Oxidative delithiation of alkaline nickel oxide

Abstract

Provided are methods of making an electrochemically active cathode material, the method comprising the steps of: (a) combining a layered nickel oxide containing an alkali metal with an oxidizing agent to form a mixture, wherein A comprises an alkali metal and 0 < a < 0.2, the oxidizing agent comprising a peroxodisulfate and / or monopersulfate; (b) heating the mixture to form a mixture containing Ni(IV), the mixture containing Ni(IV) comprising an electrochemically active cathode material containing Ni(IV); (c) adding a mineral acid to the mixture containing Ni(IV) of step (b); and (d) heating the mixture of step (c) to form an additional amount of the electrochemically active cathode material containing Ni(IV), the electrochemically active cathode material containing Ni(IV) formed in steps (b) and (d) having the general formula A 1‑a Ni 1+a O2wherein A comprises an alkali metal and 0 < a < 0.2. (b) heating the mixture to form a mixture containing Ni(IV), the mixture containing Ni(IV) comprising an electrochemically active cathode material containing Ni(IV); (c) adding a mineral acid to the mixture containing Ni(IV) of step (b); and (d) heating the mixture of step (c) to form an additional amount of the electrochemically active cathode material containing Ni(IV), the electrochemically active cathode material containing Ni(IV) formed in steps (b) and (d) having the general formula A x H y Ni 1+a O2wherein A comprises an alkali metal; 0.08 < x < 0.2; 0 < y < 0.3; and 0.02 < a < 0.2.

Description

Technical Field

[0001] This disclosure generally relates to the oxidative demetallization of basic nickel oxide. More specifically, this disclosure relates to the oxidative demetallization of alkali metal nickel oxide using a multi-step mixed process, said process comprising treatment with persulfate and a separate subsequent treatment with mineral acid. Background Technology

[0002] Alkali metal-containing transition metal oxides can be actively activated or "charged" to prepare highly oxidized cathode materials for use in both primary and secondary electrochemical cell units. Charging alkali metal-containing transition metal oxides involves oxidizing the transition metal and partially or completely removing the alkali metal from the metal oxide lattice to form alkali metal-deficient electrochemically active cathode materials. Alkali metal-containing transition metal oxides can be chemically or electrochemically charged. Methods for chemically charging alkali metal-containing transition metal oxides can include oxidative demetallization of the transition metal and acid-induced disproportionation, for example, treatment with mineral acids.

[0003] It is known that acid-induced disproportionation of transition metal oxides containing alkali metals such as Mn and Ni results in the extraction of virtually all alkali metal ions present in the lattice and the oxidation of up to 50% of the metal, for example, from the M(III) oxidation state to the M(IV) oxidation state. The corresponding amount of M(III) is reduced to M(II) dissolved in the acid solution.

[0004] The acid-induced disproportionation reaction can be summarized using stoichiometric layered lithium nickel oxide as an example, as shown in Equation 1 below:

[0005] LiNiO2 + 2y H2SO4 → (1-y)Li (1-2y) / (1-y) NiO2+y NiSO4+y Li2SO4+2y H2O (0≤y≤1 / 2). (1)

[0006] Ni(II) ions are soluble and dissolve in acidic aqueous solutions. Therefore, chemical charging of transition metal oxides containing alkali metals using acid-promoted metal disproportionation is very inefficient because at least half of the M(III) ions in the initial transition metal oxide are reduced to M(II) ions, which are soluble in acidic solutions and thus extracted from the crystal structure. Furthermore, the dissolution of M(II) ions reduces the average particle size of the transition metal oxide.

[0007] Chemical charging of transition metal oxides containing alkali metals using strong, soluble chemical oxidants can be used to directly oxidize the transition metals to higher oxidation states and result in the removal of proportional amounts of alkali metal ions to maintain the overall electroneutrality of the crystal lattice. Examples of such oxidants include strong oxidizing gases (e.g., ozone, chlorine, or bromine), strong oxidizing solids (e.g., nitrosium hexafluorophosphate, nitrosium tetrafluoroborate, nitrosium hexafluoroarsenate, nitronium tetrafluoroborate, nitronium hexafluorophosphate, nitronium hexafluoroarsenate), and water-soluble oxidants (e.g., alkali metal or alkaline earth metal hypochlorites, such as Na+). + K + Ca 2+ ), alkaline persulfate (e.g., Na+) + K + Ammonium persulfate and basic monopersulfates (e.g., Na+) + K + Various reagents, such as alkali metals, have been used for the chemical charging of transition metal oxides containing alkali metals. Other water-soluble oxidants include basic permanganates (e.g., K...). + Na + Li + ) and basic ferrates (e.g., K ferrates) + Methods using water-soluble oxidants are typically carried out at near room temperature for 24 to 48 hours; however, such methods generally lack sufficient oxidizing intensity to rapidly and adequately oxidize transition metals and demetallate the initial alkali metal-containing transition metal oxides to prepare a solution of formula A. x MO2 or A x M2O4 is an alkali metal-deficient metal oxide, where A is an alkali metal and M is a transition metal, for example, where x is less than about 0.3.

[0008] Therefore, known methods for chemically charging layered transition metal oxides containing alkali metals have several drawbacks, such as low yields due to disproportionation of transition metals, incomplete oxidation of transition metals and / or prolonged processing times (e.g., 12-72 hours) and expensive reagents (e.g., nitrites, nitonium salts). Summary of the Invention

[0009] One aspect of this disclosure provides a method for preparing an electrochemically active cathode material, the method comprising the steps of: (a) placing a material having formula A 1-a Ni 1+aA layered nickel oxide containing an alkali metal and O₂ is combined with a fluid composition to form a mixture, where A includes an alkali metal and 0 < a ≤ 0.2, the fluid composition contains a chemical oxidant, and the chemical oxidant includes persulfate, monopersulfate, or a combination thereof; (b) heating the mixture for at least a period sufficient to form a mixture containing Ni(IV), the mixture containing Ni(IV) includes a nickel(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material, and the mixture containing Ni(IV) has a total nickel (Ni) content; (c) combining the nickel(IV)-containing mixture of step (b) with a mineral acid, where the mineral acid is added in an amount of about 0.60 moles or less per mole of total nickel; and (d) heating the mixture of step (c) for at least a period sufficient to form an additional amount of the nickel(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material. The nickel(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material formed during steps (b) and (d) has the general formula A x H y Ni 1+a O₂, where A includes an alkali metal; 0.08 ≤ x < 0.2; 0 ≤ y < 0.3; and 0.02 ≤ a ≤ 0.2.

[0010] Another aspect of the present disclosure provides a method for preparing an electrochemically active cathode material, the method comprising the steps of: combining a non-stoichiometric alkali-metal-containing layered nickel oxide having the formula A 1-a Ni 1+a-z M z O₂ with a fluid composition to form a mixture, where A includes an alkali metal and 0 < a ≤ 0.2, M includes a transition metal or a main group metal, and 0 ≤ z ≤ 0.2, the fluid composition contains a chemical oxidant, and the chemical oxidant includes persulfate, monopersulfate, or a combination thereof; (b) heating the mixture for at least a period sufficient to form a mixture containing Ni(IV), the mixture containing Ni(IV) includes a nickel(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material, and the mixture containing Ni(IV) has a total nickel (Ni) content; (c) combining the nickel(IV)-containing mixture of step (b) with a mineral acid, where the mineral acid is added in an amount of about 0.60 moles or less per mole of total nickel; and (d) heating the mixture of step (c) for at least a period sufficient to form an additional amount of the nickel(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material. The nickel(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material formed during steps (b) and (d) has the general formula A x H y Ni1+a-z M z O₂, where A includes an alkali metal; 0.08 ≤ x < 0.2; 0 ≤ y < 0.3; 0.02 ≤ a ≤ 0.2; M includes a transition metal or a main group metal, and 0 ≤ z ≤ 0.2.

[0011] Another aspect of the present disclosure provides a method for preparing an electrochemically active cathode material, the method comprising the following steps: (i) reacting a layered nickel oxide containing an alkali metal having the formula A 1-a Ni 1+a O₂ with a chemical oxidant in a fluid composition at a high temperature for at least a period of time sufficient to form a mixture containing Ni(IV), where A includes an alkali metal and 0 < a ≤ 0.2, the chemical oxidant includes persulfate, monopersulfate or a combination thereof, the mixture containing Ni(IV) includes a Ni(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material, the mixture containing Ni(IV) has a total nickel (Ni) content; and (ii) reacting the mixture containing Ni(IV) of step (i) with a mineral acid at a high temperature for at least a period of time sufficient to form an additional amount of the Ni(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material, where the mineral acid is added in an amount of about 0.60 moles or less per mole of total nickel; the Ni(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material formed during steps (i) and (ii) has the general formula A x H y Ni 1+a O₂, where A includes an alkali metal; 0.08 ≤ x < 0.2; 0 ≤ y < 0.3; and 0.02 < a ≤ 0.2.

[0012] Another aspect of the present disclosure provides a method for preparing an additional electrochemically active cathode material from a Ni(IV)-containing alkali-metal-deficient layered nickel oxide, the method comprising treating the Ni(IV)-containing alkali-metal-deficient layered nickel oxide formed in steps (b) and (d) of the method of the present disclosure with an aqueous solution of an alkali metal hydroxide to form the additional electrochemically active cathode material having the general formula A x A' v Ni 1+a O₂·nH₂O, where A includes an alkali metal; A' includes an alkali metal different from A; 0.04 ≤ x < 0.2; 0.03 ≤ v < 0.2; 0.02 ≤ a ≤ 0.2 and 0 < n < 2; and further having a characteristic powder X-ray diffraction pattern different from that of the alkali-metal-deficient layered nickel oxide formed in steps (b) and (d).

[0013] Additional aspects and advantages will become apparent to those of ordinary skill in the art upon review of the following detailed description. While the compositions and methods may have various embodiments, the following description includes specific embodiments and is not intended to limit the disclosure to the specific embodiments described herein, understanding that the disclosure is illustrative. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Although the specification concludes with claims that particularly point out and distinctly claim the subject matter regarded as forming the invention, it is believed that the invention will be better understood from the following description taken in conjunction with the accompanying drawings.

[0015] Figure 1 is a cross - section of an embodiment of a primary alkaline battery of the present disclosure. DETAILED DESCRIPTION

[0016] The present disclosure provides a method for preparing an electrochemically active cathode material, the method comprising the steps of: (a) combining a layered nickel oxide containing an alkali metal having the formula A 1-a Ni 1+a O2 with a fluid composition to form a mixture, where A comprises an alkali metal and 0 < a ≤ 0.2, the fluid composition comprising a chemical oxidant, the chemical oxidant comprising persulfate, monopersulfate, or a combination thereof; (b) heating the mixture for at least a period sufficient to form a mixture containing Ni(IV), the mixture containing Ni(IV) comprising a Ni(IV) - containing alkali - metal - deficient layered nickel oxide electrochemically active cathode material, the mixture containing Ni(IV) having a total nickel (Ni) content; (c) combining the mixture of step (b) with a mineral acid, where the mineral acid is added in an amount of about 0.60 moles or less per mole of total nickel; and (d) heating the mixture of step (c) for at least a period sufficient to form an additional amount of Ni(IV) - containing alkali - metal - deficient layered nickel oxide electrochemically active cathode material, the Ni(IV) - containing alkali - metal - deficient layered nickel oxide electrochemically active cathode material formed during steps (b) and (d) having the general formula A x H y Ni 1+a O2, where A comprises an alkali metal; 0.08 ≤ x < 0.2; 0 ≤ y < 0.3; and 0.02 ≤ a ≤ 0.2.

[0017] The present disclosure further provides a method for preparing an electrochemically active cathode material, the method comprising the steps of: (a) combining a layered nickel oxide having the formula A 1-a Ni 1+a-z M zA layered metal-substituted nickel oxide containing an alkali metal is combined with a fluid composition to form a mixture, where A comprises an alkali metal, 0 < a ≤ 0.2, M comprises a transition metal or a main group metal, and 0 ≤ z ≤ 0.2, the fluid composition contains a chemical oxidant, and the chemical oxidant comprises persulfate, monopersulfate or a combination thereof; (b) heating the mixture for at least a period of time sufficient to form a mixture containing Ni(IV), the mixture containing Ni(IV) comprising a Ni(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material, the mixture containing Ni(IV) having a total nickel (Ni) content; (c) combining the Ni(IV)-containing mixture of step (b) with a mineral acid, where the mineral acid is added in an amount of about 0.60 moles or less per mole of total nickel; and (d) heating the mixture of step (c) for at least a period of time sufficient to form an additional amount of a Ni(IV)-containing alkali-metal-deficient layered metal-substituted nickel oxide electrochemically active cathode material, the Ni(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material formed in steps (b) and (d) having the general formula A x H y Ni 1+a-z M z O2, where A comprises an alkali metal; 0.08 ≤ x < 0.2; 0 ≤ y < 0.3; 0.02 ≤ a ≤ 0.2; M comprises a transition metal or a main group metal, and 0 ≤ z ≤ 0.2.

[0018] It is known in the art that persulfate and monopersulfate can undergo autocatalytic thermal decomposition in aqueous solution at temperatures above 50 °C (specifically at temperatures above 60 °C, 65 °C, 70 °C or at about 80 °C and above), thereby releasing oxygen and forming sulfuric acid as a decomposition product. Further, it is known in the art that layered nickel oxides containing an alkali metal can undergo acid-promoted disproportionation in the presence of a mineral acid such as sulfuric acid. This disproportionation reaction of, for example, layered lithium nickel oxide can be summarized as the following equation 2:

[0019] LiNiO2 + 2y H2SO4 → (1 - y)Li (1-2y) / (1-y) NiO2 + y NiSO4 + y Li2SO4 + 2y H2O (0 ≤ y ≤ 0.5). (2)

[0021] Therefore, one of ordinary skill in the art would expect that at temperatures greater than about 50 °C, such as about 60 °C and above, the oxidant would begin to decompose and form sulfuric acid, which is expected to promote the disproportionation of the layered nickel oxide containing an alkali metal, thereby producing a Ni(IV)-containing alkali-metal-deficient layered nickel oxide with a yield of at most about 50% or less relative to the initial amount of the layered nickel oxide containing an alkali metal.

[0022] Furthermore, it is known in the art that the dissolved Ni(II) ions formed during disproportionation can catalyze the decomposition of persulfate and monopersulfate, thereby forming sulfuric acid as a decomposition product. Due to the reduced amount of oxidant available for the oxidative demetallization reaction and the increased amount of sulfuric acid available to promote the disproportionation reaction, those skilled in the art will anticipate such further decomposition of the oxidant, potentially further reducing the yield of alkali-deficient layered nickel oxide containing Ni(IV).

[0023] Not bound by theory, it is believed that during the two-step method of this disclosure, there are three basic stages leading to nickel oxidation / reduction. The first stage is oxidative demetallization, which occurs during treatment of non-stoichiometric alkali metal-containing layered nickel oxide with an oxidant including persulfate and / or monopersulfate. In this stage, a portion of Ni(III) in the alkali metal-containing layered nickel oxide is oxidized to Ni(IV), and a portion of the alkali metal is removed from the structure of the alkali metal-containing layered nickel oxide. Not bound by theory, it is believed that the removal of alkali metal is non-uniform, and the concentration of residual alkali metal near the particle surface of the initially alkali metal-containing layered nickel oxide is lower than that at the particle center. Not bound by theory, it is further believed that the concentration of residual alkali metal at the particle center is limited by the diffusion rate of alkali metal ions, resulting in the obtained demetallized layered nickel oxide particles having a "core / shell" structure with highly demetallized local regions near their outer surfaces and almost no demetallization in their inner regions. Not bound by theory, it is believed that little or no soluble Ni is formed during the first stage. 2+ ion.

[0024] The second stage primarily involves disproportionation of partially demetallized layered nickel oxide through treatment with mineral acids. Unbound by theory, it is believed that during disproportionation, the mineral acids can penetrate the interior or core region of the partially demetallized layered nickel oxide particles, causing the remaining Ni(III) to disproportionate into Ni(IV) and soluble Ni. 2+ Ions. Furthermore, unbound by theory, it is believed that when Ni(III) within or the core region of layered nickel oxide particles is oxidized to Ni(IV), soluble Ni... 2+ Ions dissolve from the particle surface along with other alkali metal ions inside or in the core region of the particle, resulting in more uniform demetallization and a smaller alkali metal concentration gradient from the particle surface to the core region.

[0025] The third stage involves directly reducing Ni(IV) in layered nickel oxide containing Ni(IV) to soluble Ni. 2+ Ions. Unbound by theory, it is believed that Ni(IV) can be reduced to Ni(II) at highly acidic pH conditions, and the extent of this reduction is proportional to the temperature of the mixture and the concentration of the acid.

[0026] Surprisingly and unexpectedly, the method disclosed herein for converting alkali metal-containing layered nickel oxide into alkali metal-deficient layered nickel oxide containing Ni(IV) can involve heating the alkali metal-containing layered nickel oxide with an oxidant at a temperature below 60°C, for example, in the range of about 40°C to below 60°C, to remove about 50% of the alkali metal from the alkali metal-containing layered nickel oxide without significantly forming soluble Ni. 2+ ion.

[0027] Therefore, the method of this disclosure advantageously provides one or more benefits, such as providing an oxidative demetallization method with a relatively short processing time, providing Ni(IV)-containing alkali metal-deficient layered nickel oxide in a relatively high yield (e.g., greater than about 70%), and minimizing Ni content. 2+ The present invention provides Ni(IV)-containing, alkali metal-deficient layered nickel oxide particles with a larger PSD than those prepared by methods using persulfate treatment alone or acid washing alone, and / or provides Ni(IV)-containing, alkali metal-deficient layered nickel oxide particles with high discharge capacity. Additionally, the methods of this disclosure can be controlled to provide alkali metal-deficient layered nickel oxide that can be stabilized with alkali metal hydroxides without forming a large amount of γ-hydroxyl oxide (γ-NiOOH) byproduct. As used herein and unless otherwise stated, "a large amount of γ-NiOOH byproduct" means that, based on the total weight of the product, the amount of γ-NiOOH in the stabilized product is about 11% by weight or higher. In the embodiments, the amount of γ-NiOOH in the stabilized product may be less than about 10 wt.%, less than about 8 wt%, less than about 6 wt%, less than about 5 wt%, less than about 4 wt%, less than about 3 wt%, less than about 2%, or less than about 1 wt%.

[0028] The term “about” is used according to its general meaning, for example, to mean approximately or about. In one embodiment, the term “about” means the value or range of the value ±10%. In another embodiment, the term “about” means the value or range of the value ±5%. The value or range described in conjunction with the term “about” also explicitly includes a specific value and / or range (e.g., for a value described as “about 40”, “40” is also explicitly taken into account).

[0029] As used herein, a Ni(IV)-containing, alkali-metal-deficient layered nickel oxide electrochemically active cathode material with “high discharge capacity” refers to a Ni(IV)-containing, alkali-metal-deficient layered nickel oxide having a gravimetric discharge capacity equal to or greater than about 420 mAh / g when discharged at a low discharge rate as a cathode activator in an alkaline battery cell. As used herein, and unless otherwise stated, “low discharge rate” means a fully charged battery that discharges over a period of about 30 to about 40 hours, i.e., a battery with a C / 30 to about C / 40 rate. The C rate is a measurement well understood in the art, conveying the rate at which a battery discharges relative to its theoretical rated capacity. The rate is defined as the discharge current divided by the theoretical discharge current at which the battery will deliver its total nominal / theoretical rated capacity in one hour. For example, for a material with a gravimetric discharge capacity of about 420 mAh / g, a 1C discharge rate will deliver a total capacity of 420 mAh / g in one hour. For a material with a gravimetric discharge capacity of approximately 420 mAh / g, a 2C rate will deliver the total 420 mAh / g capacity in 0.5 hours. For a material with a gravimetric discharge capacity of approximately 420 mAh / g, a C / 2 rate will deliver the total 420 mAh / g capacity in 2 hours. Therefore, for a material with a gravimetric discharge capacity of approximately 420 mAh / g, a C / 40 rate will deliver the total 420 mAh / g capacity in 40 hours.

[0030] Alkali-deficient layered nickel oxide electrochemically active cathode materials, prepared solely by treating alkali-metal-containing layered nickel oxide with an aqueous sulfuric acid solution, typically exhibit low discharge rate (e.g., C / 40) gravimetric discharge capacity in the range of about 390 to about 420 mAh / g. Therefore, the methods of this disclosure can provide electrochemically active cathode materials having a low-rate discharge capacity comparable to (if not higher than) materials prepared by other methods known in the art. In the embodiments, the alkali metal-deficient layered nickel oxide electrochemically active cathode material, when discharged at a low discharge rate as the cathode activation material in an alkaline electrochemical battery cell, has a gravimetric discharge capacity equal to or greater than about 390 mAh / g, for example, ranging from about 400 mAh / g to about 550 mAh / g, about 400 mAh / g to about 500 mAh / g, about 405 mAh / g to about 490 mAh / g, about 410 mAh / g to about 480 mAh / g, about 415 mAh / g to about 470 mAh / g, about 420 mAh / g to about 460 mAh / g, greater than about 405 mAh / g, greater than about 410 mAh / g, greater than about 415 mAh / g, greater than about 420 mAh / g, for example, about 425 mAh / g, about 430 mAh / g, about 435 mAh / g, about 440 mAh / g, about 460 mAh / g, about 480 mAh / g, and / or about 500 mAh / g.

[0031] Layered nickel oxide containing an alkali metal

[0032] Generally, the layered nickel oxide containing an alkali metal to be de-metallized by oxidation can be a stoichiometric or non-stoichiometric layered nickel oxide containing an alkali metal. The non-stoichiometric layered nickel oxide containing an alkali metal has the general formula A 1-a Ni 1+a O2, where A is an alkali metal and 0 < a ≤ 0.2. In an embodiment, the layered nickel oxide containing an alkali metal can have a layered structure. A can be selected from the group consisting of: lithium, sodium, potassium, and combinations thereof. In an embodiment, A includes lithium. In an embodiment, some of the alkali metals in the layered nickel oxide containing an alkali metal can be replaced by metal ions having a similar ionic radius, such as Li + 、Ni 2+ 、Ni 3+ 、Na + 、K + 、Cs + 、Rb + 、Ag + 、Mg 2+ 、Ca 2+ 、Zn 2+ and Bi 3+ . Without wishing to be bound by theory, it is believed that the ionic radii of Rb + and Cs + are too large to be primary alkali metals because they cannot form a stable layered structure having a structure equivalent to that of lithium nickel oxide or sodium nickel oxide.

[0033] In an embodiment, the non-stoichiometric layered nickel oxide containing an alkali metal can contain a metal dopant M and have the formula A 1-a Ni 1+a-z M z O2, where A includes an alkali metal, 0 < a ≤ 0.2, M includes a transition metal or a main group metal, and 0 ≤ z ≤ 0.2.

[0034] In embodiments containing non-stoichiometric layered nickel oxide containing an alkali metal, 0 < a ≤ 0.2, for example, 0.01 to 0.20, 0.01 to 0.18, 0.01 to 0.16, 0.01 to 0.15, 0.02 to 0.20, 0.02 to 0.18, 0.02 to 0.16, 0.02 to 0.15, 0.03 to 0.20, 0.03 to 0.19, 0.03 to 0.15, 0.03 to 0.12, 0.05 to 0.19 or 0.05 to 0.15. Since a is always greater than 0, there are alkali metal sites in the lattice that do not contain alkali metal ions but may instead be vacant or occupied by excess Ni(II) ions, thereby providing a non-stoichiometric amount of nickel and alkali metal relative to the stoichiometric counterpart of the general formula ANiO2 or ANi 1-z M z O2.

[0035] In embodiments in which the layered nickel oxide containing an alkali metal contains a metal dopant M, the metal dopant may include a transition metal, a main group metal, or both. Generally, the metal dopant is a metal that can reach an oxidation state of +3 or higher and has an ionic radius (about to about ) comparable to that of Ni(III) in the low-spin or high-spin octahedral position, for example, in the range of about to about or about to about . In embodiments, the transition metals include cobalt (CO 3+ , CO 4+ ), manganese (MN 3+ , MN 4+ ), iron (FE 3+ , FE 4+ ), chromium (CR 3+ , CR 4+ ), vanadium (V 3 + , V 5+ ), titanium (TI 3+ , TI 4+ ), niobium (NB 3+ , NB 5+ ), zirconium (ZR 4+ ) or a combination thereof. In embodiments, the transition metals include cobalt, manganese, iron or a combination thereof. In embodiments, the transition metal includes cobalt. In embodiments, the transition metal includes manganese. In embodiments, the transition metal includes cobalt and manganese. The main group metals may be selected from the group consisting of: aluminum (Al 3+ ), gallium (Ga 3+ ), bismuth (Bi5+ ) and combinations thereof. In an embodiment, the main group metal includes aluminum.

[0036] In embodiments where the layered nickel oxide containing an alkali metal contains a metal dopant, z can be 0 ≤ z ≤ 0.2 or 0 < z ≤ 0.2. For example, 0 to 0.20, 0.01 to 0.20, 0.01 to 0.18, 0.01 to 0.16, 0.01 to 0.15, 0.02 to 0.20, 0.02 to 0.18, 0.02 to 0.16, 0.02 to 0.15, 0.03 to 0.20, 0.03 to 0.19, 0.03 to 0.15, 0.03 to 0.12, 0.05 to 0.19 or 0.05 to 0.15. Without wishing to be bound by theory, it is believed that as the amount of the metal dopant in the layered nickel oxide containing an alkali metal and the alkali-metal-free layered nickel oxide containing Ni(IV) prepared therefrom increases, the stability of the electrochemically active material comprising the alkali-metal-free layered nickel oxide containing Ni(IV) to an aqueous hydroxide solution such as an alkaline battery electrolyte increases, but the overall discharge capacity may decrease, for example, when the dopant metal is not electrochemically active in the same voltage window as nickel.

[0037] Generally, the layered nickel oxide containing an alkali metal is substantially non-hydrated; however, there may be an excess of alkali metal oxides and hydroxides resulting from the synthesis of the layered nickel oxide containing an alkali metal present on the surface of the layered nickel oxide particles containing an alkali metal that can absorb water from the surrounding air. The alkali metal oxides and hydroxides can also react with carbon dioxide in the surrounding air to form alkali metal carbonates on the surface of the layered nickel particles containing an alkali metal.

[0038] Alkali-metal-free layered nickel oxide electrochemically active cathode material

[0039] Generally, the general formula of the alkali-metal-free layered nickel oxide electrochemically active cathode material containing Ni(IV) formed according to the method disclosed herein is A x H y Ni 1+aO2, where A comprises an alkali metal; 0.08 ≤ x < 0.2; 0 ≤ y < 0.3; and 0.02 ≤ a ≤ 0.2. Alkali metal-deficient layered nickel oxide containing Ni(IV) is also referred to herein as α-demetallized layered nickel oxide. The average oxidation state of nickel in α-demetallized nickel oxide is typically between about 3+ and 4+, because α-demetallized layered nickel oxide will contain a large portion of nickel in the 4+ oxidation state and some nickel in the 3+ oxidation state. As described below, α-demetallized layered nickel oxide also contains a portion of nickel in the alkali metal sites located in the lattice in the 2+ or 3+ oxidation state. It should be understood that A in the formula of the α-demetallized layered nickel oxide electrochemically active cathode material will be the same as A in the formula of the alkali metal-containing layered nickel oxide material used to prepare the α-demetallized material. Therefore, A can be selected from the group consisting of lithium, sodium, potassium, and combinations thereof. In the examples, A is lithium. In the embodiments, some alkali metals in the layered nickel oxide containing alkali metals can be replaced by metal ions with similar ionic radii, such as Li. + Ni 2+ Ni 3+ Na + K + Cs + 、Rb + Ag + Mg 2+ Ca 2 + Zn 2+ and Bi 3+ .

[0040] In an embodiment, α-demetallized layered nickel oxide may contain a metal dopant M and have formula A x H y Ni 1+a- z M z O2, where A includes alkali metals, 0.08≤x<0.2; 0≤y<0.3; 0.02≤a≤0.2, and M includes transition metals or main group metals, 0≤z≤0.2.

[0041] In embodiments comprising α - de - metalated layered nickel oxide containing a metal dopant, the x value of the α - de - metalated layered nickel oxide can be in the range of 0.08 < x < 0.2. For example, 0.08 to 0.20, 0.08 to 0.18, 0.08 to 0.16, 0.08 to 0.15, 0.09 to 0.20, 0.09 to 0.19, 0.09 to 0.15, 0.09 to 0.12, 0.10 to 0.19 or 0.10 to 0.15. An x value of the α - de - metalated layered nickel oxide below about 0.08 may be the result of one or more excessive oxidants provided during oxidative de - metalation, too high reaction temperature during oxidative de - metalation, and / or too long reaction time during oxidative de - metalation. And thus it is desirable to control these parameters. An x value of the α - de - metalated layered nickel oxide greater than about 0.2 may be the result of one or more insufficient oxidants provided during oxidative de - metalation, too low reaction temperature during oxidative de - metalation, and / or too short reaction time during oxidative de - metalation, further indicating the desirability of controlling these parameters. Without wishing to be bound by theory, it is believed that as the amount x of alkali metal A in the α - de - metalated layered nickel oxide decreases to less than about 0.08, such as 0.06, 0.04, 0.02 or less, the α - de - metalated layered nickel oxide is more likely to form γ - nickel oxyhydroxide (with additional alkali metal ions inserted into the vacant sites in its layers and having the formula A x A' v Ni 1+a O2·nH2O, where A comprises Li or Na; A' comprises K, Rb or Cs; 0.08 ≤ x < 0.2; 0.03 < v < 0.20; 0.02 < a ≤ 0.2; and 0 < n < 2. Further, without wishing to be bound by theory, it is believed that as the amount x of alkali metal A in the α - de - metalated layered nickel oxide increases to greater than about 0.2, the capacity of the prepared α - de - metalated layered nickel oxide (and the stable layered nickel oxide prepared therefrom) decreases due to the presence of unoxidized Ni(III) (i.e., un - converted alkali - metal - containing layered nickel oxide starting material).

[0042] In embodiments comprising α - de - metalated layered nickel oxide containing a metal dopant, the y value of the α - de - metalated layered nickel oxide can be in the range of 0 ≤ y < 0.3. For example, 0 to 0.29, 0.05 to 0.29, 0.05 to 0.25, 0.05 to 0.20, 0.05 to 0.15, 0.08 to 0.29, 0.08 to 0.25, 0.08 to 0.20, 0.08 to 0.15, 0.10 to 0.29, 0.10 to 0.25, 0.10 to 0.20 or 0.10 to 0.15. H +It can be introduced into the crystal structure during the oxidative demetallization process via ion exchange with alkali metal cations. Specifically, when oxidative demetallization is carried out in aqueous solution, under certain conditions water can react with the oxidant to form H+, which can subsequently undergo partial ion exchange with alkali metal cations. + Ions, especially at high temperatures.

[0043] In embodiments comprising α-demetallized layered nickel oxide containing metal dopants, the α-value of the α-demetallized layered nickel oxide can be in the range of 0.02 ≤ a ≤ 0.2, for example, 0.02 to 0.20, 0.02 to 0.18, 0.02 to 0.16, 0.02 to 0.15, 0.03 to 0.20, 0.03 to 0.18, 0.03 to 0.16, 0.03 to 0.15, 0.04 to 0.20, 0.04 to 0.18, 0.04 to 0.15, 0.04 to 0.12, 0.05 to 0.19, or 0.05 to 0.15. Because α must be greater than 0, the lattice contains alkali metal ions but is instead doped by Ni. 2+ or Ni 3+ The alkali metal sites occupied by ions provide an excess, non-stoichiometric amount of nickel. Those skilled in the art will understand that some alkali metal sites in the lattice can be vacant, and further, by using 2 Li... + Ions replace one Ni 2+ Ions or using 3 Li + ions (or a Ni) 2+ ions and a Li + (ion) replaces one Ni 3+ Ions are used to maintain the electroneutrality of the structure. Furthermore, H+ is used... + Replace Li + This will maintain the electrical neutrality of the structure.

[0044] In embodiments where the starting material comprising layered nickel oxide containing an alkali metal includes a metal dopant M, it should be understood that M in the formula of the α-demetallized layered nickel oxide electrochemically active cathode material will be the same as M in the formula of the alkali metal-containing layered nickel oxide material used to prepare the α-demetallized material. Therefore, M can comprise a transition metal, a main group metal, or both. Typically, the metal dopant is a metal that can reach an oxidation state of +3 or higher and has an ionic radius comparable to that of Ni(III).

[0045] In an embodiment, the transition metal includes cobalt (CO). 3+ CO 4+ ), manganese (MN) 3+ MN 4+ ), iron (FE) 3+ FE 4+ ), chromium (CR)3+ , CR 4+ ), vanadium (V 3+ , V 5+ ), titanium (TI 3+ , TI 4+ ), niobium (NB 3+ , NB 5+ ), zirconium (ZR 4+ ), or a combination thereof. In an embodiment, the transition metal includes cobalt, manganese, or a combination thereof. In an embodiment, the transition metal includes cobalt. In an embodiment, the transition metal includes manganese. In an embodiment, the transition metal includes cobalt and manganese. In an embodiment, the transition metal includes cobalt and manganese. The main group metal may be selected from the group consisting of: aluminum (Al 3+ ), gallium (Ga 3+ ), bismuth (Bi 5+ ), and combinations thereof. In an embodiment, the main group metal includes aluminum.

[0046] In embodiments where the α - de - metal layered nickel oxide material contains metal dopants, the value of z may be in the range of 0 ≤ z ≤ 0.2 or 0 < z ≤ 0.2. For example, 0 to 0.20, 0.01 to 0.20, 0.01 to 0.18, 0.01 to 0.16, 0.01 to 0.15, 0.02 to 0.20, 0.02 to 0.18, 0.02 to 0.16, 0.02 to 0.15, 0.03 to 0.20, 0.03 to 0.19, 0.03 to 0.15, 0.03 to 0.12, 0.05 to 0.19, or 0.05 to 0.15. Without being bound by theory, it is believed that as the amount of metal dopants in the α - de - metal layered nickel oxide increases, the stability of the electrochemically active material containing α - de - metal layered nickel oxide to an aqueous solution of an alkali metal hydroxide such as an alkaline battery electrolyte increases, but the overall discharge capacity may decrease, for example, in the case where the dopant metal is not electrochemically active in the same voltage window as nickel.

[0047] Method for preparing an electrochemically active cathode material

[0048] Generally, the method for preparing an electrochemically active cathode material includes the following: (a) having the general formula A 1-a Ni 1+aA layered nickel oxide containing an alkali metal is combined with a fluid composition (e.g., a suspension, dispersion, or solution) to form a mixture (e.g., a suspension, dispersion, or solution), where A includes an alkali metal and 0 < a ≤ 0.2. The fluid composition contains an oxidizing agent, and the oxidizing agent includes persulfate, monopersulfate, or a combination thereof; (b) heating the mixture for at least a period of time sufficient to form a mixture containing Ni(IV), the mixture containing Ni(IV) includes a Ni(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material, and the mixture containing Ni(IV) has a total nickel (Ni) content; (c) adding a mineral acid to the Ni(IV)-containing mixture of step (b), where the mineral acid is added in an amount of about 0.60 moles or less per mole of total nickel; and (d) heating the mixture of step (c) for at least a period of time sufficient to form an additional amount of the Ni(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material, where the Ni(IV)-containing alkali-metal-deficient layered nickel oxide electrochemically active cathode material formed during steps (b) and (d) has the general formula A x H y Ni 1+a O2, where A includes an alkali metal; 0.08 ≤ x < 0.2, 0 ≤ y < 0.3, and 0.02 < a ≤ 0.2, or has the general formula A x H y Ni 1+a-z M z O2, where A includes an alkali metal; 0.08 ≤ x < 0.2; 0 ≤ y < 0.3; 0.02 ≤ a ≤ 0.2; M includes a transition metal or a main group metal, and 0 ≤ z ≤ 0.2.

[0049] As used herein, and unless otherwise specified, the "total nickel content" of a mixture containing Ni(IV) refers to the total amount of nickel present in the mixture, regardless of the oxidation state. The Ni(IV)-containing mixture of step (b) may contain Ni(III) in the form of unreacted starting material of the layered nickel oxide containing an alkali metal, A 1-a Ni 1+a O2 or A 1-a Ni 1+a-z M z O2, Ni(IV) in the form of oxidized alkali-metal-deficient layered nickel oxide, A x H y Ni 1+a O2 or A x H y Ni 1+a-z M zO2, and excess Ni (Ni2+) present in the alkali metal layer of any of the aforementioned starting materials in the form of Ni(II) or Ni(III). 2+ or layered nickel oxide (Ni) lacking alkali metals 2+ and Ni 3+ The total nickel content in step (b) corresponds to the total nickel content of the starting material in step (a) containing alkali metals in the layered nickel oxide, wherein in step (a), nickel exists in the nickel oxide layer as Ni(III) and in the interlayer alkali metal sites of the lattice as Ni. 2+ It exists in the form of.

[0050] The oxidizing agent may comprise persulfate, monopersulfate, or a combination thereof. The terms persulfate and persulfate are used interchangeably herein. In examples, the oxidizing agent comprises persulfate. In examples, the oxidizing agent comprises monopersulfate. In examples, the oxidizing agent comprises a combination of persulfate and monopersulfate. Persulfate and monopersulfate are generally water-soluble. As used herein, "water-soluble" means that at least about 10 mg of persulfate or monopersulfate is soluble in 1 ml of water at 25°C. Persulfate, monopersulfate, or both may comprise a counter cation selected from the group consisting of sodium, potassium, lithium, ammonium, or a combination thereof. In examples, the counter cation of the oxidizing agent comprises sodium ions. In examples, the counter cation of the oxidizing agent comprises potassium ions. In examples, the counter cation of the oxidizing agent comprises two different cations selected from the group consisting of ammonium, sodium, and potassium. In examples, the oxidizing agent is persulfate, and the counter cation is selected from the group consisting of ammonium, sodium, potassium, lithium, and a combination thereof. In the embodiments, the oxidizing agent is persulfate, and the countercation includes two different countercations selected from the group consisting of ammonium, sodium, and potassium. In the embodiments, the oxidizing agent is persulfate, and the countercation includes sodium. In the embodiments, the oxidizing agent is persulfate, and the countercation includes potassium. In the embodiments, the oxidizing agent is persulfate, and the countercation includes ammonium. In the embodiments, the oxidizing agent includes persulfate, and the persulfate is a combination of sodium persulfate and potassium persulfate.

[0051] In an embodiment, in step (a), the oxidant may be provided in an amount of about 0.25 mol to about 0.70 mol per mole of the alkali metal-containing layered nickel oxide, for example, in an amount of about 0.25 mol, about 0.30 mol, about 0.35 mol, about 0.40 mol, about 0.45 mol, about 0.50 mol, about 0.55 mol, about 0.60 mol, about 0.65 mol, or about 0.70 mol per mole of the alkali metal-containing layered nickel oxide. In an embodiment, in step (a), the oxidant may be provided in an amount between about 0.25 mol and about 0.60 mol per mole of the alkali metal-containing layered nickel oxide. In an embodiment, in step (a), the oxidant may be provided in an amount between about 0.25 mol and about 0.45 mol per mole of the alkali metal-containing layered nickel oxide. In an embodiment, in step (a), the layered nickel oxide containing alkali metal and the oxidant may be provided in the following molar ratio: about 1 mol of layered nickel oxide containing alkali metal : 0.25 mol of oxidant to about 1 mol of layered nickel oxide containing alkali metal : 0.70 mol of oxidant (also expressed as "1:0.25 to about 1:0.70"), for example about 1:0.25 to about 1:0.65, about 1:0.25 to about 1:60, about 1:0.25 to about 1:0.50, about 1:0.25 to about 1: 0.45, about 1:0.30 to about 1:0.70, about 1:0.30 to about 1:0.65, about 1:0.30 to about 1:0.55, about 1:0.30 to about 1:0.45, about 1:0.35 to about 1:0.70, about 1:0.35 to about 1:0.65, about 1:0.35 to about 1:0.60, about 1:0.35 to about 1:0.55, about 1:0.35 to about 1:0.50, about 1:0.35 to about 1:0.45 or about 1:0.35 to about 1:0.40.

[0052] Generally, without being bound by theory, it is believed that each persulfate secondary anion can form two sulfate radical anions. Furthermore, without being bound by theory, it is believed that each sulfate radical anion can accept one electron to form a sulfate secondary anion, and therefore each mole of persulfate can theoretically oxidize two moles of alkali metal-containing layered nickel oxide. Without being bound by theory, it is believed that when alkali metal-containing layered nickel oxide and persulfate as an oxidant react at a temperature of about 45°C to less than about 60°C, the maximum amount of Ni(III) oxidized to Ni(IV) is only about 50% of the total amount within a relatively short reaction time (i.e., less than about 4 hours), even when the oxidant is provided in amounts greater than 0.25 moles per mole of alkali metal-containing layered nickel oxide. Therefore, when the reaction is carried out at temperatures ranging from approximately 45°C to below 60°C, although increasing the amount of persulfate oxidant relative to the amount of alkali metal-containing layered nickel oxide can increase the apparent demetallization rate of alkali metal-containing layered nickel oxide, it is not expected that increasing the amount of persulfate oxidant relative to the amount of alkali metal-containing layered nickel oxide will proportionally increase the yield of Ni(IV)-containing alkali metal-deficient layered nickel oxide in the Ni(IV) mixture. Furthermore, not intending to be bound by theory, it is believed that when the amount of persulfate oxidant is increased to more than approximately 0.70 moles of oxidant per mole of alkali metal-containing layered nickel oxide (i.e., nearly 50% higher than the stoichiometric amount of 0.50 moles of oxidant), the increase in the demetallization rate is negligible relative to the rate when the amount of oxidant is approximately 0.50 moles of persulfate oxidant per mole of alkali metal-containing layered nickel oxide. Advantageously, the use of substoichiometric amounts of persulfate (i.e., less than 0.5 moles of persulfate per mole of nickel) minimizes the formation of sulfuric acid as a byproduct from the thermal decomposition of persulfate. Not intended to be bound by theory, it is believed that at reaction temperatures below approximately 60 °C, the decomposition of persulfate is kinetically slower than the electron transfer process of Ni(III) containing alkali metal layered nickel oxide.

[0053] On the other hand, not intended to be bound by theory, it is believed that when the amount of persulfate oxidant provided significantly exceeds the stoichiometric ratio theoretically required to completely oxidize Ni(III) in alkali metal-containing layered nickel oxide (e.g., provided in an amount greater than 1:1, e.g., about 1.3 moles or about 1.5 moles or more of persulfate oxidant per mole of alkali metal-containing layered nickel oxide), and when the persulfate oxidant and alkali metal-containing layered nickel oxide react at a temperature in the range of about 50°C to about 60°C, up to about 60% of Ni(III) in the alkali metal-containing layered nickel oxide can be converted to Ni(IV) to form alkali metal-deficient layered nickel oxide. Therefore, in embodiments, the persulfate oxidant may be provided in amounts of about 1 to 2 moles of oxidant, about 1.3 to 2 moles of oxidant, about 1.5 to 2 moles of oxidant, about 1 to 1.9 moles of oxidant, about 1.3 to 1.8 moles of oxidant, or about 1.4 to 1.7 moles of oxidant per mole of the alkali metal-containing layered nickel oxide. In embodiments, the persulfate oxidant may be provided in amounts of about 1.5 to 1.6 moles of oxidant per mole of the alkali metal-containing layered nickel oxide.

[0054] The fluid composition including the oxidant can be any fluid composition that allows the oxidant to react with layered nickel oxide containing an alkali metal. The fluid composition can be, for example, an aqueous solution, a suspension, a slurry, or other mixture of the oxidant with water and layered nickel oxide containing an alkali metal. Without intending to be theoretically constrained, it is believed that the solubility of the oxidant in the fluid composition affects the rate of the oxidative demetallization reaction and the thermal stability of the oxidant. Without intending to be theoretically constrained, it is believed that for oxidative demetallization to occur, at least a portion of the oxidant should be dissolved in the fluid composition, and that the rate of the oxidative demetallization reaction increases with increasing solubility of the oxidant in the fluid composition. In embodiments, the fluid composition includes water. In embodiments, the fluid composition is provided by an aqueous solution of the oxidant. In embodiments, the fluid composition is provided by a suspension of the oxidant, for example, where the oxidant is sparingly soluble or supersaturated. In embodiments, the fluid composition includes water, and the oxidant is soluble in water at a temperature of about 25°C. In embodiments, the fluid composition includes water, and the oxidant is soluble in water at a temperature of about 45°C and a temperature of about 50°C. In one embodiment, the fluid composition comprises water, and the oxidant is at least partially soluble in water at a temperature of about 25°C. In another embodiment, the fluid composition comprises water, and the oxidant is at least partially soluble in water at a temperature of about 45°C and about 50°C. In another embodiment, the fluid composition comprises water, and the persulfate comprises sodium persulfate. In another embodiment, the fluid composition comprises water, and the persulfate comprises ammonium persulfate. In another embodiment, the fluid composition comprises water, and the persulfate comprises potassium persulfate.

[0055] Generally, the order of operations for combining layered nickel oxide containing alkali metals and an oxidant is not limiting, as long as at least a portion of the oxidant dissolves in the fluid composition during the combination, thereby allowing oxidative demetallization to proceed. In one embodiment, layered nickel oxide containing alkali metals is added to the oxidant. In another embodiment, an oxidant is added to layered nickel oxide containing alkali metals. For example, solid layered nickel oxide containing alkali metals is added to a fluid composition containing an oxidant. In another example, a solid oxidant is added to a fluid composition containing solid layered nickel oxide containing alkali metals. In yet another example, a fluid composition containing an oxidant is added to a second fluid composition containing solid layered nickel oxide containing alkali metals. In any of the foregoing examples, the result of the addition is the combination of a solid layered nickel oxide containing alkali metals and a fluid composition containing at least a portion of a solubilized dissolved oxidant.

[0056] Typically, the initial pH of a fluid composition containing persulfate and / or monopersulfate is, for example, in the range of 8 to 12. When the oxidative demetallization of persulfate and monopersulfate is carried out at temperatures above about 45°C or 50°C, the pH of the fluid composition decreases to about 4 due to the thermal decomposition of the persulfate or monopersulfate. Therefore, in the embodiments, during step (b), the pH of the fluid composition is in the range of about 4 to 12, for example, about 4 to about 11, about 4 to about 10, or about 4 to about 9, about 9 to about 12, about 10 to about 12, or about 11 to about 12. Not intended to be theoretically rigorous, it is believed that although the pH of the fluid composition decreases during step (b) due to the decomposition of persulfate and the oxidation of water by sulfate to form sulfuric acid, the rate of thermal decomposition and oxidation of water is lower than the rate of oxidation of nickel (II) and nickel (III) in the nickel oxide material at temperatures below 60°C, therefore, the acid disproportionation of nickel has no significant effect in step (b). The pH of a fluid composition can be adjusted by including an alkali metal hydroxide or ammonium hydroxide in the composition. Therefore, in some embodiments, the fluid composition further includes an alkali metal hydroxide, ammonium hydroxide, or a combination thereof. In some embodiments, the fluid composition is substantially free of hydroxide salts. As used herein, and unless otherwise specified, a fluid composition is “substantially free of hydroxide salts” when no hydroxide salts are intentionally added to the fluid composition and the presence of any incidental hydroxide salts is less than about 5 wt.% of the total weight of the fluid composition.

[0057] Typically, the reaction in step (b) provides at least a portion of the alkali metal-containing layered nickel oxide for oxidative demetallization. In embodiments, in step (b), approximately 50% of the Ni(III) in the initial alkali metal-containing layered nickel oxide is oxidized to Ni(IV). In some embodiments, in step (b), a portion of the Ni(II) at the lithium sites in the initial non-stoichiometric alkali metal-containing layered nickel oxide is oxidized to Ni(III). Not intended to be theoretically rigorous, it is believed that the removal of alkali metals from alkali metal-containing layered nickel oxide to form Ni(IV)-containing alkali metal-deficient layered nickel oxide is limited by the rate of diffusion of alkali metal ions from the alkali metal-containing layered nickel oxide particles, resulting in a non-uniform, gradient distribution of residual alkali metal ions in the Ni(IV)-containing alkali metal-deficient layered nickel oxide particles, while exhibiting a higher level of depletion at the particle surface or shell region. Furthermore, not intended to be bound by theory, it is believed that the diffusion-limited demetallization of the layered nickel oxide containing alkali metals in step (b) effectively removes up to about 50% of the alkali metals without resulting in the formation of large amounts of soluble Ni. 2+ ion.

[0058] Typically, a mixture of an oxidant and alkali metal-containing layered nickel oxide can be heated to a temperature of about 45°C to less than about 60°C, for example, about 45°C to about 55°C, about 45°C to about 50°C, about 50°C to less than about 60°C, or about 50°C to about 55°C. In an example, the mixture of an oxidant and alkali metal-containing layered nickel oxide can be heated to a temperature of about 50°C to less than 60°C. In an example, the mixture of an oxidant and alkali metal-containing layered nickel oxide can be processed at a temperature of about 45°C to about 55°C. In an example, the mixture of an oxidant and alkali metal-containing layered nickel oxide can be heated at a temperature of about 50°C to about 55°C. In an example, the mixture of an oxidant and alkali metal-containing layered nickel oxide can be heated at a temperature of about 50°C. In an example, a mixture of alkali metal-containing layered nickel oxide, an oxidant, and a fluid composition is prepared, and then the mixture is heated. Typically, the dissolution of solid persulfate and monopersulfate is exothermic. Therefore, in the improved embodiment described above, the components of the mixture can be mixed at ambient temperature (about 23-25°C) and, if necessary, heated to the desired heating temperature at a rate of about 1°C per minute or about 2°C per minute, as described above.

[0059] Typically, the time sufficient to form a Ni(IV)-containing mixture is any time that allows at least about 25%, about 30%, about 35%, about 40%, about 45%, or about 50% of the alkali metal-containing layered nickel oxide to be converted to α-demetallized layered nickel oxide. Those skilled in the art can readily determine a suitable reaction time by monitoring the percentage conversion of the alkali metal-containing layered nickel oxide to α-demetallized layered nickel oxide. In embodiments, the time sufficient to form α-demetallized layered nickel oxide may depend on the temperature of the fluid composition. In embodiments, the time sufficient to form a Ni(IV)-containing mixture may be about 15 minutes to about 6 hours, for example, about 15 minutes to about 6 hours, about 15 minutes to about 5 hours, about 15 minutes to about 4 hours, about 20 minutes to about 4 hours, about 20 minutes to about 3 hours, about 30 minutes to about 2 hours, about 30 minutes to about 1 hour, about 15 minutes to about 45 minutes, about 1 hour to about 5 hours, or about 2 hours to about 4 hours. Not intended to be theoretically construed, in embodiments in which a mixture of layered nickel oxide containing an alkali metal, an oxidant, and a fluid composition is mixed at ambient temperature (e.g., about 23-25°C) and heated at a rate of about 1°C to about 2°C to a temperature in the range of about 45°C to less than about 60°C, it is believed that about 30% to about 40% of the Ni(III) in the layered nickel oxide containing the alkali metal is converted to Ni(IV) within about 30 minutes. Furthermore, not intended to be theoretically construed, in embodiments in which the heating temperature is in the range of about 45°C to less than about 60°C, it is believed that substantially all of the Ni(III) that can be oxidized to Ni(IV) by an oxidative demetallization reaction is oxidized to Ni(IV) within the first six hours and only a negligible additional amount of Ni(III) is oxidized to Ni(IV) after six hours. In embodiments, the mixture of layered nickel oxide containing an alkali metal and an oxidant can be heated at a temperature of about 45°C to about 55°C for about 2 to 6 hours. In one embodiment, the mixture of layered nickel oxide containing alkali metal and an oxidant can be heated at a temperature of about 50°C to about 60°C for about 2 to 4 hours. In another embodiment, the mixture of layered nickel oxide containing alkali metal and an oxidant can be heated at a temperature of about 50°C for about 3 hours.

[0060] Advantageously, the Ni(IV)-containing mixture obtained by oxidative delithiation in step (b) is substantially free of soluble Ni. 2+ Ions. As used herein, and unless otherwise stated, "substantially free of soluble Ni". 2+ "Ion" refers to a mixture containing Ni(IV) containing less than 5 wt.% soluble Ni. 2+ Ions, less than 3 wt.% soluble Ni 2+ Ions and / or less than 1 wt.% soluble Ni 2+The ions, dissolved in solvents containing Ni(IV) mixtures, are as determined using UV-Vis spectroscopy and appropriate calibration curves. Soluble Ni 2+ The ions differ from the alkali metal sites that can be contained in the lattices of alkali metal-containing layered nickel oxide and alkali metal-deficient layered nickel oxide containing Ni(IV). 2+ Ions. Soluble Ni in mixtures containing Ni(IV) 2+ The amount of ions can be determined using UV-Vis spectroscopy, and the Beer-Lambert law can be used to estimate the amount of Ni dissolved in the solution. 2+ The concentration of ions.

[0061] In embodiments, steps (a) and (b) may optionally be repeated a second or another time before step (c). In an improved embodiment of the foregoing, a second aliquot of the fluid composition containing the oxidant may be added to the Ni(IV)-containing mixture of step (b), and the heating of step (b) may be repeated. Optionally, at least a portion of the fluid composition may be removed from the Ni(IV)-containing mixture of step (b) before adding the second aliquot of the fluid composition containing the oxidant to the Ni(IV)-containing mixture of step (b) and repeating the heating of step (b). In embodiments, the Ni(IV)-containing mixture of step (b) may be separated from the fluid composition and washed with water before adding the second aliquot of the fluid composition containing the oxidant to the Ni(IV)-containing mixture of step (b) and repeating the heating of step (b). Not intended to be bound by theory, it is believed that Li + The diffusion of ions from layered nickel oxide containing alkali metals can be facilitated by the presence of Li in the fluid composition. + The presence of ions inhibits this. Therefore, by adding additional aliquots of the fluid composition containing an oxidant, the Li in the fluid composition is reduced. + The relative concentration of ions decreases, promoting Li + Ions further diffuse out layered nickel oxide containing alkali metals. Additionally, by removing at least a portion of the fluid composition before adding a second or another aliquot of the fluid composition containing the oxidant, the Li in the fluid composition... + The relative concentration of ions can even be further reduced, promoting the formation of additional Li groups. + Ions diffuse out from the layered nickel oxide containing alkali metal. In embodiments in which steps (a) and (b) are repeated, the conditions for the second and further implementations of steps (a) and (b) may be the same as those for steps (a) and (b) disclosed above.

[0062] In embodiments, the method of this disclosure can be carried out in a single reaction vessel. Therefore, in embodiments, when the mineral acid and the Ni(IV)-containing mixture are added together in step (c), residual, unreacted persulfate or monopersulfate may be present in the Ni(IV)-containing mixture from step (b). In embodiments where residual persulfate and / or monopersulfate is present when the mineral acid and the Ni(IV)-containing mixture are added together, the residual persulfate and / or monopersulfate will decompose, leading to water oxidation and the formation of additional sulfuric acid. In embodiments, the method of this disclosure can be carried out in one or more reaction vessels. In embodiments, the Ni(IV)-containing mixture can be separated from the fluid composition and optionally washed with water before adding the mineral acid and the Ni(IV)-containing mixture together. Generally, the order of addition of the Ni(IV)-containing mixture and the mineral acid is non-limiting. In embodiments, the mineral acid is added to the Ni(IV)-containing mixture. In embodiments, the Ni(IV)-containing mixture is added to the mineral acid.

[0063] Typically, the mineral acid in step (c) can be any strong mineral acid that promotes the disproportionation reaction of layered nickel oxide containing alkali metals. In embodiments, strong mineral acids include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, perchloric acid, hydroiodic acid, or combinations thereof. In embodiments, mineral acids include sulfuric acid, nitric acid, hydrochloric acid, or combinations thereof. In embodiments, mineral acids include sulfuric acid. Not intended to be theoretically constrained, it is believed that mineral acids promote the diffusion of alkali metal ions from the center or core region of nickel oxide particles by increasing the porosity (i.e., average pore size). Specifically, it is believed that when Ni(III) disproportionates during Ni(III) disproportionation... 2+ When ions dissolve from the nickel oxide lattice, the increased porosity of the nickel oxide lattice can increase the rate at which alkali metal ions diffuse out of the lattice.

[0064] Typically, mineral acid can be added in any amount that allows at least about 10%, at least about 15%, at least about 20%, at least about 25%, or at least 50% of the remaining Ni(III)-containing alkali metal-containing layered nickel oxide to be converted to α-demetallized layered nickel oxide. As used herein, and unless otherwise stated, the terms “Ni(IV)-containing alkali metal-deficient layered nickel oxide,” “α-demetallized layered nickel oxide,” and “alkali metal-deficient layered nickel oxide” are used interchangeably. Those skilled in the art can readily determine the appropriate amount of mineral acid by monitoring the percentage conversion of (remaining) alkali metal-containing layered nickel oxide to α-demetallized layered nickel oxide. Mineral acid promotes the acid-induced disproportionation of alkali metal-containing layered nickel oxide. Any unoxidized alkali metal-containing layered nickel oxide remaining after the initial reaction with persulfate and / or monopersulfate oxidants can disproportionately convert to Ni(IV)-containing alkali metal-deficient layered nickel oxide and soluble Ni 2+ Ions. In an embodiment, about 50% of the Ni(III) in the layered nickel oxide containing alkali metal is converted to Ni(IV) during the oxidative demetallization step (b), and about 50% of the remaining Ni(III) is converted to Ni(IV) during the acid disproportionation step (d), thereby advantageously achieving a total conversion of about 75%. In an embodiment, the mineral acid is provided in amounts of about 0.40 to about 0.55 moles of mineral acid per mole containing the total nickel in the Ni(IV) mixture, for example, about 0.40 to about 0.55, about 0.45 to about 0.55, about 0.50 to about 0.55, about 0.40 to about 0.45, and about 0.45 to about 0.50 moles of mineral acid per mole containing the total nickel in the Ni(IV) mixture. In an embodiment, the mineral acid is provided in an amount of about 0.40 to about 0.55 moles of mineral acid per mole containing the total nickel in the Ni(IV) mixture. In one embodiment, the mineral acid is provided in an amount of about 0.40 to about 0.50 moles of mineral acid per mole containing the total nickel in the Ni(IV) mixture. In another embodiment, the mineral acid is provided in an amount of about 0.45 to about 0.50 moles of mineral acid per mole containing the total nickel in the Ni(IV) mixture.

[0065] In embodiments where a significant excess of persulfate and / or monopersulfate is used in the oxidative demetallization of layered nickel oxide containing alkali metals in step (b), a reduced amount of mineral acid may be used in step (c). In such embodiments, the amount of mineral acid in step (c) may range from about 0.20 moles of mineral acid to about 0.40 moles of mineral acid per mole of total nickel in a mixture containing Ni(IV), for example, from about 0.25 moles to about 0.35 moles or about 0.30 moles of mineral acid per mole of total nickel in a mixture containing Ni(IV).

[0066] By monitoring the percentage conversion of Ni(III)-containing alkali metal-containing layered nickel oxide to α-demetallized layered nickel oxide, those skilled in the art can readily determine the appropriate reaction time between the mineral acid and the (remaining) Ni(III)-containing alkali metal-containing layered nickel oxide. The percentage conversion of alkali metal-containing layered nickel oxide to α-demetallized layered nickel oxide can be monitored by measuring the average nickel oxidation state, measuring the amount of residual alkali metal by ICP-AES, and / or preparing an alkaline battery cell containing α-demetallized layered nickel oxide as the cathode active material and testing the capacity of the battery cell using any suitable method known in the art. Typically, the time sufficient to form the additional Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material can be from about 1 hour to about 6 hours, for example, from about 1 hour to about 5.5 hours, from about 1 hour to about 5 hours, from about 2 hours to about 4 hours, or about 3 hours. In an embodiment, the time sufficient to form an additional amount of the additional Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material can be from about 1 hour to about 6 hours. In an embodiment, the time sufficient to form an additional amount of the Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material can be from about 2 hours to about 4 hours. In an embodiment, the time sufficient to form an additional amount of the Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material can be from about 3 hours. Not intended to be theoretically rigorous, it is believed that during acid disproportionation, substantially all remaining Ni(III) that could be oxidized to Ni(IV) is converted to Ni(IV) within six hours, and after six hours only a negligible amount of Ni(III) is oxidized to Ni(IV). Furthermore, not intended to be theoretically rigorous, it is believed that when the time sufficient to form an additional alkali metal-deficient layered nickel oxide exceeds 6 hours, the Ni(IV)-containing α-demetallized layered nickel oxide formed during both the oxidative demetallization step (b) and the acid disproportionation step (d) will undergo reductive dissolution to form soluble Ni. 2+ This reduces the overall yield of α-demetallized layered nickel oxide.

[0067] Typically, mixtures of mineral acids and ni(IV)-containing compounds can be heated to approximately 60°C to approximately 80°C, for example, approximately 60°C to approximately 80°C, approximately 60°C to approximately 75°C, approximately 60°C to approximately 70°C, approximately 65°C to approximately 75°C, approximately 68°C to approximately 72°C, approximately 60°C, approximately 65°C, approximately 70°C, approximately 75°C, or approximately 80°C. Not intended to be theoretically constrained, it is believed that when the temperature of a ni(IV)-containing compound undergoing acid disproportionation increases above approximately 70°C, soluble ni is formed. 2+The reductive dissolution of Ni(IV) ions increases. In an example, the mixture of mineral acid and Ni(IV)-containing compound can be heated to a temperature of about 60°C to about 70°C. In an example, the mixture can be heated to a temperature of about 70°C. In an example, the mixture of mineral acid and Ni(IV)-containing compound can be heated to about 60°C to about 70°C for about 2 to 4 hours. In an example, the mixture of mineral acid and Ni(IV)-containing compound can be heated to about 65°C to about 75°C for about 2 to 4 hours. In an example, the mixture of mineral acid and Ni(IV)-containing compound can be heated to about 70°C for about 3 hours.

[0068] In the embodiments, after both steps (b) and (d), the α-demetallized layered nickel oxide electrochemically active cathode material is formed with a product yield greater than about 50 wt.% based on the weight of the initial layered nickel oxide containing alkali metal, for example, in the range of greater than about 50 wt.% to about 95%, about 50 wt.% to about 90%, about 50 wt.% to about 85%, about 55% to about 80%, about 60% to about 80%, about 60% to about 75%, about 65% to about 80%, about 65% to about 75%, or about 70% to about 80%. In the embodiments, after both steps (b) and (d), the α-demetallized layered nickel oxide electrochemically active cathode material is formed with a product yield greater than about 55 wt.% based on the weight of the initial layered nickel oxide containing alkali metal. In the embodiments, the α-demetallized layered nickel oxide electrochemically active cathode material is formed with a product yield greater than about 60 wt.% based on the weight of the initial layered nickel oxide containing alkali metal. In the embodiments, after both steps (b) and (d), the α-demetallized layered nickel oxide electrochemically active cathode material is formed with a product yield of more than about 70 wt.% based on the weight of the initial layered nickel oxide containing alkali metal. In the embodiments, after both steps (b) and (d), the α-demetallized layered nickel oxide electrochemically active cathode material is formed with a product yield of more than about 70 wt.% to about 80 wt.% based on the weight of the initial layered nickel oxide containing alkali metal. In the embodiments, after both steps (b) and (d), the α-demetallized layered nickel oxide electrochemically active cathode material is formed with a product yield of more than about 75 wt.% based on the weight of the initial layered nickel oxide containing alkali metal.

[0069] In an embodiment, the method of this disclosure includes the following: (a) having formula A 1-a Ni 1+aThe non-stoichiometric alkali metal-containing layered nickel oxide of O2 is combined with a fluid composition comprising water and sodium persulfate to form a mixture, wherein A comprises lithium and 0 < a ≤ 0.2, and wherein the sodium persulfate is provided in an amount of from about 0.25 to about 0.45 moles per mole of the alkali metal-containing layered nickel oxide; (b) heating the mixture at about 45°C to about 55°C for about 2 to about 4 hours to form a Ni(IV)-containing mixture, the Ni(IV)-containing mixture comprising a Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material, and the Ni(IV)-containing mixture having a total nickel (Ni) content; (c) adding a mineral acid comprising sulfuric acid to the Ni(IV)-containing mixture of step (b), wherein the mineral acid is added in an amount of from about 0.40 to about 0.55 moles per mole of total nickel; and (d) heating the mixture of step (c) at a temperature of about 65°C to about 75°C for about 2 to about 4 hours to form an additional amount of the Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material, wherein the Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material formed during steps (b) and (d) has the general formula A x H y Ni 1+a O2, wherein A comprises an alkali metal, 0.08 ≤ x < 0.2, 0 ≤ y < 0.3, and 0.02 < a ≤ 0.2.

[0070] The present disclosure further provides a method for preparing an electrochemically active cathode material, the method comprising the steps of: (i) reacting an alkali metal-containing layered nickel oxide having the formula A 1-a Ni 1+a O2 with a chemical oxidant in a fluid composition at a high temperature for at least a period of time sufficient to form a Ni(IV)-containing mixture, wherein A comprises an alkali metal and 0 < a ≤ 0.2, the chemical oxidant comprises persulfate, monopersulfate or a combination thereof, the Ni(IV)-containing mixture comprises a Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material, and the Ni(IV)-containing mixture has a total nickel (Ni) content; and (ii) reacting the Ni(IV)-containing mixture of step (i) with a mineral acid at a high temperature for at least a period of time sufficient to form an additional amount of the Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material, wherein the mineral acid is added in an amount of about 0.60 moles or less per mole of total nickel; the Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material formed during steps (i) and (ii) has the general formula A x H y Ni 1+aO2, where A includes an alkali metal; 0.08 ≤ x < 0.2; 0 ≤ y < 0.3; and 0.02 < a ≤ 0.2.

[0071] Generally, the layered nickel oxide containing an alkali metal, chemical oxidant, and fluid composition in step (i) can be any layered nickel oxide containing an alkali metal, chemical oxidant, and fluid composition described herein. Generally, the high temperature in step (i) can be any temperature disclosed herein for step (b) of the method disclosed herein. Generally, the period of time sufficient to form a mixture containing Ni(IV) in step (i) can be any period of time sufficient to form the mixture containing Ni(IV) disclosed herein for step (b) of the method disclosed herein.

[0072] Generally, the mineral acid in step (ii) can be any mineral acid disclosed herein. Generally, the high temperature in step (ii) can be any temperature disclosed herein for step (d) of the method disclosed herein. Generally, the period of time sufficient to form a mixture containing Ni(IV) in step (ii) can be any period of time sufficient to form the mixture containing Ni(IV) disclosed herein for step (d) of the method disclosed herein.

[0073] Generally, for formula A x H y Ni 1+a O2, A can be any suitable alkali metal disclosed herein, x can be any suitable value disclosed herein; y can be any suitable value disclosed herein; and a can be any suitable value disclosed herein.

[0074] The method disclosed herein can further comprise treating α - demetallated nickel oxide with an aqueous solution of an alkali metal hydroxide to form a stable β - demetallated layered nickel oxide, the demetallated layered nickel oxide having a second different alkali metal inserted into its layers, according to formula A x A' v Ni 1+a O2·nH2O, where A comprises Li or Na; A' comprises K, Cs or Rb; 0.04 ≤ x < 0.2; 0.03 < v < 0.20; 0.02 < a ≤ 0.2; and 0 < n < 2. In an embodiment, the α - demetallated layered nickel oxide can be doped with a metal M such that the resulting β - demetallated layered nickel oxide has the formula A x A’ v Ni 1+a-z M z O2·nH2O, where A includes Li or Na, 0 < x ≤ 0.2, A' includes K, Cs or Rb, 0.03 < v < 0.20, M includes a transition metal or main group metal, 0 ≤ z ≤ 0.2, 0.02 < a ≤ 0.2, and 0 < n < 2.

[0075] Typically, A can be Li or Na. In an embodiment, A comprises Li. Typically, A' can be K, Rb or Cs, and A' and A are different. In an embodiment, A' comprises K. In an embodiment, A' comprises Rb, or Cs or a combination thereof. In an embodiment, A comprises Li and A' comprises K. In an embodiment, x can range from 0.04 to 0.2, for example, 0.04 to 0.18, 0.04 to 0.16, 0.04 to 0.15, 0.08 to 0.2, for example 0.08 to 0.18, 0.08 to 0.16, 0.08 to 0.15, 0.09 to 0.20, 0.09 to 0.19, 0.09 to 0.15, 0.09 to 0.12, 0.10 to 0.19 or 0.10 to 0.15. In an embodiment, v can range from 0.03 to 0.20, for example, 0.03 to 0.17, 0.03 to 0.15, 0.03 to 0.13, 0.06 to 0.20, 0.06 to 0.17, 0.06 to 0.15, 0.06 to 0.13, 0.08 to 0.17, 0.08 to 0.15 or 0.08 to 0.13. In an embodiment, a can range from 0.02 ≤ a ≤ 0.20, for example, 0.02 to 0.18, 0.02 to 0.16, 0.03 to 0.20, 0.03 to 0.17, 0.03 to 0.15, 0.04 to 0.20, 0.04 to 0.17, 0.04 to 0.15, 0.04 to 0.13 or 0.04 to 0.11. In an embodiment, n can range from 0 < n < 2, for example, about 0.01 to about 1.9, about 0.02 to about 1.8, about 0.05 to about 1.8, about 0.05 to about 1.5, about 0.05 to about 1.25, about 0.05 to about 1.0, about 0.1 to about 1.8, about 0.1 to about 1.5, about 0.1 to about 1.25, about 0.1 to about 1.0, about 0.15 to about 1.8, about 0.15 to about 1.5, about 0.15 to about 1.25, about 0.15 to about 1, about 0.15 to about 0.8, about 0.15 to about 0.75, about 0.15 to about 0.7 or about 0.15 to about 0.6. In an embodiment, the value of z can range from 0 ≤ z ≤ 0.2 or 0 < z ≤ 0.2, for example 0 to 0.20, 0.01 to 0.20, 0.01 to 0.18, 0.01 to 0.16, 0.01 to 0.15, 0.02 to 0.20, 0.02 to 0.18, 0.02 to 0.16, 0.02 to 0.15, 0.03 to 0.20, 0.03 to 0.19, 0.03 to 0.15, 0.03 to 0.12, 0.05 to 0.19 or 0.05 to 0.15.

[0076] The aqueous solution of the alkaline hydroxide is not specifically limited and may be selected from potassium salt solutions, rubidium salt solutions, cesium salt solutions, or any combination thereof. The concentration of the alkali metal salt in the alkaline solution may be any concentration sufficient to achieve substantially complete conversion of α-demetallized layered nickel oxide to β-demetallized layered nickel oxide. As used herein, and unless otherwise stated, “substantially complete conversion” means the conversion of α-demetallized layered nickel oxide to β-demetallized layered nickel oxide, wherein the residual α-demetallized layered nickel oxide is present in an amount of 5 wt.% or less based on the total weight of the nickel oxide material. In some embodiments, the concentration of the alkali metal hydroxide in the solution may range from about 0.5 M to about 10 M, about 1 M to about 10 M, about 3 M to about 9 M, or about 5 M to about 8.75 M. In some embodiments, the alkali metal hydroxide solution comprises at least one or a combination of potassium hydroxide, cesium hydroxide, and rubidium hydroxide provided at a concentration of about 0.5 M to about 10 M. When combined with the alkali metal hydroxide solution, the α-demetallized layered nickel oxide may be provided in the form of a free-flowing powder. The α-demetallized layered nickel oxide powder and the alkali metal hydroxide solution can be combined in a weight ratio of about 10:1 to about 1:5, about 9:1 to about 1:4, about 8:1 to about 1:3, about 7:1 to about 1:2, about 6:1 to about 1:2, about 5:1 to about 1:2, or about 4:1 to about 1:2, or about 3:1 to about 1:1, for example, about 3:1, about 2:1, or about 1:1.

[0077] α-Demetallized layered nickel oxide can be treated with an alkali metal hydroxide solution for a sufficient period of time to ensure complete conversion to β-demetallized layered nickel oxide. The α-demetallized layered nickel oxide and the alkali metal hydroxide solution can initially be stirred at ambient temperature for 5 to 15 minutes to ensure thorough mixing and wetting. After mixing the α-demetallized layered nickel oxide and the alkali metal hydroxide solution, the mixture is maintained at ambient temperature for 2 to 24 hours. Optionally, the mixture can be stirred during this 2 to 24-hour period. After 2 to 24 hours, the resulting β-demetallized layered nickel oxide can optionally be washed with water to remove any residual alkali metal hydroxide. Analysis of the powder X-ray diffraction pattern of the resulting material confirms that the conversion to β-demetallized layered nickel oxide is substantially complete. For example, α-delithiated layered nickel oxide exhibits a characteristic powder X-ray diffraction pattern different from that of β-delithiated layered nickel oxide. For α-delithiated layered nickel oxide treated with potassium hydroxide solution, as potassium ions and water molecules from the potassium hydroxide solution insert into the α-delithiated layered nickel oxide layer, the intensity of the diffraction peaks at approximately 18° to 20°2θ in the X-ray diffraction pattern of α-delithiated layered nickel oxide decreases, and very broad peaks appear at approximately 14.9° to approximately 16.0°2θ and approximately 21.3° to approximately 22.7°2θ in the X-ray diffraction pattern of β-delithiated layered nickel oxide. Therefore, upon complete conversion to β-delithiated layered nickel oxide, the powder X-ray diffraction pattern will have broad diffraction peaks at approximately 10.8° to approximately 12.0°2θ and approximately 14.9° to approximately 16.0°2θ, and the peaks at approximately 21.3° to approximately 22.7°2θ will have greater intensity than those in the powder X-ray diffraction pattern of the α-delithiated layered nickel oxide precursor, and no diffraction peaks with significant intensity will appear in the range of approximately 18° to 20°2θ. The obtained β-demetallized layered nickel oxide can be repeatedly washed with deionized water until the pH of the resulting filtrate is approximately 10. The solid powder can then be collected and air-dried at approximately 70°C for a period of approximately 12 to 20 hours.

[0078] In an embodiment, α-demetallized layered nickel oxide is treated with an aqueous solution of an alkali metal hydroxide, wherein the alkali metal is different from the alkali metal in the α-demetallized layered nickel oxide, to form γ-nitroglycerin oxide (γ-NiOOH) as a byproduct, which is less than about 10% by weight based on the total weight of the reaction products. For example, it is less than about 8%, less than about 6%, less than about 5%, less than about 4%, less than about 3%, less than about 2%, or less than about 1% based on the total weight of the solid reaction products. In an embodiment, treatment of α-demetallized layered nickel oxide with an aqueous solution of an alkali metal hydroxide can form less than about 6% by weight of γ-nitroglycerin oxide (γ-NiOOH) as a reaction byproduct.

[0079] Advantageously, the method of this disclosure provides α-demetallized layered nickel oxide with a relatively larger particle size than existing methods, which can further be used to prepare β-demetallized layered nickel oxide with a relatively larger particle size than β-demetallized layered nickel oxide particles formed from α-demetallized layered nickel oxide using conventional methods. Not intended to be theoretically rigorous, it is believed that the particle size of the layered nickel oxide material remains substantially unchanged between the α and β forms. As used herein, and unless otherwise stated, if the average particle size of the β-demetallized layered nickel oxide is within about 10% of the average particle size of the α-demetallized layered nickel oxide, the particle size “remains substantially unchanged” between the α and β forms. Not intended to be theoretically rigorous, it is believed that the performance of batteries containing β-demetallized layered nickel oxide decreases as the particle size of the β-demetallized layered nickel oxide decreases. Specifically, not intended to be theoretically rigorous, it is believed that under closed battery conditions, β-demetallized layered nickel oxide can undergo reactions with conductive carbon particles in the cathode and electrolyte, which may result in lower-than-expected high-rate discharge performance of the battery cell. However, as the particle size of β-demetallized layered nickel oxide increases, its overall surface area decreases, reducing the number of potential contact points with carbon particles and lowering the likelihood of oxidation reactions between carbon particles and β-demetallized layered nickel oxide particles. Oxidation of the carbon particle surface reduces its conductivity, leading to increased cathode resistance and consequently decreasing the high-rate performance of the battery cell.

[0080] Battery

[0081] Electrochemical battery cells or batteries can be primary or secondary. A primary battery is defined as one that is discharged only once, for example, to deplete, and then discarded. A primary battery is described, for example, in David Linden's *Handbook of Batteries* (4th edition, 2011). A secondary battery is intended for recharging. A secondary battery can be discharged and recharged multiple times, for example, more than fifty, one hundred, or more times. A secondary battery is described, for example, in David Linden's *Handbook of Batteries* (4th edition, 2011). Therefore, batteries can contain a variety of electrochemical couples and electrolyte combinations. Although the descriptions and examples provided herein are generally directed to primary alkaline electrochemical battery cells or batteries, it should be understood that the invention applies to both primary and secondary batteries having aqueous, non-aqueous, ionic liquid, and solid electrolyte systems. Primary and secondary batteries containing the aforementioned electrolytes are therefore within the scope of this application, and the invention is not limited to any specific embodiment.

[0082] refer to Figure 1This diagram illustrates a primary alkaline electrochemical battery cell or battery 10, comprising a cathode 12, an anode 14, a separator 16, and a casing 18. Battery 10 also includes a current collector 20, a seal 22, and an end cap 24. The end cap 24 serves as the negative terminal of battery 10. A positive tip 26 is located at the end of battery 10 opposite to the end cap 24. The positive tip 26 can serve as the positive terminal of battery 10. The electrolyte is dispersed throughout battery 10. The cathode 12, anode 14, separator 16, electrolyte, current collector 20, and seal 22 are contained within the casing 18. Battery 10 can be, for example, an alkaline battery of AA, AAA, AAAA, C, or D size.

[0083] The housing 18 can be any conventional type of housing commonly used in primary alkaline batteries and can be made of any suitable substrate, such as cold-rolled steel or nickel-plated cold-rolled steel. The housing 18 can have a cylindrical shape. The housing 18 can have any other suitable non-cylindrical shape. The housing 18 can, for example, have a shape comprising at least two parallel plates, such as a rectangular, square, or prismatic shape. The housing 18 can, for example, be deep-drawn from a substrate sheet such as cold-rolled steel or nickel-plated steel. The housing 18 can, for example, be drawn into a cylindrical shape. The housing 18 can have at least one open end. The housing 18 can have a closed end and an open end, with a sidewall between them. The inner surface of the sidewall of the housing 18 can be treated with a material that provides low contact resistance between the inner surface of the sidewall of the housing 18 and an electrode such as the cathode 12. The inner surface of the sidewall of the housing 18 can be plated with, for example, nickel, cobalt, and / or sprayed with a carbon-loaded coating to reduce, for example, the contact resistance between the inner surface of the sidewall of the housing 18 and the cathode 12.

[0084] Cathode 12 comprises at least one electrochemically active cathode material. The electrochemically active cathode material may comprise α-demetallized layered nickel oxide and / or non-stoichiometric β-delithiation layered nickel oxide prepared according to the methods of this disclosure. In embodiments, when non-stoichiometric β-delithiation layered nickel oxide is provided as the electrochemically active cathode material, the non-stoichiometric β-delithiation layered nickel oxide comprises less than 5 wt.%, less than 3 wt.%, less than 1 wt.%, or less than 0.5 wt.% of residual non-stoichiometric α-delithiation layered nickel oxide based on the total weight of the delithiation layered nickel oxide electrochemically active cathode material. Further, based on the total weight of the delithiation layered nickel oxide electrochemically active cathode material, the non-stoichiometric β-delithiation layered nickel oxide may comprise less than about 10 wt%, less than about 8 wt%, less than about 6 wt%, less than about 4 wt%, less than about 3 wt%, less than about 2 wt%, and / or less than about 1 wt% of γ-hydroxyl nickel oxide (as a byproduct). Similarly, the battery cell containing non-stoichiometric β-delithiated layered nickel oxide, as described herein, is configured from scratch with non-stoichiometric β-delithiated layered nickel oxide.

[0085] Cathode 12 may also include at least one or more other electrochemically active cathode materials. Other electrochemically active cathode materials may include manganese oxide, manganese dioxide, electrolytic manganese dioxide (EMD), chemically active manganese dioxide (CMD), high-power electrolytic manganese dioxide (HP EMD), λ manganese dioxide, γ manganese dioxide, orthorhombic manganese oxide, and any combination thereof. Other electrochemically active cathode materials include, but are not limited to, silver oxide; nickel oxide, nickel hydroxyoxide; copper oxide; silver copper oxide; silver nickel oxide; bismuth oxide; silver bismuth oxide; oxygen; and any combination thereof. Nickel hydroxyoxide may include β-nickel hydroxyoxide, γ-nickel hydroxyoxide, β-nickel hydroxyoxide and / or symbionts of γ-nickel hydroxyoxide, and cobalt hydroxyoxide-coated β-nickel hydroxyoxide. Cobalt hydroxyoxide-coated nickel hydroxyoxide may include cobalt hydroxyoxide-coated β-nickel hydroxyoxide, cobalt hydroxyoxide-coated γ-nickel hydroxyoxide, and / or β-nickel hydroxyoxide and γ-nickel hydroxyoxide-cobalt hydroxyoxide-coated symbionts.

[0086] In the embodiments, the electrochemically active material of the cathode 12 comprises at least 5 wt.%, at least 10 wt.%, at least 15 wt.%, at least 20 wt.%, at least 25 wt.%, at least 30 wt.%, at least 35 wt.%, at least 40 wt.%, at least 45 wt.%, at least 50 wt.%, at least 55 wt.%, at least 60 wt.%, at least about 70 wt.%, or at least about 75 wt.% of non-stoichiometric β-delithiation layered nickel oxide, for example, in the range of about 5 wt.% to about 95 wt.%, about 10 wt.% to about 90 wt.%, about 10 wt.% to about 80 wt.%, about 20 wt.% to about 70 wt.%, about 30 wt.% to about 60 wt.%, 40 wt.% to about 60 wt.%, or about 50 wt.% based on the total weight of the electrochemically active cathode material. In an embodiment, the electrochemically active material of cathode 12 comprises about 40 wt.% to about 60 wt.% of non-stoichiometric β-delithiated nickel oxide based on the total weight of the electrochemically active cathode material, and about 60 wt.% to about 40 wt.% of manganese oxide, manganese dioxide, electrolytic manganese dioxide (EMD), chemical manganese dioxide (CMD), high-power electrolytic manganese dioxide (HP EMD), λ manganese dioxide, or γ manganese dioxide based on the total weight of the electrochemically active cathode material. It has been found that a combination of about 5 wt.% to about 60 wt.% or about 10 wt.% to about 60 wt.%, for example 10 wt.%, 20 wt.%, 30 wt.%, 40 wt.%, or 50 wt.% of non-stoichiometric β-delithiated layered nickel oxide with the remainder of the electrochemically active cathode material including electrolytic manganese dioxide (EMD) provides unexpectedly favorable battery performance in both high-rate discharge and low-rate discharge applications.

[0087] The cathode 12 may contain conductive additives (such as carbon) and optionally a binder. The cathode 12 may also contain other additives. Carbon can increase the conductivity of the cathode 12 by promoting electron transport within the solid structure of the cathode 12. The carbon can be graphite, such as natural graphite, synthetic graphite, antioxidant graphite, graphene, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon fibers, carbon nanofibers, carbon nanoribbons, carbon nanosheets, and mixtures thereof. Preferably, the amount of carbon in the cathode is relatively low, for example less than about 12%, less than about 10%, less than about 9%, less than about 8%, less than about 6%, less than about 5%, less than about 3.75%, or even less than about 3.5%, for example, from about 3.0 wt% to about 5 wt% or from about 2.0 wt% to about 3.5 wt%. A lower carbon content allows for a higher loading of electrochemically active cathode material within the cathode 12 without increasing the volume of the cathode 12 or reducing the void volume. Suitable graphite for use within the battery (e.g., within the cathode) can be, for example, Timrex MX-15, SFG-15, and MX-25, all available from Imerys Graphite and Carbon (Bodio, Switzerland). For highly reactive cathode active materials such as non-stoichiometric β-delithiated layered nickel oxide, antioxidant graphite such as SFG-15, SFG-10, and SFG-6 can be used.

[0088] Cathode 12 may contain an optional binder. As used herein, “binder” refers to a polymeric material that provides cohesion within the cathode and does not contain graphite. Examples of optional binders that may be used in cathode 12 include polyethylene, polyacrylic acid, or fluorocarbon resins such as PVDF or PTFE. Optional binders used within cathode 12 may be, for example, COATHYLENE HA-1681, available from DuPont de Nemours and Company (Wilmington, DE, USA). Examples of other cathode additives are described, for example, in U.S. Patents 5,698,315, 5,919,598, 5,997,775, and 7,351,499. In some embodiments, cathode 12 is substantially binder-free. As used herein, “substantially binder-free” means that the cathode contains less than about 5 wt.%, less than about 3 wt.%, or less than about 1 wt.% binder.

[0089] The content of electrochemically active cathode material within cathode 12 can be referred to as cathode load. The load of cathode 12 can vary depending on the electrochemically active cathode material used within battery 10 and the battery size. For example, the cathode load of an AA battery having β-delithiated layered nickel oxide as the electrochemically active cathode material can be at least about 6 grams of β-delithiated layered nickel oxide. The cathode load can be, for example, at least about 7 grams of non-stoichiometric β-delithiated layered nickel oxide. The cathode load can be, for example, about 7.2 grams to about 11.5 grams of non-stoichiometric β-delithiated layered nickel oxide. The cathode load can be about 8 grams to about 10 grams of non-stoichiometric β-delithiated layered nickel oxide. The cathode load can be about 8.5 grams to about 9.5 grams of non-stoichiometric β-delithiated layered nickel oxide. The cathode load can be about 9.5 grams to about 11.5 grams of non-stoichiometric β-delithiated layered nickel oxide. The cathode load can be about 10.4 grams to about 11.5 grams of non-stoichiometric β-delithiated layered nickel oxide. For AAA batteries, the cathode loading can be at least about 3 grams of nonstoichiometric β-delithiated layered nickel oxide electrochemically active cathode material. The cathode loading can be from about 3 grams to about 5 grams of nonstoichiometric β-delithiated layered nickel oxide. The cathode loading can be from about 3.5 grams to about 4.5 grams of nonstoichiometric β-delithiated layered nickel oxide. The cathode loading can be from about 3.9 grams to about 4.3 grams of nonstoichiometric β-delithiated layered nickel oxide. For AAAA batteries, the cathode loading can be from about 1.5 grams to about 2.5 grams of nonstoichiometric β-delithiated layered nickel oxide electrochemically active cathode material. For C batteries, the cathode loading can be from about 27.0 grams to about 40.0 grams (e.g., about 33.5 grams) of nonstoichiometric β-delithiated layered nickel oxide electrochemically active cathode material. For D batteries, the cathode loading can be from about 60.0 grams to about 84.0 grams (e.g., about 72.0 grams) of nonstoichiometric β-delithiated layered nickel oxide electrochemically active cathode material.

[0090] Cathode components (such as active cathode material, carbon particles, binder, and any other additives) can be combined, blended, and compacted into granules with a liquid such as an electrolyte in an aqueous solution of potassium hydroxide for use in the assembly of battery 10. For optimal cathode granule processing, it is generally preferred that the moisture content of the cathode granules be in the range of about 2% to about 5% by weight or about 2.8% to about 4.6% by weight. During the assembly of battery 10, the granules are placed within housing 18 and are typically recompacted to form a uniform cathode assembly within housing 18. The cathode granules may have a cylindrical shape including a central hole. The size of the granules may vary depending on the size of the battery, for example, granules will be used in AA, AAA, AAAA, C, and D sizes. The central hole may define the inner diameter (ID) of the granule. The inner diameter of the granules used for AA batteries may be, for example, about 9.1 mm to about 9.9 mm. The inner diameter of the granules used for AA batteries may be, for example, about 9.3 mm to about 9.7 mm. The inner diameter of the pellets used in AAA batteries can be, for example, from about 6.6 mm to about 7.2 mm. The inner diameter of the pellets used in AAA batteries can be, for example, from about 6.7 mm to about 7.1 mm. The inner diameter of the pellets used in AAAA batteries can be, for example, from about 5 mm to about 5.5 mm. The inner diameter of the pellets used in C batteries can be, for example, from about 16 mm to about 19 mm. The inner diameter of the pellets used in D batteries can be, for example, from about 21 mm to about 25 mm.

[0091] The cathode 12 will have a porosity that can be calculated during cathode manufacturing. The porosity of the cathode 12 can be from about 20% to about 40%, between about 22% and about 35%, and for example, about 26%. The porosity of the cathode 12 can be calculated during manufacturing, for example after cathode pellet processing, because the porosity of the cathode 12 within the battery 10 may change over time, especially due to cathode expansion associated with electrolyte wetting of the cathode and discharge of the battery 10. The porosity of the cathode 12 can be calculated as follows. The true density of each solid cathode assembly can be obtained from reference books, such as Lange's Handbook of Chemistry (16th edition, 2005). The solid weight of each cathode assembly is defined by the battery design. The solid weight of each cathode assembly can be divided by the true density of each cathode assembly to determine the cathode solid volume. The volume occupied by the cathode 12 within the battery 10 is again defined by the battery design. The volume occupied by the cathode 12 can be calculated using a computer-aided design (CAD) program. Porosity can be determined by the following formula:

[0092] Cathode porosity = [1 – (cathode solid volume ÷ cathode volume)] × 100

[0093] For example, the cathode 12 of an AA battery can contain approximately 9.0 grams of nonstoichiometric β-delithiated layered nickel oxide and approximately 0.90 grams of graphite (BNC-30) as solids within the cathode 12. The actual densities of the nonstoichiometric β-delithiated layered nickel oxide and graphite can be approximately 4.9 g / cm³ and approximately 2.15 g / cm³, respectively. Dividing the solid weight by the corresponding actual densities yields a volume of approximately 1.8 cm³ occupied by the nonstoichiometric β-delithiated layered nickel oxide and approximately 0.42 cm³ occupied by the graphite. The total solid volume is approximately 2.2 cm³. The battery designer can choose a volume of approximately 3.06 cm³ for the cathode 12. Calculating the cathode porosity [1 - (2.2 cm³ ÷ 3.06 cm³)] according to the above equation yields a cathode porosity of approximately 0.28% or 28%.

[0094] The anode 14 may be formed from at least one electrochemically active anode material, a gelling agent, and small amounts of additives such as organic and / or inorganic outgassing inhibitors. The electrochemically active anode material may include zinc; zinc oxide; zinc hydroxide; metal hydrides such as AB5(H), AB2(H), and A2B7(H); alloys thereof; and any combination thereof.

[0095] The content of electrochemically active anode material within anode 14 can be referred to as the anode load. The load of anode 14 can vary depending on the electrochemically active anode material used in the battery and the battery size. For example, an AA battery with zinc electrochemically active anode material can have an anode load of at least about 3.3 grams of zinc. The anode load can be, for example, at least about 3.5 grams, about 3.7 grams, about 3.9 grams, about 4.1 grams, about 4.3 grams, or about 4.5 grams of zinc. The anode load can be from about 4.0 grams to about 5.5 grams of zinc. The anode load can be from about 4.2 grams to about 5.3 grams of zinc. For example, an AAA battery with zinc electrochemically active anode material can have an anode load of at least about 1.8 grams of zinc. For example, the anode load can be from about 1.8 grams to about 2.5 grams of zinc. The anode load can be, for example, from about 1.9 grams to about 2.4 grams of zinc. For example, an AAAA battery with zinc electrochemically active anode material can have an anode load of at least about 0.6 grams of zinc. For example, the anode load can be from about 0.7 grams to about 1.3 grams of zinc. For example, a C-cell having a zinc electrochemically active anode material can have an anode load of at least about 9.3 grams of zinc. For example, the anode load can be from about 10.0 grams to about 19.0 grams of zinc. Similarly, a D-cell having a zinc electrochemically active anode material can have an anode load of at least about 30.0 grams of zinc. For example, the anode load can be from about 30.0 grams to about 45.0 grams of zinc. The anode load can also be, for example, from about 33.0 grams to about 39.5 grams of zinc.

[0096] Examples of gelling agents that can be used within anode 14 include polyacrylic acid; polyacrylic acid crosslinked with a polyolefin ether of diethylene glycol; grafted starch materials; salts of polyacrylic acid; carboxymethyl cellulose; salts of carboxymethyl cellulose (e.g., sodium carboxymethyl cellulose); or combinations thereof. Anode 14 may contain an outgassing inhibitor, which may comprise an inorganic material such as bismuth, tin, or indium. Alternatively, the outgassing inhibitor may comprise an organic compound such as a phosphate ester, an ionic surfactant, or a nonionic surfactant. The electrolyte may be dispersed throughout cathode 12, anode 14, and separator 16. The electrolyte comprises an ionicly conductive component in an aqueous solution. The ionicly conductive component may be an alkaline hydroxide. The alkaline hydroxide may be, for example, potassium hydroxide, sodium hydroxide, lithium hydroxide, cesium hydroxide, and any combination thereof. The concentration of the ionicly conductive component can be selected according to the battery design and its desired performance. Based on the weight of the total electrolyte within battery 10, the concentration of alkaline hydroxide within the electrolyte may be from about 0.20 to about 0.40 or from about 20% to about 40%. For example, based on the weight of the total electrolyte within battery 10, the hydroxide concentration of the electrolyte can be from about 0.25% to about 0.32%, or from about 25% to about 32%. The alkaline electrolyte aqueous solution may also contain zinc oxide (ZnO). ZnO can be used to inhibit zinc corrosion within the anode. The concentration of ZnO contained in the electrolyte can be about 5% by weight of the total electrolyte within battery 10. The ZnO concentration can, for example, be from about 1% by weight to about 3% by weight of the total electrolyte within battery 10.

[0097] For example, the total weight of the alkaline electrolyte aqueous solution in an AA alkaline battery can be from about 3.0 grams to about 4.4 grams. The total weight of the alkaline electrolyte in an AA battery can, for example, be from about 3.3 grams to about 3.8 grams. The total weight of the alkaline electrolyte in an AA battery can, for example, be from about 3.4 grams to about 3.65 grams. For example, the total weight of the alkaline electrolyte aqueous solution in an AAA alkaline battery can be from about 1.0 grams to about 2.0 grams. The total weight of the electrolyte in an AAA battery can, for example, be from about 1.2 grams to about 1.8 grams. The total weight of the electrolyte in an AAA battery can, for example, be from about 1.4 grams to about 1.8 grams. The total weight of the electrolyte in an AAAA battery can be from about 0.68 grams to about 1 gram, for example, from about 0.85 grams to about 0.95 grams. The total weight of the electrolyte in a C battery can be from about 11 grams to about 14 grams, for example, from about 12.6 grams to about 13.6 grams. The total weight of the electrolyte in a D battery can be from about 22 grams to about 30 grams, for example, from about 24 grams to about 29 grams.

[0098] Separator 16 comprises a material that can be wetted by or is wetted by an electrolyte. Material is said to be wetted by a liquid when the contact angle between the liquid and the material surface is less than 90° or when the liquid tends to spontaneously diffuse across the material surface; both conditions often coexist. Separator 16 may comprise a single or multiple layers of woven or nonwoven paper or fabric. Separator 16 may include a layer of cellophane, for example, combined with a layer of nonwoven material. Separator 16 may also include additional layers of nonwoven material. Separator 16 may also be formed in situ within battery 10. For example, U.S. Patent 6,514,637 discloses such separator materials and methods that may be applicable to their application. The separator material can be thin. For example, separator 16 may have a dry material thickness of less than 250 micrometers. Separator 16 may have a dry material thickness of about 50 micrometers to about 175 micrometers. Separator 16 may have a dry material thickness of about 70 micrometers to about 160 micrometers. Separator 16 may have a basis weight of approximately 40 g / m² or less. Separator 16 may have a basis weight of approximately 15 g / m² to approximately 40 g / m². Separator 16 may have a basis weight of approximately 20 g / m² to approximately 30 g / m². Separator 16 may have an air permeability value. Separator 16 may have an air permeability value as defined in International Organization for Standardization (ISO) Standard 2965. The air permeability value of separator 16 may be approximately 2000 cm³ / cm²·min at 1 kPa to approximately 5000 cm³ / cm²·min at 1 kPa. The air permeability value of separator 16 may be approximately 3000 cm³ / cm²·min at 1 kPa to approximately 4000 cm³ / cm²·min at 1 kPa. The air permeability value of separator 16 can be from about 3500 cm3 / cm2·min at 1 kPa to about 3800 cm3 / cm2·min at 1 kPa.

[0099] The current collector 20 can be made into any suitable shape for a particular battery design using any methods known in the art. The current collector 20 can have, for example, a nail-like shape. The current collector 20 can have a columnar body and a head located at one end of the columnar body. The current collector 20 can be made of a metal (e.g., zinc, copper, brass, silver) or any other suitable material. The current collector 20 can optionally be plated with tin, zinc, bismuth, indium, or another suitable material that presents low contact resistance between the current collector 20 and, for example, the anode 14. When the current collector 20 is in contact with the anode 14, the plating material can also exhibit the ability to suppress gas formation.

[0100] The seal 22 can be prepared by injection molding the following into a shape having a predetermined size: polymers such as polyamide, polypropylene, polyether urethane, etc.; polymer composites; and any combination thereof. The seal 22 can be made from, for example, nylon 6,6; nylon 6,10; nylon 6,12; nylon 11; polypropylene; polyether urethane; copolymers; composites; and any combination thereof. Exemplary injection molding methods include both cold runner and hot runner methods. The seal 22 can contain other known functional materials such as plasticizers, nucleating agents, antioxidants, release agents, lubricants, and antistatic agents. The seal 22 can also be coated with a sealant. The seal 22 can be wetted before use within the battery 10. For example, depending on the sealant material, the seal 22 can have a moisture content of about 1.0% by weight to about 9.0% by weight. The current collector 20 can be inserted into and pass through the seal 22.

[0101] End cap 24 can be formed in any shape sufficient to enclose the battery. End cap 24 can have, for example, a cylindrical or prismatic shape. End cap 24 can be formed by pressing material into the desired shape with suitable dimensions. End cap 24 can be made of any suitable material that conducts electrons during the discharge of battery 10. End cap 24 can be made of, for example, nickel-plated steel or tin-plated steel. End cap 24 can be electrically connected to current collector 20. End cap 24 can be electrically connected to current collector 20, for example, by welding to current collector 20. End cap 24 may also include one or more apertures (such as orifices) to release any gas pressure caused by electrolyte leakage or to allow the battery to release due to excessive internal pressure buildup. Current collector 20, seal 22, and end cap 24 can be collectively referred to as an end cap assembly.

[0102] Example

[0103] Example 1. Preparation of α-delithiated layered nickel oxide by sequentially treating non-stoichiometric layered lithium nickel oxide with sodium persulfate and sulfuric acid.

[0104] Under rapid stirring, excess nickel (Li) was added to deionized water in a 1-liter glass reactor equipped with a heating mantle. 1-a Ni 1+aNon-stoichiometric layered lithium nickel oxide (LNO) that has been ground and passed through a 20-mesh (US standard) sieve (O2, 0.02 ≤ a ≤ 0.2) is used to form a suspension. Solid sodium persulfate (i.e., Na2S2O8 or "SPS") is added to the stirred LNO suspension such that the amount of persulfate added is 0.35 moles of persulfate per mole of LNO. The initial pH of the mixture is 9–12. The stirred mixture is heated to 50°C at a rate of approximately 1°C / min. After stirring the mixture at 50°C for 3 hours, approximately 50% of the lithium is removed from the LNO using UV-Vis spectroscopy and an appropriate concentration calibration curve, and less than 3 wt% of soluble Ni is detected in the solution. 2+ Ions. Without cooling the resulting mixture, sulfuric acid at a concentration of 0.40 to 0.50 moles of acid per mole of total nickel was added with stirring, and the mixture was heated to 60°C at a rate of about 1°C / min, followed by stirring at 60°C for 3 hours. Stirring was stopped, and the solid product was allowed to settle. The supernatant was poured off while still heating. The resulting solid α-delithiated layered nickel oxide product was washed with deionized water. After washing, the solid product was allowed to stand again, and the clear supernatant was poured off. The washing process was repeated to remove soluble Ni. 2+ The complex, soluble nickel sulfate and lithium sulfate, and residual sulfuric acid were collected. The solid product was collected by vacuum filtration and dried in air at 60-80°C for about 12 hours. The yield of the dried α-delithiated layered nickel oxide product was about 70% by weight. The average primary particle size (i.e., D) of the α-delithiated layered nickel oxide product was... 50 The particle size is approximately 5.3 micrometers. This represents a reduction in the average primary particle size of approximately 16% compared to the average primary particle size of the precursor layered nickel oxide. The resulting dried material was provided as the cathode active material to a 635-type alkaline button cell, which exhibited a low-rate (e.g., 10 mA / g, approximately C / 40) discharge capacity in the range of 360 to 411 mAh / g. The yield of α-delithiated layered nickel oxide, the amount of residual lithium in the lattice, and the discharge capacity for different sulfuric acid:LNO molar ratios are provided in Table 1 below.

[0105] The dried α-delithiated layered nickel oxide was treated with an 8.7M aqueous solution of potassium hydroxide, wherein each gram of α-delithiated layered nickel oxide contained 0.069 g of potassium hydroxide. The mixture was sealed in a polyethylene bottle and kept at room temperature for 12–24 hours to form β-delithiated layered nickel oxide. The semi-solid mixture was washed with deionized water in multiple equal aliquots to remove unreacted KOH. The washed β-delithiated layered nickel oxide product was dried in air at 70°C for approximately 12 hours.

[0106] Table 1:

[0107]

[0108] Therefore, Example 1 demonstrates that when sulfuric acid reacts with a mixture containing Ni(IV) at 60°C, changing the molar ratio of acid to LNO within the range of 0.40 to 0.50 moles of acid per mole of total nickel content does not significantly affect the yield of α-delithiated layered nickel oxide, but has a moderate (<15%) effect on the discharge capacity. Example 1 further demonstrates that, under the conditions of Example 1, the discharge capacity of α-delithiated layered nickel oxide can be increased while maintaining the product yield.

[0109] Example 2. Preparation of α-delithiated layered nickel oxide by treating non-stoichiometric layered lithium nickel oxide with sodium persulfate and sulfuric acid.

[0110] Under stirring, excess nickel (Li) was added to deionized water in a 1-liter glass reactor equipped with a heating mantle. 1-a Ni 1+a Non-stoichiometric layered lithium nickel oxide (LNO) that had been ground and passed through a 20-mesh (US standard) sieve (O2, 0.02 ≤ a ≤ 0.2) was used to form a suspension. Solid sodium persulfate (i.e., Na2S2O8, SPS) was added to the stirred LNO suspension such that the amount of persulfate added relative to the LNO was 0.35 moles of persulfate per mole of LNO. The initial pH of the mixture was 9–12. The stirred mixture was heated to 50 °C at a rate of approximately 1 °C / min. After stirring the mixture at 50 °C for 3 hours, approximately 50% of the lithium had been removed from the LNO, and less than 3 wt% of soluble Ni was detected in the solution. 2+ Without cooling the resulting mixture, sulfuric acid was added at a rate of 0.43 to 0.53 moles of acid per mole of total nickel, with stirring. The mixture was heated to 70°C at a rate of approximately 1°C / min, and then stirred at 70°C for 3 hours. Stirring was stopped, and the solid product was allowed to settle. The supernatant was poured off while still heating. The resulting solid α-delithiated layered nickel oxide product was washed with deionized water. After washing, the solid product was allowed to stand again, and the clear supernatant was poured off. The washing process was repeated to remove soluble Ni. 2+ The complex, soluble nickel sulfate and lithium sulfate, and residual sulfuric acid were collected. The solid product was collected by vacuum filtration and dried in air at 60-80°C for about 12 hours. The yield of the dried product was about 60-70%. The average primary particle size (i.e., D) of the α-delithiated layered nickel oxide product was... 50The particle size is approximately 5.5 micrometers. This represents a reduction in the average primary particle size of approximately 14% compared to the average primary particle size of the precursor layered nickel oxide. The resulting dried material was provided as the cathode active material to a 635-type alkaline button cell, which exhibited a low-rate (e.g., 10 mA / g, approximately C / 40) discharge capacity in the range of 400–approximately 430 mAh / g. The yield of α-delithiated layered nickel oxide, the amount of residual lithium in the lattice, and the discharge capacity for different sulfuric acid:LNO molar ratios are provided in Table 2 below.

[0111] Dry α-delithiated layered nickel oxide was thoroughly mixed with an 8.7M potassium hydroxide aqueous solution to form a semi-solid mixture containing 0.069 g of potassium hydroxide per gram of α-delithiated layered nickel oxide material. The mixture was sealed in a polyethylene bottle and kept at room temperature for 12–24 hours to form β-delithiated layered nickel oxide. The semi-solid mixture was washed with deionized water in multiple equal aliquots to remove unreacted KOH. The washed β-delithiated layered nickel oxide product was dried in air at 70°C for approximately 12 hours.

[0112] Table 2:

[0113]

[0114] Therefore, compared to Example 1, Example 2 demonstrates the formation of an α-delithiated layered nickel oxide electrochemically active cathode material using a higher reaction temperature for the acid-promoted disproportionation step according to the method of this disclosure, which has a slightly higher gravimetric discharge capacity than the α-delithiated layered nickel oxide material of Example 1. Example 2 further demonstrates the formation of the β-delithiated layered nickel oxide electrochemically active cathode material of this disclosure.

[0115] Example 3. Preparation of α-delithiated layered nickel oxide by treating non-stoichiometric layered lithium nickel oxide with sulfuric acid only.

[0116] While stirring, non-stoichiometric layered lithium nickel oxide (LiNiO2) with excess nickel content was added to deionized water in a 1-liter glass reactor equipped with a heating mantle. 1-a Ni 1+aO2 (0.02≤a≤0.2) was used to form a suspension nominally containing 20 wt% solids. The stirred suspension was heated to approximately 50-55°C at a rate of approximately 1°C / min. A 60 wt% sulfuric acid solution was added in portions over a 30-minute period, keeping the temperature below approximately 65°C, with the total amount of acid added being 0.95 moles of acid per mole of nickel. The resulting mixture containing approximately 17 wt% solids was maintained at 60°C and stirred for a total of 5-6 hours. The solid product was allowed to settle and separated from the green supernatant by decantation while still warm. The solid product was repeatedly washed with deionized water to remove soluble Ni(II) complexes, nickel and lithium sulfates, and any residual sulfuric acid. The washed solid product was collected by vacuum filtration and then dried in air at 60-80°C for approximately 12 hours. The yield of the dried product was approximately 45-49% (wt / wt). As determined by ICP-AES, the dried product still contains approximately 0.3% by weight of residual lithium in the crystal lattice. The low-rate (e.g., 10 mA / g, C / 40) discharge capacity of the dried product, provided as a cathode active material in a 635-type alkaline button cell, is approximately 420 to 425 mAh / g. The average Ni oxidation state is typically in the range of 3.45 to 3.50. The average primary particle size (i.e., D0) of the α-delithiated layered nickel oxide product is... 50 The size is approximately 5.0 micrometers. This represents a reduction of nearly 20% in the average primary particle size compared to the average primary particle size of the precursor layered lithium nickel oxide.

[0117] Dry α-delithiated layered nickel oxide was thoroughly mixed with a suitable volume of 8.7M potassium hydroxide aqueous solution to form a semi-solid mixture containing 0.2 moles of KOH (salt) per mole of nickel oxide. The mixture was sealed in a polyethylene bottle and kept at room temperature for 12–24 hours to form β-delithiated layered nickel oxide. The semi-solid mixture was washed with deionized water in multiple aliquots to remove unreacted KOH. The washed β-delithiated layered nickel oxide product was dried in air at 70°C for approximately 12 hours. However, β-delithiated layered nickel oxide also contains a variable amount of γ-NiOOH as a byproduct, typically less than 10% by weight, as estimated by comparing its powder X-ray diffraction pattern with the X-ray diffraction patterns of a series of weighed physical blends containing almost undetectable levels of γ-NiOOH and nominally pure γ-NiOOH.

[0118] Therefore, Example 3 demonstrates the preparation of α-delithiated layered nickel oxide by a method that is undisclosed and comprises only the acid disproportionation of a non-stoichiometric layered nickel-lithium oxide with Ni(III) to Ni(IV) and water-soluble Ni(II) using a sulfuric acid solution. Applying acid disproportionation to the lithium-nickel oxide precursor results in approximately 50% of the nickel being converted to Ni. 2+The nickel dissolves in a form that provides less than 50% by weight of solid reaction product yield, for example, 47%. Example 3 further demonstrates that, due to over 50% nickel dissolution, the average primary particle size of the α-delithiated layered nickel oxide product is 20 to 30% smaller than the corresponding particle size of the layered nickel oxide precursor. Thus, Examples 2 and 3 together demonstrate that, compared to existing delithiation methods using only acid disproportionation, the method of this disclosure can be used to prepare β-delithiated layered nickel oxide in higher yields, exhibiting comparable or higher electrochemical discharge capacity and larger primary particle size in alkaline battery cells, while maintaining comparable or lower amounts of γ-NiOOH byproducts in the final material.

[0119] Example 4. Preparation of α-delithiated layered nickel oxide by treating non-stoichiometric layered lithium nickel oxide with only excess sodium persulfate.

[0120] While stirring, non-stoichiometric layered lithium nickel oxide (LiNiO2) with excess nickel content was added to deionized water in a 1-liter glass reactor equipped with a heating mantle. 1-a Ni 1+a O2 (0.02≤a≤0.2) was used to form a suspension nominally containing 25% by weight of solids. Solid sodium persulfate was added in batches to the stirred suspension such that the total amount of persulfate added was 0.75 moles of persulfate per mole of nickel oxide. The stirred mixture was heated to 85°C at a rate of about 1°C / min and held at said temperature for 5 hours. Before the addition of persulfate, the initial pH of the lithium nickel oxide precursor suspension was greater than 12. After the addition of persulfate was completed and the temperature reached 60°C, the pH decreased to 10. After stirring at 85°C for 5 hours, the pH further decreased to less than 5. At this point, stirring was stopped and the solid product was allowed to settle. While still warm, the solid product was separated from the dark green supernatant containing Ni2+ by decantation. The solid product was repeatedly washed with deionized water and decanted to remove soluble nickel sulfate and lithium sulfate, as well as unreacted sodium persulfate. Finally, the washed solid product was collected by suction filtration and dried in air at 60-80°C for approximately 12 hours. The yield of the dried product was approximately 65-70% (wt / wt). As determined by ICP-AES, the dried product still contained approximately 0.6% by weight of residual lithium in the crystal lattice. In a 635-type alkaline button cell, the low-rate (e.g., 10 mA / g, °C / 40) discharge capacity of α-delithiated layered nickel oxide was approximately 425 to 430 mAh / g. The average primary particle size (i.e., D0) of the α-delithiated layered nickel oxide was... 50 The size is approximately 5.1 micrometers. This represents a 20% reduction in average primary particle size compared to the average primary particle size of the precursor layered lithium nickel oxide.

[0121] α-Delithiated layered nickel oxide was thoroughly mixed with a suitable volume of 8.7M potassium hydroxide aqueous solution to form a semi-solid mixture containing 0.2 moles of KOH (salt) per mole of nickel oxide. The mixture was sealed in a polyethylene bottle and kept at room temperature for 12–24 hours to form β-delithiated layered nickel oxide. The semi-solid mixture was washed with deionized water in multiple equal aliquots to remove unreacted KOH. The washed β-delithiated layered nickel oxide product was dried in air at 70°C for approximately 12 hours. However, β-delithiated layered nickel oxide also contains a variable amount of γ-NiOOH as a byproduct, which, as estimated from its powder X-ray diffraction pattern, is typically less than 10% by weight.

[0122] Therefore, Example 4 demonstrates the preparation of α-delithiated layered nickel oxide by a method not disclosed and involving only the oxidative delithiation of a non-stoichiometric layered nickel oxide precursor using an excess of sodium persulfate. The yield of α-delithiated layered nickel oxide decreases as the rate of thermal decomposition of persulfate to sulfuric acid accelerates at 85°C, as demonstrated by the decrease in pH with reaction time. The presence of sulfuric acid also promotes some disproportionation reactions, resulting in an average primary particle size of α-delithiated layered nickel oxide that is 20 to 30% smaller than that of the lithium nickel oxide precursor. Furthermore, the process in Example 4 requires treatment with more than 50% sodium persulfate at 85°C for 5 hours, whereas, in contrast to Example 2, the method disclosed herein is carried out with less sodium persulfate and achieves similar yields by heating to 50°C for 3 hours and 70°C for 3 hours. Therefore, Examples 2 and 4 together demonstrate that, compared to prior art delithiation methods using large amounts of sodium persulfate at higher reaction temperatures, the method of this disclosure can be used to prepare β-delithiated layered nickel oxide with higher yields and less energy consumption (i.e., energy use of 85°C for 5 hours > 50°C for 3 hours + 70°C for 3 hours), which has comparable or higher electrochemical discharge capacity in alkaline battery cells, and with larger primary particle size using less than 50% sodium persulfate, while maintaining comparable or lower amounts of γ-NiOOH byproducts in the final material.

[0123] The foregoing description has been provided for clarity of understanding only, and should not be construed as unnecessarily limiting, as modifications within the scope of this disclosure will be readily apparent to those skilled in the art.

[0124] All patents, publications, and references cited in this document are hereby incorporated herein by reference in their entirety. In the event of any conflict between this disclosure and the incorporated patents, publications, and references, this disclosure shall prevail.

Claims

1. A method for preparing an electrochemically active cathode material, the method comprising: (a) Having formula A 1-a Ni 1+a O2 or formula A 1-a Ni 1+a-z M z O2 containing alkali metal layered nickel oxide is combined with a fluid composition to form a mixture, wherein A comprises an alkali metal, 0 < a ≤ 0.2, M is a doped metal M, and 0 ≤ z ≤ 0.2, and the fluid composition contains a chemical oxidizing agent, which includes persulfate, monopersulfate, or a combination thereof. (b) Heating the mixture for a period of time sufficient to form a mixture containing Ni(IV), the mixture containing Ni(IV) comprising a layered nickel oxide electrochemically active cathode material lacking alkali metal containing Ni(IV), the mixture containing Ni(IV) having a total nickel (Ni) content, the total nickel content being the total amount of nickel present in the mixture containing Ni(IV), regardless of oxidation state; (c) Add mineral acid to the Ni(IV)-containing mixture of step (b), wherein the mineral acid is added in an amount of 0.60 moles or less per mole of total nickel; as well as (d) Heating the mixture from step (c) sufficient to form an additional amount of the Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material for at least a period of time, wherein the Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material formed during steps (b) and (d) has the general formula A. x H y Ni 1+a O2 or A x H y Ni 1+a- z M z O2: in A includes alkali metals; 0.08 ≤ x < 0.2； 0 ≤ y < 0.3； 0.02 < a ≤ 0.2； M is a doped metal; and 0 ≤ z ≤ 0.2。 2. The method according to claim 1, wherein the oxidant comprises persulfate.

3. The method according to claim 1 or claim 2, wherein A comprises Li, Na, or a combination thereof.

4. The method according to claim 1 or claim 2, wherein A comprises Li.

5. The method according to claim 1 or claim 2, wherein M comprises a transition metal, a main group metal, or both.

6. The method according to claim 1 or claim 2, wherein M comprises cobalt (Co), manganese (Mn), iron (Fe), chromium (Cr), vanadium (V), titanium (Ti), niobium (Nb), zirconium (Zr), or a combination thereof.

7. The method according to claim 1 or claim 2, wherein M comprises cobalt (Co), manganese (Mn), or a combination thereof.

8. The method according to claim 1 or claim 2, wherein M comprises cobalt (Co).

9. The method according to claim 1 or claim 2, wherein M comprises manganese (Mn).

10. The method according to claim 1 or claim 2, wherein M comprises cobalt (Co) and manganese (Mn).

11. The method according to claim 1 or claim 2, wherein M comprises aluminum (Al), gallium (Ga), bismuth (Bi), or a combination thereof.

12. The method of claim 11, wherein M comprises aluminum (Al), magnesium (Mg), or a combination thereof.

13. The method of claim 11, wherein M comprises aluminum (Al).

14. The method according to claim 1 or claim 2, wherein in step (b), the heating is performed for 15 minutes to 6 hours.

15. The method of claim 14, wherein in step (b), the heating is performed for 15 minutes to 4 hours.

16. The method of claim 14, wherein in step (b), the heating time is 2 to 4 hours.

17. The method according to claim 1 or claim 2, wherein in step (d), the heating is performed for 1 hour to 6 hours.

18. The method of claim 16, wherein in step (d), the heating is performed for 2 to 4 hours.

19. The method according to claim 1 or claim 2, wherein in step (c), the mineral acid comprises sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, perchloric acid, hydroiodic acid, or a combination thereof.

20. The method according to claim 1 or claim 2, wherein in step (c), the mineral acid comprises sulfuric acid, nitric acid, hydrochloric acid, or a combination thereof.

21. The method according to claim 1 or claim 2, wherein in step (c), the mineral acid comprises sulfuric acid.

22. The method according to claim 1 or claim 2, wherein the fluid composition contains less than 5 wt.% of a hydroxide salt based on the total weight of the fluid composition.

23. The method according to claim 1 or claim 2, wherein in step (a), the oxidant is provided in an amount of 0.25 to 0.70 moles per mole of the alkali metal-containing layered nickel oxide.

24. The method of claim 23, wherein in step (a), the oxidant is provided in an amount of 0.25 to 0.45 moles per mole of the alkali metal-containing layered nickel oxide.

25. The method according to claim 1 or claim 2, wherein in step (b), the heating is performed at a temperature less than 60°C.

26. The method of claim 25, wherein in step (b), the temperature is in the range of 45°C to 55°C.

27. The method according to claim 1 or claim 2, wherein in step (c), the mineral acid is provided in an amount of 0.40 to 0.55 moles per mole of total nickel.

28. The method according to claim 1 or claim 2, wherein in step (d), the heating is performed at a temperature of 60°C to 80°C.

29. The method according to claim 28, wherein in step (d), the temperature is 65°C to 75°C.

30. The method according to claim 28, wherein in step (d), the temperature is 68°C to 72°C.

31. The method according to claim 1 or claim 2, wherein in step (a), the oxidant is provided in an amount of 1 mole per mole of the alkali metal-containing layered nickel oxide.

32. The method of claim 31, wherein in step (b), the heating is performed at a temperature of 45°C to less than 60°C.

33. The method of claim 31, wherein in step (c), the mineral acid is provided in an amount of 0.20 to 0.40 mol per mole of total nickel.

34. The method according to claim 31, wherein in step (d), the heating is performed at a temperature of 60°C to 80°C.

35. The method of claim 1 or claim 2, wherein the oxidant comprises a counter cation selected from the group consisting of ammonium, sodium, potassium, lithium, or combinations thereof.

36. The method according to claim 1 or claim 2, wherein the value of x is from 0.01 to 0.

20.

37. The method according to claim 1 or claim 2, wherein the value of z is from 0 to 0.

20.

38. The method according to claim 1 or claim 2, wherein the value of y is from 0 to 0.

29.

39. The method according to claim 1 or claim 2, wherein the value of a is from 0.02 to 0.

20.

40. The method according to claim 1 or claim 2, wherein in step (a), the layered nickel oxide containing alkali metal and the oxidant are provided in the following molar ratio: 1 mol layered nickel oxide containing alkali metal: 0.25 mol oxidant to 1 mol layered nickel oxide containing alkali metal: 0.70 mol oxidant.

41. The method according to claim 1 or claim 2, wherein in step (a), the pH of the fluid composition is in the range of 4 to 12.

42. The method according to claim 1 or claim 2, wherein when the mineral acid is added to the Ni(IV)-containing mixture in step (c), the unreacted persulfate from step (b) may be present in the Ni(IV)-containing mixture.

43. The method according to claim 1 or claim 2, further comprising separating the Ni(IV)-containing mixture from the fluid composition prior to step (c).

44. The method according to claim 1 or claim 2, further comprising treating the Ni(IV)-containing alkali metal-deficient nickel oxide with an aqueous solution of an alkaline hydroxide according to the following formula to form a compound: A x A' v Ni 1+a O2·nH2O or A x A' v Ni 1+a-z M z O2·nH2O, Where A includes Li or Na; M includes transition metals; A' includes K, Rb, or Cs; 0.04 ≤ x < 0.2； 0.03 < v < 0.20； 0.02 ≤ a ≤ 0.2； 0 ≤ z ≤ 0.2; and 0 < n < 2。 45. The method of claim 44, wherein the alkaline hydroxide comprises potassium hydroxide, rubidium hydroxide, cesium hydroxide, or a combination thereof.

46. ​​The method of claim 44, wherein A comprises Li and A' comprises K.

47. The method of claim 44, wherein the nickel oxide containing Ni(IV) and lacking alkali metal is treated with an aqueous solution of alkaline hydroxide to form γ-hydroxy nickel oxide (γ-NiOOH) as a byproduct, which is less than 10 wt% of the total weight of the reaction products.

48. The method of claim 47, wherein the alkali-deficient nickel oxide containing Ni(IV) is treated with an aqueous solution of alkaline hydroxide to form γ-hydroxy nickel oxide (γ-NiOOH) as a byproduct, which is less than 6 wt% of the total weight of the reaction products.

49. The method according to claim 1 or claim 2, wherein in step (a), the oxidant comprises persulfate and is provided in an amount of 0.25 to 0.45 moles per mole of the alkali metal-containing layered nickel oxide; in step (b), the mixture is heated to a temperature of 45°C to 55°C for 2 to 4 hours; in step (c), the mineral acid comprises sulfuric acid and is provided in an amount of 0.4 to 0.55 moles per mole of total nickel; and in step (d), the mixture is heated to a temperature of 65°C to 75°C for 2 to 4 hours.

50. A method for preparing an electrochemically active cathode material, the method comprising: (i) Make it have the formula A 1-a Ni 1+a O2 or formula A 1-a Ni 1+a-z M z O2-containing alkali metal-based layered nickel oxide reacts with a chemical oxidant in a fluid composition at high temperature for at least a certain period of time sufficient to form a Ni(IV)-containing mixture, wherein A comprises an alkali metal, 0 < a ≤ 0.2, M is a doped metal, and 0 ≤ z ≤ 0.2, the chemical oxidant comprises persulfate, monopersulfate, or a combination thereof, the Ni(IV)-containing mixture comprises an alkali metal-deficient layered nickel oxide electrochemically active cathode material containing Ni(IV), the Ni(IV)-containing mixture having a total nickel (Ni) content, the total nickel content referring to the total amount of nickel present in the Ni(IV)-containing mixture, regardless of oxidation state; and (ii) The Ni(IV)-containing mixture of step (i) is reacted with a mineral acid at a high temperature to form an additional amount of the Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material for at least a period of time, wherein the mineral acid is added in an amount of 0.60 moles or less per mole of total nickel. The Ni(IV)-containing, alkali metal-deficient layered nickel oxide electrochemically active cathode material formed during steps (i) and (ii) has the general formula A. x H y Ni 1+a O2 or A x H y Ni 1+a-z M z O2: in A includes alkali metals; 0.08 ≤ x < 0.2； 0 ≤ y < 0.3； 0.02 < a ≤ 0.2； M is a doped metal; and 0 ≤ z ≤ 0.2。 51. The method of claim 50, wherein the oxidant comprises persulfate.

52. The method according to claim 50 or claim 51, wherein A comprises Li.

53. The method of claim 50, wherein M comprises a transition metal, a main group metal, or both.

54. The method of claim 50, wherein M comprises cobalt (Co), manganese (Mn), iron (Fe), chromium (Cr), vanadium (V), titanium (Ti), niobium (Nb), zirconium (Zr), or a combination thereof.

55. The method of claim 50, wherein M comprises cobalt (Co), manganese (Mn), or a combination thereof.

56. The method of claim 50, wherein M comprises aluminum (Al), gallium (Ga), bismuth (Bi), or a combination thereof.

57. The method according to claim 50 or claim 51, wherein in step (i), the reaction time is from 15 minutes to 6 hours.

58. The method of claim 57, wherein in step (ii), the reaction time is from 15 minutes to 4 hours.

59. The method according to claim 57, wherein in step (ii), the reaction time is 2 to 4 hours.

60. The method according to claim 50 or claim 51, wherein in step (ii), the reaction time is from 1 hour to 6 hours.

61. The method according to claim 60, wherein in step (ii), the reaction time is 2 to 4 hours.

62. The method according to claim 50 or claim 51, wherein in step (ii), the mineral acid comprises sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, perchloric acid, hydroiodic acid, or a combination thereof.

63. The method according to claim 50 or claim 51, wherein in step (ii), the mineral acid comprises sulfuric acid, nitric acid, hydrochloric acid, or a combination thereof.

64. The method according to claim 50 or claim 51, wherein in step (ii), the mineral acid comprises sulfuric acid.

65. The method according to claim 50 or claim 51, wherein in step (i), the oxidant is provided in an amount of 0.25 to 0.70 moles per mole of the alkali metal-containing layered nickel oxide.

66. The method of claim 65, wherein in step (i), the oxidant is provided in an amount of 0.25 to 0.45 moles per mole of the alkali metal-containing layered nickel oxide.

67. The method according to claim 50 or claim 51, wherein in step (i), the reaction is carried out at a temperature in the range of 40°C to 60°C.

68. The method according to claim 50 or claim 51, wherein in step (ii), the mineral acid is provided in an amount of 0.40 to 0.55 moles per mole of total nickel.

69. The method according to claim 50 or claim 51, wherein in step (ii), the reaction is carried out at a temperature of 60°C to 80°C.

70. The method according to claim 69, wherein in step (ii), the temperature is 65°C to 75°C.

71. The method according to claim 69, wherein in step (ii), the temperature is 68°C to 72°C.

72. The method according to claim 50 or claim 51, wherein in step (i), the oxidant is provided in an amount of 1 to 2 moles of oxidant per mole of the alkali metal-containing layered nickel oxide.

73. The method according to claim 72, wherein in step (i), the reaction is carried out at a temperature of 45°C to less than 60°C.

74. The method of claim 72, wherein in step (ii), the mineral acid is provided in an amount of 0.20 to 0.40 mol per mole of total nickel.

75. The method according to claim 72, wherein in step (ii), the reaction is carried out at a temperature of 60°C to 80°C.

76. The method of claim 50 or claim 51, wherein the oxidant comprises a counter cation selected from the group consisting of ammonium, sodium, potassium, lithium, or combinations thereof.

77. The method of claim 50 or claim 51, wherein the value of x is from 0.01 to 0.

20.

78. The method of claim 50 or claim 51, wherein the value of z is from 0 to 0.

20.

79. The method of claim 50 or claim 51, wherein the value of y is from 0 to 0.

29.

80. The method of claim 50 or claim 51, wherein the value of a is from 0.02 to 0.

20.

81. The method according to claim 50 or claim 51, wherein in step (i), the layered nickel oxide containing alkali metal and the oxidant are provided in the following molar ratio: 1 mol layered nickel oxide containing alkali metal: 0.25 mol oxidant to 1 mol layered nickel oxide containing alkali metal: 0.70 mol oxidant.

82. The method according to claim 50 or claim 51, wherein in step (i), the pH of the fluid composition is in the range of 4 to 12.

83. The method according to claim 50 or claim 51, wherein when the mineral acid is added to the Ni(IV)-containing mixture in step (ii), the unreacted persulfate from step (i) may be present in the Ni(IV)-containing mixture.

84. The method according to claim 50 or claim 51, further comprising separating the Ni(IV)-containing mixture from the fluid composition prior to step (ii).

85. The method according to claim 50 or claim 51, further comprising treating the Ni(IV)-containing alkali metal-deficient nickel oxide with an aqueous solution of an alkaline hydroxide according to the following formula to form a compound: A x A' v Ni 1+a O2·nH2O or A x A' v Ni 1+a-z M z O2·nH2O, Where A includes Li or Na; M includes transition metals; A' includes K, Rb, or Cs; 0.04 ≤ x < 0.2； 0.03 < v < 0.20； 0.02 ≤ a ≤ 0.2； 0 ≤ z ≤ 0.2; and 0 < n < 2。 86. The method according to claim 85, wherein the alkaline hydroxide comprises potassium hydroxide, rubidium hydroxide, cesium hydroxide, or a combination thereof.

87. The method of claim 85, wherein A comprises Li and A' comprises K.

88. The method according to claim 85, wherein the nickel oxide containing Ni(IV) and lacking alkali metal is treated with an aqueous solution of alkaline hydroxide to form γ-hydroxy nickel oxide (γ-NiOOH) as a byproduct, which is less than 10 wt% of the total weight of the reaction products.

89. The method according to claim 88, wherein the alkali-deficient nickel oxide containing Ni(IV) is treated with an aqueous solution of alkaline hydroxide to form γ-hydroxy nickel oxide (γ-NiOOH) as a byproduct, which is less than 6 wt% of the total weight of the reaction products.

90. The method according to claim 50 or claim 51, wherein in step (i), the oxidant comprises persulfate and is provided in an amount of 0.25 to 0.45 moles per mole of the alkali metal-containing layered nickel oxide, the reaction temperature is 45°C to 55°C, and the reaction time is 2 to 4 hours, and in step (ii), the mineral acid comprises sulfuric acid and is provided in an amount of 0.4 to 0.55 moles per mole of total nickel, the reaction temperature is 65°C to 75°C, and the reaction time is 2 to 4 hours.

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