Precursor materials for Li-ion battery cathode synthesis

Abstract

Particles are provided for use as precursor materials for the synthesis of a Li-ion cathode active material for a lithium-ion cell, wherein the particles are non-lithiated nickel oxide particles of the chemical formula MOx, wherein M contains 80 at% or more of Ni, x is 0.7 to 1.2, and M selectively excludes boron from the MOx crystal structure; and a modifying oxide that is mixed with, coated upon, or present therein with the non-lithiated nickel oxide particles, wherein the modifying oxide is combined with the non-lithiated nickel oxide and calcined at 500°C for 2 hours results in crystallite growth of 2 nanometers or less as measured by XRD. Additionally, a method for forming electrochemically active particles using the precursor nickel oxide is provided.

Description

Technology Field

[0001] Cross-reference regarding related applications

[0002] This specification relies on and claims priority to U.S. Patent Application No. 16 / 662,616 filed on October 24, 2019, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] A precursor material for a lithium nickel-oxide-based cathode material is disclosed. Background Technology

[0005] Layered lithium nickelate (LiNiO2)-based materials have been developed for lithium-ion battery cathodes because they generally offer lower costs, higher capacitance, and higher rate performance compared to the historically dominant LiCoO2 cathode materials. Unfortunately, the electrochemical performance of stoichiometric LiNiO2 is poor due to a rapid degradation with cycling. To address this drawback, non-nickel, elemental additives (e.g., Co and Mn) can be formulated into LiNiO2 to enable reproducible synthesis and improve the cycling performance of cathode materials in Li-ion batteries. With increasing demands for energy density, current research focuses on reducing the amount of stabilizing elements, such as Co, to capture the capacitance of high-Ni materials while maintaining cycling performance. However, LiNiO2 materials with low levels of Co are difficult to synthesize. Furthermore, the quality of the resulting cathode material depends significantly on the quality of the metal hydroxide precursor material.

[0006] Therefore, new precursor materials are required to meet the demand for high-capacity materials with a long lifespan.

[0007] The following is provided to facilitate understanding of some of the innovative features unique to the present disclosure, and is not intended to be an exhaustive description. A complete understanding of the various embodiments of the present disclosure can be obtained by taking the entire specification, claims, drawings, and summary in their entirety.

[0008] Particles are provided that can be used in the synthesis of a final electrochemically active material used in the cathode of a lithium-ion cell. The particles comprise: non-lithiated nickel oxide particles of the formula MOx, wherein M contains 80 at% or more of Ni, x is 0.7 to 1.2, and M selectively excludes boron from the MOx crystal structure; and boron oxide comprising a boron oxide that is mixed with, coated upon, or present therein with the non-lithiated nickel oxide particles, wherein the boron oxide is combined with the non-lithiated nickel oxide, such that calcination at 500°C for 2 hours results in the growth of crystallites smaller than 2 nanometers as measured by XRD, and optionally crystallites smaller than 20 nm in size. These particles provide a new synthesis route for electrochemically active cathode materials that promote long cycle life while utilizing the excellent capacity of these materials to facilitate the use of high Ni content. Brief explanation of the drawing

[0009] The embodiments described in the drawings are by nature exemplary and illustrative and are not intended to limit the subject matter of the claims as defined by the claims. The following detailed description of exemplary embodiments can be understood in conjunction with the following drawings, wherein: FIG. 1 is a titration curve illustrating that the boron species is water-soluble and is not present in the crystallites or crystal structure of the cathode material synthesized from precursor particles as provided herein; FIG. 2 illustrates the cycle life of a cathode material made of particles according to some embodiments provided herein, measured at 45 °C in a coin whole cell having a graphite anode; FIG. 3 illustrates an impedance increase corresponding to the cycle life data in FIG. 2; FIG. 4 illustrates the cycle life of a cathode material using a standard hydroxide precursor but with added boron oxide, measured at 45 °C in a coin whole cell having a graphite anode; and Figure 5 illustrates an increase in impedance corresponding to the cycle life data in Figure 4. Specific details for implementing the invention

[0010] A precursor material for the synthesis of an electrochemically active cathode material suitable for use in lithium-ion cells is described herein. The precursor material contains nickel-based oxide particles that optionally incorporate boron as a boron oxide. Such a precursor material can be used in the synthesis of a final lithiated cathode material for Li-ion batteries. It has been found that the electrochemical performance of a cathode material prepared from such a nickel oxide containing the elements listed above is significantly improved.

[0011] The term "non-lithiated" as used herein is defined as the absence of Li in the particles and the absence of any lithium previously present in the particles, so that the resulting crystallinity of the particles is not defined by the presence of Li in the structure or composition.

[0012] Typically, metal oxides are undesirable as precursors for the synthesis of high-nickel cathode materials for Li-ion batteries because the resulting cathode material exhibits poor electrochemical performance. The reaction between a metal oxide and a lithium source (e.g., LiOH) can lead to the formation of layered metal oxides; however, the reaction rate between the metal oxide and the lithium source is typically slow. As time and temperature increase, the primary crystallite size of the metal oxide increases rapidly. As the primary crystallite size of the metal oxide increases, the reaction rate with lithium decreases further. Consequently, layered lithium metal oxides formed from metal oxides possess poor crystalline quality (containing many crystalline defects).

[0013] The quality of layered lithium metal oxides can be improved by calcining at high temperatures for an extended period. However, as the nickel content of the precursor material (and consequently the cathode material) increases, the maximum time and maximum temperature must be limited to reduce the tendency of the layered metal oxide to decompose. For this reason, the synthesis of the cathode material typically begins with a precipitated metal hydroxide precursor, which is then mixed with a lithium source and calcined.

[0014] Similar problems as previously described can occur during the calcination step in the synthesis of lithiated oxides from metal hydroxides. Essentially, two parallel reactions occur during the synthesis of cathode materials from metal hydroxide precursors. The first involves dehydrating the metal hydroxide to form a metal oxide, and the second involves lithiating the metal hydroxide and / or oxide to form a layered lithiated metal oxide structure. Typically, the overall reaction rate between the metal oxide and the lithium source is slower than the reaction rate between the metal hydroxide and lithium. Initially, the metal oxide forms with a specific primary crystallite size. However, as time and temperature increase, the crystallite size of the metal oxide increases rapidly. As the primary crystallite size of the metal oxide increases, the reaction rate with lithium decreases further. Consequently, layered lithium metal oxides formed from metal oxides have inferior quality (possessing many crystalline defects) compared to layered lithium metal oxides formed from metal hydroxides. As previously explained, high-quality cathode materials are difficult to synthesize with metal oxides.

[0015] The inventors have now produced metal oxide particles capable of being lithiated to form electrochemically active particles used in the cathode of a lithium-ion battery. These particles do not suffer from the disadvantages of prior materials, do not undergo significant and undesirable crystal growth, do not exhibit crystalline defects, and thus enable the lithiation of metal oxides at lower temperatures, thereby improving performance. The provided material incorporates an oxide of boron into a dehydrated metal oxide material. The incorporation of boron has been found to produce oxide particles that are more easily lithiated, of more uniform quality, and serve as material precursors favorable for the synthesis of cathode materials for Li-ion batteries.

[0016] Chemical formula MO xNon-lithiated nickel oxide particles are provided, wherein M contains 80 at% or more of Ni and x is 0.7 to 1.2. The particles further comprise a modifier which is an oxide of boron, wherein the modifier is coated on the particles, is present within the particles, or a combination thereof. As used herein, the term "present within" excludes the incorporation of the modifier into the crystal structure of the particles. However, the modifier may be present in the intercrystalline space, coated on the particles, or otherwise bonded to the particles. The presence of the modifier produces particles having crystallite growth characteristics with an overall crystallite size (average cross-sectional diameter) of 2 nanometers (nm) or less and / or optionally 30 nm or less, optionally 20 nm or less, as measured by XRD upon calcination at 500°C (°F) for 2 hours. This lack of crystallite growth is optionally present throughout the entire particle or within a part of the particle.

[0017] In the chemical formula MOx, M contains Ni or is Ni. Ni is present in at least 80 atomic percent (at%) of the total M. Optionally, M is present in at least 85 atomic percent, optionally at least 90 atomic percent, optionally at least 91 atomic percent, optionally at least 92 atomic percent, optionally at least 93 atomic percent, optionally at least 94 atomic percent, optionally at least 95 atomic percent, optionally at least 96 atomic percent, optionally at least 97 atomic percent, optionally at least 98 atomic percent, optionally at least 99 atomic percent, optionally at least 99.5 atomic percent, optionally at least 99.6 atomic percent, optionally at least 99.7 atomic percent, optionally at least 99.8 atomic percent, and optionally at least 99.9 atomic percent.

[0018] M optionally comprises one or more additional metals. The second metal is optionally Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Nb, Ta, Cr, Fe, Mo, W, Hf, B, or a combination thereof. The additional metal is optionally present in an amount of about 0.1 at% to about 20 at%. Optionally, M is cobalt or comprises an additional metal containing cobalt, with a cobalt concentration in the range of 0.1 at% to about 20 at%, optionally in the range of 1 at% to about 15 at%. In some embodiments, the additional metal is Mn or comprises Mn present in an amount of about 0.1 at% to about 20 at%. Optionally, the additional metal is Al or comprises Al present in an amount of about 0.1 at% to about 20 at%.

[0019] In some embodiments, M comprises 80 at% or more of Ni, 0.1 at% to 20 at% of Co, and 0.1 at% to 20 at% of Mn. Optionally, M comprises 80 at% or more of Ni and 0.1 at% to 20 at% of Co.

[0020] Particles as provided herein contain a modifying element which is an oxide of boron. In some embodiments, the modifying element is coated onto the particles. Being coated onto means optionally coating the particles completely or partially. In some embodiments, the modifying element is present within the particles. Being present within means optionally being present throughout the particles as a substantially uniform material or being distributed at varying concentrations over a portion of the total particle volume. Optionally, the modifying element is present within the particles while being coated onto them.

[0021] The modifying element is optionally present in the oxide particles in a weight percentage (wt%) of 1 wt% or less. In some embodiments, the modifying element is present in a weight percentage of 0.9 wt% or less, optionally 0.8 wt% or less, optionally 0.7 wt% or less, optionally 0.6 wt% or less, optionally 0.5 wt% or less, optionally 0.4 wt% or less, optionally 0.3 wt% or less, optionally 0.2 wt% or less, and optionally 0.1 wt% or less.

[0022] In some embodiments, the modifying element present in the nickel-based oxide material is water-insoluble.

[0023] Particles as provided herein may be prepared by combining one or more hydroxide precursor materials in powder form and a modifying element oxide (optional micronized) and mixing the materials. The hydroxide precursor material may be formed by a precipitation or co-precipitation process as recognized in the art. Optionally, the precursor material powder may be formed by ball milling or other milling procedures recognized in the art. The mixed material is then subjected to a first calcination at a temperature of 600 °C or lower for a calcination time of 6 hours or less. The resulting crystalline particles contain crystals of the metal oxide mixed with the modifying element. Not limited to one specific theory, when prepared as provided herein, the modifying element is considered to be present within the intercrystalline space. The presence of this modifying element then delays the additional or excessive rate of crystal growth during successive calcination alone or in the presence of other desired elements, such as Li, for example, LiOH.

[0024] For the formation of particles as provided herein, the mixed particles are first calcined at a calcination temperature of 600 °C or lower. In the formation of the precursor material as provided herein, a second calcination, such as subsequent calcination with Li or other additional treatment, is not required until electrochemically active particles are not formed or are formed. As such, the term “first calcination” is provided herein for exemplary purposes only. Optionally, the first calcination temperature is less than 550 °C; optionally less than 500 °C; and optionally less than 400 °C. The first calcination time is optionally 6 hours, optionally 3 hours, optionally 2 hours, optionally 1 hour, and optionally 0.5 hours or less.

[0025] The generated precursor particles are characterized by an arrangement of modifying elements within or on the particles such that a second calcination at 500°C for 2 hours results in additional crystallite growth of less than 2 nanometers as measured by XRD and / or a generated crystallite size of less than 40 nm, optionally less than 35 nm, optionally less than 30 nm, optionally less than 25 nm, and optionally less than 20 nm. This delayed crystallite growth occurring during subsequent calcination is believed to allow the particles to be successfully used as a precursor material for the formation of electrochemically active lithium metal oxides in the cathode of a lithium-ion cell. Delayed crystallite growth allows for the formation of a material that is free of or substantially free of crystalline defects.

[0026] In some embodiments, the particles are nickel oxide further comprising a modifying element B. A boron-containing nickel oxide precursor can be synthesized by mixing a boron oxide and a nickel-containing hydroxide and calcining the resulting mixture at a specific temperature for a specific time. The weight ratio of boron oxide to nickel hydroxide may be < 1%; < 0.75%; < 0.5%, < 0.25%, or < 0.1%. The specific temperature of the first calcination may be less than 600°C; optionally less than 550°C; optionally less than 500°C; optionally less than 400°C. The specific time may be less than 6 hours, optionally less than 3 hours, optionally less than 2 hours, optionally less than 1 hour, or optionally less than 0.5 hours.

[0027] In some embodiments, the precursor material is a Ni-Co mixed oxide incorporating a boron modifying element. Optionally, the amount of Ni (total Ni and Co) is less than 99 at%, optionally less than 95 at%, optionally less than 90 at%. Optionally, the amount of Ni (total Ni and Co) is 70 at% or more, optionally 75 at% or more, optionally 80 at% or more, optionally 85 at% or more, optionally 90 at% or more, optionally 91 at% or more, optionally 92 at% or more, optionally 93 at% or more, optionally 94 at% or more, optionally 95 at% or more, optionally 96 at% or more, optionally 97 at% or more, optionally 98 at% or more, optionally 99 at% or more.

[0028] In some embodiments, the precursor material is a Ni-Co-Mn mixed oxide incorporating urea boron. The amount of Ni relative to total Ni, Co and Mn is 99 at% or less, optionally 98 at% or less, optionally 95 at% or less; optionally 85 at% or less. Optionally, the amount of Ni (relative to total Ni, Co and Mn) is 70 at% or more, optionally 75 at% or more, optionally 80 at% or more, optionally 85 at% or more, optionally 90 at% or more, optionally 91 at% or more, optionally 92 at% or more, optionally 93 at% or more, optionally 94 at% or more, optionally 95 at% or more, optionally 96 at% or more, optionally 97 at% or more, optionally 98 at% or more, optionally 99 at% or more.

[0029] The generated non-lithiated oxide particles are groupings of crystallites throughout part or all of the particles. The average crystallite size measured by X-ray diffraction is optionally 40 nm or less, optionally 30 nm or less, optionally 25 nm or less, optionally 20 nm or less. Optionally, when exposed to a second calcination in the absence of any added element, or optionally in the presence of Li, a second calcination at 500°C for 2 hours results in crystallite growth of 2 nanometers or less measured by XRD and / or crystallite sizes of less than 40 nm, optionally less than 35 nm, optionally less than 30 nm, optionally less than 25 nm, optionally less than 20 nm.

[0030] Thus, according to some embodiments, the chemical formula MO x Non-lithiated nickel oxide particles are provided, wherein M comprises 80 at% or more of Ni, x is 0.7 to 1.2, and M is optionally MO xBoron is excluded from the crystal structure and has an average crystallite size of less than 40 nm, optionally less than 30 nm, optionally less than 25 nm, and optionally less than 20 nm as measured by X-ray diffraction. These non-lithiated nickel oxide particles contain Ni optionally 99 at% or less, optionally 98 at% or less, optionally 95 at% or less relative to the total metal; optionally 85 at% or less. Optionally, the amount of Ni (relative to the total metal) is 70 at% or more, optionally 75 at% or more, optionally 80 at% or more, optionally 85 at% or more, optionally 90 at% or more, optionally 91 at% or more, optionally 92 at% or more, optionally 93 at% or more, optionally 94 at% or more, optionally 95 at% or more, optionally 96 at% or more, optionally 97 at% or more, optionally 98 at% or more, and optionally 99 at% or more. The particles optionally contain Ni and one or more additional metals. The additional metal is optionally Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Nb, Ta, Cr, Fe, Mo, W, Hf, B, or a combination thereof. The additional metal is optionally present in an amount of about 0.1 at% to about 20 at%. Optionally, the additional metal is or contains cobalt, with a cobalt concentration in the range of 0.1 at% to about 20 at%, optionally in the range of 1 at% to about 15 at%. In some embodiments, the additional metal is or contains Mn present in an amount of about 0.1 at% to about 20 at%. Optionally, the additional metal is or contains Al present in an amount of about 0.1 at% to about 20 at%.Optionally, these particles are Ni-Co mixed oxides incorporating a boron modifying element, optionally Ni-Co-Mn mixed oxides incorporating a boron modifying element, wherein the Ni-Co oxide or Ni-Co-Mn oxide is as otherwise described herein.

[0031] Additionally, a hydroxide precursor of lithiated nickel oxide as described herein is provided, wherein the hydroxide precursor contains boron within the particles to also reduce the crystal growth of the oxide during the formation of the final lithiated nickel oxide particles. As previously described, during the lithiation process of a conventional metal hydroxide, two competing reactions occur: the first is the dehydration of the metal hydroxide to the metal oxide; and the second is the simultaneous lithiation of the metal hydroxide / oxide to form a layered lithiated metal oxide structure. Since the reaction rate between the metal oxide and the lithium source is slower than the reaction rate between the metal hydroxide and lithium, metal oxide crystal growth occurs during the sintering reaction, resulting in crystals that reduce the reaction rate with lithium relative to the hydroxide material. This produces a non-uniform lithiated product with crystal defects. The present disclosure addresses this problem in a second manner by forming a co-precipitated boron-containing nickel hydroxide in which boron reduces the oxide crystal growth rate during lithiation, so that more uniform lithiated particles are formed with fewer crystal defects.

[0032] Thus, non-lithiated nickel hydroxide is provided, comprising boron within the particles arranged to act as an oxide crystal growth inhibitor during a subsequent high-temperature reaction in the presence or absence of lithium. The non-lithiated nickel hydroxide particles are of the formula M(OH) x It has, where M contains 80 at% or more of Ni, and x is 0.7 to 1.2. The particles are boron or additionally contain a boron-containing modifier, wherein the modifier is co-precipitated so as to be present in the particles after precipitation.

[0033] Chemical formula M(OH) x In this, M contains Ni or is Ni. Ni is present in the total M at least 80 atomic percent (at%). Optionally, Ni is present in the total M at least 85 atomic percent, optionally at least 90 atomic percent, optionally at least 91 atomic percent, optionally at least 92 atomic percent, optionally at least 93 atomic percent, optionally at least 94 atomic percent, optionally at least 95 atomic percent, optionally at least 96 atomic percent, optionally at least 97 atomic percent, optionally at least 98 atomic percent, optionally at least 99 atomic percent, optionally at least 99.5 atomic percent, optionally at least 99.6 atomic percent, optionally at least 99.7 atomic percent, optionally at least 99.8 atomic percent, and optionally at least 99.9 atomic percent.

[0034] Chemical formula M(OH) x In this, M optionally comprises one or more additional metals. The second metal is optionally Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Nb, Ta, Cr, Fe, Mo, W, Hf, B, or a combination thereof. The additional metal is optionally present in an amount of about 0.1 at% to about 20 at%. Optionally, M is cobalt or comprises an additional metal containing cobalt, with a cobalt concentration in the range of 0.1 at% to about 20 at%, optionally in the range of 1 at% to about 15 at%. In some embodiments, the additional metal is Mn or comprises Mn present in an amount of about 0.1 at% to about 20 at%. Optionally, the additional metal is Al or comprises Al present in an amount of about 0.1 at% to about 20 at%. In some embodiments, the formula M(OH) xIn this, M comprises 80 at% or more of Ni, 0.1 at% to 20 at% of Co, and 0.1 at% to 20 at% of Mn. Optionally, M comprises 80 at% or more of Ni and 0.1 at% to 20 at% of Co.

[0035] In metal hydroxide particles, the modifying element is present within the particle and distributed as a result of co-precipitation with the metal in the formation of the metal hydroxide particle. The boron modifying element is optionally present throughout the particle in a substantially uniform manner or distributed at varying concentrations over a portion of the total particle volume.

[0036] The modifying element is optionally present in the hydroxide particles in a weight percentage (wt%) of 1 wt% or less. In some embodiments, the modifying element is present in an amount of 0.9 wt% or less, optionally 0.8 wt% or less, optionally 0.7 wt% or less, optionally 0.6 wt% or less, optionally 0.5 wt% or less, optionally 0.4 wt% or less, optionally 0.3 wt% or less, optionally 0.2 wt% or less, and optionally 0.1 wt% or less.

[0037] Non-lithiated metal hydroxide particles can be prepared by a co-precipitation method in which a metal and boron are simultaneously precipitated from one or more components in an aqueous solution or suspension. For example, a nickel salt is combined with a boron modifier as described herein, and optionally with one or more other metal salts (e.g., cobalt salt, manganese salt, magnesium salt), wherein these salts may be sulfates, nitrates, acetates, halides, hydroxides, or oxyhydroxides of the metal, respectively. A base material may be added to this solution or suspension to precipitate boron and metal into particles, thereby designing the metal to be distributed substantially uniformly throughout the particles, or distributed in some other manner such as a gradient or others, so that the boron is incorporated into the resulting hydroxide particles so that it can be used to delay the crystal growth of the metal oxide during a subsequent lithiation reaction.

[0038] Optionally, a non-lithiated metal oxide precursor material can be prepared from a non-lithiated metal hydroxide precursor co-precipitated with a boron modifier by calcining at a specific temperature for a specific time. The specific temperature may be less than 600 °C; optionally less than 550 °C; optionally less than 500 °C; optionally less than 400 °C. The specific time may be less than 3 hours, optionally less than 2 hours, optionally less than 1 hour, and optionally less than 0.5 hours. Subsequently, as otherwise described herein, such a precursor may be used to prepare a lithiated metal oxide cathode material.

[0039] In addition, a method for forming electrochemically active particles suitable for use in primary or secondary batteries, exemplary in lithium-ion batteries, is provided, comprising: a modifying element oxide and a chemical formula M(OH) xA step of forming precursor particles as provided herein by mixing particles of non-lithiated nickel hydroxide, wherein M contains 80 at% or more of Ni and x is 1.7 to 2.3; and a step of calcining the precursor mixture at a calcination temperature of about 600 degrees or less and for a calcination time of about 6 hours or less to form a first calcined product which is a boron-containing metal oxide. Alternatively, the boron-containing metal hydroxide precursor is formed by mixing or co-precipitation reaction to form a boron-containing metal hydroxide precursor. By doing so, the oxide precursor, the hydroxide precursor, or both may subsequently be combined with a lithium source, and the process further comprises the step of calcining the precursor oxide or hydroxide and the lithium source to form electrochemically active particles.

[0040] Lithium sources may include lithium salts such as lithium nitrate, lithium carbonate, lithium hydroxide, or combinations thereof.

[0041] The lithium source and precursor particles provided herein are sintered. Sintering can be performed by heating to approximately 450°C at a rate of approximately 5°C per minute and maintaining the temperature at approximately 450°C for approximately 2 hours. Then, the temperature can be raised to approximately 680°C at a rate of approximately 2°C per minute and maintained for approximately 6 hours. The sample can then be naturally cooled to room temperature. The resulting electrochemically active material is used as an active material in the cathode of a lithium-ion cell.

[0042] A method for forming an electrochemically active material optionally further comprises the step of enriching the grain boundaries of the generated electrochemically active material with one or more of Co and Al. An exemplary process for enriching grain boundaries with Co is described in U.S. Patent No. 9,391,317. A process for enriching grain boundaries with Co, Al, or both Co and Al is described in U.S. Patent Application No. 16 / 250,615. Such Co, Al, or Co and Al grain boundary concentrated materials can be easily prepared by calcining a green body formulation containing LiOH and the precursor material particles provided herein, forming electrochemically active particles having defined grain boundaries, and then concentrating the grain boundaries with Co, Al, or a combination of Co and Al so that the resulting particles have an external surface defining the edges of the grain boundaries in the secondary particles, and optionally, the grain boundaries in the secondary particles are larger than in the primary crystallites, and the concentration of Co, Al, or Co and Al is greater than before concentration in the grain boundaries.

[0043] For example, a method for forming electrochemically active particles suitable for use in the cathode of a secondary battery comprises: immersing the electrochemically active particles in a process solution containing Co alone or Co and Al; drying the electrochemically active particles after immersion; and heat-treating the electrochemically active particles after drying to form particles in which the concentration of Co, Al, or both at the grain boundaries is greater than the concentration of Al, Co, or both at the crystallites.

[0044] Grain boundary-concentrated particles can be formed by a multi-stage process, wherein the precursor particle material is formed as an oxide or hydroxide mixed with a modifying element as provided herein, and optionally calcined in the presence of Li to establish the formation of grain boundaries selectively defined as primary particles having an α-NaFeO2 structure with almost no crystal defects. The particles are then treated by a liquid process, in which Co, Al, or Co and Al are applied to a desired concentration level, followed by drying and heat treatment, to selectively move Co or Al precipitated species from the surface to the grain boundaries, thereby forming secondary particles having Co and Al concentrations at grain boundaries higher than the crystallites.

[0045] For example, according to a method for preparing secondary particles having a base of nickel oxide as provided herein, the formation comprises: a step of forming a mixture by combining a lithium compound and one or more nickel oxide or hydroxide precursors of a metal or metalloid (e.g., combined with Ni, Co, and Mg) as provided herein; a step of forming a dried mixture by heat-treating the mixture by a second calcination at about 30 to about 200 °C; a step of heat-treating the dried mixture at about 200 to about 500 °C for about 0.1 to about 5 hours; and then, a step of preparing lithiated secondary particles by heat-treating at 600 °C to less than about 800 °C for about 0.1 to about 10 hours. The maximum temperature of the second calcination is relative and specific to the material used for the oxide precursor. Optionally, in the second calcination, the maximum temperature may be 850°C or less, optionally 720°C or less, optionally 715°C or less, 710°C or less, optionally 710°C or less, optionally less than 705°C, and optionally 700°C or less. Optionally, the maximum temperature of the second calcination may be about 680°C or less. Optionally, the maximum temperature may be about 660°C or less. Optionally, the maximum temperature may be about 640°C or less. In another aspect, the maximum temperature may be less than about 700 degrees Celsius, less than about 695 degrees Celsius, less than about 690 degrees Celsius, less than about 685 degrees Celsius, less than about 680 degrees Celsius, less than about 675 degrees Celsius, less than about 670 degrees Celsius, less than about 665 degrees Celsius, less than about 660 degrees Celsius, less than about 655 degrees Celsius, less than about 650 degrees Celsius, less than about 645 degrees Celsius, or less than about 640 degrees Celsius. The residence time at the maximum temperature is optionally less than 10 hours.Optionally, the residence time at the maximum temperature is 8 hours or less; optionally 7 hours or less; optionally 6 hours or less; optionally 5 hours or less; optionally 4 hours or less; optionally 3 hours or less; optionally 2 hours or less.

[0046] After calcination, subsequent treatment may include a step of crushing the electrochemically active material using a mortar and pestle so that the resulting powder passes through a desired sieve, optionally a #35 sieve. The powder is then bottle-milled in a 1-gallon jar with optionally 2 cm drum YSZ medium for optionally 5 minutes or for an appropriate time during which the material can optionally pass through a #270 sieve.

[0047] The electrochemically active product of the second calcination (or the first calcination if metal hydroxide precursor particles are used) may be subsequently processed in a manner that optionally produces concentrated grain boundaries after the third calcination. Grain boundary-concentrated Co or Al may optionally be applied by suspending the milled product in an aqueous slurry containing Co, Al, or Co / Al and a lithium compound at a temperature of about 60 degrees Celsius, thereby allowing Co and Al to be present in the aqueous solution (process solution) at desired concentrations. The slurry may then be spray-dried to form a free-flowing powder, and then optionally, the third calcination may be performed using a heating curve after two ramp / residence processes. The first two ramp / residence temperature profiles may be ambient (about 25 degrees Celsius) to 450 degrees Celsius, and optionally may be maintained at 450 degrees Celsius for one hour at a rate of 5 degrees Celsius per minute. Subsequently, the second ramp / stay may be maintained at the maximum temperature for 2 hours at a rate of 2 degrees Celsius per minute from 450 degrees Celsius to the maximum temperature. In some embodiments, the maximum temperature is less than about 725 degrees Celsius, optionally 700 degrees Celsius or about 700 degrees Celsius.

[0048] The amounts of Co, Al, or Co and Al present in the process solution are relative to the total M in the precursor particles as follows.

[0049] The amount of Co in the process solution is optionally 0.01 at% to 10 at%, optionally 9 at% or less, optionally 8 at% or less, optionally 7 at% or less, optionally 6 at% or less, optionally 5 at% or less, optionally 4 at% or less, optionally 3 at% or less, optionally 2 at% or less, optionally 1 at% or less, optionally 0.1 to 1 at%, and optionally 0.5 to 1 at%.

[0050] The amount of Al in the process solution is optionally 0.01 at% to 10 at%, optionally 9 at% or less, optionally 8 at% or less, optionally 7 at% or less, optionally 6 at% or less, optionally 5 at% or less, optionally 4 at% or less, optionally 3 at% or less, optionally 2 at% or less, optionally 1 at% or less, optionally 0.1 to 1 at%, and optionally 0.5 to 1 at%. Optionally, the amount of Al in the process solution is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5 atomic percent or less.

[0051] In some embodiments, the amount of Co in the process solution is optionally 0.01 at% to 10 at%, optionally 9 at% or less, optionally 8 at% or less, optionally 7 at% or less, optionally 6 at% or less, optionally 5 at% or less, optionally 4 at% or less, optionally 3 at% or less, optionally 2 at% or less, optionally 1 at% or less, optionally 0.1 to 1 at%, and optionally 0.5 to 1 at%; the amount of Al in the process solution is optionally 0.01 at% to 10 at%, optionally 9 at% or less, optionally 8 at% or less, optionally 7 at% or less, optionally 6 at% or less, optionally 5 at% or less, optionally 4 at% or less, optionally 3 at% or less, optionally 2 at% or less, optionally 1 at% or less, optionally 0.1 to 1 at%, and optionally 0.5 to 1 at%. Optionally, the amount of Al in the process solution is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5 atomic percent or less.

[0052] Various embodiments of the present disclosure are illustrated by the following non-limiting examples. The examples are for illustrative purposes only and are not intended to limit the practice of the invention. It will be understood that variations and modifications may be made without departing from the spirit and scope of the invention.

[0053] Examples

[0054] Example 1: Synthesis of a boron-containing transition metal oxide precursor

[0055] Three transition metal hydroxide precursor materials with a 5 micrometer D50 size, each containing 8 at% cobalt and 92% nickel, were mixed with 0.25 wt% boron oxide and calcined in air at 500 °C for 5 hours. The three materials were sourced from different lots or manufacturers. As a control, the three metal hydroxide precursors were calcined at 500 °C for 5 hours without the addition of boron oxide. Powder XRD analysis of the six resulting black-gray powders revealed that the crystallite size of the 0.25% boron oxide sample was substantially smaller than that formed without boron oxide (Table 1).

[0056] Table 1: Metal oxide crystallite size measured by X-ray diffraction

[0057] Precursor Boron oxide Oxide crystallite size (nm) 536-165 0.0% 26.5 536-166 0.0% 24.5 536-167-3 0.0% 24.9 536-165B 0.25% 16.3 536-166B 0.25% 16.8 536-167-3B 0.25% 17.7

[0058] Next, 1 gram (g) of each calcined sample was mixed with 10 g of water and stirred at room temperature for 20 minutes. The resulting pH of all samples formed without boron oxide was greater than 7. The samples formed with boron oxide mixed with water showed a pH < 6, consistent with the expected acidity of boron oxide in water. Thus, the calcination of metal hydroxides using boron oxide resulted in materials in which the boron oxide remained available for aqueous extraction.

[0059] Example 2: Preparation of a cathode material using boron-containing nickel oxide

[0060] Nickel oxides containing varying levels of boron (0.66 wt%, 1.66 wt%, or 2.62 wt%) were prepared by the method discussed in Example 1. These nickel oxides were then mixed with LiOH and calcined to form an electrochemically active cathode material. The cathode samples were then washed with water (1 gram of sample and 10 g of water for 5 minutes), centrifuged, and the supernatant was filtered through a 0.45 µm syringe filter. The supernatant was then titrated with 0.1 N HCl—the titration curve is shown in Fig. 1. As boron doping increases, more buffering is observed, consistent with the presence of soluble borate species outside the particles.

[0061] In the titration curve analysis, the range of lithiated borate species is set to 7 to 12.3. To remove the titration of LiOH extracted from the particles by external particle or water washing, the titrated equivalents for the control group of 12.3 to 11.0 are subtracted from other materials. To remove the carbonates present, the titrated equivalents of less than 7 are subtracted from the 7-12.3 equivalents. In this way, the carbonate contribution is subtracted to the 7-12.3 range using the titration of bicarbonate ions.

[0062] The calculated boron extracted from the sample matches the amount formulated into the product, assuming a lithium-to-boron ratio "LiB" of 4. This species would be the specific Li8B2O7. However, when the more common lithium orthoborate species Li3BO3 with a Li:B ratio of 3 is assumed, more obvious boron is found than in the formulation. The highly lithiated borate species is essentially characterized by a very high pH in the first buffer range of 12. In both cases, it is evident that most of the boron is observed outside the particles due to the borate buffer observed around pH 9.5. Factor analysis of the wash water and unwashed material also supports the conclusion that the borate species are easily washed away from the cathode product completed with the lithiated borate species; therefore, boron doping in the final product is expected to be minimal.

[0063] Table 2: Titration summary corresponding to Fig. 1.

[0064] Sample Formulated Appropriate LiB=3 Appropriate LiB=4 0 - - B 0.66% 1.2% 0.89% C 1.66% 2.1% 1.55% D 2.62% 3.1% 2.30%

[0065] Table 3: Factor analysis to estimate the amount of boron in completed cathode particles and wash water.

[0066] Sample Formulated Boron in unwashed solids Boron in wash water A 0.00% BDL BDL B 0.66% 0.61% 0.57% C 1.66% 1.72% 1.31% D 2.62% 2.52% 2.35%

[0067] Example 3: Synthesis of cathode material for Li-ion batteries

[0068] Two electrochemically active materials suitable for use in the cathode of a lithium-ion battery were prepared from a single transition metal precursor containing 8% cobalt and 92% nickel as the total metal. One sample was used as a control, and the other was mixed with 0.25 wt% finely pulverized boron oxide. Both samples were calcined at 500 °C for 5 hours. After calcination, each sample was first blended with finely pulverized lithium hydroxide to convert it into a cathode material in stoichiometric amounts, thereby preparing Li3BO3 for the sample containing lithium transition metal oxide and boron. The two mixtures were then calcined at 700 °C for 6 hours under CO2-free air. Subsequently, the electrochemically active cathode material was milled and sieved through a 325 mesh sieve.

[0069] The cathode product was grain boundary-condensed with Co and Al. As such, the powder was blended with an equivalent mass of water containing cobalt nitrate, the cobalt content was 4 at% relative to the total metal of the cathode material, the final lithium-to-transition ratio was 1.01, and the final Al content was 0.064% of the final transition metal content of the cathode material. The slurry was spray-dried and heat-treated at 700 °C for 2 hours to form the final cathode material.

[0070] The cathode powder was blended with NMP, conductive carbon, and a PVDF binder, and an electrode was fabricated by coating it onto aluminum foil. The coin cell was fabricated with an MCMB anode and cycled for 200 cycles at 45°C. The results are shown in Figures 2 and 3.

[0071] Example 4: Boron extraction from formed precursor particles

[0072] Two nickel oxide materials were formed from a hydroxide material containing 100% nickel using the process described in Example 1. One had 0.25 wt% B2O3 in the initial formulation along with the hydroxide, and the other did not have B2O3. Then, 1 gram of each was added to 10 ml (mL) of nitric acid containing 10 mM sodium dodecyl sulfonate (SDS), stirred for 5 hours, and left overnight. The supernatant was then removed, filtered through a 0.45 µm syringe filter, and tested for nickel and boron using ICP-OES. The results are shown in Table 4.

[0073] Sample ID Ni (mg extracted) B (mg extracted) A: NiO-B 27 0.6 B: NiO-B 30 0.5 C: NiO 21 0.09

[0074] The amount of boron formulated into the oxide was 1.2 mg per g of NiO. This process extracted approximately 50% of the boron and removed only 0.05% of the nickel. This supports the conclusion that boron exists outside the nickel crystallites and does not dope them. Not all boron was extracted because the porous nickel oxide particles have very small pores inaccessible to aqueous extractants.

[0075] Access to all porous oxide particles was found to be problematic due to previous results where the same experiment was performed for boron extraction but with an exposure of only 20 minutes. In this case, one sample was formulated as described above with added 10 mM SDS, and one was formulated without it. The SDS sample extracted 0.3 mg of boron, while the sample without surfactant extracted only 0.2 mg. Therefore, limited access to nitric acid extractants for the entire porous matrix is ​​expected to be problematic, which is partially mitigated by the use of interfacial tension-reducing agents such as SDS.

[0076] Comparative Example 1: Boron oxide as a cathode additive

[0077] A lithium transition-metal oxide cathode material was synthesized by blending transition metal hydroxide powder with sufficient lithium hydroxide and calcined at 700 °C for 6 hours under CO2-free air. After heat treatment, the product was milled and sieved through a 325 mesh sieve.

[0078] The product was then divided into three portions, each of which was grain boundary-enriched with cobalt (according to U.S. Patent No. 9,391,317). As such, the cathode material was suspended in an equivalent mass of water containing cobalt and lithium nitrate. The cobalt was 4 at% of the material, and the final lithium-to-transition metal ratio was 1.01. As in Example 2, boron oxide was added to two slurries to mimic the formulation of blended 0.1 wt% or 0.25 wt% boron oxide. To these solutions, lithium was additionally added to allow for the formation of Li3BO3. Each slurry was spray-dried and then heat-treated at 700 °C for 2 hours under CO2-free air.

[0079] Then, the final product was slurried with NMP, conductive carbon, and PVDF binder to prepare an electrode, which was then coated onto aluminum foil. The final electrode had 94% activity with an evenly divided balance between the binder and the conductive additive. Then, a coin cell was fabricated as an MCMB anode and cycled at 45°C.

[0080] The capacitance reduction of the above materials is illustrated in Fig. 4. The degradation for all materials is similar, but the materials containing boron perform slightly worse than the control group. The impedance increase over time at constant voltage during charging is illustrated in Fig. 5. Here, more differences between the materials are visible. Greater impedance growth was observed for the comparison materials prepared with boron additives, where more boron exhibits a higher impedance growth rate.

[0081] These results demonstrate that simple additives to the cathode material during the cobalt coating step result in poorer electrochemical performance. In the case of the oxide-treatment process, since all originally formulated boron is released as lithiated oxide during cathode synthesis, adding boron oxide at the time of cobalt coating should be chemically equivalent. Nevertheless, worse or inferior electrochemical performance is observed. This indicates that the boron oxide modifier is actually present at the time of initial heat treatment and subsequent synthesis, rather than simply as a cathode-surface additive to the final product. Indeed, despite the harmful effects of lithiated borate byproducts remaining in the final product, benefits resulting from the boron modifier process are observed in the product.

[0082] The foregoing description of specific embodiment(s) is by nature merely illustrative and is by no means intended to limit the scope of the disclosure, its application, or its use, which may, of course, be modified. Materials and processes are described in relation to the non-limiting definitions and terms contained herein. These definitions and terms are not designed to function as limitations on the scope or practice of the disclosure and are provided solely for illustrative and illustrative purposes. While processes or compositions are described in a sequence of individual steps or using specific materials, it is understood that steps or materials may be interchangeable to include a number of parts or steps arranged in various ways as readily recognized by those skilled in the art.

[0083] Terms such as "first," "second," "third," etc., may be used herein to describe various elements, components, regions, layers, and / or sections, but it will be understood that such elements, components, regions, layers, and / or sections are not limited to these terms. These terms are used solely to distinguish one element, component, region, layer, or section from another. Therefore, unless otherwise specified, the "first element," "component," "region," "layer," or "section" discussed below may be referred to as the second (or other) element, component, region, layer, or section without departing from the teachings herein.

[0084] The terms used herein are used merely to describe specific embodiments and are not intended to be limiting. As used herein, the singular forms “one,” “one,” and “it” are intended to include the plural form including “at least one” unless the content clearly indicates otherwise. “Or” means “and / or.” As used herein, the term “and / or” includes any combination of one or more of the related listed items. As used herein, the terms “comprise” and / or “comprising,” or “include” and / or “including” will be further understood to specify the presence of the stated features, regions, integers, steps, operations, elements, and / or components, but not to exclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof. The term “or combination thereof” means a combination including at least one of the aforementioned elements.

[0085] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Additionally, terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with that meaning in the context of the relevant technology and the present disclosure, and should be further understood not to be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0086] In addition to what is shown and described herein, various modifications will be apparent to those skilled in the art of the art described above. Such modifications are also intended to fall within the scope of this disclosure.

[0087] Unless otherwise specified, it is understood that all reagents can be obtained from sources known in the art.

[0088] The patents, publications, and applications mentioned in the specification represent the level of a person skilled in the art to which this disclosure pertains. Such patents, publications, and applications are incorporated herein by reference to the same extent as each individual patent, publication, or application is incorporated herein by reference specifically and individually.

[0089] The foregoing description illustrates specific aspects of the present invention, but does not imply limitations on the practice of the present invention.

Claims

Claim 1 A particle to be used as a precursor material for the synthesis of a Li-ion cathode active material of a lithium-ion cell, comprising a non-lithiated nickel oxide particle of the chemical formula MOx, wherein M contains 80 at% or more of Ni, x is 0.7 to 1.2, and M selectively excludes boron from the MOx crystal structure; a particle comprising a boron oxide that is mixed with, coated upon, or present therein with the non-lithiated nickel oxide particle, wherein the boron oxide is combined with the non-lithiated nickel oxide and calcination at 500 degrees for 2 hours results in crystallite growth of 2 nanometers or less as measured by XRD. Claim 2 In paragraph 1, a particle in which nickel is present in at least 92 atomic percent of the total M. Claim 3 In paragraph 1, a particle in which nickel is present in at least 99 atomic percent of the total M. Claim 4 In claim 1, the particles in which boron oxide is present in an amount of less than 1 wt% relative to the non-lithiated nickel oxide particles. Claim 5 In paragraph 4, a particle in which boron oxide is present in an amount of 0.25 wt% or less. Claim 6 A particle according to claim 1, wherein M comprises one or more elements selected from Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Nb, Ta, Cr, Fe, Mo, W, Hf, B or combinations thereof, and Ni. Claim 7 In paragraph 1, the particle in which M includes Ni and Co. Claim 8 In claim 1, the non-lithiated nickel oxide particles have an average crystallite size measured by X-ray diffraction of less than 30 nm, or less than 25 nm, or less than 20 nm. Claim 9 In paragraph 8, a particle in which Ni is present in an amount of 92 atomic percent or more. Claim 10 In claim 9, the particle, wherein M comprises one or more elements of Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Nb, Ta, Cr, Fe, Mo, W, Hf, B or a combination thereof, and Ni. Claim 11 In paragraph 10, particles in which boron oxide is present in an amount of less than 1 wt% relative to non-lithiated nickel oxide particles. Claim 12 In claim 1, the particles are particles that do not contain any components soluble in water at 1 atmosphere and 25 degrees Celsius. Claim 13 As a particle, a non-lithiated nickel oxide of the chemical formula MOx, wherein M contains 80 at% or more of Ni and x is 0.7 to 1.2; and a boron oxide mixed with the non-lithiated nickel oxide to form a mixed particle, wherein the mixed particle is formed by calcining the boron oxide with the non-lithiated nickel hydroxide at a temperature of 600 degrees or less for a calcination time of 6 hours or less, wherein the boron oxide acts as a crystal growth inhibitor. Claim 14 In Paragraph 13, particles having a temperature of 500 degrees or less. Claim 15 In Paragraph 13, particles with a calcination time of 5 hours or less. Claim 16 In paragraph 13, particles in which boron oxide is present in an amount of less than 1 wt% relative to non-lithiated nickel oxide. Claim 17 In Clause 16, particles in which boron oxide is present in an amount of 0.25 wt% or less. Claim 18 In paragraph 13, the particle in which nickel is present at 92 atomic percent or more of the total M, or at least 99 atomic percent. Claim 19 A particle according to any one of claims 13 to 18, wherein M comprises one or more elements selected from Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Nb, Ta, Cr, Fe, Mo, W, Hf, B, or combinations thereof, and Ni. Claim 20 In paragraph 19, M is a particle containing Ni and Co. Claim 21 In any one of claims 13 to 18, the non-lithiated nickel oxide particles have an average crystallite size of less than 30 nm, or less than 25 nm, or less than 20 nm as measured by X-ray diffraction. Claim 22 A method for forming electrochemically active particles suitable for use in the cathode of a secondary battery, comprising the steps of: mixing particles of non-lithiated nickel hydroxide of the formula M(OH)x to form a precursor mixture, wherein M contains 80 at% or more of Ni and x is 1.7 to 2.3; calcining the precursor mixture at a calcination temperature of 600 degrees or less and for a calcination time of 6 hours or less to form a first calcined product, wherein the boron oxide acts as a crystal growth inhibitor; and combining the first calcined product with a lithium source and calcining the first calcined product and the lithium source to form electrochemically active particles. Claim 23 A method according to claim 22, comprising the steps of: immersing the electrochemically active particles in a process solution containing Co alone or Co and Al; drying the electrochemically active particles after immersion; and heat-treating the electrochemically active particles after drying to form particles, wherein the concentration of Co, Al, or both at the grain boundaries is greater than the concentration of Al, Co, or both at the crystallites. Claim 24 In paragraph 22, a method in which nickel is present in at least 92 atomic percent of total M. Claim 25 In paragraph 24, a method in which nickel is pre-set to be 99 atomic percent or more of total M. Claim 26 A method according to claim 22, wherein boron oxide is present in an amount of less than 1 wt% or 0.25 wt% or less with respect to non-lithiated nickel oxide particles. Claim 27 A method according to claim 22, wherein M comprises one or more elements of Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Nb, Ta, Cr, Fe, Mo, W, Hf, B or a combination thereof, and Ni. Claim 28 In paragraph 22, a method in which M includes Ni and Co. Claim 29 In claim 22, the method wherein the first calcined product has an average crystallite size measured by X-ray diffraction of less than 30 nm, or less than 25 nm, or less than 20 nm. Claim 30 In paragraph 29, a method in which Ni is present in 92 atomic percent or more. Claim 31 A method according to claim 30, wherein M comprises one or more elements of Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Nb, Ta, Cr, Fe, Mo, W, Hf, B or a combination thereof, and Ni. Claim 32 In claim 31, the method wherein boron oxide is present in an amount of less than 1 wt% relative to non-lithiated nickel oxide particles. Claim 33 An electrode comprising a combination of electrochemically active particles and a binder manufactured by a method according to any one of claims 23 to 32, wherein the electrochemically active particles and the binder are coated on a current collector. Claim 34 A lithium-ion battery comprising electrochemically active particles manufactured by a method according to any one of claims 23 to 32.

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