THEREOF

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR

DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION This invention relates to a new synthetic Manganese Oxide material i-Mhq2, a method of synthesis of the new material i-Mhq2, and use of the new synthetic Manganese Oxide i-Mhq2 as a secondary battery active cathode material in an electrochemical application.

Manganese oxides of general formula Mn0 ₂ -x. have a variety of applications, including but not limited to pigments/coloring agents, components to produce specialty alloys, catalysts, water purifying agents, and oxidants in organic synthesis. Energy storage applications such as Li and Li-ion batteries, supercapacitors and alkaline (primary) batteries have increasingly dominated the MnCh-x market.

Traditional alkaline batteries commonly employ electrolytic manganese dioxide (EMD) as the active material in the cathode. The EMD structure or g-MnCh is generally described as an intergrowth of Ramsdellite (R-MnCE) and Pyrolusite ((B-MnCh) tunnel Mn0 ₂ phases with a considerable amount of defects in the crystalline lattice.

During battery discharge and reduction of the EMD, protons intercalate into the tunnel manganese oxide structures forming a MhOOHc solid solution, which preserves the tunnel structure of the starting manganese oxide. The final product for traditional 1 -electron reduction of Mn(IV) to Mn(III) is d-MnOOH. Theoretically, this d-MhOOH can be further reduced to Mn(OH) ₂ . In practice, however, the dissolution-precipitation mechanism which results in the formation of spinels Hausmannite (M Cri) and Hetaerolite (ZnM Cri) is more favorable (References: A. Kozawa, J.F. Yeager, JES, 1965, 959-963; D. Im, A. Manthiram, B. Coffey, JES 2003, A165159; D. Boden et al, JES1967, 415-417; Bode et al, JES 1997, 792-801; C.

Mandoloni et al, JES, 1992, 954-59; M. R. Bailey, S. W. Donne, JES, 2012, A2010-15).

Structural differences between tunnel manganese(III) oxy-hydroxide and layered manganese(II) hydroxide may be the reason why the second electron transferred is hindered. Restoring the original tunnel manganese oxide structure during charge or oxidation is also problematic.

BRIEF SUMMARY OF THE INVENTION In one aspect, the present invention features a composition of matter including a material having a general formula of Mn0 _2-x ; wherein x is in a range of 0 to 0.35; wherein the material is crystalline; and wherein the material has an X-ray diffraction pattern according to the following table:

In an embodiment of this aspect of the invention, the material has a space grouping of

P3ml.

In another embodiment of this aspect of the invention, the material has a distance between manganese atoms in the c-direction of about 4.487 Angstroms.

In another aspect, the present invention features a method of preparing a crystalline material including manganese and oxygen, the method including a step of contacting a solid b-MhOOH with a component selected from the group consisting of an ozone species, a radical oxygen species, and a combination of the aforementioned species, in an absence of water, said crystalline material having after the contacting step an X-ray pattern according to the following table:

In an embodiment of this method, the crystalline material has a space grouping of P3ml.

In another embodiment of the method, the crystalline material has a distance between manganese atoms in the c-direction of about 4.487 Angstroms.

In another aspect, the invention features a composition of matter including a material defined by a general formula MnCh- _x , where x in in a range of 0 to 0.35; wherein the material is crystalline, and wherein the material has a space grouping of P3ml .

In an embodiment of this aspect of the invention, the material has a distance between manganese atoms in the c-direction of about 4.487 Angstroms.

In another aspect, the present invention features a method of preparing a crystalline material including manganese and oxygen, the method including the steps of contacting a solid b-MhOOH species with a component selected from the group consisting of an ozone species, a radical oxygen species, and a combination of the aforementioned species, in an absence of water, said crystalline material after the contacting step being defined by a general formula MnCh- _x , where x in in a range of 0 to 0.35; and wherein the crystalline material has a space grouping of P3m\.

These and other aspects, features, advantages, and objects will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The appended drawings support the detailed description of the invention and refer to exemplary embodiments. The appended drawings are considered to be in no way limiting to the full scope of the invention.

In the drawings:

FIG. 1 shows crystalline lattice structures for Ramsdellite and Pyrolusite manganese dioxide materials;

FIG. 2 shows a synthetic Bimessite structure as compared to b-MhOOH and Mn(OH) ₂ structures;

FIG. 3 shows a synthetic Mn0 ₂ structure according to an ideal desired structure and b- MnOOH and Mn(OH) ₂ structures;

FIG. 4 shows an X-Ray Diffraction Analysis for a new synthetic manganese oxide material i-Mn0 ₂ according to a non-limiting embodiment of the invention as compared to an expected peak position for an ideal structure;

FIG. 5 shows a scanning electron micrograph (SEM) image of a new synthetic manganese oxide material i-MnCE according to a non-limiting embodiment of the invention;

FIG. 6 shows a voltage profile for a 2032 coil cell manufactured with a secondary battery active cathode material including a new synthetic manganese oxide i-Mn0 ₂ according to a non- limiting embodiment of the invention; and

FIG. 7 shows Mn0 ₂ specific capacity versus cycle number for a 2032 coil cell

manufactured with a secondary battery active cathode material including a new synthetic manganese oxide i-Mn0 ₂ according to a non-limiting embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

The EMD or g-Manganese Oxide is an intergrowth of Ramsdellite (1x2 channels) and Pyrolusite (lxl channels) phases. FIG. 1 shows the crystalline lattice structures of both Ramsdellite and Pyrolusite phases. The channels of each are formed by comer sharing atoms. The different crystalline structures react differently when undergoing proton insertion during their electrochemical reduction. The Ramsdellite phase is reduced to a Groutite, and the

Pyrolusite phase is reduced to Manganite. Further reduction of the tunnel MnOOH to Mn(II) should form Pyrochroite, which has a completely different layered crystal structure. The structural rearrangement of the tunnel phase, either Groutite or Manganite, may impose an energy barrier preventing discharge to Mn(II) at meaningful voltage. Re-forming the original tunnel material from the layered structure, Pyrochroite, is also problematic, which negatively impacts cyclability. Dissolution of Mn(III) species with subsequent precipitation of stable (inactive) phases, such as Hausmannite seems more favorable, thus limiting tunnel MnC discharge to 1.33 electrons per Mn (A. Kozawa, J.F. Yeager, JES, 1965, 959-963; D. Im, A. Manthiram, B. Coffey, JES 2003, A1651-59; D. Boden et al, JES1967, 415-417; Bode et al, JES 1997, 792-

801; C. Mandoloni et al, JES, 1992, 954-59; M. R. Bailey, S. W. Donne, JES, 2012, A2010-15). Layered manganese oxides, such as synthetic Bimessite have been also studied for battery applications. FIG. 2 shows the synthetic Bimessite structure is substantially different from manganese hydroxide, most notably in d-spacing, symmetry, presence of interlayer species and hydration. Bimessite reduction usually occurs in two distinct steps, with the 2 ^nd electron being transferred at a voltage too low for practical applications (e.g. less than 0.8V). Synthetic Bimessite does not form b-MhOOH and subsequently Mn(OH) ₂ upon discharge in a Zn/MnCh cell. Synthetic Bimessite is also prone to forming more stable phases upon discharge, such as the tunnel structures and spinels. (Manthiram, J. Electrochem. Soc. 149 (4) A483, 2002; Swinkels, J.

Electrochem. Soc. 144 (9) 2949, 1997; Yadav/Baneqee Nature Communications 2017, 8

14424).

In an aspect of the invention, layered manganese(IV) oxide isostructural to the manganese(II) hydroxide is desired to facilitate 2 ^nd electron transfer and facilitate

rechargeability. The space group description for the desired layered manganese(IV) oxide is trigonal crystal system (bravais lattice) with a P3m\ space group (#164 international short symbol). FIG. 3 shows the b-MhOOH and manganese hydroxide from FIG. 2 in comparison with an ideal desired synthetic layered manganese(IV) oxide which is isostructural to both the b-MhOOH and manganese hydroxide. The similar structures of the synthetic layered manganese(IV) oxide and the b-MhOOH and manganese hydroxide structures allows for oxidation to manganese(IV) from the manganese(III) and manganese(II) oxides.

Traditionally, manganese oxides are synthesized by oxidation of Mn(II) salts or decomposition of permanganates. However, these routes lead exclusively to a

thermodynamically more stable tunnel or Bimessite structures. Spontaneous oxidation of manganese hydroxide by oxygen, as well as attempts to oxidize b-MhOOH by soluble oxidants result in formation of Manganosite, Bixbyite, Hausmannite, Bimessite or no change in structure or oxidation state. No method to synthesize ideal layered manganese(IV) oxide structures is available in the prior art.

Example 1 :

Oxidation of b-MhOOH was performed in multiple ways according to methods described in Table 1. The dissolved oxidant and observed result are also described in Table 1.

TABLE 1

Example 2:

The new synthetic manganese oxide material i-MnC was synthesized by oxidation of anhydrous solid b-MhOOH powder with a dry ozone/oxygen gas mixture. For each gram of b- MnOOH, 5 grams of a 10% ozone gas was added. The reaction was performed at 25 °C and pressure of 1 atmosphere. After 2 molar equivalents of ozone were passed through the reaction vessel, the powder changed color from metallic brown to dull gray.

The mechanism of ozone oxidation can involve direct interaction or proceed via radical oxygen intermediates. In the latter case, other gasses containing or producing radical oxygen species can be used in place of ozone (oxygen plasma, -OH, gaseous peroxide species, etc.).

Oxidation of Mn(III) to Mn(IV) was confirmed by titration with Ferrous Sulfate, indicating the 4.0 average oxidation state. The titration was performed according to the method described in [Katz,. (I, Nye, W. F., & Clarke, R. C. (1956). Available Oxygen in Manganese Dioxide. Analytical Chemistry, 28(4), 507-508. https://doi.org/10. lQ21/ac50161a028) 1. This method is hereby incorporated in its entirety herein by reference.

A Powder X-ray diffraction (PXRD) analysis of the new synthesized manganese oxide powder i-Mhq2 was performed on a Panalytical Empyrean diffractometer with Cu K-a radiation operating at 45 kV and 40 mA. The sample was scanned from 10-70 °20 with a step size of 0.141° at a rate of 0.0090 steps per second.

FIG. 4 shows the X-ray diffraction (XRD) pattern for the new synthetic manganese oxide material i-MnCh as compared to expected peak positions for a desired ideal layered structure as shown by the theoretical XRD vertical lines.

The XRD pattern shown in FIG. 4 for the new synthetic manganese oxide material i- MnCh does not fit XRD patterns for a-MnCh (Cryptomelane), b-MhOE^GqI^ίίb), R-MnCh (Ramsdellite), y-MnCh(EMD). e-MnCh (Ahktenskite), 5-MnCh (Bimessite/Buserite), or l-MnCh (Spinel). The XRD pattern shown in FIG. 4 for the new synthetic manganese oxide material i- MnCh shows an excellent fit to the theoretical XRD lines simulated for a desired ideal layered structure, iso-structural to manganese hydroxide P3m 1 space group (#164 international short symbol)). The theoretical XRD lines for the ideal layered MnC crystal structure were created in VESTA, using the cif file for T1S2 as a starting point. T1S2 was used because T1S2 has a 2D layered structure with the stoichiometry of atoms similar to Mn(OH)2, has no interlayer species and occupies the same space group as Mn(OH)2. First, the structure parameters were changed so that the electron densities for Ti were changed to those of Mn and the electron densities for S were changed to O. Next, the bond distances were changed to reflect manganese in the 4+ oxidation state. With respect to other MnCh compounds, the average bond length for Mn ⁴⁺ is 1.95 A. After the structure was complete, a powder pattern was simulated and is shown in FIG. 4.

The excellent fit between the XRD pattern for the new synthetic manganese oxide i-MnCE structure and the theoretical vertical XRD lines of the ideal layered Mn02 crystal structure confirms that the new synthetic i-MnCE has the same space group and atomic connectivity as the starting structure of layered b-MhOOH and Mn(OH)2. Changes in the charge of the manganese cation from 3+ to 4+ results in a decrease in bond distances while retaining the same bond structure and symmetry. FIG. 4 shows a major PXRD 2 Theta peak is found at 37 degrees, and other peaks are found at 20, 42, 56, and 67 degrees. The space grouping (international short symbol) is P ^' 3m\, and number 164. The following table shows the data of FIG. 4 including both relative and normalized intensities as follows:

The dimensionality of a structure can be defined by the bond connectivity within the crystallographic supercell. For a 3D structure, strong chemical bonds such as ionic, covalent and metallic bonds are formed between atoms in all 3 dimensions while any weak chemical bonds such as Van der Waals forces and hydrogen bonding do not contribute to the atomic connectivity of the supercell. For a 2D structure, strong chemical bonds are formed between atoms in two dimensions while any weak chemical bonds contribute to the atomic connectivity of the remaining dimension of the supercell. For a 1D structure, strong chemical bonds are formed between atoms along one dimension while any weak chemical bonds contribute to the atomic connectivity in the remaining two dimensions of the supercell. Good examples of 3D, 2D and 1D structures are diamond, graphene and polyacetylene respectively.

The structure of the new synthesized manganese oxide material i-MnCh consists of strong Mn-0 bonds connected in two dimensions (the a and b axes of the crystallographic unit cell). The third dimension (c axis) being held together solely by Van der Waals interactions. There are no interlayer species such as water molecules or ions between the layers of new synthesized manganese oxide material i-MnCh. The layers of new synthesized manganese material i-MnCh are aligned; they are symmetrically stacked in the same way as Pyrochroite. In contrast, the layers of Bimessites are staggered from one another, which is reflected in the different space group, and the Birnessites typically have interlayer species including, but not limited to water molecules and ions.

The scanning electron microscopy (SEM) image of FIG. 5 elucidates the morphology of the new synthetic manganese oxide material i-MnCh. The new synthetic manganese oxide material i-MnCh material has a sheet-like morphology. The sheets are roughly 10-50 nanometers thick and between 50 and 600 nanometers in length and width. The sheets adopt a hexagonal pattern with 120° angles between edges, which is corroborated by the PXRD and ideal crystal structure.

Example 3 :

Cathodes made with the new synthetic i-manganese oxide material i-MnCh were evaluated in standard 2032 coin cells using a Zn powder anode and a commercial NKK separator soaked with 2M zinc sulfate aqueous solution containing 0.1M manganese sulfate.

Cathodes and anodes for the coin cells were slurry-casted using NMP solvent and PVDF binder. Appropriate amount of carbon was added for electronic conductivity.

FIG. 6 indicates smooth voltage profile and FIG. 7 confirms stable charge-discharge for 150 cycles for the coin cells including the secondary battery active cathode material made with the new synthetic manganese oxide material i-MnCh according to an embodiment of the invention.

While the invention has been described in detail herein in accordance with certain preferred embodiments, modifications and changes therein may be affected by those skilled in the art without departing from the spirit of the invention. Accordingly, it is the intent to be limited only by the scope of the appending claims and not by way of the details and instrumentalities describing the embodiments shown herein.

It is to be understood that variations and modifications can be made on the compositions, articles, devices, systems, and methods without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.

A wide range of further embodiments of the present invention is possible without departing from its spirit and essential characteristics. The embodiments as discussed here are to be considered as being illustrative only in all aspect and not restrictive. The following claims indicate the scope of the invention rather than the foregoing description.