Cathode having an irregular rock salt type material and method for forming the cathode.

Abstract

To provide a cathode with a disordered rocksalt material and a method of forming the same.SOLUTION: A method of forming a cathode includes a process of milling a suspension of precursors via a micromedia mill to form a mixture of primary particles in the suspension. The precursors include one or more metal compounds. The method includes spray drying the suspension after the milling process to form secondary particles. The secondary particles are agglomerations of the primary particles. The method also includes a process of annealing the secondary particles to form a disordered rocksalt powder.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention belongs to the field of battery technology. [Background technology]

[0002] Lithium metal oxides have been used to formulate cathode materials for lithium-ion batteries. The cathodes originate from several basic crystal structure types, such as spinel, olivine, and layered oxide structures. Layered oxide structures include lithium-rich structures where additional lithium is present in the structure.

[0003] In recent years, attention has been focused on irregular rock salt structures, such as those formed from specific lithium metal oxides. Formula: xLi3NbO4·(1-x)LiMO2(1) Compounds represented by formula (1), where M is a divalent or trivalent cation, have been shown to be a promising type of transition metal oxide for use as a cathode in lithium-ion batteries. Compounds of formula (1) are thought to be disordered rock salts in which random atomic arrangements of lithium and transition metal ions are packed in a close-packed cubic structure. These disordered rock salt-type compositions offer the ability to contain three or fewer lithium atoms per formula unit, which is more than conventional lithium-rich layered materials. Formula (1) is Li x M y N z O w It can be expressed by transforming it as follows:

[0004] Irregular rock salt structures are attractive cathode materials for next-generation lithium-ion batteries because they have a higher intrinsic energy density (e.g., a higher theoretical energy density) than current cathode materials, such as layered lithium metal oxide structures. For example, certain irregular rock salt structures have a theoretical energy density of approximately 1120 Wh / kg, while LiMn2O4 active materials have a theoretical energy density of approximately 492 Wh / kg. 1.5 Ni 0.5O4 has a theoretical energy density of approximately 691 Wh / kg. This energy density is particularly attractive when lower-cost raw materials, such as manganese, are used as components in the disordered rock salt structure. Thus, disordered rock salt materials can achieve relatively high energy densities with relatively low material costs. To achieve relatively high energy densities, known cathode materials require higher-cost raw materials, such as cobalt or nickel.

[0005] A drawback of disordered rock salt materials is their relatively poor conductivity. One way to improve the conductivity of battery materials is to reduce particle size to shorten the transport pathways for electrons and ions. Reducing particle size can increase conductivity by shortening the transport pathways for electrons and ions. Unfortunately, smaller particle sizes also inherently limit the energy density per unit volume of electrodes, which reduces the energy density of the battery cell. Thus, at least some of the advantages of high energy density, which are inherent in disordered rock salt materials, are sacrificed to mitigate the conductivity problem. [Overview of the project]

[0006] In one or more embodiments, a method for forming a cathode is provided, comprising the step of grinding a suspension of a precursor with a micromedia mill to form a mixture of primary particles in the suspension. The precursor comprises one or more metal compounds. The method further comprises the step of spray-drying the suspension after the grinding step to form secondary particles. The secondary particles are aggregates of primary particles. The method further comprises the step of annealing the secondary particles to form an irregular rock salt type powder.

[0007] In one or more embodiments, a cathode for a rechargeable battery is provided. The cathode comprises an irregular rock salt powder characterized by secondary particles having an average particle size of 1 micrometer or more and 20 micrometers or less. Each of the secondary particles is an aggregate of primary particles. The primary particles have an average particle size of 400 nanometers or less.

[0008] In one or more embodiments, a method is provided for forming a lithium-ion battery, comprising the step of grinding a precursor suspension to form a mixture of primary particles in the suspension. The precursor comprises one or more metal compounds. The method comprises the step of spray-drying the suspension after the grinding step to form secondary particles. The secondary particles are aggregates of primary particles. The method comprises the step of annealing the secondary particles to form an irregular rock salt type powder, and, after the annealing step, grinding the irregular rock salt type powder together with one or more carbon precursors. The method further comprises the steps of mixing the irregular rock salt type powder with one or more solvents to form a slurry, drying the slurry on a metal current collector to form a composite cathode film, inserting the composite cathode film into a cell casing such that a separator is positioned between the composite cathode film and the anode, and supplying an electrolyte into the cell casing. [Brief explanation of the drawing]

[0009] [Figure 1] This is a flowchart of a method for forming the cathode of a lithium-ion battery according to one embodiment. [Figure 2] This is a magnified image of a suspension showing irregular rock salt-type secondary particles after a spray-drying process, according to one embodiment. [Figure 3] This is a magnified image of irregular rock salt-type secondary particles after the annealing process, according to one embodiment. [Figure 4] This is an enlarged image showing a magnified view of a single irregular rock salt secondary particle, according to one embodiment, as shown in Figure 3. [Figure 5]This graph plots the voltage profiles of spherical secondary particles of disordered rock salt-type phase powder at discharge rates of 0.1C and 1C. [Modes for carrying out the invention]

[0010] Detailed explanation The following definitions apply to some of the embodiments described for several embodiments of the present invention. Similarly, these definitions may be extended herein. Each term is further explained and illustrated through the description, drawings, and examples. Any interpretation of the terms herein should take into account the entire description, drawings, and examples provided herein.

[0011] The singular terms "a," "an," and "the" can include plural forms unless the context explicitly states otherwise. Therefore, for example, a reference to an object can include multiple objects unless the context explicitly states otherwise.

[0012] The term "transition metals" refers to the chemical elements in groups 3 through 12 of the periodic table, including scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), and rhodium (R). h) contains palladium (Pd), silver (Ag), cadmium (Cd), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), mercury (Hg), rusthordium (Rf), dubnium (Db), seaborgium (Sg), bohrium (Bh), hassium (Hs), and meitnerium (Mt).

[0013] Depending on the context, rate “C” refers to either a discharge current as a fraction or multiple of the current value of “1C” at which a battery in a (substantially fully charged state) discharges substantially fully in one hour, or a charge current as a fraction or multiple of the current value of “1C” at which a battery in a (substantially fully discharged state) charges substantially fully in one hour.

[0014] Unless the context otherwise clearly dictates, for any particular battery characteristic that may vary with temperature, such a characteristic is specified at 30 °C.

[0015] The ranges provided herein include their endpoints. Thus, for example, the range 1 - 3 includes the values 1 and 3, as well as intermediate values.

[0016] Embodiments of the subject matter of the present invention provide a disordered rock salt-type composition and morphology (e.g., structure) for use in the formulation of an electrode of an electrochemical cell. More specifically, the disordered rock salt-type materials disclosed herein can be used to form a cathode. An electrochemical cell that utilizes a disordered rock salt-type material disclosed herein may be a lithium-ion battery. The lithium-ion battery may be a secondary battery or a rechargeable battery. For example, discharge and recharge of a lithium-ion battery can be achieved by intercalation and deintercalation of lithium ions into and from the cathode, respectively. A lithium-ion battery includes an electrolyte formulation having a lithium salt present at a concentration suitable for conducting lithium ions through the electrolyte formulation between the cathode and the anode during discharge and recharge operations.

[0017] In disordered rock salt compositions, both lithium and transition metals occupy cubic close-packed lattices of octahedral sites. In electrochemical reactions, lithium diffusion proceeds by hopping from one octahedral site to another via intermediate tetrahedral sites. Lithium in intermediate tetrahedral sites is in an activated state during lithium diffusion. Activated tetrahedral lithium ions share faces with four octahedral sites: (i) sites previously occupied by the lithium ion itself; (ii) vacancies into which the lithium ion migrates; and (iii and iv) two sites that may be occupied by lithium, transition metals, or vacancies.

[0018] To provide short electron and ion transport pathways and suitable conductivity without sacrificing electrode energy density, the disordered rock salt morphology in the cathode described herein includes micro-sized clusters or aggregates of sub-micro-sized particles. In this specification, micro-sized clusters are also referred to as secondary particles. Secondary particles have an average particle size (e.g., diameter) on a micrometer scale, for example, 1 to 20 micrometers. Clusters of sub-micro-sized particles form secondary particles. In this specification, sub-micro-sized particles are also referred to as primary particles. The terms “primary” and “secondary” indicate that primary particles are formed before secondary particles, and that secondary particles are aggregates of primary particles. Primary particles have an average particle size (e.g., diameter) on a nanometer scale, for example, less than 400 nanometers. Sub-micro primary particles in disordered rock salt materials provide desirable conductivity, while micro-sized secondary particles in disordered rock salt materials result in high electrode energy density. Thus, forming an irregular rock salt morphology with micro-sized aggregates of sub-micro-sized particles provides the high energy density associated with irregular rock salt materials without impairing conductivity.

[0019] One or more embodiments disclose the synthesis of an irregular rock salt type cathode active material. The morphology of the active material includes microsized spherical secondary particles, which are aggregates of smaller primary particles, as described above. The synthesis involves grinding a metal precursor to produce a homogeneous mixture of nanosized precursor particles. The mixture is then spray-dried to produce spherical precursor particles having a controlled particle size. The spray-drying results in microsized spherical precursor particles, which are clusters or aggregates of nanosized precursor particles. The spherical precursor particles are then subjected to annealing, which results in an irregular rock salt type phase. The annealing conditions are selected to maintain the particle morphology such that the resulting irregular rock salt type phase has microsized spherical secondary particles, which are aggregates of smaller primary particles. Experimental tests of the embodiments disclosed herein showed good rate performance of 272 mAh / g when cycled at C / 10, 30°C, and 1.5V to 4.8V, and 193 mAh / g when cycled at 1C, 30°C, and 1.5V to 4.8V.

[0020] Known disordered rock salt morphologies lack spherical, micro-sized secondary particles, which are clusters of smaller primary particles, as described in the embodiments herein. For example, known disordered rock salt materials are synthesized by conventional solid-state chemistry and / or molten salt methods, resulting in large single-crystal and polycrystalline particle sizes. Partly due to the large particle size, disordered rock salt materials produced by known methods suffer from poor conductivity.

[0021] The irregular rock salt type cathode active material formed by the process described herein and comprising the secondary particle morphology described herein may have various compositions. For example, compositions of a plurality of irregular rock salt type materials are disclosed in US Patent Application Publication No. 15 / 222377 (now US Patent No. 10280092), the entire disclosure of which is incorporated herein by reference. Generally, irregular rock salt type compositions contain lithium, transition metals, and oxygen. One or more of the transition metal or oxygen sites can be doped to improve electrochemical performance. In a non-limiting example, the oxygen site is doped with fluorine. The general formula for doping at the oxygen site is Li x N y M z O 2-a F a (1) where 1.0 < x < 1.65; 0.01 < y < 0.55; 0.1 < z < 1; 0 ≦ a < 0.5; N is one of Ti, Ta, Zr, W, Nb or Mo; and M is one of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Y, Mo, Ru, Rh or Sb. These compositions have shown excellent intrinsic capacity or energy density, for example, ~350 mAh / g at 55 °C and C / 40, and ~300 mAh / g at 30 °C and C / 15.

[0022] When a > 0, the presence of fluorine dopants at oxygen sites in the irregular rock salt can improve the electrochemical performance of a lithium ion battery cell. Without being bound by a particular theory or mechanism of action, the anionic substitution of fluorine for oxygen (forming an oxyfluoride) can improve cycle performance by having greater resistance to attack by hydrogen fluoride from electrolyte decomposition at high voltages. Alternatively, the higher ionic nature of the metal-fluorine bond relative to the ionic nature of the metal-oxygen bond can result in less transition metal leaching from the cathode into the electrolyte, further stabilizing the structure.

[0023] In non-limiting examples, the disordered rock salt type composition may lack niobium. In another non-limiting example, N sites and / or M transition metal sites may be doped in place of, or in addition to, oxygen sites.

[0024] Figure 1 is a flowchart of Method 100 for forming a cathode of a lithium-ion battery according to one embodiment. Method 100 can be carried out using one or more components of laboratory or industrial equipment. Method 100 is used to produce an irregular rock salt type (DR) active material for the cathode, which provides high energy density and sufficient conductivity. Optionally, Method 100 may include more steps than described herein, fewer steps than described herein, and / or steps different from those described herein.

[0025] In step 102, the precursor suspension is pulverized to form a mixture of primary particles in the suspension. The precursors include metal compounds and are selected based on the desired composition of the DR material. One or more of the precursors are metal oxides, e.g., Mn2O3, LiOH, Nb2O5. For doping with fluorine at oxygen sites, at least one precursor contains fluorine. Possible fluorine-containing precursors may include LiF, NbF5 and / or similar. In non-limiting examples, the precursors may include one or more of Mn2O3, Li2CO3, LiF, LiOH, Nb2O5, NbF5 and / or similar. The precursors can be mixed in stoichiometric amounts in deionized water to produce a suspension. Pulverization can be carried out by a micromedia mill. A micromedia mill may comprise concentric cylinders having milling media present in an annular gap between the cylinders. The milling media pulverizes the precursors in the suspension so that the cylinders rotate relative to each other to produce small nano-sized primary particles. A micromedia mill can also be designed to form homogeneous particles, such that all primary precursor particles are approximately the same size within the designed range. Primary particles exiting the mill may have an average particle size of 400 nanometers (nm) or less. Optionally, the average particle size may be 200 nm or less, 100 nm or less, or even smaller. For example, the average particle size may be 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, or similar sizes or smaller. In non-limiting examples, a micromedia mill is a laboratory bead mill, such as the Buhler PML2 product, a trademark of the Buhler Group.

[0026] In 104, after grinding the suspension, the suspension containing a mixture of nano-sized precursor particles is spray-dried to form secondary particles. The step of spray-drying the suspension involves releasing the suspension under high pressure through a nozzle, which causes the suspension to form an aerosol. In non-limiting examples, spray-drying can be carried out using a small spray dryer, for example, the Buchi B-290 model, a trademark of Buchi. Each drop of the aerosol contains a solvent, such as water, along with small primary particles. As the aerosol dries rapidly, the solvent evaporates and the primary particles coalesce to form secondary particles. Secondary precursor particles are clusters or aggregates of primary particles. The small, relatively homogeneous size profile of the primary particles in the aerosol allows the primary particles to aggregate during the drying process. In some embodiments, spray-drying gives the secondary particles a spherical shape. For example, the secondary particles are nearly spherical and can be seen as spherical when viewed under a microscope.

[0027] Figure 2 is a magnified image 200 of a suspension showing DR secondary particles 202 after a spray-drying step according to one embodiment. The image is magnified to a micrometer scale and includes an indicator 204 representing 10 micrometers (μm). As shown in Figure 2, the secondary particles 202 are spherical in shape and have a size of approximately 1 μm to approximately 10 μm. Optionally, some of the secondary particles 202 may be larger than those shown in Figure 2, for example, having a diameter of approximately 20 μm, while other secondary particles 202 may be slightly smaller than 1 μm, for example, 0.5 μm.

[0028] Returning to method 100, after the spray-drying step, in 106, the secondary particles are annealed to form a DR phase powder. The relatively high temperature to which they are exposed causes the precursors in the secondary particles to react and form a unit phase. The phase is formed at the elemental level, but the conditions of the annealing step are selected to maintain the morphology during firing. For example, the resulting DR phase powder maintains micro-sized spherical secondary particles. The annealing conditions may include heating the particles at a temperature of 750°C to 900°C for a period of 6 to 24 hours. Annealing for a period longer or shorter than the specified period at a temperature outside the specified range may cause the secondary particles to bond or fuse into larger structures, which significantly reduces the conductivity of the resulting DR phase. Furthermore, the annealing step may be carried out under a flow of argon gas. Alternatively, the annealing environment may be nitrogen gas or air instead of argon gas. In other embodiments, the annealing conditions may be selected based on the composition of the disordered rock salt type precursor, for example, the metals present. For example, a manganese-based composition may utilize the above conditions (e.g., 750-900°C for 6-24 hours), while a composition based on another metal may have a wider temperature range, a higher or lower range, and / or a wider, longer or shorter range. In an unrestricted example, the temperature range could be 500°C-1200°C for a period of 3-48 hours.

[0029] Figure 3 is a magnified image 300 of secondary particles 202 of the DR phase powder 302 after the annealing process. The scale of image 300 is slightly smaller than that of image 200 shown in Figure 2. For example, the indicator 304 representing 10 μm is slightly shorter than the length of the indicator 204 in Figure 2. The secondary particles 202 after firing in Figure 3 look slightly different from the particles 202 before firing in Figure 2, but maintain the same shape and size.

[0030] Figure 4 is a magnified image 400 showing an enlarged field of view of one secondary particle 202 of DR phase powder 302 according to one embodiment. The indicator 404 represents a length of 5 μm. As shown in Figure 4, the secondary particle 202 has a size (e.g., diameter) of approximately 10 μm. The surface of the particle 202 is a patchwork of small irregularities 402, which represent nano-sized primary particles that aggregate to form the secondary particle 202.

[0031] In an alternative embodiment, instead of the steps of grinding the lithium-containing precursor together with other precursors and spray-drying, the lithium source can be kept separate until the annealing step. For example, spherical secondary particles can be produced in the same manner as described above, except that lithium is absent. In 106, the lithium source, for example Li2CO3, LiOH and / or LiF, can be mixed and annealed together with the pre-made secondary particles and subjected to calcination together with the secondary particles. The secondary particles 202 of the DR phase powder 302 shown in Figures 3 and 4 can be the same or similar, regardless of whether lithium is present in the grinding step of 102 or not until the annealing step of 106.

[0032] In another alternative embodiment, the DR phase can be formed before the grinding step. For example, the DR phase can be formed by a solid-state chemical method, for example, by a solid oxidation-reduction reaction of oxide ions. In 102, the formed DR phase, rather than the precursor, is ground to form a suspension of primary particles. Then, in 104, the suspension of primary particles of the pre-formed DR phase is spray-dried to form secondary particles. Since the DR phase is pre-formed, the annealing step in 106 may have reduced conditions, such as a lower temperature and / or a shorter duration, compared to the embodiments described earlier, or may be omitted entirely. Alternatively, the annealing step in 106 may remain unchanged from the embodiments described earlier.

[0033] Returning to method 100 in Figure 1, after the annealing step, in 108, the DR phase powder is pulverized with one or more carbon precursors. Pulverization with carbon precursors can form a carbon coating on the secondary particles. One or more carbon precursors may include acetylene black, carbon black, carbon fibers, graphite, carbon nanotubes, KJ600 and / or similar. In some embodiments, one or more carbon precursors are pulverized in a ratio in which the irregular rock salt type powder constitutes the majority and the carbon precursor constitutes the minority. For example, the ratio may be 60:40, 70:30, 80:20, or 90:10 DR phase powder:carbon precursor ratios. In a non-limiting example used in experimental testing, the ratio is 80:20 DR phase powder:carbon precursor.

[0034] In step 110, the DR phase powder is mixed with one or more solvents to form a slurry. Non-limiting examples of one or more solvents include poly(vinylidene fluoride) and 1-methyl-2-pyrrolidinone. In step 112, the resulting slurry is deposited on a metal current collector. The metal current collector may be stainless steel. In step 114, the slurry is dried on the metal current collector to form a composite cathode film.

[0035] In one embodiment, the cathode film produced by the method 100 described above, as shown in Figure 1, has an irregular rock salt powder. The irregular rock salt powder is characterized by secondary particles having an average particle size of 1 micrometer or more and 20 micrometers or less. Each of the secondary particles is an aggregate of primary particles. The primary particles have an average particle size of 400 nanometers or less.

[0036] The cathode active materials described herein can be used in rechargeable lithium-ion battery cells. The battery cell comprises a cathode and an anode separated by a polymer separator. The battery cell comprises an electrolyte that enables the transport of ions and electrons between the cathode and the anode. The cathode active materials described herein can be used with various types and compositions of anodes and electrolytes.

[0037] In non-limiting examples, rechargeable batteries were formed in a glove box (M-Braun, O2, and moisture content <0.1 ppm) filled with high-purity argon. A DR composite cathode membrane was used as the cathode. For the anode, thin Li foil was cut to the required size. Each battery cell consisted of a composite cathode membrane, a polypropylene separator, and a lithium foil anode. The electrolyte, along with additives, contained lithium hexafluorophosphate in a mixture of ethylene carbonate solvent and ethyl methyl carbonate solvent. The battery cells were sealed and cycled at 1.5V to 4.8V at 55°C, or in some cases 30°C.

[0038] Figure 5 is a graph 500 plotting the voltage profiles 502 and 504 of spherical secondary particles of DR phase powder at discharge rates of 0.1C and 1C. Voltage profiles 502 and 504 show experimental data measured when the battery cell described above was cycled at 1.5V to 4.8V at 30°C. Profile 502 represents a discharge rate of 0.1C (or C / 10), and profile 504 represents a discharge rate of 1C. Figure 5 shows that the tested battery cell exhibits capacities of 272mAh / g at 0.1C (1.5V to 4.8V) and 193mAh / g at 1C. These results demonstrate good rate performance with a 71% 1C / 0.1C capacity retention (e.g., 193mAh / g divided by 272mAh / g).

[0039] In one embodiment, a method for forming a cathode includes milling a suspension of a precursor with a media mill to form a mixture of primary particles in the suspension. The precursor includes one or more metal compounds. The method includes spray drying the suspension after the milling step to form secondary particles. The secondary particles are aggregates of the primary particles. The method further includes annealing the secondary particles to form an irregular rock salt-type powder.

[0040] Optionally, the spray drying step forms secondary particles having an average particle size of 1 micrometer or more and 20 micrometers or less. The milling step can form a mixture of primary particles such that the primary particles have an average particle size of 400 nanometers or less. Optionally, the precursor includes Mn2O3, Li2CO3, LiF, LiOH, Nb2O5, and / or NbF5. The annealing step can be performed under an argon gas flow. The annealing step can be performed in a temperature range of 750°C to 900°C for 6 hours or more and 24 hours or less. Optionally, the spray drying step forms secondary particles having a spherical shape.

[0041] Optionally, the irregular rock salt-type powder has the formula (i): <00001​​​​​​​​​​​​​​​​Optionally, the method further comprises a step of grinding the irregular rock salt powder together with one or more carbon precursors after the annealing step. The irregular rock salt powder can be ground together with one or more carbon precursors in a ratio in which the irregular rock salt powder constitutes the majority and one or more carbon precursors constitute the minority. Optionally, the method further comprises a step of mixing the irregular rock salt powder with one or more solvents to form a slurry, a step of depositing the slurry on a metal current collector, and a step of drying the slurry on the metal current collector to form a composite cathode film.

[0043] In one embodiment, the cathode for a rechargeable battery comprises an irregular rock salt powder characterized by secondary particles having an average particle size of 1 micrometer or more and 20 micrometers or less. Each of the secondary particles is an aggregate of primary particles, which have an average particle size of 400 nanometers or less.

[0044] Optionally, the secondary particles are spherical in shape. The secondary particles may have a carbon coating. The particle size of the secondary particles may be 10 micrometers or less.

[0045] In one embodiment, a method for forming a lithium-ion battery comprises the steps of grinding a precursor suspension to form a mixture of primary particles in the suspension. The precursor comprises one or more metal compounds. The method further comprises the steps of spray-drying the suspension after the grinding step to form secondary particles. The secondary particles are aggregates of primary particles. The method further comprises annealing the secondary particles to form an irregular rock salt type powder, and grinding the irregular rock salt type powder together with one or more carbon precursors after the annealing step. The method further comprises mixing the irregular rock salt type powder with one or more solvents to form a slurry, drying the slurry on a metal current collector to form a composite cathode film, inserting the composite cathode film into a cell casing such that a separator is positioned between the composite cathode film and the anode, and supplying an electrolyte into the cell casing.

[0046] The electrolyte contains a lithium salt present at a concentration suitable for conducting lithium ions between the composite cathode film and the anode through the electrolyte. The spray drying process can form secondary particles having an average particle size of 1 micrometer or more and 20 micrometers or less.

[0047] When used herein, value modifiers inserted before a number, such as “about,” “substantially,” and “almost,” mean that the value may represent other values ​​within a specified threshold range that are greater than and / or less than the specified value, for example, values ​​within 5%, 10%, or 15% of the specified value.

[0048] The above description is intended to be illustrative and not restrictive. For example, the embodiments (and / or aspects thereof) described above can be used in combination with one another. In addition, many modifications can be made to adapt specific situations or materials to what the various embodiments of this disclosure teach, without departing from their scope. The dimensions and types of materials described herein are intended to define the parameters of the various embodiments of this disclosure, but the embodiments are not restrictive and are illustrative. Many other embodiments will become apparent to those skilled in the art by reading the above description. Accordingly, the scope of the various embodiments of this disclosure should be defined with reference to the appended claims, along with the maximum scope of the equivalents to which the claims are granted. In the appended claims and the detailed description herein, the terms “including” and “in which” are used as plain English equivalents to the terms “comprising” and “wherein,” respectively. Furthermore, terms such as “first,” “second,” and “third” are used merely as symbols and are not intended to impose any numerical requirements on their objects. Moreover, the following limitation of claims is not written in means-plus-function form unless the limitation of the claim specifically uses the phrase “means for” before a description of a function that lacks further structure, and is not intended to be interpreted under Section 112(f) of the U.S. Patent Act.

[0049] This description, using examples, discloses various embodiments of the Disclosure, including the best form, and enables any person skilled in the art to also carry out various embodiments of the Disclosure, including manufacturing and using any device or system to carry out any incorporated method. The scope of the various embodiments of the Disclosure is defined by the claims and may include other examples found by a person skilled in the art. Such other examples are intended to be within the claims if they have structural elements that are not different from the literal wording of the claims, or if they include equivalent structural elements that do not substantially differ from the literal wording of the claims. The following embodiments can be cited as examples of the present invention. (Note 1) A method for forming a cathode, A step of grinding a suspension of precursors using a micromedia mill to form a mixture of primary particles in the suspension, wherein the precursors include one or more metal compounds; A spray drying step, which involves spray-drying the suspension after the grinding step to form secondary particles, wherein the secondary particles are aggregates of the primary particles; and Annealing process to form irregular rock salt type powder by annealing the secondary particles. Methods that include... (Note 2) The method according to Appendix 1, wherein the spray drying step forms the secondary particles having an average particle size of 1 micrometer or more and 20 micrometers or less. (Note 3) The method according to Appendix 1, wherein the grinding step forms a mixture of primary particles such that the primary particles have an average particle size of 400 nanometers or less. (Note 4) The method according to Appendix 1, wherein the precursor comprises one or more of Mn2O3, Li2CO3, LiF, LiOH, Nb2O5, or NbF5. (Note 5) The method according to Appendix 1, wherein the annealing step is carried out under an argon gas flow. (Note 6) The method according to appended claim 1, wherein the annealing step is carried out at a temperature of 750°C to 900°C for a time of 6 hours or more and 24 hours or less. (Appended claim 7) The irregular rock salt-type powder is represented by formula (i): Li x N y M z O 2-a F a (i) where 1.0 < x < 1.65; 0.01 < y < 0.55; 0.1 < z < 1; 0 ≤ a < 0.5; N is one of Ti, Ta, Zr, W, Nb or Mo; and M is one of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Y, Mo, Ru, Rh or Sb, the method according to appended claim 1. (Appended claim 8) The method according to appended claim 1, wherein the spray drying step forms the secondary particles in a spherical shape. (Appended claim 9) The method according to appended claim 1, further comprising a step of grinding the irregular rock salt-type powder together with one or more carbon precursors after the annealing step. (Appended claim 10 ) The method according to appended claim 9, wherein the irregular rock salt-type powder is ground together with the one or more carbon precursors in a ratio such that the irregular rock salt-type powder corresponds to a majority and the one or more carbon precursors correspond to a minority. (Appended claim 11) A step of mixing the irregular rock salt-type powder with one or more solvents to form a slurry; A step of depositing the slurry on a metal current collector; and A step of drying the slurry on the metal current collector to form a composite cathode film, the method according to appended claim 1. (Appended claim 12) A cathode for a rechargeable battery, comprising irregular rock salt-type powder characterized by secondary particles having an average particle size of 1 micrometer or more and 20 micrometers or less, each of the secondary particles being an aggregate of primary particles, and the primary particles having an average particle size of 400 nanometers or less. (Appendix 13) The irregular rock salt-type powder is represented by formula (i): Li x N y M z O 2-a F a (i) where 1.0 < x < 1.65; 0.01 < y < 0.55; 0.1 < z < 1; 0 ≤ a < 0.5; N is one of Ti, Ta, Zr, W, Nb or Mo; M is one of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Y, Mo, Ru, Rh or Sb, the cathode according to Appendix 12. (Appendix 14)' The secondary particles are spherical in shape, the cathode according to Appendix 12. (Appendix 15) a > 0, the cathode according to Appendix 12. ​​​​​​​​​​​​​​​​​​A step following the annealing step, in which the irregular rock salt type powder is pulverized together with one or more carbon precursors; A step of mixing the aforementioned irregular rock salt type powder with one or more solvents to form a slurry; A step of drying the slurry on a metal current collector to form a composite cathode film; A step of inserting the composite cathode membrane into the cell casing such that the separator is positioned between the composite cathode membrane and the anode; and Step of supplying electrolyte into the cell casing. Methods that include... (Note 19) The method according to Appendix 18, wherein the electrolyte contains a lithium salt present in a concentration suitable for conducting lithium ions between the composite cathode membrane and the anode through the electrolyte. (Note 20) The method according to Appendix 18, wherein the spray drying step forms the secondary particles having an average particle size of 1 micrometer or more and 20 micrometers or less.

Claims

1. A cathode for a rechargeable battery, comprising an irregular rock salt powder characterized by secondary particles having an average particle size of 1 micrometer or more and 20 micrometers or less, each of which is an aggregate of primary particles, the secondary particles being spherical in shape, and the primary particles having an average particle size of 400 nanometers or less.

2. The aforementioned irregular rock salt type powder is given by formula (i): Li x N y M z O 2-a F a (i) The cathode according to claim 1, expressed as follows, where 1.0 < x < 1.65; 0.01 < y < 0.55; 0.1 < z < 1; 0 ≤ a < 0.5; N is one of Ti, Ta, Zr, W, Nb or Mo; M is one of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Y, Mo, Ru, Rh or Sb.

3. The cathode according to claim 2, wherein a > 0.

4. The cathode according to claim 1, wherein the secondary particles have a carbon coating.

5. The cathode according to claim 1, wherein the average particle size of the secondary particles is 10 micrometers or less.

6. The cathode according to any one of claims 1 to 5, wherein the irregular rock salt type powder maintains the shape of the secondary particles.

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