Patent Description:
Alkali metal-containing transition metal oxides can be energetically activated or "charged" for the purpose of preparing highly oxidized cathode materials for use in both primary and secondary electrochemical cells. Charging of the alkali metal-containing transition metal oxides comprises oxidation of the transition metal and removal of the alkali metal from the metal oxide crystal lattice, in part or in whole, to form an alkali metal-deficient transition metal oxide electrochemically active cathode material. The alkali metal-containing transition metal oxides can be chemically charged or electrochemically charged. Methods of chemically charging the alkali metal-containing transition metal oxides can include oxidative demetallation and acid-promoted disproportionation of the transition metal, e.g., by treatment with a mineral acid.

It is known that acid-promoted disproportionation of alkali metal-containing transition metal oxides including metals such as Mn and Ni results in extraction of essentially all the alkali metal ions present from the crystal lattice as well as oxidation of at most <NUM>% of the metal, for example from an M(III) oxidation state to an M(IV) oxidation state. A corresponding amount of the M(III) is reduced to M(II), which dissolves in the acid solution.

The acid-promoted disproportionation reaction can be summarized, using stoichiometric layered lithium nickel oxide as an example, as follows in Equation <NUM>:.

LiNiO<NUM> + 2y H<NUM>SO<NUM> → (<NUM> -y)Li(<NUM>-2y)/(<NUM>-y)NiO<NUM> + y NiSO<NUM> + y Li<NUM>SO<NUM> + 2y H<NUM>O (<NUM> ≤ y ≤ ½).

The Ni(ll) ions are soluble and dissolve in the aqueous acid solution. Thus, use of an acid-promoted metal disproportionation reaction to chemically charge an alkali metal containing transition metal oxide is very inefficient since at least half of the M(III) ions in the starting transition metal oxide are reduced to M(II) ions that can dissolve in the acid solution and, thus, are extracted out of the crystal structure Further, the dissolution of M(II) ions results in a reduction in the average particle size of the transition metal oxide.

Chemically charging an alkali metal-containing transition metal oxide with a strong, soluble chemical oxidant can be used to directly oxidize the transition metal to a higher oxidation state and result in the removal of a proportional amount of alkali metal ions to maintain overall electroneutrality of the crystal lattice. Various reagents such as strongly oxidizing gases (e.g., ozone, chlorine or bromine), strongly oxidizing solid reagents (e.g., nitrosonium hexafluorophosphate, nitrosonium tetrafluorborate, nitrosonium hexafluoroarsenate, nitronium tetrafluoroborate, nitronium hexafluorophosphate, nitronium hexafluoroarsenate), and water soluble oxidizing agents (e.g., alkali or alkaline earth metal hypochlorites (e.g., Na+, K+, Ca<NUM>+), alkali peroxydisulfates (e.g., Na+, K+), ammonium peroxydisulfate, and alkali monopersulfates (e.g., Na+, K+) have been used to chemically charge alkali metal-containing transition metal oxides. Other water soluble oxidizing agents include alkali permanganates (e.g., K+, Na+, Li+) and alkali ferrates (e.g., K+). Methods using water soluble oxidizing agents are typically performed near room temperature over <NUM> to <NUM> hours; however such methods often lack sufficient oxidation strengths to rapidly and sufficiently oxidize the transition metal and demetallate the starting alkali metal-containing transition metal oxide to prepare an alkali metal-deficient metal oxide having a formula of AxMO<NUM> or AxM<NUM>O<NUM> where A is the alkali metal and M is the transition metal, for example, wherein x is less than about <NUM>. <CIT> discloses non-stoichiometric beta-delithiated layered nickel oxide having a chemical formula. The chemical formula is LixAyNi<NUM>+a-zMzO<NUM> with <NUM> ≤ x ≤ <NUM>; <NUM> ≤ y ≤ <NUM>; <NUM> ≤ a ≤ <NUM>; <NUM> ≤ z ≤ <NUM>; and <NUM> ≤ n ≤ <NUM>. Within the chemical formula, A is an alkali metal and includes potassium, rubidium, cesium, and any combination thereof. Within the chemical formula M comprises an alkaline earth metal, a transition metal, a non-transition metal, and any combination thereof. The method for producing the non-stoichiometric beta-delithiated layered nickel oxide is described in only a general manner, starting from non-stoichiometric lithium nickelate, which is chemically oxidized to form first a non-stoichiometric alpha-delithiated layered nickel oxide. As suitable oxidants, sodium hypochlorite, sodium peroxydisulfate, potassium peroxydisulfate, ammonium peroxydisulfate, sodium permanganate, potassium permanganate, sodium dichromate, potassium dichromate, ozone gas, chlorine gas, bromine gas, sulfuric acid, hydrochloric acid, and nitric acid are mentioned.

Thus, known methods of chemically charging alkali metal-containing, layered transition metal oxides have multiple drawbacks such as low yields due to the disproportionation of the transition metal, incomplete oxidation of the transition metal, and/or extended treatment times, for example, <NUM>-<NUM> hours, and expensive reagents (e.g., nitrosonium salts, nitronium salts).

The invention provides a method of preparing an electrochemically active cathode material, including the steps of (i) reacting an alkali metal-containing layered nickel oxide having a formula A<NUM>-aNi<NUM>+aO<NUM>, wherein A comprises an alkali metal and <NUM> < a ≤ <NUM>, and a chemical oxidant comprising a peroxydisulfate salt, a monopersulfate salt, or a combination thereof, in a fluid composition at an elevated temperature for at least a period of time sufficient 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, the Ni(IV) containing mixture having a total nickel (Ni) content; and (ii) reacting the Ni(IV)-containing mixture of step (i) with a mineral acid, wherein the mineral acid is added in an amount of about <NUM> moles or less per mole of total nickel, at an elevated 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; the Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material formed during steps (i) and (ii) having the general formula AxHyNi<NUM>+aO<NUM>, wherein A comprises an alkali metal; <NUM> ≤ x < <NUM>; <NUM> ≤ y < <NUM>; and <NUM> < a ≤ <NUM>.

Further aspects and advantages will be apparent to those of ordinary skill in the art from a review of the following detailed description. While the compositions and methods are susceptible of embodiments in various forms, the description hereafter includes specific embodiments with the understanding that the disclosure is illustrative, and is not intended to limit the disclosure to the specific embodiments described herein.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter, which is regarded as forming the present invention, it is believed that the invention will be better understood from the following description taken in conjunction with the accompanying drawings.

<FIG> is a cross-section of an embodiment of a primary alkaline battery of the disclosure.

It is known in the art that peroxydisulfate salts and monopersulfate salts can undergo autocatalytic thermal decomposition in aqueous solutions, evolving oxygen gas and forming sulfuric acid as decomposition products, at temperatures above <NUM>, in particular, at temperatures above <NUM>, <NUM>, <NUM> or at about <NUM>° and above. Further, it is known in the art that alkali metal-containing layered nickel oxides can undergo acid promoted disproportionation in the presence of a mineral acid such as sulfuric acid. This disproportionation reaction can be summarized, for example, as follows for the layered lithium nickel oxide, as follows in Equation <NUM>:.

LiNiOs + 2y H<NUM>SO<NUM> → (<NUM>-y)Li(<NUM>-2y)/(<NUM>-y)NiO<NUM> + y NiSO<NUM> + y Li<NUM>SO<NUM> + 2y H<NUM>O (<NUM> ≤ y ≤ <NUM>).

Thus, one of ordinary skill in the art would expect that at temperatures of greater than about <NUM>, for example about <NUM> and above, the oxidant would begin decomposing and forming sulfuric acid, which would be expected to promote disproportionation of the alkali metal-containing layered nickel oxide, resulting in a maximum of about a <NUM>% or less yield of the Ni(IV) containing alkali metal-deficient layered nickel oxide, relative to the initial amount of the alkali metal-containing layered nickel oxide.

Moreover, it is known in the art that solubilized Ni(II) ions, which are formed during disproportionation, can catalyze the decomposition of peroxydisulfate salts and monopersulfate salts forming sulfuric acid as a decomposition product. Such further breakdown of the oxidant would be expected by one of ordinary skill in the art to reduce yields of the Ni(IV) containing alkali metal-deficient layered nickel oxide even further, due to decreased amounts of oxidant available for the oxidative demetallation reaction as well as the generation of increased amounts of sulfuric acid available to promote the disproportionation reaction.

Without intending to be bound by theory, it is believed that there are three basic stages resulting in the oxidation/reduction of nickel during the two step methods of the disclosure. The first stage is an oxidative demetallation that occurs during the treatment of the non-stoichiometric alkali metal-containing layered nickel oxide with the oxidant comprising the peroxydisulfate salt and/or the monopersulfate salt. In this stage, a portion of the Ni(III) of the alkali metal-containing layered nickel oxide is oxidized to Ni(IV) and a portion of the alkali metal is removed from the alkali metal-containing layered nickel oxide structure. Without intending to be bound by theory, it is believed that the removal of the alkali metal is non-uniform and the concentration of residual alkali metal near the surface of particles of the starting alkali metal-containing layered nickel oxide is lower than that in the center of the particles. Without intending to be bound by theory, it is further believed that the concentration of residual alkali metal at the center of the particles is limited by the rate of alkali metal ion diffusion, such that the resulting particles of demetallated layered nickel oxide have a "core/shell" type of structure, with localized regions of high degree of demetallation adjacent to the outer surfaces thereof and little to no demetallation in the interior regions thereof. Without intending to be bound by theory, it is believed that little or no soluble Ni<NUM>+ ions are formed during the first stage.

The second stage includes predominantly disproportionation of the partially demetallated layered nickel oxide by treatment with the mineral acid. Without intending to be bound by theory, it is believed that during disproportionation, the mineral acid is able to access the interior or core regions of particles of the partially demetallated layered nickel oxide material such that the remaining Ni(III) undergoes disproportionation to Ni(IV) and soluble Ni<NUM>+ ions. Further, without intending to be bound by theory, it is believed that as the Ni(lll) in the interior or core regions of the particles of the layered nickel oxide is oxidized to Ni(IV), soluble Ni<NUM>+ ions dissolve from the surface of the particles along with additional alkali metal ions from the interior or core regions of the particles, such that the demetallation is more uniform and there is less of a gradient in alkali metal concentration from the surface to the core regions of the particles.

The third stage is direct reduction of the Ni(IV) in the Ni(IV) containing layered nickel oxide to soluble Ni<NUM>+ ions. Without intending to be bound by theory, it is believed that at highly acidic pH, Ni(IV) can be reduced to Ni(II) and the extent of this reduction is proportional to the temperature of the mixture as well as the concentration of the acid.

It was surprisingly and unexpectedly found that the method of the disclosure for the conversion of the alkali metal-containing layered nickel oxide to the Ni(IV) containing alkali metal-deficient layered nickel oxide can include heating the alkali metal-containing layered nickel oxide with the oxidant at a temperature of less than <NUM>, for example, in a range of from about <NUM> to less than <NUM>, to remove approximately <NUM>% of the alkali metal from the alkali metal-containing layered nickel oxide, without significant formation of soluble Ni<NUM>+ ions.

Thus, the method of the disclosure advantageously provide one or more benefits, for example, providing an oxidative demetallation process having relatively short treatment time, providing Ni(IV) containing alkali metal-deficient layered nickel oxides in relatively high yield (e.g., greater than about <NUM>%), minimizing environmentally hazardous waste solutions containing Ni<NUM>+ and sulfuric acid, providing Ni(IV) containing alkali metal-deficient layered nickel oxide particles having a larger particle size distribution (PSD) than Ni(IV) containing alkali metal-deficient layered nickel oxide particles prepared from a method using a persulfate treatment alone or an acid-wash treatment alone, and/or providing Ni(IV) containing alkali metal-deficient layered nickel oxides having high discharge capacity. Additionally, the method of the disclosure can be controlled to provide an alkali metal deficient layered nickel oxides that can be stabilized with alkali metal hydroxides without forming significant amounts of gamma-nickel oxyhydroxide (γ-NiOOH) as a side product. As used herein, and unless specified otherwise, "significant amounts of γ-NiOOH side products" refers to an amount of γ-NiOOH in the stabilized product of about <NUM>% by weight or greater, based on the total weight of the product. In embodiments, the amount of γ-NiOOH in the stabilized product can be less than about <NUM> wt. %, less than about <NUM>%, less than about <NUM>%, less than about <NUM>%, less than about <NUM>%, less than about <NUM>%, less than about <NUM>%, or less than about <NUM>%, by weight.

The term "about" is used according to its ordinary meaning, for example, to mean approximately or around. In one embodiment, the term "about" means ±<NUM>% of a stated value or range of values. In another embodiment, the term "about" means ±<NUM>% of a stated value or range of values. A value or range described in combination with the term "about" expressly includes the specific value and/or range as well (e.g., for a value described as "about <NUM>," "<NUM>" is also expressly contemplated).

As used herein, a Ni(IV) containing alkali metal-deficient layered nickel oxide electrochemically active cathode material that has a "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 <NUM> mAh/g, when discharged at a low discharge rate as the cathode active material in an alkaline cell. As used herein, and unless specified otherwise, a "low discharge rate" refers to a fully charged battery that discharges over the course of about <NUM> to about <NUM> hours, i.e., a battery having about C/<NUM> to about C/<NUM> rate. The C-rate is a well understood measurement in the art that communicates the rate at which a battery is discharged relative to its theoretical rated capacity. It is defined as the discharge current divided by the theoretical discharge current under which the battery would deliver its total nominal/theoretical rated capacity in <NUM> hour. For example, a 1C discharge rate for a material having a gravimetric discharge capacity of about <NUM> mAh/g would deliver the total <NUM> mAh/g capacity in <NUM> hour. A 2C rate for the material having a gravimetric discharge capacity of about <NUM> mAh/g would deliver the total <NUM> mAh/g capacity in <NUM> hour. A C/<NUM> rate for the material having a gravimetric discharge capacity of about <NUM> mAh/g would deliver the <NUM> mAh/g in <NUM> hours. Thus, a C/<NUM> rate for the material having a gravimetric discharge capacity of about <NUM> mAh/g would deliver the total <NUM> mAh/g capacity in <NUM> hours.

Alkali metal-deficient layered nickel oxide electrochemically active cathode materials prepared solely by treatment of alkali metal-containing layered nickel oxide with aqueous sulfuric acid typically have a low discharge rate (e.g., C/<NUM>) gravimetric discharge capacity in a range of about <NUM> to about <NUM> mAh/g. Thus, the methods of the disclosure can provide electrochemically active cathode materials having comparable, if not higher, low rate discharge capacities than materials prepared by other methods known in the art. In embodiments, the alkali metal-deficient layered nickel oxide electrochemically active cathode material has a gravimetric discharge capacity equal to or greater than about <NUM> mAh/g when discharged at a low discharge rate as the cathode active material in an alkaline electrochemical cell, for example, in a range of about <NUM> mAh/g to about <NUM> mAh/g, about <NUM> mAh/g to about <NUM> mAh/g, about <NUM> mAh/g to about <NUM> mAh/g, about <NUM> mAh/g to about <NUM> mAh/g, about <NUM> mAh/g to about <NUM> mAh/g, about <NUM> mAh/g to about <NUM> mAh/g, greater than about <NUM> mAh/g, greater than about <NUM> mAh/g, greater than about <NUM> mAh/g, greater than about <NUM> mAh/g, for example, about <NUM> mAh/g, about <NUM> mAh/g, about <NUM> mAh/g, about <NUM> mAh/g, about <NUM> mAh/g, about <NUM> mAh/g and/or about <NUM> mAh/g.

In general, the alkali metal-containing layered nickel oxide to be oxidatively demetallated can be a stoichiometric or non-stoichiometric alkali metal-containing layered nickel oxide. The non-stoichiometric alkali metal-containing layered nickel oxide has a general formula A<NUM>-aNi1+aO<NUM>, wherein A is an alkali metal and <NUM> < a ≤ <NUM>. In embodiments, the alkali metal-containing layered nickel oxide can have a layered structure. A can be selected from the group consisting of lithium, sodium, potassium, and a combination thereof. In embodiments, A comprises lithium. In embodiments, some of the alkali metal in the alkali metal-containing layered nickel oxide can be substituted with a metal ion having a similar ionic radii, for example, Li+, Ni<NUM>+, Ni<NUM>+, Na+, K+, Cs+, Rb+, Ag+, Mg<NUM>+, Ca<NUM>+, Zn<NUM>+, and Bi<NUM>+, in a range of <NUM> to about <NUM> wt. %, based on the total weight of A in the structure. Without intending to be bound by theory, it is believed that the ionic radii of Rb+ and Cs+ are too large to be the primary alkali metal as they are unable to form a stable layered structure having a structure equivalent to lithium nickel oxide or sodium nickel oxide.

In embodiments, the non-stoichiometric alkali metal-containing layered nickel oxide can include a metal dopant, M, and have a formula Ai-aNi<NUM>+a-zMzO<NUM>, wherein A comprises an alkali metal, <NUM> < a ≤ <NUM>, M comprises a transition metal or main group metal, and <NUM> ≤ z ≤ <NUM>.

In embodiments of the non-stoichiometric alkali metal-containing layered nickel oxide, <NUM> < a ≤ <NUM>, for example, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. Because a is always greater than <NUM>, there are alkali metal sites in the crystal lattice which do not include alkali metal ions but, instead, can be vacant or occupied by excess Ni(ll) ions, thereby providing a non-stoichiometric amount of nickel and alkali metal, relative to the stoichiometric counterpart having a general formula ANiO<NUM> or ANi<NUM>-zMzO<NUM>.

In embodiments, wherein the alkali metal-containing layered nickel oxide includes a metal dopant, M, the metal dopant can include a transition metal, main group metal, or both. In general, the metal dopant is a metal that can access an oxidation state of +<NUM> or greater and has an ionic radius comparable to that of the Ni(lll) in a low-spin or high-spin octahedral site (about <NUM>Å to about <NUM>Å), for example, in a range of about <NUM>Å to about <NUM>Å, or about <NUM>Å to about <NUM>Å. In embodiments, the transition metal comprises cobalt (Co<NUM>+, Co<NUM>+), manganese (Mn<NUM>+, Mn<NUM>+), iron (Fe<NUM>+, Fe<NUM>+), chromium (Cr<NUM>+, Cr<NUM>+), vanadium (V<NUM>+, V<NUM>+), titanium (Ti<NUM>+, Ti<NUM>+), niobium (Nb<NUM>+, Nb<NUM>+), zirconium (Zr<NUM>+) or a combination thereof. In embodiments, the transition metal comprises cobalt, manganese, iron or a combination thereof. In embodiments, the transition metal comprises cobalt. In embodiments, the transition metal comprises manganese. In embodiments, the transition metal comprises cobalt and manganese. The main group metal can be selected from the group consisting of aluminum (Al<NUM>+), gallium (Ga<NUM>+), bismuth (Bi<NUM>+), and a combination thereof. In embodiments, the main group metal comprises aluminum.

In embodiments wherein the alkali metal-containing layered nickel oxide includes a metal dopant, z can be <NUM> ≤ z ≤ <NUM> or <NUM> < z ≤ <NUM>, for example, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. Without intending to be bound by theory, it is believed that as the amount of metal dopant in the alkali metal-containing layered nickel oxide and the Ni(IV) containing alkali metal-deficient layered nickel oxide prepared therefrom increases, the stability of an electrochemically active material including the Ni(IV) containing alkali metal-deficient layered nickel oxide to an aqueous hydroxide solution, such as an alkaline battery electrolyte, increases but the total discharge capacity can decrease, for example, when the dopant metal is not electrochemically active in the same voltage window as nickel.

In general, the alkali metal-containing layered nickel oxide is essentially non-hydrated; however, there may be excess alkali metal oxide and hydroxide from the synthesis of the alkali metal-containing layered nickel oxide present on the surface of the alkali metal-containing layered nickel oxide particles which can absorb water from ambient air. The alkali metal oxide and hydroxide also can react with carbon dioxide in the ambient air to form alkali metal carbonate on the surface of the alkali metal-containing layered nickel particles.

In general, the Ni(IV) containing alkali metal-deficient layered nickel oxide electrochemically active cathode material that is formed according to the method disclosed herein has a general formula AxHyNi<NUM>+aO<NUM>, wherein A comprises an alkali metal; <NUM> ≤ x < <NUM>; <NUM> ≤ y < <NUM>; and <NUM> ≤ a ≤ <NUM>. The Ni(IV) containing alkali metal-deficient layered nickel oxide is also referred to herein as alpha-demetallated layered nickel oxide. The average oxidation state of the nickel in the alpha-demetallated nickel oxide is generally between <NUM>+ and <NUM>+ as the alpha-demetallated layered nickel oxide will include a significant portion of nickel in the <NUM>+ oxidation state as well as some nickel in the <NUM>+ oxidation state. As described below, the alpha-demetallated layered nickel oxide also includes a portion of nickel in the <NUM>+ or <NUM>+ oxidation state located in alkali metal sites of the crystal lattice. It will be understood that the A in the formula for the alpha-demetallated layered nickel oxide electrochemically active cathode material will be the same as the A in the formula for the alkali-metal containing layered nickel oxide material used to prepare the alpha-demetallated material. Thus, A can be selected from the group consisting of lithium, sodium, potassium, and a combination thereof. In embodiments, A is lithium. In embodiments, some of the alkali metal in the alkali metal-containing layered nickel oxide can be substituted with a metal ion having a similar ionic radii, for example, Li+, Ni<NUM>+, Ni<NUM>+, Na+, K+, Cs+, Rb+, Ag+, Mg<NUM>+, Ca<NUM>+, Zn<NUM>+, and Bi<NUM>+.

In embodiments, the alpha-demetallated layered nickel oxide can include a metal dopant, M, and have a formula AxHyNi<NUM>+a-zMzO<NUM>, wherein A comprises an alkali metal; <NUM> ≤ x < <NUM>; <NUM> ≤ y < <NUM>; <NUM> ≤ a ≤ <NUM>; M comprises a transition metal or a main group metal, <NUM> ≤ z ≤ <NUM>.

In embodiments, including those including a metal dopant, the alpha-demetallated layered nickel oxide can have a value of x in a range of <NUM> < x < <NUM>, for example, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. A value of x for the alpha-demetallated layered nickel oxide below about <NUM> can be the result of one or more of an excess amount of the oxidant provided during the oxidative demetallation, too high of a reaction temperature during the oxidative demetallation, and/or too long reaction time for the oxidative demetallation, and thus it is desirable to control these parameters. A value of x for the alpha-demetallated layered nickel oxide above about <NUM> can be the result of one or more of an insufficient amount of the oxidant provided during the oxidative demetallation, too low of a reaction temperature for the oxidative demetallation, and/or too short reaction time for the oxidation demetallation, further demonstrating that it is desirable to control these parameters. Without intending to be bound by theory, it is believed that as the amount, x, of alkali metal, A, in the alpha-demetallated layered nickel oxide decreases below about <NUM>, for example, <NUM>, <NUM>, <NUM>, or less, the alpha-demetallated layered nickel oxide is disadvantageously more likely to form gamma-nickel oxyhydroxide when treated with an aqueous solution of an alkali hydroxide rather than the desirable stabilized form of the Ni(IV) containing alkali metal-deficient layered nickel oxide (which has an additional alkali metal ion inserted into vacant sites in layers thereof and has the formula AxA'vNi<NUM>+aO<NUM>·nH<NUM>O, wherein A includes Li or Na; A' includes K, Rb, or Cs; <NUM> ≤ x < <NUM>; <NUM> < v < <NUM>; <NUM> < a ≤ <NUM>; and <NUM> < n < <NUM>, as described in detail below). Further, without intending to be bound by theory, it is believed that as the amount, x, of alkali metal, A, of the alpha-demetallated layered nickel oxide increases above about <NUM>, the capacity of the prepared alpha-demetallated layered nickel oxide (as well as the stabilized layered nickel oxide prepared therefrom) decreases as a result of the presence of unoxidized Ni(lll) (i.e., unconverted alkali metal-containing layered nickel oxide starting material).

In embodiments, including those including a metal dopant, the alpha-demetallated layered nickel oxide can have a value of y in a range of <NUM> ≤ y < <NUM>, for example, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. H+ can be introduced into the crystal structure during the oxidative demetallation process via ion-exchange with the alkali metal cation. In particular, when the oxidative demetallation is performed in an aqueous solution, under some conditions water can react with the oxidant to form H+ ions which can subsequently partially ion exchange with the alkali metal cations, especially at high temperatures.

In embodiments, including those including a metal dopant, the alpha-demetallated layered nickel oxide can have a value of a in a range of <NUM> ≤ a ≤ <NUM>, for example, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. Because a must be greater than <NUM>, there are alkali metal sites in the crystal lattice which do not include an alkali metal ion but, instead, are occupied by Ni<NUM>+ or Ni<NUM>+ ions thereby providing an excess, non-stoichiometric amount of nickel. It will be appreciated by one of ordinary skill in the art that some alkali metal sites in the crystal lattice can be vacant and, further, that charge neutrality of the structure will be maintained by substitution of one Ni<NUM>+ ion for <NUM> Li+ ions, or one Ni<NUM>+ ion for <NUM> Li+ ions (or one Ni<NUM>+ ion and one Li+ ion). Also, substitution of H+ for Li+ will maintain charge neutrality of the structure.

In embodiments wherein the alkali metal-containing layered nickel oxide containing starting material includes a metal dopant, M, it will be understood that the M in the formula for the alpha-demetallated layered nickel oxide electrochemically active cathode material will be the same as the M in the formula for the alkali-metal containing layered nickel oxide material used to prepare the alpha-demetallated material. Thus, M can include a transition metal, main group metal, or both. In general, the metal dopant is a metal that can access an oxidation state of +<NUM> or greater and has an ionic radius comparable to that of the Ni(III).

In embodiments, the transition metal comprises cobalt (Co<NUM>+, Co<NUM>+), manganese (Mn<NUM>+, Mn<NUM>+), iron (Fe<NUM>+, Fe<NUM>+), chromium (Cr<NUM>+, Cr<NUM>+,), vanadium (V<NUM>+, V<NUM>+), titanium (Ti<NUM>+, Ti<NUM>+), niobium (Nb<NUM>+, Nb<NUM>+), zirconium (Zr<NUM>+) or a combination thereof. In embodiments, the transition metal comprises cobalt, manganese, or a combination thereof. In embodiments, the transition metal comprises cobalt. In embodiments, the transition metal comprises manganese. In embodiments, the transition metal comprises cobalt and manganese. In embodiments, the transition metal comprises cobalt and manganese. The main group metal can be selected from the group consisting of aluminum (Al<NUM>+), gallium (Ga<NUM>+), bismuth (Bi<NUM>+), and a combination thereof. In embodiments, the main group metal comprises aluminum.

In embodiments wherein the alpha-demetallated layered nickel oxide material includes a metal dopant, z can have a value in a range of <NUM> ≤ z ≤ <NUM> or <NUM> < z ≤ <NUM>, for example, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. Without intending to be bound by theory, it is believed that as the amount of metal dopant in the alpha-demetallated layered nickel oxide increases, the stability of an electrochemically active material including the alpha-demetallated layered nickel oxide to an aqueous alkali metal hydroxide solution, such as an alkaline battery electrolyte, increases but the total discharge capacity can decrease, for example, when the dopant metal is not electrochemically active in the same voltage window as nickel.

The disclosure provides a method of preparing an electrochemically active cathode material, including the steps of (i) reacting an alkali metal-containing layered nickel oxide having a formula A<NUM>-aNi<NUM>+aO<NUM>, wherein A comprises an alkali metal and <NUM> < a ≤ <NUM> and a chemical oxidant comprising a peroxydisulfate salt, a monopersulfate salt, or a combination thereof, in a fluid composition at an elevated temperature for at least a period of time sufficient 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, the Ni(IV) containing mixture having a total nickel (Ni) content; and (ii) reacting the Ni(IV)-containing mixture of step (i) with a mineral acid, wherein the mineral acid is added in an amount of about <NUM> moles or less per mole of total nickel, at an elevated 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; the Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material formed during steps (i) and (ii) having the general formula AxHyNi<NUM>+aO<NUM>, wherein A comprises an alkali metal; <NUM> ≤ x < <NUM>; <NUM> ≤ y < <NUM>; and <NUM> < a ≤ <NUM>.

In general, the alkali metal-containing layered nickel oxide, chemical oxidant, and fluid composition of step (i) can be any alkali metal-containing layered nickel oxide, chemical oxidant, and fluid composition as described herein. In general, the elevated temperature in step (i) can be any temperature disclosed herein for step (b) of the methods disclosed herein. In general, the period of time sufficient to form the Ni(IV)-containing mixture in step (i) can be any period of time sufficient to form the Ni(IV)-containing mixture disclosed herein for step (b) of the methods disclosed herein.

In general, the mineral acid of step (ii) can be any mineral acid disclosed herein. In general, the elevated temperature in step (ii) can be any temperature disclosed herein for step (d) of the methods disclosed herein. In general, the period of time sufficient to form the Ni(IV)-containing mixture in step (ii) can be any period of time sufficient to form the Ni(IV)-containing mixture disclosed herein for step (d) of the methods disclosed herein.

In general, the for the formula AxHyNi<NUM>+aO<NUM>, 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.

The method disclosed herein can further include treating an alpha-demetallated nickel oxide with an aqueous solution of an alkali metal hydroxide to form the stabilized beta-demetallated layered nickel oxide having a second, different alkali metal inserted into the layers thereof, according to the formula AxA'vNi<NUM>+aO<NUM>·nH<NUM>O, wherein A includes Li or Na; A' includes K, Cs, or Rb; <NUM> ≤ x < <NUM>; <NUM> < v < <NUM>; <NUM> < a ≤ <NUM>; and <NUM> < n < <NUM>. In embodiments, the alpha-demetallated layered nickel oxide can be doped with a metal, M, such that the resulting beta-demetallated layered nickel oxide has a formula AxA'vNi<NUM>+a-zMzO<NUM>·nH<NUM>O, wherein A comprises Li or Na, <NUM> < x ≤ <NUM>, A' comprises K, Cs, or Rb, <NUM>< v <<NUM>, M comprises a transition metal or main group metal, <NUM> ≤ z ≤ <NUM>, <NUM> < a ≤ <NUM>, and <NUM> < n < <NUM>.

In general, A can be Li or Na. In embodiments, A comprises Li. In general, A' can be K, Rb or Cs, and A' and A are different. In embodiments, A' comprises K. In embodiments, A' comprises Rb or Cs, or a combination thereof. In embodiments, A comprises Li and A' comprises K. In embodiments, x can be in a range of <NUM> to <NUM>, for example, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, for example, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. In embodiments, v can be in a range of <NUM> to <NUM>, for example, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. In embodiments, a can be in a range of <NUM> ≤ a ≤ <NUM>, for example <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. In embodiments, n can be in a range of <NUM> < n < <NUM>, for example, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. In embodiments, z can have a value in a range of <NUM> ≤ z ≤ <NUM> or <NUM> < z ≤ <NUM>, for example, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>.

The aqueous solution of an alkali hydroxide is not particularly limited and can be selected from a potassium salt solution, a rubidium salt solution, a cesium salt solution, or any combination thereof. The concentration of alkali metal salt in the alkaline solution can be any concentration sufficient to achieve substantially complete conversion of the alpha-demetallated layered nickel oxide to the beta-demetallated layered nickel oxide. As used herein, and unless specified otherwise, "substantially complete conversion" refers to conversion of the alpha-demetallated layered nickel oxide to the beta-demetallated layered nickel oxide wherein residual alpha-demetallated layered nickel oxide is present in an amount of <NUM> wt. % or less, based on the total weight of the nickel oxide materials. In some embodiments, the concentration of alkali metal hydroxide in the solution can be in a range of about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. In some embodiments, the alkali metal hydroxide solution includes at least one of potassium hydroxide, cesium hydroxide, and rubidium hydroxide, or a combination thereof, provided at a concentration of about <NUM> to about <NUM>. The alpha-demetallated layered nickel oxide can be provided as a free-flowing powder when combined with the alkali metal hydroxide solution. The alpha-demetallated layered nickel oxide powder and alkali metal hydroxide solution can be combined in a weight ratio of about <NUM>:<NUM> to about <NUM>:<NUM>, about <NUM>:<NUM> to about <NUM>:<NUM>, about <NUM>:<NUM> to about <NUM>:<NUM>, about <NUM>:<NUM> to about <NUM>:<NUM>, about <NUM>:<NUM> to about <NUM>:<NUM>, about <NUM>:<NUM> to about <NUM>:<NUM>, or about <NUM>:<NUM> to about <NUM>:<NUM>, or about <NUM>:<NUM> to about <NUM>:<NUM>, for example, about <NUM>:<NUM>, about <NUM>:<NUM>, or about <NUM>:<NUM>.

The alpha-demetallated layered nickel oxide can be treated with the alkali metal hydroxide solution for a period of time sufficient to ensure that the alpha-demetallated layered nickel oxide is fully converted to the beta-demetallated layered nickel oxide. The alpha-demetallated layered nickel oxide and alkali metal hydroxide solution can be agitated initially for <NUM> to <NUM> minutes at ambient temperature to ensure adequate mixing and wetting. Following mixing of the alpha-demetallated layered nickel oxide and the alkali metal hydroxide solution, the mixture is held at ambient temperature for <NUM> to <NUM> hours. Optionally, the mixture can be stirred during the <NUM> to <NUM> hour period. After the <NUM> to <NUM> hours, the resulting beta-demetallated layered nickel oxide can optionally be washed with water to remove any residual alkali metal hydroxide. Substantially complete conversion to the beta-demetallated layered nickel oxide can be confirmed by analyzing the powder X-ray diffraction pattern of the resulting material. For example, the alpha-delithiated layered nickel oxide has a characteristic powder X-ray diffraction pattern different from that of the beta-delithiated layered nickel oxide. For alpha-delithiated layered nickel oxide treated with a potassium hydroxide solution, as the potassium ion and water molecules from the potassium hydroxide solution insert into layers of the alpha-delithiated layered nickel oxide, the intensity of a diffraction peak located at about <NUM>° to <NUM>°2θ in the X-ray diffraction pattern of the alpha-delithiated layered nickel oxide decreases and very broad peaks appear in the X-ray diffraction pattern of the beta-delithiated layered nickel oxide at about <NUM>° to about <NUM>°2θ, and about <NUM>° to about <NUM>° 2θ. Thus, at full conversion to the beta-delithiated layered nickel oxide, the powder X-ray diffraction pattern will have broad diffraction peaks at about <NUM>° to about <NUM>°2θ, about <NUM>° to about <NUM>°2θ, and about <NUM>° to about <NUM>° 2θ having greater intensities than in the powder X-ray diffraction pattern of the alpha-delithiated layered nickel oxide precursor, and there will be no diffraction peak having significant intensity in the range of about <NUM>° to <NUM>° 2θ. The resulting beta-demetallated layered nickel oxide can be washed repeatedly with deionized water until the pH of the filtrate from washing is about <NUM>. The solid powder can be collected and dried in air at about <NUM> for a period of about <NUM> to <NUM> hours.

In embodiments, treating the alpha-demetallated layered nickel oxide with an aqueous solution of an alkali metal hydroxide, wherein the alkali metal is different from that of the alpha-demetallated layered nickel oxide, forms less than about <NUM>%, by weight, of gamma-nickel oxyhydroxide (γ-NiOOH) as a side product, based on the total weight of the reaction products, for example, less than about <NUM>%, less than about <NUM>%, less than about <NUM>%, less than about <NUM>%, less than about <NUM>%, less than about <NUM>%, or less than about <NUM>%, based on the total weight of the solid reaction products. In embodiments, treating the alpha-demetallated layered nickel oxide with an aqueous solution of an alkali metal hydroxide can form less than about <NUM>% by weight of gamma-nickel oxyhydroxide (γ-NiOOH) as a reaction side product.

Advantageously, the method of the disclosure provide alpha-demetallated layered nickel oxides having relatively larger particle sizes than current methods which, in turn, can be used to prepare beta-demetallated layered nickel oxides having relatively larger particle sizes than beta-demetallated layered nickel oxide particles formed from alpha-demetallated layered nickel oxides using conventional methods. Without intending to be bound by theory, it is believed that the particle size of the layered nickel oxide material does not substantially change between the alpha and the beta forms. As used herein and unless specified otherwise, a particle size does not "substantially change" between the alpha and the beta forms if the average particle size of the beta-demetallated layered nickel oxide is within about <NUM>% of the average particle size of the alpha-demetallated layered nickel oxide. Without intending to be bound by theory, it is believed that the performance of a battery including the beta-demetallated layered nickel oxide can decrease as the particle size of the beta-demetallated layered nickel oxide decreases. In particular, without intending to be bound by theory, it is believed that under the conditions of a closed battery, the beta-demetallated layered nickel oxide can be subject to a reaction with conductive carbon particles in the cathode and the electrolyte, which can result in the high-rate discharge performance of the cell to be less than expected. However, as the particle size of the beta-demetallated layered nickel oxide increases, the surface area of the beta-demetallated layered nickel oxide decreases overall, reducing the number of potential points of contact with the carbon particles, and reducing the likelihood of an oxidative reaction between the carbon particles and the beta-demetallated layered nickel oxide particles. Oxidation of the surface of the carbon particles can decrease their conductivity resulting in an increase in cathode resistance, thereby decreasing high-rate performance of the cell.

Electrochemical cells, or batteries, may be primary or secondary. Primary batteries are meant to be discharged, e.g., to exhaustion, only once and then discarded. Primary batteries are described, for example, in David Linden, Handbook of Batteries (4th ed. Secondary batteries are intended to be recharged. Secondary batteries may be discharged and recharged many times, e.g., more than fifty times, a hundred times, or more. Secondary batteries are described, for example, in <NPL>). Accordingly, batteries may include various electrochemical couples and electrolyte combinations. Although the description and examples provided herein are generally directed towards primary alkaline electrochemical cells, or batteries, it should be appreciated that the invention applies to both primary and secondary batteries having aqueous, nonaqueous, ionic liquid, and solid state electrolyte systems.

Referring to <FIG>, there is shown a primary alkaline electrochemical cell, or battery, <NUM> including a cathode <NUM>, an anode <NUM>, a separator <NUM>, and a housing <NUM>. Battery <NUM> also includes a current collector <NUM>, a seal <NUM>, and an end cap <NUM>. The end cap <NUM> serves as the negative terminal of the battery <NUM>. A positive pip <NUM> is at the opposite end of the battery <NUM> from the end cap <NUM>. The positive pip <NUM> may serve as the positive terminal of the battery <NUM>. An electrolytic solution is dispersed throughout the battery <NUM>. The cathode <NUM>, anode <NUM>, separator <NUM>, electrolyte, current collector <NUM>, and seal <NUM> are contained within the housing <NUM>. Battery <NUM> can be, for example, a AA, AAA, AAAA, C, or D size alkaline battery.

The housing <NUM> can be of any conventional type of housing commonly used in primary alkaline batteries and can be made of any suitable base material, for example cold-rolled steel or nickel-plated cold-rolled steel. The housing <NUM> may have a cylindrical shape. The housing <NUM> may be of any other suitable, non-cylindrical shape. The housing <NUM>, for example, may have a shape comprising at least two parallel plates, such as a rectangular, square, or prismatic shape. The housing <NUM> may be, for example, deep-drawn from a sheet of the base material, such as cold-rolled steel or nickel-plated steel. The housing <NUM> may be, for example, drawn into a cylindrical shape. The housing <NUM> may have at least one open end. The housing <NUM> may have a closed end and an open end with a sidewall therebetween. The interior surface of the sidewall of the housing <NUM> may be treated with a material that provides a low electrical-contact resistance between the interior surface of the sidewall of the housing <NUM> and an electrode, such as the cathode <NUM>. The interior surface of the sidewall of the housing <NUM> may be plated, e.g., with nickel, cobalt, and/or painted with a carbon-loaded paint to decrease contact resistance between, for example, the internal surface of the sidewall of the housing <NUM> and the cathode <NUM>.

The cathode <NUM> includes at least one electrochemically active cathode material. The electrochemically active cathode material can include an alpha-demetallated layered nickel oxide and/or a non-stoichiometric beta-delithiated layered nickel oxide prepared according to methods of the disclosure. In embodiments, when a non-stoichiometric beta-delithiated layered nickel oxide is provided as an electrochemically active cathode material, the non-stoichiometric beta-delithiated layered nickel oxide comprises less than <NUM> wt. %, less than <NUM> wt%, less than <NUM> wt%, or less than <NUM> wt% residual non-stoichiometric alpha-delithiated layered nickel oxide, based on the total weight of the delithiated layered nickel oxide electrochemically active cathode material. Further, the non-stoichiometric beta-delithiated layered nickel oxide can comprise less than about <NUM> wt%, less than about <NUM> wt%, less than about <NUM> wt%, less than about <NUM> wt%, less than about <NUM> wt%, less than about <NUM> wt%, and/or less than about <NUM> wt% of gamma-nickel oxyhydroxide (as a side product) based on the total weight of the delithiated layered nickel oxide electrochemically active cathode material. Similarly, a cell that includes a non-stoichiometric beta-delithiated layered nickel oxide, as described herein, is provided with the non-stoichiometric beta-delithiated layered nickel oxide ab initio.

The cathode <NUM> may also include at least one or more additional electrochemically active cathode materials. The additional electrochemically active cathode material may include manganese oxide, manganese dioxide, electrolytic manganese dioxide (EMD), chemical manganese dioxide (CMD), high power electrolytic manganese dioxide (HP EMD), lambda manganese dioxide, gamma manganese dioxide, ramsdellite, and any combination thereof. Other electrochemically active cathode materials include, but are not limited to, silver oxide; nickel oxide, nickel oxyhydroxide; copper oxide; silver copper oxide; silver nickel oxide; bismuth oxide; silver bismuth oxide; oxygen; and any combination thereof. The nickel oxyhydroxide can include beta-nickel oxyhydroxide, gamma-nickel oxyhydroxide, intergrowths of beta-nickel oxyhydroxide and/or gamma-nickel oxyhydroxide, and cobalt oxyhydroxide-coated beta-nickel oxyhydroxide. The cobalt oxyhydroxide-coated nickel oxyhydroxide can include cobalt oxyhydroxide-coated beta-nickel oxyhydroxide, cobalt oxyhydroxide-coated gamma-nickel oxyhydroxide, and/or cobalt oxyhydroxide-coated intergrowths of beta-nickel oxyhydroxide and gamma-nickel oxyhydroxide.

In embodiments, the electrochemically active material of cathode <NUM> comprises at least <NUM> wt. %, at least <NUM> wt. %, at least <NUM> wt. %, at least <NUM> wt. %, at least <NUM> wt. %, at least <NUM> wt. %, at least <NUM> wt. %, at least <NUM> wt. %, at least <NUM> wt. %, at least <NUM> wt. at least <NUM> wt. %, at least <NUM> wt. %, at least about <NUM> wt. %, or at least about <NUM> wt. %, of the non-stoichiometric beta-delithiated layered nickel oxide, based on the total weight of the electrochemically active cathode material, for example, in a range of about <NUM> wt. % to about <NUM> wt. %, about <NUM> wt. % to about <NUM> wt. %, about <NUM> wt. % to about <NUM> wt. %, about <NUM> wt. % to about <NUM> wt. %, about <NUM> wt. % to about <NUM> wt. %, about <NUM> wt. % to about <NUM> wt. %, or about <NUM> wt. %, based on the total weight of the electrochemically active cathode material. In embodiments, the electrochemically active material of cathode <NUM> comprises about <NUM> wt. % to about <NUM> wt. % of the non-stoichiometric beta-delithiated nickel oxide, based on the total weight of the electrochemically active cathode material and about <NUM> wt. % to about <NUM> wt. % of one or more of manganese oxide, manganese dioxide, electrolytic manganese dioxide (EMD), chemical manganese dioxide (CMD), high power electrolytic manganese dioxide (HP EMD), lambda manganese dioxide, or gamma manganese dioxide, based on the total weight of the electrochemically active cathode material. A combination of between about <NUM> wt. % and about <NUM> wt. % or between about <NUM> wt. % and about <NUM> wt. %, for example, <NUM> wt. %, <NUM> wt. %, <NUM> wt. %, <NUM> wt. % or <NUM> wt. %, of the non-stoichiometric beta-delithiated layered nickel oxide with the balance of the electrochemically active cathode material comprising electrolytic manganese dioxide (EMD) has been found to provide unexpectedly advantageous battery performance in both high-rate discharge applications and low-rate discharge applications.

The cathode <NUM> may include a conductive additive, such as carbon, and optionally, a binder. The cathode <NUM> may also include other additives. The carbon may increase the conductivity of the cathode <NUM> by facilitating electron transport within the solid structure of the cathode <NUM>. The carbon may be graphite, such as natural graphite, synthetic graphite, oxidation resistant graphite, graphene, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon fibers, carbon nanofibers, carbon nanoribbons, carbon nanoplatelets, and mixtures thereof. It is preferred that the amount of carbon in the cathode is relatively low, e.g., less than about <NUM>%, less than about <NUM>%, less than about <NUM>%, less than about <NUM>%, less than about <NUM>%, less than about <NUM>% less than about <NUM>%, or even less than about <NUM>%, for example from about <NUM>% to about <NUM>% by weight or from about <NUM>% to about <NUM>% by weight. The lower carbon level can enable inclusion of a higher loading of electrochemically active cathode material within the cathode <NUM> without increasing the volume of the cathode <NUM> or reducing the void volume. Suitable graphite for use within a battery, e.g., within the cathode, may be, for example, Timrex MX-<NUM>, SFG-<NUM>, MX-<NUM>, all available from Imerys Graphite and Carbon (Bodio, Switzerland). In the case of a highly reactive cathode active material such as non-stoichiometric beta-delithiated layered nickel oxide, an oxidation-resistant graphite, for example, SFG-<NUM>, SFG-<NUM>, and SFG-<NUM>, can be used.

The cathode <NUM> can include an optional binder. As used herein, "binder" refers to a polymeric material that provides cathode cohesion and does not encompass graphite. Examples of optional binders that may be used in the cathode <NUM> include polyethylene, polyacrylic acid, or a fluorocarbon resin, such as PVDF or PTFE. An optional binder for use within the cathode <NUM> may be, for example, COATHYLENE HA-<NUM>, available from E. du Pont de Nemours and Company (Wilmington, DE, USA). Examples of other cathode additives are described in, for example, <CIT>, <CIT>, <CIT> and <CIT>. In some embodiments, the cathode <NUM> is substantially free of a binder. As used herein, "substantially free of a binder" means that the cathode includes less than about <NUM> wt. %, less than about <NUM> wt. %, or less than about <NUM> wt. % of a binder.

The content of electrochemically active cathode material within the cathode <NUM> may be referred to as the cathode loading. The loading of the cathode <NUM> may vary depending upon the electrochemically active cathode material used within, and the size of, the battery <NUM>. For example, a AA battery with a beta-delithiated layered nickel oxide as the electrochemically active cathode material may have a cathode loading of at least about <NUM> grams of beta-delithiated layered nickel oxide. The cathode loading may be, for example, at least about <NUM> grams of non-stoichiometric beta-delithiated layered nickel oxide. The cathode loading may be, for example, between about <NUM> grams to about <NUM> grams of non-stoichiometric beta-delithiated layered nickel oxide. The cathode loading may be from about <NUM> grams to about <NUM> grams of non-stoichiometric beta-delithiated layered nickel oxide. The cathode loading may be from about <NUM> grams to about <NUM> grams of non-stoichiometric beta-delithiated layered nickel oxide. The cathode loading may be from about <NUM> grams to about <NUM> grams of non-stoichiometric beta-delithiated layered nickel oxide. The cathode loading may be from about <NUM> grams to about <NUM> grams of non-stoichiometric beta-delithiated layered nickel oxide. For a AAA battery, the cathode loading may be at least about <NUM> grams of non-stoichiometric beta-delithiated layered nickel oxide electrochemically active cathode material. The cathode loading may be from about <NUM> grams to about <NUM> grams of non-stoichiometric beta-delithiated layered nickel oxide. The cathode loading may be from about <NUM> grams to about <NUM> grams of non-stoichiometric beta-delithiated layered nickel oxide. The cathode loading may be from about <NUM> grams to about <NUM> grams of non-stoichiometric beta-delithiated layered nickel oxide. For a AAAA battery, the cathode loading may be from about <NUM> grams to about <NUM> grams of non-stoichiometric beta-delithiated layered nickel oxide electrochemically active cathode material. For a C battery, the cathode loading may be from about <NUM> grams to about <NUM> grams, for example about <NUM> grams, of non-stoichiometric beta-delithiated layered nickel oxide electrochemically active cathode material. For a D battery, the cathode loading may be from about <NUM> grams to about <NUM> grams, for example about <NUM> grams, of non-stoichiometric beta-delithiated layered nickel oxide electrochemically active cathode material.

The cathode components, such as active cathode material(s), carbon particles, binder, and any other additives, may be combined with a liquid, such as an aqueous potassium hydroxide electrolyte, blended, and pressed into pellets for use in the assembly of the battery <NUM>. For optimal cathode pellet processing, it is generally preferred that the cathode pellet have a moisture level in the range of about <NUM>% to about <NUM>% by weight, or about <NUM>% to about <NUM>% by weight. The pellets, are placed within the housing <NUM> during the assembly of the battery <NUM>, and are typically re-compacted to form a uniform cathode assembly within the housing <NUM>. The cathode pellet may have a cylindrical shape that includes a central bore. The size of the pellet may vary by the size of the battery, for example AA size, AAA size, AAAA size, C size, and D size, that the pellet will be used within. The central bore may define an inside diameter (ID) of the pellet. The inside diameter of the pellet for a AA battery may be, for example, from about <NUM> to about <NUM>. The inside diameter of the pellet for a AA battery may be, for example, from about <NUM> to about <NUM>. The inside diameter of the pellet for a AAA battery may be, for example, from about <NUM> to about <NUM>. The inside diameter of the pellet for a AAA battery may be, for example, from about <NUM> to about <NUM>. The inside diameter of the pellet for a AAAA battery may be, for example, from about <NUM> to about <NUM>. The inside diameter of the pellet for a C battery may be, for example, from about <NUM> to about <NUM>. The inside diameter of the pellet for a D battery may be, for example, from about <NUM> to about <NUM>.

The cathode <NUM> will have a porosity that may be calculated at the time of cathode manufacture. The porosity of the cathode <NUM> may be from about <NUM>% to about <NUM>%, between about <NUM>% and about <NUM>%, and, for example, about <NUM>%. The porosity of the cathode <NUM> may be calculated at the time of manufacturing, for example after cathode pellet processing, since the porosity of the cathode <NUM> within the battery <NUM> may change over time due to, inter alia, cathode swelling associated with electrolyte wetting of the cathode and discharge of the battery <NUM>. The porosity of the cathode <NUM> may be calculated as follows. The true density of each solid cathode component may be taken from a reference book, for example <NPL>). The solids weight of each of the cathode components are defined by the battery design. The solids weight of each cathode component may be divided by the true density of each cathode component to determine the cathode solids volume. The volume occupied by the cathode <NUM> within the battery <NUM> is defined, again, by the battery design. The volume occupied by the cathode <NUM> may be calculated by a computer-aided design (CAD) program. The porosity may be determined by the following formula: <MAT>.

For example, the cathode <NUM> of a AA battery may include about <NUM> grams of non-stoichiometric beta-delithiated layered nickel oxide and about <NUM> grams of graphite (BNC-<NUM>) as solids within the cathode <NUM>. The true densities of the non-stoichiometric beta-delithiated layered nickel oxide and graphite may be, respectively, about <NUM>/cm3 and about <NUM>/cm3. Dividing the weight of the solids by the respective true densities yields a volume occupied by the non-stoichiometric beta-delithiated layered nickel oxide of about <NUM> cm3 and a volume occupied by the graphite of about <NUM> cm3. The total solids volume is about <NUM> cm3. The battery designer may select the volume occupied by the cathode <NUM> to be about <NUM> cm3. Calculating the cathode porosity per the equation above [<NUM>-(<NUM> cm3 ÷ <NUM> cm3)] yields a cathode porosity of about <NUM>, or <NUM>%.

The anode <NUM> can be formed of at least one electrochemically active anode material, a gelling agent, and minor amounts of additives, such as organic and/or inorganic gassing inhibitor. The electrochemically active anode material may include zinc; zinc oxide; zinc hydroxide; metal hydride, such as AB5(H), AB2(H), and A2B7(H); alloys thereof; and any combination thereof.

The content of electrochemically active anode material within the anode <NUM> may be referred to as the anode loading. The loading of the anode <NUM> may vary depending upon the electrochemically active anode material used within, and the size of, the battery. For example, a AA battery with a zinc electrochemically active anode material may have an anode loading of at least about <NUM> grams of zinc. The anode loading may be, for example, at least about <NUM> grams, about <NUM> grams, about <NUM> grams, about <NUM> grams, about <NUM> grams, or about <NUM> grams of zinc. The anode loading may be from about <NUM> grams to about <NUM> grams of zinc. The anode loading may be from about <NUM> grams to about <NUM> grams of zinc. For example, a AAA battery with a zinc electrochemically active anode material may have an anode loading of at least about <NUM> grams of zinc. For example, the anode loading may be from about <NUM> grams to about <NUM> grams of zinc. The anode loading may be, for example, from about <NUM> grams to about <NUM> grams of zinc. For example, a AAAA battery with a zinc electrochemically active anode material may have an anode loading of at least about <NUM> grams of zinc. For example, the anode loading may be from about <NUM> grams to about <NUM> grams of zinc. For example, a C battery with a zinc electrochemically active anode material may have an anode loading of at least about <NUM> grams of zinc. For example, the anode loading may be from about <NUM> grams to about <NUM> grams of zinc. For example, a D battery with a zinc electrochemically active anode material may have an anode loading of at least about <NUM> grams of zinc. For example, the anode loading may be from about <NUM> grams to about <NUM> grams of zinc. The anode loading may be, for example, from about <NUM> grams to about <NUM> grams of zinc.

Examples of a gelling agent that may be used within the anode <NUM> include a polyacrylic acid; a polyacrylic acid cross-linked with polyalkenyl ether of divinyl glycol; a grafted starch material; a salt of a polyacrylic acid; a carboxymethylcellulose; a salt of a carboxymethylcellulose (e.g., sodium carboxymethylcellulose); or combinations thereof. The anode <NUM> may include a gassing inhibitor that may include an inorganic material, such as bismuth, tin, or indium. Alternatively, the gassing inhibitor can include an organic compound, such as a phosphate ester, an ionic surfactant or a nonionic surfactant. The electrolyte may be dispersed throughout the cathode <NUM>, the anode <NUM>, and the separator <NUM>. The electrolyte comprises an ionically conductive component in an aqueous solution. The ionically conductive component may be an alkali hydroxide. The alkali hydroxide may be, for example, potassium hydroxide, sodium hydroxide, lithium hydroxide, cesium hydroxide, and any combination thereof. The concentration of the ionically conductive component may be selected depending on the battery design and its desired performance. The concentration of the alkali hydroxide within the electrolyte may be from about <NUM> to about <NUM>, or from about <NUM>% to about <NUM>%, on a weight basis of the total electrolyte within the battery <NUM>. For example, the hydroxide concentration of the electrolyte may be from about <NUM> to about <NUM>, or from about <NUM>% to about <NUM>%, on a weight basis of the total electrolyte within the battery <NUM>. The aqueous alkaline electrolyte may also include zinc oxide (ZnO). The ZnO may serve to suppress zinc corrosion within the anode. The concentration of ZnO included within the electrolyte may be less than about <NUM>% by weight of the total electrolyte within the battery <NUM>. The ZnO concentration, for example, may be from about <NUM>% by weight to about <NUM>% by weight of the total electrolyte within the battery <NUM>.

The total weight of the aqueous alkaline electrolyte within a AA alkaline battery, for example, may be from about <NUM> grams to about <NUM> grams. The total weight of the alkaline electrolyte within a AA battery may be, for example, from about <NUM> grams to about <NUM> grams. The total weight of the alkaline electrolyte within a AA battery may be, for example, from about <NUM> grams to about <NUM> grams. The total weight of the aqueous alkaline electrolyte within a AAA alkaline battery, for example, may be from about <NUM> grams to about <NUM> grams. The total weight of the electrolyte within a AAA battery may be, for example, from about <NUM> grams to about <NUM> grams. The total weight of the electrolyte within a AAA battery may be, for example, from about <NUM> grams to about <NUM> grams. The total weight of the electrolyte within a AAAA battery may be from about <NUM> grams to about <NUM> gram, for example, from about <NUM> grams to about <NUM> grams. The total weight of the electrolyte within a C battery may be from about <NUM> grams to about <NUM> grams, for example, from about <NUM> grams to about <NUM> grams. The total weight of the electrolyte within a D battery may be from about <NUM> grams to about <NUM> grams, for example, from about <NUM> grams to about <NUM> grams.

The separator <NUM> comprises a material that is wettable or wetted by the electrolyte. A material is said to be wetted by a liquid when the contact angle between the liquid and the surface of the material is less than <NUM>° or when the liquid tends to spread spontaneously across the surface of the material; both conditions normally coexist. The separator <NUM> may comprise a single layer, or multiple layers, of woven or nonwoven paper or fabric. The separator <NUM> may include a layer of, for example, cellophane combined with a layer of non-woven material. The separator <NUM> also can include an additional layer of non-woven material. The separator <NUM> may also be formed in situ within the battery <NUM>. <CIT>, for example, discloses such separator materials, and potentially suitable methods of their application. The separator material may be thin. The separator <NUM>, for example, may have a dry material thickness of less than <NUM> micrometers (microns). The separator <NUM> may have a dry material thickness from about <NUM> microns to about <NUM> microns. The separator <NUM> may have a dry material thickness from about <NUM> microns to about <NUM> microns. The separator <NUM> may have a basis weight of about <NUM>/m2 or <NUM> less. The separator <NUM> may have a basis weight from about <NUM>/m2 to about <NUM>/m2. The separator <NUM> may have a basis weight from about <NUM>/m2 to about <NUM>/m2. The separator <NUM> may have an air permeability value. The separator <NUM> may have an air permeability value as defined in International Organization for Standardization (ISO) Standard <NUM>. The air permeability value of the separator <NUM> may be from about <NUM> cm3/cm2•min @ 1kPa to about <NUM> cm3/cm2•min @ 1kPa. The air permeability value of the separator <NUM> may be from about <NUM> cm3/cm2•min @ 1kPa to about <NUM> cm3/cm2•min @ 1kPa. The air permeability value of the separator <NUM> may be from about <NUM> cm3/cm2•min @ 1kPa to about <NUM> cm3/cm2•min @ 1kPa.

The current collector <NUM> may be made into any suitable shape for the particular battery design by any known methods within the art. The current collector <NUM> may have, for example, a nail-like shape. The current collector <NUM> may have a columnar body and a head located at one end of the columnar body. The current collector <NUM> may be made of metal, e.g., zinc, copper, brass, silver, or any other suitable material. The current collector <NUM> may be optionally plated with tin, zinc, bismuth, indium, or another suitable material presenting a low electrical-contact resistance between the current collector <NUM> and, for example, the anode <NUM>. The plating material may also exhibit an ability to suppress gas formation when the current collector <NUM> is contacted by the anode <NUM>.

The seal <NUM> may be prepared by injection molding a polymer, such as polyamide, polypropylene, polyetherurethane, or the like; a polymer composite; and any combination thereof into a shape with predetermined dimensions. The seal <NUM> may be made from, for example, Nylon <NUM>,<NUM>; Nylon <NUM>,<NUM>; Nylon <NUM>,<NUM>; Nylon <NUM>; polypropylene; polyetherurethane; co-polymers; composites; and any combination thereof. Exemplary injection molding methods include both the cold runner method and the hot runner method. The seal <NUM> may contain other known functional materials such as a plasticizer, a crystalline nucleating agent, an antioxidant, a mold release agent, a lubricant, and an antistatic agent. The seal <NUM> may also be coated with a sealant. The seal <NUM> may be moisturized prior to use within the battery <NUM>. The seal <NUM>, for example, may have a moisture content of from about <NUM> weight percent to about <NUM> weight percent depending upon the seal material. The current collector <NUM> may be inserted into and through the seal <NUM>.

The end cap <NUM> may be formed in any shape sufficient to close the battery. The end cap <NUM> may have, for example, a cylindrical or prismatic shape. The end cap <NUM> may be formed by pressing a material into the desired shape with suitable dimensions. The end cap <NUM> may be made from any suitable material that will conduct electrons during the discharge of the battery <NUM>. The end cap <NUM> may be made from, for example, nickel-plated steel or tin-plated steel. The end cap <NUM> may be electrically connected to the current collector <NUM>. The end cap <NUM> may, for example, make electrical connection to the current collector <NUM> by being welded to the current collector <NUM>. The end cap <NUM> may also include one or more apertures, such as holes, for venting any gas pressure due to electrolyte leakage or venting of the battery due to buildup of excessive internal pressure. The current collector <NUM>, the seal <NUM>, and the end cap <NUM> may be collectively referred to as the end cap assembly.

To deionized water in a <NUM> liter glass reactor fitted with a heating mantle, non-stoichiometric layered lithium nickel oxide (LNO) having an excess of nickel (Li<NUM>-aNi<NUM>+aO<NUM>, <NUM> ≤ a ≤ <NUM>) that had been ground and passed through a <NUM> mesh (U. Standard) sieve was added with rapid stirring to form a suspension. To the stirred suspension of LNO, solid sodium peroxydisulfate (i.e., Na<NUM>S<NUM>O<NUM>, or "SPS") was added such that the amount of persulfate added relative to LNO was <NUM> moles of persulfate per mole of LNO. The initial pH of the mixture was <NUM>-<NUM>. The stirred mixture was heated at a rate of about <NUM>/min to <NUM>. After stirring the mixture at <NUM> for <NUM> hours, about <NUM>% of the lithium had been removed from the LNO and less than <NUM> wt% of soluble Ni<NUM>+ ions detected in solution, using UV-visible spectroscopy and an appropriate concentration calibration curve. Without cooling the resulting mixture, sulfuric acid was added with stirring in an amount of from <NUM> to <NUM> moles of acid per mole of total nickel and the mixture heated at a rate of about <NUM>/min to <NUM>, followed by continued stirring at <NUM> for <NUM> hours. Stirring was stopped and the solid product allowed to settle. The supernatant solution was decanted while still warm. The resulting solid alpha-delithiated layered nickel oxide product was washed with deionized water. After washing, the solid product was again allowed to settle and the clear supernatant decanted. The washing process was repeated to remove soluble Ni<NUM>+complexes, soluble nickel and lithium sulfates, and residual sulfuric acid. The solid product was collected by vacuum filtration and dried at <NUM>-<NUM> in air for at about <NUM> hours. Yield of the dried alpha-delithiated layered nickel oxide product was about <NUM>% by weight. The mean primary particle size (i.e., D<NUM>) of the alpha-delithiated layered nickel oxide product was about <NUM> microns. This represented about a <NUM>% reduction in mean primary particle size compared to that of the precursor layered lithium nickel oxide. The resulting dried material was provided as the cathode active material in a <NUM> type alkaline button cell, which demonstrated a low-rate (e.g., <NUM> mA/g, -C/<NUM>) discharge capacity in the range of <NUM> to <NUM> mAh/g. The product yields of alpha-delithiated layered nickel oxides, the amount of residual lithium in the crystal lattice, and the discharge capacities re provided in Table <NUM>, below, for various sulfuric acid:LNO molar ratios.

The dried alpha-delithiated layered nickel oxide was treated with an <NUM> aqueous potassium hydroxide solution including <NUM> of potassium hydroxide per gram of the alpha-delithiated layered nickel oxide. The mixture was sealed in a polyethylene bottle and held at room temperature for <NUM>-<NUM> hours to form the beta-delithiated layered nickel oxide. The semi-solid mixture was washed with multiple aliquots of deionized water to remove unreacted KOH. The washed beta-delithiated layered nickel oxide product was dried at <NUM> in air for about <NUM> hours.

Thus, Example <NUM> demonstrates that when the sulfuric acid is reacted with the Ni(IV) containing mixture at <NUM>, varying the acid to LNO molar ratio in a range of <NUM> to <NUM> moles of acid per mole of total nickel content does not have a large effect on yield of alpha-delithiated layered nickel oxide, but does have a moderate (<<NUM>%) effect on the discharge capacity Example <NUM> further demonstrates that, under the conditions of Example <NUM>, it is possible to increase the discharge capacity of the alpha-delithiated layered nickel oxide while maintaining the product yield.

To deionized water in a <NUM> liter glass reactor fitted with a heating mantle, non-stoichiometric layered lithium nickel oxide (LNO) having an excess of nickel (Li<NUM>-aNi<NUM>+aO<NUM>, <NUM> ≤ a ≤ <NUM>) that had been ground and passed through a <NUM> mesh (U. Standard) sieve was added with stirring to form a suspension. To the stirred suspension of LNO, solid sodium peroxydisulfate (i.e., Na<NUM>S<NUM>O<NUM>, SPS) was added such that the amount of persulfate added relative to LNO was <NUM> moles of persulfate per mole of LNO. The initial pH of the mixture was <NUM>-<NUM>. The stirred mixture was heated at a rate of about <NUM>/min to <NUM>. After stirring the mixture at <NUM> for <NUM> hours, about <NUM>% of the lithium had been removed from the LNO and less than <NUM> wt% soluble Ni<NUM>+ detected in solution. Without cooling the resulting mixture, sulfuric acid was added with stirring in an amount of <NUM> to <NUM> moles of acid per mole of total nickel and the mixture was heated at a rate of about <NUM>/min to <NUM>, followed by continued stirring at <NUM> for <NUM> hours. Stirring was stopped and the solid product allowed to settle. The supernatant solution was decanted while still warm. The resulting solid alpha-delithiated layered nickel oxide product was washed with deionized water. After washing, the solid product was allowed to settle again and the clear supernatant decanted. The washing process was repeated to remove soluble Ni<NUM>+ complexes, soluble nickel and lithium sulfates, and residual sulfuric acid. The solid product was collected by vacuum filtration and dried at <NUM>-<NUM> in air for at about <NUM> hours. Yield of dried product was about <NUM>-<NUM>%. The mean primary particle size (i.e., D<NUM>) of the alpha-delithiated layered nickel oxide product was about <NUM> microns. This represented about a <NUM>% reduction in mean primary particle size compared to that of the precursor layered lithium nickel oxide. The resulting dried material was provided as the cathode active material in a <NUM> type alkaline button cell, which demonstrated a low-rate (e.g., <NUM> mA/g, -C/<NUM>) discharge capacity in a range of about <NUM>-about <NUM> mAh/g. The product yields of the alpha-delithiated layered nickel oxides, the amounts of residual lithium in the crystal lattice, and discharge capacities are provided in Table <NUM>, below, for the various sulfuric acid:LNO molar ratios.

The dried alpha-delithiated layered nickel oxide was thoroughly mixed with an <NUM> aqueous potassium hydroxide solution to form a semi-solid mixture including <NUM> of potassium hydroxide per gram of the alpha-delithiated layered nickel oxide material. The mixture was sealed in a polyethylene bottle and held at room temperature for <NUM>-<NUM> hours to form the beta-delithiated layered nickel oxide. The semi-solid mixture was washed with multiple aliquots of deionized water to remove unreacted KOH. The washed beta-delithiated layered nickel oxide product was dried at <NUM> in air for about <NUM> hours.

Thus, Example <NUM> demonstrates forming alpha-delithiated layered nickel oxide electrochemically active cathode materials according to methods of the disclosure using a higher reaction temperature for the acid-promoted disproportionation step relative to Example <NUM>, having somewhat higher gravimetric discharge capacities than those of the alpha-delithiated layered nickel oxide materials of Example <NUM>. Example <NUM> further demonstrates the formation of a beta-delithiated layered nickel oxide electrochemically active cathode material of the disclosure.

To deionized water in a <NUM> liter glass reactor fitted with a heating mantle, non-stoichiometric layered lithium nickel oxide having excess nickel content (Li<NUM>-aNi<NUM>+aO<NUM>, <NUM> ≤ a ≤ <NUM>) was added with stirring to form a suspension having nominally <NUM> percent solids by weight. The stirred suspension was heated at a rate of about <NUM>/min to about <NUM>-<NUM>. A <NUM>% by weight sulfuric acid solution was added in portions during a period of <NUM> minutes such that the temperature remained below about <NUM> and the total amount of acid added was <NUM> moles of acid per mole of nickel. The resulting mixture containing about <NUM>% by weight solids was held at <NUM> and stirred for a total of <NUM>-<NUM> hours. The solid product was allowed to settle and was separated from the green-colored supernatant solution containing by decantation while still warm. The solid product was washed repeatedly with deionized water to remove soluble Ni(ll) complexes, nickel and lithium sulfates, and any residual sulfuric acid. The washed solid product was collected by vacuum filtration and then dried at <NUM>-<NUM> in air for about <NUM> hours. Yield of dried product was about <NUM>-<NUM>% (wt/wt). The dried product still contained about <NUM>% by weight of residual lithium in the crystal lattice as determined by ICP-AES. The low-rate (e.g., <NUM> mA/g, C/<NUM>) discharge capacity of dried product provided as the cathode active material in a <NUM>-type alkaline button cell was about <NUM> to <NUM> mAh/g. The average Ni oxidation state typically ranged from <NUM> to <NUM>. The mean primary particle size (i.e., D<NUM>) of the alpha-delithiated layered nickel oxide product was about <NUM> microns. This represented a nearly <NUM>% reduction in mean primary particle size compared to that of the precursor layered lithium nickel oxide.

The dried alpha-delithiated layered nickel oxide was thoroughly mixed with a suitable volume of <NUM> potassium hydroxide aqueous solution to form a semi-solid mixture containing <NUM> mole KOH (salt) per mole of the nickel oxide. The mixture was sealed in a polyethylene bottle and held at room temperature for <NUM>-<NUM> hours to form the beta-delithiated layered nickel oxide. The semi-solid mixture was washed with multiple aliquots of deionized water to remove unreacted KOH. The washed beta-delithiated layered nickel oxide product was dried at <NUM> in air for about <NUM> hours. However, the beta-delithiated layered nickel oxide also contains a variable amount of gamma-NiOOH as a side product, typically less than <NUM>% by weight as estimated by comparison of its powder x-ray diffraction pattern with the x-ray diffraction patterns for a series of weighed physical blends of a beta-delithiated layered nickel oxide sample having a nearly undetectable level of gamma-NiOOH and a sample of nominally pure gamma-NiOOH.

Thus, Example <NUM> demonstrates the preparation of alpha-delithiated layered nickel oxide by a method not of the disclosure and including only the acid-promoted disproportionation of Ni(III) of the nonstoichiometric layered lithium nickel oxide to Ni(IV) and water soluble Ni(ll) with sulfuric acid solution. The use of acid-promoted disproportionation for delithiation of the lithium nickel oxide precursor results in dissolution of about <NUM>% of the nickel as Ni<NUM>+ and thereby affords a solid reaction product yield of less than <NUM>% by weight, for example, <NUM>% yield. Example <NUM> further demonstrates that as a consequence of the dissolution of more than <NUM>% of the nickel, the mean primary particle size of the alpha-delithiated layered nickel oxide product is from <NUM> to <NUM>% smaller than that of corresponding particles of the layered lithium nickel oxide precursor. Thus, Examples <NUM> and <NUM>, together, demonstrate that the methods of the disclosure can be used to prepare beta-delithiated layered nickel oxide at higher yield, having comparable or higher electrochemical discharge capacity in an alkaline cell and larger primary particle size, while maintaining comparable or lower amounts of gamma-NiOOH side product in the final material relative to a prior art delithiation method using only acid-promoted disproportionation.

Example <NUM>. Preparation of alpha-delithiated layered nickel oxide via treatment of non-stoichiometric layered lithium nickel oxide with an excess amount of sodium peroxydisulfate only.

To deionized water in a <NUM> liter glass reactor fitted with a heating mantle, non-stoichiometric layered lithium nickel oxide having excess nickel content (Li<NUM>-aNi<NUM>+aO<NUM>, <NUM> ≤ a ≤ <NUM>) was added with stirring to form a suspension having nominally <NUM> percent solids by weight. Solid sodium peroxydisulfate was added in portions to the stirred suspension such that the total amount of persulfate added was <NUM> mole of persulfate per mole of nickel oxide. The stirred mixture was heated at a rate of about <NUM>/min to <NUM> and held at that temperature for <NUM> hours. The initial pH of the suspension of lithium nickel oxide precursor was greater than <NUM> prior to the addition of persulfate. After addition of persulfate was complete and the temperature had reached <NUM>, the pH decreased to <NUM>. After stirring for <NUM> hours at <NUM>, the pH decreased further to less than <NUM>. At this time, stirring was stopped and the solid product allowed to settle. The solid product was separated from the dark green-colored supernatant solution containing Ni<NUM>+ by decantation while still warm. The solid product was washed repeatedly with deionized water and decanted to remove soluble nickel and lithium sulfates, and unreacted sodium persulfate. Finally, the washed solid product was collected by suction filtration and dried at <NUM>-<NUM> in air for about <NUM> hours. Yield of dried product was about <NUM>-<NUM>% (wt/wt). The dried product still contained about <NUM>% by weight of residual lithium in the crystal lattice as determined by ICP-AES. The low-rate (e.g., <NUM> mA/g, ∼C/<NUM>) discharge capacity of the alpha-delithiated layered nickel oxide in a <NUM>-type alkaline button cell was about <NUM> to <NUM> mAh/g. The mean primary particle size (i.e., D<NUM>) of the alpha-delithiated layered nickel oxide was about <NUM> microns. This represents a <NUM>% reduction in mean primary particle size compared to that of the precursor layered lithium nickel oxide.

The alpha-delithiated layered nickel oxide was thoroughly mixed with a suitable volume of <NUM> potassium hydroxide aqueous solution to form a semi-solid mixture containing <NUM> mole KOH (salt) per mole of the nickel oxide. The mixture was sealed in a polyethylene bottle and held at room temperature for <NUM>-<NUM> hours to form the beta-delithiated layered nickel oxide. The semi-solid mixture was washed with multiple aliquots of deionized water to remove unreacted KOH. The washed beta-delithiated layered nickel oxide product was dried at <NUM> in air for about <NUM> hours. However, the beta-delithiated layered nickel oxide also contains a variable amount of gamma-NiOOH as a side product, typically less than <NUM>% by weight as estimated from its powder x-ray diffraction pattern.

Thus, Example <NUM> demonstrates the preparation of alpha-delithiated layered nickel oxide by a method not of the disclosure and including only the oxidative delithiation of the non-stoichiometric layered nickel oxide precursor using an excess amount of sodium persulfate. Because of the accelerated rate of thermal decomposition of persulfate at <NUM> to form sulfuric acid, as evidenced by the decrease in pH with reaction time, the yield of alpha-delithiated layered nickel oxide was decreased. The presence of sulfuric acid also promoted some disproportionation to take place resulting in the mean primary particle size of the alpha-delithiated layered nickel oxide to range from <NUM> to <NUM>% smaller than that of the lithium nickel oxide precursor. Additionally, the process of Example <NUM> required treatment with <NUM>% more sodium persulfate at <NUM> for <NUM> hours, in contrast to Example <NUM>, a method of the disclosure that was completed with less sodium persulfate and only needed to be heated to <NUM> for <NUM> hours and <NUM> for <NUM> hours to arrive at similar yields. Thus, Examples <NUM> and <NUM>, together, demonstrate that the methods of the disclosure can be used to prepare beta-delithiated layered nickel oxide at higher yield, less energy consumption (i.e., energy use of <NUM> for <NUM> hours > <NUM> for <NUM> hours + <NUM> for <NUM> hours), having comparable or higher electrochemical discharge capacity in an alkaline cell, and a larger primary particle size, using <NUM>% less sodium persulfate, while maintaining comparable or lower amounts of gamma-NiOOH side product in the final material relative to a prior art delithiation method using a substantially larger amount of sodium peroxydisulfate at a higher reaction temperature.

Claim 1:
A method of preparing an electrochemically active cathode material, comprising:
(i) reacting an alkali metal-containing layered nickel oxide having a formula A<NUM>-aNi<NUM>+aO<NUM>, wherein A comprises an alkali metal and <NUM> < a ≤ <NUM> and a chemical oxidant comprising a peroxydisulfate salt, a monopersulfate salt, or a combination thereof, in a fluid composition at an elevated temperature for at least a period of time sufficient 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, the Ni(IV) containing mixture having a total nickel (Ni) content; and
(ii) reacting the Ni(IV)-containing mixture of step (i) with a mineral acid, wherein the mineral acid is added in an amount of <NUM> moles or less per mole of total nickel, at an elevated 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;
the Ni(IV)-containing alkali metal-deficient layered nickel oxide electrochemically active cathode material formed during steps (i) and (ii) having the general formula AxHyNi<NUM>+aO<NUM>:
wherein
A comprises an alkali metal; <MAT> <MAT> and <MAT>