Fe2p composite materials and methods of making and using thereof

Abstract

Disclosed herein are Fe2P composite materials as well as methods of making and using thereof.

Description

[0001] Attorney Docket No. 10034-407W01

[0002] GT Ref.: 2025-046 Fe P Composite Materials and Methods of Making and Using Thereof

[0003] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims benefit of priority of U. S. Provisional Application No. 63 / 729,937, filed December 9, 2024, which is hereby incorporated herein by reference in its entirety.

[0004] BACKGROUND

[0005] Lithium-ion batteries are widely used in consumer electronics, electric vehicles, industrial energy-storage systems, and other applications due to their high energy density, long cycle life, and favorable performance characteristics. Atypical lithium-ion cell includes a negative electrode, a positive electrode, a separator, and an electrolyte that enables the reversible intercalation and de-intercalation of lithium ions during charge and discharge. Although lithium-ion technology has become well established, continued improvements in safety, energy density, power capability, lifespan, and manufacturing efficiency remain important. Conventional electrode materials, separators, electrolytes, and other cell components can suffer from limitations such as thermal instability, limited cycling durability, insufficient ionic conductivity, or mechanical degradation under demanding operating conditions. As the performance requirements for lithium-ion batteries increase, there is a need for improved components and materials that address these shortcomings and enable higher-performance, more reliable, and safer battery systems.

[0006] SUMMARY

[0007] Lithium (Li)-metal batteries (LMBs) are being developed to leverage their high energy densities, making them highly suitable for applications in electric vehicles (EVs) and portable electronics. Maintaining dense and planar Li metal anodes (LMAs) during charge and discharge cycles is key to commercializing LMBs. While three-dimensional (3D) scaffold / hosts for LMAs have ensured planar Li metal growth, the challenge has been their large volume and weight ratio. Attorney Docket No. 10034-407W01

[0008] GT Ref.: 2025-046

[0009] Described herein are composites that comprise Fe2P nanoparticles into a carbonbased scaffold / host, facilitating their conversion to Fe / Li3P during Li plating. This promotes rapid lateral diffusion and planar Li metal growth, while the lithiophobic carbon framework suppresses void formation, effectively preventing dendrite formation. Using this strategy, the Fe2P nanoparticles and carbon nanocomposite (Fe2P / C) host plated with 4 mAh·cm-2of Li, combined with a 2.5 mAh·cm-2LiFePO4(LFP) cathode, achieved a high capacity of 141 mAh·g-1at 1C and retained 89.5% of its initial capacity over 480 cycles. These findings highlight the importance of utilizing 3D nanostructures and combining lithiophilic and lithiophobic materials to improve the growth of Li metal. These composite can be used as Li host materials for various types of LMBs, including those based on liquid electrolytes, all- solid-state LMBs (ASSLMBs), and even anode-free LMBs. By addressing the urgent need for higher energy densities and safer battery technologies, this development aims to enhance the commercial viability and sustainability of LMBs for widespread use in EVs and beyond.

[0010] DESCRIPTION OF DRAWINGS

[0011] Figures 1A-1C. Material characterization of Fe2P / C nanocomposite. (1A) XRD pattern of Fe2P. XPS of (1B) Fe 2p, and (1C) P 2p.

[0012] Figure 2. Morphological characterization of Fe2P / C film on Cu foil. Cross-Sectional SEM analysis.

[0013] Figure 3. Elemental dispersion X-ray (EDX) analysis of Fe2P / C.

[0014] Figure 4. Comparative Li Plating Morphologies on Different Substrates. Digital photographs of 4 mAh·cm-2Li plated on Fe2P / C, Cu, and C substrates.

[0015] Figure 5. Morphological Analysis of Li Plating on Different Substrates. Cross-sectional SEM images of 0.5, 2, 4 mAh·cm-2Li plated on Fe2P / C, Cu, and C substrates.

[0016] Figures 6A-6D. Electrochemical Performance of Fe2P / C Nanocomposite in Half-Cell Configurations. (6A) Schematic drawing of the half-cell configuration and EIS spectra comparing the Rctof Fe2P / C nanocomposite and Cu foil. Half-cell cycling performance at (6B) 1 mAh·cm-2and 1 mA·cm-2, (6C) 1 mAh·cm-2and 5 mA·cm-2, and (6D) 3 mAh·cm-2a

[0017]

[0018] nd 1 mA·cm-2.

[0019] Figure 7. Cycling Performance of Fe2P / C Nanocomposite in Full-Cell

[0020] Configurations. Attorney Docket No. 10034-407W01

[0021] GT Ref.: 2025-046

[0022] DETAILED DESCRIPTION

[0023] The present invention can be understood more readily by reference to the following detailed description, examples, drawings, and claims, and their previous and following description. However, before the present articles, systems, and / or methods are disclosed and described, it is to be understood that this invention is not limited to the specific or exemplary aspects of articles, systems, and / or methods disclosed unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

[0024] The following description of the invention is provided as an enabling teaching of the invention in its best, currently known aspect. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects of the invention described herein, while still obtaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be obtained by selecting some of the features of the present invention without utilizing other features. Accordingly, those of ordinary skill in the pertinent art will recognize that many modifications and adaptations to the present invention are possible and may even be desirable in certain circumstances and are a part of the present invention. Thus, the following description is again provided as illustrative of the principles of the present invention and not in limitation thereof.

[0025] Definitions

[0026] It is appreciated that certain features of the disclosure, which are, for clarity, described in the context of separate aspects, can also be provided in combination in a single aspect. Conversely, various features of the disclosure, which are, for brevity, described in the context of a single aspect, can also be provided separately or in any suitable subcombination.

[0027] As used in the description and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0028] As used herein, the terms “optional” or “optionally” mean that the subsequently described event or circumstance may or may not occur and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0029] It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. As used in the specification and in the claims, the term “comprising” can include the aspects “consisting Attorney Docket No. 10034-407W01

[0030] GT Ref.: 2025-046

[0031] of’ and “consisting essentially of.” Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In this specification and in the claims, which follow, reference will be made to a number of terms that shall be defined herein.

[0032] For the terms "for example" and "such as," and grammatical equivalences thereof, the phrase "and without limitation" is understood to follow unless explicitly stated otherwise.

[0033] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values inclusive of the recited values may be used. Further, ranges can be expressed herein as from “about” one particular value and / or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and / or to the other particular value.

[0034] Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint and independently of the other endpoint. Unless stated otherwise, the term “about” means within 5% (e.g., within 2% or 1%) of the particular value modified by the term “about.”

[0035] Throughout this disclosure, various aspects of the invention can be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2. to 6, from 3 to 6, etc., as well as individual numbers within that range, for example, 1, 2, 2.7, 3, 4, 5, 5.3, 6 and any whole and partial increments therebetween. This applies regardless of the breadth of the range. Attorney Docket No. 10034-407W01

[0036] GT Ref.: 2025-046

[0037] It will be understood that, although the terms "first," "second," etc., may be used herein to describe various elements, components, regions, layers, and / or sections. These elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or a section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of example embodiments.

[0038] As used herein, the term "substantially" means that the subsequently described event or circumstance completely occurs or that the subsequently described event or circumstance generally, typically, or approximately occurs.

[0039] As used herein, the term “substantially,” in, for example, the context “substantially identical” or “substantially similar” refers to a method or a system, or a component that is at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% by similar to the method, system, or the component it is compared to.

[0040] “Nanoparticle”, as used herein, refers to any entity having a diameter of less than 1 micron (pm). Typically, particles have a greatest dimension (e.g., diameter) of 1000 nm or less. In some embodiments, particles have a diameter of 300 nm or less. In some embodiments, nanoparticles have a diameter of 200 nm or less. In some embodiments, nanoparticles have a diameter of 100 nm or less.

[0041] “Mean particle size,” as used herein, generally refers to the statistical mean particle size (diameter) of the particles in a population of particles. The diameter of an essentially spherical particle may be referred to as the physical or hydrodynamic diameter. The diameter of a non-spherical particle may refer preferentially to the hydrodynamic diameter. As used herein, the diameter of a non-spherical particle may refer to the largest linear distance between two points on the surface of the particle. Mean particle size can be measured using methods known in the art, such as dynamic light scattering or electron microscopy.

[0042] “Monodisperse” and “homogeneous size distribution,” are used interchangeably herein and describe a plurality of liposomal nanoparticles or microparticles where the particles have the same or nearly the same diameter or aerodynamic diameter. As used Attorney Docket No. 10034-407W01

[0043] GT Ref.: 2025-046

[0044] herein, a monodisperse distribution refers to particle distributions in which 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 86, 88, 89, 90, 91, 92, 93, 94, 95% or greater of the distribution lies within 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, or 10% of the mass median diameter or aerodynamic diameter.

[0045] While aspects of the present invention can be described and claimed in a particular statutory class, such as the system statutory class, this is for convenience only, and one of ordinary skill in the art will understand that each aspect of the present invention can be described and claimed in any statutory class. Unless otherwise expressly stated, it is in no way intended that any method or aspect set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not specifically state in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that an order be inferred in any respect. This holds for any possible non-express basis for interpretation, including matters of logic with respect to arrangement of steps or operational flow, plain meaning derived from grammatical organization or punctuation, or the number or type of aspects described in the specification.

[0046] The present invention may be understood more readily by reference to the following detailed description of various aspects of the invention and the examples included therein and to the Figures and their previous and following description.

[0047] Provided herein are composite materials comprising a population of Fe2P particles dispersed in a conductive carbon matrix.

[0048] In some embodiments, the Fe2P particles comprise Fe2P nanoparticles.

[0049] In some embodiments, the population of Fe2P particles exhibits a monodisperse particle size distribution.

[0050] In some embodiments, the population of Fe2P particles comprise Fe2P nanoparticles. In some embodiments, the population of Fe2P particles exhibit an average particle size, as measured by scanning electron microscopy (SEM), of at least 5 nm (e.g., at least 10 nm, at least 15 nm, at least 20 nm, at least 25 nm, at least 30 nm, at least 35 nm, at least 40 nm, at least 45 nm, at least 50 nm, at least 55 nm, at least 60 nm, at least 65 nm, at least 70 nm, at least 75 nm, at least 80 nm, at least 85 nm, at least 90 nm, at least 95 nm, at least 100 nm, at least 150 nm, at least 200 nm, at least 250 nm, at least 300 nm, at least 350 nm, at least 400 nm, at least 450 nm, at least 500 nm, at least 550 nm, at least 600 nm, at least 650 nm, at least 700 nm, at least 750 nm, at least 800 nm, at least 850 nm, at least 900 nm, or at least Attorney Docket No. 10034-407W01

[0051] GT Ref.: 2025-046

[0052] 950 nm). In some embodiments, the population of Fe2P particles exhibit an average particle size, as measured by scanning electron microscopy (SEM), of less than 1 micron (e.g., 950 nm or less, 900 nm or less, 850 nm or less, 800 nm or less, 750 nm or less, 700 nm or less, 650 nm or less, 600 nm or less, 550 nm or less, 500 nm or less, 450 nm or less, 400 nm or less, 350 nm or less, 300 nm or less, 250 nm or less, 200 nm or less, 150 nm or less, 100 nm or less, 95 nm or less, 90 nm or less, 85 nm or less, 80 nm or less, 75 nm or less, 70 nm or less, 65 nm or less, 60 nm or less, 55 nm or less, 50 nm or less, 45 nm or less, 40 nm or less, 35 nm or less, 30 nm or less, 25 nm or less, 20 nm or less, 15 nm or less, or 10 nm or less).

[0053] The population of Fed’ particles exhibit an average particle size ranging from any of the minimum values described above to any of the maximum values described above. For example, population of Fed* particles can exhibit an average particle size, as measured by SEM, of from 5 nm to less than 1 micron (e.g., from 5 nm to 500 nm, from 5 nm to 250 nm, from 5 nm to 150 nm, from 5 nm to 100 nm, or from 5 nm to 80 nm, from 25 nm to 500 nm, from 25 nm to 250 nm, from 25 nm to 150 nm, from 25 nm to 100 nm, or from 25 nm to 80 nm, from 50 nm to 500 nm, from 50 nm to 250 nm, from 50 nm to 150 nm, from 50 nm to 100 nm, or from 50 nm to 80 nm).

[0054] The conductive carbon matrix can comprise any suitable material or combination of carbonaceous materials. By way of example, in some embodiments, the conductive carbon matrix can comprise graphite, carbon fibers, carbon black (e.g., amorphous carbon black), mesoporous carbon, microporous carbon, carbon nanotubes (including single-walled and multi-walled nanotubes), carbon nanofibers, carbon nanospheres, carbon onions, graphene and graphene-derived materials (such as reduced graphene oxide), hard carbon, soft carbon, carbon aerogels, carbon xerogels, pitch-derived carbon, and coke- derived carbon. In certain embodiments, the conductive carbon matrix comprises graphite, carbon fibers, amorphous carbon black, or a combination thereof. These materials may be used individually or in combination to form conductive matrices that facilitate electron transport, enhance mechanical robustness, and improve overall electrochemical performance in lithium-ion battery components.

[0055] In some embodiments, the conductive carbon matrix is prepared by a process that comprises heat treating a blend of carbon black and Fel’Ch under conditions effective to afford carbothermal and / or hydrogen reduction of FePCX resulting in the formation of Fe2P within the reduced carbon matrix. In some embodiments, the heat treatment comprises heating the blend of carbon black and FePO4at a temperature of from 750°C to 1,250°C. In Attorney Docket No. 10034-407W01

[0056] GT Ref.: 2025-046

[0057] some embodiments, the heat treatment comprises heating the blend of carbon black and FePO4under a hydrogen (H2) / argon (Ar) atmosphere.

[0058] In some embodiments, the composite material further comprises a binder. Examples of binders known to one of ordinary skill which are chemically stable in the potential window of use of the cell may include thermoplastics and thermosetting resins. For example, suitable binders may include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), Polyvinylidene fluoride (PVDF), styrene butadiene rubber, a tetrafluoroethylene hexafluoro ethylenic copolymer, a tetrafluoroethylene hexafluoropropylene copolymer (FEP), a

[0059] tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PF A), ethylene¬ tetrafluoroethylene copolymer (ETFE resin), polychlorotrifluoroethylene resin (PCTFE), a propylene- tetrafluoroethylene copolymer, an ethylene-chlorotrifluoroethylene copolymer (ECTFE) and an ethylene-acrylic acid copolymer. These binders may be used independently, or mixtures may be used. In certain embodiments, the binder comprises PVDF.

[0060] Also described herein are electrodes (e.g., anodes) comprising the composites described herein disposed upon a current collector. In some examples, the current collector comprises a Cu current collector.

[0061] Also described herein are electrochemical cells (e.g., batteries, such as Li ion batteries) comprising the electrodes described herein.

[0062] In some embodiments, the electrochemical cell comprises an anode comprising an electrode described above; a cathode comprising a cathode active material; and an electrolyte disposed between and in electrochemical contact with the anode and the cathode.

[0063] In some embodiments, the cathode comprises a carbon electrode and the cathode active material disposed on and / or dispersed with the carbon electrode.

[0064] In some embodiments, the cathode comprises a current collector, a coating comprising a conductive material disposed on the current collector, and the cathode active material disposed on the coating. In some embodiments, the coating comprises conductive carbon, graphite, or a mixture thereof.

[0065] In some embodiments, the cathode active material comprises a lithium insertion transition metal oxide, phosphate, or sulfate. In certain embodiments, the cathode active material comprises LiCoO2; spinel LiMn2O4; chromium-doped spinel lithium manganese oxides; layered LiMnO2; LiNiO2; LiNixCo1-xO2, wherein x is 0<x<1; LiNi1-x-yCoxMnyO2, Attorney Docket No. 10034-407W01

[0066] GT Ref.: 2025-046

[0067] wherein x is 0<x<1 and y is 0<y<1; vanadium oxides; LiFePO4; LiMnPO4; LiVPO4;

[0068] LiFeTi(SO4)3, or combinations thereof.

[0069] In some embodiments, the cathode comprises a LiFePO₄ electrode.

[0070] The electrolyte composition can vary. Examples of suitable electrolytes include, but are not limited to, tetrabutylammonium salts (e.g., TBANO3, TBACIO4, etc.), nitrate salts, and lithium salts (e.g., LiPF6, LiClO4, LiAsF6, LiBF4, LiN(CF3SO2)2(LiTFSI), Li(CF3SO3), LiN(C2F5SO2)2, etc.).

[0071] In some embodiments, the electrolyte comprises a nonaqueous electrolyte solution. Examples of such electrolytes include solutions comprising a salt and one or more organic solvents such as cyclic carbonates, chain carbonates, cyclic esters, cyclic ethers and chain ethers. Examples of a cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate. Examples of a chain carbonate includes dimethyl carbonate, diethyl carbonate and methylethyl carbonate. Examples of a cyclic ester carbonate include gamma butyrolactone and gamma valerolactone. Examples of a cyclic ether include tetrahydro furan and 2-methyltetrahydrofuran. Examples of a chain ether include dimethoxyethane and ethyleneglycol dimethyl ether. In some examples, the solvent can comprise DMSO. In some examples, the solvent can comprise DMF. In some examples, the solvent may be a nitrile system solvent such as acetonitrile. In other embodiments, the electrolyte comprises an aqueous electrolyte (e.g., a water-in-salt electrolyte). In some examples, the solvent can comprise an ionic liquid. Examples of ionic liquids include any of cations such as imidazolium cation, piperidinium cation, pyrrolidinium cation and ammonium cation and any of anions such as bis(trifluoromethanesulfonyl)imide anion, bis(fluorosulfonyl)imide anion, tetrafluoroborate anion and hexafluorophosphate anion. In one example, the solvent is an ionic liquid such as N-methyl-N-propylpiperidiniumbis(trifluoromethylsulfonyl)imide (PP13TFSI).

[0072] In some embodiments, the battery further comprises a separator disposed between the anode and cathode. In some examples, the separator can comprise a membrane separator. Such membrane separators can comprise a gel, a polymer, a ceramic, a composite of a polymer and a ceramic, or a combination thereof. In some embodiments, the membrane separator comprises a ceramic Li-ion conducting membrane.

[0073] In some embodiments, the anode, the cathode, and the electrolyte are disposed within a housing. The housing can be formed from any suitable material, such as stainless Attorney Docket No. 10034-407W01

[0074] GT Ref.: 2025-046

[0075] steel, a polymer, a fluoropolymer such as polytetrafluoroethylene (PTFE), quartz, or a combination thereof.

[0076] In some embodiments, the Fe2P particles facilitate planar Li metal growth by converting into a Li3P solid electrolyte interface (SEI) layer with lithiophilic Fe nanoparticles.

[0077] In some embodiments, the Fe2P particles promote dendrite-free Li growth at the anode.

[0078] In some embodiments, the Fe2P particles enhance cyclic stability of the electrochemical cell.

[0079] Having generally described this invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified.

[0080] EXAMPLES

[0081] The invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of non- critical parameters which can be changed or modified to yield essentially tire same results.

[0082] Example 1. Fe2P / Carbon Anode: Advancing Lithium Metal Stability and Energy Density with Lithiophilic-Lithiophobic Structures

[0083] Summary

[0084] Lithium (Li)-metal batteries (LMBs) are highly valued for their exceptional energy densities, making them ideal for electric vehicles (E Vs) and portable electronics. However, achieving long cyclic stability requires controlling the Li nucleation and growth of the Limetai anode (LMA) in a planar and dense manner. To address this, we have pioneered the use of the Fe2P nanoparticles and carbon nanocomposite (Fe2P / C) anode host. Fe2P facilitates planar Li metal growth by converting into a Li3P solid electrolyte interface (SEI) layer with lithiophilic Fe nanoparticles, enabling rapid lateral diffusion at both the Li / SEI and Li / Fe interfaces. This approach promotes dendrite-free Li growth, enhancing cyclic stability. Additionally, FePO4, a precursor to Fe2P, is cost-effective and can be recycled from mass-produced LiFePO4(LFP) cathodes. Attorney Docket No. 10034-407W01

[0085] GT Ref.: 2025-046

[0086] Our strategy involves synthesizing Fe₂P / C, analyzing Li plating morphology, evaluating the electrochemical performance of Fe₂P / C anode hosts, and assessing the electrochemical performance of LMBs. The desired Fe₂P / C was fabricated by simply mixing FePO4 and carbon black followed by heat treatment. Li plating on Fe₂P / C results in smooth, dense growth, contrasting with the rough, dendritic growth on carbon and copper (Cu) substrates. The Fe₂P / C promotes planar Li formation, enabling stable cycling. In half¬ cell configurations, the Fe₂P / C exhibits significantly lower charge-transfer resistance and prolonged cycle life compared to Cu and carbon electrodes. The Fe₂P / C nanocomposite cell demonstrates extended cycle life and high Coulombic efficiency (C. E.) under various current densities and capacities.

[0087] In full-cell configurations with -2.5 mAh- cm-2LFP cathodes and 4 mAh·cm-2of Li, the Fe₂P / C full cell exhibits stable cycling over 480 cycles, retaining 89.5% of its initial capacity, significantly outperforming the Cu counterpart. This demonstrates the Fe2P / C nanocomposite's potential for advancing LMB technologies. In conclusion, the Fe2P / C nanocomposite shows enhanced cycling stability and efficiency, making it a promising candidate for high-performance LMBs.

[0088] Introduction

[0089] LMBs are highly valued for their exceptional energy densities, making them ideal for EVs and portable electronics. The stability of the LMA is crucial for their longevity, significantly influenced by the formation of a robust SEI and efficient nucleation and growth mechanisms. Both chemical and mechanical approaches have been applied to address these factors. The development of new electrolytes, particularly localized high- concentration electrolytes, has significantly extended the cycle life of LMBs. Mechanically, applying a pressure of 1,200 kPa has been shown to effectively reduce Li-metal porosity, thus extending the cycle life of LMBs, though applying such pressure in commercial-format cells poses practical challenges.

[0090] Despite significant advancements in performance, fundamental approaches to controlling Li nucleation and growth are essential for further enhancing the cyclic stability of LMBs under high current densities. In crystal growth theory, planar and dense growth of Li requires rapid lateral Li-ion diffusion. This necessitates fast Li diffusion at both the Li / SEI and Li -ion / Li -nucleates interfaces. The presence of SEI layers such as LiF, Li₂C₂O₄, Li₃N, and Li₃P on the surface where Li nucleates ensures rapid Li-ion movement due to their high ion conductivity, chemical stability, and compatibility with Li metal. This Attorney Docket No. 10034-407W01

[0091] GT Ref.: 2025-046

[0092] promotes planar growth of Li metal, minimizes porosity, and enhances cyclic stability. Furthermore, using lithiophilic materials (e.g., Ag, Au, Fe) at the Li nucleation sites enables rapid Li diffusion at both the Li / SEI and Li-ion / Li-seed interfaces.

[0093] To further enhance the energy and power densities of rechargeable batteries, we have explored the use of a Fe2P / C anode host. The Fe2P / C promotes the immediate formation of a highly ionically conductive Li₃P SEI and provides lithiophilic nucleation sites with Fe NPs within a lithiophobic carbon framework. LiaP and Fe nanoparticles (Li₃P / Fe) enable swift Li diffusion at the Li / SEI and Li / Fe interfaces. The lithiophobic carbon helps to focus Li on Li₃P / Fe during plating and aids in more effective stripping. Our research demonstrates the successful conversion of Fe?!’ to Fe / LijP, allowing for dense Li layer growth, minimizing substrate porosity, and enhancing cyclic stability compared to Cu substrates or pure carbon hosts. Additionally, FePO4, a precursor to Fe2P, is relatively inexpensive due to the abundance and low cost of raw materials such as iron and phosphorus. LFP, currently used as a mass-produced cathode material, can be efficiently recycled to create cost-effective and sustainable anode materials.

[0094] In summary, our approach integrates the Fe2P / C nanocomposite host into LMBs, ensuring structural integrity during Li plating and stripping processes. The successful adoption of Fe2P / C composites has the potential to revolutionize LMB manufacturing, enhancing battery performance and advancing LMB technology for various applications.

[0095] To achieve our objectives, we focus on four strategic goals:

[0096] 1. Synthesis and characterization of Fe₂P / C composites

[0097] 2. Analyzing Li plating morphology

[0098] 3. Evaluating the electrochemical performance of Fe2P / C nanocomposite anode hosts

[0099] 4. Assessing the electrochemical performance of LMBs

[0100] Success in these areas could propel Fe₂P / C composites to transform LMB manufacturing, enhancing battery performance and advancing Li battery technology towards greater viability and sustainability for widespread application.

[0101] Technical Approach

[0102] As described herein, we aim to promote planar Li metal growth using a Fe₂P / C nanocomposite anode host. Our goal is to build an anode host that enhances Li nucleation and growth by initially converting Li₃P on Fe nanostructures and providing rapid lateral Attorney Docket No. 10034-407W01

[0103] GT Ref.: 2025-046

[0104] diffusion at both the Li / SEI and Li / substrate interfaces, serving as a stable and effective LMA host.

[0105] Synthesis and characterization of Fe2P / C Composites

[0106] To synthesize Fe₂P / C, commercial FePO4 and carbon black underwent a heat treatment at 950°C in a hydrogen (H₂) / argon (Ar) atmosphere, leading to the carbothermal and / or hydrogen reduction of FePO₄, resulting in the formation of Fe₂P within the reduced carbon matrix. X-ray diffraction (XRD) analysis confirmed the formation of Fe2P as its major peaks match those of reference data (ICSD-70115) (Figure 1A). The round peak at -25 degrees is due to the presence of amorphous carbon black. Additionally, X-ray photoelectron spectroscopy (XPS) analysis further verified the presence of Fe2P. In Fe 2p spectra, the two peaks at 707.2eV and 720. leV are associated with metal phosphide bond from Fe2P, and the other two at 710.6eV and 724.2eV are indicative of Fe3+species due to surface-oxidation of Fe₂P particles in air (Figure 1B). In P 2p spectra, the two peaks at 130.2eV and 133.7eV are assigned to metal phosphide bond from Fe2P and phosphate bond from surface-oxidized Fe2P species, respectively (Figure 1C).

[0107] Following this synthesis, the resulting Fe₂P / C was mixed with polyvinylidene fluoride (PVDF) to create a homogeneous slurry, which was then coated as a thin film onto a Cu current collector, forming the Li metal anode host. Cross-sectional scanning electron microscopy (SEM) analysis revealed a uniform Fe2P / C film of approximately 5 μm thickness on the Cu foil, with Fe₂P particles well dispersed in the range of 80–150 μm (Figure 2). EDX analysis of the nano-sized Fe particles showed uniform dispersion of P, confirming the successful dispersion of Fe2P (Figure 3).

[0108] This comprehensive characterization demonstrates that Fe2P was successfully synthesized and uniformly dispersed within the carbon matrix, laying a solid foundation for its application as an effective electrode material in LMBs.

[0109] Morphological Analysis of Li Plating

[0110] To investigate the Li plating mechanism, we plated various amounts (0.5, 1, 4 mAh·cm-2) of Li onto Fe2P / C host, bare carbon host, and Cu film substrates. Observing the plating with 4 mAh·cm-2of Li, distinct differences were noted among the substrates.

[0111] Fe2P / C exhibited exceptionally smooth and dense Li plating, whereas bare carbon showed non-uniform and rough Li growth, and Cu displayed a similarly rough surface (Figure 4).

[0112] Detailed examination through SEM revealed that Li plating on bare Cu resulted in progressively uneven and dendritic growth, particularly evident when plating 4 mAh·cm-2, Attorney Docket No. 10034-407W01

[0113] GT Ref.: 2025-046

[0114] forming a sponge-like porous structure with a thickness measuring 33.3 ± 5.2 pm (Figure 5). In contrast, Li plating on carbon exhibited sharp, dendritic growth, forming small pores and increasing to a thickness of 59.3 ± 2.3 μm when plated with 4 mAh·cm-2(Figure 5). This highlighted carbon's lithiophobic nature, promoting high-surface-area dendritic Li growth that is thick, porous, and sharp-edged.

[0115] In contrast, plating Li on Fe2P / C resulted in dense growth, with a thickness of 21.4 ± 3.6 pm when plated with 4 mAh-cm”2(Figure 5). Despite the initial presence of 5 μm Fe₂P / C, the formation of dense Li layers suggests efficient Li accumulation facilitated by Fe2P to Fe / Li₃P conversion, enabling the growth of dense Li seeds.

[0116] These findings underscore the role of Fe2P / C as a catalyst for smooth and dense Li plating, contrasting with the rough and dendritic growth observed on carbon and Cu substrates. This mechanism highlights Fe₂P / C's potential in enhancing the stability and efficiency of LMBs, offering insights into improving electrode materials for advanced energy storage applications.

[0117] Electrochemical Performance of Fe2P Nanocomposite Anode Host To evaluate the performance of the Fe₂P / C nanocomposite host, we conducted tests in half-cell configurations, focusing on Li nucleation behavior and subsequent deposition morphology. The half-cell configurations used were LilICu, Lillcarbon, and Li||Fe₂P / C nanocomposite. We assessed the cycling performance under various current densities and capacities: 1 mAh·cm-2at 1 mA·cm-2, 1 mAh-cm"2at 5 mA-cm”2, and 3 mAh-cm”2at 1 mA-cm"2. For the electrolyte, we used a 1 M Li bis(trifluoromethanesulfonyl)imide (LiTFSI) salt solution in a dimethoxyethane (DME) / l,3-dioxolane (DOL) (1:1, v / v) solvent with 2 wt. % Li nitrate (LiNO₃) additive.

[0118] The charge-transfer resistances (Ret), indicated by the diameter of the semicircle in electrochemical impedance spectroscopy (EIS) spectra, were significantly lower for Fe₂P / C nanocomposite-based electrodes compared to metal Cu-foil-based electrodes (Figure 6A). 'This reduction in Rctis attributed to the 3D structure of the Fe₂P / C nanocomposite, which offers a larger electrochemical surface area (ECSA) than planar metal foil.

[0119] Remarkably, at 1 mAh·cm-2and 1 mA·cm-2, the Fe2P / C nanocomposite cell exhibited a prolonged cycle life of over 430 cycles with a C. E. greater than 98.5%, whereas the carbon cell and Cu cell failed prematurely at around 150thand 120thcycle, respectively (Figure 6B). To test performance at higher current densities, we examined 1 mAh-cm"2at 5 mA·cm-2. Here, the Fe2P / C nanocomposite cell demonstrated an extended cycle life of Attorney Docket No. 10034-407W01

[0120] GT Ref.: 2025-046

[0121] over 650 cycles with a C. E. exceeding 99.9%, while the carbon cell and Cu cell failed at 276thand 312thcycle, respectively (Figure 6C). These results indicate that our strategy of converting Fe?. P nanostructures into a Li₃P SEI layer with lithiophilic Fe nanoparticles enables rapid lateral diffusion at both the Li / SEI and Li / Fe interfaces, facilitating efficient Li plating and stripping even at high current densities.

[0122] Furthermore, to observe changes with high Li capacity, we tested at 3 mAh- cm"2and 1 mA- cm”2. The Fe?. P / C nanocomposite cell exhibited a prolonged cycle life of over 130 cycles with a C. E. greater than 98.2%, while the Cu cell failed prematurely at 21stcycle (Figure 6D). This demonstrates that the Fe2P / C nanocomposite effectively supports dense Li plating without dendrite formation, maintaining high performance even with significant Li movement over multiple cycles.

[0123] In summary, the Fe2P / C nanocomposite host shows superior performance in LMBs, providing enhanced cycle life and C. E. under various operating conditions. Its 3D structure and the conversion of FezP to a Li₃P-rich SEI layer with lithiophilic Fe nanoparticles enable rapid Li-ion diffusion and stable, dendrite-free Li deposition, making it a promising candidate for high-performance LMBs.

[0124] Assessing the electrochemical performance of the LMBs

[0125] Moving to full-cell configurations with ~2.5 mAh·cm-2LFP cathodes, we deposited 4 mAh- cm”2of Li on Fe2P / C nanocomposite and Cu substrates, achieving an N / P ratio of -1.6 (Figure 7). The Fe₂P / C nanocomposite full cell exhibited stable cycling over 480 cycles, retaining 89.5% of its initial capacity. This significantly outperformed the Cu counterpart, which degraded rapidly within 200 cycles. The rapid decay in the Cu substrate is attributed to cyclic Li plating and stripping, which induces porous and dendritic Li formation, leading to unstable cyclic stability. In contrast, the Fe₂P / C nanocomposite promoted planar Li formation, resulting in dense growth and enabling stable cycling.

[0126] In conclusion, the Fe2P / C nanocomposite demonstrated enhanced cycling stability and efficiency in both half-cell and full-cell configurations, showcasing its potential for advancing LMB technologies, particularly under high-rate and lean-electrolyte conditions.

[0127] Impacts

[0128] The development and implementation of the Fe₂P / C nanocomposite anode host has significant broader impacts on the LMB industry. This anode host is not only suitable for operation in liquid electrolytes but also shows great potential for use in polymer electrolytes and inorganic electrolytes, making it highly applicable to all-solid-state LMBs (ASSLMBs). Attorney Docket No. 10034-407W01

[0129] GT Ref.: 2025-046

[0130] Moreover, this technology can be extended to anode-free ASSLMBs, further enhancing its versatility and utility in advanced battery technologies.

[0131] Additionally, by utilizing recycled LFP from spent batteries as a precursor for Fe₂P, this approach effectively reduces the overall hi usage in the production of new batteries. This recycling strategy offers a more sustainable and economical solution for the battery industry by minimizing waste and lowering raw material costs. Consequently, the adoption of the Fe₂P / C nanocomposite anode host not only improves the performance and stability of LMBs across various electrolyte systems but also provides a cost-effective and environmentally friendly pathway for the future of high-energy-density batteries.

[0132] In summary, the broader impacts of this research lie in its potential to revolutionize battery manufacturing processes, reduce production costs, and contribute to the sustainability of the battery industry. By addressing critical challenges in energy density and safety, this innovation paves the way for more viable and widespread applications of LMBs, particularly in EVs and other high-demand electronic devices.

[0133] The compositions and methods of the appended claims are not limited in scope by the specific compositions and methods described herein, which are intended as illustrations of a few aspects of the claims. Any compositions and methods that are functionally equivalent are intended to fall within the scope of the claims. Various modifications of the compositions and methods in addition to those shown and described herein are intended to fall within the scope of the appended claims. Further, while only certain representative compounds, components, compositions, and method steps disclosed herein are specifically described, other combinations of the compounds, components, compositions, and method steps also are intended to fall within the scope of the appended claims, even if not specifically recited. Thus, a combination of steps, elements, components, or constituents may be explicitly mentioned herein or less, however, other combinations of steps, elements, components, and constituents are included, even though not explicitly stated.

[0134] The term “comprising” and variations thereof as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms. Although the terms “comprising” and “including” have been used herein to describe various embodiments, the terms “consisting essentially of’ and “consisting of’ can be used in place of “comprising” and “including” to provide for more specific embodiments of the invention and are also disclosed. Other than where noted, all numbers expressing geometries, Attorney Docket No. 10034-407W01

[0135] GT Ref.: 2025-046

[0136] dimensions, and so forth used in the specification and claims are to be understood at the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, to be construed in light of the number of significant digits and ordinary rounding approaches.

[0137] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of skill in the art to which the disclosed invention belongs. Publications cited herein and the materials for which they are cited are specifically incorporated by reference.

Claims

Attorney Docket No. 10034-407W01GT Ref.: 2025-046WHAT IS CLAIMED IS:

1. A composite material comprising a population of Fe₂P particles dispersed in a conductive carbon matrix.

2. The composite material of claim 1, wherein theparticles comprise Fe₂P nanoparticles.

3. The composite material of any one of claims 1-2, wherein the population of Fe2P particles exhibits a monodisperse particle size distribution.

4. The composite material of any one of claims 1-3, wherein the population of Fe2P particles exhibits an average particle size of from 50 nm to 500 nm, as measured by electron microscopy.

5. The composite material of any one of claims 1-4, wherein the conductive carbon matrix comprises graphite, carbon fibers, amorphous carbon black, or a combination thereof.

6. The composite material of any one of claims 1-5, wherein the composite material is prepared by a process that comprises heat treating a blend of carbon black and FePCU under conditions effective to afford carbothermal and / or hydrogen reduction of FePO₄, resulting in the formation of Fe2P within the reduced carbon matrix.

7. The composite material of claim 6, wherein the heat treatment comprises heating the blend of carbon black and FePO₄ at a temperature of from 750°C to l,250°C.

8. The composite material of any one of claims 6-7, wherein the heat treatment comprises heating the blend of carbon black and FePO₄ under a hydrogen (H2) / argon (Ar) atmosphere.Attorney Docket No. 10034-407W01GT Ref.: 2025-0469. The composite material of any one of claims 1-8, wherein the composite material further comprises a binder.

10. The composite material of claim 9, wherein the binder comprises polyethylene, polypropylene, polytetrafluoroethylene (PTFE), Polyvinylidene fluoride (PVDF), styrene butadiene rubber, a tetrafluoroethylene hexafluoro ethylenic copolymer, a tetrafluoroethylene hexafluoropropylene copolymer (FEP), a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE resin),polychlorotriflu oroethylene resin (PCTFE), a propylene- tetrafluoroethylene copolymer, an ethylene-chlorotrifluoroethylene copolymer (ECTFE), an ethylene- acrylic acid copolymer, or a blend thereof.

11. The composite material of any of claims 9 or 10, wherein the binder comprises P VDF.

12. An electrode comprising the composite defined by any one of claims 1-11 disposed upon a current collector.

13. The electrode of claim 12, wherein the current collector comprises a Cu current collector.

14. The electrode of claim 12 or 13, wherein the electrode comprises an anode.

15. An electrochemical cell comprising the electrode defined by any one of claims 12-14.

16. The electrochemical cell of claim 15, wherein the electrochemical cell comprises a battery.

17. The electrochemical cell of claim 16, wherein the electrochemical cell comprises a lithium-ion battery.Attorney Docket No. 10034-407W01GT Ref.: 2025-04618. The electrochemical cell of any one of claims 15-17, wherein the electrochemical cell comprisesan anode comprising the electrode defined by any one of claims 12-14;a cathode comprising a cathode active material; andan electrolyte disposed between and in electrochemical contact with the anode and the cathode.

19. The electrochemical cell of claim 18, wherein the cathode comprises a carbon electrode and the cathode active material disposed on and / or dispersed with the carbon electrode.

20. The electrochemical cell of claim 18, wherein the cathode comprises a current collector, a coating comprising a conductive material disposed on the current collector, and the cathode active material disposed on the coating.

21. The electrochemical cell of claim 20, wherein the coating comprises conductive carbon, graphite, or a mixture thereof.

22. The electrochemical cell of any one of claims 18-21, wherein the cathode active material comprises a lithium insertion transition metal oxide, phosphate, or sulfate.

23. The electrochemical cell of any one of claims 18-22, wherein the cathode active material comprises LiCoO₂; spinel LiMn₂O₄; chromi um-doped spinel lithium manganese oxides; layered LiMnO₂; LiNiCh; LiNixCo1-xO₂, wherein x is 0<x<l; LiNi1-x-yCoxMnyO₂, wherein x is 0<x<l and y is 0<y<l; vanadium oxides; LiFePO4; LiMnPO₄; LiVPO₄; LiFeTi(SO₄)₃, or combinations thereof.

24. The electrochemical cell of any one of claims 18-23, wherein the cathode comprises a LiFePO₄ electrode.Attorney Docket No. 10034-407W01GT Ref.: 2025-04625. The electrochemical cell of any one of claims 18-24, wherein the cell further comprises a separator disposed between the anode and cathode.

26. The electrochemical cell of claim 25, wherein the separator comprises membrane separator.

27. The electrochemical cell of claim 26, wherein the membrane separator comprises a gel, a polymer, a ceramic, a composite of a polymer and a ceramic, or a combination thereof.

28. The electrochemical cell of any one of claims 25-27, wherein the separator is Li permeable.

29. The electrochemical cell of any one of claims 18-28, wherein the electrolyte comprises a solid-state electrolyte.

30. The electrochemical cell of any one of claims 18-28, wherein the electrolyte comprises a nonaqueous electrolyte solution.

31. The electrochemical cell of any one of claims 18-30, wherein the Fe₂P particles facilitate planar Li metal growth by converting into a Li₃P solid electrolyte interface (SEI) layer with lithiophilic Fe nanoparticles.

32. The electrochemical cell of any one of claims 18-31, wherein the Fe₂P particles promote dendrite-free Li growth at the anode.

33. The electrochemical cell of any one of claims 18-32, wherein the Fe₂P particles enhance cyclic stability of the electrochemical cell.

Images