Lithium-rich aluminum iron sulfide lithium ion battery cathode

Abstract

Provided herein are compositions, devices, electrochemical systems, and methods related to lithium-rich iron sulfide lithium ion battery cathodes. In some embodiments, the composition is characterized by the formula FX1: Liw-[delta] AlxFezS2. In some embodiments, w may be greater than or equal to 2 and less than or equal to 2.5. In some embodiments, x may be greater than 0 and less than or equal to 0.5. In some embodiments, z may be greater than 0 and less than or equal to 1. In some embodiments, delta may be greater than or equal to 0 and less than w. In some embodiments, the composition may have a net charge of 0.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 408,025, filed on September 19, 2022, which is incorporated herein by reference in its entirety.

[0003] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0004] This invention was made with Government support under Grant No. DE-SC0019281 awarded by the Department of Energy. The Government has certain rights in this invention. Background Art

[0005] The theoretical energy density limit of current lithium-ion battery cathode materials is determined by the single-electron intercalation transition metal redox mechanism. Recently, the scarcity of battery-grade cobalt and nickel has prompted a surge in LiFePO4, which is seen as a more scalable material due to the relative abundance and low cost of Fe and PO4. However, the energy density of LiFePO4 is significantly lower than that of NMC 811. The single-electron redox itself imposes a theoretical limit on energy density. Therefore, new cathode materials that both use abundant elements and go beyond the single-electron redox paradigm must be developed to meet global energy storage needs. Summary of the invention

[0006] Compositions, materials, devices, device components, systems and methods are provided herein, for example, relating to electrochemical systems and components thereof, such as lithium ion batteries and lithium-rich iron sulfide lithium ion battery cathodes. For example, in aspects of the present invention, a composition characterized by formula FX1 is provided: Li w-δ Al x Fe z S2. In certain aspects, compositions characterized by formula FX1 are provided, wherein w is greater than or equal to 2 and less than or equal to 2.5; x is greater than 0 and less than or equal to 0.5; z is greater than 0 and less than or equal to 1; and δ is greater than or equal to 0 and less than w; optionally, wherein the net charge of the composition is 0, optionally, wherein the composition has an average net charge of 0, optionally, wherein the composition is charge balanced, and optionally, wherein the composition has a bulk phase characterized by an average charge of 0 and / or a charge balanced bulk phase. In some aspects, the compositions of the present invention do not include Li w-δ Al x Fe z S2, wherein x is equal to 0 and / or wherein z is equal to 0.

[0007] In some aspects, provided herein are devices, device components or systems comprising compositions disclosed herein (e.g., electrode compositions). In some aspects, provided herein are electrochemical systems (e.g., batteries or flow batteries) having electrodes comprising compositions disclosed herein. In some aspects, provided herein are cathodes of electrochemical systems (e.g., lithium ion batteries), wherein the cathodes comprise compositions disclosed herein.

[0008] In some aspects, provided herein is a method for preparing a composition, comprising: (i) providing a first amount of Li2FeS2 and a second amount of Li 2.5 Al 0.5 S2; (ii) a first amount of Li2FeS2 and a second amount of Li 2.5 Al 0.5 S2 combination, thereby forming a combination; and (iii) heating the combination to form a composition having a lithium aluminum iron sulfide composition; wherein the lithium aluminum iron sulfide composition is characterized by the formula FX1: Li w-δ Al x Fe z S2; wherein w is greater than or equal to 2 and less than or equal to 2.5; x is greater than 0 and less than or equal to 0.5; z is greater than 0 and less than or equal to 1, and wherein δ is greater than or equal to 0 and less than w; optionally, wherein the lithium aluminum iron sulfide composition has a net charge of 0, optionally, wherein the average net charge of the composition is 0, optionally, wherein the composition is charge balanced, and optionally, wherein the composition has a bulk phase characterized by an average charge of 0 and / or a charge balanced bulk phase.

[0009] In some aspects, provided herein are methods of preparing a composition, comprising: (i) providing a first amount of Li2S, a second amount of FeS, and a third amount of Al2S3; (ii) combining the first amount of Li2S, the second amount of FeS, and the third amount of Al2S to form a combination; and (iii) heating the combination to form a composition having a lithium aluminum iron sulfide composition; wherein the lithium aluminum iron sulfide composition is characterized by the formula FX1: Li w-δ Al x Fe z S2; wherein w is greater than or equal to 2 and less than or equal to 2.5; x is greater than 0 and less than or equal to 0.5; z is greater than 0 and less than or equal to 1; and δ is greater than or equal to 0 and less than w; optionally, wherein the composition has an average net charge of 0, optionally, wherein the composition is charge balanced, and optionally, wherein the composition has a bulk phase characterized by an average charge of 0 and / or a charge balanced bulk phase.

[0010] In some aspects, provided herein is a compound characterized by the formula FX7: Li 2-δ FeS u Sev a composition; wherein u is greater than 0 and less than 2; v is greater than 0 and less than 2; and δ is greater than or equal to 0 and less than 2; optionally, wherein the average net charge of the composition is 0, optionally, wherein the composition is charge balanced, and optionally, wherein the composition has a bulk phase characterized by an average charge of 0 and / or a charge balanced bulk phase.

[0011] In some aspects, the present invention provides a method characterized by FX9: Li 2-ε Al x Fe r QqS2 composition; wherein x is greater than or equal to 0 and less than or equal to 0.67; r is greater than or equal to 0 and less than or equal to 1; q is greater than or equal to 0 and less than or equal to 0.33; ε is greater than or equal to 0 and less than or equal to 2; wherein the external cation vacancy is represented by Q in the chemical formula; optionally, wherein the average net charge of the composition is 0, optionally, wherein the composition is charge balanced, and optionally, wherein the composition has a bulk phase characterized by an average charge of 0 and / or a charge balanced bulk phase.

[0012] Without wishing to be bound by any particular theory, beliefs or understandings of the underlying principles associated with the devices and methods disclosed herein may be discussed herein. It is recognized that regardless of the ultimate correctness of any mechanistic explanation or hypothesis, embodiments of the invention may still operate and be used.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figures 1A-1D :( Figure 1A )The crystal structure of Li2FeS2 projected along the a-axis, ( Figure 1B )The crystal structure of Li2FeS2 projected along the c-axis, and ( Figure 1C )The crystal structure of Li5AlS4 projected along the b axis, ( Figure 1D ) Crystal structure projected along the c-axis.

[0015] Figures 2A-2D :( Figure 2A )y=0、( Figure 2B )y=0.2 and ( Figure 2C )y=0.4 powder X-ray diffraction pattern, and ( Figure 2D ) The trend of the unit cell volume as a function of y. The Rietveld refinement and the resulting difference trajectory are shown for each material. The tick marks identify the positions of the Bragg reflections of the phases included in the fit (excluding the Li2S impurity). Panel Figure 2D The linear fit in shows that the unit cell volume is a linear function of y, where R 2= 0.966; the error bars are the standard deviation of the unit cell volume from at least two separate refinements of the diffraction patterns of separate syntheses of the same material, ie the standard deviation between two replicates.

[0016] Figures 3A-3C : Based on 1 e - / chemical formula unit, at C / 10 ( Figure 3A )y=0、( Figure 3B )y=0.2 and ( Figure 3C ) Constant current cycle with y=0.4.

[0017] Figure 4 : Comparison of long term cycling performance at C / 10 for y=0 and y=0.2 based on 1 electron / formula unit. The performance is comparable.

[0018] Figure 5A-5B : Representative C / 10 trace ( Figure 5A )y=0 and ( Figure 5B ) Comparison of the constant current intermittent titration (GITT) of the first cycle with y=0.2. The GITT was obtained based on 1 electron / formula unit at C / 10 for 20 minutes separated by 4 hours dwell time at OCV. The GITT is comparable, i.e. the overpotentials for Fe and S redox are similar at y=0 and y=0.2.

[0019] Fig. 6A : y=0 galvanostatic cycle with extracted Fe K-edge sites overlapped, ( Figure 6B ) XANES spectra of y = 0 at various SOCs.

[0020] Fig. 7A : y = 0.2 galvanostatic cycles with extracted Fe K-edge sites overlapped, ( Figure 7B ) XANES spectra at y = 0.2 at various SOCs.

[0021] Figure 8 : S K-edge XANES spectra at y = 0 and 0.2 at different SOCs.

[0022] Figures 9A-9D : When y = 0.2, ( Fig.9A ) Original to medium slope, ( Fig. 9B ) mid-slope to transition, ( Fig. 9C ) transition to the middle platform, ( Fig.9D ) as the hypothesized redox mechanism from plateau to charging SOC.

[0023] Fig.10 : Fe as a ratio of their respective total theoretical capacities 2+ / 3+ Redox and 2S 2- / (S2)2- Redox amount. Errors are the standard deviation of three replicates.

[0024] Fig.11 : PXRD of y values ​​between 0 and 0.5 with an increment of 0.05.

[0025] Fig.12 : Comparison of galvanostatic cycling curves for cycle 1 and cycle 2 at y values ​​between 0 and 0.4 with increments of 0.1 (y = 0.5 indicates electrochemical inactivity).

[0026] Fig.13 : Schematic diagram showing how conventional intercalation materials undergo single-electron reduction upon lithiation.

[0027] Fig.14 : Schematic diagram showing the effect and reversibility of reduction and lithiation of TiS2.

[0028] Fig.15 : Schematic diagram showing a multi-electron cathode that employs a mechanism that goes beyond conventional intercalation.

[0029] Fig.16 : Schematic diagram comparing the voltages at which redox occurs at oxide and sulfide cathodes.

[0030] Fig.17 : Diagram showing the relative abundance of Fe, Co and Ni and the geographical distribution of said elements.

[0031] Fig.18 : Graph comparing the redox cycling reproducibility of Li2FeS2 and Li2RuO3.

[0032] Fig.19 : Graph of the absorbance of Li2FeS at different energies obtained using X-ray absorption spectroscopy.

[0033] Fig. 20 : A graph showing the variation of voltage with the number of moles of electrons per chemical formula unit.

[0034] Fig.21 : Diagrams obtained using extended X-ray absorption fine structure (EXAFS) showing the variation of radius, voltage and normalized absorption at different energies.

[0035] Fig. 22 : Schematic diagram showing the changes in the structure of Li2FeS2 as it is reduced.

[0036] Figures 23A-23B :shows that with the Li 2-x FeS 2-y Se y Schematic diagram of the change in charge voltage due to S oxidation with increasing Se substitution.

[0037] Figures 24A-24B : Schematic diagram showing how constant current intermittent titration (GITT) can be used to approach the equilibrium potential and how the potential varies with changes in Se content.

[0038] Fig.25 : Diagram illustrating how substitution of S with Se results in greater Fe-anion covalency, resulting in concomitant cation and anion oxidation throughout the charging process.

[0039] Fig.26 : Schematic diagram showing how replacing Fe with Al (charge balanced by Li) increases the average voltage of the charging curve by shifting the charge compensation to the anions.

[0040] Fig. 27 :It shows that as the material is electrochemically oxidized, Fe 2+ How to over-oxidize the diagram.

[0041] Figures 28A-28B : Shown with Li2TiS3(Li(Li 0.33 Ti 0.67 )S2) compared to the charging curve of LiTiS2.

[0042] Fig.29 :Shown that with LiTi 8 / 9 S2 is reduced, preferentially forming a SS bond adjacent to the vacancy.

[0043] Figures 30A-30B : It shows that the lack of Li in the formation reaction + Graph showing the change in the oxidation state of Ti.

[0044] Fig.31 : shows how replacing Li with Ti allows the introduction of vacancies while maintaining Ti in the Ti 4+ Schematic diagram of the formal oxidation states of .

[0045] Fig.32 : Diagram of whether a material contains the expected vacancy content determined by electrochemical techniques.

[0046] Fig.33 : Show Li(Li 0.33-1.33z Ti 0.67+0.33z □ z ) Diagram of how the increase in the number of vacancies in S2 affects the redox changes of the cations.

[0047] Fig.34 : Schematic diagram showing the change of anion redox as the average redox contribution / S atom increases.

[0048] Fig.35 : A figure obtained using extended X-ray absorption fine structure (EXAFS), showing that although the 2S in Li 2.2 Al 0.2 Fe 0.6 S2 has a stronger redox, the local structural change of Li 2- / (S2) 2- Al 2.2 Al 0.2 Fe 0.6 S2 is smaller than that in Li2FeS2.

[0049] Fig.36 : A figure showing the annealing of Li 2.2 Al 0.2 Fe 0.6 S2, which supports the hypothesis of electron transfer.

[0050] Fig.37 : A flowchart showing a method for preparing a composition.

[0051] Fig.38 : A flowchart showing another method for preparing a composition.

[0052] Figures 39A-39B : EIS measurement values for the original ( Fig.39A ) y = 0 and ( Fig.39B ) y = 0.2. The size of the pellets is listed in the corresponding text.

[0053] Figures 40A-40B : DC polarization measurement and linear fitting for y = 0 and y = 0.2.

[0054] Fig.41 : Schematic diagram of the heterovalent substitution of 2Al x Fe 1-1.5x Q 0.5x S2 by 3Fe 2+ and 1 vacancy, where 0 < x < 2 / 3 and Q represents a vacancy. 3+

[0055] Fig.42 : Crystal structure comparison of three materials: Li2FeS2, Li5AlS4, and Li3AlS3.

[0056] Figures 43A-43E : A figure showing the diffraction pattern, which is the Rietveld refinement for ( Fig.43A ) x = 0.2, ( Fig.43B ) x = 0.33, ( Fig.43C ) x = 0.53, ( Fig.43D ) x = 0.6, and ( Fig.43E ) x = 0.67.

[0057] Fig.44 : Li2Al synthesized at values ​​of x = 0, 0.2, 0.33, 0.53 and 0.6 x Fe 1-1.5x Q 0.5x Lattice parameter trends of S2 materials, refined to the P3ml space group.

[0058] Fig.45 :Li2Al x Fe 1-1.5x Q 0.5x Galvanostatic cycling data of S2 at different x values.

[0059] Statement on Compounds and Terminology

[0060] In general, the terms and phrases used herein have their art-recognized meanings, which can be found by reference to standard texts, journal literature and context known to those skilled in the art. The following definitions are provided to clarify their specific use in the context of the present invention.

[0061] The term "solid solution" refers to a homogeneous mixture of at least two crystalline materials in a solid state, such that the mixture can be described by (or optionally approximately) a single crystal structure, rather than a phase-separated mixture of the crystal structures of the individual components. In such a solid solution, the solid solution can be described by (or optionally approximately) a single empirical molecular formula. Within the composition range encompassed by the term "solid solution", the parameters describing the crystal structure (e.g., lattice parameters, unit cell volume, etc.) may be substantially linear trends between the end members of the solid solution (i.e., the parameters should follow Vegard's law). In some examples, the single crystal structure can be characterized by a trigonal or monoclinic space group. In some examples, the single crystal structure can be characterized by a P21 / m monoclinic space group.

[0062] The term "extrinsic vacancies" refers to vacancies in a crystal lattice that are reflected in the nominal formula of the lattice. Extrinsic vacancies may be intentionally introduced into the crystal lattice, for example by targeted chemical substitution. The number of extrinsic vacancies in a given crystal lattice may be independent of temperature.

[0063] The term "intrinsic vacancies" refers to vacancies in the crystal lattice that are not reflected in the nominal formula of the lattice. Types of intrinsic vacancies include those due to Frenkel defects and Schottky defects. Intrinsic vacancies exist naturally in all crystalline materials. The number of intrinsic vacancies in a given crystal lattice varies with temperature. This temperature dependence can be modeled by the following equation: Where N v is the vacancy concentration, Q v is the energy required for vacancy formation, k B is the Boltzmann constant, T is the absolute temperature, and N is the atomic site concentration.

[0064] The terms "cation vacancy concentration" and "anion vacancy concentration" refer to the concentration of extrinsic and intrinsic vacancies in the crystal lattice that can accept cations or anions, respectively. The vacancy concentration may vary with temperature. It is usually expressed as the ratio of vacant lattice sites to lattice sites containing atoms.

[0065] Similarly, the terms "intrinsic cation vacancy concentration" and "extrinsic anion vacancy concentration" refer to the concentration of extrinsic vacancies in the crystal lattice that can accept cations or anions, respectively.

[0066] An "electrochemical cell" is a device that generates electrical energy through a chemical reaction. Some examples include voltaic cells, galvanic cells, electrolytic cells, and fuel cells. Electrochemical cells include primary and secondary batteries, such as lithium batteries and lithium-ion batteries.

[0067] The term "rechargeable" refers to the ability of an electrochemical cell or battery to be charged, discharged to a load, and then recharged multiple times. Such electrochemical cells and batteries can be recharged due to the reversibility of the chemical reactions occurring within them.

[0068] The term "lithium battery" or "lithium-ion battery" includes batteries or electrochemical cells that use lithium ions (for example) as charge carriers to offset the charge deficit created by electrons moving from the cathode to the anode during discharge. Alternatively or in addition, a lithium battery or lithium-ion battery may use lithium ions to offset the charge deficit created by electrons moving from the anode to the cathode during charging.

[0069] In one embodiment, the compositions or compounds (e.g., alloys or alloy precursors) of the invention are isolated or substantially purified. In one embodiment, the isolated or purified compounds are at least partially isolated or substantially purified, as understood in the art. In one embodiment, the chemical purity of the substantially purified compositions, compounds, or formulations of the invention is 95%, optionally 99% for some applications, optionally 99.9% for some applications, optionally 99.99% for some applications, and optionally 99.999% for some applications. DETAILED DESCRIPTION

[0070] In the following description, in order to thoroughly explain the precise nature of the present invention, numerous specific details of the device, device components and methods of the present invention are set forth. However, it is obvious to those skilled in the art that the present invention can be implemented without these specific details.

[0071] Certain exemplary aspects and embodiments:

[0072] Various aspects are contemplated and disclosed herein, several of which are listed in the following paragraphs. It is expressly contemplated and disclosed that any aspect or portion thereof may be combined to form an aspect. In addition, it is expressly contemplated and disclosed that any reference to aspect 1 includes reference to aspects 1a, 1b, 1c, 1d...1n and / or 1o and any combination thereof (i.e., any reference to an aspect includes a reference to a letter version of that aspect). In addition, the terms "any previous aspect" and "any of the aforementioned aspects" represent any aspect that appears before the aspect containing such phrases (e.g., the sentence "Aspect 15: materials, devices, electrolytes or methods of any of the aforementioned aspects..." represents any aspect before citing aspect 15, including letter versions). For example, it is contemplated and disclosed that, optionally, any composition, method or formulation of any of the following aspects may be used or combined with any other aspect provided below. In addition, for example, it is contemplated and disclosed that any of the above embodiments or aspects are optionally combined with any of the following aspects or any portion thereof.

[0073] Aspect 1a: A composition characterized by formula FX1:

[0074] Li w-δ Al x Fe z S2(FX1);

[0075] Where w is greater than or equal to 2 and less than or equal to 2.5;

[0076] Where x is greater than 0 and less than or equal to 0.5;

[0077] where z is greater than 0 and less than or equal to 1; and

[0078] Where δ is greater than or equal to 0 and less than w.

[0079] Aspect 1b: A composition characterized by formula FX1:

[0080] Li w-δ Al x Fe z S2(FX1);

[0081] Where w is greater than or equal to 2 and less than or equal to 2.5;

[0082] Where x is greater than 0 and less than or equal to 0.5;

[0083] Where z is greater than or equal to 0 and less than or equal to 1;

[0084] where δ is greater than or equal to 0 and less than w; and

[0085] wherein the composition has an average net charge of zero, optionally wherein the composition is charge balanced, and optionally wherein the composition has a bulk phase characterized by an average charge of zero and / or a charge balanced bulk phase.

[0086] Aspect 1c: A composition characterized by formula FX1:

[0087] Li w-δ Al x Fe z S2(FX1);

[0088] Where w is greater than or equal to 2 and less than or equal to 2.5;

[0089] Where x is greater than 0 and less than or equal to 0.5;

[0090] Where z is greater than or equal to 0 and less than or equal to 1;

[0091] where δ is greater than or equal to 0 and less than w; and

[0092] wherein the composition is charge balanced.

[0093] Aspect 1d: The composition or method of any of Aspects 1a-1c or 39-54, wherein:

[0094] The composition is characterized by the formula FX2:

[0095] Li 2+y-δ Al y Fe 1-2y S2(FX2);

[0096] Where y is greater than 0 and less than 0.5;

[0097] Wherein δ is greater than or equal to 0 and less than 2+y.

[0098] Aspect 1e: The composition or method of any of Aspects 1a-1d or 39-54, wherein:

[0099] The composition is characterized by the formula FX3:

[0100] Li 2+y Al y Fe 1-2y S2(FX3);

[0101] Where y is greater than 0 and less than 0.5.

[0102] Aspect 1f: A composition characterized by formula FX7:

[0103] Li 2-δ FeS u Sev (FX7)

[0104] Where u is greater than 0 and less than 2;

[0105] where v is greater than 0 and less than 2; and

[0106] Where δ is greater than or equal to 0 and less than 2.

[0107] Aspect 1g: The composition or method according to any one of Aspects 1f or 39-54, characterized in that:

[0108] The composition is characterized by the formula FX8:

[0109] Li 2-δ FeS 2-k Se(FX8);

[0110] where k is greater than 0 and less than 2; and

[0111] Where δ is greater than or equal to 0 and less than 2.

[0112] Aspect 1h: A composition characterized by formula FX9:

[0113] Li 2-ε Al x Fe r Q q S2(FX9); where:

[0114] x is greater than or equal to 0 and less than or equal to 0.67;

[0115] r is greater than or equal to 0 and less than or equal to 1;

[0116] q is greater than or equal to 0 and less than or equal to 0.33;

[0117] ε is greater than or equal to 0 and less than or equal to 2;

[0118] The composition comprises an extrinsic cation vacancy, wherein the extrinsic cation vacancy is represented in the chemical formula as Q; and

[0119] The net charge of the composition is zero.

[0120] Aspect 1i: The composition or method of any one of Aspects 1h or 39-54, wherein:

[0121] The composition is characterized by the formula FX10:

[0122] Li 2-ε Al x Fe 1-1.5x Q 0.5x S2(FX10); where:

[0123] x is greater than or equal to 0 and less than or equal to 0.67;

[0124] ε is greater than or equal to 0 and less than or equal to 2; and

[0125] The composition comprises an extrinsic cation vacancy, wherein the extrinsic cation vacancy is represented as Q in the chemical formula.

[0126] Aspect 1j: A device comprising the composition of any of the preceding aspects.

[0127] Aspect 1k: An electrochemical system comprising a cathode comprising the composition of any of the preceding aspects.

[0128] Aspect 11: A cathode of an electrochemical system, the cathode comprising the composition of any of the preceding aspects.

[0129] Aspect 1m: A method of preparing the composition of any of the preceding aspects.

[0130] Aspect 1n: The method according to aspect 1m, the method comprising:

[0131] Provide a first amount of Li2FeS2 and a second amount of Li 2.5 Al 0.5 S2; (operation 3710)

[0132] The first amount of Li2FeS and the second amount of Li 2.5 Al 0.5 S2 performs combination, thereby forming a combination; (operation 3720), and

[0133] heating a combination having a lithium aluminum iron sulfide composition; (operation 3730)

[0134] Wherein, the lithium aluminum iron sulfide composition is characterized by formula FX1:

[0135] Li w-δ Al x Fe z S2(FX1);

[0136] Where w is greater than or equal to 2 and less than or equal to 2.5;

[0137] Where x is greater than 0 and less than or equal to 0.5;

[0138] Where z is greater than 0 and less than or equal to 1;

[0139] where δ is greater than or equal to 0 and less than w; and

[0140] wherein the composition has an average net charge of zero, optionally wherein the composition is charge balanced, and optionally wherein the composition has a bulk phase characterized by an average charge of zero and / or a charge balanced bulk phase.

[0141] Aspect 1o: The method of aspect 1m or 1n, the method comprising:

[0142] Providing a first amount of Li2S, a second amount of FeS, and a third amount of Al2S3; (operation 3810)

[0143] combining a first amount of Li2S, a second amount of FeS, and a third amount of Al2S3 to form a combination; (operation 3820), and

[0144] heating the combination to form a composition having a composition of lithium aluminum iron sulfide; (operation 3830)

[0145] Among them, the lithium aluminum iron sulfide composition is characterized by formula FX1:

[0146] Li w-δ Al x Fe z S2(FX1);

[0147] Where w is greater than or equal to 2 and less than or equal to 2.5;

[0148] Where x is greater than 0 and less than or equal to 0.5;

[0149] Where z is greater than 0 and less than or equal to 1;

[0150] where δ is greater than or equal to 0 and less than w; and

[0151] wherein the composition has an average net charge of zero, optionally wherein the composition is charge balanced, and optionally wherein the composition has a bulk phase characterized by an average charge of zero and / or a charge balanced bulk phase.

[0152] Aspect 2a: The composition or method of any of Aspects 1b-1c or 39-54, wherein y is selected from the range of 0.1 to 0.3.

[0153] Aspect 2b: The composition or method of any of Aspects 1b-1c or 2a or 39-54, wherein y is selected from the range of 0.15 to 0.25.

[0154] Aspect 2c: The composition or method of any of Aspects 1b-1c or 2a-2b or 39-54, wherein y is equal to 0.2.

[0155] Aspect 2d: The composition or method of any of Aspects 1b-1c or 2a-2c or 39-54, wherein y is optionally less than 0.5, less than 0.45, less than 0.4, less than 0.35, less than 0.3, less than 0.25, less than 0.2, less than 0.15, less than 0.1 or less than 0.05.

[0156] Aspect 2e: The composition or method of any of Aspects 1b-1c or 2a-2c or 39-54, wherein y is optionally greater than 0, greater than 0.05, greater than 0.1, greater than 0.15, greater than 0.2, greater than 0.25, greater than 0.3, greater than 0.35, greater than 0.4, or greater than 0.45.

[0157] Aspect 2f: The composition or method of any of Aspects 1b-1c or 2a-2c or 39-54, wherein y is optionally selected from a range of 0 to 0.5, a range of 0.05 to 0.5, a range of 0.1 to 0.5, a range of 0.15 to 0.5, a range of 0.2 to 0.5, a range of 0.25 to 0.5, a range of 0.3 to 0.5, a range of 0.35 to 0.5, a range of 0.4 to 0.5, a range of 0.45 to 0.5, a range of 0 to 0.45 , a range of 0 to 0.4, a range of 0 to 0.35, a range of 0 to 0.3, a range of 0 to 0.25, a range of 0 to 0.2, a range of 0 to 0.15, a range of 0 to 0.1, a range of 0 to 0.05, a range of 0.05 to 0.45, a range of 0.1 to 0.4, a range of 0.15 to 0.35, a range of 0.2 to 0.3, a range of 0.05 to 0.35, a range of 0.1 to 0.3, or a range of 0.15 to 0.25.

[0158] Aspect 3: The composition or method of any of the preceding aspects or aspects 39-54, wherein the composition is prepared by reacting a first precursor comprising Li2FeS2 with a first precursor comprising Li 2.5 Al 0.5 S2 is formed by contacting and / or annealing a second precursor.

[0159] Aspect 4: The composition or method of any of the preceding aspects or aspects 39-54, wherein the composition is formed by contacting and / or annealing a first precursor comprising Li2S with a second precursor comprising FeS and a third precursor comprising Al2S3.

[0160] Aspect 5: The composition of any of the preceding aspects, characterized by being a solid solution.

[0161] Aspect 6: The composition of Aspect 5, wherein the solid solution follows Feigard's law with respect to the variation of the lattice constant with the relative concentration of Al or Fe.

[0162] Aspect 7: The composition or method of any one of the preceding aspects or aspects 39-54, wherein the composition comprises only intrinsic vacancies and no extrinsic vacancies.

[0163] Aspect 8: The composition or method of any of the preceding aspects or aspects 39-54, wherein the composition comprises both intrinsic vacancies and extrinsic vacancies.

[0164] Aspect 9: The composition or method of any of the preceding aspects or aspects 39-54, wherein the composition and crystal structure of the composition corresponds to the composition and crystal structure of Li2FeS2 modified by replacing about 2n Fe ions in the crystal structure with n Al ions and n Li ions, wherein n is an integer greater than 0, and wherein the composition is characterized by the formula FX3:

[0165] Li 2+y Al y Fe 1-2y S2(FX3);

[0166] Where y is greater than 0 and less than 0.5.

[0167] Aspect 10a: The composition or method of any of the preceding aspects or aspects 39-54, wherein the composition is characterized by the formula FX4:

[0168] Li 2-ε Al 2y Fe 1-3y Q y S2(FX4); where:

[0169] y is greater than or equal to 0 and less than or equal to 0.33;

[0170] ε is greater than or equal to 0 and less than or equal to 2; and

[0171] The composition comprises an extrinsic cation vacancy, wherein the extrinsic cation vacancy is represented as Q in the chemical formula.

[0172] Aspect 10b: The composition or method of any of the preceding aspects or aspects 39-54, wherein the composition is characterized by formula FX10:

[0173] Li 2-ε Al x Fe 1-1.5x Q 0.5x S2(FX10); where:

[0174] x is greater than or equal to 0 and less than or equal to 0.67;

[0175] ε is greater than or equal to 0 and less than or equal to 2; and

[0176] The composition comprises an extrinsic cation vacancy, wherein the extrinsic cation vacancy is represented as Q in the chemical formula.

[0177] Aspect 11a: The composition or method of any of the preceding aspects or aspects 39-54, wherein the composition and crystal structure of the composition corresponds to that obtained by using 2n Al 3+ Ions replace about 3n Fe in the crystal structure 2+ ions and modified Li2FeS2; wherein n is an integer greater than 0.

[0178] Aspect 11b: The composition or method of any of the preceding aspects or aspects 39-54, wherein the composition and crystal structure of the composition correspond to the composition and crystal structure of Li2FeS modified by replacing about 3n Fe ions in the crystal structure with 2n Al ions; wherein n is an integer greater than 0.

[0179] Aspect 12a: The composition or method of any of the preceding aspects or aspects 39-54, wherein the lattice constant or lattice volume of the composition has a linear correlation with x in FX1, the linear regression or R-squared value of which is greater than 0.91.

[0180] Aspect 12b: The composition or method of Aspect 12a, wherein the linear regression or R-squared value of the linear correlation is optionally greater than 0.92, greater than 0.93, greater than 0.94, greater than 0.95, greater than 0.96, greater than 0.97, greater than 0.98, greater than 0.99, greater than 0.995, greater than 0.999 or greater than 0.9995.

[0181] Aspect 12c: The composition or method of any of the preceding aspects or aspects 39-54, wherein the lattice constant or lattice volume of the composition has a linear correlation with x in FX1 when measured on a laboratory-based diffractometer, the linear regression or R-squared value of the linear correlation being greater than 0.91.

[0182] Aspect 12d: The composition or method of Aspect 12c, wherein the linear regression or R-squared value of the linear correlation is optionally greater than 0.92, greater than 0.93, greater than 0.94, greater than 0.95, greater than 0.96, greater than 0.97, greater than 0.98, greater than 0.99, greater than 0.995, greater than 0.999 or greater than 0.9995 when measured on a laboratory-based diffractometer.

[0183] Aspect 13a: The composition or method of any of the preceding aspects or aspects 39-54, wherein the lattice constant or lattice volume of the composition has a linear correlation with y in FX3, the linear regression or R-squared value of which is 0.91; wherein the composition is characterized by the formula FX3:

[0184] Li 2+y Al y Fe 1-2y S2(FX3);

[0185] Where y is greater than 0 and less than 0.5.

[0186] Aspect 13b: The composition or method of Aspect 13a, wherein the linear regression or R-squared value of the linear correlation is optionally greater than 0.92, greater than 0.93, greater than 0.94, greater than 0.95, greater than 0.96, greater than 0.97, greater than 0.98, greater than 0.99, greater than 0.995, greater than 0.999 or greater than 0.9995.

[0187] Aspect 13c: The composition or method of any of the preceding aspects or aspects 39-54, wherein the lattice constant or lattice volume of the composition has a linear correlation with y in FX2, and the linear correlation linear regression or R square value is greater than 0.91; wherein the composition is characterized by formula FX2:

[0188] Li 2+y-δ Al y Fe 1-2y S2(FX2);

[0189] Where y is greater than 0 and less than 0.5;

[0190] Wherein δ is greater than or equal to 0 and less than 2+y.

[0191] Aspect 13d: The composition or method of Aspect 13b, wherein the linear regression or R-squared value of the linear correlation is optionally greater than 0.92, greater than 0.93, greater than 0.94, greater than 0.95, greater than 0.96, greater than 0.97, greater than 0.98, greater than 0.99, greater than 0.995, greater than 0.999 or greater than 0.9995.

[0192] Aspect 14: The composition or method of any of the preceding aspects or aspects 39-54, wherein: the composition is characterized by an atomic unit cell of formula FX1, FX2, FX3 or FX4.

[0193] Aspect 15a: The composition or method of any of the preceding aspects or aspects 39-54, wherein:

[0194] The lattice parameters of the composition are a, b, c and β;

[0195] The lattice parameter a is selected from to scope;

[0196] The lattice parameter b is selected from to scope;

[0197] The lattice parameter c is selected from to the scope of

[0198] The lattice parameter β is selected from the range of 89.98° to 90.34°.

[0199] Aspect 15b: The composition or method of any of the preceding aspects or aspects 39-54, wherein:

[0200] The lattice parameters of the composition are a, b, c and β;

[0201] The lattice parameter a is selected from to scope;

[0202] The lattice parameter b is selected from to scope;

[0203] The lattice parameter c is selected from to the scope of

[0204] The lattice parameter β is selected from the range of 90° to 90.333°.

[0205] Aspect 15c: The composition or method of any one of the preceding aspects or aspects 39-54 (excluding aspect 15b), wherein:

[0206] The lattice parameters of the composition are a, b, c and β;

[0207] The lattice parameter a is selected from to scope;

[0208] The lattice parameter b is selected from to scope;

[0209] The lattice parameter c is selected from to the scope of

[0210] The lattice parameter β is selected from the range of 89.986° to 90.248°.

[0211] Aspect 16: The composition of any of the preceding aspects, having a crystal structure characterized by a trigonal or monoclinic space group.

[0212] Aspect 17: The composition of any of the preceding aspects, having a crystal structure characterized by a P21 / m monoclinic space group.

[0213] Aspect 18a: The composition or method of any of the preceding aspects or aspects 39-54, wherein the composition has a gravimetric energy density of greater than or equal to 900 Wh / kg.

[0214] Aspect 18b: The composition or method of any of the preceding aspects or aspects 39-54, wherein the composition has a gravimetric energy density greater than or equal to 1000 Wh / kg.

[0215] Aspect 18c: The composition or method of any of the preceding aspects or aspects 39-54, wherein the composition has a gravimetric energy density greater than or equal to 1100 Wh / kg.

[0216] Aspect 18d: The composition or method of any of the preceding aspects or aspects 39-54, wherein the volumetric energy density of the composition is greater than or equal to 2500 Wh / L.

[0217] Aspect 19: The composition of any of the preceding aspects, which is capable of undergoing one or more multi-electron redox reactions and one or more anion redox reactions.

[0218] Aspect 20a: The composition or method of any one of the preceding aspects or aspects 39-54, wherein the conductivity of the composition is selected from 1.25×10 -2 S cm -1 to 1.75×10 -2 S cm -1 range.

[0219] Aspect 21: The composition or method of any one of the preceding aspects or aspects 39-54, wherein the conductivity of the composition is selected from 1.00×10 -2 S cm -1 to 2.00×10 -2 S cm -1 , 1.10×10 -2 S cm -1 to 1.90×10 -2 S cm -1 , 1.20×10 -2 S cm -1 to 1.80×10 -2 S cm -1 , 1.30×10 -2 S cm -1 to 1.70×10 -2 S cm -1 , 1.40×10 -2 S cm -1 to 1.60×10 -2 S cm -1 , 1.50×10-2 S cm -1 to 1.60×10 -2 S cm -1 , 1.53×10 -2 S cm -1 to 1.62×10 -2 S cm -1 , 1.55×10 -2 S cm -1 to 1.59×10 -2 S cm -1 or 1.56×10 -2 S cm -1 to 1.58×10 -2 S cm -1 range.

[0220] Aspect 22: A device comprising any of the preceding compositions.

[0221] Aspect 23: The device of Aspect 22, which is an electrochemical battery, such as a primary battery or a secondary battery.

[0222] Aspect 24: The device of Aspect 22 or 23, which is a lithium battery or a lithium ion battery, such as a rechargeable battery.

[0223] Aspect 25: The device of any of Aspects 22-24, comprising an electrode (eg, a cathode) comprising the composition of any of Aspects 1-21.

[0224] Aspect 26a: The device of Aspect 25, wherein the cathode is characterized by an operating voltage selected from the group consisting of Li / Li + 1.7V to Li / Li + range of 3.0V.

[0225] Aspect 26b: The device of Aspect 25 or 26a, wherein the cathode is characterized by an operating voltage selected from the group consisting of Li / Li + 2.0V to Li / Li + range of 3.0V.

[0226] Aspect 26c: The device of Aspect 25 or 26a, wherein the cathode is characterized by an operating voltage selected from the group consisting of Li / Li + 1.7V to Li / Li + range of 2.5V.

[0227] Aspect 26d: The device of Aspect 25 or 26a, wherein the cathode is characterized by an operating voltage selected from the group consisting of Li / Li + 2.2V to Li / Li + range of 2.6V.

[0228] Aspect 27: An electrochemical system comprising a cathode comprising the composition of any of Aspects 1-21.

[0229] Aspect 28: An electrochemical system comprising:

[0230] A cathode comprising a composition characterized by formula FX1:

[0231] Li w-δ Al x Fe z S2(FX1);

[0232] Where w is greater than or equal to 2 and less than or equal to 2.5;

[0233] Where x is greater than 0 and less than or equal to 0.5;

[0234] Where z is greater than or equal to 0 and less than or equal to 1;

[0235] where δ is greater than or equal to 0 and less than w; and

[0236] wherein the composition has an average net charge of zero, optionally wherein the composition is charge balanced, and optionally wherein the composition has a bulk phase characterized by an average charge of zero and / or a charge balanced bulk phase.

[0237] Aspect 29: The system of Aspect 27 or 28, wherein:

[0238] The composition is characterized by the formula FX2:

[0239] Li 2+y-δ Al y Fe 1-2y S2(FX2);

[0240] Where y is greater than 0 and less than 0.5;

[0241] Wherein δ is greater than or equal to 0 and less than 2+y.

[0242] Aspect 30: The system of any one of Aspects 27-29, wherein:

[0243] The composition is characterized by the formula FX3:

[0244] Li 2+y Al y Fe 1-2y S2(FX3);

[0245] Where y is greater than 0 and less than 0.5.

[0246] Aspect 31: The system of any of Aspects 27-30, comprising an electrochemical cell, such as a primary cell or a secondary cell.

[0247] Aspect 32: The system of any one of Aspects 27-31, comprising a lithium battery or a lithium ion battery.

[0248] Aspect 33: A cathode of an electrochemical system, comprising the composition of any of Aspects 1-21.

[0249] Aspect 34: A cathode of an electrochemical system, the cathode comprising:

[0250] Characterized by a composition of formula FX1:

[0251] Li w-δ Al x Fe z S2(FX1);

[0252] Where w is greater than or equal to 2 and less than or equal to 2.5;

[0253] Where x is greater than 0 and less than or equal to 0.5;

[0254] Where z is greater than or equal to 0 and less than or equal to 1;

[0255] where δ is greater than or equal to 0 and less than w; and

[0256] wherein the composition has an average net charge of zero, optionally wherein the composition is charge balanced, and optionally wherein the composition has a bulk phase characterized by an average charge of zero and / or a charge balanced bulk phase.

[0257] Aspect 35: The cathode of Aspect 33 or 34, wherein the composition is characterized by Formula FX2:

[0258] Li 2+y-δ Al y Fe 1-2y S2(FX2);

[0259] Where y is greater than 0 and less than 0.5;

[0260] Wherein δ is greater than or equal to 0 and less than 2+y.

[0261] Aspect 36: The cathode of any one of Aspects 33-35, wherein the composition is characterized by Formula FX3:

[0262] Li 2+y Al y Fe 1-2y S2(FX3);

[0263] Where y is greater than 0 and less than 0.5.

[0264] Aspect 37: The cathode of any of Aspects 33-36, wherein the cathode is used in an electrochemical cell, such as a primary cell or a secondary cell.

[0265] Aspect 38: The positive electrode according to any one of Aspects 33-37, wherein the cathode is used in a lithium battery or a lithium ion battery.

[0266] Now refer to Fig.37 , Aspect 39: A method 3700 of preparing a composition, the method comprising:

[0267] Provide a first amount of Li2FeS2 and a second amount of Li 2.5 Al 0.5 S2; (operation 3710)

[0268] The first amount of Li2FeS2 and the second amount of Li 2.5 Al 0.5 S2 performs combination, thereby forming a combination; (operation 3720), and

[0269] heating a combination having a lithium aluminum iron sulfide composition; (operation 3730)

[0270] Wherein, the lithium aluminum iron sulfide composition is characterized by formula FX1:

[0271] Li w-δ Al x Fe z S2(FX1);

[0272] Where w is greater than or equal to 2 and less than or equal to 2.5;

[0273] Where x is greater than 0 and less than or equal to 0.5;

[0274] Where z is greater than 0 and less than or equal to 1;

[0275] where δ is greater than or equal to 0 and less than w; and

[0276] wherein the composition has an average net charge of zero, optionally wherein the composition is charge balanced, and optionally wherein the composition has a bulk phase characterized by an average charge of zero and / or a charge balanced bulk phase.

[0277] Aspect 40: The method of Aspect 39, wherein the combination is heated to a temperature above 600°C, optionally above 700°C, optionally above 800°C; optionally above 850°C; and optionally at a temperature of about 900°C.

[0278] Aspect 41: The method of aspect 39 or 40, wherein the first amount and the second amount are such that Li2FeS2 and Li 2.5 Al 0.5 S2.

[0279] Aspect 42: The method of any one of Aspects 39-41, wherein the method comprises reacting a first amount of Li2FeS2 and a second amount of Li 2.5 Al 0.5 S2 performs annealing.

[0280] Aspect 43: The method of any one of Aspects 39-42, wherein the method further comprises a first amount of Li2FeS2 and a second amount of Li 2.5 Al 0.5 S2 is sealed in a carbon-coated quartz ampoule.

[0281] Now refer to Fig.38 , Aspect 44: A method 3800 of preparing a composition, the method comprising:

[0282] Providing a first amount of Li2S, a second amount of FeS, and a third amount of Al2S3; (operation 3810)

[0283] combining a first amount of Li2S, a second amount of FeS, and a third amount of Al2S3 to form a combination; (operation 3820), and

[0284] heating the combination to form a composition having a composition of lithium aluminum iron sulfide; (operation 3830)

[0285] Among them, the lithium aluminum iron sulfide composition is characterized by formula FX1:

[0286] Li w-δ Al x Fe z S2(FX1);

[0287] Where w is greater than or equal to 2 and less than or equal to 2.5;

[0288] Where x is greater than 0 and less than or equal to 0.5;

[0289] Where z is greater than or equal to 0 and less than or equal to 1;

[0290] where δ is greater than or equal to 0 and less than w; and

[0291] wherein the composition has an average net charge of zero, optionally wherein the composition is charge balanced, and optionally wherein the composition has a bulk phase characterized by an average charge of zero and / or a charge balanced bulk phase.

[0292] Aspect 45: The method of any one of Aspects 39-44, wherein the combination is heated at a rate greater than 0.1°C / min, optionally greater than 0.5°C / min, optionally greater than 0.7°C / min; optionally greater than 0.8°C / min; optionally greater than 0.8°C / min; optionally selected from the range of 0.1°C / min to 1°C / min; optionally 0.5°C / min to 1°C / min; optionally 0.8°C / min to 1°C / min; and optionally about 1°C / min.

[0293] Aspect 46: The method of any of Aspects 39-45, wherein the combination is maintained at a temperature of greater than 600°C, optionally greater than 700°C, optionally greater than 800°C; optionally greater than 850°C; and optionally about 900°C, optionally for more than 5 hours, optionally for more than 8 hours; optionally for more than 10 hours; optionally for 5-12 hours, optionally for 8-12 hours; and optionally for about 12 hours; and then cooled to room temperature.

[0294] Aspect 47: The method of any one of Aspects 39-46, wherein the providing operation comprises synthesizing a first amount of Li2FeS2 and a second amount of Li 2.5 Al 0.5 S2.

[0295] Aspect 48: The method of any of Aspects 39-47, wherein the synthesizing operation comprises grinding stoichiometric Li2S, FeS, and Al2S3 powders.

[0296] Aspect 49: The method of Aspect 48, wherein the synthesizing operation further comprises pressing the ground powder into at least one pellet.

[0297] Aspect 50a: The method of Aspect 49, wherein each of the at least one pellet comprises a mass of less than 1 g.

[0298] Aspect 50b: The method of Aspect 49, wherein each of the at least one pellet comprises a mass selected from the range of 1 mg to 500 mg.

[0299] Aspect 50c: The method of Aspect 49, wherein each of the at least one pellet comprises a mass selected from the range of 100 mg to 400 mg.

[0300] Aspect 50d: The method of Aspect 49, wherein each of the at least one pellet comprises a mass selected from the range of 200 mg to 300 mg.

[0301] Aspect 50e: The method of Aspect 49, wherein each of the at least one pellet comprises a mass selected from the range of 225 mg to 275 mg.

[0302] Aspect 50f: The method of Aspect 49, wherein each of the at least one pellet comprises a mass of about 250 mg.

[0303] Aspect 51: The method of Aspect 49 or 50, wherein the method further comprises sealing each of the at least one pellet in a carbon-coated quartz ampoule.

[0304] Aspect 52: The method of any of Aspects 49-51, wherein each of at least one pellet is heated to a temperature above 600°C, optionally above 700°C, optionally above 800°C, optionally above 850°C; optionally selected from a temperature in the range of 600°C to 900°C; optionally a temperature of 700°C to 900°C; optionally a temperature of 800°C to 900°C; optionally selected from a temperature in the range of 600°C to 900°C; optionally a temperature of 700°C to 900°C; optionally a temperature of 800°C to 900°C; and optionally heated to a temperature of about 900°C.

[0305] Aspect 53: The method of any of Aspects 49-52, wherein each of at least one pellet is heated at a rate greater than 0.1°C / min, optionally greater than 0.5°C / min, optionally greater than 0.7°C / min, optionally greater than 0.8°C / min, optionally selected from a rate in the range of 0.1°C / min to 1°C / min; optionally 0.5°C / min to 1°C / min; optionally 0.8°C / min to 1°C / min; and optionally at a rate of about 1°C / min.

[0306] Aspect 54: The method of any of Aspects 49-53, wherein each of at least one pellet is maintained at a temperature above 600°C, optionally above 700°C, optionally above 800°C; optionally above 850°C; optionally selected from a temperature in the range of 600°C to 900°C; optionally a temperature of 700°C to 900°C; optionally 800°C to 900°C; and optionally at about 900°C, optionally for more than 5 hours, optionally for more than 8 hours; optionally for more than 10 hours; optionally for 5-12 hours, optionally for 8-12 hours; and optionally for about 12 hours; and subsequently cooled to room temperature.

[0307] Aspect 55: A composition characterized by formula FX7:

[0308] Li 2-δ FeS u Se v (FX7)

[0309] Where u is greater than 0 and less than 2;

[0310] Where v is greater than 0 and less than 2;

[0311] where δ is greater than or equal to 0 and less than 2; and

[0312] wherein the composition has an average net charge of zero, optionally wherein the composition is charge balanced, and optionally wherein the composition has a bulk phase characterized by an average charge of zero and / or a charge balanced bulk phase.

[0313] Aspect 56: The composition or method of any one of Aspects 39-55, wherein:

[0314] The composition is characterized by the formula FX8:

[0315] Li 2-δ FeS 2-k Se k (FX8);

[0316] where k is greater than 0 and less than 2; and

[0317] Where δ is greater than or equal to 0 and less than 2.

[0318] Aspect 57: A composition characterized by formula FX9:

[0319] Li 2-ε Al x Fe r Q q S2(FX9); where:

[0320] x is greater than or equal to 0 and less than or equal to 0.67;

[0321] r is greater than or equal to 0 and less than or equal to 1;

[0322] q is greater than or equal to 0 and less than or equal to 0.33;

[0323] ε is greater than or equal to 0 and less than or equal to 2;

[0324] The composition comprises an extrinsic cation vacancy, wherein the extrinsic cation vacancy is represented in the chemical formula as Q; and

[0325] The composition has an average net charge of zero, optionally wherein the composition is charge balanced, and optionally wherein the composition has a bulk phase characterized by an average charge of zero and / or a charge balanced bulk phase.

[0326] Aspect 58: The composition or method of any one of Aspects 39-56, wherein:

[0327] The composition is characterized by the formula FX10:

[0328] Li 2-ε Al xFe 1-1.5x Q 0.5x S2(FX10); where:

[0329] x is greater than or equal to 0 and less than or equal to 0.67;

[0330] ε is greater than or equal to 0 and less than or equal to 2; and

[0331] The composition comprises an extrinsic cation vacancy, wherein the extrinsic cation vacancy is represented as Q in the chemical formula.

[0332] The present invention can be further understood by the following non-limiting examples.

[0333] Example 1: Multi-electron redox in lithium-rich aluminum iron sulfide

[0334] summary

[0335] Multi-electron redox reactions that initiate the redox of transition metals and anions in cathode materials for lithium-ion batteries enable higher energy density than single-electron redox materials currently used commercially. Storing and removing electrons from both transition metals and anions requires that both must have electronic states close to the Fermi level, and multi-electron redox reactions are inherently complex compared to single-electron redox reactions where the Fermi level is dominated by transition metal d-electron states.

[0336] This example studies Li2FeS2 (y=0) and Li 2.2 Al 0.2 Fe 0.6 The reversible electrochemical redox of S2 (y = 0.2) is derived from the Li 2+y Al y Fe 1-2y S2 material series, where 0≤y≤0.5. Both are Fe 2+ / 3+ and 2S 2- / (S2) 2- The redox couple exhibits multi-electron redox. When y = 0.2, ~80% of the S in the anion sublattice of the original material 2- is oxidized during charging, compared to ~50% when y=0.

[0337] ~80% of anions are reversibly oxidized / reduced, one of the highest reported levels of anion redox in lithium-rich transition metal chalcogenide cathodes. The total multi-electron redox at y = 0.2 yields a gravimetric energy density of ~1100 Wh kg-1 and ~2500 Wh L -1 volume energy density.

[0338] This example shows that the electrochemical oxidation / delithiation of y = 0.2 is achieved by partial Fe2+ / 2.6+ oxidation, followed by extensive 2S 2- / (S2) 2- Oxidation, causing Fe 2.6+ This is in contrast to y = 0, where electrochemical oxidation / delithiation occurs via partial reduction of Fe 2+ / 2.6+ oxidation, followed by a less extensive 2S reduction that does not induce a similar reduction of Fe 2- / (S2) 2- Oxidation.

[0339] The results provided in this example support the understanding that electrochemical anion oxidation in alkali-rich cathodes induces dynamic transition metal redox and supports its use in designing materials with similar redox capabilities as a pathway for next generation high energy density cathodes.

[0340] introduction

[0341] The theoretical energy density limit of current lithium-ion battery cathode materials is determined by the single electron insertion transition metal redox mechanism. Examples include LiNi x Mn y Co z＝1-x-y O2(NMC xyz) and LiFePO4, where the electrons (e - ) removal is mediated by transition metal oxidation (e.g., Co 3+ →Co 4+ or Fe 2+ →Fe 3+ ). Recently, the scarcity of battery-grade Co and Ni has prompted a surge in LiFePO4, which is viewed as a more scalable material given the relative abundance and low cost of Fe and PO4 precursors. 1 However, LiFePO4 ((~577Wh kg -1 , ~2068Wh·L -1 ) is significantly lower than NMC 811 (~950Wh·kg -1 , ~4499Wh·L -1 ). The single-electron redox itself imposes a theoretical limit on the energy density; at most 1e - / transition metal capacities and voltages within the stability window of state-of-the-art carbonate electrolytes (for Li / Li + As a reminder, energy density is the product of capacity and voltage. Therefore, new cathode materials that both use highly abundant elements and go beyond the single-electron redox paradigm must be developed to meet global energy storage needs.

[0342] One approach to achieve higher energy density is multi-electron redox, which is the storage / removal of electrons for both transition metals and anions, exceeding the 1e efficiency of single-electron redox. - / transition metal limit. Therefore, multi-electron redox requires transition metals and anions to have electronic states close to the Fermi level. While transition metal redox supports existing single-electron redox, initiating anion redox leads to structural distortions because it often induces the rearrangement of highly directional or localized p orbitals to access high-energy anion p electrons. 2 .

[0343] 2O 2- / (O2) n- Structural distortions and high voltages in redox reactions are the main practical challenges facing multi-electron redox reactions in oxides. These distortions generate peroxide species (O2) n- , they are generally unstable and tend to form molecular O2(g). 3,4 The high voltage is at or near the stability limit of the electrolyte, so 2O 2- / (O2) n- Redox reactions are accompanied by decomposition of the electrolyte. 5 These two effects combine to make multi-electron redox in oxides largely irreversible. The few reversible systems that do occur are 4d or 5d transition metals (e.g., Li 1.33 Ru 0.67 O2 and Li 1.33 Ir 0.67 O3); diffuse metal track makes (O2) n- and related distortions are stable, but electrolyte decomposition still exists - and Ru and Ir are very scarce anyway.

[0344] To overcome the challenges of multi-electron redox in oxides, we turned to sulfides. n- In comparison, persulfide (i.e. (S2) 2- ) are stable in many crystalline materials; perhaps the best-known example is the pyrite FeS2, in which the formal oxidation state is Fe 2+ and (S2) 2- . With the priority formation of O 2(g) (O2) n- The higher energy and more diffuse S 3p electrons (relative to O 2p) can even stabilize 3d transition metals (S2 2- Therefore, sulfides are a promising family of next-generation multi-electron redox cathode materials composed of highly abundant elements.

[0345] Previous studies on the lithium-rich sulfide Li2FeS2 have shown that multi-electron redox occurs through the stepwise Fe2+ / 3+ and 2S 2 / (S2) 2- Redox pairs occur. Li2FeS2 reversibly cycles ~1.6Li + / chemical formula unit (relative to ~2Li + / theoretical capacity in chemical formula units), where Fe 2+ Oxidized to Fe 3+ Remove ~0.6 Li + , and the average oxidation state of Fe 2.6+ Next, by adding 2S 2- Oxidized to (S2) 2- And remove ~1 Li + (About ~50% S 2- Anions are oxidized during charging). 6 At the same time, there is residual unoxidized Fe 2+ and S 2- , which can be used to approach the theoretical 2Li + / chemical formula unit. However, studies on Li2FeS2 indicate an intrinsic stability limit for Fe oxidation states close to ~2.6+; similar limits have been observed in other Fe-S binary and Li-Fe-S ternary materials. 7 Therefore, in order to increase the total multi-electron redox capacity to the theoretical limit, we aim to increase the S-redox capacity to more than ∼1e - / Chemical formula unit.

[0346] To obtain additional S-redox, we prepared Li 2+y Al y Fe 1-2y New materials for S2 (where 0≤y≤0.5) and observed Li 2.2 Al 0.2 Fe 0.6 The redox capacity of S2 (i.e., y = 0.2) increases. Although the Fe content is lower when y = 0.2 than Li2FeS2 (i.e., y = 0), about 80% of S in the entire multi-electron redox reaction 2- anions are used. Therefore, relative to y = 0, y = 0.2 operates in a state of excess anionic redox relative to the transition metal redox. By combining structural, electrochemical and spectroscopic characterizations, we demonstrate a new dynamic transition metal redox at y = 0.2 caused by excess anionic redox, which is not observed at y = 0.

[0347] Experimental Section

[0348] Material preparation

[0349] All materials and precursors were handled in an argon-filled glove box (H2O and O2 < 1 ppm). 2+ y Al y Fe 1-2y S2 (where 0≤y≤0.5) materials were all prepared by solid phase synthesis. Powders of Li2S (Thermo Fisher Scientific, 99.9%), FeS (Sigma Aldrich, 99.9%), and Al2S3 (Thermo Fisher Scientific, 99+%) were weighed to an accuracy of ±0.1 mg to obtain a total of 250 mg of the required stoichiometry (i.e., y value), and then mixed manually in an agate mortar and pestle. The mixed precursor powders were pressed into 1 / 4 inch pellets using a manual axial press. The mixed precursor particles were light gray. The pellets were placed in a carbon-coated glass silicon ampoule, evacuated to ≤50m Torr, and sealed with a methane-oxygen torch without exposure to air. First, a thin layer of acetone was applied to the inner wall of the empty ampoule, and then the acetone was pyrolyzed with a methane-oxygen torch to coat the ampoule. Repeat the pyrolysis at least twice to obtain a conformal, continuous coating. The ampoule was heated to 900°C at a rate of 1°C / min with a residence time of 12 hours. After ambient cooling to room temperature, the ampoule was opened in a glove box and the pellets were ground into a fine powder again in an agate mortar and pestle for further characterization. Only the y=0 pellets melted into polycrystalline ingots when heated to 900°C. The rest of the synthesized materials mostly retained the shape of the original pressed pellets. All products (whether pellets or powders) were black, except for y=0.4 which was dark brown and y=0.5 (i.e., Fe-free) which was light orange.

[0350] Electrochemical characterization

[0351] Electrode manufacturing

[0352] All electrode preparations were performed in an argon or argon-filled glove box. Individual electrodes were prepared by mixing 60 / 20 / 20 (wt%) active material, carbon (SuperP, Alfa Aesar, >99%), and PTFE binder (Sigma, 1 μm powder), respectively, in an agate mortar and pestle. The active material and carbon were mixed first, and then the binder was added so that the active material and carbon were evenly distributed within the framework provided by the binder. Manual grinding with a binder produced small (~1 mm) 2 ) flakes were manually broken into smaller fragments / powders using a stainless steel spatula. About 6 to 10 mg of the composite fragment mixture was weighed and pressed into 6 mm diameter electrodes using a manual hydraulic press (Vivtek) at a force of about 2 tons.

[0353] Electrochemical testing

[0354] All electrochemical cells were assembled in an argon-filled glove box (H2O and O2 <1 ppm). Unless otherwise stated, all electrochemical reactions were performed in 2032 coin cells (MTI) using a lithium foil counter electrode (Sigma, 99.9%, 0.75 mm, mechanically cleaned with an X-Acto blade before cell assembly), a glass fiber (Whatman, GF / D) or polypropylene (Celgard2400) separator, a separate working electrode as described above or a slurry-cast electrode and 100 μL of electrolyte (30 μL on the counter electrode, 40 μL on the separator, and 30 μL on the working electrode). Glass fiber separators were used for the separate electrodes and polypropylene was used for the slurry-cast electrodes. The coin cells were crimped closed with a manual crimper (Pred Materials).

[0355] The electrolyte was a 1M LiPF6 solution (Oakwood Chemical, battery grade) in a 1 / 1 (volume) mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) (both from Sigma, ≥99%), i.e., LP30. The electrolyte was made by mixing carbonate and salt in a dry HDPE bottle. All button cell components and HDPE bottles, etc., were dried overnight in a vacuum oven at 60°C before use in the glove box.

[0356] All electrochemical experiments were performed using a VMP3 multichannel potentiostat (Bio-Logic) or a BCS 805 battery cycler (Bio-Logic).

[0357] Galvanostatic Cycling & Galvanostatic Intermittent Titration Technique (GITT)

[0358] All Li 2+y Al y Fe 1-2y S2 composite electrodes are all charged at the rates shown (based on 1e - / chemical formula units) to 3 V and discharged to 1.7 V at the rates shown. All voltages are relative to the Li foil counter electrode and are expected to be Li / Li + Reference potential.

[0359] The current in the GITT experiment was C / 10 based on 1 electron / chemical formula unit and lasted for 20 minutes with 4 hours of dwell time.

[0360] Electrochemical Impedance Spectroscopy (EIS) & DC Polarization

[0361] In an argon-filled glove box, 90 to 120 mg of y=0 and y=0.2 powders were pressed into electrodes with a diameter of 6 mm using a manual hydraulic press (Vivtek) at a pressure of about 2 tons. The thickness of the pellets was roughly between 1.4 and 2 mm. Au was sputtered on both flat surfaces of the pellets using a Ted Pella 108 automatic sputter coater at 40 mA for 60 seconds in an argon-filled glove box.

[0362] EIS and DC polarization measurements were collected using a Bio-Logic VSP300 multi-channel potentiostat. Symmetric cells were assembled in a spring-loaded Swagelok cell with an inner diameter of 0.25 inches using Au sputtered pellets. During measurements, the cell was kept in a home-made Faraday cage.

[0363] Figures 39A-39B The EIS spectra were collected in the frequency range of 3 MHz to 1 kHz using a sinusoidal voltage amplitude of 50 mV and 10 measurements were averaged.

[0364] DC polarization (i.e., chronoamperometry) current versus time data were collected at fixed voltages of 50, 40, 30, 20, 10, and 5 mV for 2 minutes each. Between voltages, the cell was held at open circuit voltage (OCV) for 5 minutes before EIS was measured.

[0365] like Figures 39A-39B As shown, EIS measurements of pellets with y=0 and y=0.2 show that the electronic conductivity is at least several orders of magnitude higher than the ionic conductivity. This difference makes simple electromechanical measurements of the ionic conductivity impossible, even for estimation purposes (at least by EIS). The resistance (electronic conductivity) can be measured by the x-intercept of the EIS. The table below lists the rough x-intercept values ​​for y=0 and y=0.2, which are comparable to the resistance values ​​obtained from DC polarization measurements.

[0366] Table 1. x-intercept values ​​of EIS measurements at y=0 and y=2.

[0367] Material x-intercept of EIS measurement (Ω) y＝0 31.5 y＝0.2 51.0

[0368] Electronic conductivity was calculated from DC polarization measurements. The data are plotted on Figures 40A-40B and the pellet sizes listed in the table below.

[0369] Table 2 Particle sizes at y=0 and y=0.2.

[0370] y＝0 y＝0.2 Diameter(m) <![CDATA[6.05×10 -3 ]]> <![CDATA[6.05×10 -3 ]]> Thickness(m) <![CDATA[1.44×10 -3 ]]> <![CDATA[1.92×10 -3 ]]>

[0371] Figures 40A-40BThe slope of the linear fit is the resistance value (i.e., R) obtained according to Ohm's law (i.e., V = I × R). Using the equation (where σ is the electronic conductivity), the electronic conductivity of y = 0 and y = 0.2 is 1.57 S cm -1 .

[0372] CuKɑ powder X-ray diffraction (PXRD)

[0373] CuKɑ PXRD patterns were collected on a Rigaku SmartLab diffractometer. To prevent oxidation during the measurement, approximately 10 to 20 mg of powder sample was placed in a low-background silicon sample holder and compressed (by hand using the edge of a glass slide). The diffraction pattern was fitted by the Rietveld method using the General Structure Analysis System II (GSAS-II). The crystal structure was visualized using VESTA.

[0374] Synchrotron PXRD

[0375] High-resolution synchrotron PXRD patterns were collected on samples packed into 20 mm long, 0.5 mm diameter polyimide tubes, i.e. capillaries (Avantor), sealed at both ends with clay and Torr Seal (Varian). Samples were collected at beamline BXDS-WLE at the Canadian Light Source (CLS). The instrument parameters were refined by the Rietveld method for patterns collected on the LaB6 standard. All refinements were done in GSAS-II. The crystal structure was visualized using VESTA.

[0376] Samples were sealed in argon in aluminized Mylar bags (2 to 3 layers) using an impulse heat sealer (Uline) for transport to the synchrotron.

[0377] X-ray absorption spectroscopy (XAS)

[0378] Samples for ex situ XAS were prepared in 2032 coin cells (MTI) with a separate working electrode as described previously. The electrodes were measured in the following states: pristine, charged to approximately half of the sloped portion of the charge curve (i.e., mid-slope), charged to the transition between the sloped portion and the plateau portion (i.e., transition), charged to approximately half of the plateau (i.e., mid-plateau), charged to 3 V (i.e., charging), and discharged to 1.7 V (i.e., discharging). After oxidation or reduction to one of the cutoff values ​​defined above, the crimping of the cell was unwound and opened using a manual disassembly tool (Pred Materials) in an argon-filled glove box. The ex situ cathode was manually scraped off the current collector with a stainless steel scraper. The ex situ cathode was immersed in ~300 μL DMC to wash away residual electrolyte. The DMC was gently wiped with a dry Kim rag, leaving a small amount of residual DMC, and then dried under vacuum for approximately 30 minutes until completely dry. The dried intact cathode was then manually broken into small pieces / powder using a stainless steel spatula.

[0379] For Fe K-edge, loose powder was loaded as received into an aluminum sample holder provided by the Stanford Synchrotron Radiation Lightsource (SSRL) at the SLAC National Accelerator Laboratory, encapsulated between two pieces of Kapton tape (1 mil film thickness, 2.5 mil total thickness, Uline).

[0380] For the S K-edge, the sample powder was ground and mixed with boron nitride (BN) (Alfa Aesar, 99.5%) to a total sample concentration of ≤5 mass%. Approximately 10 to 15 mg of each composite BN sample mixture was pressed into pellets with a diameter of 1 / 4 inch under a force of about 1 ton in a manual axial press. The pellets were then loaded into a plastic sample holder provided by the National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory.

[0381] The loaded sample holders were sealed in argon in aluminized Mylar bags (2 to 3 layers) using an impulse heat sealer (Uline) for transport to the corresponding synchrotron.

[0382] The Fe K-edge was measured in both fluorescence and transmission modes at beamline 4-3 at SSRL. The data shown are merged transmission data from three scans per sample. The Fe K-edge data were calibrated to a collinear Fe foil standard.

[0383] SK edges were measured in fluorescence mode on beamline 8-BM. Gypsum (i.e., sulfate) standards were added to the sample holder to ensure a constant energy offset. Data collection in a limited window in k-space would hamper EXAFS analysis.

[0384] Calibration, background correction and data processing of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) were performed using Athena and Artemis in the IFEFFIT suite.

[0385] Mossbauer spectrum

[0386] The ex situ Mössbauer samples were prepared as described above for ex situ XAS. However, after rinsing in DMC and drying, the cathode was left intact and placed on a small piece of Kapton tape (1 mil film thickness, 2.5 mil total thickness, Uline). The Kapton tape was then taped inside an electrostatic shielding bag (Uline) and sealed with an impulse heat sealer (Uline) in argon.

[0387] A 5.5 mm hole was punched in an approximately 2 mm thick Pb metal sheet, and a square hole of approximately 0.5 in x 0.5 in was punched in a second 2 mm Pb metal sheet. The sample was enclosed in a sealed bag between the two Pb sheets to prevent excess background gamma rays from reaching the Mössbauer detector, and fixed in situ with scotch tape so that the 5.5 mm hole only exposed the ex situ cathode.

[0388] Mössbauer measurements were performed in constant acceleration mode in transmission geometry using 57 Co(Rh) source with an initial activity of 25 mCi and a half-life of about 272 days. The nominal activity at the time of measurement was about 19 mCi. The velocity scale was calibrated with α-Fe foil at room temperature (±3 mm / s).

[0389] Results and Discussion

[0390] Structural characterization

[0391] Li2FeS2 has alternating layers of tetrahedral and octahedral coordinated cation sites. The octahedral layers contain only Li + , tetrahedral layer mixed occupation Li + / Fe 2+ sites. The mixed occupation defines a high-symmetry trigonal P-3m1 space group. The new material we developed in this study follows the 2 Fe 2+ Replace 1 Li + and 1 Al 3+ The co-substitution pattern is that of a heterovalent homoatomic substitution that saves charge and atomic number. We can make this substitution because of the close structural similarity between Li2FeS2 and Li5AlS4. Li5AlS4 also has alternating layers of tetrahedral and octahedral coordinated cation sites. The main difference is that the tetrahedral layers of Li5AlS4 have different, ordered Li + and Al3+ site. This may be due to Al 3+ High charge density enhanced Al 3+ The ordered sites subtly distort the anion sublattice, reducing the symmetry to the monoclinic P21 / m space group. 8,9

[0392] Figure 2A , 2B Figures 2C and 2C show the powder X-ray diffraction (PXRD), Rietveld refinement, and difference curves for y = 0, y = 0.2, and y = 0.4. While the y = 0 pattern fits the high symmetry trigonal P-3m1 Li2FeS2 model, the y = 0.2 and y = 0.4 patterns fit the hybrid model, in which the ordered Al 3+ The site and low-symmetry monoclinic P2 1 / m Li5AlS4 model are preserved (but Li + and Fe 2+ sites are mixed like Li2FeS2). The mixing model gives satisfactory results (R wp <10%). However, higher resolution synchrotron PXRD remains to be achieved.

[0393] Electrochemical characterization

[0394] The materials with y=0, y=0.2 and y=0.4 were electrochemically characterized by current cycling experiments in half-cells with lithium metal anode and LP30 electrolyte. Figure 3A , 3B 3C and 3C show the charge and discharge curves of the first cycle for each material. The charge curve has an initial slope, i.e., the solid solution Fe 2+ / 3+ Redox, followed by a plateau, i.e., the conversion state of 2S 2- / (S2) 2- Oxidation reduction. Fe 2+ / 3+ The redox capacity varies linearly with y, supporting the expected linear variation of Fe content with y. The linear trend also shows that the rough stability limit of Fe at the oxidation state of ~2.6+ at y = 0 persists at all y and indicates that it is an intrinsic thermodynamic stability limit rather than a kinetic stability limit. 2+ / 3+ Different redox, 2S 2- / (S2) 2- The redox reaction reaches its maximum value at y=0.2. Fig.10 Shows Figures 3A-3C The error bars for the differences in median capacity are based on three replicates and are all within ±5%.

[0395] The additional anion redox production at y = 0.2 was 1123 ± 5 Wh kg- 1、2617.8Wh·L -1 The charging energy density is 1034±22Wh·kg -1 、2455.4Wh·L -1 of discharge energy density. The gravimetric energy density is worse than that of NMC811, and although the volumetric energy density is not as good as that of NMC811, it is better than that of LiFePO4. Importantly, the high energy density is highly reversible between the first charge and discharge, that is, ~80% of the anion sublattice is reversibly redoxed. Similar levels of anion redox in lithium-rich transition metal chalcogenides have not been reported before. Although the level of anion redox at y = 0.4 is also higher than that at y = 0, in this paper we focus on the comparison of y = 0 and y = 0.2 to understand the impact of excess anion redox. The degree of anion redox at y = 0.2 is greater than that at y = 0.4, and the hysteresis and overpotential of anion redox at y = 0.4 are significantly increased compared to y = 0 and 0.2.

[0396] Characterization of redox processes

[0397] To characterize the redox process of Fe, we measured Fe K-edge X-ray absorption spectra (XAS) at six different SOCs at y = 0 and y = 0.2. The front-edge and near-edge data for y = 0 and y = 0.2 are plotted in Figure 6A-6B and Figure 7A-7B middle.

[0398] The Fe K-edge spectra of different SOCs at y = 0 show that Fe 2+ / 3+ and 2S 2- / (S2) 2- are distinct, sequential events during charging; the rising edge does not migrate between the transition SOC and the charging SOC, suggesting that the ~1e - The oxidation does not involve Fe. However, the Fe K-edge spectrum at y = 0.2 shows that 2- / (S2) 2- Dynamic Fe redox occurs during the redox process - specifically, partial Fe reduction or changes in Fe-S covalency during the observed excess S redox. The rising edge shifts to lower energy at full charge compared to the transition. The shift to lower energy indicates that reduction has occurred, consistent with the broad ~2e range of y = 0.2 during charge. - Overall oxidation contrasts.

[0399] To characterize the S redox process, we also measured the S K-edge X-ray absorption spectra (XAS) at the same six different SOCs for y = 0 and y = 0.2. Hansen et al. demonstrated that the front edge feature at 2471.8 eV indicates that 2S 2- / (S2)2- form. 6 Figure 8 Comparison of the S K-edge XANES spectra at full charge in y shows a much stronger front-edge feature at 2471.8 eV for y = 0.2 compared to y = 0, confirming the oxidation of most (~80%) of the anion sublattice.

[0400] Additional information

[0401] Fig.11 and 12 The ability to synthesize and recycle materials at many values ​​of y is demonstrated. Fig.11 In Figure 2, PXRD patterns are shown for y increments of 0.05. These patterns show that each material can be refined to the mixing model described in the discussion of Figure 2, i.e., Fig.11 All principal reflections in all patterns in are interpreted. It is observed that despite the change in space group from P-3m1 to P21 / m between y = 0 and y = 0.5, the principal reflections are retained, i.e., any lower symmetry reflections unique to P21 / m are also of lower intensity than the principal reflections defined by the lattice site. These patterns were obtained from samples encapsulated between a glass slide and Kapton tape and diffracted using CuKɑ radiation, which limits the resolution and 2θ range to between 25 and 60. The patterns in Figure 2 were obtained from samples in inert argon in a sealed chamber with an X-ray transparent window; they therefore have higher resolution and a wider 2θ range between 10 and 60. To verify the systematic tunability of the electrochemical properties with y, Fig.12 Galvanostatic cycling data for cycles 1 and 2 are shown for increments of y of 0.1. The overall trend is consistent with the data in Figure 3, where the capacity in the initial sloped portion of the charge curve corresponds directly to the Fe content, i.e., 1-2y. The capacity of the later charge curve plateau does not show any obvious trend with y (our research focus is on excess anion redox at y = 0.2). The capacity decay from cycle 1 to cycle 2 becomes more obvious at y = 0.3, and even more so at y = 0.4. Galvanostatic cycling data for y = 0.5 are not shown because cycling attempts showed it to be electrochemically inactive, i.e., no capacity. Overall, the data confirm that the stoichiometry of y is tunable, the structural differences are minimal (e.g., no obvious phase transitions, abrupt changes in symmetry between P-3m1 and P21 / m, etc.), and that the electrochemical properties of y undergo continuous and systematic changes.

[0402] References corresponding to Example 1

[0403] (1)Armstrong, R.; Chiang, Y.-M.; Gruenspecht, H. The Future of EnergyStorage; MIT Future of.

[0404] (2)Zak,J.J.;Kim,S.S.;Laskowski,F.A.L.;See,K.A.An Exploration ofSulfur Redox in Lithium Battery Cathodes.J.Am.Chem.Soc.2022,144(23),10119–10132.

[0405] (3)House,R.A.;Marie,J.-J.;Pérez-Osorio,M.A.;Rees,G.J.;Boivin,E.;Bruce,P.G.The Role of O 2in O-Redox Cathodes for Li-Ion Batteries.NatureEnergy 2021,1–9.

[0406] (4)House,R.A.;Rees,G.J.;McColl,K.;Marie,J.-J.;Garcia-Fernandez,M.;Nag,A.;Zhou,K.-J.;Cassidy,S.;Morgan,B.J.;Saiful Islam,M.;Bruce,P.G.Delocalized Electron Holes on Oxygen in a Battery Cathode.Nat Energy2023,1–10.https: / / doi.org / 10.1038 / s41560-023-01211-0.

[0407] (5)McCalla,E.;Sougrati,M.T.;Rousse,G.;Berg,E.J.;Abakumov,A.;Recham,N.;Ramesha,K.;Sathiya,M.;Dominko,R.;Van Tendeloo,G.;Novák,P.;Tarascon,J.-M.Understanding the Roles of Anionic Redox and Oxygen Release duringElectrochemical Cycling of Lithium-Rich Layered Li4FeSbO6.J.Am.Chem.Soc.2015,137(14),4804–4814.https: / / doi.org / 10.1021 / jacs.5b01424.

[0408] (6)Hansen,C.J.;Zak,J.J.;Martinolich,A.J.;Ko,J.S.;Bashian,N.H.;Kaboudvand,F.;Van der Ven,A.;Melot,B.C.;Nelson Weker,J.;See,K.A.Multielectron,Cation and Anion Redox in Lithium-Rich Iron SulfideCathodes.J.Am.Chem.Soc.2020,142(14),6737–6749.https: / / doi.org / 10.1021 / jacs.0c00909.

[0409] (7)Goodenough,J.B.Structural Chemistry of Iron Sulfides.MaterialsResearch Bulletin 1978,13(12),1305–1314.https: / / doi.org / 10.1016 / 0025-5408(78)90121-6.

[0410] (8)Lim,H.;Kim,S.-C.;Kim,J.;Kim,Y.-I.;Kim,S.-J.Structure of Li5AlS4and Comparison with Other Lithium-Containing Metal Sulfides.Journal of SolidState Chemistry 2018,257,19–25.https: / / doi.org / 10.1016 / j.jssc.2017.09.018.

[0411] (9) Gamon, J.; Dyer, MS; Duff, BB; Vasylenko, A.; Daniels, LM; Zanella, M.; Gaultois, MW; Blanc, F.; Claridge, JB; Rosseinsky, MJ Conductivity.Chem.Mater.2021,33(22),8733–8744.https: / / doi.org / 10.1021 / acs.chemmater.1c02751.

[0412] Spectroscopic and structural implications of multi-electron redox in lithium-rich battery cathodes

[0413] The redox in the cathode is formally localized on the metal. Conventional intercalation materials, such as LiCoO2 or NMC, undergo a one-electron (or less) reduction upon lithiation. Charge compensation is formally localized on the metal.

[0414] Fig.13 This process is shown in Figure 1, which follows the formula:

[0415] zL + +ze - +Li 1-z (Ni 1-x-y Mn x Co y )O2→Li(Ni 1-x-y Mn x Co y )O2.

[0416] The embedding chemistry causes minimal changes to the cathode structure, e.g. Fig.14 As shown in Figure 2, when TiS2 is lithiated, lithium ions are intercalated between the layers of TiS2. When TiS2 is delithiated, the process is reversed.

[0417] In contrast, multi-electron cathodes employ mechanisms that go beyond conventional intercalation. For example, Fig.15 As shown, conventional LiMO2-type materials (with only one Li per M transition metal) can only call upon at most one transition metal redox electron. However, in lithium-rich materials, e.g. Fig.15In the example of Li2MO3 shown, there is an excess of Li relative to the M transition metal content. Therefore, in order to obtain the additional redox capacity provided by the excess Li, the redox must exceed 1 electron on the transition metal, effectively invoking redox on the anion. Fig.15 In the case of the example in , this is shown as the removal of electrons from the O (i.e., oxide anion) component of the material.

[0418] Multi-electron cathodes use bands with anionic characteristics to facilitate more than one electron transfer per transition metal. Fig.16 As shown, the location of the anion band plays an important role in the technological feasibility and stability of anion redox in practical batteries. Although oxides can exhibit anionic redox, the oxide redox voltage lies outside the electrolyte stability window and therefore often leads to electrolyte decomposition. In contrast, sulfides can be used as a model system to understand anionic redox because the sulfide redox voltage lies within the electrolyte stability window. This provides a fundamental clarification for studying redox reactions and makes them more technologically feasible with existing commercial electrolytes / batteries.

[0419] Iron is a more abundant element than nickel or cobalt. Its most common form is hematite, or Fe2O3. Abundance and criticality are often quoted interchangeably. However, abundance is only one dimension of criticality.

[0420] Criticality is defined by multiple dimensions and is dynamic: abundance, geographic distribution, geopolitics, environmental and / or social costs (mining / extraction), existence / feasibility of alternatives, refining costs, incumbency / economy of scale, etc.

[0421] One way to measure the criticality of iron is to use the Herfindahl-Hirschman Index (HHI), which is proportional to the geographical distribution. The HHI is calculated using the following formula:

[0422]

[0423] where N is the total number of countries involved, and s i is the market share percentage of country i.

[0424] from Fig.17 As can be seen in Figure 1, the HHI for iron indicates a moderate enrichment. However, the crustal abundance of iron is very high. Therefore, iron is a non-critical material.

[0425] Having demonstrated the noncriticality of iron in a global sense, we proceed to discuss the feasibility of using sulfides as a model system to understand anionic redox. Fig.18 The charge / discharge cycles of Li2FeS2 and Li2RuO3 were compared. Fig.18As can be seen in Figure 2, the first and second cycles of Li2FeS2 overlap closely, indicating that the redox mechanism invoked in the first cycle is highly reversible and is subsequently invoked again in the second cycle. In contrast, the first and second cycles of the oxide material Li2RuO3 do not overlap, indicating that the redox mechanism invoked in the second cycle is different from the first; and the redox reaction invoked in the first cycle is largely irreversible. One source of irreversibility could be electrolyte decomposition or O2 gas release, such as Fig.16 Therefore, the higher reversibility and stability of the multi-electron redox mechanism in Li2FeS2 make it a viable candidate for further development / optimization of functional materials for commercial batteries.

[0426] Now refer to Fig.19 , X-ray absorption spectroscopy (XAS) shows oxidation of Fe and S. The Fe front edge is attributed to a weakly allowed Fe 1s to Fe 3d transition that is suppressed due to a slight displacement of Fe in the tetrahedron. The S K-edge spectrum of Li2FeS2 shows front edge features due to S1s to Fe 3d transitions. The intensity is a probe of covalency.

[0427] The Fe K-edge undergoes an edge shift when Li2FeS2 is oxidized to 2.5 V. After Fe oxidation, the covalency of the Fe-S bond increases, resulting in an increase in the front edge strength of the S K-edge.

[0428] Oxidation to 3 V does not cause a shift in the Fe K-edge. When oxidized to 3 V, the S K-edge spectrum shows new front-edge features and a shift in the edge, confirming that S is involved in charge compensation.

[0429] The shifts in the Fe and S K-edge spectra upon oxidation are mostly reversible upon reduction. Changes in both spectra were observed after the edge, indicating that the structural changes are irreversible.

[0430] like Fig. 20 As shown, the initial tilted region can be attributed to Fe 2+ Oxidized to Fe 2+ / 3+ , while the platform area is mainly attributed to S 2- Oxidized to S2 2- .

[0431] The local structure around Fe does not change when the anion is oxidized. Fig.21 As shown, EXAFS shows that the local structure of Fe hardly changes between 2.5 V and 3 V. The tilt of FeS4 tetrahedrons can allow SS bonds to form without distorting the local structure of Fe.

[0432] Li2FeS2 undergoes anionic redox. The reversibility is determined by the structure. Specifically, Fig. 22 As shown, Li2FeS2 is able to carry out >1 mol e - / Reversible redox of the formula unit. The structural distortion associated with the second oxidation determines the reversibility.

[0433] Example 3: Study on the structure-property relationship of multi-electron metal sulfide cathode

[0434] The A2MS2 phase provides tunability in crystal chemistry, allowing us to explore the effects of electronic structure on anion redox. Figures 23A-23B As shown, Se substitution can controllably change the redox potential, and Li2FeS 2-y Se y The solid solution exhibits tunable anionic redox. With increasing Se substitution, the charge voltage attributed to S oxidation shifts to lower potentials.

[0435] The constant current intermittent titration showed that the overpotential decreased with the increase of Se content. Figures 24A-24B As shown, constant current intermittent titration (GITT) can be used to approach the equilibrium potential. The voltage shift in the anion redox plateau is a thermodynamic shift. Higher Se content produces lower overpotentials, especially in the plateau region of the charge curve. Li2FeSe2 is a better electron conductor than Li2FeS2.

[0436] like Fig.25 As shown, the substitution of Se for S results in greater Fe-anion covalency, resulting in synchronized cationic and anionic oxidation over the entire charge cycle. Both S and Se contribute to anionic redox in the hybrid material. Electrochemistry and spectroscopy indicate that the electronic states are well mixed.

[0437] Example 4: Adjusting the electronic structure to increase voltage

[0438] like Fig.26 As shown, the average voltage of the charge curve can be increased by shifting the charge compensation to the anion.

[0439] like Figures 3A-3C As shown in Figure 10, adjusting the crystal chemistry will adjust the charge compensation mechanism. As the Fe content decreases and the Al content increases, the Fe 2+ The contribution of oxidation also decreases. However, the overall capacity can still be kept high due to the charge compensation migration to the anions.

[0440] Table 3. Capacity, voltage and energy density of various cathodes.

[0441]

[0442] Now refer to Fig. 27 , Al-containing materials seem to stabilize Fe 3+When the material is electrochemically oxidized, due to the kinetic overpotential of anion oxidation, Fe 2+ is "overoxidized". The electrochemical products are kinetic products. In chemical electron transfer, "Fe 3 + "Being S 2- reduction.

[0443] Example 5: LiTiS2 / Li2TiS3 family as a model system.

[0444] like Figures 28A-28B As shown, LiTiS2 exhibits a significant capacity in the first oxidation due to the redox interaction of Ti and S. Replacing Ti with Li results in a material with negligible capacity because Ti 4+ Inactivity and lack of vacancies.

[0445] Now refer to Fig.29 , DFT calculations show that SS bonds are formed around vacancies. 8 / 9 Taking S2 as a case study, we observed that SS bonds are preferentially formed near vacancies.

[0446] Now refer to Figures 30A-30B , control Li during synthesis + Stoichiometry can be used to introduce vacancies and control the Ti formal oxidation state. + The reaction results in a higher oxidation state of Ti, namely Ti 4+ Relative to Ti 3+ Higher. The characteristic tilted area at the beginning of charging will increase with Ti 3+ grows with the increase of .

[0447] Now refer to Fig.31 , replacing Li with Ti allows the introduction of vacancies while maintaining the formal oxidation state of Ti as Ti 4+ :

[0448]

[0449] Now refer to Fig.32 , confirming the presence of vacancies by electrochemical techniques. To determine if the material contains the vacancy content we expect from the synthesis, first lithiate (reduce) the material. The capacity will be approximately equal to the vacancy concentration. When intercalating divalent cations, the capacity should be twice the vacancy concentration. Confirm the Ti:S ratio by electron probe microanalysis (EPMA).

[0450] Now refer to Fig.33 , the capacity increases significantly after the introduction of vacancies. The introduction of vacancies “turns on” anion oxidation in the phase.

[0451] Now refer to Fig.34, anion redox is a sliding scale.

[0452] References corresponding to Examples 2-5

[0453] A.Dey,Y.Jiang,P.Ortiz de Montellano,KOHodgson,B.Hedman,EISolomon,J.Am.Chem.Soc.2009,131,7869-7878

[0454] AJMartinolich,JJZak,DNAgyeman-Budu,SSKim,NHBashian,A.Irshad,SRNarayan,BCMelot,J.Nelson Weker,KASee,Chem.Mater.2021,33,378-391.

[0455] Li2TiS3 reported in:Flamary-Mespoulie,F.et al.Energy StorageMater.2020,26,213–222.

[0456] Example 6: Lithium-Rich Aluminum Iron Sulfide Lithium Ion Battery Cathode

[0457] The lithium-ion cathode is the most expensive, least energy-dense, and shortest-lived component of a lithium-ion battery. Current cathodes use transition metal redox to store energy. However, cobalt and nickel pose severe scalability limitations to current lithium-ion cathodes. There is little room for improvement in the energy density of current cathodes.

[0458] Now refer to Figures 2A-2D , the structural similarity between Li5AlS4 and Li2FeS2 enables their co-substitution. Despite the different symmetries, the monoclinic unit cell volume in the Li2FeS2-Li5AlS4 pseudosolid solution is a linear function of y.

[0459] Co-substitution at y = 0.2 enables additional S redox capacity. 2+ / 3+ The redox capacity is a linear function of y. Although there is 40% less Fe than when y = 0, y = 0.2 has a greater multi-electron capacity; 80% of the S is oxidized when y = 0.2 compared to 54% when y = 0.

[0460] Fe K-edge X-ray absorption spectroscopy (XAS) tracks the oxidation state of Fe. Fe K-edge XAS excites the core Fe1s electrons. The energy at which absorption is observed is called the "rising edge". The lower the energy, the stronger the shielding of the 1s electrons. The higher the energy, the weaker the shielding of the 1s electrons.

[0461] Now refer to Figure 6A-6B The Fe K-edge XAS of Li2FeS2 shows that the redox of Fe and S are different events. 2+ / 3+ Redox is active before transfer, and in 2S 2- / (S2) 2- The plateau phase is inactive.

[0462] Now refer to Figure 6A-6B and 7A-7B, Li 2.2 Al 0.2 Fe 0.6 The Fe K-edge XAS of S2 suggests that Fe is not harmless in S redox. Therefore, we assume that the additional S redox is caused by the addition of 2- To Fe 3+ mediated by electron transfer.

[0463] High-energy X-rays elucidate the local structure of Fe. Photoelectron scattering occurs from high-energy X-rays above the Fe K-edge. The interference pattern of the scattering can be fitted to the local structure of Fe by extended X-ray absorption fine structure analysis (EXAFS).

[0464] Now refer to Fig.35 , the change of Fe local structure at y = 0.2 is smaller than that at y = 0. EXAFS shows that although 2S 2- / (S2) 2- The redox is much stronger, but e - The change in local structure at y=0.2 is smaller than that at y=0.

[0465] Now refer to Fig.36 , annealing (ie thermodynamics) y = 0.2 supports the electron transfer hypothesis.

[0466] In summary, the internal electron density is redistributed to mediate multi-electron redox. We observed that Li 2.2 Al 0.2 Fe 0.6 Fe reduction occurs upon oxidation of excess S in S2, suggesting that multi-electron redox is stabilized by internal electron redistribution.

[0467] Example 7: As Li2Al x Fe 1-1.5x Q 0. 5xS2, 3xFe 2+ Anovalent substitution of 2 Al 3+ and 1 empty seat.

[0468] Now refer to Fig.41 The work in Example 1 corresponds to side "1" of the triangle, i.e., the material developed from the linear combination of Li2FeS2 and Li5AlS4. The additional data provided in this example is a preliminary exploration of side "2" of the triangle, i.e., the material developed from the linear combination of Li2FeS2 and Li2Al 2 / 3 Q 1 / 3 S2 (i.e. Li3AlS3). The latter linear combination introduces up to 1 / 3 of vacancies in the crystal structure. 2 / 3 Q 1 / 3 The S2 material was previously reported by Gamon et al. 10

[0469] See now Fig.42 , Li2FeS2, Li5AlS4 and Li3AlS3 consist of alternating layers of (mostly) tetrahedral and octahedral cation coordination. In Li5AlS4 and Li3AlS3, the tetrahedral Al sites are ordered, whereas in Li2FeS2 the tetrahedral sites are occupied by a mixture of Li and Fe. This distorts the anion sublattice, thus destroying the Symmetry of space groups. The structures can be compared by looking at the pseudo-unit cells in the lower symmetry P21 / m space groups of Li2FeS2 and Li3AlS3 (drawn in blue on each of the three crystal structures).

[0470] Li2Al2O3 with x=0.2, 0.33, 0.53, 0.6 and 0.67 was synthesized at 900℃. x Fe 1-1.5x S2 alloy. Li2FeS2 and Li3AlS3 end members were annealed at 900℃ for 16 hours. The x=0.67 end member annealed at 900℃ could not be refined to space group, while all other alloys are OK. Figures 43A-43E The diffraction pattern and Rietveld refinement of the alloy are shown. Other experimental details of the synthesis conditions, ie how the precursors were treated, how the reactants were heated, etc., were the same as described in Example 1.

[0471] Now refer to Fig.44 , the lattice parameters of the alloys systematically shift with attempted substitutions (trends suggest that the x=0.33 compound should be reannealed). The Li3AlS3 end-members cannot be refined into space groups. Therefore, the expected linear trend between end-members cannot be determined. PXRD patterns for x=0.63 (Fe content=0.05) and x=0.653 (Fe content=0.02) have not yet been collected.

[0472] Now refer to Fig.45 , the data show that Li2Al x Fe1-1.5x Q 0.5x S2 material is electrochemically active. After substitution exceeds x = 0.33, the capacity decreases significantly. 3+ and the mechanical impact of vacancies are the subject of further / ongoing research.

[0473] References corresponding to Example 7

[0474] (10) Gamon, J.; Duff, BB; Dyer, MS; Collins, C.; Daniels, LM; Surta, TW; Sharp, PM; Gaultois, MW; Blanc, F.; Claridge, JB; Rosseinsky, MJ Computationally Guided Discovery of the Sulfide Li3AlS3 in the Li–Al–SPhase Field: Structure and Lithium Conductivity.Chem.Mater.2019,31(23),9699–9714.https: / / doi.org / 10.1021 / acs.chemmater.9b03230.

[0475] Statement on citations and variations

[0476] All references in this application, such as patent documents, including issued or granted patents or equivalents; patent application publications; and non-patent literature documents or other source materials; are hereby incorporated by reference in their entirety as if individually incorporated by reference, provided that each reference is not at least partially inconsistent with the disclosure in this application (e.g., a partially inconsistent reference is incorporated by reference except for the partially inconsistent portion of the reference).

[0477] The terms and expressions employed herein are used as terms of description rather than terms of limitation, and the use of such terms and expressions is not intended to exclude any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications may be made within the scope of the claimed invention. Therefore, it should be understood that although the present invention has been specifically disclosed through preferred embodiments, exemplary embodiments, and optional features, those skilled in the art may make modifications and changes to the concepts disclosed herein, and such modifications and changes are considered to be within the scope of the invention as defined by the appended claims. The specific embodiments provided herein are examples of useful embodiments of the present invention, and it is obvious to those skilled in the art that the present invention can be implemented using a large number of variations of the devices, device components, and method steps set forth in this specification. It is obvious to those skilled in the art that the methods and devices used for the present method may include a large number of optional compositions and processing elements and steps.

[0478] As used herein and in the appended claims, the singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to "a cell" includes a plurality of such cells and equivalents thereof known to those skilled in the art. Likewise, the terms "one" (or "a"), "one or more", and "at least one" may be used interchangeably herein. Note also that the terms "comprising", "including", and "having" may be used interchangeably. The expression "any of claims XX-YY" (where XX and YY refer to claim numbers) is intended to provide multiple dependent claims in an alternative form and is interchangeable with the expression "any of claims XX-YY" in some embodiments.

[0479] When a group of substituents is disclosed herein, it is understood that all individual members of the group and all subgroups (including any isomers, enantiomers and diastereomers of group members) are disclosed separately. When Markush groups or other groupings are used herein, all individual members of the group and all possible combinations and subcombinations of the group are intended to be included in the disclosure separately. When compounds are described herein, such that (for example) a specific isomer, enantiomer or diastereomer of a compound is not specified in a formula or chemical name, the description is intended to include each isomer and enantiomer of the compound described alone or in any combination. In addition, unless otherwise indicated, all isotopic variants of compounds disclosed herein are intended to be included in the disclosure. For example, it is understood that any one or more hydrogens in the disclosed molecules can be replaced by deuterium or tritium. Isotopic variants of molecules are generally used as standards for molecular determination and standards for chemical and biological studies related to molecules or their uses. Methods for making such isotopic variants are known in the art. The specific names of compounds are intended to be exemplary, because it is known that a person of ordinary skill in the art can name the same compound differently.

[0480] Certain molecules disclosed herein may contain one or more ionizable groups [groups from which a proton can be removed (e.g., -COOH) or a proton can be added (e.g., amine) or a proton can be quaternized (e.g., amine)]. All possible ionic forms of such molecules and their salts are intended to be individually included in the disclosure herein. With respect to salts of the compounds herein, one of ordinary skill in the art can select from a variety of available counterions those available counterions suitable for preparing salts of the invention for a given application. In a particular application, the selection of a given anion or cation to prepare a salt may result in an increase or decrease in the solubility of the salt.

[0481] Each device, system, composition, or method described or illustrated herein can be used to implement the present invention unless otherwise indicated.

[0482] Whenever a range is given in the specification, such as a temperature range, a time range, or a composition or concentration range, all intermediate ranges and subranges, as well as all individual values ​​contained in the given range, are intended to be included in the disclosure. It should be understood that any subrange or range or individual value within a subrange contained in the description herein may be excluded from the claims herein.

[0483] All patents and publications mentioned in the specification are indicative of the skill level of those skilled in the art to which the invention belongs. The references cited herein are incorporated herein in their entirety to indicate the state of the art as of their publication or filing date, and this information may be used herein to exclude specific embodiments in the prior art, if desired. For example, when claiming a composition of matter, it is understood that compounds known and available in the art prior to the applicant's invention, including compounds for which sufficient disclosure is provided in the references cited herein, are not intended to be included in the composition of matter claims herein.

[0484] As used herein, "comprising" is synonymous with "including," "containing," or "characterized by," and is inclusive or open-ended and does not exclude additional, unlisted elements or method steps. As used herein, "consisting of" excludes any element, step, or ingredient not specified in the claim elements. As used herein, "consisting essentially of" does not exclude materials or steps that do not substantially affect the basic and novel characteristics of the claim. In each case herein, any of the terms "comprising," "consisting essentially of," and "consisting of" may be replaced with any of the other two terms. The inventions described schematically and appropriately herein may be implemented in the absence of any one or more elements, one or more limitations not specifically disclosed herein.

[0485] As used herein, "about" means within an acceptable error range for a particular value as determined by one of ordinary skill in the art, which is part of how that value is measured or determined, i.e., the limits of the measurement system. Unless otherwise indicated in an explicit description in the Examples, aspects, or elsewhere herein in connection with a particular assay, result, or implementation, "about" means within one standard deviation or up to or within 5%, whichever is greater, as practiced in the art.

[0486] Those of ordinary skill in the art will appreciate that, in addition to those specifically exemplified, starting materials, biomaterials, reagents, synthesis methods, purification methods, analytical methods, assay methods, and biomethods can be used in the practice of the present invention without resorting to excessive experimentation. All functional equivalents known in the art for any such materials and methods are intended to be included in the present invention. The terms and expressions employed are used only as descriptive terms rather than limiting terms, and the use of such terms and expressions is not intended to exclude any equivalents of the features shown and described or parts thereof, but it should be recognized that various modifications can be made within the scope of the claimed invention. Therefore, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, those skilled in the art may modify and change the concepts disclosed herein, and such modifications and changes are considered to be within the scope of the present invention as defined by the appended claims.

Claims

1. A composition, characterized in that Formula FX1: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> w-δ <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> x <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> z <h2 style=";text-align:left;direction:ltr"> S2(FX1); Where w is greater than or equal to 2 and less than or equal to 2.5; Where x is greater than 0 and less than or equal to 0.5; Where z is greater than or equal to 0 and less than or equal to 1; where δ is greater than or equal to 0 and less than w; and wherein the composition has an average net charge of zero.

2. The composition of claim 1, wherein: The composition is characterized by the formula FX2: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> 2+y-δ <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 1-2y <h2 style=";text-align:left;direction:ltr"> S2(FX2); Where y is greater than 0 and less than 0.5; Wherein δ is greater than or equal to 0 and less than 2+y.

3. The composition of claim 1, wherein: The composition is characterized by the formula FX3: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> 2+y <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 1-2y <h2 style=";text-align:left;direction:ltr"> S2(FX3); Where y is greater than 0 and less than 0.

5.

4. The composition of claim 2 or 3, wherein y is selected from the range of 0.1 to 0.

3.

5. The composition of claim 2 or 3, wherein y is selected from the range of 0.15 to 0.

25.

6. The composition of claim 2 or 3, wherein y is equal to 0.

2.

7. The composition of any one of claims 1 to 6, wherein the composition is prepared by mixing a first precursor comprising Li2FeS2 with a first precursor comprising Li 2.5 Al 0.5 S2 is formed by contacting and / or annealing a second precursor.

8. The composition of any one of claims 1-6, wherein the composition is formed by contacting and / or annealing a first precursor comprising Li2S with a second precursor comprising FeS and with a third precursor comprising Al2S3.

9. The composition according to any one of claims 1 to 8, characterized in that It is a solid solution.

10. The composition of claim 9, wherein the solid solution obeys Feigard's law regarding the lattice constant as a function of the relative concentration of Al or Fe.

11. The composition of any of the preceding claims, wherein the composition comprises only intrinsic vacancies and no extrinsic vacancies.

12. The composition of any of the preceding claims, wherein the composition and crystal structure of the composition corresponds to the composition and crystal structure of Li2FeS2 modified by replacing about 2n Fe ions in the crystal structure with n Al ions and n Li ions, wherein n is an integer greater than 0, and wherein the composition is characterized by the formula FX3: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> 2+y <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 1-2y <h2 style=";text-align:left;direction:ltr"> S2(FX3); Where y is greater than 0 and less than 0.

5.

13. The composition of any of the preceding claims, wherein the composition is characterized by the formula FX4: Li 2-ε Al 2y Fe 1-3y Q y S2(FX4); where: y is greater than or equal to 0 and less than or equal to 0.33; ε is greater than or equal to 0 and less than or equal to 2; and The composition comprises an extrinsic cation vacancy, wherein the extrinsic cation vacancy is represented as Q in the chemical formula.

14. The composition of any of the preceding claims, wherein the composition and the crystal structure of the composition correspond to that obtained by using 2n Al 3+ ions replace about 3n Fe in the crystal structure 2+ The composition and crystal structure of Li2FeS2 modified by ions; wherein n is an integer greater than 0.

15. The composition of any of the preceding claims, wherein the lattice constant or lattice volume of the composition has a linear correlation with x in FX1, the linear regression or R-squared value of the linear correlation being greater than 0.

91.

16. The composition of any of the preceding claims, wherein the lattice constant or lattice volume of the composition has a linear correlation with y in FX3, the linear regression or R-squared value of the linear correlation being greater than 0.91; wherein the composition is characterized by the formula FX3: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> 2+y <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 1-2y <h2 style=";text-align:left;direction:ltr"> S2(FX3); Where y is greater than 0 and less than 0.

5.

17. The composition of any of the preceding claims, wherein the composition is characterized by an atomic unit cell having the formula FX1, FX2, FX3, or FX4.

18. The composition of any one of the preceding claims, wherein: The lattice parameters of the composition are a, b, c and β; The lattice parameter a is selected from to scope; The lattice parameter b is selected from to scope; The lattice parameter c is selected from to the scope of The lattice parameter β is selected from the range of 89.98° to 90.34°.

19. The composition of any of the preceding claims, having a crystal structure characterized by a trigonal or monoclinic space group.

20. A composition as claimed in any one of the preceding claims, having a 1 / m A crystal structure characterized by a monoclinic space group.

21. The composition of any of the preceding claims, wherein the composition has a gravimetric energy density greater than or equal to 900 Wh / kg.

22. The composition of any of the preceding claims, capable of undergoing one or more multi-electron redox reactions and one or more anionic redox reactions.

23. The composition of any of the preceding claims, wherein the electrical conductivity of the composition is selected from 1.25×10 - 2 S cm -1 to 1.75×10 -2 S cm -1 range.

24. A device comprising a composition as claimed in any one of the preceding claims.

25. The device of claim 24 which is an electrochemical cell.

26. The device of claim 25, which is a rechargeable lithium battery.

27. The device of any one of claims 24-26 having a cathode comprising the composition of any one of claims 1-23.

28. The device of claim 27, wherein the cathode is characterized by an operating voltage selected from the group consisting of Li / Li + 1.7V to Li / Li + range of 3.0V.

29. An electrochemical system comprising: A cathode comprising a composition characterized by formula FX1: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> w-δ <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> x <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> z <h2 style=";text-align:left;direction:ltr"> S2(FX1); Where w is greater than or equal to 2 and less than or equal to 2.5; Where x is greater than 0 and less than or equal to 0.5; Where z is greater than 0 and less than or equal to 1; where δ is greater than or equal to 0 and less than w; and wherein the composition has an average net charge of zero.

30. The system of claim 29, wherein: The composition is characterized by the formula FX2: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> 2+y-δ <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 1-2y <h2 style=";text-align:left;direction:ltr"> S2(FX2); Where y is greater than 0 and less than 0.5; Wherein δ is greater than or equal to 0 and less than 2+y.

31. The system of claim 29, wherein: The composition is characterized by the formula FX3: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> 2+y <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 1-2y <h2 style=";text-align:left;direction:ltr"> S2(FX3); Where y is greater than 0 and less than 0.

5.

32. The system of claim 29, comprising an electrochemical cell.

33. The system of claim 29, comprising a lithium ion battery.

34. A cathode of an electrochemical system, the cathode comprising: Characterized by a composition of formula FX1: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> w-δ <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> x <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> z <h2 style=";text-align:left;direction:ltr"> S2(FX1); Where w is greater than or equal to 2 and less than or equal to 2.5; Where x is greater than 0 and less than or equal to 0.5; Where z is greater than 0 and less than or equal to 1; where δ is greater than or equal to 0 and less than w; and wherein the composition has an average net charge of zero.

35. The cathode of claim 34, wherein the composition is characterized by the formula FX2: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> 2+y-δ <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 1-2y <h2 style=";text-align:left;direction:ltr"> S2(FX2); Where y is greater than 0 and less than 0.5; Wherein δ is greater than or equal to 0 and less than 2+y.

36. The cathode of claim 34, wherein the composition is characterized by the formula FX3: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> 2+y <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 1-2y <h2 style=";text-align:left;direction:ltr"> S2(FX3); Where y is greater than 0 and less than 0.

5.

37. The cathode of claim 34, wherein the cathode is for use in an electrochemical cell.

38. The cathode of claim 34, wherein the cathode is for use in a lithium ion battery.

39. A method of preparing a composition, the method comprising: Provide a first amount of Li2FeS2 and a second amount of Li 2.5 Al 0.5 S2; The first amount of Li2FeS2 and the second amount of Li 2.5 Al 0.5 S2 combines to form a combination; and heating the combination to form a composition having a composition of lithium aluminum iron sulfide; Wherein, the lithium aluminum iron sulfide composition is characterized by formula FX1: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> w-δ <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> x <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> z <h2 style=";text-align:left;direction:ltr"> S2(FX1); Where w is greater than or equal to 2 and less than or equal to 2.5; Where x is greater than 0 and less than or equal to 0.5; Where z is greater than 0 and less than or equal to 1; where δ is greater than or equal to 0 and less than w; and The lithium aluminum iron sulfide composition has a net charge of zero.

40. The method of claim 39, wherein the composition is heated to about 900°C.

41. The method of claim 39 or 40, wherein the first amount and the second amount are such that Li2FeS2 and Li 2.5 Al 0.5 S2 is provided in a stoichiometric ratio.

42. The method of any one of claims 39-41, wherein the method comprises treating the first amount of Li2FeS2 and the second amount of Li 2.5 Al 0.5 S2 performs annealing.

43. The method of any one of claims 39-42, wherein the method further comprises mixing the first amount of Li2FeS2 and the second amount of Li 2.5 Al 0.5 S2 is sealed in a carbon-coated quartz ampoule.

44. A method of preparing a composition, the method comprising: providing a first amount of Li2S, a second amount of FeS, and a third amount of Al2S3; combining the first amount of Li2S, the second amount of FeS, and the third amount of Al2S3 to form a combination; and heating the combination to form a composition having a composition of lithium aluminum iron sulfide; Wherein, the lithium aluminum iron sulfide composition is characterized by formula FX1: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> w-δ <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> x <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> z <h2 style=";text-align:left;direction:ltr"> S2(FX1); Where w is greater than or equal to 2 and less than or equal to 2.5; Where x is greater than 0 and less than or equal to 0.5; Where z is greater than 0 and less than or equal to 1; where δ is greater than or equal to 0 and less than w; and The lithium aluminum iron sulfide composition has a net charge of zero.

45. The method of any one of claims 39-44, wherein the composition is heated at a rate of about 1 °C / minute.

46. ​​The method of any one of claims 39-45, wherein the composition is maintained at about 900°C for about 12 hours and then cooled to room temperature.

47. The method of any one of claims 39-46, wherein the providing operation comprises synthesizing the first amount of Li2FeS2 and the second amount of Li 2.5 Al 0.5 S2.

48. The method of claim 47, wherein the synthesizing operation comprises grinding stoichiometric Li2S, FeS, and Al2S3 powders.

49. The method of claim 48, wherein the synthesizing operation further comprises pressing the ground powder into at least one pellet.

50. The method of claim 49, wherein each of the at least one pellet has a mass of about 250 mg.

51. The method of claim 49 or 50, wherein the method further comprises sealing each of the at least one pellet in a carbon coated quartz ampoule.

52. The method of any one of claims 49-51, wherein each of the at least one pellet is heated to about 900°C.

53. The method of any one of claims 49-52, wherein each of the at least one pellet is heated at a rate of about 1 °C / minute.

54. The method of any one of claims 49-53, wherein each of the at least one pellet is maintained at about 900°C for about 12 hours and then cooled to room temperature.

55. A composition characterized in that Type FX7: Li 2-δ FeS u Yes v (FX7); Where u is greater than 0 and less than 2; Where v is greater than 0 and less than 2; where δ is greater than or equal to 0 and less than 2; and wherein the composition has an average net charge of zero.

56. The composition of claim 55, wherein: The composition is characterized by the formula FX8: Li 2-δ FeS 2-k Se(FX8); where k is greater than 0 and less than 2; and Where δ is greater than or equal to 0 and less than 2.

57. A composition characterized in that Formula FX9: The 2-ε Al x Fe r Q q S2(FX9); x is greater than or equal to 0 and less than or equal to 0.67; r is greater than or equal to 0 and less than or equal to 1; q is greater than or equal to 0 and less than or equal to 0.33; ε is greater than or equal to 0 and less than or equal to 2; The composition comprises an extrinsic cation vacancy, wherein the extrinsic cation vacancy is represented in the chemical formula as Q; and The net charge of the composition is zero.

58. The composition of claim 57, wherein: The composition is characterized by the formula FX10: Li 2-ε Al x Fe 1-1.5x Q 0.5x S2(FX10); where: x is greater than or equal to 0 and less than or equal to 0.67; ε is greater than or equal to 0 and less than or equal to 2; and The composition comprises an extrinsic cation vacancy, wherein the extrinsic cation vacancy is represented as Q in the chemical formula.

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