Polycrystalline metal oxides with enriched grain boundaries

Abstract

Electrochemically active secondary particles are provided that provide excellent capacity and improved cycle life. The particles are characterized by selectively enriched grain boundaries, wherein the grain boundaries are enriched in Al. The Al enrichment reduces impedance growth during cycling, thereby improving capacity and cycle life. Also provided are methods of forming electrochemically active materials, as well as electrodes and electrochemical cells using the secondary particles.

Description

[0001] This application is a divisional application of patent application number 201980094065.8, which was filed on October 23, 2019, and is entitled "Polycrystalline metal oxide with enriched grain boundaries".

[0002] Cross-reference to related applications

[0003] This application depends on and claims priority to the following applications: U.S. Patent Application No. 16 / 250,615, filed January 17, 2019; U.S. Patent Application No. 16 / 250,762, filed January 17, 2019; and U.S. Patent Application No. 16 / 250,622, filed January 17, 2019, the entire contents of which are hereby incorporated herein by reference. field

[0004] Polycrystalline metal oxide particles, their manufacturing methods, and electrochemical cells or battery packs containing them are disclosed. background

[0005] Layered lithium nickel oxide (LiNiO2)-based materials have been developed for lithium-ion battery cathodes due to their generally lower cost, higher capacity, and higher rate capability compared to the previously dominant LiCoO2 cathode materials. However, pure LiNiO2 materials exhibit poor electrochemical stability and cycling performance. To address this, non-nickel elemental additives have been formulated into LiNiO2 to stabilize the structure and improve cycling performance, but typically at the expense of discharge capacity. With increasing demands for energy density, research has focused on optimizing and reducing these non-nickel additives to achieve high-Ni capacity while maintaining cycling performance.

[0006] Therefore, there is a need for new materials that address the demand for high-capacity materials with long cycle lives. The materials and methods for forming these materials presented in this paper address this need by maintaining high capacity over a long cycle life. Overview

[0007] The following overview is provided to facilitate understanding of some of the innovative features unique to this disclosure and is not intended to be an exhaustive description. A full understanding of the various aspects of this disclosure can be obtained by considering the entire specification, claims, drawings, and abstract as a whole.

[0008] Secondary particles were provided and found to exhibit significantly reduced impedance growth when used as cathode electrochemical active materials in lithium-ion secondary cells. Improved impedance properties were discovered by selectively enriching the grain boundaries between microcrystals in the secondary particles with a combination of Co and Al, and these improved impedance properties were achieved in many electrochemically active materials with varying compositions.

[0009] Therefore, particles are provided comprising: a plurality of microcrystals containing a first composition of lithium, nickel, and oxygen; and layers between adjacent microcrystals of the plurality of microcrystals. -Grain boundaries of a second composition comprising a NaFeO2-type structure, a cubic structure, a spinel structure, or a combination thereof; wherein the aluminum concentration at the grain boundaries is greater than the aluminum concentration in the crystallites, and wherein the cobalt concentration at the grain boundaries is greater than the cobalt concentration in the crystallites. In some aspects, Al enrichment at the grain boundaries is found to be non-uniform, incomplete, or unrealized, but Al grain boundary enrichment, optionally with Co and Al grain boundary enrichment, can be achieved using the manufacturing methods provided herein. Thus, in some aspects, Al is substantially uniformly distributed among the numerous particles.

[0010] In some aspects, the Al content at the grain boundary is 0.01 at% to 10 at% of the total transition metal content in the remainder of the secondary particles. Optionally, the Co content at the grain boundary is 0 at% to 10 at% of the total transition metal content in the remainder of the secondary particles, or optionally 0.1 at% to 10 at%. Optionally, the Al content at the grain boundary is 0.01 at% to 5 at% of the total transition metal content in the remainder of the secondary particles, and the Co content at the grain boundary is 0.01 at% to 10 at%. Optionally, the aluminum content at the grain boundary is equal to or less than the Co content at the grain boundary.

[0011] In some respects, the numerous microcrystals have α-NaFeO2 type layered structure, cubic structure, spinel structure, or a combination thereof.

[0012] Optionally, the first composition, the second composition, or both of any of the above or other aspects are made by Li 1+ x MO 2+y Defining, among which

[0013] -0.1 ≤ x ≤ 0.3,

[0014] -0.3 ≤ y ≤ 0.3 and

[0015] M comprises 10 atomic percent or more of nickel. Optionally, M comprises 75 at% or more of nickel. Optionally, the entire grain boundary comprises about 2 at% to about 99 at% of cobalt and about 2 at% to about 99 at% of aluminum. Optionally, in the first composition, the second composition, or both, M further comprises an additional metal, wherein the additional metal is present in an amount of about 1 at% to about 90 at%; the additional metal is selected from Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Nb, Ta, Cr, Fe, Mo, W, Hf, B, and any combination thereof, wherein said one or more additional elements are optionally located in the Li layer, the M layer, or both.

[0016] Optionally, the microcrystals contain cobalt, having a cobalt concentration in the range of 1 at% to about 50 at%, optionally in the range of 1 at% to about 15 at%. In some aspects, the microcrystals contain Mn present in an amount of about 1 at% to about 60 at%, and the grain boundaries contain Mn present in an amount of about 1 at% to about 60 at%. In other aspects, the grain boundaries contain Ni, Co, and Al. Optionally, the Ni concentration at the grain boundaries is greater than 75 at%.

[0017] Some aspects of the particles include an outer coating on the particle surface, the outer coating comprising: an oxide of one or more elements selected from Al, Zr, Y, Co, Ni, Mg and Li; a fluoride comprising one or more elements selected from Al, Zr and Li; a carbonate comprising one or more elements selected from Al, Co, Ni, Mn and Li; or a phosphate or sulfate comprising one or more elements selected from Al and Li.

[0018] In other aspects provided herein, an electrochemically active polycrystalline secondary particle is provided, comprising: a plurality of microcrystals, said plurality of microcrystals comprising Li 1+x MO 2+y The first composition is defined as follows: -0.1 ≤ x ≤ 0.3, -0.3 ≤ y ≤ 0.3, and M contains greater than or equal to 80 atomic percent nickel; and grain boundaries between adjacent crystallites of the plurality of microcrystals and comprising a second composition, the second composition optionally being composed of Li where -0.1 ≤ x ≤ 0.3, -0.3 ≤ y ≤ 0.3. 1+ x MO 2+yThe structure is defined and optionally has an α-NaFeO2 type layered structure, cubic structure, or a combination thereof, wherein the aluminum concentration at the grain boundaries is greater than the aluminum concentration in the microcrystals, and optionally the cobalt concentration at the grain boundaries is greater than the cobalt concentration in the microcrystals, and wherein aluminum is substantially uniformly distributed in the grain boundaries. Optionally, the cobalt concentration in the microcrystals is about 0 to about 17 atomic% of M in the first composition, and the cobalt amount at the grain boundaries is about 0 to about 10 atomic% of M in the microcrystals. Optionally, M further comprises one or more elements selected from Na, K, Al, Mg, Co, Mn, Ca, Sr, Ba, Zn, Ti, Zr, Y, Cr, Mo, Fe, V, Si, Ga, and B, said one or more elements being located in the Li layer, M layer, or both of the microcrystals. Optionally, M comprises greater than or equal to 90% nickel atoms.

[0019] An electrochemical cell is also provided. This electrochemical cell includes a cathode active material. The cathode active material optionally includes any particles provided above or elsewhere herein. The electrochemical cell is optionally characterized in that the impedance increase at 4.2V is less than 100% for more than 100 cycles at 45°C, and optionally less than 100% for more than 200 cycles at 45°C.

[0020] An electrochemical battery, optionally a secondary battery, optionally a lithium-ion secondary battery, is also provided, comprising an anode, an electrolyte, and a cathode, wherein the cathode comprises an electrochemically active cathode active material containing a plurality of particles, the plurality of particles comprising: a plurality of microcrystals, each comprising a first composition containing lithium, nickel, and oxygen; and layers between adjacent microcrystals. The grain boundaries of a second composition having a NaFeO2-type structure, a cubic structure, a spinel structure, or a combination thereof; wherein the electrochemically active cathode material has an initial discharge capacity of 180 mAh / g or greater; and wherein the electrochemical cell has an impedance increase of less than 50% at 4.2V for more than 100 cycles at 45°C. The electrochemical cell is optionally characterized in that the impedance increase at a 50% charge state is less than 50% at 45°C for more than 200 cycles, and optionally less than 120% at 45°C for more than 200 cycles. In some aspects, the electrochemical cell is characterized in that the impedance increase at a 50% charge state is less than 50% at 45°C for more than 200 cycles. Optionally, each microcrystal comprises lithium, nickel, cobalt, and oxygen. Optionally, the microcrystals comprise Al, Mn, Mg, or a combination thereof.

[0021] Optionally, the first composition, the second composition, or both of any of the above or other aspects are made by Li 1+ x MO 2+y Defining, among which

[0022] -0.95≤ x ≤ 0.3,

[0023] -0.3 ≤ y ≤ 0.3 and

[0024] M comprises 80 atomic percent or more nickel. Optionally, M in the first composition comprises 75 at% or more atomic percent nickel relative to the total transition metals in the first composition. In the second composition, M optionally comprises less than or equal to 90 at% relative to the total transition metals in the second composition. Optionally, the entire grain boundary comprises about 2 at% to about 99 at% of cobalt and about 2 at% to about 99 at% of aluminum. Optionally, in the first composition, the second composition, or both, M further comprises additional metal, wherein the additional metal is present in an amount of about 1 at% to about 90 at% relative to the total metals in the respective first or second composition; the additional metal is selected from Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Nb, Ta, Cr, Fe, Mo, W, Hf, B, and any combination thereof, wherein said one or more additional elements are optionally located in the Li layer, the M layer, or both.

[0025] Optionally, the microcrystals comprise cobalt, having a cobalt concentration in the range of 1 at% to about 50 at% relative to the total transition metals in the first composition, optionally in the range of 1 at% to about 15 at%. In some aspects, the microcrystals comprise Mn present in an amount of about 1 at% to about 60 at%, and the grain boundaries comprise Mn present in an amount of about 1 at% to about 60 at%. In other aspects, the grain boundaries comprise Ni, Co, and Al. Optionally, the Ni concentration in the grain boundaries is greater than 75 at%. Brief description of the attached diagram

[0026] The aspects illustrated in the accompanying drawings are illustrative and exemplary and are not intended to limit the subject matter defined by the claims. The following detailed description of the exemplary aspects may be understood when read in conjunction with the following drawings, and wherein:

[0027] Figure 1 This is a schematic perspective view of a cross-section of a secondary particle provided in accordance with some of the aspects described herein;

[0028] Figure 2 The diagram illustrates the capacity decay of a full cell using secondary particles based on some aspects provided in this article;

[0029] Figure 3 The diagram illustrates the impedance growth of a full cell using secondary particles based on some aspects provided in this article;

[0030] Figure 4 The diagram illustrates the EDS mapping of secondary particles provided in this article, where grain boundaries are enriched with Al only or Al in the presence of Co.

[0031] Figure 5 The illustration shows a scanning transmission electron microscopy (STEM) image of a small slice containing several microcrystals of secondary particles according to one aspect provided herein, the secondary particles being derived from and made by enriching grain boundaries with 1.9 at% Al and 4 at% Co, and shows the location of three EDS point analyses.

[0032] Figure 6 Diagram Figure 5 The EDS spectra of the three points shown;

[0033] Figure 7 The illustration shows a STEM image of a small slice containing several microcrystals of secondary particles according to one aspect provided herein, the secondary particles being derived from and produced by enriching the grain boundaries with 1.9 at% Al in the absence of Co in the process solution, and shows the location of two EDS point analyses.

[0034] Figure 8 Diagram Figure 7 The EDS spectra of the three points shown;

[0035] Figure 9 The diagram illustrates the EDS mapping of the secondary particles provided in this paper, which are produced by non-aqueous processing of Al in a process solution using only Al or Al in the presence of Co during the manufacturing process to enrich the grain boundaries of the original particles.

[0036] Figure 10 The diagram illustrates the cycle capacity decay of cells formed using cathodes containing active materials enriched at grain boundaries according to one aspect provided herein, prepared in process solutions with 0 at% Al and 0.5 at% Al in process solutions.

[0037] Figure 11 The diagram illustrates the impedance growth of cells formed using cathodes containing active materials enriched at grain boundaries according to one aspect provided herein, prepared in process solutions with 0 at% Al and 0.5 at% Al in process solutions.

[0038] Figure 12 The diagram illustrates the synergistic benefits observed in the presence of Al in addition to Co enrichment at grain boundaries;

[0039] Figure 13The diagram illustrates the cycle capacity decay and impedance growth of a battery with a cathode material having grain boundary enrichment according to some aspects provided herein, the cathode material being enriched at grain boundaries by a 3 at% Co process with different Al contents.

[0040] Figure 14 The diagram illustrates the impedance growth of the cathode active materials presented in this article at various Al / Co enrichment atomic percentage ratios.

[0041] Figure 15 The figure illustrates the STEM and EDS analysis results of three points in a small slice of secondary NCA particles prepared in this article, showing the grain boundaries of Al enrichment in the presence of Co.

[0042] Figure 16 The diagram illustrates the cycle capacity decay of a battery formed with a cathode containing a control or an NCA active material enriched at grain boundaries according to one aspect provided herein.

[0043] Figure 17 The diagram illustrates the impedance growth of a cell formed with a cathode containing a control or an NCA active material enriched at grain boundaries according to one aspect provided herein.

[0044] Figure 18 The diagram illustrates the cycle capacity decay of a battery formed using a cathode containing a control or an NCM active material enriched at grain boundaries according to one aspect provided herein; and

[0045] Figure 19 The diagram illustrates the impedance growth of a cell formed with a cathode containing a control or an NCM active material enriched at grain boundaries according to one aspect provided herein. Detailed Explanation

[0046] The following descriptions of specific aspects are merely exemplary and in no way intended to limit the scope, application, or use of this disclosure, which are of course variable. The materials and methods are described in connection with the non-limiting definitions and terms included herein. These definitions and terms are not intended to limit the scope or practice of this disclosure but are used for exemplary and descriptive purposes only. Although the method or composition is described as a sequence of steps or the use of specific materials, it is to be understood that the steps or materials are interchangeable so that the description of the invention may include multiple portions or steps arranged in a number of ways readily understood by those skilled in the art.

[0047] It is to be understood that although the terms “first,” “second,” “third,” etc., may be used herein to describe various elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer, or segment from another. Therefore, unless otherwise specified, “first element,” “component,” “region,” “layer,” or “segment” discussed below may be referred to as a second (or other) element, component, region, layer, or segment without departing from the teachings of this document.

[0048] The terminology used herein is for descriptive purposes only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular articles “a,” “an,” and “the” used herein are intended to include the plural forms, including “at least one.” “Or” means “and / or.” The term “and / or” as used herein includes any and all combinations of one or more of the related enumerations. It should also be understood that the terms “comprising” or “including” as used in this specification specify the presence of the stated features, regions, integers, steps, operations, elements, and / or components, but do not exclude the presence or inclusion of one or more other features, regions, integers, steps, operations, elements, components, and / or combinations thereof. The term “or a combination thereof” means a combination comprising at least one of the foregoing elements.

[0049] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It shall also be understood that terms as defined in common dictionaries shall be interpreted as having the same meaning as they have in the relevant field and in this disclosure, and shall not be interpreted in an idealized or overly formal sense, unless expressly stated herein.

[0050] LiMO2-type Ni-based crystalline materials are dense polycrystalline agglomerates of primary crystals. These are typically manufactured using standard solid-state methods at temperatures ranging from 600°C to 900°C from various precursor materials. Precursor materials are typically transition metal hydroxides (M(OH)2), lithium precursors (e.g., LiOH or Li2CO3), or inorganic precursors with other dopants (e.g., hydroxides, carbonates, nitrates). During the heating of the precursor mixture, polycrystalline LiMO2 is formed as gases such as H2O, CO2, or NO2 are released.

[0051] The result of sintering under the correct conditions and with the use of appropriate precursors is the formation of numerous primary crystallites, which are shaped into larger secondary particles that can serve as electrochemical active materials. It has previously been found that the regions between these primary crystallites, i.e., grain boundaries, can selectively accumulate Co (as discovered in U.S. Patent No. 9,209,455). In this disclosure, the inventors have discovered that significant further improvements can be achieved by replacing some of the Co-enriched areas at the grain boundaries with Al, thereby further reducing impedance growth and improving cycle life. It is to be understood that the synergistic relationship between Co and Al at the grain boundaries, particularly at Co contents of 2 mol% Co to 5 mol% Co (relative to the total M content in the crystallites) combined with a lower relative Al content, significantly reduces impedance growth and improves the cycle life of electrochemical cells using this material as the cathode active material.

[0052] Accordingly, this disclosure provides improved electrochemically active materials, such as those suitable for the cathode (positive electrode) of Li-ion secondary batteries, which reduce the rate of impedance growth and / or capacity decay during charge / discharge cycles of the battery pack compared to existing materials. Various methods for achieving high discharge capacity cathode active materials are also provided, which exhibit reduced impedance growth and reduced capacity decay during cycling compared to the same materials in which Co and Al enrichment is absent at grain boundaries.

[0053] The polycrystalline layered lithium-ion metal oxides presented herein exhibit enhanced electrochemical performance and stability. This composition prevents performance degradation of Ni-containing polycrystalline LiMO2-based materials during electrochemical cycling, while maintaining other desirable end-use product properties, such as the electrochemical capacity of rechargeable lithium-ion cathodes made from such layered metal oxides, by reducing the impedance growth rate during electrochemical cycling. Such Co and Al grain boundary enriched materials can be readily manufactured as follows: a green body formulation comprising LiOH and precursor hydroxides or carbonates is calcined to form particles with defined grain boundaries; then, the grain boundaries are enriched with a combination of Co and Al so that the resulting particles have grain boundaries in which the concentration of Co and Al at the grain boundaries is greater than before enrichment and optionally greater than the concentration within the primary crystallites, the outer surface of which defines the edges of the grain boundaries in the secondary particles.

[0054] Therefore, compositions, systems, and methods of lithium metal oxides with polycrystalline layered structures having Co and Al enriched grain boundaries are provided for manufacturing and in use in lithium-ion secondary batteries as a means to achieve high initial discharge capacity and low impedance growth during cycling, thereby overcoming previous challenges in high-nickel formulations that may also have high discharge capacity (e.g., >205 mAh / g at C / 20).

[0055] The provided material comprises particles containing a plurality of microcrystals, each microcrystal containing a first composition. The particles formed from the plurality of microcrystals may be referred to as secondary particles. The particles provided herein are uniquely tailored to have grain boundaries between the primary microcrystals. After their formation, these grain boundaries are enriched with a combination of Co and Al, optionally at specific relative concentrations of Co and Al, to produce particles that provide reduced impedance growth during cycling, thereby improving the performance and cycle life of cells containing these particles as cathode components.

[0056] The particles are considered to include grain boundaries formed by or comprising the second composition, wherein the concentrations of, for example, cobalt and aluminum in the grain boundaries are greater than the concentrations of, for example, cobalt and aluminum in the adjacent primary crystallites. The concentrations of Co and Al in the grain boundaries are optionally greater on average than the average Co and Al concentrations within the adjacent crystallites. The materials provided herein optionally have relatively uniform Co and / or Al concentrations (if either is present) within the crystallites. Whether uniform or not, the concentrations of Co and Al in the grain boundaries are greater than the average Co and Al concentrations within the adjacent crystallites (individually or in combination). Optionally, the provided materials include an additional outer coating that can be disposed on the outer surface of the secondary particles to provide coated secondary particles.

[0057] In some aspects of the particles provided herein, the first composition comprises a composition of Li 1+x MO 2+yThe definition refers to a polycrystalline layered lithium metal oxide structure, and optionally a cell or cell pack formed therefrom, wherein -0.1 ≤ x ≤ 0.3 and -0.3 ≤ y ≤ 0.3. In some aspects, x is -0.1, optionally 0, optionally 0.1, optionally 0.2, or optionally 0.3. Optionally, x is greater than or equal to -0.10, -0.09, -0.08, -0.07, -0.06, -0.05, -0.04, -0.03, -0.02, -0.01, 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, or 0.30. In some respects, y is -0.3, optionally -0.2, optionally -0.1, optionally 0, optionally 0.1, optionally 0.2, or optionally 0.3. Optionally, y is greater than or equal to -0.30, -0.29, -0.28, -0.27, -0.26, -0.25, -0.24, -0.23, -0.22, -0.21, -0.20, -0.19, -0.18, -0.17, -0.16, -0.15, -0.14, -0.13, -0.12, -0.11, -0.10, -0.09, -0.08, -0.07, -0.06, -0.05, -0.04, -0.03, -0.02, -0.01, 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29 or 0.3.

[0058] It should be recognized that, in some respects, Li need not be entirely Li, but may be partially substituted by one or more elements selected from Mg, Sr, Na, K, and Ca. The one or more elements substituting for Li may optionally be present in 10 atomic percent or less, optionally 5 atomic percent or less, optionally 3 atomic percent or less, optionally no more than 2 atomic percent, where the percentage is relative to the total Li in the material.

[0059] M provided in the first composition comprises Ni. The amount of Ni in the first composition is optionally from 10 atomic% to 100 atomic% (at%) of the total M. Optionally, the Ni composition of M is greater than or equal to 75 at%. Optionally, the Ni composition of M is greater than or equal to 80 at%. Optionally, the Ni composition of M is greater than or equal to 85 at%. Optionally, the Ni composition of M is greater than or equal to 90 at%. Optionally, the Ni composition of M is greater than or equal to 95 at%. Optionally, the Ni composition of M is greater than or equal to 75 at%, 76 at%, 77 at%, 78 at%, 79 at%, 80 at%, 81 at%, 82 at%, 83 at%, 84 at%, 85 at%, 86 at%, 87 at%, 88 at%, 89 at%, 90 at%, 91 at%, 92 at%, 93 at%, 94 at%, 95 at%, 96 at%, 97 at%, 98 at%, 99 at%, 99.5 at%, 99.9 at%, or 100 at%.

[0060] In some aspects, M in the first composition is Ni, alone or in combination with one or more additional elements. The additional elements are optionally metals. Optionally, the additional elements may include one or more of Al, Mg, Co, Mn, Ca, Sr, Zn, Ti, Y, Cr, Mo, Fe, V, Si, Ga, or B. In certain aspects, the additional elements may include Mg, Co, Al, or combinations thereof. Optionally, the additional elements may be Mg, Al, V, Ti, B, or Mn, or combinations thereof. Optionally, the additional elements are selected from Mg, Al, V, Ti, B, or Mn. Optionally, the additional elements are selected from Mg, Co, and Al. Optionally, the additional elements are selected from Ca, Co, and Al. In some aspects, the additional elements are Mn or Mg, or Mn and Mg. Optionally, the additional elements are Mn, Co, Al, or any combination thereof. Optionally, the additional elements include Co and Mn. Optionally, the additional elements are Co and Al. Optionally, the additional elements are Co.

[0061] The additional element in the first composition may be present in an amount of about 1 to about 90 at%, particularly about 5 to about 80 at%, and more particularly about 10 to about 70 at%. Optionally, the additional element may be present in an amount of about 1 to about 20 at%, particularly about 2 to about 18 at%, and more particularly about 4 to about 16 at%. In some exemplary examples, M is about 75-100 at% Ni, 0-15 at% Co, 0-15 at% Mn, and 0-10 at% additional element.

[0062] Within this polycrystalline material, each crystallite can have any suitable shape, and they can be the same or different within each particle. Furthermore, the shapes of the crystallites can be the same or different in different particles. Due to its crystalline properties, the crystallites can be befaceted, have many flat surfaces, and their shapes can approximate geometric shapes. In some aspects, a crystallite can be fused with adjacent crystallites having mismatched crystal planes. The crystallite can optionally be a polyhedron. The crystallite can have a linear shape, and when viewed in cross-section, a portion or the entire crystallite can be linear. The crystallite can be square, hexagonal, rectangular, triangular, or a combination thereof.

[0063] In certain respects, secondary particles have grain boundaries enriched in Co and Al, optionally with a higher atomic percentage of Co and Al in the grain boundaries than in the overall average atomic percentage of Co and Al in the microcrystals. Reference Figure 1 As an exemplary illustration, grain boundaries 20, 21 are between adjacent crystallites 10 and include a second composition. The second composition, as described in U.S. Patent Nos. 9,391,317 and 9,209,455, requires that Co and Al be independently enriched in the grain boundaries, in addition to their respective independent concentrations in the crystallites, and in some respects, the concentrations of Co and Al within a certain range can provide a synergistic effect in reducing impedance or improving cycle life. The second composition optionally has a layered α-NaFeO2 type structure, a cubic structure, or a combination thereof. As mentioned above, the concentrations of Co and Al in the grain boundaries can be greater than the concentrations of Co and Al in the crystallites. Specifically, the aspect in which the grain boundaries have a layered α-NaFeO2 type structure is mentioned. Specifically, another aspect in which the grain boundaries have a defective α-NaFeO2 type structure is mentioned. Specifically, another aspect in which a portion of the grain boundaries has a cubic or spinel structure is mentioned.

[0064] The second composition, which may be partially or wholly present at the grain boundaries, optionally includes the composition Li 1+x MO 2+yThe defined lithium metal oxides, wherein -0.1 ≤ x ≤ 0.3 and -0.3 ≤ y ≤ 0.3. Optionally, the second composition is identical to the first composition, except that Co and Al are present in the second composition, or the concentrations of Co and Al are increased relative to those in the first composition. In some aspects of the second composition, x is -0.1, optionally 0, optionally 0.1, optionally 0.2, or optionally 0.3. Optionally, x is greater than or equal to -0.10, -0.09, -0.08, -0.07, -0.06, -0.05, -0.04, -0.03, -0.02, -0.01, 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, or 0.30. In some respects, y is -0.3, optionally -0.2, optionally -0.1, optionally 0, optionally 0.1, optionally 0.2, or optionally 0.3. Optionally, y is greater than or equal to -0.30, -0.29, -0.28, -0.27, -0.26, -0.25, -0.24, -0.23, -0.22, -0.21, -0.20, -0.19, -0.18, -0.17, -0.16, -0.15, -0.14, -0.13, -0.12, -0.11, -0.10, -0.09, -0.08, -0.07, -0.06, -0.05, -0.04, -0.03, -0.02, -0.01, 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29 or 0.3.

[0065] M provided in the second composition comprises Co and Al. If present, the amount of Ni is optionally from 0.01 atomic% to 99 atomic% (at%) of M. Optionally, M in the second composition is Ni-free. Optionally, the amount of Ni in the second composition (i.e., relative concentration) is lower than the amount of Ni in the first composition, in relative atomic% (relative to the respective compositions containing Ni). Optionally, the Ni composition of M is less than or equal to 1 at%. Optionally, the Ni composition of M is less than or equal to 5 at%. Optionally, the Ni composition of M is less than or equal to 10 at%. Optionally, the Ni composition of M is less than or equal to 20 at%. Optionally, the Ni composition of M is less than or equal to 75 at%. Optionally, the Ni composition of M is less than or equal to 80 at%. Optionally, the Ni composition of M is less than or equal to 85 at%. Optionally, the Ni composition of M is less than or equal to 90 at%. Optionally, the Ni composition of M is less than or equal to 95 at. Optionally, the Ni composition of M is less than or equal to 75 at%, 76 at%, 77 at%, 78 at%, 79 at%, 80 at%, 81 at%, 82 at%, 83 at%, 84 at%, 85 at%, 86 at%, 87 at%, 88 at%, 89 at%, 90 at%, 91 at%, 92 at%, 93 at%, 94 at%, 95 at%, 96 at%, 97 at%, 98 at%, 99 at%, or 99.9 at%.

[0066] For any of the materials provided herein, the nominal or total formulation of secondary particles (e.g., characterized by inductively coupled plasma (ICP)), optionally a first composition or optionally a second composition, defined by the formula LiMO, where M is Ni and optionally one or more additional metals, must include at least Co and Al in the second composition. If present, the molar fractions of Co and Al in the first composition defining the microcrystalline composition are lower than the molar fractions of total Co and Al (individually or collectively) in the total particle composition as determined by ICP. The molar fractions of Co and Al (individually or collectively) in the first composition may be 0. The molar fractions of Co and Al (individually or collectively) in the second composition defining the grain boundaries are higher than the molar fractions of total Co and Al (individually or collectively) in the total particles as determined by ICP.

[0067] The second composition located within the grain boundaries comprises Co and Al, optionally wherein the concentration of Co and Al (individually or in combination) at the grain boundaries is greater than the concentration of Co and Al (individually or in combination) in the crystallites, optionally wherein the CO concentration at the grain boundaries is greater than the Co concentration in the crystallites, and optionally wherein the Al concentration at the grain boundaries is greater than the Al concentration in the crystallites. It has been found that by using a method capable of enriching Co and Al at grain boundaries, 0.01 at% to 10 at% Al, optionally 1.5 at% or less, can be added to a liquid solution comprising an amount of Co equal to or between 0 at% and 8 at% and optionally between 3 at% and 5 at% Co, relative to the total transition metals of the first composition to be enriched, and forming a material exhibiting a significantly reduced impedance growth during cycling, wherein the added Co and Al are incorporated into the grain boundaries of the secondary particles.

[0068] The volume fraction of grain boundaries within a given secondary particle will vary because the primary particle size distribution varies with the overall composition and synthesis conditions. Accordingly, the final concentrations of Co and Al in the second composition will also vary between different secondary particles and within individual secondary particles, while always remaining greater than the concentrations of Co and Al in the first composition. Therefore, it is most useful to specify the amount of Co and Al added to the grain boundaries relative to the first composition.

[0069] The amounts of Co and Al provided in the process solution are considered to be the average amounts of Co and Al added to the secondary particles and distributed throughout the grain boundaries of the secondary particles, and are given relative to M of the first composition. When the secondary particles described herein are manufactured, it is found that almost all of the Co and Al in the process solution adheres to the particles before calcination. Therefore, the amount of Co and Al available for enriching the grain boundaries is the amount in the process solution. Thus, when describing a process solution, for example, 1 at% Al and 2 at% Co, this listed at% is relative to the amount M in the first composition before grain boundary enrichment. Therefore, the at% of Al and Co in the process solution used herein is always relative to the total M in the primary particles to be enriched at the grain boundaries.

[0070] The amount of Al in the process solution is optionally from 0.01 at% to 10 at%, optionally 9 at% or less, optionally 8 at% or less, optionally 7 at% or less, optionally 6 at% or less, optionally 5 at% or less, optionally 4 at% or less, optionally 3 at% or less, optionally 2 at% or less, optionally 1 at% or less, optionally from 0.1 to 1 at%, optionally from 0.5 to 1 at%. Optionally, the amount of Al in the process solution is equal to or less than 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5 atomic percentages.

[0071] Optionally, the Co content in the process solution is greater than 3 at% and at most 4 at%, and the Al content is less than 1 at%, optionally from 0.1 to 1 at%, optionally from 0.1 to less than 1 at%. Optionally, the Co content in the process solution is 0.5 at% to 4 at%, and the Al content is 0.01 at% to 10 at%.

[0072] In some respects, the amount of Co in the process fluid is approximately 3 at%. At this Co concentration, the amount of Al is optionally less than 1 at%. An Al amount of approximately 0.3 at% to 0.7 at%, optionally approximately 0.5 at%, is most suitable for reducing impedance growth during cycling. Optionally, Al is substantially uniformly distributed among the numerous secondary particles.

[0073] In some aspects, the Co content in the process fluid is approximately 3.5 at%. At this Co content, the Al content is optionally less than 1 at%. An Al content of approximately 0.3 to 0.7 at%, optionally approximately 0.5 at%, is most suitable for reducing impedance growth during cycling. Optionally, the Al is substantially uniformly distributed among the numerous secondary particles.

[0074] In some respects, the amount of Co in the process fluid is approximately 4 at%. At this Co concentration, the amount of Al is optionally less than 1.5 at%. An Al amount of approximately 0.7 to 1.3 at%, optionally approximately 1.0 at%, is most suitable for reducing impedance growth during cycling. Optionally, Al is substantially uniformly distributed among the numerous secondary particles.

[0075] In some aspects, the amount of Co in the process fluid is approximately 4.5 at%. At this Co concentration, the amount of Al is optionally less than 1 at%. An Al amount of approximately 0.3 to 0.7, optionally approximately 0.5 at%, is most suitable for reducing impedance growth during cycling. Optionally, Al is substantially uniformly distributed among the numerous secondary particles.

[0076] In some respects, the amount of Co in the process fluid is approximately 3 at%. At this Co concentration, the amount of Al is optionally less than 1.5 at%. An Al amount of approximately 0.5 to 1.3 at%, optionally approximately 1.0 at%, is most suitable for reducing impedance growth during cycling. Optionally, Al is substantially uniformly distributed among the numerous secondary particles.

[0077] In some respects, the amount of Co in the process fluid is approximately 3 at% to approximately 4 at%. At this Co concentration, the amount of Al is optionally less than 1 at%. An Al amount of approximately 0.3 to 0.13, optionally approximately 0.5 at% or approximately 1.0 at% is most suitable for reducing impedance growth during cycling. Optionally, Al is substantially uniformly distributed among the numerous secondary particles.

[0078] In some respects, the amount of Co in the process fluid is approximately 3 at%. At this Co concentration, the amount of Al is optionally less than 1.5 at%. An Al amount of approximately 0.5 to 1.3 at% is most suitable for reducing impedance growth during cycling. Optionally, Al is substantially uniformly distributed among the numerous secondary particles.

[0079] In some respects, the amount of Co in the process fluid is approximately 4 at%. At this Co concentration, the amount of Al is optionally less than 1.0 at%. An Al amount of approximately 0.5 to 0.7 at% is most suitable for reducing impedance growth during cycling. Optionally, Al is substantially uniformly distributed among the numerous secondary particles.

[0080] Therefore, in some respects, as the Co content increases from 3 at% to 4 at%, the Al content that produces the greatest improvement shifts from less than 1.3 at% to less than 0.7 at%. Optionally, Al is substantially uniformly distributed among the many secondary particles.

[0081] Optionally, as described in some aspects of secondary particles herein, the amount of Al in the second composition is equal to or less than 100 at% relative to the amount of Co, meaning that the amount of Al is optionally equal to or less than the amount of Co. Optionally, the amount of Al is less than 90 at%, optionally less than 80 at%, optionally less than 70 at%, optionally less than 60 at%, optionally less than 50 at%, optionally less than 40 at%, optionally less than 30 at%, optionally less than 20 at%, optionally less than 10 at%, optionally less than 9 at%, optionally less than 8 at%, optionally less than 7 at%, optionally less than 6 at%, optionally less than 4 at%, optionally less than 3 at%, optionally less than 2 at%, optionally less than 1 at%. It has been found that an amount of Co greater than the amount of Al can achieve a synergistic relationship, which unexpectedly reduces impedance growth compared to Co alone at the same or higher concentrations.

[0082] Optionally, among the plurality of secondary particles, the Al present in the second composition or distributed partially or entirely at the grain boundaries is substantially uniform. For example, when Al is introduced by the method described herein for grain boundary enrichment of Al alone, powder EDS performed by standard techniques shows the presence of Al-rich “hot spots,” indicating that Al is not uniformly or inefficiently absorbed into the grain boundaries, resulting in a separate phase of Al. However, in the presence of Co and Al at concentrations described herein in the process solution, the result is a much more uniform Al distribution, indicating that the hot spots observed by EDS are almost or completely absent. In some respects, the number and / or size of Al hot spots are reduced by 50% or more, optionally 60% or more, optionally 70% or more, optionally 80% or more, compared to Al grain boundary enrichment in the absence of Co co-enrichment.

[0083] Aluminum uniformity can also be assessed by comparing EDS at two magnifications. Table 2 of Example 1 shows the aluminum concentration obtained by EDS for a wide area (approximately 150 μm x 150 μm) as the first value in the table, followed by the second value, which is the average EDS analysis of a much narrower area (approximately 1 μm x 1 μm) concentrated on particles without obvious hot spots. When 4% cobalt is used in the process liquid, these two values ​​are close. However, when cobalt is not used, the narrow area without hot spots has much less aluminum than the wider area, indicating that much more aluminum is concentrated in the hot spots rather than uniformly distributed among the many secondary particles.

[0084] In some aspects, M in the second composition further comprises one or more Ni-substituting elements (substituted elements). The Ni-substituting elements are optionally metals and not Co or Al, as the presence of these elements leads to an observed synergistic reduction in impedance growth. Optionally, the substituting elements may include one or more of Mg, Mn, Ca, Sr, Zn, Ti, Zr, Hf, Y, Cr, Mo, W, Fe, V, Nb, Ta, Si, Ga, or B. The substituting elements in the second composition may be present in an amount from about 1 to about 90 at%, particularly from about 5 to about 80 at%, and more particularly from about 10 to about 70 at%, of the first composition. Optionally, additional elements may be present in an amount from about 1 to about 20 at%, particularly from about 2 to about 18 at%, and more particularly from about 4 to about 16 at%, of the first composition.

[0085] Optionally, the Li in the second composition need not be entirely Li, but may be partially substituted by one or more Li-substituting elements selected from Mg, Sr, Na, K, and Ca. The one or more Li-substituting elements may optionally be present at 10 atomic percent or less, optionally 5 atomic percent or less, optionally 3 atomic percent or less, optionally no more than 2 atomic percent, where the percentage is relative to the total Li in the as-made material.

[0086] The secondary particles provided herein can be prepared by synthesizing a green body from at least two components (optionally in powder form). The at least two components may include micronized (or non-micronized) lithium hydroxide or its hydrate and a precursor hydroxide containing nickel and optionally one or more other elements, wherein the precursor hydroxide is optionally obtained by co-precipitation. It should be recognized that the final overall composition (although not necessarily the distribution) of the elements in the final particles can be adjusted by increasing or decreasing the relative amount of the precursor material during the formation of the green body. In some respects, lithium hydroxide or its hydrate is micronized. Two or more powders forming the green body can be combined and shaken on a paint shaker to thoroughly mix the precursors. The green body is then calcined to the maximum temperature under a controlled air or pure oxygen atmosphere. Calcination may optionally follow a heating profile. The calcined product can then be processed to form a free-flowing powder.

[0087] In some aspects, the precursor hydroxide may be a mixed metal hydroxide. In some aspects, the mixed metal hydroxide may comprise a metal composition of Ni, Co, and Mg. Optionally, the mixed metal hydroxide comprises 10–100 at% Ni, 0–15 at% Co, and 0–5 at% Mg as metal components. Optionally, the mixed metal hydroxide comprises 10–100 at% Ni, 0–30 at% Co, and 0.1–80 at% Mn. Optionally, the mixed metal hydroxide comprises 10–100 at% Ni, 0–30 at% Co, and 0–10 at% Al. Optionally, the metals of the mixed metal hydroxide are 92 at% Ni and 8 at% Co. Optionally, the metals of the mixed metal hydroxide are 90 at% Ni, 8 at% Co, and 2 at% Mg. Optionally, the metals of the mixed metal hydroxide are 89 at% Ni, 8 at% Co, and 3 at% Mg. Optionally, the metals in the mixed metal hydroxide are 91 at% Ni, 8 at% Co, and 1 at% Mg. Optionally, the metals in the mixed metal hydroxide are 100 at% Ni. For example, the precursor hydroxide can be manufactured by a precursor supplier, such as Hunan Brunp Recycling Technology Co., Ltd., using standard methods for preparing nickel hydroxide-based materials.

[0088] Secondary particles can be formed through a multi-step process, thereby forming and calcining primary material particles to establish clear grain boundaries, optionally containing a small number of defects. Primary particles with a NaFeO2 structure. These particles are then subjected to a liquid process, incorporating Co and Al at desired concentration levels, followed by drying and secondary calcination to selectively migrate Co and Al precipitates at the surface to the grain boundaries, thereby forming secondary particles with higher Co and Al concentrations at the grain boundaries than in the microcrystals. According to a method for manufacturing secondary particles having a Ni, Co, and Mg substrate provided as an example herein, the formation process may include: combining a lithium compound with one or more metal or metalloid hydroxide precursor compounds (e.g., previously generated combined Ni, Co, and Mg, for example, generated via a co-precipitation reaction) to form a mixture; heat-treating the mixture at about 30 to about 200 °C to form a dried mixture; heat-treating the dried mixture at about 200 to about 500 °C for about 0.1 to about 5 hours; and then heat-treating at 600 °C to less than about 800 °C for about 0.1 to about 10 hours to produce secondary particles. The maximum temperature for the first calcination is relative and specific to the material used in the hydroxide precursor. Optionally, in a single calcination, the maximum temperature may be equal to or less than 850°C, optionally equal to or less than 720°C, optionally equal to or less than 715°C, optionally equal to or less than 710°C, optionally equal to or less than 705°C, or optionally equal to or less than 700°C. Optionally, the maximum temperature in a single calcination may be approximately 680°C or less. Optionally, the maximum temperature may be approximately 660°C or less. Optionally, the maximum temperature may be approximately 640°C or less. In other aspects, the maximum temperature may be less than approximately 700°C, approximately 695°C, approximately 690°C, approximately 685°C, approximately 680°C, approximately 675°C, approximately 670°C, approximately 665°C, approximately 660°C, approximately 655°C, approximately 650°C, approximately 645°C, or approximately 640°C. The residence time at the maximum temperature may optionally be less than 10 hours. Optionally, the residence time at the maximum temperature is less than or equal to 8 hours; optionally less than or equal to 7 hours; optionally less than or equal to 6 hours; optionally less than or equal to 5 hours; optionally less than or equal to 4 hours; optionally less than or equal to 3 hours; optionally less than or equal to 2 hours.

[0089] Following calcination, subsequent processing may include pulverizing the calcined material with a mortar and pestle to pass the resulting powder through a desired sieve, optionally a #35 sieve. The powder may then optionally be cannulated in a 1-gallon jar containing 2 cm drum YSZ media for an optional 5 minutes or sufficient time to allow the material to pass through an optional #270 sieve.

[0090] The product from a single calcination or grinding can be subsequently processed, optionally in a method for producing enriched grain boundaries after a second calcination. The method for enriching grain boundaries within primary particles can be carried out using the methods or compositions shown in U.S. Patent Nos. 9,391,317 and 9,209,455, except that the application process uses a liquid solution comprising a certain amount of Co and a certain amount of Al, optionally in amounts such that synergistic enrichment of Co and Al occurs at the grain boundaries of secondary particles. The grain-boundary-enriching element can optionally be applied by suspending the ground product in an aqueous slurry containing Co, Al, and lithium compounds at a temperature of approximately 60°C, whereby Co and Al are present in the aqueous solution at the concentrations described herein. This slurry can then be spray-dried to form a free-flowing powder, which is then subjected to a second calcination, optionally with a heating profile following a two-step ramp / dwell process. The first ramp / dwell temperature profile in the two steps can be from ambient temperature (approximately 25°C) to 450°C and optionally at a rate of 5°C / min, with a dwell time of 1 hour at 450°C. Subsequently, the second ramp / dwell can be from 450°C to the maximum temperature at a rate of 2°C / min, with a dwell time of 2 hours at the maximum temperature. In some respects, the maximum temperature is less than approximately 725°C, optionally approximately 700°C. In other respects, the maximum temperature is approximately 725°C, optionally 750°C.

[0091] By combining a primary calcination at the maximum temperature described above with a process of applying grain boundary enrichment elements, followed by a secondary calcination also described above, it was found that the resulting particles can be used in cathodes to produce significantly improved impedance enhancement and / or capacity decay. Such a combination was found to result in additional cycle life and reduced impedance growth, significantly improving the electrochemical performance of the material. Therefore, it should be recognized that, in some aspects, the particles comprise numerous microcrystals having a composition consisting of Li... 1+x MO 2+yA first composition of a polycrystalline layered lithium metal oxide, wherein -0.1 ≤ x ≤ 0.3 and -0.3 ≤ y ≤ 0.3. In some aspects, x is -0.1, optionally 0, optionally 0.1, optionally 0.2, or optionally 0.3. Optionally, x is greater than or equal to -0.10, -0.09, -0.08, -0.07, -0.06, -0.05, -0.04, -0.03, -0.02, -0.01, 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, or 0.30. In some respects, y is -0.3, optionally -0.2, optionally -0.1, optionally 0, optionally 0.1, optionally 0.2, or optionally 0.3. Optionally, y is greater than or equal to -0.30, -0.29, -0.28, -0.27, -0.26, -0.25, -0.24, -0.23, -0.22, -0.21, -0.20, -0.19, -0.18, -0.17, -0.16, -0.15, -0.14, -0.13, -0.12, -0.11, -0.10, -0.09, -0.08, -0.07, -0.06, -0.05, -0.04, -0.03, -0.02, -0.01, 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, or 0.3. The microcrystals contain 10 atomic% to 100 atomic% (at%) of Ni as element M. Optionally, the Ni composition of M is greater than or equal to 75 at%. Optionally, the Ni composition of M is greater than or equal to 80 at%. Optionally, the Ni composition of M is greater than or equal to 85 at. Optionally, the Ni composition of M is greater than or equal to 90 at%. Optionally, the Ni composition of M is greater than or equal to 95 at%.Optionally, the Ni composition of M is greater than or equal to 75 at%, 76 at%, 77 at%, 78 at%, 79 at%, 80 at%, 81 at%, 82 at%, 83 at%, 84 at%, 85 at%, 86 at%, 87 at%, 88 at%, 89 at%, 90 at%, 91 at%, 92 at%, 93 at%, 94 at%, 95 at%, 96 at%, 98 at%, 99 at%, or 100 at%. The M composition may include one or more additional elements. The additional elements are optionally metals. Optionally, the additional elements may include one or more of Al, Mg, Co, Mn, Ca, Sr, Zn, Ti, Y, Cr, Mo, Fe, V, Si, Ga, or B. In certain aspects, the additional elements may include Mg, Co, Al, or combinations thereof. Optionally, the additional elements may be Mg, Al, V, Ti, B, or Mn, or combinations thereof. Optionally, the additional elements consist of Mg, Al, V, Ti, B, or Mn. In some aspects, the additional element is Mn or Mg, or Mn and Mg. The additional element in the first composition may be present in an amount of about 1 to about 90 at%, particularly about 5 to about 80 at%, and more particularly about 10 to about 70 at%. Optionally, the additional element may be present in an amount of about 1 to about 20 at%, particularly about 2 to about 18 at%, and more particularly about 4 to about 16 at%. In some exemplary examples, M is about 75-100 at% Ni, 0-15 at% Co, 0-15 at% Mn, and 0-10 at% of the additional element. The resulting secondary particles have grain boundaries, wherein the amounts of Co and Al are greater than those in the microcrystals.

[0092] The resulting particles optionally exhibit a reduced impedance growth compared to particles with only Co enrichment at grain boundaries, optionally at Co contents considered insufficient to significantly improve the cycling characteristics of particles without Co enrichment at grain boundaries. When the resulting secondary particles are the active material of a Li-ion battery cathode, the battery cycling at 45°C between 4.2V and 2.7V optionally exhibits less than 50% impedance growth at a fully charged state (4.2V) for the following cycles: greater than 50 cycles, optionally greater than 60 cycles, optionally greater than 70 cycles, optionally greater than 80 cycles, optionally greater than 90 cycles, optionally greater than 100 cycles, optionally greater than 110 cycles, optionally greater than 120 cycles, optionally greater than 130 cycles, optionally greater than 140 cycles, optionally greater than 150 cycles, optionally greater than 200 cycles.

[0093] In other respects, batteries cycled between 4.2V and 2.7V at 45°C optionally exhibit impedance increases of less than 100% at a fully charged (4.2V) state for the following cycles: greater than 100 cycles, optionally greater than 110 cycles, optionally greater than 120 cycles, optionally greater than 130 cycles, optionally greater than 140 cycles, optionally greater than 150 cycles, optionally greater than 160 cycles, optionally greater than 170 cycles, optionally greater than 180 cycles, optionally greater than 190 cycles, optionally greater than 200 cycles, optionally greater than 210 cycles, and optionally greater than 220 cycles.

[0094] In other respects, batteries cycling between 4.2V and 2.7V at 45°C optionally exhibit impedance growth of less than 50% at 50% state of charge (SOC) for more than 200 cycles, optionally less than 40% for more than 200 cycles, and optionally less than 30% for more than 200 cycles.

[0095] The electrochemical batteries provided in this article may optionally use the particles provided in this article as electrochemical active materials, which may optionally have an initial discharge capacity of 180 mAh / g particles or greater, optionally 185 mAh / g, optionally 190 mAh / g, optionally 195 mAh / g, optionally 200 mAh / g, or optionally 210 mAh / g.

[0096] according to Figure 1 The diagram discloses a particle comprising microcrystals 10 containing a first composition and grain boundaries 20, 21 containing a second composition, wherein the Al concentration in the grain boundaries is greater than the Al concentration in the microcrystals, and the cobalt concentration in the grain boundaries is greater than the cobalt concentration in the microcrystals. The particle comprises a plurality of microcrystals and is referred to as a secondary particle. Optionally, deposition may be performed on the outer surface of the particle. Figure 1 The outer layer, as shown in 30, may be a passivation layer or a protective layer. The outer layer may completely or partially cover the secondary particles. This layer may be amorphous or crystalline. The layer may contain oxides, phosphates, pyrophosphates, fluorophosphates, carbonates, fluorides, fluoride oxides, or combinations thereof of elements such as Al, Ti, B, Li, or Si, or combinations thereof. In some aspects, the outer layer comprises borates, aluminates, silicates, fluoroaluminates, or combinations thereof. Optionally, the outer layer comprises carbonates. Optionally, the outer layer comprises ZrO2, Al2O3, TiO2, AlPO4, AlF3, B2O3, SiO2, Li2O, Li2CO3, or combinations thereof. Optionally, the outer layer comprises either AlPO4 or Li2CO3. This layer may be deposited by any method or technique that does not adversely affect the desired properties of the particles. Representative methods include, for example, spraying and dip coating.

[0097] Electrodes are also provided that contain secondary particles as a component or sole electrochemically active material, as described herein. The active component optionally serving as the cathode contains the secondary particles described herein. The cathode optionally contains the secondary particles disclosed above as the active material and may further contain a conductive agent and a binder. The conductive agent may include any conductive agent that provides suitable properties and may be amorphous, crystalline, or a combination thereof. The conductive agent may include carbon black, such as acetylene black or lampblack, mesocarbon, graphite, graphene, carbon fibers, carbon nanotubes such as single-walled carbon nanotubes or multi-walled carbon nanotubes, or combinations thereof. The adhesive can be any adhesive that provides suitable properties and may include, for example, polyvinylidene fluoride, copolymers of polyvinylidene fluoride and hexafluoropropylene, poly(vinyl acetate), poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate), poly(methyl methacrylate-co-ethyl acrylate), polyacrylonitrile, polyvinyl chloride-co-vinyl acetate, polyvinyl alcohol, poly(l-vinylpyrrolidone-co-vinyl acetate), cellulose acetate, polyvinylpyrrolidone, polyacrylate, polymethyl methacrylate, polyolefin, polyurethane, polyvinyl ether, acrylonitrile-butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene-styrene, triblock polymers of sulfonated styrene / ethylene-butene / styrene, polyethylene oxide, or combinations thereof.

[0098] The cathode can be manufactured by combining the particles, conductive agent, and binder described herein in suitable ratios, for example, approximately 80 to approximately 98% by weight of particles, approximately 1 to approximately 20% by weight of conductive agent, and approximately 1 to approximately 10% by weight of binder based on the total weight of particles, conductive agent, and binder. The particles, conductive agent, and binder can be suspended in a suitable solvent, such as N-methylpyrrolidone, arranged on a suitable substrate (such as aluminum foil), and dried in air. It should be noted that the substrate and solvent are given as examples only. Other suitable substrates and solvents can be used or combined to form the cathode.

[0099] The cathode described in this paper, when cycled in a 2025 coin cell with an MCMB 10-28 graphite anode, a polyolefin separator, and an electrolyte of 1 M LiPF6 in 1 / 1 / 1 (vol.) EC / DMC / EMC containing 1 wt. % VC, optionally exhibits a significantly reduced impedance growth compared to materials enriched only in Co or without grain boundary enrichment. A measure of impedance growth can be obtained through high-rate cycling of the cell, in which 1C / 1C charge / discharge cycles are interspersed at 20-cycle intervals. The cell is charged to 4.2V at 1C and then held at 4.2V until the current decays to the C / 10 rate, after which the cell is allowed to rest in an open circuit for 5 minutes. When the fully charged cell is subsequently discharged, the voltage drop experienced in the first 10 seconds of discharge and the 1C discharge rate are input into Ohm's law (V=IR) to calculate the DCR (DC resistance) measurement of the cell impedance. The impedance measurements plotted against the cycle number yield a curve with a specified slope. Compared to particles without such grain boundary enrichment or particles with grain boundaries enriched only in Co, the impedance slope is lower when the active particle material has grain boundaries enriched in both Co and Al as described herein. In some aspects, the impedance increase of the cell is equal to or less than 25% in the first 50 cycles, optionally 50% or less in the first 100 cycles, optionally 63% or less in the first 125 cycles, and optionally 75% or less in the first 150 cycles. Optionally, the impedance increase is equal to or less than 25% after 50 cycles, optionally 50% or less after 100 cycles, optionally 63% or less after 125 cycles, and optionally 75% or less after 150 cycles.

[0100] A battery pack including a cathode is also disclosed. This battery pack can be, for example, a lithium-ion battery pack, a lithium-polymer battery pack, or a lithium battery pack. The battery pack may include a cathode, an anode, and a separator between the cathode and the anode. The separator may be a microporous membrane and may include a porous film comprising polypropylene, polyethylene, or a combination thereof, or may be a woven or nonwoven material, such as fiberglass mat. The anode may include a coating on a current collector. The coating may include suitable carbon, such as graphite, coke, hard carbon, or mesophase carbon, such as mesophase carbon microspheres. The current collector may be, for example, copper foil.

[0101] The battery pack also includes an electrolyte that can contact the positive electrode (cathode), negative electrode (anode), and separator. The electrolyte may include an organic solvent and a lithium salt. The organic solvent can be a linear or cyclic carbonate. Representative organic solvents include ethylene carbonate, propylene carbonate, butyl carbonate, and propylene trifluorocarbonate. Butyrolactone, sulfolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 3-methyl-1,3-dioxolane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, methyl propyl carbonate, propanesulfonate lactone, or combinations thereof. On the other hand, the electrolyte is a polymeric electrolyte.

[0102] Representative lithium salts that can be used in electrolytes include, but are not limited to, LiPF6, LiBF4, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiN(SO2C2F5)2, LiSbF6, LiC(CF3SO2)3, LiC4F9SO3, and LiAlCl4. Lithium salts are soluble in organic solvents. Combinations containing at least one of the above can be used. The concentration of the lithium salt in the electrolyte can be from 0.1 to 2.0 M.

[0103] The electrolyte can be a solid ceramic electrolyte.

[0104] The battery pack can have any suitable configuration or shape and can be cylindrical or square.

[0105] Various aspects of this disclosure are illustrated by the following non-limiting examples. These examples are for illustrative purposes and not for limiting any practice of the invention. It is to be understood that variations and modifications can be made without departing from the spirit and scope of the invention.

[0106] Example

[0107] Example 1: Polycrystalline 2D α-NaFeO2 type layered structure particles enriched with Al and Co at grain boundaries

[0108] Electrochemically active polycrystalline 2D α-NaFeO2 type layered structure particles with or without different types of grain boundary enrichment and each having high nickel content in the cathode material were prepared.

[0109] By dry mixing 252.1 g of Li(OH)2 (dehydrated, micronized LiOH from FMC) in a 1-liter tank H2O), 961.6Ni 0.91 Co 0.08 Mg 0.01 (OH)2 (customized), prepared with Li 1.03 Mg 0.01 Ni 0.92 Co 0.08 The materials are O2. These compounds are mixed by shaking the can in a paint shaker.

[0110] The mixed compound was placed in an alumina crucible and sintered. Sintering was performed by heating to approximately 450°C at a rate of approximately 5°C / min and holding at approximately 450°C for approximately 2 hours. The temperature was then increased to approximately 700°C at a rate of approximately 2°C / min and held for approximately 6 hours. The sample was then allowed to cool naturally to room temperature. The cooled sample was ground for approximately 5 minutes to break up any agglomerates to provide Li. 1.03 Mg 0.01 Ni 0.92 Co 0.08 O2. XRD analysis of the material confirmed... -NaFeO2 type structure.

[0111] Samples of 100g each of Co and Al grain boundary enriched secondary particles were prepared using the above-mentioned basic materials. Li, Co, and Al nitrates were dissolved in 100g of H₂O heated to 60°C. (The last sentence appears to be incomplete and possibly refers to a different sample.) 1.03 Mg 0.01 Ni 0.92 Co 0.08 Based on Ni+Co in the first O2 composition, the added Al and Co amounts correspond to 1.9 at% and 4 at%, respectively. The amount of LiNO3 prepared results in a final Li / transition metal + Al ratio of 1.01.

[0112] Add 100 grams of the Li prepared above to it. 1.03 Mg 0.01 Ni 0.92 Co 0.08 O2 was used to stir the resulting slurry for 30 to 120 minutes. The slurry was then spray-dried to produce a powder. The resulting powder was placed in an alumina crucible and heated to approximately 450°C at a rate of approximately 5°C / min and held at approximately 450°C for approximately 1 hour. The temperature was then increased to approximately 700°C at a rate of approximately 2°C / min and held for approximately 2 hours. The materials were then allowed to cool naturally to 100°C. The calcined materials were first ground independently in a mortar and pestle, and then ground in a pot mill.

[0113] Overall, four materials with or without Al and / or Co enrichment at grain boundaries were prepared using the procedures described above with the final overall compositions shown in Table 1 (based on their synthetic formulations).

[0114] Table 1:

[0115]

[0116] The resulting materials, along with controls, were each mixed with PVDF binder and conductive carbon in an NMP solvent slurry and coated onto an aluminum foil current collector. Similar coatings of the selected materials were also prepared on Cu foils so that Al distribution could be analyzed by FIB-STEM-EDS without detecting the risk of Al originating from the foil. A cathode electrode was then stamped from the foil and combined with an MCMB 10-28 graphite anode, a porous polypropylene separator, and a carbonate-based electrolyte in a Li-ion “full” coin cell format for electrochemical cycle life testing. This cathode electrode was also combined with a lithium metal anode, a porous polypropylene separator, and a carbonate-based electrolyte in a “half” coin cell format for electrochemical discharge capacity testing.

[0117] The full cell was cycled at 45°C through a series of charge and fast discharge cycles. Low-rate discharge capacity and impedance were measured every 20 charge / discharge cycles. Some materials were further analyzed by EDS and cross-sectional TEM / EDX before being used to form the cathode.

[0118] Figure 2 and 3 The data shows the capacity fade and associated impedance increase of a full cell cycled at 45°C. Figure 2 The results show that samples from the "No Grain-Boundary-Enriching Process" (no slurry, spray drying, or secondary calcination) and the "No Grain-Boundary-Enriching Elements" (no Co or Al solute in the aqueous slurry, spray drying, and secondary calcination) exhibit capacity decay at approximately the same high rate. The "No Grain-Boundary-Enriching Elements" material undergoes an aqueous slurry and subsequent calcination process, but uses only water free of grain-boundary-enriching elements. Figure 3 This indicates that both materials exhibit similar impedance enhancement rates, confirming that water immersion, spray drying, and secondary calcination processes have no significant effect. The aluminum-only sample showed a modest improvement compared to the baseline without grain boundary enrichment, but the most significant improvement was observed for cobalt-only grain boundary enrichment, with a 10% decay over 300 cycles.

[0119] Samples enriched with cobalt and aluminum at the grain boundaries (GB) did not show improved capacity decay compared to cobalt-only samples. However, according to Figure 3 As observed, it exhibits significantly lower impedance growth, with approximately 50% impedance growth after 100 cycles and approximately 115% impedance growth after 200 cycles in a fully charged state. The GB-enriched Co and Al material provides 30% lower impedance growth than the GB-enriched Co material alone, and this is achieved without using any additional Co.

[0120] Cobalt significantly improves aluminum absorption because, in the absence of Co in the process solution, a separate phase of lithium-ionized alumina is observed and shown in the EDS mapping of the calcined material. Figure 4 The image below the EDS elemental distribution plot of aluminum (highlights) shows that the material formulated with only Al in the process solution has stronger and more Al "hot spots" than the material formulated with Co and Al together in the process solution. This indicates that the addition of Co to the process formulation results in a more uniform distribution of Al among the many secondary particles and that Co causes a significant amount of Al to be absorbed by the particles during calcination.

[0121] A comparison of quantitative EDS results for Al analysis of particles over a large area (approximately 150 µm x 150 µm) with results obtained by averaging three points (approximately 1 µm x 1 µm) at non-hotspot locations also shows a more uniform Al distribution and absorption among the many secondary particles when formulated with Co in the process solution. Table 2 shows these comparisons for cathode particles formulated with Al alone and Al-Co, and demonstrates that local non-hotspot analysis with Co and Al produces similar Al content results to those obtained over a wide area, indicating a substantially uniform Al distribution among the many secondary particles. Conversely, materials formulated with Al alone have significantly lower non-hotspot Al analysis results than those over a wide area, indicating that a large amount of Al is concentrated in hotspot particles rather than uniformly distributed among the many secondary particles.

[0122] Table 2: EDS analysis results of cathode material powder

[0123]

[0124] Quantitative spot analysis by STEM / EDS on the thin films of these two materials confirmed that the presence of Co in the process formulation, along with Al, promotes Al absorption into the grain boundaries during subsequent calcination. Secondary particles of each material coated on Cu foil as described above were then sliced ​​using focused ion beam (FIB) milling to produce a thin film approximately 100 nm thick. Figure 5 This image shows a scanning transmission electron microscopy (STEM) image of a small slice containing several microcrystals from particles prepared by grain boundary enrichment method using 1.9 at% Al and 4 at% Co in a process liquid. The images also show the locations of three EDS point analyses: locations 1 and 3 are inside adjacent microcrystals, and location 2 is at the intermediate grain boundary. Figure 6 Displayed Figure 5EDS spectra were collected at three locations marked in the image. Spectrum 2 at the grain boundary shows a clear Al peak at approximately 1.5 keV, while spectra 1 and 3 inside the grains do not. As shown by comparing the 6.9 keV Co peak with the 8.3 keV Ni peak in each spectrum, spectrum 2 at the grain boundary also exhibits a higher Co / Ni ratio than seen in spectra 1 and 3 inside the grains. Figure 6 The quantitative results obtained by spectral integration are shown in Table 3, which indicate that Al and Co are enriched at the grain boundary sites in spectrum 2.

[0125] Table 3: Results of 3 EDS point analysis of particles made from liquid materials produced using a 1.9 at% Al and 4 at% Co process.

[0126]

[0127] ND: Undetectable

[0128] Particles prepared by a grain boundary enrichment method in a Co-free process solution containing 1.9 at% Al were subjected to the same type of STEM-EDS analysis, and the positions of the STEM images and EDS point analyses were shown in the images. Figure 7 In the middle. Spectrum 1 is located at the grain boundary, while spectrum 2 is located inside the microcrystals. Figure 8 Displayed Figure 7 EDS spectra were collected at two locations marked in the middle, and neither spectrum indicated the presence of Al, and there was almost no difference between their Co peaks. By... Figure 8 The quantitative results obtained by spectral integration are shown in Table 4, and show that the composition of the grain boundaries and bulk microcrystals is the same, indicating that there is almost no Al uptake or enrichment at the grain boundaries in the secondary particles.

[0129] Table 4: Results of 2 EDS point analysis of only 1.9 at% Al in the process fluid

[0130]

[0131] The above-mentioned type of STEM-EDS point analysis was performed at a total of 11 grain boundaries and 10 microcrystal interior locations in the 1.9 at% Al, 4 at% Co grain boundary enriched material, and at 16 grain boundaries and 7 microcrystal interior locations in the 1.9 at% Al-only enriched material. Table 5 presents the average results of these analyses compared with bulk formulated compositions of these materials and shows that applying an Al-only liquid process and subsequent calcination resulted in almost no Al enrichment at the grain boundaries (measurable amounts of Al were detected at 3 of the 16 locations), while processing with Al and Co and subsequent calcination resulted in significant enrichment of both elements at the grain boundaries.

[0132] Table 5: Average EDS point analysis results of grain boundaries (second composition) and microcrystal interiors (first composition) of materials enriched only with 1.9 at% Al or 1.9 at% Al and 4 at% Co.

[0133]

[0134] Example 2: Grain boundary enrichment of Al and Co using a non-crystal grain boundary enrichment method

[0135] Polycrystalline 2D α-NaFeO2-type layered structure particles with different types of grain boundary enrichment and each exhibiting high nickel content in the cathode material were prepared using a non-crystalline grain boundary enrichment method. Li-based particles were prepared using the method described in Example 1. 1.03 Mg 0.01 Ni 0.92 Co 0.08 The material was prepared using O2. 30 g of this material was then dispersed in 40 mL of methanol containing 1.9 at % Al as dissolved nitrate, with or without 4 at % cobalt nitrate, and with sufficient LiNO3 to achieve a final Li / transition metal + Al ratio of 1.01. The resulting slurry was rotary evaporated to dryness, and the recovered material was subsequently subjected to the same calcination process applied to the spray-dried material in Example 1. Figure 9 The Al EDS mapping of the calcined material is shown, and it is demonstrated that, as seen in the aqueous process material of Example 1, the material formulated with Al alone has stronger and more Al “hot spots” than the material formulated with Co and Al together. This result indicates that the effect of solution processing using Co in promoting more uniform absorption of Al by secondary particles is not an illusion of aqueous processes, and that enrichment of elements at grain boundaries through non-aqueous deposition via solvent evaporation produces the same results as aqueous deposition via acid-base precipitation.

[0136] Example 3: Synergistic benefits obtained by enriching Al and Co at grain boundaries

[0137] By Li 1.03 Mg 0.01 Ni 0.92 Co 0.08 The O2-based materials were prepared using the method described in Example 1, resulting in electrochemically active polycrystalline 2D α-NaFeO2-type layered particles with different types of grain boundary enrichment, each exhibiting high nickel content in the cathode material. The Al and Co process formulations used to manufacture these materials are shown in Table 6.

[0138] Table 6: Al and Co content in the process solution used to manufacture the grain boundary enrichment material of Example 3

[0139]

[0140] Li-ion button cells were constructed using the materials enriched in Table 6 and cycled according to the method of Example 1. Figure 10 The diagram illustrates the cycle capacity decay of batteries using 0 at% Al grain boundary enriched materials and batteries using 0.5 at% Al grain boundary enriched materials, and their dependence on the Co content in the formulation. As the Co content in the formulation increases, the capacity of the various materials decreases, but their capacity decay rates do not differ significantly, ranging from 4% to 6% after 200 cycles and are largely unaffected by the presence or absence of 0.5 at% Al in the formulation. However, Figure 11 The results show that increasing the Co content in the formulation reduces impedance growth. When the Co content in the formulation increases from 3 at% to 4 at% in the formulation, the impedance growth at 4.2V over 200 cycles decreases from 250% to 130%. Furthermore, the addition of 0.5 at% Al in the solution process formulation significantly reduces impedance growth at all Co contents in the formulation. As the Co content in the solution process formulation increases from 3 at% to 4.5 at% in the formulation, the impedance growth over 200 cycles decreases from 150% to 90%. Figure 12 Further evidence shows that the inclusion of Al in the solution-process formulation resulted in a synergistic effect, with the impedance reduction being greater than that achievable by simply increasing the Co concentration.

[0141] Figure 13 The graph shows the cycle capacity decay (left) and impedance growth (right) of cells with cathode materials formulated using a 3 at% Co solution process with varying Al content. The figure indicates that increasing the Al content reduces the cathode material's capacity without significantly affecting capacity decay (all cells decayed in the 6%–8% range after 200 cycles), but increasing the Al content from 0 at% to 1 at% reduced the impedance growth at 4.2V after 200 cycles from 200% to 120%, while higher Al contents resulted in a slightly increased impedance growth. (Plotted on...) Figure 13 The impedance increase in the middle is summarized as follows Figure 14 The results show that when 3 at% Co is present in the process solution along with Al, the lowest impedance growth is obtained when the Al / Co atomic percentage ratio of the process solution is about 0.3-0.4.

[0142] Example 4: Al and Co grain boundary enrichment in NCA material

[0143] Two NCA materials with similar overall compositions were fabricated, one with enriched Co and Al grain boundaries and the other without. In each case, the base material was fabricated by incorporating hydroxide precursors together and calcining in an oxygen atmosphere until the final lithiated oxide was formed and then sintering.

[0144] Material 1: Containing the first composition LiNi 0.93 Co 0.04 Al 0.03 O2-based NCA materials, with an additional 4 at% Co and 0.6 at% Al grain boundaries relative to the total M in the first composition.

[0145] A precursor transition metal hydroxide is used in this method. It contains 4 at% Co and 3 at% Al by transition metal and the balance Ni. Micronized LiOH powder is prepared by placing 51 g of LiOH together with 500 g of Y-stabilized zirconia ¼” spheres in a plastic can and shaking on a paint shaker for 45 minutes. This micronized powder is then transferred to another plastic can containing 190.15 g of the transition metal hydroxide precursor and the two powders are blended by shaking the can on a paint shaker for an additional 10 minutes. After blending, approximately 240 g of the blended powder is divided into two crucibles and calcined in an oxygen atmosphere by first ramping to 450 °C at 5 °C / min and homogenizing at that temperature for 2 hours, and then ramping to 680 °C at 2 °C / min and homogenizing for 6 hours. When this heating process is complete, the furnace is allowed to cool to 130 °C, the powder is removed, and placed in a can mill. This can mill contains ½” drum media and is used to grind the powder for 2 minutes. The powder was then sieved through a 270-mesh sieve. XRD analysis of the material confirmed... -NaFeO2 type structure.

[0146] The powder was then coated with Co and Al by preparing a solution of 80 g water, 9.5 g cobalt nitrate (4 at% Co relative to the total M in the LiMO2 base composition), 1.9 g aluminum nitrate (0.6 at% Al relative to the total M in the LiMO2 base composition), and 2.7 g lithium nitrate, and heating it to 60 °C. 80 g of the previously prepared powder was added to this solution. The slurry was stirred for 25 minutes, and then spray-dried to remove water and prepare a dry powder. This powder was then calcined in air by first heating to 450 °C at 5 °C / min and homogenizing for 1 hour, and then heating to 700 °C at 2 °C / min and homogenizing for 2 hours. The furnace was then allowed to cool to 130 °C, the powder was removed from the furnace, and sieved through a 270-mesh sieve. Figure 15 This image shows a STEM micrograph of a thin slice of secondary particles of the material thus prepared, coated on Cu foil as described in Example 1. Figure 15 The results also provide Al / Ni and Co / Ni atomic ratios from three EDS point analyses of the internal grain boundaries (GB) and the bulk region of adjacent primary particles, indicating that the grain boundaries are enriched in Co and Al.

[0147] Material 2: LiNi with uniform first composition 0.89 Co 0.08 Al 0.03 O2 vs. NCA basic materials

[0148] A precursor transition metal hydroxide was used in this method. It contained 8 at% Co and 3 at% Al with the balance Ni. Micronized LiOH powder was prepared by placing 25.5 g of LiOH with 500 g of Y-stabilized zirconia ¼” spheres in a plastic can and shaking it on a paint shaker for 45 minutes. This micronized powder was then transferred to another plastic can containing 95.1 g of the transition metal hydroxide and the two were blended by shaking the can on a paint shaker for an additional 10 minutes. After blending, approximately 120 g of the powder was placed in a crucible and calcined in an oxygen atmosphere by first ramping to 450 °C at 5 °C / min and homogenizing at that temperature for 2 hours, and then ramping to 680 °C at 2 °C / min and homogenizing for 6 hours. The furnace was then allowed to cool to 130 °C, the powder was removed, and placed in a can mill containing ½” drum media for grinding the powder for 2 minutes. The powder was then sieved through a 270-mesh sieve. XRD analysis of the material confirmed... -NaFeO2 type structure.

[0149] The cathode materials 1 and 2 described above were assembled in a coin cell as described in Example 1. The cell was cycled at 45°C at 1C / 1C, with the discharge rate (DCR) measured for 10 seconds at 100% state of charge (SOC) per cycle and at 50% SOC every 20 cycles. The capacity decay and impedance growth results of the Li-ion coin cells made with each material are shown in the figures below. Figure 16 and Figure 17 Although the overall compositions of the two materials are nearly identical, grain boundary enriched material #1 contains Co enriched at the grain boundaries between bulk microcrystals, while material #2 contains an equal total amount of Co uniformly distributed in secondary particles. Material #1 has only slightly higher total Al content than material #2, but the additional Al (~16% more Al than material #2) is concentrated at the grain boundaries. Compared to the homogeneous material, the GBE material exhibits significantly improved capacitance decay and impedance growth. Figure 16 The results show that grain boundary enriched material #1 has a slightly higher capacity (~1%) than uniform material #2, and also has only 8% capacity decay over 200 cycles, compared to >30% decay for material #2. Figure 17 The results show that the cell with grain boundary enriched material #1 has a 100% impedance increase at full SOC (4.2V) and a 30% impedance increase at 50% SOC after 200 cycles, while the cell with material #2 has a >800% impedance increase at full SOC and a >200% impedance increase at 50% SOC after 200 cycles.

[0150] Example 5: Al and Co grain boundary enrichment in NCM materials

[0151] LiNi was prepared from a co-precipitated precursor transition metal hydroxide containing 10 at% Co and 10 at% Mn and the balance Ni. 0.8 Co 0.1 Mn 0.1O2-based NCM material (NCM 811). Micronized LiOH powder was prepared by placing 87.7 g of LiOH with 500 g of Y-stabilized zirconia ¼” spheres in a plastic container and shaking on a paint shaker for 45 minutes. This micronized powder was then transferred to another plastic container containing 335.7 g of precursor transition metal hydroxide and blended by shaking on a paint shaker for an additional 10 minutes. After blending, approximately 440 g of powder was divided into three crucibles and calcined in an oxygen atmosphere by first ramping to 450 °C at 5 °C / min and homogenizing at that temperature for 2 hours, and then ramping to 770 °C at 2 °C / min and homogenizing at 770 °C for 10 hours. The furnace was then allowed to cool to 130 °C, the powder was removed, and placed in a can mill containing ¾” drum media for grinding the powder for 2 minutes. The powder was then sieved through a 270-mesh sieve.

[0152] The powder was then separated into a substrate (without further processing) or a grain boundary enriched with Co and Al—by preparing a solution of 200 g water, 11.9 g cobalt nitrate (2 at% Co relative to the base composition), 3.1 g aluminum nitrate (0.4 at% Al), and 3.4 g lithium nitrate and heating it to 60 °C. 200 g of the previously prepared lithiation precursor powder was added to this solution. The slurry was stirred for 10 minutes, after which it was spray-dried to remove water and prepare a dry powder. This powder was then calcined in air atmosphere by first ramping up to 450 °C at 5 °C / min and homogenizing at that temperature for 1 hour, and then ramping up to 770 °C at 2 °C / min and homogenizing for 0.25 hours. The furnace was then allowed to cool to 130 °C, the powder was removed from the furnace, and sieved through a 270-mesh sieve. The overall composition of the synthesized cathode powder was LiNi. 0.079 Co 0.11 Mn 0.09 Al 0.006 O2.

[0153] The aforementioned substrate and grain boundary-enriched NCM material were then assembled into a Li-ion coin cell, which was cycled at 45°C using the methods described in Examples 1 and 4. The capacity decay and impedance growth results of the two-cell Li-ion coin cells made with each material are shown in […]. Figure 18 and Figure 19 Both materials exhibit good cycle stability. Figure 18 The grain boundary enriched material exhibits slightly lower attenuation (approximately 4% attenuation over 200 cycles vs. approximately 5% attenuation for the base material) and a slightly lower initial capacity. Nevertheless, the grain boundary enriched material demonstrates a significantly lower impedance growth than the similarly composed homogeneous base material. Figure 19The NCM exhibited a 45% impedance increase at 100% SOC and a 38% impedance increase at 50% SOC after 200 cycles, compared to a 225% impedance increase at 100% SOC and a 70% impedance increase at 50% SOC for the base material after 200 cycles. These results confirm the benefits of NCM with relatively low amounts of Al and Co enriched at grain boundaries.

[0154] In addition to those shown and described herein, various modifications will be apparent to those skilled in the art from the foregoing specification. Such modifications are also intended to fall within the scope of this disclosure.

[0155] It should be recognized that, unless otherwise specified, all reagents are available from sources known in the art.

[0156] The patents, publications, and applications mentioned in this specification indicate the level of skill of a person skilled in the art to which this disclosure pertains. These patents, publications, and applications are incorporated herein by reference as if each patent, publication, or application were specifically and individually incorporated herein by reference.

[0157] The above description is an illustrative example of a particular aspect of the invention but is not intended to limit its practice.

Claims

1. A particle comprising: Contains numerous microcrystals of a first composition containing lithium, nickel, and oxygen; Between adjacent microcrystals of the plurality of microcrystals and comprising a layered structure -Grain boundaries of a second composition of NaFeO2 type structure, cubic structure, spinel structure or combinations thereof; The aluminum concentration at the grain boundaries is greater than that in the microcrystals, and optionally, the cobalt concentration at the grain boundaries is greater than that in the microcrystals.

2. The particles of claim 1, wherein aluminum is substantially uniformly distributed among the plurality of particles.

3. The particles of claim 1, wherein the amount of aluminum at the grain boundaries is from 0.01 at% to 10 at% relative to the total transition metals in the first composition.

4. The particles of claim 1, wherein the aluminum concentration in the second composition is equal to or less than the Co concentration in the second composition.

5. The particles of any one of claims 1-4, wherein the plurality of microcrystals have an α-NaFeO2 type layered structure, a cubic structure, a spinel structure, or a combination thereof.

6. The particles of any one of claims 1-4, wherein the microcrystals comprise Li 1+x MO 2+y The first composition is defined, wherein -0.1 ≤ x ≤ 0.3, -0.3 ≤ y ≤ 0.3 and M contains 10 atomic percent or more of nickel.

7. The particle of claim 6, wherein M comprises 75 at% or more of nickel atoms.

8. The particles of any one of claims 1-4, wherein the grain boundaries comprise cobalt in an amount of about 2 at% to about 99 at% relative to the total transition metals in the second composition and aluminum in an amount of about 0.5 at% to about 99 at% relative to the total transition metals in the second composition.

9. The particle of claim 6, wherein M further comprises an additional metal, wherein the additional metal is present in an amount of about 1 at% to about 90 at%; The additional metal is selected from Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Cr, Fe, Mo, B, and any combination thereof.

10. The particles of claim 6, wherein the microcrystals comprise cobalt, the cobalt concentration being in the range of 0 at% to about 50 at% relative to the total transition metals in the first composition, optionally from 1 at% to about 50 at% relative to the total transition metals in the first composition.

11. The particles of claim 6, wherein the microcrystals comprise cobalt, the cobalt concentration being in the range of 1 at% to about 10 at% relative to the total transition metals in the first composition.

12. The particle according to any one of claims 1-4, wherein The microcrystals contain Mn in amounts ranging from about 1 at% to about 60 at%, and The grain boundaries contain Mn in amounts ranging from about 1 at% to about 60 at%, where at% is relative to the total transition metal in the microcrystals or grain boundaries, respectively.

13. The particles of any one of claims 1-4, wherein the grain boundaries comprise Ni, Co, and Al.

14. The particles of any one of claims 1-4, wherein the Ni concentration at the grain boundary is less than 90 at relative to the total transition metal at the grain boundary.

15. The particle of any one of claims 1-4, further comprising an outer coating on the particle surface, said outer coating comprising: Oxides of one or more elements selected from Al, Zr, Y, Co, Ni, Mg, and Li; Fluorides containing one or more elements selected from Al, Zr, and Li; Carbonates containing one or more elements selected from Al, Co, Ni, Mn and Li; Sulfates containing one or more elements selected from Al, Co, Ni, Mn, and Li; or Phosphates containing one or more elements selected from Al and Li.

16. An electrochemically active polycrystalline secondary particle, comprising: Numerous microcrystals, the numerous microcrystals comprising Li 1+x MO 2+y The first composition is defined, wherein -0.1≤x≤0.3, -0.3≤y≤0.3 and M contains 80 atomic percent or more nickel; and Between adjacent microcrystals of the plurality of microcrystals are grain boundaries comprising a second composition optionally having an α-NaFeO2 type layered structure, a cubic structure, a spinel structure or a combination thereof, wherein the aluminum concentration in the grain boundaries is greater than the aluminum concentration in the microcrystals, and wherein the cobalt concentration in the grain boundaries is greater than the cobalt concentration in the microcrystals, and wherein aluminum is substantially uniformly distributed in the grain boundaries.

17. The particles of claim 16, wherein the cobalt concentration at the grain boundaries is greater than the aluminum concentration at the grain boundaries.

18. The particles of claim 16, wherein the cobalt concentration in the microcrystals is from about 0 to about 17 atomic percent, and The cobalt concentration at the grain boundaries is from about 0.5 to about 32 atomic percent, each based on the total atomic transition metal composition of the particles.

19. The particles of claim 16, wherein M further comprises one or more elements selected from Al, Mg, Co, Mn, Ca, Sr, Ba, Zn, Ti, Zr, Y, Cr, Mo, Fe, V, Si, Ga, and B, said one or more elements being located in the Li layer, M layer, or both of said microcrystals.

20. The particle of claim 16, wherein M comprises 90% or more of nickel atoms.

21. An electrochemical battery comprising a cathode active material, said cathode active material comprising particles of any one or more of claims 1-20.

22. The electrochemical battery of claim 21, characterized in that... The impedance increase at 4.2V is less than 100% over more than 100 cycles at 45°C.

23. The electrochemical battery of claim 21, characterized in that... The impedance increase at 4.2V is less than 100% over more than 200 cycles at 45°C.

24. A particle comprising: An overall composition comprising lithium, nickel, cobalt, aluminum, and oxygen; The particles comprise primary microcrystals having a first composition; Between adjacent microcrystals of these numerous microcrystals and comprising layered structures -Grain boundaries of a second composition with a NaFeO2-type structure, cubic structure, spinel structure, or a combination thereof. The atomic fraction of aluminum relative to nickel at the grain boundaries is greater than that in the crystallites, and the atomic fraction of cobalt relative to nickel at the grain boundaries is greater than that in the crystallites; or The atomic fraction of aluminum relative to nickel at the grain boundaries is greater than the atomic fraction of aluminum relative to nickel in the overall composition, and the atomic fraction of cobalt relative to nickel at the grain boundaries is greater than the atomic fraction of cobalt relative to nickel in the overall composition; or The atomic fraction of aluminum relative to nickel at the grain boundaries is greater than the atomic fraction of aluminum relative to nickel in the overall composition, and the atomic fraction of cobalt relative to nickel in the primary crystallites is less than the atomic fraction of cobalt relative to nickel in the overall composition; or Their combination.

25. A method for forming the particles of any one of claims 1-4, comprising: Combining lithium compounds and nickel compounds to form a mixture; The mixture is heat-treated to produce a precursor comprising a plurality of microcrystals and grain boundaries between adjacent microcrystals of the plurality of microcrystals, wherein the plurality of microcrystals comprises a first composition containing Li, Ni and O; The precursor is impregnated in a process solution containing Co and Al; Dry the precursor; and The precursor is heat-treated to form particles, wherein the aluminum concentration at the grain boundaries is greater than the aluminum concentration in the microcrystals, and wherein the cobalt concentration at the grain boundaries is greater than the cobalt concentration in the microcrystals.

26. The method of claim 25, wherein the liquid is aqueous or contains an organic solvent, optionally methanol.

27. The method of claim 25, wherein the process solution comprises an amount of aluminum of 0.01 at% to 10 at% relative to the total transition metals in the precursor particles and an amount of cobalt of 0.5 at% to 10 at% relative to the total transition metals in the precursor particles.

28. The method of any one of claims 25-27, wherein at% Al in the process solution is equal to or less than at% Co in the process solution.

29. The method of any one of claims 25-27, wherein the plurality of microcrystals have an α-NaFeO2 type layered structure, a cubic structure, a spinel structure, or a combination thereof.

30. The method of any one of claims 25-27, wherein the microcrystals comprise Li 1+x MO 2+y The first composition is defined, wherein -0.1 ≤ x ≤ 0.3, -0.3 ≤ y ≤ 0.3 and M contains 10 atomic percent or more of nickel.

31. The method of claim 30, wherein M comprises 75 at% or more of nickel atoms.

32. The method of claim 30, wherein M further comprises an additional metal, wherein the additional metal is present in an amount of about 1 at% to about 90 at%; The additional metal is selected from Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Cr, Fe, Mo, B, and any combination thereof.

33. The method of any one of claims 25-27, wherein the grain boundary comprises cobalt in an amount of about 2 at% to about 99 at% relative to the total transition metals in the grain boundary and aluminum in an amount of about 0.5 at% to about 99 at% relative to the total transition metals in the grain boundary.

34. An electrochemical battery comprising: anode, Electrolytes, and The cathode comprises an electrochemically active cathode active material containing a plurality of particles, the plurality of particles comprising a plurality of microcrystals, each microcrystal comprising a first composition containing lithium, nickel and oxygen; Between adjacent microcrystals of the plurality of microcrystals and comprising a layered structure -Grain boundaries of a second composition of NaFeO2 type structure, cubic structure, spinel structure or combinations thereof; The electrochemically active cathode material described herein has an initial discharge capacity of 180 mAh / g or greater; and The electrochemical cell described therein exhibits an impedance increase of less than 50% at 4.2V for more than 100 cycles at 45°C.

35. The battery of claim 34, wherein the electrochemical battery has an impedance increase of less than 120% at 4.2V for more than 200 cycles at 45°C.

36. The battery of claim 34, characterized in that... The impedance increase at 50% charge is less than 50% for more than 200 cycles at 45°C.

37. The battery of claim 34, wherein each microcrystal comprises lithium, nickel, cobalt and oxygen.

38. The battery of claim 37, wherein each microcrystal further comprises Al.

39. The battery of claim 37, wherein each microcrystal further comprises Mn.

40. The battery of claim 37, wherein each microcrystal further comprises Mg.

41. The battery of claim 34, wherein the first composition and the second composition have the same elements.

42. The battery of any one of claims 34-41, wherein the first composition is composed of Li 1+x MO 2+y Defining, among which -0.95≤x≤0.3, -0.3≤y≤0.3 and M contains 80 atomic percent or more of nickel.

43. The battery of claim 42, wherein M further comprises one or more elements selected from Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Nb, Ta, Cr, Fe, Mo, W, Hf and B, said one or more elements being located in the Li layer, M layer or both of the microcrystals.

44. The battery of claim 42, wherein M comprises 90% or more nickel atoms.

45. The battery of any one of claims 34-41, wherein the microcrystals comprise cobalt, the cobalt concentration being in the range of 1 at% to about 50 at% relative to the total transition metals in the first composition.

46. ​​The battery of any one of claims 34-41, wherein the microcrystals comprise cobalt, the cobalt concentration being in the range of 1 at% to about 15 at% relative to the total transition metals in the microcrystals.

47. The battery of any one of claims 34-41, wherein the microcrystals comprise Co and Mg.

48. The battery of any one of claims 34-41, wherein the second composition comprises Al.

49. The battery of any one of claims 34-41, wherein the first composition does not include Al.

50. The battery of any one of claims 34-41, wherein the Al in the second composition is substantially uniformly distributed among the plurality of particles.

51. The battery of any one of claims 34-41, wherein Al is present in a concentration of less than 4 atomic percent relative to the total transition metals in the first composition.

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