Oxides for high energy cathode materials

Abstract

To provide a battery with improved performance.SOLUTION: A battery comprising electrodes comprising an active material, wherein the active material is characterized by a disordered rocksalt crystal structure comprising LixNbyMzO2, wherein 1.2 <x ≤ 1.65, y is 0 <y <0.55, z is 0.1 <z <1, and M is an element that charge compensates for an increase in lithium, wherein M is comprised of Mn and at least one other element, wherein the at least one other element is comprised of one or more of W and Ti.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to the field of battery technology, and more particularly to the field of high energy materials for use in electrodes of electrochemical cells. [Background technology]

[0002] Lithium metal oxides have been used to formulate cathode materials for lithium-ion batteries. Cathodes are available from several basic crystal structure types, such as spinel, olivine, and layered oxide structures. Layered oxide structures include lithium-rich structures where additional lithium is present in the structure.

[0003] Recently, rock salt structures such as those formed from certain lithium metal oxides have attracted attention. The formula: [ka] (wherein M is a trivalent cation.) Compounds represented by the formula (1) have been shown to be a promising class of transition metal oxides for use as cathodes in lithium-ion batteries. Compounds of formula (1) are believed to be disordered rock salts, in which random atomic arrangements of lithium and transition metal ions are packed into a cubic close-packed system. These disordered rock salt compositions offer the ability to contain up to three lithium atoms per formula unit, more than conventional lithium-rich layered materials, which is shown in Figure 1. By rearranging formula (1) to give Li x M y N z O w It can be expressed as:

[0004] The disordered rock salt structure has the following advantages and challenges when used as a cathode material in lithium-ion batteries: Advantageously, the disordered rock salt structure has a significantly higher theoretical energy density compared to other state-of-the-art cathode materials. For example, some disordered rock salt structure materials have a theoretical gravimetric energy density of about 1120 Wh / kg, while LiMn2O4 active materials have a theoretical gravimetric energy density of about 492 Wh / kg, and LiMn 1.5 Ni 0.5 O4 has a theoretical gravimetric energy density of approximately 691 Wh / kg. This energy density is particularly attractive when manganese is used as the primary component, because the irregular rock salt structure achieves this higher energy density using manganese, a relatively low-cost raw material; compounds with comparable energy densities use more expensive raw materials.

[0005] Research on disordered rock-salt for use in lithium-ion batteries includes Wang, R; Li, X.; Liu, L.; Lee, J.; Seo, D.-H.; Bo, S.-H.; Urban, A.; Ceder, G. A Disordered Rock-Salt Li-Excess Cathode Material with High Capacity and Substantial Oxygen Redox Activity: Li 1.25 Nb 0.25 Mn 0.5 O2. Electrochem. Commun. 2015, 60, 70-73. In this publication, the formula Li 1.25 Nb 0.25 Mn 0.5 A disordered rock salt compound with O2 was synthesized and tested. This material contains Mn 3+ / Mn 4+ The capacity was higher than the theoretical capacity based on the redox reaction. 1.25 Nb 0.25 Mn 0.5However, the embodiments disclosed herein provide variations in disordered rock salt structure and composition that are not disclosed or suggested in this publication.

[0006] Another example of research on disordered rock salt for use in lithium-ion batteries is Yabuuchi, N.; Takeuchi, M.; Nakayama, M.; Shiiba, H.; Ogawa, M.; Nakayama, K.; Ohta, T.; Endo, D.; Ozaki, T.; Inamasu, T.; et al. High-Capacity Electrode Materials for Rechargeable Lithium Batteries: Li3NbO4-Based System with Cation-Disordered Rock Salt Structure. Proc. Natl. Acad. Sci. 2015, 112, 7650-7655. This publication describes the structure of disordered rock salts with the formula Li 1.3 Nb 0.3 Mn 0.4 O2, Li 1.3 Nb 0.3 Fe 0.4 O2, Li 1.3 Nb 0.43 Ni 0.27 O2 and Li 1.3 Nb 0.43 Co 0.27 The publication discloses the performance of several compositions of O. Thus, while this publication demonstrates some performance attributes of disordered rock salt compositions with some variation in the "3d" metals (defined below), it does not disclose or suggest variations in the disordered rock salt structure and composition of the embodiments disclosed herein.

[0007] Yet another example of research on disordered rock salts for use in lithium-ion batteries is Ceder, G; Lee, J.; Li, X.; Kim, S.; Hautier, G., High-Capacity Positive Electrode Active Material. US 2014 / 0099549, April 10, 2014. This publication discloses a general disordered rock salt composition of Li x M y O2 (where 0.6 ≦ y ≦ 0.85, 0 ≦ x + y ≦ 2, and M is one or more of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Sn, and Sb). However, the embodiments disclosed herein provide variations in disordered rock salt structures and compositions not disclosed or suggested in this publication.

[0008] Yet another example of research on disordered rock salts for use in lithium-ion batteries is Takeuchi, M.; Yabuuchi, N.; Komaba, S.; Endo, D., Active Material For Nonaqueous Electrolyte Electricity Storage Elements. US2016 / 049640, February 18, 2016. This publication discloses a general disordered rock salt composition of Li 1+x Nb y Me z A p O2 (where Me is a transition metal such as Fe and / or Mn, 0.6 < x < 1, 0 < y < 0.5, and 0.25 ≦ z < 1, A is an element other than Nb and Me, and 0 ≦ p ≦ 0.2). However, the embodiments disclosed herein provide variations in disordered rock salt structures and compositions not disclosed or suggested in this publication.

[0009] The embodiments disclosed herein can exhibit improved capacity, energy density, voltage decay, rate performance, and capacity retention compared to known disordered rock salt compositions, and in some cases, have been demonstrated. SUMMARY OF THE INVENTION

[0010] Embodiments of the present invention include an active material for use in a lithium-ion battery. In some embodiments, the active material is characterized by an irregular rock salt crystal structure and has the chemical formula (i): [Chemical Formula] (where 1.2 < x ≤ 1.75, 0 ≤ y < 0.55, 0.1 < z < 1, 0 ≤ a < 0.5, 0 ≤ b < 1, and 0 ≤ c < 0.8, and M, N, and P are each independently one or more of Ti, Ta, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Y, Mo, Ru, Rh, and Sb.) represented by

[0011] Embodiments of the present invention include a battery having an electrode formed from any of the active materials disclosed above. Embodiments of the present invention include a method for manufacturing the active materials disclosed above herein.

Brief Description of the Drawings

[0012] [Figure 1A] FIG. 1A shows the electrochemical characterization of a battery including some embodiments of the present invention, where an improvement in energy density is shown as a result of an increase in lithium content.

[0013] [Figure 1B] FIG. 1B shows the voltage trace of a battery including some embodiments of the present invention, where the stoichiometric lithium content increases from 1.2 to 1.5 and the stoichiometric manganese content decreases from 0.6 to 0.5. <0​​​​​​​​FIG. 2A shows voltage traces for cells containing several embodiments of the present invention in which the ratio of niobium to manganese was systematically varied.

[0016] [Figure 2B] FIG. 2B shows the corresponding differential capacitance as a function of voltage for the embodiment of the invention of FIG. 2A.

[0017] [Figure 3] FIG. 3 shows voltage traces for cells containing several embodiments of the present invention in which various transition metal dopants are doped into niobium site.

[0018] [Figure 4] FIG. 1 shows a series of X-ray diffraction patterns for some embodiments of the present invention in which the stoichiometric lithium content increases from 1.2 to 1.65 and the stoichiometric manganese content decreases from 0.83 to 0.70.

[0019] [Figure 5A] FIG. 5A shows the electrochemical characterization of batteries incorporating some embodiments of the present invention, measuring first cycle performance when annealing a disordered rock salt composition in various atmospheres at 1000 degrees Celsius.

[0020] [Figure 5B] FIG. 5B shows electrochemical characterization of batteries incorporating some embodiments of the present invention, measuring first cycle performance when annealing a disordered rock salt composition in various atmospheres at 1000 degrees Celsius.

[0021] [Figure 6A] FIG. 6A shows the electrochemical characterization of batteries incorporating some embodiments of the present invention, where first cycle performance was measured for disordered rock salt compositions with various substitutions of niobium in the composition.

[0022] [Figure 6B]FIG. 6B shows the electrochemical characterization of batteries incorporating some embodiments of the present invention, where first cycle performance was measured for disordered rock salt compositions with various double dopants substitutions for niobium in the composition.

[0023] [Figure 7A] FIG. 7A shows the electrochemical characterization of cells including some embodiments of the present invention, where first cycle performance was measured for a disordered rock salt composition with fluorine doping on the oxygen sites.

[0024] [Figure 7B] FIG. 7B shows the corresponding discharge capacity as a function of cycle number for the embodiment of the invention of FIG. 2A. DETAILED DESCRIPTION OF THE INVENTION

[0025] The following definitions apply to some aspects described with respect to some embodiments of the present invention. These definitions may be expanded upon in the present specification. Each term is further explained and exemplified through the detailed description, figures, and examples. Any interpretation of a term in this description should take into account the complete description, figures, and examples provided herein.

[0026] The singular terms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. Thus, for example, a reference to an object can include a plural object unless the context clearly dictates otherwise.

[0027] The terms "substantially" and "substantial" refer to a great extent or degree. When used in conjunction with an event or circumstance, these terms refer to the event or circumstance occurring exactly or approximately occurring, for example, to account for the typical tolerance level or variability of the embodiments described herein.

[0028] The term "transition metal" includes scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (A), and zinc (Zn). It refers to the chemical elements in groups 3 to 12 of the periodic table, such as cadmium (Cd), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), mercury (Hg), rutherfordium (Rf), dubnium (Db), seaborgium (Sg), bohrium (Bh), hassium (Hs), and meitnerium (Mt).

[0029] The term "3d elements" refers to transition metals in which the 3d subshell of the M shell is incompletely filled, and "3d elements" include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn.

[0030] The term "4d elements" refers to transition metals in which the 4d subshell of the N-shell is incompletely filled, and "4d elements" include Y, Zr, Nb, Mo, Tc, Ru, and Rh.

[0031] Rate "C" refers to either the discharge current as a fraction or multiple of a "1C" current value at which a battery (in a substantially fully charged state) would be substantially fully discharged in 1 hour, or the charge current as a fraction or multiple of a "1C" current value at which a battery (in a substantially fully discharged state) would be substantially fully charged in 1 hour (depending on the context).

[0032] To the extent that some battery characteristics may change with temperature, such characteristics are specified at 30°C unless the context clearly dictates otherwise.

[0033] Ranges presented herein are inclusive of their endpoints, so for example, the range 1 to 3 includes the values ​​1 and 3 and any intermediate values ​​therebetween.

[0034] Embodiments of the present invention provide disordered rock salt compositions for use in formulating cathodes in electrochemical cells. Compared to prior art disordered rock salt compositions, cathodes formed from some embodiments of the disordered rock salt disclosed herein provide improved electrochemical performance in lithium-ion batteries. The embodiments disclosed herein enable, and in some cases have demonstrated, improved capacity, energy density, voltage fade, rate capability, and capacity retention. The compositions disclosed herein exhibit superior performance compared to the base disordered rock salt composition.

[0035] In disordered rock salt compositions, both lithium and transition metals occupy a cubic close-packed lattice of octahedral sites. In the electrochemical reaction, lithium diffusion proceeds by lithium hopping from one octahedral site to another via an intermediate tetrahedral site. The lithium at the intermediate tetrahedral site is the active state for lithium diffusion. The active tetrahedral lithium ion shares faces with four octahedral sites: (i) the site previously occupied by the lithium ion itself; (ii) a vacancy to which the lithium ion may migrate; and (iii and iv) two sites that may be occupied by lithium, a transition metal, or a vacancy.

[0036] According to some embodiments of the present invention, changing and controlling the lithium content in irregular rock salt results in improved electrochemical performance in lithium-ion battery cells having cathodes formed from compositions of some of these embodiments. Prior art irregular rock salt materials typically use a stoichiometric lithium content of 1.4 or less, more preferably about 1.25 or 1.3. In contrast, some embodiments of the present invention include irregular rock salt compositions in which lithium is present at a higher stoichiometric content than is typical.

[0037] In some preferred embodiments, the stoichiometric amount of lithium is 1.20 or more, 1.25 or more, 1.30 or more, 1.35 or more, 1.40 or more, 1.45 or more, 1.50 or more, 1.55 or more, 1.60 or more, 1.65 or more, 1.70 or more, or 1.75 or more.

[0038] In such embodiments, the stoichiometric content of the other elements in the irregular rock salt composition decreases to compensate for the difference in net charge caused by the increase in lithium content. The relationship between the increased lithium and the decreased element is given by the exemplary formula:

Chemical formula

Chemical formula

[0039] Table 1 shows the stoichiometric amounts of lithium and niobium in a wider range, and the amount of M used to compensate for the charge difference due to the increase in lithium content.

Table 1

[0040] The vertical axis of Table 1 lists the stoichiometric amount of lithium present in Formula 3, and the horizontal axis lists the stoichiometric amount of niobium present in Formula 3. The data in Table 1 are the stoichiometric amounts of M (in this case, manganese) used to compensate for these various stoichiometric amounts of lithium. Therefore, Table 1 lists the ranges of Formula 3 as follows: 1.0 ≤ x ≤ 3.7, 0.00 ≤ y ≤ 0.55, 0.017 ≤ z ≤ 1. These ranges include preferred embodiments of the present invention and other embodiments of the present invention.

[0041] In the results presented herein, embodiments of the present invention with increased stoichiometric amounts of lithium have been shown to improve the electrochemical performance of the disordered rock salt composition. In contrast to the prior art, embodiments of the present invention compensate for the disordered rock salt composition and increase the stoichiometric amount of lithium. The above specific relationships between the components of the disordered rock salt composition are at least one matter that distinguishes this embodiment from the prior art. Without being bound by any particular theory or mechanism of action, by changing the ratio of 4d to 3d, O2 dimers can be captured, and as a result, the amount of oxygen released from the structure can be made significantly less than that in conventional disordered rock salts. This mechanism is related to the reductive coupling that can occur at a specific ratio of 4d to 3d.

[0042] According to some embodiments of the present invention, changing and controlling the ratios of various cations in irregular rock salt results in improved electrochemical performance in lithium-ion battery cells having cathodes formed from the compositions of some of these embodiments. While the prior art has identified and / or preferred the ratios between various cations in prior art irregular rock salt compositions, the ratio derived from 3d / 4d is typically 2.0. That is, the 3d element is present in a stoichiometric amount twice that of the 4d element.

[0043] The general formula for the relationship in the stoichiometric amounts of the 3d and 4d elements in these embodiments is

Chemical formula

[0044] In some embodiments, the stoichiometric ratio of the 3d element to the 4d element is at least 2.0, at least 2.5, at least 3.0, at least 3.5, at least 4.0, at least 4.5, at least 5.0, at least 5.5, at least 6.0, at least 6.5, at least 7.0, at least 7.5, at least 8.0, at least 8.5, at least 9.0, at least 9.5, at least 10.0, at least 10.5, at least 11.0, at least 11.5, at least 12.0, at least 12.5, at least 13.0, at least 13.5, at least 14.0, at least 14.5, at least 15.5, at least 15.5, at least 16.0, at least 16.5, at least 17.0, at least 17.5, or at least 18.0.

[0045] In the results presented herein, embodiments of the present invention with a relatively high ratio between the stoichiometric amount of the 3d element and the stoichiometric amount of the 4d element are shown to improve the electrochemical performance of the disordered rock salt composition. In contrast to the prior art, embodiments of the present invention demonstrate the usefulness of a specific ratio between the stoichiometric amount of the 3d element and the stoichiometric amount of the 4d element in the disordered rock salt composition, and this ratio is at least one matter that distinguishes this embodiment from the prior art.

[0046] According to some embodiments of the present invention, varying and controlling the dopant content at the 3d element sites and 4d element sites in the disordered rock salt results in improved electrochemical performance in lithium ion battery cells having cathodes formed from the compositions of these some embodiments. Conventional disordered rock salt materials typically do not contain dopants at either the 3d or 4d sites. In some embodiments, the preferred 4d element is niobium and the preferred 3d element is manganese. Doped synthesis of the disordered rock salt can be achieved by solid state reaction.

[0047] In these embodiments, the general formula of the composition showing doping at the sites of the 3d and 4d elements, where manganese is selected as the 3d element and niobium is selected as the 4d element, is

Chemical formula

[0048] <gro In some preferred embodiments, one of a or b is equal to zero. That is, the dopant is present in either the niobium site or the manganese site, but not in both sites. An example where a = 0 is as follows. [Chemical formula] Here, 0 < b < 0.8, and P is one or more of Fe, Cr, Al, and Sb. An example where b = 0 is as follows. [Chemical formula] Here, 0 < a < 0.2, and N is one or more of V, Mo, Sb, Ta, Ti, Zr, and Y.

[0049] In some preferred embodiments, both a and b are equal to zero.

[0050] The results shown herein indicate that embodiments of the present invention having a dopant at a 3d or 4d element site in the disordered rock salt improve the electrochemical performance of the disordered rock salt composition. In contrast to the prior art, embodiments of the present invention demonstrate the usefulness of dopants at 3d or 4d element sites in the disordered rock salt, and the presence of these dopants is at least one matter that distinguishes these embodiments from the prior art. The dopant has been found to improve one or more electrochemical performance indicators such as energy density, rate performance, and capacity retention.

[0051] According to some embodiments of the present invention, varying and controlling the presence of niobium in the disordered rock salt results in improved electrochemical performance in a lithium-ion battery cell having a cathode formed from the compositions of these some embodiments. Prior art disordered rock salt materials typically contain niobium. In some embodiments, niobium is completely replaced by one or more other elements.

[0052] According to these embodiments, the general formula of the composition in which niobium is completely replaced is [Chemical formula] where M and N are metals, 1.2 < x ≤ 1.75, 0 < y < 0.55, 0 ≤ u ≤ 0.55, and 0.2 < z < 1.0. In some preferred embodiments, M is selected from Ti, Ta, Zr, W, and Mo, and N is independently selected from Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Al, Zr, Y, Mo, Ru, and Sb. In some preferred embodiments, a single dopant is present (i.e., one of y or u is zero), and in other preferred embodiments, two dopants are present.

[0053] The results presented herein show that embodiments of the present invention having a single dopant and two dopants that completely replace niobium in the disordered rock salt improve the electrochemical performance of the disordered rock salt composition. In contrast to the prior art, embodiments of the present invention demonstrate the usefulness of completely replacing niobium in the disordered rock salt, and the absence of niobium is at least one matter that distinguishes these embodiments from the prior art. Similarly, a specific 4d to 3d ratio can shift the stabilization of the O2 dimer.

[0054] According to some embodiments of the present invention, varying and controlling the amount of oxygen in the disordered rock salt results in improved electrochemical performance in a lithium-ion battery cell having a cathode formed from the composition of some of these embodiments. Specifically, doping some of the oxygen sites with fluorine results in improved electrochemical performance.

[0055] Prior art disordered rock salt materials typically do not contain dopants at the oxygen sites and instead synthesize the material to the target stoichiometric composition without including a doping step. Furthermore, prior art disordered rock salt compositions typically do not contain fluorine. A synthetic route for fluorine-substituted disordered rock salt is disclosed below.

[0056] The general formula for doping at oxygen sites in these embodiments is [Chemical Formula] Here, 1.2 < x ≤ 1.75, 0 ≤ y ≤ 0.55, 0.1 < z < 1, 0 ≤ a < 0.5, 0 ≤ b < 1, and 0 < c < 0.8, and M, N, and P are each independently one or more of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Y, Mo, Ru, and Rh.

[0057] In the results presented herein, embodiments of the present invention having fluorine dopants at oxygen sites in disordered rock salt have been shown to improve the electrochemical performance of disordered rock salt compositions. In contrast to the prior art, embodiments of the present invention demonstrate the usefulness of dopants at oxygen sites in disordered rock salt, and the presence of these dopants, particularly fluorine dopants, is at least one matter that distinguishes these embodiments from the prior art.

[0058] Without being bound by a particular theory or mechanism of action, substituting oxygen with fluorine (formation of oxyfluoride) can improve cycle performance by providing greater resistance to HF attack from electrolyte decomposition at high voltages. Alternatively, the higher ionic nature of metal-fluorine bonds compared to metal-oxygen bonds can result in a reduction in the leaching of transition metals from the cathode to the electrolyte, further stabilizing the structure.

[0059] According to some embodiments of the present invention, varying and controlling the atmosphere in which the disordered rock salt composition is annealed results in improved electrochemical performance in lithium-ion battery cells having cathodes formed from the compositions of some of these embodiments. Specifically, varying between argon gas flow, nitrogen gas flow, and air flow results in improved electrochemical performance. In particular, the improvement provided by the annealing environment depends on the starting composition and dopants. Without being bound to a particular theory or mechanism of action, in an argon or nitrogen environment, oxygen stoichiometry is preserved, while in air annealing, oxygen may be released, affecting stoichiometry and resulting in poorer electrochemical performance.

[0060] According to some embodiments of the present invention, varying and controlling the presence of various carbon precursors used to mill the irregular rock salt compositions results in improved electrochemical performance in lithium-ion battery cells having cathodes formed from the compositions of some of these embodiments. Examples of carbon precursors include, but are not limited to, acetylene black, carbon black, carbon fiber, graphite, or KJ600. The precursors can be present at about 10% to about 40% by weight of the cathode material.

[0061] The following examples illustrate specific aspects of some embodiments of the present invention and provide guidance to those of ordinary skill in the art. The examples are intended merely to provide specific methodologies useful in understanding and practicing some embodiments of the present invention and should not be construed as limiting the invention. [Example]

[0062] standard synthesis Disordered rock salt materials were synthesized using a two-step process: milling and annealing. Typically, stoichiometric amounts of precursors (e.g., Mn2O3, Li2CO3, Nb2O5, etc.) were milled. The milled powder was then annealed under flowing argon gas (approximately 19 L / min) at temperatures between approximately 900 and approximately 1000 °C for approximately 6 to approximately 12 hours. In some cases, annealing was performed under flowing nitrogen gas or air. Following the annealing step, the powder was again milled with a carbon precursor (e.g., acetylene black, carbon black, carbon fiber, graphite, or KJ600) in an 80:20 mass ratio (annealed powder:carbon).

[0063] Nb-free synthesis Nb-free disordered rock salt materials were synthesized using a two-step process: milling and annealing. Typically, stoichiometric amounts of precursors (e.g., Mn2O3, Li2CO3, and other 4d oxides (Ta2O5, TiO2, MoO2, WO3)) were milled. The milled powder was then annealed under argon gas flow (approximately 19 L / min) at temperatures between approximately 900°C and approximately 1000°C for approximately 6 to approximately 12 hours. Following the annealing step, the powder was again milled with a carbon precursor (e.g., acetylene black, carbon black, carbon fiber, graphite, graphene, carbon single-walled or double-walled nanotubes, or KJ600) in an 80:20 mass ratio (annealed powder:carbon).

[0064] Fluorine-doped Synthesis Disordered rock salt materials doped (substituted) with fluorine at the oxygen sites were synthesized using a two-step process: milling and annealing. Typically, stoichiometric amounts of precursors (e.g., Mn2O3, Li2CO3, Nb2O5, NbF5, etc. (or other fluoride precursors)) were milled. The milled powder was then annealed under argon gas flow (approximately 19 L / min) at temperatures between approximately 900°C and approximately 1000°C for approximately 6 to approximately 12 hours. Following the annealing step, the powder was again milled with a carbon precursor (e.g., acetylene black, carbon black, carbon fiber, graphite, graphene, carbon single-walled or double-walled nanotubes, or KJ600) in an 80:20 mass ratio (annealed powder:carbon).

[0065] Cell Assembly Battery cells were fabricated in a high-purity argon-filled glovebox (M-Braun, O2 and moisture content <0.1 ppm). Irregular rock salt powder was mixed with poly(vinylidene fluoride) (Sigma-Aldrich) and 1-methyl-2-pyrrolidinone (Sigma-Aldrich), and the resulting slurry was deposited onto a stainless steel current collector and dried to form a composite cathode film. For the anode, thin lithium foil was cut to the required size. Each battery cell contained the composite cathode film, a polypropylene separator, and a lithium foil anode. An electrolyte containing lithium hexafluorophosphate in a mixture of ethylene carbonate, ethyl methyl carbonate, and additives was used. The battery cells were sealed and cycled between 1.5 V and 4.8 V at 55 °C, occasionally at 30 °C.

[0066] result Figure 1A shows electrochemical characterization of batteries incorporating some embodiments of the present invention, demonstrating improved energy density as a result of increasing lithium content. Figure 1B shows voltage traces for batteries incorporating some embodiments of the present invention in which the stoichiometric lithium content was increased from 1.2 to 1.5 and the stoichiometric manganese content was decreased from 0.6 to 0.5. Figure 1C shows the corresponding differential capacity as a function of voltage for the embodiments of the present invention in Figure 1B.

[0067] In Figure 1A, the stoichiometric lithium content was increased, the stoichiometric niobium content was held constant, the stoichiometric manganese content was decreased to charge compensate the lithium content, and the stoichiometric oxygen content was held constant. The various disordered rocksalt compositions were characterized by the addition of Li 1.20 Nb 0.20 Mn 0.60 O2 (as a control), Li 1.25 Nb 0.20 Mn 0.58 O2, Li 1.35 Nb 0.20 Mn 0.55 O2, Li 1.40 Nb 0.20 Mn 0.53 O2, Li 1.50 Nb 0.20 Mn 0.50 O2 and Li 1.65 Nb 0.20 Mn 0.45 It was O2.

[0068] Figure 1B demonstrates the improvement in first-cycle capacity with increasing lithium content, which is commensurate with decreasing manganese content. The highest stoichiometric lithium content resulted in a roughly 36% improvement in first-cycle charge capacity and a roughly 40% improvement in first-cycle discharge capacity.

[0069] Figure 2A shows voltage traces for batteries containing several embodiments of the invention in which the ratio of niobium to manganese is systematically varied, and Figure 2B shows the corresponding differential capacity as a function of voltage for the embodiments of the invention in Figure 2A.

[0070] Figure 2A shows that a higher 3d / 4d ratio leads to improved electrochemical performance. The ratios in Figure 2A were 2 (0.50 / 0.25); 4 (0.60 / 0.15); 14 (0.70 / 0.05); and 16.6 (0.83 / 0.05). The higher ratios resulted in approximately a 17% improvement in first-cycle discharge capacity.

[0071] Figure 3 shows voltage traces for batteries incorporating several embodiments of the present invention in which various transition metal dopants were doped into the niobium site. Table 2 discloses the results of the doping with niobium site, as well as the respective first cycle discharge capacities and specific energy densities. These data were generated from cycling between 4.8 V and 1.5 V at a C rate of C / 40. [Table 2]

[0072] Figure 3 shows voltage traces for several doped disordered rock salt compositions in Table 2. Many of the doped disordered rock salt compositions performed better than the undoped disordered rock salt compositions.

[0073] Table 3 discloses the results of doping at the manganese site, as well as the respective first cycle discharge capacities and specific energy densities. These data were obtained from cycling between 4.8 V and 1.5 V at a C rate of C / 40. [Table 3]

[0074] 4 shows a series of X-ray diffraction patterns for some embodiments of the present invention where the stoichiometric lithium content is increased from 1.2 to 1.65 and the stoichiometric manganese content is decreased from 0.85 to 0.70. The (*) symbol indicates the Fm-3m rock salt crystal structure.

[0075] Figure 5A shows the electrochemical characterization of batteries including some embodiments of the present invention, where first cycle performance was measured for annealing the disordered rock salt composition in various atmospheres at 1000 degrees Celsius. Figure 5B shows the electrochemical characterization of batteries including some embodiments of the present invention, where first cycle performance was measured for annealing the disordered rock salt composition in various atmospheres at 1000 degrees Celsius. Two different systems, Li 1.25 Nb 0.25 Mn 0.5 The basic disordered rock salt composition of O2 and Li 1.4 Nb 0.2 Mn 0.53 At higher lithium content compositions of O2, the nitrogen atmosphere resulted in improved first cycle performance.

[0076] Figure 6A shows the electrochemical characterization of batteries comprising some embodiments of the present invention, where first cycle performance was measured for disordered rock salt compositions with various substitutions of niobium in the composition. Figure 6B shows the electrochemical characterization of batteries comprising some embodiments of the present invention, where first cycle performance was measured for disordered rock salt compositions with various double dopant substitutions of niobium in the composition.

[0077] FIG. 6A shows the improvement when substituting tantalum for niobium, and FIG. 6B shows that several double substitutions, including combinations of tantalum, tungsten, titanium, and zirconium, result in improved first cycle performance.

[0078] Figure 7A shows electrochemical characterization of batteries incorporating some embodiments of the present invention, where first cycle performance was measured for a disordered rock salt composition with fluorine doping at the oxygen sites. Figure 7B shows the corresponding discharge capacity as a function of cycle number for the embodiment of the present invention of Figure 2A. Figure 7A shows that fluorine doping at the oxygen sites improves first cycle performance, and Figure 7B shows the improved performance of fluorine doping at the oxygen sites even at higher cycles.

[0079] The embodiments disclosed herein enable, and in some cases have demonstrated, improved capacity, energy density, voltage decay, rate capability, and capacity retention. The compositions disclosed herein exhibit superior performance compared to the base disordered rock salt composition.

[0080] While the present invention has been described with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various modifications and equivalent substitutions can be made without departing from the spirit and scope of the invention, as defined by the appended claims. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, method, or process to the objective, spirit, and scope of the present invention. All such modifications are intended to be within the scope of the appended claims. In particular, although methods disclosed herein have been described with reference to specific acts performed in a particular order, these acts may be combined, sub-divided, or reordered to form equivalent methods without departing from the teachings of the invention. Accordingly, unless specifically indicated herein, the order and grouping of acts is not a limitation of the invention. Some of the embodiments of the invention related to the present invention are shown below. [Aspect 1] 1. A composition for forming an electrode, characterized by a disordered rock salt crystal structure and having the chemical formula (i): [ka] (In the formula, 1.2 <x≦1.75、0≦y<0.55、0.1<z<1、0≦a<0.5、0≦b<1、0≦c<0.8であり、m、n及びpは、それぞれ独立して、ti、ta、v、cr、mn、fe、co、ni、cu、zn、al、zr、y、mo、ru、rh及びsbのうちの1種又は2種以上である。)A composition comprising an active material represented by: [Aspect 2] The composition of embodiment 1, wherein x≧1.25. [Aspect 3] The composition of embodiment 1, wherein x≧1.35. [Aspect 4] The composition of embodiment 1, wherein x≧1.45. [Aspect 5] The composition of embodiment 1, wherein x≧1.55. [Aspect 6] The composition of embodiment 1, wherein x≧1.65. [Aspect 7] The composition of embodiment 1, wherein x=1.75. [Aspect 8] 2. The composition of embodiment 1, wherein a=0, b=0, and 1≦z / y≦18. [Aspect 9] The composition of embodiment 8, wherein z / y=2. [Aspect 10] The composition of embodiment 8, wherein z / y=4. [Aspect 11] The composition of embodiment 8, wherein z / y=14. [Aspect 12] The composition of embodiment 8, wherein z / y=16.6. [Aspect 13] The composition of embodiment 1, wherein only one of a or b is equal to zero. [Aspect 14] y=0.5, a=0, z=0.8, 0 <b<0.8であり、mがマンガンであり、pがfe、cr、al及びsbから選択される、態様13に記載の組成物。[Aspect 15] y=0.2, 0 <a<0.2、z=0.57、b=0であり、nがv、mo、sb、ta、ti、zr及びyから選択される、態様13に記載の組成物。[Aspect 16] 2. The composition of embodiment 1, wherein ya=0. [Aspect 17] 0

Claims

1. 1. A battery including an electrode comprising an active material, The active material is Li ｘ Nb ｙ M ｚ O ２ wherein 1.2<x≦1.65, y is 0<y<0.55, z is 0.1<z<1, M is an element that charge compensates for lithium gain, and M is composed of Mn and at least one other element, wherein the at least one other element is one or more of W and Ti.

2. 2. The battery of claim 1, wherein 1≦z / y≦18.

3. 3. The battery of claim 2, wherein 2≦z / y≦18.

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