Stable cathode material

Abstract

Electrochemically active particles suitable for use as an active material in a cathode of a lithium-ion electrochemical cell are provided, comprising: a plurality of crystallites comprising a first composition containing lithium, nickel, and oxygen; and grain boundaries between adjacent crystallites of the plurality of crystallites, the grain boundaries comprising a second composition containing lithium, nickel, and oxygen; wherein the grain boundaries have a greater electrochemical affinity for lithium than the crystallites. The higher electrochemical affinity for Li increases Li retention at the grain boundaries during charging compared to the bulk crystallites and stabilizes the structure of the grain boundaries and crystallites for improved cycling stability with little loss of capacity.

Description

[Technical Field]

[0001] Cross-reference of related applications This application is dependent on and claims priority under U.S. Patent Application No. 62 / 796,950 filed on 25 January 2019, U.S. Patent Application No. 16 / 728,379 filed on 27 December 2019, U.S. Patent Application No. 16 / 250,615 (currently U.S. Patent No. 10,501,335) filed on 17 January 2019, U.S. Patent Application No. 16 / 250,762 filed on 17 January 2019, U.S. Patent Application No. 16 / 250,622 filed on 17 January 2019, and PCT Application No. PCT / US2019 / 057630 filed on 23 October 2019, the entire contents of each of these are incorporated herein by reference.

[0002] This disclosure relates to an electrochemical active material for use in the cathode of a secondary battery.

[0003] Background of the Invention LiMO2 materials, based on layered lithium nickel oxide (LiNiO2), are generally preferred as lithium battery cathode materials because they offer lower cost, higher capacity, and higher rated capacity than lithium cobalt oxide (LiCoO2). However, pure LiNiO2 materials exhibit insufficient electrochemical stability and cycle performance. It has been found that replacing some or most of the bulk material Ni in LiNiO2 with varying amounts of other metals provides several advantages in terms of capacity and cost, along with improved electrochemical cycle stability.

[0004] Furthermore, it has been found that even with such substituted LiNiO2 materials, stability may be insufficient when charged to high capacities (e.g., ≥220mAh / g). Therefore, novel materials with improved capacity and / or cycle life are needed.

[0005] Summary of the Invention The following summary is provided to facilitate understanding of some of the innovative features inherent in this disclosure and is not intended to be a complete description. A full understanding of the various aspects of this disclosure can be achieved by interpreting the entire specification, claims, drawings, and abstract as a whole.

[0006] Electrochemically active particles containing grain boundaries with higher electrochemical affinity to lithium are provided, exhibiting improved cycling capability at comparable capacity compared to a stabilized, grain boundary-less base material. The inventors have found that by selectively increasing the oxidation potential of the grain boundary regions of the particles, thereby enhancing the electrochemical affinity to Li, capacity retention can be increased and impedance increase during cycling reduced without a significant decrease in capacity compared to an active material without grain boundary stabilization.

[0007] Therefore, there is provided an electrochemically active particle that can be used as an active material in the cathode of an electrochemical cell (or other such device), comprising a plurality of crystallites comprising a first composition containing lithium, nickel, and oxygen, and grain boundaries between adjacent crystallites of the plurality of crystallites comprising a second composition containing lithium, nickel, and oxygen, wherein the grain boundaries have an electrochemical affinity for lithium that is larger than the crystallites.

[0008] Also provided are electrochemically active particles comprising a plurality of crystallites containing a first composition containing lithium, nickel, and oxygen, and grain boundaries between adjacent crystallites of the plurality of crystallites, the grain boundaries containing a second composition containing lithium, nickel, and oxygen, wherein lithium is present at the grain boundaries at a higher concentration than lithium in the crystallites when the particles are charged to 10 percent or more.

[0009] The present invention also provides electrochemically active particles comprising: a plurality of crystallites comprising a first composition containing lithium, nickel, and oxygen; and grain boundaries between adjacent crystallites of the plurality of crystallites comprising a second composition containing lithium, nickel, and oxygen; wherein lithium is present at the grain boundaries at a higher concentration than lithium in the crystallites when the electrode containing the particles is charged to a potential of 4.1V or higher relative to lithium, or at a higher concentration than lithium in the crystallites when the charging capacity is 40mAh / g or higher.

[0010] Electrodes containing one or more electrochemically active particles provided herein are also provided. Electrochemical cells containing one or more electrochemically active particles provided herein in a cathode are also provided.

[0011] The embodiments shown in the drawings are illustrative and illustrative in nature and are not intended to limit the subject matter as defined by the claims. The following detailed description of the illustrative embodiments can be understood by reading in conjunction with the following drawings. Similar structures in the drawings are indicated by the same reference numerals. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows that as the amount of Ni substitution in LiMO2 by other metals increases, the amount of Li extracted from LiMO2 when charged to a given potential decreases. [Figure 2] This figure shows that LiMO2 materials with a lower Ni content than LiNiO2 undergo less delithiation than LiNiO2 when the materials are charged to the same potential. [Figure 3] This figure shows the position of the EDS line scan in a thin lamellar fabricated from grain boundary-modified LiMO2 material particles of Example 4. [Figure 4]This figure shows the results of EDS line scanning in thin lamellae fabricated from grain boundary-modified LiMO2 material particles of Example 4, where A and C represent the LS1 scan lines in Figure 3, and B and D represent the LS2 scan lines in Figure 3. [Figure 5] This figure shows the XRD results of the grain boundary-modified LiO2 material of Example 3 and its uniform composition LiO2-based charged cathode electrode and initial cathode electrode. [Figure 6] This figure shows the high-resolution XRD results of the grain boundary-modified LiMO2 material of Example 3 and the LiMO2-based charged electrode of its uniform composition, with the peak positions offset and scaled to the (10⁴) peak. [Figure 7] This figure shows the discharge capacity as a function of the number of cycles for the grain boundary-modified LiMO2 material of Example 1 and its uniform composition LiMO2 precursor during cycling at 45°C in a full coin cell. [Figure 8] This figure shows a comparison of the impedance increase during cycle lifetime measurement at 45°C for the materials shown in Figure 7 in a full coin cell. [Figure 9] This figure shows the discharge capacity as a function of the number of cycles for the grain boundary-modified LiMO2 material of Example 2 and its uniform composition LiMO2 precursor during cycling at 45°C in a full coin cell. [Figure 10] This figure shows a comparison of the impedance increase during cycle lifetime measurement at 45°C for the materials shown in Figure 9 in a full coin cell. [Figure 11] This figure shows the discharge capacity as a function of the number of cycles for the grain boundary-modified LiMO2 materials of Examples 3-5 and their uniform composition LiMO2 precursors during cycling at 45°C in a full coin cell. [Figure 12] This figure shows a comparison of the impedance increase during cycle lifetime measurement at 45°C for the materials shown in Figure 11 in a full coin cell. [Figure 13] This figure shows the increase in fracture toughness of low-Ni particles at grain boundaries compared to adjacent crystallites. [Figure 14]This figure shows the reduction in the impedance ratio of the materials provided herein in several embodiments, where the open-circle symbols represent bulk materials and the black-filled areas indicate a selective reduction in Ni at grain boundaries.

[0013] Detailed explanation The inventors of this disclosure have found that electrochemical extraction of high levels of lithium from a polycrystalline LiMO2-based material having a 2D α-NaFeO2-type layered structure results in the formation of 2D layers of transition metal atoms within the crystallite grain boundaries, reconfiguration into a NiO-type rock salt structure, and consequently, a decrease in the oxidation state of the transition metals, oxygen loss, and the introduction of defects such as oxygen vacancies in the ceramic and nickel mixing between the nickel and lithium layers. This reconfiguration begins at the grain boundaries and propagates deep into the crystallites with repeated cycles. This reconfiguration may be associated with mechanical damage, including the appearance of cracks between adjacent crystallites. This loss of stability in the material during high-level lithium extraction leads to a decrease in capacity and an increase in the impedance of the cathode material as the cathode material is cycled.

[0014] This disclosure is based on the finding that the performance of LiNiO2-based materials can be improved by designing the material so that more lithium is retained in the grain boundary regions at the end of charging by increasing the oxidation potential of the grain boundary regions, thereby preventing or slowing down grain boundary reconstruction, reducing the ease of NiO and Li2O formation, and reducing the rate of impedance increase of these materials as shown in this disclosure. Accordingly, this disclosure provides polycrystalline LiMO2-based materials including 2D α-NaFeO2-type layered structures that selectively retain more Li at grain boundaries than in the internal structure of the crystallite when the material is charged and / or has increased stability in specific regions of the particles, in order to reduce the rate of impedance increase during battery charge / discharge cycles and to optionally improve cycle life. These materials provide high cycle capacity by still releasing Li from the bulk crystallite structure, even when charged, while retaining Li at grain boundaries where delithiation of the crystallite material is necessary to stabilize against structural reconstruction propagating from the grain boundaries. The retention of higher Li levels at grain boundaries in charged materials compared to bulk crystallites can be achieved by selectively increasing the local oxidation potential of the grain boundary region, thereby preventing the grain boundaries from being delithified to the same extent as LiMO2 bulk crystallites when the material is charged to a predetermined electrochemical potential.

[0015] The nature of the role that increasing the local oxidation potential in the composition of LiMO2 grain boundaries plays in promoting the retention of Li at those grain boundaries can be understood by referring to Figure 1, which shows the initial C / 20 charging curves in the anode half-cells of Li metal for cathode materials with varying ratios of Ni as M in LiMO2. These data show that for a series of conventional LiMO2-based Li-ion cathode materials, the potential at which Li is extracted during charging increases, and the amount of Li extracted at a given potential decreases as the proportion of Ni in LiMO2 decreases. Table 1 summarizes the data from Figure 1, showing that the amount of Li retained when charged to 4.3V relative to lithium increases as the Ni content of the LiMO2 material decreases. The data in Figure 1 and Table 1 are based on in-house coin cell measurements, with the exception of NM-11, which is based on results from Kang, K., et al., Science, 311 (17), 2006, p.977.

[0016] [Table 1]

[0017] The metals that replace some of the Ni in the bulk of the LNO materials in Figure 1 and Table 1 (not selective localization) include Co and Mn, which are representative metals that effectively reduce the oxidation tendency of LiMO2 compared to Ni when the LiMO2 material is charged, and Al, which is representative of metals that are not oxidized at all when the LiMO2 material is charged. The relative amounts of such metal substitutions affect the degree of oxidation of these bulk materials and the retention of Li. Therefore, although both NCM811 and NCA have Ni, which makes up 80% of the M in LiMO2, Co and Mn in NCM811 can both be oxidized, while Al in NCA is not, so NCA retains more Li when charged to 4.3V relative to lithium.

[0018] The various effects of raising the local oxidation potential in the LiMO2 structure can generally be understood by considering simplified concepts such as the oxidation potential and / or the number of electrons of the metal in relation to crystal field theory. In the LiMO2 stoichiometry, the average oxidation state of M in the structure is +3. In the 2D α-NaFeO2-type layered structure, since the M atoms are in a relatively strong octahedral field, this is d 6 (t 6 2g crystal field configuration) and d 3 (t 3 2g crystal field configuration) and is stabilized by the metal having the number of electrons. Ni 3+ has d 7 while Co 3+ has d 6 . Therefore, when LiNiO2 is oxidized, it acquires a stable t 6 2g crystal field configuration, while when LiCoO2 is oxidized, it loses the t 6 2g crystal field configuration. Thus, LiNiO2 has a greater tendency to be oxidized than LiCoO2. From published X-ray absorption studies, it has been shown that when Ni is replaced by Mn, Mn is accommodated in a stable +4 oxidation state (t 3 2g crystal field configuration) and is charge-compensated by Ni in the +2 oxidation state (t 6 2g e 2 g crystal field configuration). Therefore, in order to oxidize the Ni atoms to a more stable t 6 2g configuration, it is necessary to simultaneously move two electrons and the Li + ions that compensate the charge, while the oxidation of the Ni atoms in LiNiO2 proceeds by an easier single-electron / single-ion process. Al in LiMO2 is already in the 3+ oxidation state and does not have an available 4+ oxidation state at the potential of a real battery cathode material.

[0019] The above explanation regarding oxidation and Li retention in bulk LiMO2 cathode materials demonstrates how increasing the oxidation potential of grain boundaries in LiMO2 materials can lead to greater Li retention at the grain boundaries than in bulk crystallites when these materials are charged. Therefore, for example, if a material with an LNO bulk crystallite composition (where M in LiMO2 is 100% Ni) has grain boundaries with a composition corresponding to one of the other materials in Figure 1, the reconstructed data from Figure 1 plotted in Figure 2 shows how much more Li is retained at the grain boundaries compared to the amount of Li retained in the LNO bulk crystallite when the material is oxidized (charged) to a given potential. This figure shows that at any potential or charged state up to 4.3V relative to lithium, the grain boundaries retain more Li than the bulk crystallite. Similarly, these data can be normalized to the Li content of one of the other materials to show that a material having, for example, an NCM(811) bulk crystallite and an NCM(523) grain boundary also retains more Li at the grain boundaries than in the bulk crystallite when they are charged. Note that 4.3V relative to lithium is merely an example; even if the material is charged to a potential higher or lower than 4.3V relative to lithium, it can similarly retain more Li at the grain boundaries than the bulk.

[0020] As used herein, the term “State of Charge” (SoC) refers to the charge level of a battery relative to its capacity. The unit of SoC is percentage points (0% = empty or discharged; 100% = full or fully charged). For lithium nickel oxide materials provided herein, a full charge is achieved at a potential of 4.1V or higher relative to Li, optionally 4.2V or higher, optionally 4.3V or higher, and optionally 4.4V or higher.

[0021] As used herein, the term “electrochemical affinity” for lithium is defined as the tendency to retain lithium when oxidized to a certain potential or voltage. Therefore, materials with high electrochemical affinity will retain more lithium when charged to a certain potential than materials with low electrochemical affinity for lithium. This potential can be a reasonable range. A material with high electrochemical affinity for lithium means that, when both materials are at the same potential, the material (or a portion of the material) has a higher lithium content compared to a material with low electrochemical affinity.

[0022] Therefore, a particle is provided comprising a plurality of crystallites comprising a first composition containing lithium, nickel, and oxygen and having a layered α-NaFeO2 type structure, and grain boundaries between adjacent crystallites comprising a second composition having a layered α-NaFeO2 type structure, a cubic structure, a spinel structure, a monoclinic structure, or a combination thereof, wherein the second composition has a higher electrochemical affinity for lithium compared to the first composition and / or compared to a material with a lower electrochemical affinity when both materials are at the same potential; and / or nickel is present in the second composition at a lower concentration than nickel in the first composition.

[0023] According to some aspects of the present disclosure, there are also provided particles comprising a plurality of crystallites comprising a first composition containing a layered-layered composition having the general formula zLiMO2·(1−z)Li2M’O3, where z ranges from 0.7 < z < 1.0, optionally from 0.8 < z < 0.95 moles per mole of the composition. The layered-layered material also includes grain boundaries between adjacent crystallites of the plurality of crystallites, the grain boundaries containing a second composition having a layered α-NaFeO2-type structure, a cubic structure, a spinel structure, a monoclinic structure, or a combination thereof. In some exemplary aspects, M can include Ni, Co, Mn, or a combination thereof, and M’ can include one or more of Mn, Ti, or Cr. Note that the oxidation potential and electrochemical affinity of the grain boundary region of the layered-layered material can be as described for the other materials shown herein.

[0024] In the layered-layered material, M optionally includes Ni alone or in combination with one or more of Co, Mn, V, or Fe. The Ni component of M is optionally from 0.3 moles to 0.95 moles per mole of M. When Co is present in M, it is optionally present from 0 moles to 0.33 moles per mole of M. When Mn is present in M, it is optionally present from 0.05 moles to 0.8 moles per mole of M. In some aspects, M includes from 0.3 moles to 0.95 moles of Ni per mole of M, from 0 moles to 0.33 moles of Co per mole of M, and from 0.05 moles to 0.5 moles of Mn per mole of M. In the layered-layered material, M’ includes Mn alone or in addition to one or more of Ti, Zr, Ru, Re, and Pt.

[0025] In compositions having a layered α-NaFeO2-type structure, the hexagonal metal oxide layers are separated by alkali metal (e.g., Li) planes. The metal oxide layers form metal-centered oxygen octahedra separated by alkali metal ions. These metal oxide layers are laterally offset to provide a three-layer structure. In the layered α-NaFeO2-type structure, alkali metal atoms occupy the so-called "3a" sites (x=0, y=0, z=0) in the structure, metal atoms occupy the "3b" sites (x=0, y=0, z=0.5), and oxygen atoms occupy the "6c" sites (x=0, y=0, z=0.25). The atomic coordinates and cell parameters can vary depending on the composition. Compositions of this structural type may have cell parameters where a is about 2.75 to about 2.95 angstroms (Å) and c is about 13.9 to about 14.6 Å. By selectively substituting the 3b sites of the grain boundaries with a metal having a higher oxidation potential than Ni, the entire particle can be stabilized compared to an unstabilized material with otherwise identical overall composition.

[0026] In some embodiments, the material provided herein comprises particles comprising a plurality of crystallites, each containing a first composition. Particles formed from a plurality of crystallites may be referred to as secondary particles. The particles provided herein are uniquely tuned to have grain boundaries containing a second composition between primary crystallites. Stabilizing these grain boundaries by increasing the electrochemical affinity to Li compared to bulk crystallites yields improved performance and cycle lifetime of cells containing the particles as cathode components, and particles with reduced impedance increase during cycling.

[0027] It is understood that the particles are formed from or contain grain boundaries comprising the second composition, the second composition differing from the first composition in that it has an increased electrochemical affinity for Li in the second composition compared to the first composition defining the crystallites of the secondary particles, and / or the second composition has a lower concentration of Ni compared to the first composition. Optionally, the particles provided herein can retain more Li at the grain boundaries than in the crystallites at any particular charge state greater than zero. Optionally, the particles provided herein can retain more Li at the grain boundaries than in the crystallites when the particles are at a given potential, or over a range of potentials. Optionally, the material provided has a lower concentration of Ni in the grain boundary regions compared to adjacent crystallites. Optionally, the material provided includes an additional outer coating layer which may be placed on the outer surface of the secondary particles to obtain coated secondary particles.

[0028] In some embodiments provided, electrochemically active particles are provided, comprising: a plurality of crystallites comprising a first composition comprising lithium, nickel, and oxygen; grain boundaries between adjacent crystallites comprising a second composition comprising lithium, nickel, and oxygen; wherein the grain boundaries have a higher electrochemical affinity for lithium than the crystallites. A higher electrochemical affinity for Li at the grain boundaries results in a higher concentration of Li at the grain boundaries compared to crystallites in any particular charge state.

[0029] Also provided are electrochemically active particles comprising: a plurality of crystallites comprising a first composition comprising lithium, nickel, and oxygen; grain boundaries between adjacent crystallites comprising a second composition comprising lithium, nickel, and oxygen; wherein nickel is present at the grain boundaries at a concentration lower than the nickel concentration within the crystallites.

[0030] Optionally, the molar content of lithium per mole of the second composition defining grain boundaries relative to the molar content of Li per mole of the first composition defining crystallites is found to be higher at 10% or more, optionally 20% or more, optionally 30% or more, optionally 40% or more, optionally 50% or more, optionally 60% or more, optionally 70% or more, optionally 80% or more, optionally 90% or more, optionally 95% or more, optionally 96% or more, optionally 97% or more, optionally 98% or more, optionally 99% or more, and optionally 100% in a charged state.

[0031] In some embodiments, electrochemically active particles are provided, comprising: a plurality of crystallites comprising a first composition comprising lithium, nickel, and oxygen; grain boundaries between adjacent crystallites comprising a second composition comprising lithium, nickel, and oxygen; wherein the grain boundaries have a higher electrochemical affinity for lithium than the crystallites when charged to 10% or more.

[0032] In some embodiments, electrochemically active particles are provided, comprising: a plurality of crystallites comprising a first composition comprising lithium, nickel, and oxygen; grain boundaries between adjacent crystallites comprising a second composition comprising lithium, nickel, and oxygen; wherein the grain boundaries have a higher electrochemical affinity for lithium than the crystallites when charged to 80% or more.

[0033] In some embodiments, electrochemically active particles are provided, comprising: a plurality of crystallites comprising a first composition comprising lithium, nickel, and oxygen; grain boundaries between adjacent crystallites comprising a second composition comprising lithium, nickel, and oxygen; wherein the grain boundaries have a higher electrochemical affinity for lithium than the crystallites when in a 100% charged state.

[0034] Also provided are electrochemically active particles comprising: a plurality of crystallites comprising a first composition comprising lithium, nickel, and oxygen; grain boundaries between adjacent crystallites comprising a second composition comprising lithium, nickel, and oxygen; wherein when the particles are charged to 10 percent or more, lithium is present at the grain boundaries at a higher concentration than the lithium in the crystallites.

[0035] Optionally, the molar concentration of lithium per mole of the second composition defining grain boundaries relative to the molar concentration of Li per mole of the first composition defining crystallites is found to be higher at 10% or more, optionally 20% or more, optionally 30% or more, optionally 40% or more, optionally 50% or more, optionally 60% or more, optionally 70% or more, optionally 80% or more, optionally 90% or more, optionally 95% or more, optionally 96% or more, optionally 97% or more, optionally 98% or more, optionally 99% or more, and optionally 100% charge state.

[0036] Also provided are electrochemically active particles comprising: a plurality of crystallites comprising a first composition comprising lithium, nickel, and oxygen; grain boundaries between adjacent crystallites comprising a second composition comprising lithium, nickel, and oxygen; wherein when the particles are charged to 20 percent or more, lithium is present at the grain boundaries at a higher concentration than lithium in the crystallites.

[0037] Also provided are electrochemically active particles comprising: a plurality of crystallites comprising a first composition comprising lithium, nickel, and oxygen; grain boundaries between adjacent crystallites of the plurality of crystallites comprising a second composition comprising lithium, nickel, and oxygen; wherein when the particles are charged to 80 percent or more, lithium is present at the grain boundaries at a higher concentration than the lithium in the crystallites.

[0038] Also provided are electrochemically active particles that can be used in the cathode of an electrochemical cell which may include a plurality of crystallites comprising a first composition comprising lithium, nickel, and oxygen; and grain boundaries between adjacent crystallites comprising a second composition comprising lithium, nickel, and oxygen, wherein when the electrode containing the particles is charged to a potential of 4.00 V or higher relative to lithium, lithium is present at the grain boundaries at a higher concentration than the lithium in the crystallites.

[0039] In some embodiments, the electrochemical properties of the material are improved when the Ni mole fraction in the second region is 0.95 or less. It has been found that the overall stability of the particles is enhanced by reducing the Ni level in the grain boundary regions of the particles. Optionally, the ratio of the mole fraction of Ni in the second composition to the mole fraction of Ni in the first composition is in the range of 0.95 to 0.5. Optionally, the ratio of the mole fraction of Ni in the second composition to the mole fraction of Ni in the first composition is 0.95 or less, optionally 0.90 or less, optionally 0.85 or less, optionally 0.80 or less, optionally 0.75 or less, optionally 0.7 or less, optionally 0.65 or less, optionally 0.6 or less, and optionally 0.55 or less.

[0040] Optionally, when the electrode containing the particles is charged to a potential of 4.1V or higher relative to lithium, lithium is present at the grain boundaries (second composition) at a higher concentration than lithium in the crystallites (first composition). Optionally, when the electrode containing the particles is charged to a potential of 4.2V or higher relative to lithium, lithium is present at the grain boundaries at a higher concentration than lithium in the crystallites. Optionally, when the electrode containing the particles is charged to a potential of 4.25V or higher relative to lithium, lithium is present at the grain boundaries at a higher concentration than lithium in the crystallites. Optionally, when the electrode containing the particles is charged to a potential of 4.3V or higher relative to lithium, lithium is present at the grain boundaries at a higher concentration than lithium in the crystallites.

[0041] The increase in the amount of Li retained in the second composition at the grain boundaries compared to the bulk is, at the potential shown in the previous paragraph, optionally 0.02 moles or more of Li per mole of the second composition. Optionally, at the potential shown in the previous paragraph, the number of moles of Li per mole of the second composition is 0.01 or more, optionally 0.02 or more, optionally 0.05 or more, optionally 0.1 or more, optionally 0.15 or more, optionally 0.2 or more, optionally 0.25 or more, and optionally 0.3 or more greater than the number of moles of Li per mole of the first composition.

[0042] In some embodiments, the elemental compositions of the first and second compositions are identical except for the relative amounts of the individual metallic components, provided that the amount of Ni in the second composition is less than the amount of Ni in the first composition. In other embodiments, the second composition contains one or more additional metals not present in the first composition, which can replace Ni in the crystal lattice of the second region, thereby promoting increased order, improved cycle lifetime, and reduced internal resistance in these regions.

[0043] Also provided are electrochemically active particles that can be used in the cathode of an electrochemical cell which may include: a plurality of crystallites comprising a first composition comprising lithium, nickel, and oxygen; and grain boundaries between adjacent crystallites comprising a second composition comprising lithium, nickel, and oxygen, wherein the electrochemically active particles have a particle charge capacity of 40 mAh / g or more and lithium is present at the grain boundaries at a higher concentration than lithium in the crystallites.

[0044] When a particle is charged to a capacity of 50 mAh / g or more, 60 mAh / g or more, 70 mAh / g or more, 80 mAh / g or more, 90 mAh / g or more, 100 mAh / g or more, 110 mAh / g or more, 120 mAh / g or more, 130 mAh / g or more, 140 mAh / g or more, 150 mAh / g or more, 160 mAh / g or more, 170 mAh / g or more, 180 mAh / g or more, 190 mAh / g or more, 200 mAh / g or more, or 220 mAh / g or more (optionally), the concentration of Li at the grain boundaries increases compared to that of the crystallite.

[0045] Optionally, at a predetermined potential or a charging capacity of 40 mAh / g or more, the number of moles of Li per mole of the second composition is 0.01, optionally 0.02, optionally 0.05, optionally 0.1, optionally 0.15, optionally 0.2, optionally 0.25, and optionally 0.3 greater than the number of moles of Li per mole of the first composition. Optionally, the increase in the amount of Li retained in the grain boundaries of the second composition compared to the amount of Li retained in the crystallites of the first composition is 0.01 moles or more of Li per mole of the second composition, optionally 0.15 moles or more of Li per mole of the second composition, optionally 0.2 moles or more of Li per mole of the second composition, optionally 0.25 moles or more of Li per mole of the second composition, and optionally 0.3 moles or more of Li per mole of the second composition. Optionally, the amount of Li retained in the second composition is optionally greater than the amount of Li retained in the first composition with a particle charge capacity of 50 mAh / g or more, optionally 60 mAh / g, optionally 70 mAh / g or more, optionally 80 mAh / g or more, optionally 90 mAh / g or more, optionally 100 mAh / g or more, optionally 110 mAh / g or more, optionally 120 mAh / g or more, optionally 130 mAh / g or more, optionally 140 mAh / g or more, optionally 150 mAh / g or more, optionally 160 mAh / g or more, optionally 170 mAh / g or more, optionally 180 mAh / g or more, optionally 190 mAh / g or more, optionally 200 mAh / g or more, and optionally 220 mAh / g or more, by the amounts specified above.

[0046] Particles containing a second composition, optionally present in the grain boundary region, or optionally only in the grain boundary region, having a lower concentration of Ni compared to the concentration of Ni in the first composition of the crystallite, enhance the physical stability of the particles and increase their fracture toughness or fracture resistance.

[0047] One method for measuring particle stability is by measuring fracture toughness. Fracture toughness can be measured by placing a known amount of particles, as provided herein, into a die, applying an appropriate amount of pressure, optionally 900 MPa, and then measuring the increase in the amount of fine particles generated in the material by the pressure. This serves as a direct measurement of physical particle stability, which the inventors have found to directly correspond to the rate of decrease in impedance increase during cycling. Optionally, the amount of fine particles in the particles obtained after applying pressures of 890 MPa or 900 MPa increases by less than 50 percent in number. Measurement of fine particles in a sample after pressure application can be performed by particle size analysis using recognized techniques. Fine particles, as defined herein, are particles (or particle fragments) having a size of 3.5 μm or less as measured by particle size analysis. For example, in some particle size analyses, the absolute number of particles is known, and the percentage passability is the number of fine particles relative to the total number of particles determined by the analysis. In some embodiments, particle surface area correlates with improved performance, such as cycle life or reduced impedance increase. In this disclosure, the increased surface area can be measured by techniques such as the Brunauer-Emmett-Teller (BET) surface area measurement. The method used herein relates to the number of fine particles with a size of 3.5 μm or less, as a rapid and easily reproducible method for determining improved particle performance.

[0048] As an exemplary method for quantifying the percentage of fine particles, a sample of granular material can be pulverized to the desired pressure in a 2 cm diameter die using a hydraulic press. A total mass of 2.5 g of powder can be placed in the die and pulverized to form a pellet. The pellet can then be placed in 20 mL of water and subjected to ultrasonic dispersion for 30 minutes. After dispersion, a small amount of the dispersed slurry can be placed in a Malvern Mastersizer 3000 laser particle size analyzer equipped with a liquid cell. To ensure complete dispersion of the fine particles, the ultrasonic function can be used during measurement, and the final result can be calculated using an average of five measurements. The distribution can be calculated using NiO properties obtained from the instrument's library.

[0049] The percentage of fine powder generated by applying pressure to the die decreases as the relative Ni concentration at the grain boundaries compared to the crystallite decreases. Optionally, the percentage of fine powder generated by applying pressure to the die is 50, 40, 35, 30, 25, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, or less than 2 percent. In some embodiments, the nickel concentration in the second composition is lower than that in the first composition, and the fracture resistance is such that less than 15% fine powder is generated when the material is pressed to a pressure of 900 MPa.

[0050] If the material is an NCA material containing 80 atomic percent or more Ni in the bulk particles, the number of fine particles generated is less than 15 percent, optionally less than 14 percent, optionally less than 13 percent, optionally less than 12 percent, optionally less than 11 percent, optionally less than 10 percent, optionally less than 9 percent, optionally less than 8 percent, optionally less than 7 percent, and optionally less than 6 percent. If the material is an NCA material containing 90 atomic percent or more Ni, the number of fine particles generated is less than 7 percent, optionally less than 6 percent, optionally less than 5 percent, optionally less than 4 percent, and optionally less than 3 percent. If the material is an NCM material containing 80 atomic percent or more Ni, the number of fine particles generated is less than 6 percent, optionally less than 5 percent, optionally less than 4 percent, optionally less than 3 percent, and optionally less than 2 percent.

[0051] In some embodiments of the particles provided herein, the first composition defining the crystallite of the secondary particles is a polycrystalline layered structure of lithium metal oxide defined by the composition defined by formula I: Li 1+x MO 2+y (I) Includes, optionally including a cell or battery formed therefrom, where -0.1≦x≦0.3 and -0.3≦y≦0.3 when discharged, or -0.9≦x≦0.1 and -0.3≦y≦0.3 when charged. In some embodiments, x is -0.1, optionally 0, optionally 0.1, optionally 0.2, or optionally 0.3. Optionally, x is -0.10 or greater, -0.09 or greater, -0.08 or greater, -0.07 or greater, -0.06 or greater, -0.05 or greater, -0.04 or greater, -0.03 or greater, -0.02 or greater, -0.01 or greater, 0.02 or greater, 0.03 or greater, 0.04 or greater, 0.05 or greater, 0.06 or greater, 0.07 or greater, 0.08 or greater, 0.0 9 or greater, 0.10 or greater, 0.11 or greater, 0.12 or greater, 0.13 or greater, 0.14 or greater, 0.15 or greater, 0.16 or greater, 0.17 or greater, 0.18 or greater, 0.19 or greater, 0.20 or greater, 0.21 or greater, 0.22 or greater, 0.23 or greater, 0.24 or greater, 0.25 or greater, 0.26 or greater, 0.27 or greater, 0.28 or greater, 0.29 or greater, or 0.30 or greater. In some embodiments, y is -0.3, optionally -0.2, optionally -0.1, optionally 0, optionally 0.1, optionally 0.2, or optionally 0.3.Optionally, y can be -0.30 or greater, -0.29 or greater, -0.28 or greater, -0.27 or greater, -0.26 or greater, -0.25 or greater, -0.24 or greater, -0.23 or greater, -0.22 or greater, -0.21 or greater, -0.20 or greater, -0.19 or greater, -0.18 or greater, -0.17 or greater, -0.16 or greater, -0.15 or greater, -0.14 or greater, -0.13 or greater, -0.12 or greater, -0.11 or greater, -0.10 or greater, -0.09 or greater, -0.08 or greater, -0.07 or greater, -0.06 or greater, -0.05 or greater, -0.04 or greater, -0.03 or greater, - 0.02 or higher, -0.01 or higher, 0.00 or higher, 0.01 or higher, 0.02 or higher, 0.03 or higher, 0.04 or higher, 0.05 or higher, 0.06 or higher, 0.07 or higher, 0.08 or higher, 0.09 or higher, 0.10 or higher, 0.11 or higher, 0.12 or higher, 0.13 or higher, 0.14 or higher, 0.15 or higher, 0.16 or higher, 0.17 or higher, 0.18 or higher, 0.19 or higher, 0.20 or higher, 0.21 or higher, 0.22 or higher, 0.23 or higher, 0.24 or higher, 0.25 or higher, 0.26 or higher, 0.27 or higher, 0.28 or higher, 0.29 or higher, or 0.3 or higher.

[0052] In some embodiments, it is understood that Li does not have to be Li alone, but may be partially replaced by one or more elements selected from the group consisting of Mg, Sr, Na, K, and Ca. The one or more elements replacing Li may be present in amounts of 10 atomic percent or less, 5 atomic percent or less, 3 atomic percent or less, or 2 atomic percent or less, with these percentages relative to the total Li in the material.

[0053] In the first composition, M contains Ni. The amount of Ni in the first composition is optionally 10 atomic percent to 100 atomic percent (at%) of the total M. Optionally, the Ni component of M is 75 atomic percent or more. Optionally, the Ni component of M is 80 at% or more. Optionally, the Ni component of M is 85 at% or more. Optionally, the Ni component of M is 90 at% or more. Optionally, the Ni component of M is 95 at% or more. Selectively, the Ni component of M is 75 at% or more, 76 at% or more, 77 at% or more, 78 at% or more, 79 at% or more, 80 at% or more, 81 at% or more, 82 at% or more, 83 at% or more, 84 at% or more, 85 at% or more, 86 at% or more, 87 at% or more, 88 at% or more, 89 at% or more, 90 at% or more, 91 at% or more, 92 at% or more, 93 at% or more, 94 at% or more, 95 at% or more, 96 at% or more, 97 at% or more, 98 at% or more, 99 at% or more, 99.5 at% or more, 99.9 at% or more, or 100 at% or more.

[0054] In some embodiments, 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, or be, one or more of, Mg, Sr, Co, Al, Ga, Ca, Cu, Zn, Mn, V, Ba, Y, Nb, Zr, Ti, Cr, Fe, Mo, W, B, and any combination thereof. In certain embodiments, 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 the group consisting of Mg, Al, V, Ti, B, or Mn. Optionally, the additional elements are selected from the group consisting of Mg, Co, and Al. Optionally, the additional elements are selected from the group consisting of Ca, Co, and Al. In some embodiments, the additional element is Mn or Mg, or both Mn and Mg. Optionally, the additional element is Mn, Co, Al, or any combination thereof. Optionally, the additional element includes Co and Mn. Optionally, the additional element is Co and Al. Optionally, the additional element is Co.

[0055] The additional elements in the first composition may be present in amounts of about 1 to about 90 at% of the total M, more specifically about 5 to about 80 at% of M in the first composition, and more specifically about 10 to about 70 at%. Optionally, the additional elements may be present in amounts of about 1 to about 20 at% of M in the first composition, more specifically about 2 to about 18 at%, and more specifically about 4 to about 16 at%. In some exemplary examples, M consists of about 75 to 100 at% Ni, 0 to 15 at% Co, 0 to 15 at% Mn, and 0 to 10 at% of the additional elements.

[0056] Within a polycrystalline material, each crystallite may have any suitable shape, which may be the same or different within each particle. Furthermore, the shape of each crystallite may be the same or different within different particles or within different particles. Due to its crystalline properties, crystallites can be faceted, crystallites may have multiple flat surfaces, and the shape of a crystallite can approximate a geometric shape. In some embodiments, crystallites may fuse with adjacent crystallites having mismatched crystal planes. Crystallites may optionally be polyhedra. Crystallites may have a linear shape, and when viewed in cross-section, part or all of the crystallite may be linear. Crystallites may be square, hexagonal, rectangular, triangular, or a combination thereof. Crystallites may optionally be single crystals, and particles may optionally be aggregates of single crystals.

[0057] The particles contain grain boundaries that separate two adjacent crystallites. The grain boundaries contain a second composition. In some embodiments, the grain boundaries contain a second composition having an α-NaFeO2 type structure having general formula II: Li 1+x M'O 2+y (II) [In the formula, M' is defined as M in the first composition, but has a relatively low number of moles of Ni per mole of LiMO2]. The Ni sites in the crystal structure are substituted with one or more substitutional elements that enhance the electrochemical affinity of the structure to lithium compared to the unsubstituted material, and as a result the amount of substitutional elements is greater in the second composition in terms of moles per molar concentration than in the first composition, and optionally, at a charge state of 80% or more or a charge capacity of 150 mAh / g or more, -0.6 ≤ x ≤ -0.2. In some embodiments, x is -0.6, optionally -0.65, optionally -0.7, optionally -0.75, optionally -0.8, optionally -0.9, and optionally -0.95. In some embodiments, 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 -0.30 or greater, -0.29 or greater, -0.28 or greater, -0.27 or greater, -0.26 or greater, -0.25 or greater, -0.24 or greater, -0.23 or greater, -0.22 or greater, -0.21 or greater, -0.20 or greater, -0.19 or greater, -0.18 or greater, -0.17 or greater, -0.16 or greater, -0.15 or greater, -0.14 or greater, -0.13 or greater, -0.12 or greater, -0.11 or greater, -0.10 or greater, -0.09 or greater, -0.08 or greater, -0.07 or greater, -0.06 or greater, -0.05 or greater, -0.04 or greater, -0.03 or greater, -0 It is 0.02 or higher, -0.01 or higher, 0.00 or higher, 0.01 or higher, 0.02 or higher, 0.03 or higher, 0.04 or higher, 0.05 or higher, 0.06 or higher, 0.07 or higher, 0.08 or higher, 0.09 or higher, 0.10 or higher, 0.11 or higher, 0.12 or higher, 0.13 or higher, 0.14 or higher, 0.15 or higher, 0.16 or higher, 0.17 or higher, 0.18 or higher, 0.19 or higher, 0.20 or higher, 0.21 or higher, 0.22 or higher, 0.23 or higher, 0.24 or higher, 0.25 or higher, 0.26 or higher, 0.27 or higher, 0.28 or higher, 0.29 or higher, or 0.3 or higher.When particles having the stabilized second composition are contained in a cathode electrochemically charged to approximately 4.3V (this may be lower or higher depending on the specific application), improved performance is observed due to an increased electrochemical affinity for Li compared to the crystallite.

[0058] Optionally, the amount of Ni in the second composition may be in the range of 0 to 0.99 moles per mole of M' in the second composition. Optionally, M' in the second composition does not contain Ni. Optionally, the amount of Ni in the second composition (i.e., relative concentration) is less than the amount of Ni in the first composition in relative atomic percentage (for each composition in which Ni is present). Optionally, the Ni component of M' is 1 mole or less per mole of M'. Optionally, the Ni component of M' is 0.5 moles or less per mole of M'. Optionally, the Ni component of M' is 0.10 moles or less per mole of M'. Optionally, the Ni component of M' is 0.20 moles or less per mole of M'. Optionally, the Ni component of M' is 0.75 moles or less per mole of M'. Optionally, the Ni component of M' is 0.80 moles or less per mole of M'. Selectively, the Ni component of M' is 0.85 moles or less per mole of M'. Selectively, the Ni component of M' is 0.90 moles or less per mole of M'. Selectively, the Ni component of M' is 0.95 moles or less per mole of M'. Selectively, the Ni component of M' is 0.75 moles or less per mole of M', 0.76 moles or less per mole of M', 0.77 moles or less per mole of M', 0.78 moles or less per mole of M', 0.79 moles or less per mole of M', 0.80 moles or less per mole of M', 0.81 moles or less per mole of M', 0.82 moles or less per mole of M', 0.83 moles or less per mole of M', 0.84 moles or less per mole of M', 0.85 moles or less per mole of M', 0.86 moles or less per mole of M', and 0.87 moles per mole of M'. The values ​​are less than or equal to a mole, less than or equal to 0.88 moles per mole of M', less than or equal to 0.89 moles per mole of M', less than or equal to 0.90 moles per mole of M', less than or equal to 0.91 moles per mole of M', less than or equal to 0.92 moles per mole of M', less than or equal to 0.93 moles per mole of M', less than or equal to 0.94 moles per mole of M', less than or equal to 0.95 moles per mole of M', less than or equal to 0.96 moles per mole of M', less than or equal to 0.97 moles per mole of M', less than or equal to 0.98 moles per mole of M', less than or equal to 0.99 moles per mole of M', or less than or equal to 0.999 moles per mole of M'.

[0059] In the materials provided herein, the nominal or overall compositional composition of secondary particles (e.g., characterized by inductively coupled plasma (ICP)), optionally the first composition, or optionally the second composition, is defined by the compositional formula LiMO2, where M is Ni, and optionally, one or more substitutional elements in the second composition must include at least one element that substitutes for Ni in the crystal structure, conferring a greater electrochemical affinity to Li to the second composition than to the first composition. The mole fraction of the substitutional elements in the first composition defining the crystallite composition is lower than the individual or total mole fraction of the substitutional elements in the overall particle composition, if present, as determined by ICP. The individual or total mole fraction of the substitutional elements in the first composition may be zero. The individual or total mole fraction of the substitutional elements in the second composition defining the grain boundaries is higher than the individual or total mole fraction of the substitutional elements in the overall particle composition as measured by ICP.

[0060] Examples of substitutional elements that may be included in M' of formula II and can promote the retention of Li at grain boundaries in charged high-Ni LiMO2 cathode materials include various elements that can substitute for Ni in the LiM'O2 structure. Such doping elements can promote Li retention (i.e., greater electrochemical affinity for Li) by being more resistant to oxidation (having a higher oxidation potential) than the Ni atom they substitute for, by stabilizing the structure against oxidation, or by inductively increasing the oxidation potential of neighboring Ni atoms. 3+ If trivalent (3+) ions of doping elements that can directly substitute for Ni ions are less susceptible to oxidation than Ni ions when the material is charged, they promote the retention of Li. Substitution of Ni(III) by Al(III) is one example. Tetravalent (4+) ions of Ni 3+When substituting Ni, these ions are charge-compensated by 2+ Ni ions, and their inductive effect raises the potential at which these Ni ions are oxidized to the 4+ state. Substitution of Ni(III) by Mn(IV) is one example. Alternatively, if it is difficult to oxidize the 2+ ions substituting Ni, they are charge-compensated by 4+ Ni ions. Substitution of Ni(III) by Mg(II) is one example. To substitute Ni in a LiM'O2 structure, the doping ions must be comparable in size to the Ni ions, and to promote Li retention, they must raise the local oxidation potential. The relative effect of a given ion on the oxidation potential is often Ni 3+ It can be estimated from the ionization energy compared with Ni. Therefore, Ni 3+ Ions of comparable size and possessing equivalent or greater ionization energy can potentially function to stabilize grain boundaries in oxidized cathodes by increasing Li retention. The table below shows the ionization energy and hexa-coordinate (octahedral environment) ionic radius for examples of ions that can stabilize grain boundaries in charged high-Ni LiMO2 cathode materials by increasing Li grain boundary retention.

[0061] [Table 2]

[0062] In the second composition, M' further comprises one or more substitutional elements that can be selected from groups that are less susceptible to oxidation than nickel when electrochemically charged to 4.3V or higher over a Li metal anode. In one example, M' may include Ni and a combination of Co and Mn that are less susceptible to oxidation than nickel when charged to 4.3V. In another embodiment, M' may include Ni and one or more elements selected from the group including Mn, Cr, Fe, Ti, V, Co, Cu, Zn, Zr, Nb, Sb, W, Sc, Al, Mo, Y, etc., that are less susceptible to oxidation than Ni when charged to 4.3V over lithium metal. Optionally, M' may exclude Co alone, Al alone, or a combination of Co and Al and Ni, while Co, Al, or both may be present with doping of one or more additional substitutional elements as shown herein. In some embodiments, M' may include elements selected from the group of elements that do not oxidize when charged to lithium up to 4.3V, such as Y, Sc, Ga, In, Tl, Si, Ge, Sn, and Pb.

[0063] It should be noted here that 4.3V is merely a representative example. The voltage can be lower (e.g., 4.0, 4.1, 4.2V relative to Li) or higher (4.35, 4.4, 4.5V, 4.6V, 4.7V relative to Li). The specific voltage to be used depends on the operating potential of the battery when the cathode is paired with the anode.

[0064] In some embodiments, the second composition of the grain boundaries has a greater electrochemical affinity for Li, and as a result, when the electrode containing the particles is charged to a potential of 4.1V or higher relative to lithium, optionally 4.2V or higher relative to lithium, and optionally 4.3V or higher relative to lithium, the grain boundaries hold more than 0.15 moles of lithium per mole of the second composition at the said potential.

[0065] In some embodiments, the second composition of the grain boundaries has a greater electrochemical affinity for Li, and as a result, when the electrode containing the particles is charged to a capacity of 100 mAh / g or more, optionally 200 mAh / g or more, the grain boundaries hold more than 0.15 moles of lithium per mole of the second composition at the aforementioned potential.

[0066] Optionally, at the potential or capacity shown herein, the second composition comprises: lithium in an amount of about 0.1 to about 1.3 moles per mole of the second composition, specifically about 0.15 to about 1.2 moles, more specifically about 0.3 to about 1.1 moles; nickel in an amount of about 0.1 to about 0.999 moles per mole of the second composition, specifically about 0.2 to about 0.90 moles, more specifically about 0.3 to about 0.85 moles; manganese in an amount of about 0.02 to about 0.99 moles per mole of the second composition, specifically about 0.04 to about 0.90 moles, more specifically about 0.06 to about 0.80 moles; and oxygen in an amount of about 1.7 to about 2.3 moles per mole of the second composition, specifically about 1.8 to about 2.2 moles, more specifically about 1.9 to about 2.1 moles.

[0067] The second composition may further contain additional metals, the additional metals of the second composition present in amounts of about 0.01 to about 0.9 moles per mole of the second composition, specifically about 0.05 to about 0.8 moles, and more specifically about 0.1 to about 0.7 moles. In one embodiment, the additional metals of the second composition may be present in amounts of about 0.01 to about 0.2 moles per mole of the second composition, specifically about 0.02 to about 0.18 moles, and more specifically about 0.04 to about 0.16 moles.

[0068] The additional metal in the second composition may include Mg, Sr, Ca, Cu, Zn, Mn, Al, V, Ba, Zr, Ti, Cr, Fe, Mo, B, or a combination thereof. Optionally, the additional metal in the second composition may include Mg, Al, V, Ti, B, Zr, or Mn, or a combination thereof. Optionally, the additional metal in the second composition may include Mg, Al, V, Ti, B, Zr, or Mn. Embodiments in which the additional metal in the second composition is Mn or Mg are specifically mentioned. Optionally, the additional metal in the first composition and the additional metal in the second composition are both Mg. Optionally, the first composition further contains Mn, which is present in the first composition in an amount of about 0.01 to about 0.6 moles per mole of the first composition, specifically about 0.02 to about 0.5 moles, and the second composition contains Mn, which is present in the second composition in an amount of about 0.01 to about 0.6 moles per mole of the second composition, specifically about 0.02 to about 0.5 moles.

[0069] The grain boundaries are located between adjacent crystallites, on the surface of crystallites, and comprise or consist of a second composition. The second composition has a layered α-NaFeO2 type structure, a cubic structure, a monoclinic structure, or a combination thereof. As described above, the grain boundaries contain at least one substitutional element such that the electrochemical affinity of the second composition to Li is greater than the electrochemical affinity of the first composition found in the bulk crystallites. Embodiments in which the grain boundaries comprise or consist of a layered α-NaFeO2 type structure are specifically mentioned.

[0070] The shape of a grain boundary is determined by the shape of the crystallites adjacent to the grain boundary. The shape of a grain boundary can be approximated by a geometric shape. A grain boundary may have a linear shape, and may appear linear when viewed in cross-section. A grain boundary may be a square, hexagon, rectangle, triangle, or a combination thereof.

[0071] The orientation of the grain boundary surface corresponds to the orientation of the adjacent crystallite surface. The grain boundary surface and the crystallite surface can have any various orientations with respect to the outer surface of the secondary particle. Therefore, the orientation of the crystallite surface and the grain boundary surface may be parallel to or different from the orientation of the nearest outer surface of the secondary particle. In some embodiments, the direction of the tangency to the nearest outer surface of the particle is different from the orientation of the grain boundary surface and the orientation of the adjacent particle surface.

[0072] Grain boundaries can intersect, forming an angle between them. In some embodiments, a first grain boundary and a second grain boundary are located on adjacent planes of a crystallite. The first and second grain boundaries intersect at an angle E. Angle E may be determined by the shape of the crystallite on which the first and second grain boundaries are located. In general, the shape of a crystallite is influenced by the crystal structure of the crystallite. While we do not wish to be bound by theory, it is understood that the angle between the first and second grain boundaries is influenced by the crystal structure of the first composition, since the crystal structure of the first composition governs the shape of the crystallite. The first and second grain boundaries can intersect at any angle, specifically about 10 to about 170 degrees, specifically about 20 to about 160 degrees, and more specifically about 30 to about 150 degrees, as long as the angle matches the crystal structure of the first composition.

[0073] The dimensions of the grain boundaries are not particularly limited. The length and width of the grain boundaries may be independently about 10 to about 1000 nm, specifically about 60 to about 900 nm, and more specifically about 70 to about 800 nm. The length and width of the grain boundaries are perpendicular to each other and parallel to the surfaces of adjacent crystallites. The thickness of the grain boundaries may be about 0.5 to about 30 nm, specifically about 1 to about 20 nm, and more specifically about 1 to about 10 nm. The thickness of the grain boundaries may be substantially perpendicular to the length and width of the grain boundaries and perpendicular to the surfaces of adjacent crystallites. The composition of the grain boundaries may be substantially uniform or may vary along the thickness.

[0074] The average grain boundary length and average grain boundary width of multiple grain boundaries may be, independently, approximately 10 to approximately 1000 nm, specifically approximately 60 to approximately 900 nm, and more specifically approximately 70 to approximately 800 nm. Similarly, the average grain boundary thickness of multiple grain boundaries may be approximately 0.1 to approximately 30 nm, specifically approximately 1 to approximately 20 nm, and more specifically approximately 1 to approximately 10 nm.

[0075] Optionally, the particles provided herein include an outer coating, such as a passivation layer or protective layer, which may be provided on the outer surface of the secondary particles to obtain coated secondary particles. The coating may completely or partially cover the secondary particles. The outer coating layer may be amorphous or crystalline. The outer coating layer may include metal oxides such as Zr, Al, Ti, Al, B, or Si, or combinations thereof, sulfates, phosphates, pyrophosphates, fluorophosphates, carbonates, fluorides, oxyfluorides, or combinations thereof. Optionally, the outer coating layer may include borates, aluminates, silicates, fluoroaluminates, or combinations thereof. Optionally, the outer coating layer may include carbonates. In one embodiment, the layer includes ZrO2, Al2O3, TiO2, AlPO4, AlF3, B2O3, SiO2, Li2O, Li2CO3, or combinations thereof. A layer containing AlPO4 or Li2CO3 is specifically mentioned. Optionally, the outer coating layer may contain an oxide of one or more elements selected from Al, Zr, Y, Co, Ni, Mg, and Li. Optionally, the outer coating layer may contain a fluoride containing one or more elements selected from Al, Zr, and Li. Optionally, the outer coating layer may contain a carbonate containing one or more elements selected from Al, Co, Ni, Mn, and Li. Optionally, the outer coating may contain a sulfate containing one or more elements selected from Al, Co, Ni, Mn, and Li. Optionally, the outer coating may contain a phosphate containing one or more elements selected from Al and Li. The layer may be provided by any process or technique that does not adversely affect the desired properties of the secondary particles. Typical methods include, for example, spray coating and dipping coating.

[0076] Secondary particles can be formed by a multi-step process, thereby forming particles of the first composition, which are then calcined to create grain boundaries optionally defined by crystallites having a low defect α-NaFeO2 structure. The resulting secondary particles are then subjected to a liquid process in which one or more substitutional elements are applied at a desired concentration level, followed by drying, and then a second calcination. As a result, precipitated species of substitutional elements on the surface selectively migrate to the grain boundaries, thereby forming secondary particles with stable grain boundaries that have a higher electrochemical affinity for Li than bulk crystallites. As an example, according to the method for producing secondary particles having Ni, Co, and Mg bases provided herein, the formation may include: mixing a lithium compound with one or more metal or metalloid hydroxide precursor compounds (e.g., combined Ni, Co, and Mg, pre-produced by a coprecipitation reaction, etc.) to form a mixture; heat-treating the mixture at about 30 to about 200°C to form a dry mixture; heat-treating the dry mixture at about 200 to about 500°C for about 0.1 to about 5 hours; and then heat-treating at 600°C or higher but less than about 950°C for about 0.1 to about 20 hours to produce secondary particles. The maximum temperature of the initial calcination is relative and specific to the material used for the hydroxide precursor. Optionally, in the initial calcination, the maximum temperature may be 850°C or less, optionally 720°C or less, optionally 715°C or less, optionally 710°C or less, optionally 705°C or less, or optionally 700°C or less. Optionally, the maximum temperature of the initial roasting may be approximately 680°C or lower. Optionally, the maximum temperature may be approximately 660°C or lower. Optionally, the maximum temperature may be approximately 640°C or lower. In yet another embodiment, the maximum temperature may be less than approximately 700°C, less than approximately 695°C, less than approximately 690°C, less than approximately 685°C, less than approximately 680°C, less than approximately 675°C, less than approximately 670°C, less than approximately 665°C, less than approximately 660°C, less than approximately 655°C, less than approximately 645°C, or less than approximately 640°C. The time spent at the maximum temperature is optionally less than 10 hours.The optional duration of exposure to the highest temperature is 8 hours or less, 7 hours or less, 6 hours or less, 5 hours or less, 4 hours or less, 3 hours or less, or 2 hours or less.

[0077] After the initial calcination, subsequent processing may include grinding the calcined material in a mortar and pestle so that the resulting powder passes through the desired sieve, optionally a #35 sieve. The powder is then optionally ball-milled in a 1-gallon jar containing a 2 cm drum of YSZ media for optionally 5 minutes, or for a time sufficient for the material to pass through the optionally #270 sieve.

[0078] The product of the first calcination or the pulverized product can then be optionally treated in such a way that stable grain boundaries are obtained after the second calcination. The process of stabilizing the grain boundaries and forming an electrochemical affinity of the grain boundaries to Li greater than the crystallites in the primary particles can be carried out by optionally suspending the product of the first calcination in an aqueous slurry containing one or more substitutional elements and a lithium compound at a temperature of about 60°C, thereby ensuring that the substitutional elements are present in the aqueous solution at the desired concentration for stabilization. The slurry is then spray-dried to form a free-flowing powder, which subsequently undergoes a second calcination, with the heating curve optionally following a two-step heating / holding process. Alternatively, the substitutional elements can be dispersed in a non-aqueous solvent together with the suspended polycrystalline material. The non-aqueous solvent can be removed by evaporation, and the substitutional elements precipitate on the surface of the polycrystalline material. The polycrystalline material then undergoes a second calcination, with the heating curve optionally following a two-step heating / holding process. The first of the two heating / holding temperature profiles is from ambient temperature (approximately 25°C) to 450°C, optionally at a rate of 5°C per minute, and held at 450°C for 1 hour. Subsequently, the second heating / holding step is from 450°C to the maximum temperature at a rate of 2°C per minute, and held at the maximum temperature for 2 hours. In some embodiments, the maximum temperature is approximately 850°C or less.

[0079] By combining the initial calcination at the highest temperature described above with a process of incorporating one or more substitutional elements into the grain boundaries obtained by the second calcination, also described above, it was found that the resulting particles could be used in the cathode to significantly improve cycle lifetime, reduce capacity degradation, reduce impedance increase, and / or significantly improve the electrochemical properties of the material.

[0080] Cathodes for lithium-ion batteries containing secondary particles are also provided. The cathode comprises the secondary particles disclosed above as an active material and may further comprise a conductive agent and a binder. The conductive agent may comprise any conductive agent that imparts suitable properties and may be amorphous, crystalline, or a combination thereof. The conductive agent may comprise carbon black such as acetylene black or lamp black, mesocarbons, graphite, carbon fibers, carbon nanotubes such as single-walled carbon nanotubes or multi-walled carbon nanotubes, or a combination thereof. Examples of binders that impart appropriate properties 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(1-vinylpyrrolidone-co-vinyl acetate), cellulose acetate, polyvinylpyrrolidone, polyacrylate, polymethacrylate, polyolefin, polyurethane, polyvinyl ether, acrylonitrile-butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene-styrene, sulfonated styrene / ethylene-butylene / styrene triblock polymer, polyethylene oxide, or combinations thereof.

[0081] The cathode can be manufactured by mixing secondary particles, a conductive agent, and a binder in appropriate ratios, for example, about 80 to 98 weight percent of secondary particles, about 2 to 20 weight percent of the conductive agent, and about 2 to 10 weight percent of the binder, based on the total weight of the secondary particles, conductive agent, and binder. The secondary particles, conductive agent, and binder can be suspended in a suitable solvent such as N-methylpyrrolidone, placed on a suitable substrate such as aluminum foil, and dried in the air.

[0082] A battery including a cathode is also disclosed. The battery may be, for example, a lithium-ion battery, a lithium polymer battery, or a lithium battery. The battery may include a cathode, an anode, and a separator sandwiched between the cathode and the anode. The separator may be a microporous film, which may include a porous film containing polypropylene, polyethylene, or a combination thereof, or it may be a woven or nonwoven material such as a glass fiber mat. The anode may include a coating on the current collector. The coating may include, for example, a suitable carbon such as graphite, coke, or hard carbon, or a graphitized mesocarbon such as mesocarbon microbeads. The anode may also include lithium metal, or a material capable of alloying with lithium (e.g., Si, Ge, etc.) or undergoing a conversion reaction (e.g., metal oxides or sulfides). Alternatively, the anode may be lithium spinel titanate (Li4Ti5O 12 ), or titanium-containing materials such as titanium niobium oxide, titanium niobium tungsten oxide, or titanium oxide. The current collector may be, for example, copper foil, nickel foil, titanium foil, or aluminum foil.

[0083] The battery also includes an electrolyte that can come into contact with the positive electrode (cathode), the negative electrode (anode), and the separator. The electrolyte may include an organic solvent and a lithium salt. The organic solvent may be a linear or cyclic carbonate. Typical organic solvents include ethylene carbonate, propylene carbonate, butylene carbonate, trifluoropropylene carbonate, γ-butyrolactone, sulfolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 3-methyl-1,3-dioxolane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methylpropyl carbonate, propanesultone, or combinations thereof. In another embodiment, the electrolyte is a polymer electrolyte.

[0084] Representative lithium salts useful 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 can be dissolved in organic solvents. A combination containing at least one of the above can be used. The concentration of the lithium salt in the electrolyte can be 0.1 to 2.0 M.

[0085] The electrolyte may be a solid ceramic electrolyte.

[0086] Various aspects of this disclosure are illustrated by the following non-limiting examples. These examples are illustrative and not limit the implementation of the invention. It will be understood that changes and modifications can be made without departing from the spirit and scope of the invention.

[0087] Examples Example 1: Li 1.01 Mg 0.01 Ni 0.90 Co 0.08 Y 0.02 O 2 Manufacturing and testing The overall composition is Li 1.01 Mg 0.01 Ni 0.92 Co 0.08 A polycrystalline base material of O2 was synthesized using a standard solid-phase synthesis method. 2.7 grams (g) of yttrium nitrate hexahydrate (Y(NO3)3·6H2O) (99.9%, Alfa Aesar, Ward Hill, MA) was dissolved in 30 ml (ml) of methanol at 40°C in a glass beaker. After dissolution, 35 grams (g) of the polycrystalline base material (Li 1.01 Mg 0.01 Ni 0.92 Co 0.08 O2 was added to the solution. The solution was stirred for 3 minutes to ensure that the base was properly distributed into the methanol solution. Methanol was removed from the solution by evaporation using a rotary evaporator at 40 degrees Celsius (°C) and 20 mmHg.

[0088] The dried powder was placed in an alumina crucible and calcined. Calcination was carried out by heating at a rate of 5°C per minute to approximately 130°C, and then holding at approximately 130°C for approximately 6 hours. Next, the temperature was raised at a rate of approximately 5°C per minute to approximately 450°C, and then held for approximately 1 hour. Then, the temperature was raised at a rate of approximately 2°C per minute to 700°C, and held at approximately 700°C for approximately 2 hours. After that, the sample was allowed to cool naturally to room temperature.

[0089] The material synthesized above was cast onto the cathode electrode. This material was first mixed with PVdF, conductive carbon, and NMP solvent to prepare the electrode slurry. The electrode slurry was coated onto aluminum foil using the doctor blade method. The coated foil was dried at 130°C to remove the NMP, leaving the coated electrode. The electrode was then pressed and punched out, assembled into a coin cell using a Li metal anode (half cell) or a graphite anode (full cell), and tested.

[0090] Comparative Example 1 The polycrystalline base material used above (Li 1.01 Mg 0.01 Ni 0.92 Co 0.08 O2) was used as a control material without additional calcination. Li according to the method described in Example 1. 1.01 Mg 0.01 Ni 0.92 Co 0.08 An electrode containing an O2 cathode powder control was fabricated.

[0091] Table 3 shows the half-cell results for the electrodes of Example 1 and Comparative Example 1 tested at 4.3 volts (V) to 3.0 V, demonstrating that the yttrium treatment does not significantly alter the discharge capacity measured in the half-cell. Figures 7 and 8 show the full-cell results for accelerated cycle lifetime measurements performed at 45°C. The yttrium-containing material exhibits more stable cycles and a significantly reduced impedance increase compared to the base material. The presence of yttrium in the grain boundary regions enhances lithium retention at the end of charging, thereby reducing material damage and improving cycle lifetime at 45°C. The capacity retention and impedance increase rates during the accelerated cycle lifetime test at 45°C are shown in Figures 7 and 8, respectively.

[0092] [Table 3]

[0093] Example 2: Li 1.01 Mg 0.01 Ni 0.87 Co 0.11 Fe 0.02 O2 production and testing 0.61 g of iron acetate (Fe(C2H3O2)2) (Alfa Aesar, Ward Hill, MA) and 3.08 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) were dissolved in 30 ml of methanol at 40°C in a glass beaker. After dissolution, 35 g of base (Li 1.01 Ni 0.92 Co 0.08 Mg 0.01O2 was added to the solution. The solution was stirred for 3 minutes to ensure that the base was properly distributed into the methanol solution. Methanol was removed from the solution by evaporation using a rotary evaporator at 40°C and 20 mmHg.

[0094] The dried powder was placed in an alumina crucible and calcined. Calcination was carried out by heating at a rate of 5°C per minute to approximately 130°C and holding at approximately 130°C for approximately 6 hours. Next, the temperature was raised at a rate of approximately 5°C per minute to approximately 450°C and held for approximately 1 hour. Then, the temperature was raised at a rate of approximately 2°C per minute to 700°C and held at approximately 700°C for approximately 2 hours. After that, the sample was allowed to cool naturally to room temperature.

[0095] Li 1.01 Mg 0.01 Ni 0.87 Co 0.11 Fe 0.02 O2 cathode material, Li 1.01 Ni 0.92 Co 0.08 Mg 0.01 Full coin cells were electrochemically tested with an untreated base material control having an O2 composition, a graphite anode on the opposite side, 1 M LiPF6 in an electrolyte with EC:DMC:EMC of 1:1:1 including 1% VC(EDEV1), and a polymer separator. The full coin cells were cycled between 2.7 V and 4.2 V at 45 °C using accelerated charge and discharge rates. Figures 9 and 10 show the rates of capacitance degradation and impedance increase during the accelerated cycle lifetime test, respectively.

[0096] Example 3: Li 1.01 Mg 0.01 Ni 0.8975 Co 0.0897 Mn 0.0128 O2 production. To enable higher levels of Li at grain boundaries with a 4.3V charge, a coating with a 1 / 1 / 1 Ni / Co / Mn composition was incorporated for grain boundary concentration. A LiMO2 material with this composition is expected to retain 37% of lithium when charged to 4.3V relative to Li. The base material used is Li 1.01 Mg0.01 Ni 0.92 Co 0.08 It was O2. A 4% grain boundary concentrated composition with a Ni / Co / Mn composition of 1 / 1 / 1 was applied thereto. For this purpose, 1.33% of each of Ni, Co, and Mn was blended based on the total content of the base transition metal.

[0097] An aqueous solution of 200 ml was prepared using manganese nitrate tetrahydrate (6.78 g), nickel nitrate heptahydrate (8.34 g), cobalt nitrate hexahydrate (7.86 g), and lithium nitrate (2.85 g), and this was heated to 60 °C. 200 g of the base material was added thereto, and the dispersion was stirred for 2 minutes. Thereafter, the dispersion was spray-dried to produce a free-flowing powder. Then, this powder was calcined at 700 °C for 2 hours (NCM111 concentrate - Sample 1) and at 715 °C for 0.25 hours (NCM111 concentrate - Sample 2) under a flow of air not containing CO2.

[0098] Thereafter, the samples were characterized for residual LiOH and average oxidation state and compared with the base material. The decrease in residual LiOH while maintaining the oxidation state strongly suggests that an ordered material was produced. Furthermore, a separate phase of the LiMO2 material containing the NCM111 composition was not detected in the XRD spectrum. This also suggests that the coating composition does not form a separate NCM111 LiMO2 phase but concentrates in the grain boundary (GB) region.

[0099]

Table 4

[0100] Example 4: Li 1.01 Mg 0.01 Ni 0.8975 Co 0.0769 Al 0.0128 Mn 0.0128 Production of O2. The overall composition is Li 1.01 Mg 0.01 Ni 0.92 Co 0.08A polycrystalline base cathode material (base material) of O2 was synthesized using a standard solid-phase synthesis method. Subsequently, the grain boundaries of the base material were reinforced with elements that form a layered 2D α-NaFeO2 structure in combination with nickel, but exhibit a significantly reduced degree of oxidation at 4.3V. It was shown that the incorporation of these elements, particularly Al and Mn, promoted the retention of Li. The overall composition of this material with Al and Mn concentrated at the grain boundaries (referred to as NAM111 concentration) was Li 1.01 Mg 0.01 Ni 0.8975 Co 0.0769 Al 0.0128 Mn 0.0128 It was O2. The materials were synthesized according to the following procedure.

[0101] A 100 ml aqueous solution was prepared using manganese nitrate tetrahydrate (3.38 g), nickel nitrate heptahydrate (3.92 g), aluminum nitrate nonahydrate (5.05 g), and lithium nitrate (1.42 g), and this was heated to 60°C. 100 g of the base material was added to this, and the dispersion was stirred for 20 minutes. The dispersion was then spray-dried to produce a free-flowing powder. This powder was then calcined at 700°C for 2 hours under a CO2-free airflow (NAM111 concentration).

[0102] Next, we analyzed the NAM111 enrichment, a polycrystalline cathode material, to confirm that Al and Mn are indeed enriched at the grain boundaries. Focused ion beam milling was used to fabricate a 100 nm thick portion of polycrystalline grains in the NAM111 enrichment. EDS line scans were performed across two different grain boundaries at the locations shown in Figure 3. Figures 4A and 4B show the atomic ratios of aluminum, manganese, and cobalt to nickel across these grain boundaries. As can be seen, aluminum and manganese are clearly enriched at these grain boundaries, but cobalt is not. That is, the concentration of manganese at the grain boundaries is higher than the concentration of manganese in the crystallites. Also, the concentration of aluminum at the grain boundaries is higher than the concentration of aluminum in the crystallites.

[0103] Figures 4C and D show the atomic percent of nickel relative to the total atomic content of nickel, aluminum, manganese, and cobalt across these grain boundaries. As can be seen, the concentration of nickel at the grain boundaries is lower than that in the crystallites.

[0104] Example 5: Li 1.01 Mg 0.01 Ni 0.9038 Co 0.0769 Mn 0.0192 Production of O2. The overall composition of Examples 3 and 4 Li 1.01 Mg 0.01 Ni 0.92 Co 0.08 The same polycrystalline base cathode material (base material) with O2 was used for the synthesis of a material in which Ni and Mn were concentrated at the grain boundaries (referred to as NM11 enrichment). The final overall composition was Li 1.01 Mg 0.01 Ni 0.9038 Co 0.0769 Mn 0.0192 O2. The material was synthesized according to the following procedure.

[0105] A 100 ml aqueous solution was prepared using manganese(II) nitrate tetrahydrate (5.90 g), nickel(II) nitrate hexahydrate (5.09 g), and lithium nitrate (1.42 g), and this was heated to 60 °C. 100 g of the base material was added thereto, and the dispersion was stirred for 10 minutes. Thereafter, the dispersion was spray-dried to produce a free-flowing powder. Then, this powder was calcined at 700 °C for 2 hours under a stream of CO2-free air.

[0106] Example 6: Electrochemical tests of NCM111, NAM111, and NM11 grain boundary enriched materials. Cathode electrodes were prepared and electrochemically tested using the NCM111 concentrate-sample 1 described in Example 3, the base material and NAM111 concentrate described in Example 4, and the NM11 concentrate described in Example 5. The cathode active material was first mixed with a PVdF binder, conductive carbon, and NMP solvent to prepare the electrode slurry. The electrode slurry was coated onto aluminum foil using a drawdown table. The coated foil was dried at 130°C to remove the NMP, leaving the coated electrode. The electrodes were then pressed, punched out, assembled into coin cells using a Li metal anode (half cell) or a graphite anode (full cell), and tested.

[0107] The cycle lifetimes of the three materials in a full coin cell were tested using the same electrochemical procedure. Figures 11 and 12 show the capacity retention and impedance increase, respectively, during accelerated cycle lifetime testing at 45°C. In addition to the high-rate cycle step, a continuous discharge step of 1C was included every 10 high-rate cycles. Figure 12 shows the DCR measured with a 10-second 2C pulse at the end of each 10 high-rate cycle. These measurements confirm the superior performance of the grain boundary-enriched material in terms of both reduced capacity degradation and reduced impedance increase. Selective enrichment of Al and Mn at the grain boundaries promotes additional retention of Li at the end of charging.

[0108] Example 7: XRD analysis of charged grain boundary concentrated material. Figure 5 shows homogeneous Li 1.01 Mg 0.01 Ni 0.92 Co 0.08 O2-based material and Li 1.01 Mg 0.01 Ni 0.8975 Co 0.0897 Mn 0.0128The X-ray diffraction data for the NCM111 grain boundary-enriched material (Sample 1) of Example 3, which has an overall O2 composition, are shown. The cathode electrode coated on an Al current collector was X-ray analyzed in either its initial state or after being charged to 4.3V against Li. The electrode was charged in a coin cell on the opposite side of the Li metal counter electrode. The charged electrode was recovered, washed, and dried before X-ray diffraction. X-ray diffraction spectra were collected using an automated Shimadzu XRD-6000 diffractometer with a Cu X-ray tube, using continuous scans of 12–120 degrees at 2θ at 0.75 degrees / min. The two cathode materials have essentially identical diffractograms, and many of the peaks in both materials shift to significantly larger 2θ values ​​when charged.

[0109] However, when comparing the XRD of the two charged materials, a significant difference becomes apparent. The charged grain boundaries are modified Li 1.01 Mg 0.01 Ni 0.8975 Co 0.0897 Mn 0.0128 The peaks at 2θ = 19° and 46° in the O2 cathode are homogeneous Li, as shown in Figure 6. 1.01 Mg 0.01 Ni 0.92 Co 0.08 Compared to the O2 cathode peak, it is broader and has a shoulder at a low 2θ.

[0110] The peaks at 2θ=19° and 46° in the XRD of LiMO2 are related to the 003 and 104 crystal orientations of the 2D α-NaFeO2 crystal structure, respectively, and are most directly affected by the c-axis heterogeneity resulting from the Li distribution heterogeneity. Thus, the charged grain boundary modified Li in Figure 6... 1.01 Mg 0.01 Ni 0.8975 Co 0.0897 Mn 0.0128 The low 2θ shoulder of the O2 cathode indicates that more Li is retained at grain boundaries than in bulk crystallites when charged.

[0111] Example 8: Li 1.01 Mg0.01 Ni 0.90 Co 0.08 Nd 0.02 O2 production. Li 1.01 Mg 0.01 Ni 0.90 Co 0.08 Nd 0.02 A polycrystalline grain boundary-enriched material having an overall O2 composition was synthesized as follows: 2.7 grams (g) of neodymium nitrate hexahydrate (Nd(Nd(NO3)3·6H2O) (99.9%, Sigma Aldrich Milwaukee, WI) was dissolved in 30 milliliters (ml) of methanol at 40°C in a glass beaker. After dissolution, 30 grams (g) of polycrystalline base material (Li 1.01 Mg 0.01 Ni 0.92 Co 0.08 O2 was added to the solution. The solution was stirred for 3 minutes to ensure that the base was properly distributed into the methanol solution. Methanol was removed from the solution by evaporation using a rotary evaporator at 40 degrees Celsius (°C) and 20 mmHg.

[0112] The dried powder was placed in an alumina crucible and calcined. Calcination was carried out by heating at a rate of 5°C per minute to approximately 130°C and holding at approximately 130°C for approximately 6 hours. Next, the temperature was raised at a rate of approximately 5°C per minute to approximately 450°C and held there for approximately 1 hour. Then, the temperature was raised at a rate of approximately 2°C per minute to 700°C and held at approximately 700°C for approximately 2 hours. After that, the sample was allowed to cool naturally to room temperature.

[0113] Example 9: Li 1.01 Mg 0.01 Ni 0.90 Co 0.08 Ga 0.02 O2 production. Li 1.01 Mg 0.01 Ni 0.90 Co 0.08 Ga 0.02A polycrystalline grain boundary-enriched material having an overall O2 composition was synthesized as follows: 1.55 grams (g) of gallium nitrate hydrate ((Ga(NO3)3·H2O) (99.999%, Sigma Aldrich Milwaukee, WI) was dissolved in 30 milliliters (ml) of ethanol at 40°C in a glass beaker. After dissolution, 30 grams (g) of polycrystalline base material (Li 1.01 Mg 0.01 Ni 0.92 Co 0.08 O2 was added to the solution. The solution was stirred for 3 minutes to ensure that the base was properly distributed into the methanol solution. Methanol was removed from the solution by evaporation using a rotary evaporator at 40 degrees Celsius (°C) and 20 mmHg.

[0114] The dried powder was placed in an alumina crucible and calcined. Calcination was carried out by heating at a rate of 5°C per minute to approximately 130°C, and then holding at approximately 130°C for approximately 6 hours. Next, the temperature was raised at a rate of approximately 5°C per minute to approximately 450°C and held there for approximately 1 hour. Then, the temperature was raised at a rate of approximately 2°C per minute to 700°C and held at approximately 700°C for approximately 2 hours. After that, the sample was allowed to cool naturally to room temperature.

[0115] Example 10: Li 1.01 Mg 0.01 Ni 0.90 Co 0.08 B 0.02 O2 production. Li 1.01 Mg 0.01 Ni 0.90 Co 0.08 B 0.02 A polycrystalline grain boundary-enriched material having an overall O2 composition was synthesized as follows: 0.21 grams (g) of boron trioxide (B2O3) (99%, Sigma Aldrich Milwaukee, WI) was dissolved in 40 milliliters (ml) of methanol at 40°C in a glass beaker. After dissolution, 30 grams (g) of polycrystalline base material (Li 1.01 Mg 0.01 Ni 0.92 Co 0.08O2 was added to the solution. The solution was stirred for 3 minutes to ensure that the base was properly distributed into the methanol solution. Methanol was removed from the solution by evaporation using a rotary evaporator at 40 degrees Celsius (°C) and 20 mmHg.

[0116] The dried powder was placed in an alumina crucible and calcined. Calcination was carried out by heating at a rate of 5°C per minute to approximately 130°C, and then holding at approximately 130°C for approximately 6 hours. Next, the temperature was raised at a rate of approximately 5°C per minute to approximately 450°C, and then held for approximately 1 hour. Then, the temperature was raised at a rate of approximately 2°C per minute to 700°C, and held at approximately 700°C for approximately 2 hours. After that, the sample was allowed to cool naturally to room temperature.

[0117] Example 11: Li 1.01 Mg 0.01 Ni 0.90 Co 0.08 Fe 0.02 O2 production. Li 1.01 Mg 0.01 Ni 0.90 Co 0.08 Fe 0.02 A grain boundary-enriched material having an overall O2 composition was synthesized as follows: 1.23 grams (g) of anhydrous iron acetate (Fe(OOCH3)2) (99.9%, Alfa Aesar, Ward Hill, MA) was dissolved in 30 ml (ml) of methanol at 40°C in a glass beaker. After dissolution, 35 grams (g) of polycrystalline base material (Li 1.01 Mg 0.01 Ni 0.92 Co 0.08 O2 was added to the solution. The solution was stirred for 3 minutes to ensure that the base was properly distributed into the methanol solution. Methanol was removed from the solution by evaporation using a rotary evaporator at 40 degrees Celsius (°C) and 20 mmHg.

[0118] The dried powder was placed in an alumina crucible and calcined. Calcination was carried out by heating at a rate of 5°C per minute to approximately 130°C, and then holding at approximately 130°C for approximately 6 hours. Next, the temperature was raised at a rate of approximately 5°C per minute to approximately 450°C, and then held for approximately 1 hour. Then, the temperature was raised at a rate of approximately 2°C per minute to 700°C, and held at approximately 700°C for approximately 2 hours. After that, the sample was allowed to cool naturally to room temperature.

[0119] Example 12: Electrochemical testing of the cathode materials from Examples 1 and 8-11. The cathode active materials of Examples 1, 8, 9, 10, and 11 were incorporated into the cathode electrodes. The materials were first mixed with PVdF, conductive carbon, and NMP solvent to prepare an electrode slurry. The electrode slurry was then coated onto aluminum foil using the doctor blade method. The coated foil was dried at 130°C to remove the NMP, leaving the coated electrode. The electrodes were then pressed and punched out to assemble coin cells with a Li metal counter electrode, a polymer separator, and a carbonate electrolyte. The half-cells were then tested for capacity and rated capacity (charged to 4.3V and discharged to 3.0V). Electrochemical performance data for concentrated and unconcentrated polycrystalline-based materials are shown in Table 5.

[0120] [Table 5]

[0121] While not limited to a single specific theory, as can be inferred from the examples described above, the superior cycle stability of materials with modified grain boundaries is thought to be related to their selective retention of more Li at the grain boundaries when they are charged.

[0122] Example 13: First composition LiNi 0.8 Co 0.1 Mn 0.1NCM-based materials containing O2(NCM811) were prepared from co-precipitated precursor transition metal hydroxides containing 10 at% Co, 10 at% Mn, and the remainder Ni. NCA materials having a first composition of varying amounts of Ni, Co, and Al (atomic ratios of 86:12:2, 89:8:3, or 93:4:3, respectively) were prepared from co-precipitated precursor transition metal hydroxides containing appropriate amounts of Ni, Co, and Al. Micronized LiOH powder was prepared by placing 87.7 g of LiOH in a plastic jar containing 500 g of Y-stabilized 1 / 4-inch zirconia spheres and shaking in a paint shaker for 45 minutes. This micronized powder was then transferred to another plastic jar containing 335.7 g of NCM or NCA transition metal hydroxide precursors and blended by shaking the two in a paint shaker for a further 10 minutes. After blending, approximately 440g of powder was divided into three crucibles and calcined in an oxygen atmosphere by first raising the temperature to 450°C at a rate of 5°C / min and allowing it to soak at that temperature for 2 hours, then raising the temperature to 770°C at a rate of 2°C / min and allowing it to soak at 770°C for 10 hours. Next, the furnace was cooled to 130°C, the powder was removed and placed in a ball mill. The ball mill contained a 3 / 4-inch drum media, which was used to grind the powder for 2 minutes. The powder was then sieved through a 270-mesh sieve.

[0123] The sieved powder was then separated into the base (no further processing) and the base (where Co and Al were concentrated at the grain boundaries) by preparing a solution of 200 g of water, 11.9 g of cobalt nitrate (2 at% Co relative to the total metal content of the base composition), 3.1 g of aluminum nitrate (0.4 at% Al relative to the total metal content of the base composition), and 3.4 g of lithium nitrate, and then heating it to 60°C. 200 g of the pre-prepared lithiumation precursor powder (base material) was added to this. The slurry was stirred for 10 minutes, and then spray-dried to remove water from the slurry and prepare a dry powder. Next, this powder was calcined in an air atmosphere by first raising the temperature to 450°C at a rate of 5°C / min, soaking it at that temperature for 1 hour, and then raising the temperature to 770°C at a rate of 2°C / min and soaking it for 0.25 hours. Next, the furnace was allowed to cool to 130°C, the powder was removed from the furnace, and sieved through a 270-mesh sieve.

[0124] The obtained base particles or grain boundary-concentrated particles were pulverized in a 2 cm diameter die using a hydraulic press to the target pressure. A total mass of 2.5 g of powder was placed in the die and pulverized to form pellets. The pellets were then placed in 20 mL of water and ultrasonically dispersed for 30 minutes. After dispersion, a small amount of the dispersed slurry was tested with a Malvern Mastersizer 3000 laser particle size analyzer equipped with a liquid cell. To ensure complete dispersion of the fine particles, the ultrasonic function was used during measurement, and the final results were calculated using an average of 5 measurements. The particle distribution was calculated using NiO properties obtained from the instrument's library. The results of this process using exemplary NCM811 materials with or without Ni-poor grain boundary regions are shown in Figure 13.

[0125] Various materials were assembled as cathodes and tested as shown in Example 6. As shown in Figure 13, the impedance decreases when a relatively low Ni concentration is present at the grain boundaries compared to the base material.

[0126] The above-mentioned descriptions of specific embodiments are illustrative in nature and are not intended in any way to limit the scope of the disclosure or its application or use, which may naturally change. Materials and processes are described in relation to the non-limiting definitions and terms contained herein. These definitions and terms are not intended to function as limitations on the scope or practice of this disclosure and are presented for illustrative and descriptive purposes only. Processes or compositions are described as a sequence of individual steps or using specific materials, but it is understood that steps or materials may be interchangeable so as to include multiple parts or steps arranged in many ways so as to be readily understood by those skilled in the art.

[0127] Terms such as “first,” “second,” and “third” may be used herein to describe various elements, components, regions, layers, and / or parts, but it will be understood that these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are used solely to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, unless otherwise specified, the “first element,” “component,” “region,” “layer,” or “part” described below may be referred to as the second (or another) element, component, region, layer, or part without deviation from the teachings herein.

[0128] The terms used herein are intended solely to describe and not to limit to specific aspects. The singular forms “a,” “an,” and “the” as used herein are intended to include the plural form, which includes “at least one,” unless the context clearly indicates otherwise. “Or” means “and / or.” The term “and / or” as used herein includes any combination of one or more of the related enumerated items. Where used herein, the terms “comprises” and / or “comprising,” or “includes” and / or “including” specify the presence of the described features, regions, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof. The term “or any combination thereof” means any combination that includes at least one of the elements described herein.

[0129] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as those generally understood by those skilled in the art to which this disclosure belongs. Furthermore, terms as defined in commonly used dictionaries should be construed to have the meaning consistent with their meanings in the context of the relevant art and this disclosure, and not in an ideal or overly formal sense unless expressly defined herein.

[0130] Those skilled in the art will see various modifications in addition to those shown and described herein. Such modifications are also intended to be included within the scope of this disclosure.

[0131] Unless otherwise specified, it is understood that all reagents are available from suppliers known in the relevant art.

[0132] The patents, publications, and applications described herein are indicators of the level of expertise of those skilled in the art relating to this disclosure. These patents, publications, and applications are incorporated herein by reference to the same extent that individual patents, publications, or applications are incorporated herein by reference specifically and individually.

[0133] The above description illustrates specific aspects of the present invention, but does not mean to limit its implementation.

Claims

1. A plurality of crystallites comprising a first composition containing lithium, nickel, and oxygen, A grain boundary between adjacent crystallites of the plurality of crystallites, comprising a second composition containing lithium, nickel, and oxygen, Electrochemically active particles for use in the cathode of an electrochemical cell, including, A particle wherein, when the electrode containing the particle is charged, lithium is reversibly present at the grain boundary at a higher concentration than the lithium in the crystallite.

2. The particle according to claim 1, wherein the particle is charged and has a potential of 4.0V or higher relative to lithium, 4.2V or higher relative to lithium, or 4.3V or higher relative to lithium.

3. The particle according to claim 1, wherein lithium is present at the grain boundary at a higher concentration than the lithium in the crystallite, with a charging capacity of 40 mAh / g or more, or 200 mAh / g or more.

4. The particle according to claim 2 or 3, wherein the grain boundary contains more than 0.1 moles of lithium per mole of the second composition in terms of potential or volume.

5. The particle according to claim 2 or 3, wherein the grain boundary contains more than 0.15 moles of lithium per mole of the second composition in terms of potential or volume.

6. A plurality of crystallites comprising a first composition containing lithium, nickel, and oxygen, A grain boundary between adjacent crystallites of the plurality of crystallites, comprising a second composition containing lithium, nickel, and oxygen, Electrochemically active particles for use in the cathode of an electrochemical cell, including, A particle in which lithium is reversibly present at the grain boundary at a higher concentration than the lithium in the crystallite when the particle is in a charged state of 10 percent or more.

7. The particle according to claim 6, wherein when the particle is in a charged state of 20 percent or more, lithium is present at the grain boundary at a higher concentration than lithium in the crystallite.

8. The particle according to claim 6, wherein when the particle is in a charged state of 80 percent or more, lithium is present at the grain boundary at a higher concentration than lithium in the crystallite.

9. The grain boundary is α-NaFeO ２ Particles according to any one of claims 1 to 8, having a layered structure, cubic structure, spinel structure, monoclinic structure, or a combination thereof.

10. The second composition is Li １＋ｘ M'O ２＋ｙ The particle according to any one of claims 1 to 8, wherein the amount of Ni based on the moles of Ni per mole of the second composition is -0 ≤ Ni ≤ 0.

99.

11. The particles according to claim 10, wherein the amount of Ni based on the number of moles of Ni per 1 mole of M' in the second composition is 0.9 or less.

12. The particle according to claim 10, wherein M' contains an element having a higher oxidation potential than Ni.

13. The aforementioned element is Li １＋ｘ M'O ２＋ｙ The particle according to claim 12, wherein Ni can be substituted at the 3b site of the structure.

14. The particle according to claim 12, wherein the element comprises Mn, Ti, Cr, Fe, Y, Ga, Sb, W, Sc, Zr, Nb, Mo, Zn, Cu, In, Ge, Al, or any combination thereof.

15. The particle according to claim 12, wherein the element comprises two or more elements selected from the group consisting of Mn, Ti, Cr, Fe, Co, Y, Ga, Sb, W, Sc, Zr, Nb, Mo, Zn, Cu, In, Ge, and Al.

16. The particle according to claim 12, wherein M' comprises two or more elements selected from the group consisting of Co, Mn, Ti, Cr, Fe, Y, Ga, Sb, W, Sc, Zr, Nb, Mo, Zn, Cu, In, Ge, and Al.

17. The particle according to claim 12, wherein M' comprises three or more elements selected from the group consisting of Co, Mn, Ti, Cr, Fe, Y, Ga, Sb, W, Sc, Zr, Nb, Mo, Zn, Cu, In, Ge, and Al.

18. The first composition is Li １＋ｘ MO ２＋ｙ A particle according to any one of claims 1 to 8, defined by and containing 0.1 moles or more of nickel per mole of M.

19. The particle according to claim 18, wherein M contains 0.75 moles or more of nickel per mole of M, or 0.90 moles or more of nickel per mole of M.

20. M further contains additional metals, the additional metals present in an amount of about 0.01 to about 0.90 moles per mole of M, The particle according to claim 19, wherein the additional metal is selected from the group consisting of Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Cr, Fe, Mo, B, and any combination thereof.

21. The surface of the particles further includes an outer coating, and the outer coating is 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; Particles according to any one of claims 1 to 8, including

22. An electrochemical cell comprising a cathode, an anode, and an electrolyte, wherein the cathode comprises a cathode active material comprising particles according to any one of claims 1 to 21.

23. The electrochemical cell according to claim 22, characterized by the particles that provide a discharge capacity of 170 mAh / g or more for more than 175 cycles at 45°C.

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