° C. to 80° C. to co-precipitate nickel, manganese, and cobalt hydroxides to provide solid hydroxide precursors; and drying the solid hydroxide precursor, wherein the solid hydroxide precursor comprises particles having an average particle size of 0.5 μm to 2.5 μm; 6. The solid phase method of any one of items 1 to 5, further comprising preparing the solid hydroxide precursor by: (Item 7) Validity period t 1 in an oxygen-containing atmosphere at temperature T M1 By NixMn y M z Co 1-x-y-z (OH) 2 wherein M represents one or more dopant metals, and x≧0.6, 0.01≦y<0.2, 0≦z≦0.05, and x+y+z≦1.0; combining said solid oxide precursor with a molar excess of a lithium compound and a sintering agent to form a mixture; The mixture is heated in an oxygen-containing atmosphere at a temperature T M2 In period t 2 heating over a period of The temperature T M3 >Temperature T M2 At temperature T M3 and the mixture is heated to the temperature T M3 In period t 3 heating for a period of time to form the first product and the sintering agent; separating the sintering agent from the first product; drying the first product; and The first product is heated to a temperature T M4 Validity period t 4 to form a compound of formula LiNixMn y M z Co 1-x-y-z O 2 forming a single crystalline lithium nickel manganese cobalt oxide having 1. A molten salt process comprising preparing a single crystalline lithium nickel manganese cobalt oxide by: (Item 8) (i) the solid hydroxide precursor has an average particle size of 0.5 μm to 10 μm, or (ii) the single crystalline lithium nickel manganese cobalt oxide has a particle size of 0.5 μm to 5 μm; having an average particle size of μm, or (iii) the dopant metal M comprises Mg, Ti, Al, Zn, Fe, Zr, Sn, Sc, V, Cr, Fe, Cu, Zu, Ga, Y, Zr, Nb, Mo, Ru, Ta, W, Ir, or any combination thereof; or (iv) Any combination of (i) to (iii) 8. The molten salt method according to Item 7, wherein (Item 9) (i) The temperature T M1 is between 400°C and 1000°C, or (ii) the validity period t 1 is between 1 hour and 30 hours, or (iii) the temperature T M2 is between 400°C and 1000°C, or (iv) said period t 2 is between 1 hour and 30 hours, or (v) Said temperature T M3 is between 600°C and 1000°C, or (vi) said period t 3 is between 1 hour and 30 hours, or (vii) said temperature T M4 is between 500°C and 1000°C, or (viii) the validity period t 4 is between 1 hour and 30 hours, or (ix) Any combination of (i) to (viii) 8. The molten salt method according to Item 7, wherein (Item 10) (i) heating the solid hydroxide precursor to a temperature T M1 In the validity period t 1 Heating over a period of time raises the temperature to the temperature T M1 at a rate of 1 to 300°C / min to raise the temperature of the solid hydroxide precursor to the temperature T M1 In the validity period t 1 or (ii) subjecting the mixture to an oxygen-containing atmosphere at the temperature T M2 In the period t 2 heating for a period of time includes heating the mixture in air or pure oxygen; or (iii) subjecting the mixture to an oxygen-containing atmosphere at the temperature T M2 In the period t 2 heating the temperature over a period of time further comprises heating the temperature over a period of time ... M2 at a rate of 1 to 300°C / min, and the mixture is heated to the temperature T M2 In the period t 2 or (iv) heating the first product in an oxygen-containing atmosphere at the temperature T M4 In the validity period t 4 heating for a period of time includes heating the first product in pure oxygen; or (v) Any combination of (i) to (iv) 8. The molten salt method according to Item 7, wherein (Item 11) (i) x = 0.65 to 0.9, y = 0.05 to 0.2, z = 0 to 0.02, and x + y + z = 0.7 to 0.95, or (ii) the lithium compound comprises lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium peroxide, or any combination thereof; or (iii) the solid oxide precursor and the lithium compound are combined in a molar ratio of Li:solid oxide precursor of 1:1 to 5:1; or (iv) the sintering agent comprises NaCl; or (v) the weight ratio of the sintering agent to the combination of the solid oxide precursor and lithium compound is from 0.2:1 to 1:0.2; or (vi) Any combination of (i) to (v) 8. The molten salt method according to Item 7, wherein (Item 12) preparing a 1.5-2.5M solution of metal salts in water, the metal salts comprising a nickel(II) salt, a manganese(II) salt, a cobalt(II) salt, and optionally one or more dopant metal salts, wherein the molar fraction x of the nickel(II) salt in the solution is ≧0.6, the molar fraction y of the manganese(II) salt is 0.01≦y<0.2, the molar fraction z of the one or more dopant metal salts is 0≦z≦0.05, and the molar fraction of the cobalt(II) salt is 1−xyz, where x+y+z≦1.0; thing, The solution containing metal salts in water is treated with aqueous NH 3 and with aqueous NaOH or KOH to provide a combination solution having a pH of 10.5-12 and a combined metal salt concentration of 0.1M to 3M; aging the combined solution for 5 to 48 hours at a temperature of 25° C. to 80° C. to co-precipitate nickel, manganese, and cobalt hydroxides to provide the solid hydroxide precursor; and drying the solid hydroxide precursor, wherein the solid hydroxide precursor comprises particles having an average particle size of 0.5 to 10 μm; 12. The molten salt method of any one of items 7 to 11, further comprising preparing the solid hydroxide precursor by: (Item 13) NixMn y M z Co1-x-y-z (OH) 2 with a molar excess of a lithium compound to form a hydroxide mixture, wherein M represents one or more dopant metals, and x≧0.6, 0.01≦y<0.2, 0≦z≦0.05, and x+y+z≦1.0; The hydroxide mixture is heated in an oxygen-containing atmosphere at a temperature T F1 Validity period t 1 to form an oxide mixture comprising oxides of nickel, manganese, cobalt, lithium, and, if present, said one or more dopant metals, or combinations thereof; The temperature is increased to a temperature T F2 and The oxide mixture is heated in an oxygen-containing atmosphere at the temperature T F2 Validity period t 2 to form a compound of formula LiNixMn y M z Co 1-x-y-z O 2 forming a single crystalline lithium nickel manganese cobalt oxide having By this, single crystalline lithium nickel manganese cobalt oxide can be prepared. A flash sintering method comprising: (Item 14) (i) the solid hydroxide precursor has an average particle size of 0.5 μm to 10 μm, or (ii) the monocrystalline lithium nickel manganese cobalt oxide has an average particle size of 0.5 μm to 5 μm; or (iii) the dopant metal M comprises Mg, Ti, Al, Zn, Fe, Zr, Sn, Sc, V, Cr, Fe, Cu, Zu, Ga, Y, Zr, Nb, Mo, Ru, Ta, W, Ir, or any combination thereof; or (iv) Any combination of (i) to (iii) Item 14. The flash sintering method according to item 13, wherein (Item 15) (i) The temperature T F1 is between 400°C and 600°C, or (ii) the validity period t 1 is between 1 hour and 30 hours, or (iii) the temperature T F2 is between 600°C and 1000°C, or (iv) the validity period t 2 is between 1 hour and 30 hours, or (v) Any combination of (i) to (iv) Item 14. The flash sintering method according to item 13, wherein (Item 16) (i) x = 0.65 to 0.9, y = 0.05 to 0.2, z = 0 to 0.02, and x + y + z = 0.7 to 0.95, or (ii) the lithium compound comprises lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium peroxide, or any combination thereof; or (iii) the solid hydroxide precursor and the lithium compound are combined in a molar ratio of Li:solid hydroxide precursor of 0.9:1 to 3:1; or (iv) any combination of (i), (ii), and (iii). Item 14. The flash sintering method according to item 13, wherein (Item 17) preparing a 1.5M to 2.5M solution of metal salts in water, the metal salts comprising a nickel(II) salt, a manganese(II) salt, a cobalt(II) salt, and optionally one or more dopant metal salts, wherein the molar fraction x of the nickel(II) salt in the solution is ≧0.6, the molar fraction y of the manganese(II) salt is 0.01≦y<0.2, the molar fraction z of the one or more dopant metal salts is 0≦z≦0.05, and the molar fraction of the cobalt(II) salt is 1−xyz, where x+y+z≦1.0; The solution containing metal salts in water is treated with aqueous NH 3 and with aqueous NaOH or KOH to provide a combination solution having a pH of 10.5-12 and a combined metal salt concentration of 0.1M to 3M; aging the combined solution for 5 to 48 hours at a temperature of 25° C. to 80° C. to co-precipitate nickel, manganese, and cobalt hydroxides to provide the solid hydroxide precursor; and drying the solid hydroxide precursor hydroxide, wherein the solid hydroxide precursor comprises particles having an average particle size of 0.5 μm to 10 μm; 17. The flash sintering method of any one of items 13 to 16, further comprising preparing the solid hydroxide precursor by: (Item 18) Single crystalline LiNixMn y M z Co 1-x-y-z O 2 A cathode comprising: M represents one or more dopant metals; x≧0.6, 0.01≦y<0.2, z≦0.05, and x+y+z≦1.0, y M z Co 1-x-y-z O 2 The cathode has an average particle size of 0.5 μm to 5 μm. (Item 19) x=0.65~0.9、 y=0.05~0.2、 z=0~0.02, and x+y+z=0.7~0.95 Item 19. The cathode according to item 18, wherein (Item 20) Item 18 or 19, the cathode according to item 18 or 19, anode, electrolytes, and a separator positioned between the anode and the cathode Including the battery system.

Claims

1. Validity period t １ in an oxygen-containing atmosphere at a temperature T Ｓ１ NixMn ｙ M ｚ Co １－ｘ－ｙ－ｚ (OH) ２ wherein M represents one or more dopant metals, and x≧0.6, 0.01≦y≦0.2, 0≦z≦0.05, and x+y+z≦1.0; combining said solid oxide precursor with a molar excess of a lithium compound; The solid oxide precursor and the lithium compound are heated to a temperature T Ｓ２ and validity period t ２ to form a first product; cooling the first product to ambient temperature; reducing the average particle size of said first product to between 0.1 μm and 10 μm; The first product having the reduced average particle size is heated to a temperature T Ｓ３ and validity period t ３ to form a second product; cooling the second product to ambient temperature; reducing the average particle size of the second product to between 0.1 μm and 10 μm; and The second product having the reduced average particle size is heated to a temperature T Ｓ４ and validity period t ４ to form a compound of the formula LiNixMn ｙ M ｚ Co １－ｘ－ｙ－ｚ O ２ forming a single crystalline lithium nickel manganese cobalt oxide having By this, single crystalline lithium nickel manganese cobalt oxide can be prepared. A solid phase method comprising:

2. (i) the solid hydroxide precursor has an average particle size of 0.5 μm to 2.5 μm; or (ii) the monocrystalline lithium nickel manganese cobalt oxide has an average particle size of 0.5 μm to 5 μm; or (iii) the dopant metal M comprises Mg, Ti, Al, Zn, Fe, Zr, Sn, Sc, V, Cr, Fe, Cu, Zu, Ga, Y, Zr, Nb, Mo, Ru, Ta, W, Ir, or any combination thereof; or (iv) Any combination of (i) to (iii) The solid phase method according to claim 1, wherein

3. (i) The temperature T Ｓ１ is between 400°C and 1000°C, or (ii) the validity period t １ is between 1 hour and 30 hours, or (iii) the temperature T Ｓ２ is between 400°C and 1000°C, or (iv) the validity period t ２ is between 1 hour and 30 hours, or (v) the temperature T Ｓ３ is between 600°C and 1000°C, or (vi) the validity period t ３ is between 1 hour and 30 hours, or (vii) the temperature T Ｓ４ is between 600°C and 1000°C, or (viii) the validity period t ４ is between 1 hour and 30 hours, or (ix) Any combination of (i) to (viii) The solid phase method according to claim 1, wherein

4. The solid hydroxide precursor is heated in the oxygen-containing atmosphere at the temperature T Ｓ１ and the validity period t １ Further, heating over a period of (i) increasing the temperature to the temperature T Ｓ１ and heating the solid hydroxide precursor to the temperature T Ｓ１ and the validity period t １ or (ii) heating the solid hydroxide precursor in pure oxygen or air, or (iii) both (i) and (ii).

2. The solid phase method of claim 1, comprising:

5. (i) x = 0.65 to 0.9, y = 0.05 to 0.2, z = 0 to 0.02, and x + y + z = 0.7 to 0.95, or (ii) the lithium compound comprises lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium peroxide, or any combination thereof; or (iii) the solid oxide precursor and the lithium compound are combined in a molar ratio of Li:solid oxide precursor of 0.9:1 to 3:1; or (iv) any combination of (i), (ii), and (iii). The solid phase method according to claim 1, wherein

6. preparing a 1.5-2.5M solution of metal salts in water, the metal salts comprising a nickel(II) salt, a manganese(II) salt, a cobalt(II) salt, and optionally one or more dopant metal salts, wherein the mole fraction x of the nickel(II) salt in the solution is ≧0.6, the mole fraction y of the manganese(II) salt is 0.01≦y<0.2, the mole fraction z of the one or more dopant metal salts is 0≦z≦0.05, and the mole fraction of the cobalt(II) salt is 1−x−y−z, where x+y+z≦1.0; The solution containing metal salts in water is treated with aqueous NH ３ and aqueous NaOH or KOH to provide a combination solution having a pH of 10.5-12 and a combined metal salt concentration of 0.1 M to 3 M; aging the combined solution for 5 to 48 hours at a temperature of 25° C. to 80° C. to co-precipitate nickel, manganese, and cobalt hydroxides to provide a solid hydroxide precursor; and drying the solid hydroxide precursor, wherein the solid hydroxide precursor comprises particles having an average particle size of 0.5 μm to 2.5 μm; 6. The solid state method of claim 1, further comprising preparing the solid hydroxide precursor by:

7. Validity period t １ in an oxygen-containing atmosphere at a temperature T Ｍ１ NixMn ｙ M ｚ Co １－ｘ－ｙ－ｚ (OH) ２ wherein M represents one or more dopant metals, and x≧0.6, 0.01≦y≦0.2, 0≦z≦0.05, and x+y+z≦1.0; combining said solid oxide precursor with a molar excess of a lithium compound and a sintering agent to form a mixture; The mixture is heated in an oxygen-containing atmosphere at a temperature T Ｍ２ In period t ２ heating over a period of The temperature is defined as temperature T Ｍ３ >Temperature T Ｍ２ The temperature T Ｍ３ and the mixture is heated to the temperature T Ｍ３ In period t ３ to form a first product and said sintering agent; separating the sintering agent from the first product; drying the first product; and The first product is heated to a temperature T Ｍ４ and validity period t ４ to form a compound of the formula LiNixMn ｙ M ｚ Co １－ｘ－ｙ－ｚ O ２ forming a single crystalline lithium nickel manganese cobalt oxide having 1. A molten salt process comprising preparing a single crystalline lithium nickel manganese cobalt oxide by:

8. (i) the solid hydroxide precursor has an average particle size of 0.5 μm to 10 μm; or (ii) the single crystalline lithium nickel manganese cobalt oxide has a particle size of 0.5 μm to 5 μm; μm average particle size, or (iii) the dopant metal M comprises Mg, Ti, Al, Zn, Fe, Zr, Sn, Sc, V, Cr, Fe, Cu, Zu, Ga, Y, Zr, Nb, Mo, Ru, Ta, W, Ir, or any combination thereof; or (iv) Any combination of (i) to (iii) 8. The molten salt method according to claim 7, wherein

9. (i) The temperature T Ｍ１ is between 400°C and 1000°C, or (ii) the validity period t １ is between 1 hour and 30 hours, or (iii) the temperature T Ｍ２ is between 400°C and 1000°C, or (iv) the period t ２ is between 1 hour and 30 hours, or (v) the temperature T Ｍ３ is between 600°C and 1000°C, or (vi) said period t ３ is between 1 hour and 30 hours, or (vii) the temperature T Ｍ４ is between 500°C and 1000°C, or (viii) the validity period t ４ is between 1 hour and 30 hours, or (ix) Any combination of (i) to (viii) 8. The molten salt method according to claim 7, wherein

10. (i) heating the solid hydroxide precursor to a temperature T Ｍ１ and the validity period t １ heating the temperature over a period of time to the temperature T Ｍ１ at a rate of 1 to 300°C / min to raise the temperature of the solid hydroxide precursor to T Ｍ１ and the validity period t １ or (ii) subjecting the mixture to an oxygen-containing atmosphere at the temperature T Ｍ２ In the period t ２ heating for a period of time includes heating the mixture in air or pure oxygen; or (iii) heating the mixture in an oxygen-containing atmosphere at the temperature T Ｍ２ In the period t ２ heating the temperature over a period of time further comprises heating the temperature over a period of time ... Ｍ２ at a rate of 1 to 300°C / min, and the mixture is heated to the temperature T Ｍ２ In the period t ２ or (iv) heating the first product in an oxygen-containing atmosphere at the temperature T Ｍ４ and the validity period t ４ heating for a period of time includes heating the first product in pure oxygen; or (v) Any combination of (i) to (iv).

8. The molten salt method according to claim 7, wherein

11. (i) x = 0.65 to 0.9, y = 0.05 to 0.2, z = 0 to 0.02, and x + y + z = 0.7 to 0.95, or (ii) the lithium compound comprises lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium peroxide, or any combination thereof; or (iii) the solid oxide precursor and the lithium compound are combined in a molar ratio of Li:solid oxide precursor of 1:1 to 5:1; or (iv) the sintering agent comprises NaCl, or (v) the weight ratio of the sintering agent to the combination of the solid oxide precursor and lithium compound is from 0.2:1 to 1:0.2; or (vi) Any combination of (i) to (v).

8. The molten salt method according to claim 7, wherein

12. preparing a 1.5-2.5M solution of metal salts in water, the metal salts comprising a nickel(II) salt, a manganese(II) salt, a cobalt(II) salt, and optionally one or more dopant metal salts, wherein the mole fraction x of the nickel(II) salt in the solution is ≧0.6, the mole fraction y of the manganese(II) salt is 0.01≦y<0.2, the mole fraction z of the one or more dopant metal salts is 0≦z≦0.05, and the mole fraction of the cobalt(II) salt is 1−x−y−z, where x+y+z≦1.0; thing, The solution containing metal salts in water is treated with aqueous NH ３ and aqueous NaOH or KOH to provide a combination solution having a pH of 10.5-12 and a combined metal salt concentration of 0.1 M to 3 M; aging the combined solution for 5 to 48 hours at a temperature of 25° C. to 80° C. to co-precipitate nickel, manganese, and cobalt hydroxides to provide the solid hydroxide precursor; and drying the solid hydroxide precursor, wherein the solid hydroxide precursor comprises particles having an average particle size of 0.5 to 10 μm; 12. The molten salt method of any one of claims 7 to 11, further comprising preparing the solid hydroxide precursor by:

13. NixMn ｙ M ｚ Co １－ｘ－ｙ－ｚ (OH) ２ with a molar excess of a lithium compound to form a hydroxide mixture, wherein M represents one or more dopant metals, and x≧0.6, 0.01≦y≦0.2, 0≦z≦0.05, and x+y+z≦1.0; The hydroxide mixture is heated in an oxygen-containing atmosphere at a temperature T Ｆ１ and validity period t １ to form an oxide mixture comprising oxides of nickel, manganese, cobalt, lithium, and, if present, said one or more dopant metals, or combinations thereof; The temperature is increased to a temperature T Ｆ２ and The oxide mixture is heated in an oxygen-containing atmosphere at the temperature T Ｆ２ and validity period t ２ to form a compound of the formula LiNixMn ｙ M ｚ Co １－ｘ－ｙ－ｚ O ２ forming a single crystalline lithium nickel manganese cobalt oxide having By this, single crystalline lithium nickel manganese cobalt oxide can be prepared. A flash sintering method comprising:

14. (i) the solid hydroxide precursor has an average particle size of 0.5 μm to 10 μm; or (ii) the monocrystalline lithium nickel manganese cobalt oxide has an average particle size of 0.5 μm to 5 μm; or (iii) the dopant metal M comprises Mg, Ti, Al, Zn, Fe, Zr, Sn, Sc, V, Cr, Fe, Cu, Zu, Ga, Y, Zr, Nb, Mo, Ru, Ta, W, Ir, or any combination thereof; or (iv) Any combination of (i) to (iii) 14. The flash sintering method of claim 13, wherein:

15. (i) The temperature T Ｆ１ is between 400°C and 600°C, or (ii) the validity period t １ is between 1 hour and 30 hours, or (iii) the temperature T Ｆ２ is between 600°C and 1000°C, or (iv) the validity period t ２ is between 1 hour and 30 hours, or (v) Any combination of (i) to (iv).

14. The flash sintering method of claim 13, wherein:

16. (i) x = 0.65 to 0.9, y = 0.05 to 0.2, z = 0 to 0.02, and x + y + z = 0.7 to 0.95, or (ii) the lithium compound comprises lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium peroxide, or any combination thereof; or (iii) the solid hydroxide precursor and the lithium compound are combined in a molar ratio of Li:solid hydroxide precursor of 0.9:1 to 3:1; or (iv) any combination of (i), (ii), and (iii).

14. The flash sintering method of claim 13, wherein:

17. preparing a 1.5M to 2.5M solution of metal salts in water, the metal salts comprising a nickel(II) salt, a manganese(II) salt, a cobalt(II) salt, and optionally one or more dopant metal salts, wherein the mole fraction x of the nickel(II) salt in the solution is ≧0.6, the mole fraction y of the manganese(II) salt is 0.01≦y<0.2, the mole fraction z of the one or more dopant metal salts is 0≦z≦0.05, and the mole fraction of the cobalt(II) salt is 1−x−y−z, where x+y+z≦1.0; The solution containing metal salts in water is treated with aqueous NH ３ and aqueous NaOH or KOH to provide a combination solution having a pH of 10.5-12 and a combined metal salt concentration of 0.1 M to 3 M; aging the combined solution for 5 to 48 hours at a temperature of 25° C. to 80° C. to co-precipitate nickel, manganese, and cobalt hydroxides to provide the solid hydroxide precursor; and drying the solid hydroxide precursor hydroxide, wherein the solid hydroxide precursor comprises particles having an average particle size of 0.5 μm to 10 μm; 17. The flash sintering method of any one of claims 13 to 16, further comprising preparing the solid hydroxide precursor by:

Images