Process for preparing lithium cathode materials made from transition metal phosphates

Abstract

The present disclosure is directed to a method for forming lithium transition metal phosphate and fluorophosphate materials within a conductive carbon matrix. The disclosed method is advantageous in that it utilizes inexpensive reactants, can reduce the formation of impurities during synthesis while providing a more homogeneous product, and can provide a cathode material with improved tap density compared to conventional lithium transition metal phosphates. The lithium transition metal phosphate and fluorophosphate materials prepared by the disclosed method are intimately mixed with carbon within a continuous three-dimensional conductive carbon matrix. The materials prepared according to the disclosed method are suitable for use in environments involving electrochemical reactions, for example as cathode materials in lithium ion batteries.

Description

[Technical Field]

[0001] Cross-reference of related applications This application incorporates, by reference, the entirety of the following: U.S. Provisional Patent Application No. 63 / 381777 filed November 1, 2022; U.S. Provisional Patent Application No. 63 / 381771 filed November 1, 2022; U.S. Provisional Patent Application No. 63 / 381694 filed October 31, 2022; U.S. Provisional Patent Application No. 63 / 381687 filed October 31, 2022; U.S. Provisional Patent Application No. 63 / 381681 filed October 31, 2022; and U.S. Provisional Patent Application No. 63 / 381681 filed October 31, 2022. We claim priority and interest in U.S. Provisional Patent Application No. 3 / 381672, U.S. Provisional Patent Application No. 63 / 381666 filed October 31, 2022, U.S. Provisional Patent Application No. 63 / 416996 filed October 18, 2022, U.S. Provisional Patent Application No. 63 / 378756 filed October 7, 2022, U.S. Provisional Patent Application No. 63 / 352571 filed June 15, 2022, U.S. Provisional Patent Application No. 63 / 336640 filed April 29, 2022, and U.S. Provisional Patent Application No. 63 / 326353 filed April 1, 2022.

[0002] This disclosure generally relates to cathode active materials for use in lithium-ion batteries and processes for producing them. [Background technology]

[0003] One of the most common forms of rechargeable batteries is the lithium-ion battery (LIB). LIBs are widely found in a variety of applications, from handheld electronics to automobiles. LIBs are 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 (recharge). Traditionally, the anode of an LIB is made of graphite and / or alloyed material (e.g., Si) or oxide (e.g., Li4Ti5O) in which lithium ions intercalate within a graphite layer during the charge cycle. 12) are formed from materials that provide energy storage. LIB cathode materials are generally nickel, cobalt, or manganese ("NCM"), or aluminum oxide compounds. NCM cathode materials are targeted because they have a higher charging capacity (approximately 200 milliampere-hours / gram (mAh / g)) compared to other types of cathode materials. However, these materials can be expensive to prepare, requiring the acquisition and processing of expensive ores to provide the necessary precursors, and can have adverse environmental impacts due to the generation of toxic waste materials during acquisition and processing.

[0004] Another LIB cathode material is lithium iron phosphate (e.g., LiFePO4, "LFP"). Such LFP cathode materials have a lower theoretical charge capacity (approximately 170 mAh / g) than NCM cathode materials. Nevertheless, LFP has many commercial advantages, including, but not limited to, a reduced environmental impact, as well as cheaper precursors compared to the ore used to prepare NCM. However, LFP has 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.

[0005] Therefore, it would be desirable in the art to provide a method for preparing lithium transition metal phosphate cathode active materials that are efficient, relatively inexpensive, and have a low environmental impact. [Overview of the project]

[0006] This technology generally relates to a method for preparing lithium phosphate cathode materials within a conductive carbon matrix.

[0007] Various solid-phase and solution-phase methods for forming lithium iron phosphate (LFP) materials have been previously reported. See, for example, U.S. Patent Publication No. 2011 / 0110838 to Wang et al., U.S. Patent Publication No. 2008 / 0099720 to Huang et al., U.S. Patent Publication Nos. 2010 / 0065787 and 2011 / 0091772 to Mishima et al., U.S. Patent No. 7,988,879 to Park et al., U.S. Patent No. 7,060,238 to Saidi et al., European Patent Publication No. 1,921,698 to Dong, and International Patent Publication No. WO2004 / 092065 to Barker et al.

[0008] The method disclosed herein has advantages, in at least some aspects, compared to previously reported methods for preparing LFP materials, which include LFPs within a conductive carbon matrix. Previously reported methods, for example, provide LFP cathode materials containing carbon, which is typically added using either carbon particles (e.g., carbon black) or the thermal decomposition of a mixture of LFP precursors and sugar molecules. None of these conventional methods for introducing carbon into a cathode material provide a conductive matrix equivalent to that provided by the method disclosed herein.

[0009] Some or all of the benefits of the embodiments described herein involve eliminating various process steps in LFP synthesis compared to more conventional methods by which LFP cathode materials are synthesized. For example, many conventional LFP processes use solution chemistry techniques that can generate large amounts of wastewater (e.g., aqueous ammonia solutions). Wastewater generation is almost completely avoided in some embodiments of this disclosure. Furthermore, conventional solid-phase reactions that produce LFP (and largely avoid wastewater generation) have the disadvantage of requiring considerable energy input to mix and grind large amounts of high-density solid-phase powder. Also, due to the difficulty in achieving and maintaining a compositionally homogeneous mixture of precursors, the product of powder mixtures is unlikely to be a homogeneous and uniform LFP. Since embodiments of this disclosure maintain close contact between reactants in a viscous medium, the degree and duration of mixing and grinding are reduced compared to conventional techniques. This reduces the energy and process complexity required for LFP synthesis. A further advantage is that the method requires only thermal decomposition under an inert (e.g., nitrogen) atmosphere. In contrast, certain conventional methods require a reducing (hydrogen) atmosphere, adding complexity, cost, and risk to carrying out such synthesis. The disclosed method, remarkably, allows for control of the carbon content in the lithium transition metal phosphate cathode material within a conductive carbon matrix to a range of approximately 1–10 wt%, providing an LFP active material utilization rate of 85–90% (suitable for commercial products), and is scalable and inexpensive. Furthermore, in some embodiments, the disclosed method provides lithium transition metal phosphate with improved tap density compared to conventional lithium transition metal phosphate, thereby improving the commercial viability of such materials in battery packs. The disclosed method, and the materials prepared by this method, have additional advantages further described below herein.

[0010] The methods disclosed herein generally include 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 gelling initiator to the precursor mixture, enabling gelation of one or more carbon precursors to form a solid organogel, and thermally decomposing 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 gelling initiator, and the solid organogel is configured to form a conductive carbon matrix upon thermal decomposition. It is understood that the solid organogel produced by the methods disclosed is formed by the gelation of the carbon precursors, and the thermal decomposition of the organogel generates a conductive carbon matrix. Throughout this disclosure, in the context of the described methods, the terms “solid organogel” and “organogel” are intended to be interpreted as further including precursors and / or intermediate reaction products of various precursors for synthesizing lithium transition metal phosphate cathode materials, unless the context otherwise makes it clear that only organogels are being described. In the disclosed methods, at least a first precursor from 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 from the group comprises a liquid phase having a second density, the second density being less than the first density. The solid organogel prevents the solid phase components in the group of precursors from separating from the liquid phase components in the group of precursors (e.g., settling due to a density gradient between the solid and liquid phases). In particular, solid organogels maintain uniform contact of the lithium transition metal phosphate groups of the precursors within the mixture, allowing the precursors to react and form lithium transition metal phosphate cathode materials (e.g., lithium iron phosphate (LFP)). Furthermore, solid organogels can also contribute to the commercially viable synthesis of LFPs by being converted into the conductive carbon matrix required for the use of LFPs as cathode materials.

[0011] As described above, the method disclosed herein is advantageous for maintaining uniform contact between various precursor materials, for example, an Fe precursor and lithium phosphate. Importantly, the solid organogel material used in the method is selected to maintain a solid state at fairly high temperatures (e.g., up to at least about 300°C), so that 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 with LFP and not undergo phase separation, even if LiH2PO4 melts into the liquid phase at the LFP synthesis reaction temperature. The organogel precursor and conditions are selected to allow for rapid gelation (e.g., less than 15 minutes, such as a few seconds to about 15 minutes), so the advantage of the solid organogel in maintaining contact between precursors is rapidly realized. Furthermore, in some embodiments, the method provides closer mixing and interaction of precursor materials at a smaller scale (e.g., nanoscale solvation molecules) compared to methods of mixing constituent components as solid-phase (e.g., micron-sized) particles. This closer mixing can mitigate the formation of impurities during synthesis and provide a more homogeneous product. Surprisingly, such close mixing can achieve a reduction or even elimination of the high-consumption grinding required in previously reported processes. Another advantage of the disclosed method is that the gelation of organogel precursors in the presence of a lithium phosphate transition metal precursor allows for the production of a cathode material that, after thermal decomposition, is closely mixed with carbon in a continuous three-dimensional conductive carbon matrix.

[0012] Therefore, in one embodiment, a method for preparing a lithium transition metal phosphate cathode material in a conductive carbon matrix, wherein the method is The combination of a group of precursors for synthesizing a lithium transition metal phosphate cathode material, wherein at least one first precursor from the group comprises a solid phase having a first density greater than 1 gram (g) / cubic centimeter (cc), and at least one second precursor from the group comprises a liquid phase having a second density, the second density being less than the first density. To provide one or more carbon precursors in a fluid state, wherein the one or more carbon precursors are configured to form a solid organogel in the presence of a gelling initiator, and the solid organogel is configured to form a conductive carbon matrix upon thermal decomposition. The process involves mixing a group of precursors with one or more carbon precursors to form a precursor mixture, Adding a gelling initiator to the precursor mixture, This enables the gelation of one or more carbon precursors, forming a solid organogel. A method is provided which includes thermally decomposing a solid organogel to form a lithium transition metal phosphate cathode material within a conductive carbon matrix.

[0013] In some embodiments, the solid organogel is formed within 5 seconds to 15 minutes after the addition of the gelling initiator.

[0014] In some embodiments, the solid organogel comprises a porous network of interconnected solid-phase polymer structures.

[0015] In some embodiments, the porous network maintains contact between a first precursor of the group and a second precursor of the group.

[0016] In some embodiments, the contact is maintained at a temperature of at least about 300°C.

[0017] In some embodiments, the first precursor comprises iron, the second precursor comprises a lithium source and phosphoric acid, and the phosphate transition metal lithium cathode material is lithium iron phosphate.

[0018] In some embodiments, iron exists in the form of iron(II) salts, iron(III) salts, iron(II) oxide (FeO), iron(III) oxide (Fe2O3), mixed iron oxides (Fe3O4), or combinations thereof.

[0019] In some embodiments, the solid organogel comprises a phloroglucinol-furfural polymer or a resorcinol-furfural polymer, wherein one or more carbon precursors are phloroglucinol or resorcinol and furfural. In some embodiments, the gelation initiator is an amine base or an acid.

[0020] 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 gelling initiator comprises an alkylamine.

[0021] In some embodiments, the organogel comprises a polyamic acid polymer, and the gelling initiator comprises acetic anhydride, acetic acid, or a combination thereof.

[0022] In some embodiments, the group of precursors includes microwave-sensitive precursors, and thermal decomposition is carried out by applying microwave radiation. In some embodiments, the microwave-sensitive precursors include one or more of carbon, magnetite, and maghemite. In some embodiments, the microwave-sensitive precursors include one or more nanoparticles of magnetite and maghemite having characteristic dimensions of 20 nm to 100 nm.

[0023] In some embodiments, the first precursor comprises manganese, vanadium, or both; the second precursor comprises a lithium source and phosphoric acid; and the phosphate transition metal lithium cathode material is lithium manganese phosphate or lithium vanadium phosphate.

[0024] In some embodiments, the method further includes drying a lithium phosphate cathode material by applying microwave radiation.

[0025] In some embodiments, the solid phase having a first density greater than 1 gram comprises a ferromagnetic iron compound, a ferrimagnetic iron compound, or both.

[0026] In some embodiments, ferromagnetic iron compounds, ferrimagnetic iron compounds, or both are synthesized by a method comprising oxidizing an iron-containing anode in an electrochemical cell containing a porous carbon substrate, an oxygen cathode, and an electrolyte in contact with both the iron-containing anode and the porous carbon substrate, thereby producing particles of ferromagnetic iron compounds, ferrimagnetic iron compounds, or both having characteristic dimensions of 20 nm to 100 nm.

[0027] In some embodiments, the method further includes removing particles by magnetic filtration.

[0028] In some embodiments, the method further includes drying the particles by applying microwave radiation.

[0029] In some embodiments, the operation of the electrochemical cell and the formation of ferromagnetic iron compounds, ferrimagnetic iron compounds, or both are carried out at a temperature of 15°C to 35°C.

[0030] In another embodiment, a lithium transition metal phosphate cathode material prepared by the method disclosed herein is provided.

[0031] In yet another embodiment, an energy storage system is provided that includes a lithium transition metal phosphate cathode material prepared by a method disclosed herein.

[0032] In a further embodiment, a composition comprising olivine-type lithium iron phosphate and nanoparticles integrated with a conductive carbon matrix, wherein the nanoparticles have characteristic dimensions of 20 nm to 1000 nm and 10 m 2(m 2 ) / gram (g) to 65 m 2 / g, a composition is provided. In some embodiments, the characteristic dimension is from 30 nm to 70 nm, and the specific surface area is 20 m 2 / g to 65 m 2 / g. In some embodiments, the characteristic dimension is from 30 nm to 60 nm, and the specific surface area is 22 m 2 / g to 40 m 2 / g. In some embodiments, the characteristic dimension is from 20 nm to 40 nm, and the specific surface area is 60 m 2 / g to 80 m 2 / g.

[0033] In some embodiments, the nanoparticles further comprise magnetite, maghemite, or both.

[0034] In some embodiments, the nanoparticles further comprise manganese.

[0035] In some embodiments, the conductive carbon matrix comprises a carbonized organogel polymer matrix.

[0036] In yet another embodiment, an energy storage system comprising the composition disclosed herein is provided.

[0037] This disclosure includes, but is not limited to, the following embodiments.

[0038] Embodiment 1: A method of preparing a lithium transition metal phosphate cathode material within a conductive carbon matrix, the method comprising combining a group of precursors for synthesizing the lithium transition metal phosphate cathode material, wherein 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, the second density being less than the first density, the combining; To provide one or more carbon precursors in a fluid state, wherein the one or more carbon precursors are configured to form a solid organogel in the presence of a gelling initiator, and the solid organogel is configured to form a conductive carbon matrix upon thermal decomposition, The group of precursors is mixed with one or more carbon precursors to form a precursor mixture. Adding the gelation initiator to the precursor mixture, To enable gelation of one or more carbon precursors and to form the solid organogel, The method comprising thermally decomposing the solid organogel to form the lithium phosphate transition metal cathode material within the conductive carbon matrix.

[0039] Embodiment 2: The method according to Embodiment 1, wherein the solid organogel is formed within 5 seconds to 15 minutes after the addition of the gelling initiator.

[0040] Embodiment 3: The method according to Embodiment 1 or 2, wherein the solid organogel comprises a porous network of interconnected solid-phase polymer structures.

[0041] Embodiment 4: The method according to any one of Embodiments 1 to 3, wherein the porous network maintains contact between the first precursor of the group and the second precursor of the group.

[0042] Embodiment 5: The method according to any one of Embodiments 1 to 4, wherein the contact is maintained at a temperature of at least about 300°C.

[0043] Embodiment 6: The method according to any one of Embodiments 1 to 5, wherein the first precursor comprises iron, the second precursor comprises a lithium source and phosphoric acid, and the phosphate transition metal lithium cathode material is lithium iron phosphate.

[0044] Embodiment 7: The method according to any one of Embodiments 1 to 6, wherein the first precursor comprises iron, the second precursor comprises a lithium source and phosphoric acid, and the phosphate transition metal lithium cathode material is lithium iron phosphate.

[0045] Embodiment 8: The method according to any one of Embodiments 1 to 7, wherein the iron exists in the form of an iron(II) salt, an iron(III) salt, iron(II) oxide (FeO), iron(III) oxide (Fe2O3), mixed iron oxide (Fe3O4), or a combination thereof.

[0046] Embodiment 9: The method according to any one of Embodiments 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.

[0047] Embodiment 10: The method according to Embodiment 9, wherein the gelation initiator is an amine base or an acid.

[0048] Embodiment 11: The method according to any one of Embodiments 1 to 8, wherein the solid organogel comprises a polyurethane polymer and the one or more carbon precursors comprises a polyol and an isocyanate.

[0049] Embodiment 12: The method according to Embodiment 11, wherein the gelling initiator comprises an alkylamine.

[0050] Embodiment 13: The method according to any one of Embodiments 1 to 8, wherein the organogel comprises a polyamic acid polymer and the gelling initiator comprises acetic anhydride, acetic acid, or a combination thereof.

[0051] Embodiment 14: The method according to any one of Embodiments 1 to 13, wherein the group of precursors includes a microwave-sensitive precursor, and the thermal decomposition is carried out by applying microwave radiation.

[0052] Embodiment 15: The method according to Embodiment 14, wherein the microwave-sensitive precursor comprises one or more of carbon, magnetite, and maghemite.

[0053] Embodiment 16: The method according to Embodiment 14, wherein the microwave-sensitive precursor comprises one or more nanoparticles of magnetite and maghemite having characteristic dimensions of 20 nm to 100 nm.

[0054] Embodiment 17: The method according to any one of the prior embodiments, wherein the first precursor comprises manganese, vanadium, or both, the second precursor comprises a lithium source and phosphoric acid, and the phosphate transition metal lithium cathode material is lithium manganese phosphate or lithium vanadium phosphate.

[0055] Embodiment 18: The method according to any one of the prior embodiments, further comprising drying the lithium transition metal phosphate cathode material by applying microwave radiation.

[0056] Embodiment 19: The method according to any one of the prior embodiments, wherein the solid phase having a first density of more than 1 gram comprises a ferromagnetic iron compound, a ferrimagnetic iron compound, or both.

[0057] Embodiment 20: The method according to any one of the prior embodiments, wherein the ferromagnetic iron compound, the ferrimagnetic iron compound, or both are synthesized by a method comprising oxidizing an iron-containing anode in an electrochemical cell containing 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 ferrimagnetic iron compound, or both having characteristic dimensions of 20 nm to 100 nm.

[0058] Embodiment 21: The method according to Embodiment 20, further comprising removing the particles by magnetic filtration.

[0059] Embodiment 22: The method according to any one of the prior embodiments, further comprising drying the particles by applying microwave radiation.

[0060] Embodiment 23: The method according to Embodiment 20, wherein the operation of the electrochemical cell and the formation of the ferromagnetic iron compound, the ferromagnetic iron compound, or both are carried out at a temperature of 15°C to 35°C.

[0061] Embodiment 24: A lithium transition metal phosphate cathode material prepared by a method disclosed herein.

[0062] Embodiment 25: An energy storage system comprising a lithium transition metal phosphate cathode material prepared by a method disclosed herein.

[0063] Embodiment 26: A composition comprising olivine-type lithium iron phosphate and nanoparticles integrated with a conductive carbon matrix, wherein the nanoparticles have characteristic dimensions of 20 nm to 1000 nm and 10 m 2 (m 2 ) / grams (g) ~ 65m 2 The composition having a specific surface area of ​​ / g.

[0064] Embodiment 27: The characteristic dimensions are 30 nm to 70 nm, and the specific surface area is 20 m². 2 / g~65m 2 The composition according to embodiment 26, wherein the amount is / g.

[0065] Embodiment 28: The characteristic dimensions are 30 nm to 60 nm, and the specific surface area is 22 m². 2 / g~40m 2 The composition according to embodiment 26, wherein the amount is / g.

[0066] Embodiment 29: The characteristic dimensions are 20 nm to 40 nm, and the specific surface area is 60 m². 2 / g~80m 2 The composition according to embodiment 26, wherein the amount is / g.

[0067] Embodiment 30: The composition according to any one of Embodiments 26 to 29, wherein the nanoparticles further comprise magnetite, maghemite, or both.

[0068] Embodiment 31: The composition according to any one of Embodiments 26 to 30, wherein the nanoparticles further comprise manganese.

[0069] Embodiment 32: The composition according to any one of Embodiments 26 to 31, wherein the conductive carbon matrix comprises a carbide organogel polymer matrix.

[0070] Embodiment 33: An energy storage system comprising the composition disclosed herein.

[0071] These and other features, aspects, and advantages of this 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 above aspects, and any combination of any two, three, four, or more features or elements described herein, whether such features or elements are expressly combined in the description of a particular aspect herein. This disclosure is intended to be read as a whole so that, unless the context clearly indicates otherwise, any separable features or elements of the disclosed invention in any of its various aspects should be considered as intended to be combinable.

[0072] To provide an understanding of the aspects of the technology, accompanying drawings, not necessarily drawn to scale, are referenced. The drawings are illustrative only and should not be construed as limiting the technology. The disclosure described herein is shown in the accompanying drawings as illustrative, not limiting. [Brief explanation of the drawing]

[0073] [Figure 1] Figure 1 is a schematic diagram of the conventional solid-state synthesis pathway for lithium iron phosphate in a carbon matrix. [Figure 2] Figure 2 is a schematic diagram of a slurry / sol-gel synthesis pathway to lithium iron phosphate in a carbon matrix, according to a non-limiting aspect of this disclosure. [Figure 3] Figure 3 schematically illustrates a system for oxidizing transition metals, including but not limited to iron, using carbon aerogel components in a non-limiting embodiment. [Figure 4] Figure 4 schematically shows an electrochemical cell for oxidizing transition metals, including but not limited to iron, using carbon aerogel components in a non-limiting embodiment. [Figure 5A] Figure 5A is a scanning electron microscope image at 100,000x magnification of a sample of nanoparticle magnetite (Fe3O4) prepared by forced-air anodic oxidation of iron, according to a non-limiting aspect of this disclosure. [Figure 5B] Figure 5B shows the powder X-ray diffraction (XRD) pattern of a sample of nanoparticle magnetite prepared by forced-air anodic oxidation of iron, according to a non-limiting aspect of this disclosure. [Figure 6] Figure 6 is a schematic diagram of a semi-continuous method, according to a non-limiting aspect of the present disclosure, for preparing nanoparticle magnetite from forced-air anodic oxidation of iron and converting it to lithium iron phosphate in a carbon matrix. [Figure 7] Figures 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 this disclosure. [Figure 8] Figure 8 shows the powder X-ray diffraction (XRD) pattern of a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of this disclosure. [Figure 9] Figures 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 this disclosure. [Figure 10]Figure 10 shows the powder XRD pattern of a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of this disclosure. [Figure 11] Figures 11A and 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. [Figure 12] Figure 12 shows the powder XRD pattern of a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of this disclosure. [Figure 13] Figures 13A and 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 this disclosure. [Figure 14] Figure 14 shows the powder XRD pattern of a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of this disclosure. [Figure 15] Figures 15A and 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 this disclosure. [Figure 16] Figure 16 shows the powder XRD pattern of a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of this disclosure. [Figure 17] Figure 17 shows the powder XRD pattern of a sample of lithium iron phosphate in a carbon matrix prepared according to a non-limiting aspect of this disclosure. [Modes for carrying out the invention]

[0074] Before describing some exemplary embodiments of this technology, it should be understood that this technology is not limited to the configuration or process step details described below. Other embodiments of this technology are possible and can be practiced or implemented in various ways.

[0075] Generally, this technology relates to a method for preparing lithium transition metal phosphate cathode materials in a conductive carbon matrix. Surprisingly, according to this disclosure, the lithium transition metal phosphate cathode materials prepared as disclosed herein provide a more homogeneous product without requiring a high-consumption grinding step, and also provide a cathode material with improved tap density compared to conventional methods for preparing lithium transition metal phosphate. Furthermore, the method disclosed provides a lithium transition metal phosphate cathode material closely mixed with carbon in a continuous three-dimensional conductive carbon matrix.

[0076] Accordingly, provided herein are methods for preparing lithium iron phosphate, lithium transition metal phosphate, and lithium vanadium fluorophosphate cathode materials in a conductive carbon matrix. As a general, non-limiting description, the methods disclosed generally include combining a group of precursors for synthesizing lithium transition metal phosphate cathode materials, 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 gelling initiator to the precursor mixture, enabling gelation of one or more carbon precursors to form a solid organogel, and thermally decomposing the solid organogel to form a lithium transition metal phosphate cathode material in a conductive carbon matrix. Further provided are a lithium transition metal phosphate cathode material prepared by the methods disclosed, a composition comprising olivine-type lithium iron phosphate and nanoparticles integrated with a conductive carbon matrix, and an energy storage system comprising the lithium transition metal phosphate cathode material or composition described herein. Each of the components, materials, and products comprising the materials of the methods is further described below herein.

[0077] definition The following definitions are provided for terms used in this disclosure. This application uses the following terms, as defined below, unless the context of the text requires a different meaning for any other term that appears.

[0078] The articles “a” and “an” are used herein to refer to one or more (i.e., at least one) of the grammatical objects of the article.

[0079] The term “about” as used throughout this specification is used to describe and explain small variations. For example, the term “about” may mean ±10% or less, or ±2%, ±1%, ±0.5%, ±0.2%, ±0.1%, or ±0.05%, etc., up to ±5%. All numerical values ​​in this specification, whether explicitly stated or not, are modified by the term “about.” Naturally, values ​​modified by the term “about” include a specific value. For example, “about 5.0” must include 5.0.

[0080] Any scope cited herein is exhaustive.

[0081] As used herein, the terms “including” and “including,” and their variations thereof, mean to include the specified feature, step, or integer. This term shall not be construed as excluding the presence of other features, steps, or components. The present invention includes, consists of, or is essentially derived from the features disclosed and claimed.

[0082] In the context of this disclosure, the terms “framework” or “framework structure” refer to a network of interconnected oligomers, polymers, or colloidal particles that form a solid structure in 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 structures of this disclosure may also include a network of interconnected oligomers, polymers, or colloidal particles of all diameter sizes that form a solid structure within a gel or xerogel.

[0083] In some embodiments, the gel material may be specifically referred to herein as a xerogel. As used herein, the term “xerogel” refers to a type of gel comprising an open, non-fluid colloid or polymer network formed by removing all leavening agents from a corresponding wet gel without taking precautions to avoid substantial volume reduction or delay compression. Xerogels generally consist of a compact structure. Xerogels undergo substantial volume reduction during ambient pressure drying, generally measured by nitrogen adsorption analysis, to about 0 to about 20 m³. 2 0-100mg (e.g., / g) 2 It has a surface area of ​​ / g.

[0084] As used herein, the terms “gelation” or “gel transition” refer to the formation of a wet gel from a polymer system, e.g., PF or polyimide as described herein. At the point of polymerization, imidization, or drying as described herein, defined as the “gel point,” the sol loses its fluidity. While not intended to be bound by any particular theory, the gelation point can be considered the point at which the gelling 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 polyamic acid) through a highly viscous dispersion state, solidifying into a sol-gel (gel point), resulting in a wet gel (e.g., a polyimide gel). The time it takes for a polymer in solution to transform into a gel in a form that can no longer flow is referred to as the “phenomenological gelation time.” Formally, the gelation time is measured using rheology. At the gel point, the elastic properties of the solid gel begin to outweigh the viscous properties of the fluid sol. The formal gelation time is close to the time when the complex moduli of the real and hypothetical components of the gelling sol intersect. The two moduli are monitored in correlation with time using a rheometer. Time measurement begins the moment the last component of the sol is added to the solution. For example, see the discussion of gelation in 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; and M. Muthukumar, “Screening effect on viscoelasticity near the gel point,” Macromolecules, 1989, 22, 4656-4658.In some embodiments, gelation is induced by the addition of a suitable gelation initiator. In other embodiments, gelation can be induced, for example, by the removal of the solvent from a solution containing a salt of a polyamic acid. Such solvent removal can be achieved by various drying techniques, including, but not limited to, spray drying.

[0085] As used herein, the term “wet gel” refers to a gel in which a mobile interposing phase within a network of interconnected pores is primarily composed of a liquid phase such as a conventional solvent or water. Examples of wet gels include, but are not limited to, alcohol gels, hydrogels, ketogels, carbon gels, and other wet gels known to those skilled in the art.

[0086] As used herein, the term “carbon xerogel” refers to a porous carbon-based material. Some non-limiting examples of carbon xerogels include carbide xerogels such as carbide polyimide gels. In the context of xerogels, the term “carbide” refers to an organogel (e.g., PF polymer or polyimide) that has been thermally decomposed or converted into at least substantially pure carbon. As used herein, the terms “thermal decomposition,” “thermal decomposition,” or “carbide” refer to the decomposition or conversion of an organic matrix into pure or substantially pure carbon caused by heat. During such thermal decomposition as described below herein, reactions occur among the various components present in the matrix, and simultaneously or subsequently, the respective phosphoric acid or fluorophosphate transition metal lithium cathode materials are formed within the carbon matrix.

[0087] As used herein, the term "average particle size" refers to D 50This is synonymous with meaning that half of the particles in a population have a particle size above this point, and the other half have a particle size below this point. Particle size can be measured by laser light scattering techniques or by microscopy techniques. Unless otherwise indicated, the average particle size reported herein is obtained by a calibration scale bar and visual interpretation of SEM images using image processing software (such as ImageJ). Multiple particles are measured randomly, the results are averaged, and the standard deviation is calculated. For secondary particles and aggregates, laser diffraction particle size analysis is used.

[0088] In the context of this disclosure, the term “density” refers to a measure of mass per unit volume of a material. The term “density” generally refers to the true or He true density of a material, the bulk density of a material or composition, or the tap density of a material or composition. Density is typically expressed in kg / m³. 3 or g / cm 3 It is reported as such.

[0089] The true density of He in a material is the ratio of the mass to the volume of the material, excluding pores and interparticle gaps within the material. The true density of He can be determined by methods known in the art, including, but not limited to, helium pycnometry.

[0090] The bulk density of a material is the ratio of the mass to the volume of the material, including pores within the material and voids between particles. Also referred to as "envelope density," bulk density can be determined by methods known in the art, including, but not limited to, the 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 Determination of the apparent density of preformed pipe insulation (ISO 18098, International Organization for Standardization, Switzerland). In the context of this disclosure, unless otherwise stated, density measurements are obtained in accordance with the ASTM C167 standard.

[0091] In the context of this disclosure, the terms “tap density” or “tapped density” of a material refer to the ratio of the mass to the volume of the material measured when the material is vibrated or tapped under specific conditions. The tap density of a powder represents its random, high-density packing. Tap density values ​​are higher for particles with a more regular shape (e.g., spheres) compared to particles with an irregular shape. Tap density is expressed in the formula where M = mass in grams and V f = cubic centimeters (cm) 3 The volume tapped at ) is given by the formula M / V fTap density can be calculated using the following method. Tap density is generally measured by first gently introducing a known sample mass into a graduated cylinder and carefully leveling the powder without compression. Then, the cylinder is mechanically tapped by raising it and allowing it to fall under its own weight using a suitable mechanical tap density tester that provides a suitable fixed drop distance and nominal drop velocity. Standard test methods for tap density measurement are described in MPIF-46, ASTM B-52722, and ISO 3953. Unless otherwise indicated, the tap density of the materials described herein is obtained by the method of ASTM B-52722.

[0092] As used herein, the term “positive electrode” is used interchangeably with “cathode.” Similarly, the term “negative electrode” is used interchangeably with “anode.”

[0093] In the context of this disclosure, the term “electrical conductivity” refers to a measure of a material’s ability to conduct electric current, or any other measure that enables the flow of electrons through or within it. Electrical conductivity is specifically measured as the electrical conductance / susceptance / admittance of a material per unit size of the material. Typically, it is recorded as S / m (siemens per meter) or S / cm (siemens per centimeter). The electrical conductivity or resistivity of a material can be determined by methods known in the art, including, but not limited to, in-line four-point resistivity (using the ASTM F84-99 dual-configuration test method). In the context of this disclosure, unless otherwise stated, measurements of electrical conductivity are obtained according to the ASTM F84 resistivity (R) measurement, which is obtained by measuring the voltage (V) divided by the current (I). In certain embodiments, the materials of the present disclosure have 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 in the range between any two of these values.

[0094] As used herein, the term “substantially” means, unless otherwise indicated, a percentage of the referenced characteristic, quantity, etc., that is, for example, more than 95%, more than 99%, more than 99.9%, more than 99.99%, or even about 100%, in relation to a particular context (e.g., substantially pure, substantially identical, etc.).

[0095] I. Method for preparing lithium phosphate transition metal cathode material in a conductive carbon matrix In one embodiment, a method is provided for preparing a lithium phosphate transition metal cathode material in a conductive carbon matrix. As described herein above, many previously reported synthesis processes for preparing lithium phosphate transition metal 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 close contact between precursors necessary to provide a homogeneous product. Furthermore, such solid-phase schemes utilize multiple energy-intensive steps. For example, Figure 1 provides a schematic diagram of a typical solid-phase process method 100. Referring to Figure 1, drying, mixing, grinding, calcination, and firing all require significant energy input, time, or both, increasing production costs. Energy-intensive steps are indicated by asterisks. In contrast, the methods disclosed herein are advantageous, at least in terms of reducing the number of energy and / or time-intensive steps. For example, Figure 2 provides a schematic diagram of process 200 in a non-limiting embodiment using the slurry / sol-gel synthesis method described herein. Referring to Figure 2, the total number of steps, specifically the number of energy-intensive steps, is reduced compared to the scheme in Figure 1. Furthermore, as mentioned above, the disclosed method allows for closer mixing and interaction of the components at a smaller scale (e.g., nanoscale solvation molecules), which can mitigate the formation of impurities during synthesis and provide a more homogeneous product. Another advantage of the disclosed method is that the organogel matrix formed during gelation inhibits phase separation of the reaction components, while the gelation of the organogel precursor in the presence of a lithium phosphate transition metal precursor allows for the generation of a cathode material that is closely mixed with carbon in a continuous three-dimensional conductive carbon matrix.

[0096] In another embodiment, phase separation of reaction components can be inhibited during the removal of a liquid phase (e.g., water), an immiscible solvent, a precursor (e.g., an aqueous solution of phosphoric acid), or a combination thereof from various solutions, suspensions, or emulsions as disclosed herein. For example, the formation of a self-supporting solid phase containing various components during such removal by drying or concentration of a solution, suspension, or emulsion may play the same role as a self-supporting solid-phase organogel formed by gelling a gelling precursor in the presence of a gelling initiator.

[0097] As a general, non-limiting description, the disclosed method generally includes 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 gelling initiator to the precursor mixture, enabling gelation of one or more carbon precursors to form a solid organogel, and thermally decomposing the solid organogel to form a lithium transition metal phosphate cathode material in a conductive carbon matrix. Each of the individual components of the method and each of its preparation operations are further described below herein.

[0098] A. Precursors of lithium cathode materials made from transition metal phosphates The disclosed method comprises combining a group of precursors for synthesizing a lithium cathode material of a transition metal phosphate, wherein at least a second precursor from the group comprises a liquid phase having a second density, the second density being less than a first density.

[0099] 1. First precursor At least a first precursor from 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, such as about 1, about 2, about 3, about 4, or about 5 g / cc.

[0100] In some embodiments, the group of precursors includes a first precursor, which 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 mixtures of two or more transition metals. As used herein, the term “transition metal” refers to any metallic element in block d of the periodic table, which includes groups 3 through 12 of the periodic table, excluding the platinum group metals. Transition metal salts or oxides may include various oxidation states of transition metals. With respect to oxides, these include, but are not limited to, the valence of a particular transition metal (e.g., 2 + , 3 + , 4 + , or 5 + Depending on the state, examples include monooxides, dioxides, etc. Generally, one or more transition metals present in a salt or oxide are in the (II) or (III) oxidation state. 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 each salt, oxide, or mixed oxide can be determined by those skilled in the art based on the intended battery cell voltage or other performance parameters, availability, cost, toxicity, and other variables.

[0101] In some embodiments, the first precursor comprises a transition metal oxide. The particle size of the transition metal oxide suitable for use in the methods of disclosure (e.g., iron oxides such as Fe3O4 and / or Fe2O3) can vary. Generally, small particle sizes, such as about 5 microns or less, are particularly preferred because such particle sizes allow for close contact of the transition metal oxide with 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, such as in the range of about 1 to about 5 microns. In some embodiments, the transition metal oxide may be synthesized to have an average particle size of about 5 nanometers (nm) to about 200 nm, such as in the range of about 20 nm to about 100 nm (as described below). Alternatively, a transition metal oxide having an average particle size of about 5 microns or more may be pulverized to provide a desired particle size range. Such pulverization may be carried out before mixing with other reaction components, or in situ, as further described below herein.

[0102] The density of the transition metal oxide before use in the disclosed method may vary. Generally, transition metal oxides with high tap density are particularly preferred. As used herein, the term “high density” means about 1.1 g / cm³. 3 This refers to materials with ultra-high tap density. While we do not wish to be bound by any particular theory, it is thought that high tap density transition metal oxides function to template the physical properties of the final lithium iron phosphate cathode material (e.g., via "isomorphic" reactions), resulting in the desired high-density product. High-density cathode materials are considered desirable for battery applications because more power is generated per unit volume of cathode material (i.e., a greater volumetric energy density is provided). Surprisingly, in some embodiments, the methods of disclosure yield approximately 0.8 to approximately 1.1 g / cm³. 3 Approximately 0.8 g / cm³ in the range of 3 A cathode material having the above tap density is provided. Therefore, the tap density of the cathode material of this disclosure is within the range of commercial viability (i.e., equivalent to that of previously available LFPs).

[0103] In some embodiments, the transition metal of the transition metal oxide includes manganese, vanadium, iron, or a combination thereof. In some embodiments, the transition metal of the transition metal oxide is manganese or vanadium.

[0104] In some embodiments, the transition metal of the transition metal oxide is manganese. Suitable examples of 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).

[0105] In some embodiments, the transition metal oxide is V2O3, VO2O3. 2, , or vanadium oxide such as V2O5. In some embodiments, the transition metal oxide is vanadium oxide, and the lithium vanadium phosphate cathode material has the structural type Li3Sc2(PO4)3.

[0106] In some embodiments, the transition metal of the transition metal oxide is iron. The oxidation state of iron in iron oxide can vary. For example, the iron oxide may be iron(II) oxide (FeO), iron(III) oxide (Fe2O3), or a combination thereof (e.g., Fe3O4).

[0107] In certain embodiments, iron oxide is iron(III) oxide (Fe2O3). Iron(III) oxide is an inexpensive, readily available, oxidation-stable oxide and therefore does not require special handling (as may be the case with iron(II) oxide, for example). Furthermore, iron oxide (e.g., Fe2O3) with an average particle size of about 5 microns or less can be commercially available. Commercial bulk Fe2O3 (i.e., Fe2O3 with a particle size greater than about 1 micron) can be pulverized to produce the desired nanoparticle material, but this is a time-consuming, energy-intensive process. Such reduced-size 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 a maximum of about 100 nanometers, such as in the range of about 30 to about 50 nanometers. However, such nanoparticle iron(III) oxide is very expensive on a commercial scale. Surprisingly, according to this disclosure, it has been found that inexpensive and readily available iron(II) oxalate (FeC2O4) can be heated in air while releasing carbon dioxide to provide nanoporous iron(III) oxide. For example, it has been found that heating iron oxalate in an air atmosphere to a temperature in the range of about 350 to about 450°C for about 1 hour converts the iron oxalate to nanoporous iron(III) oxide. In particular, the iron(III) oxide particles produced by the thermal decomposition of iron oxalate have an average particle size of several microns, but exhibit internally penetrating porosity with a pore diameter of about 100 nm. Therefore, such 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.

[0108] In some embodiments, iron oxide is in the form of a solid solution or mixture of magnetite (Fe3O4) or maghemite (Fe2O3), or both, with an average composition of Fe 3-xHaving O4, (0 ≤ x ≤ 0.33), these are referred to herein as magnetic iron oxide nanoparticles (magnetic IONPs). Such IONPs can be purchased or prepared according to known methods. In some embodiments, IONPs are prepared by oxidation of iron with air in an electrochemical cell. According to this disclosure, certain types of carbon aerogels or other porous carbon structures (e.g., a combination of carbide polyurethane foam, or carbon aerogels in the pores of carbide polyurethane foam) can act as “air cathodes” for catalytic reduction of oxygen at room temperature. When placed in an electrochemical cell having an aqueous electrolyte, oxygen can be reduced to hydroxide anions while oxidizing transition metals such as iron. In some embodiments, iron can be oxidized to produce iron hydroxide, magnetite, maghemite, or a combination thereof. Using the catalytic effect of the carbon aerogels described herein, solid iron can be oxidized at room temperature (e.g., 5°C to 25°C).

[0109] Figure 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 iron-containing electrode 316, and a conductor 320. While not wishing to be bound by theory, it is thought that the carbon aerogel element 304 can reduce the activation energy for the reduction of oxygen, thereby allowing the electrically connected iron electrode to participate in the redox reaction at room temperature.

[0110] In various embodiments, the porous conductive carbon element 304 (synonymous with “substrate”) can be synthesized and / or produced according to techniques including the thermal decomposition of polyimide aerogel. In some examples, the thermally decomposed polyimide aerogel may contain residual nitrogen or other heteroatoms (i.e., non-carbon atoms) that are not removed during the synthesis or thermal decomposition of the aerogel. By using the porous conductive carbon element 304 as a catalyst for oxidizing the iron electrode 316, cathode precursor materials including, but not limited to, Fe(OH)2, Fe(OH)3, Fe3O4, and Fe2O3 can be produced. The processes described herein, using air, water, and iron metal as the sole reactant, can produce solid iron oxide / iron hydroxide without generating large amounts of wastewater.

[0111] Many of the embodiments described herein describe the use of carbon aerogel elements in electrochemical cells, but the embodiments herein are not limited to those containing carbon aerogels. More generally, the porous conductive carbon element 304 may be any of a variety of porous carbon substrates that can act as an air cathode. Carbon aerogel materials (e.g., polyimide-derived carbon aerogels) are thought to support the high oxidation rates of transition metals such as iron at room temperature, but other porous carbons may also have the same effect under appropriate experimental conditions. Additional examples of porous carbon substrates that can be used instead of or in addition to carbon aerogel substrates include, but are not limited to, porous graphite carbon substrates, carbon substrates made from 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. 2 It may be / g. For example, the porous conductive carbon element 304 of this disclosure has a specific surface area in the range of an undecomposed aerogel precursor (e.g., 100m²). 2 / g~600m 2It may be a carbon aerogel having ( / g). The porous conductive carbon element 304 may be a carbon aerogel in monolithic form, particulate form, or a combination thereof.

[0112] In certain embodiments, the porous conductive carbon material or composition of the present disclosure has an electrical conductivity in the range of about 1 siemens (S) / cm (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 between any two of these values.

[0113] In some cases, the rate of a redox reaction (more specifically, the oxidation of iron metal) can be selected by modifying one or more conditions under which the reaction is carried out (e.g., it can be increased or decreased compared to a reference reaction rate). In some cases, the reaction rate can 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 (therefore increasing the rate of hydroxyanion formation), increasing the concentration of the electrolyte (e.g., from a 1 molar (M) solution to a multi-molar solution), and / or increasing the magnitude of the potential difference applied to the carbon aerogel / transition metal system 300. Similarly, the reaction rate can be decreased by limiting any of the aforementioned parameters. In addition, the reaction rate, as well as the composition and morphology of the reaction product(s), can be affected by changing the pH or composition of the electrolyte. Furthermore, the electrolyte concentration can be reduced (e.g., from 1 M to 0.2 M), and / or the electrolyte cation (e.g., Na + From K + By making this change, it was unexpectedly found that the average diameter of the nanoparticles could be reduced from approximately 100 nm to about 5 nm to 20 nm lower. These nanoparticles can then react favorably to form lithium metal phosphate cathode materials of similar size with very high surface area (as shown in Table 1 below).

[0114] In some cases, the reaction products can be affected by excluding gases other than oxygen. For example, the presence of carbonate species in the reaction products can be reduced by using a mixture of gases other than pure oxygen or carbon dioxide. This, in turn, can reduce and / or eliminate the presence of undesirable reaction products (e.g., carbonates) in the iron oxide metal compound.

[0115] The separator 308 is an electrically insulating material that provides a structure through which ions can move. This combination prevents electrical short circuits in the system 300 while allowing current to flow via ion movement between the porous conductive carbon element 304 and the iron metal electrode 316. Examples of the separator 308 include, among others, cellulosic paper, fibrous polymer fabrics, or felt.

[0116] The electrolyte 312, placed within the separator 308, facilitates ion transfer from the porous conductive carbon element 304 to the iron metal electrode 316. Examples of electrolytes include, in particular, sodium chloride (NaCl). (水溶液) ), ammonia chloride (NH3Cl (水溶液) )), sodium carbonate (NaCO) 3(水溶液) Examples include aqueous solutions of potassium chloride (KCl) (e.g., distilled water, deionized water, distilled deionized water, tap water). In some cases, the concentration of the electrolyte may be saturated with the solute. In other cases, the concentration of the electrolyte may be less than the saturated solution. In some cases, 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 (generally higher concentrations accelerate the oxidation rate), the form and / or composition of the oxide reaction product at the iron metal anode.

[0117] While we do not wish to be bound by theory, it has been observed that the presence of chlorides in the electrolyte facilitates the separation of hydroxylated reaction products from the surface of the iron metal electrode 316. Therefore, when using a chloride-containing electrolyte, the process can spontaneously convert the entire mass of iron metal electrode 316 into reaction products, as the fresh surface of the iron metal electrode 316 is naturally exposed as the reaction proceeds.

[0118] The iron metal electrode 316 may be an iron metal piece in electrical and ionic communication with the porous conductive carbon element 304, as shown in Figure 3. In some examples, the iron metal electrode 316 may contain compositional components that are added to improve conductivity, improve oxidation reaction rates, or both.

[0119] The conductor 320 may be an electrical conductor such as copper wire, aluminum wire, gold wire, or 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 the oxidation reaction at the iron metal electrode 316.

[0120] In some examples, the minimum applied potential applied from an external source via the conductor 320 varies depending on the iron metal selected for the iron electrode 316. The minimum applied potential required to promote the oxidation reaction at the iron metal oxide 316 may be an indicator of the catalytic activity of the carbon catalyst used to reduce oxygen to the iron metal electrode 316 (for example, for hydroxyanion formation). The maximum potential may be selected to avoid electrolysis (electrically induced decomposition) of the electrolyte.

[0121] Figure 4 is a schematic diagram of an electrochemical cell 400 according to one aspect of the present disclosure. The electrochemical cell 400 is an alternative representation of several aspects of the system 300. The electrochemical cell 400 includes 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.

[0122] Many of the elements shown in the electrochemical cell 400 in Figure 4 are identical to the elements described above in the context of the system 300 shown in Figure 3. The electrode 404 may be an electrical contact in which the iron metal component 408 (which is identical to the iron metal electrode 316) is electrically connected. The conductor 412 is identical to the conductor 320. The porous conductive carbon element 416 is identical to the porous conductive carbon element 304.

[0123] In addition to the elements already described in the context of Figure 3, Figure 4 schematically illustrates the redox reaction occurring within the electrochemical cell 400 when an external voltage of magnitude 1 volt (V) is applied. The minimum magnitude of the applied voltage required to promote the oxidation reaction ("start voltage") can be determined by the specific transition metal (i.e., iron) of 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 cannot occur at applied voltages less than the minimum magnitude.

[0124] In particular, Figure 4 schematically illustrates the exposure of the porous conductive carbon element 416 to oxygen. In some examples, the oxygen may be gaseous, such as from air or a commercial gas mixture having a higher oxygen concentration than that found in air. The oxygen can enter the porous conductive carbon element 416 that has been pre-moistened with the electrolyte 424. Upon encountering the porous conductive carbon element 416, which also contains and / or is coated with the electrolyte 424, the oxygen can ultimately be converted to a hydroxyanion solvated by the electrolyte 424.

[0125] Subsequently, the hydroxyanion may react with the iron oxide metal component 408 to form one or more of the iron metal oxides, hydroxides, and / or other reaction products 420 resulting from the reaction of iron metal and hydroxyanion. These reaction products are indicated by the shaded regions 420 in Figure 4. The reaction products 420 shown in Figure 4 are in direct contact with the iron metal component 408, but this is not required. Different electrolyte compositions, as shown above, can result in different physical compositions in the reaction products 420. For example, the presence of chloride in the electrolyte 424 produces a reaction product 420 that is separated from the iron metal component 408.

[0126] In some examples, oxygen is the cathode within the electrochemical cell 400. That is, oxygen that encounters the porous conductive carbon element 416 (which functions as the "air cathode") is reduced during the operation of the electrochemical cell 400. - The arrow in Figure 4, labeled "", indicates that the oxygen entering the carbon aerogel element 416 is the recipient of electrons generated by the operation of the electrochemical cell 400. Since the amount of oxygen can come from an inexhaustible source (e.g., the Earth's atmosphere) or from a source having a number of moles greater than or equal to the number of moles of iron metal in electrode 408, the iron metal electrode 408 can optionally react to completion. In particular, the iron metal electrode 408 can react to completion if a fresh reaction surface is exposed when the reaction product 420 is separated from the iron metal component 408. In other examples, the iron metal electrode can react partially or completely when hydroxyl ions diffuse into the unreacted portion of the iron metal electrode 408 through the adhesive layer of reaction product 420. The electrolytic reaction proceeds, oxidizing the iron metal 408 to iron(II) hydroxide Fe(OH)2 and / or its partially oxidized form Fe(OH)2-xO x This produces "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 the separate chamber, the (partially oxidized) iron hydroxide can be treated with air under basic conditions (e.g., pH > 8) to obtain magnetic IONP.

[0127] The operation of the electrochemical cell and the formation of iron oxide metal products (e.g., ferromagnetic iron compounds, ferrimagnetic iron compounds, or both) can be carried out at a variety of temperatures. In some embodiments, the operation is performed at temperatures between 15°C and 35°C.

[0128] While the preparation of iron oxide metal products is described herein, it should be noted that 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 oxide products. Although we do not wish to be bound by theory, for all metals (M) capable of forming stable divalent cations (e.g., Fe, Mn, Ni, Co, Cu, Zn, Sn, etc.), the immediate reaction product formed on the surface of the M anode is considered to be the corresponding metal bihydroxylated salt, M(OH)2. When using metals where +2 is the highest possible oxidation state (e.g., Zn), or when the metal is in an oxidation state higher than +2 (e.g., Ni, Co, Cu), it is not energetically favorable for formation in cold air, and M(OH)2 is similarly considered to be the final reaction product. In the specific cases of Fe (and Mn), since the +3 oxidation state is readily available in cold air, M(OH)2 tends to be an intermediate, resulting in higher oxidation states depending on the potential pH conditions described below herein.

[0129] Magnetic IONPs (e.g., magnetite, maghemite, and / or their solid solutions) are ferromagnetic and can be magnetically separated from the reaction mixture (note that iron hydroxide is paramagnetic). The recovered magnetite is then washed and dried, for example, for pretreatment as an iron source in LFP synthesis.

[0130] As described above, the generated magnetic IONPs were subjected to XRD analysis, and it was confirmed that the observed XRD patterns matched the calculated patterns of cubic spinel. The magnetic particles produced by this method are nanoparticles, i.e., particles with a size in the 20–100 nm range when observed using a scanning electron microscope. Surprisingly, it was observed that the concentration of the electrolyte used in the process could affect the particle size of the generated particles.

[0131] In specific examples of Fe, Fe(OH)2 and / or its partial oxidation form FeO x (OH) 2-x (i.e., "green rust") appears to be the first intermediate that is formed. In some embodiments, the iron hydroxide / iron oxide product is iron(I)(Fe(OH)2) or a partially oxidized form (iron oxyhydroxide; FeO x (OH) 2-x Therefore, in some embodiments, the method further comprises the oxidative conversion of iron hydroxide or iron oxyhydroxide to magnetite (Fe3O4) or maghemite (Fe2O3), respectively. In some embodiments, the oxidative conversion involves aeration under alkaline conditions. Without any specific further treatment at neutral pH, green rust slowly oxidizes to goetite, FeOOH. On the other hand, raising the pH above 8 and controlled oxidation with air yields magnetite (Fe3O4) with dehydration. Further oxidation of magnetite with air yields maghemite (Fe2O3; or Fe8 / 3V1 / 3O4 in spinel notation for magnetite, where V = vacancy). Due to the availability of the +3 oxidation state of manganese, similar conversions are expected.

[0132] In some embodiments, the electrochemical air oxidation of iron is carried out in an alkaline environment, yielding a non-magnetic form of iron oxide / iron hydroxide. In other embodiments, the electrochemical air oxidation of iron is carried out as described herein, and the resulting iron hydroxide or iron oxyhydroxide is isolated and then exposed to an aqueous environment having a pH greater than about 8, such as about 8, about 9, or about 10 to a maximum of about 11, about 12, about 13, or about 14, and then brought into contact with an oxygen source such as air. In one embodiment, air is bubbled through an alkaline aqueous system containing iron hydroxide / iron oxyhydroxide suspended or dissolved in it. Such an alkaline aqueous system may be provided, for example, by an aqueous solution of a base such as a carbonate or hydroxide.

[0133] In some embodiments, iron hydroxide / iron oxide products do not require purification and / or washing to remove contaminants. In cases where sodium chloride is present in the electrolyte, the reaction products may include benign sodium chloride (NaCl), which can be simply removed by washing the reaction products with water. Sodium chloride causes less environmental pollution and poses less of a threat to human health than sulfates and ammonia produced by alternative processing techniques. In cases where the electrolyte contains ammonium chloride (NH4Cl), reprocessing is also less problematic than other processes. Ammonium chloride decomposes into a gaseous mixture of NH3 and HCl at 338°C during calcination. The temperature of the gaseous mixture can be reduced to below 338°C after gas generation so that NH4Cl can be recondensed into a solid form that can be recycled. For this reason, impurities in the NH4Cl salt do not require washing and therefore do not generate wastewater.

[0134] In some embodiments, the IONP is magnetic, such as magnetite, maghemite, or a solid solution or mixture thereof, and is separated from the electrolyte 424 by a magnetic process. In particular, when the oxide product 420 is exposed to a magnetic field (e.g., from a permanent magnet or electromagnet), the magnetic IONP product is attracted to and retained by the magnetic field. The retained magnetite can then be washed, for example, with water and then collected. For example, the magnetic field may be removed, or the magnetite may be physically separated from the magnet. The magnetic IONP may optionally be dried by any suitable conventional means, or may be utilized in a wet or partially dried form in the manner of the disclosure described below. Since magnetite and maghemite are microwave-sensitive, their reaction products can be heated and thus dried using microwave radiation, which is more energy-efficient than using indirect heating through a furnace.

[0135] In some embodiments, the group of precursors includes microwave-sensitive precursors. In one particular embodiment, magnetite is a preferred transition metal oxide (i.e., a microwave susceptor) given its microwave sensitivity. By receiving microwave energy and converting it into heat, magnetite enables the carbonization of the organogel and the conversion of the reactants to LFP without wasteful and energy-inefficient furnace treatment. As magnetite is consumed during the reaction and carbonization process, its microwave sensitivity decreases. However, during the consumption of magnetite, the organogel is increasingly converted to carbon. Since carbon is also a microwave susceptor, it gradually converts more microwave radiation into heat, thereby maintaining the conversion of the reactants to LFP. The magnetic sensitivity of these components (e.g., ferromagnetic, paramagnetic, or both) also supports the microwave drying of reagents and the finished LFP without relying on energy-intensive and inconvenient thermal drying.

[0136] In some embodiments, the iron oxide produced by the air anodic oxidation process of the disclosure is in the form of nanoparticles. A scanning electron microscope image of the nanoparticle-like iron oxide produced by the air anodic oxidation described herein is provided as Figure 5A, showing that the average (approximately cubic) particle size is about 60 nm. Surprisingly, the average particle size reduces the concentration of the electrolyte and / or the electrolyte anion Na + From K + It was found that this could be reduced by changing to . The powder X-ray diffraction pattern is provided as Figure 5B, and Fe 3-x The cubic structure of the O4 (0 ≤ x ≤ 0.33) product is demonstrated. In some embodiments, IONP is composed of Fe 3-x It is formed as a magnetite-maghemite solid solution having O4 (0 ≤ x ≤ 0.333). In such embodiments, the oxidation state of iron is 2.67 to 3. The nitrogen adsorption BET surface area of ​​IONP prepared as disclosed may vary with changes in, for example, the identity and concentration of the electrolyte. For example, according to this disclosure, Fe obtained using 1 M NaCl as the electrolyte. 3-x O4 is 22.46m 2 It has a BET surface area of ​​ / g, while Fe obtained with 0.2M KCl as the electrolyte. 3-x O4 is 40.22m 2 It was found that the BET surface area was 1 / g. Therefore, the process can be adjusted to produce particles of different sizes depending on the intended end use. In this case, the term "size" refers to the characteristic dimensions of the particles. For roughly 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 the width, length, and / or depth.

[0137] Table 1 shows the particle size and specific surface area data for iron oxide and the corresponding LFPs prepared therefrom in this disclosure under various experimental conditions described herein. Note that some examples involve ball milling to approach a specific surface area unexpectedly large by up to 10 times that of commercially available materials. [Table 1]

[0138] The air anodic oxidation method disclosed for preparing magnetic IONP can be implemented in a semi-continuous or continuous process, particularly when combined with magnetic separation and washing. A non-limiting flow diagram of a production scheme for the semi-continuous synthesis of magnetite is provided in Figure 6. Each of the processes shown in Figure 6 is described herein in a different context and does not require further explanation.

[0139] In some embodiments, the transition metal of the transition metal oxide is a combination of manganese and iron (e.g., an iron-manganese mixed oxide). In some embodiments, the transition metal oxide is represented by the formula Fe, where 0.0 ≤ x ≤ 1.5. 3-x Mn x It is a mixed iron oxide-manganese having O4. In some embodiments, the resulting lithium phosphate transition metal cathode material is given by the formula LiFe, where 0.0 ≤ y ≤ 0.5. 1-y Mn y It has O4.

[0140] 2. Second precursor i. Phosphate At least a second precursor among the group of precursors comprises a liquid phase having a second density, the second density being 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).

[0141] In some embodiments, the group of precursors comprises a liquid phase containing an aqueous phosphoric acid solution (H3PO4). Generally, an aqueous solution of phosphoric acid is 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) can vary. Generally, phosphoric acid is obtained in a transition metal to phosphate (PO4) ratio of approximately 1:1 for the LiMPO4 cathode family and approximately 1:1.5 for the Li3M2(PO4)3 cathode family. 3-The amount is provided to give 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 1 to about 5 moles, such as about 0.1 to about 10 moles (i.e., moles per liter), or about 2 to 3 moles.

[0142] ii. Lithium ion source In some embodiments, the liquid phase includes a lithium ion source. Any lithium compound that is water-soluble or can be dissolved in an aqueous phosphoric acid solution may be used. Examples of suitable lithium salts, but are not limited to, lithium hydroxide, lithium carbonate, lithium acetate, and lithium chloride. One particularly suitable lithium ion source is lithium carbonate (Li2CO3), which is relatively inexpensive and readily available. Lithium carbonate gradually dissolves in the aqueous phosphoric acid solution with the generation of carbon dioxide gas. At least a portion of the lithium ions present may associate with phosphate ions as monobasic lithium phosphate. The amount of lithium ion source added (e.g., lithium carbonate) may vary. Generally, the lithium ion source is added in an amount sufficient to provide a lithium ion to phosphate and transition metal ion molar ratio of about 1:1:1.

[0143] iii. Substitutes for the first or second precursor The first and second precursors have been described above with respect to transition metal oxides and lithium / phosphate, respectively, but it is assumed in this specification that the identity of the first and second precursors may be reversed. Therefore, the description of the first and second precursors is not intended to be limited to the embodiments described above.

[0144] Furthermore, other sources of transition metals (e.g., iron) are assumed herein. For example, while the transition metal may be iron, the source may be something other than an oxide. Such alternatives are described below.

[0145] Alternative transition metal sources (ferrous oxalate) In some embodiments, the transition metal is iron, and the iron source is iron oxalate. Surprisingly, according to this disclosure, it has been found that iron oxalate can be used directly in the method without first being converted to iron(III) oxide. Thus, in another embodiment, the method comprises combining iron oxalate (FeC2O4), an aqueous phosphoric acid solution (H3PO4), and lithium carbonate as a group of precursors. It has been found that the lithium iron phosphate cathode material produced in a conductive carbon matrix has a nanoparticle morphology equivalent to that prepared by a continuous method (in which iron oxalate is first converted to iron(III) oxide).

[0146] In some embodiments, the transition metal is iron, and the iron source is iron oxalate. However, in this permutation, iron oxalate is first converted to iron phosphate, and the iron phosphate is reacted with lithium carbonate and one or more organogel precursor materials. Thus, in another embodiment, the method combines iron oxalate (FeC2O4) and an aqueous phosphoric acid solution (H3PO4) to form a compound of the formula Fe, where x is 1 and y is 1, or x is 3 and y is 2. x (PO4) y This includes forming a mixture of iron phosphates having [a certain property] and combining the iron phosphate mixture with a lithium ion source. While we do not wish to be bound by theory, the chemical reactions occurring during mixing and thermal decomposition can be expressed by the following equation: (1) 3Fe2(C2O4)3 + 2H3PO4 → Fe x (PO4) y +3H2C2O4, where x=y=1 (2) Fe x (PO4) y + 1 / 2Li2CO3+PAA / H2O→LFP / C, where x=y=1 (3) Fe x (PO4) y +Li3PO4+PAA / H2O→LFP / C, where x=3, y=2.

[0147] Alternative transition metal sources (iron sulfate and manganese sulfate) In some embodiments, the transition metals are iron and manganese. In one permutation, iron sulfate and manganese sulfate are reacted with oxalic acid to form a mixed oxalate, which is then converted to a mixed iron-manganese oxalate, which is then reacted 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 Formation of a precipitate of mixed iron-manganese oxalate in C2O4, and suspension of nanoporous mixed iron-manganese oxide in an aqueous phosphoric acid solution (H3PO4) of formula Fe 2-2x Mn 2x O 3t Or Fe 3-x Mn x A method is provided comprising: exposing mixed iron-manganese oxalate to air at a temperature in the range of about 350 to about 450°C for a period of time sufficient to convert the mixed iron-manganese oxalate to nanoporous mixed iron-manganese oxide of O4; mixing the suspension for a certain period of time; and adding a lithium ion source to the suspension to form a reaction mixture. The lithium iron-manganese phosphate cathode material thus prepared is given by the formula LiFe, where x is [0 ≤ x ≤ 1]. 1-x Mn x It has PO4. Formula Fe prepared by the decomposition of the corresponding mixed oxalate according to this disclosure 2-2x Mn 2x The nanoporous mixed iron oxide-manganese of O3 was found to have particles with an average size of several microns; however, high-resolution imaging revealed the presence of internally penetrating porosity with a pore diameter of approximately 100 nm. Furthermore, Fe 1-x Fe2- obtained by thermal decomposition of MnxC2O4.2H2O 2x Mn 2x O3 is approximately 11.93 m 2 It was found to have a BET nitrogen surface area of ​​1 / g.

[0148] While we do not wish to be bound by theory, the chemical reactions that occur during mixing and thermal decomposition can be expressed by the following equation: (1) xFeSO4 + 1 - xMnSO4 + H2C2O4 + H2O → Fe x Mn 1-x C2O 4(s) +H + (aqueous solution) + SO4 2- (水溶液) (2) Fe x Mn 1-x C2O4 + air → Fe 2-2x Mn 2x O 3(ナノ多孔質) + CO2 (350~450 °C) (3) Fe 2-2x Mn 2x O 3(ナノ多孔質) + 2H3PO4 + Li2CO3 + PAA / H2O → LMFP / C (ナノ粒子状)

[0149] In another permutation, iron sulfate and manganese sulfate are reacted together with oxalic acid to form a mixed oxalate, and the mixed oxalate is reacted with phosphoric acid and lithium carbonate. Thus, in another embodiment, the method comprises combining iron(II) sulfate, manganese(II) sulfate, and oxalic acid in water to form a mixture containing iron-manganese mixed oxalate of the formula Fe 1-x Mn x C2O4, adding lithium carbonate and aqueous phosphoric acid solution (H3PO4), and after thermal decomposition, forming lithium iron manganese phosphate of the formula LiFe 1-x Mn x PO4, where x is [0 ≦ x ≦ 1]. Without wishing to be bound by theory, it is believed that the chemical reactions occurring during mixing and thermal decomposition can be represented by the following equations: (1) xFeSO4 + 1 - xMnSO4 + H2C2O4 + H2O → Fe x Mn 1-x C2O 4(s) +H + (aqueous solution) + SO4 2- (水溶液) (2) Fe x Mn 1-x C2O4 + 1 / 2Li2CO3 + H3PO4 + PAA / H2O → LMFP / C (nanoparticle form)

[0150] In yet another permutation, iron sulfate and manganese sulfate are reacted with oxalic acid to form a mixed oxalate, and this mixed oxalate is reacted with phosphoric acid to form an intermediate mixed iron-manganese phosphate. This mixed phosphate is then reacted with lithium phosphate. Thus, in another embodiment, the method involves combining iron(II) sulfate, manganese(II) sulfate, and oxalic acid in water, and formula Fe 1-x Mn x Formation of a precipitate of mixed iron-manganese oxalate in C2O4, suspension of the mixed iron-manganese oxalate in an aqueous solution of phosphoric acid (H3PO4) to convert the mixed metal oxalates into mixed metal phosphates, and addition of lithium phosphate, followed by thermal decomposition, where x is [0≦x≦1], the formula LiFe 1-x Mn x This includes forming lithium iron manganese phosphate containing PO4. While we do not wish to be bound by theory, the chemical reactions occurring during mixing and thermal decomposition can be considered to be expressible by the following equation: (1)xFeSO4+1-xMnSO4+H2C2O4+H2O→Fe x Mn 1-x C2O 4(s) +H + (Aqueous solution) + SO4 2- (水溶液) (2)3Fe x Mn 1-x C2O4 + 2H3PO4 → (Fe x Mn 1-x )3(PO4)2+3H2C2O4 (3)(Fe x Mn 1-x )3(PO4)2+Li3PO4+PAA / H2O→3LiFe x Mn 1-x PO4 / C

[0151] B. Carbon precursor The method comprises providing one or more carbon precursors in a fluid state, where a mixture containing them is fluid, has no fixed shape, and has low or no resistance to external stress. The one or more carbon precursors in the fluid state are configured to form a solid organogel in the presence of a gelling initiator, and the solid organogel is configured to form a conductive carbon matrix upon thermal decomposition. In alternative embodiments, the solid organogel may be formed by removing the liquid phase (e.g., solvent) from a solution. For example, in some embodiments, partial or complete removal of the solvent by a drying method may produce an organogel in the absence of gelling induced by a gelling initiator. Generally, the conductive carbon matrix comprises the carbonized form of the organogel and / or its precursor material, surrounding the LMP particles and / or their precursors. The conductive carbon matrix may comprise graphite carbon, amorphous carbon, or a mixture thereof. The conductive carbon matrix is ​​maintained despite any subsequent reduction in particle size during grinding.

[0152] In some embodiments, the method comprises mixing a group of lithium transition metal phosphate cathode material precursors with one or more carbon precursors to form a precursor mixture, adding a gelling initiator to the precursor mixture, and enabling gelation of one or more carbon precursors to form a solid organogel. As described herein above, such a solid organogel is formed in the presence of lithium-transition metal-phosphate material precursors and is therefore understood to include such precursors, their reaction products, and intermediates, which ultimately yield lithium transition metal phosphate material upon thermal decomposition of the solid organogel containing such species.

[0153] "Carbon precursor" means a material that can be subjected to polymerization or other gelation reactions to produce a solid organogel, which can then be thermally decomposed to form a conductive carbon matrix. Generally, solid organogels are inherently porous and can form a conductive carbon matrix when exposed to the high-temperature conditions described below herein. In some embodiments, a catalyst or gelation initiator is used to initiate and / or complete the gelation. Suitable organogels include, but are not limited to, phloroglucinol-furfuralaldehyde polymers, resorcinol-furfuralaldehyde polymers, phenol-formaldehyde polymers, polyurethanes, melaimin-aldehyde polymers, polyacrylamide polymers, polybenzoxazine polymers, polyamic acids, and polyimides. Each of these organogels and their respective precursor materials (i.e., carbon precursors), as well as each of the gelation conditions, are further described below herein.

[0154] 1. Phloroglucinol-Furfural, Resorcinol-Furfural, and Phenol-Formaldehyde Polymer In some embodiments, the solid organogel is a phloroglucinol-furfural (PF) polymer. In such embodiments, the organogel precursor material is phloroglucinol and furfural. In such embodiments, the method generally comprises adding phloroglucinol and furfural to a reaction mixture, reacting the phloroglucinol and furfural, and forming an organic matrix containing the PF organogel. Gelation of the phloroglucinol and furfural mixture occurs almost instantaneously (e.g., 30 seconds or less, 15 seconds or less, 5 seconds or less). Therefore, phloroglucinol and furfural are added individually and sequentially to the reaction mixture in any order. In some embodiments, phloroglucinol and furfural are each provided separately as ethanol solutions. No catalyst or initiator is required. However, in some embodiments, a gelation initiator is used. In some embodiments, the gelation initiator is an amine base or an acid. When phloroglucinol and furfural are optionally combined with an initiator, gelation of the PF polymer occurs rapidly (e.g., in about 30 seconds or less). The resulting PF polymer contains several 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.

[0155] In other embodiments, the solid organogel is a resorcinol-furfural polymer. Such polymers can be prepared as described above by substituting phloroglucinol with resorcinol.

[0156] In other embodiments, the solid organogel is a phenol-formaldehyde (PF) polymer. Such polymers can be prepared as described above by substituting phloroglucinol with phenol and furfural with formaldehyde.

[0157] 2. Polyurethane polymer In some embodiments, the solid organogel comprises or is a polyurethane polymer. In such embodiments, the precursor comprises a polyol and an isocyanate. In some embodiments, the polyol is cellulose. In such embodiments, the gelling initiator comprises an alkylamine (e.g., triethylamine).

[0158] 3. Polyamic acid 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 carboxamide group, and an aromatic or aliphatic moiety containing diamines and tetracarboxylic acids from which the polyamic acid is derived. A “repeating unit” as defined herein is a portion of a polyamic acid (or corresponding polyimide) from which the repeating units will, by being linked together in a continuous manner along a polymer chain, produce a complete polymer chain (excluding terminal amino groups or unreacted anhydride ends). Those skilled in the art will recognize that polyamic acid repeating units arise from the partial condensation of the carboxyl group of a tetracarboxylic dianhydride with the amino group of a diamine.

[0159] In some embodiments, the polyamic acid is any commercially available polyamic acid. In other embodiments, the polyamic acid is pre-formed ("pre-formed") and isolated, for example, prepared, by the reaction of a diamine and a tetracarboxylic dianhydride in an organic solvent according to conventional synthetic methods. In any case, whether purchased or prepared and isolated, a suitable polyamic acid is in substantially pure form. Pre-formed, isolated, or commercially available polyamic acids may be in solid form, such as powder or crystalline form, or in liquid form.

[0160] Suitable polyamic acids, polyimides, and methods for preparing them are provided, for example, in U.S. Patent Application Publication US2022 / 0069290 to Zafiropoulos, U.S. Patent Application No. 17 / 546,761 to Leventis, and U.S. Patent Application No. 17 / 546,529 to Begag, each of which is incorporated herein in whole.

[0161] In some embodiments, the polyamic acid is provided in the form of a water-soluble salt, which can then be precipitated from the reaction mixture as an insoluble polyamic acid by acidification of the reaction mixture. In such embodiments, the organogel precursor material is ammonium polyamate or an alkali metal salt, and the method further comprises adding a gelling initiator to the reaction mixture.

[0162] 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 polyamic acid with 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 polyamic acid with triethylamine. In some embodiments, the ammonium salt is a salt of polyamic acid with diisopropylethylamine.

[0163] In some embodiments, the organogel precursor material is an alkali metal salt of a polyamic acid, such as a lithium, sodium, or potassium salt.

[0164] A gelation initiator is generally an acid, or a substance that can be hydrolyzed to form an acid. One non-limiting example of a suitable acid is acetic acid. Another non-limiting example of a suitable substance that can be hydrolyzed to form an acid is acetic anhydride. Thus, in some embodiments, the method involves adding acetic acid, acetic anhydride, a natural protonated phosphate, or a combination thereof as a gelation initiator. In some embodiments, the method involves adding acetic anhydride and hydrolyzing the acetic anhydride to form acetic acid and induce the gelation of the polyamic acid.

[0165] 4. Polyimide In some embodiments, the solid organogel contains or is a polyimide. In some embodiments, the polyimide is formed from the imidation of a polyamic acid. Suitable polyimides and methods for preparing them are provided, for example, in U.S. Patent Application Publication US2022 / 0069290 for Zafiropoulos, U.S. Patent Application 17 / 546,761 for Leventis, and U.S. Patent Application 17 / 546,529 for Begag, each of which is incorporated herein in whole.

[0166] In some embodiments, imidizing a polyamic acid salt involves thermally imidizing the corresponding polyamic acid. Irradiation of a wet gel polyamine acid material with microwave frequency energy is one particularly preferred heat treatment.

[0167] In other embodiments, imidizing a polyamic acid salt involves carrying out chemical imidization, which includes adding a gelling initiator to an aqueous solution of a salt of a polyamic acid to form a gelling mixture ("sol") and gelling the gelling mixture (for example, in a mold, or by casting onto a sheet, or in various other formats such as beads). In such embodiments, the gelling initiator is added to initiate and drive the imidization to form a polyimide wet gel from the polyamic acid salt.

[0168] The structure of gelation initiators can vary, but generally they are at least partially soluble in the reaction solution, reactive with the carboxylate groups of polyamic acid salts, and effective reagents for driving the imidation of the carboxyl and amide groups of polyamic acid while minimizing reactivity with aqueous solutions. Examples of suitable gelation initiators include carboxylic anhydrides such as acetic anhydride and propionic anhydride. In some embodiments, the gelation initiator is acetic anhydride.

[0169] In some embodiments, the amount of gelling initiator may vary based on the amount of tetracarboxylic dianhydride or polyamic acid. For example, in some embodiments, the gelling initiator is present in various molar ratios with tetracarboxylic dianhydride. In some embodiments, the gelling initiator is present in various molar ratios with polyamic acid. The molar ratio of gelling initiator to tetracarboxylic 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, such as 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 ratio is about 2 to about 5.

[0170] The temperature required for the gelation reaction to proceed can vary, but is generally below 50°C, such as between approximately 10°C and 50°C, or between approximately 15°C and 25°C.

[0171] 5. Other polymer organogels 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 gelling initiators suitable for their formation are known to those skilled in the art.

[0172] 6. Concentration of organogel precursor material In some cases, the organogel precursor material exists at a concentration of the entire mixture (i.e., including the transition metal lithium cathode material precursor) that collectively approximates the carbon content of the resulting lithium metal phosphate material. For example, the organogel precursor may exist in approximately 1 wt% to 5 wt% of lithium, transition metal, and phosphorus precursors in a stoichiometric ratio of 1:1:1.

[0173] C. Mixed The method involves mixing a group of precursors for synthesizing lithium transition metal phosphate with one or more carbon precursors in a fluid state for a period of time to form a precursor mixture, followed by the addition of a gelling initiator. Mixing is generally carried out by stirring the mixture (i.e., as a suspension) at room temperature (e.g., approximately 20°C) for a period of about 1 to about 12 hours, typically about 2 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 in the range of about 1 to about 3 microns. Depending on the initial particle size, in some embodiments it may be desirable to carry out the reduction of the active particle size by grinding, abrasion, etc. In other embodiments, such particle size reduction is not carried out beyond the stirring described. The mixture is generally mixed (e.g., by stirring) for a period of time sufficient to allow complete dissolution of the lithium ion source in the aqueous suspension.

[0174] D. Solid organogels As described herein, the method includes forming a solid organogel by subjecting one or more organogel precursor materials to gelation. The term “solid” as used herein in reference to organogels means that the organogel is self-supporting, for example, a solid organogel maintains a defined shape in the absence of any restraint.

[0175] Solid organogels, whether they contain PF polymers, polyamic acids, polyimides, or other polymers described herein, have a three-dimensional external (i.e., macro) and internal (micro) structure, such as fibrils / pores. In some embodiments, the solid organogel is a polyamic acid, a polyimide, or a combination thereof. For example, in certain embodiments, after gelation, the ammonium polyamic acid salts described herein are partially converted to the corresponding polyamic acid and the corresponding polyimide. The relative proportions of polyamic acid and polyimide can vary. Each proportion can be determined by methods known in the art, such as nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). While not wishing to be bound by theory, it is thought that a higher proportion of polyimide in the organic matrix would result in a harder solid lithium metal phosphate material embedded in a carbon matrix after thermal decomposition. Furthermore, surprisingly, according to this disclosure, in at least some embodiments, the presence of a relatively large amount of polyamic acid in the organic matrix has been found to provide lithium transition metal phosphate / carbon matrix products with fewer impurities, higher particle size uniformity, higher morphological uniformity, or a combination thereof, compared to products obtained in the presence of a relatively large amount of polyimide. These differences can be inferred by several observational techniques, including, but not limited to, X-ray diffraction, electron microscopy, and acoustic density measurement.

[0176] Solid organogels contain lithium ions, transition metal oxide particles (e.g., iron(II or III) oxide), and phosphoric acid (PO4). 3The reaction mixture further includes additional components present in the reaction mixture, such as lithium ions and suspended water. At least a portion of the lithium ions and phosphate ions may associate 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. While we do not wish to be bound by any particular theory, this close physical contact is thought to facilitate the formation of the cathode material during thermal decomposition and, advantageously, provide the cathode material with desirable physical properties. As described herein, the use of organogels inhibits phase separation of precursor materials during the formation of lithium transition metal phosphate cathode materials. 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 is generally selected such that, at room temperature and atmospheric pressure, the viscosity of the organogel is sufficient to prevent sedimentation 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 density differences.

[0177] In some cases, organogel precursor materials can gel almost instantaneously (e.g., less than 30 seconds, less than 15 seconds, less than 5 seconds), thereby allowing other precursors (e.g., 1 gram / cm³) to gel. 3 A solid phase with a density of over 1 gram / cm³ 3 This prevents phase separation of the liquid phase (which has a density of ). In some examples, gelation occurs via the polymerization reaction described above, rather than through 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 energy-intensive drying processes. In particular, the solid aerogel produced by such gelation is distinct from other solid phase materials utilized in previously reported synthesis of LFP materials in a carbon matrix (e.g., non-gelling sugars or starches).

[0178] Furthermore, as described herein, the precursors and gelation conditions are selected so that the resulting organogel maintains a desired solid form, thereby maintaining close contact between reactants during the heat treatment (thermal decomposition) necessary to convert the precursors into lithium phosphate transition metal cathode materials. In some embodiments, the solid organogel comprises a porous network of interconnected solid-phase polymer structures, the porous network maintaining contact between a first precursor of the group and a second precursor of the group, e.g., iron oxide and a transition metal species such as lithium / phosphate (e.g., LiH2PO4). In particular, lithium phosphate (LiH2PO4) melts above 300°C. Therefore, in some embodiments, the organogel maintains contact between precursors at a temperature of at least about 300°C. This property of the organogels disclosed is distinct from other solid-phase materials used in previously reported synthesis of LFP materials in carbon matrices (e.g., sugars or starches that do not maintain structural rigidity upon heating).

[0179] E. Thermal decomposition Next, a solid organogel containing a lithium transition metal phosphate precursor material (e.g., lithium ions, one or more transition metal oxides, and phosphate ions) is thermally decomposed (e.g., carbonized), where thermal decomposition (e.g., carbonization) means that the organogel 1) converts substantially all of the organogel material to carbon, forming a conductive carbon matrix; 2) optionally reduces the transition metal in a higher oxidation state to a lower state (e.g., reducing Fe(III) in Fe2O3 to Fe(II) as required in LiFePO4); and 3) forms a lithium transition metal phosphate cathode material contained within the conductive carbon matrix. As used herein in the context of thermal decomposition, “substantially all” means that more than 95% of the organogel material is converted to carbon, such as 99%, 99.9%, 99.99%, or even 100% of the organogel being converted to carbon. The thermal decomposition of an organogel converts it into an isomorphic carbon matrix, meaning that the physical properties of the organogel (e.g., porosity, surface area, pore size, diameter, etc.) are substantially retained within the corresponding carbon matrix. While not wishing to be bound by theory, it is believed that carbonization helps promote the good electrical conductivity of the resulting matrix and, at the same time, initiates and drives to completion reactions between transition metal oxides, lithium ions, and phosphate ions, forming a lithium-transition metal-phosphate cathode material within the conductive carbon matrix. Furthermore, the organogel materials disclosed herein are rich in aromatic rings that, upon thermal decomposition, produce a highly conductive carbon matrix. Moreover, the uniform distribution of lithium-transition metal-phosphate cathode material throughout a continuous three-dimensional conductive carbon matrix provides excellent performance characteristics for batteries utilizing such cathode materials, as further described below herein.

[0180] While we do not wish to be bound by theory, it is thought that during thermal decomposition, the lithium-transition metal-phosphate cathode material inherits the morphology of the precursor transition metal oxide and is formed on top of the transition metal oxide by a template process. This is considered to be distinct from the previously reported process for forming LiFePO4, in which water evaporates from the slurry and loose precursor ions associate during evaporation.

[0181] In embodiments where the transition metal of the transition metal oxide is in a higher oxidation state than that present in the lithium-transition metal-phosphate cathode materials described herein, a portion of the carbon produced during thermal decomposition is thought to function to reduce the oxidation state of the transition metal (for example, from iron(III) to iron(II) present in Fe2O3).

[0182] The temperature required for pyrolysis can vary. In some embodiments, the organogel matrix is ​​subjected to a treatment temperature of approximately 600°C or higher, or between any two of these values, such as approximately 600°C, approximately 650°C, approximately 700°C, approximately 750°C, approximately 800°C, approximately 850°C, approximately 900°C, or approximately 950°C, to carbonize the organogel matrix and complete the formation of the lithium-transition metal-phosphate cathode material. In some embodiments, the pyrolysis temperature is approximately 600 to approximately 800°C. Generally, pyrolysis is carried out under an inert or slightly reduced atmosphere to prevent combustion of the organic and / or carbon materials and to prevent re-oxidation of the transition metals. Preferred atmospheres include, but are not limited to, nitrogen, argon, hydrogen, methane, or combinations thereof. In some embodiments, pyrolysis is carried out under nitrogen.

[0183] In some embodiments, pyrolysis is carried out 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. Typical microwave devices are operated with microwaves at a frequency of 2450 MHz. In some embodiments, the group of precursors includes microwave-sensitive precursors, and pyrolysis is carried out by applying microwave radiation.

[0184] 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-sized 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.

[0185] In some embodiments, as the magnetic IONP is gradually converted to LiFe(PO4) and the organogel precursor is thermally decomposed into carbon, the microwave-absorbing components change from the magnetic phase to the carbonized components. This is because LiFe(PO4) itself does not respond strongly to microwave radiation, but the carbon materials described herein are efficiently heated when exposed to microwave radiation.

[0186] The time required to complete pyrolysis can vary and depend on temperature and specific matrix components. Generally, the matrix is ​​subjected to pyrolysis conditions for a period ranging from about 4 to about 20 hours, such as about 8 hours. In some examples, microwave pyrolysis using a 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, may be more energy-efficient and faster.

[0187] Another advantage of the disclosed method is that the carbon source (e.g., organogels such as polyamic acid or polyimide) has a high carbon yield, and therefore the weight percentage of the carbon source required (about 20 wt%) relative to the overall reactant composition is relatively low, resulting in high efficiency and cost reduction. In particular, a small amount of carbon source is sufficient during thermal decomposition to reduce all higher oxidation state transition metal species (e.g., from Fe(III) to Fe(II) in the case of iron(III) oxide precursors) and leave about 2-3% conductive carbon on the surface of the lithium-transition metal-phosphate.

[0188] Furthermore, the carbon sources disclosed herein (e.g., organogels such as polyamic acids, polyimides, and other polymers mentioned above) contain abundant aromatic rings. Thus, these materials produce a lithium-transition metal-phosphate graphite carbon coating during thermal decomposition. The graphite carbon produced during the carbonization of these materials offers better electrical properties (e.g., higher conductivity) than saturated carbon found from the carbonization of other carbon sources such as sugars or starches.

[0189] F. Grinding In some embodiments, the lithium-transition metal-phosphate cathode material in a conductive carbon matrix is ​​optionally subjected to one or more grinding procedures to reduce the particle size or to provide a uniform particle size distribution. Any suitable grinding technique can be used. In some embodiments, grinding may be carried out using a ball mill. In some embodiments, grinding is carried out in a stainless steel planetary ball mill for a time ranging from about 30 minutes to about 48 hours at a speed ranging from about 100 to 400 rpm.

[0190] The need for grinding, the type of grinding, and its duration can vary depending on the properties of the conductive carbon matrix. For example, in some embodiments, cathode material particles prepared from the thermal decomposition of polyimide organogels may have a hard carbon matrix and require grinding to provide a powder material (i.e., uniformly small particle size). In contrast, cathode material particles prepared from the thermal decomposition of polyamic acid organogels tend to be softer and may require relatively less grinding.

[0191] II. Properties of Lithium Cathode Materials made from Transition Metal Phosphates Following thermal decomposition, 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 the embodiment where M is a combination of Fe and Mn, the Fe-to-Mn stoichiometry can vary. For example, the Fe-to-Mn molar ratio can be in the range of about 0.1 to about 10, such as 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 molar ratio of Fe to Mn is approximately 4:1 to approximately 1:4, approximately 2:1 to approximately 1:2, or approximately 1:1.

[0192] In some embodiments, the lithium-transition metal-phosphate cathode material in a conductive carbon matrix has the formula LiM(PO4), where M is iron (Fe), manganese (Mn), or a combination of Fe and Mn. 、The transition metal oxide sources used in the method include magnetite, maghemite, or combinations thereof. In some such embodiments, residual amounts of magnetite, maghemite, or combinations thereof may remain present in the lithium-transition metal-phosphate cathode material within a conductive carbon matrix. The residual amount may vary, but is generally present in an amount sufficient to confer magnetic susceptibility to the cathode material. The magnetic susceptibility conferred by the residual magnetic iron oxide material may vary, but is generally weak, but sufficient to be observed at least qualitatively through the interaction of a sample of lithium-transition metal-phosphate cathode material within a conductive carbon matrix with a strong neodymium magnet. Quantitative measurements may be carried out according to known methods for susceptibility measurement, including, but not limited to, Gouy's magnetic balance (where the sample is suspended between the poles of an electromagnet, and the change in weight when the electromagnet is turned on is proportional to the susceptibility) and Evans balance (where the force on the magnet itself is measured).

[0193] 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, the concentration is approximately 0.6 to approximately 1.1 g / cm³. 3 It has a tap density in the range of [range].

[0194] In some embodiments, the lithium-transition metal-phosphate cathode material is olivine-type lithium iron phosphate. Thus, in another embodiment, a composition comprising olivine-type lithium iron phosphate and nanoparticles integrated with a conductive carbon matrix, wherein the nanoparticles have characteristic dimensions of 20 nm to 1000 nm and 10 m 2 (m 2 ) / grams (g) ~ 65m 2 A composition having a specific surface area of ​​1 / g is provided. In some embodiments, the characteristic dimensions are 30 nm to 70 nm, and the specific surface area is 20 m². 2 / g~65m 2 It is / g. In some embodiments, the characteristic dimensions are 30nm to 60nm, and the specific surface area is 22m². 2 / g~40m2 It is / g. In some embodiments, the characteristic dimensions are 20nm to 40nm, and the specific surface area is 60m². 2 / g~80m 2 It is / g.

[0195] In some embodiments, the nanoparticles further comprise magnetite, maghemite, or both.

[0196] In some embodiments, the nanoparticles further contain manganese.

[0197] In some embodiments, the conductive carbon matrix comprises a carbide organogel as described herein.

[0198] III. Method for forming a lithium vanadium fluorophosphate cathode material in a conductive carbon matrix; fluorophosphate ion Another aspect of this disclosure provides a method for preparing a lithium vanadium fluorophosphate cathode material in a conductive carbon matrix. The method involves using phosphoric acid as a source of fluorophosphate ions (FPO4). 2- The method is substantially the same as the method for forming the phosphate transition metal lithium cathode material described herein, except that it is replaced with ) and vanadium oxide is selected as the transition metal oxide. The mixing, lithium ion source, organogel precursor material, gelation, solid organogel, and their thermal decomposition are each as described herein.

[0199] 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).

[0200] The source of fluorophosphate ions can vary. For example, fluorophosphate, or fluorophosphates such as sodium monofluorophosphate or ammonium monofluorophosphate, may be used to provide fluorophosphate ions. Alternatively, fluorophosphate ions may be formed in situ from a lithium ion source, a phosphate ion source, and a fluoride ion source. The lithium, phosphate, and fluoride sources may be individual or provided in various combinations. For example, the method may utilize the lithium source described herein, along with separate sources of fluoride and phosphate, such as hydrofluoric acid or ammonium fluoride, and either phosphoric acid, or an alkali metal or ammonium salt of phosphoric acid. Alternatively, the method may utilize a combined source of lithium and fluoride, such as lithium fluoride. Those skilled in the art will recognize the various combinations of lithium, fluoride, and phosphate that can be used to provide lithium and fluorophosphate ions in the reaction mixture, and all such combinations are assumed herein. The order in which any such components (lithium ion source, fluoride ion, and phosphate ion source, fluorophosphate source, etc.) are added may vary and may be sequential or simultaneous.

[0201] Following thermal decomposition, the lithium vanadium fluorophosphate cathode material in the conductive carbon matrix has the formula LiVFPO4. The resulting cathode material may optionally be pulverized as described above for lithium transition metal phosphate materials.

[0202] IV. Method for forming a lithium vanadium fluorophosphate cathode material in a conductive carbon matrix; F - Fluoropolymers as a source Another aspect of this disclosure provides an alternative method for preparing a lithium vanadium fluorophosphate cathode material in a conductive carbon matrix. The method is substantially similar to the method for forming the lithium vanadium fluorophosphate cathode material described herein, except that the fluorophosphate ion source is replaced with phosphoric acid and the fluoride is provided in the form of a fluoropolymer. Each of the mixing, lithium ion source, organogel precursor material, gelation, solid organogel, and their thermal decomposition is as described herein. The method further comprises adding a fluoropolymer to the precursor mixture before gelation.

[0203] 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).

[0204] Suitable fluoropolymers include, but are not limited to, polytetrafluoroethylene, polyvinylidene fluoride, and combinations thereof. While not wishing to be constrained by theory, such fluoropolymers are thought to be physically incorporated into the organogel matrix (e.g., as a physical combination) rather than chemically incorporated into the organogel polymer, and during subsequent thermal decomposition, the fluoropolymer is thought to decompose, releasing fluorine species, which then react with phosphate ions to form fluorophosphates in situ and / or directly with vanadium oxide species to form the final intermediate, with the fluorine in the intermediate cooperating with vanadium. Such alternative methods address potential problems with using fluorophosphate sources such as fluorophosphoric acid (H2FPO3). Specifically, fluorophosphoric acid is gradually hydrolyzed to H3PO4 and hydrogen fluoride (HF). HF is volatile and toxic and may leak from the reaction mixture upon drying, making it difficult to maintain the required 1:1:1:1 lithium:vanadium:phosphate:fluorine stoichiometry. The methods disclosed herein that use fluoropolymers avoid the need to use fluorophosphate.

[0205] V. Method for forming a lithium vanadium fluorophosphate cathode material in a conductive carbon matrix; fluoromonomer Another aspect of this disclosure provides a further alternative method for preparing a lithium vanadium fluorophosphate cathode material in a conductive carbon matrix. The method is substantially similar to the method for forming a lithium vanadium fluorophosphate cathode material using the fluoropolymer described herein, except that the fluoropolymer is replaced with a fluoromonomer, and the fluoromonomer copolymerizes with an organogel precursor material to form an organogel in which at least a portion of the hydrogen atom substituents are replaced with fluorine atoms.

[0206] Similar to the method for preparing a lithium vanadium fluorophosphate cathode material in a conductive carbon matrix using the fluoropolymer disclosed above, this alternative method uses a fluorinated monomer, which is chemically incorporated into the organogel polymer. “At least a portion of one or more organogel precursor materials contains a fluorinated monomer” means that a certain amount of one or more organogel precursor materials is fluorinated. The amount of fluorinated monomer present in the organogel precursor material can vary, for example, from about 1% to about 100% of the total amount of organogel precursor material used. Furthermore, the degree of fluorination in the monomer (i.e., the number of fluorine substituents present on a given organogel precursor monomer structure) can vary. In some embodiments, the organogel is a polyimide, and some portion of the polyimide organogel precursor material (e.g., diamines and tetracarboxylic dianhydrides, or polyamic acids) supports one or more fluorine substituents. In some embodiments, the polyimide is formed in situ from organogel precursor materials which are phenylenediamine and tetracarboxylic dianhydride, and which phenylenediamine, tetracarboxylic dianhydride, or both support one or more fluorine substituents. In certain embodiments, the fluoride monomer is 1,4-phenylenediamine, e.g., 2,3,5,6-tetrafluorobenzene-1,4-diamine, which supports one or more fluorine atoms. Again, utilizing organogel precursor materials that support fluorine substituents as the fluoride source avoids the loss of volatile and toxic HF gases during the initial stages of solvent evaporation and initial drying.

[0207] VI. Energy Storage Systems Another aspect of this disclosure provides an energy storage system comprising a lithium transition metal phosphate cathode material described herein. Another aspect of this disclosure provides a composition comprising olivine-type lithium iron phosphate and nanoparticles integrated with a conductive carbon matrix, wherein the nanoparticles have characteristic dimensions of 20 nm to 1000 nm and 10 m 2 (m 2 ) / grams (g) ~ 65m 2An energy storage system is provided that includes a composition having a specific surface area of ​​ / g.

[0208] Examples of energy storage systems include batteries such as lithium-ion batteries, which contain the compositions or cathode materials described herein. Further disclosed herein are battery cells, battery modules, battery packs, electronic devices, and electric vehicles, which contain the compositions or cathode materials described herein.

[0209] This application incorporates, by reference, certain U.S. patents, U.S. patent applications, and other materials (e.g., articles). 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 inconsistency between such text and other descriptions and drawings contained herein. Where such inconsistency arises, none of the inconsistent texts in the U.S. patents, U.S. patent applications, and other materials incorporated by reference are specifically incorporated by reference into this patent. In combination with this disclosure, protection for any feature of the disclosure can be sought in any one or more published documents referenced herein. All methods described herein may be performed in any preferred order, unless otherwise indicated herein or unless otherwise clearly contradicted by the context. The use of any examples or illustrative language provided herein (e.g., "etc.") is intended solely to better describe the materials and methods and does not impose any limitation on their scope unless otherwise claimed. Nothing in this specification should be construed as indicating that any unclaimed element is essential for carrying out the materials and methods of the disclosure.

[0210] It will be readily apparent to those skilled in the art that suitable modifications and adaptations of the compositions, methods, and uses described herein can be made without departing from the scope or aspects of any of their embodiments. The compositions and methods provided are illustrative and are not intended to limit the scope of the claimed embodiments. All of the various embodiments and options disclosed herein can be combined in all variations. The scope of the compositions, formulations, methods, and processes described herein includes all actual or potential combinations of the embodiments, options, examples, and preferences herein.

[0211] While the art described herein has been described with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the art. It will be apparent to those skilled in the art that various modifications and variations can be made to the methods and apparatus of the art without departing from the spirit and scope of the art. Therefore, the art is intended to include modifications and variations within the scope of the appended claims and their equivalents.

[0212] Throughout this specification, references to "one aspect", "a particular aspect", "one or more aspects", or "an aspect" mean that the particular feature, structure, material, or characteristic described in relation to the aspect is included in at least one aspect of the technology. Thus, phrases such as "in one or more aspects", "in a particular aspect", "in one aspect", or "in an aspect" that appear in various places throughout this specification do not necessarily refer to the same aspect of the technology. Further, the particular feature, structure, material, or characteristics may be combined in any suitable manner in one or more aspects. The invention also broadly includes that the parts, elements, steps, examples, and / or features mentioned or shown individually or collectively in this specification may consist of any combination of two or more of such parts, elements, steps, examples, and / or features. In particular, one or more features in any of the aspects, examples, and aspects described in this specification may be combined with one or more features from any other examples and aspects described in this specification.

[0213] Aspects of the technology are more fully illustrated by reference to the following examples. Before describing some exemplary aspects of the technology, it is understood that the technology is not limited to the details of the construction or process steps described in the following description. The technology is capable of other aspects and of being practiced or carried out in various ways.

[0214] Further modifications and alternative aspects of the present invention will be apparent to those skilled in the art in view of this description. Accordingly, this description should be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the present invention. It is understood that the forms of the present invention shown and described herein are to be construed as examples of aspects. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the present invention may be utilized independently so that all will be apparent to those skilled in the art after obtaining the benefit of this description of the present invention. Changes may be made in the elements described herein without departing from the spirit and scope of the present invention as set forth in the following claims.

[0215] While certain exemplary aspects of the present invention have been described, the appended claims are not intended to be limited to only these aspects. The claims are to be construed literally, intentionally, and / or to include equivalents.

[0216] The following examples are described to illustrate certain aspects of the present technology and are not to be construed as limiting it.

Example

[0217] The present invention may be further illustrated by the following non-limiting examples of methods.

[0218] Example 1: Synthesis of lithium iron phosphate (Fe2O3 / phloroglucinol / furfuraldehyde) in a carbon matrix. A sample of lithium iron phosphate in a carbon matrix was prepared using iron(III) oxide (Fe2O3) as the iron source and phloroglucinol-furfural aldehyde polymer as the carbon source. Iron(III) oxide (2.8 g, 13 mmol, particle size ≤ 5 microns) 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 stopped. In a separate container, phloroglucinol (1.68 g) was dissolved in 10 ml of ethanol. Furfural aldehyde (1.68 ml) was added to the phloroglucinol solution, and the solution was mixed for 5 minutes. After mixing, the solution was added all at once to the iron oxide / 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, which was then thermally decomposed under nitrogen using the temperature gradient provided in Table 2 to provide lithium iron phosphate powder in a carbon matrix. [Table 2]

[0219] Samples of lithium iron phosphate powder in a carbon matrix were analyzed by scanning electron microscopy. Micrographs at two magnifications (1,490x and 5,050x) are provided as Figures 7A and 7B, respectively. Referring to Figures 7A and 7B, the lithium iron phosphate is formed as primary particles ranging in size from submicrons to several microns. These primary particles aggregate into secondary particles with diameters of several tens of microns, which are interconnected via the carbon matrix. Powder X-ray diffraction (XRD) analysis of the sample also demonstrated that the main phase of the material is olivine-type LiFePO4, accompanied by a subphase containing unidentified impurities (Figure 8).

[0220] Example 2: Synthesis of lithium iron phosphate (Fe(OH)3 / phloroglucinol / furfuralaldehyde) in a carbon matrix A sample of lithium iron phosphate was prepared in a carbon matrix using iron(III) hydroxide (Fe(OH)3) as the iron source and phloroglucinol-furfural aldehyde polymer as the carbon source. 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). To this solution, a solution of sodium hydroxide (2.1 g; 52.5 mmol) in deionized water (15 ml) was added to induce the instantaneous formation of an aqueous suspension of iron(III) hydroxide gel. The iron hydroxide gel was aged overnight in the mother liquor, then separated and purified by a cycle of centrifugation and resuspension in deionized water (total of 5 cycles). Phosphoric acid (85% H3PO4; 0.7 ml, 8.7 mmol), followed by 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. Furfural aldehyde (0.57 ml) was added to the phloroglucinol solution, and the solution was mixed for 5 minutes. After mixing, the solution was added all at once 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, which was thermally decomposed under nitrogen using the protocol described in Example 1 to provide lithium iron phosphate in the carbon matrix.

[0221] Samples of lithium iron phosphate powder in a carbon matrix were analyzed by scanning electron microscopy. Micrographs at two magnifications (10,000x and 49,900x) are provided as Figures 9A and 9B, respectively. Referring to Figures 9A and 9B, the LFP was formed as fine crystalline material with a diameter of approximately 100 nm to 1 micron and was uniformly dispersed within the conductive carbon network. Aggregates of secondary particles varied in size from approximately 1 micron to several microns and had an open framework structure that allowed electrolyte permeability. Powder X-ray diffraction (XRD) analysis of the sample was also performed, demonstrating that the main phase of the material was olivine-type LiFePO4, accompanied by a secondary phase containing approximately 2% iron (Figure 10). The iron impurity phase can be separated by magnetism or used as a ferromagnetic agent to increase the packing density of particles in the cathode film, for example, during magnetic electrode film casting.

[0222] Example 3: Synthesis of lithium iron phosphate (Fe(OH)3 / phloroglucinol / furfuralaldehyde) in a carbon matrix To evaluate the effect of residual carbon on particle size distribution and impurity profile, a second sample of lithium iron phosphate in a carbon matrix was prepared following the procedure of Example 2, but using a 2:1 ratio of PF precursor to LFP precursor.

[0223] Samples of lithium iron phosphate powder in a carbon matrix were analyzed by scanning electron microscopy at two magnifications (10,000x and 100,000x). Micrographs at each magnification are provided as Figures 11A and 11B, respectively. Referring to Figures 11A and 11B, the LFP was formed as fine crystalline material with a diameter of approximately 100 nm to 1 micron and was uniformly dispersed within the conductive carbon network. Aggregates of secondary particles varied in size from approximately 1 micron to several microns and had an open framework structure that allowed electrolyte permeability. Powder X-ray diffraction (XRD) analysis of the sample was also performed, demonstrating that the main phase of the material was olivine-type LiFePO4, accompanied by a subphase containing approximately 3% iron (Figure 12). The iron impurity phase can be separated by magnetism or used as a ferromagnetic agent to increase the packing density of particles in the cathode film, for example, during magnetic electrode film casting.

[0224] Example 4: Synthesis of lithium iron phosphate (Fe2O3 / pyromellitic dianhydride / 1,4-phenylenediamine; PAA / low PI gel) in a carbon matrix A sample of lithium iron phosphate was prepared in a carbon matrix 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 stopped. In separate containers, 1,4-phenylenediamine (PDA; 2.0 g), pyromellitic 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. Acetic anhydride (11.3 ml) was added to this solution to initiate imidization. After mixing for 1 minute, the gelling solution was added to the iron suspension all at once. The resulting reaction mixture was loosely covered 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 consisted of a mixture of polyamic acid-rich polyimide and polyamic acid. This dry powder was thermally decomposed using the protocol described in Example 1 to provide lithium iron phosphate within the carbon matrix.

[0225] Samples of lithium iron phosphate powder in a carbon matrix were analyzed by scanning electron microscopy. Micrographs at two magnifications (2,000x and 20,000x) are provided as Figures 13A and 13B, respectively. Referring to Figures 13A and 13B, the LFP was formed as aggregates of submicron primary particles held together by a conductive carbon network, resulting in secondary particles with a diameter of approximately 10 microns. Powder X-ray diffraction (XRD) analysis of the sample was also performed, demonstrating that the main phase of the material is olivine-type LiFePO4, accompanied by a subphase containing unidentified impurities (Figure 14).

[0226] Example 5: Synthesis of lithium iron phosphate (Fe2O3 / pyromellitic dianhydride / 1,4-phenylenediamine; PAA / low PI gel) in a carbon matrix A sample of lithium iron phosphate was prepared in a carbon matrix using iron(III) oxide (Fe2O3) as the iron source and polyamic acid 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 stopped. In separate containers, 1,4-phenylenediamine (PDA; 2.0 g), pyromellitic dianhydride (PMDA; 6.8 g), and triethylamine (9.3 ml) were added to deionized water (100 ml). The mixtures were reacted overnight to form a solution of triethylammonium polyamic acid salt. Next, the gel precursor mixture was added to the iron oxide suspension, and acetic anhydride (11.3 ml) was immediately added. The resulting reaction mixture was loosely covered 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 consisted mainly of polyamic acid and a small amount of polyimide. Although we do not wish to be bound by theory, it is thought that the acidic environment resulted in the hydrolysis of acetic anhydride to acetic acid and the gelation of insoluble polyamic acid, accompanied by minimal imidation. This dry powder was thermally decomposed using the protocol described in Example 1 to provide lithium iron phosphate within the carbon matrix.

[0227] Samples of lithium iron phosphate powder in a carbon matrix were analyzed by scanning electron microscopy. Micrographs at two magnifications (2,000x and 50,000x) are provided as Figures 15A and 15B, respectively. Referring to Figures 15A and 15B, the LFP forms as aggregates of uniform 2-micron primary particles, which assemble into 10-micron secondary particles within a porous network that allows electrolyte permeability. Powder X-ray diffraction (XRD) analysis of the sample also demonstrated that the main phase of the material is olivine-type LiFePO4, accompanied by a subphase containing unidentified impurities (Figure 16).

[0228] Example 6: Synthesis of lithium iron phosphate (Fe2O3 / pyromellitic dianhydride / 1,4-phenylenediamine; PAA / moderate PI gel) in a carbon matrix A sample of lithium iron phosphate was prepared in a carbon matrix using iron(III) oxide (Fe2O3) as the iron source and polyamic acid 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 stopped. In separate containers, 1,4-phenylenediamine (PDA; 2.0 g), pyromellitic dianhydride (PMDA; 6.8 g), and triethylamine (9.3 ml) were added to deionized water (100 ml). The mixtures were reacted overnight to form a solution of triethylammonium polyamic acid salt. Triethylamine (approximately 20 mL) was added to the iron oxide suspension to raise the pH (from the initial 4.0) to approximately 8.0. The entire gel precursor solution was then added at once to the iron oxide suspension, followed by 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 consisted mainly of polyamic acids along with several polyimides. While not wishing to be constrained by theory, the relatively neutral environment is thought to have resulted in increased imidation / gelation of the polyamic acid compared to Examples 4 and 5. This dry powder was thermally decomposed using the protocol described in Example 1 to provide lithium iron phosphate within the carbon matrix.

[0229] Powder X-ray diffraction (XRD) analysis of the product sample demonstrated that the material was a mixture of LiFePO4 (less than 70% by weight), unreacted Li3PO4 (approximately 30% by weight), and the remainder being Fe (Figure 17). Surprisingly, this example shows that a significant portion of the unreacted reagent is present in the final product, even with a higher PI / PAA ratio in the organogel. While we do not wish to be constrained by theory, it is thought that the rigid polyimide gel leads to reduced efficient contact between LFP precursors, resulting in low reaction homogeneity and low product yield.

[0230] Example 7: Raman Spectroscopy of Carbon Matrix The electronic structure of carbon formed in situ in Examples 1 to 7 is evaluated by Raman spectroscopy. Although not wishing to be bound by theory, it is considered that the carbon matrix formed according to the disclosed method can be more conductive than particulate carbon added to a lithium metal phosphate cathode material.

[0231] Example 8: Analysis of Carbon Nanostructure The nanostructure of the carbon matrix of the cathode material formed in Examples 1 to 7 is evaluated by eluting lithium metal phosphate from the carbon matrix. The remaining carbon material is analyzed to determine porosity, pore size, and carbon strut size. Specifically, the He true density is determined by He pycnometry and the surface and pore structure via N2 adsorption isotherms. For medium- and long-term microstructure analysis, SEM, TEM, Raman, and X-ray scattering are performed. Also, CHN elemental analysis is performed. Some embodiments of the present invention are shown below. [Embodiment 1] A method for preparing a lithium transition metal phosphate cathode material in a conductive carbon matrix, wherein the method is The combination of a group of precursors for synthesizing the phosphate transition metal lithium cathode material, wherein at least a first precursor from the group comprises a solid phase having a first density greater than 1 gram (g) / cubic centimeter (cc), and at least a second precursor from the group comprises a liquid phase having a second density, wherein the second density is less than the first density. To provide one or more carbon precursors in a fluid state, wherein the one or more carbon precursors are configured to form a solid organogel in the presence of a gelling initiator, and the solid organogel is configured to form a conductive carbon matrix upon thermal decomposition, The group of precursors is mixed with one or more carbon precursors to form a precursor mixture. Adding the gelation initiator to the precursor mixture, To enable gelation of one or more carbon precursors and to form the solid organogel, The method comprising thermally decomposing the solid organogel to form the lithium phosphate transition metal cathode material within the conductive carbon matrix. [Embodiment 2] The method according to Embodiment 1, wherein the solid organogel is formed within 5 seconds to 15 minutes after the addition of the gelling initiator. [Embodiment 3] The method according to Embodiment 1, wherein the solid organogel includes a porous network of interconnected solid-phase polymer structures. [Embodiment 4] The method according to Embodiment 3, wherein the porous network maintains contact between the first precursor of the group and the second precursor of the group. [Embodiment 5] The method according to Embodiment 4, wherein the contact is maintained at a temperature of at least about 300°C. [Embodiment 6] The first precursor contains iron, The second precursor comprises a lithium source and phosphoric acid, The method according to Embodiment 1, wherein the lithium transition metal phosphate cathode material is lithium iron phosphate. [Embodiment 7] The aforementioned iron is iron(II) salt, iron(III) salt, iron(II) oxide (FeO), iron(III) oxide (Fe 2 O 3 ), mixed iron oxide (Fe 3 O 4 The method according to Embodiment 6, which exists in the form of ), or a combination thereof. [Embodiment 8] The method according to Embodiment 1, 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. [Embodiment 9] The method according to Embodiment 8, wherein the gelation initiator is an amine base or an acid. [Embodiment 10] The method according to Embodiment 1, wherein the solid organogel comprises a polyurethane polymer, and the one or more carbon precursors comprises a polyol and an isocyanate. [Embodiment 11] The method according to Embodiment 10, wherein the gelation initiator comprises an alkylamine. [Embodiment 12] The method according to Embodiment 1, wherein the organogel comprises a polyamic acid polymer, and the gelling initiator comprises acetic anhydride, acetic acid, or a combination thereof. [Embodiment 13] The method according to Embodiment 1, wherein the group of precursors includes a microwave-sensitive precursor, and the thermal decomposition is carried out by applying microwave radiation. [Embodiment 14] The method according to Embodiment 13, wherein the microwave-sensitive precursor comprises one or more of carbon, magnetite, and maghemite. [Embodiment 15] The method according to Embodiment 14, comprising one or more nanoparticles of magnetite and maghemite having characteristic dimensions of 20 nm to 100 nm. [Embodiment 16] The first precursor comprises manganese, vanadium, or both. The second precursor comprises a lithium source and phosphoric acid, The method according to Embodiment 1, wherein the phosphate transition metal lithium cathode material is lithium manganese phosphate or lithium vanadium phosphate. [Embodiment 17] The method according to Embodiment 1, further comprising drying the lithium phosphate transition metal cathode material by applying microwave radiation. [Embodiment 18] The method according to Embodiment 1, wherein the solid phase having a first density of more than 1 gram comprises a ferromagnetic iron compound, a ferrimagnetic iron compound, or both. [Embodiment 19] The ferromagnetic iron compound, the ferrimagnetic iron compound, or both, The iron-containing anode is synthesized by a method comprising oxidizing it in an electrochemical cell containing a porous carbon substrate, an oxygen cathode, and an electrolyte in contact with both the iron-containing anode and the porous carbon substrate. The method according to Embodiment 18, wherein the oxidation process produces particles of the ferromagnetic iron compound, the ferrimagnetic iron compound, or both having characteristic dimensions of 20 nm to 100 nm. [Embodiment 20] The method according to embodiment 19, further comprising removing the particles by magnetic filtration. [Embodiment 21] The method according to embodiment 19, further comprising drying the particles by applying microwave radiation. [Embodiment 22] The method according to Embodiment 19, wherein the operation of the electrochemical cell and the formation of the ferromagnetic iron compound, the ferromagnetic iron compound, or both are carried out at a temperature of 15°C to 35°C. [Embodiment 23] A lithium transition metal phosphate cathode material prepared by the method described in Embodiment 1. [Embodiment 24] An energy storage system comprising a lithium transition metal phosphate cathode material prepared by the method described in Embodiment 1. [Embodiment 25] A composition comprising olivine-type lithium iron phosphate and nanoparticles integrated with a conductive carbon matrix, wherein the nanoparticles have characteristic dimensions of 20 nm to 1000 nm and 10 m 2 (m 2 ) / grams (g) ~ 65m 2 The composition having a specific surface area of ​​ / g. [Embodiment 26] The aforementioned characteristic dimensions are 30 nm to 70 nm, and the specific surface area is 20 m². 2 / g~65m 2 The composition according to Embodiment 25, wherein the concentration is / g. [Embodiment 27] The aforementioned characteristic dimensions are 30 nm to 60 nm, and the specific surface area is 22 m². 2 / g~40m 2 The composition according to Embodiment 25, wherein the concentration is / g. [Embodiment 28] The aforementioned characteristic dimensions are 20 nm to 40 nm, and the specific surface area is 60 m². 2 / g~80m 2 The composition according to Embodiment 25, wherein the concentration is / g. [Embodiment 29] The composition according to Embodiment 25, wherein the nanoparticles further comprise magnetite, maghemite, or both. [Embodiment 30] The composition according to Embodiment 25, wherein the nanoparticles further comprise manganese. [Embodiment 31] The composition according to Embodiment 25, wherein the conductive carbon matrix comprises a carbide organogel polymer matrix. [Embodiment 32] An energy storage system comprising the composition described in Embodiment 25.

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