Processes for preparing lithium transition metal phosphate cathode materials

Abstract

The present disclosure relates to a method for forming lithium transition metal phosphate and fluorophosphate materials in a conductive carbon matrix. The disclosed methods are advantageous for using inexpensive reactants and can mitigate the formation of impurities during synthesis, thereby providing a more homogeneous product and a cathode material having an improved tap density compared to conventional lithium transition metal phosphates. The lithium transition metal phosphate and fluorophosphate materials produced by the disclosed methods are intimately mixed with carbon within a continuous three-dimensional conductive carbon matrix. The materials produced according to the disclosed methods are suitable for use as electrode materials in environments involving electrochemical reactions, for example, in lithium-ion batteries.

Description

Technology Field

[0001] Cross-reference of related applications

[0002] The present application is based on U.S. Provisional Application No. 63 / 381777 filed November 1, 2022; U.S. Provisional Application No. 63 / 381771 filed November 1, 2022; U.S. Provisional Application No. 63 / 381694 filed October 31, 2022; U.S. Provisional Application No. 63 / 381687 filed October 31, 2022; U.S. Provisional Application No. 63 / 381681 filed October 31, 2022; U.S. Provisional Application No. 63 / 381672 filed October 31, 2022; U.S. Provisional Application No. 63 / 381666 filed October 31, 2022; and on October 18, 2022 Claiming priority and interest in U.S. provisional application No. 63 / 416996, U.S. provisional application No. 63 / 378756 filed on October 7, 2022, U.S. provisional application No. 63 / 352571 filed on June 15, 2022, U.S. provisional application No. 63 / 336640 filed on April 29, 2022, and U.S. provisional application No. 63 / 326353 filed on April 1, 2022, the full text of each of these is incorporated herein by reference.

[0003] Technology field

[0004] The present disclosure relates to a cathode active material for general use in lithium-ion batteries and a method for manufacturing the same. Background Technology

[0005] One of the most common types of rechargeable batteries is the lithium-ion battery (LIB). LIBs have been widely used in a variety of applications, ranging from portable electronic devices to automobiles. A LIB is a type of battery in which lithium ions move from the anode to the cathode during discharge and from the cathode to the anode during a charge cycle (recharging). Traditionally, the anode of a LIB is made of graphite and / or alloy materials (e.g., Si), or oxides (e.g., Li4Ti5O). 12 It is formed as a graphite layer, and during the charging cycle, lithium ions are intercalated within the graphite layer to provide energy storage. LIB cathode materials are typically oxide compounds of nickel, cobalt, or manganese ("NCM") or aluminum. NCM cathode materials are interesting because they have a high charge capacity (~200 milliampere-hours / gram (mAh / g)) compared to other types of cathode materials. However, these materials can be expensive to manufacture, and they can have an adverse effect on the environment because expensive ores must be obtained and processed to provide the necessary precursors, and toxic waste is generated during this process.

[0006] Another LIB cathode material is lithium iron phosphate (e.g., LiFePO4; "LFP"). These LFP cathode materials have a lower theoretical charge capacity (~170 mAh / g) than NCM cathode materials. Nevertheless, LFP possesses numerous commercial advantages, including reduced environmental impact and, compared to the ores used to manufacture NCM, less expensive precursors, though not limited to these. However, LFPs have synthetic disadvantages that offset some of these advantages. For example, most previously reported synthesis processes involve extensive mechanical mixing of solid-phase precursor materials (e.g., via ball milling) to achieve the close contact between precursors necessary to provide a homogeneous product.

[0007] Therefore, it would be desirable in the art to provide a method for manufacturing a lithium transition metal phosphate cathode active material that is efficient, relatively inexpensive, and has low environmental impact.

[0008] The present invention generally relates to a method for manufacturing a lithium transition metal phosphate cathode material within a conductive carbon matrix.

[0009] Various solid and solution-phase methods for forming lithium iron phosphate (LFP) materials have been previously reported. For example, see U.S. Patent Application No. 2011 / 0110838 (Wang et al.), No. 2008 / 0099720 (Huang et al.), No. 2010 / 0065787, and No. 2011 / 0091772 (Mishima et al.); U.S. Patent No. 7,988,879 (Park et al.) and No. 7,060,238 (Saidi et al.); European Patent Application No. 1,921,698 (Dong); and International Patent Application No. WO2004 / 092065 (Barker et al.).

[0010] The method disclosed herein has advantages over previously reported methods for producing LFP materials, comprising LFP within a conductive carbon matrix in at least some embodiments. Previously reported methods provide, for example, LFP cathode materials containing carbon, but such carbon is typically added using carbon particles (e.g., carbon black) or the pyrolysis of a mixture of an LFP precursor and sugar molecules. None of these traditional methods for introducing carbon into cathode materials provide a conductive matrix comparable to the conductive matrix provided according to the disclosed method.

[0011] The advantages of some or all of the embodiments described herein include eliminating various process steps of LFP synthesis compared to more traditional methods in which LFP cathode materials are synthesized. For example, many traditional LFP processes use solution chemistry techniques that can generate large amounts of wastewater (e.g., aqueous ammonia solutions). The generation of wastewater is almost completely avoided in some of the embodiments of the present disclosure. Furthermore, conventional solid-phase reactions that produce LFP (and largely avoid wastewater generation) have the disadvantage of requiring a significant energy input to mix and mill large amounts of high-density solid-phase powder. The product of the powder mixing is also unlikely to be homogeneous and uniform LFP due to the difficulty of achieving and maintaining a compositionally homogeneous mixture of precursors. Because the embodiments of the present disclosure maintain close contact between the reactants in a viscous medium, the degree and duration of mixing and milling are reduced compared to traditional techniques. This reduces the energy and process complexity required to synthesize LFP. An additional advantage is that this method requires pyrolysis only under an inert (e.g., nitrogen) atmosphere. In contrast, certain conventional methods require a reducing (hydrogen) atmosphere, adding complexity, cost, and risk to performing such synthesis. The disclosed method remarkably enables the carbon content in lithium transition metal phosphate cathode materials within a conductive carbon matrix to be controlled to approximately 1-10% by weight, provides an LFP active material utilization rate in the range of 85-90% (suitable for commercial products), and is scalable and inexpensive. Furthermore, in some embodiments, the method disclosed herein improves the commercial viability of such materials in battery packs by providing lithium transition metal phosphates having improved tap density compared to conventional lithium transition metal phosphates. The disclosed method and the materials produced by the method have additional advantages further described below.

[0012] The method disclosed herein generally comprises the steps of combining a group of precursors for synthesizing a lithium transition metal phosphate cathode material; providing one or more carbon precursors in a fluid state; mixing the group of precursors with one or more carbon precursors to form a precursor mixture; adding a gelation initiator to the precursor mixture; enabling one or more carbon precursors to gel to form a solid organogel; and pyrolyzing the solid organogel to form a lithium transition metal phosphate cathode material within a conductive carbon matrix. One or more carbon precursors are configured to form a solid organogel in the presence of a gelation initiator, and the solid organogel is configured to form a conductive carbon matrix upon pyrolysis. It should be understood that the solid organogel produced by the disclosed method is formed by the gelation of the carbon precursors, and the pyrolysis of the organogel produces a conductive carbon matrix. Additionally, throughout this disclosure, in the context of the described method, it should be understood that the terms “solid organogel” and “organogel” are intended to be interpreted as further comprising precursors for synthesizing lithium transition metal phosphate cathode materials and / or intermediate reaction products of these various precursors, unless the context makes it clear that only organogel is being described. In the disclosed method, at least a first precursor of the group of precursors for synthesizing lithium transition metal phosphate cathode materials comprises a solid phase having a first density greater than 1 gram (g) / cubic centimeter (cc), and at least a second precursor of the group comprises a liquid phase having a second density, wherein the second density is lower than the first density. The solid organogel prevents the solid phase components within the group of precursors from being separated from the liquid phase components within the group of precursors (e.g., precipitation due to a density gradient between the solid phase and the liquid phase).In particular, the solid organogel maintains uniform contact of the lithium transition metal phosphate groups of the precursors in the mixture, so that the precursors can react to form a lithium transition metal phosphate cathode material (e.g., lithium iron phosphate (LFP)). Furthermore, the solid organogel can also contribute to the synthesis of commercially viable LFP by being converted into a conductive carbon matrix necessary for using LFP as a cathode material.

[0013] As described above, the method disclosed herein is advantageous for maintaining uniform contact between various precursor materials, e.g., an Fe precursor and a lithium phosphate. Significantly, because the solid organogel material used in these methods is selected to maintain the solid state at a fairly high temperature (e.g., at least up to about 300°C), the solid organogel maintains contact between the transition metal (e.g., Fe) precursor and the intermediate lithium phosphate (LiH2PO4) beyond the melting temperature of LiH2PO4. This allows the precursor to react into LFP without phase separation even when LiH2PO4 melts into a liquid phase at the LFP synthesis reaction temperature. Since the organogel precursor and conditions are selected to enable rapid gelation (e.g., less than 15 minutes, e.g., a few seconds to about 15 minutes), the advantages of the solid organogel for maintaining contact between the precursors are realized quickly. In addition, in some embodiments, the present method provides more intimate mixing and interaction of precursor materials on a smaller scale (e.g., nanoscale, dissolved molecular scale) compared to methods of mixing components as solid-phase (e.g., micron-sized) particles. This more intimate mixing can mitigate the formation of impurities during synthesis and provide a more homogeneous product. Surprisingly, this intimate mixing can be realized with a reduction or even elimination of the intensive milling required in previously reported processes. Another advantage of the disclosed method is that the gelation of organogel precursors in the presence of lithium transition metal phosphate precursors enables the production of a cathode material that is intimately mixed with carbon within a continuous three-dimensional conductive carbon matrix after pyrolysis.

[0014] Accordingly, in one embodiment, a method for manufacturing a lithium transition metal phosphate cathode material within a conductive carbon matrix is ​​provided, and the method comprises:

[0015] A step of combining a group of precursors for synthesizing a lithium transition metal phosphate cathode material — at least a first precursor of the group comprises a solid phase having a first density greater than 1 gram (g) / cubic centimeter (cc), and at least a second precursor of the group comprises a liquid phase having a second density, wherein the second density is lower than the first density —;

[0016] A step of providing one or more carbon precursors in a fluid state — one or more carbon precursors are configured to form a solid organogel in the presence of a gelation initiator, and the solid organogel is configured to form a conductive carbon matrix upon pyrolysis —;

[0017] A step of forming a precursor mixture by mixing a group of precursors with one or more carbon precursors;

[0018] A step of adding a gelation initiator to a precursor mixture;

[0019] A step of forming a solid organogel by enabling one or more carbon precursors to gel; and

[0020] It includes the step of thermally decomposing a solid organogel to form a lithium transition metal phosphate cathode material within a conductive carbon matrix.

[0021] In some embodiments, the solid organogel is formed within 5 seconds to 15 minutes after the addition of the gelation initiator.

[0022] In some embodiments, the solid organogel comprises a porous network of interconnected solid-phase polymer structures.

[0023] In some embodiments, the porous network maintains contact between the first precursor of the group and the second precursor of the group.

[0024] In some embodiments, the contact is maintained at a temperature of at least about 300°C.

[0025] In some embodiments, the first precursor comprises iron; the second precursor comprises a lithium source and a phosphoric acid; and the lithium transition metal phosphate cathode material is lithium iron phosphate.

[0026] In some embodiments, iron exists in the form of iron(II) salts, iron(III) salts, iron oxide(II) (FEO), iron(III) oxide (Fe2O3), mixed iron oxide (Fe3O4), or a combination thereof.

[0027] In some embodiments, the solid organogel comprises a phloroglucinol-furfural polymer or a resorcinol-furfural polymer, and one or more carbon precursors are phloroglucinol or resorcinol and furfural. In some embodiments, the gelation initiator is an amine base or an acid.

[0028] In some embodiments, the solid organogel comprises a polyurethane polymer, and one or more carbon precursors comprise a polyol and an isocyanate. In some embodiments, the gelation initiator comprises an alkylamine.

[0029] In some embodiments, the organogel comprises a polyamic acid polymer, and the gelation initiator comprises acetic anhydride, acetic acid, or a combination thereof.

[0030] In some embodiments, the group of precursors comprises a microwave-sensitive precursor, and pyrolysis is performed by applying microwave radiation. In some embodiments, the microwave-sensitive precursor comprises one or more of carbon, magnetite, and maghemite. In some embodiments, the microwave-sensitive precursor comprises one or more nanoparticles of magnetite and maghemite having characteristic dimensions of 20 nm to 100 nm.

[0031] In some embodiments: the first precursor comprises manganese, vanadium, or both; the second precursor comprises a lithium source and a phosphoric acid; and the lithium transition metal phosphate cathode material is lithium manganese phosphate or lithium vanadium phosphate.

[0032] In some embodiments, the method further includes the step of drying a lithium transition metal phosphate cathode material by applying microwave radiation.

[0033] In some embodiments, the solid phase having a first density greater than 1 gram comprises a ferromagnetic iron compound, a quasi-ferromagnetic iron compound, or both.

[0034] In some embodiments, a ferromagnetic iron compound, a ferromagnetic iron compound, or both are synthesized by a method comprising the step of oxidizing an iron-containing anode in an electrochemical cell having a porous carbon substrate, an oxygen cathode, and an electrolyte in contact with both the iron-containing anode and the porous carbon substrate, wherein the oxidation produces particles of the ferromagnetic iron compound, the ferromagnetic iron compound, or both, having characteristic dimensions of 20 nm to 100 nm.

[0035] In some embodiments, the method further includes the step of removing particles by magnetic filtration.

[0036] In some embodiments, the method further includes the step of drying particles by applying microwave radiation.

[0037] In some embodiments, the operation of the electrochemical cell and the formation of ferromagnetic iron compounds, ferromagnetic iron compounds, or both are carried out at a temperature between 15°C and 35°C.

[0038] In another embodiment, a lithium transition metal phosphate cathode material produced by the method disclosed herein is provided.

[0039] In another aspect, an energy storage system comprising a lithium transition metal phosphate cathode material manufactured by the method disclosed herein is provided.

[0040] In another embodiment, the nanoparticle comprises olivine lithium iron phosphate and is integral with a conductive carbon matrix, wherein the nanoparticle has characteristic dimensions of 20 nm to 1000 nm and 10 meters 2 (m 2 ) / gram(g) to 65 m 2 A composition is provided having a specific surface area of ​​ / g. In some embodiments, the characteristic dimension is 30 nm to 70 nm and the specific surface area is 20 m² 2 / g to 65 m 2 / g. In some embodiments, the characteristic dimension is 30 nm to 60 nm, and the specific surface area is 22 m². 2 / g to 40 m 2 / g. In some embodiments, the characteristic dimension is 20 nm to 40 nm, and the specific surface area is 60 m². 2 / g to 80 m 2 / g is.

[0041] In some embodiments, the nanoparticles further comprise magnetite, maghemite, or both.

[0042] In some embodiments, the nanoparticles further contain manganese.

[0043] In some embodiments, the conductive carbon matrix comprises a carbonized organogel polymer matrix.

[0044] In another aspect, an energy storage system comprising a composition as disclosed in the present specification is provided.

[0045] The present disclosure includes, without limitation, the following embodiments.

[0046] Embodiment 1: A method for manufacturing a lithium transition metal phosphate cathode material within a conductive carbon matrix,

[0047] A step of combining a group of precursors for synthesizing a lithium transition metal phosphate cathode material — at least a first precursor of the group comprises a solid phase having a first density greater than 1 gram (g) / cubic centimeter (cc), and at least a second precursor of the group comprises a liquid phase having a second density, wherein the second density is lower than the first density —;

[0048] A step of providing one or more carbon precursors in a fluid state — one or more carbon precursors are configured to form a solid organogel in the presence of a gelation initiator, and the solid organogel is configured to form a conductive carbon matrix upon pyrolysis —;

[0049] A step of forming a precursor mixture by mixing a group of precursors with one or more carbon precursors;

[0050] A step of adding a gelation initiator to a precursor mixture;

[0051] A step of forming a solid organogel by enabling one or more carbon precursors to gel; and

[0052] A method comprising the step of pyrolyzing a solid organogel to form a lithium transition metal phosphate cathode material within a conductive carbon matrix.

[0053] Embodiment 2: The method of Embodiment 1, wherein the solid organogel is formed within 5 seconds to 15 minutes after the addition of a gelation initiator.

[0054] Embodiment 3: The method of Embodiment 1 or 2, wherein the solid organogel comprises a porous network of interconnected solid-phase polymer structures.

[0055] Aspect 4: A method in any one of Aspects 1-3, wherein the porous network maintains contact between the first precursor of the group and the second precursor of the group.

[0056] Embodiment 5: A method in which, in any one of Embodiments 1-4, the contact is maintained at a temperature of at least about 300°C.

[0057] Aspect 6: A method in any one of Aspects 1-5, wherein the first precursor comprises iron; the second precursor comprises a lithium source and a phosphoric acid; and the lithium transition metal phosphate cathode material is lithium iron phosphate.

[0058] Aspect 7: A method in any one of Aspects 1-6, wherein the first precursor comprises iron; the second precursor comprises a lithium source and a phosphoric acid; and the lithium transition metal phosphate cathode material is lithium iron phosphate.

[0059] Aspect 8: A method in any one of Aspects 1-7 in which iron is present in the form of an iron(II) salt, an iron(III) salt, an iron(II) oxide (FEO), an iron(III) oxide (Fe2O3), a mixed iron oxide (Fe3O4), or a combination thereof.

[0060] Embodiment 9: A method in any one of Embodiments 1-8, wherein the solid organogel comprises a phloroglucinol-furfural polymer or a resorcinol-furfural polymer, and one or more carbon precursors are phloroglucinol or resorcinol and furfural.

[0061] Embodiment 10: The method of Embodiment 9, wherein the gelation initiator is an amine base or an acid.

[0062] Embodiment 11: A method in any one of Embodiments 1-8, wherein the solid organogel comprises a polyurethane polymer and one or more carbon precursors comprise a polyol and an isocyanate.

[0063] Embodiment 12: The method of Embodiment 11, wherein the gelling initiator comprises an alkylamine.

[0064] Embodiment 13: A method in any one of Embodiments 1-8, wherein the organogel comprises a polyamic acid polymer and the gelation initiator comprises acetic anhydride, acetic acid, or a combination thereof.

[0065] Aspect 14: A method in any one of Aspects 1-13, wherein the group of precursors comprises a precursor having microwave sensitivity, and the pyrolysis is performed by applying microwave radiation.

[0066] Embodiment 15: The method of Embodiment 14, wherein the microwave-sensitive precursor comprises one or more of carbon, magnetite, and maghemite.

[0067] Embodiment 16: The method of Embodiment 14, wherein the microwave-sensitive precursor comprises one or more nanoparticles selected from magnetite and maghemite having characteristic dimensions of 20 nm to 100 nm.

[0068] Aspect 17: In any one of the aforementioned aspects, the first precursor comprises manganese, vanadium, or both; the second precursor comprises a lithium source and a phosphoric acid; and the lithium transition metal phosphate cathode material is lithium manganese phosphate or lithium vanadium phosphate.

[0069] Embodiment 18: A method comprising, in any one of the aforementioned embodiments, further a step of drying a lithium transition metal phosphate cathode material by applying microwave radiation.

[0070] Aspect 19: A method in which, in any one of the aforementioned aspects, the solid phase having a first density greater than 1 gram comprises a ferromagnetic iron compound, a quasi-ferromagnetic iron compound, or both.

[0071] Embodiment 20: In any one of the aforementioned embodiments, the ferromagnetic iron compound, the quasi-ferromagnetic iron compound, or both are synthesized by a method comprising the step of oxidizing an iron-containing anode in an electrochemical cell having a porous carbon substrate, an oxygen cathode, and an electrolyte in contact with both the iron-containing anode and the porous carbon substrate, wherein the oxidation produces particles of the ferromagnetic iron compound, the quasi-ferromagnetic iron compound, or both, having characteristic dimensions of 20 nm to 100 nm.

[0072] Embodiment 21: The method of Embodiment 20, further comprising the step of removing particles by magnetic filtration.

[0073] Aspect 22: A method comprising, in any one of the aforementioned aspects, further a step of drying particles by applying microwave radiation.

[0074] Embodiment 23: The method of Embodiment 20, wherein the operation of the electrochemical cell and the formation of the ferromagnetic iron compound, the quasi-ferromagnetic iron compound, or both are carried out at a temperature between 15°C and 35°C.

[0075] Aspect 24: A lithium transition metal phosphate cathode material produced by the method disclosed herein.

[0076] Aspect 25: An energy storage system comprising a lithium transition metal phosphate cathode material manufactured by the method disclosed herein.

[0077] Embodiment 26: As a composition, comprising olivine lithium iron phosphate and nanoparticles integral with a conductive carbon matrix, wherein the nanoparticles have characteristic dimensions of 20 nm to 1000 nm and 10 meters 2 (m 2 ) / gram(g) to 65 m 2 A composition having a specific surface area of ​​ / g.

[0078] Embodiment 27: In Embodiment 26, the characteristic dimension is 30 nm to 70 nm, and the specific surface area is 20 m² 2 / g to 65 m 2 A composition that is / g.

[0079] Embodiment 28: In Embodiment 26, the characteristic dimension is 30 nm to 60 nm, and the specific surface area is 22 m² 2 / g to 40 m 2 A composition that is / g.

[0080] Embodiment 29: In Embodiment 26, the characteristic dimension is 20 nm to 40 nm, and the specific surface area is 60 m² 2 / g to 80 m 2 A composition that is / g.

[0081] Embodiment 30: A composition in any one of embodiments 26-29, wherein the nanoparticles further comprise magnetite, maghemite, or both.

[0082] Aspect 31: A composition in any one of Aspects 26-30, wherein the nanoparticles further comprise manganese.

[0083] Aspect 32: A composition in any one of Aspects 26-31, wherein the conductive carbon matrix comprises a carbonized organogel polymer matrix.

[0084] Aspect 33: An energy storage system comprising a composition as disclosed herein.

[0085] These and other features, embodiments, and advantages of the present disclosure will become apparent from reading the following detailed description together with the accompanying drawings, which are briefly described below. The present invention includes any combination of two, three, four, or more of the embodiments described above, as well as any combination of two, three, four, or more features or elements presented in the present disclosure, regardless of whether such features or elements are explicitly combined in the description of specific embodiments of the present specification. The present disclosure is intended to be read in its whole form so that any separable features or elements of the disclosed invention are intended to be combined in any one of its various embodiments, unless the context clearly indicates otherwise. Brief explanation of the drawing

[0086] To provide an understanding of the embodiments of the present technology, reference is made to the attached drawings, which do not necessarily need to be drawn to a specific scale. The drawings are merely illustrative and should not be construed as limiting the technology. The disclosures described herein are illustrated in the attached drawings as examples, not limitations. Figure 1 is a schematic diagram of a conventional solid-state synthesis route to lithium iron phosphate in a carbon matrix. FIG. 2 is a schematic diagram of a slurry / sol-gel synthesis route into lithium iron phosphate in a carbon matrix according to a non-limiting aspect of the present disclosure. FIG. 3 schematically illustrates a system for oxidizing transition metals, including but not limited to iron, using a carbon aerogel component according to a non-limiting embodiment. FIG. 4 schematically illustrates an electrochemical cell for oxidizing transition metals, including but not limited to iron, using a carbon aerogel component according to a non-limiting embodiment. FIG. 5a is a scanning electron microscope image at 100,000x magnification of a sample of nanoparticle magnetite (Fe3O4) prepared by forced aero-anodization of iron according to a non-limiting aspect of the present disclosure. FIG. 5b is a powder X-ray diffraction (XRD) pattern of a sample of nanoparticle magnetite prepared by forced aero-anodization of iron according to a non-limiting aspect of the present disclosure. FIG. 6 is a schematic diagram of a semi-continuous method for producing nanoparticle magnetite from forced anodic oxidation according to a non-limiting aspect of the present disclosure and converting it into lithium iron phosphate in a carbon matrix. FIGS. 7a and 7b are scanning electron microscope images at two magnifications (1,490x and 5,050x, respectively) of a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of the present disclosure. FIG. 8 is a powder X-ray diffraction (XRD) pattern for a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of the present disclosure. FIGS. 9a and 9b are scanning electron microscope images at two magnifications (10,000x and 49,900x, respectively) of a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of the present disclosure. FIG. 10 is a powder XRD pattern for a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of the present disclosure. FIGS. 11a and FIGS. 11b are scanning electron microscope images at two magnifications (10,000x and 100,000x, respectively) of a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of the present disclosure. FIG. 12 is a powder XRD pattern for a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of the present disclosure. FIGS. 13a and FIGS. 13b are scanning electron microscope images at two magnifications (2,000x and 20,000x, respectively) of a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of the present disclosure. FIG. 14 is a powder XRD pattern for a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of the present disclosure. FIGS. 15a and FIGS. 15b are scanning electron microscope images at two magnifications (2,000x and 50,000x, respectively) of a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of the present disclosure. FIG. 16 is a powder XRD pattern for a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of the present disclosure. FIG. 17 is a powder XRD pattern for a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of the present disclosure. Specific details for implementing the invention

[0087] Before describing some exemplary embodiments of the present technology, it will be understood that the present technology is not limited to the details of the configurations or process steps presented in the following description. Other embodiments of the present technology are possible and may be implemented or carried out in various ways.

[0088] Generally, the present technology relates to a method for manufacturing a lithium transition metal phosphate cathode material within a conductive carbon matrix. According to the present disclosure, surprisingly, the lithium transition metal phosphate cathode material manufactured as disclosed herein has been found to provide a more homogeneous product without requiring intensive milling steps and also provides a cathode material having an improved tap density compared to conventional methods for manufacturing lithium transition metal phosphates. Furthermore, the disclosed methods provide a lithium transition metal phosphate cathode material that is intimately mixed with carbon within a continuous three-dimensional conductive carbon matrix.

[0089] Accordingly, the present specification provides a method for preparing lithium iron phosphate, lithium transition metal phosphate, and lithium vanadium fluorophosphate cathode materials within a conductive carbon matrix. As a general, non-limiting description, the disclosed method comprises the steps of combining a group of precursors for synthesizing a lithium transition metal phosphate cathode material; providing one or more carbon precursors in a fluid state; mixing the group of precursors with one or more carbon precursors to form a precursor mixture; adding a gelation initiator to the precursor mixture; enabling one or more carbon precursors to gel to form a solid organogel; and pyrolyzing the solid organogel to form a lithium transition metal phosphate cathode material within a conductive carbon matrix. Additionally, the present specification provides a lithium transition metal phosphate cathode material prepared by the disclosed method, a composition comprising olivine lithium iron phosphate and nanoparticles integral with the conductive carbon matrix, and an energy storage system comprising the lithium transition metal phosphate cathode material as described herein. Each of the components, materials, and products comprising the materials of the present method is further described below in this specification.

[0090] definition

[0091] With respect to terms used in this disclosure, the following definitions are provided. This application will use the following terms as defined below, unless the context in which the terms appear requires a different meaning.

[0092] The singular expression is used in this specification to refer to one or more than one (i.e., at least one) grammatical object.

[0093] Throughout this specification, the term “about” is used to describe and account for small variations. For example, the term “about” may refer to ±10% or less, ±5%, such as ±2% or less, ±1% or less, ±0.5% or less, ±0.2% or less, ±0.1% or less, or ±0.05% or less. All numerical values ​​in this specification are modified by the term “about”, whether or not explicitly indicated. Values ​​modified by the term “about” include specific values. For example, “about 5.0” must include 5.0.

[0094] All scopes cited in this specification are comprehensive.

[0095] As used herein, the terms “comprising” and “comprising” and their variations mean that certain features, steps, or integers are included. The terms should not be interpreted to exclude the presence of other features, steps, or components. The present invention comprises, consists of, or is essentially composed of the disclosed and claimed features.

[0096] In the context of the present disclosure, the terms “framework” or “framework structure” refer to a network of interconnected oligomers, polymers, or colloidal particles forming a solid structure of a gel or xerogel. The polymers or particles (e.g., carbon) constituting the framework structure typically have a diameter of about 100 angstroms. However, the framework structure of the present disclosure may also comprise a network of interconnected oligomers, polymers, or colloidal particles of any diameter size forming a solid structure within a gel or xerogel.

[0097] In some embodiments, the gel material may be specifically referred to herein as a zerogel. As used herein, the term “zerogel” refers to a type of gel comprising an open, non-solid colloidal or polymeric network formed by removing all swelling agents from a corresponding wet gel without the need to take any precautions to avoid substantial volume reduction or delay compression. Zerogels generally comprise a compact structure. Zerogels undergo significant volume reduction during ambient pressure drying and are typically 0–100 m when measured by nitrogen adsorption analysis. 2 / g, for example, about 0 to about 20 m 2 It has a surface area of ​​ / g.

[0098] As used herein, the terms “gelation” or “gel transition” refer to the formation of a wet gel from a polymer system, for example, PF or polyimide as described herein. At any point during polymerization, imidization, or drying as described herein—which is defined as the “gel point”—the sol loses its fluidity. Without being bound by any particular theory, the gel point may be considered as the point where the gelation solution exhibits resistance to flow. In this context, gelation proceeds from an initial sol state (e.g., a liquid solution of an ammonium salt of a polyamic acid), through a highly viscous dispersion state, until the dispersion state solidifies and the sol gels (gel point), forming a wet gel (e.g., a polyimide gel). The time taken for a polymer in solution to transition into a gel form that can no longer flow is called the "phenomenological gelation time." Formally, gelation time is measured using rheology. At the gel point, the elastic properties of the solid gel begin to prevail over the viscous properties of the fluid sol. The formal gelation time is near the time when the real and imaginary components of the complex elastic modulus of the gelled sol cross. The two elastic moduli are monitored as a function of time using a rheometer. Time begins counting from the moment the final component of the sol is added to the solution. For example, HH Winter "Can the Gel Point of a Cross-linking Polymer Be Detected by the G'-G' Crossover?" Polym. Eng. Sci., 1987, 27, 1698-1702; S.-Y. Kim, D.-G. Choi and S.-M. Yang "Rheological analysis of the gelation behavior of tetraethylorthosilane / vinyltriethoxysilane hybrid solutions" Korean J. Chem. Eng., 2002, 19, 190-196; andM.Discussion on gelation in Muthukumar "Screening effect on viscoelasticity near the gel point" Macromolecules, 1989, 22, 4656-4658. reference In some embodiments, gelation is induced by the addition of a suitable gelation initiator. In other embodiments, gelation may be induced, for example, by the removal of a solvent from a solution containing a salt of a polyamic acid. Such solvent removal may be achieved by various drying techniques, including but not limited to spray drying.

[0099] As used herein, the term “wet gel” refers to a gel in which the moving gap phase within a network of interconnected pores consists mainly of a liquid phase such as a conventional solvent or water. Examples of wet gels include, but are not limited to, alcogels, hydrogels, ketogels, carbonogels, and any other wet gels known in the art.

[0100] As used herein, the term “carbon zerogel” refers to a porous carbon-based material. Some non-limiting examples of carbon zerogels include carbonized zerogels, such as carbonized polyimide gels. In the context of zerogels, the term “carbonized” refers to an organic gel (e.g., PF polymer or polyimide) that has undergone pyrolysis to decompose or convert the organogel composition into at least substantially pure carbon. As used herein, the terms “pyrolyze,” “pyrolysis,” or “carbonize” refer to the decomposition or conversion of an organic matrix into pure or substantially pure carbon caused by heat. As described below in this specification, during such pyrolysis, reactions of the various components present in the matrix occur to form, either simultaneously or subsequently, respective lithium transition metal phosphate or fluorophosphate cathode materials within the carbon matrix.

[0101] As used in this specification, the term "average particle size" refers to D 50 It is synonymous with [this point], meaning that half of the particle population has a particle size greater than this point, and half has a particle size less than this point. Particle size can be measured by laser light scattering techniques or microscopy techniques. Unless otherwise indicated, the average particle size reported herein is obtained by visual interpretation of SEM images using a calibration scale bar and image processing software (e.g., ImageJ). Multiple particles are measured randomly, the results are averaged, and standard deviations are calculated. For secondary particles and aggregates, laser diffraction particle size analysis is used.

[0102] In the context of this disclosure, the term "density" refers to a measurement of mass per unit volume of a material. The term "density" generally refers to the true density or skeletal density of a material, the apparent density of a material or composition, or the tap density of a material or composition. Density is typically kg / m³ 3 or g / cm 3 It is reported as.

[0103] The skeletal density of a material is the ratio of the mass of the material to the volume of the material, excluding any voids within the material and any empty spaces between the particles of the material. Skeletal density can be determined by methods known in the art, including but not limited to helium specific gravity measurement.

[0104] The apparent density of a material is the ratio of the mass of the material to the volume of the material, including any voids within the material and any empty spaces between the particles of the material. The apparent density, also referred to as "envelope density," may be determined by methods known in the art, including but not limited to: Standard Test Method for Dimensions and Density of Preformed Block and Board-Type Thermal Insulation (ASTM C303, ASTM International, West Conshohocken, Pa.); Standard Test Methods for Thickness and Density of Blanket or Batt Thermal Insulations (ASTM C167, ASTM International, West Conshohocken, Pa.); or methods known in the art, including but not limited to Determination of the apparent density of preformed pipe insulation (ISO 18098, International Organization for Standardization, Switzerland). Within the context of this disclosure, unless otherwise noted, density measurements are obtained in accordance with the ASTM C167 standard.

[0105] In the context of this disclosure, the material term "tap density" or "tapping density" is the ratio of the mass of a material to the volume of a material measured when the material is vibrated or tapped under specific conditions. The tapping density of a powder indicates the random high-density packing of the powder. Tapping density values ​​are higher for particles of more regular shape (e.g., spheres) compared to particles of irregular shape. Tapping density is given by the formula M / V f It can be calculated using, whereM = Mass in grams, and V f = cubic centimeter (cm) 3 Tapping density is the tapping volume in units. Tapping density is generally measured by first slowly introducing a known sample mass into a graduated cylinder and carefully leveling the powder without compressing it. Then, the cylinder is mechanically tapped by raising the cylinder and allowing it to fall below its own weight using a suitable mechanical tapping density tester that provides a suitable fixed drop distance and nominal drop rate. Standard test methods for measuring tap density are described in MPIF-46, ASTM B-52722, and ISO 3953. Unless otherwise indicated, the tap density of the materials described herein is obtained according to the method of ASTM B-52722.

[0106] As used herein, the term "positive electrode" is used interchangeably with "cathode." Likewise, the term "negative electrode" is used interchangeably with "anode."

[0107] In the context of this disclosure, the term “electrical conductivity” refers to a measure of a material’s ability to conduct an electric current or otherwise allow the flow of electrons through or within it. Electrical conductivity is specifically measured as the electrical conductance / susceptance / admittance of the material per unit size of the material. This is typically expressed in S / m (Siemens / meter) or S / cm (Siemens / centimeter). The electrical conductivity or resistivity of a material may be determined by methods known in the art, including, but not limited to, In-line Four Point Resistivity (using the dual-configuration test method of ASTM F84-99). In the context of this disclosure, unless otherwise noted, the measurement of electrical conductivity is obtained according to the ASTM F84 – Resistivity (R) measurement, which is obtained by measuring the value obtained by dividing the voltage (V) by the current (I). In certain embodiments, the material of the present disclosure has an electrical conductivity of about 10 S / cm or more, 20 S / cm or more, 30 S / cm or more, 40 S / cm or more, 50 S / cm or more, 60 S / cm or more, 70 S / cm or more, 80 S / cm or more, or within a range between any two of these values.

[0108] As used herein, the term “substantially” means most of the mentioned characteristics, quantities, etc., when associated with a particular context (e.g., substantially pure, substantially identical, etc.), e.g., more than about 95%, more than about 99%, more than about 99.9%, more than 99.99%, or even 100%, unless otherwise indicated.

[0109] I. Method for manufacturing lithium transition metal phosphate cathode materials within a conductive carbon matrix

[0110] In one embodiment, a method for manufacturing a lithium transition metal phosphate cathode material within a conductive carbon matrix is ​​provided. As described in detail herein, many previously reported synthesis processes for manufacturing lithium transition metal phosphate cathode materials, such as lithium iron phosphate (LFP), involve extensive mechanical mixing of solid-phase precursor materials (e.g., via ball milling) to achieve the intimate contact between precursors necessary to provide a homogeneous product. Furthermore, these solid-phase techniques utilize a number of energy-intensive steps. For example, FIG. 1 provides a schematic diagram of a typical solid-phase process method (100). Referring to FIG. 1, drying, mixing, milling, calcination, and sintering all require significant energy input, time, or both, thereby increasing production costs. Energy-intensive steps are indicated by asterisks. In contrast, the methods disclosed herein are advantageous in that they reduce the number of at least energy and / or time-intensive steps. For example, FIG. 2 provides a schematic diagram of a process (200) according to a non-limiting embodiment using the slurry / sol-gel synthesis methods described herein. Referring to FIG. 2, the total number of steps, specifically the number of energy-intensive steps, is reduced compared to the method of FIG. 1. Additionally, as described above, the disclosed method enables more intimate mixing and interaction of components on a smaller scale (e.g., nanoscale dissolved molecular scale), which can mitigate the formation of impurities during synthesis and provide a more homogeneous product. Another advantage of the disclosed methods is that the gelation of organogel precursors in the presence of lithium transition metal phosphate precursors enables the production of a cathode material that is intimately mixed with carbon within a continuous three-dimensional conductive carbon matrix, while the organogel matrix formed during gelation suppresses phase separation of the reaction components.

[0111] In another embodiment, phase separation of reaction components may be inhibited during the removal of a liquid phase (e.g., water), an immiscible solvent, a precursor (e.g., aqueous phosphoric acid), or a combination thereof from various solutions, suspensions, or emulsions disclosed herein. During such removal, for example, by drying or concentrating the solution, suspension, or emulsion, the formation of a self-supporting solid phase comprising various components may serve the same purpose as the formation of a self-supporting solid phase organogel formed by the gelation of a gel precursor.

[0112] By general and non-limiting description, the disclosed method comprises the steps of combining a group of precursors for synthesizing a lithium transition metal phosphate cathode material; providing one or more carbon precursors in a fluid state; mixing the group of precursors with one or more carbon precursors to form a precursor mixture; adding a gelation initiator to the precursor mixture; enabling one or more carbon precursors to gel to form a solid organogel; and pyrolyzing the solid organogel to form a lithium transition metal phosphate cathode material within a conductive carbon matrix. The individual components of the method and their respective manufacturing operations are further described below.

[0113] A. Precursor of lithium transition metal phosphate cathode material

[0114] The disclosed method comprises the step of combining a group of precursors for synthesizing a lithium transition metal phosphate cathode material, wherein at least a second precursor of the group comprises a liquid phase having a second density, the second density being lower than the first density.

[0115] 1. First precursor

[0116] At least one first precursor of the group of precursors comprises a solid phase having a first density greater than 1 gram (g) / cubic centimeter (cc). In some embodiments, the density is in the range of about 1 to about 5, e.g., about 1, about 2, about 3, about 4, or about 5 g / cc.

[0117] In some embodiments, the group of precursors comprises a first precursor that is a transition metal salt or a transition metal oxide. As used herein, the terms “transition metal salt” and “transition metal oxide” refer to any salt or oxide of a transition metal and may include a mixture of more than one transition metal. As used herein, the term “transition metal” refers to any metallic element in the d-block of the periodic table, including groups 3 through 12 of the periodic table, excluding platinum group metals. Transition metal salts or oxides may include various oxidation states of the transition metal. With respect to oxides, they have the valence of a particular transition metal (e.g., 2 + , 3 + , 4 + , or 5 + Depending on the, it may include monooxides, dioxides, etc., but is not limited thereto. Generally, the transition metals or metals present in the salt or oxide are in an oxidation state (II) or (III). Suitable transition metals include, for example, vanadium, titanium, manganese, iron, cobalt, copper, and nickel. Particularly suitable transition metals include one or more of manganese, iron, and vanadium. The selection of specific transition metals in the form of their respective salts, oxides, or mixed oxides may be determined by a person skilled in the art based on the intended battery cell voltage or other performance parameters, availability, cost, toxicity, and other variables.

[0118] In some embodiments, the first precursor comprises a transition metal oxide. The particle size of the transition metal oxide (e.g., iron oxide, e.g., Fe3O4 and / or Fe2O3) suitable for use in the disclosed method may vary. Generally, small particle sizes, such as about 5 microns or less, are particularly suitable, as such particle sizes enable close contact between the transition metal oxide and other reaction components (e.g., lithium and phosphate ions and organogel precursor materials). In some embodiments, the transition metal oxide has an average particle size of about 5 microns or less, e.g., in the range of about 1 micron to about 5 microns. In some embodiments, the transition metal oxide may be synthesized (as described below) to have an average particle size in the range of about 5 nanometers (nm) to about 200 nm, e.g., in the range of about 20 nm to about 100 nm. Alternatively, the transition metal oxide having an average particle size of about 5 microns or more may be milled to provide a desired particle size range. Such milling may be performed before mixing with other reaction components, or as further described below in this specification In situ It can be performed (in situ).

[0119] The density of the transition metal oxide prior to use in the disclosed method may vary. Generally, high tap density transition metal oxides are particularly suitable. As used herein, the term "high density" refers to about 1.1 g / cm³. 3It refers to materials having a higher tap density. Without being bound by any specific theory, high tap density transition metal oxides are believed to serve to template the physical properties of the final lithium iron phosphate cathode material (e.g., via an "isomorphic" reaction), thereby resulting in a desirablely high-density product. High-density cathode materials are considered desirable for battery applications because they generate more power per unit volume of the cathode material (i.e., provide a higher volumetric energy density). Surprisingly, in some embodiments, the disclosed method is about 0.8 g / cm³ 3 Above, for example, about 0.8 g / cm³ 3 Up to about 1.1 g / cm³ 3 A cathode material having a tap density within a range is provided. Accordingly, the tap density of the cathode material of the present disclosure is within the range of commercial feasibility (i.e., similar to the tap density of previously available LFP).

[0120] In some embodiments, the transition metal of the transition metal oxide comprises manganese, vanadium, iron, or a combination thereof. In some embodiments, the transition metal of the transition metal oxide is manganese or vanadium.

[0121] In some embodiments, the transition metal of the transition metal oxide is manganese. Examples of suitable manganese oxides include, but are not limited to, MnO, MnO2, and Mn2O3. In some embodiments, the transition metal oxide is manganese(II) oxide (MNO) or manganese(III) oxide (Mn2O3).

[0122] In some embodiments, the transition metal oxide is a vanadium oxide such as V2O3, VO2, or V2O5. In some embodiments, the transition metal oxide is a vanadium oxide, and the lithium vanadium phosphate cathode material has a Li3Sc2(PO4)3 structural type.

[0123] In some embodiments, the transition metal of the transition metal oxide is iron. The oxidation state of iron in the iron oxide may vary. For example, the iron oxide may be iron(II) oxide (FEO), iron(III) oxide (Fe2O3), or a combination thereof (e.g., Fe3O4).

[0124] In certain embodiments, the iron oxide is iron(III) oxide (Fe2O3). Iron(III) oxide is an inexpensive and readily available oxide that is stable with respect to oxidation and, accordingly, does not require special handling (such as in the case of iron(II) oxide to avoid oxidation). Additionally, iron oxides (e.g., Fe2O3) having an average particle size of about 5 microns or less are commercially available. Commercial bulk Fe2O3 (i.e., Fe2O3 having a particle size larger than about 1 micron) can be milled to produce the desired nanoparticle material, but this is a time-consuming and energy-intensive process. Such downsized Fe2O3 is referred to herein as "nanoparticle iron(III) oxide" and may have an average particle size in the range of about 10 nanometers to about 100 nanometers, such as about 30 nanometers to about 50 nanometers. However, such nanoparticle iron(III) oxide is very expensive on a commercial scale. Surprisingly, according to the present disclosure, it has been revealed that inexpensive and readily available iron(II) oxalate (FeC2O4) can be heated in air to release carbon dioxide and provide nanoporous iron(III) oxide. For example, it has been revealed that heating iron oxalate in an air atmosphere for about 1 hour at a temperature in the range of about 350 to about 450°C converts the iron oxalate into nanoporous iron(III) oxide. In particular, iron(III) oxide particles produced by the thermal decomposition of iron oxalate have an average particle size of about several microns but develop an internal osmotic porosity with a pore diameter of about 100 nm. Accordingly, these particles are referred to herein as "nanoporous". In some embodiments, FeC2O4 . Fe2O3 obtained by the thermal decomposition of 2H2O is approximately 9.95 m 2 It has a BET nitrogen surface area of ​​ / g.

[0125] In some embodiments, the iron oxide is in the form of magnetite (Fe3O4) or maghemite (Fe2O3) or a solid solution or a mixture of both, with an average composition of Fe 3-x It has O4 (0 ≤ x ≤ 0.33) and is referred to herein as magnetic iron oxide nanoparticles (magnetic IONPs). Such IONPs can be purchased or manufactured according to known methods. In some embodiments, IONPs are manufactured by the oxidation of iron by air within an electrochemical cell. According to the present disclosure, it has been discovered that certain types of carbon aerogels or other porous carbon structures (e.g., carbonized polyurethane foam, or a combination of carbon aerogels within the pores of carbonized polyurethane foam) can act as an "air cathode" for catalytically reducing oxygen at room temperature. When arranged in an electrochemical cell having an aqueous electrolyte, oxygen can be reduced to hydroxide anions while oxidizing a transition metal, such as iron. In some embodiments, iron is oxidized to produce iron hydroxide, magnetite, maghemite, or a combination thereof. The catalytic effect of the carbon aerogel described in this specification can be used to oxidize solid iron at room temperature (e.g., 5°C to 25°C).

[0126] FIG. 3 is a schematic diagram of a system (300) used for oxidizing iron at room temperature according to one or more embodiments described herein. The system (300) comprises a porous conductive carbon element (304), a separator (308), an electrolyte (312), an electrode (316) containing iron, and a conductor (320). Without being bound by theory, it is believed that the carbon aerogel element (304) can reduce the activation energy for oxygen reduction, thereby enabling the electrically connected iron electrode to participate in a redox reaction at room temperature.

[0127] In various embodiments, a porous conductive carbon element (304) (referred to as "substrate" synonymously) may be synthesized and / or produced according to techniques involving the pyrolysis of a polyimide aerogel. In some examples, the pyrolyzed polyimide aerogel may contain residual nitrogen or other heteroatoms (i.e., non-carbon atoms) that are not removed during aerogel synthesis or pyrolysis. Using the porous conductive carbon element (304) as a catalyst for oxidizing the iron electrode (316) may produce cathode precursor materials including, but not limited to, Fe(OH)2, Fe(OH)3, Fe3O4, and Fe2O3. The process described herein may produce iron oxide / hydroxide in a solid state without generating large amounts of wastewater by using air, water, and iron metal as the only reactants.

[0128] Many of the embodiments described herein describe the use of carbon aerogel elements in electrochemical cells, but the embodiments of this specification are not limited to those comprising carbon aerogel. More generally, the porous conductive carbon element (304) may be any of various porous carbon substrates capable of acting as an air cathode. Carbon aerogel materials (e.g., polyimide-derived carbon aerogels) are believed to support high oxidation rates of transition metals such as iron at room temperature, but other porous carbons may have the same effect under appropriate experimental conditions. Additional examples of porous carbon substrates that may be used instead of or in addition to the carbon aerogel substrate include porous graphite carbon substrates, carbon substrates made of carbon nanotubes, carbonized polymer foams (e.g., carbonized polyurethane foams), carbon fullerenes, graphene, graphene oxide, and / or activated carbon. In some examples, the specific surface area of ​​these substrates is at least 100 m² 2It may be / g. For example, the porous conductive carbon element (304) of the present disclosure is in the range of a non-thermally decomposed aerogel precursor (e.g., 100 m 2 / g to 600 m 2 It may be a carbon aerogel having a specific surface area within / g). The porous conductive carbon element (304) may be a carbon aerogel in a monolithic form, a microparticle form, or a combination thereof.

[0129] In certain embodiments, the porous conductive carbon material or composition of the present disclosure has an electrical conductivity of about 1 Siemens (S) / centimeter (cm) or more, about 5 S / cm or more, about 10 S / cm or more, 20 S / cm or more, 30 S / cm or more, 40 S / cm or more, 50 S / cm or more, 60 S / cm or more, 70 S / cm or more, 80 S / cm or more, or within a range between any two of these values.

[0130] In some examples, the redox reaction rate (and more specifically, the oxidation of iron metal) may be selected by modifying one or more conditions under which the reaction is carried out (e.g., increased or decreased relative to a reference reaction rate). In some examples, the reaction rate may be increased by one or more of the following: increasing the temperature under which the reaction is carried out, increasing the partial pressure of oxygen (thereby increasing the rate of hydroxyl anion generation), increasing the concentration of the electrolyte (e.g., from a 1 molar (M) solution to a multimolar solution), and / or increasing the magnitude of the potential difference applied to the carbon aerogel / transition metal system (300). Similarly, the reaction rate may be decreased by limiting any of the aforementioned parameters. Changing the pH of the electrolyte or the composition of the electrolyte may also affect the reaction rate as well as the composition and morphology of the reaction product(s). In addition, if the concentration of the electrolyte is reduced (e.g., from 1 M to 0.2 M) and / or the electrolyte cation (e.g., Na₂ + From K + It was unexpectedly found that changing the ρ) could reduce the average diameter of the nanoparticles from approximately 100 nm to as low as 5 nm to 20 nm. Subsequently, these nanoparticles can be favorably reacted to form lithium metal phosphate cathode materials of similar size with a very high surface area (described in Table 1 below).

[0131] In some examples, excluding gases other than oxygen can affect the reaction products. For example, using pure oxygen or a mixture of gases that exclude carbon dioxide can reduce the presence of carbonate species in the reaction products. This can then reduce and / or eliminate the presence of unwanted reaction products (e.g., carbonates) in the oxidized iron metal compound.

[0132] The separator (308) is an electrical insulating material that provides a structure through which ions can move. This combination prevents electrical short circuits in the system (300) while enabling current flow through ion transfer between the porous conductive carbon element (304) and the iron metal electrode (316). Examples of the separator (308) may include, in particular, cellulose-based paper, fibrous polymer fabric, or felt.

[0133] The electrolyte (312) placed within the separator (308) facilitates the transfer of ions from the porous conductive carbon element (304) to the iron metal electrode (316). Examples of electrolytes include, in particular, sodium chloride (NaCl (aq) ), ammonium chloride (NH3Cl (aq) ), sodium carbonate (NaCO₃ 3(aq) It includes an aqueous solution (e.g., distilled water, deionized water, distilled deionized water, tap water) of potassium chloride (KCl). In some examples, the concentration of the electrolyte may be saturated with the solute. In other examples, the concentration of the electrolyte may be lower than that of the saturated solution. In some examples, the concentration of the electrolyte may be selected according to various criteria, including but not limited to the desired reaction rate at the iron metal anode (typically a higher concentration that accelerates the oxidation rate), the morphology and / or composition of the oxide reaction products at the iron metal anode.

[0134] Regardless of theory, it has been observed that the presence of chloride in the electrolyte promotes the separation of hydroxylated reaction products from the surface of the iron metal electrode (316). Accordingly, when using a chloride-containing electrolyte, the process can naturally convert the entire mass of the iron metal electrode (316) into reaction products because the fresh surface of the iron metal electrode (316) is naturally exposed as the reaction proceeds.

[0135] The iron metal electrode (316) may be an iron metal piece that is electrically and ionically connected to the porous conductive carbon element (304) as illustrated in FIG. 3. In some examples, the iron metal electrode (316) may include a compositional component added to improve conductivity, to improve oxidation reaction kinetics, or both.

[0136] The conductor (320) may be an electrical conductor such as a copper wire, an aluminum wire, a gold wire, and an alloy thereof connecting the carbon aerogel element (304) and the transition metal electrode (316). In some examples, the conductor (320) may also be used to apply a potential to the system (300) to initiate and maintain an oxidation reaction at the iron metal electrode (316).

[0137] In some examples, the minimum applied potential applied through the conductor (320) from an external source depends on the iron metal selected for the iron electrode (316). The minimum applied potential required to promote the oxidation reaction in the iron metal oxide (316) may be an indication of the catalytic activity of the carbon catalyst used to reduce oxygen relative to the iron metal electrode (316) (e.g., for the generation of hydroxyl anions). A maximum electric potential may be selected to avoid electrolysis (electrically induced decomposition) of the electrolyte.

[0138] FIG. 4 is a schematic diagram of an electrochemical cell (400) according to an embodiment of the present disclosure. The electrochemical cell (400) is an alternative representation of some embodiments of the system (300). The electrochemical cell (400) comprises an electrode (404), an iron metal component (408), a conductor (412), a porous conductive carbon element (416), an oxidation reaction product layer (420), and an electrolyte (424).

[0139] Many of the elements shown in the electrochemical cell (400) of FIG. 4 are similar to the elements described above in the context of the system (300) shown in FIG. 3. The electrode (404) may be an electrical contact part through which an iron metal component (408) (similar to the iron metal electrode (316)) conducts electrically. The conductor (412) is similar to the conductor (320). The porous conductive carbon element (416) is similar to the porous conductive carbon element (304).

[0140] In addition to the elements already described in the context of FIG. 3, FIG. 4 schematically illustrates a redox reaction occurring within an electrochemical cell (400) upon the application of an external electric voltage of magnitude 1 volt (V). The magnitude of the minimum value of the applied voltage required to promote the oxidation reaction ("initiation voltage") may be determined by the specific transition metal (i.e., iron) of the component (408) and the catalytic efficiency of the porous conductive carbon element (416). In some examples, oxidation of the iron metal within the electrochemical cell (400) may not occur for applied voltages of magnitude smaller than the minimum value.

[0141] In particular, FIG. 4 schematically illustrates the exposure of a porous conductive carbon element (416) to oxygen. In some examples, the oxygen may be air, or a gas from a commercial gas mixture having a higher oxygen concentration than that found in air. Oxygen may enter a porous conductive carbon element (416) that has been previously wetted with an electrolyte (424). Oxygen may also be finally converted into hydroxyl anions dissolved by the electrolyte (424) when it comes into contact with a porous conductive carbon element (416) that contains and / or is coated with the electrolyte (424).

[0142] Then, the hydroxyl anion may react with the oxidized iron metal component (408) to form one or more of the iron metal oxide, hydroxide, and / or other reaction products (420) resulting from the reaction between the iron metal and the hydroxyl anion. These reaction products are indicated by the shaded area (420) in FIG. 4. The reaction product (420) as shown in FIG. 4 is in direct contact with the iron metal component (408), but is not necessarily required to be. As indicated above, different electrolyte compositions may produce different physical compositions in the reaction product (420). For example, the presence of chloride in the electrolyte (424) produces a reaction product (420) that separates from the iron metal component (408).

[0143] In some examples, oxygen is the cathode within the electrochemical cell (400). That is, oxygen coming into contact with the porous conductive carbon element (416) (functioning as an "air cathode") is reduced during the operation of the electrochemical cell (400). -The arrows in FIG. 4 labeled "" indicate that the oxygen entering the carbon aerogel element (416) is the receiver of electrons generated by the operation of the electrochemical cell (400). Since a large amount of oxygen may come from an inexhaustible source (e.g., from the Earth's atmosphere) or from a source having a mole count equal to or greater than the mole of iron metal in the electrode (408), the iron metal electrode (408) may be selectively reacted and completed. In particular, the iron metal electrode (408) may be reacted and completed when unused reaction surfaces are exposed during the separation of the reaction product (420) from the iron metal component (408). In other examples, the iron metal electrode may be partially or completely reacted upon the diffusion of hydroxyl ions into the unreacted portions of the iron metal electrode (408) through the adhesive layer of the reaction product (420). The electrolytic reaction oxidizes the iron metal (408) to iron(II) hydroxide (Fe(OH)2) and / or a partially oxidized form thereof. Fe(OH)2-xO x The process proceeds to produce "green rust." In practice, this material falls to the bottom of the reaction chamber and can be removed, for example, by gravity or by pumping it into a separate chamber. In a separate chamber, the (partially oxidized) iron hydroxide is treated with air under basic conditions (e.g., pH > 8) to produce magnetic IONP.

[0144] The operation of the electrochemical cell and the formation of oxidized iron metal products (e.g., ferromagnetic iron compounds, ferrimagnetic iron compounds, or both) can be carried out at various temperatures. In some embodiments, the operation is carried out at a temperature between 15°C and 35°C.

[0145] It should be noted that while the preparation of oxidized iron metal products is described herein, the electrochemical / air oxidation process is not limited to iron. Other metals may be used, and those skilled in the art will recognize suitable metals and their oxidation products. Without being bound by theory, if any metal (M) capable of forming a stable divalent cation (e.g., Fe, Mn, Ni, Co, Cu, Zn, Sn, etc.) is used, the immediate reaction product formed on the surface of the M anode is considered to be the corresponding metal dihydroxide salt (M(OH)2). If a metal is used where +2 is the highest possible oxidation state (e.g., Zn) or where an oxidation state higher than +2 is not energetically favorable to form at low temperatures in air (e.g., Ni, Co, Cu), M(OH)2 is also considered to be the final reaction product. For specific cases of Fe (and Mn), since the +3 oxidation state is readily available in low-temperature air, M(OH)2 tends to be an intermediate, resulting in a higher oxidation state depending on the potential-pH conditions as described below in this specification.

[0146] Magnetic IONP (e.g., magnetite, maghemite, and / or solid solutions thereof) is ferromagnetic and can be magnetically separated from the reaction mixture (note that iron hydroxide is paramagnetic). Then, the recovered magnetite is washed and dried for future processing, for example, as an iron source during LFP synthesis.

[0147] As described above, the generated magnetic IONPs underwent XRD analysis, and it was confirmed that the observed XRD pattern matched the calculated pattern of cubic spinel. The magnetic particles produced by this method are in the form of nanoparticles, that is, particles with a size within the 20-100 nm range when observed using a scanning electron microscope. Surprisingly, it was observed that the concentration of the electrolyte used in this process can affect the particle size of the generated particles.

[0148] In certain examples of Fe, Fe(OH)2 and / or its partially oxidized form, FeO x (OH) 2-x It appears to be a first intermediate in which (i.e., "blue rust") is formed. In some embodiments, the iron hydroxide / iron oxide product is an iron-containing hydroxide (Fe(OH)2) or a partially oxidized form (iron oxyhydroxide; FeO). x (OH) 2-x ) is. Accordingly, in some embodiments, the present method further comprises the oxidative conversion of iron hydroxide or iron oxyhydroxide into magnetite (Fe3O4) or maghemite (Fe2O3), respectively. In some embodiments, the oxidative conversion includes aeration under alkaline conditions. Without any specific additional treatment at neutral pH, blue rust is slowly oxidized to goethite (FeOOH). On the other hand, increasing the pH above 8 and oxidation controlled by air produces magnetite (Fe3O4) through dehydration. Further oxidation of magnetite by air yields mahemite (Fe2O3; or Fe8 / 3V1 / 3O4 in spinel notation for magnetite, where V = vacancy). Due to the availability of the +3 oxidation state for manganese, a similar conversion is expected.

[0149] In some embodiments, electrochemical aerooxidation of iron is performed in an alkaline environment, which produces non-magnetic iron oxide / hydroxide forms. In other embodiments, electrochemical aerooxidation of iron is performed as described herein, and the resulting iron hydroxide or iron oxyhydroxide is isolated and subsequently exposed to an aqueous environment having a pH greater than about 8, e.g., about 8, about 9, or about 10, up to about 11, about 12, about 13, or about 14, and then contacted with an oxygen source such as air. In one embodiment, air is bubbled through the iron hydroxide or iron oxyhydroxide suspended or dissolved in an alkaline aqueous system. This alkaline aqueous system may be provided by a solution of a base, such as, for example, a carbonate or hydroxide in water.

[0150] In some embodiments, iron hydroxide / oxide products do not require purification and / or washing to remove contaminants. For examples where sodium chloride is present in the electrolyte, the reaction product may contain positive sodium chloride (NaCl), which can be simply removed by washing the reaction product with water. Sodium chloride causes less environmental pollution and poses a lower threat to human health than sulfates and ammonia produced by alternative treatment technologies. For examples where the electrolyte contains ammonium chloride (NH4Cl), remediation is also less of a concern than in other processes. During calcination, ammonium chloride decomposes into a gaseous mixture of NH3 and HCl at 338°C. The temperature of the gaseous mixture can be reduced to below 338°C after gas generation, causing the NH4Cl to condense back into a solid form, which can be recycled. For this reason, impurities in the NH4Cl salt do not require washing and consequently do not generate wastewater.

[0151] In some embodiments, IONPs such as magnetite, maghemite, or solid solutions or mixtures thereof are magnetic and are separated from the electrolyte (424) by a magnetic process. In particular, exposing the oxide product (420) to a magnetic field (e.g., from a permanent or electromagnet) causes the magnetic IONP product to be attracted to the magnetic field and retained by the magnetic field. The retained magnetite can then be washed, for example, with water and subsequently collected. For example, the magnetic field can be removed, or the magnetite can be physically separated from the magnet. The magnetic IONP can be selectively dried by any suitable traditional means or utilized in the disclosed methods described below in a wet or partially dried form. Since magnetite and maghemite exhibit microwave sensitivity, these reaction products can be heated and, accordingly, dried using microwave radiation, which is more energy-efficient than using indirect heating through a furnace.

[0152] In some embodiments, the group of precursors includes a precursor having microwave sensitivity. In one specific embodiment, magnetite is a preferred transition metal oxide considering the microwave sensitivity of magnetite (i.e., it is a microwave susceptor). By receiving microwave energy and converting it into heat, magnetite enables the carbonization of the organogel and the conversion of the reactants into LFP without wasteful and energy-inefficient furnace processing. As magnetite is consumed during the reaction and carbonization processes, the microwave sensitivity of magnetite decreases. However, during the consumption of magnetite, the organogel is increasingly converted into carbon. Since carbon is also a microwave susceptor, this sustains the conversion of the reactants into LFP by progressively converting more microwave radiation into heat. The magnetic sensitivity of these components (e.g., ferromagnetism, paramagnetism, or both) also supports microwave drying of the reagents and the finished LFP without relying on energy-intensive and cumbersome thermal drying.

[0153] In some embodiments, the iron oxide produced by the disclosed aero-anodization process is nanoparticles. A scanning electron microscope image of the nanoparticle iron oxide produced by the aero-anodization described above is provided as FIG. 5a, which shows an average (approximately cubic) particle size of about 60 nm. Surprisingly, the average particle size reduces the concentration of the electrolyte and / or the electrolyte anions Na + From K + It was found that it can be reduced by changing to. Fe 3-x A powder X-ray diffraction pattern showing the cubic structure of the O4 (0 ≤ x ≤ 0.33) product is provided as FIG. 5B. In some embodiments, IONP is composed of Fe 3-xIt is formed as a solid solution of magnetite-magnhemite having O4 (0 ≤ x ≤ 0.333). In these embodiments, the oxidation state of iron is between 2.67 and 3. The nitrogen BET surface area of ​​the IONP prepared as disclosed may vary, for example, depending on changes in electrolyte identity and concentration. For example, according to the present disclosure, Fe obtained using 1 M NaCl as the electrolyte 3-x O4 is 22.46 m 2 Fe obtained using 0.2 M KCl as an electrolyte, while having a BET surface area of ​​ / g 3-x O4 is 40.22 m 2 It was found that it has a BET surface area of ​​1 / g. Accordingly, the process can be customized to produce particles of different sizes depending on the intended end use. In this case, the term "size" refers to the characteristic dimension of the particle. For approximately spherical particles, the characteristic dimension may be the diameter. In other cases, depending on the shape of the particle, the characteristic dimension may be one or more of width, length, and / or depth.

[0154] Table 1 presents particle size and specific surface area data for the iron oxides of the present disclosure and the corresponding LFPs prepared under various experimental conditions as described herein. It should be noted that some examples involve ball milling to approach a specific surface area unexpectedly 10 times larger than that of commercially available materials.

[0155] Table 1. Particle size and specific surface area data for iron oxide and corresponding LFP

[0156]

[0157] a Embedded inside the LFP carbon network

[0158] b LFP particles are in loose contact with carbon particles as a result of ball milling.

[0159] The disclosed aero-anodization method for producing magnetic IONP can be implemented as a semi-continuous or continuous process, particularly when combined with magnetic separation and cleaning. A non-limiting flowchart of a production method for the semi-continuous synthesis of magnetite is provided as FIG. 6. Each of the processes illustrated in FIG. 6 is described herein in different contexts and requires no further explanation.

[0160] In some embodiments, the transition metal of the transition metal oxide is a combination of manganese and iron (e.g., iron-manganese mixed oxide). In some embodiments, the transition metal oxide is of the formula Fe 3-x Mn x It is a mixed iron manganese oxide having O4 (where 0.0 ≤ x ≤ 1.5). In some embodiments, the resulting lithium transition metal phosphate cathode material is of the formula LiFe 1-y Mn y It has O4 (where 0.0 ≤ y ≤ 0.5).

[0161] Second precursor

[0162] i. Phosphoric acid

[0163] At least a second precursor of the group of precursors comprises a liquid phase having a second density, wherein the second density is less than the first density (e.g., less than about 1, less than about 2, less than about 3, less than about 4, or less than about 5 g / cc).

[0164] In some embodiments, the group of precursors comprises a liquid phase containing aqueous phosphoric acid (H3PO4). An aqueous phosphoric acid solution is generally provided by adding a desired volume of concentrated phosphoric acid to a desired volume of water. The volume of the aqueous solution and the amount of phosphoric acid present in the solution (i.e., concentration) may vary. Generally, phosphoric acid is a transition metal to phosphoric acid (PO4) of approximately 1:1 for the LiMPO4 cathode series and 1:1.5 for the Li3M2(PO4)3 cathode series. 3-It is provided in an amount to provide a molar ratio of ). In some embodiments, the volume of the aqueous solution is selected to provide a phosphoric acid concentration in the range of about 0.1 to about 10 moles (i.e., moles per liter), or about 1 to about 5 moles, such as about 2 to 3 moles.

[0165] ii. Lithium-ion source

[0166] In some embodiments, the liquid phase contains a source of lithium ions. Any lithium compound that is water-soluble or soluble in aqueous phosphoric acid may be used. Examples of suitable lithium salts include, but are not limited to, lithium hydroxides, carbonates, acetates, chlorides, etc. One particularly suitable lithium ion source is lithium carbonate (Li2CO3), which is relatively inexpensive and readily available. Lithium carbonate dissolves gradually in aqueous phosphoric acid, and carbon dioxide gas is generated. At least some of the lithium ions present may be associated with phosphate ions as lithium monophosphate. The amount of the lithium ion source (e.g., lithium carbonate) added may vary. Generally, the lithium ion source is added in an amount sufficient to provide a molar ratio of lithium ions to phosphate and transition metal ions of about 1:1:1.

[0167] iii. Alternative examples for the first or second precursor

[0168] Although the first and second precursors have been described above for transition metal oxides and lithium / phosphate, respectively, it is taken into consideration here that the identities of the first and second precursors may be reversed. Accordingly, the description of the first and second precursors is not intended to be limited to the aforementioned embodiments.

[0169] In addition, other sources of transition metals (e.g., iron) are considered here. For example, the transition metal may be iron, but the source may be something other than an oxide. These alternative examples are now described.

[0170] Alternative transition metal source (iron oxalate)

[0171] In some embodiments, the transition metal is iron, and the source of iron is iron oxalate. Surprisingly, according to the present disclosure, it was discovered that iron oxalate can be used directly in the method without first being converted to iron(III) oxide. Accordingly, in another embodiment, the method comprises the step of combining iron oxalate (FeC2O4), aqueous phosphoric acid (H3PO4), and lithium carbonate as a group of precursors. The resulting lithium iron phosphate cathode material in a conductive carbon matrix was found to have a nanoparticle morphology comparable to that produced by a sequential method (in which iron oxalate is first converted to iron(III) oxide).

[0172] In some embodiments, the transition metal is iron, and the source of iron is iron oxalate. However, in these substitution examples, the iron oxalate is first converted to iron phosphate, which becomes capable of reacting with lithium carbonate and one or more organogel precursor materials. Thus, in another embodiment, the present method combines iron oxalate (FeC2O4) and aqueous phosphoric acid (H3PO4) to form the formula Fe x (PO4) y The method includes the steps of forming a mixture of iron phosphates having (where x is 1 and y is 1, or x is 3 and y is 2), and combining the mixture of iron phosphates with a source of lithium ions. Without being bound by theory, the chemical reactions occurring during mixing and pyrolysis are believed to be represented by the following equations:

[0173] (1) 3 Fe2(C2O4)3+ 2 H3PO4→ Fe x (PO4) y + 3 H2C2O4(for x = y = 1)

[0174] (2) Fe x (PO4) y + ½ Li2CO3+ PAA / H2O → LFP / C (for x = y = 1)

[0175] (3) Fe x (PO4) y + Li3PO4+ PAA / H2O → LFP / C (for x = 3, y = 2).

[0176] Alternative transition metal sources (iron and manganese sulfate)

[0177] In some embodiments, the transition metals are iron and manganese. In one substitution example, iron sulfate and manganese sulfate are made to react with oxalic acid to form a mixed oxalate, which is converted into a mixed iron-manganese oxalate, which is made to react with lithium carbonate and phosphoric acid. Thus, in another embodiment, iron(II) sulfate, manganese(II) sulfate, and oxalic acid are combined in water to form the formula Fe 1-x Mn x A step of forming a precipitate of mixed iron-manganese oxalate of C2O4; the mixed iron-manganese oxalate of formula Fe 2-2x Mn 2x O 3t or Fe 3-x Mn x A method is provided comprising the steps of: exposing a mixed iron-manganese oxalate to air at a temperature within the range of about 350 to about 450°C for a time period sufficient to convert it into a nanoporous mixed iron-manganese oxide of O4, thereby suspending the nanoporous mixed iron-manganese oxide in an aqueous solution of phosphoric acid (H3PO4); mixing the suspension for a certain time period; and adding a source of lithium ions to the suspension to form a reaction mixture. A lithium iron-manganese phosphate cathode material prepared according to this method is of the formula LiFe 1-x Mn x It has PO4 (where x is [0 ≤ x ≤ 1]). Formula Fe prepared by the decomposition of the corresponding mixed oxalate. 2-2x Mn 2xAccording to the present disclosure, the nanoporous mixed iron-manganese oxide of O3 was found to have particles with an average size of approximately several microns, but high-resolution imaging reveals the presence of internal osmotic porosity with a pore diameter of about 100 nm. In addition, Fe 1-x Mn x Fe obtained by the thermal decomposition of C2O4.2H2O 2-2x Mn 2x O3 is about 11.93 m 2 It was found to have a BET nitrogen surface area of ​​ / g.

[0178] Regardless of theory, the chemical reactions occurring during mixing and pyrolysis are believed to be represented by the following equations:

[0179] (1) x FeSO4+ 1-x MnSO4+ H2C2O4+ H2O → Fe x Mn 1-x C2O 4(s) + H + (aq) + SO4 2- (aq)

[0180] (2) Fe x Mn 1-x C2O4 + air → Fe 2-2x Mn 2x O 3(나노다공성) + CO2(350-450℃)

[0181] (3) Fe 2-2x Mn 2x O 3(나노다공성) + 2 H3PO4 + Li2CO3+ PAA / H2O → LMFP / C (나노 미립자)

[0182] In another substitution example, iron sulfate and manganese sulfate can react with oxalic acid to form a mixed oxalate, which can react with phosphoric acid and lithium carbonate. Thus, in another embodiment, the present method comprises: combining iron(II) sulfate, manganese(II) sulfate, and oxalic acid in water, of the formula Fe 1-xMn x A step of forming a mixture containing mixed iron manganese oxalic acid of C2O4; and adding lithium carbonate and aqueous phosphoric acid (H3PO4) to obtain the formula LiFe after pyrolysis. 1-x Mn x It includes the step of forming lithium iron manganese phosphate having PO4 (where x is [0 ≤ x ≤ 1]). Without being bound by theory, the chemical reactions occurring during mixing and pyrolysis are believed to be representable by the following equations:

[0183] (1) x FeSO4+ 1-x MnSO4+ H2C2O4+ H2O → Fe x Mn 1-x C2O 4(s) + H + (aq) + SO4 2- (aq)

[0184] (2) Fe x Mn 1-x C2O4 + ½ Li2CO3 + H3PO4 + PAA / H2O → LMFP / C (nano-particles)

[0185] In another substitution example, iron sulfate and manganese sulfate can be reacted with oxalic acid to form a mixed oxalate, which can then be reacted with phosphoric acid to form an intermediate mixed iron-manganese phosphate. Then, this mixed phosphate can be reacted with lithium phosphate. Thus, in another embodiment, the present method combines iron(II) sulfate, manganese(II) sulfate, and oxalic acid in water to form the formula Fe 1-x Mn x A step of forming a precipitate of mixed iron-manganese oxalate of C2O4; a step of suspending the mixed iron-manganese oxalate in an aqueous phosphoric acid (H3PO4) solution to convert the mixed metallic oxalate into a mixed metallic phosphate; and adding lithium phosphate to obtain the formula LiFe after pyrolysis. 1-x Mn xIt includes the step of forming lithium iron manganese phosphate having PO4 (where x is [0 ≤ x ≤ 1]). Without being bound by theory, the chemical reactions occurring during mixing and pyrolysis are believed to be representable by the following equations:

[0186] (1) x FeSO4+ 1-x MnSO4+ H2C2O4+ H2O → Fe x Mn 1-x C2O 4(s) + H + (aq) + SO4 2- (aq)

[0187] (2) 3 Fe x Mn 1-x C2O4 + 2 H3PO4 → (Fe x Mn 1-x )3(PO4)2+ 3 H2C2O4

[0188] (3) (Fe x Mn 1-x )3(PO4)2+ Li3PO4+ PAA / H2O → 3 LiFe x Mn 1-x PO4 / C

[0189] B. Carbon precursor

[0190] The present method comprises the step of providing one or more carbon precursors in a fluid state, which means that a mixture containing them is flowable, does not have a fixed shape, and is provided with low or no resistance to external stress. One or more carbon precursors in a fluid state are configured to form a solid organogel in the presence of a gelation initiator, and the solid organogel is configured to form a conductive carbon matrix upon pyrolysis. In alternative embodiments, the solid organogel may be formed by removing the liquid phase (e.g., solvent) from the solution. For example, in some embodiments, partial or complete removal of the solvent by drying methods may result in an organogel without gelation induced by the gelation initiator. Generally, the conductive carbon matrix comprises a carbonized form of the organogel and / or its precursor material and surrounds LMP particles and / or its precursors. The conductive carbon matrix may comprise graphitic carbon, amorphous carbon, or a mixture thereof. Upon any subsequent milling, the conductive carbon matrix is ​​retained despite the reduction in particle size.

[0191] In some embodiments, the present method comprises the steps of: mixing a group of lithium transition metal phosphate cathode material precursors with one or more carbon precursors to form a precursor mixture; adding a gelation initiator to the precursor mixture; and allowing one or more carbon precursors to gel to form a solid organogel. As described above in this specification, such a solid organogel is formed in the presence of a precursor for a lithium transition metal phosphate material, and thus, including such precursor, its reaction products, and intermediates, will ultimately result in a lithium transition metal phosphate material upon thermal decomposition of the solid organogel containing such species.

[0192] "Carbon precursor" refers to a material capable of undergoing polymerization or other gelation reactions to produce a solid organogel, and then pyrolyzing to form a conductive carbon matrix. Generally, solid organogels are inherently porous and can form a conductive carbon matrix when exposed to elevated temperature conditions as described below in this specification. In some embodiments, a catalyst or gelation initiator is utilized to initiate and / or complete gelation. Suitable organogels include, but are not limited to, phloroglucinol-furfuraldehyde polymers, resorcinol-furfuraldehyde polymers, phenol-formaldehyde polymers, polyurethanes, melamine-aldehyde polymers, polyacrylamide polymers, polybenzoxazine polymers, polyamic acids, and polyimides. Each of these organogels, each of its precursor materials (i.e., carbon precursors), and gelation conditions are further described below.

[0193] 1. Phloroglucinol-furfural, resorcinol-furfural, and phenol-formaldehyde polymers

[0194] In some embodiments, the solid organogel is a phloroglucinol-furfural (PF) polymer. In these embodiments, the organogel precursor material is phloroglucinol and furfural. In these embodiments, the method generally comprises the steps of adding phloroglucinol and furfural to a reaction mixture, and allowing the phloroglucinol and furfural to react to form an organic matrix containing the PF organogel. Gelation of the phloroglucinol and furfural mixture occurs almost immediately (e.g., 30 seconds or less, 15 seconds or less, 5 seconds or less). Thus, phloroglucinol and furfural are added to the reaction mixture sequentially and individually in any order. In some embodiments, phloroglucinol and furfural are provided separately as ethanol solutions, respectively. A catalyst or initiator is not required. However, in some embodiments, a gelation initiator is utilized. In some embodiments, the gelation initiator is an amine base or an acid. When phloroglucinol and furfural are optionally combined with the initiator, the gelation of the PF polymer occurs rapidly (e.g., within about 30 seconds or less). The resulting PF polymer comprises a number of repeating units ("n") which may vary depending on the reaction conditions and reactant ratios. Generally, the resulting PF organogel has a rigid three-dimensional structure.

[0195] In other embodiments, the solid organogel is a resorcinol-furfural polymer. Such a polymer can be prepared as above, except that phloroglucinol is replaced with resorcinol.

[0196] In other embodiments, the solid organogel is a phenol-formaldehyde (PF) polymer. Such a polymer can be prepared as above, except that phloroglucinol is replaced with phenol and furfural is replaced with formaldehyde.

[0197] 2. Polyurethane polymer

[0198] In some embodiments, the solid organogel comprises or is a polyurethane polymer. In these embodiments, the precursors comprise a polyol and an isocyanate. In some embodiments, the polyol is cellulose. In these embodiments, the gelation initiator comprises an alkylamine (e.g., triethylamine).

[0199] 3. Polyamic acid

[0200] In some embodiments, the organogel is a polyamic acid. A polyamic acid is a polymer amide having repeating units comprising a carboxylic acid group, a carboxyl group, and an aromatic or aliphatic moiety comprising a diamine and a tetracarboxylic acid from which the polyamic acid is derived. A “repeating unit” as defined herein is a part of a polyamic acid (or corresponding polyimide) in which repeating units are connected together continuously along a polymer chain (excluding terminal amino groups or unreacted anhydride terminals) to form a complete polymer chain. Those skilled in the art will recognize that polyamic acid repeating units are derived from the partial condensation of the amino group of a diamine and the carboxyl group of a tetracarboxylic acid dianhydride.

[0201] In some embodiments, the polyamic acid is any commercially available polyamic acid. In other embodiments, the polyamic acid is previously formed ("pre-formed") and isolated, for example, by the reaction of a diamine and a tetracarboxylic acid dianhydride in an organic solvent according to traditional synthesis methods. In either case, whether purchased or manufactured and isolated, the suitable polyamic acid is in a substantially pure form. The pre-formed and isolated or commercially available polyamic acid may be in a solid form, such as a powder or crystal form, for example, or in a liquid form.

[0202] Suitable polyamic acids, polyamides, and methods for producing them are provided, for example, in U.S. Patent Application No. US2022 / 0069290 (Zafiropoulos et al.), and U.S. Patent Applications No. 17 / 546,761 (Leventis) and No. 17 / 546,529 (Begag), the full text of each of which is incorporated herein.

[0203] In some embodiments, the polyamic acid is provided in the form of a water-soluble salt, which can then be precipitated as an insoluble polyamic acid from the reaction mixture by acidifying the reaction mixture. In these embodiments, the organogel precursor material is an ammonium polyamicate or an alkali metal salt, and the method further comprises the step of adding a gelation initiator to the reaction mixture.

[0204] In some embodiments, the organogel precursor material is an ammonium polyamic acid salt comprising, but not limited to, an ammonium salt containing a trialkylamine. In some embodiments, the ammonium salt is a salt of a polyamic acid and trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine, N-methylpyrrolidine, N-methylpiperidine, diisopropylethylamine, or a combination thereof. In some embodiments, the ammonium salt is a salt of a polyamic acid and triethylamine. In some embodiments, the ammonium salt is a salt of a polyamic acid and diisopropylethylamine.

[0205] In some embodiments, the organogel precursor material is an alkali metal salt of a polyamic acid, such as a lithium, sodium, or potassium salt.

[0206] A gelation initiator is generally an acid or substance that can be hydrolyzed to form an acid. One non-limiting example of a suitable acid is acetic acid. One non-limiting example of a suitable material that can be hydrolyzed to form an acid is acetic anhydride. Accordingly, in some embodiments, the method comprises the step of adding acetic acid, acetic anhydride, natural protonated phosphate, or a combination thereof as a gelation initiator. In some embodiments, the method comprises the steps of adding acetic anhydride and allowing the acetic anhydride to be hydrolyzed to form acetic acid, and inducing gelation of the polyamic acid.

[0207] 4. Polyimide

[0208] In some embodiments, the solid organogel comprises or is a polyimide. In some embodiments, the polyimide is formed from the imidation of a polyamic acid. Suitable polyamides and methods for preparing the same are provided, for example, in U.S. Patent Application No. US2022 / 0069290 (Zafiropoulos et al.), and U.S. Patent Applications No. 17 / 546,761 (Leventis) and No. 17 / 546,529 (Begag), the full text of which is incorporated herein.

[0209] In some embodiments, imidizing the polyamic acid salt involves thermally imidizing the corresponding polyamic acid. Irradiation of a wet gel polyamic acid material using microwave frequency energy is a particularly suitable heat treatment.

[0210] In other embodiments, imidizing a polyamic acid salt involves performing chemical imidization, wherein chemical imidization involves adding a gelation initiator to an aqueous solution of the polyamic acid salt to enable the gelation mixture to gel (e.g., in a mold, or cast onto a sheet, or in various other formats such as beads). In these embodiments, the gelation initiator is added to initiate and induce imidization to form a polyimide wet gel from the polyamic acid salt.

[0211] Although the structure of the gelation initiator may vary, it is generally a reagent that is at least partially soluble in the reaction solution while minimizing reactivity with the aqueous solution, reacts with the carboxylic acid groups of the polyamic acid salt, and is effective in inducing the imidation of the polyamic acid carboxylic and amide groups. An example of a suitable class of gelation initiators is a carboxylic acid anhydride, such as acetic anhydride, propionic anhydride, etc. In some embodiments, the gelation initiator is acetic anhydride.

[0212] In some embodiments, the amount of gelation initiator may vary based on the amount of tetracarboxylic acid dianhydride or polyamic acid. For example, in some embodiments, the gelation initiator is present in various molar ratios with the tetracarboxylic acid dianhydride. In some embodiments, the gelation initiator is present in various molar ratios with the polyamic acid. The molar ratio of the gelation initiator to the tetracarboxylic acid dianhydride or polyamic acid may vary depending on the desired reaction time, reagent structure, and desired material properties. In some embodiments, the molar ratio is about 2 to about 10, e.g., about 2, about 3, about 4, or about 5 to about 6, about 7, about 8, about 9, or about 10. In some embodiments, the molar ratio is about 2 to about 5.

[0213] The temperature at which the gelation reaction can proceed may vary, but is generally less than about 50°C, such as about 10 to about 50°C, or about 15 to about 25°C.

[0214] 5. Other Polymer Organogels

[0215] In some embodiments, the solid organogel comprises a melamine-aldehyde polymer. In some embodiments, the solid organogel comprises a polyacrylamide polymer. In some embodiments, the solid organogel comprises a polybenzoxazine polymer. Such polymers, their precursors, and suitable gelation initiators for their formation are known to those skilled in the art.

[0216] 6. Concentration of organogel precursor material

[0217] In some examples, the organogel precursor materials are collectively present at a concentration of the total mixture (i.e., including lithium transition metal phosphate cathode material precursors) that approximates the concentration of the carbon content of the resulting lithium metal phosphate material. For example, the organogel precursor may be present in an amount of approximately 1 wt% to 5 wt% of stoichiometric amounts of lithium, transition metal, and phosphorus precursors in a 1:1:1 ratio.

[0218] C. Mixing

[0219] The present method comprises the step of mixing a group of precursors for synthesizing a lithium transition metal phosphate and one or more carbon precursors in a fluid state for a specified period of time to form a precursor mixture, and then adding a gelation initiator. Mixing is generally performed by stirring the mixture (i.e., as a suspension) at room temperature (e.g., about 20°C) for a period of about 1 hour to about 12 hours, and typically for about 2 hours to about 4 hours. During this time, the particle size of the transition metal oxide is generally reduced from the initial particle size to a particle size within the range of about 1 micron to about 3 microns. Depending on the initial particle size, in some embodiments, it may be desirable to perform active particle size reduction, such as milling or grinding. In other embodiments, such particle size reduction is not performed after the described stirring. The mixture is generally made to be mixed (e.g., by stirring) for a period of time sufficient to enable complete dissolution of the lithium ion source in the aqueous suspension.

[0220] D. Solid Organogel

[0221] As described above in this specification, the method comprises the step of forming a solid organogel by allowing one or more organogel precursor materials to undergo gelation. The term “solid” as used herein with respect to the organogel means that the organogel is self-supporting, for example, that the solid organogel maintains a defined shape without any containment.

[0222] The solid organogel has a three-dimensional external (i.e., macro) and internal (e.g., micro, such as fibrils / pores) structure, whether it comprises a PF polymer, a polyamic acid, or other polymers as described herein. In some embodiments, the solid organogel is a polyamic acid, a polyimide, or a combination thereof. For example, in certain embodiments, the ammonium polyamic acid salt as described above is converted partially to the corresponding polyamide and partially to the corresponding polyimide after gelation. The relative ratio of the polyamic acid to the polyimide may vary. Each ratio may be determined by methods known in the art, such as nuclear magnetic resonance (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). Regardless of theory, a larger proportion of polyimide in the organic matrix is ​​believed to result in a harder solid lithium metal phosphate material embedded in a carbon matrix after pyrolysis. Furthermore, surprisingly, according to the present disclosure, the presence of a relatively larger amount of polyamic acid in the organic matrix provides, in at least some embodiments, a lithium transition metal phosphate / carbon matrix product that has fewer impurities, more uniform particle size, more uniform morphology, or a combination thereof, compared to a product obtained in the presence of a relatively larger amount of polyimide. These differences can be inferred by a number of observation techniques, including but not limited to X-ray diffraction measurements, electron microscopy, and acoustic densitography.

[0223] Solid organogels contain lithium ions, transition metal oxide particles (e.g., iron(II or III) oxide), and phosphate (PO4) suspended therein. 3-It further includes additional components present in the reaction mixture, such as lithium ions and water. At least some of the lithium ions and phosphate ions may be associated as lithium phosphate. Generally, the various species present (lithium and phosphate ions or their salts, transition metal oxides, and water) are held together in close proximity within the organogel. Without being bound by any specific theory, this close physical contact is believed to facilitate the formation of the cathode material during pyrolysis and, preferably, provide desirable physical properties to the cathode material. As described above in this specification, the use of the organogel suppresses phase separation of the precursor materials during the formation of the lithium transition metal phosphate cathode material. Since the formation of the cathode material is a diffusion-limited process, maintaining close contact between the lithium transition metal phosphate precursor materials is particularly important for the efficient and effective synthesis of lithium transition metal phosphate cathode materials. The viscosity of the organogel, the reaction mixture containing the organogel precursor material, or both may vary, and generally, at room temperature and atmospheric pressure, the viscosity of the organogel is selected to be sufficient to prevent precipitation of the solid phase material (including but not limited to transition metal sources such as transition metal oxides and liquid phase material(s)) from the reaction mixture due to the density difference.

[0224] In some examples, the organogel precursor material can gel almost immediately (e.g., less than 30 seconds, less than 15 seconds, less than 5 seconds), thereby causing phase separation of other precursors (e.g., 1 gram / cm³). 3 Solid phase with greater density and about 1 gram / cm³ 3It can prevent a liquid phase having a density of . In some examples, gelation occurs through the polymerization reaction described above without the removal of the solvent. This can reduce the energy input required to produce lithium iron phosphate cathode materials by avoiding or reducing the need for an energy-intensive drying process. In particular, the solid aerogel produced by this gelation is different and distinct from other solid phase materials (e.g., non-gel sugars or starches) utilized in previously reported syntheses of LFP materials within a carbon matrix.

[0225] Additionally, as described in detail herein, the conditions of the precursor and gelation are selected to maintain intimate contact between the reactants during the heat treatment (pyrolysis) required to convert the precursor into a lithium transition metal phosphate cathode material, by ensuring that the resulting organogel maintains a desired solid form. In some embodiments, the solid organogel comprises a porous network of interconnected solid-phase polymer structures, and the porous network maintains contact between the first precursor of the group and the second precursor of the group, e.g., iron oxide and transition metal species such as lithium / phosphate species (e.g., LiH2PO4). In particular, lithium phosphate (LiH2PO4) melts at temperatures above 300°C. Thus, in some embodiments, the organogel maintains contact between the precursors up to a temperature of at least about 300°C. Again, these properties of the disclosed organogel are different from and distinct from other solid-phase materials utilized in previously reported syntheses of LFP materials within a carbon matrix (e.g., sugars or starches that do not maintain structural stiffness when heated).

[0226] E. Pyrolysis

[0227] Then, a solid organogel comprising a lithium transition metal phosphate precursor material (e.g., lithium ions, one or more transition metal oxides, and phosphate ions) is pyrolyzed (e.g., carbonized), which means that the organogel is heated at a constant temperature for a time sufficient to 1) convert substantially all of the organogel material into carbon to form a conductive carbon matrix; 2) optionally reduce a transition metal in a higher oxidation state to a lower state (e.g., the reduction of Fe(III) in Fe2O3 to Fe(II) required in LiFePO4); and 3) form a transition metal phosphate cathode material contained within the conductive carbon matrix. As used herein in the context of pyrolysis, "substantially all" means that more than 95% of the organogel material is converted into carbon, e.g., 99%, or 99.9%, or 99.99%, or even 100% of the organogel. Pyrolysis of an organogel converts it into an isometric carbon matrix, which means that the physical properties of the organogel (e.g., porosity, surface area, pore size, diameter, etc.) are substantially maintained within the corresponding carbon matrix. Without being bound by theory, carbonization is believed to promote good electrical conductivity of the resulting matrix and simultaneously initiate and complete reactions between transition metal oxides, lithium ions, and phosphate ions to form a lithium transition metal phosphate cathode material within the conductive carbon matrix. Furthermore, the organogel material disclosed herein is rich in aromatic rings, which causes the carbon matrix to possess high conductivity upon pyrolysis. Additionally, the uniform distribution of the lithium transition metal phosphate cathode material throughout a continuous three-dimensional conductive carbon matrix provides excellent performance properties for a battery utilizing the cathode material as further described herein.

[0228] Regardless of theory, it is believed that during pyrolysis, the lithium transition metal phosphate cathode material inherits the form of the precursor transition metal oxide and is formed on the transition metal oxide by a templating process. This is considered to be different and distinct from previously reported processes for forming LiFePO4, in which water evaporates from the slurry during evaporation and loose precursor ions are associated.

[0229] In embodiments where the transition metal of the transition metal oxide exists in a higher oxidation state than that present in the lithium transition metal phosphate cathode material as described in detail herein, it is believed that some of the carbon generated during pyrolysis (e.g., from iron(III) to iron(II) present in Fe2O3) plays a role in reducing the oxidation state of the transition metal.

[0230] The temperature required for pyrolysis may vary. In some embodiments, a processing temperature of about 600°C or higher, such as about 600°C, about 650°C, about 700°C, about 750°C, about 800°C, about 850°C, about 900°C, or about 950°C, or within a range between any two of these values, is applied to the organogel matrix to carbonize the organogel matrix and complete the formation of the lithium transition metal phosphate cathode material. In some embodiments, the pyrolysis temperature is about 600 to about 800°C. Generally, pyrolysis is carried out under an inert or somewhat reducing atmosphere to prevent combustion of the organic and / or carbon material and to prevent reoxidation of the transition metal. Suitable atmospheres include, but are not limited to, nitrogen, argon, hydrogen, methane, or combinations thereof. In some embodiments, pyrolysis is carried out under nitrogen.

[0231] In some embodiments, pyrolysis is performed using microwave irradiation. Microwaves are low-energy electromagnetic waves having wavelengths in the range of 0.001 to 0.3 meters and frequencies in the range of 1,000 to 300,000 MHz. A typical microwave device operates as a microwave at a frequency of 2450 MHz. In some embodiments, a group of precursors comprises a precursor that is microwave-sensitive, and pyrolysis is performed by applying microwave radiation.

[0232] In some embodiments, the microwave-sensitive precursor comprises one or more of carbon, magnetite, and maghemite. In some embodiments, the precursor comprises magnetic iron oxide nanoparticles (magnetic IONP), such as nanoparticle magnetite or maghemite. In some embodiments, the microwave-sensitive precursor comprises one or more nanoparticles of magnetite and maghemite having characteristic dimensions of 20 nm to 100 nm.

[0233] In some embodiments, as the magnetic IONP is gradually converted to LiFe(PO4) and the organogel precursor is pyrolyzed into carbon, the microwave absorbing component changes from the magnetic phase to the carbonized component. This is because LiFe(PO4) itself does not react strongly to microwave radiation, but the carbon material is efficiently heated when exposed to microwave radiation as described in detail herein.

[0234] The time required for the completion of pyrolysis may vary and may depend on the temperature and specific matrix components. Generally, pyrolysis conditions are applied to the matrix for a time period ranging from about 4 hours to about 20 hours, such as about 8 hours. In some examples, microwave pyrolysis can be more energy-efficient and faster by using a time period of about 10 minutes to about 3 hours, such as about 10 minutes to about 1 hour, or about 1 hour to about 3 hours.

[0235] Another advantage of the disclosed method is that the carbon source (e.g., an organogel such as polyamide or polyimide) has a high carbon yield; accordingly, a relatively low weight percentage (~20 wt%) of carbon source is required relative to the total reactant composition, leading to high efficiency and cost reduction. In particular, this small amount of carbon source is sufficient to reduce all higher oxidation state transition metal species (e.g., Fe(III) to Fe(II) for magnetic oxide precursors) during pyrolysis and leave about 2-3% of conductive carbon on the surface of the lithium transition metal phosphate.

[0236] Additionally, the carbon sources disclosed herein (e.g., organogels such as the polyamic acids, polyimides, and other polymers described above) contain abundant aromatic rings. Accordingly, during pyrolysis, these materials produce a graphite carbon coating of lithium transition metal phosphates. The graphite carbon produced upon the carbonization of these materials provides better electrical properties (e.g., higher conductivity) than the saturated carbon found from the carbonization of other carbon sources, such as sugars or starches.

[0237] F. Milling

[0238] In some embodiments, one or more milling procedures are optionally applied to the lithium transition metal phosphate cathode material in a conductive carbon matrix to reduce the particle size or to provide a uniform distribution of particle sizes. Any suitable milling technique may be utilized. In some embodiments, milling may be performed using a ball mill. In some embodiments, milling is performed in a stainless steel planetary ball mill at a speed in the range of about 100 rpm to 400 rpm and for a time in the range of about 30 minutes to about 48 hours.

[0239] The necessity of milling, the type of milling, and its duration may vary based on the properties of the conductive carbon matrix. For example, in some embodiments, cathode material particles prepared from the pyrolysis of polyimide organogels have a hard carbon matrix and may require milling to provide a powder material (i.e., having a uniformly small particle size). In contrast, cathode material particles prepared from the pyrolysis of polyamic acid organogels tend to be softer and may require relatively less milling.

[0240] II. Lithium transition metal phosphate cathode material properties

[0241] After pyrolysis, the lithium transition metal phosphate cathode material in the conductive carbon matrix has the formula LiM(PO4) (where M is iron (Fe), manganese (Mn), or a combination of Fe and Mn), or the lithium transition metal phosphate cathode material in the conductive carbon matrix has the formula Li3M(PO4)3 (where M is vanadium (V). In embodiments where M is a combination of Fe and Mn, the stoichiometry of Fe versus Mn may vary. In some embodiments, the Fe to Mn molar ratio may be in the range of about 0.1 to about 10, e.g., about 0.1, about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, or about 1 to about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, or about 10. In some embodiments, the Fe to Mn molar ratio is about 4:1 to about 1:4, about 2:1 to about 1:2, or about 1:1.

[0242] In some embodiments, the lithium transition metal phosphate cathode material in the conductive carbon matrix has the formula LiM(PO4) (where M is iron (Fe), manganese (Mn), or a combination of Fe and Mn), and the source of the transition metal oxide utilized in the method comprises magnetite, maghemite, or a combination thereof. In some of these embodiments, a remainder of magnetite, maghemite, or a combination thereof may remain in the lithium transition metal phosphate cathode material in the conductive carbon matrix. The remainder may vary, but is generally present in an amount sufficient to impart magnetic susceptibility to the cathode material. The magnetic susceptibility imparted by the residual magnetic iron oxide material is generally weak, but may vary sufficiently to be observed at least qualitatively through the interaction of a sample of the lithium transition metal phosphate cathode material in the conductive carbon matrix with a strong neodymium magnet. Quantitative measurements can be performed according to known methods for measuring susceptibility, including but not limited to Gouy balances (where a sample is suspended between the poles of an electromagnet and the change in weight when the electromagnet is switched on is proportional to susceptibility) and Evans balances (measuring the force on the magnet itself).

[0243] In some embodiments, when the lithium transition metal phosphate cathode material in the conductive carbon matrix is ​​prepared from magnetite, maghemite, or a combination thereof, it is about 0.6 to about 1.1 g / cm³ 3 It has a tap density within the range of.

[0244] In some embodiments, the lithium transition metal phosphate cathode material is olivine lithium iron phosphate. Accordingly, in other embodiments, it comprises nanoparticles comprising olivine lithium iron phosphate and integral with a conductive carbon matrix, wherein the nanoparticles have characteristic dimensions of 20 nm to 1000 nm and 10 meters 2 (m 2 ) / gram(g) to 65 m 2A composition is provided having a specific surface area of ​​ / g. In some embodiments, the characteristic dimension is 30 nm to 70 nm and the specific surface area is 20 m² 2 / g to 65 m 2 / g. In some embodiments, the characteristic dimension is 30 nm to 60 nm, and the specific surface area is 22 m². 2 / g to 40 m 2 / g. In some embodiments, the characteristic dimension is 20 nm to 40 nm, and the specific surface area is 60 m². 2 / g to 80 m 2 / g is.

[0245] In some embodiments, the nanoparticles further comprise magnetite, maghemite, or both.

[0246] In some embodiments, the nanoparticles further contain manganese.

[0247] In some embodiments, the conductive carbon matrix comprises a carbonized organogel as described herein.

[0248] III. Method for forming a lithium vanadium fluorophosphate cathode material within a conductive carbon matrix; fluorophosphate ions

[0249] In another aspect of the present disclosure, a method for preparing a lithium vanadium fluorophosphate cathode material in a conductive carbon matrix is ​​provided. The method uses phosphoric acid as a source of fluorophosphate ions (FPO4 2- Except for replacing with ) and selecting vanadium oxide as the transition metal oxide, the method for forming a lithium transition metal phosphate cathode material is substantially similar to the method described in detail herein. The mixing, the source of lithium ions, the organogel precursor material, the gelation, the solid organogel, and the thermal decomposition thereof are each as described in detail herein.

[0250] Vanadium oxide can be any readily available oxide of vanadium, such as vanadium(III) oxide (V2O3), vanadium(IV) oxide (VO2), vanadium(V) oxide (V2O5), or ammonium metavanadate (NH4VO3).

[0251] The source of fluorophosphate ions can vary. For example, fluorophosphates, or fluorophosphate salts, such as sodium or ammonium monofluorophosphate, can be utilized to provide fluorophosphate ions. Alternatively, fluorophosphate ions can be obtained from lithium ion sources, phosphate ion sources, and fluoride ion sources. In situ It may be formed as follows. Sources of lithium, phosphate, and fluoride may be individual or provided in various combinations. For example, the present method may utilize a lithium source as described in detail herein, in combination with a separate source of fluoride and phosphate, such as hydrofluoric acid or ammonium fluoride, and any one of an ammonium salt of an alkali metal or phosphate. Alternatively, the present method may utilize a combined source of lithium and fluoride, such as lithium fluoride. Those skilled in the art will recognize various combinations of lithium, fluoride, and phosphate that may be utilized to provide lithium and fluorophosphate ions in the reaction mixture, and all such combinations are considered herein. The order of addition of any of these components (lithium ion source, fluoride ion and phosphate ion source, fluorophosphate source, etc.) may vary, be sequential, or be simultaneous.

[0252] After pyrolysis, the lithium vanadium fluorophosphate cathode material in the conductive carbon matrix has the formula LiVFPO4. The resulting cathode material can be optionally milled as described above with respect to the lithium transition metal phosphate material.

[0253] IV. Method for forming a lithium vanadium fluorophosphate cathode material within a conductive carbon matrix; F - Fluoropolymer as a source

[0254] In another aspect of the present disclosure, an alternative method for preparing a lithium vanadium fluorophosphate cathode material within a conductive carbon matrix is ​​provided. The method is substantially similar to the method for forming a lithium vanadium fluorophosphate cathode material as described herein, except that the source of the fluorophosphate ions is replaced with phosphoric acid and the fluoride is provided in the form of a fluoropolymer. The mixing, the source of the lithium ions, the organogel precursor material, the gelation, the solid organogel, and the pyrolysis thereof are each as described herein. The method further adds a fluoropolymer to the precursor mixture prior to gelation.

[0255] Vanadium oxide can be any readily available oxide of vanadium, such as vanadium(III) oxide (V2O3), vanadium(IV) oxide (VO2), vanadium(V) oxide (V2O5), or ammonium metavanadate (NH4VO3).

[0256] Examples of suitable fluoropolymers include, but are not limited to, polytetrafluoroethylene, polyvinylidene difluoride, and combinations thereof. Without being bound by theory, it is considered that these fluoropolymers are not chemically incorporated into the organogel polymer (e.g., as a physical combination) but are physically incorporated into the organogel matrix, and during subsequent pyrolysis, the fluoropolymer reacts with phosphate ions to form fluorophosphate. In situFluorine species are decomposed and liberated, forming or reacting directly with vanadium oxide species, to form intermediates of final species in which fluorine harmonizes with vanadium. This alternative method addresses potential problems associated with employing fluorophosphate sources such as fluorophosphoric acid (H2FPO3). Specifically, fluorophosphoric acid is progressively hydrolyzed into H3PO4 and hydrofluoric acid (HF). HF is volatile and toxic, and since it can avoid the reaction mixture upon drying, it is difficult to maintain the required 1:1:1:1 lithium:vanadium:phosphate:fluorine stoichiometry. The method disclosed herein using a fluoropolymer avoids the burden of using fluorophosphoric acid.

[0257] V. Method for forming a lithium vanadium fluorophosphate cathode material within a conductive carbon matrix; fluoromonomer

[0258] In another aspect of the present disclosure, an alternative method for preparing a lithium vanadium fluorophosphate cathode material in a conductive carbon matrix is ​​provided. The present method is substantially similar to the method for forming a lithium vanadium fluorophosphate cathode material using a fluoropolymer as described above, except that the fluoropolymer is replaced with a fluoride monomer that copolymerizes with an organogel precursor material to form an organogel in which at least some of the hydrogen atom substituents are replaced with fluorine atoms.

[0259] Similar to the method for preparing a lithium vanadium fluorophosphate cathode material within a conductive carbon matrix using a fluoropolymer as disclosed above, this alternative method employs a fluorinated monomer that is chemically incorporated into the organogel polymer. The phrase “at least a portion of one or more organogel precursor materials comprises a fluorinated monomer” means that some amount of one or more organogel precursor materials is fluorinated. The amount of fluorinated monomer present as an organogel precursor material can vary, for example, from about 1% to about 100% of the total amount of organogel precursor material utilized. Additionally, the degree of fluorination within the monomer (i.e., the number of fluorinated substituents present on a given organogel precursor monomer structure) may vary. In some embodiments, the organogel is a polyimide, and a portion of the polyimide organogel precursor material (e.g., a diamine and a tetracarboxylic acid dianhydride, or a polyamic acid) has one or more fluorinated substituents. In some embodiments, the polyamide is derived from an organogel precursor material which is phenylenediamine and tetracarboxylic acid dianhydride. In situ It is formed as phenylenediamine, tetracarboxylic acid dianhydride, or both, having one or more fluorine substituents. In certain embodiments, the fluoride monomer is 1,4-phenylenediamine having one or more fluorine atoms, e.g., 2,3,5,6-tetrafluorobenzene-1,4-diamine. Again, utilizing an organogel precursor material having fluorine substituents as a fluoride source avoids the loss of volatile and toxic HF gas during the initial stages of solvent evaporation and initial drying.

[0260] VI. Energy storage system

[0261] In another aspect of the present disclosure, an energy storage system is provided comprising a lithium transition metal phosphate cathode material as described herein. In another aspect of the present disclosure, the system comprises olivine lithium iron phosphate and nanoparticles integral with a conductive carbon matrix, wherein the nanoparticles have characteristic dimensions of 20 nm to 1000 nm and 10 meters 2 (m 2 ) / gram(g) to 65 m 2 An energy storage system comprising a composition having a specific surface area of ​​ / g is provided.

[0262] Examples of energy storage systems include batteries such as lithium-ion batteries comprising a composition or cathode material as described herein. Further disclosed herein are battery cells, battery modules, battery packs, electronic devices, and electric vehicles comprising a composition or cathode material as described herein.

[0263] In this application, certain U.S. patents, U.S. patent applications, and other materials (e.g., papers) are incorporated by reference. However, the text of such U.S. patents, U.S. patent applications, and other materials is incorporated by reference only to the extent that there is no conflict between such text and other statements and drawings presented in this specification. In the event that such conflict arises, any conflicting text incorporated by the U.S. patents, U.S. patent applications, and other materials is not incorporated by reference in this patent. In combination with this disclosure, any feature disclosed in any one or more published documents referenced in this specification is to be protected. All methods described in this specification may be performed in any suitable order unless otherwise specified in this specification or clearly contradictory in the context. Any and all examples provided in this application, or the use of representative language (e.g., “e.g., for example”), are intended only to better elucidate the materials and methods and do not impose any limitation on the scope unless otherwise claimed. No language in the specification should be construed as indicating any unclaimed element as essential to the practice of the materials and methods disclosed in this specification.

[0264] It will be readily apparent to those skilled in the art that other suitable modifications and adaptations to the compositions, methods, and examples of application described herein may be made without departing from the scope of the embodiments or any of such embodiments. The provided compositions and methods are exemplary and are not intended to limit the scope of the claimed embodiments. All of the various embodiments and options disclosed herein may be combined in any modifications. The scope of the compositions, formulations, methods, and processes described herein includes all actual or potential combinations of the embodiments, options, examples, and preferred examples described herein.

[0265] Although the technology described herein has been explained with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the technology. It will be apparent to those skilled in the art that various modifications and variations may be made to the methods and apparatus of the technology without departing from the spirit and scope of the technology. Accordingly, the technology is intended to include modifications and variations within the scope of the appended claims and their equivalents.

[0266] Throughout this specification, references to “one embodiment,” “some embodiments,” “one or more embodiments,” or “modions” mean that a specific feature, structure, material, or characteristic described in relation to an embodiment is included in at least one embodiment of the technology. Accordingly, the appearance of phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment,” or “in an embodiment” in various places throughout this specification does not necessarily refer to the same embodiment of the technology. Furthermore, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. The invention may also be extensively made of parts, elements, steps, examples, and / or features mentioned or indicated herein, individually or collectively, in any and all combinations of two or more of the said parts, elements, steps, examples, and / or features. In particular, one or more features in any of the embodiments, examples, and embodiments described herein may be combined with one or more features from any other examples and embodiments described herein.

[0267] Aspects of the present technology are more fully illustrated by reference to the following examples. Before describing some exemplary aspects of the present technology, it will be understood that the present technology is not limited to the details of the configurations or process steps presented in the following description. Other aspects of the present technology may be implemented or carried out in various ways.

[0268] Further modifications and alternative embodiments of the present invention will be apparent to those skilled in the art by taking into account this description. Accordingly, this description should be interpreted merely as illustrative and is intended to teach those skilled in the art the general manner of carrying out the present invention. It should be understood that the forms of the present invention shown and described herein are to be taken as examples of embodiments. Elements and materials may be replaced with those exemplified and described herein, parts and processes may be reversed, and certain features of the present invention may be used independently, all of which will be apparent to those skilled in the art after taking advantage of this description of the present invention. Modifications to the elements described herein may be made without departing from the spirit and scope of the present invention as described in the following claims.

[0269] Although certain exemplary embodiments of the invention have been described, the scope of the appended claims is not intended to be limited only to these embodiments. The claims should be interpreted to include, by design, and / or equivalents.

[0270] The following examples are provided to illustrate certain embodiments of the present technology and should not be construed as limiting.

[0271] Examples

[0272] The present invention may be further illustrated by the following non-limiting examples describing the methods.

[0273] Example 1: Synthesis of lithium iron phosphate in a carbon matrix (Fe 2 O 3 / phloroglucinol / furfuraldehydride).

[0274] Samples of lithium iron phosphate in a carbon matrix were prepared using iron(III) oxide (Fe2O3) as the iron source and a phloroglucinol-furfuraldehydride polymer as the carbon source. Iron(III) oxide (2.8 g, 13 mmol; particle size of 5 microns or less) was added to deionized water (10 ml), and the suspension was stirred at room temperature for 5 minutes. Phosphoric acid (85% H3PO4; 2 ml, 26 mmol) was added, and the suspension was stirred for 2 hours. Lithium carbonate (Li2CO3; 0.96 g, 13 mmol) was added, and the resulting suspension was stirred until the generation of carbon dioxide ceased. In a separate container, phloroglucinol (1.68 g) was dissolved in 10 ml of ethanol. Furfuraldehydride (1.68 ml) was added to the phloroglucinol solution, and the solution was mixed for 5 minutes. After mixing, the solution was added as a portion to the iron oxide / lithium / phosphate suspension. The suspension was stirred overnight at room temperature to produce a viscous mixture. The solvent (ethanol and water) was evaporated by stirring at 100°C. A homogeneous dry powder was obtained by pyrolysis under nitrogen using the temperature gradient provided in Table 2 to provide pulverized lithium iron phosphate in a carbon matrix.

[0275] Table 2. Pyrolysis protocol

[0276]

[0277] Samples of powdered lithium iron phosphate within a carbon matrix were analyzed by scanning electron microscopy. Microscopic images at two magnifications (1,490x and 5,050x) are provided as Figs. 7a and 7b, respectively. Referring to Figs. 7a and 7b, the lithium iron phosphate is formed as primary particles with sizes ranging from submicrons to several microns. The primary particles aggregate into secondary particles with diameters of tens of microns and are interconnected through the carbon matrix. The samples were also subjected to powder X-ray diffraction (XRD) analysis, which demonstrated that the major phase of the material is olivine-type LiFePO4, and the minor phase contains unidentified impurities (Fig. 8).

[0278] Example 2: Synthesis of lithium iron phosphate in a carbon matrix (Fe(OH) 3 / Phloroglucinol / Furfuraldehydride)

[0279] Samples of lithium iron phosphate in a carbon matrix were prepared using iron(III) hydroxide (Fe(OH)3) as the iron source and a phloroglucinol-furfuraldehydride polymer as the carbon source. The iron(III) hydroxide was prepared by dissolving iron(III) nitrate hydrate (Fe(NO3)-3.9H2O; 3.50 g; 8.7 mmol) in deionized water (30 ml). A solution of sodium hydroxide (2.1 g; 52.5 mmol) was added to this solution in deionized water (15 ml) to immediately form an aqueous suspension of the iron(III) hydroxide gel. The iron hydroxide gel was aged overnight in the mother solution, after which it was separated and purified by cycles of centrifugation and resuspension in deionized water (total 5 cycles). After adding phosphoric acid (85% H3PO4; 0.7 ml, 8.7 mmol), lithium carbonate (Li2CO3; 0.32 g, 4.3 mmol) was added, and the resulting suspension was stirred until the generation of carbon dioxide ceased. In a separate container, phloroglucinol (1.05 g) was dissolved in 4 ml of ethanol. Furfuraldehydride (0.57 ml) was added to the phloroglucinol solution, and the solution was mixed for 5 minutes. After mixing, the solution was added in part to the iron hydroxide / lithium / phosphate suspension. The suspension was stirred overnight at room temperature to produce a viscous mixture. The solvents (ethanol and water) were evaporated by stirring at 100°C. A homogeneous dry powder was obtained by pyrolysis under nitrogen using the protocol described in Example 1 to provide lithium iron phosphate in a carbon matrix.

[0280] Samples of powdered lithium iron phosphate within a carbon matrix were analyzed by scanning electron microscopy. Microscopic images at two magnifications (10,000x and 49,900x) are provided as Figs. 9a and 9b, respectively. Referring to Figs. 9a and 9b, the LFP is formed as microcrystals with a diameter of about 100 nm to about 1 micron, which are uniformly dispersed in a conductive carbon network. Aggregates of secondary particles vary in size from about 1 micron to several microns and have an open framework structure through which the electrolyte can penetrate. The samples were also subjected to powder X-ray diffraction (XRD) analysis, which demonstrated that the major phase of the material is olivine-type LiFePO4, and the minor phase contains approximately 2% iron (Fig. 10). The iron impurity phase can be magnetically separated or, for example, can be used as a ferromagnetic agent to increase the packing density of particles within the cathode film during magnetic electrode film casting.

[0281] Example 3: Synthesis of lithium iron phosphate in a carbon matrix (Fe(OH) 3 / phloroglucinol / furfuraldehydride

[0282] A second sample of lithium iron phosphate in a carbon matrix was prepared according to the procedure of Example 2, except that twice the ratio of PF precursors to LFP precursors was used to evaluate the effect of residual carbon on the particle size distribution and impurity profile.

[0283] Samples of powdered lithium iron phosphate within a carbon matrix were analyzed by scanning electron microscopy at two magnifications (10,000x and 100,000x). Microscopic images for each magnification are provided as Figs. 11a and 11b, respectively. Referring to Figs. 11a and 11b, the LFP is formed as microcrystals with a diameter of about 100 nm to about 1 micron, which are uniformly dispersed in a conductive carbon network. Aggregates of secondary particles vary in size from about 1 micron to several microns and have an open framework structure through which the electrolyte can penetrate. The samples were also subjected to powder X-ray diffraction (XRD) analysis, which demonstrated that the major phase of the material is olivine-type LiFePO4, and the minor phase contains approximately 3% iron (Fig. 12). The iron impurity phase can be magnetically separated or, for example, can be used as a ferromagnetic agent to increase the packing density of particles within the cathode film during magnetic electrode film casting.

[0284] Example 4: Synthesis of lithium iron phosphate in a carbon matrix (Fe 2 O 3 / Pyromellitic acid dianhydride / 1,4-phenylenediamine; PAA / low PI gel)

[0285] Samples of lithium iron phosphate in a carbon matrix were prepared using iron(III) oxide (Fe2O3) as the iron source and polyimide gel as the carbon source. Iron(III) oxide (10.38 g, 65 mmol) was added to deionized water (50 ml), and the suspension was stirred at room temperature for 5 minutes. Phosphoric acid (85% H3PO4; 10 ml, 130 mmol) was added, and the suspension was stirred for 2 hours. Lithium carbonate (Li2CO3; 5.05 g, 68.2 mmol) was added, and the resulting suspension was stirred until the generation of carbon dioxide ceased. In a separate container, 1,4-phenylenediamine (PDA; 2.0 g), pyromellitic acid dianhydride (PMDA; 6.8 g), and triethylamine (9.3 ml) were added to deionized water (100 ml). The mixture was reacted overnight to form a solution of polyamic acid triethylammonium salt. Acetic anhydride (11.3 ml) was added to this solution to initiate imidization. After mixing for 1 minute, the gelation solution was partially added to the iron suspension. The resulting reaction mixture was loosely capped and heated at 100°C with stirring for 24 hours. During this time, the solvent evaporated, and a homogeneous dry powder was obtained. The organic matrix contained a mixture of polyamic acid and polyimide abundant within the polyamic acid. This dry powder was pyrolyzed using the protocol described in Example 1 to provide lithium iron phosphate in a carbon matrix.

[0286] Samples of powdered lithium iron phosphate within a carbon matrix were analyzed by scanning electron microscopy. Microscopic images at two magnifications (2,000x and 20,000x) are provided as Figs. 13a and 13b, respectively. Referring to Figs. 13a and 13b, the LFP is formed as aggregates of submicron primary particles held together by a conductive carbon network into secondary particles with a diameter of approximately 10 microns. The samples were also subjected to powder X-ray diffraction (XRD) analysis, which demonstrated that the major phase of the material is olivine-type LiFePO4, and the minor phase contains unidentified impurities (Fig. 14).

[0287] Example 5: Synthesis of lithium iron phosphate in a carbon matrix (Fe 2 O 3 / Pyromellitic acid dianhydride / 1,4-phenylenediamine; PAA / low PI gel)

[0288] Samples of lithium iron phosphate in a carbon matrix were prepared using iron(III) oxide (Fe2O3) as the iron source and a polyamic acid gel as the carbon source. Iron(III) oxide (10.38 g, 65 mmol) was added to deionized water (50 ml), and the suspension was stirred at room temperature for 5 minutes. Phosphoric acid (85% H3PO4; 10 ml, 130 mmol) was added, and the suspension was stirred for 2 hours. Lithium carbonate (Li2CO3; 5.05 g, 68.2 mmol) was added, and the resulting suspension was stirred until the generation of carbon dioxide ceased. In a separate container, 1,4-phenylenediamine (PDA; 2.0 g), pyromellitic acid dianhydride (PMDA; 6.8 g), and triethylamine (9.3 ml) were added to deionized water (100 ml). The mixture was reacted overnight to form a solution of triethylammonium polyamic acid salt. Then, immediately after adding the gel precursor mixture to the iron oxide suspension, acetic anhydride (11.3 ml) was added. The resulting reaction mixture was loosely capped and heated with stirring at 100°C for 24 hours. During this time, the solvent evaporated, and a homogeneous dry powder was obtained. The organic matrix mainly contains polyamic acid and has a small amount of polyimide. Without being bound by theory, the acidic environment is believed to have caused minimal imidization, resulting in the hydrolysis of acetic anhydride into acetic acid and the gelation of the insoluble polyamic acid. This dry powder was pyrolyzed using the protocol described in Example 1 to provide lithium iron phosphate in a carbon matrix.

[0289] Samples of powdered lithium iron phosphate within a carbon matrix were analyzed by scanning electron microscopy. Microscopic images at two magnifications (2,000x and 50,000x) are provided as Figs. 15a and 15b, respectively. Referring to Figs. 15a and 15b, the LFP is formed as aggregates of uniform 2-micron primary particles assembled into 10-micron secondary particles within a porous network into which the electrolyte can penetrate. The samples were also subjected to powder X-ray diffraction (XRD) analysis, which demonstrated that the major phase of the material is olivine-type LiFePO4, and the minor phase contains unidentified impurities (Fig. 16).

[0290] Example 6: Synthesis of lithium iron phosphate in a carbon matrix (Fe 2 O 3 / Pyromellitic acid dianhydride / 1,4-phenylenediamine; PAA / Intermediate PI gel)

[0291] Samples of lithium iron phosphate in a carbon matrix were prepared using iron(III) oxide (Fe2O3) as the iron source and a polyamic acid gel as the carbon source. Iron(III) oxide (10.38 g, 65 mmol) was added to deionized water (50 ml), and the suspension was stirred at room temperature for 5 minutes. Phosphoric acid (85% H3PO4; 10 ml, 130 mmol) was added, and the suspension was stirred for 2 hours. Lithium carbonate (Li2CO3; 5.05 g, 68.2 mmol) was added, and the resulting suspension was stirred until the generation of carbon dioxide ceased. In a separate container, 1,4-phenylenediamine (PDA; 2.0 g), pyromellitic acid dianhydride (PMDA; 6.8 g), and triethylamine (9.3 ml) were added to deionized water (100 ml). The mixture was reacted overnight to form a solution of the polyamic acid triethylammonium salt. Triethylamine (approximately 20 mL) was added to the iron oxide suspension to raise the pH to approximately 8.0 (from an initial 4.0). Then, the gel precursor solution was added all at once into the iron oxide suspension, followed by the addition of acetic anhydride (11.3 mL) to initiate chemical imidation. The resulting reaction mixture was loosely capped and heated with stirring at 100°C for 24 hours. During this time, the solvent evaporated, yielding a homogeneous dry powder. The organic matrix contained primarily polyamic acid along with some polyimide. Without being constrained by theory, a relatively neutral environment is believed to have increased the imidation / gelation of the polyamic acid salt compared to Examples 4 and 5. This dry powder was pyrolyzed using the protocol described in Example 1 to provide lithium iron phosphate in a carbon matrix.

[0292] A sample of the product was subjected to powder X-ray diffraction (XRD) analysis, which confirmed that the material is a mixture of LiFePO4 (<70% wt.) and unreacted Li3PO4 (~30% wt.), with the balance being Fe (Fig. 17). This example surprisingly indicates that, due to the higher PI / PAA ratio within the organogel, a significant portion of the unreacted reagent is present in the final product. Regardless of theory, rigid polyimide gels are believed to result in less efficient contact between LFP precursors, leading to poor reaction homogeneity and low production yield.

[0293] Example 7: Raman spectroscopy of a carbon matrix

[0294] Examples 1 to 7 In situ The electronic structure of the formed carbon is evaluated by Raman spectroscopy. Regardless of theory, the carbon matrix formed according to the disclosed methods is believed to be more conductive than the particulate carbon added to the lithium metal phosphate cathode material.

[0295] Example 8: Analysis of carbon nanostructures

[0296] The nanostructures of the carbon matrix of the cathode material formed in Examples 1 to 7 are evaluated by dissolving lithium metal phosphate from the carbon matrix. The remaining carbon material is analyzed to determine porosity, pore size, and carbon strut size. Specifically, framework density is determined by pore structure and surface via He specific gravity measurement and N2 sorption isotherms. SEM, TEM, Raman, and X-ray scattering are performed for mid-to-long-range microstructure analysis. Elemental analysis of CHN is also performed.

Claims

Claim 1 A method for preparing an olivine lithium iron phosphate cathode material within a conductive carbon matrix, comprising the steps of: providing a suspension in which iron oxide is suspended in an aqueous solution of phosphoric acid (H3PO4); mixing the suspension for a certain period of time; adding a source of lithium ions to the suspension to form a reaction mixture; adding one or more organogel precursor materials to the reaction mixture; and enabling the one or more organogel precursor materials to gel, thereby forming an organogel, lithium ions, iron (II or III) oxide, and phosphate (PO4 3- A method comprising: a step of forming an organic matrix containing ions; and a step of pyrolyzing the organic matrix for a certain period of time and at a temperature sufficient to form the lithium iron phosphate cathode material within the conductive carbon matrix. Claim 2 A method for preparing a lithium iron phosphate cathode material within a conductive carbon matrix, comprising the steps of: providing a suspension in which magnetite is suspended in an aqueous solution of phosphoric acid (H3PO4); adding a source of lithium ions to the suspension to form a reaction mixture; adding one or more organogel precursor materials to the reaction mixture; and enabling the one or more organogel precursor materials to gel, thereby allowing the organogel, lithium ions, magnetite, and phosphate (PO4 3- A method comprising: a step of forming an organic matrix containing ions; and a step of pyrolyzing the organic matrix for a certain period of time and at a temperature sufficient to form the lithium iron phosphate cathode material within the conductive carbon matrix, wherein the pyrolysis comprises applying microwave radiation to the organic matrix. Claim 3 A method for preparing an olivine lithium iron phosphate cathode material within a conductive carbon matrix, comprising the steps of: providing iron oxalate (FeC2O4); exposing the iron oxalate to air at a temperature within the range of about 350°C to about 450°C for a period sufficient to convert the iron oxalate into nanoporous Fe2O3; suspending the nanoporous Fe2O3 in an aqueous solution of phosphoric acid (H3PO4); mixing the suspension for a certain period of time; adding a source of lithium ions to the suspension to form a reaction mixture; adding one or more organogel precursor materials to the reaction mixture; allowing the one or more organogel precursor materials to gel, thereby forming an organogel, lithium ions, iron (II or III) oxide, and phosphate (PO4 3- A method comprising: a step of forming an organic matrix containing ions; and a step of pyrolyzing the organic matrix for a certain period of time and at a temperature sufficient to form the lithium iron phosphate cathode material within the conductive carbon matrix. Claim 4 A method for manufacturing a lithium vanadium fluorophosphate cathode material within a conductive carbon matrix, comprising: combining a group of precursors for synthesizing the lithium vanadium fluorophosphate cathode material — said group of precursors includes vanadium oxide, a source of lithium ions, and a source of fluorophosphate ions —; providing one or more carbon precursors in a fluid state — said one or more carbon precursors are configured to form a solid organogel in the presence of a gelation initiator, said solid organogel is configured to form a conductive carbon matrix upon pyrolysis —; mixing the group of precursors with said one or more carbon precursors to form a precursor mixture; adding said gelation initiator to said precursor mixture; and enabling said one or more carbon precursors to gel to form a solid organogel. A method comprising the step of pyrolyzing the solid organogel to form the lithium vanadium fluorophosphate cathode material within the conductive carbon matrix, wherein the lithium vanadium fluorophosphate cathode material has the formula LiVFPO4. Claim 5 A method for preparing a lithium vanadium fluorophosphate cathode material within a conductive carbon matrix, comprising: combining a group of precursors for synthesizing the lithium vanadium fluorophosphate cathode material — said group of precursors includes vanadium oxide, a source of lithium ions, and phosphoric acid —; providing one or more carbon precursors in a fluid state — said one or more carbon precursors are configured to form a solid organogel in the presence of a gelation initiator, said solid organogel is configured to form a conductive carbon matrix upon pyrolysis —; adding a fluoropolymer to the precursor mixture before gelation; mixing the group of precursors with said one or more carbon precursors to form a precursor mixture; adding the gelation initiator to the precursor mixture; causing said one or more carbon precursors to gel to form a solid organogel; and pyrolyzing said solid organogel to form the lithium vanadium fluorophosphate cathode material within the conductive carbon matrix. Claim 6 A method for preparing a lithium vanadium fluorophosphate cathode material within a conductive carbon matrix, comprising: combining a group of precursors for synthesizing the lithium vanadium fluorophosphate cathode material — said group of precursors includes vanadium oxide, a source of lithium ions, and phosphoric acid —; providing one or more carbon precursors in a fluid state — said one or more carbon precursors are configured to form a solid organogel in the presence of a gelation initiator, said solid organogel is configured to form a conductive carbon matrix upon pyrolysis, said one or more carbon precursors include a fluoride monomer —; mixing the group of precursors with said one or more carbon precursors to form a precursor mixture; adding the gelation initiator to the precursor mixture; and enabling said one or more carbon precursors to gel to form a solid organogel — said fluoride monomer copolymerizes with said one or more carbon precursors so that at least some of the hydrogen atom substituents in said solid organogel are replaced with fluorine atoms —; A method comprising the step of pyrolyzing the solid organogel to form the lithium vanadium fluorophosphate cathode material within the conductive carbon matrix. Claim 7 A method for manufacturing a lithium iron manganese phosphate cathode material within a conductive carbon matrix, wherein the lithium iron manganese phosphate is of the formula LiFe 1-x Mn x Having PO4 (where x is [0 ≤ x ≤ 1]), the method comprises: combining iron(II) sulfate, manganese(II) sulfate, and oxalic acid in water, with formula Fe 1-x Mn x A step of forming a mixture comprising a mixed iron manganese oxalate of C2O4; a step of adding a lithium carbonate, aqueous phosphoric acid (H3PO4), and one or more organogel precursor materials to the mixture; a step of enabling the one or more organogel precursor materials to gel, thereby forming an organogel, lithium ions, a mixed iron manganese oxide, and a phosphate (PO4 3- A method comprising: a step of forming an organic matrix containing ions; and a step of pyrolyzing the organic matrix for a certain period of time and at a temperature sufficient to form the lithium iron manganese phosphate cathode material within the conductive carbon matrix. Claim 8 A method for manufacturing a lithium iron manganese phosphate cathode material within a conductive carbon matrix, wherein the lithium iron manganese phosphate is of the formula LiFe 1-x Mn x Having PO4 (where x is [0 ≤ x ≤ 1]), the method comprises: combining iron(II) sulfate, manganese(II) sulfate, and oxalic acid in water, with formula Fe 1-x Mn x A step of forming a precipitate of mixed iron-manganese oxalate of C2O4; said mixed iron-manganese oxalate of formula Fe 2-2x Mn 2x O3 or Fe 3-x Mn x A method comprising: exposing the mixed iron-manganese oxalate to air at a temperature within the range of about 350°C to about 450°C for a time period sufficient to convert it into a nanoporous mixed iron-manganese oxide of O4; suspending the mixed iron-manganese oxalate in an aqueous solution of phosphoric acid (H3PO4); adding a lithium carbonate and one or more organogel precursor materials to the mixture; allowing the one or more organogel precursor materials to gel to form an organic matrix comprising an organogel, lithium ions, mixed iron-manganese oxide, and phosphate ions; and pyrolyzing the organic matrix for a certain time period and at a temperature sufficient to form the lithium iron-manganese phosphate cathode material within the conductive carbon matrix. Claim 9 A method according to any one of claims 1 to 8, wherein the solid organogel is formed within 5 seconds to 15 minutes after the addition of the gelation initiator. Claim 10 A method according to any one of claims 1 to 8, wherein the solid organogel comprises a porous network of interconnected solid phase polymer structures. Claim 11 A method according to claim 10, wherein the porous network maintains contact between the first precursor of the group and the second precursor of the group. Claim 12 A method according to claim 11, wherein the contact is maintained at a temperature of at least about 300°C. Claim 13 A method according to any one of claims 1 to 8, wherein the solid organogel comprises a phloroglucinol-furfural polymer or a resorcinol-furfural polymer, and the one or more carbon precursors are phloroglucinol or resorcinol and furfural. Claim 14 In paragraph 13, the method wherein the gelation initiator is an amine base or an acid. Claim 15 A method according to any one of claims 1 to 8, wherein the solid organogel comprises a polyurethane polymer and the one or more carbon precursors comprise a polyol and an isocyanate. Claim 16 A method according to claim 15, wherein the gelling initiator comprises an alkylamine. Claim 17 A method according to any one of claims 1 to 8, wherein the organogel comprises a polyamic acid polymer and the gelation initiator comprises acetic anhydride, acetic acid, or a combination thereof. Claim 18 A method for producing nanoporous iron(III) oxide (Fe2O3), comprising the steps of: providing iron oxalate (FeC2O4); and exposing the iron oxalate to air at a temperature within the range of about 350°C to about 450°C for a period of time sufficient to convert the iron oxalate into the nanoporous Fe2O3. Claim 19 Formula Fe 2-2x Mn 2x A method for preparing a nanoporous mixed iron-manganese oxide of O3, comprising combining iron(II) sulfate, manganese(II) sulfate, and oxalic acid in water, wherein the formula Fe 1-x Mn x A method comprising: a step of forming a precipitate of mixed iron manganese oxalate of C2O4; and a step of exposing the mixed iron manganese oxalate to air at a temperature within the range of about 350°C to about 450°C for a period sufficient to convert the mixed iron manganese oxalate into the nanoporous mixed iron manganese oxide.

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