Air- and moisture-stable high-capacity cathode materials for sodium-ion batteries

Abstract

The present invention relates to sodium-ion batteries that include a positive electrode composition having improved battery performance and moisture and air stability. The positive electrode composition has the general formula Na x A z Ni i M y Mn j Ti k Sb f O2 (wherein A is an alkali metal or alkaline earth metal selected from Ca and Li, M is a divalent or trivalent element selected from Fe, Mg, Zn, Cu, Al, and Co, Ni is a divalent element, Mn and Ti are tetravalent elements, and Sb is a pentavalent / trivalent element, and (i+j+k+f+y=1), 0.7≦x≦1, 0≦z≦0.2, 0.1≦i≦0.6, 0≦y≦0.5, 0.1≦j≦0.5, 0.05≦k≦0.4, and 0≦f≦0.2). The present invention is applicable to energy storage applications.

Description

[Technical Field]

[0001] The present invention relates to sodium-ion batteries containing positive electrode compositions with improved battery performance and moisture and air stability. More particularly, the present invention relates to manganese transition metals and other transition metals, such as Ni and Fe, as well as Ca, Cu, and Ti, incorporated into the structure of sodium for better air and moisture stability. Furthermore, the present invention relates to a compound of the general formula Na x A z Ni i M y Mn j Ti k Sb f O2 (wherein A is an alkali metal or alkaline earth metal selected from Ca and Li, M is a divalent or trivalent element selected from Fe, Mg, Zn, Cu, Al, and Co, Ni is a divalent element, Mn and Ti are tetravalent elements, and Sb is a pentavalent / trivalent element, and (i+j+k+f+y=1), 0.7≦x≦1, 0≦z≦0.2, 0≦y≦0.5, 0.1≦i≦0.6, 0.1≦j≦0.5, 0.05≦k≦0.4, and 0≦f≦0.2). The present invention relates to grid storage applications. [Background technology]

[0002] Large-scale energy storage systems have attracted increasing interest in recent years. However, the relatively small abundance of lithium, cobalt, and nickel resources on Earth and their uneven distribution cannot meet the growing demand for large-scale energy storage systems. Sodium-ion secondary batteries are a potential alternative to Li-ion secondary batteries. High demand and cost considerations may necessitate the utilization of Na-ion batteries (NIBs) rather than Li-ion batteries due to the abundance and wide distribution of sodium resources. In many aspects, sodium behaves electrochemically similarly to lithium.

[0003] According to the coordination environment of the sodium ion in the structure, Na xTMO2 (where TM = transition metal, e.g., Co, Ni, Mn, Fe, Cu, etc.) can be broadly divided into P-type (prismatic coordination) and O-type (octahedral coordination), with the P2 and O3 phases being the most common structural types. Various categories of potential cathode materials have been explored, including transition metal oxides, Prussian blue analogues, and polyanionic compounds. Among them, layered transition metal oxides are attractive candidates due to their advantages of facile synthesis, high energy density, and feasibility of mass production.

[0004] One of the key issues with layered oxide cathode materials is their air and moisture stability. Air-sensitive materials require special manufacturing conditions, and they must be prepared, stored, and assembled in a dry or even inert atmosphere, which inevitably increases costs. Since the target application of sodium-ion batteries is large-scale grid energy storage systems, cost is of paramount importance. We need an effective technology to endow the cathode with water-handling properties. To facilitate the practical application of sodium-ion batteries, their poor air and moisture stability needs to be understood and resolved. This invention addresses this issue.

[0005] Here, the inventors have devised a key strategy to improve the air and moisture stability of the cathode material. By substituting elements at either the transition metal or sodium sites, and by decreasing the sodium content and increasing the open-circuit voltage, the layered material achieves anti-oxidation stability. The introduction of copper, calcium, and titanium is a key factor in improving the air and moisture stability while maintaining a specific capacity value of 120-140 mAh / g.

[0006] Reference can be made to the article by Feng Lin et al., Journal of The Electrochemical Society, 2019, 166(2) A251-A257, which describes the material P2-Na 0.67 Ni 0.22 Cu 0.11 Mn 0.56 Ti 0.11Its performance under O2 and water treatment conditions is reported. This material has a capacity of 180 mAhg at 22°C. -1 discharge capacity of 544Whkg -1 Aging experiments demonstrated its excellent stability in water, with minimal bulk structural or chemical changes. However, the P2-phase is sodium-deficient, making it impractical to fabricate full cells without using sodiated negative electrode materials. Furthermore, the high specific capacity in this composition is due to manganese redox, which occurs below 2 V. Surface-sensitive soft X-ray absorption spectroscopy indicates that the positive electrode has a stable interfacial chemistry in aqueous solutions. Furthermore, cells with water-treated positive electrodes exhibited stable cycling performance with minimal voltage decay due to a decrease in cell impedance.

[0007] Please refer to the paper by Mark N. Obrovac et al., ACS applied materials and interfaces 2018, 10, 44, pp. 38246-38254, which describes the effects of NaNi on atmospheric exposure. 0.5 Mn 0.5 The O2 sensitivity was investigated in detail by XRD structural analysis, surface analysis by SEM images and FTIR spectroscopy, and electrochemical measurements. 0.5 Mn 0.5 The reactions that occur when O2 is exposed to air are complex. 0.5 Mn 0.5 Washing with O2 completely destroys the structure, whereas washing with ethanol does not cause significant structural damage. Instead, the ethanol wash 0.5 Mn 0.5 Removes most of the sodium residue on the O2 surface.

[0008] Yunming Li et al., Advanced Sciences 2015, 2(6):1500031, which describes a novel air-stable cathode, P2-type Na with high sodium content. 7 / 9 Cu 2 / 9 Fe 1 / 9 Mn2 / 3 O2 was designed and its electrochemical performance as a cathode material for rechargeable sodium-ion batteries was investigated. This material produced 89 mAhg at a 0.1 C rate. -1 The attractive performance is the long-term cycling stability demonstrated by 85% capacity retention after 150 cycles at 1C rate without phase transformation. When coupled with a hard carbon anode, it exhibits a reversible capacity of 313 mAhg -1 High reversible capacity of 195Whkg at 0.2C rate, high initial coulombic efficiency of 79% -1 This high energy density demonstrated promising prospects for use.

[0009] Shi-Xue Dou et al., Advanced energy materials, 2018, 8, 1701610, describes a novel air-stable O3-type Na[Li ZnO ... 0.05 Mn 0.50 Ni 0.30 Cu 0.10 Mg 0.05 ]O2 cathode, which reported 172mAhg at 0.1C. -1 and a remarkable capacity retention of 70.4% after 1000 cycles at 20 C. More importantly, it provides good compatibility with pristine hard carbon as the anode in sodium-ion full cells. It can provide up to 215 Wh / kg at 0.1 C. -1 This resulted in a high energy density and good rate performance.

[0010] Yu-Guo et al., Journal of American Chemical Society, 2017, 139, 25, pp. 8440-8443, which proposes that the interlayer distance of the Na layer can be reduced and simultaneously Cu / Ti co-doped to form a positive electrode NaNi 0.5 Mn 0.5 We report that a combined structural engineering approach is proposed to improve the air stability of O3-type cathode materials by enhancing the valence state of the O2 transition metal.0.45-x Cu 0x Mn 0.4-y Ti y O₂ (where 0.05 ≤ x ≤ 0.1 and 0 ≤ y ≤ 0.1) shows a 20-fold increase in the stable air exposure period and a 9-fold increase in the capacity retention rate after 500 cycles, and even maintains its original structure and capacity after being immersed in water.

[0011] Reference can be made to WO2016 / 188877, which describes applying doping of one or more of specific divalent metal ions, more particularly Cu, Ni, and Zn, to a sodium cathode material in order to provide a sodium ion battery having high rate performance and good calendar life. The cathode has the composition Na x M y Mn 1-y Li y’ A z O₂ or Na x M y Mn 1-y O₂ (0.60 < x < 0.95), where M consists of one or more elements from the group consisting of Cu, Zn, and Ni, 0.05 ≤ y < 0.20, A consists of one or more elements from the group consisting of Mg, Ti, Fe, Cr, and Co, 0 ≤ z < 0.2, 0 ≤ y’ < 0.33, and z + y’ > 0. This invention also provides a method for preparing sodium layered oxide materials and their uses.

[0012] Reference can be made to US2022 / 0013772A1, which relates to a cathode material for a sodium ion battery. The cathode active material for a sodium ion battery has the following formula: Na x Ni 0.5-y Cu y Mn 0.5-z Ti zO2, where x varies from 0.9 to 1; y varies from 0.05 to 0.1; and Z varies from 0.1 to 0.3. When z equals 0.1 and x equals 1, y is not 0.05. This invention relates to methods of making the claimed sodium metal oxide compositions. Finally, this invention also relates to specific cycling methods for Na-ion batteries containing specific positive electrode active materials.

[0013] Therefore, keeping in view the shortcomings of the prior art reported thus far, there is room for improving the properties of cathode materials by providing multivalent layered oxide compositions to improve capacity performance, average operating voltage, cycle life, structural stability, moisture and air stability, and large-scale manufacturing. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] International Publication No. 2016 / 188877 [Patent Document 2] US Patent Application Publication No. 2022 / 0013772 [Non-patent literature]

[0015] [Non-Patent Document 1] Feng Lin et al., Journal of The Electrochemical Society 2019, 166(2) pages A251-A257 [Non-patent document 2] Mark N. Obrovac et al., ACS applied materials and interfaces 2018, 10, 44, pp. 38246-38254 [Non-patent document 3] Yunming Li et al., Advanced Sciences 2015, 2(6):1500031 [Non-patent document 4] Shi-Xue Dou et al., Advanced energy materials, 2018, 8, 1701610 [Non-Patent Document 5] Yu-Guo et al., Journal of American Chemical Society, 2017, 139, 25, pp. 8440-8443 Summary of the Invention [Problem to be solved by the invention]

[0016] The primary objective of the present invention is to develop a high capacity, cost effective, moisture and air stable cathode material for sodium ion battery applications.

[0017] Another object of the present invention is a multivalent positive electrode composition in which the elements are selected so that the combination of elements provides improved structural stability, thermal stability, air stability, and moisture stability, a higher average potential, a faster redox rate contributing to increased capacity, and an improved sodium ion diffusion rate.

[0018] Another object of the present invention is to provide a cost-effective electrode containing an active material that is simple to prepare and easy to handle and store.

[0019] Another object of the present invention is the incorporation of small amounts of Ca in the sodium sites and Cu in the transition metal sites, which improves structural, moisture and air stability.

[0020] Yet another object of the present invention is to provide a method for manufacturing a +2 / M +3 / M +4 To obtain higher specific capacitance values ​​by utilizing the complete redox state of Sb, the structure is designed to stabilize the lower valence state of the 3d metal. +5 Furthermore, the glass-forming properties of antimony oxide lend themselves to easy synthesis and the formation of pure phases.

[0021] Another object of the present invention is to provide a sodium metal oxide composition as a positive electrode for sodium ion batteries that is less expensive than prior art compositions and is easily scalable to mass production. [Means for solving the problem]

[0022] In the present invention, alkali and alkaline earth metals, as well as transition metals, are used to obtain sodium cathode materials that have high capacity and are moisture and air stable. The compositions have the general formula Na x A z Ni i M y Mn j Ti k Sb f O2 (wherein A is an alkali metal or alkaline earth metal selected from Ca and Li, M is a divalent or trivalent element selected from Fe, Mg, Zn, Cu, Al, and Co, Ni is a divalent element, Mn and Ti are tetravalent elements, and Sb is a pentavalent / trivalent element, (i+j+k+e+y=1), 0.7≦x≦1, 0≦z≦0.2, 0≦y≦0.5, 0.1≦i≦0.6, 0.1≦j≦0.5, 0.05≦k≦0.4, and 0≦f≦0.2. According to an embodiment of the present invention, the concentration "x" of element Na may be in the range of 0.7 to 1, and the concentration "z" of element A may be in the range of 0 to 0.2. Preferably, the concentration "i" of element Ni may range from 0.1 to 0.6 and is a divalent element, the concentration "y" of element M may range from 0 to 0.5 and is a divalent or trivalent element selected from Fe, Mg, Zn, Cu, Al, Co, or a combination thereof, the concentration "j" of element Mn may range from 0.1 to 0.5 and is a tetravalent element, the concentration "d" of element Ti may range from 0.05 to 0.4 and is a tetravalent element, and the concentration "f" of element Sb may range from 0 to 0.2 and is a pentavalent / trivalent element (where x, i, j, k, f, and y are selected to maintain overall electrical neutrality).

[0023] According to an embodiment of the present invention, the composition was synthesized by a convenient solid phase method.

[0024] According to embodiments of the present invention, the positive electrode material composition exhibits good cycle stability, high operating voltage, and good rate capability.

[0025] According to an embodiment of the present invention, the composition is a single phase O3-type layered structure having a space group of R-3m.

[0026] In an embodiment of the present invention, the potential window of the positive electrode active material composition is in the range of 2V to 4.4V.

[0027] In a further embodiment of the present invention, the capacity of the cathode material composition ranges from 70 mAh / g to 195 mAh / g.

[0028] In a further embodiment of the present invention, the morphology of the composition of the cathode material is irregular particulate, plate-like particulate, hexagonal, cubic, spherical, and elongated hexagonal.

[0029] In a further embodiment of the invention, a sodium-ion battery (100) contains a biphasic multivalent layered oxide positive electrode material composition (106) coated on an aluminum foil; an aluminum foil-coated negative electrode (102); an electrolyte (108); and a porous separator (104).

[0030] These and other advantages will become apparent from the present application of the embodiments described herein.

[0031] The foregoing is a simplified summary to provide an understanding of some embodiments of the invention. This summary is not an extensive or exhaustive overview of the invention and its various embodiments. The summary presents selected concepts of embodiments of the invention in a simplified form as a prelude to the more detailed description that is presented below. It will be understood that other embodiments of the invention may utilize, alone or in combination, one or more of the features set forth above or described in detail below. The above and still further features and advantages of embodiments of the present invention will become apparent from the following detailed description of the embodiments thereof, particularly when taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a schematic diagram of a sodium-ion battery according to an embodiment of the present disclosure. [Figure 2A] FIG. 1 shows an X-ray diffraction pattern of a NaCaNiCuAlMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2B] FIG. 1 shows an X-ray diffraction pattern of a water-treated NaCaNiCuAlMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2C] FIG. 1 shows an X-ray diffraction pattern of a NaNiCuMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2D] FIG. 1 shows an X-ray diffraction pattern of a water-treated NaNiCuMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2E] FIG. 1 shows an X-ray diffraction pattern of a NaCaNiCuMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2F] FIG. 1 shows an X-ray diffraction pattern of a water-treated NaCaNiCuMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2G] FIG. 1 shows an X-ray diffraction pattern of a NaCaNiMnTiO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2H] FIG. 1 shows an X-ray diffraction pattern of a water-treated NaCaNiMnTiO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2I]FIG. 1 shows an X-ray diffraction pattern of a NaNi1 / 6Mg1 / 6Cu1 / 6Co1 / 6Fe1 / 6Mn1 / 8Ti1 / 8O2 positive electrode material composition according to an embodiment of the present disclosure. [Figure 2J] FIG. 1 shows an X-ray diffraction pattern of a water-treated NaNi1 / 6Mg1 / 6Cu1 / 6Co1 / 6Fe1 / 6Mn1 / 8Ti1 / 8O2 cathode material composition according to an embodiment of the present disclosure. [Figure 2K] FIG. 1 shows an X-ray diffraction pattern of a NaCaNiCuAlMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2L] FIG. 1 shows an X-ray diffraction pattern of a water-treated NaCaNiCuAlMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2M] FIG. 1 shows an X-ray diffraction pattern of a NaCaNiMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2N] FIG. 1 shows an X-ray diffraction pattern of a water-treated NaCaNiMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2O] FIG. 1 shows an X-ray diffraction pattern of a NaCaNiCuMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2P] FIG. 1 shows an X-ray diffraction pattern of a water-treated NaCaNiCuMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2Q] FIG. 1 shows an X-ray diffraction pattern of a NaCaLiNiCuMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2R]FIG. 1 illustrates an X-ray diffraction pattern of a water-treated NaCaLiNiCuMnTiSbO material composition according to an embodiment of the present disclosure. [Figure 2S] FIG. 1 shows an X-ray diffraction pattern for a NaCuNiFeMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 2T] FIG. 1 shows an X-ray diffraction pattern of a water-treated NaCuNiFeMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 3A] FIG. 1 shows a voltage-time plot of a sodium half-cell assembled using NaCaNiCuAlMnTiSbO positive electrode material according to an embodiment of the present disclosure. [Figure 3B] FIG. 1 shows a plot of capacity versus cycle number for a sodium half-cell assembled using water-washed NaCaNiCuAlMnTiSbO material for the positive electrode, according to an embodiment of the present disclosure. [Figure 3C] FIG. 1 shows a voltage-time plot of a sodium half-cell assembled using NaNiCuMnTiSbO positive electrode material according to an embodiment of the present disclosure. [Figure 3D] FIG. 1 shows a plot of capacity versus cycle number for a sodium half-cell assembled using NaNiCuMnTiSbO material for the positive electrode, according to an embodiment of the present disclosure. [Figure 3E] FIG. 1 shows a voltage-time plot of a sodium half-cell assembled using NaCaNiCuMnTiSbO positive electrode material according to an embodiment of the present disclosure. [Figure 3F]FIG. 1 shows a plot of capacity versus cycle number for a sodium half-cell assembled using NaCaNiCuMnTiSbO material for the positive electrode, according to an embodiment of the disclosure. [Figure 3G] FIG. 1 shows a voltage-time plot of a sodium half-cell assembled using NaCaNiMnTiO positive electrode material according to an embodiment of the present disclosure. [Figure 3H] FIG. 1 shows a voltage-time plot of a sodium half-cell assembled using NaNi1 / 6Mg1 / 6Cu1 / 6Co1 / 6Fe1 / 6Mn1 / 8Ti1 / 8O2 cathode material, according to an embodiment of the present disclosure. [Figure 3I] FIG. 1 shows a voltage-time plot of a sodium half-cell assembled using NaCaNiCuMnTiSbO material for the positive electrode, according to an embodiment of the present disclosure. [Figure 3J] FIG. 1 shows a voltage-time plot of a sodium half-cell assembled using NaCaLiNiCuMnTiSbO cathode material for the cathode according to an embodiment of the present disclosure. [Figure 4A] FIG. 1 shows an FESEM image of a NaCaNiCuAlMnTiSbO cathode material composition according to an embodiment of the present disclosure. [Figure 4B] FIG. 1 shows an FESEM image of a NaNiCuMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. [Figure 4C] FIG. 1 shows an FESEM image of a NaCaNiCuMnTiSbO cathode material composition according to an embodiment of the present disclosure. [Figure 4D]FIG. 1 shows an FESEM image of a NaCaNiCuMnTiSbO positive electrode material composition according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0033] The following description includes a preferred best mode of one embodiment of the present invention. From this description of the invention, it will be apparent that the invention is not limited to these described embodiments, but that the invention also encompasses various modifications and embodiments thereof. Accordingly, the description of the invention is to be considered illustrative and not limiting. While the invention is susceptible to various modifications and alternative constructions, it should be understood that there is no intention to limit the invention to the particular forms disclosed; on the contrary, the invention is intended to cover all modifications, alternative constructions, and equivalents included within the spirit and scope of the invention as defined by the appended claims.

[0034] In any embodiment described herein, the open-ended terms "comprising," "comprises," etc. (which are synonymous with "including," "having," and "characterized by") may be replaced by the respective partial expressions "consisting essentially of," "consisting essentially of," etc., or the respective limiting expressions "consisting of," "consisting of," etc.

[0035] As used herein, the singular forms "a," "an," and "the" designate both the singular and the plural unless expressly stated to designate only the singular.

[0036] According to an embodiment of the present invention, positive electrode compositions were synthesized by a simple and facile solid-state method. Stoichiometric amounts of precursors were thoroughly mixed and ground or ball-milled in an agate mortar for 30 minutes to 5 hours, then calcined in air or an argon atmosphere at 400-700°C for 2-10 hours, followed by intermediate grinding or ball-milling for 1-10 hours. The milled powder was then calcined in air or an argon atmosphere at 700-1000°C for 5-20 hours. After cooling, the resulting positive electrode compositions were stored in an Ar-filled glove box to protect them from moisture.

[0037] Preferably the mixture of precursor materials is Na2CO3, Li2CO3, LiOH.xH2O, NiO, NiCO3, Ni(OH) 2.x It comprises one or more compounds selected from H2O, MnO2, MnO, Mn2O3, Mg(OH)2, MgO, TiO2, Al(OH)3, Al2O3, CuO, ZnO, Sb2O3, Sb2O5.

[0038] 1 shows a schematic diagram of a sodium-ion battery 100 according to an embodiment of the present invention. A sodium-ion battery consists of two electrodes, one positive electrode 106 and the other a hard carbon negative electrode 102, separated by a porous separator 104 immersed in a non-aqueous sodium-ion conducting liquid electrolyte 108 that uses sodium salts in a mixture of organic solvents and additives.

[0039] According to an embodiment of the present invention, a positive electrode is prepared by solvent-casting a slurry of the active positive electrode material 106, conductive carbon, binder, and solvent. The conductive carbon used is Super P, the binder used is PVDF, and N-methyl-2-pyrrolidone (NMP) is the solvent. The positive electrode material is coated with aluminum foil (112); the negative electrode is coated with aluminum foil or copper foil (110). The slurry is then cast onto aluminum foil and then placed in an oven at 120°C for 12 hours to dry, resulting in a positive electrode.

[0040] According to an embodiment of the present invention, during charging, Na ions migrate from the NaMO2 layered structure of the positive electrode (106) to the negative electrode (102), and during discharging, Na ions return to the MO2 host framework while electrons are transferred to the external circuit.

[0041] FIG. 2A shows a Na 0.97 Ca 0.03 Ni 0.4 Cu 0.1 Al 0.05 Mn 0.3 Ti 0.1 Sb 0.05 1 shows the X-ray diffraction pattern of the O2 cathode material. X-ray diffraction (XRD) is a rapid method for identifying the formation of desired cathode material composition phases through crystal structure analysis. In an embodiment of the present invention, the cathode material composition is characterized using a Bruker D8 ADVANCE diffractometer. According to an embodiment of the present invention, the diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition has a single-phase O3-type layered structure with a space group of R-3m.

[0042] FIG. 2B shows a water-treated NaCl solution according to an embodiment of the present invention. 0.97 Ca 0.03 Ni 0.4 Cu 0.1 Al 0.05 Mn 0.3 Ti 0.1 Sb 0.05 The X-ray diffraction pattern of the O2 cathode material is shown. The sample was stirred in water for 30 minutes. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with the space group R-3m.

[0043] FIG. 2C shows a Na 0.98 Ni 0.25 Cu 0.091 Mn 0.375 Ti 0.2 Sb 0.0833The X-ray diffraction pattern of the O2 cathode material is shown. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with a space group of R-3m.

[0044] FIG. 2D shows a water-treated NaCl solution according to an embodiment of the present invention. 0.98 Ni 0.25 Cu 0.091 Mn 0.375 Ti 0.2 Sb 0.0833 The X-ray diffraction pattern of the O2 cathode material is shown. The sample was stirred in water for 30 minutes. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with the space group R-3m.

[0045] FIG. 2E illustrates a Na 0.96 Ca 0.04 Ni 0.25 Cu 0.125 Mn 0.375 Ti 0.166 Sb 0.083 The X-ray diffraction pattern of the O2 cathode material is shown. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with a space group of R-3m.

[0046] FIG. 2F shows a water-treated NaCl solution according to an embodiment of the present invention. 0.96 Ca 0.04 Ni 0.25 Cu 0.125 Mn 0.375 Ti 0.166 Sb 0.083 The X-ray diffraction pattern of the O2 cathode material is shown. The sample was stirred in water for 30 minutes. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with the space group R-3m.

[0047] FIG. 2G illustrates a Na 0.8 Ca 0.2 Ni 0.6 Mn 0.2 Ti 0.2 The X-ray diffraction pattern of the O2 cathode material is shown. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with a space group of R-3m.

[0048] FIG. 2H shows a graph of the water-treated NaCl solution according to an embodiment of the present invention. 0.8 Ca 0.2 Ni 0.6 Mn 0.2 Ti 0.2 The X-ray diffraction pattern of the O2 cathode material is shown. The sample was stirred in water for 30 minutes. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with the space group R-3m.

[0049] FIG. 2I illustrates a NaNi 1 / 6 Mg 1 / 6 Cu 1 / 6 Co 1 / 6 Fe 1 / 6 Mn 1 / 8 Ti 1 / 8 The X-ray diffraction pattern of the O2 cathode material is shown. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with a space group of R-3m.

[0050] FIG. 2J shows a water-treated NaNi 1 / 6 Mg 1 / 6 Cu 1 / 6 Co 1 / 6 Fe 1 / 6 Mn 1 / 8 Ti 1 / 8The X-ray diffraction pattern of the O2 cathode material is shown. The sample was stirred in water for 30 minutes. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with the space group R-3m.

[0051] FIG. 2K shows a Na 0.95 Ca 0.05 Ni 0.4 Cu 0.1 Al 0.05 Mn 0.3 Ti 0.1 Sb 0.05 The X-ray diffraction pattern of the O2 cathode material is shown. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with a space group of R-3m.

[0052] FIG. 2L shows a graph of the water-treated NaCl solution according to an embodiment of the present invention. 0.95 Ca 0.05 Ni 0.4 Cu 0.1 Al 0.05 Mn 0.3 Ti 0.1 Sb 0.05 The X-ray diffraction pattern of the O2 cathode material is shown. The sample was stirred in water for 30 minutes. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with the space group R-3m.

[0053] FIG. 2M illustrates a Na 0.95 Ca 0.05 Ni 0.6 Mn 0.2 Ti 0.1 Sb 0.1The X-ray diffraction pattern of the O2 cathode material is shown. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with a space group of R-3m.

[0054] FIG. 2N shows a water-treated NaCl solution according to an embodiment of the present invention. 0.95 Ca 0.05 Ni 0.6 Mn 0.2 Ti 0.1 Sb 0.1 The X-ray diffraction pattern of the O2 cathode material is shown. The sample was stirred in water for 30 minutes. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with the space group R-3m.

[0055] FIG. 2O illustrates a Na 0.96 Ca 0.02 Ni 0.45 Cu 0.1 Mn 0.25 Ti 0.1 Sb 0.1 The X-ray diffraction pattern of the O2 cathode material is shown. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with a space group of R-3m.

[0056] FIG. 2P shows a water-treated NaCl solution according to an embodiment of the present invention. 0.96 Ca 0.02 Ni 0.45 Cu 0.1 Mn 0.25 Ti 0.1 Sb 0.1 The X-ray diffraction pattern of the O2 cathode material is shown. The sample was stirred in water for 30 minutes. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with the space group R-3m.

[0057] FIG. 2Q shows a Na 0.97 Ca 0.03 Li 0.02 Ni 0.5 Cu 0.05 Mn 0.2 Ti 0.1 Sb 0.13 The X-ray diffraction pattern of the O2 cathode material is shown. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with a space group of R-3m.

[0058] FIG. 2R shows a graph of the water-treated NaCl solution according to an embodiment of the present invention. 0.97 Ca 0.03 Li 0.02 Ni 0.5 Cu 0.05 Mn 0.2 Ti 0.1 Sb 0.13 The X-ray diffraction pattern of the O2 cathode material is shown. The sample was stirred in water for 30 minutes. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with the space group R-3m.

[0059] FIG. 2S illustrates a NaCu 0.1 Ni 0.15 Fe 0.30 Mn 0.35 Ti 0.05 Sb 0.02 The X-ray diffraction pattern of the O2 cathode material is shown. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with a space group of R-3m.

[0060] FIG. 2T shows a water-treated NaCu solution according to an embodiment of the present invention. 0.1 Ni 0.15 Fe 0.30 Mn 0.35Ti 0.05 Sb 0.02 The X-ray diffraction pattern of the O2 cathode material is shown. The sample was stirred in water for 30 minutes. The diffraction peaks correspond to layered compounds, and no other impurity peaks are observed. The high intensity peaks confirm that the material is crystalline. The XRD pattern indicates that the cathode composition is a single-phase O3-type layered structure with the space group R-3m.

[0061] Figure 3A shows the Na 0.97 Ca 0.03 Ni 0.4 Cu 0.1 Al 0.05 Mn 0.3 Ti 0.1 Sb 0.05 This figure shows a voltage-time plot of a sodium half-cell assembled using O2 cathode material. According to an embodiment of the present invention, the active cathode material composition was characterized using a BioLogic BCS-800 series battery cycler. The voltage-time plot helps determine the time of charge, potential window, and cycling stability of the cathode active material. The present invention exhibited charge and discharge capacities of approximately 152 mAh / g and approximately 123 mAh / g, respectively, within a cell potential window of 2 to 4 V at a current density corresponding to C / 25. Approximately 0.52 moles of Na are reversibly intercalated into the structure. The discharge capacity decay for the first two cycles is 1.02%, with a coulombic efficiency of 81%.

[0062] Figure 3B shows Na 0.97 Ca 0.03 Ni 0.4 Cu 0.1 Al 0.05 Mn 0.3 Ti 0.1 Sb 0.05 Figure 1 shows a specific capacity vs. cycle number plot for a sodium half-cell assembled using O2 cathode material. According to embodiments of the present invention, capacity cycling is useful for determining the potential window and cycling stability of the cathode active material. The present invention exhibits charge and discharge capacities of approximately 152 mAh / g and approximately 123 mAh / g, respectively, within the cell potential window of 2 to 4 V at a current density corresponding to C / 25. The capacity retention after 20 cycles is 93%.

[0063] Figure 3C shows Na 0.98 Ni 0.25 Cu 0.091 Mn 0.375 Ti 0.2 Sb 0.0833 Figure 1 shows a voltage-time plot of a sodium half-cell assembled using O2 cathode material. According to an embodiment of the present invention, the voltage-time plot is useful for determining the time of charge, potential window, and cycling stability of the cathode active material. The present invention exhibited charge and discharge capacities of approximately 141.27 mAh / g and approximately 140.956 mAh / g, respectively, within a cell potential window of 2 to 4 V at a current density corresponding to C / 25. Approximately 0.6 moles of Na are reversibly intercalated into the structure. The discharge capacity decay for the first two cycles is 1.03%, with a coulombic efficiency of 99%.

[0064] Figure 3D shows Na 0.98 Ni 0.25 Cu 0.091 Mn 0.375 Ti 0.2 Sb 0.0833 Figure 1 shows a specific capacity vs. cycle number plot for a sodium half-cell assembled using O2 cathode material. According to embodiments of the present invention, capacity cycling is useful for determining the potential window and cycling stability of the cathode active material. The present invention exhibits charge and discharge capacities of approximately 141.27 mAh / g and approximately 140.95 mAh / g, respectively, within the cell potential window of 2 to 4 V at a current density corresponding to C / 25. The capacity retention after 16 cycles is 95%.

[0065] Figure 3E shows Na 0.96 Ca 0.04 Ni 0.25 Cu 0.125 Mn 0.375 Ti 0.166 Sb 0.083Figure 1 shows a voltage-time plot of a sodium half-cell assembled using O2 cathode material. According to an embodiment of the present invention, the voltage-time plot is useful for determining the time of charge, potential window, and cycling stability of the cathode active material. The present invention exhibited charge and discharge capacities of approximately 121 mAh / g and approximately 114.9 mAh / g, respectively, within a cell potential window of 2 to 4 V at a current density corresponding to C / 25. Approximately 0.6 moles of Na are reversibly intercalated into the structure. The discharge capacity decay for the first two cycles is 1.014%, with a coulombic efficiency of 94%.

[0066] Figure 3F shows Na 0.96 Ca 0.04 Ni 0.25 Cu 0.125 Mn 0.375 Ti 0.166 Sb 0.083 Figure 1 shows a specific capacity vs. cycle number plot for a sodium half-cell assembled using O2 cathode material. According to embodiments of the present invention, capacity cycling is useful for determining the potential window and cycling stability of the cathode active material. The present invention exhibited charge and discharge capacities of approximately 121 mAh / g and approximately 114.9 mAh / g, respectively, within the cell potential window of 2 to 4 V at a current density corresponding to C / 25. The capacity retention after 20 cycles is 90%.

[0067] Figure 3G shows Na 0.8 Ca 0.2 Ni 0.6 Mn 0.2 Ti 0.2 Figure 1 shows a voltage-time plot of a sodium half-cell assembled using O2 cathode material. According to an embodiment of the present invention, the voltage-time plot is useful for determining the time of charge, potential window, and cycling stability of the cathode active material. The present invention exhibited charge and discharge capacities of approximately 127 mAh / g and approximately 109 mAh / g, respectively, within a cell potential window of 2 to 4 V at a current density corresponding to C / 25. Approximately 0.46 moles of Na are reversibly intercalated into the structure. The discharge capacity decay for the first two cycles is 1.016%, with a coulombic efficiency of 86%.

[0068] Figure 3H shows NaNi 1 / 6 Mg 1 / 6 Cu 1 / 6 Co 1 / 6 Fe 1 / 6 Mn 1 / 8 Ti 1 / 8 Figure 1 shows a voltage-time plot of a sodium half-cell assembled using O2 cathode material. According to an embodiment of the present invention, the voltage-time plot is useful for determining the time of charge, potential window, and cycling stability of the cathode active material. The present invention exhibited charge and discharge capacities of approximately 103 mAh / g and approximately 90 mAh / g, respectively, within a cell potential window of 2 to 4 V at a current density corresponding to C / 25. Approximately 0.38 moles of Na are reversibly intercalated into the structure. The discharge capacity decay for the first two cycles is 1.013%, with a coulombic efficiency of 86%.

[0069] Figure 3I shows Na 0.96 Ca 0.02 Ni 0.45 Cu 0.1 Mn 0.25 Ti 0.1 Sb 0.1 Figure 1 shows a voltage-time plot of a sodium half-cell assembled using O2 cathode material. According to an embodiment of the present invention, the voltage-time plot is useful for determining the time of charge, potential window, and cycling stability of the cathode active material. The present invention exhibited charge and discharge capacities of approximately 138 mAh / g and approximately 117 mAh / g, respectively, within a cell potential window of 2 to 4.4 V at a current density corresponding to C / 25. Approximately 0.52 moles of Na are reversibly intercalated into the structure. The discharge capacity decay for the first two cycles is 1.015%, with a coulombic efficiency of 84%.

[0070] Figure 3J shows Na 0.97 Ca 0.03 Li 0.02 Ni 0.5 Cu 0.05 Mn 0.2 Ti 0.1 Sb 0.13Figure 1 shows a voltage-time plot of a sodium half-cell assembled using O2 cathode material. According to an embodiment of the present invention, the voltage-time plot is useful for determining the time of charge, potential window, and cycling stability of the cathode active material. The present invention exhibited charge and discharge capacities of approximately 126 mAh / g and approximately 118 mAh / g, respectively, within a cell potential window of 2 to 4 V at a current density corresponding to C / 25. Approximately 0.50 moles of Na are reversibly intercalated into the structure. The discharge capacity decay for the first two cycles is 1.02%, with a coulombic efficiency of 93%.

[0071] FIG. 4A shows a Na 0.97 Ca 0.03 Ni 0.4 Cu 0.1 Al 0.05 Mn 0.3 Ti 0.1 Sb 0.05 1 shows a field emission scanning electron microscope (FESEM) image of an O2 cathode active material composition. The morphology of the cathode active material composition was examined using a Carl Zeiss 130 VP field emission scanning electron microscope (FESEM). In an embodiment of the present invention, the micrograph shows that the morphology of the solid-phase synthesized cathode active material composition results in irregular granular morphology and polygonal-shaped particles. Furthermore, the cathode active material composition is composed of various morphologies, including, but not limited to, rhombohedral, hexagonal, polygonal, cubic, spherical, and elongated hexagonal.

[0072] FIG. 4B shows a Na 0.98 Ni 0.25 Cu 0.091 Mn 0.375 Ti 0.2 Sb 0.0833 1 shows an FESEM image of an O2 positive electrode active material composition. The micrograph shows that the morphology of the solid-phase synthesized positive electrode active material composition results in an irregular granular morphology. Furthermore, the positive electrode active material composition is composed of various morphologies, including, but not limited to, rhombohedral, hexagonal, cubic, polygonal, spherical, and elongated hexagonal.

[0073] FIG. 4C shows a Na 0.96 Ca 0.04 Ni 0.25 Cu 0.125 Mn 0.375 Ti 0.166 Sb 0.083 1 shows an FESEM image of an O2 cathode active material composition. The micrograph shows that the morphology of the solid-phase synthesized cathode active material composition results in a plate-like particle morphology. Furthermore, the cathode active material composition is comprised of various morphologies, including, but not limited to, rhombohedral, hexagonal, cubic, spherical, polygonal, and elongated hexagonal.

[0074] FIG. 4D shows a Na 0.96 Ca 0.02 Ni 0.45 Cu 0.1 Mn 0.25 Ti 0.1 Sb 0.1 1 shows an FESEM image of an O2 positive electrode active material composition. The micrograph shows that the morphology of the solid-phase synthesized positive electrode active material composition results in an unclear granular morphology. Furthermore, the positive electrode active material composition is composed of various morphologies, including, but not limited to, rhombohedral, hexagonal, cubic, spherical, polygonal, and elongated hexagonal.

[0075] While the present invention has been described in connection with what is presently considered to be its most practical and various embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0076] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any device or system and performing any incorporated methods. The patentable scope of the invention is defined in the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal words of the claims, or if they include equivalent structural elements that are substantially different in scope from the literal words of the claims. [Example]

[0077] The following examples are given as illustrations of the implementation of the invention in practice and therefore should not be construed to limit the scope of the invention.

[0078] Example 1 Na 0.97 Ca 0.03 Ni 0.4 Cu 0.1 Al 0.05 Mn 0.3 Ti 0.1 Sb 0.05A multivalent cathode material composition represented by O2 was prepared according to an embodiment of the present invention by a solid-state method. Stoichiometric amounts of precursors CaCO3, NiO, CuO, Al2O3, MnO2, TiO2, Sb2O3, and Na2CO3 were thoroughly mixed and ground in an agate mortar over 30 minutes, calcined in air at 400°C for 2 hours, and then subjected to intermediate ball milling for 3 hours. The milled powder was calcined in air at 700°C for 20 hours. The X-ray diffraction (XRD) pattern, shown in Figure 2A, confirmed that the composition was single-phase, with all peaks consistent with the O3 phase, which belongs to a rhombohedral crystal structure with the space group R-3m. Moisture sensitivity was evaluated by immersing cathode material samples in water for 30 minutes to 10 hours, followed by filtering and drying in an oven at 100°C. According to an embodiment of the present invention, a field emission scanning electron microscopy (FESEM) micrograph shown in Figure 4A indicated that the morphology of the cathode material composition was irregularly shaped and plate-like. According to an embodiment of the present invention, a voltage vs. time plot shown in Figure 3A indicated that a sodium half-cell assembled using the cathode material exhibited charge and discharge capacities of about 152 and about 123 mAh / g, respectively, at a current density corresponding to C / 25 within a cell potential window of 2 to 4 V.

[0079] Example 2 Na 0.98 Ni 0.25 Cu 0.091 Mn 0.375 Ti 0.2 Sb 0.0833A multivalent positive electrode material composition represented by O2 was prepared according to an embodiment of the present invention by a solid-state method. Stoichiometric amounts of precursors NiO, CuO, Mn2O3, TiO2, Sb2O3, and Na2CO3 were thoroughly mixed and ball-milled for 10 hours, calcined in air at 700°C for 10 hours, followed by 10 minutes of intermediate ball-milling. The milled powder was then calcined in air at 800°C for 10 hours. The XRD pattern shown in Figure 2C confirmed that the composition was single-phase, with all peaks consistent with the O3 phase, which belongs to a rhombohedral crystal structure with the space group R-3m. The moisture sensitivity was evaluated by immersing the sample in water for 30 minutes to 10 hours, followed by filtering and drying in an oven at 100°C. According to an embodiment of the present invention, the FESEM micrograph shown in Figure 4B indicated that the morphology of the composition was irregular. According to an embodiment of the present invention, the voltage versus time plot depicted in FIG. 3C shows that a sodium half-cell assembled using the cathode material exhibits charge and discharge capacities of about 141 and about 140 mAh / g, respectively, at a current density corresponding to C / 25 within a cell potential window of 2 to 4 V.

[0080] Example 3 Na 0.96 Ca 0.04 Ni 0.25 Cu 0.125 Mn 0.375 Ti 0.166 Sb 0.083 O2. According to an embodiment of the present invention, the composition was prepared by a solid-state method. The precursors were stoichiometric amounts of CaCO3, Ni(OH), 2.xH2O, CuO, MnO2, TiO2, Sb2O3, and Na2CO3 were thoroughly mixed and ball-milled for 2 hours, calcined in air at 500 °C for 3 hours, followed by 2 hours of intermediate ball-milling. The milled powder was calcined in air at 800 °C for 15 hours. The XRD pattern shown in Figure 2E confirms that the composition is single-phase, with all peaks consistent with the O3 phase, which belongs to the rhombohedral crystal structure with space group R-3m. Moisture sensitivity was evaluated by immersing the sample in water for 30 minutes to 10 hours, followed by filtering and drying in an oven at 100 °C. According to an embodiment of the present invention, the FESEM micrograph shown in Figure 4C indicates that the morphology of the composition is irregularly shaped and plate-like. According to an embodiment of the present invention, the voltage versus time plot depicted in FIG. 3E shows that a sodium half-cell assembled using the cathode material exhibits charge and discharge capacities of about 121 and about 114 mAh / g, respectively, at a current density corresponding to C / 25 within a cell potential window of 2 to 4 V.

[0081] Example 4 Na 0.96 Ca 0.02 Ni 0.45 Cu 0.1 Mn 0.25 Ti 0.1 Sb 0.1A multivalent cathode material composition represented by O2 was prepared according to an embodiment of the present invention by a solid-state method. Stoichiometric amounts of precursors CaCO3, NiCO3, CuO, MnO2, TiO2, Sb2O3, and Na2CO3 were thoroughly mixed and ball-milled for 5 hours, calcined in air at 600 °C for 5 hours, followed by 5 hours of intermediate ball-milling. The milled powder was then calcined in air at 900 °C for 5 hours. The XRD pattern shown in Figure 2O confirms that the composition is single-phase, with all peaks consistent with the O3 phase, which belongs to a rhombohedral crystal structure with the space group R-3m. The moisture sensitivity was evaluated by immersing the sample in water for 30 minutes to 10 hours, followed by filtering and drying in an oven at 100 °C. According to an embodiment of the present invention, the FESEM micrograph shown in Figure 4D indicates that the morphology of the composition is irregularly shaped and plate-like. According to an embodiment of the present invention, the voltage versus time plot depicted in FIG. 3I shows that a sodium half-cell assembled using the cathode material exhibits charge and discharge capacities of about 138 and about 117 mAh / g, respectively, at a current density corresponding to C / 25 within a cell potential window of 2 to 4 V.

[0082] Example 5 Na 0.8 Ca 0.2 Ni 0.6 Mn 0.2 Ti 0.2A multivalent cathode material composition represented by O2 was prepared according to an embodiment of the present invention by a solid-state method. Stoichiometric amounts of precursors, CaCO3, NiO, CuO, MnO2, TiO2, Sb2O3, and Na2CO3, were thoroughly mixed and ground in an agate mortar over a period of 3 hours, calcined at 500 °C in air for 3 hours, and then subjected to intermediate ball milling for 5 hours. The milled powder was calcined at 850 °C in air for 20 hours. The XRD pattern, shown in Figure 2G, confirmed that the composition was single-phase, with all peaks consistent with the O3 phase, which belongs to a rhombohedral crystal structure with the space group R-3m. Moisture sensitivity was evaluated by immersing the sample in water for 30 minutes to 10 hours, followed by filtering and drying in an oven at 100 °C. According to an embodiment of the present invention, the voltage versus time plot depicted in FIG. 3G shows that a sodium half-cell assembled using the cathode material exhibits charge and discharge capacities of about 127 and about 109 mAh / g, respectively, at a current density corresponding to C / 25 within a cell potential window of 2 to 4 V.

[0083] Example 6 NaNi 1 / 6 Mg 1 / 6 Cu 1 / 6 Co 1 / 6 Fe 1 / 6 Mn 1 / 8 Ti 1 / 8A multivalent cathode material composition represented by O2 was prepared according to an embodiment of the present invention by a solid-state method. Stoichiometric amounts of precursors NiO, MgO, CuO, CO3O4, MnO2, Fe3O4O, TiO2, Sb2O3, and Na2CO3 were thoroughly mixed and ground in an agate mortar for 1 hour, calcined in air at 400°C for 2 hours, and then subjected to intermediate ball milling for 3 hours. The milled powder was calcined in air at 700°C for 20 hours. The XRD pattern shown in Figure 2I confirms that the composition is a single phase, with all peaks consistent with the O3 phase, which belongs to a rhombohedral crystal structure with the space group R-3m. Moisture sensitivity was evaluated by immersing the sample in water for 30 minutes to 10 hours, followed by filtering and drying in an oven at 100°C. According to an embodiment of the present invention, the voltage versus time plot depicted in FIG. 3H shows that a sodium half-cell assembled using the cathode material exhibits charge and discharge capacities of about 103 and about 90 mAh / g, respectively, at a current density corresponding to C / 25 within a cell potential window of 2 to 4 V.

[0084] Example 7 Na 0.97 Ca 0.03 Li 0.02 Ni 0.5 Cu 0.05 Mn 0.2 Ti 0.1 Sb 0.13A multivalent cathode material composition represented by O2 was prepared according to an embodiment of the present invention by a solid-state method. Stoichiometric amounts of precursors CaCO3, Li2CO3, NiO, CuO, MnO2, TiO2, Sb2O3, and Na2CO3 were thoroughly mixed and ball-milled for 10 hours, calcined in air at 700°C for 10 hours, followed by 10 hours of intermediate ball-milling. The milled powder was then calcined in air at 800°C for 10 hours. The XRD pattern shown in Figure 2A confirms that the composition is a single phase, with all peaks consistent with the O3 phase, which belongs to a rhombohedral crystal structure with the space group R-3m. Moisture sensitivity was evaluated by immersing the samples in water for 30 minutes to 10 hours, then filtering and drying in an oven at 100°C. According to an embodiment of the present invention, the voltage versus time plot depicted in FIG. 3Q shows that a sodium half-cell assembled using the cathode material exhibits charge and discharge capacities of about 126 and about 118 mAh / g, respectively, at a current density corresponding to C / 25 within a cell potential window of 2 to 4 V.

[0085] The present invention is not limited to these materials, and other examples of positive electrodes include: Na 0.95 Ca 0.05 Ni 0.4 Cu 0.1 Al 0.05 Mn 0.3 Ti 0.1 Sb 0.05 O2 Na 0.99 Ca 0.01 Ni 0.4 Cu 0.1 Al 0.05 Mn 0.3 Ti 0.1 Sb 0.05 O2 Na 0.94 Ca 0.03 Ni 0.5 Cu 0.1 Mn 0.1 Ti 0.1 Sb 0.2 O2 Na 0.95 Ca 0.05 Ni 0.6 Mn 0.2 Ti 0.1 Sb0.1 O2 NaCa 0.03 Cu 0.1 Ni 0.3 Fe 0.32 Mn 0.25 Ti 0.05 O2 NaCu 0.1 Ni 0.15 Fe 0.30 Mn 0.35 Ti 0.05 Sb 0.02 O2 Na 0.98 Ca 0.02 Ni 1 / 7 Cu 1 / 7 Al 1 / 7 Co 1 / 7 Fe 1 / 7 Mn 1 / 7 Ti 1 / 7 O2 Na 0.97 Ca 0.03 Ni 0.12 Cu 0.15 Mn 0.5 Ti 0.23 O2 Examples include:

[0086] Advantages of the Invention The main advantages of the present invention are as follows: 1. Moisture-stable and air-stable cathode material composition. 2. Improved cycle performance and high voltage performance of the cathode material. 3. The positive electrode material composition can be used in the battery industry. 4. The composition formula contains abundant and low-cost elements. 5. Cathode material composition easily scalable to mass production. [Explanation of symbols]

[0087] 100 sodium ion batteries 102 Negative electrode 104 Porous separator 106 Positive electrode 108 Electrolytes 110 Aluminum foil or copper foil 112 Aluminum foil

Claims

1. Formula Na ｘ A ｚ Ni ｉ M ｙ Mn ｊ Ti ｋ Sb ｆ O ２ 1. An air- and moisture-stable layered oxide cathode material having the formula: (i+j+k+f+y=1), 0.7≦x≦1, 0≦z≦0.2, 0≦y≦0.5, 0.1≦i≦0.6, 0.1≦j≦0.5, 0.05≦k≦0.4, 0≦f≦0.2; a) A is an alkali or alkaline earth metal selected from divalent Ca or monovalent Li; b) M is a divalent or trivalent element selected from Fe, Mg, Zn, Cu, Al, Co, or combinations thereof, having oxidation states of +2 and +3, respectively; c) Ni is a divalent element having an oxidation state of +2; d) Mn and Ti are tetravalent elements having an oxidation state of +4; e) Sb is a pentavalent / trivalent element with +5 / +3 oxidation states; Positive electrode material.

2. The positive electrode material is ! ０．９７ . ０．０３ i ０．４ u ０．１ B. ０．０５ * ０．３ () ０．１ 3) ０．０５ . ２ 4 ! ０．９５ . ０．０５ i ０．４ u ０．１ B. ０．０５ * ０．３ () ０．１ 3) ０．０５ . ２ 4 ! ０．９９ . ０．０１ i ０．４ u ０．１ B. ０．０５ * ０．３ () ０．１ 3) ０．０５ . ２ 4 ! ０．９４ . ０．０３ i ０．５ u ０．１ * ０．１ () ０．１ 3) ０．２ . ２ 4 Yes ０．９５ Ca ０．０５ Yes ０．６ MỎ ０．２ Till ０．１ Sb ０．１ Oh ２ ; ! ０．９６ . ０．０２ i ０．４５ u ０．１ * ０．２５ () ０．１ 3) ０．１ . ２ 4 Na ０．８ Ca ０．２ ii ０．６ 7N ０．２ Ti ０．２ 9 ２ ; Na ０．９７ Ca ０．０３ Li ０．０２ Ni ０．５ Cu ０．０５ Mn ０．２ Ti ０．１ Sb ０．１３ O ２ ; NaCa ０．０３ Cu ０．１ Ni ０．３ Fe ０．３２ Mn ０．２５ Ti ０．０５ O ２ ; NaCu ０．１ Yes ０．１５ Fe ０．３０ MỎ ０．３５ Till ０．０５ Sb ０．０２ Oh ２ ; Nai １／６ MM １／６ Cu １／６ Co １／６ Fe １／６ Mn １／８ Ti １／８ O ２ ; Na ０．９８ Ca ０．０２ Ni １／７ Cu １／７ Al １／７ Co １／７ Fe １／７ Mn １／７ Ti １／７ O ２ ; ! ０．９６ . ０．０４ i ０．２５ u ０．１２５ * ０．３７５ () ０．１６６ 3) ０．０８３ . ２ 4 Na ０．９８ Ni ０．２５ Cu ０．０９１ Mn ０．３７５ Ti ０．２ Sb ０．０８３３ O ２ ; or Na ０．９７ Ca ０．０３ Ni ０．１２ Cu ０．１５ Mn ０．５ Ti ０．２３ O ２ The cathode material of claim 1 , wherein the cathode material is selected from the group consisting of:

3. The positive electrode material is O ３ The cathode material of claim 2 having a type layered structure.

4. 3. The cathode material of claim 2, wherein the cathode material is a single phase having a rhombohedral crystal structure and space group R-3m.

5. 3. The cathode material of claim 2, wherein the cathode material exhibits a capacity of 70 mAh / g to 195 mAh / g.

6. 3. The cathode material of claim 2, wherein the cathode material operates in a voltage range of 2V to 4.5V.

7. (i) a positive electrode (106) comprising the single-phase positive electrode material of claim 1 or 2; (ii) a negative electrode (102); (iii) a non-aqueous electrolyte (108); and a separator (104).

10. A sodium-ion battery (100) containing the air-stable and moisture-stable layered oxide cathode material of claim 1, comprising:

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